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Sample records for aluminum hydrogen cluster

  1. Theoretical Study of Hydrogenated Tetrahedral Aluminum Clusters

    CERN Document Server

    Ichikawa, Kazuhide; Wagatsuma, Ayumu; Watanabe, Kouhei; Szarek, Pawel; Tachibana, Akitomo

    2011-01-01

    We report on the structures of aluminum hydrides derived from a tetrahedral aluminum Al4 cluster using ab initio quantum chemical calculation. Our calculation of binding energies of the aluminum hydrides reveals that stability of these hydrides increases as more hydrogen atoms are adsorbed, while stability of Al-H bonds decreases. We also analyze and discuss the chemical bonds of those clusters by using recently developed method based on the electronic stress tensor.

  2. Hydrogen atom adsorption on aluminum icosahedral clusters: A DFT study

    International Nuclear Information System (INIS)

    Graphical abstract: Energy barriers for H atom migrating from the interstitial sites to surface adsorption sites for f.c.c. Al(1 1 1) surface and icosahedral surface. The icosahedral surface lowers the migration barriers of H atom both within the subsurface and between the surface and the subsurface. Research highlights: → Energetic properties of aluminum clusters absorbed with hydrogen atoms were investigated for the 'magic' clusters with icosahedral symmetry based on the first-principles calculation. → The slab model is made for representing the surface of icosahedral clusters by deforming the f.c.c. surface model. → The hydrogen diffusion barriers are calculated for interstitial sites of aluminum clusters and compared to those of bulk aluminum system. → The icosahedral surface lowers the migration barriers to H atoms between the surface and subsurface compared to the f.c.c. surface. - Abstract: Properties of hydrogenated, icosahedral aluminum clusters were investigated using density functional theory in comparison with those of aluminum bulk systems. The most stable site for H adsorption to Al13 was the hollow HCP site. The H binding energy suggests that the top and the bridge configurations are transition states. Results for Al13H were compared with those obtained for two surface models simulating f.c.c. and icosahedral (1 1 1) surfaces. Results show that the H atom interacts weakly with surface of clusters when the cluster size is increased. The migration energy of H atom between neighboring T and O sites becomes smaller for icosahedral subsurface than for either bulk material or the f.c.c. subsurface. A similar relation between the two surface models was found for the migration energy between surface and subsurface sites. These results indicate that the icosahedral surface lowers the migration barriers of H atom both within the subsurface and between the surface and the subsurface.

  3. Hydrogen hosting on aluminum-doped boron clusters: Density functional theory

    Science.gov (United States)

    Böyükata, Mustafa; Güvenç, Ziya B.

    2009-11-01

    The geometries, stabilities, and energetics of aluminum doped boron clusters, up to 13-atom, and their various hydrogenated complexes have been investigated via the density functional theory (DFT). The geometry optimizations have been carried out by using B3LYP functional and 6-311++G11 basis set. Up to 5-atom clusters arrangements of the atoms, in the most stable structures, have two-dimensional forms. From 6- to 13-atom clusters three-dimensional forms are favored by the lowest energy structures. Hydrogen hosting effects the structures of AlBn clusters. Adding an Al atom to the cage B12 leads structural changes but hydrogenated boron, B12H12 can resist to Al effect.

  4. Hydrogen Embrittlement of Aluminum: the Crucial Role of Vacancies

    OpenAIRE

    Lu, Gang; Kaxiras, Efthimios

    2005-01-01

    We report first-principles calculations which demonstrate that vacancies can combine with hydrogen impurities in bulk aluminum and play a crucial role in the embrittlement of this prototypical ductile solid. Our studies of hydrogen-induced vacancy superabundant formation and vacancy clusterization in aluminum lead to the conclusion that a large number of H atoms (up to twelve) can be trapped at a single vacancy, which over-compensates the energy cost to form the defect. In the presence of tra...

  5. Hydrogen effects in aluminum alloys

    International Nuclear Information System (INIS)

    The permeability of six commercial aluminum alloys to deuterium and tritium was determined by several techniques. Surface films inhibited permeation under most conditions; however, contact with lithium deuteride during the tests minimized the surface effects. Under these conditions phi/sub D2/ = 1.9 x 10-2 exp (--22,400/RT) cc (NTP)atm/sup --1/2/ s-1cm-1. The six alloys were also tested before, during, and after exposure to high pressure hydrogen, and no hydrogen-induced effects on the tensile properties were observed

  6. Aluminum Zintl anion moieties within sodium aluminum clusters

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Haopeng; Zhang, Xinxing; Ko, Yeon Jae; Grubisic, Andrej; Li, Xiang; Ganteför, Gerd; Bowen, Kit H., E-mail: AKandalam@wcupa.edu, E-mail: kiran@mcneese.edu, E-mail: kbowen@jhu.edu [Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Schnöckel, Hansgeorg [Institute of Inorganic Chemistry, Karlsruhe Institute of Technology, 76128 Karlsruhe (Germany); Eichhorn, Bryan W. [Department of Chemistry, University of Maryland at College Park, College Park, Maryland 20742 (United States); Lee, Mal-Soon; Jena, P. [Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284 (United States); Kandalam, Anil K., E-mail: AKandalam@wcupa.edu, E-mail: kiran@mcneese.edu, E-mail: kbowen@jhu.edu [Department of Physics, West Chester University of Pennsylvania, West Chester, Pennsylvania 19383 (United States); Kiran, Boggavarapu, E-mail: AKandalam@wcupa.edu, E-mail: kiran@mcneese.edu, E-mail: kbowen@jhu.edu [Department of Chemistry, McNeese State University, Lake Charles, Louisiana 70609 (United States)

    2014-02-07

    Through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations, we have established that aluminum moieties within selected sodium-aluminum clusters are Zintl anions. Sodium–aluminum cluster anions, Na{sub m}Al{sub n}{sup −}, were generated in a pulsed arc discharge source. After mass selection, their photoelectron spectra were measured by a magnetic bottle, electron energy analyzer. Calculations on a select sub-set of stoichiometries provided geometric structures and full charge analyses for both cluster anions and their neutral cluster counterparts, as well as photodetachment transition energies (stick spectra), and fragment molecular orbital based correlation diagrams.

  7. Study of aluminum-doped silicon clusters

    International Nuclear Information System (INIS)

    Using full-muffin-tin-orbital molecular-dynamics (FP-LMTO-MD) method, we have investigated the effect of aluminum heteroatoms on the geometric structures and bond characteristics of Si n (n=5-10) clusters in detail. It is found that the geometric framework of the ground state structures for Si n (n=5-10) clusters change to some extent upon the substitution of Al atoms in some Si atoms. The effect of aluminum doping on the silicon clusters depends on the geometric structures of Si n (n=5-10) clusters. In particular, the calculations suggest that the aluminum doping would improve the bond strength of some Si-Si bonds in the mixed Si n-m Al m clusters

  8. Activated aluminum hydride hydrogen storage compositions and uses thereof

    Science.gov (United States)

    Sandrock, Gary; Reilly, James; Graetz, Jason; Wegrzyn, James E.

    2010-11-23

    In one aspect, the invention relates to activated aluminum hydride hydrogen storage compositions containing aluminum hydride in the presence of, or absence of, hydrogen desorption stimulants. The invention particularly relates to such compositions having one or more hydrogen desorption stimulants selected from metal hydrides and metal aluminum hydrides. In another aspect, the invention relates to methods for generating hydrogen from such hydrogen storage compositions.

  9. Hydrogen in aluminum during alkaline corrosion

    Energy Technology Data Exchange (ETDEWEB)

    Adhikari, Saikat; Ai, Jiahe [Department of Chemical and Biological Engineering, Iowa State University, Ames, IA 50011 (United States); Hebert, Kurt R., E-mail: krhebert@iastate.ed [Department of Chemical and Biological Engineering, Iowa State University, Ames, IA 50011 (United States); Ho, K.M.; Wang, C.Z. [US DOE, Ames Laboratory, Ames, IA 50011 (United States)] [Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States)

    2010-07-30

    The thermodynamic state of hydrogen in aluminum during alkaline corrosion was investigated, using a two-compartment hydrogen permeation cell with an Al/Pd bilayer membrane. The open-circuit potential of the Pd layer in a pH 7.0 buffer solution was monitored to sense the hydrogen chemical potential, {mu}{sub H}. At pH 12.5-13.5, the measurements established a minimum {mu}{sub H} of 0.55 eV relative to the ideal gas reference, equivalent to a H{sub 2} gas pressure of 5.7 GPa. Statistical mechanics calculations show that vacancy-hydrogen defects are stable in Al at this condition. A dissolution mechanism was proposed in which H at very high {mu}{sub H} is produced by oxidation of interfacial aluminum hydride. The mechanism explains the observed rapid accumulation of H in the metal by extensive formation of vacancy-hydrogen defects.

  10. Hydrogen embrittlement of aluminum: the crucial role of vacancies.

    Science.gov (United States)

    Lu, Gang; Kaxiras, Efthimios

    2005-04-22

    We report first-principles calculations which demonstrate that vacancies can combine with hydrogen impurities in bulk aluminum and play a crucial role in the embrittlement of this prototypical ductile solid. Our studies of hydrogen-induced vacancy superabundant formation and vacancy clusterization in aluminum lead to the conclusion that a large number of H atoms (up to 12) can be trapped at a single vacancy, which overcompensates the energy cost to form the defect. In the presence of trapped H atoms, three nearest-neighbor single vacancies which normally would repel each other, aggregate to form a trivacancy on the slip plane of Al, acting as embryos for microvoids and cracks and resulting in ductile rupture along these planes. PMID:15904157

  11. The viability of aluminum Zintl anion moieties within magnesium-aluminum clusters

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Haopeng; Jae Ko, Yeon; Zhang, Xinxing; Gantefoer, Gerd; Bowen, Kit H., E-mail: kiran@mcneese.edu, E-mail: akandalam@wcupa.edu, E-mail: kbowen@jhu.edu [Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Schnoeckel, Hansgeorg [Institute of Inorganic Chemistry, Karlsruhe Institute of Technology, 76128 Karlsruhe (Germany); Eichhorn, Bryan W. [Department of Chemistry, University of Maryland, College Park, Maryland 20742 (United States); Jena, Puru [Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284 (United States); Kiran, Boggavarapu, E-mail: kiran@mcneese.edu, E-mail: akandalam@wcupa.edu, E-mail: kbowen@jhu.edu [Department of Chemistry, McNeese State University, Lake Charles, Louisiana 70609 (United States); Kandalam, Anil K., E-mail: kiran@mcneese.edu, E-mail: akandalam@wcupa.edu, E-mail: kbowen@jhu.edu [Department of Physics, West Chester University, West Chester, Pennsylvania 19383 (United States)

    2014-03-28

    Through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations, we have investigated the extent to which the aluminum moieties within selected magnesium-aluminum clusters are Zintl anions. Magnesium-aluminum cluster anions were generated in a pulsed arc discharge source. After mass selection, photoelectron spectra of Mg{sub m}Al{sub n}{sup −} (m, n = 1,6; 2,5; 2,12; and 3,11) were measured by a magnetic bottle, electron energy analyzer. Calculations on these four stoichiometries provided geometric structures and full charge analyses for the cluster anions and their neutral cluster counterparts, as well as photodetachment transition energies (stick spectra). Calculations revealed that, unlike the cases of recently reported sodium-aluminum clusters, the formation of aluminum Zintl anion moieties within magnesium-aluminum clusters was limited in most cases by weak charge transfer between the magnesium atoms and their aluminum cluster moieties. Only in cases of high magnesium content, e.g., in Mg{sub 3}Al{sub 11} and Mg{sub 2}Al{sub 12}{sup −}, did the aluminum moieties exhibit Zintl anion-like characteristics.

  12. A quantitative analysis of the hydrogen-vacancy complexes in the aluminum-hydrogen system

    International Nuclear Information System (INIS)

    Full text: Aluminum foils of 99.99% purity were charged with hydrogen using a gas plasma method. The nature of the H-vacancy complexes in the Aluminium are investigated experimentally (XRD, INS, SANS, USANS, TEM, SEM and Archimedes technique) and quantitatively. It is shown experimentally and quantitatively that H does not remain in the bulk as dispersed H-vacancy defects, but instead resides within the bulk as H2 - bubbles. These bubbles are formed from the clustering of the H-vacancy complexes and extra vacancies created by the initial 1 keV ions

  13. Photoelectron spectroscopy of boron aluminum hydride cluster anions

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Haopeng; Zhang, Xinxing; Ko, Yeon Jae; Gantefoer, Gerd; Bowen, Kit H., E-mail: kbowen@jhu.edu, E-mail: kiran@mcneese.edu [Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Li, Xiang [Center for Space Science and Technology, University of Maryland–Baltimore County, Baltimore, Maryland 21250 (United States); Kiran, Boggavarapu, E-mail: kbowen@jhu.edu, E-mail: kiran@mcneese.edu [Department of Chemistry and Physics, McNeese State University, Lake Charles, Louisiana 70609 (United States); Kandalam, Anil K. [Department of Physics, West Chester University, West Chester, Pennsylvania 19383 (United States)

    2014-04-28

    Boron aluminum hydride clusters are studied through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations. Boron aluminum hydride cluster anions, B{sub x}Al{sub y}H{sub z}{sup −}, were generated in a pulsed arc cluster ionization source and identified by time-of-flight mass spectrometry. After mass selection, their photoelectron spectra were measured by a magnetic bottle-type electron energy analyzer. The resultant photoelectron spectra as well as calculations on a selected series of stoichiometries reveal significant geometrical changes upon substitution of aluminum atoms by boron atoms.

  14. Electron exchange between an H{sup -} ion and a spherical cluster of aluminum atoms

    Energy Technology Data Exchange (ETDEWEB)

    Shestakov, D.K.; Polivnikova, T.Yu. [Department of Physics, Moscow State University, Moscow 119992 (Russian Federation); Gainullin, I.K. [Department of Physics, Moscow State University, Moscow 119992 (Russian Federation)], E-mail: Ivan.Gainullin@gmail.com; Urazgildin, I.F. [Department of Physics, Moscow State University, Moscow 119992 (Russian Federation)

    2009-08-15

    The resonant charge transfer (RCT) between a hydrogen anion and a cluster of aluminum atoms is investigated by means of the wave-packet propagation method that does not exploit the perturbation theory. The RCT on a spherical cluster is found to exhibit quantum size effects due to the finite size of the cluster. The survival amplitude of an ion state has been calculated as a function of the distance to the ion-surface in a normal collision. It is shown that depending on the velocity of the impinging particle, the cluster can behave either as a bulk metal or as a quantum structure with discrete energy states existing over two coordinates.

  15. Electron exchange between an H- ion and a spherical cluster of aluminum atoms

    International Nuclear Information System (INIS)

    The resonant charge transfer (RCT) between a hydrogen anion and a cluster of aluminum atoms is investigated by means of the wave-packet propagation method that does not exploit the perturbation theory. The RCT on a spherical cluster is found to exhibit quantum size effects due to the finite size of the cluster. The survival amplitude of an ion state has been calculated as a function of the distance to the ion-surface in a normal collision. It is shown that depending on the velocity of the impinging particle, the cluster can behave either as a bulk metal or as a quantum structure with discrete energy states existing over two coordinates.

  16. Hydrogen storage in sodium aluminum hydride.

    Energy Technology Data Exchange (ETDEWEB)

    Ozolins, Vidvuds; Herberg, J.L. (Lawrence Livermore National Laboratories, Livermore, CA); McCarty, Kevin F.; Maxwell, Robert S. (Lawrence Livermore National Laboratories, Livermore, CA); Stumpf, Roland Rudolph; Majzoub, Eric H.

    2005-11-01

    Sodium aluminum hydride, NaAlH{sub 4}, has been studied for use as a hydrogen storage material. The effect of Ti, as a few mol. % dopant in the system to increase kinetics of hydrogen sorption, is studied with respect to changes in lattice structure of the crystal. No Ti substitution is found in the crystal lattice. Electronic structure calculations indicate that the NaAlH{sub 4} and Na{sub 3}AlH{sub 6} structures are complex-ionic hydrides with Na{sup +} cations and AlH{sub 4}{sup -} and AlH{sub 6}{sup 3-} anions, respectively. Compound formation studies indicate the primary Ti-compound formed when doping the material at 33 at. % is TiAl{sub 3} , and likely Ti-Al compounds at lower doping rates. A general study of sorption kinetics of NaAlH{sub 4}, when doped with a variety of Ti-halide compounds, indicates a uniform response with the kinetics similar for all dopants. NMR multiple quantum studies of solution-doped samples indicate solvent interaction with the doped alanate. Raman spectroscopy was used to study the lattice dynamics of NaAlH{sub 4}, and illustrated the molecular ionic nature of the lattice as a separation of vibrational modes between the AlH{sub 4}{sup -} anion-modes and lattice-modes. In-situ Raman measurements indicate a stable AlH{sub 4}{sup -} anion that is stable at the melting temperature of NaAlH{sub 4}, indicating that Ti-dopants must affect the Al-H bond strength.

  17. Evolution of ConAl clusters and chemisorption of hydrogen on ConAl clusters

    International Nuclear Information System (INIS)

    The growth behavior of ConAl (n = 1–15) and the chemisorptions of hydrogen on the ground state geometries have been studied using the density functional theory (DFT) within the generalized gradient approximation (GGA). The growth pattern for ConAl is Al-substituted Con+1 clusters, and it keeps the similar frameworks of the most stable Con+1 clusters except for n = 2, 3, and 6. The Al atom substitutes the surface atom of the Con+1 clusters for n ≤ 13. Starting from n = 14, the Al atom completely falls into the center of the Co-frame. The dissociation energy, the second-order energy differences, and the HOMO–LUMO gaps indicate that the magic numbers of the calculated ConAl clusters are 7, 9, and 13, corresponding to the high symmetrical structures. To my knowledge, this is the first time that a systematic study of chemisorption of hydrogen on cobalt aluminum clusters. The twofold bridge site is identified to be the most favorable chemisorptions site for one hydrogen adsorption on ConAl (n = 1–6, 8, 10), and two hydrogen adsorption on ConAl (n = 1–7), while threefold hollow site is preferred for one hydrogen adsorption on ConAl (n = 7, 9, 11–15) and two hydrogen adsorption on ConAl (n = 8–10, 12–15) clusters. The ground state structure of two hydrogen adsorption on Co11Al is exceptional. In general, the binding energy of both H and 2H of ConAl (n = 1–12) is found to increase with the cluster size. And the result shows that large binding energies of the hydrogen atoms and large fragmentation energies for Co11AlH and Co12AlH make these species behaving like magic clusters.

  18. Analytic Force Field for Clusters and Nanoparticles of Aluminum and Its Hydride

    Science.gov (United States)

    Zhang, Qingfan; Tang, Enoch; Xi, Yongjie; Han, Bo; Legenski, Nicole; Chalas, Guadalupe; Chan, Frankie; Cheng, Hansong; Forrey, Robert C.

    2014-06-01

    An analytic potential energy function is developed for simulating clusters and nanoparticles of aluminum and its hydride. An embedded-atom method is used which modulates the background electron density as a function of the number of nearest-neighbor atoms. The method is parametrized and tested using an extensive training set computed from first-principle density-functional theory. The potential energy function is found to be reliable for clusters of arbitrary size, shape, and composition ratio. The force field obtained from the analytic potential energy function is computationally efficient and well suited for simulating large systems of aluminum and aluminum hydride particles. A proposed molecular dynamics simulation related to hydrogen-storage technologies for onboard automotive applications is briefly discussed.

  19. Dissociation of H2 on carbon doped aluminum cluster Al6C

    International Nuclear Information System (INIS)

    The dissociation of H2 molecule is the first step for chemical storage of hydrogen, and the energy barrier of the dissociation is the key factor to decide the kinetics of the regeneration of the storage material. As a light element, aluminum is an important candidate component for storage materials with high gravimetric density. This paper investigates the adsorption and dissociation of H2 on carbon doping aluminum cluster Al6C. The study shows that doping carbon into aluminum cluster can significantly change the electronic structure and increase the stability. Al6C has a few stable isomers with close energies and their structures are quite flexible. The molecular adsorption of H2 on Al6C is very weak, but the H2 molecule can be dissociated easily on this cluster. The stable product of the dissociated adsorption is searched and the different paths for the dissociation are investigated. During the dissociation of H2, the structure of the cluster adjusts accordingly, and strong orbital interaction between the hydrogen and the cluster occurs. The calculated energy barrier for the dissociation is only 0.30 eV, which means the dissociation can take place at moderate temperatures

  20. Hydrogen generation through massive corrosion of deformed aluminum in water

    Energy Technology Data Exchange (ETDEWEB)

    Czech, E.; Troczynski, T. [Materials Engineering Department, University of British Columbia, 309-6350 Stores Rd., Vancouver, BC V6T 1Z4 (Canada)

    2010-02-15

    Aluminum, one of most reactive metals, rapidly corrodes in strong acidic or alkaline solutions but passivates at pH of about 5-9. We have determined that the passivation of aluminum in this range of pH, and in particular in regular tap water, can be substantially prevented after milling of aluminum with water-soluble inorganic salts (referred to as ''WIS''), such as KCl or NaCl. Ensuing corrosion of Al in tap water, with accompanying release of hydrogen and precipitation of aluminum hydroxide, at normal pressure and moderate temperatures ({proportional_to}55 C) is rapid and substantial. For example, {proportional_to}92% of the Al in the Al-WIS system when milled for 1 h and {proportional_to}81% when milled for 15 min, corrodes in 1 h, with the release of 1.5 mol of hydrogen per each mole of Al consumed in the reaction. Besides gaseous hydrogen, only solid aluminum hydroxides were formed as the reaction byproducts, opening up the possibility of straightforward recycling of the system. The effects of WIS concentration, chemistry of other additives, powder particle size, temperature, and milling conditions on the reaction kinetics are reported. (author)

  1. Hydrogen solubility in aluminum-copper alloys

    International Nuclear Information System (INIS)

    Hydrogen solubility(S (10-2 cm3g-1atm-0.5)) in Al-(0-50mass%) Cu alloys were measured by a desorption technique for the thermally gas-charged cylindrical samples which were solidified unidirectionally in the pure nitrogen gas flow (sample ND). The solubility was compared with that in samples melted and cast in vacuum (sample VM) and with that in samples melted in air and cast into a metal mould (sample AM). Since the solubility S (ND) was almost equal to S (VM), samples ND were found to have no voids of gas defects such as porosity and cavity. In the region of α-solid solution (Cuθ) and got to the higher hydrogen solubility in the θ-phase (Sθ), according to the equation S (ND) = Sα (1-fθ) + Sθfθ. S (AM) was greater than S (ND) due to the trapped hydrogen gas in the voids. In the alloy of the eutectic composition (33 mass%Cu) which had little voids, S (33AM) was smaller than S (33ND). This was attributed to anon-equilibrium or suppressed charging of hydrogen due to the trapping of hydrogen in a finer metallic structure of a sample AM. (author)

  2. Growth of metalloid aluminum clusters on graphene vacancies

    Science.gov (United States)

    Alnemrat, Sufian; Mayo, Dennis H.; DeCarlo, Samantha; Hooper, Joseph P.

    2016-01-01

    Ab initio simulations are used to show that graphene vacancy sites may offer a means of templated growth of metalloid aluminum clusters from their monohalide precursors. We present density functional theory and ab initio molecular dynamics simulations of the aluminum halide AlCl interacting with a graphene surface. Unlike a bare Al adatom, AlCl physisorbs weakly on vacancy-free graphene with little charge transfer and no hybridization with carbon orbitals. The barrier for diffusion of AlCl along the surface is negligible. Covalent bonding is seen only with vacancies and results in strong chemisorption and considerable distortion of the nearby lattice. Car-Parrinello molecular dynamics simulations of AlCl liquid around a graphene single vacancy show spontaneous metalloid cluster growth via a process of repeated insertion reactions. This suggests a means of templated cluster nucleation and growth on a carbon substrate and provides some confirmation for the role of a trivalent aluminum species in nucleating a ligated metalloid cluster from AlCl and AlBr solutions.

  3. Sequential desorption energy of hydrogen from nickel clusters

    Energy Technology Data Exchange (ETDEWEB)

    Deepika,; Kumar, Rakesh, E-mail: rakesh@iitrpr.ac.in [Department of Physics, Indian Institute of Technology Ropar, Rupnagar-140001 (India); R, Kamal Raj. [Indian Institute of Science Education and Research Kolkata, Mohanpur-741246 (India); Kumar, T. J. Dhilip [Department of Chemistry, Indian Institute of Technology Ropar, Rupnagar-140001 (India)

    2015-06-24

    We report reversible Hydrogen adsorption on Nickel clusters, which act as a catalyst for solid state storage of Hydrogen on a substrate. First-principles technique is employed to investigate the maximum number of chemically adsorbed Hydrogen molecules on Nickel cluster. We observe a maximum of four Hydrogen molecules adsorbed per Nickel atom, but the average Hydrogen molecules adsorbed per Nickel atom decrease with cluster size. The dissociative chemisorption energy per Hydrogen molecule and sequential desorption energy per Hydrogen atom on Nickel cluster is found to decrease with number of adsorbed Hydrogen molecules, which on optimization may help in economical storage and regeneration of Hydrogen as a clean energy carrier.

  4. Sequential desorption energy of hydrogen from nickel clusters

    International Nuclear Information System (INIS)

    We report reversible Hydrogen adsorption on Nickel clusters, which act as a catalyst for solid state storage of Hydrogen on a substrate. First-principles technique is employed to investigate the maximum number of chemically adsorbed Hydrogen molecules on Nickel cluster. We observe a maximum of four Hydrogen molecules adsorbed per Nickel atom, but the average Hydrogen molecules adsorbed per Nickel atom decrease with cluster size. The dissociative chemisorption energy per Hydrogen molecule and sequential desorption energy per Hydrogen atom on Nickel cluster is found to decrease with number of adsorbed Hydrogen molecules, which on optimization may help in economical storage and regeneration of Hydrogen as a clean energy carrier

  5. Radical attached aluminum nanoclusters: an alternative way of cluster stabilization.

    Science.gov (United States)

    Sengupta, Turbasu; Pal, Sourav

    2016-08-21

    The stability and electronic structure of radical attached aluminum nanoclusters are investigated using density functional theory (DFT). A detailed investigation shows good correlation between the thermodynamic stability of radical attached clusters and the stability of the attached radical anions. All other calculated parameters like HOMO-LUMO gap and charge transfer are also found to be consistent with the observed thermodynamic stabilities of the complexes. Investigation of the electronic structure of radical attached complexes further shows the presence of jellium structures within the core similar to the ligated clusters. Comparison with available experimental and theoretical data also proves the validity of superatomic complex theory for the radical attached clusters as well. Based on the evaluated thermodynamic parameters, selected radical attached clusters are observed to be more thermodynamically stable in comparison with experimentally synthesized ligated clusters. Stabilization of small metal clusters is one of the greatest challenges in current cluster science and the present investigation confirms the fact that radical attached clusters can provide a viable alternative to ligated clusters in the future. PMID:27435912

  6. Hydrogen bonds in methane-water clusters.

    Science.gov (United States)

    Salazar-Cano, Juan-Ramón; Guevara-García, Alfredo; Vargas, Rubicelia; Restrepo, Albeiro; Garza, Jorge

    2016-08-24

    Characterization of hydrogen bonds in CH4-(H2O)12 clusters was carried out by using several quantum chemistry tools. An initial stochastic search provided around 2 500 000 candidate structures, then, using a convex-hull polygon criterion followed by gradient based optimization under the Kohn-Sham scheme, a total of 54 well defined local minima were located in the Potential Energy Surface. These structures were further analyzed through second-order many-body perturbation theory with an extended basis set at the MP2/6-311++G(d,p) level. Our analysis of Gibbs energies at several temperatures clearly suggests a structural preference toward compact water clusters interacting with the external methane molecule, instead of the more commonly known clathrate-like structures. This study shows that CH4-(H2O)12 clusters may be detected at temperatures up to 179 K, this finding provides strong support to a recently postulated hypothesis that suggests that methane-water clusters could be present in Mars at these conditions. Interestingly, we found that water to water hydrogen bonding is strengthened in the mixed clusters when compared to the isolated water dimer, which in turn leads to a weakening of the methane to water hydrogen bonding when compared to the CH4-(H2O) dimer. Finally, our evidence places a stern warning about the abilities of popular geometrical criteria to determine the existence of hydrogen bonds. PMID:27492605

  7. Hydrogen-induced initiation of corrosion in aluminum

    Energy Technology Data Exchange (ETDEWEB)

    Sergey N. Rashkeev; K. W. Sohlberg; S. P. Zhuo; S. T. Pantelides

    2007-05-01

    Corrosion resistance of aluminum alloys is related to the presence of a thin, passivating aluminum oxide film on the surface. In this paper, we perform first-principles quantum-mechanical calculations to provide atomic scale understanding of the initiation of corrosion in Al. Our results support the hypothesis that hydrogen plays an important role at different stages of the Al corrosion process. In particular, atomic hydrogen can penetrate into the oxide film and cause structural damage in both the oxide and at the Al/Al2O3 interface. The corrosion is then initiated by a breakdown of the oxide film and a subsequent pit development on the surface of the metal exposed to the environment.

  8. Hydrogen interactions in aluminum-lithium alloys

    Science.gov (United States)

    Smith, S. W.; Scully, J. R.

    1991-01-01

    A program is described which seeks to develop an understanding of the effects of dissolved and trapped hydrogen on the mechanical properties of selected Al-Li-Cu-X alloys. A proposal is made to distinguish hydrogen (H2) induced EAC from aqueous dissolution controlled EAC, to correlate H2 induced EAC with mobile and trapped concentrations, and to identify significant trap sites and hydride phases (if any) through use of model alloys and phases. A literature review shows three experimental factors which have impeded progress in the area of H2 EAC for this class of alloys. These are as listed: (1) inter-subgranular fracture in Al-Li alloys when tested in the S-T orientation in air or vacuum make it difficult to readily detect H2 induced fracture based on straight forward changes in fractography; (2) the inherently low H2 diffusivity and solubility in Al alloys is further compounded by a native oxide which acts as a H2 permeation barrier; and (3) H2 effects are masked by dissolution assisted processes when mechanical testing is performed in aqueous solutions.

  9. Ground state structures and properties of small hydrogenated silicon clusters

    Indian Academy of Sciences (India)

    R Prasad

    2003-01-01

    We present results for ground state structures and properties of small hydrogenated silicon clusters using the Car–Parrinello molecular dynamics with simulated annealing. We discuss the nature of bonding of hydrogen in these clusters. We find that hydrogen can form a bridge like Si–H–Si bond connecting two silicon atoms. We find that in the case of a compact and closed silicon cluster hydrogen bonds to the silicon cluster from outside. To understand the structural evolutions and properties of silicon cluster due to hydrogenation, we have studied the cohesive energy and first excited electronic level gap of clusters as a function of hydrogenation. We find that first excited electronic level gap of Si and SiH fluctuates as function of size and this may provide a first principle basis for the short-range potential fluctuations in hydrogenated amorphous silicon. The stability of hydrogenated silicon clusters is also discussed.

  10. In situ generation of hydrogen from water by aluminum corrosion in solutions of sodium aluminate

    OpenAIRE

    Soler Turu, Lluis; Candela Soto, Angélica Maria; Macanás de Benito, Jorge; Muñoz Tapia, Maria; Casado Giménez, Juan

    2009-01-01

    A new process to obtain hydrogen from water using aluminum in sodium aluminate solutions is described and compared with results obtained in aqueous sodium hydroxide. This process consumes only water and aluminum, which are raw materials much cheaper than other compounds used for in situ hydrogen generation, such as hydrocarbons and chemical hydrides, respectively. As a consequence, our process could be an economically feasible alternative for hydrogen to supply fuel cells. Results showed an i...

  11. Coupling a PEM fuel cell and the hydrogen generation from aluminum waste cans

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, Susana Silva; Albanil Sanchez, Loyda; Alvarez Gallegos, Alberto A. [Centro de Investigacion en Ingenieria y Ciencias Aplicadas, Av. Universidad 1001, Col. Chamilpa, Cuernavaca, Mor. CP 62210 (Mexico); Sebastian, P.J. [Centro de Investigacion en Energia-UNAM, 62580 Temixco, Morelos (Mexico); Cuerpo Academico de Energia y Sustentabilidad, UPCH, Tuxtla Gutierrez, Chiapas (Mexico)

    2007-10-15

    High purity hydrogen was generated from the chemical reaction of aluminum and sodium hydroxide. The aluminum used in this study was obtained from empty soft drink cans and treated with concentrated sulfuric acid to remove the paint and plastic film. One gram of aluminum was reacted with a solution of 2moldm{sup -3} of sodium hydroxide to produce hydrogen. The hydrogen produced from aluminum cans and oxygen obtained from a proton exchange membrane electrolyzer or air, was fed to a proton exchange membrane (PEM) fuel cell to produce electricity. Yields of 44 mmol of hydrogen contained in a volume of 1.760dm{sup 3} were produced from one gram of aluminum in a time period of 20 min. (author)

  12. Influence of Elemental Iron on Hydrogen Content in Superheated Aluminum-iron Melts

    Institute of Scientific and Technical Information of China (English)

    HU Li-na; BIAN Xiu-fang; ANANDA Mahto; DUAN You-feng

    2004-01-01

    The hydrogen content in liquid binary aluminum alloys with 1,3,5 and 8 wt% iron has been determined in the temperature range from 973K to 1103K.The hydrogen content in molten Al-Fe alloys increases remarkably when the temperature of the melt rises to about 1053K.This work indicates that the alloying element iron plays an important role in hydrogen content in superheated Al-Fe alloy melts below about 1053K.The results make it clear that the hydrogen content in the melt aluminum reduces with the increasing element levels.A conclusion is drawn that the degree of gassing in molten Al-Fe alloys is bound up with the properties of oxide film of aluminum alloy melts.The element iron has no effect on the compact structure of oxide film in aluminum melts.The effects of alloying element are theoretically analyzed in terms of Wagner interaction parameter.According to the values of the first order interaction parameter,it is concluded that the interaction between iron atom and aluminum is much stronger than that between hydrogen atom and aluminum,and the addition of the alloying element decreases the affinity of liquid aluminum for hydrogen.

  13. A study of hydrogen permeation in aluminum alloy treated by various oxidation processes

    International Nuclear Information System (INIS)

    A set of oxide coatings was formed on the surface of an Al alloy (wt%: Fe, 0.24; Si, 1.16; Cu, 0.05-0.2; Zn, 0.1; Al, residual) by means of various oxidation processes. The hydrogen permeability through the aluminum alloy and its coating materials was determined by a vapor phase permeation technique at temperatures ranging from 400 to 500 C using high-purity H2 (99.9999%) gas with an upstream hydrogen pressure of 104-105 Pa. The experimental results show that the hydrogen permeability through aluminum oxide coating is 100-2000 times lower than that through the aluminum alloy substrate. This means that the aluminum oxide is a significant hydrogen permeation barrier. A high hydrogen permeation resistance was observed in an oxide layer prefilmed in 200 C water, while an anodized aluminum oxide film had a less obstructive effect, possibly caused by the porous structure of the anodic oxide. The hydrogen permeability through films of aluminum oxide was not a simple function of the aluminum-oxide phase configuration. (orig.)

  14. Qijiang Plans to Build 50 Billion Yuan Industrial Cluster for Transport-use Aluminum

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    The reporter learned from the China International Transport-use Aluminum Forum2015 that 5 years later Qijiang District is expected to develop transport-use aluminum industrial cluster with annual output of 50billion yuan.According to statistics,last year 1 in every 9automobile OEM manufacturers nationwide

  15. Research progress of hydrogen clusters and their applications

    International Nuclear Information System (INIS)

    As the most simplest and abundant molecule in the universe, neutral hydrogen clusters are research prototype for structures and dynamics of molecular clusters. Meanwhile, as the material of the laser fusion and tokamak fusion, hydrogen molecule clusters greatly impact the efficiency of fusion. In this paper, the main content focuses on the significance, contents and status in basic area, superfluid area, tokamak area and laser fusion area. (authors)

  16. Structural, energetic, and electronic properties of hydrogenated titanium clusters.

    Science.gov (United States)

    Dhilip Kumar, T J; Tarakeshwar, P; Balakrishnan, N

    2008-05-21

    Hydrogen undergoes dissociative chemisorption on small titanium clusters. How the electronic structure of the cluster changes as a function of the number of adsorbed hydrogen atoms is an important issue in nanocatalysis and hydrogen storage. In this paper, a detailed theoretical investigation of the structural, energetic, and electronic properties of the icosahedral Ti13 cluster is presented as a function of the number of adsorbed hydrogen atoms. The results show that hydrogen loaded Ti13H20 and Ti13H30 clusters are exceptionally stable and are characterized by hydrogen multicenter bonds. In Ti13H20, the dissociated hydrogen atoms are bound to each of the 20 triangular faces of Ti13, while in Ti13H30, they are bound to the 30 Ti-Ti edges of Ti13. Consequently, the chemisorption and desorption energies of the Ti13H20 (1.93 eV, 3.10 eV) are higher than that of Ti13H30 (1.13 eV, 1.95 eV). While increased hydrogen adsorption leads to an elongation of the Ti-Ti bonds, there is a concomitant increase in the electrostatic interaction between the dissociated hydrogen atoms and the Ti13 cluster. This enhanced interaction results from the participation of the subsurface titanium atom at higher hydrogen concentrations. Illustrative results of hydrogen saturation on the larger icosahedral Ti55 cluster are also discussed. The importance of these results on hydrogen saturated titanium clusters in elucidating the mechanism of hydrogen adsorption and desorption in titanium doped complex metal hydrides is discussed. PMID:18500893

  17. Angular-dependent interatomic potential for the aluminum-hydrogen system

    Science.gov (United States)

    Apostol, F.; Mishin, Y.

    2010-10-01

    We report on the development of an angular-dependent interatomic potential for hydrogen and the aluminum-hydrogen system. The potential reproduces properties of diatomic hydrogen gas, accurate solution energies of hydrogen atoms in crystalline Al, the energetic preference of the tetrahedral interstitial site occupation over octahedral, the hydrogen diffusion barrier in Al, and a number of other properties. Some of the results predicted by the potential have been tested by molecular dynamics simulations. It is suggested that the new potential can be used in atomistic simulations of the effect of dissolved hydrogen on deformation and fracture of Al, a problem which is relevant to hydrogen-induced degradation of Al alloys.

  18. Hydrogen Embrittlement Susceptibility and Hydrogen-Induced Additive Stress of 7050 Aluminum Alloy Under Various Aging States

    Science.gov (United States)

    Qi, W. J.; Song, R. G.; Qi, X.; Li, H.; Wang, Z. X.; Wang, C.; Jin, J. R.

    2015-09-01

    Hydrogen embrittlement susceptibility of 7050 aluminum alloy under various aging states has been investigated by means of cathodic hydrogen permeation, slow strain rate test, hydrogen determinator, x-ray diffraction, and scanning electron microscope, and effect of hydrogen on atomic binding force of charged alloy has been calculated by free electron theory in this paper. Simultaneously, hydrogen-induced additive stress (σad) of 7050 aluminum alloy hydrogen charged with different current densities under various aging states have been investigated by flowing stress differential method. The results showed that hydrogen concentration of examined alloy increased with increasing charging time or current density under the same aging state. Hydrogen segregation occurred at grain boundaries which enlarged the crystal lattice constant, meanwhile, it reduced the average bonding energy and interatomic bonding force of the grain boundary atoms, thus resulting in hydrogen embrittlement; moreover, σad of 7050 aluminum alloy increased linearly with increasing hydrogen concentration under the same aging state, i.e., under aged: σad = -1.61 + 9.93 × 105 C H, peak aged: σad = -1.55 + 9.67 × 105 C H, over aged: σad = -0.16 + 9.35 × 105 C H, correspondingly, σad increased the susceptibility to hydrogen embrittlement ( I HE) further. Under the same charging condition, aging states had a great influence on σad and I HE, the under-aged state alloy was of the highest, the over-aged state alloy was of the lowest, and peak-aged was in the middle.

  19. Hydrogen binding in vacancy clusters in platinum

    International Nuclear Information System (INIS)

    The binding of hydrogen in different vacancy complexes in platinum metal was investigated with atomic-scale sensitivity using perturbed angular correlations of gamma rays (PAC). Hydrogen was introduced by cathodic charging. Detrapping was monitored microscopically during desorption at 294 K by changes in site fractions of hydrogen-decorated and undecorated complexes. Analysis of desorption includes effects of retrapping of hydrogen at other sites. Assuming a trap concentration of 10-3, binding enthalpies of 0.23(2), 0.28(1), 0.24(1) and >0.20 eV are obtained for hydrogen atoms in 1V to 4V complexes, respectively. The small differences between the binding enthalpies demonstrate that hydrogen binding is insensitive to the detailed geometrical structure of small vacancy complexes. However, the magnitudes found here are a factor of two smaller than in the literature. (orig.)

  20. Nanoscale microstructure effects on hydrogen behavior in rapidly solidified aluminum alloys

    International Nuclear Information System (INIS)

    The present work summarizes recent progress in the investigation of nanoscale microstructure effects on hydrogen behavior in rapidly solidified aluminum alloys foils produced at exceptionally high cooling rates. We focus here on the potential of modification of hydrogen desorption kinetics in respect to weak and strong trapping sites that could serve as hydrogen sinks in Al materials. It is shown that it is important to elucidate the surface microstructure of the Al alloy foils at the submicrometer scale because rapidly solidified microstructural features affect hydrogen trapping at nanostructured defects. We discuss the profound influence of solute atoms on hydrogen−lattice defect interactions in the alloys. with emphasis on role of vacancies in hydrogen evolution; both rapidly solidified pure Al and conventionally processed aluminum samples are considered

  1. Nanoscale microstructure effects on hydrogen behavior in rapidly solidified aluminum alloys

    Energy Technology Data Exchange (ETDEWEB)

    Tashlykova-Bushkevich, Iya I. [Belarusian State University of Informatics and Radioelectronics, Minsk (Belarus)

    2015-12-31

    The present work summarizes recent progress in the investigation of nanoscale microstructure effects on hydrogen behavior in rapidly solidified aluminum alloys foils produced at exceptionally high cooling rates. We focus here on the potential of modification of hydrogen desorption kinetics in respect to weak and strong trapping sites that could serve as hydrogen sinks in Al materials. It is shown that it is important to elucidate the surface microstructure of the Al alloy foils at the submicrometer scale because rapidly solidified microstructural features affect hydrogen trapping at nanostructured defects. We discuss the profound influence of solute atoms on hydrogen−lattice defect interactions in the alloys. with emphasis on role of vacancies in hydrogen evolution; both rapidly solidified pure Al and conventionally processed aluminum samples are considered.

  2. Precipitation hardening and hydrogen embrittlement of aluminum alloy AA7020

    Indian Academy of Sciences (India)

    Santosh Kumar; T K G Namboodhiri

    2011-04-01

    AA7020 Al–Mg–Zn, a medium strength aluminium alloy, is used in welded structures in military and aerospace applications. As it may be subjected to extremes of environmental exposures, including high pressure liquid hydrogen, it could suffer hydrogen embrittlement. Hydrogen susceptibility of alloy AA7020 was evaluated by slow strain-rate tensile testing, and delayed failure testing of hydrogen-charged specimens of air-cooled, duplexaged, and water-quenched duplex agedmaterials. The resistance to hydrogen embrittlement of the alloy was found to be in the order of air-cooled duplex aged alloy > as-received (T6 condition) > water quenched duplex aged material.

  3. EU Policies and Cluster Development of Hydrogen Communities

    OpenAIRE

    Bleischwitz, Raimund; Bader, Nikolas; Dannemand, Per; Nygaard, Anne

    2008-01-01

    This study takes on the issue of political and socio-economic conditions for the hydrogen economy as part of a future low carbon society in Europe. It is subdivided into two parts. A first part reviews the current EU policy framework in view of its impact on hydrogen and fuel cell development. In the second part an analysis of the regional dynamics and possible hydrogen and fuel cell clusters is carried out. The current EU policy framework does not hinder hydrogen development. Yet it does not...

  4. New nanomaterials for hydrogen storage. A new class of aluminum hydrides; Neue Nanomaterialien zur Wasserstoffspeicherung. Eine neue Klasse von Aluminiumhydriden

    Energy Technology Data Exchange (ETDEWEB)

    Cordes, Joern

    2009-02-13

    In this work, Aluminum was vaporized in a PACIS cluster source, while molecular Hydrogen was also provided, thus producing Aluminum hydride clusters. These clusters were mass selected and investigated via Photoelectron Spectroscopy with anions in order to determine their electronic structure. In a cooperation with Puru Jena et al. at the Virginia Commonwealth University, electronic and geometric structures of the clusters were also calculated using Density Functional Theory. A group of clusters, specifically Al{sub 4}H{sub 4}, Al{sub 4}H{sub 6} and a series of clusters Al{sub n}H{sub n+2} (5 {<=} n {<=} 8) showed large HOMO-LUMO-Gaps and relatively small adiabatic electron affinities, hinting towards an increased stability of these clusters. The resemblance of the structures of already known and stable Boranes (BnHm) led to investigations whether ''Wade's Rules'' could also be applied to the new Alanes Al{sub n}H{sub m}. Comparison of the experimentally found values for the HOMO-LUMO-Gap, Adiabatic electron Affinity and Vertical Detachment Energy with the calculated values led to geometric structures of the ground states that, in case of the clusters Al{sub n}H{sub n+2} (5 {<=} n {<=} 8) follow Wade's (n+1) rule: They adopt hollow, cage-like closo-structures with one terminal Hydrogen atom per Aluminum atom and two additional Hydrogen atoms on bridge-sites. The clusters Al{sub 4}H{sub 4} and Al{sub 4}H{sub 6} have tetrahedron-shaped structures. While Al{sub 4}H{sub 4} is a perfect tetrahedron, Al{sub 4}H{sub 6} adopts a slightly distorted tetrahedral geometry with D{sub 2d} symmetry and two Hydrogen atoms on bridge sites. Furthermore, Al{sub 4}H{sub 6} showed the biggest HOMO-LUMO-Gap of all investigated clusters with a value of 1.9 {+-} 0.1 eV. These findings seem to contradict Wade's (n+1) rule, but can be understood in terms of the Polyhedral Skeletal Electron Pair Theory (PSEPT). The molecular orbitals predicted by the PSEPT

  5. The effect of hydrogen embrittlement on the localized plastic deformation of aluminum alloy

    Science.gov (United States)

    Bochkareva, Anna; Lunev, Aleksey; Barannikova, Svetlana; Gorbatenko, Vadim; Shlyakhova, Galina; Zuev, Lev

    2015-10-01

    The effect of hydrogen embrittlement on the localized plastic deformation of aluminum alloy D1 was investigated. The studies were performed for the test samples of aluminum alloy subjected to electrolytic hydrogenation. It is found that the mechanical properties and localized plastic deformation parameters of aluminum alloy are affected adversely by hydrogen embrittlement. The hydrogenated counterpart of alloy has a lower degree of ductility relative to the original alloy; however, the plastic flow behavior of material remains virtually unaffected. Using scanning electron and atomic force microscopy methods, the changes in the fracture surface were investigated. The deformation diagrams were examined for the deformed samples of aluminum alloy. These are found to show all the plastic flow stages: the linear, parabolic and pre-failure stages would occur for the respective values of the exponent n from the Ludwik-Holomon equation. Using digital speckle image technique, the local strain patterns were being registered for the original alloy D1 and the counterpart subjected to electrolytic hydrogenation for 100 h.

  6. The effect of hydrogen embrittlement on the localized plastic deformation of aluminum alloy

    International Nuclear Information System (INIS)

    The effect of hydrogen embrittlement on the localized plastic deformation of aluminum alloy D1 was investigated. The studies were performed for the test samples of aluminum alloy subjected to electrolytic hydrogenation. It is found that the mechanical properties and localized plastic deformation parameters of aluminum alloy are affected adversely by hydrogen embrittlement. The hydrogenated counterpart of alloy has a lower degree of ductility relative to the original alloy; however, the plastic flow behavior of material remains virtually unaffected. Using scanning electron and atomic force microscopy methods, the changes in the fracture surface were investigated. The deformation diagrams were examined for the deformed samples of aluminum alloy. These are found to show all the plastic flow stages: the linear, parabolic and pre-failure stages would occur for the respective values of the exponent n from the Ludwik-Holomon equation. Using digital speckle image technique, the local strain patterns were being registered for the original alloy D1 and the counterpart subjected to electrolytic hydrogenation for 100 h

  7. Study on improving the lowest limit for determination of hydrogen in aluminum

    International Nuclear Information System (INIS)

    The purpose of this experiment was to improve the limit of determination of hydrogen in aluminum. As variation of surface gases on samples affected the limit of determination in an usual analytical method (a method of determing internal hydrogen by correcting surface hydrogen), a way of removing surface gases by discharge cleaning prior to analysis was studied in the present work. The results were as follows; 1) Aluminum surface gases consisted of mainly H2, H2O, CO, and CO2. In those gases, H2 and CO were remarkably detected. 2) Those surface gases could be removed by He discharge cleaning. CO as surface gas was 1 x 10-5 torr.l (3.5 x 1013 molec./cm2) after discharge cleaning, and was about 1 x 10-3 torr.l (3.5 x 1015 molec./cm2) with no discharge cleaning. 3) Analyzing aluminum sample which contained internal hydrogen of 0.11 cc/100 g Al after discharge cleaning, all internal hydrogen measured by an usual analytical method. Improvement of the limit of determination of internal hydrogen by discharge cleaning is considered to be possible. (author)

  8. Influence of hydrogen content on the behavior of grain refinement in hypereutectic aluminum-silicon alloy

    Institute of Scientific and Technical Information of China (English)

    Lina Hu; Xiufang Bian; Youfeng Duan

    2004-01-01

    Dissolved hydrogen is harmful to mechanical properties of refined hypereutectic aluminum-silicon alloys. In the present work, by using a stepped-form mold and the hydrogen-detecting instrument HYSCAN Ⅱ, the relationship between the initial hydrogen content in the melt and the refinement effect on the casting of hypereutectic aluminum-silicon alloy was investigated. The experimental results show that the cooling rate, the hydrogen content and the grain refinement effect are three interactive factors. When the hydrogen content is above 0.20 mL/100 g and the cooling rate is lower than that in 50 mm-thick step, hydrogen dissolved in the alloy melt influences the grain refinement effect. With increasing the cooling rate, the critical hydrogen content increases too. It is expected that much hydrogen in the melt make the net interfacial energy larger than or equal to zero, resulting in the shielding of the particles AlP during solidification and that the critical gas content is closely related to the critical radius of embryo bubbles.

  9. Hydrogenation of deformable aluminum alloy semiproducts during water quenching and artificial aging

    Science.gov (United States)

    Antipin, V. P.; Tul'Pakova, R. V.

    2007-10-01

    The surface layers of rods made of magnesium-containing aluminum alloys are shown to undergo strong hydrogenation during water quenching. Hydrogenation is detected during vacuum heating after artificial aging (D16 alloy) or long-term storage (V95, AK4-1ch alloys). Very high hydrogen concentrations in the surface layers of semiproducts that appear in regions with a minimum cooling rate during quenching are likely to cause bubble formation on the surface of the heat-treated semiproducts. Compared to the V95 alloy, hydrogen dissolved in the AK4-1ch alloy rods behaves differently during air annealing. Specifically, hydrogen is rapidly absorbed by the degassed rods and is slowly extracted from the saturated rods. This behavior is most likely to be caused by hydrogen-ion entrapment by FeNiAl9 intermetallic particles.

  10. A nine-atom rhodium–aluminum oxide cluster oxidizes five carbon monoxide molecules

    Science.gov (United States)

    Li, Xiao-Na; Zhang, Hua-Min; Yuan, Zhen; He, Sheng-Gui

    2016-01-01

    Noble metals can promote the direct participation of lattice oxygen of very stable oxide materials such as aluminum oxide, to oxidize reactant molecules, while the fundamental mechanism of noble metal catalysis is elusive. Here we report that a single atom of rhodium, a powerful noble metal catalyst, can promote the transfer of five oxygen atoms to oxidize carbon monoxide from a nine-atom rhodium–aluminum oxide cluster. This is a sharp improvement in the field of cluster science where the transfer of at most two oxygen atoms from a doped cluster is more commonly observed. Rhodium functions not only as the preferred trapping site to anchor and oxidize carbon monoxide by the oxygen atoms in direct connection with rhodium but also the primarily oxidative centre to accumulate the large amounts of electrons and the polarity of rhodium is ultimately transformed from positive to negative. PMID:27094921

  11. A nine-atom rhodium-aluminum oxide cluster oxidizes five carbon monoxide molecules.

    Science.gov (United States)

    Li, Xiao-Na; Zhang, Hua-Min; Yuan, Zhen; He, Sheng-Gui

    2016-01-01

    Noble metals can promote the direct participation of lattice oxygen of very stable oxide materials such as aluminum oxide, to oxidize reactant molecules, while the fundamental mechanism of noble metal catalysis is elusive. Here we report that a single atom of rhodium, a powerful noble metal catalyst, can promote the transfer of five oxygen atoms to oxidize carbon monoxide from a nine-atom rhodium-aluminum oxide cluster. This is a sharp improvement in the field of cluster science where the transfer of at most two oxygen atoms from a doped cluster is more commonly observed. Rhodium functions not only as the preferred trapping site to anchor and oxidize carbon monoxide by the oxygen atoms in direct connection with rhodium but also the primarily oxidative centre to accumulate the large amounts of electrons and the polarity of rhodium is ultimately transformed from positive to negative. PMID:27094921

  12. Hydrogen absorption line profiles of ionizing star clusters

    OpenAIRE

    Angeles I. Díaz

    1988-01-01

    This is an electronic version of an article published in Monthly Notices of the Royal Astronomical Society. Díaz, A.I. Hydrogen absorption line profiles of ionizing star clusters. Monthly Notices of the Royal Astronomical Society 231 (1988): 57-67 and Microfiche MN 231/1

  13. Aluminum hydride as a hydrogen and energy storage material: Past, present and future

    International Nuclear Information System (INIS)

    Aluminum hydride (AlH3) and its associated compounds make up a fascinating class of materials that have motivated considerable scientific and technological research over the past 50 years. Due primarily to its high energy density, AlH3 has become a promising hydrogen and energy storage material that has been used (or proposed for use) as a rocket fuel, explosive, reducing agent and as a hydrogen source for portable fuel cells. This review covers the past, present and future research on aluminum hydride and includes the latest research developments on the synthesis of α-AlH3 and the other polymorphs (e.g., microcrystallization reaction, batch and continuous methods), crystallographic structures, thermodynamics and kinetics (e.g., as a function of crystallite size, catalysts and surface coatings), high-pressure hydrogenation experiments and possible regeneration routes.

  14. Influence of element Cu on hydrogen content in superheated aluminum melt

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The hydrogen content in molten Al-Cu alloy increases remarkably when the temperature of the melt rises to about 780  ℃. The effects of alloying element are theoretically analyzed in terms of Wagner interaction parameter. Furthermore, analyses indicate that the alloy element Cu plays an important role in the hydrogen content in superheated Al-Cu alloy melt below about 780  ℃. The conclusion is drawn that the degree of gassing in molten Al-Cu alloy is bound up with the properties of oxide film of Al alloy melts. The results make it clear that the hydrogen content in the molten aluminum reduces with increasing element Cu dissolved in aluminum melts at the same temperature.

  15. Interaction of hydrogen with palladium clusters deposited on graphene

    International Nuclear Information System (INIS)

    Hydrogen adsorption on nanoporous carbon materials is a promising technology for hydrogen storage. However, pure carbon materials do not meet the technological requirements due to the week binding of hydrogen to the pore walls. Experimental work has shown that doping with Pd atoms and clusters enhances the storage capacity of porous carbons. Therefore, we have investigated the role played by the Pd dopant on the enhancement mechanisms. By performing density functional calculations, we have found that hydrogen adsorbs on Pd clusters deposited on graphene following two channels, molecular adsorption and dissociative chemisorption. However, desorption of Pd-H complexes competes with desorption of hydrogen, and consequently desorption of Pd-H complexes would spoil the beneficial effect of the dopant. As a way to overcome this difficulty, Pd atoms and clusters can be anchored to defects of the graphene layer, like graphene vacancies. The competition between molecular adsorption and dissociative chemisorption of H2 on Pd6 anchored on a graphene vacancy has been studied in detail

  16. Interaction of hydrogen with palladium clusters deposited on graphene

    Energy Technology Data Exchange (ETDEWEB)

    Alonso, Julio A.; Granja, Alejandra; Cabria, Iván; López, María J. [Departamento de Física Teórica, Atómica y Optica, Universidad de Valladolid, 47011 Valladolid (Spain)

    2015-12-31

    Hydrogen adsorption on nanoporous carbon materials is a promising technology for hydrogen storage. However, pure carbon materials do not meet the technological requirements due to the week binding of hydrogen to the pore walls. Experimental work has shown that doping with Pd atoms and clusters enhances the storage capacity of porous carbons. Therefore, we have investigated the role played by the Pd dopant on the enhancement mechanisms. By performing density functional calculations, we have found that hydrogen adsorbs on Pd clusters deposited on graphene following two channels, molecular adsorption and dissociative chemisorption. However, desorption of Pd-H complexes competes with desorption of hydrogen, and consequently desorption of Pd-H complexes would spoil the beneficial effect of the dopant. As a way to overcome this difficulty, Pd atoms and clusters can be anchored to defects of the graphene layer, like graphene vacancies. The competition between molecular adsorption and dissociative chemisorption of H{sub 2} on Pd{sub 6} anchored on a graphene vacancy has been studied in detail.

  17. Two step novel hydrogen system using additives to enhance hydrogen release from the hydrolysis of alane and activated aluminum

    Science.gov (United States)

    Zidan, Ragaiy; Teprovich, Joseph A.; Motyka, Theodore

    2015-12-01

    A system for the generation of hydrogen for use in portable power systems is set forth utilizing a two-step process that involves the thermal decomposition of AlH.sub.3 (10 wt % H.sub.2) followed by the hydrolysis of the activated aluminum (Al*) byproduct to release additional H.sub.2. Additionally, a process in which water is added directly without prior history to the AlH.sub.3:PA composite is also disclosed.

  18. Revealing the multi-bonding state between hydrogen and graphene-supported Ti clusters

    CERN Document Server

    Takahashi, Keisuke; Omori, Kengo; Mashoff, Torge; Convertino, Domenica; Miseikis, Vaidotas; Coletti, Camilla; Tozzini, Valentina; Heun, Stefan

    2016-01-01

    Hydrogen adsorption on graphene-supported metal clusters has brought much controversy due to the complex nature of the bonding between hydrogen and metal clusters. The bond types of hydrogen and graphene-supported Ti clusters are experimentally and theoretically investigated. Transmission electron microscopy shows that Ti clusters of nanometer-size are formed on graphene. Thermal desorption spectroscopy captures three hydrogen desorption peaks from hydrogenated graphene-supported Ti clusters. First principle calculations also found three types of interaction: Two types of bonds with different partial ionic character and physisorption. The physical origin for this rests on the charge state of the Ti clusters: when Ti clusters are neutral, H2 is dissociated, and H forms bonds with the Ti cluster. On the other hand, H2 is adsorbed in molecular form on positively charged Ti clusters, resulting in physisorption. Thus, this work clarifies the bonding mechanisms of hydrogen on graphene-supported Ti clusters.

  19. Remarkable Hydrogen Storage on Beryllium Oxide Clusters: First Principles Calculations

    CERN Document Server

    Shinde, Ravindra

    2016-01-01

    Since the current transportation sector is the largest consumer of oil, and subsequently responsible for major air pollutants, it is inevitable to use alternative renewable sources of energies for vehicular applications. The hydrogen energy seems to be a promising candidate. To explore the possibility of achieving a solid-state high-capacity storage of hydrogen for onboard applications, we have performed first principles density functional theoretical calculations of hydrogen storage properties of beryllium oxide clusters (BeO)$_{n}$ (n=2 -- 8). We observed that polar BeO bond is responsible for H$_{2}$ adsorption. The problem of cohesion of beryllium atoms does not arise, as they are an integral part of BeO clusters. The (BeO)$_{n}$ (n=2 -- 8) adsorbs 8--12 H$_{2}$ molecules with an adsorption energy in the desirable range of reversible hydrogen storage. The gravimetric density of H$_{2}$ adsorbed on BeO clusters meets the ultimate 7.5 wt% limit, recommended for onboard practical applications. In conclusion,...

  20. Electrocoagulation of palm oil mill effluent as wastewater treatment and hydrogen production using electrode aluminum.

    Science.gov (United States)

    Nasution, M Ansori; Yaakob, Z; Ali, Ehsan; Tasirin, S M; Abdullah, S R S

    2011-01-01

    Palm oil mill effluent (POME) is highly polluting wastewater generated from the palm oil milling process. Palm oil mill effluent was used as an electrolyte without any additive or pretreatment to perform electrocoagulation (EC) using electricity (direct current) ranging from 2 to 4 volts in the presence of aluminum electrodes with a reactor volume of 20 L. The production of hydrogen gas, removal of chemical oxygen demand (COD), and turbidity as a result of electrocoagulation of POME were determined. The results show that EC can reduce the COD and turbidity of POME by 57 and 62%, respectively, in addition to the 42% hydrogen production. Hydrogen production was also helpful to remove the lighter suspended solids toward the surface. The production of Al(OH)XHO at the aluminum electrode (anode) was responsible for the flocculation-coagulation process of suspended solids followed by sedimentation under gravity. The production of hydrogen gas from POME during EC was also compared with hydrogen gas production by electrolysis of tap water at pH 4 and tap water without pH adjustment under the same conditions. The main advantage of this study is to produce hydrogen gas while treating POME with EC to reduce COD and turbidity effectively. PMID:21712603

  1. Effect of aluminum on the equilibrium solubility of hydrogen in vanadium

    International Nuclear Information System (INIS)

    A part from the temperature and pressure the solubility of hydrogen in a given matrix is also affected by the composition of the matrix. In metal matrices the presence of one or more substitutional as well as interstitial alloying components can have a significant effect on the solubility of hydrogen. As vanadium is an important refractory metal and vanadium based alloys having high melting point, low solubility of hydrogen isotopes, and most importantly resistance to irradiation properties make it a potential structural material for fusion reactor. It is essential to study the solubility of hydrogen in this metal and its alloys to understand the hydrogen solubility in the service conditions. Vanadium metal, a BCC crystal structure can accommodate more hydrogen in the open voids but solubility of hydrogen substantially affected by the presence of s and p block elements. Aluminothermy reduction of vanadium pentaoxide is one of the method of preparing vanadium metal and therefore aluminium is usually present in unrefined vanadium metal. The alloying effects on the solubility of hydrogen were investigated experimentally in binary V-14%Al (crude),V-10%Al (electron beam melted) and V-5%Al (electron beam melted followed by vacuum arc melting) alloys prepared by aluminothermy followed by refining process mentioned in bracket. It was found that solubility of hydrogen is substantially affected by the presence of aluminum

  2. Hydrogen Storage Materials Based on Single-Layer Aluminum Nitride Nanostructures

    Institute of Scientific and Technical Information of China (English)

    WANG Yu-Sheng; YUAN Peng-Fei; LI Meng; SUN Qiang; JIA Yu

    2011-01-01

    Using the first-principles method based on density functional theory, we study the hydrogen storage properties of Li-doped single-layer aluminum nitride nanostructures (A1N). For the pristine A1N sheet, each Al atom adsorbs one H2 with an average binding energy of 0.14eV/H2. The hydrogen binding energies and storage capacities can be markedly increased by doping Li atoms onto the A1N sheet. The charge analysis shows that there are charges transferring from the Li atoms to the A1N sheet, thus the charged Li atoms can polarize hydrogen molecules and enhance the interaction between hydrogen molecules and the A1N sheet. In the fully loaded cases, the Li-doped A1N sheet can contain up to 8.25wt% of molecular hydrogen with an average binding energy of 0.20eV/H2.%Using the first-principles method based on density functional theory,we study the hydrogen storage properties of Li-doped single-layer aluminum nitride nanostructures (AlN).For the pristine AlN sheet,each Al atom adsorbs one H2 with an average binding energy of 0.14 eV/H2.The hydrogen binding energies and storage capacities can be markedly increased by doping Li atoms onto the AlN sheet.The charge analysis shows that there are charges transferring from the Li atoms to the AlN sheet,thus the charged Li atoms can polarize hydrogen molecules and enhance the interaction between hydrogen molecules and the AlN sheet.In the fully loaded cases,the Li-doped AlN sheet can contain up to 8.25wt% of molecular hydrogen with an average binding energy of 0.20eV/H2.Hydrogen has long been considered as a carbondioxide-free energy carrier of the future.[1-3] One of the primary barriers preventing the large-scale use of hydrogen is the lack of an economic,effective and safe hydrogen storage medium.To achieve eventual economic feasibility,the materials should store hydrogen with large gravimetric and volumetric densities and operate under ambient thermodynamic conditions.[4]To meet these criteria,hydrogen storage media should only

  3. Molecular dynamics simulations of cluster distribution from femtosecond laser ablation in aluminum

    Science.gov (United States)

    Sonntag, S.; Trichet Paredes, C.; Roth, J.; Trebin, H.-R.

    2011-08-01

    Femtosecond laser ablation and plume evolution of aluminum is investigated for various inhomogeneous laser pulses. For the simulations of the atoms the molecular dynamics code IMD is used. The ablated gas-phase is scanned by a cluster algorithm (DBSCAN), from which we gain a cluster size distribution of the ablated material. Per single pulse, only a small portion of the total volume evaporates into the gas phase. Therefore—to have reasonable statistics—we have to deal with huge samples (6×107 atoms). The ablation threshold is determined by comparing the depth of the holes to the applied fluence. Angular and velocity distributions of the plume are compared to experiments.

  4. Composite aluminum conductors for pulsed power applications at liquid hydrogen temperatures

    International Nuclear Information System (INIS)

    High-purity, stress-free aluminum has extremely low electrical resistance at liquid hydrocarbon temperatures and strong magnetic fields. A composite conductor constructed with this high-purity, fine-filament material can allow fast current penetration to the filaments embedded in a high-electrical, low-thermal-resistance matrix to minimize loss problems. This composite conductor can be effectively used in pulsed power applications where liquid hydrogen is available, and where liquid helium normally needed for superconducting devices is absent. Major manufacturing concerns require that the matrix material have workability compatible with that of aluminum and practically zero impurity diffusion to ensure the high purity of aluminum filaments in the final product. They report favorable results of a feasibility study on fabricating such a composite conductor. An aluminum-base alloy containing iron and cerium, recently developed as a high-temperature material with dispersion strengthening, was used as the matrix material. It satisfies most of the aforementioned requirements. Using a streamlined die, billets of this alloy with pure aluminum inserts were successfully extruded in steps. Processing parameters were selected based on results of computer-aided processing simulation

  5. In situ generation of hydrogen from water by aluminum corrosion in solutions of sodium aluminate

    Energy Technology Data Exchange (ETDEWEB)

    Soler, Lluis; Candela, Angelica Maria; Munoz, Maria; Casado, Juan [Centre Grup de Tecniques de Separacio en Quimica (GTS), Unitat de Quimica Analitica, Departament de Quimica, Universitat Autonoma de Barcelona, Campus UAB s/n, 08193 Bellaterra, Barcelona, Catalonia (Spain); Macanas, Jorge [Laboratoire de Genie Chimique, UMR 5503 CNRS-INPT-UPS, Universite de Toulouse, Toulouse (France)

    2009-07-01

    A new process to obtain hydrogen from water using aluminum in sodium aluminate solutions is described and compared with results obtained in aqueous sodium hydroxide. This process consumes only water and aluminum, which are raw materials much cheaper than other compounds used for in situ hydrogen generation, such as hydrocarbons and chemical hydrides, respectively. As a consequence, our process could be an economically feasible alternative for hydrogen to supply fuel cells. Results showed an improvement of the maximum rates and yields of hydrogen production when NaAlO{sub 2} was used instead of NaOH in aqueous solutions. Yields of 100% have been reached using NaAlO{sub 2} concentrations higher than 0.65 M and first order kinetics at concentrations below 0.75 M has been confirmed. Two different heterogeneous kinetic models are verified for NaAlO{sub 2} aqueous solutions. The activation energy (E{sub a}) of the process with NaAlO{sub 2} is 71 kJ mol{sup -1}, confirming a control by a chemical step. A mechanism unifying the behavior of Al corrosion in NaOH and NaAlO{sub 2} solutions is presented. The application of this process could reduce costs in power sources based on fuel cells that nowadays use hydrides as raw material for hydrogen production. (author)

  6. Chemical Hydrogen Storage Using Polyhedral Borane Anions and Aluminum-Ammonia-Borane Complexes

    Energy Technology Data Exchange (ETDEWEB)

    Hawthorne, M. Frederick; Jalisatgi, Satish S.; Safronov, Alexander V.; Lee, Han Beak; Wu, Jianguo

    2010-10-01

    Phase 1. Hydrolysis of borohydride compounds offer the potential for significant hydrogen storage capacity, but most work to date has focused on one particular anion, BH4-, which requires high pH for stability. Other borohydride compounds, in particular polyhedral borane anions offer comparable hydrogen storage capacity without requiring high pH media and their long term thermal and hydrolytic stability coupled with non-toxic nature make them a very attractive alternative to NaBH4. The University of Missouri project provided the overall program focal point for the investigation of catalytic hydrolysis of polyhedral borane anions for hydrogen release. Due to their inherent stability, a transition metal catalyst was necessary for the hydrolysis of polyhedral borane anions. Transition metal ions such as cobalt, nickel, palladium and rhodium were investigated for their catalytic activity in the hydrolysis of nido-KB11H14, closo-K2B10H10, and closo-K2B12H12. The rate of hydrolysis follows first-order kinetics with respect to the concentration of the polyhedral borane anion and surface area of the rhodium catalyst. The rate of hydrolysis depends upon a) choice of polyhedral borane anion, c) concentration of polyhedral borane anion, d) surface area of the rhodium catalyst and e) temperature of the reaction. In all cases the yield of hydrogen was 100% which corresponds to ~7 wt% of hydrogen (based on material wt%). Phase 2. The phase 2 of program at the University of Missouri was focused upon developing aluminum ammonia-boranes (Al-AB) as chemical hydrogen storage materials, specifically their synthesis and studies of their dehydrogenation. The ammonia borane molecule (AB) is a demonstrated source of chemically stored hydrogen (19.6 wt%) which meets DOE performance parameters except for its regeneration from spent AB and elemental hydrogen. The presence of an aluminum center bonded to multiple AB residues might combine the efficiency of AB dehydrogenation with an aluminum

  7. Hydrogen transfer in excited pyrrole-ammonia clusters

    Science.gov (United States)

    David, O.; Dedonder-Lardeux, C.; Jouvet, C.; Kang, H.; Martrenchard, S.; Ebata, T.; Sobolewski, A. L.

    2004-06-01

    The excited state hydrogen atom transfer reaction (ESHT) has been studied in pyrrole-ammonia clusters [PyH-(NH3)n+hν→Py•+•NH4(NH3)n-1]. The reaction is clearly evidenced through two-color R2P1 experiments using delayed ionization and presents a threshold around 235 nm (5.3 eV). The cluster dynamics has also been explored by picosecond time scale experiments. The clusters decay in the 10-30 ps range with lifetimes increasing with the cluster size. The appearance times for the reaction products are similar to the decay times of the parent clusters. Evaporation processes are also observed in competition with the reaction, and the cluster lifetime after evaporation is estimated to be around 10 ns. The kinetic energy of the reaction products is fairly large and the energy distribution seems quasi mono kinetic. These experimental results rule out the hypothesis that the reaction proceeds through a direct N-H bond rupture but rather imply the existence of a fairly long-lived intermediate state. Calculations performed at the CASSCF/CASMP2 level confirm the experimental observations, and provide some hints regarding the reaction mechanism.

  8. Electronic stress tensor analysis of hydrogenated palladium clusters

    CERN Document Server

    Ichikawa, Kazuhide; Szarek, Pawel; Zhou, Chenggang; Cheng, Hansong; Tachibana, Akitomo

    2011-01-01

    We study the chemical bonds of small palladium clusters Pd_n (n=2-9) saturated by hydrogen atoms using electronic stress tensor. Our calculation includes bond orders which are recently proposed based on the stress tensor. It is shown that our bond orders can classify the different types of chemical bonds in those clusters. In particular, we discuss Pd-H bonds associated with the H atoms with high coordination numbers and the difference of H-H bonds in the different Pd clusters from viewpoint of the electronic stress tensor. The notion of "pseudo-spindle structure" is proposed as the region between two atoms where the largest eigenvalue of the electronic stress tensor is negative and corresponding eigenvectors forming a pattern which connects them.

  9. Metalloid aluminum and gallium clusters: element modifications on the molecular scale?

    Science.gov (United States)

    Schnepf, Andreas; Schnöckel, Hansgeorg

    2002-10-01

    As members of the same group in the periodic table, the industrially significant elements aluminum and gallium exhibit strong similarities in the majority of their compounds. In contrast there are significant differences in the structures of the two elemental forms: Aluminum forms a typical closest-packed metallic structure whereas gallium demonstrates a diversity of molecular bonding principles in its seven structural modifications. It can therefore be expected that differences between Al and Ga compounds will arise when, as for the elemental forms, many metal-metal bonds are formed. To synthesize such cluster compounds, we have developed the following synthesis procedure: Starting from gaseous monohalides at around 1000 degrees C, metastable solutions are generated from which the elements ultimately precipitate by means of a disproportionation reaction at room temperature. On the way to the elemental forms, molecular Al and Ga cluster compounds can be obtained by selection of suitable ligands (protecting groups), in which a core of Al or Ga atoms are protected from the formation of the solid element by a ligand shell. Since the arrangement of atoms in such clusters corresponds to that in the elements, we have designated these clusters as metalloid or elementoid. In accordance with the Greek word [see text] (ideal, prototype), the atomic arrangement in metalloid clusters represents the prototypic or ideal atomic arrangement in the elements at the molecular level. The largest clusters of this type contain 77 Al or 84 Ga atoms and have diameters of up to two nanometers. They hold the world record with respect to the naked metal-atom core for structurally characterized metalloid clusters. PMID:12370894

  10. Excited electronic state decomposition mechanisms of clusters of dimethylnitramine and aluminum

    Indian Academy of Sciences (India)

    Anupam Bera; Atanu Bhattacharya

    2015-01-01

    In this report, electronically non-adiabatic decomposition pathways of clusters of dimethylnitramine and aluminum (DMNA-Al and DMNA-Al2) are discussed in comparison to isolated dimethylnitramine (DMNA). Electronically excited state processes of DMNA-Al and DMNA-Al2 are explored using the complete active space self-consistent field (CASSCF) and the restricted active space self-consistent field (RASSCF) theories, respectively. Similar to the nitro-nitrite isomerization reaction pathway of DMNA, DMNA-Al clusters also exhibit isomerization pathway. However, it involves several other steps, such as, first Al-O bond dissociation, then N-N bond dissociation followed by isomerization and finally NO elimination. Furthermore, DMNA-Al clusters exhibit overall exothermic decomposition reaction pathway and isolated DMNA shows overall endothermic reaction channel.

  11. Infrared Spectroscopy of Hydrogen-Bonded Clusters of Protonated Histidine

    Science.gov (United States)

    Kondo, Makoto; Kasahara, Yasutoshi; Ishikawa, Haruki

    2015-06-01

    Histidine(His), one of the essential amino acids, is involved in active sites in many enzyme proteins, and known to play fundamental roles in human body. Thus, to gain detailed information about intermolecular interactions of His as well as its structure is very important. In the present study, we have recorded IR spectra of hydrogen-bonded clusters of protonated His (HisH^+) in the gas phase to discuss the relation between the molecular structure and intermolecular interaction of HisH^+. Clusters of HisH^+-(MeOH)_n (n = 1, 2) were generated by an electrospray ionization of the MeOH solution of L-His hydrochloride monohydrate. IR photodissociation spectra of HisH^+-(MeOH)1,2 were recorded. By comparing with the results of the DFT calculations, we determined the structures of these clusters. In the case of n = 1 cluster, MeOH is bonded to the imidazole ring as a proton acceptor. The most of vibrational bands observed were well explained by this isomer. However, a free NH stretch band of the imidazole ring was also observed in the spectrum. This indicates an existence of an isomer in which MeOH is bounded to the carboxyl group of HisH^+. Furthermore, it is found that a protonated position of His is influenced by a hydrogen bonding position of MeOH. In the case of n = 2 cluster, one MeOH molecule is bonded to the amino group, while the other MeOH molecule is separately bonded to the carboxyl group in the most stable isomer. However, there is a possibility that other conformers also exist in our experimental condition. The details of the experimental and theoretical results will be presented in the paper.

  12. Complex rare-earth aluminum hydrides: mechanochemical preparation, crystal structure and potential for hydrogen storage.

    Science.gov (United States)

    Weidenthaler, Claudia; Pommerin, André; Felderhoff, Michael; Sun, Wenhao; Wolverton, Christopher; Bogdanović, Borislav; Schüth, Ferdi

    2009-11-25

    A novel type of complex rare-earth aluminum hydride was prepared by mechanochemical preparation. The crystal structure of the REAlH(6) (with RE = La, Ce, Pr, Nd) compounds was calculated by DFT methods and confirmed by preliminary structure refinements. The trigonal crystal structure consists of isolated [AlH(6)](3-) octahedra bridged via [12] coordinated RE cations. The investigation of the rare-earth aluminum hydrides during thermolysis shows a decrease of thermal stability with increasing atomic number of the RE element. Rare-earth hydrides (REH(x)) are formed as primary dehydrogenation products; the final products are RE-aluminum alloys. The calculated decomposition enthalpies of the rare-earth aluminum hydrides are at the lower end for reversible hydrogenation under moderate conditions. Even though these materials may require somewhat higher pressures and/or lower temperatures for rehydrogenation, they are interesting examples of low-temperature metal hydrides for which reversibility might be reached. PMID:19886669

  13. Oxidation Phase Diagram of Small Aluminum Clusters Based on First-Principles Calculations

    Science.gov (United States)

    Wang, Ligen; Kuklja, Maija

    2009-06-01

    It is important to understand the properties of individual nanometals before we can exploit their efficiency as energetic materials or as enhancement additives to other energetic formulations. In this paper, we construct the (p, T) phase diagram for the O/Al13 system based on first-principles atomistic thermodynamics. The temperature and pressure is taken into account via the oxygen chemical potential. The optimized Al13 cluster has an icosahedral shape. We find that O adsorption on the Al13 surface is site-specific; in particular, O adsorption at the bridge sites is most stable, whereas adsorption at the hollow sites is slightly unfavorable. For various oxygen adsorption layers, we determine the adsorption configurations/patterns by performing Monte Carlo calculations. We assume that the metal cluster becomes completely oxidized and calculate formation enthalpies of various oxidized metal clusters. The obtained phase diagram shows that an intact Al13 cluster is stable at the low O chemical potential range and the fully oxidized metal cluster is stable at the high O chemical potential range. However, the O adsorption phases are never thermodynamically stable. This study provides important insights into basic behavior of small aluminum clusters in the presence of oxygen, and may affect reliable predictions of behavior of Al-high explosive composites.

  14. Orientationally ordered ridge structures of aluminum films on hydrogen terminated silicon

    DEFF Research Database (Denmark)

    Quaade, Ulrich; Pantleon, Karen

    2006-01-01

    > directions on the silicon substrate. The ridge structure appears when the film thickness is above 500 nm, and increasing the film thickness makes the structure more distinct. Anodic oxidation enhances the structure even further. X-ray diffraction indicates that grains in the film have mostly (110) facets......Films of aluminum deposited onto Si(100) substrates show a surface structure of parallel ridges. On films deposited on oxidized silicon substrates the direction of the ridges is arbitrary, but on films deposited on hydrogen-terminated Si(100) the ridges are oriented parallel to the < 110...

  15. Hydrogenation of Levulinic Acid over Nickel Catalysts Supported on Aluminum Oxide to Prepare γ-Valerolactone

    OpenAIRE

    Jie Fu; Dong Sheng; Xiuyang Lu

    2015-01-01

    Four types of nickel catalysts supported on aluminum oxide (Ni/Al2O3) with different nickel loadings were synthesized using the co-precipitation method and were used for the hydrogenation of levulinic acid (LA) to prepare γ-valerolactone (GVL). The synthesized Ni/Al2O3 catalysts exhibited excellent catalytic activity in dioxane, and the activity of the catalysts was excellent even after being used four times in dioxane. The catalytic activity in dioxane as a solvent was found to be superior t...

  16. Energetics of hydrogen impurities in aluminum and their effect on mechanical properties

    OpenAIRE

    Lu, Gang; Orlikowski, Daniel; Park, Ickjin; Politano, Olivier; Kaxiras, Efthimios

    2001-01-01

    The effects of hydrogen impurities in the bulk and on the surface of aluminum are theoretically investigated. Within the framework of density functional theory, we have obtained the dependence on H concentration of the stacking fault energy, the cleavage energy, the Al/H surface energy and the Al/H/Al interface formation energy. The results indicate a strong dependence of the slip energy barrier in the $[\\bar 211]$ direction the cleavage energy in the [111] direction and the Al/H/Al interface...

  17. Molecular dynamics simulations of cluster distribution from femtosecond laser ablation in aluminum

    Energy Technology Data Exchange (ETDEWEB)

    Sonntag, S.; Trichet Paredes, C.; Roth, J.; Trebin, H.R. [University of Stuttgart, Institute for Theoretical and Applied Physics, Stuttgart (Germany)

    2011-08-15

    Femtosecond laser ablation and plume evolution of aluminum is investigated for various inhomogeneous laser pulses. For the simulations of the atoms the molecular dynamics code IMD is used. The ablated gas-phase is scanned by a cluster algorithm (DBSCAN), from which we gain a cluster size distribution of the ablated material. Per single pulse, only a small portion of the total volume evaporates into the gas phase. Therefore - to have reasonable statistics - we have to deal with huge samples (6 x 10{sup 7} atoms). The ablation threshold is determined by comparing the depth of the holes to the applied fluence. Angular and velocity distributions of the plume are compared to experiments. (orig.)

  18. Ab initio search for global minimum structures of neutral and anionic hydrogenated Li5 clusters

    International Nuclear Information System (INIS)

    Highlights: • Stochastic search method is used to obtain global minimum of hydrogenated clusters. • The anionic hydrogenated Li5 clusters are firstly studied. • The fragmentation channels and energies of H atom and H2 dimer are investigated. • In hydrogenated Li5 clusters are easier to fragmentation the H2 dimer than H atom. • Li5Hn clusters is too high for the reversible hydrogen storage systems. - Abstract: The structure and some electronic properties of neutral and anionic Li5Hn (n = 0–6) clusters have been studied by using the stochastic search method with the B3LYP/6-31G level of theory. After searching possible isomers, first few isomers with the lowest energy have been recalculated by the B3LYP/6-311G++(2d,2p) and CCSD(T)/6-311G++(2d,2p) level of theory. The method used in this study has been compared with the previously reported ab initio calculations, and its reliability has been confirmed. The anionic Li5Hn (n = 0–6) clusters are reported in this study for the first time. Our results show that in general, stability increases with increasing number of hydrogen atoms. The fragmentation energies of hydrogenated Li5 clusters are easier to fragmentation the two hydrogen atoms than one hydrogen atom in hydrogenated clusters, and it is too high for the reversible hydrogen storage systems

  19. Hydrogenation of Levulinic Acid over Nickel Catalysts Supported on Aluminum Oxide to Prepare γ-Valerolactone

    Directory of Open Access Journals (Sweden)

    Jie Fu

    2015-12-01

    Full Text Available Four types of nickel catalysts supported on aluminum oxide (Ni/Al2O3 with different nickel loadings were synthesized using the co-precipitation method and were used for the hydrogenation of levulinic acid (LA to prepare γ-valerolactone (GVL. The synthesized Ni/Al2O3 catalysts exhibited excellent catalytic activity in dioxane, and the activity of the catalysts was excellent even after being used four times in dioxane. The catalytic activity in dioxane as a solvent was found to be superior to the activity in water. Nitrogen physisorption, X-ray diffraction, and transmission electron microscopy were employed to characterize the fresh and used catalysts. The effects of the nickel loading, temperature, hydrogen pressure, and substrate/catalyst ratio on the catalytic activity were investigated.

  20. Aluminum abundances of multiple stellar generations in the globular cluster NGC 1851

    CERN Document Server

    Carretta, Eugenio; Gratton, Raffaele G; Lucatello, Sara

    2012-01-01

    We study the distribution of aluminum abundances among red giants in the peculiar globular cluster NGC 1851. Aluminum abundances were derived from the strong doublet Al I 8772-8773 A measured on intermediate resolution FLAMES spectra of 50 cluster stars acquired under the Gaia-ESO public survey. We coupled these abundances with previously derived abundance of O, Na, Mg to fully characterize the interplay of the NeNa and MgAl cycles of H-burning at high temperature in the early stellar generation in NGC 1851. The stars in our sample show well defined correlations between Al,Na and Si; Al is anticorrelated with O and Mg. The average value of the [Al/Fe] ratio steadily increases going from the first generation stars to the second generation populations with intermediate and extremely modified composition. We confirm on a larger database the results recently obtained by us (Carretta et al. 2011a): the pattern of abundances of proton-capture elements implies a moderate production of Al in NGC 1851. We find evidenc...

  1. Chemisorption of O and H on an Al-13 cluster

    Science.gov (United States)

    Patridge, H.; Bauschlicher, C. W., Jr.

    1986-01-01

    Chemisorption of oxygen and hydrogen atoms onto a 13 atom aluminum cluster is investigated theoretically. Oxygen atoms are found to remain on the outside of the cluster, and at low coverage, to expand the Al-Al bond length by 0.42 bohr. Hydrogen atoms penetrate into the cluster resulting in a sizeable, 0.57 bohr expansion at high coverage. The difference between chemisorption on aluminum and beryllium clusters is discussed.

  2. Hydrogen plasma treatment for improved conductivity in amorphous aluminum doped zinc tin oxide thin films

    Directory of Open Access Journals (Sweden)

    M. Morales-Masis

    2014-09-01

    Full Text Available Improving the conductivity of earth-abundant transparent conductive oxides (TCOs remains an important challenge that will facilitate the replacement of indium-based TCOs. Here, we show that a hydrogen (H2-plasma post-deposition treatment improves the conductivity of amorphous aluminum-doped zinc tin oxide while retaining its low optical absorption. We found that the H2-plasma treatment performed at a substrate temperature of 50 °C reduces the resistivity of the films by 57% and increases the absorptance by only 2%. Additionally, the low substrate temperature delays the known formation of tin particles with the plasma and it allows the application of the process to temperature-sensitive substrates.

  3. Atomic layer deposition of aluminum sulfide thin films using trimethylaluminum and hydrogen sulfide

    International Nuclear Information System (INIS)

    Sequential exposures of trimethylaluminum and hydrogen sulfide are used to deposit aluminum sulfide thin films by atomic layer deposition (ALD) in the temperature ranging from 100 to 200 °C. Growth rate of 1.3 Å per ALD cycle is achieved by in-situ quartz crystal microbalance measurements. It is found that the growth rate per ALD cycle is highly dependent on the purging time between the two precursors. Increased purge time results in higher growth rate. Surface limited chemistry during each ALD half cycle is studied by in-situ Fourier transformed infrared vibration spectroscopy. Time of flight secondary ion-mass spectroscopy measurement is used to confirm elemental composition of the deposited films

  4. Hydrogen spillover on DV (555-777) graphene – vanadium cluster system: First principles study

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, E. Mathan, E-mail: ranjit.t@res.srmuniv.ac.in, E-mail: mathanranjitha@gmail.com; Thapa, Ranjit, E-mail: ranjit.t@res.srmuniv.ac.in, E-mail: mathanranjitha@gmail.com [SRM Research Institute, SRM University, Kattankulathur, Tamil Nadu - 603203 (India); P, Sabarikirishwaran [Department of Physics and Nanotechnology, SRM University, Kattankulathur, Tamil Nadu - 603203 (India)

    2015-06-24

    Using dispersion corrected density functional theory (DFT+D), the interaction of Vanadium adatom and cluster with divacancy (555-777) defective graphene sheet has been studied elaborately. We explore the prospect of hydrogen storage on V{sub 4} cluster adsorbed divacancy graphene system. It has been observed that V{sub 4} cluster (acting as a catalyst) can dissociate the H{sub 2} molecule into H atoms with very low barrier energy. We introduce the spillover of the atomic hydrogen throughout the surface via external mediator gallane (GaH{sub 3}) to form a hydrogenated system.

  5. Hydrogen spillover on DV (555-777) graphene – vanadium cluster system: First principles study

    International Nuclear Information System (INIS)

    Using dispersion corrected density functional theory (DFT+D), the interaction of Vanadium adatom and cluster with divacancy (555-777) defective graphene sheet has been studied elaborately. We explore the prospect of hydrogen storage on V4 cluster adsorbed divacancy graphene system. It has been observed that V4 cluster (acting as a catalyst) can dissociate the H2 molecule into H atoms with very low barrier energy. We introduce the spillover of the atomic hydrogen throughout the surface via external mediator gallane (GaH3) to form a hydrogenated system

  6. A Dark Hydrogen Cloud in the Virgo Cluster

    CERN Document Server

    Minchin, R; Disney, M; Boyce, P; García, D; Jordan, C; Kilborn, V; Lang, R; Roberts, S; Sabatini, S; Van Driel, W; Minchin, Robert; Davies, Jonathan; Disney, Michael; Boyce, Peter; Garcia, Diego; Jordan, Christine; Kilborn, Virginia; Lang, Robert; Roberts, Sarah; Sabatini, Sabina; Driel, Wim van

    2005-01-01

    VIRGOHI21 is an HI source detected in the Virgo Cluster survey of Davies et al. (2004) which has a neutral hydrogen mass of 10^8 M_solar and a velocity width of Delta V_20 = 220 km/s. From the Tully-Fisher relation, a galaxy with this velocity width would be expected to be 12th magnitude or brighter; however deep CCD imaging has failed to turn up a counterpart down to a surface-brightness level of 27.5 B mag/sq. arcsec. The HI observations show that it is extended over at least 16 kpc which, if the system is bound, gives it a minimum dynamical mass of ~10^11 M_solar and a mass to light ratio of M_dyn/L_B > 500 M_solar/L_solar. If it is tidal debris then the putative parents have vanished; the remaining viable explanation is that VIRGOHI21 is a dark halo that does not contain the expected bright galaxy. This object was found because of the low column density limit of our survey, a limit much lower than that achieved by all-sky surveys such as HIPASS. Further such sensitive surveys might turn up a significant n...

  7. Partially oxidized iridium clusters within dendrimers: size-controlled synthesis and selective hydrogenation of 2-nitrobenzaldehyde

    Science.gov (United States)

    Higaki, Tatsuya; Kitazawa, Hirokazu; Yamazoe, Seiji; Tsukuda, Tatsuya

    2016-06-01

    Iridium clusters nominally composed of 15, 30 or 60 atoms were size-selectively synthesized within OH-terminated poly(amidoamine) dendrimers of generation 6. Spectroscopic characterization revealed that the Ir clusters were partially oxidized. All the Ir clusters efficiently converted 2-nitrobenzaldehyde to anthranil and 2-aminobenzaldehyde under atmospheric hydrogen at room temperature in toluene via selective hydrogenation of the NO2 group. The selectivity toward 2-aminobenzaldehyde over anthranil was improved with the reduction of the cluster size. The improved selectivity is ascribed to more efficient reduction than intramolecular heterocyclization of a hydroxylamine intermediate on smaller clusters that have a higher Ir(0)-phase population on the surface.Iridium clusters nominally composed of 15, 30 or 60 atoms were size-selectively synthesized within OH-terminated poly(amidoamine) dendrimers of generation 6. Spectroscopic characterization revealed that the Ir clusters were partially oxidized. All the Ir clusters efficiently converted 2-nitrobenzaldehyde to anthranil and 2-aminobenzaldehyde under atmospheric hydrogen at room temperature in toluene via selective hydrogenation of the NO2 group. The selectivity toward 2-aminobenzaldehyde over anthranil was improved with the reduction of the cluster size. The improved selectivity is ascribed to more efficient reduction than intramolecular heterocyclization of a hydroxylamine intermediate on smaller clusters that have a higher Ir(0)-phase population on the surface. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01460g

  8. Analysis of a 'cluster' strategy for introducing hydrogen vehicles in Southern California

    International Nuclear Information System (INIS)

    The cost and logistics of building early hydrogen refueling infrastructure are key barriers to the commercialization of fuel cell vehicles. In this paper, we explore a 'cluster strategy' for introducing hydrogen vehicles and refueling infrastructure in Southern California over the next decade, to satisfy California's Zero Emission Vehicle regulation. Clustering refers to coordinated introduction of hydrogen vehicles and refueling infrastructure in a few focused geographic areas such as smaller cities (e.g. Santa Monica, Irvine) within a larger region (e.g. Los Angeles Basin). We analyze several transition scenarios for introducing hundreds to tens of thousands of vehicles and 8-42 stations, considering: · Station placement; · Convenience of the refueling network; · Type of hydrogen supply; · Economics (capital and operating costs of stations, hydrogen cost). A cluster strategy provides good convenience and reliability with a small number of strategically placed stations, reducing infrastructure costs. A cash flow analysis estimates infrastructure investments of $120-170 million might be needed to build a network of 42 stations serving the first 25,000 vehicles. As more vehicles are introduced, the network expands, larger stations are built and the cost of hydrogen becomes competitive on a cents per mile basis with gasoline. - Research Highlights: → Hydrogen infrastructure strategy based on 'clustering' early stations and vehicles. → Good fuel accessibility with sparse station networks. → As hydrogen use grows, fuel network expands and hydrogen becomes cost competitive.

  9. Hydra observations of aluminum abundances in the red giants ofthe globular clusters M80 and NGC 6752

    Energy Technology Data Exchange (ETDEWEB)

    Suntzeff, N B; Cavallo, R M; Pilachowski, C A

    2004-01-05

    Aluminum and other metal abundances were determined in 21 red giants in the globular clusters NGC 6752 and M80 as part of a larger study to determine whether the aluminum distribution on the red giant branch is related to the second parameter effect that causes clusters of similar metallicity to display different horizontal branch morphologies. The observations were obtained of the Al I lines near 6700 Angstroms with the CTIO Blanco 4-m telescope and Hydra multi-object spectrograph. The spectra have a resolving power of 18000 or 9400, with typical S/N ratios of 100-200. Mean [Fe/H] values obtained from the spectra are -1.58 for NGC 6751 and -1.73 for M80; this represents the spectroscopic iron abundance determination for M80. Both NGC 6752 and M80 display a spread in aluminum abundance with mean [Al/Fe] ratios of +0.51 and +0.37 respectively. No trend in the variation of the mean AI abundance with position on the giant branch is discernible in either cluster with our small sample.

  10. Catalysis by Oxide-Supported Clusters of Iridium and Rhodium: Hydrogenation of Ethene, Propene, and Toluene

    International Nuclear Information System (INIS)

    The hydrogenation reactions of ethene, propene, and toluene were used as probes of the catalytic properties of small clusters of rhodium (Rh6) and of iridium (Ir4 and Ir6) (as well as of larger aggregates of these metals) on oxide supports (γ-Al2O3, MgO, and La2O3). The catalysts were characterized in the working state by extended X-ray absorption fine structure (EXAFS) spectroscopy, providing evidence of the cluster structures and cluster-support interactions; by infrared spectroscopy, providing evidence of hydrocarbon adsorbates and possible reaction intermediates on the clusters; and by kinetics of the hydrogenation reactions. The EXAFS data indicate that the metal clusters, while remaining intact and maintaining their bonding to the support during catalysis, underwent slight rearrangements to accommodate reactive intermediates. As the concentrations of reactive intermediates such as π-bonded alkenes and alkyls on the clusters increased, the cluster frames swelled, and the clusters flexed away from the support. The data indicate self-inhibition of reaction by adsorbed hydrocarbons and differences between ethene hydrogenation and propene hydrogenation that may arise primarily from different adsorbate-adsorbate interactions

  11. Molecular dynamics simulations of anisotropic explosions of small hydrogen clusters in intense laser pulses

    International Nuclear Information System (INIS)

    The explosion dynamics of small hydrogen clusters irradiated by intense femtosecond infrared laser pulses is investigated by classical molecular dynamics simulations. We find a spatial anisotropy in these explosions with proton energies enhanced along the laser polarization direction. Our simulations can identify the origin of this anisotropy: the interplay between the space charge separation in the early stage of cluster ionization and the Coulomb attraction between the rescattered electrons and protons during cluster explosion. (paper)

  12. Colloidal CdS nanorods decorated with subnanometer sized Pt clusters for photocatalytic hydrogen generation

    International Nuclear Information System (INIS)

    Colloidal CdS nanorods have been decorated with extremely small, subnanometer sized Pt clusters and used for photocatalytic hydrogen production. We also show highly selective decoration of CdS nanorods with uniform, relatively large (4.8 nm mean size) Pt nanoparticles, with a remarkably high (90%) yield of samples decorated with exactly one Pt particle per rod. Samples with large Pt particles show no increase in hydrogen evolution rate compared to small Pt clusters, which implies that efficient hydrogen production utilizing CdS nanorods with reduced amounts of Pt is possible.

  13. Hydrogen binding effect on charged P2 ( = 1-7) clusters

    Indian Academy of Sciences (India)

    Zhicong Fang; Xiangjun Kuang

    2013-11-01

    An all-electron (AE) calculation of the hydrogen binding effect on charged phosphorus clusters has been performed under the framework of density functional theory (DFT). Compared with the P$^{\\pm}_{2n}$ ( = 1-7) clusters, the HP$^{\\pm}_{2n}$ ( = 1-7), cluster has shorter average P-P bond length, larger binding energy and HOMOLUMO gap (HLG), higher chemical hardness and frequency of P-P mode. After binding with one hydrogen atom, the electronic structure is changed from open electronic shell to closed electronic shell. Geometrical stability, chemical stability and electronic stability are strengthened. These stability enhancements may be simply understood considering the electron pairing effect.

  14. Evaluation of mechanical property data on the 2219 aluminum alloy and application of the data to the design of liquid hydrogen tankage

    Science.gov (United States)

    Witzell, W. E.

    1977-01-01

    The potential use of thin guage 2219 aluminum alloy for airborne liquid hydrogen tankage was examined. Existing data were processed using the Newman two parameter equation, a prediction was made for the life expectancy of a hypothetical liquid hydrogen tank, and additional experimental data were generated in an attempt to correct the deficiencies in the existing data.

  15. Studies on hollow spherical aluminum silicate cluster. Synthesis of environment friendly materials; Chuku kyujo aluminium keisan`en cluster ni kansuru kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Ohashi, F.; Maeda, M.; Suzuki, M.; Watamura, S. [National Industrial Research Institute of Nagoya,Nagoya (Japan)

    1999-01-25

    Synthesis of microfine particles of nanometer size, their surface adulteration and control of microstructure take an important position in different areas, such as electronics, chemical, machine and metal industries. However, reports on the established methods for synthesizing hollow spherical particles of nanometer size, which may be applied to micro capsules, cannot be found except for fullerene composed of carbon. This paper introduces a new method for synthesizing hollow spherical amorphous aluminum silicate cluster called allophane as an earth environmental material, and the derived properties of allophane. (translated by NEDO)

  16. Electronic characterization and reactivity of bimetallic clusters of the Ti(Mg){sub n} type for hydrogen storage applications

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Wilber [Institute of Chemistry, University of Antioquia, A.A. 1226, Medellin (Colombia); Truong, Thanh N. [Henry Eyring, Center for Theoretical Chemistry, Department of Chemistry, University of Utah, 315 South 1400 East, Rm 2020, Salt Lake City, UT 84112 (United States); Mondragon, Fanor, E-mail: fmondra@udea.edu.co [Institute of Chemistry, University of Antioquia, A.A. 1226, Medellin (Colombia)

    2011-08-25

    Highlights: > Magnesium-titanium clusters were modeled employing DFT and MP2. > Bimetallic systems have larger stability than monometallic magnesium clusters. > Reactivity of the bimetallic cluster is centered in the transition metal. > Bimetallic clusters are more reactive towards hydrogen to produce more stable hydrides. > Magnesium titanium systems are better for hydrogen storage than pure magnesium systems. - Abstract: This paper describes the variations in the properties, characteristics and hydrogenation energy barriers of magnesium clusters induced by titanium. DFT approach was used to determine the most stable structures at this theory level and then MP2 was used to refine the energy calculations with the basis set 6-311g(d) for magnesium and hydrogen, and pseudopotential lanl2dz for titanium. Bimetallic clusters showed higher stability and reactivity than the corresponding magnesium ones. Titanium induces a change in the magnesium atoms in their electronic configuration reflected in an increase of the population of their orbitals. At the same time titanium electronic populations is modified. These changes cause variations in some reactivity parameters such as the Fukui indexes which modify the hydrogenation of the magnesium clusters and bimetallic clusters. For example, there is a reduction in the energy barrier for dissociation of the H{sub 2} molecule in the bimetallic clusters. In the hydrogenated cluster the hydrogen atoms form bridges between all of the magnesium or magnesium-titanium atoms. These results indicate that, energetically, bimetallic systems can be more promising systems for hydrogen storage.

  17. Production of hydrogen in the reaction between aluminum and water in the presence of NaOH and KOH

    Directory of Open Access Journals (Sweden)

    C. B. Porciúncula

    2012-06-01

    Full Text Available The objective of this work is to investigate the production of hydrogen as an energy source by means of the reaction of aluminum with water. This reaction only occurs in the presence of NaOH and KOH, which behave as catalysts. The main advantages of using aluminum for indirect energy storage are: recyclability, non-toxicity and easiness to shape. Alkali concentrations varying from 1 to 3 mol.L-1 were applied to different metallic samples, either foil (0.02 mm thick or plates (0.5 and 1 mm thick, and reaction temperatures between 295 and 345 K were tested. The results show that the reaction is strongly influenced by temperature, alkali concentration and metal shape. NaOH commonly promotes faster reactions and higher real yields than KOH.

  18. Raman Vibrational Shifts of Small Clusters of Hydrogen Isotopologues.

    Science.gov (United States)

    Schmidt, Matthew; Fernández, José M; Faruk, Nabil; Nooijen, Marcel; Le Roy, Robert J; Morilla, Juan H; Tejeda, Guzmán; Montero, Salvador; Roy, Pierre-Nicholas

    2015-12-17

    Raman vibrational shifts of small parahydrogen (pH2), orthodeuterium (oD2), and paratritium (pT2) clusters with respect to the free molecules are calculated by combining a first order perturbation theory approach with Langevin equation Path Integral Ground State (LePIGS) simulations [ J. Phys. Chem. A 2013 , 117 , 7461 ]. Our theoretical predictions are compared to existing cryogenic free jet expansion results for pure (pH2)N clusters [ Phys. Rev. Lett. 2004 , 92 , 223401 ] and to new measurements for (oD2)N clusters reported here. This method has been successfully used before to predict the Raman vibrational shifts of (pH2)N clusters [ J. Chem. Phys. 2014 , 141 , 014310 ]. The 6-D interaction potential of Hinde [ J. Chem. Phys. 2008 , 128 , 154308 ] is reduced to 1-D using the Adiabatic Hindered Rotor approximation to yield effective pair potentials for both molecules being in the ground vibrational state, and for one of them carrying one quantum of vibrational excitation. These reduced 1-D potentials are fitted to a Morse Long Range analytic form for later convenience. Good agreement between experiment and theory is found for the smaller clusters, but significant deviations remain for the larger ones. PMID:26517305

  19. Hydrogen bonding in cubic (H2O)8 and OH·(H2O)7 clusters

    International Nuclear Information System (INIS)

    A systematic study is presented for OH·(H2O)7 clusters derived from the cubic (H2O)8 octamer by replacing one water with a hydroxyl radical. The system is a prototype for atmospheric water clusters containing the environmentally important OH species, and for OH adsorbed at the surface of ice. The full set of 39 symmetry-distinct cubic OH·(H2O)7 clusters is enumerated, and the structures are determined using ab initio quantum chemical methods. Graph invariants are employed to obtain a unified analysis of the stability and structure of cubic (H2O)8 and OH·(H2O)7, relating these physical properties to the various hydrogen-bond topologies present in these clusters. To accomplish this the graph invariant formalism is extended to treat a hydrogen bonding impurity within a pure water network

  20. Application of genetic algorithms to hydrogenated silicon clusters

    Indian Academy of Sciences (India)

    N Chakraborti; R Prasad

    2003-01-01

    We discuss the application of biologically inspired genetic algorithms to determine the ground state structures of a number of Si–H clusters. The total energy of a given configuration of a cluster has been obtained by using a non-orthogonal tight-binding model and the energy minimization has been carried out by using genetic algorithms and their recent variant differential evolution. Our results for ground state structures and cohesive energies for Si–H clusters are in good agreement with the earlier work conducted using the simulated annealing technique. We find that the results obtained by genetic algorithms turn out to be comparable and often better than the results obtained by the simulated annealing technique.

  1. Foil dissociation of 40-120 keV/p hydrogen clusters

    International Nuclear Information System (INIS)

    We report on measurements of angular and charge state distributions of hydrogen fragments resulting from the dissociation of fast Hn+ clusters (n ≤ 13) in a carbon foil. The proximity effects on the fragment neutralization has been investigated for beam velocities above and around the Bohr velocity. At a given velocity the angular width and the yield of neutral atoms are observed to saturate at n ≥ 5 and n ≥ 7, respectively. The interpretation of these behaviours provides some insight on the collective aspects of the collisions and on the structure of hydrogen clusters

  2. Mass spectrometry of hydrogen bonded clusters of heterocyclic molecules: Electron ionization vs. photoionization

    Czech Academy of Sciences Publication Activity Database

    Poterya, Viktoriya; Tkáč, Ondřej; Fedor, Juraj; Fárník, Michal; Slavíček, P.; Buck, U.

    2010-01-01

    Roč. 290, 2-3 (2010), s. 85-93. ISSN 1387-3806 R&D Projects: GA AV ČR KAN400400651; GA AV ČR KJB400400902; GA ČR GA203/09/0422 Institutional research plan: CEZ:AV0Z40400503 Keywords : cluster photochemistry * hydrogen bonded clusters * heterocyclic molecule Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.009, year: 2010

  3. Photoelectron Spectroscopy of Transition Metal Hydride Cluster Anions and Their Roles in Hydrogenation Reactions

    Science.gov (United States)

    Zhang, Xinxing; Bowen, Kit

    The interaction between transition metals and hydrogen has been an intriguing research topic for such applications as hydrogen storage and catalysis of hydrogenation and dehydrogenation. Special bonding features between TM and hydrogen are interesting not only because they are scarcely reported but also because they could help to discover and understand the nature of chemical bonding. Very recently, we discovered a PtZnH5- cluster which possessed an unprecedented planar pentagonal coordination between the H5- moiety and Pt, and exhibited special σ-aromaticity. The H5-kernel as a whole can be viewed as a η5-H5 ligand for Pt. As the second example, an H2 molecule was found to act as a ligand in the PdH3-cluster, in which two H atoms form a η2-H2 type of ligation to Pd. These transition metal hydride clusters were considered to be good hydrogen sources for hydrogenation. The reactions between PtHn- and CO2 were investigated. We observed formate in the final product H2Pt(HCO2)- .

  4. Pickup and Photodissociation of Hydrogen Halides in Floppy Neon Clusters

    Czech Academy of Sciences Publication Activity Database

    Slavíček, Petr; Jungwirth, Pavel; Lewerenz, M.; Nahler, N. H.; Fárnik, M.; Buck, U.

    2003-01-01

    Roč. 107, - (2003), s. 7743-7754. ISSN 1089-5639 R&D Projects: GA MŠk LN00A032 Institutional research plan: CEZ:AV0Z4040901 Keywords : photodissociation * neon clusters Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.792, year: 2003

  5. Quantum monte carlo study of the energetics of small hydrogenated and fluoride lithium clusters.

    Science.gov (United States)

    Moreira, N L; Brito, B G A; Rabelo, J N Teixeira; Cândido, Ladir

    2016-06-30

    An investigation of the energetics of small lithium clusters doped either with a hydrogen or with a fluorine atom as a function of the number of lithium atoms using fixed-node diffusion quantum Monte Carlo (DMC) simulation is reported. It is found that the binding energy (BE) for the doped clusters increases in absolute values leading to a more stable system than for the pure ones in excellent agreement with available experimental measurements. The BE increases for pure, remains almost constant for hydrogenated, and decreases rapidly toward the bulk lithium for the fluoride as a function of the number of lithium atoms in the clusters. The BE, dissociation energy as well as the second difference in energy display a pronounced odd-even oscillation with the number of lithium atoms. The electron correlation inverts the odd-even oscillation pattern for the doped in comparison with the pure clusters and has an impact of 29%-83% to the BE being higher in the pure cluster followed by the hydrogenated and then by the fluoride. The dissociation energy and the second difference in energy indicate that the doped cluster Li3 H is the most stable whereas among the pure ones the more stable are Li2 , Li4 , and Li6 . The electron correlation energy is crucial for the stabilization of Li3 H. © 2016 Wiley Periodicals, Inc. PMID:26992447

  6. Photoinduced Processes in Hydrogen Bonded System: Photodissociation of Imidazole Clusters

    Czech Academy of Sciences Publication Activity Database

    Poterya, Viktoriya; Profant, V.; Fárník, Michal; Šištík, L.; Slavíček, P.; Buck, U.

    2009-01-01

    Roč. 113, č. 52 (2009), s. 14583-14590. ISSN 1089-5639 R&D Projects: GA AV ČR KAN400400651; GA AV ČR KJB400400902; GA ČR GA203/09/0422 Institutional research plan: CEZ:AV0Z40400503 Keywords : scattering analysis * molecules * imidazole clusters Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.899, year: 2009

  7. Li{sub 2}O clusters for high-capacity hydrogen storage: A first principles study

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yusheng [College of Mathematics and Information Science, North China University of Water Resources and Electric Power, Zhengzhou, Henan 450011 (China); International Joint Research Laboratory for Quantum Functional Materials of Henan, and School of Physics and Engineering, Zhengzhou University, Zhengzhou, Henan 450001 (China); Li, Xingfu [College of Mathematics and Information Science, North China University of Water Resources and Electric Power, Zhengzhou, Henan 450011 (China); Wang, Fei [International Joint Research Laboratory for Quantum Functional Materials of Henan, and School of Physics and Engineering, Zhengzhou University, Zhengzhou, Henan 450001 (China); Xu, Bin; Zhang, Jing [College of Mathematics and Information Science, North China University of Water Resources and Electric Power, Zhengzhou, Henan 450011 (China); Sun, Qiang [International Joint Research Laboratory for Quantum Functional Materials of Henan, and School of Physics and Engineering, Zhengzhou University, Zhengzhou, Henan 450001 (China); Jia, Yu, E-mail: jiayu@zzu.edu.cn [International Joint Research Laboratory for Quantum Functional Materials of Henan, and School of Physics and Engineering, Zhengzhou University, Zhengzhou, Henan 450001 (China)

    2013-03-29

    Highlights: ► Li{sub 2}O clusters as hydrogen storage media. ► The average adsorption energy of hydrogen molecule is 0.19–0.22 eV/H{sub 2}. ► It can operate under ambient thermodynamic conditions. - Abstract: First-principles calculations based on density functional theory were carried out to study the geometries, electronic structures, and hydrogen storage properties of (Li{sub 2}O){sub n} clusters. The results show that for a given n its ground-state structure usually has the maximum Li–O bond. Due to transferring of charges from Li to O, the Li–O bond is polar. The orbital hybridization and the polarization are two main reasons for the adsorption of H{sub 2}. The (Li{sub 2}O){sub n} (n = 1–6) clusters each can bind 12–24 hydrogen molecules with average adsorption energy of 0.19–0.22 eV/H{sub 2}, desirable for reversible hydrogen storage.

  8. Probing the structures of gold-aluminum alloy clusters AuxAly(-): a joint experimental and theoretical study.

    Science.gov (United States)

    Khetrapal, Navneet Singh; Jian, Tian; Pal, Rhitankar; Lopez, Gary V; Pande, Seema; Wang, Lai-Sheng; Zeng, Xiao Cheng

    2016-05-01

    Besides the size and structure, compositions can also dramatically affect the properties of alloy nanoclusters. Due to the added degrees of freedom, determination of the global minimum structures for multi-component nanoclusters poses even greater challenges, both experimentally and theoretically. Here we report a systematic and joint experimental/theoretical study of a series of gold-aluminum alloy clusters, AuxAly(-) (x + y = 7,8), with various compositions (x = 1-3; y = 4-7). Well-resolved photoelectron spectra have been obtained for these clusters at different photon energies. Basin-hopping global searches, coupled with density functional theory calculations, are used to identify low-lying structures of the bimetallic clusters. By comparing computed electronic densities of states of the low-lying isomers with the experimental photoelectron spectra, the global minima are determined. It is found that for y ≥ 6 there is a strong tendency to form the magic-number square bi-pyramid motif of Al6(-) in the AuxAly(-) clusters, suggesting that the Al-Al interaction dominates the Au-Au interaction in the mixed clusters. A closely related trend is that for x > 1, the gold atoms tend to be separated by Al atoms unless only the magic-number Al6(-) square bi-pyramid motif is present, suggesting that in the small-sized mixed clusters, Al and Au components do not completely mix with one another. Overall, the Al component appears to play a more dominant role due to the high robustness of the magic-number Al6(-) square bi-pyramid motif, whereas the Au component tends to be either "adsorbed" onto the Al6(-) square bi-pyramid motif if y ≥ 6, or stays away from one another if x < y < 6. PMID:27119726

  9. Evolution of the vibrational spectra of doped hydrogen clusters with pressure

    Science.gov (United States)

    Santamaria, Ruben; Soullard, Jacques; Bokhimi, Xim; Martínez-Alanis, Paulina R.

    2014-05-01

    The evolution of the vibrational spectra of the isoelectronic hydrogen clusters H26, H24He, and H24Li+ is determined with pressure. We establish the vibrational modes with collective character common to the clusters, identify their individual vibrational fingerprints and discuss frequency shifts in the giga-Pascal pressure region. The results are of interest for the identification of doping elements such as inert He and ionic Li+ in hydrogen under confinement or, conversely, establish the pressure of doped hydrogen when the vibrational spectrum is known. At high pressure, the spectra of the nanoclusters resemble the spectrum of a solid, and the nanoclusters may be considered crystals of nanometer scale. The computations are performed at the gradient-corrected level of density functional theory. The investigation is the first of its kind.

  10. Mobility of hydrogen-helium clusters in tungsten studied by molecular dynamics

    Science.gov (United States)

    Grigorev, Petr; Terentyev, Dmitry; Bonny, Giovanni; Zhurkin, Evgeny E.; van Oost, Guido; Noterdaeme, Jean-Marie

    2016-06-01

    Tungsten is a primary candidate material for plasma facing components in fusion reactors. Interaction of plasma components with the material is unavoidable and will lead to degradation of the performance and the lifetime of the in-vessel components. In order to gain better understanding the mechanisms driving the material degradation at atomic level, atomistic simulations are employed. In this work we study migration, stability and self-trapping properties of pure helium and mixed helium-hydrogen clusters in tungsten by means of molecular dynamics simulations. We test two versions of an embedded atom model interatomic potential by comparing it with ab initio data regarding the binding properties of He clusters. By analysing the trajectories of the clusters during molecular dynamics simulations at finite temperatures we obtain the diffusion parameters. The results show that the diffusivity of mixed clusters is significantly lower, than that of pure helium clusters. The latter suggest that the formation of mixed clusters during mixed hydrogen helium plasma exposure will affect the helium diffusivity in the material.

  11. OCS in small para-hydrogen clusters: energetics and structure with N=1-8 complexed hydrogen molecules

    CERN Document Server

    Paesani, F; Whaley, K B

    2003-01-01

    We determine the structure and energetics of complexes of the linear OCS molecule with small numbers of para-hydrogen molecules, N=1-8, using zero temperature quantum Monte Carlo methods. Ground state calculations are carried out with importance-sampled rigid body diffusion Monte Carlo (IS-RBDMC) and excited state calculations with the projection operator imaginary time spectral evolution (POITSE) methodology. The ground states are found to be highly structured, with a gradual build up of two axial rings as N increases to 8. Analysis of the azimuthal density correlations around the OCS molecule shows that these rings are quite delocalized for small N values, but become strongly localized for N \\geq 5 . Excited state calculations are made for a range of total cluster angular momentum values and the rotational energy levels fitted to obtain effective rotational and distortion constants of the complexed OCS molecule as a function of cluster size N. Detailed analysis of these spectroscopic constants indicates tha...

  12. Effect of implanted silicon on hydrogen behavior in aluminum and nickel

    International Nuclear Information System (INIS)

    We have used elastic recoil detection (ERD) to study the behavior of hydrogen in Si-implanted Al and Ni samples, with a particular emphasis on the effect of the grain boundaries formed by implanting additive elements on hydrogen precipitation. From the measured H depth profiles and their thermal behavior, it is shown that the presence of an Al-Si layer in the near-surface region obstructs the annihilation of vacancies formed by hydrogen implantation in the pure Al region. In the case of Si-implanted Ni samples, hydrogen hardly precipitates except for the case of annealing procedure done at a relatively low temperature at which silicides are not formed but vacancies produced by the Si implantation are removed from the samples. These hydrogen trap sites were identified and the observed facts are explained well by taking into account the interface formed by the Si implantation

  13. Hydrogen cluster-like behaviour during supersonic molecular beam injection on the HL-1M tokamak

    International Nuclear Information System (INIS)

    Pulsed supersonic molecular beam injection (SMBI) has been developed successfully and used in the HL-1M tokamak. It is an attempt to enhance the penetration depth and fuelling efficiency. With a penetration depth of hydrogen particles beyond 8 cm, the rising rate of electron density, dn-bare/dt, was up to 7.6x1020m-3·s-1 without disruption, and reached the highest plasma density n-bare=8.2x1019m-3 on HL-1M. With SMBI the plasma energy confinement time, τE, measured by diamagnetism is 10-30 % longer than that with gas puffing when other discharge conditions are kept the same. The fuelling method of SMBI has recently been improved to make a survey of the cluster effects within the beam. A series of new phenomena show the interaction of the beam (including clusters) with the toroidal plasma. Hydrogen clusters may be produced in the beam according to the Hagena empirical scaling law of clustering onset, Γ*=(kd0.85P0)/T02.29). If Γ*>100, clusters will form. In the present experiment Γ* is about 127. (author)

  14. Hydrogen reverses the clustering tendency of carbon in amorphous silicon oxycarbide

    OpenAIRE

    Hepeng Ding; Demkowicz, Michael J.

    2015-01-01

    Amorphous silicon oxycarbide (SiOC) is of great technological interest. However, its atomic-level structure is not well understood. Using density functional theory calculations, we show that the clustering tendency of C atoms in SiOC is extremely sensitive to hydrogen (H): without H, the C-C interaction is attractive, leading to enrichment of aggregated SiC[subscript 4] tetrahedral units; with hydrogen, the C-C interaction is repulsive, leading to enrichment of randomly distributed SiCO[subsc...

  15. Chemisorption of hydrogen and oxygen atoms on a cobalt surface: A quantum chemical cluster model study

    International Nuclear Information System (INIS)

    The chemisorption of atomic hydrogen and oxygen on a cobalt surface has been studied on a five-atom cluster model using one-electron effective core potential (le- ECP) and all-electron calculations at the ab initio SCF and MCPF levels. Also, density functional calculations have been carried out. The different approaches are evaluated. The le- ECP has been compared to similar ECPS for nickel and copper. Our results indicate that this approach is valid also for cobalt. Different contributions to the cluster-adsorbate bonding energy are discussed. 31 refs., 1 fig., 1 tab

  16. Addition of Ethylene or Hydrogen to a Main-Group Metal Cluster under Mild Conditions

    OpenAIRE

    Vasko, Petra; Wang, Shuai; TUONONEN, Heikki; Power, Philip P.

    2015-01-01

    Reaction of the tin cluster Sn8(Arinline image)4 (Arinline image=C6H2-2,6-(C6H3-2,4,6-Me3)2) with excess ethylene or dihydrogen at 25 °C/1 atmosphere yielded two new clusters that incorporated ethylene or hydrogen. The reaction with ethylene yielded Sn4(Arinline image)4(C2H2)5 that contained five ethylene moieties bridging four aryl substituted tin atoms and one tin–tin bond. Reaction with H2 produced a cyclic tin species of formula (Sn(H)Arinline image)4, which could also be synthesized by t...

  17. Dynamics of two interacting hydrogen bubbles in liquid aluminum under the influence of a strong acoustic field

    Science.gov (United States)

    Lebon, Gerard S. B.; Pericleous, Koulis; Tzanakis, Iakovos; Eskin, Dmitry G.

    2015-10-01

    Ultrasonic melt processing significantly improves the properties of metallic materials. However, this promising technology has not been successfully transferred to the industry because of difficulties in treating large volumes of melt. To circumvent these difficulties, a fundamental understanding of the efficiency of ultrasonic treatment of liquid metals is required. In this endeavor, the dynamics of two interacting hydrogen bubbles in liquid aluminum are studied to determine the effect of a strong acoustic field on their behavior. It is shown that coalescence readily occurs at low frequencies in the range of 16 to 20 kHz; forcing frequencies at these values are likely to promote degassing. Emitted acoustic pressures from relatively isolated bubbles that resonate with the driving frequency are in the megapascal range and these cavitation shock waves are presumed to promote grain refinement by disrupting the growth of the solidification front.

  18. The Role of Molecule Clustering by Hydrogen Bond in Hydrous Ethanol on Laminar Burning Velocity

    Directory of Open Access Journals (Sweden)

    I Made Suarta

    2016-01-01

    Full Text Available The role of hydrogen bond molecule clustering in laminar burning velocities was observed. The water in hydrous ethanol can change the interaction between water-ethanol molecules. A certain amount of water can become oxygenated which increases the burning velocity. The hydrogen bond interaction pattern of ethanol and water molecules was modeled. Based on the molecular model, azeotropic behavior emerges from ethanol-water hydrogen bond, which is at a 95.1%v composition. The interaction with water molecule causes the ethanol molecule to be clustered with centered oxygenated compound. So, it supplies extra oxygen and provides intermolecular empty spaces that are easily infiltrated by the air. In the azeotropic composition, the molecular bond chain is the shortest, so hypothetically the burning velocity is anticipated to increase. The laminar burning velocity of ethanol fuel was tested in a cylindrical explosion bomb in lean, stoichiometric, and rich mixtures. The experimental result showed that the maximum burning velocity occurred at hydrous ethanol of 95.5%v composition. This discrepancy is the result of the addition of energy from 7.7% free ethanol molecules that are not clustered. At the rich mixture, the burning velocity of this composition is higher than that of anhydrous ethanol.

  19. A density functional study on the adsorption of hydrogen molecule onto small copper clusters

    Indian Academy of Sciences (India)

    Xiang-Jun Kuang; Xin-Qiang Wang; Gao-Bin Liu

    2011-09-01

    An all-electron scalar relativistic calculation on the adsorption of hydrogen molecule onto small copper clusters has been performed by using density functional theory with the generalized gradient approximation (GGA) at PW91 level. Our results reveal that after adsorption of H2 molecule, the Cu-Cu interaction is strengthened and the H-H interaction is weakened, the reactivity enhancement of H2 molecule is obvious. The VIPs, HLGs and VEAs of CuH2 clusters show an obvious odd-even oscillation. It is suggested that the H2 molecule is more favourable to be adsorbed by the even-numbered small copper clusters. Meanwhile, the odd-even alteration of magnetic moments is also observed and may be served as the material with tunable code capacity of `0’ and `1' by adsorbing hydrogen molecule onto odd or even-numbered small copper clusters. Some discrepancies of dissociative adsorption between our work and previous works are found and may be understood in terms of the electron pairing effect and the scalar relativistic effect.

  20. Probing the structures of gold-aluminum alloy clusters AuxAly-: a joint experimental and theoretical study

    Science.gov (United States)

    Khetrapal, Navneet Singh; Jian, Tian; Pal, Rhitankar; Lopez, Gary V.; Pande, Seema; Wang, Lai-Sheng; Zeng, Xiao Cheng

    2016-05-01

    Besides the size and structure, compositions can also dramatically affect the properties of alloy nanoclusters. Due to the added degrees of freedom, determination of the global minimum structures for multi-component nanoclusters poses even greater challenges, both experimentally and theoretically. Here we report a systematic and joint experimental/theoretical study of a series of gold-aluminum alloy clusters, AuxAly- (x + y = 7,8), with various compositions (x = 1-3 y = 4-7). Well-resolved photoelectron spectra have been obtained for these clusters at different photon energies. Basin-hopping global searches, coupled with density functional theory calculations, are used to identify low-lying structures of the bimetallic clusters. By comparing computed electronic densities of states of the low-lying isomers with the experimental photoelectron spectra, the global minima are determined. It is found that for y >= 6 there is a strong tendency to form the magic-number square bi-pyramid motif of Al6- in the AuxAly- clusters, suggesting that the Al-Al interaction dominates the Au-Au interaction in the mixed clusters. A closely related trend is that for x > 1, the gold atoms tend to be separated by Al atoms unless only the magic-number Al6- square bi-pyramid motif is present, suggesting that in the small-sized mixed clusters, Al and Au components do not completely mix with one another. Overall, the Al component appears to play a more dominant role due to the high robustness of the magic-number Al6- square bi-pyramid motif, whereas the Au component tends to be either ``adsorbed'' onto the Al6- square bi-pyramid motif if y >= 6, or stays away from one another if x = 6 there is a strong tendency to form the magic-number square bi-pyramid motif of Al6- in the AuxAly- clusters, suggesting that the Al-Al interaction dominates the Au-Au interaction in the mixed clusters. A closely related trend is that for x > 1, the gold atoms tend to be separated by Al atoms unless only the magic

  1. Oxidation of hydrogen-passivated silicon surfaces by scanning near-field optical lithography using uncoated and aluminum-coated fiber probes

    DEFF Research Database (Denmark)

    Madsen, Steen; Bozhevolnyi, Sergey I.; Birkelund, Karen;

    1997-01-01

    Optically induced oxidation of hydrogen-passivated silicon surfaces using a scanning near-field optical microscope was achieved with both uncoated and aluminum-coated fiber probes. Line scans on amorphous silicon using uncoated fiber probes display a three-peak profile after etching in potassium...... hydroxide. Numerical simulations of the electromagnetic field around the probe-sample interaction region are used to explain the experimental observations. With an aluminum-coated fiber probe, lines of 35 nm in width were transferred into the amorphous silicon layer. (C) 1997 American Institute of Physics....

  2. Hydrogen nano-storage in metal clusters: low-temperature release option

    International Nuclear Information System (INIS)

    'Full text': Aggregates of hydrogen molecules with small clusters of a light metal are predicted to have H2atM(n) isomers with the dihydrogen trapped inside the metal cage. The H2 core significantly re-structures the surrounding M(n) shell via strong interaction between these oppositely charged components. The molecule steadily stretches with increasing cage size, up to dissociation, due to increasing electron donation from the cage. The dihydrogen may thus be stored inside the metal cluster in either dissociated or non-dissociated form. It should be noted that the weight-efficiency of such storage is rather low (∼1% of hydrogen). Future work will be aimed at increasing the hydrogen content. The system stability to dissociation into H2 + M(n) increases with size from slightly metastable to weakly bound (at ∼0.1 eV scale) systems. The charge-transfer stabilization is thus nearly compensated by the molecule and cage deformations, allowing a relatively easy release of hydrogen, unlike the high-temperature release from bulk MgH2 solid. In fact, the cluster systems may actually be stable only at low temperatures. The closed-shell H2atM(n) species also show stability in terms of electronic excitation, ionization and electron-attachment, which should favour their low chemical reactivity and efficient formation in experiments. Their detection can be assisted by high IR intensities of the vibrational modes associated with relative translations of the oppositely charged dihydrogen and cage. (author)

  3. Trends in Energies and Geometric Structures of Neutral and Charged Aluminum Clusters.

    Science.gov (United States)

    Fournier, René

    2007-05-01

    The minimum energy geometric structures of Aln, A[Formula: see text] , and A[Formula: see text] (4 ≤ n ≤ 15) are predicted from the results of "Tabu Search" (TS) global optimizations performed directly on the BPW91/LANL2DZ potential energy surface. In 24 of the 36 cases investigated, the TS delivered a lower energy structure than previously reported, in one case (A[Formula: see text] ) it failed to find the global minimum, and in the remaining 11 cases TS confirmed previous structures. All clusters (with 4 ≤ n ≤ 15) have the lowest spin state as their ground state except Al4 (triplet), A[Formula: see text] (quartet), A[Formula: see text] (triplet), and maybe A[Formula: see text] (singlet and triplet are degenerate). The 20-electron A[Formula: see text] and 40-electron A[Formula: see text] clusters are relatively stable compared to other clusters, on several criteria; to a lesser degree, Al7, Al12, and A[Formula: see text] are also stable. PMID:26627412

  4. The Assessment of Hydrogen Energy Systems for Fuel Cell Vehicles Using Principal Componenet Analysis and Cluster Analysis

    DEFF Research Database (Denmark)

    Ren, Jingzheng; Tan, Shiyu; Dong, Lichun

    2012-01-01

    Hydrogen energy which has been recognized as an alternative instead of fossil fuel has been developed rapidly in fuel cell vehicles. Different hydrogen energy systems have different performances on environmental, economic, and energy aspects. A methodology for the quantitative evaluation and...... verify the correctness and accuracy of the principal components (PCs) determined by PCA in this paper. A case including 11 different hydrogen energy systems for fuel cell vehicles has been studied in this paper, and the system using steam reforming of natural gas for hydrogen production, pipeline for...... transportation of hydrogen, hydrogen gas tank for the storage of hydrogen at refueling stations, and gaseous hydrogen as power energy for fuel cell vehicles has been recognized as the best scenario. Also, the clustering results calculated by CA are consistent with those determined by PCA, denoting that the...

  5. Hydrogen Content and Porosity Behavior of Hypereutectic Aluminum-silicon Alloy with Phosphorus

    Institute of Scientific and Technical Information of China (English)

    HU Li-na; BIAN Xiu-fang; DUAN You-feng

    2004-01-01

    By making castings that pick up gas from moisture in red sand molds,the porosity generated at different cooling rates was discussed during solidification of hypereutectic Al-25%Si alloy without and with phosphorus additions. The effect of phosphorus addition on hydrogen content in the melt was also studied. It was observed that the phosphorus addition made hydrogen content in alloy melts present a "see-saw" tendency.In addition to primary silicon refinement,the phosphorus promoted gas porosity formed not only in slowly cooled sections, but also in rapidly cooled sections. There was a small difference in density of full dense sample between P-refined and unrefined castings, with a larger density associated with phosphorous addition. The change of the surface tension seemed more reasonable to explain the mechanism of porosity behavior.

  6. Electrocatalytic Hydrogen Production by an Aluminum(III) Complex: Ligand-Based Proton and Electron Transfer.

    Science.gov (United States)

    Thompson, Emily J; Berben, Louise A

    2015-09-28

    Environmentally sustainable hydrogen-evolving electrocatalysts are key in a renewable fuel economy, and ligand-based proton and electron transfer could circumvent the need for precious metal ions in electrocatalytic H2 production. Herein, we show that electrocatalytic generation of H2 by a redox-active ligand complex of Al(3+) occurs at -1.16 V vs. SCE (500 mV overpotential). PMID:26249108

  7. Trimeric cluster of lithium amidoborane-the smallest unit for the modeling of hydrogen release mechanism.

    Science.gov (United States)

    Pomogaeva, Anna V; Morokuma, Keiji; Timoshkin, Alexey Y

    2016-05-30

    A detailed first-principle DFT M06/6-311++G(d.p) study of dehydrogenation mechanism of trimeric cluster of lithium amidoborane is presented. The first step of the reaction is association of two LiNH2 BH3 molecules in the cluster. The dominant feature of the subsequent reaction pathway is activation of H atom of BH3 group by three Li atoms with formation of unique Li3 H moiety. This Li3 H moiety is destroyed prior to dehydrogenation in favor of formation of a triangular Li2 H moiety, which interacts with protic H atom of NH2 group. As a result of this interaction, Li2 H2 moiety is produced. It features N(-) H(+) H(-) group suited near the middle plane between two Li(+) in the transition state that leads to H2 release. The transition states of association and hydrogen release steps are similar in energy. It is concluded that the trimer, (LiNH2 BH3 )3 , is the smallest cluster that captures the essence of the hydrogen release reaction. © 2016 Wiley Periodicals, Inc. PMID:26854644

  8. Hydrogen reverses the clustering tendency of carbon in amorphous silicon oxycarbide.

    Science.gov (United States)

    Ding, Hepeng; Demkowicz, Michael J

    2015-01-01

    Amorphous silicon oxycarbide (SiOC) is of great technological interest. However, its atomic-level structure is not well understood. Using density functional theory calculations, we show that the clustering tendency of C atoms in SiOC is extremely sensitive to hydrogen (H): without H, the C-C interaction is attractive, leading to enrichment of aggregated SiC4 tetrahedral units; with hydrogen, the C-C interaction is repulsive, leading to enrichment of randomly distributed SiCO3 tetrahedral units. Our results suggest that conflicting experimental characterizations of C distributions may be due to differing amounts of H present in the samples investigated. Our work also opens a path for tailoring the properties of SiOC by using the total H content to control the C distribution. PMID:26269200

  9. Neutral hydrogen in galaxy clusters: impact of AGN feedback and implications for intensity mapping

    CERN Document Server

    Villaescusa-Navarro, Francisco; Borgani, Stefano; Viel, Matteo; Rasia, Elena; Murante, Giuseppe; Dolag, Klaus; Steinborn, Lisa K; Biffi, Veronica; Beck, Alexander M; Ragone-Figueroa, Cinthia

    2016-01-01

    By means of zoom-in hydrodynamic simulations we quantify the amount of neutral hydrogen (HI) hosted by groups and clusters of galaxies. Our simulations, which are based on an improved formulation of smoothed particle hydrodynamics (SPH), include radiative cooling, star formation, metal enrichment and supernova feedback, and can be split in two different groups, depending on whether feedback from active galactic nuclei (AGN) is turned on or off. Simulations are analyzed to account for HI self-shielding and the presence of molecular hydrogen. We find that the mass in neutral hydrogen of dark matter halos monotonically increases with the halo mass and can be well described by a power-law of the form $M_{\\rm HI}(M,z)\\propto M^{3/4}$. Our results point out that AGN feedback reduces both the total halo mass and its HI mass, although it is more efficient in removing HI. We conclude that AGN feedback reduces the neutral hydrogen mass of a given halo by $\\sim50\\%$, with a weak dependence on halo mass and redshift. The...

  10. Electron-induced hydrogen loss in uracil in a water cluster environment

    Energy Technology Data Exchange (ETDEWEB)

    Smyth, M.; Kohanoff, J. [Atomistic Simulation Centre, Queen' s University Belfast, Belfast BT7 1NN, Northern Ireland (United Kingdom); Fabrikant, I. I., E-mail: ifabrikant1@unl.edu [Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588, USA and Department of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom)

    2014-05-14

    Low-energy electron-impact hydrogen loss due to dissociative electron attachment (DEA) to the uracil and thymine molecules in a water cluster environment is investigated theoretically. Only the A{sup ′}-resonance contribution, describing the near-threshold behavior of DEA, is incorporated. Calculations are based on the nonlocal complex potential theory and the multiple scattering theory, and are performed for a model target with basic properties of uracil and thymine, surrounded by five water molecules. The DEA cross section is strongly enhanced when the attaching molecule is embedded in a water cluster. This growth is due to two effects: the increase of the resonance lifetime and the negative shift in the resonance position due to interaction of the intermediate negative ion with the surrounding water molecules. A similar effect was earlier found in DEA to chlorofluorocarbons.

  11. Motional modes in bulk powder and few-molecule clusters of tris(8-hydroxyquinoline aluminum) and their relation to spin dephasing

    Science.gov (United States)

    Das, Lopamudra; Mateo, Jennette; Bandyopadhyay, Saumil; Bandyopadhyay, Supriyo; Edwards, Jarrod D.; Anderson, John

    2011-02-01

    The ensemble averaged spin dephasing rate of localized electrons in the organic molecule tris(8-hydroxyquinoline aluminum) or Alq3 has been found to be significantly larger in bulk powder than in single- or few-molecule clusters confined within 1-2 nm sized nanocavities [B. Kanchibotla et al., Phys. Rev. B 78, 193306 (2008)]. To understand this observation, we have compared the midinfrared absorption spectra of bulk powder and single- or few-molecule clusters. It appears that molecules have additional vibrational modes in bulk powder possibly due to multimerization. Their coupling with spin may be responsible for the increased spin dephasing rate in bulk powder.

  12. Computational investigation of hydrogen adsorption in silicon-lithium binary clusters

    Indian Academy of Sciences (India)

    Naresh K Jena; K Srinivasu; Swapan K Ghosh

    2012-01-01

    Theoretical studies on hydrogen adsorption properties of silicon-lithium binary clusters are carried out. We have considered three different clusters viz., Si5Li−5, Si5Li6 and Si5Li$^{+}_{7}$ and for each cluster, the geometries of different possible isomers are optimized. In all the minimum energy isomers of the three clusters considered, two of the lithium atoms are found to be situated in the axial positions and the remaining lithium atoms are in the equatorial position in the Si5 plane. The lithium atoms which are in Si5 plane are bonded to the Si-Si edge through a bridged bond instead of a corner in the Si5 ring. From the calculated atomic charges, it is found that there is a charge transfer from lithium to silicon leaving a partial positive charge on the Li atoms and the axial lithium atoms are more charged as compared to the remaining lithium atoms. In the case of Si5Li6 and Si5Li$^{+}_{7}$, the Li sites can trap a total of 14 and 17 H2 molecules, respectively, with each bridge bonded Li site adsorbing three H2 molecules and each axial Li adsorbing one H2 molecule which corresponds to a gravimetric density of 13.33 wt% and 15.25 wt%, respectively.

  13. Theoretical study of hydrogen adsorption on Ca-decorated C48B12 clusters

    International Nuclear Information System (INIS)

    The hydrogen adsorption on Ca-decorated C48B12 clusters is studied using density functional theory. The favorable binding site for Ca atom is the hexagonal C4B2 rings. The strong interaction between Ca atoms and C48B12 cluster hinders the aggregation of Ca atoms on the cluster surface. C48B12 is an electron deficient system with a large electron affinity of 2.952 eV. The decorated Ca atoms transfer their electrons to the cluster easily. The net charges on the Ca atoms are in the range of 1.101 to 1.563 e. When H2 molecules approach the Ca atoms, they are moderately polarized and adsorbed around the Ca atoms in molecular form. The adsorption strength can reach up to 0.133 eV/H2. Each Ca atom in the Ca-decorated C48B12 complexes can adsorb three H2 molecules. The fully decorated C48B12Ca6 can hold up to 18 H2 molecules

  14. Neutral hydrogen in galaxy clusters: impact of AGN feedback and implications for intensity mapping

    Science.gov (United States)

    Villaescusa-Navarro, Francisco; Planelles, Susana; Borgani, Stefano; Viel, Matteo; Rasia, Elena; Murante, Giuseppe; Dolag, Klaus; Steinborn, Lisa K.; Biffi, Veronica; Beck, Alexander M.; Ragone-Figueroa, Cinthia

    2016-03-01

    By means of zoom-in hydrodynamic simulations, we quantify the amount of neutral hydrogen (H I) hosted by groups and clusters of galaxies. Our simulations, which are based on an improved formulation of smoothed particle hydrodynamics, include radiative cooling, star formation, metal enrichment and supernova feedback, and can be split into two different groups, depending on whether feedback from active galactic nuclei (AGN) is turned on or off. Simulations are analysed to account for H I self-shielding and the presence of molecular hydrogen. We find that the mass in neutral hydrogen of dark matter haloes monotonically increases with the halo mass and can be well described by a power law of the form M_{H I}(M,z)∝ M^{3/4}. Our results point out that AGN feedback reduces both the total halo mass and its H I mass, although it is more efficient in removing H I. We conclude that AGN feedback reduces the neutral hydrogen mass of a given halo by ˜50 per cent, with a weak dependence on halo mass and redshift. The spatial distribution of neutral hydrogen within haloes is also affected by AGN feedback, whose effect is to decrease the fraction of H I that resides in the halo inner regions. By extrapolating our results to haloes not resolved in our simulations, we derive astrophysical implications from the measurements of Ω _{H I}(z): haloes with circular velocities larger than ˜25 km s-1 are needed to host H I in order to reproduce observations. We find that only the model with AGN feedback is capable of reproducing the value of Ω _{H I}b_{H I} derived from available 21 cm intensity mapping observations.

  15. Hydrogen bonding in (substituted benzene)·(water)n clusters with n≤4

    International Nuclear Information System (INIS)

    Infrared ion-depletion spectroscopy, a double resonance method combining vibrational predissociation with resonant two-photon ionization (R2PI) spectroscopy, has been applied to study mixed clusters of the type (substituted benzene)·(H2O)n with n≤4. The UV chromophores were p-difluorobenzene, fluorobenzene, benzene, toluene, p-xylene and anisole. From the IR depletion spectra in the region of the OH stretching vibrations it could be shown that the water molecules are attached as subclusters to the chromophores. Size and configuration of the subclusters could be deduced from the IR depletion spectra. In the anisole·(H2O)1and2 complexes the water clusters form an ordinary hydrogen bond to the oxygen atom of the methoxy group. In all other mixed complexes a π-hydrogen bond is formed between one of the free OH groups of a water subcluster and the π-system of the chromophore. According to the strength of this interaction the frequency of the respective absorption band exhibits a characteristic red-shift which could be related to the total atomic charges in the aromatic ring. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

  16. DFT model cluster studies of O₂ adsorption on hydrogenated titania sub-nanoparticles.

    Science.gov (United States)

    Andreev, Alexey S; Kuznetsov, Vyacheslav N; Chizhov, Yuri V

    2013-11-01

    In the present paper, we examine the general applicability of different TiO2 model clusters to study of local chemical events on TiO2 sub-nanoparticles. Our previous DFT study of TiO2 activation through H adsorption and following deactivation by O2 adsorption using small amorphous Ti8O16 cluster were complemented by examination of rutile-type and spherical Ti15O30 nanoclusters. The obtained results were thoroughly compared with experimental data and results of related computational studies using other TiO2 models including periodic structures. It turned out that all considered model TiO2 model systems provide qualitatively similar results. It was shown that atomic hydrogen is adsorbed with negligible activation energy on surface O atoms, which is accompanied by the appearance of reduced Ti(3+) species and corresponding localized band gap 3d-Ti states. Oxygen molecule is adsorbed on Ti(3+) sites spontaneously forming molecular O2 (-) species by capturing an extra electron of Ti(3+) ion, which results in disappearance of Ti(3+) species and corresponding band gap states. Calculated g-tensor values of Ti(3+) and O2 (-) species agree well with the results of EPR studies and do not depend on the used TiO2 model cluster. Additionally, it was shown that the various cluster calculations provide results comparable with the calculations of periodic structures with respect to the modeling of chemical processes under study. As a whole, the present study approves the validity of molecular cluster approach to study of local chemical events on TiO2 sub-nanoparticles. PMID:24085538

  17. Cluster-variation calculation for random-field systems: Application to hydrogen in niobium alloys

    International Nuclear Information System (INIS)

    The cluster-variation method is applied to random-field lattice systems and specifically used to model the disorder-disorder phase transition of hydrogen in niobium-molybdenum and niobium-vanadium alloys. A small concentration of molybdenum or vanadium in the niobium lattice is treated as adding at each hydrogen site a random energy with a known probability distribution. Pairwise interactions between hydrogen atoms are included out to the first fifty shells on the bcc tetrahedral interstitial lattice, allowing for the effect of site blocking for the first three shells. The results show the small and large depression in the critical temperature for Nb/sub 1-//sub y/V/sub y/H/sub x/ and Nb/sub 1-//sub y/Mo/sub y/H/sub x/, respectively, with increasing concentration of V or Mo, as observed in experiments. Comparison is made with Monte Carlo calculations of other workers with use of the same interaction parameters, and the effects of variations in the random-energy distribution are described

  18. Cluster virial expansion for the equation of state of partially ionized hydrogen plasma.

    Science.gov (United States)

    Omarbakiyeva, Y A; Fortmann, C; Ramazanov, T S; Röpke, G

    2010-08-01

    We study the contribution of electron-atom interaction to the equation of state for partially ionized hydrogen plasma using the cluster-virial expansion. We use the Beth-Uhlenbeck approach to calculate the second virial coefficient for the electron-atom (bound cluster) pair from the corresponding scattering phase shifts and binding energies. Experimental scattering cross-sections as well as phase shifts calculated on the basis of different pseudopotential models are used as an input for the Beth-Uhlenbeck formula. By including Pauli blocking and screening in the phase shift calculation, we generalize the cluster-virial expansion in order to cover also near solid density plasmas. We present results for the electron-atom contribution to the virial expansion and the corresponding equation of state, i.e. pressure, composition, and chemical potential as a function of density and temperature. These results are compared with semiempirical approaches to the thermodynamics of partially ionized plasmas. Avoiding any ill-founded input quantities, the Beth-Uhlenbeck second virial coefficient for the electron-atom interaction represents a benchmark for other, semiempirical approaches. PMID:20866926

  19. Synergistic hydrogen desorption behavior of magnesium aluminum hydride synthesized by mechano-chemical activation method

    International Nuclear Information System (INIS)

    Highlights: ► Mg(AlH4)2 could release 3.1 wt% H2 at initial temperature as low as 100 °C. ► The synergistic and mutual catalytic effects of NaAlH4 and Mg(AlH4)2 were noticed. ► In situ synchrotron XRD confirmed the two-step dehydrogenation process of Mg(AlH4)2. - Abstract: A mechano-chemical activation synthesis (MCAS) is employed to fabricate Mg(AlH4)2 via milling the precursors, specifically NaAlH4 and MgCl2. The corresponding dehydrogenation behavior of the synthesized powders is investigated. The experimental results showed that incomplete synthesis or premature dehydrogenation may occur if the milling process was not properly controlled. The hydrogen content of each synthesized powder is determined by using a thermal gravimetric analyzer (TGA). The dehydrogenation reactions of the synthesized powders are investigated by employing ex situ X-ray diffraction (XRD), in situ synchrotron XRD and differential thermal analysis (DTA). The results showed that the incompletely synthesized powder consisted of residual NaAlH4 in the synthesized Mg(AlH4)2, which demonstrated an initial dehydrogenation temperature as low as 100 °C and accompanied with a maximum amount (3.1 wt%) of H2 released below 350 °C. The mutual catalytic effect of both NaAlH4 and Mg(AlH4)2 on lowering their initial dehydrogenation temperature is confirmed.

  20. Adsorption of carbon monoxide on small aluminum oxide clusters: Role of the local atomic environment and charge state on the oxidation of the CO molecule

    International Nuclear Information System (INIS)

    We present extensive density functional theory (DFT) calculations dedicated to analyze the adsorption behavior of CO molecules on small AlxOy± clusters. Following the experimental results of Johnson et al. [J. Phys. Chem. A 112, 4732 (2008)], we consider structures having the bulk composition Al2O3, as well as smaller Al2O2 and Al2O units. Our electron affinity and total energy calculations are consistent with aluminum oxide clusters having two-dimensional rhombus-like structures. In addition, interconversion energy barriers between two- and one-dimensional atomic arrays are of the order of 1 eV, thus clearly defining the preferred isomers. Single CO adsorption on our charged AlxOy± clusters exhibits, in general, spontaneous oxygen transfer events leading to the production of CO2 in line with the experimental data. However, CO can also bind to both Al and O atoms of the clusters forming aluminum oxide complexes with a CO2 subunit. The vibrational spectra of AlxOy + CO2 provides well defined finger prints that may allow the identification of specific isomers. The AlxOy+ clusters are more reactive than the anionic species and the final Al2O+ + CO reaction can result in the production of atomic Al and carbon dioxide as observed from experiments. We underline the crucial role played by the local atomic environment, charge density distribution, and spin-multiplicity on the oxidation behavior of CO molecules. Finally, we analyze the importance of coadsorption and finite temperature effects by performing DFT Born-Oppenheimer molecular dynamics. Our calculations show that CO oxidation on AlxOy+ clusters can be also promoted by the binding of additional CO species at 300 K, revealing the existence of fragmentation processes in line with the ones experimentally inferred

  1. DISCOVERY OF RELATIVELY HYDROGEN-POOR GIANTS IN THE GALACTIC GLOBULAR CLUSTER ω CENTAURI

    International Nuclear Information System (INIS)

    In this Letter, the results of our low-resolution spectroscopic survey for identifying hydrogen-deficient stars in the red giant sample of the globular cluster ω Cen are reported. Spectral analyses were carried out on the basis of the strengths of the (0, 0) MgH band and the Mg b triplet. In our sample, four giants were identified with weak/absent MgH bands in their observed spectra, which was unexpected for their well determined stellar parameters. The Mg abundances for the program stars were determined from the subordinate lines of the MgH band to the blue of the Mg b triplet, using the spectral synthesis technique. The derived Mg abundances for the program stars were as expected for the red giants of ω Cen, except for the four identified candidates. The determined Mg abundances of these four candidates are much lower than that expected for the red giants of ω Cen, and are unacceptable based on the strengths of the Mg b triplet in their observed spectra. Hence, a plausible explanation for the weak/absent MgH bands in the observed spectra of these stars is a relatively lower abundance of hydrogen in their atmospheres. These giants may belong to the group of helium-enriched red giants of ω Cen

  2. DISCOVERY OF RELATIVELY HYDROGEN-POOR GIANTS IN THE GALACTIC GLOBULAR CLUSTER ω CENTAURI

    Energy Technology Data Exchange (ETDEWEB)

    Hema, B. P.; Pandey, Gajendra, E-mail: hema@iiap.res.in, E-mail: pandey@iiap.res.in [Indian Institute of Astrophysics, Bengaluru, Karnataka 560034 (India)

    2014-09-10

    In this Letter, the results of our low-resolution spectroscopic survey for identifying hydrogen-deficient stars in the red giant sample of the globular cluster ω Cen are reported. Spectral analyses were carried out on the basis of the strengths of the (0, 0) MgH band and the Mg b triplet. In our sample, four giants were identified with weak/absent MgH bands in their observed spectra, which was unexpected for their well determined stellar parameters. The Mg abundances for the program stars were determined from the subordinate lines of the MgH band to the blue of the Mg b triplet, using the spectral synthesis technique. The derived Mg abundances for the program stars were as expected for the red giants of ω Cen, except for the four identified candidates. The determined Mg abundances of these four candidates are much lower than that expected for the red giants of ω Cen, and are unacceptable based on the strengths of the Mg b triplet in their observed spectra. Hence, a plausible explanation for the weak/absent MgH bands in the observed spectra of these stars is a relatively lower abundance of hydrogen in their atmospheres. These giants may belong to the group of helium-enriched red giants of ω Cen.

  3. Graph theoretical enumeration of topology-distinct structures for hydrogen fluoride clusters (HF)n (n ≤ 6).

    Science.gov (United States)

    Jelil, Mahmutjan; Abaydulla, Alimjan

    2015-07-28

    A graph theoretical procedure to generate all the possible topology-distinct structures for hydrogen fluoride (HF) clusters is presented in this work. The hydrogen bond matrix is defined and used to enumerate the topology-distinct structures of hydrogen fluoride (HF)n (n = 2-8) clusters. From close investigation of the structural patterns obtained, several restrictions that should be satisfied for a structure of the HF clusters to be stable are found. The corresponding digraphs of generated hydrogen bond matrices are used as the theoretical framework to obtain all the topology-distinct local minima for (HF)n (n ≤ 6), at the level of MP2/6-31G**(d, p) of ab initio MO method and B3LYP/6-31G**(d, p) of density functional theory method. For HF clusters up to tetramers, the local minimum structures that we generated are same as those in the literature. For HF pentamers and hexamers, we found some new local minima structures which had not been obtained previously. PMID:26233123

  4. Graph theoretical enumeration of topology-distinct structures for hydrogen fluoride clusters (HF)n (n ≤ 6)

    Science.gov (United States)

    Jelil, Mahmutjan; Abaydulla, Alimjan

    2015-07-01

    A graph theoretical procedure to generate all the possible topology-distinct structures for hydrogen fluoride (HF) clusters is presented in this work. The hydrogen bond matrix is defined and used to enumerate the topology-distinct structures of hydrogen fluoride (HF)n (n = 2-8) clusters. From close investigation of the structural patterns obtained, several restrictions that should be satisfied for a structure of the HF clusters to be stable are found. The corresponding digraphs of generated hydrogen bond matrices are used as the theoretical framework to obtain all the topology-distinct local minima for (HF)n (n ≤ 6), at the level of MP2/6-31G**(d, p) of ab initio MO method and B3LYP/6-31G**(d, p) of density functional theory method. For HF clusters up to tetramers, the local minimum structures that we generated are same as those in the literature. For HF pentamers and hexamers, we found some new local minima structures which had not been obtained previously.

  5. Eddy Current Loss Induced in Aluminum Thermal Conduction Strips for ASPCS Coils Indirectly Cooled by Liquid Hydrogen through Thermo-siphon System

    Science.gov (United States)

    Ota, Narumi; Katsura, Masashi; Ando, Kennosuke; Takao, Tomoaki; Shintomi, Takakazu; Makida, Yasuhiro; Hamajima, Takataro; Tsuda, Makoto; Miyagi, Daisuke; Tsujigami, Hiroshi; Fujikawa, Shizuichi; Semba, Toshiaki; Iwaki, Katsuya

    To promote renewable energy sources, we proposed a new system called the Advanced Superconducting Power Conditioning System (ASPCS), which consists of Superconducting Magnetic Energy Storage-system (SMES), Electrolyzer, and Fuel Cell, and is also combined with a liquid hydrogen station for vehicles. The SMES plays a role to compensate the fast fluctuations generated by the renewable energies. In case of the ASPCS with a capacity of 5 MW, we designed the 50 MJ-class SMES composed of 4 solenoid coils. The winding of the solenoid coils is double pancake and a basic coil is 2 m in diameter and 0.5 m in height. Each SMES coil is wound with MgB2 conductor and indirectly cooled at 20 K by liquid hydrogen flowing through a thermo-siphon cooling system. Pure aluminum strips are inserted between the double-pancake coils and the pure aluminum plates gathering the strips lead to liquid hydrogen pipes. This scheme enables the strips and the plates to transfer the heat load in the coils to the cooling pipes and keep the coils at low temperature. On the other hand, we must consider that the strips generate eddy current loss which is strongly affected by a width of the strips. At the same time as the primary study of the SMES coils, we experimented on the thermo-siphon cooling system and investigated the relationship between the heat load and the heat extraction ability of the cooling system. The experiments showed that the cooling system could proficiently function. The estimation of eddy current loss from the particular cooling aluminum strips for the SMES in the ASPCS is reported with the results of the thermo-siphon driving experiment.

  6. Reactive ion beam etching of aluminum indium antimonide, gallium indium antimonide heterostructures in electron cyclotron resonance methane/hydrogen/nitrogen/silicon tetrachloride discharges at room temperature

    OpenAIRE

    Sendra, J. R.; Anguita, José Virgilio; Pérez Camacho, J. J.; Briones Fernández-Pola, Fernando

    1995-01-01

    Reactive ion beam etching of aluminum indium antimonide, gallium indium antimonide heterostructures in electron cyclotron resonance plasma using methane/hydrogen/nitrogen/silicon tetrachloride (CH4/H2/N2/SiCl4) mixtures has been performed at room temperature. Due to the ratio of chlorine to methane, formation of an indium chloride layer on the etched surface is avoided, thus resulting, in etched surfaces as smooth as the original ones and flat mesa sidewalls. Infrared diodes (2.3µm) have been...

  7. Hydrogen bonded networks in formamide [HCONH2] ( = 1 − 10) clusters: A computational exploration of preferred aggregation patterns

    Indian Academy of Sciences (India)

    A Subha Mahadevi; Y Indra Neela; G Narahari Sastry

    2012-01-01

    Application of quantum chemical calculations is vital in understanding hydrogen bonding observed in formamide clusters, a prototype model for motifs found in protein secondary structure. DFT calculations have been performed on four arrangements of formamide clusters [HCONH2], ( = 1 − 10) linear, circular, helical and stacked forms. These studies reveal the maximum cooperativity in the stacked arrangement followed by the circular, helical and linear arrangements and is based on interaction energy per monomer. In all these arrangements as we increase cluster size, an increasing trend in cooperativity of hydrogen bonding is observed. Atoms-in-molecule analysis establishes the nature of bonding between the formamide monomers on the basis of electron density values obtained at the bond critical point (BCP).

  8. Hydrogen diffusion in aluminum

    International Nuclear Information System (INIS)

    Recent findings on the H-Al system are discussed in terms of the kinetic behavior predicted for solutions of H in metals where there is a high concentration of vacancies in thermal equilibrium. Solubility and diffusivity plots for H in Al are presented together with the corresponding equations. An analysis of the results obtained suggests that direct thermodynamic measurement of the i-vacancy binding energy may be possible through equilibrating with a second phase where the chemical potential of i is such that all the vacancy-related sites are occupied

  9. Hydrogen activation, diffusion, and clustering on CeO₂(111): a DFT+U study.

    Science.gov (United States)

    Fernández-Torre, Delia; Carrasco, Javier; Ganduglia-Pirovano, M Verónica; Pérez, Rubén

    2014-07-01

    We present a comprehensive density functional theory+U study of the mechanisms underlying the dissociation of molecular hydrogen, and diffusion and clustering of the resulting atomic species on the CeO2(111) surface. Contrary to a widely held view based solely on a previous theoretical prediction, our results show conclusively that H2 dissociation is an activated process with a large energy barrier ~1.0 eV that is not significantly affected by coverage or the presence of surface oxygen vacancies. The reaction proceeds through a local energy minimum--where the molecule is located close to one of the surface oxygen atoms and the H-H bond has been substantially weaken by the interaction with the substrate--, and a transition state where one H atom is attached to a surface O atom and the other H atom sits on-top of a Ce(4+) ion. In addition, we have explored how several factors, including H coverage, the location of Ce(3+) ions as well as the U value, may affect the chemisorption energy and the relative stability of isolated OH groups versus pair and trimer structures. The trimer stability at low H coverages and the larger upward relaxation of the surface O atoms within the OH groups are consistent with the assignment of the frequent experimental observation by non-contact atomic force and scanning tunneling microscopies of bright protrusions on three neighboring surface O atoms to a triple OH group. The diffusion path of isolated H atoms on the surface goes through the adsorption on-top of an oxygen in the third atomic layer with a large energy barrier of ~1.8 eV. Overall, the large energy barriers for both, molecular dissociation and atomic diffusion, are consistent with the high activity and selectivity found recently in the partial hydrogenation of acetylene catalyzed by ceria at high H2/C2H2 ratios. PMID:25005299

  10. Hydrogen storage on metal oxide model clusters using density-functional methods and reliable van der Waals corrections.

    Science.gov (United States)

    Gebhardt, Julian; Viñes, Francesc; Bleiziffer, Patrick; Hieringer, Wolfgang; Görling, Andreas

    2014-03-21

    We investigate the capability of low-coordinated sites on small model clusters to act as active centers for hydrogen storage. A set of small magic clusters with the formula (XY)6 (X = Mg, Ba, Be, Zn, Cd, Na, Li, B and Y = O, Se, S, F, I, N) and a "drumlike" hexagonal shape showing a low coordination number of three was screened. Oxide clusters turned out to be the most promising candidates for hydrogen storage. For these ionic compounds we explored the suitability of different van der Waals (vdW) corrections to density-functional calculations by comparing the respective H2 physisorption profile to highly accurate CCSD(T) (Coupled Cluster Singles Doubles with perturbative Triples) calculations. The Grimme D3 vdW correction in combination with the Perdew-Burke-Ernzerhof exchange-correlation functional was found to be the best approach compared to CCSD(T) hydrogen physisorption profiles and is, therefore, suited to study these and other light metal oxide systems. H2 adsorption on sites of oxide model clusters is found to meet the adsorption energy criteria for H2 storage, with bond strengths ranging from 0.15 to 0.21 eV. Energy profiles and estimates of kinetic constants for the H2 splitting reaction reveal that H2 is likely to be adsorbed molecularly on sites of (MgO)6, (BaO)6, and (BeO)6 clusters, suggesting a rapid H2 uptake/release at operating temperatures and moderate pressures. The small mass of beryllium and magnesium makes such systems appealing for meeting the gravimetric criterion for H2 storage. PMID:24499810

  11. Size dependent transition to solid hydrogen and argon clusters probed via spectroscopy of PTCDA embedded in helium nanodroplets

    Science.gov (United States)

    Dvorak, Matthieu; Müller, Markus; Bünermann, Oliver; Stienkemeier, Frank

    2014-04-01

    Complexes made of either ArN or (H2)N clusters (N = 1-170) and a single PTCDA molecule (3,4,9,10-perylene-tetracarboxylic-dianhydride) are assembled inside helium droplets and spectroscopically studied via laser-induced fluorescence spectroscopy. The frequency shift and line-broadening are analyzed as a function of N and of the pick-up order of the PTCDA and cluster material in order to track liquid or solid properties of the clusters. For argon, the solid phase is observed for N > 10 above which the pick-up order dramatically influences the localization of the chromophore with respect to the Ar cluster. If the droplets are doped first with Ar, the chromophore remains on the surface of a solid cluster whereas for the reversed pick-up order the molecule is surrounded by an argon shell. At N < 10 wetting and the formation of the first solvation shell are observed. For para-hydrogen, a transition to the solid is observed at N ˜ 20-25, confirming previous theoretical predictions on the existence of a liquid-like phase at such small sizes, even below the bulk hydrogen freezing temperature.

  12. Discovery of relatively hydrogen-poor giants in the Galactic globular cluster Omega Centauri

    CERN Document Server

    Hema, B P

    2014-01-01

    In this letter, the results of our low-resolution spectroscopic survey for identifying the hydrogen-deficient (H-deficient) stars in the red giant sample of the globular cluster Omega Cen are reported. Spectral analyses were carried out on the basis of the strengths of (0,0) MgH band and the Mg b triplet. In our sample, four giants were identified with weak/absent MgH bands in their observed spectra not as expected for their well determined stellar parameters. The Mg abundances for the program stars were determined from subordinate lines of the MgH band to the blue of the Mg b triplet, using the spectral synthesis technique. The derived Mg abundances for the program stars were as expected for the red giants of Omega Cen (Norris & Da Costa 1995), except for the four identified candidates. Determined Mg abundances of these four candidates are much lower than that expected for the red giants of Omega Cen, and are unacceptable based on the strengths of Mg b triplet in their observed spectra. Hence, the plausi...

  13. Hydrogen bond network fluctuations in small (H2O)n clusters (n=8-12-24)

    Science.gov (United States)

    Masella, Michel; Flament, Jean-Pierre

    1999-09-01

    Molecular dynamic studies of three (H2O)n clusters (n=8-12-24) were performed using our recently developed many-body model TCPE [J. Chem. Phys. 107, 9105 (1997)] in the microcanonical ensemble. The trajectories were analyzed using a new structural local index derived from one of the many-body energetic term of TCPE. In the energy domain where the clusters are in a liquidlike state, a dynamical equilibrium is theoretically predicted to exist among molecules in the PHB1 and the PHB2 state (i.e., among molecules which one of their protons is involved in one hydrogen bond, the PHB1 state, and molecules which both of their protons are involved in two hydrogen bonds, the PHB2 state). The enthalpy and entropy changes corresponding to that equilibrium for the three clusters range from 0.75 to 1.10 kcal mol-1 and from -7 to -3.8 cal mol-1 K-1. Such an equilibrium between two species of hydrogen bonded molecules could be related to that experimentally observed in the case of liquid water at ambient conditions. In particular, the entropy changes corresponding to PHB2/PHB1 equilibrium in the case of the three clusters are very close to those experimentally reported for liquid water (about 6.6±0.5 cal mol-1 K-1), suggesting that the equilibrium observed in the case of liquid water could correspond to a PHB2/PHB1 equilibrium. The analysis of hydrogen bond networks in terms of PHBm states appears thus to be an encouraging way in characterising the dynamical properties of water systems.

  14. Plasma behavior with hydrogen supersonic molecular beam and cluster jet injection in the HL-2A tokamak

    International Nuclear Information System (INIS)

    The experimental results of low pressure supersonic molecular beam injection (SMBI) into the HL-2A plasma indicated that during the period of SMB pulse injection the power density convected at the divertor target plate surfaces was 0.4 times of that before or after the beam injection. The clusters are produced at nitrogen temperature in a supersonic adiabatic expansion of moderate pressure hydrogen gases into vacuum through a Laval nozzle. The averaged cluster size was measured by Rayleigh scattering as large as hundreds atoms. Multifold diagnostics for the cluster jet injection (CJI) experiments have given a coincident evidence that there was a terminal area where a great deal particles from the clusters deposited at, rather than the clusters uniformly ablating along the injection path. A SMB with large clusters, which are like micro-pellets, was of benefit for deeper fuelling and the fuelling efficiency is distinctly better than that of the room temperature SMBI. Another important effect of the CJI or the high pressure SMBI was that the runaway electrons were cooled down to thermal velocity due to a combination of collision and radiative stopping in such a massive fuelling. So the new fuelling technique may become a good treatment to mitigate fast plasma shutdowns and disruptions. (author)

  15. Synthesis and characterization of Co and Ni catalysts supported on alumina, synthesized from aluminum industry wastes and its use in the reforming reaction of ethanol, to hydrogen production

    International Nuclear Information System (INIS)

    Alumina was synthesized from aluminum anodizing process wastes through a process of mechanical and thermal treatment of calcination,1373 K with a heating rate of 5 K/min to 8h, obtaining a pure alumina of corundum type, a crystal size of 9.77 nm. This material is used as a microporous support and have elaborated Cobalt heterogeneous catalysts (CO3O4 / Al2O3) and Nickel (NiO/Al2O3) which were calcined at different temperatures (573 K, 773 K, 973 K, 1173 K). From these is produced hydrogen by ethenol catalytic reforming. Two techniques were used for driving the mixture EtOH:H2O (1:3) of starting gas. A first technique has involved trawling through boiling of the mixture. High percentages were obtained of hydrogen but to a lesser reaction time, consuming all starting reagent, the most efficient catalyst has been the CO2O3 / Al2O3 calcined at 973K with a production of H2 of 50% v/v as well as CH4 and CO of 10%v/v. The second type of starting reagent carryover has been mild heating at 333 K and nitrogen sweep, with the following results 11% v/v H2, 12% v/v CH4 and 7% v/v CO. Addition of ethanol conversion maximums of 76% and hydrogen yield of 29%, of the theoretical yield based on the ethanol consumed. (author)

  16. Plasma behaviour with hydrogen supersonic molecular beam and cluster jet injection in the HL-2A tokamak

    International Nuclear Information System (INIS)

    The experimental results of low pressure supersonic molecular beam injection (SMBI) fuelling on the HL-2A closed divertor indicate that during the period of pulsed SMBI the power density convected at the target plate surfaces was 0.4 times of that before or after the beam injection. An empirical scaling law used for the SMBI penetration depth for the HL-2A plasma was obtained. The cluster jet injection (CJI) is a new fuelling method which is based on and developed from the experiments of SMBI in the HL-1M tokamak. The hydrogen clusters are produced at liquid nitrogen temperature in a supersonic adiabatic expansion of moderate backing pressure gases into vacuum through a Laval nozzle and are measured by Rayleigh scattering. The measurement results have shown that the averaged cluster size of as large as hundreds of atoms was found at the backing pressures of more than 0.1 MPa. Multifold diagnostics gave coincidental evidence that when there was hydrogen CJI in the HL-2A plasma, a great deal of particles from the jet were deposited at a terminal area rather than uniformly ablated along the injecting path. SMB with clusters, which are like micro-pellets, will be of benefit for deeper fuelling, and its injection behaviour was somewhat similar to that of pellet injection. Both the particle penetration depth and the fuelling efficiency of the CJI were distinctly better than that of the normal SMBI under similar discharge operation. During hydrogen CJI or high-pressure SMBI, a combination of collision and radiative stopping forced the runaway electrons to cool down to thermal velocity due to such a massive fuelling

  17. Clustering

    Directory of Open Access Journals (Sweden)

    Jinfei Liu

    2013-04-01

    Full Text Available DBSCAN is a well-known density-based clustering algorithm which offers advantages for finding clusters of arbitrary shapes compared to partitioning and hierarchical clustering methods. However, there are few papers studying the DBSCAN algorithm under the privacy preserving distributed data mining model, in which the data is distributed between two or more parties, and the parties cooperate to obtain the clustering results without revealing the data at the individual parties. In this paper, we address the problem of two-party privacy preserving DBSCAN clustering. We first propose two protocols for privacy preserving DBSCAN clustering over horizontally and vertically partitioned data respectively and then extend them to arbitrarily partitioned data. We also provide performance analysis and privacy proof of our solution..

  18. Boron, hydrogen and silicon adatoms on the Si(111) surface: an ab initio Hartree-Fock/density functional cluster study

    International Nuclear Information System (INIS)

    Full text: Silicon and boron adatoms on the Si(111) surface have been studied using atomic clusters and the Hartree-Fock/Density Functional Theory components of the Gaussian94/DFT package. The binding energies for the adatom, Si(A), located at the T4 position, and the Si(A)H species formed by the chemisorption of a single hydrogen atom, have been obtained for the corresponding equilibrium minimum energy configurations. We find that the most stable adatom structure results from boron occupying the S5 substitutional position in the second layer directly below the Si adatom (B-S5 topology). The binding energy of the Si adatom in this case is 7.49eV while the binding energy for the Si adatom without the boron (Si-T4 topology) is only 6.34 eV. When a boron atom is chemisorbed in the T4 position, instead of a silicon atom (B-T4 structure), the binding energy is found to be 5.56 eV. The chemisorption of atomic hydrogen onto these clusters stabilizes the Si-T4 geometry through the formation of a silicon adatom-hydrogen Si(A)H complex located at the three-fold T4 position with a binding energy of 5.18 eV. In contrast to this, a hydrogen bonded Si adatom of the B-S5 structure is observed to move away from its 3-fold T4 position to an adjacent bridge site and give an Si(A)H binding energy of 4.68 eV. Similar reconstruction has been observed when a hydrogen atom chemisorbs onto a boron adatom in the B-T4 topology with the binding energy of the BH complex being 5.03 eV. An interpretation of these results will be given in the context of the available experimental data

  19. MODIFICATION OF TRANSITION METAL CATIONS TO POLYMER- STABILIZED PLATINUM COLLOIDAL CLUSTERS IN ENANTIOSELECTIVE HYDROGENATION OF METHYL PYRUVATE

    Institute of Scientific and Technical Information of China (English)

    Xiao-ping Yan; Bao-lin He; Jie Zhang; Han-fan Liu

    2005-01-01

    Modification of transition metal cations to polymer-stabilized Pt colloidal clusters modified with cinchonidine was studied in enantioselective hydrogenation of methyl pyruvate. Compared to the enantiomeric excess (e.e.) value (71.4%)obtained without the presence of metal cations, obvious e.e. enhancement (up to 82.5%) was resulted from the addition of Zn2+ but with a certain decrease in activity. The reaction parameters in the presence of Zn2+ were also studied. It was found that the Pt colloidal catalysts in the presence of metal cations performed very differently from that in the absence of metal cations.

  20. ZnO-dotted porous ZnS cluster microspheres for high efficient, Pt-free photocatalytic hydrogen evolution

    OpenAIRE

    Aiping Wu; Liqiang Jing; Jianqiang Wang; Yang Qu; Ying Xie; Baojiang Jiang; Chungui Tian; Honggang Fu

    2015-01-01

    The Pt-free photocatalytic hydrogen evolution (PHE) has been the focus in the photocatalysis field. Here, the ZnO-dotted porous ZnS cluster microsphere (PCMS) is designed for high efficient, Pt-free PHE. The PCMS is designed through an easy “controlling competitive reaction” strategy by selecting the thiourea as S2− source and Zn(Ac)2 ·2H2O as Zn source in ethylene glycol medium. Under suitable conditions, one of the PCMS, named PCMS-1, with high SBET specific area of 194 m2g−1, microsphere s...

  1. 临朐县铝型材产业集群形成机制研究%Study on the Formation Mechanism of Aluminum Profile Industry Cluster in Linqu county

    Institute of Scientific and Technical Information of China (English)

    井东; 王慧

    2016-01-01

    产业集群作为当今世界普遍的经济现象,是促进地方经济发展、提高区域竞争力的重要生产组织形式。本文结合临朐县铝型材产业集群现状特征,从社会网络机制的角度具体分析了临朐县铝型材产业集群的形成机理。此研究对提高临朐县铝型材产业集群竞争力、促进铝型材产业集群快速发展具有一定的理论和实践意义。%Industrial cluster as a common economic phenomenon in today's world, is an important production organization form to promote local economic development and improve regional competitiveness. In combination with the Linqu County aluminum material industry cluster status and characteristics, this paper from two aspects: social network mechanism and transaction costs mechanism specific research Linqu aluminum industry cluster internal social network and cluster and the local community in close contact is of great significance to improve the cluster competitiveness, promote cluster development.

  2. Core-electron excitation and fragmentation processes of hydrogen bonded acetic-acid clusters in the oxygen K-edge region

    International Nuclear Information System (INIS)

    Research highlights: → Core-electron excitation spectra and fragmentation processes of acetic-acid clusters. → O1s(CO) → π*CO transitions shift by +0.37/-0.92 eV upon cluster formation. → Hydrogen-bond strength of RCOOH clusters determines the cluster-band shift. → We propose 'local-fragmentation' and 'low-energy MnX+ formation' mechanisms. → Fragmentation after electronic relaxation follows either of these two mechanisms. - Abstract: In order to examine inner-shell electron excitation and induced chemical processes of hydrogen-bonded (HB) molecular clusters, time-of-flight (TOF) fragment-mass and excitation spectra of deuterium-labeled acetic-acid-d (AAD) have been studied under the effusive and cluster beam conditions. With O1s(CO) → π*CO excitation at 532 eV, the TOF spectra of AAD clusters were compared with those of the free molecule. Transient intensity-enhancement of CH3+/CH3CO+ fragments and growth of mixed-cluster cations, MnD+/MnCH3CO+ could be ascertained in the cluster beams, where AAD molecule is denoted by M. Cluster-specific excitation spectra have been generated by monitoring partial-ion-yields of the mixed-cluster cations. Resonance transitions of O1s(CO/OH) → π*CO were found to shift in energy by +0.37/-0.92 eV upon cluster formation. The production of MnD+ can be attributed to a low-energy pathway of deuteron (proton) transfer following fast electronic decays within the clusters made up of a stable dimer-unit with doubly-bridged HBs. The CH3+/CH3CO+ intensity variation in beam stagnation pressure clearly shows that a local-fragmentation mechanism as previously proposed is also applicable to the fragmentation processes of the small AAD clusters.

  3. The roles of aluminum and hydrogen in impurity contamination of AlGaAs grown by MOMBE

    Energy Technology Data Exchange (ETDEWEB)

    Abernathy, C.R.; Pearton, S.J. (AT and T Bell Labs., Murray Hill, NJ (USA)); Bohling, D.A.; Muhr, G.T. (Air Products and Chemicals, Inc., Allentown, PA (USA))

    1991-05-01

    We have investigated the effect of Al in the form of triethylaluminum (TEAl), trimethylamine alane (TMAAl), or elemental Al, and hydrogen, bonded to Group III or Group V precursors, on the oxygen and carbon concentrations of AlGaAs grown by metalorganic molecular beam epitaxy (MOMBE). Al was found to increase both the oxygen and carbon incorporation rates relative to GaAs. The primary source of the oxygen has been determined to be alkoxide contamination of the alkyl Group III sources. Similarly, the carbon contamination is due to carbon released from the decomposition of the alkyl Ga sources. For films grown with TEGa, this enhancement of the carbon uptake can be suppressed through the use of TMAAl which releases atomic hydrogen at the growth surface. Hydrogen does not appear to remove carbon generated from methyl radicals, as AlGaAs grown from TMGa exhibits hole concentrations >10{sup 19} cm{sup -3}, regardless of Al source, which increase with increasing AsH{sub x}/As{sub 2} ratio. We have also determined that increasing the AsH{sub x}/As{sub 2} ratio does not improve the crystallinity of the AlGaAs layers as determined by ion channelling analysis. (orig.).

  4. Controlling Ethylene Hydrogenation Reactivity on Pt13 Clusters by Varying the Stoichiometry of the Amorphous Silica Support.

    Science.gov (United States)

    Crampton, Andrew S; Rötzer, Marian D; Schweinberger, Florian F; Yoon, Bokwon; Landman, Uzi; Heiz, Ueli

    2016-07-25

    Ethylene hydrogenation was investigated on size-selected Pt13 clusters supported on three amorphous silica (a-SiO2 ) thin films with different stoichiometries. Activity measurements of the reaction at 300 K revealed that on a silicon-rich and a stoichiometric film, Pt13 exhibits a similar activity to that of Pt(111), in line with the known structure insensitivity of the reaction. On an oxygen-rich film, a threefold increased rate was measured. Pulsing ethylene at 400 K, then measuring the activity at 300 K, resulted in complete loss of activity on the silicon-rich surface compared to only marginal losses on the other surfaces. The measured reactivity trends correlate with charging characteristics of a Pt13 cluster on the SiO2 films, predicted through first-principle calculations. The results reveal that the stoichiometry-dependent charging by the support can be used to tune the selectivity of reaction pathways during a catalytic hydrogenation reaction. PMID:27356301

  5. Fabrication of Pd Micro-Membrane Supported on Nano-Porous Anodized Aluminum Oxide for Hydrogen Separation.

    Science.gov (United States)

    Kim, Taegyu

    2015-08-01

    In the present study, nano-porous anodized aluminum oxide (AAO) was used as a support of the Pd membrane. The AAO fabrication process consists of an electrochemical polishing, first/second anodizing, barrier layer dissolving and pores widening. The Pd membrane was deposited on the AAO support using an electroless plating with ethylenediaminetetraacetic acid (EDTA) as a plating agent. The AAO had the regular pore structure with the maximum pore diameter of ~100 nm so it had a large opening area but a small free standing area. The 2 µm-thick Pd layer was obtained by the electroless plating for 3 hours. The Pd layer thickness increased with increasing the plating time. However, the thickness was limited to ~5 µm in maximum. The H2 permeation flux was 0.454 mol/m2-s when the pressure difference of 66.36 kPa0.5 was applied at the Pd membrane under 400 °C. PMID:26369167

  6. Isotope dependent, temperature regulated, energy repartitioning in a low-barrier, short-strong hydrogen bonded cluster

    International Nuclear Information System (INIS)

    We investigate and analyze the vibrational properties, including hydrogen/deuterium isotope effects, in a fundamental organic hydrogen bonded system using multiple experimental (infrared multiple photon dissociation and argon-tagged action spectroscopy) and computational techniques. We note a qualitative difference between the two experimental results discussed here and employ ab initio molecular dynamics simulations to explain these results. A deeper understanding of the differences between the isotopically labeled systems arises from an analysis of the simulated cluster spectroscopy and leads to a system-bath coupling interpretation. Specifically, when a few active modes, involving the shared hydrogen/deuterium stretch, are identified and labeled as “system,” with all other molecular vibrational modes being identified as “bath” modes, we find critical differences in the coupling between the system modes for the shared proton and shared deuteron cases. These differences affect the energy repartitioning between these modes resulting in a complex spectral evolution as a function of temperature. Furthermore, intensity borrowing across modes that are widely distributed in the frequency domain plays an important role on the simulated spectra

  7. Li修饰的C24团簇的储氢性能∗%Hydrogen storage prop erties of Li-decorated C24 clusters

    Institute of Scientific and Technical Information of China (English)

    祁鹏堂; 陈宏善

    2015-01-01

    Hydrogen is considered as a potentially ideal substitution for fossil fuels in the future sustainable energy system because it is an abundant, clean and renewable energy carrier. A safe, efficient and economic storage method is the crucial prerequistite and the biggest challenge for the wide scale use of hydrogen. The nanomaterial is one of the most promising hydrogen storage materials because of its high surface to volume ratio, unique electronic structure and novel chemical and physical properties. It has been demonstrated that pristine nanostructures are not suitable for hydrogen storage, since they interact weakly with hydrogen molecule and their hydrogen storage density is very low. However, the hydrogen storage capacity of the nanostructures can be significantly enhanced through substitutional doping or decoration by metal atoms. Using density functional theory, we investigate the properties of hydrogen adsorption on Li-decorated C24clusters. Results show that the preferred binding site for Li atom is the pentagonal rings. The interaction of Li atoms with the clusters is stronger than that among Li atoms, thus hindering effectively aggregation of Li atoms on the surface of the cluster. The decorated Li atoms are positively charged due to electron transfer from Li to C atoms. When H2 molecules approach Li atoms, they are moderately polarized under the electric field, and adsorbed around the Li atoms in molecular form. Each Li atom in the Li-decorated C24 complexes can adsorb two to three H2 molecules. The H–H bond lengths of the adsorbed H2 molecules are slightly stretched. The average adsorption energies are in the range of 0.08 to 0.13 eV/H2, which are intermediate between physisorption and chemisorption. C24Li6 can hold up to 12 H2 molecules, corresponding to a hydrogen uptake density of 6.8 wt%. This value exceeds the 2020 hydrogen storage target of 5.5 wt%proposed by the U. S. Department of Energy.

  8. Ab initio LCAO-MO cluster-type calculation of the self-consistent electronic screening charge density around a single hydrogen impurity in a nickel crystal

    International Nuclear Information System (INIS)

    The electronic structure for a Ni atom cluster embedded in bulk Ni by use of a spin-averaged local exchange SCF Ni crystal potential is calculated with an ab initio LCAO-Mo variational method. A single hydrogen impurity is added at the cluster center (fcc octahedral interstitial site) and the electronic structure computed iteratively until the change in electron density from the pure Ni cluster density is self-consistent. The H-Ni6 self-consistent density change is compared to the charge density around a free hydrogen atom and to the initial-response density change in H-Ni14 and H-Ni38 clusters. 14 references

  9. Aluminum-Scandium Alloys: Material Characterization, Friction Stir Welding, and Compatibility With Hydrogen Peroxide (MSFC Center Director's Discretionary Fund Final Report, Proj. No. 04-14)

    Science.gov (United States)

    Lee, J. A.; Chen, P. S.

    2004-01-01

    This Technical Memorandum describes the development of several high-strength aluminum (Al) alloys that are compatible with hydrogen peroxide (H2O2) propellant for NASA Hypersonic-X (Hyper-X) vehicles fuel tanks and structures. The yield strengths for some of these Al-magnesium-based alloys are more than 3 times stronger than the conventional 5254-H112 Al alloy, while maintaining excellent H2O2 compatibility similar to class 1 5254 alloy. The alloy development strategy is to add scandium, zirconium, and other transitional metals with unique electrochemical properties, which will not act as catalysts, to decompose the highly concentrated 90 percent H2O2. Test coupons are machined from sheet metals for H2O2 long-term exposure testing and mechanical properties testing. In addition, the ability to weld the new alloys using friction stir welding has also been explored. The new high-strength alloys could represent an enabling material technology for Hyper-X vehicles, where flight weight reduction is a critical requirement.

  10. Benchmarking ab initio binding energies of hydrogen-bonded molecular clusters based on FTIR spectroscopy

    DEFF Research Database (Denmark)

    Bork, Nicolai Christian; Du, Lin; Reiman, Heidi;

    2014-01-01

    Gibbs free binding energies in molecular complexes and clusters based on gas phase FTIR spectroscopy. The acetonitrile-HCl molecular complex is identified via its redshifted H-Cl stretching vibrational mode. We determine the Gibbs free binding energy, ΔG°295 K, to between 4.8 and 7.9 kJ mol(-1) and......Models of formation and growth of atmospheric aerosols are highly dependent on accurate cluster binding energies. These are most often calculated by ab initio electronic structure methods but remain associated with significant uncertainties. We present a computational benchmarking study of the...

  11. Electron attachment to clusters composed of closed shell, hydrogen containing molecules

    International Nuclear Information System (INIS)

    Electron attachment to clusters of HCl, H2O, D2O, C2H4(OH)2, NH3, and ND3 is compared. The clusters are produced in a seeded supersonic beam traversing a sustained gas discharge. For the first four molecules Nmin=2 is the lowest number of molecules necessary to support a bound negative ion state. A much larger Nmin and an isotope effect is observed for ammonia, Nmin(NH3)=35, and Nmin(ND3)=41. (orig.)

  12. Hydrogen

    OpenAIRE

    John O’M. Bockris

    2011-01-01

    The idea of a “Hydrogen Economy” is that carbon containing fuels should be replaced by hydrogen, thus eliminating air pollution and growth of CO2 in the atmosphere. However, storage of a gas, its transport and reconversion to electricity doubles the cost of H2 from the electrolyzer. Methanol made with CO2 from the atmosphere is a zero carbon fuel created from inexhaustible components from the atmosphere. Extensive work on the splitting of water by bacteria shows that if wastes are used as the...

  13. Path-integral molecular dynamics simulations of hydrated hydrogen chloride cluster HCl(H2O)4 on a semiempirical potential energy surface

    International Nuclear Information System (INIS)

    Path-integral molecular dynamics simulations for the HCl(H2O)4 cluster have been performed on the ground-state potential energy surface directly obtained on-the-fly from semiempirical PM3-MAIS molecular orbital calculations. It is found that the HCl(H2O)4 cluster has structural rearrangement above the temperature of 300 K showing a liquid-like behavior. Quantum mechanical fluctuation of hydrogen nuclei plays a significant role in structural arrangement processes in this cluster.

  14. Photostability of small heterocyclic molecules in hydrogen bonded clusters: Evidence from photodissociation and mass spectrometric experiments

    Czech Academy of Sciences Publication Activity Database

    Tkáč, Ondřej; Poterya, Viktoriya; Pysanenko, Andriy; Slavíček, P.; Buck, U.; Fárník, Michal

    Innsbruck : Innsbruck University Press, 2010, s. 258-261. ISBN 978-3-902719-52-2. [XVII Symposium on Atomic, Cluster and Surface Physics 2010. Obergurgl (AT), 24.01.2010-29.01.2010] R&D Projects: GA AV ČR KJB400400902; GA AV ČR KAN400400651 Institutional research plan: CEZ:AV0Z40400503 Keywords : heterocyclic molecules * photochemistry * photodissociation Subject RIV: CF - Physical ; Theoretical Chemistry

  15. UNDER PRESSURE: STAR CLUSTERS AND THE NEUTRAL HYDROGEN MEDIUM OF TIDAL TAILS

    International Nuclear Information System (INIS)

    Using archival data from ATCA, WHISP, and the Very Large Array, we have analyzed the H I emission of 22 tidal tail regions of the Mullan et al. sample of pairwise interacting galaxies. We have measured the column densities, line-of-sight velocity dispersions, and kinetic energy densities on ∼kpc scales. We also constructed a tracer of the line-of-sight velocity gradient over ∼10 kpc scales. We compared the distributions of these properties between regions that do and do not contain massive star cluster candidates (MV 4-106 M☉ as observed in Hubble Space Telescope WFPC2 VI data). In agreement with Maybhate et al., we find that a local, ∼kpc-scale column density of log NHI ∼> 20.6 cm–2 is frequently required for detecting clustered star formation. This H I gas also tends to be turbulent, with line-of-sight velocity dispersions σlos ≈ 10-75 km s–1, implying high kinetic energy densities (log ΣKE > 46 erg pc–2). Thus, high H I densities and pressures, partly determined by the tail dynamical age and other interaction characteristics, are connected to large-scale cluster formation in tidal tails overall. Last, we find that the high mechanical energy densities of the gas are likely not generally due to feedback from star formation. Rather, these properties are more likely to be a cause of star formation than a result.

  16. Aluminum Hydroxide

    Science.gov (United States)

    Aluminum hydroxide is used for the relief of heartburn, sour stomach, and peptic ulcer pain and to ... Aluminum hydroxide comes as a capsule, a tablet, and an oral liquid and suspension. The dose and ...

  17. ZnO-dotted porous ZnS cluster microspheres for high efficient, Pt-free photocatalytic hydrogen evolution

    Science.gov (United States)

    Wu, Aiping; Jing, Liqiang; Wang, Jianqiang; Qu, Yang; Xie, Ying; Jiang, Baojiang; Tian, Chungui; Fu, Honggang

    2015-03-01

    The Pt-free photocatalytic hydrogen evolution (PHE) has been the focus in the photocatalysis field. Here, the ZnO-dotted porous ZnS cluster microsphere (PCMS) is designed for high efficient, Pt-free PHE. The PCMS is designed through an easy ``controlling competitive reaction'' strategy by selecting the thiourea as S2- source and Zn(Ac)2.2H2O as Zn source in ethylene glycol medium. Under suitable conditions, one of the PCMS, named PCMS-1, with high SBET specific area of 194 m2g-1, microsphere size of 100 nm and grain size of 3 nm can be obtained. The formation of PCMS is verified by TEM, XAES, XPS, Raman and IR methods. Importantly, a series of the experiments and theoretical calculation demonstrate that the dotting of ZnO not only makes the photo-generated electrons/hole separate efficiently, but also results in the formation of the active catalytic sites for PHE. As a result, the PCMS-1 shows the promising activity up to 367 μmol h-1 under Pt-free condition. The PHE activity has no obvious change after addition 1 wt.% Pt, implying the presence of active catalytic sites for hydrogen evolution in the PCMS-1. The easy synthesis process, low preparation cost of the PCMS makes their large potential for Pt-free PHE.

  18. Selective Propene Epoxidation on Immobilized Au6-10 Clusters: The Effect of Hydrogen and Water on Activity and Selectivity

    DEFF Research Database (Denmark)

    Lee, Sungsik; Molina, Luis M.; López, María J.;

    2009-01-01

    Epoxidation made easy: Subnanometer gold clusters immobilized on amorphous alumina result in a highly active and selective catalyst for propene epoxidation. The highest selectivity is found for gas mixtures involving oxygen and water, thus avoiding the use of hydrogen. Ab initio DFT calculations ...

  19. Hydrogen

    Directory of Open Access Journals (Sweden)

    John O’M. Bockris

    2011-11-01

    Full Text Available The idea of a “Hydrogen Economy” is that carbon containing fuels should be replaced by hydrogen, thus eliminating air pollution and growth of CO2 in the atmosphere. However, storage of a gas, its transport and reconversion to electricity doubles the cost of H2 from the electrolyzer. Methanol made with CO2 from the atmosphere is a zero carbon fuel created from inexhaustible components from the atmosphere. Extensive work on the splitting of water by bacteria shows that if wastes are used as the origin of feed for certain bacteria, the cost for hydrogen becomes lower than any yet known. The first creation of hydrogen and electricity from light was carried out in 1976 by Ohashi et al. at Flinders University in Australia. Improvements in knowledge of the structure of the semiconductor-solution system used in a solar breakdown of water has led to the discovery of surface states which take part in giving rise to hydrogen (Khan. Photoelectrocatalysis made a ten times increase in the efficiency of the photo production of hydrogen from water. The use of two electrode cells; p and n semiconductors respectively, was first introduced by Uosaki in 1978. Most photoanodes decompose during the photoelectrolysis. To avoid this, it has been necessary to create a transparent shield between the semiconductor and its electronic properties and the solution. In this way, 8.5% at 25 °C and 9.5% at 50 °C has been reached in the photo dissociation of water (GaP and InAs by Kainthla and Barbara Zeleney in 1989. A large consortium has been funded by the US government at the California Institute of Technology under the direction of Nathan Lewis. The decomposition of water by light is the main aim of this group. Whether light will be the origin of the post fossil fuel supply of energy may be questionable, but the maximum program in this direction is likely to come from Cal. Tech.

  20. Regeneration of aluminum hydride

    Science.gov (United States)

    Graetz, Jason Allan; Reilly, James J; Wegrzyn, James E

    2012-09-18

    The present invention provides methods and materials for the formation of hydrogen storage alanes, AlH.sub.x, where x is greater than 0 and less than or equal to 6 at reduced H.sub.2 pressures and temperatures. The methods rely upon reduction of the change in free energy of the reaction between aluminum and molecular H.sub.2. The change in free energy is reduced by lowering the entropy change during the reaction by providing aluminum in a state of high entropy, and by increasing the magnitude of the change in enthalpy of the reaction or combinations thereof.

  1. Hydrogen bonding interaction of small acetaldehyde clusters studied with core-electron excitation spectroscopy in the oxygen K-edge region

    International Nuclear Information System (INIS)

    In order to examine inner-shell electron excitation spectra of molecular clusters with strong multipole interactions, excitation spectra and time-of-flight (TOF) fragment-mass spectra of small acetaldehyde (AA) clusters have been studied under the beam conditions. The TOF spectra at the oxygen K-edge region showed an intense growth of the protonated clusters, MnH+ (M=CH3CHO) in the cluster beams. 'cluster-specific' excitation spectra could be generated by monitoring partial-ion-yields of the protonated clusters. The most intense band of O1s→π*CO was found to shift to a higher energy by 0.15 eV relative to the monomer band upon clusterization. X-ray absorption spectra (XAS) were also calculated for the representative dimer configurations using a computer modelling program based on the density functional theory. The XAS prediction for the most stable (non-planar) configuration was found to give a close comparison with the cluster-band shift observed. The band shift was interpreted as being due to the HOMO-LUMO interaction within the complex where a contribution of vibrationally blue-shifting hydrogen bonding could be identified.

  2. Hydrogen activation, diffusion, and clustering on CeO2(111): A DFT+U study

    International Nuclear Information System (INIS)

    We present a comprehensive density functional theory+U study of the mechanisms underlying the dissociation of molecular hydrogen, and diffusion and clustering of the resulting atomic species on the CeO2(111) surface. Contrary to a widely held view based solely on a previous theoretical prediction, our results show conclusively that H2 dissociation is an activated process with a large energy barrier ∼1.0 eV that is not significantly affected by coverage or the presence of surface oxygen vacancies. The reaction proceeds through a local energy minimum – where the molecule is located close to one of the surface oxygen atoms and the H–H bond has been substantially weaken by the interaction with the substrate –, and a transition state where one H atom is attached to a surface O atom and the other H atom sits on-top of a Ce4+ ion. In addition, we have explored how several factors, including H coverage, the location of Ce3+ ions as well as the U value, may affect the chemisorption energy and the relative stability of isolated OH groups versus pair and trimer structures. The trimer stability at low H coverages and the larger upward relaxation of the surface O atoms within the OH groups are consistent with the assignment of the frequent experimental observation by non-contact atomic force and scanning tunneling microscopies of bright protrusions on three neighboring surface O atoms to a triple OH group. The diffusion path of isolated H atoms on the surface goes through the adsorption on-top of an oxygen in the third atomic layer with a large energy barrier of ∼1.8 eV. Overall, the large energy barriers for both, molecular dissociation and atomic diffusion, are consistent with the high activity and selectivity found recently in the partial hydrogenation of acetylene catalyzed by ceria at high H2/C2H2 ratios

  3. Electronic origin of the dependence of hydrogen bond strengths on nearest-neighbor and next-nearest-neighbor hydrogen bonds in polyhedral water clusters (H2O)n, n = 8, 20 and 24

    Energy Technology Data Exchange (ETDEWEB)

    Iwata, Suehiro; Akase, Dai; Aida, Misako; Xantheas, Sotiris S.

    2016-08-04

    The relative stability and the characteristics of the hydrogen bond networks in the cubic cages of (H2O)8, dodecahedral cages of (H2O)20,and tetrakaidodecahedral cages of (H2O)24 are studied. The charge-transfer and dispersion interaction terms of every pair of the hydrogen bonds are evaluated by using the perturbation theory based on the locally-projected molecular orbital (LPMO PT). Every water molecule and every hydrogen-bonded pair in polyhedral clusters are classified by the types of the adjacent molecules and hydrogen bonds. The relative binding energies among the polyhedral clusters are grouped by these classifications. The necessary condition for the stable conformers and the rules of the ordering of the relative stability among the isomers are derived from the analysis. The O–O distances and the pair-wise charge-transfer terms are dependent not only on the types of the hydrogen donor and acceptor waters but also on the types of the adjacent waters. This dependence is analyzed with Mulliken’s charge-transfer theory. The work is partially supported by the Grant-in-Aid for Science Research of JSPS (SI, DA, MA). SSX was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences. Battelle operates the Pacific Northwest National Laboratory for the US Department of Energy.

  4. Penetration of Hydrogen clusters from 10 to 120 kev/u in carbon foils. Study of their slowing-down and charge distribution of emerging fragments

    International Nuclear Information System (INIS)

    This work is devoted to the experimental study of the interaction between fast (10 to 120 keV/p) hydrogen clusters with thin solid targets. First, we have studied the slowing-down of Hn+(2≤n≤21) clusters through carbon foils. Up to date this had been made only with molecular ions. We obtain evidence for vicinage effects on the energy loss of proton-clusters. We show that for projectile energies larger than 50 keV/p, the energy loss of a proton in a cluster is enhanced when compared to that of an isolated proton of the same velocity. At lower incident energies, it is a decrease of the energy loss which is observed. The same effect is also observed in the energy lost in the entrance window of a surface barrier detector bombarded by clusters. This phenomenon is interpreted in terms of interferences between individual polarisation wakes induced by each proton of the cluster. In the second part, we propose an accurate method to study the charge state of the atomic fragments resulting from the dissociation of fast Hn+ (2≤n≤15) clusters through a carbon foil. This method gives also the distribution of the neutral atoms among the emerging fragments. These distributions are finally compared with binomial laws expected from independent particles

  5. Mass analyzed threshold ionization of hydrogen bonded clusters of biological molecules: the 3-methylindole·C6H6 complex

    International Nuclear Information System (INIS)

    The mass analyzed threshold ionization (MATI) technique has been used for measuring the adiabatic ionization energy of the 3-methylindole·C6H6 cluster (58 018 cm-1) and the binding energies in its ground ionic (4448 cm-1) and ground neutral state (1775 cm-1). We compare our results with those recently obtained for the 3-methylindole·H2O and the indole·C6H6 cluster. The small influence of methylation on the binding energies confirms the π-hydrogen bonding character in the 3-methylindole·C6H6 complex

  6. Selective propene epoxidation on immobilized Au{sub 6-10} clusters : the effect of hydrogen and water on activity and selectivity.

    Energy Technology Data Exchange (ETDEWEB)

    Lee, S.; Molina, J. M.; Lopez, M. J.; Alonso, J. A.; Hammer, B.; Lee, B.; Siefert, S.; Winans, R. W.; Elam, J. W.; Pellin, M. J.; Vajda, S.; Univ. de Valladolid; Univ. of Aarhus

    2009-01-01

    Subnanometer gold clusters immobilized on amorphous alumina result in a highly active and selective catalyst for propene epoxidation. The highest selectivity is found for gas mixtures involving oxygen and water, thus avoiding the use of hydrogen. Ab initio DFT calculations are used to identify key reaction intermediates and reaction pathways. The results confirm the high catalyst activity owing to the formation of propene oxide metallacycles. Al green, Au yellow, O red, and C gray.

  7. High Catalytic Activity and Chemoselectivity of Sub-nanometric Pd Clusters on Porous Nanorods of CeO2 for Hydrogenation of Nitroarenes.

    Science.gov (United States)

    Zhang, Sai; Chang, Chun-Ran; Huang, Zheng-Qing; Li, Jing; Wu, Zhemin; Ma, Yuanyuan; Zhang, Zhiyun; Wang, Yong; Qu, Yongquan

    2016-03-01

    Sub-nanometric Pd clusters on porous nanorods of CeO2 (PN-CeO2) with a high Pd dispersion of 73.6% exhibit the highest catalytic activity and best chemoselectivity for hydrogenation of nitroarenes to date. For hydrogenation of 4-nitrophenol, the catalysts yield a TOF of ∼44059 h(-1) and a chemoselectivity to 4-aminophenol of >99.9%. The superior catalytic performance can be attributed to a cooperative effect between the highly dispersed sub-nanometric Pd clusters for hydrogen activation and unique surface sites of PN-CeO2 with a high concentration of oxygen vacancy for an energetically and geometrically preferential adsorption of nitroarenes via nitro group. The high concentration of surface defects of PN-CeO2 and large Pd dispersion contribute to the enhanced catalytic activity for the hydrogenation reactions. The high chemoselectivity is mainly governed by the high Pd dispersion on the support. The catalysts also deliver high catalytic activity and selectivity for nitroaromatics with various reducible substituents into the corresponding aminoarenes. PMID:26828123

  8. Hydrogen-bonded ring closing and opening of protonated methanol clusters H(+)(CH3OH)(n) (n = 4-8) with the inert gas tagging.

    Science.gov (United States)

    Li, Ying-Cheng; Hamashima, Toru; Yamazaki, Ryoko; Kobayashi, Tomohiro; Suzuki, Yuta; Mizuse, Kenta; Fujii, Asuka; Kuo, Jer-Lai

    2015-09-14

    The preferential hydrogen bond (H-bond) structures of protonated methanol clusters, H(+)(MeOH)n, in the size range of n = 4-8, were studied by size-selective infrared (IR) spectroscopy in conjunction with density functional theory calculations. The IR spectra of bare clusters were compared with those with the inert gas tagging by Ar, Ne, and N2, and remarkable changes in the isomer distribution with the tagging were found for clusters with n≥ 5. The temperature dependence of the isomer distribution of the clusters was calculated by the quantum harmonic superposition approach. The observed spectral changes with the tagging were well interpreted by the fall of the cluster temperature with the tagging, which causes the transfer of the isomer distribution from the open and flexible H-bond network types to the closed and rigid ones. Anomalous isomer distribution with the tagging, which has been recently found for protonated water clusters, was also found for H(+)(MeOH)5. The origin of the anomaly was examined by the experiments on its carrier gas dependence. PMID:26235389

  9. Hydrogen activation, diffusion, and clustering on CeO{sub 2}(111): A DFT+U study

    Energy Technology Data Exchange (ETDEWEB)

    Fernández-Torre, Delia [Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Instituto de Estructura de la Materia, CSIC, C/ Serrano 121, E-28006 Madrid (Spain); Carrasco, Javier [CIC Energigune, Albert Einstein 48, 01510 Miñano, Álava (Spain); Instituto de Catálisis y Petroleoquímica, CSIC, C/ Marie Curie 2, E-28049 Madrid (Spain); Ganduglia-Pirovano, M. Verónica [Instituto de Catálisis y Petroleoquímica, CSIC, C/ Marie Curie 2, E-28049 Madrid (Spain); Pérez, Rubén, E-mail: ruben.perez@uam.es [Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, E-28049 Madrid (Spain)

    2014-07-07

    We present a comprehensive density functional theory+U study of the mechanisms underlying the dissociation of molecular hydrogen, and diffusion and clustering of the resulting atomic species on the CeO{sub 2}(111) surface. Contrary to a widely held view based solely on a previous theoretical prediction, our results show conclusively that H{sub 2} dissociation is an activated process with a large energy barrier ∼1.0 eV that is not significantly affected by coverage or the presence of surface oxygen vacancies. The reaction proceeds through a local energy minimum – where the molecule is located close to one of the surface oxygen atoms and the H–H bond has been substantially weaken by the interaction with the substrate –, and a transition state where one H atom is attached to a surface O atom and the other H atom sits on-top of a Ce{sup 4+} ion. In addition, we have explored how several factors, including H coverage, the location of Ce{sup 3+} ions as well as the U value, may affect the chemisorption energy and the relative stability of isolated OH groups versus pair and trimer structures. The trimer stability at low H coverages and the larger upward relaxation of the surface O atoms within the OH groups are consistent with the assignment of the frequent experimental observation by non-contact atomic force and scanning tunneling microscopies of bright protrusions on three neighboring surface O atoms to a triple OH group. The diffusion path of isolated H atoms on the surface goes through the adsorption on-top of an oxygen in the third atomic layer with a large energy barrier of ∼1.8 eV. Overall, the large energy barriers for both, molecular dissociation and atomic diffusion, are consistent with the high activity and selectivity found recently in the partial hydrogenation of acetylene catalyzed by ceria at high H{sub 2}/C{sub 2}H{sub 2} ratios.

  10. Luminescent properties of aluminum hydride

    International Nuclear Information System (INIS)

    We studied cathodoluminescence and photoluminescence of α-AlH3– a likely candidate for use as possible hydrogen carrier in hydrogen-fueled vehicles. Luminescence properties of original α-AlH3 and α-AlH3 irradiated with ultraviolet were compared. The latter procedure leads to activation of thermal decomposition of α-AlH3 and thus has a practical implementation. We showed that the original and UV-modified aluminum hydride contain luminescence centers ‐ structural defects of the same type, presumably hydrogen vacancies, characterized by a single set of characteristic bands of radiation. The observed luminescence is the result of radiative intracenter relaxation of the luminescence center (hydrogen vacancy) excited by electrons or photons, and its intensity is defined by the concentration of vacancies, and the area of their possible excitation. UV-activation of the dehydrogenation process of aluminum hydride leads to changes in the spatial distribution of the luminescence centers. For short times of exposure their concentration increases mainly in the surface regions of the crystals. At high exposures, this process extends to the bulk of the aluminum hydride and ends with a decrease in concentration of luminescence centers in the surface region. - Highlights: • Aluminum hydride contains hydrogen vacancies which serve as luminescence centers. • The luminescence is the result of radiative relaxation of excited centers. • Hydride UV-irradiation alters distribution and concentration of luminescence centers

  11. Luminescent properties of aluminum hydride

    Energy Technology Data Exchange (ETDEWEB)

    Baraban, A.P.; Gabis, I.E.; Dmitriev, V.A. [Saint-Petersburg State University, Department of Physics, Saint-Petersburg 198504 (Russian Federation); Dobrotvorskii, M.A., E-mail: mstislavd@gmail.com [Saint-Petersburg State University, Department of Physics, Saint-Petersburg 198504 (Russian Federation); Kuznetsov, V.G. [Saint-Petersburg State University, Department of Physics, Saint-Petersburg 198504 (Russian Federation); Matveeva, O.P. [National Mineral Resources University, Saint Petersburg 199106 (Russian Federation); Titov, S.A. [Petersburg State University of Railway Transport, Saint-Petersburg 190031 (Russian Federation); Voyt, A.P.; Elets, D.I. [Saint-Petersburg State University, Department of Physics, Saint-Petersburg 198504 (Russian Federation)

    2015-10-15

    We studied cathodoluminescence and photoluminescence of α-AlH{sub 3}– a likely candidate for use as possible hydrogen carrier in hydrogen-fueled vehicles. Luminescence properties of original α-AlH{sub 3} and α-AlH{sub 3} irradiated with ultraviolet were compared. The latter procedure leads to activation of thermal decomposition of α-AlH{sub 3} and thus has a practical implementation. We showed that the original and UV-modified aluminum hydride contain luminescence centers ‐ structural defects of the same type, presumably hydrogen vacancies, characterized by a single set of characteristic bands of radiation. The observed luminescence is the result of radiative intracenter relaxation of the luminescence center (hydrogen vacancy) excited by electrons or photons, and its intensity is defined by the concentration of vacancies, and the area of their possible excitation. UV-activation of the dehydrogenation process of aluminum hydride leads to changes in the spatial distribution of the luminescence centers. For short times of exposure their concentration increases mainly in the surface regions of the crystals. At high exposures, this process extends to the bulk of the aluminum hydride and ends with a decrease in concentration of luminescence centers in the surface region. - Highlights: • Aluminum hydride contains hydrogen vacancies which serve as luminescence centers. • The luminescence is the result of radiative relaxation of excited centers. • Hydride UV-irradiation alters distribution and concentration of luminescence centers.

  12. Tracking Rh atoms in Zeolite HY: First Steps of Metal Cluster Formation and Influence of Metal Nuclearity on Catalysis of Ethylene Hydrogenation and Ethylene Dimerization

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Dong; Xu, Pinghong; Browning, Nigel D.; Gates, Bruce C.

    2016-07-07

    The initial steps of rhodium cluster formation from zeolite-supported mononuclear Rh(C2H4)2 complexes in H2 at 373 K and 1 bar were investigated by infrared and extended X-ray absorption fine structure spectroscopies and scanning transmission electron microscopy (STEM). The data show that ethylene ligands on the rhodium react with H2 to give supported rhodium hydrides and trigger the formation of rhodium clusters. STEM provided the first images of the smallest rhodium clusters (Rh2) and their further conversion into larger clusters. The samples were investigated in a plug-flow reactor as catalysts for the conversion of ethylene + H2 in a molar ratio of 4:1 at 1 bar and 298 K, with the results showing how the changes in catalyst structure affect the activity and selectivity; the rhodium clusters are more active for hydrogenation of ethylene than the single-site complexes, which are more selective for dimerization of ethylene to give butenes

  13. Tracking Rh Atoms in Zeolite HY: First Steps of Metal Cluster Formation and Influence of Metal Nuclearity on Catalysis of Ethylene Hydrogenation and Ethylene Dimerization.

    Science.gov (United States)

    Yang, Dong; Xu, Pinghong; Browning, Nigel D; Gates, Bruce C

    2016-07-01

    The initial steps of rhodium cluster formation from zeolite-supported mononuclear Rh(C2H4)2 complexes in H2 at 373 K and 1 bar were investigated by infrared and extended X-ray absorption fine structure spectroscopies and scanning transmission electron microscopy (STEM). The data show that ethylene ligands on the rhodium react with H2 to give supported rhodium hydrides and trigger the formation of rhodium clusters. STEM provided the first images of the smallest rhodium clusters (Rh2) and their further conversion into larger clusters. The samples were investigated in a plug-flow reactor as catalysts for the conversion of ethylene + H2 in a molar ratio of 4:1 at 1 bar and 298 K, with the results showing how the changes in catalyst structure affect the activity and selectivity; the rhodium clusters are more active for hydrogenation of ethylene than the single-site complexes, which are more selective for dimerization of ethylene to give butenes. PMID:27315020

  14. Cooperative effects and strengths of hydrogen bonds in open-chain cis-triaziridine clusters (n = 2-8): a DFT investigation.

    Science.gov (United States)

    Song, Hua-Jie; Xiao, He-Ming; Dong, Hai-Shan; Zhu, Wei-Hua

    2006-02-16

    We employ DFT/B3LYP method to investigate linear open-chain clusters (n = 2-8) of the cis-triaziridine molecule that is a candidate molecule for high energy density materials (HEDM). Our calculations indicate that the pervasive phenomena of cooperative effects are observed in the clusters of n = 3-8, which are reflected in changes in lengths of N...H hydrogen bonds, stretching frequencies, and intensities of N-H bonds, dipole moments, and charge transfers as cluster size increases. The n(N) --> sigma*(N-H) interactions, i.e., the charge transfers from lone pairs (n(N)) of the N atoms into antibonds (sigma*) of the N-H bonds acting as H-donors, can be used to explain the observed cooperative phenomena. The approaches based upon natural bond orbital (NBO) method and theory of atoms in molecule (AIM) to evaluating N...H strengths are found to be equivalent. In the process of N...H bonding, cooperative nature of n(N) --> sigma*(N-H) interactions promotes formation of stronger N...H bonds as reflected in increases in the capacities of cis-triaziridine clusters to concentrate electrons at the bond critical points of N...H bonds. The calculated nonadditive energies also show that the cooperative effects due to n(N) --> sigma*(N-H) interactions indeed provide additional stabilities for the clusters. PMID:16466259

  15. Hydride mobility in trinuclear sulfido clusters with the core [Rh3(μ-H)(μ3-S)2]: molecular models for hydrogen migration on metal sulfide hydrotreating catalysts.

    Science.gov (United States)

    Jiménez, M Victoria; Lahoz, Fernando J; Lukešová, Lenka; Miranda, José R; Modrego, Francisco J; Nguyen, Duc H; Oro, Luis A; Pérez-Torrente, Jesús J

    2011-07-11

    The treatment of [{Rh(μ-SH){P(OPh)(3)}(2)}(2)] with [{M(μ-Cl)(diolef)}(2)] (diolef=diolefin) in the presence of NEt(3) affords the hydrido-sulfido clusters [Rh(3)(μ-H)(μ(3)-S)(2)(diolef){P(OPh)(3)}(4)] (diolef=1,5-cyclooctadiene (cod) for 1, 2,5-norbornadiene (nbd) for 2, and tetrafluorobenzo[5,6]bicyclo[2.2.2]octa-2,5,7-triene (tfb) for 3) and [Rh(2)Ir(μ-H)(μ(3)-S)(2)(cod){P(OPh)(3)}(4)] (4). Cluster 1 can be also obtained by treating [{Rh(μ-SH){P(OPh)(3)}(2)}(2)] with [{Rh(μ-OMe)(cod)}(2)], although the main product of the reaction with [{Ir(μ-OMe)(cod)}(2)] was [RhIr(2)(μ-H)(μ(3)-S)(2)(cod)(2){P(OPh)(3)}(2)] (5). The molecular structures of clusters 1 and 4 have been determined by X-ray diffraction methods. The deprotonation of a hydrosulfido ligand in [{Rh(μ-SH)(CO)(PPh(3))}(2)] by [M(acac)(diolef)] (acac=acetylacetonate) results in the formation of hydrido-sulfido clusters [Rh(3)(μ-H)(μ(3)-S)(2)(CO)(2) (diolef)(PPh(3))(2)] (diolef=cod for 6, nbd for 7) and [Rh(2)Ir(μ-H)(μ(3)-S)(2)(CO)(2)(cod)(PPh(3))(2)] (8). Clusters 1-3 and 5 exist in solution as two interconverting isomers with the bridging hydride ligand at different edges. Cluster 8 exists as three isomers that arise from the disposition of the PPh(3) ligands in the cluster (cis and trans) and the location of the hydride ligand. The dynamic behaviour of clusters with bulky triphenylphosphite ligands, which involves hydrogen migration from rhodium to sulfur with a switch from hydride to proton character, is significant to understand hydrogen diffusion on the surface of metal sulfide hydrotreating catalysts. PMID:21633978

  16. Hydrogen evolution reaction catalyst

    Science.gov (United States)

    Subbaraman, Ram; Stamenkovic, Vojislav; Markovic, Nenad; Tripkovic, Dusan

    2016-02-09

    Systems and methods for a hydrogen evolution reaction catalyst are provided. Electrode material includes a plurality of clusters. The electrode exhibits bifunctionality with respect to the hydrogen evolution reaction. The electrode with clusters exhibits improved performance with respect to the intrinsic material of the electrode absent the clusters.

  17. Cluster-assisted generation of multi-charged ions in nanosecond laser ionization of pulsed hydrogen sulfide beam at 1064 and 532 nm

    Institute of Scientific and Technical Information of China (English)

    Niu Dong-Mei; Li Hai-Yang; Luo Xiao-Lin; Liang Feng; Cheng Shuang; Li An-Lin

    2006-01-01

    The multi-charged sulfur ions of Sq+ (q ≤ 6) have been generated when hydrogen sulfide cluster beams are irradiated by a nanosecond laser of 1064 and 532 nm with an intensity of 1010 ~ 1012W·cm-2. S6+ is the dominant multicharged species at 1064 nm, while S4+, S3+ and S2+ ions are the main multi-charged species at 532 nm. A three-step model (i.e., multiphoton ionization triggering, inverse bremsstrahlung heating, electron collision ionizing) is proposed to explain the generation of these multi-charged ions at the laser intensity stated above. The high ionization level of the clusters and the increasing charge state of the ion products with increasing laser wavelength are supposed mainly due to the rate-limiting step, i.e., electron heating by absorption energy from the laser field via inverse bremsstrahlung, which is proportional to λ2, λ being the laser wavelength.

  18. Structural, electronic, and magnetic properties of boron cluster anions doped with aluminum:BnAlˉ (2 ≤ n ≤ 9)

    Institute of Scientific and Technical Information of China (English)

    Gu Jian-Bing; Yang Xiang-Dong; Wang Huai-Qian; Li Hui-Fang

    2012-01-01

    The geometrical structures,relative stabilities,electronic and magnetic properties of small BnAlˉ (2 ≤ n ≤ 9) clusters are systematically investigated by using the first-principles density functional theory.The results show that the Al atom prefers to reside either on the outer-side or above the surface,but not in the centre of the clusters in all of the most stable BnAlˉ (2 ≤ n ≤ 9) isomers and the one excess electron is strong enough to modify the geometries of some specific sizes of the neutral clusters.All the results of the analysis for the fragmentation energies,the second-order difference of energies,and the highest occupied-lowest unoccupied molecular orbital energy gaps show that B4Alˉ and B8Alˉ clusters each have a higher relative stability.Especially,the B8Alˉ cluster has the most enhanced chemical stability.Furthermore,both the local magnetic moments and the total magnetic moments display a pronounced oddeven oscillation with the number of boron atoms,and the magnetic effects arise mainly from the boron atoms except for the B7Alˉ and B9Alˉ clusters.

  19. Neutral hydrogen gas, past and future star formation in galaxies in and around the `Sausage' merging galaxy cluster

    Science.gov (United States)

    Stroe, Andra; Oosterloo, Tom; Röttgering, Huub J. A.; Sobral, David; van Weeren, Reinout; Dawson, William

    2015-09-01

    CIZA J2242.8+5301 (z = 0.188, nicknamed `Sausage') is an extremely massive (M200 ˜ 2.0 × 1015 M⊙), merging cluster with shock waves towards its outskirts, which was found to host numerous emission line galaxies. We performed extremely deep Westerbork Synthesis Radio Telescope H I observations of the `Sausage' cluster to investigate the effect of the merger and the shocks on the gas reservoirs fuelling present and future star formation (SF) in cluster members. By using spectral stacking, we find that the emission line galaxies in the `Sausage' cluster have, on average, as much H I gas as field galaxies (when accounting for the fact cluster galaxies are more massive than the field galaxies), contrary to previous studies. Since the cluster galaxies are more massive than the field spirals, they may have been able to retain their gas during the cluster merger. The large H I reservoirs are expected to be consumed within ˜0.75-1.0 Gyr by the vigorous SF and active galactic nuclei activity and/or driven out by the outflows we observe. We find that the star formation rate (SFR) in a large fraction of H α emission line cluster galaxies correlates well with the radio broad-band emission, tracing supernova remnant emission. This suggests that the cluster galaxies, all located in post-shock regions, may have been undergoing sustained SFR for at least 100 Myr. This fully supports the interpretation proposed by Stroe et al. and Sobral et al. that gas-rich cluster galaxies have been triggered to form stars by the passage of the shock.

  20. Neutral hydrogen gas, past and future star-formation in galaxies in and around the 'Sausage' merging galaxy cluster

    CERN Document Server

    Stroe, Andra; Rottgering, Huub J A; Sobral, David; van Weeren, Reinout; Dawson, William

    2015-01-01

    CIZA J2242.8+5301 ($z = 0.188$, nicknamed 'Sausage') is an extremely massive ($M_{200}\\sim 2.0 \\times 10^{15}M_\\odot$ ), merging cluster with shock waves towards its outskirts, which was found to host numerous emission-line galaxies. We performed extremely deep Westerbork Synthesis Radio Telescope HI observations of the 'Sausage' cluster to investigate the effect of the merger and the shocks on the gas reservoirs fuelling present and future star formation (SF) in cluster members. By using spectral stacking, we find that the emission-line galaxies in the 'Sausage' cluster have, on average, as much HI gas as field galaxies (when accounting for the fact cluster galaxies are more massive than the field galaxies), contrary to previous studies. Since the cluster galaxies are more massive than the field spirals, they may have been able to retain their gas during the cluster merger. The large HI reservoirs are expected to be consumed within $\\sim0.75-1.0$ Gyr by the vigorous SF and AGN activity and/or driven out by t...

  1. Fundamental studies of methanol synthesis from CO(2) hydrogenation on Cu(111), Cu clusters, and Cu/ZnO(0001).

    Science.gov (United States)

    Yang, Yixiong; Evans, Jaime; Rodriguez, Jose A; White, Michael G; Liu, Ping

    2010-09-01

    A combination of experimental and theoretical methods were employed to investigate the synthesis of methanol via CO(2) hydrogenation (CO(2) + 3H(2)--> CH(3)OH + H(2)O) on Cu(111) and Cu nanoparticle surfaces. High pressure reactivity studies show that Cu nanoparticles supported on a ZnO(0001[combining macron]) single crystal exhibit a higher catalytic activity than the Cu(111) planar surface. Complementary density functional theory (DFT) calculations of methanol synthesis were also performed for a Cu(111) surface and unsupported Cu(29) nanoparticles, and the results support a higher activity for Cu nanoparticles. The DFT calculations show that methanol synthesis on Cu surfaces proceeds through a formate intermediate and the overall reaction rate is limited by both formate and dioxomethylene hydrogenation. Moreover, the superior activity of the nanoparticle is associated with its fluxionality and the presence of low-coordinated Cu sites, which stabilize the key intermediates, e.g. formate and dioxomethylene, and lower the barrier for the rate-limiting hydrogenation process. The reverse water-gas-shift (RWGS) reaction (CO(2) + H(2)--> CO + H(2)O) was experimentally observed to compete with methanol synthesis and was also considered in our DFT calculations. In agreement with experiment, the rate of the RWGS reaction on Cu nanoparticles is estimated to be approximately 2 orders of magnitude faster than methanol synthesis at T = 573 K. The experiments and calculations also indicate that CO produced by the fast RWGS reaction does not undergo subsequent hydrogenation to methanol, but instead simply accumulates as a product. Methanol production from CO hydrogenation via the RWGS pathway is hindered by the first hydrogenation of CO to formyl, which is not stable and prefers to dissociate into CO and H atoms on Cu. Our calculated results suggest that the methanol yield over Cu-based catalysts could be improved by adding dopants or promoters which are able to stabilize formyl

  2. Cross section measurements of the processes occurring in the fragmentation of Hn+ (3 ≤ n ≤ 35) hydrogen clusters induced by high speed (60 keV/u) collisions on helium atoms

    International Nuclear Information System (INIS)

    Different processes involved in the fragmentation of ionised hydrogen clusters H3 + (H2)(n-3)/2 (n = 5-35) have been studied in the same experiment: the fragmentation of the cluster is induced by the collision with an helium atom at high velocity (≅ c/100). The collision is realised in reversed kinematic - clusters are accelerated - which allows the detection of neutral and charged fragments. The different channels of fragmentation are identified by using coincidence techniques. For all the cluster sizes studied the capture cross sections of one electron of the target by the cluster is equal to the capture cross section of the H3+ ion. In the same way, the dissociation cross section of the H3+ core of the cluster does not depend on cluster size. These fragmentation processes are due to the interaction of H3+ core of the cluster and the helium atom without ionization of another component of the cluster. On the contrary, the cross sections of loss of one, two and three molecules by the cluster and the dissociation cross section of the cluster in all its molecular components depends strongly on the cluster size. This dependence is different from the one measured for the metastable decay of the cluster. Thus, the process of loss of molecules induced by a collision should correspond to a different dissociation mechanism. In regard of the singularities observed for the size dependence, the H9+, H15+, H19+ and H29+ clusters could be the 'core' of the biggest clusters. These observation are in agreement with the size effects of smaller magnitude observed for the dissociation cross section (all the processes). The values of the cross section for the process of at least one ionization of the cluster indicate that about 80% of the fragmentation events result from this process. (author)

  3. Aluminum-induced cell death of barley-root border cells is correlated with peroxidase- and oxalate oxidase-mediated hydrogen peroxide production.

    Science.gov (United States)

    Tamás, L; Budíková, S; Huttová, J; Mistrík, I; Simonovicová, M; Siroká, B

    2005-06-01

    The function of root border cells (RBC) during aluminum (Al) stress and the involvement of oxalate oxidase, peroxidase and H(2)O(2) generation in Al toxicity were studied in barley roots. Our results suggest that RBC effectively protect the barley root tip from Al relative to the situation in roots cultivated in hydroponics where RBC are not sustained in the area surrounding the root tip. The removal of RBC from Al-treated roots increased root growth inhibition, Al and Evans blue uptake, inhibition of RBC production, the level of dead RBC, peroxidase and oxalate oxidase activity and the production of H(2)O(2). Our results suggest that even though RBC actively produce active oxygen species during Al stress, their role in the protection of root tips against Al toxicity is to chelate Al in their dead cell body. PMID:15759117

  4. Concerted Use of Slab and Cluster Models in an ab initio Study of Hydrogen Desorption from the Si(100) Surface

    Czech Academy of Sciences Publication Activity Database

    Steckel, J. A.; Phung, T.; Jordan, K. D.; Nachtigall, Petr

    2001-01-01

    Roč. 105, č. 18 (2001), s. 4031-4038. ISSN 1089-5647 Institutional research plan: CEZ:AV0Z4040901 Keywords : silicon * surface * hydrogen Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.379, year: 2001

  5. Investigation of Inner Vacuum Sucking method for degassing of molten aluminum

    International Nuclear Information System (INIS)

    Hydrogen is a harmful gas element that is appreciably soluble in aluminum and its alloys. Removal of hydrogen from molten aluminum has been one of the most important tasks in aluminum melt processing. In this paper, a patented degassing process, which is based on principle of vacuum metallurgy, is proposed. A porous head that connects a vacuum system is immersed in the molten aluminum. The vacuum is created within the porous head and the dissolved hydrogen will diffuse unidirectionally towards the porous head according to Sievert's law. In this way, the hydrogen in the molten aluminum can be removed. The Fick's diffusion equation is used to explain hydrogen transfer in the molten aluminum. RPT experiments are carried out to evaluate the effectiveness of the new degassing process. The experiments indicate that the hydrogen content can be dramatically reduced by use of this process.

  6. Investigation of Inner Vacuum Sucking method for degassing of molten aluminum

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Jianmin, E-mail: zjmg2008@gmail.com [Key Lab. of Nonferrous Materials and New Processing Technology, Guangxi University, Nanning, Guangxi 530004 (China); Gu, Ping, E-mail: clxy3693@126.com [Key Lab. of Nonferrous Materials and New Processing Technology, Guangxi University, Nanning, Guangxi 530004 (China); Wang, Youbing, E-mail: zjmg2004@163.com [Key Lab. of Nonferrous Materials and New Processing Technology, Guangxi University, Nanning, Guangxi 530004 (China)

    2012-11-20

    Hydrogen is a harmful gas element that is appreciably soluble in aluminum and its alloys. Removal of hydrogen from molten aluminum has been one of the most important tasks in aluminum melt processing. In this paper, a patented degassing process, which is based on principle of vacuum metallurgy, is proposed. A porous head that connects a vacuum system is immersed in the molten aluminum. The vacuum is created within the porous head and the dissolved hydrogen will diffuse unidirectionally towards the porous head according to Sievert's law. In this way, the hydrogen in the molten aluminum can be removed. The Fick's diffusion equation is used to explain hydrogen transfer in the molten aluminum. RPT experiments are carried out to evaluate the effectiveness of the new degassing process. The experiments indicate that the hydrogen content can be dramatically reduced by use of this process.

  7. Assembly of organic moiety with metal-oxide cluster to generate a new three dimensional supramolecular/hydrogen bonded network based on isopolymolybdate

    Indian Academy of Sciences (India)

    DONIA ZAMMEL; ICHRAF NAGAZI; AMOR HADDAD

    2016-07-01

    A new octa-molybdate formulated as (C₂H₆N₄)₂ [β-Mo₈O₂₆].4H₂O (1) has been isolated by conventional solution method and structurally characterized by single-crystal X-ray diffraction method, IR spectroscopy, UV-Vis absorption, thermogravimetric analysis and cyclic voltammetry. Compound 1 crystallizes in the Triclinic system, space group P-1 with unit cell dimensions, a = 8.348 (2)Å, b = 10.154 (2)Å, c = 10.823 (3)Å, α = 68.35◦ (2), β = 71.59◦ (2), γ= 78.55◦ (2), V = 805.5 (3)ų, and Z = 2. The crystal structure of 1 is built up from octa-molybdate [β-Mo₈O₂₆]⁴⁻ clusters connected through hydrogen-bonding interactions into a three-dimensional supramolecular network.

  8. Fabrication of Low Adsorption Energy Ni-Mo Cluster Cocatalyst in Metal-Organic Frameworks for Visible Photocatalytic Hydrogen Evolution.

    Science.gov (United States)

    Zhen, Wenlong; Gao, Haibo; Tian, Bin; Ma, Jiantai; Lu, Gongxuan

    2016-05-01

    An effective cocatalyst is crucial for enhancing the visible photocatalytic performance of the hydrogen generation reaction. By using density-functional theory (DFT) and frontier molecular orbital (FMO) theory calculation analysis, the hydrogen adsorption free energy (ΔGH) of Ni-Mo alloy (458 kJ·mol(-1)) is found to be lower than that of Ni itself (537 kJ·mol(-1)). Inspired by these results, the novel, highly efficient cocatalyst NiMo@MIL-101 for photocatalysis of the hydrogen evolution reaction (HER) was fabricated using the double solvents method (DSM). In contrast with Ni@MIL-101 and Mo@MIL-101, NiMo@MIL-101 exhibited an excellent photocatalytic performance (740.2 μmol·h(-1) for HER), stability, and high apparent quantum efficiency (75.7%) under 520 nm illumination at pH 7. The NiMo@MIL-101 catalyst also showed a higher transient photocurrent, lower overpotential (-0.51 V), and longer fluorescence lifetime (1.57 ns). The results uncover the dependence of the photocatalytic activity of HER on the ΔGH of Ni-Mo (MoNi4) alloy nanoclusters, i.e., lower ΔGH corresponding to higher HER activity for the first time. The NiMo@MIL-101 catalyst could be a promising candidate to replace precious-metal catalysts of the HER. PMID:27070204

  9. Density functional theory study of the adsorption of hydrogen atoms on Cu2X (X = 3d) clusters

    Science.gov (United States)

    Li, Jiao; Liu, Yanqi; Zhang, Jingjing; Liang, Xiaogang; Duan, Haiming

    2016-05-01

    Density functional theory is carried out to calculate the ground-state structures and electronic properties of Cu2X (X = Sc-Zn) and Cu2X-nH (n = 1-6) clusters. It is found that the dissociation adsorption of H2 molecules of Cu2Ti has obvious advantages over the other mixed clusters. Variations of adsorption energies of Cu2X-nH (n = 1-6) are almost opposite to the energy gaps of Cu2X-(n - 1)H (n = 1-6), which is especially evident in Cu and Zn. Odd-even variations of the distribution of d electrons near the Fermi energy in Cu3-nH and Cu2Zn-nH are opposite, which are strongly correlated to the number of H atoms.

  10. Toward an Understanding of the Hydrogenation Reaction of MO2 Gas-Phase Clusters (M = Ti, Zr, and Hf)

    OpenAIRE

    González Navarrete, Patricio; Calatayud Antonino, Mónica; Andrés Bort, Juan; Ruipérez, F.; Roca Sanjuan, Daniel

    2013-01-01

    A theoretical investigation using density functional theory (DFT) has been carried out in order to understand the molecular mechanism of dihydrogen activation by means of transition metal dioxides MO2 (M = Ti, Zr, and Hf) according to the following reaction: MO2 + H-2 -> MO + H2O. B3LYP/6-311++G(2df,2pd)/SDD methodology was employed considering two possible reaction pathways. As the first step hydrogen activation by M=O bonds yields to metal-oxo hydride intermediates O=MH(OH). This process is...

  11. The Rapidly Rotating, Hydrogen Deficient, Hot Post-Asymptotic Giant Branch Star ZNG 1 in the Globular Cluster M5

    OpenAIRE

    Dixon, W. Van Dyke; Brown, Thomas M.; Landsman, Wayne B.

    2003-01-01

    We report observations of the hot post-asymptotic giant branch star ZNG 1 in the globular cluster M5 (NGC 5904) with the Far Ultraviolet Spectroscopic Explorer (FUSE). From the resulting spectrum, we derive an effective temperature T_eff = 44300 +/- 300 K, a surface gravity log g = 4.3 +/- 0.1, a rotational velocity v sin i = 170 +/- 20 km/s, and a luminosity log (L/L_sun) = 3.52 +/- 0.04. The atmosphere is helium-rich (Y = 0.93), with enhanced carbon (2.6% by mass), nitrogen (0.51%) and oxyg...

  12. A study on aromatic C-H⋯X (X = N, O) hydrogen bonds in 1,2,4,5-tetrafluorobenzene clusters using infrared spectroscopy and ab initio calculations

    Science.gov (United States)

    Venkatesan, V.; Fujii, A.; Mikami, N.

    2005-06-01

    The (1:1) clusters of 1,2,4,5-tetrafluorobenzene (TFB) with CH 3CN, CH 3OCH 3, and NH 3 were studied both experimentally and computationally. Using fluorescence-detected infrared (FDIR) spectroscopy, the aromatic C-H⋯X (X = N, O) hydrogen bond formation in the clusters was directly evidenced by a low-frequency shift and intensity enhancement of the aromatic C-H stretching vibration in the TFB moiety. The molecular structures, stabilization energies, and vibrational frequencies of the clusters were computed at the MP2/6-31+G* level. The observed low-frequency shifts of the aromatic C-H stretch in the clusters correlate with the proton affinities of the acceptor molecules.

  13. Toward an understanding of the hydrogenation reaction of MO2 gas-phase clusters (M = Ti, Zr, and Hf).

    Science.gov (United States)

    González-Navarrete, P; Calatayud, M; Andrés, J; Ruipérez, F; Roca-Sanjuán, D

    2013-06-27

    A theoretical investigation using density functional theory (DFT) has been carried out in order to understand the molecular mechanism of dihydrogen activation by means of transition metal dioxides MO2 (M = Ti, Zr, and Hf) according to the following reaction: MO2 + H2 → MO + H2O. B3LYP/6-311++G(2df,2pd)/SDD methodology was employed considering two possible reaction pathways. As the first step hydrogen activation by M═O bonds yields to metal-oxo hydride intermediates O═MH(OH). This process is spontaneous for all metal dioxides, and the stability of the O═MH(OH) species depends on the transition metal center. Subsequently, the reaction mechanism splits into two paths: the first one takes place passing through the M(OH)2 intermediates yielding to products, whereas the second one corresponds to direct formation of the product complex OM(H2O). A two-state reactivity mechanism was found for the TiO2 system, whereas for ZrO2 and HfO2 no spin-crossing processes were observed. This is confirmed by CASSCF/CASPT2 calculations for ZrO2 that lead to the correct ordering of electronic states not found by DFT. The results obtained in the present paper for MO2 molecules are consistent with the observed reactivity on surfaces. PMID:23706045

  14. Hydrogen environment embrittlement of metals

    Science.gov (United States)

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

    1973-01-01

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

  15. Effect of Polar Environments on the Aluminum Oxide Shell Surrounding Aluminum Particles: Simulations of Surface Hydroxyl Bonding and Charge.

    Science.gov (United States)

    Padhye, Richa; Aquino, Adelia J A; Tunega, Daniel; Pantoya, Michelle L

    2016-06-01

    Density functional theory (DFT) calculations were performed to understand molecular variations on an alumina surface due to exposure to a polar environment. The analysis has strong implications for the reactivity of aluminum (Al) particles passivated by an alumina shell. Recent studies have shown a link between the carrier fluid used for Al powder intermixing and the reactivity of Al with fluorine containing reactive mixtures. Specifically, flame speeds show a threefold increase when polar liquids are used to intermix aluminum and fluoropolymer powder mixtures. It was hypothesized that the alumina lattice structure could be transformed due to hydrogen bonding forces exerted by the environment that induce modified bond distances and charges and influence reactivity. In this study, the alumina surface was analyzed using DFT calculations and model clusters as isolated systems embedded in polar environments (acetone and water). The conductor-like screening model (COSMO) was used to mimic environmental effects on the alumina surface. Five defect models for specific active -OH sites were investigated in terms of structures and vibrational -OH stretching frequencies. The observed changes of the surface OH sites invoked by the polar environment were compared to the bare surface. The calculations revealed a strong connection between the impact of carrier fluid polarity on the hydrogen bonding forces between the surface OH sites and surrounding species. Changes were observed in the OH characteristic properties such as OH distances (increase), atomic charges (increase), and OH stretching frequencies (decrease); these consequently improve OH surface reactivity. The difference between medium (acetone) and strong (water) polar environments was minimal in the COSMO approximation. PMID:27175545

  16. The Aluminum Smelting Process

    OpenAIRE

    Kvande, Halvor

    2014-01-01

    This introduction to the industrial primary aluminum production process presents a short description of the electrolytic reduction technology, the history of aluminum, and the importance of this metal and its production process to modern society. Aluminum's special qualities have enabled advances in technologies coupled with energy and cost savings. Aircraft capabilities have been greatly enhanced, and increases in size and capacity are made possible by advances in aluminum technology. The me...

  17. Purification technology of molten aluminum

    Institute of Scientific and Technical Information of China (English)

    孙宝德; 丁文江; 疏达; 周尧和

    2004-01-01

    Various purification methods were explored to eliminate the dissolved hydrogen and nonmetallic inclusions from molten aluminum alloys. A novel rotating impeller head with self-oscillation nozzles or an electromagnetic valve in the gas circuit was used to produce pulse gas currents for the rotary impeller degassing method. Water simulation results show that the size of gas bubbles can be decreased by 10%-20% as compared with the constant gas current mode. By coating ceramic filters or particles with active flux or enamels, composite filters were used to filter the scrap A356 alloy and pure aluminum. Experimental results demonstrate that better filtration efficiency and operation performance can be obtained. Based on numerical calculations, the separation efficiency of inclusions by high frequency magnetic field can be significantly improved by using a hollow cylinder-like separator or utilizing the effects of secondary flow of the melt in a square separator. A multi-stage and multi-media purification platform based on these methods was designed and applied in on-line processing of molten aluminum alloys. Mechanical properties of the processed scrap A356 alloy are greatly improved by the composite purification.

  18. Dynamics and fragmentation of van der Waals and hydrogen bonded cluster cations: (NH3)n and (NH3BH3)n ionized at 10.51 eV

    Science.gov (United States)

    Yuan, Bing; Shin, Joong-Won; Bernstein, Elliot R.

    2016-04-01

    description of the valence electron distribution for the various clusters and monomers. Comparison of the present results with those found for solid NH3BH3 suggests that NH3BH3 can be a good hydrogen storage material.

  19. Dynamics and fragmentation of van der Waals and hydrogen bonded cluster cations: (NH3)n and (NH3BH3)n ionized at 10.51 eV.

    Science.gov (United States)

    Yuan, Bing; Shin, Joong-Won; Bernstein, Elliot R

    2016-04-14

    natural bond orbital description of the valence electron distribution for the various clusters and monomers. Comparison of the present results with those found for solid NH3BH3 suggests that NH3BH3 can be a good hydrogen storage material. PMID:27083729

  20. Graphene-aluminum nanocomposites

    International Nuclear Information System (INIS)

    Highlights: → We investigated the mechanical properties of aluminum and aluminum nanocomposites. → Graphene composite had lower strength and hardness compared to nanotube reinforcement. → Processing causes aluminum carbide formation at graphene defects. → The carbides in between grains is a source of weakness and lowers tensile strength. - Abstract: Composites of graphene platelets and powdered aluminum were made using ball milling, hot isostatic pressing and extrusion. The mechanical properties and microstructure were studied using hardness and tensile tests, as well as electron microscopy, X-ray diffraction and differential scanning calorimetry. Compared to the pure aluminum and multi-walled carbon nanotube composites, the graphene-aluminum composite showed decreased strength and hardness. This is explained in the context of enhanced aluminum carbide formation with the graphene filler.

  1. Graphene-aluminum nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Bartolucci, Stephen F., E-mail: stephen.bartolucci@us.army.mil [U.S. Army Benet Laboratories, Armaments Research Development and Engineering Center, Watervliet, NY 12189-4000 (United States); Paras, Joseph [U.S. Army Benet Laboratories, Armaments Research Development and Engineering Center, Watervliet, NY 12189-4000 (United States); Rafiee, Mohammad A. [Department of Mechanical Engineering and Materials Science, Rice University, Houston, TX 77005 (United States); Rafiee, Javad [Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Lee, Sabrina; Kapoor, Deepak [U.S. Army Benet Laboratories, Armaments Research Development and Engineering Center, Watervliet, NY 12189-4000 (United States); Koratkar, Nikhil, E-mail: koratn@rpi.edu [Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

    2011-10-15

    Highlights: {yields} We investigated the mechanical properties of aluminum and aluminum nanocomposites. {yields} Graphene composite had lower strength and hardness compared to nanotube reinforcement. {yields} Processing causes aluminum carbide formation at graphene defects. {yields} The carbides in between grains is a source of weakness and lowers tensile strength. - Abstract: Composites of graphene platelets and powdered aluminum were made using ball milling, hot isostatic pressing and extrusion. The mechanical properties and microstructure were studied using hardness and tensile tests, as well as electron microscopy, X-ray diffraction and differential scanning calorimetry. Compared to the pure aluminum and multi-walled carbon nanotube composites, the graphene-aluminum composite showed decreased strength and hardness. This is explained in the context of enhanced aluminum carbide formation with the graphene filler.

  2. Escherichia coli FtnA Acts as an Iron Buffer for Re-assembly of Iron-Sulfur Clusters in Response to Hydrogen Peroxide Stress

    OpenAIRE

    Bitoun, Jacob P.; Wu, Genfu; Ding, Huangen

    2008-01-01

    Iron-sulfur clusters are one of the most ubiquitous redox centers in biology. Ironically, iron-sulfur clusters are highly sensitive to reactive oxygen species. Disruption of iron-sulfur clusters will not only change the activity of proteins that host iron-sulfur clusters, the iron released from the disrupted iron-sulfur clusters will further promote the production of deleterious hydroxyl free radicals via the Fenton reaction. Here, we report that ferritin A (FtnA), a major iron-storage protei...

  3. The Density Functional Study of Thiophene Adsorption on Zeolite Clusters

    Institute of Scientific and Technical Information of China (English)

    Lü Renqing; Cao Zuogang; Shen Guoping

    2007-01-01

    The density functional theory and the cluster model methods have been employed to investigate the interactions between thiophene and the HZSM-5 zeolites. The molecular complexes formed by the adsorption of thiophene on silanol H3SiOH with two coordination forms, and the model Br(o)nsted acid sites of zeolite cluster H3Si(OH)Al(OH)2SiH3 upon the interaction with thiophene have been comparatively studied.Full optimization and frequency analysis of all cluster models have been carried out using the B3LYP hybrid method at 6-31G basis level for hydrogen atoms and 6-31+G(d) basis set level for silicon, aluminum, oxygen,carbon, and sulfur atoms. The calculated results showed that the nature of interactions leading to the formation of the zeolite cluster-thiophene and silanol-thiophene complexes was associated with the van der Waals force confirmed by a slight change of geometric structures and properties. Thiophene is adsorbed on bridging hydroxyl group prior to silanol OH group judging from the magnitude of adsorption heat. The cluster model calculation reproducing the experimental prediction to form the experimental adsorption spectra of thiophene in HZSM-5 zeolite has illustrated the validity of the proposed adsorption models.

  4. Aluminum powder metallurgy processing

    Energy Technology Data Exchange (ETDEWEB)

    Flumerfelt, J.F.

    1999-02-12

    The objective of this dissertation is to explore the hypothesis that there is a strong linkage between gas atomization processing conditions, as-atomized aluminum powder characteristics, and the consolidation methodology required to make components from aluminum powder. The hypothesis was tested with pure aluminum powders produced by commercial air atomization, commercial inert gas atomization, and gas atomization reaction synthesis (GARS). A comparison of the GARS aluminum powders with the commercial aluminum powders showed the former to exhibit superior powder characteristics. The powders were compared in terms of size and shape, bulk chemistry, surface oxide chemistry and structure, and oxide film thickness. Minimum explosive concentration measurements assessed the dependence of explosibility hazard on surface area, oxide film thickness, and gas atomization processing conditions. The GARS aluminum powders were exposed to different relative humidity levels, demonstrating the effect of atmospheric conditions on post-atomization processing conditions. The GARS aluminum powders were exposed to different relative humidity levels, demonstrating the effect of atmospheric conditions on post-atomization oxidation of aluminum powder. An Al-Ti-Y GARS alloy exposed in ambient air at different temperatures revealed the effect of reactive alloy elements on post-atomization powder oxidation. The pure aluminum powders were consolidated by two different routes, a conventional consolidation process for fabricating aerospace components with aluminum powder and a proposed alternative. The consolidation procedures were compared by evaluating the consolidated microstructures and the corresponding mechanical properties. A low temperature solid state sintering experiment demonstrated that tap densified GARS aluminum powders can form sintering necks between contacting powder particles, unlike the total resistance to sintering of commercial air atomization aluminum powder.

  5. Device for hydrogen separation and method

    Science.gov (United States)

    Paglieri, Stephen N.; Anderson, Iver E.; Terpstra, Robert L.

    2009-11-03

    A device for hydrogen separation has a porous support and hydrogen separation material on the support. The support is prepared by heat treatment of metal microparticles, preferably of iron-based or nickel-based alloys that also include aluminum and/or yttrium. The hydrogen separation material is then deposited on the support. Preferred hydrogen separation materials include metals such as palladium, alloys, platinum, refractory metals, and alloys.

  6. A comparative study between all-electron scalar relativistic calculation and all-electron calculation on the adsorption of hydrogen molecule onto small gold clusters

    Indian Academy of Sciences (India)

    Xiang-Jun Kuang; Xin-Qiang Wang; Gao-Bin Liu

    2013-03-01

    A comparative study between all-electron relativistic (AER) calculation and all-electron (AE) calculation on the H2 molecule adsorption onto small gold clusters has been performed. Compared with the corresponding AuH2 cluster obtained by AE method, the AuH2 cluster obtained by AER method has much shorter Au-H bond-length, much longer H-H distance, larger binding energy and adsorption energy, higher vertical ionization potentials (VIP), greater charge transfer, higher vibrational frequency of Au-H mode and lower vibrational frequency of H-H mode. The delocalization of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) for AuH2 cluster obtained by AER method is obvious. All these characteristics suggest that the scalar relativistic effect might strengthen the Au-H bond and weaken the H-H bond. It is believed that the scalar relativistic effect is favourable to the H2 molecule adsorption onto small gold cluster and the reactivity enhancement of H2 molecule. It may be one of the reasons why the dissociative adsorptions take place in some AuH2 clusters. With increasing size of AuH2 clusters, the influence of scalar relativistic effect becomes more significant. Some further studies focused on the influence of scalar relativistic effect on the adsorption behaviour of other small molecules onto gold clusters are necessary in the future.

  7. Investigation of the NH-π hydrogen bond interaction in the aniline-alkene (C2H4,C3H6,C4H8) cluster cations by infrared depletion spectroscopy

    International Nuclear Information System (INIS)

    The vibrational spectra of the NH stretching vibrations of aniline-alkene cluster cations have been measured using infrared depletion method. Aniline-ethene cation showed three strong absorption bands at 3448, 3314 and 3220 cm-1. The comparison with MO calculation has shown that the main intermolecular interaction is the NH-π type hydrogen bond between one of the NH bonds of aniline cation and π-electron of ethene, which is different from that observed for the neutral aniline-ethene cluster. The bands at 3448 and 3220 cm-1 have been assigned to the stretching vibrations of free NH and bonded NH, respectively, and the band at 3314 cm-1 to the binary overtone of the NH2 deformation vibration. Similar results have been obtained for aniline-propene and aniline-butene cluster cations. The red shift of the stretching vibration of free NH bond of aniline cation agreed with that expected from the correlation with the proton affinity of the acceptor molecule obtained for the aniline-aromatic cluster cations (NH-π type)

  8. The corrosion of aluminum in dilute solutions: laboratory studies

    Energy Technology Data Exchange (ETDEWEB)

    Draley, J.E.; Arendt, J.W.; English, G.C.; Story, E.F.; Wainscott, M.M.; Berger, R.W.

    1945-06-19

    After it had been decided that aluminum was to be used as a corrosion-resistant material with good heat transfer properties, it was desired to determine the operating conditions to be used in the water-cooled Handford plant in order to avoid danger of corrosion penetration of thin aluminum parts. The studies here reported were undertaken with the object of determining these conditions by investigating the effects of all the known variables which might influence the corrosion behavior of aluminum in a water-coolded plant at HEW. The addition of hydrogen peroxide to the testing solutions was the only effort made to simulate special conditions at the plant.

  9. Is the Aluminum Hypothesis Dead?

    OpenAIRE

    Lidsky, Theodore I.

    2014-01-01

    The Aluminum Hypothesis, the idea that aluminum exposure is involved in the etiology of Alzheimer disease, dates back to a 1965 demonstration that aluminum causes neurofibrillary tangles in the brains of rabbits. Initially the focus of intensive research, the Aluminum Hypothesis has gradually been abandoned by most researchers. Yet, despite this current indifference, the Aluminum Hypothesis continues to attract the attention of a small group of scientists and aluminum continues to be viewed w...

  10. Synthesis of Aluminum-Aluminum Nitride Nanocomposites by a Gas-Liquid Reaction II. Microstructure and Mechanical Properties

    Science.gov (United States)

    Borgonovo, Cecilia; Makhlouf, Makhlouf M.

    2016-04-01

    In situ fabrication of the reinforcing particles in the metal matrix is an answer to many of the challenges encountered in manufacturing aluminum matrix nanocomposites. In this method, the nanoparticles are formed directly within the melt by means of a chemical reaction between a specially designed aluminum alloy and a gas. In this publication, we describe a process for synthesizing aluminum-aluminum nitride nanocomposites by reacting a nitrogen-containing gas with a molten aluminum-lithium alloy. We quantify the effect of the process parameters on the average particle size and particle distribution, as well as on the tendency of the particles to cluster in the alloy matrix, is quantified. Also in this publication, we present the measured room temperature and elevated temperature tensile properties of the nanocomposite material as well as its measured room temperature impact toughness.

  11. New Process for Grain Refinement of Aluminum. Final Report; FINAL

    International Nuclear Information System (INIS)

    A new method of grain refining aluminum involving in-situ formation of boride nuclei in molten aluminum just prior to casting has been developed in the subject DOE program over the last thirty months by a team consisting of JDC, Inc., Alcoa Technical Center, GRAS, Inc., Touchstone Labs, and GKS Engineering Services. The Manufacturing process to make boron trichloride for grain refining is much simpler than preparing conventional grain refiners, with attendant environmental, capital, and energy savings. The manufacture of boride grain refining nuclei using the fy-Gem process avoids clusters, salt and oxide inclusions that cause quality problems in aluminum today

  12. New Process for Grain Refinement of Aluminum. Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Joseph A. Megy

    2000-09-22

    A new method of grain refining aluminum involving in-situ formation of boride nuclei in molten aluminum just prior to casting has been developed in the subject DOE program over the last thirty months by a team consisting of JDC, Inc., Alcoa Technical Center, GRAS, Inc., Touchstone Labs, and GKS Engineering Services. The Manufacturing process to make boron trichloride for grain refining is much simpler than preparing conventional grain refiners, with attendant environmental, capital, and energy savings. The manufacture of boride grain refining nuclei using the fy-Gem process avoids clusters, salt and oxide inclusions that cause quality problems in aluminum today.

  13. Nanostructures from hydrogen implantation of metals.

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-09-01

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

  14. Anodizing Aluminum with Frills.

    Science.gov (United States)

    Doeltz, Anne E.; And Others

    1983-01-01

    "Anodizing Aluminum" (previously reported in this journal) describes a vivid/relevant laboratory experience for general chemistry students explaining the anodizing of aluminum in sulfuric acid and constrasting it to electroplating. Additions to this procedure and the experiment in which they are used are discussed. Reactions involved are also…

  15. Initiating, growing and cracking of hydrogen blisters

    Institute of Scientific and Technical Information of China (English)

    REN Xuechong; SHAN Guangbin; CHU Wuyang; SU Yanjing; GAO Kewei; QIAO Lijie; JIANG Bo; CHEN Gang; CUI Yinhui

    2005-01-01

    The growing process of a hydrogen blister in a wheel steel was observed in situ with an optical microscope, and the fracture surfaces formed from broken blisters on a wheel steel and bulk metallic glass were investigated. The initiating, growing, cracking and breaking of hydrogen blisters are as follows. Supersaturated vacancies can increase greatly during charging and gather together into a vacancy cluster (small cavity). Hydrogen atoms become hydrogen molecules in the vacancy cluster and hydrogen molecules can stabilize the vacancy cluster. The small cavity becomes the nucleus of hydrogen blister. The blister will grow with entering of vacancies and hydrogen atoms. With increasing hydrogen pressure, plastic deformation occurs first, the hydrogen blister near the surface extrudes, and then cracks initiate along the wall of the blister with further increasing hydrogen pressure. A cracked blister can grow further through propagating of cracks until it breaks.

  16. The aluminum smelting process.

    Science.gov (United States)

    Kvande, Halvor

    2014-05-01

    This introduction to the industrial primary aluminum production process presents a short description of the electrolytic reduction technology, the history of aluminum, and the importance of this metal and its production process to modern society. Aluminum's special qualities have enabled advances in technologies coupled with energy and cost savings. Aircraft capabilities have been greatly enhanced, and increases in size and capacity are made possible by advances in aluminum technology. The metal's flexibility for shaping and extruding has led to architectural advances in energy-saving building construction. The high strength-to-weight ratio has meant a substantial reduction in energy consumption for trucks and other vehicles. The aluminum industry is therefore a pivotal one for ecological sustainability and strategic for technological development. PMID:24806722

  17. Apparatus For Tests Of Embrittlement By Hydrogen

    Science.gov (United States)

    Christianson, Rollin C.; Lycou, Peter P.

    1992-01-01

    Test apparatus exposes disk specimens to hydrogen in controlled, repeatable way simulating conditions in use. Disk specimen constitutes thin wall between pressure and vacuum chambers. Test proceeds until hydrogen weakens disk enough that it ruptures. Aluminum impact plate absorbs debris from ruptured disk. Apparatus replicates aspects of service environments relevant to embrittlement by hydrogen in such equipment as storage tanks, valves, and fluid-handling components containing hydrogen at high absolute or gauge pressure. Hydrogen inside permeates stressed material and produces gradient of concentration as hydrogen diffuses through material to low-pressure side.

  18. Burning characteristics of individual aluminum/aluminum oxide particles

    OpenAIRE

    Ruttenberg, Eric C.

    1996-01-01

    Approved for public release; distribution is unlimited An experimental investigation was conducted in which the burning characteristics of individual aluminum/aluminum oxide particles were measured using a windowed combustion bomb at atmospheric pressure and under gravity-fall conditions. A scanning electron microscope (SEM) was used to measure the size distribution of the initial aluminum particles and the aluminum oxide residue. Analysis of the residue indicated that the mass of aluminum...

  19. Purifying Aluminum by Vacuum Distillation

    Science.gov (United States)

    Du Fresne, E. R.

    1985-01-01

    Proposed method for purifying aluminum employs one-step vacuum distillation. Raw material for process impure aluminum produced in electrolysis of aluminum ore. Impure metal melted in vacuum. Since aluminum has much higher vapor pressure than other constituents, boils off and condenses on nearby cold surfaces in proportions much greater than those of other constituents.

  20. Modeling of hydrogen desorption from tungsten surface

    International Nuclear Information System (INIS)

    Hydrogen retention in metallic plasma-facing components is among key-issues for future fusion devices. For tungsten, which has been chosen as divertor material in ITER, hydrogen desorption parameters experimentally measured for fusion-related conditions show large discrepancies. In this paper, we therefore investigate hydrogen recombination and desorption on tungsten surfaces using molecular dynamics simulations and accelerated molecular dynamics simulations to analyze adsorption states, diffusion, hydrogen recombination into molecules, and clustering of hydrogen on tungsten surfaces. The quality of tungsten hydrogen interatomic potential is discussed in the light of MD simulations results, showing that three body interactions in current interatomic potential do not allow to reproduce hydrogen molecular recombination and desorption. Effects of surface hydrogen clustering on hydrogen desorption are analyzed by introducing a kinetic model describing the competition between surface diffusion, clustering and recombination. Different desorption regimes are identified and reproduce some aspects of desorption regimes experimentally observed

  1. Modeling of hydrogen desorption from tungsten surface

    Energy Technology Data Exchange (ETDEWEB)

    Guterl, J., E-mail: jguterl@ucsd.edu [University of California, San Diego, La Jolla, CA 92093 (United States); Smirnov, R.D. [University of California, San Diego, La Jolla, CA 92093 (United States); Krasheninnikov, S.I. [University of California, San Diego, La Jolla, CA 92093 (United States); Nuclear Research National University MEPhI, Moscow 115409 (Russian Federation); Uberuaga, B.; Voter, A.F.; Perez, D. [Los Alamos National Laboratory, Los Alamos, NM 8754 (United States)

    2015-08-15

    Hydrogen retention in metallic plasma-facing components is among key-issues for future fusion devices. For tungsten, which has been chosen as divertor material in ITER, hydrogen desorption parameters experimentally measured for fusion-related conditions show large discrepancies. In this paper, we therefore investigate hydrogen recombination and desorption on tungsten surfaces using molecular dynamics simulations and accelerated molecular dynamics simulations to analyze adsorption states, diffusion, hydrogen recombination into molecules, and clustering of hydrogen on tungsten surfaces. The quality of tungsten hydrogen interatomic potential is discussed in the light of MD simulations results, showing that three body interactions in current interatomic potential do not allow to reproduce hydrogen molecular recombination and desorption. Effects of surface hydrogen clustering on hydrogen desorption are analyzed by introducing a kinetic model describing the competition between surface diffusion, clustering and recombination. Different desorption regimes are identified and reproduce some aspects of desorption regimes experimentally observed.

  2. Dimeric [Mo₂S₁₂]²⁻ Cluster: A Molecular Analogue of MoS₂ Edges for Superior Hydrogen-Evolution Electrocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Zhongjie; Luo, Wenjia; Ma, Lu; Yu, Mingzhe; Ren, Xiaodi; He, Mingfu; Polen, Shan; Click, Kevin; Garrett, Benjamin R.; Lu, Jun; Amine, Khalil

    2015-12-07

    Proton reduction is one of the most fundamental and important reactions in nature. MoS2 edges have been identified as the active sites for hydrogen evolution reaction (HER) electrocatalysis. Designing molecular mimics of MoS2 edge sites is an attractive strategy to understand the underlying catalytic mechanism of different edge sites and improve their activities. Herein we report a dimeric molecular analogue [Mo₂S₁₂]²⁻, as the smallest unit possessing both the terminal and bridging disulfide ligands. Our electrochemical tests show that [Mo₂S₁₂]²⁻ is a superior heterogeneous HER catalyst under acidic conditions. Computations suggest that the bridging disulfide ligand of [Mo₂S₁₂]²⁻ exhibits a hydrogen adsorption free energy near zero (-0.05eV). This work helps shed light on the rational design of HER catalysts and biomimetics of hydrogen-evolving enzymes.

  3. Dimeric [Mo2 S12 ](2-) Cluster: A Molecular Analogue of MoS2 Edges for Superior Hydrogen-Evolution Electrocatalysis.

    Science.gov (United States)

    Huang, Zhongjie; Luo, Wenjia; Ma, Lu; Yu, Mingzhe; Ren, Xiaodi; He, Mingfu; Polen, Shane; Click, Kevin; Garrett, Benjamin; Lu, Jun; Amine, Khalil; Hadad, Christopher; Chen, Weilin; Asthagiri, Aravind; Wu, Yiying

    2015-12-01

    Proton reduction is one of the most fundamental and important reactions in nature. MoS2 edges have been identified as the active sites for hydrogen evolution reaction (HER) electrocatalysis. Designing molecular mimics of MoS2 edge sites is an attractive strategy to understand the underlying catalytic mechanism of different edge sites and improve their activities. Herein we report a dimeric molecular analogue [Mo2 S12 ](2-) , as the smallest unit possessing both the terminal and bridging disulfide ligands. Our electrochemical tests show that [Mo2 S12 ](2-) is a superior heterogeneous HER catalyst under acidic conditions. Computations suggest that the bridging disulfide ligand of [Mo2 S12 ](2-) exhibits a hydrogen adsorption free energy near zero (-0.05 eV). This work helps shed light on the rational design of HER catalysts and biomimetics of hydrogen-evolving enzymes. PMID:26482571

  4. Implications of hydrogen/halogen-bond in the stabilization of confined water and anion-water clusters by a cationic receptor

    Science.gov (United States)

    Hoque, Md. Najbul; Das, Gopal

    2016-03-01

    Anion complexation of benzene capped flexible tripodal receptor and solid state stabilization of discrete hybrid anion-water or infinite water clusters by various supramolecular interactions are reported here. The crystal structure of the receptor in protonated states shows all the three arms projected in one direction. We structurally demonstrate discrete fluoride-water cluster [F2-H2O]2- and square shaped chloride-water cluster [Cl2-(H2O)2]2- inside the cationic channel of the receptor. Structural analysis also reveals that these clusters are stabilized inside the channel through active participation of N/C/Ow‧H⋯Ow, N/C/Ow‧H⋯X- (X- = F-, Cl- and I-) H-bonds and electrostatic interactions. Moreover, C-H⋯π and π⋯π types weak intermolecular interactions appear to play crucial role in supramolecular assembly of receptor. Additionally, on treatment with hydroiodic acid (HI) L resulted zwitterionic iodide complex. Crystal structure reveals the presence of S···I halogen bonded dimer, I2···I halogen bond, 1D infinite water chain and neutral iodine molecules. It is comprehensible that ligand basal structure (benzene capped and N-bridge head in two tripodal) play crucial roles in the formation of diverse halide-water cluster. All structures were well examined by different techniques such as NMR, IR, TGA, DSC, PXRD and XRD.

  5. Corrosion Inhibitors for Aluminum.

    Science.gov (United States)

    Muller, Bodo

    1995-01-01

    Describes a simple and reliable test method used to investigate the corrosion-inhibiting effects of various chelating agents on aluminum pigments in aqueous alkaline media. The experiments that are presented require no complicated or expensive electronic equipment. (DDR)

  6. Advances in aluminum anodizing

    Science.gov (United States)

    Dale, K. H.

    1969-01-01

    White anodize is applied to aluminum alloy surfaces by specific surface preparation, anodizing, pigmentation, and sealing techniques. The development techniques resulted in alloys, which are used in space vehicles, with good reflectance values and excellent corrosive resistance.

  7. The mechanism of nucleation of hydrogen blister in metals

    Institute of Scientific and Technical Information of China (English)

    REN XueChong; ZHOU QingJun; CHU WuYang; LI JinXu; SU YanJing; QIAO LiJie

    2007-01-01

    The nucleating, growing and cracking of hydrogen blister have been investigated experimentally and theoretically. The results show that atomic hydrogen induces superabundant vacancies in metals. The superabundant vacancies and hydrogen aggregate into a hydrogen-vacancy cluster (microcavity). The hydrogen atoms in the microcavity become hydrogen molecules which can stabilize the cluster. And the hydrogen blister nucleates. With the entry of vacancies and hydrogen atoms, the blister nucleus grows and the pressure in the cavity increases. When the stress induced by hydrogen pressure on the blister is up to the cohesive strength, cracks will initiate from the wall of the blister.

  8. Is It Homogeneous or Heterogeneous Catalysis Derived from [RhCp*Cl2]2? In Operando-XAFS, Kinetic and Crucial Kinetic Poisoning Evidence for Subnanometer Rh4 Cluster-Based Benzene Hydrogenation Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Bayram, Ercan; Linehan, John C.; Fulton, John L.; Roberts, John A.; Szymczak, Nathaniel; Smurthwaite, Tricia D.; Ozkar, Saim; Balasubramanian, Mahalingam; Finke, Richard G.

    2011-11-23

    Determining the true, kinetically dominant catalytically active species, in the classic benzene hydrogenation system pioneered by Maitlis and co-workers 34 years ago starting with [RhCp*Cl2]2 (Cp* = [{eta}5-C5(CH3)5]), has proven to be one of the most challenging case studies in the quest to distinguish single-metal-based 'homogeneous' from polymetallic, 'heterogeneous' catalysis. The reason, this study will show, is the previous failure to use the proper combination of (i) operando spectroscopy to determine the dominant form(s) of the precatalyst's mass under catalysis (i.e., operating) conditions, plus then and crucially also (ii) the previous lack of the necessary kinetic studies, catalysis being a 'wholly kinetic phenomenon' as J. Halpern long ago noted. An important contribution from this study will be to reveal the power of quantitiative kinetic poisoning experiments for distinguishing single-metal, or in this case subnanometer Rh4 cluster-based catalysis from larger, polymetallic Rh(0)n nanoparticle catalysis, at least under favorable conditions. The combined operando-XAFS (X-ray absorption fine structure) spectroscopy and kinetic evidences provide a compelling case for Rh4-based, with average stoichiometry 'Rh4Cp*2.4Cl4Hc', benzene hydrogenation catalysis in 2-propanol with added Et3N and at 100 C and 50 atm initial H2 pressure. The results also reveal, however, that if even ca. 1.4% of the total soluble Rh(0)n had formed nanoparticles, then those Rh(0)n nanoparticles would have been able to account for all the observed benzene hydrogenation catalytic rate (using commercial, ca. 2 nm, polyethyleneglycol-dodecylether hydrosol stabilized Rh(0)n nanoparticles as a model system). The results 'especially the poisoning methodology developed and employed' are of significant, broader interest since determining the nature of the true catalyst continues to be a central, often vexing issue in any and all catalytic

  9. Defect recovery in aluminum irradiated with protons at 20 K

    DEFF Research Database (Denmark)

    Linderoth, S.; Rajainmäki, H.; Nieminen, R. M.

    1987-01-01

    Aluminum single crystals have been irradiated with 7.0-MeV protons at 20 K. The irradiation damage and its recovery are studied with positron-lifetime spectroscopy between 20 and 500 K. Stage-I recovery is observed at 40 K. At 240 K, loss of freely migrating vacancies is observed. Hydrogen in...

  10. Size- and shape-controlled synthesis and catalytic performance of iron–aluminum mixed oxide nanoparticles for NO{sub X} and SO{sub 2} removal with hydrogen peroxide

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Jie [School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing, Jiangsu 210094 (China); Nanjing AIREP Environmental Protection Technology Co., Ltd., Nanjing, Jiangsu 210091 (China); Zhong, Qin, E-mail: zq304@mail.njust.edu.cn [School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing, Jiangsu 210094 (China); Nanjing AIREP Environmental Protection Technology Co., Ltd., Nanjing, Jiangsu 210091 (China); Zhang, Shule; Cai, Wei [School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing, Jiangsu 210094 (China); Nanjing AIREP Environmental Protection Technology Co., Ltd., Nanjing, Jiangsu 210091 (China)

    2015-02-11

    Graphical abstract: - Highlights: • The size- and shape-controllable synthesis of NIAO(x/y) is introduced. • The catalytic decomposition of H{sub 2}O{sub 2} on NIAO(x/y) is utilized for NO{sub X} and SO{sub 2} removal. • NIAO(7/3) shows highest NO{sub X} (80%) and SO{sub 2} (100%) removal. • The aluminum dramatically improves the structure and surface properties of catalysts. • The catalytic mechanism and well stability is investigated. - Abstract: A novel, simple, reproducible and low-cost strategy is introduced for the size- and shape-controlled synthesis of iron–aluminum mixed oxide nanoparticles (NIAO(x/y)). The as-synthesized NIAO(x/y) catalyze decomposition of H{sub 2}O{sub 2} yielding highly reactive hydroxyl radicals (·OH) for NO{sub X} and SO{sub 2} removal. 100% SO{sub 2} removal is achieved. NIAO(x/y) with Fe/Al molar ratio of 7/3 (NIAO(7/3)) shows the highest NO{sub X} removal of nearly 80% at >170 °C, whereas much lower NO{sub X} removal (<63%) is obtained for NIAO(3/7). The melting of aluminum oxides in NIAO(7/3) promotes the formation of lamellar products, thus improving the specific surface areas and mesoporous distribution, benefiting the production of ·OH radicals. Furthermore, the NIAO(7/3) leads to the minor increase of points of zero charges (PZC), apparent enhancement of FeOH content and high oxidizing ability of Fe(III), further improving the production of ·OH radicals. However, the NIAO(3/7) results in the formation of aluminum surface-enriched spherical particles, thus decreasing the surface atomic ratio of iron oxides, decreasing ·OH radical production. More importantly, the generation of FeOAl causes the decline of active sites. Finally, the catalytic decomposition of H{sub 2}O{sub 2} on NIAO(x/y) is proposed. And the well catalytic stability of NIAO(7/3) is obtained for evaluation of 30 h.

  11. Hydrogen energy

    International Nuclear Information System (INIS)

    This book consists of seven chapters, which deals with hydrogen energy with discover and using of hydrogen, Korean plan for hydrogen economy and background, manufacturing technique on hydrogen like classification and hydrogen manufacture by water splitting, hydrogen storage technique with need and method, hydrogen using technique like fuel cell, hydrogen engine, international trend on involving hydrogen economy, technical current for infrastructure such as hydrogen station and price, regulation, standard, prospect and education for hydrogen safety and system. It has an appendix on related organization with hydrogen and fuel cell.

  12. Characterization of aluminum nanopowders after long-term storage

    International Nuclear Information System (INIS)

    Highlights: • The aluminum nanopowders produced by electrical explosion of wires after long-term storage (27 and 10 years) under natural conditions are characterized. • The phase composition and thermal stability of aluminum nanopowders after long-term storage are determined. • The surface chemical changes in the aged aluminum nanopowders are examined. • The high reactivity of aluminum nanopowder is due to the presence of the protective oxide–hydroxide layer on the particles surface. - Abstract: The characteristics of aluminum nanopowders obtained by electrical explosion of wires, passivated by air and stored for a long time under natural conditions are analyzed. The aluminum nanopowder produced in hydrogen had been stored for 27 years; the nanopowders produced in argon and nitrogen had been stored for 10 years. The powders were studied using X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetry (TG) and Fourier transform infrared spectrometry (FTIR). The influence of the obtaining conditions and storage period of nanopowders on their thermal stability under heating in air is shown. The aluminum nanopowders after long-term storage in air under ambient conditions are found to be extremely active

  13. Fabrication of aluminum foam from aluminum scrap Hamza

    OpenAIRE

    O. A. Osman1 ,; Mining and Petroleum Engineering, Faculty of Engineering- Qena, Al_Azhar University, Egypt

    2015-01-01

    In this study the optimum parameters affecting the preparation of aluminum foam from recycled aluminum were studied, these parameters are: temperature, CaCO3 to aluminum scrap wt. ratio as foaming agent, Al2O3 to aluminum scrap wt. ratio as thickening agent, and stirring time. The results show that, the optimum parameters are the temperature ranged from 800 to 850oC, CaCO3 to aluminum scrap wt. ratio was 5%, Al2O3 to aluminum scrap wt. ratio was 3% and stirring time was 45 second ...

  14. Vanadium alloy membranes for high hydrogen permeability and suppressed hydrogen embrittlement

    International Nuclear Information System (INIS)

    The structural properties and hydrogen permeation characteristics of ternary vanadium–iron–aluminum (V–Fe–Al) alloy were investigated. To achieve not only high hydrogen permeability but also strong resistance to hydrogen embrittlement, the alloy composition was modulated to show high hydrogen diffusivity but reduced hydrogen solubility. We demonstrated that matching the lattice constant to the value of pure V by co-alloying lattice-contracting and lattice-expanding elements was quite effective in maintaining high hydrogen diffusivity of pure V

  15. Electron attachment to HCl clusters

    International Nuclear Information System (INIS)

    Negatively charged cluster ions of hydrogen chloride are formed by electron attachment to HCl clusters, which are produced in a seeded supersonic beam traversing a sustained gas discharge. Cluster ions of (HCl)n-, with n = 2, and tentatively with n = 3 and 4 are observed. Cluster ions like Cln-, Cln- (HCl)m, and with Ar attached to them are also seen. The relevance to radiation chemistry of HCl is briefly discussed. Atoms evaporating from the hot, thoriated tungsten filament of the glow discharge lead to clusters such as Thn- and its oxides. (orig.)

  16. Selection of a mineral binder with potentialities for the stabilization/solidification of aluminum metal

    Energy Technology Data Exchange (ETDEWEB)

    Cau Dit Coumes, C., E-mail: celine.cau-dit-coumes@cea.fr [Commissariat à l’Energie Atomique et aux Energies Alternatives, CEA/DEN/MAR/DTCD/SPDE, BP17171, 30207 Bagnols-sur-Cèze cedex (France); Lambertin, D.; Lahalle, H.; Antonucci, P. [Commissariat à l’Energie Atomique et aux Energies Alternatives, CEA/DEN/MAR/DTCD/SPDE, BP17171, 30207 Bagnols-sur-Cèze cedex (France); Cannes, C.; Delpech, S. [Institut de Physique Nucléaire, CNRS, Univ. Paris-Sud 11, 91406 Orsay Cedex (France)

    2014-10-15

    Highlights: • Binders capable of reducing the pore solution pH compared with Portland cements are reviewed. • The binders are then tested against aluminum corrosion. • Corrosion of aluminum metal is minimal with magnesium phosphate cement. • The H{sub 2} release can be reduced still further by adding LiNO{sub 3} to the mixing solution. • Electrochemical characterizations show that aluminum tends to a passive state. - Abstract: In a strongly alkaline medium, such as that encountered in conventional cementitious materials based on Portland cement, aluminum metal is corroded, with continued production of hydrogen. In order to develop a mineral matrix having enhanced compatibility with aluminum, a literature review was first undertaken to identify binders capable of reducing the pore solution pH compared with Portland cement. An experimental study was then carried out to measure the hydrogen production resulting from corrosion of aluminum metal rods encapsulated in the different selected cement pastes. The best results were achieved with magnesium phosphate cement, which released very little hydrogen over the duration of the study. This production could be reduced still further by adding a corrosion inhibitor (lithium nitrate) to the mixing solution. Open circuit potential measurement and Electrochemical Impedance Spectroscopy of aluminum electrode encapsulated in two pastes based on Portland cement and magnesium phosphate cement showed different redox behaviors. In the Portland cement paste, the electrochemical data confirmed the corrosion of aluminum whereas this latter tended to a passive state in the magnesium phosphate binder.

  17. Selection of a mineral binder with potentialities for the stabilization/solidification of aluminum metal

    International Nuclear Information System (INIS)

    Highlights: • Binders capable of reducing the pore solution pH compared with Portland cements are reviewed. • The binders are then tested against aluminum corrosion. • Corrosion of aluminum metal is minimal with magnesium phosphate cement. • The H2 release can be reduced still further by adding LiNO3 to the mixing solution. • Electrochemical characterizations show that aluminum tends to a passive state. - Abstract: In a strongly alkaline medium, such as that encountered in conventional cementitious materials based on Portland cement, aluminum metal is corroded, with continued production of hydrogen. In order to develop a mineral matrix having enhanced compatibility with aluminum, a literature review was first undertaken to identify binders capable of reducing the pore solution pH compared with Portland cement. An experimental study was then carried out to measure the hydrogen production resulting from corrosion of aluminum metal rods encapsulated in the different selected cement pastes. The best results were achieved with magnesium phosphate cement, which released very little hydrogen over the duration of the study. This production could be reduced still further by adding a corrosion inhibitor (lithium nitrate) to the mixing solution. Open circuit potential measurement and Electrochemical Impedance Spectroscopy of aluminum electrode encapsulated in two pastes based on Portland cement and magnesium phosphate cement showed different redox behaviors. In the Portland cement paste, the electrochemical data confirmed the corrosion of aluminum whereas this latter tended to a passive state in the magnesium phosphate binder

  18. Cross section measurements of the processes occurring in the fragmentation of H{sub n}{sup +} (3 {<=} n {<=} 35) hydrogen clusters induced by high speed (60 keV/u) collisions on helium atoms; Mesure des sections efficaces des differents processus intervenant dans la fragmentation d`agregats d`hydrogene H{sub n}{sup +} (3 {<=} n {<=} 35) induite par collision a haute vitesse (60 keV/u) sur un atome d`helium

    Energy Technology Data Exchange (ETDEWEB)

    Louc, Sandrine [Inst. de Physique Nucleaire, Lyon-1 Univ., 69 - Villeurbanne (France)

    1997-09-15

    Different processes involved in the fragmentation of ionised hydrogen clusters H{sub 3} + (H{sub 2}){sub (n-3)/2} (n = 5-35) have been studied in the same experiment: the fragmentation of the cluster is induced by the collision with an helium atom at high velocity ({approx_equal} c/100). The collision is realised in reversed kinematic - clusters are accelerated - which allows the detection of neutral and charged fragments. The different channels of fragmentation are identified by using coincidence techniques. For all the cluster sizes studied the capture cross sections of one electron of the target by the cluster is equal to the capture cross section of the H{sub 3}{sup +} ion. In the same way, the dissociation cross section of the H{sub 3}{sup +} core of the cluster does not depend on cluster size. These fragmentation processes are due to the interaction of H{sub 3}{sup +} core of the cluster and the helium atom without ionization of another component of the cluster. On the contrary, the cross sections of loss of one, two and three molecules by the cluster and the dissociation cross section of the cluster in all its molecular components depends strongly on the cluster size. This dependence is different from the one measured for the metastable decay of the cluster. Thus, the process of loss of molecules induced by a collision should correspond to a different dissociation mechanism. In regard of the singularities observed for the size dependence, the H{sub 9}{sup +}, H{sub 15}{sup +}, H{sub 19}{sup +} and H{sub 29}{sup +} clusters could be the `core` of the biggest clusters. These observation are in agreement with the size effects of smaller magnitude observed for the dissociation cross section (all the processes). The values of the cross section for the process of at least one ionization of the cluster indicate that about 80% of the fragmentation events result from this process. (author) 114 refs., 74 figs., 9 tabs.

  19. Internal Heterogeneous Processes in Aluminum Combustion

    Science.gov (United States)

    Dreizin, E. L.

    1999-01-01

    This paper discusses the aluminum particle combustion mechanism which has been expanded by inclusion of gas dissolution processes and ensuing internal phase transformations. This mechanism is proposed based on recent normal and microgravity experiments with particles formed and ignited in a pulsed micro-arc. Recent experimental findings on the three stages observed in Al particle combustion in air and shows the burning particle radiation, trajectory (streak), smoke cloud shapes, and quenched particle interiors are summarized. During stage I, the radiation trace is smooth and the particle flame is spherically symmetric. The temperature measured using a three-color pyrometer is close to 3000 K. Because it exceeds the aluminum boiling point (2730 K), this temperature most likely characterizes the vapor phase flame zone rather than the aluminum surface. The dissolved oxygen content within particles quenched during stage I was below the detection sensitivity (about 1 atomic %) for Wavelength Dispersive Spectroscopy (WDS). After an increase in the radiation intensity (and simultaneous decrease in the measured color temperature from about 3000 to 2800 K) indicative of the transition to stage II combustion, the internal compositions of the quenched particles change. Both oxygen-rich (approx. 10 atomic %) and oxygen-lean (aluminum particle combustion behavior and the evolution of its internal composition, the change from the spherically symmetric to asymmetric flame shape occurring upon the transition from stage I to stage II combustion could not be understood based only on the fact that dissolved oxygen is detected in the particles. The connection between the two phenomena appeared even less significant because in earlier aluminum combustion studies carried in O2/Ar mixtures, flame asymmetry was not observed as opposed to experiments in air or O2/CO mixtures. It has been proposed that the presence of other gases, i.e., hydrogen, or nitrogen causes the change in the

  20. Fabrication of aluminum foam from aluminum scrap Hamza

    Directory of Open Access Journals (Sweden)

    O. A. Osman1 ,

    2015-02-01

    Full Text Available In this study the optimum parameters affecting the preparation of aluminum foam from recycled aluminum were studied, these parameters are: temperature, CaCO3 to aluminum scrap wt. ratio as foaming agent, Al2O3 to aluminum scrap wt. ratio as thickening agent, and stirring time. The results show that, the optimum parameters are the temperature ranged from 800 to 850oC, CaCO3 to aluminum scrap wt. ratio was 5%, Al2O3 to aluminum scrap wt. ratio was 3% and stirring time was 45 second with stirring speed 1200 rpm. The produced foam apparent densities ranged from 0.40-0.60 g/cm3. The microstructure of aluminum foam was examined by using SEM, EDX and XRD, the results show that, the aluminum pores were uniformly distributed along the all matrices and the cell walls covered by thin oxide film.

  1. ALUMINUM RECLAMATION BY ACIDIC EXTRACTION OF ALUMINUM-ANODIZING SLUDGES

    Science.gov (United States)

    Extraction of aluminum-anodizing sludges with sulfuric acid was examined to determine the potential for production of commercial-strength solutions of aluminum sulfate, that is liquid alum. The research established kinetic and stoichiometric relationships and evaluates product qu...

  2. The effect of grain size on aluminum anodes for Al-air batteries in alkaline electrolytes

    Science.gov (United States)

    Fan, Liang; Lu, Huimin

    2015-06-01

    Aluminum is an ideal material for metallic fuel cells. In this research, different grain sizes of aluminum anodes are prepared by equal channel angular pressing (ECAP) at room temperature. Microstructure of the anodes is examined by electron backscatter diffraction (EBSD) in scanning electron microscope (SEM). Hydrogen corrosion rates of the Al anodes in 4 mol L-1 NaOH are determined by hydrogen collection method. The electrochemical properties of the aluminum anodes are investigated in the same electrolyte using electrochemical impedance spectroscopy (EIS) and polarization curves. Battery performance is also tested by constant current discharge at different current densities. Results confirm that the electrochemical properties of the aluminum anodes are related to grain size. Finer grain size anode restrains hydrogen evolution, improves electrochemical activity and increases anodic utilization rate. The proposed method is shown to effectively improve the performance of Al-air batteries.

  3. H-plasma-assisted aluminum induced crystallization of amorphous silicon

    Institute of Scientific and Technical Information of China (English)

    Li Juan; Liu Ning; Luo Chong; Meng Zhiguo; Xiong Shaozhen; Hoi Sing Kwok

    2012-01-01

    A technique to improve and accelerate aluminum induced crystallization (AIC) by using hydrogen plasma is proposed.Raman spectroscopy and secondary ion mass spectrometry of crystallized poly-Si thin films show that hydrogen plasma radicals reduce the crystallization time of AIC.This technique shortens the annealing time from 10 to 4 h and increases the Hall mobility from 22.1 to 42.5 cm2/(V·s).The possible mechanism of AIC assisted by hydrogen radicals is also discussed.

  4. Hydrogen production

    Science.gov (United States)

    England, C.; Chirivella, J. E.; Fujita, T.; Jeffe, R. E.; Lawson, D.; Manvi, R.

    1975-01-01

    The state of hydrogen production technology is evaluated. Specific areas discussed include: hydrogen production fossil fuels; coal gasification processes; electrolysis of water; thermochemical production of hydrogen; production of hydrogen by solar energy; and biological production of hydrogen. Supply options are considered along with costs of hydrogen production.

  5. Cluster Automorphisms

    OpenAIRE

    Assem, Ibrahim; Schiffler, Ralf; Shramchenko, Vasilisa

    2010-01-01

    In this article, we introduce the notion of cluster automorphism of a given cluster algebra as a $\\ZZ$-automorphism of the cluster algebra that sends a cluster to another and commutes with mutations. We study the group of cluster automorphisms in detail for acyclic cluster algebras and cluster algebras from surfaces, and we compute this group explicitly for the Dynkin types and the Euclidean types.

  6. Aluminum Hydroxide and Magnesium Hydroxide

    Science.gov (United States)

    Aluminum Hydroxide, Magnesium Hydroxide are antacids used together to relieve heartburn, acid indigestion, and upset stomach. They ... They combine with stomach acid and neutralize it. Aluminum Hydroxide, Magnesium Hydroxide are available without a prescription. ...

  7. Retention and release of tritium in aluminum clad, Al-Li alloys

    International Nuclear Information System (INIS)

    Tritium retention in and release from aluminum clad, aluminum-lithium alloys is modeled from experimental and operational data developed during the thirty plus years of tritium production at the Savannah River Site. The model assumes that tritium atoms, formed by the 6Li(n,α)3He reaction, are produced in solid solution in the Al-Li alloy. Because of the low solubility of hydrogen isotopes in aluminum alloys, the irradiated Al-Li rapidly becomes supersaturated in tritium. Newly produced tritium atoms are trapped by lithium atoms to form a lithium tritide. The effective tritium pressure required for trap or tritide stability is the equilibrium decomposition pressure of tritium over a lithium tritide-aluminum mixture. The temperature dependence of tritium release is determined by the permeability of the cladding to tritium and the local equilibrium at the trap sites. This model is used to calculate tritium release from aluminum clad, aluminum-lithium alloys. 9 refs., 3 figs

  8. Statistical analysis of constituent particles in 7075-T6 aluminum alloy

    Science.gov (United States)

    Harlow, D. G.; Wei, R. P.; Wang, M. Z.

    2006-11-01

    Pitting corrosion is a primary degradation mechanism that affects the durability and integrity of aluminum alloy structures especially in aircraft. The heterogeneity of aluminum alloys is directly responsible for pitting corrosion because about 200 constituent particles per mm2 are on polished surfaces. Corrosion pits commence at surface particles and evolve into severe pits by sustained growth through particle clusters. Severe pits are nuclei for subsequent corrosion fatigue cracking. Thus, heterogeneous clusters of constituent particles are critical to the quality of aluminum alloys subjected to deleterious environments. Models for structural reliability including corrosion fundamentally depend on quantitative descriptions of the spatial statistics of the particles and particle clusters, including their location, size, and density. The primary purpose of this effort is to statistically estimate the distribution functions of the key geometrical properties of the constituent particles in 7075-T6 aluminum alloy and their role in pitting corrosion.

  9. RECLAMATION OF ALUMINUM FINISHING SLUDGES

    Science.gov (United States)

    The research study of the reclamation of aluminum-anodizing sludges was conducted in two sequential phases focused on enhanced dewatering of aluminum-anodizing sludges to produce commercial-strength solutions of aluminum sulfate, i.e., liquid alum. The use of high-pressure (14 to...

  10. Electrically conductive anodized aluminum coatings

    Science.gov (United States)

    Alwitt, Robert S. (Inventor); Liu, Yanming (Inventor)

    2001-01-01

    A process for producing anodized aluminum with enhanced electrical conductivity, comprising anodic oxidation of aluminum alloy substrate, electrolytic deposition of a small amount of metal into the pores of the anodized aluminum, and electrolytic anodic deposition of an electrically conductive oxide, including manganese dioxide, into the pores containing the metal deposit; and the product produced by the process.

  11. Invisible Display in Aluminum

    DEFF Research Database (Denmark)

    Prichystal, Jan Phuklin; Hansen, Hans Nørgaard; Bladt, Henrik Henriksen

    2005-01-01

    integrated display in a metal surface is often ruled by design and functionality of a product. The integration of displays in metal surfaces requires metal removal in order to clear the area of the display to some extent. The idea behind an invisible display in Aluminum concerns the processing of a metal...

  12. Aluminum Sulfate 18 Hydrate

    Science.gov (United States)

    Young, Jay A.

    2004-01-01

    A chemical laboratory information profile (CLIP) of the chemical, aluminum sulfate 18 hydrate, is presented. The profile lists physical and harmful properties, exposure limits, reactivity risks, and symptoms of major exposure for the benefit of teachers and students using the chemical in the laboratory.

  13. Hot pressing aluminum nitride

    International Nuclear Information System (INIS)

    Experiment was performed on the hot pressing of aluminum nitride, using three kinds of powder which are: a) made by electric arc method, b) made by nitrifying aluminum metal powder, and c) made from alumina and carbon in nitrogen atmosphere. The content of oxygen of these powders was analyzed by activation analysis using high energy neutron irradiation. The density of hot pressed samples was classified into two groups. The high density group contained oxygen more than 3 wt. %, and the low density group contained about 0.5 wt %. Typical density vs. temperature curves have a bending point near 1,5500C, and the sample contains iron impurity of 0.5 wt. %. Needle crystals were found to grow near 1,5500C by VLS mechanism, and molten iron acts a main part of mechanism as a liquid phase. According to the above-mentioned curve, the iron impurity in aluminum nitride prevents densification. The iron impurity accelerates crystal growth. Advance of densification may be expected by adding iron impurity, but in real case, the densification is delayed. Densification and crystal growth are greatly accelerated by oxygen impurity. In conclusion, more efforts must be made for the purification of aluminum nitride. In the present stage, the most pure nitride powder contains about 0.1 wt. % of oxygen, as compared with good silicon carbide crystals containing only 10-5 wt. % of nitrogen. (Iwakiri, K.)

  14. Oriented aluminum nanocrystals in a one-step process

    International Nuclear Information System (INIS)

    Aluminum coatings were deposited on glass substrates by chemical vapor deposition using N-methylpiperidine (nmp) stabilized dichloroalane [Cl2AlH·2nmp] as aluminum precursor. With regard to temperature, the experimental conditions were varied between 75 °C and 125 °C for the precursor and between 250 °C and 450 °C for the substrate. Depending on these parameters, highly textured layers could be deposited. The substrates have been consistently covered by a layer of idiomorphic, mostly distorted octahedra of aluminum single crystals. The morphologies of the structures and the degree of orientation of the crystals were investigated by a scanning electron microscopy and X-ray diffraction measurements. The high order of [111] orientation was found to decrease with increasing precursor and substrate temperature. We propose a mechanism for the generation of the octahedral structures based on the formation of mesocrystals. On heating, the dichloroalane (stabilized with nmp) loses the nmp ligands together with hydrogen and chlorine. The amine (nmp) seems to trigger the formation of aluminum crystals depending on the temperature and thus influences the texture of the Al-layer and the formation of well-formed octahedron-like structures. - Highlights: • An original chemical gas phase synthesis of aluminum single crystals is shown. • N-methylpiperidine triggers a preferred crystal growth in [111] direction. • A decomposition mechanism of the dichloroalane adduct is discussed. • Agglomeration to larger aluminum meso-crystals is observed at a higher gas flow

  15. Dependence of hydrogen-induced lattice defects and hydrogen embrittlement of cold-drawn pearlitic steels on hydrogen trap state, temperature, strain rate and hydrogen content

    International Nuclear Information System (INIS)

    The effects of the hydrogen state, temperature, strain rate and hydrogen content on hydrogen embrittlement susceptibility and hydrogen-induced lattice defects were evaluated for cold-drawn pearlitic steel that absorbed hydrogen in two trapping states. Firstly, tensile tests were carried out under various conditions to evaluate hydrogen embrittlement susceptibility. The results showed that peak 2 hydrogen, desorbed at temperatures above 200 °C as determined by thermal desorption analysis (TDA), had no significant effect on hydrogen embrittlement susceptibility. In contrast, hydrogen embrittlement susceptibility increased in the presence of peak 1 hydrogen, desorbed from room temperature to 200 °C as determined by TDA, at temperatures higher than −30 °C, at lower strain rates and with higher hydrogen content. Next, the same effects on hydrogen-induced lattice defects were also evaluated by TDA using hydrogen as a probe. Peak 2 hydrogen showed no significant effect on either hydrogen-induced lattice defects or hydrogen embrittlement susceptibility. It was found that hydrogen-induced lattice defects formed under the conditions where hydrogen embrittlement susceptibility increased. This relationship indicates that hydrogen embrittlement susceptibility was higher under the conditions where the formation of hydrogen-induced lattice defects tended to be enhanced. Since hydrogen-induced lattice defects formed by the interaction between hydrogen and strain were annihilated by annealing at a temperature of 200 °C, they were presumably vacancies or vacancy clusters. One of the common atomic-level changes that occur in cold-drawn pearlitic steel showing higher hydrogen embrittlement susceptibility is the formation of vacancies and vacancy clusters

  16. XRD and NMR investigation of Ti-compound formation in solution-doping of sodium aluminum hydrides: solubility of Ti in NaAlH4 crystals grown in THF

    International Nuclear Information System (INIS)

    Sodium aluminum hydrides have gained attention due to their high hydrogen weight percent (5.5% ideal) compared to interstitial hydrides, and as a model for hydrides with even higher hydrogen weight fraction. The purpose of this paper is to investigate the Ti-compounds that are formed under solution-doping techniques, such as wet doping in solvents such as tetrahydrofuran (THF). Compound formation in Ti-doped sodium aluminum hydrides is investigated using X-ray diffraction (XRD) and magic angle spinning (MAS) nuclear magnetic resonance (NMR). We present lattice parameter measurements of crushed single crystals, which were exposed to Ti during growth. Rietveld refinements indicate no lattice parameter change and thus no solubility for Ti in NaAlH4 by this method of exposure. In addition, X-ray diffraction data indicate that no Ti substitutes in NaH, the final decomposition product for the alanate. Reaction products of completely reacted (33.3 at.%-doped) samples that were solvent-mixed or mechanically milled are investigated. Formation of TiAl3 is observed in mechanically milled materials, but not solution mixed samples, where bonding to THF likely stabilizes Ti-based nano-clusters. The Ti in these clusters is activated by mechanical milling

  17. Cluster-assisted generation of multi-charged ions in nanosecond laser ionization of pulsed hydrogen sulfide beam at 1064 and 532 nm

    Science.gov (United States)

    Niu, Dong-Mei; Li, Hai-Yang; Luo, Xiao-Lin; Liang, Feng; Cheng, Shuang; Li, An-Lin

    2006-07-01

    The multi-charged sulfur ions of Sq+ (qlaser of 1064 and 532 nm with an intensity of 1010~ 1012W.cm-2. S6+ is the dominant multi-charged species at 1064 nm, while S4+, S3+ and S2+ ions are the main multi-charged species at 532 nm. A three-step model (i.e., multiphoton ionization triggering, inverse bremsstrahlung heating, electron collision ionizing) is proposed to explain the generation of these multi-charged ions at the laser intensity stated above. The high ionization level of the clusters and the increasing charge state of the ion products with increasing laser wavelength are supposed mainly due to the rate-limiting step, i.e., electron heating by absorption energy from the laser field via inverse bremsstrahlung, which is proportional to λ2, λ being the laser wavelength.

  18. Experimental study for the assessment of conditioning matrices of the radioactive aluminum wastes

    International Nuclear Information System (INIS)

    In Romania there are aluminum radioactive wastes produced in the decommissioning of the research reactor WWR-S at Magurele and from decommissioning of the multi-area zero power reactors from INR platform. Internationally there are two basic options regarding the management of the aluminum radioactive wastes: (1) decontamination of the aluminum and reuse of the aluminum recovered under governmental authority control and (2) processing and conditioning in safe conditions in view of final disposal. A method of conditioning the aluminum radioactive wastes comprises the steps of reacting metallic aluminum with an alkali solution to generate hydrogen gas and mixing the resulting reaction liquid with a solidifying material. It contains a latent hydraulic material as a main component to effect the conversion into a conditioned waste form which minimizes the probability of radionuclides release to the environment during interim storage, transportation and final disposal. LiNO3 addition to the cement solidified miscellaneous wastes has been proposed for preventing hydrogen gas generation caused by the corrosion of aluminum materials contained in the wastes. Results of a series of experimental tests performed to determine the influence of matrix characteristics on the properties of aluminum immobilized into cement matrices are presented. (authors)

  19. Water's Hydrogen Bond Strength

    CERN Document Server

    Chaplin, Martin

    2007-01-01

    Water is necessary both for the evolution of life and its continuance. It possesses particular properties that cannot be found in other materials and that are required for life-giving processes. These properties are brought about by the hydrogen bonded environment particularly evident in liquid water. Each liquid water molecule is involved in about four hydrogen bonds with strengths considerably less than covalent bonds but considerably greater than the natural thermal energy. These hydrogen bonds are roughly tetrahedrally arranged such that when strongly formed the local clustering expands, decreasing the density. Such low density structuring naturally occurs at low and supercooled temperatures and gives rise to many physical and chemical properties that evidence the particular uniqueness of liquid water. If aqueous hydrogen bonds were actually somewhat stronger then water would behave similar to a glass, whereas if they were weaker then water would be a gas and only exist as a liquid at sub-zero temperature...

  20. Cooperative effects in blue-shifted hydrogen bonded cluster of CF3H···(HF)1≤n≤3 from first principles simulations

    International Nuclear Information System (INIS)

    Ab initio molecular dynamics technique has been used to estimate the structural, electronic and vibrational properties of the blue-shifted hydrogen bonded CF3H···(HF)1≤n≤3 complexes. Different reaction pathways and aggregation products have been studied as a function of temperature. The self-aggregation of HF molecules and the formation of CF3H···HF)2 and CF3H···HF)3 cyclic structures have been found at the temperature of 50 K. The estimated energetic cooperative effects stabilize these structures even at higher temperature which is not the case in the CF3H···(HF) complex. The structural cooperative effects manifest in the (HF)2-3 chain formation which size determines the binding energy. The anharmonic spectra obtained from molecular dynamics simulations show the pronounced vibrational cooperative effects and might support future low temperature experiments utilizing molecular beam, supersonic jet or ultracold Helium droplet technique.

  1. Aluminum microstructures on anodic alumina for aluminum wiring boards.

    Science.gov (United States)

    Jha, Himendra; Kikuchi, Tatsuya; Sakairi, Masatoshi; Takahashi, Hideaki

    2010-03-01

    The paper demonstrates simple methods for the fabrication of aluminum microstructures on the anodic oxide film of aluminum. The aluminum sheets were first engraved (patterned) either by laser beam or by embossing to form deep grooves on the surface. One side of the sheet was then anodized, blocking the other side by using polymer mask to form the anodic alumina. Because of the lower thickness at the bottom part of the grooves, the part was completely anodized before the complete oxidation of the other parts. Such selectively complete anodizing resulted in the patterns of metallic aluminum on anodic alumina. Using the technique, we fabricated microstructures such as line patterns and a simple wiring circuit-board-like structure on the anodic alumina. The aluminum microstructures fabricated by the techniques were embedded in anodic alumina/aluminum sheet, and this technique is promising for applications in electronic packaging and devices. PMID:20356280

  2. Hydrogen sensor

    Science.gov (United States)

    Duan, Yixiang; Jia, Quanxi; Cao, Wenqing

    2010-11-23

    A hydrogen sensor for detecting/quantitating hydrogen and hydrogen isotopes includes a sampling line and a microplasma generator that excites hydrogen from a gas sample and produces light emission from excited hydrogen. A power supply provides power to the microplasma generator, and a spectrometer generates an emission spectrum from the light emission. A programmable computer is adapted for determining whether or not the gas sample includes hydrogen, and for quantitating the amount of hydrogen and/or hydrogen isotopes are present in the gas sample.

  3. Thermal compatibility studies of unirradiated uranium silicide dispersed in aluminum

    International Nuclear Information System (INIS)

    Powder metallurgy dispersions of uranium silicides in an aluminum matrix have been developed by the international Reduced Enrichment for Research and Test Reactors program as a new generation of proliferation-resistant fuels. A major issue of concern is the compatibility of the fuel with the matrix material and the dimensional stability of this fuel type. A total of 45 miniplate-type fuel plates were annealed at 4000C for up to 1981 hours. A data base for the thermal compatibility of unirradiated uranium silicide dispersed in aluminum was established. No modification tested of a standard fuel plate showed any significant reduction of the plate swelling. The cause of the thermal growth of silicide fuel plates was determined to be a two-step process: (1) the reaction of the uranium silicide with aluminum to form U(AlSi)3 and (2) the release of hydrogen and subsequent creep and pillowing of the fuel plate. 9 references, 4 figures, 6 tables

  4. Reversible hydrogen storage materials

    Science.gov (United States)

    Ritter, James A.; Wang, Tao; Ebner, Armin D.; Holland, Charles E.

    2012-04-10

    In accordance with the present disclosure, a process for synthesis of a complex hydride material for hydrogen storage is provided. The process includes mixing a borohydride with at least one additive agent and at least one catalyst and heating the mixture at a temperature of less than about 600.degree. C. and a pressure of H.sub.2 gas to form a complex hydride material. The complex hydride material comprises MAl.sub.xB.sub.yH.sub.z, wherein M is an alkali metal or group IIA metal, Al is the element aluminum, x is any number from 0 to 1, B is the element boron, y is a number from 0 to 13, and z is a number from 4 to 57 with the additive agent and catalyst still being present. The complex hydride material is capable of cyclic dehydrogenation and rehydrogenation and has a hydrogen capacity of at least about 4 weight percent.

  5. Aluminum recycling from reactor walls: A source of contamination in a-Si:H thin films

    International Nuclear Information System (INIS)

    In this article, the authors investigate the contamination of hydrogenated amorphous silicon thin films with aluminum recycled from the walls and electrodes of the deposition reactor. Thin films of hydrogenated amorphous silicon were prepared under various conditions by a standard radio frequency plasma enhanced chemical vapor deposition process in two reactors, the chambers of which were constructed of either aluminum or stainless steel. The authors have studied the electronic properties of these thin films and have found that when using an aluminum reactor chamber, the layers are contaminated with aluminum recycled from the chamber walls and electrode. This phenomenon is observed almost independently of the deposition conditions. The authors show that this contamination results in slightly p-doped films and could be detrimental to the deposition of device grade films. The authors also propose a simple way to control and eventually suppress this contamination.

  6. Selection of a mineral binder for the stabilization - solidification of waste containing aluminum metal

    International Nuclear Information System (INIS)

    The dismantling of nuclear facilities produces radioactive waste materials, some of which may contain aluminum metal. In a strongly alkaline medium, such as that encountered in conventional cementitious materials based on Portland cement, aluminum metal becomes corroded, with a continued production of dihydrogen. In order to develop a mineral matrix having enhanced compatibility with aluminum, a literature review was first undertaken to identify binders capable of reducing the pore solution pH compared with Portland cement. An experimental study was then carried out to measure the hydrogen production resulting from corrosion of aluminum metal rods encapsulated in the different selected cement pastes. The best results were achieved with magnesium phosphate cement, which released very little hydrogen over the duration of the study. This production could be reduced further by adding a corrosion inhibitor (lithium nitrate) to the mixing solution

  7. Hydrogen system (hydrogen fuels feasibility)

    International Nuclear Information System (INIS)

    This feasibility study on the production and use of hydrogen fuels for industry and domestic purposes includes the following aspects: physical and chemical properties of hydrogen; production methods steam reforming of natural gas, hydrolysis of water; liquid and gaseous hydrogen transportation and storage (hydrogen-hydride technology); environmental impacts, safety and economics of hydrogen fuel cells for power generation and hydrogen automotive fuels; relevant international research programs

  8. Weighted Clustering

    DEFF Research Database (Denmark)

    Ackerman, Margareta; Ben-David, Shai; Branzei, Simina;

    2012-01-01

    We investigate a natural generalization of the classical clustering problem, considering clustering tasks in which different instances may have different weights.We conduct the first extensive theoretical analysis on the influence of weighted data on standard clustering algorithms in both the...... partitional and hierarchical settings, characterizing the conditions under which algorithms react to weights. Extending a recent framework for clustering algorithm selection, we propose intuitive properties that would allow users to choose between clustering algorithms in the weighted setting and classify...

  9. Cluster Headache

    OpenAIRE

    Frederick G Freitag

    1985-01-01

    Learning Objectives: Review the current understanding of the pathophysiology of cluster headache Be able to recognize the clinical features of cluster headache Be able to develop a strategy for treatment of cluster headache Cluster headache is divided into multiple subtypes under the IHC classification criteria. The vast majority of patients present with episodic cluster headache (3.1.1). This will be the focus of the presentation. The syndrome is characterized by repeated at...

  10. 21 CFR 73.1645 - Aluminum powder.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Aluminum powder. 73.1645 Section 73.1645 Food and... ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1645 Aluminum powder. (a) Identity. (1) The color additive aluminum powder shall be composed of finely divided particles of aluminum prepared from virgin aluminum....

  11. Aluminum ions accelerated the oxidative stress of copper-mediated melanin formation

    Science.gov (United States)

    Di, Junwei; Bi, Shuping

    2003-11-01

    A comparison between the effects of aluminum and cupric ions on the dopachrome (DC) conversion and the cooperation effect of the both ions in the DOPA oxidation to melanin pathway has been studied by UV-Vis spectrophotometric method. Both aluminum and cupric ions catalyze the DC conversion reaction, which is an important step in the melanin synthesis pathway. However, cupric ions catalyze the conversion of DC to yield 5,6-dihydroxyindole-2-carboxylic acid (DHICA) but the product of DC conversion catalyzed by aluminum is 5,6-dihydroxyindole (DHI). DOPA oxidation catalyzed by aluminum and cupric ions is studied in the presence of hydrogen peroxide. The results from our experiments provide evidence that aluminum can markedly increase the oxidative stress of copper-mediated the melanin formation and influence the properties of the melanin by means of changing the ratio of DHICA/DHI in the acidic environment (pH 5.5).

  12. Gas Contamination In Plasma-Arc-Welded Aluminum

    Science.gov (United States)

    Mcclure, John C.; Torres, Martin R.; Gurevitch, Alan C.; Newman, Robert A.

    1992-01-01

    Document describes experimental investigation on visible and tactile effects of gaseous contaminants in variable-polarity plasma arc (VPPA) welding of 2219 T-87 aluminum alloy. Contaminant gases (nitrogen, methane, oxygen, and hydrogen) introduced in argon arc and in helium shield gas in various controlled concentrations. Report represents results of experiments in form of photographs of fronts, backs, polished cross sections, and etched cross sections of welds made with various contaminants at various concentrations. Provides detailed discussion of conditions under which welds made.

  13. Hybrid Aluminum Composite Materials Based on Carbon Nanostructures

    Directory of Open Access Journals (Sweden)

    Tatiana S. Koltsova

    2015-09-01

    Full Text Available We investigated formation of carbon nanofibers grown by chemical deposition (CVD method using an acetylene-hydrogen mixture on the surface of micron-sized aluminum powder particles. To obtain uniform distribution of the carbon nanostructures on the particles we deposited nickel catalyst on the surface by spraying from the aqueous solution of nickel nitrate. It was found that increasing the time of the synthesis lowers the rate of growth of carbon nanostructures due to the deactivation of the catalyst. The Raman spectroscopy measurements confirm the presence of disordered carbon corresponding to CNFs in the specimen. X-ray photoelectron spectroscopy showed the presence of aluminum carbide in the hot pressed samples. An aluminum composite material prepared using 1 wt.% CNFs obtained by uniaxial cold pressing and sintering showed 30% increase in the hardness compared to pure aluminum, whereas the composites prepared by hot pressing showed 80% increase in the hardness. Composite materials have satisfactory ductility. Thus, the aluminum based material reinforced with carbon nanostructures should be appropriate for creating high-strength and light compacts for aerospace and automotive applications and power engineering.DOI: http://dx.doi.org/10.5755/j01.ms.21.3.7355

  14. Hydrogen physics

    International Nuclear Information System (INIS)

    The workshop on hydrogen bond was restarted changing its name to 'Hydrogen Physics' for grasping hydrogen bond from wider viewpoint and expecting the new development in this field hereafter. As the basic attitude, the phenomena related to hydrogen bond are reviewed from two different systems: hydrogen-lattice system and hydrogen-electron system. The Hydrogen Physics meeting was held on September 29 and 30, 1992, at National Laboratory for High Energy Physics, and 19 lectures were given. The themes were proton dynamics of hydrogen bond, water science and water with good taste, collective movement and fluctuation of water, neutron diffraction of water, hydrogen bond in water as seen from Raman scattering, electron and proton movements in organic crystals, new deuterium substitution effect of proton transfer in hydrogen bond in solids, infrared spectroscopy for one-dimensional hydrogen bond crystals, MSR in solid hydrogen, hydrogen in alkali metal-graphite intercalation compounds, lattice anomalies and Grueneisen parameters in high Tc superconducting salts, bio-substances and hydrogen, hydrogen bond net in nucleotide and control of crystalline structure change by hydrogen vapor pressure, ATP and structural change and crystal water of guanosine, spread of protons and electrons in hydrogen bond, anisotropy of loose scattering according to ice rule, high pressure effect and isotope mixed crystal effect of KHS crystals without hydrogen crystal network, state of motion and phase transformation of hydrogen in KDP, and development of hydrogen bond research by neutron scattering. This publication contains the papers and the transparencies presented at the meeting. (J.P.N.)

  15. Tritium permeability of nickel plated stainless steel 21-6-9 and of gold plated aluminum

    International Nuclear Information System (INIS)

    Tritium permeabilities of alloy 21-6-9 and of aluminum have been determined over the 200 to 750 0C and 300 to 460 0C ranges, respectively. Permeation behavior through cold worked alloy 21-6-9 was similar to that for other austenitic alloys, but behavior of annealed alloy 21-6-9 was markedly different and suggested a structural transition near 560 0C. Permeabilities determined for nonoxidized aluminum were different from those given in earlier publications, but are believed to represent better hydrogen permeation through aluminum

  16. Globular cluster winds

    International Nuclear Information System (INIS)

    Current evolutionary theory indicates that the evolving stars in globular clusters arrive on the horizontal branch with approx. 30% less mass than they had on the main sequence. If, as seems likely, this mass loss results from the outflow of unprocessed material at the stellar surface during the giant stage, and if the ejected mass were retained within the cluster during the giant stage, and if the ejected mass were retained within the cluster between successive sweeps through the galactic plane (about 108 yr), sufficient hydrogen (100-2000Msub(o)) should accumulate for detection. Radio searches have failed to find evidence for either neutral or ionized gas. The search was therefore extended into the optical region and the time independant gas flow models were calculated to resolve this anomaly. (R.L.)

  17. Heredity of Aluminum Melt by Electric Pulse Modification (Ⅱ)

    Institute of Scientific and Technical Information of China (English)

    QI Jin-gang; WANG Jian-zhong; DU Hui-ling; CAO Li-yun

    2007-01-01

    Heredity of high pure aluminum melts under different pulse electric field was investigated by means of repetitious remelt experiment. The results indicate that the genetic coefficient by measurement of grain size of cast structure has a close relation with pulse voltage. Moreover, the hereditary law accords with the function of In=1+e-αn+β. The stability of genetic carrier (cluster) comprises in the competition between repetitious cooling and heating impulse and the effect of electric pulse modification.

  18. Photoemission study of tris(8-hydroxyquinoline) aluminum/aluminum oxide/tris(8-hydroxyquinoline) aluminum interface

    International Nuclear Information System (INIS)

    The evolution of the interface electronic structure of a sandwich structure involving aluminum oxide and tris(8-hydroxyquinoline) aluminum (Alq), i.e. (Alq/AlOx/Alq), has been investigated with photoemission spectroscopy. Strong chemical reactions have been observed due to aluminum deposition onto the Alq substrate. The subsequent oxygen exposure releases some of the Alq molecules from the interaction with aluminum. Finally, the deposition of the top Alq layer leads to an asymmetry in the electronic energy level alignment with respect to the AlOx interlayer

  19. Selective Adsorption of Sodium Aluminum Fluoride Salts from Molten Aluminum

    Energy Technology Data Exchange (ETDEWEB)

    Leonard S. Aubrey; Christine A. Boyle; Eddie M. Williams; David H. DeYoung; Dawid D. Smith; Feng Chi

    2007-08-16

    Aluminum is produced in electrolytic reduction cells where alumina feedstock is dissolved in molten cryolite (sodium aluminum fluoride) along with aluminum and calcium fluorides. The dissolved alumina is then reduced by electrolysis and the molten aluminum separates to the bottom of the cell. The reduction cell is periodically tapped to remove the molten aluminum. During the tapping process, some of the molten electrolyte (commonly referred as “bath” in the aluminum industry) is carried over with the molten aluminum and into the transfer crucible. The carryover of molten bath into the holding furnace can create significant operational problems in aluminum cast houses. Bath carryover can result in several problems. The most troublesome problem is sodium and calcium pickup in magnesium-bearing alloys. Magnesium alloying additions can result in Mg-Na and Mg-Ca exchange reactions with the molten bath, which results in the undesirable pickup of elemental sodium and calcium. This final report presents the findings of a project to evaluate removal of molten bath using a new and novel micro-porous filter media. The theory of selective adsorption or removal is based on interfacial surface energy differences of molten aluminum and bath on the micro-porous filter structure. This report describes the theory of the selective adsorption-filtration process, the development of suitable micro-porous filter media, and the operational results obtained with a micro-porous bed filtration system. The micro-porous filter media was found to very effectively remove molten sodium aluminum fluoride bath by the selective adsorption-filtration mechanism.

  20. Neurofibrillary pathology and aluminum in Alzheimer's disease

    OpenAIRE

    Shin, R. W.; Lee, V. M. Y; Trojanowski, J Q

    1995-01-01

    Since the first reports of aluminum-induced neurofibrillary degeneration in experimental animals, extensive studies have been performed to clarify the role played by aluminum in the pathogenesis of Alzheimer's disease (AD). Additional evidence implicating aluminum in AD includes elevated levels of aluminum in the AD brain, epidemiological data linking aluminum exposure to AD, and interactions between aluminum and protein components in the pathological lesions o...

  1. In-situ processing of aluminum nitride particle reinforced aluminum alloy composites

    Science.gov (United States)

    Zheng, Qingjun

    Discontinuously reinforced aluminum alloy composites (DRACs) have potential applications in automotive, electronic packaging, and recreation industries. Conventional processing of DRACs is by incorporation of ceramic particles/whiskers/fibers into matrix alloys. Because of the high cost of ceramic particles, DRACs are expensive. The goal of this work was to develop a low-cost route of AlN-Al DRACs processing through bubbling and reacting nitrogen and ammonia gases with aluminum alloy melt in the temperature range of 1373--1523 K. Thermodynamic analysis of AlN-Al alloy system was performed based on Gibbs energy minimization theory. AlN is stable in aluminum, Al-Mg, Al-Si, Al-Zn, and Al-Li alloys over the whole temperature range for application and processing of DRACs. Experiments were carried out to form AlN by bubbling nitrogen and ammonia gases through aluminum, Al-Mg, and Al-Si alloy melts. Products were characterized with XRD, SEM, and EDX. The results showed that in-situ processing of AlN reinforced DRACs is technically feasible. Significant AlN was synthesized by bubbling deoxidized nitrogen and ammonia gases. When nitrogen gas was used as the nitrogen precursor, the AlN particles formed in-situ are small in size, (interface. In comparison with nitrogen gas, bubbling ammonia led to formation of AlN particles in smaller size (about 2 mum or less) at a significantly higher rate. Ammonia is not stable and dissociated into nitrogen and hydrogen at reaction temperatures. The hydrogen functions as oxygen-getter at the interface and benefits chemisorption of nitrogen, thereby promoting the formation of AlN. The overall process of AlN formation was modeled using two-film model. For nitrogen bubbling gas, the whole process is controlled by chemisorption of nitrogen molecules at the gas bubble - aluminum melt interface. For ammonia precursor, the rate of the overall process is limited by the mass transfer of nitrogen atoms in the liquid boundary layer. The models agree

  2. Cluster headache

    Science.gov (United States)

    Histamine headache; Headache - histamine; Migrainous neuralgia; Headache - cluster; Horton's headache ... Doctors do not know exactly what causes cluster headaches. They ... (chemical in the body released during an allergic response) or ...

  3. Isotopic clusters

    International Nuclear Information System (INIS)

    Spectra of isotopically mixed clusters (dimers of SF6) are calculated as well as transition frequencies. The result leads to speculations about the suitability of the laser-cluster fragmentation process for isotope separation. (Auth.)

  4. Aluminum Nanoholes for Optical Biosensing

    Directory of Open Access Journals (Sweden)

    Carlos Angulo Barrios

    2015-07-01

    Full Text Available Sub-wavelength diameter holes in thin metal layers can exhibit remarkable optical features that make them highly suitable for (biosensing applications. Either as efficient light scattering centers for surface plasmon excitation or metal-clad optical waveguides, they are able to form strongly localized optical fields that can effectively interact with biomolecules and/or nanoparticles on the nanoscale. As the metal of choice, aluminum exhibits good optical and electrical properties, is easy to manufacture and process and, unlike gold and silver, its low cost makes it very promising for commercial applications. However, aluminum has been scarcely used for biosensing purposes due to corrosion and pitting issues. In this short review, we show our recent achievements on aluminum nanohole platforms for (biosensing. These include a method to circumvent aluminum degradation—which has been successfully applied to the demonstration of aluminum nanohole array (NHA immunosensors based on both, glass and polycarbonate compact discs supports—the use of aluminum nanoholes operating as optical waveguides for synthesizing submicron-sized molecularly imprinted polymers by local photopolymerization, and a technique for fabricating transferable aluminum NHAs onto flexible pressure-sensitive adhesive tapes, which could facilitate the development of a wearable technology based on aluminum NHAs.

  5. Aluminum Nanoholes for Optical Biosensing

    Science.gov (United States)

    Barrios, Carlos Angulo; Canalejas-Tejero, Víctor; Herranz, Sonia; Urraca, Javier; Moreno-Bondi, María Cruz; Avella-Oliver, Miquel; Maquieira, Ángel; Puchades, Rosa

    2015-01-01

    Sub-wavelength diameter holes in thin metal layers can exhibit remarkable optical features that make them highly suitable for (bio)sensing applications. Either as efficient light scattering centers for surface plasmon excitation or metal-clad optical waveguides, they are able to form strongly localized optical fields that can effectively interact with biomolecules and/or nanoparticles on the nanoscale. As the metal of choice, aluminum exhibits good optical and electrical properties, is easy to manufacture and process and, unlike gold and silver, its low cost makes it very promising for commercial applications. However, aluminum has been scarcely used for biosensing purposes due to corrosion and pitting issues. In this short review, we show our recent achievements on aluminum nanohole platforms for (bio)sensing. These include a method to circumvent aluminum degradation—which has been successfully applied to the demonstration of aluminum nanohole array (NHA) immunosensors based on both, glass and polycarbonate compact discs supports—the use of aluminum nanoholes operating as optical waveguides for synthesizing submicron-sized molecularly imprinted polymers by local photopolymerization, and a technique for fabricating transferable aluminum NHAs onto flexible pressure-sensitive adhesive tapes, which could facilitate the development of a wearable technology based on aluminum NHAs. PMID:26184330

  6. Cluster beam investigation with MCPs

    International Nuclear Information System (INIS)

    High intensity cluster-jet beams produced in Laval nozzles represent a very attractive and extremely interesting tool for studies at storage ring experiments, such as PANDA, or for laser-induced particle acceleration. Since the cluster properties vary with increasing number of constituents, it is essential to perform systematic measurements on the target thickness and especially on the cluster masses. For this purpose a monitoring system based on Micro Channel Plates (MCPs) combined with a phosphor screen has been developed and installed at the beam dump of the PANDA prototype cluster-jet target in Muenster. It could be shown that this MCP system allows for a direct observation of an ionised cluster beam. In addition, with this setup the possibility to visualise the vertex zone at the ANKE cluster-jet target at COSY was succesfully demonstrated, where a proton beam with a momentum of 2.09 GeV/c interacted with a hydrogen cluster-jet beam. Furthermore, cluster mass investigations can be performed in conjunction with a retardation field. In this presentation an overview of the MCP detection system, images of the cluster-jet beam and the vertex zone as well as the results of the current cluster mass measurements are presented and discussed.

  7. Concept Car Hybrid Power Plant Based on the Air Aluminum Electrochemical Generator

    Directory of Open Access Journals (Sweden)

    Pavel Viktorovich Bulat

    2015-05-01

    Full Text Available Aim of the study is development of the concept of a hybrid car with aluminum-hydrogen battery power, the assessment of its performance. The concept of a hybrid car powered by an aluminum-hydrogen electrochemical generator. Vehicle schematic diagrams, power supply layouts, estimation of the power supply were given. Different variants of power storage: battery, super capacitors. Conclusion about their application prospects for power peak flattering. Estimations demonstrate the competitiveness of the proposed diagrams as compared to conventional hybrid vehicles.

  8. Weighted Clustering

    OpenAIRE

    Ackerman, Margareta; Ben-David, Shai; Branzei, Simina; Loker, David

    2012-01-01

    We investigate a natural generalization of the classical clusteringproblem, considering clustering tasks in which differentinstances may have different weights.We conduct the firstextensive theoretical analysis on the influence of weighteddata on standard clustering algorithms in both the partitionaland hierarchical settings, characterizing the conditions underwhich algorithms react to weights. Extending a recent frameworkfor clustering algorithm selection, we propose intuitiveproperties that...

  9. Meaningful Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Sanfilippo, Antonio P.; Calapristi, Augustin J.; Crow, Vernon L.; Hetzler, Elizabeth G.; Turner, Alan E.

    2004-05-26

    We present an approach to the disambiguation of cluster labels that capitalizes on the notion of semantic similarity to assign WordNet senses to cluster labels. The approach provides interesting insights on how document clustering can provide the basis for developing a novel approach to word sense disambiguation.

  10. Thermal coatings for titanium-aluminum alloys

    Science.gov (United States)

    Cunnington, George R.; Clark, Ronald K.; Robinson, John C.

    1993-01-01

    Titanium aluminides and titanium alloys are candidate materials for use in hot structure and heat-shield components of hypersonic vehicles because of their good strength-to-weight characteristics at elevated temperature. However, in order to utilize their maximum temperature capability, they must be coated to resist oxidation and to have a high total remittance. Also, surface catalysis for recombination of dissociated species in the aerodynamic boundary layer must be minimized. Very thin chemical vapor deposition (CVD) coatings are attractive candidates for this application because of durability and very light weight. To demonstrate this concept, coatings of boron-silicon and aluminum-boron-silicon compositions were applied to the titanium-aluminides alpha2 (Ti-14Al-21Nb), super-alpha2 (Ti-14Al-23-Nb-2V), and gamma (Ti-33Al-6Nb-1Ta) and to the titanium alloy beta-21S (Ti-15Mo-3Al-3Nb-0.2Si). Coated specimens of each alloy were subjected to a set of simulated hypersonic vehicle environmental tests to determine their properties of oxidation resistance, surface catalysis, radiative emittance, and thermal shock resistance. Surface catalysis results should be viewed as relative performance only of the several coating-alloy combinations tested under the specific environmental conditions of the LaRC Hypersonic Materials Environmental Test System (HYMETS) arc-plasma-heated hypersonic wind tunnel. Tests were also conducted to evaluate the hydrogen transport properties of the coatings and any effects of the coating processing itself on fatigue life of the base alloys. Results are presented for three types of coatings, which are as follows: (1) a single layer boron silicon coating, (2) a single layer aluminum-boron-silicon coating, and (3) a multilayer coating consisting of an aluminum-boron-silicon sublayer with a boron-silicon outer layer.

  11. Reaction of the C3(X1Σg+) carbon cluster with H2S(X1A1), hydrogen sulfide: Photon-induced formation of C3S, tricarbon sulfur

    International Nuclear Information System (INIS)

    In this paper we report on the neutral-neutral reaction of the C3 carbon cluster with H2S in solid inert argon at 12 K, conditions that mimic, in part, the surfaces of interstellar grains. In the first step of the reaction, a C3•H2S complex is formed via an almost barrierless entrance addition mechanism. This complex, stabilized by an estimated 7.45 kJ/mol (CCSD(T)/aug-cc-pVTZ//B3LYP/6-311++G(d,p) level), is formed by the interaction of a terminal carbon of C3 with a hydrogen in H2S. This con-covalent complex displays a band at 2044.1 cm−1 observed via Fourier transform infrared absorption spectroscopy. With the help of the MP2/aug-ccpVDZ level method, this band is assigned to the CC asymmetric vibration mode. When the complex is exposed to UV-visible photons (hν < 5.5 eV) the tricarbon sulfur C3S molecule is identified, based on the appearance of a characteristic CC stretching band at 2047.5 cm−1. Calculated ground-state potential energy surfaces also confirm the concomitant formation of molecular H2. This facile reaction pathway involves an attainable transition state of 174.4 kJ/mol. Conversely, competing lower-energy reaction pathways that would lead to the generation of H2C3S (propadienethione), or C2H2 (acetylene) and CS, involve much more complex, multi-stage pathways, and are not observed experimentally

  12. Hualu Aluminum Will Construct Large Coal-Power-Aluminum Aluminum Processing Industrial Chain

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    The reporter learned from relevant departments of Baiyin City that in order to further push forward industrial upgrading,fulfill expansion and consolidation of the enterprise,Gansu Hualu Aluminum Co.,Ltd(Hualu Aluminum)will implement Out-Of-City-Into-Park project,

  13. Understanding of radiation effect on sink in aluminum base structure materials

    International Nuclear Information System (INIS)

    In case of aluminum, a slightly different approach is needed for the evaluation of radiation damage. Unlikely other structure materials such as zirconium alloy and iron based alloy, aluminum generate not only matrix defect but also much transmutation. Quantitative analysis of radiation damage of aluminum have been done in two research method. First research method is calculation of radiation damage quantity in the matrix. In this research, quantity of transmutation and matrix damage are evaluated by KMC simulation from ENDF database of IAEA. Most recently, radiation damage such as defect and transmutation are calculated in the MNSR reactor environment. The second research method is evaluation of sink morphology change by irradiation, which research method focus on accumulating behavior of radiation defects. Matrix defect and transmutation are clustering or dissolved by thermal diffusion and energy statue. These clustering defect such as dislocation loop, void and bubble directly affect mechanical properties. In this research area, it is hard to using deterministic method because it should describe envious and various reaction module in detail. However, in case of probabilistic method, it could be explained without detail reaction module. Most recently, there was KMC modeling about vacancy and helium cluster. From this cluster modeling, transmutation is quantitatively analyzed. After that cluster effect on swelling are explained. Unfortunately, silicon, which is another transmutation of aluminum, effect are neglected. Also primary cluster, which is generated by cascade, effect are neglected. For the fundamental understanding of radiation effect on aluminum alloy, it is needed that more various parameter such as alloy element and primary cluster effect should be researched. However, until now there was not general modeling which include alloy element and primary cluster effect on aluminum. However, there was not specified KMC platform for the quantitative analysis of

  14. Gas evolution in aluminum electrolytic capacitors

    Energy Technology Data Exchange (ETDEWEB)

    Gomez-Aleixandre, C.; Albella, J.M.; Martinez-Duart, J.M.

    1984-03-01

    Gas evolution in aluminum electrolytic capacitors constitutes one of their main drawbacks in comparison to other types of capacitors lacking a liquid electrolyte. In this respect, one of the most common causes of failure shown by liquid electrolyte capacitors is electrolyte leakage through the seal or even explosions produced by internal pressure buildup. In order to prevent these hazards, some substances, known as depolarizers, are usually added to the capacitor electrolyte with the purpose of absorbing the hydrogen evolved at the cathode (1, 2). Although the gas evolution problem in electrolytic capacitors has been known for a long time, there is a lack of literature on both direct measurements of the gas evolved and assessments of the amount of depolarizer active for the hydrogen absorption process. Aluminum electrolytic capacitors of 100..mu..F and 40V nominal voltage, miniature type (diam 8 mm, height 18.5 mm), were manufactured under standard specifications. The capacitors were filled with about 0.5 ml of an electrolyte consisting essentially of a solution of boric, adipic, and phosphoric acids in ethylene glycol. Picric acid and p-benzoquinone in molar concentrations of 0.01M and 0.05M, respectively, were added as depolarizers, yielding an electrolyte with a resistivity of about 80 ..cap omega..-cm and a pH of 5.1. The pressure inside the capacitors was monitored by a conventional Ushaped manometer made from a capillary glass tube filled with distilled water. The number of mols of gas generated in the capacitor (/eta/ /SUB g/ ) was calculated from the measured pressure (sensitivity 0.1 mm Hg) and the value of the internal volume of the manometercapacitor system.

  15. Cluster Lenses

    CERN Document Server

    Kneib, Jean-Paul; 10.1007/s00159-011-0047-3

    2012-01-01

    Clusters of galaxies are the most recently assembled, massive, bound structures in the Universe. As predicted by General Relativity, given their masses, clusters strongly deform space-time in their vicinity. Clusters act as some of the most powerful gravitational lenses in the Universe. Light rays traversing through clusters from distant sources are hence deflected, and the resulting images of these distant objects therefore appear distorted and magnified. Lensing by clusters occurs in two regimes, each with unique observational signatures. The strong lensing regime is characterized by effects readily seen by eye, namely, the production of giant arcs, multiple-images, and arclets. The weak lensing regime is characterized by small deformations in the shapes of background galaxies only detectable statistically. Cluster lenses have been exploited successfully to address several important current questions in cosmology: (i) the study of the lens(es) - understanding cluster mass distributions and issues pertaining...

  16. Spray Rolling Aluminum Strip

    Energy Technology Data Exchange (ETDEWEB)

    Lavernia, E.J.; Delplanque, J-P; McHugh, K.M.

    2006-05-10

    Spray forming is a competitive low-cost alternative to ingot metallurgy for manufacturing ferrous and non-ferrous alloy shapes. It produces materials with a reduced number of processing steps, while maintaining materials properties, with the possibility of near-net-shape manufacturing. However, there are several hurdles to large-scale commercial adoption of spray forming: 1) ensuring strip is consistently flat, 2) eliminating porosity, particularly at the deposit/substrate interface, and 3) improving material yield. Through this program, a new strip/sheet casting process, termed spray rolling, has been developed, which is an innovative manufacturing technique to produce aluminum net-shape products. Spray rolling combines the benefits of twin-roll casting and conventional spray forming, showing a promising potential to overcome the above hurdles associated with spray forming. Spray rolling requires less energy and generates less scrap than conventional processes and, consequently, enables the development of materials with lower environmental impacts in both processing and final products. Spray Rolling was developed as a collaborative project between the University of California-Davis, the Colorado School of Mines, the Idaho National Engineering and Environmental Laboratory, and an industry team. The following objectives of this project were achieved: (1) Demonstration of the feasibility of the spray rolling process at the bench-scale level and evaluation of the materials properties of spray rolled aluminum strip alloys; and (2) Demonstration of 2X scalability of the process and documentation of technical hurdles to further scale up and initiate technology transfer to industry for eventual commercialization of the process.

  17. Validity of the Aluminum Equivalent Approximation in Space Radiation Shielding

    Science.gov (United States)

    Badavi, Francis F.; Adams, Daniel O.; Wilson, John W.

    2009-01-01

    thickness, the current range will be sufficient to evaluate the qualitative usefulness of the aluminum equivalent approximation. Upon establishing the inaccuracies of the aluminum equivalent approximation through numerical simulations of the GCR radiation field attenuation for PE and aluminum equivalent PE spherical shells, we Anther present results for a limited set of commercially available, hydrogen rich, multifunctional polymeric constituents to assess the effect of the aluminum equivalent approximation on their radiation attenuation response as compared to the generic PE.

  18. Ultrahigh vacuum system with aluminum

    International Nuclear Information System (INIS)

    A bakeable vacuum chamber (1500C continuous) consists of aluminum alloy beam pipe (6063-T6) and bellows (5052-F) with an aluminum alloy flange (2219-T87) and a metal seal [Helicoflex-HN: pure aluminum (1050) O-ring with an elastic core (Ni base super alloy Inconel 750) which supplies the sealing force] has been constructed. The beam pipe and the flange (6063-T6/2219-T87), and the bellows and the flange (5052-F/2219-T87) were welded by an alternate current (50 Hz) TIG process using an aluminum alloy filler wire (4043). The mechanical properties of the aluminum alloy (2219-T87) is suitable for using the Helicoflex O-ring but the groove surface for the gasket is weak for scratching. Cromium-nitride coating by ion plating method was carried out on the aluminum surface of the gasket groove [thickness: 16 μm, micro Vickers hardness: 1800]. Ordinary stainless steel vacuum system can be replaced by the aluminum vacuum system in an accelerator. (author)

  19. Hydrogen Production

    Energy Technology Data Exchange (ETDEWEB)

    None

    2014-09-01

    This 2-page fact sheet provides a brief introduction to hydrogen production technologies. Intended for a non-technical audience, it explains how different resources and processes can be used to produce hydrogen. It includes an overview of research goals as well as “quick facts” about hydrogen energy resources and production technologies.

  20. The OLYMPUS Internal Hydrogen Target

    CERN Document Server

    Bernauer, J C; Ciullo, G; Henderson, B S; Ihloff, E; Kelsey, J; Lenisa, P; Milner, R; Schmidt, A; Statera, M

    2014-01-01

    An internal hydrogen target system was developed for the OLYMPUS experiment at DESY, in Hamburg, Germany. The target consisted of a long, thin-walled, tubular cell within an aluminum scattering chamber. Hydrogen entered at the center of the cell and exited through the ends, where it was removed from the beamline by a multistage pumping system. A cryogenic coldhead cooled the target cell to counteract heating from the beam and increase the density of hydrogen in the target. A fixed collimator protected the cell from synchrotron radiation and the beam halo. A series of wakefield suppressors reduced heating from beam wakefields. The target system was installed within the DORIS storage ring and was successfully operated during the course of the OLYMPUS experiment in 2012. Information on the design, fabrication, and performance of the target system is reported.

  1. [Microbiological corrosion of aluminum alloys].

    Science.gov (United States)

    Smirnov, V F; Belov, D V; Sokolova, T N; Kuzina, O V; Kartashov, V R

    2008-01-01

    Biological corrosion of ADO quality aluminum and aluminum-based construction materials (alloys V65, D16, and D16T) was studied. Thirteen microscopic fungus species and six bacterial species proved to be able to attack aluminum and its alloys. It was found that biocorrosion of metals by microscopic fungi and bacteria was mediated by certain exometabolites. Experiments on biocorrosion of the materials by the microscopic fungus Alternaria alternata, the most active biodegrader, demonstrated that the micromycete attack started with the appearance of exudate with pH 8-9 on end faces of the samples. PMID:18669265

  2. Data Clustering

    Science.gov (United States)

    Wagstaff, Kiri L.

    2012-03-01

    On obtaining a new data set, the researcher is immediately faced with the challenge of obtaining a high-level understanding from the observations. What does a typical item look like? What are the dominant trends? How many distinct groups are included in the data set, and how is each one characterized? Which observable values are common, and which rarely occur? Which items stand out as anomalies or outliers from the rest of the data? This challenge is exacerbated by the steady growth in data set size [11] as new instruments push into new frontiers of parameter space, via improvements in temporal, spatial, and spectral resolution, or by the desire to "fuse" observations from different modalities and instruments into a larger-picture understanding of the same underlying phenomenon. Data clustering algorithms provide a variety of solutions for this task. They can generate summaries, locate outliers, compress data, identify dense or sparse regions of feature space, and build data models. It is useful to note up front that "clusters" in this context refer to groups of items within some descriptive feature space, not (necessarily) to "galaxy clusters" which are dense regions in physical space. The goal of this chapter is to survey a variety of data clustering methods, with an eye toward their applicability to astronomical data analysis. In addition to improving the individual researcher’s understanding of a given data set, clustering has led directly to scientific advances, such as the discovery of new subclasses of stars [14] and gamma-ray bursts (GRBs) [38]. All clustering algorithms seek to identify groups within a data set that reflect some observed, quantifiable structure. Clustering is traditionally an unsupervised approach to data analysis, in the sense that it operates without any direct guidance about which items should be assigned to which clusters. There has been a recent trend in the clustering literature toward supporting semisupervised or constrained

  3. Hydrogen economy

    Energy Technology Data Exchange (ETDEWEB)

    Pahwa, P.K.; Pahwa, Gulshan Kumar

    2013-10-01

    In the future, our energy systems will need to be renewable and sustainable, efficient and cost-effective, convenient and safe. Hydrogen has been proposed as the perfect fuel for this future energy system. The availability of a reliable and cost-effective supply, safe and efficient storage, and convenient end use of hydrogen will be essential for a transition to a hydrogen economy. Research is being conducted throughout the world for the development of safe, cost-effective hydrogen production, storage, and end-use technologies that support and foster this transition. This book discusses hydrogen economy vis-a-vis sustainable development. It examines the link between development and energy, prospects of sustainable development, significance of hydrogen energy economy, and provides an authoritative and up-to-date scientific account of hydrogen generation, storage, transportation, and safety.

  4. Cluster Chemistry

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    @@ Cansisting of eight scientists from the State Key Laboratory of Physical Chemistry of Solid Surfaces and Xiamen University, this creative research group is devoted to the research of cluster chemistry and creation of nanomaterials.After three-year hard work, the group scored a series of encouraging progresses in synthesis of clusters with special structures, including novel fullerenes, fullerene-like metal cluster compounds as well as other related nanomaterials, and their properties study.

  5. Biomimetic hydrogen production

    Energy Technology Data Exchange (ETDEWEB)

    Krassen, Henning

    2009-05-15

    Hydrogenases catalyze the reduction of protons to molecular hydrogen with outstanding efficiency. An electrode surface which is covered with active hydrogenase molecules becomes a promising alternative to platinum for electrochemical hydrogen production. To immobilize the hydrogenase on the electrode, the gold surface was modified by heterobifunctional molecules. A thiol headgroup on one side allowed the binding to the gold surface and the formation of a self-assembled monolayer. The other side of the molecules provided a surface with a high affinity for the hydrogenase CrHydA1 from Chlamydomonas reinhardtii. With methylviologen as a soluble energy carrier, electrons were transferred from carboxy-terminated electrodes to CrHydA1 and conducted to the active site (H-cluster), where they reduce protons to molecular hydrogen. A combined approach of surface-enhanced infrared absorption spectroscopy, gas chromatography, and surface plasmon resonance allowed quantifying the hydrogen production on a molecular level. Hydrogen was produced with a rate of 85 mol H{sub 2} min{sup -1} mol{sup -1}. On a 1'- benzyl-4,4'-bipyridinum (BBP)-terminated surface, the electrons were mediated by the monolayer and no soluble electron carrier was necessary to achieve a comparable hydrogen production rate (approximately 50% of the former system). The hydrogen evolution potential was determined to be -335 mV for the BBP-bound hydrogenase and -290 mV for the hydrogenase which was immobilized on a carboxy-terminated mercaptopropionic acid SAM. Therefore, both systems significantly reduce the hydrogen production overpotential and allow electrochemical hydrogen production at an energy level which is close to the commercially applied platinum electrodes (hydrogen evolution potential of -270 mV). In order to couple hydrogen production and photosynthesis, photosystem I (PS1) from Synechocystis PCC 6803 and membrane-bound hydrogenase (MBH) from Ralstonia eutropha were bound to each other

  6. Chrome - Free Aluminum Coating System

    Science.gov (United States)

    Bailey, John H.; Gugel, Jeffrey D.

    2010-01-01

    This slide presentation concerns the program to qualify a chrome free coating for aluminum. The program was required due to findings by OSHA and EPA, that hexavalent chromium, used to mitigate corrosion in aerospace aluminum alloys, poses hazards for personnel. This qualification consisted of over 4,000 tests. The tests revealed that a move away from Cr+6, required a system rather than individual components and that the maximum corrosion protection required pretreatment, primer and topcoat.

  7. Refinement of Aluminum Thermal Chrome

    International Nuclear Information System (INIS)

    Refinement of aluminum thermal chrome of the X98.5 mark by a high-temperature annealing in high vacuum is explored experimentally. It is shown that at the temperature of annealing 1150 C during 1...6 hours the content of such interstitial impurity as nitrogen is essentially depressed in chrome, and also the content of aluminum and iron admixtures is noticeably moderated

  8. Anodized aluminum on LDEF

    Science.gov (United States)

    Golden, Johnny L.

    1993-01-01

    A compilation of reported analyses and results obtained for anodized aluminum flown on the Long Duration Exposure Facility (LDEF) was prepared. Chromic acid, sulfuric acid, and dyed sulfuric acid anodized surfaces were exposed to the space environment. The vast majority of the anodized surface on LDEF was chromic acid anodize because of its selection as a thermal control coating for use on the spacecraft primary structure, trays, tray clamps, and space end thermal covers. Reports indicate that the chromic acid anodize was stable in solar absorptance and thermal emittance, but that contamination effects caused increases in absorptance on surfaces exposed to low atomic oxygen fluences. There were some discrepancies, however, in that some chromic acid anodized specimens exhibited significant increases in absorptance. Sulfuric acid anodized surfaces also appeared stable, although very little surface area was available for evaluation. One type of dyed sulfuric acid anodize was assessed as an optical baffle coating and was observed to have improved infrared absorptance characteristics with exposure on LDEF.

  9. Compositional changes of Pd-Au bimetallic nanoclusters upon hydrogenation

    OpenAIRE

    Di Vece, M; Bals, S.; Verbeeck, J.; Lievens, P.; van Tendeloo, G.

    2009-01-01

    Changes in the size distribution and composition of bimetallic Pd-Au nanoclusters have been observed after hydrogen exposure. This effect is caused by hydrogen-induced Ostwald ripening whereby the hydrogen reduces the binding energy of the cluster atoms leading to their detachment from the cluster. The composition changes due to a difference in mobility of the detached palladium and gold atoms on the surface. Fast palladium atoms contribute to the formation of larger nanoclusters, while the s...

  10. Model Experiment of Thermal Runaway Reactions Using the Aluminum-Hydrochloric Acid Reaction

    Science.gov (United States)

    Kitabayashi, Suguru; Nakano, Masayoshi; Nishikawa, Kazuyuki; Koga, Nobuyoshi

    2016-01-01

    A laboratory exercise for the education of students about thermal runaway reactions based on the reaction between aluminum and hydrochloric acid as a model reaction is proposed. In the introductory part of the exercise, the induction period and subsequent thermal runaway behavior are evaluated via a simple observation of hydrogen gas evolution and…

  11. Electrical properties of aluminum-doped zinc oxide (AZO) nanoparticles synthesized by chemical vapor synthesis

    International Nuclear Information System (INIS)

    Aluminum-doped zinc oxide nanoparticles have been prepared by chemical vapor synthesis, which facilitates the incorporation of a higher percentage of dopant atoms, far above the thermodynamic solubility limit of aluminum. The electrical properties of aluminum-doped and undoped zinc oxide nanoparticles were investigated by impedance spectroscopy. The impedance is measured under hydrogen and synthetic air between 323 and 673 K. The measurements under hydrogen as well as under synthetic air show transport properties depending on temperature and doping level. Under hydrogen atmosphere, a decreasing conductivity with increasing dopant content is observed, which can be explained by enhanced scattering processes due to an increasing disorder in the nanocrystalline material. The temperature coefficient for the doped samples switches from positive temperature coefficient behavior to negative temperature coefficient behavior with increasing dopant concentration. In the presence of synthetic air, the conductivity firstly increases with increasing dopant content by six orders of magnitude. The origin of the increasing conductivity is the generation of free charge carriers upon dopant incorporation. It reaches its maximum at a concentration of 7.7% of aluminum, and drops for higher doping levels. In all cases, the conductivity under hydrogen is higher than under synthetic air and can be changed reversibly by changing the atmosphere.

  12. Cancer Clusters

    Science.gov (United States)

    ... of cancer. Cancer clusters can help scientists identify cancer-causing substances in the environment. For example, in the early 1970s, a cluster ... the area and time period over which the cancers were diagnosed. They also ask about specific environmental hazards or concerns in the affected area. If ...

  13. Clustering processes

    CERN Document Server

    Ryabko, Daniil

    2010-01-01

    The problem of clustering is considered, for the case when each data point is a sample generated by a stationary ergodic process. We propose a very natural asymptotic notion of consistency, and show that simple consistent algorithms exist, under most general non-parametric assumptions. The notion of consistency is as follows: two samples should be put into the same cluster if and only if they were generated by the same distribution. With this notion of consistency, clustering generalizes such classical statistical problems as homogeneity testing and process classification. We show that, for the case of a known number of clusters, consistency can be achieved under the only assumption that the joint distribution of the data is stationary ergodic (no parametric or Markovian assumptions, no assumptions of independence, neither between nor within the samples). If the number of clusters is unknown, consistency can be achieved under appropriate assumptions on the mixing rates of the processes. (again, no parametric ...

  14. Application of selective CVD tungsten for low contact resistance via filling to aluminum multilayer interconnection

    Science.gov (United States)

    Rang, S.; Chow, R.; Wilson, R. H.; Gorowitz, B.; Williams, A. G.

    1988-05-01

    Process parameters for selective chemical vapor deposition of tungsten to fill vias between aluminum or aluminum alloy multilevel metallization have been identified and demonstrated. By controlling two competing parallel reactions: Aluminum and hydrogen reductions of tungsten hexafluoride in one reduction step process, the specific contact resistivity was found to be in the range of 2.5 to 8.0 x 10-9 ohm-cm2 for 1.8 micron diameter vias. This is at least one order of magnitude lower than the values reported by the previous workers. It was also observed that alloying the aluminum did not appear to affect the contact resistance significantly. In this experiment one cold wall experimental reactor, two cold wall production systems of two different models and one hot wall tube furnace were used to deposit selective CVD tungsten on aluminum or aluminum with 1% silicon first level metal. As a consequence of these findings, problems associated with filling straight wall vias of high aspect ratio in VLSI multilevel interconnection (i.e., high contact resistance, poor step coverage, electromigration, etc.) can now be alleviated or resolved. Therefore, the use of selective CVD tungsten in the existing aluminum IC metallization becomes very attractive and feasible.

  15. A method to study the history of a double oxide film defect in liquid aluminum alloys

    Science.gov (United States)

    Raiszadeh, R.; Griffiths, W. D.

    2006-12-01

    Entrained double oxide films have been held responsible for reductions in mechanical properties in aluminum casting alloys. However, their behavior in the liquid metal, once formed, has not been studied directly. It has been proposed that the atmosphere entrapped in the double oxide film defect will continue to react with the liquid metal surrounding it, perhaps leading to its elimination as a significant defect. A silicon-nitride rod with a hole in one end was plunged into liquid aluminum to hold a known volume of air in contact with the liquid metal at a constant temperature. The change in the air volume with time was recorded by real-time X-ray radiography to determine the reaction rates of the trapped atmosphere with the liquid aluminum, creating a model for the behavior of an entrained double oxide film defect. The results from this experiment showed that first oxygen, and then nitrogen, was consumed by the aluminum alloy, to form aluminum oxide and aluminum nitride, respectively. The effect of adding different elements to the liquid aluminum and the effect of different hydrogen contents were also studied.

  16. Ultrafast Electron-Ion Dynamics Near Aluminum Surfaces

    Science.gov (United States)

    Schleife, Andre; Wells, Kai; Knewstub, Sam

    Computational physics and materials research have greatly benefited from high-performance computing; modern first-principles simulations allow insight with unprecedented accuracy and detail. Here we use a recent highly parallel implementation of Ehrenfest molecular dynamics based on real-time time-dependent density functional theory to describe non-adiabatic ultrafast electron-ion dynamics using accurate first-principles calculations. We investigate aluminum subject to highly energetic particle radiation (hydrogen projectile) and study energy deposition due to the fast projectiles. Their high velocity makes it necessary to overcome the Born-Oppenheimer approximation. Using our first-principles calculations we study the behavior of fast ions near the surface of aluminum slabs and investigate, for instance, the influence of velocity and impact angle of the projectile ion. From the emerging non-adiabatic electron-ion dynamics we gain insight into the material on an atto-second time scale.

  17. Why hydrogen

    International Nuclear Information System (INIS)

    The energy consumption increase and the associated environmental risks, led to develop new energy sources. The authors present the potentialities of the hydrogen in this context of energy supply safety. They detail the today market and the perspectives, the energy sources for the hydrogen production (fossils, nuclear and renewable), the hydrogen transport, storage, distribution and conversion, the application domains, the associated risks. (A.L.B.)

  18. Low-aluminum content iron-aluminum alloys

    Energy Technology Data Exchange (ETDEWEB)

    Sikka, V.K.; Goodwin, G.M.; Alexander, D.J. [and others

    1995-06-01

    The low-aluminum-content iron-aluminum program deals with the development of a Fe-Al alloy with aluminum content such as a produce the minimum environmental effect at room temperature. The FAPY is an Fe-16 at. % Al-based alloy developed at the Oak Ridge National Laboratory as the highest aluminum-containing alloy with essentially no environmental effect. The chemical composition for FAPY in weight percent is: aluminum = 8.46, chromium = 5.50, zirconium = 0.20, carbon = 0.03, molybdenum = 2.00, yttrium = 0.10 and iron = 83.71. The ignots of the alloy can be hot worked by extrusion, forging, and rolling processes. The hot-worked cast structure can be cold worked with intermediate anneals at 800{degrees}C. Typical room-temperature ductility of the fine-grained wrought structure is 20 to 25% for this alloy. In contrast to the wrought structure, the cast ductility at room temperature is approximately 1% with a transition temperature of approximately 100 to 150{degrees}C, above which ductility values exceed 20%. The alloy has been melted and processed into bar, sheet, and foil. The alloy has also been cast into slabs, step-blocks of varying thicknesses, and shapes. The purpose of this section is to describe the welding response of cast slabs of three different thicknesses of FAPY alloy. Tensile, creep, and Charpy-impact data of the welded plates are also presented.

  19. Hydrogen millennium

    International Nuclear Information System (INIS)

    The 10th Canadian Hydrogen Conference was held at the Hilton Hotel in Quebec City from May 28 to May 31, 2000. The topics discussed included current drivers for the hydrogen economy, the international response to these drivers, new initiatives, sustainable as well as biological and hydrocarbon-derived production of hydrogen, defense applications of fuel cells, hydrogen storage on metal hydrides and carbon nanostructures, stationary power and remote application, micro-fuel cells and portable applications, marketing aspects, fuel cell modeling, materials, safety, fuel cell vehicles and residential applications. (author)

  20. Gas evolution behavior of aluminum in mortar

    International Nuclear Information System (INIS)

    As a part of study of leaching behavior for solidified dry low level radioactive waste, gas evolution behavior of aluminum in mortar was investigated, and a plan of our research was proposed. The effect of pH on corrosion rate of aluminum, corrosion product, time dependency of corrosion rate of aluminum in mortar, change of corrosion mechanism, the effects of Na, Ca and Cl ions on corrosion rate of aluminum in mortar and corrosion behavior of aluminum when aluminum was used as sacrificed anode in reinforced concrete were previously clarified. Study of the effects of environmental factors such as pH, kind of ions and temperature on gas evolution behavior of aluminum and the effect of aluminum/carbon steel surface ratio no gas evolution behavior of aluminum were planed. (author). 75 refs

  1. Hydrogen generation from water and aluminum promoted by sodium stannate

    OpenAIRE

    Soler Turu, Lluis; Candela Soto, Angélica Maria; Macanás de Benito, Jorge; Muñoz Tapia, Maria; Casado Giménez, Juan

    2010-01-01

    A new process to obtain H2 from H2O using Al corrosion in Na2SnO3 solutions is described. Results showed an enhancement of H2 production rates using Na2SnO3 instead of NaOH at the same pH. A side reaction of Al in Na2SnO3 solutions has been found, which consumes Al to produce metallic Sn. H2 yield depends chiefly on Al/Na2SnO3 molar ratio for experiments with Na2SnO3 concentrations above 0.025 M, reaching higher yields with higher Al/Na2SnO3 ratios. The maximum H2 production rates are proport...

  2. Synthesis and formation process of Al2CuHx: A new class of interstitial aluminum-based alloy hydride

    Directory of Open Access Journals (Sweden)

    Hiroyuki Saitoh

    2013-09-01

    Full Text Available Aluminum-based alloy hydride Al2CuHx (x ∼ 1 is synthesized by hydrogenating Al2Cu alloy using high-temperature and high-pressure hydrogen atmosphere. Al8Cu square antiprisms in Al2Cu twist around the c axis of a tetragonal unit cell by hydrogenation. The twist enlarges the interstitial spaces for accommodating hydrogen atoms which align linearly parallel to the c axis in Al2CuHx. Thermodynamic stability of Al2CuHx results from the balance of stabilization by H 1s and Al 3sp hybridization and destabilization owing to the Fermi-level lifting upon hydrogenation. The crystal and electronic structures of Al2CuHx illustrate the formation of an interstitial hydride of aluminum-based alloy.

  3. The effects of surface treatment and stannate as an electrolyte additive on the corrosion and electrochemical performances of pure aluminum in an alkaline methanol-water solution

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, X.X. [Department of Chemistry, Zhejiang University, Zheda Road 38, Hangzhou 310027, Zhejiang (China); Wang, J.M., E-mail: wjm@zju.edu.cn [Department of Chemistry, Zhejiang University, Zheda Road 38, Hangzhou 310027, Zhejiang (China); Wang, Q.L.; Kong, D.S.; Shao, H.B. [Department of Chemistry, Zhejiang University, Zheda Road 38, Hangzhou 310027, Zhejiang (China); Zhang, J.Q.; Cao, C.N. [Department of Chemistry, Zhejiang University, Zheda Road 38, Hangzhou 310027, Zhejiang (China); State Key Laboratory for Corrosion and Protection of Metal, Institute of Metal Research, Chinese Academy of Sciences, 62 Wencui Road, Shenyang 110016 (China)

    2010-06-01

    Pure aluminum electrodes were treated in alkaline stannate solutions, and the effects of some factors such as NaOH content and treating time were explored. The corrosion and electrochemical performances of the modified aluminum anodes in 4.0 M KOH methanol-water mixed solutions containing a methanol/water volume ratio of 7:3 (30% water) with and without stannate were investigated by means of hydrogen collection, polarization curve, galvanostatic discharge, scanning electron microscopy (SEM), and energy dispersive analysis of X-ray (EDAX). Metallic tin with high hydrogen evolution overpotential was deposited in aluminum surfaces by the modification treatments using stannate, resulting in the relatively low corrosion rate and markedly enhanced discharge performance of the modified aluminum anodes. In our experimental range the aluminum electrode treated in the solution with 0.1 M NaOH for 30 min showed lower corrosion rate and better discharge performance. The addition of Na{sub 2}SnO{sub 3} in 4.0 M KOH methanol-water mixed solutions with 30% water inhibited the corrosion of the aluminum electrodes modified in the treating solution with 0.1 M NaOH for 30 min, resulting from the deposition of tin with high hydrogen evolution overpotential in aluminum surfaces. The deposition of metallic tin on the electrode surface and the existence of stannate in the electrolytes were responsible for the notable enhancement in the discharge performance of the modified aluminum anode.

  4. Rapid fabrication of aluminum nitride with high thermal conductivity by millimeter-wave heating method

    International Nuclear Information System (INIS)

    Full text: Aluminum nitride has been interested for the usage of heat-sink substrate in the semiconductor device on account of its high thermal conductivity. But aluminum nitride is not so easily sintered similarly as other nitrides. Polycrystalline bulk aluminum nitride is generally sintered by adding some sintering aids. However, high sintering temperature around 2000 deg C is still required for attaining full densification with the conventional sintering method. In the present study, we show millimeter-wave heating method is the rapid and low temperature process for producing aluminum nitride with high thermal conductivity. Importance in the selection of sintering aid is indicated in the millimeter-wave sintering of aluminum nitride. The relation between thermal conductivity and microstructure is also discussed. AlN powder with the average size of 1μm (Mitsui Kagaku, MAN-2) was used as the starting raw material and Y2O3 or Yb2O3 (Shin-etsu Kagaku, average size; 0.25μm and 1.2μm, UU- and RU-grades, respectively) were used as sintering aids, respectively. After mixing AlN powder and sintering aid at a desired content, the mixed powder with 1-propanol and dispersant was milled for 20 hr with alumina balls in an alumina pot. The milled powder was shaped to the circular disk with 40 mm in diameter and 4-5 mm in thickness by slip-casting method. After drying enough, the slip-casted body was calcined at 600 deg C for 1 h in nitrogen atmosphere. The calcined body was sintered in nitrogen without hydrogen or with several % hydrogen by using millimeter-wave heating method. Millimeter-wave heating was performed in a multi-mode applicator (Fuji Denpa Kogyo, FGS-10-28) combined with a high power 28 GHz gyrotron generator. Density of sintered body was calculated from measured size and weight, and when the relative density was over 90%, the precise density was measured by Archimedean method using oleic acid as immersion liquid. Thermal conductivity of sintered body was

  5. Thin films of aluminum nitride and aluminum gallium nitride for cold cathode applications

    Science.gov (United States)

    Sowers, A. T.; Christman, J. A.; Bremser, M. D.; Ward, B. L.; Davis, R. F.; Nemanich, R. J.

    1997-10-01

    Cold cathode structures have been fabricated using AlN and graded AlGaN structures (deposited on n-type 6H-SiC) as the thin film emitting layer. The cathodes consist of an aluminum grid layer separated from the nitride layer by a SiO2 layer and etched to form arrays of either 1, 3, or 5 μm holes through which the emitting nitride surface is exposed. After fabrication, a hydrogen plasma exposure was employed to activate the cathodes. Cathode devices with 5 μm holes displayed emission for up to 30 min before failing. Maximum emission currents ranged from 10-100 nA and required grid voltages ranging from 20-110 V. The grid currents were typically 1 to 104 times the collector currents.

  6. Clustering analysis

    International Nuclear Information System (INIS)

    Cluster analysis is the name of group of multivariate techniques whose principal purpose is to distinguish similar entities from the characteristics they process.To study this analysis, there are several algorithms that can be used. Therefore, this topic focuses to discuss the algorithms, such as, similarity measures, and hierarchical clustering which includes single linkage, complete linkage and average linkage method. also, non-hierarchical clustering method, which is popular name K-mean method' will be discussed. Finally, this paper will be described the advantages and disadvantages of every methods

  7. Cluster editing

    DEFF Research Database (Denmark)

    Böcker, S.; Baumbach, Jan

    2013-01-01

    The Cluster Editing problem asks to transform a graph into a disjoint union of cliques using a minimum number of edge modifications. Although the problem has been proven NP-complete several times, it has nevertheless attracted much research both from the theoretical and the applied side. The...... algorithms for biological problems. © 2013 Springer-Verlag....... problem has been the inspiration for numerous algorithms in bioinformatics, aiming at clustering entities such as genes, proteins, phenotypes, or patients. In this paper, we review exact and heuristic methods that have been proposed for the Cluster Editing problem, and also applications of these...

  8. Cluster analysis

    CERN Document Server

    Everitt, Brian S; Leese, Morven; Stahl, Daniel

    2011-01-01

    Cluster analysis comprises a range of methods for classifying multivariate data into subgroups. By organizing multivariate data into such subgroups, clustering can help reveal the characteristics of any structure or patterns present. These techniques have proven useful in a wide range of areas such as medicine, psychology, market research and bioinformatics.This fifth edition of the highly successful Cluster Analysis includes coverage of the latest developments in the field and a new chapter dealing with finite mixture models for structured data.Real life examples are used throughout to demons

  9. Scaleable Clean Aluminum Melting Systems

    Energy Technology Data Exchange (ETDEWEB)

    Han, Q.; Das, S.K. (Secat, Inc.)

    2008-02-15

    The project entitled 'Scaleable Clean Aluminum Melting Systems' was a Cooperative Research and Development Agreements (CRADAs) between Oak Ridge National Laboratory (ORNL) and Secat Inc. The three-year project was initially funded for the first year and was then canceled due to funding cuts at the DOE headquarters. The limited funds allowed the research team to visit industrial sites and investigate the status of using immersion heaters for aluminum melting applications. Primary concepts were proposed on the design of furnaces using immersion heaters for melting. The proposed project can continue if the funding agency resumes the funds to this research. The objective of this project was to develop and demonstrate integrated, retrofitable technologies for clean melting systems for aluminum in both the Metal Casting and integrated aluminum processing industries. The scope focused on immersion heating coupled with metal circulation systems that provide significant opportunity for energy savings as well as reduction of melt loss in the form of dross. The project aimed at the development and integration of technologies that would enable significant reduction in the energy consumption and environmental impacts of melting aluminum through substitution of immersion heating for the conventional radiant burner methods used in reverberatory furnaces. Specifically, the program would couple heater improvements with furnace modeling that would enable cost-effective retrofits to a range of existing furnace sizes, reducing the economic barrier to application.

  10. Spitzer Clusters

    Science.gov (United States)

    Krick, Kessica

    This proposal is a specific response to the strategic goal of NASA's research program to "discover how the universe works and explore how the universe evolved into its present form." Towards this goal, we propose to mine the Spitzer archive for all observations of galaxy groups and clusters for the purpose of studying galaxy evolution in clusters, contamination rates for Sunyaev Zeldovich cluster surveys, and to provide a database of Spitzer observed clusters to the broader community. Funding from this proposal will go towards two years of support for a Postdoc to do this work. After searching the Spitzer Heritage Archive, we have found 194 unique galaxy groups and clusters that have data from both the Infrared array camera (IRAC; Fazio et al. 2004) at 3.6 - 8 microns and the multiband imaging photometer for Spitzer (MIPS; Rieke et al. 2004) at 24microns. This large sample will add value beyond the individual datasets because it will be a larger sample of IR clusters than ever before and will have sufficient diversity in mass, redshift, and dynamical state to allow us to differentiate amongst the effects of these cluster properties. An infrared sample is important because it is unaffected by dust extinction while at the same time is an excellent measure of both stellar mass (IRAC wavelengths) and star formation rate (MIPS wavelengths). Additionally, IRAC can be used to differentiate star forming galaxies (SFG) from active galactic nuclei (AGN), due to their different spectral shapes in this wavelength regime. Specifically, we intend to identify SFG and AGN in galaxy groups and clusters. Groups and clusters differ from the field because the galaxy densities are higher, there is a large potential well due mainly to the mass of the dark matter, and there is hot X-ray gas (the intracluster medium; ICM). We will examine the impact of these differences in environment on galaxy formation by comparing cluster properties of AGN and SFG to those in the field. Also, we will

  11. Hydrogen generation by aluminum corrosion in seawater promoted by suspensions of aluminum hydroxide

    Energy Technology Data Exchange (ETDEWEB)

    Soler, Lluis; Candela, Angelica Maria; Macanas, Jorge; Munoz, Maria; Casado, Juan [Centre Grup de Tecniques de Separacio en Quimica (GTS), Unitat de Quimica Analitica, Departament de Quimica, Universitat Autonoma de Barcelona, Edifici C - Campus de la UAB s/n, 08193 Bellaterra, Barcelona, Catalonia (Spain)

    2009-10-15

    Nowadays, new processes of H{sub 2} generation from water via Al corrosion are mainly limited by Al passivation. Here we report on the systematic assessment of H{sub 2} production by corrosion of Al in seawater suspensions prepared with NaAlO{sub 2}. The reported results are encouraging, since it was observed that seawater suspensions tested can prevent Al passivation during H{sub 2} evolution, reaching 100% yields at ca. 700 cm{sup 3} H{sub 2} min{sup -1}. XRD analysis revealed the formation of solid Al(OH){sub 3} (bayerite) in initial seawater suspensions. So, model suspensions were prepared using NaAlO{sub 2} + Al(OH){sub 3} in distilled water, which even improved the results obtained in seawater. Suspended particles of Al(OH){sub 3} act as nuclei in a mechanism of seeded crystallization, which prevents Al surface passivation. Moreover, a synergistic effect of Al(OH){sub 3} suspensions in combination with NaAlO{sub 2} solutions was key in promoting Al corrosion. The effect of NaCl in aqueous suspensions was also studied, but it was insignificant compared to this synergistic effect. The composition of suspensions was optimized and a 0.01 M NaAlO{sub 2} solution with 20 g dm{sup -3} Al(OH){sub 3} was selected as candidate to generate H{sub 2} at pH ca. 12 with high efficiency. Consecutive runs of the selected composition were performed obtaining ca. 90% yields in all of them. (author)

  12. Use of Hydrogen Peroxide to Disinfect Hydroponic Plant Growth Systems

    Science.gov (United States)

    Barta, Daniel J.; Henderson, Keith

    2000-01-01

    Hydrogen peroxide was studied as an alternative to conventional bleach and rinsing methods to disinfect hydroponic plant growth systems. A concentration of 0.5% hydrogen peroxide was found to be effective. Residual hydrogen peroxide can be removed from the system by repeated rinsing or by flowing the solution through a platinum on aluminum catalyst. Microbial populations were reduced to near zero immediately after treatment but returned to pre-disinfection levels 2 days after treatment. Treating nutrient solution with hydrogen peroxide and planting directly into trays being watered with the nutrient solution without replenishment, was found to be detrimental to lettuce germination and growth.

  13. Cluster Bulleticity

    OpenAIRE

    Massey, Richard; Kitching, Thomas D.; Nagai, Daisuke

    2010-01-01

    The unique properties of dark matter are revealed during collisions between clusters of galaxies, like the bullet cluster (1E 0657-56) and baby bullet (MACSJ0025-12). These systems provide evidence for an additional, invisible mass in the separation between the distribution of their total mass, measured via gravitational lensing, and their ordinary 'baryonic' matter, measured via its X-ray emission. Unfortunately, the information available from these systems is limited by th...

  14. Cluster Bulleticity

    OpenAIRE

    Massey, R; Kitching, T.; Nagai, D.

    2010-01-01

    The unique properties of dark matter are revealed during collisions between clusters of galaxies, such as the bullet cluster (1E 0657−56) and baby bullet (MACS J0025−12). These systems provide evidence for an additional, invisible mass in the separation between the distributions of their total mass, measured via gravitational lensing, and their ordinary ‘baryonic’ matter, measured via its X-ray emission. Unfortunately, the information available from these systems is limited by their rarity. C...

  15. Cluster generator

    Science.gov (United States)

    Donchev, Todor I.; Petrov, Ivan G.

    2011-05-31

    Described herein is an apparatus and a method for producing atom clusters based on a gas discharge within a hollow cathode. The hollow cathode includes one or more walls. The one or more walls define a sputtering chamber within the hollow cathode and include a material to be sputtered. A hollow anode is positioned at an end of the sputtering chamber, and atom clusters are formed when a gas discharge is generated between the hollow anode and the hollow cathode.

  16. Experimental studies of thermal and chemical interactions between molten aluminum and nuclear dispersion fuels with water

    International Nuclear Information System (INIS)

    Because of the possibility of rapid physical and chemical molten fuel-water interactions during a core melt accident in noncommercial or experimental reactors, it is important to understand the interactions that might occur if these materials were to contact water. An existing vertical 1-D shock tube facility was improved and a gas sampling device to measure the gaseous hydrogen in the upper chamber of the shock tube was designed and built to study the impact of a water column driven downward by a pressurized gas onto both molten aluminum (6061 alloy) and oxide and silicide depleted nuclear dispersion fuels in aluminum matrices. The experiments were carried out with melt temperatures initially at 750 to 1,000 C and water at room temperature and driving pressures of 0.5 and 1 MPa. Very high transient pressures, in many cases even larger than the thermodynamic critical pressure of the water (∼ 20 MPa), were generated due to the interactions between the water and the crucible and its contents. The molten aluminum always reacted chemically with the water but the reaction did not increase consistently with increasing melt temperature. An aluminum ignition occurred when water at room temperature impacted 28.48 grams of molten aluminum at 980.3 C causing transient pressures greater than 69 MPa. No signs of aluminum ignition were observed in any of the experiments with the depleted nuclear dispersion fuels, U3O8-Al and U3Si2-Al. The greater was the molten aluminum-water chemical reaction, the finer was the debris recovered for a given set of initial conditions. Larger coolant velocities (larger driving pressures) resulted in more melt fragmentation but did not result in more molten aluminum-water chemical reaction. Decreasing the water temperature also resulted in more melt fragmentation and did not suppress the molten aluminum-water chemical reaction

  17. SCALEUP OF ALUMINUM PHOSPHATE CATALYST FOR PILOT PLANT LPDMEtm RUN

    Energy Technology Data Exchange (ETDEWEB)

    Andrew W. Wang

    2002-01-01

    The Liquid Phase Dimethyl Ether (LPDME{trademark}) process converts synthesis gas to dimethyl ether in a single slurry bubble column reactor. A mixed slurry of methanol synthesis catalyst and methanol dehydration catalyst in a neutral mineral oil simultaneously synthesizes methanol from syngas and converts some of it to dimethyl ether and water. The reaction scheme is shown below: 2H{sub 2} + CO = CH{sub 3}OH; 2CH{sub 3}OH = CH{sub 3}OCH{sub 3} + H{sub 2}O; H{sub 2}O + CO = CO{sub 2} + H{sub 2}. Most of the water produced in this reaction is converted to hydrogen by reduction with carbon monoxide (water gas shift reaction). This synergy permits higher per pass conversion than methanol synthesis alone. The enhancement in conversion occurs because dehydration of the methanol circumvents the equilibrium constraint of the syngas-to-methanol step. The slurry bubble column reactor provides the necessary heat transfer capacity to handle the greater heat duty associated with high conversion. In order to improve the stability of the catalyst system, non-stoichiometric aluminum phosphate was proposed as the dehydration catalyst for the LPDME{trademark} process. This aluminum phosphate material is a proprietary catalyst. This catalyst system of a standard methanol catalyst and the aluminum phosphate provided stable process performance that met the program targets under our standard test process conditions in the laboratory. These targets are (1) an initial methanol equivalent productivity of 28 gmol/kg/hr, (2) a CO{sub 2}-free, carbon selectivity of 80% to dimethyl ether and (3) stability of both catalysts equivalent to that of the methanol catalyst in the absence of the aluminum phosphate. A pilot plant trial of the LPDME{trademark} process using the aluminum phosphate catalyst was originally planned for March 1998 at the DOE-owned, Air Products (APCI)-operated facility at LaPorte, Texas. Because the aluminum phosphate catalyst is not commercially available, we initiated a

  18. SCALEUP OF ALUMINUM PHOSPHATE CATALYST FOR PILOT PLANT LPDMEtm RUN

    Energy Technology Data Exchange (ETDEWEB)

    Andrew W. Wang

    2002-05-15

    The Liquid Phase Dimethyl Ether (LPDME{trademark}) process converts synthesis gas to dimethyl ether in a single slurry bubble column reactor. A mixed slurry of methanol synthesis catalyst and methanol dehydration catalyst in a neutral mineral oil simultaneously synthesizes methanol from syngas and converts some of it to dimethyl ether and water. The reaction scheme is: 2H{sub 2} + CO = CH{sub 3}OH 2CH{sub 3}OH = CH{sub 3}OCH{sub 3} + H{sub 2}O H{sub 2}O + CO = CO{sub 2} + H{sub 2}. Most of the water produced in this reaction is converted to hydrogen by reduction with carbon monoxide (water gas shift reaction). This synergy permits higher per pass conversion than methanol synthesis alone. The enhancement in conversion occurs because dehydration of the methanol circumvents the equilibrium constraint of the syngas-to-methanol step. The slurry bubble column reactor provides the necessary heat transfer capacity to handle the greater heat duty associated with high conversion. In order to improve the stability of the catalyst system, non-stoichiometric aluminum phosphate was proposed as the dehydration catalyst for the LPDME{trademark} process. This aluminum phosphate material is a proprietary catalyst. This catalyst system of a standard methanol catalyst and the aluminum phosphate provided stable process performance that met the program targets under our standard test process conditions in the laboratory. These targets are (1) an initial methanol equivalent productivity of 28 gmol/kg/hr, (2) a CO{sub 2}-free, carbon selectivity of 80% to dimethyl ether and (3) stability of both catalysts equivalent to that of the methanol catalyst in the absence of the aluminum phosphate. A pilot plant trial of the LPDME{trademark} process using the aluminum phosphate catalyst was originally planned for March 1998 at the DOE-owned, Air Products (APCI)-operated facility at LaPorte, Texas. Because the aluminum phosphate catalyst is not commercially available, we initiated a scaleup project

  19. Recrystallization in Commercially Pure Aluminum

    DEFF Research Database (Denmark)

    Bay, Bent; Hansen, Niels

    1984-01-01

    Recrystallization behavior in commercial aluminum with a purity of 99.4 pct was studied by techniques such as high voltage electron microscopy, 100 kV transmission electron microscopy, and light microscopy. Sample parameters were the initial grain size (290 and 24 microns) and the degree of...... are discussed and compared with results from an earlier study1 covering the recrystallization behavior of commercial aluminum of the same purity deformed at higher degrees of deformation (50 to 90 pct reduction in thickness by cold-rolling)....

  20. Baise to Build Ecological Aluminum Industry Base

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    <正>The government of Baise announced the construction of an ecological aluminum industry base over the next few years,pledging to turn the city into a major aluminum industry base in China and the rest of Asia.

  1. Decreasing residual aluminum level in drinking water

    Institute of Scientific and Technical Information of China (English)

    王志红; 崔福义

    2004-01-01

    The relativity of coagulant dosage, residual turbidity, temperature, pH etc. with residual aluminum concentration were investigated, and several important conclusions were achieved. Firstly, dosage of alum-coagulant or PAC1 influences residual aluminum concentration greatly. There is an optimal-dosage-to-aluminum, a bit less than the optimal-dosage-to-turbidity. Secondly, it proposes that decreasing residual aluminum concentration can be theoretically divided into two methods, either decreasing (even removing) the concentration of particulate aluminum component, or decreasing dissolved aluminum. In these tests there is an optimal value of residual turbidity of postprecipitation at 7.0 NTU. Thirdly, residual aluminum level will increase while water temperature goes higher. At the last, optimal pH value corresponds a minimum dissolved aluminum at a given turbidity. Data shows the optimal pH value decreases with water temperature's increasing.

  2. Experimental studies of the chemistry of metal clusters

    International Nuclear Information System (INIS)

    The procedures for studying chemical reactions of metal clusters in a continuous-flow reactor are described, and examples of such studies are given. Experiments to be discussed include kinetics and thermodynamics measurements, and determination of the composition of clusters saturated with various adsorbate reagents. Specific systems to be covered include the reaction of iron clusters with ammonia and with hydrogen, the reaction of nickel clusters with hydrogen and with ammonia, and the reaction of platinum clusters with ethylene. The last two reactions are characterized by complex, multi-step processes that lead to adsorbate decomposition and hydrogen desorption from the clusters. Methods for probing these processes will be discussed. 26 refs., 8 figs

  3. Ground state structures and properties of Si3H ( = 1–6) clusters

    Indian Academy of Sciences (India)

    D Balamurugan; R Prasad

    2003-01-01

    The ground state structures and properties of Si3H (1 ≤ ≤ 6) clusters have been calculated using Car–Parrinello molecular dynamics with simulated annealing and steepest descent optimization methods. We have studied cohesive energy per particle and first excited electronic level gap of the clusters as a function of hydrogenation. Hydrogenation is done till all dangling bonds of silicon are saturated. Our results show that over coordination of hydrogen is favoured in Si3H clusters and the geometry of Si3 cluster does not change due to hydrogenation. Cohesive energy per particle and first excited electronic level gap study of the clusters show that Si3H6 cluster is most stable and Si3H3 cluster is most unstable among the clusters considered here.

  4. 75 FR 70689 - Kaiser Aluminum Fabricated Products, LLC; Kaiser Aluminum-Greenwood Forge Division; Currently...

    Science.gov (United States)

    2010-11-18

    ... in the Federal Register on November 17, 2009 (74 FR 59254). At the request of the State agency and a... Employment and Training Administration Kaiser Aluminum Fabricated Products, LLC; Kaiser Aluminum- Greenwood... Aluminum Fabricated Products, LLC, Kaiser Aluminum-Greenwood Forge Division, including on- site...

  5. Studies of a granular aluminum anode in an alkaline fuel cell

    Science.gov (United States)

    Popovich, Neil A.; Govind, Rakesh

    A granular aluminum anode was investigated for use in an alkaline aluminum/hydrogen peroxide fuel cell. The fuel cell utilizes granules of aluminum (8-12 mm in diameter) as an anode, potassium hydroxide (KOH) as an anolyte and hydrogen peroxide as a catholyte. Granular anodes have a significantly higher surface area than planar surfaces, thereby resulting in higher utilization of the anode material. Polarization experiments were performed as well as closed circuit power production experiments. KOH concentrations were varied in the experiments. Polarization experiments achieved a current density of 10.02 mA/cm 2 using 2 M KOH and granular aluminum with a surface area of 205.6 cm 2. Power production experiments sustained a current density of 0.05 mA/cm 2 using 1.5 M KOH and granular aluminum with a surface area of 59.8 cm 2. Results indicate that granular metal anodes have potential for use in high energy density fuel cells.

  6. Corrosion and electrochemical behaviors of pure aluminum in novel KOH-ionic liquid-water solutions

    Energy Technology Data Exchange (ETDEWEB)

    Wang, J.M.; Wang, J.B.; Shao, H.B.; Zeng, X.X. [Department of Chemistry, Zhejiang University, Hangzhou 310027, (China); Zhang, J.Q.; Cao, C.N. [Department of Chemistry, Zhejiang University, Hangzhou 310027, (China); State Key Laboratory for Corrosion and Protection of Metal, Institute of Metal Research, Chinese Academy of Sciences, 62 Wencui Road, Shenyang 110016, (China)

    2009-12-15

    The corrosion and electrochemical behaviors of pure aluminum in KOH-ionic liquid-water solutions with variable volume ratios of water and the ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate (BMIMBF{sub 4}) were for the first time investigated by means of hydrogen collection, polarization curve, galvanostatic discharge, and electrochemical impedance spectroscopy (EIS). The results of hydrogen collection experiments showed that aluminum has a low corrosion rate in KOH-BMIMBF{sub 4}-H{sub 2}O solutions, and the corrosion rate decreases with increase in BMIMBF{sub 4} content in the electrolytes. The results of electrochemical experiments revealed that aluminum is electrochemically active over a very wide potential window in the KOH-BMIMBF{sub 4}-H{sub 2}O solutions, and its electrochemically kinetic mechanism is similar to that in the corresponding aqueous solution; the increase in KOH and water contents in the electrolytes may improve the anodic dissolution performance of aluminum. It was found that aluminum presents excellent galvanostatic discharge performance in the 2.0 M KOH BMIMBF{sub 4}-H{sub 2}O mixed solution with 60% water. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  7. Effect of LiNO3 on corrosion prevention of aluminum wastes after their land disposal

    International Nuclear Information System (INIS)

    After their land disposal, LiNO3 added to cement solidified miscellaneous wastes inhibits hydrogen gas generation due to alkaline corrosion of aluminum contained in the wastes. We considered the presence of an Li-Al preservation film prevents hydrogen gas generation, and then, we assumed a scenario in which the amount of LiNO3 included in the waste packages is lowered by underground water penetration, resulting in dissolution of the Li-Al preservation film. This dissolution allows the alkaline underground water to reach and corrode the aluminum materials. The loss of Na2O and K2O in cement by underground water penetration lowers the pH, so that the aluminum corrosion in the waste packages with LiNO3, expected when the Li-Al preservation film dissolves, is less than that without LiNO3. To test this scenario, we measured solubility of the Li-Al preservation film, Li+ ion concentration, pH variation by underground water penetration, and aluminum corrosion when the Li-Al preservation film had dissolved. The measured solubility of the Li-Al preservation film was 3x10-4 M at 283 K. At that time, pH was lowered from 12.9-13.0 to 12.2-12.3. As a result, with LiNO3 addition the aluminum corrosion amount was reduced to 10% of that without LiNO3 addition, because of the pH decrease. (author)

  8. Electrochemical Behavior of Aluminum in Nitric Acid

    Institute of Scientific and Technical Information of China (English)

    CHEN; Hui; ZHU; Li-yang; LIN; Ru-shan; TAN; Hong-bin; HE; Hui

    2013-01-01

    Aluminum is one of cladding materials for nuclear fuel,it is important to investigate the electrolytic dissolution of aluminum in nitric acid.The electrochemical impedance spectroscopy,polarization curve and cyclic voltammetry cure of anodic aluminum electrode in nitric acid under various conditions were collected(Fig.1).It turns out,under steady state,the thickness of the passivated film of aluminum

  9. Mineral resource of the month: aluminum

    Science.gov (United States)

    Bray, E. Lee

    2012-01-01

    The article offers information on aluminum, a mineral resource which is described as the third-most abundant element in Earth's crust. According to the article, aluminum is the second-most used metal. Hans Christian Oersted, a Danish chemist, was the first to isolate aluminum in the laboratory. Aluminum is described as lightweight, corrosion-resistant and an excellent conductor of electricity and heat.

  10. Evaluation of Aluminum in Iranian Consumed Tea

    OpenAIRE

    Alireza Asgari; Mahdi Ahmadi Moghaddam; Amirhossein Mahvi; Masoud Yonesian

    2008-01-01

    Introduction: Black tea leaf is one of the most important sources of Aluminum in dietary. Therefore this research was conducted to assess the amount of Aluminum in Iranian tea infusion. Methods: To assess Aluminum in Iranian consumed tea, 27 tea samples were analyzed for Al concentration for 10 and 60 min infusion, aluminum concentration was measured with atomic absorption and the results were analyzed by SPSS.13 version. Results: The results showed that minimum and maximum concentration of A...

  11. Interplay between experiments and calculations for organometallic clusters and caged clusters

    International Nuclear Information System (INIS)

    Clusters consisting of 10-1000 atoms exhibit size-dependent electronic and geometric properties. In particular, composite clusters consisting of several elements and/or components provide a promising way for a bottom-up approach for designing functional advanced materials, because the functionality of the composite clusters can be optimized not only by the cluster size but also by their compositions. In the formation of composite clusters, their geometric symmetry and dimensionality are emphasized to control the physical and chemical properties, because selective and anisotropic enhancements for optical, chemical, and magnetic properties can be expected. Organometallic clusters and caged clusters are demonstrated as a representative example of designing the functionality of the composite clusters. Organometallic vanadium-benzene forms a one dimensional sandwich structure showing ferromagnetic behaviors and anomalously large HOMO-LUMO gap differences of two spin orbitals, which can be regarded as spin-filter components for cluster-based spintronic devices. Caged clusters of aluminum (Al) are well stabilized both geometrically and electronically at Al12X, behaving as a “superatom”

  12. Interplay between experiments and calculations for organometallic clusters and caged clusters

    Science.gov (United States)

    Nakajima, Atsushi

    2015-12-01

    Clusters consisting of 10-1000 atoms exhibit size-dependent electronic and geometric properties. In particular, composite clusters consisting of several elements and/or components provide a promising way for a bottom-up approach for designing functional advanced materials, because the functionality of the composite clusters can be optimized not only by the cluster size but also by their compositions. In the formation of composite clusters, their geometric symmetry and dimensionality are emphasized to control the physical and chemical properties, because selective and anisotropic enhancements for optical, chemical, and magnetic properties can be expected. Organometallic clusters and caged clusters are demonstrated as a representative example of designing the functionality of the composite clusters. Organometallic vanadium-benzene forms a one dimensional sandwich structure showing ferromagnetic behaviors and anomalously large HOMO-LUMO gap differences of two spin orbitals, which can be regarded as spin-filter components for cluster-based spintronic devices. Caged clusters of aluminum (Al) are well stabilized both geometrically and electronically at Al12X, behaving as a "superatom".

  13. Interplay between experiments and calculations for organometallic clusters and caged clusters

    Energy Technology Data Exchange (ETDEWEB)

    Nakajima, Atsushi [Department of Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Yokohama 223-8522 (Japan); Nakajima Designer Nanocluster Assembly Project, ERATO, JST, KSP, 3-2-1 Sakado, Kawasaki 213-0012 (Japan); Keio Institute of Pure and Applied Sciences (KiPAS), Keio University, 3-14-1 Hiyoshi, Yokohama 223-8522 (Japan)

    2015-12-31

    Clusters consisting of 10-1000 atoms exhibit size-dependent electronic and geometric properties. In particular, composite clusters consisting of several elements and/or components provide a promising way for a bottom-up approach for designing functional advanced materials, because the functionality of the composite clusters can be optimized not only by the cluster size but also by their compositions. In the formation of composite clusters, their geometric symmetry and dimensionality are emphasized to control the physical and chemical properties, because selective and anisotropic enhancements for optical, chemical, and magnetic properties can be expected. Organometallic clusters and caged clusters are demonstrated as a representative example of designing the functionality of the composite clusters. Organometallic vanadium-benzene forms a one dimensional sandwich structure showing ferromagnetic behaviors and anomalously large HOMO-LUMO gap differences of two spin orbitals, which can be regarded as spin-filter components for cluster-based spintronic devices. Caged clusters of aluminum (Al) are well stabilized both geometrically and electronically at Al{sub 12}X, behaving as a “superatom”.

  14. Hydrogen permeation through plasma facing materials

    International Nuclear Information System (INIS)

    An electrical analog approach was applied to calculate hydrogen permeation flux in simultaneous gas-driven permeation (GDP) and plasma-driven permeation (PDP) for various materials such as beryllium, tungsten, molybdenum, copper, SS316, vanadium, titanium, nickel and aluminum. Permeation sources were developed to distinguish between GDP and PDP, and two transport parameters were used to discriminate further among four regimes in PDP. (author)

  15. Guangxi Aluminum Giant Made Investment in Changfeng

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    <正>A aluminum processing and supporting project (450,000 tons) of Hefei Guangyin Aluminum Company kicked off in Xiatang Town of Changfeng County recently. It is a project jointly invested by Guangxi Investment Group and Guangxi Baise Guangyin Aluminum in Xiatang Town of Changfeng County.

  16. 21 CFR 172.310 - Aluminum nicotinate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Aluminum nicotinate. 172.310 Section 172.310 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Special Dietary and Nutritional Additives § 172.310 Aluminum nicotinate. Aluminum nicotinate may be...

  17. 21 CFR 73.2645 - Aluminum powder.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Aluminum powder. 73.2645 Section 73.2645 Food and... ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2645 Aluminum powder. (a) Identity and specifications. The color additive aluminum powder shall conform in identity and specifications to the requirements...

  18. 21 CFR 182.1125 - Aluminum sulfate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Aluminum sulfate. 182.1125 Section 182.1125 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Substances § 182.1125 Aluminum sulfate. (a) Product. Aluminum sulfate. (b) Conditions of use. This...

  19. 21 CFR 582.1125 - Aluminum sulfate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Aluminum sulfate. 582.1125 Section 582.1125 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1125 Aluminum sulfate. (a) Product. Aluminum sulfate. (b) Conditions of use. This...

  20. 75 FR 80527 - Aluminum Extrusions From China

    Science.gov (United States)

    2010-12-22

    ... Affirmative Countervailing Duty Determination, 75 FR 54302, September 7, 2010, and Aluminum Extrusions From... Antidumping Duty Determination, 75 FR 57441, September 21, 2010. \\3\\ See Aluminum Extrusions From the People's... Determination of Targeted Dumping, 75 FR 69403, November 12, 2010, and Aluminum Extrusions From the...

  1. Direct current-induced electrogenerated chemiluminescence of hydrated and chelated Tb(III) at aluminum cathodes

    International Nuclear Information System (INIS)

    Cathodic DC polarization of oxide-covered aluminum produces electrogenerated chemiluminescence from hydrated and chelated Tb(III) ions in aqueous electrolyte solutions. At the moment of cathodic voltage onset, a strong cathodic flash is observed, which is attributed to a tunnel emission of hot electrons into the aqueous electrolyte solution and the successive chemical reactions with the luminophores. However, within a few milliseconds the insulating oxide film is damaged and finally dissolved due to (i) indiffusion of protons or alkali metal ions into the thin oxide film, (ii) subsequent hydrogen evolution at the aluminum/oxide interface and (iii) alkalization of the electrode surface induced by hydrogen evolution reaction. When the alkalization of the electrode surface has proceeded sufficiently, chemiluminescence is generated with increasing intensity. Aluminum metal, short-lived Al(II), Al(I) or atomic hydrogen and its conjugated base form, hydrated electron, can act as highly reducing species in addition to the less energetic heterogeneously transferred electrons from the aluminum electrode. Tb(III) added as a hydrated ion in the solution probably luminesces in the form of Tb(OH)3 or Tb(OH)4- by direct redox reactions of the central ion whereas multidentate aromatic ligand chelated Tb(III) probably luminesces by ligand sensitized chemiluminescence mechanism in which ligand is first excited by one-electron redox reactions, which is followed by intramolecular energy transfer to the central ion which finally emits light

  2. Indication of a size-dependent transition from molecular to dissociative chemisorption on clusters

    OpenAIRE

    Burkart, Stefan; Blessing, Nico; Ganteför, Gerd

    1999-01-01

    We report experimental indications for a size-dependent change of the chemical nature of chemisorption on small atomic clusters. We studied chemisorption of atomic hydrogen on negatively charged Tin- clusters using mass and photoelectron spectroscopy. Our experimental data support the assumption that for clusters with up to four Ti atoms, adsorption of intact H2 molecules is the energetically preferred configuration. For larger Tin clusters with n>4, dissociative hydrogen chemisorption is the...

  3. Denominators of cluster variables

    OpenAIRE

    Buan, Aslak Bakke; Marsh, Robert J.; Reiten, Idun

    2007-01-01

    Associated to any acyclic cluster algebra is a corresponding triangulated category known as the cluster category. It is known that there is a one-to-one correspondence between cluster variables in the cluster algebra and exceptional indecomposable objects in the cluster category inducing a correspondence between clusters and cluster-tilting objects. Fix a cluster-tilting object T and a corresponding initial cluster. By the Laurent phenomenon, every cluster variable can be written as a Laurent...

  4. Characterization of ultrafine aluminum nanoparticles

    International Nuclear Information System (INIS)

    Aluminum nanopowders with particle sizes ranging from ∼25 nm to 80 nm were characterized by a variety of methods. We present and compare the results from common powder characterization techniques including transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), BET gas adsorption surface area analysis, thermogravimetric analysis (TGA), photon correlation spectroscopy (PCS), and low angle laser light scattering (LALLS). Aluminum nanoparticles consist of an aluminum core with an aluminum oxide coating. HRTEM measurements of both the particle diameter and oxide layer thickness tend to be larger than those obtained from BET and TGA. LALLS measurements show a large degree of particle agglomeration in solution; therefore, primary particle sizes could not be determined. Furthermore, results from small-angle scattering techniques (SAS), including small-angle neutron (SANS) and x-ray (SAXS) scattering are presented and show excellent agreement with the BET, TGA, and HRTEM. The suite of analytical techniques presented in this paper can be used as a powerful tool in the characterization of many types of nanosized powders.

  5. Hydrogen Effect against Hydrogen Embrittlement

    Science.gov (United States)

    Murakami, Yukitaka; Kanezaki, Toshihiko; Mine, Yoji

    2010-10-01

    The well-known term “hydrogen embrittlement” (HE) expresses undesirable effects due to hydrogen such as loss of ductility, decreased fracture toughness, and degradation of fatigue properties of metals. However, this article shows, surprisingly, that hydrogen can have an effect against HE. A dramatic phenomenon was found in which charging a supersaturated level of hydrogen into specimens of austenitic stainless steels of types 304 and 316L drastically improved the fatigue crack growth resistance, rather than accelerating fatigue crack growth rates. Although this mysterious phenomenon has not previously been observed in the history of HE research, its mechanism can be understood as an interaction between hydrogen and dislocations. Hydrogen can play two roles in terms of dislocation mobility: pinning (or dragging) and enhancement of mobility. Competition between these two roles determines whether the resulting phenomenon is damaging or, unexpectedly, desirable. This finding will, not only be the crucial key factor to elucidate the mechanism of HE, but also be a trigger to review all existing theories on HE in which hydrogen is regarded as a dangerous culprit.

  6. Pore formation during C.W.Nd: YAG laser welding of aluminum alloys for automotive applications

    International Nuclear Information System (INIS)

    Pore formation is an important concern in laser welding of automotive aluminum alloys. This paper investigates the influence of the laser beam defocusing on pore formation during continuous wave Nd:YAG laser welding of aluminum automotive alloys 5182 and 5754. It was found that the instability of the keyhole during welding was a dominant cause of pore formation while hydrogen rejection played an insignificant role. The defocusing of the laser beam greatly affected the stability of the keyhole. Finally, the mechanism of the collapse of the keyhole and pore formation is proposed. (Author) 45 refs

  7. DFT studies of the bonding mechanism of 8-hydroxyquinoline and derivatives on the (111) aluminum surface

    OpenAIRE

    Chiter, Fatah; Lacaze-Dufaure, Corinne; Tang, Hao; Pébère, Nadine

    2015-01-01

    The 8-hydroxyquinoline (8-HQ) molecule is an efficient corrosion inhibitor for aluminum and is also used in organic electronic devices. In this paper, the adsorption modes of 8-HQ and its derivatives (tautomer, dehydrogenated and hydrogenated species) on the Al(111) surface are characterized using dispersion corrected density functional theory calculations. The 8-HQ molecule is physisorbed and is chemisorbed on the aluminum surface with similar adsorption energy (-0.86 eV to -1.11 eV) and the...

  8. Contrasting LME in aluminum and nickel alloys, with overtones to SCC

    International Nuclear Information System (INIS)

    The susceptibility of Alloys 400, 600, 200 and 800 to liquid metal embrittlement (LME), hydrogen embrittlement and stress corrosion cracking are in that order (most to least). Correlations exist, too, in the cracking mode, intergranular or transgranular. Accordingly, understanding LME and LME tests have potential uses in alloy development and screening. The use of a quick indentation test for LME is described that worked admirably for aluminum alloys but did not work for nickel-base alloys. The problem is that LME is strain rate sensitive in nickel alloys but not in aluminum alloys. This is believed to be a wetting issue

  9. Cluster Bulleticity

    CERN Document Server

    Massey, Richard; Nagai, Daisuke

    2010-01-01

    The unique properties of dark matter are revealed during collisions between clusters of galaxies, like the bullet cluster (1E 0657-56) and baby bullet (MACSJ0025-12). These systems provide evidence for an additional, invisible mass in the separation between the distribution of their total mass, measured via gravitational lensing, and their ordinary 'baryonic' matter, measured via its X-ray emission. Unfortunately, the information available from these systems is limited by their rarity. Constraints on the properties of dark matter, such as its interaction cross-section, are therefore restricted by uncertainties in the individual systems' impact velocity, impact parameter and orientation with respect to the line of sight. Here we develop a complementary, statistical measurement in which every piece of substructure falling into every massive cluster is treated as a bullet. We define 'bulleticity' as the mean separation between dark matter and ordinary matter, and we measure a positive signal in hydrodynamical si...

  10. Statistical theory for hydrogen bonding fluid system of AaDd type (Ⅱ): Properties of hydrogen bonding networks

    Institute of Scientific and Technical Information of China (English)

    WANG HaiJun; HONG XiaoZhong; GU Fang; BA XinWu

    2007-01-01

    Making use of the invariant property of the equilibrium size distribution of the hydrogen bonding clusters formed in hydrogen bonding system of AaDd type, the analytical expressions of the free energy in pregel and postgel regimes are obtained. Then the gel free energy and the scaling behavior of the number of hydrogen bonds in gel phase near the critical point are investigated to give the corresponding scaling exponents and scaling law. Meanwhile, some properties of intermolecular and intramolecular hydrogen bonds in the system, sol and gel phases are discussed. As a result, the explicit relationship between the number of intramolecular hydrogen bonds and hydrogen bonding degree is obtained.

  11. Efficient Synthesis of an Aluminum Amidoborane Ammoniate

    Directory of Open Access Journals (Sweden)

    Junzhi Yang

    2015-08-01

    Full Text Available A novel species of metal amidoborane ammoniate, [Al(NH2BH363−][Al(NH363+] has been successfully synthesized in up to 95% via the one-step reaction of AlH3·OEt2 with liquid NH3BH3·nNH3 (n = 1~6 at 0 °C. This solution based reaction method provides an alternative pathway to the traditional mechano-chemical ball milling methods, avoiding possible decomposition. MAS 27Al NMR spectroscopy confirms the formulation of the compound as an Al(NH2BH363− complex anion and an Al(NH363+ cation. Initial dehydrogenation studies of this aluminum based M-N-B-H compound demonstrate that hydrogen is released at temperatures as low as 65 °C, totaling ~8.6 equivalents of H2 (10.3 wt % upon heating to 105 °C. This method of synthesis offers a promising route towards the large scale production of metal amidoborane ammoniate moieties.

  12. Structure and stability of silicon nanoclusters passivated by hydrogen and oxygen: evolutionary algorithm and first- principles study

    Science.gov (United States)

    Baturin, V. S.; Lepeshkin, S. V.; Matsko, N. L.; Uspenskii, Yu A.

    2016-02-01

    We investigate the structural and thermodynamical properties of small silicon clusters. Using the graph theory applied to previously obtained structures of Si10H2m clusters we trace the connection between geometry and passivation degree. The existing data on these clusters and structures of Si10O4n clusters obtained here using evolutionary calculations allowed to analyze the features of Si10H2m clusters in hydrogen atmosphere and Si10O4n clusters in oxygen atmosphere. We have shown the basic differences between structures and thermodynamical properties of silicon clusters, passivated by hydrogen and silicon oxide clusters.

  13. Cryogenic hydrogen-induced air liquefaction technologies

    Science.gov (United States)

    Escher, William J. D.

    1990-01-01

    Extensively utilizing a special advanced airbreathing propulsion archives database, as well as direct contacts with individuals who were active in the field in previous years, a technical assessment of cryogenic hydrogen-induced air liquefaction, as a prospective onboard aerospace vehicle process, was performed and documented. The resulting assessment report is summarized. Technical findings are presented relating the status of air liquefaction technology, both as a singular technical area, and also that of a cluster of collateral technical areas including: compact lightweight cryogenic heat exchangers; heat exchanger atmospheric constituents fouling alleviation; para/ortho hydrogen shift conversion catalysts; hydrogen turbine expanders, cryogenic air compressors and liquid air pumps; hydrogen recycling using slush hydrogen as heat sink; liquid hydrogen/liquid air rocket-type combustion devices; air collection and enrichment systems (ACES); and technically related engine concepts.

  14. Decarbonization process for carbothermically produced aluminum

    Energy Technology Data Exchange (ETDEWEB)

    Bruno, Marshall J.; Carkin, Gerald E.; DeYoung, David H.; Dunlap, Sr., Ronald M.

    2015-06-30

    A method of recovering aluminum is provided. An alloy melt having Al.sub.4C.sub.3 and aluminum is provided. This mixture is cooled and then a sufficient amount of a finely dispersed gas is added to the alloy melt at a temperature of about 700.degree. C. to about 900.degree. C. The aluminum recovered is a decarbonized carbothermically produced aluminum where the step of adding a sufficient amount of the finely dispersed gas effects separation of the aluminum from the Al.sub.4C.sub.3 precipitates by flotation, resulting in two phases with the Al.sub.4C.sub.3 precipitates being the upper layer and the decarbonized aluminum being the lower layer. The aluminum is then recovered from the Al.sub.4C.sub.3 precipitates through decanting.

  15. Time exposure studies on stress corrosion cracking of aluminum 2014-T6, aluminum 7075-T651, and titanium 6Al-4V

    Science.gov (United States)

    Terrell, J.

    1972-01-01

    The effect of a constant applied stress in crack initiation of aluminum 2014-T6, 7075-T651 and titanium 6A1-4V has been investigated. Aluminum c-ring specimens (1-inch diameter) and u-band titanium samples were exposed continuously to a 3.5% NaCl solution (pH 6) and organic fluids of ethyl, methyl, and iso-propyl alcohol (reagent purity). Corrosive action was observed to begin during the first and second day of constant exposure as evidenced by accumulation of hydrogen bubbles on the surface of stressed aluminum samples. However, a similar observation was not noted for titanium stressed specimens. Results of this investigation seems to suggest that aluminum 2014-T6, aluminum 7075-T651 are susceptible to stress corrosion cracking in chloride solution (NaCl); while they (both alloys) seem to resist stress corrosion cracking in methyl alcohol, ethyl alcohol, iso-propyl alcohol, and demineralized distilled water. Titanium 6A1-4V showed some evidence of susceptibility to SCC in methanol, while no such susceptibility was exhibited in ethanol, iso-propyl alcohol and demineralized distilled water.

  16. Conjugation in hydrogen-bonded systems

    CERN Document Server

    Novakovskaya, Yulia V

    2012-01-01

    Analysis of the electron density distribution in clusters composed of hydrogen fluoride, water, and ammonia molecules, especially within the hydrogen-bond domains, reveals the existence of both \\sigma- and \\pi-binding between molecules. The \\sigma-kind density distribution determines the mutual orientation of molecules. A \\pi-system may be delocalized conjugated, which provides additional stabilization of molecular clusters. In those clusters where the sequence of hydrogen bonds is not planar, a peculiar kind of \\pi-conjugation exists. HF anion and H5O2 cation are characterized by quasi-triple bonds between the electronegative atoms. The most long-lived species stabilized by delocalized \\pi-binding are rings and open or closed hoops composed of fused rings. It is conjugated \\pi-system that determines cooperativity phenomenon.

  17. Electrodeposition of aluminum on aluminum surface from molten salt

    Institute of Scientific and Technical Information of China (English)

    Wenmao HUANG; Xiangyu XIA; Bin LIU; Yu LIU; Haowei WANG; Naiheng MA

    2011-01-01

    The surface morphology,microstructure and composition of the aluminum coating of the electrodeposition plates in AlC13-NaC1-KC1 molten salt with a mass ratio of 8:1:1 were investigated by SEM and EDS.The binding force was measured by splat-cooling method and bending method.The results indicate that the coatings with average thicknesses of 12 and 9 μm for both plates treated by simple grinding and phosphating are compacted,continuous and well adhered respectively. Tetramethylammonium chloride (TMAC) can effectively prevent the growth of dendritic crystal,and the anode activation may improve the adhesion of the coating. Binding force analysis shows that both aluminum coatings are strongly adhered to the substrates.

  18. Fuzzy Clustering

    DEFF Research Database (Denmark)

    Berks, G.; Keyserlingk, Diedrich Graf von; Jantzen, Jan;

    2000-01-01

    and clustering are the basic concerns in medicine. Classification depends on definitions of the classes and their required degree of participant of the elements in the cases' symptoms. In medicine imprecise conditions are the rule and therefore fuzzy methods are much more suitable than crisp ones...

  19. Amphoteric Aqueous Hafnium Cluster Chemistry.

    Science.gov (United States)

    Goberna-Ferrón, Sara; Park, Deok-Hie; Amador, Jenn M; Keszler, Douglas A; Nyman, May

    2016-05-17

    Selective dissolution of hafnium-peroxo-sulfate films in aqueous tetramethylammonium hydroxide enables extreme UV lithographic patterning of sub-10 nm HfO2 structures. Hafnium speciation under these basic conditions (pH>10), however, is unknown, as studies of hafnium aqueous chemistry have been limited to acid. Here, we report synthesis, crystal growth, and structural characterization of the first polynuclear hydroxo hafnium cluster isolated from base, [TMA]6 [Hf6 (μ-O2 )6 (μ-OH)6 (OH)12 ]⋅38 H2 O. The solution behavior of the cluster, including supramolecular assembly via hydrogen bonding is detailed via small-angle X-ray scattering (SAXS) and electrospray ionization mass spectrometry (ESI-MS). The study opens a new chapter in the aqueous chemistry of hafnium, exemplifying the concept of amphoteric clusters and informing a critical process in single-digit-nm lithography. PMID:27094575

  20. 若干氢键团簇的纳秒和飞秒激光光电离及从头计算研究%Nanosecond and Femtosecond Laser Photoionization and Ab Initio Calculation Studies of Some Hydrogen Bonded Clusters

    Institute of Scientific and Technical Information of China (English)

    张柏林; 楼南泉; 王秀岩

    2003-01-01

    The multiphoton ionization and dissociation of azabenzenes-solvent clusters were studied using a time-of-flight mass spectrometer, nano- and femtosecond lasers. Due to the fact that the problem was resolved technically, the experiments about multiphoton ionization of pyrimidine-water in gas phase were performed successfully. The multiphoton ionization mass spectroscopy of the clusters was observed for the first time. The experimental results indicate sequences of protonated cluster ions are formed. Based on both ab initio calculations results and dependence of cluster ion intensity on the laser power, the processes of proton transfer and charge transfer within the clusters were presented. During the femtosecond laser photonionization of pyridine clusters, the coexistencephenomena of protonated and unprotonated cluster ions was observed first. The existence of pyridine dimmer ions and relevant calculation results indicate that the C-H…Nbonds can be formed between pyridine molecules, which corrected some reported results and also provided with a good example for the study of weak bond clusters. The multiphoton ionization results of pyrimidine-methanol and pyridazine-methanol clusters are presented for the first time. It is also found that only the protonated cluster ions are produced after clusters' ionization. The stable structures of all clusters were obtained theoretically, and the mechanisms and processes of proton transfer after ionization were elucidated.%利用纳秒和飞秒激光及飞行时间质谱仪对氮化苯-溶剂分子团簇的多光子电离和离解进行了研究.通过解决实验中的技术难题,实现了在气相条件下实验研究嘧啶与水团簇的多光子电离.首次观测到该团簇的多光子电离质谱,发现电离后形成了质子化团簇系列,通过团簇浓度随激光强度的变化以及理论计算,阐明了团簇内质子转移过程,以及电荷分布和质子转移过程随着团簇尺寸的变化;首次观测

  1. Effects of filter gap of cluster-eliminating filter on cluster eliminating efficiency

    International Nuclear Information System (INIS)

    We have developed a cluster-eliminating filter which reduces amount of amorphous silicon nanoparticles (clusters) incorporated into a-Si:H films. We have measured film thickness dependence of a ratio of a hydrogen content associated with Si-H2 bonds (CSiH2) to that with Si-H bonds (CSiH) as a parameter of the filter gap (dgap). The cluster removal efficiency increases with decreasing dgap. CSiH2 and the ratio of CSiH2 to CSiH decrease with increasing the film thickness, suggesting the amount of incorporated clusters is high near the interface between the film and the substrate

  2. Determination of the dominant catalyst derived from the classic [RhCp*Cl₂]₂ precatalyst system: Is it single-metal Rh₁Cp*-based, subnanometer Rh₄ cluster-based, or Rh(0)n nanoparticle-based cyclohexene hydrogenation catalysis at room temperature and mild pressures?

    Energy Technology Data Exchange (ETDEWEB)

    Bayram, Ercan [Colorado State Univ., Fort Collins, CO (United States); Linehan, John C. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Fulton, John L. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Szymczak, Nathaniel K. [Univ. of Michigan, Ann Arbor, MI (United States); Finke, Richard G. [Colorado State Univ., Fort Collins, CO (United States)

    2015-05-27

    Determining the kinetically dominant catalyst in a given catalytic system is a forefront topic in catalysis. The [RhCp*Cl₂]₂ (Cp* =[η⁵-C₅(CH₃)₅]) system pioneered by Maitlis and co-workers is a classic precatalyst system from which homogeneous mononuclear Rh₁, subnanometer Rh₄ cluster, and heterogeneous polymetallic Rh(0)n nanoparticle have all arisen as viable candidates for the true hydrogenation catalyst, depending on the precise substrate, H₂ pressure, temperature, and catalyst concentration conditions. Addressed herein is the question of whether the prior assignment of homogeneous, mononuclear Rh₁Cp*-based catalysis is correct, or are trace Rh₄ subnanometer clusters or possibly Rh(0)n nanoparticles the dominant, actual cyclohexene hydrogenation catalyst at 22 °C and 2.7 atm initial H₂ pressure? The observation herein of Rh₄ species by in operando-X-ray absorption fine structure (XAFS) spectroscopy, at the only slightly more vigorous conditions of 26 °C and 8.3 atm H₂ pressure, and the confirmation of Rh₄ clusters by ex situ mass spectroscopy raises the question of the dominant, room temperature, and mild pressure cyclohexene hydrogenation catalyst derived from the classic [RhCp*Cl₂]₂ precatalyst pioneered by Maitlis and co-workers. Ten lines of evidence are provided herein to address the nature of the true room temperature and mild pressure cyclohexene hydrogenation catalyst derived from [RhCp*Cl₂]₂. Especially significant among those experiments are quantitative catalyst poisoning experiments, in the present case using 1,10-phenanthroline. Those poisoning studies allow one to distinguish mononuclear Rh₁, subnanometer Rh₄ cluster, and Rh(0)n nanoparticle catalysis hypotheses. The evidence obtained provides a compelling case for a mononuclear, Rh₁Cp*-based cyclohexene hydrogenation catalyst at 22 °C and 2.7 atm H₂ pressure. The resultant methodology, especially the quantitative

  3. Quotients of cluster categories

    OpenAIRE

    Jorgensen, Peter

    2007-01-01

    Higher cluster categories were recently introduced as a generalization of cluster categories. This paper shows that in Dynkin types A and D, half of all higher cluster categories are actually just quotients of cluster categories. The other half can be obtained as quotients of 2-cluster categories, the "lowest" type of higher cluster categories. Hence, in Dynkin types A and D, all higher cluster phenomena are implicit in cluster categories and 2-cluster categories. In contrast, the same is not...

  4. Microstructure and Mechanical Properties of AA1235 Aluminum Foil Stocks Produced Directly from Electrolytic Aluminum Melt

    Science.gov (United States)

    Xiong, Hanqing; Yu, Kun; Wen, Li; Yao, Sujuan; Dai, Yilong; Wang, Zhifeng

    2016-02-01

    A new process is developed to obtain high-quality AA1235 aluminum foil stocks and to replace the traditional manufacture process. During the new manufacture process, AA1235 aluminum sheets are twin-roll casted directly through electrolytic aluminum melt (EAM), and subsequently the sheets are processed into aluminum foil stocks by cold rolling and annealing. Microstructure and mechanical properties of the AA1235 aluminum sheets produced through such new process are investigated in each state by optimal microscope, scanning electron microscopy, X-ray diffraction, orientation imaging microscopy, transmission electron microscopy, etc. The results show that compared with the traditional AA1235 aluminum foil stocks produced through re-melted aluminum melt (RAM), the amount of impurities is decreased in the EAM aluminum foil stocks. The EAM aluminum foil stock obtains less β-FeSiAl5 phases, but more α-Fe2SiAl8 phases. The elongation of EAM aluminum foil stocks is improved significantly owing to more cubic orientation. Especially, the elongation value of the EAM aluminum foil stocks is approximately 25 pct higher than that of the RAM aluminum foil stocks. As a result, the EAM aluminum foil stocks are at an advantage in increasing the processing performance for the aluminum foils during subsequent processes.

  5. Hexane radiation - heterogeneous conversions on the surface of aluminum

    International Nuclear Information System (INIS)

    Full text: In present paper the peculiarities of radiation and radiation-thermal hexane conversion processes on the surface of aluminum have been studied. A spectro-kinetic investigations are carried out using the IR reflection - adsorption spectroscopy method. The formation of molecular hydrogen (H2) and other decomposition products is controlled chromatographically.The thin polished aluminum plates of the mark AD-00 were used as the test material. Spectroscopically pure hexane was used. The samples were irradiated by 60Co γ-rays with a radiation dose 1.03 Gy/s. Analysis of IR reflection-adsorption spectra of adsorbed hexane (C6H14) at temperature range 300-673 K on the surface of aluminum is indicated on formation a H-bonded hydrocarbon complex (ν∼2680 cm-1) with C-H bond loose and proceeding of possibility of dissociative adsorption with formation of the methyl alkyls (ν∼2880, 2920, 2970 cm-1). The probability of last process proceeded on defect centers increases with increasing of the interaction temperature. It was established, that the radiation processes in hetero system Al/ads. C6H14 accelerate the radiolysis of the hexane. Along with molecular H2 also hydrocarbons an C1-C5 also are. This is testified by appearance in IR spectra the bands of pendulum modes of (CH2)n, where with n>6 maxima 770, 790, 825, 900 and 950 cm-1. The rates of surface decomposition processes increase with temperature increasing. Based on the experimental data, a possible mechanisms of the hexane radiation-heterogeneous decomposition on the surface of aluminum are suggested

  6. Regional Innovation Clusters

    Data.gov (United States)

    Small Business Administration — The Regional Innovation Clusters serve a diverse group of sectors and geographies. Three of the initial pilot clusters, termed Advanced Defense Technology clusters,...

  7. Hydrogen program overview

    Energy Technology Data Exchange (ETDEWEB)

    Gronich, S. [Dept. of Energy, Washington, DC (United States). Office of Utility Technologies

    1997-12-31

    This paper consists of viewgraphs which summarize the following: Hydrogen program structure; Goals for hydrogen production research; Goals for hydrogen storage and utilization research; Technology validation; DOE technology validation activities supporting hydrogen pathways; Near-term opportunities for hydrogen; Market for hydrogen; and List of solicitation awards. It is concluded that a full transition toward a hydrogen economy can begin in the next decade.

  8. Implants of aluminum into silicon

    Science.gov (United States)

    Galvagno, G.; Scandurra, A.; Raineri, V.; Rimini, E.; La Ferla, A.; Sciascia, V.; Frisina, F.; Raspagliesi, M.; Ferla, G.

    1993-04-01

    The electrical behaviour of ion implanted aluminum into silicon was investigated by varying the beam energy in the 80 keV-6 MeV range, the dose in the 1 × 10 13-1 × 10 14/cm 2 range and the annealing procedure. Aluminum atoms precipitate into exten defects at the end of range damage and where the concentration exceeds the solid solubility value (about 2 × 10 19/cm 3 at 1200°C Escape of Al atoms occurs very easily as soon as they reach the external surface during the thermal diffusion. Using high energy implants, 6 MeV, it was possible to follow in detail the broadening of the diffused profiles. The measured trends between the retained dose and the junction depth and between the outdiffused dose and the annealing time are quite well predicted by the solution of the diffusion equation with the surface acting as a perfect sink for the dopant.

  9. Electrically Conductive Anodized Aluminum Surfaces

    Science.gov (United States)

    Nguyen, Trung Hung

    2006-01-01

    Anodized aluminum components can be treated to make them sufficiently electrically conductive to suppress discharges of static electricity. The treatment was conceived as a means of preventing static electric discharges on exterior satin-anodized aluminum (SAA) surfaces of spacecraft without adversely affecting the thermal-control/optical properties of the SAA and without need to apply electrically conductive paints, which eventually peel off in the harsh environment of outer space. The treatment can also be used to impart electrical conductivity to anodized housings of computers, medical electronic instruments, telephoneexchange equipment, and other terrestrial electronic equipment vulnerable to electrostatic discharge. The electrical resistivity of a typical anodized aluminum surface layer lies between 10(exp 11) and 10(exp 13) Omega-cm. To suppress electrostatic discharge, it is necessary to reduce the electrical resistivity significantly - preferably to anodized surface becomes covered and the pores in the surface filled with a transparent, electrically conductive metal oxide nanocomposite. Filling the pores with the nanocomposite reduces the transverse electrical resistivity and, in the original intended outer-space application, the exterior covering portion of the nanocomposite would afford the requisite electrical contact with the outer-space plasma. The electrical resistivity of the nanocomposite can be tailored to a value between 10(exp 7) and 10(exp 12) Omega-cm. Unlike electrically conductive paint, the nanocomposite becomes an integral part of the anodized aluminum substrate, without need for adhesive bonding material and without risk of subsequent peeling. The electrodeposition process is compatible with commercial anodizing production lines. At present, the electronics industry uses expensive, exotic, electrostaticdischarge- suppressing finishes: examples include silver impregnated anodized, black electroless nickel, black chrome, and black copper. In

  10. Ab initio Calculations of Optical Properties of Clusters

    CERN Document Server

    Shinde, Ravindra

    2016-01-01

    We have performed systematic large-scale all-electron correlated calculations on boron Bn, aluminum Aln and magnesium Mgn clusters (n=2--5), to study their linear optical absorption spectra. Several possible isomers of each cluster were considered, and their geometries were optimized at the coupled-cluster singles doubles (CCSD) level of theory. Using the optimized ground-state geometries, excited states of different clusters were computed using the multi-reference singles-doubles configuration interaction (MRSDCI) approach, which includes electron correlation effects at a sophisticated level. These CI wavefunctions were used to compute the transition dipole matrix elements connecting the ground and various excited states of different clusters, eventually leading to their linear absorption spectra. The convergence of our results with respect to the basis sets, and the size of the CI expansion was carefully examined. Isomers of a given cluster show a distinct signature spectrum, indicating a strong structure p...

  11. Microbial corrosion of aluminum alloy.

    Science.gov (United States)

    Yang, S S; Chen, C Y; Wei, C B; Lin, Y T

    1996-11-01

    Several microbes were isolated from the contaminated fuel-oil in Taiwan and the microbial corrosion of aluminum alloy A356-T6 was tested by MIL-STD-810E test method. Penicillium sp. AM-F5 and Cladosporium resinac ATCC 22712 had significant adsorption and pitting on the surface of aluminum alloy, Pseudomonas acruginosa AM-B5 had weak adsorption and some precipitation in the bottom, and Candida sp. AM-Y1 had the less adsorption and few cavities formation on the surface. pH of the aqueous phase decreased 0.3 to 0.7 unit for 4 months of incubation. The corrosion of aluminum alloy was very significant in the cultures of Penicillium sp. AM-F2, Penicillium sp. AM-F5 and C. resinac ATCC 22712. The major metabolites in the aqueous phase with the inoculation of C. resinac were citric acid and oxalic acid, while succinic acid and fumaric acid were the minors. PMID:10592801

  12. Aluminum-lithium target behavior

    Energy Technology Data Exchange (ETDEWEB)

    McDonell, W.R.

    1989-10-01

    Information on physical properties and irradiation behavior of aluminum-lithium target alloys employed for the production of tritium in Savannah River reactors has been reviewed to support development of technology for the New Production Reactor (NPR). Phase compositions and microstructures, thermal conductivity, mechanical properties, and constituent diffusion phenomena of the alloys, established in prior site studies, are presented. Irradiation behavior, including distributions of product tritium and helium and related exposure limits due to swelling and cracking of the target alloys is discussed, along with gas release processes occurring during subsequent product recovery operations. The property review supports designation of the aluminum-lithium alloys as ideally well-suited target materials for low-temperature, tritium-producing reactors, demonstrated over 35 years of Savannah River reactor operation. Low temperature irradiation and reaction with lithium in the alloy promotes tritium retention during reactor exposure, and the aluminum provides a matrix from which the product is readily recovered on heating following irradiation. 33 refs., 26 figs., 8 tabs.

  13. Effects of internal hydrogen on the vacancy loop formation probability in Al

    International Nuclear Information System (INIS)

    The effect of internal hydrogen on the formation of vacancy dislocation loops from heavy-ion generated displacement cascades in Al has been investigated. Samples of high-purity aluminum and aluminum containing 900 and 1300 appM of hydrogen were irradiated at room temperature with 50 keV Kr+ ions. The ion dose rate was typically 2 x 1010ions cm-2 sec-1 and the ion dose was between 1011 and 1013 ion cm-2. Under these irradiation conditions, dislocation loops were observed in all compositions, although the formation probability was relatively low (less than 10 percent of the displacement cascades produced a vacancy loop). The loop formation probability was further reduced by the presence of hydrogen. No difference in the geometry or the size of the loops created in the hydrogen free and hydrogen charged samples was found. These results are difficult to interpret, and the explanation may lie in the distribution and form of the hydrogen. To account for the large hydrogen concentrations and from calculations of the energy associated with hydrogen entry into aluminum, it has been suggested that the hydrogen enters the aluminum lattice with an accompanying vacancy. This will create hydrogen-vacancy complexes in the material; two dimensional complexes have been detected in the hydrogen-charged, but unirradiated, samples by the small-angle x-ray scattering technique. The possibility of these complexes trapping the vacancies produced by the cascade process exists thus lowering the formation probability. However, such a mechanism must occur within the lifetime of the cascade. Alternatively, if a displacement cascade overlaps with the hydrogen-vacancy complexes, the lower atomic density of the region will result in an increase in the cascade volume (decrease in the local vacancy concentration) which will also reduce the loop formation probability

  14. Clustering experiments

    CERN Document Server

    Wang, Zhengwei; Tan, Ken; Di, Zengru; Roehner, Bertrand M

    2011-01-01

    It is well known that bees cluster together in cold weather, in the process of swarming (when the ``old'' queen leaves with part of the colony) or absconding (when the queen leaves with all the colony) and in defense against intruders such as wasps or hornets. In this paper we describe a fairly different clustering process which occurs at any temperature and independently of any special stimulus or circumstance. As a matter of fact, this process is about four times faster at 28 degree Celsius than at 15 degrees. Because of its simplicity and low level of ``noise'' we think that this phenomenon can provide a means for exploring the strength of inter-individual attraction between bees or other living organisms. For instance, and at first sight fairly surprisingly, our observations showed that this attraction does also exist between bees belonging to different colonies. As this study is aimed at providing a comparative perspective, we also describe a similar clustering experiment for red fire ants.

  15. Effect of tunnel structure on the specific capacitance of etched aluminum foil

    Institute of Scientific and Technical Information of China (English)

    Ning Peng; Li-Bo Liang; Ye-Dong He; Hong-Zhou Song; Xiao-Fei Yang; Xiao-Yu Cai

    2014-01-01

    The morphology of etched aluminum foil was observed using scanning electron microscopy, which led to the establishment of a cylindrical model and two merged models, considering the fixed weight loss of etching. The maximum of specific capacitance and the cor-responding optimum values for tunnel sizes at various anodization voltages were predicted. The increased size distribution and taper of tun-nels were demonstrated to decrease the specific capacitance, whereas the addition of polymeric additive into the tunnel widening solution was demonstrated to increase the capacitance. The formation of merged tunnels on the etched aluminum surface, irrespective of the presence of row-merged tunnels or cluster-merged tunnels, resulted in a dramatic decrease in the specific capacitance. It is concluded that, enhancing the uniformity of tunnel size and distribution and avoiding the formation of merged tunnels are the effective approach to achieving the higher capacitance for the tunnel etched and formed aluminum foil.

  16. Microstructure and tensile properties of bulk nanostructured aluminum/graphene composites prepared via cryomilling

    International Nuclear Information System (INIS)

    In order to develop high strength metal–matrix composites with acceptable ductility, bulk nanostructured aluminum–matrix composites reinforced with graphene nanoflakes were fabricated by cryomilling and hot extrusion processes. Microstructure and mechanical properties were characterized and determined using transmission electron microscopy, electron dispersion spectroscopy, as well as static tensile tests. The results show that, with an addition of only 0.5 wt% graphene nanoflakes, the bulk nanostructured aluminum/graphene composite exhibited increased strength and unsubdued ductility over pure aluminum. Besides, the mechanical properties of the composites with higher content of graphene nanoflakes were also measured and investigated. Above 1.0 wt% of graphene nanoflakes, however, this strengthening effect sharply dropped due to the clustering of graphene nanoflakes. Furthermore, the optimal addition of graphene nanoflakes into the nanocrystalline aluminum matrix was calculated and discussed

  17. Hydrogen technologies

    International Nuclear Information System (INIS)

    To the non-nonsense engineer, any talk of a hydrogen economy may seem like so much hot air. This paper reports that as legislative, safety and environmental issues continue to tighten, they're promoting hydrogen's chances as an energy source and, more immediately, its prospects as a chemical feedstock. Paradoxically, the environmental demands that are stimulating hydrogen demand are also inhibiting the gas's production. Previously, gasoline was made with benzene, which means that H2 was rejected. But now that the laws mandate lower aromatic and higher oxygenate levels in gasolines, there's less H2 available as byproduct. At the same time, H2 demand is rising in hydrodesulfurization units, since the same laws require refiners to cut sulfur levels in fuels. Supplementary sources for the gas are also shrinking. In the chlor-alkali industry, H2 output is dropping, as demand for its coproduct chlorine weakens. At the same time, H2 demand for the making of hydrogen peroxide is growing, as that environmentally safer bleach gains chlorine's market share

  18. Double-layer Modiifcation of Water-based Aluminum with SiO2 and Polyacrylic Acid by Sol-gel Process and in situPolymerization

    Institute of Scientific and Technical Information of China (English)

    HE Yuhang; LI Houbin

    2016-01-01

    A double-layer aluminum consisting of an aluminum core and a shell of SiO2 and polyacrylic acid was synthesized. This modiifed aluminum was used to improve the corrosion resistance and dispersive property of aluminum in waterborne media. TEM, FTIR, XPS, and EDX determination showed that PAA and SiO2 were coated on the surface of aluminum. Evolved hydrogen detection showed that the corrosion resistance of composite particle had been markedly improved. Maximum corrosion inhibition efifciency of SiO2 coated aluminum (SiO2@Al) was 95.1% while that of double-layer coated aluminum (PAA/SiO2@Al) was 98.8%. Meanwhile, polyacrylic acid layer improved the agglomeration of aluminum significantly. According to the dispersibility test, the particle size of 50% volume fraction [d(0.5)] of aluminum, SiO2@Al and PAA/SiO2@Al were 42, 53, and 34 μm, respectively.

  19. Factor PD-Clustering

    OpenAIRE

    Gettler Summa, Mireille; Palumbo, Francesco; Tortora, Cristina

    2012-01-01

    Factorial clustering methods have been developed in recent years thanks to the improving of computational power. These methods perform a linear transformation of data and a clustering on transformed data optimizing a common criterion. Factorial PD-clustering is based on Probabilistic Distance clustering (PD-clustering). PD-clustering is an iterative, distribution free, probabilistic, clustering method. Factor PD-clustering make a linear transformation of original variables into a reduced numb...

  20. Metallic Hydrogen

    Science.gov (United States)

    Silvera, Isaac; Zaghoo, Mohamed; Salamat, Ashkan

    2015-03-01

    Hydrogen is the simplest and most abundant element in the Universe. At high pressure it is predicted to transform to a metal with remarkable properties: room temperature superconductivity, a metastable metal at ambient conditions, and a revolutionary rocket propellant. Both theory and experiment have been challenged for almost 80 years to determine its condensed matter phase diagram, in particular the insulator-metal transition. Hydrogen is predicted to dissociate to a liquid atomic metal at multi-megabar pressures and T =0 K, or at megabar pressures and very high temperatures. Thus, its predicted phase diagram has a broad field of liquid metallic hydrogen at high pressure, with temperatures ranging from thousands of degrees to zero Kelvin. In a bench top experiment using static compression in a diamond anvil cell and pulsed laser heating, we have conducted measurements on dense hydrogen in the region of 1.1-1.7 Mbar and up to 2200 K. We observe a first-order phase transition in the liquid phase, as well as sharp changes in optical transmission and reflectivity when this phase is entered. The optical signature is that of a metal. The mapping of the phase line of this transition is in excellent agreement with recent theoretical predictions for the long-sought plasma phase transition to metallic hydrogen. Research supported by the NSF, Grant DMR-1308641, the DOE Stockpile Stewardship Academic Alliance Program, Grant DE-FG52-10NA29656, and NASA Earth and Space Science Fellowship Program, Award NNX14AP17H.

  1. Determination of the Hydrogenation Degree of Telechelic Polybutadiene by {sup 1}H NMR

    Energy Technology Data Exchange (ETDEWEB)

    Lira, C.H.; Nicolini, L.F.; Dolinsky, M.C.B. [Petroflex Industria e Comercio S.A., Duque de Caxias, RJ (Brazil)]. E-mail: clira@petroflex.com.br; Oliveira, C.M.F.; Gomes, A.S. [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Inst. de Macromoleculas Professora Eloisa Mano

    2006-07-01

    The liquid hydroxyl terminated polybutadiene (HTPB) was hydrogenated to improve its thermal and oxidative resistance. Hydrogenation was carried out using cyclohexane as solvent and a soluble catalyst system consisting of diisobutyl aluminum hydride (DIBAL-H) and Co{sup III} acetylacetonate, at a molar ratio of 6:1. Hydrogenation was only possible after esterification of hydroxyl groups due to interactions with the catalyst system. {sup 1}H NMR technique was used to confirm the esterification and hydrogenation of the polymeric material. This method can be also used to determine the degree of hydrogenation in different reaction times. (author)

  2. Cluster ion impacts on solids

    International Nuclear Information System (INIS)

    Experimental methods for the production of cluster ions by expansion of weakly ionized plasmas through a supersonic nozzle and skimmer were described. Techniques for the production of relatively narrow mass distributions of singly charged ions containing as many as thousands of molecules of Hydrogen, Argon, Water, Alcohols and Hydrocarbons were reviewed with an explanation of the dependence of the mean cluster ion size on stagnation conditions in the ion source and the orifice geometry in nozzle or free jet expansions. Diagnostic techniques for the mass analysis and detection of these high molecule weight cluster ions were reviewed. A description of the BNL 400 kilovolt post-acceleration detection system and the advantages of secondary electron pulse distributions were presented and discussed. The application of energetic cluster ion impacts for deposition of large amounts of translational energy in thin films and solid surfaces was the main topic of the presentation. Cluster ions can be used to generate assemblies of atoms in solid surfaces with energies determined by available acceleration facilities. The production of assemblies of thousands of atoms with energies of in excess of several hundred volts per atom is readily achieved. The consequence of the ability of generate high energy densities is among other things the production of craters, cavities and in thin films holes of sizes that are smaller than those achievable by atomic ion bombardment and wet etching techniques. Examples of such results were presented showing holes in thin carbon films obtained by transmissions electron microscopy

  3. Aluminum exclusion and aluminum tolerance in woody plants

    OpenAIRE

    Brunner, Ivano; Sperisen, Christoph

    2013-01-01

    The aluminum (Al) cation Al3 + is highly rhizotoxic and is a major stress factor to plants on acid soils, which cover large areas of tropical and boreal regions. Many woody plant species are native to acid soils and are well adapted to high Al3 + conditions. In tropical regions, both woody Al accumulator and non-Al accumulator plants occur, whereas in boreal regions woody plants are non-Al accumulators. The mechanisms of these adaptations can be divided into those that facilitate the exclusio...

  4. Hydrogen - High pressure production and storage

    International Nuclear Information System (INIS)

    The development of simple, safe and more and more efficient technologies for the production and the storage of hydrogen is necessary condition for the transition towards the economy of hydrogen.In this work the hydrogen production studies experimentally to high pressure by electrolysis of alkaline solutions without the intervention of compressing systems and its direct storage in safe containers.The made tests show that the process of electrolysis to high pressure is feasible and has better yield than to low pressure, and that is possible to solve the operation problems, with relatively simple technology.The preliminary studies and tests indicate that the system container that studied is immune to the outbreak and can have forms and very different sizes, nevertheless, to reach or to surpass the efficiency of storage of the conventional systems the investments necessary will be due to make to be able to produce aluminum alloy tubes of high resistance

  5. Investigations of Aluminum-Doped Self-Healing Zircaloy Surfaces in Context of Accident-Tolerant Fuel Cladding Research

    Science.gov (United States)

    Carr, James; Vasudevamurthy, Gokul; Snead, Lance; Hinderliter, Brian; Massey, Caleb

    2016-06-01

    We present here some important results investigating aluminum as an effective surface dopant for increased oxidation resistance of zircaloy nuclear fuel cladding. At first, the transport behavior of aluminum into reactor grade zircaloy was studied using simple diffusion couples at temperatures greater than 770 K. The experiments revealed the formation of tens of microns thick graded Zr-Al layers. The activation energy of aluminum in zircaloy was found to be ~175 kJ/mol (~1.8 eV), indicating the high mobility of aluminum in zircaloy. Subsequently, aluminum sputter-coated zircaloy coupons were heat-treated to achieve surface doping and form compositionally graded layers. These coupons were then tested in steam environments at 1073 and 1273 K. The microstructure of the as-fabricated and steam-corroded specimens was compared to those of pure zircaloy control specimens. Analysis of data revealed that aluminum effectively competed with zircaloy for oxygen up until 1073 K blocking oxygen penetration, with no traces of large scale spalling, indicating mechanically stable interfaces and surfaces. At the highest steam test temperatures, aluminum was observed to segregate from the Zr-Al alloy under layers and migrate to the surface forming discrete clusters. Although this is perceived as an extremely desirable phenomenon, in the current experiments, oxygen was observed to penetrate into the zirconium-rich under layers, which could be attributed to formation of surface defects such as cracks in the surface alumina layers.

  6. Investigations of Aluminum-Doped Self-Healing Zircaloy Surfaces in Context of Accident-Tolerant Fuel Cladding Research

    Science.gov (United States)

    Carr, James; Vasudevamurthy, Gokul; Snead, Lance; Hinderliter, Brian; Massey, Caleb

    2016-05-01

    We present here some important results investigating aluminum as an effective surface dopant for increased oxidation resistance of zircaloy nuclear fuel cladding. At first, the transport behavior of aluminum into reactor grade zircaloy was studied using simple diffusion couples at temperatures greater than 770 K. The experiments revealed the formation of tens of microns thick graded Zr-Al layers. The activation energy of aluminum in zircaloy was found to be ~175 kJ/mol (~1.8 eV), indicating the high mobility of aluminum in zircaloy. Subsequently, aluminum sputter-coated zircaloy coupons were heat-treated to achieve surface doping and form compositionally graded layers. These coupons were then tested in steam environments at 1073 and 1273 K. The microstructure of the as-fabricated and steam-corroded specimens was compared to those of pure zircaloy control specimens. Analysis of data revealed that aluminum effectively competed with zircaloy for oxygen up until 1073 K blocking oxygen penetration, with no traces of large scale spalling, indicating mechanically stable interfaces and surfaces. At the highest steam test temperatures, aluminum was observed to segregate from the Zr-Al alloy under layers and migrate to the surface forming discrete clusters. Although this is perceived as an extremely desirable phenomenon, in the current experiments, oxygen was observed to penetrate into the zirconium-rich under layers, which could be attributed to formation of surface defects such as cracks in the surface alumina layers.

  7. Investigating aluminum alloy reinforced by graphene nanoflakes

    Energy Technology Data Exchange (ETDEWEB)

    Yan, S.J., E-mail: shaojiuyan@126.com [Beijing Institute of Aeronautical Materials, Beijing 100095 (China); Dai, S.L.; Zhang, X.Y.; Yang, C.; Hong, Q.H.; Chen, J.Z. [Beijing Institute of Aeronautical Materials, Beijing 100095 (China); Lin, Z.M. [Aviation Industry Corporation of China, Beijing 100022 (China)

    2014-08-26

    As one of the most important engineering materials, aluminum alloys have been widely applied in many fields. However, the requirement of enhancing their mechanical properties without sacrificing the ductility is always a challenge in the development of aluminum alloys. Thanks to the excellent physical and mechanical properties, graphene nanoflakes (GNFs) have been applied as promising reinforcing elements in various engineering materials, including polymers and ceramics. However, the investigation of GNFs as reinforcement phase in metals or alloys, especially in aluminum alloys, is still very limited. In this study, the aluminum alloy reinforced by GNFs was successfully prepared via powder metallurgy approach. The GNFs were mixed with aluminum alloy powders through ball milling and followed by hot isostatic pressing. The green body was then hot extruded to obtain the final GNFs reinforced aluminum alloy nanocomposite. The scanning electron microscopy and transmission electron microscope analysis show that GNFs were well dispersed in the aluminum alloy matrix and no chemical reactions were observed at the interfaces between the GNFs and aluminum alloy matrix. The mechanical properties' testing results show that with increasing filling content of GNFs, both tensile and yield strengths were remarkably increased without losing the ductility performance. These results not only provided a pathway to achieve the goal of preparing high strength aluminum alloys with excellent ductilitybut they also shed light on the development of other metal alloys reinforced by GNFs.

  8. Investigating aluminum alloy reinforced by graphene nanoflakes

    International Nuclear Information System (INIS)

    As one of the most important engineering materials, aluminum alloys have been widely applied in many fields. However, the requirement of enhancing their mechanical properties without sacrificing the ductility is always a challenge in the development of aluminum alloys. Thanks to the excellent physical and mechanical properties, graphene nanoflakes (GNFs) have been applied as promising reinforcing elements in various engineering materials, including polymers and ceramics. However, the investigation of GNFs as reinforcement phase in metals or alloys, especially in aluminum alloys, is still very limited. In this study, the aluminum alloy reinforced by GNFs was successfully prepared via powder metallurgy approach. The GNFs were mixed with aluminum alloy powders through ball milling and followed by hot isostatic pressing. The green body was then hot extruded to obtain the final GNFs reinforced aluminum alloy nanocomposite. The scanning electron microscopy and transmission electron microscope analysis show that GNFs were well dispersed in the aluminum alloy matrix and no chemical reactions were observed at the interfaces between the GNFs and aluminum alloy matrix. The mechanical properties' testing results show that with increasing filling content of GNFs, both tensile and yield strengths were remarkably increased without losing the ductility performance. These results not only provided a pathway to achieve the goal of preparing high strength aluminum alloys with excellent ductilitybut they also shed light on the development of other metal alloys reinforced by GNFs

  9. Gut: An underestimated target organ for Aluminum.

    Science.gov (United States)

    Vignal, C; Desreumaux, P; Body-Malapel, M

    2016-06-01

    Since World War II, several factors such as an impressive industrial growth, an enhanced environmental bioavailability and intensified food consumption have contributed to a significant amplification of human exposure to aluminum. Aluminum is particularly present in food, beverages, some drugs and airbone dust. In our food, aluminum is superimposed via additives and cooking utensils. Therefore, the tolerable intake of aluminum is exceeded for a significant part of the world population, especially in children who are more vulnerable to toxic effects of pollutants than adults. Faced with this oral aluminum influx, intestinal tract is an essential barrier, especially as 38% of ingested aluminum accumulates at the intestinal mucosa. Although still poorly documented to date, the impact of oral exposure to aluminum in conditions relevant to real human exposure appears to be deleterious for gut homeostasis. Aluminum ingestion affects the regulation of the permeability, the microflora and the immune function of intestine. Nowadays, several arguments are consistent with an involvement of aluminum as an environmental risk factor for inflammatory bowel diseases. PMID:26970682

  10. Hydrogen environment embrittlement.

    Science.gov (United States)

    Gray, H. R.

    1972-01-01

    Hydrogen embrittlement is classified into three types: internal reversible hydrogen embrittlement, hydrogen reaction embrittlement, and hydrogen environment embrittlement. Characteristics of and materials embrittled by these types of hydrogen embrittlement are discussed. Hydrogen environment embrittlement is reviewed in detail. Factors involved in standardizing test methods for detecting the occurrence of and evaluating the severity of hydrogen environment embrittlement are considered. The effects of test technique, hydrogen pressure, purity, strain rate, stress concentration factor, and test temperature are discussed.

  11. 40 CFR 180.1091 - Aluminum isopropoxide and aluminum secondary butoxide; exemption from the requirement of a...

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 23 2010-07-01 2010-07-01 false Aluminum isopropoxide and aluminum... PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions From Tolerances § 180.1091 Aluminum isopropoxide and aluminum secondary butoxide; exemption from the requirement of a tolerance. Aluminum isopropoxide (CAS Reg. No....

  12. The Aluminum Deep Processing Project of North United Aluminum Landed in Qijiang

    Institute of Scientific and Technical Information of China (English)

    2014-01-01

    <正>On April 10,North United Aluminum Company respectively signed investment cooperation agreements with Qijiang Industrial Park and Qineng Electricity&Aluminum Co.,Ltd,signifying the landing of North United Aluminum’s aluminum deep processing project in Qijiang.

  13. [The corrosion resistance of aluminum and aluminum-based alloys studied in artificial model media].

    Science.gov (United States)

    Zhakhangirov, A Zh; Doĭnikov, A I; Aboev, V G; Iankovskaia, T A; Karamnova, V S; Sharipov, S M

    1991-01-01

    Samples of aluminum and its alloys, designed for orthodontic employment, were exposed to 4 media simulating the properties of biologic media. The corrosion resistance of the tested alloys was assessed from the degree of aluminum migration to simulation media solutions, which was measured by the neutron activation technique. Aluminum alloy with magnesium and titanium has shown the best corrosion resistance. PMID:1799002

  14. First principles investigation of cluster consisting of hydrogen–helium atoms interstitially-trapped in tungsten

    International Nuclear Information System (INIS)

    We evaluate the binding energies of mixed helium and hydrogen clusters consisted of interstitially trapped atoms in bcc tungsten by first-principles calculations based on density functional theories. It is shown that helium-rich interstitially-trapped clusters have the positive binding energies and the low electron-density region expand as the number of helium in the cluster increase. Thus, the helium-rich interstitially trapped clusters can act as a trapping site for hydrogen, and interstitially trapped helium interrupts or disturbs the hydrogen diffusion in tungsten

  15. Silicon and aluminum doping effects on the microstructure and properties of polymeric amorphous carbon films

    Science.gov (United States)

    Liu, Xiaoqiang; Hao, Junying; Xie, Yuntao

    2016-08-01

    Polymeric amorphous carbon films were prepared by radio frequency (R.F. 13.56 MHz) magnetron sputtering deposition. The microstructure evolution of the deposited polymeric films induced by silicon (Si) and aluminum(Al) doping were scrutinized through infrared spectroscopy, multi-wavelength Raman spectroscopy, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The comparative results show that Si doping can enhance polymerization and Al doping results in an increase in the ordered carbon clusters. Si and Al co-doping into polymeric films leads to the formation of an unusual dual nanostructure consisting of cross-linked polymer-like hydrocarbon chains and fullerene-like carbon clusters. The super-high elasticity and super-low friction coefficients (amorphous carbon films with different elements doping are also discussed in detail.

  16. Multiphoton ionization of large water clusters

    International Nuclear Information System (INIS)

    Water clusters are multimers of water molecules held together by hydrogen bonds. In the present work, multiphoton ionization in the UV range coupled with time of flight mass spectrometry has been applied to water clusters with up to 160 molecules in order to obtain information on the electronic states of clusters of different sizes up to dimensions that can approximate the bulk phase. The dependence of ion intensities of water clusters and their metastable fragments produced by laser ionization at 355 nm on laser power density indicates a (3+1)-photon resonance-enhanced multiphoton ionization process. It also explains the large increase of ionization efficiency at 355 nm compared to that at 266 nm. Indeed, it was found, by applying both nanosecond and picosecond laser ionization with the two different UV wavelengths, that no water cluster sequences after n = 9 could be observed at 266 nm, whereas water clusters up to m/z 2000 Th in reflectron mode and m/z 3000 Th in linear mode were detected at 355 nm. The agreement between our findings on clusters of water, especially true in the range with n > 10, and reported data for liquid water supports the hypothesis that clusters above a critical dimension can approximate the liquid phase. It should thus be possible to study clusters just above 10 water molecules, for getting information on the bulk phase structure

  17. The Solubility of Aluminum in Cryolite-Based Electrolyte-Containing KF

    Science.gov (United States)

    Zhang, Yu; Yu, Jiangyu; Gao, Bingliang; Liu, Yibai; Hu, Xianwei; Shi, Zhongning; Wang, Zhaowen

    2016-04-01

    The solubility of aluminum in NaF-AlF3-CaF2-KF-A12O3 electrolyte system at 1253 K (980 °C) has been measured by the analysis of quenched samples saturated with aluminum. The content of the dissolved metal in the quenched melt was determined by collecting the volume of hydrogen gas when a finely crushed sample is treated with HCl. Addition of 0 to 5 pct KF has no obvious effect on the solubility of aluminum in cryolite-based melts with molar ratio of NaF/AlF3 (cryolite ratio) ranging from 2.2 to 3.0. The solubility of aluminum increases from 0.015 to 0.026 wt pct with cryolite ratio increases from 2.2 to 4.0 in the NaF-AlF3-5 wt pct CaF2-3 wt pct A12O3 electrolyte at 1253 K (980 °C). Aluminum solubility was affected by both chemical replacement reaction of Al + 3NaF = AlF3 + 3Na and physical dissolution.

  18. Development Of A Novel Discontinuously-Reinforced Aluminum For Space Applications

    Science.gov (United States)

    Pandey, A. B.; Shah, S.; Shadoan, M.

    2002-01-01

    Discontinuously-reinforced aluminum (DRA) has been used in aerospace structures such as Ventral Fins and Fan Exit Guide Vanes owing to its superior specific stiffness, specific strength, wear resistance, and thermal resistance as compared to the unreinforced aluminum alloys. In order to reduce engine weight, DRA materials are now being considered for space applications. Higher specific strength at ambient and cryogenic temperatures is one of the main requirements in certain rocket applications. The commercial DRA materials use 6xxx and 2xxx precipitation hardened aluminum alloys as matrices which have limited strengths. Therefore, an aluminum alloy which can provide significantly higher ambient and cryogenic strengths is required. In this paper, a novel aluminum alloy based on Al-Sc-X composition with improved ambient and cryogenic temperature strengthening capability is proposed. In addition, this alloy showed promise for improved strength at elevated temperature. The monolithic alloy and the composite with 15 volume percent SiC and B4C particles were processed using a powder metallurgy approach. The influence of processing parameters on the microstructures and mechanical properties of the monolithic and composite materials is discussed. The alloy showed very high strength and moderate ductility. The influence of hydrogen on the properties of monolithic and composite materials is discussed. The thermal stability of these materials is also evaluated. The strength of the material is discussed in terms of solid solution strengthening, Orowan strengthening, and antiphase boundary strengthening models.

  19. Experimental studies of thermal and chemical interactions between molten aluminum and water

    Energy Technology Data Exchange (ETDEWEB)

    Farahani, A.A.; Corradini, M.L. [Univ. of Wisconsin, Madison, WI (United States)

    1995-09-01

    The possibility of rapid physical and chemical aluminum/water interactions during a core melt accident in a noncommercial reactor (e.g., HFIR, ATR) has resulted in extensive research to determine the mechanism by which these interactions occur and propagate on an explosive time scale. These events have been reported in nuclear testing facilities, i.e., during SPERT 1D experiment, and also in aluminum casting industries. Although rapid chemical reactions between molten aluminum and water have been subject of many studies, very few reliable measurements of the extent of the chemical reactions have thus far been made. We have modified an existing 1-D shock tube facility to perform experiments in order to determine the extent of the explosive thermal/chemical interactions between molton aluminum and water by measuring important physical quantities such as the maximum dynamic pressure and the amount of the generated hydrogen. Experimental results show that transient pressures greater than 69 MPa with a rise time of less than 125 {mu}sec can occur as the result of the chemical reaction of 4.2 grams of molton aluminum (approximately 15% of the total mass of the fuel of 28 grams) at 980 C with room temperature water.

  20. Cluster automorphisms and compatibility of cluster variables

    OpenAIRE

    Assem, Ibrahim; Schiffler, Ralf; Shramchenko, Vasilisa

    2013-01-01

    In this paper, we introduce a notion of unistructural cluster algebras, for which the set of cluster variables uniquely determines the clusters. We prove that cluster algebras of Dynkin type and cluster algebras of rank 2 are unistructural, then prove that if $\\mathcal{A}$ is unistructural or of Euclidean type, then $f: \\mathcal{A}\\to \\mathcal{A}$ is a cluster automorphism if and only if $f$ is an automorphism of the ambient field which restricts to a permutation of the cluster variables. In ...

  1. Globular Cluster Formation in the Virgo Cluster

    CERN Document Server

    Moran, C Corbett; Lake, G

    2014-01-01

    Metal poor globular clusters (MPGCs) are a unique probe of the early universe, in particular the reionization era. Systems of globular clusters in galaxy clusters are particularly interesting as it is in the progenitors of galaxy clusters that the earliest reionizing sources first formed. Although the exact physical origin of globular clusters is still debated, it is generally admitted that globular clusters form in early, rare dark matter peaks (Moore et al. 2006; Boley et al. 2009). We provide a fully numerical analysis of the Virgo cluster globular cluster system by identifying the present day globular cluster system with exactly such early, rare dark matter peaks. A popular hypothesis is that that the observed truncation of blue metal poor globular cluster formation is due to reionization (Spitler et al. 2012; Boley et al. 2009; Brodie & Strader 2006); adopting this view, constraining the formation epoch of MPGCs provides a complementary constraint on the epoch of reionization. By analyzing both the l...

  2. Structure and stability of small H clusters on graphene

    DEFF Research Database (Denmark)

    Sljivancanin, Zeljko; Andersen, Mie; Hammer, Bjørk

    2011-01-01

    The structure and stability of small hydrogen clusters adsorbed on graphene is studied by means of density functional theory (DFT) calculations. Clusters containing up to six H atoms are investigated systematically, with the clusters having either all H atoms on one side of the graphene sheet (cis......-clusters) or having the H atoms on both sides in an alternating manner (trans-clusters). The most stable cis-clusters found have H atoms in ortho- and para-positions with respect to each other (two H’s on neighboring or diagonally opposite carbon positions within one carbon hexagon), while the most stable...... trans-clusters found have H atoms in ortho-trans-positions with respect to each other (two H’s on neighboring carbon positions, but on opposite sides of the graphene). Very stable trans-clusters with 13–22 H atoms were identified by optimizing the number of H atoms in ortho-trans-positions and thereby...

  3. Simulation of precipitation in an aluminum scandium alloy using kinetic Monte Carlo and DBSCAN algorithms

    OpenAIRE

    Moura, Alfredo de; Esteves, António

    2013-01-01

    The present paper reports the precipitation process of Al3Sc structures in an aluminum scandium alloy, which has been simulated with a kinetic Monte Carlo (kMC) method. The kMC implementation is based on the vacancy diffusion mechanism. To filter the raw data generated by the kMC simulation, the density-based clustering with noise (DBSCAN) method was employed. kMC and DBSCAN algorithms were implemented in the C language. The undertaken simulations were conducted in the SeARCH cluster at the U...

  4. Positron lifetimes in voids and other defects in annealed, neutron-irradiated aluminum

    International Nuclear Information System (INIS)

    Positron lifetimes were measured in neutron-irradiated high-purity aluminum single crystals, and companion small-angle x-ray scattering experiments were performed to determine the radius of gyration and volume fraction of radiation-induced voids. The lifetime data are consistent with a model in which positrons are trapped both in voids and in other defects which are tentatively identified as vacancy clusters bound to transmutation-produced silicon. The lifetime in the latter defects increased from 230 to 430 ps as the voids annealed out (around 3060C), suggesting that the clusters grow in size as voids disappear. The lifetime in voids remained constant at (550 +- 30) ps

  5. Fully Hydrogenated Beryllium Nanoclusters.

    Science.gov (United States)

    Koukaras, Emmanuel N; Sgouros, Aris P; Sigalas, Michael M

    2016-03-01

    We present the ground state and energetically low structures of BenH2n nanoclusters as predicted using density functional theory (DFT) and employing the M06 meta-hybrid exchange-correlation functional. Results using the M06 functional are benchmarked against high accuracy coupled-cluster CCSD(T) and found to be in excellent agreement. For small values of n, the linear or polymeric form is the lowest energy geometry, while for sizes larger, n > 9 ring type and link type structures are the energetically lowest configurations. This trend has also been observed through ab initio molecular dynamics (AIMD) simulations at finite temperatures. In addition to the binding energies of the structures we report on polymerization energies, Be-H bond energies with respect to coordination details, hydrogen desorption energies of saturated and oversaturated species, as well as computed infrared spectra of all the ground state and energetically low lying structures presented. Furthermore, we find that the saturated polymeric forms of the nanoclusters cannot retain molecular hydrogen, in contrast to what is expected when zero point energy corrections are not taken into account. PMID:26906563

  6. Adaptive Evolutionary Clustering

    OpenAIRE

    Xu, Kevin S.; Kliger, Mark; Hero III, Alfred O.

    2011-01-01

    In many practical applications of clustering, the objects to be clustered evolve over time, and a clustering result is desired at each time step. In such applications, evolutionary clustering typically outperforms traditional static clustering by producing clustering results that reflect long-term trends while being robust to short-term variations. Several evolutionary clustering algorithms have recently been proposed, often by adding a temporal smoothness penalty to the cost function of a st...

  7. Relational visual cluster validity

    OpenAIRE

    Ding, Y.; Harrison, R F

    2007-01-01

    The assessment of cluster validity plays a very important role in cluster analysis. Most commonly used cluster validity methods are based on statistical hypothesis testing or finding the best clustering scheme by computing a number of different cluster validity indices. A number of visual methods of cluster validity have been produced to display directly the validity of clusters by mapping data into two- or three-dimensional space. However, these methods may lose too much information to corre...

  8. Proton transfer in gas-phase ammonium dinitramide clusters

    Science.gov (United States)

    Alavi, Saman; Thompson, Donald L.

    2003-02-01

    Proton transfer in gaseous ammonium dinitramide (ADN) clusters up to (ADN)2 is studied by using density-functional theory. Proton transfer between the hydrogen dinitramide and ammonia units does not occur in the ADN monomer, rather the ammonia-hydrogen dinitramide complex is stabilized by strong hydrogen bonding. However, proton transfer between hydrogen dinitramide and ammonia is observed in the ADN dimer [NH3HN(NO2)2]2, ADN solvated with a single ammonia molecule [NH3NH(NO2)2]NH3, and ADN solvated with a hydrogen dinitramide molecule [NH3HN(NO2)2]HN(NO2)2. Structural changes in the complexes relative to the free molecules and the binding energies of the clusters are given. Using population analysis, the total electrostatic interaction energy in each cluster is calculated. The electrostatic energy is a measure that distinguishes between the ionic or hydrogen-bonded nature of the clusters. Some implications of proton transfer in ADN clusters on the decomposition mechanism of ADN are discussed.

  9. Hydrogen and Oxygen Gas Production in the UT TRIGA Reflector

    International Nuclear Information System (INIS)

    In December 1999, The University of Texas at Austin (UT) reported an unusual condition associated with the annular graphite reflector surrounding the Nuclear Engineering Teaching Laboratory (NETL) TRIGA reactor. The aluminum container encapsulating the graphite showed signs of bulging or swelling. Further, during an investigation of this occurrence, bubbles were detected coming from a weld in the aluminum. The gas composition was approximately 2:1 hydrogen to oxygen. After safety review and equipment fabrication, the reflector was successfully vented and flooded. The ratio of the gases produced is unusual, and the gas production mechanism has not yet been explained

  10. Hydrogen Peroxide Storage in Small Sealed Tanks

    Energy Technology Data Exchange (ETDEWEB)

    Whitehead, J.

    1999-10-20

    Unstabilized hydrogen peroxide of 85% concentration has been prepared in laboratory quantities for testing material compatibility and long term storage on a small scale. Vessels made of candidate tank and liner materials ranged in volume from 1 cc to 2540 cc. Numerous metals and plastics were tried at the smallest scales, while promising ones were used to fabricate larger vessels and liners. An aluminum alloy (6061-T6) performed poorly, including increasing homogeneous decay due to alloying elements entering solution. The decay rate in this high strength aluminum was greatly reduced by anodizing. Better results were obtained with polymers, particularly polyvinylidene fluoride. Data reported herein include ullage pressures as a function of time with changing decay rates, and contamination analysis results.

  11. Aluminum corrosion product release kinetics

    International Nuclear Information System (INIS)

    Highlights: • Release of Al corrosion product was measured in simulated post-LOCA sump solutions. • Increased boron was found to enhance Al release kinetics at similar pH. • Models of Al release as functions of time, temperature, and pH were developed. - Abstract: The kinetics of aluminum corrosion product release was examined in solutions representative of post-LOCA sump water for both pressurized water and pressurized heavy-water reactors. Coupons of AA 6061 T6 were exposed to solutions in the pH 7–11 range at 40, 60, 90 and 130 °C. Solution samples were analyzed by inductively coupled plasma atomic emission spectroscopy, and coupon samples were analyzed by secondary ion mass spectrometry. The results show a distinct “boron effect” on the release kinetics, expected to be caused by an increase in the solubility of the aluminum corrosion products. New models were developed to describe both sets of data as functions of temperature, time, and pH (where applicable)

  12. Aluminum corrosion product release kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Edwards, Matt, E-mail: Matthew.Edwards@cnl.ca; Semmler, Jaleh; Guzonas, Dave; Chen, Hui Qun; Toor, Arshad; Hoendermis, Seanna

    2015-07-15

    Highlights: • Release of Al corrosion product was measured in simulated post-LOCA sump solutions. • Increased boron was found to enhance Al release kinetics at similar pH. • Models of Al release as functions of time, temperature, and pH were developed. - Abstract: The kinetics of aluminum corrosion product release was examined in solutions representative of post-LOCA sump water for both pressurized water and pressurized heavy-water reactors. Coupons of AA 6061 T6 were exposed to solutions in the pH 7–11 range at 40, 60, 90 and 130 °C. Solution samples were analyzed by inductively coupled plasma atomic emission spectroscopy, and coupon samples were analyzed by secondary ion mass spectrometry. The results show a distinct “boron effect” on the release kinetics, expected to be caused by an increase in the solubility of the aluminum corrosion products. New models were developed to describe both sets of data as functions of temperature, time, and pH (where applicable)

  13. Laboratory Powder Metallurgy Makes Tough Aluminum Sheet

    Science.gov (United States)

    Royster, D. M.; Thomas, J. R.; Singleton, O. R.

    1993-01-01

    Aluminum alloy sheet exhibits high tensile and Kahn tear strengths. Rapid solidification of aluminum alloys in powder form and subsequent consolidation and fabrication processes used to tailor parts made of these alloys to satisfy such specific aerospace design requirements as high strength and toughness.

  14. Sanmenxia strives to create aluminum industrial base

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    <正>Contradiction between rich alumina resource and relatively weak electrolytic aluminum production capacity is the "bottleneck" inhibiting development of aluminum industry in San-menxia. During the period of "11th Five-Year Development", Sanmenxia will relay on its

  15. Aluminum induced proteome changes in tomato cotyledons

    Science.gov (United States)

    Cotyledons of tomato seedlings that germinated in a 20 µM AlK(SO4)2 solution remained chlorotic while those germinated in an aluminum free medium were normal (green) in color. Previously, we have reported the effect of aluminum toxicity on root proteome in tomato seedlings (Zhou et al. J Exp Bot, 20...

  16. Optimization of the HIRFL-CSR cluster target

    International Nuclear Information System (INIS)

    A new gas delivery system is designed and installed for HIRFL-CSR cluster target. The original blocked nozzle is replaced by a new one with the throat diameter of 0.12mm. New test of hydrogen and argon gases are performed. The stable jets can be obtained for these two operation gases. The attenuation of the jet caused by the collision with residual gas is studied. The maximum achievable H2 target density is 1.75 x 1013 atoms/cm3 with a target thickness of 6.3 x 1012 atoms/cm2 for HIRFL-CSR cluster target. The running stability of the cluster source is tested both for hydrogen and argon. The operation parameters for obtaining hydrogen jet are optimized. The results of long time running for H2 and Ar cluster jets look promising. The jet intensity has no essential change during the test for H2 and Ar. (authors)

  17. The hydrogen; L'hydrogene

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2004-07-01

    The hydrogen as an energy system represents nowadays a main challenge (in a scientific, economical and environmental point of view). The physical and chemical characteristics of hydrogen are at first given. Then, the challenges of an hydrogen economy are explained. The different possibilities of hydrogen production are described as well as the distribution systems and the different possibilities of hydrogen storage. Several fuel cells are at last presented: PEMFC, DMFC and SOFC. (O.M.)

  18. Gating of Permanent Molds for ALuminum Casting

    Energy Technology Data Exchange (ETDEWEB)

    David Schwam; John F. Wallace; Tom Engle; Qingming Chang

    2004-03-30

    This report summarizes a two-year project, DE-FC07-01ID13983 that concerns the gating of aluminum castings in permanent molds. The main goal of the project is to improve the quality of aluminum castings produced in permanent molds. The approach taken was determine how the vertical type gating systems used for permanent mold castings can be designed to fill the mold cavity with a minimum of damage to the quality of the resulting casting. It is evident that somewhat different systems are preferred for different shapes and sizes of aluminum castings. The main problems caused by improper gating are entrained aluminum oxide films and entrapped gas. The project highlights the characteristic features of gating systems used in permanent mold aluminum foundries and recommends gating procedures designed to avoid common defects. The study also provides direct evidence on the filling pattern and heat flow behavior in permanent mold castings.

  19. Trends in the global aluminum fabrication industry

    Science.gov (United States)

    Das, Subodh; Yin, Weimin

    2007-02-01

    The aluminum fabrication industry has become more vital to the global economy as international aluminum consumption has grown steadily in the past decades. Using innovation, value, and sustainability, the aluminum industry is strengthening its position not only in traditional packaging and construction applications but also in the automotive and aerospace markets to become more competitive and to face challenges from other industries and higher industrial standards. The aluminum fabrication industry has experienced a significant geographical shift caused by rapid growth in emerging markets in countries such as Brazil, Russia, India, and China. Market growth and distribution will vary with different patterns of geography and social development; the aluminum industry must be part of the transformation and keep pace with market developments to benefit.

  20. Aluminum-based metal-air batteries

    Science.gov (United States)

    Friesen, Cody A.; Martinez, Jose Antonio Bautista

    2016-01-12

    Provided in one embodiment is an electrochemical cell, comprising: (i) a plurality of electrodes, comprising a fuel electrode that comprises aluminum and an air electrode that absorbs gaseous oxygen, the electrodes being operable in a discharge mode wherein the aluminum is oxidized at the fuel electrode and oxygen is reduced at the air electrode, and (ii) an ionically conductive medium, comprising an organic solvent; wherein during non-use of the cell, the organic solvent promotes formation of a protective interface between the aluminum of the fuel electrode and the ionically conductive medium, and wherein at an onset of the discharge mode, at least some of the protective interface is removed from the aluminum to thereafter permit oxidation of the aluminum during the discharge mode.

  1. Aluminum recovery as a product with high added value using aluminum hazardous waste

    International Nuclear Information System (INIS)

    Highlights: • Granular and compact aluminum dross were physically and chemically characterized. • A relationship between density, porosity and metal content from dross was established. • Chemical reactions involving aluminum in landfill and negative consequences are shown. • A processing method for aluminum recovering from aluminum dross was developed. • Aluminum was recovered as an value product with high grade purity such as alumina. -- Abstract: The samples of hazardous aluminum solid waste such as dross were physically and chemically characterized. A relationship between density, porosity and metal content of dross was established. The paper also examines the chemical reactions involving aluminum dross in landfill and the negative consequences. To avoid environmental problems and to recovery the aluminum, a processing method was developed and aluminum was recovered as an added value product such as alumina. This method refers to a process at low temperature, in more stages: acid leaching, purification, precipitation and calcination. At the end of this process aluminum was extracted, first as Al3+ soluble ions and final as alumina product. The composition of the aluminum dross and alumina powder obtained were measured by applying the leaching tests, using atomic absorption spectrometry (AAS) and chemical analysis. The mineralogical composition of aluminum dross samples and alumina product were determined by X-ray diffraction (XRD) and the morphological characterization was performed by scanning electron microscopy (SEM). The method presented in this work allows the use of hazardous aluminum solid waste as raw material to recover an important fraction from soluble aluminum content as an added value product, alumina, with high grade purity (99.28%)

  2. Aluminum phosphate shows more adjuvanticity than Aluminum hydroxide in recombinant hepatitis –B vaccine formulation

    Directory of Open Access Journals (Sweden)

    2008-08-01

    Full Text Available Background: Although a number of investigation have been carried out to find alternative adjuvants to aluminum salts in vaccine formulations, they are still extensively used due to their good track record of safety, low cost and proper adjuvanticity with a variety of antigens. Adsorption of antigens onto aluminum compounds depends heavily on electrostatic forces between adjuvant and antigen. Commercial recombinant protein hepatitis B vaccines containing aluminum hydroxide as adjuvant is facing low induction of immunity in some sections of the vaccinated population. To follow the current global efforts in finding more potent hepatitis B vaccine formulation, adjuvanticity of aluminum phosphate has been compared to aluminum hydroxide. Materials and methods: The adjuvant properties of aluminum hydroxide and aluminum phosphate in a vaccine formulation containing a locally manufactured hepatitis B (HBs surface antigen was evaluated in Balb/C mice. The formulations were administered intra peritoneally (i.p. and the titers of antibody which was induced after 28 days were determined using ELISA technique. The geometric mean of antibody titer (GMT, seroconversion and seroprotection rates, ED50 and relative potency of different formulations were determined. Results: All the adjuvanicity markers obtained in aluminum phosphate formulation were significantly higher than aluminum hydroxide. The geometric mean of antibody titer of aluminum phosphate was approximately three folds more than aluminum hydroxide. Conclusion: Aluminum phosphate showed more adjuvanticity than aluminum hydroxide in hepatitis B vaccine. Therefore the use of aluminum phosphate as adjuvant in this vaccine may lead to higher immunity with longer duration of effects in vaccinated groups.

  3. Laser Assisted Joining of Hybrid Polyamide-aluminum Structures

    Science.gov (United States)

    Lamberti, Christian; Solchenbach, Tobias; Plapper, Peter; Possart, Wulff

    The demand for hybrid polymer-metal structures is continuously growing due to their great potential in automotive, aerospace and packaging applications. The expected capabilities are highly diverse and include functional, chemical and mechanical as well as economical and ecological aspects. A novel laser beam joining process for hybrid polyamide-aluminum structures is reported. The spatial and temporal heat input is optimized for optimal bonding quality. At the interface it was proven that the polyamide was not decomposed as a result of excessive thermal stress. It was shown that laser or electro-chemical surface pre-treatment of the aluminum substrate has a distinctive effect on the shear strength of the joint. However, the bond quality does not correspond to a change of surface roughness. Therefore, mechanical interlocking in direct relation to surface topology of the pre-treated substrate is not the principal cause for the bonding phenomenon. Chemical analysis in terms of IR-spectroscopy has shown a physicochemical interaction based on hydrogen bonds.

  4. Mechanism of vacancy formation induced by hydrogen in tungsten

    Directory of Open Access Journals (Sweden)

    Yi-Nan Liu

    2013-12-01

    Full Text Available We report a hydrogen induced vacancy formation mechanism in tungsten based on classical molecular dynamics simulations. We demonstrate the vacancy formation in tungsten due to the presence of hydrogen associated directly with a stable hexagonal self-interstitial cluster as well as a linear crowdion. The stability of different self-interstitial structures has been further studied and it is particularly shown that hydrogen plays a crucial role in determining the configuration of SIAs, in which the hexagonal cluster structure is preferred. Energetic analysis has been carried out to prove that the formation of SIA clusters facilitates the formation of vacancies. Such a mechanism contributes to the understanding of the early stage of the hydrogen blistering in tungsten under a fusion reactor environment.

  5. Oxidation dynamics of aluminum nanorods

    International Nuclear Information System (INIS)

    Aluminum nanorods (Al-NRs) are promising fuels for pyrotechnics due to the high contact areas with oxidizers, but their oxidation mechanisms are largely unknown. Here, reactive molecular dynamics simulations are performed to study thermally initiated burning of oxide-coated Al-NRs with different diameters (D = 26, 36, and 46 nm) in oxygen environment. We found that thinner Al-NRs burn faster due to the larger surface-to-volume ratio. The reaction initiates with the dissolution of the alumina shell into the molten Al core to generate heat. This is followed by the incorporation of environmental oxygen atoms into the resulting Al-rich shell, thereby accelerating the heat release. These results reveal an unexpectedly active role of the alumina shell as a “nanoreactor” for oxidation

  6. Process for anodizing aluminum foil

    International Nuclear Information System (INIS)

    In an integrated process for the anodization of aluminum foil for electrolytic capacitors including the formation of a hydrous oxide layer on the foil prior to anodization and stabilization of the foil in alkaline borax baths during anodization, the foil is electrochemically anodized in an aqueous solution of boric acid and 2 to 50 ppm phosphate having a pH of 4.0 to 6.0. The anodization is interrupted for stabilization by passing the foil through a bath containing the borax solution having a pH of 8.5 to 9.5 and a temperature above 800 C. and then reanodizing the foil. The process is useful in anodizing foil to a voltage of up to 760 V

  7. A perfect starburst cluster made in one go: The NGC 3603 young cluster

    Energy Technology Data Exchange (ETDEWEB)

    Banerjee, Sambaran [Argelander-Institut für Astronomie, Auf dem Hügel 71, D-53121 Bonn (Germany); Kroupa, Pavel [Helmholtz-Institut für Strahlen-und Kernphysik, Auf dem Hügel 71, D-53121 Bonn (Germany)

    2014-06-01

    Understanding how distinct, near-spherical gas-free clusters of very young, massive stars shape out of vast, complex clouds of molecular hydrogen is one of the biggest challenges in astrophysics. A popular thought dictates that a single gas cloud fragments into many newborn stars which, in turn, energize and rapidly expel the residual gas to form a gas-free cluster. This study demonstrates that the above classical paradigm remarkably reproduces the well-observed central, young cluster (HD 97950) of the Galactic NGC 3603 star-forming region, in particular, its shape, internal motion, and mass distribution of stars naturally and consistently follow from a single model calculation. Remarkably, the same parameters (star formation efficiency, gas expulsion timescale, and delay) reproduce HD 97950, as were found to reproduce the Orion Nebula Cluster, Pleiades, and R136. The present results therefore provide intriguing evidence of formation of star clusters through single-starburst events followed by significant residual gas expulsion.

  8. A perfect starburst cluster made in one go: The NGC 3603 young cluster

    International Nuclear Information System (INIS)

    Understanding how distinct, near-spherical gas-free clusters of very young, massive stars shape out of vast, complex clouds of molecular hydrogen is one of the biggest challenges in astrophysics. A popular thought dictates that a single gas cloud fragments into many newborn stars which, in turn, energize and rapidly expel the residual gas to form a gas-free cluster. This study demonstrates that the above classical paradigm remarkably reproduces the well-observed central, young cluster (HD 97950) of the Galactic NGC 3603 star-forming region, in particular, its shape, internal motion, and mass distribution of stars naturally and consistently follow from a single model calculation. Remarkably, the same parameters (star formation efficiency, gas expulsion timescale, and delay) reproduce HD 97950, as were found to reproduce the Orion Nebula Cluster, Pleiades, and R136. The present results therefore provide intriguing evidence of formation of star clusters through single-starburst events followed by significant residual gas expulsion.

  9. Partitional clustering algorithms

    CERN Document Server

    2015-01-01

    This book summarizes the state-of-the-art in partitional clustering. Clustering, the unsupervised classification of patterns into groups, is one of the most important tasks in exploratory data analysis. Primary goals of clustering include gaining insight into, classifying, and compressing data. Clustering has a long and rich history that spans a variety of scientific disciplines including anthropology, biology, medicine, psychology, statistics, mathematics, engineering, and computer science. As a result, numerous clustering algorithms have been proposed since the early 1950s. Among these algorithms, partitional (nonhierarchical) ones have found many applications, especially in engineering and computer science. This book provides coverage of consensus clustering, constrained clustering, large scale and/or high dimensional clustering, cluster validity, cluster visualization, and applications of clustering. Examines clustering as it applies to large and/or high-dimensional data sets commonly encountered in reali...

  10. Advances in molecular vibrations and collision dynamics molecular clusters

    CERN Document Server

    Bacic, Zatko

    1998-01-01

    This volume focuses on molecular clusters, bound by van der Waals interactions and hydrogen bonds. Twelve chapters review a wide range of recent theoretical and experimental advances in the areas of cluster vibrations, spectroscopy, and reaction dynamics. The authors are leading experts, who have made significant contributions to these topics.The first chapter describes exciting results and new insights in the solvent effects on the short-time photo fragmentation dynamics of small molecules, obtained by combining heteroclusters with femtosecond laser excitation. The second is on theoretical work on effects of single solvent (argon) atom on the photodissociation dynamics of the solute H2O molecule. The next two chapters cover experimental and theoretical aspects of the energetics and vibrations of small clusters. Chapter 5 describes diffusion quantum Monte Carlo calculations and non additive three-body potential terms in molecular clusters. The next six chapters deal with hydrogen-bonded clusters, refle...

  11. Oxidation kinetics of aluminum diboride

    Science.gov (United States)

    Whittaker, Michael L.; Sohn, H. Y.; Cutler, Raymond A.

    2013-11-01

    The oxidation characteristics of aluminum diboride (AlB2) and a physical mixture of its constituent elements (Al+2B) were studied in dry air and pure oxygen using thermal gravimetric analysis to obtain non-mechanistic kinetic parameters. Heating in air at a constant linear heating rate of 10 °C/min showed a marked difference between Al+2B and AlB2 in the onset of oxidation and final conversion fraction, with AlB2 beginning to oxidize at higher temperatures but reaching nearly complete conversion by 1500 °C. Kinetic parameters were obtained in both air and oxygen using a model-free isothermal method at temperatures between 500 and 1000 °C. Activation energies were found to decrease, in general, with increasing conversion for AlB2 and Al+2B in both air and oxygen. AlB2 exhibited O2-pressure-independent oxidation behavior at low conversions, while the activation energies of Al+2B were higher in O2 than in air. Differences in the composition and morphology between oxidized Al+2B and AlB2 suggested that Al2O3-B2O3 interactions slowed Al+2B oxidation by converting Al2O3 on aluminum particles into a Al4B2O9 shell, while the same Al4B2O9 developed a needle-like morphology in AlB2 that reduced oxygen diffusion distances and increased conversion. The model-free kinetic analysis was critical for interpreting the complex, multistep oxidation behavior for which a single mechanism could not be assigned. At low temperatures, moisture increased the oxidation rate of Al+2B and AlB2, but both appear to be resistant to oxidation in cool, dry environments.

  12. Molecular Cluster Perturbation Theory. I. Formalism

    CERN Document Server

    Byrd, Jason N; Molt,, Robert W; Bartlett, Rodney J; Sanders, Beverly A; Lotrich, Victor F

    2014-01-01

    We present second-order molecular cluster perturbation theory (MCPT(2)), a methodology to calculate arbitrarily large systems with explicit calculation of individual wavefunctions in a coupled cluster framework. This new MCPT(2) framework uses coupled cluster perturbation theory and an expansion in terms of molecular dimer interactions to obtain molecular wavefunctions that are infinite order in both the electronic fluctuation operator and all possible dimer (and products of dimers) interactions. The MCPT(2) framework has been implemented in the new SIA/ACES parallel architecture, making use of the advanced dynamic memory control and fine grained parallelism to perform very large explicit molecular cluster calculations. To illustrate the power of this method, we have computed energy shifts and lattice site dipole moments for the polar and non-polar configurations of solid hydrogen fluoride by scaling an explicit lattice to the bulk limit. The explicit lattice size without periodic boundary conditions was scal...

  13. Superhydrophobic coating deposited directly on aluminum

    Energy Technology Data Exchange (ETDEWEB)

    Escobar, Ana M., E-mail: annaescobarromero@ub.edu; Llorca-Isern, Nuria

    2014-06-01

    This study develops an alternative method for enhancing superhydrophobicity on aluminum surfaces with an amphiphilic reagent such as the dodecanoic acid. The goal is to induce superhydrophobicity directly through a simple process on pure (99.9 wt%) commercial aluminum. The initial surface activation leading to the formation of the superhydrophobic coating is studied using confocal microscopy. Superhydrophobic behavior is analyzed by contact angle measurements, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The highest contact angle (approaching 153°) was obtained after forming hierarchical structures with a particular roughness obtained by grinding and polishing microgrooves on the aluminum surface together with the simultaneous action of HCl and dodecanoic acid. The results also showed that after immersion in the ethanol-acidic-fatty acid solutions, they reacted chemically through the action of the fatty acid, on the aluminum surface. The mechanism is analyzed by TOF-SIMS and XPS in order to determine the molecules involved in the reaction. The TOF-SIMS analysis revealed that the metal and its oxides seem to be necessary, and that free-aluminum is anchored to the fatty acid molecules and to the alumina molecules present in the medium. Consequently, both metallic aluminum and aluminum oxides are necessary in order to form the compound responsible for superhydrophobicity.

  14. Modification of galvannealed steel through aluminum addition

    International Nuclear Information System (INIS)

    Aluminum is believed to modify and to some extent control the coating characteristics of commercially produced galvanneal sheet steel. These include mechanical, chemical, and aesthetic properties. Whereas the aluminum added to the molten zinc bath is known to form intermetallics before the steel is annealed, our research is primarily concerned with the effect aluminum has on suppression or enhancement of the particular iron-zinc alloy phases in the coating during galvannealing. The microstructure of four commercially important iron-zinc intermetallic phases containing varying aluminum content between 0-1.5 weight percent has been studied. It is also believed that an iron-aluminum alloy, known as the inhibition layer, forms on the steel surface following hot dipping and prior to annealing. Transmission and scattering Moessbauer spectroscopy as well as X-ray diffraction have been used to identify iron-zinc and iron-aluminum alloys present in the coatings. Discussion will be presented on the effect aluminum has on phase suppression for Fe-Zn alloys prepared in commercially produced galvanneal

  15. Cluster Evaluation of Density Based Subspace Clustering

    OpenAIRE

    Sembiring, Rahmat Widia; Zain, Jasni Mohamad

    2010-01-01

    Clustering real world data often faced with curse of dimensionality, where real world data often consist of many dimensions. Multidimensional data clustering evaluation can be done through a density-based approach. Density approaches based on the paradigm introduced by DBSCAN clustering. In this approach, density of each object neighbours with MinPoints will be calculated. Cluster change will occur in accordance with changes in density of each object neighbours. The neighbours of each object ...

  16. Clustering with Spectral Methods

    OpenAIRE

    Gaertler, Marco

    2002-01-01

    Grouping and sorting are problems with a great tradition in the history of mankind. Clustering and cluster analysis is a small aspect in the wide spectrum. But these topics have applications in most scientific disciplines. Graph clustering is again a little fragment in the clustering area. Nevertheless it has the potential for new pioneering and innovative methods. One such method is the Markov Clustering presented by van Dongen in 'Graph Clustering by Flow Simulation'. We investigated the qu...

  17. Sparse Convex Clustering

    OpenAIRE

    Wang, Binhuan; Zhang, Yilong; Sun, Wei; Fang, Yixin

    2016-01-01

    Convex clustering, a convex relaxation of k-means clustering and hierarchical clustering, has drawn recent attentions since it nicely addresses the instability issue of traditional nonconvex clustering methods. Although its computational and statistical properties have been recently studied, the performance of convex clustering has not yet been investigated in the high-dimensional clustering scenario, where the data contains a large number of features and many of them carry no information abo...

  18. Lead exposure from aluminum cookware in Cameroon

    Energy Technology Data Exchange (ETDEWEB)

    Weidenhamer, Jeffrey D.; Kobunski, Peter A. [Department of Chemistry, Geology and Physics, 401 College Ave., Ashland University, Ashland, OH 44805 (United States); Kuepouo, Gilbert [Research and Education Centre for Development (CREPD), Yaounde (Cameroon); Corbin, Rebecca W. [Department of Chemistry, Geology and Physics, 401 College Ave., Ashland University, Ashland, OH 44805 (United States); Gottesfeld, Perry, E-mail: pgottesfeld@okinternational.org [Occupational Knowledge International, San Francisco, CA (United States)

    2014-10-15

    Blood lead levels have decreased following the removal of lead from gasoline in most of the world. However, numerous recent studies provide evidence that elevated blood lead levels persist in many low and middle-income countries around the world at much higher prevalence than in the more developed countries. One potential source of lead exposure that has not been widely investigated is the leaching of lead from artisanal aluminum cookware, which is commonly used in the developing world. Twenty-nine samples of aluminum cookware and utensils manufactured by local artisans in Cameroon were collected and analyzed for their potential to release lead during cooking. Source materials for this cookware included scrap metal such as engine parts, radiators, cans, and construction materials. The lead content of this cookware is relatively low (< 1000 ppm by X-ray fluorescence), however significant amounts of lead, as well as aluminum and cadmium were released from many of the samples using dilute acetic acid extractions at boiling and ambient temperatures. Potential exposures to lead per serving were estimated to be as high as 260 μg, indicating that such cookware can pose a serious health hazard. We conclude that lead, aluminum and cadmium can migrate from this aluminum cookware during cooking and enter food at levels exceeding recommended public health guidelines. Our results support the need to regulate lead content of materials used to manufacture these pots. Artisanal aluminum cookware may be a major contributor to lead poisoning throughout the developing world. Testing of aluminum cookware in other developing countries is warranted. - Highlights: • Cookware is manufactured in Cameroon from scrap aluminum including car parts. • Twenty-nine cookware samples were evaluated for their potential to leach lead. • Boiling extractions to simulate the effects of cooking released significant lead. • Potential lead exposures per serving are estimated as high as 260 μg.

  19. Lead exposure from aluminum cookware in Cameroon

    International Nuclear Information System (INIS)

    Blood lead levels have decreased following the removal of lead from gasoline in most of the world. However, numerous recent studies provide evidence that elevated blood lead levels persist in many low and middle-income countries around the world at much higher prevalence than in the more developed countries. One potential source of lead exposure that has not been widely investigated is the leaching of lead from artisanal aluminum cookware, which is commonly used in the developing world. Twenty-nine samples of aluminum cookware and utensils manufactured by local artisans in Cameroon were collected and analyzed for their potential to release lead during cooking. Source materials for this cookware included scrap metal such as engine parts, radiators, cans, and construction materials. The lead content of this cookware is relatively low (< 1000 ppm by X-ray fluorescence), however significant amounts of lead, as well as aluminum and cadmium were released from many of the samples using dilute acetic acid extractions at boiling and ambient temperatures. Potential exposures to lead per serving were estimated to be as high as 260 μg, indicating that such cookware can pose a serious health hazard. We conclude that lead, aluminum and cadmium can migrate from this aluminum cookware during cooking and enter food at levels exceeding recommended public health guidelines. Our results support the need to regulate lead content of materials used to manufacture these pots. Artisanal aluminum cookware may be a major contributor to lead poisoning throughout the developing world. Testing of aluminum cookware in other developing countries is warranted. - Highlights: • Cookware is manufactured in Cameroon from scrap aluminum including car parts. • Twenty-nine cookware samples were evaluated for their potential to leach lead. • Boiling extractions to simulate the effects of cooking released significant lead. • Potential lead exposures per serving are estimated as high as 260 μg.

  20. Fatigue analysis of aluminum drill pipes

    Directory of Open Access Journals (Sweden)

    João Carlos Ribeiro Plácido

    2005-12-01

    Full Text Available An experimental program was performed to investigate the fundamental fatigue mechanisms of aluminum drill pipes. Initially, the fatigue properties were determined through small-scale tests performed in an optic-mechanical fatigue apparatus. Additionally, full-scale fatigue tests were carried out with three aluminum drill pipe specimens under combined loading of cyclic bending and constant axial tension. Finally, a finite element model was developed to simulate the stress field along the aluminum drill pipe during the fatigue tests and to estimate the stress concentration factors inside the tool joints. By this way, it was possible to estimate the stress values in regions not monitored during the fatigue tests.

  1. Spray Rolling Aluminum Strip for Transportation Applications

    Energy Technology Data Exchange (ETDEWEB)

    Kevin M. McHugh; Y. Lin; Y. Zhou; E. J. Lavernia; J.-P. Delplanque; S. B. Johnson

    2005-02-01

    Spray rolling is a novel strip casting technology in which molten aluminum alloy is atomized and deposited into the roll gap of mill rolls to produce aluminum strip. A combined experimental/modeling approach has been followed in developing this technology with active participation from industry. The feasibility of this technology has been demonstrated at the laboratory scale and it is currently being scaled-up. This paper provides an overview of the process and compares the microstructure and properties of spray-rolled 2124 aluminum alloy with commercial ingot-processed material

  2. Recycling of Aluminum from Fibre Metal Laminates

    OpenAIRE

    Zhu, G.; Xiao, Y; Yang, Y.; Wang, J.; Sun, B; Boom, R.

    2012-01-01

    Recycling of aluminum alloy scrap obtained from delaminated fibre metal laminates (FMLs) was studied through high temperature refining in the presence of a salt flux. The aluminum alloy scrap contains approximately mass fraction w(Cu) = 4.4%, w(Mg) = 1.1% and w(Mn) = 0.6% (2024 aluminum alloy). The main objective of this research is to obtain a high metal yield, while maintaining its original alloy compositions. The work focuses on the metal yield and quality of recycled Al alloy under differ...

  3. Nanoscalic metal-hydrogen systems

    International Nuclear Information System (INIS)

    In the present thesis first the influences of the special microstructure of nanoscalic M-H systems are considered, whereby studies respective results on free model systems are presented. Then the influence of lattice distortions is discussed, and the interaction of dislocations with hydrogen is studied. For this measurements on plastically deformed metal are presented. Then the determination of the local and mean hydrogen concentration in nanoscalic systems is discussed. The next chapter deals with influences of the support on the behaviour of nanoscalic M-H systems. For this first a description of the strongly adhering system on a substrate in the framework of the linear elasticity theory is presented. It is shown that by the adhesion high H-induced stresses in the GPa region can occur. Furthermore the possibility of nanoscalic systems is discussed to meet such stresses. For this models, which were developed for the growth of layers and their mechanical behaviour, are transferred to M-H systems. In the second part of the chapter the case of weak adhesion on the substrate is studied. Hereby especially the H-induced local layer separation is discussed. In the next chapter studies on M-H layers are presented. Hereby by comparison of differently fabricated and after-treated layers especially the influence of the microstructure on the stress and strain behaviour of the layers is presented. Furthermore H-induced changes of the layer morphology are considered. While the first part of this chapter is concentrated on Nb-H layers in the second part results on other M-H systems like Pd-H, Gd-H-, and Y-H are summarized. By comparison of the results it is tried to get an as unique as possible picture of the layer behaviour. Thereafter the view is put on the influence of interfaces. Here the study of the local chemistry of the metal lattice and the local distribution of the hydrogen holds the spotlight. Finally studies on M-H clusters on the example of palladium-hydrogen are

  4. Changes in porosity of foamed aluminum during solidification

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    In order to control the porosity of foamed aluminum, the changes in the porosity of foamed aluminum melt in the processes of foaming and solidification, the distribution of the porosity of foamed aluminum, and the relationship between them were studied. The results indicated that the porosity of foamed aluminum coincides well with the foaming time.

  5. 46 CFR 154.195 - Aluminum cargo tank: Steel enclosure.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 5 2010-10-01 2010-10-01 false Aluminum cargo tank: Steel enclosure. 154.195 Section... Equipment Hull Structure § 154.195 Aluminum cargo tank: Steel enclosure. (a) An aluminum cargo tank and its... the aluminum cargo tank must meet the steel structural standards of the American Bureau of...

  6. 49 CFR 229.51 - Aluminum main reservoirs.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Aluminum main reservoirs. 229.51 Section 229.51... Aluminum main reservoirs. (a) Aluminum main reservoirs used on locomotives shall be designed and fabricated as follows: (1) The heads and shell shall be made of Aluminum Association Alloy No. 5083-0,...

  7. Formulation and method for preparing gels comprising hydrous aluminum oxide

    Science.gov (United States)

    Collins, Jack L.

    2014-06-17

    Formulations useful for preparing hydrous aluminum oxide gels contain a metal salt including aluminum, an organic base, and a complexing agent. Methods for preparing gels containing hydrous aluminum oxide include heating a formulation to a temperature sufficient to induce gel formation, where the formulation contains a metal salt including aluminum, an organic base, and a complexing agent.

  8. 49 CFR 178.505 - Standards for aluminum drums.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Standards for aluminum drums. 178.505 Section 178... PACKAGINGS Non-bulk Performance-Oriented Packaging Standards § 178.505 Standards for aluminum drums. (a) The following are the identification codes for aluminum drums: (1) 1B1 for a non-removable head aluminum...

  9. Nanshan Aluminum Reached Strategic Cooperation with CSR Corporation Limited

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    As a key supplier of aluminum profiles and aluminum plate,sheet and trip products for CSR Corporation Limited,Nanshan Aluminum will join hands with CSR Corporation Limited to reach strategic cooperation.On January 5,Nanshan Aluminum signed strategic cooperation agreement with CSR Sifang Locomotive&Rolling; Stock Co.,Ltd,both

  10. X-ray photoelectron spectroscopy study of catalyzed aluminum carbide formation at aluminum-carbon interfaces

    Science.gov (United States)

    Rabenberg, L.; Maruyama, Benji

    1990-01-01

    Aluminum carbide may form at aluminum-graphite interfaces during the high-temperature processing of graphite fiber-reinforced aluminum metal matrix composites. The chemical interactions leading to the formation of the aluminum carbide in the solid state involve the breaking of the carbon-carbon bonds within the graphite, the transport of the carbon atoms across the interface, and the reaction with the aluminum to form Al4C3. The aluminum carbide formation process has been followed using X-ray photoelectron spectroscopy of model, thin-film, reaction couples. The overall reaction is shown to be catalyzed by the presence of water vapor. Water at the interface increases reaction kinetics by apparently weakening the bonds between the surface carbon atoms and their substrate. This result is in general agreement with what is known to occur during the oxidation of graphite in air.

  11. A simple aluminum gasket for use with both stainless steel and aluminum flanges

    International Nuclear Information System (INIS)

    A technique has been developed for making aluminum wire seal gaskets of various sizes and shapes for use with both stainless steel and aluminum alloy flanges. The gasket material used is 0.9999 pure aluminum, drawn to a diameter of 3 mm. This material can be easily welded and formed into various shapes. A single gasket has been successfully used up to five times without baking. The largest gasket tested to date is 3.5 m long and was used in the shape of a parallelogram. Previous use of aluminum wire gaskets, including results for bakeout at temperatures from 20 to 660 degree C, is reviewed. A search of the literature indicates that this is the first reported use of aluminum wire gaskets for aluminum alloy flanges. The technique is described in detail, and the results are summarized. 11 refs., 4 figs

  12. Chemisorption and reactions on clusters of nickel atoms

    Science.gov (United States)

    Waber, J. T.; Adachi, H.; Yu, T.

    1982-01-01

    The nucleation and growth of metallic clusters on a substantially amorphous substrate are discussed with emphasis on the geometrical and electronic structure of the clusters. Several clusters of different symmetry containing five to nine nickel atoms were studied. It was found that the energy range of primary d-like states is not significantly different from the width of the d-band states in nickel metal, as long as the interatomic distance is comparable to that in the bulk metal. The approach of one or more molecules to the cluster is examined using at the hydrogenation of acetylene and the dehydrogenation of ethylene as examples.

  13. Final Report: Metal Perhydrides for Hydrogen Storage

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-07-26

    H 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

  14. Cluster categories and cluster-tilted algebras

    OpenAIRE

    Torkildsen, Hermund Andre

    2006-01-01

    We have given an introduction to the theory of cluster categories and cluster-tilted algebras, and this was one of our main objectives in this thesis. We have seen that cluster-tilted algebras are relation-extension algebras, and this gave us a way of constructing the quiver of a cluster-tilted algebra from a tilted algebra. A cluster-tilted algebra of finite representation type is determined by its quiver, and this raised questions about the generality of this result. We defined a new class...

  15. Coordination Structure of Aluminum in Magnesium Aluminum Hydroxide Studied by 27Al NMR

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The coordination structure of aluminum in magnesium aluminum hydroxide was studiedby 27Al NMR. The result showed that tetrahedral aluminum (AlⅣ) existed in magnesiumaluminum hydroxide, and the contents of AlⅣ increased with the increase of the ratio of Al/Mg andwith the peptizing temperature. AlⅣ originated from the so-called Al13 polymer with the structureof one Al tetrahedron surrounded by twelve Al octahedrons.

  16. Diffuse Parenchymal Diseases Associated With Aluminum Use and Primary Aluminum Production

    OpenAIRE

    Taiwo, Oyebode A.

    2014-01-01

    Aluminum use and primary aluminum production results in the generation of various particles, fumes, gases, and airborne materials with the potential for inducing a wide range of lung pathology. Nevertheless, the presence of diffuse parenchymal or interstitial lung disease related to these processes remains controversial. The relatively uncommon occurrence of interstitial lung diseases in aluminum-exposed workers—despite the extensive industrial use of aluminum—the potential for concurrent exp...

  17. Differences of growth response to aluminum excess of two Melaleuca trees differing in aluminum resistance

    OpenAIRE

    Houman, Yoshifumi; Tahara, Ko; Shinmachi, Fumie; Noguchi, Akira; Satohiko, Sasaki; Hasegawa, Isao

    2009-01-01

    Factors that inhibit the growth of plants in strongly acidic soils include low pH and aluminum excess. We evaluated two Myrtaceae species (Melaleuca cajuputi and Melaleuca bracteata), which are useful trees in tropical regions due to their resistance to low pH and excessive aluminum, to determine their response characteristics to environmental stresses. The results revealed that M.cajuputi, the growth by the aluminum concentration was not inhibited. However, the root growth of M.bracteata, by...

  18. Aluminum hydroxide nanoparticles show a stronger vaccine adjuvant activity than traditional aluminum hydroxide microparticles

    OpenAIRE

    Li, Xinran; Aldayel, Abdulaziz M.; Cui, Zhengrong

    2013-01-01

    Aluminum hydroxide is used as a vaccine adjuvant in various human vaccines. Unfortunately, despite its favorable safety profile, aluminum hydroxide can only weakly or moderately potentiate antigen-specific antibody responses. When dispersed in an aqueous solution, aluminum hydroxide forms particulates of 1–20 µm. There is increasing evidence that nanoparticles around or less than 200 nm as vaccine or antigen carriers have a more potent adjuvant activity than large microparticles. In the prese...

  19. The effect of relatively low hydrogen dilution on the properties of carbon-rich hydrogenated amorphous silicon carbide films

    International Nuclear Information System (INIS)

    Carbon-rich hydrogenated amorphous silicon carbide (a-Si1-xCx:H) films were deposited by plasma enhanced chemical vapor deposition (PECVD) using silane, ethylene and hydrogen as gas sources. The effect of relatively low hydrogen dilution on the properties of as-deposited samples was investigated. A variety of techniques including Scanning Electron Microscope (SEM), Fourier transform infrared spectroscopy (FTIR), Raman scattering (RS), UV-VIS spectrophotometer and photoluminescence (PL) spectroscopy were used to characterize the grown films. The deposition rate decreases with hydrogen dilution. The silicon to carbon ratio increases slightly with the addition of hydrogen. The phenomenon can be attributed to the dissipation of power density caused by hydrogen dilution. Raman G peak position shifting to a lower wave number indicates that hydrogen dilution reduces the size and concentration of sp2 carbon clusters, which is caused by the etching effect by atomic hydrogen. The optical band gap, which is controlled by the sp2 carbon clusters and Si/C ratio, changes unmonotonously. The as-deposited samples exhibited a blue-green room-temperature (RT) PL well visible to the naked eye with UV excitation. The PL band can be attributed to the radiative recombination of electron-hole pairs within small sp2 clusters containing C=C and C-H units in a sp3 amorphous matrix.

  20. Characterization of Al30 in commercial poly-aluminum chlorohydrate by solid-state (27)Al NMR spectroscopy.

    Science.gov (United States)

    Phillips, Brian L; Vaughn, John S; Smart, Scott; Pan, Long

    2016-08-15

    Investigation of commercially produced hydrolysis salts of aluminum by solid-state (27)Al NMR spectroscopy and size-exclusion chromatography (SEC) reveals well-defined and distinct Al environments that can be related to physicochemical properties. (27)Al MAS and MQ-MAS NMR spectroscopic data show that the local structure of the solids is dominated by moieties that closely resemble the Al30 polyoxocation (Al30O8(OH)56(H2O)26(18+)), accounting for 72-85% of the total Al. These Al30-like clusters elute as several size fractions by SEC. Comparison of the SEC and NMR results indicates that the Al30-like clusters includes intact isolated clusters, moieties of larger polymers or aggregates, and possibly fragments resembling δ-Al13 Keggin clusters. The coagulation efficacy of the solids appears to correlate best with the abundance of intact Al30-like clusters and of smaller species available to promote condensation reactions. PMID:27232539