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1

Hydrogen-permeable composite metal membrane and uses thereof  

DOEpatents

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

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

1993-06-08

2

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

PubMed Central

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

Hyman, Lynne M.; Franz, Katherine J.

2011-01-01

3

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

4

Determination of hydrogen permeability in commercial and modified superalloys  

NASA Technical Reports Server (NTRS)

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

Bhattacharyya, S.; Peterman, W.

1983-01-01

5

Metallic hydrogen research  

Microsoft Academic Search

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

T. J. Burgess; R. S. Hawke

1978-01-01

6

The interaction of hydrogen with metal alloys  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

7

Permeability of hydrogen and deuterium of Hastelloy XR  

Microsoft Academic Search

Permeation of hydrogen isotope through a high-temperature alloy used as heat exchanger and steam reformer pipes is an important problem in the hydrogen production system connected to be a high-temperature engineering test reactor (HTTR). An experiment of hydrogen (H2) and deuterium (D2) permeation was performed to obtain permeability of H2 and D2 of Hastelloy XR, which is adopted as heat

Tetsuaki Takeda; Jin Iwatsuki; Yoshiyuki Inagaki

2004-01-01

8

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

9

Hydrogen permeability measurement through Pd, Ni and Fe membranes  

Microsoft Academic Search

An ultrahigh vacuum apparatus for the measurement of hydrogen gas permeation through metal membranes has been developed to perform studies in the ranges of low pressure and medium temperature. The sealing of the hydrogen gas at the specimen is done by gold O-rings which yield vacuum tightness. The hydrogen permeation is measured for pure Pd, Ni and Fe membranes over

Kohji Yamakawa; Michael Ege; Bernd Ludescher; Michael Hirscher; Helmut Kronmüller

2001-01-01

10

Structural determinants of the hydrogen peroxide permeability of aquaporins.  

PubMed

Aquaporins (AQP) conduct small, uncharged molecules, such as water (orthodox AQPs), ammonia (aquaammoniaporins) or glycerol (aquaglyceroporins). The physiological functions of AQPs are involved in osmotic volume regulation or the transport of biochemical precursors and metabolic waste products. The recent identification of hydrogen peroxide (H?O?) as a permeant of certain AQPs suggests additional roles in mitigating oxidative stress or enabling paracrine H?O? signalling. Yet, an analysis of the structural requirements of the H?O? permeability of AQPs is missing. We subjected a representative set of wild-type and mutant AQPs to a newly established quantitative phenotypic assay. We confirmed high H?O? permeability of the human aquaammoniaporin AQP8 and found intermediate H?O? permeability of the prototypical orthodox water channel AQP1 from the rat. Differences from an earlier report showing an absence of H?O? permeability of human AQP1 can be explained by expression levels. By generating point mutations in the selectivity filter of rat orthodox aquaporin AQP1, we established a correlation of H?O? permeability primarily with water permeability and secondarily with the pore diameter. Even the narrowest pore of the test set (i.e. rat orthodox aquaporin AQP1 H180F with a pore diameter smaller than that of natural orthodox AQPs) conducted water and H?O?. We further found that H?O? permeability of the aquaglyceroporin from the malaria parasite Plasmodium falciparum was lower despite its wider pore diameter. The data suggest that all water-permeable AQPs are H?O? channels, yet H?O? permeability varies with the isoform. Thus, generally, AQPs must be considered as putative players in situations of oxidative stress (e.g. in Plasmodium-infected red blood cells, immune cells, the cardiovascular system or cells expressing AQP8 in their mitochondria). PMID:24286224

Almasalmeh, Abdulnasser; Krenc, Dawid; Wu, Binghua; Beitz, Eric

2014-02-01

11

Annealing effect of cermet membranes on hydrogen permeability.  

SciTech Connect

Ni--SrCe{sub 0.8}Yb{sub 0.2}O{sub 3-{delta}} cermet membranes are being developed to separate hydrogen from hydrogen-containing gas mixtures at high temperature. The hydrogen flux of an annealed membrane showed higher flux than that of an as-sintered membrane. The major contribution to overall flux was from ambipolar diffusion through the metal-to-oxide grain boundary. The higher hydrogen permeation flux of an annealed membrane may be understood by its larger metal grains and lower tortuosity, leading to a less-effective length for proton diffusion.

Song, S.-J.; Wachsman, E. D.; Lee, T. H.; Chen, L.; Dorris, S. E.; Balachandran, U.; Energy Systems; Univ. of Florida

2006-11-11

12

Hydrogen permeability and Integrity of hydrogen transfer pipelines  

E-print Network

& Computational Mechanics) J. G. Blencoe and Larry. M. Anovitz (Oak Ridge National Laboratory, Chemical Sciences Natural Gas Pipelines Hydrogen embrittlement What is the relevance to hydrogen pipelines? ORNL research of liquefaction Lack of cost effective carrier technology Key challenges for pipelines: Retro-fitting existing

13

Compositional variation of hydrogen permeability in ferritic alloys and steels  

Microsoft Academic Search

From a compilation of permeation data of hydrogen in ferritic\\/martensitic alloys and steels dependences are derived of activation energies and prefactors in Arrhenius-type relations on concentration of constituents. By most constituents the prefactor is reduced and the activation energy is increased compared to pure iron. The permeabilities of ferritic\\/martensitic stainless steels can be approximated within the scatter of data by

P. Jung

1996-01-01

14

Hydrogen environment embrittlement of metals  

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

15

Metal salt catalysts for enhancing hydrogen spillover  

DOEpatents

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

Yang, Ralph T; Wang, Yuhe

2013-04-23

16

Hydrogen Permeability of Polymer Matrix Composites at Cryogenic Temperatures  

NASA Technical Reports Server (NTRS)

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

Grenoble, Ray W.; Gates, Thomas S

2005-01-01

17

Effects of hydrogen on metals  

NASA Technical Reports Server (NTRS)

Several rules to guide choice of materials, and methods of welding, electroplating, and heat treatment will provide a method for minimizing failures in storage tanks and related hardware. Failures are caused by high-pressure hydrogen effects, the formation of hydrides in titanium, and hydrogen absorption through various metals processing techniques.

Cataldo, C. E.

1969-01-01

18

Hydrogen in semiconductors and metals  

SciTech Connect

Major highlights of the conference include further understanding of the structure of extended hydrogen clusters in semiconductors, switchable optical properties of metal-hydride films, reversible changes in the magnetic coupling in metallic superlattices, and increased lifetime of integrated circuits due to deuterium device passivation. Continued progress has also been achieved in understanding hydrogenation of defects in compound semiconductors and on surfaces. Total energy calculations in semiconductors have progressed sufficiently to predict energetics and vibration frequencies as measured by experiment. Similarly, electronic structure calculations of hydrogen-metal systems provide a deeper understanding of stability, bonding, and phase changes. Various nuclear techniques have been refined to yield important information regarding the concentration and transport of hydrogen in condensed matter. Finally, the interaction of hydrogen to create thermal donors has been used to create deep p-n junctions without the need for deep diffusion of dopants. The volume has been organized along the order of presentation within the conference. Similar methods and subjects have been grouped together. The authors have attempted to keep similar metal and semiconductor papers together in order to further promote cross-fertilization between the fields. Major categories include hydrogen on surfaces, theory and thermodynamics, hydrogen transport phenomena, nuclear characterization techniques, compound semiconductors, metal bulk, devices and applications, bulk silicon, and carbon and carbon-like materials. Separate abstracts were prepared for most papers.

Nickel, N.H. [ed.] [Hahn-Meitner-Inst., Berlin (Germany); Jackson, W.B. [ed.] [Xerox Palo Alto Research Center, CA (United States); Bowman, R.C. [ed.] [Jet Propulsion Lab., Pasadena, CA (United States); Leisure, R.G. [ed.] [Colorado State Univ., Fort Collins, CO (United States)

1998-12-31

19

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

20

Composite Metal-hydrogen Electrodes for Metal-Hydrogen Batteries  

SciTech Connect

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

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

1997-04-01

21

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

22

Hydrogen permeation resistant layers for liquid metal reactors  

SciTech Connect

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. The work described is part of an HEDL-ANL cooperative research program on Tritium Permeation in Liquid Metal Cooled Reactors. This includes permeation work on hydrogen, deuterium, and tritium with the hydrogen-deuterium research leading to the developments presented.

McGuire, J.C.

1980-03-01

23

Hydrogen recovery with metal hydrides  

SciTech Connect

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

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

1982-03-01

24

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

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

25

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

NASA Technical Reports Server (NTRS)

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

Stokes, Eric H.

2003-01-01

26

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

27

Permeability of hydrogen isotopes through nickel-based alloys  

SciTech Connect

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

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

1983-04-01

28

Improved permeability and selectivity in porous graphene for hydrogen purification.  

PubMed

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

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

2014-12-21

29

Hydrogen permeability through beryllium films and the impact of surface oxides  

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

30

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

31

Permeability  

NSDL National Science Digital Library

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

2010-02-19

32

Permeability  

NSDL National Science Digital Library

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

2007-10-12

33

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

34

Hydrogen trapping and the interaction of hydrogen with metals  

NASA Technical Reports Server (NTRS)

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

Danford, Merlin D.

1987-01-01

35

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

NASA Technical Reports Server (NTRS)

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

ONISCHAK

1976-01-01

36

Dislocation-hydrogen correlation in metals  

SciTech Connect

We present a method using SANS experiments to measure correlation between dislocations and absorbed hydrogen in metals. The technique involves sequential measurements first on a metal with dislocation networks, then two further measurements on the same sample infused with deuterium and normal hydrogen. SANS experiments on metals with dislocations networks have been performed a number of times and some results have appeared in the literature. We have computer estimates of the contribution of absorbed hydrogen and deuterium to SANS cross sections. The results show that we can expect to see the hydrogen contribution in the SANS cross section and see any possible correlations of the hydrogen positions and the dislocations. 8 refs., 2 figs., 2 tabs.

Summerfield, G.C.; King, J.S.; Heuser, B.; Epperson, J.E. (Michigan Univ., Ann Arbor, MI (USA). Dept. of Nuclear Engineering; Argonne National Lab., IL (USA))

1987-11-01

37

Process for forming a nickel foil with controlled and predetermined permeability to hydrogen  

DOEpatents

The present invention provides a novel process for forming a nickel foil having a controlled and predetermined hydrogen permeability. This process includes the steps of passing a nickel plating bath through a suitable cation exchange resin to provide a purified nickel plating bath free of copper and gold cations, immersing a nickel anode and a suitable cathode in the purified nickel plating bath containing a selected concentration of an organic sulfonic acid such as a napthalene-trisulfonic acid, electrodepositing a nickel layer having the thickness of a foil onto the cathode, and separating the nickel layer from the cathode to provide a nickel foil. The anode is a readily-corrodible nickel anode. The present invention also provides a novel nickel foil having a greater hydrogen permeability than palladium at room temperature.

Engelhaupt, Darell E. (Kansas City, MO)

1981-09-22

38

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

2013-01-01

39

Final Report: Metal Perhydrides for Hydrogen Storage  

SciTech Connect

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

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

2011-07-26

40

Abundant Metals Give Precious Hydrogenation Performance  

SciTech Connect

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

Bullock, R. Morris

2013-11-29

41

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

42

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

43

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

E-print Network

Accepted M anuscript N otC opyedited 1 Leaching of Metals from Fly ash-Amended Permeable Reactive Demirkan 4 ABSTRACT One beneficial reuse of high carbon content (HCC) fly ashes is in reactive barrier applications for remediation of contaminated groundwater. However, leaching of metals from the coal fly ashes

Aydilek, Ahmet

44

Metallization in hydrogen-helium mixtures  

NASA Astrophysics Data System (ADS)

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

Lorenzen, Winfried; Holst, Bastian; Redmer, Ronald

2011-12-01

45

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

46

The effect of carbon monoxide and steam on the hydrogen permeability of a Pd\\/stainless steel membrane  

Microsoft Academic Search

Measurements of the hydrogen permeation rate through a Pd\\/stainless steel membrane have been carried out in the presence of carbon monoxide and steam and with mixtures of these two additives. Significant reductions in hydrogen permeability were observed, the extent of the reduction being dependent on the amount of CO or steam added. At low concentrations of additive (high feed flux),

A Li; W Liang; R Hughes

2000-01-01

47

Hydrogen Storage on Metal-Doped Ordered Mesoporous Carbons  

E-print Network

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

Johnson, Eric E.

48

Powered by DFT: Screening Methods That Accelerate Materials Development for Hydrogen in Metals Applications.  

PubMed

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

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

2014-11-18

49

Permeable Reactive Biobarriers for the Containment of Heavy Metal  

E-print Network

and Environmental Engineering University of Arizona #12;What Is Acid Mine Drainage? Acid Mine Drainage (AMDPermeable Reactive Biobarriers for the Containment of Heavy Metal Contamination in Acid Mine) is defined as the presence heavy metals, increased acidity, and sulfate as a direct result of mining

Fay, Noah

50

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

EPA Science Inventory

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

51

Supported Molten Metal Membranes for Hydrogen Separation  

SciTech Connect

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

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

2013-09-30

52

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

53

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

PubMed Central

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 permeability sequence: Na+ ? Li+ > Tl+ > K+. The ratio PK/PNa is 1/12. The permeabilities to Rb+, Cs+, Ca++, and Mg++ are too small to measure. The permeability ratios agree with observations on the squid giant axon and show that the reversal potential ENa differs significantly from the Nernst potential for Na+ in normal axons. Opening and closing rates for sodium channels are relatively insensitive to the ionic composition of the bathing medium, implying that gating is a structural property of the channel rather than a result of the movement or accumulation of particular ions around the channel. A previously proposed pore model of the channel accommodates the permeant metal cations in a partly hydrated form. The observed sequence of permeabilities follows the order expected for binding to a high field strength anion in Eisenman's theory of ion exchange equilibria. PMID:5025743

Hille, Bertil

1972-01-01

54

The evolution of hydrogen from a hot-rolled metal  

Microsoft Academic Search

A study of the paths of the penetration and evolution of hydrogen from a metal permits drawing a conclusion as to the sites of its localization and the character of the diffusion, which is inseparably bound up with the tendency of the metal toward the formation of defects of hydrogen origin. Macroscopic investigation of the evolution of hydrogen into the

V. S. Sapiro; V. T. Tereshchenko

1974-01-01

55

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

56

How absorbed hydrogen affects the catalytic activity of transition metals.  

PubMed

Heterogeneous catalysis is commonly governed by surface active sites. Yet, areas just below the surface can also influence catalytic activity, for instance, when fragmentation products of catalytic feeds penetrate into catalysts. In particular, H absorbed below the surface is required for certain hydrogenation reactions on metals. Herein, we show that a sufficient concentration of subsurface hydrogen, H(sub) , may either significantly increase or decrease the bond energy and the reactivity of the adsorbed hydrogen, H(ad) , depending on the metal. We predict a representative reaction, ethyl hydrogenation, to speed up on Pd and Pt, but to slow down on Ni and Rh in the presence of H(sub) , especially on metal nanoparticles. The identified effects of subsurface H on surface reactivity are indispensable for an atomistic understanding of hydrogenation processes on transition metals and interactions of hydrogen with metals in general. PMID:25294745

Aleksandrov, Hristiyan A; Kozlov, Sergey M; Schauermann, Swetlana; Vayssilov, Georgi N; Neyman, Konstantin M

2014-12-01

57

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

58

Hydrogen peroxide effects on ionic and non-ionic permeability of the rabbit corneal endothelium.  

PubMed

Perfusion of the isolated rabbit corneal endothelium with 0.3 mM hydrogen peroxide (H2O2) caused an increased passive permeability to bicarbonate relative to control tissues. This was accompanied by a reduction in the active flux that resulted in a reduced net bicarbonate flux. Perfusion with 0.3 mM H2O2 resulted in a marked increase in the active and net flux of sodium beginning at two hours. By four hours the net sodium flux had increased by nine-fold over control values. Perfusion with 0.3 mM H2O2 resulted in a 16% and 30% increase in endothelial permeability to inulin and dextran, respectively. Suppression of catalase activity by in vivo pretreatment with intravenous 3-aminotriazole (3AT) did not result in an increased sensitivity of the corneal endothelium to 0.2 mM H2O2: both bicarbonate and sodium fluxes were normal. Inhibition of glutathione synthesis with intravitreal buthionine sulfoximine (BSO) increased the sensitivity of the corneal endothelium to 0.2 mM H2O2 only in the case of sodium flux, with a 4.8-fold increase in net sodium flux at 3 hours after initiation of perfusion. Bicarbonate fluxes were unaffected after BSO pretreatment. The data show that ionic and non-ionic fluxes are altered by H2O2, that pretreatment with 3AT has a minimal effect on ion fluxes while BSO markedly alters sodium flux without changing bicarbonate fluxes, and that sodium and bicarbonate movement are not locked in a symport. PMID:1710927

Hull, D S; Pendarvis, R W; Cheeks, L; Green, K

1991-01-01

59

Electrochemical investigation of hydrogen storage in metal hydrides  

Microsoft Academic Search

One of the problems regarding the use of hydrogen as an energy carrier is related to storage. One approach for a solution is related to the use of solid metal hydrides. Many studies regarding the formation of metal hydrides have included the conduction of absorption experiments in which hydrogen from the gas phase reacts with solid alloys. However, electrochemical methods

C. M. Luedecke; G. Deublein; R. A. Huggins

1985-01-01

60

Technical and economic aspects of hydrogen storage in metal hydrides  

NASA Technical Reports Server (NTRS)

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

Schmitt, R.

1981-01-01

61

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

62

Electrical properties of transition metal hydrogen complexes in silicon  

SciTech Connect

A summary is given on the electrical properties of transition-metal hydrogen complexes in silicon. Contrary to the general understanding, hydrogen leads not only to passivation of deep defect levels but also creates several new levels in the band gap due to electrically active transition-metal complexes. The author presents detailed data for Pt-H complexes and summarize briefly the results on the transition metals Ti, Co, Ni, Pd, and Ag. The introduction of hydrogen at room temperature by wet chemical etching, followed by specific annealing steps allows us to study the formation of the different complexes. In particular, depth profiles of the defect concentrations give an estimate of the number of hydrogen atoms involved in the complexes. Transition-metals binding up to four hydrogen atoms are identified.

Weber, J. [Max-Planck-Inst. fuer Festkoerperforschung, Stuttgart (Germany)

1998-12-31

63

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

SciTech Connect

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

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

2004-07-01

64

Disposal pathway for tritiated reactive metals and tritiated hydrogen gas  

SciTech Connect

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

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

2008-07-15

65

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

66

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

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

67

Hydrogen permeation through metal membrane with protective coating in contact with atomic or ionized hydrogen  

NASA Astrophysics Data System (ADS)

The use of protective coatings is one of the most common methods to reduce the hydrogen permeation through structural materials. Considering the hydrogen permeation through such multilayer membrane it is usually suggested that the ratio of hydrogen concentrations at the interface is equal to that of the hydrogen equilibrium solubilities in these materials. However, during diffusion permeation the hydrogen concentrations at the interface are not equilibrium values but they are determined by diffusion input D1/ d1 and output D2/ d2 rates and by passage rate through interface which is proportional to the ratio of equilibrium solubilities S1 and S2 ( di, Di - thickness of and hydrogen diffusivity in i-layer, respectively). Therefore the ratio of hydrogen concentrations at the interface can be adopted by the ratio ( S1D1/ d1)/( S2D2/ d2). By this approximation the analysis of hydrogen permeation through the duplex membrane in a diffusion-limited regime showed that the coating of the same materials can both decrease and increase the hydrogen permeability of the system depending on the ratio of these parameters. In this case it is possible to explain the contradictory results of experiments on hydrogen permeation through duplex membranes.

Sharapov, V. M.

2002-12-01

68

Metal-dispersed porous graphene for hydrogen storage  

NASA Astrophysics Data System (ADS)

First-principles calculations are carried out to study the role of various metal atoms on porous graphene for molecular hydrogen (H2) adsorption. The binding sites of each metal atom on porous graphene are investigated and the binding energies are determined. It is shown that H2 exhibits different adsorption characteristics onto alkaline, alkaline-earth, or transition metals in porous graphene. In particular, Ca-decorated porous graphene is investigated and found to be feasible for high-capacity hydrogen storage. Our results provide a general picture on the interactions of H2 with porous graphene decorated with various metals.

Reunchan, Pakpoom; Jhi, Seung-Hoon

2011-02-01

69

Negative effective permeability of multilayers of ordered arrays of metal-dielectric nanosandwiches  

NASA Astrophysics Data System (ADS)

We present a thorough theoretical study of the optical properties of periodic structures built of silver and silica nanodisks in a sandwich-like configuration, by means of full electrodynamic calculations using the extended layer-multiple-scattering method. The strong coupling of the metallic nanoparticles and the resulting plasmon hybridization lead to collective electric and magnetic resonant modes, which can be tuned by changing the structural parameters, such as nanoparticle size and lattice constant. We analyze the response of single- and multi-layer architectures of ordered arrays of such nanosandwiches on a dielectric substrate to externally incident light and evaluate the corresponding effective permittivity and permeability functions. Our results reveal the existence of optical magnetism, with a strong negative effective permeability over a tunable spectral range at near-infrared and visible frequencies. We introduce the complex photonic band structure as a tool in the study of three-dimensional metamaterials and establish additional criteria for the validity of their effective-medium description. Our work demonstrates the efficiency of the recently developed extended layer-multiple-scattering method in the study of metamaterials of composite metal-dielectric particles of arbitrary shape.

Tserkezis, C.; Stefanou, N.; Gantzounis, G.; Papanikolaou, N.

2009-05-01

70

Hydrogen evolution by a metal-free electrocatalyst  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

71

Metal-hydrogen battery. [17. 5 A, 35 Ah  

Microsoft Academic Search

A rechargeable metal oxide-hydrogen battery that operates on the back-to-back electrode placement theory as opposed to single metal oxide-hydrogen couple cells is disclosed. Interconnecting of electrodes in series and construction of an electrode stack of series-connected electrodes is utilized in one embodiment in place of bipolar construction to achieve high voltage operation. In a second embodiment, back-to-back construction is used

G. Van Ommering; J. F. Stockel; J. D. Dunlop

1978-01-01

72

Theoretical Study of the Interaction of Hydrogen with Metals.  

NASA Astrophysics Data System (ADS)

Electronic structure calculations are carried out for simple metal hydrides and hydrogen adsorption on simple metal surfaces. The studies are based on the ab initio pseudopotential method and the local-density approximation. Structural and electronic properties of magnesium hydride are studied. The calculated structural properties include equilibrium lattice parameters, cohesive energy, elastic constants, bulk modulus, and phonon frequency. The electronic band structure, density of states, charge density distribution are also obtained. Superconductivity in doped magnesium hydride is proposed. Lithium beryllium hydride is studied because of its proposed metallic behavior. The relative stability of two perovskite structures of lithium beryllium hydride is investigated. Band structures are calculated under ambient and high pressure conditions to determine whether the structures are metallic. The adsorption of hydrogen on the close-packed surface of Be and Mg are studied. The equilibrium distance between hydrogen and the surfaces, the adsorption energy, and the hydrogen oscillation frequency are calculated for hydrogen in the high-symmetry adsorption sites. The energetics for hydrogen to go into a subsurface site is also investigated. Charge density distribution, work function and potential are studied for the clean and hydrogen-covered surfaces. Electronic band structure and H-induced surface states are determined for hydrogen adsorption on Be. Surface energy of the clean surfaces is also calculated.

Yu, Rici

73

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

E-print Network

Enviro-Friendly Hydrogen Generation From Steel Mill-Scale via Metal-Steam Reforming Abdul: hydrogen generation; metal-steam reform- ing; mill-scale; nanoscale iron; electron microscopy Hydrogen of generating hydrogen is by the reaction of certain metals with steam, also appropri- ately called metal-steam

Azad, Abdul-Majeed

74

Hydrogen storage in carbon nanomaterials: Investigation of fiber structure, metal content, and hydrogen spillover  

NASA Astrophysics Data System (ADS)

Hydrogen storage in carbon nanomaterials was enhanced through hydrogen spillover. Carbon nanomaterials, including multi-wall nanotubes (MWNTs), single-wall nanotubes (SWNTs), and graphite nanofibers (GNFs), were synthesized via catalytic methods and tested for hydrogen uptake through volumetric and thermogravimetric experiments designed to reduce common experimental artifacts. A desorption activation energy of 96.9 kJ/mol and in situ carbon formation supported a hydrogen spillover hypothesis: hydrogen dissociates on a catalytic site then migrates to the carbon surface. This catalytic hydrogen spillover could be induced through residual metal oxide catalysts, controlled metal doping, or the formation of carbon defects. Further, the chemical and physical nature of the carbon structure determined the enhancement of hydrogen storage via hydrogen spillover and could be controlled through judicious selection of synthesis conditions, synthesis catalyst, and pretreatment. To understand and optimize the effects of carbon structure and metal content on hydrogen uptake, characterization included electron microscopy, chemical titration, surface area determinations, temperature-programmed studies, elemental analysis, x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS). After saturation at a pressure of 69 bar, a desorbable hydrogen yield of 3.7% was observed for a MWNT/NiMgO composite and up to 3.8% for GNF synthesized from a Ni-Cu catalyst.

Lueking, Angela Dawn

2003-10-01

75

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

76

Why Alkali Metal Doped Carbon Nanotubes Poses High Hydrogen Uptake?  

NASA Astrophysics Data System (ADS)

The nature of the molecular hydrogen adsorption in pure and alkali metal doped single-walled carbon nanotubes (SWNTs) is investigated by a mixed Quantum Mechanics / Molecular Mechanics (QM/MM) model. For the QM part the B3LYP (DFT) functional is used while for the MM we employ the universal force field (UFF). Our results demonstrate that the charge transfer from the alkali metal to the tube polarizes the hydrogen molecule and this charge induced dipole interaction is responsible for the higher hydrogen uptake of the doped tube.

Froudakis, George

2002-03-01

77

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

78

Ordered ground states of metallic hydrogen and deuterium  

NASA Technical Reports Server (NTRS)

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

Ashcroft, N. W.

1981-01-01

79

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

PubMed

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

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

2014-01-01

80

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

81

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

82

Influence of gaseous hydrogen on metals  

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

83

Hydrogen storage in metal-organic frameworks by bridged hydrogen spillover.  

PubMed

The possible utilization of hydrogen as the energy source for fuel-cell vehicles is limited by the lack of a viable hydrogen storage system. Metal-organic frameworks (MOFs) belong to a new class of microporous materials that have recently been shown to be potential candidates for hydrogen storage; however, no significant hydrogen storage capacity has been achieved in MOFs at ambient temperature. Here we report substantially increased hydrogen storage capacities of modified MOFs by using a simple technique that causes and facilitates hydrogen spillover. Thus, the storage of 4 wt % is achieved at room temperature and 100 atm for the modified IRMOF-8. The adsorption is reversible, and the rates are fast. That has made MOFs truly promising for hydrogen storage application. PMID:16787068

Li, Yingwei; Yang, Ralph T

2006-06-28

84

Modeling of Hydrogen Retention in Metallic Plasma Facing Components  

NASA Astrophysics Data System (ADS)

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

Guterl, Jerome; Smirnov, R.

2012-10-01

85

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

86

Hydrogen storage in microporous metal-organic frameworks.  

PubMed

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. PMID:12750515

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

2003-05-16

87

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

88

The temperature variation of hydrogen diffusion coefficients in metal alloys  

NASA Technical Reports Server (NTRS)

Hydrogen diffusion coefficients were measured as a function of temperature for a few metal alloys using an electrochemical evolution technique. Results from these measurements are compared to those obtained by the time-lag method. In all cases, diffusion coefficients obtained by the electrochemical method are larger than those by the time-lag method by an order of magnitude or more. These differences are attributed mainly to hydrogen trapping.

Danford, M. D.

1990-01-01

89

Interaction of hydrogen with metal nitrides and imides  

NASA Astrophysics Data System (ADS)

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

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

2002-11-01

90

Optical hydrogen sensors based on metal-hydrides  

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

91

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

DOEpatents

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

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

1991-01-01

92

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

DOEpatents

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

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

1991-10-15

93

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

DOEpatents

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

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

1990-08-28

94

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

DOEpatents

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

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

1990-01-01

95

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

96

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

SciTech Connect

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

Way, J.; Wolden, Colin

2013-09-30

97

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

98

Understanding atomistic phenomenon for hydrogen storage in complex metal hydrides  

NASA Astrophysics Data System (ADS)

The storage of hydrogen into metals in the form of complex metal hydrides is one of the most promising methods. However, the incorporation and release of hydrogen requires very high temperatures. The discovery that the addition of Ti compounds lowers NaAlH4 decomposition barriers closer to ambient conditions, has re-ignited the field, and it is believed that surface processes are responsible for H2 dissociation and mass transport required to form the hydrogenated materials. Such surface reactions mechanisms are however difficult to study with typical spectroscopic and imaging surface science tools. Alanes lack contrast under electron microscopes and can modify the Scanning Tunneling Microscopy (STM) tips. Infrared spectroscopy would be a sensitive probe to investigate the adsorption of hydrogen providing, but has so far failed to detect chemisorbed hydrogen on Ti-doped Al surfaces due to the weak Al-H dynamic dipole moment. Thus despite extensive investigations, the fundamental mechanisms of the role of Ti and alane formation have remained elusive. In this study combining surface infrared (IR) spectroscopy and density functional theory (DFT), we provide atomistic details about the role of Ti as a catalyst for hydrogen uptake and alane formation and evolution on single crystal Al(111) and Al(100) surfaces. We are able to detect H indirectly by using CO as a probe molecule of the weak Al-H species. We demonstrate that aluminum doped with very small amounts of titanium (in a specific configuration) can activate molecular hydrogen at temperatures as low as 90K. Once dissociated, hydrogen spills over from these catalytic sites on to the Al surface and protects the surface from further reactions. We also show that, on Ti-doped Al surfaces, the diffusion dynamics are severely altered by Ti doping (Atomic hydrogen and AlH3 are trapped at the Ti sites) as indicated by a marked decrease of higher alane concentrations, which is deleterious for hydrogen storage for which mass transport is required. These results provide an understanding of the reaction mechanisms for hydrogen storage in the alanates (NaAlH4) that can help in identifying and realizing other complex metal hydrides for an effective hydrogen based economy.

Chopra, Irinder Singh

99

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

E-print Network

Effects of hydrogen adsorption on single-wall carbon nanotubes: Metallic hydrogen decoration O. Gu of carbon nanotubes undergo dramatic changes with hydrogen chemisorption from first principle calculations other isomers can be insulating. For both zigzag and armchair nanotubes, hydrogenation of each carbon

Yildirim, Taner

100

Hydrogen Production From Metal-Water Reactions  

E-print Network

size, metal-steam interactions, and scaling energy inputs for theoretical automobile use. Work shouldAl = 4Al2O3 + 3H2 HP H2 H2 O Cell Bubbler - condenser Flowmeter High-pressure water cylinder Metering

Barthelat, Francois

101

The hydrogenation of methyl on metallic surfaces  

NASA Astrophysics Data System (ADS)

The stream technique was used to comparatively analyze the characteristics of the deposition of a-C:H films from methyl radicals transferred by a carrier gas CH4/C2H y /H2 ( y = 2, 4, 6) in a quartz tube with cylindrical insets made of Cu, Ni, Fe, W, Si, and stainless steel (SS), initial and coated with thin Pd or Rh films, over the temperature range 300-1000 K. The deposition of methyl was fully suppressed in a tube section heated to 380-800 K with all the insets specified. During further mixture movement outside this section in the tube with a decreasing wall temperature, carbon deposition resumed. The most effective catalyst of the hydrogenation reaction was stainless steel. Radicals and unsaturated hydrocarbons capable of polymerization at 300-400 K were fully removed from the carrier gas flow (CH4/C2H y /H2) after several hundreds of collisions with the surface of SS heated to 420-470 K. The possibility of creating an SS recombination filter for hydrocarbon radicals (the performance of radical hydrogenation reactions) transferred by a CH4/C2H y /H2 laminar flow was demonstrated. The deposition of a thin Pd film (˜10 nm) on steel did not increase the effectiveness of the surface with respect to radical recombination reactions. At the same time, Rh films increased the catalytic effectiveness of the surface of SS with respect to the hydrogenation of methyl and unsaturated hydrocarbons (380-420 K). The data obtained were used to select temperature conditions and mutual arrangement for the construction elements of an ITER diverter made of tungsten and stainless steel.

Gorodetskii, A. E.; Zalavutdinov, R. Kh.; Bukhovets, V. L.; Vnukov, S. P.; Zakharov, A. P.

2008-12-01

102

Determination of Very Small Hydrogen Amounts in Metals.  

National Technical Information Service (NTIS)

We describe a set up essentially aimed at the determination of very small hydrogen amounts in metals and specially uranium alloys. This set up designed and built up in our laboratory is characterized by its very high sensitivity due on one side to experim...

J. Devaux, R. Arnould-Laurent, J. P. Fidelle

1980-01-01

103

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

Microsoft Academic Search

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

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

2006-01-01

104

Composite hydrogen separation element and module  

DOEpatents

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

Edlund, David J. (Redmond, OR)

1996-03-12

105

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

106

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

E-print Network

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

107

Noble-metal-free plasmonic photocatalyst: hydrogen doped semiconductors  

PubMed Central

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

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

2014-01-01

108

Hydrogen permeability study of the thin Pd–Ag alloy membranes in the temperature range across the ?–? phase transition  

Microsoft Academic Search

A series of Pd–Ag membranes with different atomic ratio (Ag=0, 5, 10, 15, 20 and 23%) was fabricated by controlling the chemical components in the electroless plating bath followed by thermal annealing of the deposited metals. Gas permeation of the membranes was examined at the temperature ranges at 100–300°C. The hydrogen flux for the membranes of low Ag content gave

Junya Okazaki; David A. Pacheco Tanaka; Margot A. Llosa Tanco; Yoshito Wakui; Fujio Mizukami; Toshishige M. Suzuki

2006-01-01

109

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

PubMed

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

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

2012-12-01

110

Backflow correlations for the electron gas and metallic hydrogen M. Holzmann,1,2  

E-print Network

Backflow correlations for the electron gas and metallic hydrogen M. Holzmann,1,2 D. M. Ceperley,2 and diffusion Monte Carlo calculations of the electron gas and of solid and liquid metallic hydrogen with previous QMC calculations for the elec- tron gas and metallic crystal hydrogen, and present results using

111

Nanoparticulate gellants for metallized gelled liquid hydrogen with aluminum  

NASA Technical Reports Server (NTRS)

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

Palaszewski, Bryan; Starkovich, John; Adams, Scott

1996-01-01

112

Hydrogen evolution from water through metal sulfide reactions  

SciTech Connect

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

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

2013-11-28

113

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

114

Hot Hydrogen Testing of Refractory Metals and Ceramics  

NASA Technical Reports Server (NTRS)

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

Zee, Ralph; Chin, Bryan; Cohron, Jon

1993-01-01

115

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

NASA Astrophysics Data System (ADS)

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; Jouinot, Patrice

2010-01-01

116

CO2 hydrogenation on a metal hydride surface.  

PubMed

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

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

2012-04-28

117

On-site electrolysis sodium metal production by offshore wind or solar energy for hydrogen storage and hydrogen fuel cycle  

Microsoft Academic Search

If hydrogen can be solidified at room temperature or under atmospheric pressure, its long-distance transportation and long-term storage become possible. It is, then, considered to convert hydrogen into sodium metal. This sodium metal will be produced by electrolyzing seawater salt or rock salt and stored in kerosene to transport to a consumption place; when water is added to the sodium

Masataka Murahara; Kazuichi Seki

2010-01-01

118

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

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

119

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

PubMed

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

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

2011-04-01

120

First-Principles Study of the Hydrogen-Metal System  

NASA Astrophysics Data System (ADS)

The ab initio pseudopotential method within the local-density-functional formalism with a plane-wave basis is implemented to investigate the various properties of hydrogen in yttrium. With a "soft" pseudopotential scheme, satisfactory convergence is achieved with an energy cutoff of 30-40 Ry. It is found that a correction in the exchange -correlation functional is needed to handle the outer core contribution in this early transition metal. The overall results for the structural properties of bulk yttrium are in good agreement with experiments. In the solid solution phase of hydrogen in hexagonal close-packed yttrium ( alpha-YH_{x}, x < 0.5), the occupation of the tetrahedral site is found to be energetically favorable. The calculated vibrational frequency in a one-dimensional double-well potential along the c axis and the diffusion barrier from one tetrahedral site to the neighboring octahedral site are in excellent agreement with experiments. It is found that the pairing of hydrogen across a metal atom is indeed energetically favorable, which is explained from the electronic structure of the system. The study of beta -YH_{2 + x} is carried out with the metal atoms forming a face-centered cubic lattice and with 0 <= x <= 1. The total energy, electronic and structural properties, density of states (DOS), angular-momentum-decomposed DOS, and charge transfers are investigated by employing the supercell modeling method. Interesting phenomena such as the volume contraction with increasing x and the (420) -plane ordering of hydrogen are studied. Finally, yttrium trihydride with the metal atoms in the hexagonal close -packed (HCP) structure is examined. The calculations confirm that hexagonal YH_3 with wave-like hydrogen displacements is energetically more stable than the cubic structure, and is consistent with the neutron diffraction data for YD_3 and HoD _3. These hydrogen displacements are found to be Peierls-like distortions and are associated with the charge density wave in this three-dimensional system. The calculated final LDA band structure for YH _3 yields a semimetal rather than a semiconductor. However, the possible existence of an excitonic insulating ground state is speculated based on the unusual electronic structure in this system.

Wang, Yan

121

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

2008-07-01

122

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

DOEpatents

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

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

2009-10-20

123

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

NASA Technical Reports Server (NTRS)

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

Easter, R. W.

1974-01-01

124

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

E-print Network

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

Harilal, S. S.

125

Electrical Properties of MetalSilicon NitrideHydrogenated Amorphous Silicon Capacitor Elucidated Using Admittance Spectroscopy  

E-print Network

Electrical Properties of Metal­Silicon Nitride­Hydrogenated Amorphous Silicon Capacitor Elucidated online December 19, 2008) Detailed admittance spectroscopy was performed on a metal­silicon nitride­hydrogenated amorphous silicon (MIAS) structure. On the basis of the properties of hydrogenated amorphous silicon (a

126

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

Microsoft Academic Search

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

Sapru

1998-01-01

127

First-row transition metal dichalcogenide catalysts for hydrogen evolution reaction  

E-print Network

First-row transition metal dichalcogenide catalysts for hydrogen evolution reaction Desheng Kong­4 State-of-the-art hydrogen evolution reaction (HER) catalysts contain noble metals such as Pt expand and enrich the family of high performance HER catalysts. The efficient generation of hydrogen

Cui, Yi

128

Physics of Hydrogen Storage in Metal-Hydrides  

NASA Astrophysics Data System (ADS)

Physical aspects of the hydrogenation-dehydrogenation mechanisms of metal-metal hydride systems were examined. Experimental investigation was conducted for magnesium hydride as a case study. Theoretical analysis and computational study were carried out. The kinetics of hydrogenation-dehydrogenation of traditionally prepared Mg-MgH_2 and chemically synthesized Mg-MgH_2 were experimentally investigated. A detailed investigation was carried out to determine the reasons for the improved performance of a chemically synthesized Mg-MgH _2 previously reported by Bogdanovic and co-workers. A scanning electron microscope was used to examine the surface morphology of the samples. The surface of chemically prepared samples appeared to be covered with micro-spheroidal beads ranging in radius between 0.5 ?m and 0.05 ?m formed in a fractal-like configuration. Theoretical analysis indicated that the unusual surface structure of the chemically prepared samples could be responsible for the rapid uptake and release of hydrogen. The uptake and release enhancement is believed to be partially due to the substantial increase in the surface area and partially due fast diffusion into the smaller particles. The effect of the addition of nickel to the surface was also investigated. Theoretical analysis was carried out. Models for the process at the surface as well as in the bulk were developed. Diffusion equation was examined taking into account the diffusion coefficient being function of concentration. A non-linear differential equation resulted for this case. The differential equation was numerically solved.

Abdelfattah-Zidan, Ragaiy

129

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

130

Phase separation of metallic hydrogen-helium alloys  

NASA Technical Reports Server (NTRS)

Calculations are presented for the thermodynamic functions and phase-separation boundaries of solid metallic hydrogen-helium alloys at temperatures between zero and 19,000 K and at pressures between 15 and 90 Mbar. Expressions for the band-structure energy of a randomly disordered alloy (including third order in the electron-ion interaction) are derived and evaluated. Short- and long-range orders are included by the quasi-chemical method, and lattice dynamics in the virtual-crystal harmonic approximation. It is concluded that at temperatures below 4000 K, there is essentially complete phase separation of hydrogen-helium alloys and that a miscibility gap remains at the highest temperatures and pressures considered. The relevance of these results to models of the deep interior of Jupiter is briefly discussed.

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

1977-01-01

131

Capture of liquid hydrogen boiloff with metal hydride absorbers  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

132

A stable hydrogen-sensitive Pd gate metal-oxide semiconductor capacitor  

Microsoft Academic Search

A palladium gate metal-oxide semiconductor device has serious hydrogen-induced drift problems. We have shown that this drift can be eliminated through the introduction of a thin alumina layer between the metal and the silicon dioxide. This makes it possible to use Pd metal-oxide semiconductor devices as stable and accurate sensors for hydrogen.

M. Armgarth; C. Nylander

1981-01-01

133

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

E-print Network

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

Di Leo, Claudio V

2012-01-01

134

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

135

Sensors for detecting molecular hydrogen based on Pd metal alloys  

SciTech Connect

A simple process using a shadow mask is described to fabricate Nd/Ni resistors for detecting H{sub 2}. The performance of the resistive sensors is studied in relation to annealing the devices at different temperatures in 2% H{sub 2} in N{sub 2} for 2 h. The Pd/Ni film surface morphology is also examined in relation to the resistor response when exposed to H{sub 2}. The detailed information learned about the performance of the prototype resistors is used to fabricate wide-range-hydrogen microsensors, which combine a Pd/Ni chemiresistor and metal-oxide semiconductor capacitor along with a thin film metal heater and temperature sensor. These studies provide an important step for improving the reliability of microsensors used to detect H{sub 2} over concentrations ranging from 1 mTorr to 700 Torr.

Thomas, R.C.; Hughes, R.C. [Sandia National Labs., Albuquerque, NM (United States). Microsensor Research and Development Dept.

1997-09-01

136

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

137

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

138

Radiative proton-capture nuclear processes in metallic hydrogen  

NASA Astrophysics Data System (ADS)

Protons being the lightest nuclei, metallic hydrogen may exhibit the features of quantum liquids most relevant to enormous enhancement of nuclear reactions; thermonuclear and pycnonuclear rates and associated enhancement factors of radiative proton captures of high-Z nuclei as well as of deuterons are evaluated. Atomic states of high-Z impurities are determined in a way consistent with the equations of state and screening characteristics of the metallic hydrogen. Rates of pycnonuclear p-d reactions are prodigiously high at densities ?20 g/cm3, pressures ?1 Gbar, and temperatures ?950 K near the conditions of solidification. It is also predicted that proton captures of nuclei such as C, N, O, and F may take place at considerable rates, owing to strong screening by K-shell electrons, if the densities ?60-80 g/cm3, the pressures ?7-12 Gbar, and the temperatures just above solidification. The possibilities and significance of pycnonuclear p-d fusion experiments are specifically remarked.

Ichimaru, Setsuo

2001-10-01

139

Physics of hydrogen storage in metal-hydrides  

SciTech Connect

Physical aspects of the hydrogenation-dehydrogenation mechanisms of metal-metal hydride systems were examined. Experimental investigation was conducted for magnesium hydride as a case study. Theoretical analysis and computational study were carried out. The kinetics of hydrogenation-dehydrogenation of traditionally prepared Mg-MgH{sub 2} and chemically synthesized Mg-MgH{sub 2} were experimentally investigated. A detailed investigation was carried out to determine the reasons for the improved performance of a chemically synthesized Mg-MgH{sub 2} previously reported by Bogdanovic and co-workers. A scanning electron microscope was used to examine the surface morphology of the samples. The surface of chemically prepared samples appeared to be covered with micro-spheroidal beads ranging in radius between 0.5 {mu}m and 0.05 {mu}m formed in a fractal-like configuration. Theoretical analysis indicated that the unusual surface structure of the chemically prepared samples could be responsible for the rapid uptake and release of hydrogen. The uptake and release enhancement is believed to be partially due to the substantial increase n the surface area and partially due fast diffusion into the smaller particles. The effect of the addition to nickel to the surface was also investigated. Theoretical analysis was carried, out. Models for the process at the surface as well as in the bulk were developed. Diffusion equation was examined taking into account the diffusion coefficient being function of concentration. A nonlinear differential equation resulted for this case. The differential equation was numerically solved.

Abdelfattah-Zidan, R.

1992-12-31

140

The effect of tensile stress on hydrogen diffusion in metal alloys  

NASA Technical Reports Server (NTRS)

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

Danford, M. D.

1992-01-01

141

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

SciTech Connect

A series of transition metal phosphides, including MoP, WP, CoP, Co{sub 2}P, and Ni{sub 2}P, 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. - Graphical abstract: Metal phosphides were obtained stoichiometrically from their oxidic precursors by hydrogen plasma reaction under mild conditions.

Guan Jie [Department of Catalytic Chemistry and Engineering, State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012 (China); Wang Yao [Liaoning Key Laboratory of Petrochemical Technology and Equipments, Dalian University of Technology, Dalian 116012 (China); Qin Minglei; Yang Ying [Department of Catalytic Chemistry and Engineering, State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012 (China); Li Xiang [Department of Catalytic Chemistry and Engineering, State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012 (China); Liaoning Key Laboratory of Petrochemical Technology and Equipments, Dalian University of Technology, Dalian 116012 (China); Wang Anjie, E-mail: ajwang@dlut.edu.c [Department of Catalytic Chemistry and Engineering, State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012 (China); Liaoning Key Laboratory of Petrochemical Technology and Equipments, Dalian University of Technology, Dalian 116012 (China)

2009-06-15

142

Effect of vacancy defects in graphene on metal anchoring and hydrogen adsorption  

NASA Astrophysics Data System (ADS)

The dispersion of transition and alkaline-earth metals on defective graphenes is studied using first-principles calculations. The effect of vacancy defects on binding properties of metal atoms to the graphene and with hydrogen molecules is particularly investigated. It is shown that vacancy defects enhance efficiently the metal binding energy and thus its dispersion, particularly for alkaline-earth metals. Mg on vacancy defects shows a substantial increase in its binding energy and hydrogen uptake capacity. Among metals considered, Ca-vacancy complexes are found to exhibit the most favorable hydrogen adsorption characteristics in terms of the binding energy and the capacity.

Kim, Gyubong; Jhi, Seung-Hoon; Lim, Seokho; Park, Noejung

2009-04-01

143

Effect of hydrogen on the frequency of breaks in a metal during continuous casting of steel  

NASA Astrophysics Data System (ADS)

Data from a number of metallurgical works in Ukraine are used to analyze the possibility of break formation in a metal at a various hydrogen content in a liquid steel during continuous casting. A critical hydrogen content in the metal to be cast at which the probability of breaks in the metal increases sharply is revealed. Possible mechanisms of the suspension of the skin of an ingot in a continuous-casting mold and of breaks in a metal are considered.

Smirnov, A. N.; Epishev, M. V.; Kislitsa, V. V.; Nagornyi, S. A.

2009-12-01

144

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

Microsoft Academic Search

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

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

2011-01-01

145

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

NASA Technical Reports Server (NTRS)

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

Danford, M. D.

1983-01-01

146

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

E-print Network

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

Cafarella, Michael J.

147

Palladium and platinum gate metal-oxide-semiconductor capacitors in hydrogen and oxygen mixtures  

Microsoft Academic Search

A comparison is made between palladium (Pd) and platinum (Pt) as gates in metal-oxide-semiconductor devices in different hydrogen\\/oxygen mixtures. We have shown that Pd is superior as gate material for detection of small amounts of hydrogen in room ambient. At high hydrogen concentrations Pt would be more suitable.

M. Armgarth

1982-01-01

148

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. Sřrensen; Claus H. Christensen; Jens K. Nřrskov

2008-01-01

149

Hydrogen-bonded ferroelectrics based on metal-organic coordination.  

PubMed

Metal-organic coordination (MOC)-type ferroelectrics, cobalt(II) (R)-2-methylpiperazine (MPPA) trichloride [Co(II)Cl(3)(H-MPPA)], was constructed through hydrogen bonds. It is a good ferroelectric candidate with a P(s) = 6.8 microC.cm(-2) as high as almost twice that of triglycine sulfate (P(s) = 3.5 microC.cm(-2)) and significantly larger than that of KH(2)PO(4) at the low-temperature ferroelectric phase Fdd2. [Co(II)Cl(3)(H-MPPA)] is the first example of ferroelectric MOC that can really reach the spontaneous polarization status and opens up a new avenue to explore novel MOC-based ferroelectrics. PMID:19128170

Ye, Heng-Yun; Fu, Da-Wei; Zhang, Yi; Zhang, Wen; Xiong, Ren-Gen; Huang, Songping D

2009-01-14

150

``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 ˇ nH2O type. Here, original compositions, such as Pd|(NaOH + KOH)|Pd, Pd|CsHSO4|Pd, Ti|KOH ˇ H2O|C, and Ti|KOH ˇ 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

151

Transport of hydrogen in metals with occupancy dependent trap energies  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

152

Standard practice for evaluation of hydrogen uptake, permeation, and transport in metals by an electrochemical technique  

E-print Network

1.1 This practice gives a procedure for the evaluation of hydrogen uptake, permeation, and transport in metals using an electrochemical technique which was developed by Devanathan and Stachurski. While this practice is primarily intended for laboratory use, such measurements have been conducted in field or plant applications. Therefore, with proper adaptations, this practice can also be applied to such situations. 1.2 This practice describes calculation of an effective diffusivity of hydrogen atoms in a metal and for distinguishing reversible and irreversible trapping. 1.3 This practice specifies the method for evaluating hydrogen uptake in metals based on the steady-state hydrogen flux. 1.4 This practice gives guidance on preparation of specimens, control and monitoring of the environmental variables, test procedures, and possible analyses of results. 1.5 This practice can be applied in principle to all metals and alloys which have a high solubility for hydrogen, and for which the hydrogen permeation is ...

American Society for Testing and Materials. Philadelphia

1997-01-01

153

Bi-metallic Catalyst for Hydrogen Sorption of Magnesium Hydride  

NASA Astrophysics Data System (ADS)

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

Zahiri-Sabzevar, Beniamin

154

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

155

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

156

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

157

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

PubMed

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

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

2013-11-01

158

Thickness dependence of hydrogen permeability for Ni-BaCe{sub 0.8}Y{sub 0.2}O{sub 3-{delta}}.  

SciTech Connect

The hydrogen separation properties and thickness dependence of the hydrogen flux for Ni-BCY membranes, containing a proton-conductor (BaCe{sub 0.8}Y{sub 0.2}O{sub 3-{alpha}}, i.e., BCY) and an electron-conductor (Ni metal), were studied as a function of temperature in the thickness range of 0.08-1.16 mm. Feed gas was composed of 3.8% H{sub 2} balanced with He (pH{sub 2}O = 0.03 atm) gas and sweep gas contained 100 ppm hydrogen balanced with nitrogen. The hydrogen permeation flux due to ambipolar diffusion dominates over the entire experimental temperature range, but the hydrogen permeation flux through the Ni-metal increases with temperature due to its endothermic hydrogen solubility. The hydrogen flux through the Ni-BCY membranes is inversely proportional to the thickness, indicating that bulk diffusion is the rate limiting step down to a thickness of 80 {micro}m. For thicker (> 640 {micro}m) membranes, the flux decreases monotonically as the temperature increases up to 900 C, whereas the flux for thinner (< 200 {micro}m) membranes increases as temperature increases up to {approx} 750 C and then remains nearly constant as the temperature is further increased.

Song, S.-J.; Moon, J.-H.; Lee, T. H.; Dorris, S. E.; Balachandran, U.; Energy Systems; Chonnam National Univ.

2008-10-01

159

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

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

160

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

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

161

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

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

162

Transforming nonselective into chemoselective metal catalysts for the hydrogenation of substituted nitroaromatics.  

PubMed

It is generally accepted that good hydrogenation noble and nonnoble metal catalysts such as Pt, Ru, or Ni are not chemoselective for hydrogenation of nitro groups in substituted aromatic molecules. We have found that it is possible to transform nonchemoselective into highly chemoselective metal catalysts by controlling the coordination of metal surface atoms while introducing a cooperative effect between the metal and a properly selected support. Thus, highly chemoselective and general hydrogenation Pt, Ru, and Ni catalysts can be prepared by generating nanosized crystals of the metals on the surface of a TiO 2 support and decorating the exposed (111) and (100) crystal faces by means of a simple catalyst activation procedure. By doing this, it has been possible to change the relative rate for hydrogenating competitive groups present in the molecule by almost 2 orders of magnitude, increasing the chemoselectivity from less than 1% to more than 95%. PMID:18597431

Corma, Avelino; Serna, Pedro; Concepción, Patricia; Calvino, José Juan

2008-07-01

163

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

NASA Astrophysics Data System (ADS)

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

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

164

Prediction of Hydrogen Entry and Permeation in Metals and Alloys.  

National Technical Information Service (NTIS)

This report summarizes results of the past year on our continuing experiments directed to the problem of hydrogen entry and degradation of materials both of planar surfaces and for the more complicated recessed surface. For the planar surface the hydrogen...

H. W. Pickering

1993-01-01

165

Heat energy from hydrogen-metal nuclear interactions  

NASA Astrophysics Data System (ADS)

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

Hadjichristos, John; Gluck, Peter

2013-11-01

166

Critical concentration for hydrogen bubble formation in metals  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

167

Heat energy from hydrogen-metal nuclear interactions  

SciTech Connect

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

Hadjichristos, John [Defkalion GT SA, 1140 Homer Street, Suite 250, Vancouver BC V682X6 (Canada)] [Defkalion GT SA, 1140 Homer Street, Suite 250, Vancouver BC V682X6 (Canada); Gluck, Peter [Retired from INCDTIM Cluj-Napoca in 1999 (Romania)] [Retired from INCDTIM Cluj-Napoca in 1999 (Romania)

2013-11-13

168

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

169

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. PMID:19082087

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

2009-01-01

170

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

171

New isoreticular metal-organic framework materials for high hydrogen storage capacity  

NASA Astrophysics Data System (ADS)

We propose new isoreticular metal-organic framework (IRMOF) materials to increase the hydrogen storage capacity at room temperature. Based on the potential-energy surface of hydrogen molecules on IRMOF linkers and the interaction energy between hydrogen molecules, we estimate the saturation value of hydrogen sorption capacity at room temperature. We discuss design criteria and propose new IRMOF materials that have high gravimetric and volumetric hydrogen storage densities. These new IRMOF materials may have gravimetric storage density up to 6.5wt% and volumetric storage density up to 40kgH2/m3 at room temperature.

Sagara, Tatsuhiko; Ortony, Julia; Ganz, Eric

2005-12-01

172

Advanced Hydrogen Transport Membranes for Vision 21 Fossil Fuel Plants  

Microsoft Academic Search

During this quarter composite layered membrane size was scaled-up and tested for permeation performance. Sintering conditions were optimized for a new cermet containing a high permeability metal and seals were developed to allow permeability testing. Theoretical calculations were performed to determine potential sulfur tolerant hydrogen dissociation catalysts. Finally, work was finalized on mechanical and process & control documentation for a

Carl R. Evenson; Harold A. Wright; Adam E. Calihman; U. Balachandran; Richard N. Kleiner; James E. Stephan; Frank E. Anderson; Chandra Ratnasamy; Mahendra Sunkara; Jyothish Thangala; Clive Brereton; Warren Wolfs; James Lockhart

2005-01-01

173

Frontispiece: engineering catalyst microenvironments for metal-catalyzed hydrogenation of biologically derived platform chemicals.  

PubMed

Catalyst Stability In their Communication on page?12718?ff., J.?A. Dumesic and co-workers show that microenvironments formed around the catalytic sites of supported metal hydrogenation catalysts can mitigate deactivation caused by biogenic impurities. PMID:25388933

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

2014-11-17

174

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

E-print Network

to have potential for hydrogen separation technology. These were Edible Fats and Oils, Float Glass, Germanium, Heat Treating of Metal Parts, Molybdenum Powder, Powder Metallurgy, Rhenium, Silicon (Electronics) and Tungsten. While these industries... to have potential for hydrogen separation technology. These were Edible Fats and Oils, Float Glass, Germanium, Heat Treating of Metal Parts, Molybdenum Powder, Powder Metallurgy, Rhenium, Silicon (Electronics) and Tungsten. While these industries...

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

175

Hydrogenation of a 4-benzylpyridine derivative over supported precious metal catalysts  

Microsoft Academic Search

The heterogeneous catalytic hydrogenation of 4-(4-fluorobenzyl)pyridine resulted in 4-(4-fluorobenzyl)piperidine, an important and valuable pharmaceutical intermediate. The effects of solvents, temperature, catalytic metals and amount of catalyst on the conversion and the rate of the hydrogenation were investigated. Among the precious metal catalysts applied, the best result was obtained by using a rhodium on carbon catalyst. Palladium or platinum on carbon

Ágnes Proszenyák; Béla Ágai; László Heged?s; Ferenc Faigl

2004-01-01

176

Optical studies of hydrogen above 200 gigapascals - Evidence for metallization by band overlap  

NASA Technical Reports Server (NTRS)

Direct optical observations of solid hydrogen to pressures in the 250-gigapascal range at 77 K are reported. Hydrogen samples appear nearly opaque at the maximum pressures. Measurements of absorption and Raman spectra provide evidence that electronic excitations in the visible region begin at about 200 gigapascals. The optical data are consistent with a band-overlap mechanism of metallization.

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

1989-01-01

177

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

178

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

PubMed Central

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

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

2013-01-01

179

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

180

Applications of hydrogenation and dehydrogenation on noble metal catalysts  

E-print Network

catalysts have undergone considerable evolution over the past several decades. The first generation industrial catalysts in selective hydrogenation were sulfides such as nickel sulfide 20 or nickel- tungsten sulfide. 21 Some copper based catalysts were... via continuous injection of sulfur compounds Second generation selective hydrogenation catalysts were introduced in the late 1960s. 23, 24 They contained palladium dispersed on porous support and are selective to the hydrogenation of alkyne...

Wang, Bo

2009-05-15

181

Characteristics of the boundary layer with hydrogen combustion with variations of thermal conditions on a permeable wall  

Microsoft Academic Search

The paper describes a numerical study of the influence of thermal and boundary conditions on the structure of laminar and\\u000a turbulent diffusion flames in the cases with hydrogen injection through a porous surface and with hydrogen combustion in an\\u000a air flow. Two types of boundary conditions are compared: with a given constant temperature T\\u000a \\u000a w\\u000a = const over the length

É. P. Volchkov; V. V. Terekhov; V. I. Terekhov

2009-01-01

182

A metal-free strategy to release chemisorbed h2 from hydrogenated boron nitride nanotubes.  

PubMed

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

Roy, Lisa; Bhunya, Sourav; Paul, Ankan

2014-11-10

183

Self-discharge mechanism of nickel-hydrogen batteries using metal hydride anodes  

NASA Astrophysics Data System (ADS)

The self-discharge mechanism of nickel-hydrogen batteries using metal hydride anodes has been investigated and discussed by dividing the capacity loss during the storage in open-circuit conditions into two parts, i.e., reversible and irreversible ones. The reversible capacity loss was attributed to the desorption of hydrogen from the metal hydride anode and the irreversible capacity loss to the deterioration of the hydrogen-absorbing alloy. Microencapsulation of the alloy with a thin copper layer was found to improve the self-discharge characteristics.

Iwakura, Chiaki; Kajiya, Yoshio; Yoneyama, Hiroshi; Sakai, Tetsuo; Oguro, Keisuke

1989-05-01

184

The chemical potential of hydrogen in Mg-films and metal-doped carbon nanostructures  

NASA Astrophysics Data System (ADS)

We use first-principles density functional theory to study the binding mechanism of hydrogen to nanoscale systems. We investigate the performance of the exchange-correlation functional in describing the interaction between hydrogen and metal systems and the importance of the vibrational contribution in the formation enthalpy. In ultrathin Mg films the stability of hydrides is much lower than in the corresponding bulk systems and it can be modified by metal alloying. We calculate the chemical potential of hydrogen in Mg films for different dopant species and film thicknesses while including all vibrational degrees of freedom. By comparing the chemical potential with that of free hydrogen gas at finite temperature and pressure, we construct a hydrogenation phase diagram and identify the conditions for hydrogen absorption/desorption. The vibrational contribution to the chemical potential of hydrogen becomes more prominent for dihydrogen adsorption to metals, where its significance dramatically changes depending on the binding characteristics. This feature is illustrated by the example of metal-doped nanocarbon systems.

Yoon, Mina; Weitering, Hanno; Zhang, Zhenyu

2011-03-01

185

Physics of Strongly Coupled Plasmas 2. Statistical Physics of Dense Plasma Materials: Metallic Hydrogen  

NASA Astrophysics Data System (ADS)

Classical and quantum simulation methods based on Monte Carlo and density functional approaches are described; these play vital parts in elucidation of fundamental properties of condensed plasmas. Issues of metallization and magnetization in ultradense hydrogen matter are reviewed in conjunction with experiments In recent ultrahigh-pressure metal physics and with stellar structure and magnetism.

Ichimaru, Setsuo; Iyetomi, Hiroshi

186

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

Microsoft Academic Search

An economically viable and environmental friendly method of generating hydrogen for fuel cells is by the reaction of certain metals with steam, called metalsteam 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 environmental benignity, and attractive economics, iron appears to be the metal of

Abdul-Majeed Azad; Sathees Kesavan

2006-01-01

187

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

188

Solubility of iron in metallic hydrogen and stability of dense cores in giant planets  

E-print Network

Solubility of iron in metallic hydrogen and stability of dense cores in giant planets Sean M. Wahl. In this study, we perform ab initio calculations to study the solubility of an innermost metallic core. We find. We compare with and summarize the results for solubilities on other probable core constituents

Militzer, Burkhard

189

Recent developments in transition metal carbides and nitrides as hydrogen evolution electrocatalysts.  

PubMed

The production of hydrogen by the electrolysis of water, a sustainable and greenhouse-gas-free source, requires an efficient and abundant electrocatalyst that minimizes energy consumption. Interest in transition metal carbides and nitrides has been aroused by their promising properties that make them potential substitutes for Pt-group metals as catalysts for the hydrogen evolution reaction. In this review, we discuss systematically the recent progress in the development of group IV-VI metal carbides and nitrides toward the hydrogen evolution reaction. Some strategies for designing such catalysts and improving their efficiency and reliability, including nanostructuring, optimizing hydrogen binding energy, interaction with the supporting material, and exploiting hybrid structures, are highlighted. We conclude with an outlook on the challenges in designing future HER electrocatalysts. PMID:23982806

Chen, Wei-Fu; Muckerman, James T; Fujita, Etsuko

2013-10-11

190

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

191

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

Microsoft Academic Search

Detection of explosive gas leaks such as hydrogen (H2) becomes key element in the wake of counter-terrorism threats, introduction of hydrogen powered vehicles and use of hydrogen as a fuel for space explorations. In recent years, a significant interest has developed on metal oxide nanostructured sensors for the detection of hydrogen gas. Gas sensors properties such as sensitivity, selectivity and

Sameer Arun Deshpande

2007-01-01

192

Hot hydrogen testing of metallic turbo pump materials  

NASA Technical Reports Server (NTRS)

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

Zee, Ralph; Chin, Bryan; Inamdar, Rohit

1993-01-01

193

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

DOEpatents

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

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

2012-11-13

194

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

E-print Network

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

195

Mechanism of Hydrogen-Permeation Through Oxidized Metals.  

National Technical Information Service (NTIS)

The mechanism of hydrogen permeation through high-temperature alloys and through oxidizied high-temperature alloys which probably will be used in the project 'Nukleare Prozesswaerme', is examined. The examined steels are 'Hastelloy X' and 'Inconel 617' wh...

M. Andritschky

1986-01-01

196

Vanadium diaphragm electrode serves as hydrogen diffuser in lithium hydride cell  

NASA Technical Reports Server (NTRS)

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

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

1967-01-01

197

[Regulation of sulfates, hydrogen sulfide and heavy metals in technogenic reservoirs by sulfate-reducing bacteria].  

PubMed

Sulfate-reducing bacteria Desulfovibrio desulfuricans Ya-11 in the presence of sulfates and organic compounds in the medium reduce sulfates to hydrogen sulfide (dissimilatory sulfate reduction). Heavy metals in concentration over 2 mM inhibit this process. Pb2+, Zn2+, Ni2+, Co2+, Fe2+ and Cd2+ ions in concentration 1-1.5 mM display insignificant inhibiting effect on sulfate reduction process, and metals precipitate in the form of sulfides. At concentrations of heavy metals 2-3 mM one can observe a decrease of sulfates reduction intensity, and a percent of metals binding does not exceed 72%. Obtained results give reason to confirm, that sulfate-reducing bacteria play an important role in regulation of the level of sulfates, hydrogen sulfide and heavy metals in reservoirs and they may be used for purification of water environment from these compounds. PMID:21598657

Hudz', S P; Peretiatko, T B; Moroz, O M; Hnatush, S O; Klym, I R

2011-01-01

198

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

NASA Technical Reports Server (NTRS)

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

Lee, Jonathan A.

2010-01-01

199

Electrical Properties of Metal-Silicon Nitride-Hydrogenated Amorphous Silicon Capacitor Elucidated Using Admittance Spectroscopy  

Microsoft Academic Search

Detailed admittance spectroscopy was performed on a metal-silicon nitride-hydrogenated amorphous silicon (MIAS) structure. On the basis of the properties of hydrogenated amorphous silicon (a-Si:H), three simplified equivalent circuit models under various operating conditions (accumulation, depletion and full depletion) are presented along with an alternative direct measurement method at room temperature. Admittance spectroscopy shows that the interface states density between silicon

Ming-Ta Hsieh; Jenn-Fang Chen; Kuo-Hsi Yen; Hsiao-Wen Zan; Chan-Ching Chang; Chih-Hsien Chen; Ching-Chieh Shih; Yeong-Shyang Lee

2008-01-01

200

Hydrogenation of Aromatic Nitrogroups with Precious Metal Powder Catalysts: Influence of Modifier on Selectivity and Activity  

Microsoft Academic Search

The development of new improved catalysts for the selective hydrogenation of aromatic nitrogroups is still a field of high\\u000a interest for the chemical industry. Hydrogenation of aromatic nitrogroups to the corresponding aromatic amines is one of the\\u000a most important applications for precious metal powder catalysts (PMPC). In this paper various commercial PMPC technologies\\u000a such as palladium, platinum, platinum modified with

Konrad MobusDorit; Dorit Wolf; Holger Benischke; Ulrike Dittmeier; Klaus Simon; Uwe Packruhn; Ralf Jantke; Stefan Weidlich; Christoph Weber; Baoshu Chen

2010-01-01

201

Systems and methods for selective hydrogen transport and measurement  

DOEpatents

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

Glatzmaier, Gregory C

2013-10-29

202

Tuning hydrogen sorption properties of metal-organic frameworks by postsynthetic covalent modification.  

PubMed

Postsynthetic modification is presented as a means to tune the hydrogen adsorption properties of a series of metal-organic frameworks (MOFs). IRMOF-3 (isoreticular metal-organic framework), UMCM-1-NH(2) (University of Michigan crystalline material), and DMOF-1-NH(2) (DABCO metal-organic framework) have been covalently modified with a series of anhydrides or isocyanates and the hydrogen sorption properties have been studied. Both the storage capacities and isosteric heats of adsorption clearly show that covalent postsynthetic modification can significantly enhance the sorption affinity of MOFs with hydrogen and in some cases increase both gravimetric and volumetric uptake of the gas as much as 40 %. The significance of the present study is illustrated by: 1) the nature of the substituents introduced by postsynthetic modification result in different effects on the binding of hydrogen; 2) the covalent postsynthetic modification approach allows for systematic modulation of hydrogen sorption properties; and 3) the ease of postsynthetic modification of MOFs allows a direct evaluation of the interplay between MOF structure, hydrogen uptake, and heat of adsorption. The findings presented herein show that postsynthetic modification is a powerful method to manipulate and better understand the gas sorption properties of MOFs. PMID:19918824

Wang, Zhenqiang; Tanabe, Kristine K; Cohen, Seth M

2010-01-01

203

New approach in the study of hydrogen dynamics in metal hydrides by neutron transmission experiments  

NASA Astrophysics Data System (ADS)

We propose a new approach to the analysis of total cross-section measurements of hydrogen in metal hydrides, aimed at obtaining primary information about the dynamics of hydrogen in these compounds, including the characteristic frequencies and mean-square displacement of the proton. We use a simplified model to describe the hydrogen vibrational spectra and a translational effective mass to take into account the hydrogen diffusive motion. This approach is based on the splitting of the total incoherent cross-section in two well-defined terms: a quasi-elastic contribution - depending on the translational effective mass and the mean-square displacement of hydrogen atoms - and an inelastic contribution, related to the vibrational frequency spectra. In this work we present the starting approximations and develop the formalism involved in the analysis, illustrating its application through experiments performed on zircaloy-4, magnesium and niobium hydrides.

Santisteban, J. R.; Granada, J. R.; Dawidowski, J.

1999-09-01

204

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

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

205

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

206

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

NASA Technical Reports Server (NTRS)

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

Gales, C.; Perroud, P.

1981-01-01

207

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

208

Generation of hydrogen from aluminum and water – Effect of metal oxide nanocrystals and water quality  

Microsoft Academic Search

Metal Oxides nanocrystals such as TiO2, Co3O4, Cr2O3, Fe2O3, Mn2O3, NiO, CuO and ZnO were used as modifiers on the metallic aluminum (Al) powders for the production of hydrogen in deionized water or tap water at room temperature. In particular, the influences of TiO2 nanocrystals with various crystal sizes on the production of hydrogen from the reaction in tap water

Hong-Wen Wang; Hsing-Wei Chung; Hsin-Te Teng; Guozhong Cao

2011-01-01

209

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

PubMed

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

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

2013-08-01

210

Defect structure and transport properties of Ni-SrCeO{sub 3-delta} cermet for hydrogen separation membrane.  

SciTech Connect

Research on hydrogen separation membranes is motivated by the increasing demand for an environmentally benign, inexpensive technology for separating hydrogen from gas mixtures. Although most studies of hydrogen separation membranes have focused on proton-conducting oxides by themselves, the addition of metal to these oxides increases their hydrogen permeability and improves their mechanical stability. This study began by determining hydrogen permeation properties of SrCe0.8Yb0.2O3-delta (SCYb). The results showed that at the investigated temperatures (600-900 degrees C), the hydrogen permeation rate is limited by electron flow. To further enhance hydrogen permeability, a cermet (i.e., ceramic-metal composite) membrane was made by adding Ni to the SCYb. At 900 degrees C, with 20% H-2/balance He as a feed gas (p(H2O) = 0.03 atm), the hydrogen permeation rate was 0.105 cm(3)/min cm(2) for 0.25-mm-thick Ni/SCYb and 0.008 cm(3)/min cm(2) for SCYb (0.7-mm thick). The dependence of hydrogen permeability on temperature and hydrogen partial-pressure gradients was also determined. The proton conductivity (approximate to ambipolar conductivity) was extracted from the dependence of hydrogen permeability on hydrogen potential gradients. The results demonstrate that adding Ni to SCYb considerably increases its hydrogen permeability by increasing its electron conductivity.

Song, S.-J.; Lee, T. H.; Wachsman, E. D.; Chen, L.; Dorris, S. E.; Balachandran, U.; Energy Technology; Univ. of Florida

2005-01-01

211

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

PubMed

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

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

2014-07-01

212

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

EPA Science Inventory

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

213

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

214

Investigation of the feasibility of developing low permeability polymeric films  

NASA Technical Reports Server (NTRS)

The feasibility of reducing the gas permeability rate of Mylar and Kapton films without drastically effecting their flexibility characteristics at cryogenic temperatures was considered. This feasibility was established using a concept of diffusion bonding two layers of metallized films together forming a film-metal-film sandwich laminate. The permeability of kapton film to gaseous helium was reduced from a nominal ten = to the minus 9 power cc-mm/sq cm sec. cm Hg to ten to the minus 13 power cc-mm/ sq cm - sec. cm Hg with some values as low as ten to the minus 15 power cc - mm/sq cm m-sec - cm Hg being obtained. Similar reductions occurred in the liquid hydrogen permeability at -252 C. In the course of the program the permeability, flexibility and bond strength of plain, metalized and diffusion bond film were determined at +25 C, -195 C and -252 C. The cryogenic flexibility of Kapton film was reduced slightly due to the metallization process but no additional loss in flexibility resulted from the diffusion bonding process.

Hoggatt, J. T.

1971-01-01

215

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 Brřnsted-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

216

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

Microsoft Academic Search

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

H. Bach; S. Black; W. Chamberlin

1997-01-01

217

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

DOEpatents

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

Dhooge, Patrick M. (Corrales, NM)

1987-10-13

218

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

E-print Network

Modeling hydrogen and helium entrapment in flowing liquid metal surfaces as plasma of adequate helium self-trapping in flowing lithium as PFC without active pumping. Ă? 2002 Published.g., Li, Sn, Ga, flibe) to work satisfactorily depends on whether particles with negligible chemical

Harilal, S. S.

219

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

E-print Network

-precious-metal catalysts Hongqiang Hu, Yanzhen Fan, Hong Liu* Department of Biological and Ecological Engineering, Oregon August 2009 Keywords: Hydrogen production Microbial electrolysis cells (MECs) NiMo NiW Cathode catalyst catalyst in microbial electrolysis cells (MECs). Its high cost, however, limits the practical applications

Tullos, Desiree

220

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

Microsoft Academic Search

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

G. L. Mackie

1989-01-01

221

Homogeneous and heterogeneous asymmetric reactions. Part 13. Clay-supported noble metal catalysts in enantioselective hydrogenations  

Microsoft Academic Search

The preparation, characterization and application of new clay-supported Pt and Pd catalysts containing cinchonidine as chiral modifier are described. The preparation was carried out by deposition of the metal by impregnation followed by the immobilization of the modifier. The catalysts were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The samples were tested in enantioselective hydrogenation of ethyl

Béla Török; Katalin Balázsik; Istvá Kun; György Szöllösi; Gerda Szakonyi; Mihály Bartók

1999-01-01

222

Direct Observation of Hydrogen Adsorption Sites and Nanocage Formation in Metal-Organic Frameworks  

SciTech Connect

The hydrogen adsorption sites in MOF5 were determined using neutron powder diffraction along with first-principles calculations. The metal-oxide cluster is primarily responsible for the adsorption while the organic linker plays only a secondary role. Equally important, at low temperatures and high-concentration, H{sub 2} molecules form unique interlinked high-symmetry nanoclusters with intermolecular distances as small as 3.0 A ring and H{sub 2} uptake as high as 11 wt %. These results hold the key to optimizing metal-organic framework (MOF) materials for hydrogen storage applications and also suggest that MOFs can be used as templates to create artificial interlinked hydrogen nanocages with novel properties.

Yildirim, T.; Hartman, M.R. [NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)

2005-11-18

223

Hydrogen transport by group 5 metals: Achieving the maximal flux density through a vanadium membrane  

NASA Astrophysics Data System (ADS)

Hydrogen transport by 100-?m-thick vanadium and palladium membranes was studied in the pressure range from 1 × 10-8 to 4.5 × 10-1 MPa at a temperature of 400°C. Both sides of the vanadium membrane were covered by 2 ?m of palladium (Pd-V-Pd) for facilitating the dissociative absorption and associative desorption of H2 molecules. At low pressures, hydrogen flux densities through vanadium and palladium membranes are nearly the same; at high pressures, the flux through the vanadium membrane becomes 16 times larger than the flux through the palladium membrane and attains a value of 2.4 scc cm-2 s-1. This flux of permeating hydrogen is larger than all values ever observed earlier for membranes made of group 5 metals or any other unsupported metal membranes.

Alimov, V. N.; Busnyuk, A. O.; Notkin, M. E.; Livshits, A. I.

2014-03-01

224

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

NASA Astrophysics Data System (ADS)

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 predetermined duration. Tools are therefore needed to identify and quantify the terminal electron acceptor processes (TEAPs) that are being achieved during bioremediation in an aquifer, and that this is done at a high spatial resolution. Hydrogen holds the promise of being a key parameter that may be used to identify TEAPs. Theoretical analysis have shown that steady-state hydrogen levels in the subsurface are solely dependent upon the physiological parameters of the hydrogen-consuming microorganisms, and that hydrogen concentrations increase 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. The objective of the research is to gain a basic understanding of the hydrogen dynamics in an aquifer during a trace metal/radionuclide bioremediation scheme. For this purpose, a series of batch studies have been conducted during the first year of this project. In these studies the utilization of acetate and hydrogen by geobacter sulfurreducens were studied. In all cases Fe(III) was the electron acceptor. Microcosms were set up to investigate the utilization of hydrogen and acetate when either of them is the sole electron donor and when both are present and utilized simultaneously as electron donor. These experiments were conducted for varying initial conditions of the hydrogen and acetate concentration, and the disappearance of these compounds plus the evolution of Fe(II) as well as biomass was monitored over time. The results of these studies indicate that the biokinetic coefficients describing the rate of hydrogen utilization are not affected by the simultaneous utilization of acetate. While there is no difference in acetate and/or hydrogen utilization when they are the sole electron donor or used simultaneously, evolution of Fe(II) and biomass over time is increased by the simultaneous utilization of hydrogen and acetate compared to the case where either of them is the sole electron donor due to the increased biomass production. These results are being tested against hydrogen profiles in continuous flow column experiments.

Jaffe, P. R.; Komlos, J.; Brown, D. G.; Lovley, D. R.

2002-05-01

225

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

PubMed

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

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

2014-01-28

226

Activation of Supported Pd Metal Catalysts for Selective Oxidation of Hydrogen to Hydrogen Peroxide  

Microsoft Academic Search

Catalytic activity of supported Pd metal catalysts (Pd metal deposited on carbon, alumina, gallia, ceria or thoria) showing almost no activity in the liquid-phase direct oxidation of H2 to H2O2 (at 295 K) in acidic medium (0.02 M H2SO4) can be increased drastically by oxidizing them using different oxidizing agents, such as perchloric acid, H2O2, N2O and air. In the

Vasant R. Choudhary; Abaji G. Gaikwad; Subhash D. Sansare

2002-01-01

227

Hydrogen as a fuel  

NASA Astrophysics Data System (ADS)

Electrolysis-produced hydrogen employing hydroelectric or nuclear generation of electricity is expected to be available in Canada, at prices that are competitive with other transportation energy forms, before the end of this century. Attention is presently given to the use of carbon-free, electrolytically produced hydrogen as a motor vehicle fuel and as a vehicular fuel cell fuel. An assessment of alternative onboard hydrogen storage systems, including metal hydride tanks, pressure vessels, permeable glass microspheres, and cryogenic tanks, indicates that hydrogen-fueled vehicles must be considerably more efficient than present gasoline-fueled internal combustion engines in order to compensate for the greater size and weight typical of the hydrogen storage systems. Fuel cells are considered as inherently more efficient systems than internal combustion engines for vehicular propulsion.

Wallace, J. S.; Ward, C. A.

228

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

229

Characterization and high throughput analysis of metal hydrides for hydrogen storage  

NASA Astrophysics Data System (ADS)

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

Barcelo, Steven James

230

Influence of surface contaminations on the hydrogen storage behaviour of metal hydride alloys.  

PubMed

Hydrogen storage in metal hydrides is a promising alternative to common storage methods. The surface of a metal hydride plays an important part in the absorption of hydrogen, since important partial reaction steps take place here. The development of surface contaminations and their influence on hydrogen absorption is examined by means of absorption experiments and surface analysis, using X-ray photoelectron spectroscopy (XPS), thermal desorption mass spectrometry (TDMS) and secondary neutral mass spectrometry (SNMS), in this work. All investigations were carried out on a modern AB(2) metal hydride alloy, namely Ti(0.96)Zr(0.04)Mn(1.43)V(0.45)Fe(0.08). Surface analysis (SNMS, XPS) shows that long-term air storage (several months) leads to oxide layers about 15 nm thick, with complete oxidation of all main alloy components. By means of in situ oxygen exposure at room temperature and XPS analysis, it can be shown that an oxygen dose of about 100 Langmuirs produces an oxide layer comparable to that after air storage. Manganese enrichment (segregation) is also clearly observed and is theoretically described here. This oxide layer hinders hydrogen absorption, so an activation procedure is necessary in order to use the full capacity of the metal hydride. This procedure consists of heating (T = 120 degrees C) in vacuum and hydrogen flushing at pressures like p = 18 bar. During the activation process the alloy is pulverized to particles of approximately 20 microm through lattice stretches. It is shown that this pulverization of the metal hydride (creating clean surface) during hydrogen flushing is essential for complete activation of the material. Re-activation of powder contaminated by small doses of air (p approximately 0.1 bar) does not lead to full absorption capacity. In ultrahigh vacuum, hydrogen is only taken up by the alloy after sputtering of the surface (which is done in order to remove oxide layers from it), thus creating adsorption sites for the hydrogen. This is shown by TDMS measurements with and without sputtering and oxygen exposure. PMID:18210095

Schülke, Mark; Paulus, Hubert; Lammers, Martin; Kiss, Gábor; Réti, Ferenc; Müller, Karl-Heinz

2008-03-01

231

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

232

Permeability Test  

NSDL National Science Digital Library

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

2008-05-16

233

Permeable Pavement  

NSDL National Science Digital Library

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

Integrated Teaching And Learning Program

234

The Role of Water in the Storage of Hydrogen in Metals  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

235

3-Glycidoxypropyltrimethoxysilane mediated in situ synthesis of noble metal nanoparticles: application to hydrogen peroxide sensing.  

PubMed

The in situ synthesis is reported of noble metal nanoparticles via 3-glycidoxypropyltrimethoxysilane mediated reduction of 3-aminopropyltrimethoxysilane treated metal salts during sol-gel processing. The method described involves the synthesis of uniform spherical nanoparticles of gold, silver and palladium with controlled size that can be directly utilized for thin film preparation. A detailed study of the synthesis and application of gold nanoparticles to the electrochemical detection of hydrogen peroxide was carried out and reveals that the amplification of hydrogen peroxide sensing is size-dependent. In addition, these nanoparticles exhibit excellent compatibility towards composite preparation. As an example, a nanocomposite with Prussian Blue (PB) is synthesized and found to be useful for the fabrication of chemically modified electrodes (CME). The resulting CME shows dramatic improvement in the electrochemistry of PB with gradual enhancement in electrocatalytic efficiency towards hydrogen peroxide sensing. The nanocomposite is used to study the direct and horseradish peroxidase (HRP)-catalyzed reduction of hydrogen peroxide. The results recorded for hydrogen peroxide analysis show an improvement in sensitivity and limit of detection on decreasing the size of gold nanoparticles in all cases. PMID:22081133

Pandey, Prem Chandra; Chauhan, Dheeraj Singh

2012-01-21

236

Superstable advanced hydrogen peroxide transducer based on transition metal hexacyanoferrates.  

PubMed

We report on a superstable hydrogen peroxide (H(2)O(2)) transducer made by sequential deposition of the iron- and nickel-hexacyanoferrate (NiHCF) layers. Both chemical and mechanical stability of the latter, as well as similarity of its structure to Prussian Blue (PB) provide a substantial stabilization of the most advantageous H(2)O(2) transducer. The electrochemically deposited five bilayers of PB-NiHCF exhibit a complete stability under the continuous wall-jet flow of 1 mM of H(2)O(2) during more than 2 h, maintaining current at a level of 0.2 mA cm(-2), whereas common Prussian Blue loses half of its response within the first 20-25 min. Even being deposited in the open circuit regime on screen-printed electrodes, PB-NiHCF bilayers dramatically improve tolerance of the resulting transducer to alkaline solutions and iron ligands. Despite their 2-2.5 times decreased sensitivity (compared to common Prussian Blue), the sequentially deposited bilayers of PB-NiHCF provide a similar dynamic range of the transducer due to the decreased noise level. PMID:21348441

Sitnikova, Natalya A; Borisova, Anastasiya V; Komkova, Maria A; Karyakin, Arkady A

2011-03-15

237

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

238

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 ą 10 and 10 ą 5 nm for Au and Pt, respectively. Furthermore, the calculated number density was (6.0 ą 0.8) × 10(9) Au NPs cm(-2) and (6.6 ą 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

2013-01-23

239

DIRECT DECOMPOSITION OF METHANE TO HYDROGEN ON METAL LOADED ZEOLITE CATALYST  

SciTech Connect

The manufacture of hydrogen from natural gas is essential for the production of ultra clean transportation fuels. Not only is hydrogen necessary to upgrade low quality crude oils to high-quality, low sulfur ultra clean transportation fuels, hydrogen could eventually replace gasoline and diesel as the ultra clean transportation fuel of the future. Currently, refinery hydrogen is produced through the steam reforming of natural gas. Although efficient, the process is responsible for a significant portion of refinery CO2 emissions. This project is examining the direct catalytic decomposition of methane as an alternative to steam reforming. The energy required to produce one mole of hydrogen is slightly lower and the process does not require water-gas-shift or pressure-swing adsorption units. The decomposition process does not produce CO2 emissions and the product is not contaminated with CO -- a poison for PEM fuel cells. In this work we examined the direct catalytic decomposition of methane over a metal modified zeolite catalyst and the recovery of catalyst activity by calcination. A favorable production of hydrogen was obtained, when compared with previously reported nickel-zeolite supported catalysts. Reaction temperature had a strong influence on catalyst activity and on the type of carbon deposits. The catalyst utilized at 873 and 973 K could be regenerated without any significant loss of activity, however the catalyst utilized at 1073 K showed some loss of activity after regeneration.

Lucia M. Petkovic; Daniel M. Ginosar; Kyle C. Burch; Harry W. Rollins

2005-08-01

240

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

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

241

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

242

Cryogenic gellant and fuel formulation for metallized gelled propellants: Hydrocarbons and hydrogen with aluminum  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

243

Superconducting state in the atomic metallic hydrogen just above the pressure of the molecular dissociation  

NASA Astrophysics Data System (ADS)

Above the pressure of ˜500 GPa, the molecular metallic hydrogen gets converted into the atomic phase. The properties of the superconducting state in the metallic hydrogen just above the molecular-atomic phase transition have been examined in the paper (p=539 GPa). The numerical calculations have been conducted in the framework of the Eliashberg formalism. It has been stated that the critical temperature (TC) is equal to 360 K when the Coulomb pseudopotential takes the value of 0.1. In the considered case, TC considerably exceeds the value calculated with the help of the McMillan or Allen-Dynes formula. The remaining thermodynamic parameters significantly diverge from the canonical values predicted by the BCS theory. In particular: R??2?(0)/kBTC=4.95, RC??C(TC)/CN(TC)=2.78, and RH?TCCN(TC)/HC2(0)=0.126.

Szcze&?acute; niak, R.; Szcze&?acute; niak, D.; Drzazga, E. A.

2012-11-01

244

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

245

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

Microsoft Academic Search

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

Steven C. Witczak; Peter S. Winokur; Ronald C. Lacoe; Donald C. Mayer

2000-01-01

246

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

Microsoft Academic Search

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

Steven C. Witczak; Peter S. Winokur; Ronald C. Lacoe; Donald C. Mayer

2000-01-01

247

Development of reactively sputtered metal oxide films for hydrogen-producing hybrid multijunction photoelectrodes  

Microsoft Academic Search

The multijunction hybrid photoelectrode for hydrogen production developed at UH incorporates a metal-oxide photoelectrochemical top junction which is deposited onto an underlying solid state junction which generates additional voltage bias for efficient water splitting. Initial attempts to fabricate hybrid photoelectrodes using nano-structured iron-oxide films deposited by spray pyrolysis were largely unsuccessful because the pyrolysis temperatures of approximately 400°C were high

Eric L. Miller; Daniela Paluselli; Bjorn Marsen; Richard E. Rocheleau

2005-01-01

248

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

Microsoft Academic Search

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

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

2002-01-01

249

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

Microsoft Academic Search

Glassy carbon felt electrodes have been modified by electrodeposition of poly(pyrrole-viologen) films (derived from N,Nâ˛-dialkyl-4,4â˛-bipyridinium salts), followed by electroprecipitation of precious metal (Pt, Pd, Rh, or Ru) microparticles. The resulting electrodes have been proved to be active for the electrocatalytic hydrogenation of conjugated enones (2-cyclohexen-1-one, cryptone, carvone, isophorone), styrene, and benzonitrile in aqueous media (pH 1). Despite low loadings of

Liliane Coche; Bernadette Ehui; Daniele Limosin; Jean Claude Moutet

1990-01-01

250

From Cold Fusion to Low Energy Long Distant Nuclear Reactions of Hydrogen in Host Metals  

Microsoft Academic Search

After the confusing reports about cold fusion, a systematic approach (H. Hora, J.C. Kelly, J.U. patel, M.A. Prelas, G.H. Miley and J.W. Tompkins, Physics Letters A 175, 138 (1993)) led to the study of surface effects in thin layers or multilayers of hydrogen-saturated host metals (nickel, palladium, etc.). This led to the unexpected observation of generating nuclides from the whole

H. Hora; G. H. Miley; J. C. Kelly

1998-01-01

251

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

252

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

SciTech Connect

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

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

2010-11-01

253

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

PubMed

Hydrides of period 2 and 3 elements are promising candidates for hydrogen storage, but typically have heats of reaction that are too high to be of use for fuel cell vehicles. Recent experimental work has focused on destabilizing metal hydrides through mixing metal hydrides with other compounds. A very large number of possible destabilized metal hydride reaction schemes exist, but the thermodynamic data required to assess the enthalpies of these reactions are not available in many cases. We have used density functional theory calculations to predict the reaction enthalpies for more than 300 destabilization reactions that have not previously been reported. The large majority of these reactions are predicted not to be useful for reversible hydrogen storage, having calculated reaction enthalpies that are either too high or too low, and hence these reactions need not be investigated experimentally. Our calculations also identify multiple promising reactions that have large enough hydrogen storage capacities to be useful in practical applications and have reaction thermodynamics that appear to be suitable for use in fuel cell vehicles and are therefore promising candidates for experimental work. PMID:17356751

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

2007-03-28

254

Nucleosynthesis of the elements and the liquid metallic hydrogen model of the Sun  

NASA Astrophysics Data System (ADS)

Modern nucleosynthesis theory stems from the anticipated life cycle of stellar objects. Within this framework, the Sun, as a relatively young and light main sequence star, is unable to synthesize any element beyond helium. All metallic elements in our solar system have consequently been hypothesized to arise from the explosion of early stars which previously populated this region of the galaxy. Much of nucleosynthesis theory currently rests on gaseous stellar models and has developed in a direction consistent which such objects. In this presentation, the problem of nucleosynthesis is briefly reconsidered within the context of a condensed Sun. Such an object, built from liquid metallic hydrogen provides a new avenue for nucleosynthesis. Nuclei and protons contained within a metallic hydrogen lattice, will be subjected to vibrational modes which should be conducive to promoting internuclear reaction. The pressures within the Sun should make the synthesis of all the elements possible based on the combination of lighter elements. In stark contrast to current theory, it is advanced that all elements, beyond hydrogen, can be made within such a thermonuclear furnace.

Robitaille, Pierre-Marie

2012-10-01

255

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

PubMed

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

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

2013-07-01

256

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

257

The influence of raw material prices on the development of hydrogen storage materials: The case of metal hydrides  

Microsoft Academic Search

Hydrogen holds a prominent role as renewable energy carrier of the future due to its high gravimetric energy density. However, the most urgent technological challenge - especially concerning mobile applications in fuel cell vehicles - is the development of appropriate hydrogen storage options. In this context, metal hydrides are a promising candidate, especially concerning development potential and storage density. Our

Nathalie Sick; Matthias Blug; Jens Leker

2011-01-01

258

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

E-print Network

of hydrogen-powered cars," he says. But a major hurdle remains: the cost of platinum metal needed cars," says Holdcroft. The new research network will determine if the amount of platinum can be reduced for hydrogen-powered cars in mass production facilities," says SFU chemistry professor Steve Holdcroft, who

259

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

260

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

261

Hydrogen Permeability and Integrity of Hydrogen  

E-print Network

¡ To develop suitable welding technology for H2 pipeline construction and repair ¡ To develop technical basis pressure permeation test ¡ Edison Welding Institute - Pipeline materials ¡ Lincoln Electric Company - Welding electrode and weld materials for pipelines ¡ Trans Canada - Commercial welding of pipelines

262

Polyurea-supported metal nanocatalysts: synthesis, characterization and application in selective hydrogenation of o-chloronitrobenzene.  

PubMed

Polyurea (PU) spheres with size of 2-10 ?m were derived through the polymerization of CO2 with 1,4-butanediamine, and characterized by FTIR spectroscopy, scanning electron microscopy and TG analysis. It was demonstrated that the PU spheres displayed flower-like morphology with the betel thickness around 30 nm, and they had high thermal stability. The resultant PU spheres were used to immobilize metal particles, and a series of PU-supported metal nanocatalysts including Pt/PU, Au/PU, Pd/PU were prepared via just mixing the metal precursors with the PU spheres in water, followed by the reduction of metal ions by NaBH4. Transmission electron microscopy examination indicated that the metal nanoparticles were distributed uniformly on the surface of the PU spheres with mean particle size less than 3.0 nm, and the Pt particles existed mainly in the form of metallic state as confirmed by the X-ray photoelectron spectroscopy analysis. The performance of the Pt/PU catalyst was tested in the catalytic hydrogenation of o-chloronitrobenzene, and a high selectivity of 99.5% toward o-chloroaniline at complete conversion of o-chloronitrobenzene was obtained at room temperature. PMID:24767496

Hao, Leiduan; Zhao, Yanfei; Yu, Bo; Zhang, Hongye; Xu, Huanjun; Xu, Jilei; Liu, Zhimin

2014-06-15

263

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

SciTech Connect

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

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

2009-09-03

264

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

265

Metal-organic frameworks impregnated with magnesium-decorated fullerenes for methane and hydrogen storage.  

PubMed

A new concept is described for methane and hydrogen storage materials involving the incorporation of magnesium-decorated fullerenes within metal-organic frameworks (MOFs). The system is modeled using a novel approach underpinned by surface potential energies developed from Lennard-Jones parameters. Impregnation of MOF pores with magnesium-decorated Mg(10)C(60) fullerenes, denoted as Mg-C(60)@MOF, places exposed metal sites with high heats of gas adsorption into intimate contact with large surface area MOF structures. Perhaps surprisingly, given the void space occupied by C(60), this impregnation delivers remarkable gas uptake, according to our modeling, which predicts exceptional performance for the Mg-C(60)@MOF family of materials. These predictions include a volumetric methane uptake of 265 v/v, the highest reported value for any material, which significantly exceeds the U.S. Department of Energy target of 180 v/v. We also predict a very high hydrogen adsorption enthalpy of 11 kJ mol(-1) with relatively little decrease as a function of H(2) filling. This value is close to the calculated optimum value of 15.1 kJ mol(-1) and is achieved concurrently with saturation hydrogen uptake in large amounts at pressures under 10 atm. PMID:19583258

Thornton, Aaron W; Nairn, Kate M; Hill, James M; Hill, Anita J; Hill, Matthew R

2009-08-01

266

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

E-print Network

Adsorption and Diffusion of Hydrogen in a New Metal-Organic Framework Material: [Zn(bdc)(ted)0 pressure of 50 bar in a recently developed metal-organic framework material, [Zn(bdc)(ted)0.5] (bdc ) benzenedicarboxylate, ted ) triethylenediamine). This material has a tetragonal structure and relatively small pores

Li, Jing

267

First-principles study of hydrogen dissociation and diffusion on transition metal-doped Mg(0 0 0 1) surfaces  

NASA Astrophysics Data System (ADS)

First-principles calculations within the density functional theory (DFT) have been carried out to study hydrogen molecules dissociation and diffusion on clean and transition metals (TMs) doped Mg(0 0 0 1) surfaces following Pozzo et al. work. Firstly, the stability of Mg(0 0 0 1) surface doped with transition metals atom has been studied. The results showed that transition metals on the left of the table tend to substitute Mg in the second layer, while the other transition metals prefer to substitute Mg in the first layer. Secondly, we studied hydrogen molecules dissociation and diffusion on clean and Mg(0 0 0 1) surfaces which the transition metal atoms substituted both in the first layer and second layer. When transition metal atoms substitute in the first layer, the results agree with the Pozzo et al. result; when transition metal atoms substitute in the second layer, the results showed that the transition metals on the left of the periodic table impact on the dissociation barriers is less. However, for the transition metals (Mn, Fe, Co, Ni) on the right, there is a great impact on the barriers. The transition metals doped surfaces bind the dissociated H atoms loosely, making them easily diffused. The results further reveal that the Fe dopant on the Mg surface is the best choice for H2 dissociation and hydrogen storage.

Wang, Zhiwen; Guo, Xinjun; Wu, Mingyi; Sun, Qiang; Jia, Yu

2014-06-01

268

Compact hydrogenator  

NASA Technical Reports Server (NTRS)

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

Simmonds, P. G. (inventor)

1974-01-01

269

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

270

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

SciTech Connect

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

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

2013-07-01

271

Attaching molecular hydrogen to metal cations: perspectives from gas-phase infrared spectroscopy.  

PubMed

In this perspective article we describe recent infrared spectroscopic investigations of mass-selected M(+)-H(2) and M(+)-D(2) complexes in the gas-phase, with targets that include Li(+)-H(2), B(+)-H(2), Na(+)-H(2), Mg(+)-H(2), Al(+)-H(2), Cr(+)-D(2), Mn(+)-H(2), Zn(+)-D(2) and Ag(+)-H(2). Interactions between molecular hydrogen and metal cations play a key role in several contexts, including in the storage of molecular hydrogen in zeolites, metal-organic frameworks, and doped carbon nanostructures. Arguably, the clearest view of the interaction between dihydrogen and a metal cation can be obtained by probing M(+)-H(2) complexes in the gas phase, free from the complicating influences of solvents or substrates. Infrared spectra of the complexes in the H-H and D-D stretch regions are obtained by monitoring M(+) photofragments as the excitation wavelength is scanned. The spectra, which feature full rotational resolution, confirm that the M(+)-H(2) complexes share a common T-shaped equilibrium structure, consisting essentially of a perturbed H(2) molecule attached to the metal cation, but that the structural and vibrational parameters vary over a considerable range, depending on the size and electronic structure of the metal cation. Correlations are established between intermolecular bond lengths, dissociation energies, and frequency shifts of the H-H stretch vibrational mode. Ultimately, the M(+)-H(2) and M(+)-D(2) infrared spectra provide a comprehensive set of benchmarks for modelling and understanding the M(+)ˇˇˇH(2) interaction. PMID:23034736

Dryza, Viktoras; Poad, Berwyck L J; Bieske, Evan J

2012-11-21

272

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

PubMed

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

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

2014-12-01

273

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

PubMed

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

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

2014-11-17

274

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

275

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

PubMed

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

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

2013-03-21

276

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

277

Dynamic compression of materials: metallization of fluid hydrogen at high pressures  

NASA Astrophysics Data System (ADS)

Dynamic high pressure is 1 GPa (10 kbar) or greater with a rise time and a duration ranging from 1 ps (10-12 s) to 1 ľs (10-6 s). Today it is possible in a laboratory to achieve pressures dynamically up to ~500 GPa (5 Mbar) and greater, compressions as much as ~15-fold greater than initial density in the case of hydrogen and temperatures from ~0.1 up to several electronvolts (11 600 K). At these conditions materials are extremely condensed semiconductors or degenerate metals. Temperature can be tuned independently of pressure by a combination of shock and isentropic compression. As a result, new opportunities are now available in condensed matter physics at extreme conditions. The basic physics of the dynamic process, experimental methods of generating and diagnosing matter at these extreme conditions and a technique to recover metastable materials intact from ~100 GPa shock pressures are discussed. Results include (i) generation of pressure standards at static pressures up to ~200 GPa (2 Mbar) at 300 K, (ii) single-shock compression of small-molecular fluids, including resolution of the recent controversy over the correct shock-compression curve of liquid D2 at 100 GPa pressures, (iii) the first observations of metallization of fluid hydrogen, nitrogen and oxygen compressed quasi-isentropically at 100 GPa pressures, (iv) implications for the interiors of giant planets within our solar system, extrasolar giant planets and brown dwarfs discovered recently and the equation of state of deuterium-tritium in inertial confinement fusion (ICF) and (v) prospects of recovering novel materials from extreme conditions, such as metastable solid metallic hydrogen. Future research is suggested.

Nellis, W. J.

2006-05-01

278

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

279

Structure and spectroscopy of hydrogen adsorbed in a nickel metal-organic framework  

NASA Astrophysics Data System (ADS)

The structure of Ni2(dobdc) (dobdc4- = 2,5-dioxido-1,4-benzenedicarboxylate) as a function of deuterium adsorption has been determined through the application of in situ neutron powder diffraction. Detailed information concerning the local adsorption potential for hydrogen at each site has also been probed using inelastic neutron scattering techniques. These results are compared to those previously published on isostructural analogs and the Ni2+ variant shows the shortest deuterium-metal distance in the M2(dobdc) series (M = Mg, Zn, Co, Fe) that have been studied so far.

Brown, Craig M.; Ramirez-Cuesta, Anibal Javier; Her, Jae-Hyuk; Wheatley, Paul S.; Morris, Russell E.

2013-12-01

280

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

SciTech Connect

We have studied the interaction of atomic coinage metal anions with water molecules by infrared photodissociation spectroscopy of M{sup -}{center_dot}H{sub 2}O{center_dot}Ar{sub n} 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 [Institut fuer Physikalische Chemie, Universitaet Karlsruhe, D-76128 Karlsruhe (Germany); Institute of Nanotechnology, Forschungszentrum Karlsruhe, P.O. Box 3640, D-76021 Karlsruhe (Germany); Institut fuer Physikalische Chemie, Universitaet Karlsruhe, D-76128 Karlsruhe (Germany)

2005-08-22

281

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 Mřller-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 6.28kJ/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 4.16kJ/mol for IRMOF-1, 4.72kJ/mol for IRMOF-3, 4.86kJ/mol for IRMOF-6, 4.54kJ/mol for IRMOF-8, 5.50 and 4.90kJ/mol for IRMOF-12, 4.87 and 4.84kJ/mol for IRMOF-14, 5.42kJ/mol for IRMOF-18, and 4.97 and 4.66kJ/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

282

The thermodynamic and kinetic behavior of metal-vacancy-hydrogen systems  

SciTech Connect

The thermodynamics of metal-hydrogen solid solutions have been studied using a Fermi-Dirac distribution function in order to describe the formation of H-vacancy clusters. The H-vacancy interaction energies for clusters (decorated vacancies) containing up to six H-atoms have been taken from effective medium calculations. The solute metals Pd, Ni, Fe, Mo and Nb have been considered. The calculations enable the relative fractions of clusters of a given order to be calculated as a function of H-concentration and temperature. A mathematical model for the simultaneous diffusion of H-atoms, vacancies and H-VAC clusters has been developed. The numerical evaluation of the basic kinetic equations is based upon finite difference methods. Kinetic calculations have been made based upon Ni-H solutions as a model system.

Carr, Nan Z.; McLellan, Rex B

2004-06-21

283

Hydrogen Storage in metal-modified single-walled carbon nanotubes  

SciTech Connect

It has been known for over thirty years that potassium-intercalated graphites can readily adsorb and desorb hydrogen at {approx}1 wt% at 77 K. These levels are much higher than can be attained in pure graphite, owing to a larger thermodynamic enthalpy of adsorption. This increased enthalpy may allow hydrogen sorption at higher temperatures. Potassium has other beneficial effects that enable the design of a new material: (a) Increased adsorption enthalpy in potassium-intercalated graphite compared to pure graphite reduces the pressure and increases the temperature required for a given fractional coverage of hydrogen adsorption. We expect the same effects in potassium-intercalated SWNTs. (b) As an intercalant, potassium separates c-axis planes in graphite. Potassium also separates the individual tubes of SWNTs ropes producing swelling and increased surface area. Increased surface area provides more adsorption sites, giving a proportionately higher capacity. The temperature of adsorption depends on the enthalpy of adsorption. The characteristic temperature is roughly the adsorption enthalpy divided by Boltzmann's constant, k{sub B}. For the high hydrogen storage capacity of SWNTs to be achieved at room temperature, it is necessary to increase the enthalpy of adsorption. Our goal for this project was to use metal modifications to the carbon surface of SWNTs in order to address both enhanced adsorption and surface area. For instance, the enthalpy of sorption of hydrogen on KC8 is 450 meV/H{sub 2}, whereas it is 38 meV/H{sub 2} for unmodified SWNTs. By adsorption thermodynamics we expect approximately that the same performance of SWNTs at 77 K will be achieved at a temperature of [450/38] 77 K = 900 K. This is a high temperature, so we expect that adsorption on nearly all the available sites for hydrogen will occur at room temperature under a much lower pressure. This pressure can be estimated conveniently, since the chemical potential of hydrogen is approximately proportional to the logarithm of the pressure. Using 300 K for room temperature, the 100 bar pressure requirement is reduced to exp(-900/300) 100 bar = 5 bar at room temperature. This is in the pressure range used for prior experimental work such as that of Colin and Herold in the late 1960's and early 1970's.

Dr. Ahn

2004-04-30

284

Understanding hydrogen sorption in a polar metal-organic framework with constricted channels  

NASA Astrophysics Data System (ADS)

A high fidelity molecular model is developed for a metal-organic framework (MOF) with narrow (approximately 7.3 A?) nearly square channels. MOF potential models, both with and neglecting explicit polarization, are constructed. Atomic partial point charges for simulation are derived from both fragment-based and fully periodic electronic structure calculations. The molecular models are designed to accurately predict and retrodict material gas sorption properties while assessing the role of induction for molecular packing in highly restricted spaces. Thus, the MOF is assayed via grand canonical Monte Carlo (GCMC) for its potential in hydrogen storage. The confining channels are found to typically accommodate between two to three hydrogen molecules in close proximity to the MOF framework at or near saturation pressures. Further, the net attractive potential energy interactions are dominated by van der Waals interactions in the highly polar MOF - induction changes the structure of the sorbed hydrogen but not the MOF storage capacity. Thus, narrow channels, while providing reasonably promising isosteric heat values, are not the best choice of topology for gas sorption applications from both a molecular and gravimetric perspective.

Stern, Abraham C.; Belof, Jonathan L.; Eddaoudi, Mohamed; Space, Brian

2012-01-01

285

Understanding hydrogen sorption in a polar metal-organic framework with constricted channels.  

PubMed

A high fidelity molecular model is developed for a metal-organic framework (MOF) with narrow (approximately 7.3 A?) nearly square channels. MOF potential models, both with and neglecting explicit polarization, are constructed. Atomic partial point charges for simulation are derived from both fragment-based and fully periodic electronic structure calculations. The molecular models are designed to accurately predict and retrodict material gas sorption properties while assessing the role of induction for molecular packing in highly restricted spaces. Thus, the MOF is assayed via grand canonical Monte Carlo (GCMC) for its potential in hydrogen storage. The confining channels are found to typically accommodate between two to three hydrogen molecules in close proximity to the MOF framework at or near saturation pressures. Further, the net attractive potential energy interactions are dominated by van der Waals interactions in the highly polar MOF - induction changes the structure of the sorbed hydrogen but not the MOF storage capacity. Thus, narrow channels, while providing reasonably promising isosteric heat values, are not the best choice of topology for gas sorption applications from both a molecular and gravimetric perspective. PMID:22280775

Stern, Abraham C; Belof, Jonathan L; Eddaoudi, Mohamed; Space, Brian

2012-01-21

286

Influence of oxygen on permeation of hydrogen isotopes through group 5 metals  

SciTech Connect

Group 5 metals (V, Nb and Ta) are potential candidates of tube material in vacuum permeator for tritium recovery from Pb-17Li liquid blanket system. From this viewpoint, the influence of oxygen on the surface reaction rates of hydrogen on V and Ta were examined in an ultra-high vacuum apparatuses at elevated temperatures, and the results were compared with the data on Nb acquired in a previous study. The surface reaction rates of hydrogen on V and Ta, and consequently permeation rates, decreased with increasing oxygen concentration in the bulk as previously observed for Nb. These observations were ascribed to the increase in surface oxygen coverage with increasing bulk oxygen concentration. The weakest influence of oxygen on hydrogen permeation rate was observed for V. The expected permeation rate through V under typical blanket conditions, however, was not necessarily high due to high oxygen solubility in V. The evaluation indicated that the highest permeation rate should be obtained with Nb under typical blanket conditions. (authors)

Hatano, Y. [Hydrogen Isotope Research Center, Univ. of Toyama, Gofuku 3190, Toyam 930-8555 (Japan); Busnyuk, A.; Alimov, V.; Livshits, A. [Bonch-Bruyevich Univ., 61 Moika, St. Petersberg 191186 (Russian Federation); Nakamura, Y. [National Inst. for Fusion Science, Toki 509-5292 (Japan); Matsuyama, M. [Hydrogen Isotope Research Center, Univ. of Toyama, Gofuku 3190, Toyam 930-8555 (Japan)

2008-07-15

287

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

PubMed

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

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

2014-07-01

288

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

PubMed

Hydrides of period 2 and 3 elements are promising candidates for hydrogen storage but typically have heats of reaction that are too high to be of use for fuel cell vehicles. Recent experimental work has focused on destabilizing metal hydrides through alloying with other elements. A very large number of possible destabilized metal hydride reaction schemes exist. The thermodynamic data required to assess the enthalpies of these reactions, however, are not available in many cases. We have used first principles density functional theory calculations to predict the reaction enthalpies for more than 100 destabilization reactions that have not previously been reported. Many of these reactions are predicted not be useful for reversible hydrogen storage, having calculated reaction enthalpies that are either too high or too low. More importantly, our calculations identify five promising reaction schemes that merit experimental study: 3LiNH(2) + 2LiH + Si --> Li(5)N(3)Si + 4H(2), 4LiBH(4) + MgH(2) --> 4LiH + MgB(4) + 7H(2), 7LiBH(4) + MgH(2) --> 7LiH + MgB(7) + 11.5H(2), CaH(2) + 6LiBH(4) --> CaB(6) + 6LiH + 10H(2), and LiNH(2) + MgH(2) --> LiMgN + 2H(2). PMID:16640434

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

2006-05-01

289

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

290

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

PubMed Central

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

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

1994-01-01

291

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

E-print Network

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

Wahl, Sean; Militzer, Burkhard

2013-01-01

292

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

SciTech Connect

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

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

2011-02-14

293

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

PubMed

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

Lin, Tzu-Pin; Peters, Jonas C

2014-10-01

294

Computational study of silica-supported transition metal fragments for Kubas-type hydrogen storage.  

PubMed

To verify the role of the Kubas interaction in transition metal grafted mesoporous silicas, and to rationalize unusual rising enthalpy trends with surface coverage by hydrogen in these systems, computational studies have been performed. Thus, the interaction of H2 with the titanium centers in molecular models for experimentally characterized mesoporous silica-based H2 absorption materials has been studied quantum chemically using gradient corrected density functional theory. The interaction between the titanium and the H2 molecules is found to be of a synergic, Kubas type, and a maximum of four H2 molecules can be bound to each titanium, in good agreement with previous experiments. The average Ti-H2 interaction energies in molecules incorporating benzyl ancillary ligands (models of the experimental systems) increase as the number of bound H2 units increases from two to four, in agreement with the experimental observation that the H2 adsorption enthalpy increases as the number of adsorbed H2 molecules increases. The Ti-H2 interaction is shown to be greater when the titanium is bound to ancillary ligands, which are poor ?-acceptors, and when the ancillary ligand causes the least steric hindrance to the metal. Extension of the target systems to vanadium and chromium shows that, for molecules containing hydride ancillary ligands, a good relationship is found between the energies of the frontier molecular orbitals of the molecular fragments, which interact with incoming H2 molecules, and the strength of the M-H2 interaction. For the benzyl systems, both the differences in M-H2 interaction energies and the energy differences in frontier orbital energies are smaller than those in the hydrides, such that conclusions based on frontier orbital energies are less robust than for the hydride systems. Because of the high enthalpies predicted for organometallic fragments containing hydride ligands, and the low affinity of Cr(III) for hydrogen in this study, these features may not be ideal for a practical hydrogen storage system. PMID:21077628

Skipper, Claire V J; Hamaed, Ahmad; Antonelli, David M; Kaltsoyannis, Nikolas

2010-12-01

295

Bioinspired hydrogen bond motifs in ligand design: the role of noncovalent interactions in metal ion mediated activation of dioxygen.  

PubMed

Hydrogen bonds influence secondary coordination spheres around metal ions in many proteins. To duplicate these features of molecular architecture in synthetic systems, urea-based ligands have have been developed that create rigid organic frameworks when bonded to metal ions. These frameworks position hydro-gen bond donors proximal to metal ion(s) to form specific chem-ical microenvironments. Iron(II) and manganese(II) complexes with constrained cavities activate O(2), yielding M(III) (M(III) = Fe and Mn) complexes with terminal oxo ligands. Installation of anionic sites within the cavity assists the formation of complexes with M(II/III)-OH and M(III)-O units derived directly from water. Opening the cavity promotes M(mu-O)(2)M rhombs, as illustrated by isolation of a cobalt(III) analogue, the stability of which is promoted by the hydrogen bonds surrounding the bridging oxo ligands. PMID:15654737

Borovik, A S

2005-01-01

296

Effect of Metal Oxide Catalysts on Degradation of Waste Polystyrene in Hydrogen at Elevated Temperature and Pressure in Benzene Solution  

Microsoft Academic Search

Degradation of waste polystyrene is carried out in presence of hydrogen using several metal oxide catalysts at elevated temperature\\u000a and pressure for recycling. Benzene is used as a solvent for degradation. Initial hydrogen pressure in the autoclave is kept\\u000a at 7.0 kg\\/cm2 (g) and polystyrene degradation is carried out at 240 °C. After degradation, degraded polystyrene residue is separated and\\u000a analyzed by

Praphulla Tiwary; Chandan Guria

2010-01-01

297

Photochemically engineering the metal-semiconductor interface for room-temperature transfer hydrogenation of nitroarenes with formic Acid.  

PubMed

A mild photochemical approach was applied to construct highly coupled metal-semiconductor dyads, which were found to efficiently facilitate the hydrogenation of nitrobenzene. Aniline was produced in excellent yield (>99?%, TOF: 1183) using formic acid as hydrogen source and water as solvent at room temperature. This general and green catalytic process is applicable to a wide range of nitroarenes without the involvement of high-pressure gases or sacrificial additives. PMID:25331634

Li, Xin-Hao; Cai, Yi-Yu; Gong, Ling-Hong; Fu, Wei; Wang, Kai-Xue; Bao, Hong-Liang; Wei, Xiao; Chen, Jie-Sheng

2014-12-01

298

Hydrogen from Formic Acid through Its Selective Disproportionation over Sodium Germanate-A Non-Transition-Metal Catalysis System.  

PubMed

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

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

2014-10-13

299

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

SciTech Connect

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

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

1999-08-31

300

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

PubMed

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

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

2013-06-17

301

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

302

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

SciTech Connect

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

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

2006-03-29

303

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

PubMed

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

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

2008-07-30

304

Advanced Hydrogen Transport Membranes for Vision 21 Fossil Fuel Plants  

SciTech Connect

Eltron Research Inc. and team members CoorsTek, Sued Chemie, Argonne National Laboratory, and NORAM are developing an environmentally benign, inexpensive, and efficient method for separating hydrogen from gas mixtures produced during industrial processes, such as coal gasification. This project was motivated by the National Energy Technology Laboratory (NETL) Vision 21 initiative, which seeks to economically eliminate environmental concerns associated with the use of fossil fuels. Currently, this project is focusing on four basic categories of dense membranes: (1) mixed conducting ceramic/ceramic composites, (2) mixed conducting ceramic/metal (cermet) composites, (3) cermets with hydrogen permeable metals, and (4) layered composites containing hydrogen permeable alloys. Ultimately, these materials must enable hydrogen separation at practical rates under ambient and high-pressure conditions, without deactivation in the presence of feedstream components such as carbon dioxide, water, and sulfur. During this final quarter of the no cost extension several planar membranes of a cermet composition referred to as EC101 containing a high permeability metal and a ceramic phase were prepared and permeability testing was performed.

Carl R. Evenson; Richard N. Kleiner; James E. Stephan; Frank E. Anderson

2006-04-30

305

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

PubMed

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 Moller-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. PMID:16035857

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

2005-07-01

306

Effect of ion bombardment and annealing on the electrical properties of hydrogenated amorphous silicon metal-semiconductor-metal structures  

NASA Astrophysics Data System (ADS)

The electrical properties of hydrogenated amorphous silicon (a-Si:H) metal-semiconductor-metal (MSM) devices are investigated as a function of Si bombardment dose prior to and after annealing. We observe that conduction in unbombarded devices is surface-barrier controlled whereas it is bulk controlled in bombarded devices. The resistance decreases with bombardment dose in a manner consistent with increased hopping conductivity in highly damaged structures. A relative permittivity of between 8 and 12, depending on dose, was calculated from experimental Poole-Frenkel plots for bombarded devices. These values compare closely with the theoretical relative permittivity for amorphous silicon of 11.7 and confirm that conduction is by Poole-Frenkel mechanism. For bulk-controlled conduction, we observe an increase in the zero-field Coulombic trap barrier height with decreasing dose, ranging from 0.53 for a Si dose of 5×1013cm-2 to 0.89 for a dose of 2×1012cm-2. We attribute this to a decrease in the concentration of charged defects with decreasing dose and find that the change in concentration of charged centers needs to be about 4×1019cm-3 to account for the change of 0.35eV from the lower to the upper dose. Activation energies obtained from Arrhenius plots of current density against temperature varied with dose and temperature in a similar way as Coulombic barrier height. We explain these results in terms of the variation in the number of charged defect centers with dose and annealing temperature and a shift in the Fermi level.

Orwa, J. O.; Shannon, J. M.; Gateru, R. G.; Silva, S. R. P.

2005-01-01

307

Hydrogen purifier module with membrane support  

DOEpatents

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

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

2012-07-24

308

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)] [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)] [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)] [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)] [The Aerospace Corporation, P.O. Box 92957, M2-244, Los Angeles, California 90009-2957 (United States)

2000-06-01

309

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

PubMed Central

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

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

2014-01-01

310

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

NASA Technical Reports Server (NTRS)

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

Caron, L. G.

1974-01-01

311

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

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

312

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

PubMed Central

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

2013-01-01

313

Pore with gate: modulating hydrogen storage in metal-organic framework materials via cation exchange.  

PubMed

A range of anionic metal-organic framework (MOF) materials has been prepared by combination of In(III) with tetracarboxylate isophthalate-based ligands. These materials incorporate organic cations, either H2ppz2+ (ppz = piperazine) or Me2NH2+, that are hydrogen bonded to the pore wall. These cations act as a gate controlling entry of N2 and H2 gas into and out of the porous host. Thus, hysteretic adsorption/desorption for N2 and H2 is observed in these systems, reflecting the role of the bulky hydrogen bonded organic cations in controlling the kinetic trapping of substrates. Post-synthetic cation exchange with Li+ leads to removal of the organic cation and the formation of the corresponding Li+ salts. Replacement of the organic cation with smaller Li+ leads to an increase in internal surface area and pore volume of the framework material, and in some cases to an increase in the isosteric heat of adsorption of H2 at zero coverage, as predicted by theoretical modelling. The structures, characterisation and analysis of these charged porous materials as storage portals for H2 are discussed. Inelastic neutron scattering experiments confirm interaction of H2 with the carboxylate groups of the isophthalate ligands bound to In(III) centres. PMID:22455060

Yang, Sihai; Callear, Samantha K; Ramirez-Cuesta, Anibal J; David, William I F; Sun, Junliang; Blake, Alexander J; Champness, Neil R; Schröder, Martin

2011-01-01

314

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

PubMed

The role of nuclear quantum effects on the adsorption of molecular hydrogen in metal-organic frameworks (MOFs) has been investigated on grounds of Grand-Canonical Quantized Liquid Density-Functional Theory (GC-QLDFT) calculations. For this purpose, we have carefully validated classical H2-host interaction potentials that are obtained by fitting Born-Oppenheimer ab initio reference data. The hydrogen adsorption has first been assessed classically using Liquid Density-Functional Theory and the Grand-Canonical Monte Carlo methods. The results have been compared against the semi-classical treatment of quantum effects by applying the Feynman-Hibbs correction to the Born-Oppenheimer-derived potentials, and by explicit treatment within the GC-QLDFT. The results are compared with experimental data and indicate pronounced quantum and possibly many-particle effects. After validation calculations have been carried out for IRMOF-1 (MOF-5), GC-QLDFT is applied to study the adsorption of H2 in a series of MOFs, including IRMOF-4, -6, -8, -9, -10, -12, -14, -16, -18, and MOF-177. Finally, we discuss the evolution of the H2 quantum fluid with increasing pressure and lowering temperature. PMID:25134591

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

2014-08-14

315

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

316

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

317

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

PubMed

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

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

2014-09-15

318

Hydrogen Storage in Metal-Modified Single-Walled Carbon Nanotubes Channing C. Ahn, John J. Vajoa  

E-print Network

graphene layers as shown below. The stacking sequence is a- K-a-b, in which the a and b designation sequences for potassium layers. Each potassium layer of the Stage 2 compound is separated by an a-b grapheneHydrogen Storage in Metal-Modified Single-Walled Carbon Nanotubes Channing C. Ahn, John J. Vajoa

319

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

320

A computational experiment to study hydrogenations of various unsaturated compounds catalyzed by a rationally designed metal-free catalyst.  

PubMed

Metal-free hydrogenation has been proposed to be a green alternative to the conventional hydrogenation mediated by precious transition metal complexes. Thanks to the discovery of FLP (frustrated Lewis pair) chemistry, the field has recently witnessed significant progress. Inspired by the FLP idea of synergically utilizing the catalytic effects of Lewis acid and base, we previously proposed a strategy to construct metal-free active sites for H(2) activation and designed a metal-free molecule (1) that shows high reactivity toward H(2). Encouraged by the recent experimental successes in applying the strategy, we have computationally explored if 1 can go further to serve as a catalyst to promote the hydrogenations of various unsaturated compounds examined by ethylene (CH(2)=CH(2) (4)), silyl enol ether (CH(2)=C(Me)OSiMe(3) (5)), imines (Me(2)C=NMe (6) and Ph(Me)C=NMe (7)), and ketone (Ph(Me)C=O (9)). The energetic results predicted at the M05-2X(IEFPCM, solvent = THF)/6-311++G** level indicate that these reactions have feasible kinetics and thermodynamics for experimental realization. The hydride transfer step follows the concerted mechanism, although the transfer process has asynchronous character for silyl enol ether (5) and imines (6 and 7). In addition, we have investigated the binding of CO(2) to 1 and the 1-mediated hydrogenation of CO(2). PMID:22382438

Zhao, Lili; Lu, Gang; Huang, Fang; Wang, Zhi-Xiang

2012-04-21

321

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

PubMed Central

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

Sakthivel, Mariappan; Weppner, Werner

2006-01-01

322

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

PubMed

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

Jayaranjan, Madawala Liyanage Duminda; Annachhatre, Ajit P

2013-01-01

323

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

PubMed

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

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

2012-02-15

324

Quasiparticle energies and excitonic effects in dense solid hydrogen near metallization  

NASA Astrophysics Data System (ADS)

We investigate the crucial metallization pressure of the Cmca-12 phase of solid hydrogen (H) using many-body perturbation theory within the GW approximation. We consider the effects of self-consistency, plasmon-pole models, and the vertex correction on the quasiparticle band gap (Eg). Our calculations show that self-consistency leads to an increase in Eg by 0.33 eV over the one-shot G0W0 approach. Because of error cancellation between the effects of self-consistency and the vertex correction, the simplest G0W0 method underestimates Eg by only 0.16 eV compared with the prediction of the more accurate GW? approach. Employing the plasmon-pole models underestimates Eg by 0.1-0.2 eV compared to the full-frequency numerical integration results. We thus predict a metallization pressure around 280 GPa, instead of 260 GPa predicted previously. Furthermore, we compute the optical absorption including the electron-hole interaction by solving the Bethe-Salpeter equation (BSE). The resulting absorption spectra demonstrate substantial redshifts and enhancement of absorption peaks compared to the calculated spectra neglecting excitonic effects. We find that the exciton binding energy decreases with increasing pressure from 66 meV at 100 GPa to 12 meV at 200 GPa due to the enhanced electronic screening as solid H approaches metallization. Because optical measurements are so important in identifying the structure of solid H, our BSE results should improve agreement between theory and experiment.

Dvorak, Marc; Chen, Xiao-Jia; Wu, Zhigang

2014-07-01

325

Development of high catalytic activity disordered hydrogen-storage alloys for electrochemical application in nickel-metal hydride batterie  

NASA Astrophysics Data System (ADS)

Multi-element, multiphase disordered metal hydride alloys have enabled the widespread commercialization of nickel-metal hydride (NiMH) batteries by allowing high capacity and good kinetics while overcoming the crucial barrier of unstable oxidation/corrosion behavior to obtain long cycle life. Alloy-formula optimization and advanced materials processing have been used to promote a high concentration of active hydrogen-storage sites vital for raising NiMH specific energy. New commercial applications demand fundamentally higher specific power and discharge-rate kinetics. Disorder at the metal/electrolyte interface has enabled a surface oxide with less than 70 Ĺ metallic nickel alloy inclusions suspended within the oxide, which provide exceptional catalytic activity to the metal hydride electrode surface.

Ovshinsky, S. R.; Fetcenko, M. A.

2001-04-01

326

Pd-sensitized single vanadium oxide nanowires: highly responsive hydrogen sensing based on the metal-insulator transition.  

PubMed

Exceptionally sensitive hydrogen sensors were produced using Pd-nanoparticle-decorated, single vanadium dioxide nanowires. The high-sensitivity arises from the large downward shift in the insulator to metal transition temperature following the adsorption on and incorporation of atomic hydrogen, produced by dissociative chemisorption on Pd, in the VO(2), producing approximately 1000-fold current increases. During a rapid initial process, the insulator to metal transition temperature is decreased by >10 degrees C even when exposed to trace amounts of hydrogen gas. Subsequently, hydrogen continues to diffuse into the VO(2) for several hours before saturation is achieved with only a modest change in the insulator to metal transition temperature but with a significant increase in the conductivity. The two time scales over which H-related processes occur in VO(2) likely signal the involvement of two distinct mechanisms influencing the electronic structure of the material one of which involves electron-phonon coupling pursuant to the modification of the vibrational normal modes of the solid by the introduction of H as an impurity. PMID:19911806

Baik, Jeong Min; Kim, Myung Hwa; Larson, Christopher; Yavuz, Cafer T; Stucky, Galen D; Wodtke, Alec M; Moskovits, Martin

2009-12-01

327

Kinetic and mechanistic studies of carbon-to-metal hydrogen atom transfer involving Os-centered radicals: evidence for tunneling.  

PubMed

We have investigated the kinetics of novel carbon-to-metal hydrogen atom transfer reactions, in which homolytic cleavage of a C-H bond is accomplished by a single metal-centered radical. Time-resolved IR spectroscopic measurements revealed efficient hydrogen atom transfer from xanthene, 9,10-dihydroanthracene, and 1,4-cyclohexadiene to Cp(CO)2Os(•) and (?(5)-(i)Pr4C5H)(CO)2Os(•) radicals, formed by photoinduced homolysis of the corresponding osmium dimers. The rate constants for hydrogen abstraction from these hydrocarbons are in the range 1.5 × 10(5) M(-1) s(-1) to 1.7 × 10(7) M(-1) s(-1) at 25 °C. For the first time, kinetic isotope effects for carbon-to-metal hydrogen atom transfer were determined. Large primary deuterium kinetic isotope effects of 13.4 ą 1.0 and 16.8 ą 1.4 were observed for the hydrogen abstraction from xanthene to form Cp(CO)2OsH and (?(5)-(i)Pr4C5H)(CO)2OsH, respectively, at 25 °C. Temperature-dependent measurements of the kinetic isotope effects over a 60 °C temperature range were carried out to obtain the difference in activation energies (E(D) - E(H)) and the pre-exponential factor ratio (A(H)/A(D)). For hydrogen atom transfer from xanthene to (?(5)-(i)Pr4C5H)(CO)2Os(•), the (E(D) - E(H)) = 3.3 ą 0.2 kcal mol(-1) and A(H)/A(D) = 0.06 ą 0.02 values suggest a quantum mechanical tunneling mechanism. PMID:24498925

Lewandowska-Andralojc, Anna; Grills, David C; Zhang, Jie; Bullock, R Morris; Miyazawa, Akira; Kawanishi, Yuji; Fujita, Etsuko

2014-03-01

328

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

SciTech Connect

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

Britton, M.D.

1995-01-19

329

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

330

Concentration of Hydrogen Peroxide  

NASA Technical Reports Server (NTRS)

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

Parrish, Clyde F. (Inventor)

2006-01-01

331

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

PubMed Central

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

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

2009-01-01

332

Metal-Insulator Transitions in Dense Hydrogen: Equations of State, Phase Diagrams and Interpretation of Shock-Compression Experiments  

NASA Astrophysics Data System (ADS)

First-principles formulations of the equations of state for hydrogenin metallic and insulator phases are presented, leading to a phasediagram predicting first-order metal-insulator transitions in dense hydrogen. The theory explicitly takes into account the effects ofstrong electron-ion coupling near the transitions as well as those oflowering or elimination of the atomic and/or molecular levels due toplasma screening. It is shown that the results of recentshock-compression experiments prove consistent withsuch first-order insulator-to-metal transitions. These observations predict a discontinuous distribution of density and resistivity with alarge magnetic Reynolds number near the Jovian surface; the latentheat through the metal-to-insulator transitions is estimated.

Kitamura, Hikaru; Ichimaru, Setsuo

1998-03-01

333

Tristate electrochemical metallization memory based in the hydrogenated nanocrystalline silicon films  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

334

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

Microsoft Academic Search

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

Wynn

1977-01-01

335

Hot-electron-induced hydrogen redistribution and defect generation in metal-oxide-semiconductor capacitors  

Microsoft Academic Search

Redistribution of hydrogen caused by hot-electron injection has been studied by hydrogen depth profiling with 15N nuclear reaction analysis and electrical methods. Internal photoemission and Fowler–Nordheim injection were used for electron injection into large Al-gate and polysilicon-gate capacitors, respectively. A hydrogen-rich layer (?1015 atoms\\/cm2) observed at the Al\\/SiO2 interface was found to serve as the source of hydrogen during the

D. A. Buchanan; A. D. Marwick; D. J. DiMaria; L. Dori

1994-01-01

336

Analysis of hydrogen isotope mixtures  

Microsoft Academic Search

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

Villa-Aleman; Eliel

1994-01-01

337

Analysis of hydrogen isotope mixtures  

Microsoft Academic Search

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

Villa-Aleman

1994-01-01

338

Analysis of hydrogen isotope mixtures  

Microsoft Academic Search

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

Villa-Aleman

1992-01-01

339

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

SciTech Connect

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

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

2013-04-29

340

Effect of electrolytical hydrogenation on the thermal stability and crystallization kinetics of metallic glass Fe79Si9B12  

NASA Astrophysics Data System (ADS)

The effect of electrolytical hydrogenation on both the surface and volume crystallization kinetics and thermal stability of amorphous alloy Fe79Si9B12 has been investigated. The parameters of the surface and volume crystallization (temperature, activation energy) have been determined applying the exoelectron emission (EEE) and differential thermal analysis (DTA) methods, respectively. It has been found that the surface crystallization of investigated material occurs at temperature much lower and with activation energy smaller than the volume crystallization. The determination of the activation energies for the volume and surface crystallization by the combination of DTA and EEE techniques enables the determination of activation energies for both the nucleation and growth of the crystalline phase in metallic glasses and other amorphous materials. Hydrogenation of the investigated metallic glass reduces its thermal stability, what is manifested by an decrease in the activation energies for both the surface and volume crystallization.

Górecki, Cz; Górecki, T.

2011-04-01

341

Ultrasonics in heterogeneous metal catalysis: sonochemical chemo- and enantioselective hydrogenations over supported platinum catalysts  

Microsoft Academic Search

Sonochemical chemo- and enantioselective hydrogenations over supported platinum catalysts are described. We disclose our results with respect to a sonochemical modification of the chemoselective hydrogenation of cinnamaldehyde over supported platinum catalysts, and the asymmetric hydrogenation of ethyl pyruvate promoted by various ultrasonic pretreatments.The ultrasonic pretreatment of the supported platinum catalysts was found to be highly beneficial in almost every case,

Béla Török; György Szöllösi; Katalin Balázsik; Károly Felföldi; István Kun; Mihály Bartók

1999-01-01

342

Desorption of hydrogen from light metal hydrides: concerted electronic rearrangement and role of HˇˇˇH interactions.  

PubMed

A theoretical study of the desorption of hydrogen from rhombic Group 1 metal hydride dimers reveals a concerted reorganisation of the electron density for the M-H and H-H moieties as the reaction coordinate is traversed and a closed-shell HˇˇˇH interaction evolves into a covalent H2 bond. The central role played by homopolar dihydrogen bonding in this process is revealed and analysed. PMID:24589845

Wolstenholme, David J; Roy, Matthew M D; Thomas, Michael E; McGrady, G Sean

2014-04-14

343

Application of HSQ (hydrogen silsesquioxane) based SOG to pre-metal dielectric planarization in STC (stacked capacitor) DRAM  

Microsoft Academic Search

We investigated a new planarization process by employing a flowable HSQ (hydrogen silsesquioxane) based inorganic SOG (spin-on-glass) for pre-metal dielectric material, in order to develop a simple planarization process with low thermal budget and good planarity in STC (stacked capacitor) DRAM devices. We implemented this process in 256 Mb DRAM devices, and achieved lower TaO leakage current and better Al-reflow

H. J. Lee; J. H. Choi; B. K. Hwang; J. S. Goo; K. Fujihara; U. I. Chung; K. H. Kim; S. I. Lee; M. Y. Lee

1996-01-01

344

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

345

The Role of Partial Crystallinity on Hydrogen Permeation in Fe–Ni–B–Mo Based Metallic Glass Membranes  

SciTech Connect

A potentially exciting material for membrane separations are metallic glass materials due to their low cost, high elastic toughness and resistance to hydrogen embrittlement as compared to crystalline Pd-based membrane systems. However, at elevated temperatures and extended operation times structural changes including partial crystallinity may appear in these amorphous metallic systems. This study reports on the investigation of time and temperature dependent crystalline phase formation in conjunction with in situ crystallization/hydrogen permeation experiments at elevated temperatures. At temperatures near 400 C a FeNi crystalline phase appears as 22 vol.% inside the host amorphous matrix and the resulting composite structure remains stable over 3 h at temperature. The hydrogen permeation at 400 C of the partially crystalline material is similar to the fully amorphous material near 5 x 10{sup -9} mol H{sub 2}/m s Pa{sup 1/2}, while ambient temperature electrochemical permeation at 25 C revealed an order of magnitude decrease in the permeation of partially crystalline materials due to differences in the amorphous versus crystalline phase activation energy for hydrogen permeation.

Brinkman, K.; Su, D.; Fox, E.; Korinko, P.; Missimer, D.; Adams, T.

2011-08-15

346

Hydrogen adsorption in the nanoporous metal-benzenedicarboxylate M(OH)(O2C-C6H4-CO2) (M = Al3+, Cr3+), MIL-53.  

PubMed

Hydrogen adsorption has been studied in the nanoporous metal-benzenedicarboxylate M(OH)(O2C-C6H4-CO2) (M = Al3+, Cr3+); these solids show a hydrogen storage capacity of 3.8 and 3.1 wt.% respectively when loaded at 77 K under 1.6 MPa. PMID:14703815

Férey, Gérard; Latroche, Michel; Serre, Christian; Millange, Franck; Loiseau, Thierry; Percheron-Guégan, Annick

2003-12-21

347

Hydrogen storage in metal-organic frameworks: An investigation of structure-property relationships  

NASA Astrophysics Data System (ADS)

Metal-organic frameworks (MOFs) have been identified as candidate hydrogen storage materials due to their ability to physisorb large quantities of small molecules. Thirteen compounds (IRMOF-1, -2, -3, -6, -8, -9, -11, -13, -18, -20, MOF-74, MOF-177 and HKUST-1) have been prepared and fully characterized for the evaluation of their dihydrogen (H2) adsorption properties. All compounds display approximately type I isotherms with no hysteresis at 77 K up to 1 atm. The amount adsorbed ranges from 0.89 to 2.54 wt%; however, saturation is not achieved under these conditions. The influences of link functionalization, catenation and topology are examined for the eleven MOFs composed of Zn4O(O2C-)6 clusters. Enhanced H2 uptake by catenated compounds is rationalized by increased overlap of the surface potentials within their narrower pores. This is corroborated by the larger isosteric heat of adsorption of IRMOF-11 compared to IRMOF-1. Inelastic neutron scattering spectroscopic analysis of four Zn4O-based materials (IRMOF-1, -8, -11, and MOF-74) under a range of H2 loading suggests the presence of multiple localized adsorption sites on both the inorganic and organic moieties. To determine the structural details of the adsorption sites, variable temperature single crystal X-ray diffraction was used to analyze adsorbed argon and dinitrogen molecules in IRMOF-1. The principle binding site was found to be the same for both adsorbates and is located on faces of the octahedral Zn4O(O2C-)6 clusters with close contacts to three carboxylate groups. A total of eight symmetry-independent adsorption sites were identified for argon at 30 K. Similar sites were observed for dinitrogen, suggesting that they are good model adsorbates for the behaviour of dihydrogen. Two additional materials composed of inorganic clusters with coordinatively unsaturated metal sites (MOF-74, HKUST-1) were examined and their increased capacities and isosteric heats of adsorption provide further evidence that the interaction is strongest at the inorganic clusters. This enhancement becomes less important at high pressure, where large pore volume proves to be the greater contributor to capacity.

Rowsell, Jesse

348

Insight into association reactions on metal surfaces: Density-functional theory studies of hydrogenation reactions on Rh(111)  

NASA Astrophysics Data System (ADS)

Hydrogenation reaction, as one of the simplest association reactions on surfaces, is of great importance both scientifically and technologically. They are essential steps in many industrial processes in heterogeneous catalysis, such as ammonia synthesis (N2+3H2-->2NH3). Many issues in hydrogenation reactions remain largely elusive. In this work, the NHx (x=0,1,2) hydrogenation reactions (N+H-->NH, NH+H-->NH2 and NH2+H-->NH3) on Rh(111) are used as a model system to study the hydrogenation reactions on metal surfaces in general using density-functional theory. In addition, C and O hydrogenation (C+H-->CH and O+H-->OH) and several oxygenation reactions, i.e., C+O, N+O, O+O reactions, are also calculated in order to provide a further understanding of the barrier of association reactions. The reaction pathways and the barriers of all these reactions are determined and reported. For the C, N, NH, and O hydrogenation reactions, it is found that there is a linear relationship between the barrier and the valency of R (R=C, N, NH, and O). Detailed analyses are carried out to rationalize the barriers of the reactions, which shows that: (i) The interaction energy between two reactants in the transition state plays an important role in determining the trend in the barriers; (ii) there are two major components in the interaction energy: The bonding competition and the direct Pauli repulsion; and (iii) the Pauli repulsion effect is responsible for the linear valency-barrier trend in the C, N, NH, and O hydrogenation reactions. For the NH2+H reaction, which is different from other hydrogenation reactions studied, the energy cost of the NH2 activation from the IS to the TS is the main part of the barrier. The potential energy surface of the NH2 on metal surfaces is thus crucial to the barrier of NH2+H reaction. Three important factors that can affect the barrier of association reactions are generalized: (i) The bonding competition effect; (ii) the local charge densities of the reactants along the reaction direction; and (iii) the potential energy surface of the reactants on the surface. The lowest energy pathway for a surface association reaction should correspond to the one with the best compromise of these three factors.

Liu, Zhi-Pan; Hu, P.; Lee, Ming-Hsien

2003-09-01

349

Analysis of hydrogen isotope mixtures  

DOEpatents

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

Villa-Aleman, Eliel (Aiken, SC)

1994-01-01

350

Hot-electron-induced hydrogen redistribution and defect generation in metal-oxide-semiconductor capacitors  

Microsoft Academic Search

Redistribution of hydrogen caused by hot-electron injection has been studied by hydrogen depth profiling with N-15 nuclear reaction analysis and electrical methods. Internal photoemission and Fowler-Nordheim injection were used for electron injection into large Al-gate and polysilicon-gate capacitors, respectively. A hydrogen-rich layer (about 10(exp 15) atoms\\/sq cm) observed at the Al\\/SiO2 interface was found to serve as the source of

D. A. Buchanan; A. D. Marwick; D. J. Dimaria; L. Dori

1994-01-01

351

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

PubMed

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

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

2014-10-28

352

P-67: Investigation on the Hydrogen-Assisted Al Induced Metal Crystallization Poly-Si  

E-print Network

Abstract The hydrogen plasma-assistant Al induced crystallization (HAIC) technology has been proposed-Si thin film. In this paper, the aluminum induced crystallization assisted by hydrogen plasma technology-Electronics, Nankai University, The Tianjin Key Laboratory for Photo-Electronic Thin Film Devices and Technology

353

Hydrogen adsorption equilibrium and kinetics in metal–organic framework (MOF-5) synthesized with DEF approach  

Microsoft Academic Search

MOF-5, also known as isoreticular MOF-1 (IRMOF-1) was successfully synthesized with diethyl formamide (DEF) as a solvent using modified procedures aiming at improving its crystal structure, pore texture and ultimately the hydrogen adsorption performance. The MOF-5 adsorbent was characterized with nitrogen adsorption for pore textural properties, scanning electron microscopy for crystal structure, and XRD for phase structure. Hydrogen adsorption in

Dipendu Saha; Zuojun Wei; Shuguang Deng

2009-01-01

354

Metal Oxides As Selective Hydrogen Combustion (SHC) Catalysts and Their Potential in Light Paraffin Dehydrogenation  

Microsoft Academic Search

An alternative approach to light paraffin dehydrogenation (thermodynamically limited) and oxydehydrogenation (thermodynamically not limited) is a combination process of dehydrogenation (DH) with selective hydrogen combustion (SHC). By selectively combusting the hydrogen produced in the DH reaction, the overall combination process becomes thermodynamically not limited. While dehydrogenation is commercially practiced, the olefin yields are equilibrium limited, and the process is endothermic,

John G. Tsikoyiannis; David L. Stern; Robert K. Grasselli

1999-01-01

355

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

E-print Network

1 Identification of a new pseudo-binary hydroxide during calendar corrosion of (La, Mg)2Ni7-type hydrogen storage alloys for Nickel-Metal Hydride batteries J. Monnier 1 , H. Chen 1 , S. Joiret2,3 , J Abstract To improve the performances of Nickel-Metal Hydride batteries, an important step

Boyer, Edmond

356

First-principles study of half-metallicity in semi-hydrogenated BC3, BC5, BC7, and B-doped graphone sheets  

PubMed Central

Using first principles calculations, we investigate the electronic structures of semi-hydrogenated BC3, BC5, BC7, and B-doped graphone sheets. We find that all the semi-hydrogenated boron-carbon sheets exhibit half-metallic behaviors. The magnetism originates from the non-bonding pz orbitals of carbon atoms, which cause the flat bands to satisfy the Stoner criterion. On the other hand, boron atoms weaken the magnetic moments of nearby carbon atoms and act as holes doped in the sheets. It induces the down shift of the Fermi level and the half-metallicity in semi-hydrogenated sheets. Our studies demonstrate that the semi-hydrogenation is an effective route to achieve half-metallicity in the boron-carbon systems. PMID:21711690

2011-01-01

357

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

SciTech Connect

We have experimentally measured hydrogen isotherms at 77 and 298 K up to a hydrogen pressure of 50 bar in a recently developed metal-organic framework material, [Zn(bdc)(ted)0.5] (bdc ) benzenedicarboxylate, ted ) triethylenediamine). This material has a tetragonal structure and relatively small pores. We have used atomically detailed simulations to compute adsorption isotherms of hydrogen over the same temperature and pressure ranges studied experimentally. The agreement between experiments and simulations is very good. We have included quantum effects through the Feynman-Hibbs effective potential approach; quantum effects must be included at 77 K to achieve agreement with experiments. We have used equilibrium molecular dynamics to compute self- and transport diffusivities of hydrogen in [Zn(bdc)(ted)0.5] at both 77 and 298 K over a range of pore loadings. Quantum effects are found to decrease the self-diffusivity compared with classical simulations at fixed loading. Conversely, at fixed pressure, quantum effects lead to a lower loading and therefore a higher self-diffusion coefficient compared with classical simulation results. Transport diffusivities with and without quantum corrections are essentially indistinguishable. The diffusivities for H2 in [Zn(bdc)-(ted)0.5] are comparable to H2 in IRMOF-1 at 298 K.

Liu, J.; Lee, J.Y.; Pan, L.; Obermyer, R.T.; Simizu, S.; Zande, B.; Li, J.; Sankar, S.G.; Johnson, J.K

2008-02-28

358

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

NASA Astrophysics Data System (ADS)

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

Deshpande, Sameer Arun

359

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

Microsoft Academic Search

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

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

2001-01-01

360

Hydrogen production by aqueous phase reforming of sorbitol using bimetallic Ni–Pt catalysts: metal support interaction  

Microsoft Academic Search

Hydrogen was produced by Aqueous Phase Reforming (APR) of 10% (w\\/w) sorbitol using mono- and bi-metallic catalysts of Ni and\\u000a Pt supported on alumina nano-fibre (Alnf), mesoporous ZrO2 and mixed oxides of ceria–zirconia–silica (CZxS) with varying concentration of silica (where x is silica concentration). X-ray diffraction, TEM\\/EDS and temperature programmed reduction were also carried on these catalysts\\u000a to study the

A. Tanksale; C. H. Zhou; J. N. Beltramini; G. Q. Lu

2009-01-01

361

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

362

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

SciTech Connect

Pressure-Composition-Temperature (PCT) data are presented for the plutonium-hydrogen (Pu-H) and plutonium-deuterium (Pu-D) systems in the solubility region up to terminal solubility (precipitation of PuH{sub 2}). The heats of solution for PuH{sub s} and PuD{sub s} are determined from PCT data in the ranges 350-625 C for gallium alloyed Pu and 400-575 C for unalloyed Pu. The solubility of high purity plutonium alloyed with 2 at.% gallium is compared to high purity unalloyed plutonium. Significant differences are found in hydrogen solubility for unalloyed Pu versus gallium alloyed Pu. Differences in hydrogen solubility due to an apparent phase change are observable in the alloyed and unalloyed solubilities. The effect of iron impurities on Pu-Ga alloyed Pu is shown via hydrogen solubility data as preventing complete homogenization.

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

2009-01-01

363

Kinetics of dissolution of uranium metal foil by alkaline hydrogen peroxide  

Microsoft Academic Search

To develop a new process for the production of ⁚⁚Mo using low-enriched uranium targets, uranium dissolution in alkaline hydrogen peroxide was studied. Molybdenum-99 is a parent of the widely used medical isotope {sup 99m}Tc. The rates of uranium dissolution in alkaline hydrogen peroxide solution were measured in an open, batch-type reactor and were found to be a 0.25th order reaction

D. Dong; G. F. Vandegrift

1996-01-01

364

ADVANCED HYDROGEN TRANSPORT MEMBRANES FOR VISION 21 FOSSIL FUEL PLANTS  

SciTech Connect

Eltron Research Inc. and team members CoorsTek, Sued Chemie, and Argonne National Laboratory are developing an environmentally benign, inexpensive, and efficient method for separating hydrogen from gas mixtures produced during industrial processes, such as coal gasification. This project was motivated by the National Energy Technology Laboratory (NETL) Vision 21 initiative, which seeks to economically eliminate environmental concerns associated with the use of fossil fuels. Currently, this project is focusing on four basic categories of dense membranes: (i) mixed conducting ceramic/ceramic composites, (ii) mixed conducting ceramic/metal (cermet) composites, (iii) cermets with hydrogen permeable metals, and (iv) hydrogen permeable alloys. Ultimately, these materials must enable hydrogen separation at practical rates under ambient and high-pressure conditions, without deactivation in the presence of feedstream components such as carbon dioxide, water, and sulfur. This report describes resent results for long-term hydrogen permeation and chemical stability measurements, new mixed conducting cermets, progress in cermet, thin film, and thin-walled tube fabrication, hydrogen absorption measurements for selected compositions, and membrane facilitated alkane to olefin conversion.

Shane E. Roark; Anthony F. Sammells; Richard A. Mackay; Lyrik Y. Pitzman; Thomas A. Zirbel; Stewart Schesnack; Thomas F. Barton; Sara L. Rolfe; U. (Balu) Balachandran; Richard N. Kleiner; James E. Stephan; Frank E. Anderson; Aaron L. Wagner; Jon P. Wagner

2003-04-30

365

Gas distribution equipment in hydrogen service - Phase II  

NASA Technical Reports Server (NTRS)

The hydrogen permeability of three different types of commercially available natural gas polyethylene pipes was determined. Ring tensile tests were conducted on permeability-exposed and as-received samples. Hydrogen-methane leakage experiments were also performed. The results show no selective leakage of hydrogen via Poiseuille, turbulent, or orifice flow (through leaks) on the distribution of blends of hydrogen and methane. The data collected show that the polyethylene pipe is 4 to 6 times more permeable to hydrogen than to methane.

Jasionowski, W. J.; Huang, H. D.

1980-01-01

366

Effects of microencapsulation of hydrogen storage alloy on the performances of sealed nickel/metal hydride batteries  

NASA Astrophysics Data System (ADS)

The effect of microencapsulation of hydrogen storage alloy, LaNi(4.7)Al(03), used in sealed nickel/metal hydride batteries, on the battery cycle life, temperature dependence, and charge-discharge and self-discharge characteristics were investigated. Particles of activated alloy powder were microencapsulated by immersion into a plating solution containing Cu(II) tartrate, and the microencapsulated powder was used as an anode material. Compared with a sealed nickel/metal hydride battery made with a noncoated alloy anode, the experimental battery had a four times longer cycle life (due to the role of Cu as an oxygen barrier) and greatly improved charge-discharge characteristics, especially at high rates and low temperatures. The charge retention was 65 percent after a storage for 30 days at 20 C.

Sakai, Tetsuo; Ishikawa, Hiroshi; Oguro, Keisuke; Iwakura, Chiaki; Yoneyama, Hiroshi

1987-03-01

367

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

E-print Network

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

Halpin, Carolyn F.

2012-06-07

368

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

Microsoft Academic Search

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

O. A. Alexandrov; O. I. Steklov; A. V. Alexeev

1993-01-01

369

Production of hydrogen for fuel cells by steam reforming of ethanol over supported noble metal catalysts  

Microsoft Academic Search

The catalytic performance of supported noble metal catalysts for the steam reforming (SR) of ethanol has been investigated in the temperature range of 600–850°C with respect to the nature of the active metallic phase (Rh, Ru, Pt, Pd), the nature of the support (Al2O3, MgO, TiO2) and the metal loading (0–5wt.%). It is found that for low-loaded catalysts, Rh is

Dimitris K Liguras; Dimitris I Kondarides; Xenophon E Verykios

2003-01-01

370

Solar light-driven photocatalytic hydrogen evolution over ZnIn2S4 loaded with transition-metal sulfides  

NASA Astrophysics Data System (ADS)

A series of Pt-loaded MS/ZnIn2S4 (MS = transition-metal sulfide: Ag2S, SnS, CoS, CuS, NiS, and MnS) photocatalysts was investigated to show various photocatalytic activities depending on different transition-metal sulfides. Thereinto, CoS, NiS, or MnS-loading lowered down the photocatalytic activity of ZnIn2S4, while Ag2S, SnS, or CuS loading enhanced the photocatalytic activity. After loading 1.0 wt.% CuS together with 1.0 wt.% Pt on ZnIn2S4, the activity for H2 evolution was increased by up to 1.6 times, compared to the ZnIn2S4 only loaded with 1.0 wt.% Pt. Here, transition-metal sulfides such as CuS, together with Pt, acted as the dual co-catalysts for the improved photocatalytic performance. This study indicated that the application of transition-metal sulfides as effective co-catalysts opened up a new way to design and prepare high-efficiency and low-cost photocatalysts for solar-hydrogen conversion.

Shen, Shaohua; Chen, Xiaobo; Ren, Feng; Kronawitter, Coleman X.; Mao, Samuel S.; Guo, Liejin

2011-12-01

371

Noble-metal-free BODIPY-cobaloxime photocatalysts for visible-light-driven hydrogen production.  

PubMed

In this study a series of supramolecular BODIPY-cobaloxime systems Co-Bn (n = 1-4): [{Co(dmgH)2Cl}{4,4-difluoro-8-(4-pyridyl)-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene}] (Co-B1), [{Co(dmgH)2Cl}{4,4-difluoro-8-(4-pyridyl)-1,3,5,7-tetramethyl-2,6-diiodo-4-bora-3a,4a-diaza-s-indacene}] (Co-B2), [{Co(dmgH)2Cl}{4,4-difluoro-8-(3-pyridyl)-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene}] (Co-B3), and [{Co(dmgH)2Cl}{4,4-difluoro-8-(3-pyridyl)-1,3,5,7-tetramethyl-2,6-diiodo-4-bora-3a,4a-diaza-s-indacene}] (Co-B4) (BODIPY = boron dipyrromethene, dmgH = dimethylglyoxime) have been synthesized by replacing one axial chlorine of cobaloxime moieties with the pyridine residues of BODIPYs, and structurally characterized. Absorption spectra show that the optical properties of the BODIPY-cobaloximes are essentially the sum of their constituent components, indicating weak interactions between the cobaloxime units and BODIPY chromophores in the ground state. If any, electronic communications may take place through the intramolecular electron transfer across their orthogonal structures. The possibility of intramolecular electron transfer is further supported by the results of the density functional theory (DFT) calculations at UB3LYP/LANL2DZ levels on Co-B2?(-) and Co-B4?(-), which show that the highest occupied molecular orbitals (HOMOs) possess predominantly BODIPY character, while the lowest unoccupied molecular orbitals (LUMOs) are located on the cobalt centers. The HOMO ? LUMO transition is an electron-transfer process (BODIPY?(-) radical anions ? cobaloxime fragments). In view of the possible occurrence of electron transfer, these noble-metal-free BODIPY-cobaloximes are studied as single-component homogeneous photocatalysts for H2 generation in aqueous media. Under optimized conditions, the 2,6-diiodo BODIPY-sensitized cobaloxime Co-B4 that contains a meta-pyridyl at the 8-position of BODIPY presents excellent H2 photoproduction catalytic activity with a turnover number (TON) of 85, which is comparable to that of its analogue Co-B2 that has a para-pyridyl attached onto 2,6-diiodo BODIPY (TON = 82); however, both of the noniodinated BODIPY-sensitizer cobaloximes (Co-B1, Co-B3) exhibit a complete lack of activity under the same experimental conditions. These results show that the presence of heavy atoms in the core of BODIPY is essential for the catalytic process and reductive quenching pathways (namely, the intramolecular electron transfers from BODIPY?(-) species to the cobalt centers) for these photocatalytically active systems of Co-Bn (n = 2 and 4) are thermodynamically feasible for the hydrogen-evolving reaction. PMID:25277723

Luo, Geng-Geng; Fang, Kai; Wu, Ji-Huai; Dai, Jing-Cao; Zhao, Qing-Hua

2014-11-21

372

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

E-print Network

that the binding of small gas molecules (such as NO, CO, NH3, and so on) to these molecules results in a change 11 July 2013) Metal phthalocyanine (MPc, M Âź Mn, Fe) molecules grown on reconstructed Au(111 microscopy. It is found out that the attachment of H atoms to the central metal of the MnPc molecules leads

Gao, Hongjun

373

Surface Modification to Improve Hydrogen Entry Efficiency and Storage Capabilities of Metal Hydride Alloys  

E-print Network

Engineering, University of South Carolina Objectives: To develop anode materials for Ni-MH cells with high) Recognize the importance of particle pulverization and corrosion processes in developing high cycle life Metal Hydride Test Station (top) and alloy oxidation in bare metal hydrides (bottom) #12;Ni-MH Battery

Popov, Branko N.

374

Use of Hydrogen in the Production of Bullion and Metal Powders  

Microsoft Academic Search

It is known that after completion of the chloride process in the refining of silver and gold, the purity of the metals is 998?999 for silver and 995?996 for gold [1]. Metals of such purity do not meet the requirements of modern technology. To raise the purity level, sponge silver or gold is remelted into anodes for subsequent electrolytic refining.

V. N. Ermilin; Yu. V. Litvinov; S. L. Andreev; B. A. Spiridonov

2004-01-01

375

The Influence of Grain Boundary Phosphorus Concentration on Liquid Metal and Hydrogen Embrittlement of Monel 400  

NASA Astrophysics Data System (ADS)

The susceptibility of Monel 400Ž to embrittlement by mercury and by hydrogen was measured as affected by thermal treatment. Specimens were annealed at 900°C and either quenched or furnace cooled. Auger analysis revealed phosphorus segregated to the grain boundaries; furnace cooling causes the boundary concentration to be about twice that of the quenched material. Tensile tests were conducted with specimens (1) in air, (2) coated with mercury, or (3) cathodically precharged with hydrogen. Fractures in air were completely ductile, and ductility was not affected by thermal treatment. Fractures of mercury-coated and hydrogen-charged samples were brittle and intergranular; elongation to fracture increased significantly with increasing concentration of grain boundary phosphorus. The results are discussed in terms of additive and interactive mechanisms.

Funkenbusch, A. W.; Heldt, L. A.; Stein, D. F.

1982-04-01

376

Improvement of charge trapping by hydrogen post-oxidation annealing in gate oxide of 4H-SiC metal-oxide-semiconductor capacitors  

Microsoft Academic Search

The effect of hydrogen postoxidation annealing (POA) on the reliability of gate oxide formed in 4H-SiC metal-oxide-semiconductor (MOS) capacitors has been investigated. Argon POA at 1200 °C and hydrogen POA were carried out over a temperature range of 400-1000 °C to improve the properties of 4H-SiC\\/SiO2 interface and thermal gate oxide. Interface state density Dit decreases as the temperature of

Won-Ju Cho; Ryoji Kosugi; Kenji Fukuda; Kazuo Arai; Seiji Suzuki

2000-01-01

377

Impedance and initial magnetic permeability of gadolinium  

Microsoft Academic Search

In the present work we report on measurements of the complex impedance and the magnetoimpedance of a textured sample of gadolinium metal. The preferential c-axis orientation of the Gd hexagonal structure is perpendicular to the long axis of the sample. From the experimental data, the complex initial magnetic permeability, ?=??+i??, was obtained as a function of temperature and frequency of

G. L. F. Fraga; P. Pureur; L. P. Cardoso

2010-01-01

378

Impedance and initial magnetic permeability of gadolinium  

Microsoft Academic Search

In the present work we report on measurements of the complex impedance and the magnetoimpedance of a textured sample of gadolinium metal. The preferential c -axis orientation of the Gd hexagonal structure is perpendicular to the long axis of the sample. From the experimental data, the complex initial magnetic permeability, mu=mu'+imu'', was obtained as a function of temperature and frequency

G. L. F. Fraga; P. Pureur; L. P. Cardoso

2010-01-01

379

Development of membranes for hydrogen separation: Pd-coated V-10Pd  

SciTech Connect

Numerous Group IVB and VB alloys were prepared and tested as potential membrane materials but most of these materials were brittle or exhibited cracking during hydrogen exposure. One of the more ductile alloys, V-10Pd (at. %), was fabricated into a thin (107-{micro}m thick) composite membrane coated with 100 nm of Pd on each side. The material was tested for hydrogen permeability, resistance to hydrogen embrittlement, and long term hydrogen flux stability. The hydrogen permeability, {phi}, of the V-10Pd membrane was 3.86 x 10{sup -8} mol H{sub 2} m{sup -1} s{sup -1} Pa{sup -0.5} (avg. of three different samples) at 400 C, which is slightly higher than the permeability of Pd-23Ag at that temperature. A 1400 h hydrogen flux test at 400 C demonstrated that the rate of metallic interdiffusion was slow between the V-10Pd foil and the 100-nm-thick Pd coating on the surface. However, at the end of testing the membrane cracked at 118 C because of hydrogen embrittlement.

Paglieri, Stephen N [Los Alamos National Laboratory; Wermer, Joseph R [Los Alamos National Laboratory; Buxbaum, Robert E [REB RESEARCH AND CONSULTING; Ciocco, Michael V [NETL; Howard, Bret H [NETL; Morreale, Bryan D [NETL

2009-01-01

380

Metallization and Dissociation of Fluid Hydrogen and Other Diatomics at 100 GPa Pressures.  

National Technical Information Service (NTIS)

Dynamic compression of diatomic liquids using both single-shock (Hugoniot) and multiple-shock (reverberating-shock) compression achieves pressures which range up to a few 100 GPa (Mbar), densities as high as tenfold of initial liquid density in hydrogen, ...

W. J. Nellis

2002-01-01

381

Competitive hydrogenation of benzene and toluene on group VIII metals: correlation with the electronic structure  

Microsoft Academic Search

It has been shown previously that the ratio K\\/sub T\\/B\\/ of the adsorption coefficients of toluene and benzene determined from a kinetic analysis of the competitive hydrogenation of these hydrocarbons can be used to probe the electronic structure of platinum. Because toluene is more of an electron donor than benzene, the larger the electron deficiency of platinum, the larger the

T. T. Phuong; J. Massardier; P. Gallezot

1986-01-01

382

An investigation of the kinetics for hydrogen chemisorption on iron metal surfaces  

NASA Technical Reports Server (NTRS)

A quasi-isothermal approach was used to study the kinetics of hydrogen and hydrogen sulfide chemisorption onto iron film in an effort to understand the environmental degradation of steels. The coverage of chemisorbed hydrogen or chemisorbed sulfur was observed as a function of time for fixed conditions of substrate temperature. Auger electron spectroscopy was used to observe the sulfur and chemisorption-induced resistance change was employed to monitor hydrogen coverage. To compare the results obtained from studying the kinetics by two different techniques, the kinetics of oxygen chemisorption onto iron films was also studied. A reaction model utilized to interpret the H2/Fe2 chemisorption kinetics was applied to data from an earlier study on the desorption kinetics for H2 chemisorbed onto nicket films in the vicinity of the Curie temperature of the film. This analysis permitted a separation of the gross desorption process into individual components so that the influence of the magnetic phase transition on the rate constants could be determined.

Shanabarger, M. R.

1980-01-01

383

Metalized T graphene: A reversible hydrogen storage material at room temperature  

NASA Astrophysics Data System (ADS)

Lithium (Li)-decorated graphene is a promising hydrogen storage medium due to its high capacity. However, homogeneous mono-layer coating graphene with lithium atoms is metastable and the lithium atoms would cluster on the surface, resulting in the poor reversibility. Using van der Waals-corrected density functional theory, we demonstrated that lithium atoms can be homogeneously dispersed on T graphene due to a nonuniform charge distribution in T graphene and strong hybridizations between the C-2p and Li-2p orbitals. Thus, Li atoms are not likely to form clusters, indicating a good reversible hydrogen storage. Both the polarization mechanism and the orbital hybridizations contribute to the adsorption of hydrogen molecules (storage capacity of 7.7 wt. %) with an optimal adsorption energy of 0.19 eV/H2. The adsorption/desorption of H2 at ambient temperature and pressure is also discussed. Our results can serve as a guide in the design of new hydrogen storage materials based on non-hexagonal graphenes.

Ye, Xiao-Juan; Liu, Chun-Sheng; Zhong, Wei; Zeng, Zhi; Du, You-Wei

2014-09-01

384

Photocatalytic hydrogen evolution from carbon-neutral oxalate with 2-phenyl-4-(1-naphthyl)quinolinium ion and metal nanoparticles.  

PubMed

Photocatalytic hydrogen evolution has been made possible by using oxalate as a carbon-neutral electron source, metal nanoparticles as hydrogen-evolution catalysts and the 2-phenyl-4-(1-naphthyl)quinolinium ion (QuPh(+)-NA), which forms the long-lived electron-transfer state upon photoexcitation, as a photocatalyst. The hydrogen evolution was conducted in a deaerated mixed solution of an aqueous buffer and acetonitrile (MeCN) [1:1 (v/v)] by photoirradiation (? > 340 nm). The gas evolved during the photocatalytic reaction contained H(2) and CO(2) in a molar ratio of 1:2, indicating that oxalate acts as a two-electron donor. The hydrogen yield based on the amount of oxalate reached more than 80% under pH conditions higher than 6. Ni and Ru nanoparticles as well as Pt nanoparticles act as efficient hydrogen-evolution catalysts in the photocatalytic hydrogen evolution. The photocatalyst for hydrogen evolution can be used several times without significant deactivation of the catalytic activity. Nanosecond laser flash photolysis measurements have revealed that electron transfer from oxalate to the photogenerated QuPh?-NA?(+), which forms a ?-dimer radical cation with QuPh(+)-NA [(QuPh?-NA?(+))(QuPh(+)-NA)], occurs followed by subsequent electron transfer from QuPh?-NA to the hydrogen-evolution catalyst in the photocatalytic hydrogen evolution. Oxalate acts as an efficient electron source under a wide range of reaction conditions. PMID:22751574

Yamada, Yusuke; Miyahigashi, Takamitsu; Ohkubo, Kei; Fukuzumi, Shunichi

2012-08-14

385

Multielemental elution behavior of metal ions adsorbed on iminodiacetic acid chelating resin by using hydrogen peroxide as an eluent.  

PubMed

In the present work, we investigated the multielemental elution behavior of metal ions absorbed on iminodiacetic acid (IDA) chelating resin by using hydrogen peroxide (H(2)O(2)) as an eluent. As a result, V(V), Mo(VI), W(VI), Nb(V) and Ta(V) were efficiently eluted by H(2)O(2). In contrast, other metal ions were rarely recovered. The oxidation states of V(V), Mo(VI), and W(VI) were not changed through the H(2)O(2) eluting process, checked by X-ray photoelectron analysis. In addition, the UV-vis adsorption spectra and IR spectra of V(V), Mo(VI) and W(VI) in the H(2)O(2) eluent suggested the formation of metal-peroxo complexes through H(2)O(2) elution. The desorption of these metal ions from IDA functional groups is explained in term of destabilization along with the coordination of peroxo-ligands to the V(V)-, Mo(VI)- and W(VI)-IDA complexes, and a decrease in the adsorption capacity by electrostatic repulsion between dissociated carboxylic groups of IDA and the oxoanions in the neutral pH shown in 30 wt% H(2)O(2). When this method was applied to the selective separation of V(V), Mo(VI) and W(VI) from other metals in an acid soluble fraction of fly-ash, 83.4 ą 2.5% of V(V), 88.1 ą 3.3% of Mo(VI), and 69.3 ą 5.4% of W(VI) were recovered in a 30 wt% H(2)O(2) eluent. PMID:22687925

Yabutani, Tomoki; Sumi, Hidehiko; Nakamura, Takamasa; Akatsuki, Shinsuke; Thuy, Le Thi Xuan

2012-01-01

386

Sulfides in the Anaerobic Environment: The Determination of Hydrogen Sulfide and Acid-Soluble Metallic Sulfides in Sea-Floor Sediment  

NASA Astrophysics Data System (ADS)

A procedure for the determination of hydrogen sulfide and acid-soluble metallic sulfides in sea floor sediment has been developed and tested as part of a laboratory course in analytical and environmental chemistry. The procedure includes (i) anaerobic sampling of sediment, (ii) a volatilization method, which discriminates between hydrogen sulfide and acid-soluble metallic sulfides in the sediment, and (iii) a quantitative determination of these sulfide components using an ion-selective electrode approach. The paper describes all experimental details and gives a brief summary of sulfide generation processes in sea-floor sediments, underlining the importance of sulfides in anaerobic environments. Representative results obtained during the laboratory course are discussed.

Christensen, Joan Kai; Hřyer, Boy; Kryger, Lars; Pind, Niels; Kong, Lee Sing

1998-12-01

387

High-Performance Palladium Based Membrane for Hydrogen Separation and Purification  

SciTech Connect

The mission of the DOE's Fuel Cell Technologies'Â?Hydrogen Fuels R&D effort is to research, develop, and validate technologies for producing, storing, and delivering hydrogen in an efficient, clean, safe, reliable, and affordable manner. A key program technical milestone for hydrogen technology readiness is to produce hydrogen from diverse, domestic resources at $2.00-$3.00 per gallon of gasoline equivalent (gge) delivered, untaxed. Low-cost, high-temperature hydrogen separation membranes represent a key enabling technology for small-scale distributed hydrogen production units. Availability of such membranes with high selectivity and high permeability for hydrogen will allow their integration with hydrocarbon reforming and water gas shift reactions, potentially reducing the cost of hydrogen produced. Pd-metal-based dense membranes are known for their excellent hydrogen selectivity and permeability characteristics, however, utilization of these membranes has so far been limited to small scale niche markets for hydrogen purification primarily due to the relatively high cost of Pd-alloy tubes compared to pressure swing adsorption (PSA) units. This project was aimed at development of thin-film Pd-alloy membranes deposited on Pall Corporation's DOE-based AccuSepÂŽ porous metal tube substrates to form a composite hydrogen separation membrane for these applications. Pall's composite membrane development addressed the typical limitations of composite structures by developing robust membranes capable of withstanding thermal and mechanical stresses resulting from high temperature (400C), high pressure (400 psi steam methane reformer and 1000 psi coal) operations and thermal cycling involved in conventional hydrogen production. In addition, the Pd-alloy membrane composition was optimized to be able to offer the most stability in the typical synthesis gas environments produced by reforming of natural gas and bio-derived liquid fuels (BILI) validating the technical effectiveness and economic feasibility of the technology demonstrated. Results from this research added technology and product design information that offers the potential to significantly advance the commercial viability of hydrogen production.

Scott Hopkins

2012-01-31

388

Influence of clamping plate permeability and metal screen structures on three-dimensional magnetic field and eddy current loss in end region of a turbo-generator by numerical analysis  

NASA Astrophysics Data System (ADS)

A significant problem of turbogenerators on complex end structures is overheating of local parts caused by end losses in the end region. Therefore, it is important to investigate the 3-D magnetic field and eddy current loss in the end. In end region of operating large turbogenerator at thermal power plants, magnetic leakage field distribution is complex. In this paper, a 3-D mathematical model used for the calculation of the electromagnetic field in the end region of large turbo-generators is given. The influence of spatial locations of end structures, the actual shape and material of end windings, clamping plate, and copper screen are considered. Adopting the time-step finite element (FE) method and taking the nonlinear characteristics of the core into consideration, a 3-D transient magnetic field is calculated. The objective of this paper is to investigate the influence of clamping plate permeability and metal screen structures on 3-D electromagnetic field distribution and eddy current loss in end region of a turbo-generator. To reduce the temperature of copper screen, a hollow metal screen is proposed. The eddy current loss, which is gained from the 3D transient magnetic field, is used as heat source for the thermal field of end region. The calculated temperatures are compared with test data.

Likun, Wang; Weili, Li; Yi, Xue; Chunwei, Guan

2013-11-01

389

ADVANCED HYDROGEN TRANSPORT MEMBRANES FOR VISION 21 FOSSIL FUELS PLANTS  

SciTech Connect

Eltron Research Inc. and team members CoorsTek, Sued Chemie, and Argonne National Laboratory are developing an environmentally benign, inexpensive, and efficient method for separating hydrogen from gas mixtures produced during industrial processes, such as coal gasification. This project was motivated by the National Energy Technology Laboratory (NETL) Vision 21 initiative, which seeks to economically eliminate environmental concerns associated with the use of fossil fuels. Currently, this project is focusing on four basic categories of dense membranes: (1) mixed conducting ceramic/ceramic composites, (2) mixed conducting ceramic/metal (cermet) composites, (3) cermets with hydrogen permeable metals, and (4) layered composites containing hydrogen permeable alloys. Ultimately, these materials must enable hydrogen separation at practical rates under ambient and high-pressure conditions, without deactivation in the presence of feedstream components such as carbon dioxide, water, and sulfur. This report presents hydrogen permeation data during long term tests and tests at high pressure in addition to progress with cermet, ceramic/ceramic, and thin film membranes.

Shane E. Roark; Anthony F. Sammells; Richard Mackay; Stewart Schesnack; Scott Morrison; Thomas A. Zirbel; Thomas F. Barton; Sara L. Rolfe; U. Balachandran; Richard N. Kleiner; James E. Stephan; Frank E. Anderson; Aaron L. Wagner; Jon P. Wagner

2003-07-31

390

Noble metal doped graphene nanocomposites and its study of photocatalytic hydrogen evolution  

NASA Astrophysics Data System (ADS)

This work reports the deposition of platinum (Pt) nanoparticles on the surface of graphene nanosheet by a simple approach, using a microwave-assisted method. The photocatalytic activity has been investigated for hydrogen evolution. The hydrogen evolutions were attributed to graphene, due to its high photoelectron transport properties, and the Pt nanoparticles attached on the surface of graphene sheet, which act as reaction centers for H2 evolution. The “as-prepared” composites were characterized by Brunauer Emmett Teller (BET) surface area measurement, X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectra (DRS). This work highlights the potential application of graphene-based materials in the field of energy conversion.

Ullah, Kefayat; Ye, Shu; Zhu, Lei; Jo, Sun Bok; Jang, Won Kweon; Cho, Kwang-Youn; Oh, Won-Chun

2014-05-01

391

Hydrogen as a working atmosphere for manufacturing permanent magnets based on rare-earth metals  

Microsoft Academic Search

The phase compositions and magnetic properties of permanents magnets of the systems Sm – Co and Nd – Fe – B are analyzed.\\u000a Features of the hydrogenation–disproportionation–desorption–recombination (HDDR) process in the Nd2 Fe14 B intermetallic are considered. Using the Dd – Fe – B system as an example, we assess stages of manufacture of commercial\\u000a permanent magnets and show the

V. V. Fedorov; I. I. Bulyk; V. V. Panasyuk

2009-01-01

392

Photochemical electron storage on colloidal metals and hydrogen formation by free radicals  

SciTech Connect

Photolytically produced 1-hydroxy-1-methylethyl radicals were found to form hydrogen in the presence of colloidal platinum, gold, silver, and cadmium. Conductivity measurements showed that electrons stored on the colloidal particles are intermediates to H/sub 2/ formation. A 1.25 x 10/sup -4/ M silver solution was found to store electrons up to more than 0.3 C/L (electrical capacity per liter) during illumination.

Henglein, A.; Lindig, B.; Westerhausen, J.

1981-06-11

393

Effect of hydrogen implantation on semiconductor–metal transition and high-pressure thermopower in Si  

Microsoft Academic Search

In the present work Czochralski-grown silicon single crystals were investigated implanted with different doses of H+ ions. The Si wafers were characterized by the Raman scattering technique. Thermoelectric power was studied in a pressure range of 0–20GPa of p-type Si single crystal wafers containing a thin hydrogenated layer consisting of amorphous Si, nanocrystalline Si and H-rich Si layers. In the

Sergey V. Ovsyannikov; Vladimir V. Shchennikov; Irina V. Antonova; Vsevolod V. Shchennikov; Yuri S. Ponosov

2007-01-01

394

Enhancing hydrogen spillover and storage  

DOEpatents

Methods for enhancing hydrogen spillover and storage are disclosed. One embodiment of the method includes doping a hydrogen receptor with metal particles, and exposing the hydrogen receptor to ultrasonication as doping occurs. Another embodiment of the method includes doping a hydrogen receptor with metal particles, and exposing the doped hydrogen receptor to a plasma treatment.

Yang, Ralph T; Li, Yingwei; Lachawiec, Jr., Anthony J

2013-02-12

395

Enhancing hydrogen spillover and storage  

DOEpatents

Methods for enhancing hydrogen spillover and storage are disclosed. One embodiment of the method includes doping a hydrogen receptor with metal particles, and exposing the hydrogen receptor to ultrasonification as doping occurs. Another embodiment of the method includes doping a hydrogen receptor with metal particles, and exposing the doped hydrogen receptor to a plasma treatment.

Yang, Ralph T. (Ann Arbor, MI); Li, Yingwel (Ann Arbor, MI); Lachawiec, Jr., Anthony J. (Ann Arbor, MI)

2011-05-31

396

A homogeneous transition metal complex for clean hydrogen production from methanol-water mixtures.  

PubMed

The development of an efficient catalytic process that mimics the enzymatic function of alcohol dehydrogenase is critical for using biomass alcohols for both the production of H2 as a chemical energy carrier and fine chemicals under waste-free conditions. Dehydrogenation of alcohol-water mixtures into their corresponding acids with molecular hydrogen as the sole by-product from the reaction can be catalysed by a ruthenium complex with a chelating bis(olefin) diazadiene ligand. This complex, [K(dme)2][Ru(H)(trop2dad)], stores up to two equivalents of hydrogen intramolecularly, and catalyses the production of H2 from alcohols in the presence of water and a base under homogeneous conditions. The conversion of a MeOH-H2O mixture proceeds selectively to CO2/H2 gas formation under neutral conditions, thereby allowing the use of the entire hydrogen content (12% by weight). Isolation and characterization of the ruthenium complexes from these reactions suggested a mechanistic scenario in which the trop2dad ligand behaves as a chemically 'non-innocent' co-operative ligand. PMID:23511424

Rodríguez-Lugo, Rafael E; Trincado, Mónica; Vogt, Matthias; Tewes, Friederike; Santiso-Quinones, Gustavo; Grützmacher, Hansjörg

2013-04-01

397

Hydrogen production using solid oxide membrane electrolyzer with solid carbon reductant in liquid metal anode  

SciTech Connect

A laboratory-scale solid oxide membrane (SOM) steam electrolyzer that can potentially utilize the energy value of coal or any hydrocarbon reductant to produce high purity hydrogen has been fabricated and evaluated. The SOM electrolyzer consists of an oxygen-ion-conducting yttria-stabilized zirconia (YSZ) electrolyte with a Ni-YSZ cermet cathode coated on one side and liquid tin anode on the other side. Hydrogen production using the SOM electrolyzer was successfully demonstrated between 900 and 1000{sup o}C by feeding a steam-rich gas to the Ni-YSZ cermet cathode and solid carbon reductant into the liquid tin anode. It was confirmed that the energy required for hydrogen production can be effectively lowered by feeding a solid carbon reductant in the liquid tin anode. A polarization model for the SOM electrolyzer was developed. The experimental data obtained under different operating conditions were curve fitted into the model to identify the various polarization losses. Based on the results of this study, work needed toward increasing the electrochemical performance of the SOM electrolyzer is discussed.

Pati, S.; Yoon, K.J.; Gopalan, S.; Pal, U.B. [Boston University, Boston, MA (United States). Dept. of Mechanical Engineering

2009-07-01

398

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

E-print Network

Background Hydrogen permeation and related stress corrosion cracking (SCC) can limit the use, laser surface modification and shot preening have been proposed to decrease hydrogen permeation out which helps in mitigating hydrogen permeation through hard steel. A drawback with zinc plating

Popov, Branko N.

399

Intrinsic stress and high temperature properties of metal-containing hydrogenated amorphous carbon coatings  

NASA Astrophysics Data System (ADS)

A detailed examination of the intrinsic stress development and mechanical properties of titanium-containing hydrogenated amorphous carbon (Ti-C:H) and W-C:H coatings, deposited in an inductively coupled plasma (ICP) assisted hybrid chemical/physical vapor deposition (CVD/PVD) environment was carried out. Intrinsic stresses within those coatings were found to be compressive and dependent on compositions. The intrinsic compression within Ti-C:H was further shown to be significantly influenced by the energy of ionic species bombarding the substrate during growth. The results suggested that ion bombardment played a significant role in intrinsic stress generation within Ti-C:H, and was likely to influence stress development in other low temperature deposited amorphous hydrocarbon (a-C:H) based ceramic nanocomposite coatings. A higher deposition temperature, ˜600°C, promoted TiC precipitation and resulted in little Ti dissolution within the a-C:H matrix. High-temperature deposited Ti-C:H specimens were found to possess lower modulus and hardness values as compared to those deposited at low temperature, ˜250°C, especially at low Ti compositions. This is rationalized by electron microscopy evidence of increased short and medium range graphitic order within the a-C:H matrix of high-temperature deposited Ti-C:H, and supported by additional Raman spectroscopic observations. Annealing treatment at 600°C combined with Raman scattering measurements showed that the a-C:H matrix in high temperature deposited Ti-C:H specimens appears to be less structurally sensitive to additional high temperature annealing. The effective coefficients of thermal expansion (CTE) of Ti-C:H coatings were measured through temperature induced changes in the curvature of film/substrate assemblies. Measured effective CTE values for Ti-C:H are consistent with previous measurements on a-C:H thin films, and show little dependence on the Ti composition. Highly hydrogenated carbon coatings with hydrogen content approaching 60 atomic percent were deposited with a modified ICP-assisted CVD technique. The hydrogen release temperature was found to be above 500°C, which was 150°C higher than findings in previous experiments. Plasma diagnostics suggested that a decreased ratio of ionic species flux to activated neutral species flux at the substrate during deposition was responsible for the increased hydrogen incorporation into the film.

Shi, Bo

400

Oxidation of phenol by hydrogen peroxide catalyzed by metal-containing poly(amidoxime) grafted starch.  

PubMed

Polyamidoxime chelating resin was obtained from polyacrylonitrile (PAN) grafted starch. The nitrile groups of the starch-grafted polyacrylonitrile (St-g-PAN) were converted into amidoximes by reaction with hydroxylamine under basic conditions. The synthesized graft copolymer and polyamidoxime were characterized by FTIR, TGA and elemental microanalysis. Metal chelation of the polyamidoxime resin with iron, copper and zinc has been studied. The produced metal-polyamidoxime polymer complexes were used as catalysts for the oxidation of phenol using H(2)O(2) as oxidizing agent. The oxidation of phenol depends on the central metal ion present in the polyamidoxime complex. Reuse of M-polyamidoxime catalyst/H(2)O(2) system showed a slight decrease in catalytic activities for all M-polyamidoxime catalysts. PMID:22127293

El-Hamshary, Hany; El-Newehy, Mohamed H; Al-Deyab, Salem S

2011-01-01

401

Mechanism of hydrogen transfer in arsane generation by aqueous tetrahydridoborate: Interference effects of Au III and other noble metals  

NASA Astrophysics Data System (ADS)

The generation of arsane by reaction of either NaBH 4 (THB) or NaBD 4 (TDB) in aqueous solution with As III (1 mg L -1) has been studied in the presence of several transition and noble metals at trace levels. A continuous flow generation system coupled with both atomic absorption spectrometry (AAS) and gas chromatography mass spectrometry (GC-MS) were employed to measure the effect of Au III (0.5 - 20 mg L -1) on reaction yield and isotopic composition of arsane. In a different set of batch experiments, GC-MS was employed to measure the effect of Au III, Pd II, Pt II, Ni II and Cu II on the isotopic composition of arsane. Au III, Pd II and Pt II induce a significant perturbation in the mechanism of hydride generation, promoting the incorporation of a large amount of hydrogen derived from the solvent into the final arsane. This effect takes place at metal concentration levels which hardly affect the generation efficiency of arsane and can likely be addressed by the action of intermediate species formed in the early stage of the reaction between the metal ion and the TDB-arsenic complex. Nanoparticles and colloids arising from the interaction of the metal and TDB are able to capture the final arsane but they do not promote H/D exchange on the already formed arsane. This evidence reveals the existence of a new type of interference in chemical generation of volatile hydrides - a "mechanistic interference" - in addition to the already known yield interferences.

Pagliano, Enea; Onor, Massimo; Meija, Juris; Mester, Zoltan; Sturgeon, Ralph E.; D'Ulivo, Alessandro

2011-09-01

402

Survival of hydrogen anions near atomically flat metal surfaces: Band gap confinement and image state recapture effects  

NASA Astrophysics Data System (ADS)

Resonant charge transfer (RCT) between ions and surfaces is a key intermediate step in surface-chemical processes as well as in micro- and nano-fabrications on the surface. The RCT process in the collision of hydrogen anions with metal surfaces is described within a wave packet propagation methodology using Crank-Nicholson algorithm [1]. The ion-survival probability is found to strongly enhance at two different ion velocities perpendicular to the surface. The low velocity enhancement is induced from a dynamical confinement of the ion level inside the band gap, while the high velocity enhancement emerges owing to the recapture from transiently populated image states [2]. These structures are found to be somewhat sensitive to the ion's distance of closest approach to the surface and the choice of inter-atomic potentials between the ion and the surface atoms. [1] Chakraborty et al., Phys. Rev. A 70, 052903 (2004); [2] Schmitz et al., Phys. Rev. A (submitted).

Schmitz, Andrew; Shaw, John; Chakraborty, Himadri; Thumm, Uwe

2010-03-01

403

Metal/graphene nanocomposites synthesized with the aid of supercritical fluid for promoting hydrogen release from complex hydrides.  

PubMed

With the aid of supercritical CO2, Fe-, Ni-, Pd-, and Au-nanoparticle-decorated nanostructured carbon materials (graphene, activated carbon, carbon black, and carbon nanotubes) are synthesized for catalyzing the dehydrogenation of LiAlH4. The effects of the metal nanoparticle size and distribution, and the type of carbon structure on the hydrogen release properties are investigated. The Fe/graphene nanocomposite, which consists of ?2 nm Fe particles highly dispersed on graphene nanosheets, exhibits the highest catalytic performance. With this nanocomposite, the initial dehydrogenation temperature can be lowered (from ?135 °C for pristine LiAlH4) to ?40 °C without altering the reaction route (confirmed by in situ X-ray diffraction), and 4.5 wt% H2 can be released at 100 °C within 6 min, which is faster by more than 135-fold than the time required to release the same amount of H2 from pristine LiAlH4. PMID:25182863

Jiang, De-Hao; Yang, Cheng-Hsien; Tseng, Chuan-Ming; Lee, Sheng-Long; Chang, Jeng-Kuei

2014-10-01

404

A malonitrile-functionalized metal-organic framework for hydrogen sulfide detection and selective amino acid molecular recognition  

PubMed Central

A novel porous polymeric fluorescence probe, MN-ZIF-90, has been designed and synthesized for quantitative hydrogen sulfide (H2S) fluorescent detection and highly selective amino acid recognition. This distinct crystalline structure, derived from rational design and malonitrile functionalization, can trigger significant enhancement of its fluorescent intensity when exposed to H2S or cysteine molecules. Indeed this new metal-organic framework (MOF) structure shows high selectivity of biothiols over other amino acids and exhibits favorable stability. Moreover, in vitro viability assays on HeLa cells show low cytotoxicity of MN-ZIF-90 and its imaging contrast efficiency is further demonstrated by fluorescence microscopy studies. This facile yet powerful strategy also offers great potential of using open-framework materials (i.e. MOFs) as the novel platform for sensing and other biological applications. PMID:24621614

Li, Haiwei; Feng, Xiao; Guo, Yuexin; Chen, Didi; Li, Rui; Ren, Xiaoqian; Jiang, Xin; Dong, Yuping; Wang, Bo

2014-01-01

405

High proton conduction at above 100 °C mediated by hydrogen bonding in a lanthanide metal-organic framework.  

PubMed

A lanthanide metal-organic framework (MOF) compound of the formulation [Eu2(CO3)(ox)2(H2O)2]ˇ4H2O (1, ox = oxalate) was prepared by hydrothermal synthesis with its structure determined crystallographically. Temperature-dependent but humidity-independent high proton conduction was observed with a maximum of 2.08 × 10(-3) S cm(-1) achieved at 150 °C, well above the normal boiling point of water. Results from detailed structural analyses, comparative measurements of conductivities using regular and deuterated samples, anisotropic conductivity measurements using a single-crystal sample, and variable-temperature photoluminescence studies collectively establish that the protons furnished by the Eu(III)-bound and activated aqua ligands are the charge carriers and that the transport of proton is mediated along the crystallographic a-axis by ordered hydrogen-bonded arrays involving both aqua ligands and adjacent oxalate groups in the channels of the open framework. Proton conduction was enhanced with the increase of temperature from room temperature to about 150 °C, which can be rationalized in terms of thermal activation of the aqua ligands and the facilitated transport between aqua and adjacent oxalate ligands. A complete thermal loss of the aqua ligands occurred at about 160 °C, resulting in the disintegration of the hydrogen-bonded pathway for proton transport and a precipitous drop in conductivity. However, the structural integrity of the MOF was maintained up to 350 °C, and upon rehydration, the original structure with the hydrogen-bonded arrays was restored, and so was its high proton-conduction ability. PMID:25137095

Tang, Qun; Liu, Yiwei; Liu, Shuxia; He, Danfeng; Miao, Jun; Wang, Xingquan; Yang, Guocheng; Shi, Zhan; Zheng, Zhiping

2014-09-01

406

Synthesis, Structure Determination, and Hydrogen Sorption Studies of New Metal-Organic Frameworks Using Triazole and Naphthalenedicarboxylic Acid  

SciTech Connect

Two new metal-organic framework compounds were synthesized under solvothermal conditions using Zn{sup 2+} ion, 1,2,4-triazole (TRZ), and 1,4- and 2,6-naphthalenedicarboxylic acids (NDC): Zn{sub 4}(TRZ){sub 4}(1,4-NDC){sub 2}-2DMF-2H{sub 2}O (1) and Zn{sub 4}(TRZ){sub 4}(2,6-NDC){sub 2}-2DMF-4H{sub 2}O (2). Their crystal structures were characterized by single-crystal X-ray diffraction. Structure 1 crystallizes in the P2{sub 1}/n space group with a = 13.609(2) {angstrom}, b = 27.181(5){angstrom}, c = 13.617(3) {angstrom}, {beta} = 92.46(1){sup o}, V = 5032.4(16) {angstrom}{sup 3}, and Z = 4. Structure 2 crystallizes in orthorhombic Pna2{sub 2} space group with a = 30.978(6) {angstrom}, b = 12.620(3) {angstrom}, c = 13.339(3) {angstrom}, V = 5215(2) {angstrom}{sup 3}, and Z = 4. Both structures are analogues of the previously reported Zn{sub 4}(TRZ){sub 4}(1,4-BDC){sub 2}-16H{sub 2}O where the layers of Zn-triazole moieties are pillared by aromatic dicarboxylates to create 3-D open frameworks. Nitrogen sorption studies revealed that these structures have Brunaer-Emmett-Teller (BET) surface areas of 362.1-584.1 m{sup 2}/g. Hydrogen sorption experiments showed they can store 0.84-1.09 wt % H{sub 2} at 77 K and 1 atm. Although they do not contain large pores or surface areas, they possess the hydrogen sorption capacities comparable to those of highly porous metal-organic frameworks.

Park,H.; Britten, J.; Mueller, U.; Lee, J.; Li, J.; Parise, J.

2007-01-01

407

Long-Term Evolution and Revival Structure of Rydberg Wave Packets for Hydrogen and Alkali-Metal Atoms  

E-print Network

This paper begins with an examination of the revival structure and long-term evolution of Rydberg wave packets for hydrogen. We show that after the initial cycle of collapse and fractional/full revivals, which occurs on the time scale $t_{\\rm rev}$, a new sequence of revivals begins. We find that the structure of the new revivals is different from that of the fractional revivals. The new revivals are characterized by periodicities in the motion of the wave packet with periods that are fractions of the revival time scale $t_{\\rm rev}$. These long-term periodicities result in the autocorrelation function at times greater than $t_{\\rm rev}$ having a self-similar resemblance to its structure for times less than $t_{\\rm rev}$. The new sequence of revivals culminates with the formation of a single wave packet that more closely resembles the initial wave packet than does the full revival at time $t_{\\rm rev}$, i.e., a superrevival forms. Explicit examples of the superrevival structure for both circular and radial wave packets are given. We then study wave packets in alkali-metal atoms, which are typically used in experiments. The behavior of these packets is affected by the presence of quantum defects that modify the hydrogenic revival time scales and periodicities. Their behavior can be treated analytically using supersymmetry-based quantum-defect theory. We illustrate our results for alkali-metal atoms with explicit examples of the revival structure for radial wave packets in rubidium.

Robert Bluhm; Alan Kostelecky

1995-06-07

408

Tuning the acid/metal balance of carbon nanofiber-supported nickel catalysts for hydrolytic hydrogenation of cellulose.  

PubMed

Carbon nanofibers (CNFs) are a class of graphitic support materials with considerable potential for catalytic conversion of biomass. Earlier, we demonstrated the hydrolytic hydrogenation of cellulose over reshaped nickel particles attached at the tip of CNFs. The aim of this follow-up study was to find a relationship between the acid/metal balance of the Ni/CNFs and their performance in the catalytic conversion of cellulose. After oxidation and incipient wetness impregnation with Ni, the Ni/CNFs were characterized by various analytical methods. To prepare a selective Ni/CNF catalyst, the influences of the nature of oxidation agent, Ni activation, and Ni loading were investigated. Under the applied reaction conditions, the best result, that is, 76 % yield in hexitols with 69 % sorbitol selectivity at 93 % conversion of cellulose, was obtained on a 7.5 wt % Ni/CNF catalyst prepared by chemical vapor deposition of CH(4) on a Ni/?-Al(2)O(3) catalyst, followed by oxidation in HNO(3) (twice for 1 h at 383 K), incipient wetness impregnation, and reduction at 773 K under H(2). This preparation method leads to a properly balanced Ni/CNF catalyst in terms of Ni dispersion and hydrogenation capacity on the one hand, and the number of acidic surface-oxygen groups responsible for the acid-catalyzed hydrolysis on the other. PMID:22730195

Van de Vyver, Stijn; Geboers, Jan; Schutyser, Wouter; Dusselier, Michiel; Eloy, Pierre; Dornez, Emmie; Seo, Jin Won; Courtin, Christophe M; Gaigneaux, Eric M; Jacobs, Pierre A; Sels, Bert F

2012-08-01

409

Pulse-reverse electrodeposition for mesoporous metal films: combination of hydrogen evolution assisted deposition and electrochemical dealloying.  

PubMed

Hydrogen evolution assisted electrodeposition is a new bottom-up technique allowing the fast and simple synthesis of nanometals. Electrochemical dealloying is a top-down approach with the same purpose. In this work, we show that a combination of these two methods in sequence by pulse-reverse electrodeposition can be used to prepare high-surface-area nanostructured metals. Highly porous adherent platinum is obtained by the deposition of CuPt alloy during the cathodic cycles and the selective dissolution of copper during the anodic cycles. The convection created by the movement of the hydrogen bubbles increases the deposition rate and removes the dissolved copper ions from the diffusion layer, which ensures the deposition of a film with the same stoichiometry throughout the whole process. Due to the relatively high ratio of copper atoms on the surface in the as-deposited layer, it is proposed that the dealloying kinetics is significantly higher than that usually observed during the dealloying process in a model system. The proposed approach has several advantages over other methods, such as a very high growth rate and needlessness of any post-treatment processes. A detailed analysis of the effect of pulse-reverse waveform parameters on the properties of the films is presented. Mesoporous platinum with pores and ligaments having characteristic sizes of less than 10 nm, an equivalent surface area of up to ca. 220 m(2) cm(-3), and a roughness factor of more than 1000 is fabricated. PMID:22139451

Cherevko, Serhiy; Kulyk, Nadiia; Chung, Chan-Hwa

2012-01-21

410

Catalytic effect of nanoparticle 3d-transition metals on hydrogen storage properties in magnesium hydride MgH2 prepared by mechanical milling.  

PubMed

We examined the catalytic effect of nanoparticle 3d-transition metals on hydrogen desorption (HD) properties of MgH(2) prepared by mechanical ball milling method. All the MgH(2) composites prepared by adding a small amount of nanoparticle Fe(nano), Co(nano), Ni(nano), and Cu(nano) metals and by ball milling for 2 h showed much better HD properties than the pure ball-milled MgH(2) itself. In particular, the 2 mol % Ni(nano)-doped MgH(2) composite prepared by soft milling for a short milling time of 15 min under a slow milling revolution speed of 200 rpm shows the most superior hydrogen storage properties: A large amount of hydrogen ( approximately 6.5 wt %) is desorbed in the temperature range from 150 to 250 degrees C at a heating rate of 5 degrees C/min under He gas flow with no partial pressure of hydrogen. The EDX micrographs corresponding to Mg and Ni elemental profiles indicated that nanoparticle Ni metals as catalyst homogeneously dispersed on the surface of MgH(2). In addition, it was confirmed that the product revealed good reversible hydriding/dehydriding cycles even at 150 degrees C. The hydrogen desorption kinetics of catalyzed and noncatalyzed MgH(2) could be understood by a modified first-order reaction model, in which the surface condition was taken into account. PMID:16851820

Hanada, Nobuko; Ichikawa, Takayuki; Fujii, Hironobu

2005-04-21

411

ADVANCED HYDROGEN TRANSPORT MEMBRANES FOR VISION 21 FOSSIL FUEL PLANTS  

SciTech Connect

Eltron Research Inc. and team members CoorsTek, Sued Chemie, Argonne National Laboratory, and NORAM are developing an environmentally benign, inexpensive, and efficient method for separating hydrogen from gas mixtures produced during industrial processes, such as coal gasification. This project was motivated by the National Energy Technology Laboratory (NETL) Vision 21 initiative, which seeks to economically eliminate environmental concerns associated with the use of fossil fuels. Over the past 12 months, this project has focused on four basic categories of dense membranes: (1) mixed conducting ceramic/ceramic composites, (2) mixed conducting ceramic/metal (cermet) composites, (3) cermets with hydrogen permeable metals, and (4) layered composites containing hydrogen permeable alloys. Ultimately, these materials must enable hydrogen separation at practical rates under ambient and high-pressure conditions, without deactivation in the presence of feedstream components such as carbon dioxide, water, and sulfur. The ceramic/ceramic composites demonstrate the lowest hydrogen permeation rates, with a maximum of approximately 0.1 mL/min/cm{sup 2} for 0.5-mm thick membranes at 800 to 950 C. Under equivalent conditions, cermets achieve a hydrogen permeation rate near 1 mL/min/cm{sup 2}, and the metal phase also improves structural stability and surface catalysis for hydrogen dissociation. Furthermore, if metals with high hydrogen permeability are used in cermets, permeation rates near 4 mL/min/cm{sup 2} are achievable with relatively thick membranes. Layered composite membranes have by far the highest permeation rates with a maximum flux in excess of 200 mL {center_dot} min{sup -1} {center_dot} cm{sup -2}. Moreover, these permeation rates were achieved at a total pressure differential across the membrane of 450 psi. Based on these results, effort during the next year will focus on this category of membranes. This report contains long-term hydrogen permeation data over eight-months of continuous operation, and permeation results as a function of operating conditions at high pressure for layered composite membranes. Additional progress with cermet and thin film membranes also is presented.

Shane E. Roark; Anthony F. Sammells; Richard Mackay; Stewart R. Schesnack; Scott R. Morrison; Thomas F. Barton; Sara L. Rolfe; U. Balachandran; Richard N. Kleiner; James E. Stephan; Frank E. Anderson; Aaron L. Wagner; Jon P. Wagner

2003-10-30

412

Hydrogen-on-Demand Using Metallic Alloy Nanoparticles in Water Kohei Shimamura,,,,,  

E-print Network

energy cycle. However, its practical application is hampered by the low reaction rate and poor yield energy cycles.1 In a two-step thermochemical cycle, an exothermic reaction between metal and water to Lewis-base sites. While this superatomic design achieves high reaction rates in nanometer-size clusters

Southern California, University of

413

The effect of surface hydrogenation of metal oxides on the nanomorphology and the charge generation efficiency of polymer blend solar cells.  

PubMed

In this work, the effect of surface hydrogenation of different metal oxides, in particular molybdenum and tungsten oxides widely used to enhance hole extraction and zinc and titanium oxides widely used to enhance electron extraction, on the nanomorphology and the charge generation efficiency of polymer blend solar cells is investigated. It was found that photoactive layers based on blends using different polymers, in particular poly(3-hexythiophene) (P3HT) and poly[(9-(1-octylnonyl)-9H-carbazole-2,7-diyl)-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] (PCDTBT), which normally differ in both morphology and electronic structure, benefited, for both polymers, from deposition on metal oxides with high surface hydrogen content, in the sense that they exhibited improved crystallinity/order as revealed from X-ray diffraction, UV-vis absorption and elipsometric measurements. As a result, increased charge generation efficiencies and reduced recombination losses were measured in solar cells using metal oxides with highly hydrogenated surfaces at bottom electrodes and based on blends of either P3HT or PCDTBT, with a fullerene acceptor, as was verified by transient photocurrent measurements. The power conversion efficiency (PCE) of those cells reached values of 4.5% and 7.2%, respectively, an increase of about 30% compared with the cells using metal oxides with low surface hydrogen content. PMID:25286014

Vasilopoulou, Maria

2014-10-24

414

Transfer hydrogenation of alkenes using Ni/Ru/Pt/Au heteroquatermetallic nanoparticle catalysts: sequential cooperation of multiple nano-metal species.  

PubMed

Quatermetallic alloy nanoparticles of Ni/Ru/Pt/Au were prepared and found to promote the catalytic transfer hydrogenation of non-activated alkenes bearing conjugating units (e.g., 4-phenyl-1-butene) with 2-propanol, where the composition metals, Ni, Ru, Pt, and Au, act cooperatively to provide significant catalytic ability. PMID:25177750

Ito, Yoshikazu; Ohta, Hidetoshi; Yamada, Yoichi M A; Enoki, Toshiaki; Uozumi, Yasuhiro

2014-10-18

415

Metallic Membrane Materials Development for Hydrogen Production from Coal Derived Syngas  

SciTech Connect

The goals of Office of Clean Coal are: (1) Improved energy security; (2) Reduced green house gas emissions; (3) High tech job creation; and (4) Reduced energy costs. The goals of the Hydrogen from Coal Program are: (1) Prove the feasibility of a 40% efficient, near zero emissions IGCC plant that uses membrane separation technology and other advanced technologies to reduce the cost of electricity by at least 35%; and (2) Develop H{sub 2} production and processing technologies that will contribute {approx}3% in improved efficiency and 12% reduction in cost of electricity.

O.N. Dogan; B.H. Howard; D.E. Alman

2012-02-26

416

Silica supported transition metal substituted polyoxotungstates: Novel heterogeneous catalysts in oxidative transformations with hydrogen peroxide  

Microsoft Academic Search

The preparation and characterization (FT-IR, FT-Raman, diffuse reflectance, elemental analysis) of novel catalysts with iron or manganese substituted polyoxotungstates [XMIII(H2O)W11O39]n? (X=P, M=Fe or Mn; X=Si or B, M=Fe) immobilized on a functionalized silica matrix are reported. The new materials were tested as heterogeneous catalysts in the oxidation of cis-cyclooctene and cyclooctane at 80°C, using environmentally safe hydrogen peroxide as oxidant

Ana C. Estrada; Isabel C. M. S. Santos; Mário M. Q. Simőes; M. Graça P. M. S. Neves; José A. S. Cavaleiro; Ana M. V. Cavaleiro

2011-01-01

417

Seismic waves increase permeability.  

PubMed

Earthquakes have been observed to affect hydrological systems in a variety of ways--water well levels can change dramatically, streams can become fuller and spring discharges can increase at the time of earthquakes. Distant earthquakes may even increase the permeability in faults. Most of these hydrological observations can be explained by some form of permeability increase. Here we use the response of water well levels to solid Earth tides to measure permeability over a 20-year period. At the time of each of seven earthquakes in Southern California, we observe transient changes of up to 24 degrees in the phase of the water level response to the dilatational volumetric strain of the semidiurnal tidal components of wells at the Pińon Flat Observatory in Southern California. After the earthquakes, the phase gradually returns to the background value at a rate of less than 0.1 degrees per day. We use a model of axisymmetric flow driven by an imposed head oscillation through a single, laterally extensive, confined, homogeneous and isotropic aquifer to relate the phase response to aquifer properties. We interpret the changes in phase response as due to changes in permeability. At the time of the earthquakes, t