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Sample records for aluminum hydride phases

  1. Hydride vapor phase epitaxy of aluminum nitride

    NASA Astrophysics Data System (ADS)

    Kamber, Derrick Shane

    AlN is a promising substrate material for AlGaN-based UV optoelectronic devices and high-power, high-frequency electronic devices. Since large-area bulk AlN crystals are not readily available, one approach to prepare AlN substrates is to heteroepitaxially deposit thick (e.g., 10-300+ mum) AlN layers by hydride vapor phase epitaxy. Initial efforts focused on growing AlN layers on sapphire substrates with growth rates up to 75 mum/hr. The resulting layers were colorless, smooth, and specular. Subsurface cracking, attributed to the plastic relief of tensile strain from island coalescence, was observed but did not adversely affect the surface morphology of the AlN layers. The surfaces possessed rms roughnesses as low as 0.316 nm over 5 x 5 mum2 sampling areas, but hexagonal hillock formation was observed for thick films grown at high growth rates. TEM revealed that the threading dislocation (TD) density of the films was 2 x 109 cm-2. The high TD densities for direct growth of AlN films on foreign substrates motivated the development of lateral epitaxial overgrowth approaches for defect reduction. Growth of AlN layers on patterned SiC substrates produced coalesced AlN films possessing TD densities below 8.3 x 106 cm -2 in the laterally grown wing regions, as compared to 1.8 x 109 cm-2 in the seed regions. These films, however, cracked on cooldown due to the difference in thermal expansion coefficients for AlN and SiC. To avoid this cracking, AlN layers were grown on patterned sapphire substrates. Although the films were able to be coalesced and contained few or no cracks, the TDs in these films were not confined to the seed regions. This produced a relatively uniform distribution of TDs over the surfaces of the films, with only a modest reduction in the TD density of 1 x 10 8 cm-2. Selective area growth of AlN was also pursued using Si3N4, SiO2, and Ti masks. Growth selectivity and film coalescence was observed for films grown on each masking material, but none of the

  2. Solid State NMR Studies of the Aluminum Hydride Phases

    NASA Technical Reports Server (NTRS)

    Hwang, Son-Jong; Bowman, R. C., Jr.; Graetz, Jason; Reilly, J. J.

    2006-01-01

    Several solid state NMR techniques including magic-angle-spinning (MAS) and multiple-quantum (MQ) MAS experiments have been used to characterize various AlH3 samples. MAS-NMR spectra for the 1H and 27Al nuclei have been obtained on a variety of AlH3 samples that include the (beta)- and (gamma)- phases as well as the most stable (alpha)-phase. While the dominant components in these NMR spectra correspond to the aluminum hydride phases, other species were found that include Al metal, molecular hydrogen (H2), as well as peaks that can be assigned to Al-O species in different configurations. The occurrence and concentration of these extraneous components are dependent upon the initial AlH3 phase composition and preparation procedures. Both the (beta)-AlH3 and (gamma)-AlH3 phases were found to generate substantial amounts of Al metal when the materials were stored at room temperature while the (alpha)-phase materials do not exhibit these changes.

  3. Solid State NMR Studies of the Aluminum Hydride Phases

    NASA Technical Reports Server (NTRS)

    Hwang, Son-Jong; Bowman, R. C., Jr.; Graetz, Jason; Reilly, J. J.

    2006-01-01

    Several solid state NMR techniques including magic-angle-spinning (MAS) and multiple-quantum (MQ) MAS experiments have been used to characterize various AlH3 samples. MAS-NMR spectra for the 1H and 27Al nuclei have been obtained on a variety of AlH3 samples that include the (beta)- and (gamma)- phases as well as the most stable (alpha)-phase. While the dominant components in these NMR spectra correspond to the aluminum hydride phases, other species were found that include Al metal, molecular hydrogen (H2), as well as peaks that can be assigned to Al-O species in different configurations. The occurrence and concentration of these extraneous components are dependent upon the initial AlH3 phase composition and preparation procedures. Both the (beta)-AlH3 and (gamma)-AlH3 phases were found to generate substantial amounts of Al metal when the materials were stored at room temperature while the (alpha)-phase materials do not exhibit these changes.

  4. Cubic metallic phase of aluminum hydride showing improved hydrogen desorption

    NASA Astrophysics Data System (ADS)

    Scheicher, R. H.; Kim, D. Y.; Lebègue, S.; Arnaud, B.; Alouani, M.; Ahuja, R.

    2008-05-01

    We report on our results calculated from density functional theory and GW of the dehydrogenation properties in a cubic phase of AlH3. The metallic nature of the electronic structure entails a more favorable hydrogen removal energy which is lowered by 75% compared to the insulating hexagonal phase. This remarkable reduction in the Al-H bond strength bears important consequences for feasible applications of AlH3 as an on-board hydrogen storage material for mobile applications. We suggest that the cubic phase could be prepared and stabilized experimentally at ambient pressure by off-board quenching.

  5. Cubic Metallic Phase of Aluminum Hydride Showing Improved Hydrogen Desorption

    NASA Astrophysics Data System (ADS)

    Scheicher, Ralph H.; Kim, Duck Young; Ahuja, Rajeev

    2009-03-01

    AlH3 is of great interest for hydrogen storage applications, with a particularly attractive feature being its large hydrogen capacity of 10 wt.%. Here we report the results of our density functional theory study of the dehydrogenation properties in a cubic phase of AlH3. The metallic nature of the electronic structure entails a more favorable hydrogen removal energy which is lowered by 75% compared to the insulating hexagonal phase. This remarkable reduction in the Al--H bond strength might bear important consequences for feasible applications of AlH3 as an on-board hydrogen storage material for mobile applications. Suggestions are made how the cubic phase could be prepared and stabilized at ambient pressure by off-board quenching. See also: R. H. Scheicher, D. Y. Kim, S. Lebègue, B. Arnaud, M.Alouani, and R. Ahuja, Appl. Phys. Lett. 92, 201903 (2008) and D. Y. Kim, R. H. Scheicher, and R. Ahuja, Phys. Rev. B 78, 100102(R) (2008).

  6. Stability Studies of Aluminum Hydride

    NASA Astrophysics Data System (ADS)

    Tang, Xia; Laube, Bruce; Anton, Donald; Hwang, Son-Jong; Bowman, Robert

    2007-03-01

    Aluminum hydride has attracted research attention recently as a promising hydrogen storage material due to its high gravimetric, volumetric storage capacity and very low enthalpy. AlH3 forms several phases, all of which are sensitive to moisture. In this study, the discharge kinetics of a stabilized form of alpha aluminum hydride newly synthesized was evaluated. Its desorption kinetics were measured in the temperature range of 60-120^oC at one atmosphere of hydrogen pressure. The material was stable at ambient temperature and no significant dehydrogenation was observed at 60^oC after 70 hours. Approximately 10 wt% hydrogen was rapidly (quantify in wt%/min.) released at 100^oC with no additional catalization. The activation energy for desorption was measured at 97.0 KJ/mole H2. The surface and bulk characterization methods Auger, SEM, XRD, and solid state NMR were used to investigate the mechanism of stabilization.

  7. The Oxidation Products of Aluminum Hydride and Boron Aluminum Hydride Clusters

    DTIC Science & Technology

    2016-01-04

    AFRL-AFOSR-VA-TR-2016-0075 The Oxidation Products of Aluminum Hydride and Boron Aluminum Hydride Clusters KIT BOWEN JOHNS HOPKINS UNIV BALTIMORE MD...Hydride and Boron Aluminum Hydride Clusters 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA9550-14-1-0324 5c.  PROGRAM ELEMENT NUMBER 61102F 6. AUTHOR(S) KIT...of both Aluminum Hydride Cluster Anions and Boron Aluminum Hydride Cluster Anions with Oxygen: Anionic Products The anionic products of reactions

  8. Regeneration of aluminum hydride

    DOEpatents

    Graetz, Jason Allan; Reilly, James J.

    2009-04-21

    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, by increasing the magnitude of the change in enthalpy of the reaction or combinations thereof.

  9. Regeneration of aluminum hydride

    DOEpatents

    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.

  10. Activated aluminum hydride hydrogen storage compositions and uses thereof

    DOEpatents

    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.

  11. Aluminum Hydride Catalyzed Hydroboration of Alkynes.

    PubMed

    Bismuto, Alessandro; Thomas, Stephen P; Cowley, Michael J

    2016-12-05

    An aluminum-catalyzed hydroboration of alkynes using either the commercially available aluminum hydride DIBAL-H or bench-stable Et3 Al⋅DABCO as the catalyst and H-Bpin as both the boron reagent and stoichiometric hydride source has been developed. Mechanistic studies revealed a unique mode of reactivity in which the reaction is proposed to proceed through hydroalumination and σ-bond metathesis between the resultant alkenyl aluminum species and HBpin, which acts to drive turnover of the catalytic cycle. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Thermal- and photoactivation of aluminum hydride decomposition

    NASA Astrophysics Data System (ADS)

    Gabis, I. E.; Elets, D. I.; Kuznetsov, V. G.; Baraban, A. P.; Dobrotvorskii, M. A.; Dobrotvorskii, A. M.

    2012-11-01

    Processes occurring in the phase of AlH3 dehydrogenation incubation that precedes the active decomposition of the hydride and is evidently accompanied by a change in its material properties are investigated by thermal desorption spectroscopy and barometry. The electronic structures of α-AlH3 and α-AlH3:V(H0) (i.e., aluminum hydride with a neutral hydrogen atom removed) are calculated by the density functional method. It is shown that hydrogen vacancies are the source of nuclei for the metallic phase, and their emergence could be thermally activated. It is established that UV irradiation also leads to the formation of hydrogen vacancies in α-AlH3. A description of the probable mechanism for the accumulation of hydrogen vacancies at elevated temperatures and finally to the appearance of metallic phase nuclei is offered. It is shown that UV irradiation allows us to lower the temperature of the dehydrogenation of α-AlH3 crystals.

  13. Photoelectron spectroscopic study of carbon aluminum hydride cluster anions.

    PubMed

    Zhang, Xinxing; Wang, Haopeng; Ganteför, Gerd; Eichhorn, Bryan W; Kiran, Boggavarapu; Bowen, Kit H

    2016-10-21

    Numerous previously unknown carbon aluminum hydride cluster anions were generated in the gas phase, identified by time-of-flight mass spectrometry and characterized by anion photoelectron spectroscopy, revealing their electronic structure. Density functional theory calculations on the CAl5-9H(-) and CAl5-7H2(-) found that several of them possess unusually high carbon atom coordination numbers. These cluster compositions have potential as the basis for new energetic materials.

  14. Photoelectron spectroscopic study of carbon aluminum hydride cluster anions

    NASA Astrophysics Data System (ADS)

    Zhang, Xinxing; Wang, Haopeng; Ganteför, Gerd; Eichhorn, Bryan W.; Kiran, Boggavarapu; Bowen, Kit H.

    2016-10-01

    Numerous previously unknown carbon aluminum hydride cluster anions were generated in the gas phase, identified by time-of-flight mass spectrometry and characterized by anion photoelectron spectroscopy, revealing their electronic structure. Density functional theory calculations on the CAl5-9H- and CAl5-7H2- found that several of them possess unusually high carbon atom coordination numbers. These cluster compositions have potential as the basis for new energetic materials.

  15. Regeneration of Aluminum Hydride Using Trimethylamine

    SciTech Connect

    D Lacina; J Reilly; Y Celebi; J Wegrzyn; J Johnson; J Graetz

    2011-12-31

    Aluminum hydride is an attractive reducing agent and energy storage compound possessing a low decomposition temperature and a high gravimetric and volumetric hydrogen density. However, it is thermodynamically unstable at room temperature and requires extremely high pressures to form the hydride from aluminum and hydrogen gas. Here, we describe an alternate method of synthesizing AlH{sub 3} using Ti-catalyzed Al powder, H{sub 2}, and trimethylamine (TMA) to form an alane adduct. The formation of trimethylamine alane occurs at modest hydrogen pressures ({approx}100 bar), forming the 2:1 bis complex (2 trimethylamine/AlH{sub 3}). Along with the hydrogenation product, mono (1:1) and bis (2:1) standards of TMA-AlH{sub 3} were prepared and characterized using X-ray diffraction and Raman spectroscopy. X-ray absorption spectroscopy of the reaction products showed that the Ti catalyst remains with the unreacted Al powder after hydrogenation and is not present in the alane adduct. We also demonstrate that TMA can be transaminated with triethylamine to form triethylamine alane, which can easily be separated to recover AlH{sub 3}.

  16. Parametrization of a reactive force field for aluminum hydride.

    PubMed

    Ojwang, J G O; van Santen, Rutger A; Kramer, Gert Jan; van Duin, Adri C T; Goddard, William A

    2009-07-28

    A reactive force field, REAXFF, for aluminum hydride has been developed based on density functional theory (DFT) derived data. REAXFF(AlH(3)) is used to study the dynamics governing hydrogen desorption in AlH(3). During the abstraction process of surface molecular hydrogen charge transfer is found to be well described by REAXFF(AlH(3)). Results on heat of desorption versus cluster size show that there is a strong dependence of the heat of desorption on the particle size, which implies that nanostructuring enhances desorption process. In the gas phase, it was observed that small alane clusters agglomerated into a bigger cluster. After agglomeration molecular hydrogen was desorbed from the structure. This thermodynamically driven spontaneous agglomeration followed by desorption of molecular hydrogen provides a mechanism on how mobile alane clusters can facilitate the mass transport of aluminum atoms during the thermal decomposition of NaAlH(4).

  17. Parametrization of a reactive force field for aluminum hydride

    NASA Astrophysics Data System (ADS)

    Ojwang, J. G. O.; van Santen, Rutger A.; Kramer, Gert Jan; van Duin, Adri C. T.; Goddard, William A.

    2009-07-01

    A reactive force field, REAXFF, for aluminum hydride has been developed based on density functional theory (DFT) derived data. REAXFFAlH3 is used to study the dynamics governing hydrogen desorption in AlH3. During the abstraction process of surface molecular hydrogen charge transfer is found to be well described by REAXFFAlH3. Results on heat of desorption versus cluster size show that there is a strong dependence of the heat of desorption on the particle size, which implies that nanostructuring enhances desorption process. In the gas phase, it was observed that small alane clusters agglomerated into a bigger cluster. After agglomeration molecular hydrogen was desorbed from the structure. This thermodynamically driven spontaneous agglomeration followed by desorption of molecular hydrogen provides a mechanism on how mobile alane clusters can facilitate the mass transport of aluminum atoms during the thermal decomposition of NaAlH4.

  18. Parametrization of a reactive force field for aluminum hydride

    SciTech Connect

    Ojwang, J. G. O.; Santen, Rutger A. van; Kramer, Gert Jan; Duin, Adri C. T. van; Goddard, William A. III

    2009-07-28

    A reactive force field, REAXFF, for aluminum hydride has been developed based on density functional theory (DFT) derived data. REAXFF{sub AlH{sub 3}} is used to study the dynamics governing hydrogen desorption in AlH{sub 3}. During the abstraction process of surface molecular hydrogen charge transfer is found to be well described by REAXFF{sub AlH{sub 3}}. Results on heat of desorption versus cluster size show that there is a strong dependence of the heat of desorption on the particle size, which implies that nanostructuring enhances desorption process. In the gas phase, it was observed that small alane clusters agglomerated into a bigger cluster. After agglomeration molecular hydrogen was desorbed from the structure. This thermodynamically driven spontaneous agglomeration followed by desorption of molecular hydrogen provides a mechanism on how mobile alane clusters can facilitate the mass transport of aluminum atoms during the thermal decomposition of NaAlH{sub 4}.

  19. Hydrogen storage in sodium aluminum hydride.

    SciTech Connect

    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.

  20. Photoelectron spectroscopy of boron aluminum hydride cluster anions

    SciTech Connect

    Wang, Haopeng; Zhang, Xinxing; Ko, Yeon Jae; Gantefoer, Gerd; Bowen, Kit H. E-mail: kiran@mcneese.edu; Li, Xiang; Kiran, Boggavarapu E-mail: kiran@mcneese.edu; Kandalam, Anil K.

    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.

  1. Regeneration of Aluminum Hydride studied with Raman Microscopy.

    NASA Astrophysics Data System (ADS)

    Lacina, David; Graetz, Jason; Reilly, J. J.

    2009-03-01

    We are interested in developing new methods to form aluminum hydride directly from aluminum powder and hydrogen. Due to the low free energy of formation, aluminum and hydrogen require extremely high pressures to react and form the hydride. It is possible to form alane directly at low pressure when it is catalyzed with a small amount of titanium (2 mol %) and stabilized as an adduct. We have studied the formation of amine-alanes by direct hydrogenation of aluminum and have attempted to understand the mechanisms behind these reversible reactions and the role of the catalyst. We will present the results from our recent survey of possible reactions between aluminum, hydrogen and various amines. We will also present the results of a Raman spectroscopy study of the alane polymorphs at ambient and high pressure and alane amines.

  2. Use of triammonium salt of aurin tricarboxylic acid as risk mitigant for aluminum hydride

    DOEpatents

    Cortes-Concepcion, Jose A.; Anton, Donald L.

    2017-08-08

    A process and a resulting product by process of an aluminum hydride which is modified with by physically combining in a ball milling process an aluminum hydride with a triammonium salt of aurin tricarboxylic acid. The resulting product is an aluminum hydride which is resistant to air, ambient moisture, and liquid water while maintaining useful hydrogen storage and release kinetics.

  3. Synthesis and Hydrogen Desorption Properties of Aluminum Hydrides.

    PubMed

    Jeong, Wanseop; Lee, Sang-Hwa; Kim, Jaeyong

    2016-03-01

    Aluminum hydride (AlH3 or alane) is known to store maximum 10.1 wt.% of hydrogen at relatively low temperature (< 100 degrees C), which partially fulfills the U.S. department of energy requirements for gravimetric loading capacity. However, its detailed mechanisms of appearing of different phases, structural stability, and dynamics of hydrogen desorption are still not clear. To understand the desorption properties of hydrogen in alane, thermodynamically stable α-AlH3 was synthesized by employing an ethereal reaction method. The dependence of pathways on phase formation and the properties of hydrogen evolution were investigated, and the results were compared with the ones for γ-AlH3. It was found that γ-AlH3 requires 10 degrees C higher than that of γ-AlH3 to form, and its decomposition rate demonstrated enhanced endothermic stabilities. For desorption, all hydrogen atoms of alane evolved under an isothermal condition at 138 degrees C in less than 1 hour, and the sample completely transformed to pure aluminum. Our results show that the total amount of desorbed hydrogen from α-AlH3 exceeded 9.05 wt.%, with a possibility of further increase. Easy synthesis, thermal stability, and a large amount of hydrogen desorption of alane fulfill the requirements for light-weight hydrogen storage materials once the pathway of hydrogen cycling is provided.

  4. Low-pressure Structural Modification of Aluminum Hydride

    DTIC Science & Technology

    2011-02-01

    pressure release. 15. SUBJECT TERMS High - pressure , Diamond anvil cell, aluminum hydride 16. SECURITY CLASSIFICATION OF...loaded into the diamond anvil cell using a specialized high - pressure gas loading system (18). The in-situ pressure within the diamond anvil cell was...Visible Absorption Study of AlH3. Journal of Physics: Conference Series 2010, 215, 012047. 18. Jayaraman, A. Diamond Anvil Cell and High -

  5. Vacancy Mechanism of the Photolysis of Aluminum Hydride

    NASA Astrophysics Data System (ADS)

    Goryaev, M. A.

    2000-01-01

    Within the framework of the thermodynamic model of formation of intrinsic defects in a lattice during the decay of photoexcitations in a solid, the formation of hydrogen vacancies in aluminum hydride is analyzed. The evolution of a system with excess vacancy concentration leads to the formation of micropores under the crystal surface. The results of calculations agree well with the experimental data on photochemically induced absorption obtained in electron-microscopic studies of AlH3 decomposition.

  6. Metallization of aluminum hydride at high pressures: A first-principles study

    NASA Astrophysics Data System (ADS)

    Pickard, Chris J.; Needs, R. J.

    2007-10-01

    We have used first-principles density-functional-theory electronic structure methods and a random searching technique to identify stable high pressure phases of aluminum hydride (AlH3) . We find a transition from the insulating low-pressure α phase to an insulating layered structure of space group Pnma at 34GPa , and a transition to a semimetallic Pm3¯n phase at 73GPa . These phases are predicted to be stable against dehydridation (the evolution of H2 molecules), and they could be formed at pressures easily attainable within diamond-anvil-cell experiments.

  7. Pressure-induced hydrogen-dominant metallic state in aluminum hydride.

    PubMed

    Goncharenko, Igor; Eremets, M I; Hanfland, M; Tse, J S; Amboage, M; Yao, Y; Trojan, I A

    2008-02-01

    Two structural transitions in covalent aluminum hydride AlH3 were characterized at high pressure. A metallic phase stable above 100 GPa is found to have a remarkably simple cubic structure with shortest first-neighbor H-H distances ever measured except in H2 molecule. Although the high-pressure phase is predicted to be superconductive, this was not observed experimentally down to 4 K over the pressure range 120-164 GPa. The results indicate that the superconducting behavior may be more complex than anticipated.

  8. Pressure-Induced Hydrogen-Dominant Metallic State in Aluminum Hydride

    NASA Astrophysics Data System (ADS)

    Goncharenko, Igor; Eremets, M. I.; Hanfland, M.; Tse, J. S.; Amboage, M.; Yao, Y.; Trojan, I. A.

    2008-02-01

    Two structural transitions in covalent aluminum hydride AlH3 were characterized at high pressure. A metallic phase stable above 100 GPa is found to have a remarkably simple cubic structure with shortest first-neighbor H-H distances ever measured except in H2 molecule. Although the high-pressure phase is predicted to be superconductive, this was not observed experimentally down to 4 K over the pressure range 120 164 GPa. The results indicate that the superconducting behavior may be more complex than anticipated.

  9. Studying aluminum hydride by means of thermal analysis

    NASA Astrophysics Data System (ADS)

    Milekhin, Yu. M.; Koptelov, A. A.; Matveev, A. A.; Baranets, Yu. N.; Bakulin, D. A.

    2015-07-01

    Chemical reactions and physical transformations that occur upon heating aluminum hydride (AlH3, alane), stored for 25 years, in the temperature range of 50-1200°C in an atmosphere of nitrogen, argon, and air are studied by means of thermogravimetric analysis and differential scanning calorimetry. The heat of thermal decomposition and the hydrogen content are determined for the AlH3 samples and are found to be 318 ± 25 J/g and 9.32 ± 0.24 wt %, respectively. It is established that the estimated enthalpy of formation of AlH3 in stoichiometric composition (Δf H ≈ -10.3 kJ/mol) agrees with the literature data. After the release of hydrogen, the mass of the precipitate increases by 0.5 ± 0.3%, relative to the initial mass of the AlH3 samples; the most likely reason for this effect is the adsorption of nitrogen (argon) in the micropores and mesopores that form. Thermal phenomena associated with the crystallization of the amorphous aluminum that forms after hydrogen is released from the alane particles are analyzed. It is established that the aluminum contained in initial AlH3 samples is almost completely transformed into aluminum nitride and oxide (AlN and Al3O3) upon heating to 1200°C in nitrogen and air, respectively.

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

    PubMed

    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.

  11. Wall pressure exerted by hydrogenation of sodium aluminum hydride.

    SciTech Connect

    Perras, Yon E.; Dedrick, Daniel E.; Zimmerman, Mark D.

    2009-06-01

    Wall pressure exerted by the bulk expansion of a sodium aluminum hydride bed was measured as a function of hydrogen content. A custom apparatus was designed and loaded with sodium alanates at densities of 1.0, 1.1, and 1.16 g/cc. Four complete cycles were performed to identify variations in measured pressure. Results indicated poor correlation between exerted pressure and hydrogen capacity of the sodium alanate beds. Mechanical pressure due to the hydrogenation of sodium alanates does not influence full-scale system designs as it falls within common design factors of safety. Gas pressure gradients within the porous solid were identified and may limit reaction rates, especially for high aspect ratio beds.

  12. Advances in the electrochemical regeneration of aluminum hydride

    NASA Astrophysics Data System (ADS)

    Martínez-Rodríguez, Michael J.; García-Díaz, Brenda L.; Teprovich, Joseph A.; Knight, Douglas A.; Zidan, Ragaiy

    2012-03-01

    In previous work, a reversible cycle that uses electrolysis and catalytic hydrogenation of spent Al(s) for the regeneration of alane (AlH3) was reported. In this study, the electrochemical synthesis of alane is improved. Advances in the electrochemical regeneration of alane have been achieved via the use of lithium aluminum hydride (LiAlH4) and lithium chloride (LiCl). Lithium chloride reacts in a cyclic process and functions as an electro-catalytic additive that enhances the electrochemical process by increasing the cell efficiency and the alane production. Electrochemical techniques are used to show that the increased rate of alane generation is due to the electro-catalytic effect of lithium chloride, rather than an electrolyte enhanced effect.

  13. Superconductivity of strontium aluminum germanide and barium aluminum germanide Structure and Dynamics of strontium aluminum germanium hydride and barium aluminum germanium hydride

    NASA Astrophysics Data System (ADS)

    Kranak, Verina Franika

    The discovery of the superconductor MgB2 led to the increase of research activity for more compounds adopting the AlB 2 structure type and containing superconductive properties. The prominent successor compounds were the silicide systems, AeAlSi (Ae=Sr, Ba, Ca). Presented here is an extension of this investigation to the germanides, SrAlGe and BaAlGe. The ternary structures were synthesized through arc-melting elemental stoichiometric mixtures and structurally characterized by x-ray powder diffraction. Both crystallize as the hexagonal SrPtSb space group (P m2), a variant of the AlB2 structure type (P 6/mmm). The low temperature region was measured on a Vibrating Sample Magnetometer (VSM) and both present the onset of superconductivity below 7K. These compounds are susceptible to hydrogen absorption and the new polyanionic hydrides, SrAlGeH and BaAlGeH, structural and dynamic properties are presented. The hydrides were synthesized via two distinct methods. One method is the reaction of SrH2 (BaH2) with elemental mixture of the Al and Ge under pressurized hydrogen and the other is a hydrogenation of the SrAlGe and BaAlGe. Both crystallize in the trigonal SrAlSiH structure type (P3m1), as determined from Rietveld analysis on powder neutron diffraction measurements. The hydrogen is coordinated by both the active metal and aluminum atoms, providing a unique environment for studying metal-hydrogen interactions. When exposed to air, both the hydrides and alloys transform from a crystalline grey to an amorphous yellow powder accompanied by a dramatic volume increase. Infrared spectroscopy shows the disappearance of the bands associated with the Al-H bond and the appearance of Ge-H and O-H bands. This indicates the material reacts with atmospheric water.

  14. Multi-scale characterization of nanostructured sodium aluminum hydride

    NASA Astrophysics Data System (ADS)

    NaraseGowda, Shathabish

    instruments were utilized for this work and their data collection and analysis are reported. Quasielastic neutron scattering experiments were conducted at NIST Center for Neutron Research to characterize atomic hydrogen diffusion in bulk and nano-confined NaAlH4. It was observed that upon confinement of NaAlH4, a significantly higher fraction of hydrogen atoms were involved in diffusive motion on the pico-second to nano-second timescales. However, the confinement had no impact on the lattice diffusivities (jump/hopping rates) of atomic hydrogen, indicating that the improved hydrogen release rates were not due to any kinetic destabilization effects. Instead, the investigation strongly suggested thermodynamic destabilization as the major effect of nano-confinement. The local interaction of the metal sites in metal organic frameworks with the infiltrated hydride was studied using extended x-ray absorption spectroscopy technique. The experiments were conducted at Center for Advanced Microstructures and Devices at Louisiana State University. The metal sites were found to be chemically un-altered, hence ruling out any catalytic role in the dehydrogenation at room temperatures. The fractal morphology of NaAlH4 was characterized by ultra-small angle x-ray scattering experiments performed at Argonne National Lab. The studies quantitatively estimated the extent of densification in the course of one desorption cycle. The particle sizes were found to increase two-fold during heat treatment. Also, the nano-confinement procedure was shown to produce dense mass fractals as opposed to pristine NaAlH4, exhibiting a surface fractal morphology. Based on this finding, a new method to identify confined material from un-confined material in nano-composites was developed and is presented. Preliminary results of modeling and correlating multi-scale phenomena using a phase-field approach are also presented as the foundation for future work.

  15. Gas-phase acidities of binary hydrides.

    NASA Technical Reports Server (NTRS)

    Brauman, J. I.; Eyler, J. R.; Blair, L. K.; White, M. J.; Comisarow, M. B.; Smyth, K. C.

    1971-01-01

    The preferred direction of proton transfer in a reaction between a hydride molecule and a hydride ion was studied in order to determine the relative acidities of some binary hydrides. Sufficient data are presented to make clear the periodic trends in acidities and the underlying trends in other fundamental thermochemical quantities which influence acidity. The bond dissociation energies and electron affinities of the hydrides considered are listed in a table.

  16. ALUMINUM HYDRIDE, A1H3, AS A HYDROGEN STORAGE COMPOUND.

    SciTech Connect

    GRAETZ, J.; REILLY, J.; SANDROCK, G.; JOHNSON, J.; ZHOU, W.M.; WEGRZYN, J.

    2006-11-27

    Aluminum hydride is a covalent, binary hydride that has been known for more than 60 years and is an attractive medium for on-board automotive hydrogen storage, since it contains 10.1% by wt. hydrogen with a density of 1.48 g/ml. There are at least 7 non-solvated AlH{sub 3} phases, namely {alpha}, {alpha}{prime}, {beta}, {gamma}, {var_epsilon} and {zeta}. The properties of {alpha}-AlH{sub 3}, obtained from the Dow Chemical Co. in 1980, have been previously reported. Here we present a description of the thermodynamic and kinetic properties of freshly prepared {alpha}, {beta} and {gamma} phases of AlH{sub 3}. In all cases the decomposition kinetics are appreciable below 100 C and all will meet the DOE 2010 gravimetric and volumetric vehicular system targets (6 wt% H{sub 2} and 0.045 kg/L). However, further research will be required to develop an efficient and economical process to regenerate AlH{sub 3} from the spent Al powder.

  17. Transmission Electron Microscopy Studies on Titanium-doped Sodium Aluminum Hydride

    NASA Astrophysics Data System (ADS)

    Culnane, Lance F.

    Hydrogen fuel cells play an important role in today's diverse and blossoming alternative energy industry. One of the greatest technological barriers for vehicular applications is the storage of hydrogen (which is required to power hydrogen fuel cells). Storing hydrogen as a gas is not volume efficient, and storing it as a liquid is not cost effective, therefore solid-state storage of hydrogen, such as in metal hydrides offers the most potential for success since many metal hydrides have attractive qualities for hydrogen storage such as: high volumetric capacity, cost efficiency, weight efficiency, low refueling times, and most importantly, high safety. Unfortunately, a compound has not been discovered which contains all of the attractive hydrogen storage qualities for vehicular applications. Sodium aluminum hydride (NaAlH 4) is one of the few compounds which is close to meeting requirements for car manufacturers, and has perhaps been researched the most extensively out of all metal hydrides in the last 15 years. This arises from the remarkable discovery by Bogdanovic who found that doping NaAlH4 with Ti dopants enabled the reversible dehydrogenation and hydrogenation of NaAlH 4 at mild conditions. Various evidence and theories have been proposed to suggest explanations for the enhanced kinetic effect that Ti-doping and ball-milling provide. However, the research community has not reached a consensus as to the exact role of Ti-dopants. If the role of titanium in the NaAlH4 dehydrogenation/hydrogenation mechanism could be understood, then more attractive metal hydrides could be designed. To this end, we conducted Transmission Electron Microscopy (TEM) studies to explain the role of the Ti dopants. The first known thorough particle size analysis of the NaAlH4 system was conducted, as well as TEM-EELS (Electron Energy Loss Spectroscopy), TEM-EDS (Energy Dispersive X-ray Spectroscopy), and in-situ imaging studies. Preparation methods were found to be important for the

  18. Adhesion of oxide layer to metal-doped aluminum hydride surface: Density functional calculations

    NASA Astrophysics Data System (ADS)

    Takezawa, Tomoki; Itoi, Junichi; Kannan, Takashi

    2017-07-01

    The density functional theory (DFT) calculations were carried out to evaluate the adhesion energy of the oxide layer to the metal-doped surface of hydrogen storage material, aluminum hydride (alane, AlH3). The total energy calculations using slab model revealed that the surface doping of some metals to aluminum hydride weakens the adhesion strength of the oxide layer. The influence of titanium, iron, cobalt, and zirconium doping on adhesion strength were evaluated. Except for iron doping, the adhesion strength becomes weak by the doping.

  19. Aluminum-titanium hydride-boron carbide composite provides lightweight neutron shield material

    NASA Technical Reports Server (NTRS)

    Poindexter, A. M.

    1967-01-01

    Inexpensive lightweight neutron shield material has high strength and ductility and withstands high internal heat generation rates without excessive thermal stress. This composite material combines structural and thermal properties of aluminum, neutron moderating properties of titanium hydride, and neutron absorbing characteristics of boron carbide.

  20. Structural phase stability in fluorinated calcium hydride

    NASA Astrophysics Data System (ADS)

    Varunaa, R.; Ravindran, P.

    2017-05-01

    In order to improve the hydrogen storage properties of calcium hydride (CaH2), we have tuned its thermodynamical properties through fluorination. Using ab-initio total energy calculations based on density functional theory, the structural stability, electronic structure and chemical bonding of CaH2-xFx systems are investigated. The phase transition of fluorinated systems from orthorhombic to cubic structure has been observed at 18% fluorine doped CaH2. The phase stability analysis shows that CaH2-xFx systems are highly stable and the stability is directly correlating with their ionicity. Density of states (DOS) plot reveals that CaH2-xFx systems are insulators. Partial DOS and charge density analyses conclude that these systems are governed by ionic bonding. Our results show that H closer to F can be removed more easily than that far away from F and this is due to disproportionation induced in the bonding interaction by fluorination.

  1. Hydride phase formation in carbon supported palladium hydride nanoparticles by in situ EXAFS and XRD

    NASA Astrophysics Data System (ADS)

    Bugaev, A. L.; Guda, A. A.; Lomachenko, K. A.; Lazzarini, A.; Srabionyan, V. V.; Vitillo, J. G.; Piovano, A.; Groppo, E.; Bugaev, L. A.; Soldatov, A. V.; Dmitriev, V. P.; Pellegrini, R.; van Bokhoven, J. A.; Lamberti, C.

    2016-05-01

    In the current work we present a detailed analysis of the hydride phase formation in industrial Pd/C nanocatalysts by means of combined in situ X-ray absorption spectroscopy (EXAFS), X-ray diffraction (XRD) and volumetric measurements for the temperatures from - 10 to 50 °C in the hydrogen pressure range from 0 to 1000 mbar. α- and β- hydride phases are clearly distinguished in XRD. For the first time, H/Pd atomic ratio were obtained by theoretical fitting of the near-edge region of the absorption spectra (XANES) and compared with volumetric measurements.

  2. ALUMINUM HYDRIDE: A REVERSIBLE STORAGE MATERIAL FOR HYDROGEN STORAGE

    SciTech Connect

    Zidan, R; Christopher Fewox, C; Brenda Garcia-Diaz, B; Joshua Gray, J

    2009-01-09

    One of the challenges of implementing the hydrogen economy is finding a suitable solid H{sub 2} storage material. Aluminium (alane, AlH{sub 3}) hydride has been examined as a potential hydrogen storage material because of its high weight capacity, low discharge temperature, and volumetric density. Recycling the dehydride material has however precluded AlH{sub 3} from being implemented due to the large pressures required (>10{sup 5} bar H{sub 2} at 25 C) and the thermodynamic expense of chemical synthesis. A reversible cycle to form alane electrochemically using NaAlH{sub 4} in THF been successfully demonstrated. Alane is isolated as the triethylamine (TEA) adduct and converted to unsolvated alane by heating under vacuum. To complete the cycle, the starting alanate can be regenerated by direct hydrogenation of the dehydrided alane and the alkali hydride (NaH) This novel reversible cycle opens the door for alane to fuel the hydrogen economy.

  3. ALUMINUM HYDRIDE: A REVERSIBLE MATERIAL FOR HYDROGEN STORAGE

    SciTech Connect

    Zidan, R; Christopher Fewox, C; Brenda Garcia-Diaz, B; Joshua Gray, J

    2009-01-09

    Hydrogen storage is one of the challenges to be overcome for implementing the ever sought hydrogen economy. Here we report a novel cycle to reversibly form high density hydrogen storage materials such as aluminium hydride. Aluminium hydride (AlH{sub 3}, alane) has a hydrogen storage capacity of 10.1 wt% H{sub 2}, 149 kg H{sub 2}/m{sup 3} volumetric density and can be discharged at low temperatures (< 100 C). However, alane has been precluded from use in hydrogen storage systems because of the lack of practical regeneration methods. The direct hydrogenation of aluminium to form AlH{sub 3} requires over 10{sup 5} bars of hydrogen pressure at room temperature and there are no cost effective synthetic means. Here we show an unprecedented reversible cycle to form alane electrochemically, using alkali metal alanates (e.g. NaAlH{sub 4}, LiAlH{sub 4}) in aprotic solvents. To complete the cycle, the starting alanates can be regenerated by direct hydrogenation of the dehydrided alane and the alkali hydride being the other compound formed in the electrochemical cell. The process of forming NaAlH{sub 4} from NaH and Al is well established in both solid state and solution reactions. The use of adducting Lewis bases is an essential part of this cycle, in the isolation of alane from the mixtures of the electrochemical cell. Alane is isolated as the triethylamine (TEA) adduct and converted to pure, unsolvated alane by heating under vacuum.

  4. ALUMINUM HYDRIDE: A REVERSIBLE MATERIAL FOR HYDROGEN STORAGE

    SciTech Connect

    Fewox, C; Ragaiy Zidan, R; Brenda Garcia-Diaz, B

    2008-12-31

    Hydrogen storage is one of the greatest challenges for implementing the ever sought hydrogen economy. Here we report a novel cycle to reversibly form high density hydrogen storage materials such as aluminium hydride. Aluminium hydride (AlH{sub 3}, alane) has a hydrogen storage capacity of 10.1 wt% H{sub 2}, 149 kg H{sub 2}/m{sup 3} volumetric density and can be discharged at low temperatures (< 100 C). However, alane has been precluded from use in hydrogen storage systems because of the lack of practical regeneration methods; the direct hydrogenation of aluminium to form AlH{sub 3} requires over 10{sup 5} bars of hydrogen pressure at room temperature and there are no cost effective synthetic means. Here we show an unprecedented reversible cycle to form alane electrochemically, using alkali alanates (e.g. NaAlH{sub 4}, LiAlH{sub 4}) in aprotic solvents. To complete the cycle, the starting alanates can be regenerated by direct hydrogenation of the dehydrided alane and the alkali hydride being the other compound formed in the electrochemical cell. The process of forming NaAlH{sub 4} from NaH and Al is well established in both solid state and solution reactions. The use of adducting Lewis bases is an essential part of this cycle, in the isolation of alane from the mixtures of the electrochemical cell. Alane is isolated as the triethylamine (TEA) adduct and converted to pure, unsolvated alane by heating under vacuum.

  5. Evaluation of Raney-nickel cathodes prepared with aluminum powder and titanium hydride powder

    SciTech Connect

    Tanaka, Shinichi |; Hirose, Norimitsu; Tanaki, Toshiyuki

    1999-07-01

    Raney-nickel (Ni) cathodes were prepared on nickel wire from aluminum powder and titanium hydride powder by heat-treatment. The influence of the addition of titanium to the Raney-Ni electrode on the polarization characteristics of the hydrogen evolution reaction was studied in 1 M NaOH at 303 K. Although the coated layer was composed of nickel with a small amount of aluminum and titanium, the titanium was enriched the most. The relative surface area of the Raney-Ni cathodes was about 3500 independent of the presence of titanium, but titanium could decrease the hydrogen overpotential.

  6. Secondary Amine Stabilized Aluminum Hydrides Derived from N,N'-Di-tert-butylethylenediamines.

    PubMed

    Gardiner, Michael G.; Lawrence, Stacey M.; Raston, Colin L.

    1996-02-28

    The metalation of substituted N,N'-di-tert-butylethylenediamines by various aluminum hydride sources has been investigated. HN(t-Bu)CH(t-Bu)CH(2)N(H)(t-Bu) forms a dimeric lithium chelated adduct of LiAlH(4), [{[HN(t-Bu)CH(t-Bu)CH(2)N(H)(t-Bu)]Li(&mgr;-H)(2)AlH(2)}(2)], 4, which thermally decomposes to yield the tetrameric lithium diamidoaluminum hydride [{Li[N(t-Bu)CH(t-Bu)CH(2)N(t-Bu)]AlH(2)}(4)], 5. The same diamine reacts with AlH(3).NMe(3) or AlH(3) diethyl etherate to give the secondary amine stabilized amidoaluminum hydride species [{HN(t-Bu)CH(t-Bu)CH(2)N(t-Bu)}AlH(2)], 2. Similarly, the same aluminum hydride sources react with the diamine rac-HN(t-Bu)CH(Me)CH(Me)N(H)(t-Bu) to yield [{rac-HN(t-Bu)CH(Me)CH(Me)N(t-Bu)}AlH(2)], 3. Compounds 2 and 3 are stable with respect to elimination of hydrogen to form diamidoaluminum hydrides, but can be converted to the alane rich species, [H(2)Al{N(t-Bu)CH(t-Bu)CH(2)N(t-Bu)}AlH(2)],6, and [H(2)Al{rac-N(t-Bu)CH(Me)CH(Me)N(t-Bu)}AlH(2)], 7, by reaction with AlH(3).NMe(3) under special conditions. The varying reactivity of the three aluminum hydride sources in these reactions has enabled mechanistic information to be gathered, and the effect of the different steric requirements in the diamines on the stability of the complexes is discussed. Crystals of 3are monoclinic, space group P2(1)/n (No. 14), with a = 8.910(4), b = 14.809(1), and c = 12.239(6) Å, beta = 109.76(2) degrees, V = 1520(1) Å(3), and Z = 4. Crystals of 4 are orthorhombic, space group Pbca (No. 61), with a = 15.906(9), b = 24.651(7), and c = 9.933(7) Å, V = 3895(3) Å(3), and Z = 4. Crystals of 6 are monoclinic, space group P2(1)/c (No. 14), with a = 8.392(1), b = 17.513(2), and c = 12.959(1) Å, beta = 107.098(8) degrees, V = 1820.4(3) Å(3), and Z = 4.

  7. Phase I. Lanthanum-based Start Materials for Hydride Batteries

    SciTech Connect

    Gschneidner, K. A.; Schmidt, F. A.; Frerichs, A. E.; Ament, K. A.

    2013-08-20

    The purpose of Phase I of this work is to focus on developing a La-based start material for making nickel-metal (lanthanum)-hydride batteries based on our carbothermic-silicon process. The goal is to develop a protocol for the manufacture of (La1-xRx)(Ni1-yMy)(Siz), where R is a rare earth metal and M is a non-rare earth metal, to be utilized as the negative electrode in nickel-metal hydride (NiMH) rechargeable batteries.

  8. Hydride vapor phase epitaxy of AlN using a high temperature hot-wall reactor

    NASA Astrophysics Data System (ADS)

    Baker, Troy; Mayo, Ashley; Veisi, Zeinab; Lu, Peng; Schmitt, Jason

    2014-10-01

    Aluminum nitride (AlN) was grown on c-plane sapphire substrates by hydride vapor phase epitaxy (HVPE). The experiments utilized a two zone inductively heated hot-wall reactor. The surface morphology, crystal quality, and growth rate were investigated as a function of growth temperature in the range of 1450-1575 °C. AlN templates grown to a thickness of 1 μm were optimized with double axis X-ray diffraction (XRD) rocking curve full width half maximums (FWHMs) of 135″ for the (002) and 513″ for the (102).

  9. Non-Chromate Aluminum Pretreatments, Phase 2

    DTIC Science & Technology

    2004-09-01

    September 2004 78 ALUMINUM AL2024-T3 ALUMINUM AL7075 -T6 PNL ID 4 Control 5...ALUMINUM - AL2024-T3 192 ALUMINUM - AL7075 -T6 112 Table 5.13: AMCOM – NAVAIR PANEL TEST MATRIX OCTOBER 2003 NCAP Phase II Interim Report

  10. Reversible metal-hydride phase transformation in epitaxial films

    NASA Astrophysics Data System (ADS)

    Roytburd, Alexander L.; Boyerinas, Brad M.; Bruck, Hugh A.

    2015-03-01

    Metal-hydride phase transformations in solids commonly proceed with hysteresis. The extrinsic component of hysteresis is the result of the dissipation of energy of internal stress due to plastic deformation and fracture. It can be mitigated on the nanoscale, where plastic deformation and fracture are suppressed and the transformation proceeds through formation and evolution of coherent phases. However, the phase coherency introduces intrinsic thermodynamic hysteresis, preventing reversible transformation. In this paper, it is shown that thermodynamic hysteresis of coherent metal-hydride transformation can be eliminated in epitaxial film due to substrate constraint. Film-substrate interaction leads to formation of heterophase polydomain nanostructure with variable phase fraction which can change reversibly by varying temperature in a closed system or chemical potential in an open system.

  11. Reversible metal-hydride phase transformation in epitaxial films.

    PubMed

    Roytburd, Alexander L; Boyerinas, Brad M; Bruck, Hugh A

    2015-03-11

    Metal-hydride phase transformations in solids commonly proceed with hysteresis. The extrinsic component of hysteresis is the result of the dissipation of energy of internal stress due to plastic deformation and fracture. It can be mitigated on the nanoscale, where plastic deformation and fracture are suppressed and the transformation proceeds through formation and evolution of coherent phases. However, the phase coherency introduces intrinsic thermodynamic hysteresis, preventing reversible transformation. In this paper, it is shown that thermodynamic hysteresis of coherent metal-hydride transformation can be eliminated in epitaxial film due to substrate constraint. Film-substrate interaction leads to formation of heterophase polydomain nanostructure with variable phase fraction which can change reversibly by varying temperature in a closed system or chemical potential in an open system.

  12. Micro-scale fracture experiments on zirconium hydrides and phase boundaries

    NASA Astrophysics Data System (ADS)

    Chan, H.; Roberts, S. G.; Gong, J.

    2016-07-01

    Fracture properties of micro-scale zirconium hydrides and phase boundaries were studied using microcantilever testing methods. FIB-machined microcantilevers were milled on cross-sectional surfaces of hydrided samples, with the most highly-stressed regions within the δ-hydride film, within the α-Zr or along the Zr-hydride interface. Cantilevers were notched using the FIB and then tested in bending using a nanoindenter. Load-displacement results show that three types of cantilevers have distinct deformation properties. Zr cantilevers deformed plastically. Hydride cantilevers fractured after a small amount of plastic flow; the fracture toughness of the δ-hydride was found to be 3.3 ± 0.4 MPam1/2 and SEM examination showed transgranular cleavage on the fracture surfaces. Cantilevers notched at the Zr-hydride interface developed interfacial voids during loading, at loads considerably lower than that which initiate brittle fracture of hydrides.

  13. Hydride-based silica stationary phases for HPLC: fundamental properties and applications.

    PubMed

    Pesek, Joseph J; Matyska, Maria T

    2005-10-01

    Silica hydride is a recent development in chromatographic support materials for HPLC where hydride groups replace 95% of the silanols on the surface. This conversion changes many of the fundamental properties of the material as well as the bonded stationary phases that are the result of further chemical modification of the hydride surface. The general approach for fabricating the silica hydride and subsequent bonded phases is reviewed. Properties of the silica hydride surface are compared to those of the standard material obtained in the preparation of most commercial HPLC stationary phases. Some unique chromatographic properties of hydride-based phases are described as well as some general application areas where these bonded materials may be used in preference to or have advantages not available from typical stationary phases.

  14. A new approach to bioanalysis: aqueous normal-phase chromatography with silica hydride stationary phases.

    PubMed

    Pesek, Joseph J; Matyska, Maria T

    2012-04-01

    Stationary phases based on silica hydride have demonstrated a number of unique properties that are especially advantageous for bioanalyses. They have excellent retention capabilities for hydrophilic compounds, which have been the most difficult to analyze by standard reversed-phase methods and, in many cases, can outperform newer approaches for the analysis of polar molecules, such as hydrophilic liquid interaction chromatography. In addition, all columns utilizing silica-hydride materials can be used in either the normal-phase or reversed-phase modes, sometimes retaining both polar and nonpolar compounds simultaneously. These stationary phases have a high degree of reproducibility and long-term stability.

  15. Transition-metal-doped aluminum hydrides as building blocks for supramolecular assemblies.

    PubMed

    Liu, Jianjun; Yu, Jiamei; Ge, Qingfeng

    2010-11-25

    Density functional theory calculations were carried out to characterize a series of transition-metal-doped aluminum hydrides, forming TMAl(n)H(2n) and TMAl(n)H(2n+1) (TM = Sc, Ti, V; n = 3,4), in either charged or neutral form. A new electron-counting rule for these clusters was formulated as PSEN (paired skeleton electron number) = 4n, which can characterize both closed-shell and open-shell clusters. On the basis of this electron-counting rule, the superatomic clusters such as TiAl(4)H(9) and TiAl(3)H(6) were identified and can be used to assemble supramolecular structures. Electronic structure analysis showed that three-centered TM-H-Al bonds largely contributed to the structural stability. Also, the spin state of a wide range of clusters in their ground state can be predicted by the electron-counting rule.

  16. Modeling of Gallium Nitride Hydride Vapor Phase Epitaxy

    NASA Technical Reports Server (NTRS)

    Meyyappan, Meyya; Arnold, James O. (Technical Monitor)

    1997-01-01

    A reactor model for the hydride vapor phase epitaxy of GaN is presented. The governing flow, energy, and species conservation equations are solved in two dimensions to examine the growth characteristics as a function of process variables and reactor geometry. The growth rate varies with GaCl composition but independent of NH3 and H2 flow rates. A change in carrier gas for Ga source from H2 to N2 affects the growth rate and uniformity for a fixed reactor configuration. The model predictions are in general agreement with observed experimental behavior.

  17. High-pressure phase transition observed in barium hydride

    NASA Astrophysics Data System (ADS)

    Smith, Jesse S.; Desgreniers, Serge; Tse, John S.; Klug, Dennis D.

    2007-08-01

    The pressure-dependent structural and vibrational properties of barium hydride have been studied up to 22 GPa at room temperature by means of powder x-ray diffraction, Raman spectroscopy, and first-principles calculations. At ambient conditions, BaH2 crystallizes in the cotunnite structure (Pnma). A reversible, first-order structural phase transition is observed at 1.6 GPa. The high-pressure phase can be indexed by a hexagonal unit cell with a proposed Ni2In structure (P63/mmc), with the Ba and H atoms in special positions. The experimental volume compression of the high-pressure phase yields an isothermal bulk modulus B0=24(1) GPa (B0' fixed at 4.13). This compares favorably with the results of the first-principles calculations, which reproduce the first-order nature of the transition. The relevance of these results is discussed in the contexts of metal hydrides in particular and ionic AX2(A =metal) compounds in general.

  18. Spontaneous formation of GaN/AlN core-shell nanowires on sapphire by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Trassoudaine, Agnès; Roche, Elissa; Bougerol, Catherine; André, Yamina; Avit, Geoffrey; Monier, Guillaume; Ramdani, Mohammed Réda; Gil, Evelyne; Castelluci, Dominique; Dubrovskii, Vladimir G.

    2016-11-01

    Spontaneous GaN/AlN core-shell nanowires with high crystal quality were synthesized on sapphire substrates by vapor-liquid-solid hydride vapor phase epitaxy (VLS-HVPE) without any voluntary aluminum source. Deposition of aluminum is difficult to achieve in this growth technique which uses metal-chloride gaseous precursors: the strong interaction between the AlCl gaseous molecules and the quartz reactor yields a huge parasitic nucleation on the walls of the reactor upstream the substrate. We open up an innovative method to produce GaN/AlN structures by HVPE, thanks to aluminum etching from the sapphire substrate followed by redeposition onto the sidewalls of the GaN core. The paper presents the structural characterization of GaN/AlN core-shell nanowires, speculates on the growth mechanism and discusses a model which describes this unexpected behavior.

  19. Hydriding process

    DOEpatents

    Raymond, J.W.; Taketani, H.

    1973-12-01

    BS>A method is described for hydriding a body of a Group IV-B metal, preferably zirconium, to produce a crack-free metal-hydride bedy of high hydrogen content by cooling the body at the beta to beta + delta boundary, without further addition of hydrogen, to precipitate a fine-grained delta-phase metal hydride in the beta + delta phase region and then resuming the hydriding, preferably preceded by a reheating step. (Official Gazette)

  20. Crystal structure of the superconducting phase of sulfur hydride

    NASA Astrophysics Data System (ADS)

    Einaga, Mari; Sakata, Masafumi; Ishikawa, Takahiro; Shimizu, Katsuya; Eremets, Mikhail I.; Drozdov, Alexander P.; Troyan, Ivan A.; Hirao, Naohisa; Ohishi, Yasuo

    2016-09-01

    A superconducting critical temperature above 200 K has recently been discovered in H2S (or D2S) under high hydrostatic pressure. These measurements were interpreted in terms of a decomposition of these materials into elemental sulfur and a hydrogen-rich hydride that is responsible for the superconductivity, although direct experimental evidence for this mechanism has so far been lacking. Here we report the crystal structure of the superconducting phase of hydrogen sulfide (and deuterium sulfide) in the normal and superconducting states obtained by means of synchrotron X-ray diffraction measurements, combined with electrical resistance measurements at both room and low temperatures. We find that the superconducting phase is mostly in good agreement with the theoretically predicted body-centred cubic (bcc) structure for H3S. The presence of elemental sulfur is also manifest in the X-ray diffraction patterns, thus proving the decomposition mechanism of H2S to H3S + S under pressure.

  1. Molecular aluminum hydrides identified by inelastic neutron scattering during H2 regeneration of catalyst-doped NaAlH4.

    PubMed

    Fu, Qi Jia; Ramirez-Cuesta, A J; Tsang, Shik Chi

    2006-01-19

    Catalyst-doped sodium aluminum hydrides have been intensively studied as solid hydrogen carriers for onboard proton-exchange membrane (PEM) fuel cells. Although the importance of catalyst choice in enhancing kinetics for both hydrogen uptake and release of this hydride material has long been recognized, the nature of the active species and the mechanism of catalytic action are unclear. We have shown by inelastic neutron scattering (INS) spectroscopy that a volatile molecular aluminum hydride is formed during the early stage of H2 regeneration of a depleted, catalyst-doped sodium aluminum hydride. Computational modeling of the INS spectra suggested the formation of AlH3 and oligomers (AlH3)n (Al2H6, Al3H9, and Al4H12 clusters), which are pertinent to the mechanism of hydrogen storage. This paper demonstrates, for the first time, the existence of these volatile species.

  2. Aqueous normal-phase retention of nucleotides on silica hydride columns.

    PubMed

    Pesek, Joseph J; Matyska, Maria T; Hearn, Milton T W; Boysen, Reinhard I

    2009-02-13

    The use of silica hydride-based stationary phases for the retention and analysis of nucleotides has been investigated. Both reversed-phase columns with a hydride surface underneath as well as those with an unmodified or a minimally modified hydride material were tested. With these systems, an aqueous normal-phase mode was used with high organic content mobile phases in combination with an additive to control pH for the retention of the hydrophilic nucleotides. Isocratic and gradient elution formats have been used to optimize separations for mixtures containing up to seven components. All conditions developed are suitable for methods that utilize mass spectrometry detection.

  3. Synthesis and evaluation of silica hydride-based fluorinated stationary phases.

    PubMed

    Pesek, Joseph J; Matyska, Maria T; Prajapati, Kavita V

    2010-10-01

    Two novel silica hydride-based fluorinated bonded phases have been synthesized using a hydrosilation procedure to test combined fluorine and hydride selectivity. The bonded moieties were characterized by elemental and spectral analysis. Chromatographic testing was done using hydrophilic analytes in the aqueous normal phase mode. At higher amounts of the nonpolar solvent in the mobile phase, there should be increased retention for solutes such as acids, bases and other polar compounds, whereas nonpolar solutes can be retained when water is increased as in RP chromatography. The synergistic effects of the fluorinated phase selectivity and aqueous normal phase retention on a hydride surface have been explored for small polar molecules. The stability and repeatability of the hydride-based fluorinated stationary phases were evaluated. The use of acetone as the organic component in the mobile phase was also tested.

  4. On the thermodynamics of phase transitions in metal hydrides

    NASA Astrophysics Data System (ADS)

    Vita, Andrea

    2012-02-01

    Metal hydrides are solutions of hydrogen in a metal, where phase transitions may occur depending on temperature, pressure etc. We apply Le Chatelier's principle of thermodynamics to a particular phase transition in TiHx, which can approximately be described as a second-order phase transition. We show that the fluctuations of the order parameter correspond to fluctuations both of the density of H+ ions and of the distance between adjacent H+ ions. Moreover, as the system approaches the transition and the correlation radius increases, we show -with the help of statistical mechanics-that the statistical weight of modes involving a large number of H+ ions (`collective modes') increases sharply, in spite of the fact that the Boltzmann factor of each collective mode is exponentially small. As a result, the interaction of the H+ ions with collective modes makes a tiny suprathermal fraction of the H+ population appear. Our results hold for similar transitions in metal deuterides, too. A violation of an -insofar undisputed-upper bound on hydrogen loading follows.

  5. On the thermodynamics of phase transitions in metal hydrides

    NASA Astrophysics Data System (ADS)

    di Vita, Andrea

    2012-02-01

    Metal hydrides are solutions of hydrogen in a metal, where phase transitions may occur depending on temperature, pressure etc. We apply Le Chatelier's principle of thermodynamics to a particular phase transition in TiH x , which can approximately be described as a second-order phase transition. We show that the fluctuations of the order parameter correspond to fluctuations both of the density of H+ ions and of the distance between adjacent H+ ions. Moreover, as the system approaches the transition and the correlation radius increases, we show -with the help of statistical mechanics-that the statistical weight of modes involving a large number of H+ ions (`collective modes') increases sharply, in spite of the fact that the Boltzmann factor of each collective mode is exponentially small. As a result, the interaction of the H+ ions with collective modes makes a tiny suprathermal fraction of the H+ population appear. Our results hold for similar transitions in metal deuterides, too. A violation of an -insofar undisputed-upper bound on hydrogen loading follows.

  6. Hydride-phase formation and its influence on fatigue crack propagationbehavior in a Zircaloy-4 alloy

    SciTech Connect

    Garlea, Elena; Choo, H.; Wang, G Y; Liaw, Peter K; Clausen, B; Brown, D. W.; Park, Jae-Sung; Rack, P. D.; Kenik, Edward A

    2010-01-01

    The hydride-phase formation and its influence on the fatigue behavior of a Zircaloy-4 alloy charged with hydrogen gas are investigated. First, the microstructure and fatigue crack propagation rate of the alloy in the as-received condition are studied. Second, the formation and homogeneous distribution of delta zirconium hydride ( -ZrH2) in the bulk, and its effect on the fatigue crack propagation rate are presented. The results show that in the presence of hydrides the zirconium alloy exhibits reduced toughness and enhanced crack growth rates. Finally, the influence of a pre-existing fatigue crack in the specimen and the subsequent hydride formation were investigated. The residual lattice strain profile around the fatigue crack tip was measured using neutron diffraction. The combined effects of residual strains and hydride precipitation on the fatigue behavior are discussed.

  7. Well-defined silica supported aluminum hydride: another step towards the utopian single site dream?

    PubMed

    Werghi, Baraa; Bendjeriou-Sedjerari, Anissa; Sofack-Kreutzer, Julien; Jedidi, Abdesslem; Abou-Hamad, Edy; Cavallo, Luigi; Basset, Jean-Marie

    2015-10-01

    Reaction of triisobutylaluminum with SBA15700 at room temperature occurs by two parallel pathways involving either silanol or siloxane bridges. It leads to the formation of a well-defined bipodal [( 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 SiO)2Al-CH2CH(CH3)2] 1a, silicon isobutyl [Si-CH2CH(CH3)2] 1b and a silicon hydride [Si-H] 1c. Their structural identity was characterized by FT-IR and advanced solid-state NMR spectroscopies ((1)H, (13)C, (29)Si, (27)Al and 2D multiple quantum), elemental and gas phase analysis, and DFT calculations. The reaction involves the formation of a highly reactive monopodal intermediate: [SiO-Al-[CH2CH(CH3)2]2], with evolution of isobutane. This intermediate undergoes two parallel routes: transfer of either one isobutyl fragment or of one hydride to an adjacent silicon atom. Both processes occur by opening of

  8. A benign synthesis of alane by the composition-controlled mechanochemical reaction of sodium hydride and aluminum chloride

    DOE PAGES

    Hlova, Ihor; Goldston, Jennifer F.; Gupta, Shalabh; ...

    2017-05-30

    Solid-state mechanochemical synthesis of alane (AlH3) starting from sodium hydride (NaH) and aluminum chloride (AlCl3) has been achieved at room temperature. The transformation pathway of this solid-state reaction was controlled by a stepwise addition of AlCl3 to the initial reaction mixture that contained sodium hydride in excess of stoichiometric amount. As in the case of previously investigated LiH–AlCl3 system, complete selectivity was achieved whereby formation of unwanted elemental aluminum was fully suppressed, and AlH3 was obtained in quantitative yield. Reaction progress during each step was investigated by means of solid-state NMR and powder X-ray diffraction, which revealed that the overallmore » reaction proceeds through a series of intermediate alanates that may be partially chlorinated. The NaH–AlCl3 system presents some subtle differences compared to LiH–AlCl3 system particularly with respect to optimal concentrations needed during one of the reaction stages. Based on the results, we postulate that high local concentrations of NaH may stabilize chlorine-containing derivatives and prevent decomposition into elemental aluminum with hydrogen evolution. As a result, complete conversion with quantitative yield of alane was confirmed by both SSNMR and hydrogen desorption analysis.« less

  9. Electronic structure and crystal phase stability of palladium hydrides

    NASA Astrophysics Data System (ADS)

    Houari, Abdesalem; Matar, Samir F.; Eyert, Volker

    2014-11-01

    The results of electronic structure calculations for a variety of palladium hydrides are presented. The calculations are based on density functional theory and used different local and semilocal approximations. The thermodynamic stability of all structures as well as the electronic and chemical bonding properties are addressed. For the monohydride, taking into account the zero-point energy is important to identify the octahedral Pd-H arrangement with its larger voids and, hence, softer hydrogen vibrational modes as favorable over the tetrahedral arrangement as found in the zincblende and wurtzite structures. Stabilization of the rocksalt structure is due to strong bonding of the 4d and 1s orbitals, which form a characteristic split-off band separated from the main d-band group. Increased filling of the formerly pure d states of the metal causes strong reduction of the density of states at the Fermi energy, which undermines possible long-range ferromagnetic order otherwise favored by strong magnetovolume effects. For the dihydride, octahedral Pd-H arrangement as realized, e.g., in the pyrite structure turns out to be unstable against tetrahedral arrangement as found in the fluorite structure. Yet, from both heat of formation and chemical bonding considerations, the dihydride turns out to be less favorable than the monohydride. Finally, the vacancy ordered defect phase Pd3H4 follows the general trend of favoring the octahedral arrangement of the rocksalt structure for Pd:H ratios less or equal to one.

  10. Electronic structure and crystal phase stability of palladium hydrides

    SciTech Connect

    Houari, Abdesalem; Matar, Samir F.; Eyert, Volker

    2014-11-07

    The results of electronic structure calculations for a variety of palladium hydrides are presented. The calculations are based on density functional theory and used different local and semilocal approximations. The thermodynamic stability of all structures as well as the electronic and chemical bonding properties are addressed. For the monohydride, taking into account the zero-point energy is important to identify the octahedral Pd-H arrangement with its larger voids and, hence, softer hydrogen vibrational modes as favorable over the tetrahedral arrangement as found in the zincblende and wurtzite structures. Stabilization of the rocksalt structure is due to strong bonding of the 4d and 1s orbitals, which form a characteristic split-off band separated from the main d-band group. Increased filling of the formerly pure d states of the metal causes strong reduction of the density of states at the Fermi energy, which undermines possible long-range ferromagnetic order otherwise favored by strong magnetovolume effects. For the dihydride, octahedral Pd-H arrangement as realized, e.g., in the pyrite structure turns out to be unstable against tetrahedral arrangement as found in the fluorite structure. Yet, from both heat of formation and chemical bonding considerations, the dihydride turns out to be less favorable than the monohydride. Finally, the vacancy ordered defect phase Pd{sub 3}H{sub 4} follows the general trend of favoring the octahedral arrangement of the rocksalt structure for Pd:H ratios less or equal to one.

  11. Phases in lanthanum-nickel-aluminum alloys

    SciTech Connect

    Mosley, W.C.

    1992-01-01

    Lanthanum-nickel-aluminum (LANA) alloys will be used to pump, store and separate hydrogen isotopes in the Replacement Tritium Facility (RTF). The aluminum content (y) of the primary LaNi{sub 5}-phase is controlled to produce the desired pressure-temperature behavior for adsorption and desorption of hydrogen. However, secondary phases cause decreased capacity and some may cause undesirable retention of tritium. Twenty-three alloys purchased from Ergenics, Inc. for development of RTF processes have been characterized by scanning electron microscopy (SEM) and by electron microprobe analysis (EMPA) to determine the distributions and compositions of constituent phases. This memorandum reports the results of these characterization studies. Knowledge of the structural characteristics of these alloys is a useful first step in selecting materials for specific process development tests and in interpreting results of those tests. Once this information is coupled with data on hydrogen plateau pressures, retention and capacity, secondary phase limits for RTF alloys can be specified.

  12. Cubic and orthorhombic structures of aluminum hydride Al H3 predicted by a first-principles study

    NASA Astrophysics Data System (ADS)

    Ke, Xuezhi; Kuwabara, Akihide; Tanaka, Isao

    2005-05-01

    The most stable structure of aluminum hydride AlH3 is believed to be a hexagonal symmetry. However, using the density functional theory, we have identified two more stable structures for the AlH3 with the cubic and orthorhombic symmetries. Based on the quasiharmonic approximation, the cubic and orthorhombic AlH3 are almost degenerate when the zero-point energies are included. The geometric and electronic structures, the phonon, and the thermodynamic properties for the hexagonal, cubic, and orthorhombic AlH3 have been studied by means of density functional theory and direct ab initio force constant approach. The calculated electronic structures, phonon density of states, and thermodynamic functions [including S(T) and H(T)-H(0) ] for the three hydrides are similar. The results show that these three hydrides have negative enthalpies of formation, but positive free energies of formation. This conclusion is the same as that made by Wolverton for the hexagonal AlH3 [Phys. Rev. B 69, 144109 (2004)]. The thermodynamic properties indicate that the orthorhombic and cubic AlH3 should be more difficult to dissociate than the hexagonal AlH3 .

  13. Lightweight hydride storage materials

    SciTech Connect

    Thomas, G.J.; Guthrie, S.E.; Bauer, W.

    1995-09-01

    The need for lightweight hydrides in vehicular applications has prompted considerable research into the use of magnesium and its alloys. Although this earlier work has provided some improved performance in operating temperature and pressure, substantial improvements are needed before these materials will significantly enhance the performance of an engineered system on a vehicle. We are extending the work of previous investigators on Mg alloys to reduce the operating temperature and hydride heat of formation in light weight materials. Two important results will be discussed in this paper: (1) a promising new alloy hydride was found which has better pressure-temperature characteristics than any previous Mg alloy and, (2) a new fabrication process for existing Mg alloys was developed and demonstrated. The new alloy hydride is composed of magnesium, aluminum and nickel. It has an equilibrium hydrogen overpressure of 1.3 atm. at 200{degrees}C and a storage capacity between 3 and 4 wt.% hydrogen. A hydrogen release rate of approximately 5 x 10{sup -4} moles-H{sub 2}/gm-min was measured at 200{degrees}C. The hydride heat of formation was found to be 13.5 - 14 kcal/mole-H{sub 2}, somewhat lower than Mg{sub 2}Ni. The new fabrication method takes advantage of the high vapor transport of magnesium. It was found that Mg{sub 2}Ni produced by our low temperature process was better than conventional materials because it was single phase (no Mg phase) and could be fabricated with very small particle sizes. Hydride measurements on this material showed faster kinetic response than conventional material. The technique could potentially be applied to in-situ hydride bed fabrication with improved packing density, release kinetics, thermal properties and mechanical stability.

  14. Doped Sodium Aluminum Hydride: Fundamental Studies and Practical Development of a Promising New Hydrogen Storage Material

    NASA Astrophysics Data System (ADS)

    Jensen, Craig

    2004-03-01

    In 1997, Bogdanovic and Schwickardi reported that the elimination of hydrogen from solid NaAlH4 is markedly accelerated and rendered reversible under moderate conditions upon mixing the hydride with a few mole percent of selected transition metal complexes. We found that doping the hydride through an alternative, mechanical milling method leads to considerable improvements in the practical hydrogen cycling performance of the hydride. It now appears that a variation of the doped hydride could possibly be developed as a viable means for the onboard storage of hydrogen. However, no dopant precursors have been found that give a greater kinetic enhancement than those cataloged in Bogdanovic's original, 1995 patent. Similarly, only the sodium and mixed sodium, lithium salts of the alanates have been found undergo largely reversible dehydrogenation under moderate conditions upon doping. This lack of progress is surprising in view of the recent "gold rush" flurry of activity that has been direct towards the development of alanates as practical onboard hydrogen carriers. Clearly, these efforts have been handicapped by a lack of understanding of the nature and mechanism of action the dopants. We have therefore initiated efforts to elucidate the fundamental basis of the remarkable hydrogen storage properties of this material. Our efforts have pointed to a model of the material in which the dopants are substituted into the bulk hydride lattice. A detailed version of this model has emerged from our recent infra red, Raman, and electron paramagnetic resonance spectroscopic studies as well as neutron diffraction, inelastic neutron scattering, and kinetic investigations of the doped hydride. The results of these studies will be presented and discussed in terms of their relationship to our "substitutional" model of the doped hydride.

  15. Sapphire surface preparation and gallium nitride nucleation by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Dwikusuma, Fransiska

    The nucleation and initial growth of gallium nitride (GaN) films on sapphire substrates using hydride vapor phase epitaxy (HVPE) technique depends on many factors including the chemical treatment of sapphire surface, nitridation, and the specific growth conditions. Liquid and gas phase treatments of the sapphire surface were systematically studied as a function of temperature and time. Phosphoric acid (H3PO4) etches sapphire preferentially at defect sites and resulted in pits formation on the surface, while etching in sulfuric acid (H2SO4) can produce a smooth, pit-free surface. Air-annealing the sapphire at 1400°C produces an atomically smooth surface consisting of a terrace-and-step structure. The mechanism of sapphire nitridation within the HVPE environment was elucidated. During nitridation, nitrogen is incorporated into the sapphire surface. The sapphire nitridation mechanism can be modeled as a diffusion couple of aluminum nitride (AlN) and aluminum oxide (Al2O 3), where N3- and O2- inter-diffuse in the 'rigid' Al3+ framework. Nitrogen diffuses into sapphire and substitutes for oxygen to bond with aluminum. The replaced oxygen diffuses out to the surface. The overall nitridation rate is controlled by the diffusion of oxygen. Sapphire surface treatments of air-annealing and liquid-based etchings have different effects on nitridation and HVPE GaN nucleation. Upon nitridation, the air-annealed sapphire has ˜1.5 times higher nitrogen content compared to liquid-based etchings. Nevertheless, the air-annealed sapphire yields the lowest density of GaN islands. Sapphire nitridation, which yields a thin AlN layer, results in the growth of higher GaN island densities with a smaller mosaic spread. Sapphire surface, which is etched in H2SO4 and then nitridated, produces a high density GaN islands resulting in improved-quality of thick GaN films. The nucleation and initial growth kinetics of GaN on sapphire grown by HVPE were investigated. As the growth temperature

  16. Method of production of pure hydrogen near room temperature from aluminum-based hydride materials

    DOEpatents

    Pecharsky, Vitalij K.; Balema, Viktor P.

    2004-08-10

    The present invention provides a cost-effective method of producing pure hydrogen gas from hydride-based solid materials. The hydride-based solid material is mechanically processed in the presence of a catalyst to obtain pure gaseous hydrogen. Unlike previous methods, hydrogen may be obtained from the solid material without heating, and without the addition of a solvent during processing. The described method of hydrogen production is useful for energy conversion and production technologies that consume pure gaseous hydrogen as a fuel.

  17. Phase Diagram and High-Temperature Superconductivity of Compressed Selenium Hydrides

    PubMed Central

    Zhang, Shoutao; Wang, Yanchao; Zhang, Jurong; Liu, Hanyu; Zhong, Xin; Song, Hai-Feng; Yang, Guochun; Zhang, Lijun; Ma, Yanming

    2015-01-01

    Recent discovery of high-temperature superconductivity (Tc = 190 K) in sulfur hydrides at megabar pressures breaks the traditional belief on the Tc limit of 40 K for conventional superconductors, and opens up the doors in searching new high-temperature superconductors in compounds made up of light elements. Selenium is a sister and isoelectronic element of sulfur, with a larger atomic core and a weaker electronegativity. Whether selenium hydrides share similar high-temperature superconductivity remains elusive, but it is a subject of considerable interest. First-principles swarm structure predictions are performed in an effort to seek for energetically stable and metallic selenium hydrides at high pressures. We find the phase diagram of selenium hydrides is rather different from its sulfur analogy, which is indicated by the emergence of new phases and the change of relative stabilities. Three stable and metallic species with stoichiometries of HSe2, HSe and H3Se are identified above ~120 GPa and they all exhibit superconductive behaviors, of which the hydrogen-rich HSe and H3Se phases show high Tc in the range of 40–110 K. Our simulations established the high-temperature superconductive nature of selenium hydrides and provided useful route for experimental verification. PMID:26490223

  18. Phase Diagram and High-Temperature Superconductivity of Compressed Selenium Hydrides.

    PubMed

    Zhang, Shoutao; Wang, Yanchao; Zhang, Jurong; Liu, Hanyu; Zhong, Xin; Song, Hai-Feng; Yang, Guochun; Zhang, Lijun; Ma, Yanming

    2015-10-22

    Recent discovery of high-temperature superconductivity (Tc = 190 K) in sulfur hydrides at megabar pressures breaks the traditional belief on the Tc limit of 40 K for conventional superconductors, and opens up the doors in searching new high-temperature superconductors in compounds made up of light elements. Selenium is a sister and isoelectronic element of sulfur, with a larger atomic core and a weaker electronegativity. Whether selenium hydrides share similar high-temperature superconductivity remains elusive, but it is a subject of considerable interest. First-principles swarm structure predictions are performed in an effort to seek for energetically stable and metallic selenium hydrides at high pressures. We find the phase diagram of selenium hydrides is rather different from its sulfur analogy, which is indicated by the emergence of new phases and the change of relative stabilities. Three stable and metallic species with stoichiometries of HSe2, HSe and H3Se are identified above ~120 GPa and they all exhibit superconductive behaviors, of which the hydrogen-rich HSe and H3Se phases show high Tc in the range of 40-110 K. Our simulations established the high-temperature superconductive nature of selenium hydrides and provided useful route for experimental verification.

  19. Phase Diagram and High-Temperature Superconductivity of Compressed Selenium Hydrides

    NASA Astrophysics Data System (ADS)

    Zhang, Shoutao; Wang, Yanchao; Zhang, Jurong; Liu, Hanyu; Zhong, Xin; Song, Hai-Feng; Yang, Guochun; Zhang, Lijun; Ma, Yanming

    2015-10-01

    Recent discovery of high-temperature superconductivity (Tc = 190 K) in sulfur hydrides at megabar pressures breaks the traditional belief on the Tc limit of 40 K for conventional superconductors, and opens up the doors in searching new high-temperature superconductors in compounds made up of light elements. Selenium is a sister and isoelectronic element of sulfur, with a larger atomic core and a weaker electronegativity. Whether selenium hydrides share similar high-temperature superconductivity remains elusive, but it is a subject of considerable interest. First-principles swarm structure predictions are performed in an effort to seek for energetically stable and metallic selenium hydrides at high pressures. We find the phase diagram of selenium hydrides is rather different from its sulfur analogy, which is indicated by the emergence of new phases and the change of relative stabilities. Three stable and metallic species with stoichiometries of HSe2, HSe and H3Se are identified above ~120 GPa and they all exhibit superconductive behaviors, of which the hydrogen-rich HSe and H3Se phases show high Tc in the range of 40-110 K. Our simulations established the high-temperature superconductive nature of selenium hydrides and provided useful route for experimental verification.

  20. Analysis of polar peptides using a silica hydride column and high aqueous content mobile phases.

    PubMed

    Yang, Yuanzhong; Boysen, Reinhard I; Kulsing, Chadin; Matyska, Maria T; Pesek, Joseph J; Hearn, Milton T W

    2013-09-01

    The retention behavior of a set of polar peptides separated on a silica hydride stationary phase was examined with a capillary HPLC system coupled to ESI-MS detection. The mobile phases consisted of formic acid or acetic acid/acetonitrile/water mixtures with the acetonitrile content ranging from 5 to 80% v/v. The effects on peptide retention of these two acidic buffer additives and their concentrations in the mobile phase were systematically investigated. Strong retention of the peptides on the silica hydride phase was observed with relatively high-organic low-aqueous mobile phases (i.e. under aqueous normal-phase conditions). However, when low concentrations of acetic acid were employed as the buffer additive, strong retention of the peptides was also observed even when high aqueous content mobile phases were employed. This unique feature of the stationary phase therefore provides an opportunity for chromatographic analysis of polar peptides with water-rich eluents, a feature usually not feasible with traditional RP sorbents, and thus under conditions more compatible with analytical green chemistry criteria. In addition, both isocratic and gradient elution procedures can be employed to optimize peptide separations with excellent reproducibility and resolution under these high aqueous mobile phase conditions with this silica hydride stationary phase.

  1. Mathematical model of metal-hydride phase change applied to Yttrium

    NASA Astrophysics Data System (ADS)

    Chernov, I. A.; Manicheva, S. V.; Gabis, I. E.

    2013-08-01

    We present a mathematical model for the kinetics of hydriding and dehydriding of metal powders. The single powder particle is considered. Its shape is approximated by one of the symmetric ones: sphere, long thin cylinder (wire), or flat thin plate. A few concurrent processes are considered. The model equations are derived from the mass conservation law. We consider the case of the "shrinking core" morphology, i.e. formation of the hydride skin on the surface of the particle with subsequent growth of this skin. We consider three successive stages of the phase change: skin development, skin growth, and final saturation or degassing. We apply the model to experimental data for Yttrium and show that the approximation of the experimental curves by the model ones is comparable for different cycles and different shapes for similar sets of the kinetic parameters. This also shows that shape of powder particles do not influence significantly on the kinetics of hydriding and dehydriding.

  2. GAS-PHASE REACTIONS OF HYDRIDE ANION, H{sup -}

    SciTech Connect

    Martinez, Oscar; Yang Zhibo; Demarais, Nicholas J.; Bierbaum, Veronica M.; Snow, Theodore P. E-mail: Zhibo.Yang@colorado.ed E-mail: Veronica.Bierbaum@colorado.ed

    2010-09-01

    Rate constants were measured at 300 K for the reactions of the hydride anion, H{sup -}, with neutral molecules C{sub 2}H{sub 2}, H{sub 2}O, CH{sub 3}CN, CH{sub 3}OH, (CH{sub 3}){sub 2}CO, CH{sub 3}CHO, N{sub 2}O, CO{sub 2}, O{sub 2}, CO, CH{sub 3}Cl, (CH{sub 3}){sub 3}CCl, (CH{sub 3}CH{sub 2}){sub 2}O, C{sub 6}H{sub 6}, and D{sub 2} using a flowing-afterglow instrument. Experimental work was supplemented by ab initio calculations to provide insight into the viability of reaction pathways. Our reported rate constants should prove useful to models of astrophysical environments where conditions prevail for the existence of both H{sup -} and neutral species. The variety of neutral reactants studied includes representative species from prototypical chemical groups, effectively mapping reactivity trends for the hydride anion.

  3. Spray Forming Aluminum - Final Report (Phase II)

    SciTech Connect

    D. D. Leon

    1999-07-08

    The U.S. Department of Energy - Office of Industrial Technology (DOE) has an objective to increase energy efficient and enhance competitiveness of American metals industries. To support this objective, ALCOA Inc. entered into a cooperative program to develop spray forming technology for aluminum. This Phase II of the DOE Spray Forming Program would translate bench scale spray forming technology into a cost effective world class process for commercialization. Developments under DOE Cooperative Agreement No. DE-FC07-94ID13238 occurred during two time periods due to budgetary constraints; April 1994 through September 1996 and October 1997 and December 1998. During these periods, ALCOA Inc developed a linear spray forming nozzle and specific support processes capable of scale-up for commercial production of aluminum sheet alloy products. Emphasis was given to alloys 3003 and 6111, both being commercially significant alloys used in the automotive industry. The report reviews research performed in the following areas: Nozzel Development, Fabrication, Deposition, Metal Characterization, Computer Simulation and Economics. With the formation of a Holding Company, all intellectual property developed in Phases I and II of the Project have been documented under separate cover for licensing to domestic producers.

  4. Evaluation of the dual retention properties of stationary phases based on silica hydride: Perfluorinated bonded material.

    PubMed

    Pesek, Joseph J; Matyska, Maria T; Natekar, Harshada

    2016-03-01

    The synthesis of a new perfluorinated stationary phase based on silica hydride using a hydrosilation reaction was investigated. The material was characterized by elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy and (13) C cross-polarization magic-angle spinning NMR spectroscopy. The retention properties of this new material were tested in the reversed-phase and normal-phase mode. Variable buffer strength experiments at two pH conditions for selected polar compounds were used to compare the new phase to hydrophilic interaction liquid chromatography retention. These results and previous data reported in the literature were used to postulate differences in the retention mechanism between hydrophilic interaction liquid chromatography and silica hydride-based stationary phases. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Hydride phase dissolution enthalpy in neutron irradiated Zircaloy-4

    NASA Astrophysics Data System (ADS)

    Vizcaíno, P.; Banchik, A. D.; Abriata, J. P.

    2005-01-01

    The differential calorimetric technique has been applied to measure the dissolution enthalpy, ΔHδ→αirrad, of zirconium hydrides precipitated in structural components removed from the Argentine Atucha 1 PHWR nuclear power plant after 10.3 EFPY. An average value of ΔHδ→αirrad=5 kJ/mol H was obtained after the first calorimetric run. That value is seven times lower than the value of Δ Hδ→α = 37.7 kJ/mol H recently determined in Zircaloy-4 specimens taken from similar unirradiated structural components using the same calorimetric technique [P. Vizcaı´no, PhD thesis, Number TD-11/03, Inst. Tech. 'Prof. Jorge A. Sábato', CICAC, CNEA, Buenos Aires, Argentina, 24 June 2003]. Post-irradiation thermal treatments gradually increase that low value towards the unirradiated value with increasing annealing temperature similar to that observed for TSSd irrad [P. Vizcaı´no, A.D. Banchik, J.P. Abriata. J. Nucl. Mater. 304/2-3 (2002) 96-106]. Therefore the same H atom trapping mechanism during reactor operation already proposed to explain the evolution of TSSd irrad is also valid for Qδ→αirrad. As the ratio Q/Δ H is proportional to the number NH of H atoms precipitated as hydrides, the increment of Qδ→αirrad with the thermal treatment indicates that the value of NH also grows with the annealing reaching the value corresponding to the bulk H concentration when ΔHδ→αirrad≈37 kJ/mol H. That is a direct indication that the post-irradiation thermal treatment releases the H atoms from their traps increasing the number of H atoms available to precipitate at the end of each calorimetric run and/or isothermal treatment.

  6. Role of grain/phase boundary nature on the formation of hydrides in Zr-2.5%Nb alloy

    NASA Astrophysics Data System (ADS)

    Mani Krishna, K. V.; Srivastava, D.; Dey, G. K.; Hiwarkar, V.; Samajdar, I.; Banerjee, S.

    2011-07-01

    Hydride formation in a fully recrystallized Zr-2.5%Nb alloy having equiaxed grains of α and β was studied. Primarily the electron back scatter diffraction (EBSD) technique was used for the characterization of the hydrides in conjunction with optical and transmission electron microscopy. Hydrides were found to have preferentially formed along the α/β interfaces. Microtexture measurements showed that the orientation relationship (OR) between α and δ-hydride phase was (0 0 0 1) α || (1 1 1) δ and [2 1¯ 1 0]α || [1 1 0] δ. It was shown that the hydrides have higher preference to form along such α/β interfaces which have one of the low index planes of the β phase constituting the interface.

  7. Novel 3-hydroxypropyl bonded phase by direct hydrosilylation of allyl alcohol on amorphous hydride silica

    PubMed Central

    Gómez, Jorge E.; Navarro, Fabián H.; Sandoval, Junior E.

    2015-01-01

    A novel 3-hydroxypropyl (propanol) bonded silica phase has been prepared by hydrosilylation of allyl alcohol on a hydride silica intermediate, in the presence of platinum (0)-divinyltetramethyldisiloxane (Karstedt's catalyst). The regio-selectivity of this synthetic approach had been correctly predicted by previous reports involving octakis(dimethylsiloxy)octasilsesquioxane (Q8M8H) and hydrogen silsesquioxane (T8H8), as molecular analogs of hydride amorphous silica. Thus, C-silylation predominated (~ 94%) over O-silylation, and high surface coverages of propanol groups (5±1 µmol/m2) were typically obtained in this work. The propanol-bonded phase was characterized by spectroscopic (IR and solid state NMR on silica microparticles), contact angle (on fused-silica wafers) and CE (on fused-silica tubes) techniques. CE studies of the migration behavior of pyridine, caffeine, tris(2,2’-bipyridine)Ru(II) chloride and lysozyme on propanol-modified capillaries were carried out. The adsorption properties of these select silanol-sensitive solutes were compared to those on the unmodified and hydride-modified tubes. It was found that hydrolysis of the SiH species underlying the immobilized propanol moieties leads mainly to strong ion-exchange based interactions with the basic solutes at pH 4, particularly with lysozyme. Interestingly, and in agreement with water contact angle and electroosmotic mobility figures, the silanol-probe interactions on the buffer-exposed (hydrolyzed) hydride surface are quite different from those of the original unmodified tube. PMID:24934906

  8. Evaluation of Protective Coatings for Aluminum Torpedoes. Phase 2.

    DTIC Science & Technology

    1988-04-01

    48 is primarily made of 6000 and 7000 series aluminum , both of which are lightweight and strong, but have poor -~ resistance to corrosion. On the...D-A195 153 EVALUATION OF PROTECTIVE COATINGS FOR ALUMINUM 1 TORPEDOES PHASE 20U) CONSTRUCTION ENGINEERING RESEARCH LAB (ARMY) CHAMPAIGN IL S R...Engineering Research Laboratory AD-A195 153 Evaluation of Protective Coatings for Aluminum Torpedoes: Phase II by Susan A. Johnston This report

  9. Photoelectron spectroscopy of the aluminum hydride anions: AlH2-, AlH3-, Al2H6-, Al3H9-, and Al4H12-

    NASA Astrophysics Data System (ADS)

    Zhang, Xinxing; Wang, Haopeng; Collins, Evan; Lim, Alane; Ganteför, Gerd; Kiran, Boggavarapu; Schnöckel, Hansgeorg; Eichhorn, Bryan; Bowen, Kit

    2013-03-01

    We report measurements of the negative ion photoelectron spectra of the simple aluminum hydride anions: AlH2-, AlH3-, Al2H6-, Al3H9-, and Al4H12-. From these spectra, we measured the vertical detachment energies of the anions, and we estimated the electron affinities of their neutral counterparts. Our results for AlH2-, AlH3-, and Al2H6- were also compared with previous predictions by theory.

  10. Photoelectron spectroscopy of the aluminum hydride anions: AlH2(-), AlH3(-), Al2H6(-), Al3H9(-), and Al4H12(-).

    PubMed

    Zhang, Xinxing; Wang, Haopeng; Collins, Evan; Lim, Alane; Ganteför, Gerd; Kiran, Boggavarapu; Schnöckel, Hansgeorg; Eichhorn, Bryan; Bowen, Kit

    2013-03-28

    We report measurements of the negative ion photoelectron spectra of the simple aluminum hydride anions: AlH2(-), AlH3(-), Al2H6(-), Al3H9(-), and Al4H12(-). From these spectra, we measured the vertical detachment energies of the anions, and we estimated the electron affinities of their neutral counterparts. Our results for AlH2(-), AlH3(-), and Al2H6(-) were also compared with previous predictions by theory.

  11. Strontium vanadium oxide-hydrides: "square-planar" two-electron phases.

    PubMed

    Denis Romero, Fabio; Leach, Alice; Möller, Johannes S; Foronda, Francesca; Blundell, Stephen J; Hayward, Michael A

    2014-07-14

    A series of strontium vanadium oxide-hydride phases prepared by utilizing a low-temperature synthesis strategy in which oxide ions in Sr(n+1)V(n)O(3n+1) (n=∞, 1, 2) phases are topochemically replaced by hydride ions to form SrVO2H, Sr2VO3H, and Sr3V2O5H2, respectively. These new phases contain sheets or chains of apex-linked V(3+)O4 squares stacked with SrH layers/chains, such that the n=∞ member, SrVO2H, can be considered to be analogous to "infinite-layer" phases, such as Sr(1-x)Ca(x)CuO2 (the parent phase of the high-T(c) cuprate superconductors), but with a d(2) electron count. All three oxide-hydride phases exhibit strong antiferromagnetic coupling, with SrVO2H exhibiting an antiferromagnetic ordering temperature, T(N)>300 K. The strong antiferromagnetic couplings are surprising given they appear to arise from π-type magnetic exchange.

  12. Hydrogen, lithium, and lithium hydride production

    DOEpatents

    Brown, Sam W.; Spencer, Larry S.; Phillips, Michael R.; Powell, G. Louis; Campbell, Peggy J.

    2017-06-20

    A method is provided for extracting hydrogen from lithium hydride. The method includes (a) heating lithium hydride to form liquid-phase lithium hydride; (b) extracting hydrogen from the liquid-phase lithium hydride, leaving residual liquid-phase lithium metal; (c) hydriding the residual liquid-phase lithium metal to form refined lithium hydride; and repeating steps (a) and (b) on the refined lithium hydride.

  13. Capillary liquid chromatography and capillary electrochromatography using silica hydride stationary phases.

    PubMed

    Pesek, Joseph J; Matyska, Maria T; Sukul, Dipti

    2008-05-16

    A hydride-based octadecyl stationary phase on both 4.0 and 1.8 microm silica particles is tested in both the capillary LC and the pressurized capillary electrochromatography (pCEC) modes. These two materials are compared to standard C18 stationary phase made by organosilanization and to the hydride material packed into a convention 4.6mm I.D. column. The performance of the capillary columns is evaluated in terms of analysis times for various mixtures as well as efficiency. Of particular interest are the differences between the LC mode where only laminar flow is present and pCEC operation where a flat electrodriven flow profile is superimposed on the parabolic pressurized flow. Differences in performance between columns packed with 4.0 and 1.8 microm particle silica are also evaluated.

  14. Possible "Magnéli" Phases and Self-Alloying in the Superconducting Sulfur Hydride

    NASA Astrophysics Data System (ADS)

    Akashi, Ryosuke; Sano, Wataru; Arita, Ryotaro; Tsuneyuki, Shinji

    2016-08-01

    We theoretically give an infinite number of metastable crystal structures for the superconducting sulfur hydride HxS under pressure. Previously predicted crystalline phases of H2S and H3S have been thought to have important roles for experimentally observed low and high Tc, respectively. The newly found structures are long-period modulated crystals where slablike H2S and H3S regions intergrow on a microscopic scale. The extremely small formation enthalpy for the H2S -H3S boundary indicated by first-principles calculations suggests possible alloying of these phases through the formation of local H3S regions. The modulated structures and gradual alloying transformations between them not only explain the peculiar pressure dependence of Tc in sulfur hydride observed experimentally, but also could prevail in the experimental samples under various compression schemes.

  15. CHARACTERIZATION OF THE LOCAL TITANIUM ENVIRONMENT IN DOPED SODIUM ALUMINUM HYDRIDE USING X-RAY ADSORPTION SPECTROSCOPY.

    SciTech Connect

    GRAETZ, J.; IGNATOV, A. YU; TYSON, T.A.; REILLY, J.J.; JOHNSON, J.

    2004-11-30

    Ti K-edge x-ray absorption spectroscopy was used to explore the local titanium environment and valence in 2-4 mol% Ti-doped sodium alanate. An estimate of the oxidation state of the dopant, based upon known standards, revealed a zero-valent titanium atom. An analysis of the near-edge and extended fine structures indicates that the Ti does not enter substitutional or interstitial sites in the NaAlH{sub 4} lattice. Rather, the Ti is located on/near the surface and is coordinated by 10.2 {+-} 1 aluminum atoms with an interatomic distance of 2.82 {+-} 0.01 {angstrom}, similar to that of TiAl{sub 3}. The Fourier transformed EXAFS spectra reveals a lack of long-range order around the Ti dopant indicating that the Ti forms nano-clusters of TiAl{sub 3}. The similarity of the spectra in the hydrided and dehydrided samples suggests that the local Ti environment is nearly invariant during hydrogen cycling.

  16. Synthesis and characterization of endcapped C18 stationary phases using a silica hydride intermediate.

    PubMed

    Pesek, Joseph J; Matyska, Maria T; Yu, Raymond J

    2002-02-22

    The effect of endcapping on an octdecyl bonded phase synthesized by the silanization/hydrosilation method is investigated. The endcapping reagent is a 1:1 molar ratio of trimethylchlorosilane (TMCS) and hexamethyldisilizane (HMDS). Two approaches for endcapping are possible for this synthetic method that produces a silica hydride intermediate: bonding of TMCS-HMDS after silanization (on the hydride intermediate) or after hydrosilation (on the C18 product stationary phase). The use of TMCS-HMDS is designed to eliminate the few remaining silanols on the silica hydride intermediate. The endcapping process is characterized spectroscopically by diffuse reflectance infrared Fourier transform (DRIFT), 29Si cross polarization magic angle spinning nuclear magnetic resonance spectroscopy (CP-MAS-NMR) and 13-C-CP-MAS-NMR. The octadecyl bonded phases are characterized chromatographically by measuring the capacity factors of several hydrophobic and basic test solutes as well as the separation factors among various solute pairs. Finally, long-term stability tests are done on both products at high and low pH.

  17. Phase compositions of the products in the electrical explosion of mixtures of tantalum hydride and carbon

    SciTech Connect

    Pavlov, I.E.

    1986-10-01

    This paper presents information on the phase compositions of the products formed in the electrical explosion in water of mixtures of tantalum hydride with carbon. The initial materials were powders of TaH /SUB 0.58/ and ultrapure graphite. The data shows that all products contained a cubic phase (NaC type) and a hexagonal one, which were indicated by the cell parameters as being cubic tantalum carbide containing some dissolved oxygen, and hexagonal tantalum oxycarbide. The contents of the phases are determined by the composition of the initial mixture and by the particle size.

  18. The Zr20Nb-H phase diagram and the characterisation of hydrides in β-Zr

    NASA Astrophysics Data System (ADS)

    Barrow, L.; Barrow, A. T. W.; Almer, J.; Daymond, M. R.

    2013-11-01

    In this work a combination of synchrotron X-ray diffraction, transmission electron microscopy and differential scanning calorimetry have been used to characterise the Zr20Nb-H phase diagram and hydrides in β-Zr. A single hydride phase, termed γ' was found to be present in β-Zr over a wide range of H concentrations up to 1559 wppm. γ'-hydride had an orthorhombic crystal structure with the composition ZrH0.4 ± 0.2, and was found to be stable during heating to 450 °C; it can therefore be considered the equilibrium hydride in β-Zr. Accompanying hydride nucleation is a volumetric strain of 10.4% that is accommodated elastically and plastically by the β-Zr. The body-centre cubic to orthorhombic martensitic transformation is analogous to the Au-Cd system where the basal plane in the hydride is constructed from the (0 1 1)β to give the Bain correspondence. There are strong similarities between the Zr20Nb-H and Nb-H phase diagrams with the former having a lower solubility for H at room temperature, ˜130 wppm and ˜290 wppm respectively. The room temperature solubility difference between body-centre cubic Nb and β-Zr can be attributed to their electron configurations and the reduction in energy associated with the metallic Zr/Nb-H bonding. The hydrides were found to have a plate morphology and consisted of sub-platelets analogous to δ-hydride in α-Zr. The hydride had an orthorhombic crystal structure and the (0‖(0,[0‖[0 and [1‖[ orientation relationship with the β-Zr matrix, consistent with the Au-Cd system. gamma;'-hydride formation was accompanied by a volumetric strain of 10.4% that is accommodated elastically and plastically in the matrix. Sympathetic hydride nucleation occurs in the elastic strain field of the parent hydride. In all instances the long axis of the hydride was consistent with the <0 1 1>β. beta;-Zr has a H solubility of 128 ± 5 wppm at room temperature and considerably higher than α-Zr. The solubility difference between the BCC and

  19. Cationic aluminum hydride complexes: reactions of carbene-alane adducts with trityl-borate.

    PubMed

    Cao, Levy L; Daley, Erika; Johnstone, Timothy C; Stephan, Douglas W

    2016-04-18

    Reaction of (Idipp)AlH3 with [Ph3C][B(C6F5)4] in toluene affords the dimeric aluminum dication [((Idipp)AlH(μ-H))2][B(C6F5)4]22. In contrast, the reaction of (IBn)AlH3 with [Ph3C][B(C6F5)4] in bromobenzene gives a redistribution product, the salt of a monomeric dication [(IBn)2AlH][B(C6F5)4]24.

  20. Phase separation of lanthanum hydride under high pressure

    NASA Astrophysics Data System (ADS)

    Machida, A.; Watanuki, T.; Kawana, D.; Aoki, K.

    2011-02-01

    Structural change of lanthanum dihydride LaH2.3, which has a face-centered-cubic (fcc) metal lattice with tetrahedral interstitial sites fully occupied with hydrogen atoms and partially occupied octahedral sites, has been investigated at high pressures up to 20 GPa at ambient temperature by synchrotron radiation x-ray diffraction. Additional Bragg reflections appear just on higher angle sides of the original ones at ~11 GPa and their peak intensities increase gradually on further compression. The coexistence state of two fcc metal lattices thus observed above 11 GPa is interpreted in terms of phase separation or disproportionation reaction from the dihydride toward a solid solution and trihydride states, in both of which the octahedral interstitial sites are partially occupied with hydrogen atoms. A gradual distortion from the cubic to a tetragonal lattice is observed prior to the phase separation. The coexistence phase goes back to the dihydride fcc phase via the lattice distorted phase with decreasing pressure.

  1. Novel 3-hydroxypropyl-bonded phase by direct hydrosilylation of allyl alcohol on amorphous hydride silica.

    PubMed

    Gómez, Jorge E; Navarro, Fabián H; Sandoval, Junior E

    2014-09-01

    A novel 3-hydroxypropyl (propanol)-bonded silica phase has been prepared by hydrosilylation of allyl alcohol on a hydride silica intermediate, in the presence of platinum (0)-divinyltetramethyldisiloxane (Karstedt's catalyst). The regio-selectivity of this synthetic approach had been correctly predicted by previous reports involving octakis(dimethylsiloxy)octasilsesquioxane (Q8 M8 (H) ) and hydrogen silsesquioxane (T8 H8 ), as molecular analogs of hydride amorphous silica. Thus, C-silylation predominated (∼94%) over O-silylation, and high surface coverages of propanol groups (5 ± 1 μmol/m(2) ) were typically obtained in this work. The propanol-bonded phase was characterized by spectroscopic (infrared (IR) and solid-state NMR on silica microparticles), contact angle (on fused-silica wafers) and CE (on fused-silica tubes) techniques. CE studies of the migration behavior of pyridine, caffeine, Tris(2,2'-bipyridine)Ru(II) chloride and lysozyme on propanol-modified capillaries were carried out. The adsorption properties of these select silanol-sensitive solutes were compared to those on the unmodified and hydride-modified tubes. It was found that hydrolysis of the SiH species underlying the immobilized propanol moieties leads mainly to strong ion-exchange-based interactions with the basic solutes at pH 4, particularly with lysozyme. Interestingly, and in agreement with water contact angle and electroosmotic mobility figures, the silanol-probe interactions on the buffer-exposed (hydrolyzed) hydride surface are quite different from those of the original unmodified tube. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. An Aluminum Hydride That Functions like a Transition-Metal Catalyst.

    PubMed

    Yang, Zhi; Zhong, Mingdong; Ma, Xiaoli; De, Susmita; Anusha, Chakkittakandiyil; Parameswaran, Pattiyil; Roesky, Herbert W

    2015-08-24

    The reaction of [LAlH2 ] (L=HC(CMeNAr)2 , Ar=2,6-iPr2 C6 H3 ) with MeOTf (Tf=SO2 CF3 ) resulted in the formation of [LAlH(OTf)] (1) in high yield. The triflate substituent in 1 increases the positive charge at the aluminum center, which implies that 1 has a strong Lewis acidic character. The excellent catalytic activity of 1 for the hydroboration of organic compounds with carbonyl groups was investigated. Furthermore, it was shown that 1 effectively initiates the addition reaction of trimethylsilyl cyanide (TMSCN) to both aldehydes and ketones. Quantum mechanical calculations were carried out to explore the reaction mechanism.

  3. Stable High-Energy Density Super-Atom Clusters of Aluminum Hydride

    NASA Astrophysics Data System (ADS)

    Lian, Ke-yan; Jiang, Yuan-fei; Fei, De-hou; Feng, Wei; Jin, Ming-xing; Ding, Da-jun; Luo, Yi

    2012-04-01

    With the concept of super-atom, first principles calculations propose a new type of super stable cage clusters AlnH3n that are much more energetic stable than the well established clusters, AlnHn+2. In the new clusters, the aluminum core-frame acts as a super-atom with n vertexes and 2n Al-Al edges, which allow to adsorb n hydrogen atoms at the top-site and 2n at the bridge-site. Using Al12H36 as the basic unit, stable chain structures, (Al12H36)m, have been constructed following the same connection mechanism as for (AlH3)n linear polymeric structures. Apart from high hydrogen percentage per molecule, calculations have shown that these new clusters possess large heat of formation values and their combustion heat is about 4.8 times of the methane, making them a promising high energy density material.

  4. Multiphysics phase field modeling of hydrogen diffusion and delta-hydride precipitation in alpha-zirconium

    NASA Astrophysics Data System (ADS)

    Jokisaari, Andrea M.

    Hydride precipitation in zirconium is a significant factor limiting the lifetime of nuclear fuel cladding, because hydride microstructures play a key role in the degradation of fuel cladding. However, the behavior of hydrogen in zirconium has typically been modeled using mean field approaches, which do not consider microstructural evolution. This thesis describes a quantitative microstructural evolution model for the alpha-zirconium/delta-hydride system and the associated numerical methods and algorithms that were developed. The multiphysics, phase field-based model incorporates CALPHAD free energy descriptions, linear elastic solid mechanics, and classical nucleation theory. A flexible simulation software implementing the model, Hyrax, is built on the Multiphysics Object Oriented Simulation Environment (MOOSE) finite element framework. Hyrax is open-source and freely available; moreover, the numerical methods and algorithms that have been developed are generalizable to other systems. The algorithms are described in detail, and verification studies for each are discussed. In addition, analyses of the sensitivity of the simulation results to the choice of numerical parameters are presented. For example, threshold values for the CALPHAD free energy algorithm and the use of mesh and time adaptivity when employing the nucleation algorithm are studied. Furthermore, preliminary insights into the nucleation behavior of delta-hydrides are described. These include a) the sensitivities of the nucleation rate to temperature, interfacial energy, composition and elastic energy, b) the spatial variation of the nucleation rate around a single precipitate, and c) the effect of interfacial energy and nucleation rate on the precipitate microstructure. Finally, several avenues for future work are discussed. Topics encompass the terminal solid solubility hysteresis of hydrogen in zirconium and the effects of the alpha/delta interfacial energy, as well as thermodiffusion, plasticity

  5. Emergent Magnéli-type crystal phases and their mixture in pressurized sulfur hydride

    NASA Astrophysics Data System (ADS)

    Akashi, Ryosuke; Sano, Wataru; Arita, Ryotaro; Tsuneyuki, Shinji

    2017-01-01

    The pressure-induced superconductivity in sulfur hydride has recently received tremendous amount of interest for its record-breaking transition temperature (Tc) of 203 K. We extensively discuss an infinite sequence of metastable structures of sulfur hydride under high pressure which has been recently proposed theoretically [R. Akashi et al., Phys. Rev. Lett. 117, 075503 (2016)]. The newly found structures are understood as the stacked layers of H2S and H3S, showing close similarity to the Magnéli phases formed in transition-metal oxides. The possible emergence of the "HxS Magnéli" phases are discussed as intermediate metastable phases in the formation of the high-Tc H3S phase. Superconducting transition temperatures and the Xray diffraction patterns are simulated with the first-principles calculations. It is demonstrated that the HxS Magnéli phases could serve as the silver bullet to explain the complicated dependences of the observed Tcs and diffraction patterns on the experimental protocol.

  6. Silica hydride intermediate for octadecylsilica and phenyl bonded phase preparation via heterogeneous hydrosilation in supercritical carbon dioxide.

    PubMed

    Scully, N M; Ashu-Arrah, B A; Nagle, A P; Omamogho, J O; O'Sullivan, G P; Friebolin, V; Dietrich, B; Albert, K; Glennon, J D

    2011-04-15

    Investigations into the preparation of silica hydride intermediate in supercritical carbon dioxide (sc-CO(2)) that avoids the use of organic solvents such as toluene or dioxane are described. The effects of reaction temperature, pressure and time on the surface coverage of the supercritical fluid generated silica hydride intermediate were studied. Under optimised supercritical conditions of 120°C, 483 bar and 3 h reaction time, silica hydride (Si-H) conversion efficiencies of ca. 40% were achieved for the hydride intermediate prepared from a monofunctional silane reagent (dimethylmethoxysilane). Si-H conversion efficiencies (as determined from (29)Si CP-MAS NMR spectral analysis) for the hydride intermediate prepared from triethoxysilane (TES) in sc-CO(2) were found to be comparable to those obtained using a TES silanisation approach in an organic solvent. (13)C and (29)Si CP-MAS-NMR spectroscopy was employed to provide a complete structural assignment of the silica hydride intermediates. Furthermore, supercritical CO(2) was subsequently employed as a reaction medium for the heterogenous hydrosilation of silica hydride with octadecene and with styrene, in the presence of a free radical initiator. These supercritical fluid generated reversed-phase materials were prepared in a substantially reduced reaction time (3 h) compared to organic solvent based methods (100 h reaction time). Silica functionalisation in sc-CO(2) presents an efficient and clean alternative to organic solvent based methods for the preparation of important silica hydride intermediate and silica bonded stationary phases via a hydrosilation approach. Copyright © 2010 Elsevier B.V. All rights reserved.

  7. Superconductivity in metastable phases of phosphorus-hydride compounds under high pressure

    NASA Astrophysics Data System (ADS)

    Flores-Livas, José A.; Amsler, Maximilian; Heil, Christoph; Sanna, Antonio; Boeri, Lilia; Profeta, Gianni; Wolverton, Chris; Goedecker, Stefan; Gross, E. K. U.

    2016-01-01

    Hydrogen-rich compounds have been extensively studied both theoretically and experimentally in the quest for novel high-temperature superconductors. Reports on sulfur hydride attaining metallicity under pressure and exhibiting superconductivity at temperatures as high as 200 K have spurred an intense search for room-temperature superconductors in hydride materials. Recently, compressed phosphine was reported to metallize at pressures above 45 GPa, reaching a superconducting transition temperature (TC) of 100 K at 200 GPa. However, neither the exact composition nor the crystal structure of the superconducting phase have been conclusively determined. In this work, the phase diagram of PHn (n =1 ,2 ,3 ,4 ,5 ,6 ) was extensively explored by means of ab initio crystal structure predictions using the minima hopping method (MHM). The results do not support the existence of thermodynamically stable PHn compounds, which exhibit a tendency for elemental decomposition at high pressure even when vibrational contributions to the free energies are taken into account. Although the lowest energy phases of PH1 ,2 ,3 display TC's comparable to experiments, it remains uncertain if the measured values of TC can be fully attributed to a phase-pure compound of PHn.

  8. Phase diagram and superconductivity of compressed zirconium hydrides.

    PubMed

    Li, Xiao-Feng; Hu, Zi-Yu; Huang, Bing

    2017-02-01

    It is known that pressure can be applied to fundamentally alter the bonding patterns between the chemical elements. By employing an unbiased structure search method based on a particle swarm optimization (PSO) methodology, the phase diagram and crystal structures of Zr-H compounds are systematically investigated at a high pressure up to 150 GPa. Interestingly, some unexpectedly stable compounds with unusual chemical and physical properties are predicted to be formed, for example, four stable and metallic species with stoichiometries of ZrH, ZrH2, ZrH3, and ZrH6 are identified for the first time. It is interesting to note that Cmc21-ZrH6 adopts intriguing structures with H2 units. Surprisingly, it is found that Cmcm-ZrH is superconducting with Tc as high as 10.6 K. Our study opens a novel avenue for designing superconducting Zr-H compounds by applying pressure.

  9. Correlations between the zeta potentials of silica hydride-based stationary phases, analyte retention behaviour and their ionic interaction descriptors.

    PubMed

    Kulsing, Chadin; Yang, Yuanzhong; Munera, Caesar; Tse, Colby; Matyska, Maria T; Pesek, Joseph J; Boysen, Reinhard I; Hearn, Milton T W

    2014-03-19

    In this study, the zeta potentials of type-B silica, bare silica hydride, the so-called Diamond Hydride™ and phenyl substituted silica hydride stationary phases have been measured in aqueous-organic media and correction procedures developed to account for the more negative zeta potential values in media containing different acetonitrile contents. Retention studies of 16 basic, acidic and neutral compounds were also performed with these four stationary phases with mobile phases containing 0.1% (v/v) formic acid and various acetonitrile-water compositions ranging from 0-90% (v/v) acetonitrile. The retention properties of these analytes were correlated to the corrected stationary phase zeta potentials measured under these different mobile phase conditions with R(2) values ranging from 0.01 to 1.00, depending on the stationary phase and analyte type. Using linear solvation energy relationships, stationary phase descriptors for each stationary phase have been developed for the different mobile phase conditions. Very high correlations of the zeta potentials with the ionic interaction descriptors were obtained for the type-B silica and the Diamond Hydride™ phases and good correlation with bare silica hydride material whilst there was no correlation observed for the phenyl substituted silica hydride phase. The nature of the retention mechanisms which gives rise to these different observations is discussed. The described methods represent a useful new approach to characterize and assess the retention properties of silica-hydride based chromatographic stationary phases of varying bonded-phase coverage and chemistries, as would be broadly applicable to other types of stationary phase used in the separation sciences. Copyright © 2014 Elsevier B.V. All rights reserved.

  10. Mass transport growth and optical emission properties of hydride vapor phase epitaxy GaN

    NASA Astrophysics Data System (ADS)

    Paskova, T.; Goldys, E. M.; Paskov, P. P.; Wahab, Q.; Wilzen, L.; de Jong, M. P.; Monemar, B.

    2001-06-01

    The optical emission properties of mass-transport regions of GaN grown by hydride vapor phase epitaxy are studied by cathodoluminescence imaging and spectroscopy. A strong donor-acceptor pair emission is observed from the mass-transport regions. Spatially resolved cathodoluminescence reveals a strong intensity contrast between the exciton and donor-acceptor bands from mass-transport and nontransport regions. Focused Auger electron and x-ray photoelectron spectroscopies were employed to investigate the impurity incorporation in the different regions. A preferential moderate increase of residual impurity incorporation or redistribution in mass-transport regions is suggested to be responsible for the observed change of the dominant radiative mechanism.

  11. Evaluation of stationary phases based on silica hydride for the analysis of drugs of abuse.

    PubMed

    Pesek, Joseph J; Matyska, Maria T; Kim, Amy M

    2013-09-01

    Several stationary phases based on silica hydride were evaluated as possible separation media for drugs of abuse. In the RP mode both a C18 and a phenyl column were tested using ACN/water and methanol/water mobile phases with formic acid or ammonium formate as modifiers. Detection was performed using MS, so separation of isobaric species was a factor in selecting the column, mobile phase composition, and gradient. A number of sample preparation procedures were also included as part of determining the most appropriate experimental protocol on these types of stationary phases. Morphine was used as a model for developing a protocol that would be suitable for the analysis of hydrophilic drugs. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Aluminum Foam-Phase Change Material Composites as Heat Exchangers

    SciTech Connect

    Hong, Sung-tae; Herling, Darrell R.

    2007-04-07

    The effects of geometric parameters of open-cell aluminum foams on the performance of aluminum foam-phase change material (PCM) composites as heat sinks are investigated by experiments. Three types of open-cell aluminum 6061 foams with similar relative densities and different cell sizes are used. Paraffin is selected as the PCM due to its excellent thermal stability and ease of handling. The experimental results show that the performance of the heat sink is significantly affected by the surface area density of the aluminum foam. In general, as the surface area density of the foam increases, the performance of the heat sink is improved regardless of the current phase of the PCM.

  13. Suitability of silica hydride stationary phase, aqueous normal phase chromatography for untargeted metabolomic profiling of Enterococcus faecium and Staphylococcus aureus.

    PubMed

    Weisenberg, Scott A; Butterfield, Tiffany R; Fischer, Steven M; Rhee, Kyu Y

    2009-07-01

    We report the robustness of silica hydride stationary phase, aqueous normal phase (ANP) chromatography to the chemical complexity of the intracellular metabolomes of Staphylococcus aureus and Enterococcus faecium. We specifically demonstrate that the chromatographic behavior of known metabolites is unaffected by the intracellular chemical matrix of these microbes and that this method enables untargeted profiling of their intracellular metabolites using accurate mass-retention time (AMRT) identifiers. We further demonstrate the ability of AMRT-based metabolite profiling to differentiate bacteria along genetic and phenotypic lines. Overall, these data commend the utility of ANP-based chromatography for untargeted metabolomics-based studies of microbial physiology and antibiotic resistance.

  14. Profiling of polar metabolites in biological extracts using diamond hydride-based aqueous normal phase chromatography.

    PubMed

    Callahan, Damien L; De Souza, David; Bacic, Antony; Roessner, Ute

    2009-07-01

    Highly polar metabolites, such as sugars and most amino acids are not retained by conventional RP LC columns. Without sufficient retention low concentration compounds are not detected due ion suppression and structural isomers are not resolved. In contrast, hydrophilic interaction chromatography (HILIC) and aqueous normal phase chromatography (ANP) retain compounds based on their hydrophilicity and therefore provides a means of separating highly polar compounds. Here, an ANP method based on the diamond hydride stationary phase is presented for profiling biological small molecules by LC. A rapid separation system based upon a fast gradient that delivers reproducible chromatography is presented. Approximately 1000 compounds were reproducibly detected in human urine samples and clear differences between these samples were identified. This chromatography was also applied to xylem fluid from soyabean (Glycine max) plants to which 400 compounds were detected. This method greatly increases the metabolite coverage over RP-only metabolite profiling in biological samples. We show that both forms of chromatography are necessary for untargeted comprehensive metabolite profiling and that the diamond hydride stationary phase provides a good option for polar metabolite analysis.

  15. Etched succinate-functionalized silica hydride stationary phase for open-tubular CEC.

    PubMed

    Chen, Jian-Lian

    2009-11-01

    An open-tubular (OT) CEC column was designed to anchor ionizable succinate-functionalized ligands onto a silica hydride-based stationary phase through surface etching, silanization, and hydrosilation reactions beginning from a bare fused-silica tube. The modified columns that were produced in each step were monitored by analysis of the effect of performance of EOF on the changes of pH values, concentrations, and the amount of ACN added in the running buffers. By tracking the EOF patterns between columns, the author determined that the surface composition of the final product column was a combination of silanols, silica hydrides, and succinate ligands. Furthermore, lower loading volumes of the succinate ligands prepared for the hydrosilation reaction served to complete the mixed-mode OT-CEC columns, and subsequently to carry out the separation of six phenyl alcohols. Studies on the elution order of these alcohols identified the presence of chromatographic interactions in addition to electrophoresis. Based on the employment of a solvation parameter model, these interactions likely included dispersion interactions, dipole-type interactions, and interactions arising through the polarizable electrons in the solute. The optimum buffer conditions for CEC separations of phenyl alcohols, carbonyl-substituted phenols, and a mixture of nucleosides and thymine were a phosphate buffer (50 mM, pH 10.51), a borate buffer (50 mM, pH 8.62), and a borate buffer (50 mM, pH 9.50), respectively. Overall, the hydride-based stationary phases with ionizable ligands were successfully applied to the OT-CEC separations, and these results confidently propose an ideal route to the synthesis of novel OT-CEC columns.

  16. Verification and Validation Strategy for Implementation of Hybrid Potts-Phase Field Hydride Modeling Capability in MBM

    SciTech Connect

    Jason D. Hales; Veena Tikare

    2014-04-01

    The Used Fuel Disposition (UFD) program has initiated a project to develop a hydride formation modeling tool using a hybrid Potts­phase field approach. The Potts model is incorporated in the SPPARKS code from Sandia National Laboratories. The phase field model is provided through MARMOT from Idaho National Laboratory.

  17. Three-dimensional imaging of dislocation dynamics during the hydriding phase transformation

    DOE PAGES

    Ulvestad, A.; Welland, M. J.; Cha, W.; ...

    2017-01-16

    Crystallographic imperfections can significantly alter material properties and responses to external stimuli, including solute induced phase transformations and crystal growth and dissolution . Despite recent progress in imaging defects using both electron and x-ray techniques, in situ three-dimensional imaging studies of defect dynamics, necessary to understand and engineer nanoscale processes, remains challenging. Here, we report in situ three-dimensional imaging of defect dynamics during the hydriding phase transformation of individual palladium nanocrystals by Bragg Coherent Diffractive Imaging (BCDI) . During constant pressure experiments, we observed that the phase transformation begins after the nucleation of dislocations in large (300 nm) particles. Themore » 3D dislocation network shows that dislocations are close to the phase boundary. The 3D phase morphology resolved by BCDI suggests that the hydrogen-rich phase is more similar to a spherical cap on the hydrogen-poor phase than the core-shell model commonly assumed. We substantiate this conclusion using 3D phase field modeling and demonstrate how phase morphology affects the critical size for dislocation nucleation. We determine the size dependence of the transformation pressure for large (150-300 nm) palladium nanocrystals using variable pressure experiments. Our results reveal a pathway for solute induced structural phase transformations in nanocrystals and demonstrate BCDI as a novel method for understanding dislocation dynamics in phase transforming systems at the nanoscale.« less

  18. Metal hydride/chemical heat-pump development project. Phase I. Final report

    SciTech Connect

    Argabright, T.A.

    1982-02-01

    The metal hydride/chemical heat pump (MHHP) is a chemical heat pump containing two hydrides for the storage and/or recovery of thermal energy. It utilizes the heat of reaction of hydrogen with specific metal alloys. The MHHP design can be tailored to provide heating and/or cooling or temperature upgrading over a wide range of input and ambient temperatures. The system can thus be used with a variety of heat sources including waste heat, solar energy or a fossil fuel. The conceptual design of the MHHP was developed. A national market survey including a study of applications and market sectors was conducted. The technical tasks including conceptual development, thermal and mechanical design, laboratory verification of design and material performance, cost analysis and the detailed design of the Engineering Development Test Unit (EDTU) were performed. As a result of the market study, the temperature upgrade cycle of the MHHP was chosen for development. Operating temperature ranges for the upgrader were selected to be from 70 to 110/sup 0/C (160 to 230/sup 0/F) for the source heat and 140 to 190/sup 0/C (280 to 375/sup 0/F) for the product heat. These ranges are applicable to many processes in industries such as food, textile, paper and pulp, and chemical. The hydride pair well suited for these temperatures is LaNi/sub 5//LaNi/sub 4/ /sub 5/Al/sub 0/ /sub 5/. The EDTU was designed for the upgrade cycle. It is a compact finned tube arrangement enclosed in a pressure vessel. This design incorporates high heat transfer and low thermal mass in a system which maximizes the coefficient of performance (COP). It will be constructed in Phase II. Continuation of this effort is recommended.

  19. Shock phase transformation and release properties of aluminum nitride

    SciTech Connect

    Kipp, M.E.; Grady, D.E.

    1993-12-31

    Aluminum nitride is characterized by a non-recoverable volume phase transformation from the wurtzite (hexagonal) to the rocksalt (cubic) structure that commences about 22 GPa, accompanied by a volume strain of about 20%. A study of the manifestation of this large volume change under shock loading was made with four uniaxial strain impact experiments. Particle velocity histories of the shock and release states were obtained corresponding to impact pressures of 40 GPa, including the evolution of the shock and release waves with propagation distance. Stress-strain features characterizing aluminum nitride, including the phase transformation, were determined with numerical analysis techniques.

  20. Lattice dynamics and phase diagram of aluminum at high temperatures

    SciTech Connect

    Kudasov, Yu. B. Surdin, O. M.; Korshunov, A. S.; Pavlov, V. N.; Frolova, N. V.; Kuzin, R. S.

    2013-10-15

    The dispersion of phonons in the fcc, hcp, and bcc phases of aluminum is calculated at ultrahigh pressures by the method of small displacements in a supercell. The stability of the phonon subsystem is studied. The thermodynamic characteristics are calculated in the quasi-harmonic approximation, and a phase diagram of aluminum is plotted. As compared to the Debye model, the use of a phonon spectrum calculated in the quasi-harmonic approximation significantly broadens the hcp phase field and strongly shifts the phase boundary between the fcc and bcc phases. The normal isentrope is calculated at megabar pressures. It is shown to intersect the fcc-hcp and hcp-bcc phase boundaries. The sound velocity along the normal isentrope is calculated. It is shown to have a nonmonotonic character.

  1. Lattice dynamics and phase diagram of aluminum at high temperatures

    NASA Astrophysics Data System (ADS)

    Kudasov, Yu. B.; Surdin, O. M.; Korshunov, A. S.; Pavlov, V. N.; Frolova, N. V.; Kuzin, R. S.

    2013-10-01

    The dispersion of phonons in the fcc, hcp, and bcc phases of aluminum is calculated at ultrahigh pressures by the method of small displacements in a supercell. The stability of the phonon subsystem is studied. The thermodynamic characteristics are calculated in the quasi-harmonic approximation, and a phase diagram of aluminum is plotted. As compared to the Debye model, the use of a phonon spectrum calculated in the quasi-harmonic approximation significantly broadens the hcp phase field and strongly shifts the phase boundary between the fcc and bcc phases. The normal isentrope is calculated at megabar pressures. It is shown to intersect the fcc-hcp and hcp-bcc phase boundaries. The sound velocity along the normal isentrope is calculated. It is shown to have a nonmonotonic character.

  2. First-Principles Studies of Phase Stability and Reaction Dynamics in Complex Metal Hydrides

    NASA Astrophysics Data System (ADS)

    Chou, Mei-Yin

    2009-03-01

    Complex metal hydrides are believed to be one of the promising materials for developing hydrogen storage systems that can operate under desirable conditions. At the same time, these are also a class of materials that exhibit intriguing properties. We have applied state-of-the-art computational techniques to study the structural, dynamic, and electronic properties of these materials. This talk will focus on the critical role played by the Ti catalyst in helping hydrogen cycling in the alanates, which remains a challenging topic for this hydrogen storage material. We have performed a series of calculations to address the hydrogen interaction on the aluminum surface in the presence of the Ti ``dopant,'' focusing on the effect of near-surface alloying on the Al(100) surface. It is found that Ti occupies subsurface sites near the Al surface. This subsurface Ti arrangement not only enhances H binding with the Al surface layer, but also improves H mobility on the surface. Based on existing experimental data and our preliminary results, we propose a model in which the catalyst does not enter the bulk, but facilitates hydrogen dissociation-recombination near the surface. In the dehydrogenation cycle, the catalyst kinetically facilitates the release and decomposition of AlH3 from the solid-state alanate. In the hydrogenation cycle, the catalyst helps the adsorption of hydrogen and the formation of AlH3 oligomers on Al surfaces. The implication of Ti as a catalyst for the hydrogenation reactions will be discussed.

  3. Uncovering the intrinsic size dependence of hydriding phase transformations in nanocrystals

    NASA Astrophysics Data System (ADS)

    Bardhan, Rizia; Hedges, Lester O.; Pint, Cary L.; Javey, Ali; Whitelam, Stephen; Urban, Jeffrey J.

    2013-10-01

    A quantitative understanding of nanocrystal phase transformations would enable more efficient energy conversion and catalysis, but has been hindered by difficulties in directly monitoring well-characterized nanoscale systems in reactive environments. We present a new in situ luminescence-based probe enabling direct quantification of nanocrystal phase transformations, applied here to the hydriding transformation of palladium nanocrystals. Our approach reveals the intrinsic kinetics and thermodynamics of nanocrystal phase transformations, eliminating complications of substrate strain, ligand effects and external signal transducers. Clear size-dependent trends emerge in nanocrystals long accepted to be bulk-like in behaviour. Statistical mechanical simulations show these trends to be a consequence of nanoconfinement of a thermally driven, first-order phase transition: near the phase boundary, critical nuclei of the new phase are comparable in size to the nanocrystal itself. Transformation rates are then unavoidably governed by nanocrystal dimensions. Our results provide a general framework for understanding how nanoconfinement fundamentally impacts broad classes of thermally driven solid-state phase transformations relevant to hydrogen storage, catalysis, batteries and fuel cells.

  4. Avalanching strain dynamics during the hydriding phase transformation in individual palladium nanoparticles

    DOE PAGES

    Ulvestad, A.; Welland, M. J.; Collins, S. S. E.; ...

    2015-12-11

    Phase transitions in reactive environments are crucially important in energy and information storage, catalysis and sensors. Nanostructuring active particles can yield faster charging/ discharging kinetics, increased lifespan and record catalytic activities. However, establishing the causal link between structure and function is challenging for nanoparticles, as ensemble measurements convolve intrinsic single-particle properties with sample diversity. Here we study the hydriding phase transformation in individual palladium nanocubes in situ using coherent X-ray diffractive imaging. The phase transformation dynamics, which involve the nucleation and propagation of a hydrogen-rich region, are dependent on absolute time (aging) and involve intermittent dynamics (avalanching). A hydrogen-rich surfacemore » layer dominates the crystal strain in the hydrogen-poor phase, while strain inversion occurs at the cube corners in the hydrogen-rich phase. A three-dimensional phase-field model is used to interpret the experimental results. In conclusion, our experimental and theoretical approach provides a general framework for designing and optimizing phase transformations for single nanocrystals in reactive environments.« less

  5. Avalanching strain dynamics during the hydriding phase transformation in individual palladium nanoparticles

    SciTech Connect

    Ulvestad, A.; Welland, M. J.; Collins, S. S. E.; Harder, R.; Maxey, E.; Wingert, J.; Singer, A.; Hy, S.; Mulvaney, P.; Zapol, P.; Shpyrko, O. G.

    2015-12-11

    Phase transitions in reactive environments are crucially important in energy and information storage, catalysis and sensors. Nanostructuring active particles can yield faster charging/ discharging kinetics, increased lifespan and record catalytic activities. However, establishing the causal link between structure and function is challenging for nanoparticles, as ensemble measurements convolve intrinsic single-particle properties with sample diversity. Here we study the hydriding phase transformation in individual palladium nanocubes in situ using coherent X-ray diffractive imaging. The phase transformation dynamics, which involve the nucleation and propagation of a hydrogen-rich region, are dependent on absolute time (aging) and involve intermittent dynamics (avalanching). A hydrogen-rich surface layer dominates the crystal strain in the hydrogen-poor phase, while strain inversion occurs at the cube corners in the hydrogen-rich phase. A three-dimensional phase-field model is used to interpret the experimental results. In conclusion, our experimental and theoretical approach provides a general framework for designing and optimizing phase transformations for single nanocrystals in reactive environments.

  6. Avalanching strain dynamics during the hydriding phase transformation in individual palladium nanoparticles

    PubMed Central

    Ulvestad, A.; Welland, M. J.; Collins, S. S. E.; Harder, R.; Maxey, E.; Wingert, J.; Singer, A.; Hy, S.; Mulvaney, P.; Zapol, P.; Shpyrko, O. G.

    2015-01-01

    Phase transitions in reactive environments are crucially important in energy and information storage, catalysis and sensors. Nanostructuring active particles can yield faster charging/discharging kinetics, increased lifespan and record catalytic activities. However, establishing the causal link between structure and function is challenging for nanoparticles, as ensemble measurements convolve intrinsic single-particle properties with sample diversity. Here we study the hydriding phase transformation in individual palladium nanocubes in situ using coherent X-ray diffractive imaging. The phase transformation dynamics, which involve the nucleation and propagation of a hydrogen-rich region, are dependent on absolute time (aging) and involve intermittent dynamics (avalanching). A hydrogen-rich surface layer dominates the crystal strain in the hydrogen-poor phase, while strain inversion occurs at the cube corners in the hydrogen-rich phase. A three-dimensional phase-field model is used to interpret the experimental results. Our experimental and theoretical approach provides a general framework for designing and optimizing phase transformations for single nanocrystals in reactive environments. PMID:26655832

  7. Avalanching strain dynamics during the hydriding phase transformation in individual palladium nanoparticles

    NASA Astrophysics Data System (ADS)

    Ulvestad, A.; Welland, M. J.; Collins, S. S. E.; Harder, R.; Maxey, E.; Wingert, J.; Singer, A.; Hy, S.; Mulvaney, P.; Zapol, P.; Shpyrko, O. G.

    2015-12-01

    Phase transitions in reactive environments are crucially important in energy and information storage, catalysis and sensors. Nanostructuring active particles can yield faster charging/discharging kinetics, increased lifespan and record catalytic activities. However, establishing the causal link between structure and function is challenging for nanoparticles, as ensemble measurements convolve intrinsic single-particle properties with sample diversity. Here we study the hydriding phase transformation in individual palladium nanocubes in situ using coherent X-ray diffractive imaging. The phase transformation dynamics, which involve the nucleation and propagation of a hydrogen-rich region, are dependent on absolute time (aging) and involve intermittent dynamics (avalanching). A hydrogen-rich surface layer dominates the crystal strain in the hydrogen-poor phase, while strain inversion occurs at the cube corners in the hydrogen-rich phase. A three-dimensional phase-field model is used to interpret the experimental results. Our experimental and theoretical approach provides a general framework for designing and optimizing phase transformations for single nanocrystals in reactive environments.

  8. Avalanching strain dynamics during the hydriding phase transformation in individual palladium nanoparticles.

    PubMed

    Ulvestad, A; Welland, M J; Collins, S S E; Harder, R; Maxey, E; Wingert, J; Singer, A; Hy, S; Mulvaney, P; Zapol, P; Shpyrko, O G

    2015-12-11

    Phase transitions in reactive environments are crucially important in energy and information storage, catalysis and sensors. Nanostructuring active particles can yield faster charging/discharging kinetics, increased lifespan and record catalytic activities. However, establishing the causal link between structure and function is challenging for nanoparticles, as ensemble measurements convolve intrinsic single-particle properties with sample diversity. Here we study the hydriding phase transformation in individual palladium nanocubes in situ using coherent X-ray diffractive imaging. The phase transformation dynamics, which involve the nucleation and propagation of a hydrogen-rich region, are dependent on absolute time (aging) and involve intermittent dynamics (avalanching). A hydrogen-rich surface layer dominates the crystal strain in the hydrogen-poor phase, while strain inversion occurs at the cube corners in the hydrogen-rich phase. A three-dimensional phase-field model is used to interpret the experimental results. Our experimental and theoretical approach provides a general framework for designing and optimizing phase transformations for single nanocrystals in reactive environments.

  9. Avalanching strain dynamics during the hydriding phase transformation in individual palladium nanoparticles

    DOE PAGES

    Ulvestad, A.; Welland, M. J.; Collins, S. S. E.; ...

    2015-12-11

    Phase transitions in reactive environments are crucially important in energy and information storage, catalysis and sensors. Nanostructuring active particles can yield faster charging/ discharging kinetics, increased lifespan and record catalytic activities. However, establishing the causal link between structure and function is challenging for nanoparticles, as ensemble measurements convolve intrinsic single-particle properties with sample diversity. Here we study the hydriding phase transformation in individual palladium nanocubes in situ using coherent X-ray diffractive imaging. The phase transformation dynamics, which involve the nucleation and propagation of a hydrogen-rich region, are dependent on absolute time (aging) and involve intermittent dynamics (avalanching). A hydrogen-rich surfacemore » layer dominates the crystal strain in the hydrogen-poor phase, while strain inversion occurs at the cube corners in the hydrogen-rich phase. A three-dimensional phase-field model is used to interpret the experimental results. In conclusion, our experimental and theoretical approach provides a general framework for designing and optimizing phase transformations for single nanocrystals in reactive environments.« less

  10. Avalanching strain dynamics during the hydriding phase transformation in individual palladium nanoparticles

    SciTech Connect

    Ulvestad, A.; Welland, M. J.; Collins, S. S. E.; Harder, R.; Maxey, E.; Wingert, J.; Singer, A.; Hy, S.; Mulvaney, P.; Zapol, P.; Shpyrko, O. G.

    2015-12-11

    Phase transitions in reactive environments are crucially important in energy and information storage, catalysis and sensors. Nanostructuring active particles can yield faster charging/ discharging kinetics, increased lifespan and record catalytic activities. However, establishing the causal link between structure and function is challenging for nanoparticles, as ensemble measurements convolve intrinsic single-particle properties with sample diversity. Here we study the hydriding phase transformation in individual palladium nanocubes in situ using coherent X-ray diffractive imaging. The phase transformation dynamics, which involve the nucleation and propagation of a hydrogen-rich region, are dependent on absolute time (aging) and involve intermittent dynamics (avalanching). A hydrogen-rich surface layer dominates the crystal strain in the hydrogen-poor phase, while strain inversion occurs at the cube corners in the hydrogen-rich phase. A three-dimensional phase-field model is used to interpret the experimental results. In conclusion, our experimental and theoretical approach provides a general framework for designing and optimizing phase transformations for single nanocrystals in reactive environments.

  11. Uncovering the intrinsic size dependence of hydriding phase transformations in nanocrystals.

    PubMed

    Bardhan, Rizia; Hedges, Lester O; Pint, Cary L; Javey, Ali; Whitelam, Stephen; Urban, Jeffrey J

    2013-10-01

    A quantitative understanding of nanocrystal phase transformations would enable more efficient energy conversion and catalysis, but has been hindered by difficulties in directly monitoring well-characterized nanoscale systems in reactive environments. We present a new in situ luminescence-based probe enabling direct quantification of nanocrystal phase transformations, applied here to the hydriding transformation of palladium nanocrystals. Our approach reveals the intrinsic kinetics and thermodynamics of nanocrystal phase transformations, eliminating complications of substrate strain, ligand effects and external signal transducers. Clear size-dependent trends emerge in nanocrystals long accepted to be bulk-like in behaviour. Statistical mechanical simulations show these trends to be a consequence of nanoconfinement of a thermally driven, first-order phase transition: near the phase boundary, critical nuclei of the new phase are comparable in size to the nanocrystal itself. Transformation rates are then unavoidably governed by nanocrystal dimensions. Our results provide a general framework for understanding how nanoconfinement fundamentally impacts broad classes of thermally driven solid-state phase transformations relevant to hydrogen storage, catalysis, batteries and fuel cells.

  12. CRADA (AL-C-2009-02) Final Report: Phase I. Lanthanum-based Start Materials for Hydride Batteries

    SciTech Connect

    Gschneidner, Jr., Karl; Schmidt, Frederick; Frerichs, A. E.; Ament, Katherine A.

    2013-05-01

    The purpose of Phase I of this work is to focus on developing a La-based start material for making nickel-metal (lanthanum)-hydride batteries based on our carbothermic-silicon process. The goal is to develop a protocol for the manufacture of (La{sub 1-x}R{sub x})(Ni{sub 1-y}M{sub y})(Si{sub z}), where R is a rare earth metal and M is a non-rare earth metal, to be utilized as the negative electrode in nickel-metal hydride (NiMH) rechargeable batteries.

  13. Ab initio study of H and He migrations in β-phase Sc, Y, and Er hydrides

    SciTech Connect

    Chen, Ru-Cheng; Yang, Li; Dai, Yunya; Zhu, Zi Qiang; Peng, SM; Long, XG; Gao, Fei; Zu, Xiaotao

    2012-05-01

    Ab initio calculations based on the density functional theory have been performed to investigate the migrations of hydrogen (H) and helium (He) atoms in {beta}-phase scandium (Sc), yttrium (Y), and erbium (Er) hydrides with three different ratios of H to metal. The results show that the migration mechanisms of H and He atoms mainly depend on the crystal structures of hydrides, but their energy barriers are affected by the host-lattice in metal hydrides. The formation energies of octahedral-occupancy H (H{sub oct}) and tetrahedral vacancy (V{sub tet}) pairs are almost the same (about 1.2 eV). It is of interest to note that the migration barriers of H increase with increasing host-lattice atomic number. In addition, the results show that the favorable migration mechanism of He depends slightly on the V{sub tet} in the Sc hydride, but strongly on that in the Y and Er hydrides, which may account for different behaviours of initial He release from ScT{sub 2} and ErT{sub 2}.

  14. Loss of benzaldehyde in the fragmentation of protonated benzoylamines: Benzoyl cation as a hydride acceptor in the gas phase.

    PubMed

    Chai, Yunfeng; Shao, Yunlong; Wang, Lu; Wang, Lin

    2017-07-14

    In electrospray ionization tandem mass spectrometry of protonated 1-benzoylamines (1-benzoylpiperadine, 1-benzoylmorpholine, and 1-benzoyl-4-methylpiperazine), the dominant fragmentation pathway was amide bond cleavage to form benzoyl cation and neutral amine. Meanwhile, in their fragmentations, an interesting loss of benzaldehyde (106 Da) was observed and identified to derive from hydride transfer reaction between the benzoyl cation and amine. A stepwise mechanism for loss of 106 Da (benzene and CO) could be excluded with the aid of deuterium labeling experiment. Theoretical calculations indicated that hydride transfers from amines (piperadine, morpholine and 1-methylpiperazine) to benzoyl cation were thermodynamically permitted and 1-methylpiperazine was the best hydride donor among the three amines. The mass spectrometric experimental results were consistent with the computational results. The relative abundance of the iminium cation (relative to the benzoyl cation) in the fragmentation of protonated 1-benzoyl-4-methylpiperazine was higher than that in the fragmentation of the other two protonated 1-benzoylamines. By comparing the fragmentations of protonated 1-benzyl-4-methylpiperazine and protonated 1-benzoyl-4-methylpiperazine and the energetics of their hydride transfer reactions, this study revealed that benzoyl cation was a hydride acceptor in the gas phase, but which was weaker than benzyl cation. This article is protected by copyright. All rights reserved.

  15. Aluminum Hydride Propellant Shelflife

    DTIC Science & Technology

    1974-11-01

    PODE propellants, namely a model PCDE propellant processed at LPC using di-n-butylphthalate -: a chemically inert plasticizer, and a ballistically...prepolymer. The propellant processed at LPC used PCDE prepared by the Shell Development Company, while the Aerojet propellant was processed with PCDE...failures after 180 days storage at 40 and 60 0 C, nor was there any noticeable deformation of the elliptical tubes to suggest internal gas pressure

  16. Separation Differences Among Phenyl Hydride, UDC Cholesterol and Bidentate C8 Stationary Phases for Stability Indicating Methods of Tetracyclines

    PubMed Central

    Young, Joshua E.; Matyska, Maria T.; Azad, Anil K.; Yoc, Sergio E.; Pesek, Joseph J.

    2014-01-01

    Formulation extracts of tetracycline hydrochloride (HCl), minocycline hydrochloride (HCl), and doxycycline hyclate were degraded by strong acidic conditions and heating. Subsequently, components of the extracts were separated by Bidentate C8, Phenyl Hydride and Cholesterol (UDC) HPLC columns operating in the reverse phase mode. The Phenyl Hydride column was able to baseline separate minocycline from the observed degradant, while partial or total co-elution was observed with the other two columns using otherwise identical method conditions. For both the degraded tetracycline HCl and doxycycline hyclate extracts, the UDC column gave the best resolution for the critical pair. The findings suggest that the postulated secondary retention mechanisms of π–π interactions from the Phenyl Hydride and shape selectivity from the UDC can provide superior resolution for structurally similar analytes compared to hydrophobic interactions alone. PMID:24748763

  17. Simultaneous separation of hydrophobic and polar bases using a silica hydride stationary phase.

    PubMed

    Yang, Yuanzhong; Matyska, Maria T; Boysen, Reinhard I; Pesek, Joseph J; Hearn, Milton T W

    2013-04-01

    In this study, the retention behavior of selected hydrophobic and polar bases on a minimally modified silica hydride phase was investigated. From these results and the associated retention plots, significant differences in the chromatographic dependencies of these two classes of basic compounds were evident. The polar bases exhibited strong retention with mobile phases of high organic solvent content, but displayed weak retention with mobile phases of high water content. In contrast, the hydrophobic bases showed "U-shape" retention dependencies, indicative of the interplay of both RP and normal-phase retention characteristics. These studies have demonstrated that hydrophobic and polar bases can be simultaneously separated on the same column either under typical RP-like or aqueous normal-phase-like conditions, respectively, with distinctive selectivity. Finally, the effects of temperature on the RP and aqueous normal phase modality of separations with these analytes were investigated, where discrete changes in retention behavior were also observed. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Nonpolar GaN grown on Si by hydride vapor phase epitaxy using anodized Al nanomask

    NASA Astrophysics Data System (ADS)

    Polyakov, A. Y.; Markov, A. V.; Mezhennyi, M. V.; Govorkov, A. V.; Pavlov, V. F.; Smirnov, N. B.; Donskov, A. A.; D'yakonov, L. I.; Kozlova, Y. P.; Malakhov, S. S.; Yugova, T. G.; Osinsky, V. I.; Gorokh, G. G.; Lyahova, N. N.; Mityukhlyaev, V. B.; Pearton, S. J.

    2009-01-01

    GaN growth by the hydride vapor phase technique on (100) Si substrates masked by porous Al anodic oxide is described. The masks were prepared by vacuum deposition of Al with subsequent anodic oxidation in dilute sorrel acid. The grown GaN layer is nonpolar, with (112¯0) a-orientation and a full width at half maximum of the (112¯0) reflection below 500 arc sec and showing small anisotropy. This result is comparable with the results obtained for a-GaN growth using selective epitaxy or advanced buffer growth routines. Microcathodoluminescence spectra of the grown films confirm a low density of stacking faults. Possible growth mechanisms are discussed.

  19. Phases in lanthanum-nickel-aluminum alloys. Part 2

    SciTech Connect

    Mosley, W.C.

    1992-08-01

    Lanthanum-nickel-aluminum (LANA) alloys will be used to pump, store and separate hydrogen isotopes in the Replacement Tritium Facility (RTF). The aluminum content (y) of the primary LaNi{sub 5}-phase is controlled to produce the desired pressure-temperature behavior for adsorption and desorption of hydrogen. However, secondary phases cause decreased capacity and some may cause undesirable retention of tritium. Twenty-three alloys purchased from Ergenics, Inc. for development of RTF processes have been characterized by scanning electron microscopy (SEM) and by electron microprobe analysis (EMPA) to determine the distributions and compositions of constituent phases. This memorandum reports the results of these characterization studies. Knowledge of the structural characteristics of these alloys is a useful first step in selecting materials for specific process development tests and in interpreting results of those tests. Once this information is coupled with data on hydrogen plateau pressures, retention and capacity, secondary phase limits for RTF alloys can be specified.

  20. Solute hydrogen and hydride phase implications on the plasticity of zirconium and titanium alloys: a review and some recent advances

    NASA Astrophysics Data System (ADS)

    Conforto, E.; Guillot, I.; Feaugas, X.

    2017-06-01

    In this contribution, we propose a review of the possible implications of hydrogen on mechanical behaviour of Zr and Ti alloys with emphasis on the mechanisms of plasticity and strain hardening. Recent advances on the impact of oxygen and hydrogen on the activation volume show that oxygen content hinders creep but hydrogen partially screens this effect. Both aspects are discussed in terms of a locking-unlocking model of the screw dislocation mobility in prismatic slip. Additionally, possible extension of this behaviour is suggested for the slip. The low hydrogen solubility in both Zr and Ti leads in many cases to hydride precipitation. The nature of these phases depends on the hydrogen content and can show crystallographic orientation relationships with the hexagonal compact structure of the alloys. Some advances on the thermal stability of these phases are illustrated and discussed in relation with the deepening of the misfit dislocations. Under tensile loading, we showed that hydrides enhance the hardening process in relation with internal stress due to strain incompatibilities between the Zr and Ti matrix and hydride phases. Different plastic yielding processes of hydrides were identified, which progressively reduce these strain incompatibilities. This article is part of the themed issue 'The challenges of hydrogen and metals'.

  1. Synthesis of ruthenium hydride

    NASA Astrophysics Data System (ADS)

    Kuzovnikov, M. A.; Tkacz, M.

    2016-02-01

    Ruthenium hydride was synthesized at a hydrogen pressure of about 14 GPa in a diamond-anvil cell. Energy-dispersive x-ray diffraction was used to monitor the ruthenium crystal structure as a function of hydrogen pressure up to 30 GPa. The hydride formation was accompanied by phase transition from the original hcp structure of the pristine metal to the fcc structure. Our results confirmed the theoretical prediction of ruthenium hydride formation under hydrogen pressure. The standard Gibbs free energy of the ruthenium hydride formation reaction was calculated assuming the pressure of decomposition as the equilibrium pressure.

  2. Self-catalyzed GaAs nanowires on silicon by hydride vapor phase epitaxy.

    PubMed

    Dong, Zhenning; André, Yamina; Dubrovskii, Vladimir G; Bougerol, Catherine; Leroux, Christine; Ramdani, Mohammed R; Monier, Guillaume; Trassoudaine, Agnès; Castelluci, Dominique; Gil, Evelyne

    2017-03-24

    Gold-free GaAs nanowires on silicon substrates can pave the way for monolithic integration of photonic nanodevices with silicon electronic platforms. It is extensively documented that the self-catalyzed approach works well in molecular beam epitaxy but is much more difficult to implement in vapor phase epitaxies. Here, we report the first gallium-catalyzed hydride vapor phase epitaxy growth of long (more than 10 μm) GaAs nanowires on Si(111) substrates with a high integrated growth rate up to 60 μm h(-1) and pure zincblende crystal structure. The growth is achieved by combining a low temperature of 600 °C with high gaseous GaCl/As flow ratios to enable dechlorination and formation of gallium droplets. GaAs nanowires exhibit an interesting bottle-like shape with strongly tapered bases, followed by straight tops with radii as small as 5 nm. We present a model that explains the peculiar growth mechanism in which the gallium droplets nucleate and rapidly swell on the silicon surface but then are gradually consumed to reach a stationary size. Our results unravel the necessary conditions for obtaining gallium-catalyzed GaAs nanowires by vapor phase epitaxy techniques.

  3. Self-catalyzed GaAs nanowires on silicon by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Dong, Zhenning; André, Yamina; Dubrovskii, Vladimir G.; Bougerol, Catherine; Leroux, Christine; Ramdani, Mohammed R.; Monier, Guillaume; Trassoudaine, Agnès; Castelluci, Dominique; Gil, Evelyne

    2017-03-01

    Gold-free GaAs nanowires on silicon substrates can pave the way for monolithic integration of photonic nanodevices with silicon electronic platforms. It is extensively documented that the self-catalyzed approach works well in molecular beam epitaxy but is much more difficult to implement in vapor phase epitaxies. Here, we report the first gallium-catalyzed hydride vapor phase epitaxy growth of long (more than 10 μm) GaAs nanowires on Si(111) substrates with a high integrated growth rate up to 60 μm h‑1 and pure zincblende crystal structure. The growth is achieved by combining a low temperature of 600 °C with high gaseous GaCl/As flow ratios to enable dechlorination and formation of gallium droplets. GaAs nanowires exhibit an interesting bottle-like shape with strongly tapered bases, followed by straight tops with radii as small as 5 nm. We present a model that explains the peculiar growth mechanism in which the gallium droplets nucleate and rapidly swell on the silicon surface but then are gradually consumed to reach a stationary size. Our results unravel the necessary conditions for obtaining gallium-catalyzed GaAs nanowires by vapor phase epitaxy techniques.

  4. Hysteresis in Metal Hydrides.

    ERIC Educational Resources Information Center

    Flanagan, Ted B., And Others

    1987-01-01

    This paper describes a reproducible process where the irreversibility can be readily evaluated and provides a thermodynamic description of the important phenomenon of hysteresis. A metal hydride is used because hysteresis is observed during the formation and decomposition of the hydride phase. (RH)

  5. Hysteresis in Metal Hydrides.

    ERIC Educational Resources Information Center

    Flanagan, Ted B., And Others

    1987-01-01

    This paper describes a reproducible process where the irreversibility can be readily evaluated and provides a thermodynamic description of the important phenomenon of hysteresis. A metal hydride is used because hysteresis is observed during the formation and decomposition of the hydride phase. (RH)

  6. Metastable phases in mechanically alloyed aluminum germanium powders

    SciTech Connect

    Yvon, P.J.; Schwarz, R.B.

    1993-03-01

    Aluminum and germanium form a simple eutectic system with no stable intermetallic phase, and limited mutual solubility. We report the formation of a metastable rhombohedral,{gamma}{sub 1} phase by mechanically alloying aluminum and germanium powders. This phase, which appears for compositions between 20 and 50 at. % germanium, has also been observed in rapidly quenched alloys, but there is disagreement as to its composition. By measuring the heat of crystallization as a function of composition, we determined the composition of the {gamma}{sub 1} phase to be Al{sub 70}Ge{sub 30}. We also produced Al{sub 70}Ge{sub 30} by arc melting the pure elements, followed by splat-quenching at a cooling rate in the range of 10{sup 8} K s{sup {minus}1}. This method produced two metastable phases, one of which was found to be the {gamma}{sub 1} phase obtained by mechanical alloying. The other was a monoclinic phase reported earlier in the literature as {gamma}{sub 2}.

  7. Succinyl methacrylate polymerized in porous-layered phases for open-tubular capillary electrochromatography: comparison with silica hydride monolayered phases.

    PubMed

    Chen, Jian-Lian; Lin, Yi-Chen

    2010-06-25

    A polymer phase, which was constructed with butyl methacrylate (BMA), an ionizable monomer (mono-(2-(methacryloyloxy)ethyl) succinate (MES)), and a crosslinking agent (ethylene dimethacrylate), was first formed in a porous-layered open-tubular (PLOT) capillary. The PLOT capillary was characterized with SEM and electrophoretic flow as the pH level, ionic strength and addition of organic modifiers in the running buffers changed. In addition, a bare capillary and a silica hydride based capillary (SiH-MES), which bore a monolayered MES phase on it, were used to compared with the BMA-MES capillary. Besides optimizing the capillary electrochromatographic (CEC) conditions for each group of analytes, which were a mixture of nucleosides and thymine, flavonoids, and phenolic acids,comparison of the separation selectivity among analytes between the BMA-MES and SiH-MES capillaries was done according to the velocity and retention factors obtained from the CEC data. Overall, the polymeric phase formed in the PLOT mode was capable of preventing blockage of the columns and was superior to the monolayered phase bonding with the same ionizable ligands for application in CEC as well as to the bare silica phase in CE. Copyright 2010 Elsevier B.V. All rights reserved.

  8. Silica, Hybrid Silica, Hydride Silica and Non-Silica Stationary Phases for Liquid Chromatography. Part II: Chemical and Thermal Stability.

    PubMed

    Borges, Endler M; Volmer, Dietrich A

    2015-08-01

    In the first part of this review, stationary phases (silica, hybrid silica, hydride silica and non-silica stationary phases) were characterized and compared with respect to selectivity, efficiency, resolution, solvent consumption and analysis time. The present review focuses on the thermal and chemical stability of stationary phases. Stationary phases of high chemical and thermal stability are required for separations that are carried over a wide pH and/or temperature range. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  9. A Kinetic Model for GaAs Growth by Hydride Vapor Phase Epitaxy

    SciTech Connect

    Schulte, Kevin L.; Simon, John; Jain, Nikhil; Young, David L.; Ptak, Aaron J.

    2016-11-21

    Precise control of the growth of III-V materials by hydride vapor phase epitaxy (HVPE) is complicated by the fact that the growth rate depends on the concentrations of nearly all inputs to the reactor and also the reaction temperature. This behavior is in contrast to metalorganic vapor phase epitaxy (MOVPE), which in common practice operates in a mass transport limited regime where growth rate and alloy composition are controlled almost exclusively by flow of the Group III precursor. In HVPE, the growth rate and alloy compositions are very sensitive to temperature and reactant concentrations, which are strong functions of the reactor geometry. HVPE growth, particularly the growth of large area materials and devices, will benefit from the development of a growth model that can eventually be coupled with a computational fluid dynamics (CFD) model of a specific reactor geometry. In this work, we develop a growth rate law using a Langmuir-Hinshelwood (L-H) analysis, fitting unknown parameters to growth rate data from the literature that captures the relevant kinetic and thermodynamic phenomena of the HVPE process. We compare the L-H rate law to growth rate data from our custom HVPE reactor, and develop quantitative insight into reactor performance, demonstrating the utility of the growth model.

  10. Simultaneous separation of hydrophobic and hydrophilic peptides with a silica hydride stationary phase using aqueous normal phase conditions.

    PubMed

    Boysen, Reinhard I; Yang, Yuanzhong; Chowdhury, Jamil; Matyska, Maria T; Pesek, Joseph J; Hearn, Milton T W

    2011-11-04

    The application of a silica hydride modified stationary phase with low organic loading has been investigated as a new type of chromatographic material suitable for the separation and analysis of peptides with electrospray ionization mass spectrometric detection. Retention maps were established to delineate the chromatographic characteristics of a series of peptides with physical properties ranging from strongly hydrophobic to very hydrophilic and encompassing a broad range of pI values (pI 5.5-9.4). The effects of low concentrations of two additives (formic acid and acetic acid) in the mobile phase were also investigated with respect to their contribution to separation selectivity and retention under comparable conditions. Significantly, strong retention of both the hydrophobic and the hydrophilic peptides was observed when high-organic low-aqueous mobile phases were employed, thus providing a new avenue to achieve high resolution peptide separations. For example, simultaneous separation of hydrophobic and hydrophilic peptides was achieved under aqueous normal phase (ANP) chromatographic conditions with linear gradient elution procedures in a single run, whilst further gradient optimization enabled improved peak efficiencies of the more strongly retained hydrophobic and hydrophilic peptides. Copyright © 2011 Elsevier B.V. All rights reserved.

  11. Determination of arsenic and selenium by hydride generation and headspace solid phase microextraction coupled with optical emission spectrometry

    NASA Astrophysics Data System (ADS)

    Tyburska, Anna; Jankowski, Krzysztof; Rodzik, Agnieszka

    2011-07-01

    A hydride generation headspace solid phase microextraction technique has been developed in combination with optical emission spectrometry for determination of total arsenic and selenium. Hydrides were generated in a 10 mL volume septum-sealed vial and subsequently collected onto a polydimethylsiloxane/Carboxen solid phase microextraction fiber from the headspace of sample solution. After completion of the sorption, the fiber was transferred into a thermal desorption unit and the analytes were vaporized and directly introduced into argon inductively coupled plasma or helium microwave induced plasma radiation source. Experimental conditions of hydride formation reaction as well as sorption and desorption of analytes have been optimized showing the significant effect of the type of the solid phase microextraction fiber coating, the sorption time and hydrochloric acid concentration of the sample solution on analytical characteristics of the method developed. The limits of detection of arsenic and selenium were 0.1 and 0.8 ng mL - 1 , respectively. The limit of detection of selenium could be improved further using biosorption with baker's yeast Saccharomyces cerevisiae for analyte preconcentration. The technique was applied for the determination of total As and Se in real samples.

  12. Investigations into the separation behaviour of perfluorinated C8 and undecanoic acid modified silica hydride stationary phases.

    PubMed

    Kulsing, Chadin; Yang, Yuanzhong; Sepehrifar, Roshanak; Lim, Michael; Toppete, Joshua; Matyska, Maria T; Pesek, Joseph J; Boysen, Reinhard I; Hearn, Milton T W

    2016-04-15

    In this study, the surface charge properties of perfluorinated C8 (PerfluoroC8) and undecanoic acid (UDA) modified silica hydride stationary phases have been investigated. The zeta potential values of these stationary phases were measured in aqueous/acetonitrile mobile phases of different pH, buffer concentrations and acetonitrile contents. The retention behaviour of several basic, acidic and neutral compounds were then examined with these two stationary phases, with U-shaped retention dependencies evident with regard to the organic solvent content of the mobile phase. Plots of the logarithmic retention factor versus buffer concentration revealed slopes ≥ -0.41 for both stationary phases, indicating the involvement of mixed mode retention mechanisms with contributions from both ionic and non-ionic interactions. Using a linear solvation energy relationship approach, the origins of these interactions under different mobile phase conditions were differentiated and quantified. The PerfluoroC8 stationary phase exhibited stronger retention for basic compounds under high acetonitrile content mobile phase conditions, whilst stronger retention was observed for all compounds with the UDA stationary phase under high aqueous content mobile phase conditions. The more negative zeta potentials of the UDA stationary phase correlated with higher total charge density, surface charge density and charge density at the beta plane (the outer plane of the double layer) compared to the PerfluoroC8 stationary phase. With mobile phases of low buffer concentrations, more negative zeta potential values were unexpectedly observed for the PerfluoroC8 stationary phase with slight increases in the C descriptor value, reflecting also the greater accessibility of the analytes to the stationary phase surface. Comparison of the retention behaviours on these phases with other types of silica hydride stationary phases has revealed different patterns of selectivity. Copyright © 2016 Elsevier B

  13. Hydride vapor phase GaN films with reduced density of residual electrons and deep traps

    SciTech Connect

    Polyakov, A. Y.; Smirnov, N. B.; Govorkov, A. V.; Yugova, T. G.; Cox, H.; Helava, H.; Makarov, Yu.; Usikov, A. S.

    2014-05-14

    Electrical properties and deep electron and hole traps spectra are compared for undoped n-GaN films grown by hydride vapor phase epitaxy (HVPE) in the regular process (standard HVPE samples) and in HVPE process optimized for decreasing the concentration of residual donor impurities (improved HVPE samples). It is shown that the residual donor density can be reduced by optimization from ∼10{sup 17} cm{sup −3} to (2–5) × 10{sup 14} cm{sup −3}. The density of deep hole traps and deep electron traps decreases with decreased donor density, so that the concentration of deep hole traps in the improved samples is reduced to ∼5 × 10{sup 13} cm{sup −3} versus 2.9 × 10{sup 16} cm{sup −3} in the standard samples, with a similar decrease in the electron traps concentration.

  14. Epitaxial growth of three dimensionally structured III-V photonic crystal via hydride vapor phase epitaxy

    SciTech Connect

    Zheng, Qiye; Kim, Honggyu; Zhang, Runyu; Zuo, Jianmin; Braun, Paul V.; Sardela, Mauro; Balaji, Manavaimaran; Lourdudoss, Sebastian; Sun, Yan-Ting

    2015-12-14

    Three-dimensional (3D) photonic crystals are one class of materials where epitaxy, and the resultant attractive electronic properties, would enable new functionalities for optoelectronic devices. Here we utilize self-assembled colloidal templates to fabricate epitaxially grown single crystal 3D mesostructured Ga{sub x}In{sub 1−x}P (GaInP) semiconductor photonic crystals using hydride vapor phase epitaxy (HVPE). The epitaxial relationship between the 3D GaInP and the substrate is preserved during the growth through the complex geometry of the template as confirmed by X-ray diffraction (XRD) and high resolution transmission electron microscopy. XRD reciprocal space mapping of the 3D epitaxial layer further demonstrates the film to be nearly fully relaxed with a negligible strain gradient. Fourier transform infrared spectroscopy reflection measurement indicates the optical properties of the photonic crystal which agree with finite difference time domain simulations. This work extends the scope of the very few known methods for the fabrication of epitaxial III-V 3D mesostructured materials to the well-developed HVPE technique.

  15. Computational fluid dynamics-aided analysis of a hydride vapor phase epitaxy reactor

    NASA Astrophysics Data System (ADS)

    Schulte, Kevin L.; Simon, John; Roy, Abhra; Reedy, Robert C.; Young, David L.; Kuech, Thomas F.; Ptak, Aaron J.

    2016-01-01

    We report the development of a computational fluid dynamics (CFD) model of a dual chamber hydride vapor phase epitaxial (HVPE) growth reactor. Uniformity of reactant concentrations in the growth stream, transient reactor flows, and cross doping between the two growth chambers, all factors critical to the deposition of uniform, low defect semiconductor layers, were modeled. Simulation results were generated by solving the fundamental continuity, momentum and energy equations over a discretized reactor volume by a finite volume analysis with the aid of CFD-ACE+ commercial software. We demonstrated uniformity of the vapor composition within ±1% across the substrate, achieved due to specific features of the reactor design. Small compositional non-uniformity (±2% absolute) in In1-xGaxP layers grown in our reactor was correlated with calculated temperature non-uniformity across the substrate. Gas switching was modeled and the transient time predicted by the model was confirmed by measurement of doping transients in a sample grown in the reactor. Lastly the gas curtains that chemically isolate the reactor chambers were modeled and the results were compared to experimental data for cross doping between the chambers. As an example, we demonstrate, based on insight from the model, that our HVPE reactor is suitable for the deposition of GaAs PV devices. CFD modeling is a critical tool for the scale up of laboratory level processes to industrial levels.

  16. Development of GaInP Solar Cells Grown by Hydride Vapor Phase Epitaxy

    DOE PAGES

    Schulte, Kevin L.; Simon, John; Mangum, John; ...

    2017-04-30

    We demonstrate the growth of homojunction GaInP solar cells by dynamic hydride vapor phase epitaxy for the first time. Simple unpassivated n-on-p structures grown in an inverted configuration with gold back reflectors were analyzed. Short wavelength performance varied strongly with emitter thickness, since collection in the emitter was limited by the lack of surface passivation. Collection in the base increased strongly with decreasing doping density, in the range 1 x 1016 - 5 x 1017 cm-3. Optical modeling indicated that, in our best device, doped ~1 x 1016 cm-3, almost 94% of photons that passed through the emitter were collected.more » Modeling also indicated that the majority of collection occurs in the depletion region with this design, suggesting that nonradiative recombination there might limit device performance. In agreement with this observation, the experimental dark J-V curve exhibited an ideality factor near n = 2. Thus, limitation of deep level carrier traps in the material is a path to improved performance. Preliminary experiments indicate that a reduced V/III ratio, which potentially affects the density of these presumed traps, improves cell performance. With reduced V/III ratio, we demonstrate a ~13% efficient GaInP cell measured under the 1-sun AM1.5G spectrum. In conclusion, this cell had an antireflective coating, but no front surface passivation.« less

  17. Hydrogen permeation pathways for the hydrogenation reaction of aluminum

    NASA Astrophysics Data System (ADS)

    Saitoh, H.; Machida, A.; Katayama, Y.; Aoki, K.

    2010-09-01

    The hydrogenation of aluminum is inhibited by the slow diffusion of hydrogen in its hydride AlH3, which covers the surface of aluminum in the initial stages of the reaction. Thus, permeation pathways for hydrogen are introduced by either mixing aluminum powder with boron nitride powder or alloying aluminum with gallium at 10 at. % Ga. The aluminum in the composite or alloy is reacted with hydrogen at high pressure and temperature. In both cases, the hydrogenation reaction yields are significantly enhanced, confirming that boron nitride and the liquid phase produced by partial melting of the alloy work efficiently as hydrogen permeation pathways.

  18. Phase Equilibria, Crystal Structure and Hydriding/Dehydriding Mechanism of Nd4Mg80Ni8 Compound

    PubMed Central

    Luo, Qun; Gu, Qin-Fen; Zhang, Jie-Yu; Chen, Shuang-Lin; Chou, Kuo-Chih; Li, Qian

    2015-01-01

    In order to find out the optimal composition of novel Nd-Mg-Ni alloys for hydrogen storage, the isothermal section of Nd-Mg-Ni system at 400 °C is established by examining the equilibrated alloys. A new ternary compound Nd4Mg80Ni8 is discovered in the Mg-rich corner. It has the crystal structure of space group I41/amd with lattice parameters of a = b = 11.2743(1) Å and c = 15.9170(2) Å, characterized by the synchrotron powder X-ray diffraction (SR-PXRD). High-resolution transmission electron microscopy (HR-TEM) is used to investigate the microstructure of Nd4Mg80Ni8 and its hydrogen-induced microstructure evolution. The hydrogenation leads to Nd4Mg80Ni8 decomposing into NdH2.61-MgH2-Mg2NiH0.3 nanocomposites, where the high density phase boundaries provide a great deal of hydrogen atoms diffusion channels and nucleation sites of hydrides, which greatly enhances the hydriding/dehydriding (H/D) properties. The Nd4Mg80Ni8 exhibits a good cycle ability. The kinetic mechanisms of H/D reactions are studied by Real Physical Picture (RPP) model. The rate controlling steps are diffusion for hydriding reaction in the temperature range of 100 ~ 350 °C and surface penetration for dehydriding reaction at 291 ~ 347 °C. In-situ SR-PXRD results reveal the phase transformations of Mg to MgH2 and Mg2Ni to Mg2NiH4 as functions of hydrogen pressure and hydriding time. PMID:26471964

  19. Phase Equilibria, Crystal Structure and Hydriding/Dehydriding Mechanism of Nd4Mg80Ni8 Compound

    NASA Astrophysics Data System (ADS)

    Luo, Qun; Gu, Qin-Fen; Zhang, Jie-Yu; Chen, Shuang-Lin; Chou, Kuo-Chih; Li, Qian

    2015-10-01

    In order to find out the optimal composition of novel Nd-Mg-Ni alloys for hydrogen storage, the isothermal section of Nd-Mg-Ni system at 400 °C is established by examining the equilibrated alloys. A new ternary compound Nd4Mg80Ni8 is discovered in the Mg-rich corner. It has the crystal structure of space group I41/amd with lattice parameters of a = b = 11.2743(1) Å and c = 15.9170(2) Å, characterized by the synchrotron powder X-ray diffraction (SR-PXRD). High-resolution transmission electron microscopy (HR-TEM) is used to investigate the microstructure of Nd4Mg80Ni8 and its hydrogen-induced microstructure evolution. The hydrogenation leads to Nd4Mg80Ni8 decomposing into NdH2.61-MgH2-Mg2NiH0.3 nanocomposites, where the high density phase boundaries provide a great deal of hydrogen atoms diffusion channels and nucleation sites of hydrides, which greatly enhances the hydriding/dehydriding (H/D) properties. The Nd4Mg80Ni8 exhibits a good cycle ability. The kinetic mechanisms of H/D reactions are studied by Real Physical Picture (RPP) model. The rate controlling steps are diffusion for hydriding reaction in the temperature range of 100 ~ 350 °C and surface penetration for dehydriding reaction at 291 ~ 347 °C. In-situ SR-PXRD results reveal the phase transformations of Mg to MgH2 and Mg2Ni to Mg2NiH4 as functions of hydrogen pressure and hydriding time.

  20. Phase Equilibria, Crystal Structure and Hydriding/Dehydriding Mechanism of Nd4Mg80Ni8 Compound.

    PubMed

    Luo, Qun; Gu, Qin-Fen; Zhang, Jie-Yu; Chen, Shuang-Lin; Chou, Kuo-Chih; Li, Qian

    2015-10-16

    In order to find out the optimal composition of novel Nd-Mg-Ni alloys for hydrogen storage, the isothermal section of Nd-Mg-Ni system at 400 °C is established by examining the equilibrated alloys. A new ternary compound Nd4Mg80Ni8 is discovered in the Mg-rich corner. It has the crystal structure of space group I41/amd with lattice parameters of a = b = 11.2743(1) Å and c = 15.9170(2) Å, characterized by the synchrotron powder X-ray diffraction (SR-PXRD). High-resolution transmission electron microscopy (HR-TEM) is used to investigate the microstructure of Nd4Mg80Ni8 and its hydrogen-induced microstructure evolution. The hydrogenation leads to Nd4Mg80Ni8 decomposing into NdH2.61-MgH2-Mg2NiH0.3 nanocomposites, where the high density phase boundaries provide a great deal of hydrogen atoms diffusion channels and nucleation sites of hydrides, which greatly enhances the hydriding/dehydriding (H/D) properties. The Nd4Mg80Ni8 exhibits a good cycle ability. The kinetic mechanisms of H/D reactions are studied by Real Physical Picture (RPP) model. The rate controlling steps are diffusion for hydriding reaction in the temperature range of 100 ~ 350 °C and surface penetration for dehydriding reaction at 291 ~ 347 °C. In-situ SR-PXRD results reveal the phase transformations of Mg to MgH2 and Mg2Ni to Mg2NiH4 as functions of hydrogen pressure and hydriding time.

  1. Are cyclopentadienylberyllium, magnesium and calcium hydrides carbon or metal acids in the gas phase?

    PubMed

    Hurtado, Marcela; Lamsabhi, Al-Mokhtar; Mó, Otilia; Yáñez, Manuel; Guillemin, Jean-Claude

    2010-05-21

    The structure and bonding of cyclopentadienylberyllium (CpBeH), magnesium (CpMgH), and calcium (CpCaH) hydrides as well as those of their deprotonated species have been investigated by means of B3LYP/6-311+G(3df,2p)//B3LYP/6-311+G(d,p) and B3LYP/6-311+G(3df,2p)//QCISD/6-311+G(d,p) density functional theory (DFT) calculations. The three compounds exhibit C(5v) equilibrium conformations in their ground states. For CpBeH the agreement between the calculated geometry and that determined by MW spectroscopy is excellent. CpMgH and CpCaH can be viewed almost as the result of the interaction between a C₅H₅⁻ anion and a XH(+) (X = Mg, Ca) cation. Conversely, for CpBeH the interaction between the C₅H₅ and the BeH subunits is significantly covalent. These compounds exhibit a significant aromaticity, usually named three-dimension aromaticity, in contrast with the unsubstituted cyclopentadiene compound. The CpBeH derivative behaves as a C acid in the gas phase and is less acidic than cyclopentadiene. More importantly, CpMgH and CpCaH, in spite of the X(+δ)H(-δ) polarity exhibited by the X-H bond in the neutral systems, are predicted to be metal acids in the gas phase. Also surprisingly, both the Mg and the Ca derivatives are stronger acids than the Be analogue, and only slightly weaker acids than cyclopentadiene. This somewhat unexpected result is the consequence of two concomitant facts: the lower dissociation energy of the X-H (X = Mg, Ca) bonds with respect to the C-H bonds, and the significantly high electron affinity of the C₅H₅X* (X = Mg, Ca) radicals.

  2. Environmentally friendly method to grow wide-bandgap semiconductor aluminum nitride crystals: Elementary source vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Wu, Peitsen; Funato, Mitsuru; Kawakami, Yoichi

    2015-11-01

    Aluminum nitride (AlN) has attracted increasing interest as an optoelectronic material in the deep ultraviolet spectral range due to its wide bandgap of 6.0 eV (207 nm wavelength) at room temperature. Because AlN bulk single crystals are ideal device substrates for such applications, the crystal growth of bulky AlN has been extensively studied. Two growth methods seem especially promising: hydride vapor phase epitaxy (HVPE) and sublimation. However, the former requires hazardous gases such as hydrochloric acid and ammonia, while the latter needs extremely high growth temperatures around 2000 °C. Herein we propose a novel vapor-phase-epitaxy-based growth method for AlN that does not use toxic materials; the source precursors are elementary aluminum and nitrogen gas. To prepare our AlN, we constructed a new growth apparatus, which realizes growth of AlN single crystals at a rate of ~18 μm/h at 1550 °C using argon as the source transfer via the simple reaction Al + 1/2N2 → AlN. This growth rate is comparable to that by HVPE, and the growth temperature is much lower than that in sublimation. Thus, this study opens up a novel route to achieve environmentally friendly growth of AlN.

  3. Environmentally friendly method to grow wide-bandgap semiconductor aluminum nitride crystals: Elementary source vapor phase epitaxy

    PubMed Central

    Wu, PeiTsen; Funato, Mitsuru; Kawakami, Yoichi

    2015-01-01

    Aluminum nitride (AlN) has attracted increasing interest as an optoelectronic material in the deep ultraviolet spectral range due to its wide bandgap of 6.0 eV (207 nm wavelength) at room temperature. Because AlN bulk single crystals are ideal device substrates for such applications, the crystal growth of bulky AlN has been extensively studied. Two growth methods seem especially promising: hydride vapor phase epitaxy (HVPE) and sublimation. However, the former requires hazardous gases such as hydrochloric acid and ammonia, while the latter needs extremely high growth temperatures around 2000 °C. Herein we propose a novel vapor-phase-epitaxy-based growth method for AlN that does not use toxic materials; the source precursors are elementary aluminum and nitrogen gas. To prepare our AlN, we constructed a new growth apparatus, which realizes growth of AlN single crystals at a rate of ~18 μm/h at 1550 °C using argon as the source transfer via the simple reaction Al + 1/2N2 → AlN. This growth rate is comparable to that by HVPE, and the growth temperature is much lower than that in sublimation. Thus, this study opens up a novel route to achieve environmentally friendly growth of AlN. PMID:26616203

  4. Silica hydride based phases for small molecule separations using automated liquid chromatography-mass spectrometry method development.

    PubMed

    Appulage, Dananjaya K; Schug, Kevin A

    2017-07-21

    Silica hydride, or Type C silica, has been developed as an alternative chromatographic support material for liquid chromatography. There are various bonded phases available with this new support. For four such phases (Cholesterol, Bidentate C18, Diamond Hydride, and Diol), retention and selectivity behavior were investigated using liquid chromatography coupled with triple quadrupole mass spectrometry. A set of small molecules from several chemical classes of interest, and varying in their physicochemical properties, were chromatographed under both reversed-phase and aqueous normal phase modes. To screen the columns, column switching was performed using an automated platform controlled by associated software and an additional valve. A typical scouting gradient was implemented. The separation conditions were not further optimized since the goal was simply to evaluate the variable retention behavior of the phases and selectivity under generic conditions. Further, retention of the analytes were evaluated under isocratic conditions with varying percentages of organic phase to visualize the potential for dual retention modes on the same column for certain analytes. Four analytes (fentanyl, hydrocodone, hydromorphone, and matrine) showed dual mode retention behavior with all four phases. Especially, fentanyl exhibited dramatic "U-shaped" retention profiles on Cholesterol and Bidentate C18 phases. Overall, changes in the retention order between reversed phase and aqueous normal phases emphasized the potential for altered selectivity. Results showed that the Cholesterol phase provided the highest retention for most analytes compared to the other phases. The more polar Diol phase still provided good retention in reversed phase mode. Retention and selectivity were all highly reproducible. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Analysis of hydrophilic metabolites in physiological fluids by HPLC-MS using a silica hydride-based stationary phase.

    PubMed

    Pesek, Joseph J; Matyska, Maria T; Loo, Joseph A; Fischer, Steven M; Sana, Theodore R

    2009-07-01

    Aqueous normal-phase chromatography was used for the analysis of metabolites in human saliva and urine samples. The column was packed with a silica hydride type separation material. Several gradients were tested with different mobile phase additives in order to produce retention for amino acids, small organic acids, and carbohydrates. Detection was done by TOF MS. In some cases the relative concentration levels of various metabolites in human saliva were compared for normal patients and patients with pancreatic cancer or pancreatitis. The reproducibility of retention of individual metabolites in these complex matrices was tested for several compounds.

  6. Hydride formation and thermal desorption spectra of hydrogen of cathodically charged single-phase gamma titanium aluminide

    SciTech Connect

    Takasaki, Akito; Furuya, Yoshio

    1999-02-05

    The authors have previously reported thermal desorption spectra of hydrogen obtained from cathodically charged two-phase (Ti{sub 3}Al ({alpha}{sub 2}) + TiAl ({gamma})) titanium aluminides by means of thermal desorption spectroscopy (TDS), in which hydrogen ion current (H{sub 2}{sup +}) corresponding to hydrogen evolution rate during heating was measured by a quadrupole mass spectrometer in an ultra-high vacuum condition. Several accelerated hydrogen evolutions (TDS peak temperatures) have been observed in a series of TDS measurement, and then the authors have suggested that these peaks were dependent on the microstructures ({alpha}{sub 2} and {gamma} phases) as well as dissociation of the hydride phase which formed during cathodic charging. A comparison with the TDS spectra from other series of titanium aluminides, such as a single-phase {gamma} alloy, might give clearer views of the microstructural dependence on hydrogen evolution kinetics. In this paper, hydride formation, hydrogen uptake and hydrogen evolution kinetic of a cathodically charged single-phase {gamma} titanium aluminide are investigated, and these results are compared with the previous ones obtained in two-phase ({alpha}{sub 2} + {gamma}) titanium aluminides.

  7. Flow injection on-line solid phase extraction for ultra-trace lead screening with hydride generation atomic fluorescence spectrometry.

    PubMed

    Wan, Zhuo; Xu, Zhangrun; Wang, Jianhua

    2006-01-01

    A flow injection (FI) on-line solid phase extraction (SPE) procedure for ultra-trace lead separation and preconcentration was developed, followed by hydride generation and atomic fluorescence spectrometric (AFS) detection. Lead is retained on an iminodiacetate chelating resin packed microcolumn, and is afterward eluted with 2.5% (v/v) hydrochloric acid to facilitate the hydride generation by reaction with alkaline tetrahydroborate solution with 1% (m/v) potassium ferricyanide as an oxidizing (or sensitizing) reagent. The hydride was separated from the reaction medium in the gas-liquid separator and swept into the atomizer for quantification. The chemical variables and the FI flow parameters were carefully optimized. With a sample loading volume of 4.8 ml, quantitative retention of lead was obtained, along with an enrichment factor of 11.3 and a sampling frequency of 50 h(-1). A detection limit of 4 ng l(-1), defined as 3 times the blank standard deviation (3 sigma), was achieved along with a RSD value of 1.6% at the 0.4 microg l(-1) level. The procedure was validated by determining lead contents in two certified reference materials, and its practical applicability was further demonstrated by analysing a variety of biological and environmental samples.

  8. Polycrystalline indium phosphide on silicon by indium assisted growth in hydride vapor phase epitaxy

    SciTech Connect

    Metaferia, Wondwosen; Sun, Yan-Ting Lourdudoss, Sebastian; Pietralunga, Silvia M.; Zani, Maurizio; Tagliaferri, Alberto

    2014-07-21

    Polycrystalline InP was grown on Si(001) and Si(111) substrates by using indium (In) metal as a starting material in hydride vapor phase epitaxy (HVPE) reactor. In metal was deposited on silicon substrates by thermal evaporation technique. The deposited In resulted in islands of different size and was found to be polycrystalline in nature. Different growth experiments of growing InP were performed, and the growth mechanism was investigated. Atomic force microscopy and scanning electron microscopy for morphological investigation, Scanning Auger microscopy for surface and compositional analyses, powder X-ray diffraction for crystallinity, and micro photoluminescence for optical quality assessment were conducted. It is shown that the growth starts first by phosphidisation of the In islands to InP followed by subsequent selective deposition of InP in HVPE regardless of the Si substrate orientation. Polycrystalline InP of large grain size is achieved and the growth rate as high as 21 μm/h is obtained on both substrates. Sulfur doping of the polycrystalline InP was investigated by growing alternating layers of sulfur doped and unintentionally doped InP for equal interval of time. These layers could be delineated by stain etching showing that enough amount of sulfur can be incorporated. Grains of large lateral dimension up to 3 μm polycrystalline InP on Si with good morphological and optical quality is obtained. The process is generic and it can also be applied for the growth of other polycrystalline III–V semiconductor layers on low cost and flexible substrates for solar cell applications.

  9. InGaAsP Solar Cells Grown by Hydride Vapor Phase Epitaxy

    SciTech Connect

    Jain, Nikhil; Simon, John; Schulte, Kevin L.; Dippo, Patricia; Young, Michelle; Young, David L.; Ptak, Aaron J.

    2016-11-21

    Hydride vapor phase epitaxy (HVPE) has recently reemerged as a low-cost, high-throughput alternative to metalorganic chemical vapor deposition (MOCVD) for the growth of high-efficiency III-V solar cells. Quaternary InGaAsP solar cells in the bandgap range of ~1.7-1.8 eV are promising top-cell candidates for integration in Ill-V/Si tandem cells with projected one-sun efficiencies exceeding 30%. In this work, we report on the development of lattice-matched InGaAsP solar cells grown on GaAs substrates via HVPE at very high growth rates of ~0.7 um/min. We demonstrate prototype 1.7 eV InGaAsP solar cells with an open-circuit voltage of 1.11 V. The short-circuit current is limited by the lack of a window layer in these early stage devices. The photo response of 1.7 InGaAsP solar cell with ~1.1 um thick base layer is found to be nearly insensitive to variation in p-type base doping concentration in the range from Na - 4x1016 to - 1x1017 cm-3, indicating an effective carrier collection length on the order of - 1.1 um or higher in our devices. These initial InGaAsP cell results are encouraging and highlight the viability of HVPE to produce mixed arsenide-phosphide solar cells grown lattice-matched on GaAs.

  10. Next Generation Energetic Materials: New Cluster Hydrides and Metastable Alloys of Aluminum in Very Low Oxidation States

    DTIC Science & Technology

    2016-10-01

    nanoparticle (NP) alloys, where M = Si, Zn by using AlCl and AlBr precursors prepared from our unique metal-halide co-condensation reactor, and 3) fully...terminal GaPR2 moieties.[14,19] These clusters have been discussed to be precursors for core-shell nanoparticles containing a metallic gallium core and a... nanoparticle nucleation on functionalized graphene surfactants from aluminum monochloride solutions. This data shows a strong affinity of AlCl units for

  11. Gas-Phase Combustion Synthesis of Aluminum Nitride Powder

    NASA Technical Reports Server (NTRS)

    Axelbaum, R. L.; Lottes, C. R.; Huertas, J. I.; Rosen, L. J.

    1996-01-01

    Due to its combined properties of high electrical resistivity and high thermal conductivity aluminum nitride (AlN) is a highly desirable material for electronics applications. Methods are being sought for synthesis of unagglomerated, nanometer-sized powders of this material, prepared in such a way that they can be consolidated into solid compacts having minimal oxygen content. A procedure for synthesizing these powders through gas-phase combustion is described. This novel approach involves reacting AlCl3, NH3, and Na vapors. Equilibrium thermodynamic calculations show that 100% yields can be obtained for these reactants with the products being AlN, NaCl, and H2. The NaCl by-product is used to coat the AlN particles in situ. The coating allows for control of AlN agglomeration and protects the powders from hydrolysis during post-flame handling. On the basis of thermodynamic and kinetic considerations, two different approaches were employed to produce the powder, in co-flow diffusion flame configurations. In the first approach, the three reactants were supplied in separate streams. In the second, the AlCl3 and NH3 were premixed with HCl and then reacted with Na vapor. X-ray diffraction (XRD) spectra of as-produced powders show only NaCl for the first case and NaCl and AlN for the second. After annealing at 775 C tinder dynamic vacuum, the salt was removed and XRD spectra of powders from both approaches show only AlN. Aluminum metal was also produced in the co-flow flame by reacting AlCl3 with Na. XRD spectra of as-produced powders show the products to be only NaCl and elemental aluminum.

  12. First Principles Studies of Phase Stability and Reaction Dynamics in Complex Metal Hydrides

    SciTech Connect

    Chou, Mei-Yin

    2014-09-29

    Complex metal hydrides are believed to be one of the most promising materials for developing hydrogen storage systems that can operate under desirable conditions. At the same time, these are also a class of materials that exhibit intriguing properties. We have used state-of-the-art computational techniques to study the fundamental properties of these materials.

  13. Growth of low-threading-dislocation-density GaN on graphene by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    He, Shunyu; Xu, Yu; Qi, Lin; Li, Zongyao; Cao, Bing; Wang, Chinhua; Zhang, Jicai; Wang, Jianfeng; Xu, Ke

    2017-03-01

    Recently, gallium nitride (GaN) films grown on graphene have been widely studied. Here, we have grown low-threading-dislocation-density GaN films on graphene by hydride vapor phase epitaxy (HVPE). The full widths at half maximum (FWHMs) of X-ray rocking curves (XRCs) of the GaN films were 276 and 350 arcsec at the 0002 and 10\\bar{1}2 reflections, respectively. This shows that the threading dislocation densities are on the order of magnitude of 108 cm‑2, which is consistent with the results of cathodoluminescence (CL).

  14. Aluminum-Containing Phases in Tank Waste: Precipitation and Deposition of Aluminum-Containing Phases

    SciTech Connect

    Mattigod, Shas; Hobbs, D.T.; Wellman, D.M.; Aksay, I.

    2006-06-01

    Aluminosilicate deposit buildup experienced during the tank waste volume-reduction process at the Savannah River Site (SRS) required an evaporator to be shut down in October 1999. Recent investigations illustrated the accumulation 7 wt% uranium, 3% was 235U and absent of neutron poisons, within these deposits and presented a criticality concern. The Waste Processing Technology Section of Westinghouse Savannah River Company at SRS is now collaborating with a team from Pacific Northwest National Laboratory in efforts to identify the phases controlling uranium solubility and understand the conditions under which they precipitate.

  15. Materials engineering of metal hydrides

    SciTech Connect

    Gruen, D.M.; Mendelsohn, M.H.

    1981-01-01

    Intermetallic hydrides of the AB/sub 5/ type have enthalpies in the range valid for chemical heat pumps. A scheme for manufacturing hydrides with optimal properties for a chemical heat pump is described, using LaNi/sub 5-x/Al/sub x/ and ZrV/sub 2x/Cr/sub x as examples. The Laves-phase ternary hydrides appear to be good candidates for gettering hydrogen in the Tokamak Fusion Test Reactor. (DLC)

  16. Liquid Chromatography with mass spectrometry analysis of mycotoxins in food samples using silica hydride based stationary phases.

    PubMed

    Pesek, Joseph J; Matyska, Maria T; Hoffmann, Jessica F; Madruga, Nathalia A; Crizel, Rosane L; Elias, Moacir C; Vanier, Nathan L; Chaves, Fabio C

    2017-05-01

    Liquid chromatography with mass spectrometry analysis of selected food samples using silica hydride stationary phases allowed for the identification and quantification of common mycotoxins including aflatoxin B1, B2, G1, G2, ochratoxin A, and fumosinin B1. Phenyl and C18 columns showed relatively similar selectivity based on hydrophobicity but the phenyl phase provides an additional mechanism, π-π interaction. The most hydrophobic of the analyzed compounds was more strongly retained on the C18 column and also has fewer unsaturated sites, which limited the interaction with the phenyl phase. Bean, maize, rice, and wheat samples were harvested and stored under conditions conducive to fungal development, and all samples presented toxin contamination exceeding the maximum tolerable limits. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Analysis of silica hydride and surface hydrosilation reactions by solid-state NMR in the preparation of p-chlorobenzamide bonded silica phase.

    PubMed

    Lynch, B; Müller, G H; Healy, L O; Glennon, J D; Pursch, M; Albert, K

    2003-11-01

    29Si and (13)C CP-MAS NMR spectroscopy was used to follow the conversion of native silica to a p-chlorobenzamide bonded silica material. The benzamide bonded phase was prepared via a hydrosilation reaction of a hydride silica intermediate with p-chloro- N-allylbenzamide. Solid-state NMR was used to show the disappearance of reactive surface hydride species (M(H)) and to identify newly formed bonded chemical species on the silica surface. DRIFT spectroscopy, elemental analysis, and specific surface-area determinations (BET) of the prepared phases are also reported.

  18. Structural and Electronic Flexibility in Hydrides of Zintl Phases with Tetrel-Hydrogen and Tetrel-Tetrel Bonds.

    PubMed

    Auer, Henry; Schlegel, Robert; Oeckler, Oliver; Kohlmann, Holger

    2017-07-20

    The hydrogenation of Zintl phases enables the formation of new structural entities with main-group-element-hydrogen bonds in the solid state. The hydrogenation of SrSi, BaSi, and BaGe yields the hydrides SrSiH5/3-x, BaSiH5/3-x and BaGeH5/3-x . The crystal structures show a sixfold superstructure compared to the parent Zintl phase and were solved by a combination of X-ray, neutron, and electron diffraction and the aid of DFT calculations. Layers of connected HSr4 (HBa4 ) tetrahedra containing hydride ions alternate with layers of infinite single- and double-chain polyanions, in which hydrogen atoms are covalently bound to silicon and germanium. The idealized formulae AeTtH5/3 (Ae=alkaline earth, Tt=tetrel) can be rationalized with the Zintl-Klemm concept according to (Ae(2+) )3 (TtH(-) )(Tt2 H(2-) )(H(-) )3 , where all Tt atoms are three-binding. The non-stoichiometry (SrSiH5/3-x , x=0.17(2); BaGeH5/3-x , x=0.10(3)) can be explained by additional π-bonding of the Tt chains. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Ca2LiC3H: a new complex carbide hydride phase grown in metal flux.

    PubMed

    Lang, David A; Zaikina, Julia V; Lovingood, Derek D; Gedris, Thomas E; Latturner, Susan E

    2010-12-15

    The reaction of carbon and CaH2 in a calcium/lithium flux mixture produces crystals of the new compound Ca2LiC3H. This phase forms with a new structure type in tetragonal space group P4/mbm (a = 6.8236(1) Å, c = 3.7518(1) Å, Z = 2, R1 = 0.0151). This is a stuffed variant of the Cs2(NH2)N3 structure, containing hydride anions in octahedral sites; the structure determination by single-crystal X-ray diffraction surprisingly allowed the hydrogen to be detected. The Ca2LiC3H structure also features the rarely seen C3(4-) carbide anion; the protolysis reaction of this compound with ammonium chloride produces C3H4. The electronic properties of Ca2LiC3H were studied by quantum-chemical calculations including band structure and electron localization function (ELF) analysis; the phase is a charge-balanced semiconductor with a calculated band gap of 0.48 eV. This is in agreement with (7)Li, (13)C, and (1)H MAS NMR data, which show resonances in the ionic region instead of the Knight shifted region. ELF analysis of the theoretical nonhydrided Ca2LiC3 structure confirms the ability of these calculations to properly locate hydrides and supports the structural model based on X-ray diffraction data.

  20. Determination of antimony in environment samples by gas phase chemiluminescence detection following flow injection hydride generation and cryotrapping.

    PubMed

    Ye, Yousheng; Sang, Jianchi; Ma, Hongbing; Tao, Guanhong

    2010-06-15

    A novel method for the determination of antimony in environmental samples was developed with gas phase chemiluminescence detection following flow injection hydride generation and cryotrapping. The stibine, generated from samples by borohydride reduction of antimony using flow injection technique, was separated by using a new gas-liquid separator, dried with an ice-salt cryogenic bath and concentrated in a glass U-tube immersed in liquid nitrogen. Re-vaporization of stibine based on its boiling point was achieved by allowing the tube to warm at room temperature. A gas phase chemiluminescence signal was produced during the ozonation of the hydride in a reflective chamber. Under optimal conditions, the proposed method was characterized by a wide linear calibration range from 1.0microgL(-1) to 10.0mgL(-1) with a detection limit of 0.18microgL(-1) (n=11). The relative standard deviation for 10.0microgL(-1) antimony was 3.56% (n=11) and the sampling rate was 15 samples h(-1). Blank signal was reduced by the purification of reagents and the interference from transition metal ions was eliminated by the addition of L-cysteine into samples. The method was applied to the determination of antimony in environmental samples with satisfactory results.

  1. Synthesis and evaluation of a C8 stationary phase on a silica hydride surface by hydrosilation of 1-octyne.

    PubMed

    Pesek, Joseph J; Matyska, Maria T; Pan, Xiaofan

    2003-04-11

    The silanization/hydrosilation method is used to bond an alkyne (1-octyne) to a silica hydride surface. The new bonded material is characterized by elemental analysis and diffuse reflectance infrared Fourier transform spectroscopy. The hydrophobic behavior of this material was determined by the retention characteristics of aromatic solutes and the shape selectivity as well as phase classification (monomeric or polymeric) was measured by the polycyclic aromatic hydrocarbon mixture standard reference material 869. The presence of residual silanols on the bonded phase was probed by several basic solutes at pH 7. Long-term stability studies were conducted by measuring retention and peak symmetry of basic compounds over several thousand column volumes at pH 10.

  2. A Ti-V-based bcc phase alloy for use as metal hydride electrode with high discharge capacity.

    PubMed

    Yu, X B; Wu, Z; Xia, B J; Xu, N X

    2004-07-08

    The electrochemical characteristics of single bcc phase Ti-30V-15Cr-15Mn alloy were investigated. It was demonstrated that the single bcc phase alloy has high electrochemical discharge performance at high temperature. Its discharge capacity is closely related with temperature and discharge current. The first discharge capacities of 580-814 mAh g(-1) of the alloy powder were obtained at discharge current of 45-10 mA g(-1) in 6 M KOH solution at 353 K. Although the electrochemical cycle life of the alloy is unsatisfactory at present, it opens up prospects for developing a new hydrogen storage alloy with high hydrogen capacity for use as high performance metal hydride electrodes in rechargeable Ni-MH battery.

  3. EFFECTS OF SURFACE AREA DENSITY OF ALUMINUM FOAMS ON THERMAL CONDUCTIVITY OF ALUMINUM FOAM-PHASE CHANGE MATERIAL COMPOSITES

    SciTech Connect

    Hong, Sung-tae; Herling, Darrell R.

    2007-07-01

    The effects of the surface area density of open-cell aluminum foams on the effective thermal conductivity of aluminum foam-phase change material (PCM) composites were investigated. Paraffin was selected as the PCM. The experimental results show that the effective thermal conductivity increases as the temperature increases. The experimental results suggest that the effective thermal conductivities can be different for different surface area densities of foams even though the relative densities of foams are similar. Therefore, for an accurate estimation of the effective thermal conductivity, a correlation including the surface area density effect is needed.

  4. Hydrogen, lithium, and lithium hydride production

    DOEpatents

    Brown, Sam W; Spencer, Larry S; Phillips, Michael R; Powell, G. Louis; Campbell, Peggy J

    2014-03-25

    A method of producing high purity lithium metal is provided, where gaseous-phase lithium metal is extracted from lithium hydride and condensed to form solid high purity lithium metal. The high purity lithium metal may be hydrided to provide high purity lithium hydride.

  5. Hydrogenation using hydrides and acid

    DOEpatents

    Bullock, R. Morris

    1990-10-30

    A process for the non-catalytic hydrogenation of organic compounds, which contain at least one reducible functional group, which comprises reacting the organic compound, a hydride complex, preferably a transition metal hydride complex or an organosilane, and a strong acid in a liquid phase.

  6. Direct synthesis of catalyzed hydride compounds

    DOEpatents

    Gross, Karl J.; Majzoub, Eric

    2004-09-21

    A method is disclosed for directly preparing alkali metal aluminum hydrides such as NaAlH.sub.4 and Na.sub.3 AlH.sub.6 from either the alkali metal or its hydride, and aluminum. The hydride thus prepared is doped with a small portion of a transition metal catalyst compound, such as TiCl.sub.3, TiF.sub.3, or a mixture of these materials, in order to render them reversibly hydridable. The process provides for mechanically mixing the dry reagents under an inert atmosphere followed by charging the mixed materials with high pressure hydrogen while heating the mixture to about 125.degree. C. The method is relatively simple and inexpensive and provides reversible hydride compounds which are free of the usual contamination introduced by prior art wet chemical methods.

  7. Determination of inorganic arsenic in algae using bromine halogenation and on-line nonpolar solid phase extraction followed by hydride generation atomic flourescence spectrometry

    USDA-ARS?s Scientific Manuscript database

    Accurate, stable and fast analysis of toxic inorganic arsenic (iAs) in complicated and arsenosugar-rich algae matrix is always a challenge. Herein, a novel analytical method for iAs in algae was reported, using bromine halogenation and on-line nonpolar solid phase extraction (SPE) followed by hydrid...

  8. High-Pressure Raman and X-ray Diffraction Study of [beta]- and [gamma]-Polymorphs of Aluminum Hydride

    SciTech Connect

    Drozd, Vadym; Garimella, Subrahmanyam; Saxena, Surendra; Chen, Jiuhua; Palasyuk, Taras

    2012-03-26

    Three polymorphs of alane, AlH{sub 3}, ({alpha}, {beta}, and {gamma}) were synthesized and studied at high-pressure in diamond anvil cell by Raman spectroscopy and synchrotron X-ray diffraction. According to synchrotron X-ray diffraction study, {beta}-AlH{sub 3} is stable up to 6 GPa, followed by transformation into {alpha} phase at higher pressures. X-ray-induced decomposition {gamma}-AlH{sub 3} into constituent elements was found at 15 GPa. Raman scattering study at high pressure for both {beta}- and {gamma}-AlH{sub 3} reveals transition into the {alpha} phase with high concentration of structural defects. DFT calculations (VASP code) show that instability of cubic {beta}-alane crystal structure at high pressure is caused by the strong deformation of the [AlH{sub 6}] polyhedra.

  9. Separation Differences Among Phenyl Hydride, UDC Cholesterol and Bidentate C8 Stationary Phases for Stability Indicating Methods of Tetracyclines: Journal of Liquid Chromatography & Related Technologies.

    PubMed

    Young, Joshua E; Matyska, Maria T; Azad, Anil K; Yoc, Sergio E; Pesek, Joseph J

    2013-04-01

    Formulation extracts of tetracycline hydrochloride (HCl), minocycline hydrochloride (HCl), and doxycycline hyclate were degraded by strong acidic conditions and heating. Subsequently, components of the extracts were separated by Bidentate C8, Phenyl Hydride and Cholesterol (UDC) HPLC columns operating in the reverse phase mode. The Phenyl Hydride column was able to baseline separate minocycline from the observed degradant, while partial or total co-elution was observed with the other two columns using otherwise identical method conditions. For both the degraded tetracycline HCl and doxycycline hyclate extracts, the UDC column gave the best resolution for the critical pair. The findings suggest that the postulated secondary retention mechanisms of π-π interactions from the Phenyl Hydride and shape selectivity from the UDC can provide superior resolution for structurally similar analytes compared to hydrophobic interactions alone.

  10. Superconductivity and the structural phase transitions in palladium hydride and palladium deuteride

    SciTech Connect

    Standley, Robert Wendell

    1980-01-01

    The results of two experimental studies of the superconducting transition temperature, T/sub c/, of palladium hydride, PdH/sub x/, and palladium deuteride, PdD/sub x/, are presented. In the first study, the superconducting transition temperature of PdH/sub x/(D/sub x/) is studied as a function of H(D) concentration, x, in the temperature range from 0.2 K to 4K. The data join smoothly with those reported previously by Miller and Satterthwaite at higher temperatures, and the composite data are described by the empirical relation T/sub c/ = 150.8 (x-x/sub o/)/sup 2/ /sup 244/, where x/sub o/ = 0.715 for hydride samples and 0.668 for deuteride samples. The results, when compared with the theoretical predictions of Klein and Papaconstantopoulos, et al., raise questions about the validity of their explanation of the reverse isotope effect, which is based solely on a difference in force constants. In the second study, the effect of the order-disorder structural transition associated with the 50 K anomaly on the superconductivity of PdH/sub x/(D/sub x/) is investigated. Samples were quenched to low temperatures in the disordered state, and their transition temperatures measured. The samples were then annealed just below the anomaly temperature, and the ordering process followed by monitoring the change in sample resistance. The transition temperatures in the ordered state were then measured.

  11. Growth of thick GaN layers on laser-processed sapphire substrate by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Koyama, Koji; Aida, Hideo; Kim, Seong-Woo; Ikejiri, Kenjiro; Doi, Toshiro; Yamazaki, Tsutomu

    2014-10-01

    A 600 μm thick GaN layer was successfully grown by hydride vapor phase epitaxy by replacing the standard sapphire substrate with that processed by a focused laser beam within the substrate. The effects of the laser processing on the curvature and cracking of the GaN layer were investigated. Microscopic observations of the interior of the thick GaN layer revealed that the laser-processed substrate suppressed the generation of microcracks in the GaN layer. In addition, the laser processing was also found to reduce the change in the curvature during the GaN layer growth in comparison to that on the standard substrate. It is shown that the overlapping microcracks observed in the GaN layer on the standard sapphire substrate lead to serious cracking after thick GaN layer growth.

  12. Highly resistive C-doped hydride vapor phase epitaxy-GaN grown on ammonothermally crystallized GaN seeds

    NASA Astrophysics Data System (ADS)

    Iwinska, Malgorzata; Piotrzkowski, Ryszard; Litwin-Staszewska, Elzbieta; Sochacki, Tomasz; Amilusik, Mikolaj; Fijalkowski, Michal; Lucznik, Boleslaw; Bockowski, Michal

    2017-01-01

    GaN crystals were grown by hydride vapor phase epitaxy (HVPE) and doped with C. The seeds were high-structural-quality ammonothermally crystallized GaN. The grown crystals were highly resistive at 296 K and of high structural quality. High-temperature Hall effect measurements revealed p-type conductivity and a deep acceptor level in the material with an activation energy of 1 eV. This is in good agreement with density functional theory calculations based on hybrid functionals as presented by the Van de Walle group. They obtained an ionization energy of 0.9 eV when C was substituted for N in GaN and acted as a deep acceptor.

  13. Preparation of Freestanding GaN Wafers by Hydride Vapor Phase Epitaxy with Void-Assisted Separation

    NASA Astrophysics Data System (ADS)

    Oshima, Yuichi; Eri, Takeshi; Shibata, Masatomo; Sunakawa, Haruo; Kobayashi, Kenji; Ichihashi, Toshinari; Usui, Akira

    2003-01-01

    We have developed a novel technique for preparing large-scale freestanding GaN wafers. Hydride vapor phase epitaxy (HVPE) growth of thick GaN layer was performed on a GaN template with a thin TiN film on the top. After the cooling process of the HVPE growth, the thick GaN layer was easily separated from the template by the assistance of many voids generated around the TiN film. As a result, a freestanding GaN wafer was obtained. The wafer obtained had a diameter of 45 mm, and a mirror-like surface. The-full-width-at-half-maximum (FWHM) of (0002) and (10\\bar{1}0) peaks in the X-ray rocking curve profile were 60 and 92 arcsec, respectively. The dislocation density was evaluated at 5× 106 cm-3 by etch pit density measurement.

  14. Solubility and Reaction Rates of Aluminum Solid Phases Under Geothermal Conditions

    SciTech Connect

    Benezeth, P.; Palmer, D.A.; Wesolowski, D.J.; Anovitz, L.M.

    2000-05-28

    Experimental studies involving equilibrium solubility and dissolution/precipitation rates were initiated on aluminum hydroxide phases prevalent under geothermal reservoir conditions. A large capacity, hydrogen-electrode concentration cell (HECC) was constructed specifically for this purpose.

  15. Cast Aluminum Structures Technology (CAST). Phase I. Preliminary Design

    DTIC Science & Technology

    1977-05-01

    49 26 Assumed Crack Growth Rate -- A357 . . . . . . . . . .. 50 27 Flaw Growth at Hole of Gear Attachment Point .... .... 52 28 A357 S-N...wo TABLES Number ?Ile 1 Statistics on.16 Classes of A357 Aluminum Casting Data .. 14 2 "CAST" Preliminary Design Allowables .. .. .. ....... 20 3...damage tolerance criteria; development of preliminary design allowables data for A357 aluminum casting alloy to be used for design until completion

  16. Precipitation and Deposition of Aluminum-Containing Phases in Tank Wastes

    SciTech Connect

    Daniel M. Dabbs; Ilhan A. Aksay

    2005-01-12

    Aluminum-containing phases compose the bulk of solids precipitating during the processing of radioactive tank wastes. Processes designed to minimize the volume of high-level waste through conversion to glassy phases require transporting waste solutions near-saturated with aluminum-containing species from holding tank to processing center. The uncontrolled precipitation within transfer lines results in clogged pipes and lines and fouled ion exchangers, with the potential to shut down processing operations.

  17. Aqueous normal phase retention of nucleotides on silica hydride-based columns: method development strategies for analytes relevant in clinical analysis.

    PubMed

    Matyska, Maria T; Pesek, Joseph J; Duley, John; Zamzami, Mazin; Fischer, Steven M

    2010-03-01

    An aqueous normal phase HPLC method coupled with UV or ESI/MS detection was used for the determination of a wide variety of nucleotides, essential in metabolomics studies. Fifteen nucleotides were tested in clinically relevant mixtures at levels of 100 microg/mL for UV detection and 1 microg/mL for ESI-MS detection. Analysis times for all protocols developed were less than 20 min. The chromatographic conditions were changed to achieve optimized retention and separation of the nucleotides studied. The aqueous normal phase-HPLC methods were developed utilizing two columns, one having a minimally modified hydride surface another having an undecanoic acid moiety on a hydride surface. Volatile, low ionic strength mobile phases were used. Negative ion mode ESI-MS at near neutral pH mobile phase, combined with a TOF detector provided a highly sensitive and specific method, which is equally suitable for quadrupole and ion trap instruments.

  18. Hydride Generation for Headspace Solid-Phase Extraction with CdTe Quantum Dots Immobilized on Paper for Sensitive Visual Detection of Selenium.

    PubMed

    Huang, Ke; Xu, Kailai; Zhu, Wei; Yang, Lu; Hou, Xiandeng; Zheng, Chengbin

    2016-01-05

    A low-cost, simple, and highly selective analytical method was developed for sensitive visual detection of selenium in human urine both outdoors and at home, by coupling hydride generation with headspace solid-phase extraction using quantum dots (QDs) immobilized on paper. The visible fluorescence from the CdTe QDs immobilized on paper was quenched by H2Se from hydride generation reaction and headspace solid-phase extraction. The potential mechanism was investigated by using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) as well as Density Functional Theory (DFT). Potential interferences from coexisting ions, particularly Ag(+), Cu(2+), and Zn(2+), were eliminated. The selectivity was significantly increased because the selenium hydride was effectively separated from sample matrices by hydride generation. Moreover, due to the high sampling efficiency of hydride generation and headspace solid phase extraction, the sensitivity and the limit of detection (LOD) were significantly improved compared to conventional methods. A LOD of 0.1 μg L(-1) and a relative standard deviation (RSD, n = 7) of 2.4% at a concentration of 20 μg L(-1) were obtained when using a commercial spectrofluorometer as the detector. Furthermore, a visual assay based on the proposed method was developed for the detection of Se, 5 μg L(-1) of selenium in urine can be discriminated from the blank solution with the naked eye. The proposed method was validated by analysis of certified reference materials and human urine samples with satisfactory results.

  19. Hydride compositions

    DOEpatents

    Lee, Myung, W.

    1994-01-01

    Disclosed are a composition for use in storing hydrogen and a method for making the composition. The composition comprises a mixture of two or more hydrides, each hydride having a different series of hydrogen sorption isotherms that contribute to the overall isotherms of the mixture. The hydrides are chosen so that the isotherms of the mixture have regions wherein the H equilibrium pressure increases with increasing hydrogen, preferably linearly. The isotherms of the mixture can be adjusted by selecting hydrides with different isotherms and by varying the amounts of the individual hydrides, or both. Preferably, the mixture is made up of hydrides that have isotherms with substantially flat plateaus and in nearly equimolar amounts. The composition is activated by degassing, exposing to H, and then heating below the softening temperature of any of the constituents. When the composition is used to store hydrogen, its hydrogen content can be found simply by measuring P{sub H}{sub 2} and determining H/M from the isothermic function of the composition.

  20. Hydride compositions

    DOEpatents

    Lee, Myung W.

    1995-01-01

    A composition for use in storing hydrogen, and a method for making the composition. The composition comprises a mixture of two or more hydrides, each hydride having a different series of hydrogen sorption isotherms that contribute to the overall isotherms of the mixture. The hydrides are chosen so that the isotherms of the mixture have regions wherein the hydrogen equilibrium pressure increases with increasing hydrogen, preferably linearly. The isotherms of the mixture can be adjusted by selecting hydrides with different isotherms and by varying the amounts of the individual hydrides, or both. Preferably, the mixture is made up of hydrides that have isotherms with substantially flat plateaus and in nearly equimolar amounts. The composition is activated by degassing, exposing to hydrogen and then heating at a temperature below the softening temperature of any of the. constituents so that their chemical and structural integrity is preserved. When the composition is used to store hydrogen, its hydrogen content can be found simply by measuring P.sub.H.sbsb.2 and determining H/M from the isothermic function of the composition.

  1. Prediction of the zeta potentials and ionic descriptors of a silica hydride stationary phase with mobile phases of different pH and ionic strength.

    PubMed

    Kulsing, Chadin; Yang, Yuanzhong; Matyska, Maria T; Pesek, Joseph J; Boysen, Reinhard I; Hearn, Milton T W

    2015-02-15

    In this study, the zeta potentials of a silica hydride stationary phase (Diamond Hydride™) in the presence of different water-acetonitrile mixtures (from 0-80% (v/v) acetonitrile) of different ionic strengths (from 0-40mM) and pH values (from pH 3.0-7.0) have been investigated. Debye-Hückel theory was applied to explain the effect of changes in the pH and ionic strength of these aqueous media on the negative zeta potential of this stationary phase. The experimental zeta potentials of the Diamond Hydride™ particles as a function of acetonitrile content up to 50% (v/v) correlated (R(2)=0.998) with the predicted zeta potential values based on this established theory, when the values of the dissociation constant of all related species, as well as viscosity, dielectric constant and refractive index of the aqueous medium were taken into consideration. Further, the retention behavior of basic, acidic and neutral analytes was investigated under mobile phase conditions of higher pH and lower ionic strength. Under these conditions, the Diamond Hydride™ stationary phase surface became more negative, as assessed from the increasingly more negative zeta potentials, resulting in the ion exchange characteristics becoming more dominant and the basic analytes showing increasing retention. Ionic descriptors were derived from these chromatographic experiments based on the assumption that linear solvation energy relationships prevail. The results were compared with predicted ionic descriptors based on the different calculated zeta potential values resulting in an overall correlation of R(2)=0.888. These studies provide fundamental insights into the impact on the separation performance of changes in the zeta potential of the Diamond Hydride™ surface with the results relevant to other silica hydride and, potentially, to other types of stationary phase materials. Copyright © 2015. Published by Elsevier B.V.

  2. Comparision of succinate- and phthalate-functionalized etched silica hydride phases for open-tubular capillary electrochromatography.

    PubMed

    Chen, Jian-Lian

    2009-08-21

    Two open-tubular (OT) capillary electrochromatographic (CEC) columns were prepared by chemically bonding ionizable mono-(2-(methacryloyloxy)ethyl) succinate (MES) and phthalate-functionalized (MEP) ligands onto silica hydride-based phases through surface etching, silanization, and hydrosilation reactions, starting with a bare fused-silica tube. An analysis of the effect of performance of electrophoretic flow (EOF) on the changes in pH values, ionic strength, and the amount of acetonitrile modifiers helped to reveal that some silanol groups remained in the surface composite of the modified capillaries and to prove that MEP capillaries actually exerted greater EOF than MES ones. To explore the potential utilization of these two columns in various fields, three categories of samples, which spanned a wide range of polarities, were prepared and analyzed through many systematic trials of optimizing CEC conditions. For the separation of a mixture of nucleosides and thymine, guanine and adenine with purine uncleobases, which exhibit greater aromaticity than pyrimidine nucleobases, performed a higher retention in the MEP capillary through a pi-pi interaction than in the MES capillary. While four steroids were used as test samples, their migration order revealed that the MES stationary phase is hydrophilic in comparison with the MEP. An addition of methanol modifier (30%, v/v) into 10 mM borate buffer (pH 9.55 for MEP; pH 10.0 for MES) was necessary to accomplish a baseline separation of nine flavonoids in the MEP and MES capillaries. Studies on the elution order of these solutes revealed the presence of chromatographic activity in addition to electrophoretic migration. Especially in the MEP capillary, hydrophobic characteristics and pi-pi interactions with aromatic solutes were found and further improved to resolve an enantiomeric pair, catechin and epicatechin. Overall, the hydride-based stationary phases with ionizable ligands were successfully applied to the OT

  3. Upright and Inverted Single-Junction GaAs Solar Cells Grown by Hydride Vapor Phase Epitaxy

    DOE PAGES

    Simon, John; Schulte, Kevin L.; Jain, Nikhil; ...

    2016-10-19

    Hydride vapor phase epitaxy (HVPE) is a low-cost alternative to conventional metal-organic vapor phase epitaxy (MOVPE) growth of III-V solar cells. In this work, we show continued improvement of the performance of HVPE-grown single-junction GaAs solar cells. We show over an order of magnitude improvement in the interface recombination velocity between GaAs and GaInP layers through the elimination of growth interrupts, leading to increased short-circuit current density and open-circuit voltage compared with cells with interrupts. One-sun conversion efficiencies as high as 20.6% were achieved with this improved growth process. Solar cells grown in an inverted configuration that were removed frommore » the substrate showed nearly identical performance to on-wafer cells, demonstrating the viability of HVPE to be used together with conventional wafer reuse techniques for further cost reduction. As a result, these devices utilized multiple heterointerfaces, showing the potential of HVPE for the growth of complex and high-quality III-V devices.« less

  4. Upright and Inverted Single-Junction GaAs Solar Cells Grown by Hydride Vapor Phase Epitaxy

    SciTech Connect

    Simon, John; Schulte, Kevin L.; Jain, Nikhil; Johnston, Steve; Young, Michelle; Young, Matthew R.; Young, David L.; Ptak, Aaron J.

    2016-10-19

    Hydride vapor phase epitaxy (HVPE) is a low-cost alternative to conventional metal-organic vapor phase epitaxy (MOVPE) growth of III-V solar cells. In this work, we show continued improvement of the performance of HVPE-grown single-junction GaAs solar cells. We show over an order of magnitude improvement in the interface recombination velocity between GaAs and GaInP layers through the elimination of growth interrupts, leading to increased short-circuit current density and open-circuit voltage compared with cells with interrupts. One-sun conversion efficiencies as high as 20.6% were achieved with this improved growth process. Solar cells grown in an inverted configuration that were removed from the substrate showed nearly identical performance to on-wafer cells, demonstrating the viability of HVPE to be used together with conventional wafer reuse techniques for further cost reduction. As a result, these devices utilized multiple heterointerfaces, showing the potential of HVPE for the growth of complex and high-quality III-V devices.

  5. Investigation of cracks in GaN films grown by combined hydride and metal organic vapor-phase epitaxial method

    NASA Astrophysics Data System (ADS)

    Liu, Jianming; Liu, Xianlin; Li, Chengming; Wei, Hongyuan; Guo, Yan; Jiao, Chunmei; Li, Zhiwei; Xu, Xiaoqing; Song, Huaping; Yang, Shaoyan; Zhu, Qinsen; Wang, Zhanguo; Yang, Anli; Yang, Tieying; Wang, Huanhua

    2011-12-01

    Cracks appeared in GaN epitaxial layers which were grown by a novel method combining metal organic vapor-phase epitaxy (MOCVD) and hydride vapor-phase epitaxy (HVPE) in one chamber. The origin of cracks in a 22-μm thick GaN film was fully investigated by high-resolution X-ray diffraction (XRD), micro-Raman spectra, and scanning electron microscopy (SEM). Many cracks under the surface were first observed by SEM after etching for 10 min. By investigating the cross section of the sample with high-resolution micro-Raman spectra, the distribution of the stress along the depth was determined. From the interface of the film/substrate to the top surface of the film, several turnings were found. A large compressive stress existed at the interface. The stress went down as the detecting area was moved up from the interface to the overlayer, and it was maintained at a large value for a long depth area. Then it went down again, and it finally increased near the top surface. The cross-section of the film was observed after cleaving and etching for 2 min. It was found that the crystal quality of the healed part was nearly the same as the uncracked region. This indicated that cracking occurred in the growth, when the tensile stress accumulated and reached the critical value. Moreover, the cracks would heal because of high lateral growth rate.

  6. Numerical Simulation of Aluminum Dust Detonations with Different Product Phases

    NASA Astrophysics Data System (ADS)

    Teng, H. H.; Jiang, Z. L.

    Detonation waves are waves of supersonic combustion induced by strong coupling shock and heat release. Detonation research has attracted much attention in recent years owing to its potential applications in hypersonic propulsion. Aluminum (Al) particle detonation is a type of dust detonation, and its research is important in the prevention of industrial explosions. Al dust detonations for flake and spherical particles have been studied , which is found to be very sensitive to the specific area[1].

  7. Cast Aluminum Structures Technology (CAST) Phase VI. Technology Transfer.

    DTIC Science & Technology

    1980-04-01

    system and ultimately fill the mold cavity to produce a casting. The fluidity of a given metal is measured with standard fluidity test molds. One...showed that the pouring temperature for large, thin-wall aluminum castings must be (1) high enough to provide sufficient fluidity for complete filling of...castings should have the following specific characteristics: good flowability , permeability, tensile strength, and compressive strength; high hot

  8. Predicting impurity gases and phases during hydrogen evolution from complex metal hydrides using free energy minimization enabled by first-principles calculations.

    PubMed

    Kim, Ki Chul; Allendorf, Mark D; Stavila, Vitalie; Sholl, David S

    2010-09-07

    First-principles calculations represent a potent tool for screening metal hydride mixtures that can reversibly store hydrogen. A number of promising new hydride systems with high hydrogen capacity and favorable thermodynamics have been predicted this way. An important limitation of these studies, however, is the assumption that H(2) is the only gas-phase product of the reaction, which is not always the case. This paper summarizes new theoretical and numerical approaches that can be used to predict thermodynamic equilibria in complex metal hydride systems with competing reaction pathways. We report thermochemical equilibrium calculations using data obtained from density functional theory (DFT) computations to describe the possible occurrence of gas-phase products other than H(2) in three complex hydrides, LiNH(2), LiBH(4), and Mg(BH(4))(2), and mixtures of these with the destabilizing compounds LiH, MgH(2), and C. The systems under investigation contain N, C, and/or B and thus have the potential to evolve N(2), NH(3), hydrocarbons, and/or boranes as well as H(2). Equilibria as a function of both temperature and total pressure are predicted. The results indicate that significant amounts of these species can form under some conditions. In particular, the thermodynamic model predicts formation of N(2) and NH(3) as products of LiNH(2) decomposition. Comparison with published experimental data indicates that N(2) formation must be kinetically limited. Our examination of C-containing systems indicates that methane is the stable gas-phase species at low temperatures, not H(2). On the other hand, very low amounts of boranes (primarily BH(3)) are predicted to form in B-containing systems.

  9. Ar{sup +}-irradiation-induced damage in hydride vapor-phase epitaxy GaN films

    SciTech Connect

    Nakano, Yoshitaka Ogawa, Daisuke; Nakamura, Keiji; Kawakami, Retsuo; Niibe, Masahito

    2015-07-15

    The authors have investigated the electrical characteristics of hydride vapor-phase epitaxy GaN films exposed to Ar{sup +} irradiation, employing Schottky barrier diodes. The Ar{sup +} irradiation tends to largely increase the effective carrier concentration in the near surface region of GaN up to ∼25 nm, due to the generation of donor-type N vacancy defects, compared to the original value before the irradiation. More interestingly, acceptor-type deep-level defects are found to be formed at ∼2.1, ∼2.9, and ∼3.2 eV below the conduction band in the subsequently deeper region, in which Ga vacancies introduced by the Ar{sup +} irradiation are considered to be in-diffused and immediately combined with hydrogen. These N vacancies and hydrogenated Ga vacancies formed are dominantly responsible for changing the depth profiles of the effective carrier concentration via the carrier generation, the carrier trapping, and/or carrier compensation.

  10. Defect reduction of SiNx embedded m-plane GaN grown by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Woo, Seohwi; Kim, Minho; So, Byeongchan; Yoo, Geunho; Jang, Jongjin; Lee, Kyuseung; Nam, Okhyun

    2014-12-01

    Nonpolar (1 0 -1 0) m-plane GaN has been grown on m-plane sapphire substrates by hydride vapor phase epitaxy (HVPE). We studied the defect reduction of m-GaN with embedded SiNx interlayers deposited by ex-situ metal organic chemical vapor deposition (MOCVD). The full-width at half-maximum values of the X-ray rocking curves for m-GaN with embedded SiNx along [1 1 -2 0]GaN and [0 0 0 1]GaN were reduced to 528 and 1427 arcs, respectively, as compared with the respective values of 947 and 3170 arcs, of m-GaN without SiNx. Cross-section transmission electron microscopy revealed that the basal stacking fault density was decreased by approximately one order to 5×104 cm-1 due to the defect blocking of the embedded SiNx. As a result, the near band edge emission intensities of the room-temperature and low-temperature photoluminescence showed approximately two-fold and four-fold improvement, respectively.

  11. Defects responsible for lifetime degradation in electron irradiated n-GaN grown by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Lee, In-Hwan; Polyakov, A. Y.; Yakimov, E. B.; Smirnov, N. B.; Shchemerov, I. V.; Tarelkin, S. A.; Didenko, S. I.; Tapero, K. I.; Zinovyev, R. A.; Pearton, S. J.

    2017-03-01

    The effects of room temperature 6 MeV electron irradiation on the donor concentration, deep trap spectra, and diffusion lengths of nonequilibrium charge carriers were studied for undoped n-GaN grown by hydride vapor phase epitaxy. Changes in these parameters begin at a threshold electron fluence of 5 × 1015 cm-2. The diffusion lengths after this fluence decrease by a factor of 3, accompanied by a drastic increase in the density of deep electron traps with the level near Ec - 1 eV. There is a strong correlation between the changes in the density of these traps and the diffusion length of irradiated n-GaN, indicating that these centers control the lifetime in radiation damaged n-GaN. This is in sharp contrast to the starting material, where the lifetimes are controlled by other deep electron traps at Ec - 0.56 eV. The concentration of the latter is not strongly affected by high energy electron irradiation.

  12. Selective-area growth of GaN microrods on strain-induced templates by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Lekhal, Kaddour; Bae, Si-Young; Lee, Ho-Jun; Mitsunari, Tadashi; Tamura, Akira; Deki, Manato; Honda, Yoshio; Amano, Hiroshi

    2016-05-01

    In this paper, we discuss the influence of parameters such as type of carrier gas and NH3/HCl flow ratio on the growth of vertical GaN microstructures by selective-area growth (SAG) hydride vapor phase epitaxy (HVPE). On various strain-induced templates such as GaN/sapphire, GaN/Si, and AlN/Si, regular arrays of Ga-polar GaN microrods were properly achieved by adjusting the growth parameters. The photoluminescence and micro-Raman measurements reveal not only the crystal quality of the GaN microrods but also strain distribution. These results will give insight into the control of the morphology of GaN microrods in terms of the strain induced from templates in SAG-HVPE. The precisely controlled arrays of GaN microrods can be used for next-generation light-emitting diodes (LEDs) by realizing InGaN/GaN multi-quantum wells (MQWs) with a radial structure.

  13. Hydride development for hydrogen storage

    SciTech Connect

    Thomas, G.J.; Guthrie, S.E.; Bauer, W.; Yang, N.Y.C.; Sandrock, G.

    1996-10-01

    The purpose of this project is to develop and demonstrate improved hydride materials for hydrogen storage. The work currently is organized into four tasks: hydride development, bed fabrication, materials support for engineering systems, and IEA Annex 12 activities. At the present time, hydride development is focused on Mg alloys. These materials generally have higher weight densities for storing hydrogen than rare earth or transition metal alloys, but suffer from high operating temperatures, slow kinetic behavior and material stability. The authors approach is to study bulk alloy additions which increase equilibrium overpressure, in combination with stable surface alloy modification and particle size control to improve kinetic properties. This work attempts to build on the considerable previous research in this area, but examines specific alloy systems in greater detail, with attention to known phase properties and structures. The authors have found that specific phases can be produced which have significantly improved hydride properties compared to previous studies.

  14. Mineral phases and mobility of trace metals in white aluminum precipitates found in acid mine drainage.

    PubMed

    Kim, Yeongkyoo

    2015-01-01

    The white aluminum precipitates (S1,S2,S4-1,S4-2) collected at three different locations affected by acid mine and rock drainage were studied to characterize the mineral phases and mobility of trace metals. Chemical analysis, XRD, SEM, NMR, and sequential extraction method were mainly used. XRD data showed that most white aluminum precipitates are amorphous with small amount of gypsum, which was also confirmed by SEM. The (27)Al MAS NMR spectra provide more detailed information on the local environments of aluminum in those samples. The samples collected at two locations (S3, and S4-1 and S4-2) contain 4-coordinated aluminum, suggesting that the samples contain a significant amount of amorphous phase from Al13-tridecamer. Chemical data of calcium and sulfur with (27)Al MAS NMR spectra suggest that the relative amounts of amorphous phase from Al13-tridecamer, hydrobasaluminite, aluminum hydroxide, and gypsum are different for each sample. Different amount of amorphous phase from Al13-tridecamer in those samples are probably caused by the different geochemical conditions and hydrolysis by aging in water. Sequential extraction results show that water soluble fraction and sorbed and exchangeable fraction of trace metals in sample collected as suspended particles (S1) are higher than other samples, and can affect the ecological system in waters by releasing aluminum and trace metals. These results suggest that careful characterization of white aluminum precipitates is needed to estimate the environmental effects of those precipitates in acid mine drainage. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Effective Thermal Conductivity of an Aluminum Foam + Water Two Phase System

    NASA Technical Reports Server (NTRS)

    Moskito, John

    1996-01-01

    This study examined the effect of volume fraction and pore size on the effective thermal conductivity of an aluminum foam and water system. Nine specimens of aluminum foam representing a matrix of three volume fractions (4-8% by vol.) and three pore sizes (2-4 mm) were tested with water to determine relationships to the effective thermal conductivity. It was determined that increases in volume fraction of the aluminum phase were correlated to increases in the effective thermal conductivity. It was not statistically possible to prove that changes in pore size of the aluminum foam correlated to changes in the effective thermal conductivity. However, interaction effects between the volume fraction and pore size of the foam were statistically significant. Ten theoretical models were selected from the published literature to compare against the experimental data. Models by Asaad, Hadley, and de Vries provided effective thermal conductivity predictions within a 95% confidence interval.

  16. [Determination of Arsenic in Food Package Aluminum by Ultrasound Assisted Solid Phase Extraction/ICP-AES].

    PubMed

    Qin, Wen-xia; Gong, Qi; Li, Min; Deng, Li-xin; Mo, Li-shu; Li, Yan-lin

    2015-04-01

    Determination of arsenic in pure aluminum by inductively coupled plasma atomic emission spectrometry was interfered by aluminum matrix. The experiment showed that when the mass concentration of Al was greater than or equal to 5 000 times the As in the test solution, the measurement error was greater than 5%. In order to eliminate the interference, strong acid cation exchange fiber (SACEF) was used as solid phase extraction agent to adsorb Al(3+). The extraction conditions included amount of SACEF, extraction time, temperature and pH were investigated. The optimal extraction conditions were that 0.9000 g SACEF was used to extract the aluminum from the sample solution of pH 2.0 at 55 °C for 5 min with the ultrasonic assist, and in this case, the arsenic in the form of arsenic acid was not extracted and left in the solution for the determination. The results showed that after treating 10. 00 mL test solution containing 1.00 µg arsenic and 20.0 mg aluminum, arsenic did not lose. The mass concentration of residual aluminum in the raffinate was about 2,000 times the As, which had not interfered the determination of arsenic. The detection limit (3 s) was 0.027 µg · mL(-1) and quantification limit (10 s) was 0.0091 µg · mL(-1). The proposed method was successfully applied to the separation and determination of arsenic in the synthetic samples, the aluminum cans and the barbecue aluminum foil. Recovery was in the range of 98.3%-105% and RSD (n = 3) was in the range of 0.1%-4.3%. The results showed that the content of arsenic in the aluminum cans and the aluminum barbecue foil was below the limited value of national standard (GB/T 3190-2008).

  17. Structural phase stability, electronic structure and mechanical properties of alkali metal hydrides AMH4 (A=Li, Na; M=B, AL)

    NASA Astrophysics Data System (ADS)

    Santhosh, M.; Rajeswarapalanichamy, R.

    2016-01-01

    The structural stability of Alkali metal hydrides AMH4 (A=Li, Na; M=B, Al) is analyzed among the various crystal structures, namely hexagonal (P63mc), tetragonal (P42/nmc), tetragonal (P-421c), tetragonal (I41/a), orthorhombic (Pnma) and monoclinic (P21/c). It is observed that, orthorhombic (Pnma) phase is the most stable structure for LiBH4, monoclinic (P21/c) for LiAlH4, tetragonal (P42/nmc) for NaBH4 and tetragonal (I41/a) for NaAlH4 at normal pressure. Pressure induced structural phase transitions are observed in LiBH4, LiAlH4, NaBH4 and NaAlH4 at the pressures of 4 GPa, 36.1 GPa, 26.5 GPa and 46 GPa respectively. The electronic structure reveals that these metal hydrides are wide band gap insulators. The calculated elastic constants indicate that these metal hydrides are mechanically stable at normal pressure.

  18. A model for arsenic anti-site incorporation in GaAs grown by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Schulte, K. L.; Kuech, T. F.

    2014-12-01

    GaAs growth by hydride vapor phase epitaxy (HVPE) has regained interest as a potential route to low cost, high efficiency thin film photovoltaics. In order to attain the highest efficiencies, deep level defect incorporation in these materials must be understood and controlled. The arsenic anti-site defect, AsGa or EL2, is the predominant deep level defect in HVPE-grown GaAs. In the present study, the relationships between HVPE growth conditions and incorporation of EL2 in GaAs epilayers were determined. Epitaxial n-GaAs layers were grown under a wide range of deposition temperatures (TD) and gallium chloride partial pressures (PGaCl), and the EL2 concentration, [EL2], was determined by deep level transient spectroscopy. [EL2] agreed with equilibrium thermodynamic predictions in layers grown under conditions in which the growth rate, RG, was controlled by conditions near thermodynamic equilibrium. [EL2] fell below equilibrium levels when RG was controlled by surface kinetic processes, with the disparity increasing as RG decreased. The surface chemical composition during growth was determined to have a strong influence on EL2 incorporation. Under thermodynamically limited growth conditions, e.g., high TD and/or low PGaCl, the surface vacancy concentration was high and the bulk crystal was close to equilibrium with the vapor phase. Under kinetically limited growth conditions, e.g., low TD and/or high PGaCl, the surface attained a high GaCl coverage, blocking As adsorption. This competitive adsorption process reduced the growth rate and also limited the amount of arsenic that incorporated as AsGa. A defect incorporation model which accounted for the surface concentration of arsenic as a function of the growth conditions, was developed. This model was used to identify optimal growth parameters for the growth of thin films for photovoltaics, conditions in which a high growth rate and low [EL2] could be attained.

  19. Superconductivity in metastable phases of phosphorus-hydride compounds under high pressure

    NASA Astrophysics Data System (ADS)

    Flores Livas, Jose; Amsler, Maximilian; Sanna, Antonio; Heil, Christoph; Boeri, Lilia; Profeta, Gianni; Wolverton, Crhis; Goedecker, Stefan; Gross, E. K. U.

    Recently, compressed phosphine was reported to metallize at pressures above 45 GPa, reaching a superconducting transition temperature (Tc) of 100 K at 200 GPa. However, neither the exact composition nor the crystal structure of the superconducting phase have been conclusively determined. In this work the phase diagram of PHn (n = 1 , 2 , 3 , 4 , 5 , 6) was extensively explored by means of ab initio crystal structure prediction methods. The results do not support the existence of thermodynamically stable PHn compounds, which exhibit a tendency for elemental decomposition at high pressure even when vibrational contributions to the free energies are taken into account. Although the lowest energy phases of PH1 , 2 , 3 display Tc's comparable to experiments, it remains questionable if the measured values of Tc can be fully attributed to a phase-pure compound of PHn. This work was done within the NCCR MARVEL project.

  20. Metal Hydride Heat Storage Technology for Directed Energy Weapon Systems

    DTIC Science & Technology

    2007-11-16

    over time after the pulse operation. A compressor -driven metal hydride heat storage system was developed for efficient, compact heat storage and...principle and heat storage performance results of the compressor -driven metal hydride heat storage system through system modeling and prototype testing. The...hyd/m³] Subscripts A Metal hydride reactor B Hydrogen container C Hydrogen compressor s Hydrogen solid phase in hydride f Hydrogen fluid phase

  1. Silica, hybrid silica, hydride silica and non-silica stationary phases for liquid chromatography.

    PubMed

    Borges, Endler M

    2015-04-01

    Free silanols on the surface of silica are the "villains", which are responsible for detrimental interactions of those compounds and the stationary phase (i.e., bad peak shape, low efficiency) as well as low thermal and chemical stability. For these reasons, we began this review describing new silica and hybrid silica stationary phases, which have reduced and/or shielded silanols. At present, in liquid chromatography for the majority of analyses, reversed-phase liquid chromatography is the separation mode of choice. However, the needs for increased selectivity and increased retention of hydrophilic bases have substantially increased the interest in hydrophilic interaction chromatography (HILIC). Therefore, stationary phases and this mode of separation are discussed. Then, non-silica stationary phases (i.e., zirconium oxide, titanium oxide, alumina and porous graphitized carbon), which afford increased thermal and chemical stability and also selectivity different from those obtained with silica and hybrid silica, are discussed. In addition, the use of these materials in HILIC is also reviewed. © Crown copyright 2014.

  2. Dislocations limited electronic transport in hydride vapour phase epitaxy grown GaN templates: A word of caution for the epitaxial growers

    SciTech Connect

    Chatterjee, Abhishek Khamari, Shailesh K.; Kumar, R.; Dixit, V. K.; Oak, S. M.; Sharma, T. K.

    2015-01-12

    GaN templates grown by hydride vapour phase epitaxy (HVPE) and metal organic vapour phase epitaxy (MOVPE) techniques are compared through electronic transport measurements. Carrier concentration measured by Hall technique is about two orders larger than the values estimated by capacitance voltage method for HVPE templates. It is learnt that there exists a critical thickness of HVPE templates below which the transport properties of epitaxial layers grown on top of them are going to be severely limited by the density of charged dislocations lying at layer-substrate interface. On the contrary MOVPE grown templates are found to be free from such limitations.

  3. Synthesis and HPLC evaluation of carboxylic acid phases on a hydride surface.

    PubMed

    Pesek, Joseph J; Matyska, Maria T; Gangakhedkar, Surekha; Siddiq, Rukhsana

    2006-04-01

    Three organic moieties containing carboxylic acid functional groups are attached to a particulate silica surface through silanization/hydrosilation. Two compounds (undecylenic acid and 10-undecynoic acid) have 11 carbon chains and the other is a five-carbon acid (pentenoic acid). Bonding is confirmed through carbon elemental analysis, diffuse reflectance infrared fourier transform spectroscopy, and carbon-13 and silicon-29 CP-MAS NMR spectroscopy. The bonded phases are tested by HPLC using PTH amino acids, nucleic acids, theophylline-related compounds, anilines, benzoic acid compounds, choline, and tobramycin. The latter two compounds are used to investigate the aqueous normal phase properties of the three bonded materials.

  4. First-principles studies of phase stability and the structural and dynamical properties of metal hydrides

    SciTech Connect

    Chou, M.Y.

    1992-04-01

    This report discusses the following topics: calculation of the Structural Properties of Yttrium; dynamical and pairing properties of {alpha}-YH{chi}; electronic and structural properties of YH{sub 2} and YH{sub 3}; phase diagram of hydrogen on Ru(000); peierls distortion in hexagonal YH{sub 3}; and study of hydrogen in niobium and palladium.

  5. Microstructure of surface cerium hydride growth sites

    SciTech Connect

    Brierley, Martin; Knowles, John; Montgomery, Neil; Preuss, Michael

    2014-05-15

    Samples of cerium were exposed to hydrogen under controlled conditions causing cerium hydride sites to nucleate and grow on the surface. The hydriding rate was measured in situ, and the hydrides were characterised using secondary ion mass spectrometry, scanning electron microscopy, and optical microscopy. The results show that the hydriding rate proceeded more quickly than earlier studies. Characterisation confirmed that the hydrogen is confined to the sites. The morphology of the hydrides was confirmed to be oblate, and stressed material was observed surrounding the hydride, in a number of cases lathlike features were observed surrounding the hydride sites laterally with cracking in the surface oxide above them. It is proposed that during growth the increased lattice parameter of the CeH{sub 2} induces a lateral compressive stress around the hydride, which relieves by the ca. 16% volume collapse of the γ-Ce to α-Ce pressure induced phase transition. Cracking of the surface oxide above the laths reduces the diffusion barrier to hydrogen reaching the metal/oxide interface surrounding the hydride site and contributes to the anisotropic growth of the hydrides.

  6. Mineral phases and metals in baghouse dust from secondary aluminum production

    EPA Science Inventory

    Baghouse dust (BHD) is a solid waste generated by air pollution control systems during secondary aluminum processing (SAP). Management and disposal of BHD can be challenging in the U.S. and elsewhere. In this study, the mineral phases, metal content and metal leachability of 78...

  7. Planar gas chromatography column on aluminum plate with multi-walled carbon nanotubes as stationary phase

    NASA Astrophysics Data System (ADS)

    Platonov, I. A.; Platonov, V. I.; Pavelyev, V. S.

    2016-04-01

    The high selectivity of the adsorption layer for low-boiling alkanes is shown, the separation factor (α) couple iso-butane / butane is 1.9 at a column temperature of 50 °C.The paper presents sorption and selective properties of planar gas chromatography column on aluminum plate with multi-walled carbon nanotubes as the stationary phase.

  8. Mineral phases and metals in baghouse dust from secondary aluminum production

    EPA Science Inventory

    Baghouse dust (BHD) is a solid waste generated by air pollution control systems during secondary aluminum processing (SAP). Management and disposal of BHD can be challenging in the U.S. and elsewhere. In this study, the mineral phases, metal content and metal leachability of 78...

  9. Kinetics of hydride front in Zircaloy-2 and H release from a fractional hydrided surface

    SciTech Connect

    Diaz, M.; Gonzalez-Gonzalez, A.; Moya, J. S.; Remartinez, B.; Perez, S.; Sacedon, J. L.

    2009-07-15

    The authors study the hydriding process on commercial nuclear fuel claddings from their inner surface using an ultrahigh vacuum method. The method allows determining the incubation and failure times of the fuel claddings, as well as the dissipated energy and the partial pressure of the desorbed H{sub 2} from the outer surface of fuel claddings during the hydriding process. The correlation between the hydriding dissipated energy and the amount of zirconium hydride (formed at different stages of the hydriding process) leads to a near t{sup 1/2} potential law corresponding to the time scaling of the reaction for the majority of the tested samples. The calibrated relation between energy and hydride thickness allows one to calculate the enthalpy of the {delta}-ZrH{sub 1.5} phase. The measured H{sub 2} desorption from the external surface is in agreement with a proposed kinetic desorption model from the hydrides precipitated at the surface.

  10. Transfer of Amide and 2-Methoxyethoxy Groups and Sodium Encapsulation in the Reaction of TaCl3[N(TMS)2]2 with Sodium Bis(2-methoxyethoxy)aluminum Hydride: X-ray Structure of [NaAl{N(TMS)2}(OCH2CH2OMe)3]2

    SciTech Connect

    Huang, Shih-Huang Huang; Wang, Xiaoping; Richmond, Michael G.

    2009-01-01

    The reaction between the tantalum compound TaCl3[N(TMS)2]2 and the hydridic reducing agent sodium bis(2-methoxyethoxy)aluminum hydride (Vitride) has been investigated in toluene solution at room temperature and found to afford the dimeric aluminate complex [NaAl{N(TMS)2}(OCH2CH2OMe)3]2 as the sole isolable product. The molecular structure of the product establishes the existence of a four-coordinate aluminum atom and the formal transfer of the 2-methoxyethoxy and bis(trimethylsilyl)amide groups to the aluminate product. The aggregation of two NaAl{N(TMS)2}(OCH2CH2OMe)3 units serves to bind the two sodium cations in a crown-ether fashion through six ancillary oxygen atoms.

  11. PHASE ANALYSIS AND CRYSTAL STRUCTURE STUDIES ON BINARY ALLOYS OF ALUMINUM WITH TRANSITION METALS.

    DTIC Science & Technology

    In order to provide the necessary background for detailed crystal-chemistry studies in the field of binary aluminum - transition metal systems, extensive investigations have been carried out on the phase relations of a large number of such systems. The results of these studies are briefly summarized, as are also the results of crystal structure determinations of a few alumi num - transition metal phases. (Author)

  12. Ni/metal hydride secondary element

    DOEpatents

    Bauerlein, Peter

    2005-04-19

    A Ni/metal hydride secondary element having a positive nickel hydroxide electrode, a negative electrode having a hydrogen storage alloy, and an alkaline electrolyte, the positive electrode, provided with a three-dimensional metallic conductive structure, also contains an aluminum compound which is soluble in the electrolyte, in addition to nickel hydroxide and cobalt oxide. The aluminum compound is aluminum hydroxide and/or aluminum oxide, and the mass of the aluminum compound which is present in the positive bulk material mixture is 0.1 to 2% by weight relative to the mass of the nickel hydroxide which is present. In combination with aluminum hydroxide or aluminum oxide, the positive electrode further contains lanthanoid oxidic compounds Y.sub.2 O.sub.3, La.sub.2 O.sub.3 and Ca(OH).sub.2, as well as mixtures of these compounds.

  13. LiCa₃As₂H and Ca₁₄As₆X₇ (X = C, H, N): two new arsenide hydride phases grown from Ca/Li metal flux.

    PubMed

    Blankenship, Trevor V; Wang, Xiaoping; Hoffmann, Christina; Latturner, Susan E

    2014-10-06

    The reaction of arsenic with sources of light elements in a Ca/Li melt leads to the formation of two new arsenide hydride phases. The predominant phase Ca14As6X7 (X = C(4-), N(3-), H(-)) exhibits a new tetragonal structure type in the space group P4/mbm (a = 15.749(1) Å, c = 9.1062(9) Å, Z = 4, R1 = 0.0150). The minor phase LiCa3As2H also has a new structure type in the orthorhombic space group Pnma (a = 11.4064(7) Å, b = 4.2702(3) Å, c = 11.8762(8)Å, Z = 4, R1 = 0.0135). Both phases feature hydride and arsenide anions separated by calcium cations. The red color of these compounds indicates they should be charge-balanced. DOS calculations on LiCa3As2H confirm a band gap of 1.4 eV; UV-vis spectroscopy on Ca14As6X7 shows a band gap of 1.6 eV. Single-crystal neutron diffraction studies were necessary to determine the mixed occupancy of carbon, nitrogen, and hydrogen anions on the six light-element sites in Ca14As6X7; these data indicated an overall stoichiometry of Ca14As6C(0.445)N(1.135)H(4.915).

  14. Interferometric phase measurement of zerodur, aluminum and SXA mirrors at cryogenic temperatures

    NASA Technical Reports Server (NTRS)

    Magner, Thomas J.; Barney, Richard D.

    1988-01-01

    A research program was undertaken to determine the surface figure error of several different types of mirrors at cryogenic temperatures. Two-inch diameter parabolic, spherical and flat mirrors were fabricated from zerodur, aluminum and a metal matrix composite of silicon carbide reinforced aluminum (SXA). The ratio of silicon carbide to aluminum was selected so that the coefficient of thermal expansion (CTE) of the metal matrix matched electroless nickel. A liquuid helium dewar was modified to add an interferometric grade window, a cold electronic shutter and a strain-free copper mirror mount. Interferometric phase measurements on each mirror mounted in the dewar were made without the window, with the window, under vacuum, at around 80K and between 10K and 24K.

  15. Interferometric phase measurement of zerodur, aluminum and SXA mirrors at cryogenic temperatures

    NASA Technical Reports Server (NTRS)

    Magner, Thomas J.; Barney, Richard D.

    1988-01-01

    A research program was undertaken to determine the surface figure error of several different types of mirrors at cryogenic temperatures. Two-inch diameter parabolic, spherical and flat mirrors were fabricated from zerodur, aluminum and a metal matrix composite of silicon carbide reinforced aluminum (SXA). The ratio of silicon carbide to aluminum was selected so that the coefficient of thermal expansion (CTE) of the metal matrix matched electroless nickel. A liquuid helium dewar was modified to add an interferometric grade window, a cold electronic shutter and a strain-free copper mirror mount. Interferometric phase measurements on each mirror mounted in the dewar were made without the window, with the window, under vacuum, at around 80K and between 10K and 24K.

  16. A model for arsenic anti-site incorporation in GaAs grown by hydride vapor phase epitaxy

    SciTech Connect

    Schulte, K. L.; Kuech, T. F.

    2014-12-28

    GaAs growth by hydride vapor phase epitaxy (HVPE) has regained interest as a potential route to low cost, high efficiency thin film photovoltaics. In order to attain the highest efficiencies, deep level defect incorporation in these materials must be understood and controlled. The arsenic anti-site defect, As{sub Ga} or EL2, is the predominant deep level defect in HVPE-grown GaAs. In the present study, the relationships between HVPE growth conditions and incorporation of EL2 in GaAs epilayers were determined. Epitaxial n-GaAs layers were grown under a wide range of deposition temperatures (T{sub D}) and gallium chloride partial pressures (P{sub GaCl}), and the EL2 concentration, [EL2], was determined by deep level transient spectroscopy. [EL2] agreed with equilibrium thermodynamic predictions in layers grown under conditions in which the growth rate, R{sub G}, was controlled by conditions near thermodynamic equilibrium. [EL2] fell below equilibrium levels when R{sub G} was controlled by surface kinetic processes, with the disparity increasing as R{sub G} decreased. The surface chemical composition during growth was determined to have a strong influence on EL2 incorporation. Under thermodynamically limited growth conditions, e.g., high T{sub D} and/or low P{sub GaCl}, the surface vacancy concentration was high and the bulk crystal was close to equilibrium with the vapor phase. Under kinetically limited growth conditions, e.g., low T{sub D} and/or high P{sub GaCl}, the surface attained a high GaCl coverage, blocking As adsorption. This competitive adsorption process reduced the growth rate and also limited the amount of arsenic that incorporated as As{sub Ga}. A defect incorporation model which accounted for the surface concentration of arsenic as a function of the growth conditions, was developed. This model was used to identify optimal growth parameters for the growth of thin films for photovoltaics, conditions in which a high growth rate and low [EL2] could be

  17. Pressureless Reaction Sintering of AlON using Aluminum Orthophosphate as a Transient Liquid Phase

    SciTech Connect

    Michael Bakas; Henry Chu

    2009-01-01

    Use of aluminum oxynitride (AlON) in transparent armor systems has been difficult due to the expense and limitations of the processing methods currently necessary to achieve transparency. Development of a pressureless processing method based on direct reaction sintering of alumina and aluminum nitride powders would reduce costs and provide a more flexible and practical manufacturing method. It may be possible to develop such a processing method using liquid phase sintering; as long as the liquid phase does not remain in the final sample. AlPO4 forms a liquid phase with Al2O3 and AlN at the temperatures required to sinter AlON, and slowly decomposes into P2O5 and alumina. Therefore, it was investigated as a possible transient liquid phase for reaction-sintered AlON. Small compacts of alumina and aluminum nitride with up to of 15wt% AlPO4 additive were pressed and sintered. It was found that AlPO4 formed the requisite transient liquid phase, and it was possible to adjust the process to produce AlON samples with good transmission and densities of 3.66-3.67 g/cc. XRD confirmed the samples formed were AlON, with no trace of any remaining phosphate phases or excess alumina or aluminum nitride. Based on the results, it was concluded that AlPO4 could be utilized as a transient liquid phase to improve the density and transmission of AlON produced by pressureless reaction sintering.

  18. Mineral phases and metals in baghouse dust from secondary aluminum production.

    PubMed

    Huang, Xiao-Lan; El Badawy, Amro M; Arambewela, Mahendranath; Adkins, Renata; Tolaymat, Thabet

    2015-09-01

    Baghouse dust (BHD) is a solid waste generated by air pollution control systems during secondary aluminum processing (SAP). Management and disposal of BHD can be challenging in the U.S. and elsewhere. In this study, the mineral phases, metal content and metal leachability of 78 BHD samples collected from 13 different SAP facilities across the U.S. were investigated. The XRD semi-quantitative analysis of BHD samples suggests the presence of metallic aluminum, aluminum oxide, aluminum nitride and its oxides, spinel, elpasolite as well as diaspora. BHD also contains halite, sylvite and fluorite, which are used as fluxes in SAP activities. Total aluminum (Al) in the BHD samples averaged 18% by weight. Elevated concentrations of trace metals (>100 μg L(-1) As; >1000 μg L(-1) Cu, Mn, Se, Pb, Mn and Zn) were also detected in the leachate. The U.S. toxicity characteristic leaching procedure (TCLP) results showed that some samples leached above the toxicity limit for Cd, Pb and Se. Exceeding the TCLP limits in all sample is independent of facilities generating the BHD. From the metal content perspective only, it appears that BHD has a higher potential to exhibit toxicity characteristics than salt cake (the largest waste stream generated by SAP facilities). Published by Elsevier Ltd.

  19. Phase transformations and thermodynamics of aluminum-based metallic glasses

    NASA Astrophysics Data System (ADS)

    Gao, Changhua (Michael)

    This thesis examines the thermodynamics and associated kinetics and phase transformations of the glass forming Al-Ni-Gd and Al-Fe-Gd systems. In order to fully understand the unique glass forming ability (GFA) of Al-based metallic glasses, the ternary Al-Fe-Gd and Al-Ni-Gd systems in their Al-rich corners were examined experimentally to assist in a thermodynamic assessment. The solid-state phase equilibria are determined using XRD and TEM-EDS techniques. While this work basically confirms the solid-state equilibria in Al-Fe-Gd reported previously, the ternary phase in Al-Ni-Gd system has been identified to be Al15Ni3Gd2 rather than Al16Ni 3Gd reported in the literature. DTA analysis of 24 alloys in the Al-Fe-Gd system and 42 alloys in the Al-Ni-Gd system have yielded critical temperatures pertaining to the solid-liquid transition. Based on these data and information from the literature, a self-consistent thermodynamic database for these systems has been developed using the CALPHAD technique. Parameters describing the Gibbs free energy for various phases of the Al-Gd, Al-Fe-Gd and Al-Ni-Gd systems are manually optimized in this study. Once constructed, the database is used to calculate driving forces for nucleation of crystalline phases which can qualitatively explain the phase formation sequence during crystallization at low temperatures. It was also confirmed that alloy compositions with the lowest Gibbs free energy difference between the equilibrium state and undercooled liquid state exhibit better GFA than other chemistries. Based on 250°C isothermal devitrification phase transformations of 17 Al-Ni-Gd alloys, a phase formation sequence map is constructed. Fcc-Al nanocrystals are formed first in most of the alloys studied, but eutectic crystallization of a metastable phase and fcc-Al is also observed. Addition of Al or Ni promotes fcc-Al phase formation, while increasing Gd suppresses it. The continuous heating DSC scans revealed that crystallization in Al

  20. Densities, Electrical Conductivities, Viscosities and Phase Equilibria of 1,3-Dialkylimidazolium Chloride - Aluminum Chloride Binary and Ternary Melts.

    DTIC Science & Technology

    1982-07-01

    FRANK J. SELLER RESEARCH LABORATORY FJSRL-TR-82-0006 JULY 1982 DENSITIES, ELEC’TRICAL CONDUCTIVITIES, VISCOSITIES AND PHASE EQUILIBRIA OF 1,3...Conductivities, Viscosities and Phase Equilibria of 1,3- Interim 6/81-7/82 Dialkylimidazolium Chloride-Aluminum Chloride 6. PERFORMING ORG. REPORT NUMBER...Entered) FJSRL-TR-82-0006 DENSITIES, ELECTRICAL CONDUCTIVITIES, VISCOSITIES AND PHASE EQUILIBRIA OF 1,3-DIALKYLIMIDAZOLIUM CHLORIDE- ALUMINUM CHLORIDE

  1. Comparison of the performance of different silica hydride particles for the solid-phase extraction of non-volatile analytes from dark chocolate with analysis by gas chromatography-quadrupole mass spectrometry.

    PubMed

    Nolvachai, Yada; Kulsing, Chadin; Boysen, Reinhard I; Matyska, Maria T; Pesek, Joseph J; Marriott, Philip J; Hearn, Milton T W

    2015-05-01

    The extraction capabilities of a Diamond Hydride™ phase, as well as silica hydride phases modified with bidentate octadecyl (BDC(18)), phenyl or cholesteryl groups, were evaluated for the analysis of fatty acids, amino acids, sugars and sterols in a dark chocolate extract. These batch adsorption performances were investigated using either methanol or aqueous methanol as the solvent. The compositions of the extracted fractions were assessed by gas chromatography interfaced with quadrupole mass spectrometry (GC-qMS). The batch binding propensities of the various compound classes with silica hydride particles modified with immobilised phenyl groups or larger ligands followed trends predicted from linear solvation energy relationships. Both prediction and experiment revealed that better extraction results could be obtained with the phenyl, BDC(18) and cholesteryl hydride particles for the major chocolate components. Based on these results, separations in micro-pipette tip format with these three types of stationary phase particles have been undertaken.

  2. Structure and morphology of S-phase precipitates in aluminum

    SciTech Connect

    Radmilovic, V.; Kilaas, R.; Dahmen, U.; Shiflet, G.J.

    1999-11-12

    This work presents a crystallographic and morphological analysis of S-phase precipitation in Al alloys. Using quantitative high resolution electron microscopy, four models for the crystal structure of the S-phase (Al{sub 2}CuMg) in Al-based alloys are critically evaluated, and a new model is proposed. This model is identical to that of Perlitz and Westgren, but with an exchange of Cu and Mg. Two distinct precipitate morphologies are observed. Both are laths elongated along {l{underscore}angle}100{r{underscore}angle} directions common to the matrix and the precipitate and lie on {l{underscore}brace}021{r{underscore}brace} planes of the matrix. Type 1 precipitates have interfaces of the type (021){sub Al}{parallel}(001){sub S} while type 2 precipitates have interfaces of the type (021){sub Al}{parallel}(0.43){sub S}, i.e., the two types differ in the S-phase lattice plane that is conjugate to the {l{underscore}brace}021{r{underscore}brace}{sub Al} habit plane. The interface plane of type 1 precipitates tends to be atomically flat containing only growth ledges while that of type 2 precipitates is stepped. The orientation relationship of the two types of precipitate differs by a rotation of about 5{degree} around the lath axis. The difference between the two types of precipitate is discussed in terms of their lattice correspondence, and type 2 precipitates are shown to follow an invariant line strain. Moire analysis of lattice distortions revealed that {l{underscore}brace}020{r{underscore}brace}{sub Al} planes remain undistorted while {l{underscore}brace}002{r{underscore}brace}{sub Al} planes suffer significant shear during S-phase nucleation.

  3. Solid phosphorus phase in aluminum- and iron-treated biosolids.

    PubMed

    Huang, Xiao-Lan; Chen, Yona; Shenker, Moshe

    2007-01-01

    Stabilization of phosphorus (P) in sewage sludge (biosolids) to reduce water-soluble P concentrations is essential for minimizing P loss from amended soils and maximizing the capacity of the soil to safely serve as an outlet for this waste material. The chemical form at which P is retained in biosolids stabilized by Al(2)(SO(4))(3) x 18H(2)O (alum) or FeSO(4) x 7H(2)O (FeSul) was investigated by scanning electron microscopy (SEM) equipped with energy-dispersive X-ray elemental spectrometry (EDXS) and by X-ray diffraction (XRD). Both treatments resulted in the formation of a Ca-P phase, probably brushite. Phosphorus was further retained in the alum-treated biosolids by precipitation of an Al-P phase with an Al/P molar ratio of about 1:1, while in the FeSul-treated biosolids, P was retained by both precipitation with Fe/P molar ratios of 1:1 or 1.5:1, and by adsorption onto newly formed Fe hydroxides exhibiting an Fe/P molar ratio of up to 11:1. All of these mechanisms efficiently reduced P solubility and are crucial in biosolids environmentally safe agronomic beneficial use for this waste product; however, each P phase formed may react differently in the amended soil, depending on soil properties. Thus, the proper P stabilization method would depend on the target soil.

  4. Analysis of hydrophilic metabolites by high-performance liquid chromatography-mass spectrometry using a silica hydride-based stationary phase.

    PubMed

    Pesek, Joseph J; Matyska, Maria T; Fischer, Steven M; Sana, Theodore R

    2008-09-12

    A novel silica hydride-based stationary phase was used to evaluate the retention behavior in the aqueous normal-phase (ANP) mode of standards representing three classes of metabolites. The effects on retention behavior of amino acids, carbohydrates and small organic acids were examined by altering the column temperature, and by adding different additives to both the mobile phase and sample solvent. Gradient mode results revealed the repeatability of retention times to be very stable for these compound classes. At both 15 and 30 degrees C, excellent RSD values were obtained with less than 1% variation for over 50 injections of an amino acid mixture. The ability to separate the 19 nonderivatized amino acid standards, organic acids and carbohydrates was demonstrated as well as the potential for this material to separate polar metabolites in complex fluids such as urine.

  5. Simulation of the chromatographic separation process in HPLC employing suspended-state NMR spectroscopy - comparison of interaction behavior for monomeric and hydride-modified C18 stationary phases.

    PubMed

    Yeman, Helen; Nicholson, Tim; Matyska, Maria T; Pesek, Joseph J; Albert, Klaus

    2013-01-01

    The interactions of different analytes with monomeric and hydride-modified stationary phases have been investigated employing suspended-state NMR spectroscopy. The suspended-state high-resolution/magic-angle-spinning (1)H-NMR spectrum of an analyte in the presence of C(18) SP material shows a splitting into two sets of signals for the analyte molecule. One state reflects a closer interaction between analyte and C(18) -modified surface that results in an upfield shift and broader signal half-widths. This phenomenon suggests that the analyte exists in two environments. We report a systematic approach upon the investigation on the interaction in the interface of analyte, mobile phase, and modified silica through synthesis of differently modified silica with a gradual increase in surface coverage. The determination of the signal half-widths and chemical shifts revealed a relationship between the modification technique of the C(18) SPs and the chromatographic and NMR spectroscopic behavior. Increasing ligand density results in higher shielding of the NMR signals for the analyte in the "adsorbed" state. The measurement of spin-lattice relaxation times T(1) of the analyte molecule correlate NMR parameter together with separation behavior in HPLC. Furthermore, suspended-state and solid-state NMR measurements revealed different alkyl chain mobilities for the monomeric and hydride-modified SPs. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Metastable Phases of Dross Particles Formed in a Molten Zinc Bath and Prediction of Soluble Aluminum During Galvannealing Processes

    NASA Astrophysics Data System (ADS)

    Paik, Doo-Jin; Hong, Moon-Hi; Huh, Yoon; Park, Joo Hyun; Chae, Hong-Kook; Park, Seok-Ho; Choun, Si-Youl

    2012-06-01

    The morphology, chemistry, and crystallographic characteristics of metastable dross particles were identified. These particles are formed during the initial stage of precipitation. The particles had aluminum concentrations of 15 to 80 mass pct, with values that decreased gradually as particle size increased. These metastable dross particles were a mixture of the crystalline phase of FeZn10, which is called the "delta phase," and the high-aluminum amorphous phase, which covered the surface of the crystalline phase. The new "meta Q" concept was proposed to predict the amount of soluble aluminum in the zinc bath by considering nucleation kinetics and particle growth. The results calculated using the "meta Q" concept were compared with the values measured by the aluminum sensor, which were taken during the same period at the commercial galvanizing line. The mean of the absolute values of the differences between the calculated and measured values was 9.7 ppm.

  7. Hydride compressor

    DOEpatents

    Powell, James R.; Salzano, Francis J.

    1978-01-01

    Method of producing high energy pressurized gas working fluid power from a low energy, low temperature heat source, wherein the compression energy is gained by using the low energy heat source to desorb hydrogen gas from a metal hydride bed and the desorbed hydrogen for producing power is recycled to the bed, where it is re-adsorbed, with the recycling being powered by the low energy heat source. In one embodiment, the adsorption-desorption cycle provides a chemical compressor that is powered by the low energy heat source, and the compressor is connected to a regenerative gas turbine having a high energy, high temperature heat source with the recycling being powered by the low energy heat source.

  8. Reactivity of yttrium carboxylates toward alkylaluminum hydrides.

    PubMed

    Schädle, Christoph; Fischbach, Andreas; Herdtweck, Eberhardt; Törnroos, Karl W; Anwander, Reiner

    2013-11-25

    Yttrocene-carboxylate complex [Cp*2Y(OOCAr(Me))] (Cp*=C5Me5, Ar(Me) =C6H2Me3-2,4,6) was synthesized as a spectroscopically versatile model system for investigating the reactivity of alkylaluminum hydrides towards rare-earth-metal carboxylates. Equimolar reactions with bis-neosilylaluminum hydride and dimethylaluminum hydride gave adduct complexes of the general formula [Cp*2Y(μ-OOCAr(Me))(μ-H)AlR2] (R=CH2SiMe3, Me). The use of an excess of the respective aluminum hydride led to the formation of product mixtures, from which the yttrium-aluminum-hydride complex [{Cp*2Y(μ-H)AlMe2(μ-H)AlMe2(μ-CH3)}2] could be isolated, which features a 12-membered-ring structure. The adduct complexes [Cp*2Y(μ-OOCAr(Me))(μ-H)AlR2] display identical (1)J(Y,H) coupling constants of 24.5 Hz for the bridging hydrido ligands and similar (89)Y NMR shifts of δ=-88.1 ppm (R=CH2SiMe3) and δ=-86.3 ppm (R=Me) in the (89)Y DEPT45 NMR experiments.

  9. Aluminum-containing intergranular phases in hot-pressed silicon carbide

    SciTech Connect

    Zhang, Xiao Feng; De Jonghe, Lutgard C.

    2003-01-12

    Aluminum-containing intergranular phases, forming intergranular films and secondary phase particles at triple-junctions in SiC hot-pressed with aluminum, boron, and carbon additions, were studied by transmission electron microscopy. Statistical high-resolution electron microscopy study of intergranular films indicated that a large fraction of the vitreous intergranular films in the s-hot-pressed SiC crystallized during postannealing in argon above 1000 C. However, brief heating to 1900 C indeed re-melted 25 percent of the crystallized intergranular films. The structural transitions were reflected in the statistical width distributions of the amorphous grain boundary layers. At triple-junctions, Al2O3, Al2OC-SiC solid solution, and mullite phases were newly identified. These phases,together with others reported before are represented in a quaternary phase diagram for 1900 C. It is proposed that a SiC-Al2OC liquid domain is to be included in this phase diagram.

  10. 1H HR/MAS NMR in the suspended state: molecular recognition processes in liquid chromatography between steroids and a silica hydride-based cholesterol phase.

    PubMed

    Friebolin, Volker; Bayer, Marc P; Matyska, Maria T; Pesek, Joseph J; Albert, Klaus

    2009-05-01

    A mixture of eight steroids was separated by HPLC on a silica hydride-based stationary phase modified with a moiety of cholesteryl 10-undecanoate. Within the steroid mixture progesterone showed the longest retention time suggesting the strongest interaction with the stationary phase material. To obtain more detailed information upon the effective separation process, interaction studies were performed by high resolution/magic angle spinning (HR/MAS) NMR spectroscopy recorded in the suspended state. (1)H saturation transfer difference (STD) NMR experiments with T(1rho) suppression showed significant hydrophobic binding affinities of progesterone toward the cholesterol column material. These NMR results can be correlated directly to the chromatographic data obtained by HPLC.

  11. GaAs Solar Cells Grown by Hydride Vapor-Phase Epitaxy and the Development of GaInP Cladding Layers

    SciTech Connect

    Simon, John; Schulte, Kevin L.; Young, David L.; Haegel, Nancy M.; Ptak, Aaron J.

    2016-01-01

    The high cost of high-efficiency III-V photovoltaic devices currently limits them to niche markets. Hydride vapor-phase epitaxy (HVPE) growth of III-V materials recently reemerged as a low-cost, high-throughput alternative to conventional metal- organic vapor-phase epitaxy (MOVPE) growth of high-efficiency solar cells. Previously, we demonstrated unpassivated HVPEgrown GaAs p-n junctions with good quantum efficiency and high open-circuit voltage (Voc). In this work, we demonstrate the growth of GaInPby HVPE for use as a high-quality surface passivation layer to GaAs solar cells. Solar cells grown with GaInP window layers show significantly improved quantum efficiency compared with unpassivated cells, increasing the short-circuit current (JSC) of these low-cost devices. These results show the potential of low-cost HVPE for the growth of high-quality III-V devices.

  12. PULSED EDDY CURRENT THICKNESS MEASUREMENT OF SELECTIVE PHASE CORROSION ON NICKEL ALUMINUM BRONZE VALVES

    SciTech Connect

    Krause, T. W.; Harlley, D.; Babbar, V. K.; Wannamaker, K.

    2010-02-22

    Nickel Aluminum Bronze (NAB) is a material with marine environment applications that under certain conditions can undergo selective phase corrosion (SPC). SPC involves the removal of minority elements while leaving behind a copper matrix. Pulsed eddy current (PEC) was evaluated for determination of SPC thickness on a NAB valve section with access from the surface corroded side. A primarily linear response of PEC amplitude, up to the maximum available SPC thickness of 4 mm was observed. The combination of reduced conductivity and permeability in the SPC phase relative to the base NAB was used to explain the observed sensitivity of PEC to SPC thickness variations.

  13. Effect of Iron Impurity on the Phase Composition, Structure and Properties of Magnesium Alloys Containing Manganese and Aluminum

    NASA Astrophysics Data System (ADS)

    Volkova, E. F.

    2017-07-01

    Results of a study of the interaction between iron impurity and manganese and aluminum alloying elements during formation of phase composition in alloys of the Mg - Mn, Mg - Al, Mg - Al - Mn, and Mg - Al - Zn - Mn systems are presented. It is proved that this interaction results in introduction of Fe into the intermetallic phase. The phase compositions of model magnesium alloys and commercial alloys MA2-1 and MA5 are studied. It is shown that both manganese and aluminum may bind the iron impurity into phases. Composite Fe-containing intermetallic phases of different compositions influence differently the corrosion resistance of magnesium alloys.

  14. Liquid suspensions of reversible metal hydrides

    DOEpatents

    Reilly, J.J.; Grohse, E.W.; Winsche, W.E.

    1983-12-08

    The reversibility of the process M + x/2 H/sub 2/ ..-->.. MH/sub x/, where M is a metal hydride former that forms a hydride MH/sub x/ in the presence of H/sub 2/, generally used to store and recall H/sub 2/, is found to proceed under a liquid, thereby to reduce contamination, provide better temperature control and provide in situ mobility of the reactants. Thus, a slurry of particles of a metal hydride former with an inert solvent is subjected to temperature and pressure controlled atmosphere containing H/sub 2/, to store hydrogen (at high pressures) and to release (at low pressures) previously stored hydrogen. The direction of the flow of the H/sub 2/ through the liquid is dependent upon the H/sub 2/ pressure in the gas phase at a given temperature. When the former is above the equilibrium absorption pressure of the respective hydride the reaction proceeds to the right, i.e., the metal hydride is formed and hydrogen is stored in the solid particle. When the H/sub 2/ pressure in the gas phase is below the equilibrium dissociation pressure of the respective hydride the reaction proceeds to the left, the metal hydride is decomposed and hydrogen is released into the gas phase.

  15. Phase composition of aluminum-nickel-moybdenum oxide catalysts for hydrotreatment: The nature of the active phase

    SciTech Connect

    Gazimzyanov, N.R.; Kvashonkin, V.I.; Zhdanova, K.P.

    1995-07-01

    The phase composition of aluminum-nickel-molybdenum oxide catalysts (ANMC) with various MoO{sub 3} and NiO contents is studied by XRD, diffuse-reflectance electron spectroscopy, O{sub 2} chemisorption on the reduced samples, and selective extraction of Mo and Ni compounds. The results of the phase analysis are compared to the data on catalyst tests in thiophene hydrogenolysis. The phase composition of ANMC is shown to involve the surface analog of a heteropolymolybdenum compound (HPC). The content of the latter, which was found by extraction with water, correlates well with the O{sub 2} chemisorption data and partially with the catalytic activity. Finally, HPC is determined to be the oxide precursor of the active sulfide phase.

  16. Well-defined silica supported aluminum hydride: another step towards the utopian single site dream?† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c5sc02276b Click here for additional data file.

    PubMed Central

    Werghi, Baraa; Bendjeriou-Sedjerari, Anissa; Sofack-Kreutzer, Julien; Jedidi, Abdesslem; Abou-Hamad, Edy

    2015-01-01

    Reaction of triisobutylaluminum with SBA15700 at room temperature occurs by two parallel pathways involving either silanol or siloxane bridges. It leads to the formation of a well-defined bipodal [( 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 SiO)2Al–CH2CH(CH3)2] 1a, silicon isobutyl [Si–CH2CH(CH3)2] 1b and a silicon hydride [Si–H] 1c. Their structural identity was characterized by FT-IR and advanced solid-state NMR spectroscopies (1H, 13C, 29Si, 27Al and 2D multiple quantum), elemental and gas phase analysis, and DFT calculations. The reaction involves the formation of a highly reactive monopodal intermediate: [SiO–Al–[CH2CH(CH3)2]2], with evolution of isobutane. This intermediate undergoes two parallel routes: transfer of either one isobutyl fragment or of one hydride to an adjacent silicon atom. Both processes occur by opening

  17. A theoretical evaluation of aluminum gel propellant two-phase flow losses on vehicle performance

    NASA Technical Reports Server (NTRS)

    Mueller, Donn C.; Turns, Stephen R.

    1993-01-01

    A one-dimensional model of a hydrocarbon/Al/O2(gaseous) fueled rocket combustion chamber was developed to study secondary atomization effects on propellant combustion. This chamber model was coupled with a two dimensional, two-phase flow nozzle code to estimate the two-phase flow losses associated with solid combustion products. Results indicate that moderate secondary atomization significantly reduces propellant burnout distance and Al2O3 particle size; however, secondary atomization provides only moderate decreases in two-phase flow induced I(sub sp) losses. Despite these two-phase flow losses, a simple mission study indicates that aluminum gel propellants may permit a greater maximum payload than the hydrocarbon/O2 bi-propellant combination for a vehicle of fixed propellant volume. Secondary atomization was also found to reduce radiation losses from the solid combustion products to the chamber walls, primarily through reductions in propellant burnout distance.

  18. Polyacrylamide grafted on multi-walled carbon nanotubes for open-tubular capillary electrochromatography: comparison with silica hydride and polyacrylate phase matrices.

    PubMed

    Chen, Jian-Lian; Hsieh, Kai-Hsin

    2010-12-01

    A new nanoparticle-bound polymer stationary phase was prepared by in situ polymerization of methacrylamide (MAA), bis-acrylamide crosslinker, and carboxylated multi-walled carbon nanotubes (multi-walled CNTs; MWNTs), using the abundant double bonds in the cyclopentadienyl rings in MWNT structure, on a silanized capillary. Each intermediate capillary between the synthesis steps was characterized by SEM, by ATR-IR, and by EOF measurements varying the pH, concentration, and volumetric ratios of ACN in running buffers. The resulting EOF profile was comparable to those of two other capillaries with different phase matrices, silica hydride and polybutyl methacrylate (BMA) phases. With the complex functionality of MWNTs on the hydrophilic polyacrylamide network, the MAA-CNT capillary was capable of separating diverse samples with a wide range of polarity and dissociation properties using open-tubular CEC. Besides optimizing CEC conditions, the migration times of samples were analyzed with respect to velocity and retention factors to evaluate electrophoretic and chromatographic contributions to the CEC mechanism. The migration rates of benzoic acids were determined by the electrophoretic mobilities of the various phenolate ions, while phenolic aldehydes and ketones were additionally influenced by chromatographic interactions, such as π-π, electrostatic effects, hydrogen bonding, and hydrophobic interactions. The retention factors were greater for flavonoids, which are polyphenolic, than for simple phenols, but were smaller than those obtained from the hydrophobic BMA-CNT column. A complete well-resolved separation of the cationic forms of tetracyclines was acheived either by electrophoresis or by chromatography in the MAA-CNT capillary, but not in the BMA-CNT and silica hydride-CNT capillaries.

  19. Investigation of phase explosion in aluminum induced by nanosecond double pulse technique

    NASA Astrophysics Data System (ADS)

    Jafarabadi, Marzieh Akbari; Mahdieh, Mohammad Hossein

    2015-08-01

    In this paper, the influence of double pulse technique on phase explosion threshold in laser ablation of an aluminum target is investigated. Single and double pulse laser ablation of aluminum target was performed by a high power Nd:YAG laser beam in ambient air. In the double pulse excitation, the two pulses were from a single laser source which separated by a delay time in the range of 5-20 ns. Measuring ablation depth and rate, the phase explosion threshold was estimated in double pulse configuration as well as in the single pulse regime. The results show that in comparison between single and double pulse regimes, the phase explosion threshold fluence is decreased in double pulse configuration. The lowest phase explosion threshold fluence of 0.9 J/cm2 was obtained at 5 ns delay time. The results also show that plasma shielding effect reduced crater depth at a laser fluence which depended on the laser ablation configuration (single pulse or double pulse). The reduction of crater depth occurs at lower laser fluences for double pulse regime.

  20. Use of a Novel Sub-2 µm Silica Hydride Vancomycin Stationary Phase in Nano-Liquid Chromatography. II. Separation of Derivatized Amino Acid Enantiomers.

    PubMed

    Rocchi, Silvia; Fanali, Chiara; Fanali, Salvatore

    2015-11-01

    A novel vancomycin silica hydride stationary phase was synthesized and the particles of 1.8 µm were packed into fused silica capillaries of 75 µm internal diameter (I.D.). The chiral stationary phase (CSP) was tested for the separation of some derivatized amino acid enantiomers by using nano-liquid chromatography (nano-LC). Some experimental parameters such as the type and the content of organic modifier, the pH, and the concentration of the buffer added to the mobile phase were modified and the effect on enantioselectivity, retention time, and enantioresolution factor was studied. The separation of selected dansyl amino acids (Dns-AAs), e.g., Asp, Glu, Leu, and Phe in their enantiomers was initially achieved utilizing a mobile phase containing 85% (v/v) methanol (MeOH) and formate buffer measuring the enantioresolution factor and enantioselectivity in the range 1.74-4.17 and 1.39-1.59, respectively. Better results were obtained employing a more polar organic solvent as acetonitrile (ACN) in the mobile phase. Optimum results (Rs 1.41-6.09 and α 1.28-2.36) were obtained using a mobile phase containing formate buffer pH 2.5/water/MeOH/ACN 6:19:12.5:62.5 (v/v/v/v) in isocratic elution mode at flow rate of 130 nL/min. © 2015 Wiley Periodicals, Inc.

  1. Phase relations associated with the aluminum blast furnace: Aluminum oxycarbide melts and Al-C-X (X=Fe, Si) liquid alloys

    NASA Astrophysics Data System (ADS)

    Yokokawa, Harumi; Fujishige, Masao; Ujiie, Seiichi; Dokiya, Masayuki

    1987-06-01

    The thermodynamic properties and the phase relations were evaluated and estimated for the Al-O-C, Al-Si-C, and Al-Fe-C systems which are important to understand the chemical behavior in an aluminum blast furnace. The mixing properties of binary liquid alloys, including metal-carbon systems, were represented by the Redlich-Kister equation. The properties of liquid Al-C and Si-C alloys were estimated so as to be consistent with their phase diagrams. The coefficients of Al-Fe and Fe-C liquids were evaluated from reported values for activity and enthalpy. The extrapolation to the higher order systems was made by Maggianu's method. The aluminum oxycarbide melt was represented by a subregular solution model. In the Al-O-C system, liquid alloy/oxycarbide melt equilibria were calculated and compared with earlier experimental results and estimates. Attempts were made to clarify the volatilization of aluminum oxycarbide melts, and also the carbidation of liquid aluminum alloys. An empirical correlation between the first terms of the Redlich-Kister equation for the enthalpies and the excess entropies was discussed.

  2. Low temperature planar regrowth of semi-insulating InP by low pressure hydride vapour phase epitaxy for device application

    NASA Astrophysics Data System (ADS)

    Alexandre, F.; Parillaud, O.; Nguyen, D. C.; Azoulay, R.; Quillec, M.; Bouchoule, S.; Le Mestreallan, G.; Juhel, M.; Le Roux, G.; Rao, E. V. K.

    1998-05-01

    The growth of both undoped and iron doped InP on planar as well as non-planar (0 0 1)InP substrates has been explored using low pressure hydride vapour phase epitaxy (LP-HVPE) in the temperature range of 500-620°C. Secondary ion mass spectroscopy (SIMS), X-ray diffraction and photoluminescence measurements have shown no drastic degradation in the crystal quality with decreasing growth temperature. The Fe incorporation in the layers is found to be independent of the substrate temperature ( Ts) and in all experiments semi-insulating InP : Fe layers with resistivities close to 10 9 Ω cm have been obtained. A perfect growth selectivity with no deposition on masked areas and a good planarized regrowth on mesas has been demonstrated even at low Ts.

  3. Cross-stacked carbon nanotubes assisted self-separation of free-standing GaN substrates by hydride vapor phase epitaxy

    PubMed Central

    Wei, Tongbo; Yang, Jiankun; Wei, Yang; Huo, Ziqiang; Ji, Xiaoli; Zhang, Yun; Wang, Junxi; Li, Jinmin; Fan, Shoushan

    2016-01-01

    We report a novel method to fabricate high quality 2-inch freestanding GaN substrate grown on cross-stacked carbon nanotubes (CSCNTs) coated sapphire by hydride vapor phase epitaxy (HVPE). As nanoscale masks, these CSCNTs can help weaken the interface connection and release the compressive stress by forming voids during fast coalescence and also block the propagation of threading dislocations (TDs). During the cool-down process, thermal stress-induced cracks are initiated at the CSCNTs interface with the help of air voids and propagated all over the films which leads to full self-separation of FS-GaN substrate. Raman and photoluminescence spectra further reveal the stress relief and crystalline improvement of GaN with CSCNTs. It is expected that the efficient, low cost and mass-producible technique may enable new applications for CNTs in nitride optoelectronic fields. PMID:27340030

  4. Preparation of Ag Schottky contacts on n-type GaN bulk crystals grown in nitrogen rich atmosphere by the hydride vapor phase epitaxy technique

    SciTech Connect

    Stübner, R. Kolkovsky, Vl.; Weber, J.; Leibiger, Gunnar; Habel, Frank

    2014-10-14

    Electrical properties of Schottky contacts on n-type GaN grown in nitrogen rich atmosphere with different N/Ga ratios by hydride vapor phase epitaxy were investigated. We show that tunneling of electrons from the conduction band of GaN to the metal is dominant in our samples. The quality of Schottky contacts does not only depend on surface preparation but also on the growth conditions of the crystals. Schottky contacts on these crystals show an increasing deterioration when higher N/Ga growth ratios are used. We correlate our results with the presence of negatively charged gallium vacancies in the samples. These charges compensate the positively charged donors and lead to a significant increase in series resistance.

  5. Cross-stacked carbon nanotubes assisted self-separation of free-standing GaN substrates by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Wei, Tongbo; Yang, Jiankun; Wei, Yang; Huo, Ziqiang; Ji, Xiaoli; Zhang, Yun; Wang, Junxi; Li, Jinmin; Fan, Shoushan

    2016-06-01

    We report a novel method to fabricate high quality 2-inch freestanding GaN substrate grown on cross-stacked carbon nanotubes (CSCNTs) coated sapphire by hydride vapor phase epitaxy (HVPE). As nanoscale masks, these CSCNTs can help weaken the interface connection and release the compressive stress by forming voids during fast coalescence and also block the propagation of threading dislocations (TDs). During the cool-down process, thermal stress-induced cracks are initiated at the CSCNTs interface with the help of air voids and propagated all over the films which leads to full self-separation of FS-GaN substrate. Raman and photoluminescence spectra further reveal the stress relief and crystalline improvement of GaN with CSCNTs. It is expected that the efficient, low cost and mass-producible technique may enable new applications for CNTs in nitride optoelectronic fields.

  6. Mechanism of light emission and manufacturing process of vertical-type light-emitting diode grown by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Lee, Gang Seok; Jeon, Hunsoo; Ahn, Hyung Soo; Yang, Min; Yi, Sam Nyung; Yu, Young Moon; Lee, Sang Chil; Honda, Yoshio; Sawaki, Nobuhiko; Kim, Suck-Whan

    2017-01-01

    We developed a vertical-type light-emitting diode (LED) in which the substrate is removed using a hydride vapor phase epitaxy (HVPE) apparatus consisting of a multi-graphite boat filled with a mixed source and a high-temperature (T ≈ 900 °C) RF heating coil outside the source zone. The new chip-growth process with a significant reduction in the number of production steps is completed in only four steps, namely, photolithography, epitaxial layer growth, sorting, and metallization. We analyze the emission mechanism of these lights from measurement results to validate the characteristics of the light emitted from these vertical-type blue LEDs and white LEDs (WLEDs) without substrates, and propose that this mixed-source HVPE method may be a promising production technique for LEDs.

  7. Phase transformations of α-alumina made from waste aluminum via a precipitation technique.

    PubMed

    Matori, Khamirul Amin; Wah, Loy Chee; Hashim, Mansor; Ismail, Ismayadi; Zaid, Mohd Hafiz Mohd

    2012-12-07

    We report on a recycling project in which α-Al(2)O(3) was produced from aluminum cans because no such work has been reported in literature. Heated aluminum cans were mixed with 8.0 M of H(2)SO(4) solution to form an Al(2)(SO(4))(3) solution. The Al(2)(SO(4))(3) salt was contained in a white semi-liquid solution with excess H(2)SO(4); some unreacted aluminum pieces were also present. The solution was filtered and mixed with ethanol in a ratio of 2:3, to form a white solid of Al(2)(SO(4))(3)·18H(2)O. The Al(2)(SO(4))(3)·18H(2)O was calcined in an electrical furnace for 3 h at temperatures of 400-1400 °C. The heating and cooling rates were 10 °C /min. XRD was used to investigate the phase changes at different temperatures and XRF was used to determine the elemental composition in the alumina produced. A series of different alumina compositions, made by repeated dehydration and desulfonation of the Al(2)(SO(4))(3)·18H(2)O, is reported. All transitional alumina phases produced at low temperatures were converted to α-Al(2)O(3) at high temperatures. The X-ray diffraction results indicated that the α-Al(2)O(3) phase was realized when the calcination temperature was at 1200 °C or higher.

  8. Phase Transformations of α-Alumina Made from Waste Aluminum via a Precipitation Technique

    PubMed Central

    Matori, Khamirul Amin; Wah, Loy Chee; Hashim, Mansor; Ismail, Ismayadi; Zaid, Mohd Hafiz Mohd

    2012-01-01

    We report on a recycling project in which α-Al2O3 was produced from aluminum cans because no such work has been reported in literature. Heated aluminum cans were mixed with 8.0 M of H2SO4 solution to form an Al2(SO4)3 solution. The Al2(SO4)3 salt was contained in a white semi-liquid solution with excess H2SO4; some unreacted aluminum pieces were also present. The solution was filtered and mixed with ethanol in a ratio of 2:3, to form a white solid of Al2(SO4)3·18H2O. The Al2(SO4)3·18H2O was calcined in an electrical furnace for 3 h at temperatures of 400–1400 °C. The heating and cooling rates were 10 °C/min. XRD was used to investigate the phase changes at different temperatures and XRF was used to determine the elemental composition in the alumina produced. A series of different alumina compositions, made by repeated dehydration and desulfonation of the Al2(SO4)3·18H2O, is reported. All transitional alumina phases produced at low temperatures were converted to α-Al2O3 at high temperatures. The X-ray diffraction results indicated that the α-Al2O3 phase was realized when the calcination temperature was at 1200 °C or higher. PMID:23222685

  9. Program to Develop High Strength Aluminum Powder Metallurgy Products. Phase 4. Scale-up to 3200-lb. Billets

    DTIC Science & Technology

    1974-12-05

    AD/A-005 661 PROGRAM TO DEVELOP HIGH STRENGTH ALUMINUM POWDER METALLURGY PRODUCTS. PHASE IV. SCALE-UP TO 3200-LB. BILLETS Walter S. Cebulak Aluminum ...aW4PAk;n Uobus-w~d ALCOA December 5, 1974 U. S. ARMY FRANKFORD ARSENAL CONTRACT DAAA25-72-CO593 PROGRAM TO DEVELOP HIGH STRENGTH ALUMINUM POWDER...packing in the vacuum preheat container will replace cold isostatic pressing prior to encapsulation for vacuum preheating. Eight lots of powder were

  10. Elemental Water Impact Test: Phase 2 36-Inch Aluminum Tank Head

    NASA Technical Reports Server (NTRS)

    Vassilakos, Gregory J.

    2014-01-01

    Spacecraft are being designed based on LS-DYNA simulations of water landing impacts. The Elemental Water Impact Test (EWIT) series was undertaken to assess the accuracy of LS-DYNA water impact simulations. EWIT Phase 2 featured a 36-inch aluminum tank head. The tank head was outfitted with one accelerometer, twelve pressure transducers, three string potentiometers, and four strain gages. The tank head was dropped from heights of 1 foot and 2 feet. The focus of this report is the correlation of analytical models against test data. As a measure of prediction accuracy, peak responses from the baseline LS-DYNA model were compared to peak responses from the tests.

  11. Phase diagrams of a cold rolling emulsion for aluminum{copyright}

    SciTech Connect

    Deneuville, P.; Charbonnier, P.; Ravey, J.C.

    1995-08-01

    Emulsions are complex metalworking fluids. In metal rolling the generally accepted {open_quotes}plate{close_quotes} mechanism results in a separation of the mixture inside the roll bite into a water phase and a surfactant/oil phase. The water phase cools the tools and the oil phase lubricates the interface between the metal and the tools. Rolling emulsions can be considered as ternary systems that consist of water, oil and surfactant. The oil and its additives can be considered as a single component. This paper describes the application of phase diagrams to an aluminum cold rolling emulsion and provides insights into the separation of the water and the oil lubricant phases. It is shown that the amount of water solubilized in the separated oil phase depends on the nature and amount of additives and surfactants, and on the temperature. The emulsions studied were compared using a special rolling device developed in the authors` laboratory and their tribological properties were related to the phase diagrams. 18 refs., 13 figs., 1 tab.

  12. In-situ TEM phase formation in cold rolled aluminum-nickel multilayers

    SciTech Connect

    Sieber, H.; Perepezko, J.H.

    1998-12-31

    Multilayer samples of Nickel and Aluminum with an overall composition of Al-20Ni were prepared by cold rolling of elemental foils. The sample microstructures and phases were characterized by XRD, SEM and TEM/SAED, and the reactive phase formation was then examined by DSC measurements. XRD, SEM and TEM measurements show that the rolling procedure results in a decrease of the Al and Ni layer thicknesses (down to 100 nm in average) and a decrease of the grain size (down to less than 50 nm). No phase formation is observed during the cold rolling procedure. In isochronal DSC scans of the Al-Ni multilayers, the formation of the Al{sub 3}Ni phase was found to be a two step reaction process due to 2-dimensional nucleation and lateral growth and a 3-dimensional phase thickening. While XRD measurements showed Al{sub 3}Ni as the only phase that forms, more detailed TEM investigations of the samples after DSC treatment also showed a small amount of an amorphous Al-Ni phase, formed by a thermally activated solid state amorphization reaction (SSAR). In-situ TEM heating of the amorphous areas under the electron beam in the microscope yielded the crystallization of the amorphous phase to a B2 structure and a growth of the B2 grains up to 100 nm in size.

  13. Microstructure and Phase Constitution Near the Interface of Explosively Welded Aluminum/Copper Plates

    NASA Astrophysics Data System (ADS)

    Paul, Henryk; Lityńska-Dobrzyńska, Lidia; Prażmowski, Mariusz

    2013-08-01

    The microstructure changes and the phase constitution within the layers close to the bonding interface strongly influence the properties of bimetallic strips. In this work, the layers near the interface of explosively welded aluminum and copper plates were investigated by means of microscopic observations, mostly with the use of transmission electron microscopy (TEM) equipped with energy dispersive spectrometry (EDX). The study was focused on the identification of the intermetallic phases, the possible interdiffusion between the copper and the aluminum, and the changes in the dislocation structure of the parent plates. In macro-/mesoscale, the interfaces were outlined by a characteristic sharp transition indicating that there was no mechanical mixing between the welded metals in the solid state. In micro-/nanoscale, the layers adhering to the interface show typical deformed microstructure features, i.e., structure refinement, elongated dislocation cells, slip bands, and microtwins (in copper plate). The internal microstructure of the intermetallic inclusion is composed mostly of dendrites. The electron diffractions and TEM/EDX chemical composition measurements revealed three crystalline equilibrium phases of the γ-Al4Cu9, η-AlCu, and Θ-Al2Cu type (the last one was dominant). However, most of the observed phases of the general Cu m Al n type (also crystalline) do not appear in the equilibrium Al-Cu phase diagram. Inside the intermetallic inclusions, no significant regularity in the phase distribution with respect to the parent sheets was observed. Therefore, it was concluded that the processes occurring in the melt determined their local chemical composition.

  14. Silica Embedded Metal Hydrides

    SciTech Connect

    Heung, L.K.; Wicks, G.G.

    1998-08-01

    A method to produce silica embedded metal hydride was developed. The product is a composite in which metal hydride particles are embedded in a matrix of silica. The silica matrix is highly porous. Hydrogen gas can easily reach the embedded metal hydride particles. The pores are small so that the metal hydride particles cannot leave the matrix. The porous matrix also protects the metal hydride particles from larger and reactive molecules such as oxygen, since the larger gas molecules cannot pass through the small pores easily. Tests show that granules of this composite can absorb hydrogen readily and withstand many cycles without making fines.

  15. Cast B2-phase iron-aluminum alloys with improved fluidity

    DOEpatents

    Maziasz, Philip J.; Paris, Alan M.; Vought, Joseph D.

    2002-01-01

    Systems and methods are described for iron aluminum alloys. A composition includes iron, aluminum and manganese. A method includes providing an alloy including iron, aluminum and manganese; and processing the alloy. The systems and methods provide advantages because additions of manganese to iron aluminum alloys dramatically increase the fluidity of the alloys prior to solidification during casting.

  16. Precipitation and Deposition of Aluminum-Containing Phases in Tank Wastes

    SciTech Connect

    Dabbs, Daniel M.; Aksay, I.A.

    2005-12-01

    In the first phase of our study, we focused on the use of simple organics to raise the solubility of aluminum oxyhydroxides in high alkaline aqueous solvents. In a limited survey of common organic acids, we determined that citric acid had the highest potential to achieve our goal. However, our subsequent investigation revealed that the citric acid appeared to play two roles in the solutions: first, raising the concentration of aluminum in highly alkaline solutions by breaking up or inhibiting ''seed'' polycations and thereby delaying the nucleation and growth of particles; and second, stabilizing nanometer-sized particles in suspension when nucleation did occur. The results of this work were recently published in Langmuir: D.M. Dabbs, U. Ramachandran, S. Lu, J. Liu, L.-Q. Wang, I.A. Aksay, ''Inhibition of Aluminum Oxyhydroxide Precipitation with Citric Acid'' Langmuir, 21, 11690-11695 (2005). The second phase of our work involved the solvation of silicon, again in solutions of high alkalinity. Citric acid, due to its unfavorable pKa values, was not expected to be useful with silicon-containing solutions. Here, the use of polyols was determined to be effective in maintaining silicon-containing particles under high pH conditions but at smaller size with respect to standard suspensions of silicon-containing particles. There were a number of difficulties working with highly alkaline silicon-containing solutions, particularly in solutions at or near the saturation limit. Small deviations in pH resulted in particle formation or dissolution in the absence of the organic agents. One of the more significant observations was that the polyols appeared to stabilize small particles of silicon oxyhydroxides across a wider range of pH, albeit this was difficult to quantify due to the instability of the solutions.

  17. Nondestructive detection of an undesirable metallic phase, T.sub.1, during processing of aluminum-lithium alloys

    DOEpatents

    Buck, Otto; Bracci, David J.; Jiles, David C.; Brasche, Lisa J. H.; Shield, Jeffrey E.; Chumbley, Leonard S.

    1990-08-07

    A method is disclosed for detecting the T.sub.1 phase in aluminum-lithium alloys through simultaneous measurement of conductivity and hardness. In employing eddy current to measure conductivity, when the eddy current decreases with aging of the alloy, while the hardness of the material continues to increase, the presence of the T.sub.1 phase may be detected.

  18. Properties of nanoscale metal hydrides.

    PubMed

    Fichtner, Maximilian

    2009-05-20

    Nanoscale hydride particles may exhibit chemical stabilities which differ from those of a macroscopic system. The stabilities are mainly influenced by a surface energy term which contains size-dependent values of the surface tension, the molar volume and an additional term which takes into account a potential reduction of the excess surface energy. Thus, the equilibrium of a nanoparticular hydride system may be shifted to the hydrogenated or to the dehydrogenated side, depending on the size and on the prefix of the surface energy term of the hydrogenated and dehydrogenated material. Additional complexity appears when solid-state reactions of complex hydrides are considered and phase segregation has to be taken into account. In such a case the reversibility of complex hydrides may be reduced if the nanoparticles are free standing on a surface. However, it may be enhanced if the system is enclosed by a nanoscale void which prevents the reaction partners on the dehydrogenated side from diffusing away from each other. Moreover, the generally enhanced diffusivity in nanocrystalline systems may lower the kinetic barriers for the material's transformation and, thus, facilitate hydrogen absorption and desorption.

  19. Threshold for plasma phase transition of aluminum single crystal induced by hypervelocity impact

    SciTech Connect

    Ju, Yuanyuan; Zhang, Qingming

    2015-12-15

    Molecular dynamics method is used to study the threshold for plasma phase transition of aluminum single crystal induced by hypervelocity impact. Two effective simulation methods, piston-driven method and multi-scale shock technique, are used to simulate the shock wave. The simulation results from the two methods agree well with the experimental data, indicating that the shock wave velocity is linearly dependent on the particle velocity. The atom is considered to be ionized if the increase of its internal energy is larger than the first ionization energy. The critical impact velocity for plasma phase transition is about 13.0 km/s, corresponding to the threshold of pressure and temperature which is about 220 GPa and 11.0 × 10{sup 3 }K on the shock Hugoniot, respectively.

  20. Flow Strength of Shocked Aluminum in the Solid-Liquid Mixed Phase Region

    NASA Astrophysics Data System (ADS)

    Reinhart, William

    2011-06-01

    Shock waves have been used to determine material properties under high shock stresses and very-high loading rates. The determination of mechanical properties such as compressive strength under shock compression has proven to be difficult and estimates of strength have been limited to approximately 100 GPa or less in aluminum. The term ``strength'' has been used in different ways. For a Von-Mises solid, the yield strength is equal to twice the shear strength of the material and represents the maximum shear stress that can be supported before yield. Many of these concepts have been applied to materials that undergo high strain-rate dynamic deformation, as in uni-axial strain shock experiments. In shock experiments, it has been observed that the shear stress in the shocked state is not equal to the shear strength, as evidenced by elastic recompressions in reshock experiments. This has led to an assumption that there is a yield surface with maximum (loading)and minimum (unloading), shear strength yet the actual shear stress lies somewhere between these values. This work provides the first simultaneous measurements of unloading velocity and flow strength for transition of solid aluminum to the liquid phase. The investigation describes the flow strength observed in 1100 (pure), 6061-T6, and 2024 aluminum in the solid-liquid mixed phase region. Reloading and unloading techniques were utilized to provide independent data on the two unknowns (τc and τo) , so that the actual critical shear strength and the shear stress at the shock state could be estimated. Three different observations indicate a change in material response for stresses of 100 to 160 GPa; 1) release wave speed (reloading where applicable) measurements, 2) yield strength measurements, and 3) estimates of Poisson's ratio, all of which provide information on the melt process including internal consistency and/or non-equilibrium and rate-dependent melt behavior. The study investigates the strength properties

  1. Coordination preference of Ga in hydrides.

    PubMed

    Klaveness, A; Swang, O; Kjekshus, A; Fjellvåg, H

    2006-12-25

    Aluminum and gallium show some interesting differences in their coordination chemistry. Solid GaH3 is unknown, in contrast to solid AlH3. Ga equivalents of Li3AlH6, Na3AlH6, and other hydrides whose structure contain AlH(3-)6 ions, are unknown. We relate these differences to an instability of the hexacoordinated gallium moiety.

  2. Characterization of hydrides and delayed hydride cracking in zirconium alloys

    NASA Astrophysics Data System (ADS)

    Fang, Qiang

    This thesis tries to fill some of the missing gaps in the study of zirconium hydrides with state-of-art experiments, cutting edge tomographical technique, and a novel numerical algorithm. A new hydriding procedure is proposed. The new anode material and solution combination overcomes many drawbacks of the AECLRTM hydriding method and leads to superior hydriding result compared to the AECL RTM hydriding procedure. The DHC crack growth velocity of as-received Excel alloy and Zr-2.5Nb alloy together with several different heat treated Excel alloy samples are measured. While it already known that the DHC crack growth velocity increases with the increase of base metal strength, the finding that the transverse plane is the weaker plane for fatigue crack growth despite having higher resistance to DHC crack growth was unexpected. The morphologies of hydrides in a coarse grained Zircally-2 sample have been studied using synchrotron x-rays at ESRF with a new technique called Diffraction Contrast Tomography that uses simultaneous collection of tomographic data and diffraction data to determine the crystallographic orientation of crystallites (grains) in 3D. It has been previously limited to light metals such as Al or Mg (due to the use of low energy x-rays). Here we show the first DCT measurements using high energy x-rays (60 keV), allowing measurements in zirconium. A new algorithm of a computationally effcient way to characterize distributions of hydrides - in particular their orientation and/or connectivity - has been proposed. It is a modification of the standard Hough transform, which is an extension of the Hough transform widely used in the line detection of EBSD patterns. Finally, a basic model of hydrogen migration is built using ABAQUS RTM, which is a mature finite element package with tested modeling modules of a variety of physical laws. The coupling of hydrogen diffusion, lattice expansion, matrix deformation and phase transformation is investigated under

  3. Approach to In- Situ Producing Reinforcing Phase Within an Active-Transient Liquid Phase Bond Seam for Aluminum Matrix Composite

    NASA Astrophysics Data System (ADS)

    Zhang, Guifeng; Liao, Xianjin; Chen, Bo; Zhang, Linjie; Zhang, Jianxun

    2015-06-01

    To optimize the braze composition design route for aluminum matrix composite, the feasibility of in situ producing reinforcing phase within the transient liquid phase bond seam matrix, by adding active melting point increaser (MPI, e.g., Ti) together with general melting point depressant (MPD, e.g., Cu) into the interlayer, was demonstrated. For SiC p /A356 composite, by comparing the wettability, joint microstructure, joint shear strength, and fracture path for the developed Al-19Cu-1Ti, Al-19Cu, Al-33Cu-1Ti, Al-33Cu (wt pct), and commercial Cu foils as interlayer, the feasibility of in situ producing reinforcing phase within the bond seam by adding Ti was demonstrated. Especially for Al-19Cu-1Ti active braze, small and dispersed ternary aluminide of Al-Si-Ti phase was obtained within the bond seam as in situ reinforcement, leading to a favorable fracture path within SiC p /A356, not along the initial interface or within the bond seam. For the formation mechanism of the in situ reinforcing phase of MPI-containing intermetallic compound within the bond seam, a model of repeating concentration-precipitation-termination-engulfment during isothermal solidification is proposed.

  4. Experimental and modelling study of the plasma vapour-phase synthesis of ultrafine aluminum nitride powders

    NASA Astrophysics Data System (ADS)

    da Cruz, Antonio-Carlos

    An experimental and theoretical study of the fundamentals of the vapour phase synthesis of ultrafine aluminum nitride (AIN) particles using thermal plasma was carried out. The study used the concept of a transferred-arc reactor which produces AlN ultrafine powders in two stages: evaporation of aluminum (Al) metal by the transferred-arc in non nitriding conditions; and the reaction between Al vapour and ammonia (NH3) in a separate tubular reactor. A new version of this reactor concept was built in which the transferred-arc chamber and tubular reactor were vertically aligned. This reactor design allowed the study of both radial and axial mixing of ammonia with the plasma chamber off-gas. Ultrafine powders with a specific surface area (SSA) in the range of 38--270 m2/g were produced in two plasma chamber off-gas temperature levels (1800 and 2000 K), with different quenching intensities, and two different plasma gas compositions (pure Ar and Ar/H2 mixture). The dependence of the particle size and composition on the reactor operating conditions was investigated. Depending on the plasma gas composition, two different trends were observed for the SSA as a function of quenching intensity, with the radial injection of NH3. A two-dimensional numerical model was developed for the nucleation and growth of ultrafine particles in this system, using the method of moments. A new equation for the nucleation rate for the AlN system was developed. This equation considers the effect of reaction on the surface of clusters of the new phase. This new modelling approach could explain the trends observed experimentally. The importance of the mechanisms for the gas-to-condensed phase transition in the AlN system were examined. The sinterability of the powder produced was examined. Sintering to full density was achieved at 1550°C. Because of the high oxygen content of the powder, a second phase identified as aluminum oxynitride (ALON) was observed to form.

  5. Phase III Advanced Anodes and Cathodes Utilized in Energy Efficient Aluminum Production Cells

    SciTech Connect

    R.A. Christini; R.K. Dawless; S.P. Ray; D.A. Weirauch, Jr.

    2001-11-05

    During Phase I of the present program, Alcoa developed a commercial cell concept that has been estimated to save 30% of the energy required for aluminum smelting. Phase ii involved the construction of a pilot facility and operation of two pilots. Phase iii of the Advanced Anodes and Cathodes Program was aimed at bench experiments to permit the resolution of certain questions to be followed by three pilot cells. All of the milestones related to materials, in particular metal purity, were attained with distinct improvements over work in previous phases of the program. NiO additions to the ceramic phase and Ag additions to the Cu metal phase of the cermet improved corrosion resistance sufficiently that the bench scale pencil anodes met the purity milestones. Some excellent metal purity results have been obtained with anodes of the following composition: Further improvements in anode material composition appear to be dependent on a better understanding of oxide solubilities in molten cryolite. For that reason, work was commissioned with an outside consultant to model the MeO - cryolite systems. That work has led to a better understanding of which oxides can be used to substitute into the NiO-Fe2O3 ceramic phase to stabilize the ferrites and reduce their solubility in molten cryolite. An extensive number of vertical plate bench electrolysis cells were run to try to find conditions where high current efficiencies could be attained. TiB2-G plates were very inconsistent and led to poor wetting and drainage. Pure TiB2 did produce good current efficiencies at small overlaps (shadowing) between the anodes and cathodes. This bench work with vertical plate anodes and cathodes reinforced the importance of good cathode wetting to attain high current efficiencies. Because of those conclusions, new wetting work was commissioned and became a major component of the research during the third year of Phase III. While significant progress was made in several areas, much work needs to be

  6. A Designer Fluid For Aluminum Phase Change Devices: Aluminum Inorganic Aqueous Solutions (IAS) Chemistry and Experiments. Volume 2

    DTIC Science & Technology

    2016-11-17

    syphons and heat pipes alike are most often created by taking a hollow metal casing and, under partial vacuum, charging a small amount of liquid into the...Results of such tests can be sensitive to a variety of factors including tube preparation, cleaning, sealing, charging , etc. Although theoretical...15] conducted lifetime tests on aluminum alloy 6062 and stainless steel 321 with a wide variety of charge fluids. Their intended device application

  7. A reactive force field for lithium-aluminum silicates with applications to eucryptite phases

    NASA Astrophysics Data System (ADS)

    Narayanan, Badri; van Duin, Adri C. T.; Kappes, Branden B.; Reimanis, Ivar E.; Ciobanu, Cristian V.

    2012-01-01

    We have parameterized a reactive force field (ReaxFF) for lithium-aluminum silicates using density functional theory (DFT) calculations of structural properties of a number of bulk phase oxides, silicates and aluminates, as well as of several representative clusters. The force field parameters optimized in this study were found to predict lattice parameters and heats of formation of selected condensed phases in excellent agreement with previous DFT calculations and with experiments. We have used the newly developed force field to study the eucryptite phases in terms of their thermodynamic stability and their elastic properties. We have found that (a) these ReaxFF parameters predict the correct order of stability of the three crystalline polymorphs of eucryptite, α, β and γ, and (b) that upon indentation, a new phase appears at applied pressures >=7 GPa. The high-pressure phase obtained upon indentation is amorphous, as illustrated by the radial distribution functions calculated for different pairs of elements. In terms of elastic properties analysis, we have determined the elements of the stiffness tensor for α- and β-eucryptite at the level of ReaxFF, and discussed the elastic anisotropy of these two polymorphs. Polycrystalline average properties of these eucryptite phases are also reported to serve as ReaxFF predictions of their elastic moduli (in the case of α-eucryptite), or as tests against values known from experiments or DFT calculations (β-eucrypite). The ReaxFF potential reported here can also describe well single-species systems (e.g. Li-metal, Al-metal and condensed phases of silicon), which makes it suitable for investigating structure and properties of suboxides, atomic-scale mechanisms responsible for phase transformations, as well as oxidation-reduction reactions.

  8. Investigation of phase transitions and properties of aluminum oxides prepared by oxidation of Al/AlN nanopowder

    NASA Astrophysics Data System (ADS)

    Kazantsev, S. O.; Lozhkomoev, A. S.

    2016-11-01

    Electroexplosive Al/AlN nanopowder is used to synthesize low-dimensional particles of aluminum oxide and hydroxide phases with different shape, size, phase composition, and textural characteristics. It is shown that various conditions of production allow a synthesis of agglomerates of crumpled pseudoboehmite nanosheets, boehmite nanoplatelets, and hexagonal bayerite rods. The effect of heat treatment on phase transitions in samples as well as on the specific surface area and morphology of particles is studied.

  9. Observation of Solid-Solid Phase Transitions in Ramp-Compressed Aluminum

    NASA Astrophysics Data System (ADS)

    Polsin, D. N.; Boehly, T. R.; Delettrez, J. A.; Gregor, M. C.; McCoy, C. A.; Henderson, B.; Fratanduono, D. E.; Smith, R.; Kraus, R.; Eggert, J. H.; Collins, R.; Coppari, F.; Celliers, P. M.

    2016-10-01

    We present results of experiments using x-ray diffraction to study the crystalline structure of solid aluminum compressed up to 500 GPa. Aluminum is of interest because it is frequently used as a standard material in high-pressure compression experiments. At ambient pressure and temperature, Al is a face-centered cubic close-packed crystal and has been observed to transform to hexagonal close-packed (hcp) when compressed to 200GPa in a diamond anvil cell. It is predicted to transform from hcp to body-centered cubic when compressed to 315GPa. Laser-driven ramp waves will be used to compress Al to various constant-pressure states. The goal is to investigate the Al phase diagram along its isentrope, i.e., at temperatures 1000K and pressures ranging from 200 to 500 GPa. X-ray diffraction will be used to measure the crystalline structure of the compressed Al and observe the transformations that occur at various pressures. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

  10. Computational Modeling of Uranium Hydriding and Complexes

    SciTech Connect

    Balasubramanian, K; Siekhaus, W J; McLean, W

    2003-02-03

    Uranium hydriding is one of the most important processes that has received considerable attention over many years. Although many experimental and modeling studies have been carried out concerning thermochemistry, diffusion kinetics and mechanisms of U-hydriding, very little is known about the electronic structure and electronic features that govern the U-hydriding process. Yet it is the electronic feature that controls the activation barrier and thus the rate of hydriding. Moreover the role of impurities and the role of the product UH{sub 3} on hydriding rating are not fully understood. An early study by Condon and Larson concerns with the kinetics of U-hydrogen system and a mathematical model for the U-hydriding process. They proposed that diffusion in the reactant phase by hydrogen before nucleation to form hydride phase and that the reaction is first order for hydriding and zero order for dehydriding. Condon has also calculated and measures the reaction rates of U-hydriding and proposed a diffusion model for the U-hydriding. This model was found to be in excellent agreement with the experimental reaction rates. From the slopes of the Arrhenius plot the activation energy was calculated as 6.35 kcal/mole. In a subsequent study Kirkpatrick formulated a close-form for approximate solution to Condon's equation. Bloch and Mintz have proposed the kinetics and mechanism for the U-H reaction over a wide range of pressures and temperatures. They have discussed their results through two models, one, which considers hydrogen diffusion through a protective UH{sub 3} product layer, and the second where hydride growth occurs at the hydride-metal interface. These authors obtained two-dimensional fits of experimental data to the pressure-temperature reactions. Kirkpatrick and Condon have obtained a linear solution to hydriding of uranium. These authors showed that the calculated reaction rates compared quite well with the experimental data at a hydrogen pressure of 1 atm. Powell

  11. Europium palladium hydrides.

    PubMed

    Kohlmann, H; Fischer, H E; Yvon, K

    2001-05-21

    The first fully structurally characterized ternary europium palladium hydrides (deuterides) are reported. The most Eu rich compound is Eu(2)PdD(4). Its beta-K(2)SO(4) type structure (space group Pnma, a = 749.47(1) pm, b = 543.34(1) pm, c = 947.91(1) pm, Z = 4) contains tetrahedral 18-electron [PdD(4)](4)(-) complex anions and divalent Eu cations. The compound is presumably nonmetallic and shows paramagnetic behavior (mu(eff) = 8.0(2) mu(B)) with ferromagnetic ordering at T(C) = 15.1(4) K. A metallic compound at intermediate Eu content is EuPdD(3). It crystallizes with the cubic perovskite structure (space group Pm3m, a = 380.01(2) pm, Z = 1) in which palladium is octahedrally surrounded by fully occupied deuterium sites. Metallic hydrides at low Eu content form by reversible hydrogen absorption of intermetallic EuPd(2) (Fd3m, a = 775.91(1) pm, Z = 8). Depending on the experimental conditions at least three phases with distinctly different hydrogen contents x exist: EuPd(2)H(x) ( approximately )(0.1) (a = 777.02(2) pm, Z = 8, T = 298 K, p(H(2)) = 590 kPa), EuPd(2)H(x) ( approximately )(1.5) (a = 794.47(5) pm, Z = 8, T = 298 K, p(H(2)) = 590 kPa), and EuPd(2)H(x) ( approximately )(2.1) (a = 802.1(1) pm, Z = 8, T = 350 K, p(H(2)) = 610 kPa). All crystallize with cubic Laves phase derivative structures and have presumably disordered hydrogen distributions.

  12. Coral calcium hydride prevents hepatic steatosis in high fat diet-induced obese rats: A potent mitochondrial nutrient and phase II enzyme inducer.

    PubMed

    Hou, Chen; Wang, Yongyao; Zhu, Erkang; Yan, Chunhong; Zhao, Lin; Wang, Xiaojie; Qiu, Yingfeng; Shen, Hui; Sun, Xuejun; Feng, Zhihui; Liu, Jiankang; Long, Jiangang

    2016-03-01

    Diet-induced nonalcoholic fatty liver disease (NAFLD) is characterized by profound lipid accumulation and associated with an inflammatory response, oxidative stress and hepatic mitochondrial dysfunction. We previously demonstrated that some mitochondrial nutrients effectively ameliorated high fat diet (HFD)-induced hepatic steatosis and metabolic disorders. Molecular hydrogen in hydrogen-rich liquid or inhaling gas, which has been confirmed in scavenging reactive oxygen species and preventing mitochondrial decay, improved metabolic syndrome in patients and animal models. Coral calcium hydride (CCH) is a new solid molecular hydrogen carrier made of coral calcium. However, whether and how CCH impacts HFD-induced hepatic steatosis remains uninvestigated. In the present study, we applied CCH to a HFD-induced NAFLD rat model for 13 weeks. We found that CCH durably generated hydrogen in vivo and in vitro. CCH treatment significantly reduced body weight gain, improved glucose and lipid metabolism and attenuated hepatic steatosis in HFD-induced obese rats with no influence on food and water intake. Moreover, CCH effectively improved HFD-induced hepatic mitochondrial dysfunction, reduced oxidative stress, and activated phase II enzymes. Our results suggest that CCH is an efficient hydrogen-rich agent, which could prevent HFD-induced NAFLD via activating phase II enzymes and improving mitochondrial function. Copyright © 2016 Elsevier Inc. All rights reserved.

  13. Enantiomers separation by nano-liquid chromatography: use of a novel sub-2 μm vancomycin silica hydride stationary phase.

    PubMed

    Rocchi, Silvia; Rocco, Anna; Pesek, Joseph J; Matyska, Maria T; Capitani, Donatella; Fanali, Salvatore

    2015-02-13

    A novel sub-2 μm chiral stationary phase (CSP) was prepared immobilizing vancomycin onto 1.8 μm diol hydride-based silica particles. The CSP was packed into fused silica capillaries of 75 μm i.d. with a length of 11 cm and evaluated by means of nano-liquid chromatography (nano-LC) using model compounds of both pharmaceutical and environmental interest (some non-steroidal anti-inflammatory drugs, β-blockers and herbicides). The study of the effect of the linear velocity of the mobile phase on chromatographic efficiency showed good enantioresolutions up to a value of 5.11 at the optimal linear velocity with efficiencies in terms of number of plates per meter in the range 51,650-68,330. The results were compared with the ones obtained employing 5 μm vancomycin modified diol-silica particles packed in capillaries of the same i.d. For the acidic analytes the sub-2 μm CSP showed better performances, the baseline chiral separation of several studied compounds occurred in an analysis time of less than 3 min. Column-to-column packing reproducibility (n=3) expressed as relative standard deviation was in the range 2.2-5.8% and 0.5-7.7% for retention times and peak areas, respectively.

  14. Mechanical behavior of shock-wave consolidated nano and micron-sized aluminum/silicon carbide and aluminum/aluminum oxide two-phase systems characterized by light and electron metallography

    NASA Astrophysics Data System (ADS)

    Alba-Baena, Noe Gaudencio

    This dissertation reports the results of the exploratory study of two-phase systems consisting of 150 microm diameter aluminum powder mechanically mixed with 30 nm and 30 microm diameter SiC and Al2O3 powders (in volume fractions of 2, 4, and 21 percent). Powders were mechanically mixed and green compacted to ˜80% theorical density in a series of cylindrical fixtures (steel tubes). The compacted arrangements were explosively consolidated using ammonium nitrate-fuel oil (ANFO) to form stacks of two-phase systems. As result, successfully consolidated cylindrical monoliths of 50 mm (height) x 32 mm (in diameter) were obtained. By taking advantage of the use of SWC (shock wave consolidation) and WEDM (wire-electric discharge machining), the heterogeneous systems were machined in a highly efficiency rate. The sample cuts used for characterization and mechanical properties testing, require the use of less that 10cc of each monolith, in consequence there was preserved an average of 60% of the obtained system monoliths. Consolidated test cylinders of the pure Al and two-phase composites were characterized by optical metallography and TEM. The light micrographs for the five explosively consolidated regimes: aluminum powder, nano and micron-sized Al/Al2O3 systems, and the nano and micron-sized Al/SiC systems exhibit similar ductility in the aluminum grains. Low volume fraction systems exhibit small agglomerations at the grain boundaries for the Al/Al2O3 system and the Al/SiC system reveal a well distributed phase at the grain boundaries. Large and partially bonded agglomerations were observable in the nano-sized high volume fraction (21%) systems, while the micron-sized Al/ceramic systems exhibit homogeneous distribution along the aluminum phase grains. TEM images showed the shock-induced dislocation cell structure, which has partially recrystallized to form a nano grain structure in the consolidated aluminum powder. Furthermore, the SiC nano-agglomerates appeared to have

  15. Experimental research of phase transition's kinetics in a liquid melt of high-purity aluminum

    NASA Astrophysics Data System (ADS)

    Vorontsov, V. B.; Zhuravlev, D. V.; Cherepanov, A. S.

    2015-08-01

    This scientific work is devoted to the studying of the genetic connection structures of solid and liquid phases. Fourier analysis of signals of acoustic emission (AE) accompanying melting high purity aluminum from the melting point up to t = 860°C was performed. Based on the results of previous studies cluster formations in the melt - the micro-regions, those retain crystallinity (areas with short-range order of symmetry) were considered as the source of AE. The experimental data allowed to follow the dynamics of disorder zones range order in the melt with increasing melt temperature up to their complete destruction. The presented results of spectral analysis of the signals were analyzed from the standpoint of the theory of cluster melting metals.

  16. Single-Phase Rare-Earth Oxide/Aluminum Oxide Glasses

    NASA Technical Reports Server (NTRS)

    Weber, J. K. Richard; Abadie, John G.; Hixson, April D.; Nordine, Paul C.

    2006-01-01

    Glasses that comprise rare-earth oxides and aluminum oxide plus, optionally, lesser amounts of other oxides, have been invented. The other oxide(s) can include SiO2, B2O3, GeO2, and/or any of a variety of glass-forming oxides that have been used heretofore in making a variety of common and specialty glasses. The glasses of the invention can be manufactured in bulk single-phase forms to ensure near uniformity in optical and mechanical characteristics, as needed for such devices as optical amplifiers, lasers, and optical waveguides (including optical fibers). These glasses can also be formulated to have high indices of refraction, as needed in some of such devices.

  17. Cytotoxic properties of nanostructures based on aluminum oxide and hydroxide phases

    NASA Astrophysics Data System (ADS)

    Lozhkomoev, A. S.

    2016-11-01

    We study cytotoxic properties of low-dimensional nanostructures based on aluminum oxide and hydroxide phases with the morphology of agglomerated crumpled nanosheets. Among them are nanostructures of pseudoboehmite, γ-Al2O3 and θ-Al2O3. Nanostructures of pseudoboehmite synthesized by hydrothermal oxidation of AlN/Al nanoparticles in water. γ-Al2O3 and θ-Al2O3 nanostructures were prepared by heat treatment of pseudoboehmite. The greatest cytotoxic effect is seen for cells in contact with γ-Al2O3. An analysis of properties of the synthesized nanostructures shows that γ-Al2O3 causes a higher increase in pH values of the cell culture medium and neutralizes the acidity to a greater extent.

  18. Crystallization kinetics and phase transformations in aluminum ion-implanted electrospun TiO2 nanofibers

    NASA Astrophysics Data System (ADS)

    Albetran, H.; Low, I. M.

    2016-12-01

    Electrospun TiO2 nanofibers were implanted with aluminum ions, and their crystallization kinetics, phase transformations, and activation energies were investigated from 25 to 900 °C by in situ high-temperature synchrotron radiation diffraction. The amorphous non-implanted and Al ion-implanted TiO2 nanofibers transformed to crystalline anatase at 600 °C and to rutile at 700 °C. The TiO2 phase transformation of the Al ion-implanted material was accelerated relative to non-implanted sample. Compared with non-implanted nanofibers, the Al-implanted materials yielded a decreased activation energies from 69(17) to 29(2) kJ/mol for amorphous-to-anatase transformation and from 112(15) to 129(5) kJ/mol for anatase-to-rutile transformation. A substitution of smaller Al ions for Ti in the TiO2 crystal structure results in accelerated titania phase transformation and a concomitant reduction in the activation energies.

  19. Pole figure measurement of the initial growth of GaN nanoneedles on GaN/Si(111) by using hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Jeon, Injun; Lee, Ha Young; Noh, Ji-Yeon; Ahn, Hyung Soo; Yi, Sam Nyung; Jeon, Hunsoo; Shin, Min Jeong; Yu, Young Moon; Ha, Dong Han

    2016-09-01

    We report on crystallographic analyses of one-dimensional GaN nanoneedles grown on a n-GaN epilayer by using hydride vapor phase epitaxy. The nanoneedles were grown with a HCl:NH3 gas flow ratio of 1:38 at 600 °C. The growth time of the GaN nanoneedles affected their morphologies. As time progressed, GaN dots nucleated and then evolved as nanoneedles. The vertical growth rate of GaN nanoneedles was higher than the lateral growth rate under optimized growth conditions. X-ray pole figure measurements were carried out using a four-axis diffractometer. For the sample grown for 20 min, we obtained discrete patterns with six strong dots and weak dough-nut and cotton swab patterns, indicating that most of the nanoneedles were grown ideally, but partially, in the x- y plane with an azimuthal rotation angle ϕ = 15 ~ 45° rotated to the substrate, and a few GaN nanoneedles were tilted by ±4° or by more than 32° from the vertical c-axis.

  20. Nearly 4-Inch-Diameter Free-Standing GaN Wafer Fabricated by Hydride Vapor Phase Epitaxy with Pit-Inducing Buffer Layer

    NASA Astrophysics Data System (ADS)

    Sato, Tadashige; Okano, Shinya; Goto, Takenari; Yao, Takafumi; Seto, Ritsu; Sato, Akira; Goto, Hideki

    2013-08-01

    A free-standing GaN wafer was fabricated by depositing a GaN buffer that induced the formation of pits (hereafter, pit-inducing GaN buffer) on a low-temperature-grown GaN buffer on the sapphire substrate. A high-temperature-grown GaN layer was grown on the pit-inducing GaN buffer that induced the formation of pits on the high-temperature-grown GaN layer. The pit-inducing buffer suppresses crack formation in the thick GaN film thereby releasing growth stress. Thermal stress in GaN on a sapphire system is also discussed on the basis of calculations utilizing a bilayer model. We have succeeded in the fabrication of a nearly 4-in.-diameter free-standing GaN thick wafer with a pit-inducing GaN buffer by one-stop hydride vapor phase epitaxy, which will lead to a low-cost fabrication of free-standing GaN wafers.

  1. AlN and AlGaN layers grown on Si(111) substrate by mixed-source hydride vapor phase epitaxy method

    NASA Astrophysics Data System (ADS)

    Jeon, Hunsoo; Jeon, Injun; Lee, Gang Seok; Bae, Sung Geun; Ahn, Hyung Soo; Yang, Min; Yi, Sam Nyung; Yu, Young Moon; Honda, Yoshio; Sawaki, Nobuhiko; Kim, Suck-Whan

    2017-01-01

    High Al-composition AlGaN and AlN epilayers were grown directly on Si(111) substrate by a hydride vapor phase epitaxy (HVPE) method with a melted mixed source in a graphite boat set in a source zone with high temperatures of T = 700 and 800 °C, respectively. The presence of the Ga material in the mixed source of Ga and Al promoted the growth of AlN and AlGaN epilayers in the growth zone. When the temperature in the source zone was 800 °C, the crystalline quality of the AlN and AlGaN epilayers increased as the ratio of Ga to Al increased, and the optimum mix ratio of Ga to Al for the growth of AlN epilayers was approximately 0.35-0.42, obtained from a numerical fitting analysis of the X-ray diffraction (XRD) data for these epilayers. It appears that they can be grown directly by our melted-mixed-source HVPE method in a high-temperature source zone.

  2. Nuclear magnetic resonance studies of hydrogen motion in nanostructured Laves-phase hydrides ZrCr(2)H(x) and TaV(2)H(x).

    PubMed

    Soloninin, A V; Buzlukov, A L; Skripov, A V; Aleksashin, B A; Tankeyev, A P; Yermakov, A Ye; Mushnikov, N V; Uimin, M A; Gaviko, V S

    2008-07-09

    In order to study the mobility of hydrogen in nanostructured Laves-phase hydrides, we have measured the proton nuclear magnetic resonance (NMR) spectra and the proton spin-lattice and spin-spin relaxation rates in two nanostructured systems prepared by ball milling: ZrCr(2)H(3) and TaV(2)H(1+δ). The proton NMR measurements have been performed at the resonance frequencies of 14, 23.8 and 90 MHz over the temperature ranges 11-424 K (for coarse-grained samples) and 11-384 K (for nanostructured samples). Hydrogen mobility in the ball-milled ZrCr(2)H(3) is found to decrease strongly with increasing milling time. The experimental data suggest that this effect is related to the growth of the fraction of highly distorted intergrain regions where H mobility is much lower than in the crystalline grains. For the nanostructured TaV(2)H(1+δ) system, the ball milling is found to lead to a slight decrease in the long-range H mobility and to a suppression of the fast localized H motion in the crystalline grains.

  3. Optical in-situ monitoring system for simultaneous measurement of thickness and curvature of thick layer stacks during hydride vapor phase epitaxy growth of GaN

    NASA Astrophysics Data System (ADS)

    Semmelroth, K.; Berwian, P.; Schröter, C.; Leibiger, G.; Schönleber, M.; Friedrich, J.

    2015-10-01

    For improved real-time process control we integrated a novel optical in-situ monitoring system in a vertical reactor for hydride vapor phase epitaxy (HVPE) growth of gallium nitride (GaN) bulk crystals. The in-situ monitoring system consists of a fiber-optical interferometric sensor in combination with an optimized differential measuring head. The system only needs one small optical path perpendicular to the center of the layer stack typically consisting of sapphire as substrate and GaN. It can handle sample distances up to 1 m without difficulty. The in-situ monitoring system is simultaneously measuring the optical layer thicknesses of the GaN/sapphire layer stack and the absolute change of the distance between the measuring head and the backside of the layer stack. From this data it is possible to calculate the thickness of the growing GaN up to a thickness of about 1000 μm and the absolute change in curvature of the layer stack. The performance of the in-situ monitoring system is shown and discussed based on the measured interference signals recorded during a short-time and a long-time HVPE growth run.

  4. Hydride-vapor-phase epitaxial growth of highly pure GaN layers with smooth as-grown surfaces on freestanding GaN substrates

    NASA Astrophysics Data System (ADS)

    Fujikura, Hajime; Konno, Taichiro; Yoshida, Takehiro; Horikiri, Fumimasa

    2017-08-01

    Thick (20-30 µm) layers of highly pure GaN with device-quality smooth as-grown surfaces were prepared on freestanding GaN substrates by using our advanced hydride-vapor-phase epitaxy (HVPE) system. Removal of quartz parts from the HVPE system markedly reduced concentrations of residual impurities to below the limits of detection by secondary-ion mass spectrometry. Appropriate gas-flow management in the HVPE system realized device-quality, smooth, as-grown surfaces with an excellent uniformity of thickness. The undoped GaN layer showed insulating properties. By Si doping, the electron concentration could be controlled over a wide range, down to 2 × 1014 cm-3, with a maximum mobility of 1150 cm2·V-1·s-1. The concentration of residual deep levels in lightly Si-doped layers was in the 1014 cm-3 range or less throughout the entire 2-in. wafer surface. These achievements clearly demonstrate the potential of HVPE as a tool for epitaxial growth of power-device structures.

  5. Hydridable material for the negative electrode in a nickel-metal hydride storage battery

    DOEpatents

    Knosp, Bernard; Bouet, Jacques; Jordy, Christian; Mimoun, Michel; Gicquel, Daniel

    1997-01-01

    A monophase hydridable material for the negative electrode of a nickel-metal hydride storage battery with a "Lave's phase" structure of hexagonal C14 type (MgZn.sub.2) has the general formula: Zr.sub.1-x Ti.sub.x Ni.sub.a Mn.sub.b Al.sub.c Co.sub.d V.sub.e where ##EQU1##

  6. Flow analysis-hydride generation-gas phase derivative molecular absorption spectrophotometric determination of antimony in oral homeopathic products ("AntimoniumTartaricum") formulated under alcoholic medium.

    PubMed

    Gallignani, Máximo; Ovalles, Fernando; Brunetto, Maria Del Rosario; Burguera, Marcela; Burguera, Jose Luis

    2005-12-15

    In this work, a flow analysis-hydride generation-gas phase derivative molecular absorption-(UV) spectrophotometric method has been developed for the direct determination of antimony in aqueous and hydro-alcoholic samples. Antimony (III) from undiluted samples is directly transformed into the gaseous stibine (SbH(3)) form by on-line reaction with sodium tetrahydroborate (NaBH(4)) in acidic medium (HCl). The gaseous phase generated is separated from the liquid phase using a commercial gas-liquid separator, and swept - with the help of a carrier gas (N(2)) stream - into a quartz gas cell (10cm pathlength); where the corresponding absorption spectrum is acquired in a continuous mode over the 190-300nm wavelength range, using a conventional spectrophotometer. A derivative strategy was selected in order to avoid the strong spectral interference of the ethanol vapor on the gaseous SbH(3) absorption spectrum. In this way, the peak height at 223nm of the second order derivative spectrum appears as a clear, clean and interference free analytical signal, which allows the direct determination of antimony. The recovery values obtained from homeopathic formulations (prepared in alcoholic medium) spiked with know amounts of antimony ranged between 97.5 and 103%. The method provides a dynamic range from 0.20 to 30mgSbl(-1). The precision (RDS), evaluated by replicate analysis (n=5) of samples and standard solution containing between 2.5 and 15mgSbl(-1) was in all cases lower than 1.2%. The proposed method was applied to the determination of antimony in commercial homeopathic products ("Antimonium Tartaricum") prepared in hydro-alcoholic medium; and showed to be simple, precise, and accurate.

  7. Synthesis, structure and gas-phase reactivity of the mixed silver hydride borohydride nanocluster [Ag3(μ3-H)(μ3-BH4)LPh3]BF4 (LPh = bis(diphenylphosphino)methane)

    NASA Astrophysics Data System (ADS)

    Zavras, Athanasios; Ariafard, Alireza; Khairallah, George N.; White, Jonathan M.; Mulder, Roger J.; Canty, Allan J.; O'Hair, Richard A. J.

    2015-10-01

    Borohydrides react with silver salts to give products that span multiple scales ranging from discrete mononuclear compounds through to silver nanoparticles and colloids. The cluster cations [Ag3(H)(BH4)L3]+ are observed upon electrospray ionization mass spectrometry of solutions containing sodium borohydride, silver(i) tetrafluoroborate and bis(dimethylphosphino)methane (LMe) or bis(diphenylphosphino)methane (LPh). By adding NaBH4 to an acetonitrile solution of AgBF4 and LPh, cooled to ca. -10 °C, we have been able to isolate the first mixed silver hydride borohydride nanocluster, [Ag3(μ3-H)(μ3-BH4)LPh3]BF4, and structurally characterise it via X-ray crystallography. Combined gas-phase experiments (LMe and LPh) and DFT calculations (LMe) reveal how loss of a ligand from the cationic complexes [Ag3(H)(BH4)L3]+ provides a change in geometry that facilitates subsequent loss of BH3 to produce the dihydride clusters, [Ag3(H)2Ln]+ (n = 1 and 2). Together with the results of previous studies (Girod et al., Chem. - Eur. J., 2014, 20, 16626), this provides a direct link between mixed silver hydride/borohydride nanoclusters, silver hydride nanoclusters, and silver nanoclusters.Borohydrides react with silver salts to give products that span multiple scales ranging from discrete mononuclear compounds through to silver nanoparticles and colloids. The cluster cations [Ag3(H)(BH4)L3]+ are observed upon electrospray ionization mass spectrometry of solutions containing sodium borohydride, silver(i) tetrafluoroborate and bis(dimethylphosphino)methane (LMe) or bis(diphenylphosphino)methane (LPh). By adding NaBH4 to an acetonitrile solution of AgBF4 and LPh, cooled to ca. -10 °C, we have been able to isolate the first mixed silver hydride borohydride nanocluster, [Ag3(μ3-H)(μ3-BH4)LPh3]BF4, and structurally characterise it via X-ray crystallography. Combined gas-phase experiments (LMe and LPh) and DFT calculations (LMe) reveal how loss of a ligand from the cationic complexes [Ag

  8. Heat-mass flow enhancement system for a metal hydride assembly

    NASA Astrophysics Data System (ADS)

    Argabright, T. A.

    1985-02-01

    Southern California Gas Company and Solar Turbines Incorporated are cooperating in the development and demonstration of a metal hydride/chemical heat pump (MHHP). In the design of the MHHP, heat transfer was considered to be the key technical study area. The goal of this effort is improved heat transfer and reduced thermal mass in a hydride heat exchanger/containment assembly. Phase 1 resulted in the detailed design of an advanced hydride heat exchanger. Phase 2 consisted of the experimental verification of the hydride alloy design data, fabrication of the hydride heat exchanger module components, heat transfer testing of the single heat exchanger element and preliminary performance testing of the entire module. Phase 3 was devoted to the complete characterization of the hydride heat exchanger modules through further operation and testing. A review of other possible hydride heat transfer concepts was also conducted in Phase 2.

  9. Chemical Hydride Hydrogen Sources for Small Fuel Cells.

    DTIC Science & Technology

    1997-09-30

    This report details and investigation into the feasibility of thermal decomposition (non-hydrolytic) of aluminum hydride ( AlH3 ) for hydrogen...production. A unique new process, referred to as the self-sustaining (SS) reaction, was developed, along with a prototype generator and cartridges of AlH3 for

  10. Elemental Water Impact Test: Phase 3 Plunge Depth of a 36-Inch Aluminum Tank Head

    NASA Technical Reports Server (NTRS)

    Vassilakos, Gregory J.

    2014-01-01

    Spacecraft are being designed based on LS-DYNA water landing simulations. The Elemental Water Impact Test (EWIT) series was undertaken to assess the accuracy of LS-DYNA water impact simulations. Phase 3 featured a composite tank head that was tested at a range of heights to verify the ability to predict structural failure of composites. To support planning for Phase 3, a test series was conducted with an aluminum tank head dropped from heights of 2, 6, 10, and 12 feet to verify that the test article would not impact the bottom of the test pool. This report focuses on the comparisons of the measured plunge depths to LS-DYNA predictions. The results for the tank head model demonstrated the following. 1. LS-DYNA provides accurate predictions for peak accelerations. 2. LS-DYNA consistently under-predicts plunge depth. An allowance of at least 20% should be added to the LS-DYNA predictions. 3. The LS-DYNA predictions for plunge depth are relatively insensitive to the fluid-structure coupling stiffness.

  11. Process for production of a metal hydride

    SciTech Connect

    Allen, Nathan Tait; Butterick, III, Robert; Chin, Arthur Achhing; Millar, Dean Michael; Molzahn, David Craig

    2014-08-12

    A process for production of a metal hydride compound MH.sub.x, wherein x is one or two and M is an alkali metal, Be or Mg. The process comprises combining a compound of formula (R.sup.1O).sub.xM with aluminum, hydrogen and at least one metal selected from among titanium, zirconium, hafnium, niobium, vanadium, tantalum and iron to produce a compound of formula MH.sub.x. R.sup.1 is phenyl or phenyl substituted by at least one alkyl or alkoxy group. A mole ratio of aluminum to (R.sup.1O).sub.xM is from 0.1:1 to 1:1. The catalyst is present at a level of at least 200 ppm based on weight of aluminum.

  12. Correlation between the residual stress and the density of threading dislocations in GaN layers grown by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Barchuk, M.; Röder, C.; Shashev, Y.; Lukin, G.; Motylenko, M.; Kortus, J.; Pätzold, O.; Rafaja, D.

    2014-01-01

    The correlation between the residual stress and the density of threading dislocations was investigated in polar GaN layers that were grown by using hydride vapor phase epitaxy (HVPE) on three different GaN templates. The first template type was GaN grown on sapphire by metal-organic vapor phase epitaxy. The second template type was a closed GaN nucleation layer grown on sapphire by HVPE. The third template type was a non-closed GaN nucleation layer grown by HVPE, which formed isolated pyramids on the sapphire surface. The residual stress was determined using the combination of micro-Raman spectroscopy and modified sin2 ψ method. The interplanar spacings needed for the sin2 ψ method were obtained from the reciprocal space maps that were measured using high-resolution X-ray diffraction. The density of threading dislocations was concluded from the broadening of the reciprocal lattice points that was measured using high-resolution X-ray diffraction as well. The fitting of the reciprocal space maps allowed the character of the threading dislocations to be described quantitatively in terms of the fractions of edge and screw dislocations. It was found that the threading dislocation density increases with increasing compressive residual stress. Furthermore, the dislocation density and the residual stress decrease with increasing thickness of the GaN layers. The edge component of the threading dislocations was dominant in all samples. Still, some differences in the character of the dislocations were observed for different templates.

  13. The Use of Sodium Chloride & Aluminum as Phase Change Materials for High Temperature Thermal Energy Storage Characterized by Calorimetry

    NASA Astrophysics Data System (ADS)

    Solomon, Laura

    2013-01-01

    Encapsulated phase change materials (EPCM) have a great deal of potential for the storage of thermal energy in a wide range of applications. The present work is aimed at developing encapsulated phase change materials capable of storing thermal energy at temperatures above 700°C for use in concentrated solar power (CSP) systems. EPCM with a phase change material (PCM) with both a salt (sodium chloride) and a metal (aluminum) are considered here. Sodium chloride and aluminum are effective storage mediums because of their high melting points and large latent heats of fusion, 800°C and 660°C and 430kJ/kg and 397kJ/kg, respectively. Based on the heat capacities and the latent heat of fusion, for a 100 degree temperature range centered on the melting point of the PCM, 80% of the energy stored by the sodium chloride PCM can be attributed to the latent heat and 79% for the aluminum PCM. These large fractions attributed to latent heat have the potential for making EPCM based thermal energy storage devices smaller and less expensive. To study the performance of the candidate PCMs considered here, a specialized immersion calorimeter was designed, calibrated, and used to evaluate the storage capabilities of sodium chloride and aluminum based EPCMs. Additionally, the EPCMs were studied to ensure no loss of capacity would occur over the lifetime of the EPCM. While no reduction in the storage capacity of the sodium chloride EPCMs was found after repeated thermal cycles, there was a decrease in the storage capacity of the aluminum EPCMs after prolonged exposure to high temperatures.

  14. Spin Forming Aluminum Crew Module (CM) Metallic Aft Pressure Vessel Bulkhead (APVBH) - Phase II

    NASA Technical Reports Server (NTRS)

    Hoffman, Eric K.; Domack, Marcia S.; Torres, Pablo D.; McGill, Preston B.; Tayon, Wesley A.; Bennett, Jay E.; Murphy, Joseph T.

    2015-01-01

    The principal focus of this project was to assist the Multi-Purpose Crew Vehicle (MPCV) program in developing a spin forming fabrication process for manufacture of the Orion crew module (CM) aft pressure vessel bulkhead. The spin forming process will enable a single piece aluminum (Al) alloy 2219 aft bulkhead resulting in the elimination of the current multiple piece welded construction, simplify CM fabrication, and lead to an enhanced design. Phase I (NASA TM-2014-218163, (1)) of this assessment explored spin forming the single-piece CM forward pressure vessel bulkhead. The MPCV Program and Lockheed Martin (LM) recently made two critical decisions relative to the NESC Phase I work scope: (1) LM selected the spin forming process to manufacture a singlepiece aft bulkhead for the Orion CM, and (2) the aft bulkhead will be manufactured from Al 2219. Based on the Program's new emphasis related to the spin forming process, the NESC was asked to conduct a Phase II assessment to assist in the LM manufacture of the aft bulkhead and to conduct a feasibility study into spin forming the Orion CM cone. This activity was approved on June 19, 2013. Dr. Robert Piascik, NASA Technical Fellow for Materials at the Langley Research Center (LaRC), was selected to lead this assessment. The project plan was approved by the NASA Engineering and Safety Center (NESC) Review Board (NRB) on July 18, 2013. The primary stakeholders for this assessment are the NASA and LM MPCV Program offices. Additional benefactors are commercial launch providers developing CM concepts.

  15. Spin Forming Aluminum Crew Module (CM) Metallic Aft Pressure Vessel Bulkhead (APVBH) - Phase II

    NASA Technical Reports Server (NTRS)

    Hoffman, Eric K.; Domack, Marcia S.; Torres, Pablo D.; McGill, Preston B.; Tayon, Wesley A.; Bennett, Jay E.; Murphy, Joseph T.

    2015-01-01

    The principal focus of this project was to assist the Multi-Purpose Crew Vehicle (MPCV) Program in developing a spin forming fabrication process for manufacture of the Orion crew module (CM) aft pressure vessel bulkhead. The spin forming process will enable a single piece aluminum (Al) alloy 2219 aft bulkhead resulting in the elimination of the current multiple piece welded construction, simplify CM fabrication, and lead to an enhanced design. Phase I (NASA TM-2014-218163 (1)) of this assessment explored spin forming the single-piece CM forward pressure vessel bulkhead. The Orion MPCV Program and Lockheed Martin (LM) recently made two critical decisions relative to the NESC Phase I work scope: (1) LM selected the spin forming process to manufacture a single-piece aft bulkhead for the Orion CM, and (2) the aft bulkhead will be manufactured from Al 2219. Based on the Program's new emphasis related to the spin forming process, the NESC was asked to conduct a Phase II assessment to assist in the LM manufacture of the aft bulkhead and to conduct a feasibility study into spin forming the Orion CM cone. This activity was approved on June 19, 2013. Dr. Robert Piascik, NASA Technical Fellow for Materials at the Langley Research Center (LaRC), was selected to lead this assessment. The project plan was approved by the NASA Engineering and Safety Center (NESC) Review Board (NRB) on July 18, 2013. The primary stakeholders for this assessment were the NASA and LM MPCV Program offices. Additional benefactors are commercial launch providers developing CM concepts.

  16. Chemistry of intermetallic hydrides

    SciTech Connect

    Reilly, J.J.

    1991-01-01

    Certain intermetallic hydrides are safe, convenient and inexpensive hydrogen storage compounds. A particular advantage of such compounds is the ease with which their properties can be modified by small changes in alloy composition or preparation. This quality can be exploited to optimize their storage properties for particular applications, e.g. as intermetallic hydride electrodes in batteries. We will be concerned herein with the more important aspects of the thermodynamic and structural principles which regulate the behavior of intermetallic hydrogen systems and then illustrate their application using the archetype hydrides of LaNi5, FeTi and Mg alloys. The practical utility of these classes of materials will be briefly noted.

  17. Compression and phase diagram of lithium hydrides at elevated pressures and temperatures by first-principles calculation

    NASA Astrophysics Data System (ADS)

    Chen, Yang M.; Chen, Xiang R.; Wu, Qiang; Geng, Hua Y.; Yan, Xiao Z.; Wang, Yi X.; Wang, Zi W.

    2016-09-01

    High pressure and high temperature properties of AB (A  =  6Li, 7Li; B  =  H, D, T) are comprehensively investigated with first-principles methods. It is found that H-sublattice features in the low-pressure electronic structure near the Fermi level of LiH are shifted to that dominated by the Li+ sublattice under compression. The lattice dynamics are studied in quasi-harmonic approximation, from which the phonon contribution to the free energy and the isotopic effects are accurately modelled with the aid of a parameterized double-Debye model. The equation of state (EOS) obtained matches perfectly with available static experimental data. The calculated principal Hugoniot is also in accordance with that derived from shock wave experiments. Using the calculated principal Hugoniot and the previous theoretical melting curve, we predict a shock melting point at 56 GPa and 1923 K. In order to establish the phase diagram for LiH, the phase boundaries between the B1 and B2 solid phases are explored. The B1-B2-liquid triple point is determined at about 241 GPa and 2413 K. The remarkable shift in the phase boundaries with isotopic effect and temperature reveal the significant role played by lattice vibrations. Furthermore, the Hugoniot of the static-dynamic coupling compression is assessed. Our EOS suggests that a precompression of the sample to 50 GPa will allow the shock Hugoniot to pass through the triple point and enter the B2 solid phase. This transition leads to a discontinuity with 4.6% volume collapse—about four times greater than the same B1-B2 transition at zero temperature.

  18. Prospects of pulse phase thermography for finding disbonds in CFRP-sandwich parts with aluminum honeycomb cores compared to ultrasonic

    NASA Astrophysics Data System (ADS)

    Gruber, J.; Stotter, B.; Mayr, G.; Hendorfer, G.

    2013-01-01

    This work shows the prospects of pulse phase thermography (PPT) compared to ultrasonic testing when applied to carbon fiber reinforced polymer (CFRP) sandwich parts with aluminum honeycomb cores. Measurements were carried out on full-scale components with flaws like disbonds, septum disbonds, staggers and displaced cores, where the last two are not literally flaws, but nevertheless regions of interest. The effect of the measurement time and the feasibility of extrapolating temperature decays were evaluated. Phase images, gathered with PPT, are compared with ultrasonic Cscan images to show the capability of PPT for quality assurance purposes. Finally, the saving on inspection time when using pulse phase thermography instead of ultrasonic testing is considered.

  19. Solid phase extraction-spectrophotometric determination of dissolved aluminum in soil extracts and ground waters.

    PubMed

    Luo, Mingbiao; Bi, Shuping

    2003-09-15

    An on-line solid-phase extraction (SPE) technique, linked to spectrophotometry, has been developed to overcome the problem of high matrix concentration, which is thought to interfere with the determination of low levels of aluminum (Al) in environmental samples. Tiron modified resin was prepared and used as a SPE absorbent, which can quantitatively adsorb Al(III) at pH 4-6 with an adsorption capacity of 5.6 mg g(-1) resin. The main advantages of this novel method are: (1) a much higher sensitivity has been obtained by SPE technology; and (2) a large amount of Na(+), K(+), Ca(2+) and Mg(2+) can be removed and the interference of Fe(III), Mn(II) and F(-) can be efficiently eliminated by eluting with 0.25 mol l(-1) NaOH. It is a highly selective and sensitive method for simple and quick determination of dissolved Al in soil extracts and ground waters, particularly suitable for the analysis of complex environmental samples.

  20. Determination of inorganic arsenic in algae using bromine halogenation and on-line nonpolar solid phase extraction followed by hydride generation atomic fluorescence spectrometry.

    PubMed

    Zhang, Weihong; Qi, Yuehan; Qin, Deyuan; Liu, Jixin; Mao, Xuefei; Chen, Guoying; Wei, Chao; Qian, Yongzhong

    2017-08-01

    Accurate, stable and fast analysis of toxic inorganic arsenic (iAs) in complicated and arsenosugar-rich algae matrix is always a challenge. Herein, a novel analytical method for iAs in algae was reported, using bromine halogenation and on-line nonpolar solid phase extraction (SPE) followed by hydride generation atomic fluorescence spectrometry (HG-AFS). The separation of iAs from algae was first performed by nonpolar SPE sorbent using Br(-) for arsenic halogenation. Algae samples were extracted with 1% perchloric acid. Then, 1.5mL extract was reduced by 1% thiourea, and simultaneously reacted (for 30min) with 50μL of 10% KBr for converting iAs to AsBr3 after adding 3.5mL of 70% HCl to 5mL. A polystyrene (PS) resin cartridge was employed to retain arsenicals, which were hydrolyzed, eluted from the PS resin with H2O, and categorized as iAs. The total iAs was quantified by HG-AFS. Under optimum conditions, the spiked recoveries of iAs in real algae samples were in the 82-96% range, and the method achieved a desirable limit of detection of 3μgkg(-1). The inter-day relative standard deviations were 4.5% and 4.1% for spiked 100 and 500μgkg(-1) respectively, which proved acceptable for this method. For real algae samples analysis, the highest presence of iAs was found in sargassum fusiforme, followed by kelp, seaweed and laver. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Critical issues for homoepitaxial GaN growth by molecular beam epitaxy on hydride vapor-phase epitaxy-grown GaN substrates

    NASA Astrophysics Data System (ADS)

    Storm, D. F.; Hardy, M. T.; Katzer, D. S.; Nepal, N.; Downey, B. P.; Meyer, D. J.; McConkie, Thomas O.; Zhou, Lin; Smith, David J.

    2016-12-01

    While the heteroepitaxial growth of gallium nitride-based materials and devices on substrates such as SiC, sapphire, and Si has been well-documented, the lack of a cost-effective source of bulk GaN crystals has hindered similar progress on homoepitaxy. Nevertheless, freestanding GaN wafers are becoming more widely available, and there is great interest in growing GaN films and devices on bulk GaN substrates, in order to take advantage of the greatly reduced density of threading dislocations, particularly for vertical devices. However, homoepitaxial GaN growth is far from a trivial task due to the reactivity and different chemical sensitivities of N-polar (000_1) and Ga-polar (0001) GaN surfaces, which can affect the microstructure and concentrations of impurities in homoepitaxial GaN layers. In order to achieve high quality, high purity homoepitaxial GaN, it is necessary to investigate the effect of the ex situ wet chemical clean, the use of in situ cleaning procedures, the sensitivity of the GaN surface to thermal decomposition, and the effect of growth temperature. We review the current understanding of these issues with a focus on homoepitaxial growth of GaN by molecular beam epitaxy (MBE) on c-plane surfaces of freestanding GaN substrates grown by hydride vapor phase epitaxy (HVPE), as HVPE-grown substrates are most widely available. We demonstrate methods for obtaining homoepitaxial GaN layers by plasma-assisted MBE in which no additional threading dislocations are generated from the regrowth interface and impurity concentrations are greatly reduced.

  2. Hydride generation coupled to microfunnel-assisted headspace liquid-phase microextraction for the determination of arsenic with UV-Vis spectrophotometry.

    PubMed

    Hashemniaye-Torshizi, Reihaneh; Ashraf, Narges; Arbab-Zavar, Mohammad Hossein

    2014-12-01

    In this research, a microfunnel-assisted headspace liquid-phase microextraction technique has been used in combination with hydride generation to determine arsenic (As) by UV-Vis spectrophotometry. The method is based on the reduction of As to arsine (AsH3) in acidic media by sodium tetrahydroborate (NaBH4) followed by its subsequent reaction with silver diethyldithiocarbamate (AgDDC) to give an absorbing complex at 510 nm. The complexing reagent (AgDDC) has been dissolved in a 1:1 (by the volume ratio) mixture of chloroform/chlorobenzene microdroplet and exposed to the generated gaseous arsine via a reversed microfunnel in the headspace of the sample solution. Several operating parameters affecting the performance of the method have been examined and optimized. Acetonitrile solvent has been added to the working samples as a sensitivity enhancement agent. Under the optimized operating conditions, the detection limit has been measured to be 0.2 ng mL(-1) (based on 3sb/m criterion, n b = 8), and the calibration curve was linear in the range of 0.5-12 ng mL(-1). The relative standard deviation for eight replicate measurements was 1.9 %. Also, the effects of several potential interferences have been studied. The accuracy of the method was validated through the analysis of JR-1 geological standard reference material. The method has been successfully applied for the determination of arsenic in raw and spiked soft drink and water samples with the recoveries that ranged from 91 to 106 %.

  3. On-line electrochemically controlled in-tube solid phase microextraction of inorganic selenium followed by hydride generation atomic absorption spectrometry.

    PubMed

    Asiabi, Hamid; Yamini, Yadollah; Seidi, Shahram; Shamsayei, Maryam; Safari, Meysam; Rezaei, Fatemeh

    2016-05-30

    In this work, for the first time, a rapid, simple and sensitive microextraction procedure is demonstrated for the matrix separation, preconcentration and determination of inorganic selenium species in water samples using an electrochemically controlled in-tube solid phase microextraction (EC-in-tube SPME) followed by hydride generation atomic absorption spectrometry (HG-AAS). In this approach, in which EC-in-tube SPME and HG-AAS system were combined, the total analysis time, was decreased and the accuracy, repeatability and sensitivity were increased. In addition, to increases extraction efficiency, a novel nanostructured composite coating consisting of polypyrrole (PPy) doped with ethyleneglycol dimethacrylate (EGDMA) was prepared on the inner surface of a stainless-steel tube by a facile electrodeposition method. To evaluate the offered setup and the new PPy-EGDMA coating, it was used to extract inorganic selenium species in water samples. Extraction of inorganic selenium species was carried out by applying a positive potential through the inner surface of coated in-tube under flow conditions. Under the optimized conditions, selenium was detected in amounts as small as 4.0 parts per trillion. The method showed good linearity in the range of 0.012-200 ng mL(-1), with coefficients of determination better than 0.9996. The intra- and inter-assay precisions (RSD%, n = 5) were in the range of 2.0-2.5% and 2.7-3.2%, respectively. The validated method was successfully applied for the analysis of inorganic selenium species in some water samples and satisfactory results were obtained. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Phase transformations during the interaction of Nb2O5 and FeNb2O6 with aluminum

    NASA Astrophysics Data System (ADS)

    Mansurova, A. N.; Chumarev, V. M.; Leont'ev, L. I.; Gulyaeva, R. I.; Sel'menskikh, N. I.

    2012-11-01

    The phase transformations that occur during the interaction of niobium pentoxide and iron niobate with aluminum are studied by differential scanning calorimetry, X-ray diffraction analysis and electronprobe microanalysis. The sequence of the formation of intermediate phases based on an NbO2 solid solution is revealed. It is shown that the reduction of niobium from Nb2O5 is hindered by the formation of hard-to-reduce oxides Al2O3 · 25Nb2O5, Al2O3 · 9Nb2O5 and AlNbO4. The interaction of FeNb2O6 with aluminum is accompanied by the formation of [(Fe,Nb)O2]s.s and NbO2 solid solutions.

  5. Regenerative Hydride Heat Pump

    NASA Technical Reports Server (NTRS)

    Jones, Jack A.

    1992-01-01

    Hydride heat pump features regenerative heating and single circulation loop. Counterflow heat exchangers accommodate different temperatures of FeTi and LaNi4.7Al0.3 subloops. Heating scheme increases efficiency.

  6. Advanced Hydride Laboratory

    SciTech Connect

    Horen, A.S.

    1989-12-31

    The Replacement Tritium Facility (RTF) is a $140 million reservoir loading and unloading facility using state-of-the-art technology, scheduled for completion in 1990 and startup in 1991. In the RTF, metal hydride technology will be used to store, separate, purify, pump, and compress hydrogen isotopes. In support of the RTF, a $3.2 million ``cold`` process demonstration facility began operation in November, 1987. The purpose of the Advanced Hydride Laboratory (AHL) is to demonstrate the RFT`s metal hydride technology by integrating the various unit operations into an overall process. While much of the RTF`s metal hydride technology had been demonstrated in laboratory bench-scale and pilot-scale units, none of the units had been operated together and integrated into an overall process.

  7. Advanced Hydride Laboratory

    SciTech Connect

    Horen, A.S.

    1989-01-01

    The Replacement Tritium Facility (RTF) is a $140 million reservoir loading and unloading facility using state-of-the-art technology, scheduled for completion in 1990 and startup in 1991. In the RTF, metal hydride technology will be used to store, separate, purify, pump, and compress hydrogen isotopes. In support of the RTF, a $3.2 million cold'' process demonstration facility began operation in November, 1987. The purpose of the Advanced Hydride Laboratory (AHL) is to demonstrate the RFT's metal hydride technology by integrating the various unit operations into an overall process. While much of the RTF's metal hydride technology had been demonstrated in laboratory bench-scale and pilot-scale units, none of the units had been operated together and integrated into an overall process.

  8. Hydride heat pump

    DOEpatents

    Cottingham, James G.

    1977-01-01

    Method and apparatus for the use of hydrides to exhaust heat from one temperature source and deliver the thermal energy extracted for use at a higher temperature, thereby acting as a heat pump. For this purpose there are employed a pair of hydridable metal compounds having different characteristics working together in a closed pressure system employing a high temperature source to upgrade the heat supplied from a low temperature source.

  9. ORNL Interim Progress Report on Hydride Reorientation CIRFT Tests

    SciTech Connect

    Wang, Jy-An John; Yan, Yong; Wang, Hong

    2016-10-28

    A systematic study of H. B. Robinson (HBR) high burnup spent nuclear fuel (SNF) vibration integrity was performed in Phase I project under simulated transportation environments, using the Cyclic Integrated Reversible-Bending Fatigue Tester (CIRFT) hot cell testing technology developed at Oak Ridge National Laboratory in 2013–14. The data analysis on the as-irradiated HBR SNF rods demonstrated that the load amplitude is the dominant factor that controls the fatigue life of bending rods. However, previous studies have shown that the hydrogen content and hydride morphology has an important effect on zirconium alloy mechanical properties. To address the effect of radial hydrides in SNF rods, in Phase II a test procedure was developed to simulate the effects of elevated temperatures, pressures, and stresses during transfer-drying operations. Pressurized and sealed fuel segments were heated to the target temperature for a preset hold time and slow-cooled at a controlled rate. The procedure was applied to both non-irradiated/prehydrided and high-burnup Zircaloy-4 fueled cladding segments using the Nuclear Regulatory Commission-recommended 400°C maximum temperature limit at various cooling rates. Before testing high-burnup cladding, four out-of-cell tests were conducted to optimize the hydride reorientation (R) test condition with pre-hydride Zircaloy-4 cladding, which has the same geometry as the high burnup fuel samples. Test HR-HBR#1 was conducted at the maximum hoop stress of 145 MPa, at a 400°C maximum temperature and a 5°C/h cooling rate. On the other hand, thermal cycling was performed for tests HR-HBR#2, HR-HBR#3, and HR-HBR#4 to generate more radial hydrides. It is clear that thermal cycling increases the ratio of the radial hydride to circumferential hydrides. The internal pressure also has a significant effect on the radial hydride morphology. This report describes a procedure and experimental results of the four out-of-cell hydride reorientation tests of

  10. High H- ionic conductivity in barium hydride

    NASA Astrophysics Data System (ADS)

    Verbraeken, Maarten C.; Cheung, Chaksum; Suard, Emmanuelle; Irvine, John T. S.

    2015-01-01

    With hydrogen being seen as a key renewable energy vector, the search for materials exhibiting fast hydrogen transport becomes ever more important. Not only do hydrogen storage materials require high mobility of hydrogen in the solid state, but the efficiency of electrochemical devices is also largely determined by fast ionic transport. Although the heavy alkaline-earth hydrides are of limited interest for their hydrogen storage potential, owing to low gravimetric densities, their ionic nature may prove useful in new electrochemical applications, especially as an ionically conducting electrolyte material. Here we show that barium hydride shows fast pure ionic transport of hydride ions (H-) in the high-temperature, high-symmetry phase. Although some conductivity studies have been reported on related materials previously, the nature of the charge carriers has not been determined. BaH2 gives rise to hydride ion conductivity of 0.2 S cm-1 at 630 °C. This is an order of magnitude larger than that of state-of-the-art proton-conducting perovskites or oxide ion conductors at this temperature. These results suggest that the alkaline-earth hydrides form an important new family of materials, with potential use in a number of applications, such as separation membranes, electrochemical reactors and so on.

  11. Scattering law of a magnesium hydride moderator

    NASA Astrophysics Data System (ADS)

    Muhrer, G.; Hartl, M.; Daemen, L.; Tovesson, F.; Schnegg, A.; Russina, M.; Schachinger, E.

    2011-02-01

    Metal hydrides have long been considered possible moderator and pre-moderator materials for neutron sources. These materials have hydrogen density comparable to liquid hydrogen or light water. They usually do not undergo phase transitions in the desired operating range of 0-300 K, and display reasonable resistance to radiation damage. Magnesium hydride is such a simple, robust hydride system. To assess its neutronic usefulness as a moderator material, we determined experimentally the total scattering cross-section of the material. We compared our theoretical results to the experimental total neutron cross-section and to the data from quasi-elastic neutron scattering experiments, and produced a scattering kernel suitable for neutron transport calculations.

  12. Process for massively hydriding zirconium--uranium fuel elements

    DOEpatents

    Katz, N.H.

    1973-12-01

    A method is described of hydriding uranium-zirconium alloy by heating the alloy in a vacuum, introducing hydrogen and maintaining an elevated temperature until occurrence of the beta--delta phase transformation and isobarically cooling the composition. (Official Gazette)

  13. Aluminum alloy

    NASA Technical Reports Server (NTRS)

    Blackburn, Linda B. (Inventor); Starke, Edgar A., Jr. (Inventor)

    1989-01-01

    This invention relates to aluminum alloys, particularly to aluminum-copper-lithium alloys containing at least about 0.1 percent by weight of indium as an essential component, which are suitable for applications in aircraft and aerospace vehicles. At least about 0.1 percent by weight of indium is added as an essential component to an alloy which precipitates a T1 phase (Al2CuLi). This addition enhances the nucleation of the precipitate T1 phase, producing a microstructure which provides excellent strength as indicated by Rockwell hardness values and confirmed by standard tensile tests.

  14. Aluminum alloy

    NASA Technical Reports Server (NTRS)

    Blackburn, Linda B. (Inventor); Starke, Edgar A., Jr. (Inventor)

    1989-01-01

    This invention relates to aluminum alloys, particularly to aluminum-copper-lithium alloys containing at least about 0.1 percent by weight of indium as an essential component, which are suitable for applications in aircraft and aerospace vehicles. At least about 0.1 percent by weight of indium is added as an essential component to an alloy which precipitates a T1 phase (Al2CuLi). This addition enhances the nucleation of the precipitate T1 phase, producing a microstructure which provides excellent strength as indicated by Rockwell hardness values and confirmed by standard tensile tests.

  15. System integration and demonstration of adhesive bonded high temperature aluminum alloys for aerospace structure, phase 2

    NASA Technical Reports Server (NTRS)

    Falcone, Anthony; Laakso, John H.

    1993-01-01

    Adhesive bonding materials and processes were evaluated for assembly of future high-temperature aluminum alloy structural components such as may be used in high-speed civil transport aircraft and space launch vehicles. A number of candidate high-temperature adhesives were selected and screening tests were conducted using single lap shear specimens. The selected adhesives were then used to bond sandwich (titanium core) test specimens, adhesive toughness test specimens, and isothermally aged lap shear specimens. Moderate-to-high lap shear strengths were obtained from bonded high-temperature aluminum and silicon carbide particulate-reinforced (SiC(sub p)) aluminum specimens. Shear strengths typically exceeded 3500 to 4000 lb/in(sup 2) and flatwise tensile strengths exceeded 750 lb/in(sup 2) even at elevated temperatures (300 F) using a bismaleimide adhesive. All faceskin-to-core bonds displayed excellent tear strength. The existing production phosphoric acid anodize surface preparation process developed at Boeing was used, and gave good performance with all of the aluminum and silicon carbide particulate-reinforced aluminum alloys investigated. The results of this program support using bonded assemblies of high-temperature aluminum components in applications where bonding is often used (e.g., secondary structures and tear stoppers).

  16. Alumina solubility in molten salt systems of interest for aluminum electrolysis and related phase diagram data

    NASA Astrophysics Data System (ADS)

    Skybakmoen, Egil; Solheim, Asbjørn; Sterten, Åsmund

    1997-02-01

    The solubility of alumina in molten Na3AlF6 containing various amounts of AlF3, CaF2, and LiF was determined by measuring the weight loss of a rotating sintered corundum disc. The results were fitted to the following empirical expression: [Al_2 O_3 ]_{sat} = Aleft( {frac{t} {{1000}}} right)^B where begin{gathered} A = 11.9 - 0.062[AlF_3 ] - 0.003[AlF_3 ]^2 - 0.50[LiF] \\ - 0.20[CaF_2 ] - 0.30[MgF_2 ] + frac{{42[LiF] \\cdot [AlF_3 ]}} {{2000 + [LiF] \\cdot [AlF_3 ]}} \\ B = 4.8 - 0.048[AlF_3 ] + frac{{2.2[LiF]^{1.5} }} {{10 + [LiF] + 0.001[AlF_3 ]^3 }} \\ where the square brackets denote weight percent of components in the system Na3AlF6-Al2O3 (sat)-AlF3-CaF2-MgF2-LiF and t is the temperature in degree Celsius. The standard deviation between the equation and the experimental points in the temperature range from 1050 °C to about 850 °C was found to be 0.29 wt pct Al2O3. A series of revised phase diagram data of interest for aluminum electrolysis was derived based on the present work and recently published data for primary crystallization of Na3AlF6 in the same systems.

  17. Studies of hydrogen embrittlement and stress-corrosion cracking in an aluminum-zinc-magnesium alloy. [5. 6 Zn - 2. 6 Mg

    SciTech Connect

    Ciaraldi, S.W.; Nelson, J.L.; Yeske, R.A.; Pugh, E.N.

    1980-01-01

    Tensile tests have been carried out on a high-purity A1-5.6 Zn-2.6 Mg alloy hydrogenated by exposure to moist air. Results indicate that internal hydrogen embrittlement occurs by the formation and rupture of a stress-induced hydride at the grain boundaries. The hydride, identified by electron diffraction as A1H/sub 3/, is shown to be unstable in laboratory air, reverting to aluminum. The hydride phase was not detected in specimens failed by SCC, despite evidence that hydrogen is transported ahead of advancing stress-corrosion cracks, and this leads to the possibility that a basically different mechanism may be responsible for SCC in this alloy.

  18. High-pressure synthesis of noble metal hydrides.

    PubMed

    Donnerer, Christian; Scheler, Thomas; Gregoryanz, Eugene

    2013-04-07

    The formation of hydride phases in the noble metals copper, silver, and gold was investigated by in situ x-ray diffraction at high hydrogen pressures. In the case of copper, a novel hexagonal hydride phase, Cu2H, was synthesised at pressures above 18.6 GPa. This compound exhibits an anti-CdI2-type structure, where hydrogen atoms occupy every second layer of octahedral interstitial sites. In contrast to chemically produced CuH, this phase does not show a change in compressibility compared to pure copper. Furthermore, repeated compression (after decomposition of Cu2H) led to the formation of cubic copper hydride at 12.5 GPa, a phenomenon attributed to an alteration of the microstructure during dehydrogenation. No hydrides of silver (up to 87 GPa) or gold (up to 113 GPa) were found at both room and high temperatures.

  19. High-pressure synthesis of noble metal hydrides

    NASA Astrophysics Data System (ADS)

    Donnerer, Christian; Scheler, Thomas; Gregoryanz, Eugene

    2013-04-01

    The formation of hydride phases in the noble metals copper, silver, and gold was investigated by in situ x-ray diffraction at high hydrogen pressures. In the case of copper, a novel hexagonal hydride phase, Cu2H, was synthesised at pressures above 18.6 GPa. This compound exhibits an anti-CdI2-type structure, where hydrogen atoms occupy every second layer of octahedral interstitial sites. In contrast to chemically produced CuH, this phase does not show a change in compressibility compared to pure copper. Furthermore, repeated compression (after decomposition of Cu2H) led to the formation of cubic copper hydride at 12.5 GPa, a phenomenon attributed to an alteration of the microstructure during dehydrogenation. No hydrides of silver (up to 87 GPa) or gold (up to 113 GPa) were found at both room and high temperatures.

  20. Synthesis and properties of platinum hydride

    NASA Astrophysics Data System (ADS)

    Scheler, Thomas; Degtyareva, Olga; Marqués, Miriam; Guillaume, Christophe L.; Proctor, John E.; Evans, Shaun; Gregoryanz, Eugene

    2011-06-01

    Synchrotron x-ray diffraction experiments on compressed platinum-hydrogen mixtures reveal the formation of platinum hydride at a pressure of 27(1) GPa at room temperature. This compound exhibits two phases, PtH-I and PtH-II, coexisting up to the pressure of 42 GPa, above which the single phase of PtH-II is observed. Pt atoms in the PtH-II phase are shown to form a hexagonal closed-packed structure. This phase exhibits a high bulk modulus of 310 (10) GPa and is stable up to at least 53 GPa. Ab initio calculations show that PtH-II is superconducting with Tc = 12 K at 90 GPa, the highest temperature of superconducting transition among any known metal hydride.

  1. Submillimeter Spectroscopy of Hydride Molecules

    NASA Astrophysics Data System (ADS)

    Phillips, T. G.

    1998-05-01

    Simple hydride molecules are of great importance in astrophysics and astrochemistry. Physically they dominate the cooling of dense, warm phases of the ISM, such as the cores and disks of YSOs. Chemically they are often stable end points of chemical reactions, or may represent important intermediate stages of the reaction chains, which can be used to test the validity of the process. Through the efforts of astronomers, physicists, chemists, and laboratory spectroscopists we have an approximate knowledge of the abundance of some of the important species, but a great deal of new effort will be required to achieve the comprehensive and accurate data set needed to determine the energy balance and firmly establish the chemical pathways. Due to the low moment of inertia, the hydrides rotate rapidly and so have their fundamental spectral lines in the submillimeter. Depending on the cloud geometry and temperature profile they may be observed in emission or absorption. Species such as HCl, HF, OH, CH, CH(+) , NH_2, NH_3, H_2O, H_2S, H_3O(+) and even H_3(+) have been detected, but this is just a fraction of the available set. Also, most deduced abundances are not nearly sufficiently well known to draw definitive conclusions about the chemical processes. For example, the most important coolant for many regions, H_2O, has a possible range of deduced abundance of a factor of 1000. The very low submillimeter opacity at the South Pole site will be a significant factor in providing a new capabilty for interstellar hydride spectroscopy. The new species and lines made available in this way will be discussed.

  2. Spray forming -- Aluminum: Third annual report (Phase 2). Technical progress -- Summary

    SciTech Connect

    Kozarek, R.L.

    1998-04-20

    Commercial production of aluminum sheet and plate by spray atomization and deposition is a potentially attractive manufacturing alternative to conventional ingot metallurgy/hot-milling and to continuous casting processes because of reduced energy requirements and reduced cost. To realize the full potential of the technology, the Aluminum Company of America (Alcoa), under contract by the US Department of Energy, is investigating currently available state-of-the-art atomization devices to develop nozzle design concepts whose spray characteristics are tailored for continuous sheet production. This third technical progress report will summarize research and development work conducted during the period 1997 October through 1998 March. Included are the latest optimization work on the Alcoa III nozzle, results of spray forming runs with 6111 aluminum alloy and preliminary rolling trials of 6111 deposits.

  3. Results of NDE Technique Evaluation of Clad Hydrides

    SciTech Connect

    Kunerth, Dennis C.

    2014-09-01

    This report fulfills the M4 milestone, M4FT-14IN0805023, Results of NDE Technique Evaluation of Clad Hydrides, under Work Package Number FT-14IN080502. During service, zirconium alloy fuel cladding will degrade via corrosion/oxidation. Hydrogen, a byproduct of the oxidation process, will be absorbed into the cladding and eventually form hydrides due to low hydrogen solubility limits. The hydride phase is detrimental to the mechanical properties of the cladding and therefore it is important to be able to detect and characterize the presence of this constituent within the cladding. Presently, hydrides are evaluated using destructive examination. If nondestructive evaluation techniques can be used to detect and characterize the hydrides, the potential exists to significantly increase test sample coverage while reducing evaluation time and cost. To demonstrate the viability this approach, an initial evaluation of eddy current and ultrasonic techniques were performed to demonstrate the basic ability to these techniques to detect hydrides or their effects on the microstructure. Conventional continuous wave eddy current techniques were applied to zirconium based cladding test samples thermally processed with hydrogen gas to promote the absorption of hydrogen and subsequent formation of hydrides. The results of the evaluation demonstrate that eddy current inspection approaches have the potential to detect both the physical damage induced by hydrides, e.g. blisters and cracking, as well as the combined effects of absorbed hydrogen and hydride precipitates on the electrical properties of the zirconium alloy. Similarly, measurements of ultrasonic wave velocities indicate changes in the elastic properties resulting from the combined effects of absorbed hydrogen and hydride precipitates as well as changes in geometry in regions of severe degradation. However, for both approaches, the signal responses intended to make the desired measurement incorporate a number of contributing

  4. Hydrated hydride anion clusters

    NASA Astrophysics Data System (ADS)

    Lee, Han Myoung; Kim, Dongwook; Singh, N. Jiten; Kołaski, Maciej; Kim, Kwang S.

    2007-10-01

    On the basis of density functional theory (DFT) and high level ab initio theory, we report the structures, binding energies, thermodynamic quantities, IR spectra, and electronic properties of the hydride anion hydrated by up to six water molecules. Ground state DFT molecular dynamics simulations (based on the Born-Oppenheimer potential surface) show that as the temperature increases, the surface-bound hydride anion changes to the internally bound structure. Car-Parrinello molecular dynamics simulations are also carried out for the spectral analysis of the monohydrated hydride. Excited-state ab initio molecular dynamics simulations show that the photoinduced charge-transfer-to-solvent phenomena are accompanied by the formation of the excess electron-water clusters and the detachment of the H radical from the clusters. The dynamics of the detachment process of a hydrogen radical upon the excitation is discussed.

  5. Fabrication and Structure Characterization of Alumina-Aluminum Interpenetrating Phase Composites

    NASA Astrophysics Data System (ADS)

    Dolata, Anna J.

    2016-08-01

    Alumina-Aluminum composites with interpenetrating networks structure belong to advanced materials with potentially better properties when compared with composites reinforced by particles or fibers. The paper presents the experimental results of fabrication and structure characterization of Al matrix composites locally reinforced via Al2O3 ceramic foam. The composites were obtained using centrifugal infiltration of porous ceramics by liquid aluminum alloy. Both scanning electron microscopy (SEM + EDS) and x-ray tomography were used to determine the structure of foams and composites especially in reinforced areas. The quality of castings, degree of pore filling in ceramic foams by Al alloy, and microstructure in area of interface were assessed.

  6. Structural Characterization of Metal Hydrides for Energy Applications

    NASA Astrophysics Data System (ADS)

    George, Lyci

    Hydrogen can be an unlimited source of clean energy for future because of its very high energy density compared to the conventional fuels like gasoline. An efficient and safer way of storing hydrogen is in metals and alloys as hydrides. Light metal hydrides, alanates and borohydrides have very good hydrogen storage capacity, but high operation temperatures hinder their application. Improvement of thermodynamic properties of these hydrides is important for their commercial use as a source of energy. Application of pressure on materials can have influence on their properties favoring hydrogen storage. Hydrogen desorption in many complex hydrides occurs above the transition temperature. Therefore, it is important to study the physical properties of the hydride compounds at ambient and high pressure and/or high temperature conditions, which can assist in the design of suitable storage materials with desired thermodynamic properties. The high pressure-temperature phase diagram, thermal expansion and compressibility have only been evaluated for a limited number of hydrides so far. This situation serves as a main motivation for studying such properties of a number of technologically important hydrides. Focus of this dissertation was on X-ray diffraction and Raman spectroscopy studies of Mg2FeH6, Ca(BH4) 2, Mg(BH4)2, NaBH4, NaAlH4, LiAlH4, LiNH2BH3 and mixture of MgH 2 with AlH3 or Si, at different conditions of pressure and temperature, to obtain their bulk modulus and thermal expansion coefficient. These data are potential source of information regarding inter-atomic forces and also serve as a basis for developing theoretical models. Some high pressure phases were identified for the complex hydrides in this study which may have better hydrogen storage properties than the ambient phase. The results showed that the highly compressible B-H or Al-H bonds and the associated bond disordering under pressure is responsible for phase transitions observed in brorohydrides or

  7. Effect of adding powder on joint properties of laser penetration welding for dual phase steel and aluminum alloy

    NASA Astrophysics Data System (ADS)

    Zhou, D. W.; Liu, J. S.; Lu, Y. Z.; Xu, S. H.

    2017-09-01

    The experiments of laser penetration welding for dual phase steel and aluminum alloy were carried out, and the effect of adding Mn or Si powder on mechanical properties and microstructure of the weld was investigated. Some defects, such as spatter, inclusion, cracks and softening in heat affected zone (HAZ), can be avoided in welding joints, and the increased penetration depth is obtained by adding Mn or Si powder. The average tensile-shear strength of Si-added joint is 3.84% higher than that of Mn-added joint, and the strength of both joints exceeds that of no-added joint. In the case of adding Mn powder, small amount of liquid Al is mixed into steel molten pool, and the Al content increases in both sides of the weld, which leads to the increased weld width in aluminum molten pool. Thus, transverse area increases in jointing steel to aluminum, which is significant for the improved tensile-shear strength of joints. As far as adding Si powder is concerned, it is not the case, the enhancement of the joint properties benefits from improvement of metallurgical reaction.

  8. Boron hydride polymer coated substrates

    DOEpatents

    Pearson, Richard K.; Bystroff, Roman I.; Miller, Dale E.

    1987-01-01

    A method is disclosed for coating a substrate with a uniformly smooth layer of a boron hydride polymer. The method comprises providing a reaction chamber which contains the substrate and the boron hydride plasma. A boron hydride feed stock is introduced into the chamber simultaneously with the generation of a plasma discharge within the chamber. A boron hydride plasma of ions, electrons and free radicals which is generated by the plasma discharge interacts to form a uniformly smooth boron hydride polymer which is deposited on the substrate.

  9. Boron hydride polymer coated substrates

    DOEpatents

    Pearson, R.K.; Bystroff, R.I.; Miller, D.E.

    1986-08-27

    A method is disclosed for coating a substrate with a uniformly smooth layer of a boron hydride polymer. The method comprises providing a reaction chamber which contains the substrate and the boron hydride plasma. A boron hydride feed stock is introduced into the chamber simultaneously with the generation of a plasma discharge within the chamber. A boron hydride plasma of ions, electrons and free radicals which is generated by the plasma discharge interacts to form a uniformly smooth boron hydride polymer which is deposited on the substrate.

  10. Solution phase synthesis of aluminum-doped silicon nanoparticles via room-temperature, solvent based chemical reduction of silicon tetrachloride

    NASA Astrophysics Data System (ADS)

    Mowbray, Andrew James

    We present a method of wet chemical synthesis of aluminum-doped silicon nanoparticles (Al-doped Si NPs), encompassing the solution-phase co-reduction of silicon tetrachloride (SiCl4) and aluminum chloride (AlCl 3) by sodium naphthalide (Na[NAP]) in 1,2-dimethoxyethane (DME). The development of this method was inspired by the work of Baldwin et al. at the University of California, Davis, and was adapted for our research through some noteworthy procedural modifications. Centrifugation and solvent-based extraction techniques were used throughout various stages of the synthesis procedure to achieve efficient and well-controlled separation of the Si NP product from the reaction media. In addition, the development of a non-aqueous, formamide-based wash solution facilitated simultaneous removal of the NaCl byproduct and Si NP surface passivation via attachment of 1-octanol to the particle surface. As synthesized, the Si NPs were typically 3-15 nm in diameter, and were mainly amorphous, as opposed to crystalline, as concluded from SAED and XRD diffraction pattern analysis. Aluminum doping at various concentrations was accomplished via the inclusion of aluminum chloride (AlCl3); which was in small quantities dissolved into the synthesis solution to be reduced alongside the SiCl4 precursor. The introduction of Al into the chemically-reduced Si NP precipitate was not found to adversely affect the formation of the Si NPs, but was found to influence aspects such as particle stability and dispersibility throughout various stages of the procedure. Analytical techniques including transmission electron microscopy (TEM), FTIR spectroscopy, and ICP-optical emission spectroscopy were used to comprehensively characterize the product NPs. These methods confirm both the presence of Al and surface-bound 1-octanol in the newly formed Si NPs.

  11. The development of lightweight hydride alloys based on magnesium

    SciTech Connect

    Guthrie, S.E.; Thomas, G.J.; Yang, N.Y.C.; Bauer, W.

    1996-02-01

    The development of a magnesium based hydride material is explored for use as a lightweight hydrogen storage medium. It is found that the vapor transport of magnesium during hydrogen uptake greatly influences the surface and hydride reactions in these alloys. This is exploited by purposely forming near-surface phases of Mg{sub 2}Ni on bulk Mg-Al-Zn alloys which result in improved hydrogen adsorption and desorption behavior. Conditions were found where these near-surface reactions yielded a complex and heterogeneous microstructure that coincided with excellent bulk hydride behavior. A Mg-Al alloy hydride is reported with near atmospheric plateau pressures at temperatures below 200{degrees}C. Additionally, a scheme is described for low temperature in-situ fabrication of Mg{sub 2}Ni single phase alloys utilizing the high vapor pressure of Mg.

  12. Effects of high magnetic field on the evolutions of constituent phases in 7085 aluminum alloy during homogenization

    SciTech Connect

    He, Lizi; Li, Xiehua; Zhu, Pei; Cao, Yiheng; Guo, Yaping; Cui, Jianzhong

    2012-09-15

    The evolutions of coarse constituent phases in homogenized 7085 aluminum alloy at different conditions with or without the application of 12 T high magnetic field were examined by using differential scanning calorimetry, scanning electronic microscope, energy dispersive spectroscopy and X-ray diffraction. It is found that the main constituent phases including quaternary phase T(AlZnMgCu), Al{sub 7}Cu{sub 2}Fe, and AlTiCuFeSi are present in as-cast 7085 alloy. During homogenization, {alpha} + T eutectics become discontinuous and spheroidized, and Al{sub 2}CuMg phase nucleates and grows along {alpha} + T eutectics. High magnetic field significantly accelerates the melting of quaternary phase T and Al{sub 2}CuMg phase. When the alloy homogenized at 460 Degree-Sign C/10 h + 480 Degree-Sign C/8 h with 12 T magnetic field, the least amount of constituent phases is obtained. - Highlights: Black-Right-Pointing-Pointer Most of published reports of magnetic field are focused on ferrous alloys. Black-Right-Pointing-Pointer Effect of magnetic field on microstructure of 7085 during homogenization is studied. Black-Right-Pointing-Pointer Magnetic field accelerates the melting of AlZnMgCu and S phase.

  13. Hydride structures in Ti-aluminides subjected to high temperature and hydrogen pressure charging conditions

    NASA Technical Reports Server (NTRS)

    Legzdina, D.; Robertson, I. M.; Birnbaum, H. K.

    1991-01-01

    The distribution and chemistry of hydrides produced in single and dual phase alloys with a composition near TiAl have been investigated by using a combination of TEM and X-ray diffraction techniques. The alloys were exposed at 650 C to 13.8 MPa of gaseous H2 for 100 h. In the single-phase gamma alloy, large hydrides preferentially nucleated on the grain boundaries and matrix dislocations and a population of small hydrides was distributed throughout the matrix. X-ray and electron diffraction patterns from these hydrides indicated that they have an fcc structure with a lattice parameter of 0.45 nm. EDAX analysis of the hydrides showed that they were enriched in Ti. The hydrides were mostly removed by vacuum annealing at 800 C for 24 h. On dissolution of the hydrides, the chemistry of hydride-free regions of the grain boundary returned to the matrix composition, suggesting that Ti segregation accompanied the hydride formation rather than Ti enrichment causing the formation of the hydride.

  14. New approaches to prepare hydride silica.

    PubMed

    Gomez, Jorge E; Sandoval, Junior E

    2010-09-01

    Two synthetic schemes to produce a hydride-modified support that serves as an intermediate for the preparation of bonded phases for liquid chromatography (LC) and capillary electrophoresis (CE) are investigated. The strategies differ in the silane reagent utilized (trichlorosilane (TCS) or triethoxysilane (TES)) and the manner water is incorporated into the reaction. In the first approach, TCS in toluene reacts with a previously humidified silica substrate so that the reaction is confined to the silica surface. In the second approach, TES and a small amount of aqueous HCl are dissolved in THF, and this hydrolysate is diluted by a great factor in cyclohexane, prior to reaction with the silica substrate. Atomic force microscopy (AFM) images of the hydride film on wafers revealed that, unlike the traditional approach that produced a patchy coating, both new methods provided a homogeneous layer on the substrate's surface. IR and NMR spectra from porous silica particles clearly confirmed a successful surface modification. AFM and water contact angles (WCA) were used to examine the effect of dilution of the TES hydrolysate in cyclohexane on the trend of the film to polymerize on wafers and found that a dilution factor of at least 100 is required to attain a molecularly thin hydride layer. WCA and CE also revealed a strong susceptibility of the hydride silica intermediate to hydrolyze, even at low pH. Compared to TCS, the lower reactivity and volatility of TES resulted in a much more desirable experimental approach.

  15. Insights into the origin of the separation selectivity with silica hydride adsorbents.

    PubMed

    Kulsing, Chadin; Nolvachai, Yada; Marriott, Philip J; Boysen, Reinhard I; Matyska, Maria T; Pesek, Joseph J; Hearn, Milton T W

    2015-02-19

    In this study, the surface properties of type-B silica have been compared with an unmodified silica hydride phase, a diamond hydride phase and silica hydride phases modified with bidentate anchored octyl (BDC8), bidentate anchored octadecyl (BDC18), phenyl and cholesteryl groups. Atomic distributions of the surface elemental composition of each type of stationary phase were determined using energy-dispersive X-ray spectroscopy. For the type-B silica, unmodified silica hydride, diamond hydride as well as BDC18 and cholesteryl silica hydride phases, the increase in carbon contents correlated with more negative surface ζ potential values (R(2) = 0.92). The origin of these more negative ζ potentials has been evaluated with mobile phases up to 100% (v/v) methanol content, with this property attributed to either an increase in the amount of adsorbed hydroxide ions or a decrease in the amount of adsorbed protons on the surfaces modified silica hydride phases of higher carbon content. This property of chemically modified silica hydride phases is in accordance with the unique propensity for hydroxide ions to be preferentially adsorbed onto hydrophobic surfaces of low permittivity and effects due to the specific accumulated water molecules associated with the electrical interfacial double layer of the adsorbent.

  16. The Role of Second Phase Intermetallic Particles on the Spall Failure of 5083 Aluminum

    DTIC Science & Technology

    2016-12-01

    Thomas GJ, Hazell PJ (2010) A study on the strength of an armour -grade aluminum under high strain-rate loading. J Appl Phys 107:123508 3. Whelchel RL...weight and strain-hardened material used in high strain-rate applications such as those experienced under shock loading. Symmetric real-time (in...experienced under shock loading. Symmetric real-time (in situ) and end-state (ex situ recovery) plate impact shock experiments were conducted to

  17. Cast Aluminum Structures Technology (CAST) Structural Test and Evaluation (Phase 5). Part 3-Static Property Allowables

    DTIC Science & Technology

    1980-04-01

    mechanical properties . At first, it would appear that the mechanical properties of the A356 -T62 and those of the 320OF...Static Properties , his document contains static mechanical properties of A257-T 6 aluminum alloy castings. Properties of castings are relatable to...ELONGATION MEASUREMENTS 79 APPENDIX D. INTEGRAL COUPON PROPERTIES 83 APPENDIX E. STATIC MECHANICAL PROPERTIES DATA 91 APPENDIX F. CORRELATIVE PROPERTIES

  18. Advanced powder metallurgy aluminum alloys via rapid solidification technology, phase 2

    NASA Technical Reports Server (NTRS)

    Ray, Ranjan; Jha, Sunil C.

    1987-01-01

    Marko's rapid solidification technology was applied to processing high strength aluminum alloys. Four classes of alloys, namely, Al-Li based (class 1), 2124 type (class 2), high temperature Al-Fe-Mo (class 3), and PM X7091 type (class 4) alloy, were produced as melt-spun ribbons. The ribbons were pulverized, cold compacted, hot-degassed, and consolidated through single or double stage extrusion. The mechanical properties of all four classes of alloys were measured at room and elevated temperatures and their microstructures were investigated optically and through electron microscopy. The microstructure of class 1 Al-Li-Mg alloy was predominantly unrecrystallized due to Zr addition. Yield strengths to the order of 50 Ksi were obtained, but tensile elongation in most cases remained below 2 percent. The class 2 alloys were modified composition of 2124 aluminum alloy, through addition of 0.6 weight percent Zr and 1 weight percent Ni. Nickel addition gave rise to a fine dispersion of intermetallic particles resisting coarsening during elevated temperature exposure. The class 2 alloy showed good combination of tensile strength and ductility and retained high strength after 1000 hour exposure at 177 C. The class 3 Al-Fe-Mo alloy showed high strength and good ductility both at room and high temperatures. The yield and tensile strength of class 4 alloy exceeded those of the commercial 7075 aluminum alloy.

  19. Electrochemical process and production of novel complex hydrides

    DOEpatents

    Zidan, Ragaiy

    2013-06-25

    A process of using an electrochemical cell to generate aluminum hydride (AlH.sub.3) is provided. The electrolytic cell uses a polar solvent to solubilize NaAlH.sub.4. The resulting electrochemical process results in the formation of AlH.sub.3. The AlH.sub.3 can be recovered and used as a source of hydrogen for the automotive industry. The resulting spent aluminum can be regenerated into NaAlH.sub.4 as part of a closed loop process of AlH.sub.3 generation.

  20. Anodized aluminum wire as a solid-phase microextraction fiber for rapid determination of volatile constituents in medicinal plant.

    PubMed

    Gholivand, Mohammad Bagher; Piryaei, Marzieh; Abolghasemi, Mir Mahdi

    2011-09-02

    Headspace solid phase microextraction using anodized aluminum fiber in combination with capillary GC-MS was utilized as monitoring technique for the collection and detection of the volatile compounds of Echinophora platyloba DC. Experimental parameters, including the sample weight, extraction temperature, extraction time and humidity effect, desorption time and desorption temperature were examined and optimized. Using HS-SPME followed by GC-MS, 53 compounds were separated and identified in E. platyloba DC, which mainly included E-β ocimene (47.63%), R-D-decalactone (13.28%), α-pinene (7.43%) and nonane (6.71%). Compared with hydrodistillation (HD), HS-SPME, provides the advantages of a small amount of sample, timesaving, simplicity and cheapness. To the best of our knowledge, this is the first report on using anodized aluminum fiber in solid-phase microextraction coupled to headspace for the investigation of volatile fraction of medicinal plant. Copyright © 2011 Elsevier B.V. All rights reserved.

  1. Porous polymer nanostructures fabricated by the surface-induced phase separation of polymer solutions in anodic aluminum oxide templates.

    PubMed

    Wei, Tzu-Hui; Chi, Mu-Huan; Tsai, Chia-Chan; Ko, Hao-Wen; Chen, Jiun-Tai

    2013-08-13

    We study the formation of porous polymer nanostructures fabricated by the surface-induced phase separation of polymer solutions in anodic aluminum oxide (AAO) templates. Poly(methyl methacrylate) (PMMA) and tetrahydrofuran (THF) are used to investigate the evolution process of the surface-induced phase separation. With the longer immersion time of the AAO template in the polymer solution, the size of the solvent-rich droplet is increased by the coarsening process, resulting in the formation of porous polymer nanostructures. The coarsening mechanism is further evaluated by changing the experimental parameters including the immersion time, the polymer concentration, the polymer molecular weight, and the solvent quality. Under conditions in which polymer solutions have higher viscosities, the coarsening process is slowed down and the formation of the porous nanostructures is prohibited. The prevention of the porous nanostructures can also be realized by adding water to the PMMA/THF solution before the immersion process.

  2. Phase transformation and its role in stabilizing simulated lead-laden sludge in aluminum-rich ceramics.

    PubMed

    Lu, Xingwen; Shih, Kaimin

    2011-10-15

    This study investigated the mechanisms of stabilizing lead-laden sludge by blending it into the production process of aluminum-rich ceramics, and quantitatively evaluated the prolonged leachability of the product phases. Sintering experiments were performed using powder mixtures of lead oxide and γ-alumina with different Pb/Al molar ratios within the temperature range of 600-1000 °C. By mixing lead oxide with γ-alumina at a Pb/Al molar ratio of 0.5, the formation of PbAl2O4 is initiated at 700 °C, but an effective formation was observed when the temperature was above 750 °C for a 3-h sintering time. The formation and decomposition of the intermediate phase, Pb9Al8O21, was detected in this system within the temperature range of 800-900 °C. When the lead oxide and γ-alumina mixture was sintered with a Pb/Al molar ratio of 1:12, the PbAl12O19 phase was found at 950 °C and effectively formed at 1000 °C. In this system, an intermediate phase Pb3(CO3)2(OH)2 was observed at the temperature range of 700-950 °C. Over longer leaching periods, both PbAl2O4 and PbAl12O19 were superior to lead oxide in immobilizing lead. Comparing the leaching results of PbAl2O4 and PbAl12O19 demonstrated the higher intrinsic resistance of PbAl12O19 against acid attack. To reduce metal mobility, this study demonstrated a preferred mechanism of stabilizing lead in the aluminate structures by adding metal-bearing waste sludge to the ceramic processing of aluminum-rich products.

  3. Doping of AlH3 with alkali metal hydrides for enhanced decomposition kinetics

    NASA Astrophysics Data System (ADS)

    Sandrock, Gary; Reilly, James

    2005-03-01

    Aluminum hydride, AlH3, has inherently high gravimetric and volumetric properties for onboard vehiclular hydrogen storage (10 wt% H2 and 0.148 kg H2/L). Yet it has been widely neglected because of its kinetic limitations for low-temperature H2 desorption and the thermodynamic difficulties associated with recharging. This paper considers a scenario whereby doped AlH3 is decomposed onboard and recharged offboard. In particular, we show that particle size control and doping with small levels of alkali metal hydrides (e.g., LiH) results in accelerated H2 desorption rates nearly high enough to supply fuel-cell and ICE vehicles. The mechanism of enhanced H2 desorption is associated with the formation of alanate windows (e.g., LiAlH4) between the AlH3 particles and the external gas phase. These alanate windows can be doped with Ti to further enhance transparency, even to the point of accomplishing slow decomposition of AlH3 at room temperature. It is highly likely 2010 gravimetric and volumetric vehicular system targets (6 wt% H2 and 0.045 kg/L) can be met with AlH3. But a new, low-cost method of offboard regeneration of spent Al back to AlH3 is yet needed.

  4. Phase Transformation Behavior of Medium Manganese Steels with 3 Wt Pct Aluminum and 3 Wt Pct Silicon During Intercritical Annealing

    NASA Astrophysics Data System (ADS)

    Sun, Binhan; Fazeli, Fateh; Scott, Colin; Yue, Stephen

    2016-10-01

    Medium manganese steels alloyed with sufficient aluminum and silicon amounts contain high fractions of retained austenite adjustable to various transformation-induced plasticity/twinning-induced plasticity effects, in addition to a reduced density suitable for lightweight vehicle body-in-white assemblies. Two hot rolled medium manganese steels containing 3 wt pct aluminum and 3 wt pct silicon were subjected to different annealing treatments in the present study. The evolution of the microstructure in terms of austenite transformation upon reheating and the subsequent austenite decomposition during quenching was investigated. Manganese content of the steels prevailed the microstructural response. The microstructure of the leaner alloy with 7 wt pct Mn (7Mn) was substantially influenced by the annealing temperature, including the variation of phase constituents, the morphology and composition of intercritical austenite, the Ms temperature and the retained austenite fraction. In contrast, the richer variant 10 wt pct Mn steel (10Mn) exhibited a substantially stable ferrite-austenite duplex phase microstructure containing a fixed amount of retained austenite which was found to be independent of the variations of intercritical annealing temperature. Austenite formation from hot band ferrite-pearlite/bainite mixtures was very rapid during annealing at 1273 K (1000 °C), regardless of Mn contents. Austenite growth was believed to be controlled at early stages by carbon diffusion following pearlite/bainite dissolution. The redistribution of Mn in ferrite and particularly in austenite at later stages was too subtle to result in a measureable change in austenite fraction. Further, the hot band microstructure of both steels contained a large fraction of coarse-grained δ-ferrite, which remained almost unchanged during intercritical annealing. A recently developed thermodynamic database was evaluated using the experimental data. The new database achieved a better agreement

  5. Method for preparing porous metal hydride compacts

    DOEpatents

    Ron, Moshe; Gruen, Dieter M.; Mendelsohn, Marshall H.; Sheft, Irving

    1981-01-01

    A method for preparing porous metallic-matrix hydride compacts which can be repeatedly hydrided and dehydrided without disintegration. A mixture of a finely divided metal hydride and a finely divided matrix metal is contacted with a poison which prevents the metal hydride from dehydriding at room temperature and atmospheric pressure. The mixture of matrix metal and poisoned metal hydride is then compacted under pressure at room temperature to form porous metallic-matrix hydride compacts.

  6. Method for preparing porous metal hydride compacts

    DOEpatents

    Ron, M.; Gruen, D.M.; Mendelsohn, M.H.; Sheft, I.

    1980-01-21

    A method for preparing porous metallic-matrix hydride compacts which can be repeatedly hydrided and dehydrided without disintegration. A mixture of a finely divided metal hydride and a finely divided matrix metal is contacted with a poison which prevents the metal hydride from dehydriding at room temperature and atmospheric pressure. The mixture of matrix metal and poisoned metal hydride is then compacted under pressure at room temperature to form porous metallic-matrix hydride compacts.

  7. Superstoichiometric hydride of zirconium

    SciTech Connect

    Kupryazhkin, A.Ya.; Shchepetkin, A.A.; Zabolotskaya, E.V.; Pletnev, R.N.; Alyamovskii, S.I.; Kitaev, G.A.

    1987-12-01

    Superstoichiometric hydrides of zirconium have been obtained all the way up to the composition ZrH/sub 2.4/ by additional hydrogenation of ZrH/sub 2/ as a result of redistribution of hydrogen atoms between t- and o-positions. In the preparation of the hydrides the authors used zirconium iodide with an impurity content no greater than 10/sup -2/ to 10/sup -2/ mole %; the hydrogen and helium used in this work had a minimum purity of 99.95%. The content of hydrogen in the specimens was determined by a volumetric method. The x-ray diffraction analysis was performed in a DRON-2.0 unit (CuK/sub ..cap alpha../ radiation). PMR spectra were recorded in a broad-line spectrometer in the temperature interval 150-450 K.

  8. Hydrogen Outgassing from Lithium Hydride

    SciTech Connect

    Dinh, L N; Schildbach, M A; Smith, R A; Balazs1, B; McLean II, W

    2006-04-20

    Lithium hydride is a nuclear material with a great affinity for moisture. As a result of exposure to water vapor during machining, transportation, storage and assembly, a corrosion layer (oxide and/or hydroxide) always forms on the surface of lithium hydride resulting in the release of hydrogen gas. Thermodynamically, lithium hydride, lithium oxide and lithium hydroxide are all stable. However, lithium hydroxides formed near the lithium hydride substrate (interface hydroxide) and near the sample/vacuum interface (surface hydroxide) are much less thermally stable than their bulk counterpart. In a dry environment, the interface/surface hydroxides slowly degenerate over many years/decades at room temperature into lithium oxide, releasing water vapor and ultimately hydrogen gas through reaction of the water vapor with the lithium hydride substrate. This outgassing can potentially cause metal hydriding and/or compatibility issues elsewhere in the device. In this chapter, the morphology and the chemistry of the corrosion layer grown on lithium hydride (and in some cases, its isotopic cousin, lithium deuteride) as a result of exposure to moisture are investigated. The hydrogen outgassing processes associated with the formation and subsequent degeneration of this corrosion layer are described. Experimental techniques to measure the hydrogen outgassing kinetics from lithium hydride and methods employing the measured kinetics to predict hydrogen outgassing as a function of time and temperature are presented. Finally, practical procedures to mitigate the problem of hydrogen outgassing from lithium hydride are discussed.

  9. Energy Efficient Aluminum Production - Pilot-Scale Cell Tests - Final Report for Phase I and Phase II

    SciTech Connect

    R. A. Christini

    1999-12-30

    A cermet anode that produces oxygen and a cathode material that is wetted by aluminum can provide a dimensionally stable inter-electrode distance in the Hall-Heroult cell. This can be used to greatly improve the energy and/or productivity efficiencies. The concept, which was developed and tested, uses a system of vertically interleaved anodes and cathodes. The major advantage of this concept is the significant increase in electrochemical surface area compared to a horizontal orientation of anode and cathode that is presently used in the Hall-Heroult process. This creates an additional advantage for energy reduction of 1.3 kWh/lb or a 20% productivity improvement. The voltages obtained in an optimized cell test met the energy objectives of the project for at least two weeks. An acceptable current efficiency was never proven, however, during either pilot scale or bench scale tests with the vertical plate configuration. This must be done before a vertical cell can be considered viab le. Anode corrosion rate must be reduced by at least a factor of three in order to produce commercial purity aluminum. It is recommended that extensive theoretical and bench scale investigations be done to improve anode materials and to demonstrate acceptable current efficiencies in a vertical plate cell before pilot scale work is continued.

  10. Fracture of niobium hydride

    SciTech Connect

    Gahr, S.; Makenas, B.J.; Birnbaum, H.K.

    1980-09-01

    Consideration is given to causes for the extreme brittleness observed for most hydrides. Surface energies for cleavage of the ..beta.. NbH/sub 0.82/ f.c. orthorhombic hydride along the (100)/sub c/ and (110)/sub c/ are obtained using fracture mechanics methods. The values are shown to be about equal to those of b.c.c. niobium. The relative surface energies of niobium and NbH are consistent with measurements of phonon frequencies and elastic constants. None of the data indicates any decrease of atomic bonding due to the incorporation of hydrogen in the metal lattice. Dislocation mobility is considered on the basis of T.E.M. observations and the crystal structure. It is shown that half of the (110)/sub c/<111>/sub c/ slip systems cause hydrogen disordering and therefore experience a high lattice frictional stress. Domain boundaries also are shown to be dislocation barriers. Hydride brittleness is considered to result from the decrease in dislocation mobility and in the slip systems available to cause plastic blunting at elastic discontinuities.

  11. 17. VIEW OF HYDRIDING SYSTEM IN BUILDING 881. THE HYDRIDING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    17. VIEW OF HYDRIDING SYSTEM IN BUILDING 881. THE HYDRIDING SYSTEM WAS PART OF THE FAST ENRICHED URANIUM RECOVERY PROCESS. (11/11/59) - Rocky Flats Plant, General Manufacturing, Support, Records-Central Computing, Southern portion of Plant, Golden, Jefferson County, CO

  12. Computer-Aided Design and Manufacturing for Extrusion of Aluminum, Titanium, and Steel Structural Parts (Phase I)

    DTIC Science & Technology

    1976-03-01

    Indirect Extrusion of Aluminum Alloys without a Lubricant 1-4 1-2. Relation Between Extrusion Rate and Flow Stress for Various Aluminum Alloy...RELATION BETWEEN EXTRUSION RATE AND FLOW STRESS FOR VARIOUS ALUMINUM ALLOYS*** 1-6 By far, the greater proportion of all Aluminum extrusions consists of...for extrusion, can cause ruptures on the surface of the extrusion, and even local melting in the extru- ded material. To overcome this problem

  13. Measurement and modeling of strain fields in zirconium hydrides precipitated at a stress concentration

    SciTech Connect

    Allen, Gregory B.; Kerr, Matthew; Daymond, Mark R.

    2012-10-23

    Hydrogen adsorption into zirconium, as a result of corrosion in aqueous environments, leads to the precipitation of a secondary brittle hydride phase. These hydrides tend to first form at stress concentrations such as fretting flaws or cracks in engineering components, potentially degrading the structural integrity of the component. One mechanism for component failure is a slow crack growth mechanism known as Delayed Hydride Cracking (DHC), where hydride fracture occurs followed by crack arrest in the ductile zirconium matrix. The current work employs both an experimental and a modeling approach to better characterize the effects and behavior of hydride precipitation at such stress concentrations. Strains around stress concentrations containing hydrides were mapped using High Energy X-ray Diffraction (HEXRD). These studies highlighted important differences in the behavior of the hydride phase and the surrounding zirconium matrix, as well as the strain associated with the precipitation of the hydride. A finite element model was also developed and compared to the X-ray strain mapping results. This model provided greater insight into details that could not be obtained directly from the experimental approaches, as well as providing a framework for future modeling to predict the effects of hydride precipitation under varied conditions.

  14. A study of advanced magnesium-based hydride and development of a metal hydride thermal battery system

    NASA Astrophysics Data System (ADS)

    Zhou, Chengshang

    Metal hydrides are a group of important materials known as energy carriers for renewable energy and thermal energy storage. A concept of thermal battery based on advanced metal hydrides is studied for heating and cooling of cabins in electric vehicles. The system utilizes a pair of thermodynamically matched metal hydrides as energy storage media. The hot hydride that is identified and developed is catalyzed MgH2 due to its high energy density and enhanced kinetics. TiV0.62Mn1.5, TiMn2, and LaNi5 alloys are selected as the matching cold hydride. A systematic experimental survey is carried out in this study to compare a wide range of additives including transitions metals, transition metal oxides, hydrides, intermetallic compounds, and carbon materials, with respect to their effects on dehydrogenation properties of MgH2. The results show that additives such as Ti and V-based metals, hydride, and certain intermetallic compounds have strong catalytic effects. Solid solution alloys of magnesium are exploited as a way to destabilize magnesium hydride thermodynamically. Various elements are alloyed with magnesium to form solid solutions, including indium and aluminum. Thermodynamic properties of the reactions between the magnesium solid solution alloys and hydrogen are investigated, showing that all the solid solution alloys that are investigated in this work have higher equilibrium hydrogen pressures than that of pure magnesium. Cyclic stability of catalyzed MgH2 is characterized and analyzed using a PCT Sievert-type apparatus. Three systems, including MgH2-TiH 2, MgH2-TiMn2, and MgH2-VTiCr, are examined. The hydrogenating and dehydrogenating kinetics at 300°C are stable after 100 cycles. However, the low temperature (25°C to 150°C) hydrogenation kinetics suffer a severe degradation during hydrogen cycling. Further experiments confirm that the low temperature kinetic degradation can be mainly related the extended hydrogenation-dehydrogenation reactions. Proof

  15. Tellurium Hydrides at High Pressures: High-Temperature Superconductors

    NASA Astrophysics Data System (ADS)

    Zhong, Xin; Wang, Hui; Zhang, Jurong; Liu, Hanyu; Zhang, Shoutao; Song, Hai-Feng; Yang, Guochun; Zhang, Lijun; Ma, Yanming

    2016-02-01

    Observation of high-temperature superconductivity in compressed sulfur hydrides has generated an irresistible wave of searches for new hydrogen-containing superconductors. We herein report the prediction of high-Tc superconductivity in tellurium hydrides stabilized at megabar pressures identified by first-principles calculations in combination with a swarm structure search. Although tellurium is isoelectronic to sulfur or selenium, its heavier atomic mass and weaker electronegativity makes tellurium hydrides fundamentally distinct from sulfur or selenium hydrides in stoichiometries, structures, and chemical bondings. We identify three metallic stoichiometries of H4Te , H5Te2 , and HTe3 , which are not predicted or known stable structures for sulfur or selenium hydrides. The two hydrogen-rich H4Te and H5Te2 phases are primarily ionic and contain exotic quasimolecular H2 and linear H3 units, respectively. Their high-Tc (e.g., 104 K for H4Te at 170 GPa) superconductivity originates from the strong electron-phonon couplings associated with intermediate-frequency H-derived wagging and bending modes, a superconducting mechanism which differs substantially with those in sulfur or selenium hydrides where the high-frequency H-stretching vibrations make considerable contributions.

  16. Zirconium hydrides and Fe redistribution in Zr-2.5%Nb alloy under ion irradiation

    NASA Astrophysics Data System (ADS)

    Idrees, Y.; Yao, Z.; Cui, J.; Shek, G. K.; Daymond, M. R.

    2016-11-01

    Zr-2.5%Nb alloy is used to fabricate the pressure tubes of the CANDU reactor. The pressure tube is the primary pressure boundary for coolant in the CANDU design and is susceptible to delayed hydride cracking, reduction in fracture toughness upon hydride precipitation and potentially hydride blister formation. The morphology and nature of hydrides in Zr-2.5%Nb with 100 wppm hydrogen has been investigated using transmission electron microscopy. The effect of hydrides on heavy ion irradiation induced decomposition of the β phase has been reported. STEM-EDX mapping was employed to investigate the distribution of alloying elements. The results show that hydrides are present in the form of stacks of different sizes, with length scales from nano- to micro-meters. Heavy ion irradiation experiments at 250 °C on as-received and hydrided Zr-2.5%Nb alloy, show interesting effects of hydrogen on the irradiation induced redistribution of Fe. It was found that Fe is widely redistributed from the β phase into the α phase in the as-received material, however, the loss of Fe from the β phase and subsequent precipitation is retarded in the hydrided material. This preliminary work will further the current understanding of microstructural evolution of Zr based alloys in the presence of hydrogen.

  17. Hydriding of Titanium.

    DTIC Science & Technology

    1998-03-01

    hole. The metals used to make these couples with titanium included HY80 steel , 316 stainless steel , five-nines aluminum, 6061 aluminum, and zinc. All...the other surfaces. Titanium Coupled With Other Metals The corrosion potentials of grade 2 titanium galvanically coupled with naval brass, HY80 steel ...2 titanium; naval brass caused titanium to become an anode. At room temperature, HY80 steel and 316 stainless steel couples exhibited corrosion

  18. Dimensionally stable metallic hydride composition

    DOEpatents

    Heung, Leung K.

    1994-01-01

    A stable, metallic hydride composition and a process for making such a composition. The composition comprises a uniformly blended mixture of a metal hydride, kieselguhr, and a ballast metal, all in the form of particles. The composition is made by subjecting a metal hydride to one or more hydrogen absorption/desorption cycles to disintegrate the hydride particles to less than approximately 100 microns in size. The particles are partly oxidized, then blended with the ballast metal and the kieselguhr to form a uniform mixture. The mixture is compressed into pellets and calcined. Preferably, the mixture includes approximately 10 vol. % or more kieselguhr and approximately 50 vol. % or more ballast. Metal hydrides that can be used in the composition include Zr, Ti, V, Nb, Pd, as well as binary, tertiary, and more complex alloys of La, Al, Cu, Ti, Co, Ni, Fe, Zr, Mg, Ca, Mn, and mixtures and other combinations thereof. Ballast metals include Al, Cu and Ni.

  19. Precipitation of the {Omega} phase in 2024 and 2124 aluminum alloys

    SciTech Connect

    Wang, L.M.; Flower, H.M.; Lindley, T.C.

    1999-07-23

    Precipitation of the {Omega} phase in Al-Cu-Mg-(Ag) alloys with high Cu:Mg ratios has been ascribed to the presence of small amounts of Ag. Silver has no effect in binary Al-Cu alloys aged at elevated temperatures, but a remarkable increase in the aging response is observed if a small amount of magnesium is also present. Recently, Garg et al. reported that Ag is not required for formation of the {Omega} phase in Al-Cu-Mg (with Cu/Mg ratio {approximately} 8.5 in their work) although it only appears as a minor phase along with the predominant {theta}{prime} phase. The purpose of this study is to report that {Omega} phase can also form in commercial silver free 2000 series alloys (2024 and 2124) although in this case the {Omega} phase is nucleated heterogeneously upon Mn based dispersoids.

  20. Modeling of gamma/gamma-prime phase equilibrium in the nickel-aluminum system

    NASA Technical Reports Server (NTRS)

    Sanchez, J. M.; Barefoot, J. R.; Jarrett, R. N.; Tien, J. K.

    1984-01-01

    A theoretical model is proposed for the determination of phase equilibrium in alloys, taking into consideration dissimilar lattice parameters. Volume-dependent pair interactions are introduced by means of phenomenological Lennard-Jones potentials and the configurational entropy of the system is treated in the tetrahedron approximation of the cluster variation method. The model is applied to the superalloy-relevant, nickel-rich, gamma/gamma-prime phase region of the Ni-Al phase diagram. The model predicts reasonable values for the lattice parameters and the enthalpy of formation as a function of composition, and the calculated phase diagram closely approximates the experimental diagram.

  1. Aluminum-centered tetrahedron-octahedron transition in advancing Al-Sb-Te phase change properties.

    PubMed

    Xia, Mengjiao; Ding, Keyuan; Rao, Feng; Li, Xianbin; Wu, Liangcai; Song, Zhitang

    2015-02-24

    Group IIIA elements, Al, Ga, or In, etc., doped Sb-Te materials have proven good phase change properties, especially the superior data retention ability over popular Ge2Sb2Te5, while their phase transition mechanisms are rarely investigated. In this paper, aiming at the phase transition of Al-Sb-Te materials, we reveal a dominant rule of local structure changes around the Al atoms based on ab initio simulations and nuclear magnetic resonance evidences. By comparing the local chemical environments around Al atoms in respective amorphous and crystalline Al-Sb-Te phases, we believe that Al-centered motifs undergo reversible tetrahedron-octahedron reconfigurations in phase transition process. Such Al-centered local structure rearrangements significantly enhance thermal stability of amorphous phase compared to that of undoped Sb-Te materials, and facilitate a low-energy amorphization due to the weak links among Al-centered and Sb-centered octahedrons. Our studies may provide a useful reference to further understand the underlying physics and optimize performances of all IIIA metal doped Sb-Te phase change materials, prompting the development of NOR/NAND Flash-like phase change memory technology.

  2. Hydrogen storage and generation using light metal hydrides

    SciTech Connect

    Lynch, F.; Mork, B.J.; Wilkes, J.S.

    1998-07-01

    The storage of hydrogen for use in fuel cells employed as portable electric power sources is important. For many applications pressurized gas or cryogenic liquid storage is not acceptable from weight or safety standpoints. This is particularly true for moderate power systems in the 50--200 watt range. A potentially attractive technology for providing hydrogen for moderately sized fuel cell-based electric power supplies is chemical hydrides. In general, chemical hydrides are materials that store hydrogen that may be released by chemical reactions. The authors report here the use of light metal hydrides, such as lithium aluminum tetrahydride and trilithium aluminum hexahydride to store hydrogen in a very dense form; about four times the density of liquid hydrogen. The hydrogen can be released by reaction with simple chemical reagents, such as water or ammonia, at approximately atmospheric pressure and at modest temperatures. The reaction rate may be controlled to provide hydrogen at a rate appropriate to that needed by a fuel cell operating at the power levels mentioned above. Usually hydrogen is the sole gaseous product, along with several solid products.

  3. Spin Forming of an Aluminum 2219-T6 Aft Bulkhead for the Orion Multi-Purpose Crew Vehicle: Phase II Supplemental Report

    NASA Technical Reports Server (NTRS)

    Piascik, Robert S.; Squire, Michael D.; Domack, Marcia S.; Hoffman, Eric K.

    2015-01-01

    The principal focus of this project was to assist the Orion Multi-Purpose Crew Vehicle (MPCV) Program in developing a spin forming fabrication process for manufacture of the aft bulkhead of the pressure vessel. The spin forming process will enable a single piece aluminum (Al) 2219 aft bulkhead which will eliminate the current multiple piece welded construction, simplify fabrication, and lead to an enhanced design that will reduce vehicle weight by eliminating welds. Phase I of this assessment explored spin forming the single-piece forward pressure vessel bulkhead from aluminum-lithium 2195.

  4. Development of a Two-Phase Model for the Hot Deformation of Highly-Alloyed Aluminum

    SciTech Connect

    A. J. Beaudoin; J. A. Dantzig; I. M. Robertson; B. E. Gore; S. F. Harnish; H. A. Padilla

    2005-10-31

    Conventional processing methods for highly alloyed aluminum consist of ingot casting, followed by hot rolling and thermal treatments. Defects result in lost productivity and wasted energy through the need to remelt and reprocess the material. This research centers on developing a fundamental understanding for deformation of wrought 705X series alloys, a key alloy system used in structural airframe applications. The development of damage at grain boundaries is characterized through a novel test that provides initiation of failure while preserving a controlled deformation response. Data from these mechanical tests are linked to computer simulations of the hot rolling process through a critical measure of damage. Transmission electron microscopy provides fundamental insight into deformation at these high working temperatures, and--in a novel link between microscale and macroscale response--the evolution of microstructure (crystallographic orientation) provides feedback for tuning of friction in the hot rolling process. The key product of this research is a modeling framework for the analysis of industrial hot rolling.

  5. A study of hydriding kinetics of metal hydrides using a physically based model

    NASA Astrophysics Data System (ADS)

    Voskuilen, Tyler G.

    The reaction of hydrogen with metals to form metal hydrides has numerous potential energy storage and management applications. The metal hydrogen system has a high volumetric energy density and is often reversible with a high cycle life. The stored hydrogen can be used to produce energy through combustion, reaction in a fuel cell, or electrochemically in metal hydride batteries. The high enthalpy of the metal-hydrogen reaction can also be used for rapid heat removal or delivery. However, improving the often poor gravimetric performance of such systems through the use of lightweight metals usually comes at the cost of reduced reaction rates or the requirement of pressure and temperature conditions far from the desired operating conditions. In this work, a 700 bar Sievert system was developed at the Purdue Hydrogen Systems Laboratory to study the kinetic and thermodynamic behavior of high pressure hydrogen absorption under near-ambient temperatures. This system was used to determine the kinetic and thermodynamic properties of TiCrMn, an intermetallic metal hydride of interest due to its ambient temperature performance for vehicular applications. A commonly studied intermetallic hydride, LaNi5, was also characterized as a base case for the phase field model. The analysis of the data obtained from such a system necessitate the use of specialized techniques to decouple the measured reaction rates from experimental conditions. These techniques were also developed as a part of this work. Finally, a phase field model of metal hydride formation in mass-transport limited interstitial solute reactions based on the regular solution model was developed and compared with measured kinetics of LaNi5 and TiCrMn. This model aided in the identification of key reaction features and was used to verify the proposed technique for the analysis of gas-solid reaction rates determined volumetrically. Additionally, the phase field model provided detailed quantitative predictions of the

  6. Processing, phase equilibria and environmental degradation of molybdenum (silicom,aluminum)(2) intermetallic compound

    NASA Astrophysics Data System (ADS)

    Eason, Paul Duane

    The Mo(Si,Al)2 C40 compound was chosen for investigation as a possible high temperature structural material. To produce the C40 phase, several processing routes were explored with emphasis on obtaining microstructure/property relationships (i.e. control of grain size and minimization of secondary phases). To facilitate processing of single phase material, the phase equilibria of the Mo-Si-Al ternary system were reevaluated with respect to the phases adjacent to the C40 compound. An anomalous environmental degradation appeared to be the primary obstacle to further study of the compound and was investigated accordingly. Several processing routes were assessed for the production of dense, nearly single-phase Mo(Si,Al)2. Hot powder compaction was chosen as the method of sample production as is the case with many refractory silicide based materials. Therefore, variations in the processing techniques came from the choice of precursor materials and methods of powder production. Mechanical alloying, arc-melting and comminution, and blending of both elemental and compound powders were all employed to produce charges for hot uniaxial pressing. The final compacts were compared on the basis of density, grain size and presence of secondary phases. Establishment of a Mo-Si-Al ternary isothermal phase diagram at 1400°C was performed. Multiphase alloy compositions were selected to identify the phase boundaries of the C40, C54, T1 and Mo3Al8 phase fields, as well as to verify the existence of the C54 phase at 1400°C. The alloys were equilibrated by heat treatment and analyzed for phase identification and quantitative compositional information. The environmental degradation phenomenon was approached as a classical "pest" with an emphasis of study on grain boundary chemistry and atmospheric dependence of attack. Both Auger spectroscopy and electron microscopy revealed carbon-impurity-induced grain boundary segregation responsible for the embrittlement and material loss. Means of

  7. A twist on facial selectivity of hydride reductions of cyclic ketones: twist-boat conformers in cyclohexanone, piperidone, and tropinone reactions.

    PubMed

    Neufeldt, Sharon R; Jiménez-Osés, Gonzalo; Comins, Daniel L; Houk, K N

    2014-12-05

    The role of twist-boat conformers of cyclohexanones in hydride reductions was explored. The hydride reductions of a cis-2,6-disubstituted N-acylpiperidone, an N-acyltropinone, and tert-butylcyclohexanone by lithium aluminum hydride and by a bulky borohydride reagent were investigated computationally and compared to experiment. Our results indicate that in certain cases, factors such as substrate conformation, nucleophile bulkiness, and remote steric features can affect stereoselectivity in ways that are difficult to predict by the general Felkin-Anh model. In particular, we have calculated that a twist-boat conformation is relevant to the reactivity and facial selectivity of hydride reduction of cis-2,6-disubstituted N-acylpiperidones with a small hydride reagent (LiAlH4) but not with a bulky hydride (lithium triisopropylborohydride).

  8. METAL HYDRIDE HYDROGEN COMPRESSORS: A REVIEW

    SciTech Connect

    Bowman Jr, Robert C; Yartys, Dr. Volodymyr A.; Lototskyy, Dr. Michael V; Pollet, Dr. B.G.

    2014-01-01

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

  9. Arsenate and Selenate Scavenging by Basaluminite: Insights into the Reactivity of Aluminum Phases in Acid Mine Drainage.

    PubMed

    Carrero, Sergio; Fernandez-Martinez, Alejandro; Pérez-López, Rafael; Poulain, Agnieszka; Salas-Colera, Eduardo; Nieto, José Miguel

    2017-01-03

    Basaluminite precipitation may play an important role in the behavior of trace elements in water and sediments affected by acid mine drainage and acid sulfate soils. In this study, the affinity of basaluminite and schwertmannite for arsenate and selenate is compared, and the coordination geometries of these oxyanions in both structures are reported. Batch isotherm experiments were conducted to examine the sorption capacity of synthetic schwertmannite and basaluminite and the potential competitive effect of sulfate. In addition, synchrotron-based techniques such as differential pair distribution function (d-PDF) analysis and extended X-ray absorption fine structure (EXAFS) were used to determine the local structure of As(V) and Se(VI) complexes. The results show that oxyanion exchange with structural sulfate was the main mechanism for removal of selenate, whereas arsenate was removed by a combination of surface complexes and oxyanion exchange. The arsenate adsorption capacity of basaluminite was 2 times higher than that of schwertmannite and 3 times higher than that of selenate in both phases. The sulfate:arsenate and sulfate:selenate exchange ratios were 1:2 and 1:1, respectively. High sulfate concentrations in the solutions did not show a competitive effect on arsenate sorption capacity but had a strong impact on selenate uptake, suggesting some kind of specific interaction for arsenate. Both d-PDF and EXAFS results indicated that the bidentate binuclear inner sphere was the most probable type of ligand for arsenate on both phases and for selenate on schwertmannite, whereas selenate forms outer-sphere complexes in the aluminum octahedral interlayer of basaluminite. Overall, these results show a strong affinity of poorly crystalline aluminum phases such as basaluminite for As(V) and Se(VI) oxyanions, with adsorption capacities on the same order of magnitude as those of iron oxides. The results obtained in this study are relevant to the understanding of trace

  10. Development of metal hydride composites

    SciTech Connect

    Congdon, J.W.

    1992-12-01

    Most of current hydride technology at Savannah River Site is based on beds of metal hydride powders; the expansion upon hydridation and the cycling results in continued breakdown into finer particles. Goal is to develop a composite which will contain the fines in a dimensionally stable matrix, for use in processes which require a stable gas flow through a hydride bed. Metal hydride composites would benefit the advanced Thermal Cycling Absorption process (hydrogen isotope separation), and the Replacement Tritium Facility (storage, pumping, compression, purification of hydrogen isotopes). These composites were fabricated by cold compaction of a mixture of metal hydride granules and coarse copper powder; the porosity in the granules was introduced by means of ammonium carbonate. The composite pellets were cycled 138 times in hydrogen with the loss of LANA0.75 (LaNi{sub 4.25}Al{sub 0.75}) limited to the surface. Vacuum sintering can provide additional strength at the edges. Without a coating, the metal hydride particles exposed at the pellet surface can be removed by cycling several times in hydrogen.

  11. Determination and Uncertainty Analysis of Inorganic Arsenic in Husked Rice by Solid Phase Extraction and Atomic Absorption Spectrometry with Hydride Generation.

    PubMed

    Saxena, Sushil Kumar; Karipalli, Agnes Raju; Krishnan, Anoop A; Rangasamy, Rajesh; Malekadi, Praveen; Singh, Dhirendra P; Vasu, Vimesh; Singh, Vijay K

    2017-05-01

    This study enables the selective determination of inorganic arsenic (iAs) with a low detection limit using an economical instrument [atomic absorption spectrometer with hydride generation (HG)] to meet the regulatory requirements as per European Commission (EC) and Codex guidelines. Dry rice samples (0.5 g) were diluted using 0.1 M HNO3-3% H2O2 and heated in a water bath (90 ± 2°C) for 60 min. Through this process, all the iAs is solubilized and oxidized to arsenate [As(V)]. The centrifuged extract was loaded onto a preconditioned and equilibrated strong anion-exchange SPE column (silica-based Strata SAX 500 mg/6 mL), followed by selective and sequential elution of As(V), enabling the selective quantification of iAs using atomic absorption spectrometry with HG. In-house validation showed a mean recovery of 94% and an LOQ of 0.025 mg/kg. The repeatability (HorRatr) and reproducibility (HorRatR) values were <2, meeting the performance criteria mandated by the EC. The combined standard measurement uncertainty by this method was less than the maximum standard measurement uncertainty; thus, the method can be considered for official control purposes. The method was applied for the determination of iAs in husked rice samples and has potential applications in other food commodities.

  12. Multidimensional simulations of hydrides during fuel rod lifecycle

    NASA Astrophysics Data System (ADS)

    Stafford, D. S.

    2015-11-01

    In light water reactor fuel rods, waterside corrosion of zirconium-alloy cladding introduces hydrogen into the cladding, where it is slightly soluble. When the solubility limit is reached, the hydrogen precipitates into crystals of zirconium hydride which decrease the ductility of the cladding and may lead to cladding failure during dry storage or transportation events. The distribution of the hydride phase and the orientation of the crystals depend on the history of the spatial temperature and stress profiles in the cladding. In this work, we have expanded the existing hydride modeling capability in the BISON fuel performance code with the goal of predicting both global and local effects on the radial, azimuthal and axial distribution of the hydride phase. We compare results from 1D simulations to published experimental data. We demonstrate the new capability by simulating in 2D a fuel rod throughout a lifecycle that includes irradiation, short-term storage in the spent fuel pool, drying, and interim storage in a dry cask. Using the 2D simulations, we present qualitative predictions of the effects of the inter-pellet gap and the drying conditions on the growth of a hydride rim.

  13. Separation Using Encapsulated Metal Hydride

    SciTech Connect

    Heung, L.K.

    2001-06-01

    Metal hydride particles were encapsulated in a porous silica matrix. The encapsulation process successfully converted the small metal hydride particles into large granules suitable for packing gas separation columns. The granules absorbed hydrogen readily and withstood many hydrogen absorption cycles without producing fines. The porosity of the silica matrix was optimized so that the pores were large enough to allow hydrogen to easily move within the matrix and react with the metal hydride particles, but small enough to act as a filter to prevent passage of larger molecules including harmful impurities. An experimental apparatus has been installed to test the granules for hydrogen separation from other gases using a thermal absorption process.

  14. Novel phases of lithium-aluminum binaries from first-principles structural search

    SciTech Connect

    Sarmiento-Pérez, Rafael; Cerqueira, Tiago F. T.; Botti, Silvana; Marques, Miguel A. L.; Valencia-Jaime, Irais; Amsler, Maximilian; Goedecker, Stefan; Romero, Aldo H.

    2015-01-14

    Intermetallic Li–Al compounds are on the one hand key materials for light-weight engineering, and on the other hand, they have been proposed for high-capacity electrodes for Li batteries. We determine from first-principles the phase diagram of Li–Al binary crystals using the minima hopping structural prediction method. Beside reproducing the experimentally reported phases (LiAl, Li{sub 3}Al{sub 2}, Li{sub 9}Al{sub 4}, LiAl{sub 3}, and Li{sub 2}Al), we unveil a structural variety larger than expected by discovering six unreported binary phases likely to be thermodynamically stable. Finally, we discuss the behavior of the elastic constants and of the electric potential profile of all Li–Al stable compounds as a function of their stoichiometry.

  15. Novel phases of lithium-aluminum binaries from first-principles structural search

    NASA Astrophysics Data System (ADS)

    Sarmiento-Pérez, Rafael; Cerqueira, Tiago F. T.; Valencia-Jaime, Irais; Amsler, Maximilian; Goedecker, Stefan; Romero, Aldo H.; Botti, Silvana; Marques, Miguel A. L.

    2015-01-01

    Intermetallic Li-Al compounds are on the one hand key materials for light-weight engineering, and on the other hand, they have been proposed for high-capacity electrodes for Li batteries. We determine from first-principles the phase diagram of Li-Al binary crystals using the minima hopping structural prediction method. Beside reproducing the experimentally reported phases (LiAl, Li3Al2, Li9Al4, LiAl3, and Li2Al), we unveil a structural variety larger than expected by discovering six unreported binary phases likely to be thermodynamically stable. Finally, we discuss the behavior of the elastic constants and of the electric potential profile of all Li-Al stable compounds as a function of their stoichiometry.

  16. Vapor liquid solid-hydride vapor phase epitaxy (VLS-HVPE) growth of ultra-long defect-free GaAs nanowires: Ab initio simulations supporting center nucleation

    SciTech Connect

    André, Yamina Lekhal, Kaddour; Hoggan, Philip; Avit, Geoffrey; Réda Ramdani, M.; Monier, Guillaume; Colas, David; Ajib, Rabih; Castelluci, Dominique; Gil, Evelyne; Cadiz, Fabian; Rowe, Alistair; Paget, Daniel; Petit, Elodie; Leroux, Christine; Trassoudaine, Agnès

    2014-05-21

    High aspect ratio, rod-like and single crystal phase GaAs nanowires (NWs) were grown by gold catalyst-assisted hydride vapor phase epitaxy (HVPE). High resolution transmission electron microscopy and micro-Raman spectroscopy revealed polytypism-free zinc blende (ZB) NWs over lengths of several tens of micrometers for a mean diameter of 50 nm. Micro-photoluminescence studies of individual NWs showed linewidths smaller than those reported elsewhere which is consistent with the crystalline quality of the NWs. HVPE makes use of chloride growth precursors GaCl of which high decomposition frequency after adsorption onto the liquid droplet catalysts, favors a direct and rapid introduction of the Ga atoms from the vapor phase into the droplets. High influxes of Ga and As species then yield high axial growth rate of more than 100 μm/h. The diffusion of the Ga atoms in the liquid droplet towards the interface between the liquid and the solid nanowire was investigated by using density functional theory calculations. The diffusion coefficient of Ga atoms was estimated to be 3 × 10{sup −9} m{sup 2}/s. The fast diffusion of Ga in the droplet favors nucleation at the liquid-solid line interface at the center of the NW. This is further evidence, provided by an alternative epitaxial method with respect to metal-organic vapor phase epitaxy and molecular beam epitaxy, of the current assumption which states that this type of nucleation should always lead to the formation of the ZB cubic phase.

  17. Positional dependence of defect distribution in semipolar (20\\bar{2}1) hydride vapor phase epitaxy-GaN films grown on (22\\bar{4}3) patterned sapphire substrates

    NASA Astrophysics Data System (ADS)

    Uchiyama, Toshiro; Takeuchi, Shotaro; Kamada, Shohei; Arauchi, Takuji; Hashimoto, Yasuhiro; Yamane, Keisuke; Okada, Narihito; Imai, Yasuhiko; Kimura, Shigeru; Tadatomo, Kazuyuki; Sakai, Akira

    2016-05-01

    We have investigated the position dependence of crystalline quality and defect distribution in a semipolar (20\\bar{2}1) hydride vapor phase epitaxy (HVPE)-GaN film grown on a (22\\bar{4}3) patterned sapphire substrate (PSS). Position-dependent X-ray microdiffraction (XRMD) measurement clearly revealed the periodic fluctuation of the 20\\bar{2}1 lattice plane tilting in HVPE-GaN films. This correlated with the periodic distribution of (a + c)-type dislocations owing to the patterning pitch of the PSS as confirmed by transmission electron microscopy (TEM). In the three-dimensional reciprocal lattice space map, the diffuse streak exactly along the c-axis can be clearly detected, indicating the presence of basal plane stacking faults in HVPE-GaN films. Furthermore, we have quantitatively estimated the defect densities from the results of XRMD and TEM measurements. From the obtained results of XRMD and TEM measurements, the fluctuation of the lattice plane tilting and the defect distribution in (20\\bar{2}1) HVPE-GaN films grown on two types of metalorganic vapor phase epitaxy-GaN templates will be discussed in detail.

  18. NMR relaxation rate studies of molecular motions in NaSn, the Laves-phase metal hydride C15-ZrCr(2)H(x) and carbon/epoxy composite materials

    NASA Astrophysics Data System (ADS)

    Stoddard, Ronald Dean

    Here I present studies of molecular motions in three very different systems: NaSn, which exhibits motion characteristic of both a superionic conductor and a rotor crystal; C15-ZrCrsb2Hsbx (x < 0.5), a metal hydride which exhibits unusual characteristics in its hydrogen motion; and, finally a study of the relationship between Tsb2 and the degree of cure of carbon/epoxy materials. NaSn is characterized by Nasp+ ions and stable (Snsb4)sp{4-} tetrahedra. At high temperatures NaSn displays a disordered solid phase (alpha-NaSn). The presence of Nasp+ ions suggests that alpha-NaSn may be a superionic conductor (translationally disordered) and the presence of stable Snsb4 tetrahedra suggests it may be a rotor crystal (organizationally disordered). The purpose of this study is to gain better understanding of the motions in alpha-NaSn by monitoring Na and Sn motion using sp{23}Na and sp{119}Sn NMR, respectively. C15-ZrCrsb2Hsbx (x < 0.5) is a Laves phase metal hydride which displays extremely rapid hydrogen motion and a Tsb1 peak which cannot be explained by a model employing a single correlation time for the motion. A model employing a Gaussian distribution of correlation times has been used to successfully fit Tsb1, but the origin of this distribution in a crystalline solid solution is not known. The purpose of this study is to better understand the low temperature hydrogen motions occurring in C15-ZrCrsb2Hsbx by extending the previous NMR measurements using Tsb1p and Tsb1D, experiments which effectively push the relaxation peak to lower temperatures. New techniques for manufacturing carbon/epoxy components are under development which require partial curing of the material. At present, no method for monitoring partial curing exists. Tsb2 is a promising monitor of degree of cure because of its sensitivity to changes rates of molecular motions. The purpose of this study is to demonstrate the sensitivity of Tsb2 to changes in molecular motion due to curing, and to find a

  19. Erbium hydride decomposition kinetics.

    SciTech Connect

    Ferrizz, Robert Matthew

    2006-11-01

    Thermal desorption spectroscopy (TDS) is used to study the decomposition kinetics of erbium hydride thin films. The TDS results presented in this report are analyzed quantitatively using Redhead's method to yield kinetic parameters (E{sub A} {approx} 54.2 kcal/mol), which are then utilized to predict hydrogen outgassing in vacuum for a variety of thermal treatments. Interestingly, it was found that the activation energy for desorption can vary by more than 7 kcal/mol (0.30 eV) for seemingly similar samples. In addition, small amounts of less-stable hydrogen were observed for all erbium dihydride films. A detailed explanation of several approaches for analyzing thermal desorption spectra to obtain kinetic information is included as an appendix.

  20. Complex Hydrides for Hydrogen Storage

    SciTech Connect

    Slattery, Darlene; Hampton, Michael

    2003-03-10

    This report describes research into the use of complex hydrides for hydrogen storage. The synthesis of a number of alanates, (AIH4) compounds, was investigated. Both wet chemical and mechano-chemical methods were studied.

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

    NASA Astrophysics Data System (ADS)

    Wang, Ligen; Kuklja, Maija M.

    2009-12-01

    We present a density functional theory study of the structure and properties of Al13 and Al12Ni clusters, oxygen adsorptions on the cluster surfaces, and the completely oxidized clusters. The relative stability of various phases at various oxygen pressures and temperatures is investigated based on the "atomistic thermodynamics" which was previously employed for studying metal surfaces. We construct the two-dimensional (P, T) oxidation phase diagrams for these systems. We find that alloying the Al cluster with Ni does not improve its resistance to oxidation. The present study provides valuable insight into basic behaviors of small Al clusters in the presence of oxygen and a theoretical basis for exploring practical applications of these clusters.

  2. Laboratory investigation of aluminum solubility and solid-phase properties following alum treatment of lake waters.

    PubMed

    Berkowitz, Jacob; Anderson, Michael A; Graham, Robert C

    2005-10-01

    Water samples from two southern California lakes adversely affected by internal nutrient loading were treated with a 20 mg/L dose of Al3+ in laboratory studies to examine Al solubility and solid-phase speciation over time. Alum [Al2(SO4)3 . 18 H2O] applications to water samples from Big Bear Lake and Lake Elsinore resulted in a rapid initial decrease in pH and alkalinity followed by a gradual recovery in pH over several weeks. Dissolved Al concentrations increased following treatment, reaching a maximum of 2.54 mg/L after 17 days in Lake Elsinore water and 0.91 mg/L after 48 days in Big Bear Lake water; concentrations in both waters then decreased to <0.25 mg/L after 150 days. The solid phase was periodically collected and analyzed using X-ray diffraction (XRD), differential scanning calorimetry-thermogravimetric analysis (DSC-TGA), scanning electron microscopy (SEM), and surface area analyses to investigate the nature of the reaction products and crystallinity development over time. Poorly ordered, X-ray amorphous solid phases transformed over time to relatively well-ordered gibbsite, with strong diffraction peaks at 4.8 and 4.3 A. XRD also indicated the formation of a second (possibly aluminosilicate) crystalline phase after 150 days in Lake Elsinore water. Surface areas also decreased over time as crystals reordered to form gibbsite/microcrystalline gibbsite species. DSC-TGA results suggested that the initially formed amorphous Al(OH)3 underwent transformation to >45% gibbsite. These results were supported by geochemical modeling using Visual MINTEQ, with Al solubility putatively controlled by amorphous Al(OH)3 shortly after treatment and approaching that of microcrystalline gibbsite after about 150 days. These findings indicate that Al(OH)3 formed after alum treatment undergoes significant chemical and mineralogical changes that may alter its effectiveness as a reactive barrier to phosphorus release from lake sediments.

  3. Aluminum effect on dissolution and precipitation under hyperalkaline conditions: II. Solid phase transformations.

    PubMed

    Qafoku, Nikolla P; Ainsworth, Calvin C; Szecsody, James E; Bish, David L; Young, James S; McCready, David E; Qafoku, Odeta S

    2003-01-01

    The high-level radioactive, Al-rich, concentrated alkaline and saline waste fluids stored in underground tanks have accidentally leaked into the vadose zone at the Hanford Site in Washington State. In addition to dissolution, precipitation is likely to occur when these waste fluids contact the sediments. The objective of this study was to investigate the solid phase transformations caused by dissolution and precipitation in the sediments treated with solutions similar to the waste fluids. Batch experiments at 323 K were conducted in metal- and glass-free systems under CO2 and O2 free conditions. Results from X-ray diffraction (XRD), quantitative X-ray diffraction (QXRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and energy dispersive X-ray fluorescence spectroscopy (EDXRF) indicated that significant solid phase transformations occurred in the sediments contacted with Al-rich, hyperalkaline, and saline solutions. The XRD and QXRD analyses confirmed that smectite and most likely biotite underwent dissolution. The SEM and the qualitative EDS analyses confirmed the formation of alumino-silicates in the groups of cancrinite and probably sodalite. The morphology of the alumino-silicates secondary phases changed in response to changes in the Si/Al aqueous molar ratio. The transformations in the sediments triggered by dissolution (weathering of soil minerals) and precipitation (formation of secondary phases with high specific surface area and probably high sorption capacities) may play a significant role in the immobilization and ultimate fate of radionuclides and contaminants such as Cs, Sr, and U in the Hanford vadose zone.

  4. Low density metal hydride foams

    DOEpatents

    Maienschein, Jon L.; Barry, Patrick E.

    1991-01-01

    Disclosed is a low density foam having a porosity of from 0 to 98% and a density less than about 0.67 gm/cc, prepared by heating a mixture of powered lithium hydride and beryllium hydride in an inert atmosphere at a temperature ranging from about 455 to about 490 K for a period of time sufficient to cause foaming of said mixture, and cooling the foam thus produced. Also disclosed is the process of making the foam.

  5. The dynamics of the internal phonons tris(quinolin-8-olato) aluminum(III) in crystalline β-phase

    NASA Astrophysics Data System (ADS)

    Degli Esposti, Alessandra; Brinkmann, Martin; Ruani, Giampiero

    2002-01-01

    A new approach to the analysis of the internal phonons of tris(quinolin-8-olato) aluminum(III) is presented, which enlightens the role played by the ligands in determining the vibrational properties of the organometallic compound and evidences the importance of the contributions arising from the coupling terms among the three quinolinato fragments. An accurate exam of the normal modes of the meridianal isomer evidences the role of the interactions among the fragments in the vibrational dynamics of the ground state. Due to the special attention paid to the quinolinato fragments, a preliminary investigation on the vibrational properties of 8-hydroxyquinoline, taken as a model fragment, was also performed. The vibrational properties of the polymorph species β of the organometallic molecule were obtained refining the calculated frequencies, the dipole moment derivative matrix, and the polarizability derivative tensor derived by the hybrid density functional B3LYP/6-31G* comparing with the frequencies and intensities recorded by the infrared and the Raman spectroscopies performed on a polycrystalline sample. One thus obtains the most accurate intramolecular force constants up to date for the meridianal isomer in a crystalline phase.

  6. Structural and optical properties of ε-phase tris(8-hydroxyquinoline) aluminum crystals prepared by using physical vapor deposition method

    NASA Astrophysics Data System (ADS)

    Xie, Wanfeng; Pang, Zhiyong; Zhao, Yu; Jiang, Feng; Yuan, Huimin; Song, Hui; Han, Shenghao

    2014-10-01

    Crystals of ε-phase tris(8-hydroxyquinoline) aluminum (ε-Alq3) were prepared by using physical vapor deposition (PVD) method in a double zone tube furnace. The structural properties of the ε-Alq3 crystals were investigated by using an X-ray single crystal diffractometer (XSCD) and a high resolution scanning electron microscope (SEM). Large straight steps were observed from the side face of the pine needle-like crystals. The straight steps are parallel with each other like terraces and the widths of the steps are fixed, indicating that the ε-Alq3 crystals may have layered structures. The photoluminescence (PL) spectra at different temperatures (7 K, 66 K, 220 K, 300 K and 350 K) and the absorption spectrum were also investigated. The optical band gap of the ε-Alq3 crystals was calculated to be about 2.82 eV. This value is a little larger than that of amorphous mer-Alq3 (about 2.7 eV), indicating a minimizing of impurities, grain boundaries and defects.

  7. [Research on the phase and optical properties of nc-Si films prepared by low temperature aluminum induced crystallization].

    PubMed

    Duan, Liang-fei; Yang, Wen; Yang, Pei-zhi; Song, Zhao-ning

    2014-08-01

    In the present paper, nanocrystalline silicon thin films on glass substrates were prepared by rapid thermal annealing (RTA) of RF magnetron sputtered system and alpha-Si/Al films at a low temperature in Nz atmosphere. Optical metallographic microscope, confocal optical microscopy, X-ray diffractometer, Raman scattering and UV-Vis-NIR spectrometers were used to characterize the surface morphology and the phase and optical properties of nc-Si films. The influence of annealing process on the nc-Si films properties was studied. The results showed that nc-Si films were obtained after aluminum induced crystallization of the alpha-Si/Al films at 300 degrees C, withthe crystallization rate 15.56% and the grain size 1.75 nm. The surface uniformity and lattice distortion of nc-Si films reduced, while grain size, degree of crystallization and the optical band gap of the films increased with increasing annealing temperature from 300 to 400 degrees C. As the annealing temperature increased from 400 to 500 degrees C, although the degree of crystallization and grain size increased, the tendencies of all other characteristics were opposite. On the contrary, the surface uniformity and the lattice distortion increased, but the optical band gap of nc-Si films reduced. The optical properties of the resulting films were confirmed by the absorption model of nc-Si thin films, where the tendency of band gap changes is in consistent with the optical modeling.

  8. A nickel metal hydride battery for electric vehicles.

    PubMed

    Ovshinsky, S R; Fetcenko, M A; Ross, J

    1993-04-09

    Widespread use of electric vehicles can have significant impact on urban air quality, national energy independence, and international balance of trade. An efficient battery is the key technological element to the development of practical electric vehicles. The science and technology of a nickel metal hydride battery, which stores hydrogen in the solid hydride phase and has high energy density, high power, long life, tolerance to abuse, a wide range of operating temperature, quick-charge capability, and totally sealed maintenance-free operation, is described. A broad range of multi-element metal hydride materials that use structural and compositional disorder on several scales of length has been engineered for use as the negative electrode in this battery. The battery operates at ambient temperature, is made of nontoxic materials, and is recyclable. Demonstration of the manufacturing technology has been achieved.

  9. The formation and structure of the oxide and hydroxide chemisorbed phases at the aluminum surface, and relevance to hydrogen embrittlement

    NASA Astrophysics Data System (ADS)

    Francis, Michael; Kelly, Robert; Neurock, Matthew

    2010-03-01

    Aluminum alloys used in aerospace structures are susceptible to environmentally assisted cracking (EAC) induced by hydrogen embrittlement (HE) (Gangloff and Ives 1990). Crack growth experiments have demonstrated a linear relation between the relative humidity of the environment and crack growth rates, indicating the importance of water (Speidel and Hyatt 1972). While the presence of water has been demonstrated to be necessary for EAC of aluminum, crack growth rates have been linked to the diffusivity of hydrogen in aluminum (Gangloff 2003) and hydrogen densities at the crack tip as high as Al2H have been observed (Young and Scully 1998). While the mechanism by which hydrogen embrittles aluminum is yet not well understood, without the entry of hydrogen into the aluminum matrix, embrittlement would not occur. While at the crack tip high hydrogen concentrations exist, the solubility of hydrogen in aluminum is normal near 1 ppm (Wolverton 2004). In this work combined first principles and kinetic Monte Carlo methods will be used to examine the oxide and hydroxide structure resulting from exposure of aluminum to H2O or O2 and relevance to hydrogen entry as well as EAC is discussed.

  10. Aluminum nitride electro-optic phase shifter for backend integration on silicon.

    PubMed

    Zhu, Shiyang; Lo, Guo-Qiang

    2016-06-13

    An AlN electro-optic phase shifter with a parallel plate capacitor structure is fabricated on Si using the back-end complementary metal-oxide-semiconductor technology, which is feasible for multilayer photonics integration. The modulation efficiency (Vπ⋅Lπ product) measured from the fabricated waveguide-ring resonators and Mach-Zehnder Interferometer (MZI) modulators near the 1550-nm wavelength is ∼240 V⋅cm for the transverse electric (TE) mode and ∼320 V⋅cm for the transverse magnetic (TM) mode, from which the Pockels coefficient of the deposited AlN is deduced to be ∼1.0 pm/V for both TE and TM modes. The methods for further modulation efficiency improvement are addressed.

  11. Synthesis, structural characterization, and gas-phase unimolecular reactivity of the silver hydride nanocluster [Ag3((PPh2)2CH2)3(μ3-H)](BF4)2.

    PubMed

    Zavras, Athanasios; Khairallah, George N; Connell, Timothy U; White, Jonathan M; Edwards, Alison J; Mulder, Roger J; Donnelly, Paul S; O'Hair, Richard A J

    2014-07-21

    A bis(diphenylphosphino)methane-ligated trinuclear silver hydride nanocluster, [Ag3((Ph2P)2CH2)3(μ3-H)](BF4)2, featuring three silver(I) ions coordinated to a μ3-hydride, and its deuteride analogue, [Ag3((Ph2P)2CH2)3(μ3-D)](BF4)2, have been isolated and structurally characterized using electrospray ionization mass spectrometry (ESI-MS), X-ray crystallography, NMR and IR spectroscopy. The position of the deuteride in [Ag3((Ph2P)2CH2)3(μ3-D)](BF4)2 was determined by neutron diffraction. ESI-MS of [Ag3L3(μ3-H/D)](BF4)2 [L = ((Ph2P)2CH2)2] produces [Ag3L3(μ3-H/D)](2+) and [Ag3L3(μ3-H/D)(BF4)](+). A rich gas-phase ion chemistry of [Ag3L3(μ3-H/D)](2+) is observed under conditions of collision-induced dissociation (CID) and electron-capture dissociation (ECD). CID gives rise to the following complementary ion pairs: [Ag3L2](+) and [L+(H/D)](+); [Ag2(H/D)L2](+) and [AgL](+); [Ag2(H/D)L](+) and [AgL2](+). ECD gives rise to a number of dissociation channels including loss of the bis(phosphine) ligand, fragmentation of a coordinated bis(phosphine) ligand via C-P bond activation, and loss of a hydrogen (deuterium) atom with concomitant formation of [Ag3L3](+). Under CID conditions, [Ag3L3(μ3-H/D)(BF4)](+) fragments via ligand loss, the combined loss of a ligand and [H,B,F4], and cluster fragmentation to give [Ag2(BF4)L2](+) and [Ag2(L-H)L](+) [where (L-H) = (Ph2P)2CH(-)].

  12. Hydrides of intermetallic compounds with a H/M ratio greater than unity obtained at high hydrogen pressures

    SciTech Connect

    Semenenko, K.N.; Klyamkin, S.N.

    1993-11-01

    Novel hydride phases with H/M > 1 based on Zr{sub 2}Pd, Hf{sub 2}Pd, and Hf{sub 2}Cu (structures of the MoSi{sub 2} type) have been synthesized at high H{sub 2} pressures. The X-ray diffraction investigations of the resulting hydrides have been carried out. Some factors determining the maximum hydrogen content in the hydrides of intermetallic compounds are discussed. A model structure of the hydrides obtained is proposed, which assumes the possibility of direct H-H interactions when the interatomic distances are less than 1 {angstrom}.

  13. Low oxidation state aluminum-containing cluster anions: Cp(∗)AlnH(-), n = 1-3.

    PubMed

    Zhang, Xinxing; Ganteför, Gerd; Eichhorn, Bryan; Mayo, Dennis; Sawyer, William H; Gill, Ann F; Kandalam, Anil K; Schnöckel, Hansgeorg; Bowen, Kit

    2016-08-21

    Three new, low oxidation state, aluminum-containing cluster anions, Cp*AlnH(-), n = 1-3, were prepared via reactions between aluminum hydride cluster anions, AlnHm (-), and Cp*H ligands. These were characterized by mass spectrometry, anion photoelectron spectroscopy, and density functional theory based calculations. Agreement between the experimentally and theoretically determined vertical detachment energies and adiabatic detachment energies validated the computed geometrical structures. Reactions between aluminum hydride cluster anions and ligands provide a new avenue for discovering low oxidation state, ligated aluminum clusters.

  14. Complex and liquid hydrides for energy storage

    NASA Astrophysics Data System (ADS)

    Callini, Elsa; Atakli, Zuleyha Özlem Kocabas; Hauback, Bjørn C.; Orimo, Shin-ichi; Jensen, Craig; Dornheim, Martin; Grant, David; Cho, Young Whan; Chen, Ping; Hjörvarsson, Bjørgvin; de Jongh, Petra; Weidenthaler, Claudia; Baricco, Marcello; Paskevicius, Mark; Jensen, Torben R.; Bowden, Mark E.; Autrey, Thomas S.; Züttel, Andreas

    2016-04-01

    The research on complex hydrides for hydrogen storage was initiated by the discovery of Ti as a hydrogen sorption catalyst in NaAlH4 by Boris Bogdanovic in 1996. A large number of new complex hydride materials in various forms and combinations have been synthesized and characterized, and the knowledge regarding the properties of complex hydrides and the synthesis methods has grown enormously since then. A significant portion of the research groups active in the field of complex hydrides is collaborators in the International Energy Agreement Task 32. This paper reports about the important issues in the field of complex hydride research, i.e. the synthesis of borohydrides, the thermodynamics of complex hydrides, the effects of size and confinement, the hydrogen sorption mechanism and the complex hydride composites as well as the properties of liquid complex hydrides. This paper is the result of the collaboration of several groups and is an excellent summary of the recent achievements.

  15. Complex and liquid hydrides for energy storage

    SciTech Connect

    Callini, Elsa; Atakli, Zuleyha Özlem Kocabas; Hauback, Bjørn C.; Orimo, Shin-ichi; Jensen, Craig; Dornheim, Martin; Grant, David; Cho, Young Whan; Chen, Ping; Hjörvarsson, Bjørgvin; de Jongh, Petra; Weidenthaler, Claudia; Baricco, Marcello; Paskevicius, Mark; Jensen, Torben R.; Bowden, Mark E.; Autrey, Thomas S.; Züttel, Andreas

    2016-03-10

    The research on complex hydrides for hydrogen storage was imitated by the discovery of Ti as a hydrogen sorption catalyst in NaAlH4 by Boris Bogdanovic in 1996. A large number of new complex hydride materials in various forms and combinations have been synthesized and characterized and the knowledge on the properties of complex hydrides and the synthesis methods has grown enormously since then. A significant part of the research groups active in the field of complex hydrides are collaborators in the IEA task 32. This paper reports about the important issues in the field of the complex hydride research, i.e. the synthesis of borohydrides, the thermodynamics of complex hydrides and their thermodynamic properties, the effects of size and confinement, the hydrogen sorption mechanism and the complex hydride composites as well as the properties of liquid complex hydrides. This paper is the result of the collaboration of several groups and excellent summary of the recent achievements.

  16. First-principles calculations of niobium hydride formation in superconducting radio-frequency cavities

    SciTech Connect

    Ford, Denise C.; Cooley, Lance D.; Seidman, David N.

    2013-09-01

    Niobium hydride is suspected to be a major contributor to degradation of the quality factor of niobium superconducting radio-frequency (SRF) cavities. In this study, we connect the fundamental properties of hydrogen in niobium to SRF cavity performance and processing. We modeled several of the niobium hydride phases relevant to SRF cavities and present their thermodynamic, electronic, and geometric properties determined from calculations based on density-functional theory. We find that the absorption of hydrogen from the gas phase into niobium is exothermic and hydrogen becomes somewhat anionic. The absorption of hydrogen by niobium lattice vacancies is strongly preferred over absorption into interstitial sites. A single vacancy can accommodate six hydrogen atoms in the symmetrically equivalent lowest-energy sites and additional hydrogen in the nearby interstitial sites affected by the strain field: this indicates that a vacancy can serve as a nucleation center for hydride phase formation. Small hydride precipitates may then occur near lattice vacancies upon cooling. Vacancy clusters and extended defects should also be enriched in hydrogen, potentially resulting in extended hydride phase regions upon cooling. We also assess the phase changes in the niobium-hydrogen system based on charge transfer between niobium and hydrogen, the strain field associated with interstitial hydrogen, and the geometry of the hydride phases. The results of this study stress the importance of not only the hydrogen content in niobium, but also the recovery state of niobium for the performance of SRF cavities.

  17. Addressing the Limit of Detectability of Residual Oxide Discontinuities in Friction Stir Butt Welds of Aluminum using Phased Array Ultrasound

    NASA Technical Reports Server (NTRS)

    Johnston, P. H.

    2008-01-01

    This activity seeks to estimate a theoretical upper bound of detectability for a layer of oxide embedded in a friction stir weld in aluminum. The oxide is theoretically modeled as an ideal planar layer of aluminum oxide, oriented normal to an interrogating ultrasound beam. Experimentally-measured grain scattering level is used to represent the practical noise floor. Echoes from naturally-occurring oxides will necessarily fall below this theoretical limit, and must be above the measurement noise to be potentially detectable.

  18. Addressing the Limit of Detectability of Residual Oxide Discontinuities in Friction Stir Butt Welds of Aluminum Using Phased Array Ultrasound

    NASA Astrophysics Data System (ADS)

    Johnston, P. H.

    2009-03-01

    This activity seeks to estimate a theoretical upper bound of detectability for a layer of oxide embedded in a friction stir weld in aluminum. The oxide is theoretically modeled as an ideal planar layer of aluminum oxide, oriented normal to an interrogating ultrasound beam. Experimentally-measured grain scattering level is used to represent the practical noise floor. Echoes from naturally-occurring oxides will necessarily fall below this theoretical limit, and must be above the measurement noise to be potentially detectable.

  19. Transient liquid phase bonding of a third generation gamma-titanium aluminum alloy: Gamma Met PX

    NASA Astrophysics Data System (ADS)

    Butts, Daniel A.

    The research work presented here discusses transient liquid phase (TLP) bonding of a current (i.e. third) generation gamma-TiAl alloy known as Gamma Met PX (GMPX). Effective implementation of GMPX in service is likely to require fabrication of complicated geometries for which a high performance metallurgical joining technique must be developed. Although a number of joining processes have been investigated, all have significant disadvantages that limit their ability to achieve sound joints. TLP bonding has proved to be a successful method of producing joints with microstructures and compositions similar to that of the bulk substrates. Hence, bonds with parent-like mechanical and oxidation properties are possible. The interlayer and bonding conditions employed for joining of GMPX were based on successful wide-gap TLP joining trials of an earlier generation cast gamma-TiAl alloy with a composition of Ti-48Al-2Cr-2Nb in atomic percent (abbreviated here to 48-2-2). A composite interlayer consisting of a 6:1 weight ratio (7 vol.% copper) of gas atomized 48-2-2 powders (-270 mesh) and pure copper powders (-325 mesh) was employed. When applied to GMPX, these interlayer ratio and bonding conditions produced undesirable microstructures and poor mechanical performance in as-bonded joints. Thus, modifications to the joining technique were required. Initially these modifications were based purely on empirical and phenomenological studies, however, detailed mechanistic studies of the underlying joining mechanisms were conducted to aid in selecting these modifications. Mechanisms such as diffusion, solubility and wettability of copper in/on GMPX and 48-2-2 bulk substrates were investigated and compared. A difference in solubility of copper in GMPX and 48-2-2 bulk substrates was attributed to (at least in part) to the observed differences in GMPX and 48-2-2 bonds. The copper solubility, at the bonding temperature, in the 48-2-2 and GMPX alloys was determined to be ˜2 at.% and ˜1

  20. Transient liquid phase bonding of titanium-aluminum-niobium-chromium alloys

    NASA Astrophysics Data System (ADS)

    Zhou, Tao

    The research work presented in this study is mainly about the joining of Ti-48 at. % Al-2 at. % Nb-2 at. % Cr alloys with transient liquid phase (TLP) bonding technology. The TLP bonding technology that has been used in this project includes narrow-gap TLP bonding and wide-gap TLP bonding. Copper has been selected as the melting point depressant (MPD) for the bonding. Thin pure copper films are used for the narrow-gap TLP bonding and the composite interlayers made of 48-2-2 + Cu powders are used for the wide-gap TLP bonding. Different types of composite interlayers, including pre-sintered, manually deposited and automatically deposited composite interlayers have been used to make joints. The comparisons between the joints with all these different composite interlayers are drawn and the results suggest that all these interlayers could make sound bonds with suitable process conditions. The microstructures of the bonds, identified using light, scanning electron and transmission electron microscopy, are correlated with their mechanical properties. The mechanical tests include shear test, four point bend test and tensile test. The joints made with thin copper films usually have some excessive Cu-riched intermetallic at the bond line and the mechanical testing shows poor bonding strength. However, some joints made on Gleeble---1500 with very thin copper film (5 mum) could have some fairly high strength. The as-bonded wide-gap joints sometimes have some Cu-rich intermetallic compounds at the bond line and also have a finer microstructure than that of the substrates. These fine grains at the bond line come from the 48-2-2 powder particles in the composite interlayers. However, a fully lamellar microstructure could be formed at the bond line after post-bond heat treatment at 1350°C for 1 hour. The mechanical testing results show the strengths of the joints are quite similar to that of the bulk 48-2-2 alloys at both of the room and elevated temperature (700°). The post

  1. A new route to metal hydrides

    SciTech Connect

    Murphy, D.W.; Zahurak, S.M.; Vyas, B.; Thomas, M.; Badding, M.E.; Fang, W.C. )

    1993-06-01

    Aqueous borohydride is shown to be an effective reagent for hydriding metals and intermetallics. It is the hydriding equivalent of 20-30 atm of H[sub 2]. The reaction is a convenient way to screen materials for hydride formation and possible utility in applications such as nickel-metal hydride batteries. The reaction is also a convenient alternative to decrepitation for the production of free flowing powders. 16 refs., 1 fig., 1 tab.

  2. The microstructure and hydriding characteristics of high temperature aged U-13 at.%Nb alloy

    NASA Astrophysics Data System (ADS)

    Ji, Hefei; Shi, Peng; Li, Ruiwen; Jiang, Chunli; Yang, Jiangrong; Hu, Guichao

    2015-09-01

    Niobium as alloying element significantly improves physical and chemical properties of metallic uranium, exhibiting great application potential in uranium alloy materials. The corrosion resistance performance as well as the internal alloy phase structure of uranium-niobium alloy is closely related to aging processes. Microstructure and hydriding characteristics of the 400 °C/9 h + 500 °C/2 h aged uranium-13 at.% niobium alloys (U-13 at.%Nb) were investigated from the point of view of relationship between the microstructure and growth of the hydriding areas. The microstructure, morphology and composition of the alloy phases before and after the hydriding were well characterized by the laser scanning confocal microscopy (LSCM), scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. Experimental results indicated that the hydrogen preferentially reacted with the Nb-depleted phase α-like-U to form monolithic β-UH3Nbx, and the alloy microstructure played an important role in hydride growth.

  3. Photochemistry of Transition Metal Hydrides.

    PubMed

    Perutz, Robin N; Procacci, Barbara

    2016-08-10

    Photochemical reactivity associated with metal-hydrogen bonds is widespread among metal hydride complexes and has played a critical part in opening up C-H bond activation. It has been exploited to design different types of photocatalytic reactions and to obtain NMR spectra of dilute solutions with a single pulse of an NMR spectrometer. Because photolysis can be performed on fast time scales and at low temperature, metal-hydride photochemistry has enabled determination of the molecular structure and rates of reaction of highly reactive intermediates. We identify five characteristic photoprocesses of metal monohydride complexes associated with the M-H bond, of which the most widespread are M-H homolysis and R-H reductive elimination. For metal dihydride complexes, the dominant photoprocess is reductive elimination of H2. Dihydrogen complexes typically lose H2 photochemically. The majority of photochemical reactions are likely to be dissociative, but hydride complexes may be designed with equilibrated excited states that undergo different photochemical reactions, including proton transfer or hydride transfer. The photochemical mechanisms of a few reactions have been analyzed by computational methods, including quantum dynamics. A section on specialist methods (time-resolved spectroscopy, matrix isolation, NMR, and computational methods) and a survey of transition metal hydride photochemistry organized by transition metal group complete the Review.

  4. In situ X-ray diffraction measurement of the hydrogenation and dehydrogenation of aluminum and characterization of the recovered AlH3

    NASA Astrophysics Data System (ADS)

    Saitoh, H.; Sakurai, Y.; Machida, A.; Katayama, Y.; Aoki, K.

    2010-03-01

    Pristine aluminum was hydrogenated to form AlH3 at 8.9 GPa and 600 °C. The cyclic formation and decomposition of the hydride were measured by in situ synchrotron X-ray diffraction measurement. AlH3 synthesized under high pressure and temperature was recovered at ambient conditions. The recovered AlH3 was characterized by conventional powder X-ray diffraction measurement and Raman spectroscopy. The results of the characterization were consistent with that obtained for chemically prepared AlH3 and indicated that single phase α-AlH3 was obtained.

  5. Simultaneous speciation of inorganic arsenic and antimony in water samples by hydride generation-double channel atomic fluorescence spectrometry with on-line solid-phase extraction using single-walled carbon nanotubes micro-column

    NASA Astrophysics Data System (ADS)

    Wu, Hong; Wang, Xuecui; Liu, Bing; Liu, Yueling; Li, Shanshan; Lu, Jusheng; Tian, Jiuying; Zhao, Wenfeng; Yang, Zonghui

    2011-01-01

    A new method was developed for the simultaneous speciation of inorganic arsenic and antimony in water by on-line solid-phase extraction coupled with hydride generation-double channel atomic fluorescence spectrometry (HG-DC-AFS). The speciation scheme involved the on-line formation and retention of the ammonium pyrrolidine dithiocarbamate complexes of As(III) and Sb(III) on a single-walled carbon nanotubes packed micro-column, followed by on-line elution and simultaneous detection of As(III) and Sb(III) by HG-DC-AFS; the total As and total Sb were determined by the same protocol after As(V) and Sb(V) were reduced by thiourea, with As(V) and Sb(V) concentrations obtained by subtraction. Various experimental parameters affecting the on-line solid-phase extraction and determination of the analytes species have been investigated in detail. With 180 s preconcentration time, the enrichment factors were found to be 25.4 for As(III) and 24.6 for Sb(III), with the limits of detection (LODs) of 3.8 ng L - 1 for As(III) and 2.1 ng L - 1 for Sb(III). The precisions (RSD) for five replicate measurements of 0.5 μg L -1 of As(III) and 0.2 μg L -1 of Sb(III) were 4.2 and 4.8%, respectively. The developed method was validated by the analysis of standard reference materials (NIST SRM 1640a), and was applied to the speciation of inorganic As and Sb in natural water samples.

  6. Method of producing a chemical hydride

    DOEpatents

    Klingler, Kerry M.; Zollinger, William T.; Wilding, Bruce M.; Bingham, Dennis N.; Wendt, Kraig M.

    2007-11-13

    A method of producing a chemical hydride is described and which includes selecting a composition having chemical bonds and which is capable of forming a chemical hydride; providing a source of a hydrocarbon; and reacting the composition with the source of the hydrocarbon to generate a chemical hydride.

  7. Vanadium hydride deuterium-tritium generator

    DOEpatents

    Christensen, Leslie D.

    1982-01-01

    A pressure controlled vanadium hydride gas generator to provide deuterium-tritium gas in a series of pressure increments. A high pressure chamber filled with vanadium-deuterium-tritium hydride is surrounded by a heater which controls the hydride temperature. The heater is actuated by a power controller which responds to the difference signal between the actual pressure signal and a programmed pressure signal.

  8. Aluminum Hydroxide

    MedlinePlus

    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 ...

  9. The effect of stress state on zirconium hydride reorientation

    NASA Astrophysics Data System (ADS)

    Cinbiz, Mahmut Nedim

    correlating the finite element stress-state results with the spatial distribution of hydride microstructures observed within the optical micrographs for each sample. Experiments showed that the hydride reorientation was enhanced as the stress biaxiality increased. The threshold stress decreased from 150 MPa to 80 MPa when stress biaxiality ratio increased from uniaxial tension to near-equibiaxial tension. This behavior was also predicted by classical nucleation theory based on the Gibbs free energy of transformation being assisted by the far-field stress. An analysis of in situ X-ray diffraction data obtained during a thermo-mechanical cycle typical of vacuum drying showed a complex lattice-spacing behavior of the hydride phase during the dissolution and precipitation. The in-plane hydrides showed bilinear lattice expansion during heating with the intrinsic thermal expansion rate of the hydrides being observed only at elevated temperatures as they dissolve. For radial hydrides that precipitate during cooling under stress, the spacing of the close-packed {111} planes oriented normal to the maximum applied stress was permanently higher than the corresponding {111} plane spacing in the other directions. This behavior is believed to be a result of a complex stress state within the precipitating plate-like hydrides that induces a strain component within the hydrides normal to its "plate" face (i.e., the applied stress direction) that exceeds the lattice spacing strains in the other directions. During heat-up, the lattice spacing of these same "plate" planes actually contract due to the reversion of the stress state within the plate-like hydrides as they dissolve. The presence of radial hydrides and their connectivity with in-plane hydrides was shown to increase the ductile-to-brittle transition temperature during tensile testing. This behavior can be understood in terms of the role of radial hydrides in promoting the initiation of a long crack that subsequently propagates under

  10. Chemical synthesis of aluminum nanoparticles

    NASA Astrophysics Data System (ADS)

    Ghanta, Sekher Reddy; Muralidharan, Krishnamurthi

    2013-06-01

    An alternate synthetic route has been described for the production of aluminum nanoparticles (Al-NPs). These Al-NPs were obtained through a reduction of aluminum acetylacetonate [Al(acac)3] by lithium aluminum hydride (LiAlH4) in mestitylene at 165 °C. The side products were removed by repeated washing with dry, ice cold methanol and the reaction mixture was filtered to obtain gray-colored Al-NPs. The synthesized nanoparticles were characterized by Powder X-ray diffraction pattern and 27Al-MAS-NMR spectrum. The X-ray diffraction pattern confirmed the formation of face-centered cubic (fcc) form of aluminum. The size and morphology were investigated by scanning electron microscope and transmission electron microscope which showed particle of varying shapes with size ranging from 50 to 250 nm. The weight loss from the nanoparticles was studied by thermo gravimetric analysis which indicated that the nanoparticles were tightly bound with an unknown amorphous organic residue which cannot be removed by simple washing. The carbonaceous residue might be outcome of the decomposition of acac ligand which was responsible in stabilizing aluminum nanoparticles.

  11. An experimental and modeling investigation of the external strain, internal stress and fiber phase transformation behavior of a NiTi actuated aluminum metal matrix composite

    SciTech Connect

    Armstrong, W.D.; Lorentzen, T.; Broendsted, P.; Larsen, P.H.

    1998-06-12

    The present work reports macroscopic thermal mechanical and in-situ neutron diffraction measurements from 22.9 vol. %, 50.7 at. % Ni-Ti fiber actuated 6082-T6 aluminum matrix composite and 6082-T6 homogeneous aluminum control materials subjected to a room temperature 4% tensile elongation, a subsequent room temperature to 120 C unconstrained heating process, and a final 120 C tensile process. During the unconstrained room temperature to 120 C heating process, the composite exhibited a pronounced, non linear thermal contraction, while the homogeneous control exhibited the expected linear thermal expansion. The composite thermal contraction was clearly the result of a powerful shape memory response in the actuating NiTi fibers. The paper further presents a one-dimensional thermal strain, internal stress and fiber phase transformation composite model. Model parameters were identified from tests on extracted single fibers, calculations using these parameters quantitatively agree with experimental thermal mechanical and neutron diffraction measurements.

  12. Superconductivity and unexpected chemistry of germanium hydrides under pressure

    NASA Astrophysics Data System (ADS)

    Davari Esfahani, M. Mahdi; Oganov, Artem R.; Niu, Haiyang; Zhang, Jin

    2017-04-01

    Following the idea that hydrogen-rich compounds might be high-Tc superconductors at high pressures, and the very recent breakthrough in predicting and synthesizing hydrogen sulfide with record-high Tc=203 K , an ab initio evolutionary algorithm for crystal structure prediction was employed to find stable germanium hydrides. In addition to the earlier structure of germane with space group Ama2, we propose a C2/m structure, which is energetically more favorable at pressures above 278 GPa (with inclusion of zero-point energy). Our calculations indicate that the C2/m phase of germane is a superconductor with Tc=67 K at 280 GPa. Germane is found to become thermodynamically unstable to decomposition to hydrogen and the compound Ge3H11 at pressures above 300 GPa. Ge3H11 with space group I 4 ¯m 2 is found to become stable at above 285 GPa with Tc=43 K . We find that the pressure-induced phase stability of germanium hydrides is distinct from analogous isoelectronic systems, e.g., Si hydrides and Sn hydrides. Superconductivity stems from large electron-phonon coupling associated with the wagging, bending, and stretching intermediate-frequency modes derived mainly from hydrogen.

  13. Effects of Cr, Zr, V, Mn, Fe, and Co to the hydride properties of Laves phase-related body-centered-cubic solid solution alloys

    NASA Astrophysics Data System (ADS)

    Young, K.; Ouchi, T.; Nei, J.; Meng, T.

    2015-05-01

    Chemical composition modifications of a Laves phase-related BCC solid solution base alloy, Ti15.6Zr2.1V44Cr11.2Mn6.9Fe2.7Co1.4Ni15.7Al0.3, were investigated in order to study the function of each constituent element on the structural, gaseous phase and electrochemical hydrogen storage properties of these alloys. In general, removal of Fe and decrease in V-content in exchange for higher Ni-content were found to improve both the electrochemical capacity and high-rate dischargeability, which are related to the decrease in C14-content and increase in TiNi-content. However, total elimination of the C14 phase by removal of Zr resulted in a reduced discharge capacity, a prolonged activation period, and a less catalytic surface for electrochemical reaction. Besides the BCC and C14 phases, the TiNi phase was also found in every alloy in this study, contributing positively to the bulk diffusion of hydrogen while hindering the surface electrochemical reaction.

  14. Development of Hydrogen Storage Tank Systems Based on Complex Metal Hydrides

    PubMed Central

    Ley, Morten B.; Meggouh, Mariem; Moury, Romain; Peinecke, Kateryna; Felderhoff, Michael

    2015-01-01

    This review describes recent research in the development of tank systems based on complex metal hydrides for thermolysis and hydrolysis. Commercial applications using complex metal hydrides are limited, especially for thermolysis-based systems where so far only demonstration projects have been performed. Hydrolysis-based systems find their way in space, naval, military and defense applications due to their compatibility with proton exchange membrane (PEM) fuel cells. Tank design, modeling, and development for thermolysis and hydrolysis systems as well as commercial applications of hydrolysis systems are described in more detail in this review. For thermolysis, mostly sodium aluminum hydride containing tanks were developed, and only a few examples with nitrides, ammonia borane and alane. For hydrolysis, sodium borohydride was the preferred material whereas ammonia borane found less popularity. Recycling of the sodium borohydride spent fuel remains an important part for their commercial viability. PMID:28793541

  15. Development of Hydrogen Storage Tank Systems Based on Complex Metal Hydrides.

    PubMed

    Ley, Morten B; Meggouh, Mariem; Moury, Romain; Peinecke, Kateryna; Felderhoff, Michael

    2015-09-04

    This review describes recent research in the development of tank systems based on complex metal hydrides for thermolysis and hydrolysis. Commercial applications using complex metal hydrides are limited, especially for thermolysis-based systems where so far only demonstration projects have been performed. Hydrolysis-based systems find their way in space, naval, military and defense applications due to their compatibility with proton exchange membrane (PEM) fuel cells. Tank design, modeling, and development for thermolysis and hydrolysis systems as well as commercial applications of hydrolysis systems are described in more detail in this review. For thermolysis, mostly sodium aluminum hydride containing tanks were developed, and only a few examples with nitrides, ammonia borane and alane. For hydrolysis, sodium borohydride was the preferred material whereas ammonia borane found less popularity. Recycling of the sodium borohydride spent fuel remains an important part for their commercial viability.

  16. PROCESS OF ELECTROPLATING METALS WITH ALUMINUM

    DOEpatents

    Schickner, W.C.

    1960-04-26

    A process of electroplating aluminum on metals from a nonaqueous bath and a novel method of pretreating or conditioning the metal prior to electrodeposition of the aluminum are given. The process of this invention, as applied by way of example to the plating of uranium, comprises the steps of plating the uranium with the barrier inetal, immersing the barrier-coated uranium in fatty acid, and electrolyzing a water-free diethyl ether solution of aluminum chloride and lithium hydride while making the uranium the cathode until an aluminum deposit of the desired thickness has been formed. According to another preferred embodiment the barrier-coated uranium is immersed in an isopropyl alcohol solution of sterato chromic chloride prior to the fatty acid treatment of this invention.

  17. Temporal and spatial imaging of hydrogen storage materials: watching solvent and hydrogen desorption from aluminium hydride by transmission electron microscopy.

    PubMed

    Beattie, Shane D; Humphries, Terry; Weaver, Louise; McGrady, G Sean

    2008-10-07

    An in situ thermal desorption study of solvated aluminum hydride (alane) by transmission electron microscopy and selected area diffraction has permitted characterisation of the structural and morphological changes during desorption of solvent and hydrogen in real-time; this powerful technique for studying hydrogen storage materials complements several others already employed.

  18. Hydrogen Storage in Metal Hydrides

    DTIC Science & Technology

    1990-08-01

    Hydrogen Storage Capacity Hydride by weight (%) [1) by volume (g/ml) [2] MgH2 7.00 0.101 Mg2NiH4 3.84 0,081 Mg2CuH4 2.04 - - 27 ...Include Security Classification) Hydrogen Storage in Metal Hydrides (U) 12. PERSONAL AUTHOR(S) DelaRosa, Mark J. 13a. TYPE OF REPORT 13b. TIME...objective of this program was to develop an economical process for pr-ducing a lightweight hydrogen storage medium by the chemical vapor infiltration

  19. Characteristics and Applications of Metal Hydrides

    NASA Technical Reports Server (NTRS)

    Egan, G. J.; Lynch, F. E.

    1987-01-01

    Report discusses engineering principles of uses of metal hydrides in spacecraft. Metal hydrides absorb, store, pump, compress, and expand hydrogen gas. Additionally, they release or absorb sizeable amounts of heat as they form and decompose - property adapted for thermal-energy management or for propulsion. Describes efforts to: Identify heat sources and sinks suitable for driving metal hydride thermal cycles in spacecraft; develop concepts for hydride subsystems employing available heating and cooling methods; and produce data base on estimated sizes, masses, and performances of hydride devices for spacecraft.

  20. Characteristics and Applications of Metal Hydrides

    NASA Technical Reports Server (NTRS)

    Egan, G. J.; Lynch, F. E.

    1987-01-01

    Report discusses engineering principles of uses of metal hydrides in spacecraft. Metal hydrides absorb, store, pump, compress, and expand hydrogen gas. Additionally, they release or absorb sizeable amounts of heat as they form and decompose - property adapted for thermal-energy management or for propulsion. Describes efforts to: Identify heat sources and sinks suitable for driving metal hydride thermal cycles in spacecraft; develop concepts for hydride subsystems employing available heating and cooling methods; and produce data base on estimated sizes, masses, and performances of hydride devices for spacecraft.

  1. Aluminum and aluminum alloys as sources of hydrogen for fuel cell applications

    NASA Astrophysics Data System (ADS)

    Soler, Lluís; Macanás, Jorge; Muñoz, Maria; Casado, Juan

    Production of hydrogen using aluminum and aluminum alloys with aqueous alkaline solutions is studied. This process is based on aluminum corrosion, consuming only water and aluminum which are cheaper raw materials than other compounds used for in situ hydrogen generation, such as chemical hydrides. In principle, this method does not consume alkali because the aluminate salts produced in the hydrogen generation undergo a decomposition reaction that regenerates the alkali. As a consequence, this process could be a feasible alternative for hydrogen production to supply fuel cells. Preliminary results showed that an increase of base concentration and working solution temperature produced an increase of hydrogen production rate using pure aluminum. Furthermore, an improvement of hydrogen production rates and yields was observed varying aluminum alloys composition and increasing their reactive surface, with interesting results for Al/Si and Al/Co alloys. The development of this idea could improve yields and reduce costs in power units based on fuel cells which use hydrides as raw material for hydrogen production.

  2. Homogeneous hydride formation path in α-Zr: Molecular dynamics simulations with the charge-optimized many-body potential

    SciTech Connect

    Zhang, Yongfeng; Bai, Xian-Ming; Yu, Jianguo; Tonks, Michael R.; Noordhoek, Mark J.; Phillpot, Simon R.

    2016-06-01

    A formation path for homogeneous γ hydride formation in hcp α-Zr, from solid solution to the ζ and then the γ hydride, was demonstrated using molecular static calculations and molecular dynamic simulations with the charge-optimized many-body (COMB) potential. Hydrogen has limited solubility in α-Zr. Once the solubility limit is exceeded, the stability of solid solution gives way to that of coherent hydride phases such as the ζ hydride by planar precipitation of hydrogen. At finite temperatures, the ζ hydride goes through a partial hcp-fcc transformation via 1/3 <1¯100> slip on the basal plane, and transforms into a mixture of γ hydride and α-Zr. In the ζ hydride, slip on the basal plane is favored thermodynamically with negligible barrier, and is therefore feasible at finite temperatures without mechanical loading. The transformation process involves slips of three equivalent shear partials, in contrast to that proposed in the literature where only a single shear partial was involved. The adoption of multiple slip partials minimizes the macroscopic shape change of embedded hydride clusters and the shear strain accumulation in the matrix, and thus reduces the overall barrier needed for homogeneous γ hydride formation. In conclusion, this formation path requires finite temperatures for hydrogen diffusion without mechanical loading. Therefore, it should be effective at the cladding operating conditions.

  3. Homogeneous hydride formation path in α-Zr: Molecular dynamics simulations with the charge-optimized many-body potential

    DOE PAGES

    Zhang, Yongfeng; Bai, Xian-Ming; Yu, Jianguo; ...

    2016-06-01

    A formation path for homogeneous γ hydride formation in hcp α-Zr, from solid solution to the ζ and then the γ hydride, was demonstrated using molecular static calculations and molecular dynamic simulations with the charge-optimized many-body (COMB) potential. Hydrogen has limited solubility in α-Zr. Once the solubility limit is exceeded, the stability of solid solution gives way to that of coherent hydride phases such as the ζ hydride by planar precipitation of hydrogen. At finite temperatures, the ζ hydride goes through a partial hcp-fcc transformation via 1/3 <1¯100> slip on the basal plane, and transforms into a mixture of γmore » hydride and α-Zr. In the ζ hydride, slip on the basal plane is favored thermodynamically with negligible barrier, and is therefore feasible at finite temperatures without mechanical loading. The transformation process involves slips of three equivalent shear partials, in contrast to that proposed in the literature where only a single shear partial was involved. The adoption of multiple slip partials minimizes the macroscopic shape change of embedded hydride clusters and the shear strain accumulation in the matrix, and thus reduces the overall barrier needed for homogeneous γ hydride formation. In conclusion, this formation path requires finite temperatures for hydrogen diffusion without mechanical loading. Therefore, it should be effective at the cladding operating conditions.« less

  4. Homogeneous hydride formation path in α-Zr: Molecular dynamics simulations with the charge-optimized many-body potential

    SciTech Connect

    Zhang, Yongfeng; Bai, Xian-Ming; Yu, Jianguo; Tonks, Michael R.; Noordhoek, Mark J.; Phillpot, Simon R.

    2016-06-01

    A formation path for homogeneous γ hydride formation in hcp α-Zr, from solid solution to the ζ and then the γ hydride, was demonstrated using molecular static calculations and molecular dynamic simulations with the charge-optimized many-body (COMB) potential. Hydrogen has limited solubility in α-Zr. Once the solubility limit is exceeded, the stability of solid solution gives way to that of coherent hydride phases such as the ζ hydride by planar precipitation of hydrogen. At finite temperatures, the ζ hydride goes through a partial hcp-fcc transformation via 1/3 <1¯100> slip on the basal plane, and transforms into a mixture of γ hydride and α-Zr. In the ζ hydride, slip on the basal plane is favored thermodynamically with negligible barrier, and is therefore feasible at finite temperatures without mechanical loading. The transformation process involves slips of three equivalent shear partials, in contrast to that proposed in the literature where only a single shear partial was involved. The adoption of multiple slip partials minimizes the macroscopic shape change of embedded hydride clusters and the shear strain accumulation in the matrix, and thus reduces the overall barrier needed for homogeneous γ hydride formation. In conclusion, this formation path requires finite temperatures for hydrogen diffusion without mechanical loading. Therefore, it should be effective at the cladding operating conditions.

  5. Fabrication of large flat gallium nitride templates with extremely low dislocation densities in the 106 cm-2 range by novel two-side hydride vapor-phase epitaxial growth

    NASA Astrophysics Data System (ADS)

    Fujikura, Hajime; Konno, Taichiro

    2017-10-01

    Large GaN templates with high flatness (i.e., negligible wafer bowing and smooth as-grown surfaces) and low threading dislocation densities (TTDs) were fabricated by a novel two-side hydride vapor-phase epitaxial (HVPE) growth, beginning with deposition of polycrystalline GaN on the rear side of the wafer. Appropriate gas-flow management realized by our homemade HVPE system permitted the growth of a GaN layer with a smooth as-grown surface and excellent thickness uniformity on the front surfaces of 4- or 6-inch patterned sapphire substrates (PSSs). However, when the grown thickness exceeded 20 μm, single-side HVPE-growth induced fractures in GaN crystals. The fracture resistance of the GaN increased markedly when it was in a cleavage-resistant polycrystalline form (poly-GaN), permitting its growth to a thickness of 100 μm. In the presence of a back-side poly-GaN layer, extremely thick GaN crystal layers could be grown on the front side without fractures. An 80-μm-thick GaN template fabricated by two-side growth on a 4-inch PSS had a device-quality surface, negligible bowing, and low TDD (7 × 106 cm-2). Issues of high fabrication costs, unavailability of large-size wafers, and large off-angle variations associated with native GaN wafers could be overcome by using our high-quality GaN templates as alternative substrates.

  6. Formation and physical properties of uranium hydride under conditions relevant to metallic fuel and nuclear waste storage

    NASA Astrophysics Data System (ADS)

    Orr, Robin; Godfrey, Hugh; Broan, Chris; Goddard, Dave; Woodhouse, Guy; Durham, Peter; Diggle, Andrew; Bradshaw, John

    2016-08-01

    The formation of uranium hydride is recognised as a hazard during the storage of uranium metal owing to its potentially pyrophoric properties. This study has assessed the influence of water vapour on the potential for uranium hydride to form at low temperatures and shows that it increases the duration of the induction period but does not necessarily prevent uranium hydride formation and also does not significantly change the reaction rate with hydrogen. It is further shown that the α-UH3 fraction in the uranium hydride gradually increases at decreasing temperatures and is likely to be the dominant phase formed under typical storage conditions. Particle morphology and specific surface area of uranium hydride prepared between 30 °C and 200 °C have also been characterised but show only modest variation compared with the phase composition.

  7. High resolution transmission electron microscopy characterization of fcc --> 9R transformation in nanocrystalline palladium films due to hydriding

    NASA Astrophysics Data System (ADS)

    Amin-Ahmadi, Behnam; Idrissi, Hosni; Delmelle, Renaud; Pardoen, Thomas; Proost, Joris; Schryvers, Dominique

    2013-02-01

    Sputtered nanocrystalline palladium thin films with nanoscale growth twins have been subjected to hydriding cycles. The evolution of the twin boundaries has been investigated using high resolution transmission electron microscopy. Surprisingly, the ∑3{112} incoherent twin boundaries dissociate after hydriding into two phase boundaries bounding a 9R phase. This phase which corresponds to single stacking faults located every three {111} planes in the fcc Pd structure was not expected because of the high stacking fault energy of Pd. This observation is connected to the influence of the Hydrogen on the stacking fault energy of palladium and the high compressive stresses building up during hydriding.

  8. Cheaper Hydride-Forming Cathodes

    NASA Technical Reports Server (NTRS)

    Jones, Jack A.; Blue, Gary

    1990-01-01

    Hydride-forming cathodes for electrochemical experiments made of materials or combinations of materials cheaper and more abundant than pure palladium, according to proposal. Concept prompted by needs of experimenters in now-discredited concept of electrochemical nuclear fusion, cathodes useful in other electrochemical applications involving generation or storage of hydrogen, deuterium, or tritium.

  9. Superconductivity in Hydrides Doped with Main Group Elements Under Pressure

    NASA Astrophysics Data System (ADS)

    Shamp, Andrew; Zurek, Eva

    2017-01-01

    A priori crystal structure prediction techniques have been used to explore the phase diagrams of hydrides of main group elements under pressure. A number of novel phases with the chemical formulas MHn, n > 1 and M = Li, Na, K, Rb, Cs; MHn, n > 2 and M= Mg, Ca, Sr, Ba; HnI with n > 1 and PH, PH2, PH3 have been predicted to be stable at pressures achievable in diamond anvil cells. The hydrogenic lattices within these phases display a number of structural motifs including H2δ- , H-, H-3 , as well as one-dimensional and three-dimensional extended structures. A wide range of superconducting critical temperatures, Tcs, are predicted for these hydrides. The mechanism of metallization and the propensity for superconductivity are dependent upon the structural motifs present in these phases, and in particular on their hydrogenic sublattices. Phases that are thermodynamically unstable, but dynamically stable, are accessible experimentally. The observed trends provide insight on how to design hydrides that are superconducting at high temperatures.

  10. Kinetics of bulk and surface mass transport in complex metal hydrides

    NASA Astrophysics Data System (ADS)

    Gunaydin, Hakan

    2009-03-01

    Metal hydrides can be used to store hydrogen in high gravimetric and volumetric densities. However, the kinetics of hydrogen release and uptake are slow in complex metal hydrides. Clarification of the mechanism of hydrogen release and uptake in complex metal hydrides can aid in a rational design of new hydrogen storage materials with fast kinetics or catalysts that will catalyze the rate of hydrogen release from the existing materials. The release of hydrogen in metal hydrides requires the transport of hydrogen and/or heavier species. The kinetics of such mass transport in metal hydrides can be the rate-limiting process for the release of hydrogen. For example, the rate-determining step for the release of hydrogen from NaAlH4 is the creation and diffusion of neutral AlH3 defects in NaAlH4. The release of hydrogen from LiH destabilized LiNH2 also proceeds via the creation of neutral point defects. The mechanism of mass transport in prototypical hydrogen storage materials such as NaAlH4 and LiNH2 and the mechanism of hydrogen diffusion in aluminum will be discussed.

  11. Optimization of o-phtaldialdehyde/2-mercaptoethanol postcolumn reaction for the hydrophilic interaction liquid chromatography determination of memantine utilizing a silica hydride stationary phase.

    PubMed

    Douša, Michal; Pivoňková, Veronika; Sýkora, David

    2016-08-01

    A rapid procedure for the determination of memantine based on hydrophilic interaction chromatography with fluorescence detection was developed. Fluorescence detection after postcolumn derivatization with o-phtaldialdehyde/2-mercaptoethanol was performed at excitation and emission wavelengths of 345 and 450 nm, respectively. The postcolumn reaction conditions such as reaction temperature, derivatization reagent flow rate, and reagents concentration were studied due to steric hindrance of amino group of memantine. The derivatization reaction was applied for the hydrophilic interaction liquid chromatography method which was based on Cogent Silica-C stationary phase with a mobile phase consisting of a mixture of 10 mmol/L citric acid and 10 mmol/L o-phosphoric acid (pH 6.0) with acetonitrile using an isocratic composition of 2:8 v/v. The benefit of the reported approach consists in a simple sample pretreatment and a quick and sensitive hydrophilic interaction chromatography method. The developed method was validated in terms of linearity, accuracy, precision, and selectivity according to the International Conference on Harmonisation guidelines. The developed method was successfully applied for the analysis of commercial memantine tablets. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Aluminum Fixed Point: Impact of the Time Spent in the Liquid Phase on the Liquid-Solid Transition and Obviousness of the Pollution of the Ingot

    NASA Astrophysics Data System (ADS)

    Renaot, E.; Martin, C.

    2011-08-01

    In order to improve the uncertainty on the aluminum fixed point, a study was launched by Laboratoire Commun de Métrologie LNE-CNAM in the frame of the EURAMET Project 732 "Toward more accurate temperature fixed points" (coordinating laboratory: France, 17 partner countries). An earlier study completed in this laboratory showed that in regular realization of the melting-freezing plateaus, there is no diffusion of impurities in the thickness of the ingot, or the diffusion is excessively slow and cannot allow a uniform distribution of the impurities. On the other hand, it is frequently noticed that the experimental conditions before the freezing plateau have an impact on its characteristics (value, slope,…). Up to now, no systematic study was performed on the influence of this parameter. So, the objective of the task started recently in this laboratory is to investigate the influence of the time spent in the liquid phase on the phase transition. As a final result, it is demonstrated that in order to reach the equilibrium of the concentration of impurities, it is necessary to ensure that the metal remains in the liquid phase at least 24 h before initiating the freeze. At the end of the process, the aluminum ingot was chemically analyzed. The analyses reveal large contaminations of the surface of the ingot (sodium, sulfur, and phosphorus). One of the important outputs of this study is that the conditions of usage of the cells should be given important attention since large contaminations can be brought by the furnace.

  13. Chemical hydride hydrogen sources for small fuel cells. Final report, 1 February-30 August 1997

    SciTech Connect

    Serebrennikov, V.A.; Cleland, J.G.; Damle, A.S.; Turner, M.W.

    1997-09-30

    This report details an investigation into the feasibility of thermal decomposition (non-hydrolytic) of aluminum hydride (AlH3) for hydrogen production. A unique new process, referred to as the self-sustaining (SS) reaction, was developed, along with a prototype generator and cartridges of AlH3 for use in the generator. Tests performed indicate repeatable, rapid hydrogen production and a safe reaction. Issues of controllability are addressed for future work.

  14. Dissolution and Separation of Aluminum and Aluminosilicates

    DOE PAGES

    McFarlane, Joanna; Benker, Dennis; DePaoli, David W.; ...

    2015-12-19

    The selection of an aluminum alloy for target irradiation affects post-irradiation target dissolution and separations. Recent tests with aluminum alloy 6061 yielded greater than expected precipitation in the dissolver, forming up to 10 wt.% solids of aluminum hydroxides and aluminosilicates. Aluminosilicate dissolution presents challenges in a number of different areas, metals extraction from minerals, flyash treatment, and separations from aluminum alloys. We present experimental work that attempts to maximize dissolution of aluminum metal, along with silicon, magnesium, and copper impurities, through control of temperature, the rate of reagent addition, and incubation time. Aluminum phase transformations have been identified as amore » function of time and temperature, using X-ray diffraction. Solutions have been analyzed using wet chemical methods and X-ray fluorescence. Our data have been compared with published calculations of aluminum phase diagrams. Approaches are given to enhance the dissolution of aluminum and aluminosilicate phases in caustic solution.« less

  15. Dissolution and Separation of Aluminum and Aluminosilicates

    SciTech Connect

    McFarlane, Joanna; Benker, Dennis; DePaoli, David W.; Felker, Leslie Kevin; Mattus, Catherine H.

    2015-12-19

    The selection of an aluminum alloy for target irradiation affects post-irradiation target dissolution and separations. Recent tests with aluminum alloy 6061 yielded greater than expected precipitation in the dissolver, forming up to 10 wt.% solids of aluminum hydroxides and aluminosilicates. Aluminosilicate dissolution presents challenges in a number of different areas, metals extraction from minerals, flyash treatment, and separations from aluminum alloys. We present experimental work that attempts to maximize dissolution of aluminum metal, along with silicon, magnesium, and copper impurities, through control of temperature, the rate of reagent addition, and incubation time. Aluminum phase transformations have been identified as a function of time and temperature, using X-ray diffraction. Solutions have been analyzed using wet chemical methods and X-ray fluorescence. Our data have been compared with published calculations of aluminum phase diagrams. Approaches are given to enhance the dissolution of aluminum and aluminosilicate phases in caustic solution.

  16. Process for production of an aluminum hydride compound

    DOEpatents

    Allen, Nathan Tait; Butterick, III, Robert; Chin, Arthur Achhing; Miller, Dean Michael; Molzahn, David Craig

    2013-08-06

    A compound of formula M(AlH.sub.3OR.sup.1).sub.y, wherein R.sup.1 is phenyl substituted by at least one of: (i) an alkoxy group having from one to six carbon atoms; and (ii) an alkyl group having from three to twelve carbon atoms; wherein M is an alkali metal, Be or Mg; and y is one or two.

  17. Kinetics of Thermal Decomposition of Aluminum Hydride in Argon

    DTIC Science & Technology

    2005-05-01

    investigate the decomposition kinetics of alane ( AlH3 ) in argon atmosphere and to shed light on the mechanism of alane decomposition. Two kinetic models...fastest is due to growth of the crystals. Thus, during decomposition, hydrogen gas is liberated and the initial polyhedra AlH3 crystals yield final...INTRODUCTION Recently, the interest in alane ( AlH3 ) as a solid rocket fuel has been renewed presumably after the development of new methods of

  18. Aluminum Hydride as a Fuel Supplement to NanoThermites

    DTIC Science & Technology

    2014-01-01

    including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the... exists on its combustion behavior. Sinke et al. [3] determined the heat of formation as −2.7 kcal∕mol by bomb calorimetry in one of the earliest...Bi2O3 thermites were performedwith the CHEETAH code using the constant-volume explosion option. With the exception of the Fe2O3 based thermite, all of the

  19. Effects of outgassing of loader chamber walls on hydriding of thin films for commercial applications

    SciTech Connect

    Provo, James L.

    2014-07-01

    An important aspect of understanding industrial processing is to know the characteristics of the materials used in such processes. A study was performed to determine the effects of hydriding chamber material on the degree of hydriding for the commercial production of thin film hydride targets for various research universities, commercial companies, and government national laboratories. The goal was to increase the degree of hydriding of various thin film hydrides and to study the vacuum environment during air-exposure hydriding. For this purpose, dynamic residual gas analysis during deuterium gas hydride processing was utilized with erbium thin films, employing a special set-up for direct dynamic hydride gas sampling during processing at elevated temperature and full loading gas pressure. Complete process data for (1) a copper–(1.83 wt. %)beryllium wet hydrogen fired passivated (600 °C–1 h) externally heated pipe hydriding chamber are reported. Dynamic residual gas analysis comparisons during hydriding are presented for hydriding chambers made from (2) alumina (99.8 wt. %), (3) copper (with an interior aluminum coating ∼10 k Å thick, and (4) for a stainless-steel air-fired passivated (900 °C–1 h) chamber. Dynamic data with deuterium gas in the chamber at the hydriding temperature (450 °C) showed the presence and growth of water vapor (D{sub 2}O) and related mixed ion species(H{sub 2}O{sup +}, HDO{sup +}, D{sub 2}O{sup +}, and OD{sup +}) from hydrogen isotope exchange reactions during the 1 h process time. Peaks at mass-to-charge ratios (i.e., m/e) of 12(C{sup +}), 16(CD{sub 2}{sup +}), 17(CHD{sub 2}{sup +}), and 18(CD{sub 3}{sup +}, OD{sup +}) increased for approximately the first half hour of a 1 h hydriding process and then approach steady state. Mass-to-charge peaks at 19(HDO{sup +}) and 20(D{sub 2}O{sup +}) continue to increase throughout the process cycle. Using the m/e = 20 (D{sub 2}O{sup +}) peak intensity from chamber (1

  20. Low oxidation state aluminum-containing cluster anions: LAlH(-) and LAln(-) (n = 2-4, L = N[Si(Me)3]2).

    PubMed

    Zhang, Xinxing; Wang, Linjie; Montone, Georgia R; Gill, Ann F; Ganteför, Gerd; Eichhorn, Bryan; Kandalam, Anil K; Bowen, Kit H

    2017-06-14

    Several low oxidation state aluminum-containing cluster anions, LAlH(-) and LAln(-) (n = 2-4, L = N[Si(Me)3]2), were produced via reactions between aluminum hydride cluster anions, AlxHy(-), and hexamethyldisilazane (HMDS). These clusters were characterized by mass spectrometry, anion photoelectron spectroscopy, and density functional theory (DFT) based calculations. Agreement between the experimental and theoretical vertical detachment energies (VDEs) and adiabatic detachment energies (ADEs) validated the computed geometrical structures. Reactions between aluminum hydride cluster anions and ligands promise to be a new synthetic scheme for low oxidation state, ligated aluminum clusters.

  1. Chemical vapor synthesis and characterization of aluminum nanopowder

    NASA Astrophysics Data System (ADS)

    Choi, Jin Won; Sohn, Hong Yong; Choi, Young Joon; Fang, Zhigang Zak

    Aluminum is a component in many promising hydrogen storage materials such as aluminum hydride and complex aluminum hydrides. In this research, Al and TiAl 3-containing Al nanopowders were prepared by a chemical vapor synthesis (CVS) process using Mg as the reducing agent. XRD and EDS results indicated that the produced powder was composed of Al or Al with TiAl 3. The shape of the powder was spherical with the average size in the range of 10-50 nm measured by SEM, TEM, BET and ZetaPALS compared with the typically larger than 100 nm for commercially available fine Al powders. In addition, the effects of the operating conditions such as Ar flow rate, precursor feed rate and reaction temperature on the properties of the product powder were investigated.

  2. An empirical many-body potential-energy function for aluminum. Application to solid phases and microclusters

    NASA Astrophysics Data System (ADS)

    Johnston, Roy L.; Fang, Jian-Yun

    1992-11-01

    An empirical two-plus-three-body potential, developed by Murrell and co-workers [J. N. Murrell and R. A. Rodriguez-Ruiz, Mol. Phys. 71, 823 (1990)], is applied to the study of fcc aluminum. The parameters in the potential are derived by fitting the experimental phonon-dispersion curves and elastic constants. Calculations, using this potential, on a number of one-, two- and three-dimensional extended systems give results which are in quantitative agreement with recent ab initio calculations [I. J. Robertson, M. C. Payne, and V. Heine, Europhys. Lett. 15, 301 (1991)]. Calculations on small- and medium-sized aluminum clusters give cluster geometries and growth patterns which agree qualitatively with previous ab initio molecular-orbital and density-functional studies.

  3. Sensitive determination of As (III) and As (V) by magnetic solid phase extraction with Fe@polyethyleneimine in combination with hydride generation atomic fluorescence spectrometry.

    PubMed

    Zhou, Qingxiang; Zheng, Zhenwen; Xiao, Junping; Fan, Huili

    2016-08-15

    The magnetic nanomaterial Fe@polyethyleneimine (Fe@PEI) was successfully synthesized and used as an effective adsorbent material for magnetic solid phase extraction(MSPE) of As(III) and As(V) from water samples. Fe@SiO2 nanoparticles were prepared by one pot synthetic method using a borohydride reduction method, then modified with (3-chloropropyl)trimethoxysilane to obtain Fe@SiO2-Cl by chloropropylation, which was reacted with PEI to achieve Fe@polyethyleneimine (Fe@PEI). The microstructure and morphology of Fe@PEI were characterized by transmission electron microscoscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). The experimental results showed that Fe@PEI demonstrated excellent adsorption for As(III) and As(V). Based on this fact, the determination method for these two arsenic species earned good limits of detection (LODs) of 0.002μgL(-1) and wide calibration curves in the concentration range from 0.008 to 0.2μgL(-1). The precisions of As (III) and As (V)were 1.95% and 2.55% (RSD, n=6), respectively. The proposed method was validated with real samples and the spiked recoveries were in the range of 82.7-98.3% and the accuracies were in the range of 2-13.3%. The results demonstrated that the developed MSPE method had good advantages such as simplicity, rapid separation, low cost, easy to reuse and high-quality analytical performances, which made it attractive for rapid and efficient extraction of inorganic arsenic species in the environmental water samples.

  4. Program to Develop High Strength Aluminum Powder Metallurgy Mill Products - Phase IV-B-Scale - up to 3200 lb Billet

    DTIC Science & Technology

    1977-04-25

    Upon removing the upper rubber seal to the isostatic bag, water was observed on top of an otherwise sound-appearing compact. Within 1-1/2 minutes...the water had soaked into the compact, leaving the compact surface dry, sound and at the temperature of the water . The compact was resealed and...Inspection of the compact on the next day showed that the water that leaked past the isostatic bag seals was reacting with the aluminum in the compact

  5. Inert blanketing of a hydride bed using typical grade protium

    SciTech Connect

    Klein, J.E.

    2015-03-15

    This paper describes the impact of 500 ppm (0.05%) impurities in protium on the absorption rate of a 9.66 kg LaNi{sub 4.25}Al{sub 0.75} (LANA0.75) metal hydride bed. The presence of 500 ppm or less inerts (i.e. non-hydrogen isotopes) can significantly impact hydrogen bed absorption rates. The impact on reducing absorption rates is significantly greater than predicted assuming uniform temperature, pressure, and compositions throughout the bed. Possible explanations are discussed. One possibility considered was the feed gas contained impurity levels higher than 500 ppm. It was shown that a level of 5000 ppm of inerts would have been necessary to fit the experimental result so this possibility wa dismissed. Another possibility is that the impurities in the protium supply reacted with the hydride material and partially poisoned the hydride. If the hydride were poisoned with CO or another impurity, the removal of the over-pressure gas in the bed would not be expected to allow the hydride loading of the bed to continue as the experimental results showed, so this possibility was also dismissed. The last possibility questions the validity of the calculations. It is assumed in all the calculations that the gas phase composition, temperature, and pressure are uniform throughout the bed. These assumptions are less valid for large beds where there can be large temperature, pressure, and composition gradients throughout the bed. Eventually the impact of 0.05% inerts in protium on bed absorption rate is shown and explained in terms of an increase in inert partial pressure as the bed was loaded.

  6. Metal hydride composition and method of making

    DOEpatents

    Congdon, James W.

    1995-01-01

    A dimensionally stable hydride composition and a method for making such a composition. The composition is made by forming particles of a metal hydride into porous granules, mixing the granules with a matrix material, forming the mixture into pellets, and sintering the pellets in the absence of oxygen. The ratio of matrix material to hydride is preferably between approximately 2:1 and 4:1 by volume. The porous structure of the granules accommodates the expansion that occurs when the metal hydride particles absorb hydrogen. The porous matrix allows the flow of hydrogen therethrough to contact the hydride particles, yet supports the granules and contains the hydride fines that result from repeated absorption/desorption cycles.

  7. Rechargeable metal hydrides for spacecraft application

    NASA Technical Reports Server (NTRS)

    Perry, J. L.

    1988-01-01

    Storing hydrogen on board the Space Station presents both safety and logistics problems. Conventional storage using pressurized bottles requires large masses, pressures, and volumes to handle the hydrogen to be used in experiments in the U.S. Laboratory Module and residual hydrogen generated by the ECLSS. Rechargeable metal hydrides may be competitive with conventional storage techniques. The basic theory of hydride behavior is presented and the engineering properties of LaNi5 are discussed to gain a clear understanding of the potential of metal hydrides for handling spacecraft hydrogen resources. Applications to Space Station and the safety of metal hydrides are presented and compared to conventional hydride storage. This comparison indicates that metal hydrides may be safer and require lower pressures, less volume, and less mass to store an equivalent mass of hydrogen.

  8. The renaissance of hydrides as energy materials

    NASA Astrophysics Data System (ADS)

    Mohtadi, Rana; Orimo, Shin-Ichi

    2017-02-01

    Materials based on hydrides have been the linchpin in the development of several practical energy storage technologies, of which the most prominent example is nickel-metal hydride batteries. Motivated by the need to meet the future's energy demand, the past decade has witnessed substantial advancements in the research and development of hydrides as media for hydrogen energy storage. More recently, new and rapidly evolving discoveries have positioned hydrides as highly promising materials for future electrochemical energy storage, such as electrolytes for mono- and divalent batteries, and anodes for lithium-ion batteries. In addition, the potential of hydrides in efficient power transmission has been recently revealed. In this Review, we highlight key advances and illustrate how the versatility of hydrides has not only yielded a meaningful past, but also ensures a very bright future.

  9. The renaissance of hydrides as energy materials

    NASA Astrophysics Data System (ADS)

    Mohtadi, Rana; Orimo, Shin-Ichi

    2016-12-01

    Materials based on hydrides have been the linchpin in the development of several practical energy storage technologies, of which the most prominent example is nickel-metal hydride batteries. Motivated by the need to meet the future's energy demand, the past decade has witnessed substantial advancements in the research and development of hydrides as media for hydrogen energy storage. More recently, new and rapidly evolving discoveries have positioned hydrides as highly promising materials for future electrochemical energy storage, such as electrolytes for mono- and divalent batteries, and anodes for lithium-ion batteries. In addition, the potential of hydrides in efficient power transmission has been recently revealed. In this Review, we highlight key advances and illustrate how the versatility of hydrides has not only yielded a meaningful past, but also ensures a very bright future.

  10. Rechargeable metal hydrides for spacecraft application

    NASA Astrophysics Data System (ADS)

    Perry, J. L.

    1988-09-01

    Storing hydrogen on board the Space Station presents both safety and logistics problems. Conventional storage using pressurized bottles requires large masses, pressures, and volumes to handle the hydrogen to be used in experiments in the U.S. Laboratory Module and residual hydrogen generated by the ECLSS. Rechargeable metal hydrides may be competitive with conventional storage techniques. The basic theory of hydride behavior is presented and the engineering properties of LaNi5 are discussed to gain a clear understanding of the potential of metal hydrides for handling spacecraft hydrogen resources. Applications to Space Station and the safety of metal hydrides are presented and compared to conventional hydride storage. This comparison indicates that metal hydrides may be safer and require lower pressures, less volume, and less mass to store an equivalent mass of hydrogen.

  11. Inhibited solid propellant composition containing beryllium hydride

    NASA Technical Reports Server (NTRS)

    Thompson, W. W. (Inventor)

    1978-01-01

    An object of this invention is to provide a composition of beryllium hydride and carboxy-terminated polybutadiene which is stable. Another object of this invention is to provide a method for inhibiting the reactivity of beryllium hydride toward carboxy-terminated polybutadiene. It was found that a small amount of lecithin inhibits the reaction of beryllium hydride with the acid groups in carboxy terminated polybutadiene.

  12. Hydrogen /Hydride/-air secondary battery

    NASA Technical Reports Server (NTRS)

    Sarradin, J.; Bronoel, G.; Percheron-Guegan, A.; Achard, J. C.

    1979-01-01

    The use of metal hydrides as negative electrodes in a hydrogen-air secondary battery seems promising. However, in an unpressurized cell, more stable hydrides that LaNi5H6 must be selected. Partial substitutions of nickel by aluminium or manganese increase the stability of hydrides. Combined with an air reversible electrode, a specific energy close to 100 Wh/kg can be expected.

  13. Use of reversible hydrides for hydrogen storage

    NASA Technical Reports Server (NTRS)

    Darriet, B.; Pezat, M.; Hagenmuller, P.

    1980-01-01

    The addition of metals or alloys whose hydrides have a high dissociation pressure allows a considerable increase in the hydrogenation rate of magnesium. The influence of temperature and hydrogen pressure on the reaction rate were studied. Results concerning the hydriding of magnesium rich alloys such as Mg2Ca, La2Mg17 and CeMg12 are presented. The hydriding mechanism of La2Mg17 and CeMg12 alloys is given.

  14. Vanadium hydride deuterium-tritium generator

    DOEpatents

    Christensen, L.D.

    1980-03-13

    A pressure controlled vanadium hydride gas generator was designed to provide deuterium-tritium gas in a series of pressure increments. A high pressure chamber filled with vanadium-deuterium-tritium hydride is surrounded by a heater which controls the hydride temperature. The heater is actuated by a power controller which responds to the difference signal between the actual pressure signal and a programmed pressure signal.

  15. Multi-stage hydride-hydrogen compressor

    NASA Astrophysics Data System (ADS)

    Golben, P. M.

    A 4-stage metal hydride/hydrogen compressor that uses low temperature hot water (75 C) as its energy source has been built and tested. The compressor utilizes a new hydride heat exchanger technique that has achieved fast cycling time (with 20 C cooling water) on the order of 1 min. This refinement substantially decreases the size, weight and cost of the unit when compared to previous hydride compressors or even conventional mechanical diaphragm compressors.

  16. Diffusional exchange of isotopes in a metal hydride sphere.

    SciTech Connect

    Wolfer, Wilhelm G.; Hamilton, John C.; James, Scott Carlton

    2011-04-01

    This report describes the Spherical Particle Exchange Model (SPEM), which simulates exchange of one hydrogen isotope by another hydrogen isotope in a spherical metal hydride particle. This is one of the fundamental physical processes during isotope exchange in a bed of spherical metal particles and is thus one of the key components in any comprehensive physics-based model of exchange. There are two important physical processes in the model. One is the entropy of mixing between the two isotopes; the entropy of mixing is increased by having both isotopes randomly placed at interstitial sites on the lattice and thus impedes the exchange process. The other physical process is the elastic interaction between isotope atoms on the lattice. The elastic interaction is the cause for {beta}-phase formation and is independent of the isotope species. In this report the coupled diffusion equations for two isotopes in the {beta}-phase hydride are solved. A key concept is that the diffusion of one isotope depends not only on its concentration gradient, but also on the concentration gradient of the other isotope. Diffusion rate constants and the chemical potentials for deuterium and hydrogen in the {beta}-phase hydride are reviewed because these quantities are essential for an accurate model of the diffusion process. Finally, a summary of some of the predictions from the SPEM model are provided.

  17. Complex hydrides for hydrogen storage

    DOEpatents

    Zidan, Ragaiy

    2006-08-22

    A hydrogen storage material and process of forming the material is provided in which complex hydrides are combined under conditions of elevated temperatures and/or elevated temperature and pressure with a titanium metal such as titanium butoxide. The resulting fused product exhibits hydrogen desorption kinetics having a first hydrogen release point which occurs at normal atmospheres and at a temperature between 50.degree. C. and 90.degree. C.

  18. Ten degree Kelvin hydride refrigerator

    NASA Technical Reports Server (NTRS)

    Jones, Jack A. (Inventor)

    1987-01-01

    A compact hydride absorption refrigeration system with few moving parts for 10 Kelvin operation is disclosed and comprises liquid hydrogen producing means in combination with means for solidifying and subliming the liquid hydrogen produced. The liquid hydrogen is sublimed at about 10 Kelvin. By using a symmetrical all hydrogen redundant loop system, a 10 Kelvin refrigeration system can be operated for many years with only a fraction of the power required for prior art systems.

  19. Thermodynamic Hydricity of Transition Metal Hydrides.

    PubMed

    Wiedner, Eric S; Chambers, Matthew B; Pitman, Catherine L; Bullock, R Morris; Miller, Alexander J M; Appel, Aaron M

    2016-08-10

    Transition metal hydrides play a critical role in stoichiometric and catalytic transformations. Knowledge of free energies for cleaving metal hydride bonds enables the prediction of chemical reactivity, such as for the bond-forming and bond-breaking events that occur in a catalytic reaction. Thermodynamic hydricity is the free energy required to cleave an M-H bond to generate a hydride ion (H(-)). Three primary methods have been developed for hydricity determination: the hydride transfer method establishes hydride transfer equilibrium with a hydride donor/acceptor pair of known hydricity, the H2 heterolysis method involves measuring the equilibrium of heterolytic cleavage of H2 in the presence of a base, and the potential-pKa method considers stepwise transfer of a proton and two electrons to give a net hydride transfer. Using these methods, over 100 thermodynamic hydricity values for transition metal hydrides have been determined in acetonitrile or water. In acetonitrile, the hydricity of metal hydrides spans a range of more than 50 kcal/mol. Methods for using hydricity values to predict chemical reactivity are also discussed, including organic transformations, the reduction of CO2, and the production and oxidation of hydrogen.

  20. Coinage Metal Hydrides: Synthesis, Characterization, and Reactivity.

    PubMed

    Jordan, Abraham J; Lalic, Gojko; Sadighi, Joseph P

    2016-08-10

    Hydride complexes of copper, silver, and gold encompass a broad array of structures, and their distinctive reactivity has enabled dramatic recent advances in synthesis and catalysis. This Review summarizes the synthesis, characterization, and key stoichiometric reactions of isolable or observable coinage metal hydrides. It discusses catalytic processes in which coinage metal hydrides are known or probable intermediates, and presents mechanistic studies of selected catalytic reactions. The purpose of this Review is to convey how developments in coinage metal hydride chemistry have led to new organic transformations, and how developments in catalysis have in turn inspired the synthesis of reactive new complexes.

  1. Thermodynamic Hydricity of Transition Metal Hydrides

    DOE PAGES

    Wiedner, Eric S.; Chambers, Matthew B.; Pitman, Catherine L.; ...

    2016-08-02

    Transition metal hydrides play a critical role in stoichiometric and catalytic transformations. Knowledge of free energies for cleaving metal hydride bonds enables the prediction of chemical reactivity, such as for the bond-forming and bondbreaking events that occur in a catalytic reaction. Thermodynamic hydricity is the free energy required to cleave an M-H bond to generate a hydride ion (H-). Three primary methods have been developed for hydricity determination: the hydride transfer method establishes hydride transfer equilibrium with a hydride donor/acceptor pair of known hydricity, the H2 heterolysis method involves measuring the equilibrium of heterolytic cleavage of H2 in the presencemore » of a base, and the potential-pKa method considers stepwise transfer of a proton and two electrons to give a net hydride transfer. Using these methods, over 100 thermodynamic hydricity values for transition metal hydrides have been determined in acetonitrile or water. In acetonitrile, the hydricity of metal hydrides spans a range of more than 50 kcal/mol. Finally, methods for using hydricity values to predict chemical reactivity are also discussed, including organic transformations, the reduction of CO2, and the production and oxidation of hydrogen.« less

  2. Fundamental experiments on hydride reorientation in zircaloy

    NASA Astrophysics Data System (ADS)

    Colas, Kimberly B.

    In the current study, an in-situ X-ray diffraction technique using synchrotron radiation was used to follow directly the kinetics of hydride dissolution and precipitation during thermomechanical cycles. This technique was combined with conventional microscopy (optical, SEM and TEM) to gain an overall understanding of the process of hydride reorientation. Thus this part of the study emphasized the time-dependent nature of the process, studying large volume of hydrides in the material. In addition, a micro-diffraction technique was also used to study the spatial distribution of hydrides near stress concentrations. This part of the study emphasized the spatial variation of hydride characteristics such as strain and morphology. Hydrided samples in the shape of tensile dog-bones were used in the time-dependent part of the study. Compact tension specimens were used during the spatial dependence part of the study. The hydride elastic strains from peak shift and size and strain broadening were studied as a function of time for precipitating hydrides. The hydrides precipitate in a very compressed state of stress, as measured by the shift in lattice spacing. As precipitation proceeds the average shift decreases, indicating average stress is reduced, likely due to plastic deformation and morphology changes. When nucleation ends the hydrides follow the zirconium matrix thermal contraction. When stress is applied below the threshold stress for reorientation, hydrides first nucleate in a very compressed state similar to that of unstressed hydrides. After reducing the average strain similarly to unstressed hydrides, the average hydride strain reaches a constant value during cool-down to room temperature. This could be due to a greater ease of deforming the matrix due to the applied far-field strain which would compensate for the strains due to thermal contraction. Finally when hydrides reorient, the average hydride strains become tensile during the first precipitation regime and

  3. ENVIRONMENTAL REACTIVITY OF SOLID STATE HYDRIDE MATERIALS

    SciTech Connect

    Gray, J; Donald Anton, D

    2009-04-23

    In searching for high gravimetric and volumetric density hydrogen storage systems, it is inevitable that higher energy density materials will be used. In order to make safe and commercially acceptable condensed phase hydrogen storage systems, it is important to understand quantitatively the risks involved in using and handling these materials and to develop appropriate mitigation strategies to handle potential material exposure events. A crucial aspect of the development of risk identification and mitigation strategies is the development of rigorous environmental reactivity testing standards and procedures. This will allow for the identification of potential risks and implementation of risk mitigation strategies. Modified testing procedures for shipping air and/or water sensitive materials, as codified by the United Nations, have been used to evaluate two potential hydrogen storage materials, 2LiBH{sub 4} {center_dot} MgH{sub 2} and NH{sub 3}BH{sub 3}. The modified U.N. procedures include identification of self-reactive substances, pyrophoric substances, and gas-emitting substances with water contact. The results of these tests for air and water contact sensitivity will be compared to the pure material components where appropriate (e.g. LiBH{sub 4} and MgH{sub 2}). The water contact tests are divided into two scenarios dependent on the hydride to water mole ratio and heat transport characteristics. Air contact tests were run to determine whether a substance will spontaneously react with air in a packed or dispersed form. In the case of the 2LiBH{sub 4} {center_dot} MgH{sub 2} material, the results from the hydride mixture compared to the pure materials results showed the MgH{sub 2} to be the least reactive component and LiBH{sub 4} the more reactive. The combined 2LiBH{sub 4} {center_dot} MgH{sub 2} resulted in a material having environmental reactivity between these two materials. Relative to 2LiBH{sub 4} {center_dot} MgH{sub 2}, the chemical hydride NH{sub 3}BH

  4. A study of environmental characterization of conventional and advanced aluminum alloys for selection and design. Phase 1: Literature review

    NASA Technical Reports Server (NTRS)

    Sprowls, D. O.

    1984-01-01

    A review of the literature is presented with the objectives of identifying relationships between various accelerated stress corrosion testing techniques, and for determining the combination of test methods best suited to selection and design of high strength aluminum alloys. The following areas are reviewed: status of stress-corrosion test standards, the influence of mechanical and environmental factors on stress corrosion testing, correlation of accelerated test data with in-service experience, and procedures used to avoid stress corrosion problems in service. Promising areas for further work are identified.

  5. Gas-Phase Partial Oxidation of Lignin to Carboxylic Acids over Vanadium Pyrophosphate and Aluminum-Vanadium-Molybdenum.

    PubMed

    Lotfi, Samira; Boffito, Daria C; Patience, Gregory S

    2015-10-26

    Lignin is a complex polymer that is a potential feedstock for aromatic compounds and carboxylic acids by cleaving the β-O-4 and 5-5' linkages. In this work, a syringe pump atomizes an alkaline solution of lignin into a catalytic fluidized bed operating above 600 K. The vanadium heterogeneous catalysts convert all the lignin into carboxylic acids (up to 25 % selectivity), coke, carbon oxides, and hydrogen. Aluminum-vanadium-molybdenum mostly produced lactic acid (together with formic acid, acrylic acid, and maleic anhydride), whereas the vanadium pyrophosphate catalyst produced more maleic anhydride. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Our favorite materials: silica hydride stationary phases.

    PubMed

    Pesek, Joseph J; Matyska, Maria T

    2009-12-01

    "Chance favors the prepared mind." Louis Pasteur. "Reality is merely an illusion, albeit a very persistent one". Albert Einstein. As so succinctly stated by these two famous scientists, it is sometimes necessary to step outside the bounds of traditional thinking and look at ideas that many claim to be impossible based on preconceived notions rather than experimental data. This review is dedicated to those open-minded scientists who are willing to evaluate new concepts objectively rather than dismiss new approaches with outdated theories.

  7. Studies of gas phase reactions, nucleation and growth mechanisms of plasma promoted chemical vapor deposition of aluminum using dimethylethylamine alane as source percursor

    NASA Astrophysics Data System (ADS)

    Knorr, Andreas H.

    The work presented herein focuses on the use of plasma promoted chemical vapor deposition (PPCVD) of aluminum (Al) using dimethylethylamine alane (DMEAA) as source precursor to provide an integrated, low temperature alternative to currently employed Al deposition methods in ultra large sale integration ULSI multilevel metal wiring schemes. In this respect, key findings are reported and discussed from critical scientific and technical aspects of an research and development effort, which was successfully executed to identify a viable Al CVD deposition process. In this respect, advanced atomic scale analytical techniques were successfully employed to characterize the PPCVD deposition process at the molecular level, and document the dependence of film's structural and compositional properties on key process parameters. This led to the development and optimization of a PPCVD Al process for ULSI applications. In addition, gas phase quadrupole mass spectrometry (QMS) was employed to study the gas phase evolution during TCVD and PPCVD in order to gain a thorough understanding of the potential chemical and physical reactions that could occur in the gas phase and derive corresponding optimized reaction pathways for both CVD processes. Key reaction mechanisms involved in thermal and plasma promoted CVD as a function of processing parameters were investigated, including the role of hydrogen plasma in providing an efficient pathway to aluminum nucleation and growth. The resulting reaction mechanisms were then employed to identify the most likely precursor decomposition pathways and explore relevant implications for thermal and plasma promoted CVD Al. Furthermore, the nucleation and growth of Al in both TCVD and PPCVD were thoroughly characterized. Time evolution studies were carried out employing a variety of relevant liners and seed layers under selected surface chemical states. The surface morphology of the resulting films were analyzed by means of scanning probe microscopy

  8. Composition and structure of sputter deposited erbium hydride thin films

    SciTech Connect

    ADAMS,DAVID P.; ROMERO,JUAN A.; RODRIGUEZ,MARK A.; FLORO,JERROLD A.; BANKS,JAMES C.

    2000-05-10

    Erbium hydride thin films are grown onto polished, a-axis {alpha} Al{sub 2}O{sub 3} (sapphire) substrates by reactive ion beam sputtering and analyzed to determine composition, phase and microstructure. Erbium is sputtered while maintaining a H{sub 2} partial pressure of 1.4 x 10{sup {minus}4} Torr. Growth is conducted at several substrate temperatures between 30 and 500 C. Rutherford backscattering spectrometry (RBS) and elastic recoil detection analyses after deposition show that the H/Er areal density ratio is approximately 3:1 for growth temperatures of 30, 150 and 275 C, while for growth above {approximately}430 C, the ratio of hydrogen to metal is closer to 2:1. However, x-ray diffraction shows that all films have a cubic metal sublattice structure corresponding to that of ErH{sub 2}. RBS and Auger electron that sputtered erbium hydride thin films are relatively free of impurities.

  9. Dynamic crack nucleation, propagation, and interactions with crystalline secondary phases in aluminum alloys subjected to large deformations

    NASA Astrophysics Data System (ADS)

    Elkhodary, K. I.; Zikry, M. A.

    2012-11-01

    The major objective of this work was to model within a continuum framework the dynamic nucleation and evolution of failure surfaces in aluminum alloys with complex microstructures, using a recently developed compatibility-based fracture criterion for large deformations. Computational analyses were conducted to understand how Mn-bearing dispersoids, Ω and θ‧ precipitates affect dynamic fracture processes in an Al-Cu-Mg-Ag alloys (2139-Al). High strain-rate simulations were based on a rate-dependent dislocation-density-based crystalline plasticity formulation and a nonlinear explicit dynamic finite-element approach. Results indicate that the fracture criterion elucidated how dispersoids and precipitates have a dominant role in dynamic crack blunting,branching and arrest. Rationally orientated precipitates result in overall dynamic microstructural strengthening and enhanced uniformity of deformation. These precipitates, however, accelerated unstable crack propagation, and this is amplified in the presence of a pre-crack. In contrast, dispersoids decreased microstructural toughness and ductility, but greatly improved dynamic damage tolerance, especially in the presence of a pre-crack. It can also be predicted that low angle boundaries can change the propagation direction of ductile cracks, and contribute to damage tolerance without crack initiation. Collectively, rationally oriented precipitates and dispersoids can significantly improve the combined dynamic strength, toughness and damage tolerance of crystalline aluminum alloys.

  10. Safety and immunogenicity of inactivated poliovirus vaccine based on Sabin strains with and without aluminum hydroxide: a phase I trial in healthy adults.

    PubMed

    Verdijk, Pauline; Rots, Nynke Y; van Oijen, Monique G C T; Oberste, M Steven; Boog, Claire J; Okayasu, Hiromasa; Sutter, Roland W; Bakker, Wilfried A M

    2013-11-12

    An inactivated poliovirus vaccine (IPV) based on attenuated poliovirus strains (Sabin-1, -2 and -3) was developed for technology transfer to manufacturers in low- and middle income countries in the context of the Global Polio Eradication Initiative. Safety and immunogenicity of the Sabin-IPV was evaluated in a double-blind, randomized, controlled, phase I 'proof-of-concept' trial. Healthy male adults received a single intramuscular injection with Sabin-IPV, Sabin-IPV adjuvanted with aluminum hydroxide or conventional IPV. Virus-neutralizing titers against both Sabin and wild poliovirus strains were determined before and 28 days after vaccination. No vaccine-related serious adverse events were observed, and all local and systemic reactions were mild or moderate and transient. In all subjects, an increase in antibody titer for all types of poliovirus (both Sabin and wild strains) was observed 28 days after vaccination. Sabin-IPV and Sabin-IPV adjuvanted with aluminum hydroxide administered as a booster dose were equally immunogenic and safe as conventional IPV. EudraCTnr: 2010-024581-22, NCT01708720. Copyright © 2013 Elsevier Ltd. All rights reserved.

  11. Erbium hydride thermal desorption : controlling kinetics.

    SciTech Connect

    Ferrizz, Robert Matthew

    2007-08-01

    Thermal desorption spectroscopy (TDS) is used to study the decomposition kinetics of erbium hydride thin films. The TDS results presented in this report show that hydride film processing parameters directly impact thermal stability. Issues to be addressed include desorption kinetics for dihydrides and trihydrides, and the effect of film growth parameters, loading parameters, and substrate selection on desorption kinetics.

  12. Aluminum Analysis.

    ERIC Educational Resources Information Center

    Sumrall, William J.

    1998-01-01

    Presents three problems based on the price of aluminum designed to encourage students to be cooperative and to use an investigative approach to learning. Students collect and synthesize information, analyze results, and draw conclusions. (AIM)

  13. Aluminum Analysis.

    ERIC Educational Resources Information Center

    Sumrall, William J.

    1998-01-01

    Presents three problems based on the price of aluminum designed to encourage students to be cooperative and to use an investigative approach to learning. Students collect and synthesize information, analyze results, and draw conclusions. (AIM)

  14. Draft of M2 Report on Integration of the Hybrid Hydride Model into INL's MBM Framework for Review

    SciTech Connect

    Tikare, Veena; Weck, Philippe F.; Schultz, Peter A.; Clark, Blythe; Glazoff, Michael; Homer, Eric

    2014-07-01

    This report documents the development, demonstration and validation of a mesoscale, microstructural evolution model for simulation of zirconium hydride {delta}-ZrH{sub 1.5} precipitation in the cladding of used nuclear fuels that may occur during long-term dry storage. While the Zr-based claddings are manufactured free of any hydrogen, they absorb hydrogen during service, in the reactor by a process commonly termed ‘hydrogen pick-up’. The precipitation and growth of zirconium hydrides during dry storage is one of the most likely fuel rod integrity failure mechanisms either by embrittlement or delayed hydride cracking of the cladding. While the phenomenon is well documented and identified as a potential key failure mechanism during long-term dry storage (NUREG/CR-7116), the ability to actually predict the formation of hydrides is poor. The model being documented in this work is a computational capability for the prediction of hydride formation in different claddings of used nuclear fuels. This work supports the Used Fuel Disposition Research and Development Campaign in assessing the structural engineering performance of the cladding during and after long-term dry storage. This document demonstrates a basic hydride precipitation model that is built on a recently developed hybrid Potts-phase field model that combines elements of Potts-Monte Carlo and the phase-field models. The model capabilities are demonstrated along with the incorporation of the starting microstructure, thermodynamics of the Zr-H system and the hydride formation mechanism.

  15. Microstructure and Mechanical Properties of AA1235 Aluminum Foil Stocks Produced Directly from Electrolytic Aluminum Melt

    NASA Astrophysics Data System (ADS)

    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.

  16. First Evidence of Rh Nano-Hydride Formation at Low Pressure.

    PubMed

    Zlotea, Claudia; Oumellal, Yassine; Msakni, Mariem; Bourgon, Julie; Bastide, Stéphane; Cachet-Vivier, Christine; Latroche, Michel

    2015-07-08

    Rh-based nanoparticles supported on a porous carbon host were prepared with tunable average sizes ranging from 1.3 to 3.0 nm. Depending on the vacuum or hydrogen environment during thermal treatment, either Rh metal or hydride is formed at nanoscale, respectively. In contrast to bulk Rh that can form a hydride phase under 4 GPa pressure, the metallic Rh nanoparticles (∼2.3 nm) absorb hydrogen and form a hydride phase at pressure below 0.1 MPa, as evidenced by the presence of a plateau pressure in the pressure-composition isotherm curves at room temperature. Larger metal nanoparticles (∼3.0 nm) form only a solid solution with hydrogen under similar conditions. This suggests a nanoscale effect that drastically changes the Rh-H thermodynamics. The nanosized Rh hydride phase is stable at room temperature and only desorbs hydrogen above 175 °C. Within the present hydride particle size range (1.3-2.3 nm), the hydrogen desorption is size-dependent, as proven by different thermal analysis techniques.

  17. Study of mechanical joint strength of aluminum alloy 7075-T6 and dual phase steel 980 welded by friction bit joining and weld-bonding under corrosion medium

    SciTech Connect

    Lim, Yong Chae; Squires, Lile; Pan, Tsung-Yu; Miles, Michael; Song, Guang-Ling; Wang, Yanli; Feng, Zhili

    2014-12-30

    We have employed a unique solid-sate joining process, called friction bit joining (FBJ), to spot weld aluminum alloy (AA) 7075-T6 and dual phase (DP) 980 steel. Static joint strength was studied in the lap shear tension configuration. In addition, weld-bonding (adhesive + FBJ) joints were studied in order to evaluate the ability of adhesive to mitigate the impact of corrosion on joint properties. Accelerated laboratory cyclic corrosion tests were carried out for both FBJ only and weld-bonding joints. Furthermore, the FBJ only joints that emerged from corrosion testing had lap shear failure loads that were significantly lower than freshly prepared joints. However, weld-bonding specimens retained more than 80% of the lap shear failure load of the freshly prepared weld-bonding specimens. Moreover, examination of joint cross sections confirmed that the presence of adhesive in the weld-bonding joints mitigated the effect of the corrosion environment, compared to FBJ only joints.

  18. Gas-phase rotational spectroscopy of AlCCH (XΣ+): A model system for organo-aluminum compounds

    NASA Astrophysics Data System (ADS)

    Sun, M.; Halfen, D. T.; Min, J.; Clouthier, D. J.; Ziurys, L. M.

    2012-11-01

    The pure rotational spectrum of AlCCH in its ground electronic state (XΣ+) has been measured using Fourier transform microwave (FTMW) and mm/sub-mm direct absorption spectroscopy. AlCCH was created in a DC discharge from HCCH and aluminum vapor, either produced by a Broida-type oven, or generated from Al(CH3)3 in a supersonic jet source. Rotational transitions were measured for five isotopologues of AlCCH, with 13C and deuterium substitutions. From these data, rotational and Al and D quadrupole parameters were determined, as well as an accurate structure. AlCCH appears to exhibit an acetylenic arrangement with significant covalent character in the Al-C single bond.

  19. Zirconium hydride containing explosive composition

    DOEpatents

    Walker, Franklin E.; Wasley, Richard J.

    1981-01-01

    An improved explosive composition is disclosed and comprises a major portion of an explosive having a detonation velocity between about 1500 and 10,000 meters per second and a minor amount of a donor additive comprising a non-explosive compound or mixture of non-explosive compounds which when subjected to an energy fluence of 1000 calories/cm.sup.2 or less is capable of releasing free radicals each having a molecular weight between 1 and 120. Exemplary donor additives are dibasic acids, polyamines and metal hydrides.

  20. Energetics, equation of state, and elasticity of NAL phase: Potential host for alkali and aluminum in the lower mantle

    NASA Astrophysics Data System (ADS)

    Mookherjee, Mainak; Karki, Bijay B.; Stixrude, Lars; Lithgow-Bertelloni, Carolina

    2012-10-01

    The new aluminous (NAL) phase and aluminous phase with calcium ferrite (CF) structure constitutes more than 25 volume % of the deeply subducted crust at lower mantle depths. Using first principle simulations, we calculate the energetics, equation of state, and elasticity of NAL phase with a widely varying composition including CaMg2Al6O12, NaNa2Al3Si3O12 and KNa2Al3Si3O12. Our calculations indicate the relative stability of NAL and CF phases is a sensitive function of pressure, temperature, and composition, with increasing pressure tending to favor the CF phase, and increasing temperature, Mg-content and alkali-content tending to favor the NAL phase. The sound wave velocities of the NAL phase is significantly lower than CF phases and other major lower mantle phases. In deeply subducted MORB and CC, the faster sound velocity of silica (SiO2) and its high-pressure polymorphic phase is likely to be compensated with the slower sound wave velocities of NAL phase.