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1

Hydrogen Permeability of Mulitphase V-Ti-Ni Metallic Membranes  

SciTech Connect

Development of advanced hydrogen separation membranes in support of hydrogen production processes such as coal gasification and as front end gas purifiers for fuel cell based system is paramount to the successful implementation of a national hydrogen economy. Current generation metallic hydrogen separation membranes are based on Pd-alloys. Although the technology has proven successful, at issue is the high cost of palladium. Evaluation of non-noble metal based dense metallic separation membranes is currently receiving national and international attention. The focal point of the reported work was to evaluate a Group 5A-Ta, Nb, V-based alloy with respect to microstructural features and hydrogen permeability. Electrochemical hydrogen permeation testing of the V-Ti-Ni alloy is reported herein and compared to pure Pd measurements recorded as part of this same study. The V-Ti-Ni was demonstrated to have a steady state hydrogen permeation rate an order of magnitude higher than the pure Pd material in testing conducted at 22 C.

Adams, T. M.; Mickalonis, J.

2005-10-18

2

Review of hydrogen isotope permeability through materials  

SciTech Connect

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

Steward, S.A.

1983-08-15

3

Effect of water on hydrogen permeability  

NASA Technical Reports Server (NTRS)

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

Hulligan, David; Tomazic, William A.

1987-01-01

4

Effect of Water on Hydrogen Permeability.  

National Technical Information Service (NTIS)

Doping of hydrogen with CO and CO2 was developed to reduce hydrogen permeation in Stirling engines by forming a low permeability oxide coating on the inner surface of the heater head tubes. Although doping worked well, under certain circumstances the prot...

D. Hulligan W. A. Tomazic

1987-01-01

5

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

6

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

7

Determination of hydrogen permeability in commercial and modified superalloys  

SciTech Connect

This report summarizes the results of hydrogen permeability measurements on several iron- and cobalt-base alloys as well as on two long-range ordered alloys over the range of 705/sup 0/ to 870/sup 0/C (1300/sup 0/ to 1600/sup 0/F). 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, Ni/sub 3/Al and (Fe,Ni)/sub 3/(V,Al) were also evaluated. All tests were conducted at 20.7 MPa pressure in either pure and/or 1% CO/sub 2/-doped H/sub 2/ 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 H/sub 2/ when compared with the eight commercial alloys and their modifications. With CO/sub 2/ doping, significant decrease in permeability was observed in the commercial alloys - no doped tests were conducted with the long-range ordered alloys.

Bhattacharyya, S.; Peterman, W.

1983-05-01

8

The interaction of hydrogen with metal alloys  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

9

Determination of hydrogen permeability in uncoated and coated superalloys  

NASA Technical Reports Server (NTRS)

Hydrogen permeability, diffusivity, and solubility data were obtained for eight wrought and cast high temperature alloys over the range 650 to 815 C. Data were obtained for both uncoated alloys and wrought alloys coated with four commercially available coatings. Activation energies for permeability, diffusivity and solubility were calculated.

Bhattacharyya, S.; Vesely, E. J., Jr.; Hill, V. L.

1981-01-01

10

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

11

Measuring Hydrogen Concentrations in Metals  

NASA Technical Reports Server (NTRS)

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

Danford, M. D.

1985-01-01

12

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

NASA Astrophysics Data System (ADS)

Hydrogen and its isotopes diffusion and permeability over the laser joint weld of low-activation 10Cr9WVA ferritic steels have been studied. Welding of steel sheets were produced with the help of Russian gas laser TL-5M type ( l=10.6 mm, P=2.5 kW) in He atmosphere with the rate of 66 mm/s. Hydrogen diffusion over the joint welds was detected by the conventional method of electrical resistance measurement. By this way, the kinetics of resistance changes during hydrogenation of specimens engraved from weld metal, neighboring zone of thermal effect as well as basic metal have been determined. Coefficients of hydrogen diffusion were measured in the temperature range from 773 to 1073 K. So, for 10Cr9WVA steel at 873 K it was established that the hydrogen diffusion coefficient in the weld metal is approximately 10 times higher than in the basic metal, and three times higher than that in the zone of thermal effect. Hydrogen permeability over the joint weld specimens was measured by the Dines-Barrer method on the volummetric setup. It was established that the hydrogen flux over the laser joint weld is significantly (up to two orders) more than that over the basic metal. Using the data on the hydrogen permeability and diffusion coefficient, the hydrogen solubility in the weld metal was estimated, which is several ten times higher than that in the basic metal of the steel investigated. As a result, it was concluded that welding the steel parts of the first wall of thermonuclear reactors with magnet confinement of plasma is undesirable due to possible tritium leaking into the environment. A possible way of decreasing the joint welds hydrogen permeability, including application of protective impermeable for hydrogen coatings, is considered.

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

2002-12-01

13

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

14

Transfer of hydrogen isotopes through a hydrogen-permeable bipolar electrode  

SciTech Connect

The unit protium-tritium separation coefficients /alpha//sub H/T/ for transfer through a hydrogen-permeable bipolar electrode in KOH solutions of various concentration at a temperature of 50/degree/C have been determined. The values of /alpha//sub H/T/ obtained (11.8 /plus minus/ 0.6 for 10 M KOH and 13.4 /plus minus/ 1.9 for 2 M KOH at a current density of 0.1 A/cm/sup 2/) are in good agreement with the conception of the multistep separation of the isotopes of hydrogen in a hydrogen-permeable bipolar electrode.

Moskvin, L.N.; Gurskii, V.S.

1988-05-01

15

Effect of water on hydrogen permeability. [Stirling engines  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

16

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

17

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

18

Hydrogen storage in metal hydrides  

NASA Astrophysics Data System (ADS)

The use of metal hydrides as a hydrogen-storage medium for hydrogen-powered vehicles is discussed. Various metal hydrides are compared by their hydrogen content and energy density, and their suitability as a storage medium is evaluated against a set of criteria, such as ease of formation and decomposition, availability, cost, and safety. Compounds based on iron-titanium hydride are shown to be practical for use in motor vehicles as well as in other applications, including energy storage for peak leveling in electric power systems, compressors, pumps, and air-conditioners.

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

1980-02-01

19

Influence of medium pH on the hydrogen permeability of passivating films and the corrosion crack growth rate in 40KhN steel  

SciTech Connect

This paper investigates the interrelationship between medium pH and the hydrogen permeability of the passive layer on the electrolyte-metal interface and also of their influence on the corrosion crack growth rate in high strength low-ductility 40KhN steel. Aqueous NaC1 solutions of different concentrations were used as the corrosive medium in the experiments. It is established that the medium pH not only plays a definite role in the process of formation of hydrogen but also changes the hydrogen permeability of the passive films at the medium-metal interface.

Dmytrakh, I.N.; Grabovskii, R.S.

1986-01-01

20

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

Microsoft Academic Search

The permeability of hydrogen in bulk palladium membranes (approximately 1-mm thickness) was determined for the first time at conditions of simultaneously elevated temperature (6231173K) and hydrogen pressure (0.1106 to 2.76106Pa). When the hydrogen partial pressure exponent value was constrained to a value of 0.5, the permeability was described by an Arrhenius-type relation where the pre-exponential constant and activation energy for

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

2003-01-01

21

Hydrogen permeability of austenitic steels proposed for fusion reactor first wall  

SciTech Connect

The study of hydrogen diffusion parameters in austenitic steels EP-838, Crl2Mn20W, 316 SS, 12Crl8Ni10Ti was carried out. Temperature dependences of permeability, diffusion coefficients and hydrogen dissolution were determined and their variation with the phase and structure composition of the steel were analyzed. It is shown that change of alloy composition, thermal treatment in hydrogen and modification of surface by nitriding, oxidizing and by irradiation with H{sup +} and N{sup +} ions can lead to a decrease in hydrogen permeability and thus reduce hydrogen isotope losses through the thermonuclear reactor first wall. 10 refs., 4 figs., 3 tabs.

Fedorov, V.V.; Pokhmursky, V.I. [Physico-mechanical Inst., Lvov (Ukraine); Dyomina, E.V.; Prusakova, M.D.; Vinogradova, N.A. [Baikov Inst. of metallurgy, Moscow (Russian Federation)

1995-10-01

22

PDTI metal alloy as a hydrogen or hydrocarbon sensitive metal  

NASA Technical Reports Server (NTRS)

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

Hunter, Gary W. (Inventor)

1996-01-01

23

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

24

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

25

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

26

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

27

Pathways to a Metallic Hydrogen  

NASA Astrophysics Data System (ADS)

The primary subject of this thesis is the study of warm dense hydrogen by means of pulsed laser heating in the pressure region 1 to 2 Mbar and temperatures above the melting line, where a liquid-liquid phase transition from the insulating molecular fluid to a conducting atomic hydrogen fluid, so called plasma phase transition (PPT), was predicted to take place. The first evidence of the PPT under static compression is reported. The observations are in agreement with the negative slope phase line predicted by ab initio methods. The second subject of this thesis is the development of instrumentation and pulsed laser heating measurement techniques necessary for studying hydrogen under these high pressure and temperature conditions. This includes a design of a cryogen-free optical cryostat with a short optical distance suitable for high pressure studies; a technique of a controlled preparation (indentation) of a gasket, which is a vital part of any high pressure experiment inside a diamond anvil cell; and an in-depth discussion of spectral data reduction methods for pyrometry in the case of pulsed laser heating. The third part of this thesis, closely related to the second, is the demonstration of a successful application of the measurement techniques for a control system: study of the behavior of platinum under pulsed laser irradiation. A surface reconstruction of platinum is reported at temperatures well below the bulk melting temperature of platinum. The last subject of this thesis is a report of observation of pressure induced metallization of amorphous germanium monoxide. The transition to the amorphous metallic state is observed at 12 GPa. The resulting metallic phase is metastable: GeO stays metallic upon releasing the pressure to zero. This transition bears similarities to previously observed IM transitions in SiO and SnO, but it has its own unique features.

Dzyabura, Vasily

28

Interaction Of Hydrogen With Metal Alloys  

NASA Technical Reports Server (NTRS)

Report describes experiments on interaction of hydrogen with number of metal alloys. Discusses relationship between metallurgical and crystallographic aspects of structures of alloys and observed distributions of hydrogen on charging. Also discusses effect of formation of hydrides on resistances of alloys to hydrogen. Describes attempt to correlate structures and compositions of alloys with their abilities to resist embrittlement by hydrogen.

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

1993-01-01

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; umer, 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

Pore structure and effective permeability of metallic filters  

NASA Astrophysics Data System (ADS)

The pore structures (microstructures) of two metallic filters were reconstructed using the stochastic reconstruction method based on simulated annealing. The following microstructural descriptors were included in the description of the real microstructures: the two-point probability function, the lineal-path functions for the void or solid phases, i.e. simulated annealing was constrained by all low-order statistical measures that were accessible through the analysis of images of polished sections. An effect of the microstructural descriptors on the course of reconstruction was controlled by modifying two parameters of the reconstruction procedure [1]. Their values resulted from repeated reconstruction of two-dimensional microstructures in such a way that the reference (experimental) and calculated two-point cluster functions deviated negligibly. It was tacitly assumed that the parameters adjusted during two-dimensional reconstruction had the same influence on the formation of the three-dimensional microstructures. Since connectivity of phases is a critical property of the stochastically reconstructed media, clusters of pore and solid voxels were determined using the Hoshen-Kopelman algorithm. It was found that the solid phase formed one large cluster in accordance with the physical feasibility. The void phase created one large cluster and a few small clusters representing the isolated porosity. The percolation properties were further characterised using the local porosity theory [2]. Effective permeability of the replicas was estimated by solving the Stokes equation for creeping flow of an incompressible liquid in pore space. Calculated permeability values matched well their experimental counterparts.

Hejtmnek, Vladimr; Vesel, Martin; ?apek, Pavel

2013-02-01

32

Metal-hydrogen bridge bonding of hydrocarbons on metal surfaces  

PubMed Central

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

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

1981-01-01

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

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

35

METAL HYDRIDE HYDROGEN COMPRESSORS: A REVIEW  

SciTech Connect

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

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

2014-01-01

36

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

SciTech Connect

The permeability of hydrogen in bulk palladium membranes (approximately 1-mm thickness) was determined for the first time at conditions of simultaneously elevated temperature (6231173 K) and hydrogen pressure (0.1 106 to 2.76 106 Pa). When the hydrogen partial pressure exponent value was constrained to a value of 0.5, the permeability was described by an Arrhenius-type relation where the pre-exponential constant and activation energy for this correlation were 1.9210?7 mol/(m s Pa0.50) and 13.81 kJ/mol, respectively. These Arrhenius values were in good agreement with prior low-pressure correlations. However, the hydrogen flux results of this study were most accurately represented by an Arrhenius permeability expression where 3.21 10?8 mol/(m s Pa0.62), 13.41 kJ/mol, and 0.62 represent the pre-exponential constant, activation energy of permeation and permeability driving force, respectively. Although the partial pressure exponent value of 0.62 was slightly greater than the commonly accepted value of 0.5 (atmospheric and sub-atmospheric pressure studies), the optimal exponent value in this study decreased as the upper limit of pressure employed in the database was reduced. Therefore, the deviation in the partial pressure exponent with increasing hydrogen pressure may be attributed to variances in the product of the diffusion coefficient and Sieverts constant at elevated pressures.

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

2003-02-15

37

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

38

Transport Modeling of Hydrogen in Metals for Application to Hydrogen Assisted Cracking of Metals.  

National Technical Information Service (NTIS)

The focus of this research was on the development of a finite element code for solute transport and trapping in linear elastic mixtures for use in modeling the hydrogen transport process in metals undergoing hydrogen assisted cracking. Specific objectives...

C. E. Chopin J. P. Thomas

1995-01-01

39

On the ground state of metallic hydrogen  

NASA Technical Reports Server (NTRS)

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

Chakravarty, S.; Ashcroft, N. W.

1978-01-01

40

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

PubMed

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

Suzuki, Y; Kanamori, T; Sakai, K

1993-01-01

41

Hydrogen production from methane using oxygen-permeable ceramic membranes  

NASA Astrophysics Data System (ADS)

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

Faraji, Sedigheh

42

Ion Beam Studies of Hydrogen in Metals.  

National Technical Information Service (NTIS)

Methods based on ion implantation and nuclear reaction analysis were used to investigate the behavior of hydrogen isotopes in metals. The binding enthalpy of deuterium (D) at irradiation effects, He bubbles, D sub 2 bubbles, and metal-oxide interfaces was...

S. M. Myers W. R. Wampler F. Besenbacher S. L. Robinson N. R. Moody

1984-01-01

43

THE ROLE OF INTERFACE IN THE MECHANISM OF HYDROGEN ABSORPTION BY METAL-POLYMER COMPOSITES  

Microsoft Academic Search

We have studied the hydrogen storage capacity and sorption kinetics of composite materials made of LaNi5 particles dispersed into hydrogen permeable polymers. Samples consisted of metal particles well separated and completely\\u000a embedded in the polymeric matrix. Experimental results by Sievert analysis show that the composite material made with polysiloxane\\u000a presents negligible H2 storage capacity while in that made with polyethylene

G. Carotenuto; R. Checchetto; N. Bazzanella; A. Miotello

44

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

Microsoft Academic Search

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

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

1999-01-01

45

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

Microsoft Academic Search

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

V. A. Marichev; V. V. Molokanov

1992-01-01

46

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

Microsoft Academic Search

The goal of this experimental project is to design and fabricate a reactor and membrane test cell to dissociate hydrogen sulfide (HS) in a non-thermal plasma and recover hydrogen (H) 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),

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

2004-01-01

47

The Metal-Hydrogen System under High Hydrogen Chemical Potentials  

SciTech Connect

A brief review is given of some characteristic features of metal hydrides formed under high H chemical potentials, produced either by placing a sample in high-pressure fluid hydrogen or in contact with electrolyte in the electrodeposition process. Topics include the pH-T phase diagram and superabundant vacancy formation together with its consequences and possible implications for materials science.

Fukai, Yuh [Institute of Science and Engineering, Chuo University, Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Institute of Materials Structure Science, KEK, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)

2006-05-15

48

The Metal-Hydrogen System under High Hydrogen Chemical Potentials  

NASA Astrophysics Data System (ADS)

A brief review is given of some characteristic features of metal hydrides formed under high H chemical potentials, produced either by placing a sample in high-pressure fluid hydrogen or in contact with electrolyte in the electrodeposition process. Topics include the pH-T phase diagram and superabundant vacancy formation together with its consequences and possible implications for materials science.

Fukai, Yuh

2006-05-01

49

Membrane permeable luminescent metal complexes for cellular imaging  

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

50

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

51

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 authors 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

52

Microporous Metal Organic Materials for Hydrogen Storage  

SciTech Connect

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

S. G. Sankar; Jing Li; Karl Johnson

2008-11-30

53

An ingenious approach of determining hydrogen isotope solubilities, diffusivities and permeabilities in GWHER-1 stainless steel  

NASA Astrophysics Data System (ADS)

In this paper, by using an ingenious method, the hydrogen isotope solubilities and diffusivities in GWHER-1 stainless steel have been determined by a vacuum heating degassing approach at the temperature range of 597-1022 K on a set of specimens with different sizes previously charged for 24 h under a hydrogen isotope pressure of 105 Pa in the temperature range of 800-1000 K. The permeabilities are then derived from the relation ? = DKs. It is found D = 1.5210-6exp(-54100/RT), Ks = 2.210-6exp(-5400/RT) and ? = 3.310-12exp(-59500/RT) for hydrogen, where Ks (Sieverts' constant) is given in Pa-1/2, D in m2.s-1.Pa-1/2, T in K and R=8.31J.mol-1.K-1. By taking isotope effects into account, the corresponding Arrhenius relations for deuterium and tritium are also deduced.

Chen, Zhi; Deng, Bai-Quan; Peng, Li-Lin; Feng, Kai-Ming; Du, Jia-Ju; Mao, Ou

2006-07-01

54

Thermodynamics of hydrogen and vacancies in metals  

NASA Astrophysics Data System (ADS)

This thesis studies metal-hydrogen systems. The interaction between hydrogen-atoms and vacancies in metals have been elucidated in Fermi-Dirac statistics. Calculations have been presented and compared for specific models in which H-atoms act both as simple interstitial species and form either decorated vacancies or substitutional defects. A model has been presented to explain the superabundant vacancy formation under high hydrogen pressures. The solutions based on these models apply to much lower temperatures and higher concentrations than the traditional ones. These results show abundant vacancies will be formed in the presence of hydrogen; the vacancy concentration is many orders of magnitude larger than those in the H-free lattice. A study of the diffusion of hydrogen in the crack tip area has been provided. The slow diffusivity of H-atoms at low temperatures and the interaction between H-atoms and vacancies in the crack tip plastic zone give an explanation of the experimental data which show a maximum crack growth rate at room temperature. This work is associated with the embrittlement of steel by hydrogen.

Mao, Juanjuan

55

Method for controlling density and permeability of sintered powdered metals  

NASA Technical Reports Server (NTRS)

Improved, relatively low-cost method has been developed to produce porous metals with predetermined pore size, pore spacing, and density, utilizing powder-metal processes. The method uses angular not spherical tungsten powder.

Todd, H. H.

1968-01-01

56

Experimental Attempt to Metallize Hydrogen at Very High Pressures.  

National Technical Information Service (NTIS)

Metallic hydrogen is potential candidate as a high energy density material. The possibility of metallizing hydrogen by submitting it to very high pressures has been experimentally investigated. Great advances have been made in this study. Pressures as hig...

I. F. Silvera

1992-01-01

57

Semiempirical, Quantum Mechanical Calculation of Hydrogen Embrittlement in Metals  

NASA Astrophysics Data System (ADS)

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

Daw, Murray S.; Baskes, M. I.

1983-04-01

58

Metallic Hydrogen - Potentially a High Energy Rocket Propellant  

NASA Technical Reports Server (NTRS)

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

Cole, John; Silvera, Ike

2007-01-01

59

Hydrogen Storage in Metal-Organic Frameworks  

SciTech Connect

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

Omar M. Yaghi

2012-04-26

60

Catalytic activity of noble metals promoting hydrogen uptake  

Microsoft Academic Search

The engineering of pure and metal alloy catalysts for hydrogen absorption is needed to improve the kinetics of hydrogen-related devices. We introduce a new route to search for alloys that can yield superior catalytic behavior for hydrogen absorption, using an optical technique to measure the catalytic activity for hydrogen sorption of thin films. The catalytic activity of the noble metals

A. Borgschulte; R. J. Westerwaal; J. H. Rector; H. Schreuders; B. Dam; R. P. Griessen

2006-01-01

61

High-temperature hydrogen permeability and stability of titanium-coated steels  

SciTech Connect

The authors study the influence of hydrogen and high temperatures on the hydrogen retaining properties of diffusion titanium coatings and also of the thermal stability of such coatings in a hydrogen atmosphere. The diffusion titanium coating of 12Kh18N10T and U8 steels was done by the contact method in powder mixtures consisting of the compounds FeTi and Al/sub 2/O/sub 3/ and the activators NH/sub 4/Cl and NH/sub 4/F x HF. The results of the investigations make it possible to conclude that diffusion titanium coatings protect metals from the penetration of gaseous hydrogen at increased temperatures but their effectiveness depends upon the phase and chemical composition of the base metal.

Sidorak, I.I.; Parkheta, R.G.; Nagovskaya, V.A.

1987-07-01

62

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

SciTech Connect

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

Kane, M

2008-02-05

63

Hydrogen isotope permeability through austenitic Cr Ni steels under neutron irradiation  

Microsoft Academic Search

Experimental data on permeability and diffusion of protium and deuterium through austenitic CrNi steels 18Cr10NiTi, 16Cr11Ni3MoTi and 25Cr16Ni6MnNV are reported. The data were obtained with special equipment designed and installed at the research reactor IVV-2M. It was shown that parameters of hydrogen isotope transfer in CrNi steels increased substantially during irradiation by fast neutrons of the flux density f <

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

1996-01-01

64

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

NASA Astrophysics Data System (ADS)

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

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

65

Recovery of hydrogen from hydrogen sulfide with metals or metal sulfides  

NASA Astrophysics Data System (ADS)

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

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

66

Composite metal membranes for hydrogen separation applications  

SciTech Connect

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

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

1997-06-01

67

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

PubMed Central

An elevated level of homocysteine (Hcy), known as hyperhomocysteinmia (HHcy), was associated with neurovascular diseases. At physiological levels, hydrogen sulfide (H2S) protected the neurovascular system. Because Hcy was also a precursor of hydrogen sulfide (H2S), we sought to test whether the H2S protected the brain during HHcy. Cystathionine-?-synthase heterozygous (CBS+/?) and wild type (WT) mice were supplemented with or without NaHS (30 M/L, H2S donor) in drinking water. Blood flow and cerebral microvascular permeability in pial vessels were measured by intravital microscopy in WT, WT+NaHS, CBS?/+ and CBS?/+ + NaHS treated mice. The brain tissues were analyzed for matrix metalloproteinase (MMP) and tissue inhibitor of metalloproteinase (TIMP) by Western blot and RT-PCR. The mRNA levels of CBS and cystathionine gamma lyase (CSE, enzyme responsible for conversion of Hcy to H2S) genes were measured by RT-PCR. The results showed a significant increase in MMP-2, MMP-9, TIMP-3 protein and mRNA in CBS (?/+) mice, while H2S treatment mitigated this increase. Interstitial localization of MMPs was also apparent through Immunohistochemistry. A decrease in protein and mRNA expression of TIMP-4 was observed in CBS (?/+) mice. Microscopy data revealed increase in permeability in CBS (?/+) mice. These effects were ameliorated by H2S and suggested that physiological levels of H2S supplementation may have therapeutic potential against HHcy-induced microvascular permeability, in part, by normalizing the MMP/TIMP ratio in the brain.

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

2010-01-01

68

Tailor-made oxide architectures attained by molecularly permeable metal-oxide organic hybrid thin films.  

PubMed

Tailor-made metal oxide (MO) thin films with controlled compositions, electronic structures, and architectures are obtained via molecular layer deposition (MLD) and solution treatment. Step-wise formation of permeable hybrid films by MLD followed by chemical modification in solution benefits from the versatility of gas phase reactivity on surfaces while maintaining flexibility which is more common at the liquid phase. PMID:24993109

Sarkar, Debabrata; Taffa, Dereje Hailu; Ishchuk, Sergey; Hazut, Ori; Cohen, Hagai; Toker, Gil; Asscher, Micha; Yerushalmi, Roie

2014-07-17

69

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 C 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

70

Metal/acid ion permeable membrane fuel cell  

SciTech Connect

A fuel cell is disclosed which comprises a metal anode immersed in a base electrolyte solution and connected with an electric circuit, a cathode comprising an acid solution, a carbon catalyst and electron distributor plate in that solution and connected with an electron supply and a wettable fluid impermeable membrane and disposed between the electrolyte and cathode solution and establishing an acid-base reactor interface where hydroxyl ions are generated for conduction through the electrolyte to the anode.

Struthers, R.C.

1982-10-05

71

RF Breakdown of Metallic Surfaces in Hydrogen  

SciTech Connect

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

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

2009-05-01

72

Metallic hydrogen: The most powerful rocket fuel yet to exist  

NASA Astrophysics Data System (ADS)

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

Silvera, Isaac F.; Cole, John W.

2010-03-01

73

Hydrogen dynamics and metallic phase stabilization in VO2  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

74

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

75

Hydrogen embrittlement of weld metal of austenitic stainless steels  

Microsoft Academic Search

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

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

2002-01-01

76

High Strength Steel Weldment Reliability: Weld Metal Hydrogen Trapping.  

National Technical Information Service (NTIS)

The potential use of weld metal hydrogen getters (traps) to increase the reliability of high strength steel weldments was investigated. This research aimed to establish a fundamental understanding of the trapping mechanisms in weld metal and to evaluate t...

D. L. Olson

1998-01-01

77

Fast approximate EM induction modeling of metallic and UXO targets using a permeable prism  

NASA Astrophysics Data System (ADS)

The time-domain EM induction response of non-magnetic and magnetic targets can be approximated using a conductive permeable prism composed of six faces of conductive plates, each face being composed of a set of conductive ribbons. The effect of magnetic permeability is included by the use of two "apparent flux gathering" coefficients, and two "effective magnetic permeability" coefficients, in the axial and transverse directions. These four magnetic property coefficients are a function of physical properties and geometry of the target, but are independent of prism orientation relative to a transmitter. The approximation algorithm is computationally fast, allowing inversions for target parameters to be achieved in seconds. The model is tested on profiles acquired with a Geonics EM63 time-domain EM metal detector over a non-magnetic copper pipe target, and a steel artillery shell in horizontal and vertical orientations. Results show that this approximation to a permeable prism has a capability of fitting geometric, conductivity and magnetic parameters at both early and late sample times. The magnetic parameters show strong change from early to late times on the EMI decay curve, indicating that the magnetic properties of the target have non-linear characteristics. It is proposed that these magnetic parameters and the nature of their non-linearity may carry additional discrimination information for distinguishing between intact munitions and scrap in UXO studies.

Asten, Michael W.; Duncan, Andrew C.

2007-03-01

78

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

79

Hydrogen Sensors Using Pd-Based Metallic Glassy Alloys  

Microsoft Academic Search

Pd-based metallic glassy alloys have been investigated as materials for the hydrogen sensors. We prepared thin films of Pd-Cu-Si alloy known as typical metallic glassy alloys by r. f. magnetron sputtering method. And then, we examined their sensitivity to hydrogen by measuring the change of electric resistance of thin films when they were exposed to hydrogen gases of various concentrations

Susumu Kajita; Shin-Ichi Yamaura; Hisamichi Kimura; Kunio Yubuta; Akihisa Inoue

2008-01-01

80

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

81

Metal oxide-hydrogen battery having an outer safety shell  

SciTech Connect

A metal oxide hydrogen battery assembly is described, comprising a metal oxide hydrogen battery having an outer pressure vessel and having at least one cell module contained within the pressure vessel, said pressure vessel containing pressurized hydrogen gas, said cell module having a positive and a negative terminal, an outer gas-impermeable shell disposed around the pressure vessel to provide a space there between, electrical connecting means connected to said terminals and extending through said pressure vessel and extending to the exterior of said shell, and vent conduit means communicating with said space for venting any hydrogen gas leaking from said pressure vessel from said space to the exterior.

Jones, K.R.

1993-06-01

82

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

SciTech Connect

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

Jackson, D

2007-02-07

83

Metal dichalcogenides monolayers: novel catalysts for electrochemical hydrogen production.  

PubMed

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

Pan, Hui

2014-01-01

84

Metal Dichalcogenides Monolayers: Novel Catalysts for Electrochemical Hydrogen Production  

PubMed Central

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

Pan, Hui

2014-01-01

85

Hydrogen permeability, thermal stability and hydrogen embrittlement of NiNbZr and NiNbTaZr amorphous alloy membranes  

Microsoft Academic Search

Amorphous alloys are a promising alternative to Pd alloy membranes for hydrogen separation because of their lower cost and comparable hydrogen permeability. A series of amorphous alloy membranes consisting of Ni60Nb20Zr20 (at%), (Ni0.6Nb0.4)100?xZrx and (Ni0.6Nb0.3Ta0.1)100?xZrx (where x=0, 10, 20 or 30) were prepared by melt spinning and then coating the foil surfaces with a thin (500nm) layer of Pd using

Stephen N. Paglieri; Narendra K. Pal; Michael D. Dolan; Sang-Mun Kim; Wen-Ming Chien; Joshua Lamb; Dhanesh Chandra; Kevin M. Hubbard; David P. Moore

2011-01-01

86

High temperature equation of state of metallic hydrogen  

SciTech Connect

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

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

2007-04-15

87

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

88

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

89

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

SciTech Connect

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

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

1996-03-15

90

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

91

The structural properties of transition metal hydrogen complexes in silicon  

Microsoft Academic Search

A first-principles spin-polarised local density functional cluster method is used to explore the structural and vibrational properties of several substitutional transition-metal impurities complexed with hydrogen.

A. Resende; R. Jones; S. berg; P. R. Briddon

1999-01-01

92

Hydrogen production during processing of radioactive sludge containing noble metals.  

National Technical Information Service (NTIS)

Hydrogen was produced when radioactive sludge from Savannah River Site radioactive waste containing noble metals was reacted with formic acid. This will occur in a process tank in the Defense Waste Facility at SRS when waste is vitrified. Radioactive slud...

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

1992-01-01

93

Hydrogen evolution by a metal-free electrocatalyst.  

PubMed

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. PMID:24769657

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

2014-01-01

94

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

95

Gas chromatographic separation of hydrogen isotopes using metal hydrides  

SciTech Connect

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

Aldridge, F.T.

1984-05-09

96

Hydrogen sensors based on catalytic metals  

NASA Astrophysics Data System (ADS)

On the base of microelectronical and micromechanical technology were designed and developed converters of hydrogen concentration to electrical signals. The devices of controlling concentration of hydrogen in the air were developed. These devices were applied for ensuring fire and explosion security of complex technological teste of missile oxygen-hydrogen engine, developed for cryogenic accelerations block. The sensor block of such device was installed directly on the armor-plate, to which was attached tested engine.

Beklemyshev, V. I.; Berezine, V.; Bykov, Victor A.; Kiselev, L.; Makhonin, I.; Pevgov, V.; Pustovoy, V.; Semynov, A.; Sencov, Y.; Shkuropat, I.; Shokin, A.

1999-11-01

97

Exploring metal hydrides using autoclave and multi-anvil hydrogenations  

NASA Astrophysics Data System (ADS)

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

Puhakainen, Kati

98

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

99

On the calculation of hydrogen-metal interatomic potentials  

SciTech Connect

The London-Eyring-Polanyi-Sato (LEPS) model is a promising means for obtaining descriptions of hydrogen-metal interactions that are more realistic than those obtained via the assumption of purely pairwise interactions. This approach should be of particular value for the transition metals, for which first-principles pseudopotential methods cannot be used to derive interatomic potentials. 18 refs.

Markworth, A.J.; Wolken, G. Jr.

1981-11-01

100

Heat-actuated metal hydride hydrogen compressor testing  

SciTech Connect

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

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

1985-09-01

101

Noncovalent hydrogen bonding in metal-organic structures  

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

102

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

103

Metal-dispersed porous graphene for hydrogen storage  

Microsoft Academic Search

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

Pakpoom Reunchan; Seung-Hoon Jhi

2011-01-01

104

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

National Technical Information Service (NTIS)

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 ...

P. Calderoni

2010-01-01

105

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

106

Mechanisms of Hydrogen Related Fracture of Metals.  

National Technical Information Service (NTIS)

The number of studies of hydrogen related fracture in recent years in quite impressive both in the variety of systems studied and in the amount of materials characterization which has been obtained. Despite this effort there is still incomplete understand...

H. K. Birnbaum

1989-01-01

107

Imaging of neutron incoherent scattering from hydrogen in metals  

NASA Astrophysics Data System (ADS)

Neutron incoherent scattering is a technique that may be used to determine the concentration of hydrogen within various metallic systems. By measuring the scattered neutrons using a position-sensitive detector, we can determine the amount of hydrogen as well as its location in the matrix. Using a slit or aperture in the scattering geometry, we have demonstrated the imaging of hydrogen in layers of polypropylene sandwiched between sets of titanium plates, and also in titanium standards containing known amounts of hydrogen. We have shown the ability to image hydrogen in titanium at the 100 ?g/g level as a function of location. Analysis of the images shows that the scattering from the hydrogen increases linearly with its mass fraction within the titanium. We have also investigated the effects on the images of attenuation of the incident beam prior to scattering.

Chen-Mayer, H. H.; Mildner, D. F. R.; Lamaze, G. P.; Lindstrom, R. M.

2002-03-01

108

Mixed Gas Hydrogen Sulfide Permeability and Separation Using Supported Polyphosphazene Membranes  

SciTech Connect

Three phosphazene polymers were characterized for permeability using a suite of pure gases, including H2S where high permeabilities were measured with respect to the other gases in the study. Furthermore, mixed gas selectivities were determined and compared to the ideal gas selectivities for the H2S/CH4, CO2/CH4, and Ar/CH4 gas pairs. The three phosphazenes represent a set of membrane materials differing by their polarities. Description of the polarity of each was performed using Hansen solubility parameters derived from group contributions for each chemical structure. A good correlation was observed between the polar Hansen parameter (p) and the gas permeabilities of both CO2 and H2S. Furthermore, permeant gas critical temperatures were also found to correlate with permeability suggesting a solubility driven transport process. A comparison of the mixed gas permeabilities with the corresponding pure gas data revealed good agreement in the data, although the presence of more condensable gases hinders non-polar gas transport resulting in higher separation factors.

Frederick F. Stewart; Christopher J. Orme

2005-05-01

109

Non-conventional hydrogen bonds: pterins-metal anions.  

PubMed

In this paper, we present an analysis of the interaction of metal ions (Cu, Ag and Au) with three different pterins (pterin, isoxanthopterin and sepiapterin) to provide insights concerning the formation of conventional and non-conventional H bonds. Density functional theory calculations were performed in order to reveal the optimized structures of pterin molecules, dimers and tetramers compounds, both with and without metal anions (M). The interaction with small metal clusters (M(3)) is also considered. The formation of different systems is characterized in terms of the structural parameters and hydrogen binding energies (HBE). The HBE values for pterin-M systems presented in this study lie between 22 and 60 kcal mol(-1) and can therefore be classified as strong conventional and strong non-conventional hydrogen bonds. The HBE with small metal clusters (pterin-M(3)) are smaller than the HBE with metal atoms. Vertical electron detachment energies (VEDEs) are also reported in order to analyze the influence of the hydrogen bond on electronic properties. A direct correlation between VEDEs and HBE was found for pterin-M and pterin-M(3) complexes; i.e. as the VEDEs increase, the HBE also augment. The only exception is with Ag(3). The main conclusion derived from this study is that the strong non-conventional hydrogen bonds formed between pterins, dimers and tetramers do not affect the formation of conventional hydrogen bonds between pterins but they do influence the VEDEs. PMID:21695329

Vargas, Rubicelia; Martnez, Ana

2011-07-28

110

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

PubMed

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

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

2010-04-01

111

EDTA-assisted phytoextraction of heavy metals by turfgrass from municipal solid waste compost using permeable barriers and associated potential leaching risk  

Microsoft Academic Search

A column experiment with horizontal permeable barriers was conducted to investigate phytoextraction of heavy metals by Lolium perenne L. from municipal solid waste compost following EDTA application, as well as to study the effects of L. perenne and permeable barriers on preventing metal from leaching. In columns with barriers, EDTA addition yielded maximum concentrations of Cu, Zn and Pb of

Shulan Zhao; Fei Lian; Lian Duo

2011-01-01

112

Metal-Containing Organic and Carbon Aerogels for Hydrogen Storage  

SciTech Connect

This document and the accompanying manuscript summarize the technical accomplishments of our one-year LDRD-ER effort. Hydrogen storage and hydrogen fuel cells are important components of the 2003 Hydrogen Fuel Initiative focused on the reduction of America's dependence on oil. To compete with oil as an energy source, however, one must be able to transport and utilize hydrogen at or above the target set by DOE (6 wt.% H{sub 2}) for the transportation sector. Other than liquid hydrogen, current technology falls well short of this DOE target. As a result, a variety of materials have recently been investigated to address this issue. Carbon nanostructures have received significant attention as hydrogen storage materials due to their low molecular weight, tunable microporosity and high specific surface areas. For example, the National Renewable Energy Laboratory (NREL) achieved 5 to 10 wt.% H{sub 2} storage using metal-doped carbon nanotubes. That study showed that the intimate mix of metal nanoparticles with graphitic carbon resulted in the unanticipated hydrogen adsorption at near ambient conditions. The focus of our LDRD effort was the investigation of metal-doped carbon aerogels (MDCAs) as hydrogen storage materials. In addition to their low mass densities, continuous porosities and high surface areas, these materials are promising candidates for hydrogen storage because MDCAs contain a nanometric mix of metal nanoparticles and graphitic nanostructures. For FY04, our goals were to: (1) prepare a variety of metal-doped CAs (where the metal is cobalt, nickel or iron) at different densities and carbonization temperatures, (2) characterize the microstructure of these materials and (3) initiate hydrogen adsorption/desorption studies to determine H2 storage properties of these materials. Since the start of this effort, we have successfully prepared and characterized Ni- and Co-doped carbon aerogels at different densities and carbonization temperatures. The bulk of this work is described in the attached manuscript entitled 'Formation of Carbon Nanostructures in Cobalt- and Nickel- Doped Carbon Aerogels'. This one-year effort has lead to our incorporation into the DOE Carbon-based Hydrogen Storage Center of Excellence at NREL, with funding from DOE's Energy Efficiency and Renewable Energy (EERE) Program starting in FY05.

Satcher, Jr., J H; Baumann, T F; Herberg, J L

2005-01-10

113

Increased nuclear envelope permeability and Pep4p-dependent degradation of nucleoporins during hydrogen peroxide-induced cell death.  

PubMed

The death of yeast treated with hydrogen peroxide (H(2)O(2)) shares a number of morphological and biochemical features with mammalian apoptosis. In this study, we report that the permeability of yeast nuclear envelopes (NE) increased during H(2)O(2)-induced cell death. Similar phenomena have been observed during apoptosis in mammalian tissue culture cells. Increased NE permeability in yeast was temporally correlated with an increase in the production of reactive-oxygen species (ROS). Later, after ROS levels began to decline and viability was lost, specific nuclear pore complex (NPC) proteins (nucleoporins) were degraded. Although caspases are responsible for the degradation of mammalian nucleoporins during apoptosis, the deletion of the metacaspase gene YCA1 had no effect on the stability of yeast nucleoporins. Instead, Pep4p, a vacuolar cathepsin D homolog, was responsible for the proteolysis of nucleoporins. Coincident with nucleoporin degradation, a Pep4p-EGFP reporter migrated out of the vacuole in H(2)O(2)-treated cells. We conclude that increases in ROS and NPC permeability occur relatively early during H(2)O(2)-induced cell death. Later, Pep4p migrates out of vacuoles and degrades nucleoporins after the cells are effectively dead. PMID:16183335

Mason, D Adam; Shulga, Nataliya; Undavai, Satyen; Ferrando-May, Elisa; Rexach, Michael F; Goldfarb, David S

2005-12-01

114

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

115

Hydrogen formation in metals and alloys during fusion reactor operation  

NASA Astrophysics Data System (ADS)

The results of neutron transport calculations of the hydrogen formation based on the JENDL gas-production cross section file are discussed for some metals and alloys, namely V-51, Cr, Fe, Ni, Mo, austenitic stainless steel (Ti modified 316SS:PCA), ferritic steel (Fe-8Cr-2W:F82H) and the vanadium-base alloy (V-5Cr-5Ti). Impact of the steel fraction in steel/water homogeneous blanket/shield compositions on the hydrogen formation rate in above-mentioned metals and alloys is discussed both for the hydrogen formation in the first wall and the blanket/shield components. The results obtained for the first wall are compared with those for the helium formation obtained at JAERI by the same calculational conditions. Hydrogen formation rates at the first wall having V-51, Cr, Fe, Ni and Mo are larger than those of helium by 3-8 times.

Zimin, Sergei; Takatsu, Hideyuki; Mori, Seiji

1994-08-01

116

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

117

Hydrogen evolution from water through metal sulfide reactions  

NASA Astrophysics Data System (ADS)

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

Saha, Arjun; Raghavachari, Krishnan

2013-11-01

118

Electronic excitations and metallization of dense solid hydrogen  

PubMed Central

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

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

2013-01-01

119

Optical hydrogen sensors based on metal-hydrides  

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

120

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

121

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

122

Direct electrical measurement of the conversion of metal acetates to metal sulfides by hydrogen sulfide.  

PubMed

Copper acetate and related metal salt films react directly with hydrogen sulfide at room temperature to form metal sulfides, resulting in conductivity changes as large as 108. The observed changes in conductivity are related to the solubility product constant (Ksp) and the difference in conductivity between the metal salt and the resulting metal sulfide. A smaller Ksp indicates a more stable metal sulfide and, therefore, greater metal salt reactivity. Polyaniline nanofiber/metal salt composites were also examined and show metal sulfide conversion with changes in resistance up to 106. The direct electrical measurement of the conversion of metal salt to metal sulfide has the potential to be the basis of a new type of sensitive, thin-film chemical sensor. PMID:17173401

Virji, Shabnam; Kaner, Richard B; Weiller, Bruce H

2006-12-25

123

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

124

Cytotoxicity and dentin permeability of carbamide peroxide and hydrogen peroxide vital bleaching materials, in vitro.  

PubMed

There has been recent concern about the inadvertent exposure of dentin with patent tubules as well as gingiva to bleaching systems containing 10-15% carbamide peroxide or 2-10% hydrogen peroxide for more than a few minutes. The aims of the present study were: (1) to determine the cytotoxicity of dilutions of hydrogen peroxide in cell culture; (2) to measure hydrogen peroxide diffusion from bleaching agents through dentin in vitro; and (3) to determine the risk of hydrogen peroxide-induced cytotoxicity from exposure of dentin to these vital bleaching agents. The 50% inhibitory dose (ID50) of hydrogen peroxide to succinyl dehydrogenase activity in cultured cells was found to be 0.58 mmol/L after 1 h. All bleaching materials demonstrated diffusion of hydrogen peroxide through dentin in an "in vitro pulp chamber" device. The one- and six-hour diffusates of all bleaching agents through 0.5-mm dentin exceeded the ID50 in monolayer cultures. Inhibition of succinyl dehydrogenase activity corresponded to the amount of hydrogen peroxide that can rapidly diffuse through dentin in vitro and reach concentrations which are toxic to cultured cells in less than 1 h. PMID:8501291

Hanks, C T; Fat, J C; Wataha, J C; Corcoran, J F

1993-05-01

125

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

126

Solvus thermodynamics of metal-hydrogen interstitial solutions  

SciTech Connect

Thermodynamic equations are derived relating the solvus properties of metal-hydrogen interstitial solutions which form hydride phases to single phase and two solid phase thermodynamic parameters and standard thermodynamic reaction parameters. The role of non-ideality is examined. The influences of stress alloying and traps on solvus properties are discussed.

Flanagan, T.B.; Kishimoto, S.; Oates, W.A.

1983-01-01

127

Retention of Weld Metal Properties and Prevention of Hydrogen Cracking.  

National Technical Information Service (NTIS)

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

2003-01-01

128

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

129

Isotope effect on hydrogen site energies for two metal dihydrides  

SciTech Connect

The change in hydrogen site energy with isotope for dihydrides and dideuterides of Sc and Y has been indirectly determined using electron spin resonance (ESR) of dilute Er ions in these face-centered-cubic hosts. The ESR spectra measure the distribution of hydrogen adjacent to the Er, and the variation in this distribution with isotope and with hydrogen to metal ratio has been studied for several samples of both host metals. These data are accurately described by a lattice-gas model which yields the energy difference for protons or deuterons on octahedral and tetrahedral sites, both adjacent to the Er impurities and in the bulk host lattice. This energy difference is 10% greater for deuterons, and the change with isotope can be attributed primarily to the mass dependence of the vibrational part of the total energy associated with each site.

Venturini, E.L.

1980-01-01

130

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

131

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

132

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

133

Hydrogenation of anthraquinone on metal-containing catalysts  

SciTech Connect

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

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

1982-12-01

134

The metallization and superconductivity of dense hydrogen sulfide.  

PubMed

Hydrogen sulfide (H2S) is a prototype molecular system and a sister molecule of water (H2O). The phase diagram of solid H2S at high pressures remains largely unexplored arising from the challenges in dealing with the pressure-induced weakening of S-H bond and larger atomic core difference between H and S. Metallization is yet achieved for H2O, but it was observed for H2S above 96 GPa. However, the metallic structure of H2S remains elusive, greatly impeding the understanding of its metallicity and the potential superconductivity. We have performed an extensive structural study on solid H2S at pressure ranges of 10-200 GPa through an unbiased structure prediction method based on particle swarm optimization algorithm. Besides the findings of candidate structures for nonmetallic phases IV and V, we are able to establish stable metallic structures violating an earlier proposal of elemental decomposition into sulfur and hydrogen [R. Rousseau, M. Boero, M. Bernasconi, M. Parrinello, and K. Terakura, Phys. Rev. Lett. 85, 1254 (2000)]. Our study unravels a superconductive potential of metallic H2S with an estimated maximal transition temperature of ?80 K at 160 GPa, higher than those predicted for most archetypal hydrogen-containing compounds (e.g., SiH4, GeH4, etc.). PMID:24811660

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

2014-05-01

135

The metallization and superconductivity of dense hydrogen sulfide  

NASA Astrophysics Data System (ADS)

Hydrogen sulfide (H2S) is a prototype molecular system and a sister molecule of water (H2O). The phase diagram of solid H2S at high pressures remains largely unexplored arising from the challenges in dealing with the pressure-induced weakening of S-H bond and larger atomic core difference between H and S. Metallization is yet achieved for H2O, but it was observed for H2S above 96 GPa. However, the metallic structure of H2S remains elusive, greatly impeding the understanding of its metallicity and the potential superconductivity. We have performed an extensive structural study on solid H2S at pressure ranges of 10-200 GPa through an unbiased structure prediction method based on particle swarm optimization algorithm. Besides the findings of candidate structures for nonmetallic phases IV and V, we are able to establish stable metallic structures violating an earlier proposal of elemental decomposition into sulfur and hydrogen [R. Rousseau, M. Boero, M. Bernasconi, M. Parrinello, and K. Terakura, Phys. Rev. Lett. 85, 1254 (2000)]. Our study unravels a superconductive potential of metallic H2S with an estimated maximal transition temperature of 80 K at 160 GPa, higher than those predicted for most archetypal hydrogen-containing compounds (e.g., SiH4, GeH4, etc.).

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

2014-05-01

136

The Interaction of Hydrogen with Simple and Noble Metals Surfaces  

NASA Astrophysics Data System (ADS)

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

Sprunger, Phillip T.

137

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.

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

2014-01-01

138

Prussian blue nanocontainers: selectively permeable hollow metal-organic capsules from block ionomer emulsion-induced assembly.  

PubMed

Hollow polymer-based particles are useful for the encapsulation, protection, and release of active compounds. Adding a metal-organic coordination framework shell to nanocontainers is an attractive goal because it should help control their stability and permeability while yielding new properties and functions. We have discovered that polymer capsules with a Prussian blue analogue inner shell can be synthesized by emulsion-induced assembly of a metal-containing amphiphilic block ionomer. The capsules are selectively permeable and were used as nanocontainers to encapsulate and release a model compound. Further, these nanomaterials are tunable in size and organize into 2-D close-packed arrays in the solid state. Potential applications for these materials include the encapsulation and nanopatterning of pharmaceutical, biological, and catalytic compounds. PMID:21557609

Roy, Xavier; Hui, Joseph K-H; Rabnawaz, Muhammad; Liu, Guojun; MacLachlan, Mark J

2011-06-01

139

Effect of interaction of dissolved hydrogen atoms upon metals' strength and plasticity  

Microsoft Academic Search

In the paper, different hydrogen action upon such metals as iron and palladium is attributed to the character of interaction of hydrogen atoms in a crystal lattice. It has been shown that if an effective interaction H?H is attractive, then such a metal can be strengthened due to the hydrogen action and if this interaction is repulsive then the metal

L. I. Smirnov

1997-01-01

140

Mechanism and kinetics of electrochemical hydrogen entry and degradation of metallic systems  

Microsoft Academic Search

The purpose of this paper is to review recent advances in understanding the kinetics of the ever elusive and omnipresent hydrogen entry into metallic systems by multiple ways that cause numerous and frequently catastrophic degradation problems. The problem of hydrogen-induced damage and failures is interdisciplinary and varied. For example, in the cathodic protection of metals, in hydrogenation cells where metal

R. N. Iyer; H. W. Pickering

1990-01-01

141

Liquid Metallic Hydrogen: Building Block of a Liquid Sun  

NASA Astrophysics Data System (ADS)

The establishment by Andrews of critical temperatures (T. Andrews, Phil. Trans. 1869, v. 159, 575-590) soon became one of the great pillars in support of the gaseous models of the Sun. Gases above these temperatures simply could not be liquefied. Given that interior of the Sun was already hypothesized in the 19th century to be at temperatures well exceeding those achievable on Earth in ordinary furnaces, it became inconceivable to think of the solar interior as anything but gaseous. Hence, the models advanced by Secchi, Faye, Stoney, Lane, and Young, could easily gain acceptance. However, modern science is beginning to demonstrate that hydrogen (which under ordinary conditions has a critical point at 33 K) can become pressure ionized such that its electrons enter metallic conductions bands, given sufficiently elevated pressures, as the band gap is reduced from 15 eV to 0.3 eV. Liquid metallic hydrogen will possess a new critical temperature well above that of ordinary hydrogen. Already, experiments suggests that it can exist at temperatures of thousands of Kelvin and millions of atmospheres (S. T. Weir et al., Phys. Rev. Let. 1996, 76, 1860). The formation of liquid metallic hydrogen brings with it a new candidate for the interior of the Sun and the stars. Its existence shatters the great pillar of the gaseous models of the Sun which the critical point of ordinary gases had erected.

Robitaille, Pierre-Marie

2011-04-01

142

High pressure/high temperature hydrogen permeability in candidate Stirling engine alloys  

SciTech Connect

Hydrogen permeation tests of eight high-temperature alloys were conducted in 20.7 MPa hydrogen at 923 to 1088 K for assessing suitability in Stirling engine application for heater head and heater head tubing. The iron-nickel-base alloys investigated included N-155, Incoloy 800 (IN 800), A-286, and 19-9DL, and cast alloys CRM-6D, SAF-11, and XF-818. Low carbon alloys Stellite 6B (6BLC), a cobalt-base wrought alloy, was also investigated. 15 refs.

Bhattacharyya, S.; Vesely, E.J. Jr.; Hill, V.L.

1982-03-01

143

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

144

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 = 46) 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

145

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

146

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

SciTech Connect

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

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

2010-01-21

147

Quantum simulation of low-temperature metallic liquid hydrogen  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

148

Metallization and electrical conductivity of hydrogen in Jupiter  

SciTech Connect

Electrical conductivities of molecular hydrogen in Jupiter were calculated by scaling electrical conductivities measured at shock pressures in the range of 10 to 180 gigapascals (0.1 to 1.8 megabars) and temperatures to 4000 kelvin, representative of conditions inside Jupiter. Jupiter`s magnetic field is caused by convective dynamo motion of electrically conducting fluid hydrogen. The data imply that Jupiter should become metallic at 140 gigapascals in the fluid, and the electrical conductivity in the jovian molecular envelope at pressures up to metallization is about an order of magnitude larger than expected previously. The large magnetic field is produced in the molecular envelope closer to the surface than previously thought. 30 refs., 3 figs.

Nellis, W.J.; Weir, S.T.; Mitchell, A.C. [Lawrence Livermore National Laboratory, CA (United States)

1996-08-16

149

Metallization and electrical conductivity of hydrogen in Jupiter.  

PubMed

Electrical conductivities of molecular hydrogen in Jupiter were calculated by scaling electrical conductivities measured at shock pressures in the range of 10 to 180 gigapascals (0.1 to 1.8 megabars) and temperatures to 4000 kelvin, representative of conditions inside Jupiter. Jupiter's magnetic field is caused by convective dynamo motion of electrically conducting fluid hydrogen. The data imply that Jupiter should become metallic at 140 gigapascals in the fluid, and the electrical conductivity in the jovian molecular envelope at pressures up to metallization is about an order of magnitude larger than expected previously. The large magnetic field is produced in the molecular envelope closer to the surface than previously thought. PMID:8688072

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

1996-08-16

150

Preparation of thin metallic titanium foils as hydrogen targets  

NASA Astrophysics Data System (ADS)

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

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

2010-02-01

151

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

152

Silane plus molecular hydrogen as a possible pathway to metallic hydrogen  

PubMed Central

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

Yao, Yansun; Klug, Dennis D.

2010-01-01

153

The Designed Metal-Hydride Torches and Hydrogen Accumulators for Various Purposes  

Microsoft Academic Search

\\u000a The hydrogen storage in metal hydrides is the urgent problem of hydrogen power engineering and the demand for metal hydrides\\u000a as capacitive, safe and convenient in service sources of hydrogen has stimulated the study of hydrogen capacity of multicomponent\\u000a alloys. In recent years much attention has been given by scientists to the investigation of hydrogen-sorption and desorption\\u000a properties of different

D. V. Schur; A. F. Savenko; V. A. Bogolepov; S. Yu. Zaginaichenko; L. O. Teslenko; T. N. Veziroglu

154

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

155

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

156

Advanced Hydrogen Transport Membranes for Vision 21 Fossil Fuel Plants  

SciTech Connect

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 hydrogen separation unit.

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

2005-10-31

157

Hydrogen absorption properties of metal-ethylene complexes  

NASA Astrophysics Data System (ADS)

Recently, we have predicted [Phys. Rev. Lett. 97, 226102 (2006)] that a single ethylene molecule can form stable complexes with light transition metals (TMs) such as Ti and the resulting TMn -ethylene complex can absorb up to 12 and 14wt% hydrogen for n=1 and 2, respectively. Here we extend this study to include a large number of other metals and different isomeric structures. We obtained interesting results for light metals such as Li. The ethylene molecule is able to complex with two Li atoms with a binding energy of 0.7eV/Li which then binds up to two H2 molecules per Li with a binding energy of 0.24eV/H2 and absorption capacity of 16wt% , a record high value reported so far. The stability of the proposed metal-ethylene complexes was tested by extensive calculations such as normal-mode analysis, finite temperature first-principles molecular-dynamics (MD) simulations, and reaction path calculations. The phonon and MD simulations indicate that the proposed structures are stable up to 500K . The reaction path calculations indicate about 1eV activation barrier for the TM2 -ethylene complex to transform into a possible lower energy configuration where the ethylene molecule is dissociated. Importantly, no matter which isometric configuration the TM2 -ethylene complex possesses, the TM atoms are able to bind multiple hydrogen molecules with suitable binding energy for room-temperature storage. These results suggest that co-deposition of ethylene with a suitable precursor of TM or Li into nanopores of light-weight host materials may be a very promising route to discovering new materials with high-capacity hydrogen absorption properties.

Zhou, W.; Yildirim, T.; Durgun, E.; Ciraci, S.

2007-08-01

158

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

159

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

160

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

Microsoft Academic Search

The metal-ferrite (chromium-ferrite and zinc-ferrite) sorbents made from the heavy metal wastewater sludge have been developed for the hydrogen sulfide removal from coal gas. The high temperature absorption of hydrogen sulfide from coal gas with the metal-ferrite sorbent in a fixed bed reactor was conducted in this study. The metal-ferrite powders were the products of the ferrite process for the

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

2008-01-01

161

Transport properties of liquid metal hydrogen under high pressures  

NASA Technical Reports Server (NTRS)

A theory is developed for the compressibility and transport properties of liquid metallic hydrogen, near to its melting point and under high pressure. The interionic force law is assumed to be of the screened Coulomb type, because hydrogen has no core electrons. The random phase approximation is used to obtain the structure factor S(k) of the system in terms of the Fourier transform of this force law. The long wavelenth limit of the structure factor S(o) is related to the compressibility, which is much lower than that of alkali metals at their melting points. The diffusion constant at the melting point is obtained in terms of the Debye frequency, using a frequency spectrum analogous with the phonon spectrum of a solid. A similar argument is used to obtain the combined shear and bulk viscosities, but these depend also on S(o). The transport coefficients are found to be about the same size as those of alkali metals at their melting points.

Brown, R. C.; March, N. H.

1972-01-01

162

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

Microsoft Academic Search

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

Ragaiy Zidan; James A. Ritter; Armin D. Ebner; Jun Wang; Charles E. Holland

2008-01-01

163

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

Microsoft Academic Search

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

Nicola Moraci; Paolo S. Calabr

2010-01-01

164

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

NASA Astrophysics Data System (ADS)

Permeability, diffusivity and solubility of hydrogen in Flinak, a mixed molten salt of LiF (46.5%), NaF (11.5%) and KF (42%), were determined using a vessel supported by a Ni plate. Diffusion-limiting permeation was confirmed by experimental data where hydrogen permeation rates were in reverse proportion to the thickness of Flinak. Diffusivities determined in the range of 500-750 C were correlated to an Arrhenius equation with the activation energy of 50 kJ/mol. Since the dependence of hydrogen solubility in Flinak on pressure was almost linear, hydrogen was dissolved as H 2 in Flinak. The H 2 solubility in Flinak was correlated to a Henry law, and its solubility constant was discussed in terms of macroscopic surface tension and unspecified interaction energy between the molten salt and dissolved gaseous molecules.

Fukada, Satoshi; Morisaki, Akio

2006-11-01

165

Transition metal sulfide hydrogen evolution catalysts for hydrobromic acid electrolysis.  

PubMed

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

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

2013-01-01

166

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

167

Analysis of transient hydrogen uptake by metal alloy particles  

SciTech Connect

This paper describes a new approach to solving the equations comprising the shrinking core model for diffusion and reaction of a chemical species in a solid spherical particle. The reactant adsorbs on the particle surface, diffuses into the particle`s interior, and reacts with the particle to form a solid product. The shrinking core model assumes a fast reaction rate compared to reactant diffusion so that the reaction is localized in the interfacial zone between the unreacted solid core and the surrounding shell of reacted product. Analytical solutions of the governing conservation equations usually invoke the pseudo-steady state (PSS) approximation which neglects the transient mass accumulation and diffusion-induced convection terms in the continuity equation for the diffusing reactant. However, small particle radii and slow reactant diffusion cast doubt on the validity of the PSS approximation. Dimensional analysis reveals an approximation that is less restrictive than PSS, yet enables a semi-analytical solution for the diffusing reactant distribution and interface velocity. For sufficiently large values of the surface mass fraction of the diffusing reactant, the PSS approximation leads to serious errors in the time dependence of the interface position and fractional conversion. However, the estimate of the surface mass fraction of hydrogen in LaNi{sub 5} particles suggests the validity of the PSS approximation for hydriding of metal alloy particles. The shrinking core model thus enables an estimate of hydrogen diffusivity in metal alloy particles.

Zhang, W. [Texas A and M Univ., College Station, TX (United States); Srinivasan, S.; Ploehn, H.J. [Univ. of South Carolina, Columbia, SC (United States)

1996-12-01

168

Influence of surface barriers on hydrogen storage in MgAl films on permeable stainless steel membranes  

Microsoft Academic Search

The behavior of hydrogen in the plasma hydrogenated MgAl films on stainless steel membranes, in particular, the effect of surface and interface properties on the efficiency of hydrogenation and kinetics of hydrogen effusion were investigated. The paper aims at optimizing the processes of hydrogen retention and its thermal release on the basis of a model based on the trapping of

L. Pranevicius; C. Templier; D. Milcius

2005-01-01

169

Hydrogen generation and storage over transition metal-decorated fullerenes and related materials  

Microsoft Academic Search

Economical ways to generate and store hydrogen are crucial steps towards the hydrogen economy and fuel-cell technologies. By using first-principles density functional theory calculations, we found out that transition metal-decorated fullerenes and related materials can simultaneously dissociate small molecules like water to produce and store hydrogen. Hydrogen production from water will allow us to have a clean hydrogen economy by

Liping Huang; Erik Santiso; Keith Gubbins; Marco Buongiorno Nardelli

2007-01-01

170

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

NASA Astrophysics Data System (ADS)

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

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

2010-01-01

171

Hydrogen generation and storage over transition metal-decorated fullerenes and related materials  

NASA Astrophysics Data System (ADS)

Economical ways to generate and store hydrogen are crucial steps towards the hydrogen economy and fuel-cell technologies. By using first-principles density functional theory calculations, we found out that transition metal-decorated fullerenes and related materials can simultaneously dissociate small molecules like water to produce and store hydrogen. Hydrogen production from water will allow us to have a clean hydrogen economy by using renewable source rather than fossil fuels so that we can stop releasing carbon into the atmosphere. Our studies show that the bonding between transition metal and hydrogen is of a combination of chemical and physical adsorption, which is essential for reversible hydrogen uptake/release. Car-Parrinello molecular dynamics simulations demonstrate that these systems are stable and exhibit associative desorption of H2 upon heating without breaking the bond between carbon and transition metal. This fulfills another requirement for reversible hydrogen storage.

Huang, Liping; Santiso, Erik; Gubbins, Keith; Buongiorno Nardelli, Marco

2007-03-01

172

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

PubMed Central

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

Irokawa, Yoshihiro

2011-01-01

173

Effect Of Water On Permeation By Hydrogen  

NASA Technical Reports Server (NTRS)

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

Tomazic, William A.; Hulligan, David

1988-01-01

174

Influence of N deficiency and salinity on metal (Pb, Zn and Cu) accumulation and tolerance by Rhizophora stylosa in relation to root anatomy and permeability.  

PubMed

Effects of N deficiency and salinity on root anatomy, permeability and metal (Pb, Zn and Cu) translocation and tolerance were investigated using mangrove seedlings of Rhizophora stylosa. The results showed that salt could directly reduce radial oxygen loss (ROL) by stimulation of lignification within exodermis. N deficiency, oppositely, would reduce lignification. Such an alteration in root permeability may also influence metal tolerance by plants. The data indicated that a moderate salinity could stimulate a lignified exodermis that delayed the entry of metals into the roots and thereby contributed to a higher metal tolerance, while N deficiency would aggravate metal toxicity. The results from sand pot trail further confirmed this issue. This study provides a barrier property of the exodermis in dealing with environments. The plasticity of root anatomy is likely an adaptive strategy to regulate the fluxes of gases, nutrients and toxins at root-soil interface. PMID:22361050

Cheng, Hao; Wang, You-Shao; Ye, Zhi-Hong; Chen, Dan-Ting; Wang, Yu-Tu; Peng, Ya-Lan; Wang, Li-Ying

2012-05-01

175

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

Microsoft Academic Search

Passivation of semiconductor surfaces against chemical attack can be achieved by terminating the surface-dangling bonds with a monovalent atom such as hydrogen. Such passivation invariably leads to the removal of all surface states in the bandgap, and thus to the termination of non-metallic surfaces. Here we report the first observation of semiconductor surface metallization induced by atomic hydrogen. This result,

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

2003-01-01

176

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

NASA Technical Reports Server (NTRS)

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

Hunter, Gary W. (Inventor)

1997-01-01

177

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

178

The influence of water molecule coordination to a metal ion on water hydrogen bonds.  

PubMed

The geometry of hydrogen bonds in the crystal structures from the Cambridge Structural Database and calculated data show that water coordination to a metal ion has a remarkable influence on hydrogen bonds. The calculated energies of hydrogen bonds of coordinated water are much stronger, even if the aqua complex is neutral. PMID:22772777

Andri?, Jelena M; Janji?, Goran V; Ninkovi?, Dragan B; Zari?, Sneana D

2012-08-21

179

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 200C. 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 300C 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

180

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

NASA Technical Reports Server (NTRS)

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

Danford, M. D.

1986-01-01

181

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

PubMed

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

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

2014-08-01

182

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

183

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

184

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

SciTech Connect

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

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

2012-01-04

185

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

NASA Astrophysics Data System (ADS)

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

Jarosik, Marcin W.; Durajski, Artur P.

2014-01-01

186

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

SciTech Connect

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

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

2009-03-24

187

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

188

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

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

189

Miniaturized Metal (Metal Alloy)/PdO(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

190

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

SciTech Connect

Ion implantations into metals have been shown recently to either reduce or enhance interactions with gaseous hydrogen. Published studies concerned with modifications of these interactions are reviewed and discussed in terms of the mechanisms postulated to explain the observed changes. The interactions are hydrogenation, hydrogen permeation, and hydrogen embrittlement. In particular, the results of the reviewed studies are: uranium hydriding suppressed by implantation of oxygen and carbon; hydrogen gettered in iron and nickel using implantation of titanium; hydriding of titanium catalyzed by implanted palladium; tritium permeation of 304L stainless steel reduced using selective oxidation of implanted aluminum; and hydrogen attack of a low-alloy steel accelerated by implantation of helium. These studies revealed ion implantation to be an effective method for modifying the interactions of hydrogen gas with metals. 9 refs., 4 figs.

Musket, R.G.

1988-09-01

191

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

NASA Technical Reports Server (NTRS)

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

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

1954-01-01

192

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

PubMed

We report that ammonia borane with a high uptake capacity for hydrogen can be encapsulated in a metal-organic framework (MOF) via capillary action, where the MOF functions as a chemical guide to control the hydrogen desorption pathways of ammonia borane by releasing only pure hydrogen, lowering its hydrogen desorption temperature, and suppressing its volumetric expansion during hydrogen desorption. PMID:24842695

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

2014-05-29

193

New formula of Debye length in solid metallic hydrogen  

NASA Astrophysics Data System (ADS)

In arbitrary quasineutral states, ionic potential is somewhat screened by electrons. The degree of the screening is represented by Debye screening length. The Debye length varies proportional to square root of the temperature in plasma state. When the temperature drops to the Fermi temperature, electrons undergo Fermi degenerate and the Debye length becomes independent of the temperature. Such situation also appears in solid states. We have researched in solid metallic hydrogen because it is said to be a high temperature superconductor and is an ideal matter to treat the Debye screening by the lack of orbital electrons. By taking into account the changes in electronic quantum statistical state, the formula of the Debye length in the superconductive state was derived. The Debye length in the superconductive state again depends on the temperature by bosonization of the electrons. As a one application, we also have calculated the penetration probability by using the WKB approximation. The probability at n=10^31m-3 and T=10K is comparative that of a particle of about 7.5 eV penetrates bare Coulomb potential.

Shibata, Kazunori; Kodama, Ryosuke

2007-11-01

194

Oxidative Dissolution of Nickel Metal in Hydrogenated Hydrothermal Solutions  

SciTech Connect

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

Ziemniak SE, Guilmette PA, Turcotte RA, Tunison HM

2007-03-27

195

Hydrogen Adsorption by Alkali Metal Graphite Intercalation Compounds  

NASA Astrophysics Data System (ADS)

Adsorption occurs whenever a solid surface is exposed to a gas or liquid, and is characterized by an increase in fluid density near the interface. Adsorbents have drawn attention in the current effort to engineer materials that store hydrogen at high densities within moderate temperature and pressure regimes. Carbon adsorbents are a logical choice as a storage material due to their low costs and large surface areas. Unfortunately, carbon adsorbents suffer from a low binding enthalpy for H2 (about 5 kJ mol-1), well below the 15 to 18 kJ mol-1) that is considered optimal for hydrogen storage systems. Binding interactions can be increased by the following methods: (1) adjusting the graphite interplanar separation with a pillared structure, and (2) introducing dopant species that interact with H2 molecules by strong electrostatic forces. Graphite intercalation compounds are a class of materials that contain both pillared structures and chemical dopants, making them an excellent model system for studying the fundamentals of hydrogen adsorption in nanostructured carbons. Pressure-composition-temperature diagrams of the MC24(H 2)x graphite intercalation compounds were measured for M = (K, Rb, Cs). Adsorption enthalpies were measured as a function of H2 concentration. Notably, CsC24 had an average adsorption enthalpy of 14.9 kJ mol-1), nearly three times larger than that of pristine graphite. The adsorption enthalpies were found to be positively correlated with the alkali metal size. Adsorption capacities were negatively correlated with the size of the alkali metal. The rate of adsorption is reduced at large H2 compositions, due to the effects of site-blocking and correlation on the H2 diffusion. The strong binding interaction and pronounced molecular-sieving behavior of KC24 is likely to obstruct the translational diffusion of adsorbed H2 molecules. In this work, the diffusion of H2 adsorbed in KC24 was studied by quasielastic neutron scattering measurements and molecular dynamics simulations. As predicted, the rate of diffusion in KC24 is over an order of magnitude slower than in other carbon adsorbents (e.g. carbon nanotubes, nanohorns and carbon blacks). It is similar in magnitude to the rate of H2 diffusion in zeolites with molecular-sized cavities. This suggests that H2 diffusion in adsorbents is influenced very strongly by the pore geometry. The H2 diffusion process in KC24 contains at least two distinct jump frequencies. Bound states of adsorbed H2 in KC24 were investigated by inelastic neutron scattering measurements and density functional theory calculations. Spectral peaks in the neutron energy loss range of 5 meV to 45 meV were observed for the first time. These peaks were interpreted as single- and multi-excitation transitions of the H2 phonon and rotational modes. The rotational barrier for H2 molecules is many times larger in KC24 than in other carbon adsorbents, apparently due to the confinement of the molecules between closely-spaced graphitic layers. Evidence was found for the existence of at least three H2 sorption sites in KC24, each with a distinctive rotational barrier.

Purewal, Justin

196

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

197

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 structurefunction relationships in metal-assisted oxidative catalysis.

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

2009-01-01

198

Hydrogen storage in the form of metal hydrides  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

199

Applications of Ion Implantation for Modifying the Interactions between Metals and Hydrogen Gas.  

National Technical Information Service (NTIS)

Ion implantations into metals have been shown recently to either reduce or enhance interactions with gaseous hydrogen. Published studies concerned with modifications of these interactions are reviewed and discussed in terms of the mechanisms postulated to...

R. G. Musket

1988-01-01

200

Hydrogen-related defects and the role of metal additives in complex hydrides  

NASA Astrophysics Data System (ADS)

Complex hydrides such as NaAlH4 and Li4BN3H10 doped with selected transition metals (e.g., Ti, Ni, and Pt) are promising hydrogen storage materials. The mechanism of the enhancement in (de)hydrogenation rates caused by these metals is, however, not well understood. We have carried out first-principles studies based on density functional theory of hydrogen vacancies and interstitials, which play an important role in the (de)hydrogenation processes. We find that these defects are always charged; their formation energy therefore depends on the Fermi level. The metallic impurities can also exist in different charged states and, therefore, modify the Fermi level, thus changing the defect concentrations. Our first-principles results shed light on the role of transition-metal impurities in hydrides and lead to the design of storage materials with improved characteristics.

Hoang, Khang; van de Walle, Chris G.

2009-03-01

201

Influence of hydrogen absorption on stress changes in thin catalytic metal films dedicated for sensors application  

NASA Astrophysics Data System (ADS)

In the paper results of investigation of the influence of low concentration hydrogen on stress changes in thin catalytic metal films were discussed. The concentration of H2 was altered from 6 ppm to 1% of hydrogen (6N) in nitrogen (6N). Silicon beams covered with palladium or platinum films of various thicknesses were anchored at one end and their deflection at the other end was measured by atomic force microscope. Stress changes were determined by application of modified Stoney formula and compared with results of computer modelling. The influence of stress caused by hydrogen absorption on the alteration of output characteristics of AIII-N based hydrogen sensors was excluded. The time dependence of stress in metallic films for various hydrogen concentrations indicated dissociation limited mechanism of hydrogen absorption.

Prazmowska, Joanna; Piasecki, Tomasz; Szyszka, Adam; Paszkiewicz, Regina; T?acza?a, Marek

2011-04-01

202

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

203

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

Microsoft Academic Search

It is noted that thermochemical hydrogen cycles involving metal sulfates offer an alternative to sulfuric acid which is corrosive and has high energy requirements for drying prior to its thermal decomposition. The formation of such metal sulfates in conjunction with a low temperature hydrogen formation step is discussed. The following reaction was studied: MgSO3(c) + MgO(c) + I2(g) yields MgSO4(c)

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

1981-01-01

204

Hydrogenation of isophorone with noble metal catalysts in supercritical carbon dioxide  

Microsoft Academic Search

Catalytic hydrogenation of 3,3,5-trimethyl-2-cyclohexen-1-one (isophorone) was examined over several supported noble metal catalysts in supercritical carbon dioxide. Charcoal supported rhodium and platinum catalysts were found to be active for the isophorone hydrogenation to 3,3,5-trimethylcyclohexanone (dihydroisophorone), but undesirable successive hydrogenation to 3,3,5-trimethylcyclohexanol also proceeded. Supported palladium catalysts were less active than the supported rhodium and platinum catalysts, but were highly selective

Takafumi Sato; Chandrashekhar V. Rode; Osamu Sato; Masayuki Shirai

2004-01-01

205

Mechanism and kinetics of the selective hydrogenation of acetonitrile on some transition metals  

Microsoft Academic Search

Magnesium oxide supported Co, Ni, and Cu and also nickel-black display a high activity and 100% selectivity in the hydrogenation vapor-phase of acetonitrile to the primary amine. A mechanism for the reaction is based on kinetics and adsorption data and includes as the limiting step the reaction of acetonitrile, adsorbed on the metal, with H atoms or hydrogen molecules. The

N. V. Pavlenko; A. I. Tripolskii; E. V. Prokhorenko; G. I. Golodets

1988-01-01

206

Programmed-temperature desorption study of hydrogen adsorption on disperse and sintered group VIII metal blacks  

SciTech Connect

Data are presented on the thermodesorption of hydrogen from disperse and sintered Group VIII metal blacks. It is shown that the activation energy for desorption of chemisorbed molecular and atomic complexes of hydrogen increases in the noblemetal triads with increasing atomic number of the element, both in the case of disperse blacks (nonactivated adsorption) and in the case of sintered blacks (activated adsorption).

Babenkova, L.V.; Popova, N.M.

1986-02-01

207

Effective metal dispersion in pyridinelike nitrogen doped graphenes for hydrogen storage  

Microsoft Academic Search

We study the pyridinelike nitrogen-doped graphene (PNG) with dispersed transition metal (TM) atoms as a potential hydrogen storage medium using the pseudopotential density functional method. It is found that highly localized states near the Fermi level, which are derived from the nitrogen defects, contribute to strong TM bindings and favorable hydrogen adsorption in the PNG. The strong TM binding prevents

Gyubong Kim; Seung-Hoon Jhi

2008-01-01

208

Metal Halogen Battery Construction with Combustion Arrester to Prevent Self Propagation of Hydrogen-Halogen Reactions  

SciTech Connect

A metal halogen battery construction containing a special reactor means having a combustion arrester device and a reaction initiator device, whereby the reactor means permits controlled recombination of hydrogen gas and halogen gas in the system to form hydrogen halide, which is then dispersed into the store means of the battery.

Hammond, M. J.; Kilic, S.

1983-12-27

209

Hydrogen storage properties of catalyst metal-doped single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

In the past decade, hydrogen storage in solid-state materials has been one of the biggest hurdles to meet the storage density, safety, reliability and cost reduction needed for a hydrogen fuel economy. Single-walled carbon nanotubes (SWNTs) are particularly intriguing for hydrogen storage because each carbon atom is a surface site, and calculations have indicated that hydrogen bond strength can be tuned by adjusting the nanotube diameter. However, exposure to molecular hydrogen has resulted in only modest hydrogen uptake, as opposed to exposure to atomic hydrogen where significant hydrogen bonding has been observed. This has motivated studies of catalyst metal-doped SWNTs in order to facilitate the disassociation process of hydrogen molecules to improve hydrogen storage in these nanotubes. In this work, the hydrogen uptake and release properties were measured for undoped and catalyst metal-doped high pressure CO conversion (HiPco) SWNTs. Palladium and platinum catalytic nanoparticles were electrochemically (EC), UHV sputter (Sp)-deposited and e-beam evaporated (EE) on the surface of SWNT bundles. Rigorous and precise measurements were taken by employing a specially-designed Sieverts' volumetric apparatus up to 30 Bar of pressure that is capable of measuring hydrogen storage in milligram quantities. The undoped SWNTs exhibited a reversible hydrogen uptake capacity of 0.17 wt% in gravimetric basis at room temperature. The capacity of Pd-doped SWNTs was increased to 0.53 and 0.72 wt% for EC and Sp-doped samples, respectively. This corresponds to an increase of a factor of 3 to 4 over undoped material. For the case of Pt-doped SWNTs, the uptake capacities of EC and Sp-doped samples were also increased to 0.40 and 0.51 wt%, respectively. The increase of the stored hydrogen is explained by sequential processes of molecular hydrogen dissociation, spillover, and surface diffusion. Hydrogen uptake kinetics was also measured and compared between the samples. The formation of stable C-H bonds was confirmed by XPS and FTIR spectroscopy techniques. It was observed that the hydrogen stored in the metal catalyst-doped SWNTs could be completely removed after a prolonged evacuation process even at room temperature. A metal-catalyzed hydrogen desorption model was developed, and the curve fitting by the model replicated the experimental observation.

Lee, Yong-Won

210

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.

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

2013-01-01

211

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

212

Cathode for the electrolytic production of hydrogen  

SciTech Connect

The invention relates to a cathode for the electrolytic production of hydrogen. The cathode comprises an active surface consisting of a metal oxide obtained by the thermal decomposition of a thermally decomposable compound of a metal chosen from amongst cobalt, iron, manganese or nickel. The cathode is particularly suitable for the electrolysis of aqueous sodium chloride solutions in cells with a permeable diaphragm.

Nicolas, E.

1983-07-19

213

Novel Composite Hydrogen-Permeable Membranes for Non-Thermal Plasma Reactors for the Decomposition of Hydrogen Sulfide. Annual Report, October 1, 2004-September 30, 2005.  

National Technical Information Service (NTIS)

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

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

2005-01-01

214

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

SciTech Connect

The self-discharge mechanism of nickel-hydrogen batteries using metal hydride anodes is 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 is 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 is found to improve the self-discharge characteristics.

Iwakura, C.; Kajiya, Y.; Yoneyama, H. (Dept. of Applied Chemistry, Osaka Univ., Suita, Osaka 565 (JP)); Sakai, T.; Oguro, K.; Ishikawa, H. (Government Industrial Research Institute, Osaka, Ikeda, Osaka 563 (JP))

1989-05-01

215

Effective metal dispersion in pyridinelike nitrogen doped graphenes for hydrogen storage  

NASA Astrophysics Data System (ADS)

We study the pyridinelike nitrogen-doped graphene (PNG) with dispersed transition metal (TM) atoms as a potential hydrogen storage medium using the pseudopotential density functional method. It is found that highly localized states near the Fermi level, which are derived from the nitrogen defects, contribute to strong TM bindings and favorable hydrogen adsorption in the PNG. The strong TM binding prevents the metal aggregation and improves the material stability. The hydrogen molecular binding energy in TM+PNG complex is shown to be optimistic for room temperature storage and release.

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

2008-01-01

216

Mechanism and kinetics of electrochemical hydrogen entry and degradation of metallic systems  

SciTech Connect

The purpose of this paper is to review recent advances in understanding the kinetics of the ever elusive and omnipresent hydrogen entry into metallic systems by multiple ways that cause numerous and frequently catastrophic degradation problems. The problem of hydrogen-induced damage and failures is interdisciplinary and varied. For example, in the cathodic protection of metals, in hydrogenation cells where metal electrocatalysts such as Ni are used, in hydrogen energy producing plants, and in environments where hydrogen sulfide gas is present as in petroleum refining, hydrogen absorption into metals causing degradation of their mechanical properties is the main concern. In closed systems, however, such as nuclear reactor cooling pipes, acid container systems, fuel cells, and so on, the production of H{sub 2} gas and bubbler formation is of great concern not only because of impedances and heat generation, but also because of the explosive properties of hydrogen. Very high pressures of H{sub 2} gas produced by acid corrosion reactions can deform or crack any material employed as a container.

Iyer, R.N.; Pickering, H.W. (Dept. of Materials Science and Engineering, Pennsylvania State Univ., University Park, PA (US))

1990-01-01

217

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

ERIC Educational Resources Information Center

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

de Berg, Kevin; Chapman, Ken

1996-01-01

218

Mixed metal oxide catalyst for producing low molecular weight hydrocarbons from carbon monoxide and hydrogen  

Microsoft Academic Search

Low molecular weight hydrocarbons are produced by contacting carbon monoxide and hydrogen at elevated temperatures and pressures with a catalyst comprising oxides of chromium, molybdenum and\\/or tungsten, copper, thorium or uranium and at least one alkali or alkaline earth metal. Catalysts are provided which are prepared by the procedure of adding an alkali or alkaline earth metal carbonate to an

M. F. Lemanski; W. R. Kliewer

1984-01-01

219

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

220

Selective etching of metallic single-wall carbon nanotubes with hydrogen plasma  

Microsoft Academic Search

We present Raman scattering and scanning tunnelling microscopy (STM) measurements on hydrogen plasma etched single-wall carbon nanotubes (SWNTs). Interestingly, both the STM and Raman spectroscopy show that the metallic SWNTs are dramatically altered and highly defected by the plasma treatment. In addition, structural characterizations show that metal catalysts are detached from the ends of the SWNT bundles. For semiconducting SWNTs

A. Hassanien; M. Tokumoto; P. Umek; D. Vrbanic; M. Mozetic; D. Mihailovic; P. Venturini; S Pejovnik

2005-01-01

221

Low Hydrogen Shielded Metal Arc Welding of Carbon Steel. Welding Procedure Specification.  

National Technical Information Service (NTIS)

Procedure WPS-114-ASME-1 is qualified under Section IX of the ASME Boiler and Pressure Vessel Code for low hydrogen shielded metal arc welding of carbon steels (P-1-1), in thickness range 0.125 to 1.5 in.; filler metal is E7018. (ERA citation 11:000914)

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

1985-01-01

222

Gas Tungsten Arc and Low Hydrogen Shielded Metal Arc Welding of Carbon Steel. Welding Procedure Specification.  

National Technical Information Service (NTIS)

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

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

1985-01-01

223

Sub-Nanostructured Non Transition Metal Complex Grids for Hydrogen Storage  

SciTech Connect

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

Dr. Orhan Talu; Dr. Surendra N. Tewari

2007-10-27

224

Hydrogen transport behavior of metal coatings for plasma facing components.  

National Technical Information Service (NTIS)

Plasma-facing components for experimental and commercial fusion reactor studies may include cladding or coatings of refractory metals like tungsten on metallic structural substrates such as copper, vanadium alloys and austenitic stainless steel. Issues of...

R. A. Anderl D. F. Holland G. R. Longhurst

1990-01-01

225

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

226

Hydrogen-induced surface metallization of SrTiO3(001).  

PubMed

Surface metallization of SrTiO3(001) by hydrogen adsorption is experimentally confirmed for the first time by photoemission spectroscopy and surface conductivity measurements. The metallic state is assigned to a quantized state in the space-charge layer induced by electron doping from hydrogen atoms. The measured two-dimensional (2D) conductivity is well above the 2D Ioffe-Regel limit indicating that the system is in a metallic conduction regime. The mean free path of the surface electron is estimated to be several nanometers at room temperature. PMID:22540498

D'Angelo, M; Yukawa, R; Ozawa, K; Yamamoto, S; Hirahara, T; Hasegawa, S; Silly, M G; Sirotti, F; Matsuda, I

2012-03-16

227

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

228

Predicting reaction equilibria for destabilized metal hydride decomposition reactions for reversible hydrogen storage  

SciTech Connect

Reversible storage of hydrogen still remains one of the biggest challenges for widespread use of hydrogen as a fuel. Light metal hydrides have high hydrogen content but are typically too thermodynamically stable. Destabilization of metal hydrides is an effective way to improve their thermodynamics. First principles calculations have proven to be effective for screening potential destabilized reactions, but these calculations have previously been limited to examining approximations for reaction enthalpies. We have used density functional theory calculations to calculate the reaction free energy and vant Hoff plots for a variety of potential destabilized metal hydride reactions. Our calculations suggest a multistage approach for efficiently screening new classes of metal hydrides prior to experimental studies.

Alapati, S.V.; Johnson, J.K.; Sholl, D.S.

2007-02-01

229

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

230

Single walled carbon nanotube-metal oxide nanocomposites for reversible and reproducible storage of hydrogen.  

PubMed

Composite material consisting of single walled carbon nanotubes (SWCNTs) and metal oxide nanoparticles has been prepared and their hydrogen storage performance is evaluated. Metal oxides such as tin oxide (SnO2), tungsten trioxide (WO3), and titanium dioxide (TiO2) are chosen as the composite constituents. The composites have been prepared by means of ultrasonication. Then, the composite samples are deposited on alumina substrates and at 100 C in a Sieverts-like hydrogenation setup. Characterization techniques such as transmission electron microscopy (TEM), Raman spectroscopy, scanning electron microscopy (SEM), powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, energy dispersive spectroscopy (EDS), CHN elemental analysis, and thermogravimetric (TG) measurements are used to analyze the samples at various stages of experiments. Hydrogen storage capacity of the composites namely, SWCNT-SnO2, SWCNT-WO3, and SWCNT-TiO2 are found to be 1.1, 0.9, and 1.3 wt %, respectively. Hydrogenated composite samples are stable at room temperature and desorption of hydrogen is found to be 100% reversible. Desorption temperature ranges and binding energy ranges of hydrogen have been measured from the desorption studies. The hydrogenation, dehydrogenation temperature, and binding energy of hydrogen fall in the recommended range of a suitable hydrogen storage medium applicable for fuel cell applications. Reproducibility and deterioration level of the composite samples have also been examined. PMID:24117025

Silambarasan, D; Surya, V J; Vasu, V; Iyakutti, K

2013-11-13

231

Development of a hydrogen catalytic heater for heating metal hydride hydrogen storage systems  

Microsoft Academic Search

This paper describes the design, fabrication and performance evaluation of a high efficiency, compact heater that uses the catalytic oxidation of hydrogen to provide heat to a hydrogen storage system. The heater was designed to transfer up to 30kW of heat from the catalytic reaction to the hydrogen storage system via a recirculating heat transfer fluid.The catalytic heater consists of

Terry A. Johnson; Michael P. Kanouff

232

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

SciTech Connect

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

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

1993-11-01

233

Hot Hydrogen Testing of Metallic Turbo Pump Materials.  

National Technical Information Service (NTIS)

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 material...

R. Zee B. Chin R. Inamdar

1993-01-01

234

Photobiotechnology: Algal hydrogen production and photoconductivity of metalized chloroplasts.  

National Technical Information Service (NTIS)

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

E. Greenbaum

1991-01-01

235

Hydrogen transport through V 85Ni 10M 5 alloy membranes  

Microsoft Academic Search

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

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

2011-01-01

236

A Comparative Study on Hydrogen Diffusion in Amorphous and Crystalline Metals Using a Molecular Dynamics Simulation  

NASA Astrophysics Data System (ADS)

A comparative study on hydrogen diffusion in amorphous and simple crystalline structures has been carried out using molecular dynamics simulations. The Cu-Zr bulk metallic glass (BMG) system is selected as the model material and a modified embedded-atom method (MEAM) interatomic potential for the Cu-Zr-H ternary system is developed for the atomistic simulation. It is found that the diffusivity of hydrogen in amorphous alloys is lower than that in open structured crystals but higher than that in close-packed crystals. The hydrogen diffusion in amorphous alloys is strongly hydrogen concentration dependent compared to crystals, increasing as the hydrogen content increases, and the Arrhenius plot of hydrogen diffusion in amorphous alloys shows an upward curvature. The reasons to rationalize all the findings are discussed based on the variety of energy state and migration energy barrier for interstitial sites in amorphous alloys.

Lee, Byeong-Moon; Lee, Byeong-Joo

2014-06-01

237

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

238

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

PubMed

Batch tests and column tests were performed to determine the design factors for permeable reactive barriers (PRBs) against the contaminated groundwater by ammonium and heavy metals. Clinoptilolite, one of the natural zeolites having excellent cation exchange capacity (CEC), was chosen as the reactive material. In the batch tests, the reactivity of clinoptilolite to ammonium, lead, and copper was examined by varying the concentration of cations and the particle size of clinoptilolite. One gram of clinoptilolite showed removal efficiencies of more than 80% against those contaminants in all cases except in very high initial concentrations of ammonium (80 ppm) and copper (40 ppm). The effect of particle size of clinoptilolite was not noticeable. In the column tests, permeability was examined using a flexible-wall permeameter by varying particle sizes of clinoptilolite. When the washed clinoptilolite having the diameter of 0.42-0.85 mm was mixed with Jumunjin sands in 20:80 ratio (w/w), the highest permeability of 2 x 10(-3) to 7 x 10(-4)cm/s was achieved. The reactivity and the strength property of the mixed material were investigated using a fixed-wall column, having eight sampling ports on the wall, and the direct shear test, respectively. Clinoptilolite was found to be a suitable material for PRBs against the contaminated groundwater with ammonium and/or heavy metals. PMID:12409239

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

2002-11-11

239

First-principles pseudopotential calculations for hydrogen in 4d transition metals. II. Vibrational states for interstitial hydrogen isotopes  

Microsoft Academic Search

For pt.I see ibid. vol.4, p.5189 (1992). In this second part of the authors' first-principles study of hydrogen in transition metals within the framework of the Born-Oppenheimer and the local density-functional approximations, the mixed-basis pseudopotential method, which was outlined in the first part, is applied to calculate total energies and internal forces in PdnH supercells with n

C. Elsasser; K. M. Ho; C. T. Chan; M. Fahnle

1992-01-01

240

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

241

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

242

SPEEKzirconium hydrogen phosphate composite membranes with low methanol permeability prepared by electro-migration and in situ precipitation  

Microsoft Academic Search

Sulfonated poly(ether ether ketone) (SPK)zirconium hydrogen phosphate (ZrP) composite membranes were prepared by electro-driven migration of Zr4+ and simultaneous in situ precipitation of ZrP using phosphoric acid under different electrical gradient, in order to avoid loss in its mechanical stability. Degree of sulfonation was estimated from 1H NMR and ion-exchange capacity study that was found to be 61% and 57%,

Bijay P. Tripathi; Vinod K. Shahi

2007-01-01

243

Metal sulfite\\/sulfate reactions in thermochemical hydrogen cycles  

Microsoft Academic Search

The thermochemical cycles which have been most extensively developed all involve the thermal decomposition of sulfuric acid which is corrosive. Metal sulfate cycles have been studied as a means of circumventing handling corrosive mixtures at high temperatures. However, these metal sulfate cycles still use an electrochemical step to produce H. Alternate H producing steps to be used in conjunction with

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

1980-01-01

244

Neutron scattering investigation of the hydrogen dynamics in transition metals  

NASA Astrophysics Data System (ADS)

A study by inelastic neutron scattering of the hydrogen vibrations in titanium-based alloys containing vanadium and carbon is reported. The measurements performed at two temperatures 5 and 300K are analyzed in terms of the phonon density of states, g(??). A good separation of the optic and acoustic spectrum is observed. In the range of very low temperatures such as 5K a drastic decrease of the spectral intensity has to be noted. A clear feature in the energy loss interval is observed at ??=1.53meV. This excitation could be assigned to a resonant vibration mode of the hydrogen in the host lattice. The intensity, both of the optic, acoustic and resonant modes as well as of the quasi-elastic scattering decrease in a proportional way with the hydrogen content in the studied samples.

Padureanu, I.; Aranghel, D.; Kahn, R.; Radulescu, A.; Sumin, V. V.

2004-07-01

245

Reducing Diffusible Hydrogen Contents of Shielded Metal Arc Welds Through Addition of Flux-Oxidizing Ingredients  

NASA Astrophysics Data System (ADS)

This investigation examined the feasibility of using flux modification in the form of the addition of oxidizing ingredients to reduce the as-deposited hydrogen content of basic-type shielded metal arc welds. Additions of up to 16.3% micaceous iron oxide (MIO) to the flux formulation of an E7018-1 type electrode lowered the diffusible weld hydrogen content by approximately 70%. This can be attributed to the formation of oxygen, which lowers the partial pressure of hydrogen in the arc atmosphere, and the reaction of FeO (formed on dissociation of MIO) with hydrogen. The partitioning of deoxidizing elements (manganese and silicon) between the weld metal and slag on addition of MIO to the flux coating was also examined, but the influence of flux additions on the weld mechanical properties and the electrode operating characteristics was not evaluated during the course of this investigation.

Du Plessis, J.; Du Toit, M.

2008-02-01

246

Modeling surface effects on hydrogen permeation in metals  

NASA Astrophysics Data System (ADS)

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

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

1991-05-01

247

Modeling of hydrogen-assisted ductile crack propagation in metals and alloys  

Microsoft Academic Search

This paper presents a finite element study of the hydrogen effect on ductile crack propagation in metals and alloys by linking\\u000a effects at the microstructural level (i.e., void growth and coalescence) to effects at the macro-level (i.e., bulk material\\u000a deformation around a macroscopic crack). The purpose is to devise a mechanics methodology to simulate the conditions under\\u000a which hydrogen enhanced

D. C. Ahn; P. Sofronis; R. Dodds Jr

2007-01-01

248

Influence of metal ions on hydrogenation of o-chloronitrobenzene over platinum colloidal clusters  

Microsoft Academic Search

Hydrogenation of o-chloronitrobenzene has been studied in methanol at 303 K and atmospheric pressure over polyvinylpyrrolidone-stabilized platinum colloidal clusters. The catalytic properties of platinum clusters for the hydrogenation of o-chloronitrobenzene to o-chloroaniline were remarkably affected by the metallic cations added. Among these cations, the most favorable influence on activity and selectivity was obtained when Ni2+ ions were used as modifier.

Xinlin Yang; Hanfan Liu

1997-01-01

249

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

250

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

251

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

PubMed

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

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

2013-03-28

252

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

253

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

NASA Technical Reports Server (NTRS)

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

Mchenry, E. J.

1977-01-01

254

Hydrogen Permeation through Metal Enhanced by Low Temperature Plasma  

Microsoft Academic Search

Solving the problem of plasma wall interaction is important for developing the fusion reactor. One of the problems involved with this interaction is plasma driven permeation (PDP), the phenomenon of large hydrogen permeation by plasma. This report focuses on previous studies of PDP, and reviews the abstracts of many experimental and theoretical works regarding PDP. In addition, this report introduces

Masayuki Takizawa; Kiyoshi Kiuchi; Hidetoshi Ishizuka; Yasunori Sougawa; Takuya Endo; Yasuhiko Fujii

1999-01-01

255

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

256

Laplace DLTS investigation of transition metal-hydrogen complexes in germanium  

NASA Astrophysics Data System (ADS)

High-resolution Laplace DLTS technique has been used to examine fine structures in the carrier emission processes hidden in the broad conventional DLTS peaks recorded in germanium samples, doped by several transition metals - Ni, Cr and Fe. These structures are found to be correlated with the acceptors, related to mentioned impurities, and also with possible presence of hydrogen-related defects. A link explaining interaction of transition metals with hydrogen due to the applied chemical treatment during sample preparation process is revealed and compared to what is known in silicon.

Gurimskaya, Y.; Mesli, A.

2014-02-01

257

Metal/Hydrogen Energy Storage: Selected Technical Issues.  

National Technical Information Service (NTIS)

The report illustrates a rational approach for modeling and characterizing porous electrodes. Although the authors selected the metal hydride system for this purpose, such an approach is applicable to other systems as well and is an example of current tre...

P. A. Mosier-Boss S. J. Szpak

1994-01-01

258

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

259

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

260

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

261

Physical origin of hydrogen-adsorption-induced metallization of the SiC surface: n-type doping via formation of hydrogen bridge bond.  

PubMed

We perform first-principles calculations to explore the physical origin of hydrogen-induced semiconductor surface metallization observed in beta-SiC(001)-3 x 2 surface. We show that the surface metallization arises from a novel mechanism of n-type doping of surface band via formation of hydrogen bridge bonds (i.e., Si-H-Si complex). The hydrogen strengthens the weak Si-Si dimers in the subsurface by forming hydrogen bridge bonds, and donates electron to the surface conduction band. PMID:16384009

Chang, Hao; Wu, Jian; Gu, Bing-Lin; Liu, Feng; Duan, Wenhui

2005-11-01

262

On hydrogen transport and edge plasma modeling of liquid-metal divertors  

SciTech Connect

The steady-state operational conditions for large tokamaks impose high performance requirements that cast suspicion on the employment of conventional solid surface divertors. Flowing liquid-metal divertors are thus being considered as an alternative. A preliminary evaluation is made of some aspects of this concept. To understand the hydrogen (i.e., deuterons and tritons) recycling behavior in liquid metals, the transport and chemistry aspects of the hydrogen/liquid-metal interaction are investigated, including hydrogen gettering, tritium inventory, and blistering caused by hydrogen bubble eruptions. It is shown that when operating in the high-recycling model (i.e., as the liquid metal is filled with deuterons and tritons, one implanting ion will immediately cause the emission of one neutral particle), lithium would have a large tritium inventory. Gallium, on the other hand, does not have the same problem because of its negligible hydrogen solubility and the decomposition of its hydrides in the temperature range of interest. However, to avoid blistering, the flow speed of a gallium neutralizer has to be high. An edge plasma simulation model is briefly introduced, and its outcome for the high-recycling liquid-metal (lithium and gallium) divertors is presented. This model gives more realistic predictions of plasma temperature than some of the existing simulation models. Results of this model show that denser and cooler edge plasmas can be achieved by liquid-metal divertors than by conventional stationary surface divertors. Evaporation and sputtering of liquid-metal divertors are shown not to be as serious a problem as might be suspected at first glance. 22 refs., 2 figs., 1 tab.

Chungpin Liao; Kazimi, M.S.; Meyer, J.E. (Massachusetts Inst. of Technology, Cambridge (United States))

1993-03-01

263

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

SciTech Connect

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

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

1999-02-01

264

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

265

Study on the electronic structure and hydrogen adsorption by transition metal decorated single wall carbon nanotubes  

NASA Astrophysics Data System (ADS)

The ground state geometry and electronic structure of various 4d transition metal (TM) atom (Y, Zr, Nb and Mo) decorated single wall carbon nanotubes (SWCNTs) are obtained using density functional theory and the projector augmented wave (PAW) method. We found a systematic change in the adsorption site of the transition metal atom with increasing number of d electrons. We also predicted that Y and Zr decorated SWCNTs are metallic whereas Nb and Mo decorated SWCNTs are semiconducting. From detailed electronic structure and Bader charge analysis we found that the systematic variation of the adsorption site with the number of d electrons is related to the decreasing amount of charge transfer from the TM atom to the SWCNT along the 4d series. We have also studied the hydrogen adsorption capabilities of these decorated SWCNTs to understand the role of transition metal d electrons in binding the hydrogen molecules to the system. We found that metallic SWCNT + TM systems are better hydrogen adsorbers. We showed that the hydrogen adsorption by a TM decorated SWCNT will be maximum when all the adsorptions are physisorption and that the retention of magnetism by the system is crucial for physisorption.

Modak, P.; Chakraborty, Brahmananda; Banerjee, S.

2012-05-01

266

Ultradense hydrogen in astrophysics, high-pressure metal physics and fusion studies  

SciTech Connect

Phase diagrams of hydrogen are constructed through first-principles calculations of the equations of state for metallic and insulator phases. On the bases of these theories of the equations of state and the electric resistivity, it is shown that the results of recent shock-metallization experiments can be consistently interpreted in terms of first-order metal-insulator transitions, involving discontinuous changes in density, entropy and enthalpy. The first-order transitions then predict a discontinuous distribution of density and resistivity near the Jovian surface, with a large magnetic Reynolds number enough to sustain prominent magnetic activities. A phase diagram for freezing and ferromagnetic transitions provides a basic account of strong magnetization observed in magnetic white dwarfs. Feasibility of a novel scheme of fusion studies in ultradense metallic hydrogen is examined in light of these experimental and theoretical developments.

Ichimaru, Setsuo [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching, Germany and Department of Physics, University of Tokyo, Hongo, Tokyo 113 (Japan); Kitamura, Hikaru [Institute for Solid State Physics, University of Tokyo, Roppongi, Tokyo 106 (Japan)

1998-02-20

267

Comparison of metal and carbon catalysts for hydrogen production by methane decomposition  

Microsoft Academic Search

The COx-free hydrogen production by decomposition of methane was carried out over metal-free carbons and bulk and supported metal catalysts. Catalysts based on Ni or Fe (oxides, spinels and ex-hydrotalcite mixed oxides) and carbon-catalysts of different types (carbon black, activated carbon, carbon nanotubes and graphite) have been used and the performance of both different kinds of catalyst compared in the

R. Guil-Lopez; J. A. Botas; J. L. G. Fierro; D. P. Serrano

2011-01-01

268

High Flux Metallic Membranes for Hydrogen Recovery and Membrane Reactors  

SciTech Connect

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

Buxbaum, Robert

2010-06-30

269

DWPF Hydrogen Generation Study-Form of Noble Metal SRAT Testing  

SciTech Connect

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

Bannochie, C

2005-09-01

270

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

SciTech Connect

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

Koopman, D

2008-06-25

271

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

272

Colloidal metal dispersions as catalysts for selective surface hydrogenation of biomembranes, 1. Preparation and characterization of palladium catalysts  

Microsoft Academic Search

Paliadium sols containing largely uniform, nanosize metallic, particles stabilized by poly(N-vinyl-2-pyrrolidone) were found to be active microheterogeneous catalysts for hydrogenation of water soluble olefinic substrates as well as of unsaturated lipid dispersions. The same metallic particles were supported on the surface of crosslinked insoluble poly(N-vinyl-2-pyrrolidone) and served as easily removable macroheterogeneous hydrogenation catalysts.

Levente Ndasdi; Ibolya Horvth; Lszl Vgh; Sndor Benk?; Ferenc Jo

1996-01-01

273

Enhanced half-metallicity in the zigzag graphene nanoribbons by adsorption of the zigzag hydrogen fluoride molecular chains  

NASA Astrophysics Data System (ADS)

A comprehensive theoretical study of the half-metallicity in the zigzag graphene nanoribbons (ZGNRs) by adsorption of the zigzag hydrogen fluoride chains was presented. The ZGNR by adsorption of the hydrogen fluoride chains could be half-metallic when a critical length of the hydrogen fluoride chain is achieved on the ZGNR at low temperature. It was found that the strong dipole moments of the hydrogen fluoride chains act as the constant electric field. Our results suggest a huge possibility in spintronics device applications for achieving half-metallicity in the ZGNRs without the excessively high external electric fields.

Gong, Xue; Zhang, Jialing; Xu, Bo.; Xia, Yidong; Yin, Jiang; Liu, Zhiguo

2014-06-01

274

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

Microsoft Academic Search

Large amounts of hydrogen and helium are generated in structural metals in accelerator-driven systems. It is shown that under certain conditions, hydrogen can be stored in irradiated nickel and stainless steels at levels strongly in excess of that predicted by Sieverts law. These conditions are first, the availability of hydrogen from various radiolytic and environmental sources and second, the formation

Francis A. Garner; Edward P. Simonen; Brian M. Oliver; Lawrence R. Greenwood; M. L. Grossbeck; W. G. Wolfer; P. M. Scott

2006-01-01

275

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

Microsoft Academic Search

Large amounts of hydrogen and helium are generated in structural metals in accelerator-driven systems. It is shown that under certain conditions, hydrogen can be stored in irradiated nickel and stainless steels at levels strongly in excess of that predicted by Sieverts' law. These conditions are first, the availability of hydrogen from various radiolytic and environmental sources and second, the formation

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

2006-01-01

276

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

Microsoft Academic Search

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

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

2012-01-01

277

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

SciTech Connect

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

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

2005-07-15

278

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

279

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

PubMed

Passivation of semiconductor surfaces against chemical attack can be achieved by terminating the surface-dangling bonds with a monovalent atom such as hydrogen. Such passivation invariably leads to the removal of all surface states in the bandgap, and thus to the termination of non-metallic surfaces. Here we report the first observation of semiconductor surface metallization induced by atomic hydrogen. This result, established by using photo-electron and photo-absorption spectroscopies and scanning tunnelling techniques, is achieved on a Si-terminated cubic silicon carbide (SiC) surface. It results from competition between hydrogen termination of surface-dangling bonds and hydrogen-generated steric hindrance below the surface. Understanding the ingredient for hydrogen-stabilized metallization directly impacts the ability to eliminate electronic defects at semiconductor interfaces critical for microelectronics, provides a means to develop electrical contacts on high-bandgap chemically passive materials, particularly for interfacing with biological systems, and gives control of surfaces for lubrication, for example of nanomechanical devices. PMID:12690399

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

2003-04-01

280

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

PubMed

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

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

2008-12-30

281

The electronic properties of transition metal hydrogen complexes in silicon  

Microsoft Academic Search

The electrical levels of various combinations of transition metal-Hn defects in Si are calculated using spin-polarised local density functional cluster theory with an empirical correction. The shifts of these levels with H can be understood through a displacement and splitting of the gap t2 manifold of states due to the impurity. Passive defects are identified.

R. Jones; A. Resende; S. berg; P. R. Briddon

1999-01-01

282

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

NASA Technical Reports Server (NTRS)

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

Johnson, L. D.

1967-01-01

283

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

284

A sensitive method for measuring surface recombination of hydrogen isotopes implanted into metals  

Microsoft Academic Search

Under steady-state conditions hydrogen implanted into a metal foil will either be reemitted through the irradiated surface or diffuse through the foil to the opposite side. Whenever diffusion is sufficiently fast, the reemission through the upstream surface is limited by the recombination process, and the permeation rate is correspondingly enhanced. Providing an effective ``sink'', in the form of a thin

P. Brgesen; B. M. U. Scherzer; W. Mller

1985-01-01

285

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

Microsoft Academic Search

Using closed-orbit theory, we study the classical motion and calculate the photoabsorption spectra and recurrence spectra of the Rydberg hydrogen atom near a metal surface. The results show that when the atom-surface distance is close to the critical value dc, the number of the closed orbits is the greatest. For d > dc, with the increase of the distance d,

Dehua Wang; M. L. Du; Shenglu Lin

2006-01-01

286

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

National Technical Information Service (NTIS)

Correlation energies for simple-cubic metallic hydrogen are calculated using random-phase-approximation (RPA) methods. Hartree-Fock Bloch functions for the real lattice, including those for excited bands, were used as zeroth-order states. About 60 percent...

H. J. Monkhorst J. Oddershede

1973-01-01

287

Storage of Hydrogen in the Form of Metal Hydrides: An Application to Thermal Engines.  

National Technical Information Service (NTIS)

The possibility of using LaNi56, FeTiH2, or MgH2 as metal hydride storage systems for hydrogen fueled automobile engines is discussed. Magnesium copper and magnesium nickel hydrides studies indicate that they provide more stable storage systems than pure ...

C. Gales P. Perroud

1981-01-01

288

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

NASA Technical Reports Server (NTRS)

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

Jacobi, N.; Zmuidzinas, J. S.

1974-01-01

289

Amperometric Hydrogen Peroxide Sensors with Multivalent Metal Oxide-Modified Electrodes for Biomedical Analysis  

Microsoft Academic Search

An overview of publications (1991-2007) on amperometric sensors for hydrogen peroxide (H2O2) is presented, with emphasis on carbon electrodes modified with multivalent-metal oxides as electro-catalysts and applications\\u000a in biosensors.

Tesfaye Waryo; Petr Kotzian; Sabina Begi?; Petra Bradizlova; Negussie Beyene; Priscilla Baker; Boitumelo Kgarebe; Emir Turkui?; Emmanuel Iwuoha; Karel Vyt?as; Kurt Kalcher

290

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

291

Efficient Photoelectrochemical Hydrogen Generation Using Heterostructures of Si and Chemically Exfoliated Metallic MoS2.  

PubMed

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

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

2014-06-18

292

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

293

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.

294

Self-diffusion and macroscopic diffusion of hydrogen in amorphous metals from first-principles calculations  

NASA Astrophysics Data System (ADS)

Diffusion of interstitial hydrogen plays a key role in potential uses for amorphous metals as membranes for hydrogen purification. We show how first principles-based methods can be used to characterize diffusion of interstitial H in amorphous metals using amorphous Fe3B as an example. Net transport of interstitial H is governed by the transport diffusion coefficient that appears in Fick's law. This diffusion coefficient is strongly dependent on the interstitial concentration, and is not equal to the self-diffusion coefficient except at dilute interstitial concentrations. Under conditions of practical interest, the concentrations of interstitial H in amorphous metals are nondilute so methods to determine the transport diffusion coefficient must be used if net mass transport is to be described. We show how kinetic Monte Carlo simulations of interstitial H diffusion that use rates derived from first-principles calculations can be used to assess both self- and transport diffusion coefficients of H in amorphous metals. These methods will be helpful in efforts to screen amorphous metal alloys as potential membranes for hydrogen purification.

Hao, Shiqiang; Sholl, David S.

2009-06-01

295

Process for the purification of solutions containing alkali metal carbonate, sulphate, hydroxide or possibly hydrogen carbonate, and one at least of the metals vanadium, uranium and molybdenum  

Microsoft Academic Search

A process is claimed for extracting molybdenum from aqueous solutions containing alkali metal carbonate, sulphate, hydroxide or hydrogen carbonate and, primarily, one at least of the metals belonging to the group formed by vanadium, uranium and molybdenum, in the form of alkali metal salts, and mineral and\\/or organic impurities. The said solutions result from an ore attack cycle and are

P. Maurel; F. Nicolas

1983-01-01

296

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

NASA Astrophysics Data System (ADS)

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

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

1981-09-01

297

Metal-mediated DNA base pairing: alternatives to hydrogen-bonded Watson-Crick base pairs.  

PubMed

With its capacity to store and transfer the genetic information within a sequence of monomers, DNA forms its central role in chemical evolution through replication and amplification. This elegant behavior is largely based on highly specific molecular recognition between nucleobases through the specific hydrogen bonds in the Watson-Crick base pairing system. While the native base pairs have been amazingly sophisticated through the long history of evolution, synthetic chemists have devoted considerable efforts to create alternative base pairing systems in recent decades. Most of these new systems were designed based on the shape complementarity of the pairs or the rearrangement of hydrogen-bonding patterns. We wondered whether metal coordination could serve as an alternative driving force for DNA base pairing and why hydrogen bonding was selected on Earth in the course of molecular evolution. Therefore, we envisioned an alternative design strategy: we replaced hydrogen bonding with another important scheme in biological systems, metal-coordination bonding. In this Account, we provide an overview of the chemistry of metal-mediated base pairing including basic concepts, molecular design, characteristic structures and properties, and possible applications of DNA-based molecular systems. We describe several examples of artificial metal-mediated base pairs, such as Cu(2+)-mediated hydroxypyridone base pair, H-Cu(2+)-H (where H denotes a hydroxypyridone-bearing nucleoside), developed by us and other researchers. To design the metallo-base pairs we carefully chose appropriate combinations of ligand-bearing nucleosides and metal ions. As expected from their stronger bonding through metal coordination, DNA duplexes possessing metallo-base pairs exhibited higher thermal stability than natural hydrogen-bonded DNAs. Furthermore, we could also use metal-mediated base pairs to construct or induce other high-order structures. These features could lead to metal-responsive functional DNA molecules such as artificial DNAzymes and DNA machines. In addition, the metallo-base pairing system is a powerful tool for the construction of homogeneous and heterogeneous metal arrays, which can lead to DNA-based nanomaterials such as electronic wires and magnetic devices. Recently researchers have investigated these systems as enzyme replacements, which may offer an additional contribution to chemical biology and synthetic biology through the expansion of the genetic alphabet. PMID:22452649

Takezawa, Yusuke; Shionoya, Mitsuhiko

2012-12-18

298

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

Schlke, Mark; Paulus, Hubert; Lammers, Martin; Kiss, Gbor; Rti, Ferenc; Mller, Karl-Heinz

2008-03-01

299

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

SciTech Connect

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

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

1990-11-09

300

Thermomechanics of a metal hydride-based hydrogen tank  

NASA Astrophysics Data System (ADS)

In this paper, a thermodynamical model of a porous media made of one or two solid phases ? and ? (depending on the hydrogen concentration) and one gas phase H2 is presented. As an extension of previous works performed by Gondor and Lexcellent (Int J Hydrog Energy 34(14):5716-5725, doi:10.1016/j.ijhydene.2009.05.070, 2009), our attention is paid to the identification of the vectorial displacement and by consequence to the stress and strain states in every point of the tank. This study allows a safe design of the reservoir. In front of the complexity of the problem to solve, a synthesis and a table of unknowns, constants, and parameters will ease the reader understanding. The problem is restricted to the isotropic elastic behavior of the solid phases. A great ingredient of the investigation is the phase transformation between the two phases ? and ?.

Lexcellent, Christian; Gay, Guillaume; Chapelle, David

2014-05-01

301

Comparison of integral equations for correlations in liquid metallic hydrogen  

NASA Astrophysics Data System (ADS)

Dharma-Wardana and Perrot (DWP, 1982) calculated the radial distribution functions (RDFs) of hydrogen plasma by using an integral equation derived from the density-functional formalism with the local density approximation. The contribution from the electron-proton correlation was neglected in the effective electron-proton and proton-proton interactions, and the exchange-correlation effect of the electrons in the presence of ions was approximated by that of the jellium model. Here, the DWP equation is improved to include the contribution of electron-proton correlation, and the conventional pseudopotential theory is extended to take account of the nonlinear effect. This leads to extension of the method of Ichimaru et al. (IMTY, 1985) for calculating the RDFs of dense plasmas to include the effect of electron-proton local field correction. The extended and original equations are solved, and the results from the equations are compared with those from the quantal hypernetted chain equation.

Chihara, J.

1986-04-01

302

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

303

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

304

Interaction of hydrogen with metal sulfide catalysts - direct observation of spillover  

SciTech Connect

A combination of controlled-atmosphere electron microscopy and in-situ electron diffraction techniques have been used to study the manner by which certain metal sulfides interact with 0.2 Torr hydrogen. In these experiments single crystal graphite was used as a probe material since its reactivity in both molecular and atomic hydrogen is well characterized. When the metal sulfide was in direct contact or physically separated from the graphite probe, pitting of the basal plane regions was observed even at room temperature. This unusual behavior is believed to result from the action of atomic hydrogen which is produced via reversible dissociation of molecular hydrogen on the metal sulfide particles. These species are extremely reactive towards the [pi]-electrons present on the graphite basal planes and this action leads to the creation of pits. At the low pressures used in this work, it is clear that the atomic species can migrate not only by surface diffusion processes (spillover) but also by transport through the gas phase. 30 refs., 7 figs., 1 tab.

Rodriguez, N.M.; Baker, R.T.K. (Auburn Univ., AL (United States))

1993-04-01

305

In Situ Diffraction Study of Catalytic Hydrogenation of VO2: Stable Phases and Origins of Metallicity.  

PubMed

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

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

2014-06-01

306

Ionic hydrogenations of hindered olefins at low temperature. Hydride transfer reactions of transition metal hydrides  

SciTech Connect

Sterically hindered olefins can be hydrogenated at -50[degree]C in dichloromethane using triflic acid (CF[sub 3]SO[sub 3]H) and a hydride donor. Mechanistic studies indicate that these reactions proceed by hydride transfer to the carbenium ion that is formed by protonation of the olefin. Olefins that form tertiary carbenium ions upon protonation are hydrogenated in high yields (90-100%). Styrenes generally produce lower yields of hydrogenated products (50-60%). Suitable hydride donors include HSiE[sub 3] and several transition metal carbonyl hydrides HW(CO)[sub 3]Cp, HW(CO)[sub 3]Cp[sup +], HMo-(CO)[sub 3]Cp, HMn(CO)[sub 5], HRe(CO)[sub 3], and HO[sub 3](CO)[sub 1]Cp*; Cp = [eta][sup 5]-C[sub 3]H[sub 5+], Cp* = [eta][sup 5]-C[sub 5]Me[sub 5]. A characteristic that is required for transition metal hydrides to be effective is that the cationic dihydrides (or dihydrogen complexes) that result from their protonation must have sufficient acidity to transfer a proton to the olefin, as well as sufficient thermal stability to avoid significant decomposition on the time scale of the hydrogenation reaction. Metal hydrides that fall due to insufficient stability of their protonated forms include HMo(CO)[sub 2](PPH[sub 3])Cp, HMo(CO)[sub 3]Cp*, and HFe(CO)[sub 2]Cp*. 62 refs., 2 tabs.

Bullock, R.M.; Song, J.S. (Brookhaven National Lab., Upton, NY (United States))

1994-09-21

307

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

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

308

Metal complexes with varying intramolecular hydrogen bonding networks  

PubMed Central

Alfred Werner described the attributes of the primary and secondary coordination spheres in his development of coordination chemistry. To examine the effects of the secondary coordination sphere on coordination chemistry, a series of tripodal ligands containing differing numbers of hydrogen bond (H-bond) donors were used to examine the effects of H-bonds on Fe(II), Mn(II)acetato, and Mn(III)OH complexes. The ligands containing varying numbers of urea and amidate donors allowed for systematic changes in the secondary coordination spheres of the complexes. Two of the Fe(II) complexes that were isolated as their Bu4N+ salts formed dimers in the solid-state as determined by X-ray diffraction methods, which correlates with the number of H-bonds present in the complexes (i.e., dimerization is favored as the number of H-bond donors increases). Electron paramagnetic resonance (EPR) studies suggested that the dimeric structures persist in acetonitrile. The Mn(II) complexes were all isolated as their acetato adducts. Furthermore, the synthesis of a rare Mn(III)OH complex via dioxygen activation was achieved that contains a single intramolecular H-bond; its physical properties are discussed within the context of other Mn(III)OH complexes.

Lacy, David C.; Mukherjee, Jhumpa; Lucas, Robie L.; Day, Victor W.; Borovik, A.S.

2013-01-01

309

Radiation-enhanced exhalation of hydrogen out of stainless steel  

Microsoft Academic Search

The state and diffusion of hydrogen in solids have been studied extensively1,2, and the transport of hydrogen and its isotopes in metals has been found to involve classical diffusion and quantum effects such as tunnelling migration and small polaron hopping3,4. The permeability and diffusion of hydrogen isotopes, particularly tritium (T), have been studied in a D-T fusion device5. Diffusion of

M. Ikeya; T. Miki; M. Touge

1981-01-01

310

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

SciTech Connect

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

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

2011-03-15

311

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

PubMed Central

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

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

2013-01-01

312

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

313

Low-temperature metallic liquid hydrogen: an ab-initio path-integral molecular dynamics perspective  

NASA Astrophysics Data System (ADS)

Experiments and computer simulations have shown that the melting temperature of solid hydrogen drops with pressure above about 65 GPa, suggesting that a low temperature liquid state might exist. It has also been suggested that this liquid state might be non-molecular and metallic, although evidence for such behaviour is lacking. Using a combination of ab initio path-integral molecular dynamics and the two-phase methods, we have simulated the melting of solid hydrogen under finite temperatures. We found an atomic solid phase from 500 to 800 GPa which melts at 200 K. Beyond this and up to pressures of 1,200 GPa a metallic atomic liquid is stable at temperatures as low as 50 K. The quantum motion of the protons is critical to the low melting temperature in this system as ab initio simulations with classical nuclei lead to a considerably higher melting temperature of 300 K across the entire pressure range considered.

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

2013-03-01

314

Study on monatomic fraction improvement with alumina layer on metal electrode in hydrogen plasma ion source  

SciTech Connect

A high monatomic beam fraction is an important factor in a hydrogen ion source to increase the application efficiency. The monatomic fraction of hydrogen plasmas with different plasma electrode materials is measured in a helicon plasma ion source, and aluminum shows the highest value compared to that with the other metals such as copper and molybdenum. Formation of an aluminum oxide layer on the aluminum electrode is determined by XPS analysis, and the alumina layer is verified as the high monatomic fraction. Both experiments and numerical simulations conclude that a low surface recombination coefficient of the alumina layer on the plasma electrode is one of the most important parameters for increasing the monatomic fraction in hydrogen plasma ion sources.

Jung, Bong-Ki; Chung, Kyoung-Jae; Dang, Jeong-Jeung; Hwang, Y. S. [Department of Nuclear Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of)

2012-02-15

315

Hydrogen-induced metallicity and strengthening of MoS2  

NASA Astrophysics Data System (ADS)

The performed DFT calculations for MoS2 layers with adsorbed and intercalated hydrogen indicate that the atomic hydrogen monolayer makes the surface metallic. The physisorbed H2 does not affect electronic properties of the MoS2 monolayer, which remains a direct gap semiconductor. Due to forming S-H-S bonds, hydrogen atoms, intercalated into the space between MoS2 layers, increase the interlayer interaction from 0.12 eV to 0.60 eV. The related increase of the stiffness of the Mo-H-Mo layered system is of a primary importance for the interpretation of images of the surface obtained with the Ultrasonic Force Microscopy (Kolosov and Yamanaka, 1993) [42].

Yakovkin, I. N.; Petrova, N. V.

2014-04-01

316

Mechanical Tunability via Hydrogen Bonding in Metal-Organic Frameworks with the Perovskite Architecture.  

PubMed

Two analogous metal-organic frameworks (MOFs) with the perovskite architecture, [C(NH2)3][Mn(HCOO)3] (1) and [(CH2)3NH2][Mn(HCOO)3] (2), exhibit significantly different mechanical properties. The marked difference is attributed to their distinct modes of hydrogen bonding between the A-site amine cation and the anionic framework. The stronger cross-linking hydrogen bonding in 1 gives rise to Young's moduli and hardnesses that are up to twice those in 2, while the thermal expansion is substantially smaller. This study presents clear evidence that the mechanical properties of MOF materials can be substantially tuned via hydrogen-bonding interactions. PMID:24815319

Li, Wei; Thirumurugan, A; Barton, Phillip T; Lin, Zheshuai; Henke, Sebastian; Yeung, Hamish H-M; Wharmby, Michael T; Bithell, Erica G; Howard, Christopher J; Cheetham, Anthony K

2014-06-01

317

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

318

Molecular and dissociative adsorption of multiple hydrogen molecules on transition metal decorated C60  

Microsoft Academic Search

Recently we have predicted [Phys. Rev. Lett. 94, 175501 (2005)] that Ti-decorated carbon nanotubes can adsorb up to 8-wt. % hydrogen at ambient conditions. Here we show that a similar phenomenon occurs in light transition-metal decorated C60 . While Sc and Ti prefer the hexagon (H) sites with a binding energy of 2.1 eV , V and Cr prefer double-bond

T. Yildirim; Jorge iguez; S. Ciraci

2005-01-01

319

Effective heat transfer in a metal-hydride-based hydrogen separation process  

Microsoft Academic Search

This paper presents the results of experimental and analytical study of the thermal cycling absorption process (TCAP); which is a metal-hydride-based hydrogen separation system configured as a helical shell-and-tube heat exchanger. The column (tube side) is packed with Palladium deposited on kieselguhr (Pd\\/k). This packed column is thermally cycled by a hot and cold nitrogen gas on its exterior surface

William H Fleming; Jamil A Khan; Curtis A Rhodes

2001-01-01

320

First-principles study of hydrogen adsorption in metal-doped COF10  

Microsoft Academic Search

Covalent organic frameworks (COFs), due to their low-density, high-porosity, and high-stability, have promising applications in gas storage. In this study we have explored the potential of COFs doped with Li and Ca metal atoms for storing hydrogen under ambient thermodynamic conditions. Using density functional theory we have performed detailed calculations of the sites Li and Ca atoms occupy in COF-10

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

2010-01-01

321

First-principles study of hydrogen adsorption in metal-doped COF10  

Microsoft Academic Search

Covalent organic frameworks (COFs), due to their low-density, high-porosity, and high-stability, have promising applications in gas storage. In this study we have explored the potential of COFs doped with Li and Ca metal atoms for storing hydrogen under ambient thermodynamic conditions. Using density functional theory we have performed detailed calculations of the sites Li and Ca atoms occupy in COF-10

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

2011-01-01

322

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

Microsoft Academic Search

We have used accurate ab initio quantum chemistry calculations together with a simple model to study the hydrogen storage capacity of metal-organic and covalent-organic frameworks by spillover. Recent experiments by Tsao et al. [J. Am. Chem. Soc. 131, 1404 (2009)] {based on an earlier work by Li and Yang [J. Am. Chem. Soc. 128, 8136 (2006)]} have found that IRMOF-8

Mayur Suri; Matthew Dornfeld; Eric Ganz

2009-01-01

323

Hydrogenation of o-chloronitrobenzene on a Pd\\/C catalyst doped with metal oxide nanoparticles  

Microsoft Academic Search

Pd\\/C catalysts doped with cerium oxide and iron oxide nanoparticles were prepared by thermal decarboxylation in the presence of cetylsulfonyl acetate, and used in the hydrogenation of o-chloronitrobenzene to give high yields of 2,2?-dichlorohydrazobenzene. It was found that the stability and activity of the Pd\\/C catalysts were significantly affected by doping with the nanosized metal oxides. The chemical structure of

Gang Zhang; Legang Wang; Kaihua Shen; Defeng Zhao; Harold S. Freeman

2008-01-01

324

Neutron and Thermodynamic Studies of Hydrogen on Pd Decorated Metal Oxides  

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

325

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

326

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

327

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

328

Hydrogen Embrittlement of Metal Fasteners Due to Phosphoric Acid Containment System (PACS) Exposure. Volume 5 - Delivery Order 4, Task 2.  

National Technical Information Service (NTIS)

The objective of this study was to determine if metal fasteners are susceptible to hydrogen embrittlement due to exposure to a phosphoric acid containment system (PACS) surface preparation. A PACS is used to anodize aluminum surfaces in preparation for ad...

W. B. Pinnell

1999-01-01

329

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

330

Investigation of metal alloy catalyst for hydrogen release from sodium borohydride for polymer electrolyte membrane fuel cell application  

Microsoft Academic Search

Sodium borohydride (NaBH4) is a promising candidate for storing hydrogen in portable fuel cell systems. In order to reduce the volume and cost of the hydrogen generation systems, a high-performance catalyst containing a less precious metal is imperative. In this present investigation, a number of metal alloy compositions are compared in a high throughput screening (HTS) test. In the case

Joon-Hyun Park; Piraman Shakkthivel; Hyun-Jong Kim; Myung-Keun Han; Jae-Hyuk Jang; Yong-Rok Kim; Han-Sung Kim; Yong-Gun Shul

2008-01-01

331

Hydrogen embrittlement of metals (Citations from the American Petroleum Institute Data Base). Report for 1971-79  

Microsoft Academic Search

Research reports on hydrogen embrittlement of ferrous and nonferrous metals are cited. Studies relating to mechanical properties, corrosion, failure, testing, and inhibition are presented. Hydrogen embrittlement is described in pressure vessels, pipes, welds, and steels. Reports on materials used in pipeline, refinery, petrochemical and energy storage service are included. This updated bibliography contains 205 abstracts, 25 of which are new

Reed

1980-01-01

332

Hydrogen embrittlement of metals (citations from the American Petroleum Institute data base). Report for 1971-1978  

Microsoft Academic Search

Research reports on hydrogen embrittlement of ferrous and nonferrous metals are cited. Studies relating to mechanical properties, corrosion, failure, testing, and inhibition are presented. Hydrogen embrittlement is described in pressure vessels, pipes, welds, and steels. Reports on materials used in pipeline, refinery, petrochemical, and energy storage service are included. (Contains 181 abstracts)

Reed

1979-01-01

333

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

334

Selective oxidation of methanol to hydrogen over gold catalysts promoted by alkaline-earth-metal and lanthanum oxides  

Microsoft Academic Search

A series of alumina-supported gold catalysts was investigated for the CO-free production of hydrogen by partial oxidation of methanol. The addition of alkaline-earth metal oxide promoters resulted in a significant improvement of the catalytic performance. The methanol conversion was ca. 85 % with all studied catalyst materials, however, the selectivity for hydrogen increased from 15 % to 51 % when

2009-01-01

335

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

336

Iron group metal catalyzed hydrogasification in the presence of supported hydrogenation nickel catalyst  

SciTech Connect

The catalytic hydrogasification of coal is successfully carried out by Tomita and Huettinger and their co-workers using nickel and iron as catalysts. On the other hand, hydrogasification of coal char and carbon has attracted a little attention because of strong thermochemical suppression at higher temperature and low gasification rate compared with the gasification by H/sub 2/O or CO/sub 2/ and also because only noble metals such as platinum show high catalytic activity. But, it is known that iron group metals iron, cobalt and nickel also have catalytic activity for hydrogasification of carbonaceous materials like graphite. The activity and reaction mechanism are well studied using controlled atmosphere electron microscopy. This study shows the reactivity of iron, cobalt and nickel catalyzed char gasification with hydrogen at atmospheric pressure, and that the mixing of supported nickel catalyst with metal loaded char remarkably increases hydrogasification rate.

Matsumoto, S.

1989-01-01

337

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

338

Influence of intrinsic hydrogenation\\/dehydrogenation kinetics on the dynamic behaviour of metal hydrides: A semi-empirical model and its verification  

Microsoft Academic Search

Metal hydrides can store hydrogen at low pressures and with high volumetric capacity. For the possible application as storage medium in hydrogen stand-alone power systems, large metal hydride hydrogen storage units are usually required. A reliable and verified kinetic correlation is an important tool in the designing process of a larger storage unit. This paper describes kinetic investigation of a

T. Frde; J. P. Maehlen; V. A. Yartys; M. V. Lototsky; H. Uchida

2007-01-01

339

Multibed hydrocracking process utilizing beds with disparate particle sizes and hydrogenating metals contents  

SciTech Connect

In a process for hydrocracking a hydrocarbon feedstock having components boiling above 375 F by reacting the feedstock with hydrogen at a temperature ranging from about 600-900 F, a pressure ranging from about 500-5,000 psig, an LHSV of about 0.1-10 and a hydrogen feed to the process ranging from about 500-20,000 standard cubic feed of hydrogen per barrel of feedstock in the presence of a hydrocracking catalyst comprising a Group VIII component consisting of Ni metal, oxide, sulfide, Co metal, oxide, sulfide and mixtures thereof and a Group VIB component consisting of W metal, oxide, sulfide, Mo metal, oxide, sulfide and mixtures thereof and a carrier comprising an ultra stable zeolite Y and a binder comprising alumina in a reactor comprising five separate beds of the catalyst stacked on top of each other which process comprises (a) providing the feedstock and a hydrogen-containing gas to the top bed, (b) passing the reaction product of each bed directly to the next bed, (c) providing interbed cooling and (d) removing a hydrocracked product from the bottom bed; the improvement is described comprising using in the top bed a catalyst which contains the same hydrogenating components as in the remaining beds and which contains about 1.5 times or greater the gram atom content per gram of total catalyst of one of the Group VIB and Group VIII components and which has an average effective pellet diameter of 0.75 times or less the average effective pellet diameter of the catalyst used in the remaining beds and wherein the catalyst in the remaining beds has a Group VIB content of about 2-15% by weight of the total catalyst, a Group VIII content of about 0.2-3.5% by weight of the total catalyst, a zeolite content ranging from about 70-90% by weight, basis zeolite plus alumina and an average effective pellet diameter ranging from about 0.05-0.2 inches.

Gillespie, W.D.

1993-08-03

340

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

341

Metal and precursor effect during 1-heptyne selective hydrogenation using an activated carbon as support.  

PubMed

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

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

2013-01-01

342

Effect of hydrogen bonding and complexation with metal ions on the fluorescence of luotonin A.  

PubMed

Fluorescence characteristics of a biologically active natural alkaloid, luotonin A (LuA), were studied by steady-state and time-resolved spectroscopic methods. The rate constant of the radiationless deactivation from the singlet-excited state diminished by more than one order of magnitude when the solvent polarity was changed from toluene to water. Dual emission was found in polyfluorinated alcohols of large hydrogen bond donating ability due to photoinitiated proton displacement along the hydrogen bond. In CH2Cl2, LuA produced both 1 : 1 and 1 : 2 hydrogen-bonded complexes with hexafluoro-2-propanol (HFIP) in the ground state. Photoexcitation of the 1 : 2 complex led to protonated LuA, whose fluorescence appeared at a long wavelength. LuA served as a bidentate ligand forming 1 : 1 complexes with metal ions in acetonitrile. The stability of the complexes diminished in the series of Cd(2+) > Zn(2+) > Ag(+), and upon competitive binding of water to the metal cations. The effect of chelate formation on the fluorescent properties was revealed. PMID:23487318

Miskolczy, Zsombor; Biczk, Lszl

2013-05-01

343

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

PubMed Central

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

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

2013-01-01

344

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

SciTech Connect

The formation of the giant planets in our solar system, and likely a majority of giant exoplanets, is most commonly explained by the accretion of nebular hydrogen and helium onto a large core of terrestrial-like composition. The fate of this core has important consequences for the evolution of the interior structure of the planet. It has recently been shown that H{sub 2}O, MgO, and SiO{sub 2} dissolve in liquid metallic hydrogen at high temperature and pressure. In this study, we perform ab initio calculations to study the solubility of an innermost metallic core. We find dissolution of iron to be strongly favored above 2000 K over the entire pressure range (0.4-4 TPa) considered. We compare with and summarize the results for solubilities on other probable core constituents. The calculations imply that giant planet cores are in thermodynamic disequilibrium with surrounding layers, promoting erosion and redistribution of heavy elements. Differences in solubility behavior between iron and rock may influence evolution of interiors, particularly for Saturn-mass planets. Understanding the distribution of iron and other heavy elements in gas giants may be relevant in understanding mass-radius relationships, as well as deviations in transport properties from pure hydrogen-helium mixtures.

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

2013-08-20

345

Hydrogen-transparent metal surfaces produced by use of molten salts with very low oxygen and water activities  

Microsoft Academic Search

One can employ simple thermodynamic principles to predict conditions under which metals will not form hydrogen-blocking surface oxide layers in electrolyte environments. These principles are used to show that very low oxygen and water activities can be produced in some halide-based molten salt systems by the incorporation of alkali hydrides. Under these conditions, some normally very reactive metals will not

Gerhard Deublein; R. A. Huggins

1989-01-01

346

Welding Procedure Specification. Supplement 1. Records of Procedure Qualification Tests. Low Hydrogen Shielded Metal Arc Welding of Carbon Steel.  

National Technical Information Service (NTIS)

Procedure WPS-114-ASME-1 is qualified under Section IX of the ASME Boiler and Pressure Vessel Code for low hydrogen shielded metal arc welding of carbon steels (P-1-1), in thickness range 0.125 to 1.5 inch; filler metal is E7018. (ERA citation 11:040937)

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

1986-01-01

347

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

348

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

349

Surface plasmon resonance hydrogen sensor based on metallic grating with high sensitivity.  

PubMed

High sensitivity is obtained at larger resonant incident angle if negative diffraction order of metallic grating is used to excite the surface plasmon. A highly sensitive grating-based surface plasmon resonance (SPR) sensor is designed for the hydrogen detection. A thin palladium (Pd) film deposited on the grating surface is used as transducer. The influences of grating period and the thickness of Pd on the performance of sensor are investigated using rigorous coupled-wave analysis (RCWA) method. The sensitivity as well as the width of the SPR curves and reflective amplitude is considered simultaneously for designing the grating-based SPR hydrogen sensor, and a set of optimized structural parameters is presented. The performance of grating-based SPR sensor is also compared with that of conventional prism-based SPR sensor. PMID:19581945

Lin, Kaiqun; Lu, Yonghua; Chen, Junxue; Zheng, Rongsheng; Wang, Pei; Ming, Hai

2008-11-10

350

Hydrogen site occupancy and strength of forces in nanosized metal hydrides  

NASA Astrophysics Data System (ADS)

The dipole force components in nanosized metal hydrides are quantitatively determined with curvature and x-ray diffraction measurements. Ab initio density functional theory is used to calculate the dipole components and the symmetry of the strain field. The hydrogen occupancy in a 100-nm-thick V film is shown to be tetrahedral with a slight asymmetry at low concentration, and a transition to octahedral occupancy is shown to take place at around 0.07 [H/V] at 360 K. When the thickness of the V layer is reduced to 3 nm and biaxially strained, in a Fe0.5V0.5/V superlattice, the hydrogen unequivocally occupies octahedral z-like sites, even at and below concentrations of 0.02 [H/V].

Plsson, Gunnar K.; Wlde, Moritz; Amft, Martin; Wu, Yuanyuan; Ahlberg, Martina; Wolff, Max; Pundt, Astrid; Hjrvarsson, Bjrgvin

2012-05-01

351

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

NASA Astrophysics Data System (ADS)

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

Kelly, Thomas Glenn

352

Structure and spectroscopy of hydrogen adsorbed in a nickel metalorganic 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

353

Spin-exchange cross sections for hydrogen-atom--alkali-metal-atom collisions  

Microsoft Academic Search

The pseudopotential molecular-structure method has been used to calculate the X¹..sigma.. and a³..sigma.. interaction potentials for the alkali-metal-atom--hydrogen-atom systems. These potentials were then used in a quantum-mechanical calculation to determine the spin-exchange cross sections in the energy range from 2.5 x 10⁻⁴ eV to 2.5 eV. The cross sections follow the general form Q¹² = a-b lnv. However, abundant structure

H. R. Cole; R. E. Olson

1985-01-01

354

Spin-exchange cross sections for hydrogen-atom-alkali-metal-atom collisions  

Microsoft Academic Search

The pseudopotential molecular-structure method has been used to calculate the X1Sigma and a3Sigma interaction potentials for the alkali-metal-atom-hydrogen-atom systems. These potentials were then used in a quantum-mechanical calculation to determine the spin-exchange cross sections in the energy range from 2.510-4 eV to 2.5 eV. The cross sections follow the general form Q1\\/2=a-b lnv. However, abundant structure on the cross sections

H. R. Cole; R. E. Olson

1985-01-01

355

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

NASA Astrophysics Data System (ADS)

Recently, a new equation of state for hydrogen which predicts a molecular-metallic phase transition at finite temperature has become available. It is combined with a helium equation of state, and the resulting thermodynamic description of H/He mixtures is used to compute interior models of Jupiter and Saturn, subject to the constraints of the measured gravitational harmonics of both planets. The inferred heavy element abundance distribution in their interior and the possible consequences on their formation are discussed. In particular, the Z-element enhancement and smaller core in Saturn relative to Jupiter, a conclusion of this study, may indicate a depletion of water ice in the Jupiter formation zone.

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

1992-06-01

356

Transition Metal Carbonyls Combined with Hydrogen Donors as Initiators of the Radical Reduction of Trichloromethyl Compounds  

NASA Astrophysics Data System (ADS)

The review is devoted to new redox catalysts of the homolytic reduction of trichloromethyl compounds to dichloromethyl compounds mononuclear and dinuclear metal carbonyls [Fe(CO)5, Ni(CO)4, M(CO)6 (M = Mo, Cr, W), Mn2(CO)10] in combination with hydrogen donors (secondary alcohols, silicon hydrides, mercaptans, tertiary amines, amides, and tetrahydrofuran). The results obtained hitherto concerning the development of a new radical-chain method for the reduction of a wide variety of trichloromethyl compounds to the dichloromethyl derivatives are surveyed. The bibliography includes 78 references.

Freidlina, R. Kh; Gasanov, Rashid G.; Kuz'mina, Nadezhda A.; Chukovskaya, E. Ts

1985-07-01

357

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

NASA Astrophysics Data System (ADS)

In this work, we have theoretically analyzed the conversion process of hydrogen sulfide, H 2S, to atomic hydrogen, H 0, in a planar stagnation-point flow over an iron-metallic surface. We assume that a binary mixture of hydrogen sulfide and methane composes the laminar stagnation flow. In order to characterize this complex phenomenon with very specific chemical activities on the surface of the metallic plate, we propose a heterogeneous reaction scheme based on four reactions: two electrochemical, one adsorption and an additional exothermic reaction needed to complete the direct conversion of hydrogen sulfide to hydrogen on the surface of the iron. The nondimensional governing equations, which include the mass species and momentum conservation of the mixture and the molecular diffusion of hydrogen into the iron plate, are numerically solved by conventional finite-difference methods. The numerical results show the critical conditions of the H 2S decomposition as functions of the involved nondimensional parameters of the present model. In particular, we show parametrically the influence that has the initial concentration of H 2S on the surface coverage of the chemical products HS - H + and H 0 derived from the chemical and electrochemical reactions.

Martnez, J. C.; Mndez, F.; Trevio, C.

2006-12-01

358

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

359

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

SciTech Connect

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

Kuch, Ph. L.

1984-12-18

360

Synthesis and characterization of polymer embedded LaNi5 composite material for hydrogen storage  

Microsoft Academic Search

Composite materials consisting of powders of a standard hydride forming an intermetallic compound (LaNi5) dispersed into a hydrogen-permeable elastomer (polysiloxane) have been produced. The H2 storage capacity and the hydrogen desorption kinetics have been measured with composite samples having a metal content of 50 and 83 wt%. At a metal content of 50 wt%, the composite material consists of separated

R. Checchetto; G. Carotenuto; N. Bazzanella; A. Miotello

2007-01-01

361

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

PubMed

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

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

2013-04-01

362

Penetration mechanisms of surface-adsorbed hydrogen atoms into bulk metals: Experiment and model  

NASA Astrophysics Data System (ADS)

The conditions enabling the transition of surface-adsorbed hydrogen atoms into bulk metals are explored by comparing the response of chemisorbed H on Pd(100) and Ti(0001) single crystals to thermal activation in vacuum. Thermal desorption spectroscopy and H1(N15,??)C12 nuclear reaction analysis reveal that heating causes H2 desorption from Pd(100), whereas H atoms on Ti(0001) reversibly exchange between the surface and the Ti bulk with negligible desorption loss of H2 . A general model is proposed in which the competition between desorption and bulk absorption of surface hydrogen is, on one hand, kinetically determined by the activation energy for associative H2 desorption relative to the effective energy barrier for H absorption. On the other hand, the thermodynamic possibility to dissolve the surface H atoms into the metal must be considered to consistently explain the opposite behavior of H on Pd(100) and Ti(0001). The first experimental estimation of the energy of surface adsorption, ?s=-0.92eV , for H/Ti(0001) is presented, in good agreement with theoretical calculations.

Wilde, Markus; Fukutani, Katsuyuki

2008-09-01

363

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

SciTech Connect

A dissimilatory metal- and sulfur-reducing microorganism was isolated from surface sediments of a hydrocarbon-contaminated ditch in Norman, Oklahoma. The isolate, which was designated strain PCA, was an obligately anaerobic, nonfermentative, nonmotile, gram-negative rod. PCA grew in a defined medium with acetate as an electron donor and ferric PP[sub i], ferric oxyhydroxide, ferric citrate, elemental sulfur, CO(III)-EDTA, fumarate, or malate as the sole electron acceptor. PCA also coupled the oxidation of hydrogen to the reduction of Fe(III) but did not reduce Fe(III) with sulfur, glucose, lactate, fumarate, propionate, butyrate, isobutryate, isovalerate, succinate, yeast extract, phenol, benzoate, ethanol, propanol, or butanol as an electron donor. PCA did not reduce oxygen, Mn(IV), U(VI), nitrate, sulfate, sulfite, or thiosulfate with acetate as the electron donor. Cell suspensions of PCA exhibited dithionite-reduced minus air-oxidized difference spectra which were characteristic of c-type cytochromes. Phylogenetic analysis of the 16S rRNA sequence placed PCA in the delta subgroup of the proteobacteria. Its closest known relative is Geobacter metallireducens. The ability to utilize either hydrogen or acetate as the sole electron donor for Fe(III) reduction makes strain PCA a unique addition to the relatively small group of respiratory metal-reducing microorganisms available in pure culture. A new species name, Geobacter sulfurreducens, is proposed. 46 refs., 8 figs., 1 tab.

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

1994-10-01

364

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

SciTech Connect

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

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

2005-09-01

365

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

366

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

367

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

SciTech Connect

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

Rodriguez J. A.; Illas, F.

2012-01-01

368

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

PubMed Central

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

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

2007-01-01

369

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

PubMed

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

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

2012-12-01

370

A novel Pd\\/oxide\\/GaAs metal-insulator-semiconductor field-effect transistor (MISFET) hydrogen sensor  

Microsoft Academic Search

A novel and high-performance Pd\\/oxide\\/GaAs hydrogen sensor based on a metal-insulator-semiconductor field-effect transistor (MISFET) is fabricated and studied. In the presence of the interfacial oxide, high sensitivity and significant increase in output drain current are observed. In the presence of hydrogen, a 2200 m2 gate dimension device shows good dc characteristics including high turn-on voltage, an obvious variation of drain

Kun-Wei Lin; Chin-Chuan Cheng; Shiou-Ying Cheng; Kuo-Hui Yu; Chih-Kai Wang; Hung-Ming Chuang; Jing-Yuh Chen; Cheng-Zu Wu; Wen-Chau Liu

2001-01-01

371

Development of dissolved hydrogen sensors based on yttria-stabilized zirconia solid electrolyte with noble metal electrodes  

Microsoft Academic Search

A hydrogen sensor has been developed for in situ measurements of the concentration of hydrogen in aqueous solutions at elevated temperatures. The sensor was based on an electrochemical cell employing an yttria-stabilized zirconia (9% YO) solid electrolyte, a Ag-O (in air) reference electrode, and a noble metal working electrode (Pt or Pd) covered with a polytetrafluorene-ethyl membrane. The response of

Nobuyoshi Hara; D. D. Macdonald

1997-01-01

372

On the relationship between the structure of metalorganic frameworks and the adsorption and diffusion of hydrogen  

Microsoft Academic Search

In this work, the adsorptive and diffusive behaviours of molecular hydrogen in 10 different isoreticular metalorganic frameworks (IRMOFs) are studied using molecular-level simulation. Hydrogen adsorption isotherms and heats of adsorption at 77 and 300K were generated for 10 MOFs at low-pressure conditions (up to 10 bar) using Path Integral Grand Canonical Monte Carlo simulations. Self-diffusivities and activation energies for diffusion

Nethika S. Suraweera; Ruichang Xiong; J. P. Luna; Donald M. Nicholson; David J. Keffer

2011-01-01

373

Effects of soil ageing on the accumulation of hydrogen sulphide and metallic sulphides in mangrove areas in Singapore  

Microsoft Academic Search

The effects of soil ageing on the accumulation of hydrogen sulphide and metallic sulphides were studied in reclaimed mangrove plots of increasing ages. The analysis was carried out using a low-cost electrochemical approach, utilizing a sulphide volatilization\\/trapping procedure followed by sulphide quantification with an ion-selective electrode technique. The results showed that the content of hydrogen sulphide in the soil increased

L. Kryger; S. K. Lee

1995-01-01

374

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

SciTech Connect

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

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

2005-10-14

375

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

SciTech Connect

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

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

2005-01-01

376

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

SciTech Connect

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

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

1985-02-19

377

Enhanced hydrogen evolution catalysis from chemically exfoliated metallic MoS2 nanosheets.  

PubMed

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

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

2013-07-17

378

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

379

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

NASA Astrophysics Data System (ADS)

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

Caorlin, Marco

380

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

SciTech Connect

Simulants for the Hanford Waste Vitrification Plant (HWVP) feed containing the major non-radioactive components Al, Cd, Fe, Mn, Nd, Ni, Si, Zr, Na, CO{sub 3}{sup 2{minus}}, NO{sub 3}-, and NO{sub 2}- were used as media to evaluate the stability of formic acid towards hydrogen evolution by the reaction HCO{sub 2}H {yields} H{sub 2} + CO{sub 2} catalyzed by the noble metals Ru, Rh, and/or Pd found in significant quantities in uranium fission products. Small scale experiments using 40-50 mL of feed simulant in closed glass reactors (250-550 mL total volume) at 80-100{degree}C were used to study the effect of nitrite and nitrate ion on the catalytic activities of the noble metals for formic acid decomposition. Reactions were monitored using gas chromatography to analyze the CO{sub 2}, H{sub 2}, NO, and N{sub 2}O in the gas phase as a function of time. Rhodium, which was introduced as soluble RhCl{sub 3}{center_dot}3H{sub 2}O, was found to be the most active catalyst for hydrogen generation from formic acid above {approx}80{degree}C in the presence of nitrite ion in accord with earlier observations. The inherent homogeneous nature of the nitrite-promoted Rh-catalyzed formic acid decomposition is suggested by the approximate pseudo first-order dependence of the hydrogen production rate on Rh concentration. Titration of the typical feed simulants containing carbonate and nitrite with formic acid in the presence of rhodium at the reaction temperature ({approx}90{degree}C) indicates that the nitrite-promoted Rh-catalyzed decomposition of formic acid occurs only after formic acid has reacted with all of the carbonate and nitrite present to form CO{sub 2} and NO/N{sub 2}O, respectively. The catalytic activities of Ru and Pd towards hydrogen generation from formic acid are quite different than those of Rh in that they are inhibited rather than promoted by the presence of nitrite ion.

King, R.B.; Bhattacharyya, N.K. [Univ. of Georgia, Athens, GA (United States). Department of Chemistry; Wiemers, K.D.

1994-08-01

381

Hydrogen migration mechanism for ligand substitution reactions in metal carbonyl hydrides  

SciTech Connect

It has been known for some time that certain transition metal carbonyl hydrides are unusually labile in ligand substitution processes. A mechanism explaining this unusual lability was offered involving a ligand migration of hydrogen to a carbonyl group, attack at the vacated coordination site y the entering ligand, loss of a CO ligand, and back-migration of H to the metal. The following recent experiments offer strong support for this hydride migration. (A) In acetone at -70/sup 0/C H/sub 2/Fe(CO)/sub 4/ reacts within 3 min with PPh/sub 3/ to give H/sub 2/Fe(CO)PPh/sub 3/ and with P(OMe)/sub 3/ to give H/sub 2/Fe(CO)/sub 3/P(OMe)/sub 3/ and H/sub 2/Fe(CO)/sub 2/(P(OMe)/sub 3/)/sub 2/. The phosphine and phosphites are cis to both hydrogens, and the hydrogens are probably cis to each other. The same results are found in methanol at room temperature. These substitutions are at least 30 times as fast as the thermal decomposition of H/sub 2/Fe(CO)/sub 4/ in methanol. H/sub 2/Fe(CO)/sub 3/PPh/sub 3/ decomposes at a rate similar to that of H/sub 2/Fe(CO)/sub 4/ and yields trans-Fe(CO)/sub 3/(PPh/sub 3/)/sub 2/ in the presence of triphenylphosphine. (B) H/sub 2/Ru(CO)/sub 4/ in acetone at -70/sup 0/C also gives H/sub 2/Ru(CO)/sub 3/P(OMe)/sub 3/ in a few minutes with the phosphite cis to hydrogen. Upon warming H/sub 2/Ru(CO)/sub 2/(P(OMe)/sub 3/)/sub 2/ is formed. (C) In methanol at 25/sup 0/C the ion HRu(CO)/sub 4//sup -/, as the PPN/sup +/ salt, is converted immediately into HRu/sub 3/(CO)/sub 11//sup -/. Adding excess sodium methoxide (about 0.4 M) slows the reaction time down to about 15 min, but the same product is formed.

Pearson, R.G.; Walker, H.W.; Mauermann, H.; Ford, P.C.

1981-08-01

382

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

383

Modification of metal complex on hydrogenation of o-chloronitrobenzene over polymer-stabilized platinum colloidal clusters  

Microsoft Academic Search

The effect of metal complex on hydrogenation of o-chloronitrobenzene (CNB) over poly-vinylpyrrolidone-stabilized platinum clusters (PVP-Pt) has been studied in methanol at 303 K and atmospheric pressure. The addition of metal complexes to the catalytic system can considerably modulate both the activity and the selectivity of the catalyst. A low activity (0.41 mol H2\\/mol Pt s) and low selectivity (42.6%) were

Xinlin Yang; Zhaoli Deng; Hanfan Liu

1999-01-01

384

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

385

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

Microsoft Academic Search

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

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

1998-01-01

386

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

387

Effect of hydrogen chemisorption on the photoionization threshold of isolated transition metal clusters  

NASA Astrophysics Data System (ADS)

Large increases in the photoionization threshold energies of small V x, NB x, and Fe x clusters ( x = 3-25) induced by chemisorption of H 2 have been observed using photoionization time-of-flight mass spectrometry of a molecular beam. These shifts exhibit a definite dependence both on the number of atoms constituting the bare metal cluster and on the number of chemisorbed hydrogens, and are particularly large (? 0.8 eV) for multiple-H 2 chemisorption on small clusters. A simple frontier orbital model for the chemisorption process predicts the direction of adsorbate-induced shifts in cluster ionization threshold for both H 2 and NH 3 as adsorbates.

Zakin, M. R.; Cox, D. M.; Whetten, R. L.; Trevor, D. J.; Kaldor, A.

1987-04-01

388

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

NASA Astrophysics Data System (ADS)

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

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

2011-06-01

389

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

390

Influence of metal-Peptide complexation on fragmentation and inter-fragment hydrogen migration in electron transfer dissociation.  

PubMed

The use of metal salts in electrospray ionization (ESI) of peptides increases the charge state of peptide ions, facilitating electron transfer dissociation (ETD) in tandem mass spectrometry. In the present study, K(+) and Ca(2+) were used as charge carriers to form multiply-charged metal-peptide complexes. ETD of the potassium- or calcium-peptide complex was initiated by transfer of an electron to a proton remote from the metal cation, and a c'-z fragment complex, in which the c' and z fragments were linked together via a metal cation coordinating with several amino acid residues, was formed. The presence of a metal cation in the precursor for ETD increased the lifetime of the c'-z fragment complex, eventually generating c and z' fragments through inter-fragment hydrogen migration. The degree of hydrogen migration was dependent on the location of the metal cation in the metal-peptide complex, but was not reconciled with conformation of the precursor ion obtained by molecular mechanics simulation. In contrast, the location of the metal cation in the intermediate suggested by the ETD spectrum was in agreement with the conformation of "proton-removed" precursors, indicating that the charge reduction of precursor ions by ETD induces conformational rearrangement during the fragmentation process. PMID:24671694

Asakawa, Daiki; Takeuchi, Takae; Yamashita, Asuka; Wada, Yoshinao

2014-06-01

391

Influence of Metal-Peptide Complexation on Fragmentation and Inter-Fragment Hydrogen Migration in Electron Transfer Dissociation  

NASA Astrophysics Data System (ADS)

The use of metal salts in electrospray ionization (ESI) of peptides increases the charge state of peptide ions, facilitating electron transfer dissociation (ETD) in tandem mass spectrometry. In the present study, K+ and Ca2+ were used as charge carriers to form multiply-charged metal-peptide complexes. ETD of the potassium- or calcium-peptide complex was initiated by transfer of an electron to a proton remote from the metal cation, and a c'- z fragment complex, in which the c' and z fragments were linked together via a metal cation coordinating with several amino acid residues, was formed. The presence of a metal cation in the precursor for ETD increased the lifetime of the c'- z fragment complex, eventually generating c and z' fragments through inter-fragment hydrogen migration. The degree of hydrogen migration was dependent on the location of the metal cation in the metal-peptide complex, but was not reconciled with conformation of the precursor ion obtained by molecular mechanics simulation. In contrast, the location of the metal cation in the intermediate suggested by the ETD spectrum was in agreement with the conformation of "proton-removed" precursors, indicating that the charge reduction of precursor ions by ETD induces conformational rearrangement during the fragmentation process.

Asakawa, Daiki; Takeuchi, Takae; Yamashita, Asuka; Wada, Yoshinao

2014-06-01

392

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

393

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 metalorganic 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.

2013-01-01

394

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

NASA Astrophysics Data System (ADS)

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

Suri, Mayur; Dornfeld, Matthew; Ganz, Eric

2009-11-01

395

Hydrogen ratios and profiles in deposited amorphous and polycrystalline films and in metals using nuclear techniques  

NASA Astrophysics Data System (ADS)

Plasma- and chemical vapor deposited films containing hydrogen, Si, B and O, but of unknown thickness and stoichiometry have been assigned concentration ratios through a combination of H-profiling using the 1H( 15N, ??) 12C(4.43 MeV) reaction and RBS analysis. Relatively intense 15N ++ beams exceeding the 6.38 MeV resonance energy have been obtained from a 3.75 MeV accelerator with a commercial ion source and terminal analysis. A discussion is given of the method of obtaining film concentration ratios in some representative cases. A search was made for H at the SiO 2?Si interface. Some preliminary investigations have been made on the H concentration in several metals as supplied: Nb, V, Ta, Al, Ni, OFHC Cu, Ti, Mo and steel and on the effect of acid dips in loading H. Hydrogen in acid-loaded steel migrated under the influence of the probing 15N beam, but relaxed back when the beam was removed.

Benenson, R. E.; Feldman, L. C.; Bagley, B. G.

1980-01-01

396

Quantum dynamics of hydrogen dissociation on metal surfaces: successes and problems  

NASA Astrophysics Data System (ADS)

Quantum dynamics calculations on both H2 + Cu(100) and Pt(111) show that accurate reaction probabilities may be obtained using an accurately fitted DFT-GGA PES, if all six hydrogen molecular degrees of freedom are treated. The dependence of the reaction probability on incidence angle is also well described . Furthermore, in many cases the calculations allow useful interpretations of previous experiments. In a recent example, we were able to solve a paradox regarding the corrugation of a Pt(111) surface as seen by H2 in reaction and in scattering . However, there are also problems. The rotationally (rovibrationally) inelastic scattering of H2 from Cu(100) and of HD from Pt(111) is not well described by the present model. We are not yet able to provide a quantitatively accurate description of diffraction of hydrogen scattering from a metal surface. Furthermore, the system studied best experimentally (H2 + Cu(111)) has been left almost unaddressed. Calculations on LEPS PESs show that these PESs do not yield an accurate description of the reaction. However, these calculations also suggest that the outcomes of experiments on reaction of (v=0) H2 and D2 are inconsistent with one another.

Kroes, G. J.

2004-03-01

397

The effects of metal ions on the DNA damage induced by hydrogen peroxide.  

PubMed

The effects of metal ions on DNA damage induced by hydrogen peroxide were investigated using two methods, agarose-gel electrophoretic analysis of supercoiled DNA and sequencing-gel analysis of single end-labeled DNA fragments of defined sequences. Hydrogen peroxide induced DNA damage when iron or copper ion was present. At least two classes of DNA damage were induced, one being direct DNA-strand cleavage, and the other being base modification labile to hot piperidine. The investigation of the damaged sites and the inhibitory effects of radical scavengers revealed that hydroxyl radical was the species which attacked DNA in the reaction of H2O2/Fe(II). On the other hand, two types of DNA damage were induced by H2O2/Cu(II). Type I damage was predominant and inhibited by potassium iodide, but type II was not. The sites of the base-modification induced by type I damage were similar to those by lipid peroxidation products and by ascorbate in the presence of Cu(II), suggesting the involvement of radical species other than free hydroxyl radical in the damaging reactions. PMID:1368527

Kobayashi, S; Ueda, K; Komano, T

1990-01-01

398

Flexible Sandwich Diaphragms Are Less Permeable  

NASA Technical Reports Server (NTRS)

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

Michalovic, John G.; Vassallo, Franklin A.

1993-01-01

399

Correlation between the work functions of transition metal carbides in their homogeneity regions and surface recombination of hydrogen atoms  

Microsoft Academic Search

Since an understanding of the relationship between the surface properties of solid materials and their electronic structure is of considerable importance, in the present work a complex investigation was carried out of work functions and rates of surface recombination of hydrogen atoms for carbides of Groups IV and V metals. Refractory carbides are used in various fields of engineering, for

G. V. Samsonov; I. A. Podchernyaeva; V. S. Fomenko; V. A. Lovrenko; L. N. Okhremchuk; T. G. Protsenko

1972-01-01

400

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

401

Activating and inhibiting action of anions on hydrogen embrittlement during stress corrosion cracking of high-strength steels  

Microsoft Academic Search

This paper investigates hydrogen embrittlement during stress corrosion cracking of four high-strength steels (02N18K9M5T, 33Kh3SNMVFA, 38N4MFA, and 90Kh3M3V6F2) in electrolytes of different anionic compositions. The authors show that a number of anions which are passivators in uniform attack (phosphate, borate, and oxalate) increase the hydrogen permeability of the passivating film on the metal at the crack tip and promote hydrogen

Marichev

1986-01-01

402

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

NASA Technical Reports Server (NTRS)

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

Campbell, Sandi G.; Johnston, Chris

2004-01-01

403

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

PubMed

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

Grohol, Daniel; Blinn, Elliott L.

1997-07-30

404

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

405

The use of palladium to obtain reproducible boundary conditions for permeability measurements using galvanostatic charging  

NASA Astrophysics Data System (ADS)

The diffusion current of hydrogen through palladium in an electrochemical cell initially rises linearly with the charging current, reaches a steady plateau value, and then rises again. The diffusivity of hydrogen in palladium was measured using standard transient techniques in the initial region of low current density. Combining this value with the measured value of diffusion current at the plateau level gave a concentration of hydrogen at the entrance surface of the palladium that was the same for three different palladium thicknesses, and was equal to the saturation value in ? palladium. It is proposed that this can be used as a known and reproducible effective hydrogen pressure (0.019 atm) if palladium is plated onto other metals before measuring their permeability in an electrochemical cell. Experimental evidence for this was obtained from permeability measurements made on several thicknesses of iron. Permeation studies were also made on AISI 410 stainless steel and tin plated mild steel. The measured value for electrolytic tinplate was 107 times that expected from extrapolation of high temperature data. This could be attributed to grain boundaries or porosity covering 0.003 pct of the area. The permeability values of iron and stainless steel are 8.4 x 1012 and 2.8 x 1013 H atom/cm s ?atm, respectively.

Bowker, J.; Piercy, G. R.

1985-05-01

406

Development of dissolved hydrogen sensors based on yttria-stabilized zirconia solid electrolyte with noble metal electrodes  

SciTech Connect

A hydrogen sensor has been developed for in situ measurements of the concentration of hydrogen in aqueous solutions at elevated temperatures. The sensor was based on an electrochemical cell employing an yttria-stabilized zirconia (9% Y{sub 2}O{sub 3}) solid electrolyte, a Ag-O{sub 2} (in air) reference electrode, and a noble metal working electrode (Pt or Pd) covered with a polytetrafluorene-ethyl membrane. The response of the sensor to hydrogen has been examined in gas mixtures and aqueous solutions at temperatures as high as 300 C, and for hydrogen concentrations ranging from 0.001 to 100% or 7.61 {times} 10{sup {minus}6} to 7.61 {times} 10{sup {minus}4} mol/kg, respectively. The sensor displayed rapid responses to changes in concentration of hydrogen in both gas mixtures and aqueous solutions. Linear relationships with Nernstian slopes (2.303RT/2F) were observed between the measured potential of the sensor and the logarithm of the hydrogen concentration. Oxygen in solution had little effect on the potential of the sensor when the concentration of oxygen was lower than that of hydrogen, while there was a significant change in the potential with oxygen concentration in gas mixtures. The potential of the sensor was not affected by the pH of the solution.

Hara, Nobuyoshi; Macdonald, D.D. [Pennsylvania State Univ., University Park, PA (United States). Center for Advanced Materials

1997-12-01

407

Report on the development of low magnetic permeability reference materials  

Microsoft Academic Search

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

A. E. Drake; C. I. Ager

1993-01-01

408

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

PubMed Central

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

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

2013-01-01

409

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

SciTech Connect

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 reactions of Co and Fe complexes with TEMPO show a large, negative ground-state entropy for hydrogen atom transfer: ?SHAT = -30 2 cal mol-1 K-1 for the two iron complexes and -41 2 cal mol-1 K-1 for [CoII(H2bim)3]2+. The ?SHAT for TEMPO + RuII(acac)2(py-imH) is much closer to zero, 4.9 1.1 cal mol-1 K-1. Calorimetric measurements quantitatively confirm the enthalpy of reaction for [FeII(H2bip)3]2+ + TEMPO, thus also confirming ?SHAT. Calorimetry on TEMPOH + tBu3PhO gives ?HHAT = 11.2 0.5 kcal mol-1 which matches the enthalpy predicted from the difference in literature solution BDEs. An evaluation of the literature BDEs of both TEMPOH and tBu3PhOH is briefly presented and new estimates are included on the relative enthalpy of solvation for tBu3PhO vs. tBu3PhOH. The primary contributor to the large magnitude of the ground-state entropy |?SHAT| for the metal complexes is vibrational entropy, ?Svib. The common assumption that ?SHAT ? 0 for HAT reactions, developed for organic and small gas phase molecules, does not hold for transition metal based HAT reactions. The trend in magnitude of |?SHAT| 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, ?SET, in aprotic solvents. ?SET and ?SHAT are both affected by ?Svib and vary significantly with the metal center involved. The close connection between ?SHAT and ?SET 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. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

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

2009-03-10

410

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 1.0 and 16.8 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 0.2 kcal mol(-1) and A(H)/A(D) = 0.06 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

411

Interaction of molecular hydrogen with microporous metal organic framework materials at room temperature.  

PubMed

Infrared (IR) absorption spectroscopy measurements, performed at 300 K and high pressures (27-55 bar) on several prototypes of metal organic framework (MOF) materials, reveal that the MOF ligands are weakly perturbed upon incorporation of guest molecules and that the molecular hydrogen (H(2)) stretch mode is red-shifted (30-40 cm(-1)) from its unperturbed value (4155 cm(-1) for ortho H(2)). For MOFs of the form M(bdc)(ted)(0.5) (bdc = 1,4-benzenedicarboxylate; ted = triethylenediamine), H(2) molecules interact with the organic ligands instead of the saturated metal centers located at the corners of the unit cell. First-principles van der Waals density functional calculations identify the binding sites and further show that the induced dipole associated with the trapped H(2) depends sensitively on these sites. For M(bdc)(ted)(0.5) systems, the strongest dipole moment is of the site that is in the corner of the unit cell and is dominated by the interaction with the benzene ligand and not by the metal center. For MOFs of the M(3)[HCOO](6) type with relatively short ligands (i.e., formate) and 1-D pore structures, there is a weak dependence of H(2) vibrational frequency on the cations, due to a small change in the unit cell dimension. Furthermore, translational states of approximately +/-100 cm(-1) are clearly observed as side bands on the H(2) stretch mode in these 1-D channels interconnected by very small apertures. The H(2) stretch IR integrated areas in all the MOFs considered in this work increase linearly with H(2) pressure, consistent with isotherm measurements performed in similar conditions. However, the IR intensity varies substantially, depending on the number of benzene rings interacting with the H(2) molecules. Finally, there is no correlation between H(2) binding energies (determined by isotherm measurements) and the magnitude of the H(2) stretch shift, indicating that IR shifts are dominated by the environment (organic ligand, metal center, and structure) rather than the strength of the interaction. These results highlight the relevance of IR spectroscopy to determine the type and arrangement of ligands in the structure of MOFs. PMID:20070080

Nijem, Nour; Veyan, Jean-Franois; Kong, Lingzhu; Li, Kunhao; Pramanik, Sanhita; Zhao, Yonggang; Li, Jing; Langreth, David; Chabal, Yves J

2010-02-10

412

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

NASA Astrophysics Data System (ADS)

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

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

2009-07-01

413

Palladium membrane on TiO 2 nanotube arrays-covered titanium surface by combination of photocatalytic deposition and modified electroless plating processes and its hydrogen permeability  

Microsoft Academic Search

Palladium membrane with high hydrogen permselectivity was successfully fabricated on the TiO2 nanotube arrays-covered titanium surface by photocatalytic deposition (PCD) under ultraviolet irradiation and subsequently improved and thickened using the modified electroless plating method. The TiO2 nanotube arrays were produced in situ on the surface of asymmetric porous titanium foil in 0.5 wt% hydrofluoric acid by using the anodization method.

Rong Zhao; Ranfeng Ding; Shaojun Yuan; Wei Jiang; Bin Liang

2011-01-01

414

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

PubMed Central

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

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

2009-01-01

415

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

416

Hydrogen storage properties of metal nitroprussides M[Fe(CN)5NO], (M = Co, Ni)  

SciTech Connect

The volumetric hydrogen adsorption isotherms of two isostructural dehydrated cubic metal nitroprussides M[Fe(CN)5NO] (M = Co2+, Ni2+) have been measured up to a pressure of 760 Torr at 77 and 87 K. These materials are among the most efficient H2 sorbents based on porous coordination polymers reported to date. The H2 uptake in both materials is ?1.6 wt % at 77 K and 760 torr. These H2 capacities match those reported recently in the structurally related M3[Co(CN)6]2 compounds and are approximately 25% higher than those reported for Zn4O(1,4-benzenedicarboxylate)3 under the same conditions of temperature and pressure. The isosteric heats of H2 adsorption calculated from the 77 and 87 K isotherms for both materials were found to vary from ?7.5 kJ/mol at 0.40 wt % coverage to ?5.5 kJ/mol at 1.2 wt % coverage. The N2 BET surface areas were determined to be 634 m2/g and 523 m2/g for M = Ni and M = Co, respectively.

Culp, J.T.; Matranga, C.S.; Smith, M.; Bittner, E.W.; Bockrath, B.C.

2006-04-27

417

Hydrogen storage properties of metal nitroprussides M[Fe(CN)5NO], (M = Co, Ni).  

PubMed

The volumetric hydrogen adsorption isotherms of two isostructural dehydrated cubic metal nitroprussides M[Fe(CN)5NO] (M = Co2+, Ni2+) have been measured up to a pressure of 760 Torr at 77 and 87 K. These materials are among the most efficient H2 sorbents based on porous coordination polymers reported to date. The H2 uptake in both materials is approximately 1.6 wt % at 77 K and 760 torr. These H2 capacities match those reported recently in the structurally related M3[Co(CN)6]2 compounds and are approximately 25% higher than those reported for Zn4O(1,4-benzenedicarboxylate)3 under the same conditions of temperature and pressure. The isosteric heats of H2 adsorption calculated from the 77 and 87 K isotherms for both materials were found to vary from approximately 7.5 kJ/mol at 0.40 wt % coverage to approximately 5.5 kJ/mol at 1.2 wt % coverage. The N2 BET surface areas were determined to be 634 m2/g and 523 m2/g for M = Ni and M = Co, respectively. PMID:16623516

Culp, Jeffrey T; Matranga, Christopher; Smith, Milton; Bittner, Edward W; Bockrath, Bradley

2006-04-27

418

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

PubMed

Six 5 wt.% metal sorbents including Mn, Fe, Cu, Co, Ce and Zn supported on gamma-Al2O3, prepared by the incipient wetness impregnation method with calcination at 700 degrees C for 2 h, have been investigated for sorption of hydrogen sulfide in the temperature range of 500-700 degrees C. The sorption experiments were conducted in a fixed-bed reactor in terms of breakthrough curves and characterized by X-ray powder diffraction. The results reveal that the copper and manganese sorbents exhibit the best performance because they provide nearly 100% utilization, but the copper sorbent has a lower sulfur sorption capacity compared with the manganese sorbent. The zinc and cerium sorbents are not good candidates attributed to the vaporization of zinc and unexpected product for cerium. Effects of support materials on 5 wt.% manganese were also investigated by using gamma-Al2O3, SiO2 and TiO2 in this study. Five weight percent Mn/gamma-Al2O3 shows the best performance among support candidates. On the basis of XRPD and BET surface area analysis, TiO2 appears a huge loss in BET surface area associated with a significant formation of rutile form. PMID:15620738

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

2005-01-01

419

ADVANCED HYDROGEN TRANSPORT MEMBRANES FOR VISION 21 FOSSIL FUEL PLANTS  

SciTech Connect

During this quarter work was continued on characterizing the stability of layered composite membranes under a variety of conditions. Membrane permeation was tested up to 100 hours at constant pressure, temperature, and flow rates. In addition, design parameters were completed for a scale-up hydrogen separation demonstration unit. Evaluation of microstructure and effect of hydrogen exposure on BCY/Ni cermet mechanical properties was initiated. The fabrication of new cermets containing high permeability metals is reported and progress in the preparation of sulfur resistant catalysts is discussed. Finally, a report entitled ''Criteria for Incorporating Eltron's Hydrogen Separation Membranes into Vision 21 IGCC Systems and FutureGen Plants'' was completed.

Carl R. Evenson; Anthony F. Sammells; Richard T. Treglio; Jim Fisher; U. Balachandran; Richard N. Kleiner; James E. Stephan; Frank E. Anderson; Chandra Ratnasamy; Mahendra Sunkara; Jyothish Thangla; Clive Brereton; Warren Wolfs; James Lockhart

2005-01-28

420

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

SciTech Connect

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

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

2012-01-12