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1

Hydrogen-permeable composite metal membrane and uses thereof  

DOEpatents

Various hydrogen production and hydrogen sulfide decomposition processes are disclosed that utilize composite metal membranes that contain an intermetallic diffusion barrier separating a hydrogen-permeable base metal and a hydrogen-permeable coating metal. The barrier is a thermally stable inorganic proton conductor.

Edlund, David J. (Bend, OR); Friesen, Dwayne T. (Bend, OR)

1993-06-08

2

A Cell-Permeable Fluorescent Prochelator Responds to Hydrogen Peroxide and Metal Ions by Decreasing Fluorescence  

PubMed Central

Described here is the development of two boronic ester-based fluorescent prochelators, FloB (2-(6-hydroxy-3-oxo-3H-xanthen-9-yl)-4(5)-[2-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-benzylidene-hydrazinocarbonyl]-benzoic acid) and FloB-SI (2-(6-hydroxy-3-oxo-3Hxanthen-9-yl)-4(5)-[2-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyloxy)-benzylidene-hydrazinocarbonyl]-benzoic acid) that show a fluorescence response to a variety of transition metal ions only after reaction with H2O2. Both prochelators’ boronic ester masks are oxidized by H2O2 to reveal a fluorescein-tagged metal chelator, FloS (4(5)-(2-hydroxy-benzylidenehydrazinocarbonyl)-2-(6-hydroxy-3-oxo-3H-xanthen-9-yl)-benzoic acid). Chelation of Fe3+ or Cu2+ elicits a 70% decrease in the emission signal of FloS, while Zn2+, Ni2+, and Co2+ produce a more modest fluorescence decrease. The conversion of FloB to FloS proceeds in organic solvents, but hydrolytic decomposition of its hydrazone backbone is observed in aqueous solution. However, FloB-SI oxidizes cleanly with H2O2 within 1 h in aqueous solutions to produce FloS. Fluorescence microscopy studies in HeLa cells with FloB-SI show that the sensor’s fluorescence intensity remains unchanged until incubation with exogenous H2O2, which results in a decreased fluorescent signal. Incubation with a competitive chelator restores the emission response, thus suggesting that FloB-SI can effectively report on a H2O2-induced increase in intracellular labilized metal. PMID:22287796

Hyman, Lynne M.; Franz, Katherine J.

2011-01-01

3

Hydrogen permeability and Integrity of hydrogen transfer pipelines  

E-print Network

Natural Gas Pipelines Hydrogen embrittlement What is the relevance to hydrogen pipelines? ORNL research Plan Hydrogen-Microstructure-Stress Management Research during FY2004 Literature Review (DiffusivityHydrogen permeability and Integrity of hydrogen transfer pipelines Team: Sudarsanam Suresh Babu, Z

4

Hydrogen Permeability and Integrity of Hydrogen  

E-print Network

pressure permeation test · Edison Welding Institute - Pipeline materials · Lincoln Electric Company - Welding electrode and weld materials for pipelines · Trans Canada - Commercial welding of pipelines understanding of hydrogen permeation behavior (absorption, diffusion, trapping, etc.) and its impact on hydrogen

5

Determination of hydrogen permeability in commercial and modified superalloys  

NASA Technical Reports Server (NTRS)

The results of hydrogen permeability measurements on several iron- and cobalt-base alloys as well as on two long-ranged ordered alloys over the range of 705 to 870 C (1300 to 1600 F) are summarized. The test alloys included wrought alloys N-155, IN 800, A-286, 19-9DL, and 19-9DL modifications with aluminum, niobium, and misch metal. In addition, XF-818, CRM-6D, SA-F11, and HS-31 were evaluated. Two wrought long-range ordered alloys, Ni3Al and (Fe,Ni)3(V,Al) were also evaluated. All tests were conducted at 20.7 MPa pressure in either pure and/or 1% CO2-doped H2 for test periods as long as 133 h. Detailed analyses were conducted to determine the relative permeability rankings of these alloys and the effect of doping, exit surface oxidation, specimen design variations, and test duration on permeability coefficient, and permeation activation energies were determined. The two long-range ordered alloys had the lowest permeability coefficients in pure H2 when compared with the eight commercial alloys and their modifications. With CO2 doping, significant decrease in permeability was observed in commercial alloys--no doped tests were conducted with the long-range ordered alloys.

Bhattacharyya, S.; Peterman, W.

1983-01-01

6

Hydrogen interactions with metals  

NASA Technical Reports Server (NTRS)

Review of the literature on the nature and extent of hydrogen interactions with metals and the role of hydrogen in metal failure. The classification of hydrogen-containing systems is discussed, including such categories as covalent hydrides, volatile hydrides, polymeric hydrides, and transition metal hydride complexes. The use of electronegativity as a correlating parameter in determining hydride type is evaluated. A detailed study is made of the thermodynamics of metal-hydrogen systems, touching upon such aspects as hydrogen solubility, the positions occupied by hydrogen atoms within the solvent metal lattice, the derivation of thermodynamic functions of solid solutions from solubility data, and the construction of statistical models for hydrogen-metal solutions. A number of theories of hydrogen-metal bonding are reviewed, including the rigid-band model, the screened-proton model, and an approach employing the augmented plane wave method to solve the one-electron energy band problem. Finally, the mechanism of hydrogen embrittlement is investigated on the basis of literature data concerning stress effects and the kinetics of hydrogen transport to critical sites.

Mclellan, R. B.; Harkins, C. G.

1975-01-01

7

Metallic hydrogen research  

Microsoft Academic Search

Theoretical studies predict that molecular hydrogen can be converted to the metallic phase at very high density and pressure. These conditions were achieved by subjecting liquid hydrogen to isentropic compression in a magnetic flux compression device. Hydrogen became electrically conducting at a density of about 1.06 g\\/cu cm and a calculated pressure of about 2 Mbar. In the experimental device,

T. J. Burgess; R. S. Hawke

1978-01-01

8

The interaction of hydrogen with metal alloys  

NASA Technical Reports Server (NTRS)

Hydrogen diffusion coefficients were measured for several alloys, and these were determined to be about the same at 25 C for all alloys investigated. The relation of structure, both metallurgical and crystallographic, to the observed hydrogen distribution on charging was investigated, as well as the role of hydride formation in the hydrogen resistance of metal alloys. An attempt was made to correlate the structures and compositions of metal alloys as well as other parameters with the ratios of their notched tensile strengths in hydrogen to that in helium, R(H2/He), which are believed to represent a measure of their hydrogen resistance. Evidence supports the belief that hydrogen permeability and hydrogen resistance are increased by smaller grain sizes for a given alloy composition.

Danford, M. D.; Montano, J. W.

1991-01-01

9

Stable catalyst layers for hydrogen permeable composite membranes  

DOEpatents

The present invention provides a hydrogen separation membrane based on nanoporous, composite metal carbide or metal sulfide coated membranes capable of high flux and permselectivity for hydrogen without platinum group metals. The present invention is capable of being operated over a broad temperature range, including at elevated temperatures, while maintaining hydrogen selectivity.

Way, J. Douglas; Wolden, Colin A

2014-01-07

10

Metallization of fluid hydrogen  

SciTech Connect

The electrical activity of liquid hydrogen has been measured at the high dynamic pressures, and temperatures that can be achieved with a reverberating shock wave. The resulting data are most naturally interpreted in terms of a continuous transition from a semiconducting to a metallic, largely diatomic fluid, the latter at 140 CPa, (ninefold compression) and 3000 K. While the fluid at these conditions resembles common liquid metals by the scale of its resistivity of 500 micro-ohm-cm, it differs by retaining a strong pairing character, and the precise mechanism by which a metallic state might be attained is still a matter of debate. Some evident possibilities include (i) physics of a largely one-body character, such as a band-overlap transition, (ii) physics of a strong-coupling or many-body character,such as a Mott-Hubbard transition, and (iii) process in which structural changes are paramount.

Nellis, W.J.; Louis, A.A.; Ashcroft, N.W.

1997-05-14

11

Permeable Reactive Biobarriers for the Containment of Heavy Metal  

E-print Network

Permeable Reactive Biobarriers for the Containment of Heavy Metal Contamination in Acid Mine) is defined as the presence heavy metals, increased acidity, and sulfate as a direct result of mining. Heavy metals are leached as ground water reaches the exposed ores. Arizona has a rich history

Fay, Noah

12

Hydrogen environment embrittlement of metals  

NASA Technical Reports Server (NTRS)

Hydrogen environment embrittlement refers to metals stressed while exposed to a hydrogen atmosphere. Tested in air, even after exposure to hydrogen under pressure, this effect is not observed on similar specimens. Much high purity hydrogen is prepared by evaporation of liquid hydrogen, and thus has low levels for potential impurities which could otherwise inhibit or poison the absorbent reactions that are involved. High strength steels and nickel-base allows are rated as showing extreme embrittlement; aluminum alloys and the austenitic stainless steels, as well as copper, have negligible susceptibility to this phenomenon. The cracking that occurs appears to be a surface phenomenon, is unlike that of internal hydrogen embrittlement.

Jewett, R. P.; Walter, R. J.; Chandler, W. T.; Frohmberg, R. P.

1973-01-01

13

Metal salt catalysts for enhancing hydrogen spillover  

DOEpatents

A composition for hydrogen storage includes a receptor, a hydrogen dissociating metal doped on the receptor, and a metal salt doped on the receptor. The hydrogen dissociating metal is configured to spill over hydrogen to the receptor, and the metal salt is configured to increase a rate of the spill over of the hydrogen to the receptor.

Yang, Ralph T; Wang, Yuhe

2013-04-23

14

Hydrogen-Hydrogen Interaction in Cubic Metals  

NASA Astrophysics Data System (ADS)

The energies of strain-induced (elastic) interaction of pairs of hydrogen (deuterium) atoms are calculated for Cr, -Fe, Mo, V, W, Al, Ag, Au, Cu, and Ni taking into account the discrete atomic structure of the host lattice. The elastic constants, Born-von Karman constants of the host lattice, and coefficients of the concentration expansion of the solid solution lattice due to hydrogen atoms are the numerical parameters used. The elastic interaction in f.c.c. metals is much weaker than in b.c.c. metals. In the case of b.c.c. metals there is attraction in the first six coordination shells rapidly decreasing with the distance. It is known that this attraction is partially compensated by a screened Coulomb repulsion between charged interstitials in the nearest coordination shells. The distance of the repulsion was obtained by Monte Carlo computer simulation of tracer diffusion. It was suggested that the interatomic interaction affects diffusion by changing the arrangement and the energy of H(D) atoms in the solid solution and therefore the activation energy of the diffusion. Computer simulation was carried out with calculated values of energies of elastic interaction and with different radii of additional repulsive interaction. It was shown that the repulsive interaction extends out to the third or fourth shell in b.c.c. metals and is absent in f.c.c. metals. The behaviour of hydrogen atoms in a solid solution is determined both by a repulsion distance and by energies of elastic interaction outside the radius of repulsion.

Blanter, M. S.

1997-04-01

15

Electrolytic hydrogen-metal interactions  

SciTech Connect

The electrolyte composition and the electrodic conditions have a major effect on the entry of electrolytic hydrogen into metals. In the case of ferrous metals there is a large body of literature and various promoters have been identified. Only a few inhibitors have been found, such as organic nitriles. This paper reports the complete inhibition of the entry of hydrogen into iron by UPD Zn in concentrated alkali solutions. Less is known about the effect of electrolyte on the entry of hydrogen into palladium. The present work shows that many of the known promoters for ferrous metals actually inhibit the entry and egress of hydrogen from palladium. Permeation results on a Pd membrane in pure 0.1 M NaOH indicate that only 20% of the surface is used for the entry of hydrogen into the metal. In 0.1 M NaOH + 10{sup {minus}3} M NaCN it drops to 5%. The fraction of the surface used strongly depends on electrolyte purity. Impurity effects can account for the discrepant results for electrochemical hydrogen loading of Pd.

McBreen, J.

1991-01-01

16

Electrolyte permeable diaphragm including a polymeric metal oxide  

SciTech Connect

A liquid permeable diaphragm is described for an electrolytic cell, the diaphragm comprises: major amount of fibrillated poly-fluorocarbon, a minor amount of a perfluorinated ion exchange material and a polymeric metal oxide selected from the group consisting of polytitanic acid, polyzirconic acid, polysilicic acid, polyaluminic acid or mixtures.

Darlington, W.B.; Du Bois, D.W.

1987-07-14

17

Metallic Hydrogen and Nano-Tube Magnets  

NASA Technical Reports Server (NTRS)

When hydrogen is subjected to enough pressure the atoms will be pressed into close enough proximity that each electron is no longer bound to a single proton. The research objectives is to find whether metallic hydrogen can be produced and once produced will the metallic hydrogen be metastable and remain in the metallic form when the pressure is released.

Cole, John W.

2004-01-01

18

PDTI metal alloy as a hydrogen or hydrocarbon sensitive metal  

NASA Technical Reports Server (NTRS)

A hydrogen sensitive metal alloy contains palladium and titanium to provide a larger change in electrical resistance when exposed to the presence of hydrogen. The alloy can be used for improved hydrogen detection.

Hunter, Gary W. (Inventor)

1996-01-01

19

Hydrogen Production From Metal-Water Reactions  

E-print Network

Hydrogen Production From Metal-Water Reactions Why Hydrogen Production? Hydrogen is a critical. Current methods of hydrogen storage in automobiles are either too bulky (large storage space for gas phase) or require a high input energy (cooling or pressurization systems for liquid hydrogen), making widespread use

Barthelat, Francois

20

Method for controlled hydrogen charging of metals  

DOEpatents

A method for controlling hydrogen charging of hydride forming metals through a window of a superimposed layer of a non-hydriding metal overlying the portion of the hydride forming metals to be charged.

Cheng, Bo-Ching (Fremont, CA); Adamson, Ronald B. (Fremont, CA)

1984-05-29

21

Metallization of Fluid Hydrogen 3.1 Introduction to Metallic Hydrogen  

E-print Network

Chapter 3 Metallization of Fluid Hydrogen 3.1 Introduction to Metallic Hydrogen 3.1.1 Some background on dense hydrogen Hydrogen, out of it the Universe evolved, every atom and leaf, marine iguana and apricot­smelling chanterelle. But my, my, what alchemy: nondescript H 2 --Diane Ackerman 1 -- Hydrogen

Louis, Ard

22

Permeability of hydrogen isotopes through nickel-based alloys  

SciTech Connect

Permeabilities and diffusivities of deuterium in several nickel-based alloys were measured in this investigation. Measurements were made by the gas-phase breakthrough technique in the temperature range 200 to 450/sup 0/C with applied pressures ranging from 1 to 100 kPa. The results were extrapolated to predict the permeabilities (K) of the alloys at room temperature. The alloy with the smallest deuterium permeability is Carpenter 49, for which K = 4.3 x 10/sup -18/ mol s/sup -1/ m/sup -1/ Pa/sup -//sup 1/2/ at 22/sup 0/C. The permeability of deuterium in Kovar or Ceramvar is about 80% greater than that for Carpenter 49. Premeabilities of Inconel 625, Inconel 718, Inconel 750 and Monel K-500 are all equal to about 5 x 10/sup -17/ mol m/sup -1/ s/sup -1/ Pa/sup -//sup 1/2/ at 22/sup 0/C. The validity (from a statistical standpoint) of the extrapolation of the permeabilities to room temperature is considered in detail. Published permeabilities of stainless steels and nickel-iron alloys are also reviewed. The greatest differences in permeabilities among the nickel-based alloys appear to be associated with the tendency for some alloys to form protective oxide layers. Permeabilities of deuterium through laminates containing copper are smaller than for any of the iron-nickel alloys.

Edge, E.M.; Mitchell, D.J.

1983-04-01

23

Improved permeability and selectivity in porous graphene for hydrogen purification.  

PubMed

Porous graphene is a promising material for the realization of low-cost, large-area and lightweight gas separation. However, molecular-sieving membranes based on porous materials reported thus far generally cannot fulfill the requirements of both high permeability and high selectivity. Simultaneously meeting the goals of high permeability and high selectivity remains a great challenge. As we demonstrate here, with the development of an inter-layer-connected porous graphene bilayer, both the permeability and selectivity are significantly improved, and a high criterion of selectivity for H2 over CH4 (10(24) at room temperature) as well as a high flux of H2 (2.4 × 10(5) Gas Permeance Unit) has been reached. Our studies highlight a new approach towards the final goal of high-permeability and high-selectivity molecular-sieving membranes using simple structural engineering. PMID:25363756

Huang, Chengxi; Wu, Haiping; Deng, Kaiming; Tang, Weihua; Kan, Erjun

2014-12-21

24

Hydrogen permeability through beryllium films and the impact of surface oxides  

NASA Astrophysics Data System (ADS)

Beryllium will constitute the major part of the first wall of ITER, however, several aspects of the tritium retention and recycling in fusion reactors are still open. Studying details of the hydrogen isotope interactions on Be films is in principle easier and more accurate than on the bulk Be metal since a thin (and therefore more permeable) layer of Be film could be deposited on a desired substrate by applying well controlled methods. Results of the hydrogen permeation through 8 micrometer thick Be films deposited by the thermionic vacuum arc method on Eurofer steel membranes with exposed area of 8.4 cm2 are presented. The permeation reduction factor (PRF) at 400 °C varied on six samples from 14 to 135 with respect to the bare Eurofer membrane. The highest PRF value enables expression of the Be film permeability coefficient P by means of a simple model which gives PBe ˜ 2 × 10-15 mol H2/m s Pa0.5. Lower PRF values could be explained by microscopic imperfections which represent parallel hydrogen paths through the Be film and enhance the permeation rate. Some of them were revealed by the SEM while their presence could be confirmed also by observing permeation flux transients recorded after the hydrogen exposure. The two-step process of achieving the steady flux agrees with our numerical simulation. It was found that for unintentionally oxidized samples the extracted regular (eliminated contribution of the pinholes in Be film) permeation rate is almost identical from sample to sample and accounts to j ? 1.2 × 10-7 H2/m2 s at 1 bar hydrogen driving pressure due to BeO formation. For a non-oxidized sample this value is several times higher, j ? 6.5 × 10-7 mol H2/m2 s. From the latter follows that PBe ? 1.9 × 10-14 mol H2/m s Pa0.5, while PBeO ˜ 1 × 10-17 mol H2/m s Pa0.5 can be estimated by assuming a 35 nm thick BeO layer.

Zajec, Bojan; Nemani?, Vincenc; Žumer, Marko; Porosnicu, Corneliu; Lungu, Cristian P.

2013-11-01

25

The Effect of Carbon Monoxide on the Hydrogen Permeability of a Palladium Membrane  

NASA Astrophysics Data System (ADS)

Plating thin Palladium (Pd) film on the outer surface of a porous stainless steel tube enables very rapid hydrogen permeation with an absolute selectivity. Methane steam reforming for hydrogen production is performed in a Pd membrane reactor. In this reaction, carbon monoxide (CO) synthesized is known to affect hydrogen permeability. The effect on hydrogen permeability and the membrane stability were investigated. After hydrogen was flowed through Pd membrane for 1 hour, CO (1%, 10%, 100% diluted by helium) was flowed on the membrane for 1 hour, and hydrogen was re-permeated through the membrane. Under the all experiment, the temperature, the differential pressure and the flow rate of non-permeation side were 823K, 0.1 MPa and 10 ml·min-1, respectively. After the re-permeating hydrogen, the hydrogen permeation rate increased gradually. Finally the rate arrived at the constant value before CO was flowed. But the necessary time was depend on the concentration of CO. The necessary time for three concentration of CO 1%, 10%, and 100% were 30min, 60min, and 180min, respectively. The reason was that depositing carbon from CO affected to hydrogen permeability. The carbon was changed to methane by hydrogen flow and the membrane was recycled.

Katoh, Masahiro; Nishihara, Katsunori; Kinouchi, Koji; Chohama, Koichi; Horikawa, Toshihide; Tomida, Tahei; Sotowa, Ken-Ichiro

26

Ground State Structure of the Metallic Hydrogen  

NASA Astrophysics Data System (ADS)

By using Heine-Abarencov pseudopotential method with mono-parameter rc, the expressions for ground state energy epsilon (rs), pressure P (rs), and bulk modulus B(rs) of metallic hydrogen (fcc, bcc, and hcp structures) are derived. Based on Gibbs free energy function criterion, the calculation shows that cold metallic hydrogen lattice (T = 0K) belongs to hcp structure.

Zhu, Zai-wan; Li, Jun-jie

1998-05-01

27

Hydrogen storage in metal–organic frameworks  

Microsoft Academic Search

Metal–organic frameworks (MOFs) are a new class of crystalline materials consisting of metal ions linked together by organic ligands, resulting in a highly microporous network. Owing to their high specific surface area and tailored pore dimensions, MOFs are ideal materials for hydrogen storage based on physisorption. This review gives an overview on the progress achieved in the field of hydrogen

Michael Hirscher; Barbara Panella

2007-01-01

28

Novel Metallic Membranes for Hydrogen Separation  

SciTech Connect

To reduce dependence on oil and emission of greenhouse gases, hydrogen is favored as an energy carrier for the near future. Hydrogen can be converted to electrical energy utilizing fuel cells and turbines. One way to produce hydrogen is to gasify coal which is abundant in the U.S. The coal gasification produces syngas from which hydrogen is then separated. Designing metallic alloys for hydrogen separation membranes which will work in a syngas environment poses significant challenges. In this presentation, a review of technical targets, metallic membrane development activities at NETL and challenges that are facing the development of new technologies will be given.

Dogan, Omer

2011-02-27

29

Hydrogen trapping and the interaction of hydrogen with metals  

NASA Technical Reports Server (NTRS)

A method has been developed for the determination of trapped hydrogen in metal alloys, involving the determination of mobile hydrogen using the electrochemical method and the determination of total hydrogen with the fusion method, the difference in hydrogen concentrations being due to trapped hydrogen. It has been found that hydrogen enters body-centered cubic structures through the grain bodies rather than through the grain boundaries. Hydrogen also diffuses much more rapidly in body-centered cubic structures on charging than in face-centered cubic structures, the hydrogen distribution being more uniform in nature. The energy necessary to cause hydrogen embrittlement is postulated to arise from the changes in crystal lattice energies brought about through interaction of hydrogen with atoms in the metal lattice. The total energy change is more negative for body-centered cubic structures, believed to be the cause of a greater tendency toward hydrogen embrittlement. Finally, the agreement of hydrogen concentrations obtained at 25 C by the electrochemical method with those obtained by the fusion method are taken as a strong indication of the power and validity of the electrochemical method.

Danford, Merlin D.

1987-01-01

30

Permeability  

NSDL National Science Digital Library

This web page describes the permeability of a magnetic material. A magnetization curve with hysteresis demonstrates the relation between magnetic field and magnetic flux. This is part of a large web site on the magnetic properties of materials. This item is part of a larger collection of educational resources developed by the Non-destructive Testing Resource Center.

2007-10-12

31

Permeability  

NSDL National Science Digital Library

This web page describes the permeability of a magnetic material. A magnetization curve with hysteresis demonstrates the relation between magnetic field and magnetic flux. This is part of a large web site on the magnetic properties of materials. This item is part of a larger collection of educational resources developed by the Non-destructive Testing Resource Center.

32

Hydrogen-Hydrogen Interaction in Cubic Metals  

Microsoft Academic Search

The energies of strain-induced (elastic) interaction of pairs of hydrogen (deuterium) atoms are calculated for Cr, -Fe, Mo, V, W, Al, Ag, Au, Cu, and Ni taking into account the discrete atomic structure of the host lattice. The elastic constants, Born-von Karman constants of the host lattice, and coefficients of the concentration expansion of the solid solution lattice due to

M. S. Blanter

1997-01-01

33

Conceptual Launch Vehicles Using Metallic Hydrogen Propellant  

NASA Astrophysics Data System (ADS)

Solid molecular hydrogen is predicted to transform into an atomic solid with metallic properties under pressures >4.5 Mbar. Atomic metallic hydrogen is predicted to be metastable, limited by some critical temperature and pressure, and to store very large amounts of energy. Experiments may soon determine the critical temperature, critical pressure, and specific energy availability. It is useful to consider the feasibility of using metastable atomic hydrogen as a rocket propellant. If one assumes that metallic hydrogen is stable at usable temperatures and pressures, and that it can be affordably produced, handled, and stored, then it may be a useful rocket propellant. Assuming further that the available specific energy can be determined from the recombination of the atoms into molecules (216 MJ/kg), then conceptual engines and launch vehicle concepts can be developed. Under these assumptions, metallic hydrogen would be a revolutionary new rocket fuel with a theoretical specific impulse of 1700 s at a chamber pressure of 100 atm. A practical problem that arises is that rocket chamber temperatures may be too high for the use of this pure fuel. This paper examines an engine concept that uses liquid hydrogen or water as a diluent coolant for the metallic hydrogen to reduce the chamber temperature to usable values. Several launch vehicles are then conceptually developed. Results indicate that if metallic hydrogen is experimentally found to have the properties assumed in this analysis, then there are significant benefits. These benefits become more attractive as the chamber temperatures increase.

Cole, John W.; Silvera, Isaac F.; Foote, John P.

2008-01-01

34

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

NASA Technical Reports Server (NTRS)

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

ONISCHAK

1976-01-01

35

Hydrogen recovery with metal hydrides  

Microsoft Academic Search

Air Products pursued hydride technology because hydrides first came to our attention as a unique technology which could safely store hydrogen. The preliminary economics for using available hydrides to store hydrogen in motor vehicles were not encouraging at that time. However, the possibilities for using hydrides to selectively separate hydrogen from other components occurred to us. The authors obtained a

J. G. Santangelo; G. T. Chen

1982-01-01

36

Computer simulation of hydrogen embrittlement in metals  

Microsoft Academic Search

IT has been long known that hydrogen can substantially reduce the mechanical stability of transition metals under tensile stress1-3. This phenomenon of 'hydrogen embrittlement' has important consequences for the safety of fusion reactors and for space technology; but there remains considerable uncertainty about its microscopic origin2, 3. Here we report the results of a study of fracture of hydrogen-loaded palladium

W. Zhong; Y. Cai; D. Tománek

1993-01-01

37

Hydrogen production from methane using oxygen-permeable ceramic membranes  

NASA Astrophysics Data System (ADS)

Non-porous ceramic membranes with mixed ionic and electronic conductivity have received significant interest in membrane reactor systems for the conversion of methane and higher hydrocarbons to higher value products like hydrogen. However, hydrogen generation by this method has not yet been commercialized and suffers from low membrane stability, low membrane oxygen flux, high membrane fabrication costs, and high reaction temperature requirements. In this dissertation, hydrogen production from methane on two different types of ceramic membranes (dense SFC and BSCF) has been investigated. The focus of this research was on the effects of different parameters to improve hydrogen production in a membrane reactor. These parameters included operating temperature, type of catalyst, membrane material, membrane thickness, membrane preparation pH, and feed ratio. The role of the membrane in the conversion of methane and the interaction with a Pt/CeZrO2 catalyst has been studied. Pulse studies of reactants and products over physical mixtures of crushed membrane material and catalyst have clearly demonstrated that a synergy exists between the membrane and the catalyst under reaction conditions. The degree of catalyst/membrane interaction strongly impacts the conversion of methane and the catalyst performance. During thermogravimetric analysis, the onset temperature of oxygen release for BSCF was observed to be lower than that for SFC while the amount of oxygen release was significantly greater. Pulse injections of CO2 over crushed membranes at 800°C have shown more CO2 dissociation on the BSCF membrane than the SFC membrane, resulting in higher CO formation on the BSCF membrane. Similar to the CO2 pulses, when CO was injected on the samples at 800°C, CO2 production was higher on BSCF than SFC. It was found that hydrogen consumption on BSCF particles is 24 times higher than that on SFC particles. Furthermore, Raman spectroscopy and temperature programmed desorption studies of CO and CO2 showed a higher CO and CO2 adsorption (for temperatures ranging from room temperature to 600°C) on BSCF compared to the SFC membrane. CO2 reforming reactions on BSCF and SFC dense membranes in a membrane reactor showed higher methane conversion and H2/CO ratio on BSCF than SFC in the presence of the Pt/CeZrO2 catalyst. This high conversion and H2/CO ratio could be ascribed to higher CO, CO2, and H2 adsorption on BSCF than SFC, resulting in higher steam and CO2 reforming on the BSCF. The Pt-Ni/CeZrO2 catalyst exhibits promising performance for hydrogen production. Platinum enhances the reducibility of Ni/Al2O 3 and Ni/CeZrO2 catalysts resulting in improved catalysts for H2 production at moderate temperatures. TPR and Raman studies show an alloy formation in the Pt-Ni/Al2O3 catalyst. Further work is required to study the interaction between Pt and Ni in the bimetallic Pt-Ni/CeZrO2 and Pt-Ni/Al2O3 catalysts. Although the Pt-Ni/Al2O3 catalyst shows high methane conversion in the presence of the BSCF membrane at 800°C, the activity of this catalyst is low at 600°C. Pt-Ni/CeZrO2 bimetallic catalyst demonstrates superior performance compared to Pt-Ni/Al2O3 catalyst at 600°C. The thinner BSCF membrane (2.2 mm) demonstrates a higher methane conversion and H2:CO ratio than the thicker BSCF membrane (2.6 mm) because membrane oxygen flux is inversely proportional to thickness. Varying the pH of the precursor solution during membrane preparation has no significant effect on the oxygen flux or the reaction. The CH 4:CO2 feed ratio significantly affects the hydrogen production over the BSCF membrane. Altering the CH4:CO2 ratio has a direct impact on the oxygen flux, which in turn can influence the reaction pathway. These studies suggest that the Pt-Ni/CeZrO2 catalyst might be suitable for low-temperature hydrocarbon conversion reactions over thin BSCF ceramic membranes. Most importantly, the BSCF membrane can reduce the apparent activation energy of the CO2 reforming reaction by changing the reaction pathway to include more steam reforming.

Faraji, Sedigheh

38

Geochemistry of a permeable reactive barrier for metals and acid mine drainage  

Microsoft Academic Search

A permeable reactive barrier, designed to remove metals and generate alkalinity by promoting sulfate reduction and metal sulfide precipitation, was installed in August 1995 into an aquifer containing effluent from mine tailings. Passage of groundwater through the barrier results in striking improvement in water quality. Dramatic changes in concentrations of SOâ, Fe, trace metals, and alkalinity are observed. Populations of

S. G. Benner; D. W. Blowes; R. B. Jr. Herbert; C. J. Ptacek; W. D. Gould

1999-01-01

39

Impact of Stereospecific Intramolecular Hydrogen Bonding on Cell Permeability and Physicochemical Properties  

PubMed Central

Profiling of eight stereoisomeric T. cruzi growth inhibitors revealed vastly different in vitro properties such as solubility, lipophilicity, pKa, and cell permeability for two sets of four stereoisomers. Using computational chemistry and NMR spectroscopy, we identified the formation of an intramolecular NH?NR3 hydrogen bond in the set of stereoisomers displaying lower solubility, higher lipophilicity, and higher cell permeability. The intramolecular hydrogen bond resulted in a significant pKa difference that accounts for the other structure–property relationships. Application of this knowledge could be of particular value to maintain the delicate balance of size, solubility, and lipophilicity required for cell penetration and oral administration for chemical probes or therapeutics with properties at, or beyond, Lipinski’s rule of 5. PMID:24524242

2014-01-01

40

Nanostructures from hydrogen implantation of metals.  

SciTech Connect

This study investigates a pathway to nanoporous structures created by hydrogen implantation in aluminum. Previous experiments for fusion applications have indicated that hydrogen and helium ion implantations are capable of producing bicontinuous nanoporous structures in a variety of metals. This study focuses specifically on hydrogen and helium implantations of aluminum, including complementary experimental results and computational modeling of this system. Experimental results show the evolution of the surface morphology as the hydrogen ion fluence increases from 10{sup 17} cm{sup -2} to 10{sup 18} cm{sup -2}. Implantations of helium at a fluence of 10{sup 18} cm{sup -2} produce porosity on the order of 10 nm. Computational modeling demonstrates the formation of alanes, their desorption, and the resulting etching of aluminum surfaces that likely drives the nanostructures that form in the presence of hydrogen.

McWatters, Bruce Ray (Sandia National Laboratories, Albuquerque, NM); Causey, Rion A.; DePuit, Ryan J.; Yang, Nancy Y. C.; Ong, Markus D.

2009-09-01

41

Microporous Metal Organic Materials for Hydrogen Storage  

SciTech Connect

We have examined a number of Metal Organic Framework Materials for their potential in hydrogen storage applications. Results obtained in this study may, in general, be summarized as follows: (1) We have identified a new family of porous metal organic framework materials with the compositions M (bdc) (ted){sub 0.5}, {l_brace}M = Zn or Co, bdc = biphenyl dicarboxylate and ted = triethylene diamine{r_brace} that adsorb large quantities of hydrogen ({approx}4.6 wt%) at 77 K and a hydrogen pressure of 50 atm. The modeling performed on these materials agree reasonably well with the experimental results. (2) In some instances, such as in Y{sub 2}(sdba){sub 3}, even though the modeling predicted the possibility of hydrogen adsorption (although only small quantities, {approx}1.2 wt%, 77 K, 50 atm. hydrogen), our experiments indicate that the sample does not adsorb any hydrogen. This may be related to the fact that the pores are extremely small or may be attributed to the lack of proper activation process. (3) Some samples such as Zn (tbip) (tbip = 5-tert butyl isophthalate) exhibit hysteresis characteristics in hydrogen sorption between adsorption and desorption runs. Modeling studies on this sample show good agreement with the desorption behavior. It is necessary to conduct additional studies to fully understand this behavior. (4) Molecular simulations have demonstrated the need to enhance the solid-fluid potential of interaction in order to achieve much higher adsorption amounts at room temperature. We speculate that this may be accomplished through incorporation of light transition metals, such as titanium and scandium, into the metal organic framework materials.

S. G. Sankar; Jing Li; Karl Johnson

2008-11-30

42

Use metal hydrides to recover hydrogen  

Microsoft Academic Search

This article demonstrates the technical feasibility of a hydride separation process from the idea stage through a pilot unit operated on-site on an ammonia purge-gas stream. The proposed hydrogen separation process makes use of the reversible and selective absorption capability of metal hydrides. Attrition (powder formation) of the hydride material, heat management, and deactivation of the hydride by certain contaminants

J. G. Santangelo; G. T. Chen

1983-01-01

43

Metallization in hydrogen-helium mixtures  

NASA Astrophysics Data System (ADS)

Hydrogen-helium mixtures have long been predicted to undergo demixing at high pressures of several megabars which occur in the interiors of giant planets such as Jupiter and Saturn. This effect is most important to understand their evolution and current interior structure. Ab initio calculations have already proven their potential to give precise predictions for the demixing line for pressures above 4 Mbar, well above a first-order phase transition from molecular to metallic hydrogen. Here we calculate the miscibility gap for lower pressures between 1 and 2 Mbar using ab initio molecular dynamics simulations. By using the Kubo-Greenwood formula we obtain the electrical conductivity and reveal the close connection between metallization in the hydrogen subsystem and the location of the miscibility gap. Especially, we find direct evidence for H-He demixing by performing simulations for large particle numbers.

Lorenzen, Winfried; Holst, Bastian; Redmer, Ronald

2011-12-01

44

Metallic Hydrogen - Potentially a High Energy Rocket Propellant  

NASA Technical Reports Server (NTRS)

Pure metallic hydrogen is predicted to have a specific impulse (Isp) of 1700 seconds, but the reaction temperature is too high for current engine materials. Diluting metallic hydrogen with liquid hydrogen can reduce the reaction temperature to levels compatible with current material limits and still provide an Isp greater than 900 s. Metallic hydrogen has not yet been produced on earth, but experimental techniques exist that may change this situation. This paper will provide a brief description of metallic hydrogen and the status of experiments that may soon produce detectable quantities of this material in the lab. Also provided are some characteristics for diluted metallic hydrogen engines and launch vehicles.

Cole, John; Silvera, Ike

2007-01-01

45

Hydrogen Storage in Metal-Organic Frameworks  

SciTech Connect

Conventional storage of large amounts of hydrogen in its molecular form is difficult and expensive because it requires employing either extremely high pressure gas or very low temperature liquid. Because of the importance of hydrogen as a fuel, the DOE has set system targets for hydrogen storage of gravimetric (5.5 wt%) and volumetric (40 g L-1) densities to be achieved by 2015. Given that these are system goals, a practical material will need to have higher capacity when the weight of the tank and associated cooling or regeneration system is considered. The size and weight of these components will vary substantially depending on whether the material operates by a chemisorption or physisorption mechanism. In the latter case, metal-organic frameworks (MOFs) have recently been identified as promising adsorbents for hydrogen storage, although little data is available for their sorption behavior. This grant was focused on the study of MOFs with these specific objectives. (1) To examine the effects of functionalization, catenation, and variation of the metal oxide and organic linkers on the low-pressure hydrogen adsorption properties of MOFs. (2) To develop a strategy for producing MOFs with high surface area and porosity to reduce the dead space and increase the hydrogen storage capacity per unit volume. (3) To functionalize MOFs by post synthetic functionalization with metals to improve the adsorption enthalpy of hydrogen for the room temperature hydrogen storage. This effort demonstrated the importance of open metal sites to improve the adsorption enthalpy by the systematic study, and this is also the origin of the new strategy, which termed isoreticular functionalization and metalation. However, a large pore volume is still a prerequisite feature. Based on our principle to design highly porous MOFs, guest-free MOFs with ultrahigh porosity have been experimentally synthesized. MOF-210, whose BET surface area is 6240 m2 g-1 (the highest among porous solids), takes up 15 wt% of total H2 uptake at 80 bar and 77 K. More importantly, the total H2 uptake by MOF-210 was 2.7 wt% at 80 bar and 298 K, which is the highest number reported for physisorptive materials.

Omar M. Yaghi

2012-04-26

46

Metallic hydrogen: The most powerful rocket fuel yet to exist  

Microsoft Academic Search

Wigner and Huntington first predicted that pressures of order 25 GPa were required for the transition of solid molecular hydrogen to the atomic metallic phase. Later it was predicted that metallic hydrogen might be a metastable material so that it remains metallic when pressure is released. Experimental pressures achieved on hydrogen have been more than an order of magnitude higher

Isaac F Silvera; John W Cole

2010-01-01

47

PERMEABILITY, SOLUBILITY, AND INTERACTION OF HYDROGEN IN POLYMERS- AN ASSESSMENT OF MATERIALS FOR HYDROGEN TRANSPORT  

SciTech Connect

Fiber-reinforced polymer (FRP) piping has been identified as a leading candidate for use in a transport system for the Hydrogen Economy. Understanding the permeation and leakage of hydrogen through the candidate materials is vital to effective materials system selection or design and development of safe and efficient materials for this application. A survey of the literature showed that little data on hydrogen permeation are available and no mechanistically-based models to quantitatively predict permeation behavior have been developed. However, several qualitative trends in gaseous permeation have been identified and simple calculations have been performed to identify leakage rates for polymers of varying crystallinity. Additionally, no plausible mechanism was found for the degradation of polymeric materials in the presence of pure hydrogen. The absence of anticipated degradation is due to lack of interactions between hydrogen and FRP and very low solubility coefficients of hydrogen in polymeric materials. Recommendations are made to address research and testing needs to support successful materials development and use of FRP materials for hydrogen transport and distribution.

Kane, M

2008-02-05

48

Hydrogen Permeability of Palladium Membrane for Steam-Reforming of Bio-Ethanol Using the Membrane Reactor  

NASA Astrophysics Data System (ADS)

A Palladium membrane was prepared by electro-less plating method on porous stainless steel. The catalytic hydrogen production by steam-reforming of biomass-derived ethanol (bio-ethanol) using a Pd membrane was analyzed by comparing it with those for the reaction using reagent ethanol (the reference sample). And the hydrogen permeability of the palladium membrane was investigated using the same palladium membrane (H2/He selectivity = 249, at ?P = 0.10 MPa, 873 K). As a result, for bio-ethanol, deposited carbon had a negative influence on the hydrogen-permeability of the palladium membrane and hydrogen purity. The sulfur content in the bio-ethanol may have promoted carbon deposition. By using a palladium membrane, it was confirmed that H2 yield (%) was increased. It can be attributed that methane was converted from ethanol and produced more hydrogen by steam reforming, due to the in situ removal of hydrogen from the reaction location.

Kinouchi, Kouji; Katoh, Masahiro; Horikawa, Toshihide; Yoshikawa, Takushi; Wada, Mamoru

49

Hydrogen diffusion in the bcc metals  

Microsoft Academic Search

Hydrogen diffuses rapidly in the bcc metals even below room temperature. Thus, hydrides can easily form at low temperatures. The thermodynamic parameters of equilibrium between the bcc solid solutions and the hydride phases in the temperature range 150 to 300°K for the V-H and Ta-H systems were determined. The presence of other interstitials, especially oxygen, greatly affects the hydride formation,

Wert

1975-01-01

50

a Study of the Metal-Hydrogen Systems  

Microsoft Academic Search

The work described in this thesis on hydrogen in zirconium and zirconium-rhodium alloys constitutes a selected programme which attempts to understand the behaviour and interaction of hydrogen with metals and alloys. Three principal techniques have been used in this study of metal -hydrogen systems; (i) hydrogen solubility measurements, (ii) neutron diffraction and (iii) superconductivity. A pressure-composition-temperature diagram for hydrogen absorption

Prem Parkash Narang

1978-01-01

51

Hydrogen production from simulated hot coke oven gas by using oxygen-permeable ceramics  

SciTech Connect

Hydrogen production from simulated hot coke oven gas (HCOG) was investigated in a BaCo{sub 0.7}Fe{sub 0.2}Nb{sub 0.1}O{sub 3-{delta}} (BCFNO) membrane reactor combined with a Ni/Mg(Al)O catalyst by the partial oxidation with toluene as a model tar compound under atmospheric pressure. The reaction results indicated that toluene was completely converted to H{sub 2} and CO in the catalytic reforming of the simulated HCOG in the temperature range from 825 to 875{sup o}C. Both thermodynamically predicated values and experimental data showed that the selective oxidation of toluene took precedence over that of CH{sub 4} in the reforming reaction. At optimized reaction conditions, the dense oxygen-permeable membrane has an oxygen permeation flux around 12.3 mL cm{sup -2} min{sup -1}, and a CH{sub 4} conversion of 86%, a CO{sub 2} conversion of 99%, a H{sub 2} yield of 88%, and a CO yield of 87% have been achieved. When the toluene and methane were reformed, the amount of H{sub 2} in the reaction effluent gas was about 2 times more than that of original H{sub 2} in simulated HCOG. The results reveal that it is feasible for hydrogen production from HCOG by reforming hydrocarbon compounds in a ceramic oxygen-permeable membrane reactor. 27 refs., 10 figs., 3 abs.

Hongwei Cheng; Yuwen Zhang; Xionggang Lu; Weizhong Ding; Qian Li [Shanghai University, Shanghai (China). Shanghai Key Laboratory of Modern Metallurgy and Materials Processing

2009-01-15

52

Supported Molten Metal Membranes for Hydrogen Separation  

SciTech Connect

We describe here our results on the feasibility of a novel dense metal membrane for hydrogen separation: Supported Molten Metal Membrane, or SMMM.1 The goal in this work was to develop these new membranes based on supporting thin films of low-melting, non- precious group metals, e.g., tin (Sn), indium (In), gallium (Ga), or their alloys, to provide a flux and selectivity of hydrogen that rivals the conventional but substantially more expensive palladium (Pd) or Pd alloy membranes, which are susceptible to poisoning by the many species in the coal-derived syngas, and further possess inadequate stability and limited operating temperature range. The novelty of the technology presented numerous challenges during the course of this project, however, mainly in the selection of appropriate supports, and in the fabrication of a stable membrane. While the wetting instability of the SMMM remains an issue, we did develop an adequate understanding of the interaction between molten metal films with porous supports that we were able to find appropriate supports. Thus, our preliminary results indicate that the Ga/SiC SMMM at 550 ºC has a permeance that is an order of magnitude higher than that of Pd, and exceeds the 2015 DOE target. To make practical SMM membranes, however, further improving the stability of the molten metal membrane is the next goal. For this, it is important to better understand the change in molten metal surface tension and contact angle as a function of temperature and gas-phase composition. A thermodynamic theory was, thus, developed, that is not only able to explain this change in the liquid-gas surface tension, but also the change in the solid-liquid surface tension as well as the contact angle. This fundamental understanding has allowed us to determine design characteristics to maintain stability in the face of changing gas composition. These designs are being developed. For further progress, it is also important to understand the nature of solution and permeation process in these molten metal membranes. For this, a comprehensive microkinetic model was developed for hydrogen permeation in dense metal membranes, and tested against data for Pd membrane over a broad range of temperatures.3 It is planned to obtain theoretical and experimental estimates of the parameters to corroborate the model against mental results for SMMM.

Datta, Ravindra; Ma, Yi Hua; Yen, Pei-Shan; Deveau, Nicholas; Fishtik, Ilie; Mardilovich, Ivan

2013-09-30

53

Metallic hydrogen: The most powerful rocket fuel yet to exist  

NASA Astrophysics Data System (ADS)

Wigner and Huntington first predicted that pressures of order 25 GPa were required for the transition of solid molecular hydrogen to the atomic metallic phase. Later it was predicted that metallic hydrogen might be a metastable material so that it remains metallic when pressure is released. Experimental pressures achieved on hydrogen have been more than an order of magnitude higher than the predicted transition pressure and yet it remains an insulator. We discuss the applications of metastable metallic hydrogen to rocketry. Metastable metallic hydrogen would be a very light-weight, low volume, powerful rocket propellant. One of the characteristics of a propellant is its specific impulse, Isp. Liquid (molecular) hydrogen-oxygen used in modern rockets has an Isp of ~460s; metallic hydrogen has a theoretical Isp of 1700s! Detailed analysis shows that such a fuel would allow single-stage rockets to enter into orbit or carry economical payloads to the moon. If pure metallic hydrogen is used as a propellant, the reaction chamber temperature is calculated to be greater than 6000 K, too high for currently known rocket engine materials. By diluting metallic hydrogen with liquid hydrogen or water, the reaction temperature can be reduced, yet there is still a significant performance improvement for the diluted mixture.

Silvera, Isaac F.; Cole, John W.

2010-03-01

54

Hydrogen dynamics and metallic phase stabilization in VO2  

NASA Astrophysics Data System (ADS)

Experimental doping of VO2 with hydrogen has been shown to trigger the semiconductor-to-metal phase transition below room temperature. Here, we report the results of density functional calculations showing that hydrogen-induced lattice distortion stabilizes the metallic phase. We also show that hydrogen diffuses preferentially along the rutile [001] direction whereby surface orientations can be tailored for optimal transport. Finally, we show that hydrogen doping is energetically favored, but there is a 1.6 eV barrier for dissociation of hydrogen molecules on a (100) monoclinic surface. These results give insight into the effect of hydrogen on the properties and phase transition of VO2.

Warnick, Keith H.; Wang, Bin; Pantelides, Sokrates T.

2014-03-01

55

CALPHAD Modeling of Metal-Hydrogen Systems: A Review  

NASA Astrophysics Data System (ADS)

A review of the metal-hydrogen systems modeled or investigated with the CALPHAD method is presented. The specific features of metal-hydrogen systems in relation with the CALPHAD modeling are detailed, and the problems and needs related to the description of such systems are highlighted.

Joubert, J.-M.

2012-12-01

56

Microporous Materials Strategies for Hydrogen Storage in MetalOrganic  

E-print Network

as efficiently as internal combustion engines, only 5­10 kg of hydrogen must be stored (although 4 kg or lessMicroporous Materials Strategies for Hydrogen Storage in Metal­Organic Frameworks Jesse L. C materials · organic­inorganic hybrid composites 1. Introduction The scope of the United States Hydrogen

Yaghi, Omar M.

57

Transition metal-catalyzed enantioselective hydrogenation of enamides and enamines.  

PubMed

Transition metal-catalyzed enantioselective hydrogenation of enamides and enamines is one of the most important methods for the preparation of optically active amines. This review describes the recent developments of highly efficient catalytic asymmetric hydrogenation of enamides, and enamines. It specifically focuses on the substrates because hydrogenation of enamides and enamines is highly dependent on the substrates although the chiral metal catalysts play a significant role. PMID:24595741

Zhou, Qi-Lin; Xie, Jian-Hua

2014-01-01

58

Hydrogen separation membrane on a porous substrate  

DOEpatents

A hydrogen permeable membrane is disclosed. The membrane is prepared by forming a mixture of metal oxide powder and ceramic oxide powder and a pore former into an article. The article is dried at elevated temperatures and then sintered in a reducing atmosphere to provide a dense hydrogen permeable portion near the surface of the sintered mixture. The dense hydrogen permeable portion has a higher initial concentration of metal than the remainder of the sintered mixture and is present in the range of from about 20 to about 80 percent by volume of the dense hydrogen permeable portion.

Song, Sun-Ju (Orland Park, IL); Lee, Tae H. (Naperville, IL); Chen, Ling (Woodridge, IL); Dorris, Stephen E. (LaGrange Park, IL); Balachandran, Uthamalingam (Hinsdale, IL)

2011-06-14

59

High-Pressure Multi-Mbar Conductivity Experiments on Hydrogen: The Quest for Solid Metallic Hydrogen  

SciTech Connect

Ultra-dense hydrogen has long been the subject of intense experimental and theoretical research due to the fascinating physics which arises from this supposedly simple system. The properties of ultra-dense hydrogen also have important implications for planetary physics, since the interiors of the giant planets Jupiter and Saturn are believed to consist of cores of dense, metallic hydrogen. Finally, ultra-dense hydrogen is of direct programmatic interest, and multiple-shock compression experiments on hydrogen to the metallic state have stimulated the accelerated development of new hydrogen equation-of-state (EOS) models used for ICF and other applications. The focus of our research has often been described as the ''Holy Grail'' of high-pressure physics research: The metallization of solid hydrogen. Metallic hydrogen has long been considered to be the prototypical system for the study of insulator-to-metal (I-M) transitions. Although metallic hydrogen (Z=1) may superficially appear to be a very simple material, it is in fact an extremely challenging system for theoretical analysis due to the presence of large zero-point atomic motions and the complete absence of any core electrons. Thus, solid metallic hydrogen promises to be a fascinating material. Among its predicted properties is the possibility of being a high temperature superconductor with a critical temperature T{sub c} of the order of {approx} 100K [1]. The successful metallization of solid hydrogen would be a groundbreaking scientific discovery and open up new frontiers in science and possibly technology as well.

Jackson, D

2007-02-07

60

Metal Dichalcogenides Monolayers: Novel Catalysts for Electrochemical Hydrogen Production  

NASA Astrophysics Data System (ADS)

Catalyst-driven electrolysis of water is considered as a ``cleanest'' way for hydrogen production. Finding cheap and abundant catalysts is critical to the large-scale implementation of the technology. Two-dimensional metal dichalcogenides nanostructures have attracted increasing attention because of their catalytic performances in water electrolysis. In this work, we systematically investigate the hydrogen evolution reduction of metal dichalcogenides monolayers based on density-functional-theory calculations. We find that metal disulfide monolayers show better catalytic performance on hydrogen production than other metal dichalcogenides. We show that their hydrogen evolution reduction strongly depends on the hydrogen coverage and the catalytic performance reduces with the increment of coverage because of hydrogenation-induced lower conductivity. We further show that the catalytic performance of vanadium disulfide monolayer is comparable to that of Pt at lower hydrogen coverage and the performance at higher coverage can be improved by hybridizing with conducting nanomaterials to enhance conductivity. These metal disulfide monolayers with lower overpotentials may apply to water electrolysis for hydrogen production.

Pan, Hui

2014-06-01

61

Metal dichalcogenides monolayers: novel catalysts for electrochemical hydrogen production.  

PubMed

Catalyst-driven electrolysis of water is considered as a "cleanest" way for hydrogen production. Finding cheap and abundant catalysts is critical to the large-scale implementation of the technology. Two-dimensional metal dichalcogenides nanostructures have attracted increasing attention because of their catalytic performances in water electrolysis. In this work, we systematically investigate the hydrogen evolution reduction of metal dichalcogenides monolayers based on density-functional-theory calculations. We find that metal disulfide monolayers show better catalytic performance on hydrogen production than other metal dichalcogenides. We show that their hydrogen evolution reduction strongly depends on the hydrogen coverage and the catalytic performance reduces with the increment of coverage because of hydrogenation-induced lower conductivity. We further show that the catalytic performance of vanadium disulfide monolayer is comparable to that of Pt at lower hydrogen coverage and the performance at higher coverage can be improved by hybridizing with conducting nanomaterials to enhance conductivity. These metal disulfide monolayers with lower overpotentials may apply to water electrolysis for hydrogen production. PMID:24967679

Pan, Hui

2014-01-01

62

Metal Dichalcogenides Monolayers: Novel Catalysts for Electrochemical Hydrogen Production  

PubMed Central

Catalyst-driven electrolysis of water is considered as a “cleanest” way for hydrogen production. Finding cheap and abundant catalysts is critical to the large-scale implementation of the technology. Two-dimensional metal dichalcogenides nanostructures have attracted increasing attention because of their catalytic performances in water electrolysis. In this work, we systematically investigate the hydrogen evolution reduction of metal dichalcogenides monolayers based on density-functional-theory calculations. We find that metal disulfide monolayers show better catalytic performance on hydrogen production than other metal dichalcogenides. We show that their hydrogen evolution reduction strongly depends on the hydrogen coverage and the catalytic performance reduces with the increment of coverage because of hydrogenation-induced lower conductivity. We further show that the catalytic performance of vanadium disulfide monolayer is comparable to that of Pt at lower hydrogen coverage and the performance at higher coverage can be improved by hybridizing with conducting nanomaterials to enhance conductivity. These metal disulfide monolayers with lower overpotentials may apply to water electrolysis for hydrogen production. PMID:24967679

Pan, Hui

2014-01-01

63

High temperature equation of state of metallic hydrogen  

SciTech Connect

The equation of state of liquid metallic hydrogen is solved numerically. Investigations are carried out at temperatures from 3000 to 20 000 K and densities from 0.2 to 3 mol/cm{sup 3}, which correspond both to the experimental conditions under which metallic hydrogen is produced on earth and the conditions in the cores of giant planets of the solar system such as Jupiter and Saturn. It is assumed that hydrogen is in an atomic state and all its electrons are collectivized. Perturbation theory in the electron-proton interaction is applied to determine the thermodynamic potentials of metallic hydrogen. The electron subsystem is considered in the randomphase approximation with regard to the exchange interaction and the correlation of electrons in the local-field approximation. The proton-proton interaction is taken into account in the hard-spheres approximation. The thermodynamic characteristics of metallic hydrogen are calculated with regard to the zero-, second-, and third-order perturbation theory terms. The third-order term proves to be rather essential at moderately high temperatures and densities, although it is much smaller than the second-order term. The thermodynamic potentials of metallic hydrogen are monotonically increasing functions of density and temperature. The values of pressure for the temperatures and pressures that are characteristic of the conditions under which metallic hydrogen is produced on earth coincide with the corresponding values reported by the discoverers of metallic hydrogen to a high degree of accuracy. The temperature and density ranges are found in which there exists a liquid phase of metallic hydrogen.

Shvets, V. T. [Odessa State Academy of Refrigeration (Ukraine)], E-mail: valtar@paco.net

2007-04-15

64

Gas permeability properties of Matrimid ® membranes containing the metal-organic framework Cu–BPY–HFS  

Microsoft Academic Search

A microporous metal-organic framework Cu–4,4?-bipyridine–hexafluorosilicate (Cu–BPY–HFS), having a surface area of 2000m2\\/g, was combined with Matrimid® polymer to form free standing films. The permeability properties of Cu–BPY–HFS–Matrimid® mixed-matrix membranes were tested for the pure gases H2, N2, O2, CH4, and CO2 and the gas mixtures CO2\\/CH4, H2\\/CO2 and CH4\\/N2. The ideal selectivity of CH4\\/N2 increased from 0.95 to 1.21, which

Yanfeng Zhang; Inga H. Musselman; John P. Ferraris; Kenneth J. Balkus Jr.

2008-01-01

65

Determination of the Darcy permeability of porous media including sintered metal plugs  

NASA Technical Reports Server (NTRS)

Sintered-metal porous plugs with a normal size of the order of 1-10 microns are used to evaluate the Darcy permeability of laminar flow at very small velocities in laminar fluids. Porous media experiment results and data adduced from the literature are noted to support the Darcy law analog for normal fluid convection in the laminar regime. Low temperature results suggest the importance of collecting room temperature data prior to runs at liquid He(4) temperatures. The characteristic length diagram gives a useful picture of the tolerance range encountered with a particular class of porous media.

Frederking, T. H. K.; Hepler, W. A.; Yuan, S. W. K.; Feng, W. F.

1986-01-01

66

Disposal pathway for tritiated reactive metals and tritiated hydrogen gas  

SciTech Connect

Kinectrics and its predecessor company Ontario Hydro Research Div. (a division of Ontario Hydro) had a fully operational tritium laboratory on site since the early 1980's. During those years numerous projects and experiments were undertaken using hydrogen and tritium for the most part. Metals with an affinity for hydrogen are commonly employed as scavengers of hydrogenic gases from process streams or as hydrogen storage mediums. The two most common of these metals used were depleted uranium and a zirconium-iron alloy (SAES St198). The break-up of Ontario Hydro through deregulation activities resulted in the building of a new, smaller, tritium laboratory and the decommissioning of the original tritium laboratory. Decommissioning activities resulted in the need to safely dispose of these reactive metals. Disposal of these metals is not straight forward. For safe, long term, disposal it has been decided to oxidize the metals in a controlled fashion. The oxidized beds, containing the metals, will be sent to a radioactive waste site for long term storage. Options for disposal of tritiated hydrogen gas are presented and discussed. This paper provides a disposal pathway for tritiated reactive metals and hydrogen thereby closing the loop in tritium handling. (authors)

Antoniazzi, A. B.; Morton, C. S. [Kinectrics Inc., 800 Kipling Ave KJ105, Toronto, ON M8Z 6C4 (Canada)

2008-07-15

67

Determination of negative permeability and permittivity of metal strip coated ferrite disks using the transmission and reflection technique  

NASA Astrophysics Data System (ADS)

In this paper, a full band microwave isolator constructed from an array of metal wire-coated ferrite samples is presented. Here, the magnetic permeability of the metamaterialized structure is controlled by a relatively weak external magnetic field. The tunable permeability of the ferrites in this experiment allows us to create unidirectional wave propagation through the structure over the entire X-band frequency spectrum. The analysis presented here takes into account potential surface plasmon modes generated between the gaps of metal wires when the external magnetic field is applied. Here, we present a modification of the traditional transmission-reflection measurement method by normalizing the transmission and reflection coefficients. This modification removes the occurrence of atypical phenomena for negative imaginary components of permeability and permittivity that arises in the measurement of metamaterials. Our modified method precisely determines the refractive index, impedance, permittivity, and permeability of both traditional reciprocal networks as well as nonreciprocal networks, such as the one presented here.

Rahman, N.; Obol, M.; Sharma, A.; Afsar, M. N.

2010-05-01

68

Understanding the mechanism of hydrogen adsorption into metal organic frameworks  

Microsoft Academic Search

Hydrogen adsorption mechanism into MOF-5, a porous metal-organic framework (MOF) has been studied by density functional theory calculation. The selected functionals for the prediction of interaction energies between hydrogen and potential adsorption sites of MOF-5 were utilized after the evaluation with the various functionals for interaction energy of H2?C6H6 model system. The adsorption energy of hydrogen molecule into MOF-5 was

Tae Bum Lee; Daejin Kim; Dong Hyun Jung; Sang Beom Choi; Ji Hye Yoon; Jaheon Kim; Kihang Choi; Seung-Hoon Choi

2007-01-01

69

Interfacial synthesis of hollow metal-organic framework capsules demonstrating selective permeability  

NASA Astrophysics Data System (ADS)

Metal-organic frameworks (MOFs) are a class of crystalline materials that consist of metal ions and organic ligands linked together by coordination bonds. Because of their porosity and the possibility of combining large surface areas with pore characteristics that can be tailored, these solids show great promise for a wide range of applications. Although most applications currently under investigation are based on powdered solids, developing synthetic methods to prepare defect-free MOF layers will also enable applications based on selective permeation. Here, we demonstrate how the intrinsically hybrid nature of MOFs enables the self-completing growth of thin MOF layers. Moreover, these layers can be shaped as hollow capsules that demonstrate selective permeability directly related to the micropore size of the MOF crystallites forming the capsule wall. Such capsules effectively entrap guest species, and, in the future, could be applied in the development of selective microreactors containing molecular catalysts.

Ameloot, Rob; Vermoortele, Frederik; Vanhove, Wim; Roeffaers, Maarten B. J.; Sels, Bert F.; de Vos, Dirk E.

2011-05-01

70

Hydrogen generation using sodium borohydride solution and metal catalyst coated on metal oxide  

Microsoft Academic Search

Sodium borohydride (NaBH4) reacted slowly with water to liberate 4mol of hydrogen\\/mol of the compound at room temperature. Hydrogen generation was accelerated by applying metal–metal oxide catalysts such as Pt–TiO2, Pt–CoO and Pt–LiCoO2. As the metal crystallites size decreased and the amount increased, the hydrogen generation rate increased. It was indicated that the hydrogen generation rates using Pt and LiCoO2

Yoshitsugu Kojima; Ken-ichirou Suzuki; Kazuhiro Fukumoto; Megumi Sasaki; Toshio Yamamoto; Yasuaki Kawai; Hiroaki Hayashi

2002-01-01

71

Exploring metal hydrides using autoclave and multi-anvil hydrogenations  

NASA Astrophysics Data System (ADS)

Metal hydride materials have been intensively studied for hydrogen storage applications. In addition to potential hydrogen economy applications, metal hydrides offer a wide variety of other interesting properties. For example, hydrogen-dominant materials, which are hydrides with the highest hydrogen content for a particular metal/semimetal composition, are predicted to display high-temperature superconductivity. On the other side of the spectrum are hydrides with small amounts of hydrogen (0.1 - 1 at.%) that are investigated as viable magnetic, thermoelectric or semiconducting materials. Research of metal hydride materials is generally important to gain fundamental understanding of metal-hydrogen interactions in materials. Hydrogenation of Zintl phases, which are defined as compounds between an active metal (alkali, alkaline earth, rare earth) and a p-block metal/semimetal, were attempted by a hot sintering method utilizing an autoclave loaded with gaseous hydrogen (< 9 MPa). Hydride formation competes with oxidative decomposition of a Zintl phase. The oxidative decomposition, which leads to a mixture of binary active metal hydride and p-block element, was observed for investigated aluminum (Al) and gallium (Ga) containing Zintl phases. However, a new phase Li2Al was discovered when Zintl phase precursors were synthesized. Using the single crystal x-ray diffraction (SCXRD), the Li2Al was found to crystallize in an orthorhombic unit cell (Cmcm) with the lattice parameters a = 4.6404(8) Å, b = 9.719(2) Å, and c = 4.4764(8) Å. Increased demand for materials with improved properties necessitates the exploration of alternative synthesis methods. Conventional metal hydride synthesis methods, like ball-milling and autoclave technique, are not responding to the demands of finding new materials. A viable alternative synthesis method is the application of high pressure for the preparation of hydrogen-dominant materials. Extreme pressures in the gigapascal ranges can open access to new metal hydrides with novel structures and properties, because of the drastically increased chemical potential of hydrogen. Pressures up to 10 GPa can be easily achieved using the multi-anvil (MA) hydrogenations while maintaining sufficient sample volume for structure and property characterization. Gigapascal MA hydrogenations using ammonia borane (BH3hydrogen source were employed in the search for new hydrogen-dominant materials. Ammonia borane has high gravimetric volume of hydrogen, and additionally the thermally activated decomposition at high pressures lead to a complete hydrogen release at reasonably low temperature. These properties make ammonia borane a desired hydrogen source material. The missing member Li2PtH6 of the series of A2PtH6 compounds (A = Na to Cs) was accessed by employing MA technique. As the known heavier analogs, the Li2PtH6 also crystallizes in a cubic K2PtCl6-type structure with a cell edge length of 6.7681(3) Å. Further gigapascal hydrogenations afforded the compounds K2SiH6 and Rb2SiH6 which are isostructural to Li2PtH6. The cubic K2SiH6 and Rb2SiH6 are built from unique hypervalent SiH62 entities with the lattice parameters of 7.8425(9) and 8.1572(4) Å, respectively. Spectroscopic analysis of hexasilicides confirmed the presence of hypervalent bonding. The Si-H stretching frequencies at 1550 cm-1 appeared considerably decreased in comparison with a normal-valent (2e2c) Si-H stretching frequencies in SiH4 at around 2200 cm-1. However, the observed stretching modes in hypervalent hexasilicides were in a reasonable agreement with Ph3SiH2- (1520 cm-1) where the hydrogen has the axial (3e4c bonded) position in the trigoal bipyramidal environment.

Puhakainen, Kati

72

Interactions of Hydrogen Isotopes and Oxides with Metal Tubes  

SciTech Connect

Understanding and accounting for interaction of hydrogen isotopes and their oxides with metal surfaces is important for persons working with tritium systems. Reported data from several investigators have shown that the processes of oxidation, adsorption, absorption, and permeation are all coupled and interactive. A computer model has been developed for predicting the interaction of hydrogen isotopes and their corresponding oxides in a flowing carrier gas stream with the walls of a metallic tube, particularly at low hydrogen concentrations. An experiment has been constructed to validate the predictive model. Predictions from modeling lead to unexpected experiment results.

Glen R. Longhurst

2008-08-01

73

How are hydrogen bonds modified by metal binding?  

PubMed

We have used density functional theory calculations to investigate how the hydrogen-bond strength is modified when a ligand is bound to a metal using over 60 model systems involving six metals and eight ligands frequently encountered in metalloproteins. We study how the hydrogen-bond geometry and energy vary with the nature of metal, the oxidation state, the coordination number, the ligand involved in the hydrogen bond, other first-sphere ligands, and different hydrogen-bond probe molecules. The results show that, in general, the hydrogen-bond strength is increased for neutral ligands and decreased for negatively charged ligands. The size of the effect is mainly determined by the net charge of the metal complex, and all effects are typically decreased when the model is solvated. In water solution, the hydrogen-bond strength can increase by up to 37 kJ/mol for neutral ligands, and that of negatively charged ligands can increase (for complexes with a negative net charge) or decrease (for positively charged complexes). If the net charge of the complex does not change, there is normally little difference between different metals or different types of complexes. The only exception is observed for sulphur-containing ligands (Met and Cys) and if the ligand is redox-active (e.g. high-valence Fe-O complexes). PMID:23543233

Husberg, Charlotte; Ryde, Ulf

2013-06-01

74

Phonon echo in hydrogen-containing metals  

NASA Astrophysics Data System (ADS)

The phonon echo due to the tunneling of the hydrogen atom between two equilibrium positions in hydrogen-containing niobium NbOxHy is investigated. The time dependence of the intensity and shape of the two-pulse echo signal is obtained.

Chotorlishvili, L. L.; Tutberidze, I. A.; Kakabadze, G. R.

2001-06-01

75

Noncovalent hydrogen bonding in metal-organic structures  

NASA Astrophysics Data System (ADS)

Transition metal sites in metal-organic frameworks and in doped carbon structures are actively being studied for their binding properties of molecular hydrogen. We present a study of prototypical metal-organic structures that can be used to bind molecular hydrogen non-covalently. Due to the well known limitations of current density functional theory based descriptions of non-covalent hydrogen bonding we have focused our efforts on a consistent many-body approach based on the fixed-node diffusion Monte Carlo method. Accurate studies of binding energies and the effects of multiple hydrogens in these structures are presented. Prepared by LLNL under Contract DE-AC52-07NA27344

Tubman, Norm M.; Dubois, Jonathan L.; Hood, Randolph Q.; Hamel, Sebastien; Schwegler, Eric R.

2009-03-01

76

DEVELOPMENT OF A NON-NOBLE METAL HYDROGEN PURIFICATION SYSTEM  

SciTech Connect

Development of advanced hydrogen separation membranes in support of hydrogen production processes such as coal gasification and as front end gas purifiers for fuel cell based system is paramount to the successful implementation of a national hydrogen economy. Current generation metallic hydrogen separation membranes are based on Pd-alloys. Although the technology has proven successful, at issue is the high cost of palladium. Evaluation of non-noble metal based dense metallic separation membranes is currently receiving national and international attention. The focus of the reported work was to develop a scaled reactor with a VNi-Ti alloy membrane to replace a production Pd-alloy tube-type purification/diffuser system.

Korinko, P; Kyle Brinkman, K; Thad Adams, T; George Rawls, G

2008-11-25

77

Electrocatalytic hydrogenation and deoxygenation of glucose on solid metal electrodes.  

PubMed

This Full Paper addresses the electrocatalytic hydrogenation of glucose to sorbitol or 2-deoxysorbitol on solid metal electrodes in neutral media. Combining voltammetry and online product analysis with high-performance liquid chromatography (HPLC), provides both qualitative and quantitative information regarding the reaction products as a function of potential. Three groups of catalysts clearly show affinities toward: (1)?hydrogen formation [on early transition metals (Ti, V, Cr, Mn, Zr, Nb, Mo, Hf, Ta, We, and Re) and platinum group metals (Ru, Rh, Ir, and Pt)], (2)?sorbitol formation [on late transition metals (Fe, Co, Ni, Cu, Pd, Au, and Ag) and Al (sp metal)], and (3)?sorbitol and 2-deoxysorbitol formation [on post-transition metals (In, Sn, Sb, Pb, and Bi), as well as Zn and Cd (d metals)]. Ni shows the lowest overpotential for the onset of sorbitol formation (-0.25?V) whereas Pb generates sorbitol with the highest yield (<0.7?mM?cm(-2) ). Different from a smooth Pt electrode, a large-surface-area Pt/C electrode hydrogenates glucose to sorbitol from -0.21?V with relatively low current. This emphasizes the importance of the active sites and the surface area of the catalyst. The mechanism to form 2-deoxysorbitol from glucose and/or fructose is discussed according to the observed reaction products. The yield and selectivity of hydrogenated products are highly sensitive to the chemical nature and state of the catalyst surface. PMID:23345067

Kwon, Youngkook; Koper, Marc T M

2013-03-01

78

Influence of gaseous hydrogen on metals  

NASA Technical Reports Server (NTRS)

Tensile, fracture toughness, threshold stress intensity for sustained-load crack growth, and cyclic and sustained load crack growth rate measurements were performed on a number of alloys in high-pressure hydrogen and helium environments. The results of tensile tests performed in 34.5 MN/m2 (5000 psi) hydrogen indicated that Inconel 625 was considerable embrittled at ambient temperature but was not embrittled at 144 K (-200 F). The tensile properties of AISI 321 stainless steel were slightly reduced at ambient temperature and 144 K (-200 F). The tensile properties of Ti-5Al-2.5 Sn ELI were essentially unaffected by hydrogen at 144 K (-200 F). OFHC copper was not embrittled by hydrogen at ambient temperature or at 144 K (-200 F).

Walter, R. J.; Chandler, W. T.

1973-01-01

79

Critical behavior in the hydrogen insulator-metal transition  

NASA Technical Reports Server (NTRS)

The vibrational Raman spectrum of solid hydrogen has been measured from 77 to 295 K in the vicinity of the recently observed insulator-metal transition and low-temperature phase transition at 150 gigapascals. The measurements provide evidence for a critical point in the pressure-temperature phase boundary of the low-temperature transition. The result suggests that below the critical temperature the insulator-metal transition changes from continuous to discontinuous, consistent with the general criteria originally proposed by Mott (1949) for metallization by band-gap closure. The effect of temperature on hydrogen metallization closely resembles that of the lower-pressure insulator-metal transitions in doped V2O3 alloys.

Hemley, R. J.; Mao, H. K.

1990-01-01

80

Improved hydrogen storage in the modified metal-organic frameworks by hydrogen spillover effect  

Microsoft Academic Search

In the present work, in order to enhance hydrogen storage capacity of metal-organic frameworks (MOFs) at room temperature, two ways are carried out for MOFs modification. One is a simple doping of metal-supported carbon catalyst with MOFs; the other is doping metal-supported carbon catalyst through a carbon bridge with MOFs. Pressure-composition (P-C) isotherms of these modified and unmodified samples are

Ying-Ya Liu; Ju-Lan Zeng; Jian Zhang; Fen Xu; Li-Xian Sun

2007-01-01

81

Molecular simulation of hydrogen diffusion in interpenetrated metal organic frameworks  

Microsoft Academic Search

In this work a combined molecular dynamics simulation and dynamically corrected transition-state theory (dcTST) study was performed to investigate the effect of interpenetration (catenation) on hydrogen diffusion in metal–organic frameworks (MOFs) as well as their relationships. The results on 10 isoreticular MOFs (IRMOFs) with and without interpenetration show that catenation can reduce hydrogen diffusivity by a factor of 2 to

Bei Liu; Qingyuan Yang; Chunyu Xue; Chongli Zhong; Berend Smit

2008-01-01

82

Pressure vessel construction for a metal oxide-hydrogen battery  

SciTech Connect

This patent describes a metal oxide-hydrogen battery. It comprises: an outer vessel, a battery cell disposed within the vessel, the vessel including a flexible inner liner of a material impervious to the passage of hydrogen gas, and an outer layer of fiber reinforced resin disposed in contact with the inner liner, a fitting disposed within an opening in a wall of the vessel and having an opening therethrough, and sealing means for sealing the inner liner to the fitting.

Jones, K.R.; Sindorf, J.F.

1990-05-08

83

Electronic excitations and metallization of dense solid hydrogen.  

PubMed

Theoretical calculations and an assessment of recent experimental results for dense solid hydrogen lead to a unique scenario for the metallization of hydrogen under pressure. The existence of layered structures based on graphene sheets gives rise to an electronic structure related to unique features found in graphene that are well studied in the carbon phase. The honeycombed layered structure for hydrogen at high density, first predicted in molecular calculations, produces a complex optical response. The metallization of hydrogen is very different from that originally proposed via a phase transition to a close-packed monoatomic structure, and different from simple metallization recently used to interpret recent experimental data. These different mechanisms for metallization have very different experimental signatures. We show that the shift of the main visible absorption edge does not constrain the point of band gap closure, in contrast with recent claims. This conclusion is confirmed by measured optical spectra, including spectra obtained to low photon energies in the infrared region for phases III and IV of hydrogen. PMID:23904476

Cohen, R E; Naumov, Ivan I; Hemley, Russell J

2013-08-20

84

Electronic excitations and metallization of dense solid hydrogen  

PubMed Central

Theoretical calculations and an assessment of recent experimental results for dense solid hydrogen lead to a unique scenario for the metallization of hydrogen under pressure. The existence of layered structures based on graphene sheets gives rise to an electronic structure related to unique features found in graphene that are well studied in the carbon phase. The honeycombed layered structure for hydrogen at high density, first predicted in molecular calculations, produces a complex optical response. The metallization of hydrogen is very different from that originally proposed via a phase transition to a close-packed monoatomic structure, and different from simple metallization recently used to interpret recent experimental data. These different mechanisms for metallization have very different experimental signatures. We show that the shift of the main visible absorption edge does not constrain the point of band gap closure, in contrast with recent claims. This conclusion is confirmed by measured optical spectra, including spectra obtained to low photon energies in the infrared region for phases III and IV of hydrogen. PMID:23904476

Cohen, R. E.; Naumov, Ivan I.; Hemley, Russell J.

2013-01-01

85

Hydrogen evolution from water through metal sulfide reactions  

NASA Astrophysics Data System (ADS)

Transition metal sulfides play an important catalytic role in many chemical reactions. In this work, we have conducted a careful computational study of the structures, electronic states, and reactivity of metal sulfide cluster anions M2SX- (M = Mo and W, X = 4-6) using density functional theory. Detailed structural analysis shows that these metal sulfide anions have ground state isomers with two bridging sulfide bonds, notably different in some cases from the corresponding oxides with the same stoichiometry. The chemical reactivity of these metal sulfide anions with water has also been carried out. After a thorough search on the reactive potential energy surface, we propose several competitive, energetically favorable, reaction pathways that lead to the evolution of hydrogen. Selectivity in the initial water addition and subsequent hydrogen migration are found to be the key steps in all the proposed reaction channels. Initial adsorption of water is most favored involving a terminal metal sulfur bond in Mo2S4- isomers whereas the most preferred orientation for water addition involves a bridging metal sulfur bond in the case of W2S4- and M2S5- isomers. In all the lowest energy H2 elimination steps, the interacting hydrogen atoms involve a metal hydride and a metal hydroxide (or thiol) group. We have also observed a higher energy reaction channel where the interacting hydrogen atoms in the H2 elimination step involve a thiol (-SH) and a hydroxyl (-OH) group. For all the reaction pathways, the Mo sulfide reactions involve a higher barrier than the corresponding W analogues. We observe for both metals that reactions of M2S4- and M2S5- clusters with water to liberate H2 are exothermic and involve modest free energy barriers. However, the reaction of water with M2S6- is highly endothermic with a considerable barrier due to saturation of the local bonding environment.

Saha, Arjun; Raghavachari, Krishnan

2013-11-01

86

Hydrogen evolution from water through metal sulfide reactions.  

PubMed

Transition metal sulfides play an important catalytic role in many chemical reactions. In this work, we have conducted a careful computational study of the structures, electronic states, and reactivity of metal sulfide cluster anions M2S(X)(-) (M = Mo and W, X = 4-6) using density functional theory. Detailed structural analysis shows that these metal sulfide anions have ground state isomers with two bridging sulfide bonds, notably different in some cases from the corresponding oxides with the same stoichiometry. The chemical reactivity of these metal sulfide anions with water has also been carried out. After a thorough search on the reactive potential energy surface, we propose several competitive, energetically favorable, reaction pathways that lead to the evolution of hydrogen. Selectivity in the initial water addition and subsequent hydrogen migration are found to be the key steps in all the proposed reaction channels. Initial adsorption of water is most favored involving a terminal metal sulfur bond in Mo2S4(-) isomers whereas the most preferred orientation for water addition involves a bridging metal sulfur bond in the case of W2S4(-) and M2S5(-) isomers. In all the lowest energy H2 elimination steps, the interacting hydrogen atoms involve a metal hydride and a metal hydroxide (or thiol) group. We have also observed a higher energy reaction channel where the interacting hydrogen atoms in the H2 elimination step involve a thiol (-SH) and a hydroxyl (-OH) group. For all the reaction pathways, the Mo sulfide reactions involve a higher barrier than the corresponding W analogues. We observe for both metals that reactions of M2S4(-) and M2S5(-) clusters with water to liberate H2 are exothermic and involve modest free energy barriers. However, the reaction of water with M2S6(-) is highly endothermic with a considerable barrier due to saturation of the local bonding environment. PMID:24289348

Saha, Arjun; Raghavachari, Krishnan

2013-11-28

87

Interaction of hydrogen with metal nitrides and imides.  

PubMed

The pursuit of a clean and healthy environment has stimulated much effort in the development of technologies for the utilization of hydrogen-based energy. A critical issue is the need for practical systems for hydrogen storage, a problem that remains unresolved after several decades of exploration. In this context, the possibility of storing hydrogen in advanced carbon materials has generated considerable interest. But confirmation and a mechanistic understanding of the hydrogen-storage capabilities of these materials still require much work. Our previously published work on hydrogen uptake by alkali-doped carbon nanotubes cannot be reproduced by others. It was realized by us and also demonstrated by Pinkerton et al. that most of the weight gain was due to moisture, which the alkali oxide picked up from the atmosphere. Here we describe a different material system, lithium nitride, which shows potential as a hydrogen storage medium. Lithium nitride is usually employed as an electrode, or as a starting material for the synthesis of binary or ternary nitrides. Using a variety of techniques, we demonstrate that this compound can also reversibly take up large amounts of hydrogen. Although the temperature required to release the hydrogen at usable pressures is too high for practical application of the present material, we suggest that more investigations are needed, as the metal-N-H system could prove to be a promising route to reversible hydrogen storage. PMID:12447436

Chen, Ping; Xiong, Zhitao; Luo, Jizhong; Lin, Jianyi; Tan, Kuang Lee

2002-11-21

88

Hydrogen storage by physisorption on Metal Organic Frameworks  

NASA Astrophysics Data System (ADS)

Cryo-adsorption systems based on materials with high specific surface areas have the main advantage that they can store and release hydrogen with fast kinetics and high reversibility over multiples cycles. Recently Metal Organic Frameworks (MOFs) have been proposed as promising adsorbents for hydrogen. These crystallographically well organized hybrid solids resulting from the three dimensional connection of inorganic clusters using organic linkers show the largest specific surface areas of all known crystalline solids. The determination of the relationships between physical properties (chemistry, structure, surface area ) of the MOFs and their hydrogen storage behavior is a key step in the characterization of these materials, if they are to be designed for hydrogen storage applications. Excess hydrogen sorption measurements for different MOFs will be presented. We show that maximum hydrogen uptake at high pressure and 77K does not always scale with the specific surface area. A linear correlation trend only apply within a class of specific materials and breaks down when the surface area measurement does not represent the surface sites that are available to H2. The influence of pore size and shape will also be discussed by comparing several MOFs with different structure types. The hydrogen adsorption and binding energy at low pressure are strongly dependent on the metal ions and the pore size.

Dailly, Anne

2008-03-01

89

Optical hydrogen sensors based on metal-hydrides  

NASA Astrophysics Data System (ADS)

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.

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

2012-06-01

90

Bridged transition-metal complexes and uses thereof for hydrogen separation, storage and hydrogenation  

DOEpatents

The present invention constitutes a class of organometallic complexes which reversibly react with hydrogen to form dihydrides and processes by which these compounds can be utilized. The class includes bimetallic complexes in which two cyclopentadienyl rings are bridged together and also separately [pi]-bonded to two transition metal atoms. The transition metals are believed to bond with the hydrogen in forming the dihydride. Transition metals such as Fe, Mn or Co may be employed in the complexes although Cr constitutes the preferred metal. A multiple number of ancillary ligands such as CO are bonded to the metal atoms in the complexes. Alkyl groups and the like may be substituted on the cyclopentadienyl rings. These organometallic compounds may be used in absorption/desorption systems and in facilitated transport membrane systems for storing and separating out H[sub 2] from mixed gas streams such as the producer gas from coal gasification processes. 3 figs.

Lilga, M.A.; Hallen, R.T.

1990-08-28

91

Bridged transition-metal complexes and uses thereof for hydrogen separation, storage and hydrogenation  

DOEpatents

The present invention constitutes a class of organometallic complexes which reversibly react with hydrogen to form dihydrides and processes by which these compounds can be utilized. The class includes bimetallic complexes in which two cyclopentadienyl rings are bridged together and also separately .pi.-bonded to two transition metal atoms. The transition metals are believed to bond with the hydrogen in forming the dihydride. Transition metals such as Fe, Mn or Co may be employed in the complexes although Cr constitutes the preferred metal. A multiple number of ancilliary ligands such as CO are bonded to the metal atoms in the complexes. Alkyl groups and the like may be substituted on the cyclopentadienyl rings. These organometallic compounds may be used in absorption/desorption systems and in facilitated transport membrane systems for storing and separating out H.sub.2 from mixed gas streams such as the produce gas from coal gasification processes.

Lilga, Michael A. (Richland, WA); Hallen, Richard T. (Richland, WA)

1990-01-01

92

Bridged transition-metal complexes and uses thereof for hydrogen separation, storage and hydrogenation  

DOEpatents

The present invention constitutes a class of organometallic complexes which reversibly react with hydrogen to form dihydrides and processes by which these compounds can be utilized. The class includes bimetallic complexes in which two cyclopentadienyl rings are bridged together and also separately [pi]-bonded to two transition metal atoms. The transition metals are believed to bond with the hydrogen in forming the dihydride. Transition metals such as Fe, Mn or Co may be employed in the complexes although Cr constitutes the preferred metal. A multiple number of ancillary ligands such as CO are bonded to the metal atoms in the complexes. Alkyl groups and the like may be substituted on the cyclopentadienyl rings. These organometallic compounds may be used in absorption/desorption systems and in facilitated transport membrane systems for storing and separating out H[sub 2] from mixed gas streams such as the product gas from coal gasification processes. 3 figures.

Lilga, M.A.; Hallen, R.T.

1991-10-15

93

Bridged transition-metal complexes and uses thereof for hydrogen separation, storage and hydrogenation  

DOEpatents

The present invention constitutes a class of organometallic complexes which reversibly react with hydrogen to form dihydrides and processes by which these compounds can be utilized. The class includes bimetallic complexes in which two cyclopentadienyl rings are bridged together and also separately .pi.-bonded to two transition metal atoms. The transition metals are believed to bond with the hydrogen in forming the dihydride. Transition metals such as Fe, Mn or Co may be employed in the complexes although Cr constitutes the preferred metal. A multiple number of ancilliary ligands such as CO are bonded to the metal atoms in the complexes. Alkyl groups and the like may be substituted on the cyclopentadienyl rings. These organometallic compounds may be used in absorption/desorption systems and in facilitated transport membrane systems for storing and separating out H.sub.2 from mixed gas streams such as the product gas from coal gasification processes.

Lilga, Michael A. (Richland, WA); Hallen, Richard T. (Richland, WA)

1991-01-01

94

Trace Metal Effect on Hydrogen Production Using C.acetobutylicum  

Microsoft Academic Search

This study was carried out to study the effect of trace metal addition for hydrogen production The results show that this bacterial need a selected nutrient with selected concentration. The optimum parameters for cultivation were at initial pH of 7.0 and temperature of 30°C. Trace metal addition to the new medium showed that only iron enhanced the H2 yield. The

Hisham Alshiyab; Mohd Sahaid Kalil; Aidil Abdul Hamid; Wan Mohtar Wan Yusoff

2008-01-01

95

Structural tailoring of hydrogen-bonded poly(acrylic acid)/poly(ethylene oxide) multilayer thin films for reduced gas permeability.  

PubMed

Hydrogen bonded poly(acrylic acid) (PAA)/poly(ethylene oxide) (PEO) layer-by-layer assemblies are highly elastomeric, but more permeable than ionically bonded thin films. In order to expand the use of hydrogen-bonded assemblies to applications that require a better gas barrier, the effect of assembling pH on the oxygen permeability of PAA/PEO multilayer thin films was investigated. Altering the assembling pH leads to significant changes in phase morphology and bonding. The amount of intermolecular hydrogen bonding between PAA and PEO is found to increase with increasing pH due to reduction of COOH dimers between PAA chains. This improved bonding leads to smaller PEO domains and lower gas permeability. Further increasing the pH beyond 2.75 results in higher oxygen permeability due to partial deprotonation of PAA. By setting the assembling pH at 2.75, the negative impacts of COOH dimer formation and PAA ionization on intermolecular hydrogen bonding can be minimized, leading to a 50% reduction in the oxygen permeability of the PAA/PEO thin film. A 20 bilayer coating reduces the oxygen transmission rate of a 1.58 mm natural rubber substrate by 20×. These unique nanocoatings provide the opportunity to impart a gas barrier to elastomeric substrates without altering their mechanical behavior. PMID:25519816

Xiang, Fangming; Ward, Sarah M; Givens, Tara M; Grunlan, Jaime C

2015-01-21

96

Composite hydrogen separation element and module  

DOEpatents

There are disclosed improvements in multicomponent composite metal membranes useful for the separation of hydrogen, the improvements comprising the provision of a flexible porous intermediate layer between a support layer and a nonporous hydrogen-permeable coating metal layer, and the provision of a textured coating metal layer.

Edlund, David J. (Redmond, OR)

1996-03-12

97

Composite hydrogen separation element and module  

DOEpatents

There are disclosed improvements in multicomponent composite metal membranes useful for the separation of hydrogen, the improvements comprising the provision of a flexible porous intermediate layer between a support layer and a nonporous hydrogen-permeable coating metal layer, and the provision of a textured coating metal layer. 15 figs.

Edlund, D.J.

1996-03-12

98

HYDROGEN EMBRITTLEMENT OF METALS: A PRIMER FOR THE FAILURE ANALYST  

SciTech Connect

Hydrogen reduces the service life of many metallic components. Such reductions may be manifested as blisters, as a decrease in fatigue resistance, as enhanced creep, as the precipitation of a hydride phase and, most commonly, as unexpected, macroscopically brittle failure. This unexpected, brittle fracture is commonly termed hydrogen embrittlement. Frequently, hydrogen embrittlement occurs after the component has been is service for a period of time and much of the resulting fracture surface is distinctly intergranular. Many failures, particularly of high strength steels, are attributed to hydrogen embrittlement simply because the failure analyst sees intergranular fracture in a component that served adequately for a significant period of time. Unfortunately, simply determining that a failure is due to hydrogen embrittlement or some other form of hydrogen induced damage is of no particular help to the customer unless that determination is coupled with recommendations that provide pathways to avoid such damage in future applications. This paper presents qualitative and phenomenological descriptions of the hydrogen damage processes and outlines several metallurgical recommendations that may help reduce the susceptibility of a particular component or system to the various forms of hydrogen damage.

Louthan, M

2008-01-31

99

The volume increase of fcc metals and alloys due to interstitial hydrogen over a wide range of hydrogen contents  

Microsoft Academic Search

Interstitial hydrogen contents and their associated volume increments have been determined for a variety of fcc metals and alloys. Using high pressure techniques, hydrogen contents approaching n = 1, where n = H-to-metal (atomic ratio), have been obtained. Despite electronic and initial volume differences amongst the fcc metallic matrices, all data fall onto a common relationship.

B. Baranowski; S. Majchrzak; T. B. Flanagan

1971-01-01

100

Using Hydrogen Balloons to Display Metal Ion Spectra  

ERIC Educational Resources Information Center

We have optimized a procedure for igniting hydrogen-filled balloons containing metal salts to obtain the brightest possible flash while minimizing the quantity of airborne combustion products. We report air quality measurements in a lecture hall immediately after the demonstration. While we recommend that this demonstration be done outdoors or in…

Maynard, James H.

2008-01-01

101

Hydrogen Storage on Metal-Doped Ordered Mesoporous Carbons  

E-print Network

Materials Advanced Materials #12;Group Members Ph.D.: P. Patil, D. Saha; P. Teli; K. Pingali; V. UpadhyayulaHydrogen Storage on Metal-Doped Ordered Mesoporous Carbons Shuguang Deng New Mexico State in Ordered Mesoporous Carbon Synthesized by Soft-Template Approach" J. Porous Media, 13, 39-50 (2010). 9

Johnson, Eric E.

102

Metallacarboranes: toward promising hydrogen storage metal organic frameworks.  

PubMed

Using first principles calculations, we show the high hydrogen storage capacity of metallacarboranes, where the transition metal (TM) atoms can bind up to 5 H(2)-molecules. The average binding energy of ?0.3 eV/H favorably lies within the reversible adsorption range. Among the first row TM atoms, Sc and Ti are found to be the optimum in maximizing the H(2) storage (?8 wt %) on the metallacarborane cluster. Being an integral part of the cage, TMs do not suffer from the aggregation problem, which has been the biggest hurdle for the success of TM-decorated graphitic materials for hydrogen storage. Furthermore, the presence of carbon atom in the cages permits linking the metallacarboranes to form metal organic frameworks, which are thus able to adsorb hydrogen via Kubas interaction, in addition to van der Waals physisorption. PMID:20860355

Singh, Abhishek K; Sadrzadeh, Arta; Yakobson, Boris I

2010-10-13

103

Hydrogen Internal Combustion Engine Two Wheeler with on-board Metal Hydride Storage  

E-print Network

Hydrogen Internal Combustion Engine Two Wheeler with on-board Metal Hydride Storage K. Sapru*, S, as a transition, the hydrogen internal combustion engine can lead the way to a hydrogen economy, allowing

104

Ultra-low percolation threshold in ferrite-metal cofired ceramics brings both high permeability and high permittivity  

NASA Astrophysics Data System (ADS)

High permeability and high permittivity are hard to be achieved simultaneously, either in single-phased materials or in composite materials, such as ferrite-ferroelectric ceramic composites and ferrite-metal percolative composites. In this work, ultra-low percolation threshold is achieved in NiZnCu ferrite-Ag cofired ceramics, which endows the composite with both high permeability and high permittivity by minimizing the negative effect of nonmagnetic conductive fillers on magnetic properties. The percolation threshold is controlled by the temperature matching between ferrite densification and Ag melting. A thin and long percolative net forms between large ferrite grains under a proper cofiring process, which brings a low percolation threshold of 1.21vol%, more than one order of magnitude lower than the theoretical value of 16vol%. Near the ultra-low threshold, the composite exhibits a high permeability of 585 and a high permittivity of 78.

Wang, Liang; Bai, Yang; Lu, Xuefei; Cao, Jiang-Li; Qiao, Li-Jie

2015-01-01

105

Ultra-low percolation threshold in ferrite-metal cofired ceramics brings both high permeability and high permittivity.  

PubMed

High permeability and high permittivity are hard to be achieved simultaneously, either in single-phased materials or in composite materials, such as ferrite-ferroelectric ceramic composites and ferrite-metal percolative composites. In this work, ultra-low percolation threshold is achieved in NiZnCu ferrite-Ag cofired ceramics, which endows the composite with both high permeability and high permittivity by minimizing the negative effect of nonmagnetic conductive fillers on magnetic properties. The percolation threshold is controlled by the temperature matching between ferrite densification and Ag melting. A thin and long percolative net forms between large ferrite grains under a proper cofiring process, which brings a low percolation threshold of 1.21vol%, more than one order of magnitude lower than the theoretical value of 16vol%. Near the ultra-low threshold, the composite exhibits a high permeability of 585 and a high permittivity of 78. PMID:25557935

Wang, Liang; Bai, Yang; Lu, Xuefei; Cao, Jiang-Li; Qiao, Li-Jie

2015-01-01

106

First-principles study of the hydrogen-metal system  

SciTech Connect

The ab initio pseudopotential method within the local-density-functional formalism with a plane-wave basis is implemented to study the properties of hydrogen in yttrium. With a soft pseudopotential scheme, satisfactory convergence is achieved with an energy cutoff of 30-40 Ry. A correction in the exchange-correlation functional is needed to handle the outer core contribution in this early transition metal. The calculated structural properties of bulk yttrium are in good agreement with experiments. In the solid solution phase of hydrogen in hexagonal close-packed yttrium ({alpha}-YH{sub x}, x < 0.5), the occupation of the tetrahedral site is found to be energetically favorable. The calculated vibrational frequency in a one-dimensional double-well potential along the c axis and the diffusion barrier from one tetrahedral site to the neighboring octahedral site are in excellent agreement. The pairing of hydrogen across a metal atom is energetically favorable, which is explained from the electronic structure of the system. The study of {beta}-YH{sub 2+z} is carried out with the metal atoms forming a face-centered cubic lattice and with 0 {<=} x {<=} 1. The total energy, electronic and structural properties, density of states (DOS), angular-momentum-decomposed DOS, and charge transfer are investigated by the supercell modeling method. Volume contraction with increasing x and the (420)-plane ordering of hydrogen are studied. Yttrium trihydride with the metal atoms in the hexagonal close-packed (HCP) structure is examined. The hexagonal YH{sub 3} with wave-like hydrogen displacements is energetically more stable than the cubic structure, and is consistent with the neutron diffraction data for YD{sub 3} and HoD{sub 3}. These hydrogen displacements are found to be Peierls-like distortions. The calculated final LDA band structure for YH{sub 3} yields a semimetal rather than a semiconductor. The existence of excitonic insulating ground state is speculated.

Wang, Yan

1993-12-31

107

The metallization and superconductivity of dense hydrogen sulfide  

SciTech Connect

Hydrogen sulfide (H{sub 2}S) is a prototype molecular system and a sister molecule of water (H{sub 2}O). The phase diagram of solid H{sub 2}S at high pressures remains largely unexplored arising from the challenges in dealing with the pressure-induced weakening of S–H bond and larger atomic core difference between H and S. Metallization is yet achieved for H{sub 2}O, but it was observed for H{sub 2}S above 96 GPa. However, the metallic structure of H{sub 2}S remains elusive, greatly impeding the understanding of its metallicity and the potential superconductivity. We have performed an extensive structural study on solid H{sub 2}S at pressure ranges of 10–200 GPa through an unbiased structure prediction method based on particle swarm optimization algorithm. Besides the findings of candidate structures for nonmetallic phases IV and V, we are able to establish stable metallic structures violating an earlier proposal of elemental decomposition into sulfur and hydrogen [R. Rousseau, M. Boero, M. Bernasconi, M. Parrinello, and K. Terakura, Phys. Rev. Lett. 85, 1254 (2000)]. Our study unravels a superconductive potential of metallic H{sub 2}S with an estimated maximal transition temperature of ?80 K at 160 GPa, higher than those predicted for most archetypal hydrogen-containing compounds (e.g., SiH{sub 4}, GeH{sub 4}, etc.)

Li, Yinwei, E-mail: yinwei-li@jsnu.edu.cn; Hao, Jian; Li, Yanling [School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou 221116 (China)] [School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou 221116 (China); Liu, Hanyu [Department of Physics and Engineering Physics, University of Saskatchewan, Saskatchewan S7N 5E2 (Canada)] [Department of Physics and Engineering Physics, University of Saskatchewan, Saskatchewan S7N 5E2 (Canada); Ma, Yanming, E-mail: mym@jlu.edu.cn [State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China)] [State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China)

2014-05-07

108

Hydrogen embrittlement susceptibility and permeability of two ultra-high strength steels  

Microsoft Academic Search

Slow displacement rate tensile tests were carried out in a saturated H2S solution to investigate the effect of hydrogen embrittlement on notched tensile strength (NTS) and fracture characteristics of two ultra-high strength steels (PH 13-8 Mo stainless steel and T-200 maraging steel). Hydrogen permeation properties were determined by an electrochemical permeation method. The results of permeation tests indicated that over-aged

L. W. Tsay; M. Y. Chi; Y. F. Wu; J. K. Wu; D.-Y. Lin

2006-01-01

109

The Interaction of Hydrogen with Simple and Noble Metals Surfaces  

NASA Astrophysics Data System (ADS)

The basic concepts of adsorption are illustrated by the investigation of a simple adsorbate (hydrogen) with the "simplest" metals (simple and noble metals). Theoretically tractable, these systems serve as an excellent test of our basic understanding of chemisorption. The interaction of atomic and molecular hydrogen with the surfaces of Mg(0001), Mg(1120), Li(110), K(110), Ag(110), and Ag(111) have been studied with a variety of experimental probes. In all cases, no evidence for H_2 associative or dissociative adsorption is observed at the substrate temperature investigated (>=q90 K). In the case of the simple metals below 150 K, atomic hydrogen is bound to the surfaces in a strongly chemisorbed state (hydride). For Mg and Li, the hydride is localized to the surface wherein the substrate electron density is lower than the bulk. Because of the low electron density, hydrogen is absorbed into the bulk of K at low temperatures and forms a bulk-hydride phase. However, these low-temperature phases are metastable. In the case of Mg, hydrogen moves into lower energy configuration bonding sites which are closer to or below the surface plane. However, the hydride characteristics are absent; the H atom is effectively screened because of the higher jellium density. In contrast, upon annealing, hydrogen is absorbed into the bulk of Li and K and phase separation occurs forming regions of clean metal and bulk hydride areas. The results are compared to theoretical studies; the propensity for absorption over adsorption is understood in terms of jellium-based models. In the case of silver, at 100 K, atomic hydrogen bonds in trigonal sites on both the (110) and (111) surfaces. As a function of H concentration, a sequence of lattice gas superstructures is observed; these phases are accompanied by small H-induced displacements of the substrate surface atoms. In the case of Ag(110), the low-temperature phase is metastable; upon annealing, hydrogen desorption from low energy states is accompanied by a surface reconstruction. Although silver is a noble metal, many of the H-induced properties are characteristic of similar H/transition systems.

Sprunger, Phillip T.

110

Noble-metal-free plasmonic photocatalyst: hydrogen doped semiconductors  

PubMed Central

The unique capacity of localized surface plasmon resonance (LSPR) offers a new opportunity to overcome the limited efficiency of semiconductor photocatalyst. Here we unravel that LSPR, which usually occurs in noble metal nanoparticles, can be realized by hydrogen doping in noble-metal-free semiconductor using TiO2 as a model photocatalyst. Moreover, its LSPR is located in infrared region, which supplements that of noble metal whose LSPR is generally in the visible region, making it possible to extend the light response of photocatalyst to infrared region. The near field enhancement is shown to be comparable with that of noble-metal nanoparticles, indicating that highly enhanced light absorption rate can be expected. The present work can provide a key guideline for the creation of highly efficient noble-metal-free plasmonic photocatalysts and have a much wider impact in infrared bioimaging and spectroscopy where infrared LSPR is essential. PMID:24496400

Ma, Xiangchao; Dai, Ying; Yu, Lin; Huang, Baibiao

2014-01-01

111

Metal-catalyzed asymmetric sulfoxidation, epoxidation and hydroxylation by hydrogen peroxide  

E-print Network

1 Metal-catalyzed asymmetric sulfoxidation, epoxidation and hydroxylation by hydrogen peroxide transition-metal complexes are limited when the oxidant is hydrogen peroxide. The two main difficulties of using hydrogen peroxide in the presence of transition metal complexes are the homolytic cleavage

Paris-Sud XI, Université de

112

Aromaticity, closed-shell effects, and metallization of hydrogen.  

PubMed

Conspectus Recent theoretical and experimental studies reveal that compressed molecular hydrogen at 200-350 GPa transforms to layered structures consisting of distorted graphene sheets. The discovery of chemical bonding motifs in these phases that are far from close-packed contrasts with the long-held view that hydrogen should form simple, symmetric, ambient alkali-metal-like structures at these pressures. Chemical bonding considerations indicate that the realization of such unexpected structures can be explained by consideration of simple low-dimensional model systems based on H6 rings and graphene-like monolayers. Both molecular quantum chemistry and solid-state physics approaches show that these model systems exhibit a special stability, associated with the completely filled set of bonding orbitals or valence bands. This closed-shell effect persists in the experimentally observed layered structures where it prevents the energy gap from closing, thus delaying the pressure-induced metallization. Metallization occurs upon further compression by destroying the closed shell electronic structure, which is mainly determined by the 1s electrons via lowering of the bonding bands stemming from the unoccupied atomic 2s and 2p orbitals. Because enhanced diamagnetic susceptibility is a fingerprint of aromaticity, magnetic measurements provide a potentially important tool for further characterization of compressed hydrogen. The results indicate that the properties of dense hydrogen are controlled by chemical bonding forces over a much broader range of conditions than previously considered. PMID:25369180

Naumov, Ivan I; Hemley, Russell J

2014-12-16

113

Nanoparticulate gellants for metallized gelled liquid hydrogen with aluminum  

NASA Technical Reports Server (NTRS)

Gelled liquid hydrogen was experimentally formulated using sol-gel technology. As a follow-on to work with cryogenic simulants, hydrogen was gelled with an alkoxide material: BTMSE. Initial results demonstrated that gellants with a specific surface area of 1000 m(exp 2)/g could be repeatably fabricated. Gelled hexane and metallized gelled hexane (with 13.8-wt% Al) were produced. Propellant settling testing was conducted for acceleration levels of 2 to 10 times normal gravity and a minimum gellant percentage was determined for stable gelled hexane and metalized gelled hexane. A cryogenic capillary rheometer was also designed, constructed, and used to determine the viscosity of gelled hydrogen. Small volumes of liquid hydrogen were gelled with a 7- to 8-wt% gellant level. The gelled H2 viscosity was 1.5 to 3.7 times that of liquid hydrogen: 0.048 to 0.116 mPa-s versus 0.03 mPa-s for liquid H2 (at 16 K and approximately 1 atm pressure).

Palaszewski, Bryan; Starkovich, John; Adams, Scott

1996-01-01

114

Investigation of heat and mass transfer process in metal hydride hydrogen storage reactors, suitable for a solar powered water pump system  

NASA Astrophysics Data System (ADS)

The paper analyzes heat and mass transfer process in metal hydride hydrogen storage systems as key element in the development of a solar powered pump system. Hydrogen storage and compression performance of the developed reactors are investigated according to the type of metal alloys, the metal hydride bed parameters and system operating conditions. To reach the desired goal, some metal hydride from groups AB5 and AB2 were synthesized and characterized using elements substitution for tailoring their properties: reversible hydrogen absorption capacity between the hydrogen absorption and desorption pressures at equilibrium at small temperature differences. For the designed hydrogen storage reactors, a new technical solution which combines the effective increase of the thermal conductivity of MH bed and good permeability to hydrogen gas circulation, was implemented and tested. The results permitted us to develop a heat engine with metal hydride, the main element of the functional model of a heat operated metal hydride based water pumping system using solar energy. This is a free energy system able to deliver water, at a convenience flow and pressure, in remote places without conventional energy access.

Coldea, I.; Popeneciu, G.; Lupu, D.; Misan, I.; Blanita, G.; Ardelean, O.

2012-02-01

115

Hydrogen evolution from water through metal sulfide reactions  

SciTech Connect

Transition metal sulfides play an important catalytic role in many chemical reactions. In this work, we have conducted a careful computational study of the structures, electronic states, and reactivity of metal sulfide cluster anions M{sub 2}S{sub X}{sup ?} (M = Mo and W, X = 4–6) using density functional theory. Detailed structural analysis shows that these metal sulfide anions have ground state isomers with two bridging sulfide bonds, notably different in some cases from the corresponding oxides with the same stoichiometry. The chemical reactivity of these metal sulfide anions with water has also been carried out. After a thorough search on the reactive potential energy surface, we propose several competitive, energetically favorable, reaction pathways that lead to the evolution of hydrogen. Selectivity in the initial water addition and subsequent hydrogen migration are found to be the key steps in all the proposed reaction channels. Initial adsorption of water is most favored involving a terminal metal sulfur bond in Mo{sub 2}S{sub 4}{sup ?} isomers whereas the most preferred orientation for water addition involves a bridging metal sulfur bond in the case of W{sub 2}S{sub 4}{sup ?} and M{sub 2}S{sub 5}{sup ?} isomers. In all the lowest energy H{sub 2} elimination steps, the interacting hydrogen atoms involve a metal hydride and a metal hydroxide (or thiol) group. We have also observed a higher energy reaction channel where the interacting hydrogen atoms in the H{sub 2} elimination step involve a thiol (–SH) and a hydroxyl (–OH) group. For all the reaction pathways, the Mo sulfide reactions involve a higher barrier than the corresponding W analogues. We observe for both metals that reactions of M{sub 2}S{sub 4}{sup ?} and M{sub 2}S{sub 5}{sup ?} clusters with water to liberate H{sub 2} are exothermic and involve modest free energy barriers. However, the reaction of water with M{sub 2}S{sub 6}{sup ?} is highly endothermic with a considerable barrier due to saturation of the local bonding environment.

Saha, Arjun; Raghavachari, Krishnan [Department of Chemistry, Indiana University, Bloomington, Indiana 47405 (United States)] [Department of Chemistry, Indiana University, Bloomington, Indiana 47405 (United States)

2013-11-28

116

Hydrogen and Materials: Influence of the Hydrogen Environment on the Metallic Materials Behavior  

SciTech Connect

The materials sensitivity to hydrogen is studied and measured in this work using the disk pressure testing, whose principle is the comparison of the rupture parameters obtained with metallic membranes tested similarly under helium and hydrogen. Such technique allows various studies and reveals parameters that remain not significant with less sensitive methods. This work presents an overview of numerous experimental results concerning the influence of various factors (material and gas composition, mechanical and heat treatments, type of microstructure...) on the hydrogen embrittlement of ferrous and nonferrous alloys. There are shown synergies between such factors, related to physical and metallurgical phenomena and we give some practical considerations, which can be useful for the evaluation of the safety offered by different materials in contact with hydrogen and for searching ways to improve their behavior.

Lamani, Emil [Polytechnic University of Tirana, square 'Neenee Tereza', Nr. 4, Tirana (Albania); Jouinot, Patrice [Supmeca-LISMMA, Laboratoire de Physique des Materiaux, 3 rue Fernand Hainaut, Saint Ouen (France)

2010-01-21

117

Functionalization of hydrogenated silicene with alkali and alkaline earth metals for efficient hydrogen storage.  

PubMed

First principles density functional theory has been employed to investigate the electronic structure along with the stability, bonding mechanism, band gap and charge transfer of metal functionalized hydrogenated silicene (SiH), or silicane, in order to envisage the hydrogen storage capacity. Various metal adatoms including Li, Na, K, Be, Mg and Ca have been doped on the most stable chair like configuration of silicane. The corresponding binding energies and charge transfer mechanism have been discussed from the perspective of H2 storage ability. The Li and Na metal adatoms have been found to be ideally suitable not only for their strong metal to substrate binding and uniform distribution over the substrate but also for their high capacity for storage of hydrogen. The stability of both Li and Na functionalized SiH has also been confirmed by MD simulations. It was found that both Li(+) and Na(+) adsorbed four H2 molecules attaining reasonably high storage capacities of 6.30 wt% and 5.40 wt% respectively with average adsorption energies lying within the range suitable for practical H2 storage applications, in contrast with alkaline earth metals. PMID:24091878

Hussain, Tanveer; Kaewmaraya, Thanayut; Chakraborty, Sudip; Ahuja, Rajeev

2013-11-21

118

Hot Hydrogen Testing of Refractory Metals and Ceramics  

NASA Technical Reports Server (NTRS)

The objective of this investigation is to develop a technique with which refractory metal carbide samples can be exposed to hydrogen containing gases at high temperatures, and to use various microstructural and analytical techniques to determine the chemical and rate processes involved in hydrogen degradation in these materials. Five types of carbides were examined including WC, NbC, HfC, ZrC, and TaC. The ceramics were purchased and were all monolithic in nature. The temperature range investigated was from 850 to 1600 C with a hydrogen pressure of one atmosphere. Control experiments, in vacuum, were also conducted for comparison so that the net effects due to hydrogen could be isolated. The samples were analyzed prior to and after exposure. Gas samples were collected in selected experiments and analyzed using gas chromography. Characterization of the resulting microstructure after exposure to hydrogen was conducted using optical microscopy, x-ray diffraction, scanning electron microscopy, and weight change. The ceramics were purchased and were all monolithic in nature. It was found that all samples lost weight after exposure, both in hydrogen and vacuum. Results from the microstructure analyses show that the degradation processes are different among the five types of ceramics involved. In addition, the apparent activation energy for the degradation process is a function of temperature even within the same material. This indicates that there are more than one mechanism involved in each material, and that the mechanisms are temperature dependent.

Zee, Ralph; Chin, Bryan; Cohron, Jon

1993-01-01

119

Atomic interactions and phase transition in hydrogen metal systems  

SciTech Connect

The statistical mechanical behavior of H in pure metals and metal alloys is investigated using elasticity theory and lattice-gas models. The interactions between H atoms are separated into elastic and electronic contributions, and only the elastic contributions are evaluated. Three studies are reported: trapping of H by interstitial and substitutional impurities in bbc metals; modeling of H in impure metals; and modeling of H in concentration metal hydrides. The elastic interactions between H and interstitial and substitutional impurities in bbc metals are calculated using the method of lattice statics. Comparison with experimentally-measured trapping energies indicates that trapping by interstitial impurities is due solely to elastic energy, whereas both elastic and electronic interactions contribute to trapping by substitutional impurities. To include the effect of substitutional trapping on the phase transitions of H in metal alloys, the random-field lattice-gas model is developed. Interactions between H atoms are determined using the effective metal atom approximation. Hydrogen-impurity interactions are treated as a random field, in analogy with the random-field Ising model. Phase diagrams of the Nb/sub .95/Mo/sub .05/-H and Nb/sub .85/Mo/sub .15/-H systems are calculated by Monte Carlo simulation using the random-field model. The model gives qualitatively correct predictions of the phase behavior when the random field is included.

Shirley, A.I.

1985-01-01

120

Thermal method for fabricating a hydrogen separation membrane on a porous substrate  

DOEpatents

A thermal method of making a hydrogen permeable composition is disclosed. A mixture of metal oxide powder and ceramic oxide powder and optionally a pore former is formed and pressed to form an article. The article is dried at elevated temperatures and then sintered in a reducing atmosphere to provide a dense hydrogen permeable portion near the surface of the sintered mixture. The dense hydrogen permeable portion has a higher initial concentration of metal than the remainder of the sintered mixture and is present in the range of from about 20 to about 80 percent by volume of the dense hydrogen permeable portion.

Song, Sun-Ju (Orland Park, IL); Lee, Tae H. (Naperville, IL); Chen, Ling (Woodridge, IL); Dorris, Stephen E. (LaGrange Park, IL); Balachandran, Uthamalingam (Hinsdale, IL)

2009-10-20

121

Metal-free transfer hydrogenation of olefins via dehydrocoupling catalysis  

PubMed Central

A major advance in main-group chemistry in recent years has been the emergence of the reactivity of main-group species that mimics that of transition metal complexes. In this report, the Lewis acidic phosphonium salt [(C6F5)3PF][B(C6F5)4] 1 is shown to catalyze the dehydrocoupling of silanes with amines, thiols, phenols, and carboxylic acids to form the Si-E bond (E = N, S, O) with the liberation of H2 (21 examples). This catalysis, when performed in the presence of a series of olefins, yields the concurrent formation of the products of dehydrocoupling and transfer hydrogenation of the olefin (30 examples). This reactivity provides a strategy for metal-free catalysis of olefin hydrogenations. The mechanisms for both catalytic reactions are proposed and supported by experiment and density functional theory calculations. PMID:25002489

Pérez, Manuel; Caputo, Christopher B.; Dobrovetsky, Roman; Stephan, Douglas W.

2014-01-01

122

CO2 hydrogenation on a metal hydride surface.  

PubMed

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

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

2012-04-28

123

A van der Waals density functional theory comparison of metal decorated graphene systems for hydrogen adsorption  

NASA Astrophysics Data System (ADS)

Previous Density Functional Theory (DFT) studies on metal decorated graphene generally use local density approximation (LDA) or generalized gradient approximation (GGA) functionals which can cause inaccuracies in hydrogen binding energies as they neglect van der Waals (vdW) interactions and are difficult to compare due to their widely varying simulation parameters. We investigated the hydrogen binding ability of several metals with a consistent set of simulations using the GGA functional and incorporated vdW forces through the vdW-DF2 functional. Metal adatom anchoring on graphene and hydrogen adsorption ability for both single and double sided decoration were studied for eight metals (Al, Li, Na, Ca, Cu, Ni, Pd, and Pt). It was found that the vdW correction can have a significant impact on both metal and hydrogen binding energies. The vdW-DF2 functional led to stronger metal adatom and hydrogen binding for light metals in comparison to GGA results, while heavier transition metals displayed the opposite behaviour but still produced stronger hydrogen binding energies than light metals. Nickel was found to be the best balance between hydrogen binding ability for reversible storage and low weight. The effects on hydrogen binding energy and maximum achievable hydrogen gravimetric density were analyzed for Ni-graphene systems with varying metal coverage. Lower metal coverage was found to improve hydrogen binding but decrease hydrogen gravimetric density. The highest achieved Ni-graphene system gravimetric density was 6.12 wt. %.

Wong, Janet; Yadav, Shwetank; Tam, Jasmine; Veer Singh, Chandra

2014-06-01

124

Molecular Hydrogen Interactions Within Metal-Organic Frameworks  

NASA Astrophysics Data System (ADS)

There is much interest in understanding the details of molecular hydrogen physisorption within highly porous materials that could be used for hydrogen storage applications. Unfortunately, the structures of the most promising materials are too complex for ab inito calculations and DFT models are notoriously unreliable for weak interactions. A new approach based on so-called van der Waals DFT has been proposed for explaining the behavior of molecular hydrogen within metal-organic frameworks.1 In this talk we will present IR spectra of adsorbed hydrogen within a series of isostructural MOFs containing Mg2+ and various first-row transition metal cations. The data clearly show that H2 binds first at an open metal site, with a large vibrational redshift that correlates with the magnitude of the site binding energy. These spectra show minimal effects due to H2\\cdot\\cdotCdotH2 interactions and are significantly different from the recent findings of the Chabal group.1 After collecting spectra over a wide range of temperature and H2 pressure, we could only reproduce their experimental observations by exposing samples to moist air, which is well-known to cause occupation of the open metal sites by water. This calls into question the appropriateness of the van der Waals DFT models that were used to support their interpretations.1 We are hopeful that the spectra we present will inspire improved parametrization of such advanced computational models, or prompt the development of superior ones. 1. Nijjem et al., J. Am. Chem. Soc. 132, 14834 (2010).

Fitzgerald, S.; Pierce, C.; Schloss, J.; Thompson, B.; Rowsell, J.

2011-06-01

125

Silane plus molecular hydrogen as a possible pathway to metallic hydrogen  

PubMed Central

The high-pressure behavior of silane, SiH4, plus molecular hydrogen was investigated using a structural search method and ab initio molecular dynamics to predict the structures and examine the physical origin of the pressure-induced drop in hydrogen intramolecular vibrational (vibron) frequencies. A structural distortion is predicted at 15 GPa from a slightly strained fcc cell to a rhombohedral cell that involves a small volume change. The predicted equation of state and the pressure-induced drop in the hydrogen vibron frequencies reproduces well the experimental data (Strobel TA, Somayazulu M, Hemley RJ (2009) Phys Rev Lett 103:065701). The bond weakening in H2 is induced by intermolecular interactions between the H2 and SiH4 molecules. A significant feature of the high-pressure structures of SiH4(H2)2 is the dynamical behavior of the H2 molecules. It is found that H2 molecules are rotating in this pressure range whereas the SiH4 molecules remain rigid. The detailed nature of the interactions of molecular hydrogen with SiH4 in SiH4(H2)2 is therefore strongly influenced by the dynamical behavior of the H2 molecules in the high-pressure structure. The phase with the calculated structure is predicted to become metallic near 120 GPa, which is significantly lower than the currently suggested pressure for metallization of bulk molecular hydrogen. PMID:21078957

Yao, Yansun; Klug, Dennis D.

2010-01-01

126

Air-stable magnesium nanocomposites provide rapid and high-capacity hydrogen storage without using heavy-metal catalysts  

NASA Astrophysics Data System (ADS)

Hydrogen is a promising alternative energy carrier that can potentially facilitate the transition from fossil fuels to sources of clean energy because of its prominent advantages such as high energy density (142?MJ?kg-1 ref. 1), great variety of potential sources (for example water, biomass, organic matter), light weight, and low environmental impact (water is the sole combustion product). However, there remains a challenge to produce a material capable of simultaneously optimizing two conflicting criteria—absorbing hydrogen strongly enough to form a stable thermodynamic state, but weakly enough to release it on-demand with a small temperature rise. Many materials under development, including metal-organic frameworks, nanoporous polymers, and other carbon-based materials, physisorb only a small amount of hydrogen (typically 1-2?wt%) at room temperature. Metal hydrides were traditionally thought to be unsuitable materials because of their high bond formation enthalpies (for example MgH2 has a ?Hf˜75?kJ?mol-1), thus requiring unacceptably high release temperatures resulting in low energy efficiency. However, recent theoretical calculations and metal-catalysed thin-film studies have shown that microstructuring of these materials can enhance the kinetics by decreasing diffusion path lengths for hydrogen and decreasing the required thickness of the poorly permeable hydride layer that forms during absorption. Here, we report the synthesis of an air-stable composite material that consists of metallic Mg nanocrystals (NCs) in a gas-barrier polymer matrix that enables both the storage of a high density of hydrogen (up to 6?wt% of Mg, 4?wt% for the composite) and rapid kinetics (loading in <30?min at 200?°C). Moreover, nanostructuring of the Mg provides rapid storage kinetics without using expensive heavy-metal catalysts.

Jeon, Ki-Joon; Moon, Hoi Ri; Ruminski, Anne M.; Jiang, Bin; Kisielowski, Christian; Bardhan, Rizia; Urban, Jeffrey J.

2011-04-01

127

Air-stable magnesium nanocomposites provide rapid and high-capacity hydrogen storage without using heavy-metal catalysts.  

PubMed

Hydrogen is a promising alternative energy carrier that can potentially facilitate the transition from fossil fuels to sources of clean energy because of its prominent advantages such as high energy density (142 MJ kg(-1); ref. 1), great variety of potential sources (for example water, biomass, organic matter), light weight, and low environmental impact (water is the sole combustion product). However, there remains a challenge to produce a material capable of simultaneously optimizing two conflicting criteria--absorbing hydrogen strongly enough to form a stable thermodynamic state, but weakly enough to release it on-demand with a small temperature rise. Many materials under development, including metal-organic frameworks, nanoporous polymers, and other carbon-based materials, physisorb only a small amount of hydrogen (typically 1-2 wt%) at room temperature. Metal hydrides were traditionally thought to be unsuitable materials because of their high bond formation enthalpies (for example MgH(2) has a ?Hf~75 kJ mol(-1)), thus requiring unacceptably high release temperatures resulting in low energy efficiency. However, recent theoretical calculations and metal-catalysed thin-film studies have shown that microstructuring of these materials can enhance the kinetics by decreasing diffusion path lengths for hydrogen and decreasing the required thickness of the poorly permeable hydride layer that forms during absorption. Here, we report the synthesis of an air-stable composite material that consists of metallic Mg nanocrystals (NCs) in a gas-barrier polymer matrix that enables both the storage of a high density of hydrogen (up to 6 wt% of Mg, 4 wt% for the composite) and rapid kinetics (loading in <30 min at 200 °C). Moreover, nanostructuring of the Mg provides rapid storage kinetics without using expensive heavy-metal catalysts. PMID:21399630

Jeon, Ki-Joon; Moon, Hoi Ri; Ruminski, Anne M; Jiang, Bin; Kisielowski, Christian; Bardhan, Rizia; Urban, Jeffrey J

2011-04-01

128

Effects of hydrogen adsorption on single-wall carbon nanotubes: Metallic hydrogen decoration O. Gulseren,1,2  

E-print Network

Effects of hydrogen adsorption on single-wall carbon nanotubes: Metallic hydrogen decoration O. Gu¨lseren,1,2 T. Yildirim,1 and S. Ciraci3 1 NIST Center for Neutron Research, National Institute of Standards of carbon nanotubes undergo dramatic changes with hydrogen chemisorption from first principle calculations

Yildirim, Taner

129

Metal dependent catalytic hydrogenation of nitroarenes over water-soluble glutathione capped metal nanoparticles.  

PubMed

The water soluble glutathione capped metal nanoparticles (M-GS, where M=Pd, Pt, Au and Ag; GS=glutathione) with size 2.4±0.2nm were synthesized by borohydride reduction of metal ions in the presence of glutathione as capping ligand and used as catalyst for the hydrogenation of nitroaniline in aqueous phase. The rate of catalytic hydrogenation was dependent on metal type and the trend of catalytic activity over these M-GS nanoparticles was found to be Pd-GS (kapp=0.0227 (±3×10(-4)))s(-1)?Pt-GS (kapp=0.0043 (±1×10(-4)))s(-1)>Au-GS (kapp=0.0015 (±0.2×10(-4)))s(-1)>Ag-GS (kapp=0.0008 (±0.2×10(-4)))s(-1). The similar trend of catalytic activity was found for the hydrogenation of nitrobenzene. Our experimental results, along taking into account the theoretical calculations done by other research groups, suggest that the observed catalytic activity trend is attributed to the "different rates of H2 molecule adsorption and dissociation" on the M-GS nanoparticles. The "high rate of H2 molecule adsorption" and "highly oxidized surface" make Pd-GS nanoparticles an ideal candidate for the rapid hydrogenation. On the basis of our experimental results, we proposed that small gaps between less densely packed branched thiol "glutathione molecules" provide the access to metal nanoparticle surface for the hydrogenation reaction. PMID:25485808

Sharma, Sachil

2015-03-01

130

The solubility of hydrogen and deuterium in alloyed, unalloyed and impure plutonium metal  

SciTech Connect

Hydrogen is exothermically absorbed in many transition metals, all rare earths and the actinides. The hydrogen gas adsorbs, dissociates and diffuses into these metals as atomic hydrogen. Absorbed hydrogen is generally detrimental to Pu, altering its properties and greatly enhancing corrosion. Measuring the heat of solution of hydrogen in Pu and its alloys provides significant insight into the thermodynamics driving these changes. Hydrogen is present in all Pu metal unless great care is taken to avoid it. Heats of solution and formation are provided along with evidence for spinodal decomposition.

Richmond, Scott [Los Alamos National Laboratory; Bridgewater, Jon S [Los Alamos National Laboratory; Ward, John W [Los Alamos National Laboratory; Allen, Thomas H [Los Alamos National Laboratory

2010-01-01

131

Hydrogen and helium entrapment in flowing liquid metal plasma-facing surfaces  

E-print Network

Hydrogen and helium entrapment in flowing liquid metal plasma-facing surfaces Ahmed Hassanein the PFC surface (helium and hydrogen isotopes) while accommodating high heat loads. To study this problem. Hydrogen isotope (DT) particles are likely be trapped in the liquid metal surface (e.g., lithium) due

Harilal, S. S.

132

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

DOEpatents

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

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

2008-06-10

133

Hydrogen-induced reconstruction of transition metal surfaces  

NASA Astrophysics Data System (ADS)

This study compares the results of a number of recent papers on hydrogen adsorption on Rh(110), Rh(311) and Fe(211) as well as on Ni(111) and Fe(110) surfaces. It particularly deals with the structural aspect of these low energy electron diffraction (LEED) investigations and correlates them, if available, with respective thermodesorption data. Upon dissociative adsorption by a non activated process hydrogen induces local displacements of the atoms about the adsorption sites. With increasing coverage these displacements order to form a sequence of weakly reconstructed phases and gradually lift the surface layer relaxation of the formerly clean surface. Along close packed rows of metal surface atoms hydrogen atoms tend to occupy threefold coordinated adsorption sites which, in turn, arrange in single or double chains. The coverage dependent periodicity of these adlayer structure elements together with the respective shift buckling of the substrate surface generates the observed superstructures. Since not only open but also close packed surfaces show this weak (and sometimes strong) reconstruction upon hydrogen adsorption it should be generally considered in all adsorption systems.

Müller, Klaus

1993-04-01

134

Phase separation of metallic hydrogen-helium alloys  

NASA Technical Reports Server (NTRS)

Calculations are presented for the thermodynamic functions and phase separation boundaries of solid metallic hydrogen helium alloys at temperatures between 0 K and 19,000 K and at pressures between 15 and 90 megabars. Expressions for the band structure energy of a randomly disordered alloy (including third order in the electron ion interaction) are derived and evaluated. Short and long range order are included by the quasi-chemical method, and lattice dynamics in the virtual crystal harmonic approximation. We conclude that at temperatures below 4,000 K there is complete phase separation of hydrogen helium alloys, and that a miscibility gap remains at the highest temperatures and pressures considered. The relevance of these results to models of the deep interior of Jupiter is briefly discussed.

Straus, D. M.; Ashcroft, N. W.; Beck, H.

1976-01-01

135

Capture of liquid hydrogen boiloff with metal hydride absorbers  

NASA Technical Reports Server (NTRS)

A procedure which uses metal hydrides to capture some of this low pressure (,1 psig) hydrogen for subsequent reliquefaction is described. Of the five normally occurring sources of boil-off vapor the stream associated with the off-loading of liquid tankers during dewar refill was identified as the most cost effective and readily recoverable. The design, fabrication and testing of a proof-of-concept capture device, operating at a rate that is commensurate with the evolution of vapor by the target stream, is described. Liberation of the captured hydrogen gas at pressure .15 psig at normal temperatures (typical liquefier compressor suction pressure) are also demonstrated. A payback time of less than three years is projected.

Rosso, M. J.; Golben, P. M.

1984-01-01

136

Microscopic characterization of metal-carbon-hydrogen composites (metal = Li, Mg)  

NASA Astrophysics Data System (ADS)

Li-C-H system, which can store about 5.0 mass% of rechargeable H2, has been reported as a promising hydrogen storage system by Ichikawa et al. [Appl. Phys. Lett. 86, 241914 (2005); Mater. Trans. 46, 1757 (2005)]. This system was investigated from the thermodynamic and structural viewpoints. However, hydrogen absorption/desorption mechanism and the state of hydrogen atoms absorbed in the composite have not been clarified yet. In order to find new or better hydrogen storage system, graphite powder and nano-structural graphite ball-milled under H2 and Ar atmosphere were prepared and milled with Li and Mg under Ar atmosphere in this study. Microstructural analysis for those samples by transmission electron microscope revealed that LiC6 and/or LiC12 were formed in Li-C-H system. On the other hand, MgC2 was found in Mg-C-H system ball-milled under H2 atmosphere, but not in the system ball-milled under Ar atmosphere. These results indicated that nano-structure in composites of nano-structural graphite is different from that of alkali (-earth) metal. For these reasons, metal-C-H system can be recognized to be a new family of hydrogen storage materials.

Isobe, Shigehito; Yamada, Sumito; Wang, Yongming; Hashimoto, Naoyuki; Ohnuki, Somei; Miyaoka, Hiroki; Ichikawa, Takayuki; Kojima, Yoshitsugu

2013-09-01

137

Metal-Hydrogen Phase Diagrams in the Vicinity of Melting Temperatures  

SciTech Connect

Hydrogen-metal interaction phenomena belong to the most exciting challenges of today's physical metallurgy and physics of solids due to the uncommon behavior of hydrogen in condensed media and to the need for understanding hydrogen's strong negative impact on properties of some high-strength steels and.alloys. The paper cites and summarizes research data on fundamental thermodynamic characteristics of hydrogen in some metals that absorb it endothermally at elevated temperatures. For a number of metal-hydrogen systems, information on some phase diagrams previously not available to the English-speaking scientific community is presented.

Shapovalov, V.I.

1999-01-06

138

High hydrogen-adsorption-rate material based on graphane decorated with alkali metals  

NASA Astrophysics Data System (ADS)

The graphane with chemically bonded alkali metals (Li, Na, K) was considered as potential material for hydrogen storage. The ab initio calculations show that such material can adsorb as many as four hydrogen molecules per Li, Na, and K metal atom. These values correspond to 12.20, 10.33, and 8.56 wt% of hydrogen, respectively, and exceed the DOE requirements. The thermodynamic analysis shows that Li-graphane complex is the most promising for hydrogen storage with ability to adsorb three hydrogen molecules per metal atom at 300 K and pressure in the range of 5-250 atm.

Antipina, Liubov Yu.; Avramov, Pavel V.; Sakai, Seiji; Naramoto, Hiroshi; Ohtomo, Manabu; Entani, Shiro; Matsumoto, Yoshihiro; Sorokin, Pavel B.

2012-08-01

139

Hydrogen transport through oxide metal surface under atom and ion irradiation  

NASA Astrophysics Data System (ADS)

Both the latest and earlier achieved results on gas exchange processes on metal surfaces (including stainless steel, titanium, zirconium, tungsten with deposited aluminum oxide coating) under hydrogen atom or plasma irradiation with occasional oxygen impurity are presented in the paper. Mechanisms and regularities of these processes are discussed. It is demonstrated that surface oxide layer properties as a diffusion barrier strongly depend on external influence on the surface. In particular, it is revealed that low energy hydrogen ion irradiation could slow down hydrogen desorption from metals. Hydrogen atom or ion irradiation combined with simultaneous oxygen admixture accelerates hydrogen desorption from metals.

Begrambekov, L.; Dvoychenkova, O.; Evsin, A.; Kaplevsky, A.; Sadovskiy, Ya; Schitov, N.; Vergasov, S.; Yurkov, D.

2014-11-01

140

The possibility for superconductor fusion in metallic hydrogen  

NASA Astrophysics Data System (ADS)

Hydrogen varies its stable state in accordance with its temperature and density. Though molecular gas is stable in the environment, the monatomic state is stable in high density ranges more than about 1g/cc. Such dense hydrogen has many aspects never seen in the molecular state. For example, in the range over about 108K temperature and over 103g/cc density, great efforts are taken to realize Inertial Confinement Fusion (ICF). Additionally, in the range of temperature lower than about 105K in temperature and of density more than 104g/cc in density, pycno nuclear fusion is supposed to be occurred. We have derived the expression for the Debye screening length of inter ionic potential and investigated nuclear reaction rates in the superconductive solid metallic hydrogen. It is revealed that the screening length is shortened by correlated electron pairs follow the Bose-Einstein distribution in the superconductive state. The bosonization increases the number of the lower energy states of the electrons to increase the screening effects on the potential with decreases in the temperature, resulting in the significant enhancement of the nuclear reaction rates by more than 10 orders of magnitude.

Shibata, K.; Kodama, R.

2008-05-01

141

The effect of tensile stress on hydrogen diffusion in metal alloys  

NASA Technical Reports Server (NTRS)

The effect of tensile stress on hydrogen diffusion has been determined for Type 303 stainless steel, A286 CRES, and Waspaloy and IN100 nickel-base alloys. It was found that hydrogen diffusion coefficients are not significantly affected by stress, while the hydrogen permeabilities are greatly affected in Type 303 stainless steel and A286 CRES (iron-based alloys), but are affected little in Waspaloy (nickel-base) and not affected in all in IN100 (nickel base). These observations might be taken as an indication that hydrogen permeabilities are affected by stress in iron-based alloys, but only slightly affected in nickel-based alloys. However, it is too early to make such a generalization based on the study of only these four alloys.

Danford, M. D.

1992-01-01

142

Theory of catalytic dissociation of hydrogen atoms on a metal surface  

SciTech Connect

The model of hydrogen atom ionization near a metal surface is discussed on the basis of a comparison between the metal work function and the atom ionization energy. In the theoretical calculation, it is shown that the hydrogen atom ionization energy decreases when the atom approaches the metal surface. The ionization energy vanishes when the distance between proton and the metal surface is somewhat less than the Bohr radius.

Konstantinov, O. V., E-mail: O.Konst@mail.ioffe.ru; Dymnikov, V. D.; Mittsev, M. A. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)

2008-08-15

143

Hydrogen Sensors Using Nitride-Based Semiconductor Diodes: The Role of Metal/Semiconductor Interfaces  

PubMed Central

In this paper, I review my recent results in investigating hydrogen sensors using nitride-based semiconductor diodes, focusing on the interaction mechanism of hydrogen with the devices. Firstly, effects of interfacial modification in the devices on hydrogen detection sensitivity are discussed. Surface defects of GaN under Schottky electrodes do not play a critical role in hydrogen sensing characteristics. However, dielectric layers inserted in metal/semiconductor interfaces are found to cause dramatic changes in hydrogen sensing performance, implying that chemical selectivity to hydrogen could be realized. The capacitance-voltage (C–V) characteristics reveal that the work function change in the Schottky metal is not responsible mechanism for hydrogen sensitivity. The interface between the metal and the semiconductor plays a critical role in the interaction of hydrogen with semiconductor devises. Secondly, low-frequency C–V characterization is employed to investigate the interaction mechanism of hydrogen with diodes. As a result, it is suggested that the formation of a metal/semiconductor interfacial polarization could be attributed to hydrogen-related dipoles. In addition, using low-frequency C–V characterization leads to clear detection of 100 ppm hydrogen even at room temperature where it is hard to detect hydrogen by using conventional current-voltage (I–V) characterization, suggesting that low-frequency C–V method would be effective in detecting very low hydrogen concentrations. PMID:22346597

Irokawa, Yoshihiro

2011-01-01

144

The thermal phase of fast proton equilibration in metals: hydrogen atom diffusion  

Microsoft Academic Search

A fast proton passing through a metal slows down and captures an electron to form a hydrogen atom. Subsequent equilibration of the spatial location of the hydrogen atom proceeds by diffusion amongst interstitial sites in the crystal lattice of the metal. The diffusion coefficient is a strong function of both temperature and the isotopic mass of the H-atom. Using a

James K. Baird; Erik M. Schwartz

1995-01-01

145

Do weak magnetic fields prevent hydrogen from accreting onto metal-line white dwarf stars?  

Microsoft Academic Search

The widely accepted assumption is that metals detected in the spectra of a few cool helium-rich white dwarfs cannot be of primordial origin and therefore must be accreted from the interstellar medium. However, the observed abundances of hydrogen are much too low to be compatible with the high accretion rates inferred from metal accretion. Hydrogen accretion is therefore suppressed compared

Susanne Friedrich; Stefan Jordan; Detlev Koester

2004-01-01

146

A molecular dynamics study of hydrogen-atom diffusion in fcc-metals  

NASA Astrophysics Data System (ADS)

Using molecular dynamics, the characteristics of over-barrier hydrogen diffusion (specifically, activation energy and pre-exponential factor in the Arrhenius equation) in fcc-metals Pd, Ag, and Al are calculated. It is shown that the prevailing mechanism of the over-barrier hydrogen diffusion in fcc-metals consists in successive crossing of octahedral and tetrahedral spheres.

Kulabukhova, N. A.; Poletaev, G. M.; Starostenkov, M. D.; Kulagina, V. V.; Potekaev, A. I.

2012-05-01

147

Method and Apparatus for the Detection of Hydrogen Using a Metal Alloy  

NASA Technical Reports Server (NTRS)

A hydrogen sensitive metal alloy contains palladium and titanium to provide a larger change in electrical resistance when exposed to the presence of hydrogen. The alloy is deposited on a substrate and a thin film and connected across electrical circuitry to provide a sensor device that can be used for improved sensitivity and accuracy of hydrogen detection.

Hunter, Gary W. (Inventor)

1997-01-01

148

An electrochemical method for determining hydrogen concentrations in metals and some applications  

NASA Technical Reports Server (NTRS)

An electrochemical method was developed for the determination of hydrogen in metals using the EG&G-PARC Model 350A Corrosion Measurement Console. The method was applied to hydrogen uptake, both during electrolysis and electroplating, and to studies of hydrogen elimination and the effect of heat treatment on elimination times. Results from these studies are presented.

Danford, M. D.

1983-01-01

149

Theoretical Limits of Hydrogen Storage in Metal-Organic Frameworks: Opportunities and Trade-Offs  

E-print Network

Theoretical Limits of Hydrogen Storage in Metal-Organic Frameworks: Opportunities and Trade predict the hydrogen storage properties of these compounds. Approximately 20 000 candidate compounds were excess H2 uptake and surface area, we predict the theoretical total hydrogen storage capacity

Cafarella, Michael J.

150

Role of hydrogen in the processes of deformation and failure of metals  

Microsoft Academic Search

Two hypotheses are proposed which make it possible to analyze separately the effect of hydrogen on the plastic deformation and the fracture of metals. In accordance with one hypothesis, hydrogen reduces the width of dislocations and increases the Peierls-Nabarro forces by increasing the degree of localization of valence electrons. The other hypothesis states that r- and s-type adsorption of hydrogen

S. I. Mikitishin

1984-01-01

151

Transport of hydrogen in metals with occupancy dependent trap energies  

SciTech Connect

Common diffusion trapping models for modeling hydrogen transport in metals are limited to traps with single de-trapping energies and a saturation occupancy of one. While they are successful in predicting typical mono isotopic ion implantation and thermal degassing experiments, they fail at describing recent experiments on isotope exchange at low temperatures. This paper presents a new modified diffusion trapping model with fill level dependent de-trapping energies that can also explain these new isotope exchange experiments. Density function theory (DFT) calculations predict that even mono vacancies can store between 6 and 12?H atoms with de-trapping energies that depend on the fill level of the mono vacancy. The new fill level dependent diffusion trapping model allows to test these DFT results by bridging the gap in length and time scale between DFT calculations and experiment.

Schmid, K., E-mail: klaus.schmid@ipp.mpg.de; Toussaint, U. von; Schwarz-Selinger, T. [Max-Planck-Institut für Plasmaphysik, Boltzmannstraße 2, D-85748 Garching b. München (Germany)

2014-10-07

152

Transport of hydrogen in metals with occupancy dependent trap energies  

NASA Astrophysics Data System (ADS)

Common diffusion trapping models for modeling hydrogen transport in metals are limited to traps with single de-trapping energies and a saturation occupancy of one. While they are successful in predicting typical mono isotopic ion implantation and thermal degassing experiments, they fail at describing recent experiments on isotope exchange at low temperatures. This paper presents a new modified diffusion trapping model with fill level dependent de-trapping energies that can also explain these new isotope exchange experiments. Density function theory (DFT) calculations predict that even mono vacancies can store between 6 and 12 H atoms with de-trapping energies that depend on the fill level of the mono vacancy. The new fill level dependent diffusion trapping model allows to test these DFT results by bridging the gap in length and time scale between DFT calculations and experiment.

Schmid, K.; von Toussaint, U.; Schwarz-Selinger, T.

2014-10-01

153

``Inorganic Proton Conductor-Hydrogenated Metal'' new ionic heterostructures  

NASA Astrophysics Data System (ADS)

Hydrogenated metal-proton conductor heterostructures are of great applied and fundamental interest in connection with the possibility of forming proton heterojunctions of PdH x | KOH · nH2O type. Here, original compositions, such as Pd|(NaOH + KOH)|Pd, Pd|CsHSO4|Pd, Ti|KOH · H2O|C, and Ti|KOH · H2O|Ti, are synthesized and studied in the temperature range 320-430 K. After electrochemical activation a stable potential difference from 0.8 to 1.4 V (depending on physicochemical conditions) arises between the electrodes of the heterostructures. Part of the potential difference (?0.8 V for Pd and 0.1-0.2 V for Ti) is due to proton heterojunctions, which are found to be kinetically reversible.

Baikov, Yu. M.

2008-02-01

154

Modelling of hydrogen adsorption in the metal organic framework MOF5  

Microsoft Academic Search

Metal organic frameworks are formed by rigid organic spacer molecules linked by metal ions into a three-dimensional nano porous structure. The large internal surface (up to 4500m2g?1) provides abundant sites for the adsorption of small molecules like hydrogen, which currently generates significant interest for their potential application as reversible hydrogen storage matrix. A prerequisite for hydrogen storage at ambient conditions

F. M. Mulder; T. J. Dingemans; M. Wagemaker; G. J. Kearley

2005-01-01

155

Hydrogen storage in Pd nanocrystals covered with a metal-organic framework  

NASA Astrophysics Data System (ADS)

Hydrogen is an essential component in many industrial processes. As a result of the recent increase in the development of shale gas, steam reforming of shale gas has received considerable attention as a major source of H2, and the more efficient use of hydrogen is strongly demanded. Palladium is well known as a hydrogen-storage metal and an effective catalyst for reactions related to hydrogen in a variety of industrial processes. Here, we present remarkably enhanced capacity and speed of hydrogen storage in Pd nanocrystals covered with the metal-organic framework (MOF) HKUST-1 (copper(II) 1,3,5-benzenetricarboxylate). The Pd nanocrystals covered with the MOF have twice the storage capacity of the bare Pd nanocrystals. The significantly enhanced hydrogen storage capacity was confirmed by hydrogen pressure-composition isotherms and solid-state deuterium nuclear magnetic resonance measurements. The speed of hydrogen absorption in the Pd nanocrystals is also enhanced by the MOF coating.

Li, Guangqin; Kobayashi, Hirokazu; Taylor, Jared M.; Ikeda, Ryuichi; Kubota, Yoshiki; Kato, Kenichi; Takata, Masaki; Yamamoto, Tomokazu; Toh, Shoichi; Matsumura, Syo; Kitagawa, Hiroshi

2014-08-01

156

Hydrogen storage in Pd nanocrystals covered with a metal-organic framework.  

PubMed

Hydrogen is an essential component in many industrial processes. As a result of the recent increase in the development of shale gas, steam reforming of shale gas has received considerable attention as a major source of H2, and the more efficient use of hydrogen is strongly demanded. Palladium is well known as a hydrogen-storage metal and an effective catalyst for reactions related to hydrogen in a variety of industrial processes. Here, we present remarkably enhanced capacity and speed of hydrogen storage in Pd nanocrystals covered with the metal-organic framework (MOF) HKUST-1 (copper(II) 1,3,5-benzenetricarboxylate). The Pd nanocrystals covered with the MOF have twice the storage capacity of the bare Pd nanocrystals. The significantly enhanced hydrogen storage capacity was confirmed by hydrogen pressure-composition isotherms and solid-state deuterium nuclear magnetic resonance measurements. The speed of hydrogen absorption in the Pd nanocrystals is also enhanced by the MOF coating. PMID:25017188

Li, Guangqin; Kobayashi, Hirokazu; Taylor, Jared M; Ikeda, Ryuichi; Kubota, Yoshiki; Kato, Kenichi; Takata, Masaki; Yamamoto, Tomokazu; Toh, Shoichi; Matsumura, Syo; Kitagawa, Hiroshi

2014-08-01

157

Mechanism for high hydrogen storage capacity on metal-coated carbon nanotubes: A first principle analysis  

SciTech Connect

The hydrogen adsorption and binding mechanism on metals (Ca, Sc, Ti and V) decorated single walled carbon nanotubes (SWCNTs) are investigated using first principle calculations. Our results show that those metals coated on SWCNTs can uptake over 8 wt% hydrogen molecules with binding energy range -0.2--0.6 eV, promising potential high density hydrogen storage material. The binding mechanism is originated from the electrostatic Coulomb attraction, which is induced by the electric field due to the charge transfer from metal 4s to 3d. Moreover, we found that the interaction between the H{sub 2}-H{sub 2} further lowers the binding energy. - Graphical abstract: Five hydrogen molecules bound to individual Ca decorated (8, 0) SWCNT : a potential hydrogen-storage material. Highlights: Black-Right-Pointing-Pointer Each transition metal atom can adsorb more than four hydrogen molecules. Black-Right-Pointing-Pointer The interation between metal and hydrogen molecule is electrostatic coulomb attraction. Black-Right-Pointing-Pointer The electric field is induced by the charge transfer from metal 4s to metal 3d. Black-Right-Pointing-Pointer The adsorbed hydrogen molecules which form supermolecule can further lower the binding energy.

Lu, Jinlian; Xiao, Hong [Department of Physics and Institute for nanophysics and Rare-earth Luminescence, Xiangtan University, Xiangtan, Hunan Province 411105 (China)] [Department of Physics and Institute for nanophysics and Rare-earth Luminescence, Xiangtan University, Xiangtan, Hunan Province 411105 (China); Cao, Juexian, E-mail: jxcao@xtu.edu.cn [Department of Physics and Institute for nanophysics and Rare-earth Luminescence, Xiangtan University, Xiangtan, Hunan Province 411105 (China)] [Department of Physics and Institute for nanophysics and Rare-earth Luminescence, Xiangtan University, Xiangtan, Hunan Province 411105 (China)

2012-12-15

158

Chemical bonding of hydrogen molecules to transition metal complexes  

SciTech Connect

The complex W(CO){sub 3}(PR{sub 3}){sub 2}(H{sub 2}) (CO = carbonyl; PR{sub 3} = organophosphine) was prepared and was found to be a stable crystalline solid under ambient conditions from which the hydrogen can be reversibly removed in vacuum or under an inert atmosphere. The weakly bonded H{sub 2} exchanges easily with D{sub 2}. This complex represents the first stable compound containing intermolecular interaction of a sigma-bond (H-H) with a metal. The primary interaction is reported to be donation of electron density from the H{sub 2} bonding electron pair to a vacant metal d-orbital. A series of complexes of molybdenum of the type Mo(CO)(H{sub 2})(R{sub 2}PCH{sub 2}CH{sub 2}PR{sub 2}){sub 2} were prepared by varying the organophosphine substitutent to demonstrate that it is possible to bond either dihydrogen or dihydride by adjusting the electron-donating properties of the co-ligands. Results of infrared and NMR spectroscopic studies are reported. 20 refs., 5 fig.

Kubas, G.J.

1990-01-01

159

ACCEPTABILITY ENVELOPE FOR METAL HYDRIDE-BASED HYDROGEN STORAGE SYSTEMS  

SciTech Connect

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

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

2011-07-18

160

Membrane permeability response of lichen Bryoria fuscescens to wet deposited heavy metals and acid rain  

Microsoft Academic Search

Lichen Bryoria fuscescens were treated in the field experiment with heavy metal solutions, containing a mixture of Cu2+ and Ni2+ ions alone or in combination with acidity (H2SO4, pH 3), to study the effects of simulated acid rain and heavy metal deposition on the membrane integrity of lichen. Membrane responses to pollutant treatments were assessed by measurements of the leachate

S Tarhanen; S Metsärinne; T Holopainen; J Oksanen

1999-01-01

161

Small satellite nickel-hydrogen and nickel-metal hydride power applications  

Microsoft Academic Search

Nickel and silver-metal hydride batteries are being developed for aerospace applications. Metal hydride batteries offer a number of advantages over other aerospace battery systems. Nickel-metal hydride batteries have twice the gravimetric energy density of nickel-cadmium and twice the volumetric energy density of nickel-hydrogen. Silver-metal hydride batteries have the potential of three times the energy density of nickel-metal hydride and exhibit

William Dean Cook; Dwaine Coates

1993-01-01

162

Hydrogen absorption induced metal deposition on palladium and palladium-alloy particles  

DOEpatents

The present invention relates to methods for producing metal-coated palladium or palladium-alloy particles. The method includes contacting hydrogen-absorbed palladium or palladium-alloy particles with one or more metal salts to produce a sub-monoatomic or monoatomic metal- or metal-alloy coating on the surface of the hydrogen-absorbed palladium or palladium-alloy particles. The invention also relates to methods for producing catalysts and methods for producing electrical energy using the metal-coated palladium or palladium-alloy particles of the present invention.

Wang, Jia X. (East Setauket, NY); Adzic, Radoslav R. (East Setauket, NY)

2009-03-24

163

Investigation of the Superconducting Phase in Metallic Hydrogen Near the Pressure of Metallization  

NASA Astrophysics Data System (ADS)

In this paper, the thermodynamic properties of the superconducting state in the metallic hydrogen under the pressure at 347 GPa have been determined. In the framework of the Eliashberg formalism, it has been shown that the characteristic thermodynamic parameters deviate from the predictions of the BCS theory. In particular, the ratio ?C(TC)/CN(TC) decreases from 1.96 to 1.72 depending on the assumed value of the Coulomb pseudopotential (?* ? <0.08, 0.15>). On the other hand, the ratio TCCN(TC)/H2C(0) increases from 0.150 to 0.158.

Jarosik, Marcin W.; Durajski, Artur P.

2014-01-01

164

Miniaturized metal (metal alloy)/ PdO.sub.x/SiC hydrogen and hydrocarbon gas sensors  

NASA Technical Reports Server (NTRS)

A miniaturized Schottky diode hydrogen and hydrocarbon sensor and the method of making same is disclosed and claimed. The sensor comprises a catalytic metal layer, such as palladium, a silicon carbide substrate layer and a thin barrier layer in between the catalytic and substrate layers made of palladium oxide (PdO.sub.x). This highly stable device provides sensitive gas detection at temperatures ranging from at least 450 to 600.degree. C. The barrier layer prevents reactions between the catalytic metal layer and the substrate layer. Conventional semiconductor fabrication techniques are used to fabricate the small-sized sensors. The use of a thicker palladium oxide barrier layer for other semiconductor structures such as a capacitor and transistor structures is also disclosed.

Hunter, Gary W. (Inventor); Xu, Jennifer C. (Inventor); Lukco, Dorothy (Inventor)

2008-01-01

165

Miniaturized Metal (Metal Alloy)/PdO(x)/SiC Hydrogen and Hydrocarbon Gas Sensors  

NASA Technical Reports Server (NTRS)

A miniaturized Schottky diode hydrogen and hydrocarbon sensor and the method of making same is disclosed and claimed. The sensor comprises a catalytic metal layer, such as palladium, a silicon carbide substrate layer and a thin barrier layer in between the catalytic and substrate layers made of palladium oxide (PdO(x)). This highly stable device provides sensitive gas detection at temperatures ranging from at least 450 to 600 C. The barrier layer prevents reactions between the catalytic metal layer and the substrate layer. Conventional semiconductor fabrication techniques are used to fabricate the small-sided sensors. The use of a thicker palladium oxide barrier layer for other semiconductor structures such as a capacitor and transistor structures is also disclosed.

Hunter, Gary W. (Inventor); Xu, Jennifer C. (Inventor); Lukco, Dorothy (Inventor)

2008-01-01

166

Enhanced chitosan beads-supported Fe(0)-nanoparticles for removal of heavy metals from electroplating wastewater in permeable reactive barriers.  

PubMed

The removal of heavy metals from electroplating wastewater is a matter of paramount importance due to their high toxicity causing major environmental pollution problems. Nanoscale zero-valent iron (NZVI) became more effective to remove heavy metals from electroplating wastewater when enhanced chitosan (CS) beads were introduced as a support material in permeable reactive barriers (PRBs). The removal rate of Cr (VI) decreased with an increase of pH and initial Cr (VI) concentration. However, the removal rates of Cu (II), Cd (II) and Pb (II) increased with an increase of pH while decreased with an increase of their initial concentrations. The initial concentrations of heavy metals showed an effect on their removal sequence. Scanning electron microscope images showed that CS-NZVI beads enhanced by ethylene glycol diglycidyl ether (EGDE) had a loose and porous surface with a nucleus-shell structure. The pore size of the nucleus ranged from 19.2 to 138.6 ?m with an average aperture size of around 58.6 ?m. The shell showed a tube structure and electroplating wastewaters may reach NZVI through these tubes. X-ray photoelectron spectroscope (XPS) demonstrated that the reduction of Cr (VI) to Cr (III) was complete in less than 2 h. Cu (II) and Pb (II) were removed via predominant reduction and auxiliary adsorption. However, main adsorption and auxiliary reduction worked for the removal of Cd (II). The removal rate of total Cr, Cu (II), Cd (II) and Pb (II) from actual electroplating wastewater was 89.4%, 98.9%, 94.9% and 99.4%, respectively. The findings revealed that EGDE-CS-NZVI-beads PRBs had the capacity to remediate actual electroplating wastewater and may become an effective and promising technology for in situ remediation of heavy metals. PMID:24075723

Liu, Tingyi; Yang, Xi; Wang, Zhong-Liang; Yan, Xiaoxing

2013-11-01

167

In-situ Hydrogen Sorption 2D-ACAR Facility for the Study of Metal Hydrides for Hydrogen Storage  

NASA Astrophysics Data System (ADS)

We developed a dedicated hydrogen sorption setup coupled to a positron 2D-ACAR (two-dimensional Angular Correlation of Annihilation Radiation) setup employing a 22Na-source, which will enable to collect 2D-ACAR momentum distributions in-situ as a function of temperature, hydrogen pressure and hydrogen content. In parallel, a dedicated glovebox was constructed for handling air-sensitive metal and metal hydride samples, with a special entrance for the 2D-ACAR sample insert. The 2D-ACAR setup was tested in first measurements on a Pd0.75Ag0.25 foil and on a ball-milled MgH2 powder in both the hydrogen loaded and desorbed states. The hydrogen loaded Pd0.75Ag0.25Hx sample was kept under a 1 bar hydrogen pressure to prevent partial desorption during measurements at room temperature. The collected 2D-ACAR distributions of Pd0.75Ag0.25 and Pd0.75Ag0.25Hx showed similar features as observed in previous studies. The broadening of the ACAR distributions observed for the Mg to MgH2 metal-insulator transition was compared in a quantitative manner to ab-initio calculations reported in the literature.

Legerstee, W. J.; de Roode, J.; Anastasopol, A.; Falub, C. V.; Eijt, S. W. H.

168

Carburisation and metal dusting in hydrogen rich gas  

SciTech Connect

Common methods for large scale hydrogen production, such as steam reforming and coal gasification, also involve production of carbonaceous gases. It is therefore necessary to handle process gas streams involving various mixtures of hydrocarbons, H{sub 2}, H{sub 2}O, CO and CO{sub 2} at moderate to high temperatures. These gases pose a variety of corrosion threats to the alloys used in plant construction. Carbon is a particularly aggressive corrodent, leading to carburisation and, at high carbon activities, to metal dusting. The behaviour of commercial heat resisting alloys 602CA and 800, together with that of 304 stainless steel, was studied during thermal cycling in CO/CO{sub 2} at 700{sup o}C, and also in CO/H{sub 2}/H{sub 2}O at 680{sup o}C. Thermal cycling caused repeated scale separation which accelerated chromium depletion from the alloy subsurface regions. The CO/H{sub 2}/H{sub 2}O gas, with a{sub c} = 2.9 and PO{sub 2} = 5 x 10{sup -23} atm, caused relatively rapid metal dusting, accompanied by some internal carburisation. In contrast, the CO/CO{sub 2} gas, with a{sub c} = 7 and PO{sub 2} = 10{sup -24} - 10{sup -23} atm caused internal precipitation in all three alloys, but no dusting. Inward difflusion of oxygen led to in situ oxidation of internal carbides in the stainless steel, and the accompanying volume expansion disrupted the material. Alloy 602CA sustained limited internal carburisation and formed internal Al{sub 2}O{sub 3} rather than undergoing internal carbide oxidation. The very different reaction morphologies produced by the two gas mixtures are discussed in terms of competing gas-alloy reaction steps.

Young, D.J. [University of New South Wales, Sydney, NSW (Australia). School for Materials Science and Engineering

2007-07-01

169

The effect of microstructure on the permeability of metallic Mamoun Medraj Eric Baril Virendra Loya  

E-print Network

parameter. Control of the flow resistance, characterized by the perme- ability of the porous media online: 1 March 2007 Ã? Springer Science+Business Media, LLC 2007 Abstract Pressure drop was measured elec- trodes and filters, the resistance to fluid flow through the metallic foam is an important

Medraj, Mamoun

170

Permeability and Strength Measurements on Sintered, Porous, Hollow Turbine Blades Made by the American Electro Metal Corporation under Office of Naval Research Contract N-ONR-295 (01)  

NASA Technical Reports Server (NTRS)

An experimental investigation was made to determine the permeability and strength characteristics of a number of sintered, porous, hollow turbine rotor blades and to determine the effectiveness of the blade fabrication method on permeability control. The test blades were fabricated by the American Electro Metal Corporation under a contract with the Office of Naval Research, Department of the Navy, and were submitted to the NACA for testing. Of the 22 test blades submitted, ten were sintered but not coined, five were sintered and coined, and seven were sintered and not coined but contained perforated reinforcements integral with the blade shells. Representative samples of each group of blades were tested. Large variations in permeability in both chordwise and spanwise directions were found. Local deviations as large as 155 to -85 percent from prescribed values were found in chordwise permeability. Only one blade, an uncoined one, had a chordwise permeability variations which reasonably approached that specified. Even for this blade, local deviations exceeded 10 percent. Spanwise permeability, specified to be held constant, varied as much as 50 percent from root to tip for both an uncoined and a coined blade. Previous NACA analyses have shown that in order to maintain proper control of blade wall temperatures, permeability variations must not exceed plus or minus 10 percent. Satisfactory control of permeability in either the chordwise or the spanwise direction was not achieved in the blades tested. Spin tests made at room temperature for six blades revealed the highest material rupture strength to be 8926 pounds per square inch. This value is about one third the strength required for rotor blades in present-day turbojet engines. The lowest value of blade strength was 1436 pounds per square inch.

Richards, Hadley T.; Livingood, N.B.

1954-01-01

171

Heat energy from hydrogen-metal nuclear interactions  

NASA Astrophysics Data System (ADS)

The discovery of the Fleischmann-Pons Effect in 1989, a promise of an abundant, cheap and clean energy source was premature in the sense that theoretical knowledge, relative technologies and the experimental tools necessary for understanding and for scale-up still were not available. Therefore the field, despite efforts and diversification remained quasi-stagnant, the effect (a scientific certainty) being of low intensity leading to mainstream science to reject the phenomenon and not supporting its study. Recently however, the situation has changed, a new paradigm is in statunascendi and the obstacles are systematically removed by innovative approaches. Defkalion, a Greek company (that recently moved in Canada for faster progress) has elaborated an original technology for the Ni-H system [1-3]. It is about the activation of hydrogen and creation of nuclear active nano-cavities in the metal through a multi-stage interaction, materializing some recent breakthrough announcements in nanotechnology, superconductivity, plasma physics, astrophysics and material science. A pre-industrial generator and a novel mass-spectrometry instrumentations were created. Simultaneously, a meta-theory of phenomena was sketched in collaboration with Prof. Y. Kim (Purdue U).

Hadjichristos, John; Gluck, Peter

2013-11-01

172

Oxidative Dissolution of Nickel Metal in Hydrogenated Hydrothermal Solutions  

SciTech Connect

A platinum-lined, flowing autoclave facility is used to investigate the solubility behavior of metallic nickel in hydrogenated ammonia and sodium hydroxide solutions between 175 and 315 C. The solubility measurements were interpreted by means of an oxidative dissolution reaction followed by a sequence of Ni(II) ion hydrolysis reactions: Ni(s) + 2H+(aq) = Ni2+(aq) + H2(g) and Ni{sup 2+}(aq) + nH{sub 2}O = Ni(OH){sub n}{sup 2-n}(aq) + nH{sup +}(aq) where n = 1 and 2. Gibbs energies associated with these reaction equilibria were determined from a least-squares analysis of the data. The extracted thermochemical properties ({Delta}fG{sup 0}, {Delta}fH{sup 0} and S{sup 0}) for Ni2{sup +}(aq), Ni(OH){sup +}(aq) and Ni(OH){sub 2}(aq) were found to be consistent with those determined in a previous solubility study of NiO/Ni(OH){sub 2} conducted in our laboratory. The thermodynamic basis of the Ni/NiO phase boundary in aqueous solutions is examined to show that Ni(s) is stable relative to NiO(s) in solutions saturated at 25 C with 1 atm H{sub 2} for temperatures below 309 C.

Ziemniak SE, Guilmette PA, Turcotte RA, Tunison HM

2007-03-27

173

Critical concentration for hydrogen bubble formation in metals  

NASA Astrophysics Data System (ADS)

Employing a thermodynamic model with previously calculated first-principle energetics as inputs, we determined the hydrogen (H) concentration at the interstitial and monovacancy as well as its dependence on temperature and pressure in tungsten and molybdenum. Based on this, we predicted the critical H concentration for H bubble formation at different temperatures. The critical concentration, defined as the value when the concentration of H at a certain mH-vacancy complex first became equal to that of H at the interstitial, was 24?ppm/7.3 GPa and 410?ppm/4.7 GPa at 600?K in tungsten and molybdenum in the case of a monovacancy. Beyond the critical H concentration, numerous H atoms accumulated in the monovacancy, leading to the formation and rapid growth of H-vacancy complexes, which was considered the preliminary stage of H bubble formation. We expect that the proposed approach will be generally used to determine the critical H concentration for H bubble formation in metals.

Sun, Lu; Jin, Shuo; Zhou, Hong-Bo; Zhang, Ying; Zhang, Wenqing; Ueda, Y.; Lee, H. T.; Lu, Guang-Hong

2014-10-01

174

Nuclear spin relaxation by translational diffusion of hydrogen in BCC metals: the effect of hopping to second-nearest neighbors  

Microsoft Academic Search

Quantities relevant to the theoretical determination of D\\/T1 are calculated, where D is the tracer diffusion coefficient and T1 is the spin-lattice relaxation time for relaxation due to magnetic dipolar coupling between diffusing hydrogen spins. Calculations are performed for hydrogen spins diffusing on the tetrahedral interstitial sites of a BCC host metal and both the like-spin (hydrogen-hydrogen) and unlike-spin (metal-hydrogen)

D. A. Faux

1991-01-01

175

Characterisation of hydrocarbonaceous overlayers important in metal-catalysed selective hydrogenation reactions  

NASA Astrophysics Data System (ADS)

The hydrogenation of alkynes to alkenes over supported metal catalysts is an important industrial process and it has been shown that hydrocarbonaceous overlayers are important in controlling selectivity profiles of metal-catalysed hydrogenation reactions. As a model system, we have selected propyne hydrogenation over a commercial Pd(5%)/Al2O3 catalyst. Inelastic neutron scattering studies show that the C-H stretching mode ranges from 2850 to 3063 cm-1, indicating the mostly aliphatic nature of the overlayer and this is supported by the quantification of the carbon and hydrogen on the surface. There is also a population of strongly hydrogen-bonded hydroxyls, their presence would indicate that the overlayer probably contains some oxygen functionality. There is little evidence for any olefinic or aromatic species. This is distinctly different from the hydrogen-poor overlayers that are deposited on Ni/Al2O3 catalysts during methane reforming.

Lennon, David; Warringham, Robbie; Guidi, Tatiana; Parker, Stewart F.

2013-12-01

176

Hydrogen-induced cracking and effect of non-metallic inclusions in linepipe steels  

SciTech Connect

Results are reported on: (1) evaluation and comparison of threshold hydrogen concentration for hydrogen induced cracking (HIC) in linepipe steels; (2) threshold pH for steels at which no cracking was observed; (3) observation of cracking by an ultrasonic C-scan technique; and (4) quantitative characterization of non-metallic inclusion populations in linepipe steels. The results are discussed in terms of cracking sensitivity, HIC susceptibility and effects of non-metallic inclusions in the linepipe steels on HIC.

Elboujdaini, M.; Shehata, M.T.; Sastrir, V.S.; Revie, R.W.; Ramsingh, R.R. [CANMET, Ottawa, Ontario (Canada). Natural Resources Canada

1998-12-31

177

Hydrogen adsorption on metal-organic framework (MOF-5) synthesized by DMF approach  

Microsoft Academic Search

Metal-organic frameworks (MOFs), especially MOF-5, are believed to be promising new porous materials for hydrogen adsorption.\\u000a A comparative study of material synthesis, characterization and hydrogen adsorption was performed to examine the effects of\\u000a different synthesis conditions on crystal structure, pore textural property and hydrogen adsorption performance of MOF-5 materials.\\u000a Three MOF-5 samples synthesized with dimethyl formamide (DFM) as solvent and

Dipendu Saha; Shuguang Deng; Zhiguan Yang

2009-01-01

178

Synthesis and Hydrogen Sorption Properties of Carborane Based Metal-Organic Framework Materials  

E-print Network

report on the synthesis and hydrogen uptake properties of carborane-based MOFs that exploit some or all motors.10 As a starting point for carborane-based MOFs, we have focused on Zn(II) coordinationSynthesis and Hydrogen Sorption Properties of Carborane Based Metal-Organic Framework Materials

179

Liquid Phase Hydrogenation of Benzalacetophenone: Effect of Solvent, Catalyst Support, Catalytic Metal and Reaction Conditions  

Microsoft Academic Search

Innovative catalysts based on a “porous glass” support material were developed and investigated for the reduction of benzalacetophenone. The easy preparation conditions and possibility to use different metals (e.g. Pd, Pt, Rh) for impregnation gave a broad variety of these catalysts. Hydrogenation experiments with these supported catalysts were carried out under different hydrogen pressures and temperatures. Porous glass catalysts with

Achim STOLLE; Christine SCHMÖGER; Bernd ONDRUSCHKA; Werner BONRATH; Thomas F. KELLER; Klaus D. JANDT

2011-01-01

180

Hydrocarbon reactions over transition metals: observation of surface hydrogen  

SciTech Connect

One of the difficulties in establishing the mechanism and kinetic behavior of heterogeneous catalytic reactions has been that, typically, the experimental observables are the concentrations of reactants and products in the gas phase rather than those on the surface where the reaction actually occurs. A new technique is described which permits measurement of the thermodynamic activity of chemisorbed hydrogen under reaction conditions. The method utilizes a solid state electrochemical device to measure the thermodynamic activity of hydrogen at a gas-solid interface. The device is applied to study the sorption kinetics of pure hydrogen including hydrogen spillover and other nonidealities. The kinetics of the platinum catalyzed hydrogenations of ethylene, propylene, and acetylene were investigated over a wide range of temperatures (278-700/sup 0/K) at one atmosphere total pressure. The electrode measurements indicate that during reaction gaseous hydrogen is not in equilibrium with surface hydrogen. Multiple steady states are observed for the ethylene hydrogenation reaction over platinum. Unlike the platinum catalyzed reaction, ethylene hydrogenation over nickel exhibits gas-surface hydrogen equilibrium. The adsorption and dehydrogenation of propane, butane, and cyclohexane were also investigated. At temperatures where no reaction was observed in the gas phase, paraffins adsorb dissociatively. The energetics of the observed processes are discussed in terms of a surface intermediate stabilized by hyperconjugation of the adsorbed molecule.

Mullins, M.E.

1983-01-01

181

Highly mobile and reactive state of hydrogen in metal oxide semiconductors at room temperature  

PubMed Central

Hydrogen in metal oxides usually strongly associates with a neighboring oxygen ion through an O-H bond and thus displays a high stability. Here we report a novel state of hydrogen with unusually high mobility and reactivity in metal oxides at room temperature. We show that freshly doped hydrogen in Nb2O5 and WO3 polycrystals via electrochemical hydrogenation can reduce Cu2+ ions into Cu0 if the polycrystals are immersed in a CuSO4 solution, while this would not happen if the hydrogenated polycrystals have been placed in air for several hours before the immersion. Time-dependent studies of electrochemically hydrogenated rutile single crystals reveal two distinct states of hydrogen: one as protons covalently bonded to oxygen ions, while the other one is highly unstable with a lifetime of just a few hours. Observation of this mobile and reactive state of hydrogen will provide new insight into numerous moderate and low temperature interactions between metal oxides and hydrogen. PMID:24193143

Chen, Wan Ping; He, Ke Feng; Wang, Yu; Chan, Helen Lai Wah; Yan, Zijie

2013-01-01

182

A metal-free strategy to release chemisorbed H2 from hydrogenated boron nitride nanotubes.  

PubMed

Chemisorbed hydrogen on boron nitride nanotubes (BNNT) can only be released thermally at very high temperatures above 350?°C. However, no catalyst has been identified that could liberate H2 from hydrogenated BN nanotubes under moderate conditions. Using different density functional methods we predict that the desorption of chemisorbed hydrogen from hydrogenated BN nanotubes can be facilitated catalytically by triflic acid at low free-energy activation barriers and appreciable rates under metal free conditions and mildly elevated temperatures (40-50?°C). Our proposed mechanism shows that the acid is regenerated in the process and can further facilitate similar catalytic release of H2 , thus suggesting all the chemisorbed hydrogen on the surface of the hydrogenated nanotube can be released in the form of H2 . These findings essentially raise hope for the development of a sustainable chemical hydrogen storage strategy in BN nanomaterials. PMID:25132421

Roy, Lisa; Bhunya, Sourav; Paul, Ankan

2014-11-10

183

Short-range order of low-coverage Ti/Al,,111...: Implications for hydrogen storage in complex metal hydrides  

E-print Network

Short-range order of low-coverage Ti/Al,,111...: Implications for hydrogen storage in complex metal-coverage Ti atoms on Al 111 as a model surface system for transition metal doped alanate hydrogen storage of Physics. DOI: 10.1063/1.2722197 The storage of hydrogen in a lightweight, high-capacity medium with fast

Ciobanu, Cristian

184

Effect of radiogenic helium on stainless steel 12Cr18Ni10Ti mechanical properties and hydrogen permeability  

SciTech Connect

Samples of stainless steel 12Cr18Ni10Ti with radiogenic helium were subjected to mechanical tests with a constant extension rate. The presence of {sup 3}He does not markedly affect the strength characteristic, but significantly decreases plasticity of steel. The presence of hydrogen enhances the embrittlement of steel, containing {sup 3}He. The diffusion coefficient of hydrogen does not change significantly in the presence of helium, but the traps for hydrogen, which occur due to the presence of helium, delay the kinetics of a steady state flux onset at helium concentration of 50 appm. (authors)

Boitsov, I. [Russian Federal Nuclear Center, All-Russian Research Inst. of Experimental Physics, Mira av., 37, Sarov, Nizhny Novgorod Region 607188 (Russian Federation); Kanashenko, S. [Inst. of Physical Chemistry, Russian Academy of Sciences, Leninsky pr., 31, Moscow, 119991 (Russian Federation); Causey, R. [Sandia National Laboratories, MS 9161, P.O. Box 969, Livermore, CA 94551-0969 (United States); Denisov, E. [V.A. Fock Research Inst. of Physics, St. Petersburg State Univ., Ulyanovskaya st., 1, Peterhof, St. Petersburg 198904 (Russian Federation); Glugla, M. [Forschungszentrum Karlsruhe, Tritium Laboratory TLK, PO Box 3640, D 76021 Karlsruhe (Germany); Grishechkin, S. [Russian Federal Nuclear Center, All-Russian Research Inst. of Experimental Physics, Mira av., 37, Sarov, Nizhny Novgorod Region 607188 (Russian Federation); Hassanein, A. [Argonne National Laboratory, Bldg. 362, South Cass Avenue, Argonne, 9700 (United States); Lebedev, B. [Russian Federal Nuclear Center, All-Russian Research Inst. of Experimental Physics, Mira av., 37, Sarov, Nizhny Novgorod Region 607188 (Russian Federation); Kompaniets, T.; Kurdyumov, A. [V.A. Fock Research Inst. of Physics, St. Petersburg State Univ., Ulyanovskaya st., 1, Peterhof, St. Petersburg 198904 (Russian Federation); Malkov, I.; Yukhimchuk, A. [Russian Federal Nuclear Center, All-Russian Research Inst. of Experimental Physics, Mira av., 37, Sarov, Nizhny Novgorod Region 607188 (Russian Federation)

2008-07-15

185

Hydrogenated Graphene as Metal-free Catalyst for Fenton-like Reaction  

NASA Astrophysics Data System (ADS)

Carbonaceous catalysts are potential alternatives to metal catalysts. Graphene has been paid much attention for its high surface area and light weight. Here, hydrogenated graphene has been prepared by a simple gamma ray irradiation of graphene oxide aqueous suspension at room temperature. Transmission electron microscopic, element analysis, X-ray photoelectron spectroscopy, and UV-Vis spectrophotometer studies verified the hydrogenation of graphene. The as-prepared hydrogenated graphene can be used as a metal-free carbonaceous catalyst for the Fenton-like degradation of organic dye in water.

Zhao, Yi; Chen, Wu-feng; Yuan, Cheng-fei; Zhu, Zi-ye; Yan, Li-feng

2012-06-01

186

Hydrogen Storage Materials: Room-Temperature Wet-Chemistry Approach toward Mixed-Metal Borohydrides.  

PubMed

The poor kinetics of hydrogen evolution and the irreversibility of the hydrogen discharge hamper the use of transition metal borohydrides as hydrogen storage materials, and the drawbacks of current synthetic methods obstruct the exploration of these systems. A wet-chemistry approach, which is based on solvent-mediated metathesis reactions of precursors containing bulky organic cations and weakly coordinating anions, leads to mixed-metal borohydrides that contain only a small amount of "dead mass". The applicability of this method is exemplified by Li[Zn2 (BH4 )5 ] and M[Zn(BH4 )3 ] salts (M=Na, K), and its extension to other systems is discussed. PMID:25470241

Jaro?, Tomasz; Or?owski, Piotr A; Wegner, Wojciech; Fija?kowski, Karol J; Leszczy?ski, Piotr J; Grochala, Wojciech

2015-01-19

187

3D Metal-Organic Frameworks Based on Elongated Tetracarboxylate Building Blocks for Hydrogen Storage  

E-print Network

3D Metal-Organic Frameworks Based on Elongated Tetracarboxylate Building Blocks for Hydrogen-organic frameworks (MOFs) with a new biphenol- derived tetracarboxylate linker and CuII and ZnII metal isostructural MOFs exhibit distorted PtS network topology and show markedly different framework stability

Li, Jing

188

Enviro-Friendly Hydrogen Generation from Steel Mill-Scale via Metal-Steam Reforming  

ERIC Educational Resources Information Center

An economically viable and environmental friendly method of generating hydrogen for fuel cells is by the reaction of certain metals with steam, called metal-steam reforming (MSR). This technique does not generate any toxic by-products nor contributes to the undesirable greenhouse effect. From the standpoint of favorable thermodynamics, total…

Azad, Abdul-Majeed; Kesavan, Sathees

2006-01-01

189

Hydrogen Storage in Metal-Modified Single-Walled Carbon Nanotubes (start 9/15/01)  

E-print Network

Hydrogen Storage in Metal-Modified Single-Walled Carbon Nanotubes (start 9/15/01) Channing Ahn, PI Intercalation of carbons Characterization of intercalated single walled nanotubes Gravimetric and volumetric-metal) additions to single-walled nanotubes on H2 adsorption. Potassium intercalated graphite long known to absorb

190

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

NASA Astrophysics Data System (ADS)

Hydrogen is a promising energy carrier, for use in fuel cells, engines, and turbines for transportation or mobile applications. Hydrogen is desirable as an energy carrier, because its oxidation by air releases substantial energy (thermally or electrochemically) and produces only water as a product. In contrast, hydrocarbon energy carriers inevitably produce CO2, contributing to global warming. While CO2 capture may prove feasible in large stationary applications, implementing it in transportation and mobile applications is a daunting challenge. Thus a zero-emission energy carrier like hydrogen is especially needed in these cases. Use of H2 as an energy carrier also brings new challenges such as safe handling of compressed hydrogen and implementation of new transport, storage, and delivery processes and infrastructure. With current storage technologies, hydrogen's energy per volume is very low compared to other automobile fuels. High density storage of compressed hydrogen requires combinations of high pressure and/or low temperature that are not very practical. An alternative for storage is use of solid light weight hydrogenous material systems which have long durability, good adsorption properties and high activity. Substantial research has been conducted on carbon materials like activated carbon, carbon nanofibers, and carbon nanotubes due to their high theoretical hydrogen capacities. However, the theoretical values have not been achieved, and hydrogen uptake capacities in these materials are below 10 wt. %. In this thesis we investigated the use of silicon for hydrogen generation. Hydrogen generation via water oxidation of silicon had been ignored due to slow reaction kinetics. We hypothesized that the hydrogen generation rate could be improved by using high surface area silicon nanoparticles. Our laser-pyrolysis-produced nanoparticles showed surprisingly rapid hydrogen generation and high hydrogen yield, exceeding the theoretical maximum of two moles of H2 per mole of Si. We compare our silicon nanoparticles (˜10nm diameter) with commercial silicon nanopowder (<100nm diameter) and ball-milled silicon powder (325 mesh). The increase in rate upon decreasing the particle size to 10 nm was even greater than would be expected based upon the increase in surface area. While specific surface area increased by a factor of 6 in going from <100 nm to ˜10 nm particles, the 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.

Patki, Gauri Dilip

191

Improved retort for cleaning metal powders with hydrogen  

NASA Technical Reports Server (NTRS)

Improved cleaning retort produces uniform temperature distribution in the heated zone and minimizes hydrogen channeling through the powder bed. Retort can be used for nonmetallic powders, sintering in a reducing atmosphere, and for cleaning powders in reduction atmospheres other than hydrogen.

Arias, A.

1969-01-01

192

Change in soft magnetic properties of Fe-based metallic glasses during hydrogen absorption and desorption  

NASA Astrophysics Data System (ADS)

The stress level can be altered in soft magnetic amorphous alloys by hydrogen absorption. The resulting changes in the soft magnetic parameters are reversible or irreversible, depending on the chemical composition. Some of these effects are demonstrated in Fe-B, Fe-W-B, and Fe-V-B glassy ribbons, in which various magnetic parameters are measured mainly during hydrogen desorption. The rate of hydrogen desorption is also monitored by measuring the pressure change in a hermetically closed bomb. The observed phenomena are interpreted on the basis of induced stresses and chemical interactions between the solute metal and hydrogen.

Novák, L.; Lovas, A.; Kiss, L. F.

2005-08-01

193

Change in soft magnetic properties of Fe-based metallic glasses during hydrogen absorption and desorption  

SciTech Connect

The stress level can be altered in soft magnetic amorphous alloys by hydrogen absorption. The resulting changes in the soft magnetic parameters are reversible or irreversible, depending on the chemical composition. Some of these effects are demonstrated in Fe-B, Fe-W-B, and Fe-V-B glassy ribbons, in which various magnetic parameters are measured mainly during hydrogen desorption. The rate of hydrogen desorption is also monitored by measuring the pressure change in a hermetically closed bomb. The observed phenomena are interpreted on the basis of induced stresses and chemical interactions between the solute metal and hydrogen.

Novak, L.; Lovas, A.; Kiss, L.F. [Department of Physics, Technical University of Kosice, Kosice, Park Komenskeho 2 (Slovakia); Department of Vehicle Manufacturing and Repairing, Faculty of Transportation Engineering, Budapest University of Technology and Economics, Bertalan L. u. 2., H-1111 Budapest (Hungary); Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest (Hungary)

2005-08-15

194

Hydrogen transport through V 85Ni 10M 5 alloy membranes  

Microsoft Academic Search

Despite their inherent high permeability, unalloyed body-centred cubic (BCC) metals are prone to brittle failure due to their excessive hydrogen solubility. The primary challenge for BCC metal membrane development is therefore to control the solubility to a point where embrittlement is inhibited, while increasing the rate of hydrogen diffusion through the alloy. This can be potentially achieved through alloying, with

M. D. Dolan; G. Song; D. Liang; M. E. Kellam; D. Chandra; J. H. Lamb

2011-01-01

195

Vanadium diaphragm electrode serves as hydrogen diffuser in lithium hydride cell  

NASA Technical Reports Server (NTRS)

Lithium hydride cell uses vanadium diaphragm electrode as a hydrogen diffuser. Vanadium is high in hydrogen gas solubility and permeability, is least sensitive to adverse surface effects, maintains good mechanical strength in hydrogen atmospheres, and appears to be compatible with all alkali-halide electrolytes and lithium metals.

Crouthamel, C. E.; Heinrich, R. R.; Johnson, C. E.

1967-01-01

196

Method of producing metallized chloroplasts and use thereof in the photochemical production of hydrogen and oxygen  

DOEpatents

The invention is primarily a metallized chloroplast composition for use in a photosynthetic reaction. A catalytic metal is precipitated on a chloroplast membrane at the location where a catalyzed reduction reaction occurs. This metallized chloroplast is stabilized by depositing it on a support medium such as fiber so that it can be easily handled. A possible application of this invention is the splitting of water to form hydrogen and oxygen that can be used as a renewable energy source.

Greenbaum, Elias (Oak Ridge, TN)

1987-01-01

197

Recently published research from the National Renewable Energy Laboratory (NREL) reports that biohybrid hydrogen electrodes comprising metallic single-  

E-print Network

Recently published research from the National Renewable Energy Laboratory (NREL) reports that biohybrid hydrogen electrodes comprising metallic single- walled carbon nanotube (SWNT) networks, for application in photoelectrochemical or fuel cells. The high-performance hydrogen electrodes are based

198

Hot hydrogen testing of metallic turbo pump materials  

NASA Technical Reports Server (NTRS)

The objectives of this investigation are to expose heat resistant alloys to hydrogen at elevated temperatures and to use various microstructural and analytical techniques to determine the chemical and rate process involved in degradation of these materials due to hydrogen environment. Inconel 718 and NASA-23 (wrought and cast) are candidate materials. The degradation of these materials in the presence of 1 to 5 atmospheric pressure of hydrogen from 450 C to 1100 C was examined. The hydrogen facility at Auburn University was used for this purpose. Control experiments were also conducted wherein the samples were exposed to vacuum so that a direct comparison of the results would separate the thermal contribution from the hydrogen effects. The samples were analyzed prior to and after exposure. A residual gas collection system was used to determine the gaseous species produced by any chemical reaction that may have occurred during the exposure. Analysis of this gas sample shows only the presence of H2 as expected. Analyses of the samples were conducted using optical microscopy, x-ray diffraction, scanning electron microscopy, and weight change. There appears to be no change in weight of the samples as a result of hydrogen exposure. In addition no visible change on the surface structure was detected. This indicates that the materials of interest do not have strong interaction with hot hydrogen. This is consistent with the microstructure results.

Zee, Ralph; Chin, Bryan; Inamdar, Rohit

1993-01-01

199

Use of plasma arc welding process to combat hydrogen metallic disbonding of austenitic stainless steel claddings  

SciTech Connect

A separation type crack, metallic disbonding, occurred between austenitic stainless steel weld metal cladding and 2 1/4Cr-1Mo base metal in the hydrodesulfurizing reactor of an oil refining plant. For stainless steel cladding, the submerged arc welding (SAW) process with a strip electrode is usually applied, but the authors experimented with the plasma arc welding (PAW) process with hot wire electrode for the cladding. The metallic disbonding is considered to be attributed to hydrogen accumulation at the transition zone and has been generally studied on a laboratory scale using an autoclave. The authors used a electrolytic hydrogen charging technique for the sake of experimental simplicity and made a comparison with the results for gaseous hydrogen charging. The main conclusions obtained were follows: The PAW stainless steel weld metal cladding is more resistant to metallic disbonding with the PAW process is explained by the desirable microstructure and properties of the first layer of weld metal at the transition zone. Electrolytic hydrogen charging pretty well reproduces the results of autoclave gas phase charging.

Alexandrov, O.A. (NACAP Nederland B.V. (Netherlands)); Steklov, O.I.; Alexeev, A.V. (State Academy of Oil and Gas, Moscow (Russian Federation))

1993-11-01

200

Ultrahigh-Pressure Metallic Hydrogen: Creation by Super-Intense Laser and Application to Pycnonuclear Fusion Studies  

Microsoft Academic Search

At multi-megabar pressures ordinary hydrogen becomes metallic; protons in liquid-metallic hydrogen may undergo phase transitions such as Wigner crystallization and spin-magnetization [1]. A pycnonuclear fusion reactor utilizes p-d reactions, p + d --> ^3He (5.4 keV) + gamma (5.489 MeV), most proficient in dense liquid-metallic hydrogen near the freezing transitions [2]. In constrast to the 14.1 MeV neutrons produced by

Setsuo Ichimaru

2003-01-01

201

Metal chelator combined with permeability enhancer ameliorates oxidative stress-associated neurodegeneration in rat eyes with elevated intraocular pressure.  

PubMed

Because as many as half of glaucoma patients on intraocular pressure (IOP)-lowering therapy continue to experience optic nerve toxicity, it is imperative to find other effective therapies. Iron and calcium ions play key roles in oxidative stress, a hallmark of glaucoma. Therefore, we tested metal chelation by means of ethylenediaminetetraacetic acid (EDTA) combined with the permeability enhancer methylsulfonylmethane (MSM) applied topically on the eye to determine if this noninvasive treatment is neuroprotective in rat optic nerve and retinal ganglion cells exposed to oxidative stress induced by elevated IOP. Hyaluronic acid (HA) was injected into the anterior chamber of the rat eye to elevate the IOP. EDTA-MSM was applied topically to the eye for 3 months. Eyeballs and optic nerves were processed for histological assessment of cytoarchitecture. Protein-lipid aldehyde adducts and cyclooxygenase-2 (COX-2) were detected immunohistochemically. HA administration increased IOP and associated oxidative stress and inflammation. Elevated IOP was not affected by EDTA-MSM treatment. However, oxidative damage and inflammation were ameliorated as reflected by a decrease in formation of protein-lipid aldehyde adducts and COX-2 expression, respectively. Furthermore, EDTA-MSM treatment increased retinal ganglion cell survival and decreased demyelination of optic nerve compared with untreated eyes. Chelation treatment with EDTA-MSM ameliorates sequelae of IOP-induced toxicity without affecting IOP. Because most current therapies aim at reducing IOP and damage occurs even in the absence of elevated IOP, EDTA-MSM has the potential to work in conjunction with pressure-reducing therapies to alleviate damage to the optic nerve and retinal ganglion cells. PMID:24509160

Liu, P; Zhang, M; Shoeb, M; Hogan, D; Tang, Luosheng; Syed, M F; Wang, C Z; Campbell, G A; Ansari, N H

2014-04-01

202

Post-synthetic Ti Exchanged UiO-66 Metal-Organic Frameworks that Deliver Exceptional Gas Permeability in Mixed Matrix Membranes.  

PubMed

Gas separation membranes are one of the lowest energy technologies available for the separation of carbon dioxide from flue gas. Key to handling the immense scale of this separation is maximised membrane permeability at sufficient selectivity for CO2 over N2. For the first time it is revealed that metals can be post-synthetically exchanged in MOFs to drastically enhance gas transport performance in membranes. Ti-exchanged UiO-66 MOFs have been found to triple the gas permeability without a loss in selectivity due to several effects that include increased affinity for CO2 and stronger interactions between the polymer matrix and the Ti-MOFs. As a result, it is also shown that MOFs optimized in previous works for batch-wise adsorption applications can be applied to membranes, which have lower demands on material quantities. These membranes exhibit exceptional CO2 permeability enhancement of as much as 153% when compared to the non-exchanged UiO-66 mixed-matrix controls, which places them well above the Robeson upper bound at just a 5 wt.% loading. The fact that maximum permeability enhancement occurs at such low loadings, significantly less than the optimum for other MMMs, is a major advantage in large-scale application due to the more attainable quantities of MOF needed. PMID:25592747

Smith, Stefan J D; Ladewig, Bradley P; Hill, Anita J; Lau, Cher Hon; Hill, Matthew R

2015-01-01

203

Post-synthetic Ti Exchanged UiO-66 Metal-Organic Frameworks that Deliver Exceptional Gas Permeability in Mixed Matrix Membranes  

NASA Astrophysics Data System (ADS)

Gas separation membranes are one of the lowest energy technologies available for the separation of carbon dioxide from flue gas. Key to handling the immense scale of this separation is maximised membrane permeability at sufficient selectivity for CO2 over N2. For the first time it is revealed that metals can be post-synthetically exchanged in MOFs to drastically enhance gas transport performance in membranes. Ti-exchanged UiO-66 MOFs have been found to triple the gas permeability without a loss in selectivity due to several effects that include increased affinity for CO2 and stronger interactions between the polymer matrix and the Ti-MOFs. As a result, it is also shown that MOFs optimized in previous works for batch-wise adsorption applications can be applied to membranes, which have lower demands on material quantities. These membranes exhibit exceptional CO2 permeability enhancement of as much as 153% when compared to the non-exchanged UiO-66 mixed-matrix controls, which places them well above the Robeson upper bound at just a 5 wt.% loading. The fact that maximum permeability enhancement occurs at such low loadings, significantly less than the optimum for other MMMs, is a major advantage in large-scale application due to the more attainable quantities of MOF needed.

Smith, Stefan J. D.; Ladewig, Bradley P.; Hill, Anita J.; Lau, Cher Hon; Hill, Matthew R.

2015-01-01

204

Post-synthetic Ti Exchanged UiO-66 Metal-Organic Frameworks that Deliver Exceptional Gas Permeability in Mixed Matrix Membranes  

PubMed Central

Gas separation membranes are one of the lowest energy technologies available for the separation of carbon dioxide from flue gas. Key to handling the immense scale of this separation is maximised membrane permeability at sufficient selectivity for CO2 over N2. For the first time it is revealed that metals can be post-synthetically exchanged in MOFs to drastically enhance gas transport performance in membranes. Ti-exchanged UiO-66 MOFs have been found to triple the gas permeability without a loss in selectivity due to several effects that include increased affinity for CO2 and stronger interactions between the polymer matrix and the Ti-MOFs. As a result, it is also shown that MOFs optimized in previous works for batch-wise adsorption applications can be applied to membranes, which have lower demands on material quantities. These membranes exhibit exceptional CO2 permeability enhancement of as much as 153% when compared to the non-exchanged UiO-66 mixed-matrix controls, which places them well above the Robeson upper bound at just a 5 wt.% loading. The fact that maximum permeability enhancement occurs at such low loadings, significantly less than the optimum for other MMMs, is a major advantage in large-scale application due to the more attainable quantities of MOF needed. PMID:25592747

Smith, Stefan J. D.; Ladewig, Bradley P.; Hill, Anita J.; Lau, Cher Hon; Hill, Matthew R.

2015-01-01

205

A metal-organic framework as a chemical guide to control hydrogen desorption pathways of ammonia borane  

NASA Astrophysics Data System (ADS)

We report that ammonia borane with a high uptake capacity for hydrogen can be encapsulated in a metal-organic framework (MOF) via capillary action, where the MOF functions as a chemical guide to control the hydrogen desorption pathways of ammonia borane by releasing only pure hydrogen, lowering its hydrogen desorption temperature, and suppressing its volumetric expansion during hydrogen desorption.We report that ammonia borane with a high uptake capacity for hydrogen can be encapsulated in a metal-organic framework (MOF) via capillary action, where the MOF functions as a chemical guide to control the hydrogen desorption pathways of ammonia borane by releasing only pure hydrogen, lowering its hydrogen desorption temperature, and suppressing its volumetric expansion during hydrogen desorption. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr01296h

Jeong, Hyung Mo; Shin, Weon Ho; Park, Jung Hyo; Choi, Jung Hoon; Kang, Jeung Ku

2014-05-01

206

Diffusion of hydrogen and its isotopes in BCC metals  

Microsoft Academic Search

The diffusion constant for models of the interatomic interatomic interactions associated with an interstitial in a metal were calculated. With this procedure the conditions under which quantum-mechanical tunneling is the predominant mode of light interstitial transport in metals was investigated. In situtations characterized by interstitial tunneling motion the validity of simplifying assumptions of the formal theory were examined. There are

D. Emin; M. I. Baskes; W. D. Wilson

1979-01-01

207

Recent advances in transition metal-catalyzed enantioselective hydrogenation of unprotected enamines.  

PubMed

Transition metal-catalyzed enantioselective hydrogenation of enamines is undoubtedly a useful and environment-friendly method for the preparation of optically pure chiral amines and amine derivatives. Over the last few decades, the use of transition metal catalysts containing chiral phosphorus or phosphine-oxazoline ligands attracted much attention for the hydrogenation of unprotected enamines. A number of efficient chiral catalysts have been developed, and some of them have shown high potential for the application in the synthesis of optical chiral amines in both laboratory and industry. This tutorial review focuses on the contributions concerning the transition metal-catalyzed enantioselective hydrogenation of unprotected enamines for the synthesis of chiral amines and amine derivatives. PMID:22509499

Xie, Jian-Hua; Zhu, Shou-Fei; Zhou, Qi-Lin

2012-06-01

208

Improved thermal stability of Langmuir-Blodgett films through an intermolecular hydrogen bond and metal complex  

NASA Astrophysics Data System (ADS)

Langmuir-Blodgett (LB) films of N-octadecanoyl-L-alanine and its silver and zinc complexes have been investigated by variable-temperature Fourier transform infrared transmission spectroscopy. The thermal stability of LB films is improved through an intermolecular hydrogen bond and metal complex. The intermolecular hydrogen-bonding interaction between hydrophilic head groups in the same monolayers and the metal complex between one head group and another in the neighboring monolayers considerably increase the interaction between the corresponding hydrophobic alkyl chains. It is shown that the transformation of the triclinic subcell packing of the molecules in the LB films prior to and after the silver complex into hexagonal packing occurs before the phase transition accompanied with a change in molecular orientation. The phase transition behavior of the LB films is varied from a small temperature interval to large one depending on the hydrogen bond and metal complex.

Du, Xuezhong; Liang, Yingqiu

2004-01-01

209

Tunable hydrogen storage in magnesium-transition metal compounds: First-principles calculations  

Microsoft Academic Search

Magnesium dihydride (MgH2) stores 7.7wt% hydrogen but it suffers from a high thermodynamic stability and slow (de)hydrogenation kinetics. Alloying Mg with lightweight transition metals (TM) (=Sc,Ti,V,Cr) aims at improving the thermodynamic and kinetic properties. We study the structure and stability of MgxTM1-xH2 compounds, x=[0-1] , by first-principles calculations at the level of density functional theory. We find that the experimentally

Süleyman Er; Dhirendra Tiwari; Gilles A. de Wijs; Geert Brocks

2009-01-01

210

Liquid-Phase Citral Hydrogenation over SiO 2-Supported Group VIII Metals  

Microsoft Academic Search

Liquid-phase citral hydrogenation over SiO2-supported Group VIII metals at 300 K and 1 atm was studied in the absence of all transport limitations as verified by the Madon–Boudart test and the Weisz–Prater criterion. The initial TOF (turnover frequency) for citral hydrogenation varied by three orders of magnitude and exhibited the following trend: Pd>Pt>Ir>Os>Ru>Rh>Ni>Co?Fe (no activity was detected over Fe\\/SiO2). When

Utpal K Singh; M. Albert Vannice

2001-01-01

211

State of Hydrogen in BCC Metals: Its Quantum-Mechanical Character  

Microsoft Academic Search

A consistent quantum-mechanical description is given of some atomistic properties of hydrogen isotopes in bcc metals, including in particular the energy and wave functions of a hydrogen atom, its preference of the type of interstitial sites, distortion of the surrounding lattice, and its effects on crystal structure. A general systematics in the site-preference---a transition from T sites to O sites

Yuh Fukai

1983-01-01

212

Metallization of hydrogen using heavy-ion-beam implosion of multilayered cylindrical targets  

Microsoft Academic Search

Employing a two-dimensional simulation model, this paper presents a suitable design for an experiment to study metallization of hydrogen in a heavy-ion beam imploded multilayered cylindrical target that contains a layer of frozen hydrogen. Such an experiment will be carried out at the upgraded heavy-ion synchrotron facility (SIS-18) at the Gesellschaft für Schwerionenforschung, Darmstadt by the end of the year

N. A. Tahir; D. H. Hoffmann; A. Kozyreva; A. Tauschwitz; A. Shutov; J. A. Maruhn; P. Spiller; U. Neuner; J. Jacoby; M. Roth; R. Bock; H. Juranek; R. Redmer

2001-01-01

213

Hydrogen sulfide and ammonia removal on activated carbon fiber cloth-supported metal oxides.  

PubMed

The present investigation attempts to provide mechanisms for the influence of metal catalysts on carbon supports in odorous gas removal. For this purpose, an activated carbon fiber cloth (ACFC) was subjected to successive metal impregnation to modify its surface properties and so increase its treatment capacity. The carbon fiber cloth adsorbent was prepared by classical incipient wetness impregnation followed by calcination in order to obtain metal oxide phases. Different impregnation parameters (type of metal, level of impregnation, calcination temperature) in the removal of hydrogen sulfide and ammonia were studied. Adsorption kinetics and capacities were carried out in a batch reactor at room temperature. It was found that removal activity depended on metal loading as well as on the order of the metal addition and calcination phase. The capacity of ACFC-supported metal oxides to adsorb both pollutants showed great improvement compared to the virgin adsorbent. PMID:16335599

Le Leuch, L M; Subrenat, A; Le Cloirec, P

2005-11-01

214

PIG charged particle source with hydrogen supply from a metal-hydride cathode  

NASA Astrophysics Data System (ADS)

We present the results of an experimental investigation of a Penning-type charged-particles source with a metal-hydride cathode. The main characteristic of the experiment is internal hydrogen supply from the metal-hydride cathode under the conditions of ion-stimulated desorption; we studied its influence on the source's emissive characteristics. An additional mode of source operation was observed involving axial electron emission; the decisive effect was revealed of the desorbed hydrogen on the axial electron emission. The ion energy distribution function was measured and its dependence on the external discharge parameters was determined.

Borgun, Ie V.; Ryabchikov, D. L.; Sereda, I. N.; Tseluyko, A. F.

2014-05-01

215

Metal-free hydrogenation catalysis of polycyclic aromatic hydrocarbons.  

PubMed

The frustrated Lewis pair, B(C(6)F(5))(3)/Ph(2)PC(6)F(5), acts as an efficient catalyst for the hydrogenation of the polycyclic hydrocarbons including anthracene derivatives, tetracene and tetraphene, at 80 °C and 100 atm H(2) pressure via a mechanism involving protonation of polyaromatic species followed by hydride transfer. PMID:23128319

Segawa, Yasutomo; Stephan, Douglas W

2012-12-21

216

Nickel-hydrogen. [metal hydrides, electrochemical corrosion, and structural design  

NASA Technical Reports Server (NTRS)

Because of the disintegration of LaNi5 as the lattice expands on absorbing hydrogen, a nickel hydrogen cell similar to a nickel cadmium cell was designed. The positive electrode is wrapped in a microporous separator and the leads are insulated. A negative conducting grid is inserted and welded to the top of the can into an open ended container which is then turned upside down and filled so that LiNa5 powder occupies all the space not used by the rest of the components. The bottom of the can is then welded on. A fill tube is located either on the bottom or on the top of the can. When welded shut, the cell is put into a pressure bomb and the lanthanum nickel is activated at about 1,000 pounds of hydrogen. Electrolytes are added to the cell as well as whatever amount of hydrogen precharge desired, and the cell is sealed. Advantages and disadvantages of the cell are discussed.

Mchenry, E. J.

1977-01-01

217

Two-dimensional metal-organic surfaces for efficient hydrogen evolution from water.  

PubMed

Hydrogen production through the reduction of water has emerged as an important strategy for the storage of renewable energy in chemical bonds. One attractive scenario for the construction of efficient devices for electrochemical splitting of water requires the attachment of stable and active hydrogen evolving catalysts to electrode surfaces, which remains a significant challenge. We demonstrate here the successful integration of cobalt dithiolene catalysts into a metal-organic surface to generate very active electrocatalytic cathode materials for hydrogen generation from water. These surfaces display high catalyst loadings and remarkable stability even under very acidic aqueous solutions. PMID:25525864

Clough, Andrew J; Yoo, Joseph W; Mecklenburg, Matthew H; Marinescu, Smaranda C

2015-01-14

218

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

NASA Technical Reports Server (NTRS)

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

Gales, C.; Perroud, P.

1981-01-01

219

Catalytic Metal Free Production of Large Cage Structure Carbon Particles: A Candidate for Hydrogen Storage  

NASA Technical Reports Server (NTRS)

We will demonstrate that carbon particles consisting of large cages can be produced without catalytic metal. The carbon particles were produced in CO gas as well as by introduction of 5% methane gas into the CO gas. The gas-produced carbon particles were able to absorb approximately 16.2 wt% of hydrogen. This value is 2.5 times higher than the 6.5 wt% goal for the vehicular hydrogen storage proposed by the Department of Energy in the USA. Therefore, we believe that this carbon particle is an excellent candidate for hydrogen storage for fuel cells.

Kimura, Yuki; Nuth, Joseph A., III; Ferguson, Frank T.

2005-01-01

220

Investigation on a three-stage hydrogen thermal compressor based on metal hydrides  

NASA Astrophysics Data System (ADS)

In this paper we report our recent investigation about a there-stage hydrogen thermal compressor based on metal hydrides (HTC) in order to reach an overall compression ratio 28:1. The research was focused to: (i) elaborate hydride alloys with good storage capacity and higher thermodynamic characteristics acquired by tailoring of their properties; (ii) develop new technical solutions based on advanced materials, and fast mass and heat transfer for a hydrogen storage-compression reactor; (iii) built up a prototype of the HTC. Cyclic performance of the hydrogen compressor is studied following up the operating parameters: supply pressure, storage volumes, cold and hot fluid temperatures, cycle duration. The experiments show that the HTC can attain a high overall compression ratio 28:1, it will raise the hydrogen pressure from 2 bars to 56 bars, using three hydride compression stages working between 20 and 80°C. Cycling the compressor at a short absorption-desorption cycle, about 2 minutes, a satisfactory hydrogen flow rate was obtain 10 l/cycle, which ensures a hydrogen flow rate about 300l/hour using a small quantity of hydride alloy, about 360 g. To improve the efficiency and economics of compression process, HTC prototype based on metal hydrides must operate in conjunction with advanced hydrogen production technologies from renewable resources.

Popeneciu, G.; Almasan, V.; Coldea, I.; Lupu, D.; Misan, I.; Ardelean, O.

2009-08-01

221

In-situ hydrogen in metal determination using a minimum neutron source strength and exposure time.  

PubMed

Water is frequently present in the environment and is a source of hydrogen that can interact with many materials. Because of its small atomic size, a hydrogen atom can easily diffuse into a host metal, and though the metal may appear unchanged for a time, the metal will eventually abruptly lose its strength and ductility. Thus, measuring the hydrogen content in metals is important in many fields, such as in the nuclear industry, in automotive and aircraft fabrication, and particularly, in offshore oil and gas fields. It has been demonstrated that the use of nuclear methods to measure the hydrogen content in metals can achieve sensitivity levels on the order of parts per million. However, the use of nuclear methods in the field has not been conducted for two reasons. The first reason is due to exposure limitations. The second reason is due to the hi-tech instruments required for better accuracy. In this work, a new method using a low-strength portable neutron source is explored in conjunction with detectors based on plastic nuclear detection films. The following are the in-situ requirements: simplicity in setup, high reliability, minimal exposure dose, and acceptable accuracy at an acceptable cost. A computer model of the experimental setup is used to reproduce the results of a proof-of-concept experiment and to predict the sensitivity levels under optimised experimental conditions. PMID:23708832

Hatem, M; Agamy, S; Khalil, M Y

2013-08-01

222

REACTIVITY OF FORMULATED METAL OXIDE SORBENTS WITH HOT HYDROGEN SULFIDE  

Microsoft Academic Search

Three metal oxide sorbents, labeled TU-19, TU-24, and TU-25 were formulated with zinc oxide powder as an active sorbent ingredient, bentonite as a binding material, and titanium oxide as a supporting metal oxide. Equilibrium absorption of H2S into sorbents increases with concentrations of H2S. Reactivity of sorbents increases with increased reaction temperatures. Reaction rates of H2S with the sorbent increase

Kyung C. Kwon; Sammaiah Pallerla; Roy Sanjeev; Susan K. Joines; Charles Komar

2001-01-01

223

NOBLE METAL CHEMISTRY AND HYDROGEN GENERATION DURING SIMULATED DWPF MELTER FEED PREPARATION  

SciTech Connect

Simulations of the Defense Waste Processing Facility (DWPF) Chemical Processing Cell vessels were performed with the primary purpose of producing melter feeds for the beaded frit program plus obtaining samples of simulated slurries containing high concentrations of noble metals for off-site analytical studies for the hydrogen program. Eight pairs of 22-L simulations were performed of the Sludge Receipt and Adjustment Tank (SRAT) and Slurry Mix Evaporator (SME) cycles. These sixteen simulations did not contain mercury. Six pairs were trimmed with a single noble metal (Ag, Pd, Rh, or Ru). One pair had all four noble metals, and one pair had no noble metals. One supporting 4-L simulation was completed with Ru and Hg. Several other 4-L supporting tests with mercury have not yet been performed. This report covers the calculations performed on SRNL analytical and process data related to the noble metals and hydrogen generation. It was originally envisioned as a supporting document for the off-site analytical studies. Significant new findings were made, and many previous hypotheses and findings were given additional support as summarized below. The timing of hydrogen generation events was reproduced very well within each of the eight pairs of runs, e.g. the onset of hydrogen, peak in hydrogen, etc. occurred at nearly identical times. Peak generation rates and total SRAT masses of CO{sub 2} and oxides of nitrogen were reproduced well. Comparable measures for hydrogen were reproduced with more variability, but still reasonably well. The extent of the reproducibility of the results validates the conclusions that were drawn from the data.

Koopman, D

2008-06-25

224

Enantioselective hydrogenation. IV. Hydrogen isotope exchange in 10,11-dihydrocinchonidine and in quinoline catalyzed by platinum group metals  

SciTech Connect

Hydrogen isotope (H/D) exchange in the alkaloid 10,11-dihydrocinchonidine has been studied over 6.4% Pt/silica (EUROPT-1), 5% Ru/alumina, 5% Rh/alumina, and 5% Pd/alumina at 293 K using C{sub 2}H{sub 5}OD and D{sub 2} as solvent and deuterium source. Exchange was accompanied by hydrogenation. Over Pt, fast exchange occurred in the hydroxyl group followed by multiple exchange in which alkaloid molecules containing, 2, 3, 4 and 5 deuterium atoms were formed simultaneously. Mass spectrometry and {sup 1}H NMR showed that this multiple exchange occurred in the quinoline ring system and at C{sub 9}, but not in the quinuclidine ring system. The pattern of exchange in Ru was similar. Over Rh extensive hydrogenolysis of the quinuclidine ring system occurred, and over Pd the quinoline ring system was rapidly hydrogenated. Quinoline exchange and hydrogenation were also studied at 293 K; relatively rapid exchange occurred over Pt, Ru, and Rh, particularly at the 2- and 8-positions, whereas hydrogenation without significant exchange occurred over Pd. 10,11-Dihydrocinchonidine is adsorbed on Pt and Ru via the quinoline ring system and the multiple nature of the exchange indicates that the quinoline moiety is adsorbed approximately parallel to the metal surface by multicenter {pi}-bonding. An additional interaction of the alkaloid molecule with the surface occurs at carbon atom C{sub 9}, which may interpret the slower exchange in the alkaloid by comparison with that in quinoline. This study supports and enhances the model proposed to interpret the origin of enantioselectivity in pyruvate hydrogenation over Pt and Ir modified by cinchona alkaloids. The similarities of exchange over Pt and Ru suggest that enantioselective catalysis should be achievable over Ru. 28 refs., 2 figs., 2 tabs.

Bond, G.; Wells, P.B. [Univ. of Hull (United Kingdom)] [Univ. of Hull (United Kingdom)

1994-12-01

225

PHYSICAL REVIEW B 90, 035103 (2014) Quasiparticle energies and excitonic effects in dense solid hydrogen near metallization  

E-print Network

hydrogen near metallization Marc Dvorak,1 Xiao-Jia Chen,2,3 and Zhigang Wu1,* 1 Department of Physics Advanced Research, Shanghai 201203, China 3 Geophysical Laboratory, Carnegie Institution of Washington July 2014) We investigate the crucial metallization pressure of the Cmca-12 phase of solid hydrogen (H

Wu, Zhigang

226

High Flux Metallic Membranes for Hydrogen Recovery and Membrane Reactors  

SciTech Connect

We made and tested over 250 new alloys for use as lower cost, higher flux hydrogen extraction membrane materials. Most of these were intermetallic, or contained significant intermetallic content, particularly based on B2 alloy compositions with at least one refractory component; B2 intermetallics resemble BCC alloys, in structure, but the atoms have relatively fixed positions, with one atom at the corners of the cube, the other at the centers. The target materals we were looking for would contain little or no expensive elements, no strongly toxic or radioactive elements, would have high flux to hydrogen, while being fabricable, brazable, and relatively immune to hydrogen embrittlement and corrosion in operation. The best combination of properties of the membrane materials we developed was, in my opinion, a Pd-coated membrane consisting of V -9 atomic % Pd. This material was relatively cheap, had 5 times the flux of Pd under the same pressure differential, was reasonably easy to fabricate and braze, and not bad in terms of embrittlement. Based on all these factors we project, about 1/3 the cost of Pd, on an area basis for a membrane designed to last 20 years, or 1/15 the cost on a flux basis. Alternatives to this membrane replaced significant fractions of the Pd with Ni and or Co. The cost for these membranes was lower, but so was the flux. We produced successful brazed products from the membrane materials, and made them into flat sheets. We tested, unsuccessfully, several means of fabricating thematerials into tubes, and eventually built a membrane reactor using a new, flat-plate design: a disc and doughnut arrangement, a design that seems well- suited to clean hydrogen production from coal. The membranes and reactor were tested successfully at Western Research. A larger equipment company (Chart Industries) produced similar results using a different flat-plate reactor design. Cost projections of the membrane are shown to be attractive.

Buxbaum, Robert

2010-06-30

227

of hydrogen-powered cars," he says. But a major hurdle remains: the cost of platinum metal  

E-print Network

of hydrogen-powered cars," he says. But a major hurdle remains: the cost of platinum metal needed to make fuel cells efficient. Fuel cells work by combining hydrogen gas with oxygen from the air for hydrogen-powered cars in mass production facilities," says SFU chemistry professor Steve Holdcroft, who

228

Observation of Hydrogen Distribution Around Non-Metallic Inclusions in Steels with Tritium Microautoradiography  

SciTech Connect

Hydrogen distributions around non-metallic inclusions in steels are successfully characterized with high-resolution tritium autoradiography. The autoradiographs show that hydrogen accumulation characteristics around the inclusions depend on types of the inclusions. In the case of MnS, hydrogen was inhomogeneously distributed in the ferrite matrix surrounding the MnS inclusion, probably because hydrogen is trapped in defects formed around MnS. The inhomogeneous distribution of hydrogen may be originated from the asymmetric stress field produced by a contraction of the MnS phase in the heat treatment, i.e. the inhomogeneous volumetric change of MnS owing to its larger thermal expansion than that of the ferrite phase. In the case of Al{sub 2}O{sub 3}, hydrogen was intensely localized at boundary layers of the ferrite matrix surrounding the Al{sub 2}O{sub 3} inclusion. This could be attributed to hydrogen trapping at defects introduced by a residual stress in the boundary layers of the ferrite matrix due to larger contraction of the ferrite phase than that of the Al{sub 2}O{sub 3} phase on cooling. Similarly hydrogen was accumulated in the surrounding ferrite matrix but more widely distributed around Cr carbide probably because difference in the thermal expansion between the Cr carbide and ferrite phases is less than that between the Al{sub 2}O{sub 3} and ferrite phases.

Otsuka, Teppei; Hanada, Hitoshi; Nakashima, Hidehiko; Sakamoto, Kan; Hayakawa, Masao; Hashizume, Kenichi; Sugisaki, Masayasu [Kyushu University (Japan)

2005-07-15

229

Cation-induced kinetic trapping and enhanced hydrogen adsorption in a modulated anionic metal-organic framework  

Microsoft Academic Search

Metal-organic frameworks (MOFs)-microporous materials constructed by bridging metal centres with organic ligands-show promise for applications in hydrogen storage, which is a key challenge in the development of the `hydrogen economy'. Their adsorption capacities, however, have remained insufficient for practical applications, and thus strategies to enhance hydrogen-MOF interactions are required. Here we describe an anionic MOF material built from In(III) centres

Sihai Yang; Xiang Lin; Alexander J. Blake; Gavin S. Walker; Peter Hubberstey; Neil R. Champness; Martin Schröder

2009-01-01

230

Hydrogen sulfide removal from coal gas by the metal-ferrite sorbents made from the heavy metal wastewater sludge.  

PubMed

The metal-ferrite (chromium-ferrite and zinc-ferrite) sorbents made from the heavy metal wastewater sludge have been developed for the hydrogen sulfide removal from coal gas. The high temperature absorption of hydrogen sulfide from coal gas with the metal-ferrite sorbent in a fixed bed reactor was conducted in this study. The metal-ferrite powders were the products of the ferrite process for the heavy metal wastewater treatment. The porosity analysis results show that the number of micropores of the sorbents after sulfidation and regeneration process decreases and the average pore size increases due to the acute endothermic and exothermic reactions during the sulfidation-regeneration process. The FeS, ZnS, and MnS peaks are observed on the sulfided sorbents, and the chromium extraction of the CFR6 can fulfill the emission standard of Taiwan EPA. The suitable sulfidation temperature range for chromium-ferrite sorbent is at 500-600 degrees C. In addition, effects of various concentrations of H2 and CO were also conducted in the present work at different temperatures. By increasing the H2 concentration, the sulfur sorption capacity of the sorbent decreases and an adverse result is observed in the case of increasing CO concentration. This can be explained via water-shift reaction. PMID:18440697

Tseng, Ting Ke; Chang, Han Ching; Chu, Hsin; Chen, Hung Ta

2008-12-30

231

Phonons in quantum solids with defects. [lattice vacancies and interstitials in solid helium and metallic hydrogen  

NASA Technical Reports Server (NTRS)

A formalism was developed for temperature-dependent, self-consistent phonons in quantum solids with defects. Lattice vacancies and interstitials in solid helium and metallic hydrogen, as well as electronic excitations in solid helium, were treated as defects that modify properties of these systems. The information to be gained from the modified phonon spectrum is discussed.

Jacobi, N.; Zmuidzinas, J. S.

1974-01-01

232

Lightweight metal-hydrogen cell with improved plate stack supporting means  

Microsoft Academic Search

A metal-hydrogen cell is disclosed in which the durability of the battery is substantially increased and the system mass and volume are reduced. A plate stack within the casing is compressed by a spring which is supported from the casing without support from the terminals. The spring support is external to the cell stack; that is, it does not pass

L. E. Miller; D. Carr; L. Smith

1985-01-01

233

Quantitative analysis of hydrogen isotopes in the metal hydride of the neutron tube target  

Microsoft Academic Search

We describe an experimental system for the quantitative analyses of hydrogen isotopes in metal hydride targets. The experimental system consists of a target desorption inlet system (TDIS) and a high-resolution mass spectrometer. The TDIS has a unique design that provides complete desorption of the gas and rapid, direct, and accurate measurements of pressure, volume, and temperature of the total gas

H. Bach; S. Black; W. Chamberlin

1997-01-01

234

Tolerances of five benthic invertebrates to hydrogen ions and metals (Cd, Pb, Al)  

Microsoft Academic Search

96-hr LC50 static bioassays were carried out to determine if the hydrogen ion content and the levels of cadmium, lead, and aluminum characteristic of lakes in the Muskoka District, Ontario, are lethal to benthic macroinvertebrates in four functional groups. The results show that cadmium is the most toxic of the three metals tested to all four functional groups (filter feeders,

G. L. Mackie

1989-01-01

235

Hysteretic Adsorption and Desorption of Hydrogen by Nanoporous MetalOrganic Frameworks  

Microsoft Academic Search

Adsorption and desorption of hydrogen from nanoporous materials, such as activated carbon, is usually fully reversible. We have prepared nanoporous metal-organic framework materials with flexible linkers in which the pore openings, as characterized in the static structures, appear to be too small to allow H2 to pass. We observe hysteresis in their adsorption and desorption kinetics above the supercritical temperature

Xuebo Zhao; Bo Xiao; Ashleigh J. Fletcher; K. Mark Thomas; Darren Bradshaw; Matthew J. Rosseinsky

2004-01-01

236

Modeling hydrogen and helium entrapment in flowing liquid metal surfaces as plasma-facing components in  

E-print Network

Modeling hydrogen and helium entrapment in flowing liquid metal surfaces as plasma, the ability to use liquids as plasma-facing components (PFCs) depends on their interaction with the plasma and the magnetic field. One important issue for the moving liquid is the ability to entrain particles that strike

Harilal, S. S.

237

Butterfly valve with metal seals controls flow of hydrogen from cryogenic through high temperatures  

NASA Technical Reports Server (NTRS)

Butterfly valve with metal seals operates over a temperature range of minus 423 degrees to plus 440 degrees F with hydrogen as a medium and in a radiation environment. Media flow is controlled by an internal butterfly disk which is rotated by an actuation shaft.

Johnson, L. D.

1967-01-01

238

Cleaner pathways of hydrogen, carbon nano-materials and metals production via solar thermal processing  

Microsoft Academic Search

This paper describes various solar thermochemical processes for the production of hydrogen, carbon nano particles, industrial grade carbon black, and metals with substantially reduced CO2 emission footprint. The paper introduces an innovative approach of a three-dimensional volumetric production of carbon nano particles via thermal cracking of methane gained by carbon seeding as an alternative to the existing two dimensional modes.

Nesrin Ozalp; Michael Epstein; Abraham Kogan

2010-01-01

239

The kinetic and mechanical aspects of hydrogen-induced failure in metals. Ph.D. Thesis, 1971  

NASA Technical Reports Server (NTRS)

Premature hydrogen-induced failure observed to occur in many metal systems involves three stages of fracture: (1) crack initiation, (2) stable slow crack growth, and (3) unstable rapid crack growth. The presence of hydrogen at some critical location on the metal surface or within the metal lattice was shown to influence one or both of the first two stages of brittle fracture but has a negligible effect on the unstable rapid crack growth stage. The relative influence of the applied parameters of time, temperature, etc., on the propensity of a metal to exhibit hydrogen induced premature failure was investigated.

Nelson, H. G.

1972-01-01

240

Hydrogen storage properties of nano-structural carbon and metal hydrides composites  

NASA Astrophysics Data System (ADS)

Thermodynamic and structural properties of some ball-milled mixtures composed of the hydrogenated nanostructural carbon (C nanoH x) and metal hydride (MH; M=Li, Na, Mg and Ca) were examined from thermal desoroption mass spectroscopy and powder X-ray diffraction, respectively. The results showed that the hydrogen desorption temperatures are significantly lowered from those of each hydride (C nanoH x, MH) in the composites. This indicates that a new type of interaction exists between C nanoH x and MH, which destabilizes C-H and/or M-H bonding as well. Therefore, the above Metal-C-H system would be recognized as a new family of hydrogen storage materials.

Miyaoka, Hiroki; Ichikawa, Takayuki; Isobe, Shigehito; Fujii, Hironobu

2006-08-01

241

Metallization of hydrogen using heavy-ion-beam implosion of multilayered cylindrical targets  

NASA Astrophysics Data System (ADS)

Employing a two-dimensional simulation model, this paper presents a suitable design for an experiment to study metallization of hydrogen in a heavy-ion beam imploded multilayered cylindrical target that contains a layer of frozen hydrogen. Such an experiment will be carried out at the upgraded heavy-ion synchrotron facility (SIS-18) at the Gesellschaft für Schwerionenforschung, Darmstadt by the end of the year 2001. In these calculations we consider a uranium beam that will be available at the upgraded SIS-18. Our calculations show that it may be possible to achieve theoretically predicted physical conditions necessary to create metallic hydrogen in such experiments. These include a density of about 1 g/cm3, a pressure of 3-5 Mbar, and a temperature of a few 0.1 eV.

Tahir, N. A.; Hoffmann, D. H.; Kozyreva, A.; Tauschwitz, A.; Shutov, A.; Maruhn, J. A.; Spiller, P.; Neuner, U.; Jacoby, J.; Roth, M.; Bock, R.; Juranek, H.; Redmer, R.

2001-01-01

242

Hydrogen storage in metal hydrides. Final report, September 1989-March 1990  

SciTech Connect

The primary objective of this program was to develop an economical process for producing a lightweight hydrogen storage medium by the chemical vapor inflitration (CVI) of a metal hydride former into a reticulated foam substrate. An investigation was conducted to determine the most favorable precursors for forming the candidate hydride-forming materials, along with optimization of their transport and deposition parameters. A substrate optimization study was also performed in order to derive the greatest surface area-to-volume ratio from the resulting metal hydride-forming foam. Thermogravimetric analysis (TGA) was performed on a metal foam sample to determine its hydriding capability. Results were inconclusive, showing only slight if any hydriding.

DelaRosa, M.J.

1990-08-01

243

Highly effective hydrogen isotope separation in nanoporous metal-organic frameworks with open metal sites: direct measurement and theoretical analysis.  

PubMed

Separating gaseous mixtures that consist of very similar size is one of the critical issues in modern separation technology. Especially, the separation of the isotopes hydrogen and deuterium requires special efforts, even though these isotopes show a very large mass ratio. Conventionally, H/D separation can be realized through cryogenic distillation of the molecular species or the Girdler-sulfide process, which are among the most energy-intensive separation techniques in the chemical industry. However, costs can be significantly reduced by using highly mass-selective nanoporous sorbents. Here, we describe a hydrogen isotope separation strategy exploiting the strongly attractive open metal sites present in nanoporous metal-organic frameworks of the CPO-27 family (also referred to as MOF-74). A theoretical analysis predicts an outstanding hydrogen isotopologue separation at open metal sites due to isotopal effects, which has been directly observed through cryogenic thermal desorption spectroscopy. For H2/D2 separation of an equimolar mixture at 60 K, the selectivity of 12 is the highest value ever measured, and this methodology shows extremely high separation efficiencies even above 77 K. Our theoretical results imply also a high selectivity for HD/H2 separation at similar temperatures, and together with catalytically active sites, we propose a mechanism to produce D2 from HD/H2 mixtures with natural or enriched deuterium content. PMID:24359584

Oh, Hyunchul; Savchenko, Ievgeniia; Mavrandonakis, Andreas; Heine, Thomas; Hirscher, Michael

2014-01-28

244

Grain-boundary engineering markedly reduces susceptibility to intergranular hydrogen embrittlement in metallic materials  

SciTech Connect

The feasibility of using 'grain-boundary engineering' techniques to reduce the susceptibility of a metallic material to intergranular embrittlement in the presence of hydrogen is examined. Using thermomechanical processing, the fraction of 'special' grain boundaries was increased from 46% to 75% (by length) in commercially pure nickel samples. In the presence of hydrogen concentrations between 1200 and 3400 appm, the high special fraction microstructure showed almost double the tensile ductility; also, the proportion of intergranular fracture was significantly lower and the J{sub c} fracture toughness values were some 20-30% higher in comparison with the low special fraction microstructure. We attribute the reduction in the severity of hydrogen-induced intergranular embrittlement to the higher fraction of special grain boundaries, where the degree of hydrogen segregation at these boundaries is reduced.

Bechtle, Sabine; Kumar, Mukul; Somerday, Brian P.; Launey, Maximilien E.; Ritchie, Robert O.

2009-05-10

245

Permeability of porour rhyolite  

NASA Astrophysics Data System (ADS)

The development of permeability in bubble-bearing magmas determines the efficiency of volatile escape during their ascent through volcanic conduits, which, in turn, controls their explosive potential. As permeability requires bubble connectivity, relationships between permeability and porosity in silicic magmas must be controlled by the formation, growth, deformation and coalescence of their constituent bubbles. Although permeability data on porous volcanic pyroclasts are limited, the database can be greatly extended by including data for ceramic and metallic foams1. Several studies indicate that a single number does not adequately describe the permeability of a foam because inertial effects, which predominate at high flow rates, cause deviations from Darcy's law. These studies suggest that permeability is best modeled using the Forschheimer equation to determine both the Darcy permeability (k1) and the non-Darcian (k2) permeability. Importantly, at the high porosities of ceramic foams (75-95%), both k1 and k2 are strongly dependent on pore size and geometry, suggesting that measurement of these parameters provides important information on foam structure. We determined both the connected porosity (by He-pycnometry) and the permeability (k1 and k2) of rhyolitic samples having a wide range in porosity (22-85%) and vesicle textures. In general, these data support previous observations of a power law relationship between connected porosity and Darcy permeability2. In detail, variations in k1 increase at higher porosities. Similarly, k2 generally increases in both mean and standard deviation with increasing porosity. Measurements made on three mutually perpendicular cores from individual pumice clasts suggest that some of the variability can be explained by anisotropy in the vesicle structure. By comparison with ceramic foams, we suggest that the remaining variability results from differences either in average vesicle size or, more likely, in the size of apertures connecting individual vesicles. This interpretation is supported by the observation that clasts with high porosities but unusually low k1 and k2 also have high percentages of isolated pores (>10%), indicating extensive vesiculation but limited bubble coalescence; such clasts seem to be characteristic of ignimbrite deposits. 1Innocentini MDM, Salvini VR, Pandolfelli VC, Coury JC (1999) The permeability of ceramic foams. Amer Ceram Soc Bull 79:78-94. 2Klug C, Cashman KV (1996) Permeability development in vesiculating magmas - implications for fragmentation. Bull. Volcanol.58:87-100; Klug C, Cashman KV, Bacon C (2002) Structure and physical characteristics of pumice from the climactic eruption of Mt. Mazama (Crater Lake), Oregon. Bull Volcanol 64:486-501

Cashman, K.; Rust, A.; Wright, H.; Roberge, J.

2003-04-01

246

Advances in transition metal-catalyzed asymmetric hydrogenation of heteroaromatic compounds.  

PubMed

Transition metal-catalyzed asymmetric hydrogenation of heteroaromatic compounds is undoubtedly a straightforward and environmentally friendly method for the synthesis of a wide range of optically active heterocyclic compounds, which are widespread and ubiquitous in naturally occurring and artificial bioactive molecules. Over the past decade, a number of transition metal (Ir, Rh, Ru, and Pd) catalysts bearing chiral phosphorus ligands, amine-tosylamine ligands, and N-heterocyclic carbene ligands have been developed for such challenging transformation. This review will describe the significant contributions concerning the transition metal-catalyzed asymmetric hydrogenation of N-, O-, and S-containing heteroaromatic compounds, with emphasis on the evolution of different chiral ligands, related catalyst immobilization, and mechanism investigations. PMID:24173671

He, Yan-Mei; Song, Feng-Tao; Fan, Qing-Hua

2014-01-01

247

Oxidation of metal sulfites by iodine for use in thermochemical hydrogen cycles  

NASA Astrophysics Data System (ADS)

It is noted that thermochemical hydrogen cycles involving metal sulfates offer an alternative to sulfuric acid which is corrosive and has high energy requirements for drying prior to its thermal decomposition. The formation of such metal sulfates in conjunction with a low temperature hydrogen formation step is discussed. The following reaction was studied: MgSO3(c) + MgO(c) + I2(g) yields MgSO4(c) + MgI2(c). Although magnesium sulfite appears promising for this oxidation, a search was conducted for alternative metal sulfites which fit the following criteria for use: (1) sulfate must decompose in the temperature range available ( 1400 K); (2) iodide must hydrolyze easily; and (3) salts must not be rare, toxic, or expensive. Lanthanum and titanium fit these criteria.

Mason, C. F. V.; Bowman, M. G.

1981-09-01

248

Kondo-lattice–like effects of hydrogen in transition metals  

Microsoft Academic Search

We discuss the possibility of a Kondo like effect associated with H in metals\\u000aresulting from the strong dependence of the H1s orbital radius on the\\u000aoccupation number. We demonstrate that such a strong breathing property of the\\u000aorbital radius, which translates directly into a strong occupation dependent\\u000ahopping, results in the formation of local singlet-like bound states involving\\u000aone

R. Eder; H. F. Pen; G. A. Sawatzky

1997-01-01

249

Hydrogen as an Indicator to Assess Biological Activity During Trace-Metal Bioremediation  

SciTech Connect

The design and operation of a trace-metal or radionuclide bioremediation scheme requires that specific redox conditions be achieved at given zones of an aquifer for a pre-determined duration. Tools are therefore needed to identify and quantify the terminal electron accepting processes (TEAPs) that are being achieved during bioremediation in an aquifer, and that this be done at a high spatial resolution. Dissolved hydrogen (H{sub 2}) concentrations have been shown to correlate with specific TEAPs during bioremediation in an aquifer (Table 1). Theoretical analysis has shown that these steady-state hydrogen levels are solely dependent upon the physiological parameters of the hydrogen-consuming microorganisms, with hydrogen concentrations increasing as each successive TEAP yields less energy for bacterial growth. The assumptions for this statement may not hold during a bioremediation scheme in which an organic substrate is injected into the subsurface and where organisms may consume hydrogen and carbon simultaneously. This research examines the effects of simultaneous hydrogen and carbon utilization through obtaining kinetic parameters of both hydrogen and carbon consumption under iron reducing conditions in batch experiments. A dual-donor model was formulated and compared to flow-through column experiments.

Jaffe, Peter R.; Lovley, Derek; Komlos, John; Brown, Derick

2004-03-17

250

Characterization and high throughput analysis of metal hydrides for hydrogen storage  

NASA Astrophysics Data System (ADS)

Efficient hydrogen storage is required for fuel cell vehicles to be competitive with those driven by internal combustion engines. Current methods of storage such as compressed gas and liquid hydrogen cannot meet this standard, so novel hydrogen storage materials such as metal hydrides are required. No simple metal hydride meets the required specifications. Research is required to find new materials or improve existing materials. This thesis describes the research practices necessary to achieve legitimate and repeatable results in laboratories across the world. Examples of experiments using these techniques are presented, such as a high throughput technique to optimize materials systems with up to three components such as calcium borohydride with titanium catalyst and magnesium hydride with nickel and aluminum as destabilizing elements and catalysts. Thin films composed of gradients of each material were deposited by sputtering, creating a single thin film sample covering all potential material combinations. Optical properties of the samples under hydrogen pressure were monitored to identify the regions with largest and fastest hydrogen uptake. In the Ca-B-Ti system, titanium did not sufficiently catalyze the borohydride formation reaction at low temperature. Substantial hydrogen uptake was shown in the Mg-Ni region of the Mg-Ni-Al films. Al did not participate in the reaction at low temperature. Further investigation of the role of catalysts and destabilizing elements in improving hydrogen storage performance through X-ray Absorption and Emission Spectroscopy measurements of the Mg-Ni system during hydrogenation is presented. Typical X-ray spectroscopy measurements use a synchrotron radiation source and require ultra high vacuum conditions. For these experiments we designed a chamber which can be inserted into a vacuum chamber allowing in situ measurements of a sample under hydrogen pressure, providing information on the role of Ni in hydrogen absorption of Mg-Ni mixtures. Finally, another technique for improving hydrogen storage performance is presented which focuses on promising materials studied using the high throughput technique. TiO2 powder was ball milled together with NaBH 4, and gravimetric analysis shows a 50% improvement in the kinetics of the hydrogen desorption reaction and a reduction in desorption temperature of 60°C.

Barcelo, Steven James

251

Partial and complete reduction of O2 by hydrogen on transition metal surfaces  

SciTech Connect

The metal-catalyzed reduction of di-oxygen (O{sub 2}) by hydrogen is at the heart of direct synthesis of hydrogen peroxide (HOOH) and power generation by proton exchange membrane fuel cells. Despite its apparent simplicity, how the reaction proceeds on different metals is not yet well understood. We present a systematic study of O{sub 2} reduction on the (111) facets of eight transition metals (Rh, Ir, Ni, Pd, Pt, Cu, Ag, and Au) based on periodic density functional theory (DFT-GGA) calculations. Analysis of ten surface elementary reaction steps suggests three selectivity regimes as a function of the binding energy of atomic oxygen (BEO), delineated by the opposite demands to catalyze O-O bond scission and O-H bond formation: The dissociative adsorption of O{sub 2} prevails on Ni, Rh, Ir, and Cu; the complete reduction to water via associative (peroxyl, peroxide, and aquoxyl) mechanisms prevails on Pd, Pt, and Ag; and HOOH formation prevails on Au. The reducing power of hydrogen is decreased electrochemically by increasing the electrode potential. This hinders the hydrogenation of oxygen species and shifts the optimal selectivity for water to less reactive metals. Our results point to the important role of the intrinsic reactivity of metals in the selectivity of O{sub 2} reduction, provide a unified basis for understanding the metal-catalyzed reduction of O{sub 2} to H{sub 2}O and HOOH, and offer useful insights for identifying new catalysts for desired oxygen reduction products.

Ford, Denise [University of Wisconsin, Madison; Nilekar, Anand Udaykumar [University of Wisconsin, Madison; Xu, Ye [ORNL; Mavrikakis, Manos [University of Wisconsin, Madison

2010-01-01

252

HYDROGEN ENVIRONMENT EMBRITTLEMENT OF METALS IN HIGH-PESSURE HYDROGEN STORAGE  

Microsoft Academic Search

A new material testing equipment in 70 MPa hydrogen at room temperature was developed to facilitate the measurement of the actual load on a specimen inside a pressure vessel with an external load cell. The tensile behaviors of different types of austenitic stainless steel (SS), namely, 304, 316, 316L, 316LN and 310S, and aluminum alloy, A6061, for use in high-pressure

S. Fukuyama; L. Zhang; K. Yokogawa

253

Dissolution of Uranium Metal Without Hydride Formation or Hydrogen Gas Generation  

SciTech Connect

This study shows that metallic uranium will cleanly dissolve in carbonate-peroxide solution without generation of hydrogen gas or uranium hydride. Metallic uranium shot, 0.5 to 1 mm diameter, were reacted with ammonium carbonate - hydrogen peroxide solution ranging in concentration from 0.13M to 1.0M carbonate and 0.50M to 2.0M peroxide. The uranium beads were weighed before and after reacting with the etch solution, and from the weights of the beads, their diameters were calculated, before and after the etch. The etch rate on the beads was then calculated from the reduction in bead diameter, and independently by uranium analysis of the solution. The calculated etch rate ranged from about 4 x 10-4 to 8 x 10-4 cm per hour, dependent primarily on the peroxide concentration. A hydrogen analysis of the etched beads showed that no detectable hydrogen was introduced into the uranium metal by the etching process.

Soderquist, Chuck Z.; Oliver, Brian M.; McNamara, Bruce K.

2008-09-01

254

First-principles study of hydrogen adsorption in metal-doped COF-10  

NASA Astrophysics Data System (ADS)

Covalent organic frameworks (COFs), due to their low-density, high-porosity, and high-stability, have promising applications in gas storage. In this study we have explored the potential of COFs doped with Li and Ca metal atoms for storing hydrogen under ambient thermodynamic conditions. Using density functional theory we have performed detailed calculations of the sites Li and Ca atoms occupy in COF-10 and their interaction with hydrogen molecules. The binding energy of Li atom on COF-10 substrate is found to be about 1.0 eV and each Li atom can adsorb up to three H2 molecules. However, at high concentration, Li atoms cluster and, consequently, their hydrogen storage capacity is reduced due to steric hindrance between H2 molecules. On the other hand, due to charge transfer from Li to the substrate, O sites provide additional enhancement for hydrogen adsorption. With increasing concentration of doped metal atoms, the COF-10 substrate provides an additional platform for storing hydrogen. Similar conclusions are reached for Ca doped COF-10.

Wu, Miao Miao; Wang, Qian; Sun, Qiang; Jena, Puru; Kawazoe, Yoshiyuki

2010-10-01

255

First-principles study of hydrogen adsorption in metal-doped COF-10  

NASA Astrophysics Data System (ADS)

Covalent organic frameworks (COFs), due to their low-density, high-porosity, and high-stability, have promising applications in gas storage. In this study we have explored the potential of COFs doped with Li and Ca metal atoms for storing hydrogen under ambient thermodynamic conditions. Using density functional theory we have performed detailed calculations of the sites Li and Ca atoms occupy in COF-10 and their interaction with hydrogen molecules. The binding energy of Li atom on COF-10 substrate is found to be about 1.0 eV and each Li atom can adsorb up to three H2 molecules. However, at high concentration, Li atoms cluster and, consequently, their hydrogen storage capacity is reduced due to steric hindrance between H2 molecules. On the other hand, due to charge transfer from Li to the substrate, O sites provide additional enhancement for hydrogen adsorption. With increasing concentration of doped metal atoms, the COF-10 substrate provides an additional platform for storing hydrogen. Similar conclusions are reached for Ca doped COF-10.

Wu, M. M.; Wang, Q.; Sun, Q.; Jena, P.; Kawazoe, Y.

2011-03-01

256

The Role of Water in the Storage of Hydrogen in Metals  

NASA Technical Reports Server (NTRS)

One major problem with the use of hydrogen is safe and efficient storage. In the pure form, bulky and heavy containers are required greatly reducing the efficiency of its use. Safety is also a great concern. Storage of hydrogen in the form of a metal hydride offers distinct advantages both in terms of volumetric efficiency and in terms of safety. As a result, an enormous amount of research is currently being done on metal-hydrogen systems. Practical application of these systems to storage of hydrogen can only occur when they are very well understood. In this paper, the preliminary results of a study of the surfaces of magnesium nickel alloys will be presented. Alloys that have been rendered totally unreactive with hydrogen as well as those that have been activated with liquid water and with water vapor were studied. Data obtained from XPS (X-ray Photoelectron Spectrometer) analysis, with samples held in vacuum for the shortest possible time to minimize the hydroxide degradation will be presented. Furthermore, TEM data on samples prepared in a new way that largely protects the surface from the high vacuum will be discussed.

Hampton, Michael D.; Lomness, Janice K.; Giannuzzi, Lucille A.

2001-01-01

257

Considerations for Storage of High Test Hydrogen Peroxide (HTP) Utilizing Non-Metal Containers  

NASA Technical Reports Server (NTRS)

When working with high concentrations of hydrogen peroxide, it is critical that the storage container be constructed of the proper materials, those which will not degrade to the extent that container breakdown or dangerous decomposition occurs. It has been suggested that the only materials that will safely contain the peroxide for a significant period of time are metals of stainless steel construction or aluminum use as High Test Hydrogen Peroxide (HTP) Containers. The stability and decomposition of HTP will be also discussed as well as various means suggested in the literature to minimize these problems. The dangers of excess oxygen generation are also touched upon.

Moore, Robin E.; Scott, Joseph P.; Wise, Harry

2005-01-01

258

Standard Test Method for Determination of the Susceptibility of Metallic Materials to Hydrogen Gas Embrittlement (HGE)  

E-print Network

1.1 This test method covers the quantitative determination of the susceptibility of metallic materials to hydrogen embrittlement, when exposed to high pressure gaseous hydrogen. 1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

American Society for Testing and Materials. Philadelphia

2006-01-01

259

Formation of metallic gold chain on patterned hydrogen terminated Si(001)-2x1 surface: Density functional study  

NASA Astrophysics Data System (ADS)

Metal adsorption on silicon surface for the formation of linear metallic chain is one of the important research areas for the advancement of nanotechnology. Due to the presence of dangling bonds all over the surface of bare Si(001), metals when deposited, generally do not tend to form stable wire structures. However, patterned hydrogen terminated Si-surface may be a good choice for the formation of atomic chain structures of metals. Since patterned hydrogen terminated Si(001):2x1 surface is very stable, we consider patterning it by removing desired hydrogen atoms and adsorbing gold atoms. We have examined the structure, energetic and electrical properties of such gold adsorbed surface by varying gold coverage. We have found that linear gold chain structures may be formed by controlling gold coverage. Some of these gold chain structures are metallic in nature. We hope that our results will motivate synthesis of gold chains on patterned hydrogen terminated Si(001): 2x1 surface.

Gupta, Bikash; Jena, Purusottam

2012-02-01

260

Permeability Test  

NSDL National Science Digital Library

This resource from the Indian Institute of Technology Kanpur provides an outline of constant head and falling head permeability tests of soil. This is a great resource for anyone studying geology and soil science.

2008-05-16

261

Permeable Pavement  

NSDL National Science Digital Library

Students investigate how different riparian ground covers, such as grass or pavement, affect river flooding. They learn about permeable and impermeable materials through the measurement how much water is absorbed by several different household materials in a model river. Students use what they learn to make recommendations for engineers developing permeable pavement. Also, they consider several different limitations for design in the context of a small community.

Integrated Teaching And Learning Program

262

Hydrogen Sulfide Preconditioning Protects Rat Liver against Ischemia/Reperfusion Injury by Activating Akt-GSK-3? Signaling and Inhibiting Mitochondrial Permeability Transition  

PubMed Central

Hydrogen sulfide (H2S) is the third most common endogenously produced gaseous signaling molecule, but its impact on hepatic ischemia/reperfusion (I/R) injury, especially on mitochondrial function, remains unclear. In this study, rats were randomized into Sham, I/R, ischemia preconditioning (IPC) or sodium hydrosulfide (NaHS, an H2S donor) preconditioning groups. To establish a model of segmental (70%) warm hepatic ischemia, the hepatic artery, left portal vein and median liver lobes were occluded for 60 min and then unclamped to allow reperfusion. Preconditioning with 12.5, 25 or 50 ?mol/kg NaHS prior to the I/R insult significantly increased serum H2S levels, and, similar to IPC, NaHS preconditioning decreased alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in the plasma and prevented hepatocytes from undergoing I/R-induced necrosis. Moreover, a sub-toxic dose of NaHS (25 ?mol/kg) did not disrupt the systemic hemodynamics but dramatically inhibited mitochondrial permeability transition pore (MPTP) opening and thus prevented mitochondrial-related cell death and apoptosis. Mechanistic studies revealed that NaHS preconditioning markedly increased the expression of phosphorylated protein kinase B (p-Akt), phosphorylated glycogen synthase kinase-3 beta (p-GSK-3?) and B-cell lymphoma-2 (Bcl-2) and decreased the release of mitochondrial cytochrome c and cleaved caspase-3/9 levels. Therefore, NaHS administration prior to hepatic I/R ameliorates mitochondrial and hepatocellular damage through the inhibition of MPTP opening and the activation of Akt-GSK-3? signaling. Furthermore, this study provides experimental evidence for the clinical use of H2S to reduce liver damage after perioperative I/R injury. PMID:24058562

Zhang, Hao; Xu, Fengying; Zou, Zui; Liu, Meng; Wang, Quanxing; Miao, Mingyong; Shi, Xueyin

2013-01-01

263

Ultrahigh-Pressure Metallic Hydrogen: Creation by Super-Intense Laser and Application to Pycnonuclear Fusion Studies  

NASA Astrophysics Data System (ADS)

At multi-megabar pressures ordinary hydrogen becomes metallic; protons in liquid-metallic hydrogen may undergo phase transitions such as Wigner crystallization and spin-magnetization [1]. A pycnonuclear fusion reactor utilizes p-d reactions, p + d ? ^3He (5.4 keV) + ? (5.489 MeV), most proficient in dense liquid-metallic hydrogen near the freezing transitions [2]. In constrast to the 14.1 MeV neutrons produced by d-t reactions in thermonuclear fusion reactors, the fusion yields of p-d reactions are ^3He and ?-rays with relatively low energies, avoiding dangerous radioactive byproducts. Because pycnonuclear hydrogen fuel remains in a liquid-metallic state near freezing conditions, it could be confined and compressed more stably than a high-temperature plasma could be. To produce such a ultrahigh-pressure liquid-metallic state, slow, adiabatic compression of hydrogen fuel is necessary, starting with low-entropy, cryogenic (T ˜ 10 K) molecular-solid hydrogen. We envision a pellet of fuel hydrogen coated by heavy metal (e.g., Au), and analyze the compression attained by intense laser-ablation of the metal. We investigate the Rayleigh-Taylor instability in the projected experiments, and find that stable and adiabatic compression may be achieved by utilizing compression velocities far below the adiabatic sound velocity. We thus solve integral equations describing the evolution of compressed hydrogen for the compression power as a function of the time, and thereby identify experimental conditions necessary for stable, adiabatic compression. This provides a way to produce liquid-metallic hydrogen at ambient temperatures, and would enable demonstration of a pycnonuclear fusion reactor. See also S. Ichimaru, Phys. Plasmas 8, 48 (2001); S. Ichimaru, Phys. Plasmas 8, 4248 (2001).

Ichimaru, Setsuo

2003-10-01

264

The Use of Metal Hydrides for Hydrogen Recovery from Industrial Off-Gas Streams  

E-print Network

the development of a concept to utilize metal hydrides to recover hydrogen from industrial off-gas streams. The activity included a survey of industrial waste streams a selection of metallic hydriding alloys, testing of alloys for poison tolerance and life..., a conceptual design and an economic analysis. Of the nine alloys tested, only the lanthanium-nickel-aluminum type proved to have the durability to be used in this concept. A' fixed bed reactor system, using LaNi?. 2sAlo.7s in pelletized form...

Rebello, W. J.; Guerrero, P. S.; Goodell, P. D.

265

Diborane(4)-metal bonding: between hydrogen bridges and frustrated oxidative addition.  

PubMed

The metal complexes [M{HB(hpp)}(2)(CO)(4)] (M = Cr, Mo or W) and [M(cod){HB(hpp)}(2)Cl] (M = Rh or Ir) of the doubly-base stabilized diborane(4) ligand [HB(hpp)](2) were fully characterized and their bonding nature was investigated in detail. While bonding in the group 6 complexes predominantly occurs through the hydrogen atoms, the metal-ligand interaction in the group 9 complexes can be regarded as an early stage oxidative addition of the boron-boron bond leading to diboryl compounds. PMID:22526934

Wagner, Arne; Kaifer, Elisabeth; Himmel, Hans-Jörg

2012-05-28

266

Hydrogen  

NSDL National Science Digital Library

This article explores the possibilities of using hydrogen as a renewable energy source, pointing out that hydrogen fuel and hydrogen fuel cells are two options for generating power from hydrogen. The article gives an overview of the three methods used to isolate hydrogen for energy-production purposes: steam reforming, electrolysis, and burning. Information is also offered about the uses, limitations, and benefits of hydrogen as an energy source. Supporting web links are provided, including links to an article about fuel cell buses and to animations that demonstrate how hydrogen fuel cells operate.

Project, Iowa P.

2004-01-01

267

Two-component Fermi-liquid theory - Equilibrium properties of liquid metallic hydrogen  

NASA Technical Reports Server (NTRS)

It is reported that the transition of condensed hydrogen from an insulating molecular crystal phase to a metallic liquid phase, at zero temperature and high pressure, appears possible. Liquid metallic hydrogen (LMH), comprising interpenetrating proton and electron fluids, would constitute a two-component Fermi liquid with both a very high component-mass ratio and long-range, species-dependent bare interactions. The low-temperature equilibrium properties of LMH are examined by means of a generalization to the case of two components of the phenomenological Landau Fermi-liquid theory, and the low-temperature specific heat, compressibility, thermal expansion coefficient and spin susceptibility are given. It is found that the specific heat and the thermal expansion coefficient are vastly greater in the liquid than in the corresponding solid, due to the presence of proton quasiparticle excitations in the liquid.

Oliva, J.; Ashcroft, N. W.

1981-01-01

268

Assessing The Hydrogen Adsorption Capacity Of Single-Wall Carbon Nanotube / Metal Composites  

NASA Astrophysics Data System (ADS)

Carefully controlled and calibrated experiments indicate a maximum capacity for adsorption of hydrogen on SWNTs is ˜8 wt% under room temperature and pressure conditions. Samples displaying this maximum value were prepared by sonicating purified SWNTs in a dilute nitric acid solution with a high-energy probe. The process cuts the SWNT into shorter segments and introduces a Ti-6Al-4V alloy due to the disintegration of the ultrasonic probe. The Ti-6Al-4V alloy is a well-known metal hydride and its contribution to the measured hydrogen uptake was accounted for in order to assess the amount of hydrogen stored on the SWNT fraction. The principal purpose of this paper is to present key details associated with the measurement procedures in order to illustrate the degree of rigor with which the findings were obtained.

Heben, Michael J.; Dillon, Anne C.; Gilbert, Katherine E. H.; Parilla, Philip A.; Gennett, Thomas; Alleman, Jeffrey L.; Hornyak, G. Louis; Jones, Kim M.

2003-07-01

269

Cryogenic Gellant and Fuel Formulation for Metallized Gelled Propellants: Hydrocarbons and Hydrogen with Aluminum  

NASA Technical Reports Server (NTRS)

An experimental program to determine the viability of nanoparticulate gellant materials for gelled hydrocarbons and gelled liquid hydrogen was conducted. The gellants included alkoxides (BTMSE and BTMSH) and silica-based materials. Hexane, ethane, propane and hydrogen were gelled with the newly-formulated materials and their rheological properties were determined: shear stress versus shear rate and their attendant viscosities. Metallized hexane with aluminum particles was also rheologically characterized. The propellant and gellant formulations were selected for the very high surface area and relatively-high energy content of the gellants. These new gellants can therefore improve rocket engine specific impulse over that obtained with traditional cryogenic-fuel gellant materials silicon dioxide, frozen methane, or frozen ethane particles. Significant reductions in the total mass of the gellant were enabled in the fuels. In gelled liquid hydrogen, the total mass of gellant was reduced from 10-40 wt percent of frozen hydrocarbon particles to less that 8 wt percent with the alkoxide.

Wong, Wing; Starkovich, John; Adams, Scott; Palaszewski, Bryan; Davison, William; Burt, William; Thridandam, Hareesh; Hu-Peng, Hsiao; Santy, Myrrl J.

1994-01-01

270

Thermodynamic properties of molybdenum-transition metal-hydrogen (nitrogen) solid solutions  

NASA Astrophysics Data System (ADS)

Using the experimental values ? H {H/exc} and ? S {H/exc} (? H {N/exc} and ? S {N/exc}) for solid solutions of hydrogen and nitrogen in molybdenum, we calculate the parameters ?{H/M}and ?{N/M} of interaction between hydrogen (nitrogen) and molybdenum lattice doped with small additives of transition metals M; the values of the activity coefficients on hydrogen and nitrogen ?{H/M} and ?{N/M}, ? H H, ? H N, ? S H, ? S N; enthalpy (?{H/M} and ?{N/M}) and entropy (?{H/M} and ?{N/M}) parameters of interaction over the 1100-1300 K range for alloys of Mo1 - y M y H x and Mo1 - y M y N x types ( y = 0.01 and 0.02; x = 0.01 and 0.02).

Balabaeva, R. F.

2011-07-01

271

Anion Binding in Metal-Organic Frameworks Functionalized with Urea Hydrogen-Bonding Groups  

SciTech Connect

A series of metal-organic frameworks (MOFs) functionalized with urea hydrogen-bonding groups has been synthesized and structurally analyzed by single-crystal X-ray diffraction to evaluate the efficacy of anion coordination by urea within the structural constraints of the MOFs. We found that urea-based functionalities may be used for anion binding within metal-organic frameworks when the tendency for urea{hor_ellipsis}urea self-association is decreased by strengthening the intramolecular CH{hor_ellipsis}O hydrogen bonding of N-phenyl substituents to the carbonyl oxygen atom. Theoretical calculations indicate that N,N'-bis(m-pyridyl)urea (BPU) and N,N'-bis(m-cyanophenyl)urea (BCPU) should have enhanced hydrogen-bonding donor abilities toward anions and decreased tendencies to self-associate into hydrogen-bonded tapes compared to other disubstituted ureas. Accordingly, BPU and BCPU were incorporated in MOFs as linkers through coordination of various Zn, Cu, and Ag transition metal salts, including Zn(ClO{sub 4}){sub 2}, ZnSO{sub 4}, Cu(NO{sub 3}){sub 2}, Cu(CF{sub 3}SO{sub 3}){sub 2}, AgNO{sub 3}, and AgSO{sub 3}CH{sub 3}. Structural analysis by single-crystal X-ray diffraction showed that these linkers are versatile anion binders, capable of chelate hydrogen bonding to all of the oxoanions explored. Anion coordination by the urea functionalities was found to successfully compete with urea self-association in all cases except for that of charge-diffuse perchlorate.

Custelcean, Radu [ORNL; Moyer, Bruce A [ORNL; Bryantsev, Vyacheslav S. [Pacific Northwest National Laboratory (PNNL); Hay, Benjamin P. [Pacific Northwest National Laboratory (PNNL)

2006-01-01

272

Retention of hydrogen in fcc metals irradiated at temperatures leading to high densities of bubbles or voids  

NASA Astrophysics Data System (ADS)

Large amounts of hydrogen and helium are generated in structural metals in accelerator-driven systems. It is shown that under certain conditions, hydrogen can be stored in irradiated nickel and stainless steels at levels strongly in excess of that predicted by Sieverts' law. These conditions are first, the availability of hydrogen from various radiolytic and environmental sources and second, the formation of radiation-induced cavities to store hydrogen. These cavities can be highly pressurized bubbles or under-pressurized voids, with concurrent helium in the cavities at either low or very high levels. Transmutant sources of hydrogen are often insufficient to pressurize these cavities, and therefore environmental sources are required. The stored hydrogen appears to be stable for many years at room temperature. A conceptual model to describe such behavior requires the continuous generation of hydrogen from (n,p) reactions and possibly other radiolytic sources which can create a supersaturation of hydrogen in the metal, leading to the pressurization of voids and helium bubbles. Once captured in a bubble, the hydrogen is assumed to be in molecular form. Dissolution back into the metal requires chemisorption and dissociation on the bubble surface. Both of these processes have large activation barriers, particularly when oxygen, carbon, and other impurities poison the bubble surface. However, these chemisorbed poisons may reduce but not entirely restrict the ingress or egress of atomic hydrogen.

Garner, F. A.; Simonen, E. P.; Oliver, B. M.; Greenwood, L. R.; Grossbeck, M. L.; Wolfer, W. G.; Scott, P. M.

2006-09-01

273

Hydrogen purifier module and method for forming the same  

DOEpatents

A hydrogen purifier utilizing a hydrogen permeable membrane, and a gas-tight seal, where the seal is uses a low temperature melting point metal, which upon heating above the melting point subsequently forms a seal alloy with adjacent metals, where the alloy has a melting point above the operational temperature of the purifier. The purifier further is constructed such that a degree of isolation exists between the metal that melts to form the seal and the active area of the purifier membrane, so that the active area of the purifier membrane is not corrupted. A method of forming a hydrogen purifier utilizing a hydrogen permeable membrane with a seal of the same type is also disclosed.

DeVries, Peter David (Spokane, WA)

2012-02-07

274

Hydrogen as an Indicator to Assess Biological Activity During Trace-Metal Bioremediation  

Microsoft Academic Search

Trace-metal and\\/or radionuclide bioremediation schemes require that specific redox conditions be achieved at given zones of an aquifer. Tools are therefore needed to identify the terminal electron acceptor processes (TEAPs) that are being achieved during bioremediation in an aquifer. Dissolved hydrogen (H2) concentrations have been shown to correlate with specific TEAPs during bioremediation in an aquifer. Theoretical analysis has shown

Peter R. Jaffe; John Komlos; Derick Brown

2005-01-01

275

Synthesis and hydrogen-storage behavior of metal–organic framework MOF-5  

Microsoft Academic Search

Metal–organic framework MOF-5 (Zn4O(BDC)3), a microporous material with a high surface area and large pore volume, was synthesized by three approaches: direct mixing of triethylamine (TEA), slow diffusion of TEA, and solvothermal synthesis. The obtained materials were characterized by X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and nitrogen adsorption, and their hydrogen-storage capacities were measured. The different synthesis methods influenced

Jinping Li; Shaojuan Cheng; Qiang Zhao; Peipei Long; Jinxiang Dong

2009-01-01

276

Selective hydrogenation of citral with transition metal complexes in supercritical carbon dioxide  

Microsoft Academic Search

The activity and selectivity of the transition metal complexes formed from Ru, Rh, Pd and Ni with triphenylphosphine (TPP) have been investigated for hydrogenation of citral in supercritical carbon dioxide (scCO2). High activities are obtained with Ru\\/TPP and Pd\\/TPP catalysts, and the overall activity is in the order of Pd?Ru>Rh>Ni. The Ru\\/TPP complex is highly selective to the formation of

Ruixia Liu; Fengyu Zhao; Shin-ichiro Fujita; Masahiko Arai

2007-01-01

277

Hydrogen storage characteristics of metal oxide doped Al–MCM-41 mesoporous materials  

Microsoft Academic Search

The feasibility and perspectives of Al–MCM-41 as hydrogen storage systems were evaluated. The Al–MCM-41 with varying content of aluminum was synthesized by hydrothermal process. Different metal oxides were impregnated over Al–MCM-41 by incipient wetness impregnation (IWI) method. The crystallnity of the samples were interrogated by powder X-ray diffraction. The textural properties were measured by N2 sorption method. The structural properties

Savidha Ramachandran; Jang-Hoon Ha; Do Kyung Kim

2007-01-01

278

Activated carbon nanotubes: a highly-active metal-free electrocatalyst for hydrogen evolution reaction.  

PubMed

In this communication, for the first time, we report on the development and utilization of activated carbon nanotubes (CNTs) as a highly-active metal-free electrocatalyst for the hydrogen evolution reaction (HER) with good durability in acidic electrolytes. This catalyst shows an onset overpotential and an exchange current density of 100 mV and 16.0 × 10(-3) mA cm(-2), respectively. The possible catalytic mechanism for the HER is also proposed. PMID:25000967

Cui, Wei; Liu, Qian; Cheng, Ningyan; Asiri, Abdullah M; Sun, Xuping

2014-08-25

279

Neutron and Thermodynamic Studies of Hydrogen on Pd Decorated Metal Oxides  

NASA Astrophysics Data System (ADS)

We report our investigations of thermodynamic, inelastic and quasielastic neutron scattering (INS and QENS) studies of H2 adsorbed on bare and Pd decorated metal oxide (MO) surfaces, specifically ZnO, SBA-15 silica, and alumina. Guided by our volumetric adsorption measurements, we used INS and QENS to probe the dynamics of the adsorbed hydrogen molecules. These measurements provide insight into how the microscopic behavior of hydrogen is changed when it is confined at interfaces or interacts with a Pd catalyst. Using INS, the motion of the adsorbed hydrogen are examined as a function of surface adsorbate composition. For rotational motion we use the ortho-to-para transition as a guide and find that the rotational barrier for H2 adsorbed on some of these MO surfaces shift to lower energy (relative to bulk H2). For comparison, the hydrogen adsorption and microscopic behavior when the MO are decorated with 1% Pd metal will be discussed. Evidence for the presence of adsorbed H2, Zn hydroxide and the potential role of spillover will be discussed. This work was partially supported by the U.S. DOE, BES under contract No. DE-AC05-00OR22725 with ORNL managed and operated by UT-Battelle, LLC, the NSF under grant DMR-0412231 and a grant from the University of Tennessee, JINS.

Landry, Paige; Ramirez-Cuesta, A.; Cruz Silvia, E.; Sumpter, B.; Larese, J. Z.

2011-03-01

280

Hydrogen ordering and magnetic phenomena in (mostly rare-earth based) metal-hydrogen systems: highlights and open problems  

NASA Astrophysics Data System (ADS)

The rare-earth hydrogen systems present phase diagrams with rather extended solid solution (?-RH x) and dihydride (?-RH 2+ x) regions, leading eventually - for high-enough concentrations and low-enough temperatures - to ordering interactions between the x-hydrogens. In the case of magnetic rare earths, this gives rise to a multitude of fascinating phenomena caused by the competition between magnetic anisotropy and RKKY interactions on the one hand and the hydrogen sublattice (via the crystal field) on the other. Thus, the peculiar quasi-unidimensional chains of H-H pairs formed along the c-axis in the ?-phase of some of the HCP rare earths (? ?-RH x) affect different types of magnetic ordering in very different ways. This is demonstrated through the interactions with the conical ferromagnetism of Er on the one hand and the c-axis-oriented 3-4 ferrimagnetism of Tm on the other, as well as with their c-axis-modulated sinusoidal magnetism. A possible interpretation of the H-H chain configuration through a charge-density-wave mechanism is suggested from recent experiments on hydrogen interaction with the helical magnetism in the Y yTb 1- yH x alloy system. In the case of the ?-RH 2+ x phase, the excess x-hydrogens occupying the octahedral sites of the CaF 2-type dihydride lattice often order in a tetragonal sublattice of DO 22 symmetry corresponding to an RH 2.25 stoichiometry. This strongly modifies the various commensurate and incommensurate magnetic structures present, sometimes leading to their complete vanishing or to the appearance of short-range order. Examples using neutron scattering and resistivity data from the systems RH(D) 2+ x, with R=Ce, Tb, and Ho, shall be given as illustration. Finally, recent preliminary results from Los Alamos show that the cubic actinide hydrides AH 2+ x (A=Np, Pu, Am) exhibit very similar ordering phenomena, opening the door to large possibilities for magneto-structural interactions within the group of 5f-metals.

Vajda, P.

2000-08-01

281

Application of Proton Conductors to Hydrogen Monitoring for Liquid Metal and Molten Salt Systems  

NASA Astrophysics Data System (ADS)

The chemical control of impurity such as hydrogen and oxygen in coolants is one of the critical issues for the development of liquid metal cooled fast reactors and self-cooled liquid breeder blankets for fusion reactors. Especially, hydrogen (isotopes) level is the key parameter for corrosion and mechanical properties of the in-reactor components. For fission reactors, the monitor of hydrogen level in the melt is important for safety operation. The control of tritium is essential for the tritium breeding performance of the fusion reactors. Therefore, on-line hydrogen sensing is a key technology for these systems. In the present study, conceptual design for the on-line hydrogen sensor to be used in liquid sodium (Na), lead (Pb), lead-bismuth (Pb-Bi), lithium (Li), lead-lithium (Pb-17Li) and molten salt LiF-BeF2 (Flibe) was performed. The cell of hydrogen sensor is made of a solid electrolyte. The solid electrolyte proposed in this study is the CaZrO3-based ceramics, which is well-known as proton conducting ceramics. In this concept, the cell is immersed into the melt which is containing the hydrogen at the activity of PH1 of ambient atmosphere. Then, the cell is filled with Ar-H2 mixture gas at regulated hydrogen activity of PH2. The electromotive force (EMF) is obtained by the proton conduction in the electro chemical system expressed as Pt, Melt(PH1) | Proton conductor | PH2, Pt. The Nernst equation is used for the evaluation of the hydrogen activity from the obtained EMF. The evaluations of expected performance of the sensor in liquid Na, Pb, Pb-Bi, Pb-17Li, Li and Flibe were carried out by means of the measurement test in gas atmosphere at hydrogen activities equivalent to those for the melts in the reactor conditions. In the test, the hydrogen activity in the gas varied from 2.2x10-14 to 1. The sensor exhibited good response, stability and reproducibility.

Kondo, Masatoshi; Muroga, Takeo; Katahira, Koji; Oshima, Tomoko

282

Model based design of an automotive-scale, metal hydride hydrogen storage system.  

SciTech Connect

Sandia and General Motors have successfully designed, fabricated, and experimentally operated a vehicle-scale hydrogen storage system using the complex metal hydride sodium alanate. Over the 6 year project, the team tackled the primary barriers associated with storage and delivery of hydrogen including mass, volume, efficiency and cost. The result was the hydrogen storage demonstration system design. The key technologies developed for this hydrogen storage system include optimal heat exchange designs, thermal properties enhancement, a unique catalytic hydrogen burner and energy efficient control schemes. The prototype system designed, built, and operated to demonstrate these technologies consists of four identical hydrogen storage modules with a total hydrogen capacity of 3 kg. Each module consists of twelve stainless steel tubes that contain the enhanced sodium alanate. The tubes are arranged in a staggered, 4 x 3 array and enclosed by a steel shell to form a shell and tube heat exchanger. Temperature control during hydrogen absorption and desorption is accomplished by circulating a heat transfer fluid through each module shell. For desorption, heat is provided by the catalytic oxidation of hydrogen within a high efficiency, compact heat exchanger. The heater was designed to transfer up to 30 kW of heat from the catalytic reaction to the circulating heat transfer fluid. The demonstration system module design and the system control strategies were enabled by experiment-based, computational simulations that included heat and mass transfer coupled with chemical kinetics. Module heat exchange systems were optimized using multi-dimensional models of coupled fluid dynamics and heat transfer. Chemical kinetics models were coupled with both heat and mass transfer calculations to design the sodium alanate vessels. Fluid flow distribution was a key aspect of the design for the hydrogen storage modules and computational simulations were used to balance heat transfer with fluid pressure requirements. An overview of the hydrogen storage system will be given, and examples of these models and simulation results will be described and related to component design. In addition, comparisons of demonstration system experimental results to model predictions will be reported.

Johnson, Terry Alan; Kanouff, Michael P.; Jorgensen, Scott W. (General Motors R& D); Dedrick, Daniel E.; Evans, Gregory Herbert

2010-11-01

283

Mitigation of Hydrogen Gas Generation from the Reaction of Water with Uranium Metal in K Basins Sludge  

SciTech Connect

Means to decrease the rate of hydrogen gas generation from the chemical reaction of uranium metal with water were identified by surveying the technical literature. The underlying chemistry and potential side reactions were explored by conducting 61 principal experiments. Several methods achieved significant hydrogen gas generation rate mitigation. Gas-generating side reactions from interactions of organics or sludge constituents with mitigating agents were observed. Further testing is recommended to develop deeper knowledge of the underlying chemistry and to advance the technology aturation level. Uranium metal reacts with water in K Basin sludge to form uranium hydride (UH3), uranium dioxide or uraninite (UO2), and diatomic hydrogen (H2). Mechanistic studies show that hydrogen radicals (H·) and UH3 serve as intermediates in the reaction of uranium metal with water to produce H2 and UO2. Because H2 is flammable, its release into the gas phase above K Basin sludge during sludge storage, processing, immobilization, shipment, and disposal is a concern to the safety of those operations. Findings from the technical literature and from experimental investigations with simple chemical systems (including uranium metal in water), in the presence of individual sludge simulant components, with complete sludge simulants, and with actual K Basin sludge are presented in this report. Based on the literature review and intermediate lab test results, sodium nitrate, sodium nitrite, Nochar Acid Bond N960, disodium hydrogen phosphate, and hexavalent uranium [U(VI)] were tested for their effects in decreasing the rate of hydrogen generation from the reaction of uranium metal with water. Nitrate and nitrite each were effective, decreasing hydrogen generation rates in actual sludge by factors of about 100 to 1000 when used at 0.5 molar (M) concentrations. Higher attenuation factors were achieved in tests with aqueous solutions alone. Nochar N960, a water sorbent, decreased hydrogen generation by no more than a factor of three while disodium phosphate increased the corrosion and hydrogen generation rates slightly. U(VI) showed some promise in attenuating hydrogen but only initial testing was completed. Uranium metal corrosion rates also were measured. Under many conditions showing high hydrogen gas attenuation, uranium metal continued to corrode at rates approaching those observed without additives. This combination of high hydrogen attenuation with relatively unabated uranium metal corrosion is significant as it provides a means to eliminate uranium metal by its corrosion in water without the accompanying hazards otherwise presented by hydrogen generation.

Sinkov, Sergey I.; Delegard, Calvin H.; Schmidt, Andrew J.

2010-01-29

284

High performance hydrogen storage from Be-BTB metal-organic framework at room temperature.  

PubMed

The metal-organic framework beryllium benzene tribenzoate (Be-BTB) has recently been reported to have one of the highest gravimetric hydrogen uptakes at room temperature. Storage at room temperature is one of the key requirements for the practical viability of hydrogen-powered vehicles. Be-BTB has an exceptional 298 K storage capacity of 2.3 wt % hydrogen. This result is surprising given that the low adsorption enthalpy of 5.5 kJ mol(-1). In this work, a combination of atomistic simulation and continuum modeling reveals that the beryllium rings contribute strongly to the hydrogen interaction with the framework. These simulations are extended with a thermodynamic energy optimization (TEO) model to compare the performance of Be-BTB to a compressed H2 tank and benchmark materials MOF-5 and MOF-177 in a MOF-based fuel cell. Our investigation shows that none of the MOF-filled tanks satisfy the United States Department of Energy (DOE) storage targets within the required operating temperatures and pressures. However, the Be-BTB tank delivers the most energy per volume and mass compared to the other material-based storage tanks. The pore size and the framework mass are shown to be contributing factors responsible for the superior room temperature hydrogen adsorption of Be-BTB. PMID:23805913

Lim, Wei-Xian; Thornton, Aaron W; Hill, Anita J; Cox, Barry J; Hill, James M; Hill, Matthew R

2013-07-01

285

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

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

286

Application of closed-orbit theory to the Rydberg hydrogen atom near a metal surface  

NASA Astrophysics Data System (ADS)

Using closed-orbit theory, we study the classical motion and calculate the photoabsorption spectra and recurrence spectra of the Rydberg hydrogen atom near a metal surface. The results show that when the atom-surface distance is close to the critical value dc, the number of the closed orbits is the greatest. For d > dc, with the increase of the distance d, the number of the closed orbits decreases and the absorption spectra are shown to exhibit a damping oscillation. For d < dc, the electron can travel for a very short time before it has returned to the nucleus. At a smaller distance, some of the electronic trajectories can be absorbed onto the metal surface. In order to show the relation between the absorption spectra and the closed orbits, we calculate the Fourier transformed recurrence spectra of the Rydberg hydrogen atom near a metal surface by using the closed-orbit theory. Each resonance peak in the recurrence spectra is associated with one electron closed orbit. The agreement between the semiclassical calculation spectra and the quantum calculation spectra suggests that our analysis is correct. This study provides a different perspective on the dynamical behaviour of the Rydberg atom near a metal surface.

Wang, Dehua; Du, M. L.; Lin, Shenglu

2006-09-01

287

Electrostatic potential energy within a protein monitored by metal charge-dependent hydrogen exchange.  

PubMed

Hydrogen exchange measurements on Zn(II)-, Ga(III)-, and Ge(IV)-substituted Pyrococcus furiosus rubredoxin demonstrate that the log ratio of the base-catalyzed rate constants (Delta log k(ex)) varies inversely with the distance out to at least 12 A from the metal. This pattern is consistent with the variation of the amide nitrogen pK values with the metal charge-dependent changes in the electrostatic potential. Fifteen monitored amides lie within this range, providing an opportunity to assess the strength of electrostatic interactions simultaneously at numerous positions within the structure. Poisson-Boltzmann calculations predict an optimal effective internal dielectric constant of 6. The largest deviations between the experimentally estimated and the predicted DeltapK values appear to result from the conformationally mobile charged side chains of Lys-7 and Glu-48 and from differential shielding of the peptide units arising from their orientation relative to the metal site. PMID:17012322

Anderson, Janet S; LeMaster, David M; Hernández, Griselda

2006-12-01

288

Tethering metal ions to photocatalyst particulate surfaces by bifunctional molecular linkers for efficient hydrogen evolution.  

PubMed

A simple and versatile method for the preparation of photocatalyst particulates modified with effective cocatalysts is presented; the method involves the sequential soaking of photocatalyst particulates in solutions containing bifunctional organic linkers and metal ions. The modification of the particulate surfaces is a universal and reproducible method because the molecular linkers utilize strong covalent bonds, which in turn result in modified monolayer with a small but controlled quantity of metals. The photocatalysis results indicated that the CdS with likely photochemically reduced Pd and Ni, which were initially immobilized via ethanedithiol (EDT) as a linker, were highly efficient for photocatalytic hydrogen evolution from Na2S-Na2SO3-containing aqueous solutions. The method developed in this study opens a new synthesis route for the preparation of effective photocatalysts with various combinations of bifunctional linkers, metals, and photocatalyst particulate materials. PMID:25138439

Yu, Weili; Isimjan, Tayirjan; Del Gobbo, Silvano; Anjum, Dalaver H; Abdel-Azeim, Safwat; Cavallo, Luigi; Garcia-Esparza, Angel T; Domen, Kazunari; Xu, Wei; Takanabe, Kazuhiro

2014-09-01

289

Alkali and alkaline-earth metal amidoboranes: structure, crystal chemistry, and hydrogen storage properties.  

PubMed

Alkali- and alkaline-earth metal amidoboranes are a new class of compounds with rarely observed [NH2BH3](-) units. LiNH2BH3 and solvent-containing Ca(NH2BH3)2 x THF have been recently reported to significantly improve the dehydrogenation properties of ammonia borane. Therefore, metal amidoboranes, with accelerated desorption kinetics and suppressed toxic borazine, are of great interest for their potential applications for hydrogen storage. In this work, we successfully determined the structures of LiNH2BH3 and Ca(NH2BH3)2 using a combined X-ray diffraction and first-principles molecular dynamics simulated annealing method. Through detailed structural analysis and first-principles electronic structure calculations the improved dehydrogenation properties are attributed to the different bonding nature and reactivity of the metal amidoboranes compared to NH3BH3. PMID:18847204

Wu, Hui; Zhou, Wei; Yildirim, Taner

2008-11-01

290

Hydrogen physisorption on metal-organic framework linkers and metalated linkers: a computational study of the factors that control binding strength.  

PubMed

In order for hydrogen gas to be used as a fuel, it must be stored in sufficient quantity on board the vehicle. Efforts are being made to increase the hydrogen storage capabilities of metal-organic frameworks (MOFs) by introducing unsaturated metal sites into their linking element(s), as hydrogen adsorption centers. In order to devise successful hydrogen storage strategies there is a need for a fundamental understanding of the weak and elusive hydrogen physisorption interaction. Here we report our findings from the investigation of the weak intermolecular interactions of adsorbed hydrogen molecules on MOF-linkers by using cluster models. Since physical interactions such as dispersion and polarization have a major contribution to attraction energy, our approach is to analyze the adsorption interaction using energy decomposition analysis (EDA) that distinguishes the contribution of the physical interactions from the charge-transfer (CT) "chemical" interaction. Surprisingly, it is found that CT from the adsorbent to the ?*(H2) orbital is present in all studied complexes and can contribute up to approximately -2 kJ/mol to the interaction. When metal ions are present, donation from the ?(H2) ? metal Rydberg-like orbital, along with the adsorbent ? ?*(H2) contribution, can contribute from -2 to -10 kJ/mol, depending on the coordination mode. To reach a sufficient adsorption enthalpy for practical usage, the hydrogen molecule must be substantially polarized. Ultimately, the ability of the metalated linker to polarize the hydrogen molecule is highly dependent on the geometry of the metal ion coordination site where a strong electrostatic dipole or quadrupole moment is required. PMID:25415078

Tsivion, Ehud; Long, Jeffrey R; Head-Gordon, Martin

2014-12-24

291

Metal-and hydrogen-bonding competition during water absorption on Pd(111) and Ru(0001)  

SciTech Connect

The initial stages of water adsorption on the Pd(111) and Ru(0001) surfaces have been investigated experimentally by Scanning Tunneling Microscopy in the temperature range between 40 K and 130 K, and theoretically with Density Functional Theory (DFT) total energy calculations and STM image simulations. Below 125 K water dissociation does not occur at any appreciable rate and only molecular films are formed. Film growth starts by the formation of flat hexamer clusters where the molecules bind to the metal substrate through the O-lone pair while making H-bonds with neighboring molecules. As coverage increases, larger networks of linked hexagons are formed with a honeycomb structure, which requires a fraction of the water molecules to have their molecular plane perpendicular to the metal surface with reduced water-metal interaction. Energy minimization favors the growth of networks with limited width. As additional water molecules adsorb on the surface they attach to the periphery of existing islands, where they interact only weakly with the metal substrate. These molecules hop along the periphery of the clusters at intermediate temperatures. At higher temperatures they bind to the metal to continue the honeycomb growth. The water-Ru interaction is significantly stronger than the water-Pd interaction, which is consistent with the greater degree of hydrogen-bonded network formation and reduced water-metal bonding observed on Pd relative to Ru.

Tatarkhanov, Mouslim; Ogletree, D. Frank; Rose, Franck; Mitsui, Toshiyuki; Fomin, Evgeny; Rose, Mark; Cerda, Jorge I.; Salmeron, Miquel

2009-09-03

292

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

SciTech Connect

The overall objective was to develop commercially viable metal hydrides capable of reversibly storing at least 3 wt.% hydrogen for use with PEM fuel cells and hydrogen fueled internal combustion engine (HICE) applications. Such alloys are expected to result in system capacities of greater than 2 wt.%, making metal hydride storage systems (MHSS`s) a practical means of supplying hydrogen for many consumer applications. ECD`s (Energy Conversion Devices, Inc.) past work on sputtered thin films of transition metal-based alloys led to the commercialization of it`s nickel/metal hydride batteries, and similar work on thin film Mg-based alloys demonstrated potential to achieve very high gravimetric and volumetric energy densities approaching 2,500 Wh/Kg and 2,500 Wh/M{sup 3} respectively. Under this 2-year cost shared project with the DOE, the authors have successfully demonstrated the feasibility of scaling up the Mg-based hydrides from thin film to bulk production without substantial loss of storage capacity. ECD made progress in alloy development by means of compositional and process modification. Processes used include Mechanical Alloying, Melt spinning and novel Gas Phase Condensation. It was showed that the same composition when prepared by melt-spinning resulted in a more homogeneous material having a higher PCT plateau pressure as compared to mechanical alloying. It was also shown that mechanically alloyed Mg-Al-Zn results in much higher plateau pressures, which is an important step towards reducing the desorption temperature. While significant progress has been made during the past two years in alloy development and understanding the relationship between composition, structure, morphology, and processing parameters, additional R and D needs to be performed to achieve the goals of this work.

Sapru, K.

1998-12-04

293

Polymers of Platinurn Metals Complexes - Imrnobilised on Electrodes THEIR USE IN ELECTROCATALYTIC PROTON REDUCTION AND HYDROGENATION OF ORGANICS  

Microsoft Academic Search

Interest is growing in usingpolymeric electrode materials containing platinum group metals complexes in molecular electrochemistry. Here, the synthesis of functionalised polypyrrolefilm electrodes, formed by the oxidative electropoly- merisation of pyrrole-substituted rhodium, iridium and palladium complexes is reviewed, and recent results are presented concerning the electrocatalytic reduction of protons and the hydrogenation of unsaturated organic substrates in aqueous electrolyte. Metal hydride

Alain Deronzier; Jean-Claude Moutet

294

OPTIMIZATION OF INTERNAL HEAT EXCHANGERS FOR HYDROGEN STORAGE TANKS UTILIZING METAL HYDRIDES  

SciTech Connect

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.

Garrison, S.; Tamburello, D.; Hardy, B.; Anton, D.; Gorbounov, M.; Cognale, C.; van Hassel, B.; Mosher, D.

2011-07-14

295

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

SciTech Connect

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

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

2013-07-01

296

Coated silica shells: an advanced hydrogen storage system  

SciTech Connect

We have investigated a new concept for the storage of hydrogen gas. It consists of storing hydrogen on a bed of small metal-coated spherical shells of nearly pure silica composition. The silica shells function as high pressure containers which because of silica's high strength, can withstand the pressures required to achieve significant gas storage densities. Since pure silica is too permeable to adequately retain hydrogen, a metal (e.g., Ni, Cu, Mo) coating is added as a room temperature permeation barrier. Fortunately, the rate at which hydrogen permeates these metals varies rapidly with temperature. Consequently, to cause the hydrogen to readily permeate the metal coating as well as the silica shell requires heating the bed to only moderate temperatures.

Henderson, T.M.; Martin, A.J.

1984-01-01

297

Engineering catalyst microenvironments for metal-catalyzed hydrogenation of biologically derived platform chemicals.  

PubMed

It is shown that microenvironments formed around catalytically active sites mitigate catalyst deactivation by biogenic impurities that are present during the production of biorenewable chemicals from biologically derived species. Palladium and ruthenium catalysts are inhibited by the presence of sulfur-containing amino acids; however, these supported metal catalysts are stabilized by overcoating with poly(vinyl alcohol) (PVA), which creates a microenvironment unfavorable for biogenic impurities. Moreover, deactivation of Pd catalysts by carbon deposition from the decomposition of highly reactive species is suppressed by the formation of bimetallic PdAu nanoparticles. Thus, a PVA-overcoated PdAu catalyst was an order of magnitude more stable than a simple Pd catalyst in the hydrogenation of triacetic acid lactone, which is the first step in the production of biobased sorbic acid. A PVA-overcoated Ru catalyst showed a similar improvement in stability during lactic acid hydrogenation to propylene glycol in the presence of methionine. PMID:25196504

Schwartz, Thomas J; Johnson, Robert L; Cardenas, Javier; Okerlund, Adam; Da Silva, Nancy A; Schmidt-Rohr, Klaus; Dumesic, James A

2014-11-17

298

Molecular beam studies of atomic hydrogen with clean and adsorbate covered metal surfaces  

SciTech Connect

In an effort to elucidate the dynamics and kinetics of surface chemical reactions, we have undertaken a study of the interaction of a beam of atomic hydrogen with clean and adsorbate covered metal surfaces. Systems studied include Au(111), Au(111):H, Au(111):Cl, Pd(111), Pd(111):H and Pd(111):S. Our results indicate that recombination reactions can simultaneously occur by both Langmuir-Hinshelwood and Eley-Rideal mechanisms. We also find strong evidence for a direct displacement channel in which the adsorption of atomic H drives the desorption of atomic Cl. In addition we find that the presence of surface adsorbates can actually enhance the rate of hydrogen absorption into the bulk. Details of the experimental method, results and implications regarding the reaction dynamics will be presented.

Kay, B.D. [Pacific Northwest National Lab., Richland, WA (United States); Lykke, K.R. [Argonne National Lab., IL (United States)

1996-12-31

299

Electrodialysis of acid solutions with metallic divalent salts: cation-exchange membranes with improved permeability to protons  

Microsoft Academic Search

The electrodialysis of acid solutions (chlorhydric and sulfuric) in the presence of metallic divalent salts (chloride and sulfate) are studied. The anion-exchange membranes used in this process have been selected from several membranes manufactured by Solvay because of their low water content and their good anionic selectivity. Two kinds of cationic exchange membranes have been tested: the No. 9, a

Agnès Chapotot; Valérie Lopez; Arlette Lindheimer; Naïma Aouad; Claude Gavach

1995-01-01

300

Hydrogen peroxide modification enhances the ability of biochar (hydrochar) produced from hydrothermal carbonization of peanut hull to remove aqueous heavy metals: Batch and column tests  

Technology Transfer Automated Retrieval System (TEKTRAN)

Experimental and modeling investigations were conducted to examine the effect of hydrogen peroxide treatment on hydrothermally produced biochar (hydrochar) from peanut hull to remove aqueous heavy metals. Characterization measurements showed that hydrogen peroxide modification increased the oxygen-c...

301

Surface science and electrochemical studies of metal-modified carbides for fuel cells and hydrogen production  

NASA Astrophysics Data System (ADS)

Carbides of the early transition metals have emerged as low-cost catalysts that are active for a wide range of reactions. The surface chemistry of carbides can be altered by modifying the surface with small amounts of admetals. These metal-modified carbides can be effective replacements for Pt-based bimetallic systems, which suffer from the drawbacks of high cost and low thermal stability. In this dissertation, metal-modified carbides were studied for reactions with applications to renewable energy technologies. It is demonstrated that metal-modified carbides possess high activity for alcohol reforming and electrochemical hydrogen production. First, the surface chemistry of carbides towards alcohol decomposition is studied using density functional theory (DFT) and surface science experiments. The Vienna Ab initio Simulation Package (VASP) was used to calculate the binding energies of alcohols and decomposition intermediates on metal-modified carbides. The calculated binding energies were then correlated to reforming activity determined experimentally using temperature programmed desorption (TPD). In the case of methanol decomposition, it was found that tungsten monocarbide (WC) selectively cleaved the C-O bond to produce methane. Upon modifying the surface with a single layer of metal such as Ni, Pt, or Rh, the selectivity shifted towards scission of the C-H bonds while leaving the C-O bond intact, producing carbon monoxide (CO) and H2. High resolution energy loss spectroscopy (HREELS) was used to examine the bond breaking sequence as a function of temperature. From HREELS, it was shown that the surfaces followed an activity trend of Rh > Ni > Pt. The Au-modified WC surface possessed too low of a methanol binding energy, and molecular desorption of methanol was the most favorable pathway on this surface. Next, the ability of Rh-modified WC to break the C-C bond of C2 and C3 alcohols was demonstrated. HREELS showed that ethanol decomposed through an acetaldehyde intermediate on Rh/WC, and that the C-C bond was broken by 200 K. Finally, the suitability of metal-modified molybdenum carbide (Mo2C) as an ethanol decomposition catalyst was studied. A new reaction pathway of partial dehydrogenation to an acetaldehyde product was achieved by using Cu as an admetal. The second section of this dissertation was the study of metal-modified carbides for electrochemical hydrogen evolution. Previously, DFT calculations had predicted a similar hydrogen binding energy (HBE) between Pd-modified carbides and bulk Pd. Linear sweep voltammograms (LSV) demonstrated that Pd-modified WC and Mo2C possessed hydrogen evolution activity orders of magnitude greater than the bare carbides. The long-term stability of these surfaces under operating conditions was also examined. A two-hour chronopotentiometry experiment was performed, after which x-ray photoelectron spectroscopy (XPS) found that negligible loss of the Pd overlayer occurred. As an extension of this work, a DFT study was performed for several admetal/Mo2C combinations. It was shown that the HBE of these surfaces mostly correlated with the pure metal HBE. Some of these combinations were tested experimentally, but were unstable in the acidic electrolyte.

Kelly, Thomas Glenn

302

Anion Coordination in Metal-Organic Frameworks Functionalized with Urea Hydrogen-Bonding Groups  

SciTech Connect

A series of metal-organic frameworks (MOFs) functionalized with urea hydrogen-bonding groups have been designed, synthesized, and structurally analyzed by single crystal X-ray diffraction to evaluate the efficacy of anion binding within the structural constraints of the MOFs. We found that urea-based functionalities may be used for anion binding within metal-organic frameworks when the tendency for urea???urea self-association is decreased by strengthening the intramolelcular CH???O hydrogen bonding of N-phenyl substituents to the carbonyl oxygen atom. Theoretical calculations indicate that N,N?-bis(m-pyridyl)urea (BPU) and N,N?-bis(m-cyanophenyl)urea (BCPU) should have enhanced hydrogen-bonding donor abilities toward anions and decreased tendencies to self-associate into hydrogen-bonded chains compared to other disubstituted ureas. Accordingly, BPU and BCPU were incorporated in MOFs as linkers through coordination of various Zn, Cu, and Ag transition metal salts, including Zn(ClO4)2, ZnSO4, Cu(NO3)2, Cu(CF3SO3)2, AgNO3 and AgSO3CH3. Structural analysis by single-crystal X-ray diffraction showed that these linkers are versatile anion binders, capable of chelate hydrogen bonding to all of the oxoanions explored. Anion binding by the urea functionalities was found to successfully compete with urea self-association in all cases except for that of charge-diffuse perchlorate. This research was sponsored by the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences of the U.S. Department of Energy, under contract number DE-AC05-00OR22725 with Oak Ridge National Laboratory (managed by UT-Battelle, LLC), and performed at Oak Ridge National laboratory and Pacific Northwest National Laboratory (managed by Battelle for the U.S. Department of Energy under contract DE-AC05-76RL01830). This research was performed in part using the Molecular Science Computing Facility (MSCF) in the William R. Wiley Environmental Molecular Sciences laboratory, a national scientific user facility sponsored by the U.S. Department of Energy's Office of Biological and Environmental Research located at the Pacific Northwest National Laboratory.

Custelcean, Radu; Moyer, Bruce A.; Bryantsev, Vyacheslav; Hay, Benjamin P.

2005-12-15

303

Laser ablation direct writing of metal nanoparticles for hydrogen and humidity sensors.  

PubMed

A UV pulsed laser writing technique to fabricate metal nanoparticle patterns on low-cost substrates is demonstrated. We use this process to directly write nanoparticle gas sensors, which operate via quantum tunnelling of electrons at room temperature across the device. The advantages of this method are no lithography requirements, high precision nanoparticle placement, and room temperature processing in atmospheric conditions. Palladium-based nanoparticle sensors are tested for the detection of water vapor and hydrogen within controlled environmental chambers. The electrical conduction mechanism responsible for the very high sensitivity of the devices is discussed with regard to the interparticle capacitance and the tunnelling resistance. PMID:21188990

Beliatis, Michail J; Martin, Nicholas A; Leming, Edward J; Silva, S Ravi P; Henley, Simon J

2011-02-01

304

Hydrogen transport through tubular membranes of palladium-coated tantalum and niobium  

Microsoft Academic Search

Palladium-based membranes have been used for decades in hydrogen extraction because of their high permeability and good surface properties and because palladium, like all metals, is 100% selective for hydrogen transport. The authors describe experiments with hydrogen-extraction membranes made of palladium-coated niobium and tantalum heat-exchanger tubers. The cost was about $45\\/ft of 3\\/8 inch tubular membrane, and the fluxes were

Robert E. Buxbaum; Andrew B. Kinney

1996-01-01

305

Dynamics of a Rydberg hydrogen atom near a metal surface in the electron-extraction scheme  

NASA Astrophysics Data System (ADS)

We study the classical dynamics of a Rydberg hydrogen atom near a metal surface in the presence of a constant electric field in the electron-extraction situation [1], e.g., when the field attracts the electron to the vacuum. From a dynamical point of view, this field configuration provides a dynamics richer than in the usual ion-extraction scheme, because, depending on the values of field and the atom-surface distance, the atom can be ionized only towards the metal surface, only to the vacuum or to the both sides. The evolution of the phase space structure as a function of the atom-surface distance is explored in the bound regime of the atom. In the high energy regime, the ionization mechanism is also investigated. We find that the classical results of this work are in good agreement with the results obtained in the wave-packet propagation study carried out by So et al. [1].

Iñarrea, Manuel; Lanchares, Víctor; Palacián, Jesús; Pascual, Ana I.; Salas, J. Pablo; Yanguas, Patricia

2015-01-01

306

Trends in Ground-State Entropies for Transition Metal Based Hydrogen Atom Transfer Reactions  

Microsoft Academic Search

Reported herein are thermochemical studies of hydrogen atom transfer (HAT) reactions involving transition metal H-atom donors MIILH and oxyl radicals. [FeII(H2bip)3]2+, [FeII(H2bim)3]2+, [CoII(H2bim)3]2+ and RuII(acac)2(py-imH) [H2bip = 2,2-bi-1,4,5,6-tetrahydro¬pyrimidine, H2bim = 2,2-bi-imidazoline, acac = 2,4-pentandionato, py-imH = 2-(2-pyridyl)¬imidazole)] each react with TEMPO (2,2,6,6-tetramethyl-1-piperidinoxyl) or tBu3PhO (2,4,6-tri-tert-butylphenoxyl) to give the deprotonated, oxidized metal complex MIIIL, and TEMPOH or tBu3PhOH. Solution equilibrium measurements

Elizabeth A. Mader; Virginia W. Manner; Todd F. Markle; Adam Wu; James A. Franz; James M. Mayer

2009-01-01

307

First-Principles Study on the Grain Boundary Embrittlement of Metals by Solute Segregation: Part II. Metal (Fe, Al, Cu)Hydrogen (H) Systems  

Microsoft Academic Search

The microscopic mechanism of grain boundary (GB) embrittlement in metals by hydrogen segregation (trapping) has been not well\\u000a understood for many years. From first-principles calculations, we show here that the calculated cohesive energy of bcc Fe\\u000a ?3(111) and fcc Al(Cu) ?5(012) symmetrical tilt GBs can be significantly reduced if many hydrogen atoms segregate at the GBs.\\u000a This indicates that the

Masatake Yamaguchi; Ken-Ichi Ebihara; Mitsuhiro Itakura; Tomoko Kadoyoshi; Tomoaki Suzudo; Hideo Kaburaki

2011-01-01

308

Analysis of Pressure Variations in a Low-Pressure Nickel-Hydrogen Battery– Part 2: Cells with Metal Hydride Storage  

PubMed Central

A sub-atmospheric pressure nickel hydrogen (Ni-H2) battery with metal hydride for hydrogen storage is developed for implantable neuroprosthetic devices. Pressure variations during charge and discharge of the cell are analyzed at different states of charge and are found to follow the desorption curve of the pressure composition isotherm (PCI) of the metal hydride. The measured pressure agreed well with the calculated theoretical pressure based on the PCI and is used to predict the state of charge of the battery. Hydrogen equilibration with the metal hydride during charge/discharge cycling is fast when the pressure is in the range from 8 to 13 psia and slower in the range from 6 to 8 psia. The time constant for the slower hydrogen equilibration, 1.37h, is similar to the time constant for oxygen recombination and therefore pressure changes due to different mechanisms are difficult to estimate. The self-discharge rate of the cell with metal hydride is two times lower in comparison to the cell with gaseous hydrogen storage alone and is a result of the lower pressure in the cell when the metal hydride is used. PMID:22711974

Purushothaman, B. K.; Wainright, J. S.

2012-01-01

309

Enhancement of nuclear-spin cross-relaxation in metal-hydrogen systems  

SciTech Connect

A cross-relaxation model has previously been proposed to explain the anomalous frequency dependence of proton relaxation rates {ital R}{sub 1} in several metal-hydrogen systems at low temperatures. We report two experiments that test and unambiguously confirm the cross-relaxation model. The first experiment uses large-amplitude field modulation to sweep the proton resonance through the inhomogeneously broadened spectrum of metal resonances. The second involves rotation of the sample to sweep the metal resonances through the proton line. In both experiments, the protons are brought into spin thermal contact with an increased number of metal nuclei. Sample rotation rates of only 10 Hz increase the proton {ital R}{sub 1} by a factor of 50 for the TaH{sub {ital x}} system. A simple model explains the variation of {ital R}{sub 1} with rotation speed. Both techniques reveal increased proton relaxation rates {ital R}{sub 1}, unique signatures of the cross-relaxation model. A model is presented that explains the weaker than linear temperature dependence of {ital R}{sub 1}. The role of disorder on a length scale of 500 A or less is emphasized.

Baker, D.B.; Conradi, M.S.; Fedders, P.A.; Norberg, R.E. (Department of Physics, Washington University, St. Louis, Missouri 63130 (United States)); Torgeson, D.R.; Barnes, R.G. (Ames Laboratory and Department of Physics, Iowa State University, Ames, Iowa 50011 (United States)); Bowman, R.C. Jr. (Aerojet Electronic Systems Division, P.O. Box 296, Azusa, California 91702 (United States))

1991-12-01

310

In-Situ Cleaning of Metal Cathodes Using a Hydrogen Ion Beam  

SciTech Connect

Improving and maintaining the quantum efficiency (QE) of a metal photocathode in an s-band RF gun requires a process for cleaning the surface. In this type of gun, the cathode is typically installed and the system is vacuum baked to {approx}200 degrees C. If the QE is too low, the cathode is usually cleaned with the UV-drive laser. While laser cleaning does increase the cathode QE, it requires fluences close to the damage threshold and rastering the small diameter beam, both of which can produce nonuniform electron emission and potentially damage the cathode. This paper investigates the efficacy of a low energy hydrogen ion beam to produce high-QE metal cathodes. Measurements of the QE vs. wavelength, surface contaminants using x-ray photoelectron spectroscopy and surface roughness were performed on a copper sample, and the results showed a significant increase in QE after cleaning with a 1keV hydrogen ion beam. The H-ion beam cleaned an area approximately 1cm in diameter and had no effect on the surface roughness while significantly increasing the QE. These results and a comparison with theory as well as a scheme for installing an H-ion cleaner on an s-band gun are presented.

Dowell, D.H.; King, F.K.; Kirby, R.E.; Schmerge, J.F.; /SLAC

2005-09-01

311

Solubility of Iron in Metallic Hydrogen and Stability of Dense Cores in Giant Planets  

E-print Network

The formation of the giant planets in our solar system, and likely a majority of giant exoplanets, is commonly explained by the accretion of nebular hydrogen and helium onto a large core of terrestrial-like composition. The fate of this core has important consequences for the evolution of the interior structure of the planet. It has recently been shown that H2O, MgO and SiO2 dissolve in liquid metallic hydrogen at high temperature and pressure. In this study, we perform ab initio calculations to study the solubility of an innermost metallic core. We find dissolution of iron to be strongly favored above 2000 K over the entire pressure range (0.4-4 TPa) considered. We compare with and summarize the results for solubilities on other probable core constituents. The calculations imply that giant planet cores are in thermodynamic disequilibrium with surrounding layers, promoting erosion and redistribution of heavy elements. Differences in solubility behavior between iron and rock may influence evolution of interior...

Wahl, Sean; Militzer, Burkhard

2013-01-01

312

Geobacter sulfurreducens sp. nov., a hydrogen- and acetate-oxidizing dissimilatory metal-reducing microorganism.  

PubMed Central

A dissimilatory metal- and sulfur-reducing microorganism was isolated from surface sediments of a hydrocarbon-contaminated ditch in Norman, Okla. The isolate, which was designated strain PCA, was an obligately anaerobic, nonfermentative nonmotile, gram-negative rod. PCA grew in a defined medium with acetate as an electron donor and ferric PPi, ferric oxyhydroxide, ferric citrate, elemental sulfur, Co(III)-EDTA, fumarate, or malate as the sole electron acceptor. PCA also coupled the oxidation of hydrogen to the reduction of Fe(III) but did not reduce Fe(III) with sulfur, glucose, lactate, fumarate, propionate, butyrate, isobutyrate, isovalerate, succinate, yeast extract, phenol, benzoate, ethanol, propanol, or butanol as an electron donor. PCA did not reduce oxygen, Mn(IV), U(VI), nitrate, sulfate, sulfite, or thiosulfate with acetate as the electron donor. Cell suspensions of PCA exhibited dithionite-reduced minus air-oxidized difference spectra which were characteristic of c-type cytochromes. Phylogenetic analysis of the 16S rRNA sequence placed PCA in the delta subgroup of the proteobacteria. Its closest known relative is Geobacter metallireducens. The ability to utilize either hydrogen or acetate as the sole electron donor for Fe(III) reduction makes strain PCA a unique addition to the relatively small group of respiratory metal-reducing microorganisms available in pure culture. A new species name, Geobacter sulfurreducens, is proposed. Images PMID:7527204

Caccavo, F; Lonergan, D J; Lovley, D R; Davis, M; Stolz, J F; McInerney, M J

1994-01-01

313

First-Principles Modeling of Hydrogen Storage in Metal Hydride Systems  

SciTech Connect

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.

J. Karl Johnson

2011-05-20

314

Hydrogen-bonded inclusion compounds with reversed polarity: anionic metal-complexes and cationic organic linkers.  

PubMed

Synthesized and structurally characterized is a new series of soft-host frameworks assembled by charge-assisted hydrogen bonds between an anionic metal complex (MC) and cationic organic linkers (OL), specifically [Co(en)(ox)(2)](-) and diprotonated 4,4'-bipyridinium (H(2)bpy) or 1,2-bis(4-pyridinium)ethylene (H(2)bpye). While frameworks built of cationic complexes and anionic organic linkers are already well-known, the seven new compounds described here represent the first series of frameworks with reversed polarity, that is, made of anionic complexes and cationic organic linkers. The compounds have a general formula [OL][MC](2)·n(guest), where the guest molecules 4,4'-biphenol (bp), 4-methoxyphenol (mp), 1,4-dimethoxybenzene (dmb), 1,6-dimethoxynaphtalene (dmn), and 4-nitroanisole (na). Structurally the compounds can be described as pillared-layer frameworks with layers constructed of MC anions and linked together by hydrogen-bonded cationic OL pillars. The guest molecules occupy the galleries between the pillars while their steric, electronic, and ?-? and hydrogen-bonding capabilities influence the overall structure of the soft frameworks. PMID:22085246

Prakash, M Jaya; Sevov, Slavi C

2011-12-19

315

Significant reduction of the internuclear potential in superconductive solid metallic hydrogen  

NASA Astrophysics Data System (ADS)

Hydrogen varies its stable state in accordance with its temperature and density. Though molecular gas is stable in the environment, the monatomic state is stable in high density ranges of more than about 1 g cm-3. Such dense hydrogen has many aspects never seen in the molecular state. For example, in the range over about 108 K temperature and over 103 g cm-3 density, great efforts are being made to realize inertial confinement fusion (ICF). Additionally, in the range of temperature lower than about 105 K and of density more than 104 g cm-3 pycno nuclear fusion is supposed to occur. Here for the first time we have derived the expression for the Debye screening length of the interionic potential, taking into account correlated electron pairs, and investigated the nuclear reaction rate in superconductive solid metallic hydrogen. It is revealed that the screening length is shortened by correlated electron pairs that follow the Bose-Einstein distribution in the superconductive state. The bosonization increases the number of lower energy states of the electrons to increase the screening effects on the potential with decreases in the temperature, resulting in a significant enhancement of the nuclear reaction rate by more than 10 orders of magnitude.

Shibata, Kazunori; Kodama, Ryosuke

2008-02-01

316

Structure and energetics of hydrogen-bonded networks of methanol on close packed transition metal surfaces  

NASA Astrophysics Data System (ADS)

Methanol is a versatile chemical feedstock, fuel source, and energy storage material. Many reactions involving methanol are catalyzed by transition metal surfaces, on which hydrogen-bonded methanol overlayers form. As with water, the structure of these overlayers is expected to depend on a delicate balance of hydrogen bonding and adsorbate-substrate bonding. In contrast to water, however, relatively little is known about the structures methanol overlayers form and how these vary from one substrate to another. To address this issue, herein we analyze the hydrogen bonded networks that methanol forms as a function of coverage on three catalytically important surfaces, Au(111), Cu(111), and Pt(111), using a combination of scanning tunneling microscopy and density functional theory. We investigate the effect of intermolecular interactions, surface coverage, and adsorption energies on molecular assembly and compare the results to more widely studied water networks on the same surfaces. Two main factors are shown to direct the structure of methanol on the surfaces studied: the surface coverage and the competition between the methanol-methanol and methanol-surface interactions. Additionally, we report a new chiral form of buckled hexamer formed by surface bound methanol that maximizes the interactions between methanol monomers by sacrificing interactions with the surface. These results serve as a direct comparison of interaction strength, assembly, and chirality of methanol networks on Au(111), Cu(111), and Pt(111) which are catalytically relevant for methanol oxidation, steam reforming, and direct methanol fuel cells.

Murphy, Colin J.; Carrasco, Javier; Lawton, Timothy J.; Liriano, Melissa L.; Baber, Ashleigh E.; Lewis, Emily A.; Michaelides, Angelos; Sykes, E. Charles H.

2014-07-01

317

Structure and energetics of hydrogen-bonded networks of methanol on close packed transition metal surfaces.  

PubMed

Methanol is a versatile chemical feedstock, fuel source, and energy storage material. Many reactions involving methanol are catalyzed by transition metal surfaces, on which hydrogen-bonded methanol overlayers form. As with water, the structure of these overlayers is expected to depend on a delicate balance of hydrogen bonding and adsorbate-substrate bonding. In contrast to water, however, relatively little is known about the structures methanol overlayers form and how these vary from one substrate to another. To address this issue, herein we analyze the hydrogen bonded networks that methanol forms as a function of coverage on three catalytically important surfaces, Au(111), Cu(111), and Pt(111), using a combination of scanning tunneling microscopy and density functional theory. We investigate the effect of intermolecular interactions, surface coverage, and adsorption energies on molecular assembly and compare the results to more widely studied water networks on the same surfaces. Two main factors are shown to direct the structure of methanol on the surfaces studied: the surface coverage and the competition between the methanol-methanol and methanol-surface interactions. Additionally, we report a new chiral form of buckled hexamer formed by surface bound methanol that maximizes the interactions between methanol monomers by sacrificing interactions with the surface. These results serve as a direct comparison of interaction strength, assembly, and chirality of methanol networks on Au(111), Cu(111), and Pt(111) which are catalytically relevant for methanol oxidation, steam reforming, and direct methanol fuel cells. PMID:25005297

Murphy, Colin J; Carrasco, Javier; Lawton, Timothy J; Liriano, Melissa L; Baber, Ashleigh E; Lewis, Emily A; Michaelides, Angelos; Sykes, E Charles H

2014-07-01

318

Reactive coupling of 4-vinylaniline with hydrogen-terminated Si(100) surfaces for electroless metal and "synthetic metal" deposition.  

PubMed

Pristine and resist-patterned Si(100) substrates were etched by aqueous HF to produce hydrogen-terminated silicon (H-Si(100)) surfaces. The H-Si(100) surface was then subjected to UV-induced reactive coupling of 4-vinylaniline (VAn) to produce the VAn monolayer-modified silicon (VAn-Si) surface. The VAn-Si surface was first functionalized with a "synthetic metal" by oxidative graft polymerization of aniline with the aniline moieties of the coupled VAn molecules. The composition and topography of the VAn-Si and polyaniline (PAn)-grafted VAn-Si (PAn-VAn-Si) surfaces were characterized by X-ray photoelectron spectroscopy and atomic force microscopy, respectively. The doping-undoping (protonation-deprotonation) and redox-coupling (metal reduction) behavior, as well as the electrical conductivity, of the surface-grafted PAn were found to be similar to those of the aniline homopolymer. The VAn-Si surface was also funtionalized by the electroless plating of copper. Not only did the VAn layer provide chemisorption sites for the palladium catalyst, in the absence of prior sensitization by SnCl2, during the electroless plating process, it also served as an adhesion promotion layer and a low-temperature diffusion barrier for the electrolessly deposited copper. Finally, micropatterning of the grafted PAn and of the electrolessly deposited copper were demonstrated on the resist-patterned VAn-Si surfaces. PMID:15875865

Xu, D; Kang, E T; Neoh, K G; Tay, A A O

2004-04-13

319

Discovery of Novel Complex Metal Hydrides for Hydrogen Storage through Molecular Modeling and Combinatorial Methods  

SciTech Connect

UOP LLC, a Honeywell Company, Ford Motor Company, and Striatus, Inc., collaborated with Professor Craig Jensen of the University of Hawaii and Professor Vidvuds Ozolins of University of California, Los Angeles on a multi-year cost-shared program to discover novel complex metal hydrides for hydrogen storage. This innovative program combined sophisticated molecular modeling with high throughput combinatorial experiments to maximize the probability of identifying commercially relevant, economical hydrogen storage materials with broad application. A set of tools was developed to pursue the medium throughput (MT) and high throughput (HT) combinatorial exploratory investigation of novel complex metal hydrides for hydrogen storage. The assay programs consisted of monitoring hydrogen evolution as a function of temperature. This project also incorporated theoretical methods to help select candidate materials families for testing. The Virtual High Throughput Screening served as a virtual laboratory, calculating structures and their properties. First Principles calculations were applied to various systems to examine hydrogen storage reaction pathways and the associated thermodynamics. The experimental program began with the validation of the MT assay tool with NaAlH4/0.02 mole Ti, the state of the art hydrogen storage system given by decomposition of sodium alanate to sodium hydride, aluminum metal, and hydrogen. Once certified, a combinatorial 21-point study of the NaAlH4 â?? LiAlH4 â??Mg(AlH4)2 phase diagram was investigated with the MT assay. Stability proved to be a problem as many of the materials decomposed during synthesis, altering the expected assay results. This resulted in repeating the entire experiment with a mild milling approach, which only temporarily increased capacity. NaAlH4 was the best performer in both studies and no new mixed alanates were observed, a result consistent with the VHTS. Powder XRD suggested that the reverse reaction, the regeneration of the alanate from alkali hydride, Al and hydrogen, was hampering reversibility. The reverse reaction was then studied for the same phase diagram, starting with LiH, NaH, and MgH2, and Al. The study was extended to phase diagrams including KH and CaH2 as well. The observed hydrogen storage capacity in the Al hexahydrides was less than 4 wt. %, well short of DOE targets. The HT assay came on line and after certification with studies on NaAlH4, was first applied to the LiNH2 - LiBH4 - MgH2 phase diagram. The 60-point study elucidated trends within the system locating an optimum material of 0.6 LiNH2 â?? 0.3 MgH2 â?? 0.1 LiBH4 that stored about 4 wt. % H2 reversibly and operated below 220 °C. Also present was the phase Li4(NH2)3BH4, which had been discovered in the LiNH2 -LiBH4 system. This new ternary formulation performed much better than the well-known 2 LiNH2 â?? MgH2 system by 50 °C in the HT assay. The Li4(NH2)3BH4 is a low melting ionic liquid under our test conditions and facilitates the phase transformations required in the hydrogen storage reaction, which no longer relies on a higher energy solid state reaction pathway. Further study showed that the 0.6 LiNH2 â?? 0.3 MgH2 â?? 0.1 LiBH4 formulation was very stable with respect to ammonia and diborane desorption, the observed desorption was from hydrogen. This result could not have been anticipated and was made possible by the efficiency of HT combinatorial methods. Investigation of the analogous LiNH2 â?? LiBH4 â?? CaH2 phase diagram revealed new reversible hydrogen storage materials 0.625 LiBH4 + 0.375 CaH2 and 0.375 LiNH2 + 0.25 LiBH4 + 0.375 CaH2 operating at 1 wt. % reversible hydrogen below 175 °C. Powder x-ray diffraction revealed a new structure for the spent materials which had not been previously observed. While the storage capacity was not impressive, an important aspect is that it boron appears to participate in a low temperature reversible reaction. The last major area of study also focused

Lesch, David A; Adriaan Sachtler, J.W. J.; Low, John J; Jensen, Craig M; Ozolins, Vidvuds; Siegel, Don

2011-02-14

320

Metal and Precursor Effect during 1-Heptyne Selective Hydrogenation Using an Activated Carbon as Support  

PubMed Central

Palladium, platinum, and ruthenium supported on activated carbon were used as catalysts for the selective hydrogenation of 1-heptyne, a terminal alkyne. All catalysts were characterized by temperature programmed reduction, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. TPR and XPS suggest that the metal in all catalysts is reduced after the pretreatment with H2 at 673?K. The TPR trace of the PdNRX catalyst shows that the support surface groups are greatly modified as a consequence of the use of HNO3 during the catalyst preparation. During the hydrogenation of 1-heptyne, both palladium catalysts were more active and selective than the platinum and ruthenium catalysts. The activity order of the catalysts is as follows: PdClRX > PdNRX > PtClRX ? RuClRX. This superior performance of PdClRX was attributed in part to the total occupancy of the d electronic levels of the Pd metal that is supposed to promote the rupture of the H2 bond during the hydrogenation reaction. The activity differences between PdClRX and PdNRX catalysts could be attributed to a better accessibility of the substrate to the active sites, as a consequence of steric and electronic effects of the superficial support groups. The order for the selectivity to 1-heptene is as follows: PdClRX = PdNRX > RuClRX > PtClRX, and it can be mainly attributed to thermodynamic effects. PMID:24348168

Lederhos, Cecilia R.; Badano, Juan M.; Carrara, Nicolas; Coloma-Pascual, Fernando; Almansa, M. Cristina; Liprandi, Domingo; Quiroga, Mónica

2013-01-01

321

Activation of Noble Metals on Metal-Carbide Surfaces: Novel Catalysts for CO Oxidation, Desulfurization and Hydrogenation Reactions  

SciTech Connect

This perspective article focuses on the physical and chemical properties of highly active catalysts for CO oxidation, desulfurization and hydrogenation reactions generated by depositing noble metals on metal-carbide surfaces. To rationalize structure-reactivity relationships for these novel catalysts, well-defined systems are required. High-resolution photoemission, scanning tunneling microscopy (STM) and first-principles periodic density-functional (DF) calculations have been used to study the interaction of metals of Groups 9, 10 and 11 with MC(001) (M = Ti, Zr, V, Mo) surfaces. DF calculations give adsorption energies that range from 2 eV (Cu, Ag, Au) to 6 eV (Co, Rh, Ir). STM images show that Au, Cu, Ni and Pt grow on the carbide substrates forming two-dimensional islands at very low coverage, and three-dimensional islands at medium and large coverages. In many systems, the results of DF calculations point to the preferential formation of admetal-C bonds with significant electronic perturbations in the admetal. TiC(001) and ZrC(001) transfer some electron density to the admetals facilitating bonding of the adatom with electron-acceptor molecules (CO, O{sub 2}, C{sub 2}H{sub 4}, SO{sub 2}, thiophene, etc.). For example, the Cu/TiC(001) and Au/TiC(001) systems are able to cleave both S-O bonds of SO{sub 2} at a temperature as low as 150 K, displaying a reactivity much larger than that of TiC(001) or extended surfaces of bulk copper and gold. At temperatures below 200 K, Au/TiC is able to dissociate O{sub 2} and perform the 2CO + O{sub 2} {yields} 2CO{sub 2} reaction. Furthermore, in spite of the very poor hydrodesulfurization performance of TiC(001) or Au(111), a Au/TiC(001) surface displays an activity for the hydrodesulfurization of thiophene higher than that of conventional Ni/MoS{sub x} catalysts. In general, the Au/TiC system is more chemically active than systems generated by depositing Au nanoparticles on oxide surfaces. Thus, metal carbides are excellent supports for enhancing the chemical reactivity of noble metals.

Rodriguez J. A.; Illas, F.

2012-01-01

322

A coordinatively saturated sulfate encapsulated in a metal-organic framework functionalized with urea hydrogen-bonding groups  

Microsoft Academic Search

A functional coordination polymer decorated with urea hydrogen-bonding donor groups has been designed for optional binding of sulfate; self-assembly of a tripodal tri-urea linker with Ag2SO4 resulted in the formation of a 1D metal-organic framework that encapsulated SO42- anions via twelve complementary hydrogen bonds, which represents the highest coordination number observed for sulfate in a natural or synthetic host.

Radu Custelcean; Bruce A. Moyer; Benjamin P. Hay

2005-01-01

323

Hydrogen adsorption strength and sites in the metal organic framework MOF5: Comparing experiment and model calculations  

Microsoft Academic Search

Hydrogen adsorption in porous, high surface area, and stable metal organic frameworks (MOF’s) appears a novel route towards hydrogen storage materials [N.L. Rosi, J. Eckert, M. Eddaoudi, D.T. Vodak, J. Kim, M. O’Keeffe, O.M. Yaghi, Science 300 (2003) 1127; J.L.C. Rowsell, A.R. Millward, K. Sung Park, O.M. Yaghi, J. Am. Chem. Soc. 126 (2004) 5666; G. Ferey, M. Latroche, C.

F. M. Mulder; T. J. Dingemans; H. G. Schimmel; A. J. Ramirez-Cuesta; G. J. Kearley

2008-01-01

324

Hydrogen incorporation and radiation induced dynamics in metal-oxide-silicon structures: A study using nuclear reaction analysis  

Microsoft Academic Search

Resonant Nuclear Reaction Analysis (NRA), using the H-1\\/N-15, alpha gamma\\/c-12 reaction at 6.4 MeV, is successfully applied to the investigation of hydrogen incorporation and radiation induced migration in metal oxide silicon structures. The influence of processing parameters on the H content of thermal oxides, with and without gate material present, is studied. Hydrogen accumulation at the Si-SiO2 interface is reproducibly

M. A. Briere

1993-01-01

325

LETTER TO THE EDITOR: Migration of hydrogen in rare-earth metals at the disorder-order transition  

Microsoft Academic Search

The migration energies, which are obtained using the hydrogen disorder-order transition, of hydrogen atoms in rare-earth metals divide into two groups, high values and low values. The high values are approximately double the low values. The cause of the discrepancy is discussed and explained as a misestimate of the order of the reaction in the rate equation for the low-value

Kohji Yamakawa

1999-01-01

326

Hydrogen from formic acid through its selective disproportionation over sodium germanate--a non-transition-metal catalysis system.  

PubMed

A robust catalyst for the selective dehydrogenation of formic acid to liberate hydrogen gas has been designed computationally, and also successfully demonstrated experimentally. This is the first such catalyst not based on transition metals, and it exhibits very encouraging performance. It represents an important step towards the use of renewable formic acid as a hydrogen-storage and transport vector in fuel and energy applications. PMID:25169798

Amos, Ruth I J; Heinroth, Falk; Chan, Bun; Zheng, Sisi; Haynes, Brian S; Easton, Christopher J; Masters, Anthony F; Radom, Leo; Maschmeyer, Thomas

2014-10-13

327

Some technology gaps in the detection and prediction of hydrogen-induced degradation of metals and alloys  

Microsoft Academic Search

One hundred years of study and thousands of individual investigations have led to some understanding of the deleterious effects of hydrogen on the mechanical behavior of metals and alloys. This understanding includes a technical basis to: (a) evaluate the potential for hydrogen-induced degradation through mechanistic, phenomenological, and\\/or empirical models of the embrittlement process(es), (b) categorize the type of damage in

M. R. Louthan; M. J. Morgan

1996-01-01

328

Density functional calculations of the hydrogen adsorption on transition metals and their alloys. An application to catalysis  

SciTech Connect

Computer modeling of catalytic effects of a series of the transition metals and their alloys on the process of dissociation of molecular hydrogen has been performed. The project was composed of three stages. First, the binding energy versus the internuclear distance has been calculated for a series of metal dimers and mixed dimers: Ni{sub 2}, NiCu, Cu{sub 2}, Ag{sub 2}, AgPd, Pd{sub 2}. Then, using the fitted Morse form of the potential interaction between the metal atoms, the Molecular Dynamics (MD) simulations have been performed in order to obtain the atomic structures appearing in the alloys. The third part of the project includes the quantum-chemical calculations of hydrogen atom and hydrogen molecule positioned over the metallic dimers. The interatomic distances of the dimers were taken from the MD calculations. A range of the distances of hydrogen from the metal dimers was scanned. The evolution of energy and electron density with the hydrogen distance from certain dimers, like NiCu, AgPd and Pd{sub 2}, clearly exhibits the process of the hydrogen molecule dissociation. On a basis of these calculations a measure of catalytic power. It was found that the highest catalytic power with respect to the hydrogen dissociation process is exhibited by NiCu alloys. All the quantum-chemical calculations have been performed using the methods of the density functional theory (DFT). The nonlocal version of the DFT was applied with the gradient-corrected functional for electron exchange and correlation. The GAUSSIAN-94 and -98 suites of programs were employed in the calculations.

Romanowski, S.; Bartczak, W.M.; Wesolkowski, R.

1999-08-31

329

Hydrogen purifier module with membrane support  

DOEpatents

A hydrogen purifier utilizing a hydrogen-permeable membrane to purify hydrogen from mixed gases containing hydrogen is disclosed. Improved mechanical support for the permeable membrane is described, enabling forward or reverse differential pressurization of the membrane, which further stabilizes the membrane from wrinkling upon hydrogen uptake.

A hydrogen purifier utilizing a hydrogen-permeable membrane to purify hydrogen from mixed gases containing hydrogen is disclosed. Improved mechanical support for the permeable membrane is described, enabling forward or reverse differential pressurization of the membrane, which further stabilizes the membrane from wrinkling upon hydrogen uptake.

2012-07-24

330

In-Situ Cleaning of Metal Cathodes using a Hydrogen Ion Beam  

SciTech Connect

Metal photocathodes are commonly used in high-field RF guns because they are robust, straightforward to implement and tolerate relatively poor vacuum compared to semi-conductor cathodes. However these cathodes have low quantum efficiency (QE) even at UV wavelengths, and still require some form of cleaning after installation in the gun. A commonly used process for improving the QE is laser cleaning. In this technique the UV drive laser is focused to a small diameter close to the metal's damage threshold and then moved across the surface to remove contaminants. This method does improve the QE, but can produce non-uniform emission and potentially damage the cathode. Ideally an alternative process which produces an atomically clean, but unaltered surface is needed. In this paper we explore using a hydrogen ion (H-ion) beam to clean a copper cathode. We describe QE measurements over the wavelength range of interest as a function of integrated exposure to an H-ion beam. We also describe the data analysis to obtain the work function and derive a formula of the QE for metal cathodes. Our measured work function for the cleaned sample is in good agreement with published values, and the theoretical QE as a function of photon wavelength is in excellent agreement with the cleaned copper experimental results. Finally, we propose an in-situ installation of an H-ion gun compatible with existing s-band RF guns.

Dowell, D.H.; King, F.K.; Kirby, R.E.; Schmerge, J.F.; /SLAC

2006-03-29

331

Hydrogen Interaction with Titanium Carbide-Coated Metals for Fusion Technology Application  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. The interaction of gaseous hydrogen with TiC coatings deposited on metals by Chemical Vapour Deposition was studied. The prime aim of this study was to determine whether such coatings could affect the rate of absorption and desorption by the metallic substrate. Developing and testing simple models for the experiments in terms of diffusivity D, Sieverts' constant K_{s} and surface reaction rates k_1, k_2, was another goal of the work. Both aims are closely linked to the use of tritium in present and future fusion devices. Two manometric techniques were used. At Ispra, the hydrogen pressure increase in a closed vessel was recorded in time, after loading the sample with hydrogen to equilibrium and evacuating the chamber. Loading pressures between 10^3 Pa and 10^5 Pa were used, with temperatures in the range 673 K-873 K. At Oxford, a similar equilibrium state was perturbed by a imposed periodic volume variation. The corresponding pressure response, in a closed chamber containing the specimen immersed in hydrogen, was recorded in time. Pressures between 4 Pa and 74 Pa were used and the temperature range was 883 K-1083 K. The substrates used were the AISI 316L steel and the molybdenum alloy TZM at Ispra, while only TZM at Oxford. With both methods, a marked increase of the times to reach equilibrium was detected with respect to uncoated samples, while the equilibrium absorption behaviour of the coated specimens was not significantly different from that of the bare ones. Very low diffusivity values were obtained for hydrogen in TiC. For the Ispra samples, the temperature dependence found is D/{rm(m ^2s}^{-1}) = 1.08 times 10^{-12} exp(-{6800 over T/K})while that determined at Oxford, for different TiC specimens, is D/{rm (m^2s}^ {-1}) = 9.60 times 10^{-12} exp (-{6010over T/K}). The surface rate constants determined at Ispra are represented by eqalign {k_1/({rm mol m^{ -2}s^{-1}Pa^{-1}) }&= 4.10 times 10^{-8} exp (-{4560over T/K}), cr k_2/{rm (m^4mol^ {-1}s^{-1})}&= 6.90 times 10^{-12} exp (-{5070 over T/K})cr}and those found at Oxford by eqalign {k_1/({rm mol m^{ -2}s^{-1}Pa^{-1}) }&= 5.40 times 10^{-5} exp (-{10250over T/K}), cr k_2/{rm (m^4mol^ {-1}s^{-1})}&= 2.90 times 10^{-9} exp (-{5070 over T/K}).cr} The Sieverts' constant K_{s } for hydrogen in TiC determined at Oxford is represented by K_{s}/ {rm(mol m^{-3}Pa^ {1/2})} = 2.90 times 10^{ -9} exp (-{5070over T/K }).This gives values lower than for the steel substrate for a factor of 200, and for the TZM substrate for a factor of 2000. The results suggest that TiC would impede hydrogen permeation through steel more effectively in surface-limited regimes. TZM was also studied and was shown to be a possible permeation barrier itself. Trapping was also qualitatively detected in TZM.

Caorlin, Marco

332

181Ta perturbed-angular-correlation study of electric quadrupole interactions in yttrium metal and yttrium-hydrogen solid solutions  

Microsoft Academic Search

The perturbed-angular-correlation (PAC) technique has been used to study the electric quadrupole interaction (QI) of the nuclear probe 181Ta in yttrium metal and yttrium-hydrogen solid solutions alpha-YHx with 0<=x<=0.2. The temperature dependence of the quadrupole frequency nuq of 181Ta in yttrium metal, measured in the range 290 K<=T<=1700 K, follows the linear relation nuq(T) = nuq(0)(1-AT) with nuq(0) = 423(3)

M. Forker; U. Hütten; M. Müller

2000-01-01

333

A Phenomenological Study of the Metal-Oxide Interface: The Role of Catalysis in Hydrogen Production from Renewable Resources  

SciTech Connect

The truth about Cats: The metal-oxide interface of a Pd-Rh/CeO{sub 2} catalyst was studied in the context of developing active, selective and durable solid catalytic materials for the production of hydrogen from renewables. The presence of a stable contact between finely dispersed transition-metal clusters (Pd and Rh) on the nanoparticles of the CeO{sub 2} support leads to a highly active and stable catalyst for the steam reforming of ethanol.

Idriss, H.; Llorca, J; Chan, S; Blackford, M; Pas, S; Hill, A; Alamgir, F; Rettew, R; Petersburg, C; Barteau, M

2008-01-01

334

The effect of hydrogen iodide on the ignition of Hg-free metal-halide lamps  

NASA Astrophysics Data System (ADS)

Trace amounts of moisture (e.g. adsorbed on metal-halide salt pellets during lamp fabrication) may react with the salts during initial lamp light-up to form volatile hydrogen iodide (HI). Hg-free lamps are particularly prone to HI formation since the elemental mercury is not included. The Hg-free lamps can develop high ignition voltages due to the HI, which adversely affects lamp operation especially ignition. This work discusses the thermochemistry and spectroscopic measurements which predict and demonstrate that HI is indeed formed in the reaction of salts and moisture. Experimental confirmation of increased breakdown voltage with increasing concentration of HI (at the ppm level) was obtained in discharge cell experiments. Computer simulations of xenon and HI gas mixtures show qualitative agreement with experiments.

Estupiñán, E. G.; Pereyra, R.; Li, Y.-M.; Lapatovich, W. P.

2011-06-01

335

Methods for producing hydrogen (BI) sulfide and/or removing metals  

DOEpatents

The present invention is a process wherein sulfide production by bacteria is efficiently turned on and off, using pH adjustment. The adjustment of pH impacts sulfide production by bacteria by altering the relative amounts of H.sub.2 S and HS-- in solution and thereby control the inhibition of the bacterial metabolism that produces sulfide. This process can be used to make a bioreactor produce sulfide "on-demand" so that the production of sulfide can be matched to its use as a metal precipitation reagent. The present invention is of significance because it enables the use of a biological reactor, a cost effective sulfide production system, by making the biological reactor produce hydrogen sulfide "on demand", and therefore responsive to production schedules, waste stream generation rate, and health and safety requirements/goals.

Truex, Michael J [Richland, WA; Peyton, Brent M [Pullman, WA; Toth, James J [Kennewick, WA

2002-05-14

336

Metal-organic framework based highly selective fluorescence turn-on probe for hydrogen sulphide  

PubMed Central

Hydrogen sulphide (H2S) is known to play a vital role in human physiology and pathology which stimulated interest in understanding complex behaviour of H2S. Discerning the pathways of H2S production and its mode of action is still a challenge owing to its volatile and reactive nature. Herein we report azide functionalized metal-organic framework (MOF) as a selective turn-on fluorescent probe for H2S detection. The MOF shows highly selective and fast response towards H2S even in presence of other relevant biomolecules. Low cytotoxicity and H2S detection in live cells, demonstrate the potential of MOF towards monitoring H2S chemistry in biological system. To the best of our knowledge this is the first example of MOF that exhibit fast and highly selective fluorescence turn-on response towards H2S under physiological conditions. PMID:25394493

Nagarkar, Sanjog S.; Saha, Tanmoy; Desai, Aamod V.; Talukdar, Pinaki; Ghosh, Sujit K.

2014-01-01

337

Metal-organic framework based highly selective fluorescence turn-on probe for hydrogen sulphide  

NASA Astrophysics Data System (ADS)

Hydrogen sulphide (H2S) is known to play a vital role in human physiology and pathology which stimulated interest in understanding complex behaviour of H2S. Discerning the pathways of H2S production and its mode of action is still a challenge owing to its volatile and reactive nature. Herein we report azide functionalized metal-organic framework (MOF) as a selective turn-on fluorescent probe for H2S detection. The MOF shows highly selective and fast response towards H2S even in presence of other relevant biomolecules. Low cytotoxicity and H2S detection in live cells, demonstrate the potential of MOF towards monitoring H2S chemistry in biological system. To the best of our knowledge this is the first example of MOF that exhibit fast and highly selective fluorescence turn-on response towards H2S under physiological conditions.

Nagarkar, Sanjog S.; Saha, Tanmoy; Desai, Aamod V.; Talukdar, Pinaki; Ghosh, Sujit K.

2014-11-01

338

Effective thermal conductivities of four metal ceramic composite coatings in hydrogen-oxygen rocket firings  

NASA Technical Reports Server (NTRS)

An experimental investigation was conducted to determine the effective conductivities of four plasma-arc-sprayed, metal-ceramic gradated coatings on hydrogen-oxygen thrust chambers. The effective thermal conductivities were not a function of pressure or oxidant-to-fuel ratio. The various materials that made up these composites do not seem to affect the thermal conductivity values as much as the differences in the thermal conductivities of the parent materials would lead one to expect. Contact resistance evolving from the spraying process seems to be the controlling factor. The thermal conductivities of all the composites tested fell in the range of 0.75 to 7.5 watts per meter kelvin.

Schacht, R. L.; Price, H. G., Jr.; Quentmeyer, R. J.

1972-01-01

339

181Ta perturbed-angular-correlation study of electric quadrupole interactions in yttrium metal and yttrium-hydrogen solid solutions  

NASA Astrophysics Data System (ADS)

The perturbed-angular-correlation (PAC) technique has been used to study the electric quadrupole interaction (QI) of the nuclear probe 181Ta in yttrium metal and yttrium-hydrogen solid solutions ?-YHx with 0?x?0.2. The temperature dependence of the quadrupole frequency ?q of 181Ta in yttrium metal, measured in the range 290 K?T?1700 K, follows the linear relation ?q(T) = ?q(0)(1-AT) with ?q(0) = 423(3) MHz and A = 4.74(4)×10-4 K-1. The absorption of hydrogen enhances the temperature dependence of the QI: the parameters ?q(0) and A of the linear temperature variation of the 181Ta QI in ?-YHx measured between 25 K and 1000 K for 0?x?0.2 both increase with increasing concentration x. These trends are consistent with the anionic model of the electronic state of hydrogen in rare earth metals. At T?500 K a dynamic QI caused by diffusing hydrogen has been observed. The activation energy for hydrogen jumps in ?-YH0.10 deduced from the temperature dependence of the quadrupole relaxation rate is Ea = 0.49(15) eV.

Forker, M.; Hütten, U.; Müller, M.

2000-08-01

340

Calculation of hydrogen storage capacity of metal-organic and covalent-organic frameworks by spillover  

NASA Astrophysics Data System (ADS)

We have used accurate ab initio quantum chemistry calculations together with a simple model to study the hydrogen storage capacity of metal-organic and covalent-organic frameworks by spillover. Recent experiments by Tsao et al. [J. Am. Chem. Soc. 131, 1404 (2009)] {based on an earlier work by Li and Yang [J. Am. Chem. Soc. 128, 8136 (2006)]} have found that IRMOF-8 with bridged Pt catalysts can reversibly store up to 4.7 wt % of hydrogen at room temperature and 100 bar. We have calculated the binding energy for multiple H atoms on model molecules. By counting active storage sites, we predict a saturation excess storage density at room temperature of 5.0 wt % for IRMOF-8. We also predict storage densities of 4.5 wt % for IRMOF-1, 5.4 wt % for MOF-177, 4.5 wt % for COF-1, and 5.7 wt % for IRMOF-15 and IRMOF-16. This suggests that the current experimental H storage results for IRMOF-8 are well optimized. However, for other materials such as MOF-177 and COF-1, the experimental results are not yet optimized, and significantly more H can be stored on these materials. We also find that significant strain will result from shrinkage of the linker molecules as H atoms are loaded onto the crystals.

Suri, Mayur; Dornfeld, Matthew; Ganz, Eric

2009-11-01

341

Photoelectron spectroscopy study of metallic nanocluster arrangement at the surface of reactively sputtered amorphous hydrogenated carbon  

SciTech Connect

We report on the results of the arrangement of isolated surface metallic nanoclusters embedded in amorphous hydrogenated carbon (a-C:H) thin films, studied by photoelectron spectroscopy. As a model system we used gold-containing amorphous hydrogenated carbon (a-C:H/Au), due to the lack of reactivity between carbon and gold. The a-C:H/Au samples are obtained by simultaneous magnetron sputtering of Au target by argon and plasma-enhanced chemical vapor deposition of methane. Photoelectron spectroscopy with x-ray and ultraviolet excitation has been employed for surface studies that comprise as-deposited sample spectra recordings, measurements at off-normal takeoff angle, in situ in-depth profiling by Ar{sup +} ion etching, and thiophene adsorption at the sample surface. The results of these extended studies firmly support previously drawn conclusions [I. R. Videnovic, V. Thommen, P. Oelhafen, D. Mathys, M. Dueggelin, and R. Guggenheim, Appl. Phys. Lett 80, 2863 (2002)] that by deposition on electrically grounded substrates one obtains samples with topmost Au clusters covered with a thin layer of a-C:H. Introducing a dc substrate bias voltage results in bald Au clusters on the surface and increased sp{sup 2}/sp{sup 3} coordinated carbon ratio in the a-C:H matrix.

Videnovic, Ivan R.; Oelhafen, Peter [Institut fuer Physik, Universitaet Basel, Klingelbergstr. 82, CH-4056 Basel (Switzerland)

2005-04-01

342

Enhanced Photochemical Hydrogen Production by a Molecular Diiron Catalyst Incorporated into a Metal–Organic Framework  

PubMed Central

A molecular proton reduction catalyst [FeFe](dcbdt)(CO)6 (1, dcbdt = 1,4-dicarboxylbenzene-2,3-dithiolate) with structural similarities to [FeFe]-hydrogenase active sites has been incorporated into a highly robust Zr(IV)-based metal–organic framework (MOF) by postsynthetic exchange (PSE). The PSE protocol is crucial as direct solvothermal synthesis fails to produce the functionalized MOF. The molecular integrity of the organometallic site within the MOF is demonstrated by a variety of techniques, including X-ray absorption spectroscopy. In conjunction with [Ru(bpy)3]2+ as a photosensitizer and ascorbate as an electron donor, MOF-[FeFe](dcbdt)(CO)6 catalyzes photochemical hydrogen evolution in water at pH 5. The immobilized catalyst shows substantially improved initial rates and overall hydrogen production when compared to a reference system of complex 1 in solution. Improved catalytic performance is ascribed to structural stabilization of the complex when incorporated in the MOF as well as the protection of reduced catalysts 1– and 12– from undesirable charge recombination with oxidized ascorbate. PMID:24116734

2013-01-01

343

Final LDRD report : metal oxide films, nanostructures, and heterostructures for solar hydrogen production.  

SciTech Connect

The distinction between electricity and fuel use in analyses of global power consumption statistics highlights the critical importance of establishing efficient synthesis techniques for solar fuels-those chemicals whose bond energies are obtained through conversion processes driven by solar energy. Photoelectrochemical (PEC) processes show potential for the production of solar fuels because of their demonstrated versatility in facilitating optoelectronic and chemical conversion processes. Tandem PEC-photovoltaic modular configurations for the generation of hydrogen from water and sunlight (solar water splitting) provide an opportunity to develop a low-cost and efficient energy conversion scheme. The critical component in devices of this type is the PEC photoelectrode, which must be optically absorptive, chemically stable, and possess the required electronic band alignment with the electrochemical scale for its charge carriers to have sufficient potential to drive the hydrogen and oxygen evolution reactions. After many decades of investigation, the primary technological obstacle remains the development of photoelectrode structures capable of efficient conversion of light with visible frequencies, which is abundant in the solar spectrum. Metal oxides represent one of the few material classes that can be made photoactive and remain stable to perform the required functions.

Kronawitter, Coleman X. [Lawrence Berkeley National Laboratory, Berkeley, CA; Antoun, Bonnie R.; Mao, Samuel S. [Lawrence Berkeley National Laboratory, Berkeley, CA

2012-01-01

344

Flexible Sandwich Diaphragms Are Less Permeable  

NASA Technical Reports Server (NTRS)

Diaphragms for use in refrigerator compressors made as laminates of commercially available elastomers and metals. Diaphragms flexible, but less permeable by chlorofluorocarbon refrigerant fluids than diaphragms made of homogeneous mixtures of materials.

Michalovic, John G.; Vassallo, Franklin A.

1993-01-01

345

Polymer/Silicate Nanocomposites Used to Manufacture Gas Storage Tanks With Reduced Permeability  

NASA Technical Reports Server (NTRS)

Over the past decade, there has been considerable research in the area of polymer-layered silicate nanocomposites. This research has shown that the dispersion of small amounts of an organically modified layered silicate improves the polymer strength, modulus, thermal stability, and barrier properties. There have been several reports on the dispersion of layered silicates in an epoxy matrix. Potential enhancements to the barrier properties of epoxy/silicate nanocomposites make this material attractive for low permeability tankage. Polymer matrix composites (PMCs) have several advantages for cryogenic storage tanks. They are lightweight, strong, and stiff; therefore, a smaller fraction of a vehicle's potential payload capacity is used for propellant storage. Unfortunately, the resins typically used to make PMC tanks have higher gas permeability than metals. This can lead to hydrogen loss through the body of the tank instead of just at welds and fittings. One approach to eliminate this problem is to build composite tanks with thin metal liners. However, although these tanks provide good permeability performance, they suffer from a substantial mismatch in the coefficient of thermal expansion, which can lead to failure of the bond between the liner and the body of the tank. Both problems could be addressed with polymersilicate nanocomposites, which exhibit reduced hydrogen permeability, making them potential candidates for linerless PMC tanks. Through collaboration with Northrop Grumman and Michigan State University, nanocomposite test tanks were manufactured for the NASA Glenn Research Center, and the helium permeability was measured. An organically modified silicate was prepared at Michigan State University and dispersed in an epoxy matrix (EPON 826/JeffamineD230). The epoxy/silicate nanocomposites contained either 0 or 5 wt% of the organically modified silicate. The tanks were made by filament winding carbon fibers with the nanocomposite resin. Helium permeability was measured by Northrop Grumman, showing that the leak rate/day of the nanocomposite matrix tank was approximately 80-percent less than that of the neat epoxy matrix tank.

Campbell, Sandi G.; Johnston, Chris

2004-01-01

346

Ab Initio Free Energy Calculations of the Solubility of Silica in Metallic Hydrogen and Application to Giant Planet Cores  

NASA Astrophysics Data System (ADS)

By combining density functional molecular dynamics simulations with a thermodynamic integration technique, we determine the free energy of metallic hydrogen and silica, SiO2, at megabar pressures and thousands of degrees Kelvin. Our ab initio solubility calculations show that silica dissolves into fluid hydrogen above 5000 K for pressures from 10 and 40 Mbars, which has implications for the evolution of rocky cores in giant gas planets like Jupiter, Saturn, and a substantial fraction of known extrasolar planets. Our findings underline the necessity of considering the erosion and redistribution of core materials in giant planet evolution models, but they also demonstrate that hot metallic hydrogen is a good solvent at megabar pressures, which has implications for high-pressure experiments.

González-Cataldo, F.; Wilson, Hugh F.; Militzer, B.

2014-05-01

347

Response Behaviour of a Hydrogen Sensor Based on Ionic Conducting Polymer-metal Interfaces Prepared by the Chemical Reduction Method  

PubMed Central

A solid-state amperometric hydrogen sensor based on a protonated Nafion membrane and catalytic active electrode operating at room temperature was fabricated and tested. Ionic conducting polymer-metal electrode interfaces were prepared chemically by using the impregnation-reduction method. The polymer membrane was impregnated with tetra-ammine platinum chloride hydrate and the metal ions were subsequently reduced by using either sodium tetrahydroborate or potassium tetrahydroborate. The hydrogen sensing characteristics with air as reference gas is reported. The sensors were capable of detecting hydrogen concentrations from 10 ppm to 10% in nitrogen. The response time was in the range of 10-30 s and a stable linear current output was observed. The thin Pt films were characterized by XRD, Infrared Spectroscopy, Optical Microscopy, Atomic Force Microscopy, Scanning Electron Microscopy and EDAX.

Sakthivel, Mariappan; Weppner, Werner

2006-01-01

348

Identification of Pathways for Hydrogen Gas Migration in Fault Zones with a Discontinuous, Heterogeneous Permeability Structure and the Relationship to Particle Size Distribution of Fault Materials  

NASA Astrophysics Data System (ADS)

Previous studies have reported that high concentrations of H2 gas are released from active fault zones. Experimental studies suggest that the H2 gas is derived from the reaction of water with free radicals formed when silicate minerals are fractured at hypocenter depths during fault activities. However, the pathways for migration of deep-seated fluids to surface are still unknown. In this study we performed quick, multipoint H2 gas measurements across a fault zone using a portable gas monitor and a hand drill. The fault zone studied includes a smectite-rich fault core dividing two clearly distinguishable damage zones: granite cataclasite and welded tuff fault breccia. The measurements show that H2 gas emissions collected in 2-3 h sampling periods from start of measurement range from 320.3 to 446.2 ppm/min in the granite cataclasite and 60.5 to 137.8 ppm/min in the welded tuff fault breccias. Negligible quantities of H2 gas could be collected from the fault core. Particle size distribution analyses of fault rocks indicate that the granite cataclasite tends to be rich in particles that are finer, i.e., less cohesive and easy to disaggregate, which leads to the inference that the granite cataclasite has high permeability. Based on the H2 gas measurements and the particle size distribution analyses, the H2 gas is considered to have migrated in permeable damage zones mostly by advection with groundwater. Multipoint H2 gas measurement will be effective in qualitative delineation of variations in permeability of regional structures.

Niwa, Masakazu; Kurosawa, Hideki; Shimada, Koji; Ishimaru, Tsuneari; Kosaka, Hideki

2011-05-01

349

Precipitation of heavy metals from coal ash leachate using biogenic hydrogen sulfide generated from FGD gypsum.  

PubMed

Investigations were undertaken to utilize flue gas desulfurization (FGD) gypsum for the treatment of leachate from the coal ash (CA) dump sites. Bench-scale investigations consisted of three main steps namely hydrogen sulfide (H(2)S) production by sulfate reducing bacteria (SRB) using sulfate from solubilized FGD gypsum as the electron acceptor, followed by leaching of heavy metals (HMs) from coal bottom ash (CBA) and subsequent precipitation of HMs using biologically produced sulfide. Leaching tests of CBA carried out at acidic pH revealed the existence of several HMs such as Cd, Cr, Hg, Pb, Mn, Cu, Ni and Zn. Molasses was used as the electron donor for the biological sulfate reduction (BSR) process which produced sulfide rich effluent with concentration up to 150 mg/L. Sulfide rich effluent from the sulfate reduction process was used to precipitate HMs as metal sulfides from CBA leachate. HM removal in the range from 40 to 100% was obtained through sulfide precipitation. PMID:23168629

Jayaranjan, Madawala Liyanage Duminda; Annachhatre, Ajit P

2013-01-01

350

Metal-catalyzed reduction of N-nitrosodimethylamine with hydrogen in water.  

PubMed

There is considerable need for the rapid destruction of N-nitrosodimethylamine (NDMA) in water because current alternative treatment methods are relatively inefficient. Powdered metal catalysts in conjunction with hydrogen gas showed notable potential for rapid destruction of N-nitrosodimethylamine (NDMA) in water. Palladium, copper-enhanced palladium, and nickel catalysts showed significant efficacy for NDMA reduction, with observed half-lives on the order of hours using 10 mg L(-1) catalyst metal. Other catalysts were screened because of their well-documented efficacy for reduction of halogenated hydrocarbons, including zerovalent iron, nickel-enhanced iron, nickel, and manganese. Starting with 100 microg L(-1) NDMA, a level observed at multiple field sites, pseudo-first-order kinetics were observed for all catalysts tested. No reaction intermediates were observed in any experiment; the amine group of NDMA was cleaved and reduced to dimethylamine with carbon balance in excess of 97%. Reductive catalysis may prove an efficient technology for mitigating the health risk posed by NDMA; this study provides the foundation for mechanistic and longevity research. PMID:17180985

Davie, Matthew G; Reinhard, Martin; Shapley, John R

2006-12-01

351

Intercalative Ion Exchange of Polyamine Transition Metal Complexes into Hydrogen Uranyl Phosphate.  

PubMed

A series of derivatives of hydrogen uranyl phosphate (HUP) was prepared by displacing the butylammonium ions of butylammonium uranyl phosphate with the transition metal complexes Cu(en)(2)(2+), Cu(pn)(2)(2+), Cu(trien)(2+), Cu(14-ane)(2+), Cu(15-ane)(2+), Ni(trien)(2+), Ni(14-ane)(2+), and Ni(diene)(2+). X-ray powder patterns proved that the original tetragonal structure of the UP layers remained intact in all derivatives. The extent of the ion exchange and the interlamellar distances were found to depend mainly on the size and on the shape of a particular coordinating ligand. Electronic absorption spectra indicated that the intercalated complexes had four-coordinate square-planar geometry inside the UP lattice. Extents of hydration of the intercalates varied significantly, and they depended mostly on the shapes of the coordinating ligands and on their abilities to regularly pack between the UP layers. Results of the above-mentioned characteristics allow one to divide these transition metal complexes into two groups which differ from each other in their abilities to efficiently fill up the space between the UP layers. The steady-state luminescence spectra of intercalates showed a very weak uranyl emission which was partly due to quenching by the Cu(2+) and Ni(2+) guest complexes and partly to self-absorption. PMID:11670016

Grohol, Daniel; Blinn, Elliott L.

1997-07-30

352

A new class of electrocatalysts for hydrogen production from water electrolysis: metal monolayers supported on low-cost transition metal carbides.  

PubMed

This work explores the opportunity to substantially reduce the cost of hydrogen evolution reaction (HER) catalysts by supporting monolayer (ML) amounts of precious metals on transition metal carbide substrates. The metal component includes platinum (Pt), palladium (Pd), and gold (Au); the low-cost carbide substrate includes tungsten carbides (WC and W(2)C) and molybdenum carbide (Mo(2)C). As a platform for these studies, single-phase carbide thin films with well-characterized surfaces have been synthesized, allowing for a direct comparison of the intrinsic HER activity of bare and Pt-modified carbide surfaces. It is found that WC and W(2)C are both excellent cathode support materials for ML Pt, exhibiting HER activities that are comparable to bulk Pt while displaying stable HER activity during chronopotentiometric HER measurements. The findings of excellent stability and HER activity of the ML Pt-WC and Pt-W(2)C surfaces may be explained by the similar bulk electronic properties of tungsten carbides to Pt, as is supported by density functional theory calculations. These results are further extended to other metal overlayers (Pd and Au) and supports (Mo(2)C), which demonstrate that the metal ML-supported transition metal carbide surfaces exhibit HER activity that is consistent with the well-known volcano relationship between activity and hydrogen binding energy. This work highlights the potential of using carbide materials to reduce the costs of hydrogen production from water electrolysis by serving as stable, low-cost supports for ML amounts of precious metals. PMID:22280370

Esposito, Daniel V; Hunt, Sean T; Kimmel, Yannick C; Chen, Jingguang G

2012-02-15

353

The creation of strongly coupled plasmas using an intense heavy ion beam: low-entropy compression of hydrogen and the problem of hydrogen metallization  

NASA Astrophysics Data System (ADS)

Intense heavy ion beams deposit energy very efficiently over extended volumes of solid density targets, thereby creating large samples of strongly coupled plasmas. Intense beams of energetic heavy ions are therefore an ideal tool to research this interesting field. It is also possible to design experiments using special beam-target geometries to achieve low-entropy compression of samples of matter. This type of experiments is of particular interest for studying the problem of hydrogen metallization. In this paper we present a design study of such a proposed experiment that will be carried out at the future heavy ion synchrotron facility SIS100, at the Gesellschaft für Schwerionenforschung, Darmstadt. This study has been done using a two-dimensional hydrodynamic computer code. The target consists of a solid hydrogen cylinder that is enclosed in a thick shell of lead whose one face is irradiated with an ion beam which has an annular (ring shaped) focal spot. The beam intensity and other parameters are considered to be the same as expected at the future SIS100 facility. The simulations show that due to multiple shock reflection between the cylinder axis and the lead-hydrogen boundary, one can achieve up to 20 times solid density in hydrogen while keeping the temperature as low as a few thousand K. The corresponding pressure is of the order of 10 Mbar. These values of the physical parameters lie within the range of theoretically predicted values for hydrogen metallization. We have also carried out a parameter study of this problem by varying the target and beam parameters over a wide range. It has been found that the results are very insensitive to such changes in the input parameters.

Tahir, N. A.; Piriz, A. R.; Shutov, A.; Varentsov, D.; Udrea, S.; Hoffmann, D. H. H.; Juranek, H.; Redmer, R.; Portugues, R. F.; Lomonosov, I.; Fortov, V. E.

2003-06-01

354

Concentration of Hydrogen Peroxide  

NASA Technical Reports Server (NTRS)

Methods for concentrating hydrogen peroxide solutions have been described. The methods utilize a polymeric membrane separating a hydrogen peroxide solution from a sweep gas or permeate. The membrane is selective to the permeability of water over the permeability of hydrogen peroxide, thereby facilitating the concentration of the hydrogen peroxide solution through the transport of water through the membrane to the permeate. By utilizing methods in accordance with the invention, hydrogen peroxide solutions of up to 85% by volume or higher may be generated at a point of use without storing substantial quantities of the highly concentrated solutions and without requiring temperatures that would produce explosive mixtures of hydrogen peroxide vapors.

Parrish, Clyde F. (Inventor)

2006-01-01

355

A Pt-Ti-O gate Si-metal-insulator-semiconductor field-effect transistor hydrogen gas sensor  

NASA Astrophysics Data System (ADS)

A hydrogen gas sensor based on platinum-titanium-oxygen (Pt-Ti-O) gate silicon-metal-insulator-semiconductor field-effect transistors (Si-MISFETs) was developed. The sensor has a unique gate structure composed of titanium and oxygen accumulated around platinum grains on top of a novel mixed layer of nanocrystalline TiOx and superheavily oxygen-doped amorphous titanium formed on SiO2/Si substrates. The FET hydrogen sensor shows high reliability and high sensing amplitude (?Vg) defined by the magnitude of the threshold voltage shift. ?Vg is well fitted by a linear function of the logarithm of air-diluted hydrogen concentration C (ppm), i.e., ?Vg(V)=0.355 log C(ppm)-0.610, between 100 ppm and 1%. This high gradient coefficient of ?Vg for the wide sensing range demonstrates that the sensor is suitable for most hydrogen-safety-monitoring sensor systems. The Pt-Ti-O structures of the sensor are typically realized by annealing Pt (15 nm)/Ti (5 nm)-gate Si-metal-oxide-semiconductor structures in air at 400 °C for 2 h. The Pt-Ti-O gate MIS structures were analyzed by transmission electron microscope (TEM), x-ray diffraction, Auger electron spectroscopy, and TEM energy dispersive x-ray spectroscopy. From the viewpoint of practical sensing applications, hydrogen postannealing of the Pt-Ti-O gate Si-MISFETs is necessary to reduce the residual sensing amplitudes with long tailing profiles.

Usagawa, Toshiyuki; Kikuchi, Yota

2010-10-01

356

Correlation of Gas Permeability in a Metal-Organic Framework MIL-101(Cr)–Polysulfone Mixed-Matrix Membrane with Free Volume Measurements by Positron Annihilation Lifetime Spectroscopy (PALS)  

PubMed Central

Hydrothermally stable particles of the metal-organic framework MIL-101(Cr) were incorporated into a polysulfone (PSF) matrix to produce mixed-matrix or composite membranes with excellent dispersion of MIL-101 particles and good adhesion within the polymer matrix. Pure gas (O2, N2, CO2 and CH4) permeation tests showed a significant increase of gas permeabilities of the mixed-matrix membranes without any loss in selectivity. Positron annihilation lifetime spectroscopy (PALS) indicated that the increased gas permeability is due to the free volume in the PSF polymer and the added large free volume inside the MIL-101 particles. The trend of the gas transport properties of the composite membranes could be reproduced by a Maxwell model. PMID:24957061

Jeazet, Harold B. Tanh; Koschine, Tönjes; Staudt, Claudia; Raetzke, Klaus; Janiak, Christoph

2013-01-01

357

Constant permeability of (Fe0.75B0.20Si0.05)96Nb4 bulk metallic glass prepared by B2O3 flux melting and Cu-mold casting  

NASA Astrophysics Data System (ADS)

The effect of B2O3 flux melting on the soft magnetic properties of (Fe0.75B0.20Si0.05)96Nb4 bulk metallic glass prepared by casting has been investigated. Ring-shaped bulk specimens that were prepared by B2O3 flux melting and Cu-mold casting (fluxed specimens) show a flat hysteresis curve, indicating a good linear relationship between the magnetic induction and the applied magnetic field. Although the permeability of the fluxed specimens is lower than that of the specimens prepared by conventional Cu-mold casting by one order of magnitude, their coercivities are almost same. These results show that it is possible to develop a new soft magnetic material that exhibits constant permeability with low core loss.

Bitoh, T.; Shibata, D.

2009-04-01

358

Analysis of hydrogen isotope mixtures  

Microsoft Academic Search

An apparatus and method for determining the concentrations of hydrogen isotopes in a sample. Hydrogen in the sample is separated from other elements using a filter selectively permeable to hydrogen. Then the hydrogen is condensed onto a cold finger or cryopump. The cold finger is rotated as pulsed laser energy vaporizes a portion of the condensed hydrogen, forming a packet

Villa-Aleman; Eliel

1994-01-01

359

Analysis of hydrogen isotope mixtures  

Microsoft Academic Search

An apparatus and method are described for determining the concentrations of hydrogen isotopes in a sample. Hydrogen in the sample is separated from other elements using a filter selectively permeable to hydrogen. Then the hydrogen is condensed onto a cold finger or cryopump. The cold finger is rotated as pulsed laser energy vaporizes a portion of the condensed hydrogen, forming

Villa-Aleman

1994-01-01

360

Analysis of hydrogen isotope mixtures  

Microsoft Academic Search

Disclosed are an apparatus and a method for determining concentrations of hydrogen isotopes in a sample. Hydrogen in the sample is separated from other elements using a filter selectively permeable to hydrogen. Then the hydrogen is condensed onto a cold finger or cryopump. The cold finger is rotated as pulsed laser energy vaporizes a portion of the condensed hydrogen, forming

Villa-Aleman

1992-01-01

361

Trends in ground-state entropies for transition metal based hydrogen atom transfer reactions.  

PubMed

Reported herein are thermochemical studies of hydrogen atom transfer (HAT) reactions involving transition metal H-atom donors M(II)LH and oxyl radicals. [Fe(II)(H(2)bip)(3)](2+), [Fe(II)(H(2)bim)(3)](2+), [Co(II)(H(2)bim)(3)](2+), and Ru(II)(acac)(2)(py-imH) [H(2)bip = 2,2'-bi-1,4,5,6-tetrahydropyrimidine, H(2)bim = 2,2'-bi-imidazoline, acac = 2,4-pentandionato, py-imH = 2-(2'-pyridyl)imidazole)] each react with TEMPO (2,2,6,6-tetramethyl-1-piperidinoxyl) or (t)Bu(3)PhO(*) (2,4,6-tri-tert-butylphenoxyl) to give the deprotonated, oxidized metal complex M(III)L and TEMPOH or (t)Bu(3)PhOH. Solution equilibrium measurements for the reaction of [Co(II)(H(2)bim)(3)](2+) with TEMPO show a large, negative ground-state entropy for hydrogen atom transfer, -41 +/- 2 cal mol(-1) K(-1). This is even more negative than the DeltaS(o)(HAT) = -30 +/- 2 cal mol(-1) K(-1) for the two iron complexes and the DeltaS(o)(HAT) for Ru(II)(acac)(2)(py-imH) + TEMPO, 4.9 +/- 1.1 cal mol(-1) K(-1), as reported earlier. Calorimetric measurements quantitatively confirm the enthalpy of reaction for [Fe(II)(H(2)bip)(3)](2+) + TEMPO, thus also confirming DeltaS(o)(HAT). Calorimetry on TEMPOH + (t)Bu(3)PhO(*) gives DeltaH(o)(HAT) = -11.2 +/- 0.5 kcal mol(-1) which matches the enthalpy predicted from the difference in literature solution BDEs. A brief evaluation of the literature thermochemistry of TEMPOH and (t)Bu(3)PhOH supports the common assumption that DeltaS(o)(HAT) approximately 0 for HAT reactions of organic and small gas-phase molecules. However, this assumption does not hold for transition metal based HAT reactions. The trend in magnitude of |DeltaS(o)(HAT)| for reactions with TEMPO, Ru(II)(acac)(2)(py-imH) < [Fe(II)(H(2)bip)(3)](2+) = [Fe(II)(H(2)bim)(3)](2+) < [Co(II)(H(2)bim)(3)](2+), is surprisingly well predicted by the trends for electron transfer half-reaction entropies, DeltaS(o)(ET), in aprotic solvents. This is because both DeltaS(o)(ET) and DeltaS(o)(HAT) have substantial contributions from vibrational entropy, which varies significantly with the metal center involved. The close connection between DeltaS(o)(HAT) and DeltaS(o)(ET) provides an important link between these two fields and provides a starting point from which to predict which HAT systems will have important ground-state entropy effects. PMID:19275235

Mader, Elizabeth A; Manner, Virginia W; Markle, Todd F; Wu, Adam; Franz, James A; Mayer, James M

2009-04-01

362

Trends in Ground-State Entropies for Transition Metal Based Hydrogen Atom Transfer Reactions  

PubMed Central

Reported herein are thermochemical studies of hydrogen atom transfer (HAT) reactions involving transition metal H-atom donors MIILH and oxyl radicals. [FeII(H2bip)3]2+, [FeII(H2bim)3]2+, [CoII(H2bim)3]2+ and RuII(acac)2(py-imH) [H2bip = 2,2’-bi-1,4,5,6-tetrahydropyrimidine, H2bim = 2,2’-bi-imidazoline, acac = 2,4-pentandionato, py-imH = 2-(2’-pyridyl)-imidazole)] each react with TEMPO (2,2,6,6-tetramethyl-1-piperidinoxyl) or tBu3PhO• (2,4,6-tri-tert-butylphenoxyl) to give the deprotonated, oxidized metal complex MIIIL, and TEMPOH or tBu3PhOH. Solution equilibrium measurements for the reaction of [CoII(H2bim)3]2+ with TEMPO show a large, negative ground-state entropy for hydrogen atom transfer, ?41 ± 2 cal mol?1 K?1. This is even more negative than the ?SoHAT = ?30 ± 2 cal mol?1 K?1 for the two iron complexes and the ?SoHAT for RuII(acac)2(py-imH) + TEMPO, 4.9 ± 1.1 cal mol?1 K?1, as reported earlier. Calorimetric measurements quantitatively confirm the enthalpy of reaction for [FeII(H2bip)3]2+ + TEMPO, thus also confirming ?SoHAT. Calorimetry on TEMPOH + tBu3PhO• gives ?HoHAT = ?11.2 ± 0.5 kcal mol?1 which matches the enthalpy predicted from the difference in literature solution BDEs. A brief evaluation of the literature thermochemistry of TEMPOH and tBu3PhOH supports the common assumption that ?SoHAT ? 0 for HAT reactions of organic and small gas-phase molecules. However, this assumption does not hold for transition metal based HAT reactions. The trend in magnitude of |?SoHAT| for reactions with TEMPO, RuII(acac)2(py-imH) << [FeII(H2bip)3]2+ = [FeII(H2bim)3]2+ < [CoII(H2bim)3]2+, is surprisingly well predicted by the trends for electron transfer half-reaction entropies, ?SoET, in aprotic solvents. This is because both ?SoET and ?SoHAT have substantial contributions from vibrational entropy, which varies significantly with the metal center involved. The close connection between ?SoHAT and ?SoET provides an important link between these two fields and provides a starting point from which to predict which HAT systems will have important ground-state entropy effects. PMID:19275235

Mader, Elizabeth A.; Manner, Virginia W.; Markle, Todd F.; Wu, Adam; Franz, James A.; Mayer, James M.

2009-01-01

363

Supported transition metal catalysts for para- to ortho-hydrogen conversion  

NASA Technical Reports Server (NTRS)

The main goal of this study was to develop and improve on existing catalysts for the conversion of ortho- to para-hydrogen. Starting with a commercially available Air Products nickel silicate, which had a beta value of 20, we were trying to synthesize catalysts that would be an improvement to AP. This was accomplished by preparing silicates with various metals as well as different preparation methods. We also prepared supported ruthenium catalysts by various techniques using several metal precursors to improve present technology. What was also found was that the activation conditions prior to catalytic testing was highly important for both the silicates and the supported ruthenium catalysts. While not the initial focus of the research, we made some interesting observations into the adsorption of H2 on ruthenium. This helped us to get a better understanding of how ortho- to para-H2 conversion takes place, and what features in a catalyst are important to optimize activity. Reactor design was the final area in which some interesting conclusions were drawn. As discussed earlier, the reactor catalyst bed must be constructed using straight 1/8 feet OD stainless steel tubing. It was determined that the use of 1/4 feet OD tubing caused two problems. First, the radius from the center of the bed to the wall was too great for thermal equilibrium. Since the reaction of ortho- to para-H2 is exothermic, the catalyst bed center was warmer than the edges. Second, the catalyst bed was too shallow using a 1/4 feet tube. This caused reactant blow-by which was thought to decrease the measured activity when the flow rate was increased. The 1/8 feet tube corrected both of these concerns.

Brooks, Christopher J.; Wang, Wei; Eyman, Darrell P.

1994-01-01

364

Tristate electrochemical metallization memory based in the hydrogenated nanocrystalline silicon films  

NASA Astrophysics Data System (ADS)

The hydrogenated nanocrystalline silicon (nc-Si:H) films have been fabricated as resistive switching medium by radio frequency plasma enhanced chemical vapor deposition technology. The constructed Ag/nc-Si:H/Pt structure exhibits stable three nonvolatile resistance states. Tristate resistive states with large ratio 102 and 105, less variation of resistance, and long retention exceeding 2.3 × 105 s are observed in Ag/nc-Si:H/Pt stack. The temperature dependence of high resistance state (HRS) and intermediate resistance state (IRS) both show semiconductor behavior, and the temperature dependence of low resistance state (LRS) represents metallic property. Fitting results demonstrated that the conduction mechanism of HRS, IRS, and LRS showed space charge limited conduction (SCLC), tunneling, and ohmic characteristics, respectively. The discrete Ag filament with Si nanocrystalline and complete Ag filament is proposed to be responsible for the performance IRS and LRS. We supposed that the Ag+ ions prefer to be reduced to Ag atoms near the Si nanocrystalline location. Si nanocrystalline between Ag nanoparticles contribute to the current transport at IRS.

Yan, X. B.; Chen, Y. F.; Hao, H.; Liu, Q.; Zhang, E. P.; Shi, S. S.; Lou, J. Z.

2014-08-01

365

Placental Permeability of Lead  

PubMed Central

The detection of lead in fetal tissues by chemical analysis has long been accepted as prima facie evidence for the permeability of the placenta to this nonessential trace metal. However, only a few investigations, all on lower mammalian species, have contributed any direct experimental data bearing on this physiological process. Recent radioactive tracer and radioautographic studies on rodents have shown that lead crosses the placental membranes rapidly and in significant amounts even at relatively low maternal blood levels. While it is not possible to extrapolate directly the results of these experiments to humans because of differences in placental structure and other factors, the results do serve as a warning of the possible hazard to the human embryo and fetus of even low levels of lead in the maternal system. PMID:4857497

Carpenter, Stanley J.

1974-01-01

366

Hydrogen incorporation induced metal-semiconductor transition in ZnO:H thin films sputtered at room temperature  

SciTech Connect

The room temperature deposited ZnO:H thin films having high conductivity of 500 Ohm-Sign {sup -1} cm{sup -1} and carrier concentration reaching 1.23 Multiplication-Sign 10{sup 20} cm{sup -3} were reactively sputter deposited on glass substrates in the presence of O{sub 2} and 5% H{sub 2} in Ar. A metal-semiconductor transition at 165 K is induced by the increasing hydrogen incorporation in the films. Hydrogen forms shallow donor complex with activation energy of {approx}10-20 meV at oxygen vacancies (V{sub O}) leading to increase in carrier concentration. Hydrogen also passivates V{sub O} and V{sub Zn} causing {approx}4 times enhancement of mobility to 25.4 cm{sup 2}/V s. These films have potential for use in transparent flexible electronics.

Singh, Anil; Chaudhary, Sujeet; Pandya, D. K. [Thin Film Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016 (India)] [Thin Film Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016 (India)

2013-04-29

367

Rechargeable metal oxide--hydrogen cells. Research and development technical report. [approx. 1 Ah  

Microsoft Academic Search

Electrically rechargeable nickel oxide--hydrogen cells (rated 1.0 amperehour) were fabricated using platinum-catalyzed hydrogen anodes, nicekl--oxide cathodes, and a two component separator system, Pellon\\/PKT, saturated with 30% KOH electrolyte. Also, silver oxide--hydrogen cells (rated 1.5 ampere-hours) were fabricated using similar platinum catalyzed hydrogen anodes, silver oxide cathodes, and two different separator systems, Pellon\\/PKT and Dynel\\/cellophane\\/Pellon, saturated with 30% KOH electrolyte. The

Wynn

1977-01-01

368

Unusual metal-organic frameworks built from 2D layers through Cl?Cl contacts and hydrogen bonds  

Microsoft Academic Search

Unusual metal-organic frameworks [M(dtcp)2](SCN)2 [M=Zn, Mn; dtcp=2,6-di(1,2,4-triazol-1-ylmethyl)-4-chlorophenol] are composed of 2D rhombus-type grid networks associated mutually by remarkable Cl?Cl contacts and hydrogen bonds (C–H?N and C–H?S). Both thermogravimetric analysis and photoluminescence measurements are performed as well to characterize these supramolecular frameworks.

Hai-Bin Zhu; Zhao-Lian Chu; Da-Hua Hu; Wei Huang; Shao-Hua Gou

2007-01-01

369

Monolayer MoS2 films supported by 3D nanoporous metals for high-efficiency electrocatalytic hydrogen production.  

PubMed

The "edge-free" monolayer MoS2 films supported by 3D nanoporous gold show high catalytic activities towards hydrogen evolution reaction (HER), originating from large out-of-plane strains that are geometrically required to manage the 3D curvature of bicontinuous nanoporosity. The large lattice bending leads to local semiconductor-to-metal transition of 2H MoS2 and the formation of catalytically active sites for HER. PMID:25363090

Tan, Yongwen; Liu, Pan; Chen, Luyang; Cong, Weitao; Ito, Yoshikazu; Han, Jiuhui; Guo, Xianwei; Tang, Zheng; Fujita, Takeshi; Hirata, Akihiko; Chen, Mingwei W

2014-12-17

370

Structure, catalysis and atomic reactions on the nano-scale: a systematic approach to metal hydrides for hydrogen storage  

Microsoft Academic Search

.   We show how reducing structure, catalysis and atomic reactions to the nano-scale may be used in a systematic way to substantially\\u000a enhance the hydrogenation properties of metal hydrides. We examine, with examples from a wide range of hydrides, the direct\\u000a impact of nano-scale structure, subsequent improvements in kinetics through nano-scale solid state catalysis, the special\\u000a properties of nano-composites, and

A. Zaluska; L. Zaluski; J. O. Ström-Olsen

2001-01-01

371

Electrochemical properties of magnesium-based hydrogen storage alloys improved by transition metal boride and silicide additives  

Microsoft Academic Search

Transition metal borides and silicides prepared by mechanical alloying (MA) and chemical reduction methods (CR) were introduced to improve the corrosion resistance of magnesium-based hydrogen storage alloys. The additive of FeB prepared by MA can remarkably enhance the discharge capacity and cycling stability which has initial discharge capacity of 355.9mAhg?1 and keeps 224mAhg?1 after 100 cycles, and the exchange density

Li-Fang Jiao; Hua-Tang Yuan; Yi-Jing Wang; Yong-Mei Wang

2009-01-01

372

The Role of Partial Crystallinity on Hydrogen Permeation in Fe–Ni–B–Mo Based Metallic Glass Membranes  

SciTech Connect

A potentially exciting material for membrane separations are metallic glass materials due to their low cost, high elastic toughness and resistance to hydrogen embrittlement as compared to crystalline Pd-based membrane systems. However, at elevated temperatures and extended operation times structural changes including partial crystallinity may appear in these amorphous metallic systems. This study reports on the investigation of time and temperature dependent crystalline phase formation in conjunction with in situ crystallization/hydrogen permeation experiments at elevated temperatures. At temperatures near 400 C a FeNi crystalline phase appears as 22 vol.% inside the host amorphous matrix and the resulting composite structure remains stable over 3 h at temperature. The hydrogen permeation at 400 C of the partially crystalline material is similar to the fully amorphous material near 5 x 10{sup -9} mol H{sub 2}/m s Pa{sup 1/2}, while ambient temperature electrochemical permeation at 25 C revealed an order of magnitude decrease in the permeation of partially crystalline materials due to differences in the amorphous versus crystalline phase activation energy for hydrogen permeation.

Brinkman, K.; Su, D.; Fox, E.; Korinko, P.; Missimer, D.; Adams, T.

2011-08-15

373

Influence of the nature of hydrogen halides and metal cations on the interaction types between borazine and hydrogen halides.  

PubMed

The interactions between the H atom of borazine and hydrogen halide (HX, X = F, Cl, Br, and I) have been studied systematically. Four structures (a, b, c, and d) have been observed. The cyclic structure a is combined through a NH···X hydrogen bond and a BH···HX dihydrogen bond, a NH···X hydrogen bond and a BH···X halogen-hydride interaction are responsible for the cyclic structure b, structures c and d are maintained by a dihydrogen bond and a halogen-hydride interaction, respectively. Structures a and b are stable in energy, while structures c and d are unstable in energy. Structures a and b can transform each other through structure c or d. The interaction mode and strength are related to the nature of HX. The cation-? interaction of borazine with Li(+) and Mg(2+) causes a change in the interaction mode in structures a and b, and has an enhancing effect on the interaction strength in a and b. PMID:24526378

Zhuo, Hongying; Li, Qingzhong; An, Xiulin; Li, Wenzuo; Cheng, Jianbo

2014-02-01

374

Divalent transition metal phosphonates with new structure containing hydrogen-bonded layers of phosphonate anions  

NASA Astrophysics Data System (ADS)

A series of divalent transition metal phosphonates containing hydrogen-bonded layers of phosphonate anions, namely [ M(phen) 3]·C 6H 5PO 3·11H 2O [ M=Co(1), Ni(2), Cu(3)] and [Cd(phen) 3]·C 6H 5PO 3H·Cl·7H 2O (4) have been synthesized, structurally characterized by single-crystal X-ray diffraction method. These compounds all crystallize in the triclinic system, space group P-1. The lattice parameters are a=12.1646(5), b=12.4155(6), c=15.4117(10) Å, ?=78.216(2), ?=79.735(3), ?=77.8380(3)°, V=2205.1(2) Å 3, Z=2 for 1; a=12.097(2), b=12.606(3), c=15.742(3) Å, ?=76.66(3), ?=80.04(3), ?=77.75(3)°, V=2263.4(8) Å 3, Z=2 for 2; a=12.058(2), b=12.518(3), c=15.781(3) Å, ?=77.77(3), ?=80.02(3), ?=77.91(3)°, V=2255.5(8) Å 3, Z=2 for 3 and a=12.47680(10), b=12.6693(2), c=16.1504(3) Å, ?=82.600(1), ?=71.122(1), ?=77.355(1)°, V=2352.37(6) Å 3, Z=2 for 4. All structures are refined by full-matrix least-squares methods [for 1, R1=0.0602 using 6458 independent reflections with I>2 ?( I); for 2, R1=0.0632 using 4657 independent reflections with I>2 ?( I); for 3, R1=0.0634 using 6221 independent reflections with I>2 ?( I); for 4, R1=0.0400 using 7930 independent reflections with I>2 ?( I)]. In the crystal structures, the phenylphosphonate anions and water molecules are hydrogen-bonded to form layers, and there exist the cationic species [ M(phen) 3] 2+ between the adjacent layers of anions and water. Luminescence, thermal analysis as well as IR spectroscopic studies are also presented.

Yang, Jin; Ma, Jian-Fang; Zheng, Guo-Li; Li, Li; Li, Fang-Fang; Zhang, Yong-Mei; Liu, Jing-Fu

2003-08-01

375

Analysis of hydrogen isotope mixtures  

DOEpatents

An apparatus and method for determining the concentrations of hydrogen isotopes in a sample. Hydrogen in the sample is separated from other elements using a filter selectively permeable to hydrogen. Then the hydrogen is condensed onto a cold finger or cryopump. The cold finger is rotated as pulsed laser energy vaporizes a portion of the condensed hydrogen, forming a packet of molecular hydrogen. The desorbed hydrogen is ionized and admitted into a mass spectrometer for analysis.

Villa-Aleman, Eliel (Aiken, SC)

1994-01-01

376

Structural and kinetic studies of metal hydride hydrogen storage materials using thin film deposition and characterization techniques  

NASA Astrophysics Data System (ADS)

Hydrogen makes an attractive energy carrier for many reasons. It is an abundant chemical fuel that can be produced from a wide variety of sources and stored for very long periods of time. When used in a fuel cell, hydrogen emits only water at the point of use, making it very attractive for mobile applications such as in an automobile. Metal hydrides are promising candidates for on-board reversible hydrogen storage in mobile applications due to their very high volumetric storage capacities---in most cases exceeding even that of liquid hydrogen. The United States Department of Energy (DOE) has set fuel system targets for an automotive hydrogen storage system, but as of yet no single material meets all the requirements. In particular, slow reaction kinetics and/or inappropriate thermodynamics plague many metal hydride hydrogen storage materials. In order to engineer a practical material that meets the DOE targets, we need a detailed understanding of the kinetic and thermodynamic properties of these materials during the phase change. In this work I employed sputter deposited thin films as a platform to study materials with highly controlled chemistry, microstructure and catalyst placement using thin film characterization techniques such as in situ x-ray diffraction (XRD) and neutron reflectivity. I observed kinetic limitations in the destabilized Mg2Si system due to the slow diffusion of the host Mg and Si atoms while forming separate MgH2 and Si phases. Conversely, I observed that the presence of Al in the Mg/Al system inhibits hydrogen diffusion while the host Mg and Al atoms interdiffuse readily, allowing the material to fall into a kinetic and/or thermodynamic trap by forming intermetallic compounds such as Mg17Al 12. By using in situ XRD to analyze epitaxial Mg films grown on (001) oriented Al2O3 substrates I observed hydride growth consistent with a model of a planar hydride layer growing into an existing metal layer. Subsequent film cycling changes the hydrogen absorption and desorption kinetics and degrades the material texture. Cycling the films to greater hydrogen loading accelerates the changes to the kinetics and material texture. In addition to in situ XRD experiments, in situ neutron reflectivity experiments on epitaxial Mg films exposed to hydrogen gas reveal details about the microstructural development of the growing hydride layer as the film absorbs and releases hydrogen. Small (10 wt%) additions of Ti to epitaxial Mg films during growth result in metastable solid solution films of Ti in Mg that deposit epitaxially on (001) Al2O3 substrates with epitaxy similar to the pure Mg films. These metastable alloy films absorb hydrogen faster than pure Mg films under identical conditions. Subsequent film cycling results in altered reaction kinetics and a transition to a different kinetic mechanism during desorption than for pure Mg films.

Kelly, Stephen Thomas

377

Influence of the electronic structure of alpha, beta-unsaturated carbonyl compounds on the process of their hydrogenation on metal catalysts  

SciTech Connect

Within the framework of the method of reactivity indexes, using the INDO approximation, a quantum-chemical analysis of the presumed mechanisms of the hydrogenation of citral, cinnamaldehyde, and forcyclamenaldehyde on metallic catalysts was performed. The influence of certain factors on the selectivity of the hydrogenation of the double bond conjugated with the carbonyl is discussed.

Chuvyllein, N.D.; Kazanskii, V.B.; Pak, A.M.; Plekhanov, Y.V.

1986-07-01

378

EPA Permeable Surface Research  

EPA Science Inventory

EPA recognizes permeable surfaces as an effective post-construction infiltration-based Best Management Practice to mitigate the adverse effects of stormwater runoff. The professional user community conceptually embraces permeable surfaces as a tool for making runoff more closely...

379

Hydrogen storage in metal-organic frameworks: An investigation of structure-property relationships  

NASA Astrophysics Data System (ADS)

Metal-organic frameworks (MOFs) have been identified as candidate hydrogen storage materials due to their ability to physisorb large quantities of small molecules. Thirteen compounds (IRMOF-1, -2, -3, -6, -8, -9, -11, -13, -18, -20, MOF-74, MOF-177 and HKUST-1) have been prepared and fully characterized for the evaluation of their dihydrogen (H2) adsorption properties. All compounds display approximately type I isotherms with no hysteresis at 77 K up to 1 atm. The amount adsorbed ranges from 0.89 to 2.54 wt%; however, saturation is not achieved under these conditions. The influences of link functionalization, catenation and topology are examined for the eleven MOFs composed of Zn4O(O2C-)6 clusters. Enhanced H2 uptake by catenated compounds is rationalized by increased overlap of the surface potentials within their narrower pores. This is corroborated by the larger isosteric heat of adsorption of IRMOF-11 compared to IRMOF-1. Inelastic neutron scattering spectroscopic analysis of four Zn4O-based materials (IRMOF-1, -8, -11, and MOF-74) under a range of H2 loading suggests the presence of multiple localized adsorption sites on both the inorganic and organic moieties. To determine the structural details of the adsorption sites, variable temperature single crystal X-ray diffraction was used to analyze adsorbed argon and dinitrogen molecules in IRMOF-1. The principle binding site was found to be the same for both adsorbates and is located on faces of the octahedral Zn4O(O2C-)6 clusters with close contacts to three carboxylate groups. A total of eight symmetry-independent adsorption sites were identified for argon at 30 K. Similar sites were observed for dinitrogen, suggesting that they are good model adsorbates for the behaviour of dihydrogen. Two additional materials composed of inorganic clusters with coordinatively unsaturated metal sites (MOF-74, HKUST-1) were examined and their increased capacities and isosteric heats of adsorption provide further evidence that the interaction is strongest at the inorganic clusters. This enhancement becomes less important at high pressure, where large pore volume proves to be the greater contributor to capacity.

Rowsell, Jesse

380

Permeability of shaly sands  

NASA Astrophysics Data System (ADS)

The permeability of a sand shale mixture is analyzed as a function of shale fraction and the permeability of the two end-members, i.e., the permeability of a clay-free sand and the permeability of a pure shale. First, we develop a model for the permeability of a clay-free sand as a function of the grain diameter, the porosity, and the electrical cementation exponent. We show that the Kozeny-Carman-type relation can be improved by using electrical parameters which separate pore throat from total porosity and effective from total hydraulic radius. The permeability of a pure shale is derived in a similar way but is strongly dependent on clay mineralogy. For the same porosity, there are 5 orders of magnitude of difference between the permeability of pure kaolinite and the permeability of pure smectite. The separate end-members' permeability models are combined by filling the sand pores progressively with shale and then dispersing the sand grains in shale. The permeability of sand shale mixtures is shown to have a minimum at the critical shale content at which shale just fills the sand pores. Pure shale has a slightly higher permeability. Permeability decreases sharply with shale content as the pores of a sand are filled. The permeability of sand shale mixtures thus has a very strong dependence on shale fraction, and available data confirm this distinctive shale-fraction dependence. In addition, there is agreement (within 1 order of magnitude) between the permeabilities predicted from our model and those measured over 11 orders of magnitude from literature sources. Finally, we apply our model to predict the permeabilities of shaly sand formations in the Gulf Coast. The predictions are compared to a data set of permeability determination made on side-wall cores. The agreement between the theoretical predictions and the experimental data is very good.

Revil, A.; Cathles, L. M.

1999-03-01

381

Hydrogen embrittlement in nickel-hydrogen cells  

Microsoft Academic Search

It was long known that many strong metals can become weakened and brittle as the result of the accumulation of hydrogen within the metal. When the metal is stretched, it does not show normal ductile properties, but fractures prematurely. This problem can occur as the result of a hydrogen evolution reaction such as corrosion or electroplating, or due to hydrogen

Sidney Gross

1989-01-01

382

Strongly coupled hybrid nanostructures for selective hydrogen detection - understanding the role of noble metals in reducing cross-sensitivity  

NASA Astrophysics Data System (ADS)

Noble metal-semiconductor hybrid nanostructures can offer outperformance to gas sensors in terms of sensitivity and selectivity. In this work, a catalytically activated (CA) hydrogen sensor is realized based on strongly coupled Pt/Pd-WO3 hybrid nanostructures constructed by a galvanic replacement participated solvothermal procedure. The room-temperature operation and high selectivity distinguish this sensor from the traditional ones. It is capable of detecting dozens of parts per million (ppm) hydrogen in the presence of thousands of ppm methane gas. An insight into the role of noble metals in reducing cross-sensitivity is provided by comparing the sensing properties of this sensor with a traditional thermally activated (TA) one made from the same pristine WO3. Based on both experimental and density functional theory (DFT) calculation results, the cross-sensitivity of the TA sensor is found to have a strong dependence on the highest occupied molecular orbital (HOMO) level of the hydrocarbon molecules. The high selectivity of the CA sensor comes from the reduced impact of gas frontier orbitals on the charge transfer process by the nano-scaled metal-semiconductor (MS) interface. The methodology demonstrated in this work indicates that rational design of MS hybrid nanostructures can be a promising strategy for highly selective gas sensing applications.Noble metal-semiconductor hybrid nanostructures can offer outperformance to gas sensors in terms of sensitivity and selectivity. In this work, a catalytically activated (CA) hydrogen sensor is realized based on strongly coupled Pt/Pd-WO3 hybrid nanostructures constructed by a galvanic replacement participated solvothermal procedure. The room-temperature operation and high selectivity distinguish this sensor from the traditional ones. It is capable of detecting dozens of parts per million (ppm) hydrogen in the presence of thousands of ppm methane gas. An insight into the role of noble metals in reducing cross-sensitivity is provided by comparing the sensing properties of this sensor with a traditional thermally activated (TA) one made from the same pristine WO3. Based on both experimental and density functional theory (DFT) calculation results, the cross-sensitivity of the TA sensor is found to have a strong dependence on the highest occupied molecular orbital (HOMO) level of the hydrocarbon molecules. The high selectivity of the CA sensor comes from the reduced impact of gas frontier orbitals on the charge transfer process by the nano-scaled metal-semiconductor (MS) interface. The methodology demonstrated in this work indicates that rational design of MS hybrid nanostructures can be a promising strategy for highly selective gas sensing applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr06569c

Liu, Bin; Cai, Daoping; Liu, Yuan; Wang, Dandan; Wang, Lingling; Xie, Wuyuan; Li, Qiuhong; Wang, Taihong

2014-04-01

383

The role of grain boundaries in hydrogen diffusion in metals at 25 C  

NASA Technical Reports Server (NTRS)

The effect of grain size on hydrogen diffusion at 25 C was examined for 4340 steel (body-centered cubic) and for Inconel 718 (face-centered cubic). It was found that the effect of grain size is important for body-centered cubic structures, but plays a much less important role in face centered cubic structures. Accurate measurements of hydrogen desorption coefficients during hydrogen desorption show that these are not greatly different for both types of structures.

Danford, M. D.

1993-01-01

384

Kinetic and Mechanistic Studies of Carbon-to-Metal Hydrogen Atom Transfer Involving Os-Centered Radicals: Evidence for Tunneling  

SciTech Connect

We have investigated the kinetics of novel carbon-to-metal hydrogen atom transfer reactions, in which homolytic cleavage of a C-H bond is accomplished by a single metal-centered radical. Studies by means of time-resolved IR spectroscopic measurements revealed efficient hydrogen atom transfer from xanthene, 9,10-dihydroanthracene and 1,4-cyclohexadiene to Cp(CO)2Os• and (n5-iPr4C5H)(CO)2Os• radicals, formed by photoinduced homolysis of the corresponding osmium dimers. The rate constants for hydrogen abstraction from these hydrocarbons were found to be in the range 1.54 × 105 M 1 s 1 -1.73 × 107 M 1 s-1 at 25 °C. For the first time, kinetic isotope effects for carbon-to-metal hydrogen atom transfer were determined. Large primary kinetic isotope effects of 13.4 ± 1.0 and 16.6 ± 1.4 were observed for the hydrogen abstraction from xanthene to form Cp(CO)2OsH and (n5-iPr4C5H)(CO)2OsH, respectively, at 25 °C. Temperature-dependent measurements of the kinetic isotope effects over a 60 -C temperature range were carried out to obtain the difference in activation energies and the pre-exponential factor ratio. For hydrogen atom transfer from xanthene to (n5-iPr4C5H)(CO)2Os•, the (ED - EH) = 3.25 ± 0.20 kcal/mol and AH/AD = 0.056 ± 0.018 values are greater than the semi-classical limits and thus suggest a quantum mechanical tunneling mechanism. The work at BNL was carried out under contract DE-AC02-98CH10886 with the U.S. Department of Energy and supported by its Division of Chemical Sciences, Geosciences & Biosciences, Office of Basic Energy Sciences. RMB also thanks the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences for support. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

Lewandowska-Androlojc, Anna; Grills, David C.; Zhang, Jie; Bullock, R. Morris; Miyazawa, Akira; Kawanishi, Yuji; Fujita, Etsuko

2014-03-05

385

Effect of metal ions on the reactions of the cumyloxyl radical with hydrogen atom donors. Fine control on hydrogen abstraction reactivity determined by Lewis acid-base interactions.  

PubMed

A time-resolved kinetic study on the effect of metal ions (M(n+)) on hydrogen abstraction reactions from C-H donor substrates by the cumyloxyl radical (CumO(•)) was carried out in acetonitrile. Metal salt addition was observed to increase the CumO(•) ?-scission rate constant in the order Li(+) > Mg(2+) > Na(+). These effects were explained in terms of the stabilization of the ?-scission transition state determined by Lewis acid-base interactions between M(n+) and the radical. When hydrogen abstraction from 1,4-cyclohexadiene was studied in the presence of LiClO(4) and Mg(ClO(4))(2), a slight increase in rate constant (k(H)) was observed indicating that interaction between M(n+) and CumO(•) can also influence, although to a limited extent, the hydrogen abstraction reactivity of alkoxyl radicals. With Lewis basic C-H donors such as THF and tertiary amines, a decrease in k(H) with increasing Lewis acidity of M(n+) was observed (k(H)(MeCN) > k(H)(Li(+)) > k(H)(Mg(2+))). This behavior was explained in terms of the stronger Lewis acid-base interaction of M(n+) with the substrate as compared to the radical. This interaction reduces the degree of overlap between the ?-C-H ?* orbital and a heteroatom lone-pair, increasing the C-H BDE and destabilizing the carbon centered radical formed after abstraction. With tertiary amines, a >2-order of magnitude decrease in k(H) was measured after Mg(ClO(4))(2) addition up to a 1.5:1 amine/Mg(ClO(4))(2) ratio. At higher amine concentrations, very similar k(H) values were measured with and without Mg(ClO(4))(2). These results clearly show that with strong Lewis basic substrates variations in the nature and concentration of M(n+) can dramatically influence k(H), allowing for a fine control of the substrate hydrogen atom donor ability, thus providing a convenient method for C-H deactivation. The implications and generality of these findings are discussed. PMID:23215017

Salamone, Michela; Mangiacapra, Livia; DiLabio, Gino A; Bietti, Massimo

2013-01-01

386

Hydrogen-bond and solvent dynamics in transition metal complexes: a combined simulation and NMR-investigation.  

PubMed

Self-assembling ligands through complementary hydrogen-bonding in the coordination sphere of a transition metal provides catalysts with unique properties for carbon-carbon and carbon-heteroatom formation. Their most distinguishing chemical bonding pattern is a double-hydrogen-bonded motif, which determines much of the chemical functionality. Here, we discuss the possibility of double proton transfer (DPT) along this motif using computational and experimental methods. The infrared and NMR spectral signatures for the double-hydrogen-bonded motif are analyzed. Atomistic simulations and experiments suggest that the dynamics of the catalyst is surprisingly complex and displays at least three different dynamical regimes which can be distinguished with NMR spectroscopy and analyzed from computation. The two hydrogen bonds are kept intact and in rapid tautomeric exchange down to 125 K, which provides an estimate of 5 kcal/mol for the barrier for DPT. This is confirmed by the simulations which predict 5.8 kcal/mol for double proton transfer. A mechanistic interpretation is provided and the distribution of the solvent shell surrounding the catalyst is characterized from extensive simulations. PMID:23127212

Huang, Jing; Häussinger, Daniel; Gellrich, Urs; Seiche, Wolfgang; Breit, Bernhard; Meuwly, Markus

2012-12-13

387

Density functional theoretical investigation on structure, optical response and hydrogen adsorption properties of B9/metal-B9 clusters.  

PubMed

DFT calculations have been carried out to shed light on the electronic structure, optical properties and hydrogen adsorption capability of neutral MB9 (where M = Li3, Na3, K3, Al, Ga, In, Rh and Co) clusters. Electronic structural studies on the parent B9(3-) clusters reveal that a less aromatic hypervalent B-centred B8 ring geometry is energetically more favoured. However, GM(3+) (Al, Ga and In) in GM@B9 prefers a highly aromatic metal-centred 9-membered molecular wheel structure. In addition, the larger size of indium breaks the D9h symmetry of the molecular wheel by coming slightly out of the ring plane unlike Al@B9 and Ga@B9. B9(n-) (n = 1-3) is also neutralized with 'n' number of Li, Na and K which revealed that AM2B9 and AM2B9(-) result in pyramidal geometries while AM3B9 results in an irregular shape by retaining the B9 framework similar to the most stable conformer of B9(3-). Metal@B9 molecular wheels show optical absorption in a broad range of the spectrum (from UV to NIR: 260-1000 nm), which is attributed to the metal's ability to perturb the ring centred excited state. Ga@B9 and Co@B9 bind with hydrogen molecules in a dissociative manner, forming two covalent bonds with peripheral B atoms of the B9 ring. PMID:23615876

Banerjee, Swastika; Periyasamy, Ganga; Pati, Swapan K

2013-06-01

388

Multilayer sulfur-resistant composite metal membranes and methods of making and repairing the same  

SciTech Connect

The invention relates to thin, hydrogen-permeable, sulfur-resistant membranes formed from multi-layers of palladium or palladium-alloy coatings on porous, ceramic or metal supports, methods of making these membranes, methods of repairing layers of these membranes and devices that incorporate these membranes.

Way, J. Douglas; Hatlevik, Oyvind

2014-07-15

389

Promotion of atomic hydrogen recombination as an alternative to electron trapping for the role of metals in the photocatalytic production of H2.  

PubMed

The production of hydrogen from water with semiconductor photocatalysts can be promoted by adding small amounts of metals to their surfaces. The resulting enhancement in photocatalytic activity is commonly attributed to a fast transfer of the excited electrons generated by photon absorption from the semiconductor to the metal, a step that prevents deexcitation back to the ground electronic state. Here we provide experimental evidence that suggests an alternative pathway that does not involve electron transfer to the metal but requires it to act as a catalyst for the recombination of the hydrogen atoms made via the reduction of protons on the surface of the semiconductor instead. PMID:24843154

Joo, Ji Bong; Dillon, Robert; Lee, Ilkeun; Yin, Yadong; Bardeen, Christopher J; Zaera, Francisco

2014-06-01

390

USE OF HYDROGEN RESPIROMETRY TO DETERMINE METAL TOXICITY TO SULFATE REDUCING BACTERIA  

EPA Science Inventory

Acid mine drainage (AMD), an acidic metal-bearing wastewater poses a severe pollution problem attributed to post-mining activities. The metals (metal sulfates) encountered in AMD and considered of concern for risk assessment are: arsenic, cadmium, aluminum, manganese, iron, zinc ...

391

Characteristics of hydrogen storage by spillover on Pt-doped carbon and catalyst-bridged metal organic framework.  

PubMed

Metal dispersion is a crucially important factor for hydrogen spillover storage on metal/carbon materials. For Pt on carbon (Pt/C), dispersion into nearly 2 nm clusters or nanoparticles is necessary to facilitate spillover. On an effective Pt/C spillover sorbent, temperature-programmed desorption (TPD) results reveal the highest hydrogen signal is from the high-energy Pt edges, steps or (110) surfaces, even though the (111) faces are more abundant. Previous theoretical studies showed the high-energy sites (including the 110 face) are by far the most preferred for effective splitting of hydrogen. These are in significantly smaller fractions for larger particles, and thus the larger particles are less efficient. In addition, the rate-limiting step for spillover on effective Pt/C is identified by the susceptibility to isotopic differences, first-order behavior and isolation from catalyzed H(2)/HD/D(2) equilibrium measurements; we conclude it is the spillover step or surface diffusion. We extended our analysis to a review of our previous work, spillover on metal organic frameworks (MOFs). This has been achieved by bridging a commercial H(2) dissociation catalyst (Pt/C) to MOFs, large enhancement factors (up to 8) were observed. Unlike Pt/C sorbents, sample-to-sample consistency in storage capacity on the bridged MOF samples is difficult to achieve. Inconsistency in the enhancements by spillover is shown; however, significant enhancement factors are still observed when samples are prepared and activated properly. Common pitfalls (and their consequences) in sample preparation for both Pt/C and bridged MOFs are discussed in detail. PMID:20527946

Stuckert, Nicholas R; Wang, Lifeng; Yang, Ralph T

2010-07-20

392

Ionizing radiation-stimulated diffusion and desorption of hydrogen from metals  

NASA Astrophysics Data System (ADS)

The processes of hydrogen diffusion from a sample depth activated by electrons with an energy of tens of keV are studied. The difference from the known models of electron-stimulated desorption, which consider as a rule electron energies from 0.5 to several keV, is noted. The proposed model is shown to correspond to at least two established experimental facts: the nonlinear dependence of hydrogen isotope desorption on the electron beam current density affecting the sample and the dependence of hydrogen desorption on the irradiation time of the sample.

Tyurin, Yu. I.; Nikitenkov, N. N.; Larionov, V. V.

2011-06-01

393

Turning on catalysis: incorporation of a hydrogen-bond-donating squaramide moiety into a zr metal-organic framework.  

PubMed

Herein, we demonstrate that the incorporation of an acidic hydrogen-bond-donating squaramide moiety into a porous UiO-67 metal-organic framework (MOF) derivative leads to dramatic acceleration of the biorelevant Friedel-Crafts reaction between indole and ?-nitrostyrene. In comparison, it is shown that free squaramide derivatives, not incorporated into MOF architectures, have no catalytic activity. Additionally, using the UiO-67 template, we were able to perform a direct comparison of catalytic activity with that of the less acidic urea-based analogue. This is the first demonstration of the functionalization of a heterogeneous framework with an acidic squaramide derivative. PMID:25574688

McGuirk, C Michael; Katz, Michael J; Stern, Charlotte L; Sarjeant, Amy A; Hupp, Joseph T; Farha, Omar K; Mirkin, Chad A

2015-01-21

394

Molecular simulation studies of metal organic frameworks focusing on hydrogen purification   

E-print Network

The process of purifying hydrogen gas using pressure swing adsorption columns heavily relies on highly efficient adsorbents. Such materials must be able to selectively adsorb a large amount of impurities, and must also ...

Banu, Ana Maria

2014-06-30

395

The solubility of hydrogen and deuterium in alloyed, unalloyed and impure plutonium metal  

SciTech Connect

Pressure-Composition-Temperature (PCT) data are presented for the plutonium-hydrogen (Pu-H) and plutonium-deuterium (Pu-D) systems in the solubility region up to terminal solubility (precipitation of PuH{sub 2}). The heats of solution for PuH{sub s} and PuD{sub s} are determined from PCT data in the ranges 350-625 C for gallium alloyed Pu and 400-575 C for unalloyed Pu. The solubility of high purity plutonium alloyed with 2 at.% gallium is compared to high purity unalloyed plutonium. Significant differences are found in hydrogen solubility for unalloyed Pu versus gallium alloyed Pu. Differences in hydrogen solubility due to an apparent phase change are observable in the alloyed and unalloyed solubilities. The effect of iron impurities on Pu-Ga alloyed Pu is shown via hydrogen solubility data as preventing complete homogenization.

Richmond, Scott [Los Alamos National Laboratory; Bridgewater, Jon S [Los Alamos National Laboratory; Ward, John W [Los Alamos National Laboratory; Allen, Thomas A [Los Alamos National Laboratory

2009-01-01

396

Hydrogen production in single-chamber tubular microbial electrolysis cells using non-precious-metal catalysts  

E-print Network

warming and the finite supply of fossil fuels, hydrogen as a clean energy carrier for the future has drawn excellent catalytic capabil- ities and popularity in microbial fuel cell (MFC) studies [3]. Several

Tullos, Desiree

397

Influence of grain boundary phosphorus concentration on liquid metal and hydrogen embrittlement of Monel 400  

SciTech Connect

Susceptibility to embrittlement by mercury and hydrogen was measured as affected by thermal treatment. Specimens were annealed at 900/degree/C and either quenched or furnace cooled. Fractures in air were ductile, and not affected by thermal treatment. Fractures of mercury-coated and hydrogen-charged samples were brittle and intergranular; elongation to fracture increased with increasing concentration of grain boundary phosphorus. 45 refs.

Funkenbusch, A.W.; Heldt, L.A.; Stein, D.F.

1982-04-01

398

Hydrogenation and ring opening of tetralin on noble metal supported on zirconium doped mesoporous silica catalysts  

Microsoft Academic Search

Zirconium-doped mesoporous silica with a Si\\/Zr ratio of 5 and moderate surface acidity has been used as a support for (co)-impregnated platinum, palladium, rhodium and palladium-platinum (Pd-Pt) (2wt.%). The catalysts resulting after reduction have been extensively characterised and examined for their activity in the hydrogenation and hydrogenolysis \\/ring-opening of tetralin at 6MPa of hydrogen pressure. BET surface areas are in

Enrique Rodr??guez-Castellón; Josefa Mérida-Robles; Lourdes D??az; Pedro Maireles-Torres; Deborah J Jones; Jacques Rozière; Antonio Jiménez-López

2004-01-01

399

A fractographic study of hydrogen-assisted cracking and liquid-metal embrittlement in nickel  

Microsoft Academic Search

Metallographic and fractographic studies of crack growth in nickel polycrystals and single crystals in a number of environments are described. “Brittle” intercrystalline and transcrystalline cleavage-like fractures were observed for specimens tested in liquid mercury, liquid lithium, liquid sodium, gaseous hydrogen, and for hydrogen-charged specimens tested in air. “Brittle” fractures were associated with considerable slip, and dimples\\/tear ridges were observed on

S. P. Lynch

1986-01-01

400

Reversible hydriding and dehydriding properties of CaSi: Potential of metal silicides for hydrogen storage  

Microsoft Academic Search

We found that CaSi reversibly absorbs and desorbs hydrogen. First-principles calculations theoretically indicated that CaSi hydride is thermodynamically stable. The hydriding and dehydriding properties of CaSi were experimentally determined using pressure-composition (p-c) isotherms and x-ray diffraction analysis. The p-c isotherms clearly demonstrated plateau pressures in a temperature range of 473-573 K. The maximum hydrogen content was 1.9 wt % under

M. Aoki; N. Ohba; T. Noritake; S. Towata

2004-01-01

401

Salicylaldimine-based metal-organic framework enabling highly active olefin hydrogenation with iron and cobalt catalysts.  

PubMed

A robust and porous Zr metal-organic framework, sal-MOF, of UiO topology was synthesized using a salicylaldimine (sal)-derived dicarboxylate bridging ligand. Postsynthetic metalation of sal-MOF with iron(II) or cobalt(II) chloride followed by treatment with NaBEt3H in THF resulted in Fe- and Co-functionalized MOFs (sal-M-MOF, M = Fe, Co) which are highly active solid catalysts for alkene hydrogenation. Impressively, sal-Fe-MOF displayed very high turnover numbers of up to 145000 and was recycled and reused more than 15 times. This work highlights the unique opportunity of developing MOF-based earth-abundant catalysts for sustainable chemical synthesis. PMID:25187995

Manna, Kuntal; Zhang, Teng; Carboni, Michaël; Abney, Carter W; Lin, Wenbin

2014-09-24

402

Permeability and relative permeability in rocks  

SciTech Connect

Important features of the topology of the pore space of rocks can be usefully quantified by analyzing digitized images of rock cross sections. One approach computes statistical correlation functions using modern image processing techniques. These correlation functions contain information about porosity, specific surface area, tortuosity, formation factor, and elastic constants, as well as the fluid permeability and relative permeability. The physical basis of this approach is discussed and examples of the results for various sandstones are presented. The analysis shows that Kozeny-Carman relations and Archie's empirical laws must be modified to account for finite percolation thresholds in order to avoid unphysical behavior in the calculated relative permeabilities. 33 refs., 4 figs., 1 tab.

Blair, S.C.; Berryman, J.G.

1990-10-01

403

Selective oxidation of methanol to hydrogen over gold catalysts promoted by alkaline-earth-metal and lanthanum oxides.  

PubMed

A series of alumina-supported gold catalysts was investigated for the CO-free production of hydrogen by partial oxidation of methanol. The addition of alkaline-earth metal oxide promoters resulted in a significant improvement of the catalytic performance. The methanol conversion was ca. 85 % with all studied catalyst materials, however, the selectivity for hydrogen increased from 15 % to 51 % when going from the unpromoted to a BaO-promoted catalyst. The formation of the undesired byproducts CO, methane, and dimethyl ether was considerably reduced as well. The observed trend in catalyst performance follows the trend in increasing basicity of the studied promoter elements, indicating a chemical effect of the promoter material. Superior catalytic performance, in terms of H(2) and CO selectivity, was obtained with a Au/La(2)O(3) catalyst. At 300 degrees C the hydrogen selectivity reached 80 % with only 2 % CO formation, and the catalyst displayed a stable performance over at least 24 h on-stream. Furthermore, the formation of CO was found to be independent of the oxygen concentration in the feed. The commercial lanthanum oxide used in this study had a low specific surface area, which led to the formation of relative large gold particles. Therefore, the catalytic activity could be enhanced by decreasing the gold particle size through deposition on lanthanum oxide supported on high-surface-area alumina. PMID:19588474

Hereijgers, Bart P C; Weckhuysen, Bert M

2009-01-01

404

Urea Metal-Organic Frameworks as Effective and Size-Selective Hydrogen-Bond Catalysts  

E-print Network

Supporting Information ABSTRACT: A new urea-containing metal-organic frame- work (MOF) was synthesized to act as a heterogeneous catalyst. Ureas are well-known for self-recognition and aggrega- tion behavior, resulting in loss collective interests in MOFs and catalysis, we have developed a collaborative program aimed at merging metal

405

Velocity of action of oxygen, hydrogen sulfide, and halogens on metals  

NASA Technical Reports Server (NTRS)

This report discusses a method of determining the rate of surface oxidation of a metal by the change in the color of the surface film produced by reactions with oxygen, chlorine, or iodine. The metals studied included iron, nickel, copper, zinc, cadmium, tin, lead, cobalt, and manganese. Tables are given for surface film thickness versus color for various times.

Tammann, Gustav; Koster, Werner

1952-01-01

406

The Influence of Grain Boundary Phosphorus Concentration on Liquid Metal and Hydrogen Embrittlement of Monel 400  

NASA Astrophysics Data System (ADS)

The susceptibility of Monel 400® to embrittlement by mercury and by hydrogen was measured as affected by thermal treatment. Specimens were annealed at 900°C and either quenched or furnace cooled. Auger analysis revealed phosphorus segregated to the grain boundaries; furnace cooling causes the boundary concentration to be about twice that of the quenched material. Tensile tests were conducted with specimens (1) in air, (2) coated with mercury, or (3) cathodically precharged with hydrogen. Fractures in air were completely ductile, and ductility was not affected by thermal treatment. Fractures of mercury-coated and hydrogen-charged samples were brittle and intergranular; elongation to fracture increased significantly with increasing concentration of grain boundary phosphorus. The results are discussed in terms of additive and interactive mechanisms.

Funkenbusch, A. W.; Heldt, L. A.; Stein, D. F.

1982-04-01

407

An electrochemical study of frustrated Lewis pairs: a metal-free route to hydrogen oxidation.  

PubMed

Frustrated Lewis pairs have found many applications in the heterolytic activation of H2 and subsequent hydrogenation of small molecules through delivery of the resulting proton and hydride equivalents. Herein, we describe how H2 can be preactivated using classical frustrated Lewis pair chemistry and combined with in situ nonaqueous electrochemical oxidation of the resulting borohydride. Our approach allows hydrogen to be cleanly converted into two protons and two electrons in situ, and reduces the potential (the required energetic driving force) for nonaqueous H2 oxidation by 610 mV (117.7 kJ mol(-1)). This significant energy reduction opens routes to the development of nonaqueous hydrogen energy technology. PMID:24720359

Lawrence, Elliot J; Oganesyan, Vasily S; Hughes, David L; Ashley, Andrew E; Wildgoose, Gregory G

2014-04-23

408

An Electrochemical Study of Frustrated Lewis Pairs: A Metal-Free Route to Hydrogen Oxidation  

PubMed Central

Frustrated Lewis pairs have found many applications in the heterolytic activation of H2 and subsequent hydrogenation of small molecules through delivery of the resulting proton and hydride equivalents. Herein, we describe how H2 can be preactivated using classical frustrated Lewis pair chemistry and combined with in situ nonaqueous electrochemical oxidation of the resulting borohydride. Our approach allows hydrogen to be cleanly converted into two protons and two electrons in situ, and reduces the potential (the required energetic driving force) for nonaqueous H2 oxidation by 610 mV (117.7 kJ mol–1). This significant energy reduction opens routes to the development of nonaqueous hydrogen energy technology. PMID:24720359

2014-01-01

409

Decoupled catalytic hydrogen evolution from a molecular metal oxide redox mediator in water splitting.  

PubMed

The electrolysis of water using renewable energy inputs is being actively pursued as a route to sustainable hydrogen production. Here we introduce a recyclable redox mediator (silicotungstic acid) that enables the coupling of low-pressure production of oxygen via water oxidation to a separate, catalytic hydrogen production step outside the electrolyzer that requires no post-electrolysis energy input. This approach sidesteps the production of high-pressure gases inside the electrolytic cell (a major cause of membrane degradation) and essentially eliminates the hazardous issue of product gas crossover at the low current densities that characterize renewables-driven water-splitting devices. We demonstrated that a platinum-catalyzed system can produce pure hydrogen over 30 times faster than state-of-the-art proton exchange membrane electrolyzers at equivalent platinum loading. PMID:25214625

Rausch, Benjamin; Symes, Mark D; Chisholm, Greig; Cronin, Leroy

2014-09-12

410

Hydrogen-doping stabilized metallic VO{sub 2} (R) thin films and their application to suppress Fabry-Perot resonances in the terahertz regime  

SciTech Connect

We demonstrate that catalyst-assisted hydrogen spillover doping of VO{sub 2} thin films significantly alters the metal-insulator transition characteristics and stabilizes the metallic rutile phase at room temperature. With hydrogen inserted into the VO{sub 2} lattice, high resolution X-ray diffraction reveals expansion of the V-V chain separation when compared to the VO{sub 2}(R) phase. The donated free electrons, possibly from O-H bond formation, stabilize the VO{sub 2}(R) to low temperatures. By controlling the amount of dopants to obtain mixed insulating and metallic phases, VO{sub 2} resistivity can be continuously tuned until a critical condition is achieved that suppresses Fabry-Perot resonances. Our results demonstrate that hydrogen spillover is an effective technique to tune the electrical and optical properties of VO{sub 2} thin films.

Zhao, Yong; Pan, Xuan; Bernussi, Ayrton A.; Fan, Zhaoyang, E-mail: Zhaoyang.Fan@ttu.edu [Department of Electrical and Computer Engineering and Nano Tech Center, Lubbock, Texas 79409 (United States); Karaoglan-Bebek, Gulten [Department of Physics and Nano Tech Center, Lubbock, Texas 79409 (United States); Holtz, Mark [Department of Physics and MSEC, Texas State University, San Marcos, Texas 78666 (United States)

2014-06-16

411

Metalized T graphene: A reversible hydrogen storage material at room temperature  

SciTech Connect

Lithium (Li)-decorated graphene is a promising hydrogen storage medium due to its high capacity. However, homogeneous mono-layer coating graphene with lithium atoms is metastable and the lithium atoms would cluster on the surface, resulting in the poor reversibility. Using van der Waals-corrected density functional theory, we demonstrated that lithium atoms can be homogeneously dispersed on T graphene due to a nonuniform charge distribution in T graphene and strong hybridizations between the C-2p and Li-2p orbitals. Thus, Li atoms are not likely to form clusters, indicating a good reversible hydrogen storage. Both the polarization mechanism and the orbital hybridizations contribute to the adsorption of hydrogen molecules (storage capacity of 7.7?wt. %) with an optimal adsorption energy of 0.19?eV/H{sub 2}. The adsorption/desorption of H{sub 2} at ambient temperature and pressure is also discussed. Our results can serve as a guide in the design of new hydrogen storage materials based on non-hexagonal graphenes.

Ye, Xiao-Juan; Zhong, Wei, E-mail: csliu@njupt.edu.cn, E-mail: wzhong@nju.edu.cn; Du, You-Wei [Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093 (China); Liu, Chun-Sheng, E-mail: csliu@njupt.edu.cn, E-mail: wzhong@nju.edu.cn [Key Laboratory of Radio Frequency and Micro-Nano Electronics of Jiangsu Province, Nanjing University of Posts and Telecommunications, Nanjing 210023 (China); Zeng, Zhi [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China)

2014-09-21

412

The Influence of Grain Boundary Phosphorus Concentration on Liquid Metal and Hydrogen Embrittlement of Monel 400  

Microsoft Academic Search

The susceptibility of Monel 400® to embrittlement by mercury and by hydrogen was measured as affected by thermal treatment. Specimens were annealed at 900°C and either quenched or furnace cooled. Auger analysis revealed phosphorus segregated to the grain boundaries; furnace cooling causes the boundary concentration to be about twice that of the quenched material. Tensile tests were conducted with specimens

A. W. Funkenbusch; L. A. Heldt; D. F. Stein

1982-01-01

413

Start Up of Biohydrogen Production System and Effect of Metal Ions on Hydrogen Production  

NASA Astrophysics Data System (ADS)

Fermentative hydrogen production is a promising biochemical route to produce renewable H2. The effect of organic loading rate on the biohydrogen production during the start-up phase and effect of Fe2+ and Mg2+ concentration on biohydrogen production of a continuous stirred tank reactor using molasses wastewater as substrate were investigated. It was found that an initial biomass of 14.07 gVSS/L and an organic loading rate of 6.0 kgCOD/m3?d, an equilibrial microbial community in the butyric-type fermentation could be established with in 30 days. It was demonstrated that both Fe2+ and Mg2+ were able to enhance the hydrogen production capacity of microorganism flora. Different concentration of Fe2+ was added to the biohydrogen producing system (50 mg/L, 100 mg/L, 200 mg/L and 500 mg/L), the maximum biogas production yield of 6.78 L/d and the maximum specific hydrogen production rate of 10.1 ml/gVSS?h were obtained at Fe2+ concentration of 500 mg/L and 200 mg/L, respectively. The maximum biogas production yield of 6.84 L/d and the maximum specific hydrogen production rate of 10.2 ml/gVSS?h were obtained at Mg2+ concentration of 100 mg/L and 50 mg/L, respectively.

Jiao, An-ying; Li, Yong-feng; Yue, Li-ran; Yang, Chuan-ping

2010-11-01

414

Nanoporous metal enhanced catalytic activities of amorphous molybdenum sulfide for high-efficiency hydrogen production.  

PubMed

We fabricated a robust electrocatalyst by chemically depositing an ultrathin layer of amorphous molybdenum sulfide on the internal surface of dealloyed nanoporous gold. The catalyst exhibits superior electrocatalysis toward hydrogen evolution reaction in both acidic and neutral media with 2-6 times improvement in catalytic activies compared to other molybdenum sulfide based materials. PMID:24554595

Ge, Xingbo; Chen, Luyang; Zhang, Ling; Wen, Yuren; Hirata, Akihiko; Chen, Mingwei

2014-05-21

415

Band modes of hydrogen in the bcc metals Nb, V, and Ta  

Microsoft Academic Search

A calculation of the frequency spectrum of the band modes of hydrogen located at a tetrahedral interstitial site shows a strong resonantlike peak with very little isotope effect. This mode was observed by neutron scattering in NbH0.05 at 3.8 THz. The band modes provide a mechanism for classical diffusion with low activation energies.

V. Lottner; H. R. Schober; W. J. Fitzgerald

1979-01-01

416

An investigation of the kinetics for hydrogen chemisorption on iron metal surfaces  

NASA Technical Reports Server (NTRS)

A quasi-isothermal approach was used to study the kinetics of hydrogen and hydrogen sulfide chemisorption onto iron film in an effort to understand the environmental degradation of steels. The coverage of chemisorbed hydrogen or chemisorbed sulfur was observed as a function of time for fixed conditions of substrate temperature. Auger electron spectroscopy was used to observe the sulfur and chemisorption-induced resistance change was employed to monitor hydrogen coverage. To compare the results obtained from studying the kinetics by two different techniques, the kinetics of oxygen chemisorption onto iron films was also studied. A reaction model utilized to interpret the H2/Fe2 chemisorption kinetics was applied to data from an earlier study on the desorption kinetics for H2 chemisorbed onto nicket films in the vicinity of the Curie temperature of the film. This analysis permitted a separation of the gross desorption process into individual components so that the influence of the magnetic phase transition on the rate constants could be determined.

Shanabarger, M. R.

1980-01-01

417

Influence of high pressure hydrogen on cyclic load crack growth in metals  

NASA Technical Reports Server (NTRS)

The effect of high pressure hydrogen on the crack growth rate of various nickel-base alloys was studied at ambient temperature. Considerable enhancement of the cyclic flaw growth rate was observed for Inconel 718, wrought and cast, and Waspaloy, a nickel-base alloy similar to Inconel 718. Only slight enhancement of the flaw growth rate for Alloy 903 was observed.

Jewett, R. P.; Walter, R. J.; Chandler, W. T.

1978-01-01

418

Atomistic Models of Long-Term Hydrogen Diffusion in Metals M. P. Ariza1,a  

E-print Network

such as Molecular Dynamics (MD) and Monte Carlo (MC) methods. In this work, we present a novel deformation to hours. Molecular Dynamics (MD) and Monte Carlo (MC) methods are powerful techniques to study deformation are demonstrated in the simulation of a specific hydrogen diffu- sion problem using palladium nanofilms, which

Ortiz, Michael

419

Determination of the Relative Atomic Masses of Metals by Liberation of Molecular Hydrogen  

ERIC Educational Resources Information Center

Students determine the relative atomic masses of calcium, magnesium, and aluminum by reaction with hydrochloric acid and measurement of the volume of hydrogen gas liberated. The experiment demonstrates stoichiometry and illustrates clearly that mass of the reagent is not the determinant of the amounts in chemical reactions. The experiment is…

Waghorne, W. Earle; Rous, Andrew J.

2009-01-01

420

Enhancing hydrogen spillover and storage  

DOEpatents

Methods for enhancing hydrogen spillover and storage are disclosed. One embodiment of the method includes doping a hydrogen receptor with metal particles, and exposing the hydrogen receptor to ultrasonication as doping occurs. Another embodiment of the method includes doping a hydrogen receptor with metal particles, and exposing the doped hydrogen receptor to a plasma treatment.

Yang, Ralph T; Li, Yingwei; Lachawiec, Jr., Anthony J

2013-02-12

421

Enhancing hydrogen spillover and storage  

DOEpatents

Methods for enhancing hydrogen spillover and storage are disclosed. One embodiment of the method includes doping a hydrogen receptor with metal particles, and exposing the hydrogen receptor to ultrasonification as doping occurs. Another embodiment of the method includes doping a hydrogen receptor with metal particles, and exposing the doped hydrogen receptor to a plasma treatment.

Yang, Ralph T. (Ann Arbor, MI); Li, Yingwel (Ann Arbor, MI); Lachawiec, Jr., Anthony J. (Ann Arbor, MI)

2011-05-31

422

Noble metal doped graphene nanocomposites and its study of photocatalytic hydrogen evolution  

NASA Astrophysics Data System (ADS)

This work reports the deposition of platinum (Pt) nanoparticles on the surface of graphene nanosheet by a simple approach, using a microwave-assisted method. The photocatalytic activity has been investigated for hydrogen evolution. The hydrogen evolutions were attributed to graphene, due to its high photoelectron transport properties, and the Pt nanoparticles attached on the surface of graphene sheet, which act as reaction centers for H2 evolution. The “as-prepared” composites were characterized by Brunauer Emmett Teller (BET) surface area measurement, X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectra (DRS). This work highlights the potential application of graphene-based materials in the field of energy conversion.

Ullah, Kefayat; Ye, Shu; Zhu, Lei; Jo, Sun Bok; Jang, Won Kweon; Cho, Kwang-Youn; Oh, Won-Chun

2014-05-01

423

Influence of clamping plate permeability and metal screen structures on three-dimensional magnetic field and eddy current loss in end region of a turbo-generator by numerical analysis  

NASA Astrophysics Data System (ADS)

A significant problem of turbogenerators on complex end structures is overheating of local parts caused by end losses in the end region. Therefore, it is important to investigate the 3-D magnetic field and eddy current loss in the end. In end region of operating large turbogenerator at thermal power plants, magnetic leakage field distribution is complex. In this paper, a 3-D mathematical model used for the calculation of the electromagnetic field in the end region of large turbo-generators is given. The influence of spatial locations of end structures, the actual shape and material of end windings, clamping plate, and copper screen are considered. Adopting the time-step finite element (FE) method and taking the nonlinear characteristics of the core into consideration, a 3-D transient magnetic field is calculated. The objective of this paper is to investigate the influence of clamping plate permeability and metal screen structures on 3-D electromagnetic field distribution and eddy current loss in end region of a turbo-generator. To reduce the temperature of copper screen, a hollow metal screen is proposed. The eddy current loss, which is gained from the 3D transient magnetic field, is used as heat source for the thermal field of end region. The calculated temperatures are compared with test data.

Likun, Wang; Weili, Li; Yi, Xue; Chunwei, Guan

2013-11-01

424

Photochemical electron storage on colloidal metals and hydrogen formation by free radicals  

SciTech Connect

Photolytically produced 1-hydroxy-1-methylethyl radicals were found to form hydrogen in the presence of colloidal platinum, gold, silver, and cadmium. Conductivity measurements showed that electrons stored on the colloidal particles are intermediates to H/sub 2/ formation. A 1.25 x 10/sup -4/ M silver solution was found to store electrons up to more than 0.3 C/L (electrical capacity per liter) during illumination.

Henglein, A.; Lindig, B.; Westerhausen, J.

1981-06-11

425

Theoretical investigation on the alkali-metal doped BN fullerene as a material for hydrogen storage  

Microsoft Academic Search

First-principles calculations have been used to investigate hydrogen adsorption on alkali atom doped B36N36 clusters. The alkali atom adsorption takes place near the six tetragonal bridge sites available on the cage, thereby avoiding the notorious clustering problem. Adsorption of alkali atoms involves a charge transfer process, creating positively charged alkali atoms and this polarizes the H2 molecules thereby, increasing their

Natarajan Sathiyamoorthy Venkataramanan; Rodion Vladimirovich Belosludov; Ryoji Sahara; Hiroshi Mizuseki; Yoshiyuki Kawazoe

2010-01-01

426

The Influence of Grain Boundary Phosphorus Concentration on Liquid Metal and Hydrogen Embrittlement of Monel 400  

Microsoft Academic Search

The susceptibility of Monel 400® to embrittlement by mercury and by hydrogen was measured as affected by thermal treatment.\\u000a Specimens were annealed at 900°C and either quenched or furnace cooled. Auger analysis revealed phosphorus segregated to the\\u000a grain boundaries; furnace cooling causes the boundary concentration to be about twice that of the quenched material. Tensile\\u000a tests were conducted with specimens

A. W. Funkenbusch; L. A. Heldt; D. F. Stein

1982-01-01

427

Hydrogen cyanide formation at low reactant concentrations over noble metal catalysts  

Microsoft Academic Search

The utilization of three-way catalysts containing platinum and rhodium in catalytic converters for abatement of automative exhaust emissions has required examination of their activity for hydrogen cyanide formation under the conditions of their normal operations and under conditions created by system malfunctions. While effective in reducing nitric oxide when used in three-way catalyst systems, the platinum-rhodium catalysts have also been

W. B. Williamson; M. Shelef

1977-01-01

428

Applications of nuclear reaction analysis for determining hydrogen and deuterium distribution in metals  

SciTech Connect

The use of ion beams for materials analysis has made a successful transition from the domain of the particle physicist to that of the materials scientist. The subcategory of this field, nuclear reaction analysis, is just now undergoing the transition, particularly in applications to hydrogen in materials. The materials scientist must locate the nearest accelerator, because now he will find that using it can solve mysteries that do not yield to other techniques. 9 figures

Altstetter, C.J.

1981-01-01

429

EPA/ITRC-RTDF permeable reactive barrier short course. Permeable reactive barriers: Application and deployment  

SciTech Connect

This report focuses on the following: Permeable Reactive Barriers: Application and Deployment; Introduction to Permeable Reactive Barriers (PRBs) for Remediating and Managing Contaminated Groundwater in Situ; Collection and Interpretation of Design Data 1: Site Characterization for PRBs; Reactive Materials: Zero-Valent Iron; Collection and Interpretation of Design Data 2: Laboratory and Pilot Scale Tests; Design Calculations; Compliance Monitoring, Performance Monitoring and Long-Term Maintenance for PRBs; PRB Emplacement Techniques; PRB Permitting and Implementation; Treatment of Metals; Non-Metallic Reactive Materials; Economic Considerations for PRB Deployment; and Bibliography.

NONE

1999-11-01

430

EPA/ITRC-RTDF permeable reactive barrier short course. Permeable reactive barriers: Application and deployment  

SciTech Connect

This report focuses on the following: Permeable Reactive Barriers: Application and Deployment; Introduction to Permeable Reactive Barriers (PRBs) for Remediating and Managing Contaminated Groundwater in Situ; Collection and Interpretation of Design Data 1: Site Characterization for PRBs; Reactive Materials: Zero-Valent Iron; Collection and Interpretation of Design Data 2: Laboratory and Pilot Scale Tests; Design Calculations; Compliance Monitoring, Performance Monitoring and Long-Term Maintenance for PRBs; PRB Emplacement Techniques; PRB Permitting and Implementation; Treatment of Metals; Non-Metallic Reactive Materials; Economic Considerations for PRB Deployment; and Bibliography.

Not Available

1999-01-01

431

Hydrogen production using solid oxide membrane electrolyzer with solid carbon reductant in liquid metal anode  

SciTech Connect

A laboratory-scale solid oxide membrane (SOM) steam electrolyzer that can potentially utilize the energy value of coal or any hydrocarbon reductant to produce high purity hydrogen has been fabricated and evaluated. The SOM electrolyzer consists of an oxygen-ion-conducting yttria-stabilized zirconia (YSZ) electrolyte with a Ni-YSZ cermet cathode coated on one side and liquid tin anode on the other side. Hydrogen production using the SOM electrolyzer was successfully demonstrated between 900 and 1000{sup o}C by feeding a steam-rich gas to the Ni-YSZ cermet cathode and solid carbon reductant into the liquid tin anode. It was confirmed that the energy required for hydrogen production can be effectively lowered by feeding a solid carbon reductant in the liquid tin anode. A polarization model for the SOM electrolyzer was developed. The experimental data obtained under different operating conditions were curve fitted into the model to identify the various polarization losses. Based on the results of this study, work needed toward increasing the electrochemical performance of the SOM electrolyzer is discussed.

Pati, S.; Yoon, K.J.; Gopalan, S.; Pal, U.B. [Boston University, Boston, MA (United States). Dept. of Mechanical Engineering

2009-07-01

432

A homogeneous transition metal complex for clean hydrogen production from methanol-water mixtures  

NASA Astrophysics Data System (ADS)

The development of an efficient catalytic process that mimics the enzymatic function of alcohol dehydrogenase is critical for using biomass alcohols for both the production of H2 as a chemical energy carrier and fine chemicals under waste-free conditions. Dehydrogenation of alcohol-water mixtures into their corresponding acids with molecular hydrogen as the sole by-product from the reaction can be catalysed by a ruthenium complex with a chelating bis(olefin) diazadiene ligand. This complex, [K(dme)2][Ru(H)(trop2dad)], stores up to two equivalents of hydrogen intramolecularly, and catalyses the production of H2 from alcohols in the presence of water and a base under homogeneous conditions. The conversion of a MeOH-H2O mixture proceeds selectively to CO2/H2 gas formation under neutral conditions, thereby allowing the use of the entire hydrogen content (12% by weight). Isolation and characterization of the ruthenium complexes from these reactions suggested a mechanistic scenario in which the trop2dad ligand behaves as a chemically ‘non-innocent’ co-operative ligand.

Rodríguez-Lugo, Rafael E.; Trincado, Mónica; Vogt, Matthias; Tewes, Friederike; Santiso-Quinones, Gustavo; Grützmacher, Hansjörg

2013-04-01

433

Structure and screening in molecular and metallic hydrogen at high pressure  

NASA Technical Reports Server (NTRS)

A variational wavefunction is used to express the (spin restricted) Hartree-Fock energy as reciprocal lattice sums for static lattice FCC monatomic hydrogen and diatomic Pa3 molecular hydrogen. In the monatomic phase the hydrogenic orbital range closely parallels the inverse Thomas-Fermi wavevector; the corresponding energy E has a minimum of -0.929 Ryd/electron at r sub s = 1.67. For the diatomic phase E(r sub s) is similar, but the constituent energies, screening, and bond length reflect a qualitative change in the nature of the solid at r sub s = 2.8. This change is interpreted in terms of a transition from protons as structural units (at high density) to weakly interacting models (at low density). Insensitivity of the total energy to a rapid fall in the bond length suggests association with the rotational transition where the rapid molecular orientations characteristic of high pressures disappear and the molecules rotate freely at low pressure.

Wood, D. M.; Ashcroft, N. W.

1981-01-01

434

Advanced metal-membrane technology-commercialization  

SciTech Connect

The gasification of coal offers a potentially significant source of hydrogen for use in clean power generation and as a primary chemical feedstock. However, hydrogen derived from coal continues to be more expensive than hydrogen derived from natural gas or petroleum, due in large part to the expense of separating hydrogen from the mixture of gases produced during gasification. At Bend Research, we have been developing a novel hydrogen-permeable metal membrane that promises to be economical for hydrogen separation and purification, including the purification of hydrogen derived from gasifying coal. Furthermore, the membrane is ideally suited for use at high temperatures (200{degrees} to 500{degrees}C), making it feasible to produce pure hydrogen directly from hot gas streams. Through a partnership with Teledyne Wah Chang, we are proceeding with scale-up of prototype membrane modules and field tests to demonstrate the technology to potential users. Additionally, we are working with potential customers to estimate capital savings and operating costs for integrated systems. In this paper, we present some of the operating characteristics of the metal membrane, including its use to drive equilibrium-limited reactions toward complete conversion (e.g., the water-gas-shift reaction). We also describe our activities for commercializing this technology for a variety of applications.

Edlund, D.J.

1995-06-01

435

Micelle-Template Synthesis of Nitrogen-Doped Mesoporous Graphene as an Efficient Metal-Free Electrocatalyst for Hydrogen Production  

PubMed Central

Synthesis of mesoporous graphene materials by soft-template methods remains a great challenge, owing to the poor self-assembly capability of precursors and the severe agglomeration of graphene nanosheets. Herein, a micelle-template strategy to prepare porous graphene materials with controllable mesopores, high specific surface areas and large pore volumes is reported. By fine-tuning the synthesis parameters, the pore sizes of mesoporous graphene can be rationally controlled. Nitrogen heteroatom doping is found to remarkably render electrocatalytic properties towards hydrogen evolution reactions as a highly efficient metal-free catalyst. The synthesis strategy and the demonstration of highly efficient catalytic effect provide benchmarks for preparing well-defined mesoporous graphene materials for energy production applications. PMID:25523276

Huang, Xiaodan; Zhao, Yufei; Ao, Zhimin; Wang, Guoxiu

2014-01-01

436