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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

Tubular hydrogen permeable metal foil membrane and method of fabrication  

DOEpatents

A tubular hydrogen permeable metal membrane and fabrication process comprises obtaining a metal alloy foil having two surfaces, coating the surfaces with a metal or metal alloy catalytic layer to produce a hydrogen permeable metal membrane, sizing the membrane into a sheet with two long edges, wrapping the membrane around an elongated expandable rod with the two long edges aligned and overlapping to facilitate welding of the two together, placing the foil wrapped rod into a surrounding fixture housing with the two aligned and overlapping foil edges accessible through an elongated aperture in the surrounding fixture housing, expanding the elongated expandable rod within the surrounding fixture housing to tighten the foil about the expanded rod, welding the two long overlapping foil edges to one another generating a tubular membrane, and removing the tubular membrane from within the surrounding fixture housing and the expandable rod from with the tubular membrane.

Paglieri, Stephen N.; Birdsell, Stephen A.; Barbero, Robert S.; Snow, Ronny C.; Smith, Frank M.

2006-04-04

3

Hydrogen Permeability of Mulitphase V-Ti-Ni Metallic Membranes  

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 focal point of the reported work was to evaluate a Group 5A-Ta, Nb, V-based alloy with respect to microstructural features and hydrogen permeability. Electrochemical hydrogen permeation testing of the V-Ti-Ni alloy is reported herein and compared to pure Pd measurements recorded as part of this same study. The V-Ti-Ni was demonstrated to have a steady state hydrogen permeation rate an order of magnitude higher than the pure Pd material in testing conducted at 22 C.

Adams, T. M.; Mickalonis, J.

2005-10-18

4

Metal/ceramic composites with high hydrogen permeability  

DOEpatents

A membrane for separating hydrogen from fluids is provided comprising a sintered homogenous mixture of a ceramic composition and a metal. The metal may be palladium, niobium, tantalum, vanadium, or zirconium or a binary mixture of palladium with another metal such as niobium, silver, tantalum, vanadium, or zirconium.

Dorris, Stephen E.; Lee, Tae H.; Balachandran, Uthamalingam

2003-05-27

5

Reduced hydrogen permeability at high temperatures  

NASA Technical Reports Server (NTRS)

CO and CO2 reduce hydrogen loss through iron, nickel, and cobalt based alloy tubes. Method is based on concept that oxide film on metal surface reduces hydrogen permeability through metal; adding CO or CO2 forms oxide films continuously during operation, and hydrogen containment is improved. Innovation enhances prospects for Stirling engine system utilization.

Stephens, J. R.; Klopp, W. D.; Misencik, J. A.

1981-01-01

6

Hydrogen Permeability and Integrity of Hydrogen  

E-print Network

Hydrogen Permeability and Integrity of Hydrogen Delivery Pipelines Z. Feng*, L.M. Anovitz*, J and industry expectations · DOE Pipeline Working Group and Tech Team activities - FRP Hydrogen Pipelines - Materials Solutions for Hydrogen Delivery in Pipelines - Natural Gas Pipelines for Hydrogen Use #12;3 OAK

7

Effect of water on hydrogen permeability  

NASA Technical Reports Server (NTRS)

Doping of hydrogen with CO and CO2 was developed to reduce hydrogen permeation in Stirling engines by forming a low permeability oxide coating on the inner surface of the heater head tubes. Although doping worked well, under certain circumstances the protective oxide could be chemically reduced by the hydrogen in the engine. Some oxygen is required in the hydrogen to prevent reduction. Eventually, all the oxygen in the hydrogen gas - whatever its source - shows up as water. This is the result of hydrogen reducing the CO, CO2, or the protective inner surface oxides. This water can condense in the engine system under the right conditions. If the concentration of water vapor is reduced to a low enough level, the hydrogen can chemically reduce the oxide coating, resulting in an increase in permeability. This work was done to define the minimum water content required to avoid this reduction in the oxide coating. The results of this testing show that a minimum of approximately 750 ppm water is required to prevent an increase in permeability of CG-27, a high temperature metal alloy selected for Stirling engine heater tubes.

Hulligan, David; Tomazic, William A.

1987-01-01

8

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

9

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

10

Stable catalyst layers for hydrogen permeable composite membranes  

SciTech Connect

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

11

Gas Permeable Chemochromic Compositions for Hydrogen Sensing  

NASA Technical Reports Server (NTRS)

A (H2) sensor composition includes a gas permeable matrix material intermixed and encapsulating at least one chemochromic pigment. The chemochromic pigment produces a detectable change in color of the overall sensor composition in the presence of H2 gas. The matrix material provides high H2 permeability, which permits fast permeation of H2 gas. In one embodiment, the chemochromic pigment comprises PdO/TiO2. The sensor can be embodied as a two layer structure with the gas permeable matrix material intermixed with the chemochromic pigment in one layer and a second layer which provides a support or overcoat layer.

Bokerman, Gary (Inventor); Mohajeri, Nahid (Inventor); Muradov, Nazim (Inventor); Tabatabaie-Raissi, Ali (Inventor)

2013-01-01

12

Measuring Hydrogen Concentrations in Metals  

NASA Technical Reports Server (NTRS)

Commercial corrosion-measurement system adapted to electrochemical determination of hydrogen concentrations in metals. New technique based on diffusion of hydrogen through foil specimen of metal. In sample holder, hydrogen produced on one side of foil, either by corrosion reaction or by cathodic current. Hydrogen diffused through foil removed on other side by constant anode potential, which leads to oxidation of hydrogen to water. Anode current is measure of concentration of hydrogen diffusing through foil. System used to study hydrogen uptake, hydrogen elimination by baking, effect of heat treatment, and effect of electroplating on high-strength steels.

Danford, M. D.

1985-01-01

13

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

14

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

15

Metal salt catalysts for enhancing hydrogen spillover  

SciTech Connect

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

16

Effect of water on hydrogen permeability. [Stirling engines  

NASA Technical Reports Server (NTRS)

Doping of hydrogen with CO or CO2 was developed to reduce hydrogen permeation in Stirling engines by forming low permeability oxide coatings in the heater tubes. An end product of this process is water - which can condense in the cold parts of the engine system. If the water vapor is reduced to a low enough level, the hydrogen can reduce the oxide coating resulting in increased permeability. The equilibrium level of water (oxygen bearing gas) required to avoid reduction of the oxide coating was investigated. Results at 720 C and 13.8 MPa have shown that: (1) pure hydrogen will reduce the coating; (2) 500 ppm CO (500 ppm water equivalent) does not prevent the reduction; and (3) 500 ppm CO2 (1000 ppm water) appears to be close to the equilibrium level. Further tests are planned to define the equilibrium level more precisely and to extend the data to 820 C and 3.4, 6.9, and 13.8 MPa.

Hulligan, D. D.; Tomazic, W. A.

1984-01-01

17

Negative effective permeability in metal cluster photonic crystal  

NASA Astrophysics Data System (ADS)

We report a new metamaterial design made of a periodic array of metal nanowire clusters. For transverse-electric polarization, the metal nanowire supports an electric-dipole-like Mie resonance. When the nanowires are arranged into a regular array with sufficiently small spacing, the array exhibits a resonant behavior in effective permittivity. Furthermore, when the nanowires are arranged into a finite size cluster, they can support a magnetic Mie resonance in which magnetic field is strongly localized inside the cluster. Array of such clusters with sufficiently small spacing can then exhibit a resonant behavior in effective permeability. When the magnetic resonance is strong enough, permeability can become negative. The mechanism of producing negative permeability is similar to the ferroelectric and polaritonic photonic crystals but the metal cluster photonic crystal can exhibit stronger magnetic activity at optical frequencies. The availability of extensive synthesis and fabrication techniques for metal nanostructures makes the metal cluster photonic crystal a promising metamaterial platform for optical frequency operation.

Park, Wounjhang; Wu, Qi

2008-05-01

18

Hydrogen Permeability of Polymer Matrix Composites at Cryogenic Temperatures  

NASA Technical Reports Server (NTRS)

This paper presents experimental methods and results of an ongoing study of the correlation between damage state and hydrogen gas permeability of laminated composite materials under mechanical strains and thermal loads. A specimen made from IM-7/977-2 composite material has been mechanically cycled at room temperature to induce microcrack damage. Crack density and tensile modulus were observed as functions of number of cycles. Damage development was found to occur most quickly in the off-axis plies near the outside of the laminate. Permeability measurements were made after 170,000 cycles and 430,000 cycles. Leak rate was found to depend on applied mechanical strain, crack density, and test temperature.

Grenoble, Ray W.; Gates, Thomas S

2005-01-01

19

Hydrogen peroxide permeability of plasma membrane aquaporins of Arabidopsis thaliana.  

PubMed

Although aquaporins have been known to transport hydrogen peroxide (H(2)O(2)) across cell membranes, the H(2)O(2)-regulated expression patterns and the permeability of every family member of the plasma membrane intrinsic protein (PIP) toward H(2)O(2) have not been determined. This study investigates the H(2)O(2)-regulated expression levels of all plasma membrane aquaporins of Arabidopsis thaliana (AtPIPs), and determines the permeability of every AtPIP for H(2)O(2) in yeast. Hydrogen peroxide treatment of Arabidopsis down-regulated the expression of AtPIP2 subfamily in roots but not in leaves, whereas the expression of AtPIP1 subfamily was not affected by H(2)O(2) treatment. The growth and survival of yeast cells that expressed AtPIP2;2, AtPIP2;4, AtPIP2;5, or AtPIP2;7 was reduced in the presence of H(2)O(2), while the growth of yeast cells expressing any other AtPIP family member was not affected by H(2)O(2). These results show that only certain isoforms of AtPIPs whose expression is regulated by H(2)O(2) treatment are permeable for H(2)O(2) in yeast cells, and suggest that the integrated regulation of aquaporin expression by H(2)O(2) and the capacity of individual aquaporin to transport H(2)O(2) are important for plant response to H(2)O(2). PMID:21390558

Hooijmaijers, Cortwa; Rhee, Ji Ye; Kwak, Kyung Jin; Chung, Gap Chae; Horie, Tomoaki; Katsuhara, Maki; Kang, Hunseung

2012-01-01

20

Characterization of tungsten films and their hydrogen permeability  

SciTech Connect

Prediction of tritium migration and its retention within fusion reactors is uncertain due to a significant role of the structural disorder that is formed on the surface layer after plasma exposure. Tungsten films deposited by any of the suitable methods are always disordered and contain a high density of hydrogen traps. Experiments on such films with hydrogen isotopes present a suitable complementary method, which improves the picture of the hydrogen interaction with fusion relevant materials. The authors report on the morphology, composition, and structure of tungsten films deposited by the thermionic vacuum arc method on highly permeable Eurofer substrates. Subsequently, hydrogen permeation studies through these films were carried out in a wide pressure range from 20 to 1000 mbars at 400?°C. The final value of the permeation coefficient for four samples after 24?h at 400?°C was between P?=?3.2?×?10{sup ?14}?mol?H{sub 2}/(m?s?Pa{sup 0.5}) and P?=?1.1?×?10{sup ?15}?mol H{sub 2}/(m s Pa{sup 0.5}). From the time evolution of the permeation flux, it was shown that diffusivity was responsible for the difference in the steady fluxes, as solubility was roughly the same. This is confirmed by XRD data taken on these samples.

Nemani?, Vincenc, E-mail: vincenc.nemanic@ijs.si; Kova?, Janez [Jozef Stefan Institute, Jamova cesta 39, 1000 Ljubljana (Slovenia); Lungu, Cristian; Porosnicu, Corneliu [National Institute for Laser, Plasma and Radiation Physics, NILPRP, Magurele, Bucharest 077125 (Romania); Zajec, Bojan [Slovenian National Building and Civil Engineering Institute, Dimi?eva 12, 1000 Ljubljana (Slovenia)

2014-11-01

21

Composite Metal-hydrogen Electrodes for Metal-Hydrogen Batteries  

SciTech Connect

The purpose of this project is to develop and conduct a feasibility study of metallic thin films (multilayered and alloy composition) produced by advanced sputtering techniques for use as anodes in Ni-metal hydrogen batteries. The anodes could be incorporated in thin film solid state Ni-metal hydrogen batteries that would be deposited as distinct anode, electrolyte and cathode layers in thin film devices. The materials could also be incorporated in secondary consumer batteries (i.e. type AF(4/3 or 4/5)) which use electrodes in the form of tapes. The project was based on pioneering studies of hydrogen uptake by ultra-thin Pd-capped metal-hydrogen ratios exceeding and fast hydrogen charging and Nb films, these studies suggested that materials with those of commercially available metal hydride materials discharging kinetics could be produced. The project initially concentrated on gas phase and electrochemical studies of Pd-capped niobium films in laboratory-scale NiMH cells. This extended the pioneering work to the wet electrochemical environment of NiMH batteries and exploited advanced synchrotron radiation techniques not available during the earlier work to conduct in-situ studies of such materials during hydrogen charging and discharging. Although batteries with fast charging kinetics and hydrogen-metal ratios approaching unity could be fabricated, it was found that oxidation, cracking and corrosion in aqueous solutions made pure Nb films-and multiiayers poor candidates for battery application. The project emphasis shifted to alloy films based on known elemental materials used for NiMH batteries. Although commercial NiMH anode materials contain many metals, it was found that 0.24 µm thick sputtered Zr-Ni films cycled at least 50 times with charging efficiencies exceeding 95% and [H]/[M] ratios of 0.7-1.0. Multilayered or thicker Zr-Ni films could be candidates for a thin film NiMH battery that may have practical applications as an integrated power source for modern electronic devices.

Ruckman, M W; Wiesmann, H; Strongin, M; Young, K; Fetcenko, M

1997-04-01

22

Hydrogen Permeability of Incoloy 800H, Inconel 617, and Haynes 230 Alloys  

SciTech Connect

A potential issue in the design of the NGNP reactor and high-temperature components is the permeation of fission generated tritium and hydrogen product from downstream hydrogen generation through high-temperature components. Such permeation can result in the loss of fission-generated tritium to the environment and the potential contamination of the helium coolant by permeation of product hydrogen into the coolant system. The issue will be addressed in the engineering design phase, and requires knowledge of permeation characteristics of the candidate alloys. Of three potential candidates for high-temperature components of the NGNP reactor design, the hydrogen permeability has been documented well only for Incoloy 800H, but at relatively high partial pressures of hydrogen. Hydrogen permeability data have been published for Inconel 617, but only in two literature reports and for partial pressures of hydrogen greater than one atmosphere, far higher than anticipated in the NGNP reactor. The hydrogen permeability of Haynes 230 has not been published. To support engineering design of the NGNP reactor components, the hydrogen permeability of Inconel 617 and Haynes 230 were determined using a measurement system designed and fabricated at the Idaho National Laboratory. The performance of the system was validated using Incoloy 800H as reference material, for which the permeability has been published in several journal articles. The permeability of Incoloy 800H, Inconel 617 and Haynes 230 was measured in the temperature range 650 to 950 °C and at hydrogen partial pressures of 10-3 and 10-2 atm, substantially lower pressures than used in the published reports. The measured hydrogen permeability of Incoloy 800H and Inconel 617 were in good agreement with published values obtained at higher partial pressures of hydrogen. The hydrogen permeability of Inconel 617 and Haynes 230 were similar, about 50% greater than for Incoloy 800H and with similar temperature dependence.

Pattrick Calderoni

2010-07-01

23

Encapsulated Metal Hydride for Hydrogen Separation  

E-print Network

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

24

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

25

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

26

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

27

Hydrogen recovery with metal hydrides  

SciTech Connect

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

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

1982-03-01

28

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

29

Effect of oxide films on hydrogen permeability of candidate Stirling engine heater head tube alloys  

NASA Technical Reports Server (NTRS)

The effect of oxide films developed in situ from CO/CO2 doped hydrogen on high pressure hydrogen permeability at 820 C was studied on N-155, A-286, IN 800, 19-9DL, Nitronic 40, HS-188, and IN 718 tubing in a Stirling materials simulator. The hydrogen permeability decreased with increasing dopant levels of CO or CO2 and corresponding decreases in oxide porosity. Minor reactive alloying elements strongly influenced permeability. At high levels of CO or CO2, a liquid oxide formed on alloys with greater than 50 percent Fe. This caused increased permeability. The oxides formed on the inside tube walls were analyzed and their effective permeabilities were calculated.

Schuon, S. R.; Misencik, J. A.

1981-01-01

30

Hydrogen Permeability of a Polymer Based Composite Tank Material Under Tetra-Axial Strain  

NASA Technical Reports Server (NTRS)

In order to increase the performance of future expendable and reusable launch vehicles and reduce per-pound payload launch costs, weight reductions have been sought in vehicle components. Historically, the cryogenic propellant tanks for launch vehicles have been constructed from metal. These are some of the largest structural components in the vehicle and contribute significantly to the vehicles total dry weight. A successful replacement material will be conformable, have a high strength to weight ratio, and have a low gas-permeability to the cryogens being stored, i.e., oxygen and hydrogen. Polymer-based composites are likely candidates to fill this role. Polymer and polymer-based composites in general are known to have acceptable gas permeation properties in their as-cured state.1 The use of polymer-based composites for this application has been proposed for some time.2 Some successes have been reported with oxygen3, but other than the DC-XA experience, those with hydrogen have been limited. The primary reason for this has been the small molecular diameter of hydrogen, the lower temperatures of the liquid, and that the composite materials examined to date have all been susceptible to microcrack formation in response to the thermal-mechanical cycles experienced in the use-environment. There have been numerous accounts of composite materials with reported acceptable resistance to the formation of microcracks when exposed to various mechanical and/or thermal cycles. However, virtually all of these studies have employed uniaxial loads and there has been no discussion or empirical evidence pertaining to how these loads relate to the biaxial state of stress in the material in its use environment. Furthermore, many of these studies have suffered from a lack of instrument sensitivity in detecting hydrogen permeability, no standards, insufficient documentation of test conditions, testing of cycled materials in their unload state, and/or false assumptions about the nature of the microcracks in the material. This paper documents the results of hydrogen permeability testing on a Bismaleimide (BMI) based graphite fiber composite material under a variety of tetra-axial strain states.

Stokes, Eric H.

2003-01-01

31

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

32

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

33

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

34

Using permeable membranes to produce hydrogen and oxygen from water  

NASA Technical Reports Server (NTRS)

Concept may make it profitable to obtain hydrogen fuel from water. Laboratory tests have demonstrated that method enables decomposition of water several orders of magnitude beyond equilibrium state where only small amounts of free hydrogen are present.

Sanders, A. P.; Williams, R. J.; Downs, W. R.; Mcbryar, H.

1975-01-01

35

Metal-hydrogen bridge bonding of hydrocarbons on metal surfaces  

PubMed Central

Molecular orbital studies implicate multicenter metal-hydrogen-carbon interactions as contributors to the bonding of chemisorbed hydrocarbons on clean metal surfaces. The most stable geometries appear to be those that achieve the maximum multicenter bonding to the coordinately unsaturated metal atoms in the vicinity of the anchoring metal-carbon interaction. Energy differences between possible surface sites are of the same magnitude as stabilization energies for three-center bonding of hydrogen atoms to the metal surface. Accordingly, secondary interactions of hydrogen with neighboring metal atoms may be significant determining factors in surface structures. The model predictions are compared with known structures and are used to propose a mechanism for hydrocarbon reactions on metal surfaces. These metal-hydrogen-carbon interactions are presumed to be intermediate points or states in C—H bond-breaking processes. PMID:16593041

Gavin, Robert M.; Reutt, Janice; Muetterties, Earl L.

1981-01-01

36

Novel Composite Hydrogen-Permeable Membranes for Nonthermal Plasma Reactors for the Decomposition of Hydrogen Sulfide  

SciTech Connect

The goal of this experimental project was to design and fabricate a reactor and membrane test cell to dissociate hydrogen sulfide (H{sub 2}S) in a nonthermal plasma and to recover hydrogen (H{sub 2}) through a superpermeable multi-layer membrane. Superpermeability of hydrogen atoms (H) has been reported by some researchers using membranes made of Group V transition metals (niobium, tantalum, vanadium, and their alloys), but it was not achieved at the moderate pressure conditions used in this study. However, H{sub 2}S was successfully decomposed at energy efficiencies higher than any other reports for the high H{sub 2}S concentration and moderate pressures (corresponding to high reactor throughputs) used in this study.

Morris Argyle; John Ackerman; Suresh Muknahallipatna; Jerry Hamann; Stanislaw Legowski; Gui-Bing Zhao; Sanil John; Ji-Jun Zhang; Linna Wang

2007-09-30

37

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

38

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

39

Hydrogen transport membranes  

DOEpatents

Composite hydrogen transport membranes, which are used for extraction of hydrogen from gas mixtures are provided. Methods are described for supporting metals and metal alloys which have high hydrogen permeability, but which are either too thin to be self supporting, too weak to resist differential pressures across the membrane, or which become embrittled by hydrogen. Support materials are chosen to be lattice matched to the metals and metal alloys. Preferred metals with high permeability for hydrogen include vanadium, niobium, tantalum, zirconium, palladium, and alloys thereof. Hydrogen-permeable membranes include those in which the pores of a porous support matrix are blocked by hydrogen-permeable metals and metal alloys, those in which the pores of a porous metal matrix are blocked with materials which make the membrane impervious to gases other than hydrogen, and cermets fabricated by sintering powders of metals with powders of lattice-matched ceramic.

Mundschau, Michael V.

2005-05-31

40

METAL HYDRIDE HYDROGEN COMPRESSORS: A REVIEW  

SciTech Connect

Metal hydride (MH) thermal sorption compression is an efficient and reliable method allowing a conversion of energy from heat into a compressed hydrogen gas. The most important component of such a thermal engine the metal hydride material itself should possess several material features in order to achieve an efficient performance in the hydrogen compression. Apart from the hydrogen storage characteristics important for every solid H storage material (e.g. gravimetric and volumetric efficiency of H storage, hydrogen sorption kinetics and effective thermal conductivity), the thermodynamics of the metal-hydrogen systems is of primary importance resulting in a temperature dependence of the absorption/desorption pressures). Several specific features should be optimized to govern the performance of the MH-compressors including synchronisation of the pressure plateaus for multi-stage compressors, reduction of slope of the isotherms and hysteresis, increase of cycling stability and life time, together with challenges in system design associated with volume expansion of the metal matrix during the hydrogenation. The present review summarises numerous papers and patent literature dealing with MH hydrogen compression technology. The review considers (a) fundamental aspects of materials development with a focus on structure and phase equilibria in the metal-hydrogen systems suitable for the hydrogen compression; and (b) applied aspects, including their consideration from the applied thermodynamic viewpoint, system design features and performances of the metal hydride compressors and major applications.

Bowman Jr, Robert C [ORNL] [ORNL; Yartys, Dr. Volodymyr A. [Institute for Energy Technology (IFE)] [Institute for Energy Technology (IFE); Lototskyy, Dr. Michael V [University of the Western Cape, South Africa] [University of the Western Cape, South Africa; Pollet, Dr. B.G. [University of the Western Cape, South Africa

2014-01-01

41

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

42

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.

43

On the ground state of metallic hydrogen  

NASA Technical Reports Server (NTRS)

A proposed liquid ground state of metallic hydrogen at zero temperature is explored and a variational upper bound to the ground state energy is calculated. The possibility that the metallic hydrogen is a liquid around the metastable point (rs = 1.64) cannot be ruled out. This conclusion crucially hinges on the contribution to the energy arising from the third order in the electron-proton interaction which is shown here to be more significant in the liquid phase than in crystals.

Chakravarty, S.; Ashcroft, N. W.

1978-01-01

44

Plasmonic hydrogen sensing with nanostructured metal hydrides.  

PubMed

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

Wadell, Carl; Syrenova, Svetlana; Langhammer, Christoph

2014-12-23

45

Zeta potential of hollow fiber dialysis membranes and its effects on hydrogen phosphate ion permeability.  

PubMed

To clarify ion transport, dialysis membranes are evaluated in terms of zeta potential calculated by the Helmholtz-Smoluchowski equation from data on streaming potential delta E and pressure drop delta P, depending upon the operating conditions at which the values are measured. The objective of the current study is to design an improved method for measurement of delta E and delta P of hollow fiber dialysis membranes and to clarify the diffusive permeability of hydrogen phosphate ion. A polytetrafluoroethylene cylindrical cell with an inside diameter of 14 mm and a height of 10 mm was packed with 2,000-3,000 pieces of hollow fibers, and glass filters were set on either side of the cell. Deaerated water purified by ion exchange and reverse osmosis with an electric conductivity of approximately 150 microS/m was caused to flow in the hollows at 293 K to determine delta E and delta P. A good linear relationship between delta E and delta P and the reproducibility of the data was obtained and is shown in Figures 5 and 6, demonstrating the utility of the improved method to measure delta E and delta P, and the validity of the Helmholtz-Smoluchowski equation to calculate zeta potential from data on delta E and delta P. Hydrogen phosphate ion permeability increased with zeta potential for the membranes at about the same rate as pure water permeability. This indicates that hydrogen phosphate ion permeability depends upon the charge and internal structure of dialysis membranes. PMID:8268547

Suzuki, Y; Kanamori, T; Sakai, K

1993-01-01

46

Effect of formation of surface hydroxide on hydrogen permeability of iron membranes and hydrogen embrittlement of high-strength steels  

Microsoft Academic Search

UDC 541.138:669.788 permeability of iron membranes. The working cell consisted of two parts separated by a bipolar electrode, i.e., an iron membrane. In the polarization part of the cell, contained in the examined solution, the membrane was hydrogen-charged in the potentiostatic condition. A potential of +0.3 V (here and in the rest of the article the potential is given with

V. A. Marichev; V. V. Molokanov

1992-01-01

47

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

48

Final Report: Metal Perhydrides for Hydrogen Storage  

SciTech Connect

Hydrogen is a promising energy source for the future economy due to its environmental friendliness. One of the important obstacles for the utilization of hydrogen as a fuel source for applications such as fuel cells is the storage of hydrogen. In the infrastructure of the expected hydrogen economy, hydrogen storage is one of the key enabling technologies. Although hydrogen possesses the highest gravimetric energy content (142 KJ/g) of all fuels, its volumetric energy density (8 MJ/L) is very low. It is desired to increase the volumetric energy density of hydrogen in a system to satisfy various applications. Research on hydrogen storage has been pursed for many years. Various storage technologies, including liquefaction, compression, metal hydride, chemical hydride, and adsorption, have been examined. Liquefaction and high pressure compression are not desired due to concerns related to complicated devices, high energy cost and safety. Metal hydrides and chemical hydrides have high gravimetric and volumetric energy densities but encounter issues because high temperature is required for the release of hydrogen, due to the strong bonding of hydrogen in the compounds. Reversibility of hydrogen loading and unloading is another concern. Adsorption of hydrogen on high surface area sorbents such as activated carbon and organic metal frameworks does not have the reversibility problem. But on the other hand, the weak force (primarily the van der Waals force) between hydrogen and the sorbent yields a very small amount of adsorption capacity at ambient temperature. Significant storage capacity can only be achieved at low temperatures such as 77K. The use of liquid nitrogen in a hydrogen storage system is not practical. Perhydrides are proposed as novel hydrogen storage materials that may overcome barriers slowing advances to a hydrogen fuel economy. In conventional hydrides, e.g. metal hydrides, the number of hydrogen atoms equals the total valence of the metal ions. One LiH molecule contains one hydrogen atom because the valence of a Li ion is +1. One MgH2 molecule contains two hydrogen atoms because the valence of a Mg ion is +2. In metal perhydrides, a molecule could contain more hydrogen atoms than expected based on the metal valance, i.e. LiH1+n and MgH2+n (n is equal to or greater than 1). When n is sufficiently high, there will be plenty of hydrogen storage capacity to meet future requirements. The existence of hydrogen clusters, Hn+ (n = 5, 7, 9, 11, 13, 15) and transition metal ion-hydrogen clusters, M+(H2)n (n = 1-6), such as Sc(H2)n+, Co(H2)n+, etc., have assisted the development of this concept. Clusters are not stable species. However, their existence stimulates our approach on using electric charges to enhance the hydrogen adsorption in a hydrogen storage system in this study. The experimental and modeling work to verify it are reported here. Experimental work included the generation of cold hydrogen plasma through a microwave approach, synthesis of sorbent materials, design and construction of lab devices, and the determination of hydrogen adsorption capacities on various sorbent materials under various electric field potentials and various temperatures. The results consistently show that electric potential enhances the adsorption of hydrogen on sorbents. NiO, MgO, activated carbon, MOF, and MOF and platinum coated activated carbon are some of the materials studied. Enhancements up to a few hundred percents have been found. In general, the enhancement increases with the electrical potential, the pressure applied, and the temperature lowered. Theoretical modeling of the hydrogen adsorption on the sorbents under the electric potential has been investigated with the density functional theory (DFT) approach. It was found that the interaction energy between hydrogen and sorbent is increased remarkably when an electric field is applied. This increase of binding energy offers a potential solution for DOE when looking for a compromise between chemisorption and physisorption for hydrogen storage. Bonding of chemisorption is too

Hwang, J-Y.; Shi, S.; Hackney, S.; Swenson, D.; Hu, Y.

2011-07-26

49

Abundant Metals Give Precious Hydrogenation Performance  

SciTech Connect

Homogeneous catalysts based on precious (noble) metals have had a profound influence on modern synthetic methods, enabling highly selective synthesis of organic compounds but typically require precious metal catalysts (Ru, Rh, Ir, Pt, and Pd). Increasing efforts have been devoted to the design and discovery of homogeneous catalysts using base metals (e.g., Mn, Fe, Co, Ni, Cu, Mo). Morris et al. report Fe catalysts for asymmetric hydrogenation of C=O bonds. Cobalt catalysts for asymmetric hydrogenation of C=C bonds are described by Chirik et al., and Beller et al. report new nanoscale iron catalysts for synthesis of functionalized anilines through hydrogenation of nitroarenes. The author’s work in this area is supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

Bullock, R. Morris

2013-11-29

50

Noble Metals Would Prevent Hydrogen Embrittlement  

NASA Technical Reports Server (NTRS)

According to proposal, addition of small amounts of noble metals makes iron- and nickel-based alloys less susceptible to embrittlement by hydrogen. Metallurgists demonstrated adding 0.6 to 1.0 percent by weight of Pd or Pt eliminates stress/corrosion cracking in type 4130 steel. Proposal based on assumption that similar levels (0.5 to 1.0 weight percent) of same elements effective against hydrogen embrittlement.

Paton, N. E.; Frandsen, J. D.

1987-01-01

51

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

52

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

53

Microporous Metal Organic Materials for Hydrogen Storage  

Microsoft Academic Search

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

S. G. Sankar; Jing Li; Karl Johnson

2008-01-01

54

Critical fields of liquid superconducting metallic hydrogen  

NASA Technical Reports Server (NTRS)

Liquid metallic hydrogen, in a fully dissociated state, is predicted at certain densities to pass from dirty to clean and from type II to type I superconducting behavior as temperature is lowered. Previously announced in STAR as N82-29374

Jaffe, J.; Ashcroft, N. W.

1983-01-01

55

Optical properties of inhomogeneous metallic hydrogen plasmas  

E-print Network

We investigate the optical properties of hydrogen as it undergoes a transition from the insulating molecular to the metallic atomic phase, when heated by a pulsed laser at megabar pressures in a diamond anvil cell. Most current experiments attempt to observe this transition by detecting a change in the optical reflectance and/or transmittance. Theoretical models for this change are based on the dielectric function calculated for bulk, homogeneous slabs of material. Experimentally, one expects a hydrogen plasma density that varies on a length scale not substantially smaller than the wave length of the probing light. We show that taking this inhomogeneity into account can lead to significant corrections in the reflectance and transmittance. We present a technique to calculate the optical properties of systems with a smoothly varying density of charge carriers, determine the optical response for metallic hydrogen in the diamond anvil cell experiment and contrast this with the standard results. Analyzing recent e...

Broeck, N Van den; Tempere, J; Silvera, I F

2015-01-01

56

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

57

Treatment of dissolved metals using permeable reactive barriers  

Microsoft Academic Search

Permeable reactive barriers are a promising new approach to the treatment of dissolved contaminants in aquifers. This technology has progressed rapidly from laboratory studies to full-scale implementation over the past decade. Laboratory treatability studies indicate the potential for treatment of a large number of inorganic contaminants, including As, Cd, Cr, Cu, Hg, Fe, Mn, Mo, Ni, Pb, Se, Te, U,

D. W. BLOWES; C. J. PTACEK; S. G. BENNER; R. W. PULS

58

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

59

Powered by DFT: Screening methods that accelerate materials development for hydrogen in metals applications.  

PubMed

CONSPECTUS: Not only is hydrogen critical for current chemical and refining processes, it is also projected to be an important energy carrier for future green energy systems such as fuel cell vehicles. Scientists have examined light metal hydrides for this purpose, which need to have both good thermodynamic properties and fast charging/discharging kinetics. The properties of hydrogen in metals are also important in the development of membranes for hydrogen purification. In this Account, we highlight our recent work aimed at the large scale screening of metal-based systems with either favorable hydrogen capacities and thermodynamics for hydrogen storage in metal hydrides for use in onboard fuel cell vehicles or promising hydrogen permeabilities relative to pure Pd for hydrogen separation from high temperature mixed gas streams using dense metal membranes. Previously, chemists have found that the metal hydrides need to hit a stability sweet spot: if the compound is too stable, it will not release enough hydrogen under low temperatures; if the compound is too unstable, the reaction may not be reversible under practical conditions. Fortunately, we can use DFT-based methods to assess this stability via prediction of thermodynamic properties, equilibrium reaction pathways, and phase diagrams for candidate metal hydride systems with reasonable accuracy using only proposed crystal structures and compositions as inputs. We have efficiently screened millions of mixtures of pure metals, metal hydrides, and alloys to identify promising reaction schemes via the grand canonical linear programming method. Pure Pd and Pd-based membranes have ideal hydrogen selectivities over other gases but suffer shortcomings such as sensitivity to sulfur poisoning and hydrogen embrittlement. Using a combination of detailed DFT, Monte Carlo techniques, and simplified models, we are able to accurately predict hydrogen permeabilities of metal membranes and screen large libraries of candidate alloys, selections of which are described in this Account. To further increase the number of membrane materials that can be studied with DFT, computational costs need to be reduced either through methods development to break bottlenecks in the performance prediction algorithm, particularly related to transition state identification, or through screening techniques that take advantage of correlations to bypass constraints. PMID:24937509

Nicholson, Kelly M; Chandrasekhar, Nita; Sholl, David S

2014-11-18

60

Hydrogen Storage on Metal-Doped Ordered Mesoporous Carbons  

E-print Network

Hydrogen Storage on Metal-Doped Ordered Mesoporous Carbons Shuguang Deng New Mexico State Meeting, May 18, 2010 #12;Outline · Research group · Hydrogen storage: background and status · Synthesis of pure and metal-doped OMC · Characterization of metal-doped OMC · Hydrogen adsorption equilibrium

Johnson, Eric E.

61

Hydrogen isotope permeability through austenitic Cr sbnd Ni steels under neutron irradiation  

NASA Astrophysics Data System (ADS)

Experimental data on permeability and diffusion of protium and deuterium through austenitic Cr sbnd Ni steels 18Cr sbnd 10Ni sbnd Ti, 16Cr sbnd 11Ni sbnd 3Mo sbnd Ti and 25Cr sbnd 16Ni sbnd 6Mn sbnd N sbnd V are reported. The data were obtained with special equipment designed and installed at the research reactor IVV-2M. It was shown that parameters of hydrogen isotope transfer in Cr sbnd Ni steels increased substantially during irradiation by fast neutrons of the flux density f < 1.8 × 10 18 n/m 2s ( E ? 0.1 MeV). Radiation effects increase with a temperature decrease. Thus, at T < 673 K a relative increase of permeability can reach several orders with respect to its value. Deviations isotopic effects from their initial values and other radiation defects were observed.

Polosukhin, B. G.; Sulimov, E. M.; Zyrianov, A. P.; Kozlov, A. V.

1996-10-01

62

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

63

Cytotoxicity, permeability, and inflammation of metal oxide nanoparticles in human cardiac microvascular endothelial cells: cytotoxicity, permeability, and inflammation of metal oxide nanoparticles.  

PubMed

Wide applications and extreme potential of metal oxide nanoparticles (NPs) increase occupational and public exposure and may yield extraordinary hazards for human health. Exposure to NPs has a risk for dysfunction of the vascular endothelial cells. The objective of this study was to assess the cytotoxicity of six metal oxide NPs to human cardiac microvascular endothelial cells (HCMECs) in vitro. Metal oxide NPs used in this study included zinc oxide (ZnO), iron(III) oxide (Fe(2)O(3)), iron(II,III) oxide (Fe(3)O(4)), magnesium oxide (MgO), aluminum oxide (Al(2)O(3)), and copper(II) oxide (CuO). The cell viability, membrane leakage of lactate dehydrogenase, intracellular reactive oxygen species, permeability of plasma membrane, and expression of inflammatory markers vascular cell adhesion molecule-1, intercellular adhesion molecule-1, macrophage cationic peptide-1, and interleukin-8 in HCMECs were assessed under controlled and exposed conditions (12-24 h and 0.001-100 ?g/ml of exposure). The results indicated that Fe(2)O(3), Fe(3)O(4), and Al(2)O(3) NPs did not have significant effects on cytotoxicity, permeability, and inflammation response in HCMECs at any of the concentrations tested. ZnO, CuO, and MgO NPs produced the cytotoxicity at the concentration-dependent and time-dependent manner, and elicited the permeability and inflammation response in HCMECs. These results demonstrated that cytotoxicity, permeability, and inflammation in vascular endothelial cells following exposure to metal oxide nanoparticles depended on particle composition, concentration, and exposure time. PMID:21681618

Sun, Jing; Wang, Shaochuang; Zhao, Dong; Hun, Fei Han; Weng, Lei; Liu, Hui

2011-10-01

64

Permeable Reactive Biobarriers for the Containment of Heavy Metal  

E-print Network

and Environmental Engineering University of Arizona #12;What Is Acid Mine Drainage? Acid Mine Drainage (AMDPermeable 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

Fay, Noah

65

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

66

Hydrogen sulfide mitigates matrix metalloproteinase-9 activity and neurovascular permeability in hyperhomocysteinemic mice.  

PubMed

An elevated level of homocysteine (Hcy), known as hyperhomocysteinemia (HHcy), was associated with neurovascular diseases. At physiological levels, hydrogen sulfide (H(2)S) protected the neurovascular system. Because Hcy was also a precursor of hydrogen sulfide (H(2)S), we sought to test whether the H(2)S protected the brain during HHcy. Cystathionine-beta-synthase heterozygous (CBS+/-) and wild type (WT) mice were supplemented with or without NaHS (30 microM/L, H(2)S donor) in drinking water. Blood flow and cerebral microvascular permeability in pial vessels were measured by intravital microscopy in WT, WT+NaHS, CBS-/+ and (CBS-/+)+NaHS-treated mice. The brain tissues were analyzed for matrix metalloproteinase (MMP) and tissue inhibitor of metalloproteinase (TIMP) by Western blot and RT-PCR. The mRNA levels of CBS and cystathionine gamma lyase (CSE, enzyme responsible for conversion of Hcy to H(2)S) genes were measured by RT-PCR. The results showed a significant increase in MMP-2, MMP-9, TIMP-3 protein and mRNA in CBS (-/+) mice, while H(2)S treatment mitigated this increase. Interstitial localization of MMPs was also apparent through immunohistochemistry. A decrease in protein and mRNA expression of TIMP-4 was observed in CBS (-/+) mice. Microscopy data revealed increase in permeability in CBS (-/+) mice. These effects were ameliorated by H(2)S and suggested that physiological levels of H(2)S supplementation may have therapeutic potential against HHcy-induced microvascular permeability, in part, by normalizing the MMP/TIMP ratio in the brain. PMID:19913585

Tyagi, Neetu; Givvimani, Srikanth; Qipshidze, Natia; Kundu, Soumi; Kapoor, Shray; Vacek, Jonathan C; Tyagi, Suresh C

2010-01-01

67

A PERMEABLE REACTIVE BARRIER FOR TREATMENT OF HEAVY METALS: JOURNAL ARTICLE  

EPA Science Inventory

NRMRL-ADA-00327 Ludwig*, R., McGregor, R.G., Blowes, D.W., Benner, S.G., and Mountjoy, K. A Permeable Reactive Barrier for Treatment of Heavy Metals. Ground Water 40 (1):59-66 (2002) Historical storage of ore concentrate containing sulfid...

68

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

69

Heavy metal uptake and leaching from polluted soil using permeable barrier in DTPA-assisted phytoextraction.  

PubMed

Application of sewage sludge (SS) in agriculture is an alternative technique of disposing this waste. But unreasonable application of SS leads to excessive accumulation of heavy metals in soils. A column experiment was conducted to test the availability of heavy metals to Lolium perenne grown in SS-treated soils following diethylene triamine penta acetic acid (DTPA) application at rates of 0, 10 and 20 mmol kg(-1) soil. In order to prevent metal leaching in DTPA-assisted phytoextraction process, a horizontal permeable barrier was placed below the treated soil, and its effectiveness was also assessed. Results showed that DTPA addition significantly increased metal uptake by L. perenne shoots and metal leaching. Permeable barriers increased metal concentrations in plant shoots and effectively decreased metal leaching from the treated soil. Heavy metals in SS-treated soils could be gradually removed by harvesting L. perenne many times in 1 year and adding low dosage of DTPA days before each harvest. PMID:25354438

Zhao, Shulan; Shen, Zhiping; Duo, Lian

2015-04-01

70

Hydrogen embrittlement of weld metal of austenitic stainless steels  

Microsoft Academic Search

Using slow strain rate tests, the role of atomic hydrogen and hydrogen-induced martensites in hydrogen embrittlement of weld metals of type 308 and type 347L austenitic stainless steel (ASS) and type 304L plate was quantitatively studied. The results indicated that hydrogen-induced martensites formed in the three kinds of ASS when diffusible hydrogen concentration C0 exceeded 30 wppm, and the total

C. Pan; Y. J. Su; W. Y. Chu; Z. B. Li; D. T. Liang; L. J. Qiao

2002-01-01

71

[Hydrogen sulfide inhibits Ca(2+)-induced mitochondrial permeability transition pore opening in spontaneously hypertensive rats].  

PubMed

In experiments in vivo and in vitro on the mitochondria isolated from the control and spontaneously hypertensive rats (SHR) hearts, we studied the effects of a donor of hydrogen sulfide (H2S), NaHS, and H2S biosynthesis substrate, L-cysteine, on the sensitivity of the mitochondrial permeability transition pore (mPTP) opening to its natural inductor, Ca2+. We found that NaHS (10(-4), 10(-5) and 5 10(-5) mol/l) influenced the mitochondrial swelling in a concentration-dependent manner in control and spontaneously hypertensive rats. The H2S donor NaHS used in physiological concentrations (10(-6), 10(-5) and 5 10(-5) mol/l) exerted the inhibiting effect on the Ca(2+)-induced mPTP opening in control hearts (corresponding values of such effect were 31, 76, and 100%, respectively), while in spontaneously hypertensive rats hearts the protector effect of NaHS was observed only at its concentration of 10(-5) - 10(-4) mol/l. In experiments in vivo, single intraperitoneal injections of L-cysteine (10(-3) mol/kg) resulted in a decrease in the sensitivity of mPTP to it's inductor Ca2+ in control rats and SHR. In experiments in vivo in which we used a specific blocker of cystathionine-gamma-lyase, propargylglycine (10(-4) mol/kg), with the further injections of L-cysteine we observed a decrease in the threshold Ca2+ concentration (that induce the mitochondrial swelling) by three orders of magnitude in SHR, but in control rats did not effect of L-cysteine. Thus, both endogenous and exogenous hydrogen sulfide inhibits Ca(2+)-induced mitochondrial permeability transition pore opening, indicating its protective effect on pore formation in spontaneously hypertensive rats hearts. Therefore, our studies are indicative of the involvement of H2S in modulation of changes in the permeability of mitochondrial membranes, which can be an important regulatory factor in the development of cardiovascular diseases. PMID:23713344

Strutyns'ka, N A; Dorofeieva, N O; Vavilova, H L; Sahach, V F

2013-01-01

72

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

73

Degree of coverage by adsorbed hydrogen atoms of the surface of the passivating film on the metal at a crack tip in corrosion cracking of constructional materials  

SciTech Connect

This paper investigates the relationship to potential of the degree of coverage by hydrogen atoms of the surface of passivating films on the metal at a crack tip in the corrosion cracking of constructional materials. The method of determination of this is based on the quantitative concept of the hydrogen permeability alpha of the passivating films at a crack tip in corrosion cracking. The proposed method of determination is one of the consequences of the concept of hydrogen permeability of the passivating layers at a crack tip.

Marichev, V.A.

1985-07-01

74

Ordered pairing in liquid metallic hydrogen  

NASA Technical Reports Server (NTRS)

We study two possible types of pairing involving the protons of a proposed low-temperature liquid phase metallic hydrogen. Electron-proton pairing, which can result in an insulating phase, is investigated by using an approximate solution of an Eliashberg-type equation for the anomalous self-energy. A very low estimate of the transition temperature is obtained by including proton correlations in the effective interaction. For proton-proton pairing, we derive a new proton pair potential based on the Abrikosov wave function. This potential includes the electron-proton interaction to all orders and has a much larger well depth than is obtained with linear screening methods. This suggests the possibility of either a superfluid paired phase analogous to that in He-3, or alternatively a phase with true molecular pairing.

Carlsson, A. E.; Ashcroft, N. W.

1983-01-01

75

Novel Composite Hydrogen-Permeable Membranes for Non-Thermal Plasma Reactors for the Decomposition of Hydrogen Sulfide  

SciTech Connect

The goal of this experimental project is to design and fabricate a reactor and membrane test cell to dissociate hydrogen sulfide (H{sub 2}S) in a non-thermal plasma and recover hydrogen (H{sub 2}) through a superpermeable multi-layer membrane. Superpermeability of hydrogen atoms (H) has been reported by some researchers using membranes made of Group V transition metals (niobium, tantalum, vanadium, and their alloys), although it has yet to be confirmed in this study. Several pulsed corona discharge (PCD) reactors have been fabricated and used to dissociate H{sub 2}S into hydrogen and sulfur. Visual observation shows that the corona is not uniform throughout the reactor. The corona is stronger near the top of the reactor in argon, while nitrogen and mixtures of argon or nitrogen with H{sub 2}S produce stronger coronas near the bottom of the reactor. Both of these effects appear to be explainable base on the different electron collision interactions with monatomic versus polyatomic gases. A series of experiments varying reactor operating parameters, including discharge capacitance, pulse frequency, and discharge voltage were performed while maintaining constant power input to the reactor. At constant reactor power input, low capacitance, high pulse frequency, and high voltage operation appear to provide the highest conversion and the highest energy efficiency for H{sub 2}S decomposition. Reaction rates and energy efficiency per H{sub 2}S molecule increase with increasing flow rate, although overall H{sub 2}S conversion decreases at constant power input. Voltage and current waveform analysis is ongoing to determine the fundamental operating characteristics of the reactors. A metal infiltrated porous ceramic membrane was prepared using vanadium as the metal and an alumina tube. Experiments with this type of membrane are continuing, but the results thus far have been consistent with those obtained in previous project years: plasma driven permeation or superpermeability has not been observed. A new test cell specially designed to test the membranes has been constructed to provide basic science data on superpermeability.

Morris D. Argyle; John F. Ackerman; Suresh Muknahallipatna; Jerry C. Hamann; Stanislaw Legowski; Guibing Zhao; Sanil John

2006-09-30

76

Variations of hydrogen production and microbial community with heavy metals during fermentative hydrogen production  

Microsoft Academic Search

The effects of heavy metals on fermentative hydrogen production were examined based on metal type and concentration. Hydrogen production was stimulated by low concentrations of Cd and Zn but decreased at concentrations of 40 and 1mg\\/L, respectively. Hydrogen production was inhibited for the entire range of Cu tested. The order of toxic density was Cu>Zn>Cd at concentrations below 2mg\\/L but

Yoona Cho; Taejin Lee

2011-01-01

77

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

78

Novel Composite Hydrogen-Permeable Membranes for Non-Thermal Plasma Reactors for the Decomposition of Hydrogen Sulfide  

SciTech Connect

The goal of this experimental project is to design and fabricate a reactor and membrane test cell to dissociate hydrogen sulfide (H{sub 2}S) in a non-thermal plasma and recover hydrogen (H{sub 2}) through a superpermeable multi-layer membrane. Superpermeability of hydrogen atoms (H) has been reported by some researchers using membranes made of Group V transition metals (niobium, tantalum, vanadium, and their alloys), although it has yet to be confirmed in this study. A pulsed corona discharge (PCD) reactor has been fabricated and used to dissociate H{sub 2}S into hydrogen and sulfur. A nonthermal plasma cannot be produced in pure H{sub 2}S with our reactor geometry, even at discharge voltages of up to 30 kV, because of the high dielectric strength of pure H{sub 2}S ({approx}2.9 times higher than air). Therefore, H{sub 2}S was diluted in another gas with lower breakdown voltage (or dielectric strength). Breakdown voltages of H{sub 2}S in four balance gases (Ar, He, N{sub 2} and H{sub 2}) have been measured at different H{sub 2}S concentrations and pressures. Breakdown voltages are proportional to the partial pressure of H{sub 2}S and the balance gas. H{sub 2}S conversion and the reaction energy efficiency depend on the balance gas and H{sub 2}S inlet concentrations. With increasing H{sub 2}S concentrations, H{sub 2}S conversion initially increases, reaches a maximum, and then decreases. H{sub 2}S conversion in atomic balance gases, such as Ar and He, is more efficient than that in diatomic balance gases, such as N{sub 2} and H{sub 2}. These observations can be explained by the proposed reaction mechanism of H{sub 2}S dissociation in different balance gases. The results show that nonthermal plasmas are effective for dissociating H{sub 2}S into hydrogen and sulfur.

Morris D. Argyle; John F. Ackerman; Suresh Muknahallipatna; Jerry C. Hamann; Stanislaw Legowski; Guibling Zhao; Ji-Jun Zhang; Sanil John

2005-10-01

79

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

80

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

81

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

82

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

83

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

84

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

85

Permeable Reactive Treatment (PeRT) Wall for Rads and Metals. Innovative Technology Summary Report  

SciTech Connect

Organic and inorganic contamination of groundwater is widespread at Department of Energy (DOE), Department of Defense (DOD), other federal, and industrial sites. Contamination at a majority of these sites is present in shallow, unconfined aquifers, which may impact human health and the environment. Although there are many treatment methods, for organic contamination, relatively few technologies are effective in treating inorganic contamination, such as metals and radionuclide, in situ. Because metals are commonly adsorbed to clays and organic matter in an aquifer, groundwater pump and treat technology can be expensive and ineffective. Desorption of these metals into the aquifer is a long-term issue, difficult to address. A permeable reactive treatment (PeRT) wall, also referred to as a permeable reactive barrier, is a zone of reactive material that is placed in a contaminated aquifer so that the concentrations of dissolved inorganic contaminants are reduced as the groundwater passes through the material. The reactive material can be emplaced directly in the path of groundwater flow via trenching or injection or as a reactive liner in a landfill. This document contains information on the above-mentioned technology, including description, applicability, cost, and performance data.

None

2000-09-01

86

Thermochemical Ablation Therapy of VX2 Tumor Using a Permeable Oil-Packed Liquid Alkali Metal  

PubMed Central

Objective Alkali metal appears to be a promising tool in thermochemical ablation, but, it requires additional data on safety is required. The objective of this study was to explore the effectiveness of permeable oil-packed liquid alkali metal in the thermochemical ablation of tumors. Methods Permeable oil-packed sodium–potassium (NaK) was prepared using ultrasonic mixing of different ratios of metal to oil. The thermal effect of the mixture during ablation of muscle tissue ex vivo was evaluated using the Fluke Ti400 Thermal Imager. The thermochemical effect of the NaK-oil mixture on VX2 tumors was evaluated by performing perfusion CT scans both before and after treatment in 10 VX2 rabbit model tumors. VX2 tumors were harvested from two rabbits immediately after treatment to assess their viability using trypan blue and hematoxylin and eosin (H.E.) staining. Results The injection of the NaK–oil mixture resulted in significantly higher heat in the ablation areas. The permeable oil controlled the rate of heat released during the NaK reaction with water in the living tissue. Perfusion computed tomography and its parameter map confirmed that the NaK–oil mixture had curative effects on VX2 tumors. Both trypan blue and H.E. staining showed partial necrosis of the VX2 tumors. Conclusions The NaK–oil mixture may be used successfully to ablate tumor tissue in vivo. With reference to the controlled thermal and chemical lethal injury to tumors, using a liquid alkali in ablation is potentially an effective and safe method to treat malignant tumors. PMID:25885926

Guo, Ziyi; Zhang, Qiang

2015-01-01

87

Hydrogen evolution by a metal-free electrocatalyst  

NASA Astrophysics Data System (ADS)

Electrocatalytic reduction of water to molecular hydrogen via the hydrogen evolution reaction may provide a sustainable energy supply for the future, but its commercial application is hampered by the use of precious platinum catalysts. All alternatives to platinum thus far are based on nonprecious metals, and, to our knowledge, there is no report about a catalyst for electrocatalytic hydrogen evolution beyond metals. Here we couple graphitic-carbon nitride with nitrogen-doped graphene to produce a metal-free hybrid catalyst, which shows an unexpected hydrogen evolution reaction activity with comparable overpotential and Tafel slope to some of well-developed metallic catalysts. Experimental observations in combination with density functional theory calculations reveal that its unusual electrocatalytic properties originate from an intrinsic chemical and electronic coupling that synergistically promotes the proton adsorption and reduction kinetics.

Zheng, Yao; Jiao, Yan; Zhu, Yihan; Li, Lu Hua; Han, Yu; Chen, Ying; Du, Aijun; Jaroniec, Mietek; Qiao, Shi Zhang

2014-04-01

88

NOVEL COMPOSITE HYDROGEN-PERMEABLE MEMBRANES FOR NON-THERMAL PLASMA REACTORS FOR THE DECOMPOSITION OF HYDROGEN SULFIDE  

SciTech Connect

The goal of this experimental project is to design and fabricate a reactor and membrane test cell to dissociate hydrogen sulfide (H{sub 2}S) in a non-thermal plasma and recover hydrogen (H{sub 2}) through a superpermeable multi-layer membrane. Superpermeability of hydrogen atoms (H) has been reported by some researchers using membranes made of Group V transition metals (niobium, tantalum, vanadium, and their alloys), although it has yet to be confirmed in this study. Experiments involving methane conversion reactions were conducted with a preliminary pulsed corona discharge reactor design in order to test and improve the reactor and membrane designs using a non-toxic reactant. This report details the direct methane conversion experiments to produce hydrogen, acetylene, and higher hydrocarbons utilizing a co-axial cylinder (CAC) corona discharge reactor, pulsed with a thyratron switch. The reactor was designed to accommodate relatively high flow rates (655 x 10{sup -6} m{sup 3}/s) representing a pilot scale easily converted to commercial scale. Parameters expected to influence methane conversion including pulse frequency, charge voltage, capacitance, residence time, and electrode material were investigated. Conversion, selectivity and energy consumption were measured or estimated. C{sub 2} and C{sub 3} hydrocarbon products were analyzed with a residual gas analyzer (RGA). In order to obtain quantitative results, the complex sample spectra were de-convoluted via a linear least squares method. Methane conversion as high as 51% was achieved. The products are typically 50%-60% acetylene, 20% propane, 10% ethane and ethylene, and 5% propylene. First Law thermodynamic energy efficiencies for the system (electrical and reactor) were estimated to range from 38% to 6%, with the highest efficiencies occurring at short residence time and low power input (low specific energy) where conversion is the lowest (less than 5%). The highest methane conversion of 51% occurred at a residence time of 18.8 s with a flow rate of 39.4 x 10{sup -6} m{sup 3}/s (5 ft{sup 3}/h) and a specific energy of 13,000 J/l using niobium and platinum coated stainless steel tubes as cathodes. Under these conditions, the First Law efficiency for the system was 8%. Under similar reaction conditions, methane conversions were {approx}50% higher with niobium and platinum coated stainless steel cathodes than with a stainless steel cathode.

Morris D. Argyle; John F. Ackerman; Suresh Muknahallipatna; Jerry C. Hamann; Stanislaw Legowski; Ji-Jun Zhang; Guibing Zhao; Robyn J. Alcanzare; Linna Wang; Ovid A. Plumb

2004-07-01

89

Gas chromatographic separation of hydrogen isotopes using metal hydrides  

SciTech Connect

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

Aldridge, F.T.

1984-05-09

90

Fiber optic hydrogen detectors containing Mg-based metal hydrides  

Microsoft Academic Search

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

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

2007-01-01

91

Optical hydrogen sensing with metallic photonic crystals and plasmonic metamaterials  

Microsoft Academic Search

In this contribution, we are going to present two plasmonic concepts for hydrogen sensing. Our first concept is based on metallic photonic crystals, where a gold grating together with a thin layer of Pd in combination with a waveguide of WO3 can give a strong resonance in the extinction or reflection spectrum. Upon hydrogen exposure, the WO3 undergoes a refractive

H. Giessen; P. Mai; A. Tittl; Na Liu; C. Grossmann; A. Seidel; R. Orzekowsky; T. Meyrath

2010-01-01

92

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

93

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

94

Advective Transport Affecting Metal and Nutrient Distributions and Interfacial Fluxes in Permeable Sediments  

NASA Astrophysics Data System (ADS)

Our laboratory flume experiments demonstrate that advective porewater flows produce biogeochemical reaction zones in permeable sediments, leading to specific and reproducible complex patterns of Fe, Mn, and nutrients. Oxygenated water, forced into the sediment when boundary flows were deflected by protruding sediment structures, generated distinct zones of nitrification and ferric iron precipitation. This inflow was balanced by ammonium-rich porewater ascending from deeper sediment layers, thereby creating an anoxic channel where dissolved Fe 2+ and Mn 2+ could reach the surface. Between the zones of ferric iron precipitation and Fe 2+ upwelling, a layer with increased manganese oxide and solid phase Fe(II) concentrations formed, indicating redox reaction between these components. The establishment of topography on the previously smooth sediment surface reversed the net interfacial flux of solutes. While the smooth control core was found to be a sink for metals and nutrients, the sediment with mounds acted as a source for these substances. Our experiments show that in sandy sediment with an oxidised surface layer, reduced metal species can be released to the water column by flow-topography interactions. We conclude that advective transport processes constitute an important process controlling biogeochemical zonations and fluxes in permeable sea beds.

Huettel, M.; Ziebis, W.; Forster, S.; Luther, G. W., III

1998-02-01

95

Graphenes in the absence of metals as carbocatalysts for selective acetylene hydrogenation and alkene hydrogenation.  

PubMed

Catalysis makes possible a chemical reaction by increasing the transformation rate. Hydrogenation of carbon-carbon multiple bonds is one of the most important examples of catalytic reactions. Currently, this type of reaction is carried out in petrochemistry at very large scale, using noble metals such as platinum and palladium or first row transition metals such as nickel. Catalysis is dominated by metals and in many cases by precious ones. Here we report that graphene (a single layer of one-atom-thick carbon atoms) can replace metals for hydrogenation of carbon-carbon multiple bonds. Besides alkene hydrogenation, we have shown that graphenes also exhibit high selectivity for the hydrogenation of acetylene in the presence of a large excess of ethylene. PMID:25342228

Primo, Ana; Neatu, Florentina; Florea, Mihaela; Parvulescu, Vasile; Garcia, Hermenegildo

2014-01-01

96

Graphenes in the absence of metals as carbocatalysts for selective acetylene hydrogenation and alkene hydrogenation  

NASA Astrophysics Data System (ADS)

Catalysis makes possible a chemical reaction by increasing the transformation rate. Hydrogenation of carbon–carbon multiple bonds is one of the most important examples of catalytic reactions. Currently, this type of reaction is carried out in petrochemistry at very large scale, using noble metals such as platinum and palladium or first row transition metals such as nickel. Catalysis is dominated by metals and in many cases by precious ones. Here we report that graphene (a single layer of one-atom-thick carbon atoms) can replace metals for hydrogenation of carbon–carbon multiple bonds. Besides alkene hydrogenation, we have shown that graphenes also exhibit high selectivity for the hydrogenation of acetylene in the presence of a large excess of ethylene.

Primo, Ana; Neatu, Florentina; Florea, Mihaela; Parvulescu, Vasile; Garcia, Hermenegildo

2014-10-01

97

TRANSITION METAL ACTIVATION AND FUNCTIONALIZATION OF CARBON-HYDROGEN BONDS  

E-print Network

TRANSITION METAL ACTIVATION AND FUNCTIONALIZATION OF CARBON-HYDROGEN BONDS William D. Jones, New York 14627 FOR #12;DOE Report, 1998-2001 2 William D. Jones Overview of Research Accomplishments will extend this work to #12;DOE Report, 1998-2001 3 William D. Jones other early metal compounds during

Jones, William D.

98

Ordered ground states of metallic hydrogen and deuterium  

NASA Technical Reports Server (NTRS)

The physical attributes of some of the more physically distinct ordered states of metallic hydrogen and metallic deuterium at T = 0 and nearby are discussed. The likelihood of superconductivity in both is considered with respect to the usual coupling via the density fluctuations of the ions.

Ashcroft, N. W.

1981-01-01

99

Heat-actuated metal hydride hydrogen compressor testing  

SciTech Connect

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

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

1985-09-01

100

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

101

Production of negative hydrogen ions on metal grids  

NASA Astrophysics Data System (ADS)

Negative hydrogen ions are produced on a nickel grid with positive-ion irradiation. In order to investigate the production mechanism, a copper grid without the chemisorption of hydrogen atoms and positive helium ions without negative ionization are used for comparison. Positive hydrogen ions reflected on the metal surface obtain two electrons from the surface and become negatively ionized. It is found that the production yield of negative ions by desorption ionization of chemisorbed hydrogen atoms seems to be small, and the production is a minor mechanism.

Oohara, W.; Maetani, Y.; Takeda, Takashi; Takeda, Toshiaki; Yokoyama, H.; Kawata, K.

2015-03-01

102

Membrane for hydrogen recovery from streams containing hydrogen sulfide  

DOEpatents

A membrane for hydrogen recovery from streams containing hydrogen sulfide is provided. The membrane comprises a substrate, a hydrogen permeable first membrane layer deposited on the substrate, and a second membrane layer deposited on the first layer. The second layer contains sulfides of transition metals and positioned on the on a feed side of the hydrogen sulfide stream. The present invention also includes a method for the direct decomposition of hydrogen sulfide to hydrogen and sulfur.

Agarwal, Pradeep K.

2007-01-16

103

Permeability control of metal ions using temperature- and pH-sensitive gel membranes  

NASA Astrophysics Data System (ADS)

Temperature- and pH-sensitive copolymer gels were synthesized by the simultaneously occurring radiation-induced polymerization and self-bridging of acryloyl- L-proline methyl ester (A-ProOMe) with acrylic acid (AAc) in aqueous solutions. The gel swelling behavior and the metal permeation characteristic of its gel membrane were investigated with regard to very slight changes of temperature and pH. The pH threshold of the swelling of a copoly(A-ProOMe/AAc, 70/30 mol%) gel in the range of 5-30°C lay in the region between pH 4.0 and 5.0. The permeability results of metal ions showed that at 40°C the gel membrane blocks the permeation of lithium (Li) and cesium (Cs) ions at pH values lower than 4.75 and 4.60, respectively. The permselectivity ( PLi/Cs value) of the two metal ions at 30°C was also studied and, as a result, its value was obtained to be 1.33 at pH 4.65 and 30°C. This permeation study indicates that the selective metal separation of copoly(A-ProOMe/AAc) gel membranes can be controlled by changing temperature and pH values.

Hendri, John; Hiroki, Akihiro; Maekawa, Yasunari; Yoshida, Masaru; Katakai, Ryoichi

2001-03-01

104

A Selective, Cell-Permeable Optical Probe for Hydrogen Peroxide in Living Michelle C. Y. Chang, Arnd Pralle, Ehud Y. Isacoff, and Christopher J. Chang*,  

E-print Network

A Selective, Cell-Permeable Optical Probe for Hydrogen Peroxide in Living Cells Michelle C. Y-mail: chrischang@berkeley.edu Hydrogen peroxide is a major reactive oxygen species (ROS) in living organisms for H2O2 as a second messenger in cellular signal transduction.6-8 For example, peroxide bursts trigger

Pralle, Arnd

105

Hydrogen sulfide inhalation decreases early blood-brain barrier permeability and brain edema induced by cardiac arrest and resuscitation.  

PubMed

The effects of hydrogen sulfide (H2S) on blood-brain barrier (BBB) and brain edema after cardiac arrest (CA) and cardiopulmonary resuscitation (CPR) remain poorly understood. We investigated the effects of exogenous 80-p.p.m. H2S gas on BBB, brain water content, neurologic outcome, and survival rate after CA and CPR. Cardiopulmonary resuscitation followed CA induced in rats by ventricular fibrillation for 6?minutes. Results show that inhalation of 80-p.p.m. H2S significantly reduced the permeability of the BBB in both in the cortex and hippocampus at 24?hours after resuscitation. Hydrogen sulfide also lessened brain edema in the cortex and hippocampus, ameliorated neurologic outcome as evaluated by neurologic deficit score and tape removal test, and improved the 14-day survival rate. Hydrogen sulfide also attenuated CA and CPR-induced increases of matrix metalloproteinase-9 (MMP-9) activity and vascular endothelial growth factor (VEGF) expression, and increased the expression of angiogenin-1 (Ang-1). These results indicate that inhalation of 80-p.p.m. H2S immediately after CPR attenuated BBB permeability and brain edema, and improved neurologic outcome and 14-day survival of rats after CA. The therapeutic benefits of H2S could be associated with suppression of MMP-9 and VEGF expression and increased expression of Ang-1. PMID:25492119

Geng, Yingjie; Li, Eerdunmutu; Mu, Qier; Zhang, Yu; Wei, Xia; Li, Hangbing; Cheng, Long; Zhang, Bing

2015-03-01

106

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

107

Metal-functionalized silicene for efficient hydrogen storage.  

PubMed

First-principles calculations based on density functional theory are used to investigate the electronic structure along with the stability, bonding mechanism, band gap, and charge transfer of metal-functionalized silicene to envisage its hydrogen-storage capacity. Various metal atoms including Li, Na, K, Be, Mg, and Ca are doped into the most stable configuration of silicene. The corresponding binding energies and charge-transfer mechanisms are discussed from the perspective of hydrogen-storage compatibility. The Li and Na metal dopants are found to be ideally suitable, not only for strong metal-to-substrate binding and uniform distribution over the substrate, but also for the high-capacity storage of hydrogen. The stabilities of both Li- and Na-functionalized silicene are also confirmed through molecular dynamics simulations. It is found that both of the alkali metals, Li(+) and Na(+), can adsorb five hydrogen molecules, attaining reasonably high storage capacities of 7.75 and 6.9 wt %, respectively, with average adsorption energies within the range suitable for practical hydrogen-storage applications. PMID:24009141

Hussain, Tanveer; Chakraborty, Sudip; Ahuja, Rajeev

2013-10-21

108

Modeling of Hydrogen Retention in Metallic Plasma Facing Components  

NASA Astrophysics Data System (ADS)

The retention of hydrogen isotopes in the vacuum vessel of the ITER device is a critical plasma wall interaction issue for safety (tritium inventory) and operational reasons (hydrogen recycling). In particular, long-term retention of hydrogen have been observed both in the near-surface region and in the bulk of material in experiments reproducing ITER first wall conditions [1]. In this work, we present a modeling of the long-term hydrogen retention in a plasma exposed metallic walltaking into account processes both at the wall surface (material erosion, hydrogen adsorption, etc.) and in the bulk (hydrogen implantation, creation of trap sites, etc.). Using numerical simulations, the model is applied to analyze retention as a function of various parameters of the wall irradiated by hydrogen plasma for beryllium wall. Depth profiles of retained hydrogen for several ion energies as well as dependencies of retained hydrogen amount on wall temperature are obtained, showing good agreement with experimental data. The role of radiation-induced point-defects in the hydrogen retention as well as other aspects of retention are discussed in application to ITER conditions. [4pt] [1] R.A. Anderl, et al., J. Nucl. Mater. 273 (1999) 1

Guterl, Jerome; Smirnov, R.

2012-10-01

109

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

110

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

SciTech Connect

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 SO{sub 4}, Fe, trace metals, and alkalinity are observed. Populations of sulfate reducing bacteria are 10,000 times greater, and bacterial activity, as measured by dehydrogenase activity, is 10 times higher within the barrier compared to the up-gradient aquifer. Dissolved sulfide concentrations increase by 0.2--120 mg/L, and the isotope {sup 34}S is enriched relative to {sup 32}S in the dissolved phase SO{sub 4}{sup 2{minus}} within the barrier. Water chemistry, coupled with geochemical speciation modeling, indicates the pore water in the barrier becomes supersaturated with respect to amorphous Fe sulfide. Solid phase analysis of the reactive mixture indicates the accumulation of Fe monosulfide precipitates. Shifts in the saturated states of carbonate, sulfate, and sulfide minerals and most of the observed changes in water chemistry in the barrier and down-gradient aquifer can be attributed, either directly or indirectly, to bacterially mediated sulfate reduction.

Benner, S.G.; Blowes, D.W.; Herbert, R.B. Jr.; Ptacek, C.J. [Univ. of Waterloo, Ontario (Canada). Dept. of Earth Sciences] [Univ. of Waterloo, Ontario (Canada). Dept. of Earth Sciences; Gould, W.D. [CANMET, Ottawa, Ontario (Canada)] [CANMET, Ottawa, Ontario (Canada)

1999-08-15

111

Thermomechanics of hydrogen storage in metallic hydrides: modeling and analysis  

E-print Network

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

Tomas Roubicek; Giuseppe Tomassetti

2013-09-12

112

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

113

Treatment of percolate from metal sulfide mine tailings with a permeable reactive barrier of transformed red mud.  

PubMed

Metal sulfide tailings of the Sardinian (Italy) abandoned Baccu Locci arsenic mine show high concentrations of aluminum, arsenic, cadmium, copper, manganese, lead, and zinc in acid percolate (pH = 4) and have been classified as "dangerous waste." This paper shows that the release of toxic metals can be strongly reduced when the tailings are placed on a reactive permeable bed (7 wt %) of porous, alkaline pellets of transformed red mud (TRM). During a laboratory percolation test, two columns with 80 kg of waste, of which one contained a bottom layer of TRM pellets, were each alimented with 600 L of de-ionized water. Comparing pH, electroconductivity, metal, and sulfate concentrations of collected percolate from both columns demonstrates efficient neutralization (pH = 7.4) and removal of metals (80 to 99%) for the column with the permeable reactive bottom layer. PMID:20432649

Zijlstra, J J P; Dessì, R; Peretti, R; Zucca, A

2010-04-01

114

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

115

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

116

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

117

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

118

Nanoporous, Metal Carbide, Surface Diffusion Membranes for High Temperature Hydrogen Separations  

SciTech Connect

Colorado School of Mines (CSM) developed high temperature, hydrogen permeable membranes that contain no platinum group metals with the goal of separating hydrogen from gas mixtures representative of gasification of carbon feedstocks such as coal or biomass in order to meet DOE NETL 2015 hydrogen membrane performance targets. We employed a dual synthesis strategy centered on transition metal carbides. In the first approach, novel, high temperature, surface diffusion membranes based on nanoporous Mo{sub 2}C were fabricated on ceramic supports. These were produced in a two step process that consisted of molybdenum oxide deposition followed by thermal carburization. Our best Mo{sub 2}C surface diffusion membrane achieved a pure hydrogen flux of 367 SCFH/ft{sup 2} at a feed pressure of only 20 psig. The highest H{sub 2}/N{sub 2} selectivity obtained with this approach was 4.9. A transport model using “dusty gas” theory was derived to describe the hydrogen transport in the Mo{sub 2}C coated, surface diffusion membranes. The second class of membranes developed were dense metal foils of BCC metals such as vanadium coated with thin (< 60 nm) Mo{sub 2}C catalyst layers. We have fabricated a Mo{sub 2}C/V composite membrane that in pure gas testing delivered a H{sub 2} flux of 238 SCFH/ft{sup 2} at 600 °C and 100 psig, with no detectable He permeance. This exceeds the 2010 DOE Target flux. This flux is 2.8 times that of pure Pd at the same membrane thickness and test conditions and over 79% of the 2015 flux target. In mixed gas testing we achieved a permeate purity of ?99.99%, satisfying the permeate purity milestone, but the hydrogen permeance was low, ~0.2 SCFH/ft{sup 2}.psi. However, during testing of a Mo{sub 2}C coated Pd alloy membrane with DOE 1 feed gas mixture a hydrogen permeance of >2 SCFH/ft{sup 2}.psi was obtained which was stable during the entire test, meeting the permeance associated with the 2010 DOE target flux. Lastly, the Mo{sub 2}C/V composite membranes were shown to be stable for at least 168 hours = one week, including cycling at high temperature and alternating He/H{sub 2} exposure.

Way, J.; Wolden, Colin

2013-09-30

119

Composite metal-hydrogen electrodes for metal-hydrogen batteries. Final report, October 1, 1993--April 15, 1997  

SciTech Connect

The purpose of this project is to develop and conduct a feasibility study of metallic thin films (multilayered and alloy composition) produced by advanced sputtering techniques for use as anodes in Ni-metal hydrogen batteries that would be deposited as distinct anode, electrolyte and cathode layers in thin film devices. The materials could also be incorporated in secondary consumer batteries (i.e. type AF(4/3 or 4/5)) which use electrodes in the form of tapes. The project was based on pioneering studies of hydrogen uptake by ultra-thin Pd-capped Nb films, these studies suggested that materials with metal-hydrogen ratios exceeding those of commercially available metal hydride materials and fast hydrogen charging and discharging kinetics could be produced. The project initially concentrated on gas phase and electrochemical studies of Pd-capped niobium films in laboratory-scale NiMH cells. This extended the pioneering work to the wet electrochemical environment of NiMH batteries and exploited advanced synchrotron radiation techniques not available during the earlier work to conduct in-situ studies of such materials during hydrogen charging and discharging. Although batteries with fast charging kinetics and hydrogen-metal ratios approaching unity could be fabricated, it was found that oxidation, cracking and corrosion in aqueous solutions made pure Nb films and multilayers poor candidates for battery application. The project emphasis shifted to alloy films based on known elemental materials used for NiMH batteries. Although commercial NiMH anode materials contain many metals, it was found that 0.24 {mu}m thick sputtered Zr-Ni films cycled at least 50 times with charging efficiencies exceeding 95% and [H]/[M] ratios of 0.7-1.0. Multilayered or thicker Zr-Ni films could be candidates for a thin film NiMH battery that may have practical applications as an integrated power source for modern electronic devices.

Ruckman, M.W.; Strongin, M.; Weismann, H. [and others

1997-04-01

120

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

121

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

122

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 of carbon nanotubes undergo dramatic changes with hydrogen chemisorption from first principle calculations other isomers can be insulating. For both zigzag and armchair nanotubes, hydrogenation of each carbon

Yildirim, Taner

123

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

124

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

125

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

126

Hydrogenation of anthraquinone on metal-containing catalysts  

SciTech Connect

The present work studied the reaction of hydrogen activated on metal-containing catalysts (platinum black, Pt/Al/sub 2/O/sub 3/ (AP-15), and the hydride ZrNiH/sub 2.8/ with anthraquinone. The hydrogenation of anthraquinone bound into a strong donor-acceptor complex on the surface of Al/sub 2/O/sub 3/ and AP-15 and physically absorbed on silica gel was investigated. Results indicated that under conditions of mechanical mixing of silica gel with catalysts containing platinum or hydrides of intermetallic compounds in an atmosphere of hydrogen, anthraquinone physically adsorbed on silica gel is able to undergo hydrogenation at temperature above 100/sup 0/ C with formation of anthracene.

Lunin, V.V.; Markaryan, G.L.; Chetina, O.V.

1982-12-01

127

The metallization and superconductivity of dense hydrogen sulfide.  

PubMed

Hydrogen sulfide (H2S) is a prototype molecular system and a sister molecule of water (H2O). The phase diagram of solid H2S 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 H2O, but it was observed for H2S above 96 GPa. However, the metallic structure of H2S remains elusive, greatly impeding the understanding of its metallicity and the potential superconductivity. We have performed an extensive structural study on solid H2S 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 H2S with an estimated maximal transition temperature of ?80 K at 160 GPa, higher than those predicted for most archetypal hydrogen-containing compounds (e.g., SiH4, GeH4, etc.). PMID:24811660

Li, Yinwei; Hao, Jian; Liu, Hanyu; Li, Yanling; Ma, Yanming

2014-05-01

128

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

129

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

130

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

131

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

132

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

133

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

134

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

135

Organic substrates as electron donors in permeable reactive barriers for removal of heavy metals from acid mine drainage.  

PubMed

This research was conducted to select suitable natural organic substrates as potential carbon sources for use as electron donors for biological sulphate reduction in a permeable reactive barrier (PRB). A number of organic substrates were assessed through batch and continuous column experiments under anaerobic conditions with acid mine drainage (AMD) obtained from an abandoned lignite coal mine. To keep the heavy metal concentration at a constant level, the AMD was supplemented with heavy metals whenever necessary. Under anaerobic conditions, sulphate-reducing bacteria (SRB) converted sulphate into sulphide using the organic substrates as electron donors. The sulphide that was generated precipitated heavy metals as metal sulphides. Organic substrates, which yielded the highest sulphate reduction in batch tests, were selected for continuous column experiments which lasted over 200 days. A mixture of pig-farm wastewater treatment sludge, rice husk and coconut husk chips yielded the best heavy metal (Fe, Cu, Zn and Mn) removal efficiencies of over 90%. PMID:23437664

Kijjanapanich, P; Pakdeerattanamint, K; Lens, P N L; Annachhatre, A P

2012-12-01

136

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

137

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

138

Preparation of thin metallic titanium foils as hydrogen targets  

NASA Astrophysics Data System (ADS)

In a recently proposed study to resolve the discrepancy for the cross-section from the inverse reaction 21Ne(p,?) 18F, important in calculations of asymptotic giant branch (AGB) stellar nucleosynthesis, a hydrogen target was required. Another important consideration for studying this reaction involves the isotopic abundance of Ne measured in stellar silicon carbide (SiC) grains found in meteorites. The measurement consists of the time-reversed reaction in inverse kinematics 1H( 21Ne,?) 18F at the resonance energy. Using a stable 21Ne beam, high currents are anticipated requiring a robust hydrogen-containing target. A metal hydride foil would be more apt to withstand the bombardment over a plastic polyethylene target. For this purpose we chose titanium hydride, as the easily produced titanium foils can be reacted with hydrogen to produce the needed targets. Details of the methods of production as well as target characteristics and performance are discussed.

Greene, John P.; Young Lee, Hye; Becker, Hans-Werner

2010-02-01

139

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

140

Titanium oxide aerogels prepared from titanium metal and hydrogen peroxide  

Microsoft Academic Search

The reaction of hydrogen peroxide with excess titanium metal produces rigid titanium oxide aquagels. Subsequent solvent exchanges with ethanol and carbon dioxide, and supercritical drying produces the corresponding aerogels. The aerogels are translucent yellow in appearance, are amorphous to X-rays, and have a BET surface area of 350 m2\\/g. The empirical formula of the material, as prepared, is TiO3H2.7C0.35. Infrared

M. R Ayers; A. J Hunt

1998-01-01

141

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

142

Zero-Temperature Structures of Atomic Metallic Hydrogen  

NASA Astrophysics Data System (ADS)

Since the first prediction of an atomic metallic phase of hydrogen by Wigner and Huntington over 75 years ago, there have been many theoretical efforts aimed at determining the crystal structures of the zero-temperature phases. We present results from ab initio random structure searching with density functional theory performed to determine the ground state structures from 500 GPa to 5 TPa. We estimate that molecular hydrogen dissociates into a monatomic body-centered tetragonal structure near 500 GPa (rs= 1.225), which then remains stable to 2.5 TPa (rs= 0.969). At higher pressures, hydrogen stabilizes in an ...ABCABC... planar structure that is remarkably similar to the ground state of lithium, which compresses to the face-centered cubic lattice beyond 5 TPa (rs< 0.86). Our results provide a complete ab initio description of the atomic metallic crystal structures of hydrogen, resolving one of the most fundamental and long outstanding issues concerning the structures of the elements.

McMahon, Jeffrey; Ceperley, David

2011-03-01

143

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

144

Metal-assisted hydrogen storage on Pt-decorated single-walled carbon nanohorns  

E-print Network

Metal-assisted hydrogen storage on Pt-decorated single-walled carbon nanohorns Yun Liu a,b,*, Craig nanoparticles can assist in enhanced hydrogen storage on high-surface area supports are still under debate. Experimental mea- surements of metal-assisted hydrogen storage have been hampered by inaccurate estima- tion

Geohegan, David B.

145

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.

146

Predicted energy densitites for nickel-hydrogen and silver-hydrogen cells embodying metallic hydrides for hydrogen storage  

NASA Technical Reports Server (NTRS)

Simplified design concepts were used to estimate gravimetric and volumetric energy densities for metal hydrogen battery cells for assessing the characteristics of cells containing metal hydrides as compared to gaseous storage cells, and for comparing nickel cathode and silver cathode systems. The silver cathode was found to yield superior energy densities in all cases considered. The inclusion of hydride forming materials yields cells with very high volumetric energy densities that also retain gravimetric energy densities nearly as high as those of gaseous storage cells.

Easter, R. W.

1974-01-01

147

Alkali Metal Cation Effects on Hydrogen Uptake and Binding in Metal-Organic Frameworks  

E-print Network

attribute the behavior to structural changes accompanying framework reduction. The deployment of hydrogen with solid lithium metal.7 Since here we are interested in changing the cation and monitoring structure-177salbeit at 77 K.3 Extending the performance to ambient temperature will require substantial

148

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

149

Metal-hydrogen bond energies in protonated transition-metal complexes  

SciTech Connect

Proton affinities of 20 organotransition-metal complexes in the gas phase are reported. For 16 of these complexes protonation occurs on the metal center. The corresponding metal-hydrogen homolytic bond dissociation energies were determined and these data summarized. All proton affinities were determined by the techniques of ion cyclotron resonance spectroscopy, by examining proton-transfer reactions in mixtures with compounds of known base strength. Ionization potentials are taken from a variety of sources and experimental procedures, as noted. The site of protonation in several of these compounds has been determined by either gas-phase or solution-phase studies. These results and their interpretations are presented. (AT)

Stevens, A.E.; Beauchamp, J.L.

1981-01-14

150

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

151

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

152

A coupled theory for diffusion of hydrogen and large elastic-plastic deformations of metals  

E-print Network

A thermodynamically-consistent coupled-theory which accounts for diffusion of hydrogen, trapping of hydrogen, diffusion of heat, and large elastic-plastic deformations of metals is developed. Our theoretical framework ...

Di Leo, Claudio V

2012-01-01

153

Oxidative dissolution of nickel metal in hydrogenated hydrothermal solutions  

Microsoft Academic Search

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)andNi2+(aq)+nH2O=Ni(OH)n2-n(aq)+nH+(aq)where n=1 and 2. Gibbs energies associated with these reaction equilibria were determined from

S. E. Ziemniak; P. A. Guilmette; R. A. Turcotte; H. M. Tunison

2008-01-01

154

Metallization of ZnO nanowires from partial hydrogen adsorption  

NASA Astrophysics Data System (ADS)

First-principle density functional calculations of [0001] ZnO nanowires demonstrate that exposure of the mixed-terminated \\{01\\bar {1}0\\} side surfaces to atomic hydrogen can result in drastic changes of electronic properties. When the dangling bonds of the side surfaces are completely saturated by H atoms, the nanowires are insulating, with band gaps much higher than that of bulk solid. In contrast, the ZnO nanowires with only O atoms saturated by atomic H on the side surfaces are metallic. The physical mechanism for the remarkable changes is discussed. These theoretical results suggest a new way of band engineering ZnO nanowires.

Jia, Jianming; Shi, Daning; Zhao, Jijun; Wang, Baolin

2007-11-01

155

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

156

Distinct Metallization and Atomization Transitions in Dense Liquid Hydrogen  

NASA Astrophysics Data System (ADS)

We perform molecular dynamics simulations driven by accurate quantum Monte Carlo forces on dense liquid hydrogen. There is a recent report of a complete atomization transition between a mixed molecular-atomic liquid and a completely dissociated fluid in an almost unaccessible pressure range [Nat. Commun. 5, 3487 (2014)]. Here, instead, we identify a different transition between the fully molecular liquid and the mixed-atomic fluid at ˜400 GPa , i.e., in a much more interesting pressure range. We provide numerical evidence supporting the metallic behavior of this intermediate phase. Therefore, we predict that the metallization at finite temperature occurs in this partially dissociated molecular fluid, well before the complete atomization of the liquid. At high temperature this first-order transition becomes a crossover, in very good agreement with the experimental observation. Several systematic tests supporting the quality of our large scale calculations are also reported.

Mazzola, Guglielmo; Sorella, Sandro

2015-03-01

157

Distinct metallization and atomization transitions in dense liquid hydrogen.  

PubMed

We perform molecular dynamics simulations driven by accurate quantum Monte Carlo forces on dense liquid hydrogen. There is a recent report of a complete atomization transition between a mixed molecular-atomic liquid and a completely dissociated fluid in an almost unaccessible pressure range [Nat. Commun. 5, 3487 (2014)]. Here, instead, we identify a different transition between the fully molecular liquid and the mixed-atomic fluid at ?400??GPa, i.e., in a much more interesting pressure range. We provide numerical evidence supporting the metallic behavior of this intermediate phase. Therefore, we predict that the metallization at finite temperature occurs in this partially dissociated molecular fluid, well before the complete atomization of the liquid. At high temperature this first-order transition becomes a crossover, in very good agreement with the experimental observation. Several systematic tests supporting the quality of our large scale calculations are also reported. PMID:25815949

Mazzola, Guglielmo; Sorella, Sandro

2015-03-13

158

Preparation of thin metallic titanium foils as hydrogen targets.  

SciTech Connect

In a recently proposed study to resolve the discrepancy for the cross-section from the inverse reaction {sup 21}Ne(p,{alpha}){sup 18}F, important in calculations of asymptotic giant branch (AGB) stellar nucleosynthesis, a hydrogen target was required. Another important consideration for studying this reaction involves the isotopic abundance of Ne measured in stellar silicon carbide (SiC) grains found in meteorites. The measurement consists of the time-reversed reaction in inverse kinematics {sup 1}H({sup 21}Ne,{alpha}){sup 18}F at the resonance energy. Using a stable {sup 21}Ne beam, high currents are anticipated requiring a robust hydrogen-containing target. A metal hydride foil would be more apt to withstand the bombardment over a plastic polyethylene target. For this purpose we chose titanium hydride, as the easily produced titanium foils can be reacted with hydrogen to produce the needed targets. Details of the methods of production as well as target characteristics and performance are discussed.

Greene, J. P.; Lee, H. Y.; Becker, H.-W.; Physics; Ruhr Univ. Bochum

2010-02-11

159

Heavy metals removal and hydraulic performance in zero-valent iron\\/pumice permeable reactive barriers  

Microsoft Academic Search

Long-term behaviour is a major issue related to the use of zero-valent iron (ZVI) in permeable reactive barriers for groundwater remediation; in fact, in several published cases the hydraulic conductivity and removal efficiency were progressively reduced during operation, potentially compromising the functionality of the barrier. To solve this problem, the use of granular mixtures of ZVI and natural pumice has

Nicola Moraci; Paolo S. Calabrò

2010-01-01

160

Metal retention mechanisms for the Aznalcóllar permeable reactive barrier (SW Spain)  

Microsoft Academic Search

A permeable reactive barrier, consisting of a mixture of compost and cal- cite gravel, was built in Aznalcóllar (SW Spain) to treat acidic groundwa- ter containing zinc, aluminium and copper. Monitoring results show that practically no dissolved sulphate is reduced as water flows through the bar- rier, which has a residence time of about 1 to 2 days. Despite this

Oriol Gibert; Tobias Rötting; Joan de Pablo; José Luis Cortina; José Bolzicco; Jesús Carrera; Carlos Ayora

161

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

162

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

163

Effect Of Water On Permeation By Hydrogen  

NASA Technical Reports Server (NTRS)

Water vapor in working fluid equilibrates with permeability-reducing oxides in metal parts. Report describes study of effects of water on permeation of heater-head tubes by hydrogen in Stirling engine. Experiments performed to determine minimum concentration of oxygen and/or oxygen-bearing gas maintaining oxide coverage adequate for low permeability. Tests showed 750 ppm or more of water effective in maintaining stable, low permeability.

Tomazic, William A.; Hulligan, David

1988-01-01

164

All solution-processed inorganic/organic hybrid permeable metal-base transistor.  

PubMed

All solution-processed inorganic/organic hybrid permeable-base transistor (PMBT) based on nickel oxide emitter and P3HT collector is developed. Due to the high charge injection properties of nickel oxide and spontaneously formed nano-pinholes in the base electrode, the devices exhibit high common-base and common-emitter current gains up to 0.98 and 304, respectively with saturated output current. PMID:24811137

Kim, Jong H; Yu, Hyeonggeun; Liu, Rui; Kim, Do Young; So, Franky

2014-09-24

165

Selection of metallic materials for sucker rod pumps for hydrogen sulfide environment  

Microsoft Academic Search

This report presents general recommendations of metallic materials for the construction of sucker rod pumps for service in a hydrogen sulfide environment. Only pumps with one-piece barrels and metal plungers are considered.The recommended materials are presented in tabular form and in preferred order of listing for 9 different environments with varying degrees of abrasion and hydrogen sulfide corrosion. The materials

1973-01-01

166

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

167

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

168

High-Capacity Hydrogen Storage in Metal-Free Organic Molecular Crystals  

E-print Network

High-Capacity Hydrogen Storage in Metal-Free Organic Molecular Crystals Mina Yoon1, 2 and Matthias donor and acceptor molecules as a promising new class of hydrogen storage materials. Using quantum(Tetrathiafulvalene)/TCNQ(7,7,8,8-tetracyanoquinodimethane) become very efficient hydrogen storage media of high gravimetric

169

Microporous Metal Organic Materials: Promising Candidates as Sorbents for Hydrogen Storage  

E-print Network

Microporous Metal Organic Materials: Promising Candidates as Sorbents for Hydrogen Storage Long Pan coordination structures represent a promising new entry to the field of hydrogen storage materials.2 To fully that effectively store hydrogen are needed for use in fuel cell powered vehicles. Among the various candidate

Li, Jing

170

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.

171

Optimization of heat exchanger designs in metal hydride based hydrogen storage systems  

Microsoft Academic Search

Design of the heat exchanger in a metal hydride based hydrogen storage system influences the storage capacity, gravimetric hydrogen storage density, and refueling time for automotive on-board hydrogen storage systems. The choice of a storage bed design incorporating the heat exchanger and the corresponding geometrical design parameters is not obvious. A systematic study is presented to optimize the heat exchanger

Mandhapati Raju; Sudarshan Kumar

172

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

173

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

174

Noble metal ionic sites for catalytic hydrogen combustion: spectroscopic insights.  

PubMed

A catalytic hydrogen combustion reaction was carried out over noble metal catalysts substituted in ZrO(2) and TiO(2) in ionic form. The catalysts were synthesized by the solution combustion technique. The compounds showed high activity and CO tolerance for the reaction. The activity of Pd and Pt ion substituted TiO(2) was comparable and was higher than Pd and Pt ion substituted ZrO(2). The mechanisms of the reaction over the two supports were proposed by making use of the X-ray photoelectron spectroscopy and FT infrared spectroscopic observations. The reaction over ZrO(2) supported catalysts was proposed to take place by the utilization of the surface hydroxyl groups while the reaction over TiO(2) supported catalysts was hypothesized to be a hybrid mechanism utilizing surface hydroxyl groups and the lattice oxygen. PMID:21060910

Deshpande, Parag A; Madras, Giridhar

2011-01-14

175

Bi-metallic Catalyst for Hydrogen Sorption of Magnesium Hydride  

NASA Astrophysics Data System (ADS)

This thesis is focused on the design of a series of bi-metallic catalyst for enhancing the hydrogen sorption kinetics of magnesium hydride. We have utilized thin films deposited by magnetron sputtering technique as model systems to study various alloys and compositions. It has been known that the transition metals additions can catalyze the sorption reaction. We hypothesized that the addition of bi-metallic catalysts has superior effect over the single metal additions. In order to obtain baselines, we have examined the effect of single transition elements on the kinetics of the transformation. In our first attempt, we showed that the sorption behavior of the ternary Mg-Fe-Ti alloy is significantly improved compared to its binary alloy counterparts. Using this ternary system, we were able to perform absorption/desorption tests up to 100 cycles at a low temperature of 200°C. We further investigated the validity of our hypothesis by performing the similar cycling measurements on two more ternary systems, being Mg-Fe-V and Mg-Cr-Ti. We showed that both systems exhibit remarkably enhanced sorption characteristics over the binary alloys. In our last attempt, we examined the effect of Cr-V bi-metallic catalyst on the hydrogen sorption behavior of MgH2. The catalyst was so potent that we were able to absorb the activated samples at room temperature and a low hydrogen pressure of 2 bar. We also performed cycling tests on this systems at 300°C with the desorption pressure of 1 bar. In order to explore the microstructural origins of such performance, we utilized transmission electron microscopy (TEM) and X-ray diffraction techniques. Through a systematic grain size measurement, we found that the MgH2 in ternary systems is more resistant to grain coarsening compared to binary alloys. The cryo-stage TEM analysis of the partially absorbed sample shed light on the transformation mechanism of Mg to MgH2. It revealed the absence of a core-shell structure which is mostly assumed as the absorption mechanism for MgH 2. The cryo-stage TEM results also showed the presence of twins in the hydride microstructure which is most likely due to the fast rate of the absorption transformation. We also performed a detailed kinetics analysis in the framework of Johnson-Mehl-Avrami (JMA) model. We found that the activation energy value has a strong dependency on the driving force for the reaction. Using the value of activation energy and the calculated Avrami exponent, the possible rate limiting step for the absorption and desorption reactions was proposed. By combining the microstructural observations and the kinetics analysis we proposed a mechanism for the Mg to MgH2 transformation.

Zahiri-Sabzevar, Beniamin

176

New vistas in the determination of hydrogen in aerospace engine metal alloys  

NASA Technical Reports Server (NTRS)

The application of diffusion theory to the analysis of hydrogen desorption data has been studied. From these analyses, important information concerning hydrogen solubilities and the nature of the hydrogen distributions in the metal has been obtained. Two nickel base alloys, Rene' 41 and Waspaloy, and one ferrous alloy, 4340 steel, were studied in this work. For the nickel base alloys, it was found that the hydrogen distributions after electrolytic charging conformed closely to those which would be predicted by diffusion theory. The hydrogen distributions in electrolytically charged 4340 steel, on the other hand, were essentially uniform in nature, which would not be predicted by diffusion theory. Finally, it has been found that the hydrogen desorption is completely explained by the nature of the hydrogen distribution in the metal, and that the 'fast' hydrogen is not due to surface and subsurface hydride formation, as was originally proposed.

Danford, M. D.

1986-01-01

177

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

178

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

179

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

180

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

181

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

182

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

183

Heavy metals removal and hydraulic performance in zero-valent iron/pumice permeable reactive barriers.  

PubMed

Long-term behaviour is a major issue related to the use of zero-valent iron (ZVI) in permeable reactive barriers for groundwater remediation; in fact, in several published cases the hydraulic conductivity and removal efficiency were progressively reduced during operation, potentially compromising the functionality of the barrier. To solve this problem, the use of granular mixtures of ZVI and natural pumice has recently been proposed. This paper reports the results of column tests using aqueous nickel and copper solutions of various concentrations. Three configurations of reactive material (ZVI only, granular mixture of ZVI and pumice, and pumice and ZVI in series) are discussed. The results clearly demonstrate that iron-pumice granular mixtures perform well both in terms of contaminant removal and in maintaining the long-term hydraulic conductivity. Comparison with previous reports concerning copper removal by ZVI/sand mixtures reveals higher performance in the case of ZVI/pumice. PMID:20643500

Moraci, Nicola; Calabrò, Paolo S

2010-11-01

184

Energetics of hydrogen coverage on group VIII transition metal surfaces and a kinetic model for adsorptiondesorption  

E-print Network

Energetics of hydrogen coverage on group VIII transition metal surfaces and a kinetic model packed surface for all nine group VIII transition metals as a function of surface coverage using quantum transition metals, leading to results consistent with available surface science studies. We then use

Goddard III, William A.

185

First-row transition metal dichalcogenide catalysts for hydrogen evolution reaction  

E-print Network

First-row transition metal dichalcogenide catalysts for hydrogen evolution reaction Desheng Kong,a Judy J. Cha,a Haotian Wang,b Hye Ryoung Leec and Yi Cui*ad A group of first-row transition metal introduce a group of highly active HER cata- lysts from rst-row transition metal dichalcogenides

Cui, Yi

186

The permeability of silicone rubber to metal compounds: relevance to implanted devices.  

PubMed

Most implanted electrical devices use encapsulant as insulation. The encapsulant may remain functional for many years, bonded to the metallic surfaces, but eventually become partly detached allowing corrosion to occur. To understand whether the corrosion products will cause toxic effects, we need to know how quickly they will permeate through the encapsulant. In these experiments, silicone capsules (the encapsulant) containing metal compounds were left in jars of initially pure water for 6 months, and the concentration of the metal in the water was measured. The amount of metal depended on the type of compound; for the organometallic compounds tested, permeation was very rapid. However, for most of the other compounds, whether oxides or salts, the amount of metal was below the control level and therefore could have been the result of contamination. These compounds were tin sulfate and oxide (<10²), lead nitrate and oxide (<10²), copper sulfate (<10³), and nitrates of bismuth (<10¹), chrome (<10²), nickel (<10³) and zinc (<10²). The numbers in brackets are the maximum mass (ng) of permeated metal after 6 months. Three silver compounds were tested but without proper controls; however, the amount of permeated silver appeared to be low: silver oxide (1.3 × 10²), silver nitrate (6.3 × 10¹), and silver chloride (6 × 10?). The resolution of this method is limited by contamination that is detected by control capsules. The conclusion is that compounds that are likely corrosion products permeate through silicone encapsulant at a low rate and seem unlikely to cause toxic effects. PMID:22213669

Donaldson, Nick; Baviskar, Preeti; Cunningham, Jim; Wilson, Darren

2012-03-01

187

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

188

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)

2011-01-01

189

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

190

Polymerization effect of electrolytes on hydrogen-bonding cryoprotectants: ion-dipole interactions between metal ions and glycerol.  

PubMed

Protectants which are cell membrane permeable, such as glycerol, have been used effectively in the cryopreservation field for a number of decades, for both slow cooling and vitrification applications. In the latter case, the glass transition temperature (Tg) of the vitrification composition is key to its application, dictating the ultimate storage conditions. It has been observed that the addition of some electrolytes to glycerol, such as MgCl2, could elevate the Tg of the mixture, thus potentially providing more storage condition flexibility. The microscopic mechanisms that give rise to the Tg-enhancing behavior of these electrolytes are not yet well understood. The current study focuses on molecular dynamics simulation of glycerol mixed with a variety of metal chlorides (i.e., NaCl, KCl, MgCl2, and CaCl2), covering a temperature range that spans both the liquid and glassy states. The characteristics of the ion-dipole interactions between metal cations and hydroxyl groups of glycerol were analyzed. The interruption of the original hydrogen-bonding network among glycerol molecules by the addition of ions was also investigated in the context of hydrogen-bonding quantity and lifetime. Divalent metal cations were found to significantly increase the Tg by strengthening the interacting network in the electrolyte/glycerol mixture via strong cation-dipole attractions. In contrast, monovalent cations increased the Tg insignificantly, as the cation-dipole attraction was only slightly stronger than the original hydrogen-bonding network among glycerol molecules. The precursor of crystallization of NaCl and KCl was also observed in these compositions, potentially contributing to weak Tg-enhancing ability. The Tg-enhancing mechanisms elucidated in this study suggest a structure-enhancing role for divalent ions that could be of benefit in the design of protective formulations for biopreservation purposes. PMID:25405831

Weng, Lindong; Elliott, Gloria D

2014-12-11

191

Lab scale experiments for permeable reactive barriers against contaminated groundwater with ammonium and heavy metals using clinoptilolite (01-29B)  

Microsoft Academic Search

Batch tests and column tests were performed to determine the design factors for permeable reactive barriers (PRBs) against the contaminated groundwater by ammonium and heavy metals. Clinoptilolite, one of the natural zeolites having excellent cation exchange capacity (CEC), was chosen as the reactive material. In the batch tests, the reactivity of clinoptilolite to ammonium, lead, and copper was examined by

Jun-Boum Park; Seung-Hak Lee; Jae-Won Lee; Chae-Young Lee

2002-01-01

192

Cobalt precursors for high-throughput discovery of base metal asymmetric alkene hydrogenation catalysts.  

PubMed

Asymmetric hydrogenation of alkenes is one of the most widely used methods for the preparation of single enantiomer compounds, especially in the pharmaceutical and agrochemical industries. For more than four decades, precious metal complexes containing rhodium, iridium, and ruthenium have been predominantly used as catalysts. Here, we report rapid evaluation of libraries of chiral phosphine ligands with a set of simple cobalt precursors. From these studies, base metal precatalysts have been discovered for the hydrogenation of functionalized and unfunctionalized olefins with high enantiomeric excesses, demonstrating the potential utility of more earth-abundant metals in asymmetric hydrogenation. PMID:24288328

Friedfeld, Max R; Shevlin, Michael; Hoyt, Jordan M; Krska, Shane W; Tudge, Matthew T; Chirik, Paul J

2013-11-29

193

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

194

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

195

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

196

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

197

Leaching of Metals from Fly ash-Amended Permeable Reactive Barriers Doina L. Morar 1  

E-print Network

applications for remediation of contaminated groundwater. However, leaching of metals from the coal fly ashes is stockpiled in landfills (ACAA 2011). For example, the twelve power plants in Maryland annually generate the last decade due to the implementation of low nitrogen oxide burners in coal-burning power plants

Aydilek, Ahmet

198

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

199

Hydrogen storage in the form of metal hydrides  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

200

Interaction of hydrogen with metal nitrides and imides  

Microsoft Academic Search

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

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

2002-01-01

201

[Hydrogen sulfide inhibits Ca(2+)-induced mitochondrial permeability transition pore opening in adult and old rat heart].  

PubMed

In experiments in vivo and in vitro on the mitochondria isolated from adult and old rat hearts, we studied the effects of a donor of hydrogen sulfide (H2S), NaHS, and H2S biosynthesis substrate, L-cysteine, on the sensitivity of the mitochondrial permeability transition pore (mPTP) opening to its natural inductor, Ca(2+). We found that NaHS (10(-12) to 10(-4) mol/l) influenced mitochondrial swelling in a concentration-dependent manner. It was also demonstrated that the addition of NaHS (10(-12) to 10(-8) mol/l) to the calcium-free medium resulted in moderate a swelling of mitochondria from both adult and old rat hearts. At 10(-10) mol/l NaHS, the maximal values of the mitochondrial swelling observed in both adult and old hearts were 11 and 15 ,%, respectively. A specific inhibitor of KATP channels, 5-hydroxydecanoate (5-HD; 10(-4) mol/l) decreased the mitochondrial swelling in the presence of NaHS (10)-10) mol/l), which can be indicative of the contribution of these channels to the calcium-independent conductance of the mitochondrial membranes in the rat hearts. The H2S donor NaHS used in physiological concentrations (10(-6), 10(-5) and 5 10(-5) mol/l) exerted the inhibiting effect on the Ca(2+)-induced mPTP opening in adult hearts (corresponding values of such effect were 31, 76, and 77%, respectively), while in old hearts the protector effect of NaHS was observed only at its concentration of 10(-5) mol/l. Therefore, the donor of H2S used in the tested concentrations (10(-12) to 10(-4) mol/l) exerted ambiguous effect on the mitochondrial swelling: low concentrations of NaHS (10(-12) to 10(-8) mol/l) increased the mitochondrial swelling, while its physiological concentrations (10(-6) to 5 10(-5) mol/l) exerted the protective effect on Ca(2+)-induced mitochondrial swelling in adult and old hearts. Pre-incubation of isolated mitochondria with 5-HD (10(-4) mol/l) resulted in a decrease in the protective effect evoked by NaHS (10(-5) mol/l) on Ca(2+)-induced mPTP opening, which is indicative of the possible involvement of mitochondrial KATP-channels in the H2S-dependent inhibition of mPTP formation in both adult and old rat hearts. In experiments in vivo, single intraperitoneal injections of both NaHS (10(4) mol/kg) and L-cysteine ((10(-3) mol/kg) resulted in a decrease in the sensitivity of mPTP to its inductor Ca(2+) in adult and old rat hearts. The action of L-cysteine, as compared with that of NaHS, was more effective in prevention of Ca(2+)-induced mitochondrial swelling. We observed a rise in Ca(2+) concentration by one order of magnitude, which evoked the mitochondrial swelling in adult and old hearts. In experiments in vivo in which we used a specific blocker ofcystathionine-g-lyase, propargylglycine (10(-4) mol/kg) that is involved in the synthesis of H2S, we observed an increase in the sensitivity of mPTP opening in old hearts because of a decrease in the threshold Ca(2+) concentration required for mitochondrial swelling by two orders of magnitude. We demonstrate the involvement of endogenous H2S in the control of mPTP formation in adult and old hearts. Our studies are indicative of the involvement of H2S in modulation of changes in the permeability of mitochondrial membranes, which can be an important regulatory factor in the development of cardiovascular diseases. PMID:22420153

Strutyns'ka, N A; Semenykhina, O M; Chorna, S V; Vavilova, H L; Sahach, V F

2011-01-01

202

Metal-inorganic-organic matrices as efficient sorbents for hydrogen storage.  

PubMed

Stabilization of metal nanoparticles (MNPs) without re-aggregation is a major challenge. An unprecedented strategy is developed for achieving high dispersion of copper(0) or palladium(0) on montmorillonite-supported diethanolamine or thioglycerol. This results in novel metal-inorganic-organic matrices (MIOM) that readily capture hydrogen at ambient conditions, with easy release under air stream. Hydrogen retention appears to involve mainly physical interactions, slightly stronger on thioglycerol-based MIOM (S-MIOM). Thermal enhancement of desorption suggests also a contribution of chemical interactions. The increase of hydrogen uptake with prolonged contact times arises from diffusion hindrance, which appears to be beneficial by favoring hydrogen entrapment. Even with compact structures, MIOMs act as efficient sorbents with much higher efficiency factor (1.14-1.17?mmol?H?2?m(-2) ) than many other sophisticated adsorbents reported in the literature. This opens new prospects for hydrogen storage and potential applications in microfluidic hydrogenation reactions. PMID:25663131

Azzouz, Abdelkrim; Nousir, Saadia; Bouazizi, Nabil; Roy, René

2015-03-01

203

Rates of sulfate reduction and metal sulfide precipitation in a permeable reactive barrier  

Microsoft Academic Search

A full-scale reactive barrier, utilizing bacterially mediated SO4 reduction to promote metal sulfide precipitation and alkalinity generation, was installed in August 1995 at the Nickel Rim mine site near Sudbury, Ontario. Monitoring of groundwater chemistry over a 3-a period allows assessment of long-term reactive barrier performance. The overall rate of SO4 removal within the barrier declined with time by 30%

S. G. Benner; D. W. Blowes; C. J. Ptacek; K. U. Mayer

2002-01-01

204

Dissociation of hydrogen molecules on metal filaments in H- ion sources  

Microsoft Academic Search

Atomic hydrogen causes significant deterioration of H- ion source characteristics through vibration-translation relaxation of vibrationally excited H2 molecules. We propose a method for atomic hydrogen density determination based on its selective absorption by a metal (Ta in our case) covered with a monoatomic non-metal film. The temperature-dependence of the dissociation rate by the Ta filament and the contribution of dissociation

A. I. Livshits; F. El Balghiti; M. Bacal

1994-01-01

205

The use of silver decoration technique in the study of hydrogen transport in metallic materials  

Microsoft Academic Search

The silver decoration technique proposed by Sch?ber and Dieker[10] for revealing local hydrogen flux in terms of microstructural characteristics is reinterpreted. The results of decoration\\u000a tests in polycrystalline nickel and palladium with and without hydrogen charging show that hydrogen flux is not solely responsible,\\u000a nor even a prerequisite, for the deposition of silver crystals on metal surfaces. There is, consequently,

J. Yao; J. R. Cahoon

1990-01-01

206

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 Storage Liqing Ma, Jeong Yong Lee, Jing Li, and Wenbin Lin*, Department of Chemistry, CB#3290, Uni. The porosity and hydrogen uptake of the frameworks were determined by gas adsorption experiments. A wide range

Li, Jing

207

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

208

Metal Oxide Nanomaterials for Solar Energy to Hydrogen Fuel Conversion  

NASA Astrophysics Data System (ADS)

Photoactive metal oxide nanomaterials enable full or partial water splitting by reducing water to hydrogen and oxidizing water into oxygen through transfer of photogenerated electrons and holes, respectively, upon absorption of light of certain frequencies. Scanning Transmission Electron Microscopy (STEM) is one of the useful instruments to study these materials through observation of their atomic structures using high resolution imaging and through chemical analyses using complementary analytical techniques. Combinations of z-contrast imaging, selected area electron diffraction (SAED), electron dispersive x-ray spectroscopy (EDX), and electron energy loss spectroscopy (EELS) were used to elucidate the structures of IrO2, H2Ti4O 9, H2K2Nb6O17 and WO 3 photocatalysts. STEM techniques were also employed to observe the reduction of V2O5 nanoribbons into photoactive VO 2 and to monitor the effect of sonication on the size and crystallinity of TBACa2Nb3O10 (TBA = tetrabutylammonium) nano sheets. Aberration-corrected STEM equipped with a fluid stage was utilized to examine water catalysis by TBACa2Nb3O10 in situ under the electron beam. Phenomena associated with calcium niobate catalysis such as photodeposition of Pt and IrO2 co-catalysts and the surface poisoning with Ag particles during water oxidation were observed in real time. Formation of gas bubbles during water reduction was also detected as it occurs using dark field imaging and EELS. Electron microscopy was also employed to probe charge separation and distribution of redox-active sites on photolabeled TBACa2Nb 3O10. The sizes, shapes, and particle densities vary with the precursor concentration and the presence of sacrificial agents. Photogenerated electrons and holes were shown to be accessible throughout the nanosheets, without evidence for spatial charge separation across the sheet. To measure the relative catalytic activities of multiple photocatalysts, a comparative quantum efficiency (QE) study was carried out on the H 2Ti4O9 nanobelts, H2K2Nb 6O17 nanoscrolls, PA2K2Nb6O 17 (PA = propylammonium) and TBACa2Nb3O10 nanosheets, and their platinated counterparts. Hydrogen and oxygen evolved upon irradiation with a Xe lamp were measured using gas chromatography (GC). The QEs of these catalysts were found to be dependent on the quasi-Fermi levels (QFLs) and the mobility of the charge carriers as measured by surface photovoltage spectroscopy (SPV). A similar photocatalytic study was employed to measure the effects of exfoliation, sacrificial charge donors, presence of co-catalysts, and co-catalyst deposition conditions on the TBACa2Nb3O10 nanosheets. Factorial analysis on the hydrogen and oxygen evolution results showed the degree of dependence of catalytic activity on these factors. High resolution STEM and cyclic voltammetry showed the structural and electronic features of the nanosheets that give rise to the observed effects of the factors studied.

Sabio, Erwin Murillo

209

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 the dissociative chemisorption of hydrogen in Ti-doped alanate storage materials. © 2007 American Institute

Ciobanu, Cristian

210

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

211

Identification of non-precious metal alloy catalysts for selective hydrogenation of acetylene.  

PubMed

The removal of trace acetylene from ethylene is performed industrially by palladium hydrogenation catalysts (often modified with silver) that avoid the hydrogenation of ethylene to ethane. In an effort to identify catalysts based on less expensive and more available metals, density functional calculations were performed that identified relations in heats of adsorption of hydrocarbon molecules and fragments on metal surfaces. This analysis not only verified the facility of known catalysts but identified nickel-zinc alloys as alternatives. Experimental studies demonstrated that these alloys dispersed on an oxide support were selective for acetylene hydrogenation at low pressures. PMID:18535238

Studt, Felix; Abild-Pedersen, Frank; Bligaard, Thomas; Sørensen, Rasmus Z; Christensen, Claus H; Nørskov, Jens K

2008-06-01

212

Isolated metal atom geometries as a strategy for selective heterogeneous hydrogenations.  

PubMed

Facile dissociation of reactants and weak binding of intermediates are key requirements for efficient and selective catalysis. However, these two variables are intimately linked in a way that does not generally allow the optimization of both properties simultaneously. By using desorption measurements in combination with high-resolution scanning tunneling microscopy, we show that individual, isolated Pd atoms in a Cu surface substantially lower the energy barrier to both hydrogen uptake on and subsequent desorption from the Cu metal surface. This facile hydrogen dissociation at Pd atom sites and weak binding to Cu allow for very selective hydrogenation of styrene and acetylene as compared with pure Cu or Pd metal alone. PMID:22403387

Kyriakou, Georgios; Boucher, Matthew B; Jewell, April D; Lewis, Emily A; Lawton, Timothy J; Baber, Ashleigh E; Tierney, Heather L; Flytzani-Stephanopoulos, Maria; Sykes, E Charles H

2012-03-01

213

Selective hydrogenation of citronellal to citronellol over polymer-stabilized noble metal colloids  

Microsoft Academic Search

Citronellal was hydrogenated to citronellol by polymer-stabilized Pt and Ru colloids. The metal cations increased both the activity and the selectivity of the colloids. The modification was assumed to be due to the adsorbed metal cations activating the C?O double bonds, thus accelerating the reaction rate and increasing the selectivity to unsaturated alcohols.

Weiyong Yu; Hanfan Liu; Manhong Liu; Zhijie Liu

2000-01-01

214

Approaches for reducing the insulator-metal transition pressure in hydrogen  

NASA Technical Reports Server (NTRS)

Two possible techniques for reducing the external pressure required to induce the insulator-metal transition in solid hydrogen are described. One uses impurities to lower the energy of the metallic phase relative to that of the insulating phase. The other utilizes a negative pressure induced in the insulating phase by electron-hole pairs, created either with laser irradiation or pulsed synchrotron sources.

Carlsson, A. E.; Ashcroft, N. W.

1983-01-01

215

Determination of the Molar Volume of Hydrogen from the Metal-Acid Reaction: An Experimental Alternative.  

ERIC Educational Resources Information Center

Describes an alternative technique for determining the molar volume of hydrogen from the metal-acid reaction in which the metal sample is encased in a specially prepared cage and a pipette filler is used to fill an inverted burette with water. Eliminates some difficulties encountered with the conventional technique. (JRH)

de Berg, Kevin; Chapman, Ken

1996-01-01

216

Low hydrogen shielded metal arc welding of carbon steel. Welding procedure specification  

Microsoft Academic Search

Procedure WPS-114-ASME-1 is qualified under Section IX of the ASME Boiler and Pressure Vessel Code for low hydrogen shielded metal arc welding of carbon steels (P-1-1), in thickness range 0.125 to 1.5 in.; filler metal is E7018 (F-4, A-1).

C. H. Wodtke; D. R. Frizzell; W. A. Plunkett

1985-01-01

217

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

218

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

219

Sub-Nanostructured Non Transition Metal Complex Grids for Hydrogen Storage  

SciTech Connect

This project involved growing sub-nanostructured metal grids to increase dynamic hydrogen storage capacity of metal hydride systems. The nano particles of any material have unique properties unlike its bulk form. Nano-structuring metal hydride materials can result in: {sm_bullet}Increased hydrogen molecule dissociation rate, {sm_bullet} Increased hydrogen atom transport rate, {sm_bullet} Decreased decrepitation caused by cycling, {sm_bullet} Increased energy transfer in the metal matrix, {sm_bullet} Possible additional contribution by physical adsorption, and {sm_bullet} Possible additional contribution by quantum effects The project succeeded in making nano-structured palladium using electrochemical growth in templates including zeolites, mesoporous silica, polycarbonate films and anodized alumina. Other metals were used to fine-tune the synthesis procedures. Palladium was chosen to demonstrate the effects of nano-structuring since its bulk hydrogen storage capacity and kinetics are well known. Reduced project funding was not sufficient for complete characterization of these materials for hydrogen storage application. The project team intends to seek further funding in the future to complete the characterization of these materials for hydrogen storage.

Dr. Orhan Talu; Dr. Surendra N. Tewari

2007-10-27

220

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

221

Hydrogen permeation and related stress corrosion cracking (SCC) can limit the use of metals and alloys in aqueous environments. The interactions between hydrogen and the  

E-print Network

Background Hydrogen permeation and related stress corrosion cracking (SCC) can limit the use. These methods however, do not reduce the hydrogen entry below the threshold level that is safe of cracking of metals and alloys in aqueous environments. The interactions between hydrogen and the heterogeneities

Popov, Branko N.

222

Synchrotron radiation photoemission study of metal overlayers on hydrogenated amorphous silicon at room temperature  

SciTech Connect

In this dissertation, metals deposited on a hydrogenated amorphous silicon (a-Si:H) film at room temperature are studied. The purpose of this work is mainly understanding the electronic properties of the interface, using high-resolution synchrotron radiation photoemission techniques as a probe. Atomic hydrogen plays an important role in passivating dangling bonds of a-Si:H films, thus reducing the gap-state distribution. In addition, singly bonded hydrogen also reduces states at the top of the valence band which are now replaced by deeper Si-H bonding states. The interface is formed by evaporating metal on an a-Si:H film in successive accumulations at room temperature. Au, Ag, and Cr were chosen as the deposited metals. Undoped films were used as substrates. Since some unique features can be found in a-Si:H, such as surface enrichment of hydrogen diffused from the bulk and instability of the free surface, we do not expect the metals/a-Si:H interface to behave exactly as its crystalline counterpart. Metal deposits, at low coverages, are found to gather preferentially around regions deficient in hydrogen. As the thickness is increased, some Si atoms in those regions are likely to leave their sites to intermix with metal overlayers like Au and Cr. 129 refs., 30 figs.

Pi, J.

1990-09-21

223

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

224

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

225

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

226

Metallization of fluid hydrogen at 140 GPa (1.4 Mbar) by shock compression  

Microsoft Academic Search

.   Shock compression was used to produce the first observation of a metallic state of condensed hydrogen. The conditions of\\u000a metallization are a pressure of 140 GPa (1.4 Mbar), 0.6 g\\/cm (ninefold compression of initial liquid-H density), and 3000 K. The relatively modest temperature generated by a reverberating shock wave produced the metallic state\\u000a in a warm fluid at a

W. J. Nellis; S. T. Weir; A. C. Mitchell

1999-01-01

227

Molten metal reactor and method of forming hydrogen, carbon monoxide and carbon dioxide using the molten alkaline metal reactor  

SciTech Connect

A molten metal reactor for converting a carbon material and steam into a gas comprising hydrogen, carbon monoxide, and carbon dioxide is disclosed. The reactor includes an interior crucible having a portion contained within an exterior crucible. The interior crucible includes an inlet and an outlet; the outlet leads to the exterior crucible and may comprise a diffuser. The exterior crucible may contain a molten alkaline metal compound. Contained between the exterior crucible and the interior crucible is at least one baffle.

Bingham, Dennis N.; Klingler, Kerry M.; Turner, Terry D.; Wilding, Bruce M.

2012-11-13

228

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

229

On the hydrogen etching mechanism in plasma nitriding of metals  

NASA Astrophysics Data System (ADS)

Iron alloys and aluminum were nitrogen implanted in a controlled oxygen atmosphere and the role of hydrogen on the surface etching mechanisms studied. The surface composition was analyzed by in situ photoemission electron spectroscopy (XPS). In iron alloys, hydrogen strongly etches oxygen, improving nitrogen retention on the surface. On the other hand, hydrogen removes nitrogen from aluminum surfaces, with a deleterious effect on the nitriding effectiveness. The oxygen removal in iron alloys is associated with the catalytic effect of electrons in d-orbitals and the nitrogen removal in aluminum is associated with a steric effect.

Figueroa, C. A.; Alvarez, F.

2006-12-01

230

Hydrogenated Graphene Nanoflakes: Semiconductor to Half-Metal Transition and Remarkable Large Magnetism  

SciTech Connect

The electronic and magnetic properties of graphene nanoflakes (GNFs) can be tuned by patterned adsorption of hydrogen. Controlling the H coverage from bare GNFs to half hydrogenated and then to fully hydrogenated GNFs, the transformation of small-gap semiconductor {yields} half-metal {yields} wide-gap semiconductor occurs, accompanied by a magnetic {yields} magnetic {yields} nonmagnetic transfer and a nonmagnetic {yields} magnetic {yields} nonmagnetic transfer for triangular and hexagonal nanoflakes, respectively. The half hydrogenated GNFs, associated with strong spin polarization around the Fermi level, exhibit the unexpected large spin moment that is scaled squarely with the size of flakes. The induced spin magnetizations of these nanoflakes align parallel and lead to a substantial collective character, enabling the half hydrogenated GNFs to be spin-filtering flakes. These hydrogenation-dependent behaviors are then used to realize an attractive approach to engineer the transport properties, which provides a new route to facilitate the design of tunable spin devices.

Zhou, Yungang; Wang, Zhiguo; Yang, Ping; Sun, Xin; Zu, Xiaotao; Gao, Fei

2012-03-08

231

Applications of hydrogenation and dehydrogenation on noble metal catalysts  

E-print Network

Hydrogenation and dehydrogenation on Pd- and Pt- catalysts are encountered in many industrial hydrocarbon processes. The present work considers the development of catalysts and their kinetic modeling along a general and rigorous approach. The first...

Wang, Bo

2009-05-15

232

Photobiotechnology: Algal hydrogen production and photoconductivity of metalized chloroplasts  

Microsoft Academic Search

Sustained hydrogen photoevolution from Chlamydomonas reinhardtii and C. moewusii was measured under an anoxic, COâ-containing atmosphere. It has been discovered that light intensity and temperature influence the partitioning of reductant between the hydrogen photoevolution pathway and the Calvin cycle. Under low incident light intensity (1-3 W m⁻²) or low temperature (approx. O°C), the flow of photosynthetic reductant to the Calvin

Greenbaum

1991-01-01

233

Systems and methods for selective hydrogen transport and measurement  

DOEpatents

Systems and methods for selectively removing hydrogen gas from a hydrogen-containing fluid volume are disclosed. An exemplary system includes a proton exchange membrane (PEM) selectively permeable to hydrogen by exclusively conducting hydrogen ions. The system also includes metal deposited as layers onto opposite sides or faces of the PEM to form a membrane-electrode assembly (MEA), each layer functioning as an electrode so that the MEA functions as an electrochemical cell in which the ionic conductors are hydrogen ions, and the MEA functioning as a hydrogen selective membrane (HSM) when located at the boundary between a hydrogen-containing fluid volume and a second fluid.

Glatzmaier, Gregory C

2013-10-29

234

Empirical Method to Estimate Hydrogen Embrittlement of Metals as a Function of Hydrogen Gas Pressure at Constant Temperature  

NASA Technical Reports Server (NTRS)

High pressure Hydrogen (H) gas has been known to have a deleterious effect on the mechanical properties of certain metals, particularly, the notched tensile strength, fracture toughness and ductility. The ratio of these properties in Hydrogen as compared to Helium or Air is called the Hydrogen Environment Embrittlement (HEE) Index, which is a useful method to classify the severity of H embrittlement and to aid in the material screening and selection for safety usage H gas environment. A comprehensive world-wide database compilation, in the past 50 years, has shown that the HEE index is mostly collected at two conveniently high H pressure points of 5 ksi and 10 ksi near room temperature. Since H embrittlement is directly related to pressure, the lack of HEE index at other pressure points has posed a technical problem for the designers to select appropriate materials at a specific H pressure for various applications in aerospace, alternate and renewable energy sectors for an emerging hydrogen economy. Based on the Power-Law mathematical relationship, an empirical method to accurately predict the HEE index, as a function of H pressure at constant temperature, is presented with a brief review on Sievert's law for gas-metal absorption.

Lee, Jonathan A.

2010-01-01

235

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

236

Partial and complete reduction of O 2 by hydrogen on transition metal surfaces  

NASA Astrophysics Data System (ADS)

The metal-catalyzed reduction of di-oxygen (O 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 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 (BE O), delineated by the opposite demands to catalyze O-O bond scission and O-H bond formation: The dissociative adsorption of O 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 O2 reduction, provide a unified basis for understanding the metal-catalyzed reduction of O 2 to H 2O and HOOH, and offer useful insights for identifying new catalysts for desired oxygen reduction products.

Ford, Denise C.; Nilekar, Anand Udaykumar; Xu, Ye; Mavrikakis, Manos

2010-09-01

237

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

238

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

239

Studies on the Ionization Produced by Metallic Salts in Flames. III. Ionic Equilibria in Hydrogen\\/Air Flames Containing Alkali Metal Salts  

Microsoft Academic Search

An examination has been made of the electron concentration produced when alkali metal salts are added to various hydrogen\\/air flames containing excess hydrogen. The results have shown that although the variation of the measured electron concentration with the concentration of added alkali metal shows the thermodynamically predicted behaviour, the variation with respect to flame temperature and ionization potential of alkali

H. Smith; T. M. Sugden

1952-01-01

240

The low-temperature reduction of Pd-doped transition metal oxide surfaces with hydrogen  

Microsoft Academic Search

The reaction of hydrogen with a series of polyvalent metal oxides (Fe2O3, WO3, MoO3, V2O5, Sb2O3, PbO2, Cr2O3, NiO, CuO, Co3O4, MnO2, PdO, Ag2O) was investigated at low temperatures (77–320K) and pressures (0.001–0.7kPa). Pd-doped (0.1–0.5wt.%) transition metal oxides can be reduced by hydrogen at 77–320K whereas the onset of the reduction of the pure oxides occurs at temperatures higher than

V. M. Belousov; M. A. Vasylyev; L. V. Lyashenko; N. Yu. Vilkova; B. E. Nieuwenhuys

2003-01-01

241

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

242

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

243

Metal?organic frameworks for the storage and delivery of biologically active hydrogen sulfide  

SciTech Connect

Hydrogen sulfide is an extremely toxic gas that is also of great interest for biological applications when delivered in the correct amount and at the desired rate. Here we show that the highly porous metal-organic frameworks with the CPO-27 structure can bind the hydrogen sulfide relatively strongly, allowing the storage of the gas for at least several months. Delivered gas is biologically active in preliminary vasodilation studies of porcine arteries, and the structure of the hydrogen sulfide molecules inside the framework has been elucidated using a combination of powder X-ray diffraction and pair distribution function analysis.

Allan, Phoebe K.; Wheatley, Paul S.; Aldous, David; Mohideen, M. Infas; Tang, Chiu; Hriljac, Joseph A.; Megson, Ian L.; Chapman, Karena W.; De Weireld, Guy; Vaesen, Sebastian; Morris, Russell E. (St Andrews)

2012-04-02

244

Hall effect in Zr-Ni and Zr-Cu metallic glasses doped with hydrogen  

NASA Astrophysics Data System (ADS)

We have studied the effect of hydrogen doping on the Hall resistivity of paramagnetic Zr76Ni24, Zr40Ni60, Zr70Cu30, and Zr60Cu40 metallic glasses. All the alloys have positive Hall coefficients except the Zr40Ni60. The hydrogen dopant increases the absolute value of the Hall coefficient irrespective of its sign, except in the case of (Zr70Cu30)1-xHx, where the Hall coefficient decreases for low hydrogen concentrations (x<0.04) and increases at higher ones, while staying positive all the time. The results are explained as being due to the enhanced s-d hybridization.

Kokanovi?, I.; Leonti?, B.; Lukatela, J.; Ivkov, J.

1990-12-01

245

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

246

Carburisation and metal dusting in hydrogen rich gas  

Microsoft Academic Search

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, HO, CO and CO at moderate to high temperatures. These gases pose a variety of corrosion threats to the alloys used in plant construction. Carbon

D. J. Young

2007-01-01

247

Hydrogen-induced cracking along the fusion boundary of dissimilar metal welds  

SciTech Connect

Presented here are the results from a series of experiments in which dissimilar metals welds were made using the gas tungsten arc welding process with pure argon or argon-6% hydrogen shielding gas. The objective was to determine if cracking near the fusion boundary of dissimilar metal welds could be caused by hydrogen absorbed during welding and to characterize the microstructures in which cracking occurred. Welds consisted of ER308 and ER309LSi austenitic stainless steel and ERNiCr-3-nickel-based filler metals deposited on A36 steel base metal. Cracking was observed in welds made with all three filler metals. A ferrofluid color metallography technique revealed that cracking was confined to regions in the weld metal containing martensite. Microhardness indentations indicated that martensitic regions in which cracking occurred had hardness values from 400 to 550 HV. Cracks did not extend into bulk weld metal with hardness less than 350 HV. Martensite formed near the fusion boundary in all three filler metals due to regions of locally increased base metal dilution.

Rowe, M.D.; Nelson, T.W.; Lippold, J.C. [Ohio State Univ., Columbus, OH (United States)

1999-02-01

248

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

249

Hydroxylation of benzene with oxygen and hydrogen over catalysts containing Group VIII metals and heteropoly compounds  

Microsoft Academic Search

The vapor phase hydroxylation of benzene to phenol with a mixture of oxygen and hydrogen over silica supported bi-component catalysts containing Group VIII metals (M) and heteropoly compounds (HPC) was investigated. The productivity of the catalysts was ascertained for various metal and HPC combinations and a range of reaction conditions. The Pt–PMo12\\/SiO2 and Pd–PMo12\\/SiO2 catalysts of optimal composition provide up

N. I. Kuznetsova; L. I. Kuznetsova; V. A. Likholobov; G. P. Pez

2005-01-01

250

Metal-doped sodium aluminium hydrides as potential new hydrogen storage materials  

Microsoft Academic Search

Thermodynamics and kinetics of the reversible dissociation of metal-doped NaAlH4 as a hydrogen (or heat) storage system have been investigated in some detail. The experimentally determined enthalpies for the first (3.7 wt% of H) and the second dissociation step of Ti-doped NaAlH4 (3.0 wt% H) of 37 and 47 kJ\\/mol are in accordance with low and medium temperature reversible metal

Borislav Bogdanovi?; Richard A. Brand; Ankica Marjanovi?; Manfred Schwickardi; Joachim Tölle

2000-01-01

251

Gas tungsten arc and low hydrogen shielded metal arc welding of carbon steel. Welding procedure specification  

SciTech Connect

Procedure WPS-128-ASME-1 is qualified under Section IX of the ASME Boiler and Pressure Vessel Code for gas tungsten arc and low hydrogen shielded metal arc welding of carbon steels (P-1-1), in thickness range 0.25 to 2 inch; filler metals are ER70S-3 (F-6, A-1) (GTAW) and E7018 (F-4, A-1); shielding gas is argon (GTAW).

Wodtke, C.H.; Frizzell, D.R.; Plunkett, W.A.

1985-08-01

252

Gas tungsten arc and low hydrogen shielded metal arc welding of carbon steel. Welding procedure specification  

Microsoft Academic Search

Procedure WPS-128-ASME-1 is qualified under Section IX of the ASME Boiler and Pressure Vessel Code for gas tungsten arc and low hydrogen shielded metal arc welding of carbon steels (P-1-1), in thickness range 0.25 to 2 inch; filler metals are ER70S-3 (F-6, A-1) (GTAW) and E7018 (F-4, A-1); shielding gas is argon (GTAW).

C. H. Wodtke; D. R. Frizzell; W. A. Plunkett

1985-01-01

253

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

254

DWPF Hydrogen Generation Study-Form of Noble Metal SRAT Testing  

SciTech Connect

The Defense Waste Processing Facility, DWPF, has requested that the Savannah River National Laboratory, SRNL, investigate the factors that contribute to hydrogen generation to determine if current conservatism in setting the DWPF processing window can be reduced. A phased program has been undertaken to increase understanding of the factors that influence hydrogen generation in the DWPF Chemical Process Cell, CPC. The hydrogen generation in the CPC is primarily due to noble metal catalyzed decomposition of formic acid with a minor contribution from radiolytic processes. Noble metals have historically been added as trim chemicals to process simulations. The present study investigated the potential conservatism that might be present from adding the catalytic species as trim chemicals to the final sludge simulant versus co-precipitating the noble metals into the insoluble sludge solids matrix. Two sludge simulants were obtained, one with co-precipitated noble metals and one without noble metals. Co-precipitated noble metals were expected to better match real waste behavior than using trimmed noble metals during CPC simulations. Portions of both sludge simulants were held at 97 C for about eight hours to qualitatively simulate the effects of long term storage on particle morphology and speciation. The two original and two heat-treated sludge simulants were then used as feeds to Sludge Receipt and Adjustment Tank, SRAT, process simulations. Testing was done at relatively high acid stoichiometries, {approx}175%, and without mercury in order to ensure significant hydrogen generation. Hydrogen generation rates were monitored during processing to assess the impact of the form of noble metals. The following observations were made on the data: (1) Co-precipitated noble metal simulant processed similarly to trimmed noble metal simulant in most respects, such as nitrite to nitrate conversion, formate destruction, and pH, but differently with respect to hydrogen generation: (A) The peak hydrogen generation rate occurred three to five hours later for the regular and heat-treated co-precipitated noble metal slurries than for the slurries with trimmed noble metals. (B) The peak hydrogen generation rate was lower during processing of the co-precipitated noble metal simulant relative to the trimmed noble metal simulant data. (C) Trimmed noble metals appeared to be conservative relative to co-precipitated noble metals under the conditions of these tests as long as the peak hydrogen generation rate occurred early in the SRAT boiling period. (2) If the peak hydrogen generation rate with trimmed noble metals is near or above the DWPF limit, and if the peak occurs late in the SRAT cycle, then a potential SME cycle hydrogen generation rate issue could be anticipated when using co-precipitated noble metals, since the peak is expected to be delayed relative to trimmed noble metals. (3) The peak hydrogen generation rate increased from about 1.3 to about 3.7 lbs H{sub 2}/hr on the range of 170-190% stoichiometry, or about 0.1 lbs. H{sub 2}/hr per % change in the stoichiometric factor at DWPF scale. (4) The peak generation rate was slightly higher during processing of the heat-treated coprecipitated noble metal simulant relative to the trimmed noble metal heat-treated simulant, but this probably due to somewhat more excess acid being added to the co-precipitated noble metal test than intended. (5) The variations in the peak hydrogen generation rate appeared to track the quantity of dissolved rhodium in the SRAT product. (6) A noble metal apparently activated and then de-activated during the final hour of formic acid addition. The associated peak generation rate was <3% of the maximum rate seen in each test. Palladium may have been responsible based on literature data. (7) Planned comparisons between heat-treated and un-heat-treated simulants were complicated by the significantly altered base equivalents following heat-treatment. This necessitated making small adjustments to the stoichiometric acid factor to attempt to match the excess acid contents

Bannochie, C

2005-09-01

255

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

256

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

257

Adsorption and Diffusion of Hydrogen in a New Metal-Organic Framework Material: [Zn(bdc)(ted)0.5  

E-print Network

Adsorption and Diffusion of Hydrogen in a New Metal-Organic Framework Material: [Zn(bdc)(ted)0. Sankar,§ and J. Karl Johnson*,,| Department of Chemical Engineering, UniVersity of Pittsburgh, Pittsburgh: NoVember 29, 2007 We have experimentally measured hydrogen isotherms at 77 and 298 K up to a hydrogen

Li, Jing

258

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

259

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

260

Hydrogen-on-demand using metallic alloy nanoparticles in water.  

PubMed

Hydrogen production from water using Al particles could provide a renewable energy cycle. However, its practical application is hampered by the low reaction rate and poor yield. Here, large quantum molecular dynamics simulations involving up to 16,611 atoms show that orders-of-magnitude faster reactions with higher yields can be achieved by alloying Al particles with Li. A key nanostructural design is identified as the abundance of neighboring Lewis acid-base pairs, where water-dissociation and hydrogen-production require very small activation energies. These reactions are facilitated by charge pathways across Al atoms that collectively act as a "superanion" and a surprising autocatalytic behavior of bridging Li-O-Al products. Furthermore, dissolution of Li atoms into water produces a corrosive basic solution that inhibits the formation of a reaction-stopping oxide layer on the particle surface, thereby increasing the yield. These atomistic mechanisms not only explain recent experimental findings but also predict the scalability of this hydrogen-on-demand technology at industrial scales. PMID:24960149

Shimamura, Kohei; Shimojo, Fuyuki; Kalia, Rajiv K; Nakano, Aiichiro; Nomura, Ken-Ichi; Vashishta, Priya

2014-07-01

261

Nanochemistry at the atomic scale revealed in hydrogen-induced semiconductor surface metallization  

NASA Astrophysics Data System (ADS)

Passivation of semiconductor surfaces against chemical attack can be achieved by terminating the surface-dangling bonds with a monovalent atom such as hydrogen. Such passivation invariably leads to the removal of all surface states in the bandgap, and thus to the termination of non-metallic surfaces. Here we report the first observation of semiconductor surface metallization induced by atomic hydrogen. This result, established by using photo-electron and photo-absorption spectroscopies and scanning tunnelling techniques, is achieved on a Si-terminated cubic silicon carbide (SiC) surface. It results from competition between hydrogen termination of surface-dangling bonds and hydrogen-generated steric hindrance below the surface. Understanding the ingredient for hydrogen-stabilized metallization directly impacts the ability to eliminate electronic defects at semiconductor interfaces critical for microelectronics, provides a means to develop electrical contacts on high-bandgap chemically passive materials, particularly for interfacing with biological systems, and gives control of surfaces for lubrication, for example of nanomechanical devices.

Derycke, Vincent; Soukiassian, Patrick G.; Amy, Fabrice; Chabal, Yves J.; D'Angelo, Marie D.; Enriquez, Hanna B.; Silly, Mathieu G.

2003-04-01

262

Method for hydrogen production and metal winning, and a catalyst/cocatalyst composition useful therefor  

DOEpatents

A catalyst/cocatalyst/organics composition of matter is useful in electrolytically producing hydrogen or electrowinning metals. Use of the catalyst/cocatalyst/organics composition causes the anode potential and the energy required for the reaction to decrease. An electrolyte, including the catalyst/cocatalyst composition, and a reaction medium composition further including organic material are also described.

Dhooge, Patrick M. (Corrales, NM)

1987-10-13

263

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

264

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

265

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

266

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

267

Hydrogen production from propane in Rh-impregnated metallic microchannel reactors and alumina foams  

Microsoft Academic Search

Rh-impregnated alumina foams and metallic microchannel reactors have been studied for production of hydrogen-rich syngas through short contact time catalytic partial oxidation (POX) and oxidative steam reforming (OSR) of propane. Effects of temperature and residence time have been compared for the two catalytic systems. Temperature profiles obtained along the central axis were valuable in understanding the different behaviour of the

Ingrid Aartun; Bozena Silberova; Hilde Venvik; Peter Pfeifer; Oliver Görke; Klaus Schubert; Anders Holmen

2005-01-01

268

Trends in Selective Hydrogen Peroxide Production on Transition Metal Surfaces from First Principles  

SciTech Connect

We present a comprehensive, Density Functional Theory-based analysis of the direct synthesis of hydrogen peroxide, H2O2, on twelve transition metal surfaces. We determine the full thermodynamics and selected kinetics of the reaction network on these metals, and we analyze these energetics with simple, microkinetically motivated rate theories to assess the activity and selectivity of hydrogen peroxide production on the surfaces of interest. By further exploiting Brønsted-Evans-Polanyi relationships and scaling relationships between the binding energies of different adsorbates, we express the results in the form of a two dimensional contour volcano plot, with the activity and selectivity being determined as functions of two independent descriptors, the atomic hydrogen and oxygen adsorption free energies. We identify both a region of maximum predicted catalytic activity, which is near Pt and Pd in descriptor space, and a region of selective hydrogen peroxide production, which includes Au. The optimal catalysts represent a compromise between activity and selectivity and are predicted to fall approximately between Au and Pd in descriptor space, providing a compact explanation for the experimentally known performance of Au-Pd alloys for hydrogen peroxide synthesis, and suggesting a target for future computational screening efforts to identify improved direct hydrogen peroxide synthesis catalysts. Related methods of combining activity and selectivity analysis into a single volcano plot may be applicable to, and useful for, other aqueous phase heterogeneous catalytic reactions where selectivity is a key catalytic criterion.

Rankin, Rees B.; Greeley, Jeffrey P.

2012-10-19

269

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

270

Efficient photoelectrochemical hydrogen generation using heterostructures of Si and chemically exfoliated metallic MoS2.  

PubMed

We report the preparation and characterization of highly efficient and robust photocathodes based on heterostructures of chemically exfoliated metallic 1T-MoS2 and planar p-type Si for solar-driven hydrogen production. Photocurrents up to 17.6 mA/cm(2) at 0 V vs reversible hydrogen electrode were achieved under simulated 1 sun irradiation, and excellent stability was demonstrated over long-term operation. Electrochemical impedance spectroscopy revealed low charge-transfer resistances at the semiconductor/catalyst and catalyst/electrolyte interfaces, and surface photoresponse measurements also demonstrated slow carrier recombination dynamics and consequently efficient charge carrier separation, providing further evidence for the superior performance. Our results suggest that chemically exfoliated 1T-MoS2/Si heterostructures are promising earth-abundant alternatives to photocathodes based on noble metal catalysts for solar-driven hydrogen production. PMID:24892384

Ding, Qi; Meng, Fei; English, Caroline R; Cabán-Acevedo, Miguel; Shearer, Melinda J; Liang, Dong; Daniel, Andrew S; Hamers, Robert J; Jin, Song

2014-06-18

271

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

272

Phase transition into the metallic state in hypothetical (without molecules) dense atomic hydrogen  

SciTech Connect

A simple physical model of the metal-dielectric (vapor-liquid) phase transition in hypothetical (without molecules) atomic hydrogen is proposed. The reason for such a transition is the quantum collective cohesive energy occurring due to quantum electron-electron exchange similar to the cohesive energy in the liquid-metal phase of alkali metals. It is found that the critical parameters of the transition are P{sub c} ? 41000 atm, ?{sub c} ? 0.1 g/cm{sup 3}, and T{sub c} ? 9750 K.

Khomkin, A. L., E-mail: alhomkin@mail.ru; Shumikhin, A. S. [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation)] [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation)

2013-10-15

273

The hydrogenation of metals upon interaction with water  

NASA Technical Reports Server (NTRS)

Hydrogen evolution at 600 deg and 5 x 10 to the 7th power - 10 to the 6th power torr from AVOOO Al samples, which were pickled in 10 percent NaOH, is discussed. An H evolution kinetic equation is derived for samples of equal vol. and different surfaces (5 and 20 sq cm). The values of the H evolution coefficient K indicated an agreement with considered H diffusion mechanism through an oxide layer. The activation energy for the H evolution process, obtained from the K-temp. relation, was 13,000 2000 cal/g-atom.

Andreyev, L. A.; Gelman, B. G.; Zhukhovitskiy, A. A.; Polosina, Y. Y.

1979-01-01

274

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

275

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

276

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

277

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

278

TREATMENT OF METALS IN GROUND WATER USING AN ORGANIC-BASED SULFATE-REDUCING PERMEABLE REACTIVE BARRIER  

EPA Science Inventory

A pilot permeable reactive barrier (PRB) consisting of a mixture of leaf compost, zero-valent iron (ZVI) filings, limestone and pea gravel was evaluated at a former phosphate fertilizer manufacturing facility in Charleston, S.C. The PRB is designed to treat arsenic and heavy met...

279

Organic substrates as electron donors in permeable reactive barriers for removal of heavy metals from acid mine drainage  

Microsoft Academic Search

This research was conducted to select suitable natural organic substrates as potential carbon sources for use as electron donors for biological sulphate reduction in a permeable reactive barrier (PRB). A number of organic substrates were assessed through batch and continuous column experiments under anaerobic conditions with acid mine drainage (AMD) obtained from an abandoned lignite coal mine. To keep the

P. Kijjanapanich; K. Pakdeerattanamint; P. N. L. Lens; A. P. Annachhatre

2012-01-01

280

Electrocatalytic hydrogenation using precious metal microparticles in redox-active polymer films  

SciTech Connect

Glassy carbon felt electrodes have been modified by electrodeposition of poly(pyrrole-viologen) films (derived from N,N{prime}-dialkyl-4,4{prime}-bipyridinium salts), followed by electroprecipitation of precious metal (Pt, Pd, Rh, or Ru) microparticles. The resulting electrodes have been proved to be active for the electrocatalytic hydrogenation of conjugated enones (2-cyclohexen-1-one, cryptone, carvone, isophorone), styrene, and benzonitrile in aqueous media (pH 1). Despite low loadings of metal catalysts, high electric and products yields and a long term stability of these cathodes have been observed. The influence of the metal loading and the polymer structure on the catalytic efficiency as well as the selectivity obtained according to the metal catalyst used have been studied. Comparison with results previously reported for other catalytic cathodes like Pt/Pt, Pd/C, or Raney nickel electrodes proves the high efficiency of these metal microparticles within redox polymer film based electrodes.

Coche, L.; Ehui, B.; Limosin, D.; Moutet, J.C. (Univ. Joseph Fourier, Grenoble (France))

1990-11-09

281

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

282

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

283

In situ diffraction study of catalytic hydrogenation of VO?: stable phases and origins of metallicity.  

PubMed

Controlling electronic population through chemical doping is one way to tip the balance between competing phases in materials with strong electronic correlations. Vanadium dioxide exhibits a first-order phase transition at around 338 K between a high-temperature, tetragonal, metallic state (T) and a low-temperature, monoclinic, insulating state (M1), driven by electron-electron and electron-lattice interactions. Intercalation of VO2 with atomic hydrogen has been demonstrated, with evidence that this doping suppresses the transition. However, the detailed effects of intercalated H on the crystal and electronic structure of the resulting hydride have not been previously reported. Here we present synchrotron and neutron diffraction studies of this material system, mapping out the structural phase diagram as a function of temperature and hydrogen content. In addition to the original T and M1 phases, we find two orthorhombic phases, O1 and O2, which are stabilized at higher hydrogen content. We present density functional calculations that confirm the metallicity of these states and discuss the physical basis by which hydrogen stabilizes conducting phases, in the context of the metal-insulator transition. PMID:24825186

Filinchuk, Yaroslav; Tumanov, Nikolay A; Ban, Voraksmy; Ji, Heng; Wei, Jiang; Swift, Michael W; Nevidomskyy, Andriy H; Natelson, Douglas

2014-06-01

284

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

285

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

286

Hydrogen production by reacting water with mechanically milled composite aluminum-metal oxide powders  

Microsoft Academic Search

Several composite aluminum-metal oxide powders were prepared by mechanical milling and considered for hydrogen production in the Al–water split reaction. The powders included compositions capable of independent, highly exothermic thermite reaction between components: Al·MoO3, Al·Bi2O3, and Al·CuO, as well as chemically inert compositions Al·MgO and Al·Al2O3. Experiments used a water displacement method to quantify hydrogen production. In most experiments, the

Paul Dupiano; Demitrios Stamatis; Edward L. Dreizin

2011-01-01

287

SOLUBILITY OF WATER ICE IN METALLIC HYDROGEN: CONSEQUENCES FOR CORE EROSION IN GAS GIANT PLANETS  

SciTech Connect

Using ab initio simulations we investigate whether water ice is stable in the cores of giant planets, or whether it dissolves into the layer of metallic hydrogen above. By Gibbs free energy calculations we find that for pressures between 10 and 40 Mbar the ice-hydrogen interface is thermodynamically unstable at temperatures above approximately 3000 K, far below the temperature of the core-mantle boundaries in Jupiter and Saturn. This implies that the dissolution of core material into the fluid layers of giant planets is thermodynamically favored, and that further modeling of the extent of core erosion is warranted.

Wilson, H. F.; Militzer, B. [Department of Earth and Planetary Science, University of California, Berkeley, CA 94720 (United States)

2012-01-20

288

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

289

Micro-machined thin film hydrogen gas sensor, and method of making and using the same  

NASA Technical Reports Server (NTRS)

A hydrogen sensor including a thin film sensor element formed, e.g., by metalorganic chemical vapor deposition (MOCVD) or physical vapor deposition (PVD), on a microhotplate structure. The thin film sensor element includes a film of a hydrogen-interactive metal film that reversibly interacts with hydrogen to provide a correspondingly altered response characteristic, such as optical transmissivity, electrical conductance, electrical resistance, electrical capacitance, magnetoresistance, photoconductivity, etc., relative to the response characteristic of the film in the absence of hydrogen. The hydrogen-interactive metal film may be overcoated with a thin film hydrogen-permeable barrier layer to protect the hydrogen-interactive film from deleterious interaction with non-hydrogen species. The hydrogen sensor of the invention may be usefully employed for the detection of hydrogen in an environment susceptible to the incursion or generation of hydrogen and may be conveniently configured as a hand-held apparatus.

DiMeo, Jr., Frank (Inventor); Bhandari, Gautam (Inventor)

2001-01-01

290

Hydrogen Storage Investigation on Nanotube, Graphene and Organo-metallic Complexes  

NASA Astrophysics Data System (ADS)

New materials and methods for storing hydrogen at high gravimetric and volumetric densities are required because of the widely use of hydrogen for clean fuel. With exceptionally high surface areas, porous materials based on carbon have recently emerged as some of the most promising candidate materials. Here I reviewed our former work on hydrogen storage based on several kinds of organometallic Complexes. Maximum capacities of the hydrogen storage in organometallic compounds consisting of Co and Ni atoms bound to CmHm ring were found 3.48 wt % and 3.49 wt %, respectively; for the structures having a transition metal (TM) Co and Ni inserted in CmHm ring, the maximum number of H2 molecule bound to the inserted-type CoCmHm and NiCmHm complexes is three, and the largest hydrogen storage density is 5.13 wt % and 3.49 wt % for CoC4H4 and NiC4H4, Meanwhile, the ionic (C4H4^+ and C5H5^+) improves the capability of hydrogen storage and makes all H2 adsorbed to the charged compounds in molecular form. With the CH3 ligand bound to the compounds, the adsorption energy of H2 decreases to an ideal range, and stability of the compounds are improved. At last, the hydrogen adsorption properties on the complex structures TiRH7Si8O12 are investigated, and the kinetic stability when H2 was added to organometallic compounds is also discussed by analyzing HOMO-LUMO gaps. Here we also mentioned our results of hydrogen storage based on nanotubes and graphene.

Zhang, Hong

2013-03-01

291

Hydrogen Storage Investigation on Nanotube, Graphene and Organo-metallic Complexes  

NASA Astrophysics Data System (ADS)

New materials and methods for storing hydrogen at high gravimetric and volumetric densities are required because of the widely use of hydrogen for clean fuel. With exceptionally high surface areas, porous materials based on carbon have recently emerged as some of the most promising candidate materials. Here I reviewed our former work on hydrogen storage based on several kinds of organometallic Complexes. Maximum capacities of the hydrogen storage in organometallic compounds consisting of Co and Ni atoms bound to CmHm ring were found 3.48 wt % and 3.49 wt %, respectively; for the structures having a transition metal (TM) Co and Ni inserted in CmHm ring, the maximum number of H2 molecule bound to the inserted-type CoCmHm and NiCmHm complexes is three, and the largest hydrogen storage density is 5.13 wt % and 3.49 wt % for CoC4H4 and NiC4H4, Meanwhile, the ionic (C4H4^+ and C5H5^+) improves the capability of hydrogen storage and makes all H2 adsorbed to the charged compounds in molecular form. With the CH3 ligand bound to the compounds, the adsorption energy of H2 decreases to an ideal range, and stability of the compounds are improved. At last, the hydrogen adsorption properties on the complex structures TiRH7Si8O12 are investigated, and the kinetic stability when H2 was added to organometallic compounds is also discussed by analyzing HOMO-LUMO gaps. Here we also mentioned our results of hydrogen storage based on nanotubes and graphene.

Zhang, Hong

2012-02-01

292

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.

293

Infrared reflectance measurements of the insulator-metal transition in solid hydrogen  

NASA Technical Reports Server (NTRS)

Reflectance measurements on solid hydrogen to 177 GPa (1.77 Mbar) have been performed from near-infrared to ultraviolet wavelengths (0.5 to 3 eV). Above 150 GPa characteristic free-electron behavior in the infrared region is observed to increase sharply with increasing pressure. Analysis of volume dependence of the plasma frequency obtained from Drude-model fits to the spectra indicates that the pressure of the insulator-metal transition is 149 (+ or - 10) GPa at 295 K. The measurements are consistent with metallization by closure of an indirect gap in the molecular solid.

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

1990-01-01

294

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

295

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

296

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,

297

Magnetic Fields of Uranus and Neptune: Metallic Fluid Hydrogen  

E-print Network

The magnetic fields of the Ice Giant Planets Uranus and Neptune (U/N) are unique in the solar system. Based on a substantial database measured on Earth for representative planetary fluids at representative dynamic pressures up to 200 GPa (2 Mbar) and a few 1000 K, the complex magnetic fields of U/N are (i) probably made primarily by degenerate metallic fluid H (MFH) at or near the crossover from the H-He envelopes to Ice cores at ~100 GPa (Mbar) pressures and normalized radii of ~90% of the radii of U/N; (ii) because those magnetic fields are made relatively close to the surfaces of U/N, non-dipolar fields can be expected; (iii) the Ice cores are most probably a heterogeneous fluid mixture of H, N, O, C, Fe/Ni and silicate-oxides and their mutual reaction products at high pressures and temperatures; (iv) the shapes of the magnetic fields are probably caused by weak coupling between rotational motions of U/N and convective motions of conducting fluids in dynamos that make those magnetic fields. Ironically, the...

Nellis, W J

2015-01-01

298

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.

Iowa Public Television. Explore More Project

2004-01-01

299

Metal-catalysed steam reforming of ethanol in the production of hydrogen for fuel cell applications  

Microsoft Academic Search

A range of oxide-supported metal catalysts have been investigated for the steam reforming of ethanol\\/water mixtures for the production of hydrogen. Alumina-supported catalysts are very active at lower temperatures for the dehydration of ethanol to ethene which, at higher temperatures, is converted into H2, CO, and CO2 as the major products and CH4 as a minor product. The order of

J. P Breen; R Burch; H. M Coleman

2002-01-01

300

Cross-coupling hydrogen evolution reaction in homogeneous solution without noble metals.  

PubMed

A highly efficient noble-metal-free homogeneous system for a cross-coupling hydrogen evolution (CCHE) reaction is developed. With cheap, earth-abundant eosin Y and molecular catalyst Co(dmgH)2Cl2, good to excellent yields for coupling reactions with a variety of isoquinolines and indole substrates and H2 have been achieved without any sacrificial oxidants. Mechanistic insights provide rich information on the effective, clean, and economic CCHE reaction. PMID:24628016

Zhong, Jian-Ji; Meng, Qing-Yuan; Liu, Bin; Li, Xu-Bing; Gao, Xue-Wang; Lei, Tao; Wu, Cheng-Juan; Li, Zhi-Jun; Tung, Chen-Ho; Wu, Li-Zhu

2014-04-01

301

The sorption of hydrogen sulfide from hot syngas by metal oxides over supports  

Microsoft Academic Search

Six 5wt.% metal sorbents including Mn, Fe, Cu, Co, Ce and Zn supported on ?-Al2O3, prepared by the incipient wetness impregnation method with calcination at 700°C for 2h, have been investigated for sorption of hydrogen sulfide in the temperature range of 500–700°C. The sorption experiments were conducted in a fixed-bed reactor in terms of breakthrough curves and characterized by X-ray

Tzu-Hsing Ko; Hsin Chu; Lung-Kai Chaung

2005-01-01

302

Low Electronic States of Simple Heteropolar Diatomic Molecules: III. Hydrogen and Univalent Metal Halides  

Microsoft Academic Search

Electronic structures for the electronic states involved in the near ultraviolet spectra of AX are discussed (X=halogen, A=hydrogen or univalent metal). The upper electron levels involved are mostly among a set of levels Q 1Pi and 3II, T 3Sigma+, V 1Sigma+, or their Omega-s or case c equivalents. Tentative potential energy curves for states Q, T and V of HI,

Robert S. Mulliken

1937-01-01

303

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

304

Weld metal hydrogen cracking behavior, toughness, and microstructure in 9% Cr 1% Mo steels  

SciTech Connect

The use of 9%Cr 1%Mo steels, within various industries is increasing. The modification of the standard composition by the addition of V, Nb, and N improves the high temperature strength and creep properties. Development of welding conditions is dominated by the avoidance of hydrogen cracking while ensuring adequate mechanical properties and minimizing subcritical HAZ softening. This study was designed to evaluate compositional effects on MMA and electron beam (EB) weld metal properties and compare the weld metal hydrogen cracking sensitivity of the modified and standard grades. In comparing the hydrogen cracking sensitivity of the 9% Cr 1%Mo steels, the effect of welding and PWHT conditions on {delta}-ferrite development and SCHAZ softening were studied. An EB weld was incorporated in this study and assessment made of the CTOD behavior and microstructural development. Standard and modified grades exhibited similar hydrogen cracking sensitivity. The {delta}-ferrite content depended on welding conditions and composition. The ferrite factor gave a better indication of final ferrite content than Cr-equivalent. Softening in the SCHAZ was minimized by decreasing arc energy and preheat. The study indicates that modified grades can be welded using the procedures for standard grades. Charpy toughness was unaffected by 0.02{emdash}0.09%Nb or the PWHT schedules employed. increased Nb reduced the fracture toughness following extended PWHT.

Barnes, A.M. Panton-Kent, R.; Gooch, T.G.

1994-12-31

305

Phase, microstructure and hydrogen storage properties of Mg-Ni materials synthesized from metal nanoparticles  

NASA Astrophysics Data System (ADS)

After Mg and Ni nanoparticles were fabricated by hydrogen plasma metal reaction, Mg-rich MgxNi100-x(75 < x < 90) materials were synthesized from these metal nanoparticles to study the synergistic effects for hydrogen storage in these samples to show both good kinetics and high capacity. These MgxNi100-x materials may absorb hydrogen with a capacity of around 3.3-5.1 wt% in 1 min at 573 K. The Mg90Ni10 sample shows a hydrogen capacity of 6.1 wt%. The significant kinetic enhancement is thought to be due to the unique nanostructure from the special synthesis route, the catalytic effect of the Mg2Ni nano phase, and the synergistic effects between the Mg2Ni and Mg phases in the materials. An interesting phenomenon which has never been reported before was observed during pressure composition isotherm (PCT) measurements. One steep step in the absorption process and two obviously separated steps in the desorption process during PCT measurements of Mg80Ni20 and Mg90Ni10 samples were observed and a possible reason from the kinetic performance of the Mg2Ni and Mg phases in absorption and desorption processes was explained. These MgxNi100-x materials synthesized from Mg and Ni nanoparticles show high capacity and good kinetics, which makes these materials very promising candidates for thermal storage or energy storage and utilization for renewable power.

Shao, Huaiyu; Chen, Chunguang; Liu, Tong; Li, Xingguo

2014-04-01

306

GaN Sensors with Metal-Oxide Mixture for Sensing Hydrogen-Containing Gases of Ultralow Concentration  

Microsoft Academic Search

The roles of micro-metal-oxide (MO) interfaces inside a sensing metal formed by coevaporating Pd and SiO2 in metal-semiconductor-metal GaN sensors are investigated. The porous property of the Pd and SiO2 mixture together with the presence of micro-MO interfaces gives rise to a highly efficient dissociation of hydrogen molecules and hence an enhanced barrier height variation (DeltaphiB) of a reverse-biased Schottky

Shao-Yen Chiu; Kun-Chieh Liang; Tze-Hsuan Huang; Kang-Ping Liu; Hsuan-Wei Huang; Jung-Hui Tsai; Wen-Shiung Lour

2009-01-01

307

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

308

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

309

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

310

A thermo-mechanically-coupled theory accounting for hydrogen diffusion and large elastic–viscoplastic deformations of metals  

E-print Network

In this paper we develop a thermodynamically-consistent coupled-theory which accounts for diffusion of hydrogen, diffusion of heat, and large elastic–viscoplastic deformations of metals. The theory should be of utility in ...

Anand, Lallit

311

Curvature and ionization-induced reversible hydrogen storage in metalized hexagonal B36  

NASA Astrophysics Data System (ADS)

The synthesis of quasiplanar boron clusters (B36) with a central hexagonal hole provides the first experimental evidence that a single-atomic-layer borophene with hexagonal vacancies is potentially viable [Z. Piazza, H. Hu, W. Li, Y. Zhao, J. Li, and L. S. Wang, Nat. Commun. 5, 3113 (2014)]. However, owing to the hexagonal holes, tunning the electronic and physical properties of B36 through chemical modifications is not fully understood. Based on (van der Waals corrected-) density functional theory, we show that Li adsorbed on B36 and B^-_{36} clusters can serve as reversible hydrogen storage media. The present results indicate that the curvature and ionization of substrates can enhance the bond strength of Li due to the energetically favorable B 2p-Li 2p orbitals hybridization. Both the polarization mechanism and the orbital hybridization between H-s orbitals and Li-2s2p orbitals contribute to the adsorption of H2 molecules and the resulting adsorption energy lies between the physisorbed and chemisorbed states. Interestingly, the number of H2 in the hydrogen storage medium can be measured by the appearance of the negative differential resistance behavior at different bias voltage regions. Furthermore, the cluster-assembled hydrogen storage materials constructed by metalized B36 clusters do not cause a decrease in the number of adsorbed hydrogen molecules per Li. The system reported here is favorable for the reversible hydrogen adsorption/desorption at ambient conditions.

Liu, Chun-Sheng; Wang, Xiangfu; Ye, Xiao-Juan; Yan, Xiaohong; Zeng, Zhi

2014-11-01

312

The Combined Ortho / Para Hydrogen Assignments in H_2 Metal Chlorides  

NASA Astrophysics Data System (ADS)

The rotational spectra of H_2-AgCl and H_2-AuCl have been measured using a cavity FTMW spectrometer equipped with a laser ablation source. A combination of isotopic substitution, including HD and D_2 substitutions, and the spin-spin interaction of ortho hydrogen were used to determine the structures of these species. Trends in these structures and the strengths of the H_2 interaction will be discussed. Previous work with hydrogen containing complexes have shown that separate spectra are observed for the both the ortho and para hydrogen species. In this work, ortho and para hydrogen are assigned together. The a-axis in the present species is coincident with internal rotation axis of hydrogen. This symmetry, along with a covalent interaction of the H_2 with the metal chlorides, allows for a straightforward global assignment of the ortho and para species. The differences in the present study from the previous works will be discussed, as well as the assignment of the combined ortho and para fits. Y. Zhenhong, K. J. Higgins, W. Klemperer, M. C. McCarthy and P. Thaddeus, J. Chem. Phys., 123(2005) 221106. J. M. Michaug, W. C. Topic, W. Jäger, J. Phys. Chem. A., 115(2011) 9456 M. Ishiguro, K Harada, K. Tanaka, Y. Sumiyoshi, Y. Endo, Chem. Phys. Lett., 554(2012) 33.

Obenchain, Daniel A.; Grubbs, G. S., II; Frank, Derek S.; Pickett, Herbert M.; Novick, Stewart E.

2014-06-01

313

Influence of isotopic effect on the shift of the ionization potentials of hydrogen desorbed from the metal hydride surface  

Microsoft Academic Search

The sets of vertical ionization potentials for molecules of hydrogen (deuterium) desorbed from metal hydrides as well as for thermodynamically equilibrated molecular hydrogen (deuterium) at room temperature were obtained by means of the ionization efficiency curves method using mass-spectrometry measurements. Some sets of term differences are explained by thermoemission vibrational excitation of molecules. Comparative analysis to the data previously obtained

Yu. F. Shmal'ko; Ye. V. Klochko; M. V. Lototsky

1996-01-01

314

Mechanism of metal-free hydrogen transfer between amine-boranes and aminoboranes.  

PubMed

The kinetics of the metal-free hydrogen transfer from amine-borane Me(2)NH·BH(3) to aminoborane iPr(2)N?BH(2), yielding iPr(2)NH·BH(3) and cyclodiborazane [Me(2)N-BH(2)](2) via transient Me(2)N?BH(2), have been investigated in detail, with further information derived from isotopic labeling and DFT computations. The approach of the system toward equilibrium was monitored in both directions by (11)B{(1)H} NMR spectroscopy in a range of solvents and at variable temperatures in THF. Simulation of the resulting temporal-concentration data according to a simple two-stage hydrogen transfer/dimerization process yielded the rate constants and thermodynamic parameters attending both equilibria. At ambient temperature, the bimolecular hydrogen transfer is slightly endergonic in the forward direction (?G(1)°((295)) = 10 ± 7 kJ·mol(-1); ?G(1)(‡)((295)) = 91 ± 5 kJ·mol(-1)), with the overall equilibrium being driven forward by the subsequent exergonic dimerization of the aminoborane Me(2)N?BH(2) (?G(2)°((295)) = -28 ± 14 kJ·mol(-1)). Systematic deuterium labeling of the NH and BH moieties in Me(2)NH·BH(3) and iPr(2)N?BH(2) allowed the kinetic isotope effects (KIEs) attending the hydrogen transfer to be determined. A small inverse KIE at boron (k(H)/k(D) = 0.9 ± 0.2) and a large normal KIE at nitrogen (k(H)/k(D) = 6.7 ± 0.9) are consistent with either a pre-equilibrium involving a B-to-B hydrogen transfer or a concerted but asynchronous hydrogen transfer via a cyclic six-membered transition state in which the B-to-B hydrogen transfer is highly advanced. DFT calculations are fully consistent with a concerted but asynchronous process. PMID:23016922

Leitao, Erin M; Stubbs, Naomi E; Robertson, Alasdair P M; Helten, Holger; Cox, Robert J; Lloyd-Jones, Guy C; Manners, Ian

2012-10-10

315

Porous molybdenum carbide nano-octahedrons synthesized via confined carburization in metal-organic frameworks for efficient hydrogen production.  

PubMed

Electrochemical water splitting has been considered as a promising approach to produce clean and sustainable hydrogen fuel. However, the lack of high-performance and low-cost electrocatalysts for hydrogen evolution reaction hinders the large-scale application. As a new class of porous materials with tunable structure and composition, metal-organic frameworks have been considered as promising candidates to synthesize various functional materials. Here we demonstrate a metal-organic frameworks-assisted strategy for synthesizing nanostructured transition metal carbides based on the confined carburization in metal-organic frameworks matrix. Starting from a compound consisting of copper-based metal-organic frameworks host and molybdenum-based polyoxometalates guest, mesoporous molybdenum carbide nano-octahedrons composed of ultrafine nanocrystallites are successfully prepared as a proof of concept, which exhibit remarkable electrocatalytic performance for hydrogen production from both acidic and basic solutions. The present study provides some guidelines for the design and synthesis of nanostructured electrocatalysts. PMID:25758159

Wu, Hao Bin; Xia, Bao Yu; Yu, Le; Yu, Xin-Yao; Lou, Xiong Wen David

2015-01-01

316

Porous molybdenum carbide nano-octahedrons synthesized via confined carburization in metal-organic frameworks for efficient hydrogen production  

NASA Astrophysics Data System (ADS)

Electrochemical water splitting has been considered as a promising approach to produce clean and sustainable hydrogen fuel. However, the lack of high-performance and low-cost electrocatalysts for hydrogen evolution reaction hinders the large-scale application. As a new class of porous materials with tunable structure and composition, metal-organic frameworks have been considered as promising candidates to synthesize various functional materials. Here we demonstrate a metal-organic frameworks-assisted strategy for synthesizing nanostructured transition metal carbides based on the confined carburization in metal-organic frameworks matrix. Starting from a compound consisting of copper-based metal-organic frameworks host and molybdenum-based polyoxometalates guest, mesoporous molybdenum carbide nano-octahedrons composed of ultrafine nanocrystallites are successfully prepared as a proof of concept, which exhibit remarkable electrocatalytic performance for hydrogen production from both acidic and basic solutions. The present study provides some guidelines for the design and synthesis of nanostructured electrocatalysts.

Wu, Hao Bin; Xia, Bao Yu; Yu, Le; Yu, Xin-Yao; Lou, Xiong Wen (David)

2015-03-01

317

Porous molybdenum carbide nano-octahedrons synthesized via confined carburization in metal-organic frameworks for efficient hydrogen production  

PubMed Central

Electrochemical water splitting has been considered as a promising approach to produce clean and sustainable hydrogen fuel. However, the lack of high-performance and low-cost electrocatalysts for hydrogen evolution reaction hinders the large-scale application. As a new class of porous materials with tunable structure and composition, metal-organic frameworks have been considered as promising candidates to synthesize various functional materials. Here we demonstrate a metal-organic frameworks-assisted strategy for synthesizing nanostructured transition metal carbides based on the confined carburization in metal-organic frameworks matrix. Starting from a compound consisting of copper-based metal-organic frameworks host and molybdenum-based polyoxometalates guest, mesoporous molybdenum carbide nano-octahedrons composed of ultrafine nanocrystallites are successfully prepared as a proof of concept, which exhibit remarkable electrocatalytic performance for hydrogen production from both acidic and basic solutions. The present study provides some guidelines for the design and synthesis of nanostructured electrocatalysts. PMID:25758159

Wu, Hao Bin; Xia, Bao Yu; Yu, Le; Yu, Xin-Yao; Lou, Xiong Wen (David)

2015-01-01

318

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

319

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

320

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

321

Statistical theory of the hydrogen-induced phase decomposition of an amorphous zirconium-palladium alloy with the formation of metal hydrides. Hydrogen solubility in phases  

NASA Astrophysics Data System (ADS)

A statistical theory is developed for the decomposition of an amorphous zirconium-palladium alloy in a hydrogen atmosphere with the formation of metal hydrides. The free energies of the phases are calculated, and equations for the equilibrium states of the phases are derived. The phase-transformation temperatures are determined, and their dependences on the system composition are obtained. The temperature dependences of the hydrogen solubilities in the phases are found, and the appearance of the inflection points or jumps at the phase-transformation points, which are experimentally observed as inflections in the dependences, is grounded. Hydrogen solubility isotherms are calculated, and the possibility of a hysteresis effect is revealed.

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

2014-01-01

322

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

323

Compact hydrogenator  

NASA Technical Reports Server (NTRS)

The development and characteristics of a hydrogenating apparatus are described. The device consists of a reaction chamber which is selectively permeable to atomic hydrogen and catalytically active to a hydrogenating reaction. In one device, hydrogen is pumped out of the reaction chamber while the reactant remains inside to remove molecular hydrogen so that more atomic hydrogen can pass through the walls. In another device, the reactant is pumped through the reaction chamber, and the hydrogen is removed from the material leaving the chamber. The reactant is then cycled through the chamber.

Simmonds, P. G. (inventor)

1974-01-01

324

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

NASA Astrophysics Data System (ADS)

The formation of the giant planets in our solar system, and likely a majority of giant exoplanets, is most 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 interiors, particularly for Saturn-mass planets. Understanding the distribution of iron and other heavy elements in gas giants may be relevant in understanding mass-radius relationships, as well as deviations in transport properties from pure hydrogen-helium mixtures.

Wahl, Sean M.; Wilson, Hugh F.; Militzer, Burkhard

2013-08-01

325

SOLUBILITY OF IRON IN METALLIC HYDROGEN AND STABILITY OF DENSE CORES IN GIANT PLANETS  

SciTech Connect

The formation of the giant planets in our solar system, and likely a majority of giant exoplanets, is most 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 H{sub 2}O, MgO, and SiO{sub 2} 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 interiors, particularly for Saturn-mass planets. Understanding the distribution of iron and other heavy elements in gas giants may be relevant in understanding mass-radius relationships, as well as deviations in transport properties from pure hydrogen-helium mixtures.

Wahl, Sean M.; Wilson, Hugh F.; Militzer, Burkhard [Department of Earth and Planetary Science, University of California, Berkeley, CA 94720 (United States)

2013-08-20

326

Welding procedure specification. Supplement 1. Records of procedure qualification tests. Low hydrogen shielded metal arc welding of carbon steel  

Microsoft Academic Search

Procedure WPS-114-ASME-1 is qualified under Section IX of the ASME Boiler and Pressure Vessel Code for low hydrogen shielded metal arc welding of carbon steels (P-1-1), in thickness range 0.125 to 1.5 inch; filler metal is E7018 (F-4, A-1).

C. H. Wodtke; D. R. Frizzell; W. A. Plunkett

1986-01-01

327

Discharge Dynamics of Coupled Fuel Cell and Metal Hydride Hydrogen Storage bed for Small Wind Hybrid Systems  

Microsoft Academic Search

In small hybrid wind systems, excess wind energy is stored for later use during the deficit power generation. Excess wind energy can be stored as hydrogen in a metal hydride storage bed and reused later to generate power using a fuel cell. This paper deals with the discharge dynamics of the coupled fuel cell and metal hydride storage bed during

Siddhartha Kumar Khaitan; Mandhapati Raju

328

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

329

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

330

Complexes of earth-abundant metals for catalytic electrochemical hydrogen generation under aqueous conditions.  

PubMed

Growing global energy demands and climate change motivate the development of new renewable energy technologies. In this context, water splitting using sustainable energy sources has emerged as an attractive process for carbon-neutral fuel cycles. A key scientific challenge to achieving this overall goal is the invention of new catalysts for the reductive and oxidative conversions of water to hydrogen and oxygen, respectively. This review article will highlight progress in molecular electrochemical approaches for catalytic reduction of protons to hydrogen, focusing on complexes of earth-abundant metals that can function in pure aqueous or mixed aqueous-organic media. The use of water as a reaction medium has dual benefits of maintaining high substrate concentration as well as minimizing the environmental impact from organic additives and by-products. PMID:23034627

Thoi, V Sara; Sun, Yujie; Long, Jeffrey R; Chang, Christopher J

2013-03-21

331

Sunlight-driven hydrogen peroxide production from water and molecular oxygen by metal-free photocatalysts.  

PubMed

Design of green, safe, and sustainable process for the synthesis of hydrogen peroxide (H2 O2 ) is a very important subject. Early reported processes, however, require hydrogen (H2 ) and palladium-based catalysts. Herein we propose a photocatalytic process for H2 O2 synthesis driven by metal-free catalysts with earth-abundant water and molecular oxygen (O2 ) as resources under sunlight irradiation (?>400?nm). We use graphitic carbon nitride (g-C3 N4 ) containing electron-deficient aromatic diimide units as catalysts. Incorporating the diimide units positively shifts the valence-band potential of the catalysts, while maintaining sufficient conduction-band potential for O2 reduction. Visible light irradiation of the catalysts in pure water with O2 successfully produces H2 O2 by oxidation of water by the photoformed valence-band holes and selective two-electron reduction of O2 by the conduction band electrons. PMID:25293501

Shiraishi, Yasuhiro; Kanazawa, Shunsuke; Kofuji, Yusuke; Sakamoto, Hirokatsu; Ichikawa, Satoshi; Tanaka, Shunsuke; Hirai, Takayuki

2014-12-01

332

Performance of a metal hydride store on the "Ross Barlow" hydrogen powered canal boat.  

PubMed

This project involved the conversion of a British Waterways maintenance craft to a canal boat, powered by a combination of a solid-state hydrogen store, Proton Exchange Membrane (PEM) fuel cell, lead-acid battery pack and a high-efficiency, permanent magnet (NdFeB) electric motor. These replaced the conventional diesel engine thus eliminating water, noise, local and general atmospheric pollution. The "Protium" project applies modern technologies to a traditional mode of transportation. The TiMn2-based metal hydride store exhibited excellent performance as an effective means of storing 4 kg of hydrogen with a suitable desorption flow rate and temperature adequate for the operation of a 1 kW PEM fuel cell in a water-based environment. PMID:22455080

Bevan, A I; Züttel, A; Book, D; Harris, I R

2011-01-01

333

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...

334

Hydrogen production by auto-thermal reforming of ethanol over nickel catalyst supported on metal oxide-stabilized zirconia  

Microsoft Academic Search

Metal oxide-stabilized mesoporous zirconia supports (M–ZrO2) with different metal oxide stabilizer (M = Zr, Y, La, Ca, and Mg) were prepared by a templating sol–gel method. 20 wt% Ni catalysts supported on M–ZrO2 (M = Zr, Y, La, Ca, and Mg) were then prepared by an incipient wetness impregnation method for use in hydrogen production by auto-thermal reforming of ethanol. The effect of metal oxide

Min Hye Youn; Jeong Gil Seo; In Kyu Song

2010-01-01

335

The mechanism of mitochondrial swelling. V. Permeability of mitochondria to alkali metal salts of strong acid anions  

Microsoft Academic Search

Mitochondria do not swell appreciably when suspended in media containing the chlorides or bromides of alkali metal or ammonium ions. On the other hand, extensive swelling takes place when mitochondria are suspended in ammonium or sodium acetate. These findings have been widely interpreted to mean that the mitochondrial membrane is impermeable to chloride and bromide ions. However, the resistance of

George A. Blondin; David E. Green

1970-01-01

336

Microporous Metal?Organic Frameworks Incorporating 1,4-Benzeneditetrazolate:  Syntheses, Structures, and Hydrogen Storage Properties  

Microsoft Academic Search

The potential of tetrazolate-based ligands for forming metal-organic frameworks of utility in hydrogen storage is demonstrated with the use of 1,4-benzeneditetrazolate (BDT 2- ) to generate a series of robust, microporous materials. Reaction of H2BDT with MnCl2‚4H2O and Mn(NO3)2‚4H2 Oi nN,N- diethylformamide (DEF) produces the two-dimensional framework solids Mn3(BDT)2Cl2(DEF)6 (1) and Mn4- (BDT)3(NO3)2(DEF)6 (2), whereas reactions with hydrated salts of

Mircea Dinca?; Anta F. Yu; Jeffrey R. Long

2006-01-01

337

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

338

Solar Metal Sulfate-Ammonia Based Thermochemical Water Splitting Cycle for Hydrogen Production  

NASA Technical Reports Server (NTRS)

Two classes of hybrid/thermochemical water splitting processes for the production of hydrogen and oxygen have been proposed based on (1) metal sulfate-ammonia cycles (2) metal pyrosulfate-ammonia cycles. Methods and systems for a metal sulfate MSO.sub.4--NH3 cycle for producing H2 and O2 from a closed system including feeding an aqueous (NH3)(4)SO3 solution into a photoctalytic reactor to oxidize the aqueous (NH3)(4)SO3 into aqueous (NH3)(2)SO4 and reduce water to hydrogen, mixing the resulting aqueous (NH3)(2)SO4 with metal oxide (e.g. ZnO) to form a slurry, heating the slurry of aqueous (NH4)(2)SO4 and ZnO(s) in the low temperature reactor to produce a gaseous mixture of NH3 and H2O and solid ZnSO4(s), heating solid ZnSO4 at a high temperature reactor to produce a gaseous mixture of SO2 and O2 and solid product ZnO, mixing the gaseous mixture of SO2 and O2 with an NH3 and H2O stream in an absorber to form aqueous (NH4)(2)SO3 solution and separate O2 for aqueous solution, recycling the resultant solution back to the photoreactor and sending ZnO to mix with aqueous (NH4)(2)SO4 solution to close the water splitting cycle wherein gaseous H2 and O2 are the only products output from the closed ZnSO4--NH3 cycle.

Huang, Cunping (Inventor); T-Raissi, Ali (Inventor); Muradov, Nazim (Inventor)

2014-01-01

339

Structures of alkali metals in silica gel nanopores: new materials for chemical reductions and hydrogen production.  

PubMed

Alkali metals and their alloys can be protected from spontaneous reaction with dry air by intercalation (with subsequent heating) into the pores of silica gel (SG) at loadings up to 40 wt %. The resulting loose, black powders are convenient materials for chemical reduction of organic compounds and the production of clean hydrogen. The problem addressed in this paper is the nature of the reducing species present in these amorphous materials. The atomic pair distribution function (PDF), which considers both Bragg and diffuse scattering components, was used to examine their structures. Liquid Na-K alloys added to silica gel at room temperature (stage 0) or heated to 150 degrees C (stage I) as well as stage I Na-SG, retain the overall pattern of pure silica gel. Broad oscillations in the PDF show that added alkali metals remain in the pores as nanoscale metal clusters. 23Na MAS NMR studies confirm the presence of Na(0) and demonstrate that Na+ ions are formed as well. The relative amounts of Na(0) and Na(+) depend on both the overall metal loading and the average pore size. The results suggest that ionization occurs near or in the SiO2 walls, with neutral metal present in the larger cavities. The fate of the electrons released by ionization is uncertain, but they may add to the silica gel lattice, or form an "electride-like plasma" near the silica gel walls. A remaining mystery is why the stage I material does not show a melting endotherm of the encapsulated metal and does not react with dry oxygen. Na-SG when heated to 400 degrees C (stage II) yields a dual-phase reaction product that consists of Na(4)Si(4) and Na(2)SiO(3). PMID:17263423

Shatnawi, Mouath; Paglia, Gianluca; Dye, James L; Cram, Kevin C; Lefenfeld, Michael; Billinge, Simon J L

2007-02-01

340

Nickel-supported metal-carbon nanocomposites: New catalysts of hydrogenation of phenylacetylene  

NASA Astrophysics Data System (ADS)

Nickel-containing metal-carbon nanocomposites (Ni@C) synthesized by levitation melting in a flow of an inert gas-hydrocarbon mixture were used as catalysts of the hydrogenation of phenylacetylene (PA). The nanocomposites were characterized by X-ray photoelectron spectroscopy, simultaneous thermal analysis, and temperature-programmed reduction. The nickel-carbon nanocomposites were stable on storage in air, with only 13% of the total amount of nickel oxidized after 3.5 years of storage. In addition to nanoparticles completely covered with carbon, the composites contained partially coated metal particles, which are readily oxidized in air. Both types of particles exhibited the catalytic activity in phenylacetylene hydrogenation. At higher contents of nickel partially coated with carbon, the activity increased and the selectivity of styrene formation decreased. The minimum half-conversion temperature (75°C) was determined for a specially prepared Ni@C sample with an increased content of oxidized nickel (28%). The maximum selectivity of styrene formation (˜75% at 150°C) was recorded in the presence of the sample with the smallest amount of oxidized nickel (less than 4%).

Erokhin, A. V.; Lokteva, E. S.; Golubina, E. V.; Maslakov, K. I.; Yermakov, A. Ye.; Uimin, M. A.; Lunin, V. V.

2014-01-01

341

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

342

Preparation, characterization, and hydrogen storage capacity of MIL-53 metal-organic frameworks.  

PubMed

Metal organic frameworks (MOFs) are considered as most promising candidate for hydrogen storage material for practical application. MIL-53(Cr) MOFs were synthesized from Cr(NO3)3 x 9H2O combined with terephthalic acid organic linker. MIL-53(Cr) MOFs are octahedral in shape and the particle size was around 10 microm identified by FE-SEM. The cleaning of the MOFs crystals with different solvents at different warm temperature were found effective and approved to increase the specific surface area and porosity of MIL-53(Cr) MOFs. The XRD patterns represented that MIL-53(Cr) MOFs had well crystalline structures. Nitrogen adsorption isotherms show that Mil-53(Cr) has approximately type-I isotherm with a highest BET specific surface area of 1946 m2 g(-1) after treated with hot methanol. Hydrogen adsorption study shows that this material can store 0.45 wt.% of H2 measured at 303 K and 32 bar. The pre-edge XANES spectra confirm the existence of Cr(III) in crystalline framework of MIL-53(Cr) and the sharp feature at 6007 eV in XANES spectra represents the dipole-allowed electron transition from 1s to 4p(xy). In addition, EXAFS spectra indicate that MIL-53(Cr) metal organic frameworks structure has the Cr-O bond distance of 1.96 angstroms with a coordination number of 5.4. PMID:23763128

Lin, Kuen-Song; Adhikari, Abhijit Krishna; Tu, Mu-Ting; Wang, Chieh-Hung; Chiang, Chao-Lung

2013-04-01

343

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

344

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

345

Design of hydroforming processes for metallic liners used in high pressure hydrogen storage  

NASA Astrophysics Data System (ADS)

Within the framework of an European project concerning hydrogen storage, one analyze the way to manufacture high pressure tanks (700bars) for hydrogen storage, intended to be embarked for using in motor vehicles. These tanks consist of a metallic liner, which ensure a barrier role compared to the hydrogen atoms as well as a part of the mechanical resistance, and of a composite envelope built by filament rolling up which ensures the complementary part of the mechanical resistance. The paper describes the work completed within this framework, on the basis of the simulation of the hydroforming process thanks to the complete control of the process, in volume of fluid injected. One was thus brought to develop an optimization module based on finite element calculations. This optimization module includes MPI library in order to launch several calculations in parallel on a Linux cluster. It consists in seeking the optimal evolution of the fluid volume injected vs. time to obtain a good quality component. In our case, the optimization criterion is based on the variation thickness of the tube and the possible appearance of necking. It is shown that such a way for controlling the process provide the way to get minimal thickness variation, comparatively to standard optimization approaches where the process parameters are discretized through processing time in a more standard way.

Gelin, J. C.; Labergere, C.; Thibaud, S.; Boudeau, N.

2005-08-01

346

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

347

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

348

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

349

Boryl-metal bonds facilitate cobalt/nickel-catalyzed olefin hydrogenation.  

PubMed

New approaches toward the generation of late first-row metal catalysts that efficiently facilitate two-electron reductive transformations (e.g., hydrogenation) more typical of noble-metal catalysts is an important goal. Herein we describe the synthesis of a structurally unusual S = 1 bimetallic Co complex, [((Cy)PBP)CoH]2 (1), supported by bis(phosphino)boryl and bis(phosphino)hydridoborane ligands. This complex reacts reversibly with a second equivalent of H2 (1 atm) and serves as an olefin hydrogenation catalyst under mild conditions (room temperature, 1 atm H2). A bimetallic Co species is invoked in the rate-determining step of the catalysis according to kinetic studies. A structurally related Ni(I)Ni(I) dimer, [((Ph)PBP)Ni]2 (3), has also been prepared. Like Co catalyst 1, Ni complex 3 displays reversible reactivity toward H2, affording the bimetallic complex [((Ph)PBHP)NiH]2 (4). This reversible behavior is unprecedented for Ni(I) species and is attributed to the presence of a boryl-Ni bond. Lastly, a series of monomeric ((tBu)PBP)NiX complexes (X = Cl (5), OTf (6), H (7), OC(H)O (8)) have been prepared. The complex ((tBu)PBP)NiH (7) shows enhanced catalytic olefin hydrogenation activity when directly compared with its isoelectronic/isostructural analogues where the boryl unit is substituted by a phenyl or amine donor, a phenomenon that we posit is related to the strong trans influence exerted by the boryl ligand. PMID:25181350

Lin, Tzu-Pin; Peters, Jonas C

2014-10-01

350

Calcium as a superior coating metal in functionalization of carbon fullerenes for high-capacity hydrogen storage  

SciTech Connect

We explore theoretically the feasibility of functionalizing carbon nanostructures for hydrogen storage, focusing on the coating of C60 fullerenes with light alkaline-earth metals. Our first-principles density functional theory studies show that both Ca and Sr can bind strongly to the C60 surface, and highly prefer monolayer coating, thereby explaining existing experimental observations. The strong binding is attributed to an intriguing charge transfer mechanism involving the empty d levels of the metal elements. The charge redistribution, in turn, gives rise to electric fields surrounding the coated fullerenes, which can now function as ideal attractors upon molecular hydrogen adsorption with binding strengths strong enough for potential room temperature applications but weak enough to avoid H2 dissociation. With a hydrogen uptake of >8.4wt% on Ca32C60, Ca is superior to all the recently suggested metal coating elements.

Yoon, Mina [ORNL; Yang, Shenyuan [ORNL; Hicke, Christian [ORNL; Wang, Enge [Chinese Academy of Sciences; Geohegan, David B [ORNL; Zhang, Zhenyu [ORNL

2008-01-01

351

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

352

Effects of ligand modification and protonation on metal oxime hydrogen evolution electrocatalysts.  

PubMed

The design of hydrogen-evolving electrocatalysts that operate at modest overpotentials is important for solar energy devices. The M(II/I) reduction potential for metal diimine-dioxime and diglyoxime electrocatalysts is often related to the overpotential required for hydrogen evolution. Herein the impact of ligand modification and protonation on the M(II/I) reduction potentials for cobalt, nickel, and iron diimine-dioxime and diglyoxime complexes is investigated with computational methods. The calculations are consistent with experimental data available for some of these complexes and additionally provide predictions for complexes that have not yet been synthesized. The calculated pKa's imply that ligand protonation is likely to occur at the O-H-O bridge but not at other ligand sites for these complexes. Moreover, the calculations imply that a ligand-protonated Co(III)-hydride intermediate is formed along the H2 production pathway for catalysts containing an O-H-O bridge in the presence of sufficiently strong acid. The calculated M(II/I) reduction potentials indicate that the anodic shift due to protonation of the O-H-O bridge is greater than that due to replacing the O-H-O bridge with an O-BF2-O bridge for cobalt and nickel but not for iron complexes. Experiments suggest degradation for complexes with two O-H-O bridges and alternative mechanisms for certain iron complexes with two O-BF2-O bridges. Asymmetric cobalt, nickel, and strongly electron withdrawing substituted iron diimine-dioxime and diglyoxime complexes containing a single O-H-O bridge are proposed to be effective hydrogen evolution electrocatalysts with relatively low overpotentials in acetonitrile and water. These insights are important for the design of efficient aqueous-based hydrogen-evolving catalysts. PMID:23701462

Solis, Brian H; Yu, Yinxi; Hammes-Schiffer, Sharon

2013-06-17

353

Hydrogen Energy Technology Geoff Dutton  

E-print Network

hydrogen production Hydrogen storage and distribution Compressed gas Liquefaction Solid state hydrogen storage Metal hydride storage systems Hydride hydrolysis Glass microspheres Relative merits of hydrogen storage systems and comparison of costs Hydrogen distribution and transport Hydrogen end use systems

Watson, Andrew

354

Hydrogen purifier module with membrane support  

SciTech Connect

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

355

From hydrogen bonding to metal coordination and back: Porphyrin-based networks on Ag(111)  

NASA Astrophysics Data System (ADS)

The self-assembly of a metal-free porphyrin bearing two pyridyl coordinating sites and two pentyl chains at trans meso positions was investigated under ultrahigh vacuum on a Ag(111) surface by scanning tunneling microscopy (STM). The STM measurements revealed a well-ordered close-packed structure with a rhombic unit cell for coverages ?1 monolayer with their molecular plane parallel to the surface. The growth direction of the molecular islands is aligned along the step edges, which are restructured due to molecule-substrate interactions. The shorter unit cell vector of the molecular superstructure follows the <1-10> direction of the Ag(111) substrate. Hydrogen bonds between pyridyl and pyrrole groups of neighboring molecules as well as weak van der Waals forces between the pentyl chains stabilize the superstructure. Deposition of cobalt atoms onto the close-packed structure at room temperature leads to the formation of a hexagonal porous network stabilized by metal-ligand bonding between the pyridyl ligands and the cobalt atoms. Thermal annealing of the Co-coordination network at temperatures >450 K results in the transformation of the hexagonal network into a second close-packed structure. Changes in the molecule-substrate interactions due to metalation of the porphyrin core with Co as well as intermolecular interactions can explain the observed structural transformations.

Studener, F.; Müller, K.; Marets, N.; Bulach, V.; Hosseini, M. W.; Stöhr, M.

2015-03-01

356

Enhanced hydrogen evolution catalysis from chemically exfoliated metallic MoS2 nanosheets.  

PubMed

Promising catalytic activity from molybdenum disulfide (MoS2) in the hydrogen evolution reaction (HER) is attributed to active sites located along the edges of its two-dimensional layered crystal structure, but its performance is currently limited by the density and reactivity of active sites, poor electrical transport, and inefficient electrical contact to the catalyst. Here we report dramatically enhanced HER catalysis (an electrocatalytic current density of 10 mA/cm(2) at a low overpotential of -187 mV vs RHE and a Tafel slope of 43 mV/decade) from metallic nanosheets of 1T-MoS2 chemically exfoliated via lithium intercalation from semiconducting 2H-MoS2 nanostructures grown directly on graphite. Structural characterization and electrochemical studies confirmed that the nanosheets of the metallic MoS2 polymorph exhibit facile electrode kinetics and low-loss electrical transport and possess a proliferated density of catalytic active sites. These distinct and previously unexploited features of 1T-MoS2 make these metallic nanosheets a highly competitive earth-abundant HER catalyst. PMID:23790049

Lukowski, Mark A; Daniel, Andrew S; Meng, Fei; Forticaux, Audrey; Li, Linsen; Jin, Song

2013-07-17

357

From hydrogen bonding to metal coordination and back: Porphyrin-based networks on Ag(111).  

PubMed

The self-assembly of a metal-free porphyrin bearing two pyridyl coordinating sites and two pentyl chains at trans meso positions was investigated under ultrahigh vacuum on a Ag(111) surface by scanning tunneling microscopy (STM). The STM measurements revealed a well-ordered close-packed structure with a rhombic unit cell for coverages ?1 monolayer with their molecular plane parallel to the surface. The growth direction of the molecular islands is aligned along the step edges, which are restructured due to molecule-substrate interactions. The shorter unit cell vector of the molecular superstructure follows the ?1-10? direction of the Ag(111) substrate. Hydrogen bonds between pyridyl and pyrrole groups of neighboring molecules as well as weak van der Waals forces between the pentyl chains stabilize the superstructure. Deposition of cobalt atoms onto the close-packed structure at room temperature leads to the formation of a hexagonal porous network stabilized by metal-ligand bonding between the pyridyl ligands and the cobalt atoms. Thermal annealing of the Co-coordination network at temperatures >450 K results in the transformation of the hexagonal network into a second close-packed structure. Changes in the molecule-substrate interactions due to metalation of the porphyrin core with Co as well as intermolecular interactions can explain the observed structural transformations. PMID:25770515

Studener, F; Müller, K; Marets, N; Bulach, V; Hosseini, M W; Stöhr, M

2015-03-14

358

Electronic structure and metalization of a silane-hydrogen system under high pressure investigated using density functional and GW calculations  

NASA Astrophysics Data System (ADS)

We have computed the electronic structure and the vibrational properties of the recently discovered hydrogen-rich compound silane-hydrogen [SiH4(H2)2] from first principles, using density-functional theory. We have also studied the metallization under pressure of SiH4(H2)2 by the GW approximation, and obtained that the metallization occurs around 164 GPa, whereas the standard GGA calculations predict a metallization pressure around 145 GPa. Our results are compared with the recent experiment data of Strobel [Phys. Rev. Lett. 103, 065701 (2009)]10.1103/PhysRevLett.103.065701 and Wang [Proc. Natl. Acad. Sci. USA. 106, 14763 (2009)]10.1073/pnas.0907729106 and it is found that our calculated value of the metallization pressure is higher than the proposed experimental data. Some possible reasons for such a discrepancy are discussed in the text.

Ramzan, M.; Lebègue, S.; Ahuja, R.

2010-06-01

359

Hydrogen adsorption in a highly stable porous rare-earth metal-organic framework: sorption properties and neutron diffraction studies.  

PubMed

A highly stable porous lanthanide metal-organic framework, Y(BTC)(H2O).4.3H2O (BTC = 1,3,5-benzenetricarboxylate), with pore size of 5.8 A has been constructed and investigated for hydrogen storage. Gas sorption measurements show that this porous MOF exhibits highly selective sorption behaviors of hydrogen over nitrogen gas molecules and can take up hydrogen of about 2.1 wt % at 77 K and 10 bar. Difference Fourier analysis of neutron powder diffraction data revealed four distinct D2 sites that are progressively filled within the nanoporous framework. Interestingly, the strongest adsorption sites identified are associated with the aromatic organic linkers rather than the open metal sites, as occurred in previously reported MOFs. Our results provide for the first time direct structural evidence demonstrating that optimal pore size (around 6 A, twice the kinetic diameter of hydrogen) strengthens the interactions between H2 molecules and pore walls and increases the heat of adsorption, which thus allows for enhancing hydrogen adsorption from the interaction between hydrogen molecules with the pore walls rather than with the normally stronger adsorption sites (the open metal sites) within the framework. At high concentration H2 loadings (5.5 H2 molecules (3.7 wt %) per Y(BTC) formula), H2 molecules form highly symmetric novel nanoclusters with relatively short H2-H2 distances compared to solid H2. These observations are important and hold the key to optimizing this new class of rare metal-organic framework (RMOF) materials for practical hydrogen storage applications. PMID:18611006

Luo, Junhua; Xu, Hongwu; Liu, Yun; Zhao, Yusheng; Daemen, Luke L; Brown, Craig; Timofeeva, Tatiana V; Ma, Shengqian; Zhou, Hong-Cai

2008-07-30

360

A high-performance hydrogen generation system: Transition metal-catalyzed dissociation and hydrolysis of ammonia–borane  

Microsoft Academic Search

A high-performance hydrogen generation system based on transition metal-catalyzed dissociation and hydrolysis of ammonia–borane complex (NH3BH3) at room temperature has been achieved. NH3BH3 dissolves in water to form a solution stable in the absence of air. The addition of a catalytic amount of suitable metal catalysts such as Pt, Rh, and Pd into the solutions with various concentrations leads to

Manish Chandra; Qiang Xu

2006-01-01

361

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

362

Ti-doped alkali metal aluminium hydrides as potential novel reversible hydrogen storage materials 1 Invited paper presented at the International Symposium on Metal–Hydrogen Systems, Les Diablerets, August 25–30, 1996, Switzerland. 1  

Microsoft Academic Search

New reversible hydrogen storage systems are proposed, based on catalyzed reactions (Eqs. 4–6). The catalytic acceleration of the reactions in both directions is achieved by doping alkali metal aluminium hydrides with a few mol% of selected Ti compounds. The PCI diagrams of the Ti catalyzed systems show an absence of hysteresis and nearly horizontal pressure plateaus. The PCI of the

Borislav Bogdanovi?; Manfred Schwickardi

1997-01-01

363

Identification of a new pseudo-binary hydroxide during calendar corrosion of (La, Mg)2Ni7-type hydrogen storage alloys for Nickel-Metal Hydride batteries  

E-print Network

hydrogen storage alloys for Nickel-Metal Hydride batteries J. Monnier 1 , H. Chen 1 , S. Joiret2,3 , J hydrogen storage capacity and higher discharge capacity, eg. 356mAh/g for LaCaMgNi9 [4] compared to the AB5 market of hybrid electric vehicles (HEV) and Emergency Light Units (ELU). Hydrogen-absorbing alloys based

Boyer, Edmond

364

Hydrogen Spillover Enhanced Hydroxyl Formation and Catalytic Activity Toward CO Oxidation at the Metal/Oxide Interface.  

PubMed

H2 -promoted catalytic activity of oxide-supported metal catalysts in low-temperature CO oxidation is of great interest but its origin remains unknown. Employing an FeO(111)/Pt(111) inverse model catalyst, we herewith report direct experimental evidence for the spillover of H(a) adatoms on the Pt surface formed by H2 dissociation to the Pt?FeO interface to form hydroxyl groups that facilely oxidize CO(a) on the neighboring Pt surface to produce CO2 . Hydroxyl groups and coadsorbed water play a crucial role in the occurrence of hydrogen spillover. These results unambiguously identify the occurrence of hydrogen spillover from the metal surface to the noble metal/metal oxide interface and the resultant enhanced catalytic activity of the metal/oxide interface in low-temperature CO oxidation, which provides a molecular-level understanding of both H2 -promoted catalytic activity of metal/oxide ensembles in low-temperature CO oxidation and hydrogen spillover. PMID:25650016

Jin, Yuekang; Sun, Guanghui; Xiong, Feng; Ding, Liangbing; Huang, Weixin

2015-03-01

365

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

366

Low-temperature thermostatics of face-centered-cubic metallic hydrogen  

NASA Technical Reports Server (NTRS)

The thermostatic properties of a high-symmetry phase of metallic hydrogen with atomic sphere radius between 0.1 and 1.5 bohr are studied, with special emphasis accorded to electronic screening and quantum proton motion. The electron-proton and proton-proton interactions receive a perturbation treatment based on the Singwi dielectric function, while the proton motion is handled by self-consistent harmonic approximation. Quantum behavior is found to be less pronounced than expected, and nuclear magnetism is absent. The phonon spectrum is, however, affected by screening and large proton motion. The zero-point vibrational energy and the superconducting critical temperature are below previous estimates. The crystalline-defect formation energies are a few times the Debye energy, which implies that defects contribute significantly to melting at the lower particle densities.

Caron, L. G.

1974-01-01

367

Rydberg hydrogen atom near a metallic surface: Stark regime and ionization dynamics  

SciTech Connect

We investigate the classical dynamics of a hydrogen atom near a metallic surface in the presence of a uniform electric field. To describe the atom-surface interaction we use a simple electrostatic image model. Owing to the axial symmetry of the system, the z-component of the canonical angular momentum P{sub {phi}} is an integral and the electronic dynamics is modeled by a two degrees of freedom Hamiltonian in cylindrical coordinates. The structure and evolution of the phase space as a function of the electric field strength is explored extensively by means of numerical techniques of continuation of families of periodic orbits and Poincare surfaces of section. We find that, due to the presence of the electric field, the atom is strongly polarized through two consecutive pitchfork bifurcations that strongly change the phase space structure. Finally, by means of the phase space transition state theory and the classical spectral theorem, the ionization dynamics of the atom is studied.

Inarrea, Manuel; Salas, J. Pablo [Area de Fisica Aplicada, Universidad de La Rioja, Logrono (Spain); Lanchares, Victor; Pascual, Ana Isabel [Departamento de Matematicas y Computacion, Universidad de La Rioja, Logrono (Spain); Palacian, Jesus F.; Yanguas, Patricia [Departamento de Ingenieria Matematica e Informatica, Universidad Publica de Navarra, Pamplona (Spain)

2007-11-15

368

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

369

Metal-free hydrogenation catalyzed by an air-stable borane: use of solvent as a frustrated Lewis base.  

PubMed

In recent years 'frustrated Lewis pairs' (FLPs) have been shown to be effective metal-free catalysts for the hydrogenation of many unsaturated substrates. Even so, limited functional-group tolerance restricts the range of solvents in which FLP-mediated reactions can be performed, with all FLP-mediated hydrogenations reported to date carried out in non-donor hydrocarbon or chlorinated solvents. Herein we report that the bulky Lewis acids B(C6Cl5)x(C6F5)(3-x) (x=0-3) are capable of heterolytic H2 activation in the strong-donor solvent THF, in the absence of any additional Lewis base. This allows metal-free catalytic hydrogenations to be performed in donor solvent media under mild conditions; these systems are particularly effective for the hydrogenation of weakly basic substrates, including the first examples of metal-free catalytic hydrogenation of furan heterocycles. The air-stability of the most effective borane, B(C6Cl5)(C6F5)2, makes this a practically simple reaction method. PMID:25113014

Scott, Daniel J; Fuchter, Matthew J; Ashley, Andrew E

2014-09-15

370

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

371

Hydrogen adsorption in metal-organic frameworks: The role of nuclear quantum effects  

NASA Astrophysics Data System (ADS)

The role of nuclear quantum effects on the adsorption of molecular hydrogen in metal-organic frameworks (MOFs) has been investigated on grounds of Grand-Canonical Quantized Liquid Density-Functional Theory (GC-QLDFT) calculations. For this purpose, we have carefully validated classical H2-host interaction potentials that are obtained by fitting Born-Oppenheimer ab initio reference data. The hydrogen adsorption has first been assessed classically using Liquid Density-Functional Theory and the Grand-Canonical Monte Carlo methods. The results have been compared against the semi-classical treatment of quantum effects by applying the Feynman-Hibbs correction to the Born-Oppenheimer-derived potentials, and by explicit treatment within the GC-QLDFT. The results are compared with experimental data and indicate pronounced quantum and possibly many-particle effects. After validation calculations have been carried out for IRMOF-1 (MOF-5), GC-QLDFT is applied to study the adsorption of H2 in a series of MOFs, including IRMOF-4, -6, -8, -9, -10, -12, -14, -16, -18, and MOF-177. Finally, we discuss the evolution of the H2 quantum fluid with increasing pressure and lowering temperature.

Wahiduzzaman, Mohammad; Walther, Christian F. J.; Heine, Thomas

2014-08-01

372

Hydrogen adsorption in metal-organic frameworks: the role of nuclear quantum effects  

E-print Network

The role of nuclear quantum effects on the adsorption of molecular hydrogen in metal-organic frameworks (MOFs) has been investigated on grounds of Grand-Canonical Quantized Liquid Density-Functional Theory (GC-QLDFT) calculations. For this purpose, we have carefully validated classical H2 -host interaction potentials that are obtained by fitting Born-Oppenheimer ab initio reference data. The hydrogen adsorption has first been assessed classically using Liquid Density-Functional Theory (LDFT) and the Grand-Canonical Monte Carlo (GCMC) methods. The results have been compared against the semi-classical treatment of quantum effects by applying the Feynman-Hibbs correction to the Born-Oppenheimer-derived potentials, and by explicit treatment within the Grand-Canonical Quantized Liquid Density-Functional Theory (GC-QLDFT). The results are compared with experimental data and indicate pronounced quantum and possibly many-particle effects. After validation calculations have been carried out for IRMOF-1 (MOF-5), GC-QLD...

Wahiduzzaman, Mohammad; Heine, Thomas

2014-01-01

373

In vivo evaluation of bone-bonding of titanium metal chemically treated with a hydrogen peroxide solution containing tantalum chloride  

Microsoft Academic Search

Apatite formation on implants is important in achieving a direct bonding to bone tissue. We recently showed that titanium metal chemically treated with a hydrogen peroxide solution containing tantalum chloride has the ability to form a hydroxyapatite layer in simulated body fluid which had inorganic ion composition similar to human blood plasma. In this study, a pure titanium cylinder (4.0mm

S Kaneko; K Tsuru; S Hayakawa; S Takemoto; C Ohtsuki; T Ozaki; H Inoue; A Osaka

2001-01-01

374

The effect of a micro bubble dispersed gas phase on hydrogen isotope transport in liquid metals under nuclear irradiation  

E-print Network

The present work intend to be a first step towards the understanding and quantification of the hydrogen isotope complex phenomena in liquid metals for nuclear technology. Liquid metals under nuclear irradiation in,e.g., breeding blankets of a nuclear fusion reactor would generate tritium which is to be extracted and recirculated as fuel. At the same time that tritium is bred, helium is also generated and may precipitate in the form of nano bubbles. Other liquid metal systems of a nuclear reactor involve hydrogen isotope absorption processes, e.g., tritium extraction system. Hence, hydrogen isotope absorption into gas bubbles modelling and control may have a capital importance regarding design, operation and safety. Here general models for hydrogen isotopes transport in liquid metal and absorption into gas phase, that do not depend on the mass transfer limiting regime, are exposed and implemented in OpenFOAMR CFD tool for 0D to 3D simulations. Results for a 0D case show the impact of a He dispersed phase of na...

Fradera, Jorge

2013-01-01

375

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

E-print Network

Hydrogen  embrittlement;  Intergranular  cracking;  Grain?hydrogen  concentrations (Fig.  2), with much lower fractions of intergranular cracking cracking on the fracture surfaces of the uniaxial  tensile specimens as a function of the dissolved hydrogen 

Bechtle, Sabine

2009-01-01

376

Photoelectrochemical water splitting for hydrogen production with metal oxide (hematite and cupric oxide) based photocatalysts  

NASA Astrophysics Data System (ADS)

Solar hydrogen is one ideal energy source to replace fossil fuel, as it is sustainable and environmentally friendly. Solar hydrogen can be generated in a number of ways. Photoelectrochemical (PEC) water splitting is one of the most promising methods for solar-to-chemical energy conversion. In this research project, metal oxide-based photocatalysts, especially hematite (?-Fe 2O3) and cupric oxide (CuO), were investigated for use as electrodes in PEC water splitting for solar hydrogen production. In our research project of hematite-based electrodes, we started with the incorporation of transition metal, particularly titanium (Ti), in hematite thin films to modify the valence and conduction band edges of hematite. We found that Ti impurities improve the electron conductivity of hematite and consequently lead to significantly enhanced photocurrents. We further investigated the Ti and Mg co-alloyed hematite. In this case, Ti is the donor and Mg is the acceptor in hematite. The co-alloying approach enhanced the solubility of Mg and Ti, which led to reduced electron effective mass and therefore increased electron mobility. Also, co-alloying tunes the carrier density and therefore allows the optimization of electrical conductivity. The densities of charged defects were found to be reduced, and therefore carrier recombinations were reduced. As a result, the Ti and Mg co-alloyed hematite thin films exhibited much improved performance in PEC water splitting as compared to pure hematite thin films. For the study of cupric oxide-based electrodes, we first investigated the possibility of reducing the electrode corrosion of cupric oxide in aqueous solutions by incorporating Ti as an electrode corrosion inhibitor. We found that Ti alloying can enhance the stability of cupric oxide in base solutions at the cost of reducing its crystallinity and optical absorption, and consequently lowering its photon-to-electron conversion efficiency. In order to balance the stability and the generated photocurrent, we developed a two-layer structure in which a thin layer of Cu-Ti-O was deposited on bare CuO thin film as a protective layer. Our experimental results indicated that this two-layer structure has an ideal thickness for the protection layer and is suitable for high-performance and long-term application for PEC water splitting.

Tang, Houwen

377

Hydrogenic heavy metal pollution of alluvial soils in the city of Perm  

NASA Astrophysics Data System (ADS)

The differences in the sources and compositions of the pollutants among the alluvial soils within the city of Perm were revealed. Heavy metal pollution of hydrogenic origin is caused by unpurified sewage water. The main source of pollution of the urbanozems and replantozems of the city is the aerial input of heavy metals. The lead content in the alluvial soils of the city was twice lower and the mean Zn and Ni contents were 1.5 and 4.0 times higher than in the urbanozems and replantozems, respectively. The concentrations of Sr, Zn, Ni, Cu, and Cr did not correlate positively with the content of clay particles in the fine earth of the alluvial soils. The higher pollution of the light-textured soils showed that, nowadays, its main source was sewage water but not sludge. In the alluvial soils, small Fe-rohrensteins are formed. They serve as microgeochemical barriers for some part of the microelements. The Pb and Zn contents in the rohrensteins of the soils of the Las’va river basin reached 440 and 890 mg/kg, respectively. In the upper horizon of this soil, the contents of Pb and Zn in the rohrensteins were 42 and 17% of their concentration in the fine earth, respectively.

Vodyanitskii, Yu. N.; Vasil'Ev, A. A.; Vlasov, M. N.

2008-11-01

378

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

379

Metal aminoboranes  

DOEpatents

Metal aminoboranes of the formula M(NH2BH3)n have been synthesized. Metal aminoboranes are hydrogen storage materials. Metal aminoboranes are also precursors for synthesizing other metal aminoboranes. Metal aminoboranes can be dehydrogenated to form hydrogen and a reaction product. The reaction product can react with hydrogen to form a hydrogen storage material. Metal aminoboranes can be included in a kit.

Burrell, Anthony K.; Davis, Benjamin J.; Thorn, David L.; Gordon, John C.; Baker, R. Thomas; Semelsberger, Troy Allen; Tumas, William; Diyabalanage, Himashinie Vichalya; Shrestha, Roshan P.

2010-05-11

380

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

381

Examining the role of hydrogen in the electrical performance of in situ fabricated metal-insulator-metal trilayers using an atomic layer deposited Al2O3 dielectric  

NASA Astrophysics Data System (ADS)

Defects in electronic devices can lead to poor performance and device failure. We used deuterium doping to investigate the source of hydrogen defects in Atomic Layer Deposited (ALD) Al2O3 films and in situ fabrication techniques to produce ultraclean metal-insulator-metal trilayers. We compare leakage current and defect density of ALD Al2O3 dielectrics deposited using different oxidation conditions. The plasma O2 ALD process has lowest number of entrained defects and exhibits a leakage current 104 times lower than the thermal ALD process. Deuterium doping during the ALD process shows that the majority of the hydrogen defects contained in the ALD films are due to entrained water.

Kozen, Alexander C.; Schroeder, Marshall A.; Osborn, Kevin D.; Lobb, C. J.; Rubloff, Gary W.

2013-04-01

382

Mitigation of hydrogen by oxidation using nitrous oxide and noble metal catalysts  

SciTech Connect

This test studied the ability of a blend of nuclear-grade, noble-metal catalysts to catalyze a hydrogen/nitrous oxide reaction in an effort to mitigate a potential hydrogen (H{sub 2}) gas buildup in the Hanford Site Grout Disposal Facility. For gases having H{sub 2} and a stoichiometric excess of either nitrous oxide or oxygen, the catalyst blend can effectively catalyze the H{sub 2} oxidation reaction at a rate exceeding 380 {mu}moles of H{sub 2} per hour per gram of catalyst ({mu}mol/h/g) and leave the gas with less than a 0.15 residual H{sub 2} Concentration. This holds true in gases with up to 2.25% water vapor and 0.1% methane. This should also hold true for gases with up to 0.1% carbon monoxide (CO) but only until the catalyst is exposed to enough CO to block the catalytic sites and stop the reaction. Gases with ammonia up to 1% may be slightly inhibited but can have reaction rates greater than 250 {mu}mol/h/g with less than a 0.20% residual H{sub 2} concentration. The mechanism for CO poisoning of the catalyst is the chemisorption of CO to the active catalyst sites. The CO sorption capacity (SC) of the catalyst is the total amount of CO that the catalyst will chemisorb. The average SC for virgin catalyst was determined to be 19.3 {plus_minus} 2.0 {mu}moles of CO chemisorbed to each gram of catalyst ({mu}mol/g). The average SC for catalyst regenerated with air was 17.3 {plus_minus} 1.9 {mu}mol/g.

Britton, M.D.

1995-01-19

383

Improvement in the hydrogen desorption from MgH2 upon transition metals doping: A hybrid density functional calculations  

NASA Astrophysics Data System (ADS)

This study deals with the investigations of structural, electronic and thermodynamic properties of MgH2 doped with selected transition metals (TMs) by means of hybrid density functional theory (PBE0). On the structural side, the calculated lattice parameters and equilibrium volumes increase in case of Sc, Zr and Y opposite to all the other dopants indicating volumetrically increased hydrogen density. Except Fe, all the dopants improve the kinetics of MgH2 by reducing the heat of adsorption with Cu, Nb, Ni and V proving more efficient than others studied TM's. The electronic properties have been studied by density of states and correlated with hydrogen adsorption energies.

Hussain, Tanveer; Maark, Tuhina Adit; Pathak, Biswarup; Ahuja, Rajeev

2013-10-01

384

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

385

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

386

Studies on metal-organic frameworks of Cu(II) with isophthalate linkers for hydrogen storage.  

PubMed

Hydrogen (H2) is a promising alternative energy carrier because of its environmental benefits, high energy density, and abundance. However, development of a practical storage system to enable the "Hydrogen Economy" remains a huge challenge. Metal-organic frameworks (MOFs) are an important class of crystalline coordination polymers constructed by bridging metal centers with organic linkers. MOFs show promise for H2 storage owing to their high surface area and tuneable properties. In this Account, we summarize our research on novel porous materials with enhanced H2 storage properties and describe frameworks derived from 3,5-substituted dicarboxylates (isophthalates) that serve as versatile molecular building blocks for the construction of a range of interesting coordination polymers with Cu(II) ions. We synthesized a series of materials by connecting linear tetracarboxylate linkers to {Cu(II)2} paddlewheel moieties. These materials exhibit high structural stability and permanent porosity. Varying the organic linker modulates the pore size, geometry, and functionality to control the overall H2 adsorption. Our top-performing material in this series has a H2 storage capacity of 77.8 mg g(-1) at 77 K, 60 bar. H2 adsorption at low, medium, and high pressures correlates with the isosteric heat of adsorption, surface area, and pore volume, respectively. Another series, using tribranched C3-symmetric hexacarboxylate ligands with Cu(II), gives highly porous (3,24)-connected frameworks incorporating {Cu(II)2} paddlewheels. Increasing the length of the hexacarboxylate struts directly tunes the porosity of the resultant material from micro- to mesoporosity. These materials show exceptionally high H2 uptakes owing to their high surface area and pore volume. The first member of this family reported adsorbs 111 mg g(-1) of H2, or 55.9 g L(-1), at 77 K, 77 bar, while at 77 K, 1 bar, the material adsorbs 2.3 wt % H2. We and others have since achieved enhanced H2 adsorption in these frameworks using combinations of polyphenyl groups linked by alkynes. The maximum storage achieved for one of the enhanced materials is 164 mg g(-1) at 77 K, 70 bar, but because of its low density, its volumetric capacity is only 45.7 g L(-1). We attribute the significant adsorption of H2 at low pressures to the arrangement of the {Cu24(isophthalate)24} cuboctahedral cages within the polyhedral structure. Free metal coordination positions are the first binding sites for D2, and these frameworks have two types of Cu(II) centers, one with its vacant site pointing into the cuboctahedral cage and another pointing externally. D2 molecules bind first at the former position and then at the external open metal sites. Design of ligands and complexes is key for enhancing and maximizing H2 storage, and although current materials operate at 77 K, research continues to explore routes to high capacity H2 storage materials that can function at higher temperatures. PMID:24168725

Yan, Yong; Yang, Sihai; Blake, Alexander J; Schröder, Martin

2014-02-18

387

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

388

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

389

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

390

Effect of strong metal-support interaction on the rate of hydrogenation of adsorbed carbon monoxide over titania-supported noble metal catalysts as revealed by pulse surface reaction rate analysis  

Microsoft Academic Search

On the basis of the rate constant per active site determined by pulse surface reaction rate analysis (PSRA), the effect of the strong metal-support interaction (SMSI) on the hydrogenation of adsorbed CO was studied for titania-supported noble metal catalysts. Reduction at 773 K resulted in a drastic decrease in the amount of CO adsorbed on all noble metals examined. The

Shigeyoshi Taniguchi; Yoshihiko Mori; Tadashi Hattori; Yuichi Murakami; Toshiaki Mori

1989-01-01

391

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

392

A Theoretical Study of Methanol Synthesis from CO(2) Hydrogenation on Metal-doped Cu(111) Surfaces  

SciTech Connect

Density functional theory (DFT) calculations and Kinetic Monte Carlo (KMC) simulations were employed to investigate the methanol synthesis reaction from CO{sub 2} hydrogenation (CO{sub 2} + 3H{sub 2} {yields} CH{sub 3}OH + H{sub 2}O) on metal-doped Cu(111) surfaces. Both the formate pathway and the reverse water-gas shift (RWGS) reaction followed by a CO hydrogenation pathway (RWGS + CO-Hydro) were considered in the study. Our calculations showed that the overall methanol yield increased in the sequence: Au/Cu(111) < Cu(111) < Pd/Cu(111) < Rh/Cu(111) < Pt/Cu(111) < Ni/Cu(111). On Au/Cu(111) and Cu(111), the formate pathway dominates the methanol production. Doping Au does not help the methanol synthesis on Cu(111). Pd, Rh, Pt, and Ni are able to promote the methanol production on Cu(111), where the conversion via the RWGS + CO-Hydro pathway is much faster than that via the formate pathway. Further kinetic analysis revealed that the methanol yield on Cu(111) was controlled by three factors: the dioxomethylene hydrogenation barrier, the CO binding energy, and the CO hydrogenation barrier. Accordingly, two possible descriptors are identified which can be used to describe the catalytic activity of Cu-based catalysts toward methanol synthesis. One is the activation barrier of dioxomethylene hydrogenation, and the other is the CO binding energy. An ideal Cu-based catalyst for the methanol synthesis via CO{sub 2} hydrogenation should be able to hydrogenate dioxomethylene easily and bond CO moderately, being strong enough to favor the desired CO hydrogenation rather than CO desorption but weak enough to prevent CO poisoning. In this way, the methanol production via both the formate and the RWGS + CO-Hydro pathways can be facilitated.

Liu P.; Yang, Y.; White, M.G.

2012-01-12

393

Thermal stability, glass-forming ability and hydrogen permeability of amorphous Ni 64Zr 36? X M X (M = Ti, Nb, Mo, Hf, Ta or W) membranes  

Microsoft Academic Search

Nickel–zirconium-based amorphous alloys are promising hydrogen-selective membrane materials. These membranes can potentially be combined with a suitable water–gas-shift catalyst to form a catalytic membrane reactor, which can produce high-purity H2 and CO2 streams from coal-derived syngas at elevated temperatures. One shortcoming of amorphous alloys is that their temperature of operation is limited by the onset of crystallization, which in many

M. D. Dolan; S. Hara; N. C. Dave; K. Haraya; M. Ishitsuka; A. Y. Ilyushechkin; K. Kita; K. G. McLennan; L. D. Morpeth; M. Mukaida

2009-01-01

394

Tristate electrochemical metallization memory based in the hydrogenated nanocrystalline silicon films  

SciTech Connect

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 10{sup 2} and 10{sup 5}, less variation of resistance, and long retention exceeding 2.3?×?10{sup 5?}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{sup +} 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., E-mail: xiaobing-yan@126.com [College of Electron and Information Engineering, Hebei University, Baoding 071002 (China); The Laboratory of Nano-Fabrication and Novel Devices Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China); Chen, Y. F.; Hao, H.; Zhang, E. P.; Shi, S. S.; Lou, J. Z. [College of Electron and Information Engineering, Hebei University, Baoding 071002 (China); Liu, Q. [The Laboratory of Nano-Fabrication and Novel Devices Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China)

2014-08-18

395

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

E-print Network

Grain-boundary engineering markedly reduces susceptibility to intergranular hydrogen embrittlement. Keywords: Hydrogen embrittlement; Intergranular cracking; Grain-boundary engineering; Special boundaries,e,* a Department of Materials Science and Engineering, University of California, Berkeley, CA 94720, USA b

Ritchie, Robert

396

Dense, layered membranes for hydrogen separation  

DOEpatents

This invention provides hydrogen-permeable membranes for separation of hydrogen from hydrogen-containing gases. The membranes are multi-layer having a central hydrogen-permeable layer with one or more catalyst layers, barrier layers, and/or protective layers. The invention also relates to membrane reactors employing the hydrogen-permeable membranes of the invention and to methods for separation of hydrogen from a hydrogen-containing gas using the membranes and reactors. The reactors of this invention can be combined with additional reactor systems for direct use of the separated hydrogen.

Roark, Shane E.; MacKay, Richard; Mundschau, Michael V.

2006-02-21

397

Reversible reactions over non-metallic catalysts: A transient isotopic tracing of the isobutane-isobutene-hydrogen system over chromia  

SciTech Connect

Whether a single rate-controlling step exists in complex reversible heterogeneous catalytic reactions is difficult to establish, especially with non-metallic catalysts, which often possess fewer active sites than supported metals. This problem is treated here using transient isotopic tracing with {sup 13}C marking for the system isobutane-isobutene-hydrogen over a chromia catalyst. A statistical approach is employed for modeling the simultaneous occurrence of traced isobutane and isobutene in the product stream using the Horiuti-Polanyi, mechanism. The authors find that a single rate-controlling step that consists of the conversion of the half-hydrogenated chemisorbed species i-C{sub 4}H{sub 9}l to chemisorbed isobutene i-C{sub 4}H{sub 8}l and the reverse exists. Such information should be useful for catalyst design and prediction of performance.

Juoyu Kao (American Cyanamide Co., Wayne, NJ (United States)); Piet-Lahanier, H.; Walter, E. (CNRS-ESE, Gif-sur-Yvette (France)); Happel, J. (Columbia Univ., New York, NY (United States))

1992-02-01

398

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

399

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

E-print Network

that for hydrogen produced from steam reforming of natural gas, are at best marginal relative to the competing technologies such as cryogenic, membrane and pressure s~ing adsorption systems. INTRODUCTION Hydrogen is one of the most important chemical species... commercial technologies for hydrogen recovery ar cryogenic separation, pressure swin adsorption CPSA) and membrane separ ation. The two former processes purify the stream by adsorbing 0 freezing out the non-hydrogen com ponents. Cryogenic systems have...

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

400

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

E-print Network

the PFC surface (helium and hydrogen isotopes) while accommodating high heat loads. To study this problem rather than requiring a standard vacuum system. Hydrogen isotope (DT) particles that strike the surface the viability of specific liquid candidates as renewable di- vertor surfaces. Hydrogen isotope (DT) particles

Harilal, S. S.

401

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

402

Effects of absorbed hydrogen on the electronic properties of (Zr2Fe)(1-x)H(x) metallic glasses.  

PubMed

The electrical conductivity (?) of hydrogen doped (Zr(2)Fe)(1-x)H(x) metallic glasses has been measured in the temperature range from 290 down to 5 K. The decrease of the room temperature conductivity and the increase of its temperature coefficient are explained as consequences of increased disorder due to hydrogen doping. ?(T) for (Zr(2)Fe)(1-x)H(x) metallic glasses at low temperatures decreases with the increase of temperature, forming a minimum at T(min), before it starts a monotonic increase with increasing temperature. Both the functional forms and the magnitudes of the observed ?(T) are interpreted in terms of weak localization, electron-electron interaction and spin-fluctuation effects. Our results reveal that the electron-phonon scattering rate varies with the square of temperature from low temperatures up to 100 K and changes behaviour to a linear form at higher temperatures. At low temperatures, the minimum in ?(T) is shifted to higher temperatures, which is ascribed to the increase of the screening parameter of the Coulomb interaction F* associated with the enhancement of the spin fluctuations arising from the increase of the hydrogen doping. The spin-orbit scattering rate and the electron diffusion constant are reduced by hydrogen doping. PMID:22551780

Novak, M; Kokanovi?, I

2012-06-13

403

Hydrogen production from water decomposition by redox of Fe 2O 3 modified with single- or double-metal additives  

NASA Astrophysics Data System (ADS)

Iron oxide modified with single- or double-metal additives (Cr, Ni, Zr, Ag, Mo, Mo-Cr, Mo-Ni, Mo-Zr and Mo-Ag), which can store and supply pure hydrogen by reduction of iron oxide with hydrogen and subsequent oxidation of reduced iron oxide with steam (Fe 3O 4 (initial Fe 2O 3)+4H 2?3Fe+4H 2O), were prepared by impregnation. Effects of various metal additives in the samples on hydrogen production were investigated by the above-repeated redox. All the samples with Mo additive exhibited a better redox performance than those without Mo, and the Mo-Zr additive in iron oxide was the best effective one enhancing hydrogen production from water decomposition. For Fe 2O 3-Mo-Zr, the average H 2 production temperature could be significantly decreased to 276 °C, the average H 2 formation rate could be increased to 360.9-461.1 ?mol min -1 Fe-g -1 at operating temperature of 300 °C and the average storage capacity was up to 4.73 wt% in four cycles, an amount close to the IEA target.

Liu, Xiaojie; Wang, Hui

2010-05-01

404

Developments in permeable and low permeability barriers  

SciTech Connect

The concept of the reactive treatment zone whereby pollutants are attenuated as they move along a pathway in the ground has enabled a re-thinking of many of the concepts of containment. In particular it offers the potential for the control of the flux from a contaminated area by controlling the contaminant concentration in the pathway(s) as well as or instead of using a low permeability barrier. The paper outlines the basic concepts of the reactive treatment zone and the use of permeable and low permeability reactive systems. The paper then gives a case history of the installation of a permeable barrier using an in-situ reaction chamber.

Jefferis, S.A. [Golder Associates United Kingdom Ltd., Berkshire (United Kingdom); Norris, G.H. [Nortel Ltd., London (United Kingdom); Thomas, A.O. [Golder Associates Geoanalysis s.r.l., Turin (Italy)

1997-12-31

405

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

406

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

407

HIGH-TEMPERATURE REACTION RATES OF SEVERAL METALS WITH HYDROGEN CHLORIDE AND WATER VAPOR  

Microsoft Academic Search

An experimental study was made of the hightemperature reaction rates of ; various metal filaments with HCl and Hâ0 vapors and mixtures of the two. ; Measurements were made by an electrical method in which the change in resistance ; of the metal filament was related to the loss in pure metal due to the vapor-; metal reaction. Measurable reaction

Milton Farber

1959-01-01

408

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

409

Well-controlled metal co-catalysts synthesised by chemical vapour impregnation for photocatalytic hydrogen production and water purification.  

PubMed

As co-catalyst materials, metal nanoparticles (NPs) play crucial roles in heterogeneous photocatalysis. The photocatalytic performance strongly relies on the physical properties (i.e., composition, microstructure, and surface impurities) of the metal NPs. Here we report a convenient chemical vapour impregnation (CVI) approach for the deposition of monometallic-, alloyed, and core-shell structured metal co-catalysts onto the TiO2 photocatalyst. The as-synthesised metal NPs are highly dispersed on the support and show narrow size distributions, which suit photocatalysis applications. More importantly, the surfaces of the as-synthesised metal NPs are free of protecting ligands, enabling the photocatalysts to be ready to use without further treatment. The effect of the metal identity, the alloy chemical composition, and the microstructure on the photocatalytic performance has been investigated for hydrogen production and phenol decomposition. Whilst the photocatalytic H2 production performance can be greatly enhanced by using the core-shell structured co-catalyst (Pdshell-Aucore and Ptshell-Aucore), the Ptshell-Aucore modified TiO2 yields enhanced quantum efficiency but a reduced effective decomposition of phenol to CO2 compared to that of the monometallic counterparts. We consider the CVI approach provides a feasible and elegant process for the decoration of photocatalyst materials. PMID:24970298

Su, Ren; Forde, Michael M; He, Qian; Shen, Yanbin; Wang, Xueqin; Dimitratos, Nikolaos; Wendt, Stefan; Huang, Yudong; Iversen, Bo B; Kiely, Christopher J; Besenbacher, Flemming; Hutchings, Graham J

2014-10-28

410

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...

411

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

412

In situ spectroscopic detection of SMSI effect in a Ni/CeO2 system: hydrogen-induced burial and dig out of metallic nickel  

SciTech Connect

In situ APPES technique demonstrates that the strong metal support interaction effect (SMSI) in the Ni-ceria system is associated with the decoration and burial of metallic particles by the partially reduced support, a phenomenon reversible by evacuation at high temperature of the previously absorbed hydrogen.

Caballero, Alfonso; Holgado, Juan P.; Gonzalez-delaCruz, Victor M.; Habas, Susan e.; Herranz, Tirma; Salmeron, Miquel

2010-06-29

413

Hydrogen production in single-chamber tubular microbial electrolysis cells using non-precious-metal catalysts  

E-print Network

Hydrogen production in single-chamber tubular microbial electrolysis cells using non August 2009 Keywords: Hydrogen production Microbial electrolysis cells (MECs) NiMo NiW Cathode catalyst catalyst in microbial electrolysis cells (MECs). Its high cost, however, limits the practical applications

Tullos, Desiree

414

Unintentional carbon and hydrogen incorporation in GaNP grown by metal-organic chemical vapor deposition  

NASA Astrophysics Data System (ADS)

GaN xP 1- x and related materials are promising for light-emitting and solar cell devices grown on silicon, but have shown less-than-ideal performance. The transport properties of these materials, though, can be greatly influenced by growth conditions. We study the effects of metal-organic chemical vapor deposition growth conditions of GaN 0.02P 0.98 on the unintentional incorporation of carbon and hydrogen and the room-temperature photoluminescence (PL) decay lifetime. We find the incorporation of carbon to be dominated by either the gallium source (trimethylgallium or triethylgallium) or the nitrogen source (dimethylhydrazine), depending on growth conditions. The PL decay lifetime is found to be correlated to both the carbon and hydrogen concentration. Growth temperature, gallium source, group V flux, and growth rate can all strongly influence the carbon and hydrogen impurity incorporation, and thus, the PL lifetime. In the samples with the lowest hydrogen and carbon concentrations (˜10 17 cm -3), we have achieved room-temperature PL lifetimes as high as 3.0 ns.

Geisz, J. F.; Reedy, R. C.; Keyes, B. M.; Metzger, W. K.

2003-12-01

415

Promotion of atomic hydrogen recombination as an alternative to electron trapping for the role of metals in the photocatalytic production of H2  

PubMed Central

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

2014-01-01

416

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

SciTech Connect

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 that these steady-state H2 levels are solely dependent upon the physiological parameters of the hydrogen-consuming microorganisms, with H2 concentrations increasing as each successive TEAP yields less energy for bacterial growth. The objective of this research was to determine if H2 can still be used as an indicator of TEAPs during a uranium bioremediation scheme where an organic substrate is injected into the subsurface and organisms may consume H2 and carbon simultaneously. In addition, the effect of iron bioavailability on H2 concentrations during iron reduction was observed. The first phase of research determined the effect of a competing electron donor (acetate) on the kinetics of H2 utilization by Geobacter sulfurreducens in batch cultures under iron reducing conditions. The results indicate that, though the Monod kinetic coefficients describing the rate of H2 utilization under iron-reducing conditions correlate energetically with the coefficients found in previous experiments under methanogenic and sulfate-reducing conditions, conventionally measured growth kinetics do not predict the steady state H2 levels typical for each TEAP. In addition, with acetate and H2 as simultaneous electron donors, there is slight inhibition between the two electron donors for G. sulfurreducens, and this can be modeled through competitive inhibition terms in the classic Monod formulation, resulting in slightly higher H2 concentrations under steady state conditions in the presence of acetate. This dual-donor model indicates that the steady state H2 concentration in the presence of an organic as electron donor is not only dependent on the biokinetic coefficients of the TEAP, but also the concentration of the organic substrate, and that the H2 concentration does not start to change very dramatically as long as the organic substrate concentration remains below the half saturation constant. The results for this phase of research are provided in Section 1. The second phase of research measured steady-state H2 concentrations under iron reducing conditions using NABIR Field Research Center background soil in a simulated bioremediation scenario involving acetate injection to stimulate indigenous microbial activity in a flow-through column. Steady-state H2 concentrations measured during this long-term (500 day) column experiment were higher than observed for iron-reducing conditions in the field even though evidence suggests that iron reduction was the dominant TEAP in the column. Additional column experiments were performed to determine the effect of iron bioavailability on steady-state H2 concentrations using the humics analogue, AQDS (9,10-anthraquinone-2,6-disulfonic acid). The iron reduction rate in the column with AQDS was double the rate in a parallel column without AQDS and lower steady state H2 levels were observed in the presence of AQDS, indicating that even though iron reduction does occur, a decreased bioavailability of iron may inhibit iron reduction such that H2 concentrations increase to levels that are more typical for less energetically favorable reactions (sulfate-reduction, methanogenigesis). The results for this phase of research are in Section 2. A final phase of research measured the effect of carbon concentration and iron bioavailability on surface bound iron reduction kinetics and steady-state H2 levels using synthetic iron oxide coated sand (IOCS). Results show a significant decrease in the microbial iron reduction and acetate oxidation rates for systems with surface bound Fe(III) (IOCS) compared to soluble Fe(III) (ferric citrate). The addition of AQDS did not affect the rate of iron r

Peter R. Jaffe, John Komlos, Derick Brown

2005-09-27

417

Dimensionality aspects of nano micro integrated metal oxide based early stage leak detection room temperature hydrogen sensor  

NASA Astrophysics Data System (ADS)

Detection of explosive gas leaks such as hydrogen (H2) becomes key element in the wake of counter-terrorism threats, introduction of hydrogen powered vehicles and use of hydrogen as a fuel for space explorations. In recent years, a significant interest has developed on metal oxide nanostructured sensors for the detection of hydrogen gas. Gas sensors properties such as sensitivity, selectivity and response time can be enhanced by tailoring the size, the shape, the structure and the surface of the nanostructures. Sensor properties (sensitivity, selectivity and response time) are largely modulated by operating temperature of the device. Issues like instability of nanostructures at high temperature, risk of hydrogen explosion and high energy consumption are driving the research towards detection of hydrogen at low temperatures. At low temperatures adsorption of O2- species on the sensor surface instead of O- (since O- species reacts easily with hydrogen) result in need of higher activation energy for hydrogen and adsorbed species interaction. This makes hydrogen detection at room temperature a challenging task. Higher surface area to volume ratio (resulting higher reaction sites), enhanced electronic properties by varying size, shape and doping foreign impurities (by modulating space charge region) makes nanocrystalline materials ideal candidate for room temperature gas sensing applications. In the present work various morphologies of nanostructured tin oxide (SnO 2) and indium (In) doped SnO2 and titanium oxide (titania, TiO2) were synthesized using sol-gel, hydrothermal, thermal evaporation techniques and successfully integrated with the micro-electromechanical devices H2 at ppm-level (as low as 100ppm) has been successfully detected at room temperature using the SnO2 nanoparticles, SnO2 (nanowires) and TiO2 (nanotubes) based MEMS sensors. While sensor based on indium doped tin oxide showed the highest sensitivity (S =Ra/Rg= 80000) and minimal response time (10sec.). Highly porous SnO2 nanoparticles thin film (synthesized using template assisted) showed response time of about 25 seconds and sensitivity 4. The one dimensional tin oxide nanostructures (nanowires) based sensor showed a sensitivity of 4 and response time of 20 sec. Effect of aspect ratio of the nanowires on diffusion of hydrogen molecules in the tin oxide nanowires, effect of catalyst adsorption on nanowire surface and corresponding effect on sensor properties has been studied in detail. Nanotubes of TiO2 prepared using hydrothermal synthesis showed a sensitivity 30 with response time as low as 20 seconds where as, TiO 2 nanotubes synthesized using anodization showed poor sensitivity. The difference is mainly attributed to the issues related to integration of the anodized nanotubes with the MEMS devices. The effect of MEMS device architecture modulation, such as, finger spacing, number and length of fingers and electrode materials were studied. It has been found that faster sensor response (˜ 10 sec) was observed for smaller finger spacing. A diffusion model is proposed for elucidating the effect of inter-electrode distance variation on conductance change of a nano-micro integrated hydrogen sensor for room temperature operation. Both theoretical and experimental results showed a faster response upon exposure to hydrogen when sensor electrode gap was smaller. Also, a linear increase in the sensor sensitivity from 500 to 80000 was observed on increasing the electrode spacing from 2 to 20 mum. The improvement in sensitivity is attributed to the higher reactive sites available for the gaseous species to react on the sensor surface. This phenomenon also correlated to surface adsorbed oxygen vacancies (O-) and the rate of change of surface adsorbed oxygen vacancies. This dissertation studied in detail dimensionality aspects of materials as well as device in detecting hydrogen at room temperature.

Deshpande, Sameer Arun

418

Voltage-induced insulator-to-metal transition of hydrogen-treated NbO2 thin films  

NASA Astrophysics Data System (ADS)

We report on the voltage-induced insulator-to-metal transition (IMT) of the NbO2 thin films that are deposited under forming gas in the growth chamber. It is shown that the hydrogen in the forming gas gives rise to the abrupt voltage-induced IMT characteristics in NbO2 thin films that are sandwiched between top and bottom Pt electrodes. By a catalytic reaction at the triple boundary between NbO2 and Pt, hydrogen appears to be easily incorporated into the NbO2 lattice and doping significantly lowers the IMT temperature of NbO2 thin films, along with the reduction of NbO2 films.

Kang, Minkook; Yu, Sangbae; Son, Junwoo

2015-03-01

419

Multilayer sulfur-resistant composite metal membranes and methods of making and repairing the same  

DOEpatents

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

420

Gas phase hydrogen deuterium exchange reactions of a model peptide: FT-ICR and computational analyses of metal induced conformational mutations  

Microsoft Academic Search

We utilized gas phase hydrogen\\/deuterium (H\\/D) exchange reactions and ab initio calculations to investigate the complexation\\u000a between a model peptide (Arg-Gly-Asp?RGD) with various alkali metal ions. The peptide conformation is drastically altered\\u000a upon alkali metal ion complexation. The associated conformational changes depend on both the number and type of complexing\\u000a alkali metal ions. Sodium has a smaller ionic diameter and

T. Solouki; R. C. Fort; A. Alomary; A. Fattahi

2001-01-01

421

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 ...

422

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

NASA Astrophysics Data System (ADS)

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. Serre, F. Millange, T. Loiseau, A. Percheron-Guegan, Chem. Commun. (2003) 2976; T. Loiseau, C. Serre, C. Huguenard, G. Fink, F. Taulelle, M. Henry, T. Bataille, G. Férey, Chem. Eur. J. 10 (2004) 1373]. A prerequisite for such materials is sufficient adsorption interaction strength for hydrogen adsorbed on the adsorption sites of the material because this facilitates successful operation under moderate temperature and pressure conditions. Here we report detailed information on the geometry of the hydrogen adsorption sites, based on the analysis of inelastic neutron spectroscopy (INS). The adsorption energies for the metal organic framework MOF5 equal about 800 K for part of the different sites, which is significantly higher than for nanoporous carbon materials (˜550 K) [H.G. Schimmel, G.J. Kearley, M.G. Nijkamp, C.T. Visser, K.P. de Jong, F.M. Mulder, Chem. Eur. J. 9 (2003) 4764], and is in agreement with what is found in first principles calculations [T. Sagara, J. Klassen, E. Ganz, J. Chem. Phys. 121 (2004) 12543; F.M. Mulder, T.J. Dingemans, M. Wagemaker, G.J. Kearley, Chem. Phys. 317 (2005) 113]. Assignments of the INS spectra is realized using comparison with independently published model calculations [F.M. Mulder, T.J. Dingemans, M. Wagemaker, G.J. Kearley, Chem. Phys. 317 (2005) 113] and structural data [T. Yildirim, M.R. Hartman, Phys. Rev. Lett. 95 (2005) 215504].

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

2008-07-01

423

High-purity hydrogen generation by ultraviolet illumination with the membrane composed of titanium dioxide nanotube array and Pd layer  

NASA Astrophysics Data System (ADS)

High-purity hydrogen generation was observed by using a membrane composed of a bilayer of an anodized titanium dioxide nanotube array (TNA) and a hydrogen permeable metal. This membrane was fabricated by transferring a TNA embedded in a titanium foil onto a sputtered 10-?m-thick palladium film. Alcohols are reformed photocatalytically and concurrently generated hydrogen is purified through the Pd layer. H2 with a purity of more than 99% was obtained from liquid alcohols under ultraviolet illumination onto the membrane. Thus, we demonstrated the integration of photocatalytic hydrogen production and purification within a single membrane.

Hattori, Masashi; Noda, Kei; Matsushige, Kazumi

2011-09-01

424

Synthesis and characterization of light-metal-based hydrides for hydrogen storage materials  

NASA Astrophysics Data System (ADS)

In the past few years, research and development on the use of hydrogen as a fuel for various applications have gathered momentum in response to the demand for cleaner fuels and substitutes to fossil fuels. The use of hydrogen for automobiles, one of the most important applications of hydrogen fuel, requires an on-board hydrogen storage system that can be regenerated on-board or off-board. However, one of the key obstacles to this application is that current available storage technologies do not meet the capacity and efficiency requirements for achieving the commercial viability. In this study, two solid-state hydrogen storage systems, i.e. Mg-Ti-H and Li-Al-B-H, are investigated. Among a variety of MgH2/TiH2 ratios and milling conditions, the 10MgH2/TiH2 sample milled in a dual-planetary high-energy mill for 4 hours under 15 MPa hydrogen pressure were found to be the optimal materials, displaying a substantially reduced activation energy and enthalpy change for MgH2 dehydrogenation. PCT analysis demonstrated that the system showed excellent cycle stability attributed to the inhibition of coarsening by TiH2. Lithium borohydride (LiBH4) is one of the promising candidates as a superior hydrogen storage because of its high theoretical storage capacity (18.5 wt.%). In this work, the promising hydrogen storage properties of combined systems of Li3AlH6/LiBH4 and Al/LiBH 4, exhibiting the favorable formation of AlB2 during dehydrogenation, were presented based on TGA and XRD analyses. Additionally, the characterization of the intermediate and final products of the dehydrogenation and rehydrogenation of the above systems by solid-state NMR analyses were presented. This has verified and further clarified the paths and intermediate products of the reversible hydrogen release and uptake by the mixtures.

Choi, Young Joon

425

Phase transition in Ar(H2)2: a prediction of metallic hydrogen organized in lamellar structures  

NASA Astrophysics Data System (ADS)

The structural and electronic properties of the Ar(H2)2 compound are studied as a function of pressure by enthalpy calculations and ab initio molecular dynamics. A phase transition from a MgZn2 to an AlB2-type structure is shown to take place around 250 GPa. In the latter structure, the Ar atoms form hexagonal close-packed layers which force the overlap of hydrogen and hence its metallization within experimental reach. Dissociation of H2 molecules is seen to take place gradually, upon increasing pressure.

Bernard, S.; Loubeyre, P.; Zérah, G.

1997-03-01

426

The role of the molecular-metallic transition of hydrogen in the evolution of Jupiter, Saturn, and brown dwarfs  

NASA Technical Reports Server (NTRS)

An equation of state for hydrogen which predicts a molecular-metallic phase transition at finite temperatures has become available recently. The effect of this phase transition on the cooling histories of these two giant planets and of substellar brown dwarfs is studied. The phase transition alters the present age of Jupiter and of Saturn by a few percent. Interestingly, the cooling of brown dwarfs is most strongly affected at the time when the interior adiabat crosses the critical point of the phase transition.

Saumon, Didier; Hubbard, William B.; Chabrier, Gilles; Van Horn, Hugh M.

1992-01-01

427

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

428

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

NASA Astrophysics Data System (ADS)

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 PuH2). The heats of solution for PuHS and PuDS 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, S.; Bridgewater, J. S.; Ward, J. W.; Allen, T. H.

2010-03-01

429

Electronic structures of transition metal to hydrogen bonds: oxidative addition of dihydrogen to a square planar rhodium complex and quantum mechanical prediction of the geometry of a metal hydride  

E-print Network

ELECTRONIC STRUCTURES OF TRANSITION METAL TO HYDROGEN BONDS: OXIDATIVE ADDITION OF DIHYDROGEN TO A SQUARE PLANAR RHODIUM COMPLEX AND QUANTUM MECHANICAL PREDICTION OF THE GEOMETRY OF A METAL HYDRIDE A Thesis CAROLYN F. HALPIN Submitted... OF DIHYDROGEN TO A SQUARE PLANAR RHODIUM COMPLEX AND QUANTUM MECHAMCAL PREDICTION OF THE GEOMETRY OF A METAL HYDRlDE A Thesis by CAROLYN F. HALPIN Approved as to style and content by: ~c ae (Chairman) ona . areas o (Member) aan aane (Member) en...

Halpin, Carolyn F.

1986-01-01

430

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

431

Catalytic redistribution and polymerization of diborazanes: unexpected observation of metal-free hydrogen transfer between aminoboranes and amine-boranes.  

PubMed

Ir-catalyzed (20 °C) or thermal (70 °C) dehydrocoupling of the linear diborazane MeNH(2)-BH(2)-NHMe-BH(3) led to the formation of poly- or oligoaminoboranes [MeNH-BH(2)](x) (x = 3 to >1000) via an initial redistribution process that forms MeNH(2)·BH(3) and also transient MeNH?BH(2), which exists in the predominantly metal-bound and free forms, respectively. Studies of analogous chemistry led to the discovery of metal-free hydrogenation of the B?N bond in the "model" aminoborane iPr(2)N?BH(2) to give iPr(2)NH·BH(3) upon treatment with the diborazane Me(3)N-BH(2)-NHMe-BH(3) or amine-boranes RR'NH·BH(3) (R, R' = H or Me). PMID:22035112

Robertson, Alasdair P M; Leitao, Erin M; Manners, Ian

2011-12-01

432

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

433