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Sample records for hydride dissociation reactions

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

    Science.gov (United States)

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

    2006-02-23

    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.

  2. Comparison between different reactions of group IV hydride with H

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Shaolong; ZHANG; Xuqiang; ZHANG; Qinggang; ZHANG; Yici

    2006-01-01

    The four-dimensional time-dependent quantum dynamics calculations for reactions of group IV hydride with H are carried out by employing the semirigid vibrating rotor target model and the time-dependent wave packet method. The reaction possibility, cross section and rate constants for reactions (H+SiH4 and H+GeH4) in different initial vibrational and rotational states are obtained. The common feature for such kind of reaction process is summarized. The theoretical result is consistent with available measurement, which indicates the credibility of this theory and the potential energy surface.

  3. Equilibrium composition for the reaction of plutonium hydride with air

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    There are six independent constituents with 4 chemical elements, i.e. PuH2.7(s), PuN(s), Pu2O3(s), N2, O2 and H2, therefore , the system described involves of 2 independent reactions ,both those of the experimental, which indicates that the chemical equilibrium is nearly completely approached. Therefore, it is believed that the reaction rate of plutonium hydride with air is extremely rapid. The present paper has briefly discussed the simultaneous reactions and its thermodynamic coupling effect.

  4. Coulomb dissociation studies for astrophysical thermonuclear reactions

    Energy Technology Data Exchange (ETDEWEB)

    Motobayashi, T. [Dept. of Physics, Rikkyo Univ., Toshima, Tokyo (Japan)

    1998-06-01

    The Coulomb dissociation method was applied to several radiative capture processes of astrophysical interest. The method has an advantage of high experimental efficiency, which allow measurements with radioactive nuclear beams. The reactions {sup 13}N(p,{gamma}){sup 14}O and {sup 7}Be(p,{gamma}){sup 8}B are mainly discussed. They are the key reaction in the hot CNO cycle in massive stars and the one closely related to the solar neutrino problem, respectively. (orig.)

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

    Science.gov (United States)

    Sandhya, K S; Suresh, Cherumuttathu H

    2014-08-28

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

  6. Hydrogenation reaction characteristics and properties of its hydrides for magnetic regenerative material HoCu2

    Institute of Scientific and Technical Information of China (English)

    金滔; 吴梦茜; 黄迦乐; 汤珂; 陈立新

    2016-01-01

    The hydrogenation reaction characteristics and the properties of its hydrides for the magnetic regenerative material HoCu2 (CeCu2-type) of a cryocooler were investigated. The XRD testing reveals that the hydrides of HoCu2 were a mixture of Cu, unknown hydride I, and unknown hydride II. Based on the PCT (pressure−concentration−temperature) curves under different reaction temperatures, the relationships among reaction temperature, equilibrium pressure, and maximum hydrogen absorption capacity were analyzed and discussed. The enthalpy changeΔH and entropy changeΔS as a result of the whole hydrogenation process were also calculated from the PCT curves. The magnetization and volumetric specific heat capacity of the hydride were also measured by SQUID magnetometer and PPMS, respectively.

  7. Use of reversible hydrides for hydrogen storage

    Science.gov (United States)

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

    1980-01-01

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

  8. Hydrogen and Dihydrogen Bonds in the Reactions of Metal Hydrides.

    Science.gov (United States)

    Belkova, Natalia V; Epstein, Lina M; Filippov, Oleg A; Shubina, Elena S

    2016-08-10

    The dihydrogen bond-an interaction between a transition-metal or main-group hydride (M-H) and a protic hydrogen moiety (H-X)-is arguably the most intriguing type of hydrogen bond. It was discovered in the mid-1990s and has been intensively explored since then. Herein, we collate up-to-date experimental and computational studies of the structural, energetic, and spectroscopic parameters and natures of dihydrogen-bonded complexes of the form M-H···H-X, as such species are now known for a wide variety of hydrido compounds. Being a weak interaction, dihydrogen bonding entails the lengthening of the participating bonds as well as their polarization (repolarization) as a result of electron density redistribution. Thus, the formation of a dihydrogen bond allows for the activation of both the MH and XH bonds in one step, facilitating proton transfer and preparing these bonds for further transformations. The implications of dihydrogen bonding in different stoichiometric and catalytic reactions, such as hydrogen exchange, alcoholysis and aminolysis, hydrogen evolution, hydrogenation, and dehydrogenation, are discussed.

  9. Formation and reactivity of a porphyrin iridium hydride in water: acid dissociation constants and equilibrium thermodynamics relevant to Ir-H, Ir-OH, and Ir-CH2- bond dissociation energetics.

    Science.gov (United States)

    Bhagan, Salome; Wayland, Bradford B

    2011-11-01

    Aqueous solutions of group nine metal(III) (M = Co, Rh, Ir) complexes of tetra(3,5-disulfonatomesityl)porphyrin [(TMPS)M(III)] form an equilibrium distribution of aquo and hydroxo complexes ([(TMPS)M(III)(D(2)O)(2-n)(OD)(n)]((7+n)-)). Evaluation of acid dissociation constants for coordinated water show that the extent of proton dissociation from water increases regularly on moving down the group from cobalt to iridium, which is consistent with the expected order of increasing metal-ligand bond strengths. Aqueous (D(2)O) solutions of [(TMPS)Ir(III)(D(2)O)(2)](7-) react with dihydrogen to form an iridium hydride complex ([(TMPS)Ir-D(D(2)O)](8-)) with an acid dissociation constant of 1.8(0.5) × 10(-12) (298 K), which is much smaller than the Rh-D derivative (4.3 (0.4) × 10(-8)), reflecting a stronger Ir-D bond. The iridium hydride complex adds with ethene and acetaldehyde to form organometallic derivatives [(TMPS)Ir-CH(2)CH(2)D(D(2)O)](8-) and [(TMPS)Ir-CH(OD)CH(3)(D(2)O)](8-). Only a six-coordinate carbonyl complex [(TMPS)Ir-D(CO)](8-) is observed for reaction of the Ir-D with CO (P(CO) = 0.2-2.0 atm), which contrasts with the (TMPS)Rh-D analog which reacts with CO to produce an equilibrium with a rhodium formyl complex ([(TMPS)Rh-CDO(D(2)O)](8-)). Reactivity studies and equilibrium thermodynamic measurements were used to discuss the relative M-X bond energetics (M = Rh, Ir; X = H, OH, and CH(2)-) and the thermodynamically favorable oxidative addition of water with the (TMPS)Ir(II) derivatives.

  10. Using first principles calculations to identify new destabilized metal hydride reactions for reversible hydrogen storage.

    Science.gov (United States)

    Alapati, Sudhakar V; Karl Johnson, J; Sholl, David S

    2007-03-28

    Hydrides of period 2 and 3 elements are promising candidates for hydrogen storage, but typically have heats of reaction that are too high to be of use for fuel cell vehicles. Recent experimental work has focused on destabilizing metal hydrides through mixing metal hydrides with other compounds. A very large number of possible destabilized metal hydride reaction schemes exist, but the thermodynamic data required to assess the enthalpies of these reactions are not available in many cases. We have used density functional theory calculations to predict the reaction enthalpies for more than 300 destabilization reactions that have not previously been reported. The large majority of these reactions are predicted not to be useful for reversible hydrogen storage, having calculated reaction enthalpies that are either too high or too low, and hence these reactions need not be investigated experimentally. Our calculations also identify multiple promising reactions that have large enough hydrogen storage capacities to be useful in practical applications and have reaction thermodynamics that appear to be suitable for use in fuel cell vehicles and are therefore promising candidates for experimental work.

  11. Metal hydrides: an innovative and challenging conversion reaction anode for lithium-ion batteries

    Directory of Open Access Journals (Sweden)

    Luc Aymard

    2015-08-01

    Full Text Available The state of the art of conversion reactions of metal hydrides (MH with lithium is presented and discussed in this review with regard to the use of these hydrides as anode materials for lithium-ion batteries. A focus on the gravimetric and volumetric storage capacities for different examples from binary, ternary and complex hydrides is presented, with a comparison between thermodynamic prediction and experimental results. MgH2 constitutes one of the most attractive metal hydrides with a reversible capacity of 1480 mA·h·g−1 at a suitable potential (0.5 V vs Li+/Li0 and the lowest electrode polarization (2, TiH2, complex hydrides Mg2MHx and other Mg-based hydrides. The reversible conversion reaction mechanism of MgH2, which is lithium-controlled, can be extended to others hydrides as: MHx + xLi+ + xe− in equilibrium with M + xLiH. Other reaction paths—involving solid solutions, metastable distorted phases, and phases with low hydrogen content—were recently reported for TiH2 and Mg2FeH6, Mg2CoH5 and Mg2NiH4. The importance of fundamental aspects to overcome technological difficulties is discussed with a focus on conversion reaction limitations in the case of MgH2. The influence of MgH2 particle size, mechanical grinding, hydrogen sorption cycles, grinding with carbon, reactive milling under hydrogen, and metal and catalyst addition to the MgH2/carbon composite on kinetics improvement and reversibility is presented. Drastic technological improvement in order to the enhance conversion process efficiencies is needed for practical applications. The main goals are minimizing the impact of electrode volume variation during lithium extraction and overcoming the poor electronic conductivity of LiH. To use polymer binders to improve the cycle life of the hydride-based electrode and to synthesize nanoscale composite hydride can be helpful to address these drawbacks. The development of high-capacity hydride anodes should be inspired by the emergent

  12. Metal hydrides: an innovative and challenging conversion reaction anode for lithium-ion batteries.

    Science.gov (United States)

    Aymard, Luc; Oumellal, Yassine; Bonnet, Jean-Pierre

    2015-01-01

    The state of the art of conversion reactions of metal hydrides (MH) with lithium is presented and discussed in this review with regard to the use of these hydrides as anode materials for lithium-ion batteries. A focus on the gravimetric and volumetric storage capacities for different examples from binary, ternary and complex hydrides is presented, with a comparison between thermodynamic prediction and experimental results. MgH2 constitutes one of the most attractive metal hydrides with a reversible capacity of 1480 mA·h·g(-1) at a suitable potential (0.5 V vs Li(+)/Li(0)) and the lowest electrode polarization (hydrides Mg2MH x and other Mg-based hydrides. The reversible conversion reaction mechanism of MgH2, which is lithium-controlled, can be extended to others hydrides as: MH x + xLi(+) + xe(-) in equilibrium with M + xLiH. Other reaction paths-involving solid solutions, metastable distorted phases, and phases with low hydrogen content-were recently reported for TiH2 and Mg2FeH6, Mg2CoH5 and Mg2NiH4. The importance of fundamental aspects to overcome technological difficulties is discussed with a focus on conversion reaction limitations in the case of MgH2. The influence of MgH2 particle size, mechanical grinding, hydrogen sorption cycles, grinding with carbon, reactive milling under hydrogen, and metal and catalyst addition to the MgH2/carbon composite on kinetics improvement and reversibility is presented. Drastic technological improvement in order to the enhance conversion process efficiencies is needed for practical applications. The main goals are minimizing the impact of electrode volume variation during lithium extraction and overcoming the poor electronic conductivity of LiH. To use polymer binders to improve the cycle life of the hydride-based electrode and to synthesize nanoscale composite hydride can be helpful to address these drawbacks. The development of high-capacity hydride anodes should be inspired by the emergent nano-research prospects which

  13. Interface reactions and stability of a hydride composite (NaBH4 + MgH2).

    Science.gov (United States)

    Kato, Shunsuke; Borgschulte, Andreas; Bielmann, Michael; Züttel, Andreas

    2012-06-21

    The use of the interaction of two hydrides is a well-known concept used to increase the hydrogen equilibrium pressure of composite mixtures in comparison to that of pure systems. The thermodynamics and reaction kinetics of such hydride composites are reviewed and experimentally verified using the example NaBH(4) + MgH(2). Particular emphasis is placed on the measurement of the kinetics and stability using thermodesorption experiments and measurements of pressure-composition isotherms, respectively. The interface reactions in the composite reaction were analysed by in situ X-ray photoelectron spectroscopy and by simultaneously probing D(2) desorption from NaBD(4) and H(2) desorption from MgH(2). The observed destabilisation is in quantitative agreement with the calculated thermodynamic properties, including enthalpy and entropy. The results are discussed with respect to kinetic limitations of the hydrogen desorption mechanism at interfaces. General aspects of modifying hydrogen sorption properties via hydride composites are given.

  14. Reaction pathways of the dissociation of methylal: A DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Frey, H.-M.; Beaud, P.; Gerber, T.; Mischler, B.; Radi, P.P.; Tzannis, A.-P. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    Schemata for modelling combustion processes do not yet include reaction rates for oxygenated fuels like methylal (DMM) which is considered as an additive or replacement for diesel due to its low sooting propensity. Density functional theory (DFT) studies of the possible reaction pathways for different dissociation steps of methylal are presented. Cleavage of a hydrogen bond to the methoxy group or the central carbon atom were simulated at the BLYP/6-311++G{sup **} level of theory. The results are compared to the experiment when dissociating and/or ionising DMM with femtosecond pulses. (author) 1 fig., 1 tab., 1 ref.

  15. Hydriding and microstructure nanocrystallization of ZK60 Mg alloy by reaction milling in hydrogen

    Institute of Scientific and Technical Information of China (English)

    YUAN Yuan; WANG Heng; HU Lian-xi; SUN Hong-fei; FANG Wen-bin

    2009-01-01

    The hydriding of as-cast Mg-5.5%Zn-0.6%Zr (ZK60 Mg) (mass fraction) alloy was achieved by room-temperature reaction milling in hydrogen, with the mechanical energy serving as the driving force for the process. The hydriding progress during milling was examined by hydrogen absorption measurement, and the microstructure change was characterized by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), respectively. The results show that, by room-temperature reaction milling in hydrogen, the as-cast ZK60 Mg alloy can be fully hydrided to form a nanocrystalline MgH2 single-phase microstructure. In particular, the average grain size of the MgH2 phase obtained by room-temperature reaction milling in hydrogen for 16.2 h is about 8-10 nm, and the average particle size of the as-milled hydrided powders is 2-3 μm.

  16. Zero-Point Energy Constraint for Unimolecular Dissociation Reactions. Giving Trajectories Multiple Chances To Dissociate Correctly.

    Science.gov (United States)

    Paul, Amit K; Hase, William L

    2016-01-28

    A zero-point energy (ZPE) constraint model is proposed for classical trajectory simulations of unimolecular decomposition and applied to CH4* → H + CH3 decomposition. With this model trajectories are not allowed to dissociate unless they have ZPE in the CH3 product. If not, they are returned to the CH4* region of phase space and, if necessary, given additional opportunities to dissociate with ZPE. The lifetime for dissociation of an individual trajectory is the time it takes to dissociate with ZPE in CH3, including multiple possible returns to CH4*. With this ZPE constraint the dissociation of CH4* is exponential in time as expected for intrinsic RRKM dynamics and the resulting rate constant is in good agreement with the harmonic quantum value of RRKM theory. In contrast, a model that discards trajectories without ZPE in the reaction products gives a CH4* → H + CH3 rate constant that agrees with the classical and not quantum RRKM value. The rate constant for the purely classical simulation indicates that anharmonicity may be important and the rate constant from the ZPE constrained classical trajectory simulation may not represent the complete anharmonicity of the RRKM quantum dynamics. The ZPE constraint model proposed here is compared with previous models for restricting ZPE flow in intramolecular dynamics, and connecting product and reactant/product quantum energy levels in chemical dynamics simulations.

  17. Transition-metal-free coupling reaction of vinylcyclopropanes with aldehydes catalyzed by tin hydride.

    Science.gov (United States)

    Ieki, Ryosuke; Kani, Yuria; Tsunoi, Shinji; Shibata, Ikuya

    2015-04-13

    Donor-acceptor cyclopropanes are useful building blocks for catalytic cycloaddition reactions with a range of electrophiles to give various cyclic products. In contrast, relatively few methods are available for the synthesis of homoallylic alcohols through coupling of vinylcyclopropanes (VCPs) with aldehydes, even with transition-metal catalysts. Here, we report that the hydrostannation of vinylcyclopropanes (VCPs) was effectively promoted by dibutyliodotin hydride (Bu2 SnIH). The resultant allylic tin compounds reacted easily with aldehydes. Furthermore, the use of Bu2 SnIH was effectively catalytic in the presence of hydrosilane as a hydride source, which established a coupling reaction of VCPs with aldehydes for the synthesis of homoallylic alcohols without the use of transition-metal catalysts. In contrast to conventional catalytic reactions of VCPs, the presented method allowed the use of several VCPs in addition to conventional donor-acceptor cyclopropanes.

  18. Photochemistry of Transition Metal Hydrides.

    Science.gov (United States)

    Perutz, Robin N; Procacci, Barbara

    2016-08-10

    Photochemical reactivity associated with metal-hydrogen bonds is widespread among metal hydride complexes and has played a critical part in opening up C-H bond activation. It has been exploited to design different types of photocatalytic reactions and to obtain NMR spectra of dilute solutions with a single pulse of an NMR spectrometer. Because photolysis can be performed on fast time scales and at low temperature, metal-hydride photochemistry has enabled determination of the molecular structure and rates of reaction of highly reactive intermediates. We identify five characteristic photoprocesses of metal monohydride complexes associated with the M-H bond, of which the most widespread are M-H homolysis and R-H reductive elimination. For metal dihydride complexes, the dominant photoprocess is reductive elimination of H2. Dihydrogen complexes typically lose H2 photochemically. The majority of photochemical reactions are likely to be dissociative, but hydride complexes may be designed with equilibrated excited states that undergo different photochemical reactions, including proton transfer or hydride transfer. The photochemical mechanisms of a few reactions have been analyzed by computational methods, including quantum dynamics. A section on specialist methods (time-resolved spectroscopy, matrix isolation, NMR, and computational methods) and a survey of transition metal hydride photochemistry organized by transition metal group complete the Review.

  19. Kinetic equation for the reaction of titanium tetrachloride with hydride functional groups of diamond

    Energy Technology Data Exchange (ETDEWEB)

    Zhidkov, A.B.; Smirnov, E.P.

    1989-02-01

    This work is devoted to the study of the kinetics of the reaction of titanium tetrachloride with the hydride functional groups of diamond. The research was performed on submicron powders of ASM 0.7/0.3 grade synthetic diamond with a specific surface area of 8.0 m/sup 2//g as measured from the adsorption of nitrogen. The reaction was carried out in a flow-through quartz reactor in a flow of dry He. The content of the titanium in the samples was determined by a photocolorimetric method. A kinetic equation for the reaction of diamond with titanium tetrachloride was found on the basis of a statistical approach.

  20. Insight into the kinetics and thermodynamics of the hydride transfer reactions between quinones and lumiflavin: a density functional theory study.

    Science.gov (United States)

    Reinhardt, Clorice R; Jaglinski, Tanner C; Kastenschmidt, Ashly M; Song, Eun H; Gross, Adam K; Krause, Alyssa J; Gollmar, Jonathan M; Meise, Kristin J; Stenerson, Zachary S; Weibel, Tyler J; Dison, Andrew; Finnegan, Mackenzie R; Griesi, Daniel S; Heltne, Michael D; Hughes, Tom G; Hunt, Connor D; Jansen, Kayla A; Xiong, Adam H; Hati, Sanchita; Bhattacharyya, Sudeep

    2016-09-01

    The kinetics and equilibrium of the hydride transfer reaction between lumiflavin and a number of substituted quinones was studied using density functional theory. The impact of electron withdrawing/donating substituents on the redox potentials of quinones was studied. In addition, the role of these substituents on the kinetics of the hydride transfer reaction with lumiflavin was investigated in detail under the transition state (TS) theory assumption. The hydride transfer reactions were found to be more favorable for an electron-withdrawing substituent. The activation barrier exhibited a quadratic relationship with the driving force of these reactions as derived under the formalism of modified Marcus theory. The present study found a significant extent of electron delocalization in the TS that is stabilized by enhanced electrostatic, polarization, and exchange interactions. Analysis of geometry, bond-orders, and energetics revealed a predominant parallel (Leffler-Hammond) effect on the TS. Closer scrutiny reveals that electron-withdrawing substituents, although located on the acceptor ring, reduce the N-H bond order of the donor fragment in the precursor complex. Carried out in the gas-phase, this is the first ever report of a theoretical study of flavin's hydride transfer reactions with quinones, providing an unfiltered view of the electronic effect on the nuclear reorganization of donor-acceptor complexes.

  1. Coulomb dissociation reactions on molybdenum isotopes for astrophysics applications

    Energy Technology Data Exchange (ETDEWEB)

    Ershova, Olga

    2012-03-09

    Within the present work, photodissociation reactions on {sup 100}Mo, {sup 93}Mo and {sup 92}Mo isotopes were studied by means of the Coulomb dissociation method at the LAND setup at GSI. As a result of the analysis of the present experiment, integrated Coulomb excitation cross sections of the {sup 100}Mo({gamma},n), {sup 100}Mo({gamma},2n), {sup 93}Mo({gamma},n) and {sup 92}Mo({gamma},n) reactions were determined. A second important topic of the present thesis is the investigation of the efficiency of the CsI gamma detector. The data taken with the gamma calibration sources shortly after the experiment were used for the investigation. In addition, a test experiment in refined conditions was conducted within the framework of this thesis. Numerous GEANT3 simulations of the detector were performed in order to understand various aspects of its performance. As a result, the efficiency of the detector was determined to be approximately a factor of 2 lower than the efficiency expected from the simulation. (orig.)

  2. Hydrogen adsorption on palladium and palladium hydride at 1 bar

    DEFF Research Database (Denmark)

    Johansson, Martin; Skulason, Egill; Nielsen, Gunver

    2010-01-01

    The dissociative sticking probability for H-2 on Pd films supported on sputtered Highly Ordered Pyrolytic Graphite (HOPG) has been derived from measurements of the rate of the H-D exchange reaction at 1 bar. The sticking probability for H-2, S. is higher on Pd hydride than on Pd (a factor of 1...

  3. Large-scale screening of metal hydrides for hydrogen storage from first-principles calculations based on equilibrium reaction thermodynamics.

    Science.gov (United States)

    Kim, Ki Chul; Kulkarni, Anant D; Johnson, J Karl; Sholl, David S

    2011-04-21

    Systematic thermodynamics calculations based on density functional theory-calculated energies for crystalline solids have been a useful complement to experimental studies of hydrogen storage in metal hydrides. We report the most comprehensive set of thermodynamics calculations for mixtures of light metal hydrides to date by performing grand canonical linear programming screening on a database of 359 compounds, including 147 compounds not previously examined by us. This database is used to categorize the reaction thermodynamics of all mixtures containing any four non-H elements among Al, B, C, Ca, K, Li, Mg, N, Na, Sc, Si, Ti, and V. Reactions are categorized according to the amount of H(2) that is released and the reaction's enthalpy. This approach identifies 74 distinct single step reactions having that a storage capacity >6 wt.% and zero temperature heats of reaction 15 ≤ΔU(0)≤ 75 kJ mol(-1) H(2). Many of these reactions, however, are likely to be problematic experimentally because of the role of refractory compounds, B(12)H(12)-containing compounds, or carbon. The single most promising reaction identified in this way involves LiNH(2)/LiH/KBH(4), storing 7.48 wt.% H(2) and having ΔU(0) = 43.6 kJ mol(-1) H(2). We also examined the complete range of reaction mixtures to identify multi-step reactions with useful properties; this yielded 23 multi-step reactions of potential interest.

  4. Density functional investigations of electronic structure and dehydrogenation reactions of Al- and Si-substituted magnesium hydride.

    Science.gov (United States)

    Kelkar, Tuhina; Pal, Sourav; Kanhere, Dilip G

    2008-04-21

    The effect on the hydrogen storage attributes of magnesium hydride (MgH(2)) of the substitution of Mg by varying fractions of Al and Si is investigated by an ab initio plane-wave pseuodopotential method based on density functional theory. Three supercells, namely, 2 x 2 x 2, 3 x 1 x 1 and 5 x 1 x 1 are used for generating configurations with varying amounts (fractions x=0.0625, 0.1, and 0.167) of impurities. The analyses of band structure and density of states (DOS) show that, when a Mg atom is replaced by Al, the band gap vanishes as the extra electron occupies the conduction band minimum. In the case of Si-substitution, additional states are generated within the band gap of pure MgH(2)-significantly reducing the gap in the process. The reduced band gaps cause the Mg--H bond to become more susceptible to dissociation. For all the fractions, the calculated reaction energies for the stepwise removal of H(2) molecules from Al- and Si-substituted MgH(2) are much lower than for H(2) removal from pure MgH(2). The reduced stability is also reflected in the comparatively smaller heats of formation (DeltaH(f)) of the substituted MgH(2) systems. Si causes greater destabilization of MgH(2) than Al for each x. For fractions x=0.167 of Al, x=0.1, 0.167 of Si (FCC) and x=0.0625, 0.1 of Si (diamond), DeltaH(f) is much less than that of MgH(2) substituted by a fraction x=0.2 of Ti (Y. Song, Z. X. Guo, R. Yang, Mat. Sc. & Eng. A 2004, 365, 73). Hence, we suggest the use of Al or Si instead of Ti as an agent for decreasing the dehydrogenation reaction and energy, consequently, the dehydrogenation temperature of MgH(2), thereby improving its potential as a hydrogen storage material.

  5. Trajectory study of dissociation reactions. The single-ensemble method. II

    Science.gov (United States)

    Kutz, H. Douglas; Burns, George

    1981-04-01

    The single uniform ensemble method was previously employed in 3D classical trajectory calculations [H. D. Kutz and G. Burns, J. Chem. Phys. 72, 3652 (1980)]. Presently it is applied to the Br2+Ar system to study nonequilbrium effects in diatom dissociation over a wide temperature range. It was found that, for a given large set of trajectories, observables, such as reaction cross sections or rate constants, are indepedent within four significant figures of the initial distribution function. This indicates a high degree of reliability of the single uniform ensemble method, once the choice of a set of trajectories is made. In order to study dissociation from the low lying energy states, the uniform velocity selection method in trajectory calculations was used. It was found that dissociation from these states contributes but little to the overall dissociation reaction. The latter finding is consistent with the attractive nature of the potential energy surface used, and constitutes an argument against those current theories of diatom dissociation reaction which explains experimental data by postulating a high probability of dissociation from low lying energy states of diatoms. It was found that the contribution from the low lying states to dissociation can be estimated with good accuracy using information theory expressions. Temperature dependence of nonequilibrium effects was investigated between 1 500 and 6 000 °K. In this range the nonequilibrium correction factor varies between 0.2 and 0.5. Angular momentum dependence of such observables as reaction rate constant and reaction cross section was investigated.

  6. Reaction paths of phosphine dissociation on silicon (001)

    Science.gov (United States)

    Warschkow, O.; Curson, N. J.; Schofield, S. R.; Marks, N. A.; Wilson, H. F.; Radny, M. W.; Smith, P. V.; Reusch, T. C. G.; McKenzie, D. R.; Simmons, M. Y.

    2016-01-01

    Using density functional theory and guided by extensive scanning tunneling microscopy (STM) image data, we formulate a detailed mechanism for the dissociation of phosphine (PH3) molecules on the Si(001) surface at room temperature. We distinguish between a main sequence of dissociation that involves PH2+H, PH+2H, and P+3H as observable intermediates, and a secondary sequence that gives rise to PH+H, P+2H, and isolated phosphorus adatoms. The latter sequence arises because PH2 fragments are surprisingly mobile on Si(001) and can diffuse away from the third hydrogen atom that makes up the PH3 stoichiometry. Our calculated activation energies describe the competition between diffusion and dissociation pathways and hence provide a comprehensive model for the numerous adsorbate species observed in STM experiments.

  7. Reaction paths of phosphine dissociation on silicon (001)

    Energy Technology Data Exchange (ETDEWEB)

    Warschkow, O.; McKenzie, D. R. [Centre for Quantum Computation and Communication Technology, School of Physics, The University of Sydney, Sydney, NSW 2006 (Australia); Curson, N. J. [Centre for Quantum Computation and Communication Technology, School of Physics, The University of New South Wales, Sydney, NSW 2052 (Australia); London Centre for Nanotechnology and Department of Electronic and Electrical Engineering, University College London, 17-19 Gordon Street, London WC1H 0AH (United Kingdom); Schofield, S. R. [Centre for Quantum Computation and Communication Technology, School of Physics, The University of New South Wales, Sydney, NSW 2052 (Australia); London Centre for Nanotechnology and Department of Physics and Astronomy, University College, 17-19 Gordon Street, London WC1H 0AH (United Kingdom); Marks, N. A. [Centre for Quantum Computation and Communication Technology, School of Physics, The University of Sydney, Sydney, NSW 2006 (Australia); Discipline of Physics & Astronomy, Curtin University, GPO Box U1987, Perth, WA (Australia); Wilson, H. F. [Centre for Quantum Computation and Communication Technology, School of Physics, The University of Sydney, Sydney, NSW 2006 (Australia); CSIRO Virtual Nanoscience Laboratory, Parkville, VIC 3052 (Australia); School of Applied Sciences, RMIT University, Melbourne, VIC 3000 (Australia); Radny, M. W.; Smith, P. V. [School of Mathematical and Physical Sciences, The University of Newcastle, Callaghan, NSW 2308 (Australia); Reusch, T. C. G.; Simmons, M. Y. [Centre for Quantum Computation and Communication Technology, School of Physics, The University of New South Wales, Sydney, NSW 2052 (Australia)

    2016-01-07

    Using density functional theory and guided by extensive scanning tunneling microscopy (STM) image data, we formulate a detailed mechanism for the dissociation of phosphine (PH{sub 3}) molecules on the Si(001) surface at room temperature. We distinguish between a main sequence of dissociation that involves PH{sub 2}+H, PH+2H, and P+3H as observable intermediates, and a secondary sequence that gives rise to PH+H, P+2H, and isolated phosphorus adatoms. The latter sequence arises because PH{sub 2} fragments are surprisingly mobile on Si(001) and can diffuse away from the third hydrogen atom that makes up the PH{sub 3} stoichiometry. Our calculated activation energies describe the competition between diffusion and dissociation pathways and hence provide a comprehensive model for the numerous adsorbate species observed in STM experiments.

  8. DME Dissociation Reaction on Platinum Electrode Surface : A Quantitative Kinetic Analysis by In Situ IR Spectroscopy

    OpenAIRE

    Zhang, Yi; Tong, Yujin; Lu, Leilei; Osawa, Masatoshi; Ye, Shen

    2010-01-01

    The kinetics of electrocatalytic dissociation reaction of dimethyl ether (DME) on a platinum (Pt) polycrystalline electrode in an acidic solution yielding carbon monoxide (CO) has been quantitatively analyzed by in situ IR spectroscopy in the potential region between 100 and 500 mV (vs reversible hydrogen electrode). A two-step consecutive reaction model, an initial dehydrogenation step followed by a CO formation step, is proposed for the dissociation process of the DME molecule. The mechanis...

  9. Photoelectron Spectroscopy of Transition Metal Hydride Cluster Anions and Their Roles in Hydrogenation Reactions

    Science.gov (United States)

    Zhang, Xinxing; Bowen, Kit

    The interaction between transition metals and hydrogen has been an intriguing research topic for such applications as hydrogen storage and catalysis of hydrogenation and dehydrogenation. Special bonding features between TM and hydrogen are interesting not only because they are scarcely reported but also because they could help to discover and understand the nature of chemical bonding. Very recently, we discovered a PtZnH5- cluster which possessed an unprecedented planar pentagonal coordination between the H5- moiety and Pt, and exhibited special σ-aromaticity. The H5-kernel as a whole can be viewed as a η5-H5 ligand for Pt. As the second example, an H2 molecule was found to act as a ligand in the PdH3-cluster, in which two H atoms form a η2-H2 type of ligation to Pd. These transition metal hydride clusters were considered to be good hydrogen sources for hydrogenation. The reactions between PtHn- and CO2 were investigated. We observed formate in the final product H2Pt(HCO2)- .

  10. Dissociation of deuteron, 6He and 11Be from Coulomb dissociation reaction cross-section

    Indian Academy of Sciences (India)

    Ramendra Nath Majumdar

    2008-05-01

    The fragmentation of deuteron, 6He and 11Be have been studied during interaction with the 208Pb nucleus at various projectile energies. The Coulomb dissociation cross-sections and the momentum distribution of the break-up fragments have been analysed within the framework of the direct fragmentation model. The post-acceleration effect of deuteron during break-up and the halo structures of both the 6He and 11Be have been investigated.

  11. CO2 hydrogenation on a metal hydride surface.

    Science.gov (United States)

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

    2012-04-28

    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.

  12. Synthesis of ruthenium hydride

    Science.gov (United States)

    Kuzovnikov, M. A.; Tkacz, M.

    2016-02-01

    Ruthenium hydride was synthesized at a hydrogen pressure of about 14 GPa in a diamond-anvil cell. Energy-dispersive x-ray diffraction was used to monitor the ruthenium crystal structure as a function of hydrogen pressure up to 30 GPa. The hydride formation was accompanied by phase transition from the original hcp structure of the pristine metal to the fcc structure. Our results confirmed the theoretical prediction of ruthenium hydride formation under hydrogen pressure. The standard Gibbs free energy of the ruthenium hydride formation reaction was calculated assuming the pressure of decomposition as the equilibrium pressure.

  13. Hydride, hydrogen, proton, and electron affinities of imines and their reaction intermediates in acetonitrile and construction of thermodynamic characteristic graphs (TCGs) of imines as a "molecule ID card".

    Science.gov (United States)

    Zhu, Xiao-Qing; Liu, Qiao-Yun; Chen, Qiang; Mei, Lian-Rui

    2010-02-01

    A series of 61 imines with various typical structures were synthesized, and the thermodynamic affinities (defined as enthalpy changes or redox potentials in this work) of the imines to abstract hydride anions, hydrogen atoms, and electrons, the thermodynamic affinities of the radical anions of the imines to abstract hydrogen atoms and protons, and the thermodynamic affinities of the hydrogen adducts of the imines to abstract electrons in acetonitrile were determined by using titration calorimetry and electrochemical methods. The pure heterolytic and homolytic dissociation energies of the C=N pi-bond in the imines were estimated. The polarity of the C=N double bond in the imines was examined using a linear free-energy relationship. The idea of a thermodynamic characteristic graph (TCG) of imines as an efficient "Molecule ID Card" was introduced. The TCG can be used to quantitatively diagnose and predict the characteristic chemical properties of imines and their various reaction intermediates as well as the reduction mechanism of the imines. The information disclosed in this work could not only supply a gap of thermodynamics for the chemistry of imines but also strongly promote the fast development of the applications of imines.

  14. Mechanism and Kinetics Analysis of NO/SO2/N2/O2 Dissociation Reactions in Non-Thermal Plasma

    Institute of Scientific and Technical Information of China (English)

    WANG Xinliang; LI Tingting; WEI Dongxiang; WEI Yanli; GU Fan

    2008-01-01

    The kinetics mechanism of the dissociation reactions in a NO/SO2/N2/O2 system was investigated in consideration of energetic electrons' impacts on a non-thermal plasma. A model was derived from the Boltzmann equation and molecule collision theory to predict the dissociation reaction rate coefficients. Upon comparison with available literature, the model was confirmed to be acceptably accurate in general. Several reaction rate coefficients of the NO/SO2/N2/O2 dissociation system were derived according to the Arrhenius formula. The activation energies of each plasma reaction were calculated by quantum chemistry methods. The relation between the dissociation reaction rate coefficient and electron temperature was established to describe the importance of each reaction and to predict relevant processes of gaseous chemical reactions. The sensitivity of the mechanism of NO/SO2/N2/O2 dissociation reaction in a non-thermal plasma was also analysed.

  15. Activity and Stability of Rare Earth-Based Hydride Alloys as Catalysts of Hydrogen Absorption-Oxidation Reactions

    Institute of Scientific and Technical Information of China (English)

    Ying Taokai(应桃开); Gao Xueping(高学平); Hu Weikang(胡伟康); Noréus Dag

    2004-01-01

    Rare earth-based AB5-type hydrogen storage alloys as catalysts of hydrogen-diffusion electrodes for hydrogen absorption and oxidation reactions in alkaline fuel cells were investigated. It is demonstrated that the meta-hydride hydrogen-diffusion electrodes could be charged by hydrogen gas and electrochemically discharged at the same time to retain a stable oxidation potential for a long period. The catalytic activities and stability are almost comparable with a Pt catalyst on the active carbon. Further improvement of performances is expected via reduction of catalyst size into nanometers.

  16. Infrared spectra of the ethynyl metal hydrides produced in reactions of laser-ablated Mn and Re atoms with acetylene.

    Science.gov (United States)

    Cho, Han-Gook; Andrews, Lester

    2011-05-19

    The ethynyl metal hydride molecules (HM-C≡CH) are identified in the matrix infrared spectra from reactions of laser-ablated Mn and Re atoms with acetylene using D and (13)C isotopic substitution and density functional computed frequencies. The assignment of strong M-H as well as C≡C bond stretching product absorptions suggests oxidative C-H insertion during reagent codeposition and subsequent photolysis. The unique linear structure calculated for HMn-C≡CH is parallel to C(3v) structures found recently for Mn complexes including CH(3)-MnF.

  17. Measurement of the 92,93,94,100Mo(g,n) reactions by Coulomb Dissociation

    CERN Document Server

    Göbel, K; Altstadt, S; Alvarez-Pol, H; Aksouh, F; Aumann, T; Babilon, M; Behr, K-H; Benlliure, J; Berg, T; Böhmer, M; Boretzky, K; Brünle, A; Beyer, R; Casarejos, E; Chartier, M; Cortina-Gil, D; Chatillon, A; Pramanik, U Datta; Deveaux, L; Elvers, M; Elze, T W; Emling, H; Erhard, M; Ershova, O; Fernandez-Dominguez, B; Geissel, H; Górska, M; Heftrich, T; Heil, M; Hellstroem, M; Ickert, G; Johansson, H; Junghans, A R; Käppeler, F; Kiselev, O; Klimkiewicz, A; Kratz, J V; Kulessa, R; Kurz, N; Labiche, M; Langer, C; Bleis, T Le; Lemmon, R; Lindenberg, K; Litvinov, Y A; Maierbeck, P; Movsesyan, A; Müller, S; Nilsson, T; Nociforo, C; Paar, N; Palit, R; Paschalis, S; Plag, R; Prokopowicz, W; Reifarth, R; Rossi, D M; Schnorrenberger, L; Simon, H; Sonnabend, K; Sümmerer, K; Surówka, G; Vretenar, D; Wagner, A; Walter, S; Waluś, W; Wamers, F; Weick, H; Weigand, M; Winckler, N; Winkler, M; Zilges, A

    2013-01-01

    The Coulomb Dissociation (CD) cross sections of the stable isotopes 92,94,100Mo and of the unstable isotope 93Mo were measured at the LAND/R3B setup at GSI Helmholtzzentrum f\\"ur Schwerionenforschung in Darmstadt, Germany. Experimental data on these isotopes may help to explain the problem of the underproduction of 92,94Mo and 96,98Ru in the models of p-process nucleosynthesis. The CD cross sections obtained for the stable Mo isotopes are in good agreement with experiments performed with real photons, thus validating the method of Coulomb Dissociation. The result for the reaction 93Mo(g,n) is especially important since the corresponding cross section has not been measured before. A preliminary integral Coulomb Dissociation cross section of the 94Mo(g,n) reaction is presented. Further analysis will complete the experimental database for the (g,n) production chain of the p-isotopes of molybdenum.

  18. Mononuclear Phenolate Diamine Zinc Hydride Complexes and Their Reactions With CO2.

    Science.gov (United States)

    Brown, Neil J; Harris, Jonathon E; Yin, Xinning; Silverwood, Ian; White, Andrew J P; Kazarian, Sergei G; Hellgardt, Klaus; Shaffer, Milo S P; Williams, Charlotte K

    2014-03-10

    The synthesis, characterization, and zinc coordination chemistry of the three proligands 2-tert-butyl-4-[tert-butyl (1)/methoxy (2)/nitro (3)]-6-{[(2'-dimethylaminoethyl)methylamino]methyl}phenol are described. Each of the ligands was reacted with diethylzinc to yield zinc ethyl complexes 4-6; these complexes were subsequently reacted with phenylsilanol to yield zinc siloxide complexes 7-9. Finally, the zinc siloxide complexes were reacted with phenylsilane to produce the three new zinc hydride complexes 10-12. The new complexes 4-12 have been fully characterized by NMR spectroscopy, mass spectrometry, and elemental analyses. The structures of the zinc hydride complexes have been probed using VT-NMR spectroscopy and X-ray diffraction experiments. These data indicate that the complexes exhibit mononuclear structures at 298 K, both in the solid state and in solution (d8-toluene). At 203 K, the NMR signals broaden, consistent with an equilibrium between the mononuclear and dinuclear bis(μ-hydrido) complexes. All three zinc hydride complexes react rapidly and quantitatively with carbon dioxide, at 298 K and 1 bar of pressure over 20 min, to form the new zinc formate complexes 13-15. The zinc formate complexes have been analyzed by NMR spectroscopy and VT-NMR studies, which reveal a temperature-dependent monomer-dimer equilibrium that is dominated by the mononuclear species at 298 K.

  19. Thermochemistry and Kinetic Analysis of the Unimolecular Oxiranyl Radical Dissociation Reaction: A Theoretical Study.

    Science.gov (United States)

    Wang, Heng; Bozzelli, Joseph W

    2016-07-04

    Oxirane structures are important in organic synthesis, and they are important initial products in the oxidation reactions of alkyl radicals. The thermochemical properties (enthalpy of formation, entropy, and heat capacity) for the reaction steps of the unimolecular oxiranyl radical dissociation reaction are determined and compared with the available literature. The overall ring opening and subsequent steps involve four types of reactions: β-scission ring opening, intramolecular hydrogen transfer, β-scission hydrogen elimination, and β-scission methyl radical elimination. The enthalpies of formation of the transition states are determined and evaluated using six popular Density Functional Theory (DFT) calculation methods (B3LYP, B2PLYP, M06, M06-2X, ωB97X, ωB97XD), each combined with three different basis sets. The DFT enthalpy values are compared with five composite calculation methods (G3, G4, CBS-QB3, CBS-APNO, W1U), and by CCSD(T)/aug-cc-pVTZ. Kinetic parameters are determined versus pressure and temperature for the unimolecular dissociation pathways of an oxiranyl radical, which include the chemical activation reactions of the ring-opened oxiranyl radical relative to the ring-opening barrier. Multifrequency quantum Rice Ramsperger Kassel (QRRK) analysis is used to determine k(E) with master equation analysis for falloff. The major overall reaction pathway at lower combustion temperatures is oxiranyl radical dissociation to a methyl radical and carbon monoxide. Oxiranyl radical dissociation to a ketene and hydrogen atom is the key reaction path above 700 K.

  20. Identification of general linear relationships between activation energies and enthalpy changes for dissociation reactions at surfaces.

    Science.gov (United States)

    Michaelides, Angelos; Liu, Z-P; Zhang, C J; Alavi, Ali; King, David A; Hu, P

    2003-04-02

    The activation energy to reaction is a key quantity that controls catalytic activity. Having used ab inito calculations to determine an extensive and broad ranging set of activation energies and enthalpy changes for surface-catalyzed reactions, we show that linear relationships exist between dissociation activation energies and enthalpy changes. Known in the literature as empirical Brønsted-Evans-Polanyi (BEP) relationships, we identify and discuss the physical origin of their presence in heterogeneous catalysis. The key implication is that merely from knowledge of adsorption energies the barriers to catalytic elementary reaction steps can be estimated.

  1. A coupled transport and solid mechanics formulation with improved reaction kinetics parameters for modeling oxidation and decomposition in a uranium hydride bed.

    Energy Technology Data Exchange (ETDEWEB)

    Salloum, Maher N.; Shugard, Andrew D.; Kanouff, Michael P.; Gharagozloo, Patricia E.

    2013-03-01

    Modeling of reacting flows in porous media has become particularly important with the increased interest in hydrogen solid-storage beds. An advanced type of storage bed has been proposed that utilizes oxidation of uranium hydride to heat and decompose the hydride, releasing the hydrogen. To reduce the cost and time required to develop these systems experimentally, a valid computational model is required that simulates the reaction of uranium hydride and oxygen gas in a hydrogen storage bed using multiphysics finite element modeling. This SAND report discusses the advancements made in FY12 (since our last SAND report SAND2011-6939) to the model developed as a part of an ASC-P&EM project to address the shortcomings of the previous model. The model considers chemical reactions, heat transport, and mass transport within a hydride bed. Previously, the time-varying permeability and porosity were considered uniform. This led to discrepancies between the simulated results and experimental measurements. In this work, the effects of non-uniform changes in permeability and porosity due to phase and thermal expansion are accounted for. These expansions result in mechanical stresses that lead to bed deformation. To describe this, a simplified solid mechanics model for the local variation of permeability and porosity as a function of the local bed deformation is developed. By using this solid mechanics model, the agreement between our reacting bed model and the experimental data is improved. Additionally, more accurate uranium hydride oxidation kinetics parameters are obtained by fitting the experimental results from a pure uranium hydride oxidation measurement to the ones obtained from the coupled transport-solid mechanics model. Finally, the coupled transport-solid mechanics model governing equations and boundary conditions are summarized and recommendations are made for further development of ARIA and other Sandia codes in order for them to sufficiently implement the model.

  2. Mechanistic aspects of dinitrogen cleavage and hydrogenation to produce ammonia in catalysis and organometallic chemistry: relevance of metal hydride bonds and dihydrogen.

    Science.gov (United States)

    Jia, Hong-Peng; Quadrelli, Elsje Alessandra

    2014-01-21

    Dinitrogen cleavage and hydrogenation by transition-metal centers to produce ammonia is central in industry and in Nature. After an introductory section on the thermodynamic and kinetic challenges linked to N2 splitting, this tutorial review discusses three major classes of transition-metal systems (homogeneous, heterogeneous and biological) capable of achieving dissociation and hydrogenation of dinitrogen. Molecular complexes, solid-state Haber-Bosch catalytic systems, silica-supported tantalum hydrides and nitrogenase will be discussed. Emphasis is focused on the reaction mechanisms operating in the process of dissociation and hydrogenation of dinitrogen, and in particular on the key role played by metal hydride bonds and by dihydrogen in such reactions.

  3. Thermochemical Energy Storage through De/Hydrogenation of Organic Liquids: Reactions of Organic Liquids on Metal Hydrides.

    Science.gov (United States)

    Ulmer, Ulrich; Cholewa, Martin; Diemant, Thomas; Bonatto Minella, Christian; Dittmeyer, Roland; Behm, R Jürgen; Fichtner, Maximilian

    2016-06-08

    A study of the reactions of liquid acetone and toluene on transition metal hydrides, which can be used in thermal energy or hydrogen storage applications, is presented. Hydrogen is confined in TiFe, Ti0.95Zr0.05Mn1.49V0.45Fe0.06 ("Hydralloy C5"), and V40Fe8Ti26Cr26 after contact with acetone. Toluene passivates V40Fe8Ti26Cr26 completely for hydrogen desorption while TiFe is only mildly deactivated and desorption is not blocked at all in the case of Hydralloy C5. LaNi5 is inert toward both organic liquids. Gas chromatography (GC) investigations reveal that CO, propane, and propene are formed during hydrogen desorption from V40Fe8Ti26Cr26 in liquid acetone, and methylcyclohexane is formed in the case of liquid toluene. These reactions do not occur if dehydrogenated samples are used, which indicates an enhanced surface reactivity during hydrogen desorption. Significant amounts of carbon-containing species are detected at the surface and subsurface of acetone- and toluene-treated V40Fe8Ti26Cr26 by X-ray photoelectron spectroscopy (XPS). The modification of the surface and subsurface chemistry and the resulting blocking of catalytic sites is believed to be responsible for the containment of hydrogen in the bulk. The surface passivation reactions occur only during hydrogen desorption of the samples.

  4. Cosmic-ray-induced dissociation and reactions in warm interstellar ices

    CERN Document Server

    Kalvans, Juris

    2014-01-01

    Context. Cosmic ray particles that hit interstellar grains in dark molecular cores may induce whole-grain heating. The high temperature of a CR-heated grain allows energy barriers for bulk diffusion and reactions to be overcome. Additionally, ice molecules are destroyed by direct cosmic-ray induced dissociation. Aims. We provide a justified estimate of the significance of cosmic-ray induced surface-mantle diffusion, chemical reactions in ice, and dissociation of ice species in a star-forming interstellar cloud core. Methods. We considered a gas clump in a collapsing low-mass prestellar core and during the initial stages of protostellar envelope heating with a three-phase chemical kinetics model. The model includes a proper treatment of the stochastic aspect of whole-grain heating and new experimental data for dissociation. Results. We found that the cosmic-ray-induced effects are mostly limited to an increase in abundance for carbon-chain species. The effect on major species abundances is a few percentage poi...

  5. Multiphoton dissociation and thermal unimolecular reactions induced by infrared lasers. [REAMPA code

    Energy Technology Data Exchange (ETDEWEB)

    Dai, H.L.

    1981-04-01

    Multiphoton dissociation (MPD) of ethyl chloride was studied using a tunable 3.3 ..mu..m laser to excite CH stretches. The absorbed energy increases almost linearly with fluence, while for 10 ..mu..m excitation there is substantial saturation. Much higher dissociation yields were observed for 3.3 ..mu..m excitation than for 10 ..mu..m excitation, reflecting bottlenecking in the discrete region of 10 ..mu..m excitation. The resonant nature of the excitation allows the rate equations description for transitions in the quasicontinuum and continuum to be extended to the discrete levels. Absorption cross sections are estimated from ordinary ir spectra. A set of cross sections which is constant or slowly decreasing with increasing vibrational excitation gives good fits to both absorption and dissociation yield data. The rate equations model was also used to quantitatively calculate the pressure dependence of the MPD yield of SF/sub 6/ caused by vibrational self-quenching. Between 1000-3000 cm/sup -1/ of energy is removed from SF/sub 6/ excited to approx. > 60 kcal/mole by collision with a cold SF/sub 6/ molecule at gas kinetic rate. Calculation showed the fluence dependence of dissociation varies strongly with the gas pressure. Infrared multiphoton excitation was applied to study thermal unimolecular reactions. With SiF/sub 4/ as absorbing gas for the CO/sub 2/ laser pulse, transient high temperature pulses were generated in a gas mixture. IR fluorescence from the medium reflected the decay of the temperature. The activation energy and the preexponential factor of the reactant dissociation were obtained from a phenomenological model calculation. Results are presented in detail. (WHK)

  6. Dissociable effects of histamine H1 antagonists on reaction-time performance in rats.

    Science.gov (United States)

    Blokland, A; Scholtissen, B; Vermeeren, A; Ramaekers, J

    2001-01-01

    The most pronounced side effect of antiallergic histaminergic drugs (H1 antagonists) is sedation. These effects have been linked with the effects of histaminergic drugs on central H1 receptors. In the present study, we investigated the dose-response relationship of different antihistamines on the performance in a reaction-time task that has been developed for rats. The dose-response relationship of diphenhydramine, cetirizine and terfenadine were examined for the various behavioural measures in this task (i.e., reaction time, motor time, premature responses and number of trials completed). In addition, the effects of scopolamine were assessed to evaluate the cholinergic profile in this task. Diphenhydramine did not reliably affect the reaction time, but increased the motor time and the proportion of premature responses, and decreased the number of trials completed in a session. A low dose of cetirizine decreased the reaction time, whereas an increase in reaction time was found for the high dose. The motor time was increased after both doses of cetirizine. Terfenadine did not affect the responding of rats in the reaction-time task at the doses tested. The effects of scopolamine were very similar to those of diphenhydramine. The reaction-time task used in this study was able to dissociate different types of antihistamines on aspects of psychomotor function, which were likely to be related to central muscarinic or H1 antagonism. These findings suggest that the reaction-time task may be a sensitive tool for assessing effects of drugs on psychomotor function.

  7. Methane dissociation on Pt(111): Searching for a specific reaction parameter density functional

    Energy Technology Data Exchange (ETDEWEB)

    Nattino, Francesco, E-mail: f.nattino@chem.leidenuniv.nl; Migliorini, Davide; Kroes, Geert-Jan [Leiden Institute of Chemistry, Leiden University, Gorlaeus Laboratories, P.O. Box 9502, 2300 RA Leiden (Netherlands); Bonfanti, Matteo [Dipartimento di Chimica, Università degli Studi di Milano, via Golgi 19, 20133 Milano (Italy)

    2016-01-28

    The theoretical description of methane dissociating on metal surfaces is a current frontier in the field of gas-surface dynamics. Dynamical models that aim at achieving a highly accurate description of this reaction rely on potential energy surfaces based on density functional theory calculations at the generalized gradient approximation. We focus here on the effect that the exchange-correlation functional has on the reactivity of methane on a metal surface, using CHD{sub 3} + Pt(111) as a test case. We present new ab initio molecular dynamics calculations performed with various density functionals, looking also at functionals that account for the van der Waals (vdW) interaction. While searching for a semi-empirical specific reaction parameter density functional for this system, we find that the use of a weighted average of the PBE and the RPBE exchange functionals together with a vdW-corrected correlation functional leads to an improved agreement with quantum state-resolved experimental data for the sticking probability, compared to previous PBE calculations. With this semi-empirical density functional, we have also investigated the surface temperature dependence of the methane dissociation reaction and the influence of the rotational alignment on the reactivity, and compared our results with experiments.

  8. Formation of noble-gas hydrides and decay of solvated protons revisited: diffusion-controlled reactions and hydrogen atom losses in solid noble gases.

    Science.gov (United States)

    Tanskanen, Hanna; Khriachtchev, Leonid; Lignell, Antti; Räsänen, Markku; Johansson, Susanna; Khyzhniy, Ivan; Savchenko, Elena

    2008-02-07

    UV photolysis and annealing of C2H2/Xe, C2H2/Xe/Kr, and HBr/Xe matrices lead to complicated photochemical processes and reactions. The dominating products in these experiments are noble-gas hydrides with general formula HNgY (Ng = noble-gas atom, Y = electronegative fragment). We concentrate on distinguishing the local and global mobility and losses of H atoms, barriers of the reactions, and the decay of solvated protons. Different deposition temperatures change the amount of lattice imperfections and thus the amount of traps for H atoms. The averaged distance between reacting species influencing the reaction kinetics is controlled by varying the precursor concentration. A number of solid-state processes connected to the formation of noble-gas hydrides and decay of solvated protons are discussed using a simple kinetic model. The most efficient formation of noble-gas hydrides is connected with global (long-range) mobility of H atoms leading to the H + Xe + Y reaction. The highest concentration of noble-gas hydrides was obtained in matrices of highest optical quality, which probably have the lowest concentration of defects and H-atom losses. In matrices with high amount of geometrical imperfections, the product formation is inefficient and dominated by a local (short-range) process. The decay of solvated protons is rather local than a global process, which is different from the formation of noble-gas molecules. However, the present data do not allow distinguishing local proton and electron mobilities. Our previous results indicate that these are electrons which move to positively-charged centers and neutralize them. It is believed that the image obtained here for solid xenon is applicable to solid krypton whereas the case of argon deserves special attention.

  9. Non-oxidative coupling reaction of methane to ethane and hydrogen catalyzed by the silica-supported tantalum hydride: ([triple bond]SiO)2Ta-H.

    Science.gov (United States)

    Soulivong, Daravong; Norsic, Sébastien; Taoufik, Mostafa; Copéret, Christophe; Thivolle-Cazat, Jean; Chakka, Sudhakar; Basset, Jean-Marie

    2008-04-16

    Silica-supported tantalum hydride, (SiO)2Ta-H (1), proves to be the first single-site catalyst for the direct non-oxidative coupling transformation of methane into ethane and hydrogen at moderate temperatures, with a high selectivity (>98%). The reaction likely involves the tantalum-methyl-methylidene species as a key intermediate, where the methyl ligand can migrate onto the tantalum-methylidene affording the tantalum-ethyl.

  10. Oxidation of phenyl and hydride ligands of bis(pentamethylcyclopentadienyl)hafnium derivatives by nitrous oxide via selective oxygen atom transfer reactions: insights from quantum chemistry calculations.

    Science.gov (United States)

    Xie, Hujun; Liu, Chengcheng; Yuan, Ying; Zhou, Tao; Fan, Ting; Lei, Qunfang; Fang, Wenjun

    2016-01-21

    The mechanisms for the oxidation of phenyl and hydride ligands of bis(pentamethylcyclopentadienyl)hafnium derivatives (Cp* = η(5)-C5Me5) by nitrous oxide via selective oxygen atom transfer reactions have been systematically studied by means of density functional theory (DFT) calculations. On the basis of the calculations, we investigated the original mechanism proposed by Hillhouse and co-workers for the activation of N2O. The calculations showed that the complex with an initial O-coordination of N2O to the coordinatively unsaturated Hf center is not a local minimum. Then we proposed a new reaction mechanism to investigate how N2O is activated and why N2O selectively oxidize phenyl and hydride ligands of . Frontier molecular orbital theory analysis indicates that N2O is activated by nucleophilic attack by the phenyl or hydride ligand. Present calculations provide new insights into the activation of N2O involving the direct oxygen atom transfer from nitrous oxide to metal-ligand bonds instead of the generally observed oxygen abstraction reaction to generate metal-oxo species.

  11. Brønsted-Lowry Acid Strength of Metal Hydride and Dihydrogen Complexes.

    Science.gov (United States)

    Morris, Robert H

    2016-08-10

    Transition metal hydride complexes are usually amphoteric, not only acting as hydride donors, but also as Brønsted-Lowry acids. A simple additive ligand acidity constant equation (LAC for short) allows the estimation of the acid dissociation constant Ka(LAC) of diamagnetic transition metal hydride and dihydrogen complexes. It is remarkably successful in systematizing diverse reports of over 450 reactions of acids with metal complexes and bases with metal hydrides and dihydrogen complexes, including catalytic cycles where these reactions are proposed or observed. There are links between pKa(LAC) and pKa(THF), pKa(DCM), pKa(MeCN) for neutral and cationic acids. For the groups from chromium to nickel, tables are provided that order the acidity of metal hydride and dihydrogen complexes from most acidic (pKa(LAC) -18) to least acidic (pKa(LAC) 50). Figures are constructed showing metal acids above the solvent pKa scales and organic acids below to summarize a large amount of information. Acid-base features are analyzed for catalysts from chromium to gold for ionic hydrogenations, bifunctional catalysts for hydrogen oxidation and evolution electrocatalysis, H/D exchange, olefin hydrogenation and isomerization, hydrogenation of ketones, aldehydes, imines, and carbon dioxide, hydrogenases and their model complexes, and palladium catalysts with hydride intermediates.

  12. Steric Effect for Proton, Hydrogen-Atom, andHydride Transfer Reactions with Geometric Isomers of NADH-Model Ruthenium Complexes

    Energy Technology Data Exchange (ETDEWEB)

    Fujita E.; Cohen, B.W.; Polyansky, D.E.; Achord, P.; Cabelli, D.; Muckerman, J.T.; Tanaka, K.; Thummel, R.P.; Zong, R.

    2012-01-01

    Two isomers, [Ru(1)]{sup 2+} (Ru = Ru(bpy){sub 2}, bpy = 2,2{prime}-bipyridine, 1 = 2-(pyrid-2{prime}-yl)-1-azaacridine) and [Ru(2)]{sup 2+} (2 = 3-(pyrid-2{prime}-yl)-4-azaacridine), are bio-inspired model compounds containing the nicotinamide functionality and can serve as precursors for the photogeneration of C-H hydrides for studying reactions pertinent to the photochemical reduction of metal-C{sub 1} complexes and/or carbon dioxide. While it has been shown that the structural differences between the azaacridine ligands of [Ru(1)]{sup 2+} and [Ru(2)]{sup 2+} have a significant effect on the mechanism of formation of the hydride donors, [Ru(1HH)]{sup 2+} and [Ru(2HH)]{sup 2+}, in aqueous solution, we describe the steric implications for proton, net-hydrogen-atom and net-hydride transfer reactions in this work. Protonation of [Ru(2{sup {sm_bullet}-})]{sup +} in aprotic and even protic media is slow compared to that of [Ru(1{sup {sm_bullet}-})]{sup +}. The net hydrogen-atom transfer between *[Ru(1)]{sup 2+} and hydroquinone (H{sub 2}Q) proceeds by one-step EPT, rather than stepwise electron-proton transfer. Such a reaction was not observed for *[Ru(2)]{sup 2+} because the non-coordinated N atom is not easily available for an interaction with H{sub 2}Q. Finally, the rate of the net hydride ion transfer from [Ru(1HH)]{sup 2+} to [Ph{sub 3}C]{sup +} is significantly slower than that of [Ru(2HH)]{sup 2+} owing to steric congestion at the donor site.

  13. Break-up reactions: theoretical aspects; Reactions de dissociation: aspects theoriques

    Energy Technology Data Exchange (ETDEWEB)

    Baye, D. [Universite Libre de Bruxelles (ULB), Physique Quantique, C.P. 165/82, Physique Nucleaire Theorique et Physique Mathematique, Brussels (Belgium)

    2007-07-01

    Breakup reactions are one of the main tools for the study of exotic nuclei. In particular, Coulomb breakup is expected to provide information on spectroscopic properties of halo nuclei and on astrophysical S factors for radiative-capture reactions. The simplest studies are based on perturbation theory and especially on its first order. However the validity of the first-order approximation may be limited for extended systems such as halo nuclei and its conditions are not always satisfied in existing experiments. More elaborate reaction models are available: resolution of the semi-classical time-dependent Schroedinger equation, eikonal and dynamical eikonal approximations, method of coupled discretized-continuum channels (CDCC). These methods are reviewed and summarized. Their interest and limitations are discussed. The Be{sup 11} and B{sup 8} breakups are treated as examples of the various approximations. (author)

  14. The reaction rate for dissociative adsorption of N-2 on stepped Ru(0001): Six-dimensional quantum calculations

    DEFF Research Database (Denmark)

    van Harrevelt, Rob; Honkala, Johanna Karoliina; Nørskov, Jens Kehlet

    2005-01-01

    Quantum-mechanical calculations of the reaction rate for dissociative adsorption of N-2 on stepped Ru(0001) are presented. Converged six-dimensional quantum calculations for this heavy-atom reaction have been performed using the multiconfiguration time-dependent Hartree method. A potential...

  15. Hydrogen Outgassing from Lithium Hydride

    Energy Technology Data Exchange (ETDEWEB)

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

    2006-04-20

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

  16. A New Reducing Regent: Dichloroindium Hydride

    Institute of Scientific and Technical Information of China (English)

    A. BABA; I. SHIBATA; N. HAYASHI

    2005-01-01

    @@ 1Introduction Among the hydride derivatives of group 13 elements, various types of aluminum hydrides and boron hydrides have been employed as powerful reduction tools. Indium hydrides have not received much attention,whereas the synthesis of indium trihydride (InH3) was reported several decades ago[1]. There have been no precedents for monometallic indium hydrides having practical reactivity, while activated hydrides such as an ate complex LiPhn InH4-n (n = 0- 2) and phosphine-coordinated indium hydrides readily reduce carbonyl compounds. In view of this background, we focused on the development of dichloroindium hydrides (Cl2InH) as novel reducing agents that bear characteristic features in both ionic and radical reactions.

  17. Molecular dynamical studies of the dissociation of a diatomic molecular crystal. I. Energy exchange in rapid exothermic reactions

    Science.gov (United States)

    Tsai, D. H.; Trevino, S. F.

    1983-08-01

    We discuss the results of a study of the exothermic dissociation of a model diatomic molecular crystal. Our main purpose is to investigate the dynamics of energy transport and energy sharing in this system during the dissociation process. The crystal was prepared in a metastable molecular form, in thermal equilibrium at a low initial temperature and pressure. When we heated the system to a higher temperature, at constant volume, we observed thermally initiated dissociations which progressed rapidly to completion. During the dissociation process, we found that the sharing of the potential energy released by the metastable molecules with the rest of the system, and the sharing of the kinetic energy of the dissociated fragments with the kinetic energy of the molecules in the translational degrees of freedom, were rather efficient. But the intra- and intermolecular exchange of the kinetic energy among the various degrees of freedom, viz., translation-rotation, translation-vibration, and rotation-vibration was inefficient. Dissociation would occur in one of the regions of high local kinetic energy density, after a molecule in that region had acquired sufficient vibrational energy to break apart, and when the ``caging'' effect was favorable to allow the molecule to dissociate. From such a reaction site, and there may be others, the reaction would spread to a neighboring site, and continue this way until all the molecules became dissociated. The induction time showed an approximately logarithmic dependence on the inverse of the temperature of the system after heating. But during the process of rapid dissociation, both the potential energy and the kinetic energy of the system underwent rapid changes, and thermal equilibrium was not reached until the end of the process.

  18. H{sub 2} thermal desorption and hydride conversion reactions in Li cells of TiH{sub 2}/C amorphous nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Vitucci, F.M., E-mail: francesco.vitucci@roma1.infn.it [CNR-ISC, U.O.S. La Sapienza, Piazzale A. Moro 5, 00185 Roma (Italy); Paolone, A. [CNR-ISC, U.O.S. La Sapienza, Piazzale A. Moro 5, 00185 Roma (Italy); Brutti, S. [CNR-ISC, U.O.S. La Sapienza, Piazzale A. Moro 5, 00185 Roma (Italy); Dipartimento di Scienze, Univ. Basilicata, V.le Ateneo Lucano, 10, 85100 Potenza (Italy); Munaò, D.; Silvestri, L.; Panero, S. [Dipartimento di Chimica, Sapienza Univ. Roma, P.le A. Moro 5, 00185 Roma (Italy); Reale, P. [ENEA – Centro Ricerche Casaccia,via Anguillarese 301, 00100 Roma (Italy)

    2015-10-05

    Highlights: • Galvanostatic measurements on amorphous TiH{sub 2} is reported. • Variation of ball milling pre-treatment vary the first discharge capacity. • Relation between thermal H{sub 2} desorption and electrochemical properties is proposed. - Abstract: Here we investigate the properties of amorphous TiH{sub 2}/carbon nanocomposites as possible active material in lithium cells. Several TiH{sub 2}/C mixtures are prepared by a mechanochemical route, by varying the carbon/hydride ratio. Materials are tested in electrochemical cells versus lithium metal in EC:DMC LiPF{sub 6} electrolyte by galvanostatic cycling (GC) and are characterized by X-ray diffraction, transmission electron microscopy, thermogravimetry and mass spectrometry. Thermal dehydrogenation processes are altered by the mechanochemical treatment of the sample: milling decreases the hydrogen content of the hydride. On the other hand, the mechanochemical grinding increases the specific capacity delivered during the first GC discharge. We suggest that the electrochemical process is the result of a delicate balance between the absolute quantity of hydrogen and its availability for the hydride conversion reaction.

  19. In situ μ+SR measurements on the hydrogen desorption reaction of magnesium hydride

    Science.gov (United States)

    Umegaki, I.; Nozaki, H.; Harada, M.; Higuchi, Y.; Noritake, T.; Matsumoto, M.; Towata, S.-i.; Ansaldo, E. J.; Brewer, J. H.; Koda, A.; Miyake, Y.; Sugiyama, J.

    2014-12-01

    In order to clarify the reason why the hydrogen desorption temperature (Td) of MgH2 is lowered by milling, we have studied the change in a local nuclear magnetic field with temperature by means of μ+SR. We have found a very clear oscillation in the ZF-spectrum at 2 K for the "milled" and "milled with Nb2O5" samples, while such oscillation is weaker for the "as prepared" MgH2. It was also found that the oscillation signal is stable up to 250 K and is assigned mainly due to the formation of a H-μ-H system. At temperatures above ambient T, we also found that the ZF-μ+SR spectrum exhibits a static Kubo-Toyabe behavior due to the nuclear magnetic field of 1H. Furthermore, it was clarified that rapid H diffusion starts well below Td only in the milled samples, leading to the conclusion that the consequent enhanced diffusion rate in MgH2 is essential to accelerate the desorption reaction and to decrease Td.

  20. Rational Design in Catalysis: A Mechanistic Study of β-Hydride Eliminations in Gold(I) and Gold(III) Complexes Based on Features of the Reaction Valley.

    Science.gov (United States)

    Castiñeira Reis, Marta; López, Carlos Silva; Kraka, Elfi; Cremer, Dieter; Faza, Olalla Nieto

    2016-09-01

    β-Hydride eliminations for ethylgold(III) dichloride complexes are identified as reactions with an unusually long prechemical stage corresponding to the conformational preparation of the reaction complex and spanning six phases. The prechemical process is characterized by a geared rotation of the L-Au-L group (L = Cl) driving methyl group rotation and causing a repositioning of the ligands. This requires more than 28 kcal/mol of the total barrier of 34.0 kcal/mol, according to the unified reaction valley approach, which also determines that the energy requirements of the actual chemical process leading to the β-elimination product are only about 5.5 kcal/mol. A detailed mechanistic analysis was used as a basis for a rational design of substrates (via substituents on the ethyl group) and/or ligands, which can significantly reduce the reaction barrier. This strategy takes advantage of either a higher trans activity of the ligands or a tuned electronic demand of the ethyl group. The β-hydride elimination of gold(I) was found to suffer from strong Coulomb and exchange repulsion when a positively charged hydrogen atom enforces a coordination position in a d(10)-configured gold atom, thus triggering an unassisted σ-π Au(I)-C conversion.

  1. Computational Replication of the Primary Isotope Dependence of Secondary Kinetic Isotope Effects in Solution Hydride Transfer Reactions: Supporting the Isotopically Different Tunneling Ready State Conformations

    OpenAIRE

    2016-01-01

    We recently reported a study of the steric effect on the 1° isotope dependence of 2° KIEs for several hydride transfer reactions in solution (J. Am. Chem. Soc. 2015, 137, 6653). The unusual 2° KIEs decrease as the 1° isotope changes from H to D, and more in the sterically hindered systems. These were explained in terms of a more crowded tunneling ready state (TRS) conformation in D-tunneling, which has a shorter donor-acceptor distance (DAD), than in H-tunneling. In order to examine the isoto...

  2. Aiming for the stomach and hitting the heart: dissociable triggers and sources for disgust reactions.

    Science.gov (United States)

    Shenhav, Amitai; Mendes, Wendy Berry

    2014-04-01

    Disgust reactions can be elicited using stimuli that engender orogastric rejection (e.g., pus and vomit; core disgust stimuli) but also using images of bloody injuries or medical procedures (e.g., surgeries; blood [body] boundary violation [B-BV] disgust stimuli). These two types of disgust reaction are presumed to be connected by a common evolutionary function of avoiding either food- or blood-borne contaminants. However, reactions to bloody injuries are typically conflated with reactions to the potential pain being experienced by the victim. This may explain why the two forms of "disgust", although similarly communicated (through self-report and facial expressions), evince different patterns of physiological reactivity. Therefore, we tested whether the communicative similarities and physiological dissimilarities would hold when markers of potential contamination in the latter category are removed, leaving only painful injuries that lack blood or explicit body-envelope violations. Participants viewed films that depicted imagery associated with (a) core disgust, (b) painful injuries, or (c) neutral scenes while we measured facial, cardiovascular, and gastric reactivity. Whereas communicative measures (self-report and facial muscles) suggested that participants experienced increased disgust for core disgust and painful injuries, peripheral physiology dissociated the two: core disgust decreased normal gastric activity and painful-injury disgust decelerated heart rate and increased heart rate variability. These findings suggest that expressions of disgust toward bodily injuries may reflect a fundamentally different affective response than those evoked by core disgust and that this (cardiovascularly mediated) response may in fact be more closely tied to pain perceptions (or empathy) rather than contaminant-laden stimuli.

  3. Hydrogen release reactions of Al-based complex hydrides enhanced by vibrational dynamics and valences of metal cations.

    Science.gov (United States)

    Sato, T; Ramirez-Cuesta, A J; Daemen, L; Cheng, Y-Q; Tomiyasu, K; Takagi, S; Orimo, S

    2016-09-27

    Hydrogen release from Al-based complex hydrides composed of metal cation(s) and [AlH4](-) was investigated using inelastic neutron scattering viewed from vibrational dynamics. The hydrogen release followed the softening of translational and [AlH4](-) librational modes, which was enhanced by vibrational dynamics and the valence(s) of the metal cation(s).

  4. Capture cross-section and rate of the 14C(, )15C reaction from the Coulomb dissociation of 15C

    Indian Academy of Sciences (India)

    Shubhchintak; Neelam; R Chatterjee

    2014-10-01

    We calculate the Coulomb dissociation of 15C on a Pb target at 68 MeV/u incident beam energy within the fully quantum mechanical distorted wave Born approximation formalism of breakup reactions. The capture cross-section and the subsequent rate of the 14C(, )15C reaction are calculated from the photodisintegration of 15C, using the principle of detailed balance. Our theoretical model is free from the uncertainties associated with the multipole strength distributions of the projectile.

  5. An improved potential energy surface and multi-temperature quasiclassical trajectory calculations of N2 + N2 dissociation reactions.

    Science.gov (United States)

    Bender, Jason D; Valentini, Paolo; Nompelis, Ioannis; Paukku, Yuliya; Varga, Zoltan; Truhlar, Donald G; Schwartzentruber, Thomas; Candler, Graham V

    2015-08-01

    Accurate modeling of high-temperature hypersonic flows in the atmosphere requires consideration of collision-induced dissociation of molecular species and energy transfer between the translational and internal modes of the gas molecules. Here, we describe a study of the N2 + N2⟶N2 + 2N and N2 + N2⟶4N nitrogen dissociation reactions using the quasiclassical trajectory (QCT) method. The simulations used a new potential energy surface for the N4 system; the surface is an improved version of one that was presented previously. In the QCT calculations, initial conditions were determined based on a two-temperature model that approximately separates the translational-rotational temperature from the vibrational temperature of the N2 diatoms. Five values from 8000 K to 30,000 K were considered for each of the two temperatures. Over 2.4 × 10(9) trajectories were calculated. We present results for ensemble-averaged dissociation rate constants as functions of the translational-rotational temperature T and the vibrational temperature T(v). The rate constant depends more strongly on T when T(v) is low, and it depends more strongly on T(v) when T is low. Quasibound reactant states contribute significantly to the rate constants, as do exchange processes at higher temperatures. We discuss two sets of runs in detail: an equilibrium test set in which T = T(v) and a nonequilibrium test set in which T(v) test set, high-v and moderately-low-j molecules contribute most significantly to the overall dissociation rate, and this state specificity becomes stronger as the temperature decreases. Dissociating trajectories tend to result in a major loss of vibrational energy and a minor loss of rotational energy. In the nonequilibrium test set, as T(v) decreases while T is fixed, higher-j molecules contribute more significantly to the dissociation rate, dissociating trajectories tend to result in a greater rotational energy loss, and the dissociation probability's dependence on v weakens. In

  6. Dissociative part-dependent biopsychosocial reactions to backward masked angry and neutral faces: An fMRI study of dissociative identity disorder☆

    Science.gov (United States)

    Schlumpf, Yolanda R.; Nijenhuis, Ellert R.S.; Chalavi, Sima; Weder, Ekaterina V.; Zimmermann, Eva; Luechinger, Roger; La Marca, Roberto; Reinders, A.A.T. Simone; Jäncke, Lutz

    2013-01-01

    Objective The Theory of Structural Dissociation of the Personality (TSDP) proposes that dissociative identity disorder (DID) patients are fixed in traumatic memories as “Emotional Parts” (EP), but mentally avoid these as “Apparently Normal Parts” of the personality (ANP). We tested the hypotheses that ANP and EP have different biopsychosocial reactions to subliminally presented angry and neutral faces, and that actors instructed and motivated to simulate ANP and EP react differently. Methods Women with DID and matched healthy female actors (CON) were as ANP and EP (DIDanp, DIDep, CONanp, CONep) consecutively exposed to masked neutral and angry faces. Their brain activation was monitored using functional magnetic resonance imaging. The black-and-white dotted masks preceding and following the faces each had a centered colored dot, but in a different color. Participants were instructed to immediately press a button after a perceived color change. State anxiety was assessed after each run using the STAI-S. Final statistical analyses were conducted on 11 DID patients and 15 controls for differences in neural activity, and 13 DID patients and 15 controls for differences in behavior and psychometric measures. Results Differences between ANP and EP in DID patients and between DID and CON in the two dissociative parts of the personality were generally larger for neutral than for angry faces. The longest reaction times (RTs) existed for DIDep when exposed to neutral faces. Compared to DIDanp, DIDep was associated with more activation of the parahippocampal gyrus. Following neutral faces and compared to CONep, DIDep had more activation in the brainstem, face-sensitive regions, and motor-related areas. DIDanp showed a decreased activity all over the brain in the neutral and angry face condition. There were neither significant within differences nor significant between group differences in state anxiety. CON was not able to simulate genuine ANP and EP biopsychosocially

  7. Predicting formation enthalpies of metal hydrides

    DEFF Research Database (Denmark)

    Andreasen, A.

    2004-01-01

    In order for the hydrogen based society viz. a society in which hydrogen is the primary energy carrier to become realizable an efficient way of storing hydrogen is required. For this purpose metal hydrides are serious candidates. Metal hydrides are formedby chemical reaction between hydrogen...... and metal and for the stable hydrides this is associated with release of heat (#DELTA#H_f ). The more thermodynamically stable the hydride, the larger DHf, and the higher temperature is needed in order to desorphydrogen (reverse reaction) and vice versa. For practical application the temperature needed...

  8. Coinage Metal Hydrides: Synthesis, Characterization, and Reactivity.

    Science.gov (United States)

    Jordan, Abraham J; Lalic, Gojko; Sadighi, Joseph P

    2016-08-10

    Hydride complexes of copper, silver, and gold encompass a broad array of structures, and their distinctive reactivity has enabled dramatic recent advances in synthesis and catalysis. This Review summarizes the synthesis, characterization, and key stoichiometric reactions of isolable or observable coinage metal hydrides. It discusses catalytic processes in which coinage metal hydrides are known or probable intermediates, and presents mechanistic studies of selected catalytic reactions. The purpose of this Review is to convey how developments in coinage metal hydride chemistry have led to new organic transformations, and how developments in catalysis have in turn inspired the synthesis of reactive new complexes.

  9. An improved potential energy surface and multi-temperature quasiclassical trajectory calculations of N2 + N2 dissociation reactions

    Science.gov (United States)

    Bender, Jason D.; Valentini, Paolo; Nompelis, Ioannis; Paukku, Yuliya; Varga, Zoltan; Truhlar, Donald G.; Schwartzentruber, Thomas; Candler, Graham V.

    2015-08-01

    Accurate modeling of high-temperature hypersonic flows in the atmosphere requires consideration of collision-induced dissociation of molecular species and energy transfer between the translational and internal modes of the gas molecules. Here, we describe a study of the N2 + N2⟶N2 + 2N and N2 + N2⟶4N nitrogen dissociation reactions using the quasiclassical trajectory (QCT) method. The simulations used a new potential energy surface for the N4 system; the surface is an improved version of one that was presented previously. In the QCT calculations, initial conditions were determined based on a two-temperature model that approximately separates the translational-rotational temperature from the vibrational temperature of the N2 diatoms. Five values from 8000 K to 30 000 K were considered for each of the two temperatures. Over 2.4 × 109 trajectories were calculated. We present results for ensemble-averaged dissociation rate constants as functions of the translational-rotational temperature T and the vibrational temperature Tv. The rate constant depends more strongly on T when Tv is low, and it depends more strongly on Tv when T is low. Quasibound reactant states contribute significantly to the rate constants, as do exchange processes at higher temperatures. We discuss two sets of runs in detail: an equilibrium test set in which T = Tv and a nonequilibrium test set in which Tv rate, and this state specificity becomes stronger as the temperature decreases. Dissociating trajectories tend to result in a major loss of vibrational energy and a minor loss of rotational energy. In the nonequilibrium test set, as Tv decreases while T is fixed, higher-j molecules contribute more significantly to the dissociation rate, dissociating trajectories tend to result in a greater rotational energy loss, and the dissociation probability's dependence on v weakens. In this way, as Tv decreases, rotational energy appears to compensate for the decline in average vibrational energy in

  10. A computational study of ultrafast acid dissociation and acid-base neutralization reactions. I. The model.

    Science.gov (United States)

    Maurer, Patrick; Thomas, Vibin; Rivard, Ugo; Iftimie, Radu

    2010-07-28

    Ultrafast, time-resolved investigations of acid-base neutralization reactions have recently been performed using systems containing the photoacid 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) and various Bronsted bases. Two conflicting neutralization mechanisms have been formulated by Mohammed et al. [Science 310, 83 (2005)] and Siwick et al. [J. Am. Chem. Soc. 129, 13412 (2007)] for the same acid-base system. Herein an ab initio molecular dynamics based computational model is formulated, which is able to investigate the validity of the proposed mechanisms in the general context of ground-state acid-base neutralization reactions. Our approach consists of using 2,4,6-tricyanophenol (exp. pKa congruent with 1) as a model for excited-state HPTS( *) (pKa congruent with 1.4) and carboxylate ions for the accepting base. We employ our recently proposed dipole-field/quantum mechanics (QM) treatment [P. Maurer and R. Iftimie, J. Chem. Phys. 132, 074112 (2010)] of the proton donor and acceptor molecules. This approach allows one to tune the free energy of neutralization to any desired value as well as model initial nonequilibrium hydration effects caused by a sudden increase in acidity, making it possible to achieve a more realistic comparison with experimental data than could be obtained via a full-QM treatment of the entire system. It is demonstrated that the dipole-field/QM model reproduces correctly key properties of the 2,4,6-tricyanophenol acid molecule including gas-phase proton dissociation energies and dipole moments, and condensed-phase hydration structure and pKa values.

  11. Inhibited solid propellant composition containing beryllium hydride

    Science.gov (United States)

    Thompson, W. W. (Inventor)

    1978-01-01

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

  12. Trends in Homolytic Bond Dissociation Energies of Five- and Six-Coordinate Hydrides of Group 9 Transition Metals: Co, Rh, Ir.

    Science.gov (United States)

    Glezakou, Vassiliki-Alexandra; Rousseau, Roger; Elbert, Stephen T; Franz, James A

    2017-03-09

    The homolytic bond dissociation energies of a series of five- and six-coordinate mono- and dihydride complexes of the type HM(diphosphine)2 and [H2M(diphosphine)2](+) (where M = Co, Rh, and Ir) are calculated and compared with experimental values. This work probes the relationship between the homolytic bond dissociation energies (HMBDEs) of these complexes in these two different coordination environments and formal oxidation states. The results of these calculations and previous experimental observations suggest that for M = Rh the HMBDE of the five-coordinate HM(diphosphine)2 species are 0-2 kcal/mol larger than the HMBDE of the corresponding six-coordinate [H2M(diphosphine)2](+) species. For M = Ir the bond energies of the five- and six-coordinate complexes are nearly the same and for M = Co the six-coordinate species are 1-5 kcal/mol less than the corresponding five-coordinate species. Simplified models of large and complicated ligands seem to capture the essential trends and give very good estimates of these thermodynamic properties compared with experimentally available data that are difficult to obtain.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-07-15

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

  14. Preparation of neuroprotective condensed 1,4-benzoxazepines by regio- and diastereoselective domino Knoevenagel–[1,5]-hydride shift cyclization reaction

    Directory of Open Access Journals (Sweden)

    László Tóth

    2014-11-01

    Full Text Available Condensed O,N-heterocycles containing tetrahydro-1,4-benzoxazepine and tetrahydroquinoline moieties were prepared by a regio- and diastereoselective domino Knoevenagel–[1,5]-hydride shift cyclization reaction of a 4-aryl-2-phenyl-1,4-benzoxazepine derivative obtained from flavanone. The relative configuration of products were determined by the correlation of 3JH,H coupling data with the geometry of major conformers accessed by DFT conformational analysis. Separated enantiomers of the products were characterized by HPLC-ECD data, which allowed their configurational assignment on the basis of TDDFT-ECD calculation of the solution conformers. Two compounds showed neuroprotective activities against hydrogen peroxide (H2O2 or β-amyloid25–35 (Aβ25–35-induced cellular injuries in human neuroblastoma SH-SY5Y cells in the range of those of positive controls.

  15. Preparation of neuroprotective condensed 1,4-benzoxazepines by regio- and diastereoselective domino Knoevenagel-[1,5]-hydride shift cyclization reaction.

    Science.gov (United States)

    Tóth, László; Fu, Yan; Zhang, Hai Yan; Mándi, Attila; Kövér, Katalin E; Illyés, Tünde-Zita; Kiss-Szikszai, Attila; Balogh, Balázs; Kurtán, Tibor; Antus, Sándor; Mátyus, Péter

    2014-01-01

    Condensed O,N-heterocycles containing tetrahydro-1,4-benzoxazepine and tetrahydroquinoline moieties were prepared by a regio- and diastereoselective domino Knoevenagel-[1,5]-hydride shift cyclization reaction of a 4-aryl-2-phenyl-1,4-benzoxazepine derivative obtained from flavanone. The relative configuration of products were determined by the correlation of (3) J H,H coupling data with the geometry of major conformers accessed by DFT conformational analysis. Separated enantiomers of the products were characterized by HPLC-ECD data, which allowed their configurational assignment on the basis of TDDFT-ECD calculation of the solution conformers. Two compounds showed neuroprotective activities against hydrogen peroxide (H2O2) or β-amyloid25-35 (Aβ25-35)-induced cellular injuries in human neuroblastoma SH-SY5Y cells in the range of those of positive controls.

  16. A STUDY OF FUNDAMENTAL REACTION PATHWAYS FOR TRANSITION METAL ALKYL COMPLEXES. I. THE REACTION OF A NICKEL METHYL COMPLEX WITH ALKYNES. II. THE MECHANISM OF ALDEHYDE FORMATION IN THE REACTION OF A MOLYBDENUM HYDRIDE WITH MOLYBDENUM ALKYLS

    Energy Technology Data Exchange (ETDEWEB)

    Huggins, John Mitchell

    1980-06-01

    mixed dimers MeCpMo(CO){sub 3}-(CO){sub 3}MoCp (3b) and MeCpMo(CO){sub 2}{triple_bond}(CO){sub 2}MoCp (4b) are the predominant kinetic products of the reaction. Additionally labeling the carbonyl ligands of 1a with {sup 13}CO led to the conclusion that all three of the carbonyl ligands in 1a end up in the tetracarbonyl dimers 4a if the reaction is carried out under a continuous purge of argon Trapping studies failed to find any evidence for the intermediacy of either [CpMo(CO){sub 3}]{sup -} or [CpMo(CO){sub 3}]{sup +} in this reaction. A mechanism is proposed that involves the initial migration of the alkyl ligand in 2 to CO forming an unsaturated acyl complex which reacts with 1a to give a binuclear complex containing a three center-two electron Mo-H-Mo bond. This complex then selectively looses a carbonyl from the acyl molybdenum, migrates the hydride to that same metal, and forms a metal-metal bond. This binuclear complex with the hydride and acyl ligands on one metal reductively eliminates aldehyde, and migrates a carbonyl ligand, to give 4a directly. The other product 3a is formed by addition of two molecules of free CO to 4a.

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

    Science.gov (United States)

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

    2015-02-02

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

  18. Ab Initio Treatment of Bond-Breaking Reactions: Accurate Course of HO3 Dissociation and Revisit to Isomerization.

    Science.gov (United States)

    Varandas, A J C

    2012-02-14

    An efficient scheme is devised for accurate studies of bond-breaking/forming reactions and illustrated for HO3. It is suggested and numerically demonstrated that an accurate dissociation path for the title system can be obtained by defining the central OO bond as the reaction coordinate. The approach consists of optimizing the dissociation path at the full-valence-complete-active space level of theory followed by single-point multireference configuration interaction calculations along it. Using large diffusely augmented basis sets of the correlation consistent type, accurate dissociation curves are then obtained for both the cis- and trans-HO3 isomers by extrapolating the calculated raw energies to the complete basis set limit. The profiles show a weak van der Waals type minimum and a small barrier, both lying below the dissociation asymptote. It is shown that this barrier arises at the break-off of the central OO chemical bond and onset of the OH···O2 hydrogen bond. The calculated dissociation energies (De) are 4.5 ± 0.1 and 4.7 ± 0.1 kcal mol(-1) for the cis- and trans-HO3 isomers, respectively, with a very conservative estimate of the dissociation energy (D0) for trans-HO3 being 2.7 ± 0.2 kcal mol(-1) and a more focused one being 2.8 ± 0.1 kcal mol(-1). This result improves upon our previous estimate of this quantity while overlapping in the lower range of 2.9 ± 0.1 kcal mol(-1), the commonly accepted value from the low-temperature CRESU experiments. Since the cis-HO3 isomer is predicted to be 0.15 kcal mol(-1) less stable than trans-HO3, this may partly explain the failure to obtain a clear characterization of the former. The isomerization (torsional) potential is also revisited and a comparison presented with a curve inferred from spectroscopic measurements. Good agreement is observed, with the accuracy of the new calculated data commending its use for the reanalysis of the available vibrational-rotational spectroscopic data.

  19. A twist on facial selectivity of hydride reductions of cyclic ketones: twist-boat conformers in cyclohexanone, piperidone, and tropinone reactions.

    Science.gov (United States)

    Neufeldt, Sharon R; Jiménez-Osés, Gonzalo; Comins, Daniel L; Houk, K N

    2014-12-05

    The role of twist-boat conformers of cyclohexanones in hydride reductions was explored. The hydride reductions of a cis-2,6-disubstituted N-acylpiperidone, an N-acyltropinone, and tert-butylcyclohexanone by lithium aluminum hydride and by a bulky borohydride reagent were investigated computationally and compared to experiment. Our results indicate that in certain cases, factors such as substrate conformation, nucleophile bulkiness, and remote steric features can affect stereoselectivity in ways that are difficult to predict by the general Felkin-Anh model. In particular, we have calculated that a twist-boat conformation is relevant to the reactivity and facial selectivity of hydride reduction of cis-2,6-disubstituted N-acylpiperidones with a small hydride reagent (LiAlH4) but not with a bulky hydride (lithium triisopropylborohydride).

  20. Thermodynamic Hydricity of Transition Metal Hydrides.

    Science.gov (United States)

    Wiedner, Eric S; Chambers, Matthew B; Pitman, Catherine L; Bullock, R Morris; Miller, Alexander J M; Appel, Aaron M

    2016-08-10

    Transition metal hydrides play a critical role in stoichiometric and catalytic transformations. Knowledge of free energies for cleaving metal hydride bonds enables the prediction of chemical reactivity, such as for the bond-forming and bond-breaking events that occur in a catalytic reaction. Thermodynamic hydricity is the free energy required to cleave an M-H bond to generate a hydride ion (H(-)). Three primary methods have been developed for hydricity determination: the hydride transfer method establishes hydride transfer equilibrium with a hydride donor/acceptor pair of known hydricity, the H2 heterolysis method involves measuring the equilibrium of heterolytic cleavage of H2 in the presence of a base, and the potential-pKa method considers stepwise transfer of a proton and two electrons to give a net hydride transfer. Using these methods, over 100 thermodynamic hydricity values for transition metal hydrides have been determined in acetonitrile or water. In acetonitrile, the hydricity of metal hydrides spans a range of more than 50 kcal/mol. Methods for using hydricity values to predict chemical reactivity are also discussed, including organic transformations, the reduction of CO2, and the production and oxidation of hydrogen.

  1. Boron Hydrides

    Science.gov (United States)

    1946-07-01

    of direct interest could be b.P.4d. ’Thus the discovory of a now proj.ect, since silano is probably too readily infla-zmablo for practical usc’ this...devoted, ho specc4fie compounds vhitih a’-ould be tocdte at prescnt arc: nron tiy * silano , %;2.SiFi3 , diothyl sila~no, (C2 115 )2 Si112, mono r.-rop; ! (n...Bcrohydrido or Li h.... I .A-4A- The prepuation of Silano med of Stannane by the interaction or lithium aluzirun hydride v-ithl silicon tetrtchiorido and

  2. Thermodynamic properties of hydrogen dissociation reaction from the small system method and reactive force field ReaxFF

    Science.gov (United States)

    Trinh, Thuat T.; Meling, Nora; Bedeaux, Dick; Kjelstrup, Signe

    2017-03-01

    We present thermodynamic properties of the H2 dissociation reaction by means of the Small System Method (SSM) using Reactive Force Field (ReaxFF) simulations. Thermodynamic correction factors, partial molar enthalpies and heat capacities of the reactant and product were obtained in the high temperature range; up to 30,000 K. The results obtained from the ReaxFF potential agree well with previous results obtained with a three body potential (TBP). This indicates that the popular reactive force field method can be combined well with the newly developed SSM in realistic simulations of chemical reactions. The approach may be useful in the study of heat and mass transport in combination with chemical reactions.

  3. Dissociation dynamics of methylal

    Energy Technology Data Exchange (ETDEWEB)

    Beaud, P.; Frey, H.-M.; Gerber, T.; Mischler, B.; Radi, P.P.; Tzannis, A.-P. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    The dissociation of methylal is investigated using mass spectrometry, combined with a pyrolytic radical source and femtosecond pump probe experiments. Based on preliminary results two reaction paths of methylal dissociation are proposed and discussed. (author) 4 fig., 3 refs.

  4. Dissociative part-dependent biopsychosocial reactions to backward masked angry and neutral faces : An fMRI study of dissociative identity disorder

    NARCIS (Netherlands)

    Schlumpf, Yolanda R.; Nijenhuis, Ellert R. S.; Chalavi, Sima; Weder, Ekaterina V.; Zimmermann, Eva; Luechinger, Roger; La Marca, Roberto; Reinders, A. A. T. Simone; Jaencke, Lutz

    2013-01-01

    Objective: The Theory of Structural Dissociation of the Personality (TSDP) proposes that dissociative identity disorder (DID) patients are fixed in traumatic memories as "Emotional Parts" (EP), but mentally avoid these as "Apparently Normal Parts" of the personality (ANP). We tested the hypotheses t

  5. Observations of Photo-Dissociation Reaction of TEOS Molecules on Silicon Clean Surfaces

    Science.gov (United States)

    Yanagita, Hideaki; Uemura, Kazuhide; Yokotani, Atsushi; Kurosawa, Kou

    Tetraethoxysilane (TEOS : SiO4(C2H5)4) is widely used to fabricate silicon-dioxide insulator thin films in LSI device technologies. We have already reported that TEOS is photo-dissociated to result in oxide layer deposition at room temperature by a vacuum ultraviolet excimer lamp (λ=172 nm). In this paper, we have observed the initial stages of oxide layer deposition on silicon clean surfaces with the scanning tunneling microscope (STM) and time-of-flight (TOF) mass spectrometer. An argon excimer lamp (λ=126 nm) is used for the photo-chemical vapor deposition (CVD). TEOS molecules have been dissociated to be SiO4(C2H5)n(n=1, 2, 3) groups on the clean surfaces. The 126 nm photons dissociate the molecules or radicals to Si-Om(m=1, 3, 4) after 2 min. Finally, the Si-Om adsorbed molecules and Si atoms in the substrate are re-arranged to be a disorder structure by the photons.

  6. Determination of the 36Mg(n ,γ )37Mg reaction rate from Coulomb dissociation of 37Mg

    Science.gov (United States)

    Shubhchintak; Chatterjee, R.; Shyam, R.

    2017-08-01

    We use the Coulomb dissociation (CD) method to calculate the rate of the 36Mg(n ,γ )37Mg radiative capture reaction. The CD cross sections of the 37Mg nucleus on a 208Pb target at the beam energy of 244 MeV/nucleon, for which new experimental data have recently become available, were calculated within the framework of a finite-range distorted-wave Born approximation theory that is extended to include the projectile deformation effects. Invoking the principle of detailed balance, these cross sections are used to determine the excitation function and subsequently the rate of the 36Mg(n ,γ )37Mg reaction. We compare these rates to those of the 36Mg(α ,n )39Si reaction calculated within a Hauser-Feshbach model. We find that for T9 as large as up to 1.0 (in units of 109 K) the 36Mg(n ,γ )37Mg reaction is much faster than the 36Mg(α ,n )39Si one. The inclusion of the effects of 37Mg projectile deformation in the breakup calculations enhances the (n ,γ ) reaction rate even further. Therefore, it is highly unlikely that the (n ,γ )β -decay r -process flow will be broken at the 36Mg isotope by the α process.

  7. Unusual Reaction of β-Hydroxy α-Diazo Carbonyl Compounds with Trichloroacetonitrile (CI3CCN) and Sodium Hydride

    Institute of Scientific and Technical Information of China (English)

    SHI Wei-Feng; JIANG Nan; WANG Jian-Bo

    2003-01-01

    @@ In the process of preparing α-diazo carbonyl compound 2 by imidation of 1, we unexpectedly observed a direct conversion of the hydroxyl group into trichloroacetylamino group. In this presentation, we report this unprecedented reaction, as well as the Rh2(OAc)4-catalyzed reaction of the resulting β-(trichloroacetyl)amino β-diazo carbonylcompounds 3. [ 1

  8. Properties of nanoscale metal hydrides.

    Science.gov (United States)

    Fichtner, Maximilian

    2009-05-20

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

  9. Advanced Hydride Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Motyka, T.

    1989-01-01

    Metal hydrides have been used at the Savannah River Tritium Facilities since 1984. However, the most extensive application of metal hydride technology at the Savannah River Site is being planned for the Replacement Tritium Facility, a $140 million facility schedules for completion in 1990 and startup in 1991. In the new facility, metal hydride technology will be used to store, separate, isotopically purify, pump, and compress hydrogen isotopes. In support of the Replacement Tritium Facility, a $3.2 million, cold,'' process demonstration facility, the Advanced Hydride Laboratory began operation in November of 1987. The purpose of the Advanced Hydride Laboratory is to demonstrate the Replacement Tritium Facility's metal hydride technology by integrating the various unit operations into an overall process. This paper will describe the Advanced Hydride Laboratory, its role and its impact on the application of metal hydride technology to tritium handling.

  10. Advanced Hydride Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Motyka, T.

    1989-12-31

    Metal hydrides have been used at the Savannah River Tritium Facilities since 1984. However, the most extensive application of metal hydride technology at the Savannah River Site is being planned for the Replacement Tritium Facility, a $140 million facility schedules for completion in 1990 and startup in 1991. In the new facility, metal hydride technology will be used to store, separate, isotopically purify, pump, and compress hydrogen isotopes. In support of the Replacement Tritium Facility, a $3.2 million, ``cold,`` process demonstration facility, the Advanced Hydride Laboratory began operation in November of 1987. The purpose of the Advanced Hydride Laboratory is to demonstrate the Replacement Tritium Facility`s metal hydride technology by integrating the various unit operations into an overall process. This paper will describe the Advanced Hydride Laboratory, its role and its impact on the application of metal hydride technology to tritium handling.

  11. Effect of Hetero Atom on the Hammett’s Reaction Constant (ρ from the Physical Basis of Dissociation Equilibriums of (Dithio Benzoic Acids and (Thio Phenols and Its Application to Solvolysis Reactions and Some Free Radical Reactions

    Directory of Open Access Journals (Sweden)

    Jagannadham Vandanapu

    2012-01-01

    Full Text Available The emergence of putative Hammett equation in mid 1930s was a boon to physical-organic chemists to elucidate the reaction mechanisms of several organic reactions. Based on the concept of this equation several hundreds of papers have emerged in chemical literature in the last century on the effect of structure, on reactivity, and very few on thermodynamic stability and kinetic reactivity of intermediates. In this article an attempt is made to explain the effect of hetero atom on Hammett’s reaction constant (ρ taking the dissociation equilibriums of benzoic acids, dithiobenzoic acids, phenols, and thiophenols.

  12. DFT study on the mechanism of water-assisted dihydrogen elimination in group 6 octahedral metal hydride complexes.

    Science.gov (United States)

    Sandhya, K S; Suresh, Cherumuttathu H

    2012-08-28

    The reaction of water with octahedral bis-, tris- and tetrakis-(phosphine)tungsten, (phosphine)molybdenum and (phosphine)chromium complexes has been studied using B3LYP/def2-TZVPP level of DFT to elucidate dissociative, associative and hydride migratory insertion mechanisms for hydrogen elimination. In the dissociative mechanism, phosphine dissociation requires 19.3-28.5 kcal mol(-1) of energy. The phosphine-water ligand exchange is endergonic due to poor coordination ability of water to group 6 metals (binding energy 8.8-15.5 kcal mol(-1)). The ligand exchange leads to intermolecular M-H···H(2)O dihydrogen interaction and facilitates dihydrogen elimination (G(act) = 6.8-15.5 kcal mol(-1)). In the associative mechanism, a water molecule in the first solvation shell interacts with the M-H bond through a dihydrogen bond (interaction energy 2.7-4.0 kcal mol(-1)) and leads to the elimination of H(2) by forming a hydroxide complex. Compared to the dissociative mechanism, G(act) of associative mechanisms are ~22 kcal mol(-1) higher. In the hydride migratory insertion mechanism, the hydride ligand shifts to the CO ligand (G(act) = 25.4-30.4 kcal mol(-1)) to afford a formyl complex and subsequently the H-H bond coupling occurs between formyl and water ligand (G(act) = 2.8-4.4 kcal mol(-1)). In many cases, the migratory insertion mechanism can simultaneously operate with the dissociative mechanism as a minor pathway, whereas owing to high G(act) value, the associative mechanism can be described as inactive in the reaction. The general argument that dihydrogen elimination is preceded by the formation of a dihydrogen intermediate is not applicable for the systems studied herein as the most favoured dissociative mechanism does not pass through such an intermediate. On the other hand, irrespective of the mechanisms, dihydrogen elimination invariably occurs with the formation of a dihydrogen bonded transition state. Our results also suggest that group 6 octahedral metal

  13. Nano-engineering approach to destabilization of magnesium hydride (MgH2) by solid-state reaction with Si.

    Science.gov (United States)

    Bystrzycki, J; Polanski, M; Plocinski, T

    2009-06-01

    We studied a possibility of destabilization of MgH2 by chemical reaction with Si by using a nano-engineering method for reducing diffusion distances and increasing surface area. The structure, morphology, chemical composition and dehydriding properties were investigated by XRD, SEM, EDS, DTA-TG and the volumetric Sievert method. The commercial MgH2 and Si powder mixture corresponded to the stoichiometry of the ideal Mg2Si intermetallic compound was ball-milled under argon atmosphere to reach a nanocrystalline composite structure (MgH2-Si mixture leads to the formation only a small amount of the Mg2Si compound. Microstructural studies showed that Si after ball-milling is heterogeneously distributed on the surface of MgH2 particles and incorporated in the nanocrystalline MgH2 matrix, forming a nanocomposite structure. The sluggish destabilization of MgH2 by solid-state reaction with Si forming the Mg2Si intermetallic compound was observed at 250 degrees C. The XRD and EDS analysis confirmed that the Mg2Si compound is formed after the dehydrogenation of the synthesized MgH2-Si composite. The activation energy of the destabilization reaction for the investigated composite significantly decreased (162 kJ/mol) as compared with unmilled MgH2-Si powder mixture (213 kJ/mol).

  14. Dissociation of hedonic reaction to reward and incentive motivation in an animal model of the negative symptoms of schizophrenia.

    Science.gov (United States)

    Ward, Ryan D; Simpson, Eleanor H; Richards, Vanessa L; Deo, Gita; Taylor, Kathleen; Glendinning, John I; Kandel, Eric R; Balsam, Peter D

    2012-06-01

    We previously showed that mice that selectively and reversibly overexpress striatal D2 receptors (D2R-OE) model the negative symptoms of schizophrenia. Specifically, D2R-OE mice display a deficit in incentive motivation. The present studies investigated the basis for this deficit. First, we assessed whether hedonic reaction to reward is intact in D2R-OE mice. We assessed licking behavior and video-scored positive hedonic facial reactions to increasing concentrations of sucrose in control and D2R-OE mice. We found no difference between D2R-OE mice and controls in hedonic reactions. To further understand the basis of the motivational deficit, mice were given a choice between pressing a lever for access to a preferred reward (evaporated milk) or consuming a freely available less preferred reward (home-cage chow). D2R-OE mice pressed less for the preferred milk and consumed more of the freely available less preferred chow, indicating that striatal overexpression of postsynaptic D2Rs can alter cost/benefit computations, leading to a motivational deficit. This motivational impairment was ameliorated when the transgene was turned off and D2R levels were normalized. Such a deficit may arise from impaired ability to represent the value of future rewards. To test this, we used operant concurrent schedules and found reduced sensitivity to the value of future outcomes in D2R-OE mice. These results demonstrate for the first time in a transgenic animal model of schizophrenia a dissociation between hedonic reaction to reward and incentive motivation, and show a striking parallel to the proposed neurobiological and psychological mechanisms of impaired incentive motivation in schizophrenia.

  15. Structure and Reactivity of Homocysteine Radical Cation in the Gas Phase Studied by Ion-Molecule Reactions and Infrared Multiple Photon Dissociation

    NARCIS (Netherlands)

    Osburn, S.; Burgie, T.; G. Berden,; Oomens, J.; O' Hair, R. A. J.; Ryzhov, V.

    2013-01-01

    The reactivity of the cysteine (Cys) and homocysteine (Hcy) radical cation was studied using ion molecule reactions. The radical cations were generated via collision-induced dissociation (CID) of their S-nitrosylated precursors. Cleavage of the S-NO bond led to the formation of the radical initially

  16. Structure and Reactivity of Homocysteine Radical Cation in the Gas Phase Studied by Ion-Molecule Reactions and Infrared Multiple Photon Dissociation

    NARCIS (Netherlands)

    Osburn, S.; Burgie, T.; G. Berden,; Oomens, J.; O' Hair, R. A. J.; Ryzhov, V.

    2013-01-01

    The reactivity of the cysteine (Cys) and homocysteine (Hcy) radical cation was studied using ion molecule reactions. The radical cations were generated via collision-induced dissociation (CID) of their S-nitrosylated precursors. Cleavage of the S-NO bond led to the formation of the radical initially

  17. Electromagnetic dissociation of B-8 and the rate of the Be-7(p, gamma)B-8 reaction in the Sun

    NARCIS (Netherlands)

    Davids, B; Austin, SM; Bazin, D; Esbensen, H; Sherrill, BM; Thompson, IJ; Tostevin, JA

    2001-01-01

    In an effort to better determine the Be-7(p, gamma)B-8 reaction rate, we have performed inclusive and exclusive measurements of the Coulomb dissociation of B-8. The former was a study of longitudinal momentum distributions of Be-7 fragments emitted in the Coulomb breakup of intermediate energy B-8 b

  18. Preparation of a sample with a single MgH2 phase by horizontal ball milling and the first hydriding reaction of 90 wt% Mg-10 wt% MgH2

    Science.gov (United States)

    Hong, Seong-Hyeon; Song, Myoung Youp

    2015-03-01

    In order to prepare an additive-free sample with a single MgH2 phase, 90 wt% Mg-10 wt% MgH2 (named 90Mg-10MgH2) was milled under a hydrogen atmosphere in a horizontal ball mill, and then hydrided. The hydrogen absorption and desorption properties of the prepared samples were investigated, and compared with those of milled pure Mg and purchased MgH2. X-ray diffraction analysis, measurement of specific BET surface areas, and observation of the prepared samples by scanning electron microscope were performed. The 90Mg-10MgH2 sample after hydriding-dehydriding cycling had small and large particles with fine particles on their surfaces, and had much finer particles and more defects than the milled pure Mg sample after hydridingdehydriding cycling. The specific BET surface areas of the milled Mg and 90Mg-10MgH2 were measured as 7.81 and 99.81 m2/g, respectively. A sample that had almost a single MgH2 phase could be prepared by horizontal ball milling and the first hydriding reaction of 90Mg-10MgH2. 90Mg-10MgH2 released 5.82 wt% H for about 70 min, while unmilled MgH2 (Aldrich) released 6.04 wt% H for about 100 min, at 648 K.

  19. Reversible dissociation and ligand-glutathione exchange reaction in binuclear cationic tetranitrosyl iron complex with penicillamine.

    Science.gov (United States)

    Syrtsova, Lidia; Sanina, Natalia; Lyssenko, Konstantin; Kabachkov, Evgeniy; Psikha, Boris; Shkondina, Natal'ja; Pokidova, Olesia; Kotelnikov, Alexander; Aldoshin, Sergey

    2014-01-01

    This paper describes a comparative study of the decomposition of two nitrosyl iron complexes (NICs) with penicillamine thiolic ligands [Fe2(SC5H11NO2)2(NO)4]SO4 ·5H2O (I) and glutathione- (GSH-) ligands [Fe2(SC10H17N3O6)2(NO)4]SO4 ·2H2O (II), which spontaneously evolve to NO in aqueous medium. NO formation was measured by a sensor electrode and by spectrophotometric methods by measuring the formation of a hemoglobin- (Hb-) NO complex. The NO evolution reaction rate from (I)  k 1 = (4.6 ± 0.1)·10(-3) s(-1) and the elimination rate constant of the penicillamine ligand k 2 = (1.8 ± 0.2)·10(-3) s(-1) at 25°C in 0.05 M phosphate buffer,  pH 7.0, was calculated using kinetic modeling based on the experimental data. Both reactions are reversible. Spectrophotometry and mass-spectrometry methods have firmly shown that the penicillamine ligand is exchanged for GS(-) during decomposition of 1.5·10(-4) M (I) in the presence of 10(-3) M GSH, with 76% yield in 24 h. As has been established, such behaviour is caused by the resistance of (II) to decomposition due to the higher affinity of iron to GSH in the complex. The discovered reaction may impede S-glutathionylation of the essential enzyme systems in the presence of (I) and is important for metabolism of NIC, connected with its antitumor activity.

  20. Dissociation in children and adolescents as reaction to trauma--an overview of conceptual issues and neurobiological factors.

    Science.gov (United States)

    Diseth, Trond H

    2005-01-01

    The discovery of trauma as an aetiological factor in mental dissociation is more than a century old, but neurobiological research in the last decade has started to clarify a neurobiological basis that may shed light on the complex symptomatology observed in traumatized children. Dysfunctional stress responses, emotional-based style of functioning, hyperarousal, anxiety, irritability, impulsivity, disengaged attention and educational underachievement may thus begin to be better understood. The aim of this overview is to give an update on the concept of dissociation and the links to new neurobiological findings, hopefully to reduce unawareness, wrong diagnostics or even neglect of dissociative symptomatology by clinicians in child and adolescent psychiatry in the Nordic countries. A systematic overview of studies of mental dissociation in children and adolescents published over the last decade disclosed a total of 1019 references; 309 papers regarding the concept of dissociation, memory, trauma and the neurobiological correlates were studied in detail. The assumption of a trauma-genic basis of dissociation is still most discussed in the literature. The importance of other childhood trauma in addition to sexual abuse is outlined, focusing on childhood interpersonal trauma. Recent research on traumatized children and adolescents has demonstrated some permanent neurochemical as well as functional and structural abnormalities in brain areas that are involved in the integrative process of cognition and memory. This research begins to clarify the cerebral basis and mechanisms for the trauma-related dissociation observed in dissociative (conversion) disorders, post-traumatic stress disorder (PTSD) and somatoform disorders. New perspectives on the nature of subcortical processes linking the phenomena of dissociation and traumatic experiences may have important implications for the understanding of dissociative disorders in children and adolescents. They may be regarded as

  1. Elementary Steps of Syngas Reactions on Mo2C(001): Adsorption Thermochemistry and Bond Dissociation

    Energy Technology Data Exchange (ETDEWEB)

    Medford, Andrew

    2012-02-16

    Density functional theory (DFT) and ab initio thermodynamics are applied in order to investigate the most stable surface and subsurface terminations of Mo{sub 2}C(001) as a function of chemical potential and in the presence of syngas. The Mo-terminated (001) surface is then used as a model surface to evaluate the thermochemistry and energetic barriers for key elementary steps in syngas reactions. Adsorption energy scaling relations and Broensted-Evans-Polanyi relationships are established and used to place Mo{sub 2}C into the context of transition metal surfaces. The results indicate that the surface termination is a complex function of reaction conditions and kinetics. It is predicted that the surface will be covered by either C{sub 2}H{sub 2} or O depending on conditions. Comparisons to transition metals indicate that the Mo-terminated Mo{sub 2}C(001) surface exhibits carbon reactivity similar to transition metals such as Ru and Ir, but is significantly more reactive towards oxygen.

  2. Storing hydrogen in the form of light alloy hydrides

    Science.gov (United States)

    Freund, E.; Gillerm, C.

    1981-01-01

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

  3. Numerical simulation and performance test of metal hydride hydrogen storage system

    Directory of Open Access Journals (Sweden)

    Tzu-Hsiang Yen, Bin-Hao Chen, Bao-Dong Chen

    2011-05-01

    Full Text Available Metal hydride reactors are widely used in many industrial applications, such as hydrogen storage, thermal compression, heat pump, etc. According to the research requirement of metal hydride hydrogen storage, the thermal analyses have been implemented in the paper. The metal hydride reaction beds are considered as coupled cylindrical tube modules which combine the chemical absorption and desorption in metal hydride. The model is then used metal hydride LaNi5 as an example to predict the performance of metal hydride hydrogen storage devices, such as the position of hydration front and the thermal flux. Under the different boundary condition the characteristics of heat transfer and mass transfer in metal hydride have influence on the hydrogen absorption and desorption. The researches revealed that the scroll design can improve the temperature distribution in the reactor and the porous tube for directing hydrogen can increase the penetration depth of hydride reaction to decrease the hydrogen absorption time.

  4. Finding the transition state of quasi-barrierless reactions by a growing string method for newton trajectories: application to the dissociation of methylenecyclopropene and cyclopropane.

    Science.gov (United States)

    Quapp, Wolfgang; Kraka, Elfi; Cremer, Dieter

    2007-11-08

    A method for finding a transition state (TS) between a reactant minimum and a quasi-flat, high dissociation plateau on the potential energy surface is described. The method is based on the search of a growing string (GS) along reaction pathways defined by different Newton trajectories (NT). Searches with the GS-NT method always make it possible to identify the TS region because monotonically increasing NTs cross at the TS or, if not monotonically increasing, possess turning points that are located in the TS region. The GS-NT method is applied to quasi-barrierless and truly barrierless chemical reactions. Examples are the dissociation of methylenecyclopropene to acetylene and vinylidene, for which a small barrier far out in the exit channel is found, and the cycloaddition of singlet methylene and ethene, which is barrierless for a broad reaction channel with Cs-symmetry reminiscent of a mountain cirque formed by a glacier.

  5. "Hydro-metathesis" of olefins: A catalytic reaction using a bifunctional single-site tantalum hydride catalyst supported on fibrous silica (KCC-1) nanospheres

    KAUST Repository

    Polshettiwar, Vivek

    2011-02-18

    Tantalizing hydrocarbons: Tantalum hydride supported on fibrous silica nanospheres (KCC-1) catalyzes, in the presence of hydrogen, the direct conversion of olefins into alkanes that have higher and lower numbers of carbon atoms (see scheme). This catalyst shows remarkable catalytic activity and stability, with excellent potential of regeneration. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Hydrogen storage in the form of metal hydrides

    Science.gov (United States)

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

    1984-01-01

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

  7. A combined experimental, theoretical, and Van't Hoff model study for identity methyl, proton, hydrogen atom, and hydride exchange reactions. Correlation with three-center four-, three-, and two-electron systems

    Science.gov (United States)

    Buck, Henk M.

    We have studied carbon transfer reactions following an SN2 reaction profile. With ab initio calculations and experimental geometries concerning the nature of the various complexes indicated as stable, intermediate, and transition state we were able to show the additional value of van't Hoff's tetrahedral configuration by changing its geometry via a trigonal pyramid into a trigonal bipyramid. The ratio of the apical bond and corresponding tetrahedral bond distances is then nearly 1.333. The relevance of this approach has also been shown for identity proton-(hydrogen atom-, and hydride-) in-line reactions. The use of this geometrical transmission will be demonstrated for the hydrogen bonding distances in e.g., DNA duplexes and other biological (supra) molecular systems.

  8. The reaction enthalpy of hydrogen dissociation calculated with the Small System Method from simulation of molecular fluctuations.

    Science.gov (United States)

    Skorpa, Ragnhild; Simon, Jean-Marc; Bedeaux, Dick; Kjelstrup, Signe

    2014-09-28

    We show how we can find the enthalpy of a chemical reaction under non-ideal conditions using the Small System Method to sample molecular dynamics simulation data for fluctuating variables. This method, created with Hill's thermodynamic analysis, is used to find properties in the thermodynamic limit, such as thermodynamic correction factors, partial enthalpies, volumes, heat capacities and compressibility. The values in the thermodynamic limit at (T,V, μj) are then easily transformed into other ensembles, (T,V,Nj) and (T,P,Nj), where the last ensemble gives the partial molar properties which are of interest to chemists. The dissociation of hydrogen from molecules to atoms was used as a convenient model system. Molecular dynamics simulations were performed with three densities; ρ = 0.0052 g cm(-3) (gas), ρ = 0.0191 g cm(-3) (compressed gas) and ρ = 0.0695 g cm(-3) (liquid), and temperatures in the range; T = 3640-20,800 K. The enthalpy of reaction was observed to follow a quadratic trend as a function of temperature for all densities. The enthalpy of reaction was observed to only have a small pressure dependence. With a reference point close to an ideal state (T = 3640 K and ρ = 0.0052 g cm(-3)), we were able to calculate the thermodynamic equilibrium constant, and thus the deviation from ideal conditions for the lowest density. We found the thermodynamic equilibrium constant to increase with increasing temperature, and to have a negligible pressure dependence. Taking the enthalpy variation into account in the calculation of the thermodynamic equilibrium constant, we found the ratio of activity coefficients to be in the order of 0.7-1.0 for the lowest density, indicating repulsive forces between H and H2. This study shows that the compressed gas- and liquid density values at higher temperatures are far from those calculated under ideal conditions. It is important to have a method that can give access to partial molar properties, independent of the ideality of

  9. Hysteresis in Metal Hydrides.

    Science.gov (United States)

    Flanagan, Ted B., And Others

    1987-01-01

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

  10. Mechanism of the reaction of the [W3S4H3(dmpe)3]+ cluster with acids: evidence for the acid-promoted substitution of coordinated hydrides and the effect of the attacking species on the kinetics of protonation of the metal-hydride bonds.

    Science.gov (United States)

    Basallote, Manuel G; Feliz, Marta; Fernández-Trujillo, M Jesús; Llusar, Rosa; Safont, Vicent S; Uriel, Santiago

    2004-03-19

    The cluster [W(3)S(4)H(3)(dmpe)(3)](+) (1) (dmpe=1,2-bis(dimethylphosphino)ethane) reacts with HX (X=Cl, Br) to form the corresponding [W(3)S(4)X(3)(dmpe)(3)](+) (2) complexes, but no reaction is observed when 1 is treated with an excess of halide salts. Kinetic studies indicate that the hydride 1 reacts with HX in MeCN and MeCN-H(2)O mixtures to form 2 in three kinetically distinguishable steps. In the initial step, the W-H bonds are attacked by the acid to form an unstable dihydrogen species that releases H(2) and yields a coordinatively unsaturated intermediate. This intermediate adds a solvent molecule (second step) and then replaces the coordinated solvent with X(-) (third step). The kinetic results show that the first step is faster with HCl than with solvated H(+). This indicates that the rate of protonation of this metal hydride is determined not only by reorganization of the electron density at the M-H bonds but also by breakage of the H-X or H(+)-solvent bonds. It also indicates that the latter process can be more important in determining the rate of protonation.

  11. Unimolecular reaction mechanism of an imidazolin-2-ylidene: an iPEPICO study on the complex dissociation of an Arduengo-type carbene.

    Science.gov (United States)

    Hemberger, Patrick; Bodi, Andras; Gerber, Thomas; Würtemberger, Max; Radius, Udo

    2013-05-27

    The photoionization and dissociative photoionization of Im(iPr)2, 1,3-diisopropylimidazolin-2-ylidene, was investigated by imaging photoelectron photoion coincidence (iPEPICO) with vacuum ultraviolet (VUV) synchrotron radiation. A lone-pair electron of the carbene carbon atom is removed upon ionization and the molecular geometry changes significantly. Only 0.5 eV above the adiabatic ionization energy, IEad =7.52±0.1 eV, the carbene cation fragments, yielding propene or a methyl radical in parallel dissociation reactions with appearance energies of 8.22 and 8.17 eV, respectively. Both reaction channels appear at almost the same photon energy, suggesting a shared transition state. This is confirmed by calculations, which reveal the rate-determining step as hydrogen-atom migration from the isopropyl group to the carbene carbon center forming a resonance-stabilized imidazolium ion. Above 10.5 eV, analogous sequential dissociation channels open up. The first propene-loss fragment ion dissociates further and another methyl or propene is abstracted. Again, a resonance-stabilized imidazolium ion acts as intermediate. The aromaticity of the system is enhanced even in vertical ionization. Indeed, the coincidence technique confirms that a real imidazolium ion is produced by hydrogen transfer over a small barrier. The simple analysis of the breakdown diagram yields all the clues to disentangle the complex dissociative photoionization mechanism of this intermediate-sized molecule. Photoelectron photoion coincidence is a promising tool to unveil the fragmentation mechanism of larger molecules in mass spectrometry.

  12. The dissociative chemisorption of methane on Ni(100) and Ni(111): classical and quantum studies based on the reaction path Hamiltonian.

    Science.gov (United States)

    Mastromatteo, Michael; Jackson, Bret

    2013-11-21

    Electronic structure methods based on density functional theory are used to construct a reaction path Hamiltonian for CH4 dissociation on the Ni(100) and Ni(111) surfaces. Both quantum and quasi-classical trajectory approaches are used to compute dissociative sticking probabilities, including all molecular degrees of freedom and the effects of lattice motion. Both approaches show a large enhancement in sticking when the incident molecule is vibrationally excited, and both can reproduce the mode specificity observed in experiments. However, the quasi-classical calculations significantly overestimate the ground state dissociative sticking at all energies, and the magnitude of the enhancement in sticking with vibrational excitation is much smaller than that computed using the quantum approach or observed in the experiments. The origin of this behavior is an unphysical flow of zero point energy from the nine normal vibrational modes into the reaction coordinate, giving large values for reaction at energies below the activation energy. Perturbative assumptions made in the quantum studies are shown to be accurate at all energies studied.

  13. Metal Hydrides for Rechargeable Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Valoeen, Lars Ole

    2000-03-01

    current. For applications involving the utilisation of high currents, the activation to the required level could be as high as 100 cycles, whereas for low current applications, 5-10 activation cycles could be sufficient when the same current was used for the activation (pretreatment of the alloy might enhance the activation considerably). When an electrode made of an alloy with a relatively high hydrogen equilibrium (plateau) pressure was cycled under a moderate external inert gas pressure, a new activation process was observed when the pressure was increased. This indicated that the activated state was dependent on several factors, which indicated the need of examining each factor individually as well as combined in order to gain a complete understanding of the process. The characterization of metal hydride electrodes by means of electrochemical impedance spectroscopy, showed that this technique when used properly and in combination with other characterization techniques can be very useful in determining the significance of the different sub-processes in the overall process. The impedance response for different laboratory metal hydride electrodes were successfully modelled and fitted to experimental data for both AB{sub 5} type alloys and a MgNi type electrode. The following sub processes were found to be significant for the overall reaction rate: charge transfer resistance, double layer capacitance and impedance resulting from hydrogen diffusion within the metal lattice. The diffusion process was best modelled when using a spherical diffusion geometry. To fit the experimental data, equations describing the current distribution in porous electrodes were required. To account for possible parallel hydrogen evolution during charging, it was necessary to include this step in the model for electrodes having a more negative open circuit potential than the reversible hydrogen evolution potential. Indications of one or more parallel reduction/oxidation processes competing with

  14. Metal Hydrides for Rechargeable Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Valoeen, Lars Ole

    2000-03-01

    current. For applications involving the utilisation of high currents, the activation to the required level could be as high as 100 cycles, whereas for low current applications, 5-10 activation cycles could be sufficient when the same current was used for the activation (pretreatment of the alloy might enhance the activation considerably). When an electrode made of an alloy with a relatively high hydrogen equilibrium (plateau) pressure was cycled under a moderate external inert gas pressure, a new activation process was observed when the pressure was increased. This indicated that the activated state was dependent on several factors, which indicated the need of examining each factor individually as well as combined in order to gain a complete understanding of the process. The characterization of metal hydride electrodes by means of electrochemical impedance spectroscopy, showed that this technique when used properly and in combination with other characterization techniques can be very useful in determining the significance of the different sub-processes in the overall process. The impedance response for different laboratory metal hydride electrodes were successfully modelled and fitted to experimental data for both AB{sub 5} type alloys and a MgNi type electrode. The following sub processes were found to be significant for the overall reaction rate: charge transfer resistance, double layer capacitance and impedance resulting from hydrogen diffusion within the metal lattice. The diffusion process was best modelled when using a spherical diffusion geometry. To fit the experimental data, equations describing the current distribution in porous electrodes were required. To account for possible parallel hydrogen evolution during charging, it was necessary to include this step in the model for electrodes having a more negative open circuit potential than the reversible hydrogen evolution potential. Indications of one or more parallel reduction/oxidation processes competing with

  15. Regenerative Hydride Heat Pump

    Science.gov (United States)

    Jones, Jack A.

    1992-01-01

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

  16. Regenerative Hydride Heat Pump

    Science.gov (United States)

    Jones, Jack A.

    1992-01-01

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

  17. Submillimeter Spectroscopy of Hydride Molecules

    Science.gov (United States)

    Phillips, T. G.

    1998-05-01

    Simple hydride molecules are of great importance in astrophysics and astrochemistry. Physically they dominate the cooling of dense, warm phases of the ISM, such as the cores and disks of YSOs. Chemically they are often stable end points of chemical reactions, or may represent important intermediate stages of the reaction chains, which can be used to test the validity of the process. Through the efforts of astronomers, physicists, chemists, and laboratory spectroscopists we have an approximate knowledge of the abundance of some of the important species, but a great deal of new effort will be required to achieve the comprehensive and accurate data set needed to determine the energy balance and firmly establish the chemical pathways. Due to the low moment of inertia, the hydrides rotate rapidly and so have their fundamental spectral lines in the submillimeter. Depending on the cloud geometry and temperature profile they may be observed in emission or absorption. Species such as HCl, HF, OH, CH, CH(+) , NH_2, NH_3, H_2O, H_2S, H_3O(+) and even H_3(+) have been detected, but this is just a fraction of the available set. Also, most deduced abundances are not nearly sufficiently well known to draw definitive conclusions about the chemical processes. For example, the most important coolant for many regions, H_2O, has a possible range of deduced abundance of a factor of 1000. The very low submillimeter opacity at the South Pole site will be a significant factor in providing a new capabilty for interstellar hydride spectroscopy. The new species and lines made available in this way will be discussed.

  18. Electrochemical and Optical Properties of Magnesium-Alloy Hydrides Reviewed

    Directory of Open Access Journals (Sweden)

    Thirugnasambandam G. Manivasagam

    2012-10-01

    Full Text Available As potential hydrogen storage media, magnesium based hydrides have been systematically studied in order to improve reversibility, storage capacity, kinetics and thermodynamics. The present article deals with the electrochemical and optical properties of Mg alloy hydrides. Electrochemical hydrogenation, compared to conventional gas phase hydrogen loading, provides precise control with only moderate reaction conditions. Interestingly, the alloy composition determines the crystallographic nature of the metal-hydride: a structural change is induced from rutile to fluorite at 80 at.% of Mg in Mg-TM alloy, with ensuing improved hydrogen mobility and storage capacity. So far, 6 wt.% (equivalent to 1600 mAh/g of reversibly stored hydrogen in MgyTM(1-yHx (TM: Sc, Ti has been reported. Thin film forms of these metal-hydrides reveal interesting electrochromic properties as a function of hydrogen content. Optical switching occurs during (dehydrogenation between the reflective metal and the transparent metal hydride states. The chronological sequence of the optical improvements in optically active metal hydrides starts with the rare earth systems (YHx, followed by Mg rare earth alloy hydrides (MgyGd(1-yHx and concludes with Mg transition metal hydrides (MgyTM(1-yHx. In-situ optical characterization of gradient thin films during (dehydrogenation, denoted as hydrogenography, enables the monitoring of alloy composition gradients simultaneously.

  19. Quantum chemical study of mechanisms of dissociation and isomerization reactions in some molecules and radicals of astrophysical significance: Cyanides and related molecules

    Indian Academy of Sciences (India)

    V P Gupta; Archina Sharma

    2006-09-01

    A theoretical study of the mechanism of photodecomposition in carbonyl cyanide, diethynyl ketone, acetyl cyanide and formyl cyanide has been conducted using density functional and MP2 theories. A complete analysis of the electronic spectra of these molecules in terms of nature, energy and intensity of electronic transitions has been provided by time-dependent density functional theory. Mixing coefficients and main configurations of the electronic states have been used to identify the states leading to the photodecomposition process. While the Rydberg state 1(n,3s) is involved in the dissociation of formyl cyanide and acetyl cyanide, the $^{*}_{CC} / ^{*}_{CN}$ states are involved in the case of carbonyl cyanide and diethynyl ketone. In all cases, however, stepwise decomposition process is preferred over the concerted reaction process. Based on potential energy curves for bond dissociation and the transition state and IRC studies, it is found that besides the direct dissociation of carbonyl cyanide, a photoisomerization process through a non-planar transition state may also occur resulting in the formation of a stable and planar isomer CNC(O)CN. A complete vibrational analysis of the higher energy isomer has been conducted and several new fundamental bands are predicted. Some of the earlier experimental results on the photodecomposition mechanism and energies of photofragments in carbonyl cyanide and acetyl cyanide have also been rationalized.

  20. Heat and mass transfer in a dissociated laminar boundary layer of air with consideration of the finite rate of chemical reaction

    Science.gov (United States)

    Oyegbesan, A. O.; Algermissen, J.

    1986-01-01

    A numerical investigation of heat and mass transfer in a dissociated laminar boundary layer of air on an isothermal flat plate is carried out for different degrees of cooling of the wall. A finite-difference chemical model is used to study elementary reactions involving NO2 and N2O. The analysis is based on equations of continuity, momentum, energy, conservation and state for the two-dimensional viscous flow of a reacting multicomponent mixtures. Attention is given to the effects of both catalyticity and noncatalyticity of the wall.

  1. Lightweight hydride storage materials

    Energy Technology Data Exchange (ETDEWEB)

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

    1995-09-01

    The need for lightweight hydrides in vehicular applications has prompted considerable research into the use of magnesium and its alloys. Although this earlier work has provided some improved performance in operating temperature and pressure, substantial improvements are needed before these materials will significantly enhance the performance of an engineered system on a vehicle. We are extending the work of previous investigators on Mg alloys to reduce the operating temperature and hydride heat of formation in light weight materials. Two important results will be discussed in this paper: (1) a promising new alloy hydride was found which has better pressure-temperature characteristics than any previous Mg alloy and, (2) a new fabrication process for existing Mg alloys was developed and demonstrated. The new alloy hydride is composed of magnesium, aluminum and nickel. It has an equilibrium hydrogen overpressure of 1.3 atm. at 200{degrees}C and a storage capacity between 3 and 4 wt.% hydrogen. A hydrogen release rate of approximately 5 x 10{sup -4} moles-H{sub 2}/gm-min was measured at 200{degrees}C. The hydride heat of formation was found to be 13.5 - 14 kcal/mole-H{sub 2}, somewhat lower than Mg{sub 2}Ni. The new fabrication method takes advantage of the high vapor transport of magnesium. It was found that Mg{sub 2}Ni produced by our low temperature process was better than conventional materials because it was single phase (no Mg phase) and could be fabricated with very small particle sizes. Hydride measurements on this material showed faster kinetic response than conventional material. The technique could potentially be applied to in-situ hydride bed fabrication with improved packing density, release kinetics, thermal properties and mechanical stability.

  2. Technical and economic aspects of hydrogen storage in metal hydrides

    Science.gov (United States)

    Schmitt, R.

    1981-01-01

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

  3. Synthesis of Renewable Energy Materials, Sodium Aluminum Hydride by Grignard Reagent of Al

    Directory of Open Access Journals (Sweden)

    Jun-qin Wang

    2015-01-01

    Full Text Available The research on hydrogen generation and application has attracted widespread attention around the world. This paper is to demonstrate that sodium aluminum hydride can be synthesized under simple and mild reaction condition. Being activated through organics, aluminum powder reacts with hydrogen and sodium hydride to produce sodium aluminum hydride under atmospheric pressure. The properties and composition of the sample were characterized by FTIR, XRD, SEM, and so forth. The results showed that the product through this synthesis method is sodium aluminum hydride, and it has higher purity, perfect crystal character, better stability, and good hydrogen storage property. The reaction mechanism is also discussed in detail.

  4. Getting metal-hydrides to do what you want them to

    Energy Technology Data Exchange (ETDEWEB)

    Gruen, D.M.

    1981-01-01

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

  5. Hydrogen, lithium, and lithium hydride production

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-06-20

    A method is provided for extracting hydrogen from lithium hydride. The method includes (a) heating lithium hydride to form liquid-phase lithium hydride; (b) extracting hydrogen from the liquid-phase lithium hydride, leaving residual liquid-phase lithium metal; (c) hydriding the residual liquid-phase lithium metal to form refined lithium hydride; and repeating steps (a) and (b) on the refined lithium hydride.

  6. Oxidation of Group 8 transition-Metal Hydrides and Ionic Hydrogenation of Ketones and Aldehydes

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Kjell-Tore

    1996-08-01

    Transition-metal hydrides have received considerable attention during the last decades because of their unusual reactivity and their potential as homogeneous catalysts for hydrogenation and other reactions of organic substrates. An important class of catalytic processes where transition-metal hydrides are involved is the homogeneous hydrogenation of alkenes, alkynes, ketones, aldehydes, arenes and nitro compounds. This thesis studies the oxidation of Group 8 transition-metal hydrides and the ionic hydrogenation of ketones and aldehydes.

  7. The electrochemical impedance of metal hydride electrodes

    DEFF Research Database (Denmark)

    Valøen, Lars Ole; Lasia, Andrzej; Jensen, Jens Oluf

    2002-01-01

    The electrochemical impedance responses for different laboratory type metal hydride electrodes were successfully modeled and fitted to experimental data for AB5 type hydrogen storage alloys as well as one MgNi type electrode. The models fitted the experimental data remarkably well. Several AC......, explaining the experimental impedances in a wide frequency range for electrodes of hydride forming materials mixed with copper powder, were obtained. Both charge transfer and spherical diffusion of hydrogen in the particles are important sub processes that govern the total rate of the electrochemical...... hydrogen absorption/desorption reaction. To approximate the experimental data, equations describing the current distribution in porous electrodes were needed. Indications of one or more parallel reduction/oxidation processes competing with the electrochemical hydrogen absorption/desorption reaction were...

  8. Dissociative amnesia.

    Science.gov (United States)

    Staniloiu, Angelica; Markowitsch, Hans J

    2014-08-01

    Dissociative amnesia is one of the most enigmatic and controversial psychiatric disorders. In the past two decades, interest in the understanding of its pathophysiology has surged. In this report, we review new data about the epidemiology, neurobiology, and neuroimaging of dissociative amnesia and show how advances in memory research and neurobiology of dissociation inform proposed pathogenetic models of the disorder. Dissociative amnesia is characterised by functional impairment. Additionally, preliminary data suggest that affected people have an increased and possibly underestimated suicide risk. The prevalence of dissociative amnesia differs substantially across countries and populations. Symptoms and disease course also vary, indicating a possibly heterogeneous disorder. The accompanying clinical features differ across cultural groups. Most dissociative amnesias are retrograde, with memory impairments mainly involving the episodic-autobiographical memory domain. Anterograde dissociative amnesia occurring without significant retrograde memory impairments is rare. Functional neuroimaging studies of dissociative amnesia with prevailing retrograde memory impairments show changes in the network that subserves autobiographical memory. At present, no evidence-based treatments are available for dissociative amnesia and no broad framework exists for its rehabilitation. Further research is needed into its neurobiology, course, treatment options, and strategies to improve differential diagnoses. Copyright © 2014 Elsevier Ltd. All rights reserved.

  9. Filiform-mode hydride corrosion of uranium surfaces

    Science.gov (United States)

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

    2013-11-01

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

  10. Temperature-induced dissociation reaction and dynamics of light-harvesting complex Ⅱ isolated from purple photosynthetic bacterium Rps. palustris

    Institute of Scientific and Technical Information of China (English)

    FENG Juan; LI XueFeng; LIU Yuan

    2007-01-01

    Steady-state absorption spectroscopy, circular dichroism, and resonance Raman spectroscopy have been used to investigate the thermal stability of LH2 complex isolated from purple photosynthetic bacterium Rps. Palustris. The results show that: 1) upon increasing the temperature, a transition from B800 and B850 to free bacteriochlorophyll (B780) happens; 2) a gradual decrease and disappearance of CD signal in visible region occur; 3) a shift of the frequency, belonging to C=C and C-C stretching vibration, to higher wavenumber takes place. It is suggested that LH2 complex can be dissociated in the presence of B800, B850 and carotenoids simultaneously. Single-exponential fitting on the dynamic decay curves gives the apparent time constants of hundreds of minutes for various pigments.

  11. Role of recombination, dissociation, and competition between exciton-charge reactions in magnetoconductance of polymeric semiconductor device

    Energy Technology Data Exchange (ETDEWEB)

    Radaoui, M., E-mail: addaouimoufid@gmail.com [Laboratoire Matériaux Avancés et Phénomènes Quantiques, Faculté des Sciences de Tunis, Université El Manar, 2092 Campus Universitaire, Tunis (Tunisia); Linz Institute for Organic Solar Cells (LIOS), Johannes Kepler University Linz, Altenbergerstr. 69, 4040 Linz (Austria); Saidani, M. A.; Ben Fredj, A.; Bouchriha, H. [Laboratoire Matériaux Avancés et Phénomènes Quantiques, Faculté des Sciences de Tunis, Université El Manar, 2092 Campus Universitaire, Tunis (Tunisia); Romdhane, S. [Laboratoire Matériaux Avancés et Phénomènes Quantiques, Faculté des Sciences de Tunis, Université El Manar, 2092 Campus Universitaire, Tunis (Tunisia); Faculté des Sciences de Bizerte, 7021 Zarzouna, Bizerte, Université de Carthage (Tunisia); Havlicek, M.; Egbe, D. A. M.; Sariciftci, N. S. [Linz Institute for Organic Solar Cells (LIOS), Johannes Kepler University Linz, Altenbergerstr. 69, 4040 Linz (Austria)

    2014-11-14

    Magnetoelectrical measurements were performed on a diode structure, based on an anthracene-containing poly(arylene-ethynylylene)-alt-poly(arylene-vinylene) denoted AnE-PVstat, to clarify the role of the recombination and dissociation of electron-hole (e-h) pairs in the magnetoconductance (MC). We report the observed MC under a weak magnetic field (<1 T) at room and low temperatures. Positive MC is observed and reaches up to 2% at a magnetic field of 450 mT at room temperature. It is found that with the increase of the voltage, the MC effect decreases. We also report the difference in MC between perpendicular (θ = 90°) and parallel (θ = 0°) alignment of magnetic field with respect to the current direction. The experimental data were analyzed in the context of the e-h pair model, based on the Stochastic Liouville Equation. To interpret the experimental results on magnetoconductance measurements, anisotropic hyperfine interaction has been introduced through an anisotropic hyperfine field. The dissociation rates q{sub S} and q{sub T} of the singlet and triplet e-h pairs were determined from the best fit with experimental curves and are about 10{sup 5 }s{sup −1}, while the recombination rates of the singlet and triplet e-h pairs are k{sub S} ∼ 10{sup 9 }s{sup −1} and k{sub T} ∼ 10{sup 5 }s{sup −1}, respectively. At low temperatures (T < 60 K), an unexpected “sign-reversal phenomenon” of the magnetoconductance is observed.

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

    Energy Technology Data Exchange (ETDEWEB)

    Orimo, S.; Fujii, H. [Hiroshima Univ. (Japan). Faculty of Integrated Arts and Sciences

    2001-02-01

    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)-Mg{sub 2}Ni, (2) a mixture of n-Mg{sub 2}Ni and amorphous (a)-MgNi,(3) pure a-MgNi, and(4) n-MgNi{sub 2}. 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 MgNi{sub 2}-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. (orig.)

  13. Theoretical Investigation of Hydrogen Adsorption and Dissociation on Iron and Iron Carbide Surfaces Using the ReaxFF Reactive Force Field Method

    Energy Technology Data Exchange (ETDEWEB)

    Zou, Chenyu; van Duin, Adri C.T.; Sorescu, Dan C.

    2012-06-01

    We have developed a ReaxFF reactive force field to describe hydrogen adsorption and dissociation on iron and iron carbide surfaces relevant for simulation of Fischer–Tropsch (FT) synthesis on iron catalysts. This force field enables large system (>>1000 atoms) simulations of hydrogen related reactions with iron. The ReaxFF force field parameters are trained against a substantial amount of structural and energetic data including the equations of state and heats of formation of iron and iron carbide related materials, as well as hydrogen interaction with iron surfaces and different phases of bulk iron. We have validated the accuracy and applicability of ReaxFF force field by carrying out molecular dynamics simulations of hydrogen adsorption, dissociation and recombination on iron and iron carbide surfaces. The barriers and reaction energies for molecular dissociation on these two types of surfaces have been compared and the effect of subsurface carbon on hydrogen interaction with iron surface is evaluated. We found that existence of carbon atoms at subsurface iron sites tends to increase the hydrogen dissociation energy barrier on the surface, and also makes the corresponding hydrogen dissociative state relatively more stable compared to that on bare iron. These properties of iron carbide will affect the dissociation rate of H{sub 2} and will retain more surface hydride species, thus influencing the dynamics of the FT synthesis process.

  14. Dissociation between back pain and bone stress reaction as measured by CT scan in young cricket fast bowlers

    National Research Council Canada - National Science Library

    Millson, H B; Gray, J; Stretch, R A; Lambert, M I

    2004-01-01

    Bone stress reaction is prevalent among cricket fast bowlers. Few studies have addressed the sensitivity and specificity of imaging for diagnosis, and follow up assessment has been poorly investigated...

  15. Main Group Lewis Acid-Mediated Transformations of Transition-Metal Hydride Complexes.

    Science.gov (United States)

    Maity, Ayan; Teets, Thomas S

    2016-08-10

    This Review highlights stoichiometric reactions and elementary steps of catalytic reactions involving cooperative participation of transition-metal hydrides and main group Lewis acids. Included are reactions where the transition-metal hydride acts as a reactant as well as transformations that form the metal hydride as a product. This Review is divided by reaction type, illustrating the diverse roles that Lewis acids can play in mediating transformations involving transition-metal hydrides as either reactants or products. We begin with a discussion of reactions where metal hydrides form direct adducts with Lewis acids, elaborating the structure and dynamics of the products of these reactions. The bulk of this Review focuses on reactions where the transition metal and Lewis acid act in cooperation, and includes sections on carbonyl reduction, H2 activation, and hydride elimination reactions, all of which can be promoted by Lewis acids. Also included is a section on Lewis acid-base secondary coordination sphere interactions, which can influence the reactivity of hydrides. Work from the past 50 years is included, but the majority of this Review focuses on research from the past decade, with the intent of showcasing the rapid emergence of this field and the potential for further development into the future.

  16. Effect of surface contamination on the hydriding behaviors of LaNi{sub 4.5}Al{sub 0.5}, LaNi{sub 2.5}Co{sub 2.5} and LaNi{sub 4.5}Mn{sub 0.5}

    Energy Technology Data Exchange (ETDEWEB)

    Uchida, H. [Tokai Univ., Kanagawa (Japan). Dept. of Applied Physics; Seki, S. [Tokai Univ., Kanagawa (Japan). Dept. of Applied Physics; Seta, S. [Tokai Univ., Kanagawa (Japan). Dept. of Applied Physics

    1995-12-15

    The aim of this study was to elucidate the role of each substituent element such as Al, Co and Mn in the hydridings of LaNi{sub 4.5}Al{sub 0.5}, LaNi{sub 2.5}Co{sub 2.5} and LaNi{sub 4.5}Mn{sub 0.5} alloys exposed to contaminative conditions. The addition of Al was found effective to yield the H{sub 2}-dissociation-controlled kinetics even in extended surface contaminations. The effect of surface oxide containing Co seem to remain even in the hydriding reaction, indicating the formation of stable oxide layers for the Co-containing alloys in spite of the occurrence of a small volume expansion due to hydriding. The addition of Co yields the inhibitive pulverization, which indicates that the Co addition acts to form coherent interfaces between surface oxide layers and the alloy. The addition of Mn increases the sensitivity to contamination and markedly decreases the reaction rate in the formation of H solid solution where no pulverization takes place. However, because the pulverization is accelerated by the presence of various non-stoichiometric Mn oxides, the hydriding rate recovers to those of LaNi{sub 5} and LaNi{sub 4.5}Al{sub 0.5} with increasing number of cyclic hydriding-dehydriding reactions. The limited applicability of the Johnson-Mehl-Avrami-type equation to the measured hydriding curves is discussed from the measured kinetic results. (orig.)

  17. Accurate studies on dissociation energies of diatomic molecules

    Institute of Scientific and Technical Information of China (English)

    SUN; WeiGuo; FAN; QunChao

    2007-01-01

    The molecular dissociation energies of some electronic states of hydride and N2 molecules were studied using a parameter-free analytical formula suggested in this study and the algebraic method (AM) proposed recently. The results show that the accurate AM dissociation energies DeAM agree excellently with experimental dissociation energies Deexpt, and that the dissociation energy of an electronic state such as the 23△g state of 7Li2 whose experimental value is not available can be predicted using the new formula.

  18. Thermochemical properties and bond dissociation energies of C3-C5 cycloalkyl hydroperoxides and peroxy radicals: cycloalkyl radical + (3)O2 reaction thermochemistry.

    Science.gov (United States)

    Auzmendi-Murua, Itsaso; Bozzelli, Joseph W

    2012-07-19

    Cyclic aliphatic hydrocarbons are major components in modern fuels; they can be present in the reactants, and they can be formed during the gas-phase oxidation processes. In combustion and thermal oxidation processes, these cyclics will form radicals that react with (3)O(2) to form peroxy radicals. In this study, density functional theory and higher level ab initio calculations are used to calculate thermochemical properties and bond dissociation energies of 3-5-membered cycloalkanes, corresponding hydroperoxides, hydroperoxycycloalkyl radicals, and cycloalkyl radicals that occur in these reaction systems. Geometries, vibration frequencies, and thermochemical properties, ΔH(f 298)°, are calculated with the B3LYP/6-31 g(d,p), B3LYP/6-31 g(2d,2p), composite CBS-QB3, and G3MP2B3 methods. Standard enthalpies of formation at 298 K are evaluated using isodesmic reaction schemes with several work reactions for each species. Group additivity contributions are developed, and application of group additivity with comparison to calculated values is illustrated. Entropy and heat capacities, S°(T) and C(p)°(T) (5 K ≤ T ≤ 5000), are determined using geometric parameters and frequencies from the B3LYP/6-31 g(d,p) calculations.

  19. Assessing nanoparticle size effects on metal hydride thermodynamics using the Wulff construction.

    Science.gov (United States)

    Kim, Ki Chul; Dai, Bing; Karl Johnson, J; Sholl, David S

    2009-05-20

    The reaction thermodynamics of metal hydrides are crucial to the use of these materials for reversible hydrogen storage. In addition to altering the kinetics of metal hydride reactions, the use of nanoparticles can also change the overall reaction thermodynamics. We use density functional theory to predict the equilibrium crystal shapes of seven metals and their hydrides via the Wulff construction. These calculations allow the impact of nanoparticle size on the thermodynamics of hydrogen release from these metal hydrides to be predicted. Specifically, we study the temperature required for the hydride to generate a H(2) pressure of 1 bar as a function of the radius of the nanoparticle. In most, but not all, cases the hydrogen release temperature increases slightly as the particle size is reduced.

  20. Air and metal hydride battery

    Energy Technology Data Exchange (ETDEWEB)

    Lampinen, M.; Noponen, T. [Helsinki Univ. of Technology, Otaniemi (Finland). Lab. of Applied Thermodynamics

    1998-12-31

    The main goal of the air and metal hydride battery project was to enhance the performance and manufacturing technology of both electrodes to such a degree that an air-metal hydride battery could become a commercially and technically competitive power source for electric vehicles. By the end of the project it was possible to demonstrate the very first prototype of the air-metal hydride battery at EV scale, achieving all the required design parameters. (orig.)

  1. Well-Defined Molecular Magnesium Hydride Clusters : Relationship between Size and Hydrogen-Elimination Temperature

    NARCIS (Netherlands)

    Intemann, Julia; Spielmann, Jan; Sirsch, Peter; Harder, Sjoerd

    A new tetranuclear magnesium hydride cluster, [{NN-(MgH)2}2], which was based on a NN-coupled bis--diketiminate ligand (NN2-), was obtained from the reaction of [{NN-(MgnBu)2}2] with PhSiH3. Its crystal structure reveals an almost-tetrahedral arrangement of Mg atoms and two different sets of hydride

  2. Multiconfigurational electronic wavefunctions in the full optimized reaction space: the isomerization of nitrosyl hydride to nitrogen hydroxide in the lowest singlet and triplet states

    Energy Technology Data Exchange (ETDEWEB)

    Dombek, M. G.

    1977-12-01

    Energy curves are determined for the lowest singlet and triplet states of the HNO molecule. The geometry is varied in that the hydrogen moves through 13 positions around the NO core to describe the isomerization reaction HNO yields HON. Quantitatively determined are the stable and metastable equilibrium positions in both states, the energy differences between these two equilibrium positions and between the two states, and the barriers with respect to isomerization. The calculations are carried out using a novel configuration interaction approach called the Full Optimized Reaction Space method, which involves multiconfigurational self-consistent field calculations as an integral part. In order to interpret the bonding changes occurring during the reaction, a novel type of orbital is developed and calculated. These are called Directed Localized Reaction Orbitals. With their help it proves possible to give an interpretation of the isomerization in terms of concepts which fit chemical intuition.

  3. Effects of task complexity in young and old adults : Reaction time and P300 latency are not always dissociated

    NARCIS (Netherlands)

    Smulders, F.T.Y.; Kenemans, J.L.; Schmidt, W.F.; Albert, K.

    1999-01-01

    Twelve young and 11 elderly men (mean ages 21.1 and 70.1) performed a choice-reaction time (RT) task in which stimulus degradation and stimulus- response (S-R) compatibility were manipulated. The extant literature has suggested that the effects of age on RT are usually augmented (multiplicative) in

  4. Numerical study of a magnesium hydride tank

    Science.gov (United States)

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

    2012-11-01

    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.

  5. Novel fuel cell stack with coupled metal hydride containers

    Science.gov (United States)

    Liu, Zhixiang; Li, Yan; Bu, Qingyuan; Guzy, Christopher J.; Li, Qi; Chen, Weirong; Wang, Cheng

    2016-10-01

    Air-cooled, self-humidifying hydrogen fuel cells are often used for backup and portable power sources, with a metal hydride used as the hydrogen storage material. To provide a stable hydrogen flow to the fuel cell stack, heat must be provided to the metal hydride. Conventionally, the heat released from the exothermic reaction of hydrogen and oxygen in the fuel cell stack to the exhaust air is used to heat a separate metal hydride container. In this case, the heat is only partially used instead of being more closely coupled because of the heat transfer resistances in the system. To achieve better heat integration, a novel scheme is proposed whereby hydrogen storage and single fuel cells are more closely coupled. Based on this idea, metal hydride containers in the form of cooling plates were assembled between each pair of cells in the stack so that the heat could be directly transferred to a metal hydride container of much larger surface-to-volume ratio than conventional separate containers. A heat coupled fuel cell portable power source with 10 cells and 11 metal hydride containers was constructed and the experimental results show that this scheme is beneficial for the heat management of fuel cell stack.

  6. The lowest-lying electronic singlet and triplet potential energy surfaces for the HNO-NOH system: energetics, unimolecular rate constants, tunneling and kinetic isotope effects for the isomerization and dissociation reactions.

    Science.gov (United States)

    Bozkaya, Uğur; Turney, Justin M; Yamaguchi, Yukio; Schaefer, Henry F

    2012-04-28

    The lowest-lying electronic singlet and triplet potential energy surfaces (PES) for the HNO-NOH system have been investigated employing high level ab initio quantum chemical methods. The reaction energies and barriers have been predicted for two isomerization and four dissociation reactions. Total energies are extrapolated to the complete basis set limit applying focal point analyses. Anharmonic zero-point vibrational energies, diagonal Born-Oppenheimer corrections, relativistic effects, and core correlation corrections are also taken into account. On the singlet PES, the (1)HNO → (1)NOH endothermicity including all corrections is predicted to be 42.23 ± 0.2 kcal mol(-1). For the barrierless decomposition of (1)HNO to H + NO, the dissociation energy is estimated to be 47.48 ± 0.2 kcal mol(-1). For (1)NOH → H + NO, the reaction endothermicity and barrier are 5.25 ± 0.2 and 7.88 ± 0.2 kcal mol(-1). On the triplet PES the reaction energy and barrier including all corrections are predicted to be 7.73 ± 0.2 and 39.31 ± 0.2 kcal mol(-1) for the isomerization reaction (3)HNO → (3)NOH. For the triplet dissociation reaction (to H + NO) the corresponding results are 29.03 ± 0.2 and 32.41 ± 0.2 kcal mol(-1). Analogous results are 21.30 ± 0.2 and 33.67 ± 0.2 kcal mol(-1) for the dissociation reaction of (3)NOH (to H + NO). Unimolecular rate constants for the isomerization and dissociation reactions were obtained utilizing kinetic modeling methods. The tunneling and kinetic isotope effects are also investigated for these reactions. The adiabatic singlet-triplet energy splittings are predicted to be 18.45 ± 0.2 and 16.05 ± 0.2 kcal mol(-1) for HNO and NOH, respectively. Kinetic analyses based on solution of simultaneous first-order ordinary-differential rate equations demonstrate that the singlet NOH molecule will be difficult to prepare at room temperature, while the triplet NOH molecule is viable with respect to isomerization and dissociation reactions up to

  7. Coulomb dissociation and momentum distributions for [sup 11]Li [yields] [sup 9]Li + n + n breakup reactions

    Energy Technology Data Exchange (ETDEWEB)

    Esbensen, H.

    1993-01-01

    Momentum distributions for the [sup 11]Li [yields] [sup 9]Li+n+n breakup reaction, generated by Coulomb dipole excitations, axe calculated in a 3-body model for [sup 11]Li. The relative momentum distribution of the two neutrons is in good agreement with recent 3-body coincidence measurements but the momentum distribution for the [sup 9]Li recoil and the decay energy spectrum are much narrower than observed. These discrepancies may be due to higher order dynamical effects which have been ignored.

  8. Coulomb dissociation and momentum distributions for {sup 11}Li {yields} {sup 9}Li + n + n breakup reactions

    Energy Technology Data Exchange (ETDEWEB)

    Esbensen, H.

    1993-03-01

    Momentum distributions for the {sup 11}Li {yields} {sup 9}Li+n+n breakup reaction, generated by Coulomb dipole excitations, axe calculated in a 3-body model for {sup 11}Li. The relative momentum distribution of the two neutrons is in good agreement with recent 3-body coincidence measurements but the momentum distribution for the {sup 9}Li recoil and the decay energy spectrum are much narrower than observed. These discrepancies may be due to higher order dynamical effects which have been ignored.

  9. Complex Hydride Compounds with Enhanced Hydrogen Storage Capacity

    Energy Technology Data Exchange (ETDEWEB)

    Mosher, Daniel A.; Opalka, Susanne M.; Tang, Xia; Laube, Bruce L.; Brown, Ronald J.; Vanderspurt, Thomas H.; Arsenault, Sarah; Wu, Robert; Strickler, Jamie; Anton, Donald L.; Zidan, Ragaiy; Berseth, Polly

    2008-02-18

    between alkaline metal hydrides (AmH), Alkaline earth metal hydrides (AeH2), alane (AlH3), transition metal (Tm) hydrides (TmHz, where z=1-3) and molecular hydrogen (H2). The effort started first with variations of known alanates and subsequently extended the search to unknown compounds. In this stage, the FPM techniques were developed and validated on known alanate materials such as NaAlH4 and Na2LiAlH6. The coupled predictive methodologies were used to survey over 200 proposed phases in six quaternary spaces, formed from various combinations of Na, Li Mg and/or Ti with Al and H. A wide range of alanate compounds was examined using SSP having additions of Ti, Cr, Co, Ni and Fe. A number of compositions and reaction paths were identified having H weight fractions up to 5.6 wt %, but none meeting the 7.5 wt%H reversible goal. Similarly, MSP of alanates produced a number of interesting compounds and general conclusions regarding reaction behavior of mixtures during processing, but no alanate based candidates meeting the 7.5 wt% goal. A novel alanate, LiMg(AlH4)3, was synthesized using SBP that demonstrated a 7.0 wt% capacity with a desorption temperature of 150°C. The deuteride form was synthesized and characterized by the Institute for Energy (IFE) in Norway to determine its crystalline structure for related FPM studies. However, the reaction exhibited exothermicity and therefore was not reversible under acceptable hydrogen gas pressures for on-board recharging. After the extensive studies of alanates, the material class of emphasis was shifted to borohydrides. Through SBP, several ligand-stabilized Mg(BH4)2 complexes were synthesized. The Mg(BH4)2*2NH3 complex was found to change behavior with slightly different synthesis conditions and/or aging. One of the two mechanisms was an amine-borane (NH3BH3) like dissociation reaction which released up to 16 wt %H and more conservatively 9 wt%H when not including H2 released from the NH3. From FPM, the stability of the Mg(BH4

  10. Concerted proton-coupled electron transfer from a metal-hydride complex.

    Science.gov (United States)

    Bourrez, Marc; Steinmetz, Romain; Ott, Sascha; Gloaguen, Frederic; Hammarström, Leif

    2014-02-01

    Metal hydrides are key intermediates in the catalytic reduction of protons and CO2 as well as in the oxidation of H2. In these reactions, electrons and protons are transferred to or from separate acceptors or donors in bidirectional protoncoupled electron transfer (PCET) steps. The mechanistic interpretation of PCET reactions of metal hydrides has focused on the stepwise transfer of electrons and protons. A concerted transfer may, however, occur with a lower reaction barrier and therefore proceed at higher catalytic rates. Here we investigate the feasibility of such a reaction by studying the oxidation–deprotonation reactions of a tungsten hydride complex. The rate dependence on the driving force for both electron transfer and proton transfer—employing different combinations of oxidants and bases—was used to establish experimentally the concerted, bidirectional PCET of a metal-hydride species. Consideration of the findings presented here in future catalyst designs may lead to more-efficient catalysts.

  11. Energetics and Dynamics of the Fragmentation Reactions of Protonated Peptides Containing Methionine Sulfoxide or Aspartic Acid via Energy- and Time-Resolved Surface Induced Dissociation

    Energy Technology Data Exchange (ETDEWEB)

    Lioe, Hadi; Laskin, Julia; Reid, Gavin E.; O' Hair, Richard Aj

    2007-10-25

    The surface-induced dissociation (SID) of six model peptides containing either methionine sulfoxide or aspartic acid (GAILM(O)GAILR, GAILM(O)GAILK, GAILM(O)GAILA, GAILDGAILR, GAILDGAILK, and GAILDGAILA) have been studied using a specially configured Fourier transform ion-cyclotron resonance mass spectrometer (FT-ICR MS). In particular, we have investigated the energetics and dynamics associated with (i) preferential cleavage of the methionine sulfoxide side chain via the loss of CH3SOH (64Da), and (ii) preferential cleavage of the amide bond C-terminal to aspartic acid. The role of proton mobility on these selective bond cleavage reactions was examined by changing the C-terminal residue of the peptide from arginine (non-mobile proton conditions) to lysine (partially-mobile proton conditions) to alanine (mobile proton conditions). Time- and energy-resolved fragmentation efficiency curves (TFEC) reveals that selective cleavages due to the methionine sulfoxide and aspartic acid residues are characterized by slow fragmentation kinetics. RRKM modeling of the experimental data suggests that the slow kinetics is associated with large negative entropy effects and these may be due to the presence of rearrangements prior to fragmentation. It was found that the Arrhenius pre-exponential factor (A) for peptide fragmentations occurring via selective bond cleavages are 1–2 orders of magnitude lower than non-selective peptide fragmentation reactions, while the dissociation threshold (E0) is relatively invariant. This means that selective bond cleavage is kinetically disfavored compared to non-selective amide bond cleavage. It was also found that the energetics and dynamics for the preferential loss of CH3SOH from peptide ions containing methionine sulfoxide are very similar to selective C-terminal amide bond cleavage at the aspartic acid residue. These results suggest that while preferential cleavage can compete with amide bond cleavage energetically, dynamically, these

  12. Optimization of o-phtaldialdehyde/2-mercaptoethanol postcolumn reaction for the hydrophilic interaction liquid chromatography determination of memantine utilizing a silica hydride stationary phase.

    Science.gov (United States)

    Douša, Michal; Pivoňková, Veronika; Sýkora, David

    2016-08-01

    A rapid procedure for the determination of memantine based on hydrophilic interaction chromatography with fluorescence detection was developed. Fluorescence detection after postcolumn derivatization with o-phtaldialdehyde/2-mercaptoethanol was performed at excitation and emission wavelengths of 345 and 450 nm, respectively. The postcolumn reaction conditions such as reaction temperature, derivatization reagent flow rate, and reagents concentration were studied due to steric hindrance of amino group of memantine. The derivatization reaction was applied for the hydrophilic interaction liquid chromatography method which was based on Cogent Silica-C stationary phase with a mobile phase consisting of a mixture of 10 mmol/L citric acid and 10 mmol/L o-phosphoric acid (pH 6.0) with acetonitrile using an isocratic composition of 2:8 v/v. The benefit of the reported approach consists in a simple sample pretreatment and a quick and sensitive hydrophilic interaction chromatography method. The developed method was validated in terms of linearity, accuracy, precision, and selectivity according to the International Conference on Harmonisation guidelines. The developed method was successfully applied for the analysis of commercial memantine tablets.

  13. Chemical Hydride Slurry for Hydrogen Production and Storage

    Energy Technology Data Exchange (ETDEWEB)

    McClaine, Andrew W

    2008-09-30

    The purpose of this project was to investigate and evaluate the attractiveness of using a magnesium chemical hydride slurry as a hydrogen storage, delivery, and production medium for automobiles. To fully evaluate the potential for magnesium hydride slurry to act as a carrier of hydrogen, potential slurry compositions, potential hydrogen release techniques, and the processes (and their costs) that will be used to recycle the byproducts back to a high hydrogen content slurry were evaluated. A 75% MgH2 slurry was demonstrated, which was just short of the 76% goal. This slurry is pumpable and storable for months at a time at room temperature and pressure conditions and it has the consistency of paint. Two techniques were demonstrated for reacting the slurry with water to release hydrogen. The first technique was a continuous mixing process that was tested for several hours at a time and demonstrated operation without external heat addition. Further work will be required to reduce this design to a reliable, robust system. The second technique was a semi-continuous process. It was demonstrated on a 2 kWh scale. This system operated continuously and reliably for hours at a time, including starts and stops. This process could be readily reduced to practice for commercial applications. The processes and costs associated with recycling the byproducts of the water/slurry reaction were also evaluated. This included recovering and recycling the oils of the slurry, reforming the magnesium hydroxide and magnesium oxide byproduct to magnesium metal, hydriding the magnesium metal with hydrogen to form magnesium hydride, and preparing the slurry. We found that the SOM process, under development by Boston University, offers the lowest cost alternative for producing and recycling the slurry. Using the H2A framework, a total cost of production, delivery, and distribution of $4.50/kg of hydrogen delivered or $4.50/gge was determined. Experiments performed at Boston

  14. Functions of MgH2 in hydrogen storage reactions of the 6LiBH4-CaH2 reactive hydride composite.

    Science.gov (United States)

    Zhou, Yifan; Liu, Yongfeng; Zhang, Yu; Gao, Mingxia; Pan, Hongge

    2012-08-28

    A significant improvement of hydrogen storage properties was achieved by introducing MgH(2) into the 6LiBH(4)-CaH(2) system. It was found that ~8.0 wt% of hydrogen could be reversibly stored in a 6LiBH(4)-CaH(2)-3MgH(2) composite below 400 °C and 100 bar of hydrogen pressure with a stepwise reaction, which is superior to the pristine 6LiBH(4)-CaH(2) and LiBH(4) samples. Upon dehydriding, MgH(2) first decomposed to convert to Mg and liberate hydrogen with an on-set temperature of ~290 °C. Subsequently, LiBH(4) reacted with CaH(2) to form CaB(6) and LiH in addition to further hydrogen release. Hydrogen desorption from the 6LiBH(4)-CaH(2)-3MgH(2) composite finished at ~430 °C in non-isothermal model, a 160 °C reduction relative to the 6LiBH(4)-CaH(2) sample. JMA analyses revealed that hydrogen desorption was a diffusion-controlled reaction rather than an interface reaction-controlled process. The newly produced Mg of the first-step dehydrogenation possibly acts as the heterogeneous nucleation center of the resultant products of the second-step dehydrogenation, which diminishes the energy barrier and facilitates nucleation and growth, consequently reducing the operating temperature and improving the kinetics of hydrogen storage.

  15. Superior catalytic activity derived from a two-dimensional Ti3C2 precursor towards the hydrogen storage reaction of magnesium hydride.

    Science.gov (United States)

    Liu, Yongfeng; Du, Hufei; Zhang, Xin; Yang, Yaxiong; Gao, Mingxia; Pan, Hongge

    2016-01-14

    The superior catalytic effects derived from a 2D Ti3C2 (MXene), synthesized by the exfoliation of Ti3AlC2 powders, towards the hydrogen storage reaction of MgH2 were demonstrated. The 5 wt% Ti3C2-containing MgH2 releases 6.2 wt% H2 within 1 min at 300 °C and absorbs 6.1 wt% H2 within 30 s at 150 °C, exhibiting excellent dehydrogenation/hydrogenation kinetics.

  16. Activation of the SN2 Reaction by Adjacent π Systems: The Critical Role of Electrostatic Interactions and of Dissociative Character.

    Science.gov (United States)

    Robiette, Raphaël; Trieu-Van, Tran; Aggarwal, Varinder K; Harvey, Jeremy N

    2016-01-27

    The activation of the SN2 reaction by π systems is well documented in textbooks. It has been shown previously that this is not primarily due to classical (hyper)conjugative effects. Instead, π-conjugated substituents enhance favorable substrate-nucleophile electrostatic interactions, with electron-withdrawing groups (EWG) on the sp(2) system leading to even stronger activation. Herein we report computational and experimental results which show that this activation by sp(2) EWG-substitution only occurs in a fairly limited number of cases, when the nucleophile involves strong electrostatic interactions (usually strongly basic negatively charged nucleophiles). In other cases, where bond breaking is more advanced than bond making at the transition state, electrophile-nucleophile electrostatic interactions are less important. In such cases, (hyper)conjugative electronic effects determine the reactivity, and EWG-substitution leads to decreased reactivity. The basicity of the nucleophile as well as solvent effects can help to determine which of these two regimes occurs for a given electrophile.

  17. Experimental comparison on heat transfer-enhancing component of metal hydride bed

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Hyun-goo, E-mail: hgkang@nfri.re.kr; Chung, Dong-you; Oh, Yun Hee; Chang, Min Ho; Yun, Sei-Hun

    2016-11-01

    Highlights: • Two small ZrCo metal hydride beds were developed. • Copper foam or fin as heat transfer-enhancing component are experimentally compared. • Copper foam bed is more efficient for uniform and rapid heating of metal hydride. • Copper foam bed is more efficient in removal of reaction heat during absorption. - Abstract: Metal hydride bed will be one of the key components for safe handling of tritium in fusion fuel cycle. In case of normal or emergency shutdown of fuel cycle, metal hydride bed installed in storage and delivery system (SDS) of tritium plant will absorb tritium gas in the system as soon as possible. Supply of hydrogen isotope gas to fueling system of fusion reactor will start from the metal hydride beds. Rapid delivery, rapid recovery including rapid heating and cooling are key issues. For better performance of metal hydride bed, various forms of heat transfer enhancing component or design can be applied. This study aims to help the selection of heat transfer enhancing component. Two small ZrCo beds with copper foam and copper fin were developed and experimented with hydrogen gas. Recovery and delivery performance, heating and cooling performance are compared. Experimental results show metal hydride bed with copper foam has improved performance. Uniform heating of metal hydride during desorption and removal of reaction heat during absorption are more efficient with copper foam bed than copper fin bed.

  18. Anomalously High Isotope Ratio 3He/4He and Tritium in Deuterium-Loaded Metal: Evidence for Nuclear Reaction in Metal Hydrides at Low Temperature

    Institute of Scientific and Technical Information of China (English)

    JIANG Song-Sheng; HE Ming; WU Shao-Yong; QI Bu-Jia

    2012-01-01

    Anomalous 3He/4He ratios in deuterium-loaded titanium samples are observed to be about 1-4x10-1, much greater than the values (<10~4) in natural objects. Control experiments with the deuterium-unloaded titanium sample and original industrial deuterium gas are also carried out, but no anomalous 3He/4He values are observed. In addition, anomalous tritium in deuterium-loaded titanium samples are also observed. To explain the excess 3He and tritium in the deuterium-loaded titanium samples, it is required that the deuteron-induced nuclear reaction occurs in the samples at low temperature.%Anomalous 3He/4He ratios in deuterium-loaded titanium samples are observed to be about 1-4×10-1,much greater than the values (≤10-4) in natural objects.Control experiments with the deuterium-unloaded titanium sample and original industrial deuterium gas are also carried out,but no anomalous 3He/4He values are observed.In addition,anomalous tritium in deuterium-loaded titanium samples are also observed.To explain the excess 3He and tritium in the deuterium-loaded titanium samples,it is required that the deuteron-induced nuclear reaction occurs in the samples at low temperature.

  19. Charmonium dissociation cross sections and charmonium dissociation rates in hadronic matter

    CERN Document Server

    Liu, Feng-Rong; Xu, Xiao-Ming

    2016-01-01

    K*-charmonium dissociation reactions in hadronic matter are studied in the Born approximation, in the quark-interchange mechanism, and with a temperature-dependent quark potential. We obtain the temperature dependence of unpolarized cross sections for K*-charmonium dissociation reactions which produce charmed mesons and charmed strange mesons. We use the cross sections for charmonium dissociation in collisions with pion, rho meson, kaon, vector kaon, and eta meson to calculate dissociation rates of charmonium with the five types of mesons. Because of the temperature dependence of the meson masses, dissociation cross sections, and meson distribution functions, the charmonium dissociation rates generally increase with the increase of temperature and decrease with the increase of charmonium momentum from 2.2 GeV/c. We find that the first derivative of the dissociation rate with respect to the charmonium momentum is zero when the charmonium is at rest. While the eta + psi' and eta + chi_c dissociation reactions c...

  20. Novel Evidence for a Reversible Dissociation of Light-harvesting Complex Ⅱ from Photosystem Ⅱ Reaction Center Complex Induced by Saturating Light Illumination in Soybean Leaves

    Institute of Scientific and Technical Information of China (English)

    Yi Liao; Da-Quan Xu

    2007-01-01

    After saturating light illumination for 3 h the potential photochemical efficiency of photosystem Ⅱ (PSⅡ) (Fv/Fm, the ratio of variable to maximal fluorescence) decreased markedly and recovered basically to the level before saturating light illumination after dark recovery for 3 h in both soybean and wheat leaves, indicating that the decline in Fv/Fm is a reversible down-regulation. Also, the saturating light illumination led to significant decreases in the low temperature (77 K) chlorophyll fluorescence parameters F685 (chlorophyll a fluorescence peaked at 685 nm ) and F685/F735 (F735, chlorophyll a fluorescence peaked at 735 nm) in soybean leaves but not in wheat leaves. Moreover,trypsin (a protease) treatment resulted in a remarkable decrease in the amounts of PsbS protein (a nuclear gene psbS-encoded 22 kDa protein) in the thylakoids from saturating light-illuminated (SI), but not in those from darkadapted (DT) and dark-recovered (DRT) soybean leaves. However, the treatment did not cause such a decrease in amounts of the PsbS protein in the thylakoids from saturating light-illuminated wheat leaves. These results support the conclusion that saturating light illumination induces a reversible dissociation of some light-harvesting complex Ⅱ (LHCⅡ) from PSⅡ reaction center complex in soybean leaf but not in wheat leaf.

  1. Well-defined transition metal hydrides in catalytic isomerizations.

    Science.gov (United States)

    Larionov, Evgeny; Li, Houhua; Mazet, Clément

    2014-09-07

    This Feature Article intends to provide an overview of a variety of catalytic isomerization reactions that have been performed using well-defined transition metal hydride precatalysts. A particular emphasis is placed on the underlying mechanistic features of the transformations discussed. These have been categorized depending upon the nature of the substrate and in most cases discussed following a chronological order.

  2. Metal Hydride Compression

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Terry A. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Bowman, Robert [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Smith, Barton [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Anovitz, Lawrence [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Jensen, Craig [Hawaii Hydrogen Carriers LLC, Honolulu, HI (United States)

    2017-07-01

    Conventional hydrogen compressors often contribute over half of the cost of hydrogen stations, have poor reliability, and have insufficient flow rates for a mature FCEV market. Fatigue associated with their moving parts including cracking of diaphragms and failure of seal leads to failure in conventional compressors, which is exacerbated by the repeated starts and stops expected at fueling stations. Furthermore, the conventional lubrication of these compressors with oil is generally unacceptable at fueling stations due to potential fuel contamination. Metal hydride (MH) technology offers a very good alternative to both conventional (mechanical) and newly developed (electrochemical, ionic liquid pistons) methods of hydrogen compression. Advantages of MH compression include simplicity in design and operation, absence of moving parts, compactness, safety and reliability, and the possibility to utilize waste industrial heat to power the compressor. Beyond conventional H2 supplies of pipelines or tanker trucks, another attractive scenario is the on-site generating, pressuring and delivering pure H2 at pressure (≥ 875 bar) for refueling vehicles at electrolysis, wind, or solar generating production facilities in distributed locations that are too remote or widely distributed for cost effective bulk transport. MH hydrogen compression utilizes a reversible heat-driven interaction of a hydride-forming metal alloy with hydrogen gas to form the MH phase and is a promising process for hydrogen energy applications [1,2]. To deliver hydrogen continuously, each stage of the compressor must consist of multiple MH beds with synchronized hydrogenation & dehydrogenation cycles. Multistage pressurization allows achievement of greater compression ratios using reduced temperature swings compared to single stage compressors. The objectives of this project are to investigate and demonstrate on a laboratory scale a two-stage MH hydrogen (H2) gas compressor with a

  3. Metal hydrides for lithium-ion batteries.

    Science.gov (United States)

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

    2008-11-01

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

  4. Low-Cost Metal Hydride Thermal Energy Storage System for Concentrating Solar Power Systems

    Energy Technology Data Exchange (ETDEWEB)

    Zidan, Ragaiy [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Hardy, B. J. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Corgnale, C. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Teprovich, J. A. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Ward, P. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Motyka, Ted [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2016-01-31

    The objective of this research was to evaluate and demonstrate a metal hydride-based TES system for use with a CSP system. A unique approach has been applied to this project that combines our modeling experience with the extensive material knowledge and expertise at both SRNL and Curtin University (CU). Because of their high energy capacity and reasonable kinetics many metal hydride systems can be charged rapidly. Metal hydrides for vehicle applications have demonstrated charging rates in minutes and tens of minutes as opposed to hours. This coupled with high heat of reaction allows metal hydride TES systems to produce very high thermal power rates (approx. 1kW per 6-8 kg of material). A major objective of this work is to evaluate some of the new metal hydride materials that have recently become available. A problem with metal hydride TES systems in the past has been selecting a suitable high capacity low temperature metal hydride material to pair with the high temperature material. A unique aspect of metal hydride TES systems is that many of these systems can be located on or near dish/engine collectors due to their high thermal capacity and small size. The primary objective of this work is to develop a high enthalpy metal hydride that is capable of reversibly storing hydrogen at high temperatures (> 650 °C) and that can be paired with a suitable low enthalpy metal hydride with low cost materials. Furthermore, a demonstration of hydrogen cycling between the two hydride beds is desired.

  5. Single-Site Tetracoordinated Aluminum Hydride Supported on Mesoporous Silica. From Dream to Reality!

    KAUST Repository

    Werghi, Baraa

    2016-09-26

    The reaction of mesoporous silica (SBA15) dehydroxylated at 700 °C with diisobutylaluminum hydride, i-Bu2AlH, gives after thermal treatment a single-site tetrahedral aluminum hydride with high selectivity. The starting aluminum isobutyl and the final aluminum hydride have been fully characterized by FT-IR, advanced SS NMR spectroscopy (1H, 13C, multiple quanta (MQ) 2D 1H-1H, and 27Al), and elemental analysis, while DFT calculations provide a rationalization of the occurring reactivity. Trimeric i-Bu2AlH reacts selectively with surface silanols without affecting the siloxane bridges. Its analogous hydride catalyzes ethylene polymerization. Indeed, catalytic tests show that this single aluminum hydride site is active in the production of a high-density polyethylene (HDPE). © 2016 American Chemical Society.

  6. A study of advanced magnesium-based hydride and development of a metal hydride thermal battery system

    Science.gov (United States)

    Zhou, Chengshang

    Metal hydrides are a group of important materials known as energy carriers for renewable energy and thermal energy storage. A concept of thermal battery based on advanced metal hydrides is studied for heating and cooling of cabins in electric vehicles. The system utilizes a pair of thermodynamically matched metal hydrides as energy storage media. The hot hydride that is identified and developed is catalyzed MgH2 due to its high energy density and enhanced kinetics. TiV0.62Mn1.5, TiMn2, and LaNi5 alloys are selected as the matching cold hydride. A systematic experimental survey is carried out in this study to compare a wide range of additives including transitions metals, transition metal oxides, hydrides, intermetallic compounds, and carbon materials, with respect to their effects on dehydrogenation properties of MgH2. The results show that additives such as Ti and V-based metals, hydride, and certain intermetallic compounds have strong catalytic effects. Solid solution alloys of magnesium are exploited as a way to destabilize magnesium hydride thermodynamically. Various elements are alloyed with magnesium to form solid solutions, including indium and aluminum. Thermodynamic properties of the reactions between the magnesium solid solution alloys and hydrogen are investigated, showing that all the solid solution alloys that are investigated in this work have higher equilibrium hydrogen pressures than that of pure magnesium. Cyclic stability of catalyzed MgH2 is characterized and analyzed using a PCT Sievert-type apparatus. Three systems, including MgH2-TiH 2, MgH2-TiMn2, and MgH2-VTiCr, are examined. The hydrogenating and dehydrogenating kinetics at 300°C are stable after 100 cycles. However, the low temperature (25°C to 150°C) hydrogenation kinetics suffer a severe degradation during hydrogen cycling. Further experiments confirm that the low temperature kinetic degradation can be mainly related the extended hydrogenation-dehydrogenation reactions. Proof

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

    Science.gov (United States)

    Sun, Han-Wen; Suo, Ran

    2008-11-01

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

  8. Erbium hydride decomposition kinetics.

    Energy Technology Data Exchange (ETDEWEB)

    Ferrizz, Robert Matthew

    2006-11-01

    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.

  9. Hydride development for hydrogen storage

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, G.J.; Guthrie, S.E.; Bauer, W.; Yang, N.Y.C. [Sandia National Lab., Livermore, CA (United States); Sandrock, G. [SunaTech, Inc., Ringwood, NJ (United States)

    1996-10-01

    The purpose of this project is to develop and demonstrate improved hydride materials for hydrogen storage. The work currently is organized into four tasks: hydride development, bed fabrication, materials support for engineering systems, and IEA Annex 12 activities. At the present time, hydride development is focused on Mg alloys. These materials generally have higher weight densities for storing hydrogen than rare earth or transition metal alloys, but suffer from high operating temperatures, slow kinetic behavior and material stability. The authors approach is to study bulk alloy additions which increase equilibrium overpressure, in combination with stable surface alloy modification and particle size control to improve kinetic properties. This work attempts to build on the considerable previous research in this area, but examines specific alloy systems in greater detail, with attention to known phase properties and structures. The authors have found that specific phases can be produced which have significantly improved hydride properties compared to previous studies.

  10. Metal hydride air conditioner

    Institute of Scientific and Technical Information of China (English)

    YANG; Ke; DU; Ping; LU; Man-qi

    2005-01-01

    The relationship among the hydrogen storage properties, cycling characteristics and thermal parameters of the metal hydride air conditioning systems was investigated. Based on a new alloy selection model, three pairs of hydrogen storage alloys, LaNi4.4 Mn0.26 Al0.34 / La0.6 Nd0.4 Ni4.8 Mn0.2 Cu0. 1, LaNi4.61Mn0. 26 Al0.13/La0.6 Nd0.4 Ni4.8 Mn0.2 Cu0. 1 and LaNi4.61 Mn0.26 Al0.13/La0.6 Y0.4 Ni4.8 Mn0. 2, were selected as the working materials for the metal hydride air conditioning system. Studies on the factors affecting the COP of the system showed that higher COP and available hydrogen content need the proper operating temperature and cycling time,large hydrogen storage capacity, flat plateau and small hysterisis of hydrogen alloys, proper original input hydrogen content and mass ratio of the pair of alloys. It also needs small conditioning system was established by using LaNi4.61 Mn0.26 Al0. 13/La0.6 Y0.4 Ni4.8 Mn0.2 alloys as the working materials, which showed that under the operating temperature of 180℃/40℃, a low temperature of 13℃ was reached, with COP =0.38 and Wnet =0.09 kW/kg.

  11. Geoneutrino and Hydridic Earth model

    CERN Document Server

    Bezrukov, Leonid

    2013-01-01

    Uranium, Thorium and Potassium-40 abundances in the Earth were calculated in the frame of Hydridic Earth model. Terrestrial heat producton from U, Th and K40 decays was calculated also. We must admit the existance of Earth expansion process to understand the obtained large value of terrestrial heat producton. The geoneutrino detector with volume more than 5 kT (LENA type) must be constructed to definitely separate between Bulk Silicat Earth model and Hydridic Earth model.

  12. Iron Hydride Detection and Intramolecular Hydride Transfer in a Synthetic Model of Mono-Iron Hydrogenase with a CNS Chelate.

    Science.gov (United States)

    Durgaprasad, Gummadi; Xie, Zhu-Lin; Rose, Michael J

    2016-01-19

    We report the identification and reactivity of an iron hydride species in a synthetic model complex of monoiron hydrogenase. The hydride complex is derived from a phosphine-free CNS chelate that includes a Fe-C(NH)(═O) bond (carbamoyl) as a mimic of the active site iron acyl. The reaction of [((O═)C(HN)N(py)S(Me))Fe(CO)2(Br)] (1) with NaHBEt3 generates the iron hydride intermediate [((O═)C(HN)N(py)S(Me))Fe(H)(CO)2] (2; δFe-H = -5.08 ppm). Above -40 °C, the hydride species extrudes CH3S(-) via intramolecular hydride transfer, which is stoichiometrically trapped in the structurally characterized dimer μ2-(CH3S)2-[((O═)C(HN)N(Ph))Fe(CO)2]2 (3). Alternately, when activated by base ((t)BuOK), 1 undergoes desulfurization to form a cyclometalated species, [((O═)C(NH)NC(Ph))Fe(CO)2] (5); derivatization of 5 with PPh3 affords the structurally characterized species [((O═)C(NH)NC)Fe(CO)(PPh3)2] (6), indicating complex 6 as the common intermediate along each pathway of desulfurization.

  13. First-principles study of superabundant vacancy formation in metal hydrides.

    Science.gov (United States)

    Zhang, Changjun; Alavi, Ali

    2005-07-13

    Recent experiments have established the generality of superabundant vacancies (SAV) formation in metal hydrides. Aiming to elucidate this intriguing phenomenon and to clarify previous interpretations, we employ density-functional theory to investigate atomic mechanisms of SAV formation in fcc hydrides of Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au. We have found that upon H insertion, vacancy formation energies reduce substantially. This is consistent with experimental suggestions. We demonstrate that the entropy effect, which has been proposed to explain SAV formation, is not the main cause. Instead, it is the drastic change of electronic structure induced by the H in the SAV hydrides, which is to a large extent responsible. Interesting trends in systems investigated are also found: ideal hydrides of 5d metals and noble metals are unstable compared to the corresponding pure metals, but the SAV hydrides are more stable than the corresponding ideal hydrides, whereas opposite results exist in the cases of Ni, Rh, and Pd. These trends of stabilities of the SAV hydrides are discussed in detail and a general understanding for SAV formation is provided. Finally, we propose an alternative reaction pathway to generate a SAV hydride from a metal alloy.

  14. Síntese de 2-iodobenzamidas e 3-(iodoacetamidobenzamidas ligadas à D-galactose e suas reações de carbociclização radicalar mediadas por hidreto de tri-n-butilestanho Synthesis of 2-iodobenzamides and 3-(iodoacetamidobenzamides linked to D-galactose and their tri-n-butyltin hydride-mediated radical carbocyclization reactions

    Directory of Open Access Journals (Sweden)

    Daniel Henriques Soares Leal

    2009-01-01

    Full Text Available Starting from methyl 6-O-allyl-4-azido-2,3-di-O-benzyl-4-deoxy-α-D-galactopyranoside, four new derivatives containing 2-iodobenzamido and 3-(iodoacetamidobenzamido groups were synthesized. These four compounds were submitted to tri-n-butyltin hydride mediated radical cyclization reactions, resulting in two macrolactams from 11- and 15-endo aryl radical cyclization. The corresponding four hydrogenolysis products were also obtained. The structures of the new compounds were elucidated by ¹H and 13C NMR spectroscopy, DEPT, COSY, HMQC and HMBC experiments.

  15. Dissociated Steroids

    Directory of Open Access Journals (Sweden)

    Matthew C. Catley

    2007-01-01

    Full Text Available Glucocorticoids (GCs are some of the most important drugs in clinical use today. They are mainly used to suppress disease-related inflammation and are widely used for the treatment of many inflammatory diseases including asthma and arthritis. However, GCs are also associated with debilitating side effects that place limitations on the long-term use of these drugs. The development of a GC with reduced side effects would allow more effective treatments for patients who require long-term suppression of inflammation. GCs exert their effects by binding and activating the GC receptor (GR. The activated receptor then binds GC response elements (GREs in the promoter of genes, and activates transcription (transactivation or interferes with the activation of transcription by inhibiting the transactivating function of other transcription factors, such as AP-1 and NF-ĸB (transrepression. Transrepression is believed to be responsible for the majority of the beneficial anti-inflammatory effects of GCs, whereas transactivation is believed to play a bigger role in the unwanted side effects of GCs. Compounds that can dissociate the transactivation function of GCs from the transrepression function may, therefore, have an improved therapeutic index. A number of these dissociated corticosteroids have been developed. In vitro assays using these compounds appear to show good dissociation. However, in vivo, the dissociation appears to be lost and these compounds still produce many of the side effects associated with conventional GCs. A better understanding of the molecular mechanisms behind GC-induced effects would allow the design of novel selective GR modulators with an improved therapeutic index.

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

    Science.gov (United States)

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

    2014-02-28

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

  17. Physics of hydride fueled PWR

    Science.gov (United States)

    Ganda, Francesco

    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.

  18. Insertion of Group 12-16 Hydrides into NHCs: A Theoretical Investigation.

    Science.gov (United States)

    Iversen, Kalon J; Dutton, Jason L; Wilson, David

    2017-03-06

    The endocyclic ring expansion of N-heterocyclic carbene (NHC) rings by transition metal (Group 12) and main group (Group 13-16) element hydrides has been investigated in a computational study. In addition to previously reported insertion reactivity with Si, B, Be and Zn, similar reactivity is predicted to be feasible for heavier group 13 elements (Al, Ga, In, Tl), with the reaction barriers for Al-Tl calculated to be lower than for boron. Insertion is not expected with group 15-16 element hydrides, as the initial adduct formation is thermodynamically unfavourable. The reaction pathway with group 12 hydrides is calculated to be more favourable with two NHCs rather than a single NHC (analogous to Be), however hydride ring insertion with metal dihydrides is not feasible, but rather a reduced NHC is thermodynamically favoured. For group 14, ring-insertion reactivity is predicted to be feasible with the heavier dihydrides. Trends in reactivity of element hydrides may be related to the protic or hydridic character of the element hydrides.

  19. Hydride Olefin complexes of tantalum and niobium

    NARCIS (Netherlands)

    Klazinga, Aan Hendrik

    1979-01-01

    This thesis describes investigations on low-valent tantalum and niobium hydride and alkyl complexes, particularly the dicyclopentadienyl tantalum hydride olefin complexes Cp2Ta(H)L (L=olefin). ... Zie: Summary

  20. Complex and liquid hydrides for energy storage

    Energy Technology Data Exchange (ETDEWEB)

    Callini, Elsa; Atakli, Zuleyha Özlem Kocabas; Hauback, Bjørn C.; Orimo, Shin-ichi; Jensen, Craig; Dornheim, Martin; Grant, David; Cho, Young Whan; Chen, Ping; Hjörvarsson, Bjørgvin; de Jongh, Petra; Weidenthaler, Claudia; Baricco, Marcello; Paskevicius, Mark; Jensen, Torben R.; Bowden, Mark E.; Autrey, Thomas S.; Züttel, Andreas

    2016-03-10

    The research on complex hydrides for hydrogen storage was imitated by the discovery of Ti as a hydrogen sorption catalyst in NaAlH4 by Boris Bogdanovic in 1996. A large number of new complex hydride materials in various forms and combinations have been synthesized and characterized and the knowledge on the properties of complex hydrides and the synthesis methods has grown enormously since then. A significant part of the research groups active in the field of complex hydrides are collaborators in the IEA task 32. This paper reports about the important issues in the field of the complex hydride research, i.e. the synthesis of borohydrides, the thermodynamics of complex hydrides and their thermodynamic properties, the effects of size and confinement, the hydrogen sorption mechanism and the complex hydride composites as well as the properties of liquid complex hydrides. This paper is the result of the collaboration of several groups and excellent summary of the recent achievements.

  1. On the chemistry of hydrides of N atoms and O$^+$ ions

    CERN Document Server

    Awad, Zainab; Williams, David A

    2016-01-01

    Previous work by various authors has suggested that the detection by Herschel/HIFI of nitrogen hydrides along the low density lines of sight towards G10.6-0.4 (W31C) cannot be accounted for by gas-phase chemical models. In this paper we investigate the role of surface reactions on dust grains in diffuse regions, and we find that formation of the hydrides by surface reactions on dust grains with efficiency comparable to that for H$_2$ formation reconciles models with observations of nitrogen hydrides. However, similar surface reactions do not contribute significantly to the hydrides of O$^+$ ions detected by Herschel/HIFI present along many sight lines in the Galaxy. The O$^+$ hydrides can be accounted for by conventional gas-phase chemistry either in diffuse clouds of very low density with normal cosmic ray fluxes or in somewhat denser diffuse clouds with high cosmic ray fluxes. Hydride chemistry in dense dark clouds appears to be dominated by gas-phase ion-molecule reactions.

  2. Luminescent properties of aluminum hydride

    Energy Technology Data Exchange (ETDEWEB)

    Baraban, A.P.; Gabis, I.E.; Dmitriev, V.A. [Saint-Petersburg State University, Department of Physics, Saint-Petersburg 198504 (Russian Federation); Dobrotvorskii, M.A., E-mail: mstislavd@gmail.com [Saint-Petersburg State University, Department of Physics, Saint-Petersburg 198504 (Russian Federation); Kuznetsov, V.G. [Saint-Petersburg State University, Department of Physics, Saint-Petersburg 198504 (Russian Federation); Matveeva, O.P. [National Mineral Resources University, Saint Petersburg 199106 (Russian Federation); Titov, S.A. [Petersburg State University of Railway Transport, Saint-Petersburg 190031 (Russian Federation); Voyt, A.P.; Elets, D.I. [Saint-Petersburg State University, Department of Physics, Saint-Petersburg 198504 (Russian Federation)

    2015-10-15

    We studied cathodoluminescence and photoluminescence of α-AlH{sub 3}– a likely candidate for use as possible hydrogen carrier in hydrogen-fueled vehicles. Luminescence properties of original α-AlH{sub 3} and α-AlH{sub 3} irradiated with ultraviolet were compared. The latter procedure leads to activation of thermal decomposition of α-AlH{sub 3} and thus has a practical implementation. We showed that the original and UV-modified aluminum hydride contain luminescence centers ‐ structural defects of the same type, presumably hydrogen vacancies, characterized by a single set of characteristic bands of radiation. The observed luminescence is the result of radiative intracenter relaxation of the luminescence center (hydrogen vacancy) excited by electrons or photons, and its intensity is defined by the concentration of vacancies, and the area of their possible excitation. UV-activation of the dehydrogenation process of aluminum hydride leads to changes in the spatial distribution of the luminescence centers. For short times of exposure their concentration increases mainly in the surface regions of the crystals. At high exposures, this process extends to the bulk of the aluminum hydride and ends with a decrease in concentration of luminescence centers in the surface region. - Highlights: • Aluminum hydride contains hydrogen vacancies which serve as luminescence centers. • The luminescence is the result of radiative relaxation of excited centers. • Hydride UV-irradiation alters distribution and concentration of luminescence centers.

  3. Method of producing a chemical hydride

    Science.gov (United States)

    Klingler, Kerry M.; Zollinger, William T.; Wilding, Bruce M.; Bingham, Dennis N.; Wendt, Kraig M.

    2007-11-13

    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.

  4. Hydrogen, lithium, and lithium hydride production

    Science.gov (United States)

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

    2014-03-25

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

  5. Chemical Hydride Slurry for Hydrogen Production and Storage

    Energy Technology Data Exchange (ETDEWEB)

    McClaine, Andrew W

    2008-09-30

    The purpose of this project was to investigate and evaluate the attractiveness of using a magnesium chemical hydride slurry as a hydrogen storage, delivery, and production medium for automobiles. To fully evaluate the potential for magnesium hydride slurry to act as a carrier of hydrogen, potential slurry compositions, potential hydrogen release techniques, and the processes (and their costs) that will be used to recycle the byproducts back to a high hydrogen content slurry were evaluated. A 75% MgH2 slurry was demonstrated, which was just short of the 76% goal. This slurry is pumpable and storable for months at a time at room temperature and pressure conditions and it has the consistency of paint. Two techniques were demonstrated for reacting the slurry with water to release hydrogen. The first technique was a continuous mixing process that was tested for several hours at a time and demonstrated operation without external heat addition. Further work will be required to reduce this design to a reliable, robust system. The second technique was a semi-continuous process. It was demonstrated on a 2 kWh scale. This system operated continuously and reliably for hours at a time, including starts and stops. This process could be readily reduced to practice for commercial applications. The processes and costs associated with recycling the byproducts of the water/slurry reaction were also evaluated. This included recovering and recycling the oils of the slurry, reforming the magnesium hydroxide and magnesium oxide byproduct to magnesium metal, hydriding the magnesium metal with hydrogen to form magnesium hydride, and preparing the slurry. We found that the SOM process, under development by Boston University, offers the lowest cost alternative for producing and recycling the slurry. Using the H2A framework, a total cost of production, delivery, and distribution of $4.50/kg of hydrogen delivered or $4.50/gge was determined. Experiments performed at Boston

  6. Photogeneration of Hydride Donors and Their Use Toward CO2 Reduction

    Energy Technology Data Exchange (ETDEWEB)

    Fujita,E.; Muckerman, J.T.; Polyansky, D.E.

    2009-06-07

    Despite substantial effort, no one has succeeded in efficiently producing methanol from CO2 using homogeneous photocatalytic systems. We are pursuing reaction schemes based on a sequence of hydride-ion transfers to carry out stepwise reduction of CO2 to methanol. We are using hydride-ion transfer from photoproduced C-H bonds in metal complexes with bio-inspired ligands (i.e., NADH-like ligands) that are known to store one proton and two electrons.

  7. Direct hydride derivatization of methyl- and ethylmercury chlorides in aqueous solution with KBH4

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A convenient hydride derivatization procedure of methyl-and ethylmercury chlorides to volatile hydrides was reported. In sealed vials methylmercury and ethylmercury compounds in acidic aqueous solutions were converted into their volatile forms by the reaction with potassium tetrahydroborate(KBH4) and elvolved to the headspace of the vials. The gaseous analytes in the headspace were extracted and concentrated by solid phase microextraction(SPME) and injected into gas chromatography (GC) for separation and identified by mass selective detector(MS).

  8. Investigation of metal hydride nanoparticles templated in metal organic frameworks.

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-11-01

    Hydrogen is proposed as an ideal carrier for storage, transport, and conversion of energy. However, its storage is a key problem in the development of hydrogen economy. Metal hydrides hold promise in effectively storing hydrogen. For this reason, metal hydrides have been the focus of intensive research. The chemical bonds in light metal hydrides are predominantly covalent, polar covalent or ionic. These bonds are often strong, resulting in high thermodynamic stability and low equilibrium hydrogen pressures. In addition, the directionality of the covalent/ionic bonds in these systems leads to large activation barriers for atomic motion, resulting in slow hydrogen sorption kinetics and limited reversibility. One method for enhancing reaction kinetics is to reduce the size of the metal hydrides to nano scale. This method exploits the short diffusion distances and constrained environment that exist in nanoscale hydride materials. In order to reduce the particle size of metal hydrides, mechanical ball milling is widely used. However, microscopic mechanisms responsible for the changes in kinetics resulting from ball milling are still being investigated. The objective of this work is to use metal organic frameworks (MOFs) as templates for the synthesis of nano-scale NaAlH4 particles, to measure the H2 desorption kinetics and thermodynamics, and to determine quantitative differences from corresponding bulk properties. Metal-organic frameworks (MOFs) offer an attractive alternative to traditional scaffolds because their ordered crystalline lattice provides a highly controlled and understandable environment. The present work demonstrates that MOFs are stable hosts for metal hydrides and their reactive precursors and that they can be used as templates to form metal hydride nanoclusters on the scale of their pores (1-2 nm). We find that using the MOF HKUST-1 as template, NaAlH4 nanoclusters as small as 8 formula units can be synthesized inside the pores. A detailed picture of

  9. Determination of thermodynamic affinities of various polar olefins as hydride, hydrogen atom, and electron acceptors in acetonitrile.

    Science.gov (United States)

    Cao, Ying; Zhang, Song-Chen; Zhang, Min; Shen, Guang-Bin; Zhu, Xiao-Qing

    2013-07-19

    A series of 69 polar olefins with various typical structures (X) were synthesized and the thermodynamic affinities (defined in terms of the molar enthalpy changes or the standard redox potentials in this work) of the polar olefins obtaining hydride anions, hydrogen atoms, and electrons, the thermodynamic affinities of the radical anions of the polar olefins (X(•-)) obtaining protons and hydrogen atoms, and the thermodynamic affinities of the hydrogen adducts of the polar olefins (XH(•)) obtaining electrons in acetonitrile were determined using titration calorimetry and electrochemical methods. The pure C═C π-bond heterolytic and homolytic dissociation energies of the polar olefins (X) in acetonitrile and the pure C═C π-bond homolytic dissociation energies of the radical anions of the polar olefins (X(•-)) in acetonitrile were estimated. The remote substituent effects on the six thermodynamic affinities of the polar olefins and their related reaction intermediates were examined using the Hammett linear free-energy relationships; the results show that the Hammett linear free-energy relationships all hold in the six chemical and electrochemical processes. The information disclosed in this work could not only supply a gap of the chemical thermodynamics of olefins as one class of very important organic unsaturated compounds but also strongly promote the fast development of the chemistry and applications of olefins.

  10. The Origin of the Catalytic Activity of a Metal Hydride in CO2 Reduction.

    Science.gov (United States)

    Kato, Shunsuke; Matam, Santhosh Kumar; Kerger, Philipp; Bernard, Laetitia; Battaglia, Corsin; Vogel, Dirk; Rohwerder, Michael; Züttel, Andreas

    2016-05-10

    Atomic hydrogen on the surface of a metal with high hydrogen solubility is of particular interest for the hydrogenation of carbon dioxide. In a mixture of hydrogen and carbon dioxide, methane was markedly formed on the metal hydride ZrCoHx in the course of the hydrogen desorption and not on the pristine intermetallic. The surface analysis was performed by means of time-of-flight secondary ion mass spectroscopy and near-ambient pressure X-ray photoelectron spectroscopy, for the in situ analysis. The aim was to elucidate the origin of the catalytic activity of the metal hydride. Since at the initial stage the dissociation of impinging hydrogen molecules is hindered by a high activation barrier of the oxidised surface, the atomic hydrogen flux from the metal hydride is crucial for the reduction of carbon dioxide and surface oxides at interfacial sites.

  11. Anodematerials for Metal Hydride Batteries

    DEFF Research Database (Denmark)

    Jensen, Jens Oluf

    1997-01-01

    This report describes the work on development of hydride forming alloys for use as electrode materials in metal hydride batteries. The work has primarily been concentrated on calcium based alloys derived from the compound CaNi5. This compound has a higher capacity compared with alloys used in today......’s hydride batteries, but a much poorer stability towards repeated charge/discharge cycling. The aim was to see if the cycleability of CaNi5 could be enhanced enough by modifications to make the compound a suitable electrode material. An alloying method based on mechanical alloying in a planetary ball mill...... by annealing at 700°C for 12 hours. The alloys appeared to be nanocrystalline with an average crystallite size around 10 nm before annealing. Special steel containers was developed for the annealing of the metal powders in inert atmosphere. The use of various annealing temperatures was investigated...

  12. Hydrogen Storage in Metal Hydrides

    Science.gov (United States)

    1990-08-01

    Hydrogen Storage Capacity Hydride by weight (%) [1) by volume (g/ml) [2] MgH2 7.00 0.101 Mg2NiH4 3.84 0,081 Mg2CuH4 2.04 - - 27 ...Include Security Classification) Hydrogen Storage in Metal Hydrides (U) 12. PERSONAL AUTHOR(S) DelaRosa, Mark J. 13a. TYPE OF REPORT 13b. TIME...objective of this program was to develop an economical process for pr-ducing a lightweight hydrogen storage medium by the chemical vapor infiltration

  13. Solvent influence on the thermodynamics for hydride transfer from bis(diphosphine) complexes of nickel.

    Science.gov (United States)

    Connelly Robinson, Samantha J; Zall, Christopher M; Miller, Deanna L; Linehan, John C; Appel, Aaron M

    2016-06-14

    The thermodynamic hydricity of a metal hydride can vary considerably between solvents. This parameter can be used to determine the favourability of a hydride-transfer reaction, such as the reaction between a metal hydride and CO2 to produce formate. Because the hydricities of these species do not vary consistently between solvents, reactions that are thermodynamically unfavourable in one solvent can be favourable in others. The hydricity of a water-soluble, bis-phosphine nickel hydride complex was compared to the hydricity of formate in water and in acetonitrile. Formate is a better hydride donor than [HNi(dmpe)2](+) by 7 kcal mol(-1) in acetonitrile, and no hydride transfer from [HNi(dmpe)2](+) to CO2 occurs in this solvent. The hydricity of [HNi(dmpe)2](+) is greatly improved in water relative to acetonitrile, in that reduction of CO2 to formate by [HNi(dmpe)2](+) was found to be thermodynamically downhill by 8 kcal mol(-1). Catalysis for the hydrogenation of CO2 was pursued, but the regeneration of [HNi(dmpe)2] under catalytic conditions was unfavourable. However, the present results demonstrate that the solvent dependence of thermodynamic parameters such as hydricity and acidity can be exploited in order to produce systems with balanced or favourable overall thermodynamics. This approach should be advantageous for the design of future water-soluble catalysts.

  14. Synthesis of hydrides by interaction of intermetallic compounds with ammonia

    Energy Technology Data Exchange (ETDEWEB)

    Tarasov, Boris P., E-mail: tarasov@icp.ac.ru [Institute of Problems of Chemical Physics of the Russian Academy of Sciences, Chernogolovka 142432 (Russian Federation); Fokin, Valentin N.; Fokina, Evelina E. [Institute of Problems of Chemical Physics of the Russian Academy of Sciences, Chernogolovka 142432 (Russian Federation); Yartys, Volodymyr A., E-mail: volodymyr.yartys@ife.no [Institute for Energy Technology, Kjeller NO 2027 (Norway); Department of Materials Science and Engineering, Norwegian University of Science and Technology, Trondheim NO 7491 (Norway)

    2015-10-05

    Highlights: • Interaction of the intermetallics A{sub 2}B, AB, AB{sub 2}, AB{sub 5} and A{sub 2}B{sub 17} with NH{sub 3} was studied. • The mechanism of interaction of the alloys with ammonia is temperature-dependent. • Hydrides, hydridonitrides, disproportionation products or metal–N–H compounds are formed. • NH{sub 4}Cl was used as an activator of the reaction between ammonia and intermetallics. • Interaction with ammonia results in the synthesis of the nanopowders. - Abstract: Interaction of intermetallic compounds with ammonia was studied as a processing route to synthesize hydrides and hydridonitrides of intermetallic compounds having various stoichiometries and types of crystal structures, including A{sub 2}B, AB, AB{sub 2}, AB{sub 5} and A{sub 2}B{sub 17} (A = Mg, Ti, Zr, Sc, Nd, Sm; B = transition metals, including Fe, Co, Ni, Ti and nontransition elements, Al and B). In presence of NH{sub 4}Cl used as an activator of the reaction between ammonia and intermetallic alloys, their interaction proceeds at rather mild P–T conditions, at temperatures 100–200 °C and at pressures of 0.6–0.8 MPa. The mechanism of interaction of the alloys with ammonia appears to be temperature-dependent and, following a rise of the interaction temperature, it leads to the formation of interstitial hydrides; interstitial hydridonitrides; disproportionation products (binary hydride; new intermetallic hydrides and binary nitrides) or new metal–nitrogen–hydrogen compounds like magnesium amide Mg(NH{sub 2}){sub 2}. The interaction results in the synthesis of the nanopowders where hydrogen and nitrogen atoms become incorporated into the crystal lattices of the intermetallic alloys. The nitrogenated materials have the smallest particle size, down to 40 nm, and a specific surface area close to 20 m{sup 2}/g.

  15. Dissociations between Expectancy and Performance in Simple and Two-Choice Reaction-Time Tasks: A Test of Associative and Nonassociative Explanations

    Science.gov (United States)

    Barrett, Louise C.; Livesey, Evan J.

    2010-01-01

    Perruchet, Cleeremans, and Destrebecqz (2006) reported a striking dissociation between trends in the conscious expectancy of an event and the speed of a response that is cued by that event. They argued that this indicates the operation of independent processes in human associative learning. However, there remains a strong possibility that this…

  16. Crystallography of shear transformations in zirconium hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Cassidy, Michael Philip [Univ. of Illinois, Urbana-Champaign, IL (United States)

    1978-01-01

    The crystallography and substructure of the transformations which have been hypothesized as involving a martensitic shear, and which occur between zirconium hydrides were investigated. Specifically, the formation of gamma zirconium hydride from delta hydride and the delta hydride to epsilon hydride transformation were studied. The habit planes, orientation relationships, lattice invariant shears, and interface structures were determined by transmission electron microscopy and diffraction. Surface tilts were observed and measured with an interference microscope. The direction and magnitude of the shape strain produced by the formation of gamma were determined by the measurement of fiducial scratch displacements. These results were compared with the phenomenological crystallographic theory of martensitic transformations.

  17. Characteristics and Applications of Metal Hydrides

    Science.gov (United States)

    Egan, G. J.; Lynch, F. E.

    1987-01-01

    Report discusses engineering principles of uses of metal hydrides in spacecraft. Metal hydrides absorb, store, pump, compress, and expand hydrogen gas. Additionally, they release or absorb sizeable amounts of heat as they form and decompose - property adapted for thermal-energy management or for propulsion. Describes efforts to: Identify heat sources and sinks suitable for driving metal hydride thermal cycles in spacecraft; develop concepts for hydride subsystems employing available heating and cooling methods; and produce data base on estimated sizes, masses, and performances of hydride devices for spacecraft.

  18. Characterization of hydrides and delayed hydride cracking in zirconium alloys

    Science.gov (United States)

    Fang, Qiang

    This thesis tries to fill some of the missing gaps in the study of zirconium hydrides with state-of-art experiments, cutting edge tomographical technique, and a novel numerical algorithm. A new hydriding procedure is proposed. The new anode material and solution combination overcomes many drawbacks of the AECLRTM hydriding method and leads to superior hydriding result compared to the AECL RTM hydriding procedure. The DHC crack growth velocity of as-received Excel alloy and Zr-2.5Nb alloy together with several different heat treated Excel alloy samples are measured. While it already known that the DHC crack growth velocity increases with the increase of base metal strength, the finding that the transverse plane is the weaker plane for fatigue crack growth despite having higher resistance to DHC crack growth was unexpected. The morphologies of hydrides in a coarse grained Zircally-2 sample have been studied using synchrotron x-rays at ESRF with a new technique called Diffraction Contrast Tomography that uses simultaneous collection of tomographic data and diffraction data to determine the crystallographic orientation of crystallites (grains) in 3D. It has been previously limited to light metals such as Al or Mg (due to the use of low energy x-rays). Here we show the first DCT measurements using high energy x-rays (60 keV), allowing measurements in zirconium. A new algorithm of a computationally effcient way to characterize distributions of hydrides - in particular their orientation and/or connectivity - has been proposed. It is a modification of the standard Hough transform, which is an extension of the Hough transform widely used in the line detection of EBSD patterns. Finally, a basic model of hydrogen migration is built using ABAQUS RTM, which is a mature finite element package with tested modeling modules of a variety of physical laws. The coupling of hydrogen diffusion, lattice expansion, matrix deformation and phase transformation is investigated under

  19. Collision-Induced Dissociation of Electrosprayed NaCl Clusters: Using Molecular Dynamics Simulations to Visualize Reaction Cascades in the Gas Phase

    Science.gov (United States)

    Schachel, Tilo D.; Metwally, Haidy; Popa, Vlad; Konermann, Lars

    2016-11-01

    Infusion of NaCl solutions into an electrospray ionization (ESI) source produces [Na( n+1)Cl n ]+ and other gaseous clusters. The n = 4, 13, 22 magic number species have cuboid ground state structures and exhibit elevated abundance in ESI mass spectra. Relatively few details are known regarding the mechanisms whereby these clusters undergo collision-induced dissociation (CID). The current study examines to what extent molecular dynamics (MD) simulations can be used to garner insights into the sequence of events taking place during CID. Experiments on singly charged clusters reveal that the loss of small neutrals is the dominant fragmentation pathway. MD simulations indicate that the clusters undergo extensive structural fluctuations prior to decomposition. Consistent with the experimentally observed behavior, most of the simulated dissociation events culminate in ejection of small neutrals ([NaCl] i , with i = 1, 2, 3). The MD data reveal that the prevalence of these dissociation channels is linked to the presence of short-lived intermediates where a relatively compact core structure carries a small [NaCl] i protrusion. The latter can separate from the parent cluster via cleavage of a single Na-Cl contact. Fragmentation events of this type are kinetically favored over other dissociation channels that would require the quasi-simultaneous rupture of multiple electrostatic contacts. The CID behavior of NaCl cluster ions bears interesting analogies to that of collisionally activated protein complexes. Overall, it appears that MD simulations represent a valuable tool for deciphering the dissociation of noncovalently bound systems in the gas phase.

  20. Optimization of Internal Cooling Fins for Metal Hydride Reactors

    Directory of Open Access Journals (Sweden)

    Vamsi Krishna Kukkapalli

    2016-06-01

    Full Text Available Metal hydride alloys are considered as a promising alternative to conventional hydrogen storage cylinders and mechanical hydrogen compressors. Compared to storing in a classic gas tank, metal hydride alloys can store hydrogen at nearly room pressure and use less volume to store the same amount of hydrogen. However, this hydrogen storage method necessitates an effective way to reject the heat released from the exothermic hydriding reaction. In this paper, a finned conductive insert is adopted to improve the heat transfer in the cylindrical reactor. The fins collect the heat that is volumetrically generated in LaNi5 metal hydride alloys and deliver it to the channel located in the center, through which a refrigerant flows. A multiple-physics modeling is performed to analyze the transient heat and mass transfer during the hydrogen absorption process. Fin design is made to identify the optimum shape of the finned insert for the best heat rejection. For the shape optimization, use of a predefined transient heat generation function is proposed. Simulations show that there exists an optimal length for the fin geometry.

  1. Hydride encapsulation by molecular alkali-metal clusters.

    Science.gov (United States)

    Haywood, Joanna; Wheatley, Andrew E H

    2008-07-14

    The sequential treatment of group 12 and 13 Lewis acids with alkali-metal organometallics is well established to yield so-called ''ate' complexes, whereby the Lewis-acid metal undergoes nucleophilic attack to give an anion, at least one group 1 metal acting to counter this charge. However, an alternative, less well recognised, reaction pathway involves the Lewis acid abstracting hydride from the organolithium reagent via a beta-elimination mechanism. It has recently been shown that in the presence of N,N'-bidentate ligands this chemistry can be harnessed to yield a new type of molecular main-group metal cluster in which the abstracted LiH is effectively trapped, with the hydride ion occupying an interstitial site in the cluster core. Discussion focuses on the development of this field, detailing advances in our understanding of the roles of Lewis acid, organolithium, and amine substrates in the syntheses of these compounds. Structure-types are discussed, as are efforts to manipulate cluster geometry and composition as well as hydride-coordination. Embryonic mechanistic studies are reported, as well as attempts to generate hydride-encapsulation clusters under catalytic control.

  2. Coulomb dissociation of N-20,N-21

    NARCIS (Netherlands)

    Roeder, Marko; Adachi, Tatsuya; Aksyutina, Yulia; Alcantara, Juan; Altstadt, Sebastian; Alvarez-Pol, Hector; Ashwood, Nicholas; Atar, Leyla; Aumann, Thomas; Avdeichikov, Vladimir; Barr, M.; Beceiro, Saul; Bemmerer, Daniel; Benlliure, Jose; Bertulani, Carlos; Boretzky, Konstanze; Borge, Maria J. G.; Burgunder, G.; Caamano, Manuel; Caesar, Christoph; Casarejos, Enrique; Catford, Wilton; Cederkall, Joakim; Chakraborty, S.; Chartier, Marielle; Chulkov, Leonid; Cortina-Gil, Dolores; Crespo, Raquel; Pramanik, Ushasi Datta; Diaz-Fernandez, Paloma; Dillmann, Iris; Elekes, Zoltan; Enders, Joachim; Ershova, Olga; Estrade, A.; Farinon, F.; Fraile, Luis M.; Freer, Martin; Freudenberger, M.; Fynbo, Hans; Galaviz, Daniel; Geissel, Hans; Gernhaeuser, Roman; Goebel, Kathrin; Golubev, Pavel; Diaz, D. Gonzalez; Hagdahl, Julius; Heftrich, Tanja; Heil, Michael; Heine, Marcel; Heinz, Andreas; Henriques, Ana; Holl, Matthias; Ickert, G.; Ignatov, Alexander; Jakobsson, Bo; Johansson, Hakan; Jonson, Bjorn; Kalantar-Nayestanaki, Nasser; Kanungo, Rituparna; Kelic-Heil, Aleksandra; Knoebel, Ronja; Kroell, Thorsten; Kruecken, Reiner; Kurcewicz, J.; Kurz, Nikolaus; Labiche, Marc; Langer, Christoph; Le Bleis, Tudi; Lemmon, Roy; Lepyoshkina, Olga; Lindberg, Simon; Machado, Jorge; Marganiec, Justyna; Mostazo Caro, Magdalena; Movsesyan, Alina; Najafi, Mohammad Ali; Nilsson, Thomas; Nociforo, Chiara; Panin, Valerii; Paschalis, Stefanos; Perea, Angel; Petri, Marina; Pietri, S.; Plag, Ralf; Prochazka, A.; Rahaman, Md. Anisur; Rastrepina, Ganna; Reifarth, Rene; Ribeiro, Guillermo; Ricciardi, M. Valentina; Rigollet, Catherine; Riisager, Karsten; Rossi, Dominic; del Rio Saez, Jose Sanchez; Savran, Deniz; Scheit, Heiko; Simon, Haik; Sorlin, Olivier; Stoica, V.; Streicher, Branislav; Taylor, Jon; Tengblad, Olof; Terashima, Satoru; Thies, Ronja; Togano, Yasuhiro; Uberseder, Ethan; Van de Walle, J.; Velho, Paulo; Volkov, Vasily; Wagner, Andreas; Wamers, Felix; Weick, Helmut; Weigand, Mario; Wheldon, Carl; Wilson, G.; Wimmer, Christine; Winfield, J. S.; Woods, Philip; Yakorev, Dmitry; Zhukov, Mikhail; Zilges, Andreas; Zuber, Kai

    2016-01-01

    Neutron-rich light nuclei and their reactions play an important role in the creation of chemical elements. Here, data from a Coulomb dissociation experiment on N-20,N-21 are reported. Relativistic N-20,N-21 ions impinged on a lead target and the Coulomb dissociation cross section was determined in a

  3. Coulomb dissociation of N-20,N-21

    NARCIS (Netherlands)

    Roeder, Marko; Adachi, Tatsuya; Aksyutina, Yulia; Alcantara, Juan; Altstadt, Sebastian; Alvarez-Pol, Hector; Ashwood, Nicholas; Atar, Leyla; Aumann, Thomas; Avdeichikov, Vladimir; Barr, M.; Beceiro, Saul; Bemmerer, Daniel; Benlliure, Jose; Bertulani, Carlos; Boretzky, Konstanze; Borge, Maria J. G.; Burgunder, G.; Caamano, Manuel; Caesar, Christoph; Casarejos, Enrique; Catford, Wilton; Cederkall, Joakim; Chakraborty, S.; Chartier, Marielle; Chulkov, Leonid; Cortina-Gil, Dolores; Crespo, Raquel; Pramanik, Ushasi Datta; Diaz-Fernandez, Paloma; Dillmann, Iris; Elekes, Zoltan; Enders, Joachim; Ershova, Olga; Estrade, A.; Farinon, F.; Fraile, Luis M.; Freer, Martin; Freudenberger, M.; Fynbo, Hans; Galaviz, Daniel; Geissel, Hans; Gernhaeuser, Roman; Goebel, Kathrin; Golubev, Pavel; Diaz, D. Gonzalez; Hagdahl, Julius; Heftrich, Tanja; Heil, Michael; Heine, Marcel; Heinz, Andreas; Henriques, Ana; Holl, Matthias; Ickert, G.; Ignatov, Alexander; Jakobsson, Bo; Johansson, Hakan; Jonson, Bjorn; Kalantar-Nayestanaki, Nasser; Kanungo, Rituparna; Kelic-Heil, Aleksandra; Knoebel, Ronja; Kroell, Thorsten; Kruecken, Reiner; Kurcewicz, J.; Kurz, Nikolaus; Labiche, Marc; Langer, Christoph; Le Bleis, Tudi; Lemmon, Roy; Lepyoshkina, Olga; Lindberg, Simon; Machado, Jorge; Marganiec, Justyna; Mostazo Caro, Magdalena; Movsesyan, Alina; Najafi, Mohammad Ali; Nilsson, Thomas; Nociforo, Chiara; Panin, Valerii; Paschalis, Stefanos; Perea, Angel; Petri, Marina; Pietri, S.; Plag, Ralf; Prochazka, A.; Rahaman, Md. Anisur; Rastrepina, Ganna; Reifarth, Rene; Ribeiro, Guillermo; Ricciardi, M. Valentina; Rigollet, Catherine; Riisager, Karsten; Rossi, Dominic; del Rio Saez, Jose Sanchez; Savran, Deniz; Scheit, Heiko; Simon, Haik; Sorlin, Olivier; Stoica, V.; Streicher, Branislav; Taylor, Jon; Tengblad, Olof; Terashima, Satoru; Thies, Ronja; Togano, Yasuhiro; Uberseder, Ethan; Van de Walle, J.; Velho, Paulo; Volkov, Vasily; Wagner, Andreas; Wamers, Felix; Weick, Helmut; Weigand, Mario; Wheldon, Carl; Wilson, G.; Wimmer, Christine; Winfield, J. S.; Woods, Philip; Yakorev, Dmitry; Zhukov, Mikhail; Zilges, Andreas; Zuber, Kai

    2016-01-01

    Neutron-rich light nuclei and their reactions play an important role in the creation of chemical elements. Here, data from a Coulomb dissociation experiment on N-20,N-21 are reported. Relativistic N-20,N-21 ions impinged on a lead target and the Coulomb dissociation cross section was determined in a

  4. Effects of metastability on hydrogen sorption in fluorine substituted hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Pinatel, E.R.; Corno, M.; Ugliengo, P.; Baricco, M., E-mail: marcello.baricco@unito.it

    2014-12-05

    Highlights: • Fluorine substitution in simple metal hydrides has been modelled. • The stability of the MH{sub (1−x)}F{sub x} solid solutions has been discussed. • Conditions for reversibility of sorption reactions have been suggested. - Abstract: In this work ab initio calculations and Calphad modelling have been coupled to describe the effect of fluorine substitution on the thermodynamics of hydrogenation–dehydrogenation in simple hydrides (NaH, AlH{sub 3} and CaH{sub 2}). These example systems have been used to discuss the conditions required for the formation of a stable hydride–fluoride solid solution necessary to obtain a reversible hydrogenation reaction.

  5. Complexation of divalent metal ions with diols in the presence of anion auxiliary ligands: zinc-induced oxidation of ethylene glycol to glycolaldehyde by consecutive hydride ion and proton shifts.

    Science.gov (United States)

    Ruttink, Paul J A; Dekker, Lennard J M; Luider, Theo M; Burgers, Peter C

    2012-07-01

    Ternary complexes of the type AH•••M(2+)•••L(-) (AH = diol, including diethylene and triethylene glycol, M = Ca, Mn, Fe, Co, Ni, Cu and Zn and auxiliary anion ligand L(-)  = CH(3)COO(-), HCOO(-) and Cl(-)) have been generated in the gas phase by MALDI and ESI, and their dissociation characteristics have been obtained. Use of the auxiliary ligands enables the complexation of AH with the divalent metal ion without AH becoming deprotonated, although A(-)•••M(2+) is often also generated in the ion source or after MS/MS. For M = Ca, dissociation occurs to AH + M(2+)•••L(-) and/or to A(-)•••M(2+) + LH, the latter being produced from the H-shifted isomer A(-) •••M(2+)•••LH. For a given ligand L(-), the intensity ratio of these processes can be interpreted (barring reverse energy barriers) in terms of the quantity PA(A(-)) - Ca(aff) (A(-)), where PA is the proton affinity and Ca(aff) is the calcium ion affinity. Deuterium labeling shows that the complex ion HOCH(2)CH(2) OH•••Zn(2+)•••(-)OOCCH(3), in addition to losing acetic acid (60 Da), also eliminates glycolaldehyde (HOCH(2)CH=O, also 60 Da); it is proposed that these reactions commence with a hydride ion shift to produce the ion-dipole complex HOCH(2)CHOH(+)••• HZnOOCCH(3), which then undergoes proton transfer and dissociation to HOCH(2)CH=O + HZn(+)•••O = C(OH)CH(3). In this reaction, ethylene glycol is oxidized by consecutive hydride ion and proton shifts. A minor process leads to loss of the isomeric species HOCH=CHOH.

  6. Aluminum Hydride as a Fuel Supplement to NanoThermites

    Science.gov (United States)

    2014-01-01

    explosives and as a hydrogen storage medium. There are as many as six crystalline phases of alane, of which α-alane is themost stable and is also the...a pure nanoaluminum-corresponding metal oxide thermite. As Fig. 2 shows, the addition ofmicron-scale aluminum hydride to a nanoaluminum–copper-oxide... hydrogen does not participate in the thermite reaction. It is quite possible that the hydrogen may react with oxygen and or the metal oxide as an

  7. High-Spin Cobalt Hydrides for Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Holland, Patrick L. [Univ. of Rochester, NY (United States)

    2013-08-29

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

  8. Speculations on the existence of hydride ions in proton conducting oxides

    DEFF Research Database (Denmark)

    Poulsen, F.W.

    2001-01-01

    The chemical and physical nature of the hydride ion is briefly treated. Several reactions of the hydride ion in oxides or oxygen atmosphere are given, A number of perovskites and inverse perovskites are listed. which contain the H- ion on the oxygen or B-anion sites in the archetype ABO(3) System....... H- is stable with respect to oxide and halide anions but, among cations only with respect to oxides and halides of strongly electropositive metals such as alkaline, alkaline-earth and main group III metals. H- is only stable in combination with transition metal ions of certain elements...... in their lowest positive oxidation state. Mixed oxide/hydride containing perovskites may thus exist. Steinsvik et al. have recently suggested a defect model for a perovskite including substitutional hydride ions on the oxygen site, H-O(.), and protons associated with a lattice oxygen, OHO.. The defect equations...

  9. Activation and discharge kinetics of metal hydride electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Johnsen, Stein Egil

    2003-07-01

    Potential step chronoamperometry and Electrochemical Impedance Spectroscopy (eis) measurements were performed on single metal hydride particles. For the {alpha}-phase, the bulk diffusion coefficient and the absorption/adsorption rate parameters were determined. Materials produced by atomisation, melt spinning and conventional casting were investigated. The melt spun and conventional cast materials were identical and the atomised material similar in composition. The particles from the cast and the melt spun material were shaped like parallelepipeds. A corresponding equation, for this geometry, for diffusion coupled to an absorption/adsorption reaction was developed. It was found that materials produced by melt spinning exhibited lower bulk diffusion (1.7E-14 m2/s) and absorption/adsorption reaction rate (1.0E-8 m/s), compared to materials produced by conventionally casting (1.1E-13 m2/s and 5.5E-8 m/s respectively). In addition, the influence of particle active surface and relative diffusion length were discussed. It was concluded that there are uncertainties connected to these properties, which may explain the large distribution in the kinetic parameters measured on metal hydride particles. Activation of metal hydride forming materials has been studied and an activation procedure, for porous electrodes, was investigated. Cathodic polarisation of the electrode during a hot alkaline surface treatment gave the maximum discharge capacity on the first discharge of the electrode. The studied materials were produced by gas atomisation and the spherical shape was retained during the activation. Both an AB{sub 5} and an AB{sub 2} alloy was successfully activated and discharge rate properties determined. The AB{sub 2} material showed a higher maximum discharge capacity, but poor rate properties, compared to the AB{sub 5} material. Reduction of surface oxides, and at the same time protection against corrosion of active metallic nickel, can explain the satisfying results of

  10. Influence of lanthanon hydride catalysts on hydrogen storage properties of sodium alanates

    Institute of Scientific and Technical Information of China (English)

    WU Zhe; CHEN Lixin; XIAO Xuezhang; FAN Xiulin; LI Shouquan; WANG Qidong

    2013-01-01

    NaAlH4 complex hydrides doped with lanthanon hydrides were prepared by hydrogenation of the ball-milled NaH/Al+xmol.% RE-H composites (RE=La,Ce; x=2,4,6) using NaHl and A1 powder as raw materials.The influence of lanthanon hydride catalysts on the hydriding and dehydriding behaviors of the as-synthesized composites were investigated.It was found that the composite doped with 2 mol.% La.H3.01 displayed the highest hydrogen absorption capacity of 4.78 wt.% and desorption capacity of 4.66wt.%,respectively.Moreover,the composite doped with 6 mol% CeH2.51 showed the best hydriding/dehydriding reaction kinetics.The proposed catalytic mechanism for reversible hydrogen storage properties of the composite was attributed to the presence of active LaH3.01 and CeH2.51 particles,which were scattering on the surface of NaH and A1 particles,acting as the catalytic active sites for hydrogen diffusion and playing an important catalytic role in the improved hydriding/dehydriding reaction.

  11. Formation and physical properties of uranium hydride under conditions relevant to metallic fuel and nuclear waste storage

    Science.gov (United States)

    Orr, Robin; Godfrey, Hugh; Broan, Chris; Goddard, Dave; Woodhouse, Guy; Durham, Peter; Diggle, Andrew; Bradshaw, John

    2016-08-01

    The formation of uranium hydride is recognised as a hazard during the storage of uranium metal owing to its potentially pyrophoric properties. This study has assessed the influence of water vapour on the potential for uranium hydride to form at low temperatures and shows that it increases the duration of the induction period but does not necessarily prevent uranium hydride formation and also does not significantly change the reaction rate with hydrogen. It is further shown that the α-UH3 fraction in the uranium hydride gradually increases at decreasing temperatures and is likely to be the dominant phase formed under typical storage conditions. Particle morphology and specific surface area of uranium hydride prepared between 30 °C and 200 °C have also been characterised but show only modest variation compared with the phase composition.

  12. Hydrogen generation using silicon nanoparticles and their mixtures with alkali metal hydrides

    Science.gov (United States)

    Patki, Gauri Dilip

    mole of Si. We compare our silicon nanoparticles (˜10nm diameter) with commercial silicon nanopowder (hydrogen production rate increased by a factor of 150. However, in all cases, silicon requires a base (e.g. NaOH, KOH, hydrazine) to catalyze its reaction with water. Metal hydrides are also promising hydrogen storage materials. The optimum metal hydride would possess high hydrogen storage density at moderate temperature and pressure, release hydrogen safely and controllably, and be stable in air. Alkali metal hydrides have high hydrogen storage density, but exhibit high uncontrollable reactivity with water. In an attempt to control this explosive nature while maintaining high storage capacity, we mixed our silicon nanoparticles with the hydrides. This has dual benefits: (1) the hydride- water reaction produces the alkali hydroxide needed for base-catalyzed silicon oxidation, and (2) dilution with 10nm coating by, the silicon may temper the reactivity of the hydride, making the process more controllable. Initially, we analyzed hydrolysis of pure alkali metal hydrides and alkaline earth metal hydrides. Lithium hydride has particularly high hydrogen gravimetric density, along with faster reaction kinetics than sodium hydride or magnesium hydride. On analysis of hydrogen production we found higher hydrogen yield from the silicon nanoparticle—metal hydride mixture than from pure hydride hydrolysis. The silicon-hydride mixtures using our 10nm silicon nanoparticles produced high hydrogen yield, exceeding the theoretical yield. Some evidence of slowing of the hydride reaction rate upon addition of silicon nanoparticles was observed.

  13. Application of thermal electrochemical equation to metal-hydride half-cell system

    Institute of Scientific and Technical Information of China (English)

    LIU Kai-yu; HUANG Bai-yun; ZHANG Ping-min; HE Yue-hui; ZHOU Ke-chao; SU Geng

    2006-01-01

    Application of thermal electrochemical equation to metal-hydride half-cell system was investigated, and the influence of state of charge on the thermal electrochemical performance of hydrogen storage materials was studied. The results show that both the absolute value of the molar enthalpy change and the internal resistance of evolution hydrogen reaction are less than that of absorption hydrogen reaction at the same state of charge. The molar reaction enthalpy change of absorption and evolution of hydride electrode change contrarily with the enhancement of filling degree of hydrogen in hydride electrode. The relation curve of molar reaction enthalpy change to state of charge, both absorption and evolution hydrogen reaction, is close to a constant when the state of charge is 10%-60%, and during state of charge below 10% or state of charge above 60%, the molar reaction enthalpy change varies sharply. Meanwhile, the internal resistance of electrode reaction has an ascending trend with the enhancement on filling degree of hydrogen in hydride electrode in both absorption and evolution hydrogen reaction.

  14. The renaissance of hydrides as energy materials

    Science.gov (United States)

    Mohtadi, Rana; Orimo, Shin-Ichi

    2017-02-01

    Materials based on hydrides have been the linchpin in the development of several practical energy storage technologies, of which the most prominent example is nickel-metal hydride batteries. Motivated by the need to meet the future's energy demand, the past decade has witnessed substantial advancements in the research and development of hydrides as media for hydrogen energy storage. More recently, new and rapidly evolving discoveries have positioned hydrides as highly promising materials for future electrochemical energy storage, such as electrolytes for mono- and divalent batteries, and anodes for lithium-ion batteries. In addition, the potential of hydrides in efficient power transmission has been recently revealed. In this Review, we highlight key advances and illustrate how the versatility of hydrides has not only yielded a meaningful past, but also ensures a very bright future.

  15. Rechargeable metal hydrides for spacecraft application

    Science.gov (United States)

    Perry, J. L.

    1988-01-01

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

  16. Thin-film metal hydrides for solar energy applications

    Energy Technology Data Exchange (ETDEWEB)

    Mongstad, Trygve Tveiteraas

    2012-11-01

    Thin-film metal hydrides may become important solar energy materials in the future. This thesis demonstrates interesting material properties of metal hydride films, relevant for applications as semiconducting materials for photovoltaic (PV) solar cells and for regulation of light using smart window technology.The work presented here has comprised an experimental study, focusing on three different materials: Magnesium hydride (MgH2), magnesium nickel hydride (Mg2NiH4) and yttrium hydride (YHx). Reactive sputter deposition was used to prepare the metal hydride film samples.This synthesis method is relatively uncommon for metal hydrides. Here,the first demonstration of reactive sputtering synthesis for YHx and Mg2NiH4 is given. Different challenges in forming singlephase, pure metal hydrides were identified: MgH2 could not be deposited without 3-16% metallic Mg present in the films, and YHx was found to react strong-ly to oxygen (O) during the deposition process. On the other hand, Mg2NiH4 films formed easily and apparently without major metallic clusters and with low O content.Mg2NiH4 is a semiconductor with an optical band gap that is suitable for PV solar cells. This study has showed that films with promising electrical and optical properties can be synthesized using reactive cosputtering of Mg and Ni. Using optical methods, the band gap for the as deposited samples was estimated to 1.54-1.76 eV, depending on the Mg-Ni composition. The asdeposited films were amorphous or nano-crystalline, but could be crystallized into the high-temperature fcc structure of Mg2NiH4 using heat treatment at 523 K. The band gap of the crystalline films was 2.1-2.2 eV, depending on the composition.A pronounced photochromic reaction to visible and UV light was observed for transparent yttrium hydride (T-YHx) samples. The optical transmission was reduced when the samples were illuminated, and the original optical transmission was restored when the samples were kept under dark conditions

  17. Elucidating collision induced dissociation products and reaction mechanisms of protonated uracil by coupling chemical dynamics simulations with tandem mass spectrometry experiments.

    Science.gov (United States)

    Molina, Estefanía Rossich; Ortiz, Daniel; Salpin, Jean-Yves; Spezia, Riccardo

    2015-12-01

    In this study we have coupled mixed quantum-classical (quantum mechanics/molecular mechanics) direct chemical dynamics simulations with electrospray ionization/tandem mass spectrometry experiments in order to achieve a deeper understanding of the fragmentation mechanisms occurring during the collision induced dissociation of gaseous protonated uracil. Using this approach, we were able to successfully characterize the fragmentation pathways corresponding to ammonia loss (m/z 96), water loss (m/z 95) and cyanic or isocyanic acid loss (m/z 70). Furthermore, we also performed experiments with isotopic labeling completing the fragmentation picture. Remarkably, fragmentation mechanisms obtained from chemical dynamics simulations are consistent with those deduced from isotopic labeling.

  18. Nanostructured, complex hydride systems for hydrogen generation

    Directory of Open Access Journals (Sweden)

    Robert A. Varin

    2015-02-01

    Full Text Available Complex hydride systems for hydrogen (H2 generation for supplying fuel cells are being reviewed. In the first group, the hydride systems that are capable of generating H2 through a mechanical dehydrogenation phenomenon at the ambient temperature are discussed. There are few quite diverse systems in this group such as lithium alanate (LiAlH4 with the following additives: nanoiron (n-Fe, lithium amide (LiNH2 (a hydride/hydride system and manganese chloride MnCl2 (a hydride/halide system. Another hydride/hydride system consists of lithium amide (LiNH2 and magnesium hydride (MgH2, and finally, there is a LiBH4-FeCl2 (hydride/halide system. These hydride systems are capable of releasing from ~4 to 7 wt.% H2 at the ambient temperature during a reasonably short duration of ball milling. The second group encompasses systems that generate H2 at slightly elevated temperature (up to 100 °C. In this group lithium alanate (LiAlH4 ball milled with the nano-Fe and nano-TiN/TiC/ZrC additives is a prominent system that can relatively quickly generate up to 7 wt.% H2 at 100 °C. The other hydride is manganese borohydride (Mn(BH42 obtained by mechano-chemical activation synthesis (MCAS. In a ball milled (2LiBH4 + MnCl2 nanocomposite, Mn(BH42 co-existing with LiCl can desorb ~4.5 wt.% H2 at 100 °C within a reasonable duration of dehydrogenation. Practical application aspects of hydride systems for H2 generation/storage are also briefly discussed.

  19. Anodematerials for Metal Hydride Batteries

    DEFF Research Database (Denmark)

    Jensen, Jens Oluf

    1997-01-01

    by annealing at 700°C for 12 hours. The alloys appeared to be nanocrystalline with an average crystallite size around 10 nm before annealing. Special steel containers was developed for the annealing of the metal powders in inert atmosphere. The use of various annealing temperatures was investigated......This report describes the work on development of hydride forming alloys for use as electrode materials in metal hydride batteries. The work has primarily been concentrated on calcium based alloys derived from the compound CaNi5. This compound has a higher capacity compared with alloys used in today...... was developed. The parameters milling time, milling intensity, number of balls and form of the alloying metals were investigated. Based on this a final alloying technique for the subsequent preparation of electrode materials was established. The technique comprises milling for 4 hours twice possibly followed...

  20. Research on Metal Hydride Compressor System

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Ti-Zr series Laves phase hydrogen storage alloys with good hydrogen storage properties, such as large hydrogen capacity, rapid hydriding and dehydriding rate, high compression ratio, gentle plateau, small hysteresis, easily being activated and long cyclic stability etc. for metal hydride compressor have been investigated. In addition, a hydride compressor with special characteristics, namely, advanced filling method, good heat transfer effect and reasonable structural design etc. has also been constructed. A hydride compressor cryogenic system has been assembled coupling the compressor with a J-T micro-throttling refrigeration device and its cooling capacity can reach 0.4 W at 25 K.

  1. Crystal structure of gold hydride

    Energy Technology Data Exchange (ETDEWEB)

    Degtyareva, Valentina F., E-mail: degtyar@issp.ac.ru

    2015-10-05

    Highlights: • Volume expansion of metal hydrides is due to the increase in the s-band filling. • AuH structure is similar to that of Hg having one more s electron compared to Au. • Structure stability of both Hg and AuH is governed by the Hume-Rothery rule. - Abstract: A number of transition metal hydrides with close-packed metal sublattices of fcc or hcp structures with hydrogen in octahedral interstitial positions were obtained by the high-pressure-hydrogen technique described by Ponyatovskii et al. (1982). In this paper we consider volume increase of metals by hydrogenation and possible crystal structure of gold hydride in relation with the structure of mercury, the nearest neighbor of Au in the Periodic table. Suggested structure of AuH has a basic tetragonal body-centered cell that is very similar to the mercury structure Hg-t I 2. The reasons of stability for this structure are discussed within the model of Fermi sphere–Brillouin zone interactions.

  2. Transition-Metal Hydride Radical Cations.

    Science.gov (United States)

    Hu, Yue; Shaw, Anthony P; Estes, Deven P; Norton, Jack R

    2016-08-10

    Transition-metal hydride radical cations (TMHRCs) are involved in a variety of chemical and biochemical reactions, making a more thorough understanding of their properties essential for explaining observed reactivity and for the eventual development of new applications. Generally, these species may be treated as the ones formed by one-electron oxidation of diamagnetic analogues that are neutral or cationic. Despite the importance of TMHRCs, the generally sensitive nature of these complexes has hindered their development. However, over the last four decades, many more TMHRCs have been synthesized, characterized, isolated, or hypothesized as reaction intermediates. This comprehensive review focuses on experimental studies of TMHRCs reported through the year 2014, with an emphasis on isolated and observed species. The methods used for the generation or synthesis of TMHRCs are surveyed, followed by a discussion about the stability of these complexes. The fundamental properties of TMHRCs, especially those pertaining to the M-H bond, are described, followed by a detailed treatment of decomposition pathways. Finally, reactions involving TMHRCs as intermediates are described.

  3. Fundamental experiments on hydride reorientation in zircaloy

    Science.gov (United States)

    Colas, Kimberly B.

    In the current study, an in-situ X-ray diffraction technique using synchrotron radiation was used to follow directly the kinetics of hydride dissolution and precipitation during thermomechanical cycles. This technique was combined with conventional microscopy (optical, SEM and TEM) to gain an overall understanding of the process of hydride reorientation. Thus this part of the study emphasized the time-dependent nature of the process, studying large volume of hydrides in the material. In addition, a micro-diffraction technique was also used to study the spatial distribution of hydrides near stress concentrations. This part of the study emphasized the spatial variation of hydride characteristics such as strain and morphology. Hydrided samples in the shape of tensile dog-bones were used in the time-dependent part of the study. Compact tension specimens were used during the spatial dependence part of the study. The hydride elastic strains from peak shift and size and strain broadening were studied as a function of time for precipitating hydrides. The hydrides precipitate in a very compressed state of stress, as measured by the shift in lattice spacing. As precipitation proceeds the average shift decreases, indicating average stress is reduced, likely due to plastic deformation and morphology changes. When nucleation ends the hydrides follow the zirconium matrix thermal contraction. When stress is applied below the threshold stress for reorientation, hydrides first nucleate in a very compressed state similar to that of unstressed hydrides. After reducing the average strain similarly to unstressed hydrides, the average hydride strain reaches a constant value during cool-down to room temperature. This could be due to a greater ease of deforming the matrix due to the applied far-field strain which would compensate for the strains due to thermal contraction. Finally when hydrides reorient, the average hydride strains become tensile during the first precipitation regime and

  4. Influence of Milling Conditions on the Hydriding Properties of Mg-C Nanocomposites

    Directory of Open Access Journals (Sweden)

    Hristina Stoyadinova

    2015-01-01

    Full Text Available Mg75 at.%, CB25 at.% (CB: carbon black composites were synthesized at different ball milling conditions (milling energy, milling duration, and environment and their hydriding properties were characterized by high-pressure DSC. The SEM observations revealed that the samples consist of 5–15 μm Mg particles, surrounded and in some cases coated by carbon particles. X-ray diffraction analysis showed that the Mg phase of all as-obtained composite powders is nanocrystalline with average crystallite size in the range 20–30 nm, depending on the milling conditions. The best hydriding properties, expressed in low-temperature hydriding (below 150°C and improved cycle life, showed the composites milled at dry conditions. This is obviously due mainly to the successful Mg surface protection by the carbon. Additional decrease of the hydriding temperature (<100°C was achieved applying higher-energy milling, but at the same time the cycling stability deteriorated, due to the extremely fine particles and microstructure achieved under these conditions. The composites milled in the presence of heptane showed rapid capacity decline during cycling as well. The observed difference in the hydriding behavior of the Mg-CB composites is attributed to the different coating efficiency of the carbon milled under different conditions with Mg, which is supposed to protect magnesium from oxidation and plays a catalytic role for the hydriding reaction.

  5. Reactivity patterns of transition metal hydrides and alkyls

    Energy Technology Data Exchange (ETDEWEB)

    Jones, W.D. II

    1979-05-01

    The complex PPN/sup +/ CpV(CO)/sub 3/H/sup -/ (Cp=eta/sup 5/-C/sub 5/H/sub 5/ and PPN = (Ph/sub 3/P)/sub 2/) was prepared in 70% yield and its physical properties and chemical reactions investigated. PPN/sup +/ CpV(CO)/sub 3/H/sup -/ reacts with a wide range of organic halides. The organometallic products of these reactions are the vanadium halides PPN/sup +/(CpV(C)/sub 3/X)/sup -/ and in some cases the binuclear bridging hydride PPN/sup +/ (CpV(CO)/sub 3/)/sub 2/H/sup -/. The borohydride salt PPN/sup +/(CpV(CO)/sub 3/BH/sub 4/)/sup -/ has also been prepared. The reaction between CpV(CO)/sub 3/H/sup -/ and organic halides was investigated and compared with halide reductions carried out using tri-n-butyltin hydride. Results demonstrate that in almost all cases, the reduction reaction proceeds via free radical intermediates which are generated in a chain process, and are trapped by hydrogen transfer from CpV(CO)/sub 3/H/sup -/. Sodium amalgam reduction of CpRh(CO)/sub 2/ or a mixture of CpRh(CO)/sub 2/ and CpCo(CO)/sub 2/ affords two new anions, PPN/sup +/ (Cp/sub 2/Rh/sub 3/(CO)/sub 4/)/sup -/ and PPN/sup +/(Cp/sub 2/RhCo(CO)/sub 2/)/sup -/. CpMo(CO)/sub 3/H reacts with CpMo(CO)/sub 3/R (R=CH/sub 3/,C/sub 2/H/sub 5/, CH/sub 2/C/sub 6/H/sub 5/) at 25 to 50/sup 0/C to produce aldehyde RCHO and the dimers (CpMo(CO)/sub 3/)/sub 2/ and (CpMo(CO)/sub 2/)/sub 2/. In general, CpV(CO)/sub 3/H/sup -/ appears to transfer a hydrogen atom to the metal radical anion formed in an electron transfer process, whereas CpMo(CO)/sub 3/H transfers hydride in a 2-electron process to a vacant coordination site. The chemical consequences are that CpV(CO)/sub 3/H/sup -/ generally reacts with metal alkyls to give alkanes via intermediate alkyl hydride species whereas CpMo(CO)/sub 3/H reacts with metal alkyls to produce aldehyde, via an intermediate acyl hydride species.

  6. Reactivity patterns of transition metal hydrides and alkyls

    Energy Technology Data Exchange (ETDEWEB)

    Jones, W.D. II

    1979-05-01

    The complex PPN/sup +/ CpV(CO)/sub 3/H/sup -/ (Cp=eta/sup 5/-C/sub 5/H/sub 5/ and PPN = (Ph/sub 3/P)/sub 2/) was prepared in 70% yield and its physical properties and chemical reactions investigated. PPN/sup +/ CpV(CO)/sub 3/H/sup -/ reacts with a wide range of organic halides. The organometallic products of these reactions are the vanadium halides PPN/sup +/(CpV(C)/sub 3/X)/sup -/ and in some cases the binuclear bridging hydride PPN/sup +/ (CpV(CO)/sub 3/)/sub 2/H/sup -/. The borohydride salt PPN/sup +/(CpV(CO)/sub 3/BH/sub 4/)/sup -/ has also been prepared. The reaction between CpV(CO)/sub 3/H/sup -/ and organic halides was investigated and compared with halide reductions carried out using tri-n-butyltin hydride. Results demonstrate that in almost all cases, the reduction reaction proceeds via free radical intermediates which are generated in a chain process, and are trapped by hydrogen transfer from CpV(CO)/sub 3/H/sup -/. Sodium amalgam reduction of CpRh(CO)/sub 2/ or a mixture of CpRh(CO)/sub 2/ and CpCo(CO)/sub 2/ affords two new anions, PPN/sup +/ (Cp/sub 2/Rh/sub 3/(CO)/sub 4/)/sup -/ and PPN/sup +/(Cp/sub 2/RhCo(CO)/sub 2/)/sup -/. CpMo(CO)/sub 3/H reacts with CpMo(CO)/sub 3/R (R=CH/sub 3/,C/sub 2/H/sub 5/, CH/sub 2/C/sub 6/H/sub 5/) at 25 to 50/sup 0/C to produce aldehyde RCHO and the dimers (CpMo(CO)/sub 3/)/sub 2/ and (CpMo(CO)/sub 2/)/sub 2/. In general, CpV(CO)/sub 3/H/sup -/ appears to transfer a hydrogen atom to the metal radical anion formed in an electron transfer process, whereas CpMo(CO)/sub 3/H transfers hydride in a 2-electron process to a vacant coordination site. The chemical consequences are that CpV(CO)/sub 3/H/sup -/ generally reacts with metal alkyls to give alkanes via intermediate alkyl hydride species whereas CpMo(CO)/sub 3/H reacts with metal alkyls to produce aldehyde, via an intermediate acyl hydride species.

  7. Carbene-metal hydrides can be much less acidic than phosphine-metal hydrides: significance in hydrogenations.

    Science.gov (United States)

    Zhu, Ye; Fan, Yubo; Burgess, Kevin

    2010-05-05

    Acidities of iridium hydride intermediates were shown to be critical in some transformations mediated by the chiral analogues of Crabtree's catalyst, 1-3. To do this, several experiments were undertaken to investigate the acidities of hydrogenation mixtures formed using these iridium-oxazoline complexes. DFT calculations indicated that the acidity difference for Ir-H intermediates in these hydrogenations were astounding; iridium hydride from the N-heterocyclic carbene catalyst 1 was calculated to be around seven pK(a) units less acidic than those from the P-based complexes 2 and 3. Consistent with this, the carbene complex 1 was shown to be more effective for hydrogenations of acid-sensitive substrates. In deuteration experiments, less "abnormal" deuteration was observed, corresponding to fewer complications from acid-mediated alkene isomerization preceding the D(2)-addition step. Finally, simple tests with pH indicators provided visual evidence that phosphine-based catalyst precursors give significantly more acidic reaction mixtures than the corresponding N-heterocyclic carbene ones. These observations indicate carbene-for-phosphine (and similar) ligand substitutions may impact the outcome of catalytic reactions by modifying the acidities of the metal hydrides formed.

  8. Alkyl and Hydride-Olefin Complexes of Niobocene

    NARCIS (Netherlands)

    Klazinga, A.H.; Teuben, J.H.

    1980-01-01

    Reactions of Cp2NbCl2 with RMgCl (R = n-C3H7, i-C3H7, n-C4H9, s-C4H9 and n-C5H11) give niobocene hydride olefin complexes Cp2Nb(H)L (L = C3H6, C4H8 and C5H10). The last step of the reaction probably proceeds via a stereospecific β-H elimination from the monoalkyl species Cp2NbR. Decomposition of n-a

  9. Dissociative Electron Attachment

    Science.gov (United States)

    Arreola, Esmeralda; Esmeralda Arreola Collaboration; Leigh Hargreaves Collaboration

    Since the pioneering work of Boudiaffa et al., it has been understood that electrons, even with energies near or below the ionization threshold, are capable of initiating strand-breaks in human DNA. This discovery raised important questions for cancer treatments, since sub-ionizing electrons are known to be the most copiously produced secondary product of radiation therapy. But even to date these factors are largely excluded from dosimetry calculations. This lack of inclusion is, at least in part, certainly due to the dearth of fundamental data describing low-energy electron interactions with nucleotide molecules that form the basis of DNA. Understanding of how such slow electrons are able to damage DNA remains incomplete, but the strongly peaked nature of Boudiaffa et al.'s data gives strong hints at resonantly driven collision processes. DNA damage is therefore most likely driven by ``dissociative electron attachment'' (DEA). DEA is a rather complicated process to model due to the coupling of electronic and nuclear degrees of freedom in the molecule. At the California State University Fullerton, we are currently commissioning a new spectrometer to study dissociation channels, reaction rates and orientation effects in DEA collisions between slow electrons and nucleotide molecules. At the meeting we will present design parameters and commissioning data for this new apparatus.

  10. Protonation equilibrium and hydrogen production by a dinuclear cobalt-hydride complex reduced by cobaltocene with trifluoroacetic acid.

    Science.gov (United States)

    Mandal, Sukanta; Shikano, Shinya; Yamada, Yusuke; Lee, Yong-Min; Nam, Wonwoo; Llobet, Antoni; Fukuzumi, Shunichi

    2013-10-16

    A dinuclear Co complex with bis(pyridyl)pyrazolato (bpp(-)) and terpyridine (trpy) ligands, [Co(III)2(trpy)2(μ-bpp)(OH)(OH2)](4+) (1(4+)), undergoes three-electron reduction by cobaltocene in acetonitrile to produce 1(+), which is in the protonation equilibrium with the Co(II)Co(III)-hydride complex, and the further protonation of the hydride by trifluoroacetic acid yields hydrogen quantitatively. The kinetic study together with the detection of the Co(II)Co(III)-hydride complex revealed the mechanism of the hydrogen production by the reaction of 1(+) with trifluoroacetic acid.

  11. Ionic conduction of lithium hydride single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Pilipenko, G.I.; Oparin, D.V.; Zhuravlev, N.A.; Gavrilov, F.F.

    1987-09-01

    Using the electrical-conductivity- and NMR-measurement- methods, the ionic-conduction mechanism is established in stoichiometric lithium hydride single crystals. The activation energies of migration of anion- and cation-vacancies and the formation of Schottky-pair defects are determined. They assume that the mechanisms of self-diffusion and conductivity are different in lithium hydride.

  12. Properties of hydrogen permeation barrier on the surface of zirconium hydride

    Institute of Scientific and Technical Information of China (English)

    CHEN Weidong; WANG Lijun; HAN Lin; CHEN Song

    2008-01-01

    A hydrogen permeation barrier was manufactured by the in situ reaction of zirconium hydride with oxygen.A reduction in the hydrogen permeation of the oxide films was detected by measuring the mass difference of the zirconium hydride samples after the dehydrogenation experiment.The reaction of zirconium hydride with oxygen occurs only under the condition that the temperature is higher than 673 K in the oxygen partial pressure of 0.1 MPa.The oxide film is composed of two layers,a permeable oxide layer and a dense oxide layer,and the main phase of the oxide film is ZrO2 with baddeleyite structure.The XPS analysis shows that O-H bonds exist in the oxide film,which are helpful for resisting hydrogen diffusion through the oxide film.

  13. Dissociated Vertical Deviation

    Science.gov (United States)

    ... Frequently Asked Questions Español Condiciones Chinese Conditions Dissociated Vertical Deviation En Español Read in Chinese What is Dissociated Vertical Deviation (DVD)? DVD is a condition in which ...

  14. Dissociation and dissociative ionization of H2+ using the time-dependent surface flux method

    CERN Document Server

    Yue, Lun

    2014-01-01

    The time-dependent surface flux method developed for the description of electronic spectra [L. Tao and A. Scrinzi, New J. Phys. 14, 013021 (2012); A. Scrinzi, New J. Phys. 14, 085008 (2012)] is extended to treat dissociation and dissociative ionization processes of H2+ interacting with strong laser pulses. By dividing the simulation volume into proper spatial regions associated with the individual reaction channels and monitoring the probability flux, the joint energy spectrum for the dissociative ionization process and the energy spectrum for dissociation is obtained. The methodology is illustrated by solving the time-dependent Schr\\"{o}dinger equation (TDSE) for a collinear one-dimensional model of H2+ with electronic and nuclear motions treated exactly and validated by comparison with published results for dissociative ionization. The results for dissociation are qualitatively explained by analysis based on dressed diabatic Floquet potential energy curves, and the method is used to investigate the breakdow...

  15. Flame-in-gas-shield and miniature diffusion flame hydride atomizers for atomic fluorescence spectrometry: optimization and comparison

    OpenAIRE

    Marschner, K; Musil, S. (Stanislav); Dědina, J. (Jiří)

    2015-01-01

    A detailed optimization of relevant experimental parameters of two hydride atomizers for atomic fluorescence spectrometry: flame-in-gas-shield atomizer with a two-channel shielding unit and a standard atomizer for atomic fluorescence spectrometry, miniature diffusion flame, was performed. Arsine, generated by the reaction with NaBH4 in a flow injection arrangement, was chosen as the model hydride. Analytical characteristics of both the atomizers (sensitivity, noise, limits of detection) were ...

  16. Over or under: hydride attack at the metal versus the coordinated nitrosyl ligand in ferric nitrosyl porphyrins.

    Science.gov (United States)

    Abucayon, E G; Khade, R L; Powell, D R; Shaw, M J; Zhang, Y; Richter-Addo, G B

    2016-11-15

    Hydride attack at a ferric heme-NO to give an Fe-HNO intermediate is a key step in the global N-cycle. We demonstrate differential reactivity when six- and five-coordinate ferric heme-NO models react with hydride. Although Fe-HNO formation is thermodynamically favored from this reaction, Fe-H formation is kinetically favored for the 5C case.

  17. Alkali promotion of N-2 dissociation over Ru(0001)

    DEFF Research Database (Denmark)

    Mortensen, Jens Jørgen; Hammer, Bjørk; Nørskov, Jens Kehlet

    1998-01-01

    Using self-consistent density functional calculations, we show that adsorbed Na and Cs lower the barrier for dissociation of N2 on Ru(0001). Since N2 dissociation is a crucial step in the ammonia synthesis reaction, we explain in this way the experimental observation that alkali metals promote th...... the ammonia synthesis reaction over Ru catalysts. We also show that the origin of this effect is predominantly a direct electrostatic attraction between the adsorbed alkali atoms and the dissociating molecule....

  18. Facile preparation of an immobilized surfactant-free palladium nanocatalyst for metal hydride trapping: a novel sensing platform for TXRF analysis.

    Science.gov (United States)

    Romero, V; Costas-Mora, I; Lavilla, I; Bendicho, C

    2015-02-07

    In this work, a simple route for the synthesis of surfactant-free immobilized palladium nanoparticles (Pd NPs) and their use as effective nanocatalysts for metal hydride decomposition is described. A mixture of ethanol : water was used as the reducing agent. Ethanol was added in a large excess to reduce the ionic Pd and stabilize the obtained Pd NPs. Ethanol is adsorbed on the surface of Pd allowing steric stabilization. Freshly prepared Pd NPs were immobilized onto quartz substrates modified with 3-mercaptopropyltrimethoxysilane. Pd interacts with the thiol group of the alkoxysilane that is adsorbed on the surface of NPs without the dissociation of the S-H bond. Different parameters affecting the synthesis of Pd NPs and their immobilization onto quartz substrates were evaluated. A comprehensive characterization of the synthesized Pd NPs was carried out by transmission electron microscopy (TEM), whereas total reflection X-ray fluorescence (TXRF) spectrometry was applied in order to evaluate their catalytic activity for solid-gas reactions. Immobilized Pd NPs were applied as nanocatalysts for the dissociative chemisorption of arsine at room temperature, yielding the formation of As-Pd bonds. Quartz substrates coated with nanosized Pd could be used as novel sensing platforms for total reflection X-ray fluorescence analysis. Arsenic can be detected in situ in natural water with a limit of detection of 0.08 μg L(-1).

  19. Modellization of Metal Hydride Canister for Hydrogen Storage

    Directory of Open Access Journals (Sweden)

    Rocio Maceiras

    2015-06-01

    Full Text Available Hydrogen shows very interesting features for its use on-board applications as fuel cell vehicles. This paper presents the modelling of a tank with a metal hydride alloy for on-board applications, which provides good performance under ambient conditions. The metal hydride contained in the tank is Ti0.98Zr0.02V0.43Fe0.09Cr0.05Mn1.5. A two-dimensional model has been performed for the refuelling process (absorption and the discharge process (desorption. For that, individual models of mass balance, energy balance, reaction kinetics and behaviour of hydrogen gas has been modelled. The model has been developed under Matlab / Simulink© environment. Finally, individual models have been integrated into a global model, and simulated under ambient conditions. With the aim to analyse the temperature influence on the state of charge and filling and emptying time, other simulations were performed at different temperatures. The obtained results allow to conclude that this alloy offers a good behaviour with the discharge process under normal ambient conditions. Keywords: Hydrogen storage; metal hydrides; fuel cell; simulation; board applications

  20. Crystal structure and switchable optical properties of yttrium hydride films covered by palladium layer

    Institute of Scientific and Technical Information of China (English)

    张文魁; 甘永平; 杨晓光; 黄辉; 余厉阳

    2003-01-01

    The palladium/yttrium films were prepared using magnetron sputtering technique.The changes of crystal structure,morphology and optical properties of the films during the hydrogen absorption/desorption process were investigated.The results of SEM and AFM analysis show that yttrium films have columnar structure,and the Pd cover layers on the surface of the yttrium films are composed of nanometer-sized Pd particles,which contain a large amount of smaller crystalline grains.During the gas hydrogen absorption/desorption process,YH3 and YH2 hydrides form on the sites of Pd grains contacting with Y grains.Upon hydrogenation,YH3 hydride forms and the switchable optical properties can be observed.The light transparency of the films increases with the increasing of hydrogen loading time and the light wavelength,and the absorption limitation occurs at λ=400 nm.Upon dehydrogenation,YH3 hydride dissociates into YH2 hydride,and the maximum transparency occurs at λ=689 nm.

  1. A dehydrogenation mechanism of metal hydrides based on interactions between Hdelta+ and H-.

    Science.gov (United States)

    Lu, Jun; Fang, Zhigang Zak; Sohn, Hong Yong

    2006-10-16

    This paper describes a reaction mechanism that explains the dehydrogenation reactions of alkali and alkaline-earth metal hydrides. These light metal hydrides, e.g., lithium-based compounds such as LiH, LiAlH4, and LiNH2, are the focus of intense research recently as the most promising candidate materials for on-board hydrogen storage applications. Although several interesting and promising reactions and materials have been reported, most of these reported reactions and materials have been discovered by empirical means because of a general lack of understanding of any underlying principles. This paper describes an understanding of the dehydrogenation reactions on the basis of the interaction between negatively charged hydrogen (H-, electron donor) and positively charged hydrogen (Hdelta+, electron acceptor) and experimental evidence that captures and explains many observations that have been reported to date. This reaction mechanism can be used as a guidance for screening new material systems for hydrogen storage.

  2. Molecular dynamics - The dissociation of H2 by He.

    Science.gov (United States)

    Brown, N. J.; Munn, R. J.

    1972-01-01

    The dissociation of molecular hydrogen by helium was studied at 5500 deg K using the quasiclassical approximation. The temperature-dependent reaction cross sections were very dependent on the initial quantum states of the molecule. A rate constant was estimated for the dissociation reaction, and agreement between theory and experiment was satisfactory.

  3. The survey of Neutron moderating properties of zirconium hydride nanoparticles (ZrH2 in the reactors of nuclear powerhouse

    Directory of Open Access Journals (Sweden)

    Ahmad Nozad Golikand

    2017-01-01

    Full Text Available Metal hydrides as a Neutron Moderator (NMs have effective and impressive application in nuclear reactors. Unquestionably, Retarder should be close to the atomic mass of the neutron to be able to reduce its energy with no interaction with the neutrons. The hydrogen atom nucleons have the atomic Mass close to the Neutron. Surprisingly, Metal hydrides can absorb a high percentage of hydrogen. Metal Hydrides have very good properties at high temperatures and can also maintain it even at higher temperatures. Due to the high volume of hydrogen stored in the metal hydrides, they blurt their good mechanical properties and Moderating Effect out on the incidence of the various reactors. Since they have ultrahigh functionality of Hydrogen storage, and likewise, they reveal their unique neutron moderating and thermal properties, in the present research, it was scrutinized the feasibility and circumstance of using them in the nuclear reactors of atomic energy powerhouse. Hence, in order to sonochemical reaction synthesis of zirconium hydride noparticles (ZrH2, the precursor of zirconium tetrachloride (ZrCl4 and potassium hydroxide (KOH were utilized as neutralizing acidic environment, exposure to the ultrasound waves. Eventually, some diverse metal salts were come on competitive comparison with zirconium hydride salt that the zirconium hydride nanoparticles had the best performance as compared to all of them.

  4. Understanding of hydriding mechanisms of zircaloy-4 alloy during corrosion in PWR simulated conditions and influence of zirconium hydrides on zircaloy-4 corrosion

    Energy Technology Data Exchange (ETDEWEB)

    Bisor-Melloul, C.; Tupin, M.; Bossis, P. [DEN/DANS/DMN/SEMI, CEA/Saclay, 91191 Gif-sur-Yvette (France); Chene, J. [DEN/DANS/DPC/SCCME, CEA/Saclay, 91191 Gif-sur-Yvette (France); Bechade, J.L. [DEN/DANS/DMN/SRMA, CEA/Saclay, 91191 Gif-sur-Yvette (France); Motta, A. [Mechanical and Nuclear Engineering Department, Penn State University, 227 Reber Building, University Park, PA 16802 (United States)

    2010-07-01

    Zirconium alloys are widely used as fuel claddings in Power Water Reactors. As they represent the first containment barrier to fission products, their mechanical integrity is essential for nuclear safety. During their corrosion in primary water, some of the hydrogen involved in the oxidation reaction with water ingresses into the alloy through the oxide layer. In the metallic matrix, once the solid solution limit is reached at the irradiation temperature, hydrogen precipitates as Zr hydrides mainly located just under the metal/oxide interface due to the thermal gradient across the cladding. As these hydrides may contribute to a larger oxide thickness and to a more fragile behaviour of the cladding, the minimization of hydrogen pick-up is required. Accordingly, since the Zircaloy-4 (Zr-1.3Sn-0.2Fe-0.1Cr) alloy is known to be sensitive to this phenomenon, the understanding of its hydriding mechanism and of the influence of zirconium hydrides on its corrosion behaviour is needed. Regarding the study of the hydriding mechanism, isotopic exchanges were carried out in D{sub 2}O environment at 360 deg. C and led to the localization, in the oxide scales, of the limiting step for the hydrogen diffusion. To estimate an apparent diffusion coefficient of hydrogen in the oxide formed on Zircaloy-4, we firstly based on SIMS profiles and penetration depth of deuterium in the dense part of the oxide film. Secondly, ERDA estimation of the hydrogen content in zirconia and fusion measurements of the hydrogen content in both metal and oxide were used to estimate a hydrogen flux absorbed by the alloy and hence to deduce an apparent diffusion coefficient. Finally, these two methods lead to quite similar values (between 2.10{sup -14} cm{sup 2}/s and 6.10{sup -14} cm{sup 2}/s) which are in accordance with bibliography. Concerning the impact of hydrides on the corrosion of Zircaloy-4, several pre-hydrided and reference samples were corroded simultaneously in primary water at 360 deg. C

  5. Phenol dissociation on pristine and defective graphene

    Science.gov (United States)

    Widjaja, Hantarto; Oluwoye, Ibukun; Altarawneh, Mohammednoor; Hamra, A. A. B.; Lim, H. N.; Huang, N. M.; Yin, Chun-Yang; Jiang, Zhong-Tao

    2017-03-01

    Phenol (C6H5O‒H) dissociation on both pristine and defective graphene sheets in terms of associated enthalpic requirements of the reaction channels was investigated. Here, we considered three common types of defective graphene, namely, Stone-Wales, monovacancy and divacancy configurations. Theoretical results demonstrate that, graphene with monovacancy creates C atoms with dangling bond (unpaired valence electron), which remains particularly useful for spontaneous dissociation of phenol into phenoxy (C6H5O) and hydrogen (H) atom. The reactions studied herein appear barrierless with reaction exothermicity as high as 2.2 eV. Our study offers fundamental insights into another potential application of defective graphene sheets.

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

    Science.gov (United States)

    Fukuzumi, Shunichi; Suenobu, Tomoyoshi

    2013-01-07

    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-κN(2))benzoic acid-κC(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 β-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 (λ > 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.

  7. A DFT based investigation into the electronic structure and properties of hydride rich rhodium clusters.

    Science.gov (United States)

    Brayshaw, Simon K; Green, Jennifer C; Hazari, Nilay; Weller, Andrew S

    2007-05-14

    Density functional theory has been used to investigate the structures, bonding and properties of a family of hydride rich late transition metal clusters of the type [Rh(6)(PH(3))(6)H(12)](x) (x = 0, +1, +2, +3 or +4), [Rh(6)(PH(3))(6)H(16)](x) (x = +1 or +2) and [Rh(6)(PH(3))(6)H(14)](x) (x = 0, +1 or +2). The positions of the hydrogen atoms around the pseudo-octahedral Rh(6) core in the optimized structures of [Rh(6)(PH(3))(6)H(12)](x) (x = 0, +1, +2, +3 or +4) varied depending on the overall charge on the cluster. The number of semi-bridging hydrides increased (semi-bridging hydrides have two different Rh-H bond distances) as the charge on the cluster increased and simultaneously the number of perfectly bridging hydrides (equidistant between two Rh centers) decreased. This distortion maximized the bonding between the hydrides and the metal centers and resulted in the stabilization of orbitals related to the 2T(2g) set in a perfectly octahedral cluster. In contrast, the optimized structures of the 16-hydride clusters [Rh(6)(PH(3))(6)H(12)](x) (x = +1 or +2) were similar and both clusters contained an interstitial hydride, along with one terminal hydride, ten bridging hydrides and two coordinated H(2) molecules which were bound to two rhodium centers in an eta(2):eta(1)-fashion. All the hydrides were on the outside of the Rh(6) core in the lowest energy structures of the 14-hydride clusters [Rh(6)(PH(3))(6)H(14)] and [Rh(6)(PH(3))(6)H(14)](+), which both contained eleven bridging hydrides, one terminal hydride and one coordinated H(2) molecule. Unfortunately, the precise structure of [Rh(6)(PH(3))(6)H(14)](2+) could not be determined as structures both with and without an interstitial hydride were of similar energy. The reaction energetics for the uptake and release of two molecule of H(2) by a cycle consisting of [Rh(6)(PH(3))(6)H(12)](2+), [Rh(6)(PH(3))(6)H(16)](2+), [Rh(6)(PH(3))(6)H(14)](+), [Rh(6)(PH(3))(6)H(12)](+) and [Rh(6)(PH(3))(6)H(14)](2+) were modelled

  8. Hydrogen-storing hydride complexes

    Science.gov (United States)

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

    2012-04-10

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

  9. Reaction of bis(o-phosphinophenyl)silane with M(PPh3)4 (M = Ni, Pd, Pt): synthesis and structural analysis of η2-(Si-H) metal(0) and pentacoordinate silyl metal(II) hydride complexes of the Ni triad bearing a PSiP-pincer ligand.

    Science.gov (United States)

    Takaya, Jun; Iwasawa, Nobuharu

    2011-09-21

    Reactions of bis(o-(diphenylphosphino)phenyl)methylsilane with M(PPh(3))(4) (M = Ni, Pd, Pt) were investigated. When M = Ni or Pd, synthesis and isolation of η(2)-(Si-H) complexes of mononuclear Ni(0) and Pd(0) were achieved for the first time as frozen intermediates for oxidative addition of the Si-H bond. Structural analysis by X-ray and NMR spectroscopy disclosed that their η(2)-(Si-H) structures were maintained in both solid and solution states and coordination of the Si-H bond to the metal center was relatively weak. On the other hand, reaction with a platinum(0) complex afforded two kinds of pentacoordinate silyl platinum(II) hydride complexes having a PSiP-pincer ligand, which underwent unique thermal isomerization from a square-pyramidal cis-H-Pt-Si to a trigonal-bipyramidal trans-H-Pt-Si isomer. Mechanistic investigations revealed that this isomerization proceeded via an intramolecular rearrangement process probably through a turnstile rotation.

  10. Positive ions of the first- and second-row transition metal hydrides

    Science.gov (United States)

    Pettersson, Lars G. M.; Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Partridge, Harry

    1987-01-01

    Theoretical dissociation energies for the first- and second-row transition metal hydride positive ions are critically compared against recent experimental values obtained from ion beam reactive scattering methods. Theoretical spectroscopic parameters and dipole moments are presented for the ground and several low-lying excited states. The calculations employ large Gaussian basis sets and account for electron correlation using the single-reference single- and double-excitation configuration interaction and coupled-pair-functional methods. The Darwin and mass-velocity contributions to the relativistic energy are included in the all-electron calculations on the first-row systems using first-order perturbation theory, and in the second-row systems using the Hay and Wadt relativistic effective core potentials. The theoretical D(0) values for the second-row transition metal hydride positive ions should provide a critical measure of the experimental values, which are not as refined as many of those in the first transition row.

  11. Non-Precious Bimetallic Catalysts for Selective Dehydrogenation of an Organic Chemical Hydride System

    KAUST Repository

    Shaikh Ali, Anaam

    2015-07-06

    Methylcyclohexane (MCH)-Toluene (TOL) chemical hydride cycles as a hydrogen carrier system is successful with the selective dehydrogenation reaction of MCH to TOL, which has been achieved only using precious Pt-based catalysts. Herein, we report improved selectivity using non-precious metal nickel-based bimetallic catalysts, where the second metal occupies the unselective step sites.

  12. Hydride heat pump with heat regenerator

    Science.gov (United States)

    Jones, Jack A. (Inventor)

    1991-01-01

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

  13. The oxidation of uranium hydride during its instantaneous or gradual exposure to oxygen

    Energy Technology Data Exchange (ETDEWEB)

    Glascott, J., E-mail: joe.glascott@awe.co.uk; Findlay, I.M.

    2015-11-15

    The oxidation behaviour of uranium hydride when exposed to oxygen gas either gradually or instantaneously at an ambient temperature of approximately 37 °C has been investigated. The proportion of the sample converted to oxide and the mean hydride mound temperature rise accompanying the oxidation process were recorded. Pressure changes in the reaction cell were used to deduce the nature of the oxide generated during the oxidation process and the nature of the gaseous reaction products. For the gradual oxidation of the hydride, typically only about 15% of the hydride mass was converted to oxide during the initial period of oxidation defined by an observed temperature excursion lasting a finite time; during this oxidation period it is concluded that, despite the only moderate recoded mean temperature rises, the generated oxide is U{sub 3}O{sub 8} rather than UO{sub 2}. Typically also for such gradual exposure experiments, hydrogen was the principal gaseous reaction product with negligible water being produced. For the instantaneous exposure of the hydride to oxygen, much higher hydride mound mean temperature rises were recorded but the proportion of hydride converted to oxide was quite variable and apparently dependent on several experimental variables; for these experiments, although hydrogen was a major reaction product typically some water was also produced. The boundary between pyrophoric and non-pyrophoric oxidation of uranium hydride for given oxidising conditions is discussed in terms of a calculated particle “thermal runaway temperature”. - Highlights: • Only about 15% of UH{sub 3} is oxidised on its gradual exposure to oxygen. • During the gradual exposure of UH{sub 3} to oxygen U{sub 3}O{sub 8} rather than UO{sub 2} is generated. • For such gradual exposure, predominantly H{sub 2} rather than H{sub 2}O was generated. • For the instantaneous exposure of UH{sub 3} to O{sub 2} the amount oxidised was variable. • For these experiments, H{sub 2

  14. Identification of destabilized metal hydrides for hydrogen storage using first principles calculations.

    Science.gov (United States)

    Alapati, Sudhakar V; Johnson, J Karl; Sholl, David S

    2006-05-04

    Hydrides of period 2 and 3 elements are promising candidates for hydrogen storage but typically have heats of reaction that are too high to be of use for fuel cell vehicles. Recent experimental work has focused on destabilizing metal hydrides through alloying with other elements. A very large number of possible destabilized metal hydride reaction schemes exist. The thermodynamic data required to assess the enthalpies of these reactions, however, are not available in many cases. We have used first principles density functional theory calculations to predict the reaction enthalpies for more than 100 destabilization reactions that have not previously been reported. Many of these reactions are predicted not be useful for reversible hydrogen storage, having calculated reaction enthalpies that are either too high or too low. More importantly, our calculations identify five promising reaction schemes that merit experimental study: 3LiNH(2) + 2LiH + Si --> Li(5)N(3)Si + 4H(2), 4LiBH(4) + MgH(2) --> 4LiH + MgB(4) + 7H(2), 7LiBH(4) + MgH(2) --> 7LiH + MgB(7) + 11.5H(2), CaH(2) + 6LiBH(4) --> CaB(6) + 6LiH + 10H(2), and LiNH(2) + MgH(2) --> LiMgN + 2H(2).

  15. Kinetic behaviour of low-Co AB{sub 5}-type metal hydride electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Tliha, M., E-mail: Mohamed.Tliha@esstt.rnu.tn [Laboratoire de Mecanique, Materiaux et Procedes, ESSTT, 5 Avenue Taha Hussein, 1008 Tunis (Tunisia); Boussami, S.; Mathlouthi, H.; Lamloumi, J. [Laboratoire de Mecanique, Materiaux et Procedes, ESSTT, 5 Avenue Taha Hussein, 1008 Tunis (Tunisia); Percheron-Guegan, A. [Laboratoire de Chimie Metallurgique des Terres Rares, GLVT, 2-8 Rue Henri Dunant 94320, Thiais Cedex (France)

    2010-11-15

    The kinetic behaviour of the LaNi{sub 3.55}Mn{sub 0.4}Al{sub 0.3}Co{sub 0.4}Fe{sub 0.35} metal hydride, used as a negative electrode in the nickel/metal hydride (Ni/MH) batteries, was investigated using electrochemical impedance spectroscopy (EIS) at different state of charge (SOC). Impedance measurements were performed in the frequency range from 50 kHz to 1 mHz. Electrochemical impedance spectrum of the metal hydride electrode was interpreted by an equivalent circuit including the different electrochemical processes taking place on the interface between the MH electrode and the electrolyte. Electrochemical kinetic parameters such as the charge-transfer resistance R{sub tc}, the exchange current density I{sub 0} and the hydrogen diffusion coefficient D{sub H} were determined at different state of charge. The results of EIS measurements indicate that the electrochemical reaction activity of the LaNi{sub 3.55}Mn{sub 0.4}Al{sub 0.3}Co{sub 0.4}Fe{sub 0.35} metal hydride electrode was markedly improved with increasing state of charge (SOC). The transformation {alpha}-{beta} is probably a limiting step in the mechanisms of hydrogenation of metal hydride electrode.

  16. Hydrogen transmission/storage with a metal hydride/organic slurry

    Energy Technology Data Exchange (ETDEWEB)

    Breault, R.W.; Rolfe, J.; McClaine, A. [Thermo Power Corp., Waltham, MA (United States)

    1998-08-01

    Thermo Power Corporation has developed a new approach for the production, transmission, and storage of hydrogen. In this approach, a chemical hydride slurry is used as the hydrogen carrier and storage media. The slurry protects the hydride from unanticipated contact with moisture in the air and makes the hydride pumpable. At the point of storage and use, a chemical hydride/water reaction is used to produce high-purity hydrogen. An essential feature of this approach is the recovery and recycle of the spent hydride at centralized processing plants, resulting in an overall low cost for hydrogen. This approach has two clear benefits: it greatly improves energy transmission and storage characteristics of hydrogen as a fuel, and it produces the hydrogen carrier efficiently and economically from a low cost carbon source. The preliminary economic analysis of the process indicates that hydrogen can be produced for $3.85 per million Btu based on a carbon cost of $1.42 per million Btu and a plant sized to serve a million cars per day. This compares to current costs of approximately $9.00 per million Btu to produce hydrogen from $3.00 per million Btu natural gas, and $25 per million Btu to produce hydrogen by electrolysis from $0.05 per Kwh electricity. The present standard for production of hydrogen from renewable energy is photovoltaic-electrolysis at $100 to $150 per million Btu.

  17. Multislice simulations for in-situ HRTEM studies of nanostructured magnesium hydride at ambient hydrogen pressure.

    Science.gov (United States)

    Surrey, Alexander; Schultz, Ludwig; Rellinghaus, Bernd

    2017-01-31

    The use of transmission electron microscopy (TEM) for the structural characterization of many nanostructured hydrides, which are relevant for solid state hydrogen storage, is hindered due to a rapid decomposition of the specimen upon irradiation with the electron beam. Environmental TEM allows to stabilize the hydrides by applying a hydrogen back pressure of up to 4.5 bar in a windowed environmental cell. The feasibility of high-resolution TEM (HRTEM) investigations of light weight metals and metal hydrides in such a "nanoreactor" is studied theoretically by means of multislice HRTEM contrast simulations using Mg and its hydride phase, MgH2, as model system. Such a setup provides the general opportunity to study dehydrogenation and hydrogenation reactions at the nanoscale under technological application conditions. We analyze the dependence of both the spatial resolution and the HRTEM image contrast on parameters such as the defocus, the metal/hydride thickness, and the hydrogen pressure in order to explore the possibilities and limitations of in-situ experiments with windowed environmental cells. Such simulations may be highly valuable to pre-evaluate future experimental studies.

  18. High Density Hydrogen Storage System Demonstration Using NaAlH4 Based Complex Compound Hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Daniel A. Mosher; Xia Tang; Ronald J. Brown; Sarah Arsenault; Salvatore Saitta; Bruce L. Laube; Robert H. Dold; Donald L. Anton

    2007-07-27

    This final report describes the motivations, activities and results of the hydrogen storage independent project "High Density Hydrogen Storage System Demonstration Using NaAlH4 Based Complex Compound Hydrides" performed by the United Technologies Research Center under the Department of Energy Hydrogen Program, contract # DE-FC36-02AL67610. The objectives of the project were to identify and address the key systems technologies associated with applying complex hydride materials, particularly ones which differ from those for conventional metal hydride based storage. This involved the design, fabrication and testing of two prototype systems based on the hydrogen storage material NaAlH4. Safety testing, catalysis studies, heat exchanger optimization, reaction kinetics modeling, thermochemical finite element analysis, powder densification development and material neutralization were elements included in the effort.

  19. Deuterium distributions on delayed hydride crack fracture surfaces of Zr-2.5Nb

    Energy Technology Data Exchange (ETDEWEB)

    Laursen, T. [Queen`s Univ., Kingston, ON (Canada); Palmer, G.R. [Queen`s Univ., Kingston, ON (Canada); Shek, G.K. [Ontario Hydro Technologies, Toronto, Ontario (Canada)

    1995-02-01

    Delayed hydride cracking (DHC) fracture surfaces on unirradiated Zr-2.5Nb pressure tube material have been characterized by nuclear reaction analysis (NRA). Although the fracture surface is rough and oxidized, NRA was able to detect the deuteride on the surface and to determine an average deuteride thickness. This thickness, which represents half of the fractured hydride thickness, was 1 {mu}m in the case of a specimen containing an average D concentration of 68 wppm and fractured at 517-525 K. On a specimen selected for its large ligament zones, D distributions on a tunnelled DHC crack was compared to those on the adjacent ligament zones. The hydriding of these ligament zones - in spite of their different appearance - is consistent with fracture by a DHC mechanism. ((orig.))

  20. Tailoring Thermodynamics and Kinetics for Hydrogen Storage in Complex Hydrides towards Applications.

    Science.gov (United States)

    Liu, Yongfeng; Yang, Yaxiong; Gao, Mingxia; Pan, Hongge

    2016-02-01

    Solid-state hydrogen storage using various materials is expected to provide the ultimate solution for safe and efficient on-board storage. Complex hydrides have attracted increasing attention over the past two decades due to their high gravimetric and volumetric hydrogen densities. In this account, we review studies from our lab on tailoring the thermodynamics and kinetics for hydrogen storage in complex hydrides, including metal alanates, borohydrides and amides. By changing the material composition and structure, developing feasible preparation methods, doping high-performance catalysts, optimizing multifunctional additives, creating nanostructures and understanding the interaction mechanisms with hydrogen, the operating temperatures for hydrogen storage in metal amides, alanates and borohydrides are remarkably reduced. This temperature reduction is associated with enhanced reaction kinetics and improved reversibility. The examples discussed in this review are expected to provide new inspiration for the development of complex hydrides with high hydrogen capacity and appropriate thermodynamics and kinetics for hydrogen storage.

  1. Hydrogen storage in complex metal hydrides

    National Research Council Canada - National Science Library

    Bogdanovic, Borislav; Felderhoff, Michael; Streukens, Guido

    2009-01-01

    ...) are solid-state hydrogen-storage materials with high hydrogen capacities. They can be used in combination with fuel cells as a hydrogen source thus enabling longer operation times compared with classical metal hydrides...

  2. Method of forming metal hydride films

    Science.gov (United States)

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

    1977-01-01

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

  3. Sealed aerospace metal-hydride batteries

    Science.gov (United States)

    Coates, Dwaine

    1992-01-01

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

  4. Probing the cerium/cerium hydride interface using nanoindentation

    Energy Technology Data Exchange (ETDEWEB)

    Brierley, Martin, E-mail: martin.brierley@awe.co.uk [Atomic Weapons Establishment, Aldermaston, Berkshire RG7 4PR (United Kingdom); University of Manchester, Manchester M13 9PL (United Kingdom); Knowles, John, E-mail: john.knowles@awe.co.uk [Atomic Weapons Establishment, Aldermaston, Berkshire RG7 4PR (United Kingdom)

    2015-10-05

    Highlights: • A disparity exists between the minimum energy and actual shape of a cerium hydride. • Cerium hydride is found to be harder than cerium metal by a ratio of 1.7:1. • A zone of material under compressive stress was identified surrounding the hydride. • No distribution of hardness was apparent within the hydride. - Abstract: A cerium hydride site was sectioned and the mechanical properties of the exposed phases (cerium metal, cerium hydride, oxidised cerium hydride) were measured using nanoindentation. An interfacial region under compressive stress was observed in the cerium metal surrounding a surface hydride that formed as a consequence of strain energy generated by the volume expansion associated with precipitation of the hydride phase.

  5. C-H ACTIVATION REACTIONS BY YTTRIUM AND LUTETIUM HYDRIDE COMPLEXES - H/D EXCHANGE VS METALATION OF HYDROCARBONS - IMPORTANCE OF THE HYBRIDIZATION STATE AT THE ALPHA-CARBON

    NARCIS (Netherlands)

    DEELMAN, BJ; TEUBEN, JH; MACGREGOR, SA; EISENSTEN, O

    1995-01-01

    Extended Huckel (EHT) calculations have been used to discuss the two alternative sigma-bond C-H metathesis reactions which occur with organo-lanthanide (Ln = Y, Lu) compounds. The two reactions lead either to H/H (H/D) exchange or to metalation and have been modelled by studying the interaction of a

  6. Destabilization of magnesium hydride through interface engineering

    OpenAIRE

    Mooij, L.P.A.

    2013-01-01

    The aim of this thesis is to study the thermodynamics of hydrogenation of nanoconfined magnesium within a thin film multilayer model system. Magnesium hydride is a potential material for hydrogen storage, which is a key component in a renewable energy system based on hydrogen. In bulk form, magnesium hydride is very stable, which means that hydrogen is released only at elevated temperature. Furthermore, the kinetics of hydrogen sorption is slow, which further hampers the practical use of this...

  7. P-hydrogen-substituted 1,3,2-diazaphospholenes: molecular hydrides.

    Science.gov (United States)

    Burck, Sebastian; Gudat, Dietrich; Nieger, Martin; Du Mont, Wolf-Walther

    2006-03-29

    P-Hydrogen-substituted 1,3,2-diazaphospholenes 1 were prepared by an improved procedure from diazadienes and were characterized by spectroscopy and in one case by X-ray diffraction. A unique hydride-type reactivity of the P-H bonds was documented by extensive reactivity studies. Aldehydes and ketones were readily reduced to diazaphospholene derivatives of the corresponding alcohols, with alkyl-substituted ketones being converted at much lower rates than aldehydes or diaryl ketones. Reactions with the tetrachlorides of group 14 elements proceeded via hydride/chloride metathesis to give either partially chlorinated derivatives EH(n)Cl(4-n) (n = 0-3 for E = C, Si) or HCl and phosphenium salts 16c[ECl3] (for E = Ge, Sn) which were characterized by spectroscopic and X-ray diffraction studies. Tin dichloride was readily reduced to the element. Reactions of 1c with the P-chloro-diazaphospholene 3c and the salt 16c[OTf] allowed the first experimental detection of intermolecular exchange of a hydride, rather than a proton, between phosphine derivatives. Computational studies indicated that the hydride transfer between 1c and the cation 16c involves a transient H-bridged species with bonding properties similar to those of B2H7-. The preference for the formation of these bridged intermediates over P-P bonded phosphenium-phosphine adducts is attributed to the low electrophilicity of the diazaphospholenium cations and characterizes a novel reaction mode for phosphenium ions.

  8. Strain-Induced Water Dissociation on Supported Ultrathin Oxide Films

    CERN Document Server

    Song, Zhenjun; Xu, Hu

    2015-01-01

    Controlling the dissociation of single water molecule on an insulating surface plays a crucial role in many catalytic reactions. In this Letter, we have identified the enhanced chemical reactivity of ultrathin MgO(100) films deposited on Mo(100) substrate that causes water dissociation. We reveal that the ability to split water on insulating surface closely depends on the lattice mismatch between ultrathin films and the underlying substrate, and substrate-induced in-plane tensile strain dramatically results in water dissociation on MgO(100). Three dissociative adsorption configurations of water with lower energy are predicted, and the structural transition going from molecular form to dissociative form is almost barrierless. Our results provide an effective avenue to achieve water dissociation at the single-molecule level and shed light on how to tune the chemical reactions of insulating surfaces by choosing the suitable substrates.

  9. gamma-Zr-Hydride Precipitate in Irradiated Massive delta- Zr-Hydride

    DEFF Research Database (Denmark)

    Warren, M. R.; Bhattacharya, D. K.

    1975-01-01

    During examination of A Zircaloy-2-clad fuel pin, which had been part of a test fuel assembly in a boiling water reactor, several regions of severe internal hydriding were noticed in the upper-plenum end of the pin. Examination of similar fuel pins has shown that hydride of this type is caused...

  10. Development of a metal hydride refrigeration system as an exhaust gas-driven automobile air conditioner

    Energy Technology Data Exchange (ETDEWEB)

    Qin, Feng; Chen, Jiangping; Chen, Zhijiu [Institute of Refrigeration and Cryogenics Engineering, Shanghai Jiaotong University, Shanghai 200030 (China); Lu, Manqi; Yang, Ke [Engineering Center, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, Liaoning Province 110016 (China); Zhou, Yimin [Research Center, Zhejiang Yinlun Machinery Co. Ltd., Tiantai County, Zhejiang Province 317200 (China)

    2007-10-15

    Aiming at developing exhaust gas-driven automobile air conditioners, two types of systems varying in heat carriers were preliminarily designed. A new hydride pair LaNi{sub 4.61}Mn{sub 0.26}Al{sub 0.13}/La{sub 0.6}Y{sub 0.4}Ni{sub 4.8}Mn{sub 0.2} was developed working at 120-200 C/20-50 C/-10-0 C. P-C isotherms and reaction kinetics were tested. Reaction enthalpy, entropy and theoretical cycling coefficient of performance (COP) were deducted from Van't-Hoff diagram. Test results showed that the hydride pair has flat plateau slopes, fast reaction dynamics and small hystereses; the reaction enthalpy of the refrigeration hydride is -27.1 kJ/mol H{sub 2} and system theoretical COP is 0.711. Mean particle sizes during cycles were verified to be an intrinsic property affected by constitution, heat treatment and cycle numbers rather than initial grain sizes. Based on this work pair, cylindrical reactors were designed and a function proving metal hydride intermittent refrigeration system was constructed with heat conducting oil as heat source and water as heat sink. The reactor equivalent thermal conductivity is merely 1.3 W/(m K), which still has not meet practical requirement. Intermittent refrigeration cycles were achieved and the average cooling power is 84.6 W at 150 C/30 C/0 C with COP being 0.26. The regulations of cycling performance and minimum refrigeration temperature (MRT) were determined by altering heat source temperature. Results showed that cooling power and system COP increase while MRT decreases with the growth of heat source temperature. This study develops a new hydride pair and confirms its application in automobile refrigeration systems, while their heat transfer properties still need to be improved for better performance. (author)

  11. Preparation and Properties of Zirconium Hydride on the Surface of MCM-41 Mesoporous Molecular Sieves

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Zirconium monohydride bonded to the framework oxygen of MCM-41 surface was prepared by the reaction of tetraneopentyl zirconium with MCM-41 surface hydroxyl groups, followed by the hydrogenolysis of the resulted product. The surface hydride was characterized by using infrared spectroscopy, solid-state NMR, elemental analysis, gas-phase chromatography and chemical probing reaction. It was shown that this surface species is stable below 150 ℃ and can catalytically crack alkanes into methane and ethane at 100 ℃.

  12. Psychiatric symptoms and dissociation in conversion, somatization and dissociative disorders.

    Science.gov (United States)

    Espirito-Santo, Helena; Pio-Abreu, Jose Luis

    2009-03-01

    Conversion, dissociation and somatization are historically related in the long established concept of hysteria. Somewhere along the way they were separated due to the Cartesian dualistic view. The aim of the present study was to compare these pathologies and investigate whether symptoms of these pathologies overlap in their clinical appearance in a Portuguese sample. Twenty-six patients with conversion disorder, 38 with dissociative disorders, 40 with somatization disorder, and a comparison group of 46 patients having other psychiatric disorders answered questions about dissociation (Dissociative Experiences Scale), somatoform dissociation (Somatoform Dissociation Questionnaire), and psychopathological symptoms (Brief Symptom Inventory). Dissociative and somatoform symptoms were significantly more frequent in dissociative and conversion disorder than in somatization disorder and controls. There were no significant differences between dissociative and conversion patients. Conversion disorder is closely related to dissociative disorders. These results support the ICD-10 categorization of conversion disorder among dissociative disorders and the hypothesis of analogous psychopathological processes in conversion and dissociative disorders versus somatization disorder.

  13. Heavy hydrides: H2Te ultraviolet photochemistry

    Science.gov (United States)

    Underwood, J.; Chastaing, D.; Lee, S.; Wittig, C.

    2005-08-01

    The room-temperature ultraviolet absorption spectrum of H2Te has been recorded. Unlike other group-6 hydrides, it displays a long-wavelength tail that extends to 400 nm. Dissociation dynamics have been examined at photolysis wavelengths of 266 nm (which lies in the main absorption feature) and 355 nm (which lies in the long-wavelength tail) by using high-n Rydberg time-of-flight spectroscopy to obtain center-of-mass translational energy distributions for the channels that yield H atoms. Photodissociation at 355 nm yields TeH(Π1/22) selectively relative to the TeH(Π3/22) ground state. This is attributed to the role of the 3A' state, which has a shallow well at large RH-TeH and correlates to H +TeH(Π1/22). Note that the Π1/22 state is analogous to the P1/22 spin-orbit excited state of atomic iodine, which is isoelectronic with TeH. The 3A' state is crossed at large R only by 2A″, with which it does not interact. The character of 3A' at large R is influenced by a strong spin-orbit interaction in the TeH product. Namely, Π1/22 has a higher degree of spherical symmetry than does Π3/22 (recall that I(P1/22) is spherically symmetric), and consequently Π1/22 is not inclined to form either strongly bonding or antibonding orbitals with the H atom. The 3A'←X transition dipole moment dominates in the long-wavelength region and increases with R. Structure observed in the absorption spectrum in the 380-400 nm region is attributed to vibrations on 3A'. The main absorption feature that is peaked at ˜240nm might arise from several excited surfaces. On the basis of the high degree of laboratory system spatial anisotropy of the fragments from 266 nm photolysis, as well as high-level theoretical studies, the main contribution is believed to be due to the 4A″ surface. The 4A″←X transition dipole moment dominates in the Franck-Condon region, and its polarization is in accord with the experimental observations. An extensive secondary photolysis (i.e., of nascent TeH) is

  14. The Effect of Hydrogen and Hydrides on the Integrity of Zirconium Alloy Components Delayed Hydride Cracking

    CERN Document Server

    Puls, Manfred P

    2012-01-01

    By drawing together the current theoretical and experimental understanding of the phenomena of delayed hydride cracking (DHC) in zirconium alloys, The Effect of Hydrogen and Hydrides on the Integrity of Zirconium Alloy Components: Delayed Hydride Cracking provides a detailed explanation focusing on the properties of hydrogen and hydrides in these alloys. Whilst the focus lies on zirconium alloys, the combination of both the empirical and mechanistic approaches creates a solid understanding that can also be applied to other hydride forming metals.   This up-to-date reference focuses on documented research surrounding DHC, including current methodologies for design and assessment of the results of periodic in-service inspections of pressure tubes in nuclear reactors. Emphasis is placed on showing that our understanding of DHC is supported by progress across a broad range of fields. These include hysteresis associated with first-order phase transformations; phase relationships in coherent crystalline metallic...

  15. Proton and hydride affinities in excited states: magnitude reversals in proton and hydride affinities between the lowest singlet and triplet states of annulenyl and benzannulenyl anions and cations

    DEFF Research Database (Denmark)

    Rosenberg, Martin; Ottosson, Henrik; Kilså, Kristine

    2010-01-01

    Aromaticity has importance for proton and hydride affinities in the singlet ground state (S(0)) of annulenyl anions and cations so that, e.g., cyclopentadiene is an acidic hydrocarbon. For the lowest pipi* excited triplet state (T(1)), Baird's rule concludes that annulenes with 4n pi-electrons ar......Aromaticity has importance for proton and hydride affinities in the singlet ground state (S(0)) of annulenyl anions and cations so that, e.g., cyclopentadiene is an acidic hydrocarbon. For the lowest pipi* excited triplet state (T(1)), Baird's rule concludes that annulenes with 4n pi......-electrons are aromatic and those with 4n+2 pi-electrons are antiaromatic, opposite to Huckel's rule for aromaticity in S(0). Our hypothesis is now that the relative magnitudes of proton and hydride affinities of annulenyl anions and cations reverts systematically as one goes from S(0) to T(1) as a result of the opposite...... electron counting rules for aromaticity in the two states. Using quantum chemical calculations at the G3(MP2)//(U)B3LYP/6-311+G(d,p) level we have examined the validity of this hypothesis for eight proton and eight hydride addition reactions of anions and cations, respectively, of annulenyl...

  16. Trajectory dynamics study of the Ar + CH4 dissociation reaction at high temperatures: the importance of zero-point-energy effects.

    Science.gov (United States)

    Marques, J M C; Martínez-Núñez, E; Fernandez-Ramos, A; Vazquez, S A

    2005-06-23

    Large-scale classical trajectory calculations have been performed to study the reaction Ar + CH4--> CH3 +H + Ar in the temperature range 2500 energy surface used for ArCH4 is the sum of the nonbonding pairwise potentials of Hase and collaborators (J. Chem. Phys. 2001, 114, 535) that models the intermolecular interaction and the CH4 intramolecular potential of Duchovic et al. (J. Phys. Chem. 1984, 88, 1339), which has been modified to account for the H-H repulsion at small bending angles. The thermal rate coefficient has been calculated, and the zero-point energy (ZPE) of the CH3 product molecule has been taken into account in the analysis of the results; also, two approaches have been applied for discarding predissociative trajectories. In both cases, good agreement is observed between the experimental and trajectory results after imposing the ZPE of CH3. The energy-transfer parameters have also been obtained from trajectory calculations and compared with available values estimated from experiment using the master equation formalism; in general, the agreement is good.

  17. Preliminary development of flaw evaluation procedures for delayed hydride cracking initiation under hydride non-ratcheting conditions

    Energy Technology Data Exchange (ETDEWEB)

    Xu, S.; Cui, J.; Kawa, D.; Shek, G.K.; Scarth, D.A. [Kinectrics Inc., Toronto, Ontario (Canada)

    2006-07-01

    The flaw evaluation procedure for Delayed Hydride Cracking (DHC) initiation currently provided in the CSA Standard N285.8 was developed for hydride ratcheting conditions, in which flaw-tip hydrides do not completely dissolve at peak temperature. Test results have shown that hydrided regions formed under non-ratcheting conditions, in which flaw-tip hydrides completely dissolve at peak temperature, have significantly higher resistance to cracking than those formed under ratcheting conditions. This paper presents some preliminary work on the development of a procedure for the evaluation of DHC initiation for flaws under hydride non-ratcheting conditions. (author)

  18. Dissociation in mediation

    Directory of Open Access Journals (Sweden)

    Daniela Muraru

    2008-01-01

    Full Text Available This paper approaches several texts that are part of the so-called discourse of mediation, adopting a pragma-dialectical perspective of the theory of dissociation. It is an attempt to identify the uses of dissociative patterns, with special emphasis on the indicators of dissociation. The paper investigates the various uses of the concept of dissociation as a discursive technique in the argumentation on the different aspects that are involved in international conflict, such as the discussion of the notion of peace. The purpose is to identify the role of dissociation, as a device strategically used by the mediator to help the parties minimize the disagreement space, and come to a conflict resolution.

  19. Formation and physical properties of uranium hydride under conditions relevant to metallic fuel and nuclear waste storage

    Energy Technology Data Exchange (ETDEWEB)

    Orr, Robin, E-mail: robin.orr@nnl.co.uk [National Nuclear Laboratory, Central Laboratory, Sellafield, Seascale, Cumbria, CA20 1PG (United Kingdom); Godfrey, Hugh [National Nuclear Laboratory, Workington Laboratory, Havelock Road, Derwent Howe, Workington, Cumbria, CA14 3YQ (United Kingdom); Broan, Chris; Goddard, Dave; Woodhouse, Guy; Durham, Peter [National Nuclear Laboratory, Preston Laboratory, Springfields, Salwick, Preston, Lancashire, PR4 0XJ (United Kingdom); Diggle, Andrew [Sellafield Ltd., Sellafield, Seascale, Cumbria, CA20 1PG (United Kingdom); Bradshaw, John [Sellafield Ltd., Hinton House, Risley, Warrington, WA3 6GR (United Kingdom)

    2016-08-15

    The formation of uranium hydride is recognised as a hazard during the storage of uranium metal owing to its potentially pyrophoric properties. This study has assessed the influence of water vapour on the potential for uranium hydride to form at low temperatures and shows that it increases the duration of the induction period but does not necessarily prevent uranium hydride formation and also does not significantly change the reaction rate with hydrogen. It is further shown that the α-UH{sub 3} fraction in the uranium hydride gradually increases at decreasing temperatures and is likely to be the dominant phase formed under typical storage conditions. Particle morphology and specific surface area of uranium hydride prepared between 30 °C and 200 °C have also been characterised but show only modest variation compared with the phase composition. - Highlights: • The reaction of uranium in dry hydrogen and hydrogen/water vapour has been measured between 30 and 200 °C. • Water vapour extends the induction period but does not necessarily prevent UH{sub 3} formation or affect the reaction rate. • X-ray diffraction analysis shows a gradual increase in α-UH{sub 3} and reduction in β-UH{sub 3} with decreasing preparation temperature. • Particle morphology and specific surface area show only a modest variation with temperature.

  20. Dissociation: Cognitive capacity or dysfunction?

    NARCIS (Netherlands)

    de Ruiter, M.B.; Bernet, M.; Phaf, R.H.

    2006-01-01

    Dissociative experiences are mostly studied as a risk factor for dissociative pathology. Nonpathological dissociation is quite common in the general population, however, and may reflect a constitutionally determined cognitive style rather than a pathological trait acquired through the experience of

  1. ALUMINUM HYDRIDE: A REVERSIBLE MATERIAL FOR HYDROGEN STORAGE

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-01-09

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

  2. ALUMINUM HYDRIDE: A REVERSIBLE MATERIAL FOR HYDROGEN STORAGE

    Energy Technology Data Exchange (ETDEWEB)

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

    2008-12-31

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

  3. Thin-film metal hydrides.

    Science.gov (United States)

    Remhof, Arndt; Borgschulte, Andreas

    2008-12-01

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

  4. Fourier-Domain Analysis of Hydriding Kinetics Using Pneumato-Chemical Impedance Spectroscopy

    Directory of Open Access Journals (Sweden)

    P. Millet

    2007-10-01

    Full Text Available Analysis of phase transformation processes observed in hydrogen absorbing materials (pure metals, alloys, or compounds is still a matter of active research. Using pneumato-chemical impedance spectroscopy (PIS, it is now possible to analyze the mechanism of hydriding reactions induced by the gas phase. Experimental impedance diagrams, measured on activated LaNi5 in single- and two-phase domains, are reported in this paper. It is shown that their shape is mostly affected by the slope of the isotherm at the measurement point. By considering the details of the multistep reaction paths involved in the hydriding reaction, model impedance equations have been derived for single- and two-phase domains, and fitted to experimental impedance diagrams. The possibility of separately measuring surface and phase transformation resistances, hydrogen diffusion coefficient, and hydrogen solubility in each composition domain is discussed.

  5. Computational study of alkynes insertion into metal-hydride bonds catalyzed by bimetallic complexes.

    Science.gov (United States)

    Di Tommaso, Stefania; Tognetti, Vincent; Sicilia, Emilia; Adamo, Carlo; Russo, Nino

    2010-11-01

    Density Functional Theory investigations on the insertion mechanism of phenylacetylene into metal-hydride bonds in bimetallic (Pt,Os) catalysts have been carried out. The results obtained have been also compared with the non-reactive monometallic (Os-based) system, to elucidate the cooperative effects and to explain the observed absence of reactivity. The identified reaction path involves phenylacetylene coordination followed by the insertion into the metal-hydride bond, leading to the formation of the experimentally observed products. Both steps do not require large energies compatible with the experimental conditions. The comparison with the reaction path for the monometallic species gives some hints on the cooperative effects due to the presence of the second metal which is related to its role in the CO release for creating a coordination site for phenylacetylene and not in the insertion energetics. The calculations provide a detailed analysis of the reaction complexity and provide a rationale for the efficiency of the process.

  6. The dissociative bond.

    Science.gov (United States)

    Gordon, Nirit

    2013-01-01

    Dissociation leaves a psychic void and a lingering sense of psychic absence. How do 2 people bond while they are both suffering from dissociation? The author explores the notion of a dissociative bond that occurs in the aftermath of trauma--a bond that holds at its core an understanding and shared detachment from the self. Such a bond is confined to unspoken terms that are established in the relational unconscious. The author proposes understanding the dissociative bond as a transitional space that may not lead to full integration of dissociated knowledge yet offers some healing. This is exemplified by R. Prince's (2009) clinical case study. A relational perspective is adopted, focusing on the intersubjective aspects of a dyadic relationship. In the dissociative bond, recognition of the need to experience mutual dissociation can accommodate a psychic state that yearns for relationship when the psyche cannot fully confront past wounds. Such a bond speaks to the need to reestablish a sense of human relatedness and connection when both parties in the relationship suffer from disconnection. This bond is bound to a silence that becomes both a means of protection against the horror of traumatic memory and a way to convey unspoken gestures toward the other.

  7. High H- ionic conductivity in barium hydride

    Science.gov (United States)

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

    2015-01-01

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

  8. Nucleon-XcJ Dissociation Cross Sections

    Institute of Scientific and Technical Information of China (English)

    冯又层; 许晓明; 周代翠

    2002-01-01

    Nucleon-XcJ dissociation cross sections are calculated in a constituent interexchange model in which quark-quark potential is derived from the Buchmüller-Tye quark-anti-quark potential. These new cross sections for dominant reaction channels depend on the centre-of-mass energy of the nucleon and the charmonium.

  9. Dissociative recombination in aeronomy

    Science.gov (United States)

    Fox, J. L.

    1989-01-01

    The importance of dissociative recombination in planetary aeronomy is summarized, and two examples are discussed. The first is the role of dissociative recombination of N2(+) in the escape of nitrogen from Mars. A previous model is updated to reflect new experimental data on the electronic states of N produced in this process. Second, the intensity of the atomic oxygen green line on the nightside of Venus is modeled. Use is made of theoretical rate coefficients for production of O (1S) in dissociative recombination from different vibrational levels of O2(+).

  10. Minimum Entropy Generation Theorem Investigation and Optimization of Metal Hydride Alloy Hydrogen Storage

    Directory of Open Access Journals (Sweden)

    Chi-Chang Wang

    2014-05-01

    Full Text Available The main purpose of this paper is to carry out numerical simulation of the hydrogen storage on exothermic reaction of metal hydride LaNi5 alloy container. In addition to accelerating the reaction speed of the internal metal hydride by internal control tube water-cooled mode, analyze via the application of second law of thermodynamics the principle of entropy generation. Use COMSOL Mutilphysics 4.3 a to engage in finite element method value simulation on two-dimensional axisymmetric model. Also on the premise that the internal control tube parameters the radius ri, the flow rate U meet the metal hydride saturation time, observe the reaction process of two parameters on the tank, entropy distribution and the results of the accumulated entropy. And try to find the internal tube parameter values of the minimum entropy, whose purpose is to be able to identify the reaction process and the reaction results of internal tank’s optimum energy conservation.

  11. Structural and hydrogen storage capacity evolution of Mg2FeH6 hydride synthesized by reactive mechanical alloying

    Institute of Scientific and Technical Information of China (English)

    LI Song-lin(李松林); R.A.Varin

    2004-01-01

    Mg-based metal hydrides are promising as hydrogen storage materials for fuel cell application. In this work, Mg2 FeH6 complex hydride phase was synthesized by controlled reactive ball milling of 2Mg-Fe (atomic ratio)powder mixture in H2. Mg2 FeH6 is confirmed to be formed via the following three stages: formation of MgH2 via the reaction of Mg with H2, incubation stage and formation of Mg2 FeH6 by reaction of fully refined MgH2 and Fe.The incubation stage is characterized by no traces of Mg or hydride crystalline phase by XRD. On the other hand,Mg is observed uniformly distributed in the milled powder by SEM-EDS. Also, almost the same amount of H2 as the first stage is detected stored in the powders of the second stage by DSC and TGA.

  12. Understanding of Hydriding Mechanisms of Zircaloy-4 Alloy during Corrosion in PWR Simulated Conditions and Influence of Zirconium Hydrides on Zircaloy-4 Corrosion

    Energy Technology Data Exchange (ETDEWEB)

    Bisor-Melloul, C.; Tupin, M.; Bossis, P.; Chene, J.; Bechade, J.L. [CEA Saclay, 91 - Gif sur Yvette (France); Motta, A. [Pennsylvania State Univ. (United States)

    2011-03-15

    Zirconium alloys represent the first containment barrier to fission products, their mechanical integrity is essential for nuclear safety in PWR. During their corrosion in primary water, some of the hydrogen involved in the oxidation reaction with water ingresses into the alloy through the oxide layer. In the metallic matrix, once the solid solution limit is reached at the irradiation temperature, hydrogen precipitates as Zr hydrides mainly located just under the metal/oxide interface due to the thermal gradient across the cladding. As these hydrides may contribute to a larger oxide thickness and to a more fragile behaviour of the cladding, the minimization of hydrogen pick-up is required. Accordingly, since the Zircaloy-4 (Zr-1.3Sn-0.2Fe-0.1Cr) alloy is known to be sensitive to this phenomenon, the understanding of its hydriding mechanism, isotopic exchanges were carried out in D{sub 2}O environment at 360 C and led to the localization, in the oxide scales, of the limiting step for the hydrogen diffusion. To estimate an apparent diffusion coefficient of hydrogen in the oxide formed on Zircaloy-4, we based on SIMS profiles and penetration depth of deuterium in the dense part of the oxide film. Then ERDA estimation of the hydrogen content in zirconia and fusion measurement of the hydrogen content in both metal and oxide were used to estimate a hydrogen flux absorbed by the alloy and hence to deduce an apparent diffusion coefficient. Finally, these 2 methods lead to quite similar values (between 1.10{sup -14} cm{sup 2}/s and 6.10{sup -14} cm{sup 2}/s) which are in accordance with bibliography. Concerning the impact of hydrides on the corrosion of Zircaloy-4, several pre-hydrided and reference samples were corroded simultaneously at 360 C. The characterization of the pre-hydrided samples revealed some changes, as the presence of the Zr{sub 3}O sub-oxide at the inner metal/oxide interface, a lower fraction of -ZrO{sub 2} in the oxide and a faster diffusion of oxygen

  13. Functionalization of hydride-terminated photoluminescent silicon nanocrystals with organolithium reagents.

    Science.gov (United States)

    Höhlein, Ignaz M D; Angı, Arzu; Sinelnikov, Regina; Veinot, Jonathan G C; Rieger, Bernhard

    2015-02-09

    Hydride-terminated photoluminescent silicon nanocrystals (SiNCs) were functionalized with organolithium compounds. The reaction is proposed to proceed through cleavage of Si - Si bonds and formation of a Si - Li surface species. The method yields colloidally stabilized SiNCs at room temperature with short reaction times. SiNCs with mixed surface functionalities can be prepared in an easy two-step reaction by this method by quenching of the Si - Li group with electrophiles or by addressing free Si - H groups on the surface with a hydrosilylation reaction.

  14. Easy abstraction of a hydride anion from an alkyl C-H bond of a coordinated bis(N-heterocyclic carbene).

    Science.gov (United States)

    Cabeza, Javier A; Damonte, Marina; García-Álvarez, Pablo; Pérez-Carreño, Enrique

    2013-04-07

    The high basicity of a trimethylene-linked bis(NHC), acting as a chelating ligand in a ruthenium(0) complex, is responsible for its involvement in a room-temperature reaction in which the metal atom to which this bis(NHC) ligand is coordinated replaces a hydride anion of the ligand trimethylene linker, which can be taken by a hydride abstractor as unusual, in that role, as [Ru3(CO)12].

  15. Lattice contraction in photochromic yttrium hydride

    Energy Technology Data Exchange (ETDEWEB)

    Maehlen, Jan Petter, E-mail: jepe@ife.no; Mongstad, Trygve T.; You, Chang Chuan; Karazhanov, Smagul

    2013-12-15

    Highlights: •Photochromic yttrium hydride films (YH:O) were prepared by reactive sputtering. •Black and transparent YH:O films were studied by time-resolved synchrotron XRD. •Both YH:O samples showed a lattice contraction upon illumination. •Also exposure to the X-ray beam itself results in a lattice contraction. -- Abstract: A strong photochromic effect was recently discovered in thin films of oxygen-containing yttrium hydride taking place at room temperature and reacting to ultraviolet and visible light. In this paper, we report on a lattice contraction upon illumination observed for thin-film samples of photochromic yttrium hydride, recorded by time-resolved X-ray diffraction using synchrotron radiation. The time dependence of the lattice contraction is consistent with the observed photochromic response of the samples.

  16. Atom probe analysis of titanium hydride precipitates.

    Science.gov (United States)

    Takahashi, J; Kawakami, K; Otsuka, H; Fujii, H

    2009-04-01

    It is expected that the three-dimensional atom probe (3DAP) will be used as a tool to visualize the atomic scale of hydrogen atoms in steel is expected, due to its high spatial resolution and very low detection limit. In this paper, the first 3DAP analysis of titanium hydride precipitates in metal titanium is reported in terms of the quantitative detection of hydrogen. FIB fabrication techniques using the lift-out method have enabled the production of needle tips of hydride precipitates, of several tens of microns in size, within a titanium matrix. The hydrogen concentration estimated from 3DAP analysis was slightly smaller than that of the hydride phase predicted from the phase diagram. We discuss the origin of the difference between the experimental and predicted values and the performance of 3DAP for the quantitative detection of hydrogen.

  17. Hydrogen storage in complex metal hydrides

    Directory of Open Access Journals (Sweden)

    BORISLAV BOGDANOVIĆ

    2009-02-01

    Full Text Available Complex metal hydrides such as sodium aluminohydride (NaAlH4 and sodium borohydride (NaBH4 are solid-state hydrogen-storage materials with high hydrogen capacities. They can be used in combination with fuel cells as a hydrogen source thus enabling longer operation times compared with classical metal hydrides. The most important point for a wide application of these materials is the reversibility under moderate technical conditions. At present, only NaAlH4 has favourable thermodynamic properties and can be employed as a thermally reversible means of hydrogen storage. By contrast, NaBH4 is a typical non- -reversible complex metal hydride; it reacts with water to produce hydrogen.

  18. Iron Group Hydrides in Noyori Bifunctional Catalysis.

    Science.gov (United States)

    Morris, Robert H

    2016-12-01

    This is an overview of the hydride-containing catalysts prepared in the Morris group for the efficient hydrogenation of simple ketones, imines, nitriles and esters and the asymmetric hydrogenation and transfer hydrogenation of prochiral ketones and imines. The work was inspired by and makes use of Noyori metal-ligand bifunctional concepts involving the hydride-ruthenium amine-hydrogen HRuNH design. It describes the synthesis and some catalytic properties of hydridochloro, dihydride and amide complexes of ruthenium and in one case, osmium, with monodentate, bidentate and tetradentate phosphorus and nitrogen donor ligands. The iron hydride that has been identified in a very effective asymmetric transfer hydrogenation process is also mentioned. The link between the HMNH structure and the sense of enantioinduction is demonstrated by use of simple transition state models.

  19. Interstellar chemistry of nitrogen hydrides in dark clouds

    CERN Document Server

    Gal, Romane Le; Faure, Alexandre; Forêts, Guillaume Pineau des; Rist, Claire; Maret, Sébastien

    2013-01-01

    The aim of the present work is to perform a comprehensive analysis of the interstellar chemistry of nitrogen, focussing on the gas-phase formation of the smallest polyatomic species and in particular nitrogen hydrides. We present a new chemical network in which the kinetic rates of critical reactions have been updated based on recent experimental and theoretical studies, including nuclear spin branching ratios. Our network thus treats the different spin symmetries of the nitrogen hydrides self-consistently together with the ortho and para forms of molecular hydrogen. This new network is used to model the time evolution of the chemical abundances in dark cloud conditions. The steady-state results are analysed, with special emphasis on the influence of the overall amounts of carbon, oxygen, and sulphur. Our calculations are also compared with Herschel/HIFI observations of NH, NH$_2$, and NH$_3$ detected towards the external envelope of the protostar IRAS 16293-2422. The observed abundances and abundance ratios ...

  20. The role of water in gas hydrate dissociation

    Science.gov (United States)

    Circone, S.; Stern, L.A.; Kirby, S.H.

    2004-01-01

    When raised to temperatures above the ice melting point, gas hydrates release their gas in well-defined, reproducible events that occur within self-maintained temperature ranges slightly below the ice point. This behavior is observed for structure I (carbon dioxide, methane) and structure II gas hydrates (methane-ethane, and propane), including those formed with either H2O- or D2O-host frameworks, and dissociated at either ambient or elevated pressure conditions. We hypothesize that at temperatures above the H2O (or D2O) melting point: (1) hydrate dissociation produces water + gas instead of ice + gas, (2) the endothermic dissociation reaction lowers the temperature of the sample, causing the water product to freeze, (3) this phase transition buffers the sample temperatures within a narrow temperature range just below the ice point until dissociation goes to completion, and (4) the temperature depression below the pure ice melting point correlates with the average rate of dissociation and arises from solution of the hydrate-forming gas, released by dissociation, in the water phase at elevated concentrations. In addition, for hydrate that is partially dissociated to ice + gas at lower temperatures and then heated to temperatures above the ice point, all remaining hydrate dissociates to gas + liquid water as existing barriers to dissociation disappear. The enhanced dissociation rates at warmer temperatures are probably associated with faster gas transport pathways arising from the formation of water product.

  1. Evidence of stress-induced hydrogen ordering in zirconium hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Steuwer, A. [FaME38 at the ESRF-ILL, 6 rue J Horowitz, 38042 Grenoble (France); ESS Scandinavia, University of Lund, Stora Algatan 4, 22350 Lund (Sweden)], E-mail: steuwer@ill.fr; Santisteban, J.R. [Centro Atomico Bariloche, CNEA, San Carlos de Bariloche (Argentina); Preuss, M. [University of Manchester, Grosvenor Street, Manchester M1 7HS (United Kingdom); Peel, M.J.; Buslaps, T. [European Synchrotron Radiation Facility, 6 rue J Horowitz, 38042 Grenoble (France); Harada, M. [R and D Section, Chofu-Kita Plant, Kobe Special Tube Co, Shimonoseki 752-0953 (Japan)

    2009-01-15

    The formation of hydrides in zirconium alloys significantly affects their mechanical properties and is considered to play a critical role in their failure mechanisms, yet relatively little is known about the micromechanical behavior of hydrides in the bulk. This paper presents the result of in situ uniaxial mechanical tensioning experiments on hydrided zircaloy-2 and zircaloy-4 specimens using energy-dispersive synchrotron X-ray diffraction, which suggests that a stress-induced transformation of the {delta}-hydride to {gamma}-hydride via ordering of the hydrogen atoms occurs, akin to a Snoek-type relaxation. Subsequent annealing was found to reverse the ordering phenomenon.

  2. Dissociative disorders in medical settings.

    Science.gov (United States)

    MacPhee, Edward

    2013-10-01

    Despite the challenges of conducting research on dissociation and the dissociative disorders, our understanding has grown greatly over the past three decades, including our knowledge of the often overlooked sensorimotor manifestations of dissociation, more commonly referred to as somatoform dissociation. This article will first review the definitions and presentations of dissociation in general along with recent research on the concept of somatoform dissociation. Then, each of the dissociative disorders and conversion disorder will be discussed in further detail as well as how they might present in a medical setting. Current recommendations for diagnosis and treatment will also be provided.

  3. Catalyzed light hydride nanomaterials embedded in a micro-channels hydrogen storage container.

    Science.gov (United States)

    Dehouche, Zahir; Peretti, Hernán A; Yoo, Yeong; Belkacemi, Khaled; Goyette, Jacques

    2009-01-01

    Activated alloys synthesized by arc-melting were examined as catalysts for improving the hydrogen sorption characteristics of nanostructured magnesium hydride, proposed as a reversible hydrogen storage material. The MgH(2)-catalyst absorbing materials were prepared by ball milling of pure MgH(2) with hydrided Zr(47)Ni(53), Zr(9)Ni(11), and other alloys investigated. The nanostructured MgH(2)-intermetallic systems were tested at 250 degrees C and catalyst addition of eutectoid Zr(47)Ni(53) resulted in the fastest desorption time and highest initial desorption rate. The catalyzed Mg-hydride with activated Zr(9)Ni(11) and Zr(7)Ni(10) phases showed fast desorption kinetics. Moreover, the results demonstrated that the composition of dispersed Zr(x)Ni(y)catalysts has a strong influence on the amount of accumulated hydrogen and desorption rate of Mg-nanocomposite. Part two covers advanced micro-channels hydrogen storage module design based on the results of semi-empirical computer simulations of heat and mass transfers in the container. The micro-channels reservoir concept offers many advantages over the conventional metal hydride hydrogen storage system. It is a micro-structured system that can pack a lot of power into a small space and dissipate effectively the heat of the sorption reactions. This review summarizes recent patents related to CNTS.

  4. Enhancement of Hydrogen Storage Behavior of Complex Hydrides via Bimetallic Nanocatalysts Doping

    Directory of Open Access Journals (Sweden)

    Prakash C. Sharma

    2012-10-01

    Full Text Available Pristine complex quaternary hydride (LiBH4/2LiNH2 and its destabilized counterpart (LiBH4/2LiNH2/nanoMgH2 have recently shown promising reversible hydrogen storage capacity under moderate operating conditions. The destabilization of complex hydride via nanocrystalline MgH2 apparently lowers the thermodynamic heat values and thus enhances the reversible hydrogen storage behavior at moderate temperatures. However, the kinetics of these materials is rather low and needs to be improved for on-board vehicular applications. Nanocatalyst additives such as nano Ni, nano Fe, nano Co, nano Mn and nano Cu at low concentrations on the complex hydride host structures have demonstrated a reduction in the decomposition temperature and overall increase in the hydrogen desorption reaction rates. Bi-metallic nanocatalysts such as the combination of nano Fe and nano Ni have shown further pronounced kinetics enhancement in comparison to their individual counterparts. Additionally, the vital advantage of using bi-metallic nanocatalysts is to enable the synergistic effects and characteristics of the two transitional nanometal species on the host hydride matrix for the optimized hydrogen storage behavior.

  5. Investigations of the structural stability of metal hydride composites by in-situ neutron imaging

    Science.gov (United States)

    Herbrig, Kai; Pohlmann, Carsten; Gondek, Łukasz; Figiel, Henryk; Kardjilov, Nikolay; Hilger, André; Manke, Ingo; Banhart, John; Kieback, Bernd; Röntzsch, Lars

    2015-10-01

    Metal hydride composites (MHC) with expanded natural graphite (ENG) exhibiting enhanced thermal conductivity and reduced porosity compared to metal hydride powders can enable a reversible, compact and safe way for hydrogen storage. In this study, neutron imaging during cyclic hydrogenation was utilized to investigate the structural stability and the spatial-temporal hydrogen concentration of application-oriented MHC with 40 mm in diameter compared to a loose metal hydride powder. In particular, swelling and shrinking effects of a radially confined MHC which could freely expand upwards were studied. It was found that the loose powder bed was easily torn apart during dehydrogenation, which leads to increased thermal resistance within the hydride bed. In contrast, the thermal resistance between MHC and container wall was minimized since the initial gap closes during initial hydrogenation and does not reopen thereafter. Further cyclic hydrogenation caused MHC volume changes, i.e. an almost reversible swelling/shrinking (so-called ;MHC breathing;). Moreover, neutron imaging allowed for the observation of reaction fronts within the MHC and the powder bed that are governed by the heat transfer.

  6. Hydride formation on deformation twin in zirconium alloy

    Science.gov (United States)

    Kim, Ju-Seong; Kim, Sung-Dae; Yoon, Jonghun

    2016-12-01

    Hydrides deteriorate the mechanical properties of zirconium (Zr) alloys used in nuclear reactors. Intergranular hydrides that form along grain boundaries have been extensively studied due to their detrimental effects on cracking. However, it has been little concerns on formation of Zr hydrides correlated with deformation twins which is distinctive heterogeneous nucleation site in hexagonal close-packed metals. In this paper, the heterogeneous precipitation of Zr hydrides at the twin boundaries was visualized using transmission electron microscopy. It demonstrates that intragranular hydrides in the twinned region precipitates on the rotated habit plane by the twinning and intergranular hydrides precipitate along the coherent low energy twin boundaries independent of the conventional habit planes. Interestingly, dislocations around the twin boundaries play a substantial role in the nucleation of Zr hydrides by reducing the misfit strain energy.

  7. Shock wave structure in an ideal dissociating gas

    Science.gov (United States)

    Liu, K. H.

    1975-01-01

    Composition changes within the shock layer due to chemical reactions are considered. The Lighthill ideal dissociating gas model was used in an effort to describe the oxygen type molecule. First, the two limiting cases, when the chemical reaction rates are very slow and very fast in comparison to local convective rates, are investigated. Then, the problem is solved for arbitrary chemical reaction rates.

  8. Facile preparation of an immobilized surfactant-free palladium nanocatalyst for metal hydride trapping: a novel sensing platform for TXRF analysis

    Science.gov (United States)

    Romero, V.; Costas-Mora, I.; Lavilla, I.; Bendicho, C.

    2015-01-01

    In this work, a simple route for the synthesis of surfactant-free immobilized palladium nanoparticles (Pd NPs) and their use as effective nanocatalysts for metal hydride decomposition is described. A mixture of ethanol : water was used as the reducing agent. Ethanol was added in a large excess to reduce the ionic Pd and stabilize the obtained Pd NPs. Ethanol is adsorbed on the surface of Pd allowing steric stabilization. Freshly prepared Pd NPs were immobilized onto quartz substrates modified with 3-mercaptopropyltrimethoxysilane. Pd interacts with the thiol group of the alkoxysilane that is adsorbed on the surface of NPs without the dissociation of the S-H bond. Different parameters affecting the synthesis of Pd NPs and their immobilization onto quartz substrates were evaluated. A comprehensive characterization of the synthesized Pd NPs was carried out by transmission electron microscopy (TEM), whereas total reflection X-ray fluorescence (TXRF) spectrometry was applied in order to evaluate their catalytic activity for solid-gas reactions. Immobilized Pd NPs were applied as nanocatalysts for the dissociative chemisorption of arsine at room temperature, yielding the formation of As-Pd bonds. Quartz substrates coated with nanosized Pd could be used as novel sensing platforms for total reflection X-ray fluorescence analysis. Arsenic can be detected in situ in natural water with a limit of detection of 0.08 μg L-1.In this work, a simple route for the synthesis of surfactant-free immobilized palladium nanoparticles (Pd NPs) and their use as effective nanocatalysts for metal hydride decomposition is described. A mixture of ethanol : water was used as the reducing agent. Ethanol was added in a large excess to reduce the ionic Pd and stabilize the obtained Pd NPs. Ethanol is adsorbed on the surface of Pd allowing steric stabilization. Freshly prepared Pd NPs were immobilized onto quartz substrates modified with 3-mercaptopropyltrimethoxysilane. Pd interacts with the thiol

  9. Metal hydrides used as negative electrode materials for Li-ion batteries

    Science.gov (United States)

    Sartori, Sabrina; Cuevas, Fermin; Latroche, Michel

    2016-02-01

    Energy is a key issue for future generation. Researches are conducted worldwide to develop new efficient means for energy conversion and storage. Electrochemical storage is foreseen as an efficient way to handle intermittent renewable energy production. The most advanced batteries are nowadays based on lithium-ion technology though their specific capacities should be significantly increased to bring solution to mass storage. Conversion reactions are one way to step forward larger capacities at the anode. We here review the possibility to use metallic or complex hydrides as negative electrode using conversion reaction of hydride with lithium. Moreover, promising alloying of lithium with the metallic species might provide additional reversible capacities. Both binary and ternary systems are reviewed and results are compared in the frame of the electrochemical application.

  10. Superhalogens as Building Blocks of Complex Hydrides for Hydrogen Storage

    CERN Document Server

    Srivastava, Ambrish Kumar

    2016-01-01

    Superhalogens are species whose electron affinity (EA) or vertical detachment energy (VDE) exceed to those of halogen. These species typically consist of a central electropositive atom with electronegative ligands. The EA or VDE of species can be further increased by using superhalogen as ligands, which are termed as hyperhalogen. Having established BH4- as a superhalogen, we have studied BH4-x(BH4)x- (x = 1 to 4) hyperhalogen anions and their Li-complexes, LiBH4-x(BH4)x using density functional theory. The VDE of these anions is larger than that of BH4-, which increases with the increase in the number of peripheral BH4 moieties (x). The hydrogen storage capacity of LiBH4-x(BH4)x complexes is higher but binding energy is smaller than that of LiBH4, a typical complex hydride. The linear correlation between dehydrogenation energy of LiBH4-x(BH4)x complexes and VDE of BH4-x(BH4)x- anions is established. These complexes are found to be thermodynamically stable against dissociation into LiBH4 and borane. This stud...

  11. Destabilization of magnesium hydride through interface engineering

    NARCIS (Netherlands)

    Mooij, L.P.A.

    2013-01-01

    The aim of this thesis is to study the thermodynamics of hydrogenation of nanoconfined magnesium within a thin film multilayer model system. Magnesium hydride is a potential material for hydrogen storage, which is a key component in a renewable energy system based on hydrogen. In bulk form,

  12. Destabilization of magnesium hydride through interface engineering

    NARCIS (Netherlands)

    Mooij, L.P.A.

    2013-01-01

    The aim of this thesis is to study the thermodynamics of hydrogenation of nanoconfined magnesium within a thin film multilayer model system. Magnesium hydride is a potential material for hydrogen storage, which is a key component in a renewable energy system based on hydrogen. In bulk form, magnesiu

  13. Destabilization of magnesium hydride through interface engineering

    NARCIS (Netherlands)

    Mooij, L.P.A.

    2013-01-01

    The aim of this thesis is to study the thermodynamics of hydrogenation of nanoconfined magnesium within a thin film multilayer model system. Magnesium hydride is a potential material for hydrogen storage, which is a key component in a renewable energy system based on hydrogen. In bulk form, magnesiu

  14. High Density Hydrogen Storage in Metal Hydride Composites with Air Cooling

    OpenAIRE

    Dieterich, Mila; Bürger, Inga; Linder, Marc

    2015-01-01

    INTRODUCTION In order to combine fluctuating renewable energy sources with the actual demand of electrical energy, storages are essential. The surplus energy can be stored as hydrogen to be used either for mobile use, chemical synthesis or reconversion when needed. One possibility to store the hydrogen gas at high volumetric densities, moderate temperatures and low pressures is based on a chemical reaction with metal hydrides. Such storages must be able to absorb and desorb the hydrogen qu...

  15. Green Luminescence of Divalent Europium in the Hydride Chloride EuHCl

    NARCIS (Netherlands)

    Kunkel, Nathalie; Rudolph, Daniel; Meijerink, A; Rommel, Stefan; Weihrich, Richard; Kohlmann, Holger; Schleid, Thomas

    2015-01-01

    Luminescence properties of divalent europium in the mixed-anion hydride chloride EuHCl were studied for the first time. Olive-green single crystals of EuHCl (PbFCl-type structure: tetragonal, P4/nmm, a = 406.58(3) pm, c = 693.12(5) pm, c/a = 1.705, Z = 2) resulted from the reaction of elemental euro

  16. An experimental system to investigate kinetics and isotopic properties of the electrolytic metal hydride formation

    Energy Technology Data Exchange (ETDEWEB)

    Leardini, F. [Dpto. Fisica de Materiales, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain)]. E-mail: fabrice.leardini@uam.es; Bodega, J. [Dpto. Fisica de Materiales, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Fernandez, J.F. [Dpto. Fisica de Materiales, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Sanchez, C. [Dpto. Fisica de Materiales, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain)

    2005-12-08

    We present in this paper an experimental set-up based in a mass spectrometer connected to a closed electrolytic cell. Calibrations accomplished with a Pt cathode and H{sub 2}O/D{sub 2}O mixtures have shown new kinetics in galvanostatic electrolysis. These findings may be relevant in some important processes such as the hydrogen evolution reaction, isotopic separation factors or the electrolytic formation of metal hydrides.

  17. Encapsulation of hydride by molecular main group metal clusters: manipulating the source and coordination sphere of the interstitial ion.

    Science.gov (United States)

    Boss, Sally R; Coles, Martyn P; Eyre-Brook, Vicki; García, Felipe; Haigh, Robert; Hitchcock, Peter B; McPartlin, Mary; Morey, James V; Naka, Hiroshi; Raithby, Paul R; Sparkes, Hazel A; Tate, Christopher W; Wheatley, Andrew E H

    2006-12-21

    The sequential treatment of Lewis acids with N,N'-bidentate ligands and thereafter with ButLi has afforded a series of hydride-encapsulating alkali metal polyhedra. While the use of Me3Al in conjunction with Ph(2-C5H4N)NH gives Ph(2-C5H4N)NAlMe2 and this reacts with MeLi in thf to yield the simple 'ate complex Ph(2-C5H4N)NAlMe3Li.thf, the employment of an organolithium substrate capable of beta-hydride elimination redirects the reaction significantly. Whereas the use of ButLi has previously yielded a main group interstitial hydride in which H- exhibits micro6-coordination, it is shown here that variability in the coordination sphere of the encapsulated hydride may be induced by manipulation of the organic ligand. Reaction of (c-C6H11)(2-C5H4N)NH with Me3Al/ButLi yields [{(c-C6H11)(2-C5H4N)N}6HLi8]+[(But2AlMe2)2Li]-, which is best viewed as incorporating only linear di-coordination of the hydride ion. The guanidine 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (hppH) in conjunction with Me2Zn/ButLi yields the micro8-hydride [(hpp)6HLi8]+[But3Zn]-.0.5PhMe. Formation of the micro8-hydride [(hpp)6HLi8]+[ButBEt3]- is revealed by employment of the system Et3B/ButLi. A new and potentially versatile route to interstitial hydrides of this class is revealed by synthesis of the mixed borohydride-lithium hydride species [(hpp)6HLi8]+[Et3BH]- and [(hpp)6HLi8]+[(Et3B)2H]- through the direct combination of hppLi with Et3BHLi.

  18. Uranium and thorium hydride complexes as multielectron reductants: a combined neutron diffraction and quantum chemical study.

    Science.gov (United States)

    Grant, Daniel J; Stewart, Timothy J; Bau, Robert; Miller, Kevin A; Mason, Sax A; Gutmann, Matthias; McIntyre, Garry J; Gagliardi, Laura; Evans, William J

    2012-03-19

    The unusual uranium reaction system in which uranium(4+) and uranium(3+) hydrides interconvert by formal bimetallic reductive elimination and oxidative addition reactions, [(C(5)Me(5))(2)UH(2)](2) (1) ⇌ [(C(5)Me(5))(2)UH](2) (2) + H(2), was studied by employing multiconfigurational quantum chemical and density functional theory methods. 1 can act as a formal four-electron reductant, releasing H(2) gas as the byproduct of four H(2)/H(-) redox couples. The calculated structures for both reactants and products are in good agreement with the X-ray diffraction data on 2 and 1 and the neutron diffraction data on 1 obtained under H(2) pressure as part of this study. The interconversion of the uranium(4+) and uranium(3+) hydride species was calculated to be near thermoneutral (~-2 kcal/mol). Comparison with the unknown thorium analogue, [(C(5)Me(5))(2)ThH](2), shows that the thorium(4+) to thorium(3+) hydride interconversion reaction is endothermic by 26 kcal/mol.

  19. Mathematical Modeling of Pneumatic Artificial Muscle Actuation via Hydrogen Driving Metal Hydride-LaNi5

    Institute of Scientific and Technical Information of China (English)

    Thananchai Leephakpreeda

    2012-01-01

    Quantitative understanding of mechanical actuation of intricate Pneumatic Artificial Muscle (PAM) actuators is technically required in control system design for effective real-time implementation.This paper presents mathematical modeling of the PAM driven by hydrogen-gas pressure due to absorption and desorption of metal hydride.Empirical models of both mechanical actuation of industrial PAM and chemical reaction of the metal hydride-LaNi5 are derived systematically where their interactions comply with the continuity principle and energy balance in describing actual dynamic behaviors of the PAM actuator (PAM and hydriding/dehydriding-reaction bed).Simulation studies of mechanical actuation under various loads are conducted so as to present dynamic responses of the PAM actuators.From the promising results,it is intriguing that the heat input for the PAM actuator can be supplied to,or pumped from the reaction bed,in such a way that absorption and desorption of hydrogen gas take place,respectively,in controlling the pressure of hydrogen gas within the PAM actuator.Accordingly,this manipulation results in desired mechanical actuation of the PAM actuator in practical uses.

  20. Rules and trends of metal cation driven hydride-transfer mechanisms in metal amidoboranes.

    Science.gov (United States)

    Kim, Dong Young; Lee, Han Myoung; Seo, Jongcheol; Shin, Seung Koo; Kim, Kwang S

    2010-01-01

    Group I and II metal amidoboranes have been identified as one of the promising families of materials for efficient H(2) storage. However, the underlying mechanism of the dehydrogenation of these materials is not well understood. Thus, the mechanisms and kinetics of H(2) release in metal amidoboranes are investigated using high level ab initio calculations and kinetic simulations. The metal plays the role of catalyst for the hydride transfer with formation of a metal hydride intermediate towards the dehydrogenation. In this process, with increasing ionic character of the metal hydride bond in the intermediate, the stability of the intermediate decreases, while the dehydrogenation process involving ionic recombination of the hydridic H with the protic H proceeds with a reduced barrier. Such correlations lead directly to a U-shaped relationship between the activation energy barrier for H(2) elimination and the ionicity of metal hydride bond. Oligomerized intermediates are formed by the chain reaction of the size-driven catalytic effects of metals, competing with the non-oligomerization pathway. The kinetic rates at low temperatures are determined by the maximum barrier height in the pathway (a Lambda-shaped relation), while those at moderately high temperatures are determined by most of multiple-barriers. This requires kinetic simulations. At the operating temperatures of proton exchange membrane fuel cells, the metal amidoboranes with lithium and sodium release H(2) along both oligomerization and non-oligomerization paths. The sodium amidoboranes show the most accelerated rates, while others release H(2) at similar rates. In addition, we predict that the novel metal amidoborane-based adducts and mixtures would release H(2) with accelerated rates as well as with enhanced reversibility. This comprehensive study is useful for further developments of active metal-based better hydrogen storage materials.

  1. Dissociation kinetics of the thyrotropin-receptor complex. Characterization of a slowly dissociable component.

    Science.gov (United States)

    Powell-Jones, C H; Saltiel, A R; Thomas, C G; Nayfeh, S N

    1981-11-01

    The kinetics of the dissociation of thyrotropin (TSH) from human thyroid plasma membranes were studied in an attempt to further understand the molecular dynamics of the TSH--receptor interaction. Dissociation of bound [125I]TSH from thyroid plasma membranes was a biphasic process consisting of rapidly and slowly dissociable components, RDC and SDC, respectively. The dilution induced dissociation of bound [125I]TSH was enhanced by the addition of excess TSH (DEC). DEC was proportional to the dose of unlabeled TSH and its magnitude increased linearly with temperature. These results are in contrast to those reported for the kinetics of [125I]insulin dissociation. The functional significance of DEC remains largely unexplained. It was found that the fraction of SDC was dependent upon time of association in a temperature-dependent and apparently saturable process. It could not be attributed to alterations in the electrophoretic, immunologic or binding properties of [125I]TSH. Furthermore, no correlation was observed between generation of SDC and change in the Scatchard profile of TSH binding, in contrast to studies on growth hormone. These data suggest that, like some other polypeptide hormones, binding of TSH to its receptor does not proceed according to laws describing simple, rapidly reversible, bimolecular reactions. Furthermore, bound TSH undergoes a receptor-mediated conversion from a rapidly to a slowly dissociable state with time of incubation.

  2. Triphosphine-Ligated Copper Hydrides for CO2 Hydrogenation: Structure, Reactivity, and Thermodynamic Studies.

    Science.gov (United States)

    Zall, Christopher M; Linehan, John C; Appel, Aaron M

    2016-08-10

    The copper(I) triphosphine complex LCu(MeCN)PF6 (L = 1,1,1-tris(diphenylphosphinomethyl)ethane), which we recently demonstrated is an active catalyst precursor for hydrogenation of CO2 to formate, reacts with H2 in the presence of a base to form a cationic dicopper hydride, [(LCu)2H]PF6. [(LCu)2H](+) is also an active precursor for catalytic CO2 hydrogenation, with equivalent activity to that of LCu(MeCN)(+), and therefore may be a relevant catalytic intermediate. The thermodynamic hydricity of [(LCu)2H](+) was determined to be 41.0 kcal/mol by measuring the equilibrium constant for this reaction using three different bases. [(LCu)2H](+) and the previously reported dimer (LCuH)2 can be synthesized by the reaction of LCu(MeCN)(+) with 0.5 and 1 equiv of KB(O(i)Pr)3H, respectively. The solid-state structure of [(LCu)2H](+) shows threefold symmetry about a linear Cu-H-Cu axis and significant steric strain imposed by bringing two LCu(+) units together around the small hydride ligand. [(LCu)2H](+) reacts stoichiometrically with CO2 to generate the formate complex LCuO2CH and the solvento complex LCu(MeCN)(+). The rate of the stoichiometric reaction between [(LCu)2H](+) and CO2 is dramatically increased in the presence of bases that coordinate strongly to the copper center, e.g. DBU and TMG. In the absence of CO2, the addition of a large excess of DBU to [(LCu)2H](+) results in an equilibrium that forms LCu(DBU)(+) and also presumably the mononuclear hydride LCuH, which is not directly observed. Due to the significantly enhanced CO2 reactivity of [(LCu)2H](+) under these catalytically relevant conditions, LCuH is proposed to be the catalytically active metal hydride.

  3. Spontaneous Double Hydrometallation Induced by N→M Coordination in Organometallic Hydrides of Group 14 Elements.

    Science.gov (United States)

    Novák, Miroslav; Dostál, Libor; Turek, Jan; Alonso, Mercedes; De Proft, Frank; Růžička, Aleš; Jambor, Roman

    2016-04-11

    Our attempts to synthesise N→M intramolecularly coordinated diorganometallic hydrides L2MH2 [M=Si (4), Ge (5), Sn (6)] containing the CH=N imine group (in which L is C,N-chelating ligand {2-[(2,6-iPr2C6H3)N=CH]C6 H4}(-)) yielded 1,1'-bis(2,6-diisopropylphenyl)-2,2'-spriobi[benzo[c][1,2]azasilole] (7), 1,1'-bis(2,6-diisopropylphenyl)-2,2'-spriobi[benzo[c][1,2]azagermole] (8) and C,N-chelated homoleptic stannylene L2Sn (10), respectively. Compounds 7 and 8 are an outcome of a spontaneous double hydrometallation of the two CH=N imine moieties induced by N→M intramolecular coordination (M=Si, Ge) in the absence of any catalyst. In contrast, the diorganotin hydride L2SnH2 (6) is redox-unstable and the reduction of the tin centre with the elimination of H2 provided the C,N-chelated homoleptic stannylene L2Sn (10). Compounds 7 and 8 were characterised by NMR spectroscopy and X-ray diffraction analysis. Because the proposed N→M intramolecularly coordinated diorganometallic hydrides L2MH2 [M=Si (4), Ge (5), Sn (6)] revealed two different types of reduction reactions, DFT calculations were performed to gain an insight into the structures and bonding of the non-isolable diorganometallic hydrides as well as the products of their subsequent reactions. Furthermore, the thermodynamic profiles of the different reaction pathways with respect to the central metal atom were also investigated.

  4. Dissociative Identity Disorder

    Science.gov (United States)

    Schmidt, Tom

    2007-01-01

    Few psychological disorders in the Diagnostic Statistical Manual have generated as much controversy as Dissociative Identity Disorder (DID). For the past 35 years diagnoses of DID, previously referred to as Multiple Personality Disorder (MPD), have increased exponentially, causing various psychological researchers and clinicians to question the…

  5. Sexuality of dissocial persons

    Directory of Open Access Journals (Sweden)

    Marta Janus

    2016-02-01

    Full Text Available Introduction. The development of personality disorders as well as sexual disorders is defined by the common time spectrum as well as deficits and changes in such areas as biological, environmental and mental area. Dissocial (antisocial personality disorder is characterised by a pervasive pattern of disregard for, or violation of, the rights of others. The indices of the discussed disorder can be found in specific patterns of social inadequacy occurring during childhood and puberty. At the same time, characteristic indices of social functioning at a young age often indicate subsequent dysfunctions in the area of sexuality. Aim. The aim of this paper is to explain sexual functioning of persons with dissocial personality disorder (including the relation with sexual dysfunctions, and to ascertain issues that need further empirical studies. Method. As a result of analysis of available literature (matched with EBSCO database search fulfilling criteria of sample size, accuracy of examination procedure, conclusions and discussion 5 articles fulfilling criteria cited above has been found. Conclusions: Based on literature overview, it appeared to be impossible to determine one coherent way of sexual functioning of dissocial persons, and to establish causal relationship of sexual dysfunctions and dissocial personality disorder. However, it is possible to indicate group of most characteristic dysfunctional sexual behaviours. Noteworthy, available publication analyse only selected aspects of sexual behaviours in small, homogenous groups. There is a lack of review studies as well as multi-faceted studies.

  6. Pathological Dissociation as Measured by the Child Dissociative Checklist

    Science.gov (United States)

    Wherry, Jeffrey N.; Neil, Debra A.; Taylor, Tamara N.

    2009-01-01

    The component structure of the Child Dissociative Checklist was examined among abused children. A factor described as pathological dissociation emerged that was predicted by participants being male. There also were differences in pathological dissociation between groups of sexually abused and physically abused children. Replication of this factor…

  7. Coulomb dissociation of $^{20,21}$N

    CERN Document Server

    Röder, Marko; Aksyutina, Yulia; Alcantara, Juan; Altstadt, Sebastian; Alvarez-Pol, Hector; Ashwood, Nicholas; Atar, Leyla; Aumann, Thomas; Avdeichikov, Vladimir; Barr, M; Beceiro, Saul; Bemmerer, Daniel; Benlliure, Jose; Bertulani, Carlos; Boretzky, Konstanze; Borge, Maria J G; Burgunder, G; Caamano, Manuel; Caesar, Christoph; Casarejos, Enrique; Catford, Wilton; Cederkall, Joakim; Chakraborty, S; Chartier, Marielle; Chulkov, Leonid; Cortina-Gil, Dolores; Crespo, Raquel; Pramanik, Ushasi Datta; Diaz-Fernandez, Paloma; Dillmann, Iris; Elekes, Zoltan; Enders, Joachim; Ershova, Olga; Estrade, A; Farinon, F; Fraile, Luis M; Freer, Martin; Freudenberger, M; Fynbo, Hans; Galaviz, Daniel; Geissel, Hans; Gernhäuser, Roman; Göbel, Kathrin; Golubev, Pavel; Diaz, Diego Gonzalez; Hagdahl, Julius; Heftrich, Tanja; Heil, Michael; Heine, Marcel; Heinz, Andreas; Henriques, Ana; Holl, Matthias; Ickert, G; Ignatov, Alexander; Jakobsson, Bo; Johansson, Hakan; Jonson, Björn; Kalantar-Nayestanaki, Nasser; Kanungo, Rituparna; Kelic-Heil, Aleksandra; Knöbel, Ronja; Kröll, Thorsten; Krücken, Reiner; Kurcewicz, J; Kurz, Nikolaus; Labiche, Marc; Langer, Christoph; Bleis, Tudi Le; Lemmon, Roy; Lepyoshkina, Olga; Lindberg, Simon; Machado, Jorge; Marganiec, Justyna; Caro, Magdalena Mostazo; Movsesyan, Alina; Najafi, Mohammad Ali; Nilsson, Thomas; Nociforo, Chiara; Panin, Valerii; Paschalis, Stefanos; Perea, Angel; Petri, Marina; Pietri, S; Plag, Ralf; Prochazka, A; Rahaman, Md Anisur; Rastrepina, Ganna; Reifarth, Rene; Ribeiro, Guillermo; Ricciardi, M Valentina; Rigollet, Catherine; Riisager, Karsten; Rossi, Dominic; Saez, Jose Sanchez del Rio; Savran, Deniz; Scheit, Heiko; Simon, Haik; Sorlin, Olivier; Stoica, V; Streicher, Branislav; Taylor, Jon; Tengblad, Olof; Terashima, Satoru; Thies, Ronja; Togano, Yasuhiro; Uberseder, Ethan; Van de Walle, J; Velho, Paulo; Volkov, Vasily; Wagner, Andreas; Wamers, Felix; Weick, Helmut; Weigand, Mario; Wheldon, Carl; Wilson, G; Wimmer, Christine; Winfield, J S; Woods, Philip; Yakorev, Dmitry; Zhukov, Mikhail; Zilges, Andreas; Zuber, Kai

    2016-01-01

    Neutron-rich light nuclei and their reactions play an important role for the creation of chemical elements. Here, data from a Coulomb dissociation experiment on $^{20,21}$N are reported. Relativistic $^{20,21}$N ions impinged on a lead target and the Coulomb dissociation cross section was determined in a kinematically complete experiment. Using the detailed balance theorem, the $^{19}\\mathrm{N}(\\mathrm{n},\\gamma)^{20}\\mathrm{N}$ and $^{20}\\mathrm{N}(\\mathrm{n},\\gamma)^{21}\\mathrm{N}$ excitation functions and thermonuclear reaction rates have been determined. The $^{19}\\mathrm{N}(\\mathrm{n},\\gamma)^{20}\\mathrm{N}$ rate is up to a factor of 5 higher at $T<1$\\,GK with respect to previous theoretical calculations, leading to a 10\\,\\% decrease in the predicted fluorine abundance.

  8. A thermodynamic and kinetic study of hydride transfer of a caffeine derivative.

    Science.gov (United States)

    Han, Xiaozhen; Hao, Weifang; Zhu, Xiao-Qing; Parker, Vernon D

    2012-08-03

    One representative type of heterocyclic compound that can release a hydride ion is 7,8-dihydro-9-methylcaffeine (CAFH). The one-electron oxidation potential of CAFH [-0.294 (V vs Fc(+/0))] and the one-electron reduction potential of CAF(+) [-2.120 (V vs Fc(+/0))] were obtained using two different methods, CV and OSWV. Applying titration calorimetry data in thermodynamic cycles, the enthalpies of CAFH releasing a hydride ion [57.6 kcal/mol] and releasing a hydrogen atom [80.3 kcal/mol] and of its radical cation CAFH(•+) releasing a proton [33.0 kcal/mol] and releasing a hydrogen atom [38.4 kcal/mol] have been determined. Several conclusions can be drawn from the thermodynamic results: (1) CAFH is a very good single-electron donor whose single-electron oxidation potential is much less positive than that of NAD(P)H model compound BNAH [E(ox) = 0.219 V vs Fc(+/0)]. (2) The single-electron reduction potential of CAF(+) is much more negative than that of BNA(+) [E(red) = -1.419 V], which means that CAF(+) is not a good electron acceptor. Furthermore, CAFH is a very good hydride donor compared to BNAH. The results of non-steady-state kinetic studies, for the reaction of CAFH and AcrH(+)ClO(4)(-), show that the ratio of t(0.50)/t(0.05) is larger than 13.5 and the ratio of k(init)/k(pfo) is larger than 1. The pseudo-first-order rate constants obtained at different reaction stages decrease with the time, and the kinetic isotope was observed to be small at a short reaction time and slowly increases to 3.72 with the progress of the reaction. These kinetic results clearly display that the hydride transfer of CAFH to AcrH(+) in acetonitrile is not a one-step mechanism, while the thermodynamic results show that CAFH is a very good electron donor. The combination of the kinetic results with the thermodynamics analysis shows that the hydride transfer of the caffeine derivative CAFH takes place by a two-step reversible mechanism and there is an intermediate in the reaction.

  9. Water adsorption and dissociation on BeO (001) and (100) surfaces

    CERN Document Server

    Gómez, M A; Kress, J D; Pratt, L R; Gomez, Maria A.; Kress, Joel D.; Pratt, Lawrence R.

    2007-01-01

    Plateaus in water adsorption isotherms on hydroxylated BeO surfaces suggest significant differences between the hydroxylated (100) and (001) surface structures and reactivities. Density functional theory structures and energies clarify these differences. Using relaxed surface energies, a Wulff construction yields a prism crystal shape exposing long (100) sides and much smaller (001) faces. This is consistent with the BeO prisms observed when beryllium metal is oxidized. A water oxygen atom binds to a single surface beryllium ion in the preferred adsorption geometry on either surface. The water oxygen/beryllium bonding is stronger on the surface with greater beryllium atom exposure, namely the less-stable (001) surface. Water/beryllium coordination facilitates water dissociation. On the (001) surface, the dissociation products are a hydroxide bridging two beryllium ions and a metal coordinated hydride with some surface charge depletion. On the (100) surface, water dissociates into a hydroxide ligating a Be ato...

  10. Structure and mechanism of styrene monooxygenase reductase: new insight into the FAD-transfer reaction.

    Science.gov (United States)

    Morrison, Eliot; Kantz, Auric; Gassner, George T; Sazinsky, Matthew H

    2013-09-03

    The two-component flavoprotein styrene monooxygenase (SMO) from Pseudomonas putida S12 catalyzes the NADH- and FAD-dependent epoxidation of styrene to styrene oxide. In this study, we investigate the mechanism of flavin reduction and transfer from the reductase (SMOB) to the epoxidase (NSMOA) component and report our findings in light of the 2.2 Å crystal structure of SMOB. Upon rapidly mixing with NADH, SMOB forms an NADH → FADox charge-transfer intermediate and catalyzes a hydride-transfer reaction from NADH to FAD, with a rate constant of 49.1 ± 1.4 s(-1), in a step that is coupled to the rapid dissociation of NAD(+). Electrochemical and equilibrium-binding studies indicate that NSMOA binds FADhq ∼13-times more tightly than SMOB, which supports a vectoral transfer of FADhq from the reductase to the epoxidase. After binding to NSMOA, FADhq rapidly reacts with molecular oxygen to form a stable C(4a)-hydroperoxide intermediate. The half-life of apoSMOB generated in the FAD-transfer reaction is increased ∼21-fold, supporting a protein-protein interaction between apoSMOB and the peroxide intermediate of NSMOA. The mechanisms of FAD dissociation and transport from SMOB to NSMOA were probed by monitoring the competitive reduction of cytochrome c in the presence and absence of pyridine nucleotides. On the basis of these studies, we propose a model in which reduced FAD binds to SMOB in equilibrium between an unreactive, sequestered state (S state) and more reactive, transfer state (T state). The dissociation of NAD(+) after the hydride-transfer reaction transiently populates the T state, promoting the transfer of FADhq to NSMOA. The binding of pyridine nucleotides to SMOB-FADhq shifts the FADhq-binding equilibrium from the T state to the S state. Additionally, the 2.2 Å crystal structure of SMOB-FADox reported in this work is discussed in light of the pyridine nucleotide-gated flavin-transfer and electron-transfer reactions.

  11. Three dimensions of dissociative amnesia.

    Science.gov (United States)

    Dell, Paul F

    2013-01-01

    Principal axis factor analysis with promax rotation extracted 3 factors from the 42 memory and amnesia items of the Multidimensional Inventory of Dissociation (MID) database (N = 2,569): Discovering Dissociated Actions, Lapses of Recent Memory and Skills, and Gaps in Remote Memory. The 3 factors' shared variance ranged from 36% to 64%. Construed as scales, the 3 factor scales had Cronbach's alpha coefficients of .96, .94, and .93, respectively. The scales correlated strongly with mean Dissociative Experiences Scale scores, mean MID scores, and total scores on the Structured Clinical Interview for DSM-IV Dissociative Disorders-Revised (SCID-D-R). What is interesting is that the 3 amnesia factors exhibited a range of correlations with SCID-D-R Amnesia scores (.52, .63, and .70, respectively), suggesting that the SCID-D-R Amnesia score emphasizes gaps in remote memory over amnesias related to dissociative identity disorder. The 3 amnesia factor scales exhibited a clinically meaningful pattern of significant differences among dissociative identity disorder, dissociative disorder not otherwise specified-1, dissociative amnesia, depersonalization disorder, and nonclinical participants. The 3 amnesia factors may have greater clinical utility for frontline clinicians than (a) amnesia as discussed in the context of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, nosology of the dissociative disorders or (b) P. Janet's (1893/1977 ) 4-fold classification of dissociative amnesia. The author recommends systematic study of the phenomenological differences within specific dissociative symptoms and their differential relationship to specific dissociative disorders.

  12. Nanometer-scale hydrogen 'portals' for the control of magnesium hydride formation.

    Science.gov (United States)

    Chung, Chia-Jung; Nivargi, Chinmay; Clemens, Bruce

    2015-11-21

    Magnesium and Mg-based material systems are attractive candidates for hydrogen storage but limited by unsuitable thermodynamic and kinetic properties. In particular, the kinetics are too slow at room temperature and atmospheric pressure. To study the hydride formation kinetics in a controlled way, we have designed a unique 'nanoportal' structure of Pd nanoparticles deposited on epitaxial Mg thin films, through which the hydride will nucleate only under Pd nanoparticles. We propose a growth mechanism for the hydrogenation reaction in the nanoportal structure, which is supported by scanning electron microscopy (SEM) images of hydrogenated samples exhibiting consistent results. Interestingly, the grain boundaries of Mg films play an important role in hydride nucleation and growth processes. Kinetic modeling based on the Johnson-Mehl-Avrami-Kolmogorov (JMAK) formalism seems to agree with the two-dimensional nucleation and growth mechanism hypothesized and the overall reaction rate is limited by hydrogen flux through the interface between the Pd nanoparticle and the underlying Mg film. The fact that in our structure Mg can be transformed completely into MgH2 with only a small percentage of Pd nanoparticles offers possibilities for future on-board storage applications.

  13. Metal hydride work pair development and its application on automobile air conditioning systems

    Institute of Scientific and Technical Information of China (English)

    QIN Feng; CHEN Jiang-ping; ZHANG Wen-feng; CHEN Zhi-jiu

    2007-01-01

    Aiming at developing exhaust gas driving automobile air conditioning systems, a hydride pair LaNi4.61Mn0.26A10.13/La0.6Y0.4Ni4.8Mn0.2 was developed working at 393~473 K/293~323 K/263~273 K. Property tests showed that both alloys have flat plateau slopes and small hystereses; system theoretical coefficient of performance (COP) is 0.711. Based on this work pair, a function proving automobile metal hydride refrigeration system was constructed. The equivalent thermal conductivities of the activated reaction beds were merely 1.1~1.6 W/(m·K), which had not met practical requirement. Intermittent refrigeration cycles were achieved and the average cooling power was 84.6 W at 423 K/303 K/273 K with COP being 0.26. By altering cycling parameters, experiment data showed that cooling power and system COP increase with the growth of heat source temperature as well as pre-heating and regeneration time while decrease with heat sink temperature increment. This study confirms the feasibility of automobile metal hydride refrigeration systems, while heat transfer properties of reaction beds still need to be improved for better performance.

  14. Matrix infrared spectra and density functional calculations of transition metal hydrides and dihydrogen complexes.

    Science.gov (United States)

    Andrews, Lester

    2004-02-20

    Metal hydrides are of considerable importance in chemical synthesis as intermediates in catalytic hydrogenation reactions. Transition metal atoms react with dihydrogen to produce metal dihydrides or dihydrogen complexes and these may be trapped in solid matrix samples for infrared spectroscopic study. The MH(2) or M(H(2)) molecules so formed react further to form higher MH(4), (H(2))MH(2), or M(H(2))(2), and MH(6), (H(2))(2)MH(2), or M(H(2))(3) hydrides or complexes depending on the metal. In this critical review these transition metal and dihydrogen reaction products are surveyed for Groups 3 though 12 and the contrasting behaviour in Groups 6 and 10 is discussed. Minimum energy structures and vibrational frequencies predicted by Density Functional Theory agree with the experimental results, strongly supporting the identification of novel binary transition metal hydride species, which the matrix-isolation method is well-suited to investigate. 104 references are cited.

  15. Nickel metal hydride LEO cycle testing

    Science.gov (United States)

    Lowery, Eric

    1995-01-01

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

  16. Nanoconfined hydrides for energy storage

    Science.gov (United States)

    Nielsen, Thomas K.; Besenbacher, Flemming; Jensen, Torben R.

    2011-05-01

    The world in the 21st century is facing increasing challenges within the development of more environmentally friendly energy systems, sustainable and `green chemistry' solutions for a variety of chemical and catalytic processes. Nanomaterials science is expected to contribute strongly by the development of new nanotools, e.g. for improving the performance of chemical reactions. Nanoconfinement is of increasing interest and may lead to significantly enhanced kinetics, higher degree of stability and/or more favourable thermodynamic properties. Nanoconfined chemical reactions may have a wide range of important applications in the near future, e.g. within the merging area of chemical storage of renewable energy. This review provides selected examples within nanoconfinement of hydrogen storage materials, which may serve as an inspiration for other research fields as well. Selected nanoporous materials, methods for preparation of nanoconfined systems and their hydrogen storage properties are reviewed.The world in the 21st century is facing increasing challenges within the development of more environmentally friendly energy systems, sustainable and `green chemistry' solutions for a variety of chemical and catalytic processes. Nanomaterials science is expected to contribute strongly by the development of new nanotools, e.g. for improving the performance of chemical reactions. Nanoconfinement is of increasing interest and may lead to significantly enhanced kinetics, higher degree of stability and/or more favourable thermodynamic properties. Nanoconfined chemical reactions may have a wide range of important applications in the near future, e.g. within the merging area of chemical storage of renewable energy. This review provides selected examples within nanoconfinement of hydrogen storage materials, which may serve as an inspiration for other research fields as well. Selected nanoporous materials, methods for preparation of nanoconfined systems and their hydrogen storage

  17. Hydrogen storage systems based on magnesium hydride: from laboratory tests to fuel cell integration

    Science.gov (United States)

    de Rango, P.; Marty, P.; Fruchart, D.

    2016-02-01

    The paper reviews the state of the art of hydrogen storage systems based on magnesium hydride, emphasizing the role of thermal management, whose effectiveness depends on the effective thermal conductivity of the hydride, but also depends of other limiting factors such as wall contact resistance and convective exchanges with the heat transfer fluid. For daily cycles, the use of phase change material to store the heat of reaction appears to be the most effective solution. The integration with fuel cells (1 kWe proton exchange membrane fuel cell and solid oxide fuel cell) highlights the dynamic behaviour of these systems, which is related to the thermodynamic properties of MgH2. This allows for "self-adaptive" systems that do not require control of the hydrogen flow rate at the inlet of the fuel cell.

  18. Development of a modular room-temperature hydride storage system for vehicular applications

    Science.gov (United States)

    Capurso, Giovanni; Schiavo, Benedetto; Jepsen, Julian; Lozano, Gustavo; Metz, Oliver; Saccone, Adriana; De Negri, Serena; Bellosta von Colbe, José M.; Klassen, Thomas; Dornheim, Martin

    2016-03-01

    The subject of this paper concerns the development of a vehicular hydrogen tank system, using a commercial interstitial metal hydride as storage material. The design of the tank was intended to feed a fuel cell in a light prototype vehicle, and the chosen hydride material, Hydralloy C5 by GfE, was expected to be able to absorb and desorb hydrogen in a range of pressure suitable for this purpose. A systematic analysis of the material in laboratory scale allows an extrapolation of the thermodynamic and reaction kinetics data. The following development of the modular tank was done according to the requirements of the prototype vehicle propulsion system and led to promising intermediate results. The modular approach granted flexibility in the design, allowing both to reach carefully the design goals and to learn the limiting factors in the sorption process. Proper heat management and suitable equipment remain key factors in order to achieve the best performances.

  19. Theoretical Standard Model Rates of Proton to Neutron Conversions Near Metallic Hydride Surfaces

    CERN Document Server

    Widom, A

    2006-01-01

    The process of radiation induced electron capture by protons or deuterons producing new ultra low momentum neutrons and neutrinos may be theoretically described within the standard field theoretical model of electroweak interactions. For protons or deuterons in the neighborhoods of surfaces of condensed matter metallic hydride cathodes, such conversions are determined in part by the collective plasma modes of the participating charged particles, e.g. electrons and protons. The radiation energy required for such low energy nuclear reactions may be supplied by the applied voltage required to push a strong charged current across a metallic hydride surface employed as a cathode within a chemical cell. The electroweak rates of the resulting ultra low momentum neutron production are computed from these considerations.

  20. Plasmonic hydrogen sensing with nanostructured metal hydrides.

    Science.gov (United States)

    Wadell, Carl; Syrenova, Svetlana; Langhammer, Christoph

    2014-12-23

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

  1. Improved hydrogen desorption from lithium hydrazide by alkali metal hydride

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Liang, E-mail: liangzeng@hiroshima-u.ac.jp [Institute for Advanced Materials Research, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530 (Japan); Miyaoka, Hiroki [Institute for Sustainable Sciences and Development, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530 (Japan); Ichikawa, Takayuki; Kojima, Yoshitsugu [Institute for Advanced Materials Research, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530 (Japan)

    2013-12-15

    Highlights: •LiH can dramatically improve the hydrogen desorption properties of LiNHNH{sub 2}. •KH doping had positive effect in promoting the hydrogen desorption properties of LiNHNH{sub 2}–LiH mixture. •The reaction mechanism between LiNHNH{sub 2} and LiH was studied and discussed. -- Abstract: Lithium hydrazide (LiNHNH{sub 2}), which is a white solid with 8.0 mass% of theoretical hydrogen content, was synthesized from a reaction between anhydrous hydrazine and n-butyllithium in diethyl ether. The thermodynamic properties of this compound and its detailed decomposition pathways had been investigated in our previous work. However, a number of undesired gaseous products such as hydrazine (N{sub 2}H{sub 4}) and ammonia (NH{sub 3}) were generated during the thermal decomposition of LiNHNH{sub 2}. In this work, alkali metal hydride was used to suppress the impurities in the desorbed hydrogen and improved the hydrogen desorption properties. The reaction mechanism between LiNHNH{sub 2} and LiH was also studied and discussed in this paper.

  2. Communication: Enhanced dissociative chemisorption of CO2 via vibrational excitation

    Science.gov (United States)

    Jiang, Bin; Guo, Hua

    2016-03-01

    A fully coupled global nine-dimensional potential energy surface for the dissociative chemisorption of CO2 on Ni(100) is constructed from ˜18 000 density functional points. It reveals a complex reaction pathway dominated by two near iso-energetic transition states. The dissociation probabilities obtained by quasi-classical trajectories on the potential energy surface reproduced experimental trends, and indicate that vibrational excitations of CO2 significantly promote the dissociation. Using the sudden vector projection model, the behavior of the reactivity is rationalized by couplings with the reaction coordinate at each transition state. These results offer plausible rationalization for the observed enhancement of CO2 dissociation in non-thermal plasmas by metal surfaces.

  3. Theoretical study of hydrogen dissociation and diffusion on Nb and Ni co-doped Mg(0001): A synergistic effect

    Science.gov (United States)

    Chen, Ming; Cai, Zhen-Zhun; Yang, Xiao-Bao; Zhu, Min; Zhao, Yu-Jun

    2012-07-01

    The interaction of H2 with clean, Ni and Nb doped Mg(0001) surface are investigated by first-principles calculations. Individual Ni and Nb atoms within the outermost surface can reduce the dissociation barrier of the hydrogen molecule. They, however, prefers to substitute for the Mg atoms within the second layer, leading to a weaker catalytic effect for the dissociation of H2, a bottleneck for the hydriding of MgH2. Interestingly, co-doping of Ni and Nb stabilizes Ni at the first layer, and results in a significant reduction of the dissociation barrier of H2 on the Mg surface, coupled with an increase of the diffusion barrier of H. Although codoped Ni and Nb shows no remarkable advantage over single Nb here, it implies that the catalytic effect could be optimized by co-doping of "modest" transition metals with balanced barriers for dissociation of H2 and diffusion of H on Mg surfaces.

  4. Synthesis and investigation of [Cp(PMe(3))Rh(H)(H(2))](+) and its partially deuterated and tritiated isotopomers: evidence for a hydride/dihydrogen structure.

    Science.gov (United States)

    Taw, Felicia L; Mellows, Heather; White, Peter S; Hollander, Frederick J; Bergman, Robert G; Brookhart, Maurice; Heinekey, D Michael

    2002-05-08

    Hydrogenolysis of [Cp(PMe(3))Rh(Me)(CH(2)Cl(2))](+)BAr'(4)(-) (4, Ar' = 3,5-C(6)H(3)(CF(3))(2)) in dichloromethane afforded the nonclassical polyhydride complex [Cp*PMe(3))Rh(H)(H(2))](+)BAr'(4)(-) (1), which exhibits a single hydride resonance at all accessible temperatures in the (1)H NMR spectrum. Exposure of solutions of 1 to D(2) or T(2) gas resulted in partial isotopic substitution in the hydride sites. Formulation of 1 as a hydride/dihydrogen complex was based upon T(1) (T(1)(min) = 23 ms at 150 K, 500 MHz), J(H-D) (ca. 10 Hz), and J(H-T) (ca. 70 Hz) measurements. The barrier (Delta G(++)) to exchange of hydride with dihydrogen sites was determined to be less than ca. 5 kcal/mol. Protonation of Cp(PMe(3))Rh(H)(2) (2) using H(OEt(2))(2)BAr'(4) resulted in binuclear species [(Cp(PMe(3))Rh(H))(2)(mu-H)](+)BAr'(4)(-) (3), which is formed in a reaction involving 1 as an intermediate. Complex 3 contains two terminal hydrides and one bridging hydride ligand which exchange with a barrier of 9.1 kcal/mol as observed by (1)H NMR spectroscopy. Additionally, the structures of 3 and 4, determined by X-ray diffraction, are reported.

  5. Thermodynamic diagnosis of the properties and mechanism of dihydropyridine-type compounds as hydride source in acetonitrile with "Molecule ID Card".

    Science.gov (United States)

    Zhu, Xiao-Qing; Tan, Yue; Cao, Chao-Tun

    2010-02-11

    A series of 45 dihydropyridine-type organic compounds as hydride source were designed and synthesized. The thermodynamic driving forces (defined as enthalpy changes or redox potentials in this work) of the dihydropyridines to release hydride anions, hydrogen atoms (hydrogen for short), and electrons in acetonitrile, the thermodynamic driving forces of the radical cations of the dihydropyridines to release protons and hydrogens in acetonitrile, and the thermodynamic driving forces of the neutral pyridine-type radicals of the dihydropyridines to release electron in acetonitrile were determined by using titration calorimetry and electrochemical methods. The rates and activation parameters of hydride transfer from the dihydropyridines to acridinium perclorate, a well-known hydride acceptor, were determined by using UV-vis absorption spectroscopy technique. The relationship between the thermodynamic driving forces and kinetic rate of the hydride transfer was examined. Thermodynamic characteristic graph (TCG) of the dihydropyridines as an efficient "Molecule ID Card" was introduced. The TCG can be used to quantitatively diagnose or predict the characteristic chemical properties of the dihydropyridines and their various reaction intermediates. The mechanism of hydride transfer from the dihydropyridines to acridinium perclorate was diagnosed and elucidated by using the determined thermodynamic parameters and the activation parameters.

  6. Structure sensitivity of CO dissociation on Rh surfaces

    DEFF Research Database (Denmark)

    Mavrikakis, Manos; Baumer, M.; Freund, H.J.;

    2002-01-01

    Using periodic self-consistent density functional calculations it is shown that the barrier for CO dissociation is similar to120 kJ/mol lower on the stepped Rh(211) surface than on the close-packed Rh(111) surface. The stepped surface binds molecular CO and the dissociation products more strongly...... than the flat surface, but the effect is considerably weaker than the effect of surface structure on the dissociation barrier. Our findings are compared with available experimental data, and the consequences for CO activation in methanation and Fischer-Tropsch reactions are discussed....

  7. Alloys for hydrogen storage in nickel/hydrogen and nickel/metal hydride batteries

    Science.gov (United States)

    Anani, Anaba; Visintin, Arnaldo; Petrov, Konstantin; Srinivasan, Supramaniam; Reilly, James J.; Johnson, John R.; Schwarz, Ricardo B.; Desch, Paul B.

    1993-01-01

    Since 1990, there has been an ongoing collaboration among the authors in the three laboratories to (1) prepare alloys of the AB(sub 5) and AB(sub 2) types, using arc-melting/annealing and mechanical alloying/annealing techniques; (2) examine their physico-chemical characteristics (morphology, composition); (3) determine the hydrogen absorption/desorption behavior (pressure-composition isotherms as a function of temperature); and (4) evaluate their performance characteristics as hydride electrodes (charge/discharge, capacity retention, cycle life, high rate capability). The work carried out on representative AB(sub 5) and AB(sub 2) type modified alloys (by partial substitution or with small additives of other elements) is presented. The purpose of the modification was to optimize the thermodynamics and kinetics of the hydriding/dehydriding reactions and enhance the stabilities of the alloys for the desired battery applications. The results of our collaboration, to date, demonstrate that (1) alloys prepared by arc melting/annealing and mechanical alloying/annealing techniques exhibit similar morphology, composition and hydriding/dehydriding characteristics; (2) alloys with the appropriate small amounts of substituent or additive elements: (1) retain the single phase structure, (2) improve the hydriding/dehydriding reactions for the battery applications, and (3) enhance the stability in the battery environment; and (3) the AB(sub 2) type alloys exhibit higher energy densities than the AB(sub 5) type alloys but the state-of-the-art, commercialized batteries are predominantly manufactured using Ab(sub 5) type alloys.

  8. Ammonia-Borane and Amine-Borane Dehydrogenation Mediated by Complex Metal Hydrides.

    Science.gov (United States)

    Rossin, Andrea; Peruzzini, Maurizio

    2016-08-10

    This review is a comprehensive survey of the last 10 years of research on ammonia-borane and amine-borane dehydrogenation mediated by complex metal hydrides (CMHs), within the broader context of chemical hydrogen storage. The review also collects those cases where CMHs are the catalyst spent form or its resting state. Highlights on the reaction mechanism (strictly dependent on the CMH of choice) and the catalysts efficiency (in terms of equivalents of H2 produced and relative reaction rates) are provided throughout the discussion.

  9. Protonation of transition-metal hydrides: a not so simple process.

    Science.gov (United States)

    Besora, Maria; Lledós, Agustí; Maseras, Feliu

    2009-04-01

    The protonation of a transition-metal hydride is a formally simple process between a proton donor and a proton acceptor with several potential basic centres. The detailed mechanism is however quite subtle, with multistep reactions and involvement of different intermediates. The process is furthermore very sensitive to the nature of both the proton donor and the transition-metal complex, as well as to the solvent and to the presence and identity of eventual counteranions. This tutorial review summarizes the recent progress in the understanding of the reaction, obtained through the joint application of a number of computational and experimental techniques.

  10. Hydrogen bonding to carbonyl hydride complex Cp*Mo(PMe(3))(2)(CO)H and its role in proton transfer.

    Science.gov (United States)

    Dub, Pavel A; Filippov, Oleg A; Belkova, Natalia V; Daran, Jean-Claude; Epstein, Lina M; Poli, Rinaldo; Shubina, Elena S

    2010-02-28

    The interaction of the carbonyl hydride complex Cp*Mo(PMe(3))(2)(CO)H with Brønsted (fluorinated alcohols, (CF(3))(n)CH(3-n)OH (n = 1-3), and CF(3)COOH) and Lewis (Hg(C(6)F(5))(2), BF(3).OEt(2)) acids was studied by variable temperature IR and NMR ((1)H, (31)P, (13)C) spectroscopies in combination with DFT/B3LYP calculations. Among the two functionalities potentially capable of the interaction - carbonyl and hydride ligands - the first was found to be the preferential binding site for weak acids, yielding CO...HOR or CO...Hg complexes as well as CO...(HOR)(2) adducts. For stronger proton donors ((CF(3))(3)COH, CF(3)COOH) hydrogen-bonding to the hydride ligand can be revealed as an intermediate of the proton transfer reaction. Whereas proton transfer to the CO ligand is not feasible, protonation of the hydride ligand yields an (eta(2)-H(2)) complex. Above 230 K dihydrogen evolution is observed leading to decomposition. Among the decomposition products compound [Cp*Mo(PMe(3))(3)(CO)](+)[(CF(3))(3)CO.2HOC(CF(3))(3)](-) resulting from a phosphine transfer reaction was characterized by X-ray diffraction. Reaction with BF(3).OEt(2) was found to produce [Cp*Mo(PMe(3))(2)(CO)BF(4)] via initial attack of the hydride ligand.

  11. Dissociative recombination of HCl+

    Science.gov (United States)

    Larson, Åsa; Fonseca dos Santos, Samantha; E. Orel, Ann

    2017-08-01

    The dissociative recombination of HCl+, including both the direct and indirect mechanisms, is studied. For the direct process, the relevant electronic states are calculated ab initio by combining electron scattering calculations to obtain resonance positions and autoionization widths with multi-reference configuration interaction calculations of the ion and Rydberg states. The cross section for the direct dissociation along electronic resonant states is computed by solution of the time-dependent Schrödinger equation. For the indirect process, an upper bound value for the cross section is obtained using a vibrational frame transformation of the elements of the scattering matrix at energies just above the ionization threshold. Vibrational excitations of the ionic core from the ground vibrational state, v = 0 , to the first three excited vibrational states, v = 1 , v = 2 , and v = 3 , are considered. Autoionization is neglected and the effect of the spin-orbit splitting of the ionic potential energy upon the indirect dissociative recombination cross section is considered. The calculated cross sections are compared to measurements.

  12. Gas Phase Reactions of Ions Derived from Anionic Uranyl Formate and Uranyl Acetate Complexes

    Science.gov (United States)

    Perez, Evan; Hanley, Cassandra; Koehler, Stephen; Pestok, Jordan; Polonsky, Nevo; Van Stipdonk, Michael

    2016-12-01

    The speciation and reactivity of uranium are topics of sustained interest because of their importance to the development of nuclear fuel processing methods, and a more complete understanding of the factors that govern the mobility and fate of the element in the environment. Tandem mass spectrometry can be used to examine the intrinsic reactivity (i.e., free from influence of solvent and other condensed phase effects) of a wide range of metal ion complexes in a species-specific fashion. Here, electrospray ionization, collision-induced dissociation, and gas-phase ion-molecule reactions were used to create and characterize ions derived from precursors composed of uranyl cation (UVIO2 2+) coordinated by formate or acetate ligands. Anionic complexes containing UVIO2 2+ and formate ligands fragment by decarboxylation and elimination of CH2=O, ultimately to produce an oxo-hydride species [UVIO2(O)(H)]-. Cationic species ultimately dissociate to make [UVIO2(OH)]+. Anionic complexes containing acetate ligands exhibit an initial loss of acetyloxyl radical, CH3CO2•, with associated reduction of uranyl to UVO2 +. Subsequent CID steps cause elimination of CO2 and CH4, ultimately to produce [UVO2(O)]-. Loss of CH4 occurs by an intra-complex H+ transfer process that leaves UVO2 + coordinated by acetate and acetate enolate ligands. A subsequent dissociation step causes elimination of CH2=C=O to leave [UVO2(O)]-. Elimination of CH4 is also observed as a result of hydrolysis caused by ion-molecule reaction with H2O. The reactions of other anionic species with gas-phase H2O create hydroxyl products, presumably through the elimination of H2.

  13. Organocatalytic Synthesis of Tetrahydroquinolines from α,β-Unsaturated Ketones via 1,5-Hydride Transfer/Cyclization

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dae Young [Soonchunhyang Univ., Asan (Korea, Republic of)

    2013-11-15

    We have presented the example of a organo-catalytic enantioselective hydride transfer/cyclization reaction cascade from cyclic amines containing α,β-unsaturated ketones. The synthetically useful ring-fused tetrahydroquinoline derivatives were obtained in moderate to high yields with moderate to high diastereoselectivities. Further investigations for an asymmetric version of this organocatalytic intramolecular redox reaction of α,β-unsaturated ketones are currently underway in our laboratory. The development for direct functionalization of sp{sup 3} C-H bonds has become an area of intense interest in synthetic organic chemistry. Because such reactions offer practical methods for the construction of structurally complex and biologically active organic molecules with atom- and step economy. The 1,5-hydride transfer and subsequent cyclization process is a well-known sp{sup 3} C-H bond function-alization strategy and has attracted considerable interest for its application in the synthesis of heterocyclic compounds.

  14. Optical hydrogen sensors based on metal-hydrides

    Science.gov (United States)

    Slaman, M.; Westerwaal, R.; Schreuders, H.; Dam, B.

    2012-06-01

    For many hydrogen related applications it is preferred to use optical hydrogen sensors above electrical systems. Optical sensors reduce the risk of ignition by spark formation and are less sensitive to electrical interference. Currently palladium and palladium alloys are used for most hydrogen sensors since they are well known for their hydrogen dissociation and absorption properties at relatively low temperatures. The disadvantages of palladium in sensors are the low optical response upon hydrogen loading, the cross sensitivity for oxygen and carbon, the limited detection range and the formation of micro-cracks after some hydrogen absorption/desorption cycles. In contrast to Pd, we find that the use of magnesium or rear earth bases metal-hydrides in optical hydrogen sensors allow tuning of the detection levels over a broad pressure range, while maintaining a high optical response. We demonstrate a stable detection layer for detecting hydrogen below 10% of the lower explosion limit in an oxygen rich environment. This detection layer is deposited at the bare end of a glass fiber as a micro-mirror and is covered with a thin layer of palladium. The palladium layer promotes the hydrogen uptake at room temperature and acts as a hydrogen selective membrane. To protect the sensor for a long time in air a final layer of a hydrophobic fluorine based coating is applied. Such a sensor can be used for example as safety detector in automotive applications. We find that this type of fiber optic hydrogen sensor is also suitable for hydrogen detection in liquids. As example we demonstrate a sensor for detecting a broad range of concentrations in transformer oil. Such a sensor can signal a warning when sparks inside a high voltage power transformer decompose the transformer oil over a long period.

  15. The acid-catalyzed rearrangement CH3Oo --> oCH2OH and its involvement in the dissociation of the methanol dimer radical cation; A Quid pro Quo reaction

    NARCIS (Netherlands)

    Burgers, P.C.; Ruttink, P.J.A.

    2005-01-01

    The barrier for the radical isomerization CH3Oo --> oCH2OH is calculated by CBS-QB3 to be 29.7 kcal mol-1 and lies higher (by 5.7 kcal mol-1) than the dissociation limit CH2O+Ho. Hence, CH3Oo does not isomerize to the more stable oCH2OH on its own. However, this barrier is reduced to 15.8 kcal mol-1

  16. High psychiatric comorbidity in adolescents with dissociative disorders.

    Science.gov (United States)

    Bozkurt, Hasan; Duzman Mutluer, Tuba; Kose, Cigdem; Zoroglu, Salih

    2015-06-01

    The aim of this study was to evaluate psychiatric comorbidity rates and patterns in a sample of clinically referred adolescents diagnosed with dissociative disorders (DD) by using a structured interview. All participants completed a comprehensive test battery, which consisted of a questionnaire for sociodemographic data and clinical history, Child Posttraumatic Stress Reaction Index, Childhood Abuse and Neglect Questionnaire and the Adolescent Dissociative Experiences Scale. Diagnosis was made by the Structured Clinical Interview for DSM-IV Dissociative Disorders. Psychiatric comorbidity was assessed using the Schedule for Affective Disorders and Schizophrenia for School Age Children - Present and Lifetime Version. A total of 25 adolescent subjects aged 12-18 years participated in the study. Ten adolescents were diagnosed as having dissociative identity disorder and 15 of them were diagnosed as having dissociative disorder-not otherwise specified based on the Structured Clinical Interview for DSM-IV Dissociative Disorders findings. Adolescents with dissociative identity disorder were found to have higher scores on the Adolescent Dissociative Experiences Scale and Child Posttraumatic Stress Reaction Index than the dissociative disorder-not otherwise specified group. Sexual and physical abuses were also found to be among the main traumatic events. Incest was reported in six cases of the study sample. All subjects had at least one comorbid psychiatric disorder. The most common psychiatric diagnoses were major depressive disorder (n = 25; 100%) and post-traumatic stress disorder (n = 22; 88%). High psychiatric comorbidity rates were found in adolescents diagnosed with DD. A prevalent history of abuse and traumatic events was represented. Clinicians should be aware of the impacts of DD on adolescents' mental health. © 2014 The Authors. Psychiatry and Clinical Neurosciences © 2014 Japanese Society of Psychiatry and Neurology.

  17. Method of making crack-free zirconium hydride

    Science.gov (United States)

    Sullivan, Richard W.

    1980-01-01

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

  18. Creating nanoshell on the surface of titanium hydride bead

    Directory of Open Access Journals (Sweden)

    PAVLENKO Vyacheslav Ivanovich

    2016-12-01

    Full Text Available The article presents data on the modification of titanium hydride bead by creating titanium nanoshell on its surface by ion-plasma vacuum magnetron sputtering. To apply titanium nanoshell on the titanium hydride bead vacuum coating plant of multifunctional nanocomposite coatings QVADRA 500 located in the center of high technology was used. Analysis of the micrographs of the original surface of titanium hydride bead showed that the microstructure of the surface is flat, smooth, in addition the analysis of the microstructure of material surface showed the presence of small porosity, roughness, mainly cavities, as well as shallow longitudinal cracks. The presence of oxide film in titanium hydride prevents the free release of hydrogen and fills some micro-cracks on the surface. Differential thermal analysis of both samples was conducted to determine the thermal stability of the initial titanium hydride bead and bead with applied titanium nanoshell. Hydrogen thermal desorption spectra of the samples of the initial titanium hydride bead and bead with applied titanium nanoshell show different thermal stability of compared materials in the temperature range from 550 to 860о C. Titanium nanoshells applied in this way allows increasing the heat resistance of titanium hydride bead – the temperature of starting decomposition is 695о C and temperature when decomposition finishes is more than 1000о C. Modified in this way titanium hydride bead can be used as a filler in the radiation protective materials used in the construction or upgrading biological protection of nuclear power plants.

  19. High energy density battery based on complex hydrides

    Science.gov (United States)

    Zidan, Ragaiy

    2016-04-26

    A battery and process of operating a battery system is provided using high hydrogen capacity complex hydrides in an organic non-aqueous solvent that allows the transport of hydride ions such as AlH.sub.4.sup.- and metal ions during respective discharging and charging steps.

  20. High energy density battery based on complex hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Zidan, Ragaiy

    2016-04-26

    A battery and process of operating a battery system is provided using high hydrogen capacity complex hydrides in an organic non-aqueous solvent that allows the transport of hydride ions such as AlH.sub.4.sup.- and metal ions during respective discharging and charging steps.

  1. Synthesis, characterization and properties of some organozinc hydride complexes

    NARCIS (Netherlands)

    Koning, A.J. de; Boersma, J.; Kerk, G.J.M. van der

    1980-01-01

    The synthesis and characterization of the monopyridine complexes of ethylzinc hydride and phenylzinc hydride are described. On treatment with TMED these complexes are converted into R2Zn3H4. TMED species through a combination of ligand-exchange and disproportionation. The formation of organozinc hyd

  2. Hydride morphology and striation formation during delayed hydride cracking in Zr-2.5% Nb

    Energy Technology Data Exchange (ETDEWEB)

    Shek, G.K. [Ontario Hydro Technol., Ont. (Canada). Mater. Technol. Unit; Jovanovic, M.T. [Alberta Univ., Edmonton, AB (Canada). Dept. of Mining, Metallurgical and Petroleum Engineering; Seahra, H. [Ontario Hydro Technol., Ont. (Canada). Mater. Technol. Unit; Ma, Y. [Alberta Univ., Edmonton, AB (Canada). Dept. of Mining, Metallurgical and Petroleum Engineering; Li, D. [Alberta Univ., Edmonton, AB (Canada). Dept. of Mining, Metallurgical and Petroleum Engineering; Eadie, R.L. [Alberta Univ., Edmonton, AB (Canada). Dept. of Mining, Metallurgical and Petroleum Engineering

    1996-08-01

    These experiments were designed to study hydride formation at the crack tip, acoustic emission (AE), potential drop (PD) and striation formation during DHC (delayed hydride cracking) in Zr-2.5% Nb. The test material was taken from an especially extruded pressure tube, which showed similar strength properties to normal pressure tube material but somewhat coarser microstructure. In testing at K{sub I} below 12 MPa {radical}m at both 200 and 250 C very large striations (>40 {mu}m at 200 and >50 {mu}m at 250 C) were produced. In simultaneous monitoring with acoustic emission and potential drop, both AE and PD jumps were shown to be monolithic. The number of striations on the fracture surface corresponded to the number of monolithic AE/PD jumps. Tapered shaped hydrides with the thick end adjacent to the crack tip were observed. These hydrides grew in size during the incubation period until they reached the striation length and then fractured monolithically. However, when K{sub I} was increased beyond about 12 MPa {radical}m for these same specimens, the striation spacing decreased below 30 {mu}m, the monolithic jumping dissolved into more continuous changes in signals, although the smaller striations were still visible on the fracture surface. (orig.).

  3. Hydride morphology and striation formation during delayed hydride cracking in Zr-2.5% Nb

    Science.gov (United States)

    Shek, G. K.; Jovanoviċ, M. T.; Seahra, H.; Ma, Y.; Li, D.; Eadie, R. L.

    1996-08-01

    These experiments were designed to study hydride formation at the crack tip, acoustic emission (AE), potential drop (PD) and striation formation during DHC (delayed hydride cracking) in Zr-2.5% Nb. The test material was taken from an especially extrude pressure tube, which showed similar strength properties to normal pressure tube material but somewhat coarser microstructure. In testing at KI below 12 MPa √m at both 200 and 250°C very large striations (> 40 μ at 200 and >50 μm at 250°C) were produced. In simultaneous monitoring with acoustic emission and potential drop, both AE and PD jumps were shown to be monolithic. The number of striations on the fracture surface corresponded to the number of monolithic AE/PD jumps. Tapered shaped hydrides with the thick end adjacent to the crack tip were observed. These hydrides grew in size during the incubation period until they reached the striation length and then fractured monolithically. However, when KI was increased beyond about 12 MPa √m for these same specimens, the striation spacing decreased below 30 μ, the monolithic jumping dissolved into more continuous changes in signals, although the smaller striations were still visible on the fracture surface.

  4. High ramp rate thermogravimetric analysis of zirconium(II) hydride and titanium(II) hydride

    Energy Technology Data Exchange (ETDEWEB)

    Licavoli, Joseph J., E-mail: jjlicavo@mtu.edu; Sanders, Paul G., E-mail: sanders@mtu.edu

    2015-09-20

    Highlights: • A unique arc image device has been proposed for high ramp rate thermogravimetry. • Powder oxidation influences decomposition kinetics at temperatures below 933 K. • Particle size has a negligible effect on TiH{sub 2} decomposition behavior. • Improvements to the device are required to conduct accurate kinetic analysis. - Abstract: Zirconium and titanium hydride are utilized in liquid phase metal foam processing techniques. This application results in immediate exposure to molten metal and almost immediate decomposition at high temperatures. Most decomposition characterization techniques utilize slow heating rates and are unable to capture the decomposition behavior of hydrides under foam processing conditions. In order to address this issue a specialized high ramp rate thermogravimetric analyzer was created from a xenon arc image refiner. In addition to thermogravimetry, complimentary techniques including X-ray diffraction and scanning electron microscopy were used to characterize hydride decomposition and compare the results to literature. Hydrides were partially oxidized and separated into particles size ranges to evaluate the influence of these factors on decomposition. Oxidizing treatments were found to decrease decomposition rate only at temperatures below 933 K (660 °C) while particle size effects appeared to be negligible. Several improvements to the unique TGA apparatus presented in the current work are suggested to allow reliable kinetic modeling and analysis.

  5. ORNL Interim Progress Report on Hydride Reorientation CIRFT Tests

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jy-An John [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Yan, Yong [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Wang, Hong [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-10-28

    A systematic study of H. B. Robinson (HBR) high burnup spent nuclear fuel (SNF) vibration integrity was performed in Phase I project under simulated transportation environments, using the Cyclic Integrated Reversible-Bending Fatigue Tester (CIRFT) hot cell testing technology developed at Oak Ridge National Laboratory in 2013–14. The data analysis on the as-irradiated HBR SNF rods demonstrated that the load amplitude is the dominant factor that controls the fatigue life of bending rods. However, previous studies have shown that the hydrogen content and hydride morphology has an important effect on zirconium alloy mechanical properties. To address the effect of radial hydrides in SNF rods, in Phase II a test procedure was developed to simulate the effects of elevated temperatures, pressures, and stresses during transfer-drying operations. Pressurized and sealed fuel segments were heated to the target temperature for a preset hold time and slow-cooled at a controlled rate. The procedure was applied to both non-irradiated/prehydrided and high-burnup Zircaloy-4 fueled cladding segments using the Nuclear Regulatory Commission-recommended 400°C maximum temperature limit at various cooling rates. Before testing high-burnup cladding, four out-of-cell tests were conducted to optimize the hydride reorientation (R) test condition with pre-hydride Zircaloy-4 cladding, which has the same geometry as the high burnup fuel samples. Test HR-HBR#1 was conducted at the maximum hoop stress of 145 MPa, at a 400°C maximum temperature and a 5°C/h cooling rate. On the other hand, thermal cycling was performed for tests HR-HBR#2, HR-HBR#3, and HR-HBR#4 to generate more radial hydrides. It is clear that thermal cycling increases the ratio of the radial hydride to circumferential hydrides. The internal pressure also has a significant effect on the radial hydride morphology. This report describes a procedure and experimental results of the four out-of-cell hydride reorientation tests of

  6. Potential energy curves and electronic structure of 3d transition metal hydrides and their cations.

    Science.gov (United States)

    Goel, Satyender; Masunov, Artëm E

    2008-12-07

    We investigate gas-phase neutral and cationic hydrides formed by 3d transition metals from Sc to Cu with density functional theory (DFT) methods. The performance of two exchange-correlation functionals, Boese-Martin for kinetics (BMK) and Tao-Perdew-Staroverov-Scuseria (TPSS), in predicting bond lengths and energetics, electronic structures, dipole moments, and ionization potentials is evaluated in comparison with available experimental data. To ensure a unique self-consistent field (SCF) solution, we use stability analysis, Fermi smearing, and continuity analysis of the potential energy curves. Broken-symmetry approach was adapted in order to get the qualitatively correct description of the bond dissociation. We found that on average BMK predicted values of dissociation energies and ionization potentials are closer to experiment than those obtained with high level wave function theory methods. This agreement deteriorates quickly when the fraction of the Hartree-Fock exchange in DFT functional is decreased. Natural bond orbital (NBO) population analysis was used to describe the details of chemical bonding in the systems studied. The multireference character in the wave function description of the hydrides is reproduced in broken-symmetry DFT description, as evidenced by NBO analysis. We also propose a new scheme to correct for spin contamination arising in broken-symmetry DFT approach. Unlike conventional schemes, our spin correction is introduced for each spin-polarized electron pair individually and therefore is expected to yield more accurate energy values. We derive an expression to extract the energy of the pure singlet state from the energy of the broken-symmetry DFT description of the low spin state and the energies of the high spin states (pentuplet and two spin-contaminated triplets in the case of two spin-polarized electron pairs). The high spin states are build with canonical natural orbitals and do not require SCF convergence.

  7. Ti–V–Mn based metal hydrides for hydrogen compression applications

    Energy Technology Data Exchange (ETDEWEB)

    Pickering, Lydia, E-mail: lydia.pickering@btinternet.com; Reed, Daniel; Bevan, Alexander I.; Book, David, E-mail: d.book@bham.ac.uk

    2015-10-05

    Highlights: • Ti–V–Mn based alloys were investigated as V was substituted for Nb, Cr, Mo and Ta. • The produced alloys were found to possess C14 Laves, BCC and FCC phases. • <0.2 Nb substituted for V led to small hysteresis and high dissociation pressures. • Ti{sub 0.5}–V{sub 0.45}–Nb{sub 0.05}–Mn is a suitable alloy to be used in a metal hydride compressor. - Abstract: Ti–V–Mn based alloys, consisting mainly of the hexagonal C14 Laves and BCC phases, with nominal compositions of Ti{sub 0.5}V{sub 0.4}TM{sub 0.1}Mn, where TM = Nb, Cr, Mo, Ta and Ti{sub 0.5}V{sub 0.5−x}Nb{sub x}Mn, where x = 0.05 and 0.2, were synthesised by arc melting. It was found that small amounts of Nb substituted for V (x = 0.05 and 0.1) resulted in smaller hysteresis between absorption and desorption as well as higher hydrogen dissociation pressures, compared to Ti{sub 0.5}V{sub 0.5}Mn. These findings show that Ti{sub 0.5}–V{sub 0.45}–Nb{sub 0.05}–Mn is a suitable alloy to be used in a metal hydride compressor to deliver a pressure of 650 bar in the temperature range 303–473 K.

  8. Growth and decomposition of Lithium and Lithium hydride on Nickel

    DEFF Research Database (Denmark)

    Engbæk, Jakob; Nielsen, Gunver; Nielsen, Jane Hvolbæk

    2006-01-01

    In this paper we have investigated the deposition, structure and decomposition of lithium and lithium-hydride films on a nickel substrate. Using surface sensitive techniques it was possible to quantify the deposited Li amount, and to optimize the deposition procedure for synthesizing lithium......-hydride films. By only making thin films of LiH it is possible to study the stability of these hydride layers and compare it directly with the stability of pure Li without having any transport phenomena or adsorbed oxygen to obscure the results. The desorption of metallic lithium takes place at a lower...... temperature than the decomposition of the lithium-hydride, confirming the high stability and sintering problems of lithium-hydride making the storage potential a challenge. (c) 2006 Elsevier B.V. All rights reserved....

  9. Helium trapping at erbium oxide precipitates in erbium hydride

    Energy Technology Data Exchange (ETDEWEB)

    Foiles, Stephen M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Battaile, Corbett Chandler [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2016-02-01

    The formation of He bubbles in erbium tritides is a significant process in the aging of these materials. Due to the long-standing uncertainty about the initial nucleation process of these bubbles, there is interest in mechanisms that can lead to the localization of He in erbium hydrides. Previous work has been unable to identify nucleation sites in homogeneous erbium hydride. This work builds on the experimental observation that erbium hydrides have nano- scale erbium oxide precipitates due to the high thermodynamic stability of erbium oxide and the ubiquitous presence of oxygen during materials processing. Fundamental DFT calculations indicate that the He is energetically favored in the oxide relative to the bulk hydride. Activation energies for the motion of He in the oxide and at the oxide-hydride interface indicate that trapping is kinetically feasible. A simple kinetic Monte Carlo model is developed that demonstrates the degree of trapping of He as a function of temperature and oxide fraction.

  10. Photochromism of rare-earth metal-oxy-hydrides

    Science.gov (United States)

    Nafezarefi, F.; Schreuders, H.; Dam, B.; Cornelius, S.

    2017-09-01

    Recently, thin films of yttrium oxy-hydride (YOxHy) were reported to show an unusual color-neutral photochromic effect promising for application in smart windows. Our present work demonstrates that also oxy-hydrides based on Gd, Dy, and Er have photochromic properties and crystal structures similar to YOxHy. Compared to YOxHy, the optical bandgaps of the lanthanide based oxy-hydrides are smaller while photochromic contrast and kinetics show large variation among different cations. Based on these findings, we propose that cation alloying is a viable pathway to tailor the photochromic properties of oxy-hydride materials. Furthermore, we predict that the oxy-hydrides of the other lanthanides are also potentially photochromic.

  11. Metal hydrides for concentrating solar thermal power energy storage

    Science.gov (United States)

    Sheppard, D. A.; Paskevicius, M.; Humphries, T. D.; Felderhoff, M.; Capurso, G.; Bellosta von Colbe, J.; Dornheim, M.; Klassen, T.; Ward, P. A.; Teprovich, J. A.; Corgnale, C.; Zidan, R.; Grant, D. M.; Buckley, C. E.

    2016-04-01

    The development of alternative methods for thermal energy storage is important for improving the efficiency and decreasing the cost of concentrating solar thermal power. We focus on the underlying technology that allows metal hydrides to function as thermal energy storage (TES) systems and highlight the current state-of-the-art materials that can operate at temperatures as low as room temperature and as high as 1100 °C. The potential of metal hydrides for thermal storage is explored, while current knowledge gaps about hydride properties, such as hydride thermodynamics, intrinsic kinetics and cyclic stability, are identified. The engineering challenges associated with utilising metal hydrides for high-temperature TES are also addressed.

  12. Significantly improved electrochemical hydrogen storage properties of magnesium nickel hydride modified with nano-nickel

    Science.gov (United States)

    Chen, Wei; Zhu, Yunfeng; Yang, Chen; Zhang, Jiguang; Li, Menghuai; Li, Liquan

    2015-04-01

    Magnesium nickel hydride (Mg2NiH4) used as negative electrode material in nickel-metal hydride (Ni-MH) secondary battery is modified by nano-nickel via mechanical milling. In this paper, we systematically investigate the microstructure and electrochemical properties of the modified system with different milling durations. X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) analyses confirm the amorphous transformation of Mg2Ni-based hydride and a novel NiH0.75 nanocrystalline with a diameter of about 5 nm embedding or covering on the surface of the base particle has been observed. Its formation mechanism and positive effects on electrochemical properties of the Mg2NiH4 have also been elaborated. Electrochemical measurements show that the 5 h milled composite possesses markedly increased discharge capacity up to 896 mAh g-1. With prolonging the milling duration from 5 h to 40 h, the discharge capacity at the 10th cycle increases from 99 mAh g-1 to 359 mAh g-1. Besides, the discharging procedure changes from stepwise processes to one single-step process with increasing the milling duration. Tafel polarization test shows that the nano-nickel modified system exhibits a much better anti-corrosion ability during charging/discharging cycles. Meanwhile, both the charge-transfer reaction on the alloy surface and hydrogen diffusion inside the alloy bulk are enhanced with nano-nickel modification.

  13. OPTIMIZATION OF INTERNAL HEAT EXCHANGERS FOR HYDROGEN STORAGE TANKS UTILIZING METAL HYDRIDES

    Energy Technology Data Exchange (ETDEWEB)

    Garrison, S.; Tamburello, D.; Hardy, B.; Anton, D.; Gorbounov, M.; Cognale, C.; van Hassel, B.; Mosher, D.

    2011-07-14

    Two detailed, unit-cell models, a transverse fin design and a longitudinal fin design, of a combined hydride bed and heat exchanger are developed in COMSOL{reg_sign} Multiphysics incorporating and accounting for heat transfer and reaction kinetic limitations. MatLab{reg_sign} scripts for autonomous model generation are developed and incorporated into (1) a grid-based and (2) a systematic optimization routine based on the Nelder-Mead downhill simplex method to determine the geometrical parameters that lead to the optimal structure for each fin design that maximizes the hydrogen stored within the hydride. The optimal designs for both the transverse and longitudinal fin designs point toward closely-spaced, small cooling fluid tubes. Under the hydrogen feed conditions studied (50 bar), a 25 times improvement or better in the hydrogen storage kinetics will be required to simultaneously meet the Department of Energy technical targets for gravimetric capacity and fill time. These models and methodology can be rapidly applied to other hydrogen storage materials, such as other metal hydrides or to cryoadsorbents, in future work.

  14. Recurrent dissociative fugue

    Directory of Open Access Journals (Sweden)

    Abhishek Mamarde

    2013-01-01

    Full Text Available Dissociative fugue is a rarely reported diagnostic entity. It is one of the least understood and yet clinically one of the most fascinating disorders in mental health. Here, we describe a case of fugue in a 32-year-old man who was brought to mental hospital with complete loss of memory for events pertaining to identity of self. This case illustrates the nature of presentation in hospital setting like mental hospital and effort taken to reintegrate his identity and reunite with his family.

  15. INFLUENCE OF ORGANIC SOLVENTS ON WATER DISSOCIATION IN BIPOLAR MEMBRANE

    Directory of Open Access Journals (Sweden)

    Sheldeshov N. V.

    2015-12-01

    Full Text Available The article discusses results of experimental research of the influence of aprotic and proton solvents on reaction rate of water molecules dissociation in the bipolar membrane MB-1 by the method of electrochemical impedance frequency spectrum. It was discovered, that addition of organic component in aqueous solutions results in significant influence on the parameters of water dissociation in a bipolar region of the membrane. The reason for this influence is the reduction of the mass fraction of water in solution and, consequently, in a bipolar region of the membrane, which itself reduces the rate of the dissociation reaction. Another reason for the influence of the organic solvent is its effect on the network of hydrogen bonds existing in water and aqueous solutions. Depending on the nature of organic solvent and its concentration, the network of hydrogen bonds may be strengthened, or destroyed, thus facilitating removal of the proton involved in the reactions between water molecules and catalytic centers in cation-exchange and anion-exchange layer of bipolar membrane, or retarding removal of proton. This leads respectively to speed up or slow down the rate of dissociation in the bipolar region of the membrane, as well as changing the constants of the dissociation reaction of water. Introduction of organic solvent in solutions, which are in the contact with bipolar membrane, is a convenient method of investigating the role of solution composition on the rate of proton transfer between water molecules and catalytic centers in the membranes

  16. Results of NDE Technique Evaluation of Clad Hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Kunerth, Dennis C. [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2014-09-01

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

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

    Science.gov (United States)

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

    2014-09-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Rico, A., E-mail: alvaro.rico@urjc.es [DIMME, Departamento de Tecnología Mecánica, Universidad Rey Juan Carlos, c/Tulipán s/n, E-28933 Móstoles, Madrid (Spain); Martin-Rengel, M.A., E-mail: mamartin@mater.upm.es [Departamento de Ciencia de los Materiales, UPM, E.T.S.I. Caminos, Canales y Puertos, Profesor Aranguren SN, E-28040 Madrid (Spain); Ruiz-Hervias, J., E-mail: jesus.ruiz@upm.es [Departamento de Ciencia de los Materiales, UPM, E.T.S.I. Caminos, Canales y Puertos, Profesor Aranguren SN, E-28040 Madrid (Spain); Rodriguez, J. [DIMME, Departamento de Tecnología Mecánica, Universidad Rey Juan Carlos, c/Tulipán s/n, E-28933 Móstoles, Madrid (Spain); Gomez-Sanchez, F.J., E-mail: javier.gomez@amsimulation.com [Advanced Material Simulation, S.L, Madrid (Spain)

    2014-09-15

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

  19. Formation and characterisation of the silver hydride nanocluster cation [Ag3H2((Ph2 P)2CH2)](+) and its release of hydrogen.

    Science.gov (United States)

    Girod, Marion; Krstić, Marjan; Antoine, Rodolphe; MacAleese, Luke; Lemoine, Jérome; Zavras, Athanasios; Khairallah, George N; Bonačić-Koutecký, Vlasta; Dugourd, Philippe; O'Hair, Richard A J

    2014-12-08

    Multistage mass spectrometry and density functional theory (DFT) were used to characterise the small silver hydride nanocluster, [Ag3 H2 L](+) (where L=(Ph2 P)2 CH2 ) and its gas-phase unimolecular chemistry. Collision-induced dissociation (CID) yields [Ag2 HL](+) as the major product while laser-induced dissociation (LID) proceeds via H2 formation and subsequent release from [Ag3 H2 L](+) , giving rise to [Ag3 L](+) as the major product. Deuterium labelling studies on [Ag3 D2 L](+) prove that the source of H2 is from the hydrides and not from the ligand. Comparison of TD-DFT absorption patterns obtained for the optimised structures with action spectroscopy results, allows assignment of the measured features to structures of precursors and products. Molecular dynamics "on the fly" reveal that AgH loss is favoured in the ground state, but H2 formation and loss is preferred in the first excited state S1 , in agreement with CID and LID experimental findings. This indicates favourable photo-induced formation of H2 and subsequent release from [Ag3 H2 L](+) , an important finding in context of metal hydrides as a hydrogen storage medium, which can subsequently be released by heating or irradiation with light. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Nanostructured Magnesium Hydride for Reversible Hydrogen Storage

    Science.gov (United States)

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

    2013-05-01

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

  1. Lithium hydride - A space age shielding material

    Science.gov (United States)

    Welch, F. H.

    1974-01-01

    Men and materials performing in the environment of an operating nuclear reactor require shielding from the escaping neutron particles and gamma rays. For efficient shielding from gamma rays, dense, high atomic number elements such as iron, lead, or tungsten are required, whereas light, low atomic number elements such as hydrogen, lithium, or beryllium are required for efficient neutron shielding. The use of lithium hydride (LiH) as a highly efficient neutron-shielding material is considered. It contains, combined into a single, stable compound, two of the elements most effective in attenuating and absorbing neutrons.

  2. Highly Concentrated Palladium Hydrides/Deuterides; Theory

    Energy Technology Data Exchange (ETDEWEB)

    Papaconstantopoulos, Dimitrios

    2013-11-26

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

  3. Development of nickel-metal hydride cell

    Science.gov (United States)

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

    1993-01-01

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

  4. Dissociative Experiences in Psychiatric Inpatients

    OpenAIRE

    Ali Firoozabadi; Nooshin Reza Alizadeh

    2016-01-01

    Dissociative disorders are conditions that involve disruptions of memory, awareness, identity, or perception. Data collected in diverse geographic locations underline the consistency in clinical symptoms of dissociative disorders. In this cross-sectional descriptive study, prevalence of dissociative experiences has been screened in hospitalized patients in psychiatric wards of Shiraz University of Medical Sciences in Iran. One hundred and sixty patients in two hospitals entered the study. Our...

  5. Acute dissociation and cardiac reactivity to script-driven imagery in trauma-related disorders

    Directory of Open Access Journals (Sweden)

    Martin Sack

    2012-11-01

    Full Text Available Background: Potential acute protective functions of dissociation include modulation of stress-induced psychophysiological arousal. This study was designed to explore whether acute dissociative reactions during a stress experiment would override the effects of reexperiencing. Methods: Psychophysiological reactions during exposure to script-driven trauma imagery were studied in relation to acute responses of reexperiencing and dissociative symptoms in 61 patients with histories of exposure to a variety of traumas. Acute symptomatic responses were assessed with the Responses to Script-Driven Imagery Scale (RSDI, and participants were divided into four groups by median splits of RSDI reexperiencing and dissociation subscale scores. Results: In a comparison of the high RSDI reexperiencing groups with low versus high acute dissociative symptoms, the high dissociators exhibited significantly lower heart rate (HR during trauma script and a significantly smaller script-induced decrease in parasympathetic cardiac activity. HR reactivity to the trauma script was negatively correlated with acute dissociative symptom severity. Conclusions: Acute dissociative reactions are a potential moderator of response to experimental paradigms investigating psychologically traumatized populations. We therefore suggest that future research on psychophysiological stress reactions in traumatized samples should routinely assess for acute dissociative symptoms.

  6. Dissociative Experiences in Psychiatric Inpatients

    Directory of Open Access Journals (Sweden)

    Ali Firoozabadi

    2016-11-01

    Full Text Available Dissociative disorders are conditions that involve disruptions of memory, awareness, identity, or perception. Data collected in diverse geographic locations underline the consistency in clinical symptoms of dissociative disorders. In this cross-sectional descriptive study, prevalence of dissociative experiences has been screened in hospitalized patients in psychiatric wards of Shiraz University of Medical Sciences in Iran. One hundred and sixty patients in two hospitals entered the study. Our tool to screen the prevalence of dissociative experiences was Dissociative Experience Scale (DES. Linear regression analysis shows that gender and age are predictors of high DES scores to some extent while psychiatric disorders are not good predictors. Age, gender and psychiatric disorders are poor predictors (almost 7% of high DES scores in this study (R square=0.69. In this study, patients with Borderline Personality Disorder had higher dissociative experiences based on DES score (Mean: 56.44, followed by Schizophrenic patients (Mean: 28.22 and patients with Bipolar Personality Disorder (Mean: 25.18. This study showed that we might be able to create a new category in psychological disorders based on dissociative experiences. As age, gender and psychological disorders were poor predictors of dissociative experiences, stronger predictors such as positive childhood psychological traumas could be responsible for dissociative disorders.

  7. [Dissociative disorders and affective disorders].

    Science.gov (United States)

    Montant, J; Adida, M; Belzeaux, R; Cermolacce, M; Pringuey, D; Da Fonseca, D; Azorin, J-M

    2014-12-01

    The phenomenology of dissociative disorders may be complex and sometimes confusing. We describe here two cases who were initially misdiagnosed. The first case concerned a 61 year-old woman, who was initially diagnosed as an isolated dissociative fugue and was actually suffering from severe major depressive episode. The second case concerned a 55 year-old man, who was suffering from type I bipolar disorder and polyvascular disease, and was initially diagnosed as dissociative fugue in a mooddestabilization context, while it was finally a stroke. Yet dissociative disorders as affective disorder comorbidity are relatively unknown. We made a review on this topic. Dissociative disorders are often studied through psycho-trauma issues. Litterature is rare on affective illness comorbid with dissociative disorders, but highlight the link between bipolar and dissociative disorders. The later comorbidity often refers to an early onset subtype with also comorbid panic and depersonalization-derealization disorder. Besides, unipolar patients suffering from dissociative symptoms have more often cyclothymic affective temperament. Despite the limits of such studies dissociative symptoms-BD association seems to correspond to a clinical reality and further works on this topic may be warranted. Copyright © 2014 L’Encéphale. Published by Elsevier Masson SAS.. All rights reserved.

  8. Dissociation Energies of Diatomic Molecules

    Institute of Scientific and Technical Information of China (English)

    FAN Qun-Chao; SUN Wei-Guo

    2008-01-01

    Molecular dissociation energies of 10 electronic states of alkali molecules of KH, 7LID, 7LiH, 6LiH, NaK, NaLi and NaRb are studied using the highest three accurate vibrational energies of each electronic state, and an improved parameter-free analytical formula which is obtained starting from the LeRoy-Bernstein vibrational energy expression near the dissociation limit. The results show that as long as the highest three vibrational energies are accurate, the current analytical formula will give accurate theoretical dissociation energies Detheory, which are in excellent agreement with the experimental dissociation energies Dexpte.

  9. Dissociative State and Competence

    Directory of Open Access Journals (Sweden)

    Yu-Ju Lin

    2007-10-01

    Full Text Available This report presents the results of forensic evaluation of the civil competence of a case of alleged dissociative identity disorder (DID and discusses whether such dissociative states substantially jeopardize civil competence. A 40-year-old woman claimed that she had had many personalities since her college days. From the age of 37 to 40, she shopped excessively, which left her with millions of dollars of debt. She ascribed her shopping to a certain identity state, over which she had no control. (In this article, we use the term identity state to replace personality as an objective description of a mental state. She thus raised the petition of civil incompetence. During the forensic evaluation, it was found that the identity states were relatively stable and mutually aware of each other. The switch into another identity state was sometimes under voluntary control. The subject showed consistency and continuity in behavioral patterns across the different identity states, and no matter which identity state she was in, there was no evidence of impairment in her factual knowledge of social situations and her capacity for managing personal affairs. We hence concluded that she was civilly competent despite the claimed DID. Considering that the existence and diagnosis of DID are still under dispute and a diagnosis of DID alone is not sufficient to interdict a person's civil right, important clinical and forensic issues remain to be answered.

  10. Effect of sodium cation on metallacycle β-hydride elimination in CO2-ethylene coupling to acrylates.

    Science.gov (United States)

    Jin, Dong; Williard, Paul G; Hazari, Nilay; Bernskoetter, Wesley H

    2014-03-10

    The catalytic conversion of carbon dioxide and olefins into acrylates has been a long standing target, because society attempts to synthesize commodity chemicals in a more economical and sustainable fashion. Although nickel complexes have been known to successfully couple CO2 and ethylene for decades, a key β-hydride elimination step has proven a major obstacle to the development of a catalytic process. Recent studies have shown that Lewis acid additives can be used to create a lower-energy pathway for β-hydride elimination and facilitate a low number of catalytic turnovers. However, the exact manner, in which the Lewis acid promotes β-hydride elimination remains to be elucidated. Herein, we describe the kinetic and thermodynamic role that commercially relevant and weakly Lewis acidic sodium salts play in promoting β-hydride elimination from nickelalactones synthesized from CO2 and ethylene. This process is compared to a non-Lewis acid promoted pathway, and DFT calculations were used to identify differences between the two systems. The sodium-free isomerization reaction gave a rare CO2 -derived β-nickelalactone complex, which was structurally characterized.

  11. Identification of a Catalytic Iron-Hydride at the H-Cluster of [FeFe]-Hydrogenase

    Energy Technology Data Exchange (ETDEWEB)

    Mulder, David W.; Guo, Yisong; Ratzloff, Michael W.; King, Paul W.

    2017-01-11

    Hydrogenases couple electrochemical potential to the reversible chemical transformation of H2 and protons, yet the reaction mechanism and composition of intermediates are not fully understood. In this Communication we describe the biophysical properties of a hydride-bound state (Hhyd) of the [FeFe]-hydrogenase from Chlamydomonas reinhardtii. The catalytic H-cluster of [FeFe]-hydrogenase consists of a [4Fe-4S] subcluster ([4Fe-4S]H) linked by a cysteine thiol to an azadithiolate-bridged 2Fe subcluster ([2Fe]H) with CO and CN- ligands. Mossbauer analysis and density functional theory (DFT) calculations show that Hhyd consists of a reduced [4Fe-4S]H+ coupled to a diferrous [2Fe]H with a terminally bound Fe-hydride. The existence of the Fe-hydride in Hhyd was demonstrated by an unusually low Mossbauer isomer shift of the distal Fe of the [2Fe]H subcluster. A DFT model of Hhyd shows that the Fe-hydride is part of a H-bonding network with the nearby bridging azadithiolate to facilitate fast proton exchange and catalytic turnover.

  12. Hyperglycemia associated dissociative fugue (organic dissociative disorder in an elderly

    Directory of Open Access Journals (Sweden)

    Dushad Ram

    2015-01-01

    Full Text Available Inadequate glycemic control in patients with diabetes is known to be associated with psychiatric disorders such as depression, anxiety disorder, and cognitive impairment. However, dissociative syndrome has not been reported so far. Here we are reporting a case of repeated dissociative fugue associated with hyperglycemia, in an elderly with type II diabetes. Possible neurobiological mechanism has been discussed.

  13. Hyperglycemia associated dissociative fugue (organic dissociative disorder) in an elderly

    OpenAIRE

    Dushad Ram; Ashoka, H.G.; Basavnna Gowdappa

    2015-01-01

    Inadequate glycemic control in patients with diabetes is known to be associated with psychiatric disorders such as depression, anxiety disorder, and cognitive impairment. However, dissociative syndrome has not been reported so far. Here we are reporting a case of repeated dissociative fugue associated with hyperglycemia, in an elderly with type II diabetes. Possible neurobiological mechanism has been discussed.

  14. NATO Advanced Study Institute on Metal Hydrides

    CERN Document Server

    1981-01-01

    In the last five years, the study of metal hydrides has ex­ panded enormously due to the potential technological importance of this class of materials in hydrogen based energy conversion schemes. The scope of this activity has been worldwide among the industrially advanced nations. There has been a consensus among researchers in both fundamental and applied areas that a more basic understanding of the properties of metal/hydrogen syster;,s is required in order to provide a rational basis for the selection of materials for specific applications. The current worldwide need for and interest in research in metal hydrides indicated the timeliness of an Advanced Study Insti­ tute to provide an in-depth view of the field for those active in its various aspects. The inclusion of speakers from non-NATO coun­ tries provided the opportunity for cross-fertilization of ideas for future research. While the emphasis of the Institute was on basic properties, there was a conscious effort to stimulate interest in the applic...

  15. From permanent magnets to rechargeable hydride electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Willems, J.J.G.; Buschow, K.H.J.

    1987-02-15

    A brief historical survey is given of how the study of coercitivity mechanisms in SmCo/sub 5/ permanent-magnet materials eventually led to the discovery of the favourable hydrogen sorption properties of the compound LaNi/sub 5/. It is shown how continued research by many investigators dealing with a variety of different physical and chemical properties has resulted in an advanced understanding of some of the principles that govern hydrogen absorption and which are responsible for the changes in physical properties that accompany it. The problems associated with various applications of LaNi/sub 5/-based hydrogen-storage materials are also briefly discussed. A large part of this paper is devoted to the applicability of LaNi/sub 5/-type materials in batteries. Research in this area has resulted in the development of a new type of rechargeable battery: the nickel-hydride cell. This battery can be charged and discharged at high rates and is relatively insensitive to overcharging and overdischarging. Special attention is given to the nature of the electrode degradation process and the effect of composition variations in LaNi/sub 5/-related materials on the lifetime of the corresponding hydride electrodes when subjected to severe electrochemical charge-discharge cycles.

  16. Desorption of hydrogen from light metal hydrides: concerted electronic rearrangement and role of H···H interactions.

    Science.gov (United States)

    Wolstenholme, David J; Roy, Matthew M D; Thomas, Michael E; McGrady, G Sean

    2014-04-14

    A theoretical study of the desorption of hydrogen from rhombic Group 1 metal hydride dimers reveals a concerted reorganisation of the electron density for the M-H and H-H moieties as the reaction coordinate is traversed and a closed-shell H···H interaction evolves into a covalent H2 bond. The central role played by homopolar dihydrogen bonding in this process is revealed and analysed.

  17. PIE techniques for hydride reorientation test at NDC

    Energy Technology Data Exchange (ETDEWEB)

    Tsuda, Tomohiro; Shinohara, Yasunari; Yamaguchi, Yoichiro [Nuclear Development Corporation, Ibaraki (Japan)

    2008-11-15

    Dry storage of spent fuels in the interim storage facility is being planned in Japan. However, the gradual deterioration of the mechanical property of fuel cladding due to internal pressure and temperature during the storage term is known. Therefore, the integrity of stored fuel rods should be confirmed before the start of dry storage. For the last several years, NDC had a lot of experiences on the hydride reorientation test. The specimen preparation techniques on the hydride reorientation test and the mechanical testing techniques after the hydride reorientation are shown in this paper.

  18. Kinetic Modification on Hydrogen Desorption of Lithium Hydride and Magnesium Amide System

    OpenAIRE

    Hiroki Miyaoka; Yongming Wang,; Satoshi Hino; Shigehito Isobe; Kazuhiko Tokoyoda; Takayuki Ichikawa; Yoshitsugu Kojima

    2015-01-01

    Various synthesis and rehydrogenation processes of lithium hydride (LiH) and magnesium amide (Mg(NH2)2) system with 8:3 molar ratio are investigated to understand the kinetic factors and effectively utilize the essential hydrogen desorption properties. For the hydrogen desorption with a solid-solid reaction, it is expected that the kinetic properties become worse by the sintering and phase separation. In fact, it is experimentally found that the low crystalline size and the close contact of L...

  19. Hydrogen storage in metal hydrides and complex hydrides; Wasserstoffspeicherung in Metall- und komplexen Hydriden - Schlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Bielmann, M.; Zuettel, A.

    2007-07-01

    This final report for the Swiss Federal Office of Energy (SFOE), reports on work done in 2007 at the Swiss Federal Laboratories for Materials Science and Technology EMPA on the storage of hydrogen in metal hydrides and complex hydrides. In particular, the use of tetrahydroborates is noted. The potential of this class of materials is stressed. The structures at room-temperature were examined using neutron and X-ray diffraction methods. Thermodynamic methods helped determine the thermodynamic stability of the materials. Also, a complete energy diagram for the materials was developed. The use of silicon oxide to reduce activation energy and its catalytic effects are discussed. The challenges placed by desorption mechanisms are noted. The authors note that reversibility is basically proven.

  20. AV dissociation, an inevitable response.

    Science.gov (United States)

    Wang, Kyuhyun; Benditt, David G

    2011-07-01

    The independent activation of the atria and ventricles, AV dissociation, is a common phenomenon that occurs during a wide variety of electrophysiologic circumstances. The clinical significance of AV dissociation is often misunderstood. This article examines the basis and clinical implications of AV dissociation. AV dissociation is often an obligatory, secondary phenomenon, and should not be construed as the primary disorder; it may be due to either the AV conduction system being completely blocked (3° AV block) or the P wave and the QRS complex being generated from separate sources (usually, the AV junction or ventricle) but occurring close together during the physiologic refractory period of each other. The latter may happen in junctional or ventricular arrhythmias including escape or accelerated rhythm, tachycardia, or premature beats. The crucial clinical point is not the AV dissociation itself, but that an underlying triggering primary disorder is present and should be identified. ©2011, Wiley Periodicals, Inc.

  1. Low temperature hydrogenolysis of waxes to diesel range gasoline and light alkanes: Comparison of catalytic properties of group 4, 5 and 6 metal hydrides supported on silica-alumina

    KAUST Repository

    Norsic, Sébastien

    2012-01-01

    A series of metal hydrides (M = Zr, Hf, Ta, W) supported on silica-alumina were studied for the first time in hydrogenolysis of light alkanes in a continuous flow reactor. It was found that there is a difference in the reaction mechanism between d 0 metal hydrides of group 4 and d 0 ↔ d 2 metal hydrides of group 5 and group 6. Furthermore, the potential application of these catalysts has been demonstrated by the transformation of Fischer-Tropsch wax in a reactive distillation set-up into typical gasoline and diesel molecules in high selectivity (up to 86 wt%). Current results show that the group 4 metal hydrides have a promising yield toward liquid fuels.

  2. Synthesis and Hydrogen Desorption Properties of Aluminum Hydrides.

    Science.gov (United States)

    Jeong, Wanseop; Lee, Sang-Hwa; Kim, Jaeyong

    2016-03-01

    Aluminum hydride (AlH3 or alane) is known to store maximum 10.1 wt.% of hydrogen at relatively low temperature (hydrogen desorption are still not clear. To understand the desorption properties of hydrogen in alane, thermodynamically stable α-AlH3 was synthesized by employing an ethereal reaction method. The dependence of pathways on phase formation and the properties of hydrogen evolution were investigated, and the results were compared with the ones for γ-AlH3. It was found that γ-AlH3 requires 10 degrees C higher than that of γ-AlH3 to form, and its decomposition rate demonstrated enhanced endothermic stabilities. For desorption, all hydrogen atoms of alane evolved under an isothermal condition at 138 degrees C in less than 1 hour, and the sample completely transformed to pure aluminum. Our results show that the total amount of desorbed hydrogen from α-AlH3 exceeded 9.05 wt.%, with a possibility of further increase. Easy synthesis, thermal stability, and a large amount of hydrogen desorption of alane fulfill the requirements for light-weight hydrogen storage materials once the pathway of hydrogen cycling is provided.

  3. Effect of lanthanum hydride on microstructures and hydrogen storage performances of 2LiNH2-MgH2 system

    Institute of Scientific and Technical Information of China (English)

    朱惜林; 韩树民; 赵鑫; 李媛; 刘宝忠

    2014-01-01

    Hydrogen storage properties of 2LiNH2-MgH2 system were improved by adding lanthanum hydride (LaH3), and the role of LaH3 in hydrogen sorption process of Li-Mg-N-H system was investigated. Temperature programmed sorption results showed that the addition of lanthanum hydride reduced the dehydriding/hydriding onset temperature of 2LiNH2-MgH2 system by at least 15 K. Moreover, A 0.053 wt.%/min average rate was determined for the hydrogen desorption of 2LiNH2-MgH2-0.05LaH3 composite, while it was only 0.035 wt.%/min for 2LiNH2-MgH2 system. Hydrogen absorption capacity increased from 1.62 wt.% to 2.12 wt.% within 200 min by adding LaH3 into 2LiNH2-MgH2 system at 383 K. In the dehydrogenation of 2LiNH2-MgH2-0.05LaH3 composite, LaH2 transferred to LaN phase, which reversed to LaH2 in the following hydrogen adsorption process. The reversible reaction of LaH2 ef-fectively promoted the hydrogen sorption of Li-Mg-N-H system. Moreover, the homogenous distribution of fine La hydride was fa-vorable to improving effect of lanthanum hydride.

  4. A review of recent advances on the effects of microstructural refinement and nano-catalytic additives on the hydrogen storage properties of metal and complex hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Varin, R. A.; Zbroniec, L. [University of Waterloo, Department of Mechanical and Mechatronics Engineering, Waterloo, Ontario (Canada); Polanski, M.; Bystrzycki, J. [Faculty of Advanced Technology and Chemistry, Military University of Technology, Warsaw (Poland)

    2011-07-01

    The recent advances on the effects of microstructural refinement and various nano-catalytic additives on the hydrogen storage properties of metal and complex hydrides obtained in the last few years in the allied laboratories at the University of Waterloo (Canada) and Military University of Technology (Warsaw, Poland) are critically reviewed in this paper. The research results indicate that microstructural refinement (particle and grain size) induced by ball milling influences quite modestly the hydrogen storage properties of simple metal and complex metal hydrides. On the other hand, the addition of nanometric elemental metals acting as potent catalysts and/or metal halide catalytic precursors brings about profound improvements in the hydrogen absorption/desorption kinetics for simple metal and complex metal hydrides alike. In general, catalytic precursors react with the hydride matrix forming a metal salt and free nanometric or amorphous elemental metals/intermetallics which, in turn, act catalytically. However, these catalysts change only kinetic properties i.e. the hydrogen absorption/desorption rate but they do not change thermodynamics (e.g., enthalpy change of hydrogen sorption reactions). It is shown that a complex metal hydride, LiAlH{sub 4}, after high energy ball milling with a nanometric Ni metal catalyst and/or MnCl{sub 2} catalytic precursor, is able to desorb relatively large quantities of hydrogen at room temperature, 40 and 80 {sup o}C. This kind of behavior is very encouraging for the future development of solid state hydrogen systems. (authors)

  5. A Review of Recent Advances on the Effects of Microstructural Refinement and Nano-Catalytic Additives on the Hydrogen Storage Properties of Metal and Complex Hydrides

    Directory of Open Access Journals (Sweden)

    Jerzy Bystrzycki

    2010-12-01

    Full Text Available The recent advances on the effects of microstructural refinement and various nano-catalytic additives on the hydrogen storage properties of metal and complex hydrides obtained in the last few years in the allied laboratories at the University of Waterloo (Canada and Military University of Technology (Warsaw, Poland are critically reviewed in this paper. The research results indicate that microstructural refinement (particle and grain size induced by ball milling influences quite modestly the hydrogen storage properties of simple metal and complex metal hydrides. On the other hand, the addition of nanometric elemental metals acting as potent catalysts and/or metal halide catalytic precursors brings about profound improvements in the hydrogen absorption/desorption kinetics for simple metal and complex metal hydrides alike. In general, catalytic precursors react with the hydride matrix forming a metal salt and free nanometric or amorphous elemental metals/intermetallics which, in turn, act catalytically. However, these catalysts change only kinetic properties i.e. the hydrogen absorption/desorption rate but they do not change thermodynamics (e.g., enthalpy change of hydrogen sorption reactions. It is shown that a complex metal hydride, LiAlH4, after high energy ball milling with a nanometric Ni metal catalyst and/or MnCl2 catalytic precursor, is able to desorb relatively large quantities of hydrogen at RT, 40 and 80 °C. This kind of behavior is very encouraging for the future development of solid state hydrogen systems.

  6. Trimethylsilyl-Substituted Hydroxycyclopentadienyl Ruthenium Hydrides as Benchmarks to Probe Ligand and Metal Effects on the Reactivity of Shvo Type Complexes.

    Science.gov (United States)

    Casey, Charles P; Guan, Hairong

    2012-01-01

    The bis(trimethylsilyl)-substituted hydroxycyclopentadienyl ruthenium hydride [2,5-(SiMe(3))(2)-3,4-(CH(2)OCH(2))(η(5)-C(4)COH)]Ru(CO)(2)H (10) is an efficient catalyst for hydrogenation of aldehydes and ketones. Because 10 transfers hydrogen rapidly to aldehydes and ketones and because it does not form an inactive bridging hydride during reaction, hydrogenation of aldehydes and ketones can be performed at room temperature under relatively low hydrogen pressure (3 atm); this is a significant improvement compared with previously developed Shvo type catalysts. Kinetic and (2)H NMR spectroscopic studies of the stoichiometric reduction of aldehydes and ketones by 10 established a two-step process for the hydrogen transfer: (1) rapid and reversible hydrogen bond formation between OH of 10 and the oxygen of the aldehyde or ketone, (2) followed by slow transfer of both proton and hydride from 10 to the aldehyde or ketone. The stoichiometric and catalytic activities of complex 10 are compared to those of other Shvo type ruthenium hydrides and related iron hydrides.

  7. Universal Brønsted-Evans-Polanyi Relations for C–C, C–O, C–N, N–O, N–N, and O–O Dissociation Reactions

    DEFF Research Database (Denmark)

    Wang, Shengguang; Temel, Burcin; Shen, Juan

    2011-01-01

    It is shown that for all the essential bond forming and bond breaking reactions on metal surfaces, the reactivity of the metal surface correlates linearly with the reaction energy in a single universal relation. Such correlations provide an easy way of establishing trends in reactivity among the ...

  8. "Long-range" metal-ligand cooperation in H2 activation and ammonia-promoted hydride transfer with a ruthenium-acridine pincer complex.

    Science.gov (United States)

    Gunanathan, Chidambaram; Gnanaprakasam, Boopathy; Iron, Mark A; Shimon, Linda J W; Milstein, David

    2010-10-27

    The acridine-based pincer complex 1 exhibits an unprecedented mode of metal-ligand cooperation involving a "long-range" interaction between the distal acridine C9 position and the metal center. Reaction of 1 with H(2)/KOH results in H(2) splitting between the Ru center and C9 with concomitant dearomatization of the acridine moiety. DFT calculations show that this process involves the formation of a Ru dihydride intermediate bearing a bent acridine ligand in which C9 is in close proximity to a hydride ligand followed by through-space hydride transfer. Ammonia induces transfer of a hydride from the Ru center of 1 to C9 of the flexible acridine pincer ligand, forming an unusual dearomatized fac-acridine PNP complex.

  9. Influence of surface contaminations on the hydrogen storage behaviour of metal hydride alloys.

    Science.gov (United States)

    Schülke, Mark; Paulus, Hubert; Lammers, Martin; Kiss, Gábor; Réti, Ferenc; Müller, Karl-Heinz

    2008-03-01

    Hydrogen storage in metal hydrides is a promising alternative to common storage methods. The surface of a metal hydride plays an important part in the absorption of hydrogen, since important partial reaction steps take place here. The development of surface contaminations and their influence on hydrogen absorption is examined by means of absorption experiments and surface analysis, using X-ray photoelectron spectroscopy (XPS), thermal desorption mass spectrometry (TDMS) and secondary neutral mass spectrometry (SNMS), in this work. All investigations were carried out on a modern AB(2) metal hydride alloy, namely Ti(0.96)Zr(0.04)Mn(1.43)V(0.45)Fe(0.08). Surface analysis (SNMS, XPS) shows that long-term air storage (several months) leads to oxide layers about 15 nm thick, with complete oxidation of all main alloy components. By means of in situ oxygen exposure at room temperature and XPS analysis, it can be shown that an oxygen dose of about 100 Langmuirs produces an oxide layer comparable to that after air storage. Manganese enrichment (segregation) is also clearly observed and is theoretically described here. This oxide layer hinders hydrogen absorption, so an activation procedure is necessary in order to use the full capacity of the metal hydride. This procedure consists of heating (T = 120 degrees C) in vacuum and hydrogen flushing at pressures like p = 18 bar. During the activation process the alloy is pulverized to particles of approximately 20 microm through lattice stretches. It is shown that this pulverization of the metal hydride (creating clean surface) during hydrogen flushing is essential for complete activation of the material. Re-activation of powder contaminated by small doses of air (p approximately 0.1 bar) does not lead to full absorption capacity. In ultrahigh vacuum, hydrogen is only taken up by the alloy after sputtering of the surface (which is done in order to remove oxide layers from it), thus creating adsorption sites for the hydrogen. This

  10. Acute arsenious hydride intoxication. Four cases

    Energy Technology Data Exchange (ETDEWEB)

    Gosselin, B.; Mathieu, D.; Desprez-Nolf, M.; Cosson, A.; Goudemand, J.; Haguenoer, J.M.; Wattel, F.

    1982-02-06

    While engaged in the repair of a zinc furnace, 4 workers were accidentally exposed to arsenious hydride (AsH3) fumes. Acute intravascular haemolysis developed within a few hours. On admission, the patients immediately underwent exsanguino-transfusion; 8.2 to 10.2 l of blood were exchanged through a continuous perfusion pump at the rate of 1 l/hour. Two patients resumed diuresis during transfusion, but the other two required repeated haemodialysis. Between the 10th and 30th days, while renal function was gradually returning to normal, mildly megaloblastic anaemia developed. This was followed during the 3rd month by clinical and electric signs of polyneuritis of the lower and upper limbs, which subsequently regressed. Regular measurements of arsenic levels in the blood and urine were performed between and during exsanguino-transfusion and haemodialysis.

  11. Hydrogen desorption from nanostructured magnesium hydride composites

    Directory of Open Access Journals (Sweden)

    Brdarić Tanja P.

    2007-01-01

    Full Text Available The influence of 3d transition metal addition (Fe, Co and Ni on the desorption properties of magnesium hydride were studied. The ball milling of MgH2-3d metal blends was performed under Ar. Microstructural and morphological characterization were performed by XRD and SEM analysis, while the hydrogen desorption properties were investigated by DSC. The results show a strong correlation between the morphology and thermal stability of the composites. The complex desorption behavior (the existence of more than one desorption peak was correlated with the dispersion of the metal additive particles that appear to play the main role in the desorption. The desorption temperature can be reduced by more than 100 degrees if Fe is added as additive. The activation energy for H2 desorption from the MgH2-Fe composite is 120 kJ/mol, implying that diffusion controls the dehydration process.

  12. Review of magnesium hydride-based materials: development and optimisation

    NARCIS (Netherlands)

    Crivello, J. -C.; Dam, B.; Denys, R. V.; Dornheim, M.; Grant, D. M.; Huot, J.; Jensen, T. R.; de Jongh, P.|info:eu-repo/dai/nl/186125372; Latroche, M.; Milanese, C.; Milcius, D.; Walker, G. S.; Webb, C. J.; Zlotea, C.; Yartys, V. A.

    Magnesium hydride has been studied extensively for applications as a hydrogen storage material owing to the favourable cost and high gravimetric and volumetric hydrogen densities. However, its high enthalpy of decomposition necessitates high working temperatures for hydrogen desorption while the

  13. Direct observation of hydrides formation in cavity-grade niobium

    Directory of Open Access Journals (Sweden)

    F. Barkov

    2012-12-01

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

  14. Structure and bonding of second-row hydrides

    OpenAIRE

    Blinder, S. M.

    2014-01-01

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

  15. Artificial exomuscle investigations for applications--metal hydride.

    Science.gov (United States)

    Crevier, Marie-Charlotte; Richard, Martin; Rittenhouse, D Matheson; Roy, Pierre-Olivier; Bédard, Stéphane

    2007-03-01

    In pursuing the development of bionic devices, Victhom identified a need for technologies that could replace current motorized systems and be better integrated into the human body motion. The actuators used to obtain large displacements are noisy, heavy, and do not adequately reproduce human muscle behavior. Subsequently, a project at Victhom was devoted to the development of active materials to obtain an artificial exomuscle actuator. An exhaustive literature review was done at Victhom to identify promising active materials for the development of artificial muscles. According to this review, metal hydrides were identified as a promising technology for artificial muscle development. Victhom's investigations focused on determining metal hydride actuator potential in the context of bionics technology. Based on metal hydride properties and artificial muscle requirements such as force, displacement and rise time, an exomuscle was built. In addition, a finite element model, including heat and mass transfer in the metal hydride, was developed and implemented in FEMLAB software.

  16. DETERMINATION OF METAL HYDRIDE SYSTEMS CHARACTERISTICS WHILE HEATING

    Directory of Open Access Journals (Sweden)

    Yu. Kluchka

    2012-01-01

    Full Text Available Experimental dependence of the pressure of hydrogen in the hydride cartridge when it is heated is obtained. Experimental data prove the theoretical values with an accuracy of ≈ 6%.

  17. Bipolar Nickel-Metal Hydride Battery Being Developed

    Science.gov (United States)

    Manzo, Michelle A.

    1998-01-01

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

  18. High-pressure synthesis of noble metal hydrides.

    Science.gov (United States)

    Donnerer, Christian; Scheler, Thomas; Gregoryanz, Eugene

    2013-04-07

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

  19. Artificial exomuscle investigations for applications-metal hydride

    Energy Technology Data Exchange (ETDEWEB)

    Crevier, Marie-Charlotte; Richard, Martin; Rittenhouse, D Matheson; Roy, Pierre-Olivier; Bedard, Stephane [Victhom Human Bionics Inc., Saint-Augustin-de-Desmaures, QC (Canada)

    2007-03-01

    In pursuing the development of bionic devices, Victhom identified a need for technologies that could replace current motorized systems and be better integrated into the human body motion. The actuators used to obtain large displacements are noisy, heavy, and do not adequately reproduce human muscle behavior. Subsequently, a project at Victhom was devoted to the development of active materials to obtain an artificial exomuscle actuator. An exhaustive literature review was done at Victhom to identify promising active materials for the development of artificial muscles. According to this review, metal hydrides were identified as a promising technology for artificial muscle development. Victhom's investigations focused on determining metal hydride actuator potential in the context of bionics technology. Based on metal hydride properties and artificial muscle requirements such as force, displacement and rise time, an exomuscle was built. In addition, a finite element model, including heat and mass transfer in the metal hydride, was developed and implemented in FEMLAB software. (review article)

  20. Out-of-pile accelerated hydriding of Zircaloy fasteners

    Energy Technology Data Exchange (ETDEWEB)

    Clayton, J.C.

    1979-10-01

    Mechanical joints between Zircaloy and nickel-bearing alloys, mainly the Zircaloy-4/Inconel-600 combination, were exposed to water at 450/sup 0/F and 520/sup 0/F to study hydriding of Zircaloy in contact with a dissimilar metal. Accelerated hydriding of the Zircaloy occurred at both temperatures. At 450/sup 0/F the dissolved hydrogen level of the water was over ten times that at 520/sup 0/F. At 520/sup 0/F the initially high hydrogen ingress rate decreased rapidly as exposure time increased and was effectively shut off in about 25 days. Severely hydrided Zircaloy components successfully withstood thermal cycling and mechanical testing. Chromium plating of the nickel-bearing parts was found to be an effective and practical barrier in preventing nickel-alloy smearing and accelerated hydriding of Zircaloy.

  1. Hydrogen storage in sodium aluminum hydride.

    Energy Technology Data Exchange (ETDEWEB)

    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

    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.

  2. Stepwise formation of H3O+(H2O)n in an ion drift tube: Empirical effective temperature of association/dissociation reaction equilibrium in an electric field

    Science.gov (United States)

    Nakai, Yoichi; Hidaka, Hiroshi; Watanabe, Naoki; Kojima, Takao M.

    2016-06-01

    We measured equilibrium constants for H3O+(H2O)n-1 + H2O↔H3O+(H2O)n (n = 4-9) reactions taking place in an ion drift tube with various applied electric fields at gas temperatures of 238-330 K. The zero-field reaction equilibrium constants were determined by extrapolation of those obtained at non-zero electric fields. From the zero-field reaction equilibrium constants, the standard enthalpy and entropy changes, Δ Hn , n - 1 0 and Δ Sn , n - 1 0 , of stepwise association for n = 4-8 were derived and were in reasonable agreement with those measured in previous studies. We also examined the electric field dependence of the reaction equilibrium constants at non-zero electric fields for n = 4-8. An effective temperature for the reaction equilibrium constants at non-zero electric field was empirically obtained using a parameter describing the electric field dependence of the reaction equilibrium constants. Furthermore, the size dependence of the parameter was thought to reflect the evolution of the hydrogen-bond structure of H3O+(H2O)n with the cluster size. The reflection of structural information in the electric field dependence of the reaction equilibria is particularly noteworthy.

  3. Stepwise formation of H3O(+)(H2O)n in an ion drift tube: Empirical effective temperature of association/dissociation reaction equilibrium in an electric field.

    Science.gov (United States)

    Nakai, Yoichi; Hidaka, Hiroshi; Watanabe, Naoki; Kojima, Takao M

    2016-06-14

    We measured equilibrium constants for H3O(+)(H2O)n-1 + H2O↔H3O(+)(H2O)n (n = 4-9) reactions taking place in an ion drift tube with various applied electric fields at gas temperatures of 238-330 K. The zero-field reaction equilibrium constants were determined by extrapolation of those obtained at non-zero electric fields. From the zero-field reaction equilibrium constants, the standard enthalpy and entropy changes, ΔHn,n-1 (0) and ΔSn,n-1 (0), of stepwise association for n = 4-8 were derived and were in reasonable agreement with those measured in previous studies. We also examined the electric field dependence of the reaction equilibrium constants at non-zero electric fields for n = 4-8. An effective temperature for the reaction equilibrium constants at non-zero electric field was empirically obtained using a parameter describing the electric field dependence of the reaction equilibrium constants. Furthermore, the size dependence of the parameter was thought to reflect the evolution of the hydrogen-bond structure of H3O(+)(H2O)n with the cluster size. The reflection of structural information in the electric field dependence of the reaction equilibria is particularly noteworthy.

  4. A copper(I) homocubane collapses to a tetracapped tetrahedron upon hydride insertion.

    Science.gov (United States)

    Liao, Ping-Kuei; Liu, Kuan-Guan; Fang, Ching-Shiang; Liu, C W; Fackler, John P; Wu, Ying-Yann

    2011-09-01

    The hydrido copper(I) and silver(I) clusters incorporating 1,1-dicyanoethylene-2,2-dithiolate (i-MNT) ligands are presented in this paper. Reactions of M(I) (M = Cu, Ag) salts, [Bu(4)N](2)[S(2)CC(CN)(2)], with the anion sources ([Bu(4)N][BH(4)] for H(-), [Bu(4)N][BD(4)] for D(-)) in an 8:6:1 molar ratio in THF produce octanuclear penta-anionic Cu(I)/Ag(I) clusters, [Bu(4)N](5)[M(8)(X){S(2)CC(CN)(2)}(6)] (M = Cu, X = H, 1(H); X = D, 1(D); M = Ag, X = H, 2(H); X = D, 2(D)). They can also be produced from the stoichiometric reaction of M(8)(i-MNT)(6)(4-) with the ammonium borohydride. All four compounds have been fully characterized spectroscopically ((1)H and (13)C NMR, IR, UV-vis) and by elemental analyses. The deuteride-encapsulated Cu(8)/Ag(8) clusters of 1(D) and 2(D) are also characterized by (2)H NMR. X-ray crystal structures of 1(H) and 2(H) reveal a hydride-centered tetracapped tetrahedral Cu(8)/Ag(8) core, which is inscribed within an S(12) icosahedron formed by six i-MNT ligands, each in a tetrametallic-tetraconnective (μ(2), μ(2)) bonding mode. The encapsulated hydride in 2(H) is unequivocally characterized by both (1)H and (109)Ag NMR spectroscopies, and the results strongly suggest that the hydride is coupled to eight magnetically equivalent silver nuclei on the NMR time scale. Therefore, a fast interchange between the vertex and capping silver atoms in solution gives a plausible explanation for the perceived structural differences between the Ag(8) geometry deduced from the X-ray structure and the NMR spectra.

  5. Mechanistic Insights into Ring Cleavage and Contraction of Benzene over a Titanium Hydride Cluster.

    Science.gov (United States)

    Kang, Xiaohui; Luo, Gen; Luo, Lun; Hu, Shaowei; Luo, Yi; Hou, Zhaomin

    2016-09-14

    Carbon-carbon bond cleavage of benzene by transition metals is of great fundamental interest and practical importance, as this transformation is involved in the production of fuels and other important chemicals in the industrial hydrocracking of naphtha on solid catalysts. Although this transformation is thought to rely on cooperation of multiple metal sites, molecular-level information on the reaction mechanism has remained scarce to date. Here, we report the DFT studies of the ring cleavage and contraction of benzene by a molecular trinuclear titanium hydride cluster. Our studies suggest that the reaction is initiated by benzene coordination, followed by H2 release, C6H6 hydrometalation, repeated C-C and C-H bond cleavage and formation to give a MeC5H4 unit, and insertion of a Ti atom into the MeC5H4 unit with release of H2 to give a metallacycle product. The C-C bond cleavage and ring contraction of toluene can also occur in a similar fashion, though some details are different due to the presence of the methyl substituent. Obviously, the facile release of H2 from the metal hydride cluster to provide electrons and to alter the charge population at the metal centers, in combination with the flexible metal-hydride connections and dynamic redox behavior of the trimetallic framework, has enabled this unusual transformation to occur. This work has not only provided unprecedented insights into the activation and transformation of benzene over a multimetallic framework but it may also offer help in the design of new molecular catalysts for the activation and transformation of inactive aromatics.

  6. Electronic structure of ternary hydrides based on light elements

    Energy Technology Data Exchange (ETDEWEB)

    Orgaz, E. [Departamento de Fisica y Quimica Teorica, Facultad de Quimica, Universidad Nacional Autonoma de Mexico, CP 04510 Coyoacan, Mexico, D.F. (Mexico)]. E-mail: orgaz@eros.pquim.unam.mx; Membrillo, A. [Departamento de Fisica y Quimica Teorica, Facultad de Quimica, Universidad Nacional Autonoma de Mexico, CP 04510 Coyoacan, Mexico, D.F. (Mexico); Castaneda, R. [Departamento de Fisica y Quimica Teorica, Facultad de Quimica, Universidad Nacional Autonoma de Mexico, CP 04510 Coyoacan, Mexico, D.F. (Mexico); Aburto, A. [Departamento de Fisica, Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, CP 04510 Coyoacan, Mexico, D.F. (Mexico)

    2005-12-08

    Ternary hydrides based on light elements are interesting owing to the high available energy density. In this work we focused into the electronic structure of a series of known systems having the general formula AMH{sub 4}(A=Li,Na,M=B,Al). We computed the energy bands and the total and partial density of states using the linear-augmented plane waves method. In this report, we discuss the chemical bonding in this series of complex hydrides.

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

    Science.gov (United States)

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

    2013-06-01

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

  8. Suppression of the critical temperature in binary vanadium hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Dolan, M.D., E-mail: michael.dolan@csiro.au [CSIRO Energy Technology, 1 Technology Court, Pullenvale, QLD 4069 (Australia); McLennan, K.G. [CSIRO Energy Technology, 1 Technology Court, Pullenvale, QLD 4069 (Australia); Chandra, D. [Department of Chemical and Materials Engineering, University of Nevada, Reno, Reno, NV 89557 (United States); Kochanek, M.A. [CSIRO Energy Technology, 1 Technology Court, Pullenvale, QLD 4069 (Australia); Song, G. [CSIRO Process Science and Engineering, Gate 4, Normanby Rd, Clayton, VIC 3168 (Australia)

    2014-02-15

    Highlights: • Addition of 10 mol% Cr to V increases the β-hydride T{sub C} to >200 °C. • Addition of 10 mol% Ni to V increases the β-hydride T{sub C} to >400 °C. • Addition of 10 mol% Al to V decreases the β-hydride T{sub C} to <30 °C. • V{sub 90}Al{sub 10} membrane can be cycled to <30 °C under H{sub 2} without β-hydride formation. -- Abstract: The tendency of vanadium-based alloy membranes to embrittle is the biggest commercialisation barrier for this hydrogen separation technology. Excessive hydrogen absorption and the α → β hydride transition both contribute to brittle failure of these membranes. Alloying is known to reduce absorption, but the influence of alloying on hydride phase formation under conditions relevant to membrane operation has not been studied in great detail previously. Here, the effect of Cr, Ni, and Al alloying additions on V–H phase equilibrium has been studied using hydrogen absorption measurements and in situ X-ray diffraction studies. The addition of 10 mol% Ni increases the critical temperature for α + β hydride formation to greater than 400 °C, compared to 170 °C for V. Cr also increases the critical temperature, to between 200 and 300 °C. The addition of 10 mol% Al, however, suppresses the critical temperature to less than 30 °C, thereby enabling this material to be cycled thermally and hydrostatically while precluding formation of the β-hydride phase. This is despite Al also decreasing hydrogen absorption. The implication of this finding is that one of the mechanisms of brittle failure in vanadium-based hydrogen-selective membranes has been eliminated, thereby increasing the robustness of this material relative to V.

  9. Method of selective reduction of polyhalosilanes with alkyltin hydrides

    Science.gov (United States)

    Sharp, Kenneth G.; D'Errico, John J.

    1989-01-01

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

  10. Method of selective reduction of halodisilanes with alkyltin hydrides

    Science.gov (United States)

    D'Errico, John J.; Sharp, Kenneth G.

    1989-01-01

    The invention relates to the selective and sequential reduction of halodisilanes by reacting these compounds at room temperature or below with trialkyltin hydrides or dialkyltin dihydrides without the use of free radical intermediates. The alkyltin hydrides selectively and sequentially reduce the Si-Cl, Si-Br or Si-I bonds while leaving intact the Si-Si and Si-F bonds present.

  11. Electronic structure and optical properties of lightweight metal hydrides

    NARCIS (Netherlands)

    Setten, van M.J.; Popa, V.A.; Wijs, de G.A.; Brocks, G.

    2007-01-01

    We study the dielectric functions of the series of simple hydrides LiH, NaH, MgH2, and AlH3, and of the complex hydrides Li3AlH6, Na3AlH6, LiAlH4, NaAlH4, and Mg(AlH4)2, using first-principles density-functional theory and GW calculations. All compounds are large gap insulators with GW single-partic

  12. Phase Equilibria, Crystal Structure and Hydriding/Dehydriding Mechanism of Nd4Mg80Ni8 Compound.

    Science.gov (United States)

    Luo, Qun; Gu, Qin-Fen; Zhang, Jie-Yu; Chen, Shuang-Lin; Chou, Kuo-Chih; Li, Qian

    2015-10-16

    In order to find out the optimal composition of novel Nd-Mg-Ni alloys for hydrogen storage, the isothermal section of Nd-Mg-Ni system at 400 °C is established by examining the equilibrated alloys. A new ternary compound Nd4Mg80Ni8 is discovered in the Mg-rich corner. It has the crystal structure of space group I41/amd with lattice parameters of a = b = 11.2743(1) Å and c = 15.9170(2) Å, characterized by the synchrotron powder X-ray diffraction (SR-PXRD). High-resolution transmission electron microscopy (HR-TEM) is used to investigate the microstructure of Nd4Mg80Ni8 and its hydrogen-induced microstructure evolution. The hydrogenation leads to Nd4Mg80Ni8 decomposing into NdH2.61-MgH2-Mg2NiH0.3 nanocomposites, where the high density phase boundaries provide a great deal of hydrogen atoms diffusion channels and nucleation sites of hydrides, which greatly enhances the hydriding/dehydriding (H/D) properties. The Nd4Mg80Ni8 exhibits a good cycle ability. The kinetic mechanisms of H/D reactions are studied by Real Physical Picture (RPP) model. The rate controlling steps are diffusion for hydriding reaction in the temperature range of 100 ~ 350 °C and surface penetration for dehydriding reaction at 291 ~ 347 °C. In-situ SR-PXRD results reveal the phase transformations of Mg to MgH2 and Mg2Ni to Mg2NiH4 as functions of hydrogen pressure and hydriding time.

  13. In situ electrochemical investigations of the kinetic and thermodynamic properties of nickel-metal hydride traction batteries

    Science.gov (United States)

    Yang, Xiao Guang; Liaw, Bor Yann

    Although large ampere hour nickel-metal hydride (Ni-MH) traction batteries are in the stage of being commercialized for electric and hybrid vehicle applications, little is known about their performance characteristics. By using a standard Hg/HgO reference electrode in a commercial Ni-MH battery, we were able to conduct in situ measurements to determine both kinetic and thermodynamic properties of the system, including the characteristics of individual electrodes. Using the galvanostatic intermittent titration technique (GITT), we simultaneously and effectively determined the open-circuit voltage of the battery, the equilibrium electrode potentials, and the diffusion coefficient of proton and hydrogen in the nickel and metal hydride electrode, respectively, as a function of the states of charge (SOC). Using the current-step excitation technique, we found that the internal resistance of the battery primarily comes from the metal hydride electrode, which is greater by one order of magnitude than that of the Ni electrode. The cyclic linear micro-polarization experiments, on the other hand, showed that the charge-transfer resistance of the electrochemical reaction at the metal hydride electrode is about twice larger than that of the Ni counterpart above 20% SOC. In comparison, the internal resistance is an order of magnitude smaller than those of the electrochemical charge-transfer reactions. The micro-polarization technique also allowed us to calculate the exchange current densities of the respective electrode electrochemical reactions and the associated specific exchange current densities. These in situ, simple but detailed, characterizations of the thermodynamic and kinetic properties of the Ni-MH system provided valuable information for better understanding of the battery performance.

  14. Phase Equilibria, Crystal Structure and Hydriding/Dehydriding Mechanism of Nd4Mg80Ni8 Compound

    Science.gov (United States)

    Luo, Qun; Gu, Qin-Fen; Zhang, Jie-Yu; Chen, Shuang-Lin; Chou, Kuo-Chih; Li, Qian

    2015-10-01

    In order to find out the optimal composition of novel Nd-Mg-Ni alloys for hydrogen storage, the isothermal section of Nd-Mg-Ni system at 400 °C is established by examining the equilibrated alloys. A new ternary compound Nd4Mg80Ni8 is discovered in the Mg-rich corner. It has the crystal structure of space group I41/amd with lattice parameters of a = b = 11.2743(1) Å and c = 15.9170(2) Å, characterized by the synchrotron powder X-ray diffraction (SR-PXRD). High-resolution transmission electron microscopy (HR-TEM) is used to investigate the microstructure of Nd4Mg80Ni8 and its hydrogen-induced microstructure evolution. The hydrogenation leads to Nd4Mg80Ni8 decomposing into NdH2.61-MgH2-Mg2NiH0.3 nanocomposites, where the high density phase boundaries provide a great deal of hydrogen atoms diffusion channels and nucleation sites of hydrides, which greatly enhances the hydriding/dehydriding (H/D) properties. The Nd4Mg80Ni8 exhibits a good cycle ability. The kinetic mechanisms of H/D reactions are studied by Real Physical Picture (RPP) model. The rate controlling steps are diffusion for hydriding reaction in the temperature range of 100 ~ 350 °C and surface penetration for dehydriding reaction at 291 ~ 347 °C. In-situ SR-PXRD results reveal the phase transformations of Mg to MgH2 and Mg2Ni to Mg2NiH4 as functions of hydrogen pressure and hydriding time.

  15. Dynamics of the dissociative electron attachment in H2O and D2O: The A1 resonance and axial recoil approximation

    Indian Academy of Sciences (India)

    N Bhargava Ram; Vaibhav S Prabhudesai; E Krishnakumar

    2012-01-01

    The dynamics of the formation and decay of negative ion resonance of A1 symmetry at 8.5 eV electron energy in the dissociative electron attachment (DEA) process in H2O and D2O are investigated using the velocity slice imaging technique. While the highest energy hydride ions formed by DEA show angular distributions characteristic to the A1 symmetry, those formed with low-kinetic energy show considerably different angular distributions indicating changes in the orientation of the dissociating bond due to bending mode vibrations. Our observations are quite different from the recently reported measurements, but consistent with the fully quantum calculations.

  16. Dissociation path for H2 on Al(110)

    DEFF Research Database (Denmark)

    Hammer, Bjørk; Jacobsen, Karsten Wedel; Nørskov, Jens Kehlet

    1992-01-01

    The minimum energy path is calculated for an H2 molecule dissociating on an Al(110) surface within local density functional theory. The properties of the potential energy surface along the five H2 ionic coordinates perpendicular to the reaction path are also determined and shown to be essential...

  17. Nucleon-x sub c sub J dissociation cross sections

    CERN Document Server

    Feng You Ceng; Xu Xiao Ming

    2002-01-01

    Nucleon-x sub c sub J dissociation cross sections are calculated in a constituent inter-exchange model in which quark-quark potential is derived from the Buchmueller-Type quark-anti-quark potential. These new cross sections for dominant reaction channels depend on the centre-of-mass energy of the nucleon and the charmonium

  18. Optimization of Hydride Rim Formation in Unirradiated Zr 4 Cladding

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-09-30

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

  19. Mechanochemical synthesis of nanostructured chemical hydrides in hydrogen alloying mills

    Energy Technology Data Exchange (ETDEWEB)

    Wronski, Z. [CANMET' s Materials Technology Laboratory, Natural Resources Canada, Ottawa (Canada) and Department of Mechanical Engineering, University of Waterloo, Waterloo, Ont., Canada N2L 3G1 (Canada)]. E-mail: zwronski@nrcan.gc.ca; Varin, R.A. [Department of Mechanical Engineering, University of Waterloo, Waterloo, Ont., Canada N2L 3G1 (Canada); Chiu, C. [Department of Mechanical Engineering, University of Waterloo, Waterloo, Ont., Canada N2L 3G1 (Canada); Czujko, T. [Department of Mechanical Engineering, University of Waterloo, Waterloo, Ont., Canada N2L 3G1 (Canada); Calka, A. [Department of Materials Science and Engineering, University of Wollongong, NSW 2518 (Australia)

    2007-05-31

    Mechanical alloying of magnesium metal powders with hydrogen in specialized hydrogen ball mills can be used as a direct route for mechanochemical synthesis of emerging chemical hydrides and hydride mixtures for advanced solid-state hydrogen storage. In the 2Mg-Fe system, we have successfully synthesized the ternary complex hydride Mg{sub 2}FeH{sub 6} in a mixture with nanometric Fe particles. The mixture of complex magnesium-iron hydride and nano-iron released 3-4 wt.%H{sub 2} in a thermally programmed desorption experiment at the range 285-295 {sup o}C. Milling of the Mg-2Al powder mixture revealed a strong competition between formation of the Al(Mg) solid solution and the {beta}-MgH{sub 2} hydride. The former decomposes upon longer milling as the Mg atoms react with hydrogen to form the hydride phase, and drive the Al out of the solid solution. The mixture of magnesium dihydride and nano-aluminum released 2.1 wt.%H{sub 2} in the temperature range 329-340 {sup o}C in the differential scanning calorimetry experiment. The formation of MgH{sub 2} was suppressed in the Mg-B system; instead, a hydrogenated amorphous phase (Mg,B)H {sub x}, was formed in a mixture with nanometric MgB{sub 2}. Annealing of the hydrogen-stabilized amorphous mixture produced crystalline MgB{sub 2}.

  20. Metal Hydrides for High-Temperature Power Generation

    Directory of Open Access Journals (Sweden)

    Ewa C. E. Rönnebro

    2015-08-01

    Full Text Available Metal hydrides can be utilized for hydrogen storage and for thermal energy storage (TES applications. By using TES with solar technologies, heat can be stored from sun energy to be used later, which enables continuous power generation. We are developing a TES technology based on a dual-bed metal hydride system, which has a high-temperature (HT metal hydride operating reversibly at 600–800 °C to generate heat, as well as a low-temperature (LT hydride near room temperature that is used for hydrogen storage during sun hours until there is the need to produce electricity, such as during night time, a cloudy day or during peak hours. We proceeded from selecting a high-energy density HT-hydride based on performance characterization on gram-sized samples scaled up to kilogram quantities with retained performance. COMSOL Multiphysics was used to make performance predictions for cylindrical hydride beds with varying diameters and thermal conductivities. Based on experimental and modeling results, a ~200-kWh/m3 bench-scale prototype was designed and fabricated, and we demonstrated the ability to meet or exceed all performance targets.

  1. The use of metal hydrides in fuel cell applications

    Directory of Open Access Journals (Sweden)

    Mykhaylo V. Lototskyy

    2017-02-01

    Full Text Available This paper reviews state-of-the-art developments in hydrogen energy systems which integrate fuel cells with metal hydride-based hydrogen storage. The 187 reference papers included in this review provide an overview of all major publications in the field, as well as recent work by several of the authors of the review. The review contains four parts. The first part gives an overview of the existing types of fuel cells and outlines the potential of using metal hydride stores as a source of hydrogen fuel. The second part of the review considers the suitability and optimisation of different metal hydrides based on their energy efficient thermal integration with fuel cells. The performances of metal hydrides are considered from the viewpoint of the reversible heat driven interaction of the metal hydrides with gaseous H2. Efficiencies of hydrogen and heat exchange in hydrogen stores to control H2 charge/discharge flow rates are the focus of the third section of the review and are considered together with metal hydride – fuel cell system integration issues and the corresponding engineering solutions. Finally, the last section of the review describes specific hydrogen-fuelled systems presented in the available reference data.

  2. Metal hydrides based high energy density thermal battery

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Zhigang Zak, E-mail: zak.fang@utah.edu [Department of Metallurgical Engineering, The University of Utah, 135 South 1460 East, Room 412, Salt Lake City, UT 84112-0114 (United States); Zhou, Chengshang; Fan, Peng [Department of Metallurgical Engineering, The University of Utah, 135 South 1460 East, Room 412, Salt Lake City, UT 84112-0114 (United States); Udell, Kent S. [Department of Metallurgical Engineering, The University of Utah, 50 S. Central Campus Dr., Room 2110, Salt Lake City, UT 84112-0114 (United States); Bowman, Robert C. [Department of Metallurgical Engineering, The University of Utah, 135 South 1460 East, Room 412, Salt Lake City, UT 84112-0114 (United States); Vajo, John J.; Purewal, Justin J. [HRL Laboratories, LLC, 3011 Malibu Canyon Road, Malibu, CA 90265 (United States); Kekelia, Bidzina [Department of Metallurgical Engineering, The University of Utah, 50 S. Central Campus Dr., Room 2110, Salt Lake City, UT 84112-0114 (United States)

    2015-10-05

    Highlights: • The principle of the thermal battery using advanced metal hydrides was demonstrated. • The thermal battery used MgH{sub 2} and TiMnV as a working pair. • High energy density can be achieved by the use of MgH{sub 2} to store thermal energy. - Abstract: A concept of thermal battery based on advanced metal hydrides was studied for heating and cooling of cabins in electric vehicles. The system utilized a pair of thermodynamically matched metal hydrides as energy storage media. The pair of hydrides that was identified and developed was: (1) catalyzed MgH{sub 2} as the high temperature hydride material, due to its high energy density and enhanced kinetics; and (2) TiV{sub 0.62}Mn{sub 1.5} alloy as the matching low temperature hydride. Further, a proof-of-concept prototype was built and tested, demonstrating the potential of the system as HVAC for transportation vehicles.

  3. Are major dissociative disorders characterized by a qualitatively different kind of dissociation?

    Science.gov (United States)

    Rodewald, Frauke; Dell, Paul F; Wilhelm-Gossling, Claudia; Gast, Ursula

    2011-01-01

    A total of 66 patients with a major dissociative disorder, 54 patients with nondissociative disorders, and 30 nonclinical controls were administered the Structured Clinical Interview for DSM-IV Dissociative Disorders-Revised, the Dissociative Experiences Scale, the Multidimensional Inventory of Dissociation, and the Symptom Checklist 90-Revised. Dissociative patients reported significantly more dissociative and nondissociative symptoms than did nondissociative patients and nonclinical controls. When general psychopathology was controlled, the dissociation scores of dissociative patients were still significantly higher than those of both other groups, whereas the dissociation scores of nondissociative patients and nonclinical controls no longer differed. These findings appear to be congruent with a typological model of dissociation that distinguishes between 2 qualitatively different kinds of dissociation. Specifically, the results of this study suggest that the dissociation that occurs in major dissociative disorders (i.e., dissociative identity disorder [DID] and dissociative disorder not otherwise specified, Type 1 [DDNOS-1]) is qualitatively different from the dissociation that occurs in persons who do not have a dissociative disorder. In contrast to previous research, the dissociation of persons who do not have a dissociative disorder is not limited to absorption; it covers a much wider range of phenomena. The authors hypothesize that different mechanisms produce the dissociation of persons with DID and DDNOS-1 as opposed to the dissociation of persons who do not have a dissociative disorder.

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

    Energy Technology Data Exchange (ETDEWEB)

    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

    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.

  5. Trialkylborane-Assisted CO(2) Reduction by Late Transition Metal Hydrides.

    Science.gov (United States)

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

    2011-01-01

    Trialkylborane additives promote reduction of CO(2) to formate by bis(diphosphine) Ni(II) and Rh(III) hydride complexes. The late transition metal hydrides, which can be formed from dihydrogen, transfer hydride to CO(2) to give a formate-borane adduct. The borane must be of appropriate Lewis acidity: weaker acids do not show significant hydride transfer enhancement, while stronger acids abstract hydride without CO(2) reduction. The mechanism likely involves a pre-equilibrium hydride transfer followed by formation of a stabilizing formate-borane adduct.

  6. Polymeric Binders which Reversibly Dissociate at Elevated Temperatures

    Science.gov (United States)

    1978-05-01

    materials must be used which are capable of regenerating the free isocyana.e on heating and will not undergo undesirable side reactions . The most widely...such as imidazole, indazole and benzotriazole, exhibit a marked tendency to dissociate at temperatures as low as 80*C to 100*C. With 4,5...only undergo a Diels-Alder reaction at room temperature with a variety of dienes, but it will also react with other functional groups. Many of these

  7. Unusual dissociative adsorption of H2 over stoichiometric MgO thin film supported on molybdenum

    CERN Document Server

    Song, Zhenjun

    2015-01-01

    The dissociation of a hydrogen molecule on MgO(001) films deposited on Mo(001) surface is investigated systematically using periodic density-functional theory method. The unusual adsorption behavior of heterolytic dissociative hydrogen molecule at neighboring surface oxygen and surface magnesium, is clarified here. To my knowledge, this heterolytic dissociative state has never been found before on bulk MgO(001) or metal supported MgO(001) surfaces. The results confirm that, in all cases, the heterolytic dissociation is much more favorable that homolytic dissociation both energetically and kinetically. The energy difference between two dissociative states are very large, in the range of 1.1 eV ~ 1.5 eV for Mo supported 1 ML ~ 3 ML oxide films, which inhibits, to a great extent, the homolytic dissociation in the respect of reaction thermodynamics. The energy barrier of heterolytic dissociation are about 0.5 eV, much lower that the barrier of homolytic dissociation. The transformation reaction on thick films wil...

  8. 1,2 Migration in Carbenoid and Carbene Reactions

    Institute of Scientific and Technical Information of China (English)

    MA Ming; JIANG Nan; SHI Wei-Feng; WANG Jian-Bo

    2003-01-01

    @@ 1,2-Hydride, 1,2-alkyl and 1,2-aryl migrations are common in free carbene chemistry, and they are also fre quently encountered in the reactions of metal carbenes. In some cases, these migration reactions can compete with the typical reactions of metal carbenes, such as X-H (X = Si, C, O, N, S, etc. ) insertions and cyclopropanations. [1] The 1,2-migration also found synthetic application. An example is the SnCl2-promoted 1,2-hydride migration of α-diazo-β-hydroxy esters, known as Roskamp homologation, which leads to the formation of β-keto esters. [2

  9. Coulomb dissociation of light unstable nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Kido, Toshihiko [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Yabana, Kazuhiro; Suzuki, Yoshiyuki

    1997-05-01

    The aim of this study is that a simulation method applicable to the atomic nucleus with neutron halo structure developed till now is applied to a wider range unstable nucleus containing proton excess nucleus to also attribute understanding of nuclear reaction with interest in astronomical nuclear reaction. The proton dissociation energy in {sup 8}B nucleus is small value of 138 eV, which is thought to have a structure of proton at the most outer shell bound much weakly by core nucleus and spread in thinner thickness. For the coulomb excitation of such weak bound system, quantum theoretical and non-perturbational treatment is important. Therefore, 3-dimensional time-dependent Schroedinger equation on relative wave function of the core nucleus {sup 7}Be and halo proton p will be dissolved in time space and will execute a time developmental simulation. (G.K.)

  10. A quantitative phase field model for hydride precipitation in zirconium alloys: Part II. Modeling of temperature dependent hydride precipitation

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Zhihua [The Hong Kong Polytechnic University, Shenzhen Research Institute, Shenzhen (China); PolyU Base (Shenzhen) Limited, Shenzhen (China); Department of Mechanical Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (China); Hao, Mingjun [The Hong Kong Polytechnic University, Shenzhen Research Institute, Shenzhen (China); Department of Mechanical Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (China); Guo, Xianghua [State Key Laboratory of Explosion and Safety Science, Beijing Institute of Technology, Beijing 100081 (China); Tang, Guoyi [Advanced Materials Institute, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Shi, San-Qiang, E-mail: mmsqshi@polyu.edu.hk [The Hong Kong Polytechnic University, Shenzhen Research Institute, Shenzhen (China); PolyU Base (Shenzhen) Limited, Shenzhen (China); Department of Mechanical Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (China)

    2015-04-15

    A quantitative free energy functional developed in Part I (Shi and Xiao, 2014 [1]) was applied to model temperature dependent δ-hydride precipitation in zirconium in real time and real length scale. At first, the effect of external tensile load on reorientation of δ-hydrides was calibrated against experimental observations, which provides a modification factor for the strain energy in free energy formulation. Then, two types of temperature-related problems were investigated. In the first type, the effect of temperature transient was studied by cooling the Zr–H system at different cooling rates from high temperature while an external tensile stress was maintained. At the end of temperature transients, the average hydride size as a function of cooling rate was compared to experimental data. In the second type, the effect of temperature gradients was studied in a one or two dimensional temperature field. Different boundary conditions were applied. The results show that the hydride precipitation concentrated in low temperature regions and that it eventually led to the formation of hydride blisters in zirconium. A brief discussion on how to implement the hysteresis of hydrogen solid solubility on hydride precipitation and dissolution in the developed phase field scheme is also presented.

  11. Atrioventricular Dissociation after Electroconvulsive Therapy

    Directory of Open Access Journals (Sweden)

    Siegfried William Yu

    2011-01-01

    Full Text Available Electroconvulsive therapy (ECT is increasingly used as a treatment for psychiatric disorders. Cardiac effects are the principal cause of medical complications in these patients. We report a case of atrioventricular (AV dissociation that occurred after ECT that was treated with pacemaker implantation. The mechanisms contributing to the onset of AV dissociation in this patient, and the management and rationale for device therapy, in light of the most recent guidelines, are reviewed.

  12. Dissociative Disorder Presenting as Catatonia

    OpenAIRE

    Sarkar, P; Patra, B.; Sattar, F.A.; Chatterjee, K.; Gupta, A; Walia, T.S.

    2004-01-01

    Three cases of dissociative disorder presenting with catatonia are described. Catatonia is generally believed to be associated with schizophrenia. However, many other conditions are also known to cause catatonia. A brief review of literature is provided. All the cases improved rapidly with a few ECTs. This report aims to highlight the presentation of dissociative disorders with catatonia. It also seeks to bring to notice the need to avoid lumping all non-organic catatonics under the rubric of...

  13. Main group multiple C-H/N-H bond activation of a diamine and isolation of a molecular dilithium zincate hydride: experimental and DFT evidence for alkali metal-zinc synergistic effects.

    Science.gov (United States)

    Campbell, Ross; Cannon, Daniel; García-Álvarez, Pablo; Kennedy, Alan R; Mulvey, Robert E; Robertson, Stuart D; Sassmannshausen, Jörg; Tuttle, Tell

    2011-08-31

    The surprising transformation of the saturated diamine (iPr)NHCH(2)CH(2)NH(iPr) to the unsaturated diazaethene [(iPr)NCH═CHN(iPr)](2-) via the synergic mixture nBuM, (tBu)(2)Zn and TMEDA (where M = Li, Na; TMEDA = N,N,N',N'-tetramethylethylenediamine) has been investigated by multinuclear NMR spectroscopic studies and DFT calculations. Several pertinent intermediary and related compounds (TMEDA)Li[(iPr)NCH(2)CH(2)NH(iPr)]Zn(tBu)(2) (3), (TMEDA)Li[(iPr)NCH(2)CH(2)CH(2)N(iPr)]Zn(tBu) (5), {(THF)Li[(iPr)NCH(2)CH(2)N(iPr)]Zn(tBu)}(2) (6), and {(TMEDA)Na[(iPr)NCH(2)CH(2)N(iPr)]Zn(tBu)}(2) (11), characterized by single-crystal X-ray diffraction, are discussed in relation to their role in the formation of (TMEDA)M[(iPr)NCH═CHN(iPr)]Zn(tBu) (M = Li, 1; Na, 10). In addition, the dilithio zincate molecular hydride [(TMEDA)Li](2)[(iPr)NCH(2)CH(2)N(iPr)]Zn(tBu)H 7 has been synthesized from the reaction of (TMEDA)Li[(iPr)NCH(2)CH(2)NH(iPr)]Zn(tBu)(2)3 with nBuLi(TMEDA) and also characterized by both X-ray crystallographic and NMR spectroscopic studies. The retention of the Li-H bond of 7 in solution was confirmed by (7)Li-(1)H HSQC experiments. Also, the (7)Li NMR spectrum of 7 in C(6)D(6) solution allowed for the rare observation of a scalar (1)J(Li-H) coupling constant of 13.3 Hz. Possible mechanisms for the transformation from diamine to diazaethene, a process involving the formal breakage of four bonds, have been determined computationally using density functional theory. The dominant mechanism, starting from (TMEDA)Li[(iPr)NCH(2)CH(2)N(iPr)]Zn(tBu) (4), involves the formation of a hydride intermediate and leads directly to the observed diazaethene product. In addition the existence of 7 in equilibrium with 4 through the dynamic association and dissociation of a (TMEDA)LiH ligand, also provides a secondary mechanism for the formation of the diazaethene. The two reaction pathways (i.e., starting from 4 or 7) are quite distinct and provide excellent examples in which the

  14. Flow injection on-line solid phase extraction for ultra-trace lead screening with hydride generation atomic fluorescence spectrometry.

    Science.gov (United States)

    Wan, Zhuo; Xu, Zhangrun; Wang, Jianhua

    2006-01-01

    A flow injection (FI) on-line solid phase extraction (SPE) procedure for ultra-trace lead separation and preconcentration was developed, followed by hydride generation and atomic fluorescence spectrometric (AFS) detection. Lead is retained on an iminodiacetate chelating resin packed microcolumn, and is afterward eluted with 2.5% (v/v) hydrochloric acid to facilitate the hydride generation by reaction with alkaline tetrahydroborate solution with 1% (m/v) potassium ferricyanide as an oxidizing (or sensitizing) reagent. The hydride was separated from the reaction medium in the gas-liquid separator and swept into the atomizer for quantification. The chemical variables and the FI flow parameters were carefully optimized. With a sample loading volume of 4.8 ml, quantitative retention of lead was obtained, along with an enrichment factor of 11.3 and a sampling frequency of 50 h(-1). A detection limit of 4 ng l(-1), defined as 3 times the blank standard deviation (3 sigma), was achieved along with a RSD value of 1.6% at the 0.4 microg l(-1) level. The procedure was validated by determining lead contents in two certified reference materials, and its practical applicability was further demonstrated by analysing a variety of biological and environmental samples.

  15. Enhancement in dehydriding performance of magnesium hydride by iron incorporation: A combined experimental and theoretical investigation

    Science.gov (United States)

    Chen, Haipeng; Yu, Hao; Zhang, Qianqian; Liu, Bogu; Liu, Pei; Zhou, Xinpei; Han, Zongying; Zhou, Shixue

    2016-08-01

    Structural change and dehydriding mechanism of MgH2 with atomic Fe incorporation from reactive ball milling are characterized and simulated by first-principles calculation. Two kinds of hydrides β- and γ-MgH2 are formed from Mg powders under hydrogen atmosphere by 3.0 h of milling with pretreated anthracite as milling aid. Experimental studies suggest that the atomic Fe can be incorporated onto MgH2 surface by the shearing effect of Fe-based milling balls on Mg/MgH2 particles. The incorporated Fe has a high dispersity on MgH2 surface and can form atomic clusters FeH4/FeH2 by combining with H anions. The dehydriding reaction of the Fe-incorporated MgH2 begins at hydride surface and shows an enhanced performance with apparent activation energy of 110.3 kJ mol-1. Theoretical studies suggest that the incorporated Fe can act as a bridge that contributes to electron transfer from H anion to Mg cation before H2 molecule formation. The intrinsic reason of atomic Fe in catalyzing dehydriding reaction of MgH2 lies in its moderate strength of electron attraction.

  16. First-Principles Modeling of Hydrogen Storage in Metal Hydride Systems

    Energy Technology Data Exchange (ETDEWEB)

    J. Karl Johnson

    2011-05-20

    The objective of this project is to complement experimental efforts of MHoCE partners by using state-of-the-art theory and modeling to study the structure, thermodynamics, and kinetics of hydrogen storage materials. Specific goals include prediction of the heats of formation and other thermodynamic properties of alloys from first principles methods, identification of new alloys that can be tested experimentally, calculation of surface and energetic properties of nanoparticles, and calculation of kinetics involved with hydrogenation and dehydrogenation processes. Discovery of new metal hydrides with enhanced properties compared with existing materials is a critical need for the Metal Hydride Center of Excellence. New materials discovery can be aided by the use of first principles (ab initio) computational modeling in two ways: (1) The properties, including mechanisms, of existing materials can be better elucidated through a combined modeling/experimental approach. (2) The thermodynamic properties of novel materials that have not been made can, in many cases, be quickly screened with ab initio methods. We have used state-of-the-art computational techniques to explore millions of possible reaction conditions consisting of different element spaces, compositions, and temperatures. We have identified potentially promising single- and multi-step reactions that can be explored experimentally.

  17. Hydride transfer made easy in the oxidation of alcohols catalyzed by choline oxidase

    Energy Technology Data Exchange (ETDEWEB)

    Gadda, G.; Orville, A.; Pennati, A.; Francis, K.; Quaye, O.; Yuan, H.; Rungsrisuriyachai, K.; Finnegan, S.; Mijatovic, S.; Nguyen, T.

    2008-06-08

    Choline oxidase (E.C. 1.1.3.17) catalyzes the two-step, four-electron oxidation of choline to glycine betaine with betaine aldehyde as enzyme-associated intermediate and molecular oxygen as final electron acceptor (Scheme 1). The gem-diol, hydrated species of the aldehyde intermediate of the reaction acts as substrate for aldehyde oxidation, suggesting that the enzyme may use similar strategies for the oxidation of the alcohol substrate and aldehyde intermediate. The determination of the chemical mechanism for alcohol oxidation has emerged from biochemical, mechanistic, mutagenetic, and structural studies. As illustrated in the mechanism of Scheme 2, the alcohol substrate is initially activated in the active site of the enzyme by removal of the hydroxyl proton. The resulting alkoxide intermediate is then stabilized in the enzyme-substrate complex via electrostatic interactions with active site amino acid residues. Alcohol oxidation then occurs quantum mechanically via the transfer of the hydride ion from the activated substrate to the N(5) flavin locus. An essential requisite for this mechanism of alcohol oxidation is the high degree of preorganization of the activated enzyme-substrate complex, which is achieved through an internal equilibrium of the Michaelis complex occurring prior to, and independently from, the subsequent hydride transfer reaction. The experimental evidence that support the mechanism for alcohol oxidation shown in Scheme 2 is briefly summarized in the Results and Discussion section.

  18. Dissociative disorders in DSM-5.

    Science.gov (United States)

    Spiegel, David; Lewis-Fernández, Roberto; Lanius, Ruth; Vermetten, Eric; Simeon, Daphne; Friedman, Matthew

    2013-01-01

    The rationale, research literature, and proposed changes to the dissociative disorders and conversion disorder in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) are presented. Dissociative identity disorder will include reference to possession as well as identity fragmentation, to make the disorder more applicable to culturally diverse situations. Dissociative amnesia will include dissociative fugue as a subtype, since fugue is a rare disorder that always involves amnesia but does not always include confused wandering or loss of personality identity. Depersonalization disorder will include derealization as well, since the two often co-occur. A dissociative subtype of posttraumatic stress disorder (PTSD), defined by the presence of depersonalization or derealization in addition to other PTSD symptoms, is being recommended, based upon new epidemiological and neuroimaging evidence linking it to an early life history of adversity and a combination of frontal activation and limbic inhibition. Conversion disorder (functional neurological symptom disorder) will likely remain with the somatic symptom disorders, despite considerable dissociative comorbidity.

  19. Technical and economic evaluation of hydrogen storage systems based on light metal hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Jepsen, Julian

    2014-07-01

    Novel developments regarding materials for solid-state hydrogen storage show promising prospects. These complex hydrides exhibit high mass-related storage capacities and thus great technical potential to store hydrogen in an efficient and safe way. However, a comprehensive evaluation of economic competitiveness is still lacking, especially in the case of the LiBH4 / MgH2 storage material. In this study, an assessment with respect to the economic feasibility of implementing complex hydrides as hydrogen storage materials is presented. The cost structure of hydrogen storage systems based on NaAlH4 and LiBH4 / MgH2 is discussed and compared with the conventional high pressure (700 bar) and liquid storage systems. Furthermore, the properties of LiBH4 / MgH2, so-called Li-RHC (Reactive Hydride Composite), are scientifically compared and evaluated on the lab and pilot plant scale. To enhance the reaction rate, the addition of TiCl3 is investigated and high energy ball milling is evaluated as processing technique. The effect of the additive in combination with the processing technique is described in detail. Finally, an optimum set of processing parameters and additive content are identified and can be applied for scaled-up production of the material based on simple models considering energy input during processing. Furthermore, thermodynamic, heat transfer and kinetic properties are experimentally determined by different techniques and analysed as a basis for modelling and designing scaled-up storage systems. The results are analysed and discussed with respect to the reaction mechanisms and reversibility of the system. Heat transfer properties are assessed with respect to the scale-up for larger hydrogen storage systems. Further improvements of the heat transfer were achieved by compacting the material. In this regard, the influence of the compaction pressure on the apparent density, thermal conductivity and sorption behaviour, was investigated in detail. Finally, scaled

  20. Hydriding and Dehydriding Properties of Zinc Borohydride, Nickel, and Titanium-Added Magnesium Hydride

    Energy Technology Data Exchange (ETDEWEB)

    Kwak, Young Jun; Kwon, Sung Nam; Song, Myoung Youp [Chonbuk National University, Jeonju (Korea, Republic of)

    2015-11-15

    A Zn(BH{sub 4}){sub 2} sample was prepared by milling ZnCl{sub 2} and NaBH{sub 4} in a planetary ball mill under Ar gas. This sample contained NaCl. Then, 90 wt% MgH{sub 2}-5 wt% Zn(BH{sub 4}){sub 2}-2.5 wt% Ni-2.5 wt% Ti samples [named 90MgH{sub 2}-5Zn(BH{sub 4}){sub 2}-2.5Ni-2.5Ti] were prepared by milling in a planetary ball mill under H{sub 2} gas. The hydrogen absorption and release properties of the prepared samples were investigated. In particular, the variations of the initial hydriding and dehydriding rates with temperature were examined. SEM micrographs and XRD patterns of 90MgH{sub 2}-5Zn(BH{sub 4}){sub 2}-2.5Ni-2.5Ti after reactive mechanical grinding and after hydriding-dehydriding were also studied. Particle size distributions and BET specific surface areas of 90MgH{sub 2}-5Zn(BH{sub 4}){sub 2}-2.5Ni-2.5Ti after reactive mechanical grinding and after 11 hydriding-dehydriding cycles were analyzed. The 90MgH{sub 2}-5Zn(BH{sub 4}){sub 2}-2.5Ni-2.5Ti had an effective hydrogen storage capacity (the quantity of hydrogen absorbed for 60 min) of near 5 wt% (4.91 wt% at 593 K).

  1. Coulomb dissociation of {sup 8}B at 254 A MeV

    Energy Technology Data Exchange (ETDEWEB)

    Suemmerer, K.; Boue, F.; Baumann, T.; Geissel, H.; Hellstroem, M.; Koczon, P.; Schwab, E.; Schwab, W.; Senger, P.; Surowiecz, A. [Gesellschaft fuer Schwerionenforschung (GSI), Darmstadt (Germany); Iwasa, N.; Ozawa, A. [Gesellschaft fuer Schwerionenforschung (GSI), Darmstadt (Germany)]|[RIKEN Institute of Physical and Chemical Research, Saitama (Japan); Surowka, G. [Gesellschaft fuer Schwerionenforschung (GSI), Darmstadt (Germany)]|[Jagiellonian Univ., Krakow (Poland). Inst. of Physics; Blank, B.; Czajkowski, S.; Marchand, C.; Pravikoff, M.S. [Centre d`Etudes Nucleaires de Bordeaux-Gradignan, 33 (France); Foerster, A.; Lauer, F.; Oeschler, H.; Speer, J.; Sturm, C.; Uhlig, F.; Wagner, A. [Technische Univ. Darmstadt (Germany); Gai, M. [Connecticut Univ., Storrs, CT (United States). Dept. of Physics; Grosse, E. [Inst. fuer Kern- und Hadronenphysik, Forschungszentrum Rossendorf, Dresden (Germany); Kohlmeyer, B. [Philipps Univ., Marburg (Germany). Fachbereich Physik; Kulessa, R.; Walus, W. [Jagiellonian Univ., Krakow (Poland). Inst. of Physics; Motobayashi, T. [Rikkyo Univ., Tokyo (Japan). Dept. of Physics; Teranishi, T. [RIKEN Institute of Physical and Chemical Research, Saitama (Japan)

    1998-06-01

    As an alternative method for determining the astrophysical S-factor for the {sup 7}Be(p,{gamma}){sup 8}B reaction we have measured the Coulomb dissociation of {sup 8}B at 254 A MeV. From our preliminary results, we obtain good agreement with both the accepted direct-reaction measurements and the low-energy Coulomb dissociation study of Iwasa et al. performed at about 50 A MeV. (orig.)

  2. Simulations of dissociation constants in low pressure supercritical water

    Science.gov (United States)

    Halstead, S. J.; An, P.; Zhang, S.

    2014-09-01

    This article reports molecular dynamics simulations of the dissociation of hydrochloric acid and sodium hydroxide in water from ambient to supercritical temperatures at a fixed pressure of 250 atm. Corrosion of reaction vessels is known to be a serious problem of supercritical water, and acid/base dissociation can be a significant contributing factor to this. The SPC/e model was used in conjunction with solute models determined from density functional calculations and OPLSAA Lennard-Jones parameters. Radial distribution functions were calculated, and these show a significant increase in solute-solvent ordering upon forming the product ions at all temperatures. For both dissociations, rapidly decreasing entropy of reaction was found to be the controlling thermodynamic factor, and this is thought to arise due to the ions produced from dissociation maintaining a relatively high density and ordered solvation shell compared to the reactants. The change in entropy of reaction reaches a minimum at the critical temperature. The values of pKa and pKb were calculated and both increased with temperature, in qualitative agreement with other work, until a maximum value at 748 K, after which there was a slight decrease.

  3. Low Energy Nuclear Reactions?

    CERN Document Server

    CERN. Geneva; Faccini, R.

    2014-01-01

    After an introduction to the controversial problem of Low Energy Nuclear Reactions (LENR) catalyzed by neutrons on metallic hydride surfaces we present the results of an experiment, made in collaboration with ENEA Labs in Frascati, to search neutrons from plasma discharges in electrolytic cells. The negative outcome of our experiment goes in the direction of ruling out those theoretical models expecting LENR to occur in condensed matter systems under specific conditions. Our criticism on the theoretical foundations of such models will also be presented.

  4. Dissociative experiences and dissociative minds: Exploring a nomological network of dissociative functioning.

    Science.gov (United States)

    Schimmenti, Adriano

    2016-01-01

    In this study, the psychometric properties of the Dissociative Experiences Scale-II (DES-II) were tested in a sample of Italian adults, and a nomological network of dissociative functioning based on current psychodynamic research was examined. A total of 794 participants (55% females) ranging in age from 18 to 64 completed the DES-II and other measures of theory of mind, alexithymia, attachment style, and empathy. The Italian translation of the DES-II showed high internal consistency, adequate item-to-scale homogeneity, and good split-half reliability. A single-factor solution including the 8 items of pathological dissociation (DES-T) adequately fit the data. Participants who reported higher levels of dissociative experiences showed significantly lower scores on theory of mind and empathy than other participants. They also showed significantly higher scores on alexithymia, preoccupied attachment, and fearful attachment. Results of the study support the view that people who suffer from severe dissociative experiences may also have difficulties mentalizing and regulating affects and that they may feel uncomfortable in close relationships because they have a negative view of the self. This can inform clinical work with dissociative individuals, who could benefit from therapies that consider their potential problems with mentalization, empathy, affect regulation, and attachment.

  5. Dissociative disorders among alcohol-dependent inpatients.

    Science.gov (United States)

    Evren, Cuneyt; Sar, Vedat; Karadag, Figen; Tamar Gurol, Defne; Karagoz, Mustafa

    2007-08-30

    The aim of this study was to determine the prevalence of dissociative disorders among inpatients with alcohol dependency. The Dissociative Experiences Scale was used to screen 111 alcohol-dependent patients consecutively admitted to the inpatient unit of a dependency treatment center. Subgroups of 29 patients who scored 30.0 or above and 25 patients who scored below 10.0 were then evaluated with the Dissociative Disorders Interview Schedule and the Structured Interview for DSM-IV Dissociative Disorders. The interviewers were blind to the Dissociative Experiences Scale scores. Of the 54 patients evaluated, 10 (9.0% of the original 111) patients had a dissociative disorder. A considerable number of the remaining patients reported a high level of dissociative experiences. Among the dissociative disorder group, nine patients had dissociative disorder not otherwise specified and one patient had depersonalization disorder. Female gender, younger age, history of suicide attempt, childhood emotional and sexual abuse, and neglect were more frequent in the dissociative disorder group than among non-dissociative patients. The dissociative disorder group also had somatization disorder, borderline personality disorder, and lifetime major depression more frequently. For 9 of the 10 dissociative patients, dissociative symptoms started before the onset of alcohol use. Although the probability of having a comorbid dissociative disorder was not higher among alcohol-dependent inpatients than among the general psychiatric inpatients, the dissociative subgroup had distinct features. Many patients without a dissociative disorder diagnosis (predominantly men) provided hints of subtle dissociative psychopathology. Implications of comorbid dissociative disorders and dissociative experiences on prevention and treatment of alcohol dependency and the importance of gender-specific characteristics in this relationship require further study.

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

    Science.gov (United States)

    Zollars, G. F.

    1980-01-01

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

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

    Science.gov (United States)

    Zollars, G. F.

    1980-01-01

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

  8. Micro-scale fracture experiments on zirconium hydrides and phase boundaries

    Science.gov (United States)

    Chan, H.; Roberts, S. G.; Gong, J.

    2016-07-01

    Fracture properties of micro-scale zirconium hydrides and phase boundaries were studied using microcantilever testing methods. FIB-machined microcantilevers were milled on cross-sectional surfaces of hydrided samples, with the most highly-stressed regions within the δ-hydride film, within the α-Zr or along the Zr-hydride interface. Cantilevers were notched using the FIB and then tested in bending using a nanoindenter. Load-displacement results show that three types of cantilevers have distinct deformation properties. Zr cantilevers deformed plastically. Hydride cantilevers fractured after a small amount of plastic flow; the fracture toughness of the δ-hydride was found to be 3.3 ± 0.4 MPam1/2 and SEM examination showed transgranular cleavage on the fracture surfaces. Cantilevers notched at the Zr-hydride interface developed interfacial voids during loading, at loads considerably lower than that which initiate brittle fracture of hydrides.

  9. Metal hydride/chemical heat-pump development project. Phase I. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Argabright, T.A.

    1982-02-01

    The metal hydride/chemical heat pump (MHHP) is a chemical heat pump containing two hydrides for the storage and/or recovery of thermal energy. It utilizes the heat of reaction of hydrogen with specific metal alloys. The MHHP design can be tailored to provide heating and/or cooling or temperature upgrading over a wide range of input and ambient temperatures. The system can thus be used with a variety of heat sources including waste heat, solar energy or a fossil fuel. The conceptual design of the MHHP was developed. A national market survey including a study of applications and market sectors was conducted. The technical tasks including conceptual development, thermal and mechanical design, laboratory verification of design and material performance, cost analysis and the detailed design of the Engineering Development Test Unit (EDTU) were performed. As a result of the market study, the temperature upgrade cycle of the MHHP was chosen for development. Operating temperature ranges for the upgrader were selected to be from 70 to 110/sup 0/C (160 to 230/sup 0/F) for the source heat and 140 to 190/sup 0/C (280 to 375/sup 0/F) for the product heat. These ranges are applicable to many processes in industries such as food, textile, paper and pulp, and chemical. The hydride pair well suited for these temperatures is LaNi/sub 5//LaNi/sub 4/ /sub 5/Al/sub 0/ /sub 5/. The EDTU was designed for the upgrade cycle. It is a compact finned tube arrangement enclosed in a pressure vessel. This design incorporates high heat transfer and low thermal mass in a system which maximizes the coefficient of performance (COP). It will be constructed in Phase II. Continuation of this effort is recommended.

  10. First-principles predictions of potential hydrogen storage materials: Nanosized Ti(core)/Mg(shell) hydrides

    Science.gov (United States)

    Tao, S. X.; Notten, P. H. L.; van Santen, R. A.; Jansen, A. P. J.

    2011-05-01

    MgH2 is one of the most promising hydrogen storage materials. However MgH2 is thermodynamicly too stable, leading to a too high desorption temperature of 300°C at atmospheric pressure, which is a major impediment for practical applications. In this study, aiming to tune the thermodynamic stability of the MgH2, nanosized two-dimensional Mg/Ti/Mg sandwich and three-dimensional Ti(core)/Mg(shell) hydrides have been investigated by using density functional theory calculations. For both structures, four types of hydrogen atoms can be distinguished: on the surface of the Mg (Hsurf), within the Mg (HMg), at the Mg/Ti interface (HMgTi), and within the Ti (HTi). For the dehydrogenation reaction, the hydrogen desorption from the hydride is in the order Hsurf, HMg, HMgTi, HTi. The desorption energy of Hsurf is unexpectedly high. As expected, due to the well-preserved fluorite structure of the partially hydrogenated hydride, the desorption energy of HMg is significantly lower than that of bulk rutile MgH2. The further desorption of HMgTi and HTi becomes more difficult due to the strong Ti-H bonding. We propose that partial hydrogenation without adsorption of Hsurf and partial dehydrogenation without desorption of HMgTi and HTi would keep the fluorite symmetry with its favorable thermodynamics. The reversible hydrogen capacity (HMg) of the Mg/Ti/Mg sandwich structure is low, whereas the reversible hydrogen capacity of the Ti(core)/Mg(shell) is calculated to be reasonable high. Our results predicted Ti(core)/Mg(shell) structures are potential useful materials for hydrogen storage application.

  11. Cytochrome P450BM-3 reduces aldehydes to alcohols through a direct hydride transfer

    Energy Technology Data Exchange (ETDEWEB)

    Kaspera, Ruediger; Sahele, Tariku; Lakatos, Kyle [Department of Medicinal Chemistry, University of Washington, Box 357610, Seattle, WA 98195-7610 (United States); Totah, Rheem A., E-mail: rtotah@u.washington.edu [Department of Medicinal Chemistry, University of Washington, Box 357610, Seattle, WA 98195-7610 (United States)

    2012-02-17

    Highlights: Black-Right-Pointing-Pointer Cytochrome P450BM-3 reduced aldehydes to alcohols efficiently (k{sub cat} {approx} 25 min{sup -1}). Black-Right-Pointing-Pointer Reduction is a direct hydride transfer from R-NADP{sup 2}H to the carbonyl moiety. Black-Right-Pointing-Pointer P450 domain variants enhance reduction through potential allosteric/redox interactions. Black-Right-Pointing-Pointer Novel reaction will have implications for metabolism of xenobiotics. -- Abstract: Cytochrome P450BM-3 catalyzed the reduction of lipophilic aldehydes to alcohols efficiently. A k{sub cat} of {approx}25 min{sup -1} was obtained for the reduction of methoxy benzaldehyde with wild type P450BM-3 protein which was higher than in the isolated reductase domain (BMR) alone and increased in specific P450-domain variants. The reduction was caused by a direct hydride transfer from preferentially R-NADP{sup 2}H to the carbonyl moiety of the substrate. Weak substrate-P450-binding of the aldehyde, turnover with the reductase domain alone, a deuterium incorporation in the product from NADP{sup 2}H but not D{sub 2}O, and no inhibition by imidazole suggests the reductase domain of P450BM-3 as the potential catalytic site. However, increased aldehyde reduction by P450 domain variants (P450BM-3 F87A T268A) may involve allosteric or redox mechanistic interactions between heme and reductase domains. This is a novel reduction of aldehydes by P450BM-3 involving a direct hydride transfer and could have implications for the metabolism of endogenous substrates or xenobiotics.

  12. Investigation of Cracked Lithium Hydride Reactor Vessels

    Energy Technology Data Exchange (ETDEWEB)

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

    1999-06-01

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

  13. Control of PDMS crosslinking by encapsulating a hydride crosslinker in a PMMA microcapsule

    DEFF Research Database (Denmark)

    Ma, Baoguang; Hansen, Jens Henrik; Hvilsted, Søren;

    2014-01-01

    crosslinker in a PMMA shell. Microcapsules are mixed with vinyl-terminated PDMS to create a gelation system, which allows for storage at 50 °C, without premature gelation, and in addition allows for extensive crosslinking reaction at 120 °C. Both visual observations and rheological studies show that a robust...... PDMS elastomer is obtained upon heating the gelation system. Furthermore, the influence of stoichiometric imbalance on the equilibrium storage modulus of the PDMS network is investigated, by employing different amounts of microcapsules in vinyl-terminated PDMS. It has been found that adding...... microcapsules increases the equilibrium storage modulus of the PDMS elastomer until the diffusion of the hydride crosslinker is constricted. An optimum amount of crosslinker used in the control crosslinking reaction has also been found. However, compared to the pure PDMS elastomer, the modulus of the PDMS...

  14. Mechanism of negative hydrogen ion emission from heated saline hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Kawano, Hiroyuki; Serizawa, Naoshi; Takeda, Makiko; Hasegawa, Seiji [Ehime Univ., Matsuyama (Japan). Faculty of Science

    1997-02-01

    To find a clue to the mechanism of negative hydrogen ion emission from a heated sample ({approx}10 mg) of powdery saline hydride (LiH or CaH{sub 2}) deposited on a molybdenum ribbon ({approx}0.1 cm{sup 2}), both the ionic and electronic emission currents were measured as a function of sample temperature ({approx}700 - 800 K), thereby yielding {approx}10{sup -15} - 10{sup -12} A of H{sup -} after mass analysis and {approx}10{sup -7} - 10{sup -5} A of thermal electron. Thermophysical analysis of these data indicates that the desorption energy (E{sup -}) of H{sup -} and work function ({phi}) of the emitting sample surface are 5.1 {+-} 0.3 and 3.1 {+-} 0.2 eV for LiH, respectively, while E{sup -} is 7.7 {+-} 0.3 eV and {phi} is 5.0 {+-} 0.2 eV for CaH{sub 2}. Thermochemical analysis based on our simple model on the emissions indicates that the values of E{sup -} - {phi} are 2.35 and 2.31 eV for LiH and CaH{sub 2}, respectively, which are in fair agreement with the respective values (2.1 {+-} 0.3 and 2.6 {+-} 0.3 eV) determined experimentally. This agreement indicates that the emission of H{sup -} is reasonably explained by our model from the viewpoint of reaction energy. (author)

  15. Multidimensional simulations of hydrides during fuel rod lifecycle

    Science.gov (United States)

    Stafford, D. S.

    2015-11-01

    In light water reactor fuel rods, waterside corrosion of zirconium-alloy cladding introduces hydrogen into the cladding, where it is slightly soluble. When the solubility limit is reached, the hydrogen precipitates into crystals of zirconium hydride which decrease the ductility of the cladding and may lead to cladding failure during dry storage or transportation events. The distribution of the hydride phase and the orientation of the crystals depend on the history of the spatial temperature and stress profiles in the cladding. In this work, we have expanded the existing hydride modeling capability in the BISON fuel performance code with the goal of predicting both global and local effects on the radial, azimuthal and axial distribution of the hydride phase. We compare results from 1D simulations to published experimental data. We demonstrate the new capability by simulating in 2D a fuel rod throughout a lifecycle that includes irradiation, short-term storage in the spent fuel pool, drying, and interim storage in a dry cask. Using the 2D simulations, we present qualitative predictions of the effects of the inter-pellet gap and the drying conditions on the growth of a hydride rim.

  16. The effect of stress state on zirconium hydride reorientation

    Science.gov (United States)

    Cinbiz, Mahmut Nedim

    Prior to storage in a dry-cask facility, spent nuclear fuel must undergo a vacuum drying cycle during which the spent fuel rods are heated up to elevated temperatures of ≤ 400°C to remove moisture the canisters within the cask. As temperature increases during heating, some of the hydride particles within the cladding dissolve while the internal gas pressure in fuel rods increases generating multi-axial hoop and axial stresses in the closed-end thin-walled cladding tubes. As cool-down starts, the hydrogen in solid solution precipitates as hydride platelets, and if the multiaxial stresses are sufficiently large, the precipitating hydrides reorient from their initial circumferential orientation to radial orientation. Radial hydrides can severely embrittle the spent nuclear fuel cladding at low temperature in response to hoop stress loading. Because the cladding can experience a range of stress states during the thermo-mechanical treatment induced during vacuum drying, this study has investigated the effect of stress state on the process of hydride reorientation during controlled thermo-mechanical treatments utilizing the combination of in situ X-ray diffraction and novel mechanical testing analyzed by the combination of metallography and finite element analysis. The study used cold worked and stress relieved Zircaloy-4 sheet containing approx. 180 wt. ppm hydrogen as its material basis. The failure behavior of this material containing radial hydrides was also studied over a range of temperatures. Finally, samples from reactor-irradiated cladding tubes were examined by X-ray diffraction using synchrotron radiation. To reveal the stress state effect on hydride reorientation, the critical threshold stress to reorient hydrides was determined by designing novel mechanical test samples which produce a range of stress states from uniaxial to "near-equibiaxial" tension when a load is applied. The threshold stress was determined after thermo-mechanical treatments by

  17. Sodium-based hydrides for thermal energy applications

    Science.gov (United States)

    Sheppard, D. A.; Humphries, T. D.; Buckley, C. E.

    2016-04-01

    Concentrating solar-thermal power (CSP) with thermal energy storage (TES) represents an attractive alternative to conventional fossil fuels for base-load power generation. Sodium alanate (NaAlH4) is a well-known sodium-based complex metal hydride but, more recently, high-temperature sodium-based complex metal hydrides have been considered for TES. This review considers the current state of the art for NaH, NaMgH3- x F x , Na-based transition metal hydrides, NaBH4 and Na3AlH6 for TES and heat pumping applications. These metal hydrides have a number of advantages over other classes of heat storage materials such as high thermal energy storage capacity, low volume, relatively low cost and a wide range of operating temperatures (100 °C to more than 650 °C). Potential safety issues associated with the use of high-temperature sodium-based hydrides are also addressed.

  18. Comparison of Hydrogen Elimination from Molecular Zinc and Magnesium Hydride Clusters

    NARCIS (Netherlands)

    Intemann, J.; Sirsch, Peter; Harder, Sjoerd

    2014-01-01

    In analogy to the previously reported tetranuclear magnesium hydride cluster with a bridged dianionic bis-beta-diketiminate ligand, a related zinc hydride cluster has been prepared. The crystal structures of these magnesium and zinc hydride complexes are similar: the metal atoms are situated at the

  19. Use of triammonium salt of aurin tricarboxylic acid as risk mitigant for aluminum hydride

    Science.gov (United States)

    Cortes-Concepcion, Jose A.; Anton, Donald L.

    2017-08-08

    A process and a resulting product by process of an aluminum hydride which is modified with by physically combining in a ball milling process an aluminum hydride with a triammonium salt of aurin tricarboxylic acid. The resulting product is an aluminum hydride which is resistant to air, ambient moisture, and liquid water while maintaining useful hydrogen storage and release kinetics.

  20. Comparison of Hydrogen Elimination from Molecular Zinc and Magnesium Hydride Clusters

    NARCIS (Netherlands)

    Intemann, J.; Sirsch, Peter; Harder, Sjoerd

    2014-01-01

    In analogy to the previously reported tetranuclear magnesium hydride cluster with a bridged dianionic bis-beta-diketiminate ligand, a related zinc hydride cluster has been prepared. The crystal structures of these magnesium and zinc hydride complexes are similar: the metal atoms are situated at the

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

    Science.gov (United States)

    ONISCHAK

    1976-01-01

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

  2. Simultaneous determination of hydride and non-hydride forming elements by inductively coupled plasma optical emission spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Benzo, Z. [Instituto Venezolano de Investigaciones Cientificas, IVIC, Altos de Pipe, Caracas (Venezuela, Bolivarian Republic of); Matos-Reyes, M.N.; Cervera, M.L.; Guardia, M. de la, E-mail: m.luisa.cervera@uv.es [Department of Analytical Chemistry, University of Valencia, Valencia (Spain)

    2011-09-15

    The operating characteristics of a dual nebulization system were studied including instrumental and chemical conditions for the hydride generation and analytical figures of merit for both, hydride and non hydride forming elements. Analytical performance of the nebulization system was characterized by detection limits from 0.002 to 0.0026 {mu}g mL{sup -1} for the hydride forming elements and between 0.0034 and 0.0121 {mu}g mL{sup -1} for the non-hydride forming elements, relative standard deviation for 10 replicate measurements at 0.25 mg L{sup -1} level and recovery percentages between 97 and 103%. The feasibility of the system was demonstrated in the simultaneous determination of Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Zn, As, Bi, Sb, Se, and Te in the NIST 1549 (non-fat milk powder), NIST 1570a (spinach leaves), DORM-2 (dogfish muscle) and TORT-2 (lobster hepatopancreas) certified samples for trace elements. Results found were in good agreement with the certified ones. (author)

  3. Theoretical Estimate of Hydride Affinities of Aromatic Carbonyl Compounds

    Institute of Scientific and Technical Information of China (English)

    AI Teng; ZHU Xiao-Qing; CHENG Jin-Pei

    2003-01-01

    @@ Aromatic carbonyl compounds are one type of the most important organic compounds, and the reductions ofthem by hydride agents such as LiAlH4 or NaBH4 are widely used in organic synthesis. The reactivity of carbonyl compounds generally increases in the following order: ketone < aldehyde, and amide < acid < ester < acid halide, which could be related to their hydride affinities (HA). In the previous paper, Robert[1] calculated the absolute HAof a series of small non-aromatic carbonyl compounds. In this paper, we use DFT method at B3LYP/6-311 + + G (2d, 2p)∥B3LYP/6-31 + G* level to estimate hydride affinities of five groups of aromatic carbonyl compounds. The detailed results are listed in Table 1.

  4. A nickel metal hydride battery for electric vehicles.

    Science.gov (United States)

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

    1993-04-09

    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 power, long life, tolerance to abuse, a wide range of operating temperature, quick-charge capability, and totally sealed maintenance-free operation, is described. A broad range of multi-element metal hydride materials that use structural and compositional disorder on several scales of length has been engineered for use as the negative electrode in this battery. The battery operates at ambient temperature, is made of nontoxic materials, and is recyclable. Demonstration of the manufacturing technology has been achieved.

  5. Zirconium hydride formation in Hanford production reactor process tubes

    Energy Technology Data Exchange (ETDEWEB)

    Winegardner, W.K.; Griggs, B.

    1967-12-01

    Examination of Zircaloy-2 process tubes from Hanford Production Reactors has revealed extensive zirconium hydride formation. In general, attack is limited to the downstream portions of tubes where aluminum spacers are located. Most of the hydride platelets are contained in a case or layer on the inner surface of the tube. It is not unusual to find cases 0.004 to 0.005 in. thick. Analyses of the 0.037 in. wall tubes with such cases intact often reveal hydrogen concentrations greater than 1000 ppM. Investigation indicates that the hydriding is the result of galvanic contact between aluminum and Zircaloy-2. The galvanic couple (contact between dissimilar metals in the presence of reactor cooling water which serves as the electrolyte) results in the cathodic charging of hydrogen into the Zircaloy.

  6. CO dissociation on magnetic Fen clusters

    KAUST Repository

    Jedidi, Abdesslem

    2014-01-01

    This work theoretically investigates the CO dissociation on Fen nanoparticles, for n in the range of 1-65, focusing on size dependence in the context of the initial step of the Fischer-Tropsch reaction. CO adsorbs molecularly through its C-end on a triangular facet of the nanoparticle. Dissociation becomes easier when the cluster size increases. Then, the C atom is bonded to a square facet that is generated as a result of the adsorption if it does not yet exist in the bare cluster, while the O atom is adsorbed on a triangular facet. In the most stable situation, the two adsorbed atoms remain close together, both having in common one shared first-neighbor iron atom. There is a partial spin quenching of the neighboring Fe atoms, which become more positively charged than the other Fe atoms. The shared surface iron atom resembles a metal-cation from a complex. Despite the small size of the iron cluster considered, fluctuations due to specific configurations do not influence properties for n > 25 and global trends seem significant.

  7. Effect of high heating rate on thermal decomposition behaviour of titanium hydride (TiH2) powder in air

    Indian Academy of Sciences (India)

    A Rasooli; M A Boutorabi; M Divandari; A Azarniya

    2013-04-01

    DTA and TGA curves of titanium hydride powder were determined in air at different heating rates. Also the thermal decomposition behaviour of the aforementioned powder at high heating rates was taken into consideration. A great breakthrough of the practical interest in the research was the depiction of the H2-time curves of TiH2 powder at various temperatures in air. In accordance with the results, an increase in heating rate to higher degrees does not change the process of releasing hydrogen from titanium hydride powder, while switching it from internal diffusion to chemical reaction. At temperatures lower than 600 °C, following the diffusion of hydrogen and oxygen atoms in titanium lattice, thin layers TiH phase and oxides form on the powder surface, controlling the process. On the contrary, from 700 °C later on, the process is controlled by oxidation of titanium hydride powder. In fact, the powder oxidation starts around 650 °C and may escalate following an increase in the heating rate too.

  8. Flame-in-gas-shield and miniature diffusion flame hydride atomizers for atomic fluorescence spectrometry: optimization and comparison

    Energy Technology Data Exchange (ETDEWEB)

    Marschner, Karel, E-mail: karel.marschner@biomed.cas.cz [Institute of Analytical Chemistry of the ASCR, v. v. i., Veveří 97, 602 00 Brno (Czech Republic); Charles University in Prague, Faculty of Science, Department of Analytical Chemistry, Albertov 8, 128 43 Prague (Czech Republic); Musil, Stanislav; Dědina, Jiří [Institute of Analytical Chemistry of the ASCR, v. v. i., Veveří 97, 602 00 Brno (Czech Republic)

    2015-07-01

    A detailed optimization of relevant experimental parameters of two hydride atomizers for atomic fluorescence spectrometry: flame-in-gas-shield atomizer with a two-channel shielding unit and a standard atomizer for atomic fluorescence spectrometry, miniature diffusion flame, was performed. Arsine, generated by the reaction with NaBH{sub 4} in a flow injection arrangement, was chosen as the model hydride. Analytical characteristics of both the atomizers (sensitivity, noise, limits of detection) were compared. Under optimum conditions sensitivity obtained with flame-in-gas-shield atomizer was approximately twice higher than with miniature diffusion flame. The additional advantage of flame-in-gas-shield atomizer is significantly lower flame emission resulting in a better signal to noise ratio. The resulting arsenic limits of detection for miniature diffusion flame and flame-in-gas-shield atomizer were 3.8 ng l{sup −1} and 1.0 ng l{sup −1}, respectively. - Highlights: • We optimized and compared two hydride atomizers for atomic fluorescence spectrometry. • Miniature diffusion flame and flame-in-gas-shield atomizer were optimized. • The limit of detection for arsenic was 1.0 ng l{sup −1}.

  9. Facile synthesis of Ba1-xKxFe₂As₂ superconductors via hydride route

    Energy Technology Data Exchange (ETDEWEB)

    Zaikina, Julia V. [Univ. of California at Davis, Davis, CA (United States); Batuk, Maria [Univ. of Antwerp, Antwerp (Belgium); Abakumov, Artem M. [Univ. of Antwerp, Antwerp (Belgium); Navrotsky, Alexandra [Univ. of California at Davis, Davis, CA (United States); Kauzlarich, Susan M. [Univ. of California at Davis, Davis, CA (United States)

    2014-12-03

    We have developed a fast, easy, and scalable synthesis method for Ba1-xKxFe₂As₂ (0 ≤ x ≤ 1) superconductors using hydrides BaH₂ and KH as a source of barium and potassium metals. Synthesis from hydrides provides better mixing and easier handling of the starting materials, consequently leading to faster reactions and/or lower synthesis temperatures. The reducing atmosphere provided by the evolved hydrogen facilitates preparation of oxygen-free powders. By a combination of methods we have shown that Ba1-xKxFe₂As₂ obtained via hydride route has the same characteristics as when it is prepared by traditional solid-state synthesis. Refinement from synchrotron powder X-ray diffraction data confirms a linear dependence of unit cell parameters upon K content as well as the tetragonal to orthorhombic transition at low temperatures for compositions with x < 0.2. Magnetic measurements revealed dome-like dependence of superconducting transition temperature Tc upon K content with a maximum of 38 K for x close to 0.4. Electron diffraction and high-resolution high-angle annular dark-field scanning transmission electron microscopy indicates an absence of Ba/K ordering, while local inhomogeneity in the Ba/K distribution takes place at a scale of several angstroms along [110] crystallographic direction.

  10. An enhanced microfluidic control system for improving power density of a hydride-based micro fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Moghaddam, Saeed; Shannon, Mark [Mechanical Science and Engineering, 1206 West Green St., University of Illinois, Urbana, IL 61801 (United States); Chemical and Biomolecular Engineering, 213 Roger Adams Lab, 600 S. Mathews, Urbana, IL 61801 (United States); Pengwang, Eakkachai [Mechanical Science and Engineering, 1206 West Green St., University of Illinois, Urbana, IL 61801 (United States); Masel, Richard I. [Chemical and Biomolecular Engineering, 213 Roger Adams Lab, 600 S. Mathews, Urbana, IL 61801 (United States)

    2010-04-02

    Microfuel cells (MFCs) can potentially power emerging technologies that require power sources in the microliter size range. The recent development of a microfluidic mechanism for self-regulated generation of hydrogen has enabled fabrication of MFCs orders of magnitude smaller than previously possible. In this study, we report an order of magnitude enhancement in the power density of a microliter-scale fuel cell incorporating a new microfluidic design. The microfluidic mechanism is part of an on-board hydrogen generator that uses a reaction between a metal hydride, LiAlH{sub 4}, and water vapor to generate hydrogen. The hydrogen generated exits the hydride reactor through a porous silicon wall to reach a Nafion-based membrane electrode assembly (MEA). The microfluidic design increased the water vapor release rate to the hydride reactor by one order of magnitude over a previous design. A 9 {mu}L device incorporating the enhanced microfluidic design delivered a power density of 92 W L{sup -1}. Details of a parametric study conducted to improve the water vapor release rate of the microfluidic mechanism and performance analysis of the integrated device are presented in this paper. (author)

  11. Determination of arsenic and selenium by hydride generation and headspace solid phase microextraction coupled with optical emission spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Tyburska, Anna; Jankowski, Krzysztof, E-mail: kj@ch.pw.edu.pl; Rodzik, Agnieszka

    2011-07-15

    A hydride generation headspace solid phase microextraction technique has been developed in combination with optical emission spectrometry for determination of total arsenic and selenium. Hydrides were generated in a 10 mL volume septum-sealed vial and subsequently collected onto a polydimethylsiloxane/Carboxen solid phase microextraction fiber from the headspace of sample solution. After completion of the sorption, the fiber was transferred into a thermal desorption unit and the analytes were vaporized and directly introduced into argon inductively coupled plasma or helium microwave induced plasma radiation source. Experimental conditions of hydride formation reaction as well as sorption and desorption of analytes have been optimized showing the significant effect of the type of the solid phase microextraction fiber coating, the sorption time and hydrochloric acid concentration of the sample solution on analytical characteristics of the method developed. The limits of detection of arsenic and selenium were 0.1 and 0.8 ng mL{sup -1}, respectively. The limit of detection of selenium could be improved further using biosorption with baker's yeast Saccharomyces cerevisiae for analyte preconcentration. The technique was applied for the determination of total As and Se in real samples.

  12. An enhanced microfluidic control system for improving power density of a hydride-based micro fuel cell

    Science.gov (United States)

    Moghaddam, Saeed; Pengwang, Eakkachai; Masel, Richard I.; Shannon, Mark

    Microfuel cells (MFCs) can potentially power emerging technologies that require power sources in the microliter size range. The recent development of a microfluidic mechanism for self-regulated generation of hydrogen has enabled fabrication of MFCs orders of magnitude smaller than previously possible. In this study, we report an order of magnitude enhancement in the power density of a microliter-scale fuel cell incorporating a new microfluidic design. The microfluidic mechanism is part of an on-board hydrogen generator that uses a reaction between a metal hydride, LiAlH 4, and water vapor to generate hydrogen. The hydrogen generated exits the hydride reactor through a porous silicon wall to reach a Nafion-based membrane electrode assembly (MEA). The microfluidic design increased the water vapor release rate to the hydride reactor by one order of magnitude over a previous design. A 9 μL device incorporating the enhanced microfluidic design delivered a power density of 92 W L -1. Details of a parametric study conducted to improve the water vapor release rate of the microfluidic mechanism and performance analysis of the integrated device are presented in this paper.

  13. NUMERICAL ANALYSIS FOR HYDRIDING IN METAL HYDRIDE HYDROGEN STORAGE TANK%金属氢化物储氢器吸氢过程的数值分析

    Institute of Scientific and Technical Information of China (English)

    叶建华; 蒋利军; 李志念; 刘晓鹏; 王树茂

    2011-01-01

    Based on the principle of hydride adsorption, a one-dimensional mathematical model for hydriding in a cylindrical metal hydride hydrogen storage tank was established. The heat and mass transfer of metal hydride beds was computed by finite difference method. The variation in temperature and hydrogen concentration at different radial positions of the hydride layer was analyzed during the process of hydriding. The effects of supply pressure, heat convection coefficient and hydride layer radial thickness on the hydriding was studied. It is shown that hydride formation initially takes place uniformly all over the metal hydride layer, but with the process of hydriding, the hydriding rate at the core region is gradually slower than one at surface region. The increase of supply pressure and heat convection coefficient can accelerate the hydriding of the hydrogen storage tank. The effect of hydride layer radial thickness is significant on the hydriding rate, and the thinner hydride layer, the higher the hydriding rate.%基于金属氢化物吸氢基本特性,建立圆柱形金属氢化物储氢器吸氢过程的-维数学物理模型.采用有限差分法对金属氢化物床体的传热传质进行计算.分别研究金属氢化物床体各处温度和氢含量在吸氢过程中的变化以及氢气压力、对流传热系数和金属氢化物床体径向厚度对金属氢化物吸氢过程的影响.计算结果表明:初始阶段金属氢化物床均匀吸氢,但随着氢化过程的进行,其中心区域的吸氢速率逐渐低于边缘区域;增加吸氢压力、提高对流传热系数均可促进储氢器的吸氢;金属氢化物床的径向厚度对吸氢速率影响很大,金属氢化物床越薄,氢化反应的速度越快.

  14. High-pressure synthesis of Mg{sub 2}FeH{sub 6} complex hydride

    Energy Technology Data Exchange (ETDEWEB)

    Retuerto, M.; Sanchez-Benitez, J.; Alonso, J.A. [Instituto de Ciencia de Materiales de Madrid, C.S.I.C., Cantoblanco E-28049 Madrid (Spain); Rodriguez-Canas, E. [Servicio Interdepartamental de Investigacion, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco E-28049 Madrid (Spain); Serafini, D. [Departamento de Fisica, Facultad de Ciencias, Universidad de Santiago de Chile and Center for Interdisciplinary Research in Materials, CIMAT, Av. Lib. Bernardo O' Higgins 3363, Santiago (Chile)

    2010-08-15

    We have designed a new synthesis method for the ternary metal hydride Mg{sub 2}FeH{sub 6} based on the direct reaction of simple hydrides under high-pressure conditions. Well-crystallized samples were prepared in a piston-cylinder hydrostatic press at 2 GPa and temperatures around 750 C from mixtures of MgH{sub 2} and Fe enclosed in gold or platinum capsules. Seven different samples have been prepared under different conditions. X-ray powder diffraction analysis was used to identify and assess the purity of the samples, through Rietveld analyses of the crystal structure (K{sub 2}PtCl{sub 6}-type). Mg{sub 2}FeH{sub 6} shows a cubic symmetry with space group Fm-3m. SEM images show an average particle size of 1-2 {mu}m for Mg{sub 2}FeH{sub 6}; the microcrystals present well-grown faces and display a high homogeneity of shapes and sizes. Thermogravimetric analysis has been carried out to determine not only the hydrogen desorption temperature but also the hydrogen contents. (author)

  15. Nitrogen hydrides in the cold envelope of IRAS16293-2422

    CERN Document Server

    Hily-Blant, Pierre; Bacmann, Aurore; Bottinelli, Sandrine; Parise, Bérengère; Caux, Emmanuel; Faure, Alexandre

    2010-01-01

    Nitrogen is the fifth most abundant element in the Universe, yet the gas-phase chemistry of N-bearing species remains poorly understood. Nitrogen hydrides are key molecules of nitrogen chemistry. Their abundance ratios place strong constraints on the production pathways and reaction rates of nitrogen-bearing molecules. We observed the class 0 protostar IRAS16293-2422 with the heterodyne instrument HIFI, covering most of the frequency range from 0.48 to 1.78~THz at high spectral resolution. The hyperfine structure of the amidogen radical o-NH2 is resolved and seen in absorption against the continuum of the protostar. Several transitions of ammonia from 1.2 to 1.8~THz are also seen in absorption. These lines trace the low-density envelope of the protostar. Column densities and abundances are estimated for each hydride. We find that NH:NH2:NH3=5:1:300. {Dark clouds chemical models predict steady-state abundances of NH2 and NH3 in reasonable agreement with the present observations, whilst that of NH is underpredi...

  16. [Research on optimization of mathematical model of flow injection-hydride generation-atomic fluorescence spectrometry].

    Science.gov (United States)

    Cui, Jian; Zhao, Xue-Hong; Wang, Yan; Xiao, Ya-Bing; Jiang, Xue-Hui; Dai, Li

    2014-01-01

    Flow injection-hydride generation-atomic fluorescence spectrometry was a widely used method in the industries of health, environmental, geological and metallurgical fields for the merit of high sensitivity, wide measurement range and fast analytical speed. However, optimization of this method was too difficult as there exist so many parameters affecting the sensitivity and broadening. Generally, the optimal conditions were sought through several experiments. The present paper proposed a mathematical model between the parameters and sensitivity/broadening coefficients using the law of conservation of mass according to the characteristics of hydride chemical reaction and the composition of the system, which was proved to be accurate as comparing the theoretical simulation and experimental results through the test of arsanilic acid standard solution. Finally, this paper has put a relation map between the parameters and sensitivity/broadening coefficients, and summarized that GLS volume, carrier solution flow rate and sample loop volume were the most factors affecting sensitivity and broadening coefficients. Optimizing these three factors with this relation map, the relative sensitivity was advanced by 2.9 times and relative broadening was reduced by 0.76 times. This model can provide a theoretical guidance for the optimization of the experimental conditions.

  17. Direct Conversion of Hydride- to Siloxane-Terminated Silicon Quantum Dots

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Ryan T.; Zang, Xiaoning; Fernando, Roshan; Dzara, Michael J.; Ngo, Chilan; Sharps, Meredith; Pinals, Rebecca; Pylypenko, Svitlana; Lusk, Mark T.; Sellinger, Alan

    2016-11-17

    Peripheral surface functionalization of hydride-terminated silicon quantum dots (SiQD) is necessary in order to minimize their oxidation/aggregation and allow for solution processability. Historically thermal hydrosilylation addition of alkenes and alkynes across the Si-H surface to form Si-C bonds has been the primary method to achieve this. Here we demonstrate a mild alternative approach to functionalize hydride-terminated SiQDs using bulky silanols in the presence of free-radical initiators to form stable siloxane (~Si-O-SiR3) surfaces with hydrogen gas as a byproduct. This offers an alternative to existing methods of forming siloxane surfaces that require corrosive Si-Cl based chemistry with HCl byproducts. A 52 nm blue shift in the photoluminescent spectra of siloxane versus alkyl-functionalized SiQDs is observed that we explain using computational theory. Model compound synthesis of silane and silsesquioxane analogues is used to optimize surface chemistry and elucidate reaction mechanisms. Thorough characterization on the extent of siloxane surface coverage is provided using FTIR and XPS. TEM is used to demonstrate SiQD size and integrity after surface chemistry and product isolation.

  18. Thermodynamics of various F420 coenzyme models as sources of electrons, hydride ions, hydrogen atoms and protons in acetonitrile.

    Science.gov (United States)

    Xia, Ke; Shen, Guang-Bin; Zhu, Xiao-Qing

    2015-06-14

    32 F420 coenzyme models with alkylation of the three different N atoms (N1, N3 and N10) in the core structure (XFH(-)) were designed and synthesized and the thermodynamic driving forces (defined in terms of the molar enthalpy changes or the standard redox potentials in this work) of the 32 XFH(-) releasing hydride ions, hydrogen atoms and electrons, the thermodynamic driving forces of the 32 XFH˙ releasing protons and hydrogen atoms and the thermodynamic driving forces of XF(-)˙ releasing electrons in acetonitrile were determined using titration calorimetry and electrochemical methods. The effects of the methyl group at N1, N3 and N10 and a negative charge on N1 and N10 atoms on the six thermodynamic driving forces of the F420 coenzyme models and their related reaction intermediates were examined; the results show that seating arrangements of the methyl group and the negative charge have remarkably different effects on the thermodynamic properties of the F420 coenzyme models and their related reaction intermediates. The effects of the substituents at C7 and C8 on the six thermodynamic driving forces of the F420 coenzyme models and their related reaction intermediates were also examined; the results show that the substituents at C7 and C8 have good Hammett linear free energy relationships with the six thermodynamic parameters. Meanwhile, a reasonable determination of possible reactions between members of the F420 family and NADH family in vivo was given according to a thermodynamic analysis platform constructed using the elementary step thermodynamic parameter of F420 coenzyme model 2FH(-) and NADH model MNAH releasing hydride ions in acetonitrile. The information disclosed in this work can not only fill a gap in the chemical thermodynamics of F420 coenzyme models as a class of very important organic sources of electrons, hydride ions, hydrogen atoms and protons, but also strongly promote the fast development of the chemistry and applications of F420 coenzyme.

  19. H(+)/AuPPh(3)(+) Exchange for the Hydride Complexes CpMoH(CO)(2)(L) (L = PMe(3), PPh(3), CO). Formation and Structure of [Cp(CO)(2)(PMe(3))Mo(AuPPh(3))(2)](+)[BF(4)](-).

    Science.gov (United States)

    Galassi, Rossana; Poli, Rinaldo; Quadrelli, E. Alessandra; Fettinger, James C.

    1997-07-02

    The reaction of CpMoH(CO)(2)L with AuPPh(3)(+)BF(4)(-) in THF at -40 degrees C proceeds directly to the MoAu(2) cluster compounds [CpMo(CO)(2)L(AuPPh(3))(2)](+)BF(4)(-) (L = PMe(3) (1), PPh(3) (2)) with release of protons. A 1:1 reaction leaves 50% of the starting hydride unreacted. At lower temperature, however, the formation of a [CpMo(CO)(2)(PMe(3))(&mgr;-H)(AuPPh(3))](+) intermediate is observed. This compound evolves to the cation of 1 and CpMoH(CO)(2)(PMe(3)) upon warming and is deprotonated by 2,6-lutidine to afford CpMo(CO)(2)(PMe(3))(AuPPh(3)). The X-ray structure of 1 can be described as a four-legged piano stool with the PMe(3) and the "eta(2)-(AuPPh(3))(2)" ligands occupying relative trans positions. [Cp(CO)(2)(PMe(3))Mo(AuPPh(3))(2)](+)[BF(4)](-) (M(r) = 1298.41): monoclinic, space group P2(1)/n, a = 18.1457(13) Å, b = 9.7811(7) Å, c = 26.096(2) Å, beta = 105.086(5) degrees, V = 4472.0(5) Å(3), Z = 4. The reaction of CpMoH(CO)(2)(PMe(3)) with 3 equiv of AuPPh(3)(+) affords a MoAu(3) cluster, [CpMo(CO)(2)(PMe(3))(AuPPh(3))(3)](2+) (3), in good yields under kinetically controlled conditions. Under thermodynamically controlled conditions, 3 dissociates extensively into 1 and free AuPPh(3)(+). It is proposed that the hydride ligand helps build higher nuclearity Mo-Au clusters. The difference in reaction pathways for the interaction of AuPPh(3)(+) with CpMoH(CO)(2)L when L = PR(3) or CO and for the interaction of CpMoH(CO)(2)(PMe(3)) with E(+) when E = H, Ph(3)C or AuPPh(3) is discussed. The lower acidity and greater aurophilicity of the [CpMo(CO)(2)L(&mgr;-H)(AuPPh(3))](+) intermediate when L = PMe(3) favor attack by AuPPh(3)(+) before deprotonation.

  20. Phase I. Lanthanum-based Start Materials for Hydride Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Gschneidner, K. A. [Ames Lab., Ames, IA (United States); Schmidt, F. A. [Ames Lab., Ames, IA (United States); Frerichs, A. E. [Ames Lab., Ames, IA (United States); Ament, K. A. [Ames Lab., Ames, IA (United States)

    2013-08-20

    The purpose of Phase I of this work is to focus on developing a La-based start material for making nickel-metal (lanthanum)-hydride batteries based on our carbothermic-silicon process. The goal is to develop a protocol for the manufacture of (La1-xRx)(Ni1-yMy)(Siz), where R is a rare earth metal and M is a non-rare earth metal, to be utilized as the negative electrode in nickel-metal hydride (NiMH) rechargeable batteries.