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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  

US Patent & Trademark Office Database

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. (White Rock, NM); Birdsell; Stephen A. (Los Alamos, NM); Barbero; Robert S. (Santa Cruz, NM); Snow; Ronny C. (Los Alamos, NM); Smith; Frank M. (Espanola, NM)

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

Permeability of precious metals to hydrogen at 2kb total pressure and elevated temperatures.  

USGS Publications Warehouse

Permeabilities of several commonly used precious metals to hydrogen have been measured at 2kb total pressure and between 450o and 812oC by using the double-capsule oxygen buffer technique.- from Author

Chou, I. -M.

1986-01-01

5

Review of hydrogen isotope permeability through materials  

SciTech Connect

This report is the first part of a comprehensive summary of the literature on hydrogen isotope permeability through materials that do not readily form hydrides. While we mainly focus on pure metals with low permeabilities because of their importance to tritium containment, we also give data on higher-permeability materials such as iron, nickel, steels, and glasses.

Steward, S.A.

1983-08-15

6

Hydrogen permeability in metals under the conditions of accumulation of defects  

Microsoft Academic Search

We outline basic regularities of the processes running in “deformed-metal-hydrogen” systems characterized by the existence\\u000a of close correlations between the motion of hydrogen in the metal and the accumulation of defects. We select the specific\\u000a features of the methodological and methodical aspects of evaluation of the influence of hydrogen on the physicomechanical\\u000a properties of materials explained by the unique properties

V. S. Pavlyna; O. V. Pavlyna

2007-01-01

7

High-temperature hydrogen permeability of vanadium and niobium  

Microsoft Academic Search

We develop a technique for measuring the coefficient of hydrogen diffusion in metals of group V based on an electricaly conductivity method. By using this technique, we measured the coefficient of hydrogen diffusion in vanadium and niobium in the temperature range 573 – 1373 K and calculated the hydrogen permeability of metals of group V. A high-temperature phase transition caused

V. I. Pokhmurs'kyi; O. R. Sokolovs'kyi; V. V. Fedorov

1995-01-01

8

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

PubMed Central

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

Hyman, Lynne M.; Franz, Katherine J.

2011-01-01

9

Metallic hydrogen  

Microsoft Academic Search

Summary  With the aid of a second-order perturbation scheme, the energy of metallic hydrogen is calculated for pressures ranging from\\u000a 0 to 110 Mbar. The zero-point energy is taken into account by evaluating the density of states resulting from the phonon spectra.\\u000a For pressures higher than 3 Mbar the compressibilities as derived from the total energy and from the elastic constants

E. Stoll; P. F. Meier; T. Schneider

1974-01-01

10

Effect of Water on Hydrogen Permeability.  

National Technical Information Service (NTIS)

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 prot...

D. Hulligan W. A. Tomazic

1987-01-01

11

Molecular and Metallic Hydrogen.  

National Technical Information Service (NTIS)

This report presents a comprehensive review and analysis of the published data on metallic hydrogen and a summary of the properties of molecular hydrogen that are required to determine the molecular-to-metallic hydrogen transition pressure. The best avail...

M. Ross C. Shishkevish

1977-01-01

12

Effect of water on hydrogen permeability  

SciTech Connect

Doping of hydrogen with CO or CO/sub 2/ 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. This work was done to define the equilibrium level of water (oxygen-bearing gas) required to avoid reduction of the oxide coating. Results at 720/sup 0/C and 13.8 MPa have shown that, (a) pure hydrogen will reduce the coating, (b) 500 ppM CO (500 ppM water equivalent) does not prevent the reduction, and (c) 500 ppM CO/sub 2/ (1000 ppM water) appears to be close to the equilibrium level.

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

1984-01-01

13

Production of Metallic Hydrogen.  

National Technical Information Service (NTIS)

The report contains a discussion of predicted properties of metallic hydrogen. Ways of attaining the colossal pressures required to keep hydrogen in the metallic state at room temperature are examined.

L. F. Vereshchagin R. G. Arkhipov

1972-01-01

14

Hydrogen in metals  

Microsoft Academic Search

This article reviews the experimental and theoretical studies of the properties of hydrogen included in metals. The problem is discussed of diffusion of hydrogen atoms in a metallic matrix, and the theory of coherent and incoherent diffusion. Phase transitions caused by elastic interactions are considered in a system of hydrogen atoms included in the interstices of a metallic matrix. The

Evgenii G Maksimov; O. A. Pankratov

1975-01-01

15

Effect of a Nickel-Iron Mixture of Weld Metal on Hydrogen Permeability at Various Temperatures in 316L Stainless Steel  

NASA Astrophysics Data System (ADS)

It is important to prevent from hydrogen embrittlement cracking in the heat-affected zone of welded steels. The hydrogen permeation rate for bulk nickel at high temperatures is higher than that of stainless steel, although the reverse is true at low temperatures. Low carbon stainless 316L steel, which contained 12-15% nickel, was selected as the parent material for welding. We have investigated the affect of nickel near the heat-affected zone by measuring the hydrogen permeation at various temperatures. We performed hydrogen permeation tests into the bead on plate specimens using nickel filler. A stationary hydrogen gas flux through the stainless steel specimen was measured by using an orifice and a quadrupole mass spectrometer (QMS). The partial pressure difference for hydrogen that was applied to the specimen was able to be kept constant by maintaining a constant gas flow rate through the orifice in a low- pressure room. An orifice with a 3 mm diameter maintained stationary steady-state hydrogen gas flux from the specimen at 620K, while a 1.2 mm diameter orifice maintained the steady pressure at 520 K. The hydrogen permeability, K was calculated based on the measured steady-state hydrogen gas fluxes at various temperatures. These results plotted as log K versus 1/T (reciprocal temperature) could not be interpolated linearly. The permeability values of the specimen at 570 K and 520 K were less than interpolated ones between the value at 620 K and the value at 520K of the 316 L stainless steel substrate as received.

Yamazaki, Takahisa; Ikeshoji, Toshi-Taka; Suzumura, Akio; Kobayashi, Daigo; Kamono, Shumpei

16

Metastable metallic hydrogen glass  

SciTech Connect

The quest for metallic hydrogen has been going on for over one hundred years. Before hydrogen was first condensed into a liquid in 1898, it was commonly thought that condensed hydrogen would be a metal, like the monatomic alkali metals below hydrogen in the first column of the Periodic Table. Instead, condensed hydrogen turned out to be transparent, like the diatomic insulating halogens in the seventh column of the Periodic Table. Wigner and Huntington predicted in 1935 that solid hydrogen at 0 K would undergo a first-order phase transition from a diatomic to a monatomic crystallographically ordered solid at {approx}25 GPa. This first-order transition would be accompanied by an insulator-metal transition. Though searched for extensively, a first-order transition from an ordered diatomic insulator to a monatomic metal is yet to be observed at pressures up to 120 and 340 GPa using x-ray diffraction and visual inspection, respectively. On the other hand, hydrogen reaches the minimum electrical conductivity of a metal at 140 GPa, 0.6 g/cm{sup 3}, and 3000 K. These conditions were achieved using a shock wave reverberating between two stiff sapphire anvils. The shock wave was generated with a two-stage light-gas gun. This temperature exceeds the calculated melting temperature at 140 GPa by a factor of {approx}2, indicating that this metal is in the disordered fluid phase. The disorder permits hydrogen to become metallic via a Mott transition in the liquid at a much smaller pressure than in the solid, which has an electronic bandgap to the highest pressures reached to date. Thus, by using the finite temperature achieved with shock compression to achieve a disordered melt, metallic hydrogen can be achieved at a much lower pressure in a fluid than in a solid. It is not known how, nor even whether, metallic hydrogen can be quenched from a fluid at high pressures to a disordered solid metallic glass at ambient pressure and temperature. Because metallization occurs by simply pushing the molecules together sufficiently that an electron on one molecule can delocalize and move to an adjacent molecule, if the pressure is released the system will simply revert back to a diatomic insulator. Additives will probably be necessary to produce bonding which will inhibit the reverse transformation when pressure is released. One technique for rapidly quenching metallic fluid hydrogen is to use a thin micron-thick layer of condensed hydrogen contained between metal or diamond layers, which have a high thermal conductivity to quench shock temperature before pressure is released. An appropriate planar shock wave can probably be driven by a laser or small two-stage gun to achieve the necessary pressures, temperatures, and quench rates. In this way many experiments might be performed to find the appropriate combination of materials and shock-pressure history to achieve a shock-pressure-quenched metastable metallic hydrogen glass.

Nellis, W J

2001-02-06

17

Time lag parametric identification of a hydrogen permeability model  

NASA Astrophysics Data System (ADS)

An inverse problem with dynamic boundary conditions for determining the parameters of a hydrogen permeability nonlinear model is considered. Algorithms are proposed for estimating transport parameters of adsorption, desorption, dissolution, and diffusion depending on the body of experimental information.

Zaika, Yu. V.; Bormatova, E. P.

2010-03-01

18

Hydrogen Permeability of ÉP-838 and Kh12G20V Reactor Steels after Alloying and Thermal Treatment  

Microsoft Academic Search

We investigate the influence of alloying with rare-earth elements and metals of groups IV–VI on the hydrogen permeability, diffusion coefficient, and hydrogen solubility in ÉP-838 and Kh12G20V steels proposed as materials for the first wall of a thermonuclear reactor operating on deuterium–tritium plasma. Based on the requirements of ecological safety (hydrogen permeability must be less than 2.4 · 10-8 mole\\/(m

V. V. Fedorov; R. I. Korolyuk; T. M. Zasadnyi; Ya. M. Ivaniv

2000-01-01

19

Metallization of fluid hydrogen  

Microsoft Academic Search

The electrical resistivity of liquid hydrogen has been measured at the high\\u000adynamic pressures, densities and temperatures that can be achieved with a\\u000areverberating shock wave. The resulting data are most naturally interpreted in\\u000aterms of a continuous transition from a semiconducting to a metallic, largely\\u000adiatomic fluid, the latter at 140 GPa, (ninefold compression) and 3000 K. While\\u000athe

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

1998-01-01

20

The hydrogen permeability of Pd{sub 4}S  

SciTech Connect

Hydrogen permeates rapidly through pure Pd membranes, but H{sub 2}S, a common minor component in hydrogen-containing streams, produces a Pd{sub 4}S film on the Pd surface that severely retards hydrogen permeation. Hydrogen still permeates through the bi-layered Pd{sub 4}S/Pd structure, indicating that the Pd{sub 4}S surface is active for H{sub 2} dissociation; the low hydrogen permeability of the Pd4S film is responsible for the decreased rate of hydrogen transport. In this work, the hydrogen permeability of Pd{sub 4}S was determined experimentally in the 623-773 K temperature range. Bi-layered Pd{sub 4}S/Pd foils were produced by exposing pure Pd foils to H{sub 2}S. H{sub 2} fluxes through the bi-layered Pd{sub 4}S/Pd foils were measured during exposure to both pure H{sub 2} and a 1000 ppm H{sub 2}S in H{sub 2} gas mixture. Our results show that H{sub 2}S slows hydrogen permeation through Pd mainly by producing a Pd{sub 4}S film on the Pd surface that is roughly an order-of-magnitude less permeable to hydrogen (k{sub Pd{sub 4}S} = 10{sup ?7.5} exp(?0.22 eV/k{sub B}T) molH{sub 2}/m/s/Pa{sup 1/2}) than pure Pd. The presence of H{sub 2}S in the gas stream results in greater inhibition of hydrogen transport than can be explained by the very low permeability of Pd{sub 4}S. H{sub 2}S may block H2 dissociation sites at the Pd{sub 4}S surface.

O'Brien, Casey; Miller, James; Gellman, Andrew; Morreale, Bryan

2011-04-01

21

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

22

THE HYDROGEN EMBRITTLEMENT OF METALS  

Microsoft Academic Search

A review is given of the characteristics and mechanisms of hydrogen ; embrittlement in the body centered-cubic metals (including steel), titanium and ; its alloys, alphazirconium, and alpha-uranium. These effects are discussed in ; terms of the present knowledge of the appropriate metal-hydrogen system and the ; theory of brittle fracture in metals. The bibliography contains 143 references. ; (N.W.R.);

P COTTERILL

1961-01-01

23

Hydrogen Brittleness in Nonferrous Metals.  

National Technical Information Service (NTIS)

The book is devoted to problems concerning the interaction of hydrogen with metals, and the harmful effects this has on the properties of the metal. Considerable attention is given to processes that take place during the hydrogen-metal interaction, the st...

B. A. Kolachev

1968-01-01

24

Hydrogen Permeation through Metallic Foils.  

National Technical Information Service (NTIS)

The process of electrolytic permeation of hydrogen through metallic foils is studied. A double electrolytic cell, in glass, in which the two compartments of reaction are separated by a metallic foil to be studied, was built. As direct result, the hydrogen...

M. I. B. Bernardi J. A. Rodrigues

1987-01-01

25

Hydrogen in HY-130 Metal.  

National Technical Information Service (NTIS)

This report summarizes the first years investigation directed at improving the mechanical properties of HY-140 weld metal by controlling hydrogen contamination. The addition of 0.2 percent hydride formers (Misch Metal) to weld metal has been shown to elim...

D. G. Howden P. A. Tews

1975-01-01

26

Superconductivity in liquid metallic hydrogen  

Microsoft Academic Search

By solving the Eliashberg equations for the gap function, the super-conducting transition temperature of a proposed low-temperature liquid state of metallic hydrogen is found to be comparable to that obtained, with similar approximations, for the solid. This indicates that metallic hydrogen may be a superconducting liquid in the density range 1.6> or =r\\/sub s\\/> or =1.3, where the melting point

J. E. Jaffe; N. W. Ashcroft

1981-01-01

27

MARCKS protein mediates hydrogen peroxide regulation of endothelial permeability  

PubMed Central

Impairment of endothelial barrier function is implicated in many vascular and inflammatory disorders. One prevalent mechanism of endothelial dysfunction is an increase in reactive oxygen species under oxidative stress. Previous reports have demonstrated that hydrogen peroxide (H2O2), a highly stable reactive oxygen species that modulates physiological signaling pathways, also enhances endothelial permeability, but the mechanism of this effect is unknown. Here, we identify the actin-binding protein myristoylated alanine-rich C-kinase substrate (MARCKS) as a key mediator of the H2O2-induced permeability change in bovine aortic endothelial cells. MARCKS knockdown and H2O2 treatment alter the architecture of the actin cytoskeleton in endothelial cells, and H2O2 induces the phosphorylation and translocation of MARCKS from the cell membrane to the cytosol. Using pharmacological inhibitors and small interference RNA constructs directed against specific proteins, we uncover a signaling cascade from Rac1 to Abl1, phospholipase C?1, and PKC? that is triggered by H2O2 and leads to MARCKS phosphorylation. Our findings establish a distinct role for MARCKS in the regulation of H2O2-induced permeability change in endothelial cells, and suggest potential new therapeutic targets for the treatment of disorders involving oxidative stress and altered endothelial permeability.

Jin, Benjamin Y.; Lin, Alison J.; Golan, David E.; Michel, Thomas

2012-01-01

28

Electrolytic hydrogen-metal interactions  

SciTech Connect

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

McBreen, J.

1991-01-01

29

Electrolytic hydrogen-metal interactions  

SciTech Connect

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

McBreen, J.

1991-12-31

30

Hydrogen storage in metal hydrides  

SciTech Connect

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

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

1980-02-01

31

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

SciTech Connect

High pressure hydrogen has been selected as the working fluid for the developmental automotive Stirling engine. Containment of the working fluid during operation of the engine at high temperatures and at high hydrogen gas pressures is essential for the acceptance of the Stirling engine as an alternative to the internal combustion engine. Most commercial alloys are extremely permeable to pure hydrogen at high temperatures. A program was undertaken at NASA Lewis Research Center (LeRC) to reduce hydrogen permeability in the Stirling engine heater head tubes by doping the hydrogen working fluid with CO or CO/sub 2/. Small additions of these gases were shown to form an oxide on the inside tube wall and thus reduce hydrogen permeability. A study of the effects of dopant concentration, alloy composition, and effects of surface oxides on hydrogen permeability in candidate heater head tube alloys is summarized. Results showed that hydrogen permeability was similar for iron-base alloys (N-155, A286, IN800, 19-9DL, and Nitronic 40), cobalt-base alloys (HS-188) and nickel-base alloys (IN718). In general, the permeability of the alloys decreased with increasing concentration of CO or CO/sub 2/ dopant, with increasing oxide thickness, and decreasing oxide porosity. At high levels of dopants, highly permeable liquid oxides formed on those alloys with greater than 50% Fe content. Furthermore, highly reactive minor alloying elements (Ti, Al, Nb, and La) had a strong influence on reducing hydrogen permeability.

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

1981-01-01

32

Wannier function for metallic hydrogen  

Microsoft Academic Search

In this paper we report a variational calculation of the Wannier function of metallic hydrogen, the first such calculation for any three-dimensional crystal. With relatively simple trial functions accuracies of 2% for energies and about 20% for electron densities were obtained.

Wanda Andreoni

1976-01-01

33

REVIEWS OF TOPICAL PROBLEMS: Hydrogen in metals  

Microsoft Academic Search

This article reviews the experimental and theoretical studies of the properties of hydrogen included in metals. The problem is discussed of diffusion of hydrogen atoms in a metallic matrix, and the theory of coherent and incoherent diffusion. Phase transitions caused by elastic interactions are considered in a system of hydrogen atoms included in the interstices of a metallic matrix. The

Evgenii G. Maksimov; O. A. Pankratov

1975-01-01

34

The influence of quaternary ammonium salts on the hydrogen permeability of steel and its hydrogen embrittlement in hydrogen sulfide media  

Microsoft Academic Search

The hydrogen permeability of the steel was determined using of fiuoroplastic cell consisting of two chambers. The St.3 steel membrane with a diameter of 20 mm and a thickness of 1.5 mm was placed in the center of the cell. Into one chamber was poured a saturated solution of potassium dichromate in distilled water and it was held for a

Yu. Yu. Yusupov; I. A. Mamedov; V. N. Kozyrev

1981-01-01

35

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

36

The permeability of hydrogen in bulk palladium at elevated temperatures and pressures  

Microsoft Academic Search

The permeability of hydrogen in bulk palladium membranes (approximately 1-mm thickness) was determined for the first time at conditions of simultaneously elevated temperature (623–1173K) and hydrogen pressure (0.1×106 to 2.76×106Pa). When the hydrogen partial pressure exponent value was constrained to a value of 0.5, the permeability was described by an Arrhenius-type relation where the pre-exponential constant and activation energy for

Bryan D. Morreale; Michael V. Ciocco; Robert M. Enick; Badi I. Morsi; Bret H. Howard; Anthony V. Cugini; Kurt S. Rothenberger

2003-01-01

37

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

38

Anisotropic structures of metallic hydrogen  

Microsoft Academic Search

We analyze the mechanism of formation of anisotropic structures of metallic hydrogen using the structural expansion in the static approximation. We demonstrate the importance of the curvature in the energy-wavevector characteristics. Among the rhombohedral structures, a planar structure is stabilized in the second-order regime and a filamentary one in the third-order regime. The same mechanism works to stabilize the isotropic

Kuniyoshi Ebina; Hiroshi Miyagi

1989-01-01

39

Using First-Principles Calculations to Describe Amorphous Metal Films for Hydrogen Purification  

NASA Astrophysics Data System (ADS)

The increasing demand for clean and efficient energy has resulted in an increased global willingness to embrace the proposed hydrogen economy. The use of amorphous metal films as membranes to purify hydrogen has potential to overcome at least some of the disadvantages of existing crystalline metal membranes. We introduce a general strategy combining density functional theory and statistical mechanics to quantitatively predict solubility, diffusivity and permeability of interstitial H in amorphous metals. Our methods make it possible for the first time to quantitatively evaluate the performance of amorphous metal films as hydrogen purification membranes. These methods are introduced by examining amorphous Fe3B and a crystalline analogue with the same composition. A membrane made from the amorphous material is predicted to have a hydrogen permeability 1.5-2 orders of magnitude higher than a crystalline membrane. The methods we introduce here will be useful in accelerating the development of amorphous membranes for practical applications.

Hao, Shiqiang; Widom, Mike; Sholl, David

2009-03-01

40

On the Ground State of Metallic Hydrogen.  

National Technical Information Service (NTIS)

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) cann...

S. Chakravarty N. W. Ashcroft

1978-01-01

41

Hydrogen storage in metal–organic frameworks  

Microsoft Academic Search

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

Michael Hirscher; Barbara Panella

2007-01-01

42

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

43

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

Microsoft Academic Search

High pressure hydrogen has been selected as the working fluid for the developmental automotive Stirling engine. Containment of the working fluid during operation of the engine at high temperatures and at high hydrogen gas pressures is essential for the acceptance of the Stirling engine as an alternative to the internal combustion engine. Most commercial alloys are extremely permeable to pure

S. R. Schuon; J. A. Misencik

1981-01-01

44

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

NASA Astrophysics Data System (ADS)

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

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

45

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

46

Conceptual Launch Vehicles Using Metallic Hydrogen Propellant  

NASA Astrophysics Data System (ADS)

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

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

2008-01-01

47

Stability of Metallic Hydrogens with Cubic Structure  

Microsoft Academic Search

The structure-dependent ground-state energies of metallic hydrogens are figured out accurately up to O(rs) for cubic crystals, in critical comparison with the previous work by Brovman et al. and by Hammerberg and Ashcroft. The elastic constants are also evaluated up to the corresponding order for the purpose of looking into the mechanical stabillity of cubic metallic hydrogens under high pressures.

Hitose Nagara; Hiroshi Miyagi; Tuto Nakamura

1976-01-01

48

The permeability of hydrogen in bulk palladium at elevated temperatures and pressures  

SciTech Connect

The permeability of hydrogen in bulk palladium membranes (approximately 1-mm thickness) was determined for the first time at conditions of simultaneously elevated temperature (623–1173 K) and hydrogen pressure (0.1 × 106 to 2.76 × 106 Pa). When the hydrogen partial pressure exponent value was constrained to a value of 0.5, the permeability was described by an Arrhenius-type relation where the pre-exponential constant and activation energy for this correlation were 1.92×10?7 mol/(m s Pa0.50) and 13.81 kJ/mol, respectively. These Arrhenius values were in good agreement with prior low-pressure correlations. However, the hydrogen flux results of this study were most accurately represented by an Arrhenius permeability expression where 3.21 × 10?8 mol/(m s Pa0.62), 13.41 kJ/mol, and 0.62 represent the pre-exponential constant, activation energy of permeation and permeability driving force, respectively. Although the partial pressure exponent value of 0.62 was slightly greater than the commonly accepted value of 0.5 (atmospheric and sub-atmospheric pressure studies), the optimal exponent value in this study decreased as the upper limit of pressure employed in the database was reduced. Therefore, the deviation in the partial pressure exponent with increasing hydrogen pressure may be attributed to variances in the product of the diffusion coefficient and Sieverts constant at elevated pressures.

Rothenberger, K.S.; Cugini, A.V.; Morreale, B.D.; Enick, R.M.; Bustamante, F.

2003-02-15

49

Structure and Stability of Metallic Hydrogen  

Microsoft Academic Search

A calculation of the electronic energy and optimum atomic spacing for an equally spaced linear array of hydrogen atoms is combined with other information to yield an improved analysis of the existence and stability of metallic hydrogen. A filamentary structure postulated by others is predicted not to be stable or metastable at any pressure; previous predictions of a transition under

Frank E. Harris; J. Delhalle

1977-01-01

50

Metallic Hydrogen - Potentially a High Energy Rocket Propellant.  

National Technical Information Service (NTIS)

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 comp...

I. Silvera J. Cole

2007-01-01

51

Dependence of the hydrogen permeability of glasses on thermal expansion and the structure connectedness factor  

NASA Astrophysics Data System (ADS)

All glass properties are dependent by their structure. It was established that hydrogen permeation, characterized by lgKH as one of properties, is determined on the factor of glass network connectedness and the thermal expansion coefficient, which confirm the existing of free structure volume. Equations have been obtained for calculation of 1gKH. They may be applied for predicting the changes in hydrogen permeability as a function of the indicated criterions.

Medvedev, E. F.

2003-12-01

52

First principles study of the permeability of graphene to hydrogen atoms.  

PubMed

Using calculations from first principles and harmonic transition state theory, we investigated the permeability of a single graphene sheet to protons and hydrogen atoms. Our results show that while protons can readily pass through a graphene sheet with a low tunneling barrier, for hydrogen atoms the barriers are substantially higher. At the same time, the presence of defects in the membrane can significantly reduce the penetration barrier in a region that extends beyond the defect site itself. PMID:23986179

Miao, Meng; Nardelli, Marco Buongiorno; Wang, Qi; Liu, Yingchun

2013-08-29

53

The impact of microstructure on the permeability of metal foams P  

Microsoft Academic Search

Metal foams (MF) are complex structures made from different kinds of materials manufactured using novel technologies. Proper knowledge of pressure drop and related parameters such as permeability (K) and drag coefficient (C) are important and should be defined properly. Thus, the present study was carried out to have an understanding of permeability for different velocity range to suit various industrial

V. Loya; L. P. Lefebvre; M. Medraj

2004-01-01

54

An amorphous alloy membrane without noble metals for gaseous hydrogen separation  

Microsoft Academic Search

Hydrogen-permeable membranes have a variety of industrial applications but all of the metal membranes employed in industry are made of palladium or palladium alloys. We have been looking for a new material and found that a kind of amorphous alloy, not including noble metals, can be used by itself. It is amorphous Zr36Ni64. The amorphous membrane 30?m thick was produced

S. Hara; K. Sakaki; N. Itoh; H.-M. Kimura; K. Asami; A. Inoue

2000-01-01

55

Pair Correlation Functions in Liquid Metallic Hydrogen  

Microsoft Academic Search

The quantal hypernetted chain (QHNC) equation, derived from the Kohn-Sham-Mermin theory, is solved for the pair correlation functions in a liquid metallic hydrogen (LMH) modelled as a proton-electron mixture in the range where protons constitute a classical liquid and electrons are in a degenerate state. In the sufficiently high temperature and high density region, hydrogen atoms are found to form

Junzo Chihara

1984-01-01

56

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

57

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

58

Absence of metallization in solid molecular hydrogen  

NASA Astrophysics Data System (ADS)

Being the simplest element with just one electron and proton the electronic structure of a single Hydrogen atom is known exactly. However, this does not hold for the complex interplay between them in a solid and in particular not at high pressure that is known to alter the crystal as well as the electronic structure and eventually causes solid hydrogen to become metallic. In spite of intense research efforts the experimental realization of metallic hydrogen, as well as the theoretical determination of the crystal structure has remained elusive. Here we present a computational study showing that the distorted hexagonal P63/m structure is the most likely candidate for Phase III of solid hydrogen. We find that the pairing structure is very persistent and insulating over the whole pressure range, which suggests that metallization due to dissociation may precede eventual bandgap closure. Due to the fact that this not only resolve one of major disagreement between theory and experiment, but also excludes the conjectured existence of phonon-driven superconductivity in solid molecular hydrogen, our results involve a complete revision of the zero-temperature phase diagram of Phase III.

Azadi, S.; Kühne, Th. D.

2012-07-01

59

Metal hydrides for hydrogen isotope separation  

SciTech Connect

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

Lee, M.W.

1988-01-01

60

Critical fields of liquid superconducting metallic hydrogen  

Microsoft Academic Search

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

J. Jaffe; N. W. Ashcroft

1983-01-01

61

Hydrogen Peroxide Induces Vascular Permeability via Regulation of Vascular Endothelial Growth Factor  

Microsoft Academic Search

Oxidative stress plays critical roles in initiation and\\/or worsening of respiratory disease process. Although reactive oxygen species (ROS) are shown to cause vascular leakage, the mechanisms by which ROS induce an increase in vascular permeability are not clearly understood. In this study, we have used a murine model to evaluate the effect of hydrogen peroxide (H2O2) to examine roles of

Kyung Sun Lee; So Ri Kim; Seoung Ju Park; Hee Sun Park; Kyung Hoon Min; Min Hee Lee; Sun Mi Jin; Gong Yong Jin; Wan Hee Yoo; Yong Chul Lee

62

Membrane permeable luminescent metal complexes for cellular imaging  

NASA Astrophysics Data System (ADS)

The spectroscopic and photophysical properties of ruthenium polypyridyl polypeptide conjugates of the type [Ru(bpy)2PIC-Argn]n+2+, where bpy is 2,2-bipyridyl (bpy), PIC is 2-(4-carboxyphenyl)imidazo[4,5- f][1,10]phenanthroline and PIC-Argn is this ligand peptide bonded to polyarginine where n is 5 or 8, is described. The resonance Raman spectroscopy of the peptide conjugated complex and parent are strongly pH dependent and demonstrate a switch of lowest energy charge transfer transition between bpy and pic ligands as s function of pH. The pKa of the imidazole ring on the complex is obtained from resonance Raman spectroscopy as 7.8 +/- 0.2. The luminescence lifetime of the complex is strongly oxygen dependent and a Stern-Volmer plot of O2 quenching for [Ru(bpy)2(PIC-Arg8)]10+ yielded a KSV value of 2300 +/- 420 M-1 which was independent of pH over the range 2 to 11. The complexes, because of their large Stokes shifts can, uniquely, be used under identical conditions of probe concentration and excitation wavelength for resonance Raman and luminescence cellular imaging. Cellular imaging was conducted using SP2 myeloma cells which confirmed that the [Ru(bpy)2(PIC-Arg8)]10+ is readily taken up by mammalian cells although the parent and pentarginine analogues are not membrane permeable. Preliminary examples of multi-parameter imaging using these probes were presented. Resonance Raman maps of [Ru(bpy)2(PIC-Arg8)]10+ within living myeloma cells showed on the basis of spectral discrimination, attributed to pH, three distinct regions of the cell could be identified, ascribed to the nucleus, the cytoplasm and the membranes. Luminescence lifetime imaging showed quite large variations in the probe lifetime within the living cell which was tentatively ascribed to variation in O2 concentration about the cell. Preliminary estimates of O2 concentration were made and it was found that the membranes, both inner and outer are the most O2 rich regions of the cell. Overall, we propose that such peptide labeled luminescent metal are potentially a valuable addition to cellular imaging by providing tools for multiplexed analysis of the cell environment.

Neugebauer, Ute; Cosgrave, Lynda; Pellegrin, Yann; Devocelle, Marc; Forster, Robert J.; Keyes, Tia E.

2012-05-01

63

Semiempirical, Quantum Mechanical Calculation of Hydrogen Embrittlement in Metals  

Microsoft Academic Search

A new, semiempirical model of metals and impurities (embedded atom method) makes possible a static treatment of the brittle fracture of a transition metal in the presence of hydrogen. Results indicate that hydrogen can reduce the fracture stress in nickel.

Murray S. Daw; M. I. Baskes

1983-01-01

64

Hydrogen peroxide penetration into the pulp chamber and dental permeability after bleaching.  

PubMed

This study sought to quantify the concentration of hydrogen peroxide (HP) in the pulp chamber and evaluate changes on dental permeability after bleaching with 3 HP concentrations (10%, 35%, and 50%). This study was divided into 2 experiments and the bleaching treatments consisted of 3 applications of HP for 30 minutes during a single session. The first experiment tested HP penetration into the pulp chamber of 4 experimental groups (n = 10) of bovine crowns, which were divided by HP concentration: an unbleached control group (0% HP), 10% HP, 35% HP, and 50% HP. Acetate buffer solution was placed into the pulp chamber and after each application of HP. This solution was collected to determine spectrophotometrically the concentration of HP that reached the pulp chamber. The second experiment evaluated dental permeability. Bovine crowns were divided into 3 groups (n = 10). The crowns were connected to a permeability device and the initial permeability was measured at 10 psi. Three different concentrations of HP gels (10%, 35% and 50%) were applied to the buccal enamel surfaces and the dental permeability was measured after the first, second, and third applications of HP. The data were analyzed by 2-way ANOVA and Tukey test (P ? 0.05). All concentrations of HP reached the pulp chamber, although no significant differences were noted between the 3 concentrations tested (P > 0.05). However, the increase of dental permeability in the group that received 50% HP was significantly higher than the 10% HP group (P < 0.05). The results indicate that the HP bleaching treatments increased dental permeability. PMID:23649584

Berger, Sandrine Bittencourt; Tabchoury, Cinthia Pereira Machado; Ambrosano, Glaucia Maria Bovi; Giannini, Marcelo

65

Hydrogen storage technology for metal hydrides  

SciTech Connect

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

Strickland, G

1978-06-01

66

Kinetics of hydrogen desorption from the powders of metal hydrides  

Microsoft Academic Search

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

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

2005-01-01

67

Solubility and Diffusion of Hydrogen in Pure Metals and Alloys  

NASA Astrophysics Data System (ADS)

Basic facts are presented of the absorption of hydrogen gas by metals and the diffusion of hydrogen in metals. Specifically considered are crystalline metals without defects and lattice disorder (pure metals), low hydrogen concentrations and the possibility of high hydrogen gas pressures. The first introductory topic is a short presentation of typical phase diagrams of metal hydrogen systems. Then, hydrogen absorption is discussed and shown to be decisively determined by the enthalpy of solution, in particular by its sign which specifies whether absorption is exothermic or endothermic. The formation of high-pressure hydrogen gas bubbles in a metal, which can lead to blistering, is addressed. It is demonstrated that bubble formation will, under realistic conditions, only occur in strongly endothermically hydrogen absorbing metals. The chief aspects of hydrogen diffusion in metals are discussed, especially the large size of the diffusion coefficient and its dependence on lattice structure. It is shown that forces can act on hydrogen in metals, causing a directed hydrogen flux. Such forces arise, for instance, in the presence of stress and temperature gradients and can result in local hydrogen accumulation with potential material failure effects. The final aspect discussed is hydrogen permeation, where the absorption behavior of the hydrogen is found to be in general more decisive on the permeation rate than the value of the diffusion coefficient.

Wipf, H.

68

Transition metal based borohydrides for hydrogen storage  

NASA Astrophysics Data System (ADS)

Using ab-initio studies based on the density-functional theory, we have calculated binding energies per hydrogen molecule for decomposition reactions of transition metal borohydrides MHxB12H12 to MB12 structures, where M corresponds to Sc, Ti, or V. Depending on the valence of the transition metal, x can be 1, 2, or 3. Crystal structures considered for MB12 included both hypothetical and those found in the international crystallographic structural database. On the other hand, the crystal structure considered for MHxB12H12 belongs to C2/c (space group 15) structure as reported in a previous study [V. Ozolins et al. JACS, 131, 230 (2009)]. Among the structures investigated, Titanium-based metal borohydride structure has the lowest binding energy per hydrogen molecule relative to the cubic TiB12 structure (˜0.37 eV/H2). Our finding should be contrasted with the binding energy/H2 for simple metal based borohydrides (e.g., CaB12H12 ), which has a value of ˜ 1.5 eV/H2, suggesting that transition metals play a significant role in lowering the H2 binding energy in borohydrides.

Jayanthi, Chakram; Liu, Jianjun; Wei, Suhuai; Zhao, Yufeng

2010-03-01

69

Recovery of hydrogen from hydrogen sulfide with metals or metal sulfides  

NASA Astrophysics Data System (ADS)

Two types of reactions for the recovery of hydrogen from hydrogen sulfide using metals or metal sulfides are investigated. The first type of reaction, which involved the sulfurization of metals or metal sulfides with H2S and the thermal decomposition of the products into hydrogen, elemental sulfur and the original metals or metal sulfide, was studied by the measurement of H2 evolution in a packed bed of powders of Ag, FeS, Co9S8, Ni3S2 and various sulfide mixtures. The second type of reaction involves the sulfurization of a metal by H2S and the recovery of the metal by the oxidation of the metal sulfides formed, and was studied for the case of molten lead, molten lead with the addition of Ni or Co, Ag, Cu and Ni powders, and molten Ag-Bi alloy. Extents of reaction and temperature dependence were determined for each step of the reactions, and the repeatability of the cycles was examined.

Kiuchi, H.; Nakamura, I.; Funaki, K.; Tanaka, T.

70

Solubility of helium in metallic hydrogen  

Microsoft Academic Search

In the low-pressure limit, a helium atom embedded in the electron gas appropriate to metallic hydrogen is only weakly perturbed from its free space structure, and its interaction with the electron gas can be represented by an energy-dependent pseudopotential. A calculation is made for the Gibbs energy of mixing for H-He, using an Austin pseudopotential and a fluid state model

D. J. Stevenson

1979-01-01

71

Composite metal membranes for hydrogen separation applications  

SciTech Connect

A novel multilayer metal membrane has been developed that can be used for the separation of hydrogen from feed streams with near perfect selectivity. The membrane is comprised of very thin layers of fully dense palladium film deposited on both sides of a thin Group V metal foil, ion-milled prior to sputtering of the palladium. Palladium loading are kept low using the thin film deposition technology: 0.0012 grams of palladium per square centimeter of membrane is typically used, although thinner coatings have been employed. This membrane operates at temperatures on the order of 300 C and is capable of high rates of hydrogen flow. Flows are dependent on the pressure differential applied to the membrane, but flows of 105 sccm/cm{sup 2} and higher are regularly observed with differentials below one atmosphere. Long term testing of the membrane for a period in excess of 775 hours under constant conditions showed stable flows and an 85% hydrogen recovery efficiency. A system has been successfully applied to the hydrogen handling system of a proton exchange membrane fuel cell and was tested using a pseudo-reformate feed stream without any degradation in performance.

Moss, T.S.; Dye, R.C.

1997-06-01

72

Effect of catalytic activity on methane steam reforming in hydrogen-permeable membrane reactor  

Microsoft Academic Search

Steam reforming of methane, mainly to hydrogen and carbon dioxide, proceeds over nickel catalysts at 800K in an equilibrium-shift reactor with a thin palladium membrane 11?m-thick supported on a stainless steel porous metal filter. The methane conversion greatly exceeds its equilibrium conversion due to the hydrogen separation with the membrane. The catalytic activity affects the conversion much more than in

Jianhua Tong; Yasuyuki Matsumura

2005-01-01

73

Features of the action of low-energy gamma radiation on the hydrogen permeability of certain materials  

SciTech Connect

This paper determines the diffusion coefficients, the constants of permeability, and solubility of hydrogen in palladium, nickel, and Armco iron under the action of low-energy gamma radiation. It was established that without radiation all of the kinetic diffusion curves of hydrogen in palladium and nickel straighten well in a functional scale. In armco iron, some deviations are observed.

Tazhibaeva, I.L.; Bekman, I.N.; Rudenko, N.V.; Shestakov, V.P.

1985-07-01

74

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

75

Enhanced cell permeability of kojic acid-phenylalanine amide with metal complex.  

PubMed

Kojic acid-phenylalanine amide (KA-F-NH(2)), which showed an excellent tyrosinase inhibitory activity, did not inhibit melanogenesis in melanocyte due to its low cell permeability. To enhance its cell permeability by increasing lipophilicity, we prepared metal coordination compounds of KA-F-NH(2) and characterized them by FT-IR and ICP analysis. The metal complex of KA-F-NH(2) inhibited mushroom tyrosinase activity as much as KA-F-NH(2) and reduced melanin contents in melanocyte efficiently. PMID:19962889

Kwak, Seon-Yeong; Noh, Jin-Mi; Park, So-Hee; Byun, Jang-Woong; Choi, Hye-Ryung; Park, Kyoung-Chan; Lee, Yoon-Sik

2009-12-03

76

Hydrogen sorption in metal-polymer composites: The role of interfaces  

NASA Astrophysics Data System (ADS)

We studied the hydrogen storage capacity and sorption kinetics of composite materials made of hydride forming metal particles (LaNi5 or Pd, particle size of ~1 ?m) embedded into hydrogen permeable polymers. Experimental analysis shows that (i) the composite material consisting of LaNi5 particles dispersed into polysiloxane (PS-LaNi5) shows negligible H2 storage capacity while the LaNi5 particles dispersed into polyethylene (PE-LaNi5) are completely hydrogenated and (ii) the Pd particles dispersed both into polysiloxane (PS-Pd) and polyvinylpyrrolidone (PVP-Pd) are completely hydrogenated. The interfacial interactions in the PE-LaNi5 and in the PS-Pd composite materials have weak Van der Waals character while strong interfacial interactions occur in the PS-LaNi5 and in the PVP-Pd composites due to the formation of chemical bonds between polymer side groups and the metal surface atoms. Results indicate that in the metal-polymer composites the hydrogenation of the metallic phase cannot be obtained when the interfacial interactions between metal and polymer impede the surface activation of the metallic phase as in the PS-LaNi5 composite.

Checchetto, R.; Bazzanella, N.; Miotello, A.; Carotenuto, G.; Nicolais, L.

2009-04-01

77

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

NASA Astrophysics Data System (ADS)

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

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

78

Negative effective permeability in metal cluster photonic crystal  

Microsoft Academic Search

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

Qi Wu

2008-01-01

79

DEVELOPMENT OF A NON-NOBLE METAL HYDROGEN PURIFICATION SYSTEM  

Microsoft Academic Search

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

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

2008-01-01

80

Catalytic arene hydrogenation using early transition metal hydride compounds  

SciTech Connect

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

Rothwell, I.P.

1993-03-15

81

RF Breakdown of Metallic Surfaces in Hydrogen  

SciTech Connect

In earlier reports, microscopic images of the surfaces of metallic electrodes used in high-pressure gas-filled 805 MHz RF cavity experiments were used to investigate the mechanism of RF breakdown of tungsten, molybdenum, and beryllium electrode surfaces. Plots of remnants were consistent with the breakdown events being due to field emission, due to the quantum mechanical tunnelling of electrons through a barrier as described by Fowler and Nordheim. In the work described here, these studies have been extended to include tin, aluminium, and copper. Contamination of the surfaces, discovered after the experiments concluded, have cast some doubt on the proper qualities to assign to the metallic surfaces. However, two significant results are noted. First, the maximum stable RF gradient of contaminated copper electrodes is higher than for a clean surface. Second, the addition of as little as 0.01% of SF6 to the hydrogen gas increased the maximum stable gradient, which implies that models of RF breakdown in hydrogen gas will be important to the study of metallic breakdown.

BastaniNejad, M.; Elmustafa, A.A.; /Old Dominion U.; Yonehara, K.; Chung, M.; Jansson, A.; Hu, M.; Moretti, A.; Popovic, M.; /Fermilab; Alsharo'a, M.; Neubauer, M.; Sah, R.; /Muons Inc., Batavia

2009-05-01

82

The Permeability of the Sodium Channel to Metal Cations in Myelinated Nerve  

Microsoft Academic Search

The relative permeability of sodium channels to eight metal cations is studied in myelinated nerve fibers. Ionic currents under voltage-clamp conditions are measured in Na-free solutions containing the test ion. Measured reversal potentials and the Goldman equation are used to calculate the perme- ability sequence: Na+ ~ Li + > T1 + > K+. The ratio PK\\/PN is 1\\/12. The

BERTIL HILLE

1972-01-01

83

Microbiocidal anionic sequesterants with polyvalent metal cations for permeability correction process  

SciTech Connect

A water permeability correction process, and composition therefor, to improve the sweep efficiency of water-flooding which involves the sequential injection of an optical aqueous preflush slug to adjust connate water salinity, an aqueous sequestered polyvalent metal cation, such as chromium, wherein the sequestering anion is bactericidal, such as propionate, a gelable polymeric viscosifier, such as polyacrylamide, and preferably, an aqueous drive fluid.

Wu, Y.; Mumallah, N. A.

1985-11-12

84

Precious Metal Catalysts Supported on Ceramic and Metal Monolithic Structures for the Hydrogen Economy  

Microsoft Academic Search

Distributed hydrogen for the hydrogen economy will require new catalysts and processes. Existing large?scale hydrogen plants can not simply be reduced in size to meet the economic, safety, and frequent duty cycle requirements for applications for fuel cells, hydrogen fueling stations, and industrial uses such as hydrogenation reactions, gas turbine cooling, metal processing, etc 12. Consequently, there is a need

Robert J. Farrauto; Ye Liu; Wolfgang Ruettinger; Oleg Ilinich; Larry Shore; Tom Giroux

2007-01-01

85

Hydrogenation: a simple approach to realize semiconductor-half-metal-metal transition in boron nitride nanoribbons.  

PubMed

The intriguing electronic and magnetic properties of fully and partially hydrogenated boron nitride nanoribbons (BNNRs) were investigated by means of first-principles computations. Independent of ribbon width, fully hydrogenated armchair BNNRs are nonmagnetic semiconductors, while the zigzag counterparts are magnetic and metallic. The partially hydrogenated zigzag BNNRs (using hydrogenated BNNRs and pristine BNNRs as building units) exhibit diverse electronic and magnetic properties: they are nonmagnetic semiconductors when the percentage of hydrogenated BNNR blocks is minor, while a semiconductor-->half-metal-->metal transition occurs, accompanied by a nonmagnetic-->magnetic transfer, when the hydrogenated part is dominant. Although the half-metallic property is not robust when the hydrogenation ratio is large, this behavior is sustained for partially hydrogenated zigzag BNNRs with a smaller degree of hydrogenation. Thus, controlling the hydrogenation ratio can precisely modulate the electronic and magnetic properties of zigzag BNNRs, which endows BN nanomaterials many potential applications in the novel integrated functional nanodevices. PMID:20085366

Chen, Wei; Li, Yafei; Yu, Guangtao; Li, Chen-Zhong; Zhang, Shengbai B; Zhou, Zhen; Chen, Zhongfang

2010-02-10

86

Achieving optimum hydrogen permeability in PdAg and PdAu alloys  

NASA Astrophysics Data System (ADS)

The present work investigates both the diffusivity and permeability of hydrogen (H) in palladium-silver (PdAg) and palladium-gold (PdAu) alloys over a 400-1200 K temperature range for Pd100-XMX, M=Ag or Au and X=0%-48% using density functional theory (DFT) and kinetic Monte Carlo simulations (KMC). DFT has been employed to obtain octahedral (O)-, tetrahedral (T)-, and transition state (TS)- site energetics as a function of local alloy composition for several PdAg and PdAu alloys with compositions in supercells of X=14.18%, 25.93%, 37.07%, and 48.15% with the nearest (NNs) and next nearest neighbors (NNNs) varied over the entire range of compositions. The estimates were then used to obtain a model relating the O, T, and TS energies of a given site with NNX, NNNX, and the lattice constant. The first passage approach combined with KMC simulations was used for the H diffusion coefficient predictions. It was found that the diffusion coefficient of H in PdAg alloy decreases with increasing Ag and increases with increasing temperature, matching closely with the experimental results reported in the literature. The calculated permeabilities of H in these novel binary alloys obtained from both diffusivity and solubility predictions were found to have a maximum at ~20% Ag and ~12% Au, which agree well with experimental predictions. Specifically, the permeability of H in PdAg alloy with ~20% Ag at 456 K is three to four times that of pure Pd, while the PdAu alloy at 12% Au is four to five times that of pure Pd at 456 K.

Sonwane, Chandrashekhar G.; Wilcox, Jennifer; Ma, Yi Hua

2006-11-01

87

Highly efficient to hydrogen permeability palladium membranes supported in porous silicon  

NASA Astrophysics Data System (ADS)

Hydrogen separation from gas mixtures and purification are of great importance and interest. Technologies based on the use of metallic membranes are the most suitable ones for these purposes. Pd and its alloys with Ag, Au, Cu and Ni are the best candidates for the membranes. In the present work, technology of the membranes formation based on macroporous silicon with Pd/Ag thin film has been investigated.

Starkov, V.; Vyatkin, A.; Volkov, V.; Presting, H.; Konle, J.; Konig, U.

2005-06-01

88

Hydrogen permeability over the joint weld of the steel parts of fusion reactor with magnet confinement of plasma  

Microsoft Academic Search

Hydrogen and its isotopes diffusion and permeability over the laser joint weld of low-activation 10Cr9WVA ferritic steels have been studied. Welding of steel sheets were produced with the help of Russian gas laser TL-5M type (l=10.6 mm, P=2.5 kW) in He atmosphere with the rate of 66 mm\\/s. Hydrogen diffusion over the joint welds was detected by the conventional method

V. V. Fedorov; E. V. Dyomina; T. M. Zasadny; L. I. Ivanov; M. D. Prusakova; N. A. Vinogradova; A. M. Zabelin

2002-01-01

89

Lithium Dihydrogen Fluoride-An Approach to Metallic Hydrogen  

Microsoft Academic Search

The possibility of making a new form of hydrogen in the metallic state through preparation of the compound LiH2F is discussed. A proposed structure is specified which is believed to be nearly stable under ambient conditions. The pressures needed to stabilize this compound and to convert it to a metal are estimated. It may have an exceptionally high hydrogen density,

J. J. Gilman

1971-01-01

90

Catalytic hydrogenation and gas permeation properties of metal-containing poly(phenylene oxide) and polysulfone  

SciTech Connect

Metal-containing polymers, PPL-DPP-Pd, PPO-CPA-Pd, PSF-DPP-Pd, PSF-CPA-Pd (PDD = diphenylphosphinyl, CPA = o-carboxy phenyl amino), PPO-M (M = Pd,Cu,Co,Ni), and PSF-Pd, were prepared by incorporating metal chloride with either modified or unmodified poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and polysulfone (PSF). The Pd-containing polymers exhibit catalytic activity in the hydrogenation of cyclopentadiene under mild conditions both in alcohol solution and in the gas phase. The selectivity in the hydrogenation of diene to monoene in the gas phase can be controlled by adjusting the hydrogen partial pressure. The metal-containing polymers, PPL-M and PSF-Pd, can be cast easily into the membranes. The H[sub 2]/N[sub 2] permselectivity for PPO-M is higher than that for unmodified PPO, whereas the permeability of H[sub 2] changes slightly. The H[sub 2] permeability and H[sub 2]/N[sub 2] permselectivity for the PPO-Pd membrane are up to 67.5 barrers and 135, respectively.

Hanrong Gao; Yun Xu; Shijian Liao; Ren Liu; Daorong Yu (Chinese Academy of Sciences, Dalian (China). Dalian Inst. of Chemical Physics)

1993-11-10

91

Hydrogen permeation resistant layers for liquid metal reactors  

Microsoft Academic Search

Reviewing the literature in the tritium diffusion field one can readily see a wide divergence in results for both the response of permeation rate to pressure, and the effect of oxide layers on total permeation rates. The basic mechanism of protective oxide layers is discussed. Two coatings which are less hydrogen permeable than the best naturally occurring oxide are described.

J McGuire

1980-01-01

92

A note on the metallization of compressed liquid hydrogen  

NASA Astrophysics Data System (ADS)

We examine the molecular-atomic transition in liquid hydrogen as it relates to metallization. Pair potentials are obtained from first principles molecular dynamics and compared with potentials derived from quadratic response. The results provide insight into the nature of covalent bonding under extreme conditions. Based on this analysis, we construct a schematic dissociation-metallization phase diagram and suggest experimental approaches that should significantly reduce the pressures necessary for the realization of the elusive metallic phase of hydrogen.

Tamblyn, Isaac; Bonev, Stanimir A.

2010-04-01

93

Metals and superconductors: molecular analogs of atomic hydrogen.  

PubMed

One for the half: recent work on atomic hydrogen and neutral radical heterocyclic molecules has moved the field of spin S=1/2 solids closer to the realization of synthetic intrinsic metals and superconductors. High-pressure experiments on hydrogen and chalcogenide-nitrogen molecules show evidence of metallic character. The molecular radicals exhibit a positive temperature coefficient of resistance under pressure-the classic signature of a metal. PMID:22890938

Haddon, Robert C

2012-08-13

94

Metallization of solid hydrogen: the challenge and possible solutions.  

PubMed

The search for the means to convert molecular hydrogen to a metal under static conditions at high pressure is reviewed with emphasis on selected recent developments in both experimental studies and theoretical approaches. One approach suggested recently makes use of mixtures of hydrogen and suitable impurities. In these materials hydrogen is perturbed by impurities with the goal of obtaining the metallization of hydrogen at moderate pressures. This approach has also been extensively examined through the use of first-principles methods and we review this recently explored experimental approach and several theoretical studies that have provided an atomic-scale picture of the interaction of hydrogen with impurities under pressure. The objective of this novel approach is to help determine if metallization of hydrogen at pressures is attainable with currently available experimental techniques. PMID:21879063

Klug, Dennis D; Yao, Yansun

2011-08-30

95

Hydrogenation of coal liquid utilizing a metal carbonyl catalyst  

DOEpatents

Coal liquid having a dissolved transition metal, catalyst as a carbonyl complex such as Co.sub.2 (CO.sub.8) is hydrogenated with hydrogen gas or a hydrogen donor. A dissociating solvent contacts the coal liquid during hydrogenation to form an immiscible liquid mixture at a high carbon monoxide pressure. The dissociating solvent, e.g. ethylene glycol, is of moderate coordinating ability, while sufficiently polar to solvate the transition metal as a complex cation along with a transition metal, carbonyl anion in solution at a decreased carbon monoxide pressure. The carbon monoxide pressure is reduced and the liquids are separated to recover the hydrogenated coal liquid as product. The dissociating solvent with the catalyst in ionized form is recycled to the hydrogenation step at the elevated carbon monoxide pressure for reforming the catalyst complex within fresh coal liquid.

Feder, Harold M. (Hinsdale, IL); Rathke, Jerome W. (Bolingbrook, IL)

1979-01-01

96

Metallacarboranes: Towards promising hydrogen storage metal organic framework  

NASA Astrophysics Data System (ADS)

Using first principles calculations we show the high hydrogen storage capacity of metallacarboranes,ootnotetextA. K. Singh, A. Sadrzadeh, and B. I. Yakobson, Metallacarboranes: Toward Promising Hydrogen Storage Metal Organic Frameworks, JACS 132,14126 (2010). where the transition metal (TM) atoms bind hydrogen via Kubas interaction. The average binding energy of ˜0.3 eV/H favorably lies within the reversible adsorption range The Sc and Ti are found to be the optimum metal atoms maximizing the number of stored H2 molecules. Depending upon the structure, metallacarboranes can adsorb up to 8 wt% of hydrogen, which exceeds DOE goal for 2015. Being integral part of the cage, TMs do not suffer from the aggregation problem. Furthermore, the presence of carbon atom in the cages permits linking the metallacarboranes to form metal organic frameworks (MOF), thus able to adsorb hydrogen via Kubas interaction, in addition to van der Waals physisorption.

Singh, Abhishek; Sadrzadeh, Arta; Yakobson, Boris

2011-03-01

97

The role of hydrogen bonding in water-metal interactions  

NASA Astrophysics Data System (ADS)

The hydrogen bond interaction between water molecules adsorbed on a Pd-<111 > surface, a well known nucleator of two dimensional bilayers of ice at low temperatures, is studied using density functional theory calculations. The role of the exchange and correlation potential in the characterization of both the hydrogen bond and the water-metal interaction is analyzed in detail. We conclude that the choice of this potential is critical in determining the cohesive energy of water-metal complexes. The crucial factor nonetheless is not the description of the metal screening, even if this screening represents an important ingredient for the water-metal interaction. The different characterization of the hydrogen bonds between water molecules and the pseudo hydrogen bonds established between the water and the surface is at the heart of the large disparity we observe in our calculations. These results put in evidence the urgent need for an accurate characterization of the hydrogen bond interaction with density functional theory.

Poissier, Adrien; Ganeshan, Sriram; Fernandez-Serra, Marivi

2010-03-01

98

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

99

Hydrogen Embrittlement of Metals: Atomic hydrogen from a variety of sources reduces the ductility of many metals.  

PubMed

Hydrogen interacts with many metals to reduce their ductility (2) and frequently their strength also. It enters metals in the atomic form, diffusing very rapidly even at normal temperatures. During melting and fabrication, as well as during use, there are various ways in which metals come in contact with hydrogen and absorb it. The absorbed hydrogen may react irreversibly with oxides or carbides in some metals to produce a permanently degraded structure. It may also recombine at internal surfaces of defects of various types to form gaseous molecular hydrogen under pressures sufficiently high to form metal blisters when the recombination occurs near the outer surface. In other metals, brittle hydrides that lower the mechanical properties of the metal are formed. Another type of embrittlement is reversible, depending on the presence of hydrogen in the metal lattice during deformation for its occurrence. Under some conditions the failure may be delayed for long periods. A number of different mechanisms have been postulated to explain reversible embrittlement. According to some theories hydrogen interferes with the processes of plastic deformation in metals, while according to others it enhances the tendency for cracking. PMID:17775040

Rogers, H C

1968-03-01

100

Metal hydride beds and hydrogen supply tanks as minitype PEMFC hydrogen sources  

Microsoft Academic Search

In order to improve the properties of hydrogen tanks for hydrogen fuel cells, we studied the effect of two different matrix configurations, one being pellet pressed by Cu coating hydrogen storage alloy powders and the other foam nickel sheets filled with hydrogen storage alloy powders, on the heat and mass transfer properties of metal hydride beds. AB5-type alloy Ml0.85Ca0.15Ni5 and

Yun Chen; Cesar A. C Sequeira; Changpin Chen; Xinhua Wang; Qidong Wang

2003-01-01

101

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

102

High temperature equation of state of metallic hydrogen  

Microsoft Academic Search

The equation of state of liquid metallic hydrogen is solved numerically. Investigations are carried out at temperatures from\\u000a 3000 to 20 000 K and densities from 0.2 to 3 mol\\/cm3, which correspond both to the experimental conditions under which metallic hydrogen is produced on earth and the conditions\\u000a in the cores of giant planets of the solar system such as

V. T. Shvets

2007-01-01

103

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

104

Understanding the mechanism of hydrogen adsorption into metal organic frameworks  

Microsoft Academic Search

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

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

2007-01-01

105

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

106

On the Possibility of a Metallic Modification of Hydrogen  

Microsoft Academic Search

Any lattice in which the hydrogen atoms would be translationally identical (Bravais lattice) would have metallic properties. In the present paper the energy of a body-centered lattice of hydrogen is calculated as a function of the lattice constant. This energy is shown to assume its minimum value for a lattice constant which corresponds to a density many times higher than

E. Wigner; H. B. Huntington

1935-01-01

107

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

Microsoft Academic Search

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

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

2002-01-01

108

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

Microsoft Academic Search

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

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

2008-01-01

109

Partially pyrolyzed olive pomace sorbent of high permeability for preconcentration of metals from environmental waters.  

PubMed

The aim of this work is to develop a preconcentration procedure of Cd(2+), Zn(2+) and Cu(2+) in environmental waters using olive pomace (OP) prior to their determination by flame atomic absorption spectrometry (FAAS). Raw OP as preconcentrating sorbent was found to have low permeability towards the passed water samples and thus long time was needed. Even reducing the vacuum pressure caused cartridge blockage. Novel preconcentrating sorbents of high permeability were then prepared by heat pretreatment under inert atmosphere (partial pyrolysis) of OP at various temperatures (100, 150, 200, 250 and 300 degrees C). The permeability of OP pyrolyzed at 200 degrees C (sorbent OP-200) was enhanced 11 times relative to the raw OP, which significantly reduced the time required in the preconcentration process. A preconcentration procedure was optimized using OP-200 as preconcentrating sorbent, in which the detection limits were 42 ng L(-1) for Cu(2+), 76 ng L(-1) for Zn(2+) and 172 ng mL(-1) for Cd(2+). The method was linear within the studied concentration range (2-100 ng mL(-1)). The proposed method gave recoveries from 83+/-6 to 103+/-5% for determination of metals in tap water; and recoveries from 81+/-6 to 100+/-6% in well water. The method was validated by comparison with independent method and by analysis of lake sediments LKSD-4 certified reference material. PMID:19386412

El-Sheikh, Amjad H; Sweileh, Jamal A; Saleh, Maysoon I

2009-03-25

110

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

111

How are hydrogen bonds modified by metal binding?  

PubMed

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

Husberg, Charlotte; Ryde, Ulf

2013-03-31

112

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

113

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

114

Hydrogen Storage in Metal-Organic Frameworks.  

National Technical Information Service (NTIS)

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 ha...

O. M. Yaghi

2012-01-01

115

Hydrogen in HY-130 Weld Metal.  

National Technical Information Service (NTIS)

This is the final report on a program designed to evaluate the potential for using rare-earth materials to getter hydrogen during welding. The end objective was to reduce the potential for hydrogen embrittlement in HY-130 steel welds. This report briefly ...

D. Hauser M. D. Hayes

1979-01-01

116

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

PubMed

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. PMID:21505497

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

2011-04-10

117

Characterization of internal oxidation and permeability of oxygen in Pd/Al alloys using hydrogen isotherms  

SciTech Connect

Eastman and Ruehle have shown that substitutional fcc Pd-Al alloys can be internally oxidized to produce Al{sub 2}O{sub 3} precipitates within a metal matrix. Emphasis in this study will be characterizing of internally oxidized alloys using hydrogen at contents r > 0.01; these are easily accessible by gas phase measurements which will be carried out to p{sub H{sub 2}} {le} 5 bar. The hydrogen isotherms of palladium and a Pd{sub 0.97}Al{sub 0.03} alloy both exhibit plateau pressure regions where a dilute and hydride phase co-exist. If complete internal oxidation takes place, it is expected that the isotherm for the Pd{sub 0.97}Al{sub 0.03} alloy will change to that for pure Pd. Partial oxidation should lead to two plateau pressures, one characteristic of the alloy and one of pure Pd and their relative breadths will be proportional to the fractions of each.

Noh, H.; Flanagan, T.B. [Univ. of Vermont, Burlington, VT (United States); Balasubramaniam, R. [Indian Inst. of Technology, Kanpur (India). Dept. of Materials and Metallurgical Engineering; Eastman, J.A. [Argonne National Lab., IL (United States). Materials Science Div.

1996-03-15

118

Hydrogen storage in metal–hydrogen systems and their derivatives  

Microsoft Academic Search

During the last years, the power densities of automotive fuel cell systems have been raised dramatically. However, a major technology improvement is still needed for the on-board fuel storage system since hydrogen exhibits a rather low volumetric energy density (regardless whether it is stored as a liquid at cryogenic temperatures or as a compressed gas). Furthermore, the cost for current

U. Eberle; G. Arnold; R. von Helmolt

2006-01-01

119

The effect of ion implanting on hydrogen entry into metals  

SciTech Connect

The effectiveness of platinum ion implanting in mitigating hydrogen entry into 4340 steel is measured and quantified. Data are presented to compare the extent of hydrogen absorption by the substrate during electrolytic hydrogen charging of platinum ion-implanted and unimplanted 4340 steel substrates. Several implanting conditions were used in processing the samples, and the surface-limited mass-transfer coefficient was calculated for each case and used to quantify the effectiveness of each treatment in reducing hydrogen absorption. It is shown that the underlying mechanism for reducing hydrogen absorption by platinum ion-implanted substrates is the catalytic effect of platinum that favors hydrogen evolution at the steel`s surface over hydrogen absorption by the metal. Although scattering experiments with low energy helium ions suggest that the platinum content in the first monolayer of platinum-implanted steels is small, the ability of Pt to catalyze the hydrogen evolution reaction is still strong enough to significantly reduce the quantity of hydrogen that enters the metal.

Chou, S.C.; Makhlouf, M.M. [Worcester Polytechnic Inst., MA (United States). Dept. of Mechanical Engineering

1999-06-01

120

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

Microsoft Academic Search

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.

M. W. Ruckman; M. Strongin; H. Weismann

1997-01-01

121

Electrocatalytic hydrogenation and deoxygenation of glucose on solid metal electrodes.  

PubMed

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

Kwon, Youngkook; Koper, Marc T M

2013-01-23

122

Effects of self-induced stress on the steady concentration distribution of hydrogen in fcc metallic membranes during hydrogen diffusion  

Microsoft Academic Search

Based on the thermodynamics involving the lattice expansion due to hydrogen insertion, the interaction between hydrogen atoms and the blocking effect in hydrogen diffusion, we discuss the profiles of hydrogen concentration and self-induced stress, and their interaction in the steady state during hydrogen diffusion across elastic membranes of fcc metals or alloys. Contrary to the conventional viewpoint, it is found

Wu-Shou Zhang; Xin-Wei Zhang; Zhong-Liang Zhang

2000-01-01

123

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

2013-09-05

124

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

Microsoft Academic Search

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

Yoshihiko Takahashi; Yuuta Kaji

2011-01-01

125

Hydrogen Storage in Microporous Metal-Organic Frameworks  

NASA Astrophysics Data System (ADS)

Metal-organic framework-5 (MOF-5) of composition Zn4O(BDC)3 (BDC = 1,4-benzenedicarboxylate) with a cubic three-dimensional extended porous structure adsorbed hydrogen up to 4.5 weight percent (17.2 hydrogen molecules per formula unit) at 78 kelvin and 1.0 weight percent at room temperature and pressure of 20 bar. Inelastic neutron scattering spectroscopy of the rotational transitions of the adsorbed hydrogen molecules indicates the presence of two well-defined binding sites (termed I and II), which we associate with hydrogen binding to zinc and the BDC linker, respectively. Preliminary studies on topologically similar isoreticular metal-organic framework-6 and -8 (IRMOF-6 and -8) having cyclobutylbenzene and naphthalene linkers, respectively, gave approximately double and quadruple (2.0 weight percent) the uptake found for MOF-5 at room temperature and 10 bar.

Rosi, Nathaniel L.; Eckert, Juergen; Eddaoudi, Mohamed; Vodak, David T.; Kim, Jaheon; O'Keeffe, Michael; Yaghi, Omar M.

2003-05-01

126

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

Microsoft Academic Search

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

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

2007-01-01

127

Hydrogen storage by metalized silicene and silicane  

NASA Astrophysics Data System (ADS)

The hydrogen storage capacities of K-decorated silicene and silicane are studied using first-principles calculations. It is found that K atoms can form a uniform and stable coverage on one side of silicene and both sides of silicane. Each K atom can absorb a maximum of five H2 molecules and the hydrogen storage capacity of K-decorated silicane can reach 6.13 wt. % with an average adsorption energy of 0.133 eV/H2. This hydrogen storage capacity is in excess of 6 wt. %, the U. S. Department of Energy target. This is a remarkable result indicating another application of silicene/silicane as a potential high-capacity storage medium.

Wang, Jing; Li, Jingbo; Li, Shu-Shen; Liu, Ying

2013-09-01

128

Molecular simulation of hydrogen diffusion in interpenetrated metal organic frameworks  

Microsoft Academic Search

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

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

2008-01-01

129

Electronic excitations and metallization of dense solid hydrogen.  

PubMed

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

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

2013-07-31

130

Hydrogen-atom direct-entry mechanism into metal membranes  

SciTech Connect

The hydrogen-atom direct-entry mechanism is used to explain why the steady-state hydrogen permeation current density through a metal membrane is directly proportional to the cathodic current density, i[sub c], and is independent of the membrane thickness when i[sub c] is small. The Devanathan-Stachurski permeation technique was used to investigate the rate of hydrogen permeation through a HY-130 steel and through palladium membranes with an area of approximately 4 cm[sup 2] with thicknesses of 0.15 and 0.025 mm, respectively.

Zheng, G.; Popov, B.N.; White, R.E. (Univ. of South Carolina, Columbia, SC (United States). Dept. of Chemical Engineering)

1995-01-01

131

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; Gould, W.D. [CANMET, Ottawa, Ontario (Canada)

1999-08-15

132

Metal-organic frameworks: A new hydrogen storage system  

NASA Astrophysics Data System (ADS)

Metal-organic framework-5 (MOF-5) of composition Zn4O(BDC)3 (BDC = 1,4-benzenedi-carboxylate) with a cubic 3-D extended porous structure was found to be capable of adsorbing hydrogen up to 4.5 weight percent (17.2 hydrogen molecules per formula unit) at 78 K. At room temperature and pressures up to 20 bar this material has a hydrogen storage capacity which increases linearly as a function of the applied pressure up to 1.0 percent by weight at 20 bar. Inelastic Neutron Scattering spectroscopy of the rotational transitions of the adsorbed hydrogen molecules was performed on hydrogen loaded MOF-5 using doses equivalent to four, eight and twenty-four hydrogen molecules per formula unit at 10 K. The spectra show peaks at 10.3 and 12.3 meV that are sharper than those observed for hydrogen in other porous materials, indicating the presence of two well-defined binding sites (termed I and II), which we associate with hydrogen binding to zinc and the BDC linker, respectively. At the highest dose (twenty-four hydrogen molecules), the peak corresponding to site II splits into four peaks, suggesting that higher capacity for hydrogen may be achieved by the use of larger linkers. Indeed, preliminary studies on isoreticular (of the same topology) metal-organic framework-6 and 8 having cyclobutyl and benzene moieties respectively fused to the benzene of MOF-5 gave approximately double and quadruple (2.0 weight percent) the uptake found for MOF-5 at room temperature and 10 bar.

Yaghi, Omar

2004-03-01

133

Ion permeability of amorphous hydrogen- and fluorine-containing carbon films formed by plasma enhanced chemical vapour deposition  

NASA Astrophysics Data System (ADS)

Methane, tetra-fluoro-methane and mixtures of both gases were ionized by radiofrequency excitation at 13.56 MHz under reduced pressure. The ionic species from the plasma such as CH4+ or CF3+ were accelerated in an electrical field and deposited onto iron substrates, forming films of amorphous carbon with hydrogen and fluorine. Their sealing performance as protective coating on the iron substrates against aqueous corrosion was tested by electrochemical methods. Therefore, the ion permeability of the coating material was measured by means of the dissolution current of the substrate material. The influence of film thickness and plasma gas composition was evaluated.

Sittner, F.; Ensinger, W.

2007-04-01

134

Optical hydrogen sensors based on metal-hydrides  

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

135

Metallization of Molecular Hydrogen: Predictions from Exact-Exchange Calculations  

Microsoft Academic Search

We study metallization of molecular hydrogen under pressure using exact-exchange (EXX) Kohn-Sham density-functional theory in order to avoid well-known underestimates of band gaps associated with standard local-density or generalized-gradient approximations. Compared with the standard methods, the EXX approach leads to considerably (1-2 eV) higher gaps and significant changes in the relative energies of different structures. Metallization is predicted to occur

Martin Städele; Richard M. Martin

2000-01-01

136

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

137

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

138

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

Microsoft Academic Search

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

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

1971-01-01

139

Ab Initio Molecular Dynamics of Metallic Hydrogen at High Densities  

Microsoft Academic Search

The fully ionized (metallic) hydrogen plasma is studied by ab initio molecular dynamics simulations, for classical protons and fully degenerate electrons, in the strong coupling regime of the protons. The calculated ion-electron pair distribution function signals the breakdown of linear screening with decreasing density while the melting temperature of the proton crystal drops rapidly. The simulations reveal the remarkable persistence

Jorge Kohanoff; Jean-Pierre Hansen

1995-01-01

140

Trial wave functions for high-pressure metallic hydrogen  

Microsoft Academic Search

Many body trial wave functions are the key ingredient for accurate Quantum Monte Carlo estimates of total electronic energies in many electron systems. In the Coupled Electron-Ion Monte Carlo method, the accuracy of the trial function must be conjugated with the efficiency of its evaluation. We report recent progress in trial wave functions for metallic hydrogen implemented in the Coupled

Carlo Pierleoni; Kris T. Delaney; Miguel A. Morales; David M. Ceperley; Markus Holzmann

2008-01-01

141

High Temperature Superconductivity in Metallic Hydrogen:Electron-Electron Enhancements  

Microsoft Academic Search

We investigate the possibility of superconductivity in a dense phase of hydrogen which becomes metallic while retaining diatomic character. Correlated fluctuations between electrons and holes in the ensuring band-overlap state can lead to significant enhancements in the transition temperature (compared with monatomic phases) principally through a reduction in the associated Coulomb pseudopotential. The effective electron-electron interaction is determined by a

C. Richardson; N. Ashcroft

1997-01-01

142

Thermodynamic properties of high density metallic solid hydrogen  

Microsoft Academic Search

Isentropic compression of high density metallic solid hydrogen (above 10 to the 24th\\/cu cm), which is necessary to solve the process of inertial confinement in the laser-driven compression, is investigated. The phase diagram is obtained according to Lindemann's criterion. The pressure necessary to realize such high density and the temperature variation are estimated.

Kazuo Inoue; Tomio Ariyasu

1980-01-01

143

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

144

Retention of Weld Metal Properties and Prevention of Hydrogen Cracking.  

National Technical Information Service (NTIS)

In this project, single and multiple pass weldability tests were used to assess hydrogen-cracking resistance of weld metals used for joining conventional quenched and tempered HY-100 steel and a lower carbon HSLA-100 steel. Additional studies included eva...

2003-01-01

145

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

146

Pressure-induced metallization of Li+-doped hydrogen clusters.  

PubMed

Endohedrally encapsulated hydrogen clusters doped with inert helium (H24He) and ionic lithium (H24Li(+)) are investigated. The confinement model is a nanoscopic analogue of the experimental compression of solid hydrogen. The structural and electronic properties of the doped hydrogen clusters are determined under the effects of pressure. The results are compared with these of the isoelectronic (pure) hydrogen counterpart H26 under similar physical conditions. Pressure increase rates with respect to H26 of approximately 1.1 are observed with the insertion of helium or lithium. The changes of geometrical structures and HOMO-LUMO gap energies with the pressure point out the pressure-induced metallization of the Li(+)-doped cluster. The computations are done using density functional theory in the form implemented for molecules; they include zero-point energy effects and, to our best knowledge, are the first of their kind. PMID:23758642

Santamaria, Ruben; Bokhimi, Xim; Soullard, Jacques; Jellinek, Julius

2013-06-28

147

Application of metal hydrides for gas handling in hydrogen masers  

SciTech Connect

Reversible interaction of hydrogen with certain metals and alloys have been employed to effectively satisfy the hydrogen supply and flow regulation, as well as vacuum maintenance requirements of a hydrogen maser. In addition to providing a significant reductions in maser size, weight and power consumption, the hydride components also lead to improved system reliability. A hydrogen supply for seven years of operation of an oscillating compact maser can be stored in 50 grams of LaNi5 or LaNi4.7A10.3. The source occupies a volume of less than 50 cc, including an electrically controlled palladium-silver alloy flow regulator. A combination getter-ion vacuum pump system for the maser was developed using a zirconium graphite getter. Operational experience indicates that for reliable maser operation, a clean, bakeable vacuum system design is a critical requirement.

Wang, H.T.M.

1983-01-01

148

The recovery of chlorine from by-product hydrogen chloride Part 2: Molten metal cathode method  

Microsoft Academic Search

A new method of recovering chlorine from by-product hydrogen chloride is proposed and developed. According to the reaction Me+2HC1 = MeCl2+Ho (Me = Metal) hydrogen chloride is reduced to give hydrogen and metal chloride. Gaseous hydrogen was drawn out from the reaction system and the metal chloride dissolved in the electrolyte, where it was electrolysed to give chlorine and metal

S. Yoshizawa; A. Takehara; Y. Ito; K. Oka

1971-01-01

149

Chemical structure and bonding characteristics of metal hydrogen systems studied by the surface analytical techniques SIMS and XPS  

Microsoft Academic Search

Secondary ion mass spectrometry (SIMS) as well as photoelectron spectroscopy (XPS) are powerful tools for studying special properties of metal hydrogen systems and the interaction of hydrogen and metals. SIMS experiments have now also been extended to transition metal hydrogen systems with small hydrogen solubilities by using intelligent mass spectra accumulation. As known from studies on other metal hydrogen systems

H Züchner; J Kintrup; R Dobrileit; I Untiedt

1999-01-01

150

Future Propellants for Launch Vehicles-Metallic Hydrogen with Water and Hydrocarbon Diluents  

Microsoft Academic Search

Earlier papers have shown that the energy released from recombination of the atomic hydrogen formed when metallic hydrogen is raised above the critical metastabability temperature yields a far greater specific energy and specific impulse than the combustion of hydrogen and oxygen. Experimental efforts continue towards the challenging goal of producing metallic hydrogen in the laboratory. Progress in 2009 has significantly

J. W. Cole; I. F. Silvera

2010-01-01

151

Future Propellants for Launch Vehicles—Metallic Hydrogen with Water and Hydrocarbon Diluents  

Microsoft Academic Search

Earlier papers have shown that the energy released from recombination of the atomic hydrogen formed when metallic hydrogen is raised above the critical metastabability temperature yields a far greater specific energy and specific impulse than the combustion of hydrogen and oxygen. Experimental efforts continue towards the challenging goal of producing metallic hydrogen in the laboratory. Progress in 2009 has significantly

J. W. Cole; I. F. Silvera

2010-01-01

152

Determination of hydrogen diffusivity and permeability in W near room temperature applying a tritium tracer technique  

NASA Astrophysics Data System (ADS)

Tungsten is a primary candidate of plasma facing material in ITER and beyond, owing to its good thermal property and low erosion. But hydrogen solubility and diffusivity near ITER operation temperatures (below 500 K) have scarcely studied. Mainly because its low hydrogen solubility and diffusivity at lower temperatures make the detection of hydrogen quite difficult. We have tried to observe hydrogen plasma driven permeation (PDP) through nickel and tungsten near room temperatures applying a tritium tracer technique, which is extremely sensible to detect tritium diluted in hydrogen.The apparent diffusion coefficients for PDP were determined by permeation lag times at first time, and those for nickel and tungsten were similar or a few times larger than those for gas driven permeation (GDP). The permeation rates for PDP in nickel and tungsten were larger than those for GDP normalized to the same gas pressure about 20 and 5 times larger, respectively.

Ikeda, T.; Otsuka, T.; Tanabe, T.

2011-08-01

153

Effects of hydrogen adsorption on single-wall carbon nanotubes: Metallic hydrogen decoration  

Microsoft Academic Search

We show that the electronic and atomic structure of carbon nanotubes undergo dramatic changes with hydrogen chemisorption from first principle calculations. Upon uniform exohydrogenation at half coverage, the cross sections of zigzag nanotubes become literally square or rectangular, and they are metallic with very high density of states at the Fermi level, while other isomers can be insulating. For both

O. Gülseren; T. Yildirim; S. Ciraci

2002-01-01

154

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

Microsoft Academic Search

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

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

1990-01-01

155

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

2013-10-16

156

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

SciTech Connect

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

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

2010-01-21

157

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

Microsoft Academic Search

An elevated level of homocysteine (Hcy), known as hyperhomocysteinemia (HHcy), was associated with neurovascular diseases. At physiological levels, hydrogen sulfide (H2S) protected the neurovascular system. Because Hcy was also a precursor of hydrogen sulfide (H2S), we sought to test whether the H2S protected the brain during HHcy. Cystathionine-?-synthase heterozygous (CBS+\\/?) and wild type (WT) mice were supplemented with or without

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

2010-01-01

158

Quantum simulation of low-temperature metallic liquid hydrogen.  

PubMed

The melting temperature of solid hydrogen drops with pressure above ~65?GPa, suggesting that a liquid state might exist at low temperatures. It has also been suggested that this low-temperature liquid state might be non-molecular and metallic, although evidence for such behaviour is lacking. Here we report results for hydrogen at high pressures using ab initio methods, which include a description of the quantum motion of the protons. We determine the melting temperature as a function of pressure and find an atomic solid phase from 500 to 800?GPa, which melts at <200?K. Beyond this and up to 1,200?GPa, a metallic atomic liquid is stable at temperatures as low as 50?K. The quantum motion of the protons is critical to the low melting temperature reported, as simulations with classical nuclei lead to considerably higher melting temperatures of ~300?K across the entire pressure range considered. PMID:23807128

Chen, Ji; Li, Xin-Zheng; Zhang, Qianfan; Probert, Matthew I J; Pickard, Chris J; Needs, Richard J; Michaelides, Angelos; Wang, Enge

2013-01-01

159

CO2 hydrogenation on a metal hydride surface.  

PubMed

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

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

2012-03-20

160

Structural properties, superconductivity, and magnetism of metallic hydrogen  

Microsoft Academic Search

The electronic band structure and structural properties of paramagnetic metallic hydrogen in the simple cubic (sc), fcc, bcc, and hcp phases have been determined theoretically using our bulk fullpotential total-energy linearized augmented-plane-wave method. In the density range corresponding to 1

B. I. Min; H. J. F. Jansen; A. J. Freeman

1984-01-01

161

Determination of ultratrace metals in hydrogenated vegetable oils and fats  

Microsoft Academic Search

Ultratrace levels of nickel, chromium, copper and iron occurring in hydrogenated vegetable oil products were estimated by\\u000a dispersion of the samples in 4 methyl-2-pentanone and atomic absorption analysis by the graphite furnace technique. The principal\\u000a goals in establishing the analytical methods were improved sensitivity to metals at low levels and applicability to limited\\u000a amounts of products. Using reproducibility and linearity

A. M. Nash; T. L. Mounts; W. F. Kwolek

1983-01-01

162

Homogeneous catalytic hydrogenation of unsaturated fats: Metal acetylacetonates  

Microsoft Academic Search

Hydrogenation of linseed and soybean methyl esters was achieved at 100–180C, 100–1000 psi H2 and 0.05–0.25 moles catalyst per mole of ester. The relative activity of metal acetylacetonates in decreasing order was:\\u000a nickel (III), cobalt (III), copper (II) and iron (III). Reduction occurred readily in methanol solution but only slowly in\\u000a dimethylformamide and acetic acid. No reduction occurred in the

E. A. Emken; E. N. Frankel; R. O. Butterfield

1966-01-01

163

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.

Yao, Yansun; Klug, Dennis D.

2010-01-01

164

Strain-induced metal-hydrogen interactions across the first transition series -- An ab initio study of hydrogen embrittlement  

NASA Astrophysics Data System (ADS)

The attractive interaction between hydrogen and distorted regions of the host matrix underlies all the currently discussed mechanisms of hydrogen-induced embrittlement of metals, such as hydrogen enhanced local plasticity (HELP), hydrogen enhanced decohesion (HEDE) and stress-induced hydride formation. In this study we investigate these interactions systematically by determining heat of solutions, H-H binding energies within the metal matrix, as well as phase diagrams as a function of the lattice strain and the H chemical potential across the first transition series (3d elements) using Density Functional Theory (DFT) calculations. The results will be interpreted in terms of the likely embrittlement mechanisms of these metals.

von Pezold, Johann; Aydin, Ugur; Neugebauer, Jörg

2010-03-01

165

Hydrogen production during processing of radioactive sludge containing noble metals  

SciTech Connect

Hydrogen was produced when radioactive sludge from Savannah River Site radioactive waste containing noble metals was reacted with formic acid. This will occur in a process tank in the Defense Waste Facility at SRS when waste is vitrified. Radioactive sludges from four tanks were tested in a lab-scale apparatus. Maximum hydrogen generation rates varied from 5 {times}10{sup {minus}7} g H{sub 2}/hr/g of sludge from the least reactive sludge (from Waste Tank 51) to 2 {times}10{sup {minus}4} g H{sub 2}/hr/g of sludge from the most reactive sludge (from Waste Tank 11). The time required for the hydrogen generation to reach a maximum varied from 4.1 to 25 hours. In addition to hydrogen, carbon dioxide and nitrous oxide were produced and the pH of the reaction slurry increased. In all cases, the carbon dioxide and nitrous oxide were generated before the hydrogen. The results are in agreement with large-scale studies using simulated sludges.

Ha, B.C.; Ferrara, D.M.; Bibler, N.E.

1992-09-01

166

Effect of oxygen on hydrogen cracking in high-strength weld metal  

Microsoft Academic Search

The effect of oxygen content on the susceptibility of high-strength weld metal to hydrogen cracking is examined. Increasing\\u000a oxygen content had a detrimental effect on the cracking susceptibility of weld metal containing a d?usible hydrogen content\\u000a of 4.7 ppm. In weld metal containing a much lower d?usible hydrogen content (0.87 ppm), increasing weld metal oxygen content\\u000a had no detrimental effect

K. Shinozaki; X. Wang; T. H. North

1990-01-01

167

Role of exposed metal sites in hydrogen storage in MOFs.  

PubMed

The role of exposed metal sites in increasing the H2 storage performances in metal-organic frameworks (MOFs) has been investigated by means of IR spectrometry. Three MOFs have been considered: MOF-5, with unexposed metal sites, and HKUST-1 and CPO-27-Ni, with exposed Cu(2+) and Ni(2+), respectively. The onset temperature of spectroscopic features associated with adsorbed H2 correlates with the adsorption enthalpy obtained by the VTIR method and with the shift experienced by the H-H stretching frequency. This relationship can be ascribed to the different nature and accessibility of the metal sites. On the basis of a pure energetic evaluation, it was observed that the best performance was shown by CPO-27-Ni that exhibits also an initial adsorption enthalpy of -13.5 kJ mol(-1), the highest yet observed for a MOF. Unfortunately, upon comparison of the hydrogen amounts stored at high pressure, the hydrogen capacities in these conditions are mostly dependent on the surface area and total pore volume of the material. This means that if control of MOF surface area can benefit the total stored amounts, only the presence of a great number of strong adsorption sites can make the (P, T) storage conditions more economically favorable. These observations lead to the prediction that efficient H2 storage by physisorption can be obtained by increasing the surface density of strong adsorption sites. PMID:18533719

Vitillo, Jenny G; Regli, Laura; Chavan, Sachin; Ricchiardi, Gabriele; Spoto, Giuseppe; Dietzel, Pascal D C; Bordiga, Silvia; Zecchina, Adriano

2008-06-06

168

Hydrogen storage and evolution catalysed by metal hydride complexes.  

PubMed

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

Fukuzumi, Shunichi; Suenobu, Tomoyoshi

2013-01-01

169

Photobiotechnology: Algal hydrogen production and photoconductivity of metalized chloroplasts  

SciTech Connect

Sustained hydrogen photoevolution from Chlamydomonas reinhardtii and C. moewusii was measured under an anoxic, CO{sub 2}-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{sup {minus}2}) or low temperature (approx. O{degrees}C), the flow of photosynthetic reductant to the Calvin cycle was reduced, and reductant was partitioned to the hydrogen pathway as evidenced by sustained H{sub 2} photoevolution. Under saturating light (25 W m{sup {minus}2}) and moderate temperature 20 {plus minus} 5{degrees}C, the Calvin cycle became the absolute sink for reductant with the exception of a burst of H{sub 2} occurring at light on. A novel photobiophysical phenomenon was observed in isolated spinach chloroplasts that were metalized by precipitating colloidal platinum onto the surface of the thylakoid membranes. A two-point irradiation and detection system was constructed in which a continuous beam helium-neon laser ({lambda} = 632.8 nm) was used to irradiate the platinized chloroplasts at varying perpendicular distances from a single linear platinum electrode in pressure contact with the platinized chloroplasts. No external voltage bias was applied to the system. The key objective of the experiments reported in this report was to measure the relative photoconductivity of the chloroplast-metal composite matrix. 46 refs., 1 tab.

Greenbaum, E.

1991-01-01

170

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

171

Catalytic arene hydrogenation using early transition metal hydride compounds. Progress report  

SciTech Connect

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

Rothwell, I.P.

1993-03-15

172

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

173

Transition metal sulfide hydrogen evolution catalysts for hydrobromic acid electrolysis.  

PubMed

Mixed metal sulfides containing combinations of W, Fe, Mo, Ni, and Ru were synthesized and screened for activity and stability for the hydrogen evolution reaction (HER) in aqueous hydrobromic acid (HBr). Co- and Ni-substituted RuS(2) were identified as potentially active HER electrocatalysts by high-throughput screening (HTS), and the specific compositions Co(0.4)Ru(0.6)S(2) and Ni(0.6)Ru(0.4)S(2) were identified by optimization. Hydrogen evolution activity of Co(0.4)Ru(0.6)S(2) in HBr is greater than RuS(2) or CoS(2) and comparable to Pt and commercial Rh(x)S(y). Structural and morphological characterizations of the Co-substituted RuS(2) suggest that the nanoparticulate solids are a homogeneous solid solution with a pyrite crystal structure. No phase separation is detected for Co substitutions below 30% by X-ray diffraction. In 0.5 M HBr electrolyte, the Co-Ru electrode material synthesized with 30% Co rapidly lost approximately 34% of the initial loading of Co; thereafter, it was observed to exhibit stable activity for HER with no further loss of Co. Density functional theory calculations indicate that the S(2)(2-) sites are the most important for HER and the presence of Co influences the S(2)(2-) sites such that the hydrogen binding energy at sufficiently high hydrogen coverage is decreased compared to ruthenium sulfide. Although showing high HER activity in a flow cell, the reverse reaction of hydrogen oxidation is slow on the RuS(2) catalysts tested when compared to platinum and rhodium sulfide, leaving rhodium sulfide as the only suitable tested material for a regenerative HBr cell due its stability compared to platinum. PMID:23205859

Ivanovskaya, Anna; Singh, Nirala; Liu, Ru-Fen; Kreutzer, Haley; Baltrusaitis, Jonas; Nguyen, Trung Van; Metiu, Horia; McFarland, Eric

2012-12-18

174

Non-Abrikosov vortices in liquid metallic hydrogen  

NASA Astrophysics Data System (ADS)

We consider non-Abrikosov vortex solutions in liquid metallic hydrogen (LMH) in the framework of two-component Ginzburg-Landau model. We have shown that there are three types of non-Abrikosov vortices depending on chosen boundary conditions at the core of vortices, namely, Neumann (N)-type, Dirichlet (D)-type and Gross-Pitaevskii (GP)-type vortices. The Neumann-type vortex has a non-vanishing condensation at the core, that is different from the ordinary vortex, and the magnetic flux could be reversed as well in LMH. Furthermore, we have obtained a new type of a neutral vortex which has no magnetic field. The presence of such a vortex is related to metallic superfluid state suggested by Babaev (2004) [1].

Zou, Liping

2013-11-01

175

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

Microsoft Academic Search

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

Milan K Visaria

2011-01-01

176

Sono implantation of hydrogen and deuterium from water into metallic fine powders  

NASA Astrophysics Data System (ADS)

We observed the production of hydrogenated/deuterated metallic fine powders when various metals (Pd, Ag, Ta, Pt, and Au) were irradiated in normal and heavy water by ultrasonic waves. Mass analyses of remnant metal powders revealed substantial amounts of sono-implanted hydrogen and deuterium. The deuterium implantation (D implantation) in D2O was found to be much stronger than the hydrogen implantation (H implantation) in H2O.

Arata, Yoshiaki; Zhang, Yue-Chang

2000-04-01

177

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

178

Infrared spectroscopy of trapped hydrogen in metal-organic-frameworks  

NASA Astrophysics Data System (ADS)

We present a novel use of diffuse reflectance infrared spectroscopy to study the quantum dynamics of molecular hydrogen trapped within metal-organic-framework (MOF) hosts. This technique is particularly useful in the context of hydrogen storage since it provides detailed information about the intermolecular potential at the binding site. The spectra consist of quite sharp bands associated with the quantized vibrational and rotational motion of the trapped hydrogen. The vibrational bands are redshifted relative to the gas phase while the rotational sidebands contain an additional fine structure due to the orientational dependence of the binding potential. Results on MOF-5 reveal the presence of two primary binding sites. The first saturates at a loading concentration on the order of 4 H2 per Zn ion and has a binding energy of roughly 4 kJ/mole. The second has a somewhat lower binding energy. Both site produce an ortho to para conversion rate on the order of 30-50 % per hour.

Fitzgerald, Stephen; Allen, Kelty; Landerman, Patrick; Rowsell, Jesse

2007-03-01

179

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

180

The possibility for superconductor fusion in metallic hydrogen  

NASA Astrophysics Data System (ADS)

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

Shibata, K.; Kodama, R.

2008-05-01

181

Metal-Assisted Hydrogen Storage on Pt-Decorated Single-Walled Carbon Nanohorns  

SciTech Connect

The catalytic dissociation of hydrogen molecules by metal nanoparticles and spillover of atomic hydrogen onto various supports is a well-established phenomenon in catalysis. However, the mechanisms by which metal catalyst nanoparticles can assist in enhanced hydrogen storage on high-surface area supports are still under debate. Experimental measurements of metal-assisted hydrogen storage have been hampered by inaccurate estimation of atomically stored hydrogen deduced from comparative measurements between metal-decorated and undecorated samples. Here we report a temperature cycling technique combined with inelastic neutron scattering (INS) measurements of quantum rotational transitions of molecular H2 to more accurately quantify adsorbed hydrogen aided by catalytic particles using single samples. Temperature cycling measurements on single-wall carbon nanohorns (SWCNHs) decorated with 2-3 nm Pt nanoparticles showed 0.17 % mass fraction of metal-assisted hydrogen storage (at 0.5 MPa) at room temperature. Temperature cycling of Pt-decorated SWCNHs using a Sievert s apparatus also indicated metal-assisted hydrogen adsorption of 0.08 % mass fraction at 5 MPa at room temperature. No additional metal-assisted hydrogen storage was observed in SWCNH samples without Pt nanoparticles cycled to room temperature, or in Pt-SWCNHs when the temperature was cycled to less than 150K. The possible formation of C-H bonds due to spilled-over atomic hydrogen was also investigated using both INS and density functional theory calculations.

Liu, Yun [National Institute of Standards and Technology (NIST); Brown, Craig [National Institute of Standards and Technology (NIST); Neumann, Dan [National Institute of Standards and Technology (NIST); Geohegan, David B [ORNL; Puretzky, Alexander A [ORNL; Rouleau, Christopher M [ORNL; Hu, Hui [ORNL; Styers-Barnett, David J [ORNL; Krasnov, Pavel O. [Rice University; Yakobson, Boris I. [Rice University

2012-01-01

182

Future Propellants for Launch Vehicles-Metallic Hydrogen with Water and Hydrocarbon Diluents  

NASA Astrophysics Data System (ADS)

Earlier papers have shown that the energy released from recombination of the atomic hydrogen formed when metallic hydrogen is raised above the critical metastabability temperature yields a far greater specific energy and specific impulse than the combustion of hydrogen and oxygen. Experimental efforts continue towards the challenging goal of producing metallic hydrogen in the laboratory. Progress in 2009 has significantly extended the hydrogen high pressure melt line, a path towards metallic hydrogen. The temperature of the recombination reaction of pure metallic hydrogen will be much higher than existing rocket engine materials can withstand. The approach examined here is to dilute the metallic hydrogen, lowering the reaction temperature. Water, hydrocarbons, and liquid molecular hydrogen diluents are shown to provide an attractive specific impulse without exceeding acceptable material technology temperature limits. Analysis of a two-stage mission to the lunar surface with a liquid hydrogen diluted second-stage shows a slight advantage of water and hydrocarbon mixtures as first-stage diluents compared with water only first-stage diluents. Such two-stage in-line vehicles, a little taller than the space shuttle, could deliver very large payloads to the lunar surface or to geosynchronous orbits using the predicted characteristics of diluted metallic hydrogen.

Cole, J. W.; Silvera, I. F.

2010-01-01

183

Compact Hydrogenator.  

National Technical Information Service (NTIS)

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 pu...

P. G. Simmonds

1974-01-01

184

Theory of catalytic dissociation of hydrogen atoms on a metal surface  

SciTech Connect

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

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

2008-08-15

185

Partially pyrolyzed olive pomace sorbent of high permeability for preconcentration of metals from environmental waters  

Microsoft Academic Search

The aim of this work is to develop a preconcentration procedure of Cd2+, Zn2+ and Cu2+ in environmental waters using olive pomace (OP) prior to their determination by flame atomic absorption spectrometry (FAAS). Raw OP as preconcentrating sorbent was found to have low permeability towards the passed water samples and thus long time was needed. Even reducing the vacuum pressure

Amjad H. El-Sheikh; Jamal A. Sweileh; Maysoon I. Saleh

2009-01-01

186

Hydrogen permeability through a mixed molten salt of LiF, NaF and KF (Flinak) as a heat-transfer fluid  

NASA Astrophysics Data System (ADS)

Permeability, diffusivity and solubility of hydrogen in Flinak, a mixed molten salt of LiF (46.5%), NaF (11.5%) and KF (42%), were determined using a vessel supported by a Ni plate. Diffusion-limiting permeation was confirmed by experimental data where hydrogen permeation rates were in reverse proportion to the thickness of Flinak. Diffusivities determined in the range of 500 750 °C were correlated to an Arrhenius equation with the activation energy of 50 kJ/mol. Since the dependence of hydrogen solubility in Flinak on pressure was almost linear, hydrogen was dissolved as H2 in Flinak. The H2 solubility in Flinak was correlated to a Henry law, and its solubility constant was discussed in terms of macroscopic surface tension and unspecified interaction energy between the molten salt and dissolved gaseous molecules.

Fukada, Satoshi; Morisaki, Akio

2006-11-01

187

High capacity hydrogen absorption in transition-metal ethylene complexes: consequences of nanoclustering  

Microsoft Academic Search

We have recently shown that organo-metallic complexes formed by laser ablating transition metals in ethylene are high hydrogen absorbers at room temperature (Phillips and Shivaram 2008 Phys. Rev. Lett. 100 105505). Here we show that the absorption percentage depends strongly on the ethylene pressure. High ethylene pressures (>100 mTorr) result in a lowered hydrogen uptake. Transmission electron microscopy measurements reveal

A. B. Phillips; B. S. Shivaram

2009-01-01

188

A review of soluble transition-metal nanoclusters as arene hydrogenation catalysts  

Microsoft Academic Search

A critical review of the use of soluble transition-metal nanoclusters for the hydrogenation of monocyclic aromatic compounds is presented. The review begins with a brief introduction to arene hydrogenation and to nanocluster science. The introductory material is followed by a detailed discussion of the approximately 20 papers in the literature that deal with the use of soluble transition-metal nanoclusters for

Jason A. Widegren; Richard G. Finke

2003-01-01

189

Ab initio prediction of superconductivity in molecular metallic hydrogen under high pressure  

Microsoft Academic Search

We present a first ab initio investigation of the electron–phonon coupling (EPC) of molecular metallic hydrogen with a Cmca structure based on the linear-response approach. This molecular metallic hydrogen with overlapping bands has an elastic instability at lower pressures (<300 GPa), but stabilizes dynamically under further compression as indicated by the absence of phonon softening, thus supporting the choice of

Lijun Zhang; Yingli Niu; Quan Li; Tian Cui; Yi Wang; Yanming Ma; Zhi He; Guangtian Zou

2007-01-01

190

Anelastic relaxation and spinodal decomposition in coherent metal-hydrogen systems  

Microsoft Academic Search

Extending Cahn's description of spinodal decomposition, we derive kinetic equations for the density of dissolved hydrogen in metals by consideration of the longrange elastic interaction between the protons as given by Wagner and Horner. These equations are applied to the time dependent behaviour of the anelastic relaxation (Gorsky effect) and the spinodal decomposition in coherent metal-hydrogen systems.

Hans-Karl Janssen

1976-01-01

191

Identification of Non-Precious Metal Alloy Catalysts for Selective Hydrogenation of Acetylene  

Microsoft Academic Search

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.

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

2008-01-01

192

Analysis of hydrogen storage in metal hydride tanks introducing an induced phase transformation  

Microsoft Academic Search

Hydrogen absorption in a metal hydride tank is generally studied based on a heat and mass transfer analysis. The originality of this investigation is that the phase transformation from a solid (? phase) to hydride (? phase) solution is included in the hydrogen absorption mechanism. Toward this end, a modelling of the equilibrium pressure, composition (absorbed or desorbed hydrogen atoms

Germain Gondor; Christian Lexcellent

2009-01-01

193

Metal loaded zeolite adsorbents for hydrogen cyanide removal.  

PubMed

Metal (Cu, Co, or Zn) loaded ZSM-5 and Y zeolite adsorbents were prepared for the adsorption of hydrogen cyanide (HCN) toxic gas. The results showed that the HCN breakthrough capacity was enhanced significantly when zeolites were loaded with Cu. The physical and chemical properties of the adsorbents that influence the HCN adsorption capacity were analyzed. The maximal HCN breakthrough capacities were about the same for both zeolites at 2.2 mol of HCN/mol of Cu. The Cu2p XPS spectra showed that the possible species present were Cu2O and CuO. The N1s XPS data and FT-IR spectra indicated that CN(-) would be formed in the presence of Cu+/Cu2+ and oxygen gas, and the reaction product could be adsorbed onto Cu/ZSM-5 zeolite more easily than HCN. PMID:23923791

Ning, Ping; Qiu, Juan; Wang, Xueqian; Liu, Wei; Chen, Wei

2013-04-01

194

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

NASA Astrophysics Data System (ADS)

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

Baikov, Yu. M.

2008-02-01

195

Liquid metallic hydrogen and the structure of brown dwarfs and giant planets  

Microsoft Academic Search

Electron-degenerate, pressure-ionized hydrogen (usually referred to as metallic hydrogen) is the principal constituent of brown dwarfs, the long-sought objects which lie in the mass range between the lowest-mass stars (about eighty times the mass of Jupiter) and the giant planets. The thermodynamics and transport properties of metallic hydrogen are important for understanding the properties of these objects, which, unlike stars,

W. B. Hubbard; T. Guillot; J. I. Lunine; A. Burrows; D. Saumon; M. S. Marley; R. S. Freedman

1997-01-01

196

Modelling of hydrogen adsorption in the metal organic framework MOF5  

Microsoft Academic Search

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

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

2005-01-01

197

ACCEPTABILITY ENVELOPE FOR METAL HYDRIDE-BASED HYDROGEN STORAGE SYSTEMS  

SciTech Connect

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

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

2011-07-18

198

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

199

High hydrogen permeability in the Nb-Zr-Ni eutectic alloy containing the primary body-centered-cubic (Nb, Zr) phase  

NASA Astrophysics Data System (ADS)

Hydrogen permeability (?), i.e., the product of hydrogen diffusion coefficient (D) and hydrogen solubility (K), of the as-cast Nb40Zr30Ni30 (mol %) alloy has been investigated. This alloy is composed of the primary body-centered-cubic (bcc)-(Nb, Zr) and eutectic {(Nb,Zr)+ZrNi} phase and the chemical composition and the volume fraction of the primary phase are Nb89Zr8Ni3 and 40%, respectively. ? of this alloy increases with increasing temperature and is 4.64×10-8 [mol H2 m-1 s-1 Pa-0.5] at 673 K, which is 2.9 times larger than that of pure Pd. The present work indicates that ? of the Nb-Zr-Ni alloys increases with increasing the volume fraction of the primary bcc-(Nb, Zr) phase.

Ishikawa, K.; Takano, T.; Matsuda, T.; Aoki, K.

2005-08-01

200

Hydrogen Adsorption, Absorption and Diffusion on and in Transition Metal Surfaces: A DFT Study  

SciTech Connect

Periodic, self-consistent DFT-GGA(PW91) calculations are used to study the interaction of hydrogen with different facets of seventeen transition metals—the (100) and (111) facets of face-centered cubic (fcc) metals, the (0001) facet of hexagonal-close packed (hcp) metals, and the (100) and (110) facets of body-centered cubic (bcc) metals. Calculated geometries and binding energies for surface and subsurface hydrogen are reported and are, in general, in good agreement with both previous modeling studies and experimental data. There are significant differences between the binding on the close-packed and more open (100) facets of the same metal. Geometries of subsurface hydrogen on different facets of the same metal are generally similar; however, binding energies of hydrogen in the subsurface of the different facets studied showed significant variation. Formation of surface hydrogen is exothermic with respect to gas-phase H? on all metals studied with the exception of Ag and Au. For each metal studied, hydrogen in its preferred subsurface state is always less stable than its preferred surface state. The magnitude of the activation energy for hydrogen diffusion from the surface layer into the first subsurface layer is dominated by the difference in the thermodynamic stability of these two states. Diffusion from the first subsurface layer to one layer further into the bulk does not generally have a large thermodynamic barrier but still has a moderate kinetic barrier. Despite the proximity to the metal surface, the activation energy for hydrogen diffusion from the first to the second subsurface layer is generally similar to experimentally-determined activation energies for bulk diffusion found in the literature. There are also some significant differences in the activation energy for hydrogen diffusion into the bulk through different facets of the same metal.

Ferrin, Peter A.; Kandoi, Shampa; Nilekar, Anand U.; Mavrikakis, Manos

2012-01-04

201

Experimental and comparative study of metal hydride hydrogen tanks  

Microsoft Academic Search

Hydrogen, as an energy carrier, is a solution seriously considered at worldwide scale to enable renewable energy to be a part of our quotidian. Several challenges remain to produce, to store and to use hydrogen effectively. In our laboratory, we are interested in the discipline of hydrogen storage which is the subject of this paper. Two hydrogen storage tanks based

A. Souahlia; H. Dhaou; F. Askri; M. Sofiene; A. Jemni; S. Ben Nasrallah

2011-01-01

202

Search for metal hydrides with short hydrogen-hydrogen separation:?Ab initio calculations  

NASA Astrophysics Data System (ADS)

The present investigation is a part of a series on metal hydrides with extraordinary short H?H separations. The electronic structure, chemical bonding, and ground state properties of RTIn (R=La,Ce,Pr,Nd;T=Ni,Pd,Pt) and their saturated hydrides R3T3In3H4 (=3RTInH1.333) are systematically studied using the full-potential linear muffin-tin-orbital method. The effect of the metal matrix on the H?H separation in RTInH1.333 is analyzed in terms of chemical bonding, and bond strength is quantitatively analyzed using the crystal-orbital-Hamilton population. Force and volume optimizations reveal that all these hydrides violate the “ 2-Å rule.” The insertion of hydrogen in the metal matrix causes highly anisotropic lattice changes; a large expansion along c and a small contraction in the a direction. Among the 12 studied hydrides the hypothetical LaPtInH1.333 phase exhibits the shortest H?H separation (1.454Å) . The optimized unit-cell parameters and atomic coordinates fit very well with the experimental findings for RNiInH1.333 , R=La , Ce, and Nd. Examination of the effect of the metal matrix on the H?H separation in RTInH1.333 suggests that on a proper choice of alloying element one may be able to reduce the H?H separation below 1.45Å . The H?H separation is reduced significantly by application of pressure.

Vajeeston, P.; Ravindran, P.; Fjellvåg, H.; Kjekshus, A.

2004-07-01

203

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

204

Metallization of Hydrogen and other small molecules at 100 GPa pressures  

Microsoft Academic Search

Fluid hydrogen, oxygen, and nitrogen become metallic at 100 GPa (1 Mbar) pressures. Disorder is the primary reason for observing a metal at lower pressures in the fluid than expected for the ordered solid. This metallic transition is similar to those observed in fluid Cs and Rb by Hensel et al . All five undergo a Mott transition from a

W. J. Nellis

2002-01-01

205

Applications of ion implantation for modifying the interactions between metals and hydrogen gas  

NASA Astrophysics Data System (ADS)

Ion implantations into metals have been shown recently to either reduce or enhance interactions with gaseous hydrogen. Published studies concerned with modifications of these interactions are reviewed and discussed in terms of the mechanisms postulated to explain the observed changes. The interactions are hydrogenation, hydrogen permeation, and hydrogen embrittlement. In particular, the results of the reviewed studies are (a) uranium hydriding suppressed by implantation of oxygen and carbon, (b) hydrogen gettered in iron and nickel using implantation of titanium, (c) hydriding of titanium catalyzed by implanted palladium, (d) tritium permeation of 304L stainless steel reduced using selective oxidation of implanted aluminum, and (e) hydrogen attack of a low-alloy steel accelerated by implantation of helium. These studies revealed ion implantation to be an effective method for modifying the interactions of hydrogen gas with metals.

Musket, R. G.

1989-04-01

206

Applications of ion implantation for modifying the interactions between metals and hydrogen gas  

NASA Astrophysics Data System (ADS)

Ion implantations into metals have been shown recently to either reduce or enhance interactions with gaseous hydrogen. Published studies concerned with modifications of these interactions are reviewed and discussed in terms of the mechanisms postulated to explain the observed changes. The interactions are hydrogenation, hydrogen permeation, and hydrogen embrittlement. In particular, the results of the reviewed studies are: uranium hydriding suppressed by implantation of oxygen and carbon; hydrogen gettered in iron and nickel using implantation of titanium; hydriding of titanium catalyzed by implanted palladium; tritium permeation of 304L stainless steel reduced using selective oxidation of implanted aluminum; and hydrogen attack of a low-alloy steel accelerated by implantation of helium. These studies revealed ion implantation to be an effective method for modifying the interactions of hydrogen gas with metals.

Musket, R. G.

1988-09-01

207

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

208

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

2011-12-30

209

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

210

Frequency dispersive complex permittivity and permeability of ferromagnetic metallic granular composite at microwave frequencies  

NASA Astrophysics Data System (ADS)

We experimentally studied the frequency dependent complex permittivity ? and permeability ? of composite composed of carbonyl iron powder (CIP) and epoxy resin in the frequency range 1–18 GHz. We found that the intrinsic ? and ? of CIP extracted from the measured ? and ? of composites follow the classical Maxwell equations and the Landau–Lifshitz–Gilbert (LLG) equation, respectively. The dependences of ? and ? of composites on the volume fraction of CIP (vfCIP) were investigated using the two-exponent phenomenological percolation equation (TEPPE). We found that the TEPPE can fit the experimental results very well. Comparing the results of percolation parameters derived by experimental data at different frequencies, we show that the TEPPE is frequency independent for the composites at microwave frequencies. The results also show that the ? and ? spectrums of composites with definite vfCIP can be correctly calculated by combining the TEPPE with the theoretical models of intrinsic ? and ?.

Chen, Ping; Liu, Min; Wang, Ling; Poo, Yin; Wu, Rui-xin

2011-12-01

211

The effects of hydrogen bonds on metal-mediated O2 activation and related processes  

PubMed Central

Hydrogen bonds stabilize and direct chemistry performed by metalloenzymes. With inspiration from enzymes, we will utilize an approach that incorporates intramolecular hydrogen bond donors to determine their effects on the stability and reactivity of metal complexes. Our premise is that control of secondary coordination sphere interactions will promote new function in synthetic metal complexes. Multidentate ligands have been developed that create rigid organic structures around metal ions. These ligands place hydrogen bond (H-bond) donors proximal to the metal centers, forming specific microenvironments. One distinguishing attribute of these systems is that site-specific modulations in structure can be readily accomplished, in order to evaluate correlations with reactivity. A focus of this research is consideration of dioxygen binding and activation by metal complexes, including developing structure–function relationships in metal-assisted oxidative catalysis.

Shook, Ryan L.; Borovik, A. S.

2009-01-01

212

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

213

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

214

Transition metal activation and functionalization of carbon-hydrogen bonds  

SciTech Connect

We are investigating the fundamental thermodynamic and kinetic factors that influence carbon-hydrogen bond activation at homogeneous transition metal centers and the conversion of hydrocarbons into functionalized products of potential use to the chemical industry. Advances have been made in both understanding the interactions of hydrocarbons with metals and in the functionalization of hydrocarbons. We have found that RhCl(PR{sub 3}){sub 2}(CNR) complexes can catalyze the insertion of isonitriles into the C-H bonds or arenes upon photolysis. The mechanism of these reactions was found to proceed by way of initial phosphine dissociation, followed by C-H activation and isonitrile insertion. We have also examined reactions of a series of arenes with (C{sub 5}Me{sub 5})Rh(PMe{sub 3})PhH and begun to map out the kinetic and thermodynamic preferences for arene coordination. The effects of resonance, specifically the differences in the Hueckel energies of the bound vs free ligand, are now believed to fully control the C-H activation/{eta}{sup 2}-coordination equilibria. We have begun to examine the reactions of rhodium isonitrile pyrazolylborates for alkane and arene C-H bond activation. A new, labile, carbodiimide precursor has been developed for these studies. We have completed studies of the reactions of (C{sub 5}Me{sub 5})Rh(PMe{sub 3})H{sub 2} with D{sub 2} and PMe{sub 3} that indicate that both {eta}{sup 5} {yields} {eta}{sup 3} ring slippage and metal to ring hydride migration occur more facilely than thermal reductive elimination of H{sub 2}. We have examined the reactions of heterocycles with (C{sub 5}Me{sub 5})Rh(PMe{sub 3})PhH and found that pyrrole and furan undergo C-H or N-H activation. Thiophene, however, undergoes C-S bond oxidative addition, and the mechanism of activation has been shown to proceed through sulfur coordination prior to C-S insertion.

Jones, W.D.

1992-06-01

215

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

PubMed

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

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

2013-09-14

216

A rare earth metal hydride device for minimizing hydrogen hazards  

Microsoft Academic Search

A major application today for the use of hydrogen is with medical and industrial laboratory instrumentation and equipment. Because of the extensive energy content of compressed hydrogen gas, safety considerations are of paramount interest to these groups. For this reason, the safe storage and dispensing of hydrogen has been of concern to them for many years. A compact, portable, and

Mc Cue

1980-01-01

217

Synthesis of transition-metal phosphides from oxidic precursors by reduction in hydrogen plasma  

NASA Astrophysics Data System (ADS)

A series of transition metal phosphides, including MoP, WP, CoP, Co2P, and Ni2P, were synthesized from their oxidic precursors by means of hydrogen plasma reduction under mild conditions. The effects of reduction conditions, such as metal to phosphorus molar ratio, power input, and reduction time, on the synthesis of metal phosphides were investigated. The products were identified by means of XRD characterization. It is indicated that metal phosphides were readily synthesized stoichiometrically from their oxides in hydrogen plasma under mild conditions.

Guan, Jie; Wang, Yao; Qin, Minglei; Yang, Ying; Li, Xiang; Wang, Anjie

2009-06-01

218

Hydrogenation of CO on Alumina Supported Metals: A Tunneling Spectroscopy Study.  

National Technical Information Service (NTIS)

The hydrogenation of CO on alumina supported metals has been the subject of many research efforts. This report is about the application of a relatively new technique, tunneling spectroscopy, to the problem of identifying the reaction intermediates that ar...

P.K. Hansma R.M. Kroeker W.C. Kaska

1980-01-01

219

Noble Metal Chemistry and Hydrogen Generation During Simulated DWPF Melter Feed Preparation.  

National Technical Information Service (NTIS)

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...

D. Koopman

2008-01-01

220

Effect of metal Additions on the Hydrogen Uptake of Microporous Carbon at Near-Ambient Temperature  

SciTech Connect

Enhancing the hydrogen sorption capacity of microporous carbon materials at near-ambient temperature continue to be a challenge and the subject of intense research. Physisorption alone on microporous carbons is not strong enough to provide the desired levels of hydrogen uptake. Modifying carbons with small amounts of metals has been proven effective to increase the amounts adsorbed. However, very different mechanisms may be involved when the promoters are transition metals or alkali metals. In this presentation we compare the effect of additions of palladium and/or alkali metals on the hydrogen uptake of microporous carbons, in an attempt to differentiate between the possible mechanisms leading to enhanced hydrogen capacity and fast kinetics.

Contescu, Cristian I [ORNL; Gallego, Nidia C [ORNL; Bhat, Vinay V [ORNL

2010-01-01

221

Acoustic-phonon-assisted hydrogen diffusion in metal hydrides  

NASA Astrophysics Data System (ADS)

The theory for acoustic-phonon-induced hydrogen diffusion in model metal hydrides is presented. The general expression for the total transition probability Wpp' is obtained. The analytical expressions for Wpp' are calculated in the high- and low-temperature limits for both the dispersive and nondispersive acoustic phonons and are compared with other calculations. The diffusion rate is found to be temperature independent at low temperature and temperature dependent at higher temperature. Both the phonon emission and absorption processes contribute towards the diffusion rate at high temperature while only emission process contributes at low temperature. The phonon dispersion increases the preexponential factor and decreases the migration energy. The numerical calculations are carried out for PdHx (PdDx) and NbHx (NbDx). The migration energies Em and the preexponential factors D0 are estimated graphically. The diffusion rate increases with increase of temperature up to 170 K for PdHx (PdDx) and up to 100 K for NbHx (NbDx). At higher temperatures the diffusion rate shows an activated behavior. The inverse isotope effect is found for PdHx (PdDx) at low temperature, while it is absent at high temperature. No inverse isotope effect is found for NbHx (NbDx). At low temperature the Em and D0 for H diffusion increase with increase of temperature in both PdHx (PdDx) and NbHx (NbDx). At higher temperatures, Em and D0 become almost constant for PdHx (PdDx), while these again increase with temperature in NbHx (NbDx). It is found that the hydrogen diffuses faster in the bcc matrix than in the fcc matrix. A comparison with the results for optical-phonon-induced diffusion revealed that the acoustic-phonon contribution is larger at low temperature while the contributions of both the acoustic and optical phonons is of the same order at high temperature. The migration energies are also calculated combining the contributions of both the acoustic and optical phonons, and these are found in reasonable agreement with the experimental data.

Dhawan, L. L.; Prakash, S.

1984-03-01

222

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

Microsoft Academic Search

It is reported that the transition of condensed hydrogen from an insulating molecular crystal phase to a metallic liquid phase, at zero temperature and high pressure, appears possible. Liquid metallic hydrogen (LMH), comprising interpenetrating proton and electron fluids, would constitute a two-component Fermi liquid with both a very high component-mass ratio and long-range, species-dependent bare interactions. The low-temperature equilibrium properties

J. Oliva; N. W. Ashcroft

1981-01-01

223

A quantum fluid of metallic hydrogen suggested by first-principles calculations  

Microsoft Academic Search

It is generally assumed that solid hydrogen will transform into a metallic alkali-like crystal at sufficiently high pressure. However, some theoretical models have also suggested that compressed hydrogen may form an unusual two-component (protons and electrons) metallic fluid at low temperature, or possibly even a zero-temperature liquid ground state. The existence of these new states of matter is conditional on

Stanimir A. Bonev; Eric Schwegler; Tadashi Ogitsu; Giulia Galli

2004-01-01

224

Dissolution of uranium metal without hydride formation or hydrogen gas generation  

Microsoft Academic Search

This study shows that metallic uranium will cleanly dissolve in carbonate-peroxide solution without generation of hydrogen gas or uranium hydride. Metallic uranium shot, 0.5–1mm diameter, was reacted with ammonium carbonate–hydrogen peroxide solutions ranging in concentration from 0.13M to 1.0M carbonate and 0.50M to 2.0M peroxide. The dissolution rate was calculated from the reduction in bead mass, and independently by uranium

Chuck Z. Soderquist; Bruce McNamara; Brian Oliver

2008-01-01

225

Hydrogen Attack kinetics of 2.25 Cr1 Mo steel weld metals  

Microsoft Academic Search

The kinetics of Hydrogen Attack (HA) of the base metals and the weld metals of two Q&T 2.25 Cr-1 Mo steel weldments made by\\u000a different techniques (SMAW and SAW) were studied in the temperature range 460 to 590°C (860 to 1094 °F) and 10 to 23 MPa of\\u000a hydrogen. A sensitive dilatometer used to measure the rate of HA showed

T. A. Parthasarathy; H. F. Lopez; P. G. Shewmon

1985-01-01

226

Hydrogen Attack kinetics of 2.25 Cr1 Mo steel weld metals  

Microsoft Academic Search

The kinetics of Hydrogen Attack (HA) of the base metals and the weld metals of two Q&T 2.25 Cr-1 Mo steel weldments made by different techniques (SMAW and SAW) were studied in the temperature range 460 to 590°C (860 to 1094 °F) and 10 to 23 MPa of hydrogen. A sensitive dilatometer used to measure the rate of HA showed

T. A. Parthasarathy; H. F. Lopez; P. G. Shewmon

1985-01-01

227

Fluorinated and Hydrogenated Ethers Adsorbed at Metal Surfaces: A Surface Science Tribology Study  

Microsoft Academic Search

Fluorinated and hydrogenated ethers adsorbed at a metal surface are studied using surface science techniques. It is found that fluorinated ethers bond less strongly to both atomically rough and smooth ruthenium surfaces than hydrogenated analogs. The magnitude of the fluorinated ether-surface bond is further decreased if water is preadsorbed on the surface. For the hydrogenated ethers, 0.03 to 0.17 monolayer

M. M. Walczak; P. K. Leavitt; P. A. Thiel

1990-01-01

228

On the mechanism of action of inhibitors of hydrogenation in the process of electrodeposition of metals  

Microsoft Academic Search

We develop a new approach to the investigation of the effect of inhibitors of hydrogenation of the base in the process of\\u000a electrodeposition of metals. We established the relationship between the structure of molecules of the inhibitor, their ability\\u000a to interact with atomic hydrogen, their adsorption properties, the contents of various forms of hydrogen in steel, and physicomechanical\\u000a parameters of

Yu M. Loshkarev; A. N. Baturin; Yu É. Udovenko; L. V. Shtemenko

1996-01-01

229

A priori prediction of the cohesive energy of one-dimensional metallic hydrogen  

Microsoft Academic Search

Ab initio wave functions and properties have been calculated for 14-, 26-, 38-, 50-, and 62-membered rings of hydrogen atoms. The properties converge rather quickly (with respect to the number of atoms in the ring) to those expected for one-dimensional metallic hydrogen. Electron correlation is explicitly considered by way of extensive configuration interaction. The cohesive energy is predicted to be

D. H. Liskow; John McKelvey; Charles Bender; Henry Schaefer

1974-01-01

230

Discovery of spontaneous deformation of Pd metal during hydrogen absorption/desorption cycles  

PubMed Central

A drastic deformation was observed in Pd metal of various shapes after hydrogen absorption and desorption cycles at 150 °C at a gas pressure of 1–5 MPa. All of the phenomena observed indicate that some strong internal force is induced spontaneously during hydrogen absorption/desorption cycles to produce a collective deformation so as to minimize the surface.

Yamazaki, Toshimitsu; Sato, Masaharu; Itoh, Satoshi

2009-01-01

231

Method and pressure container for producing hydrogen-storage metal granulates  

Microsoft Academic Search

The activation of a mass of metal granules capable of storing hydrogen with the formation of hydride in a pressure vessel, instead of having to be activated before use by repeated heating in a hydrogen atmosphere followed by cooling and evacuation before the next heating, is activated in the pressure vessel used for storage by first heating a small portion

K. Klatt; S. Pietz; H. Wenzl

1983-01-01

232

Oxidation by hydrogen in the chemistry and physics of the rare-earth metals.  

PubMed

Rare-earth metals (RE) easily react with hydrogen. For decades the bonding of hydrogen has been discussed controversially in terms of either the "proton model" or the "anion model". Detailed investigations of metal-rich compounds of the rare-earth metals provide clear evidence for the incorporation of hydrogen as a hydride anion. Several categories of compounds can be distinguished regarding their behavior towards hydrogen. Low-valence compounds with metal-metal bonding frequently provide their excess electrons to form hydride ions as found with the halide hydrides REXH(n). However, there are exceptions, such as, LaI which does not react with hydrogen as a result of special electronic and electrostatic conditions. The opposite is true with La(2)C(3) although this compound does not provide excess metal valence electrons. An amorphous phase La(2)C(3)H(1.5) forms at very low temperature, around 450 K. The presence of hydrogen strongly influences the electrical and magnetic properties, for example, spin-glass formation and colossal magneto resistance arising in the presence of 4f(n) cores with the lanthanoid elements. PMID:22431365

Simon, Arndt

2012-03-16

233

HIGH TEMPERATURE OXIDATION/CORROSION BEHAVIOR OF METALS AND ALLOYS UNDER A HYDROGEN GRADIENT  

SciTech Connect

Metallic interconnects in SOFC stacks, perform in challenging environment, as they are simultaneously exposed to a reducing environment (e.g. hydrogen, reformate) on one side and an oxidizing environment (e.g. air) on the other side at elevated temperatures. To understand the oxidation/corrosion behavior of metals and alloys under the dual exposures and assess their suitability, selected metals and alloys, including nickel, Fe-Cr and Ni-Cr base chromia forming alloys, alumina forming Fecralloy®, were investigated. It was found that the oxidation/corrosion behavior of metals and alloys in the presence of dual environment can be significantly different in terms of scale structure and/or chemistry from their exposure in a single oxidizing or reducing atmosphere. The anomalous oxidization/corrosion is attributed to the presence of hydrogen diffusion flux from the fuel side to the air side under the influence of a hydrogen gradient across the metallic substrates.

Yang, Z Gary; Xia, Gordon; Walker, Matthew S.; Wang, Chong M.; Stevenson, Jeffry W.; Singh, Prabhakar

2007-11-01

234

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

235

Optical-phonon-assisted hydrogen diffusion in metal hydrides  

NASA Astrophysics Data System (ADS)

The quantum theory of diffusion for light interstitials in model nonstoichiometric systems is developed. The dispersive optical phonons are used to obtain an analytical expression for total transition probability Wpp'. In the low-temperature limit, Wpp' is found to be temperature independent, while in the high-temperature limit the preexponential and exponential factors are temperature dependent. An explicit expression for migration energy is obtained and it is compared with other theoretical results. The dispersive phonons increase the migration energy. The effect of configurational interaction on Wpp' is also studied. It is found that at low temperature the tunneling transitions dominate and that at higher temperature the hopping transitions dominate. The impurity-excited states are accounted for in evaluating the diffusion constant for model nonstoichiometric metal hydrides. The diffusion coefficient for PdDx is found lower than that for PdHx. The calculated values of preexponential factor and migration energy are found to agree reasonably well with the experimental data wherever available. The hydrogen is found diffusing faster than the deuterium at all temperatures in Pd(H,D)x. Similar calculations are carried out for Nb(H,D)x. The diffusion constant for NbDx is found to be lower than that for NbHx. At low temperature the migration energy for D is found to be lower than that for H, while at high temperature the trend reverses. The calculated migration energy is found to be lower than the experimental values for which the possible reasons are discussed.

Dhawan, L. L.; Prakash, S.

1983-12-01

236

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

National Technical Information Service (NTIS)

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 pla...

D. Jackson

2007-01-01

237

Lattice stability and superconductivity of the metallic hydrogen at high pressure  

Microsoft Academic Search

Ab initio calculations of metallic hydrogen are presented. Investigation of the lattice stability of metallic monoatomic phases confirms the main part of conclusions obtained previously by Kagan's group in the framework of the perturbation approach to fourth order in the electron–phonon interaction. The results of the ab initio calculation of the critical temperature Tc of the superconducting transition is also

E. G. Maksimov; D. Yu. Savrasov

2001-01-01

238

The hydrogen reaction at equilibrium on the metals Ni, Fe, Cu, Ag and Au  

Microsoft Academic Search

The hydrogen reaction on different metals has been treated with respect to the exchange current density as a function of pH and the equilibrium potential. The study shows that there is no significant difference between the different metals. They all follow the same equations expected with respect to the effect of pH and equilibrium potential on the exchange current density.

T. Våland

1997-01-01

239

Microporous Metal Organic Materials for Hydrogen Storage for Period June 24, 2005 through November 23, 2008.  

National Technical Information Service (NTIS)

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 fram...

J. Li K. Johnson S. G. Sankar

2009-01-01

240

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

241

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

242

Hydrogen Purification Method from Reformed Gas Containing High Concentration of CO by Using Metal Hydride  

NASA Astrophysics Data System (ADS)

The Metal Hydride Intermediate-Buffer (MIB) method has been proposed as a measure to enable flexible load following operation and immediate start-up of PEFC system with a reformer. In this method, using the property of metal hydride to absorb hydrogen selectively, hydrogen is stored and purified simultaneously from reformed gas with impurities and subsequently supplied to PEFC stack. In this paper, using the fluorinated LmNi4.4Mn0.3Al0.3 metal hydride, we have investigated to improve resistivity of the metal hydride against CO to simplify the reformer. If the resistivity against CO rises to the 1%, preferential oxidation (PROX) process in reformer can be removed. Important consideration in this method is to keep CO concentration of released hydrogen from metal hydride below 10ppm. To investigate the effect of CO, absorption and release experiments of hydrogen from simulated reformed gas containing 100, 1000ppm or 1% CO were carried out with the specimen. The result of the absorption experiment shows that, when the specimen temperature is set to 50°C or higher, hydrogen absorption rate remains nearly unaffected by existence of 1% CO. The result of the release experiment shows that, when the specimen temperature exceeds 120°C, CO concentration of released hydrogen is approximately kept below 10ppm.

Taniguchi, Yukinobu; Ishida, Masayoshi

243

Hydrogen interaction with GaN metal-insulator-semiconductor diodes  

NASA Astrophysics Data System (ADS)

Interaction mechanism of hydrogen with GaN metal-insulator-semiconductor (MIS) diodes is investigated, focusing on the metal/semiconductor interfaces. For MIS Pt-GaN diodes with a SiO2 dielectric, the current-voltage (I-V) characteristics reveal that hydrogen changes the conduction mechanisms from Fowler-Nordheim tunneling to Poole-Frenkel emission. In sharp contrast, Pt-SixNy-GaN diodes exhibit Poole-Frenkel emission in nitrogen and do not show any change in the conduction mechanism upon exposure to hydrogen. The capacitance-voltage (C-V) study suggests that the work function change of the Schottky metal is not responsible mechanism for the hydrogen sensitivity.

Irokawa, Y.

2012-08-01

244

A superconductor to superfluid phase transition in liquid metallic hydrogen  

Microsoft Academic Search

Although hydrogen is the simplest of atoms, it does not form the simplest of solids or liquids. Quantum effects in these phases are considerable (a consequence of the light proton mass) and they have a demonstrable and often puzzling influence on many physical properties, including spatial order. To date, the structure of dense hydrogen remains experimentally elusive. Recent studies of

Egor Babaev; Asle Sudbø; N. W. Ashcroft

2004-01-01

245

High-pressure chemistry of hydrogen in metals: in situ study of iron hydride.  

PubMed

Optical observations and x-ray diffraction measurements of the reaction between iron and hydrogen at high pressure to form iron hydride are described. The reaction is associated with a sudden pressure-induced expansion at 3.5 gigapascals of iron samples immersed in fluid hydrogen. Synchrotron x-ray diffraction measurements carried out to 62 gigapascals demonstrate that iron hydride has a double hexagonal close-packed structure, a cell volume up to 17% larger than pure iron, and a stoichiometry close to FeH. These results greatly extend the pressure range over which the technologically important iron-hydrogen phase diagram has been characterized and have implications for problems ranging from hydrogen degradation and embrittlement of ferrous metals to the presence of hydrogen in Earth's metallic core. PMID:17746396

Badding, J V; Hemley, R J; Mao, H K

1991-07-26

246

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

247

Quantum Nature of Hydrogen on Metals: Dissociative Adsorption  

NASA Astrophysics Data System (ADS)

When hydrogen is adsorbed on a Pd(111) surface, very simple vacancy defects -- which form quite commonly -- exhibit fundamentally quantum wavelike behavior. We show that a full quantum treatment of the hydrogen nuclear motion, in addition to electron motion, predicts that the dissociative adsorption of H2 will be strongly suppressed at divacancies---in violation of the standard description from classical Langmuir adsorption kinetics---but will easily occur at trivacancies. Recent experiments confirm that aggregates of three or more hydrogen vacancies are required for efficient H2 dissociation, while divacancies are inactive [Mitsui et al, Nature 422, 705 (2003)]. Our findings indicate that traditional classical explanations for such observations require revisiting, and suggestthat the quantum nature of hydrogen may play a surprisingly prominent role in future hydrogen technologies.

Kim, Seong-Gon; Erwin, Steven C.

2005-11-01

248

Structures and potential superconductivity in at high pressure: en route to "metallic hydrogen".  

PubMed

A way to circumvent the high pressures needed to metallize hydrogen is to "precompress" it in hydrogen-rich molecules, a strategy probed theoretically for silane. We show that phases with tetrahedral SiH4 molecules should undergo phase transitions with sixfold- and eightfold-coordinate Si appearing above 25 GPa. The most stable structure found can be metallized at under a megabar and at a compression close to the prediction of Goldhammer-Herzfeld criterion. According to a BCS-like estimate, metallic silane should be a high-temperature superconductor. PMID:16486503

Feng, Ji; Grochala, Wojciech; Jaro?, Tomasz; Hoffmann, Roald; Bergara, Aitor; Ashcroft, N W

2006-01-11

249

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

SciTech Connect

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

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

1993-11-01

250

Novel Composite Hydrogen-Permeable Membranes for Non-Thermal Plasma Reactors for the Decomposition of Hydrogen Sulfide. Quarterly Report April 1-June 30, 2004.  

National Technical Information Service (NTIS)

The goal of this experimental project is to design and fabricate a reactor and membrane test cell to dissociate hydrogen sulfide (H2S) in a non-thermal plasma and recover hydrogen (H2) through a superpermeable multi-layer membrane. Superpermeability of hy...

M. D. Argyle J. F. Ackerman S. Muknahallipatna J. C. Hamann S. Legowski

2004-01-01

251

Metallic spintronic thin film as a hydrogen sensor  

NASA Astrophysics Data System (ADS)

We investigate the ferromagnetic resonance response of palladium-cobalt bi-layer thin films to hydrogen charging at atmospheric pressure. We find that hydrogen absorption by the palladium capping layer results in the narrowing and shifting of the ferromagnetic resonance line of the underlying cobalt. We explain the observed phenomena as originating from reduction in the spin pumping effect and from variation in the magnetic anisotropy of the cobalt layer through an interface effect. The shift of the resonance frequency or field is the easiest to detect. We utilize this to demonstrate functionality of the bi-layer film as a hydrogen sensor.

Chang, Crosby S.; Kostylev, Mikhail; Ivanov, Eugene

2013-04-01

252

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

SciTech Connect

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

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

2008-07-15

253

Photobiotechnology: Algal hydrogen production and photoconductivity of metalized chloroplasts.  

National Technical Information Service (NTIS)

Sustained hydrogen photoevolution from Chlamydomonas reinhardtii and C. moewusii was measured under an anoxic, CO(sub 2)-containing atmosphere. It has been discovered that light intensity and temperature influence the partitioning of reductant between the...

E. Greenbaum

1991-01-01

254

Transition of single-walled carbon nanotubes from metallic to semiconducting in field-effect transistors by hydrogen plasma treatment.  

PubMed

We report hydrogen plasma treatment results on converting the metallic single-walled carbon nanotubes to semiconducting single-walled carbon nanotubes. We found that the as-grown single-walled carbon nanotubes (SWNTs) can be sorted as three groups which behave as metallic, as-metallic, and semiconducting SWNTs. These three groups have different changes under hydrogen plasma treatment and successive annealing process. The SWNTs can be easily hydrogenated in the hydrogen plasma environment and the as-metallic SWNTs can be transformed to semiconducting SWNTs. The successive annealing process can break the C-H bond, so the conversion is reversible. PMID:17508771

Zheng, Gang; Li, Qunqing; Jiang, Kaili; Zhang, Xiaobo; Chen, Jia; Ren, Zheng; Fan, Shoushan

2007-05-18

255

A study on hydrogen adsorption of Metal-Insulator-Silicon sensor with La2O3 as gate insulator  

Microsoft Academic Search

A new Metal-Insulator-Silicon (MIS) Schottky-diode hydrogen sensor with La2O3 as gate insulator was fabricated. Its hydrogen-sensing properties were studied from room temperature (RT) to 200°C. Results showed that the device had excellent hydrogen-sensing performance below about 250°C. Furthermore, hydrogen reaction kinetics was confirmed for the sample. The response time extracted from its hydrogen adsorption transient behavior was around 4.5 s

Gang Chen; P. T. Lai; J. Yu

2010-01-01

256

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

Microsoft Academic Search

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

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

2001-01-01

257

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

258

Modeling surface effects on hydrogen permeation in metals  

NASA Astrophysics Data System (ADS)

A new mathematical model for analyzing hydrogen permeation in solids, in which surface effects and traps influence hydrogen transport, is presented and solved. The new model combines the McNabb and Foster equations for diffusion with concomitant trapping[1] and a surface-limited mass-transfer boundary condition. An important result of the new model is the introduction of a new variable, h m, which is defined as the surface-limited mass-transfer coefficient. The h m coefficient can account for all possible surface effects and may be experimentally evaluated.

Makhlouf, M. M.; Sisson, R. D.

1991-05-01

259

A novel batch-type hydrogen transmitting system using metal hydrides  

NASA Astrophysics Data System (ADS)

In the case of transporting hydrogen by means of metal hydrides, a key problem is to reduce the weight of the portable container filled with metal hydrides. The paper describes a novel batch-type hydrogen transmitting system characterized by a portable light container filled with metal hydrides, which is not pressure-proof but only mechanically durable. Hydriding is performed by setting the portable light container in a fixed pressure-proof vessel and admitting hydrogen and nitrogen inside and outside the portable container, respectively, while adjusting the pressure difference between both gases to be zero. Using this system, 2.9 cu Nm of hydrogen can be stored in 14.3 kg of the total mass of the solid constituents including 3.5 kg of Mg-10% Ni alloy. The portable container contains twice as much hydrogen per unit weight and volume as a conventional compressed gas cylinder. Due to the advanced design of this portable container, the optimum hydrogen content could be around 5 wt % based upon the total mass of the container.

Nishimiya, N.; Suzuki, A.; Ono, S.

260

Interaction of magnetic transition metal dimers with spin-polarized hydrogenated graphene.  

PubMed

The coadsorption of hydrogen and transition metal dimers Fe2, Co2, Ni2, and FeCo on graphene is investigated using density functional theory calculations. Our work is motivated by observations that the magnetic moments of these transition metal dimers are large and that hydrogen adsorption partitions the graphene lattice into magnetic subdomains. Thus, we expect the magnetic dimers to interact strongly with the lattice. Our results show that the majority-spin direction of the lattice electronic states depends upon the dimer identity, the lattice spin polarization being in the same direction as the dimer spin polarization for Fe2 and FeCo, but opposite for Co2 and Ni2. We can understand this by examining the electronic density of states of the dimer and the lattice. We also show that coadsorption significantly increases the adsorption energies of both dimer and hydrogen leading to a more strongly-adsorbed dimer, while the bond length and magnetic moment of the upper dimer atom, the latter important for potential magnetic storage applications, are negligibly changed. Our work shows that the coadsorbed hydrogen and metal dimer interact over a long-range, this interaction being mediated by the hydrogen-induced spin-polarization of the graphene lattice. We obtain general insight into how the elemental identity of these magnetic dimers determines the spin-polarized states on the hydrogenated graphene lattice. These results could be important for potential applications of magnetic properties of decorated graphene lattices. PMID:23556744

Ong, S W; Wu, J; Thong, A Z H; Tok, E S; Kang, H C

2013-03-28

261

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

262

Formation kinetics of brittle phase nuclei in hydrogenated metals under loading  

NASA Astrophysics Data System (ADS)

It is shown that the formation of the brittle phase in hydrogenated metal under external loading is a first-order phase transition. The basic equation of the evolution of elastic stress in a uniform and isotropic hydrogenated metal during the formation of a brittle hydride phase is derived and its solution is found. Based on this data, the time dependences of all characteristics of the phase transition into a brittle phase are found; namely, the densities of nuclei of the hydride phase, the size distribution, and the formation rates of the hydride phase nuclei are found. The characteristic time of the transition into the brittle phase is found.

Indeitsev, D. A.; Osipova, E. V.

2013-03-01

263

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

264

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

NASA Astrophysics Data System (ADS)

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

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

2009-08-01

265

Cold three-body collisions in hydrogen-hydrogen-alkali-metal atomic systems  

Microsoft Academic Search

We have studied hydrogen-hydrogen-alkali three-body systems in the adiabatic hyperspherical representation. For the spin-stretched case, there exists a single XH molecular state when X is one of the bosonic alkali atoms: Li, ²³Na, ³K, Rb, or ¹³³Cs. As a result, the only recombination process is the one that leads to formation of XH molecules, H+H+XXH+H, and such molecules will be

Wang Yujun; B. D. Esry; J. P. DIncao

2011-01-01

266

Atomistic simulations of the interactions of hydrogen with dislocations in fcc metals  

NASA Astrophysics Data System (ADS)

The interactions of hydrogen with both edge and screw dislocations in face-centered-cubic (fcc) metals are investigated using molecular statics simulations of nickel-hydrogen as a model system. It is shown that the most energetically favorable sites for H occupation are octahedral sites in the perfect fcc lattice, tetrahedral sites in the stacking fault, and both octahedral and tetrahedral sites in the Shockley partial cores of dislocations. Moreover, the diffusion barrier for H is relatively high except for pipe diffusion near the Shockley partial cores. It is also shown that partial dislocation cores have the strongest interactions with hydrogen. The hydrogen-dislocation interactions (attractive or repulsive) and the change in stacking width (increase or decrease) depend on the hydrogen-occupying sites (octahedral or tetrahedral) and the positions of the hydrogen atoms relative to the strongest binding energy sites. In particular, on the dislocation glide plane, only hydrogen atoms in both of the Shockley partial core regions can result in increasing the stacking fault width, while those in the stacking fault region or in the perfect fcc lattice region have no observable effects. On the other hand, uniformly distributed hydrogen in the tension region near the center of a dislocation can result in decreasing the stacking fault width. The stable stacking fault energy also decreases with increasing hydrogen concentration due to the resulting negative binding energy of hydrogen to the stacking fault, while the unstable stacking fault energy increases with increasing hydrogen concentration. This may result in pinning the dislocation due to the nature of short-range interaction between interstitial hydrogen atoms and their neighboring Ni atoms.

Tang, Yizhe; El-Awady, Jaafar A.

2012-11-01

267

Anion Binding in MetalOrganic Frameworks Functionalized with Urea Hydrogen-Bonding Groups  

Microsoft Academic Search

A series of metal-organic frameworks (MOFs) functionalized with urea hydrogen-bonding groups has been synthesized and structurally analyzed by single-crystal X-ray diffraction to evaluate the efficacy of anion coordination by urea within the structural constraints of the MOFs. We found that urea-based functionalities may be used for anion binding within metal-organic frameworks when the tendency for urea{hor_ellipsis}urea self-association is decreased by

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

2006-01-01

268

Anion Coordination in MetalOrganic Frameworks Functionalized with Urea Hydrogen-Bonding Groups  

Microsoft Academic Search

A series of metal-organic frameworks (MOFs) functionalized with urea hydrogen-bonding groups have been designed, synthesized, and structurally analyzed by single crystal X-ray diffraction to evaluate the efficacy of anion binding within the structural constraints of the MOFs. We found that urea-based functionalities may be used for anion binding within metal-organic frameworks when the tendency for urea???urea self-association is decreased by

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

2005-01-01

269

Metallization of solid hydrogen at megabar pressures: A first-principles quasiparticle study  

Microsoft Academic Search

Quasiparticle calculations have been performed for the band gap of solid molecular hydrogen in the hcp structure. The calculations predict that the orientationally ordered phase undergoes metallization due to an indirect band overlap at the volume V=2.50 cm3\\/mol and the orientationally disordered phase at V=1.89 cm3\\/mol, which correspond to metallization pressures of 151 and 300 GPa, respectively. A quantitative relation

Hélio Chacham; Steven G. Louie

1991-01-01

270

Finite element-based simulation of a metal hydride-based hydrogen storage tank  

Microsoft Academic Search

In this paper, a novel 3D flexible tool for simulation of metal hydrides-based (LaNi5) hydrogen storage tanks is presented. The model is Finite Element-Based and considers coupled heat and mass transfer resistance through a non-uniform pressure and temperature metal hydride reactor. The governing equations were implemented and solved using the COMSOL Multiphysics simulation environment. A cylindrical reactor with different cooling

A. Freni; F. Cipitì; G. Cacciola

2009-01-01

271

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

272

Comparison of integral equations for correlations in liquid metallic hydrogen  

Microsoft Academic Search

Dharma-Wardana and Perrot (DWP, 1982) calculated the radial distribution functions (RDFs) of hydrogen plasma by using an integral equation derived from the density-functional formalism with the local density approximation. The contribution from the electron-proton correlation was neglected in the effective electron-proton and proton-proton interactions, and the exchange-correlation effect of the electrons in the presence of ions was approximated by that

Junzo Chihara

1986-01-01

273

Effect of hydrogen on corrosion failure of pipeline metal  

Microsoft Academic Search

Results are provided for a study of specimens made of steels 20, 09G2S and 14Kh2GMR for resistance to sulfide stress corrosion\\u000a cracking under (SSCC), i.e., the nature of failure for industrial pipeline and equipment for oil and gas deposits.\\u000a \\u000a The main reason for SSCC is analyzed, and this is steel hydrogenation.

I. N. Kriminskii

2007-01-01

274

Accelerated evolution of hydrogen from metals during plastic deformation  

Microsoft Academic Search

Plastic deformation accelerates the release of hydrogen from iron, Type 304L stainless steel, nickel, Inconel 718, and 5086\\u000a aluminum. The release rate is strain dependent: it increases rapidly when plastic deformation begins, reaches a maximum, and\\u000a then decreases with additional strain with a final large release at fracture. The release rate is constant during Lüder’s\\u000a extension for iron, and fluctuates

James A. Donovan

1976-01-01

275

Testing to determine the effect of high-pressure hydrogen environments on the mechanical properties of metals  

Microsoft Academic Search

Equipment and procedures used in performing tension, fracture mechanics, ; fatigue, and creep tests on metal specimens in high-pressure hydrogen are ; described. Important test parameters, in particular, hydrogen purity and methods ; of achieving high purity are considered. The interpretation and use of data ; obtained from the various tests in high-pressure hydrogen are discussed. (auth);

W. T. Chandler; R. J. Walter

1974-01-01

276

Significantly enhanced hydrogen storage in metal-organic frameworks via spillover.  

PubMed

The utilization of hydrogen in fuel-cell powered vehicles is limited by the lack of a safe and effective system for hydrogen storage. At the present time, there is no viable storage technology capable of meeting the DOE targets. Porous metal-organic frameworks (MOFs) are novel and potential candidates for hydrogen storage. Until now it is still not possible to achieve any significant hydrogen storage capacity in MOFs at ambient temperature. Here, we report, for the first time, significant amounts of hydrogen storage in MOF-5 and IRMOF-8 at ambient temperature by using a very simple technique via hydrogen dissociation and spillover. Thus, hydrogen uptakes for MOF-5 and IRMOF-8 can be enhanced by a factor of 3.3 and 3.1, respectively (to nearly 2 wt % at 10 MPa and 298 K). Furthermore, the isotherms are totally reversible. These findings suggest that our technique is suitable for hydrogen storage in a variety of MOF materials because of their similar structures as MOF-5 and IRMOF-8. PMID:16417355

Li, Yingwei; Yang, Ralph T

2006-01-25

277

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

PubMed

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

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

2008-03-20

278

Hydrogen permeation in metals near room temperature by a tritium tracer technique  

NASA Astrophysics Data System (ADS)

In a fusion reactor, tritium retention and permeation in structure materials are very important safety concerns. Most data for diffusion and permeation of hydrogen in metals so far available have been limited for rather higher temperatures and, in particular, no data are available for high-Z metals near room temperature (RT). We have tried to observe gaseous hydrogen permeation through metals near RT applying a tritium tracer technique, which is a very powerful tool to detect quite small amount of hydrogen (tritium) by a liquid scintillation counting (LSC) method. After confirming the reliability of the method for the determination of diffusion and permeation coefficients in pure Ni, it was applied to hydrogen permeation in W near RT, and diffusion and permeation coefficients of hydrogen in W were determined, D=(3.42±0.68)×10-9exp((-37.8±1.2)(kJ/mol)/RT),m2s-1, and ?=(1.21±0.24)×10-5exp((-57.8±0.9)(kJ/mol)/RT),molm-3s-1Pa-1.

Ikeda, Takahiro; Otsuka, Teppei; Tanabe, Tetsuo

2011-10-01

279

Studies of the cerium-metal–oxygen–hydrogen system (metal=Cu, Ni)  

Microsoft Academic Search

In situ X-ray diffraction (XRD), in situ X-ray photoelectron spectroscopy (XPS), electron microscopy and thermogravimetric techniques were used to characterize CeMxOy mixed oxides in the oxidized and H2 reduced state. The processes occurring during the hydrogen treatment, and the amounts of hydrogen occluded in the solids when treated at different temperatures under flowing hydrogen have also been determined. The CeMxOy

C. Lamonier; A. Ponchel; A. D'Huysser; L. Jalowiecki-Duhamel

1999-01-01

280

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

Microsoft Academic Search

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

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

2009-01-01

281

Solubility and Diffusion of Hydrogen in Metals and Alloys. I - Monocrystalline Nickel-Vanadium Alloy.  

National Technical Information Service (NTIS)

A method for measuring the solubility and diffusion coefficient of hydrogen in metal single crystals under clean conditions is described. For a nickel - 4.4 atom % vanadium alloy the diffusion coefficient is (7.2 +or- 0.4) x 0.0001 exp (-10.10 +or- 0.06 k...

Y. Ebisuzaki W. Kass M. O'Keeffe

1966-01-01

282

The molecular-metallic transition of hydrogen and the structure of Jupiter and Saturn  

Microsoft Academic Search

Recently, a new equation of state for hydrogen which predicts a molecular-metallic phase transition at finite temperature has become available. It is combined with a helium equation of state, and the resulting thermodynamic description of H\\/He mixtures is used to compute interior models of Jupiter and Saturn, subject to the constraints of the measured gravitational harmonics of both planets. The

Gilles Chabrier; Didier Saumon; William B. Hubbard; Jonathan I. Lunine

1992-01-01

283

The superconducting state in metallic hydrogen under pressure at 2000 GPa  

Microsoft Academic Search

In this study, we have analysed the properties of the superconducting phase in metallic hydrogen under pressure at 2000 GPa. In particular, we have calculated the dependence of the basic thermodynamic quantities on the value of Coulomb pseudopotential (??). The main results are the following: (i) The critical temperature (TC) is large even for high values of ??. (ii) The

M. W. Jarosik

2009-01-01

284

Coupled Electron-Ion Monte Carlo Calculations of Dense Metallic Hydrogen  

Microsoft Academic Search

We present an efficient new Monte Carlo method which couples path integrals for finite temperature protons with quantum Monte Carlo calculations for ground state electrons, and we apply it to metallic hydrogen for pressures beyond molecular dissociation. We report data for the equation of state for temperatures across the melting of the proton crystal. Our data exhibit more structure and

Carlo Pierleoni; David M. Ceperley; Markus Holzmann

2004-01-01

285

Evaluation of hydrogen content in metallic samples by neutron computed tomography  

Microsoft Academic Search

Neutron radiography is currently a well-known technique, which is employed for non-destructive testing in a number of industrial and environmental applications. Originally developed for reactor fuel examinations, it is now effective in detecting small amounts of corrosion and infiltrations of hydrogen or light materials within thick metallic structures due to the particular behaviour of total neutron cross sections. Nevertheless, improvements

M. Zanarini; P. Chirco; M. Rossi; G. Baldazzi; G. Guidi; E. Querzola; M. G. Scannavini; F. Casali; A. Garagnani; A. Festinesi

1994-01-01

286

Evaluation of hydrogen content in metallic samples by neutron computed tomography  

Microsoft Academic Search

Neutron radiography is currently a well-known technique, which is employed for non-destructive testing in a number of industrial and environmental applications. Originally developed for reactor fuel examinations, it is now effective in detecting small amounts of corrosion and infiltrations of hydrogen or light materials within thick metallic structures due to the particular behaviour of total neutron cross sections. Nevertheless, improvements

M. Zanarini; P. Chirco; M. Rossi; G. Baldazzi; G. Guidi; E. Querzola; M. G. Scannavini; F. Casali; A. Garagnani; A. Festinesi

1995-01-01

287

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

288

Experimental and numerical study of discharge process of metal–hydrogen tank  

Microsoft Academic Search

In this paper, an experimental and numerical study of a closed metal–hydrogen reactor is presented. The temperature and the pressure temporal evolutions within the reactor, which thermally solicited at a constant temperature, are experimentally investigated and analysed. In addition, a test of the validity of a theoretical model describing the dynamic behaviour of a closed reactor, by comparing the experimental

H. Dhaou; S. Mellouli; F. Askri; A. Jemni; S. Ben Nasrallah

2007-01-01

289

CONCEPTUAL DESIGN AND APPLICATION OF LIQUID METAL MHD SYSTEM FOR HYDROGEN PRODUCTION  

Microsoft Academic Search

Liquid Metal MHD Power Conversion systems have recently been proposed for direct electrical energy conversion of low grade thermal source of energy, light solar energy and waste heat. Such systems can be used for generating hydrogen by electrolysis of water. Some preliminary investigations have been presented in this paper. Introduction. The future economical growth critically depends on long term availability

A. Chandra; G. K. Pandey

290

Electrowinning of Non-Noble Metals with Simultaneous Hydrogen Evolution at Flow-Through Porous Electrodes  

Microsoft Academic Search

A mathematical model is developed to simulate the electrowinning of non-noble metals (e.g., Zn, Cr) within flow- through porous electrodes under the conditions of simultaneous evolution of hydrogen gas bubbles. The results of the model are presented as a function of several dimensionless groups representing kinetics, mass transfer, ohmic resistance, and gas bubbles. These coupled, nonlinear effects are investigated by

Mahmoud M. Saleh; John W. Weidner; Badr G. Ateya

1995-01-01

291

Ab initio studies of superconductivity in monatomic metallic hydrogen under high pressure  

NASA Astrophysics Data System (ADS)

A detailed study of the structural, electronic, dynamical, and superconducting properties in the monatomic metallic hydrogen is presented. At least up to 802 GPa, this phase is stable. Moreover, we find that a strong electron-phonon interaction drives a very high superconducting transition temperature T?291.40 K at 539 GPa.

Yan, Yan; Gong, Jie; Liu, Yanhui

2011-02-01

292

Catalytic Ring Hydrogenation of Benzoic Acid with Supported Transition Metal Catalysts in scCO2  

PubMed Central

The ring hydrogenation of benzoic acid to cyclohexanecarboxylic acid over charcoal-supported transition metal catalysts in supercritical CO2 medium has been studied in the present work. The cyclohexanecarboxylic acid can be produced efficiently in supercritical CO2 at the low reaction temperature of 323 K. The presence of CO2 increases the reaction rate and several parameters have been discussed.

Wang, Hongjun; Zhao, Fengyu

2007-01-01

293

Metal oxide photoelectrodes for hydrogen generation using solar radiation-driven water splitting  

Microsoft Academic Search

Metal oxide semiconductors are today the most promising materials for photoelectrochemical production of hydrogen by the method of the photoelectrolysis of water as the problems of the stability of photoelectrodes are basically solved only for such materials. The aim of this short review paper is the presentation of results in this field obtained both worldwide and by the authors of

V. M. Aroutiounian; V. M. Arakelyan; G. E. Shahnazaryan

2005-01-01

294

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

295

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

NASA Astrophysics Data System (ADS)

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 c ˜ 41000 atm, ? c ˜ 0.1 g/cm3, and T c ˜ 9750 K.

Khomkin, A. L.; Shumikhin, A. S.

2013-10-01

296

Process for the production of hydrogen and carbonyl sulfide from hydrogen sulfide and carbon monoxide using a metal boride, nitride, carbide and/or silicide catalyst  

SciTech Connect

Hydrogen and carbonyl sulfide are produced by a process comprising contacting gaseous hydrogen sulfide with gaseous carbon monoxide in the presence of a metal boride, carbide, nitride and/or silicide catalyst, such as titanium carbide, vanadium boride, manganese nitride or molybdenum silicide.

McGuiggan, M.F.; Kuch, P.L.

1984-05-08

297

Numerical analysis of heat and mass transfer during absorption of hydrogen in metal hydride based hydrogen storage tanks  

Microsoft Academic Search

In this paper, hydriding in a cylindrical metal hydride hydrogen storage tank containing HWT5800 (Ti0.98Zr0.02V0.43Fe0.09Cr0.05Mn1.5) is numerically studied with a two-dimensional mathematical model. The heat and mass transfer of this model is computed by finite difference method. The effects of supply pressure, cooling fluid temperature, overall heat transfer coefficient and height to the radius ratio of the tank (H\\/R) on

Jianhua Ye; Lijun Jiang; Zhinian Li; Xiaopeng Liu; Shumao Wang; Xinyu Li

2010-01-01

298

Hydrogen production from methanol on transition metals: A study of thermodynamics and kinetics on subnanometer clusters  

NASA Astrophysics Data System (ADS)

The mechanistic studies of Pd-based catalysts and its interaction with methanol have attracted huge attention because of the possibility of using methanol as an on-board source of hydrogen for fuel cells. Stabilizing subnanometer metal clusters is a challenging process that has exhibited novel catalytic properties for various industrially important reactions such as production of hydrogen from hydrogen-rich molecules. One such reaction is methanol decomposition that was modeled by applying DFT methods on metal clusters. The thermodynamics and kinetics of three decomposition routes involving C-O, C-H and O-H scission were investigated; activation energy barriers were determined with the nudged elastic band method on Pd clusters with a comparison to Co and Cu clusters. A detailed analysis of the PES for methanol decomposition shows C-O activation to be the least favorable step on all three metal clusters. However we find activation to be ˜0.30 eV smaller on Co cluster. In addition, estimated thermodynamical data for a large number of transition metals has been generated from linear correlations constructed from the binding energies of Pd, Cu and Co to broaden our understanding of the role such metal clusters can play as catalyst for such reactions.

Mehmood, Faisal; Greeley, Jeffery P.; Zapol, Peter; Curtiss, Larry A.

2010-03-01

299

Surface Chemical Behavior of Uranium Metal in Hydrogen Atmosphere Studied by XPS  

NASA Astrophysics Data System (ADS)

The surface chemical behavior of clean uranium metal in a hydrogen atmosphere at 80°C and 120°C has been studied using XPS and thermodynamic calculation. The main product is uranium oxide rather than hydride uranium on the uranium surface after the exposure of uranium to extremely pure hydrogen, and the U4f7/2 binding energy of UH3 has been found to be 378.6 ± 0.1 eV. An elevated temperature (120°C) is beneficial to the formation of UH3 species at the same hydrogen exposures. The depth profile analysis of XPS indicates that the chemical structure of the surface layer was UO2/UH3/U after the exposure of hydrogen reached 1.31 × 10-6 L (1 L = 10-6 Torr·s). Results of thermodynamic calculations are in good agreement with the above conclusions.

Wang, Xiaolin; Fu, Xiaoguo; Zhao, Zhengping

300

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

301

A quantitative investigation of hydrogen in the metal-oxide-silicon system using NRA  

SciTech Connect

The present state of development in the application of resonant nuclear reaction analysis to the direct measurement of hydrogen concentration profiles throughout the metal-oxide-silicon system is presented. Detection limits of less than 10{sup 18} cm{sup {minus}3} (10{sup 12} cm{sup {minus}2}) as well as a depth resolution of better than 10 nm are obtained. Limitations of the technique to study changes in the hydrogen profiles caused by ex-situ irradiation are discussed. It is shown that the method is sufficiently sensitive so as to provide the first clear measurements of the hydrogen distribution in the bulk SiO{sub 2} (500--10000 ppma). Also presented is a demonstration of the radiation induced migration of atomic hydrogen to both the Si-SiO{sub 2} and Al-SiO{sub 2} interface, under the action of the analyzing beam, at cryogenic temperatures.

Briere, M.A., Braunig, D. (Hahn-Meitner-Institut Berlin GmbH (Germany, F.R.))

1990-12-01

302

Vacancy trapping mechanism for hydrogen bubble formation in metal  

SciTech Connect

We reveal the microscopic vacancy trapping mechanism for H bubble formation in W based on first-principles calculations of the energetics of H-vacancy interaction and the kinetics of H segregation. Vacancy provides an isosurface of optimal charge density that induces collective H binding on its internal surface, a prerequisite for the formation of H{sub 2} molecule and nucleation of H bubble inside the vacancy. The critical H density on the vacancy surface before the H{sub 2} formation is found to be 10{sup 19}-10{sup 20} H atoms per m{sup 2}. We believe that such mechanism is generally applicable for H bubble formation in metals and metal alloys.

Liu Yuelin; Zhang Ying; Zhou Hongbo; Lu Guanghong; Liu Feng; Luo, G.-N. [Department of Physics, Beijing University of Aeronautics and Astronautics, Beijing 100191 (China); Department of Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112 (United States); Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China)

2009-05-01

303

Hydrogen adsorption in transition metal carbon nano-structures  

Microsoft Academic Search

Templated microporous carbons were synthesized from metal impregnated zeolite Y templates. Scanning Electron Microscopy (SEM)\\u000a and Transmission Electron Microscopy (TEM) were employed to characterize morphology and structure of the generated carbon\\u000a materials. The surface area, micro- and meso-pore volumes, as well as the pore size distribution of all the carbon materials\\u000a were determined by N2 adsorption at 77 K and

Yun Xia Yang; Ranjeet K. Singh; Paul A. Webley

2008-01-01

304

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

305

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

306

Mechanical damping by intercrystalline diffusion of hydrogen in metallic polycrystals.  

PubMed

Anelastic relaxation by intercrystalline atomic diffusion-analogous to thermal diffusion (i.e., thermoelastic) effects but never observed hitherto-was recently suggested as a new mechanism to explain part of the hydrogen damping spectra in intermetallic compounds. A critical experimental test of this model is now presented using a Zr65Cu17.5Ni10Al7.5 alloy, which allows for a quantitative kinetic analysis in comparison to a closely related reorientation process. The results are in full agreement with the predictions of the model and clearly corroborate the proposed "intercrystalline Gorsky effect" as a new type of mechanical damping in sufficiently fine-grained polycrystals. PMID:11019301

Sinning, H R

2000-10-01

307

Metal hydride anodes for nickel-hydrogen secondary battery  

NASA Astrophysics Data System (ADS)

The relationships between the chemical composition of La(1-x)Zr(x)Ni(5-y)Al(y) and its anode properties, such as capacity, cycle life (CL), rate capability, temperature behavior, and self-discharge character, were investigated using a pyrex test cell filled with 6 M KOH electrolyte solution for electrochemical measurements. It was found that, with increasing the Zr content in presence of Al (y = 0.5), the CL increased from 180 for x = 0, to 580 for x = 0.1, and 810 for x = 0.2. The addition of Zr was also found to depress self-discharge. However, with increasing Zr content, the hydrogen overpotentials increased, resulting in a lowering of discharge potentials and capacities at high currents and low temperatures.

Sakai, Tetsuo; Miyamura, Hiroshi; Kuriyama, Nobuhiro; Kato, Akihiko; Oguro, Keisuke

1990-03-01

308

First principles assessment of ideal fracture energies of materials with mobile impurities: implications for hydrogen embrittlement of metals  

SciTech Connect

We propose that the ideal fracture energy of a material with mobile bulk impurities can be obtained within the framework of a Born-Haber thermodynamic cycle. We show that such a definition has the advantage of initial and final states at equilibrium, connected by well-defined and measurable energetic quantities, which can also be calculated from first principles. Using this approach, we calculate the ideal fracture energy of metals (Fe and Al) in the presence of varying amounts of hydrogen, using periodic density functional theory. We find that the metal ideal fracture energy decreases almost linearly with increasing hydrogen coverage, dropping by {approx}45% at one-half monolayer of hydrogen, indicating a substantial reduction of metal crystal cohesion in the presence of hydrogen atoms and providing some insight into the cohesion-reduction mechanism of hydrogen embrittlement in metals.

Jiang, D.E. [Department of Chemistry and Biochemistry, University of California, 607 Charles Young Drive, P.O. Box 951569, Los Angeles, CA 90095-1569 (United States); Carter, Emily A. [Department of Chemistry and Biochemistry, University of California, 607 Charles Young Drive, P.O. Box 951569, Los Angeles, CA 90095-1569 (United States)]. E-mail: eac@chem.ucla.edu

2004-09-20

309

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

310

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

SciTech Connect

Covalent organic frameworks (COFs), due to their low-density, high-porosity, and high-stability, have promising applications in gas storage. In this study we have explored the potential of COFs doped with Li and Ca metal atoms for storing hydrogen under ambient thermodynamic conditions. Using density functional theory we have performed detailed calculations of the sites Li and Ca atoms occupy in COF-10 and their interaction with hydrogen molecules. The binding energy of Li atom on COF-10 substrate is found to be about 1.0 eV and each Li atom can adsorb up to three H{sub 2} molecules. However, at high concentration, Li atoms cluster and, consequently, their hydrogen storage capacity is reduced due to steric hindrance between H{sub 2} molecules. On the other hand, due to charge transfer from Li to the substrate, O sites provide additional enhancement for hydrogen adsorption. With increasing concentration of doped metal atoms, the COF-10 substrate provides an additional platform for storing hydrogen. Similar conclusions are reached for Ca doped COF-10.

Wu Miaomiao; Sun Qiang [Department of Advanced Materials and Nanotechnology and Center for Applied Physics and Technology, Peking University, Beijing 100871 (China); Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284 (United States); Wang Qian; Jena, Puru [Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284 (United States); Kawazoe, Yoshiyuki [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

2010-10-21

311

Electroless patterned assembly of metal nanoparticles on hydrogen-terminated silicon surfaces for applications in photoelectrocatalysis.  

PubMed

The deposition of gold and platinum nanoparticles (NPs) on hydrogen-terminated Si(100) (Si(100)-H) surfaces has been performed by galvanic displacement using fluoride-free sub-millimolar metallic salt solutions. The scanning electron microscopy (SEM) images showed the formation of oblate hemispherical NPs, with an average diameter of ca. 40 nm and an average height of 20 ± 10 and 10 ± 5 nm for Au and Pt, respectively. Furthermore, the calculated number density was (6.0 ± 0.8) × 10(9) Au NPs cm(-2) and (6.6 ± 1.3) × 10(9) Pt NPs cm(-2) with a larger size distribution measured for Au NPs. The Au 4f and Pt 4f X-ray photoelectron spectra of the metallized surfaces were characterized by a principal component corresponding to either the metallic gold or platinum. However, two other components located at higher binding energies were also visible and ascribed to gold or platinum silicides. Using this fluoride-free deposition process and a "reagentless" UV photolithography technique, we have also demonstrated that it was possible to prepare metallic NP micropatterns. Following this approach, single metal (Au) and two metals (Au and Pt) patterns have been produced and characterized by energy-dispersive X-ray spectroscopy (EDS) which revealed the presence of the expected metal(s). Such metallic NP micropatterned surfaces were used as photocathodes for H(2) evolution from water as a proof-of-concept experiment. These electrodes exhibited much higher electrocatalytic performance than that of nonmetallized Si(100)-H, both in the absence of light and under illumination. The overpotential for hydrogen evolution was significantly decreased by ca. 450 mV with respect to Si(100)-H (measured for a current density of 0.1 mA cm(-2)) under identical illumination conditions. PMID:23273214

Fabre, Bruno; Hennous, Leila; Ababou-Girard, Soraya; Meriadec, Cristelle

2013-01-11

312

Solar hydrogen production with semiconductor metal oxides: new directions in experiment and theory.  

PubMed

An overview of a collaborative experimental and theoretical effort toward efficient hydrogen production via photoelectrochemical splitting of water into di-hydrogen and di-oxygen is presented here. We present state-of-the-art experimental studies using hematite and TiO(2) functionalized with gold nanoparticles as photoanode materials, and theoretical studies on electro and photo-catalysis of water on a range of metal oxide semiconductor materials, including recently developed implementation of self-interaction corrected energy functionals. PMID:22083224

Valdés, Álvaro; Brillet, Jeremie; Grätzel, Michael; Gudmundsdóttir, Hildur; Hansen, Heine A; Jónsson, Hannes; Klüpfel, Peter; Kroes, Geert-Jan; Le Formal, Florian; Man, Isabela C; Martins, Rafael S; Nørskov, Jens K; Rossmeisl, Jan; Sivula, Kevin; Vojvodic, Aleksandra; Zäch, Michael

2011-11-14

313

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

314

Synthesis and hydrogen adsorption properties of a new iron based porous metal-organic framework  

Microsoft Academic Search

A new metal-organic framework [Fe3O(OOC-C6H4-COO)3(H2O)3]Cl·(H2O)x was synthesized with a specific surface area of 2823 m2\\/g and a lattice parameter of 88.61 Å. Isostructural with MIL-101, this compound exhibits similar hydrogen adsorption properties, with maximum adsorption capacity of 5.1wt.% H at 77 K. The adsorption enthalpy of hydrogen for MIL-101 and ITIM-1 (MIL-101Fe) at zero coverage was calculated for a wide temperature range of

Dan Lupu; Ovidiu Ardelean; Gabriela Blanita; Gheorghe Borodi; Mihaela D. Lazar; Alexandru R. Biris; Coldea Ioan; Maria Mihet; Ioan Misan; Gabriel Popeneciu

2011-01-01

315

Cold three-body collisions in hydrogen-hydrogen-alkali-metal atomic systems  

SciTech Connect

We have studied hydrogen-hydrogen-alkali three-body systems in the adiabatic hyperspherical representation. For the spin-stretched case, there exists a single XH molecular state when X is one of the bosonic alkali atoms: {sup 7}Li, {sup 23}Na, {sup 39}K, {sup 87}Rb, or {sup 133}Cs. As a result, the only recombination process is the one that leads to formation of XH molecules, H+H+X{yields}XH+H, and such molecules will be stable against vibrational relaxation. We have calculated the collision rates for recombination and collision-induced dissociation as well as the elastic cross sections for H+XH collisions up to a temperature of 0.5 K, including the partial wave contributions from J{sup {Pi}=}0{sup +} to 5{sup -}. We have also found that there is just one three-body bound state for such systems for J{sup {Pi}=}0{sup +} and no bound states for higher angular momenta.

Wang Yujun; Esry, B. D. [Department of Physics, Kansas State University, Manhattan, Kansas, 66506 (United States); D'Incao, J. P. [JILA, University of Colorado and NIST, Boulder, Colorado, 80309-0440 (United States)

2011-03-15

316

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

317

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

318

The Origin of BC7 Sheet Metallicity and the Tuning of its Electronic Properties by Hydrogenation  

NASA Astrophysics Data System (ADS)

Using first-principles calculations, we investigate the structural, electronic and hydrogenated properties of the hexagonal BC7 sheet. The computed energy bands and density of states indicate that the BC7 sheet is a metal, and its metallicity mainly originates from the non-bonding pz electrons of the diagonal carbon of the B atom. When these carbon atoms are fully passivated by H atoms, the BC7 sheet becomes a semiconductor with a band gap of 2.41 eV. Our studies demonstrate that changing both the proportion of the boron atoms in the boron carbon sheet and its hydrogenation can tune the electronic properties of boron carbon two-dimensional material.

Lei, Xue-Ling; Liu, Gang; Wu, Mu-Sheng; Xu, Bo; Ouyang, Chu-Ying; Pan, Bi-Cai

2013-06-01

319

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

SciTech Connect

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

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

2006-01-01

320

Passivation of impurities in semiconductors by hydrogen and light metal ions  

NASA Astrophysics Data System (ADS)

Books as well as numerous articles have been written about hydrogen passivation in classical semiconductors such as Si and GaAs. The subject has gained a renewed interest recently since hydrogen is widely considered to saturate the hole conductivity of the wide bandgap semiconductors GaN and ZnSe which are currently most promising for blue light emitting devices. Other group-I impurities are capable of compensating the electrical conductivity of semiconductors both through directly neutralising (passivating) the impurity or providing space charge of polarity opposite to that of the dominating one. The paper reviews the similarities and differences between hydrogen and its light metallic neighbour in the periodic table, lithium. Also we provide a comparison with the heavier interstitial copper which is known for its ability to passivate shallow acceptors. Finally fundamental differences between shallow-level and deep level passivation will be addressed.

Gislason, Hafliði P.

1997-01-01

321

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

NASA Astrophysics Data System (ADS)

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

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

2006-09-01

322

Prospects for the development of non-noble metal catalysts for hydrogen-air fuel cells  

Microsoft Academic Search

The purpose of this report is to review the literature on the electrocatalysis of hydrogen-air fuel cells in order to determine the prospects for replacing Pt in transportation fuel cells and to suggest research directions which might lead to the development of non-Pt (more generally, non-noble metal) catalysts. The study is restricted to catalysts for the air electrode with an

P. N. Ross Jr.; F. T. Wagner

1982-01-01

323

Properties of the superconducting state in molecular metallic hydrogen under pressure at 347 GPa  

Microsoft Academic Search

The thermodynamic properties of the superconducting state induced in metallic molecular hydrogen under the influence of pressure 347GPa were determined. In particular, it has been shown that the critical temperature (TC) changes in the range from 120 to 90K for ????0.08,0.15?, where ?? is the value of the Coulomb pseudopotential. Next, the energy gap near the temperature of zero Kelvin

M. W. Jarosik

2011-01-01

324

Random-Phase-Approximation Correlation Energy in Metallic Hydrogen Using Hartree-Fock Bloch Functions  

Microsoft Academic Search

Correlation energies for simple-cubic metallic hydrogen are calculated using random-phase-approximation (RPA) methods. Hartree-Fock Bloch functions for the real lattice, including those for excited bands, were used as zeroth-order states. About 60% of the RPA correlation energy originates from intraband excitations. The RPA correlation energy, including exchange, is estimated to be about - 0.024 hartree\\/electron near the Hartree-Fock equilibrium, leading to

Hendrik J. Monkhorst; Jens Oddershede

1973-01-01

325

Two-component Fermi-liquid theory: Transport properties of liquid metallic hydrogen  

Microsoft Academic Search

We have examined the elementary transport properties of a two-charged-component normal Fermi liquid using a generalized Landau-Silin-Boltzmann-equation approach. ''Exact'' expressions involving the phenomenologically treated quasiparticle scattering amplitudes are given for the low-temperature electrical and thermal conductivities, viscosity, and spin-diffusion constants. The results are applied to the case of a possible low-temperature normal liquid metallic phase of hydrogen, i.e., interpenetrating electron

J. Oliva; N. W. Ashcroft

1982-01-01

326

Specific heat and thermodynamic critical field for the molecular metallic hydrogen  

Microsoft Academic Search

In the framework of Eliashberg approach, the free energy difference between the superconducting and normal state for the molecular metallic hydrogen was calculated. The pressure values p1=347GPa and p2=428GPa were taken into consideration. It has been shown that the specific heat's jump at the critical temperature and the thermodynamic critical field near zero Kelvin grow with the pressure: [?C(TC)]p2\\/[?C(TC)]p1?2.33 and

M. W. Jarosik

2011-01-01

327

Electrical conductivity of metallic hydrogen in the nearly-free-electron model  

Microsoft Academic Search

The electrical resistivity of metallic hydrogen has been calculated. To do this, the perturbation theory in terms of electron-proton\\u000a interaction for the reciprocal relaxation time characterizing the electrical conductivity has been employed. The second-and\\u000a third-order terms as well as an approximate expression for the series sum have been calculated in detail. In doing so, the\\u000a random-phase approximation with allowance for

V. T. Shvets

2007-01-01

328

Structural study of peroxopolytungstic acid prepared from metallic tungsten and hydrogen peroxide  

Microsoft Academic Search

The structure of peroxotungstic acid (W-PTA) prepared from metallic W and aqueous H2O2 was investigated based on Raman, IR, and XRD analyses. W-PTA was an amorphous compound constructed of peroxo polytungstate anions, in which the anions were bound to each other through hydrogen bonding. RDF analyses suggested that the polyanion was W12O38(O2)16-6, in which a six-membered ring of corner-shared polyhedra,

Tokuro Nanba; Sanae Takano; Itaru Yasui; Tetsuichi Kudo

1991-01-01

329

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

Microsoft Academic Search

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

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

2008-01-01

330

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

Microsoft Academic Search

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

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

2009-01-01

331

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

Microsoft Academic Search

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

Savidha Ramachandran; Jang-Hoon Ha; Do Kyung Kim

2007-01-01

332

A quantitative investigation of hydrogen in the metal-oxide-silicon system using NRA  

Microsoft Academic Search

The present state of development in the application of resonant nuclear reaction analysis to the direct measurement of hydrogen concentration profiles throughout the metal-oxide-silicon system is presented. Detection limits of less than 1018 cm-3 (1012 cm-2) as well as a depth resolution of better than 10 nm are obtained. Limitations of the technique in the study of changes in the

Michael A. Briere; Dietrich Braeunig; Braunig

1990-01-01

333

Noble metal catalyzed hydrogen generation from formic acid in nitrite-containing simulated nuclear waste media  

Microsoft Academic Search

Simulants for the Hanford Waste Vitrification Plant (HWVP) feed containing the major non-radioactive components Al, Cd, Fe, Mn, Nd, Ni, Si, Zr, Na, COâ²⁻, NOâ-, and NOâ- were used as media to evaluate the stability of formic acid towards hydrogen evolution by the reaction HCOâH â Hâ + COâ catalyzed by the noble metals Ru, Rh, and\\/or Pd found in

R. B. King; N. K. Bhattacharyya; K. D. Wiemers

1994-01-01

334

Hydrogen bond-promoted metallic state in a purely organic single-component conductor under pressure.  

PubMed

Purely organic materials are generally insulating. Some charge-carrier generation, however, can provide them with electrical conductivity. In multi-component organic systems, carrier generation by intermolecular charge transfer has given many molecular metals. By contrast, in purely organic single-component systems, metallic states have rarely been realized although some neutral-radical semiconductors have been reported. Here we uncover a new type of purely organic single-component molecular conductor by utilizing strong hydrogen-bonding interactions between tetrathiafulvalene-based electron-donor molecules. These conductors are composed of highly symmetric molecular units constructed by the strong intra-unit hydrogen bond. Moreover, we demonstrate that, in this system, charge carriers are produced by the partial oxidation of the donor molecules and delocalized through the formation of the symmetric intra-unit hydrogen bonds. As a result, our conductors show the highest room-temperature electrical conductivity and the metallic state under the lowest physical pressure among the purely organic single-component systems, to our knowledge. PMID:23299894

Isono, Takayuki; Kamo, Hiromichi; Ueda, Akira; Takahashi, Kazuyuki; Nakao, Akiko; Kumai, Reiji; Nakao, Hironori; Kobayashi, Kensuke; Murakami, Youichi; Mori, Hatsumi

2013-01-01

335

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

336

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

NASA Astrophysics Data System (ADS)

The rare-earth hydrogen systems present phase diagrams with rather extended solid solution (?-RHx) and dihydride (?-RH2+x) regions, leading eventually - for high-enough concentrations and low-enough temperatures - to ordering interactions between the /x-hydrogens. In the case of magnetic rare earths, this gives rise to a multitude of fascinating phenomena caused by the competition between magnetic anisotropy and RKKY interactions on the one hand and the hydrogen sublattice (via the crystal field) on the other. Thus, the peculiar quasi-unidimensional chains of H-H pairs formed along the /c-axis in the ?-phase of some of the HCP rare earths (?*-RHx) affect different types of magnetic ordering in very different ways. This is demonstrated through the interactions with the conical ferromagnetism of Er on the one hand and the /c-axis-oriented 3-4 ferrimagnetism of Tm on the other, as well as with their /c-axis-modulated sinusoidal magnetism. A possible interpretation of the H-H chain configuration through a charge-density-wave mechanism is suggested from recent experiments on hydrogen interaction with the helical magnetism in the YyTb1-yHx alloy system. In the case of the ?-RH2+x phase, the excess /x-hydrogens occupying the octahedral sites of the CaF2-type dihydride lattice often order in a tetragonal sublattice of DO22 symmetry corresponding to an RH2.25 stoichiometry. This strongly modifies the various commensurate and incommensurate magnetic structures present, sometimes leading to their complete vanishing or to the appearance of short-range order. Examples using neutron scattering and resistivity data from the systems RH(D)2+x, with R=Ce, Tb, and Ho, shall be given as illustration. Finally, recent preliminary results from Los Alamos show that the cubic actinide hydrides AH2+x (A=Np, Pu, Am) exhibit very similar ordering phenomena, opening the door to large possibilities for magneto-structural interactions within the group of 5f-metals.

Vajda, P.

2000-08-01

337

Transition Metal Activation and Functionalization of Carbon-Hydrogen Bonds: Progress Report, December 1, 1988-November 30, 1989.  

National Technical Information Service (NTIS)

This project is directed toward the continued investigation of the fundamental thermodynamic and kinetic factors that influence carbon-hydrogen bond activation at homogeneous transition metal centers. The project is also directed toward the conversion of ...

W. D. Jones

1989-01-01

338

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

339

Structures and Potential Superconductivity in SiH4 at High Pressure: En Route to ``Metallic Hydrogen''  

Microsoft Academic Search

A way to circumvent the high pressures needed to metallize hydrogen is to ``precompress'' it in hydrogen-rich molecules, a strategy probed theoretically for silane. We show that phases with tetrahedral SiH4 molecules should undergo phase transitions with sixfold- and eightfold-coordinate Si appearing above 25 GPa. The most stable structure found can be metallized at under a megabar and at a

Ji Feng; Wojciech Grochala; Tomasz Jaron; Roald Hoffmann; Aitor Bergara; N. W. Ashcroft

2006-01-01

340

Catalytic activities of non-noble metals for hydrogen generation from aqueous ammonia–borane at room temperature  

Microsoft Academic Search

We have studied catalytic performance of supported non-noble metals for hydrogen generation from aqueous NH3BH3 at room temperature. Among the tested non-noble metals, supported Co, Ni and Cu are the most catalytically active, with which hydrogen is released with an almost stoichiometric amount from aqueous NH3BH3, whereas supported Fe is catalytically inactive for this reaction. Support effects on the catalytic

Qiang Xu; Manish Chandra

2006-01-01

341

Hydrogen  

NSDL National Science Digital Library

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

Project, Iowa P.

2004-01-01

342

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

PubMed

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

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

2013-06-27

343

Hydrogen-bond-directing effect in the ionothermal synthesis of metal coordination polymers.  

PubMed

Four new cobalt coordination polymers, (EMIm)[Co2(TMA-H)2(44bpy)3]Br 1, (EMIm)[Co(TMA-H)(44bpy)2](44bpy)Br 2, (EMIm)[Co(TMA)(Im-H)]3 and (EMIm)2[Co(TMA)2(TED-H2)] 4, were prepared from 1-ethyl-3-methyl imidazolium bromide (EMIm-Br). All the compounds have similar two-dimensional cobalt trimesate (TMA) coordination layers but different three-dimensional supramolecular architectures that contain one of three potentially ditopic amines, 4,4'-bipyridine (44bpy), imidazole (Im-H) and triethylenediamine (TED). Two-fold interpenetration of hydrogen-bonding networks was found for 1, 2 and 4. The coordination layers of 1 and 2 are neutral while 3 and 4 have anionic molecular assemblies. The use of organic amines, that act as supramolecular bridging ligands, introduces hydrogen-bond-directing effects in the ionothermal synthesis of metal coordination polymers. Hydrogen bonding helps to align the packing between the coordination layers and control the formation of 3D supramolecular networks. In 1, hydrogen bonds between the ionic species within the channels direct the alignment of non-directional electrostatic interactions between EMIm+ and Br(-) ions, which is a rare case of a hydrogen-bond-templating effect of ionic liquids in ionothermal synthesis. PMID:18648702

Lin, Zhuojia; Li, Yang; Slawin, Alexandra M Z; Morris, Russell E

2008-06-06

344

Metallization degree of hydrogen at a pressure of 1.4 Mbar and a temperature a 3000 K  

Microsoft Academic Search

The electrical resistivity of liquid metallic hydrogen at a temperature of 3000 K and a density of 0.35 mol\\/cm3 is calculated. Hydrogen is considered as a three-component system consisting of electrons, protons, and neutral hydrogen\\u000a atoms. The second order of perturbation theory in electron-proton and electron-atom interactions is used to determine the\\u000a inverse relaxation time for electric conductivity. The Coulomb

V. T. Shvets; A. S. Vlasenko; A. D. Bukhanenko

2007-01-01

345

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

2012-09-27

346

High-Density Hydrogen Storage and Lithium Super-Ionic Conduction in Metal Borohydrides  

NASA Astrophysics Data System (ADS)

Development of high-density hydrogen storage materials is a critical issue for fuel cell technologies. Candidates for the materials are metal borohydrides, (M(BH4)n with M = Li, Na, K, Cu, Mg, Mn, Zn, Sc, Ti, Y, Zr, and Hf; n = 1-4). The thermodynamical stabilities of the metal borohydrides were systematically investigated by using both the first-principles studies and hydrogen desorption measurements. Then, the Pauling electronegativity of M was found to be an indispensable indicator for appropriately producing/designing the metal borohydrides, including multi-cation (for example; Li-Zr and Li-K) systems. It was also discovered that the electrical conductivity of lithium borohydride, LiBH4, drastically jumped by three orders of magnitude due to the structural transition. The hexagonal phase above 388 K exhibited a high electrical conductivity of the order of 10-3 S/cm, lithium super(fast)-ionic conduction. The hexagonal phase of LiBH4 can be thermodynamically stabilized by anion substitutions even at room temperature. Therefore, some of the metal borohydrides (and their multi-anion systems) might be new candidates also for solid-electrolytes.

Orimo, Shin-Ichi

2010-03-01

347

Complex compounds of platinum metals as catalysts for hydrogen revolution and possibilities for their joint determination  

SciTech Connect

The authors have previously published data on the mechanism giving rise to hydrogen catalytic currents (HCCs) in solutions of complexes of metals from the first transition series with organic ligands. Recently highly sensitive methods have been described for determination of Pt and Rh, Ru and Rh, and Os and Pt from HCCs using various reagents. Yet alongside the search for new catalytically active systems there remains the important problem of the mechanism of HCCs involving complexes of platinum metals especially with respect to the nature of the catalyst and the oxidation state of the central ion. Knowledge of the elementary acts in such a complex process as catalytic evolution of hydrogen makes it possible to form judgements on the overall pattern and details of individual stages of electron transfer and the reactivity of intermediates in order to make a rational choice of optimum conditions for a maximum analytical signal. This communication is intended to systematize processes causing HCCs arising during reduction at a dropping-mercury electrode (d.m.e.) of complexes of platinum metals with nitrogen- and sulfur-containing ligands such as dithiocarbamates (DTCs), xanthogenates (SGs), 8-mercaptoquinoline and its derivatives (MOs), 2-mercaptobenzthiazole (MBT), and 3-mercaptobenzimidazole (MBI) and to establish selective methods for analysis of materials containing platinum metals. 18 refs., 2 figs., 1 tab.

Medyantseva, E.P.; Budnikov, G.K.; Romanova, O.N. [Kazan State Univ. (Russian Federation)

1992-04-10

348

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

349

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

PubMed Central

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

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

2013-01-01

350

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

PubMed

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

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

2013-09-13

351

Galvanic Corrosion Suppression of High-k/Metal Gates Using Organic Solvent-Based Hydrogen Fluoride  

NASA Astrophysics Data System (ADS)

Achieving high-performance and low-stand-by-power applications requires the integration of new metal gate materials and high-k dielectrics into LSI devices with the 45 nm technology node and beyond. The wet processes used for high-k removal involve a risk of enhanced galvanic corrosion at the gate electrode level. In this study, we investigated the galvanic corrosion between polycrystalline silicon (poly-Si) and metal in gate electrodes using organic solvents with hydrogen fluoride (HF). We succeeded in suppressing the corrosion of metal gates using a mixture of HF and isopropyl alcohol (IPA) with high selectivity for high-k/SiO2 in the front-end-of-line (FEOL) process for the fabrication of next-generation devices.

Watanabe, Daisuke; Aoki, Hidemitsu; Hotta, Saori; Kimura, Chiharu; Sugino, Takashi

2008-04-01

352

Intestinal permeability.  

PubMed Central

Damage to the mucosal barrier may be assessed, non-invasively by use of sugar probes, which permeate through the transcellular or paracellular (tight junction) routes. A standardised test, with analysis of a five hour urine collection has proved useful in studying the sequelae of non-steroid anti-inflammatory drug (NSAID) administration, untreated coeliac disease, and enteric infections. Choice of probe molecule is crucial and lactulose/l-rhamnose seem to be satisfactory, in contrast with polyethylene glycol. Significant correlations have been seen between permeability and plasma IgA concentrates in nephropathy, and between permeability and the passage of neutrophil chemotactic agents. The increased permeability associated with NSAID treatment may relate to the adverse effects of NSAIDs on enterocyte mitochondrial morphology and metabolism. These two factors may predispose the mucosa to permeation of bacterial chemoattractant molecules that elaborate a local inflammatory response. A similar mechanism may operate in patients with untreated Crohn's disease, who show abnormally high permeability. Remission induced by treatment with elemental diets coincides with a reduction in permeability. The period to relapse correlated with the inability of patients to maintain low permeability to sugar probes. These results suggest a mechanism for the benefits of elemental enteral nutrients in the treatment of Crohn's disease.

Bjarnason, I

1994-01-01

353

Theoretical Modeling of Hydrogen Bonded and Metal-Ligand Associating Polymers  

NASA Astrophysics Data System (ADS)

Applying analytical modeling in combination with Monte Carlo simulations we have studied the association behavior and properties of two types of supramolecular polymers employing 1) hydrogen bonded and 2) metal-ligand associative motifs. In the first case association between the hydrogen bonded arrays results in numerous donor-acceptor interactions between the complementary end groups of linear oligomers leading primarily to formation of linear chains or rings. Similar architectures of self-assembled polymers can also be obtained by reversible 1:2 complex formation between metal ions (such as Zn(+2), Cd(+2), Co (+2), etc.) and ligands of end-functionalized oligomers. In this case the association is strongly influenced by metal- ligand ratio. We analyze the chain-ring equilibrium and study the influence of the strength and type of association, rigidity of the complex and solution composition on the degree of association and the average molecular weight of the supramolecular polymers. For metal ions (such as La(+3), Nd(+3), Eu(+3), etc) capable of 1:3 complex formation with the ligands, self-assembly results in reversible polymers of more complex architecture, in particular a reversible network (in the percolation limit). Since the coordination sites of the metal possess unequal reactivity (having different energies of association with the first, second and third ligand) and due to the cooperativity of binding, network formation is influenced by different factors such as metal/ligand ratio, oligomer length and concentration. Predictions of an analytical model based on the equilibrium among different associating species and classical percolation theory compare favorably with simulation results for gel fraction and average molecular weight. Simulation results and theoretical predictions will be compared with available experimental data.

Dormidontova, Elena

2006-03-01

354

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

SciTech Connect

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

Sapru, K.

1998-12-04

355

Catalytic activity of transition metal borides in the oxidation of hydrogen  

SciTech Connect

The specific catalytic activity of transition metal borides in the oxidation of hydrogen at 593/sup 0/K in excess O/sub 2/ decreases in the series: Ni/sub 2/B > Mo/sub 2/B/sub 5/ > W/sub 2/B/sub 5/ > VB/sub 2/ > CrB/sub 2/ > TaB/sub 2/ > NbB/sub 2/, ZrB/sub 2/ > TiB/sub 2/ >> Co/sub 3/B, HfB/sub 2/. The reaction rate is a function of the rate of the reaction of H/sub 2/ with adsorbed oxygen ZO and decreases with decreasing Z-O bond energy. A higher rate is found in the case of excess H/sub 2/ (Ni/sub 2/B > Co/sub 3/B > ZrB/sub 2/ > VB/sub 2/ > W/sub 2/B/sub 5/, HfB/sub 2/ > Mo/sub 2/B/sub 5/ > TaB/sub 2/ > CrB/sub 2/ > TiB/sub 2/, NbB/sub 2/) as a result of the participation of dissociatively adsorbed hydrogen. The rates of hydrogen oxidation on metal-like borides and carbides were compared and the differences found were explained.

Vlasenko, N.V.; Il'chenko, N.I.; Golodets, G.I.

1987-05-01

356

The role of partial crystallinity on hydrogen permeation in Fe–Ni–B–Mo based metallic glass membranes  

Microsoft Academic Search

A potentially exciting material for membrane separations are metallic glass materials due to their low cost, high elastic toughness and resistance to hydrogen embrittlement as compared to crystalline Pd-based membrane systems. However, at elevated temperatures and extended operation times structural changes including partial crystallinity may appear in these amorphous metallic systems. This study reports on the investigation of time and

Kyle Brinkman; Elise Fox; Paul Korinko; David Missimer; Thad Adams; Dong Su

2011-01-01

357

Metal-support effects on the intramolecular selectivity of crotonaldehyde hydrogenation over platinum  

SciTech Connect

The vapor-phase hydrogenation of crotonaldehyde (CROALD) was studied at low temperature and low conversions over Pt powder and Pt dispersed on SiO{sub 2}, {eta}-Al{sub 2}O{sub 3}, and TiO{sub 2} after either a high- or a low-temperature reduction, HTR and LTR, respectively. The hydrogenation of butyraldehyde (BUTALD) and crotyl alcohol (CROALC) to butanol (BUTNOL) and the isomerization of CROALC to BUTALD were also investigated to obtain additional information about this network of reactions. The typical Pt catalysts produced 100% BUTALD. However, the TiO{sub 2}-supported Pt produced both CROALC and BUTNOL, and the best catalyst, (HTR) Pt/TiO{sub 2}, gave a selectivity of 37% CROALC with no BUTNOL formation. The turnover frequencies on the (HTR) Pt/TiO{sub 2} samples, based on sites counted by hydrogen chemisorption near reaction temperatures, were more than an order of magnitude higher than the catalysts displaying normal adsorption behavior. Activation energies were somewhat higher on the Pt/TiO{sub 2} catalysts, however. This behavior is very similar to that observed previously for CO and acetone hydrogenation over these same catalysts, and it is consistent with the proposal that sites created at the Pt-titania interface are responsible for the activation of carbonyl bonds. Previous studies of liquid-phase hydrogenation of CROALD and other molecules with conjugated C{double bond}C and C{double bond}O double bonds support this model and indicate that a 1,4 diadsorbed species, rather than 1,2 and 3,4 diadsorbed species (counting the oxygen atom as 1), is formed in polar solvents. By analogy, defect sites on the titania at the metal-support interface may interact with the O atom, polarize the C{double bond}O bond, and favor this intermediate which can react with hydrogen to give CROALC. 48 refs.

Vannic, M.A.; Sen, B. (Pennsylvania State Univ., University Park (USA))

1989-01-01

358

The action of certain antibiotics on mitochondrial, erythrocyte and artificial phospholipid membranes. The role of induced proton permeability  

PubMed Central

1. The action of the antibiotics enniatin A, valinomycin, the actin homologues, gramicidin, nigericin and dianemycin on mitochondria, erythrocytes and smectic mesophases of lecithin–dicetyl hydrogen phosphate was studied. 2. These antibiotics induced permeability to alkali-metal cations on all three membrane systems. 3. The ion specificity on each membrane system was the same. 4. Enniatin A, valinomycin and the actins did not induce permeability to protons, whereas nigericin and dianemycin rendered all three membrane systems freely permeable to protons. 5. Several differences were noted between permeability induced by nigericin and that induced by gramicidin. 6. The action of all these antibiotics on mitochondrial respiration could be accounted for by changes in passive ion permeability of the mitochondrial membrane similar to those induced in erythrocytes and phospholipid membranes, if it is assumed that a membrane potential is present in respiring mitochondria.

Henderson, P. J. F.; McGivan, J. D.; Chappell, J. B.

1969-01-01

359

Turning aluminium into a noble-metal-like catalyst for low-temperature activation of molecular hydrogen  

NASA Astrophysics Data System (ADS)

Activation of molecular hydrogen is the first step in producing many important industrial chemicals that have so far required expensive noble-metal catalysts and thermal activation. We demonstrate here that aluminium doped with very small amounts of titanium can activate molecular hydrogen at temperatures as low as 90?K. Using an approach that uses CO as a probe molecule, we identify the atomistic arrangement of the catalytically active sites containing Ti on Al(111) surfaces, combining infrared reflection-absorption spectroscopy and first-principles modelling. CO molecules, selectively adsorbed on catalytically active sites, form a complex with activated hydrogen that is removed at remarkably low temperatures (115?K possibly as a molecule). These results provide the first direct evidence that Ti-doped Al can carry out the essential first step of molecular hydrogen activation under nearly barrierless conditions, thereby challenging the monopoly of noble metals in hydrogen activation.

Chopra, Irinder S.; Chaudhuri, Santanu; Veyan, Jean François; Chabal, Yves J.

2011-11-01

360

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

SciTech Connect

Two detailed, unit-cell models, a transverse fin design and a longitudinal fin design, of a combined hydride bed and heat exchanger are developed in COMSOL{reg_sign} Multiphysics incorporating and accounting for heat transfer and reaction kinetic limitations. MatLab{reg_sign} scripts for autonomous model generation are developed and incorporated into (1) a grid-based and (2) a systematic optimization routine based on the Nelder-Mead downhill simplex method to determine the geometrical parameters that lead to the optimal structure for each fin design that maximizes the hydrogen stored within the hydride. The optimal designs for both the transverse and longitudinal fin designs point toward closely-spaced, small cooling fluid tubes. Under the hydrogen feed conditions studied (50 bar), a 25 times improvement or better in the hydrogen storage kinetics will be required to simultaneously meet the Department of Energy technical targets for gravimetric capacity and fill time. These models and methodology can be rapidly applied to other hydrogen storage materials, such as other metal hydrides or to cryoadsorbents, in future work.

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

2011-07-14

361

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

2012-10-04

362

Hydrogen adsorption measurements and modeling on metal-organic frameworks and single-walled carbon nanotubes.  

PubMed

Hydrogen adsorption measurements on Al-, Cr-, and Zn-based metal-organic frameworks (MOFs) and single-walled carbon nanotubes (SWNTs) are presented. The measurements were performed at temperatures ranging from 77 to 300 K and pressures up to 50 atm using a volumetric approach. The maximum excess adsorption at 77 K ranges from 2.3 to 3.9 wt % for the MOFs and from 1.5 to 2.5 wt % for the SWNTs. These values are reached at pressures below 40 atm. At room temperature and 40 atm, modest amounts of hydrogen are adsorbed (<0.4 wt %). A Dubinin-Astakhov (DA) approach is used to investigate the measured adsorption isotherms and to retrieve energetic and structural parameters. The adsorption enthalpy averaged over filling is about 2.9 kJ/mol for the MOF-5 and about 3.6-4.2 kJ/mol for SWNTs. PMID:17014118

Poirier, E; Chahine, R; Bénard, P; Lafi, L; Dorval-Douville, G; Chandonia, P A

2006-10-10

363

A high-efficiency power cycle in which hydrogen is compressed by absorption in metal hydrides.  

PubMed

A high-efficiency power cycle is proposed in which molecular hydrogen gas is used as a working fluid in a regenerative closed Brayton cycle. The hydrogen gas is compressed by an absorption-desorption cycle on metal hydride (FeTiH(x)) beds. Low-temperature solar or geothermal heat (temperature about 100 degrees C) is used for the compression process, and high-temperature fossil fuel or nuclear heat (temperature about 700 degrees C) supplies the expansion work in the turbine. Typically, about 90 percent of the high-temperature heat input is converted to electricity, while about 3 kilowatts of low-temperature heat is required per kilowatt of electrical output. PMID:17745726

Powell, J R; Salzano, F J; Yu, W S; Milau, J S

1976-07-23

364

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

365

Effect of the nature of platinum group metals on kinetics and selectivity of the hydrogenation of 3-methyl-4-penten-1-yn-3-ol under hydrogen pressure  

SciTech Connect

Considerable theoretical and practical interest is found in the kinetics and selectivity of the hydrogenation of 3-methyl-4-penten-1-yn-3-ol (tertiary acetylenic carbinol C/sub 6/, TAC C/sub 6/). The authors studied the effect of the nature of the metal catalyst on the kinetic features and selectivity of the hydrogenation of TAC C/sub 6/. The hydrogenation of tertiary acetylenic carbinol C/sub 6/ was carried out in the presence of Pt, Pd, Ni, Ru, and Rh blacks in 96% ethanol in a high-pressure system with broad variation of the experimental conditions. In all cases, the reaction rate upon increase in the hydrogen pressure from 1.01 to 10.10 MPa increases and the reaction is close to first-order in hydrogen. In the presence of Pt and Ru blacks and NiR, the hydrogenation of TAC C/sub 6/ is zero-order relative to the substrate and hydrogen pressures 2.02 and 8.08 MPa. The reaction converts from first-order to zero-order relative to the substrate with increasing hydrogen pressure from 2.02 to 8.08 MPa. In the case of rhenium black, the opposite is observed.

Sokol'skii, D.V.; Omarkulov, T.O.; Zhubanova, L.K.; Chernysh, G.P.

1986-11-01

366

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

SciTech Connect

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

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

2005-12-15

367

Universal transition state scaling relations for (de)hydrogenation over transition metals.  

PubMed

We analyse the transition state energies for 249 hydrogenation/dehydrogenation reactions of atoms and simple molecules over close-packed and stepped surfaces and nanoparticles of transition metals using Density Functional Theory. Linear energy scaling relations are observed for the transition state structures leading to transition state scaling relations for all the investigated reactions. With a suitable choice of reference systems the transition state scaling relations form a universality class that can be approximated with one single linear relation describing the entire range of reactions over all types of surfaces and nanoclusters. PMID:21996683

Wang, S; Petzold, V; Tripkovic, V; Kleis, J; Howalt, J G; Skúlason, E; Fernández, E M; Hvolbæk, B; Jones, G; Toftelund, A; Falsig, H; Björketun, M; Studt, F; Abild-Pedersen, F; Rossmeisl, J; Nørskov, J K; Bligaard, T

2011-10-14

368

Unusual hydrogen bonding behavior in binary complexes of coinage metal anions with water  

NASA Astrophysics Data System (ADS)

We have studied the interaction of atomic coinage metal anions with water molecules by infrared photodissociation spectroscopy of M-.H2O.Arn clusters (M=Cu, Ag, Au; n=1, 2). We compare our observations with calculations on density-functional and coupled cluster levels of theory. The gold anion is bound to the water molecule by a single ionic hydrogen bond, similar to the halide-water complexes. In contrast, zero-point motion in the silver and copper complexes leads to a deviation from this motif.

Schneider, Holger; Boese, A. Daniel; Weber, J. Mathias

2005-08-01

369

Theoretical analysis for the heterogeneous decomposition of hydrogen sulfide to hydrogen on an iron-metallic plate in a laminar stagnation-point flow  

NASA Astrophysics Data System (ADS)

In this work, we have theoretically analyzed the conversion process of hydrogen sulfide, H2S, to atomic hydrogen, H0, in a planar stagnation-point flow over an iron-metallic surface. We assume that a binary mixture of hydrogen sulfide and methane composes the laminar stagnation flow. In order to characterize this complex phenomenon with very specific chemical activities on the surface of the metallic plate, we propose a heterogeneous reaction scheme based on four reactions: two electrochemical, one adsorption and an additional exothermic reaction needed to complete the direct conversion of hydrogen sulfide to hydrogen on the surface of the iron. The nondimensional governing equations, which include the mass species and momentum conservation of the mixture and the molecular diffusion of hydrogen into the iron plate, are numerically solved by conventional finite-difference methods. The numerical results show the critical conditions of the H2S decomposition as functions of the involved nondimensional parameters of the present model. In particular, we show parametrically the influence that has the initial concentration of H2S on the surface coverage of the chemical products HS- H+ and H0 derived from the chemical and electrochemical reactions.

Martínez, J. C.; Méndez, F.; Treviño, C.

2006-12-01

370

Binding energies of hydrogen molecules to isoreticular metal-organic framework materials  

NASA Astrophysics Data System (ADS)

Recently, several novel isoreticular metal-organic framework (IRMOF) structures have been fabricated and tested for hydrogen storage applications. To improve our understanding of these materials, and to promote quantitative calculations and simulations, the binding energies of hydrogen molecules to the MOF have been studied. High-quality second-order Møller-Plesset (MP2) calculations using the resolution of the identity approximation and the quadruple zeta QZVPP basis set were used. These calculations use terminated molecular fragments from the MOF materials. For H2 on the zinc oxide corners, the MP2 binding energy using Zn4O(HCO2)6 molecule is 6.28 kJ/mol. For H2 on the linkers, the binding energy is calculated using lithium-terminated molecular fragments. The MP2 results with coupled-cluster singles and doubles and noniterative triples method corrections and charge-transfer corrections are 4.16 kJ/mol for IRMOF-1, 4.72 kJ/mol for IRMOF-3, 4.86 kJ/mol for IRMOF-6, 4.54 kJ/mol for IRMOF-8, 5.50 and 4.90 kJ/mol for IRMOF-12, 4.87 and 4.84 kJ/mol for IRMOF-14, 5.42 kJ/mol for IRMOF-18, and 4.97 and 4.66 kJ/mol for IRMOF-993. The larger linkers are all able to bind multiple hydrogen molecules per side. The linkers of IRMOF-12, IRMOF-993, and IRMOF-14 can bind two to three, three, and four hydrogen molecules per side, respectively. In general, the larger linkers have the largest binding energies, and, together with the enhanced surface area available for binding, will provide increased hydrogen storage. We also find that adding up NH2 or CH3 groups to each linker can provide up to a 33% increase in the binding energy.

Sagara, Tatsuhiko; Klassen, James; Ortony, Julia; Ganz, Eric

2005-07-01

371

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

Microsoft Academic Search

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

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

2009-01-01

372

Nonprecious-metal-assisted photochemical hydrogen production from ortho-phenylenediamine.  

PubMed

The combination of o-phenylenediamine (opda), which possesses two proton- and electron-pooling capability, with Fe(II) leads to the photochemical hydrogen-evolution reaction (HER) in THF at room temperature without addition of photosensitizers. From the THF solution, the tris(o-phenylenediamine) iron(II) complex, [Fe(II)(opda)3](ClO4)2 (1), was isolated as a photoactive species, while the deprotonated oxidized species was characterized by X-ray crystallographic analysis, electrospray ionization mass spectrometry, and UV-vis NIR spectra. Furthermore, the HER is photocatalyzed by hydroquinone, which serves as a H(+)/e(-) donor. The present work demonstrates that the use of a metal-bound aromatic amine as a H(+)/e(-) pooler opens an alternative strategy for designing nonprecious-metal-based molecular photochemical H2 production/storage materials. PMID:23544498

Matsumoto, Takeshi; Chang, Ho-Chol; Wakizaka, Masanori; Ueno, Sho; Kobayashi, Atsushi; Nakayama, Akira; Taketsugu, Tetsuya; Kato, Masako

2013-04-12

373

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

PubMed Central

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

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

2012-01-01

374

A systematic DFT study of hydrogen diffusion on transition metal surfaces  

NASA Astrophysics Data System (ADS)

Density functional theory calculations of the diffusion of hydrogen atoms on 23 transition metal surfaces in their closed-packed structure have been carried out. The d-metals chosen are all the metals in the 4th, 5th and 6th periods, from Sc to Au, except Mn, Tc, and Hf. Potential energy surfaces of H atom on these metals are constructed and the diffusion barrier from one minima to another is compared with nudged elastic band calculations. Most of the minimum energy paths have a single activation barrier, except on two surfaces where a dip in the bridge position (W and Pt) is observed. Trends in the adsorption and activation energies are observed where the former is explained with the d-band model. All the activation energies for diffusion are relatively low, or from 0.04 eV for Pt to 0.28 eV on Y and Zr. Finally, we estimate the temperature where tunneling effects should start to take place.

Kristinsdóttir, Lilja; Skúlason, Egill

2012-09-01

375

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

PubMed

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

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

2004-04-13

376

Process for producing hydrogen and carbonyl sulfide from hydrogen sulfide and carbon monoxide using a heteropolyanionic metal complex catalyst  

SciTech Connect

Hydrogen and carbonyl sulfide are produced by a process comprising contracting gaseous hydrogen sulfide with gaseous carbon monoxide in the presence of a heteropolymolybdate or tungstate complex. Use of these catalysts reduce the amount of by-product carbon dioxide and methane formation and thus enhance the make of hydrogen and carbonyl sulfide.

Kuch, Ph. L.

1984-12-18

377

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

378

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

SciTech Connect

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

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

2005-09-01

379

Evaluation of hydrogen content in metallic samples by neutron computed tomography  

SciTech Connect

Neutron radiography is currently a well-known technique, which is employed for non-destructive testing in a number of industrial and environmental applications. Originally developed for reactor fuel examinations, it is now effective in detecting small amounts of corrosion and infiltrations of hydrogen or light materials within thick metallic structures due to the particular behavior of total neutron cross sections. Nevertheless, improvements related to the development of tomographic systems, which allow far better imaging performances, have been achieved only in the last few years, as a consequence, primarily, of the production of large, charge coupled device (CCD) arrays. Nowadays, neutron computed tomography is the technique most suited for the study of the distribution of hydrogen within metallic matrices. In this field, a series of experimental tests were carried out employing a set of nickel samples containing a H{sub 2}O-D{sub 2}O solution in known percentages. It was possible, therefore, to obtain a calibration curve for the total neutron cross section vs. gray level in the reconstructed image.

Zanarini, M.; Chirco, P.; Rossi, M. [Univ. di Bologna (Italy). Dipt. di Fisica]|[I.N.F.N., Bologna (Italy)] [and others

1995-08-01

380

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

SciTech Connect

A dissimilatory metal- and sulfur-reducing microorganism was isolated from surface sediments of a hydrocarbon-contaminated ditch in Norman, Oklahoma. 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 PP[sub i], 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, isobutryate, 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. 46 refs., 8 figs., 1 tab.

Caccavo, F. Jr.; McInerney, M.J. (Univ. of Oklahoma, Norman, OK (United States)); Lonergan, D.J.; Lovley, D.R.; Stolz, J.F. (Duquesne Univ., Pittsburgh, PA (United States)); Davis, M. (Geological Survey, Reston, VA (United States))

1994-10-01

381

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

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

1994-01-01

382

Significant reduction of the internuclear potential in superconductive solid metallic hydrogen  

NASA Astrophysics Data System (ADS)

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

Shibata, Kazunori; Kodama, Ryosuke

2008-02-01

383

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

SciTech Connect

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

Rodriguez J. A.; Illas, F.

2012-01-01

384

Porous, sintered metal filter recovers 100% of catalyst in HâOâ process  

Microsoft Academic Search

Recovery of catalyst and prevention of catalyst from entering the oxidizer were plant problems for the Interox America process for production of HâOâ by the catalyzed alternative hydrogenation and oxidation of anthraquinone. A porous metal filter element was inserted in the filter unit following the hydrogenation stage to collect the catalyst which forms a permeable cake that is recovered by

G. L. Hall; M. Isaacs

1982-01-01

385

Li-decorated metal-organic framework 5: A route to achieving a suitable hydrogen storage medium  

PubMed Central

A significant improvement in molecular hydrogen uptake properties is revealed by our ab initio calculations for Li-decorated metal–organic framework 5. We have found that two Li atoms are strongly adsorbed on the surfaces of the six-carbon rings, one on each side, carrying a charge of +0.9e per Li atom. Each Li can cluster three H2 molecules around itself with a binding energy of 12 kJ (mol H2)?1. Furthermore, we show from ab initio molecular dynamics simulations with a hydrogen loading of 18 H2 per formula unit that a hydrogen uptake of 2.9 wt % at 200 K and 2.0 wt % at 300 K is achievable. To our knowledge, this is the highest hydrogen storage capacity reported for metal–organic framework 5 under such thermodynamic conditions.

Blomqvist, A.; Araujo, C. Moyses; Srepusharawoot, P.; Ahuja, R.

2007-01-01

386

Calcium as the Superior Coating Metal in Functionalization of Carbon Fullerenes for High-Capacity Hydrogen Storage  

NASA Astrophysics Data System (ADS)

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 molecular hydrogen attractors. With a hydrogen uptake of >8.4wt% on Ca32C60, Ca is superior to all the recently suggested metal coating elements.

Yoon, Mina; Yang, Shenyuan; Hicke, Christian; Wang, Enge; Geohegan, David; Zhang, Zhenyu

2008-05-01

387

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

388

Enhancing the alkaline hydrogen evolution reaction activity through the bifunctionality of Ni(OH)2/metal catalysts.  

PubMed

Active in alkaline environment: The activity of nickel, silver, and copper catalysts for the electrochemical transformation of water to molecular hydrogen in alkaline solutions was enhanced by modification of the metal surfaces by Ni(OH)(2) (see picture; I = current density and ? = overpotential). The hydrogen evolution reaction rate on a Ni electrode modified by Ni(OH)(2) nanoclusters is about four times higher than on a bare Ni surface. PMID:23129151

Danilovic, N; Subbaraman, Ram; Strmcnik, D; Chang, Kee-Chul; Paulikas, A P; Stamenkovic, V R; Markovic, Nenad M

2012-11-05

389

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

SciTech Connect

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

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

2005-10-14

390

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

SciTech Connect

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

Custelcean, Radu [ORNL; Moyer, Bruce A [ORNL; Hay, Benjamin [ORNL

2005-01-01

391

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

Microsoft Academic Search

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

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

2008-01-01

392

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

Microsoft Academic Search

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

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

2005-01-01

393

Process for the production of hydrogen and carbonyl sulfide from hydrogen sulfide and carbon monoxide using a multi-metal oxide/sulfide catalyst  

SciTech Connect

Hydrogen and carbonyl sulfide are produced by a process comprising contacting gaseous hydrogen sulfide with gaseous carbon monoxide in the presence of a catalytic composition containing an oxide and/or sulfide of at least one of molybdenum, tungsten, iron, chromium and vanadium in combination with at least one promoter metal, e.g. a catalyst of the formula Cs Cu /SUB 0.2/ Zn /SUB 0.5/ Mn /SUB 0.5/ Sn /SUB 2.4/ Mo O /SUB x/ S /SUB y/ .

Jevnikar, M. G.; Kuch, Ph. L.

1985-02-19

394

Radiative proton-capture reactions of high-Z nuclei in the sun and in liquid-metallic hydrogen  

NASA Astrophysics Data System (ADS)

Thermonuclear and pycnonuclear reaction rates and enhancement factors of radiative proton captures of high-Z nuclei as well as those of p-p and p-d reactions are evaluated for the solar interior and in dense liquid-metallic hydrogen. It is predicted that proton capture of nuclei such as 12C, 14N, 16O, and 19F may take place at considerably high rates owing to strong screening by K-shell electrons, if the density of metallic hydrogen exceeds ~70 g/cm3 and the temperature remains just above solidification.

Ichimaru, S.

2000-02-01

395

Permeability of some fat products to moisture  

Microsoft Academic Search

Summary  Films of cocoa butter, highly hydrogenated cottonseed oil, mixtures of highly hydrogenated cottonseed oil and cottonseed oil,\\u000a chocolate liquor, and sweet milk chocolate were prepared; and their permeability to water vapor was determined by the cup\\u000a method. The permeability constant was calculated in terms of grams of water diffusing through a centimeter cube in one second\\u000a under a vapor pressure

Werner Landmann; N. V. Lovegren; R. O. Feuge

1960-01-01

396

Selective adsorption of metal-phthalocyanine on Au(111) surface with hydrogen atoms  

NASA Astrophysics Data System (ADS)

Metal phthalocyanine (MPc, M = Mn, Fe) molecules grown on reconstructed Au(111) with and without hydrogen atoms at submonolayer coverage are investigated by low temperature scanning tunneling microscopy. It is found out that the attachment of H atoms to the central metal of the MnPc molecules leads to the change of the molecules' selective adsorption from fcc to hcp regions at low coverage. The two configurations of MnPc molecules on Au(111) are replaced by only one configuration of H-MnPc/Au(111). FePc molecules adsorb on fcc regions of Au(111) with two configurations, which are similar to that of MnPc. However, unlike H-MnPc, H-FePc molecules have two configurations on Au(111). Density function theory calculations show that the different configuration change by attachment of H atoms for MnPc and FePc molecules is due to the electronic structure change at the central metal atoms of the molecules.

Liu, L. W.; Yang, K.; Xiao, W. D.; Jiang, Y. H.; Song, B. Q.; Du, S. X.; Gao, H.-J.

2013-07-01

397

Van der Waals energy of a hydrogen atom placed between two parallel metal plates  

NASA Astrophysics Data System (ADS)

The self-energy of a hydrogen atom placed between two parallel metal plates is calculated. The evaluation, based on the plasmon model for the metal electrons, takes into account the often-neglected dispersion effects of the surface plasmons. Keeping the atom at the center of the gap, the self-energy is obtained as a function of the gap width. We demonstrate that the effect of plasma dispersion can be a significant factor in the determination of self-energy. The plasmon model is known to provide reasonably accurate values for the self-energy when the atom is at sufficiently large distance away from the surface. But the model is not particularly precise when the atom is very close to the surface. Nevertheless, the plasmon model is capable of providing rough estimates for the self-energy for all the separations between the metal plates. Compared to other many-body methods, the advantage of the plasmon model is that it gives the self-energy directly and with minimum of efforts.

Paranjape, V. V.; McNeill, Gary; Panat, P. V.

1999-09-01

398

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

Microsoft Academic Search

The truth about Cats: The metal-oxide interface of a Pd-Rh\\/CeO 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 support leads to a highly active and stable

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

2008-01-01

399

Phosphine-free synthesis of metal chalcogenide quantum dots by means of in situ-generated hydrogen chalcogenides  

Microsoft Academic Search

We proved that various organic solvents react with elemental chalcogens (sulfur and selenium) by liberating hydrogen chalcogenide\\u000a (H2X, X = S, Se) during the phosphine-free hot-matrix synthesis of quantum dots. The in situ-produced H2X reacts further with the metal salt to form the corresponding nanosized metal chalcogenide CdX. The effect of temperature\\u000a on the rate of H2X generation was quantitatively

Georgi G. Yordanov; Hideyuki Yoshimura; Ceco D. Dushkin

2008-01-01

400

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

401

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

2008-07-09

402

The Efficiency of Noble Metals in Reducing the Corrosion Potential in the Primary Coolant Circuits of Boiling Water Reactors Operating under Hydrogen Water Chemistry Operation  

Microsoft Academic Search

In order to promote the effectiveness of hydrogen water chemistry (HWC) and to achieve a more effective reduction in electrochemical corrosion potential (ECP) in the primary coolant circuits of boiling water reactors (BWRs), the technology of noble metal chemical addition (NMCA) was brought into practice about 10 years ago. NMCA aims at enhancing the oxidation of hydrogen on metal surfaces

Tsung-Kuang YEH; Digby D. MACDONALD

2006-01-01

403

Influence of demetallization of hydrogenated sunflower oil on changes in the forms of heavy metals and their pro-oxidative effects.  

PubMed

The effect of removing heavy metals from hydrogenated sunflower oil using a method based on changes in the contents of the various forms of the heavy metals copper, iron, zinc and nickel and their respective pro-oxidative effects was studied. A high degree of removal of dissociated and bounded ions was observed for hydrogenated oil, while there was no change in the contents of the co-ordination form. The pro-oxidative effect of the dissociated ions and of the bound metal ions in hydrogenated oil decreased nine-fold and seven-fold, respectively, compared with that of the non-hydrogenated oil, as a result of which the oxidation stability of hydrogenated oil increased two-fold. Comparative studies confirmed as appropriate the use of wash waters and auxiliary solutions that do not contain heavy metals for the processing of the hydrogenate after the classical technology. PMID:1462710

Ianov, K; Maneva, D; Ivanov, S

1992-11-01

404

Concentration of Hydrogen Peroxide.  

National Technical Information Service (NTIS)

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 perme...

C. F. Parrish

2004-01-01

405

Charge separation technique for metal-oxide-silicon capacitors in the presence of hydrogen deactivated dopants  

SciTech Connect

An improved charge separation technique for metal-oxide-silicon (MOS) capacitors is presented which accounts for the deactivation of substrate dopants by hydrogen at elevated irradiation temperatures or small irradiation biases. Using high-frequency capacitance-voltage measurements, radiation-induced inversion voltage shifts are separated into components due to oxide trapped charge, interface traps, and deactivated dopants, where the latter is computed from a reduction in Si capacitance. In the limit of no radiation-induced dopant deactivation, this approach reduces to the standard midgap charge separation technique used widely for the analysis of room-temperature irradiations. The technique is demonstrated on a p-type MOS capacitor irradiated with {sup 60}Co {gamma} rays at 100 degree sign C and zero bias, where the dopant deactivation is significant.(c) 2000 American Institute of Physics.

Witczak, Steven C. [Sandia National Laboratories, P.O. Box 5800, MS-1083, Albuquerque, New Mexico 87185-1083 (United States); Winokur, Peter S. [Sandia National Laboratories, P.O. Box 5800, MS-1083, Albuquerque, New Mexico 87185-1083 (United States); Lacoe, Ronald C. [The Aerospace Corporation, P.O. Box 92957, M2-244, Los Angeles, California 90009-2957 (United States); Mayer, Donald C. [The Aerospace Corporation, P.O. Box 92957, M2-244, Los Angeles, California 90009-2957 (United States)

2000-06-01

406

Charge separation technique for metal-oxide-silicon capacitors in the presence of hydrogen deactivated dopants  

SciTech Connect

An improved charge separation technique for metal-oxide-silicon (MOS) capacitors is presented which accounts for the deactivation of substrate dopants by hydrogen at elevated irradiation temperatures or small irradiation biases. Using high-frequency capacitance-voltage (C-V) measurements, radiation-induced inversion voltage shifts are separated into components due to oxide trapped charge, interface traps and deactivated dopants, where the latter is computed from a reduction in Si capacitance. In the limit of no radiation-induced dopant deactivation, this approach reduces to the standard midgap charge separation technique used widely for the analysis of room-temperature irradiations. The technique is demonstrated on a p-type MOS capacitor irradiated with {sup 60}Co {gamma}-rays at 100 C and zero bias, where the dopant deactivation is significant.

WITCZAK,STEVEN C.; WINOKUR,PETER S.; LACOE,RONALD C.; MAYER,DONALD C.

2000-02-01

407

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

408

Experimental observation of an atomic hydrogen material with H H bond distance of 150 pm suggesting metallic hydrogen  

Microsoft Academic Search

A phase of hydrogen Rydberg matter (RM) is formed in ultra-high vacuum by desorption of hydrogen from an alkali promoted RM emitter (Holmlid 2002 J. Phys.: Condens. Matter 14 13469). The RM phase is studied by pulsed laser-induced Coulomb explosions which is the best method for detailed studies of the RM clusters. This method gives direct information about the bonding

Shahriar Badiei; Leif Holmlid

2004-01-01

409

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

410

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

NASA Astrophysics Data System (ADS)

We report on the results of the arrangement of isolated surface metallic nanoclusters embedded in amorphous hydrogenated carbon (a-C:H) thin films, studied by photoelectron spectroscopy. As a model system we used gold-containing amorphous hydrogenated carbon (a-C:H/Au), due to the lack of reactivity between carbon and gold. The a-C:H/Au samples are obtained by simultaneous magnetron sputtering of Au target by argon and plasma-enhanced chemical vapor deposition of methane. Photoelectron spectroscopy with x-ray and ultraviolet excitation has been employed for surface studies that comprise as-deposited sample spectra recordings, measurements at off-normal takeoff angle, in situ in-depth profiling by Ar+ ion etching, and thiophene adsorption at the sample surface. The results of these extended studies firmly support previously drawn conclusions [I. R. Videnovi?, V. Thommen, P. Oelhafen, D. Mathys, M. Düggelin, and R. Guggenheim, Appl. Phys. Lett 80, 2863 (2002)] that by deposition on electrically grounded substrates one obtains samples with topmost Au clusters covered with a thin layer of a-C:H. Introducing a dc substrate bias voltage results in bald Au clusters on the surface and increased sp2/sp3 coordinated carbon ratio in the a-C:H matrix.

Videnovi?, Ivan R.; Oelhafen, Peter

2005-04-01

411

Absorption measurements of alkali-metal resonance lines broadened by He and molecular hydrogen collisions  

NASA Astrophysics Data System (ADS)

The optical and near-infrared spectroscopic observations of cool brown dwarfs exhibit very prominent signatures of sodium and potassium resonance lines. The atmospheres of these objects are mainly composed of molecular hydrogen and helium and the collisions of these species with the alkali-metal atoms induce broadening of the K and Na resonance lines by as much as 100 nm either side of the line core. Particularly important are the far line wings, where satellite features which are usually very temperature-sensitive may appear due to extrema in the difference potentials. These features are highly sensitive to pressure and temperature, whereas their position and shape depend critically on the details in the interaction potentials. Accurate line profiles can serve as valuable diagnostics of the physical characteristics of brown dwarfs and extrasolar giant planets. Experimental determinations of the far wings are indispensable in validating the theoretical models. We report here our measurements of the absorption coefficients for pressure broadening in the far wings of the 4s-4p and 4s-5p doublet lines of potassium atoms in the presence of helium and hydrogen gas at temperatures around 900 K. Supported in part by NASA grant NNG06GF06G.

Shindo, F.; Babb, J.; Kirby, K.

2007-06-01

412

Confinement effects in the hydrogen adsorption on paddle wheel containing metal-organic frameworks.  

PubMed

The confinement effects upon hydrogen adsorption in Cu(II)-paddle wheel containing metal-organic frameworks (MOFs) were evaluated and rationalized in terms of the structural properties (cavity types and pore diameters) of PCN-12, HKUST-1, MOF-505, NOTT-103 and NOTT-112. First-principles calculations were employed to identify the strongest adsorption positions at the paddle wheel inorganic building unit (IBU). The adsorption centres due to confinement were located through analysis of 3D occupancy maps obtained from the hydrogen trajectories computed via molecular dynamics simulations. It was found that the confinement enhances the adsorption on the weakest adsorption centres around the IBU in regions close to the narrowest windows and promotes the formation of new adsorption regions into the small cavities. Our results indicate that at low pressure, the high H(2) uptake in these materials is partly due to the presence of small cavities (5.3-8.5 ?) or narrow windows where the long-range contribution to the adsorption becomes important. Conversely, confinement effects in cavities with diameters >12 ? were not observed. PMID:22252608

Gomez, Diego A; Combariza, Aldo F; Sastre, German

2012-01-17

413

Metal-free intramolecular aminofluorination of alkenes mediated by PhI(OPiv)2/hydrogen fluoride-pyridine system.  

PubMed

A convenient, metal-free intramolecular aminofluorination of alkenes has been developed. Employing readily available PhI(OPiv)(2) and hydrogen fluoride-pyridine in the presence of BF(3)·OEt(2), tosyl-protected pent-4-en-1-amines were converted to 3-F-piperidines in one step in good yields as well as high stereoselectivity. PMID:23007735

Wang, Qing; Zhong, Wenhe; Wei, Xiong; Ning, Maoheng; Meng, Xiangbao; Li, Zhongjun

2012-11-21

414

Grafting of polyelectrolytes onto hydrocarbon surfaces by high-energy hydrogen induced cross-linking for making metallized polymer films.  

PubMed

Polyelectrolytes were grafted onto hydrocarbon surfaces by a dry-process and chemical-free approach using hydrogen projectiles with high kinetic energy but properly controlled to selectively cleave C-H bonds, on which electroless plating was carried out after loading Pd moieties by ion exchange, resulting in high quality metalized polymer films with excellent conductivity and mechanical stability. PMID:23584100

Wang, Xiaolong; Zhang, Tengyuan; Kobe, Brad; Lau, Woon Ming; Yang, Jun

2013-04-15

415

Electric dipole polarizabilities at imaginary frequencies for hydrogen, the alkali-metal, alkaline-earth, and noble gas atoms  

SciTech Connect

The electric dipole polarizabilities evaluated at imaginary frequencies for hydrogen, the alkali-metal atoms, the alkaline-earth atoms, and the noble gases are tabulated along with the resulting values of the atomic static polarizabilities, the atom-surface interaction constants, and the dispersion (or van der Waals) constants for the homonuclear and the heteronuclear diatomic combinations of the atoms.

Derevianko, Andrei [Physics Department, Univ. of Nevada, Reno, NV 89557-0058 (United States)], E-mail: andrei@unr.edu; Porsev, Sergey G. [Physics Department, Univ. of Nevada, Reno, NV 89557-0058 (United States); Petersburg Nuclear Physics Institute, Gatchina, Leningrad District 188300 (Russian Federation)], E-mail: sporsev@gmail.com; Babb, James F. [ITAMP, Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138-1516 (United States)], E-mail: jbabb@cfa.harvard.edu

2010-05-15

416

Hydrogen production and metal-dye bioremoval by a Nostoc linckia strain isolated from textile mill oxidation pond.  

PubMed

Biohydrogen production by Nostoc linckia HA-46, isolated from a textile-industry oxidation-pond was studied by varying light/dark period, pH, temperature and ratio of carbon-dioxide and argon in the gas-mixture. Hydrogen production rates were maximum under 18 h of light and 6 h of darkness, pH 8.0, 31°C, a CO(2):Ar ratio 2:10. Hydrogen production of the strain acclimatized to 20 mg/L of chromium/cobalt and 100 mg/L of Reactive red 198/crystal violet dye studied in N-supplemented/deficient medium was 6-10% higher in the presence of 1.5 g/L of NaNO(3). Rates of hydrogen production in the presence of dyes/metals by the strain (93-105 ?mol/h/mg Chlorophyll) were significantly higher than in medium without metals/dyes serving as control (91.3 ?mol/h/mg Chlorophyll). About 58-60% of the two metals and 35-73% of dyes were removed by cyanobacterium. Optimal conditions of temperature, pH and metals/dyes concentration for achieving high hydrogen production and wastewater treatment were found practically applicable as similar conditions are found in the effluent of regional textile-mills. PMID:21109423

Mona, Sharma; Kaushik, Anubha; Kaushik, C P

2010-11-09

417

Polysilicate esters for oil reservoir permeability control  

SciTech Connect

A method is described of recovering hydrocarbon oil from a subterranean oil-bearing formation comprising: injecting into the high permeability region or regions of the subterranean formation a permeability control agent comprising a liquid polysilicate ester, produced by the reaction of a hydroxyl group-containing organic compound with the product obtained by acidifying an alkali metal silicate, to plug the high permeability region or regions; subsequently injecting into the formation a flooding liquid; and recovering the oil from the formation.

Hoskin, D.H.; Rollman, L.D.

1987-04-28

418

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

419

Chemistry of glass-ceramic to metal bonding for header applications: 2. Hydrogen bubble formation during glass-ceramic to metal sealing  

SciTech Connect

During the formation of a glass-ceramic to metal seal with nickel-based superalloy Inconel 718, hydrogen bubble formation was observed in the glass-ceramic. This bubble formation was caused by the reaction of dissolved metals with adsorbed water, all of which are in the glass-ceramic. The dissolved metals are present in the glass from dissociation of the Inconel 718, and the water is present in the glass prior to seal formation. To inhibit bubble formation, the glass-ceramic was spiked with 1 wt % CuO. This spiking allowed competing reactions to occur, thus causing the formation of copper and/or Cu/sub 2/O in the glass-to-metal interface and reducing bubble formation. Spiking with 1 wt % Cr/sub 2/O/sub 3/ also inhibited bubble formation. Thermodynamic data suggest that hydrogen formation is responsible for bubbles in a wide variety of seal systems, including glass-to-metal seals in which the metal is or contains iron, manganese, chromium, niobium, titanium, or aluminum.

Craven, S.M.; Kramer, D.P.; Moddeman, W.E.

1986-12-03

420

Uptake Rates for Hydrogen by Nb and Ta; Effect of Thin Metallic Overlayers.  

National Technical Information Service (NTIS)

The hydrogen uptake rates of clean Nb and Ta foils were measured as a function of temperature and pressure. The sticking coefficient (number of hydrogen atoms entering the bulk / number of hydrogen atoms hitting the surface) of hydrogen on clean Nb and Ta...

M. A. Pick M. Strongin M. G. Greene

1980-01-01

421

Mechanistic insight on the hydrogenation of conjugated alkenes with h(2) catalyzed by early main-group metal catalysts.  

PubMed

Density functional theory calculations have been performed to investigate the molecular mechanism of the hydrogenation reactions of 1,1-diphenylethylene and myrcene catalyzed by the actual calcium hydride catalyst, CaH(dipp-nacnac)(thf) (dipp-nacnac = CH{(CMe)(2,6-iPr(2)-C(6)H(3)N)}(2)). The hydrogenation reactions of these two alkenes proceed via a similar pathway, which includes three steps. First, the hydride migrates from the calcium center to one olefinic carbon in the substrate. Then, the hydride transfer product can easily transform into a key ion-pair intermediate. This intermediate provides an intramolecular frustrated Lewis pair, in which the calcium center acts as a Lewis acid, and one olefinic carbon acts as a Lewis base. Next, the H-H bond is heterolytically cleaved by this frustrated Lewis pair through a concerted Lewis acid-Lewis base mechanism, producing the hydrogenation product and regenerating the catalyst. For these two reactions, the rate-limiting step is the hydride transfer step, with free energy barriers of 29.2 kcal for both substrates. In addition, our calculations indicate that the hydrogenation reaction of 1,1-diphenylethylene catalyzed by the analogous strontium hydride complex may readily occur, but the similar magnesium-mediated hydrogenation reaction is less likely to take place under similar conditions as adopted by the calcium hydride catalyst. The results can give satisfactory descriptions of experimental facts observed for these two hydrogenation reactions. The hydrogenation mechanism proposed here is different from that of the late transition metal-catalyzed alkene hydrogenation or the organolanthanide-catalyzed alkene hydrogenation. PMID:20196551

Zeng, Guixiang; Li, Shuhua

2010-04-01

422

Ammonia: A source of hydrogen dopant for InN layers grown by metal organic vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

Thermal annealing of InN layers grown by metal organic vapor phase epitaxy (MOVPE) is investigated in nitrogen atmosphere for temperatures ranging from 400 to 550 °C and for heat treatment times up to 12 h. This treatment results in hydrogen outdiffusion, lowering significantly the residual n-type background doping. This mechanism is shown to be reversible through thermal annealing under ammonia atmosphere, responsible of hydrogen incorporation during growth. These results establish a MOVPE process allowing the obtention of InN samples, which exhibit similar electrical properties than molecular beam epitaxy grown samples: a key issue in view of future industrial production of InN based devices.

Ruffenach, S.; Moret, M.; Briot, O.; Gil, B.

2009-07-01

423

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

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

424

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

NASA Astrophysics Data System (ADS)

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

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

2010-07-01

425

Effect of the strong metal-support interaction on hydrogen sorption kinetics of Pd-capped switchable mirrors  

NASA Astrophysics Data System (ADS)

The morphology and electronic structure of Pd clusters grown on oxidized yttrium surfaces are investigated by scanning tunneling microscopy and ultraviolet photoelectron spectroscopy. The hydrogen sorption mediated by the Pd clusters is determined from the optically monitored switching kinetics of the underlying yttrium film. A strong thickness dependence of the hydrogen uptake is found. The electronic structure of the as-grown Pd clusters depends only weakly on their size. Strong changes of the photoemission spectra are found after hydrogenation, in particular the oxide peak shifts and the Pd peaks vanish. Both phenomena are due to a strong metal-support interaction (SMSI) state, characterized by a complete encapsulation of the clusters by a reduced yttrium oxide layer. Scanning tunneling spectroscopy confirms the SMSI state of small Pd clusters after hydrogen exposure. The SMSI effect is less important with increasing Pd thickness. This explains the critical thickness for the catalyzed hydrogen uptake by the Pd/YOx/Y system. The results shed light on the mechanism of hydrogen absorption at the triple point gas-catalyst-oxide, which also plays an important role in today’s fuel cell technology.

Borgschulte, A.; Westerwaal, R. J.; Rector, J. H.; Dam, B.; Griessen, R.; Schoenes, J.

2004-10-01

426

Nature of water and hydrogen reactions on transition metal surfaces studied by scanning tunneling microscopy  

NASA Astrophysics Data System (ADS)

Scanning Tunneling Microscopy (STM) has already been established as a tool for the investigation of simple reaction mechanisms. In this work I present results of two parallel studies using STM: first, hydrogen on Ru(0001) surface and second, water on Ru(0001) and Pd(111). In both studies initial stages of adsorption up to saturation monolayer coverage were investigated by variable temperature scanning tunneling microscopy (VT STM). The first step of the hydrogen adsorption study was the identification and characterization of the various coverage structures on clean Ru(0001). Hydrogen was found to adsorb dissociatively forming ( 3x3 )R30°, 3 domains of (2x1), (2x2)-3H and (1x1) for increasing coverages of theta=0.3 ML, 0.5 ML, 0.75 ML and 0.1 ML respectively. Some of these structures were observed to coexist at intermediate coverage values. In addition effects of impurities such as oxygen and carbon on hydrogen adsorption has been discussed. Next, near saturation coverage the interesting mechanism of how H 2 dissociates and binds to the surface of Ru(0001) has been observed. We found that the H2 dissociation takes place only on Ru sites where the metal atom is not bound to any H atom. Such active sites are formed when at least 3 H-vacancies aggregate by thermal diffusion. Sites formed by single H-vacancies (i.e. unoccupied Ru sites) or pairs of adjoining vacancies were found to be unreactive toward H2. H-vacancies were observed as single entities diffusing on the surface at 50 K and able to form transient triangular shaped aggregations where H2 molecules dissociated. It was found that the diffusion and aggregation of the H-vacancies is essential in creation of active sites where dissociative adsorption of hydrogen occurs. The first step of water studies was the initial stages of growth of water on the hexagonal surfaces of Pd(111) and Ru(0001) in the temperature range between 40 K and 130 K. In addition, DFT calculations and STM image simulations were used to validate the models. Below 130 K water dissociation does not occur at any appreciable rate and only molecular films are formed. At these temperatures the kinetics of water growth leads to structures where the molecules bind to the metal substrate through the O-lone pair while making 3 H-bonds with neighboring molecules and form clusters of hexagonal units with a honeycomb structure. This bonding geometry imposes limitations to the size of the clusters, with unsaturated H-bonds confined to the cluster periphery. It is found that growth proceeds by attachement of water molecules to the edge of the clusters by H-bonds. These molecules bind only weakly to the metal substrate and can hop around the edges. Comparison of DFT and STM image calculations with experiments shows that on Pd the edge-attached molecules form two different structures, a metastable one where the molecule is elevated by 2.7 A with respect to the cluster molecules, and another where they are elevated by only 0.4 A. On Ru only the less elevated (0.4 A higher) edge-attached molecules are observed. In next final step, water structures on Ru(0001) were studied at temperatures above 140K. STM findings were backed by x-ray absorption spectroscopy. Additional DFT calculations and STM simulations provided validation of proposed models. It was found that while undissociated water layers are metastable below 140 K, heating above this temperature produces drastic transformations whereby a fraction of the water molecules partially dissociate and form mixed H 2O-OH structures. XPS and XAS revealed the presence of hydroxyl groups with their O-H bond essentiallymostly parallel to the surface. STM images show that the mixed H2O-OH structures consist of long narrow stripes aligned with the three crystallographic directions perpendicular to the close-packed atomic rows of the Ru(0001) substrate. The internal structure of the stripes is a honeycomb network of H-bonded water and hydroxyl species. We found that the metastable low temperature molecular phase can also be converted to a mixed H2O-OH phase through excitation

Tatarkhanov, Mouslim Magomedovich

427

Computational study of hydrogen binding by metal-organic framework-5  

NASA Astrophysics Data System (ADS)

We report the results of quantum chemistry calculations on H2 binding by the metal-organic framework-5 (MOF)-5. Density functional theory calculations were used to calculate the atomic positions, lattice constant, and effective atomic charges from the electrostatic potential for the MOF-5 crystal structure. Second-order Møller-Plesset perturbation theory was used to calculate the binding energy of H2 to benzene and H2-1,4-benzenedicarboxylate-H2. To achieve the necessary accuracy, the large Dunning basis sets aug-cc-pVTZ, and aug-cc-pVQZ were used, and the results were extrapolated to the basis set limit. The binding energy results were 4.77 kJ/mol for benzene, 5.27 kJ/mol for H2-1,4-benzenedicarboxylate-H2. We also estimate binding of 5.38 kJ/mol for Li-1,4-benzenedicarboxylate-Li and 6.86 kJ/mol at the zinc oxide corners using second-order Møller-Plesset perturbation theory. In order to compare our theoretical calculations to the experimental hydrogen storage results, grand canonical Monte Carlo calculations were performed. The Monte Carlo simulations identify a high energy binding site at the corners that quickly saturated with 1.27 H2 molecules at 78 K. At 300 K, a broad range of binding sites are observed.

Sagara, Tatsuhiko; Klassen, James; Ganz, Eric

2004-12-01

428

Metal-organic framework templated synthesis of Fe2O3/TiO2 nanocomposite for hydrogen production.  

PubMed

A new metal-organic framework (MOF)-templated method has been developed for the synthesis of a metal oxide nanocomposite with interesting photophysical properties. Fe-containing nanoscale MOFs are coated with amorphous titania, then calcined to produce crystalline Fe(2)O(3)/TiO(2) composite nanoparticles. This material enables photocatalytic hydrogen production from water using visible light, which cannot be achieved by either Fe(2)O(3) or TiO(2) alone or a mixture of the two. PMID:22431011

deKrafft, Kathryn E; Wang, Cheng; Lin, Wenbin

2012-03-19

429

Insights on Hydrogen Liberation from Water Using Anionic Transition Metal Oxide Clusters: a Combined Computational and Spectroscopic Study  

NASA Astrophysics Data System (ADS)

Transition Metal Oxides (TMOs) offer widespread applications in catalysis and the generation of alternate sources of energy. Cluster models are useful to model the defect sites in these TMO surfaces which are responsible for their catalytic activities. In this combined computational (DFT) and spectroscopic (PES/MS) study, we present the interesting features in the chemical reactions of molybdenum oxide and tungsten oxide clusters with water. The results obtained provide valuable insights on the roles played by differing metal-oxygen bond strengths, the initial electrostatic complex formed and the geometric factors involved in the liberation of hydrogen gas from water.

Ramabhadran, Raghunath O.; Mann, Jenniffer E.; Waller, Sarah. E.; Rothgeb, David W.; Jarrold, Caroline C.; Raghavachari, Krishnan

2013-06-01

430

A Theoretical Study of Methanol Synthesis from CO2 Hydrogenation on Metal-Doped Cu(111) Surfaces.  

PubMed

Density functional theory (DFT) calculations and Kinetic Monte Carlo (KMC) simulations were employed to investigate the methanol synthesis reaction from CO2 hydrogenation (CO2 + 3H2 ? CH3OH + H2O) on metal-doped Cu(111) surfaces. Both the formate pathway and the reverse water gas shift (RWGS) reaction followed by 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 towards methanol synthesis. One is the activation barrier of dioxomethylene hydrogenation; the other is the CO binding energy. An ideal Cu-based catalyst for the methanol synthesis via CO2 hydrogenation should be able to hydrogenate the dioxomethylene easily and bond CO moderately, being strong enough to favor the desired CO hydrogenation rather than CO desorption, but weak enough to prevent the CO poisoning. In this way, the methanol production via both the formate and the RWGS+CO-Hydro pathways can be facilitated. PMID:22148417

Yang, Yixiong; White, Michael G; Liu, Ping

2011-12-12

431

On the nature of the adsorbed hydrogen phase in microporous metal-organic frameworks at supercritical temperatures.  

PubMed

Hydrogen adsorption measurements on different metal-organic frameworks (MOFs) over the 0-60 bar range at 50 and 77 K are presented. The results are discussed with respect to the materials' surface area and thermodynamic properties of the adsorbed phase. A nearly linear correlation between the maximum hydrogen excess amount adsorbed and the Brunauer-Emmett-Teller (BET) surface area was evidenced at both temperatures. Such a trend suggests that the adsorbed phase on the different materials is similar in nature. This interpretation is supported by measurements of the adsorbed hydrogen phase properties near saturation at 50 K. In particular it was found that the adsorbed hydrogen consistently exhibits liquid state properties despite significant structural and chemical differences between the tested adsorbents. This behavior is viewed as a consequence of molecular confinement in nanoscale pores. The variability in the trend relating the surface area and the amount of hydrogen adsorbed could be explained by differences in the adsorbed phase densities. Importantly, the latter were found to lie in the known range of bulk liquid hydrogen densities. The chemical composition and structure (e.g., pore size) were found to influence mainly how adsorption isotherms increase as a function of pressure. Finally, the absolute isotherms were calculated on the basis of measured adsorbed phase volumes, allowing for an estimation of the total amounts of hydrogen that can be stored in the microporous volumes at 50 K. These amounts were found to reach values up to 25% higher than their excess counterparts, and to correlate with the BET surface areas. The measurements and analysis in this study provide new insights on supercritical adsorption, as well as on possible limitations and optimization paths for MOFs as hydrogen storage materials. PMID:19775144

Poirier, Eric; Dailly, Anne

2009-10-20

432

Inhibition of Hydrogen Adsorption by Submomolayer Deposition of Metals on Platinum.  

National Technical Information Service (NTIS)

Submonolayer deposition of copper, silver, lead, and gold inhibit the adsorption of hydrogen at platinum electrode is discussed. At low surface coverage, copper and silver preferentially inhibit the sites occupied by weakly adsorbed hydrogen. Lead and gol...

S. Bruckenstein S. H. Cadle

1971-01-01

433

Report on the development of low magnetic permeability reference materials  

Microsoft Academic Search

A study to select suitable reference materials for the calibration of magnetic permeability measuring instruments over their normal working range of relative magnetic permeability of 1.0025 to 1.4 was performed. With the exception of some of the rare Earth elements, the permeability of the elements is below the lower limit of this range. It was necessary, therefore, to investigate metallic

A. E. Drake; C. I. Ager

1993-01-01

434

Mesoporous zeolite-supported noble metal catalysts for low-temperature hydrogenation of aromatics in distillate fuels  

Microsoft Academic Search

The present work is concerned with deep hydrogenation of aromatics in distillate fuels at low temperatures using mesoporous zeolite-supported noble metal catalysts. This work is a part of our on-going effort to develop advanced thermally stable jet fuels from coal-derived liquids and petroleum. Saturation of naphthalene and its derivatives from only reduces aromatics contents of jet fuels, but also generates

K. M. Reddy; C. Song

1996-01-01

435

Improvement in anti-aging of metallized Nafion ® hydrogen sensors modified by chemical vapor deposition of polypyrrole  

Microsoft Academic Search

Pt\\/Nafion® and Pd\\/Nafion® electrodes were prepared by impregnation–reduction methods in detecting hydrogen. For improving their anti-aging abilities, polypyrrole (PPy) films were chemically deposited onto the metallized electrodes. After continuously aging tests for 48h, the sensitivities of the Pt\\/Nafion® and the PPy-modified Pt\\/Nafion® electrodes decrease by 68 and 32%, respectively, but the accompanying sacrifice is the loss in sensitivity from 0.0744

Yu-Chuan Liu; Bing-Joe Hwang; Wen-Cheng Hsu

2002-01-01

436

Comparative studies of the influence of different nano-sized metal oxides on the hydrogen sorption properties of magnesium hydride  

Microsoft Academic Search

The influence of the catalytic activity of metal oxide nanoparticles on the hydrogen sorption properties of nanocrystalline MgH2 prepared by mechanical (ball) milling was investigated. The simple geometrical model nano-sized particles distributed on the surface of a micro-sized particle is presented. Some trends relating different geometrical features and densities for both powders are shown. With this model, the weight quantities

M. Polanski; J. Bystrzycki

2009-01-01

437

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

Microsoft Academic Search

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

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

2007-01-01

438

Rare earth-first-row transition metal perovskites as catalysts for the autothermal reforming of hydrocarbon fuels to generate hydrogen  

Microsoft Academic Search

Perovskite oxides (ABO3) containing rare earth elements on the A-site and first-row transition metal elements on the B-site were studied as catalysts for autothermal reforming of liquid hydrocarbon fuels to produce hydrogen for fuel cell systems. Experiments were conducted in a fixed bed microreactor at temperatures of 600–800°C and gas-hourly space velocities (GHSV) ranging from 4600 to 28,000h?1 using 2,2,4-trimethylpentane

Jennifer R. Mawdsley; Theodore R. Krause

2008-01-01

439

Room temperature hydrogen generation from aqueous ammonia-borane using noble metal nano-clusters as highly active catalysts  

Microsoft Academic Search

Nano-clusters of noble metals Ru, Rh, Pd, Pt and Au have been supported on ?-Al2O3, C and SiO2, of which the catalytic activities have been investigated for hydrolysis of NH3BH3. Among these catalysts, the Ru, Rh and Pt catalysts exhibit high activities to generate stoichiometric amount of hydrogen with fast kinetics, whereas the Pd and Au catalysts are less active.

Manish Chandra; Qiang Xu

2007-01-01

440

Concentration-distance profiles resulting from the hydrogen-charging of metal lattices under high fugacity conditions  

SciTech Connect

In the hydrogenation of metals under high fugacity conditions (such as electrolytic charging), non-steady state diffusion produces concentration-distance profiles which may not be calculated by assuming simple diffusion behavior. Such profiles have been calculated using finite difference methods by considering specific models for the concentration-perturbation of the appropriate jump activation barriers. The results show that much greater H concentrations are produced for a given penetration distance than would be expected by assuming fickian diffusion.

Zang, D.; Mclellan, R.B. [William Marsh Rice Univ., Houston, TX (United States). Dept. of Mechanical Engineering

1999-05-28

441

Hydrogen generation from liquid phase catalytic reforming of sugar solutions using metal-supported catalysts  

Microsoft Academic Search

Most of the hydrogen production processes are designed for large-scale industrial uses and are not suitable for a compact hydrogen device to be used in systems like solid polymer fuel cells. Integrating the reaction step, the gas purification and the heat supply can lead to small-scale hydrogen production systems. The aim of this research is to study the influence of

A. Tanksale; Y. Wong; J. N. Beltramini; G. Q. Lu

2007-01-01

442

Integrating hydrogen generation and storage in a novel compact electrochemical system based on metal hydrides  

Microsoft Academic Search

The development of efficient and reliable energy storage systems based on hydrogen technology represents a challenge to seasonal storage based on renewable hydrogen. State of the art renewable energy generation systems include separate units such as electrolyzer, hydrogen storage vessel and a fuel cell system for the conversion of H2 back into electricity, when required. In this work, a novel

C. M. Rangel; V. R. Fernandes; Y. Slavkov; L. Bozukov

2008-01-01

443

ADVANCED HYDROGEN TRANSPORT MEMBRANES FOR VISION 21 FOSSIL FUEL PLANTS  

SciTech Connect

During this quarter work was continued on characterizing the stability of layered composite membranes under a variety of conditions. Membrane permeation was tested up to 100 hours at constant pressure, temperature, and flow rates. In addition, design parameters were completed for a scale-up hydrogen separation demonstration unit. Evaluation of microstructure and effect of hydrogen exposure on BCY/Ni cermet mechanical properties was initiated. The fabrication of new cermets containing high permeability metals is reported and progress in the preparation of sulfur resistant catalysts is discussed. Finally, a report entitled ''Criteria for Incorporating Eltron's Hydrogen Separation Membranes into Vision 21 IGCC Systems and FutureGen Plants'' was completed.

Carl R. Evenson; Anthony F. Sammells; Richard T. Treglio; Jim Fisher; U. Balachandran; Richard N. Kleiner; James E. Stephan; Frank E. Anderson; Chandra Ratnasamy; Mahendra Sunkara; Jyothish Thangla; Clive Brereton; Warren Wolfs; James Lockhart

2005-01-28

444

Hydrogen production from water decomposition by redox of Fe2O3 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 (Fe3O4 (initial Fe2O3)+4H2?3Fe+4H2O), 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 Fe2O3-Mo-Zr, the average H2 production temperature could be significantly decreased to 276 °C, the average H2 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

445

Ionization-induced enhancement of hydrogen storage in metalized C2H4 and C5H5 molecules  

NASA Astrophysics Data System (ADS)

The capacity of Li2C2H4+ and TiC5H5+ as hydrogen storage media is studied using first-principles density-functional theory. The present results indicate that these complexes not only enhance the metal bond strength but also increase the number of nondissociative hydrogen molecules attached. The adsorption capacity of Li2C2H4+(27.5wt%) is doubled compared with that of Li2C2H4 . The enhanced electrostatic field around the Li atom originating from the increased charge transfers from Li to C2H4+ accounts for the high capacity. For TiC5H5+ , the first H2 is adsorbed in molecular form, while it is adsorbed dissociatively on the TiC5H5 complex. This is due to the favorable overlap of the highest occupied molecular orbital of Ti and the lowest unoccupied molecular orbital of H2 . Furthermore, the number of adsorbed H2 on TiC5H5 is limited to only four, whereas the number increases to five on TiC5H5+ . The availability of the dz2 orbital of Ti in TiC5H5+ has been found to be responsible for the fifth H2 adsorption with a hydrogen uptake of 8.1wt% . It is demonstrated that controlling the charge state of the metal-organic molecules may play a significant role in the search for hydrogen storage media.

Liu, C. S.; Zeng, Z.

2009-06-01

446

Transition Metal Activation and Functionalization of C-H (Carbon-Hydrogen) Bonds: Progress Report for Period June 1, 1986-November 30, 1987.  

National Technical Information Service (NTIS)

The fundamental thermodynamic and kinetic factors that influence carbon-hydrogen bond activation at homogeneous transition metal centers were investigated. The project was also directed towards the conversion of hydrocarbons into functionalized products o...

W. D. Jones

1987-01-01

447

Development of a composite palladium membrane for selective hydrogen separation at high temperature  

SciTech Connect

In this paper a method is described for development of a composite palladium membrane for selective hydrogen separation at high temperature. Electroless plating is used to form a thin palladium film on a silver porous substrate. The composite formed showed excellent mechanical strength and very large selectivity for hydrogen. The studies performed so far suggest that electroless plating can be utilized in making a metal composite membrane that can be used at high temperatures. Composite properties seem fairly constant at high temperatures. The permeability of the composite membrane is comparable to theoretical permeabilities for pure palladium.

Govind, R.; Atnoor, D.

1991-03-01

448

Channelling experiments on the lattice location of hydrogen in metals using the nuclear reaction 1H(11B, ?)??  

NASA Astrophysics Data System (ADS)

In order to locate hydrogen dissolved in metals a nuclear reaction 1H(11B, ?)?? was applied to a channelling method. As an example of this application the results of the following two experiments were briefly reported. (1) The lattice location of H in V was investigated under a <001> compressive stress of 7 kg/mm2 below the elastic limit. The configuration of hydrogen is extremely sensitive to compressive stress and changes from a tetrahedral (T) site to a diplaced-T or 4T configuration. On release of this stress the hydrogen atoms returned to T-sites. (2) To elucidate the mechanism of the enhancement of the terminal solubility for hydrogen (TSH) in Nb on alloying with undersized Mo atoms, the state of hydrogen was studied in Nb-based Nb-Mo dilute alloys. It was demonstrated that H atoms are trapped by Mo atoms and located at sites displaced from T-sites by about 0.6 Å. This result supports the trapping model for the enhancement of the TSH in the region of low Mo concentration.

Yagi, Eiichi

1992-03-01

449

A Pt\\/GaN Schottky diode-type hydrogen sensor with a thin SiO2-passivated metal\\/semiconductor junction  

Microsoft Academic Search

The hydrogen sensing and response characteristics of and Pt\\/GaN Schottky diodes with thin SiO2-passivated metal\\/semiconductor junction under different-concentration hydrogen gases are studied over a wide temperature range in an air atmosphere. Experimentally, the studied device exhibits hydrogen sensing performance, including SF of 14685 and SR of 44636 (in 9970 ppm H2\\/air), DeltaphiB of 231.6 meV (in 9970 ppm H2\\/air), temperature

Tsung-Han Tsai; Huey-Ing Chen; Kun-Wei Lin; Ching-Wen Hung; Tzu-Pin Chen; Li-Yang Chen; Kuei-Yi Chu; Wen-Chau Liu

2008-01-01