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Sample records for hydride phases formed

  1. Magnesium hydrides and their phase transitions

    Czech Academy of Sciences Publication Activity Database

    Paidar, Václav

    2016-01-01

    Roč. 41, č. 23 (2016), s. 9769-9773 ISSN 0360-3199 R&D Projects: GA MŠk(CZ) LD13069 Institutional support: RVO:68378271 Keywords : hydrogen * magnesium and transition metal hydrides * crystal structure stability * displacive phase transformations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.582, year: 2016

  2. Electrocatalytic hydride-forming compounds for rechageable batteries

    NARCIS (Netherlands)

    Notten, P.H.L.; Einerhand, R.E.F.

    1991-01-01

    Non-toxic intermetallic hydride-forming compounds are attractive alternatives to cadmium as the negative electrode materials in the new generation of Ni/metal hydride rechargeable batteries. High exchange currents and discharge efficiencies even at low temperatures can be achieved using highly

  3. Electrochemical modeling of hydrogen storage in hydride-forming electrodes

    NARCIS (Netherlands)

    Ledovskikh, A.; Danilov, D.; Vermeulen, P.; Notten, P.H.L.

    2009-01-01

    An electrochemical kinetic model (EKM) is developed, describing the electrochemical hydrogen storage in hydride-forming materials under equilibrium conditions. This model is based on first principles of electrochemical reaction kinetics and statistical thermodynamics and describes the complex,

  4. Modeling of hydrogen storage in hydride-forming materials : statistical thermodynamics

    NARCIS (Netherlands)

    Ledovskikh, A.; Danilov, D.; Rey, W.J.J.; Notten, P.H.L.

    2006-01-01

    A new lattice gas model has been developed, describing the hydrogen storage in hydride-forming materials. This model is based on the mean-field theory and Bragg-Williams approximation. To describe first-order phase transitions and two-phase coexistence regions, a binary alloy approach has been

  5. Solubility of hydrogen isotopes in stressed hydride-forming metals

    International Nuclear Information System (INIS)

    Coleman, C.E.; Ambler, J.F.R.

    1983-01-01

    Components made from hydride-forming metals can be brittle when particles of hydride are present. The solid solubility limit of hydrogen in these metals needs to be known so that fracture resistance can be properly assessed. Stress affects the solubility of hydrogen in metals. As hydrogen dissolves the metal volume increases, an applied hydrostatic tensile stress supplies work to increase the solubility. Precipitation of hydrides increases the volume further. A hydrostatic tensile stress promotes the formation of hydrides and tends to reduce the terminal solubility. For materials containing hydrogen in solution in equilibrium with hydrides, the effect of stress on the terminal solubility is given. Hydrogen migrates up tensile stress gradients because of the effect of stress on the solubility and solubility limit. Consequently, hydrogen concentrates at flaws. When hydrides are present in the metal matrix, those remote from the flaw tip will preferentially dissolve in favor of those precipitated at the flaw. If the stress is large enough, at some critical condition the hydrides at the flaw will crack. This is delayed hydrogen cracking. Notched and fatigue-cracked cantilever beam specimens (6) (38 x 4 x 3 mm) were machined from the circumferential direction of several cold-worked Zr-2.5 at. % Nb pressure tubes. The chemical compositions had the ranges (in atomic %) Nb - 2.5 to 2.7; O - 0.58 to 0.71; H - 0.018 to 0.18. The effect of test temperature is for a specimen containing 0.13 at. % protium and 0.29 at .% deuterium. Between 505 K and 530 K was less than 1 hr, between 530 K and 537 K it increased to 25.8 h, while at 538 K no cracking was observed up to the 54 h

  6. Mechanisms of hydrogen induced delayed cracking in hydride forming materials

    International Nuclear Information System (INIS)

    Dutton, R.; Nuttall, K.; Puls, M.P.; Simpson, L.A.

    1977-01-01

    Mechanisms which have been formulated to describe delayed hydrogen cracking in hydride-forming metals are reviewed and discussed. Particular emphasis is placed on the commercial alloy Zr--2.5% Nb (Cb) which is extensively used in nuclear reactor core components. A quantitative model for hydrogen cracking in this material is presented and compared with available experimental data. The kinetics of crack propagation are controlled by the growth of hydrides at the stressed crack tip by the diffusive ingress of hydrogen into this region. The driving force for the diffusion flux is provided by the local stress gradient which interacts with both hydrogen atoms in solution and hydrogen atoms being dissolved and reprecipitated at the crack tip. The model is developed using concepts of elastoplastic fracture mechanics. Stage I crack growth is controlled by hydrides growing in the elastic stress gradient, while Stage II is controlled by hydride growth in the plastic zone at the crack tip. Recent experimental observations are presented which indicate that the process occurs in an intermittent fashion; hydride clusters accumulate at the crack tip followed by unstable crack advance and subsequent crack arrest in repeated cycles

  7. Mechanisms of hydrogen induced delayed cracking in hydride forming materials

    International Nuclear Information System (INIS)

    Dutton, R.; Nuttall, K.; Puls, M.P.; Simpson, L.A.

    1977-01-01

    Mechanisms which have been formulated to describe delayed hydrogen cracking in hydride-forming metals are reviewed and discussed. Particular emphasis is placed on the commercial alloy Zr-2.5 pct Nb which is extensively used in nuclear reactor core components. A quantitative model for hydrogen cracking in this material is presented and compared with available experimental data. The kinetics of crack propagation are controlled by the growth of hydrides at the stressed crack tip by the diffusive ingress of hydrogen into this region. The driving force for the diffusion flux is provided by the local stress gradient which interacts with both hydrogen atoms in solution and hydrogen atoms being dissolved and reprecipitated at the crack tip. The model is developed using concepts of elastoplastic fracture mechanics. Stage I crack growth is controlled by hydrides growing in the elastic stress gradient, while Stage II is controlled by hydride growth in the plastic zone at the crack tip. Recent experimental observations are presented which indicate that the process occurs in an intermittent fashion; hydride clusters accumulate at the crack tip followed by unstable crack advance and subsequent crack arrest in repeated cycles. 55 refs., 6 figs

  8. Microcapsulated rare earth - nickel hydride-forming materials

    International Nuclear Information System (INIS)

    Ishikawa, H.; Oguro, K.; Kato, A.; Suzuki, H.; Ishii, E.

    1985-01-01

    Fine particles of hydride-forming alloys such as LaNi/sub 5/ and MmNi/sub 4.5/Mn/sub 0.5/ (MM : mischmetal) were coated with metallic copper thin layer by chemical plating method. Hydrogen storage capacities of alloys were not appreciably affected by the plating treatment. The capsulated alloy powders were easily pressed into pellets. The pellets obtained had high thermal conductivity and porosity enough to permeate hydrogen, leading to fast reaction kinetics. These were able to withstand more than 5,000 repeated hydriding-dehydriding cycles without disintegrating

  9. Hydrides of Alkaline Earth–Tetrel (AeTt) Zintl Phases: Covalent Tt–H Bonds from Silicon to Tin

    Energy Technology Data Exchange (ETDEWEB)

    Auer, Henry; Guehne, Robin; Bertmer, Marko; Weber, Sebastian; Wenderoth, Patrick; Hansen, Thomas Christian; Haase, Jürgen; Kohlmann, Holger (Leipzig); (Saarland-MED); (ILL)

    2017-01-18

    Zintl phases form hydrides either by incorporating hydride anions (interstitial hydrides) or by covalent bonding of H to the polyanion (polyanionic hydrides), which yields a variety of different compositions and bonding situations. Hydrides (deuterides) of SrGe, BaSi, and BaSn were prepared by hydrogenation (deuteration) of the CrB-type Zintl phases AeTt and characterized by laboratory X-ray, synchrotron, and neutron diffraction, NMR spectroscopy, and quantum-chemical calculations. SrGeD4/3–x and BaSnD4/3–x show condensed boatlike six-membered rings of Tt atoms, formed by joining three of the zigzag chains contained in the Zintl phase. These new polyanionic motifs are terminated by covalently bound H atoms with d(Ge–D) = 1.521(9) Å and d(Sn–D) = 1.858(8) Å. Additional hydride anions are located in Ae4 tetrahedra; thus, the features of both interstitial hydrides and polyanionic hydrides are represented. BaSiD2–x retains the zigzag Si chain as in the parent Zintl phase, but in the hydride (deuteride), it is terminated by H (D) atoms, thus forming a linear (SiD) chain with d(Si–D) = 1.641(5) Å.

  10. Simultaneous determination of hydride and non-hydride forming elements by inductively coupled plasma optical emission spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Benzo, Z. [Instituto Venezolano de Investigaciones Cientificas, IVIC, Altos de Pipe, Caracas (Venezuela, Bolivarian Republic of); Matos-Reyes, M.N.; Cervera, M.L.; Guardia, M. de la, E-mail: m.luisa.cervera@uv.es [Department of Analytical Chemistry, University of Valencia, Valencia (Spain)

    2011-09-15

    The operating characteristics of a dual nebulization system were studied including instrumental and chemical conditions for the hydride generation and analytical figures of merit for both, hydride and non hydride forming elements. Analytical performance of the nebulization system was characterized by detection limits from 0.002 to 0.0026 {mu}g mL{sup -1} for the hydride forming elements and between 0.0034 and 0.0121 {mu}g mL{sup -1} for the non-hydride forming elements, relative standard deviation for 10 replicate measurements at 0.25 mg L{sup -1} level and recovery percentages between 97 and 103%. The feasibility of the system was demonstrated in the simultaneous determination of Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Zn, As, Bi, Sb, Se, and Te in the NIST 1549 (non-fat milk powder), NIST 1570a (spinach leaves), DORM-2 (dogfish muscle) and TORT-2 (lobster hepatopancreas) certified samples for trace elements. Results found were in good agreement with the certified ones. (author)

  11. Hydrogen storage in the form of metal hydrides

    Science.gov (United States)

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

    1984-01-01

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

  12. High-pressure boron hydride phases

    International Nuclear Information System (INIS)

    Barbee, T.W. III; McMahan, A.K.; Klepeis, J.E.; van Schilfgaarde, M.

    1997-01-01

    The stability of boron-hydrogen compounds (boranes) under pressure is studied from a theoretical point of view using total-energy methods. We find that the molecular forms of boranes known to be stable at ambient pressure become unstable at high pressure, while structures with extended networks of bonds or metallic bonding are energetically favored at high pressures. If such structures are metastable on return to ambient pressure, they would be energetic as well as dense hydrogen storage media. An AlH 3 -like structure of BH 3 is particularly interesting in that it may be accessible by high-pressure diamond anvil experiments, and should exhibit both second-order structural and metal-insulator transitions at lower pressures. copyright 1997 The American Physical Society

  13. Neutron scattering study of the phase transformation of LaNi3 induced by hydriding

    International Nuclear Information System (INIS)

    Ruan Jinghui; Zeng Xiangxin; Niu Shiwen

    1994-01-01

    The phase transformation of LaNi 3 induced by hydriding and de-hydriding is investigated using the neutron diffraction and the neutron inelastic scattering. The results show that the hydriding sample, LaNi 3 H x , is transformed from crystalline state of the LaNi 3 into amorphous state with a microcrystalline characteristic of LaNi 5 , and the de-hydriding sample produced by LaNi 3 H x dehydrated at 600 degree C is decomposed into new crystalline states composed by LaNi 5 -and La-hydrides. The procedure of phase transformation is that the result of the transformation of LaNi 3 induced by hydriding shows the properties of LaNi 5 -H 2 system

  14. Process of forming a sol-gel/metal hydride composite

    Science.gov (United States)

    Congdon, James W [Aiken, SC

    2009-03-17

    An external gelation process is described which produces granules of metal hydride particles contained within a sol-gel matrix. The resulting granules are dimensionally stable and are useful for applications such as hydrogen separation and hydrogen purification. An additional coating technique for strengthening the granules is also provided.

  15. On the thermodynamics of phase transitions in metal hydrides

    Science.gov (United States)

    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.

  16. Study on an innovative fast reactor utilizing hydride neutron absorber - Final report of phase I study

    International Nuclear Information System (INIS)

    Konashi, K.; Iwasaki, T.; Itoh, K.; Hirai, M.; Sato, J.; Kurosaki, K.; Suzuki, A.; Matsumura, Y.; Abe, S.

    2010-01-01

    These days, the demand to use nuclear resources efficiently is growing for long-term energy supply and also for solving the green house problem. It is indispensable to develop technologies to reduce environmental load with the nuclear energy supply for sustainable development of human beings. In this regard, the development of the fast breeder reactor (FBR) is preferable to utilize nuclear resources effectively and also to burn minor actinides which possess very long toxicity for more than thousands years if they are not extinguished. As one of the FBR developing works in Japan this phase I study started in 2006 to introduce hafnium (Hf) hydride and Gadolinium-Zirconium (Gd-Zr) hydride as new control materials in FBR. By adopting them, the FBR core control technology is improved by two ways. One is extension of control rod life time by using long life Hf hydride which leads to reduce the fabrication and disposal cost and the other is reduction of the excess reactivity by adopting Gd-Zr hydride which leads to reduce the number of control rods and simplifies the core upper structure. This three year study was successfully completed and the following results were obtained. The core design was performed to examine the applicability of the Hf hydride absorber to Japanese Sodium Fast Reactor (JSFR) and it is clarified that the control rod life time can be prolonged to 6 years by adopting Hf hydride and the excess reactivity of the beginning of the core cycle can be reduced to half and the number of the control rods is also reduced to half by using the Gd-Zr hydride burnable poison. The safety analyses also certified that the core safety can be maintained with the same reliability of JSFR Hf hydride and Gd-Zr hydride pellets were fabricated in good manner and their basic features for design use were measured by using the latest devices such as SEM-EDX. In order to reduce the hydrogen transfer through the stainless steel cladding a new technique which shares calorizing

  17. A quantitative phase field model for hydride precipitation in zirconium alloys: Part I. Development of quantitative free energy functional

    International Nuclear Information System (INIS)

    Shi, San-Qiang; Xiao, Zhihua

    2015-01-01

    A temperature dependent, quantitative free energy functional was developed for the modeling of hydride precipitation in zirconium alloys within a phase field scheme. The model takes into account crystallographic variants of hydrides, interfacial energy between hydride and matrix, interfacial energy between hydrides, elastoplastic hydride precipitation and interaction with externally applied stress. The model is fully quantitative in real time and real length scale, and simulation results were compared with limited experimental data available in the literature with a reasonable agreement. The work calls for experimental and/or theoretical investigations of some of the key material properties that are not yet available in the literature

  18. Preparation of freestanding GaN wafer by hydride vapor phase epitaxy on porous silicon

    Science.gov (United States)

    Wu, Xian; Li, Peng; Liang, Renrong; Xiao, Lei; Xu, Jun; Wang, Jing

    2018-05-01

    A freestanding GaN wafer was prepared on porous Si (111) substrate using hydride vapor phase epitaxy (HVPE). To avoid undesirable effects of the porous surface on the crystallinity of the GaN, a GaN seed layer was first grown on the Si (111) bare wafer. A pattern with many apertures was fabricated in the GaN seed layer using lithography and etching processes. A porous layer was formed in the Si substrate immediately adjacent to the GaN seed layer by an anodic etching process. A 500-μm-thick GaN film was then grown on the patterned GaN seed layer using HVPE. The GaN film was separated from the Si substrate through the formation of cracks in the porous layer caused by thermal mismatch stress during the cooling stage of the HVPE. Finally, the GaN film was polished to obtain a freestanding GaN wafer.

  19. Characterization of a U-Mo alloy subjected to direct hydriding of the gamma phase

    International Nuclear Information System (INIS)

    Balart, Silvia N.; Bruzzoni, Pablo; Granovsky, Marta S.

    2003-01-01

    The Reduced Enrichment for Research and Test Reactors (RERTR) program has imposed the need to develop plate-type fuel elements based on high density uranium compounds, such as U-Mo alloys. One of the steps in the fabrication of the fuel elements is the pulverization of the fissile material. In the case of the U-Mo alloys, the pulverization can be accomplished through hydriding - dehydriding. Two alternative methods of the hydriding-dehydriding process, namely the selective hydriding in alpha phase (HS-alpha) and the massive hydriding in gamma phase (HM-gamma) are currently being studied at the Comision Nacional de Energia Atomica. The HM-gamma method was reproduced at laboratory scale starting from a U-7 wt % Mo alloy. The hydrided and dehydrided materials were characterized using metallographic techniques, scanning electron microscopy, energy dispersive X-ray analysis and X-ray diffraction. These results are compared with previous results of the HS-alpha method. (author)

  20. Characterization of the whiskerlike products formed by hydriding magnesium metal powders

    DEFF Research Database (Denmark)

    Herley, P. J.; Jones, W.; Vigeholm, Bjørn

    1985-01-01

    The structure of filamentary crystals produced during the hydriding of magnesium powder has been studies in detail. The needles of small dimensions (typically 0.5 μm in diameter) have been identified by electron analytical techniques to be oriented microcrystals of metallic magnesium. Their forma......The structure of filamentary crystals produced during the hydriding of magnesium powder has been studies in detail. The needles of small dimensions (typically 0.5 μm in diameter) have been identified by electron analytical techniques to be oriented microcrystals of metallic magnesium....... Their formation has been ascribed to the melting of localized aluminum impurities within the bulk magnesium to form a liquid eutectic. In the presence of sublimed magnesium vapor and hydrogen (as a carrier gas) a vapor-liquid-solid mechanism operates to produce a rapid unidirectional extension followed...

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

    International Nuclear Information System (INIS)

    Vizcaino, Pablo; Banchik, Abraham D.

    2003-01-01

    The differential calorimetric technique has been applied to measure the dissolution enthalpy, ΔH irrad δ→α , 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 ΔH irrad δ→α = 5 kJ/mol H was obtained after the first calorimetric run. That value is seven times lower than the value of ΔH δ→α = 37.7 kJ/mol H recently determined in Zircaloy-4 specimens taken from similar unirradiated structural components using the same calorimetric technique, [1]. Post-irradiation thermal treatments gradually increase that low value towards the unirradiated value with increasing annealing temperature similar to that observed for TSSd irrad . Therefore the same H atom trapping mechanism during reactor operation already proposed to explain the evolution of TSSd irrad is also valid for Q irrad δ→α . As the ratio Q/ΔH is proportional to the number N H of H atoms precipitated as hydrides, the increment of Q irrad δ→α with the thermal treatment indicates that the value of N H also grows with the annealing reaching the value corresponding to the bulk H concentration when ΔH irrad δ→α ≅ 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. (author)

  2. Structural and optical inhomogeneities of Fe doped GaN grown by hydride vapor phase epitaxy

    Science.gov (United States)

    Malguth, E.; Hoffmann, A.; Phillips, M. R.

    2008-12-01

    We present the results of cathodoluminescence experiments on a set of Fe doped GaN samples with Fe concentrations of 5×1017, 1×1018, 1×1019, and 2×1020 cm-3. These specimens were grown by hydride vapor phase epitaxy with different concentrations of Fe. The introduction of Fe is found to promote the formation of structurally inhomogeneous regions of increased donor concentration. We detect a tendency of these regions to form hexagonal pits at the surface. The locally increased carrier concentration leads to enhanced emission from the band edge and the internal T41(G)-A61(S) transition of Fe3+. In these areas, the luminescence forms a finely structured highly symmetric pattern, which is attributed to defect migration along strain-field lines. Fe doping is found to quench the yellow defect luminescence band and to enhance the blue luminescence band due to the lowering of the Fermi level and the formation of point defects, respectively.

  3. Catalitic effect of Co on hydrogen desorption form nanostucturated magnesium hydride

    Directory of Open Access Journals (Sweden)

    Matović Ljiljana Lj.

    2008-01-01

    Full Text Available To study the influence of 3d transition metal addition on desorption kinetics of MgH2 ball milling of MgH2-Co blends was performed under Ar. Microstructural and morphological characterization, performed by XRD and SEM, show a huge correlation with thermal stability and hydrogen desorption properties investigated by DSC. A complex desorption behavior is correlated with the dispersion of the metal additive particles on hydride matrix. The activation energy for H2 desorption from MgH2-Co composite was calculated from both non-isothermal and isothermal methods to be 130 kJ/mol which means that mutually diffusion and nucleation and growth of new phase control the dehydration process.

  4. Structural, electrical and luminescent characteristics of ultraviolet light emitting structures grown by hydride vapor phase epitaxy

    Directory of Open Access Journals (Sweden)

    A.Y. Polyakov

    2017-03-01

    Full Text Available Electrical and luminescent properties of near-UV light emitting diode structures (LEDs prepared by hydride vapor phase epitaxy (HVPE were studied. Variations in photoluminescence and electroluminescence efficiency observed for LEDs grown under nominally similar conditions could be attributed to the difference in the structural quality (dislocation density, density of dislocations agglomerates of the GaN active layers, to the difference in strain relaxation achieved by growth of AlGaN/AlGaN superlattice and to the presence of current leakage channels in current confining AlGaN layers of the double heterostructure.

  5. Achievement report for 1st phase (fiscal 1974-80) Sunshine Program research and development - Hydrogen energy. Research on transportation of hydrogen in the form of metallic hydride; 1974-1980 nendo kinzoku suisokabutsu ni yoru suiso no yuso gijutsu no kenkyu seika hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1981-03-01

    This report concerns the transportation and storage of hydrogen using metallic hydrides that perform absorption and desorption of hydrogen. Alloys useable for this purpose have to be capable of reversibly absorbing and desorbing hydrogen within a certain temperature range. In the absence of guidelines to follow in the quest for such alloys, the efforts at discovering them turned out to be a continual series of trials and errors. Researches were conducted into the hydrogenation reaction of Mg and Mg-based alloys and into hydrides of V-based alloys, and into Zr-based alloy hydrides such as the ZrMn{sub 2} hydride, ZrNiMn hydride, Zr(Fe{sub x}Mn{sub 1-x}){sub 2} hydrides, TiZrFe{sub 2} hydride, Zr{sub x}Ti{sub 1-x}(Fe{sub y}Mn{sub 1-y}) hydrides, etc. Also studied were the electronics of hydrogen in metallic hydrides, rates of reaction between Mg-Ni-based alloys and hydrogen systems, endurance tests for hydrides of Mg-Ni-based alloys, effects exerted by absorbed gas molecules during the storage of hydrogen in Mg-Ni-based alloys, effective thermal conductivity in a layer filled with a metallic hydride, metallic hydride-aided hydrogen transportation systems, chemical boosters, etc. (NEDO)

  6. The Effect of Hydrogen and Hydrides on the Integrity of Zirconium Alloy Components Delayed Hydride Cracking

    CERN Document Server

    Puls, Manfred P

    2012-01-01

    By drawing together the current theoretical and experimental understanding of the phenomena of delayed hydride cracking (DHC) in zirconium alloys, The Effect of Hydrogen and Hydrides on the Integrity of Zirconium Alloy Components: Delayed Hydride Cracking provides a detailed explanation focusing on the properties of hydrogen and hydrides in these alloys. Whilst the focus lies on zirconium alloys, the combination of both the empirical and mechanistic approaches creates a solid understanding that can also be applied to other hydride forming metals.   This up-to-date reference focuses on documented research surrounding DHC, including current methodologies for design and assessment of the results of periodic in-service inspections of pressure tubes in nuclear reactors. Emphasis is placed on showing that our understanding of DHC is supported by progress across a broad range of fields. These include hysteresis associated with first-order phase transformations; phase relationships in coherent crystalline metallic...

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Science.gov (United States)

    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.

  9. Elastoplastic phase-field modeling of ζ-hydride precipitation in zirconium alloy: dynamics evolution in inhomogeneous elasticity

    International Nuclear Information System (INIS)

    Oum, G.; Thuinet, L.; Legris, A.

    2015-07-01

    A phase-field (PF) model was developed within the framework of homogeneous and heterogeneous elasticity theory to study the precipitation of ζ-hydride in zirconium. By coupling crystal plasticity to PF we show that plastic strain participates in lowering the transformation stresses, and therefore induces changes in nucleation, growth and morphology evolution of the precipitates. (authors)

  10. Hydride vapor phase epitaxy growth of GaN, InGaN, ScN, and ScAIN

    NARCIS (Netherlands)

    Bohnen, T.

    2010-01-01

    Chemical vapor deposition (CVD); hydride vapor phase epitaxy (HVPE); gallium nitride (GaN); indium gallium nitride (InGaN); scandium nitride (ScN); scandium aluminum nitride (ScAlN); semiconductors; thin films; nanowires; III nitrides; crystal growth - We studied the HVPE growth of different III

  11. Hydriding of metallic thorium

    International Nuclear Information System (INIS)

    Miyake, Masanobu; Katsura, Masahiro; Matsuki, Yuichi; Uno, Masayoshi

    1983-01-01

    Powdered thorium is usually prepared through a combination of hydriding and dehydriding processes of metallic thorium in massive form, in which the hydriding process consists of two steps: the formation of ThH 2 , and the formation of Th 4 H 15 . However, little has yet been known as to on what stage of hydriding process the pulverization takes place. It is found in the present study that the formation of Th 4 H 15 by the reaction of ThH 2 with H 2 is responsible for pulverization. Temperature of 70 deg C adopted in this work for the reaction of formation Th 4 H 15 seems to be much more effective for production of powdered thorium than 200 - 300 deg C in the literature. The pressure-composition-temperature relationships for Th-H system are determined at 200, 300, 350, and 800 deg C. From these results, a tentative equilibrium phase diagram for the Th-H system is proposed, attention being focused on the two-phase region of ThH 2 and Th 4 H 15 . Pulverization process is discussed in terms of the tentative phase diagram. (author)

  12. Crystal structure of 200 K-superconducting phase in sulfur hydride system

    Energy Technology Data Exchange (ETDEWEB)

    Einaga, Mari; Sakata, Masafumi; Ishikawa, Takahiro; Shimizu, Katsuya [KYOKUGEN, Graduate School of Engineering Science, Osaka Univ. (Japan); Eremets, Mikhail; Drozdov, Alexander; Troyan, Ivan [Max Planck Institut fuer Chemie, Mainz (Germany); Hirao, Naohisa; Ohishi, Yasuo [JASRI/SPring-8, Hyogo (Japan)

    2016-07-01

    Superconductivity with the critical temperature T{sub c} above 200 K has been recently discovered by compression of H{sub 2}S (or D{sub 2}S) under extreme pressure. It was proposed that these materials decompose under high pressure to elemental sulfur and hydride with higher content of hydrogen which is responsible for the high temperature superconductivity. In this study, we have investigated that the crystal structure of the superconducting compressed H{sub 2}S and D{sub 2}S by synchrotron x-ray diffraction measurements combined with electrical resistance measurements at room and low temperatures. We found that the superconducting phase is in good agreement with theoretically predicted body-centered cubic structure, and coexists with elemental sulfur, which claims that the formation of 3H{sub 2}S → 2H{sub 3}S + S is occured under high pressure.

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

    International Nuclear Information System (INIS)

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

    2014-01-01

    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 17  cm −3 to (2–5) × 10 14  cm −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 13  cm −3 versus 2.9 × 10 16  cm −3 in the standard samples, with a similar decrease in the electron traps concentration

  14. Size determinations, by ultrasonic techniques, of cracks in hydride blisters formed in Zr-2.5 % Nb pressure tubes

    International Nuclear Information System (INIS)

    Trujillo Badillo, Giovanna; Desimone, Carlos; Domizzi, Gladys

    1999-01-01

    Non destructive techniques (NDT) are very useful in the detection of flaws produced in structural components in service. During the service of CANDU nuclear power reactors, it is possible that pressure tubes (PT) may contact calandria tubes (CT). After the PT/CT contact, zirconium hydride blisters may form at the point of contact depending on the concentration of hydrogen/deuterium. Zirconium hydride is brittle and is therefore prone to cracking under stress. Ultrasonic NDT is routinely use during PT in service inspection. In order to be able of detecting cracked blisters, it is of great importance the development of standards to calibrate the employed equipment. On this purpose, hydride blisters were grown, in laboratory, on sections of pressure tube. The cracks in the blisters were detected and measured by ultrasonic techniques. The obtained results were compared with measurements carried out in optic microscope, on successive sections of the samples. The crack tip diffraction technique was found to be the more effective for the mentioned ends. (author)

  15. Clean Grain Boundary Found in C14/Body-Center-Cubic Multi-Phase Metal Hydride Alloys

    Directory of Open Access Journals (Sweden)

    Hao-Ting Shen

    2016-06-01

    Full Text Available The grain boundaries of three Laves phase-related body-center-cubic (bcc solid-solution, metal hydride (MH alloys with different phase abundances were closely examined by scanning electron microscopy (SEM, transmission electron microscopy (TEM, and more importantly, electron backscatter diffraction (EBSD techniques. By using EBSD, we were able to identify the alignment of the crystallographic orientations of the three major phases in the alloys (C14, bcc, and B2 structures. This finding confirms the presence of crystallographically sharp interfaces between neighboring phases, which is a basic assumption for synergetic effects in a multi-phase MH system.

  16. Atypical magnetic phase diagrams of Ce.sub.2./sub.Fe.sub.17-x./sub.Mn.sub.x./sub. alloys and their hydrides

    Czech Academy of Sciences Publication Activity Database

    Kuchin, A. G.; Prokhnenko, O.; Arnold, Zdeněk; Kamarád, Jiří; Ritter, C.; Isnard, O.; Ivasechko, V.; Drulis, H.; Teplykh, A. E.; Khrabrov, V. I.; Medvedeva, I. V.; Lapina, T.P.

    2007-01-01

    Roč. 71, č. 11 (2007), s. 1615-1616 ISSN 1062-8738 Institutional research plan: CEZ:AV0Z10100521 Keywords : magnetic phase diagram * hydrides * neutron diffraction * pressure effect Subject RIV: BM - Solid Matter Physics ; Magnetism

  17. Electrical, optical, and structural properties of GaN films prepared by hydride vapor phase epitaxy

    International Nuclear Information System (INIS)

    Polyakov, A.Y.; Smirnov, N.B.; Yakimov, E.B.; Usikov, A.S.; Helava, H.; Shcherbachev, K.D.; Govorkov, A.V.; Makarov, Yu N.; Lee, In-Hwan

    2014-01-01

    Highlights: • GaN films are prepared by hydride vapor phase epitaxy (HVPE). • Residual donors and deep traps show a minimum density versus growth temperature. • This minimum is located close to the HVPE growth temperature of 950 °C. • Good crystalline GaN with residual donor density < 10 16 cm −3 can be grown at 950 °C. - Abstract: Two sets of undoped GaN films with the thickness of 10–20 μm were prepared by hydride vapor phase epitaxy (HVPE) and characterized by capacitance–voltage (C–V) profiling, microcathodoluminescence (MCL) spectra measurements, MCL imaging, electron beam induced current (EBIC) imaging, EBIC dependence on accelerating voltage, deep levels transient spectroscopy, high resolution X-ray diffraction measurements. The difference in growth conditions was mainly related to the lower (850 °C, group 1) or higher (950 °C, group 2) growth temperature. Both groups of samples showed similar crystalline quality with the dislocation density close to 10 8 cm −2 , but very different electrical and optical properties. In group 1 samples the residual donors concentration was ∼10 17 cm −3 or higher, the MCL spectra were dominated by the band-edge luminescence, and the diffusion length of charge carriers was close to 0.1 μm. Group 2 samples had a 2–4.5 μm thick highly resistive layer on top, for which MCL spectra were determined by green, yellow and red defect bands, and the diffusion length was 1.5 times higher than in group 1. We also present brief results of growth at the “standard” HVPE growth temperature of 1050 °C that show the presence of a minimum in the net donor concentration and deep traps density as a function of the growth temperature. Possible reasons for the observed results are discussed in terms of the electrical compensation of residual donors by deep traps

  18. Effects of gas phase impurities on the topochemical-kinetic behaviour of uranium hydride development

    International Nuclear Information System (INIS)

    Bloch, J.; Brami, D.; Kremner, A.; Mintz, M.H.; Ben-Gurion Univ. of the Negev, Beersheba

    1988-01-01

    The hydriding kinetics of bulk uranium and U-0.1 wt.% Cr, in the presence of oxidizing gaseous impurities (oxygen and CO), were studied by combined rate measurements and metallographic examinations of partially reacted samples. The effect of the gaseous impurity (type and concentration) was examined metallographically, and the kinetic data were discussed in relation to these examinations. Below about 100 0 C the reaction of uranium with pure hydrogen consists of the following sequence of steps: (i) Surface nucleation; (ii) homogeneous growth (pitting); (iii) relatively fast lateral growth leading to the formation of a reaction front which penetrates into the sample at a constant rate. The effects of oxygen and CO on the hydriding kinetics were related to their abilities to block hydrogen penetration into the uranium. Thus, it was found that oxygen affects only the penetration through the oxide layer, whereas CO affects the penetration through both the oxide and hydride layers. (orig.)

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

    Energy Technology Data Exchange (ETDEWEB)

    Metaferia, Wondwosen; Sun, Yan-Ting, E-mail: yasun@kth.se; Lourdudoss, Sebastian [Laboratory of Semiconductor Materials, Department of Materials and Nano Physics, KTH—Royal Institute of Technology, Electrum 229, 164 40 Kista (Sweden); Pietralunga, Silvia M. [CNR-Institute for Photonics and Nanotechnologies, P. Leonardo da Vinci, 32 20133 Milano (Italy); Zani, Maurizio; Tagliaferri, Alberto [Department of Physics Politecnico di Milano, P. Leonardo da Vinci, 32 20133 Milano (Italy)

    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.

  20. Flow injection electrochemical hydride generation inductively coupled plasma time-of-flight mass spectrometry for the simultaneous determination of hydride forming elements and its application to the analysis of fresh water samples

    International Nuclear Information System (INIS)

    Bings, Nicolas H.; Stefanka, Zsolt; Mallada, Sergio Rodriguez

    2003-01-01

    A flow injection (FI) method was developed using electrochemical hydride generation (EcHG) as a sample introduction system, coupled to an inductively coupled plasma time-of-flight mass spectrometer (ICP-TOFMS) for rapid and simultaneous determination of six elements forming hydrides (As, Bi, Ge, Hg, Sb and Se). A novel low volume electrolysis cell, especially suited for FI experiments was designed and the conditions for simultaneous electrochemical hydride generation (EcHG; electrolyte concentrations and flow rates, electrolysis voltage and current) as well as the ICP-TOFMS operational parameters (carrier gas flow rate, modulation pulse width (MPW)) for the simultaneous determination of 12 isotopes were optimized. The compromise operation parameters of the electrolysis were found to be 1.4 and 3 ml min -1 for the anolyte and catholyte flow rates, respectively, using 2 M sulphuric acid. An optimum electrolysis current of 0.7 A (16 V) and an argon carrier gas flow rate of 0.91 l min -1 were chosen. A modulation pulse width of 5 μs, which influences the sensitivity through the amount of ions being collected by the MS per single analytical cycle, provided optimum results for the detection of transient signals. The achieved detection limits were compared with those obtained by using FI in combination with conventional nebulization (FI-ICP-TOFMS); values for chemical hydride generation (FI-CHG-ICP-TOFMS) were taken from the literature. By using a 200 μl sample loop absolute detection limits (3σ) in the range of 10-160 pg for As, Bi, Ge, Hg, Sb and 1.1 ng for Se and a precision of 4-8% for seven replicate injections of 20-100 ng ml -1 multielemental sample solutions were achieved. The analysis of a standard reference material (SRM) 1643d (NIST, 'Trace Elements in Water') showed good agreement with the certified values for As and Sb. Se showed a drastic difference, which is probably due to the presence of hydride-inactive Se species in the sample. Recoveries better than

  1. The influence of Mn on the crystallography and electrochemistry of nonstoichiometric AB5-type hydride-forming compounds

    International Nuclear Information System (INIS)

    Notten, P.H.L.; Latroche, M.; Percheron-Guegan, A.

    1999-01-01

    To design Co-free, low-pressure, hydride-forming compounds for application in rechargeable nickel metal hydride batteries, nonstoichiometric AB x materials were investigated. The influence of both the Mn content and the degree of nonstoichiometry on the crystallography, electrochemical cycling stability, and electrode morphology were studied. The investigated composition was in the range of La(Ni 1-z Mn z ) x with 5.0 le x le 6.0 and 0 le xz le 2.0. The annealing temperature was essential in preparing homogeneous compounds. In agreement with geometric considerations, both the a and c axis of the hexagonal unit cell increase with increasing Mn content. In contrast, the a axis decreases with increasing degree of nonstoichiometry. As proved by neutron-diffraction experiments, the introduction of dumbbell pairs of Ni or Mn atoms on the La positions in the crystal lattice is responsible for this behavior. The electrochemical cycling stability is found to be strongly dependent on both the chemical and nonstoichiometric composition. Electrochemically stable materials are characterized by the absence of a significant particle-size reduction upon electrode cycling, reducing the overall oxidation rate. Unstable materials suffer from severe mechanical cracking through which the oxidation rate is increased. The improved mechanical stability is attributed to the reduced discrete lattice expansion. The most stable compound has a partial hydrogen pressure of only 0.1 bar, which matches well with that desirable in practical NiMH batteries. Neutron-diffraction experiments confirmed the hypothesis that La atoms are replaced by dumbbell pairs of Ni, in the case of the binary LaNi 5.4 , and by Mn atoms in the case of the mn-containing nonstoichiometric compounds. Electron-probe microanalyses and density measurements support the dumbbell hypothesis

  2. Zirconium hydrides and Fe redistribution in Zr-2.5%Nb alloy under ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Idrees, Y.; Yao, Z. [Department of Mechanical and Materials Engineering, Queen' s University, Kingston, ON, Canada, K7L 3N6 (Canada); Cui, J.; Shek, G.K. [Kinetrics, Mississauga, ON (Canada); Daymond, M.R., E-mail: daymond@queensu.ca [Department of Mechanical and Materials Engineering, Queen' s University, Kingston, ON, Canada, K7L 3N6 (Canada)

    2016-11-15

    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. - Graphical abstract: STEM HAADF micrographs at low magnification showing the hydride structure in Zr-2.5Nb alloy.

  3. Flow analysis-hydride generation-gas phase derivative molecular absorption spectrophotometric determination of antimony in antileishmanial drugs

    Directory of Open Access Journals (Sweden)

    Máximo Gallignani

    2009-01-01

    Full Text Available In the present work, the development of a method based on the coupling of flow analysis (FA, hydride generation (HG, and derivative molecular absorption spectrophotometry (D-EAM in gas phase (GP, is described in order to determine total antimony in antileishmanial products. Second derivative order (D²224nm of the absorption spectrum (190 - 300 nm is utilized as measurement criterion. Each one of the parameters involved in the development of the proposed method was examined and optimized. The utilization of the EAM in GP as detection system in a continuous mode instead of atomic absorption spectrometry represents the great potential of the analytic proposal.

  4. YNi and its hydrides: Phase stabilities, electronic structures and chemical bonding properties from first principles

    International Nuclear Information System (INIS)

    Matar, S.F.; Nakhl, M.; Al Alam, A.F.; Ouaini, N.; Chevalier, B.

    2010-01-01

    Graphical abstract: Base centered orthorhombic YNiH X structure. For x = 3, only H1 and H2 are present. Highest hydrogen content YNiH 4 is obtained when H3 are added. - Abstract: Within density functional theory, establishing the equations of states of YNi in two different controversial structures in the literature, leads to determine the orthorhombic FeB-type as the ground state one with small energy difference. For YNiH 3 and YNiH 4 hydrides crystallizing in the orthorhombic CrB-type structure the geometry optimization and the ab initio determination of the H atomic positions show that the stability of hydrogen decreases from the tri- to the tetra- hydride. New states brought by hydrogen within the valence band lead to its broadening and to enhanced localization of metal density of states. The chemical bonding analysis shows a preferential Ni-H bonding versus Y-H.

  5. YNi and its hydrides: Phase stabilities, electronic structures and chemical bonding properties from first principles

    Energy Technology Data Exchange (ETDEWEB)

    Matar, S.F., E-mail: matar@icmcb-bordeaux.cnrs.fr [CNRS, Universite de Bordeaux, ICMCB, 87 avenue du Docteur Albert Schweitzer, F-33608 Pessac (France); Nakhl, M. [Universite Libanaise, Laboratoire de Chimie-Physique des Materiaux LCPM, Fanar (Lebanon); Al Alam, A.F.; Ouaini, N. [Universite Saint-Esprit de Kaslik, Faculte des Sciences et de Genie Informatique, Jounieh (Lebanon); Chevalier, B. [CNRS, Universite de Bordeaux, ICMCB, 87 avenue du Docteur Albert Schweitzer, F-33608 Pessac (France)

    2010-11-25

    Graphical abstract: Base centered orthorhombic YNiH{sub X} structure. For x = 3, only H1 and H2 are present. Highest hydrogen content YNiH{sub 4} is obtained when H3 are added. - Abstract: Within density functional theory, establishing the equations of states of YNi in two different controversial structures in the literature, leads to determine the orthorhombic FeB-type as the ground state one with small energy difference. For YNiH{sub 3} and YNiH{sub 4} hydrides crystallizing in the orthorhombic CrB-type structure the geometry optimization and the ab initio determination of the H atomic positions show that the stability of hydrogen decreases from the tri- to the tetra- hydride. New states brought by hydrogen within the valence band lead to its broadening and to enhanced localization of metal density of states. The chemical bonding analysis shows a preferential Ni-H bonding versus Y-H.

  6. Alkali metal hydride formation

    International Nuclear Information System (INIS)

    1976-01-01

    The present invention relates to a method of producing alkali metal hydrides by absorbing hydrogen gas under pressure into a mixture of lower alkyl mono amines and alkali metal alkyl amides selected from sodium and potassium amides formed from said amines. The present invention also includes purification of a mixture of the amines and amides which contain impurities, such as is used as a catalytic exchange liquid in the enrichment of deuterium, involving the formation of the alkali metal hydride

  7. High H⁻ ionic conductivity in barium hydride.

    Science.gov (United States)

    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.

  8. Neutral and Ionized Hydrides in Star-forming Regions. Observations with Herschel/HIFI

    DEFF Research Database (Denmark)

    O. Benz, Arnold; Bruderer, Simon; F. van Dishoeck, Ewine

    2013-01-01

    of OH, CH, NH, SH and their ions OH+, CH+, NH+, SH+, H2O+, and H3O+ were observed in star-forming regions by the HIFI spectrometer onboard the Herschel Space Observatory. Molecular column densities are derived from observed ground-state lines, models, or rotational diagrams. We report here on two...

  9. Mechanochemical synthesis of nanostructured chemical hydrides in hydrogen alloying mills

    International Nuclear Information System (INIS)

    Wronski, Z.; Varin, R.A.; Chiu, C.; Czujko, T.; Calka, A.

    2007-01-01

    Mechanical alloying of magnesium metal powders with hydrogen in specialized hydrogen ball mills can be used as a direct route for mechanochemical synthesis of emerging chemical hydrides and hydride mixtures for advanced solid-state hydrogen storage. In the 2Mg-Fe system, we have successfully synthesized the ternary complex hydride Mg 2 FeH 6 in a mixture with nanometric Fe particles. The mixture of complex magnesium-iron hydride and nano-iron released 3-4 wt.%H 2 in a thermally programmed desorption experiment at the range 285-295 o C. Milling of the Mg-2Al powder mixture revealed a strong competition between formation of the Al(Mg) solid solution and the β-MgH 2 hydride. The former decomposes upon longer milling as the Mg atoms react with hydrogen to form the hydride phase, and drive the Al out of the solid solution. The mixture of magnesium dihydride and nano-aluminum released 2.1 wt.%H 2 in the temperature range 329-340 o C in the differential scanning calorimetry experiment. The formation of MgH 2 was suppressed in the Mg-B system; instead, a hydrogenated amorphous phase (Mg,B)H x , was formed in a mixture with nanometric MgB 2 . Annealing of the hydrogen-stabilized amorphous mixture produced crystalline MgB 2

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

    International Nuclear Information System (INIS)

    Standley, R.W.

    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/) 2 244 , 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. Hydrogen Outgassing from Lithium Hydride

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Science.gov (United States)

    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...

  13. Experimental determination of the phase diagram of the system sodium-sodium hydride up to 9000C and hydrogen pressures up to 800 bar

    International Nuclear Information System (INIS)

    Klostermeier, W.

    1978-01-01

    In the present work part of the sodium-sodium hydride system phase diagram has been studied at high temperatures (up to 900 0 C) and high hydrogen pressures (up to 1000 bar). The absorption isothermal curves recorded at temperatures between 650 0 C and 900 0 C show an increase in hydride solubility in sodium from 5.5 mol% at 650 0 to 19 mol% at 900 0 C. The melting point of sodium hydride has been measured giving the value 632 0 C with a hydrogen equilibrium pressure of 106 bar. In the mixing gap region the plateau equilibrium pressure, which is independent of composition, and his temperature dependence have been obtained. The enthalpy and entropy of melting are determined. (GSCH) [de

  14. Cyclopentadiene-mediated hydride transfer from rhodium complexes.

    Science.gov (United States)

    Pitman, C L; Finster, O N L; Miller, A J M

    2016-07-12

    Attempts to generate a proposed rhodium hydride catalytic intermediate instead resulted in isolation of (Cp*H)Rh(bpy)Cl (1), a pentamethylcyclopentadiene complex, formed by C-H bond-forming reductive elimination from the fleeting rhodium hydride. The hydride transfer ability of diene 1 was explored through thermochemistry and hydride transfer reactions, including the reduction of NAD(+).

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

    Science.gov (United States)

    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.

  16. Temperature dependence of InN growth on (0001) sapphire substrates by atmospheric pressure hydride vapor phase epitaxy

    International Nuclear Information System (INIS)

    Kumagai, Yoshinao; Adachi, Hirokazu; Otake, Aya; Higashikawa, Yoshihiro; Togashi, Rie; Murakami, Hisashi; Koukitu, Akinori

    2010-01-01

    The temperature dependence of InN growth on (0001) sapphire substrates by atmospheric pressure hydride vapor phase epitaxy (HVPE) was investigated. N-polarity single-crystal InN layers were successfully grown at temperatures ranging from 400 to 500 C. The a and c lattice constants of InN layers grown at 450 C or below were slightly larger than those of InN layers grown above 450 C due to oxygen incorporation that also increased the carrier concentration. The optical absorption edge of the InN layer decreased from above 2.0 to 0.76 eV when the growth temperature was increased from 450 to 500 C. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. The status and immediate problems of the chemistry of transition metal hydrides

    International Nuclear Information System (INIS)

    Meikheeva, V.I.

    1978-01-01

    The state of the art and perspectives of the chemistry transition metal hydrides are reviewed, the hydrides being essentially compounds with interstitial hydrogen in the crystal lattice of the metals. The possibilities of hydrogenation of transition metals are considered along with that of compounds of rare earth elements with metals of the iron family. It is shown that the products of hydrogenation of many alloys are unstable and disintegrate forming simpler hydrides. The phase diagram of La-Ni-H system resembles the isotherm of a ternary metal system with the difference that no continuous series of solid solutions is formed. Most hydrogenation products across LaHsub(2-3)-NiH are X-ray amorphous. The nature of hydrogen in hydrides is discussed along with the possibilities of synthesis of new hydrides of transition metals

  18. Metal Hydride Compression

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Terry A. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Bowman, Robert [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Smith, Barton [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Anovitz, Lawrence [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Jensen, Craig [Hawaii Hydrogen Carriers LLC, Honolulu, HI (United States)

    2017-07-01

    Conventional hydrogen compressors often contribute over half of the cost of hydrogen stations, have poor reliability, and have insufficient flow rates for a mature FCEV market. Fatigue associated with their moving parts including cracking of diaphragms and failure of seal leads to failure in conventional compressors, which is exacerbated by the repeated starts and stops expected at fueling stations. Furthermore, the conventional lubrication of these compressors with oil is generally unacceptable at fueling stations due to potential fuel contamination. Metal hydride (MH) technology offers a very good alternative to both conventional (mechanical) and newly developed (electrochemical, ionic liquid pistons) methods of hydrogen compression. Advantages of MH compression include simplicity in design and operation, absence of moving parts, compactness, safety and reliability, and the possibility to utilize waste industrial heat to power the compressor. Beyond conventional H2 supplies of pipelines or tanker trucks, another attractive scenario is the on-site generating, pressuring and delivering pure H2 at pressure (≥ 875 bar) for refueling vehicles at electrolysis, wind, or solar generating production facilities in distributed locations that are too remote or widely distributed for cost effective bulk transport. MH hydrogen compression utilizes a reversible heat-driven interaction of a hydride-forming metal alloy with hydrogen gas to form the MH phase and is a promising process for hydrogen energy applications [1,2]. To deliver hydrogen continuously, each stage of the compressor must consist of multiple MH beds with synchronized hydrogenation & dehydrogenation cycles. Multistage pressurization allows achievement of greater compression ratios using reduced temperature swings compared to single stage compressors. The objectives of this project are to investigate and demonstrate on a laboratory scale a two-stage MH hydrogen (H2) gas compressor with a

  19. Identification and characterization of a new Zirconium hydride

    International Nuclear Information System (INIS)

    Zhao, Z.

    2007-01-01

    In order to control the integrity of the fuel clad, alloy of zirconium, it is necessary to predict the behavior of zirconium hydrides in the environment (temperature, stress...), at a microscopic scale. A characterization study by TEM of hydrides has been realized. It shows little hydrides about 500 nm, in hydride Zircaloy 4. Then a more detailed study identified a new hydride phase presented in this paper. (A.L.B.)

  20. Hydride embrittlement in zircaloy components

    Energy Technology Data Exchange (ETDEWEB)

    Lobo, Raquel M.; Andrade, Arnaldo H.P.; Castagnet, Mariano, E-mail: rmlobo@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2011-07-01

    Zirconium alloys are used in nuclear reactor cores under high-temperature water environment. During service, hydrogen is generated by corrosion processes, and it is readily absorbed by these materials. When hydrogen concentration exceeds the terminal solid solubility, the excess hydrogen precipitates as zirconium hydride (ZrH{sub 2}) platelets or needles. Zirconium alloys components can fail by hydride cracking if they contain large flaws and are highly stressed. Zirconium alloys are susceptible to a mechanism for crack initiation and propagation termed delayed hydride cracking (DHC). The presence of brittle hydrides, with a K{sub Ic} fracture toughness of only a few MPa{radical}m, results in a severe loss in ductility and toughness when platelet normal is oriented parallel to the applied stress. In plate or tubing, hydrides tend to form perpendicular to the thickness direction due to the texture developed during fabrication. Hydrides in this orientation do not generally cause structural problems because applied stresses in the through-thickness direction are very low. However, the high mobility of hydrogen in a zirconium lattice enables redistribution of hydrides normal to the applied stress direction, which can result in localized embrittlement. When a platelet reaches a critical length it ruptures. If the tensile stress is sufficiently great, crack initiation starts at some of these hydrides. Crack propagation occurs by repeating the same process at the crack tip. Delayed hydride cracking can degrade the structural integrity of zirconium alloys during reactor service. The paper focuses on the fracture mechanics and fractographic aspects of hydride material. (author)

  1. Anodematerials for Metal Hydride Batteries

    DEFF Research Database (Denmark)

    Jensen, Jens Oluf

    1997-01-01

    This report describes the work on development of hydride forming alloys for use as electrode materials in metal hydride batteries. The work has primarily been concentrated on calcium based alloys derived from the compound CaNi5. This compound has a higher capacity compared with alloys used in today......’s hydride batteries, but a much poorer stability towards repeated charge/discharge cycling. The aim was to see if the cycleability of CaNi5 could be enhanced enough by modifications to make the compound a suitable electrode material. An alloying method based on mechanical alloying in a planetary ball mill...

  2. Determination of phase boundaries and diffusion parameters in tantalum hydrides in pulsed NMR

    International Nuclear Information System (INIS)

    Hornung, P.A.

    1978-04-01

    Proton spin-lattice relaxation times T 1 were measured over a wide range of temperature (77 K to 470 K) and compositions (H/Ta = 0.155 to 0.677) in the tantalum-hydrogen system at a frequency of 40,000 MHz. In the high temperature solid solution α phase, the activation energy for hydrogen diffusion was found to be 0.140 +- 0.002 eV/atom, and the value of the jump rate (or its corresponding correlation time) was found to be essentially constant throughout the range of compositions studied. The conduction electron contribution to T 1 measured in the α phase agreed qualitatively with the trend shown by previously published susceptibility data. The single phase epsilon region and the α + epsilon two-phase region were particularly noted. It could also be concluded from the measurements that the hydrogen jump rate decreased by a factor of approximately 7.2 from the α phase to the ordered phases at low temperatures and slightly decreased further in the epsilon phase. Anomalous relaxation times were found in the low temperature range (77 K less than or equal to T less than or equal to K). In this region, T 1 remains essentially constant, and does not follow the usual temperature dependence for either motional or electronic relaxation. Two possible explanations for this behavior were considered. The first involves proton cross-relaxation to the 181 Ta nuclei which would sample the spectral density of magnetic fluctuations in the sample at several frequencies because of the probable very strong 181 Ta quadrupole interaction strength. The second explanation postulates that the hydrogen diffusional jump path involves an intermediate metastable state

  3. Superconducting phases of phosphorus hydride under pressure. Stabilization by mobile molecular hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Bi, Tiange; Miller, Daniel P.; Shamp, Andrew; Zurek, Eva [Department of Chemistry, State University of New York, Buffalo, NY (United States)

    2017-08-14

    At 80 GPa, phases with the PH{sub 2} stoichiometry, which are composed of simple cubic like phosphorus layers capped with hydrogen atoms and layers of H{sub 2} molecules, are predicted to be important species contributing to the recently observed superconductivity in compressed phosphine. The electron-phonon coupling in these phases results from the motions of the phosphorus atoms and the hydrogen atoms bound to them. The role of the mobile H{sub 2} layers is to decrease the Coulomb repulsion between the negatively charged hydrogen atoms capping the phosphorus layers. An insulating PH{sub 5} phase, the structure and bonding of which is reminiscent of diborane, is also predicted to be metastable at this pressure. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Chatterjee, Abhishek, E-mail: cabhishek@rrcat.gov.in; Khamari, Shailesh K.; Kumar, R.; Dixit, V. K.; Oak, S. M.; Sharma, T. K., E-mail: tarun@rrcat.gov.in [Semiconductor Physics and Devices Laboratory, Raja Ramanna Centre for Advanced Technology, Indore 452013 (India)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  7. New ternary hydride formation in U-Ti-H system

    International Nuclear Information System (INIS)

    Yamamoto, Takuya; Kayano, Hideo; Yamawaki, Michio.

    1991-01-01

    Hydrogen absorption properties of two titanium-rich uranium alloys, UTi 2 and UTi 4 , were studied in order to prepare and identify the recently found ternary hydride. They slowly reacted with hydrogen of the initial pressure of 10 5 Pa at 873K to form the ternary hydride. The hydrogenated specimen mainly consisted of the pursued ternary hydride but contained also U(or UO 2 ), TiH x , and some transient phases. X-ray powder diffraction and Electron Probe Micro Analysis proved that it was the UTi 2 H x with the expected MgCu 2 structure, though all the X-ray peaks were broad probably because of inhomogeneity. This compound had extremely high resistance to powdering on its formation, which showed high potential utilities for a non-powdering tritium storage system or for other purposes. (author)

  8. Developments in delayed hydride cracking in zirconium alloys

    International Nuclear Information System (INIS)

    Puls, Manfred P.

    2008-01-01

    Delayed hydride cracking (DHC) is a process of diffusion assisted localized hydride embrittlement at flaws or regions of high stress. Models of DHC propagation and initiation have been developed that capture the essential elements of this phenomenon in terms of parameters describing processes occurring at the micro-scale. The models and their predictions of experimental results applied to Zr alloys are assessed. The propagation model allows rationalization of the effect of direction of approach to temperature and of the effect of the state and morphology of the beta phase in Zr-2.5Nb on DHC velocity. The K I dependence of the DHC velocity can only be approximately rationalized by the propagation models. This is thought to be because these models approximate the DHC velocity by a constant and shape-invariant rate of growth of the hydride at the flaw and have not incorporated a coupling between the applied stress field due to the flaw alone and the precipitated hydrides that would result in a variation of the shape and density of the hydrided region with K I . Separately, models have been developed for DHC initiation at cracks and blunt flaws. Expressions are obtained for the threshold stress intensity factor, K IH , for DHC initiation at a crack. A model for K IH has been used to rationalize the experimental result that DHC initiation is not possible above a certain temperature, even when hydrides can form at the crack tip. For blunt flaws with root radii in the μm range, and engineering process zone procedure has been derived to determine the initiation conditions requiring that both a critical stress and a critical flaw tip displacement must be achieved for hydride fracture. The engineering process zone procedure takes account of the dependence of DHC initiation on the flaw's root radius. Although all of the foregoing models are capable of describing the essential features of DHC, they are highly idealized and in need of further refinement. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

    Schulte, K. L.; Kuech, T. F. [Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

    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

  10. Influence of temperature on δ-hydride habit plane in α-Zirconium

    International Nuclear Information System (INIS)

    Singh, R. N.; Stahle, P.; Banerjee, S.; Ristmanaa, Matti; Sauramd, K.

    2008-01-01

    Dilute Zr-alloy with hcp α-Zr as major phase is used as pressure boundary for hot coolant in CANDU, PHWR and RBMK reactors. Hydrogen / deuterium ingress during service makes the pressure boundary components like pressure tubes of the aforementioned reactors susceptible to hydride embrittlement. Hydride acquires plate shaped morphology and the broad face of the hydride plate coincides with certain crystallographic plane of α-Zr crystal, which is called habit plane. Hydride plate oriented normal to tensile stress significantly increases the degree of embrittlement. Thus key to mitigating the damage due to hydride embrittlement is to avoid the formation of hydride plates normal to tensile stress. Two different theoretical approaches are used to determine the habit plane of precipitates viz., geometrical and solid mechanics. For the geometrical approach invariant plane and invariant-line criteria have been applied successfully and for the solid mechanics approach strain energy minimization criteria have been used successfully. Solid mechanics approach using strain energy computed by FEM technique has been applied to hydride precipitation in Zr-alloys, but the emphasis has been to understand the solvus hysteresis. The objective of the present investigation is to predict the habit plane of δ-hydride precipitating in α-Zr at 25, 300, 400 and 450 .deg. C. using strain energy minimization technique. The δ-hydride phase is modeled to undergo isotropic elastic and plastic deformation. The α-Zr phase was modeled to undergo transverse isotropic elastic deformation. Both isotropic plastic and transverse isotropic plastic deformations of α-Zr were considered. Further, both perfect and linear work-hardening plastic behaviors were considered. Accommodation strain energy of δ-hydrides forming in α-Zr crystal was computed using initial strain method as a function of hydride nuclei orientation. Hydride was modeled as disk with circular edge. The simulation was carried out

  11. Determination of As(III) and total inorganic As in water samples using an on-line solid phase extraction and flow injection hydride generation atomic absorption spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Sigrist, Mirna, E-mail: msigrist@fiq.unl.edu.ar [Laboratorio Central, Facultad de Ingenieria Quimica, Universidad Nacional del Litoral, Santiago del Estero 2654-Piso 6, (3000) Santa Fe (Argentina); Albertengo, Antonela; Beldomenico, Horacio [Laboratorio Central, Facultad de Ingenieria Quimica, Universidad Nacional del Litoral, Santiago del Estero 2654-Piso 6, (3000) Santa Fe (Argentina); Tudino, Mabel [Laboratorio de Analisis de Trazas, Departamento de Quimica Inorganica, Analitica y Quimica Fisica/INQUIMAE, Facultad de Ciencias Exactas y Naturales, Pabellon II, Ciudad Universitaria (1428), Buenos Aires (Argentina)

    2011-04-15

    A simple and robust on-line sequential injection system based on solid phase extraction (SPE) coupled to a flow injection hydride generation atomic absorption spectrometer (FI-HGAAS) with a heated quartz tube atomizer (QTA) was developed and optimized for the determination of As(III) in groundwater without any kind of sample pretreatment. The method was based on the selective retention of inorganic As(V) that was carried out by passing the filtered original sample through a cartridge containing a chloride-form strong anion exchanger. Thus the most toxic form, inorganic As(III), was determined fast and directly by AsH{sub 3} generation using 3.5 mol L{sup -1} HCl as carrier solution and 0.35% (m/v) NaBH{sub 4} in 0.025% NaOH as the reductant. Since the uptake of As(V) should be interfered by several anions of natural occurrence in waters, the effect of Cl{sup -}, SO{sub 4}{sup 2-}, NO{sub 3}{sup -}, HPO{sub 4}{sup 2-}, HCO{sub 3}{sup -} on retention was evaluated and discussed. The total soluble inorganic arsenic concentration was determined on aliquots of filtered samples acidified with concentrated HCl and pre-reduced with 5% KI-5% C{sub 6}H{sub 8}O{sub 6} solution. The concentration of As(V) was calculated by difference between the total soluble inorganic arsenic and As(III) concentrations. Detection limits (LODs) of 0.5 {mu}g L{sup -1} and 0.6 {mu}g L{sup -1} for As(III) and inorganic total As, respectively, were obtained for a 500 {mu}L sample volume. The obtained limits of detection allowed testing the water quality according to the national and international regulations. The analytical recovery for water samples spiked with As(III) ranged between 98% and 106%. The sampling throughput for As(III) determination was 60 samples h{sup -1}. The device for groundwater sampling was especially designed for the authors. Metallic components were avoided and the contact between the sample and the atmospheric oxygen was carried to a minimum. On-field arsenic species

  12. Determination of As(III) and total inorganic As in water samples using an on-line solid phase extraction and flow injection hydride generation atomic absorption spectrometry

    International Nuclear Information System (INIS)

    Sigrist, Mirna; Albertengo, Antonela; Beldomenico, Horacio; Tudino, Mabel

    2011-01-01

    A simple and robust on-line sequential injection system based on solid phase extraction (SPE) coupled to a flow injection hydride generation atomic absorption spectrometer (FI-HGAAS) with a heated quartz tube atomizer (QTA) was developed and optimized for the determination of As(III) in groundwater without any kind of sample pretreatment. The method was based on the selective retention of inorganic As(V) that was carried out by passing the filtered original sample through a cartridge containing a chloride-form strong anion exchanger. Thus the most toxic form, inorganic As(III), was determined fast and directly by AsH 3 generation using 3.5 mol L -1 HCl as carrier solution and 0.35% (m/v) NaBH 4 in 0.025% NaOH as the reductant. Since the uptake of As(V) should be interfered by several anions of natural occurrence in waters, the effect of Cl - , SO 4 2- , NO 3 - , HPO 4 2- , HCO 3 - on retention was evaluated and discussed. The total soluble inorganic arsenic concentration was determined on aliquots of filtered samples acidified with concentrated HCl and pre-reduced with 5% KI-5% C 6 H 8 O 6 solution. The concentration of As(V) was calculated by difference between the total soluble inorganic arsenic and As(III) concentrations. Detection limits (LODs) of 0.5 μg L -1 and 0.6 μg L -1 for As(III) and inorganic total As, respectively, were obtained for a 500 μL sample volume. The obtained limits of detection allowed testing the water quality according to the national and international regulations. The analytical recovery for water samples spiked with As(III) ranged between 98% and 106%. The sampling throughput for As(III) determination was 60 samples h -1 . The device for groundwater sampling was especially designed for the authors. Metallic components were avoided and the contact between the sample and the atmospheric oxygen was carried to a minimum. On-field arsenic species separation was performed through the employ of a serial connection of membrane filters and

  13. Comminution by hydriding-dehydriding process of the U-Zr-Nb alloys stabilized at different phases by aging heat treatment

    Energy Technology Data Exchange (ETDEWEB)

    Cantagalli, Natalia Mattar; Pais, Rafael Witter Dias; Braga, Daniel Martins; Santos, Ana Maria Matildes dos; Ferraz, Wilmar Barbosa, E-mail: ferrazw@cdtn.b [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG) Belo Horizonte, MG (Brazil)

    2011-07-01

    Powders of the U-Zr-Nb alloys are raw materials for obtaining plate-type dispersion fuel of high density and medium enrichment for research and test reactors as well as small power reactors. U-2.5Zr-7.5Nb and U-3Zr-9Nb (wt%) alloys, initially homogenized at high temperatures, were transformed at different phases by means aging heat treatments, and then comminuted by hydriding-dehydriding process to powder production. The phases transformations were obtained by the homogenization of the U-2.5Zr-7.5Nb and U-3Zr-9Nb alloys at high temperatures (1000 deg C for 1 and 16 h), followed by aging heat treatment at 600 deg C, in times of 0.5 h, 3.0 h and 24h, and subsequently quenched in water to stabilize the desired phase. The comminution process was performed at 200 deg C for different times ranging from 20 minutes to 4 hours. The powders were then characterized by scanning electron microscopy, X-ray diffraction and determination of particle size distribution by means of laser equipment CILAS. One of the main objectives of this study was to verify the influence of the different phases in the characteristics of the obtained powders. It was found that alloys stabilized in gamma phase produced powders with smaller particles sizes than those with cellular structure of the {alpha} and {gamma} phases. Regardless of retained phases, the produced powders consist of agglomerates with irregular morphology. (author)

  14. Comminution by hydriding-dehydriding process of the U-Zr-Nb alloys stabilized at different phases by aging heat treatment

    International Nuclear Information System (INIS)

    Cantagalli, Natalia Mattar; Pais, Rafael Witter Dias; Braga, Daniel Martins; Santos, Ana Maria Matildes dos; Ferraz, Wilmar Barbosa

    2011-01-01

    Powders of the U-Zr-Nb alloys are raw materials for obtaining plate-type dispersion fuel of high density and medium enrichment for research and test reactors as well as small power reactors. U-2.5Zr-7.5Nb and U-3Zr-9Nb (wt%) alloys, initially homogenized at high temperatures, were transformed at different phases by means aging heat treatments, and then comminuted by hydriding-dehydriding process to powder production. The phases transformations were obtained by the homogenization of the U-2.5Zr-7.5Nb and U-3Zr-9Nb alloys at high temperatures (1000 deg C for 1 and 16 h), followed by aging heat treatment at 600 deg C, in times of 0.5 h, 3.0 h and 24h, and subsequently quenched in water to stabilize the desired phase. The comminution process was performed at 200 deg C for different times ranging from 20 minutes to 4 hours. The powders were then characterized by scanning electron microscopy, X-ray diffraction and determination of particle size distribution by means of laser equipment CILAS. One of the main objectives of this study was to verify the influence of the different phases in the characteristics of the obtained powders. It was found that alloys stabilized in gamma phase produced powders with smaller particles sizes than those with cellular structure of the α and γ phases. Regardless of retained phases, the produced powders consist of agglomerates with irregular morphology. (author)

  15. Development of titanium based biocomposite by powder metallurgy processing with in situ forming of Ca-P phases

    Energy Technology Data Exchange (ETDEWEB)

    Karanjai, Malobika [International Advanced Research Centre for Powder Metallurgy and New Materials, Balapur P.O., Hyderabad 500005, Andhra Pradesh (India)]. E-mail: malobika@arci.res.in; Sundaresan, Ranganathan [International Advanced Research Centre for Powder Metallurgy and New Materials, Balapur P.O., Hyderabad 500005, Andhra Pradesh (India); Rao, Gummididala Venkata Narasimha [International Advanced Research Centre for Powder Metallurgy and New Materials, Balapur P.O., Hyderabad 500005, Andhra Pradesh (India); Mohan, Tallapragada Raja Rama [Metallurgical Engineering and Materials Science Department, Indian Institute of Technology, Powai, Mumbai 400076, Maharashtra (India); Kashyap, Bhagwati Prasad [Metallurgical Engineering and Materials Science Department, Indian Institute of Technology, Powai, Mumbai 400076, Maharashtra (India)

    2007-02-25

    Composites of titanium and calcium-phosphorus phases were developed by powder metallurgy processing and evaluated for bioactivity. Titanium hydride powder and precursors of calcium and phosphorus in the form of calcium carbonate and di-ammonium hydrogen orthophosphate were mixed in different proportions, compacted and calcined in different atmospheres. The calcined compacts were subsequently crushed, recompacted and sintered in vacuum. In situ formation of bioactive phases like hydroxylapatite, tricalcium phosphate and calcium titanate during the calcination and sintering steps was studied using X-ray diffraction. The effect of calcination atmosphere on density, interconnected porosity, phase composition and modulus of rupture of sintered composites was examined. The sintered composites were immersed in simulated body fluid for 7 days to observe their in vitro behaviour with XRD and FTIR spectroscopic identification of deposits. Composites with 10 wt% precursors sintered from vacuum calcined powder gave the best results in terms of bioactive phases, density and strength.

  16. Influence of Zircaloy cladding composition on hydride formation during aqueous hydrogen charging

    Energy Technology Data Exchange (ETDEWEB)

    Rajasekhara, S. [Intel Corporation, 2501 NW 229th Av., Hillsboro, OR 97124 (United States); Kotula, P.G.; Enos, D.G.; Doyle, B.L. [Sandia National Laboratories, Albuquerque, NM, 87185 (United States); Clark, B.G., E-mail: blyclar@sandia.gov [Sandia National Laboratories, Albuquerque, NM, 87185 (United States)

    2017-06-15

    Although hydrogen uptake in Zirconium (Zr) based claddings has been a topic of many studies, hydrogen uptake as a function of alloy composition has received little attention. In this work, commercial Zr-based cladding alloys (Zircaloy-2, Zircaloy-4 and ZIRLO™), differing in composition but with similar initial textures, grain sizes, and surface roughness, were aqueously charged with hydrogen for 100, 300, and 1000 s at nominally 90 °C to produce hydride layers of varying thicknesses. Transmission electron microscope characterization following aqueous charging showed hydride phase and orientation relationship were identical in all three alloys. However, elastic recoil detection measurements confirmed that surface hydride layers in Zircaloy-2 and Zircaloy-4 were an order of magnitude thicker relative to ZIRLO™. - Highlights: •Aqueous charging was performed to produce a layer of zirconium hydride for three different Zr-alloy claddings. •Hydride thicknesses were analyzed by elastic recoil detection and transmission electron microscopy. •Zircaloy-2 and Zircaloy-4 formed thicker hydride layers than ZIRLO™ for the same charging durations.

  17. The effect of thermal cycling on the movement of the αZr/ αZr hydride phase boundary in cold-worked Zr-2.5 wt% Nb alloy

    International Nuclear Information System (INIS)

    Cox, B.; Ling, V.C.

    1980-05-01

    A piece of CW Zr-2.5 wt% Nb alloy pressure tube was hydrided at one end in 40 g/L LiOH solution at 573 K (after nickel-plating that end). The result was a solid hydride layer 0.6 mm thick plus approximately 130 ppm hydrogen in the core under the nickel plate. Thermal cycling under conditions similar to those likely to be experienced during a reactor trip did not cause any significant movement of the α+hydridephase boundary along the tube for up to 2688 cycles from 573 to 523 K. Supercharging of the core was observed in the nickel-plated area. Some conclusions have been drawn concerning the origin of the hydrogen in the nickel-plated area, and the factors controlling the supercharging process. (auth)

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

    Energy Technology Data Exchange (ETDEWEB)

    Asiabi, Hamid [Department of Chemistry, Tarbiat Modares University, P.O. Box 14115-175, Tehran (Iran, Islamic Republic of); Yamini, Yadollah, E-mail: yyamini@modares.ac.ir [Department of Chemistry, Tarbiat Modares University, P.O. Box 14115-175, Tehran (Iran, Islamic Republic of); Seidi, Shahram [Department of Analytical Chemistry, Faculty of Chemistry, K.N. Toosi University of Technology, Tehran (Iran, Islamic Republic of); Shamsayei, Maryam; Safari, Meysam; Rezaei, Fatemeh [Department of Chemistry, Tarbiat Modares University, P.O. Box 14115-175, Tehran (Iran, Islamic Republic of)

    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{sup −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. - Graphical abstract: An electrochemically controlled in-tube solid phase microextraction followed by hydride generation atomic absorption spectrometry was developed for extraction and determination ultra-trace amounts of Se in aqueous solutions. - Highlights: • A nanostructured composite coating consisting of PPy doped with EGDMA was prepared. • The coating was

  19. Elimination of macrostep-induced current flow nonuniformity in vertical GaN PN diode using carbon-free drift layer grown by hydride vapor phase epitaxy

    Science.gov (United States)

    Fujikura, Hajime; Hayashi, Kentaro; Horikiri, Fumimasa; Narita, Yoshinobu; Konno, Taichiro; Yoshida, Takehiro; Ohta, Hiroshi; Mishima, Tomoyoshi

    2018-04-01

    In vertical GaN PN diodes (PNDs) grown entirely by metal–organic chemical vapor deposition (MOCVD), large current nonuniformity was observed. This nonuniformity was induced by macrosteps on the GaN surface through modulation of carbon incorporation into the n-GaN crystal. It was eliminated in a hybrid PND consisting of a carbon-free n-GaN layer grown by hydride vapor phase epitaxy (HVPE) and an MOCVD-regrown p-GaN layer. The hybrid PND showed a fairly low on-resistance (2 mΩ cm2) and high breakdown voltage (2 kV) even without a field plate electrode. These results clearly indicated the strong advantages of the HVPE-grown drift layer for improving power device performance, uniformity, and yield.

  20. Small Form Factor RFID Applicator, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed development of a small form factor Astrobee dedicated RFID label applicator will allow current and future free flying vehicles to place RFID labels...

  1. Detection of Life Forms, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Gaia Genomics proposes to develop an instrument for the detection of earthborn and/or planetary life forms that are based on a nucleic acid paradigm. Highly...

  2. Syntheses and properties of several metastable and stable hydrides derived from intermetallic compounds under high hydrogen pressure

    Energy Technology Data Exchange (ETDEWEB)

    Filipek, S.M., E-mail: sfilipek@unipress.waw.pl [Institute of High Pressure Physics PAS, ul. Sokolowska 29, 01-142 Warsaw (Poland); Paul-Boncour, V. [ICMPE-CMTR, CNRS-UPEC, 2-8 rue Henri Dunant, 94320 Thiais (France); Liu, R.S. [Department of Chemistry, National Taiwan University, Taipei 106, Taiwan (China); Jacob, I. [Unit Nuclear Eng., Ben Gurion University of the Negev, Beer-Sheva (Israel); Tsutaoka, T. [Dept. of Sci. Educ., Grad. School of Educ., Hiroshima University, Hiroshima (Japan); Budziak, A. [Institute of Nuclear Physics PAS, 31-342 Kraków (Poland); Morawski, A. [Institute of High Pressure Physics PAS, ul. Sokolowska 29, 01-142 Warsaw (Poland); Sugiura, H. [Yokohama City University, 22-2 Seto, Kanazawa-ku, Yokohama 236-0027 (Japan); Zachariasz, P. [Institute of Electron Technology Cracow Division, ul. Zablocie 39, 30-701 Krakow (Poland); Dybko, K. [Institute of Physics, PAS, 02-668 Warsaw (Poland); Diduszko, R. [Tele and Radio Research Institute, ul. Ratuszowa 11, Warsaw (Poland)

    2016-12-01

    Brief summary of our former work on high hydrogen pressure syntheses of novel hydrides and studies of their properties is supplemented with new results. Syntheses and properties of a number of hydrides (unstable, metastable or stable in ambient conditions) derived under high hydrogen pressure from intermetallic compounds, like MeT{sub 2}, MeNi{sub 5}, Me{sub 7}T{sub 3}, Y{sub 6}Mn{sub 23} and YMn{sub 12} (where Me = zirconium, yttrium or rare earth; T = transition metal) are presented. Stabilization of ZrFe{sub 2}H{sub 4} due to surface phenomena was revealed. Unusual role of manganese in hydride forming processes is pointed out. Hydrogen induced phase transitions, suppression of magnetism, antiferromagnetic-ferromagnetic and metal-insulator or semimetal-metal transitions are described. Equations of state (EOS) of hydrides submitted to hydrostatic pressures up to 30 GPa are presented and discussed.

  3. Hydride formation on deformation twin in zirconium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ju-Seong [Korea Atomic Energy Research Institute, 989-111 Daedeokdaero, Yuseong-gu, Daejeon, 305-353 (Korea, Republic of); Kim, Sung-Dae [Korea Institute of Material Science (KIMS), 797 Changwondaero, Changwon, Gyeongnam, 642-831 (Korea, Republic of); Yoon, Jonghun, E-mail: yooncsmd@gmail.com [Department of Mechanical Engineering, Hanyang University, 1271 Sa3-dong, Sangrok-gu, Ansan-si, Gyeonggi-do, 426-791 (Korea, Republic of)

    2016-12-15

    Hydrides deteriorate the mechanical properties of zirconium (Zr) alloys used in nuclear reactors. Intergranular hydrides that form along grain boundaries have been extensively studied due to their detrimental effects on cracking. However, it has been little concerns on formation of Zr hydrides correlated with deformation twins which is distinctive heterogeneous nucleation site in hexagonal close-packed metals. In this paper, the heterogeneous precipitation of Zr hydrides at the twin boundaries was visualized using transmission electron microscopy. It demonstrates that intragranular hydrides in the twinned region precipitates on the rotated habit plane by the twinning and intergranular hydrides precipitate along the coherent low energy twin boundaries independent of the conventional habit planes. Interestingly, dislocations around the twin boundaries play a substantial role in the nucleation of Zr hydrides by reducing the misfit strain energy.

  4. Trapping of hydride forming elements within miniature electrothermal devices. Part 2. Investigation of collection of arsenic and selenium hydrides on a surface and in a cavity of a graphite rod

    International Nuclear Information System (INIS)

    Docekal, Bohumil

    2004-01-01

    The interaction of arsenic and selenium hydrides with bare and modified graphite was investigated by atomic absorption spectrometry and by radiotracer technique using 75 Se radionuclide in a laboratory made brass cylindrical chamber equipped with a vertical quartz tube torch for supporting miniature hydrogen diffusion flame atomizer. Strong interaction was observed at elevated temperatures above 800 deg. C. In contrast to the very often-reported data for conventional graphite tube atomizers, this high temperature interaction was also accompanied by a pronounced trapping of analytes at elevated temperatures close to 1100-1200 deg. C when modified graphite was used. Comparing modifiers tested (Ir, Pt and Rh), iridium appeared the only useful permanent modifier. Among various graphite-rod traps designed, the most efficient trapping of analytes was achieved in a graphite cavity. The net selenium trapping efficiencies of approximately 53% and 70% were found by radiotracer technique for the iridium-treated graphite surface and the iridium-treated graphite cavity, respectively. In contrast to the molybdenum surface, bare graphite did not exhibit any significant trapping effect. Trapping isotherms obtained at different temperatures displayed non-linear course in the range up to the upper limit of the analytical relevance of 100 ng of an analyte, indicating a limited trapping capacity of the modified graphite surface and the same trapping mechanism at low and elevated temperatures applied (300-1300 deg. C). Radiography experiments with 75 Se radiotracer showed that a major part of selenium was collected within the small cavity of the graphite rod and that selenium was also deposited after the trapping and vaporization steps in the trap chamber and on the quartz tube wall of the burner. Complementary experiments performed with the conventional transversally heated graphite tube and with bare and thermally shielded injection capillaries for hydride introduction, showed that

  5. Effects of δ-hydride precipitation at a crack tip on crack propagation in delayed hydride cracking of Zircaloy-2

    Energy Technology Data Exchange (ETDEWEB)

    Kubo, T., E-mail: kubo@nfd.co.jp [Nippon Nuclear Fuel Development Co., Ltd., 2163 Narita-cho, Oarai-machi, Ibaraki 311-1313 (Japan); Kobayashi, Y. [M.O.X. Co., Ltd., 1828-520 Hirasu-cho, Mito, Ibaraki 311-0853 (Japan)

    2013-08-15

    Highlights: • Steady state crack velocity of delayed hydride cracking in Zircaloy-2 was analyzed. • A large stress peak is induced at an end of hydride by volume expansion of hydride. • Hydrogen diffuses to the stress peak, thereby accelerating steady hydride growth. • Crack velocity was estimated from the calculated hydrogen flux into the stress peak. • There was good agreement between calculation results and experimental data. -- Abstract: Delayed hydride cracking (DHC) of Zircaloy-2 is one possible mechanism for the failure of boiling water reactor fuel rods in ramp tests at high burnup. Analyses were made for hydrogen diffusion around a crack tip to estimate the crack velocity of DHC in zirconium alloys, placing importance on effects of precipitation of δ-hydride. The stress distribution around the crack tip is significantly altered by precipitation of hydride, which was strictly analyzed using a finite element computer code. Then, stress-driven hydrogen diffusion under the altered stress distribution was analyzed by a differential method. Overlapping of external stress and hydride precipitation at a crack tip induces two stress peaks; one at a crack tip and the other at the front end of the hydride precipitate. Since the latter is larger than the former, more hydrogen diffuses to the front end of the hydride precipitate, thereby accelerating hydride growth compared with that in the absence of the hydride. These results indicated that, after hydride was formed in front of the crack tip, it grew almost steadily accompanying the interaction of hydrogen diffusion, hydride growth and the stress alteration by hydride precipitation. Finally, crack velocity was estimated from the calculated hydrogen flux into the crack tip as a function of temperature, stress intensity factor and material strength. There was qualitatively good agreement between calculation results and experimental data.

  6. Dependency of Delayed Hydride Crack Velocity on the Direction of an Approach to Test Temperatures in Zirconium Alloys

    International Nuclear Information System (INIS)

    Kim, Young Suk; Kim, Kang Soo; Im, Kyung Soo; Ahn, Sang Bok; Cheong, Yong Moo

    2005-01-01

    Recently, Kim proposed a new DHC model where a driving force for the DHC is a supersaturated hydrogen concentration as a result of a hysteresis of the terminal solid solubility (TSS) of hydrogen in zirconium alloys upon a heating and a cooling. This model was demonstrated to be valid through a model experiment where the prior plastic deformation facilitated nucleation of the reoriented hydrides, thus reducing the supersaturated hydrogen concentration at the plastic zone ahead of the crack tip and causing hydrogen to move to the crack tip from the bulk region. Thus, an approach to the test temperature by a cooling is required to create a supersaturation of hydrogen, which is a driving force for the DHC of zirconium alloys. However, despite the absence of the supersaturation of hydrogen due to an approach to the test temperature by a heating, DHC is observed to occur in zirconium alloys at the test temperatures below 180 .deg. C. As to this DHC phenomenon, Kim proposed that stress-induced transformation from γ-hydrides to δ-hydrides is likely to be a cause of this, based on Root's observation that the γ-hydride is a stable phase at temperatures lower than 180 .deg. C. In other words, the hydrides formed at the crack tip would be δ-hydrides due to the stressinduced transformation while the bulk region still maintains the initial hydride phase or γ-hydrides. It should be noted that Ambler has also assumed the crack tip hydrides to be δ-hydrides. When the δ-hydrides or ZrH1.66 are precipitated at the crack tip due to the transformation of the γ-hydrides or ZrH, the crack tip will have a decreased concentration of dissolved hydrogen in zirconium, considering the atomic ratio of hydrogen and zirconium in the γ- and δ-hydrides. In contrast, due to no stress-induced transformation of hydrides, the bulk region maintains the initial concentration of dissolved hydrogen. Hence, there develops a difference in the hydrogen concentration or .C between the bulk and the

  7. Dependency of Delayed Hydride Crack Velocity on the Direction of an Approach to Test Temperatures in Zirconium Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Young Suk; Kim, Kang Soo; Im, Kyung Soo; Ahn, Sang Bok; Cheong, Yong Moo [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    2005-07-01

    Recently, Kim proposed a new DHC model where a driving force for the DHC is a supersaturated hydrogen concentration as a result of a hysteresis of the terminal solid solubility (TSS) of hydrogen in zirconium alloys upon a heating and a cooling. This model was demonstrated to be valid through a model experiment where the prior plastic deformation facilitated nucleation of the reoriented hydrides, thus reducing the supersaturated hydrogen concentration at the plastic zone ahead of the crack tip and causing hydrogen to move to the crack tip from the bulk region. Thus, an approach to the test temperature by a cooling is required to create a supersaturation of hydrogen, which is a driving force for the DHC of zirconium alloys. However, despite the absence of the supersaturation of hydrogen due to an approach to the test temperature by a heating, DHC is observed to occur in zirconium alloys at the test temperatures below 180 .deg. C. As to this DHC phenomenon, Kim proposed that stress-induced transformation from {gamma}-hydrides to {delta}-hydrides is likely to be a cause of this, based on Root's observation that the {gamma}-hydride is a stable phase at temperatures lower than 180 .deg. C. In other words, the hydrides formed at the crack tip would be {delta}-hydrides due to the stressinduced transformation while the bulk region still maintains the initial hydride phase or {gamma}-hydrides. It should be noted that Ambler has also assumed the crack tip hydrides to be {delta}-hydrides. When the {delta}-hydrides or ZrH1.66 are precipitated at the crack tip due to the transformation of the {gamma}-hydrides or ZrH, the crack tip will have a decreased concentration of dissolved hydrogen in zirconium, considering the atomic ratio of hydrogen and zirconium in the {gamma}- and {delta}-hydrides. In contrast, due to no stress-induced transformation of hydrides, the bulk region maintains the initial concentration of dissolved hydrogen. Hence, there develops a difference in the

  8. Modifications of the hydriding kinetics of a metallic surface, using ion implantation

    International Nuclear Information System (INIS)

    Crusset, D.

    1992-10-01

    Uranium reacts with hydrogen to form an hydride: this reaction leads to the total destruction of the material. To modify the reactivity of an uranium surface towards hydrogen, ion implantation was selected, among surface treatments techniques. Four elements (carbon, nitrogen, oxygen, sulfur) were implanted to different doses. The results show a modification of the hydriding mechanism and a significant increase in the reaction induction times, notably at high implantation doses. Several techniques (SIMS, X-rays phases analysis and residual stresses determination) were used to characterize the samples and understand the different mechanisms involved

  9. δ-hydride habit plane determination in α-zirconium by strain energy minimization technique at 25 and 300 deg C

    International Nuclear Information System (INIS)

    Singh, R.N.; Stahle, P.; Sairam, K.; Ristmana, Matti; Banerjee, S.

    2008-01-01

    The objective of the present investigation is to predict the habit plane of δ-hydride precipitating in α-Zr at 25 and 300 deg C using strain energy minimization technique. The δ-hydride phase is modeled to undergo isotropic elastic and plastic deformation. The α-Zr phase was modeled to undergo transverse isotropic elastic deformation. Both isotropic plastic and transverse isotropic plastic deformations of α-Zr were considered. Further, both perfect and linear work-hardening plastic behaviors of zirconium and its hydride were considered. Accommodation strain energy of δ-hydrides forming in α-Zr crystal was computed using initial strain method as a function of hydride nuclei orientation. Hydride was modeled as disk with circular edge. The simulation was carried out using materials properties reported at 25 and 300 deg C. Contrary to several habit planes reported in literature for δ-hydrides precipitating in α-Zr crystal the total accommodation energy minima suggests only basal plane i.e. (0001) as the habit plane. (author)

  10. Complex hydrides for hydrogen storage

    Science.gov (United States)

    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.

  11. Activation and discharge kinetics of metal hydride electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Johnsen, Stein Egil

    2003-07-01

    Potential step chronoamperometry and Electrochemical Impedance Spectroscopy (eis) measurements were performed on single metal hydride particles. For the {alpha}-phase, the bulk diffusion coefficient and the absorption/adsorption rate parameters were determined. Materials produced by atomisation, melt spinning and conventional casting were investigated. The melt spun and conventional cast materials were identical and the atomised material similar in composition. The particles from the cast and the melt spun material were shaped like parallelepipeds. A corresponding equation, for this geometry, for diffusion coupled to an absorption/adsorption reaction was developed. It was found that materials produced by melt spinning exhibited lower bulk diffusion (1.7E-14 m2/s) and absorption/adsorption reaction rate (1.0E-8 m/s), compared to materials produced by conventionally casting (1.1E-13 m2/s and 5.5E-8 m/s respectively). In addition, the influence of particle active surface and relative diffusion length were discussed. It was concluded that there are uncertainties connected to these properties, which may explain the large distribution in the kinetic parameters measured on metal hydride particles. Activation of metal hydride forming materials has been studied and an activation procedure, for porous electrodes, was investigated. Cathodic polarisation of the electrode during a hot alkaline surface treatment gave the maximum discharge capacity on the first discharge of the electrode. The studied materials were produced by gas atomisation and the spherical shape was retained during the activation. Both an AB{sub 5} and an AB{sub 2} alloy was successfully activated and discharge rate properties determined. The AB{sub 2} material showed a higher maximum discharge capacity, but poor rate properties, compared to the AB{sub 5} material. Reduction of surface oxides, and at the same time protection against corrosion of active metallic nickel, can explain the satisfying results of

  12. Preparation of beryllium hydride

    International Nuclear Information System (INIS)

    Roberts, C.B.

    1975-01-01

    A process is described for preparing beryllium hydride by the direct reaction of beryllium borohydride and aluminum hydride trimethylamine adduct. Volatile by-products and unreacted reactants are readily removed from the product mass by sublimation and/or evaporation. (U.S.)

  13. Hydride vapor phase epitaxy of high structural perfection thick AlN layers on off-axis 6H-SiC

    Science.gov (United States)

    Volkova, Anna; Ivantsov, Vladimir; Leung, Larry

    2011-01-01

    The employment of more than 10 μm thick AlN epilayers on SiC substrates for AlGaN/GaN high-electron-mobility transistors (HEMTs) substantially raises their performance in high-power energy-efficient amplifiers for 4G wireless mobile stations. In this paper, structural properties and surface morphology of thick AlN epilayers deposited by hydride vapor phase epitaxy (HVPE) on off-axis conductive 6H-SiC substrates are reported. The epilayers were examined in detail by high-resolution X-ray diffraction (XRD), atomic force microscopy (AFM), Nomarski differential interference contrast (DIC), scanning electron microscopy (SEM), and selective wet chemical etching. At optimal substrate preparation and growth conditions, a full width at half-maximum (FWHM) of the XRD rocking curve (RC) for the symmetric (00.2) reflex was very close to that of the substrate (less than 40 arcsec) suggesting low screw dislocation density in the epilayer (˜10 6 cm -2) and small in-plane tilt misorientation. Reciprocal space mapping around asymmetric reflexes and measured lattice parameters indicated a fully relaxed state of the epilayers. The unit-cell-high stepped areas of the epilayers with 0.5 nm root mean square (RMS) roughness over 1×1 μm 2 scan were alternated with step-bunching instabilities up to 350 nm in height. Low warp of the substrates makes them suitable for precise epitaxy of HEMT structures.

  14. Addition of Sb as a surfactant for the growth of nonpolar a-plane GaN by using mixed-source hydride vapor phase epitaxy

    International Nuclear Information System (INIS)

    Ok, Jin Eun; Jo, Dong Wan; Yun, Wy Il; Han, Young Hun; Jeon, Hun Soo; Lee, Gang Suok; Jung, Se Gyo; Bae, Seon Min; Ahn, Hyung Soo; Yang, Min

    2011-01-01

    The influence of Sb as a surfactant on the morphology and on the structural and the optical characteristics of a-plane GaN grown on r-plane sapphire by using mixed-source hydride vapor phase epitaxy was investigated. The a-plane GaN:Sb layers were grown at various temperatures ranging from 1000 .deg. C to 1100 .deg. C, and the reactor pressure was maintained at 1 atm. The atomic force microscope (AFM), scanning electron microscope (SEM), X-ray diffraction (XRD) and photoluminescence(PL) results indicated that the surface morphologies and the structural and the optical characteristics of a-plane GaN were markedly improved, compared to the a-plane GaN layers grown without Sb, by using Sb as a surfactant. The addition of Sb was found to alter epitaxial lateral overgrowth (ELO) facet formation. The Sb was not detected from the a-plane-GaN epilayers within the detection limit of the energy dispersive spectroscopy (EDS) and x-ray photoelectron spectroscopy (XPS) measurements, suggesting that Sb act as a surfactant during the growth of a-plane GaN by using mixed-source HVPE method.

  15. Predicting formation enthalpies of metal hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Andreasen, A.

    2004-12-01

    In order for the hydrogen based society viz. a society in which hydrogen is the primary energy carrier to become realizable an efficient way of storing hydrogen is required. For this purpose metal hydrides are serious candidates. Metal hydrides are formed by chemical reaction between hydrogen and metal and for the stable hydrides this is associated with release of heat ({delta}H{sub f} ). The more thermodynamically stable the hydride, the larger {delta}H{sub f}, and the higher temperature is needed in order to desorp hydrogen (reverse reaction) and vice versa. For practical application the temperature needed for desorption should not be too high i.e. {delta}H{sub f} should not be too large. If hydrogen desorption is to be possible below 100 deg C (which is the ultimate goal if hydrogen storage in metal hydrides should be used in conjunction with a PEM fuel cell), {delta}H{sub f} should not exceed -48 kJ/mol. Until recently only intermetallic metal hydrides with a storage capacity less than 2 wt.% H{sub 2} have met this criterion. However, discovering reversible hydrogen storage in complex metal hydrides such as NaAlH{sub 4} (5.5 wt. % reversible hydrogen capacity) have revealed a new group of potential candiates. However, still many combination of elements from the periodic table are yet to be explored. Since experimental determination of thermodynamic properties of the vast combinations of elements is tedious it may be advantagous to have a predictive tool for this task. In this report different ways of predicting {delta}H{sub f} for binary and ternary metal hydrides are reviewed. Main focus will be on how well these methods perform numerically i.e. how well experimental results are resembled by the model. The theoretical background of the different methods is only briefly reviewed. (au)

  16. Formation, transformation and dissolution of phases formed on surfaces

    International Nuclear Information System (INIS)

    Shoesmith, D.W.

    1983-03-01

    The basic mechanisms of film growth, transformation, and dissolution of phases formed on surfaces are discussed. Film growth can occur via solid-state processes or via substrate (usally metal or alloy) dissolution, followed by local supersaturation and precipitation of an insoluble phase. The phase(s) formed may be metastable and transform to a more stable phase, via either solid-state or dissolution-reprecipitation processes. Film dissolution reactions can also occur via a variety of mechanisms, including: (i) direct chemical dissolution when no oxidation state change occurs; (ii) redox dissolution when the film dissolves via a redox reaction involving a reducing or oxidizing agent in solution; and (iii) autoreduction, where film dissolution is coupled to metal dissolution. Such film-growth and dissolution processes, which often produce complex multilayer films, are common in the nuclear industry. A number of examples are discussed

  17. Naturally occurring crystalline phases: analogues for radioactive waste forms

    International Nuclear Information System (INIS)

    Haaker, R.F.; Ewing, R.C.

    1981-01-01

    Naturally occurring mineral analogues to crystalline phases that are constituents of crystalline radioactive waste forms provide a basis for comparison by which the long-term stability of these phases may be estimated. The crystal structures and the crystal chemistry of the following natural analogues are presented: baddeleyite, hematite, nepheline; pollucite, scheelite;sodalite, spinel, apatite, monazite, uraninite, hollandite-priderite, perovskite, and zirconolite. For each phase in geochemistry, occurrence, alteration and radiation effects are described. A selected bibliography for each phase is included

  18. Naturally occurring crystalline phases: analogues for radioactive waste forms

    Energy Technology Data Exchange (ETDEWEB)

    Haaker, R.F.; Ewing, R.C.

    1981-01-01

    Naturally occurring mineral analogues to crystalline phases that are constituents of crystalline radioactive waste forms provide a basis for comparison by which the long-term stability of these phases may be estimated. The crystal structures and the crystal chemistry of the following natural analogues are presented: baddeleyite, hematite, nepheline; pollucite, scheelite;sodalite, spinel, apatite, monazite, uraninite, hollandite-priderite, perovskite, and zirconolite. For each phase in geochemistry, occurrence, alteration and radiation effects are described. A selected bibliography for each phase is included.

  19. Phase transitions of antibiotic clarithromycin forms I, IV and new form VII crystals.

    Science.gov (United States)

    Ito, Masataka; Shiba, Rika; Watanabe, Miteki; Iwao, Yasunori; Itai, Shigeru; Noguchi, Shuji

    2018-06-01

    Metastable crystal form I of the antibiotic clarithromycin has a pharmaceutically valuable characteristic that its crystalline phase transition can be applied for its sustained release from tablets. The phase transition of form I was investigated in detail by single crystal and powder X-ray analyses, dynamic vapor sorption analysis and thermal analysis. The single crystal structure of form I revealed that form I was not an anhydrate crystal but contained a partially occupied water molecule in the channel-like void space. Dynamic vapor sorption (DVS) analysis demonstrated that form I crystals reversibly sorbed water molecules in two steps when the relative humidity (RH) increased and finally transited to hydrate form IV at 95% RH. DVS analysis also showed that when the RH decreased form IV crystals lost water molecules at 40% RH and transited to the newly identified anhydrate crystal form VII. Form VII reversibly transited to form IV at lower RH than form I, suggesting that form I is more suitable for manufacturing a sustained-release tablet of CAM utilizing the crystalline phase transition. Copyright © 2018 Elsevier B.V. All rights reserved.

  20. NMR study of hydride systems

    International Nuclear Information System (INIS)

    Peretz, M.

    1980-02-01

    The hydrides of thorium (ThH 2 , Th 4 H 15 and Th 4 D 15 ) and the intermetallic compound system (Zr(Vsub(1-x)Cosub(x)) 2 and its hydrides were investigated using the nuclear magnetic resonance (NMR) technique. From the results for the thorium hydride samples it was concluded that the density of states at the Fermi level n(Esub(f)) is higher in Th 4 H 15 than in ThH 2 ; there is an indirect reaction between the protons and the d electrons belonging to the Th atoms in Th 4 H 15 ; n(E) has a sharp structure near Esub(f). It was also found that the hydrogen diffusion mechanism changes with temperature. From the results for the intermetallic compound system conclusions were drawn concerning variations in the electronic structure, which explain the behavior of the system. In hydrogen diffusion studies in several samples it was found that Co atoms slow the diffusion rate. Quadrupole spectra obtained at low temperatures show that the H atoms preferably occupy tetrahedral sites formed by three V atoms and one Z atom. (H.K.)

  1. High-pressure phases of S, Se, and P hydrides and their superconducting properties. Predictions from ab-initio theory

    Energy Technology Data Exchange (ETDEWEB)

    Gross, E.K.U. [Max Planck Institute of Microstructure Physics, Halle (Saale) (Germany)

    2016-07-01

    The quest for novel high-temperature superconductors in the family of hydrogen-rich compounds has recently been crowned with the experimental discovery of a record critical temperature of 190 K in a hydrogen-sulfur compound at 200 GPa. In the present contribution, we investigate the phase diagram of the H-S system, comparing the stability of H{sub n}S (n = 1,2,3,4) by means of the minima hopping method for structure prediction. Our extensive crystal structure search confirms the H{sub 3}S stoichiometry as the most stable configuration at high pressure. Superconducting properties are calculated using the fully ab-initio parameter-free approach of density functional theory for superconductors. We find a T{sub c} of 180 K at 200 GPa, in excellent agreement with experiment. We also show that Se-H has a phase diagram similar to its sulfur counterpart. We predict H{sub 3}Se to be superconducting at temperatures higher than 120 K at 100 GPa. We furthermore investigate the phase diagram of PH{sub n} (n = 1,2,3,4,5,6). The results of our crystal-structure search do not support the existence of thermodynamically stable PH{sub n} compounds, which exhibit a tendency for elemental decomposition at high pressure. Although the lowest energy phases of PH{sub n=1,2,3} display T{sub c} values comparable to experiment, it remains uncertain if the measured values of T{sub c} can be fully attributed to a phase-pure compound of PH{sub n}.

  2. Regenerative Hydride Heat Pump

    Science.gov (United States)

    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.

  3. Blistering and hydride embrittlement

    International Nuclear Information System (INIS)

    Louthan, M.R. Jr.

    1975-01-01

    The effects of hydrogen on the mechanical properties of metals have been categorized into several groups. Two of the groups, hydrogen blistering and hydride embrittlement, are reasonably well understood, and problems relating to their occurrence may be avoided if that understanding is used as a basis for selecting alloys for hydrogen service. Blistering and hydride embrittlement are described along with several techniques of materials selection and used to minimize their adverse effects. (U.S.)

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

    Science.gov (United States)

    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 %.

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

    Science.gov (United States)

    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 AsBr 3 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 H 2 O, 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.

  6. Photoluminescence investigation of thick GaN films grown on Si substrates by hydride vapor phase epitaxy

    International Nuclear Information System (INIS)

    Yang, M.; Ahn, H. S.; Chang, J. H.; Yi, S. N.; Kim, K. H.; Kim, H.; Kim, S. W.

    2003-01-01

    The optical properties of thick GaN films grown by hydried vapor phase epitaxy (HVPE) using a low-temperature intermediate GaN buffer layer grown on a (111) Si substrate with a ZnO thin film were investigated by using photoluminescence (PL) measurement at 300 K and 77 K. The strong donor bound exciton (DBE) at 357 nm with a full width at half maximum (FWHM) of 15 meV was observed at 77 K. The value of 15 meV is extremely narrow for GaN grown on Si substrate by HVPE. An impurity-related peak was also observed at 367 nm. The origin of impurity was investigated using Auger spectroscopy.

  7. Reactions of newly formed fission products in the gas phase

    International Nuclear Information System (INIS)

    Strickert, R.G.

    1976-01-01

    A dynamic gas-flow system was constructed which stopped fission products in the gas phase and rapidly separated (in less than 2 sec) volatile compounds from non-volatile ones. The filter assembly designed and used was shown to stop essentially all non-volatile fission products. Between 5 percent and 20 percent of tellurium fission-product isotopes reacted with several hydrocarbon gases to form volatile compounds, which passed through the filter. With carbon monoxide gas, volatile tellurium compound(s) (probably TeCO) were also formed with similar efficiencies. The upper limits for the yields of volatile compounds formed between CO and tin and antimony fission products were shown to be less than 0.3 percent, so tellurium nuclides, not their precursors, reacted with CO. It was found that CO reacted preferentially with independently produced tellurium atoms; the reaction efficiency of beta-produced atoms was only 27 +- 3 percent of that of the independently formed atoms. The selectivity, which was independent of the over-all reaction efficiency, was shown to be due to reaction of independently formed atoms in the gas phase. The gas phase reactions are believed to occur mainly at thermal energies because of the independence of the yield upon argon moderator mole-fraction (up to 80 percent). It was shown in some experiments that about one-half of the TeCO decomposed in passing through a filter and that an appreciable fraction (approximately 20 percent) of the tellurium atoms deposited on the filter reacted agin with CO. Other tellurium atoms on the filter surface (those formed by beta decay and those formed independently but not reacting in the gas phase) also reacted with CO, but probably somewhat less efficiently than atoms formed by TeCO decomposition. No evidence was found for formation of TeCO as a direct result of beta-decay

  8. Cationic Phospholipids Forming Cubic Phases: Lipoplex Structure and Transfection Efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Koynova, Rumiana; Wang, Li; MacDonald, Robert C. (NWU)

    2008-10-29

    The transfection activity and the phase behavior of two novel cationic O-alkyl-phosphatidylcholines, 1,2-dioleoyl-sn-glycero-3-hexylphosphocholine (C6-DOPC) and 1,2-dierucoyl-sn-glycero-3-ethylphosphocholine (di22:1-EPC), have been examined with the aim of more completely understanding the mechanism of lipid-mediated DNA delivery. Both lipids form cubic phases: C6-DOPC in the entire temperature range from -10 to 90 C, while di22:1-EPC exhibits an irreversible lamellar-cubic transition between 50 and 70 C on heating. The lipoplexes formed by C6-DOPC arrange into hexagonal phase, while the lipoplexes of di22:1-EPC are lamellar. Both lipids exhibit lower transfection activity than the lamellar-forming 1,2-dioleoyl-sn-glycero-3-ethylphosphocholine (EDOPC). Thus, for the studied cationic phospholipid-DNA systems, the lipoplex phase state is a factor that does not seem to correlate with transfection activity. The parameter that exhibits better correlation with the transfection activity within the present data set is the phase state of the lipid dispersion prior to the addition of DNA. Thus, the lamellar lipid dispersion (EDOPC) produces more efficient lipoplexes than the dispersion with coexisting lamellar and cubic aggregates (diC22:1-EPC), which is even more efficient than the purely cubic dispersions (C6-DOPC; diC22:1-EPC after heating). It could be inferred from these data and from previous research that cubic phase lipid aggregates are unlikely to be beneficial to transfection. The lack of correlation between the phase state of lipoplexes and their transfection activity observed within the present data set does not mean that lipid phase state is generally unimportant for lipofection: a viewpoint now emerging from our previous studies is that the critical factor in lipid-mediated transfection is the structural evolution of lipoplexes within the cell, upon interacting and mixing with cellular lipids.

  9. Cationic phospholipids forming cubic phases: lipoplex structure and transfection efficiency.

    Science.gov (United States)

    Koynova, Rumiana; Wang, Li; Macdonald, Robert C

    2008-01-01

    The transfection activity and the phase behavior of two novel cationic O-alkyl-phosphatidylcholines, 1,2-dioleoyl- sn-glycero-3-hexylphosphocholine (C6-DOPC) and 1,2-dierucoyl- sn-glycero-3-ethylphosphocholine (di22:1-EPC), have been examined with the aim of more completely understanding the mechanism of lipid-mediated DNA delivery. Both lipids form cubic phases: C6-DOPC in the entire temperature range from -10 to 90 degrees C, while di22:1-EPC exhibits an irreversible lamellar-cubic transition between 50 and 70 degrees C on heating. The lipoplexes formed by C6-DOPC arrange into hexagonal phase, while the lipoplexes of di22:1-EPC are lamellar. Both lipids exhibit lower transfection activity than the lamellar-forming 1,2-dioleoyl- sn-glycero-3-ethylphosphocholine (EDOPC). Thus, for the studied cationic phospholipid-DNA systems, the lipoplex phase state is a factor that does not seem to correlate with transfection activity. The parameter that exhibits better correlation with the transfection activity within the present data set is the phase state of the lipid dispersion prior to the addition of DNA. Thus, the lamellar lipid dispersion (EDOPC) produces more efficient lipoplexes than the dispersion with coexisting lamellar and cubic aggregates (diC22:1-EPC), which is even more efficient than the purely cubic dispersions (C6-DOPC; diC22:1-EPC after heating). It could be inferred from these data and from previous research that cubic phase lipid aggregates are unlikely to be beneficial to transfection. The lack of correlation between the phase state of lipoplexes and their transfection activity observed within the present data set does not mean that lipid phase state is generally unimportant for lipofection: a viewpoint now emerging from our previous studies is that the critical factor in lipid-mediated transfection is the structural evolution of lipoplexes within the cell, upon interacting and mixing with cellular lipids.

  10. Glycine phases formed from frozen aqueous solutions: Revisited

    Energy Technology Data Exchange (ETDEWEB)

    Surovtsev, N. V. [Institute of Automation and Electrometry, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Adichtchev, S. V.; Malinovsky, V. K. [Institute of Automation and Electrometry, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090 (Russian Federation); Ogienko, A. G.; Manakov, A. Yu. [Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Nikolaev Institute of Inorganic Chemistry, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090 (Russian Federation); Drebushchak, V. A. [Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Institute of Geology and Mineralogy, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090 (Russian Federation); Ancharov, A. I.; Boldyreva, E. V. [Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Institute of Solid Chemistry and Mechanochemistry, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090 (Russian Federation); Yunoshev, A. S. [Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Lavrentiev Institute of Hydrodynamics, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090 (Russian Federation)

    2012-08-14

    Glycine phases formed when aqueous solutions were frozen and subsequently heated under different conditions were studied by Raman scattering, x-ray diffraction, and differential scanning calorimetry (DSC) techniques. Crystallization of ice I{sub h} was observed in all the cases. On cooling at the rates of 0.5 K/min and 5 K/min, glassy glycine was formed as an intermediate phase which lived about 1 min or less only, and then transformed into {beta}-polymorph of glycine. Quench cooling of glycine solutions (15% w/w) in liquid nitrogen resulted in the formation of a mixture of crystalline water ice I{sub h} and a glassy glycine, which could be preserved at cryogenic temperatures (80 K) for an indefinitely long time. This mixture remained also quite stable for some time after heating above the cryogenic temperature. Subsequent heating under various conditions resulted in the transformation of the glycine glass into an unknown crystalline phase (glycine 'X-phase') at 209-216 K, which at 218-226 K transformed into {beta}-polymorph of glycine. The 'X-phase' was characterized by Raman spectroscopy; it could be obtained in noticeable amounts using a special preparation technique and tentatively characterized by x-ray powder diffraction (P2, a= 6.648 A, b= 25.867 A, c= 5.610 A, {beta}= 113.12 Masculine-Ordinal-Indicator ); the formation of 'X-phase' from the glycine glassy phase and its transformation into {beta}-polymorph were followed by DSC. Raman scattering technique with its power for unambiguous identification of the crystalline and glassy polymorphs without limitation on the crystallite size helped us to follow the phase transformations during quenching, heating, and annealing. The experimental findings are considered in relation to the problem of control of glycine polymorphism on crystallization.

  11. Glycine phases formed from frozen aqueous solutions: Revisited

    Science.gov (United States)

    Surovtsev, N. V.; Adichtchev, S. V.; Malinovsky, V. K.; Ogienko, A. G.; Drebushchak, V. A.; Manakov, A. Yu.; Ancharov, A. I.; Yunoshev, A. S.; Boldyreva, E. V.

    2012-08-01

    Glycine phases formed when aqueous solutions were frozen and subsequently heated under different conditions were studied by Raman scattering, x-ray diffraction, and differential scanning calorimetry (DSC) techniques. Crystallization of ice Ih was observed in all the cases. On cooling at the rates of 0.5 K/min and 5 K/min, glassy glycine was formed as an intermediate phase which lived about 1 min or less only, and then transformed into β-polymorph of glycine. Quench cooling of glycine solutions (15% w/w) in liquid nitrogen resulted in the formation of a mixture of crystalline water ice Ih and a glassy glycine, which could be preserved at cryogenic temperatures (80 K) for an indefinitely long time. This mixture remained also quite stable for some time after heating above the cryogenic temperature. Subsequent heating under various conditions resulted in the transformation of the glycine glass into an unknown crystalline phase (glycine "X-phase") at 209-216 K, which at 218-226 K transformed into β-polymorph of glycine. The "X-phase" was characterized by Raman spectroscopy; it could be obtained in noticeable amounts using a special preparation technique and tentatively characterized by x-ray powder diffraction (P2, a = 6.648 Å, b = 25.867 Å, c = 5.610 Å, β = 113.12°); the formation of "X-phase" from the glycine glassy phase and its transformation into β-polymorph were followed by DSC. Raman scattering technique with its power for unambiguous identification of the crystalline and glassy polymorphs without limitation on the crystallite size helped us to follow the phase transformations during quenching, heating, and annealing. The experimental findings are considered in relation to the problem of control of glycine polymorphism on crystallization.

  12. U-8 wt %Mo and 7 wt %Mo alloys powder obtained by an hydride-de hydride process

    International Nuclear Information System (INIS)

    Balart, Silvia N.; Bruzzoni, Pablo; Granovsky, Marta S.; Gribaudo, Luis M. J.; Hermida, Jorge D.; Ovejero, Jose; Rubiolo, Gerardo H.; Vicente, Eduardo E.

    2000-01-01

    Uranium-molybdenum alloys are been tested as a component in high-density LEU dispersion fuels with very good performances. These alloys need to be transformed to powder due to the manufacturing requirements of the fuels. One method to convert ductile alloys into powder is the hydride-de hydride process, which takes advantage of the ability of the U-α phase to transform to UH 3 : a brittle and relatively low-density compound. U-Mo alloys around 7 and 8 wt % Mo were melted and heat treated at different temperature ranges in order to partially convert γ -phase to α -phase. Subsequent hydriding transforms this α -phase to UH 3 . The volume change associated to the hydride formation embrittled the material which ends up in a powdered alloy. Results of the optical metallography, scanning electron microscopy, X-ray diffraction during different steps of the process are shown. (author)

  13. Simultaneous gettering of oxygen and chlorine and homogenization of the β phase by rare earth hydride additions to a powder metallurgy Ti–2.25Mo–1.5Fe alloy

    International Nuclear Information System (INIS)

    Yan, M.; Liu, Y.; Liu, Y.B.; Kong, C.; Schaffer, G.B.; Qian, M.

    2012-01-01

    A detailed transmission electron microscopy analysis has revealed that small additions of yttrium hydride to a powder metallurgy Ti–2.25Mo–1.5Fe alloy resulted in the formation of both chlorine-free yttrium oxides and essentially oxygen-free yttrium chlorides. The oxides and chlorides showed distinctly different morphologies and spatial distribution. Yttrium acted as a potent getter for both oxygen and chlorine. Additionally, the β-Ti phase was free of nanoscaled α-Ti in the presence of yttrium. These microstructural changes contribute to the substantially increased ductility (∼90%).

  14. The growth of crystals of erbium hydride

    International Nuclear Information System (INIS)

    Grimshaw, J.A.; Spooner, F.J.; Wilson, C.G.; McQuillan, A.D.

    1981-01-01

    Crystals of the rare-earth hydride ErH 2 have been produced with face areas greater than a square millimetre and corresponding volumes exceeding those of earlier crystals by orders of magnitude. The hydride, which was produced in bulk polycrystalline form by hydriding erbium metal at 950 0 C, has been examined by optical and X-ray techniques. For material of composition ErH 2 and ErHsub(1.8) the size of the grains and their degree of strain appears to depend more on oxygen contamination during formation and on the subsequent cooling procedure, than on the size of erbium metal crystals in the starting material. (author)

  15. Conference 'Chemistry of hydrides' Proceedings

    International Nuclear Information System (INIS)

    1991-07-01

    This collection of thesis of conference of Chemistry hydrides presents the results of investigations concerning of base questions of chemistry of nonorganic hydrides, including synthesis questions, studying of physical and chemical properties, thermodynamics, analytical chemistry, investigation of structure, equilibriums in the systems of metal-hydrogen, behaviour of nonorganic hydrides in non-water mediums and applying investigations in the chemistry area and technology of nonorganic hydrides

  16. Nanoindentation measurements of the mechanical properties of zirconium matrix and hydrides in unirradiated pre-hydrided nuclear fuel cladding

    International Nuclear Information System (INIS)

    Rico, A.; Martin-Rengel, M.A.; Ruiz-Hervias, J.; Rodriguez, J.; Gomez-Sanchez, F.J.

    2014-01-01

    It is well known that the mechanical properties of the nuclear fuel cladding may be affected by the presence of hydrides. The average mechanical properties of hydrided cladding have been extensively investigated from a macroscopic point of view. In addition, the mechanical and fracture properties of bulk hydride samples fabricated from zirconium plates have also been reported. In this paper, Young’s modulus, hardness and yield stress are measured for each phase, namely zirconium hydrides and matrix, of pre-hydrided nuclear fuel cladding. To this end, nanoindentation tests were performed on ZIRLO samples in as-received state, on a hydride blister and in samples with 150 and 1200 ppm of hydrogen homogeneously distributed along the hoop direction of the cladding. The results show that the measured mechanical properties of the zirconium hydrides and ZIRLO matrix (Young’s modulus, hardness and yield stress) are rather similar. From the experimental data, the hydride volume fraction in the cladding samples with 150 and 1200 ppm was estimated and the average mechanical properties were calculated by means of the rule of mixtures. These values were compared with those obtained from ring compression tests. Good agreement between the results obtained by both methods was found

  17. Method for preparation of uranium hydride

    International Nuclear Information System (INIS)

    Gorski, M.S.; Goncalves, Miriam; Mirage, A.; Lima, W. de.

    1985-01-01

    A method for preparation of Uranium Hydride starting from Hidrogen and Uranium is described. In the temperature range of 250 0 up to 350 0 C, and pressures above 10torr, Hydrogen reacts smoothly with Uranium turnings forming a fine black or dark gray powder (UH 3 ). Samples containing a significant amount of oxides show a delay before the reaction begging. (Author) [pt

  18. Effects of AlN nucleation layers on the growth of AlN films using high temperature hydride vapor phase epitaxy

    International Nuclear Information System (INIS)

    Balaji, M.; Claudel, A.; Fellmann, V.; Gélard, I.; Blanquet, E.; Boichot, R.; Pierret, A.

    2012-01-01

    Highlights: ► Growth of AlN Nucleation layers and its effect on high temperature AlN films quality were investigated. ► AlN nucleation layers stabilizes the epitaxial growth of AlN and improves the surface morphology of AlN films. ► Increasing growth temperature of AlN NLs as well as AlN films improves the structural quality and limits the formation of cracks. - Abstract: AlN layers were grown on c-plane sapphire substrates with AlN nucleation layers (NLs) using high temperature hydride vapor phase epitaxy (HT-HVPE). Insertion of low temperature NLs, as those typically used in MOVPE process, prior to the high temperature AlN (HT-AlN) layers has been investigated. The NLs surface morphology was studied by atomic force microscopy (AFM) and NLs thickness was measured by X-ray reflectivity. Increasing nucleation layer deposition temperature from 650 to 850 °C has been found to promote the growth of c-oriented epitaxial HT-AlN layers instead of polycrystalline layers. The growth of polycrystalline layers has been related to the formation of dis-oriented crystallites. The density of such disoriented crystallites has been found to decrease while increasing NLs deposition temperature. The HT-AlN layers have been characterized by X-ray diffraction θ − 2θ scan and (0 0 0 2) rocking curve measurement, Raman and photoluminescence spectroscopies, AFM and field emission scanning electron microscopy. Increasing the growth temperature of HT-AlN layers from 1200 to 1400 °C using a NL grown at 850 °C improves the structural quality as well as the surface morphology. As a matter of fact, full-width at half-maximum (FWHM) of 0 0 0 2 reflections was improved from 1900 to 864 arcsec for 1200 °C and 1400 °C, respectively. Related RMS roughness also found to decrease from 10 to 5.6 nm.

  19. Formation of gallium nitride templates and freestanding substrates by hydride vapor phase epitaxy for homoepitaxial growth of III-nitride devices

    Science.gov (United States)

    Williams, Adrian Daniel

    Gallium nitride (GaN) is a direct wide band gap semiconductor currently under heavy development worldwide due to interest in its applications in ultra-violet optoelectronics, power electronics, devices operating in harsh environments (high temperature or corrorsive), etc. While a number of devices have been demonstrated with this material and its related alloys, the unavailability of GaN substrates is seen as one of the current major bottlenecks to both material quality and device performance. This dissertation is concerned with the synthesis of high quality GaN substrates by the hydride vapor phase epitaxy method (HVPE). In this work, the flow of growth precursors in a home-built HVPE reactor was modeled by the Navier-Stokes equation and solved by finite element analysis to promote uniformity of GaN on 2'' sapphire substrates. Kinetics of growth was studied and various regimes of growth were identified to establish a methodology for HVPE GaN growth, independent of reactor geometry. GaN templates as well as bulk substrates were fabricated in this work. Realization of freestanding GaN substrates was achieved through discovery of a natural stress-induced method of separating bulk GaN from sapphire via mechanical failure of a low-temperature GaN buffer layer. Such a process eliminates the need for pre- or post-processing of sapphire substrates, as is currently the standard. Stress in GaN-on-sapphire is discussed, with the dominant contributor identified as thermal stress due to thermal expansion coefficient mismatch between the two materials. This thermal stress is analyzed using Stoney's equation and conditions for crack-free growth of thick GaN substrates were identified. An etch-back process for planarizing GaN templates was also developed and successfully applied to rough GaN templates. The planarization of GaN has been mainly addressed by chemo-mechanical polishing (CMP) methods in the literature, with notable shortcomings including the inability to effectively

  20. Design and characterization of thick InxGa1-xAs metamorphic buffer layers grown by hydride vapor phase epitaxy

    Science.gov (United States)

    Schulte, K. L.; Zutter, B. T.; Wood, A. W.; Babcock, S. E.; Kuech, T. F.

    2014-03-01

    Thick InxGa1-xAs metamorphic buffer layers (MBLs) grown by hydride vapor phase epitaxy (HVPE) were studied. Relationships between MBL properties and growth parameters such as grading rate, cap layer thickness, final xInAs, and deposition temperature (TD) were explored. The MBLs were characterized by measurement of in-plane residual strain (ɛ¦¦), surface etch pit density (EPD), and surface roughness. Capping layer thickness had a strong effect on strain relaxation, with thickly capped samples exhibiting the lowest ɛ¦¦. EPD was higher in samples with thicker caps, reflecting their increased relaxation through dislocation generation. ɛ¦¦ and EPD were weakly affected by the grading rate, making capping layer thickness the primary structural parameter which controls these properties. MBLs graded in discrete steps had similar properties to MBLs with continuous grading. In samples with identical thickness and 10-step grading style, ɛ¦¦ increased almost linearly with final xInAs, while total relaxation stayed relatively constant. Relaxation as a function of xInAs could be described by an equilibrium model in which dislocation nucleation is impeded by the energy of the existing dislocation array. EPD was constant from xInAs = 0 to 0.24 then increased exponentially, which is related to the increased dislocation interaction and blocking seen at higher dislocation densities. RMS roughness increased with xInAs above a certain strain rate (0.15%/µm) samples grown below this level possessed large surface hillocks and high roughness values. The elimination of hillocks at higher values of xInAs is attributed to increased density of surface steps and is related to the out-of-plane component of the burgers vector of the dominant type of 60° dislocation. TD did not affect ɛ¦¦ for samples with a given xInAs. EPD tended to increase with TD, indicating dislocation glide likely is impeded at higher temperatures.

  1. Preferred hydride growth orientations on oxide-coated gadolinium surfaces

    International Nuclear Information System (INIS)

    Benamar, G.M.; Schweke, D.; Kimmel, G.; Mintz, M.H.

    2012-01-01

    Highlights: ► The preferred hydride growth orientations on gadolinium metal coated by a thin oxide layer are presented. ► A preferred growth of the (1 0 0) h plane of the face centered cubic (FCC) GdH 2 is observed for the hydride spots forming below the oxidation layer. ► A change to the (1 1 1) h plane of the cubic hydride dominates for the hydride's Growth Centers. ► The texture change is attributed to the surface normal compressive stress component exerted by the oxidation layer on the developing hydride. - Abstract: The initial development of hydrides on polycrystalline gadolinium (Gd), as on some other hydride forming metals, is characterized by two sequential steps. The first step involves the rapid formation of a dense pattern of small hydride spots (referred to as the “small family” of hydrides) below the native oxidation layer. The second stage takes place when some of the “small family” nucleants (referred to as “growth centers”, GCs) break the oxide layer, leading to their rapid growth and finally to the massive hydriding of the sample. In the present study, the texture of the two hydride families was studied, by combining X-ray diffraction (XRD) analysis with a microscopic analysis of the hydride, using scanning electron microscopy (SEM) and atomic force microscopy (AFM). It has been observed that for the “small family”, a preferred growth of the (1 0 0) h plane of the cubic GdH 2 takes place, whereas for the GCs, a change to the (1 1 1) h plane of the cubic hydride dominates. These preferred growth orientations were analyzed by their structure relation with the (0 0 .1) m basal plane of the Gd metal. It has been concluded that the above texture change is due to the surface normal compressive stress component exerted by the oxidation overlayer on the developing hydride, preventing the (0 0 .1) m ||(1 1 1) h growth orientation. This stress is relieved upon the rupture of that overlayer and the development of the GCs, leading to

  2. Preparation of beryllium hydride

    International Nuclear Information System (INIS)

    Lowrance, B.R.

    1975-01-01

    A process is described for the preparation of beryllium hydride which comprises pyrolyzing, while in solution in a solvent inert under the reaction conditions, with respect to reactants and products and at a temperature in the range of about 100 0 to about 200 0 C, sufficient to result in the formation of beryllium hydride, a di-t-alkyl beryllium etherate wherein each tertiary alkyl radical contains from 4 to 20 carbon atoms. The pyrolysis is carried out under an atmosphere inert under the reaction conditions, with respect to reactants and products. (U.S.)

  3. Tritium removal using vanadium hydride

    International Nuclear Information System (INIS)

    Hill, F.B.; Wong, Y.W.; Chan, Y.N.

    1978-01-01

    The results of an initial examination of the feasibility of separation of tritium from gaseous protium-tritium mixtures using vanadium hydride in cyclic processes is reported. Interest was drawn to the vanadium-hydrogen system because of the so-called inverse isotope effect exhibited by this system. Thus the tritide is more stable than the protide, a fact which makes the system attractive for removal of tritium from a mixture in which the light isotope predominates. The initial results of three phases of the research program are reported, dealing with studies of the equilibrium and kinetics properties of isotope exchange, development of an equilibrium theory of isotope separation via heatless adsorption, and experiments on the performance of a single heatless adsorption stage. In the equilibrium and kinetics studies, measurements were made of pressure-composition isotherms, the HT--H 2 separation factors and rates of HT--H 2 exchange. This information was used to evaluate constants in the theory and to understand the performance of the heatless adsorption experiments. A recently developed equilibrium theory of heatless adsorption was applied to the HT--H 2 separation using vanadium hydride. Using the theory it was predicted that no separation would occur by pressure cycling wholly within the β phase but that separation would occur by cycling between the β and γ phases and using high purge-to-feed ratios. Heatless adsorption experiments conducted within the β phase led to inverse separations rather than no separation. A kinetic isotope effect may be responsible. Cycling between the β and γ phases led to separation but not to the predicted complete removal of HT from the product stream, possibly because of finite rates of exchange. Further experimental and theoretical work is suggested which may ultimately make possible assessment of the feasibility and practicability of hydrogen isotope separation by this approach

  4. The influence of hydride on fracture toughness of recrystallized Zircaloy-4 cladding

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, Hsiao-Hung, E-mail: 175877@mail.csc.com.tw [Institute of Nuclear Energy Research (INER), Lungtan Township, Taoyuan County 32546, Taiwan, ROC (China); China Steel Corporation, Hsiao Kang District, Kaohsiung 81233, Taiwan, ROC (China); Chiang, Ming-Feng [China Steel Corporation, Hsiao Kang District, Kaohsiung 81233, Taiwan, ROC (China); Chen, Yen-Chen [Institute of Nuclear Energy Research (INER), Lungtan Township, Taoyuan County 32546, Taiwan, ROC (China)

    2014-04-01

    In this work, RXA cladding tubes were hydrogen-charged to target hydrogen content levels between 150 and 800 wppm (part per million by weight). The strings of zirconium hydrides observed in the cross sections are mostly oriented in the circumferential direction. The fracture toughness of hydrided RXA Zircaloy-4 cladding was measured to evaluate its hydride embrittlement susceptibility. With increasing hydrogen content, the fracture toughness of hydrided RXA cladding decreases at both 25 °C and 300 °C. Moreover, highly localized hydrides (forming a hydride rim) aggravate the degradation of the fracture properties of RXA Zircaloy-4 cladding at both 25 °C and 300 °C. Brittle features in the form of quasi-cleavages and secondary cracks were observed on the fracture surface of the hydride rim, even for RXA cladding tested at 300 °C.

  5. Thermodynamic modeling of mineralogical phases formed by continuous casting powders

    International Nuclear Information System (INIS)

    Romo-Castaneda, Julio; Cruz-Ramirez, Alejandro; Romero-Serrano, Antonio; Vargas-Ramirez, Marissa; Hallen-Lopez, Manuel

    2011-01-01

    A great amount of mineralogical phases were predicted and represented in stability phase diagrams, which were obtained by the use of the thermodynamic software FACTSage considering both the chemical composition and the melting temperature of the mould flux. Melting-solidification tests on commercial mould flux glasses for thin slab casting of steel revealed the existence of cuspidine (Ca 4 Si 2 O 7 F 2 ) as the main mineralogical phase formed during the flux solidification by X-ray powder diffraction (XRD). This phase directly influences the heat transfer phenomena from the strand to the mould and it is obtained with higher fluorite content (22% CaF 2 ). Cuspidine is desirable only in fluxes to produce medium carbon (included peritectic grade) steels, because it reduces the heat flux from the strand to the mould, thus controlling the shrinkage rate during the flux solidification. The experimental results are in agreement with those obtained by the thermodynamic software. The stability phase diagrams could be used as an important tool in the flux design for continuous casting process.

  6. Thermodynamic modeling of mineralogical phases formed by continuous casting powders

    Energy Technology Data Exchange (ETDEWEB)

    Romo-Castaneda, Julio [Metallurgy and Materials Department, Instituto Politecnico Nacional-ESIQIE, Apdo. P. 118-431, 07051 Mexico D.F. (Mexico); Cruz-Ramirez, Alejandro, E-mail: alcruzr@ipn.mx [Metallurgy and Materials Department, Instituto Politecnico Nacional-ESIQIE, Apdo. P. 118-431, 07051 Mexico D.F. (Mexico); Romero-Serrano, Antonio; Vargas-Ramirez, Marissa; Hallen-Lopez, Manuel [Metallurgy and Materials Department, Instituto Politecnico Nacional-ESIQIE, Apdo. P. 118-431, 07051 Mexico D.F. (Mexico)

    2011-01-10

    A great amount of mineralogical phases were predicted and represented in stability phase diagrams, which were obtained by the use of the thermodynamic software FACTSage considering both the chemical composition and the melting temperature of the mould flux. Melting-solidification tests on commercial mould flux glasses for thin slab casting of steel revealed the existence of cuspidine (Ca{sub 4}Si{sub 2}O{sub 7}F{sub 2}) as the main mineralogical phase formed during the flux solidification by X-ray powder diffraction (XRD). This phase directly influences the heat transfer phenomena from the strand to the mould and it is obtained with higher fluorite content (22% CaF{sub 2}). Cuspidine is desirable only in fluxes to produce medium carbon (included peritectic grade) steels, because it reduces the heat flux from the strand to the mould, thus controlling the shrinkage rate during the flux solidification. The experimental results are in agreement with those obtained by the thermodynamic software. The stability phase diagrams could be used as an important tool in the flux design for continuous casting process.

  7. Quantifying the stress fields due to a delta-hydride precipitate in alpha-Zr matrix

    Energy Technology Data Exchange (ETDEWEB)

    Tummala, Hareesh [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Capolungo, Laurent [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Tome, Carlos N. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-10-19

    This report is a preliminary study on δ-hydride precipitate in zirconium alloy performed using 3D discrete dislocation dynamics simulations. The ability of dislocations in modifying the largely anisotropic stress fields developed by the hydride particle in a matrix phase is addressed for a specific dimension of the hydride. The influential role of probable dislocation nucleation at the hydride-matrix interface is reported. Dislocation nucleation around a hydride was found to decrease the shear stress (S13) and also increase the normal stresses inside the hydride. We derive conclusions on the formation of stacks of hydrides in zirconium alloys. The contribution of mechanical fields due to dislocations was found to have a non-negligible effect on such process.

  8. Internal friction study of hydrides in zirconium at low hydrogen contents

    International Nuclear Information System (INIS)

    Peretti, H.A.; Corso, H.L.; Gonzalez, O.A.; Fernandez, L.; Ghilarducci, A.A.; Salva, H.R.

    1999-01-01

    Full text: Internal friction and shear modulus measurements were carried out on crystal bar zirconium in the as received and hydride conditions using an inverted forced pendulum. Hydriding was achieved in two ways: inside and out of the pendulum. The final hydrogen content determined by fusion analysis in the 'in situ' hydride sample was of 36 ppm. Another sample was hydride by the cathodic charge method with 25 ppm. The thermal solid solubility (TSS) phase boundary presents hysteresis between the precipitation (TSSP) and the dissolution (TSSD) temperatures for the zirconium hydrides. During the first thermal cycling the anelastic effects could be attributed to the δ, ε and metastable γ zirconium hydrides. After 'in situ' annealing at 490 K, these peaks completely disappear in the electrolytically charged sample, while in the 'in situ' hydride, the peaks remain with decreasing intensity. This effect can be understood in terms of the different surface conditions of the samples. (author)

  9. Gaseous Phase and Electrochemical Hydrogen Storage Properties of Ti50Zr1Ni44X5 (X = Ni, Cr, Mn, Fe, Co, or Cu for Nickel Metal Hydride Battery Applications

    Directory of Open Access Journals (Sweden)

    Jean Nei

    2016-07-01

    Full Text Available Structural, gaseous phase hydrogen storage, and electrochemical properties of a series of the Ti50Zr1Ni44X5 (X = Ni, Cr, Mn, Fe, Co, or Cu metal hydride alloys were studied. X-ray diffraction (XRD and scanning electron microscopy (SEM revealed the multi-phase nature of all alloys, which were composed of a stoichiometric TiNi matrix, a hyperstoichiometric TiNi minor phase, and a Ti2Ni secondary phase. Improvement in synergetic effects between the main TiNi and secondary Ti2Ni phases, determined by the amount of distorted lattice region in TiNi near Ti2Ni, was accomplished by the substitution of an element with a higher work function, which consequently causes a dramatic increase in gaseous phase hydrogen storage capacity compared to the Ti50Zr1Ni49 base alloy. Capacity performance is further enhanced in the electrochemical environment, especially in the cases of the Ti50Zr1Ni49 base alloy and Ti50Zr1Ni44Co5 alloy. Although the TiNi-based alloys in the current study show poorer high-rate performances compared to the commonly used AB5, AB2, and A2B7 alloys, they have adequate capacity performances and also excel in terms of cost and cycle stability. Among the alloys investigated, the Ti50Zr1Ni44Fe5 alloy demonstrated the best balance among capacity (394 mAh·g−1, high-rate performance, activation, and cycle stability and is recommended for follow-up full-cell testing and as the base composition for future formula optimization. A review of previous research works regarding the TiNi metal hydride alloys is also included.

  10. CHEMISTRY IN A FORMING PROTOPLANETARY DISK: MAIN ACCRETION PHASE

    Energy Technology Data Exchange (ETDEWEB)

    Yoneda, Haruaki [Department of Planetology, Kobe University, Kobe 657-8501 (Japan); Tsukamoto, Yusuke [Riken, 2-1 Hirosawa, Wako, Saitama (Japan); Furuya, Kenji; Aikawa, Yuri, E-mail: aikawa@ccs.tsukuba.ac.jp [Center for Computational Sciences, University of Tsukuba (Japan)

    2016-12-10

    We investigate the chemistry in a radiation-hydrodynamics model of a star-forming core that evolves from a cold (∼10 K) prestellar core to the main accretion phase in ∼10{sup 5} years. A rotationally supported gravitationally unstable disk is formed around a protostar. We extract the temporal variation of physical parameters in ∼1.5 × 10{sup 3} SPH particles that end up in the disk, and perform post-processing calculations of the gas-grain chemistry adopting a three-phase model. Inside the disk, the SPH particles migrate both inward and outward. Since a significant fraction of volatiles such as CO can be trapped in the water-dominant ice in the three-phase model, the ice mantle composition depends not only on the current position in the disk, but also on whether the dust grain has ever experienced higher temperatures than the water sublimation temperature. Stable molecules such as H{sub 2}O, CH{sub 4}, NH{sub 3}, and CH{sub 3}OH are already abundant at the onset of gravitational collapse and are simply sublimated as the fluid parcels migrate inside the water snow line. On the other hand, various molecules such as carbon chains and complex organic molecules (COMs) are formed in the disk. The COMs abundance sensitively depends on the outcomes of photodissociation and diffusion rates of photofragments in bulk ice mantle. As for S-bearing species, H{sub 2}S ice is abundant in the collapse phase. In the warm regions in the disk, H{sub 2}S is sublimated to be destroyed, while SO, H{sub 2}CS, OCS, and SO{sub 2} become abundant.

  11. CHEMISTRY IN A FORMING PROTOPLANETARY DISK: MAIN ACCRETION PHASE

    International Nuclear Information System (INIS)

    Yoneda, Haruaki; Tsukamoto, Yusuke; Furuya, Kenji; Aikawa, Yuri

    2016-01-01

    We investigate the chemistry in a radiation-hydrodynamics model of a star-forming core that evolves from a cold (∼10 K) prestellar core to the main accretion phase in ∼10 5 years. A rotationally supported gravitationally unstable disk is formed around a protostar. We extract the temporal variation of physical parameters in ∼1.5 × 10 3 SPH particles that end up in the disk, and perform post-processing calculations of the gas-grain chemistry adopting a three-phase model. Inside the disk, the SPH particles migrate both inward and outward. Since a significant fraction of volatiles such as CO can be trapped in the water-dominant ice in the three-phase model, the ice mantle composition depends not only on the current position in the disk, but also on whether the dust grain has ever experienced higher temperatures than the water sublimation temperature. Stable molecules such as H 2 O, CH 4 , NH 3 , and CH 3 OH are already abundant at the onset of gravitational collapse and are simply sublimated as the fluid parcels migrate inside the water snow line. On the other hand, various molecules such as carbon chains and complex organic molecules (COMs) are formed in the disk. The COMs abundance sensitively depends on the outcomes of photodissociation and diffusion rates of photofragments in bulk ice mantle. As for S-bearing species, H 2 S ice is abundant in the collapse phase. In the warm regions in the disk, H 2 S is sublimated to be destroyed, while SO, H 2 CS, OCS, and SO 2 become abundant.

  12. Planktic foraminifera form their shells via metastable carbonate phases.

    Science.gov (United States)

    Jacob, D E; Wirth, R; Agbaje, O B A; Branson, O; Eggins, S M

    2017-11-02

    The calcium carbonate shells of planktic foraminifera provide our most valuable geochemical archive of ocean surface conditions and climate spanning the last 100 million years, and play an important role in the ocean carbon cycle. These shells are preserved in marine sediments as calcite, the stable polymorph of calcium carbonate. Here, we show that shells of living planktic foraminifers Orbulina universa and Neogloboquadrina dutertrei originally form from the unstable calcium carbonate polymorph vaterite, implying a non-classical crystallisation pathway involving metastable phases that transform ultimately to calcite. The current understanding of how planktic foraminifer shells record climate, and how they will fare in a future high-CO 2 world is underpinned by analogy to the precipitation and dissolution of inorganic calcite. Our findings require a re-evaluation of this paradigm to consider the formation and transformation of metastable phases, which could exert an influence on the geochemistry and solubility of the biomineral calcite.

  13. Electrolytic hydriding and hydride distribution in zircaloy-4

    International Nuclear Information System (INIS)

    Gomes, M.H.L.

    1974-01-01

    A study has been made of the electrolytic hydriding of zircaloy-4 in the range 20-80 0 C, for reaction times from 5 to 30 hours, and the effect of potential, pH and dissolved oxygen has been investigated. The hydriding reaction was more sensitive to time and temperature conditions than to the electrochemical variables. It has been shown that a controlled introduction of hydrides in zircaloy is feasible. Hydrides were found to be plate like shaped and distributed mainly along grain-boundaries. It has been shown that hydriding kinetics do not follow a simple law but may be described by a Johnson-Mehl empirical equation. On the basis of this equation an activation energy of 9.400 cal/mol has been determined, which is close to the activation energy for diffusion of hydrogen in the hydride. (author)

  14. Simulation of bulk phases formed by polyphilic liquid crystal dendrimers

    Directory of Open Access Journals (Sweden)

    J.M. Ilnytskyi

    2010-01-01

    Full Text Available A coarse-grained simulation model for a third generation liquid crystalline dendrimer (LCDr is presented. It allows, for the first time, for a successful molecular simulation study of a relation between the shape of a polyphilic macromolecular mesogen and the symmetry of a macroscopic phase. The model dendrimer consists of a soft central sphere and 32 grafted chains each terminated by a mesogen group. The mesogenic pair interactions are modelled by the recently proposed soft core spherocylinder model of Lintuvuori and Wilson [J. Chem. Phys, 128, 044906, (2008]. Coarse-grained (CG molecular dynamics (MD simulations are performed on a melt of 100 molecules in the anisotropic-isobaric ensemble. The model LCDr shows conformational bistability, with both rod-like and disc-like conformations stable at lower temperatures. Each conformation can be induced by an external aligning field of appropriate symmetry that acts on the mesogens (uniaxial for rod-like and planar for disc-like, leading to formation of a monodomain smectic A (SmA or a columnar (Col phase, respectively. Both phases are stable for approximately the same temperature range and both exhibit a sharp transition to an isotropic cubic-like phase upon heating. We observe a very strong coupling between the conformation of the LCDr and the symmetry of a bulk phase, as suggested previously by theory. The study reveals rich potential in terms of the application of this form of CG modelling to the study of molecular self-assembly of liquid crystalline macromolecules.

  15. Preparation of beryllium hydride

    International Nuclear Information System (INIS)

    Bergeron, C.R.; Baker, R.W.

    1975-01-01

    Beryllium hydride of high bulk density, suitable for use as a component of high-energy fuels, is prepared by the pyrolysis, in solution in an inert solvent, of a ditertiary-alkyl beryllium. An agitator introduces mechanical energy into the reaction system, during the pyrolysis, at the rate of 0.002 to 0.30 horsepower per gallon of reaction mixture. (U.S.)

  16. Air and metal hydride battery

    Energy Technology Data Exchange (ETDEWEB)

    Lampinen, M.; Noponen, T. [Helsinki Univ. of Technology, Otaniemi (Finland). Lab. of Applied Thermodynamics

    1998-12-31

    The main goal of the air and metal hydride battery project was to enhance the performance and manufacturing technology of both electrodes to such a degree that an air-metal hydride battery could become a commercially and technically competitive power source for electric vehicles. By the end of the project it was possible to demonstrate the very first prototype of the air-metal hydride battery at EV scale, achieving all the required design parameters. (orig.)

  17. CEMS Investigations of Fe-Silicide Phases Formed by the Method of Concentration Controlled Phase Selection

    Energy Technology Data Exchange (ETDEWEB)

    Moodley, M. K.; Bharuth-Ram, K. [University of Durban-Westville, Physics Department (South Africa); Waal, H. de; Pretorius, R. [University of Stellenbosch, Physics Department (South Africa)

    2002-03-15

    Conversion electron Moessbauer spectroscopy (CEMS) measurements have been made on Fe-silicide samples formed using the method of concentration controlled phase selection. To prepare the samples a 10 nm layer of Fe{sub 30}M{sub 70} (M=Cr, Ni) was evaporated onto Si(100) surfaces, followed by evaporation of a 60 nm Fe layer. Diffusion of the Fe into the Si substrate and the formation of different Fe-Si phases was achieved by subjecting the evaporated samples to a series of heating stages, which consisted of (a) a 10 min anneal at 800 deg. C plus etch of the residual surface layer, (b) a further 3 hr anneal at 800 deg. C, (c) a 60 mJ excimer laser anneal to an energy density of 0.8 J/cm{sup 2}, and (d) a final 3 hr anneal at 800 deg. C. CEMS measurements were used to track the Fe-silicide phases formed. The CEMS spectra consisted of doublets which, based on established hyperfine parameters, could be assigned to {alpha}- or {beta}-FeSi{sub 2} or cubic FeSi. The spectra showed that {beta}-FeSi{sub 2} had formed already at the first annealing stage. Excimer laser annealing resulted in the formation of a phase with hyperfine parameters consistent with those of {alpha}-FeSi{sub 2}. A further 3 hr anneal at 800 deg. C resulted in complete reversal to the semiconducting {beta}-FeSi{sub 2} phase.

  18. Powder production of U-Mo alloy, HMD process (Hydriding- Milling- Dehydriding)

    Energy Technology Data Exchange (ETDEWEB)

    Pasqualini, E. E.; Garcia, J.H.; Lopez, M.; Cabanillas, E.; Adelfang, P. [Dept. Combustibles Nucleares. Comision Nacional de Energia Atomica, Av. Gral. Paz 1499, 1650 Buenos Aires (Argentina)

    2002-07-01

    Uranium-molybdenum (U-Mo) alloys can be hydrided massively in metastable {gamma} (gamma) phase. The brittle hydride can be milled and dehydrided to acquire the desired size distributions needed for dispersion nuclear fuels. The developments of the different steps of this process called hydriding-milling- dehydriding (HMD Process) are described. Powder production scales for industrial fabrication is easily achieved with conventional equipment, small man-power and low investment. (author)

  19. Powder production of U-Mo alloy, HMD process (Hydriding- Milling- Dehydriding)

    International Nuclear Information System (INIS)

    Pasqualini, E. E.; Garcia, J.H.; Lopez, M.; Cabanillas, E.; Adelfang, P.

    2002-01-01

    Uranium-molybdenum (U-Mo) alloys can be hydrided massively in metastable γ (gamma) phase. The brittle hydride can be milled and dehydrided to acquire the desired size distributions needed for dispersion nuclear fuels. The developments of the different steps of this process called hydriding-milling- dehydriding (HMD Process) are described. Powder production scales for industrial fabrication is easily achieved with conventional equipment, small man-power and low investment. (author)

  20. Photophysical properties of columnar phases formed by triphenylene derivatives

    International Nuclear Information System (INIS)

    Sigal, Herve

    1997-01-01

    This research thesis reports the study of the spectroscopic properties and of the migration of excitation energy in the singlet state in columnar phases formed by alkyloxy and alkylthio derivatives of triphenylene. First, the author studied the spectroscopic properties of chromophores in solutions, and characterized excited states by using computation codes (CS-INDO-CIPSI). Then, by using the excitonic theory in the case of the considered triphenylene derivatives, the author studied the influence of molecular movements and of the intra-columnar order on the spectroscopic properties. In some circumstances, the non-radiative transfer of excitation energy is governed by a mechanism displaying a random evolution. This stochastic movement is studied by using Monte Carlo simulations. The author shows that the energy migration is one-dimensional on short times, and then becomes three-dimensional. The evolution of excitation energy in space and in time is determined [fr

  1. Hydrogenation of cyclohexene with LaNi5−xAlxHn metal hydrides suspended in cyclohexane or ethanol

    NARCIS (Netherlands)

    Snijder, E.D.; Versteeg, G.F.; Swaaij, W.P.M. van

    1993-01-01

    The hydrogenation of cyclohexene on the metal hydride forming alloys LaNi4.8Al0.2, LaNi4.9Al0.1 and LaNi5, all suspended in cyclohexane and LaNi5 suspended in ethanol, has been investigated. Two sources for hydrogen are recognized: hydrogen supplied by the gas phase and hydrogen which is available

  2. Hydrogenation of cyclohexene with LaNi@#5@#-@#x@#Al@#x@#Hn metal hydrides, suspended in cyclohexane or ethanol

    NARCIS (Netherlands)

    Snijder, E.D.; Snijder, E.D.; Versteeg, Geert; van Swaaij, Willibrordus Petrus Maria

    1993-01-01

    The hydrogenation of cyclohexene on the metal hydride forming alloys LaNi4.8Al0.2, LaNi4.9Al0.1 and LaNi5, all suspended in cyclohexane and LaNi5 suspended in ethanol, has been investigated. Two sources for hydrogen are recognized: hydrogen supplied by the gas phase and hydrogen which is available

  3. Oxidation of Alumina-Forming MAX Phases in Turbine Environments

    Science.gov (United States)

    Smialek, James; Garg, Anita; Harder, Bryan; Nesbitt, James; Gabb, Timothy; Gray, SImon

    2017-01-01

    Protective coatings for high temperature turbine components are based on YSZ thermal barriers and oxidation resistant, alumina-forming NiAl or NiCoCrAlY bond coats. Ti2AlC and Cr2AlC MAX phases are thus of special interest because of good oxidation resistance and CTE that can match Al2O3 and YSZ. Their alumina scales grow according to cubic kinetics due to grain growth in the scale, with initial heating dominated by fast TiO2 growth. Protective cubic kinetics are also found in high pressure burner rig tests of MAXthal 211 Ti2AlC, but with reduced rates due to volatile TiO(OH)2 formation in water vapor. YSZ-coatings on bulk Ti2AlC exhibit remarkable durability up to 1300C in furnace tests and at least a 25x life advantage compared to superalloys. At another extreme, Cr2AlC is resistant to low temperature Na2SO4 hot corrosion and exhibits thermal cycling stability bonded to a superalloy disk material. Accordingly, sputtered Cr2AlC coatings on disk specimens prevented hot corrosion detriments on LCF. Breakaway oxidation (Ti2AlC), scale spallation (Cr2AlC), interdiffusion, and processing as coatings still present serious challenges. However the basic properties of MAX phases provide some unusual opportunities for use in high temperature turbines.

  4. Electronic structure, bonding and chemisorption in metallic hydrides

    International Nuclear Information System (INIS)

    Ward, J.W.

    1980-01-01

    Problems that can arise during the cycling steps for a hydride storage system usually involve events at surfaces. Chemisorption and reaction processes can be affected by small amounts of contaminants that may act as catalytic poisons. The nature of the poisoning process can vary greatly for the different metals and alloys that form hydrides. A unifying concept is offered, which satisfactorily correlates many of the properties of transition-metal, rare-earth and actinide hydrides. The metallic hydrides can be differentiated on the basis of electronegativity, metallic radius (valence) and electronic structure. For those systems where there are d (transition metals) or f (early actinides) electrons near the Fermi level a broad range of chemical and catalytic behaviors are found, depending on bandwidth and energy. The more electropositive metals (rare-earths, actinides, transition metals with d > 5) dissolve hydrogen and form hydrides by an electronically somewhat different process, and as a class tend to adsorb electrophobic molecules. The net charge-transfer in either situation is subtle; however, the small differences are responsible for many of the observed structural, chemical, and catalytic properties in these hydride systems

  5. Hydridation of Ti-6Al-4V

    International Nuclear Information System (INIS)

    Domizzi, G; Luppo, M.I; Ortiz, M; Vigna, G

    2004-01-01

    The production of Ti pieces or their alloys through powder metallurgy is an economical alternative that replaces the costly methods commonly used. The Ti-6AI-4V alloy is widely used in the aerospace, chemical and medical industries. The use of powder from the alloy instead of using more pure alloyed titanium powders, further simplifies the production process. The presence of V allows the phase β to stabilize at very low temperatures and both alloys alter the Ti-H equilibrium diagram. This work analyzes to what degree these effects influence the obtaining of powders from this alloy from that of hydridation and dehydridation. Although it has slower kinetics, powders can be produced in times similar to those found for grade 2 Ti since the distribution of hydrides in the sample is uniform and the material is fragile enough for concentrations of approximately 0.7 H/Ti (CW)

  6. Zircaloy-4 hydridation

    International Nuclear Information System (INIS)

    Vizcaino, Pablo

    1997-01-01

    The objectives of this work can be summarized as: 1) To reproduce, by heat treatments, matrix microstructures and hydride morphologies similar to those observed in structural components of the CNA-1 and CNE nuclear power plants; 2) To study the evolution of the mechanical properties of the original material with different hydrogen concentrations, such as microhardness, and its capacity to distinguish these materials; 3) To find parameters that allow to estimate the hydrogen content of a material by quantitative metallographic techniques, to be used as complementary in the study of the radioactive materials from reactors

  7. SELENE - Self-Forming Extensible Lunar EVA Network, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The overall objective of this research effort (Phase I and Phase II) by Scientific Systems Company, Inc. and BBN Technologies is to develop the SELENE network --...

  8. Hydrogen desorption kinetics from zirconium hydride and zirconium metal in vacuum

    International Nuclear Information System (INIS)

    Hu, Xunxiang; Terrani, Kurt A.; Wirth, Brian D.

    2014-01-01

    The kinetics of hydrogen desorption from zirconium hydride is important in many nuclear design and safety applications. In this paper, a coordinated experimental and modeling study has been used to explicitly demonstrate the applicability of existing kinetic theories for hydrogen desorption from zirconium hydride and α-zirconium. A static synthesis method was used to produce δ-zirconium hydride, and the crystallographic phases of the zirconium hydride were confirmed by X-ray diffraction (XRD). Three obvious stages, involving δ-zirconium hydride, a two-phase region, and α-zirconium, were observed in the hydrogen desorption spectra of two zirconium hydride specimens with H/Zr ratios of 1.62 and 1.64, respectively, which were obtained using thermal desorption spectroscopy (TDS). A continuous, one-dimensional, two-phase moving boundary model, coupled with the zero- and second-order kinetics of hydrogen desorption from δ-zirconium hydride and α-zirconium, respectively, has been developed to reproduce the TDS experimental results. A comparison of the modeling predictions with the experimental results indicates that a zero-order kinetic model is valid for description of hydrogen flux away from the δ-hydride phase, and that a second-order kinetic model works well for hydrogen desorption from α-Zr if the activation energy of desorption is optimized to be 70% of the value reported in the literature

  9. The electrochemical impedance of metal hydride electrodes

    DEFF Research Database (Denmark)

    Valøen, Lars Ole; Lasia, Andrzej; Jensen, Jens Oluf

    2002-01-01

    The electrochemical impedance responses for different laboratory type metal hydride electrodes were successfully modeled and fitted to experimental data for AB5 type hydrogen storage alloys as well as one MgNi type electrode. The models fitted the experimental data remarkably well. Several AC......, explaining the experimental impedances in a wide frequency range for electrodes of hydride forming materials mixed with copper powder, were obtained. Both charge transfer and spherical diffusion of hydrogen in the particles are important sub processes that govern the total rate of the electrochemical...... hydrogen absorption/desorption reaction. To approximate the experimental data, equations describing the current distribution in porous electrodes were needed. Indications of one or more parallel reduction/oxidation processes competing with the electrochemical hydrogen absorption/desorption reaction were...

  10. Peculiarities of formation of zirconium aluminides in hydride cycle mode

    International Nuclear Information System (INIS)

    Muradyan, G.N.

    2016-01-01

    The zirconium aluminides are promising structural materials in aerospace, mechanical engineering, chemical industry, etc. They are promising for manufacturing of heat-resistant wires, that will improve the reliability and efficiency of electrical networks. In the present work, the results of study of zirconium aluminides formation in the Hydride Cycle (HC) mode, developed in the Laboratory of high-temperature synthesis of the Institute of Chemical Physics of NAS RA, are described. The formation of zirconium aluminides in HC proceeded according to the reaction xZrH_2+(1-x)Al → alloy Zr_xAl(1-x)+H_2↑. The samples were certified using: chemical analysis to determine the content of hydrogen (pyrolysis method); differential thermal analysis (DTA, derivatograph Q-1500, T_heating = 1000°C, rate 20°C/min); X-ray analysis (XRD, diffractometer DRON-0.5). The influences of the ratio of powders ZrH_2/Al in the reaction mixture, compacting pressure, temperature and heating velocity on the characteristics of the synthesized aluminides were determined. In HC, the solid solutions of Al in Zr, single phase ZrAl_2 and ZrAl_3 aluminides and Zr_3AlH_4.49 hydride were synthesized. Formation of aluminides in HC mode took place by the solid-phase mechanism, without melting of aluminum. During processing, the heating of the initial charge up to 540°C resulted in the decomposition of zirconium hydride (ZrH_2) to HCC ZrH_1.5, that interacted with aluminum at 630°C forming FCC alumohydride of zirconium. Further increase of the temperature up to 800°C led to complete decomposition of the formed alumohydride of zirconium. The final formation of the zirconium aluminide occurred at 1000-1100°C in the end of HC process. Conclusion: in the synthesis of zirconium aluminides, the HC mode has several significant advantages over the conventional modes: lower operating temperatures (1000°C instead of 1800°C); shorter duration (1.5-2 hours instead of tens of hours); the availability of

  11. Understanding hydride formation in Zr-1Nb alloy through microstructural characterization

    International Nuclear Information System (INIS)

    Neogy, S.; Srivastava, D.; Tewari, R.; Singh, R.N.; Dey, G.K.; De, P.K.; Banerjee, S.

    2003-07-01

    In this study the experimental results of hydride formation and their microstructure evolution in Zr-1Nb alloy is presented. This Zr-1Nb binary alloy and other Zr-1 Nb based ternary and quaternary alloys are being used as fuel tube materials and have the potential for meeting the requirement of high burn up fuel. Hydriding of Zr-1Nb alloy having a microstructure comprising equiaxed α grains and a uniform distribution of spherical particles of the β phase has been carried out in this study. The specimens have been hydrided by gaseous charging method to different hydrogen levels. The microstructures of hydrided samples were examined as a function of hydrogen content. The formation of δ hydride in slow cooled specimens and formation of γ hydride in rapidly cooled specimens has been studied with their morphology, habit plane and orientation relationship with the α matrix in view. The habit planes of either type of hydride phase has been determined and compared with those observed in other Zr-Nb alloys. The orientation relationship between the α matrix and the δ hydride was found to be the following: (0001) α // (111) δ and [1120] α // [110] δ . The orientation relationship between the α matrix and the γ hydride was of the following type: (0001) α // (111) γ and [1120] α // [110] γ . The internal structure of both types of hydride has been examined. The effect of the presence of the spherical β phase particles in the a matrix on the growth of the hydride plates has been investigated. (author)

  12. Multidimensional simulations of hydrides during fuel rod lifecycle

    International Nuclear Information System (INIS)

    Stafford, D.S.

    2015-01-01

    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. - Highlights: • We extend BISON fuel performance code to simulate lifecycle of fuel rods. • We model hydrogen evolution in cladding from reactor through dry storage. • We validate 1D simulations of hydrogen evolution against experiments. • We show results of 2D axisymmetric simulations predicting hydride formation. • We show how our model predicts formation of a hydride rim in the cladding.

  13. On the phase form of a deformation quantization with separation of variables

    Science.gov (United States)

    Karabegov, Alexander

    2016-06-01

    Given a star product with separation of variables on a pseudo-Kähler manifold, we obtain a new formal (1, 1)-form from its classifying form and call it the phase form of the star product. The cohomology class of a star product with separation of variables equals the class of its phase form. We show that the phase forms can be arbitrary and they bijectively parametrize the star products with separation of variables. We also describe the action of a change of the formal parameter on a star product with separation of variables, its formal Berezin transform, classifying form, phase form, and canonical trace density.

  14. Determination and Uncertainty Analysis of Inorganic Arsenic in Husked Rice by Solid Phase Extraction and Atomic Absorption Spectrometry with Hydride Generation.

    Science.gov (United States)

    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.

  15. Erbium hydride decomposition kinetics.

    Energy Technology Data Exchange (ETDEWEB)

    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.

  16. Complex Hydrides for Hydrogen Storage

    Energy Technology Data Exchange (ETDEWEB)

    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.

  17. Metal Hydride assited contamination on Ru/Si surfaces

    NARCIS (Netherlands)

    Pachecka, Malgorzata; Lee, Christopher James; Sturm, Jacobus Marinus; Bijkerk, Frederik

    2013-01-01

    In extreme ultraviolet lithography (EUVL) residual tin, in the form of particles, ions, and atoms, can be deposited on nearby EUV optics. During the EUV pulse, a reactive hydrogen plasma is formed, which may be able to react with metal contaminants, creating volatile and unstable metal hydrides that

  18. Precipitation of γ-zirconium hydride in zirconium

    International Nuclear Information System (INIS)

    Carpenter, G.J.C.

    1978-01-01

    A mechanism for the precipitation of γ-zirconium hydride in zirconium is presented which does not require the diffusion of zirconium. The transformation is completed by shears caused by 1/3 (10 anti 10) Shockley partial dislocations on alternate zirconium basal planes, either by homogeneous nucleation or at lattice imperfections. Homogeneous nucleation is considered least likely in view of the large nucleation barrier involved. Hydrides may form at dislocations by the generation of partials by means of either a pole or ratchet mechanism. The former requires dislocations with a component of Burgers vector along the c-axis, but contrast experiments show that these are not normally observed in annealed zirconium. It is therefore most likely that intragranular hydrides form at the regular 1/3 (11 anti 20) dislocations, possibly by means of a ratchet mechanism. Contrast experiments in the electron microscope show that the precipitates have a shear character consistent with the mechanism suggested. The possibility that the shear dislocations associated with the hydrides are emissary dislocations is considered and a model suggested in which this function is satisfied together with the partial relief of misfit stresses. The large shear strains associated with the precipitation mechanism may play an important role in the preferential orientation of hydrides under stress

  19. Dual phase magnetic material component and method of forming

    Science.gov (United States)

    Dial, Laura Cerully; DiDomizio, Richard; Johnson, Francis

    2017-04-25

    A magnetic component having intermixed first and second regions, and a method of preparing that magnetic component are disclosed. The first region includes a magnetic phase and the second region includes a non-magnetic phase. The method includes mechanically masking pre-selected sections of a surface portion of the component by using a nitrogen stop-off material and heat-treating the component in a nitrogen-rich atmosphere at a temperature greater than about 900.degree. C. Both the first and second regions are substantially free of carbon, or contain only limited amounts of carbon; and the second region includes greater than about 0.1 weight % of nitrogen.

  20. Hydriding failure in water reactor fuel elements

    International Nuclear Information System (INIS)

    Sah, D.N.; Ramadasan, E.; Unnikrishnan, K.

    1980-01-01

    Hydriding of the zircaloy cladding has been one of the important causes of failure in water reactor fuel elements. This report reviews the causes, the mechanisms and the methods for prevention of hydriding failure in zircaloy clad water reactor fuel elements. The different types of hydriding of zircaloy cladding have been classified. Various factors influencing zircaloy hydriding from internal and external sources in an operating fuel element have been brought out. The findings of post-irradiation examination of fuel elements from Indian reactors, with respect to clad hydriding and features of hydriding failure are included. (author)

  1. Delayed Hydride Cracking in Zr-2.5Nb Tubes with the Direction of An Approach to Temperature

    International Nuclear Information System (INIS)

    Kim, Young Suk; Im, Kyung Soo; Kim, Kang Soo; Ahn, Sang Bok; Cheong, Yong Moo

    2006-01-01

    One of the unique features of delayed hydride cracking (DHC) of zirconium alloys is that the DHC velocity (DHCV) of zirconium alloys strongly depends on the path to the test temperature. Ambler reported that the DHCV of Zr-2.5Nb tubes at temperatures above 180 .deg. C depended upon the direction of an approach to the test temperatures, and reported on a presence of the DHC arrest temperature or TDAT above which the DHCV decreased upon an approach to the test temperature by a heating. Ambler proposed a hydrogen transfer from the bulk to the crack tip assuming that the hydrides formed at the crack tip and in the bulk region are fully constrained and partially constrained at the crack tip, respectively. In other words, the terminal solid solubility (TSS) of hydrogen would be governed by elastic strain energy induced by the precipitating hydrides, leading to a higher TSS in the bulk region than that at the crack tip. In a sense, his assumption that the hydrogen concentration is higher in the bulk region than that at the crack tip due to a higher TSS in the bulk region is, in a way, similar to Kim's DHC model. Even though Ambler assumed a different strain energy of the matrix hydrides with the direction of an approach to the test temperature, the peak temperature, hydrogen concentration and the hydride phase, a feasible rationale for this assumption is yet to be given. In this study, a path dependence of DHC velocity of Zr-2.5Nb tubes will be investigated using Kim's DHC model where a driving force for DHC is the supersaturated hydrogen concentration between the crack tip and the bulk region. To this ends, the furnace cooled and water-quenched Zr-2.5Nb specimens were subjected to DHC tests at different test temperatures that were approached by a heating or by a cooling. Kim's DHC model predicts that the water-quenched Zr- 2.5Nb will have DHC crack growth even at temperatures above 180 .deg. C where the furnace-cooled Zr-2.5Nb will not. This experiment will provide

  2. Delayed Hydride Cracking in Zr-2.5Nb Tubes with the Direction of An Approach to Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Young Suk; Im, Kyung Soo; Kim, Kang Soo; Ahn, Sang Bok; Cheong, Yong Moo [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    2006-07-01

    One of the unique features of delayed hydride cracking (DHC) of zirconium alloys is that the DHC velocity (DHCV) of zirconium alloys strongly depends on the path to the test temperature. Ambler reported that the DHCV of Zr-2.5Nb tubes at temperatures above 180 .deg. C depended upon the direction of an approach to the test temperatures, and reported on a presence of the DHC arrest temperature or TDAT above which the DHCV decreased upon an approach to the test temperature by a heating. Ambler proposed a hydrogen transfer from the bulk to the crack tip assuming that the hydrides formed at the crack tip and in the bulk region are fully constrained and partially constrained at the crack tip, respectively. In other words, the terminal solid solubility (TSS) of hydrogen would be governed by elastic strain energy induced by the precipitating hydrides, leading to a higher TSS in the bulk region than that at the crack tip. In a sense, his assumption that the hydrogen concentration is higher in the bulk region than that at the crack tip due to a higher TSS in the bulk region is, in a way, similar to Kim's DHC model. Even though Ambler assumed a different strain energy of the matrix hydrides with the direction of an approach to the test temperature, the peak temperature, hydrogen concentration and the hydride phase, a feasible rationale for this assumption is yet to be given. In this study, a path dependence of DHC velocity of Zr-2.5Nb tubes will be investigated using Kim's DHC model where a driving force for DHC is the supersaturated hydrogen concentration between the crack tip and the bulk region. To this ends, the furnace cooled and water-quenched Zr-2.5Nb specimens were subjected to DHC tests at different test temperatures that were approached by a heating or by a cooling. Kim's DHC model predicts that the water-quenched Zr- 2.5Nb will have DHC crack growth even at temperatures above 180 .deg. C where the furnace-cooled Zr-2.5Nb will not. This experiment

  3. Chemical Hydride Slurry for Hydrogen Production and Storage

    Energy Technology Data Exchange (ETDEWEB)

    McClaine, Andrew W

    2008-09-30

    The purpose of this project was to investigate and evaluate the attractiveness of using a magnesium chemical hydride slurry as a hydrogen storage, delivery, and production medium for automobiles. To fully evaluate the potential for magnesium hydride slurry to act as a carrier of hydrogen, potential slurry compositions, potential hydrogen release techniques, and the processes (and their costs) that will be used to recycle the byproducts back to a high hydrogen content slurry were evaluated. A 75% MgH2 slurry was demonstrated, which was just short of the 76% goal. This slurry is pumpable and storable for months at a time at room temperature and pressure conditions and it has the consistency of paint. Two techniques were demonstrated for reacting the slurry with water to release hydrogen. The first technique was a continuous mixing process that was tested for several hours at a time and demonstrated operation without external heat addition. Further work will be required to reduce this design to a reliable, robust system. The second technique was a semi-continuous process. It was demonstrated on a 2 kWh scale. This system operated continuously and reliably for hours at a time, including starts and stops. This process could be readily reduced to practice for commercial applications. The processes and costs associated with recycling the byproducts of the water/slurry reaction were also evaluated. This included recovering and recycling the oils of the slurry, reforming the magnesium hydroxide and magnesium oxide byproduct to magnesium metal, hydriding the magnesium metal with hydrogen to form magnesium hydride, and preparing the slurry. We found that the SOM process, under development by Boston University, offers the lowest cost alternative for producing and recycling the slurry. Using the H2A framework, a total cost of production, delivery, and distribution of $4.50/kg of hydrogen delivered or $4.50/gge was determined. Experiments performed at Boston

  4. A computer model for hydride blister growth in zirconium alloys

    International Nuclear Information System (INIS)

    White, A.J.; Sawatzky, A.; Woo, C.H.

    1985-06-01

    The failure of a Zircaloy-2 pressure tube in the Pickering unit 2 reactor started at a series of zirconium hydride blisters on the outside of the pressure tube. These blisters resulted from the thermal diffusion of hydrogen to the cooler regions of the pressure tube. In this report the physics of thermal diffusion of hydrogen in zirconium is reviewed and a computer model for blister growth in two-dimensional Cartesian geometry is described. The model is used to show that the blister-growth rate in a two-phase zirconium/zirconium-hydride region does not depend on the initial hydrogen concentration nor on the hydrogen pick-up rate, and that for a fixed far-field temperature there is an optimum pressure-type/calandria-tube contact temperature for growing blisters. The model described here can also be used to study large-scale effects, such as hydrogen-depletion zones around hydride blisters

  5. Mechanical properties and fracture of titanium hydrides

    International Nuclear Information System (INIS)

    Koketsu, Hideyuki; Taniyama, Yoshihiro; Yonezu, Akio; Cho, Hideo; Ogawa, Takeshi; Takemoto, Mikio; Nakayama, Gen

    2006-01-01

    Titanium hydrides tend to suffer fracture when their thicknesses reach a critical thickness. Morphology and mechanical property of the hydrides are, however, not well known. The study aims to reveal the hydride morphology and fracture types of the hydrides. Chevron shaped plate hydrides were found to be produced on the surface of pure titanium (Grade 1) and Grade 7 titanium absorbing hydrogen. There were tree types of fracture of the hydrides, i.e., crack in hydride layer, exfoliation of the layer and shear-type fracture of the hydride plates, during the growth of the hydrides and deformation. We next estimated the true stress-strain curves of the hydrides on Grade 1 and 7 titanium using the dual Vickers indentation method, and the critical strain causing the Mode-I fine crack by indentation. Fracture strength and strain of the hydrides in Grade 1 titanium were estimated as 566 MPa and 4.5%, respectively. Those of the hydride in Grade 7 titanium were 498 MPa and 16%. Though the fracture strains estimated from the plastic instability of true stress-strain curves were approximately the half of those estimated by finite element method, the titanium hydrides were estimated to possess some extent of toughness or plastic deformation capability. (author)

  6. Formation of metastable phases in magnesium–titanium system by high-pressure torsion and their hydrogen storage performance

    International Nuclear Information System (INIS)

    Edalati, Kaveh; Emami, Hoda; Staykov, Aleksandar; Smith, David J.; Akiba, Etsuo; Horita, Zenji

    2015-01-01

    No binary phases exist in the Mg–Ti binary equilibrium phase diagram and the two elements are totally immiscible even in liquid form. This study shows that four metastable phases (two with the bcc and fcc structures and two with the hcp structures) are formed in the Mg–Ti system by severe plastic deformation (SPD) through the process of high-pressure torsion (HPT). Investigation of hydrogenation properties reveals that these metastable phases are decomposed to pure Mg and Ti during heating before they can absorb the hydrogen in the form of ternary Mg–Ti hydrides. First-principles calculations show that the hydrogenation reaction should occur thermodynamically, and ternary Mg–Ti hydrides with the cubic structure should form at low temperature. However, the slow kinetics for this reaction appears to be the limiting step. Calculations show that the binding energy of hydrogen increases and the thermodynamic stability of hydrides undesirably increases by addition of Ti to Mg

  7. Macrodefect-free, large, and thick GaN bulk crystals for high-quality 2–6 in. GaN substrates by hydride vapor phase epitaxy with hardness control

    Science.gov (United States)

    Fujikura, Hajime; Konno, Taichiro; Suzuki, Takayuki; Kitamura, Toshio; Fujimoto, Tetsuji; Yoshida, Takehiro

    2018-06-01

    On the basis of a novel crystal hardness control, we successfully realized macrodefect-free, large (2–6 in.) and thick +c-oriented GaN bulk crystals by hydride vapor phase epitaxy. Without the hardness control, the introduction of macrodefects including inversion domains and/or basal-plane dislocations seemed to be indispensable to avoid crystal fracture in GaN growth with millimeter thickness. However, the presence of these macrodefects tended to limit the applicability of the GaN substrate to practical devices. The present technology markedly increased the GaN crystal hardness from below 20 to 22 GPa, thus increasing the available growth thickness from below 1 mm to over 6 mm even without macrodefect introduction. The 2 and 4 in. GaN wafers fabricated from these crystals had extremely low dislocation densities in the low- to mid-105 cm‑2 range and low off-angle variations (2 in.: <0.1° 4 in.: ∼0.2°). The realization of such high-quality 6 in. wafers is also expected.

  8. Tritium immobilization and packaging using metal hydrides

    International Nuclear Information System (INIS)

    Holtslander, W.J.; Yaraskavitch, J.M.

    1981-04-01

    Tritium recovered from CANDU heavy water reactors will have to be packaged and stored in a safe manner. Tritium will be recovered in the elemental form, T 2 . Metal tritides are effective compounds in which to immobilize the tritium as a stable non-reactive solid with a high tritium capacity. The technology necessary to prepare hydrides of suitable metals, such as titanium and zirconium, have been developed and the properties of the prepared materials evaluated. Conceptual designs of packages for containing metal tritides suitable for transportation and long-term storage have been made and initial testing started. (author)

  9. Trapping interference effects of arsenic, antimony and bismuth hydrides in collection of selenium hydride within iridium-modified transversally-heated graphite tube atomizer

    Energy Technology Data Exchange (ETDEWEB)

    Furdikova, Zuzana [Department of Environmental Chemistry and Technology, Faculty of Chemistry, Brno University of Technology, Purkynova 118, CZ-61200 Brno (Czech Republic); Institute of Analytical Chemistry of the Academy of Sciences of the Czech Republic v.v.i., Veveri 97, CZ-60200, Brno (Czech Republic); Docekal, Bohumil [Institute of Analytical Chemistry of the Academy of Sciences of the Czech Republic v.v.i., Veveri 97, CZ-60200, Brno (Czech Republic)], E-mail: docekal@iach.cz

    2009-04-15

    Interference effects of co-generated hydrides of arsenic, antimony and bismuth on trapping behavior of selenium hydride (analyte) within an iridium-modified, transversely heated graphite tube atomizer (THGA) were investigated. A twin-channel hydride generation system was used for independent separate generation and introduction of analyte and interferent hydrides, i.e. in a simultaneous and/or sequential analyte-interferent and interferent-analyte mode of operation. The influence of the analyte and modifier mass, interferent amount, trapping temperature and composition of the gaseous phase was studied. A simple approach for the elimination of mutual interference effects by modification of the gaseous phase with oxygen in a substoichiometric ratio to chemically generated hydrogen is proposed and the suppression of these interference effects is demonstrated. A hypothesis on the mechanism of trapping and mutual interference effects is drawn.

  10. High-pressure hydriding of Zircaloy

    International Nuclear Information System (INIS)

    Kim, Y.S.

    1996-01-01

    The hydriding characteristics of Zircaloy-2(Zry), sponge zirconium (as a liner on Zry plate), and crystal-bar zirconium exposed to pure H 2 at 0.1 MPa or 7 MPa and 400 C were determined in a thermogravimetric apparatus. The morphology of the hydrided specimens was also examined by optical microscopy. For all specimen types, the rate of hydriding in 7 MPa H 2 was two orders of magnitude greater than in 0.1 MPa H 2 . For Zry, uniform bulk hydriding was revealed by hydride precipitates at room temperature and on one occasion, a sunburst hydride. In addition, all specimen types exhibited a hydride surface layer. In a duplex Zry/sponge-Zr specimen, Zry is more heavily hydrided than the sponge Zr layer. (orig.)

  11. Hydride Olefin complexes of tantalum and niobium

    NARCIS (Netherlands)

    Klazinga, Aan Hendrik

    1979-01-01

    This thesis describes investigations on low-valent tantalum and niobium hydride and alkyl complexes, particularly the dicyclopentadienyl tantalum hydride olefin complexes Cp2Ta(H)L (L=olefin). ... Zie: Summary

  12. Planktic foraminifera form their shells via metastable carbonate phases

    OpenAIRE

    Jacob, D. E.; Wirth, R.; Agbaje, O. B. A.; Branson, O.; Eggins, S. M.

    2017-01-01

    The calcium carbonate shells of planktic foraminifera provide our most valuable geochemical archive of ocean surface conditions and climate spanning the last 100 million years, and play an important role in the ocean carbon cycle. These shells are preserved in marine sediments as calcite, the stable polymorph of calcium carbonate. Here, we show that shells of living planktic foraminifers Orbulina universa and Neogloboquadrina dutertrei originally form from the unstable calcium carbonate polym...

  13. Complex Metal Hydrides for Hydrogen, Thermal and Electrochemical Energy Storage

    DEFF Research Database (Denmark)

    Moller, Kasper T.; Sheppard, Drew; Ravnsbaek, Dorthe B.

    2017-01-01

    Hydrogen has a very diverse chemistry and reacts with most other elements to form compounds, which have fascinating structures, compositions and properties. Complex metal hydrides are a rapidly expanding class of materials, approaching multi-functionality, in particular within the energy storage...... inspiration to solve the great challenge of our time: efficient conversion and large-scale storage of renewable energy....... field. This review illustrates that complex metal hydrides may store hydrogen in the solid state, act as novel battery materials, both as electrolytes and electrode materials, or store solar heat in a more efficient manner as compared to traditional heat storage materials. Furthermore, it is highlighted...

  14. Metal hydride compositions and lithium ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Young, Kwo; Nei, Jean

    2018-04-24

    Heterogeneous metal hydride (MH) compositions comprising a main region comprising a first metal hydride and a secondary region comprising one or more additional components selected from the group consisting of second metal hydrides, metals, metal alloys and further metal compounds are suitable as anode materials for lithium ion cells. The first metal hydride is for example MgH.sub.2. Methods for preparing the composition include coating, mechanical grinding, sintering, heat treatment and quenching techniques.

  15. On the phase form of a deformation quantization with separation of variables

    OpenAIRE

    Karabegov, Alexander

    2015-01-01

    Given a star product with separation of variables on a pseudo-Kaehler manifold, we obtain a new formal (1,1)-form from its classifying form and call it the phase form of the star product. The cohomology class of a star product with separation of variables equals the class of its phase form. We show that the phase forms can be arbitrary and they bijectively parametrize the star products with separation of variables. We also describe the action of a change of the formal parameter on a star prod...

  16. Evaluation of hydride blisters in zirconium pressure tube in CANDU reactor

    International Nuclear Information System (INIS)

    Cheong, Y. M.; Kim, Y. S.; Gong, U. S.; Kwon, S. C.; Kim, S. S.; Choo, K.N.

    2000-09-01

    When the garter springs for maintaining the gap between the pressure tube and the calandria tube are displaced in the CANDU reactor, the sagging of pressure tube results in a contact to the calandria tube. This causes a temperature difference between the inner and outer surface of the pressure tube. The hydride can be formed at the cold spot of outer surface and the volume expansion by hydride dormation causes the blistering in the zirconium alloys. An incident of pressure tube rupture due to the hydride blisters had happened in the Canadian CANDU reactor. This report describes the theoretical development and models on the formation and growth of hydride blister and some experimental results. The evaluation methodology and non-destructive testing for hydride blister in operating reactors are also described

  17. Roles of texture in controlling oxidation, hydrogen ingress and hydride formation in Zr alloys

    International Nuclear Information System (INIS)

    Szpunar, Jerzy A.; Qin, Wen; Li, Hualong; Kumar, Kiran

    2011-01-01

    Experimental observations shows that the oxide formed on Zr alloys are strongly textured. The texture and grain-boundary characteristics of oxide are dependent on the texture of metal substrate. Computer simulation and thermodynamic modeling clarify the effect of metal substrate on structure of oxide film, and intrinsic factors affecting the microstructure. Models of diffusion process of hydrogen atoms and oxygen diffusion through oxide are presented. Both intra-granular and inter-granular hydrides were found following (0001) α-Zr //(111) δ-ZrH1.5 relationship. The through-thickness texture inhomogeneity in cladding tubes, the effects of hoop stress on the hydride orientation and the formation of interlinked hydride structure were studied. A thermodynamic model was developed to analyze the nucleation and the stress-induced reorientation of intergranular hydrides. These works provide a framework for understanding the oxidation, the hydrogen ingress and the hydride formation in Zr alloys. (author)

  18. Evaluation of hydride blisters in zirconium pressure tube in CANDU reactor

    Energy Technology Data Exchange (ETDEWEB)

    Cheong, Y M; Kim, Y S; Gong, U S; Kwon, S C; Kim, S S; Choo, K N

    2000-09-01

    When the garter springs for maintaining the gap between the pressure tube and the calandria tube are displaced in the CANDU reactor, the sagging of pressure tube results in a contact to the calandria tube. This causes a temperature difference between the inner and outer surface of the pressure tube. The hydride can be formed at the cold spot of outer surface and the volume expansion by hydride dormation causes the blistering in the zirconium alloys. An incident of pressure tube rupture due to the hydride blisters had happened in the Canadian CANDU reactor. This report describes the theoretical development and models on the formation and growth of hydride blister and some experimental results. The evaluation methodology and non-destructive testing for hydride blister in operating reactors are also described.

  19. First-principles calculations of niobium hydride formation in superconducting radio-frequency cavities

    Science.gov (United States)

    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.

  20. First-principles calculations of niobium hydride formation in superconducting radio-frequency cavities

    International Nuclear Information System (INIS)

    Ford, Denise C; Cooley, Lance D; Seidman, David N

    2013-01-01

    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. (paper)

  1. Modeling of electrochemical hydrogen storage in metal hydride electrodes

    NARCIS (Netherlands)

    Ledovskikh, A.; Danilov, D.; Vermeulen, P.; Notten, P.H.L.

    2010-01-01

    The recently presented Electrochemical Kinetic Model (EKM), describing the electrochemical hydrogen storage in hydride-forming materials, has been extended by the description of the solid/electrolyte interface, i.e. the charge transfer kinetics and electrical double layer charging. A complete set of

  2. Modeling of electrochemical hydrogen storage in metal hydride electrodes

    NARCIS (Netherlands)

    Ledovskikh, A.; Danilov, D.; Vermeulen, P.; Notten, P.H.L.

    2010-01-01

    The recently presented electrochemical kinetic model, describing the electrochemical hydrogen storage in hydride-forming materials, was extended by the description of the solid/electrolyte interface, i.e., the charge-transfer kinetics and electrical double-layer charging. A complete set of equations

  3. Two-phase flows in the formed tornado funnel

    Science.gov (United States)

    Sinkevich, O. A.; Bortsova, A. A.

    2017-10-01

    At present, it is obvious that the problem of the tornado is important not only for our planetЮ to determine the conditions for the formation of a tornado, it is required to take into account a number of hydrodynamic and plasma processes [1 - 6]. Along to prediction of a tornado generation conditions [1 - 3] it is necessary to evaluate the characteristics of its quasi-stationary motion in a formed funnel: the mass of the moving moist air involved in the funnel and the size and form of the funnel. For a complete description of the phenomena, it is necessary to involve numerical calculations. We note that even for numerical calculations using powerful computers, the problem is very difficult because of the need to calculate multiphase turbulent flows with free, self-organizing boundaries [1, 6]. However, “strict” numerical calculations, it is impossible to do without the use of many, often mutually exclusive, models. For example, how to choice an adequate model of turbulence (algebraic, k-ε model, etc.) or the use of additional, often not accepted, hypotheses about certain processes used in calculations (mechanisms on the nature of moisture condensation, etc.). Therefore, along with numerical calculations of such flows, modeling problems that allow an exact solution and allow to determine the most important and observed characteristics of a tornado.

  4. Influence of metallurgical variables on the velocity of crack propagation by delayed hydride cracking (DHC) in Zr-Nb

    International Nuclear Information System (INIS)

    Cirimelo, Pablo G.

    2002-01-01

    In the present thesis work the propagation of cracks due to the delayed hydride cracking (DHC) mechanism in Zr-2,5 % Nb pressure tubes is analyzed. For this purpose two different type of tubes of different origin were used: CANDU type (Canada) and RBMK type (Russia). The analyzed figurative parameters were: critical temperature Tc (highest temperature at which DHC phenomenon could occur) and crack propagation velocity by DHC, Vp, in the axial direction. The influence of the memory effect (phenomenon proper of hydride precipitation) was studied, as well as the type of cracks (fatigue or DHC) on Tc. However, no influence of these effects was found. Instead, it was found that Tc varies with the hydrogen content of the specimen, in agreement with previous works. Samples obtained from tubes with different microstructures and similar amounts of hydrogen presented similar Tc values. It was also shown that DHC propagation could occur without precipitated hydrides in the volume. Besides, Vp determinations were performed in temperature ranges and hydrogen amounts of technological importance. Two techniques were set up in order to determine Vp at different temperatures in a single specimen, thus saving time and material. An Arrhenius type variation was found for Vp vs. temperature, for temperatures lower than that corresponding to precipitation. For higher temperatures, but lower than the critical one, velocity decreases with temperature. Determination of Vp vs. temperature was performed for the two above-mentioned materials, whose microstructure and hardness were previously characterized. For RBMK material, which presents a spheroidal β phase, the velocity was lower than the corresponding to CANDU material, in which β phase is formed by continuous plates. In addition, yield stress σ Y is lower in RBMK material, which presents lower Vp. However, it is considered that the effect of microstructure is more important on Vp since it highly affects diffusion of hydrogen from the

  5. Hydride-induced degradation of hoop ductility in textured zirconium-alloy tubes: A theoretical analysis

    International Nuclear Information System (INIS)

    Qin, W.; Szpunar, J.A.; Kozinski, J.

    2012-01-01

    Hydride-induced degradation of hoop ductility in Zr-alloy tubular components has been studied for many years because of its importance in the nuclear industry. In this paper the role of intergranular and intragranular δ-hydrides in the degradation of ductility of the textured Zr-alloy tubes is investigated. The correlation among hydride distribution, orientation and morphology in the tubes is formulated based on thermodynamic modeling, and then analyzed. The results show that the applied stress, the crystallographic texture of α-Zr matrix, the grain-boundary structure, and the morphology and size of Zr grains simultaneously govern the site preference and the orientation of hydrides. A criterion is proposed to determine the threshold stress of hydride reorientation. The hoop ductility of the hydrided Zr tubes is discussed using the concept of macroscopic fracture strain. It is shown that the intergranular hydrides may be more deleterious to ductility than the intragranular ones. This work defines a general framework for understanding the relation of the microstructure of hydride-forming materials to embrittlement.

  6. The effect of stress state on zirconium hydride reorientation

    Science.gov (United States)

    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

  7. Simultaneous analysis of arsenic, antimony, selenium and tellurium in environmental samples using hydride generation ICPMS

    International Nuclear Information System (INIS)

    Jankowski, L.M.; Breidenbach, R.; Bakker, I.J.I.; Epema, O.J.

    2009-01-01

    Full text: A quantitative method for simultaneous analysis of arsenic, antimony, selenium and tellurium in environmental samples is being developed using hydride generation ICPMS. These elements must be first transformed into hydride-forming oxidation states. This is particularly challenging for selenium and antimony because selenium is susceptible to reduction to the non-hydride-forming elemental state and antimony requires strong reducing conditions. The effectiveness of three reducing agents (KI, thiourea, cysteine) is studied. A comparison is made between addition of reducing agent to the sample and addition of KI to the NaBH 4 solution. Best results were obtained with the latter approach. (author)

  8. The relation of double peaks, observed in quartz hydride atomizers, to the fate of free analyte atoms in the determination of arsenic and selenium by atomic absorption spectrometry

    International Nuclear Information System (INIS)

    D'Ulivo, Alessandro; Dedina, Jiri

    2002-01-01

    The mechanism at the origin of double peaks formation in quartz hydride atomizers were investigated by continuous flow hydride generation atomic absorption spectrometry. Arsenic and selenium were used as model analytes. The effect of atomization mode (flame-in-gas-shield (FIGS), miniature diffusion flame and double flame (DF)) and some experimental parameters as oxygen supply rate for microflame and the distance from atomization to free atoms detection point, were investigated on the shape of both analytical signals and calibration graphs. Rollover of calibration graphs and double peak formation are strictly related each to the other and could be observed only in FIGS atomizer mode under some particular conditions. A mechanism based on incomplete atomization of hydrides cannot explain the collected experimental evidences because the microflame of FIGS is able to produce quantitative atomization of large amount of hydrides even at supply rate of oxygen close to extinction threshold of microflame. The heterogeneous gas-solid reactions between finely dispersed particles, formed by free atom recombination, and the free atoms in the gaseous phase are at the origin of double peak formation

  9. Dislocation/hydrogen interaction mechanisms in hydrided nanocrystalline palladium films

    International Nuclear Information System (INIS)

    Amin-Ahmadi, Behnam; Connétable, Damien; Fivel, Marc; Tanguy, Döme; Delmelle, Renaud; Turner, Stuart; Malet, Loic; Godet, Stephane; Pardoen, Thomas; Proost, Joris; Schryvers, Dominique

    2016-01-01

    The nanoscale plasticity mechanisms activated during hydriding cycles in sputtered nanocrystalline Pd films have been investigated ex-situ using advanced transmission electron microscopy techniques. The internal stress developing within the films during hydriding has been monitored in-situ. Results showed that in Pd films hydrided to β-phase, local plasticity was mainly controlled by dislocation activity in spite of the small grain size. Changes of the grain size distribution and the crystallographic texture have not been observed. In contrast, significant microstructural changes were not observed in Pd films hydrided to α-phase. Moreover, the effect of hydrogen loading on the nature and density of dislocations has been investigated using aberration-corrected TEM. Surprisingly, a high density of shear type stacking faults has been observed after dehydriding, indicating a significant effect of hydrogen on the nucleation energy barriers of Shockley partial dislocations. Ab-initio calculations of the effect of hydrogen on the intrinsic stable and unstable stacking fault energies of palladium confirm the experimental observations.

  10. Hydrogen storage in complex hydrides

    International Nuclear Information System (INIS)

    Lupu, D.; Biris, A. R.; Misan, I.

    2005-01-01

    Full text: Hydrogen storage is a key enabling technology for the advancement of hydrogen and fuel cell power technologies in mobile and stationary applications. A relevant role of the fuel cell powered vehicles on the market of the transportation systems will be achieved only if the research and development of on-board vehicular hydrogen storage are able to allow a driving range of at least 500 km. The on-board hydrogen storage systems are more challenging due to the space, weight and cost limitations. This range of autonomy between refueling requires materials able to store at least 6.5% weight hydrogen, available at moderate pressures, at the working temperature of the fuel cells and with acceptable cycling stability. The intensive research on the hydrogen storage in alloys and intermetallic of the LaNi 5 , FeTi or Laves phase type compounds, which started more than three decades ago did not resulted in materials of more than about 3% H storage capacities. The 7.5% H content of the Mg hydride is still of attracting interest but though the absorption has been achieved at lower temperatures by ball milling magnesium with various amounts of nickel, the desorption can not be attained at 1 bar H 2 below 280 deg. C and the kinetics of the process is too slow. In the last decade, the attention is focused on another class of compounds, the complex hydrides of aluminum with alkali metals (alanates), due to their high hydrogen content. It was found that doping with Ti-based catalysts improve the hydrogenation/dehydrogenation conditions of NaAlH 4 . Later on, it was shown that ball milling with solid state catalysts greatly improve the hydrogen desorption kinetics of NaAlH 4 , and this also helps to the rehydriding process. The hydrogen desorption from NaAlH 4 occurs in three steps, it shows a reversible storage capacity of 5.5% H and this led to further research work for a better knowledge of its application relating properties. In this work, ball milling experiments on Na

  11. Application of acoustic emission to hydride cracking

    International Nuclear Information System (INIS)

    Sagat, S.; Ambler, J.F.R.; Coleman, C.E.

    1986-07-01

    Acoustic emission has been used for over a decade to study delayed hydride cracking (DHC) in zirconium alloys. At first acoustic emission was used primarily to detect the onset of DHC. This was possible because DHC was accompanied by very little plastic deformation of the material and furthermore the amplitudes of the acoustic pulses produced during cracking of the brittle hydride phase were much larger than those from dislocation motion and twinning. Acoustic emission was also used for measuring crack growth when it was found that for a suitable amplitude threshold, the total number of acoustic emission counts was linearly related to the cracked area. Once the proportionality constant was established, the acoustic counts could be converted to the crack length. Now the proportionality between the count rate and the crack growth rate is used to provide feedback between the crack length and the applied load, using computer technology. In such a system, the stress at the crack tip can be maintained constant during the test by adjusting the applied load as the crack progresses, or it can be changed in a predetermined manner, for example, to measure the threshold stress for cracking

  12. Examination of parameters affecting overload fracture behavior of flaw-tip hydrides in Zr-2.5Nb pressure tubes in Candu reactors

    International Nuclear Information System (INIS)

    Cui, J.; Shek, G.K.; Wang, Z.R.

    2007-01-01

    Service-induced flaws in Zr-2.5Nb alloy pressure tubes in Candu (Canada Deuterium Uranium Reactors) nuclear reactors are susceptible to a crack initiation and growth mechanism known as Delayed Hydride Cracking (DHC), which is a repetitive process that involves hydrogen diffusion, hydride precipitation, growth and fracture of a hydride region at the flaw-tip under a constant load. Crack initiation may also occur under another loading condition when the hydride region is subjected to an overload. An overload occurs when the hydride region at the flaw tip is loaded to a stress higher than that at which this region is formed such as when the reactor experiences a transient pressure higher than the normal operating pressure where the hydride region is formed. Flaw disposition requires justification that the hydride region overload will not fracture the hydride region, and initiate DHC. In this work, monotonically increasing load experiments were performed on unirradiated Zr-2.5Nb pressure tube specimens containing simulated debris frets (V-notch) and bearing pad frets (BPF, U-shape notch) to examine overload fracture behavior of flaw-tip hydrides formed under hydride ratcheting conditions. Hydride cracking in the overload tests was detected by the acoustic emission technique and confirmed by post-test metallurgical examination. Test results indicate that the resistance to overload fracture is affected by a number of parameters including hydride formation stress, flaw shape (V-notch vs. BPF) and flaw radius (0.015 mm vs. 0.1 mm). The notch-tip hydride morphologies were examined by optical microscopy and scanning electron microscopy (SEM) which show that they are affected by the hydride formation conditions, resulting in different overload fracture resistance. Finite element stress analyses were also performed to obtain flaw-tip stress distributions for interpretation of the test results. (authors)

  13. Structural isotopic effect of the α/β-phase transition in the vanadium hydride and its influence on the equilibrium coefficient of separation of hydrogen isotopes in the gas-solid system

    International Nuclear Information System (INIS)

    Magomedbekov, Eh.P.; Bochkarev, A.V.

    1999-01-01

    Equilibrium coefficient of hydrogen isotope separation (α H-D ) in the system of vanadium hydride VH n (solid, n ∼ 0.7)-H 2 (g) is measured by the counterbalancing method in a circulation facility and by the method of laser desorption at 298, 373, and 437 K. It is shown that the combination of highly anharmonic potential in the lattice octahedral sites and in significant difference in the energy of hydrogen atom coordination for tetra- and octahedral sites is the reason for unusual behaviour of the hydrogen isotope separation coefficient and the difference in crystal structures of vanadium hydride and deuteride [ru

  14. Unexpected formation of hydrides in heavy rare earth containing magnesium alloys

    Directory of Open Access Journals (Sweden)

    Yuanding Huang

    2016-09-01

    Full Text Available Mg–RE (Dy, Gd, Y alloys show promising for being developed as biodegradable medical applications. It is found that the hydride REH2 could be formed on the surface of samples during their preparations with water cleaning. The amount of formed hydrides in Mg–RE alloys is affected by the content of RE and heat treatments. It increases with the increment of RE content. On the surface of the alloy with T4 treatment the amount of formed hydride REH2 is higher. In contrast, the amount of REH2 is lower on the surfaces of as-cast and T6-treated alloys. Their formation mechanism is attributed to the surface reaction of Mg–RE alloys with water. The part of RE in solid solution in Mg matrix plays an important role in influencing the formation of hydrides.

  15. Optimization of o-phtaldialdehyde/2-mercaptoethanol postcolumn reaction for the hydrophilic interaction liquid chromatography determination of memantine utilizing a silica hydride stationary phase.

    Science.gov (United States)

    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.

  16. PAC and μSr investigations of light interstitial diffusion in intermetallic hydrides

    International Nuclear Information System (INIS)

    Boyer, P.; Baudry, A.

    1988-01-01

    Specific aspects of the Perturbed Angular Correlation (PAC) of gamma rays concerning its application to the study of atomic diffusion in solids are presented. PAC results recently obtained on the 181 Ta probe in several crystalline and amorphous phases of Zr 2 Ni hydrides are briefly summarized. Preliminary μSR results relative to these intermetallic hydrides are presented and compared to the PAC data

  17. Delayed hydride cracking in Zr-2.5Nb pressure tubes

    International Nuclear Information System (INIS)

    Mieza, Juan I.; Domizzi, Gladys; Vigna, Gustavo L.

    2007-01-01

    Zr-2.5 Nb alloy from CANDU pressure tubes are prone to failure by hydrogen intake. One of the degradation mechanisms is delayed hydride cracking, which is characterized by the velocity of cracking. In this work, we study the effect of beta zirconium phase transformation over delayed hydride cracking velocity in Zr-2.5 Nb alloy from pressure tubes. Acoustic emission technique was used for cracking detection. (author) [es

  18. Synthesis, properties, and assimilation methods of aluminium hydride

    International Nuclear Information System (INIS)

    Mirsaidov, U.M.

    2013-01-01

    We have discovered a new source of aluminium hydride-conversion of tetrahydrofurane under influence of halogenous alkyls. We have proposed the chlorbenzene method of synthesis of AlH 3 , which excludes adhesion and ensure high quality of the product with respect to its purity, thermal stability, habits of crystals (round shape), and granulometric composition. We determined capability of benzyl chloride to fix AlH 4 -groups by the way of complexes formation. This allows increasing efficient concentration of AlH 3 solutions and their productivity. We have carried out 'direct' crystallization of aluminium hydride in one stage using interaction of binary metal hydride with aluminium chloride in the medium of ether-toluene at 60-100 d ig C a nd using solvent distillation. In the reaction of Li H with AlCl 3 , we achieved output of pure crystal AlH 3 of hexagonal modification, which was close to quantitative. We have discovered the assimilation methods of aluminium hydride in carrying out of solid-phase chemical reactions. (author)

  19. Boron hydride analogues of the fullerenes

    International Nuclear Information System (INIS)

    Quong, A.A.; Pederson, M.R.; Broughton, J.Q.

    1994-01-01

    The BH moiety is isoelectronic with C. We have studied the stability of the (BH) 60 analogue of the C 60 fullerene as well as the dual-structure (BH) 32 icosahedron, both of them being putative structures, by performing local-density-functional electronic calculations. To aid in our analysis, we have also studied other homologues of these systems. We find that the latter, i.e., the dual structure, is the more stable although the former is as stable as one of the latter's lower homologues. Boron hydrides, it seems, naturally form the dual structures used in algorithmic optimization of complex fullerene systems. Fully relaxed geometries are reported as well as electron affinities and effective Hubbard U parameters. These systems form very stable anions and we conclude that a search for BH analogues of the C 60 alkali-metal supeconductors might prove very fruitful

  20. Complex Hydride Compounds with Enhanced Hydrogen Storage Capacity

    Energy Technology Data Exchange (ETDEWEB)

    Mosher, Daniel A.; Opalka, Susanne M.; Tang, Xia; Laube, Bruce L.; Brown, Ronald J.; Vanderspurt, Thomas H.; Arsenault, Sarah; Wu, Robert; Strickler, Jamie; Anton, Donald L.; Zidan, Ragaiy; Berseth, Polly

    2008-02-18

    between alkaline metal hydrides (AmH), Alkaline earth metal hydrides (AeH2), alane (AlH3), transition metal (Tm) hydrides (TmHz, where z=1-3) and molecular hydrogen (H2). The effort started first with variations of known alanates and subsequently extended the search to unknown compounds. In this stage, the FPM techniques were developed and validated on known alanate materials such as NaAlH4 and Na2LiAlH6. The coupled predictive methodologies were used to survey over 200 proposed phases in six quaternary spaces, formed from various combinations of Na, Li Mg and/or Ti with Al and H. A wide range of alanate compounds was examined using SSP having additions of Ti, Cr, Co, Ni and Fe. A number of compositions and reaction paths were identified having H weight fractions up to 5.6 wt %, but none meeting the 7.5 wt%H reversible goal. Similarly, MSP of alanates produced a number of interesting compounds and general conclusions regarding reaction behavior of mixtures during processing, but no alanate based candidates meeting the 7.5 wt% goal. A novel alanate, LiMg(AlH4)3, was synthesized using SBP that demonstrated a 7.0 wt% capacity with a desorption temperature of 150°C. The deuteride form was synthesized and characterized by the Institute for Energy (IFE) in Norway to determine its crystalline structure for related FPM studies. However, the reaction exhibited exothermicity and therefore was not reversible under acceptable hydrogen gas pressures for on-board recharging. After the extensive studies of alanates, the material class of emphasis was shifted to borohydrides. Through SBP, several ligand-stabilized Mg(BH4)2 complexes were synthesized. The Mg(BH4)2*2NH3 complex was found to change behavior with slightly different synthesis conditions and/or aging. One of the two mechanisms was an amine-borane (NH3BH3) like dissociation reaction which released up to 16 wt %H and more conservatively 9 wt%H when not including H2 released from the NH3. From FPM, the stability of the Mg(BH4

  1. Evaluation of the low corrosion resistant phase formed during the sigma phase precipitation in duplex stainless steels

    Directory of Open Access Journals (Sweden)

    Darlene Yuko Kobayashi

    1999-10-01

    Full Text Available The duplex stainless steels, having a volumetric fraction of 50% ferrite and 50% austenite, conciliate high corrosion resistance with good mechanical properties. But, in many circumstances different phase transformations may occur, such as that responsible for sigma phase precipitation, which make the steel susceptible to localized corrosion. During the sigma phase precipitation a new austenitic phase is formed with a very low corrosion resistance. In the present research the composition of this new austenitic phase was evaluated in four duplex stainless steels, with different Mo, N and Cu contents. After the solution anneal at 1050 °C, samples of these steels were aged at 850 °C during 1 h and 5 h for sigma phase precipitation. Using the ferritoscope and an image analyzer it was possible to determine the volumetric fractions of ferrite and sigma phase, respectively, while those of austenite and the new austenitic phase were determined by difference to 100% volume. Finally, by using mass balance it was possible to determine theoretically the composition of the new austenitic phase. This phase is poor in Cr and Mo free, which explains its poor corrosion resistance.

  2. Predicting Hydride Donor Strength via Quantum Chemical Calculations of Hydride Transfer Activation Free Energy.

    Science.gov (United States)

    Alherz, Abdulaziz; Lim, Chern-Hooi; Hynes, James T; Musgrave, Charles B

    2018-01-25

    We propose a method to approximate the kinetic properties of hydride donor species by relating the nucleophilicity (N) of a hydride to the activation free energy ΔG ⧧ of its corresponding hydride transfer reaction. N is a kinetic parameter related to the hydride transfer rate constant that quantifies a nucleophilic hydridic species' tendency to donate. Our method estimates N using quantum chemical calculations to compute ΔG ⧧ for hydride transfers from hydride donors to CO 2 in solution. A linear correlation for each class of hydrides is then established between experimentally determined N values and the computationally predicted ΔG ⧧ ; this relationship can then be used to predict nucleophilicity for different hydride donors within each class. This approach is employed to determine N for four different classes of hydride donors: two organic (carbon-based and benzimidazole-based) and two inorganic (boron and silicon) hydride classes. We argue that silicon and boron hydrides are driven by the formation of the more stable Si-O or B-O bond. In contrast, the carbon-based hydrides considered herein are driven by the stability acquired upon rearomatization, a feature making these species of particular interest, because they both exhibit catalytic behavior and can be recycled.

  3. Phase selection and microstructure in directional solidification of glass forming Pd-Si-Cu alloys

    Science.gov (United States)

    Huo, Yang

    Phase selection and microstructure formation during the rapid solidification of alloy melts has been a topic of substantial interest over the last several decades, attributed mainly to the access to novel structures involving metastable crystalline and non-crystalline phases. In this work, Bridgeman type directional solidification was conducted in Pd-Si-Cu glass forming system to study such cooling rate dependent phase transition and microstructure formation. The equilibrium state for Pd-Si-Cu ternary system was investigated through three different works. First of all, phase stabilities for Pd-Si binary system was accessed with respects of first-principles and experiments, showing Pd5Si, Pd9Si2, Pd3Si and Pd 2Si phase are stable all way to zero Kevin while PdSi phase is a high temperature stable phase, and Pd2Si phase with Fe2P is a non-stoichiometry phase. A thermodynamic database was developed for Pd-Si system. Second, crystal structures for compounds with ternary compositions were studied by XRD, SEM and TEM, showing ordered and disordered B2/bcc phases are stable in Pd-rich part. At last, based on many phase equilibria and phase transitions data, a comprehensive thermodynamic discrption for Pd-Si-Cu ternary system was first time to be developed, from which different phase diagrams and driving force for kinetics can be calculated. Phase selection and microstructure formation in directional solidification of the best glass forming composition, Pd 77.5Si16.5Cu6, in this system with growth velocities from 0.005 to 7.5mm/s was systematically studied and the solidification pathways at different conditions were interpreted from thermodynamic simulation. The results show that for growth velocities are smaller than 0.1mm/s Pd 3Si phase is primary phase and Pd9Si2 phase is secondary phase, the difficulty for Pd9Si2 phase nucleation gives rise to the formation of two different eutectic structure. For growth velocities between 0.4 and 1mm/s, instead of Pd3Si phase, Pd9Si2

  4. ON THE CHEMISTRY OF HYDRIDES OF N ATOMS AND O{sup +} IONS

    Energy Technology Data Exchange (ETDEWEB)

    Awad, Zainab [Astronomy, Space Science, and Meteorology Department, Faculty of Science, Cairo University, Giza (Egypt); Viti, Serena; Williams, David A., E-mail: zma@sci.cu.edu.eg [Physics and Astronomy Department, University College London, Gower Street, London WC1E 6BT (United Kingdom)

    2016-08-01

    Previous work by various authors has suggested that the detection by Herschel /HIFI of nitrogen hydrides along the low-density lines of sight toward G10.6-0.4 (W31C) cannot be accounted for by gas-phase chemical models. In this paper we investigate the role of surface reactions on dust grains in diffuse regions, and we find that formation of the hydrides by surface reactions on dust grains with efficiency comparable to that for H{sub 2} formation reconciles models with observations of nitrogen hydrides. However, similar surface reactions do not contribute significantly to the hydrides of O{sup +} ions detected by Herschel /HIFI that are present along many sight lines in the Galaxy. The O{sup +} hydrides can be accounted for by conventional gas-phase chemistry either in diffuse clouds of very low density with normal cosmic-ray fluxes or in somewhat denser diffuse clouds with high cosmic-ray fluxes. Hydride chemistry in dense dark clouds appears to be dominated by gas-phase ion–molecule reactions.

  5. On the Chemistry of Hydrides of N Atoms and O+ Ions

    Science.gov (United States)

    Awad, Zainab; Viti, Serena; Williams, David A.

    2016-08-01

    Previous work by various authors has suggested that the detection by Herschel/HIFI of nitrogen hydrides along the low-density lines of sight toward G10.6-0.4 (W31C) cannot be accounted for by gas-phase chemical models. In this paper we investigate the role of surface reactions on dust grains in diffuse regions, and we find that formation of the hydrides by surface reactions on dust grains with efficiency comparable to that for H2 formation reconciles models with observations of nitrogen hydrides. However, similar surface reactions do not contribute significantly to the hydrides of O+ ions detected by Herschel/HIFI that are present along many sight lines in the Galaxy. The O+ hydrides can be accounted for by conventional gas-phase chemistry either in diffuse clouds of very low density with normal cosmic-ray fluxes or in somewhat denser diffuse clouds with high cosmic-ray fluxes. Hydride chemistry in dense dark clouds appears to be dominated by gas-phase ion-molecule reactions.

  6. Formation of palladium hydrides in low temperature Ar/H_2-plasma

    International Nuclear Information System (INIS)

    Wulff, H.; Quaas, M.; Deutsch, H.; Ahrens, H.; Fröhlich, M.; Helm, C.A.

    2015-01-01

    20 nm thick Pd coatings deposited on Si substrates with 800 nm SiO_2 and 1 nm Cr buffer layers were treated in a 2.45 GHz microwave plasma source at 700 W plasma power and 40 Pa working pressure without substrate heating. For obtaining information on the effect of energy influx due to ion energy on the palladium films the substrate potential was varied from U_s_u_b = 0 V to − 150 V at constant gas flow corresponding to mean ion energies E_i from 0.22 eV ∙ cm"−"2 ∙ s"−"1 to 1.28 eV ∙ cm"−"2 ∙ s"−"1. In contrast to high pressure reactions with metallic Pd, under plasma exposure we do not observe solid solutions over a wide range of hydrogen concentration. The hydrogen incorporation in Pd films takes place discontinuously. At 0 V substrate voltage palladium hydride is formed in two steps to PdH_0_._1_4 and PdH_0_._5_7. At − 50 V substrate voltage PdH_0_._5_7 is formed directly. However, substrate voltages of − 100 V and − 150 V cause shrinking of the unit cell. We postulate the formation of two fcc vacancy palladium hydride clusters PdH_V_a_c(I) and PdH_V_a_c(II). Under longtime plasma exposure the fcc PdH_V_a_c(II) phase forms cubic PdH_1_._3_3. The fcc PdH_0_._5_7 phase decomposes at temperatures > 300 °C to form metallic fcc Pd. The hydrogen removal causes a decrease of lattice defects. In situ high temperature diffractometry measurements also confirm the existence of PdH_V_a_c(II) as a palladium hydride phase. Stoichiometric relationship between cubic PdH_1_._3_3 and fcc PdH_V_a_c(II) becomes evident from XR measurements and structure considerations. We assume both phases have the chemical composition Pd_3H_4. Up to 700 °C we observe phase transformation between both the fcc PdH_V_a_c(II) and cubic PdH_1_._3_3 phases. These phase transformations could be explained analog to a Bain distortion by displacive solid state structural changes. - Highlights: • Thin Pd films were treated under low pressure conditions by an Ar/H_2-plasma. • The

  7. Formation of palladium hydrides in low temperature Ar/H{sub 2}-plasma

    Energy Technology Data Exchange (ETDEWEB)

    Wulff, H., E-mail: wulff@uni-greifswald.de [University of Greifswald, Institute of Physics, Felix-Hausdorff-Straße 6, 17487 Greifswald (Germany); Quaas, M. [LITEC-LP, Brandteichstraße 20, 17489 Greifswald (Germany); Deutsch, H.; Ahrens, H. [University of Greifswald, Institute of Physics, Felix-Hausdorff-Straße 6, 17487 Greifswald (Germany); Fröhlich, M. [Leibniz Institute for Plasma Science and Technology e.V., Felix-Hausdorff-Straße 2 (Germany); Helm, C.A. [University of Greifswald, Institute of Physics, Felix-Hausdorff-Straße 6, 17487 Greifswald (Germany)

    2015-12-01

    20 nm thick Pd coatings deposited on Si substrates with 800 nm SiO{sub 2} and 1 nm Cr buffer layers were treated in a 2.45 GHz microwave plasma source at 700 W plasma power and 40 Pa working pressure without substrate heating. For obtaining information on the effect of energy influx due to ion energy on the palladium films the substrate potential was varied from U{sub sub} = 0 V to − 150 V at constant gas flow corresponding to mean ion energies E{sub i} from 0.22 eV ∙ cm{sup −2} ∙ s{sup −1} to 1.28 eV ∙ cm{sup −2} ∙ s{sup −1}. In contrast to high pressure reactions with metallic Pd, under plasma exposure we do not observe solid solutions over a wide range of hydrogen concentration. The hydrogen incorporation in Pd films takes place discontinuously. At 0 V substrate voltage palladium hydride is formed in two steps to PdH{sub 0.14} and PdH{sub 0.57}. At − 50 V substrate voltage PdH{sub 0.57} is formed directly. However, substrate voltages of − 100 V and − 150 V cause shrinking of the unit cell. We postulate the formation of two fcc vacancy palladium hydride clusters PdH{sub Vac}(I) and PdH{sub Vac}(II). Under longtime plasma exposure the fcc PdH{sub Vac}(II) phase forms cubic PdH{sub 1.33}. The fcc PdH{sub 0.57} phase decomposes at temperatures > 300 °C to form metallic fcc Pd. The hydrogen removal causes a decrease of lattice defects. In situ high temperature diffractometry measurements also confirm the existence of PdH{sub Vac}(II) as a palladium hydride phase. Stoichiometric relationship between cubic PdH{sub 1.33} and fcc PdH{sub Vac}(II) becomes evident from XR measurements and structure considerations. We assume both phases have the chemical composition Pd{sub 3}H{sub 4}. Up to 700 °C we observe phase transformation between both the fcc PdH{sub Vac}(II) and cubic PdH{sub 1.33} phases. These phase transformations could be explained analog to a Bain distortion by displacive solid state structural changes. - Highlights: • Thin Pd films

  8. Secondary phases formed during nuclear waste glass-water interactions: Thermodynamic and derived properties

    International Nuclear Information System (INIS)

    McKenzie, W.F.

    1992-08-01

    The thermodynamic properties of secondary phases observed to form during nuclear waste glass-water interactions are of particular interest as it is with the application of these properties together with the thermodynamic properties of other solid phases, fluid phases, and aqueous species that one may predict the environmental consequences of introducing radionuclides contained in the glass into groundwater at a high-level nuclear waste repository. The validation of these predicted consequences can be obtained from laboratory experiments and field observations at natural analogue sites. The purpose of this report is to update and expand the previous compilation (McKenzie, 1991) of thermodynamic data retrieved from the literature and/or estimated for secondary phases observed to form (and candidate phases from observed chemical compositions) during nuclear waste glass-water interactions. In addition, this report includes provisionally recommended thermodynamic data of secondary phases

  9. Crystallization and Characterization of Galdieria sulphuraria RUBISCO in Two Crystal Forms: Structural Phase Transition Observed in P21 Crystal Form

    Directory of Open Access Journals (Sweden)

    Boguslaw Stec

    2007-10-01

    Full Text Available We have isolated ribulose-1,5-bisphosphate-carboxylase/oxygenase (RUBISCOfrom the red algae Galdieria Sulphuraria. The protein crystallized in two different crystalforms, the I422 crystal form being obtained from high salt and the P21 crystal form beingobtained from lower concentration of salt and PEG. We report here the crystallization,preliminary stages of structure determination and the detection of the structural phasetransition in the P21 crystal form of G. sulphuraria RUBISCO. This red algae enzymebelongs to the hexadecameric class (L8S8 with an approximate molecular weight 0.6MDa.The phase transition in G. sulphuraria RUBISCO leads from two hexadecamers to a singlehexadecamer per asymmetric unit. The preservation of diffraction power in a phasetransition for such a large macromolecule is rare.

  10. Self-consolidating concrete, applications for slip-form paving : phase II.

    Science.gov (United States)

    2011-05-01

    The goal of the project was to develop a new type of self-consolidating concrete (SCC) for slip-form paving to simplify construction and make smoother pavements. Developing the new SCC involved two phases: a feasibility study (Phase I sponsored by TP...

  11. Influence of hydride microstructure on through-thickness crack growth in zircaloy-4 sheet

    International Nuclear Information System (INIS)

    Raynaud, P.A.; Meholic, M.J.; Koss, D.A.; Motta, A.T.; Chan, K.S.

    2007-01-01

    The fracture toughness of cold-worked and stress-relieved Zircaloy-4 sheet subject to through-thickness crack growth within a 'sunburst' hydride microstructure was determined at 25 o C. The results were obtained utilizing a novel testing procedure in which a narrow linear strip of hydride blister was fractured at small loads under bending to create a well-defined sharp pre-crack that arrested at the blister-substrate interface. The hydriding procedure also forms 'sunburst' hydrides emanating from the blister that were aligned both in the plane of the crack and in the crack growth direction. Subsequent tensile loading caused crack growth initiation into the field of 'sunburst' hydrides. Specimen failure occurred under near-linear elastic behavior, and the fracture toughness for crack growth initiation into sunburst hydrides was in the range K Q ∼10-15 MPa√m. These results, when combined with those of a previous study, indicate that the through-thickness crack growth initiation toughness at 25 o C is very sensitive to the hydride microstructure. (author)

  12. Characterization of condensed phase nitric acid particles formed in the gas phase

    Institute of Scientific and Technical Information of China (English)

    Long Jia; Yongfu Xu

    2011-01-01

    The formation of nitric acid hydrates has been observed in a chamber during the dark reaction of NO2 with O3 in the presence of air.The size of condensed phase nitric acid was measured to be 40-100 nm and 20-65 nm at relative humidity (RH) ≤ 5% and RH = 67% under our experimental conditions, respectively.The nitric acid particles were collected on the glass fiber membrane and their chemical compositions were analyzed by infrared spectrum.The main components of nitric acid hydrates in particles are HNO3·3H2O and NO3-·xH2O (x≥ 4) at low RH, whereas at high RH HNO3·H2O, HNO3·2H2O, HNO3·3H2O and NO3-·xH2O (x≥ 4) all exist in the condensed phase.At high RH HNO3·xH2O (x ≤ 3) collected on the glass fiber membrane is greatly increased, while NO3-·xH2O (x ≥4) decreased, compared with low RH.To the best of our knowledge, this is the first time to report that condensed phase nitric acid can be generated in the gas phase at room temperature.

  13. Tritium processing using metal hydrides

    International Nuclear Information System (INIS)

    Mallett, M.W.

    1986-01-01

    E.I. duPont de Nemours and Company is commissioned by the US Department of Energy to operate the Savannah River Plant and Laboratory. The primary purpose of the plant is to produce radioactive materials for national defense. In keeping with current technology, new processes for the production of tritium are being developed. Three main objectives of this new technology are to ease the processing of, ease the storage of, and to reduce the operating costs of the tritium production facility. Research has indicated that the use of metal hydrides offers a viable solution towards satisfying these objectives. The Hydrogen and Fuels Technology Division has the responsibility to conduct research in support of the tritium production process. Metal hydride technology and its use in the storage and transportation of hydrogen will be reviewed

  14. Hydride Molecules towards Nearby Galaxies

    Science.gov (United States)

    Monje, Raquel R.; La, Ngoc; Goldsmith, Paul

    2018-06-01

    Observations carried out by the Herschel Space Observatory revealed strong spectroscopic signatures from light hydride molecules within the Milky Way and nearby active galaxies. To better understand the chemical and physical conditions of the interstellar medium, we conducted the first comprehensive survey of hydrogen fluoride (HF) and water molecular lines observed through the SPIRE Fourier Transform Spectrometer. By collecting and analyzing the sub-millimeter spectra of over two hundred sources, we found that the HF J = 1 - 0 rotational transition which occurs at approximately 1232 GHz was detected in a total of 39 nearby galaxies both in absorption and emission. The analysis will determine the main excitation mechanism of HF in nearby galaxies and provide steady templates of the chemistry and physical conditions of the ISM to be used in the early universe, where observations of hydrides are more scarce.

  15. Rechargeable metal hydrides for spacecraft application

    Science.gov (United States)

    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.

  16. Structural stability of complex hydrides LiBH4 revisited

    DEFF Research Database (Denmark)

    Lodziana, Zbigniew; Vegge, Tejs

    2004-01-01

    A systematic approach to study the phase stability of LiBH4 based on ab initio calculations is presented. Three thermodynamically stable phases are identified and a new phase of Cc symmetry is proposed for the first time for a complex hydride. The x-ray diffraction pattern and vibrational spectra...

  17. Nanostructured, complex hydride systems for hydrogen generation

    Directory of Open Access Journals (Sweden)

    Robert A. Varin

    2015-02-01

    Full Text Available Complex hydride systems for hydrogen (H2 generation for supplying fuel cells are being reviewed. In the first group, the hydride systems that are capable of generating H2 through a mechanical dehydrogenation phenomenon at the ambient temperature are discussed. There are few quite diverse systems in this group such as lithium alanate (LiAlH4 with the following additives: nanoiron (n-Fe, lithium amide (LiNH2 (a hydride/hydride system and manganese chloride MnCl2 (a hydride/halide system. Another hydride/hydride system consists of lithium amide (LiNH2 and magnesium hydride (MgH2, and finally, there is a LiBH4-FeCl2 (hydride/halide system. These hydride systems are capable of releasing from ~4 to 7 wt.% H2 at the ambient temperature during a reasonably short duration of ball milling. The second group encompasses systems that generate H2 at slightly elevated temperature (up to 100 °C. In this group lithium alanate (LiAlH4 ball milled with the nano-Fe and nano-TiN/TiC/ZrC additives is a prominent system that can relatively quickly generate up to 7 wt.% H2 at 100 °C. The other hydride is manganese borohydride (Mn(BH42 obtained by mechano-chemical activation synthesis (MCAS. In a ball milled (2LiBH4 + MnCl2 nanocomposite, Mn(BH42 co-existing with LiCl can desorb ~4.5 wt.% H2 at 100 °C within a reasonable duration of dehydrogenation. Practical application aspects of hydride systems for H2 generation/storage are also briefly discussed.

  18. Use of reversible hydrides for hydrogen storage

    Science.gov (United States)

    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.

  19. Thermomechanics of hydrogen storage in metallic hydrides: modeling and analysis

    Czech Academy of Sciences Publication Activity Database

    Roubíček, Tomáš; Tomassetti, G.

    2014-01-01

    Roč. 19, č. 7 (2014), s. 2313-2333 ISSN 1531-3492 R&D Projects: GA ČR GA201/09/0917 Institutional support: RVO:61388998 Keywords : metal-hydrid phase transformation * hydrogen diffusion * swelling Subject RIV: BA - General Mathematics Impact factor: 0.768, year: 2014 http://aimsciences.org/journals/pdfs.jsp?paperID=10195&mode=full

  20. On the form invariant volume transformation in phase space by focusing neutron guides: An analytic treatment

    International Nuclear Information System (INIS)

    Stüßer, N.; Hofmann, T.

    2013-01-01

    Tapered guides with supermirror coating are frequently used to focus neutron beams on specimens. The divergence distribution in the focused beam is of a great importance for the quality of neutron instrumentation. Using an analytic approach we derive the tapering which is needed to achieve a form invariant phase space transformation of a rectangular phase volume. In addition we consider the effect of beam attenuation by the finite reflectivity of supermirrors. -- Highlights: • Form invariant volume transformation in phase space. • Focusing modules for neutron beams. • Analytical approach. • Attenuation effects in linearly and nonlinearly tapered guides

  1. U-8 wt %Mo and 7 wt %Mo alloys powder obtained by an hydride-de hydride process; Obtencion de polvo de aleaciones U-8% Mo y U-7% Mo (en peso) mediante hidruracion

    Energy Technology Data Exchange (ETDEWEB)

    Balart, Silvia N; Bruzzoni, Pablo; Granovsky, Marta S; Gribaudo, Luis M.J.; Hermida, Jorge D; Ovejero, Jose; Rubiolo, Gerardo H; Vicente, Eduardo E [Comision Nacional de Energia Atomica, General San Martin (Argentina). Dept. de Materiales

    2000-07-01

    Uranium-molybdenum alloys are been tested as a component in high-density LEU dispersion fuels with very good performances. These alloys need to be transformed to powder due to the manufacturing requirements of the fuels. One method to convert ductile alloys into powder is the hydride-de hydride process, which takes advantage of the ability of the U-{alpha} phase to transform to UH{sub 3}: a brittle and relatively low-density compound. U-Mo alloys around 7 and 8 wt % Mo were melted and heat treated at different temperature ranges in order to partially convert {gamma} -phase to {alpha} -phase. Subsequent hydriding transforms this {alpha} -phase to UH{sub 3}. The volume change associated to the hydride formation embrittled the material which ends up in a powdered alloy. Results of the optical metallography, scanning electron microscopy, X-ray diffraction during different steps of the process are shown. (author)

  2. Effect of phase transformations on laser forming of Ti-6Al-4V alloy

    International Nuclear Information System (INIS)

    Fan, Y.; Cheng, P.; Yao, Y.L.; Yang, Z.; Egland, K.

    2005-01-01

    In laser forming, phase transformations in the heat-affected zone take place under steep thermal cycles, and have a significant effect on the flow behavior of Ti-6Al-4V alloy and the laser-forming process. The flow-stress data of a material are generally provided as only dependent on strain, strain rate, and temperature, while phase transformations are determined by both temperature and temperature history. Therefore, effect of phase transformations on the flow behavior of materials in thermomechanical processing is not given necessary considerations. In the present work, both the α→β transformation during heating and the decomposition of β phase, producing martensite α ' or lamellae α dependent on cooling rate, are numerically investigated. The spatial distribution of volume fractions of phases is obtained by coupling thermal and phase transformation kinetic modeling. Consequently, the flow stress of Ti-6Al-4V alloy is calculated by the rule of mixtures based on the phase ratio and the flow stress of each single phase, which is also a function of temperature, strain, and strain rate. According to the obtained flow-stress data, the laser-forming process of Ti-6Al-4V alloy is modeled by finite element method, and the deformation is predicted. A series of carefully controlled experiments are conducted to validate the theoretically predicted results

  3. Hydrogen charging, hydrogen content analysis and metallographic examination of hydride in zirconium alloys

    International Nuclear Information System (INIS)

    Singh, R.N.; Kishore, R.; Mukherjee, S.; Roychowdhury, S.; Srivastava, D.; Sinha, T.K.; De, P.K.; Banerjee, S.; Gopalan, B.; Kameswaran, R.; Sheelvantra, Smita S.

    2003-12-01

    Gaseous and electrolytic hydrogen charging techniques for introducing controlled amount of hydrogen in zirconium alloy is described. Zr-1wt%Nb fuel tube, zircaloy-2 pressure tube and Zr-2.5Nb pressure tube samples were charged with up to 1000 ppm of hydrogen by weight using one of the aforementioned methods. These hydrogen charged Zr-alloy samples were analyzed for estimating the total hydrogen content using inert gas fusion technique. Influence of sample surface preparation on the estimated hydrogen content is also discussed. In zirconium alloys, hydrogen in excess of the terminal solid solubility precipitates out as brittle hydride phase, which acquire platelet shaped morphology due to its accommodation in the matrix and can make the host matrix brittle. The F N number, which represents susceptibility of Zr-alloy tubes to hydride embrittlement was measured from the metallographs. The volume fraction of the hydride phase, platelet size, distribution, interplatelet spacing and orientation were examined metallographically using samples sliced along the radial-axial and radial-circumferential plane of the tubes. It was observed that hydride platelet length increases with increase in hydrogen content. Considering the metallographs generated by Materials Science Division as standard, metallographs prepared by the IAEA round robin participants for different hydrogen concentration was compared. It is felt that hydride micrographs can be used to estimate not only that approximate hydrogen concentration of the sample but also its size, distribution and orientation which significantly affect the susceptibility to hydride embrittlement of these alloys. (author)

  4. Fundamental experiments on hydride reorientation in zircaloy

    Science.gov (United States)

    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

  5. Manganese Silylene Hydride Complexes: Synthesis and Reactivity with Ethylene to Afford Silene Hydride Complexes.

    Science.gov (United States)

    Price, Jeffrey S; Emslie, David J H; Britten, James F

    2017-05-22

    Reaction of the ethylene hydride complex trans-[(dmpe) 2 MnH(C 2 H 4 )] (1) with Et 2 SiH 2 at 20 °C afforded the silylene hydride [(dmpe) 2 MnH(=SiEt 2 )] (2 a) as the trans-isomer. By contrast, reaction of 1 with Ph 2 SiH 2 at 60 °C afforded [(dmpe) 2 MnH(=SiPh 2 )] (2 b) as a mixture of the cis (major) and trans (minor) isomers, featuring a Mn-H-Si interaction in the former. The reaction to form 2 b also yielded [(dmpe) 2 MnH 2 (SiHPh 2 )] (3 b); [(dmpe) 2 MnH 2 (SiHR 2 )] (R=Et (3 a) and Ph (3 b)) were accessed cleanly by reaction of 2 a and 2 b with H 2 , and the analogous reactions with D 2 afforded [(dmpe) 2 MnD 2 (SiHR 2 )] exclusively. Both 2 a and 2 b engaged in unique reactivity with ethylene, generating the silene hydride complexes cis-[(dmpe) 2 MnH(R 2 Si=CHMe)] (R=Et (4 a), Ph (4 b)). Compounds trans-2 a, cis-2 b, 3 b, and 4 b were crystallographically characterized, and bonding in 2 a, 2 b, 4 a, and 4 b was probed computationally. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Palmitic acid/polypyrrole composites as form-stable phase change materials for thermal energy storage

    International Nuclear Information System (INIS)

    Silakhori, Mahyar; Metselaar, Hendrik Simon Cornelis; Mahlia, Teuku Meurah Indra; Fauzi, Hadi; Baradaran, Saeid; Naghavi, Mohammad Sajad

    2014-01-01

    Highlights: • A novel phase change composite of palmitic acid–polypyrrole(PA–PPy) was fabricated. • Thermal properties of PA–PPy are characterized in different mass ratios of PA–PPy. • Thermal cycling test showed that form stable PCM had a favorable thermal reliability. - Abstract: In this study a novel palmitic acid (PA)/polypyrrole (PPy) form-stable PCMs were readily prepared by in situ polymerization method. PA was used as thermal energy storage material and PPy was operated as supporting material. Form-stable PCMs were investigated by SEM (scanning electron microscopy) and FTIR (Fourier transform infrared spectrometer) analysis that illustrated PA Particles were wrapped by PPy particles. XRD (X-ray diffractometer) was used for crystalline phase of PA/PPy composites. Thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC) were used for investigating Thermal stability and thermal energy storage properties of prepared form-stable PCMs. According to the obtained results the form stable PCMs exhibited favorable thermal stability in terms of their phase change temperature. The form-stable PCMs (79.9 wt% loading of PA) were considered as the highest loading PCM with desirable latent heat storage of 166.3 J/g and good thermal stability. Accelerated thermal cycling tests also showed that form stable PCM had an acceptable thermal reliability. As a consequence of acceptable thermal properties, thermal stability and chemical stability, we can consider the new kind of form stable PCMs for low temperature solar thermal energy storage applications

  7. Corrosion behavior of Zircaloy 4 cladding material. Evaluation of the hydriding effect

    International Nuclear Information System (INIS)

    Blat, M.

    1997-04-01

    In this work, particular attention has been paid to the hydriding effect in PIE and laboratory test to validate a detrimental hydrogen contribution on Zircaloy 4 corrosion behavior at high burnup. Laboratory corrosion tests results confirm that hydrides have a detrimental role on corrosion kinetics. This effect is particularly significant for cathodic charged samples with a massive hydride outer layer before corrosion test. PIE show that at high burnup a hydride layer is formed underneath the metal/oxide interface. The results of the metallurgical examinations are discussed with respect to the possible mechanisms involved in this detrimental effect of hydrogen. Therefore, according to the laboratory tests results and PIE, hydrogen could be a strong contributor to explain the increase in corrosion rate at high burnup. (author)

  8. Modeling of hydrogen isotopes separation in a metal hydride bed

    International Nuclear Information System (INIS)

    Charton, S.; Corriou, J.P.; Schweich, D.

    1999-01-01

    A predictive model for hydrogen isotopes separation in a non-isothermal bed of unsupported palladium hydride particles is derived. It accounts for the non-linear adsorption-dissociation equilibrium, hydrodynamic dispersion, pressure drop, mass transfer kinetics, heat of sorption and heat losses at the bed wall. Using parameters from the literature or estimated with classical correlations, the model gives simulated curves in agreement with previously published experiments without any parameter fit. The non-isothermal behavior is shown to be responsible for drastic changes of the mass transfer rate which is controlled by diffusion in the solid-phase lattice. For a feed at 300 K and atmospheric pressure, the endothermic hydride-to-deuteride exchange is kinetically controlled, whereas the reverse exothermic exchange is nearly at equilibrium. Finally, a simple and efficient thermodynamic model for the dissociative equilibrium between a metal and a diatomic gas is proposed. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  9. Manufacture of titanium and zirconium hydrides

    International Nuclear Information System (INIS)

    Mares, F.; Hanslik, T.

    1973-01-01

    A method is described of manufacturing titanium and zirconium hydrides by hydrogenation of said metals characterized by the reaction temperature ranging between 250 to 500 degC, hydrogen pressure of 20 to 300 atm and possibly by the presence of a hydride of the respective metal. (V.V.)

  10. Hydride effect on crack instability of Zircaloy cladding

    Energy Technology Data Exchange (ETDEWEB)

    Tseng, Che-Chung, E-mail: cctseng@iner.gov.tw [Institute of Nuclear Energy Research, No. 1000, Wunhua Road, Jiaan Village, Lungtan, Township, Taoyuan County 32546, Taiwan (China); Sun, Ming-Hung [Institute of Nuclear Energy Research, No. 1000, Wunhua Road, Jiaan Village, Lungtan, Township, Taoyuan County 32546, Taiwan (China); Chao, Ching-Kong [Department of Mechanical Engineering, National Taiwan University of Science and Technology, 43 Keelung Road, Section 4, Taipei 106, Taiwan (China)

    2014-04-01

    Highlights: • Radial hydrides near the crack tip had a significant effect on crack propagation. • For radial hydrides off the crack line vertically, the effect on crack propagation was notably reduced. • The longer hydride platelet resulted in a remarkable effect on crack propagation. • A long split in the radial hydride precipitate would enhance crack propagation. • The presence of circumferential hydride among radial hydrides may play an important role in crack propagation. - Abstract: A methodology was proposed to investigate the effect of hydride on the crack propagation in fuel cladding. The analysis was modeled based on an outside-in crack with radial hydrides located near its crack tip. The finite element method was used in the calculation; both stress intensity factor K{sub I} and J integral were applied to evaluate the crack stability. The parameters employed in the analysis included the location of radial hydride, hydride dimensions, number of hydrides, and the presence of circumferential hydride, etc. According to our study, the effective distance between a radial hydride and the assumed cladding surface crack for the enhancement of crack propagation proved to be no greater than 0.06 mm. For a hydride not on the crack line, it would induce a relatively minor effect on crack propagation if the vertical distance was beyond 0.05 mm. However, a longer hydride precipitate as well as double radial hydrides could have a remarkable effect on crack propagation. A combined effect of radial and circumferential hydrides was also discussed.

  11. Synthesis and Properties of Nanoparticle Forms Saponite Clay, Cancrinite Zeolite and Phase Mixtures Thereof.

    Science.gov (United States)

    Shao, Hua; Pinnavaia, Thomas J

    2010-09-01

    The low-temperature synthesis (90°C) of nanoparticle forms of a pure phase smectic clay (saponite) and zeolite (cancrinite) is reported, along with phase mixtures thereof. A synthesis gel corresponding to the Si:Al:Mg unit cell composition of saponite (3.6:0.40:3.0) and a NaOH/Si ratio of 1.39 affords the pure phase clay with disordered nanolayer stacking. Progressive increases in the NaOH/Si ratio up to a value of 8.33 results in the co-crystallization of first garronite and then cancrinite zeolites with nanolath morphology. The resulting phase mixtures exhibit a compound particulate structure of intertwined saponite nanolayers and cancrinite nanolaths that cannot be formed through physical mixing of the pure phase end members. Under magnesium-free conditions, pure phase cancrinite nanocrystals are formed. The Si/Al ratio of the reaction mixture affects the particle morphology as well as the chemical composition of the cancrinite zeolite. Ordinarily, cancrinite crystallizes with a Si/Al ratio of 1.0, but a silicon-rich form of the zeolite (Si/Al=1.25) is crystallized at low temperature from a silica rich synthesis gel, as evidenced by (29)Si NMR spectroscopy and XEDS-TEM. Owing to the exceptionally high external surface areas of the pure phase clay (875 m(2)/g) and zeolite end members (8.9 - 40 m(2)/g), as well as their unique mixed phase composites (124 - 329 m(2)/g), these synthetic derivatives are promising model nanoparticles for studies of the bioavailability of poly-aromatic hydrocarbons immobilized in silicate bearing sediments and soils.

  12. Effects of H-H interactions on the heat of H absorption by β and delta Zr hydrides

    International Nuclear Information System (INIS)

    Ohta, Yutaka; Mabuchi, Mahito; Naito, Shizuo; Hashino, Tomoyasu

    1987-01-01

    The heat of H absorption by β and delta Zr hydrides has been measured by isoperibol calorimetry over the range of H concentration 0.1 - 1.6 H/Zr at temperatures 873-1273 K. In the β hydride the heat per H atom (differential heat) increases and then decreases as the H concentration increases. In the delta hydride only a decrease at large H concentrations is clearly observed. The increase in the β hydride is related by self-consistent calculations to a pair indirect interaction between H atoms; the decreases in the β and delta hydrides are due to a pair direct interaction which is of the form of a screened Coulomb potential. The differential heat is estimated from the pair indirect and direct interactions by the use of Monte Carlo simulations and compared with the measured differential heat. (author)

  13. Final waste forms project: Performance criteria for phase I treatability studies

    International Nuclear Information System (INIS)

    Gilliam, T.M.; Hutchins, D.A.; Chodak, P. III

    1994-06-01

    This document defines the product performance criteria to be used in Phase I of the Final Waste Forms Project. In Phase I, treatability studies will be performed to provide open-quotes proof-of-principleclose quotes data to establish the viability of stabilization/solidification (S/S) technologies. This information is required by March 1995. In Phase II, further treatability studies, some at the pilot scale, will be performed to provide sufficient data to allow treatment alternatives identified in Phase I to be more fully developed and evaluated, as well as to reduce performance uncertainties for those methods chosen to treat a specific waste. Three main factors influence the development and selection of an optimum waste form formulation and hence affect selection of performance criteria. These factors are regulatory, process-specific, and site-specific waste form standards or requirements. Clearly, the optimum waste form formulation will require consideration of performance criteria constraints from each of the three categories. Phase I will focus only on the regulatory criteria. These criteria may be considered the minimum criteria for an acceptable waste form. In other words, a S/S technology is considered viable only if it meet applicable regulatory criteria. The criteria to be utilized in the Phase I treatability studies were primarily taken from Environmental Protection Agency regulations addressed in 40 CFR 260 through 265 and 268; and Nuclear Regulatory Commission regulations addressed in 10 CFR 61. Thus the majority of the identified criteria are independent of waste form matrix composition (i.e., applicable to cement, glass, organic binders etc.)

  14. Final waste forms project: Performance criteria for phase I treatability studies

    Energy Technology Data Exchange (ETDEWEB)

    Gilliam, T.M. [Oak Ridge National Lab., TN (United States); Hutchins, D.A. [Martin Marietta Energy Systems, Inc., Oak Ridge, TN (United States); Chodak, P. III [Massachusetts Institute of Technology (United States)

    1994-06-01

    This document defines the product performance criteria to be used in Phase I of the Final Waste Forms Project. In Phase I, treatability studies will be performed to provide {open_quotes}proof-of-principle{close_quotes} data to establish the viability of stabilization/solidification (S/S) technologies. This information is required by March 1995. In Phase II, further treatability studies, some at the pilot scale, will be performed to provide sufficient data to allow treatment alternatives identified in Phase I to be more fully developed and evaluated, as well as to reduce performance uncertainties for those methods chosen to treat a specific waste. Three main factors influence the development and selection of an optimum waste form formulation and hence affect selection of performance criteria. These factors are regulatory, process-specific, and site-specific waste form standards or requirements. Clearly, the optimum waste form formulation will require consideration of performance criteria constraints from each of the three categories. Phase I will focus only on the regulatory criteria. These criteria may be considered the minimum criteria for an acceptable waste form. In other words, a S/S technology is considered viable only if it meet applicable regulatory criteria. The criteria to be utilized in the Phase I treatability studies were primarily taken from Environmental Protection Agency regulations addressed in 40 CFR 260 through 265 and 268; and Nuclear Regulatory Commission regulations addressed in 10 CFR 61. Thus the majority of the identified criteria are independent of waste form matrix composition (i.e., applicable to cement, glass, organic binders etc.).

  15. Obtaining zircaloy powder through hydriding

    International Nuclear Information System (INIS)

    Dupim, Ivaldete da Silva; Moreira, Joao M.L.

    2009-01-01

    Zirconium alloys are good options for the metal matrix in dispersion fuels for power reactors due to their low thermal neutron absorption cross-section, good corrosion resistance, good mechanical strength and high thermal conductivity. A necessary step for obtaining such fuels is producing Zr alloy powder for the metal matrix composite material. This article presents results from the Zircaloy-4 hydrogenation tests with the purpose to embrittle the alloy as a first step for comminuting. Several hydrogenation tests were performed and studied through thermogravimetric analysis. They included H 2 pressures of 25 and 50 kPa and temperatures ranging between from 20 to 670 deg C. X-ray diffraction analysis showed in the hydrogenated samples the predominant presence of ZrH 2 and some ZrO 2 . Some kinetics parameters for the Zircaloy-4 hydrogenation reaction were obtained: the time required to reach the equilibrium state at the dwell temperature was about 100 minutes; the hydrogenation rate during the heating process from 20 to 670 deg C was about 21 mg/h, and at constant temperature of 670 deg C, the hydride rate was about 1.15 mg/h. The hydrogenation rate is largest during the heating process and most of it occurs during this period. After hydrogenated, the samples could easily be comminuted indicating that this is a possible technology to obtain Zircaloy powder. The results show that only few minutes of hydrogenation are necessary to reach the hydride levels required for comminuting the Zircaloy. The final hydride stoichiometry was between 2.7 and 2.8 H for each Zr atom in the sample (author)

  16. Hydrogen storage in sodium aluminum hydride.

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-11-01

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

  17. Electron Backscatter Diffraction Studies on the Formation of Superlattice Metal Hydride Alloys

    Directory of Open Access Journals (Sweden)

    Shuli Yan

    2017-12-01

    Full Text Available Microstructures of a series of La-Mg-Ni-based superlattice metal hydride alloys produced by a novel method of interaction of a LaNi5 alloy and Mg vapor were studied using a combination of X-ray energy dispersive spectroscopy and electron backscatter diffraction. The conversion rate of LaNi5 increased from 86.8% into 98.2%, and the A2B7 phase abundance increased from 42.5 to 45.8 wt % and reduced to 39.2 wt % with the increase in process time from four to 32 h. During the first stage of reaction, Mg formed discrete grains with the same orientation, which was closely related to the orientation of the host LaNi5 alloy. Mg then diffused through the ab-phase of LaNi5 and formed the AB2, AB3, and A2B7 phases. Diffusion of Mg stalled at the grain boundary of the host LaNi5 alloy. Good alignments in the c-axis between the newly formed superlattice phases and LaNi5 were observed. The density of high-angle grain boundary decreased with the increase in process time and was an indication of lattice cracking.

  18. Acidity of first- and second-row hydrides: Effects of electronegativity and hardness

    International Nuclear Information System (INIS)

    De Proft, F.; Langenaeker, W.; Geerlings, P.

    1995-01-01

    A study is made on the influence of the electronegativity and hardness of a group X on the gas-phase acidities of the first- and second-row hydrides HX. It is shown that these two density functional theory (DFT)-based global properties are sufficient for the correct description of the gas-phase acidity sequences, the group hardness being the more important factor and describing the influence of polarizability effects in the charged forms of the acid-base equilibrium. Various calculated properties effects in the charged forms of the acid-base equilibrium. Various calculated properties of the traditional quantum chemical type (Mulliken charges and the MEP) and DFT-based (local softness), associated with the neutral form of the acid, were found to contain a certain periodicity in their description of the gas-phases acidities. The gas-phase acidities (ΔH acid and ΔG acid values) were also obtained theoretically via quantum statistical thermodynamical calculations at the Hartree-Fock level with the 6-31 + G* basis set; these calculated acidities were in fair agreement with the experimental ones. 43 refs., 7 figs., 4 tabs

  19. Application of invariant plane strain (IPS) theory to {gamma} hydride formation in dilute Zr-Nb alloys

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, D. [Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400085, Maharashtra (India)]. E-mail: dsrivastavabarc@yahoo.co.in; Neogy, S. [Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400085, Maharashtra (India); Dey, G.K. [Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400085, Maharashtra (India); Banerjee, S. [Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400085, Maharashtra (India); Ranganathan, S. [Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400085, Maharashtra (India)

    2005-04-25

    The crystallographic aspects associated with the formation of the {gamma} hydride phase (fct) from the {alpha} (hcp) phase and the {beta} (bcc) phase in Zr-Nb alloys have been studied in two distinct situations, viz., in the {alpha} matrix in pure Zr and Zr-2.5Nb and in the {beta} matrix in {beta} stabilized Zr-20Nb alloy. The {beta}-{gamma} formation can be treated primarily as a simple shear on the basal plane involving a change in the stacking sequence. A possible mechanism for {alpha}-{gamma} transformation has been presented in this paper. In this paper the {beta}->{gamma} transformation has been considered in terms of the invariant plane strain theory (IPS) in order to predict the crystallographic features of the {gamma} hydride formed. The lattice invariant shear (LIS) (110){sub {beta}}[1-bar 10]{sub {beta}}||(111){sub {gamma}}[12-bar 1]{sub {gamma}} has been considered and the crystallographic parameters associated with bcc->fct transformation, such as the habit plane and the magnitude of the LIS and the shape strain have been computed. The predictions made in the present analysis have been compared with experimentally observed habit planes. The {alpha}/{gamma} and {beta}/{gamma} interface has been examined by high resolution transmission electron microscopy (HRTEM) technique to compare with the interfaces observed in martensitic transformations.

  20. Application of invariant plane strain (IPS) theory to γ hydride formation in dilute Zr-Nb alloys

    International Nuclear Information System (INIS)

    Srivastava, D.; Neogy, S.; Dey, G.K.; Banerjee, S.; Ranganathan, S.

    2005-01-01

    The crystallographic aspects associated with the formation of the γ hydride phase (fct) from the α (hcp) phase and the β (bcc) phase in Zr-Nb alloys have been studied in two distinct situations, viz., in the α matrix in pure Zr and Zr-2.5Nb and in the β matrix in β stabilized Zr-20Nb alloy. The β-γ formation can be treated primarily as a simple shear on the basal plane involving a change in the stacking sequence. A possible mechanism for α-γ transformation has been presented in this paper. In this paper the β->γ transformation has been considered in terms of the invariant plane strain theory (IPS) in order to predict the crystallographic features of the γ hydride formed. The lattice invariant shear (LIS) (110) β [1-bar 10] β ||(111) γ [12-bar 1] γ has been considered and the crystallographic parameters associated with bcc->fct transformation, such as the habit plane and the magnitude of the LIS and the shape strain have been computed. The predictions made in the present analysis have been compared with experimentally observed habit planes. The α/γ and β/γ interface has been examined by high resolution transmission electron microscopy (HRTEM) technique to compare with the interfaces observed in martensitic transformations

  1. Zirconium hydride containing explosive composition

    Science.gov (United States)

    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.

  2. The microstructure and composition of equilibrium phases formed in hypoeutectic Te-In alloy during solidification

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Baoguang [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Hu, Jinwu [Center of Failure Analysis, Central Iron and Steel Research Institute, Beijing 100081 (China); Wang, Chongyun; Yang, Wenhui [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Tian, Wenhuai, E-mail: wenhuaitian@ustb.edu.cn [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China)

    2017-03-15

    As a key tellurium atoms evaporation source for ultraviolet detection photocathode, the hypoeutectic Te{sub 75}In{sub 25} alloy was prepared by employing a slow solidification speed of about 10{sup −2} K/s. The microstructure and chemical composition of the equilibrium phases formed in the as-prepared alloy were studied in this research work. The experimental results show that the as-prepared Te-In alloy was constituted by primary In{sub 2}Te{sub 5} phase and eutectic In{sub 2}Te{sub 5}/Te phases. The eutectic In{sub 2}Te{sub 5}/Te phases are distributed in the grain boundaries of primary In{sub 2}Te{sub 5} phase. With the slow solidification speed, a pure eutectic Te phase without any excessive indium solute was obtained, where Te content of eutectic Te phase is 100 mass%. Moreover, it can be considered that the stress between the In{sub 2}Te{sub 5} and Te phases plays an important role in reducing the tellurium vapor pressure in Te{sub 75}In{sub 25} alloy. - Highlights: • The microstructure of Te-In alloy as an evaporation source was analyzed. • A pure eutectic Te phase was obtained by using a slow solidification speed method. • The relation between vapor pressure and inner-stress in the alloy was discussed.

  3. A NOVEL METHOD OF THE HYDRIDE SEPARATION FOR THE DETERMINATION OF ARSENIC AND ANTIMONY BY AAS

    Directory of Open Access Journals (Sweden)

    Ganden Supriyanto

    2010-06-01

    Full Text Available A novel method is proposed for the hydride separation when determinining of arsenic and antimony by AAS. A chromatomembrane cell was used as preconcentration-, extraction- and separation-manifold instead of the U-tube phase separator, which is normally fitted in continuous flow vapour systems generating conventionaly the hydrides. The absorbances of the hydrides produced were measured by an atomic absorption spectrophotometer at 193.7 nm and 217.6 nm. Under optimized analytical conditions, the calibration plot for arsenic was linear from 50 to 500 ng.mL-1 (r2 = 0.9982. The precision for three subsequent measurements of 500 ng.mL-1 arsenic gave rise to a relative standard deviation of 0.4%. The detection limit was 15 ng.mL-1, which is much lower compared with that of the conventional hydride system (2000 ng.mL-1. A similar result was observed in case of antimony: the detection limit was 8 ng.mL-1 when the proposed method was applied. Consequently, the sensitivity of the novel method surpasses systems with conventional hydride generation, i.e. the precision and the acuracy increase whereas the standard deviation and the detection limit decrease. The proposed method was applied in pharmacheutial analysis and the certified As-content of a commercial product was very sufficiently confirmed.   Keywords: Chromatomembrane Cell, Hydride separation, Arsenic detection, Antimony detection, AAS

  4. Graphene/phase change material nanocomposites: light-driven, reversible electrical resistivity regulation via form-stable phase transitions.

    Science.gov (United States)

    Wang, Yunming; Mi, Hongyi; Zheng, Qifeng; Ma, Zhenqiang; Gong, Shaoqin

    2015-02-04

    Innovative photoresponsive materials are needed to address the complexity of optical control systems. Here, we report a new type of photoresponsive nanomaterial composed of graphene and a form-stable phase change material (PCM) that exhibited a 3 orders of magnitude change in electrical resistivity upon light illumination while retaining its overall original solid form at the macroscopic level. This dramatic change in electrical resistivity also occurred reversibly through the on/off control of light illumination. This was attributed to the reversible phase transition (i.e., melting/recrystallization) behavior of the microscopic crystalline domains present in the form-stable PCM. The reversible phase transition observed in the graphene/PCM nanocomposite was induced by a reversible temperature change through the on/off control of light illumination because graphene can effectively absorb light energy and convert it to thermal energy. In addition, this graphene/PCM nanocomposite also possessed excellent mechanical properties. Such photoresponsive materials have many potential applications, including flexible electronics.

  5. Process for forming a homogeneous oxide solid phase of catalytically active material

    Science.gov (United States)

    Perry, Dale L.; Russo, Richard E.; Mao, Xianglei

    1995-01-01

    A process is disclosed for forming a homogeneous oxide solid phase reaction product of catalytically active material comprising one or more alkali metals, one or more alkaline earth metals, and one or more Group VIII transition metals. The process comprises reacting together one or more alkali metal oxides and/or salts, one or more alkaline earth metal oxides and/or salts, one or more Group VIII transition metal oxides and/or salts, capable of forming a catalytically active reaction product, in the optional presence of an additional source of oxygen, using a laser beam to ablate from a target such metal compound reactants in the form of a vapor in a deposition chamber, resulting in the deposition, on a heated substrate in the chamber, of the desired oxide phase reaction product. The resulting product may be formed in variable, but reproducible, stoichiometric ratios. The homogeneous oxide solid phase product is useful as a catalyst, and can be produced in many physical forms, including thin films, particulate forms, coatings on catalyst support structures, and coatings on structures used in reaction apparatus in which the reaction product of the invention will serve as a catalyst.

  6. Lithium insertion in the two crystallographic forms of the binary-phase Mo15Se19

    Science.gov (United States)

    Tarascon, J. M.; Murphy, D. W.

    1986-02-01

    Compounds which can undergo topotactic insertion of lithium are of potential technological importance in secondary lithium batteries. In this paper we present the chemical and electrochemical insertion of lithium into the binary-phase Mo15Se19, which can exist in two crystallographic forms, denoted AA and BB, when prepared from In3Mo15Se19 and In2Mo15Se19, respectively. We show that both forms can reversibly accommodate up to eight lithium atoms, yielding two new series of compounds of formula LixMo15Se19. This behavior is consistent with the electronic structure of the host material predicted from band-structure calculations. The room-temperature phase diagram of both LixMo15Se19 systems as a function of x has been established using electrochemical test cells (based on Mo15Se19 as the cathode), and in situ x-ray measurements as the cells discharge. Both LixMo15Se19 systems contain three single-phase domains as a function of x: two hexagonal phases and an orthorhombic phase. The nature of the transitions between these single phases and the variation of the lattice parameters within a single-phase domain are reported. While the mechanism of intercalation of lithium is similar for both Mo15Se19 forms, there is a drastic difference in Li intercalation behavior for the parent indium phases In2Mo15Se19 and In3Mo15Se19. We found that In2Mo15Se19 can reversibly incorporate 6.4 lithium atoms while In3Mo15Se19 does not react. This behavior is explained on the basis of structural considerations.

  7. Lithium insertion in the two crystallographic forms of the binary-phase Mo15Se19

    International Nuclear Information System (INIS)

    Tarascon, J.M.; Murphy, D.W.

    1986-01-01

    Compounds which can undergo topotactic insertion of lithium are of potential technological importance in secondary lithium batteries. In this paper we present the chemical and electrochemical insertion of lithium into the binary-phase Mo 15 Se 19 , which can exist in two crystallographic forms, denoted AA and BB, when prepared from In 3 Mo 15 Se 19 and In 2 Mo 15 Se 19 , respectively. We show that both forms can reversibly accommodate up to eight lithium atoms, yielding two new series of compounds of formula Li/sub x/Mo 15 Se 19 . This behavior is consistent with the electronic structure of the host material predicted from band-structure calculations. The room-temperature phase diagram of both Li/sub x/Mo 15 Se 19 systems as a function of x has been established using electrochemical test cells (based on Mo 15 Se 19 as the cathode), and in situ x-ray measurements as the cells discharge. Both Li/sub x/Mo 15 Se 19 systems contain three single-phase domains as a function of x: two hexagonal phases and an orthorhombic phase. The nature of the transitions between these single phases and the variation of the lattice parameters within a single-phase domain are reported. While the mechanism of intercalation of lithium is similar for both Mo 15 Se 19 forms, there is a drastic difference in Li intercalation behavior for the parent indium phases In''Mo 15 Se 19 and In 3 Mo 15 Se 19 . We found that In 2 Mo 15 Se 19 can reversibly incorporate 6.4 lithium atoms while In 3 Mo 15 Se 19 does not react. This behavior is explained on the basis of structural considerations

  8. Positronium hydride defects in thermochemically reduced alkaline-Earth oxides

    International Nuclear Information System (INIS)

    Monge, M.A.; Pareja, R.; Gonzalez, R.; Chen, Y.

    1997-01-01

    Thermochemical reduction of both hydrogen-doped MgO and CaO single crystals results in large concentrations of hydride (H - ) ions. In MgO crystals, positron lifetime and Doppler broadening experiments show that positrons are trapped at H - centers forming positronium hydride molecules [e + - H - ]. A value of 640 ps is obtained for the lifetime of the PsH states located in an anion vacancy In MgO positrons are also trapped at H 2- sites at low temperatures. The H 2- ions were induced in the crystals by blue light illumination. The formation of PsH states in CaO could not be conclusively established. (orig.)

  9. Z-H Bond Activation in (Di)hydrogen Bonding as a Way to Proton/Hydride Transfer and H2 Evolution.

    Science.gov (United States)

    Belkova, Natalia V; Filippov, Oleg A; Shubina, Elena S

    2018-02-01

    The ability of neutral transition-metal hydrides to serve as a source of hydride ion H - or proton H + is well appreciated. The hydride ligands possessing a partly negative charge are proton accepting sites, forming a dihydrogen bond, M-H δ- ⋅⋅⋅ δ+ HX (M=transition metal or metalloid). On the other hand, some metal hydrides are able to serve as a proton source and give hydrogen bond of M-H δ+ ⋅⋅⋅X type (X=organic base). In this paper we analyse recent works on transition-metal and boron hydrides showing i) how formation of an intermolecular complex between the reactants changes the Z-H (M-H and X-H) bond polarity and ii) what is the implication of such activation in the mechanisms of hydrides reactions. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Metal Hydrides for Rechargeable Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Valoeen, Lars Ole

    2000-03-01

    Rechargeable battery systems are paramount in the power supply of modern electronic and electromechanical equipment. For the time being, the most promising secondary battery systems for the future are the lithium-ion and the nickel metal hydride (NiMH) batteries. In this thesis, metal hydrides and their properties are described with the aim of characterizing and improving those. The thesis has a special focus on the AB{sub 5} type hydrogen storage alloys, where A is a rare earth metal like lanthanum, or more commonly misch metal, which is a mixture of rare earth metals, mainly lanthanum, cerium, neodymium and praseodymium. B is a transition metal, mainly nickel, commonly with additions of aluminium, cobalt, and manganese. The misch metal composition was found to be very important for the geometry of the unit cell in AB{sub 5} type alloys, and consequently the equilibrium pressure of hydrogen in these types of alloys. The A site substitution of lanthanum by misch metal did not decrease the surface catalytic properties of AB{sub 5} type alloys. B-site substitution of nickel with other transition elements, however, substantially reduced the catalytic activity of the alloy. If the internal pressure within the electrochemical test cell was increased using inert argon gas, a considerable increase in the high rate charge/discharge performance of LaNi{sub 5} was observed. An increased internal pressure would enable the utilisation of alloys with a high hydrogen equivalent pressure in batteries. Such alloys often have favourable kinetics and high hydrogen diffusion rates and thus have a potential for improving the high current discharge rates in metal hydride batteries. The kinetic properties of metal hydride electrodes were found to improve throughout their lifetime. The activation properties were found highly dependent on the charge/discharge current. Fewer charge/discharge cycles were needed to activate the electrodes if a small current was used instead of a higher

  11. Hydrogen-storing hydride complexes

    Science.gov (United States)

    Srinivasan, Sesha S [Tampa, FL; Niemann, Michael U [Venice, FL; Goswami, D Yogi [Tampa, FL; Stefanakos, Elias K [Tampa, FL

    2012-04-10

    A ternary hydrogen storage system having a constant stoichiometric molar ratio of LiNH.sub.2:MgH.sub.2:LiBH.sub.4 of 2:1:1. It was found that the incorporation of MgH.sub.2 particles of approximately 10 nm to 20 nm exhibit a lower initial hydrogen release temperature of 150.degree. C. Furthermore, it is observed that the particle size of LiBNH quaternary hydride has a significant effect on the hydrogen sorption concentration with an optimum size of 28 nm. The as-synthesized hydrides exhibit two main hydrogen release temperatures, one around 160.degree. C. and the other around 300.degree. C., with the main hydrogen release temperature reduced from 310.degree. C. to 270.degree. C., while hydrogen is first reversibly released at temperatures as low as 150.degree. C. with a total hydrogen capacity of 6 wt. % to 8 wt. %. Detailed thermal, capacity, structural and microstructural properties have been demonstrated and correlated with the activation energies of these materials.

  12. Activated aluminum hydride hydrogen storage compositions and uses thereof

    Science.gov (United States)

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

    2010-11-23

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

  13. Hydrogen adsorption on palladium and palladium hydride at 1 bar

    DEFF Research Database (Denmark)

    Johansson, Martin; Skulason, Egill; Nielsen, Gunver

    2010-01-01

    strongly to Pd hydride than to Pd. The activation barrier for desorption at a H coverage of one mono layer is slightly lower on Pd hydride, whereas the activation energy for adsorption is similar on Pd and Pd hydride. It is concluded that the higher sticking probability on Pd hydride is most likely caused...

  14. Structural and magnetic transformations in NdMn2Hx hydrides

    International Nuclear Information System (INIS)

    Budziak, A.; Zachariasz, P.; Pełka, R.; Figiel, H.; Żukrowski, J.; Woch, M.W.

    2012-01-01

    Highlights: ► Full structural phase diagram is presented for the NdMn 2 H x (2.0 ≤ x ≤ 4.0) hydrides in the temperature range of 70–385 K. ► For samples x = 2.0, 2.5, and 4.0 a splitting into two phases with different hydrogen concentrations are observed. ► Only for samples with x = 3.0 and 3.5 no spinodal decompositions are detected. ► The effects of hydrogen absorption on structural properties are shown to be reflected in magnetic behavior. ► A huge jump of magnetic ordering temperatures from ∼104 K for host NdMn 2 to above 200 K for its hydrides is observed or anticipated. - Abstract: X-ray powder diffraction and bulk magnetization measurements were used to study structural and magnetic properties of hydrides NdMn 2 H x (2.0 ≤ x ≤ 4.0). The X-ray investigations performed in the temperature range 70–385 K have revealed many structural transformations at low temperatures. In particular, a transformation from the hexagonal to the monoclinic phase and spinodal decompositions were observed. The magnetic behavior of the hydrides is correlated with the structural transitions. A tentative structural diagram is presented. The obtained results are compared with the properties of other cubic and hexagonal RMn 2 H x hydrides.

  15. Design of a ring resonator-based optical beam forming network for phased array receive antennas

    NARCIS (Netherlands)

    van 't Klooster, J.W.J.R.; Roeloffzen, C.G.H.; Meijerink, Arjan; Zhuang, L.; Marpaung, D.A.I.; van Etten, Wim; Heideman, Rene; Leinse, Arne; Schippers, H.; Verpoorte, J.; Wintels, M.

    2008-01-01

    A novel squint-free ring resonator-based optical beam forming network (OBFN) for phased array antennas (PAA) is proposed. It is intended to provide broadband connectivity to airborne platforms via geostationary satellites. In this paper, we present the design of the OBFN and its control system. Our

  16. The effect of texture on delayed hydride cracking in Zr-2.5Nb alloy

    Energy Technology Data Exchange (ETDEWEB)

    Resta Levi, R.; Sagat, S

    1999-09-01

    Pressure tubes for CANDU reactors are made of Zr-2.5Nb alloy. They are produced by hot extrusion followed by cold work, which results in a material with a pronounced crystallographic texture with basal plane normals of its hexagonal structure around the circumferential direction. Under certain conditions, this material is susceptible to a cracking mechanism called delayed hydride cracking (DHC). Our work investigated the susceptibility of Zr-2.5Nb alloy pressure tube to DHC in this pressure tube material, in terms of crystallographic texture and grain shape. The results are presented in terms of crack velocity obtained on different planes and directions of the pressure tube. The results show that it is more difficult for a crack to propagate at right angles to crystallographic basal planes (which are close to the precipitation habit plane of hydrides) than for it to propagate parallel to the basal plane. However, if the cracking plane is oriented parallel to preexisting hydrides (hydrides formed as a result of the manufacturing process), the crack propagates along these hydrides easily, even if the hydride habit planes are not oriented favourably. (author)

  17. Thermal performance study of form-stable composite phase change material with polyacrylic

    Science.gov (United States)

    Kee, Shin Yiing; Munusamy, Yamuna; Ong, Kok Seng; Chee, Swee Yong; Sanmuggam, Shimalaa

    2017-04-01

    Phase change material (PCM) is one of the most popular and widely used as thermal energy storage material because it is able to absorb and release a large amount of latent heat during a phase change process over a narrow temperature range. In this work, the form-stable composite PCM was prepared by blending of PMMA and myristic acid in different weight percentage. PMMA was used as a supporting material while myristic acid was used as PCM. Theoretically, PCM can be encapsulated in the support material after blending. However, a small amount of liquid PCMs can leak out from supporting material due to the volume change in phase change process. Therefore, a form-stable composite PCM with polyacrylic coating was studied. Leakage test was carried out to determine the leakage percentage of the form-stable composite PCM. Fourier transform infrared spectroscopy (FTIR) was used to characterize the chemical compatibility of the form-stable PCM composite while differential scanning calorimetry (DSC) was used to study the melting, freezing point and the latent heat of melting and freezing for the form-stable composite PCM.

  18. Metal hydrides: an innovative and challenging conversion reaction anode for lithium-ion batteries

    Directory of Open Access Journals (Sweden)

    Luc Aymard

    2015-08-01

    Full Text Available The state of the art of conversion reactions of metal hydrides (MH with lithium is presented and discussed in this review with regard to the use of these hydrides as anode materials for lithium-ion batteries. A focus on the gravimetric and volumetric storage capacities for different examples from binary, ternary and complex hydrides is presented, with a comparison between thermodynamic prediction and experimental results. MgH2 constitutes one of the most attractive metal hydrides with a reversible capacity of 1480 mA·h·g−1 at a suitable potential (0.5 V vs Li+/Li0 and the lowest electrode polarization (2, TiH2, complex hydrides Mg2MHx and other Mg-based hydrides. The reversible conversion reaction mechanism of MgH2, which is lithium-controlled, can be extended to others hydrides as: MHx + xLi+ + xe− in equilibrium with M + xLiH. Other reaction paths—involving solid solutions, metastable distorted phases, and phases with low hydrogen content—were recently reported for TiH2 and Mg2FeH6, Mg2CoH5 and Mg2NiH4. The importance of fundamental aspects to overcome technological difficulties is discussed with a focus on conversion reaction limitations in the case of MgH2. The influence of MgH2 particle size, mechanical grinding, hydrogen sorption cycles, grinding with carbon, reactive milling under hydrogen, and metal and catalyst addition to the MgH2/carbon composite on kinetics improvement and reversibility is presented. Drastic technological improvement in order to the enhance conversion process efficiencies is needed for practical applications. The main goals are minimizing the impact of electrode volume variation during lithium extraction and overcoming the poor electronic conductivity of LiH. To use polymer binders to improve the cycle life of the hydride-based electrode and to synthesize nanoscale composite hydride can be helpful to address these drawbacks. The development of high-capacity hydride anodes should be inspired by the emergent

  19. Metal hydrides: an innovative and challenging conversion reaction anode for lithium-ion batteries.

    Science.gov (United States)

    Aymard, Luc; Oumellal, Yassine; Bonnet, Jean-Pierre

    2015-01-01

    The state of the art of conversion reactions of metal hydrides (MH) with lithium is presented and discussed in this review with regard to the use of these hydrides as anode materials for lithium-ion batteries. A focus on the gravimetric and volumetric storage capacities for different examples from binary, ternary and complex hydrides is presented, with a comparison between thermodynamic prediction and experimental results. MgH2 constitutes one of the most attractive metal hydrides with a reversible capacity of 1480 mA·h·g(-1) at a suitable potential (0.5 V vs Li(+)/Li(0)) and the lowest electrode polarization (lithium are subsequently detailed for MgH2, TiH2, complex hydrides Mg2MH x and other Mg-based hydrides. The reversible conversion reaction mechanism of MgH2, which is lithium-controlled, can be extended to others hydrides as: MH x + xLi(+) + xe(-) in equilibrium with M + xLiH. Other reaction paths-involving solid solutions, metastable distorted phases, and phases with low hydrogen content-were recently reported for TiH2 and Mg2FeH6, Mg2CoH5 and Mg2NiH4. The importance of fundamental aspects to overcome technological difficulties is discussed with a focus on conversion reaction limitations in the case of MgH2. The influence of MgH2 particle size, mechanical grinding, hydrogen sorption cycles, grinding with carbon, reactive milling under hydrogen, and metal and catalyst addition to the MgH2/carbon composite on kinetics improvement and reversibility is presented. Drastic technological improvement in order to the enhance conversion process efficiencies is needed for practical applications. The main goals are minimizing the impact of electrode volume variation during lithium extraction and overcoming the poor electronic conductivity of LiH. To use polymer binders to improve the cycle life of the hydride-based electrode and to synthesize nanoscale composite hydride can be helpful to address these drawbacks. The development of high-capacity hydride anodes should

  20. Differential thermal, Thermogravimetric and X-ray diffraction investigation of hydration phases in cementitious waste form

    International Nuclear Information System (INIS)

    Khalil, M.Y.; Nagy, M.E.; El-Sourougy, M.R.; Zaki, A.A.

    1996-01-01

    Hydration phases of cement determine the final properties of the product. Adding other components to the cement paste may alter the final phases formed and affect properties of the hardened products. In this work ordinary portland cement and/or blast furnace slag cement were hardened with low-or intermediate-level radioactive liquid wastes and different additives. Hydration phases were investigated using differential thermal, thermogravimetric, and X-ray diffraction techniques. Low-and intermediate-level liquid wastes were found not to affect the hydration phases of cement. The addition of inorganic exchangers and latex were found to affect the hydration properties of the cement waste system. This resulted in a reduction of compressive strength. On the contrary, addition of epoxy also affected the hydration causing increase in compressive strength. 10 figs., 2 tabs

  1. First principles characterisation of brittle transgranular fracture of titanium hydrides

    International Nuclear Information System (INIS)

    Olsson, Pär A.T.; Mrovec, Matous; Kroon, Martin

    2016-01-01

    In this work we have studied transgranular cleavage and the fracture toughness of titanium hydrides by means of quantum mechanical calculations based on density functional theory. The calculations show that the surface energy decreases and the unstable stacking fault energy increases with increasing hydrogen content. This is consistent with experimental findings of brittle behaviour of titanium hydrides at low temperatures. Based on Griffith-Irwin theory we estimate the fracture toughness of the hydrides to be of the order of 1 MPa⋅m"1"/"2, which concurs well with experimental data. To investigate the cleavage energetics, we analyse the decohesion at various crystallographic planes and determine the traction-separation laws based on the Rose's extended universal binding energy relation. The calculations predict that the peak stresses do not depend on the hydrogen content of the phases, but it is rather dependent on the crystallographic cleavage direction. However, it is found that the work of fracture decreases with increasing hydrogen content, which is an indication of hydrogen induced bond weakening in the material.

  2. Hydrogen Storage using Metal Hydrides in a Stationary Cogeneration System

    International Nuclear Information System (INIS)

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

    2006-01-01

    In the frame of the development of a hydrogen production and storage unit to supply a 40 kW stationary fuel cell, a metal hydride storage tank was chosen according to its reliability and high energetic efficiency. The study of AB5 compounds led to the development of a composition adapted to the project needs. The absorption/desorption pressures of the hydride at 75 C (2 / 1.85 bar) are the most adapted to the specifications. The reversible storage capacity (0.95 %wt) has been optimized to our work conditions and chemical kinetics is fast. The design of the Combined Heat and Power CHP system requires 5 kg hydrogen storage but in a first phase, only a 0.1 kg prototype has been realised and tested. Rectangular design has been chosen to obtain good compactness with an integrated plate fin type heat exchanger designed to reach high absorption/desorption rates. In this paper, heat and mass transfer characteristics of the Metal Hydride tank (MH tank) during absorption/desorption cycles are given. (authors)

  3. Hydride heat pump with heat regenerator

    Science.gov (United States)

    Jones, Jack A. (Inventor)

    1991-01-01

    A regenerative hydride heat pump process and system is provided which can regenerate a high percentage of the sensible heat of the system. A series of at least four canisters containing a lower temperature performing hydride and a series of at least four canisters containing a higher temperature performing hydride is provided. Each canister contains a heat conductive passageway through which a heat transfer fluid is circulated so that sensible heat is regenerated. The process and system are useful for air conditioning rooms, providing room heat in the winter or for hot water heating throughout the year, and, in general, for pumping heat from a lower temperature to a higher temperature.

  4. A procedure for preparing alkali metal hydrides

    International Nuclear Information System (INIS)

    Lemieux, R.U.; Sanford, C.E.; Prescott, J.F.

    1976-01-01

    A plain low cost, procedure for the continuous, low temperature preparation of sodium or potassium hydrides using cheap reagents is presented. Said invention is especially concerned with a process of purifying of a catalytic exchange liquid used for deuterium enrichment, in which an alkali metal hydride is produced as intermediate product. The procedure for producing the sodium and potassium hydrides consists in causing high pressure hydrogen to be absorbed by a mixture of at least a lower monoalkylamine and an alkylamide of an alkali metal from at least one of said amines [fr

  5. Hydride observations using the neutrography technique

    International Nuclear Information System (INIS)

    Meyer, G.; Baruj, A.; Borzone, E.M.; Cardenas, R.; Szames, E.; Somoza, J.; Rivas, S.; Sanchez, F.A.; Marin, J.

    2012-01-01

    Neutron radiography observations were performed at the RA-6 experimental nuclear facility in Bariloche. Images from a prototype of a hydride-based hydrogen storage device have been obtained. The technique allows visualizing the inner hydride space distribution. The hydride appeared compacted at the lower part of the prototype after several cycles of hydrogen charge and discharge. The technique has also been applied to the study of Zr/ZrH 2 samples. There is a linear relation between the sample width/hydrogen concentration and the photograph grey scale. This information could be useful for the study of nuclear engineering materials and to determine their possible degradation by hydrogen pick up (author)

  6. Hermite-Gaussian beams with self-forming spiral phase distribution

    Science.gov (United States)

    Zinchik, Alexander A.; Muzychenko, Yana B.

    2014-05-01

    Spiral laser beams is a family of laser beams that preserve the structural stability up to scale and rotate with the propagation. Properties of spiral beams are of practical interest for laser technology, medicine and biotechnology. Researchers use a spiral beams for movement and manipulation of microparticles. Spiral beams have a complicated phase distribution in cross section. This paper describes the results of analytical and computer simulation of Hermite-Gaussian beams with self-forming spiral phase distribution. In the simulation used a laser beam consisting of the sum of the two modes HG TEMnm and TEMn1m1. The coefficients n1, n, m1, m were varied. Additional phase depending from the coefficients n, m, m1, n1 imposed on the resulting beam. As a result, formed the Hermite Gaussian beam phase distribution which takes the form of a spiral in the process of distribution. For modeling was used VirtualLab 5.0 (manufacturer LightTrans GmbH).

  7. Decomposition kinetics of plutonium hydride

    Energy Technology Data Exchange (ETDEWEB)

    Haschke, J.M.; Stakebake, J.L.

    1979-01-01

    Kinetic data for decomposition of PuH/sub 1/ /sub 95/ provides insight into a possible mechanism for the hydriding and dehydriding reactions of plutonium. The fact that the rate of the hydriding reaction, K/sub H/, is proportional to P/sup 1/2/ and the rate of the dehydriding process, K/sub D/, is inversely proportional to P/sup 1/2/ suggests that the forward and reverse reactions proceed by opposite paths of the same mechanism. The P/sup 1/2/ dependence of hydrogen solubility in metals is characteristic of the dissociative absorption of hydrogen; i.e., the reactive species is atomic hydrogen. It is reasonable to assume that the rates of the forward and reverse reactions are controlled by the surface concentration of atomic hydrogen, (H/sub s/), that K/sub H/ = c'(H/sub s/), and that K/sub D/ = c/(H/sub s/), where c' and c are proportionality constants. For this surface model, the pressure dependence of K/sub D/ is related to (H/sub s/) by the reaction (H/sub s/) reversible 1/2H/sub 2/(g) and by its equilibrium constant K/sub e/ = (H/sub 2/)/sup 1/2//(H/sub s/). In the pressure range of ideal gas behavior, (H/sub s/) = K/sub e//sup -1/(RT)/sup -1/2/ and the decomposition rate is given by K/sub D/ = cK/sub e/(RT)/sup -1/2/P/sup 1/2/. For an analogous treatment of the hydriding process with this model, it can be readily shown that K/sub H/ = c'K/sub e//sup -1/(RT)/sup -1/2/P/sup 1/2/. The inverse pressure dependence and direct temperature dependence of the decomposition rate are correctly predicted by this mechanism which is most consistent with the observed behavior of the Pu--H system.

  8. Hydriding and structural characteristics of thermally cycled and cold-worked V-0.5 at.%C alloy

    International Nuclear Information System (INIS)

    Chandra, Dhanesh; Sharma, Archana; Chellappa, Raja; Cathey, William N.; Lynch, Franklin E.; Bowman, Robert C.; Wermer, Joseph R.; Paglieri, Stephen N.

    2008-01-01

    High pressure hydrides of V 0.995 C 0.005 were thermally cycled between β 2 - and γ-phases hydrides for potential use in cryocoolers/heat pumps for space applications. The effect of addition of carbon to vanadium, on the plateau enthalpies of the high pressure β 2 + γ region is minimal. This is in contrast to the calculated plateau enthalpies for low pressure (α + β 1 ) mixed phases which showed a noticeable lowering of the values. Thermal cycling between β 2 -and γ-phase hydrides increased the absorption pressures but desorption pressure did not change significantly and the free energy loss due to hysteresis also increased. Hydriding of the alloy with prior cold-work increased the pressure hysteresis significantly and lowered the hydrogen capacity. In contrast to the alloy without any prior straining (as-cast), desorption pressure of the alloy with prior cold-work also decreased significantly. Microstrains, 2 > 1/2 , in the β 2 -phase lattice of the thermally cycled hydrides decreased after 778 cycles and the domain sizes increased. However, in the γ-phase, both the microstrains and the domain sizes decreased after thermal cycling indicating no particle size effect. The dehydrogenated α-phase after 778 thermal cycles also showed residual microstrains in the lattice, similar to those observed in intermetallic hydrides. The effect of thermal cycling (up to 4000 cycles between β 2 - and γ-phases) and cold working on absorption/desorption pressures, hydrogen storage capacity, microstrains, long-range strains, and domain sizes of β 2 - and γ-phase hydrides of V 0.995 C 0.005 alloys are presented

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

    Science.gov (United States)

    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...2. REPORT TYPE Final Performance 3. DATES COVERED (From - To) 30-09-2014 to 29-09-2015 4. TITLE AND SUBTITLE The Oxidation Products of Aluminum ...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

  10. Hydrogen storage and evolution catalysed by metal hydride complexes.

    Science.gov (United States)

    Fukuzumi, Shunichi; Suenobu, Tomoyoshi

    2013-01-07

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

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

    Science.gov (United States)

    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.

  12. Influence of cooling rate on phase formation in spray-formed H13 tool steel

    Energy Technology Data Exchange (ETDEWEB)

    McHugh, K.M. [Industrial Technology Department, Idaho National Laboratory, Idaho Falls, ID 83415-2050 (United States)], E-mail: kevin.mchugh@inl.gov; Lin, Y.; Zhou, Y.; Lavernia, E.J. [Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616 (United States)

    2008-03-25

    Spray forming is an effective way to process many tool steels into near-net-shape molds, dies, and related tooling. The general approach involves depositing atomized droplets onto a refractory pattern in order to image the pattern's features. The pattern is removed and the die insert is mounted in a standard mold base or holding block. This approach results in significant cost and lead-time savings compared to conventional machining. Spray-formed dies perform well in many industrial forming operations, oftentimes exhibiting extended die life compared to conventional dies of the same material and design. Care must be exercised when spray forming tool steel dies to minimize porosity and control the nature and distribution of phases and residual stresses. Selection of post-deposition heat treatment is important to tailor the die's properties (hardness, strength, impact energy, etc.) for a particular application. This paper examines how the cooling rate during spray processing and heat treatment of H13 tool steel influences phase formation. Porosity and hardness were evaluated over a range of deposit cooling rates and residual stresses were evaluated for a die in the as-deposited condition. Finally, the performance of spray-formed dies during production runs in forging, extrusion, and die casting is described.

  13. Influence of cooling rate on phase formation in spray-formed H13 tool steel

    International Nuclear Information System (INIS)

    McHugh, K.M.; Lin, Y.; Zhou, Y.; Lavernia, E.J.

    2008-01-01

    Spray forming is an effective way to process many tool steels into near-net-shape molds, dies, and related tooling. The general approach involves depositing atomized droplets onto a refractory pattern in order to image the pattern's features. The pattern is removed and the die insert is mounted in a standard mold base or holding block. This approach results in significant cost and lead-time savings compared to conventional machining. Spray-formed dies perform well in many industrial forming operations, oftentimes exhibiting extended die life compared to conventional dies of the same material and design. Care must be exercised when spray forming tool steel dies to minimize porosity and control the nature and distribution of phases and residual stresses. Selection of post-deposition heat treatment is important to tailor the die's properties (hardness, strength, impact energy, etc.) for a particular application. This paper examines how the cooling rate during spray processing and heat treatment of H13 tool steel influences phase formation. Porosity and hardness were evaluated over a range of deposit cooling rates and residual stresses were evaluated for a die in the as-deposited condition. Finally, the performance of spray-formed dies during production runs in forging, extrusion, and die casting is described

  14. Disposal of tritium-exposed metal hydrides

    International Nuclear Information System (INIS)

    Nobile, A.; Motyka, T.

    1991-01-01

    A plan has been established for disposal of tritium-exposed metal hydrides used in Savannah River Site (SRS) tritium production or Materials Test Facility (MTF) R ampersand D operations. The recommended plan assumes that the first tritium-exposed metal hydrides will be disposed of after startup of the Solid Waste Disposal Facility (SWDF) Expansion Project in 1992, and thus the plan is consistent with the new disposal requiremkents that will be in effect for the SWDF Expansion Project. Process beds containing tritium-exposed metal hydride powder will be disposed of without removal of the powder from the bed; however, disposal of tritium-exposed metal hydride powder that has been removed from its process vessel is also addressed

  15. Method of making alkali metal hydrides

    Science.gov (United States)

    Pecharsky, Vitalij K.; Gupta, Shalabh; Pruski, Marek; Hlova, Ihor; Castle, Andra

    2017-05-30

    A method is provided for making alkali metal hydrides by mechanochemically reacting alkali metal and hydrogen gas under mild temperature (e.g room temperature) and hydrogen pressure conditions without the need for catalyst, solvent, and intentional heating or cooling.

  16. Probabilistic modeling of material resistance to crack initiation due to hydrided region overloads in CANDU Zr-2.5%Nb pressure tubes

    International Nuclear Information System (INIS)

    Gutkin, L.; Scarth, D.A.

    2014-01-01

    Zr-2.5%Nb pressure tubes in CANDU nuclear reactors are susceptible to hydride-assisted cracking at the locations of stress concentration, such as in-service flaws. Probabilistic methodology is being developed to evaluate such flaws for crack initiation due to hydrided region overloads, which occur when the applied stress acting on a flaw with an existing hydrided region at its tip exceeds the stress at which the hydrided region is formed. As part of this development, probabilistic modeling of pressure tube material resistance to overload crack initiation has been performed on the basis of a set of test data specifically designed to study the effects of non-ratcheting hydride formation conditions and load reduction prior to hydride formation. In the modeling framework, the overload resistance is represented as a power-law function of the material resistance to initiation of delayed hydride cracking under constant loading, where both the overload crack initiation coefficient and the overload crack initiation exponent vary with the flaw geometry. In addition, the overload crack initiation coefficient varies with the extent of load reduction prior to hydride formation as well as the number of non-ratcheting hydride formation thermal cycles. (author)

  17. Probabilistic modeling of material resistance to crack initiation due to hydrided region overloads in CANDU Zr-2.5%Nb pressure tubes

    Energy Technology Data Exchange (ETDEWEB)

    Gutkin, L.; Scarth, D.A. [Kinectrics Inc., Toronto, ON (Canada)

    2014-07-01

    Zr-2.5%Nb pressure tubes in CANDU nuclear reactors are susceptible to hydride-assisted cracking at the locations of stress concentration, such as in-service flaws. Probabilistic methodology is being developed to evaluate such flaws for crack initiation due to hydrided region overloads, which occur when the applied stress acting on a flaw with an existing hydrided region at its tip exceeds the stress at which the hydrided region is formed. As part of this development, probabilistic modeling of pressure tube material resistance to overload crack initiation has been performed on the basis of a set of test data specifically designed to study the effects of non-ratcheting hydride formation conditions and load reduction prior to hydride formation. In the modeling framework, the overload resistance is represented as a power-law function of the material resistance to initiation of delayed hydride cracking under constant loading, where both the overload crack initiation coefficient and the overload crack initiation exponent vary with the flaw geometry. In addition, the overload crack initiation coefficient varies with the extent of load reduction prior to hydride formation as well as the number of non-ratcheting hydride formation thermal cycles. (author)

  18. Suppression of hydride precipitates in niobium superconducting radio-frequency cavities

    Science.gov (United States)

    Ford, Denise C.; Cooley, Lance D.; Seidman, David N.

    2013-10-01

    Niobium hydride is a suspected contributor to degraded niobium superconducting radio-frequency (SRF) cavity performance by Q slope and Q disease. The concentration and distribution of hydrogen atoms in niobium can be strongly affected by the cavity processing treatments. This study provides guidance for cavity processing based on density functional theory calculations of the properties of common processing impurity species—hydrogen, oxygen, nitrogen, and carbon—in the body-centered cubic (bcc) niobium lattice. We demonstrate that some fundamental properties are shared between the impurity atoms, such as anionic character in niobium. The strain field produced, however, by hydrogen atoms is both geometrically different and substantially weaker than the strain field produced by the other impurities. We focus on the interaction between oxygen and hydrogen atoms in the lattice, and demonstrate that the elastic interactions between these species and the bcc niobium lattice cause trapping of hydrogen and oxygen atoms by bcc niobium lattice vacancies. We also show that the attraction of oxygen to a lattice vacancy is substantially stronger than the attraction of hydrogen to the vacancy. Additionally, hydrogen dissolved in niobium tetrahedral interstitial sites can be trapped by oxygen, nitrogen and possibly carbon atoms dissolved in octahedral interstitial sites. These results indicate that the concentration of oxygen in the bcc lattice can have a strong impact on the ability of hydrogen to form detrimental phases. Based on our results and a literature survey, we propose a mechanism for the success of the low-temperature annealing step applied to niobium SRF cavities. We also recommend further examination of nitrogen and carbon in bcc niobium, and particularly the role that nitrogen can play in preventing detrimental hydride phase formation.

  19. Stoichiometry of the U3O8 phase formed during calcination of some uranium compounds

    International Nuclear Information System (INIS)

    El-Fekey, S.A.; Farah, M.Y.; Rofail, N.H.

    1981-01-01

    Although recent work has shown U 3 O 8 phase to be the decomposition product obtained after calcining uranyl nitrate, sulphate or ammonium uranate, neither the necessary conditions for obtaining stoichiometric U 3 O 8 nor the details of the reaction have been established. Presence of sulphate or nitrate ions during preparation greatly affects the O/U of the obtained oxides and the physico-chemical properties of uranium tetrafluoride prepared afterwards from it (1-3). The aim of the present investigation was to study the effect of calcination regimes on the stoichiometry of the U 3 O 8 phase produced by the thermal decomposition of uranyl nitrate, sulphate, and ammonium uranate, which was prepared by precipitation from nuclear-pure uranyl sulphate. Stoichiometry of the U 3 O 8 phase formed during calcination of ammonium uranate precipitated from nuclear pure uranyl nitrate solution was reported before (1)

  20. Structural investigation of the spinel phase formed in fuel CRUD before and after zinc injection

    International Nuclear Information System (INIS)

    Chen, J.

    2002-01-01

    Spinel phase is an important constituent of fuel CRUD. Since it can accommodate 60 Co in its crystal structure, its stability in reactor water environment is crucial for the radioactivity control in LWR plants. With increasing curiosity about zinc injection technology, the mechanism of the interaction of zinc with the spinel has drawn much attention. This paper describes the crystal and microstructures of spinel phase in the fuel CRUD collected on four fuel rods of 1- and 5-cycle, respectively, from Barsebaeck 2 BWR before and after zinc injection operation. High precision X-ray powder diffraction technique has been applied to identify the phase compositions of fuel CRUD and to measure the cell length of the spinel phase formed. The results show that, after about 1-cycle zinc injection operation, the tenacious CRUD formed on the fresh fuel rod contains defective zinc oxide, in addition to hematite and spinel as commonly seen. Moreover, the phase ratio of spinel to hematite is much increased. The cell length of the spinel is increased accordingly, which is the direct evidence for the presence of zinc in the spinel structure. For the 5-cycle rod, however, neither zinc oxide nor any change in the phase ratio has been detected. The cell length of the spinel has been increased, in a less degree, however, as compared to that for the 1-cycle rod. The cell lengths of spinel are similar in both tenacious and loose CRUD layers, indicating that zinc was able to easily penetrate through the tenacious CRUD layer. (authors)

  1. Influence of hydrides orientation on strain, damage and failure of hydrided zircaloy-4

    International Nuclear Information System (INIS)

    Racine, A.

    2005-09-01

    In pressurized water reactors of nuclear power plants, fuel pellets are contained in cladding tubes, made of Zirconium alloy, for instance Zircaloy-4. During their life in the primary water of the reactor (155 bars, 300 C), cladding tubes are oxidized and consequently hydrided. A part of the hydrogen given off precipitates as Zirconium hydrides in the bulk material and embrittles the material. This embrittlement depends on many parameters, among which hydrogen content and orientation of hydrides with respect to the applied stress. This investigation is devoted to the influence of the orientation of hydrides with respect to the applied stress on strain, damage and failure mechanisms. Macroscopic and SEM in-situ ring tensile tests are performed on cladding tube material (unirradiated cold worked stress-relieved Zircaloy-4) hydrided with about 200 and 500 wppm hydrogen, and with different main hydrides orientation: either parallel or perpendicular to the circumferential tensile direction. We get the mechanical response of the material as a function of hydride orientation and hydrogen content and we investigate the deformation, damage and failure mechanisms. In both cases, digital image correlation techniques are used to estimate local and global strain distributions. Neither the tensile stress-strain response nor the global and local strain modes are significantly affected by hydrogen content or hydride orientation, but the failure modes are strongly modified. Indeed, only 200 wppm radial hydrides embrittle Zy-4: sample fail in the elastic domain at about 350 MPa before strain bands could develop; whereas in other cases sample reach at least 750 MPa before necking and final failure, in ductile or brittle mode. To model this particular heterogeneous material behavior, a non-coupled damage approach which takes into account the anisotropic distribution of the hydrides is proposed. Its parameters are identified from the macroscopic strain field measurements and a

  2. Characteristics of hydride precipitation and reorientation in spent-fuel cladding

    International Nuclear Information System (INIS)

    Chung, H. M.; Strain, R. V.; Billone, M. C.

    2000-01-01

    The morphology, number density, orientation, distribution, and crystallographic aspects of Zr hydrides in Zircaloy fuel cladding play important roles in fuel performance during all phases before and after discharge from the reactor, i.e., during normal operation, transient and accident situations in the reactor, temporary storage in a dry cask, and permanent storage in a waste repository. In the past, partly because of experimental difficulties, hydriding behavior in irradiated fuel cladding has been investigated mostly by optical microscopy (OM). In the present study, fundamental metallurgical and crystallographic characteristics of hydride precipitation and reorientation were investigated on the microscopic level by combined techniques of OM and transmission electron and scanning electron microscopy (TEM and SEM) of spent-fuel claddings discharged from several boiling and pressurized water reactors (BWRs and PWRs). Defueled sections of standard and Zr-lined Zircaloy-2 fuel claddings, irradiated to fluences of ∼3.3 x 10 21 n cm -2 and ∼9.2 x 10 21 n cm -2 (E > 1 MeV), respectively, were obtained from spent fuel rods discharged from two BWRs. Sections of standard and low-tin Zircaloy-4 claddings, irradiated to fluences of ∼4.4 x 10 21 n cm -2 , ∼5.9 x 10 21 n cm -2 , and ∼9.6 x 10 21 n cm -2 (E > 1 MeV) in three PWRs, were also obtained. Microstructural characteristics of hydrides were analyzed in as-irradiated condition and after gas-pressurization-burst or expanding-mandrel tests at 292-325 C in Ar for some of the spent-fuel claddings. Analyses were also conducted of hydride habit plane, morphology, and reorientation characteristics on unirradiated Zircaloy-4 cladding that contained dense radial hydrides. Reoriented hydrides in the slowly cooled unirradiated cladding were produced by expanding-mandrel loading

  3. Effect of magnesium hydride on the corrosion behavior of an AZ91 magnesium alloy in sodium chloride solution

    International Nuclear Information System (INIS)

    Chen Jian; Dong Junhua; Wang Jianqiu; Han Enhou; Ke Wei

    2008-01-01

    The effect of magnesium hydride on the corrosion behavior of an as-cast AZ91 alloy in 3.5 wt.% NaCl solution was investigated using gas collection method and potentiostatic test. The Pourbaix diagram of Mg-H 2 O system was built using thermodynamic calculation. It was possible that magnesium hydride could form in the whole pH range in theory. The experimental results showed that at cathodic region, magnesium hydride formed on surface, which was the controlling process for the corrosion behavior of AZ91 alloy; at anodic region and free corrosion potential, magnesium hydride model and partially protective film model, monovalent magnesium ion model and particle undermining model were responsible for the corrosion process of AZ91 alloy

  4. Hydrogen isotope exchange in a metal hydride tube

    Energy Technology Data Exchange (ETDEWEB)

    Robinson, David B. [Sandia National Lab. (SNL-CA), Livermore, CA (United States)

    2014-09-01

    This report describes a model of the displacement of one hydrogen isotope within a metal hydride tube by a different isotope in the gas phase that is blown through the tube. The model incorporates only the most basic parameters to make a clear connection to the theory of open-tube gas chromatography, and to provide a simple description of how the behavior of the system scales with controllable parameters such as gas velocity and tube radius. A single tube can be seen as a building block for more complex architectures that provide higher molar flow rates or other advanced design goals.

  5. Atom Probe Analysis of Ex Situ Gas-Charged Stable Hydrides.

    Science.gov (United States)

    Haley, Daniel; Bagot, Paul A J; Moody, Michael P

    2017-04-01

    In this work, we report on the atom probe tomography analysis of two metallic hydrides formed by pressurized charging using an ex situ hydrogen charging cell, in the pressure range of 200-500 kPa (2-5 bar). Specifically we report on the deuterium charging of Pd/Rh and V systems. Using this ex situ system, we demonstrate the successful loading and subsequent atom probe analysis of deuterium within a Pd/Rh alloy, and demonstrate that deuterium is likely present within the oxide-metal interface of a native oxide formed on vanadium. Through these experiments, we demonstrate the feasibility of ex situ hydrogen analysis for hydrides via atom probe tomography, and thus a practical route to three-dimensional imaging of hydrogen in hydrides at the atomic scale.

  6. The effect of thermal pre-treatment of titanium hydride (TiH2) powder in argon condition

    Science.gov (United States)

    Franciska P., L.; Erryani, Aprilia; Annur, Dhyah; Kartika, Ika

    2018-04-01

    Titanium hydride (TiH2) powders are used to enhance the foaming process in the formation of a highly porous metallic material with a cellular structure. But, the low temperature of hydrogen release is one of its problems. The present study, different thermal pre-treatment temperatures were employed to investigate the decomposition behavior of TiH2 to retard or delay a hydrogen gas release process during foaming. As a foaming agent, TiH2 was subjected to various heat treatments prior at 450 and 500°C during 2 hours in argon condition. To study the formation mechanism, the thermal behavior of titanium hydride and hydrogen release are investigated by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The morphology of pre-treated titanium hydride powders were examined using Scanning Electron Microscope (SEM) while unsure mapping and elemental composition of the pre-treated powders processed by Energy Dispersive Spectroscopy (EDS). To study the phase formation was characterized by X-ray diffraction analysis (XRD). In accordance with the results, an increase in pre-treatment temperature of TiH2 to higher degrees are changing the process of releasing hydrogen from titanium hydride powder. DTA/TGA results showed that thermal pre-treatment TiH2 at 450°C, released the hydrogen gas at 560°C in heat treatment when foaming process. Meanwhile, thermal pre-treatment in TiH2 at 500°C, released the hydrogen gas at 670°C when foaming process. There is plenty of direct evidence for the existence of oxide layers that showed by EDS analysis obtained in SEM. As oxygen is a light element and qualitative proof shows that the higher pre-treatment temperature produces more and thicker oxygen layers on the surface of the TiH2 powder particles. It might the thickness of oxide layer are different from different pre-treatment temperatures, which leading to the differences in the decomposition temperature. But from SEM result that oxidation of the powder does not

  7. gamma-Zr-Hydride Precipitate in Irradiated Massive delta- Zr-Hydride

    DEFF Research Database (Denmark)

    Warren, M. R.; Bhattacharya, D. K.

    1975-01-01

    During examination of A Zircaloy-2-clad fuel pin, which had been part of a test fuel assembly in a boiling water reactor, several regions of severe internal hydriding were noticed in the upper-plenum end of the pin. Examination of similar fuel pins has shown that hydride of this type is caused by...... to irradiation-induced swelling....

  8. Interface Enthalpy-Entropy Competition in Nanoscale Metal Hydrides

    Directory of Open Access Journals (Sweden)

    Nicola Patelli

    2018-01-01

    Full Text Available We analyzed the effect of the interfacial free energy on the thermodynamics of hydrogen sorption in nano-scaled materials. When the enthalpy and entropy terms are the same for all interfaces, as in an isotropic bi-phasic system, one obtains a compensation temperature, which does not depend on the system size nor on the relative phase abundance. The situation is different and more complex in a system with three or more phases, where the interfaces have different enthalpy and entropy. We also consider the possible effect of elastic strains on the stability of the hydride phase and on hysteresis. We compare a simple model with experimental data obtained on two different systems: (1 bi-phasic nanocomposites where ultrafine TiH2 crystallite are dispersed within a Mg nanoparticle and (2 Mg nanodots encapsulated by different phases.

  9. Accommodation stresses in hydride precipitates by synchrotron x-ray diffraction

    International Nuclear Information System (INIS)

    Santisteban, J R; Vicente, M A; Vizcaino, P; Banchik, A D; Almer, J

    2012-01-01

    Hydride-forming materials (Zr, Ti, Nb, etc) are affected by a sub-critical crack growth mechanism that involves the diffusion of H to the stressed region ahead of a crack, followed by nucleation and fracture of hydrides at the crack tip [1]. The phenomenon is intermittent, with the crack propagating through the hydride and stopping when it reaches the matrix. By repeating these processes, the crack propagates through a component at a rate that is highly dependent on the temperature history of the component. Most research effort to understand this phenomenon has occurred within the nuclear industry, as it affects the safe operation of pressure tubes (Zr2.5%Nb) and the long-term storage of nuclear fuel (Zircaloy cladding). Stress-induced hydride formation is a consequence of the volume dilatation that accompanies hydride formation (of the order of 15%), which is elastoplastically accommodated by the matrix and precipitate. Compressive stresses are expected within hydride precipitates due to the constraint imposed by the matrix. Such 'accommodation' stresses are essential ingredients in all theoretical models developed to assess the crack growth rate dependence on operational variables such as temperature, applied stress intensity factor, or overall H concentration [2]. Yet little experimental information is available about the magnitude and directionality of such accommodation stresses. Synchrotron X-ray diffraction is the only technique capable of quantifying such stresses. Here we briefly describe the fundaments of the technique, when used through an area detector placed in transmission geometry. The results of the experiments have allowed us to produce a comprehensive picture about the magnitude and origin of accommodation stresses in δ zirconium hydride platelets (author)

  10. Kinetics of the isothermal decomposition of zirconium hydride: terminal solid solubility for precipitation and dissolution

    Science.gov (United States)

    Denisov, E. A.; Kompaniets, T. N.; Voyt, A. P.

    2018-05-01

    The hydrogen permeation technique in the surface-limited regime (SLR) was first used to study the isothermal decomposition of zirconium hydride. It is shown that under isothermal conditions, the hydrogen terminal solid solubility in the α-phase for hydride precipitation (TSSp) and dissolution (TSSd) differ only by 6%, in contrast to the 20-30% indicated in the available literature. It is demonstrated that even the minimum heating/cooling rate (1 C/min) used in the traditional methods of studying TSSp and TSSd is too high to exclude the effect of kinetics on the results obtained.

  11. Multislice simulations for in-situ HRTEM studies of nanostructured magnesium hydride at ambient hydrogen pressure

    Energy Technology Data Exchange (ETDEWEB)

    Surrey, Alexander, E-mail: a.surrey@ifw-dresden.de [IFW Dresden, Institute for Metallic Materials, P.O. Box 270116, D-01171 Dresden (Germany); Institut für Festkörperphysik, Technische Universität Dresden, D-01062 Dresden (Germany); Schultz, Ludwig [IFW Dresden, Institute for Metallic Materials, P.O. Box 270116, D-01171 Dresden (Germany); Institut für Festkörperphysik, Technische Universität Dresden, D-01062 Dresden (Germany); Rellinghaus, Bernd, E-mail: b.rellinghaus@ifw-dresden.de [IFW Dresden, Institute for Metallic Materials, P.O. Box 270116, D-01171 Dresden (Germany)

    2017-04-15

    Highlights: • Multislice HRTEM contrast simulations of a windowed environmental cell. • Study of Mg and MgH2 nanocrystals as model system in hydrogen at ambient pressure. • Investigation of spatial resolution and contrast depending on specimen thickness, defocus, and hydrogen pressure. • Atomic resolution is expected for specimens as thin as 5  nm. - Abstract: The use of transmission electron microscopy (TEM) for the structural characterization of many nanostructured hydrides, which are relevant for solid state hydrogen storage, is hindered due to a rapid decomposition of the specimen upon irradiation with the electron beam. Environmental TEM allows to stabilize the hydrides by applying a hydrogen back pressure of up to 4.5 bar in a windowed environmental cell. The feasibility of high-resolution TEM (HRTEM) investigations of light weight metals and metal hydrides in such a “nanoreactor” is studied theoretically by means of multislice HRTEM contrast simulations using Mg and its hydride phase, MgH{sub 2}, as model system. Such a setup provides the general opportunity to study dehydrogenation and hydrogenation reactions at the nanoscale under technological application conditions. We analyze the dependence of both the spatial resolution and the HRTEM image contrast on parameters such as the defocus, the metal/hydride thickness, and the hydrogen pressure in order to explore the possibilities and limitations of in-situ experiments with windowed environmental cells. Such simulations may be highly valuable to pre-evaluate future experimental studies.

  12. Multislice simulations for in-situ HRTEM studies of nanostructured magnesium hydride at ambient hydrogen pressure

    International Nuclear Information System (INIS)

    Surrey, Alexander; Schultz, Ludwig; Rellinghaus, Bernd

    2017-01-01

    Highlights: • Multislice HRTEM contrast simulations of a windowed environmental cell. • Study of Mg and MgH2 nanocrystals as model system in hydrogen at ambient pressure. • Investigation of spatial resolution and contrast depending on specimen thickness, defocus, and hydrogen pressure. • Atomic resolution is expected for specimens as thin as 5  nm. - Abstract: The use of transmission electron microscopy (TEM) for the structural characterization of many nanostructured hydrides, which are relevant for solid state hydrogen storage, is hindered due to a rapid decomposition of the specimen upon irradiation with the electron beam. Environmental TEM allows to stabilize the hydrides by applying a hydrogen back pressure of up to 4.5 bar in a windowed environmental cell. The feasibility of high-resolution TEM (HRTEM) investigations of light weight metals and metal hydrides in such a “nanoreactor” is studied theoretically by means of multislice HRTEM contrast simulations using Mg and its hydride phase, MgH_2, as model system. Such a setup provides the general opportunity to study dehydrogenation and hydrogenation reactions at the nanoscale under technological application conditions. We analyze the dependence of both the spatial resolution and the HRTEM image contrast on parameters such as the defocus, the metal/hydride thickness, and the hydrogen pressure in order to explore the possibilities and limitations of in-situ experiments with windowed environmental cells. Such simulations may be highly valuable to pre-evaluate future experimental studies.

  13. Phenolic composition of pomegranate peel extracts using an LC-MS approach with silica hydride columns

    Science.gov (United States)

    The peels of different pomegranate cultivars (Molla Nepes, Parfianka, Purple Heart, Wonderful and Vkunsyi) were compared in terms of phenolic composition and total phenolics. Analyses were performed on two silica hydride-based stationary phases: phenyl and undecenoic acid columns. Quantitation was ...

  14. Reactivity patterns of transition metal hydrides and alkyls

    International Nuclear Information System (INIS)

    Jones, W.D. II.

    1979-05-01

    The complex PPN + CpV(CO) 3 H - (Cp=eta 5 -C 5 H 5 and PPN = (Ph 3 P) 2 ) was prepared in 70% yield and its physical properties and chemical reactions investigated. PPN + CpV(CO) 3 H - reacts with a wide range of organic halides. The organometallic products of these reactions are the vanadium halides PPN + [CpV(C) 3 X] - and in some cases the binuclear bridging hydride PPN + [CpV(CO) 3 ] 2 H - . The borohydride salt PPN + [CpV(CO) 3 BH 4 ] - has also been prepared. The reaction between CpV(CO) 3 H - and organic halides was investigated and compared with halide reductions carried out using tri-n-butyltin hydride. Results demonstrate that in almost all cases, the reduction reaction proceeds via free radical intermediates which are generated in a chain process, and are trapped by hydrogen transfer from CpV(CO) 3 H - . Sodium amalgam reduction of CpRh(CO) 2 or a mixture of CpRh(CO) 2 and CpCo(CO) 2 affords two new anions, PPN + [Cp 2 Rh 3 (CO) 4 ] - and PPN + [Cp 2 RhCo(CO) 2 ] - . CpMo(CO) 3 H reacts with CpMo(CO) 3 R (R=CH 3 ,C 2 H 5 , CH 2 C 6 H 5 ) at 25 to 50 0 C to produce aldehyde RCHO and the dimers [CpMo(CO) 3 ] 2 and [CpMo(CO) 2 ] 2 . In general, CpV(CO) 3 H - appears to transfer a hydrogen atom to the metal radical anion formed in an electron transfer process, whereas CpMo(CO) 3 H transfers hydride in a 2-electron process to a vacant coordination site. The chemical consequences are that CpV(CO) 3 H - generally reacts with metal alkyls to give alkanes via intermediate alkyl hydride species whereas CpMo(CO) 3 H reacts with metal alkyls to produce aldehyde, via an intermediate acyl hydride species

  15. Reactivity patterns of transition metal hydrides and alkyls

    Energy Technology Data Exchange (ETDEWEB)

    Jones, W.D. II

    1979-05-01

    The complex PPN/sup +/ CpV(CO)/sub 3/H/sup -/ (Cp=eta/sup 5/-C/sub 5/H/sub 5/ and PPN = (Ph/sub 3/P)/sub 2/) was prepared in 70% yield and its physical properties and chemical reactions investigated. PPN/sup +/ CpV(CO)/sub 3/H/sup -/ reacts with a wide range of organic halides. The organometallic products of these reactions are the vanadium halides PPN/sup +/(CpV(C)/sub 3/X)/sup -/ and in some cases the binuclear bridging hydride PPN/sup +/ (CpV(CO)/sub 3/)/sub 2/H/sup -/. The borohydride salt PPN/sup +/(CpV(CO)/sub 3/BH/sub 4/)/sup -/ has also been prepared. The reaction between CpV(CO)/sub 3/H/sup -/ and organic halides was investigated and compared with halide reductions carried out using tri-n-butyltin hydride. Results demonstrate that in almost all cases, the reduction reaction proceeds via free radical intermediates which are generated in a chain process, and are trapped by hydrogen transfer from CpV(CO)/sub 3/H/sup -/. Sodium amalgam reduction of CpRh(CO)/sub 2/ or a mixture of CpRh(CO)/sub 2/ and CpCo(CO)/sub 2/ affords two new anions, PPN/sup +/ (Cp/sub 2/Rh/sub 3/(CO)/sub 4/)/sup -/ and PPN/sup +/(Cp/sub 2/RhCo(CO)/sub 2/)/sup -/. CpMo(CO)/sub 3/H reacts with CpMo(CO)/sub 3/R (R=CH/sub 3/,C/sub 2/H/sub 5/, CH/sub 2/C/sub 6/H/sub 5/) at 25 to 50/sup 0/C to produce aldehyde RCHO and the dimers (CpMo(CO)/sub 3/)/sub 2/ and (CpMo(CO)/sub 2/)/sub 2/. In general, CpV(CO)/sub 3/H/sup -/ appears to transfer a hydrogen atom to the metal radical anion formed in an electron transfer process, whereas CpMo(CO)/sub 3/H transfers hydride in a 2-electron process to a vacant coordination site. The chemical consequences are that CpV(CO)/sub 3/H/sup -/ generally reacts with metal alkyls to give alkanes via intermediate alkyl hydride species whereas CpMo(CO)/sub 3/H reacts with metal alkyls to produce aldehyde, via an intermediate acyl hydride species.

  16. Manufacturing and investigation of U-Mo LEU fuel granules by hydride-dehydride processing

    International Nuclear Information System (INIS)

    Stetskiy, Y.A.; Trifonov, Y.I.; Mitrofanov, A.V.; Samarin, V.I.

    2002-01-01

    Investigations of hydride-dehydride processing for comminution of U-Mo alloys with Mo content in the range 1.9/9.2% have been performed. Some regularities of the process as a function of Mo content have been determined as well as some parameters elaborated. Hydride-dehydride processing has been shown to provide necessary phase and chemical compositions of U-Mo fuel granules to be used in disperse fuel elements for research reactors. Pin type disperse mini-fuel elements for irradiation tests in the loop of 'MIR' reactor (Dmitrovgrad) have been fabricated using U-Mo LEU fuel granules obtained by hydride-dehydride processing. Irradiation tests of these mini-fuel elements loaded to 4 g U tot /cm 3 are planned to start by the end of this year. (author)

  17. Creation of Y2Ti2O7 nanoprecipitates to strengthen the Fe-14Cr-3Al-2W steels by adding Ti hydride and Y2O3 nanoparticles

    International Nuclear Information System (INIS)

    Wang, Linbo; Bai, Zhonglian; Shen, Hailong; Wang, Chenxi; Liu, Tong

    2017-01-01

    In order to prohibit the formation of large Y-Al-O precipitates, Ti hydride nanoparticles (NPs) were prepared and used to replace Ti as raw particles to fabricate the oxide dispersion strengthened (ODS) Fe-14Cr-3Al-2W-0.35Y 2 O 3 steels by mechanical alloying (MA) and hot isostatic pressing (HIP). As the content of Ti hydride increases from 0.1 to 0.5 and 1.0 wt%, the oxide nanoprecipitates in the ODS steels changes from Y 3 Al 5 O 12 phase to Y 2 Ti 2 O 7 phase (semicoherent with the matrix), and the particle size is successfully reduced. The tensile strength of the ODS steel increases remarkably with increasing Ti hydride content. The sample with 1.0 wt% Ti hydride exhibits a high strength of 1049 MPa at 25 °C and 278 MPa at 700 °C. The creation of Y 2 Ti 2 O 7 nanoprecipitates by adding Ti hydride NPs opens a new way to control the structure and size of the oxide precipitates in the ODS steels. - Graphical abstract: The creation of Y 2 Ti 2 O 7 nanoprecipitates by adding Ti hydride nanoparticles remarkably increases the mechanical properties of the Al-containing ODS steels. - Highlights: •TiH 1.971 reacts with Y 2 O 3 to form Y 2 Ti 2 O 7 in the Al-containing ODS steel. •Addition of TiH 1.971 nanoparticles can prevent the formation of Y-Al-O phases. •Y 2 Ti 2 O 7 nanoparticles share semicoherent interface with the ferrite matrix. •The mean size of oxide dispersion is reduced to 11.2 ± 7.1 nm with 1.0 wt% TiH 1.971 . •The tensile strength of the ODS steel enlarges with increasing TiH 1.971 content.

  18. Creation of Y{sub 2}Ti{sub 2}O{sub 7} nanoprecipitates to strengthen the Fe-14Cr-3Al-2W steels by adding Ti hydride and Y{sub 2}O{sub 3} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Linbo; Bai, Zhonglian; Shen, Hailong; Wang, Chenxi; Liu, Tong, E-mail: tongliu@buaa.edu.cn

    2017-05-15

    In order to prohibit the formation of large Y-Al-O precipitates, Ti hydride nanoparticles (NPs) were prepared and used to replace Ti as raw particles to fabricate the oxide dispersion strengthened (ODS) Fe-14Cr-3Al-2W-0.35Y{sub 2}O{sub 3} steels by mechanical alloying (MA) and hot isostatic pressing (HIP). As the content of Ti hydride increases from 0.1 to 0.5 and 1.0 wt%, the oxide nanoprecipitates in the ODS steels changes from Y{sub 3}Al{sub 5}O{sub 12} phase to Y{sub 2}Ti{sub 2}O{sub 7} phase (semicoherent with the matrix), and the particle size is successfully reduced. The tensile strength of the ODS steel increases remarkably with increasing Ti hydride content. The sample with 1.0 wt% Ti hydride exhibits a high strength of 1049 MPa at 25 °C and 278 MPa at 700 °C. The creation of Y{sub 2}Ti{sub 2}O{sub 7} nanoprecipitates by adding Ti hydride NPs opens a new way to control the structure and size of the oxide precipitates in the ODS steels. - Graphical abstract: The creation of Y{sub 2}Ti{sub 2}O{sub 7} nanoprecipitates by adding Ti hydride nanoparticles remarkably increases the mechanical properties of the Al-containing ODS steels. - Highlights: •TiH{sub 1.971} reacts with Y{sub 2}O{sub 3} to form Y{sub 2}Ti{sub 2}O{sub 7} in the Al-containing ODS steel. •Addition of TiH{sub 1.971} nanoparticles can prevent the formation of Y-Al-O phases. •Y{sub 2}Ti{sub 2}O{sub 7} nanoparticles share semicoherent interface with the ferrite matrix. •The mean size of oxide dispersion is reduced to 11.2 ± 7.1 nm with 1.0 wt% TiH{sub 1.971}. •The tensile strength of the ODS steel enlarges with increasing TiH{sub 1.971} content.

  19. Fluctuations in an Inorganic Glass Forming System Capable of Liquid-Liquid Phase Separation

    Science.gov (United States)

    Bogdanov, V.; Maksimov, L.; Anan'ev, A.; Nemilov, S.; Rusan, V.

    2012-08-01

    Rayleigh and Mandel'shtam-Brillouin scattering (RMBS) spectroscopy and high temperature ultrasonic study (HTUS) are applied to PbO-Al2O3-B2O3 glass forming system characterized by over liquidus miscibility gap. Temperature dependences of ultrasonic velocity of glass melts were measured in 600-1200°C range. "Frozen-in" density fluctuations in two phase glasses were estimated from HTUS data by Macedo-Shroeder formulation. Landau-Placzek ratios were found from RMBS spectra of single phase glasses at room temperature. Results of RMBS and HTUS were compared with well-known SAXS data. It was found that contribution of "frozen-in" density fluctuations into light scattering by two-phase glasses is much smaller than the scattering on particles of the second glassy phase causing opalescence of the glasses. Abnormal "water-like" growth of ultrasonic velocity with melt temperature can be explained by coexistence of two types of packaging of structural elements.

  20. Study on polyethylene glycol/epoxy resin composite as a form-stable phase change material

    International Nuclear Information System (INIS)

    Fang Yutang; Kang Huiying; Wang Weilong; Liu Hong; Gao Xuenong

    2010-01-01

    Form-stable polyethylene glycol (PEG)/epoxy resin (EP) composite as a novel phase change material (PCM) was prepared using casting molding method. In this new material, PEG acts as the latent heat storage material and EP polymer serves as the supporting material, which provides structural strength and prevents the leakage of the melted PEG. The structure and morphology of the novel composite were observed using Fourier transformation infrared spectroscope (FTIR) and scanning electronic microscope (SEM). The thermo-mechanical property and transition behavior were characterized by polarizing optical microscope (POM), static thermo-mechanical analysis (TMA) and differential scanning calorimeter (DSC). The experimental results show that, as a result of the physical tangled function of the epoxy resin carrier to the PEG segment, the composite macroscopically presents the solid-solid phase change characteristic.

  1. Crystal phases of a glass-forming Lennard-Jones mixture

    International Nuclear Information System (INIS)

    Fernandez, Julian R.; Harrowell, Peter

    2003-01-01

    We compare the potential energy at zero temperature of a range of crystal structures for a glass-forming binary mixture of Lennard-Jones particles. The lowest-energy ordered state consists of coexisting phases of a single component face centered cubic structure and an equimolar cesium chloride structure. An infinite number of layered crystal structures are identified with energies close to this ground state. We demonstrate that the finite size increase of the energy of the coexisting crystal with incoherent interfaces is sufficient to destabilize this ordered phase in simulations of typical size. Two specific local coordination structures are identified as of possible structural significance in the amorphous state. We observe rapid crystal growth in the equimolar mixture

  2. Development of a direct hydride generation nebulizer for the determination of selenium by inductively coupled plasma optical emission spectrometry

    International Nuclear Information System (INIS)

    Carrion, Nereida; Murillo, Miguel; Montiel, Edie; Diaz, Dorfe

    2003-01-01

    A study was conducted to evaluate the performance of a new direct hydride generation nebulizer system for determination of hydride forming elements by inductively coupled plasma optical emission spectroscopy. This system was designed and optimized to obtain the highest sensitivity. Several experimental designs were used for these purposes. To optimize the individual parameters of the system, and to study the interaction between these parameters for both direct hydride generation nebulizers, a central composite orthogonal design with eight factors was set up. Significant behavioral differences were observed in the two direct hydride generation nebulizers studied. Finally, a 70 μm gas orifice nebulizer exhibits a better detection limit than the 120 μm nebulizer. Generally, for determination of selenium, this new direct hydride generation nebulizer system exhibits a linear dynamic range and detection limit (3σb) of 3 orders of magnitude and 0.2 μg l -1 for selenium, respectively. This new hydride generator is much simpler system that conventional hydride generation systems, which does not need to be changed to work in normal mode with the inductively coupled plasma, since this system may be used for hydride forming elements and those that do not form them. It produces a rapid response with low memory effect. It reduces the interference level of Ni, Co and Cu to 600, 500 and 5 mg l -1 , respectively. The accuracy of the system was verified by the determination of selenium in several standard reference materials of ambient, food and clinical sample matrices. No statistically significant differences (95 confidence level) were obtained between our method and the reference values

  3. Unconventional field induced phases in a quantum magnet formed by free radical tetramers

    Science.gov (United States)

    Saúl, Andrés; Gauthier, Nicolas; Askari, Reza Moosavi; Côté, Michel; Maris, Thierry; Reber, Christian; Lannes, Anthony; Luneau, Dominique; Nicklas, Michael; Law, Joseph M.; Green, Elizabeth Lauren; Wosnitza, Jochen; Bianchi, Andrea Daniele; Feiguin, Adrian

    2018-02-01

    We report experimental and theoretical studies on the magnetic and thermodynamic properties of NIT-2Py, a free radical based organic magnet. From magnetization and specific-heat measurements we establish the temperature versus magnetic field phase diagram which includes two Bose-Einstein condensates (BEC) and an infrequent half-magnetization plateau. Calculations based on density functional theory demonstrate that magnetically this system can be mapped to a quasi-two-dimensional structure of weakly coupled tetramers. Density matrix renormalization group calculations show the unusual characteristics of the BECs where the spins forming the low-field condensate are different than those participating in the high-field one.

  4. Well-Defined Silica Supported Aluminum Hydride: Another Step Towards the Utopian Single Site Dream?

    KAUST Repository

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

    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 [(≡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 advance 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 of a strained siloxane bridge, ≡Si-O-Si≡ but with two different mechanisms, showing that the reality of “single site” catalyst may be an utopia: DFT calculations indicate that isobutyl transfer occurs via a simple metathesis between the Al-isobutyl and O-Si bonds, while hydride transfer occurs via a two steps mechanism, the first one is a ß-H elimination to Al with elimination of isobutene, whereas the second is a metathesis step between the formed Al-H bond and a O-Si bond. Thermal treatment of 1a (at 250 °C) under high vacuum (10-5 mbar) generates Al-H through a ß-H elimination of isobutyl fragment. These supported well-defined Al-H which are highly stable with time, are tetra, penta and octa coordinated as demonstrated by IR and 27Al–1H J-HMQC NMR spectroscopy. All these observations indicate that surfaces atoms around the site of grafting play a considerable role in the reactivity of a single site system.

  5. Well-Defined Silica Supported Aluminum Hydride: Another Step Towards the Utopian Single Site Dream?

    KAUST Repository

    Werghi, Baraa

    2015-07-17

    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 [(≡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 advance 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 of a strained siloxane bridge, ≡Si-O-Si≡ but with two different mechanisms, showing that the reality of “single site” catalyst may be an utopia: DFT calculations indicate that isobutyl transfer occurs via a simple metathesis between the Al-isobutyl and O-Si bonds, while hydride transfer occurs via a two steps mechanism, the first one is a ß-H elimination to Al with elimination of isobutene, whereas the second is a metathesis step between the formed Al-H bond and a O-Si bond. Thermal treatment of 1a (at 250 °C) under high vacuum (10-5 mbar) generates Al-H through a ß-H elimination of isobutyl fragment. These supported well-defined Al-H which are highly stable with time, are tetra, penta and octa coordinated as demonstrated by IR and 27Al–1H J-HMQC NMR spectroscopy. All these observations indicate that surfaces atoms around the site of grafting play a considerable role in the reactivity of a single site system.

  6. Preparation and thermal properties of form stable paraffin phase change material encapsulation

    International Nuclear Information System (INIS)

    Liu Xing; Liu Hongyan; Wang Shujun; Zhang Lu; Cheng Hua

    2006-01-01

    Paraffin waxes are cheap and have moderate thermal energy storage density but low thermal conductivity and, hence, require large surface area to be used in energy storage. Form stable paraffin phase change materials (PCM) in which paraffin serves as a latent heat storage material and polyolefins act as a supporting material, because of paraffin leakage, are required to be improved. The form stable paraffin PCM in the present paper was encapsulated in an inorganic silica gel polymer successfully by in situ polymerization. The differential scanning calorimeter (DSC) was used to measure its thermal properties. At the same time, the Washburn equation, which measures the wetting properties of powder materials, was used to test the hydrophilic-lipophilic properties of the PCMs. The result indicated that the enthalpy of the microencapsulated PCMs was reduced little, while their hydrophilic properties were enhanced largely

  7. Azimuthally anisotropic hydride lens structures in Zircaloy 4 nuclear fuel cladding: High-resolution neutron radiography imaging and BISON finite element analysis

    Science.gov (United States)

    Lin, Jun-Li; Zhong, Weicheng; Bilheux, Hassina Z.; Heuser, Brent J.

    2017-12-01

    High-resolution neutron radiography has been used to image bulk circumferential hydride lens particles in unirradiated Zircaloy 4 tubing cross section specimens. Zircaloy 4 is a common light water nuclear reactor (LWR) fuel cladding; hydrogen pickup, hydride formation, and the concomitant effect on the mechanical response are important for LWR applications. Ring cross section specimens with three hydrogen concentrations (460, 950, and 2830 parts per million by weight) and an as-received reference specimen were imaged. Azimuthally anisotropic hydride lens particles were observed at 950 and 2830 wppm. The BISON finite element analysis nuclear fuel performance code was used to model the system elastic response induced by hydride volumetric dilatation. The compressive hoop stress within the lens structure becomes azimuthally anisotropic at high hydrogen concentrations or high hydride phase fraction. This compressive stress anisotropy matches the observed lens anisotropy, implicating the effect of stress on hydride formation as the cause of the observed lens azimuthal asymmetry. The cause and effect relation between compressive stress and hydride lens anisotropy represents an indirect validation of a key BISON output, the evolved hoop stress associated with hydride formation.

  8. Synthesis of Nano-Light Magnesium Hydride for Hydrogen Storage ...

    African Journals Online (AJOL)

    Abstract. Nano-light magnesium hydride that has the capability for hydrogen storage was synthesized from treatment of magnesium ribbon with hydrogen peroxide. The optimum time for complete hydrogenation of the magnesium hydride was 5 hours.

  9. Hydrogen Storage Engineering Center of Excellence Metal Hydride Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Motyka, T. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2014-05-31

    The Hydrogen Storage Engineering Center of Excellence (HSECoE) was established in 2009 by the U.S. Department of Energy (DOE) to advance the development of materials-based hydrogen storage systems for hydrogen-fueled light-duty vehicles. The overall objective of the HSECoE is to develop complete, integrated system concepts that utilize reversible metal hydrides, adsorbents, and chemical hydrogen storage materials through the use of advanced engineering concepts and designs that can simultaneously meet or exceed all the DOE targets. This report describes the activities and accomplishments during Phase 1 of the reversible metal hydride portion of the HSECoE, which lasted 30 months from February 2009 to August 2011. A complete list of all the HSECoE partners can be found later in this report but for the reversible metal hydride portion of the HSECoE work the major contributing organizations to this effort were the United Technology Research Center (UTRC), General Motors (GM), Pacific Northwest National Laboratory (PNNL), the National Renewable Energy Laboratory (NREL) and the Savannah River National Laboratory (SRNL). Specific individuals from these and other institutions that supported this effort and the writing of this report are included in the list of contributors and in the acknowledgement sections of this report. The efforts of the HSECoE are organized into three phases each approximately 2 years in duration. In Phase I, comprehensive system engineering analyses and assessments were made of the three classes of storage media that included development of system level transport and thermal models of alternative conceptual storage configurations to permit detailed comparisons against the DOE performance targets for light-duty vehicles. Phase 1 tasks also included identification and technical justifications for candidate storage media and configurations that should be capable of reaching or exceeding the DOE targets. Phase 2 involved bench-level testing and

  10. Economic analysis of hydride fueled BWR

    International Nuclear Information System (INIS)

    Ganda, F.; Shuffler, C.; Greenspan, E.; Todreas, N.

    2009-01-01

    The economic implications of designing BWR cores with hydride fuels instead of conventional oxide fuels are analyzed. The economic analysis methodology adopted is based on the lifetime levelized cost of electricity (COE). Bracketing values (1970 and 3010 $/kWe) are used for the overnight construction costs and for the power scaling factors (0.4 and 0.8) that correlate between a change in the capital cost to a change in the power level. It is concluded that a newly constructed BWR reactor could substantially benefit from the use of 10 x 10 hydride fuel bundles instead of 10 x 10 oxide fuel bundles design presently in use. The cost saving would depend on the core pressure drop constraint that can be implemented in newly constructed BWRs - it is between 2% and 3% for a core pressure drop constraint as of the reference BWR, between 9% and 15% for a 50% higher core pressure drop, and between 12% and 21% higher for close to 100% core pressure. The attainable cost reduction was found insensitive to the specific construction cost but strongly dependent on the power scaling factor. The cost advantage of hydride fuelled cores as compared to that of the oxide reference core depends only weakly on the uranium and SWU prices, on the 'per volume base' fabrication cost of hydride fuels, and on the discount rate used. To be economically competitive, the uranium enrichment required for the hydride fuelled core needs to be around 10%.

  11. Vanadium-based alloy hydrides for heat pumps, compressors, and isotope separation

    International Nuclear Information System (INIS)

    Libowitz, G.G.

    1988-01-01

    A series of body-centered cubic (b.c.c.) solid solution alloys have been developed which appears to be unusually suitable for several applications involving metal hydrides. It is normally very difficult to induce the body-centered cubic metals, Nb, V, and Ta, to react with hydrogen; in bulk form the reaction will simply not occur at room temperature. Alloys containing Nb exhibited very large hysteresis effects on hydride formation and thus are not suitable for most applications. However, the V-Ti based alloys showed relatively little hysteresis, and because of their unusual thermodynamic properties offer significant advantages for the specific applications discussed below. (orig./HB)

  12. Experimental investigation of strain, damage and failure of hydrided zircaloy-4 with various hydride orientations

    International Nuclear Information System (INIS)

    Racine, A; Catherine, C.S.; Cappelaere, C.; Bornert, M.; Caldemaison, D.

    2005-01-01

    This experimental investigation is devoted to the influence of the orientation of hydrides on the mechanical response of Zircaloy-4. Ring tensile tests are performed on unirradiated CWSR Zircaloy-4, charged with about 200 or 500wppm hydrogen. Hydrides are oriented either parallel ('tangential'), or perpendicular ('radial') to the circumferential tensile direction. Tangential hydrides are usually observed in cladding tubes, however, hydrides can be reoriented after cooling under stress to become radial and then trigger brittle behavior. In this investigation, we perform, 'macroscopic' or SEM in-situ tensile tests on smooth rings, at room temperature. We get the mechanical response of the material as a function of hydride orientation and hydrogen content and we investigate the deformation, damage and failure mechanisms. In both cases, digital image correlation techniques are used to estimate local and global strain distributions. The results lead to the following conclusions: neither the tensile stress-strain response nor the strain modes are affected by hydrogen content or hydride orientation, but the failure modes are. Indeed, only 200wppm radial hydrides embrittle Zy-4: sample fails in the elastic domain at about 350 MPa before strain bands could develop; whereas in other cases samples reach at least 750 MPa before failure, with ductile or brittle mode. (authors)

  13. Theoretical study of hydrogen storage in metal hydrides.

    Science.gov (United States)

    Oliveira, Alyson C M; Pavão, A C

    2018-05-04

    Adsorption, absorption and desorption energies and other properties of hydrogen storage in palladium and in the metal hydrides AlH 3 , MgH 2 , Mg(BH 4 ) 2 , Mg(BH 4 )(NH 2 ) and LiNH 2 were analyzed. The DFT calculations on cluster models show that, at a low concentration, the hydrogen atom remains adsorbed in a stable state near the palladium surface. By increasing the hydrogen concentration, the tetrahedral and the octahedral sites are sequentially occupied. In the α phase the tetrahedral site releases hydrogen more easily than at the octahedral sites, but the opposite occurs in the β phase. Among the hydrides, Mg(BH 4 ) 2 shows the highest values for both absorption and desorption energies. The absorption energy of LiNH 2 is higher than that of the palladium, but its desorption energy is too high, a recurrent problem of the materials that have been considered for hydrogen storage. The release of hydrogen, however, can be favored by using transition metals in the material structure, as demonstrated here by doping MgH 2 with 3d and 4d-transition metals to reduce the hydrogen atomic charge and the desorption energy.

  14. A structural study of lamellar phases formed by nucleoside-functionalized lipids

    Energy Technology Data Exchange (ETDEWEB)

    Berti, D.; Fratini, E.; Baglioni, P. [Department of Chemistry and CSGI, University of Florence, Via G. Capponi 9, 50121 Florence (Italy); Dante, S.; Hauss, T. [Berlin Neutron Scattering Center, Hahn Meitner Institut, Glienicker Strasse 100, Wannsee, 14109 Berlin (Germany)

    2002-07-01

    We report a neutron-scattering investigation of lamellar phases formed by novel phospholipids bearing nucleosides at the polar-head-group region. These nucleolipids can interact through stacking and H-bond interactions, following a pattern that resembles base-base coupling in natural nucleic acids (DNA, RNA), i.e. they have similar recognition properties. Bilayer stacks formed of DPP-adenosine, DPP-uridine and their 1:1 mixture were investigated after equilibration in a 98% relative humidity atmosphere. The DPP-adenosine spectrum can be accounted for (in analogy to DPPC) by a lamellar phase with a smectic period of about 60 A. DPP-uridine displays a not so straightforward behavior that we have tentatively ascribed to the coexistence of lamellae with different smectic periods. In the 1:1 mixture the lamellar mesophase of DPP-uridine is retained, suggesting a specific interaction of the uridine polar-head group with the adenosine moiety of DPP-adenosine. It should be stressed that this behavior can be considered as an indication of the recognition process occurring at the polar-head-group region of the mixed phospholiponucleoside membrane. (orig.)

  15. A structural study of lamellar phases formed by nucleoside-functionalized lipids

    CERN Document Server

    Berti, D; Baglioni, P; Dante, S; Hauss, T

    2002-01-01

    We report a neutron-scattering investigation of lamellar phases formed by novel phospholipids bearing nucleosides at the polar-head-group region. These nucleolipids can interact through stacking and H-bond interactions, following a pattern that resembles base-base coupling in natural nucleic acids (DNA, RNA), i.e. they have similar recognition properties. Bilayer stacks formed of DPP-adenosine, DPP-uridine and their 1:1 mixture were investigated after equilibration in a 98% relative humidity atmosphere. The DPP-adenosine spectrum can be accounted for (in analogy to DPPC) by a lamellar phase with a smectic period of about 60 A. DPP-uridine displays a not so straightforward behavior that we have tentatively ascribed to the coexistence of lamellae with different smectic periods. In the 1:1 mixture the lamellar mesophase of DPP-uridine is retained, suggesting a specific interaction of the uridine polar-head group with the adenosine moiety of DPP-adenosine. It should be stressed that this behavior can be considere...

  16. Comparison between two forms of vaginally administered progesterone for luteal phase support in assisted reproduction cycles.

    Science.gov (United States)

    Geber, Selmo; Moreira, Ana Carolina Ferreira; de Paula, Sálua Oliveira Calil; Sampaio, Marcos

    2007-02-01

    The use of progesterone for luteal phase support has been demonstrated to be beneficial in assisted reproduction cycles using gonadotrophin-releasing hormone analogues (GnRHa). Two micronized progesterone preparations are available for vaginal administration: capsules and gel. The objective of this study was to compare the efficacy of these two forms for luteal phase support in assisted reproduction cycles. A total of 244 couples undergoing IVF/intracytoplasmic sperm injection cycles were included in the study and were randomly allocated (sealed envelopes) into two groups: group 1 (122) received vaginal capsules of 200 mg of micronized progesterone (Utrogestan), 3 times daily, and group 2 (122) received micronized progesterone in gel (Crinone 8%), once daily. Both groups received progesterone for 13 days beginning day 1 after oocyte retrieval, continuing until the pregnancy test was performed and until 12 weeks of pregnancy. Groups were compared by clinical data and assisted reproduction results and had similar ages and causes of infertility. Although the pregnancy rate was higher for those receiving progesterone gel than capsules (44.26 and 36.06% respectively), this difference was not statistically significant. The study showed that vaginal progesterone gel and capsules used for luteal phase support in assisted reproduction cycles with long protocol GnRHa result in similar pregnancy rates.

  17. Influence of hydride orientation on fracture toughness of CWSR Zr-2.5%Nb pressure tube material between RT and 300 °C

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Rishi K. [Engineering Directorate, Nuclear Power Corporation of India Limited, Mumbai 400094 (India); Department of Mechanical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076 (India); Sunil, Saurav; Kumawat, B.K. [Mechanical Metallurgy Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Singh, R.N., E-mail: rnsingh@barc.gov.in [Mechanical Metallurgy Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Tewari, Asim [Department of Mechanical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076 (India); Kashyap, B.P. [Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Powai, Mumbai 400076 (India)

    2017-05-15

    An experimental setup was designed, fabricated and used to form radial hydrides in Zr-2.5%Nb alloy pressure tube spool. The design of setup was based on ensuring a hoop stress in the spool greater than threshold stress for reorientation of hydrides in this alloy, which was achieved by manipulating the thermal expansion coefficient of the plunger and pressure tube material and diametral interference between them. The experimental setup was loaded on a universal testing machine (UTM) fitted with an environmental chamber and subjected to a temperature cycle for the stress reorientation treatment. The metallographic examination of the hydrogen charged spools subjected to stress re-orientation treatment using this set up revealed formation of predominantly radial hydrides. The variation of fracture toughness of material containing radial hydride with test temperature showed typical ‘S’ curve behavior with transition temperatures more than that of the material containing circumferential hydride.

  18. Mechanism of n-butane hydrogenolysis promoted by Ta-hydrides supported on silica

    KAUST Repository

    Pasha, Farhan Ahmad; Cavallo, Luigi; Basset, Jean-Marie

    2014-01-01

    (III)H is rapidly trapped by molecular hydrogen to form the more stable tris-hydride (≡ Si-O-) 2Ta(V)H3. Loading of n-butane to the Ta-center occurs through C-H activation concerted with elimination of molecular hydrogen (σ-bond metathesis). Once the Ta

  19. Mathematical modeling of the nickel/metal hydride battery system

    Energy Technology Data Exchange (ETDEWEB)

    Paxton, Blaine Kermit [Univ. of California, Berkeley, CA (United States). Dept. of Chemical Engineering

    1995-09-01

    A group of compounds referred to as metal hydrides, when used as electrode materials, is a less toxic alternative to the cadmium hydroxide electrode found in nickel/cadmium secondary battery systems. For this and other reasons, the nickel/metal hydride battery system is becoming a popular rechargeable battery for electric vehicle and consumer electronics applications. A model of this battery system is presented. Specifically the metal hydride material, LaNi{sub 5}H{sub 6}, is chosen for investigation due to the wealth of information available in the literature on this compound. The model results are compared to experiments found in the literature. Fundamental analyses as well as engineering optimizations are performed from the results of the battery model. In order to examine diffusion limitations in the nickel oxide electrode, a ``pseudo 2-D model`` is developed. This model allows for the theoretical examination of the effects of a diffusion coefficient that is a function of the state of charge of the active material. It is found using present data from the literature that diffusion in the solid phase is usually not an important limitation in the nickel oxide electrode. This finding is contrary to the conclusions reached by other authors. Although diffusion in the nickel oxide active material is treated rigorously with the pseudo 2-D model, a general methodology is presented for determining the best constant diffusion coefficient to use in a standard one-dimensional battery model. The diffusion coefficients determined by this method are shown to be able to partially capture the behavior that results from a diffusion coefficient that varies with the state of charge of the active material.

  20. Stress induced reorientation of vanadium hydride

    International Nuclear Information System (INIS)

    Beardsley, M.B.

    1977-10-01

    The critical stress for the reorientation of vanadium hydride was determined for the temperature range 180 0 to 280 0 K using flat tensile samples containing 50 to 500 ppM hydrogen by weight. The critical stress was observed to vary from a half to a third of the macroscopic yield stress of pure vanadium over the temperature range. The vanadium hydride could not be stress induced to precipitate above its stress-free precipitation temperature by uniaxial tensile stresses or triaxial tensile stresses induced by a notch

  1. Structure of the novel ternary hydrides Li4Tt2D (Tt=Si and Ge)

    International Nuclear Information System (INIS)

    Wu Hui; Rush, J.J.; Maryland Univ., College Park, MD; Hartman, M.R.; Oregon State Univ., Corvallis, OR; Udovic, T.J.; Zhou Wei; Pennsylvania Univ., Philadelphia, PA; Bowman, R.C. Jr.; Vajo, J.J.

    2007-01-01

    The crystal structures of newly discovered Li 4 Ge 2 D and Li 4 Si 2 D ternary phases were solved by direct methods using neutron powder diffraction data. Both structures can be described using a Cmmm orthorhombic cell with all hydrogen atoms occupying Li 6 -octahedral interstices. The overall crystal structure and the geometry of these interstices are compared with those of other related phases, and the stabilization of this novel class of ternary hydrides is discussed. (orig.)

  2. Draft of M2 Report on Integration of the Hybrid Hydride Model into INL's MBM Framework for Review

    Energy Technology Data Exchange (ETDEWEB)

    Tikare, Veena; Weck, Philippe F.; Schultz, Peter Andrew; Clark, Blythe; Glazoff, Michael V.; Homer, Eric R.

    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.

  3. Effects of Boron-Incorporation in a V-Containing Zr-Based AB2 Metal Hydride Alloy

    Directory of Open Access Journals (Sweden)

    Shiuan Chang

    2017-11-01

    Full Text Available In this study, boron, a metalloid element commonly used in semiconductor applications, was added in a V-containing Zr-based AB2 metal hydride alloy. In general, as the boron content in the alloy increased, the high-rate dischargeability, surface exchange current, and double-layer capacitance first decreased and then increased whereas charge-transfer resistance and dot product of charge-transfer resistance and double-layer capacitance changed in the opposite direction. Electrochemical and gaseous phase characteristics of two boron-containing alloys, with the same boron content detected by the inductively coupled plasma optical emission spectrometer, showed significant variations in performances due to the difference in phase abundance of a newly formed tetragonal V3B2 phase. This new phase contributes to the increases in electrochemical high-rate dischargeability, surface exchange current, charge-transfer resistances at room, and low temperatures. However, the V3B2 phase does not contribute to the hydrogen storage capacities in either gaseous phase and electrochemical environment.

  4. Can Pearlite form Outside of the Hultgren Extrapolation of the Ae3 and Acm Phase Boundaries?

    Science.gov (United States)

    Aranda, M. M.; Rementeria, R.; Capdevila, C.; Hackenberg, R. E.

    2016-02-01

    It is usually assumed that ferrous pearlite can form only when the average austenite carbon concentration C 0 lies between the extrapolated Ae3 ( γ/ α) and Acm ( γ/ θ) phase boundaries (the "Hultgren extrapolation"). This "mutual supersaturation" criterion for cooperative lamellar nucleation and growth is critically examined from a historical perspective and in light of recent experiments on coarse-grained hypoeutectoid steels which show pearlite formation outside the Hultgren extrapolation. This criterion, at least as interpreted in terms of the average austenite composition, is shown to be unnecessarily restrictive. The carbon fluxes evaluated from Brandt's solution are sufficient to allow pearlite growth both inside and outside the Hultgren Extrapolation. As for the feasibility of the nucleation events leading to pearlite, the only criterion is that there are some local regions of austenite inside the Hultgren Extrapolation, even if the average austenite composition is outside.

  5. In situ hydride formation in titanium during focused ion milling.

    Science.gov (United States)

    Ding, Rengen; Jones, Ian P

    2011-01-01

    It is well known that titanium and its alloys are sensitive to electrolytes and thus hydrides are commonly observed in electropolished foils. In this study, focused ion beam (FIB) milling was used to prepare thin foils of titanium and its alloys for transmission electron microscopy. The results show the following: (i) titanium hydrides were observed in pure titanium, (ii) the preparation of a bulk sample in water or acid solution resulted in the formation of more hydrides and (iii) FIB milling aids the precipitation of hydrides, but there were never any hydrides in Ti64 and Ti5553.

  6. Pressure-induced transformations of molecular boron hydride

    International Nuclear Information System (INIS)

    Nakano, Satoshi; Hemley, Russell J; Gregoryanz, Eugene A; Goncharov, Alexander F; Mao, Ho-kwang

    2002-01-01

    Decaborane, a molecular boron hydride, was compressed to 131 GPa at room temperature to explore possible non-molecular phases in this system and their physical properties. Decaborane changed its colour from transparent yellow to orange/red above 50 GPa and then to black above 100 GPa, suggesting some transformations. Raman scattering and infrared (IR) absorption spectroscopy reveal significant structural changes. Above 100 GPa, B-B skeletal, B-H and B-H-B Raman/IR peaks gradually disappeared, which implies a transformation into a non-molecular phase in which conventional borane-type bonding is lost. The optical band gap of the material at 100 GPa was estimated to be about 1.0 eV

  7. Pressure-induced transformations of molecular boron hydride

    CERN Document Server

    Nakano, S; Gregoryanz, E A; Goncharov, A F; Mao Ho Kwang

    2002-01-01

    Decaborane, a molecular boron hydride, was compressed to 131 GPa at room temperature to explore possible non-molecular phases in this system and their physical properties. Decaborane changed its colour from transparent yellow to orange/red above 50 GPa and then to black above 100 GPa, suggesting some transformations. Raman scattering and infrared (IR) absorption spectroscopy reveal significant structural changes. Above 100 GPa, B-B skeletal, B-H and B-H-B Raman/IR peaks gradually disappeared, which implies a transformation into a non-molecular phase in which conventional borane-type bonding is lost. The optical band gap of the material at 100 GPa was estimated to be about 1.0 eV.

  8. Metal hydrides for hydrogen storage in nickel hydrogen batteries

    International Nuclear Information System (INIS)

    Bittner, H.F.; Badcock, C.C.; Quinzio, M.V.

    1984-01-01

    Metal hydride hydrogen storage in nickel hydrogen (Ni/H 2 ) batteries has been shown to increase battery energy density and improve battery heat management capabilities. However the properties of metal hydrides in a Ni/H 2 battery environment, which contains water vapor and oxygen in addition to the hydrogen, have not been well characterized. This work evaluates the use of hydrides in Ni/H 2 batteries by fundamental characterization of metal hydride properties in a Ni/H 2 cell environment. Hydrogen sorption properties of various hydrides have been measured in a Ni/H 2 cell environment. Results of detailed thermodynamic and kinetic studies of hydrogen sorption in LaNi 5 in a Ni/H 2 cell environment are presented. Long-term cycling studies indicate that degradation of the hydride can be minimized by cycling between certain pressure limits. A model describing the mechanism of hydride degradation is presented

  9. Characterisation of hydrides in a zirconium alloy, by EBSD

    International Nuclear Information System (INIS)

    Ubhi, H.S.; Larsen, K.

    2012-01-01

    Zirconium alloys are used in nuclear reactors owing to their low capture cross-section for thermal neutrons and good mechanical and corrosion properties. However, they do suffer from delayed hydrogen cracking (DHC) due to formation of hydride particles. This study shows how the electron back-scatter diffraction (EBSD) technique can be used to characterise hydrides and their orientation relationship with the matrix. Hydrided EB weld specimens were prepared by electro-polishing, characterised using Oxford instruments AZtecHKL EBSD apparatus and software attached to a FEG SEM. Hydrides were found to exist as fine intra granular plates and having the Blackburn orientation relationship, i.e. (0002)Zr//(111)hydride and (1120)Zr//(1-10)hydride. The hydrides were also found to contain sigma 3 boundaries as well as local misorientations. (author)

  10. A Study on the Radial Hydride Assisted Delayed Hydride Cracking of Zircaloy

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Jin-Ho; Lee, Ji-Min; Kim, Yong-Soo [Hanyang University, Seoul (Korea, Republic of)

    2015-05-15

    Extensive studies have been done on understanding of DHC(Delayed hydride cracking) phenomenon since several zirconium alloy pressure tubes failed in nuclear reactor in the 1970s. Recently, long-term dry storage strategy has been considered seriously in order to manage spent nuclear fuel in Korea and other countries around the world. Consequentially, many researches have been investigated the degradation mechanisms which will threaten the spent fuel integrity during dry storage and showed that hydrogen related phenomenon such as hydride reorientation and DHC are the critical factors. Especially, DHC is the direct cracking mechanism which can cause not only a through-wall defect but also a radiation leak to the environment. In addition, DHC can be enhanced by radial hydride as reported by Kim who demonstrate that radial hydrides clearly act as crack linkage path. This phenomenon is known as the radial hydride assisted DHC (RHA-DHC). Therefore, study on DHC is essential to ensure the safety of spent fuel. Finite element analysis will be carried out for the stress gradient evaluation around notch tip. A variation in thermal cycle which leads to change in hydrogen solid solution trajectory may be required. If the radial hydride precipitates at notch tip, we will investigate what conditions should be met. Ultimately, we will suggest the regulation criteria for long-term dry storage of spent nuclear fuel.

  11. Electron and nuclear magnetic resonances in compounds and metallic hydrides

    International Nuclear Information System (INIS)

    Brasil Filho, N.

    1985-11-01

    Proton pulsed Nuclear Magnetic Resonance measurements were performed on the metallic hydrides ZrCr 2 H x (x = 2, 3, 4) and ZrV 2 H y (y = 2, 3, 4, 5) as a function of temperature between 180 and 400K. The ultimate aim was the investigation of the relaxation mechanisms in these systems by means of the measurement of both the proton ( 1 H) spin-lattice (T 1 ) and spin-spin (T 2 ) relaxation times and to use these data to obtain information about the diffusive motion of the hydrogen atoms. The diffusional activation energies, the jump frequencies and the Korringa constant, C k , related with the conduction electron contribution to the 1 H relaxation were determined for the above hydrides as a function of hydrogen concentration. Our results were analysed in terms of the relaxation models described by Bloembergen, Purcell and Pound (BPP model) and by Torrey. The Korringa type relaxation due to the conduction electrons in metallic systems was also used to interpret the experimental results. We also present the Electron Paramagnetic Ressonance (EPR) study of Gd 3+ , Nd 3+ and Er 3+ ions as impurities in several AB 3 intermetallic compounds where A = LA, Ce, Y, Sc, Th, Zr and B = Rh, Ir, Pt. The results were analysed in terms of the multiband model previously suggested to explain the behaviour of the resonance parameter in AB 2 Laves Phase compounds. (author) [pt

  12. Gas desorption properties of ammonia borane and metal hydride composites

    International Nuclear Information System (INIS)

    Matin, M.R.

    2009-01-01

    'Full text': Ammonia borane (NH 3 BH 3 ) has been of great interest owing to its ideal combination of low molecular weight and high H 2 storage capacity of 19.6 mass %, which exceeds the current capacity of gasoline. DOE's year 2015 targets involve gravimetric as well as volumetric energy densities. In this work, we have investigated thermal decomposition of ammonia borane and calcium hydride composites at different molar ratio. The samples were prepared by planetary ball milling under hydrogen gas atmosphere pressure of 1Mpa at room temperature for 2, and 10 hours. The gas desorption properties were examined by thermal desorption mass spectroscopy (TDMS). The identification of phases was carried out by X-ray diffraction. The results obtain were shown in fig (a),(b),and (c). Hydrogen desorption properties were observed at all molar ratios, but the desorption temperature is significantly lower at around 70 o C at molar ratio 1:1 as shown in fig (c), and unwanted gas (ammonia) emissions were remarkably suppressed by mixing with the calcium hydride. (author)

  13. Electronic structure of the palladium hydride studied by compton scattering

    CERN Document Server

    Mizusaki, S; Yamaguchi, M; Hiraoka, N; Itou, M; Sakurai, Y

    2003-01-01

    The hydrogen-induced changes in the electronic structure of Pd have been investigated by Compton scattering experiments associated with theoretical calculations. Compton profiles (CPs) of single crystal of Pd and beta phase hydride PdH sub x (x=0.62-0.74) have been measured along the [100], [110] and [111] directions with a momentum resolution of 0.14-0.17 atomic units using 115 keV x-rays. The theoretical Compton profiles have been calculated from the wavefunctions obtained utilizing the full potential linearized augmented plane wave method within the local density approximation for Pd and stoichiometric PdH. The experimental and the theoretical results agreed well with respect to the difference in the CPs between PdH sub x and Pd, and the anisotropy in the CPs of Pd or PdH sub x. This study provides lines of evidence that upon hydride formation the lowest valance band of Pd is largely modified due to hybridization with H 1s-orbitals and the Fermi energy is raised into the sp-band. (author)

  14. Microchip power compensated calorimetry applied to metal hydride characterization

    Energy Technology Data Exchange (ETDEWEB)

    Sepulveda, A.; Lopeandia, A.F.; Domenech-Ferrer, R.; Garcia, G.; Pi, F.; Rodriguez-Viejo, J. [Nanomaterials and Microsystems Group, Physics Department, Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain); Munoz, F.J. [Instituto de Microelectronica de Barcelona, Centro Nacional de Microelectronica, Campus UAB, 08193 Bellaterra (Spain)

    2008-06-15

    In this work, we show the suitability of the thin film membrane-based calorimetric technique to measure kinetically limited phase transitions such as the dehydrogenation of metallic hydrides. Different compounds such as Mg, Mg/Al and Mg{sub 80}Ti{sub 20} have been deposited over the active area of the microchip by electron beam evaporation. After several hydrogenation treatments at different temperatures to induce the hydride formation, calorimetric measurements on the dehydrogenation process of those thin films, either in vacuum or in air, are performed at a heating rate of 10 C/min. We observe a significant reduction in the onset of dehydrogenation for Mg{sub 80}Ti{sub 20} compared with pure Mg or Mg/Al layers, which confirms the beneficial effect of Ti on dehydrogenation. We also show the suitability of the membrane-based nanocalorimeters to be used in parallel with optical methods. Quantification of the energy released during hydrogen desorption remains elusive due to the semi-insulating to metallic transition of the film which affects the calorimetric trace. (author)

  15. Isomers and conformational barriers of gas phase nicotine, nornicotine and their protonated forms

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, Tomoki; Farone, William A.; Xantheas, Sotiris S.

    2014-07-17

    We report extensive conformational searches of the neutral nicotine, nornicotine and their protonated analogs that are based on ab-initio second order Møller-Plesset perturbation (MP2) electronic structure calculations. Initial searches were performed with the 6-31G(d,p) and the energetics of the most important structures were further refined from geometry optimizations with the aug-cc-pVTZ basis set. Based on the calculated free energies at T=298 K for the gas phase molecules, neutral nicotine has two dominant trans conformers, whereas neutral nornicotine is a mixture of several conformers. For nicotine, the protonation on both the pyridine and the pyrrolidine sites is energetically competitive, whereas nornicotine prefers protonation on the pyridine nitrogen. The protonated form of nicotine is mainly a mixture of two pyridine-protonated trans conformers and two pyrrolidine-protonated trans conformers, whereas the protonated form of nornicotine is a mixture of four pyridine-protonated trans conformers. Nornicotine is conformationally more flexible than nicotine, however it is less protonated at the biologically important pyrrolidine nitrogen site. The lowest energy isomers for each case were found to interconvert via low (< 6 kcal/mol) rotational barriers around the pyridine-pyrrolidine bond.

  16. Removal of pyridine from liquid and gas phase by copper forms of natural and synthetic zeolites

    International Nuclear Information System (INIS)

    Rehakova, Maria; Fortunova, Lubica; Bastl, Zdenek; Nagyova, Stanislava; Dolinska, Silvia; Jorik, Vladimir; Jona, Eugen

    2011-01-01

    Zeoadsorbents on the basis of copper forms of synthetic zeolite ZSM5 and natural zeolite of the clinoptilolite type (CT) have been studied taking into account their environmental application in removing harmful pyridine (py) from liquid and gas phase. Sorption of pyridine by copper forms of zeolites (Cu-ZSM5 and Cu-CT) has been studied by CHN, X-ray photoelectron spectroscopy, X-ray powder diffractometry, FTIR spectroscopy, thermal analysis (TG, DTA and DTG) and analysis of the surface areas and the pore volumes by low-temperature adsorption of nitrogen. The results of thermal analyses of Cu-ZSM5, Cu-(py) x ZSM5, Cu-CT and Cu-(py) x CT zeolitic products with different composition (x depends on the experimental conditions of sorption of pyridine) clearly confirmed their different thermal properties as well as the sorption of pyridine. In the zeolitic pyridine containing samples the main part of the pyridine release process occurs at considerably higher temperatures than is the boiling point of pyridine, which proves strong bond and irreversibility of py-zeolite interaction. FTIR spectra of Cu-(py) x zeolite samples showed well resolved bands of pyridine. The results of thermal analysis and FTIR spectroscopy are in a good agreement with the results of other used methods.

  17. Hydrogen isotope exchange in metal hydride columns

    International Nuclear Information System (INIS)

    Wiswall, R.; Reilly, J.; Bloch, F.; Wirsing, E.

    1977-01-01

    Several metal hydrides were shown to act as chromatographic media for hydrogen isotopes. The procedure was to equilibrate a column of hydride with flowing hydrogen, inject a small quantity of tritium tracer, and observe its elution behavior. Characteristic retention times were found. From these and the extent of widening of the tritium band, the heights equivalent to a theoretical plate could be calculated. Values of around 1 cm were obtained. The following are the metals whose hydrides were studied, together with the temperature ranges in which chromatographic behavior was observed: vanadium, 0 to 70 0 C; zirconium, 500 to 600 0 C; LaNi 5 , -78 to +30 0 C; Mg 2 Ni, 300 to 375 0 C; palladium, 0 to 70 0 C. A dual-temperature isotope separation process based on hydride chromatography was demonstrated. In this, a column was caused to cycle between two temperatures while being supplied with a constant stream of tritium-traced hydrogen. Each half-cycle was continued until ''breakthrough,'' i.e., until the tritium concentration in the effluent was the same as that in the feed. Up to that point, the effluent was enriched or depleted in tritium, by up to 20%

  18. Are RENiAl hydrides metallic?

    Czech Academy of Sciences Publication Activity Database

    Eichinger, K.; Havela, L.; Prokleška, J.; Stelmakhovych, O.; Daniš, S.; Šantavá, Eva; Miliyanchuk, K.

    2009-01-01

    Roč. 100, č. 9 (2009), s. 1200-1202 ISSN 1862-5282 Grant - others:GA ČR(CZ) GA202/07/0418 Institutional research plan: CEZ:AV0Z10100520 Keywords : rare earth metals * magnetism * hydrides Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.862, year: 2009

  19. Lithium hydride hydrolysis: experimental and kinetic study

    International Nuclear Information System (INIS)

    Charton, S.; Maupoix, C.; Brevet, A.; Delaunay, F.; Heintz, O.; Saviot, L.

    2006-01-01

    In this work has been studied the contribution of various analyses techniques in the framework, on the one hand of revealing the mechanisms implied in lithium hydride hydrolysis, and on the other hand of studying the kinetics of hydrogen production. Among the methods recently investigated, Raman spectroscopy, XPS and SIMS seem to be particularly attractive. (O.M.)

  20. Highly sensitive and interference-free determination of bismuth in environmental samples by electrothermal vaporization atomic fluorescence spectrometry after hydride trapping on iridium-coated tungsten coil

    International Nuclear Information System (INIS)

    Liu Rui; Wu Peng; Xu Kailai; Lv Yi; Hou Xiandeng

    2008-01-01

    Bismuthine was on-line trapped on tungsten coil and subsequently electrothermally vaporized for the determination by atomic fluorescence spectrometry (AFS). Several noble metals, including Pd, Rh, Pt, and Ir, were explored as permanent chemical modifier for tungsten coil on-line trapping. Investigation showed that Ir gave the best performance, in which bismuthine was on-line trapped on Ir-coated tungsten coil at 560 o C, and then released at 1550 o C for subsequent transfer to AFS by a mixture of Ar and H 2 . Under optimum instrumental conditions, the trapping efficiency was found to be 73 ± 3%. With 120 s (12 mL sample volume) trapping time, a limit of detection (LOD) of 4 ng L -1 was obtained, compared to conventional hydride generation AFS (0.09 μg L -1 ); the LOD can be lowered down to 1 ng L -1 by increasing the trapping time to 480 s. The LOD was found to be better or at least comparable to literature levels involving on-line trapping and some other sophisticated instrumental methods such as ICP-MS and GF-AAS. A comprehensive interference study involving conventional hydride-forming elements and some transition metals was carried out, and the result showed that the gas phase interference from other hydride-forming elements was largely reduced, thanks to the use of on-line tungsten coil trapping. Finally, the proposed method was applied to the determination of bismuth in several biological and environmental standard reference materials, and a t-test shows that the analytical results by the proposed method have no significant difference from the certified values at the confidence level of 95%

  1. New sulfur hydride H{sub 3}S and excellent superconductivity at high

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Tian [State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun (China)

    2016-07-01

    It is predicted theoretically that molecular hydrogen would dissociate into an atomic phase with metallic properties at high pressures. Metallic hydrogen is believed to be a room-temperature superconductor. However, metallization of hydrogen is still debates in laboratory. As an alternative, hydrogen-rich compounds are extensively explored since their metallization can happen at relatively lower pressures by means of chemical pre-compressions. Here, a new sulfur hydride H{sub 3}S that hardly occur at atmospheric pressure was predicted to be formed at high pressure by two main ways. We also found two intriguing metallic structures with R3m and Im-3m symmetries above 111 GPa and 180 GPa, respectively. Remarkably, the estimated T{sub c} of Im-3m phase at 200 GPa achieves a very high value of 191-204 K, reaching an order of 200 K. Further calculation shown that the H atoms play a significant role in superconductivity. The experimental discovery of superconductivity with a high T{sub c} = 203 K in H-S system at high pressure has verified our theoretically predicted results. Furthermore, the predicted R3m and Im-3m structures have been recently confirmed experimentally by synchrotron XRD.

  2. U-Mo Alloy Powder Obtained Through Selective Hydriding. Particle Size Control

    International Nuclear Information System (INIS)

    Balart, S.N.; Bruzzoni, P.; Granovsky, M.S.

    2002-01-01

    Hydride-dehydride methods to obtain U-Mo alloy powder for high-density fuel elements have been successfully tested by different authors. One of these methods is the selective hydriding of the α phase (HSα). In the HSα method, a key step is the partial decomposition of the γ phase (retained by quenching) to α phase and an enriched γ phase or U 2 Mo. This transformation starts mainly at grain boundaries. Subsequent hydrogenation of this material leads to selective hydriding of the α phase, embrittlement and intergranular fracture. According to this picture, the particle size of the final product should be related to the γ grain size of the starting alloy. The feasibility of controlling the particle size of the product by changing the γ grain size of the starting alloy is currently investigated. In this work an U-7 wt% Mo alloy was subjected to various heat treatments in order to obtain different grain sizes. The results on the powder particle size distribution after applying the HSα method to these samples show that there is a strong correlation between the original γ grain size and the particle size distribution of the powder. (author)

  3. Thermodynamic and structural properties of ball-milled mixtures composed of nano-structural graphite and alkali(-earth) metal hydride

    International Nuclear Information System (INIS)

    Miyaoka, Hiroki; Ichikawa, Takayuki; Fujii, Hironobu

    2007-01-01

    Hydrogen desorption properties of mechanically milled materials composed of nano-structural hydrogenated-graphite (C nano H x ) and alkali(-earth) metal hydride (MH; M = Na, Mg and Ca) were investigated from the thermodynamic and structural points of view. The hydrogen desorption temperature for all the C nano H x and MH composites was obviously lower than that of the corresponding each hydride. In addition, the desorption of hydrocarbons from C nano H x was significantly suppressed by making composite of C nano H x with MH, even though C nano H x itself thermally desorbs a considerably large amount of hydrocarbons. These results indicate that an interaction exists between C nano H x and MH, and hydrogen in both the phases is destabilized by a close contact between polar C-H groups in C nano H x and the MH solid phase. Moreover, a new type of chemical bonding between the nano-structural carbon (C nano ) and the Li, Ca, or Mg metal atoms may be formed after hydrogen desorption. Thus, the above metal-C-H system would be recognized as a new family of H-storage materials

  4. Stability Indicating Reverse Phase HPLC Method for Estimation of Rifampicin and Piperine in Pharmaceutical Dosage Form.

    Science.gov (United States)

    Shah, Umang; Patel, Shraddha; Raval, Manan

    2018-01-01

    High performance liquid chromatography is an integral analytical tool in assessing drug product stability. HPLC methods should be able to separate, detect, and quantify the various drug-related degradants that can form on storage or manufacturing, plus detect any drug-related impurities that may be introduced during synthesis. A simple, economic, selective, precise, and stability-indicating HPLC method has been developed and validated for analysis of Rifampicin (RIFA) and Piperine (PIPE) in bulk drug and in the formulation. Reversed-phase chromatography was performed on a C18 column with Buffer (Potassium Dihydrogen Orthophosphate) pH 6.5 and Acetonitrile, 30:70), (%, v/v), as mobile phase at a flow rate of 1 mL min-1. The detection was performed at 341 nm and sharp peaks were obtained for RIFA and PIPE at retention time of 3.3 ± 0.01 min and 5.9 ± 0.01 min, respectively. The detection limits were found to be 2.385 ng/ml and 0.107 ng/ml and quantification limits were found to be 7.228ng/ml and 0.325ng/ml for RIFA and PIPE, respectively. The method was validated for accuracy, precision, reproducibility, specificity, robustness, and detection and quantification limits, in accordance with ICH guidelines. Stress study was performed on RIFA and PIPE and it was found that these degraded sufficiently in all applied chemical and physical conditions. Thus, the developed RP-HPLC method was found to be suitable for the determination of both the drugs in bulk as well as stability samples of capsule containing various excipients. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  5. The effect of hydrides on the growth of zirconia

    International Nuclear Information System (INIS)

    Ekbom, L.R.

    1982-01-01

    The purpose of the present experiment has been to verify a hypothesis that accelerated corrosion of hydride containin Zircaloy is caused by small pores formed in the oxide by the evolution of hydrogen during oxidation of hydrides. The work has been divided into two parts: specimen preparation and microscopy. ZrO 2 is difficult to work with because of the high compressive stress which exists in the oxide. The most interesting area to study if any hydrogen pores exist, is the metal-oxide interface. Both transmission and scanning electron microscopy were used in the study. Neither of these methods gave any useful information with regard to the original hypothesis. However, a few interesting observations were made on the structure of the oxide at the metal-oxide interface. When the metal had been removed by electropolishing it was seen that the inner surface of the oxide consisted of 0,2-0.3 μ long and 0.1 μ thick wormlike protuberances of oxide. These features could not be seen when the metal had been removed by chemical etching. An attempt to determine whether or not this structure is an artefact introduced by electropolishing was inconclusive but indicated that the structure probably is real. (Author)

  6. Oxidation of Al2O3 Scale-Forming MAX Phases in Turbine Environments

    Science.gov (United States)

    Smialek, James L.

    2018-03-01

    High temperature oxidation of alumina-forming MAX phases, Ti2AlC and Cr2AlC, were examined under turbine engine environments and coating configurations. Thermogravimetric furnace tests of Ti2AlC showed a rapid initial transient due to non-protective TiO2 growth. Subsequent well-behaved cubic kinetics for alumina scale growth were shown from 1273 K to 1673 K (1000 °C to 1400 °C). These possessed an activation energy of 335 kJ/mol, consistent with estimates of grain boundary diffusivity of oxygen ( 375 kJ/mol). The durability of Ti2AlC under combustion conditions was demonstrated by high pressure burner rig testing at 1373 K to 1573 K (1100 °C to 1300 °C). Here good stability and cubic kinetics also applied, but produced lower weight gains due to volatile TiO(OH)2 formation in water vapor combustion gas. Excellent thermal stability was also shown for yttria-stabilized zirconia thermal barrier coatings deposited on Ti2AlC substrates in 2500-hour furnace tests at 1373 K to 1573 K (1100 °C to 1300 °C). These sustained a record 35 µm of scale as compared to 7 μm observed at failure for typical superalloy systems. In contrast, scale and TBC spallation became prevalent on Cr2AlC substrates above 1423 K (1150 °C). Cr2AlC diffusion couples with superalloys exhibited good long-term mechanical/oxidative stability at 1073 K (800 °C), as would be needed for corrosion-resistant coatings. However, diffusion zones containing a NiAl-Cr7C3 matrix with MC and M3B2 particulates were commonly formed and became extensive at 1423 K (1150 °C).

  7. Ceramic Single Phase High-Level Nuclear Waste Forms: Hollandite, Perovskite, and Pyrochlore

    Science.gov (United States)

    Vetter, M.; Wang, J.

    2017-12-01

    The lack of viable options for the safe, reliable, and long-term storage of nuclear waste is one of the primary roadblocks of nuclear energy's sustainable future. The method being researched is the incorporation and immobilization of harmful radionuclides (Cs, Sr, Actinides, and Lanthanides) into the structure of glasses and ceramics. Borosilicate glasses are the main waste form that is accepted and used by today's nuclear industry, but they aren't the most efficient in terms of waste loading, and durability is still not fully understood. Synroc-phase ceramics (i.e. hollandite, perovskite, pyrochlore, zirconolite) have many attractive qualities that glass waste forms do not: high waste loading, moderate thermal expansion and conductivity, high chemical durability, and high radiation stability. The only downside to ceramics is that they are more complex to process than glass. New compositions can be discovered by using an Artificial Neural Network (ANN) to have more options to optimize the composition, loading for performance by analyzing the non-linear relationships between ionic radii, electronegativity, channel size, and a mineral's ability to incorporate radionuclides into its structure. Cesium can be incorporated into hollandite's A-site, while pyrochlore and perovskite can incorporate actinides and lanthanides into their A-site. The ANN is used to predict new compositions based on hollandite's channel size, as well as the A-O bond distances of pyrochlore and perovskite, and determine which ions can be incorporated. These new compositions will provide more options for more experiments to potentially improve chemical and thermodynamic properties, as well as increased waste loading capabilities.

  8. Gas phase hydrolysis of formaldehyde to form methanediol: impact of formic acid catalysis.

    Science.gov (United States)

    Hazra, Montu K; Francisco, Joseph S; Sinha, Amitabha

    2013-11-21

    We find that formic acid (FA) is very effective at facilitating diol formation through its ability to reduce the barrier for the formaldehyde (HCHO) hydrolysis reaction. The rate limiting step in the mechanism involves the isomerization of a prereactive collision complex formed through either the HCHO···H2O + FA and/or HCHO + FA···H2O pathways. The present study finds that the effective barrier height, defined as the difference between the zero-point vibrational energy (ZPE) corrected energy of the transition state (TS) and the HCHO···H2O + FA and HCHO + FA···H2O starting reagents, are respectively only ∼1 and ∼4 kcal/mol. These barriers are substantially lower than the ∼17 kcal/mol barrier associated with the corresponding step in the hydrolysis of HCHO catalyzed by a single water molecule (HCHO + H2O + H2O). The significantly lower barrier heights for the formic acid catalyzed pathway reveal a new important role that organic acids play in the gas phase hydrolysis of atmospheric carbonyl compounds.

  9. Boron-nitrogen based hydrides and reactive composites for hydrogen storage

    DEFF Research Database (Denmark)

    Jepsen, Lars H.; Ley, Morten B.; Lee, Young-Su

    2014-01-01

    Hydrogen forms chemical compounds with most other elements and forms a variety of different chemical bonds. This fascinating chemistry of hydrogen has continuously provided new materials and composites with new prospects for rational design and the tailoring of properties. This review highlights...... a range of new boron and nitrogen based hydrides and illustrates how hydrogen release and uptake properties can be improved. © 2014 Elsevier Ltd....

  10. Studies of hydrogen absorption and desorption processes in advanced intermetallic hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Masashi

    2005-07-01

    This work is a part of the research program performed in the Department of Energy Systems, Institute for Energy Technology (Kjeller, Norway), which is focused on the development of the advanced hydrogen storage materials. The activities are aimed on studies of the mechanisms of hydrogen interactions with intermetallic alloys with focus on establishing an interrelation between the crystal structure, thermodynamics and kinetics of the processes in the metal-hydrogen systems, on the one hand, and hydrogen storage properties (capacity, rates of desorption, hysteresis). Many of the materials under investigation have potential to be applied in applications, whereas some already have been commercialised in the world market. A number of metals take up considerable amounts of hydrogen and form chemical compounds with H, metal hydrides. Unfortunately, binary hydrides are either very stable (e.g. for the rare earth metals [RE], Zr, Ti, Mg: metal R) or are formed at very high applied pressures of hydrogen gas (e.g. for the transition metals, Ni, Co, Fe, etc.: Metal T). However, hydrogenation process becomes easily reversible at very convenient from practical point of view conditions, around room temperature and at H2 pressures below 1 MPa for the two-component intermetallic alloys R{sub x}T{sub y}. This raised and maintains further interest to the intermetallic hydrides as solid H storage materials. Materials science research of this thesis is focused on studies of the reasons staying behind the beneficial effect of two non-transition elements M(i.e., In and Sn) contributing to the formation of the ternary intermetallic alloys R{sub x}T{sub y}M{sub 2}., on the hydrogen storage behaviours. Particular focus is on two aspects where the remarkable improvement of ordinary metal hydrides is achieved via introduction of In and Sn: a) Increase of the volume density of stored hydrogen in solid materials to the record high level. b) Improvement of the kinetics of hydrogen charge and

  11. Multi-scale characterization of nanostructured sodium aluminum hydride

    Science.gov (United States)

    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.

  12. Hydrogen storage in metallic hydrides: the hydrides of magnesium-nickel alloys

    International Nuclear Information System (INIS)

    Silva, E.P. da.

    1981-01-01

    The massive and common use of hydrogen as an energy carrier requires an adequate solution to the problem of storing it. High pressure or low temperatures are not entirely satisfactory, having each a limited range of applications. Reversible metal hydrides cover a range of applications intermediate to high pressure gas and low temperature liquid hydrogen, retaining very favorable safety and energy density characteristics, both for mobile and stationary applications. This work demonstrates the technical viability of storing hydrogen in metal hydrides of magnesium-nickel alloys. Also, it shows that technology, a product of science, can be generated within an academic environment, of the goal is clear, the demand outstanding and the means available. We review briefly theoretical models relating to metal hydride properties, specially the thermodynamics properties relevant to this work. We report our experimental results on hydrides of magnesium-nickel alloys of various compositions including data on structure, hydrogen storage capacities, reaction kinetics, pressure-composition isotherms. We selected a promising alloy for mass production, built and tested a modular storage tank based on the hydrides of the alloy, with a capacity for storing 10 Nm sup(3) of hydrogen of 1 atm and 20 sup(0)C. The tank weighs 46,3 Kg and has a volume of 21 l. (author)

  13. SYNTHESIS AND STRUCTURE OF BIS(PHENYLTETRAMETHYLCYCLOPENTADIENYL)TITANIUM(III) HYDRIDE - THE FIRST MONOMERIC BIS(CYCLOPENTADIENYL)TITANIUM(III) HYDRIDE : The First Monomeric Bis(cyclopentadienyl)titanium(III) Hydride

    NARCIS (Netherlands)

    de Wolf, J.M.; Meetsma, A.; Teuben, J.H

    1995-01-01

    The first structurally characterized monomeric bis(cyclopentadienyl)titanium(III) hydride, (C(5)PhMe(4))(2)TiH (4), was synthesized by hydrogenolysis of (C(5)PhMe(4))(2)TiMe (5). Hydride 4 was found to be a monomeric bent sandwich by X-ray diffraction methods, and the pentamethylcyclopentadienyl

  14. Direct hydride shift mechanism and stereoselectivity of P450nor confirmed by QM/MM calculations.

    Science.gov (United States)

    Krámos, Balázs; Menyhárd, Dóra K; Oláh, Julianna

    2012-01-19

    Nitric oxide reductase (P450(nor)) found in Fusarium oxysporum catalyzes the reduction of nitric oxide to N(2)O in a multistep process. The reducing agent, NADH, is bound in the distal pocket of the enzyme, and direct hydride transfer occurs from NADH to the nitric oxide bound heme enzyme, forming intermediate I. Here we studied the possibility of hydride transfer from NADH to both the nitrogen and oxygen of the heme-bound nitric oxide, using quantum chemical and combined quantum mechanics/molecular mechanics (QM/MM) calculations, on two different protein models, representing both possible stereochemistries, a syn- and an anti-NADH arrangement. All calculations clearly favor hydride transfer to the nitrogen of nitric oxide, and the QM-only barrier and kinetic isotope effects are good agreement with the experimental values of intermediate I formation. We obtained higher barriers in the QM/MM calculations for both pathways, but hydride transfer to the nitrogen of nitric oxide is still clearly favored. The barriers obtained for the syn, Pro-R conformation of NADH are lower and show significantly less variation than the barriers obtained in the case of anti conformation. The effect of basis set and wide range of functionals on the obtained results are also discussed.

  15. Metal hydrides based high energy density thermal battery

    International Nuclear Information System (INIS)

    Fang, Zhigang Zak; Zhou, Chengshang; Fan, Peng; Udell, Kent S.; Bowman, Robert C.; Vajo, John J.; Purewal, Justin J.; Kekelia, Bidzina

    2015-01-01

    Highlights: • The principle of the thermal battery using advanced metal hydrides was demonstrated. • The thermal battery used MgH 2 and TiMnV as a working pair. • High energy density can be achieved by the use of MgH 2 to store thermal energy. - Abstract: A concept of thermal battery based on advanced metal hydrides was studied for heating and cooling of cabins in electric vehicles. The system utilized a pair of thermodynamically matched metal hydrides as energy storage media. The pair of hydrides that was identified and developed was: (1) catalyzed MgH 2 as the high temperature hydride material, due to its high energy density and enhanced kinetics; and (2) TiV 0.62 Mn 1.5 alloy as the matching low temperature hydride. Further, a proof-of-concept prototype was built and tested, demonstrating the potential of the system as HVAC for transportation vehicles

  16. Pressure and high-Tc superconductivity in sulfur hydrides.

    Science.gov (United States)

    Gor'kov, Lev P; Kresin, Vladimir Z

    2016-05-11

    The paper discusses fundamentals of record-TC superconductivity discovered under high pressure in sulfur hydride. The rapid increase of TC with pressure in the vicinity of Pcr ≈ 123GPa is interpreted as the fingerprint of a first-order structural transition. Based on the cubic symmetry of the high-TC phase, it is argued that the lower-TC phase has a different periodicity, possibly related to an instability with a commensurate structural vector. In addition to the acoustic branches, the phonon spectrum of H3S contains hydrogen modes with much higher frequencies. Because of the complex spectrum, usual methods of calculating TC are here inapplicable. A modified approach is formulated and shown to provide realistic values for TC and to determine the relative contributions of optical and acoustic branches. The isotope effect (change of TC upon Deuterium for Hydrogen substitution) originates from high frequency phonons and differs in the two phases. The decrease of TC following its maximum in the high-TC phase is a sign of intermixing with pairing at hole-like pockets which arise in the energy spectrum of the cubic phase at the structural transition. On-pockets pairing leads to the appearance of a second gap and is remarkable for its non-adiabatic regime: hydrogen mode frequencies are comparable to the Fermi energy.

  17. Hydrides and Borohydrides of Light Elements

    Science.gov (United States)

    1947-12-04

    Troy, Attn: Inst. of Naval Science (30) Solar Aircraft Cu,, San Diego, Attn: Dr. M. A. Williamson " (31) INSMAT. N. J. for Itandard Oil Co., Esso Lab...with the other# iLD F.Re p. 8 ilt -ms" #61ggSotod that.. ir addition to thc impurity in the t~y..thr, an impurkty, prosumably aluminum hydride, in

  18. Facile Synthesis of Permethyl Yttrocene Hydride

    NARCIS (Netherlands)

    Haan, Klaas H. den; Teuben, Jan H.

    1984-01-01

    A convenient three step synthesis of (Cp*2YH)n (Cp* = C5Me5) is described starting with YCl3.3thf, in which Cp*2YCl.thf and Cp*2YCH(SiMe3)2 are intermediates, which could be isolated and characterized. The hydride is active in the activation of sp2 and sp3 C-H bonds as was demonstrated by the H-D

  19. Atom probe tomography of intermetallic phases and interfaces formed in dissimilar joining between Al alloys and steel

    International Nuclear Information System (INIS)

    Lemmens, B.; Springer, H.; Duarte, M.J.; De Graeve, I.; De Strycker, J.; Raabe, D.; Verbeken, K.

    2016-01-01

    While Si additions to Al are widely used to reduce the thickness of the brittle intermetallic seam formed at the interface during joining of Al alloys to steel, the underlying mechanisms are not clarified yet. The developed approach for the site specific atom probe tomography analysis revealed Si enrichments at grain and phase boundaries between the θ (Fe 4 Al 13 ) and η (Fe 2 Al 5 ) phase, up to about ten times that of the concentration in Al. The increase in Si concentration could play an important role for the growth kinetics of the intermetallic phases formed for example in hot-dip aluminizing of steel. - Highlights: •Si additions to Al reduce thickness of intermetallic seam in joining with steel. •Approach developed for the site specific APT analysis of the intermetallic seam •Si enrichment at grain and phase boundaries possibly affects growth of intermetallics.

  20. HYDRIDE-RELATED DEGRADATION OF SNF CLADDING UNDER REPOSITORY CONDITIONS

    International Nuclear Information System (INIS)

    McCoy, K.

    2000-01-01

    The purpose and scope of this analysis/model report is to analyze the degradation of commercial spent nuclear fuel (CSNF) cladding under repository conditions by the hydride-related metallurgical processes, such as delayed hydride cracking (DHC), hydride reorientation and hydrogen embrittlement, thereby providing a better understanding of the degradation process and clarifying which aspects of the process are known and which need further evaluation and investigation. The intended use is as an input to a more general analysis of cladding degradation

  1. Small angle neutron scattering form polymer melts: structural investigation and phase behaviour

    International Nuclear Information System (INIS)

    Ertugrul, O.

    2004-01-01

    The Small-Angle Neutron Scattering (SANS) techniques have been used to study the structural properties and phase behavior of polymer melts. A model based on Random Phase Approximation (RPA) is proposed to predict the experimental data. By fitting the model to data we could be able to obtain radius of gyration (a measure of size of a polymer) and phase transition for the sample. (author)

  2. Method of forming an oxide superconducting thin film having an R1A2C3 crystalline phase over an R2A1C1 crystalline phase

    International Nuclear Information System (INIS)

    Lelental, M.; Romanofsky, H.J.

    1992-01-01

    This patent describes a process which comprises forming a mixed rare earth alkaline earth copper oxide layer on a substrate and converting the mixed rare earth alkaline earth copper oxide layer to an electrically conductive layer. It comprises crystalline R 1 A 2 C 3 oxide phase by heating in the presence of oxygen, wherein rare earth and R is in each instance chosen from among yttrium, lanthanum, samarium, europium, gadolinium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium and alkaline earth and A is in each instance chosen from among calcium, strontium and barium, characterized in that a crystalline R 2 A 1 C 1 oxide phase is first formed as a layer on the substrate and the crystalline R 1 A 2 C 3 oxide phase is formed over the crystalline R 2 A 1 C 1 oxide phase by coating a mixed rare earth alkaline earth copper oxide on the crystalline R 2 A 1 C 1 oxide phase and heating the mixed rare earth alkaline earth copper oxide to a temperature of at least 1000 degrees C

  3. Direct visualization of β phase causing intergranular forms of corrosion in Al–Mg alloys

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Young-Ki, E-mail: deltag@naver.com; Allen, Todd

    2013-06-15

    For a more effective examination of microstructure in Al–Mg alloys, a new etching solution has been developed; dissolved ammonium persulfate in water. It is demonstrated how β phase (Al{sub 3}Mg{sub 2}) in Al–Mg alloys respond to this solution using samples of a binary Al–Mg alloy and a commercial 5083 aluminum alloy. Nanometer sized β phase is clearly visualized for the first time using scanning electron microscopy (SEM) instead of transmission electron microscopy (TEM). It is anticipated that direct and unambiguous visualization of β phase will greatly augment intergranular corrosion research in 5xxx series aluminum alloys. - Highlights: • Nanometer sized β phase in Al-10% Mg is first clearly visualized with SEM. • Nanometer sized β phase in wrought alloy 5083 is first clearly visualized with SEM. • Grain boundary decorating β phase and isolated sponge-like β phase are shown. • This phase is confirmed to be β phase using composition analysis.

  4. Spectrophotometric determination of volautile inorganic hydrides in binary gaseous mixtures

    International Nuclear Information System (INIS)

    Rezchikov, V.G.; Skachkova, I.N.; Kuznetsova, T.S.; Khrushcheva, V.V.

    1985-01-01

    A study was made on possibility of single and continuons analysis of binary mixtures (hydride-gas) for the content of volatile inorganic hydrides (VIH) from absorption spectra in the 185-280 nm band. Dependences of the percentage of VIH transmission on the wavelength are presented. It is shown that the maximum of their absorption depends on the element-hydrogen the bond length and binding energy. Detection limit for boron hydride was established to be n x 10 -3 % vol at 185-190 nm wavelength. Technique for spectrophotometric hydride determination in binary mixtures with hydrogen, argon, helium was developed. The technique provides the continuous control of gaseous mixture composition

  5. Identification of the zirconium hydrides metallography in zircaloy-2

    International Nuclear Information System (INIS)

    Garcia Gonzalez, F.

    1968-01-01

    Technique for the Identification of the zirconium hydrides in metallographic specimens have been developed. Microhardness, quantitative estimation and relative orientation of the present hydrides as well as grain size determination of the different Zircaloy-2 tube specimens have also been made. The specimens used were corrosion- tested in water during various periods of time at 300 degree castrating, prior to the metallographic examination. Reference specimens, as received, and heavily hydride specimens in a hydrogen atmosphere at 800 degree centigrees, have been used in the previous stages of the work. No difficulties have been met in this early stage of acquaintanceship with the zirconium hydrides. (Author) 5 refs

  6. Modeling of hydride precipitation and re-orientation

    Energy Technology Data Exchange (ETDEWEB)

    Tikare, Veena [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Weck, Philippe F. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Mitchell, John Anthony [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-09-18

    In this report, we present a thermodynamic-­based model of hydride precipitation in Zr-based claddings. The model considers the state of the cladding immediately following drying, after removal from cooling-pools, and presents the evolution of precipitate formation upon cooling as follows: The pilgering process used to form Zr-based cladding imparts strong crystallographic and grain shape texture, with the basal plane of the hexagonal α-Zr grains being strongly aligned in the rolling-­direction and the grains are elongated with grain size being approximately twice as long parallel to the rolling direction, which is also the long axis of the tubular cladding, as it is in the orthogonal directions.

  7. Suppressed Release of Clarithromycin from Tablets by Crystalline Phase Transition of Metastable Polymorph Form I.

    Science.gov (United States)

    Fujiki, Sadahiro; Watanabe, Narumi; Iwao, Yasunori; Noguchi, Shuji; Mizoguchi, Midori; Iwamura, Takeru; Itai, Shigeru

    2015-08-01

    The pharmaceutical properties of clarithromycin (CAM) tablets containing the metastable form I of crystalline CAM were investigated. Although the dissolution rate of form I was higher than that of stable form II, the release of CAM from form I tablet was delayed. Disintegration test and liquid penetration test showed that the disintegration of the tablet delayed because of the slow penetration of an external solution into form I tablet. Investigation by scanning electron microscopy revealed that the surface of form I tablet was covered with fine needle-shaped crystals following an exposure to the external solution. These crystals were identified as form IV crystals by powder X-ray diffraction. The phenomenon that CAM releases from tablet was inhibited by fine crystals spontaneously formed on the tablet surface could be applied to the design of sustained-release formulation systems with high CAM contents by minimizing the amount of functional excipients. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

  8. Initiation of delayed hydride cracking in zirconium-2.5 wt% niobium

    International Nuclear Information System (INIS)

    Shalabi, A.F.; Meneley, D.A.

    1990-01-01

    Delayed hydride cracking in zirconium alloys is caused by the repeated precipitation and cracking of brittle hydrides. The growth kinetic of the hydrides have been measured to evaluate the critical hydride length for crack initiation. Hydride growth leading to crack initiation follows an approximate (time) 1/3 law on the average; crack propagation proceeds in a stepwise fashion. The critical length of hydride for crack initiation increases with stress and temperature. The fracture criterion for crack initiation predicts the critical hydride length at a give stress level and temperature. The fracture initiation mechanism of the hydride confirms the temperature effects for heating and cooling cycles under services loads. (orig.)

  9. Mechanism of n-butane hydrogenolysis promoted by Ta-hydrides supported on silica

    KAUST Repository

    Pasha, Farhan Ahmad

    2014-06-06

    The mechanism of hydrogenolysis of alkanes, promoted by Ta-hydrides supported on silica via 2 ≡ Si-O- bonds, has been studied with a density functional theory (DFT) approach. Our study suggests that the initial monohydride (≡ Si-O-)2Ta(III)H is rapidly trapped by molecular hydrogen to form the more stable tris-hydride (≡ Si-O-) 2Ta(V)H3. Loading of n-butane to the Ta-center occurs through C-H activation concerted with elimination of molecular hydrogen (σ-bond metathesis). Once the Ta-alkyl species is formed, the C-C activation step corresponds to a β-alkyl transfer to the metal with elimination of an olefin. According to these calculations, an α-alkyl transfer to the metal to form a Ta-carbene species is of higher energy. The olefins formed during the C-C activation step can be rapidly hydrogenated by both mono- and tris-Ta-hydride species, making the overall process of alkane cracking thermodynamically favored. © 2014 American Chemical Society.

  10. Topotactic Solid-State Metal Hydride Reductions of Sr2MnO4.

    Science.gov (United States)

    Hernden, Bradley C; Lussier, Joey A; Bieringer, Mario

    2015-05-04

    We report novel details regarding the reactivity and mechanism of the solid-state topotactic reduction of Sr2MnO4 using a series of solid-state metal hydrides. Comprehensive details describing the active reducing species are reported and comments on the reductive mechanism are provided, where it is shown that more than one electron is being donated by H(-). Commonly used solid-state hydrides LiH, NaH, and CaH2, were characterized in terms of reducing power. In addition the unexplored solid-state hydrides MgH2, SrH2, and BaH2 are evaluated as potential solid-state reductants and characterized in terms of their reductive reactivities. These 6 group I and II metal hydrides show the following trend in terms of reactivity: MgH2 < SrH2 < LiH ≈ CaH2 ≈ BaH2 < NaH. The order of the reductants are discussed in terms of metal electronegativity and bond strengths. NaH and the novel use of SrH2 allowed for targeted synthesis of reduced Sr2MnO(4-x) (0 ≤ x ≤ 0.37) phases. The enhanced control during synthesis demonstrated by this soft chemistry approach has allowed for a more comprehensive and systematic evaluation of Sr2MnO(4-x) phases than previously reported phases prepared by high temperature methods. Sr2MnO3.63(1) has for the first time been shown to be monoclinic by powder X-ray diffraction and the oxidative monoclinic to tetragonal transition occurs at 450 °C.

  11. Preparation and Characterization of Membranes Formed by Nonsolvent Induced Phase Separation: A Review

    KAUST Repository

    Guillen, Gregory R.; Pan, Yinjin; Li, Minghua; Hoek, Eric M. V.

    2011-01-01

    . The body of knowledge has grown exponentially in the past fifty years, which suggests the need for a critical review of the literature. Here we present a review of nonsolvent induced phase separation membrane preparation and characterization for many

  12. High-Speed, Low-Power ADC for Digital Beam Forming (DBF) Systems, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — In Phase 1, Ridgetop Group designed a high-speed, yet low-power silicon germanium (SiGe)-based, analog-to-digital converter (ADC) to be a key element for digital...

  13. Break Differed Induced by Hydrides (BDIH) in Zr-2,5Nb: Microstructure effect

    International Nuclear Information System (INIS)

    Mieza, J. Ignacio; Domizzi, Gladys; Vigna, Gustavo L

    2006-01-01

    The alloys of Zr-2,5%Nb are susceptible to be degraded for the incorporation of hydrogen in their matrix. One of the mechanisms of the damage by hydrogen known as Break Differed Induced by Hydrides (BDIH) consists of the evolution, in discreet steps, of a crack inside the matrix by the fragile break of the hydride phase. The parameter utilized to characterize the severity of the process of BDIH is the velocity of advance of the crack. The variables that affect to the velocity are the solicitations of external load, the thermal cycles, the content of hydrogen and the microstructure of the material. The Zr-2, 5% Nb of nuclear use is a two-phase alloy (α-β) constituted by the phase alpha (rich in Zr) and β-Zr (rich in Nb) retained since high temperature. In service, the phase metastable evolves toward the stable phase depending on the time and the temperature of operation. In this work the effects of the evolution of the phase β-Zr on the velocity of BDIH are studied, measure with emission acoustics. The microstructural characterization was done by means of obtained dust X-rays diffraction by anodic dissolution of the material. The results obtained show the decrease of the velocity of propagation of the crack with the degree of advance of the transformation toward the phase β-Nb, consistent effect with the differences observed in the coefficients of diffusion of each phase (AG)

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

    Science.gov (United States)

    Easter, R. W.

    1974-01-01

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

  15. Hydrogen storage systems based on magnesium hydride: from laboratory tests to fuel cell integration

    Science.gov (United States)

    de Rango, P.; Marty, P.; Fruchart, D.

    2016-02-01

    The paper reviews the state of the art of hydrogen storage systems based on magnesium hydride, emphasizing the role of thermal management, whose effectiveness depends on the effective thermal conductivity of the hydride, but also depends of other limiting factors such as wall contact resistance and convective exchanges with the heat transfer fluid. For daily cycles, the use of phase change material to store the heat of reaction appears to be the most effective solution. The integration with fuel cells (1 kWe proton exchange membrane fuel cell and solid oxide fuel cell) highlights the dynamic behaviour of these systems, which is related to the thermodynamic properties of MgH2. This allows for "self-adaptive" systems that do not require control of the hydrogen flow rate at the inlet of the fuel cell.

  16. Pyrophoric behaviour of uranium hydride and uranium powders

    Science.gov (United States)

    Le Guyadec, F.; Génin, X.; Bayle, J. P.; Dugne, O.; Duhart-Barone, A.; Ablitzer, C.

    2010-01-01

    Thermal stability and spontaneous ignition conditions of uranium hydride and uranium metal fine powders have been studied and observed in an original and dedicated experimental device placed inside a glove box under flowing pure argon. Pure uranium hydride powder with low amount of oxide (Oxidation mechanisms are proposed.

  17. Ultra-sonic observation in niobium hydride precipitation

    International Nuclear Information System (INIS)

    Florencio, O.; Pinatti, Dyonisio G.

    1982-01-01

    The hidrogen embrittlement of exothermic ocluders, had been considered as due to applied stress induced hydride precipitates leading to brittle fracture. The results of simultaneous measurements of macroscopic deformation and elastic change due to hydride precipitation, using the ultrasonic pulse-echo technique are showed. THen it was tested the possibility of kinectis precipitation parameters evoluation. (Author) [pt

  18. Creating nanoshell on the surface of titanium hydride bead

    Directory of Open Access Journals (Sweden)

    PAVLENKO Vyacheslav Ivanovich

    2016-12-01

    Full Text Available The article presents data on the modification of titanium hydride bead by creating titanium nanoshell on its surface by ion-plasma vacuum magnetron sputtering. To apply titanium nanoshell on the titanium hydride bead vacuum coating plant of multifunctional nanocomposite coatings QVADRA 500 located in the center of high technology was used. Analysis of the micrographs of the original surface of titanium hydride bead showed that the microstructure of the surface is flat, smooth, in addition the analysis of the microstructure of material surface showed the presence of small porosity, roughness, mainly cavities, as well as shallow longitudinal cracks. The presence of oxide film in titanium hydride prevents the free release of hydrogen and fills some micro-cracks on the surface. Differential thermal analysis of both samples was conducted to determine the thermal stability of the initial titanium hydride bead and bead with applied titanium nanoshell. Hydrogen thermal desorption spectra of the samples of the initial titanium hydride bead and bead with applied titanium nanoshell show different thermal stability of compared materials in the temperature range from 550 to 860о C. Titanium nanoshells applied in this way allows increasing the heat resistance of titanium hydride bead – the temperature of starting decomposition is 695о C and temperature when decomposition finishes is more than 1000о C. Modified in this way titanium hydride bead can be used as a filler in the radiation protective materials used in the construction or upgrading biological protection of nuclear power plants.

  19. Improving solid-state hydriding and dehydriding properties of the LiBH{sub 4} plus MgH{sub 2} system with the addition of Mn and V dopants

    Energy Technology Data Exchange (ETDEWEB)

    Crosby, Kyle; Wan, Xuefei; Shaw, Leon L. [Department of Chemical, Materials and Biomolecular Engineering, University of Connecticut, 97 North Eagleville Road, U-3136, Storrs, CT 06269 (United States)

    2010-11-01

    The hydriding process of the 2LiH + MgB{sub 2} mixture is controlled by outward diffusion of Mg and inward diffusion of Li and H within MgB{sub 2} crystals to form LiBH{sub 4}. This study explores the feasibility of using transition metal dopants, such as Mn and V, to enhance the diffusion rate and thus the hydriding kinetics. It is found that Mn can indeed enhance the hydriding kinetics of the 2LiH + MgB{sub 2} mixture, while V does not. The major factor in enhancing the diffusion rate and thus the hydriding kinetics is related to the dopant's ability to induce the lattice distortion of MgB{sub 2} crystals. This study demonstrates that the kinetics of the diffusion controlled solid-state hydriding process can be improved by doping if the dopant is properly selected. (author)

  20. Investigation of the thermodynamics governing metal hydride synthesis in the molten state process

    International Nuclear Information System (INIS)

    Stowe, Ashley C.; Berseth, Polly A.; Farrell, Thomas P.; Laughlin, Laura; Anton, Donald; Zidan, Ragaiy

    2008-01-01

    This work is aimed at utilizing a new synthetic technique to form novel complex hydrides for hydrogen storage. This technique is based on fusing different complex hydrides at elevated temperatures and pressures to form new species with improved hydrogen storage properties. Under conditions of elevated hydrogen overpressures and temperatures the starting materials can reach melting or near-melting point without decomposing (molten state processing), allowing for enhanced diffusion and exchange of elements among the starting materials. The formation and stabilization of these compounds, using the molten state process, is driven by the thermodynamic and kinetic properties of the starting and resulting compounds. Complex hydrides (e.g. NaK 2 AlH 6 , Mg(AlH 4 ) 2 ) were formed, structurally characterized and their hydrogen desorption properties were tested. In this paper we report on investigations of the thermodynamic aspects governing the process and products. We also report on the role of molar ratio in determining the final products. The effectiveness of the molten state process is compared with chemomechanical synthetic methods (ball milling)

  1. Preparation and Characterization of Membranes Formed by Nonsolvent Induced Phase Separation: A Review

    KAUST Repository

    Guillen, Gregory R.

    2011-04-06

    The methods and mechanisms of nonsolvent induced phase separation have been studied for more than fifty years. Today, phase inversion membranes are widely used in numerous chemical industries, biotechnology, and environmental separation processes. The body of knowledge has grown exponentially in the past fifty years, which suggests the need for a critical review of the literature. Here we present a review of nonsolvent induced phase separation membrane preparation and characterization for many commonly used membrane polymers. The key factors in membrane preparation discussed include the solvent type, polymer type and concentration, nonsolvent system type and composition, additives to the polymer solution, and film casting conditions. A brief introduction to membrane characterization is also given, which includes membrane porosity and pore size distribution characterization, membrane physical and chemical properties characterization, and thermodynamic and kinetic evaluation of the phase inversion process. One aim of this review is to lay out the basics for selecting polymer solvent nonsolvent systems with appropriate film casting conditions to produce membranes with the desired performance, morphology, and stability, and to choose the proper way to characterize these properties of nonsolvent induced phase inversion membranes. © 2011 American Chemical Society.

  2. Successive heterolytic cleavages of H2 achieve N2 splitting on silica-supported tantalum hydrides: A DFT proposed mechanism

    KAUST Repository

    Solá ns, Xavier Luis; Chow, Catherine; Gouré , Eric; Kaya, Yasemin; Basset, Jean-Marie; Taoufik, Mostafa; Quadrelli, Elsje Alessandra; Eisenstein, Odile

    2012-01-01

    DFT(B3PW91) calculations have been carried out to propose a pathway for the N2 cleavage by H2 in the presence of silica-supported tantalum hydride complexes [(≡ SiO)2TaHx] that forms [(≡SiO)2Ta(NH)(NH2)] (Science2007, 317, 1056). The calculations

  3. Characterization of the martensite phase formed during hydrogen ion irradiation in austenitic stainless steel

    Science.gov (United States)

    Jin, Hyung-Ha; Lim, Sangyeob; Kwon, Junhyun

    2017-10-01

    Microstructural changes in austenitic stainless steel caused by hydrogen ion irradiation were investigated using transmission electron microscopy (TEM). It has been confirmed that the irradiation induced the formation of martensite along the grain boundary; the martensite phase exhibited a crystal orientation relationship with the adjacent austenite phase. The results of this study also indicate that the concentration of Cr in the martensite phase is lower compared to that in the austenite matrix. The TEM results showed the development of asymmetric radiation-induced segregation (RIS) near the grain boundary, which leads to local changes in the chemical composition such as reduction of Cr near the grain boundary. The asymmetric RIS serves as a prerequisite for the formation of the martensite under hydrogen irradiation.

  4. Growth and decomposition of Lithium and Lithium hydride on Nickel

    DEFF Research Database (Denmark)

    Engbæk, Jakob; Nielsen, Gunver; Nielsen, Jane Hvolbæk

    2006-01-01

    In this paper we have investigated the deposition, structure and decomposition of lithium and lithium-hydride films on a nickel substrate. Using surface sensitive techniques it was possible to quantify the deposited Li amount, and to optimize the deposition procedure for synthesizing lithium......-hydride films. By only making thin films of LiH it is possible to study the stability of these hydride layers and compare it directly with the stability of pure Li without having any transport phenomena or adsorbed oxygen to obscure the results. The desorption of metallic lithium takes place at a lower...... temperature than the decomposition of the lithium-hydride, confirming the high stability and sintering problems of lithium-hydride making the storage potential a challenge. (c) 2006 Elsevier B.V. All rights reserved....

  5. Minimizing hydride cracking in zirconium alloys

    International Nuclear Information System (INIS)

    Coleman, C.E.; Cheadle, B.A.; Ambler, J.F.R.; Eadie, R.L.

    1985-01-01

    Zirconium alloy components can fail by hydride cracking if they contain large flaws and are highly stressed. If cracking in such components is suspected, crack growth can be minimized by following two simple operating rules: components should be heated up from at least 30K below any operating temperature above 450K, and when the component requires cooling to room temperature from a high temperature, any tensile stress should be reduced as much and as quickly as is practical during cooling. This paper describes the physical basis for these rules

  6. Low-frequency excitations in zirconium hydrides

    International Nuclear Information System (INIS)

    Radulescu, A.; Padureanu, I.; Rapeanu, S.N.; Beldiman, A.; Kozlov, Zh.A.; Semenov, V.A.

    1999-01-01

    The slow inelastic neutron scattering (INS) on ZrH x systems (x = 0.38, 0.52) revealed new excitations located within the energy range 2-10 MeV. Besides the acoustic vibrations specific to α-HCP Zr and γ-FCO Zr hydride the fine structure of these excitations is clearly observed. The origin of the new observed peaks is not very clear but a proton tunneling or a resonance effect in α-Zr lattice could be taken into account

  7. Effect of Gaseous Impurities on Long-Term Thermal Cycling and Aging Properties of Complex Hydrides for Hydrogen Storage

    Energy Technology Data Exchange (ETDEWEB)

    Chandra, Dhanesh [Primary Contact; Lamb, Joshua; Chien, Wen-Ming; Talekar, Anjali; and Pal, Narendra

    2011-03-28

    stored in the material after the first desorption. The activation energy was found to be 51 kJ/mol, as compared to 81 kJ/mol for pure lithium alanate. It is proposed that based on the data obtained and CALPHAD modeling that the improvement in cycling is due to the formation of pure lithium (liquid at 255°C), which is able to react with nitrogen specifically forming Li3N. The presence of nitrogen in the 80/20 molar mixtures in a hydride bed along with hydrogen causes Li to form Li3N rather than LiH, and subsequently regenerates the Li2NH phase and yields a ~10 wt.%H reversibly.

  8. Temperature- and moisture-dependent phase changes in crystal forms of barbituric acid

    International Nuclear Information System (INIS)

    Zencirci, Neslihan; Gstrein, Elisabeth; Langes, Christoph; Griesser, Ulrich J.

    2009-01-01

    The dihydrate of barbituric acid (BAc) and its dehydration product, form II were investigated by means of moisture sorption analysis, hot-stage microscopy, differential scanning calorimetry, thermogravimetry, solution calorimetry, IR- and Raman-spectroscopy as well as powder X-ray diffraction. The dihydrate desolvates already at and below 50% relative humidity (RH) at 25 deg. C whereas form II is stable up to 80% RH, where it transforms back to the dihydrate. The thermal dehydration of barbituric acid dihydrate (BAc-H2) is a single step, nucleation controlled process. The peritectic reaction of the hydrate was measured at 77 deg. C and a transformation enthalpy of Δ trs H H2-II = 17.3 kJ mol -1 was calculated for the interconversion between the hydrate and form II. An almost identical value of 17.0 kJ mol -1 was obtained from solution calorimetry in water as solvent (Δ sol H H2 = 41.5, Δ sol H II = 24.5 kJ mol -1 ). Additionally a high-temperature form (HT-form) of BAc, which is enantiotropically related to form II and unstable at ambient conditions has been characterized. Furthermore, we observed that grinding of BAc with potassium bromide (KBr) induces a tautomeric change. Therefore, IR-spectra recorded with KBr-discs usually display a mixture of tautomers, whereas the IR-spectra of the pure trioxo-form of BAc are obtained if alternative preparation techniques are used

  9. Thermodynamic and kinetics models of hydrogen absorption bound to phase transformations

    International Nuclear Information System (INIS)

    Gondor, G.; Lexcellent, Ch.

    2007-01-01

    In order to design hydrogen gaseous pressure tanks, the absorption (desorption) of hydrogen has to be described and modelled. The equilibrium state can be described by the 'H 2 gas pressure - H 2 composition in the intermetallic compounds - isotherms' (PCI) curves. Several models of PCI curves already exist. At the beginning of the absorption, the hydrogen atoms and the intermetallic compounds form a solid solution (α phase). When the hydrogen concentration increases, a phase transformation appears changing the α solid solution into an hydridephase) (solid solution + H 2 ↔ hydride). When all the solid solution has been transformed into hydride, the absorbed hydrogen atoms are in β phase. A new thermodynamic model has been developed in order to take into account this transition phase. The equilibrium state is then given by a relation between the H 2 gas pressure and the H 2 concentration in the intermetallic compound for a fixed external temperature. Two kinetics models have been developed too; at first has been considered that the kinetics depend only of the entire concentration in the intermetallic compound and of the difference between the applied pressure and the equilibrium pressure. Then, has been considered that the hydrogen concentration changes in the metallic matrix. In this last case, for each hydrogenation process, the absorption velocity is calculated to determine the slowest local process which regulates the local evolution of the hydrogen concentration. These two models are based on the preceding thermodynamic model of the PCI curves. (O.M.)

  10. The shape and dynamics of the generation of the splash forms in single-phase systems after drop hitting

    Science.gov (United States)

    Sochan, Agata; Beczek, Michał; Mazur, Rafał; RyŻak, Magdalena; Bieganowski, Andrzej

    2018-02-01

    The splash phenomenon is being increasingly explored with the use of modern measurement tools, including the high-speed cameras. Recording images at a rate of several thousand frames per second facilitates parameterization and description of the dynamics of splash phases. This paper describes the impact of a single drop of a liquid falling on the surface of the same liquid. Three single-phase liquid systems, i.e., water, petrol, and diesel fuel, were examined. The falling drops were characterized by different kinetic energy values depending on the height of the fall, which ranged from 0.1 to 7.0 m. Four forms, i.e., waves, crowns, semi-closed domes, and domes, were distinguished depending on the drop energy. The analysis of the recorded images facilitated determination of the static and dynamic parameters of each form, e.g., the maximum height of each splash form, the width of the splash form at its maximum height, and the rate of growth of the splash form. We, Re, Fr, and K numbers were determined for all analyzed liquid systems. On the basis of the obtained values of dimensionless numbers, the areas of occurrence of characteristic splash forms were separated.

  11. Automatic segmentation of phase-correlated CT scans through nonrigid image registration using geometrically regularized free-form deformation

    International Nuclear Information System (INIS)

    Shekhar, Raj; Lei, Peng; Castro-Pareja, Carlos R.; Plishker, William L.; D'Souza, Warren D.

    2007-01-01

    Conventional radiotherapy is planned using free-breathing computed tomography (CT), ignoring the motion and deformation of the anatomy from respiration. New breath-hold-synchronized, gated, and four-dimensional (4D) CT acquisition strategies are enabling radiotherapy planning utilizing a set of CT scans belonging to different phases of the breathing cycle. Such 4D treatment planning relies on the availability of tumor and organ contours in all phases. The current practice of manual segmentation is impractical for 4D CT, because it is time consuming and tedious. A viable solution is registration-based segmentation, through which contours provided by an expert for a particular phase are propagated to all other phases while accounting for phase-to-phase motion and anatomical deformation. Deformable image registration is central to this task, and a free-form deformation-based nonrigid image registration algorithm will be presented. Compared with the original algorithm, this version uses novel, computationally simpler geometric constraints to preserve the topology of the dense control-point grid used to represent free-form deformation and prevent tissue fold-over. Using mean squared difference as an image similarity criterion, the inhale phase is registered to the exhale phase of lung CT scans of five patients and of characteristically low-contrast abdominal CT scans of four patients. In addition, using expert contours for the inhale phase, the corresponding contours were automatically generated for the exhale phase. The accuracy of the segmentation (and hence deformable image registration) was judged by comparing automatically segmented contours with expert contours traced directly in the exhale phase scan using three metrics: volume overlap index, root mean square distance, and Hausdorff distance. The accuracy of the segmentation (in terms of radial distance mismatch) was approximately 2 mm in the thorax and 3 mm in the abdomen, which compares favorably to the

  12. High-Speed, Low-Power ADC for Digital Beam Forming (DBF) Systems, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Ridgetop Group will design a high-speed, low-power silicon germanium (SiGe)-based, analog-to-digital converter (ADC) to be a key element for digital beam forming...

  13. Preparation and characterization of form-stable paraffin/polyurethane composites as phase change materials for thermal energy storage

    International Nuclear Information System (INIS)

    Chen, Keping; Yu, Xuejiang; Tian, Chunrong; Wang, Jianhua

    2014-01-01

    Highlights: • Paraffin/polyurethane composite as form-stable phase change material was prepared by bulk polymerization. • Paraffin/polyurethane composite possesses typical character of dual phase transition. • Total latent heat of n-eicosane/PUPCM is as high as 141.2 J/g. • Maximum encapsulation ratio for n-octadecane/PUPCM composites is 25% w/w. - Abstract: Polyurethane phase change material (PUPCM) has been demonstrated to be effective solid–solid phase change material for thermal energy storage. However, the high cost and complex process on preparation of PUPCMs with high enthalpy and broad phase transition temperature range can prohibit industrial-scale applications. In this work, a series of novel form-stable paraffin/PUPCMs composites (n-octadecane/PUPCM, n-eicosane/PUPCM and paraffin wax/PUPCM) with high enthalpy and broad phase transition temperature range (20–65 °C) were directly synthesized via bulk polymerization. The composites were prepared at different mass fractions of n-octadecane (10, 20, 25, 30% w/w). The results indicated that the maximum encapsulation ratio for n-octadecane/PUPCM10000 composites was around 25% w/w. The chemical structure and crystalline properties of these composites were characterized by Fourier transform infrared spectroscopy (FT-IR), polarizing optical microscopy (POM), wide-angle X-ray diffraction (WAXD). Thermal properties and thermal reliability of the composites were determined using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). From DSC analysis, the composites showed a typical dual phase change temperature. The enthalpy for the composite with 25% w/w n-eicosane was as high as 141.2 J/g. TGA analysis indicated that the composites degraded at considerably high temperatures. The process of preparation of PUPCMs and their composites was very simple, inexpensive, environmental friendly and easy to process into desired shapes, which could find the promising applications in solar

  14. Alumina-Forming Austenitic Stainless Steels Strengthened by Laves Phase and MC Carbide Precipitates

    Science.gov (United States)

    Yamamoto, Y.; Brady, M. P.; Lu, Z. P.; Liu, C. T.; Takeyama, M.; Maziasz, P. J.; Pint, B. A.

    2007-11-01

    Creep strengthening of Al-modified austenitic stainless steels by MC carbides or Fe2Nb Laves phase was explored. Fe-20Cr-15Ni-(0-8)Al and Fe-15Cr-20Ni-5Al base alloys (at. pct) with small additions of Nb, Mo, W, Ti, V, C, and B were cast, thermally-processed, and aged. On exposure from 650 °C to 800 °C in air and in air with 10 pct water vapor, the alloys exhibited continuous protective Al2O3 scale formation at an Al level of only 5 at. pct (2.4 wt pct). Matrices of the Fe-20Cr-15Ni-5Al base alloys consisted of γ (fcc) + α (bcc) dual phase due to the strong α-Fe stabilizing effect of the Al addition and exhibited poor creep resistance. However, adjustment of composition to the Fe-15Cr-20Ni-5Al base resulted in alloys that were single-phase γ-Fe and still capable of alumina scale formation. Alloys that relied solely on Fe2Nb Laves phase precipitates for strengthening exhibited relatively low creep resistance, while alloys that also contained MC carbide precipitates exhibited creep resistance comparable to that of commercially available heat-resistant austenitic stainless steels. Phase equilibria studies indicated that NbC precipitates in combination with Fe2Nb were of limited benefit to creep resistance due to the solution limit of NbC within the γ-Fe matrix of the alloys studied. However, when combined with other MC-type strengtheners, such as V4C3 or TiC, higher levels of creep resistance were obtained.

  15. Temperature- and moisture-dependent phase changes in crystal forms of barbituric acid

    Energy Technology Data Exchange (ETDEWEB)

    Zencirci, Neslihan; Gstrein, Elisabeth; Langes, Christoph [Institute of Pharmacy, Faculty of Chemistry and Pharmacy, University of Innsbruck, Innrain 52, 6020 Innsbruck (Austria); Griesser, Ulrich J. [Institute of Pharmacy, Faculty of Chemistry and Pharmacy, University of Innsbruck, Innrain 52, 6020 Innsbruck (Austria)], E-mail: ulrich.griesser@uibk.ac.at

    2009-03-10

    The dihydrate of barbituric acid (BAc) and its dehydration product, form II were investigated by means of moisture sorption analysis, hot-stage microscopy, differential scanning calorimetry, thermogravimetry, solution calorimetry, IR- and Raman-spectroscopy as well as powder X-ray diffraction. The dihydrate desolvates already at and below 50% relative humidity (RH) at 25 deg. C whereas form II is stable up to 80% RH, where it transforms back to the dihydrate. The thermal dehydration of barbituric acid dihydrate (BAc-H2) is a single step, nucleation controlled process. The peritectic reaction of the hydrate was measured at 77 deg. C and a transformation enthalpy of {delta}{sub trs}H{sub H2-II} = 17.3 kJ mol{sup -1} was calculated for the interconversion between the hydrate and form II. An almost identical value of 17.0 kJ mol{sup -1} was obtained from solution calorimetry in water as solvent ({delta}{sub sol}H{sub H2} = 41.5, {delta}{sub sol}H{sub II} = 24.5 kJ mol{sup -1}). Additionally a high-temperature form (HT-form) of BAc, which is enantiotropically related to form II and unstable at ambient conditions has been characterized. Furthermore, we observed that grinding of BAc with potassium bromide (KBr) induces a tautomeric change. Therefore, IR-spectra recorded with KBr-discs usually display a mixture of tautomers, whereas the IR-spectra of the pure trioxo-form of BAc are obtained if alternative preparation techniques are used.

  16. Matched-filtering generalized phase contrast using LCoS pico-projectors for beam-forming.

    Science.gov (United States)

    Bañas, Andrew; Palima, Darwin; Glückstad, Jesper

    2012-04-23

    We report on a new beam-forming system for generating high intensity programmable optical spikes using so-called matched-filtering Generalized Phase Contrast (mGPC) applying two consumer handheld pico-projectors. Such a system presents a low-cost alternative for optical trapping and manipulation, optical lattices and other beam-shaping applications usually implemented with high-end spatial light modulators. Portable pico-projectors based on liquid crystal on silicon (LCoS) devices are used as binary phase-only spatial light modulators by carefully setting the appropriate polarization of the laser illumination. The devices are subsequently placed into the object and Fourier plane of a standard 4f-setup according to the mGPC spatial filtering configuration. Having a reconfigurable spatial phase filter, instead of a fixed and fabricated one, allows the beam shaper to adapt to different input phase patterns suited for different requirements. Despite imperfections in these consumer pico-projectors, the mGPC approach tolerates phase aberrations that would have otherwise been hard to overcome by standard phase projection. © 2012 Optical Society of America

  17. Development of low angle grain boundaries in lightly deformed superconducting niobium and their influence on hydride distribution and flux perturbation

    Science.gov (United States)

    Sung, Z.-H.; Wang, M.; Polyanskii, A. A.; Santosh, C.; Balachandran, S.; Compton, C.; Larbalestier, D. C.; Bieler, T. R.; Lee, P. J.

    2017-05-01

    This study shows that low angle grain boundaries (LAGBs) can be created by small 5% strains in high purity (residual resistivity ratio ≥ 200) superconducting radio frequency (SRF)-grade single crystalline niobium (Nb) and that these boundaries act as hydrogen traps as indicated by the distribution of niobium hydrides (Nb1-xHx). Nb1-xHx is detrimental to SRF Nb cavities due to its normal conducting properties at cavity operating temperatures. By designing a single crystal tensile sample extracted from a large grain (>5 cm) Nb ingot slice for preferred slip on one slip plane, LAGBs and dense dislocation boundaries developed. With chemical surface treatments following standard SRF cavity fabrication practice, Nb1-xHx phases were densely precipitated at the LAGBs upon cryogenic cooling (8-10 K/min). Micro-crystallographic analysis confirmed heterogeneous hydride precipitation, which included significant hydrogen atom accumulation in LAGBs. Magneto-optical imaging analysis showed that these sites can then act as sites for both premature flux penetration and eventually flux trapping. However, this hydrogen related degradation at LAGBs did not completely disappear even after an 800 °C/2 h anneal typically used for hydrogen removal in SRF Nb cavities. These findings suggest that hydride precipitation at an LAGB is facilitated by a non-equilibrium concentration of vacancy-hydrogen (H) complexes aided by mechanical deformation and the hydride phase interferes with the recovery process under 800 °C annealing.

  18. Rapid PMR determination of hydrogen in titanium hydride and dehydrogenated titanium powders

    International Nuclear Information System (INIS)

    Il'enko, V.S.; Demidenko, L.M.

    1987-01-01

    Proton magnetic resonance (PMR) enables determining hydrogen quantitatively in titanium hydride and dehydrogenated titanium powders without destroying the specimen and is also more informative than high-temperature extraction methods. PMR provides data on the electron-nuclear interactions and the activation energies for hydrogen diffusion while also providing conclusions on the forms and positives of the hydrogen in the lattice and the binding to the metal atoms. The authors have developed a rapid method for determining hydrogen in titanium hydride and dehydrogenated titanium powders which reduces the analysis time and improves the metrological characteristics. The authors use a YaMR-5535 spectrometer working at 40 MHz upgraded for use with hydrogen in solids. The authors used specimens of mass about 2 g ground to 0.1 mm powder

  19. Social climber attachment in forming networks produces a phase transition in a measure of connectivity

    Science.gov (United States)

    Taylor, Dane; Larremore, Daniel B.

    2012-09-01

    The formation and fragmentation of networks are typically studied using percolation theory, but most previous research has been restricted to studying a phase transition in cluster size, examining the emergence of a giant component. This approach does not study the effects of evolving network structure on dynamics that occur at the nodes, such as the synchronization of oscillators and the spread of information, epidemics, and neuronal excitations. We introduce and analyze an alternative link-formation rule, called social climber (SC) attachment, that may be combined with arbitrary percolation models to produce a phase transition using the largest eigenvalue of the network adjacency matrix as the order parameter. This eigenvalue is significant in the analyses of many network-coupled dynamical systems in which it measures the quality of global coupling and is hence a natural measure of connectivity. We highlight the important self-organized properties of SC attachment and discuss implications for controlling dynamics on networks.

  20. NATO Advanced Study Institute on Metal Hydrides

    CERN Document Server

    1981-01-01

    In the last five years, the study of metal hydrides has ex­ panded enormously due to the potential technological importance of this class of materials in hydrogen based energy conversion schemes. The scope of this activity has been worldwide among the industrially advanced nations. There has been a consensus among researchers in both fundamental and applied areas that a more basic understanding of the properties of metal/hydrogen syster;,s is required in order to provide a rational basis for the selection of materials for specific applications. The current worldwide need for and interest in research in metal hydrides indicated the timeliness of an Advanced Study Insti­ tute to provide an in-depth view of the field for those active in its various aspects. The inclusion of speakers from non-NATO coun­ tries provided the opportunity for cross-fertilization of ideas for future research. While the emphasis of the Institute was on basic properties, there was a conscious effort to stimulate interest in the applic...

  1. Identification of secondary phases formed during unsaturated reaction of UO2 with EJ-13 water

    International Nuclear Information System (INIS)

    Bates, J.K.; Tani, B.S.; Veleckis, E.

    1989-01-01

    A set of experiments, wherein UO 2 has been contacted by dripping water, has been conducted over a period of 182.5 weeks. The experiments are being conducted to develop procedures to study spent fuel reaction under unsaturated conditions that are expected to exist over the lifetime of the proposed Yucca Mountain repository site. One half of the experiments have been terminated, while one half are ongoing. Analyses of solutions that have dripped from the reacted UO 2 have been performed for all experiments, while the reacted UO 2 surfaces have been examined for the terminated experiments. A pulse of uranium release from the UO 2 solid, combined with the formation of schoepite on the surface of the UO 2 , was observed between 39 and 96 weeks of reaction. Thereafter, the uranium release decreased and a second set of secondary phases was observed. The latter phases incorporated cations from the EJ-13 water and included boltwoodite, uranophane, sklodowskite, compreignacite, and schoepite. The experiments are continuing to monitor whether additional changes in solution chemistry or secondary phase formation occurs. 6 refs., 2 figs., 2 tabs

  2. Nanoscale phase transition behavior of shape memory alloys — closed form solution of 1D effective modelling

    Science.gov (United States)

    Li, M. P.; Sun, Q. P.

    2018-01-01

    We investigate the roles of grain size (lg) and grain boundary thickness (lb) on the stress-induced phase transition (PT) behaviors of nanocrystalline shape memory alloys (SMAs) by using a Core-shell type "crystallite-amorphous composite" model. A non-dimensionalized length scale lbarg(=lg /lb) is identified as the governing parameter which is indicative of the energy competition between the crystallite and the grain boundary. Closed form analytical solutions of a reduced effective 1D model with embedded microstructure length scales of lg and lb are presented in this paper. It is shown that, with lbarg reduction, the energy of the elastic non-transformable grain boundary will gradually become dominant in the phase transition process, and eventually bring fundamental changes of the deformation behaviors: breakdown of two-phase coexistence and vanishing of superelastic hysteresis. The predictions are supported by experimental data of nanocrystalline NiTi SMAs.

  3. The pion form factor and δ11-phase of ππ-scattering in the quark confinement model

    International Nuclear Information System (INIS)

    Efimov, G.V.; Ivanov, M.A.; Mashnik, S.G.

    1988-01-01

    The pion form factor F π 1 (t) in the space- and time-like regions, p-wave phase of the ππ-scattering σ 1 1 (t) and the pion electromagnetic radius r π 2 =0.43 fm 2 are calculated in the quark confinement model. The comparison with experimental data and other approaches is performed. The agreement with experimental data in the region -10 GeV 2 2 is obtained

  4. forme des budgets publics en Chine - phase II | IDRC ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    orientation à donner aux réformes, facilitera les expériences de budgétisation participative dans toute la Chine, favorisera les échanges d'idées entre les organismes oeuvrant dans le domaine des finances et des budgets publics et informera les élus, ...

  5. forme des budgets publics en Chine - phase II | CRDI - Centre de ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    orientation à donner aux réformes, facilitera les expériences de budgétisation participative dans toute la Chine, favorisera les échanges d'idées entre les organismes oeuvrant dans le domaine des finances et des budgets publics et informera les élus, ...

  6. Rad52 forms DMA repair and recombination centers during S phase

    DEFF Research Database (Denmark)

    Lisby, M.; Rothstein, R.; Mortensen, Uffe Hasbro

    2001-01-01

    fluorescent protein (GFP) is fully functional in DNA repair and recombination. After induction of DNA double-strand breaks by gamma -irradiation, meiosis, or the HO endonuclease, Rad52-GFP relocalizes from a diffuse nuclear distribution to distinct foci. Interestingly, Rad52 foci are formed almost exclusively...

  7. A Novel Manufacturing Processing Route for Forming High-Density Ceramic Armor Materials: Phase I - SBIR

    National Research Council Canada - National Science Library

    Raman, Ramas

    1999-01-01

    .... The effects of applied pressure and pressure-transmitting media (PTM) temperature in controlling density, as well as thermal management issues to prevent cracking in applying the CS/Ceracon process to form TiC and TiB2, have been identified...

  8. Measurements of delayed hydride cracking propagation rate in the radial direction of Zircaloy-2 cladding tubes

    Energy Technology Data Exchange (ETDEWEB)

    Kubo, T., E-mail: kubo@nfd.co.jp [Nippon Nuclear Fuel Development Co., Ltd., 2163 Narita-cho, Oarai-machi, Ibaraki 311-1313 (Japan); Kobayashi, Y. [M.O.X. Co., Ltd., 1828-520 Hirasu-cho, Mito, Ibaraki 311-0853 (Japan); Uchikoshi, H. [Nippon Nuclear Fuel Development Co., Ltd., 2163 Narita-cho, Oarai-machi, Ibaraki 311-1313 (Japan)

    2012-08-15

    Highlights: Black-Right-Pointing-Pointer The delayed hydride cracking (DHC) velocity of Zircaloy-2 was measured. Black-Right-Pointing-Pointer The velocity followed the Arrhenius law up to 270 Degree-Sign C. Activation energy was 49 kJ/mol. Black-Right-Pointing-Pointer The threshold stress intensity factor for the DHC was from 4 to 6 MPa m{sup 1/2}. Black-Right-Pointing-Pointer An increase in material strength accelerated the DHC. Black-Right-Pointing-Pointer Precipitation and fracture of hydrides at a crack tip is responsible for the DHC. - Abstract: Delayed hydride cracking (DHC) tests of Zircaloy-2 cladding tubes were performed in the chamber of a scanning electron microscope (SEM) to directly observe the crack propagation and measure the crack velocity in the radial direction of the tubes. Pre-cracks were produced at the outer surfaces of the tubes. Hydrogen contents of the tubes were from 90 ppm to 130 ppm and test temperatures were from 225 Degree-Sign C to 300 Degree-Sign C. The crack velocity followed the Arrhenius law at temperatures lower than about 270 Degree-Sign C with apparent activation energy of about 49 kJ/mol. The upper temperature limit for DHC, above which DHC did not occur, was about 280 Degree-Sign C. The threshold stress intensity factor for the initiation of the crack propagation, K{sub IH}, was from about 4 MPa m{sup 1/2} to 6 MPa m{sup 1/2}, almost independent of temperature. An increase in 0.2% offset yield stress of the material accelerated the crack velocity and slightly decreased K{sub IH}. Detailed observations of crack tip movement showed that cracks propagated in an intermittent fashion and the propagation gradually approached the steady state as the crack depth increased. The SEM observations also showed that hydrides were formed at a crack tip and a number of micro-cracks were found in the hydrides. It was presumed from these observations that the repetition of precipitation and fracture of hydrides at the crack tip would be

  9. Organic and inorganic speciation of particulate matter formed during different combustion phases in an improved cookstove.

    Science.gov (United States)

    Leavey, Anna; Patel, Sameer; Martinez, Raul; Mitroo, Dhruv; Fortenberry, Claire; Walker, Michael; Williams, Brent; Biswas, Pratim

    2017-10-01

    Residential solid fuel combustion in cookstoves has established health impacts including bladder and lung cancers, cataracts, low birth weight, and pneumonia. The chemical composition of particulate matter (PM) from 4 commonly-used solid fuels (coal, dung, ambient/dry applewood, and oakwood pellets), emitted from a gasifier cookstove, as well as propane, were examined. Temporal changes between the different cookstove burn-phases were also explored. Normalized concentrations of non-refractory PM 1 , total organics, chloride, ammonium, nitrate, sulfate, and 41 particle-phase polycyclic aromatic hydrocarbons (PAHs) were measured using a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) and a Thermal desorption Aerosol Gas chromatograph (TAG), respectively. Coal demonstrated the highest fraction of organic matter in its particulate emission composition (98%), followed by dung (94%). Coal and dung also demonstrated the highest numbers and concentrations of PAHs. While dry applewood emitted ten times lower organic matter compared to ambient applewood, a higher fraction of these organics was composed of PAHs, especially the more toxic ones such as benzo(a)pyrene (9.63ng/L versus 0.04ng/L), and benzo(b)fluoranthene (31.32ng/L versus 0.19ng/L). Data from the AMS demonstrated no clear trends for any of the combustion fuels over the different combustion phases unlike the previously reported trends observed for the physical characteristics. Of the solid fuels, pellets demonstrated the lowest emissions. Emissions from propane were below the quantification limit of the instruments. This work highlights the benefits of incorporating additional metrics into the cookstove evaluation process, thus enriching the existing PM data inventory. Copyright © 2017. Published by Elsevier Inc.

  10. Isotope exchange between gaseous hydrogen and uranium hydride powder

    International Nuclear Information System (INIS)

    Shugard, Andrew D.; Buffleben, George M.; Johnson, Terry A.; Robinson, David B.

    2014-01-01

    Highlights: • Isotope exchange between hydrogen gas and uranium hydride powder can be rapid and reversible. • Gas–solid exchange rate is controlled by transport within ∼0.7 μm hydride particles. • Gas chromatographic separation of hydrogen isotopes using uranium hydride is feasible. - Abstract: Isotope exchange between gaseous hydrogen and solid uranium hydride has been studied by flowing hydrogen (deuterium) gas through packed powder beds of uranium deuteride (hydride). We used a residual gas analyzer system to perform real-time analysis of the effluent gas composition. We also developed an exchange and transport model and, by fitting it to the experimental data, extracted kinetic parameters for the isotope exchange reaction. Our results suggest that, from approximately 70 to 700 kPa and 25 to 400 °C, the gas-to-solid exchange rate is controlled by hydrogen and deuterium transport within the ∼0.7 μm diameter uranium hydride particles. We use our kinetic parameters to show that gas chromatographic separation of hydrogen and deuterium using uranium hydride could be feasible

  11. A study of stress reorientation of hydrides in zircaloy

    Energy Technology Data Exchange (ETDEWEB)

    Yourong, Jiang; Bangxin, Zhou [Nuclear Power Inst. of China, Chengdu, SC (China)

    1994-10-01

    Under the conditions of circumferential tensile stress from 70 to 180 MPa for Zircaloy tubes or the tensile stress from 55 to 180 MPa for Zircaloy-4 plates and temperature cycling between 150 and 400 degree C, the effects of stress and the number of temperature cycling on hydride reorientation in Zircaloy-4 tubes and plates and Zircaloy-2 tubes containing about 220 {mu}g/g hydrogen have been investigated. With the increase of stress and/or the number of temperature cycling, the level of hydride reorientation increases. When hydride reorientation takes place, there is a threshold stress concerned with the number of temperature cycling. Below the threshold stress, hydride reorientation is not obvious. When applied stress is higher than the threshold stress, the level of hydride reorientation increases with the increase of stress and the number of temperature cycling. Hydride reorientation in Zircaloy-4 tubes develops gradually from the outer surface to inner surface. It might be related to the difference of texture between outer surface and inner surface. The threshold stress is affected by both the texture and the value of B. So controlling texture could still restrict hydride reorientation under tensile stress.

  12. Analysis of Ni-HYDRIDE Thin Film after Surface Plasmon Generation by Laser Technique

    Science.gov (United States)

    Violante, V.; Castagna, E.; Sibilia, C.; Paoloni, S.; Sarto, F.

    2005-12-01

    A nickel hydride thin film was studied by the attenuated total reflection method. The differences in behavior between a "black" film, and a pure nickel film "blank," are shown. The black nickel hydride film has been obtained by a short electrolysis with 1 M Li2SO4 electrolyte in light water, A shift in the minimum of the observed reflected light occurs, together with a change in the minimum shape (i.e. its half-height width increases). These two phenomenon are due to the change in the electronic band structure of the metal induced by electrons added to the lattice by hydrogen. The change of the electronic structure, revealed by the laser coupling conditions, leads us to consider that a hydride phase was created. Both the blank (not hydrogenated) and black (hydrogenated) specimens were taken under He-Ne laser beam at the reflectance minimum angle for about three hours. A SIMS analysis was also implemented to reveal differences in the isotopic composition of Cu, as marker element between the blank and black films, in order to study the coupled effect of electrolysis and plasmon-polariton excitation on LENR processes in condensed matter.

  13. The role of chemical free energy and elastic strain in the nucleation of zirconium hydride

    International Nuclear Information System (INIS)

    Barrow, A.T.W.; Toffolon-Masclet, C.; Almer, J.; Daymond, M.R.

    2013-01-01

    In this work a combination of synchrotron X-ray diffraction and thermodynamic modelling has been used to study the dissolution and precipitation of zirconium hydride in α-Zr establishing the role of elastic misfit strain and chemical free energy in the α → α + δ phase transformation. The nucleation of zirconium hydride is dominated by the chemical free energy where the chemical driving force for hydride precipitation is proportional to the terminal-solid solubility for precipitation and can be predicted by a function that is analogous to the universal nucleation parameter for the bainite transformation in ferrous alloys. The terminal-solid solubility for precipitation was found to be kinetically limited ⩾287 °C at a cooling rate of 5 °C min −1 or greater. The terminal solubilities were established using an offset method applied to the lattice strain data where a resolution of ∼10 wppm H can be achieved in the 〈c〉-direction. This is aided by the introduction of intra-granular strains in the 〈c〉-direction during cooling as a result of the thermal expansion anisotropy which increases the anisotropy associated with the misfitting H atoms within the α-Zr lattice

  14. Oxygen-Rich Lithium Oxide Phases Formed at High Pressure for Potential Lithium-Air Battery Electrode.

    Science.gov (United States)

    Yang, Wenge; Kim, Duck Young; Yang, Liuxiang; Li, Nana; Tang, Lingyun; Amine, Khalil; Mao, Ho-Kwang

    2017-09-01

    The lithium-air battery has great potential of achieving specific energy density comparable to that of gasoline. Several lithium oxide phases involved in the charge-discharge process greatly affect the overall performance of lithium-air batteries. One of the key issues is linked to the environmental oxygen-rich conditions during battery cycling. Here, the theoretical prediction and experimental confirmation of new stable oxygen-rich lithium oxides under high pressure conditions are reported. Three new high pressure oxide phases that form at high temperature and pressure are identified: Li 2 O 3 , LiO 2 , and LiO 4 . The LiO 2 and LiO 4 consist of a lithium layer sandwiched by an oxygen ring structure inherited from high pressure ε-O 8 phase, while Li 2 O 3 inherits the local arrangements from ambient LiO 2 and Li 2 O 2 phases. These novel lithium oxides beyond the ambient Li 2 O, Li 2 O 2 , and LiO 2 phases show great potential in improving battery design and performance in large battery applications under extreme conditions.

  15. New milarite/osumilite-type phase formed during ancient glazing of an Egyptian scarab

    Science.gov (United States)

    Artioli, G.; Angelini, I.; Nestola, F.

    2013-02-01

    A scarab found in grave 25 of the Monte Prama necropolis, near Cabras, Oristano, Sardinia, is of special importance for the archaeological interpretation and dating of this important archaeological site. The object has been misinterpreted in the past as composed by bone: recent archaeometric analyses showed that it is a glazed steatite of Egyptian origin and that the altered surface contains interesting phases crystallized during the high-temperature interaction of the Mg-rich talc core with the alkali-rich glass used for glazing. A novel single crystal X-ray diffraction analysis of one of the phases indicates that it is a new compound having the milarite-osumilite structure type, with a peculiar composition close to (Na1.52K0.12□0.36)(Mg3)(Mg1.72Cu0.16Fe0.12)(Si11.4Al0.6)O30, not reported for naturally occurring minerals. The structural and crystal chemical features of the compound, together with the known high-temperature stability of the series, allow a complete interpretation of the glazing process and conditions, based on direct application of the glaze on the steatite core with subsequent treatment at temperatures above 1000 °C.

  16. Expanding Thorium Hydride Chemistry Through Th²⁺, Including the Synthesis of a Mixed-Valent Th⁴⁺/Th³⁺ Hydride Complex.

    Science.gov (United States)

    Langeslay, Ryan R; Fieser, Megan E; Ziller, Joseph W; Furche, Filipp; Evans, William J

    2016-03-30

    The reactivity of the recently discovered Th(2+) complex [K(18-crown-6)(THF)2][Cp″3Th], 1 [Cp'' = C5H3(SiMe3)2-1,3], with hydrogen reagents has been investigated and found to provide syntheses of new classes of thorium hydride compounds. Complex 1 reacts with [Et3NH][BPh4] to form the terminal Th(4+) hydride complex Cp″3ThH, 2, a reaction that formally involves a net two-electron reduction. Complex 1 also reacts in the solid state and in solution with H2 to form a mixed-valent bimetallic product, [K(18-crown-6)(Et2O)][Cp″2ThH2]2, 3, which was analyzed by X-ray crystallography, electron paramagnetic resonance and optical spectroscopy, and density functional theory. The existence of 3, which formally contains Th(3+) and Th(4+), suggested that KC8 could reduce [(C5Me5)2ThH2]2. In the presence of 18-crown-6, this reaction forms an analogous mixed-valent product formulated as [K(18-crown-6)(THF)][(C5Me5)2ThH2]2, 4. A similar complex with (C5Me4H)(1-) ligands was not obtained, but reaction of (C5Me4H)3Th with H2 in the presence of KC8 and 2.2.2-cryptand at -45 °C produced two monometallic hydride products, namely, (C5Me4H)3ThH, 5, and [K(2.2.2-cryptand)]{(C5Me4H)2[η(1):η(5)-C5Me3H(CH2)]ThH]}, 6. Complex 6 contains a metalated tetramethylcyclopentadienyl dianion, [C5Me3H(CH2)](2-), that binds in a tuck-in mode.

  17. Hydrogen storage in metal hydrides and complex hydrides; Wasserstoffspeicherung in Metall- und komplexen Hydriden - Schlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Bielmann, M.; Zuettel, A.

    2007-07-01

    This final report for the Swiss Federal Office of Energy (SFOE), reports on work done in 2007 at the Swiss Federal Laboratories for Materials Science and Technology EMPA on the storage of hydrogen in metal hydrides and complex hydrides. In particular, the use of tetrahydroborates is noted. The potential of this class of materials is stressed. The structures at room-temperature were examined using neutron and X-ray diffraction methods. Thermodynamic methods helped determine the thermodynamic stability of the materials. Also, a complete energy diagram for the materials was developed. The use of silicon oxide to reduce activation energy and its catalytic effects are discussed. The challenges placed by desorption mechanisms are noted. The authors note that reversibility is basically proven.

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

    Energy Technology Data Exchange (ETDEWEB)

    Sapru, K.

    1998-12-04

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

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

    Science.gov (United States)

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

    1993-01-01

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

  20. Phase Transformation and Hydrogen Storage Properties of an La7.0Mg75.5Ni17.5 Hydrogen Storage Alloy

    Directory of Open Access Journals (Sweden)

    Lin Hu

    2017-10-01

    Full Text Available X-ray diffraction showed that an La7.0Mg75.5Ni17.5 alloy prepared via inductive melting was composed of an La2Mg17 phase, an LaMg2Ni phase, and an Mg2Ni phase. After the first hydrogen absorption/desorption process, the phases of the alloy turned into an La–H phase, an Mg phase, and an Mg2Ni phase. The enthalpy and entropy derived from the van’t Hoff equation for hydriding were −42.30 kJ·mol−1 and −69.76 J·K−1·mol−1, respectively. The hydride formed in the absorption step was less stable than MgH2 (−74.50 kJ·mol−1 and −132.3 J·K−1·mol−1 and Mg2NiH4 (−64.50 kJ·mol−1 and −123.1 J·K−1·mol−1. Differential thermal analysis showed that the initial hydrogen desorption temperature of its hydride was 531 K. Compared to Mg and Mg2Ni, La7.0Mg75.5Ni17.5 is a promising hydrogen storage material that demonstrates fast adsorption/desorption kinetics as a result of the formation of an La–H compound and the synergetic effect of multiphase.

  1. Complex metal hydrides for hydrogen, thermal and electrochemical energy storage

    DEFF Research Database (Denmark)

    Møller, Kasper T.; Sheppard, Drew; Ravnsbæk, Dorthe B.

    2017-01-01

    field. This review illustrates that complex metal hydrides may store hydrogen in the solid state, act as novel battery materials, both as electrolytes and electrode materials, or store solar heat in a more efficient manner as compared to traditional heat storage materials. Furthermore, it is highlighted...... how complex metal hydrides may act in an integrated setup with a fuel cell. This review focuses on the unique properties of light element complex metal hydrides mainly based on boron, nitrogen and aluminum, e.g., metal borohydrides and metal alanates. Our hope is that this review can provide new...

  2. Finite difference program for calculating hydride bed wall temperature profiles

    International Nuclear Information System (INIS)

    Klein, J.E.

    1992-01-01

    A QuickBASIC finite difference program was written for calculating one dimensional temperature profiles in up to two media with flat, cylindrical, or spherical geometries. The development of the program was motivated by the need to calculate maximum temperature differences across the walls of the Tritium metal hydrides beds for thermal fatigue analysis. The purpose of this report is to document the equations and the computer program used to calculate transient wall temperatures in stainless steel hydride vessels. The development of the computer code was motivated by the need to calculate maximum temperature differences across the walls of the hydrides beds in the Tritium Facility for thermal fatigue analysis

  3. Investigation process of alcoholysis of hydride aluminium-adobe

    International Nuclear Information System (INIS)

    Numanov, M.I.; Normatov, I.Sh.; Mirsaidov, U.M.

    2001-01-01

    Considering of that process of acid treatment of aluminium-adobe hydride realizes in the ethyl alcohol media it was necessary study the process of alcoholysis of AlH 3 and aluminium additives. In the end of article authors became to conclusion that deficiency of spontaneous alcoholysis of AlH 3 in adobe caused by protective action of fiber; solvate ability of LiCl and alkoxy aluminium hydride of lithium-LiCl·CO 2 H 5 OH, Li Al(OC 2 H 5 ) 4 ·nC 2 H 5 OH decreasing the expectancy of responding of alcohol with aluminium hydride

  4. The Separation of Hydrogen Tritium and Tritium Hydride by Gas Chromatography; Separation de l'hydrogene, du tritium et de l'hydrure de tritium par chromatographic en phase gazeuse; Razdelenie vodoroda, tritiya i gidrida tritiya posredstvom gazovoj khromatografii; Separacion del hidrogeno, tritio e hidruro de tritio por cromatografia de gases

    Energy Technology Data Exchange (ETDEWEB)

    Smith, H A; Carter, Jr, E H [University of Tennessee, Knoxville, TN (United States)

    1962-01-15

    Now that successful separation of hydrogen, deuterium and hydrogen deuteride has been achieved by gas chromatography, similar studies are being made dealing with mixtures of hydrogen, tritium and tritium hydride. Since tritium is used in tracer quantities the usual katharometer cannot be employed for its detection. This difficulty has been overcome by providing immediately following the katharometer a vibrating reed electrometer equipped with a high resistance leak which allows continuous monitoring of the activity of any tritium or tritium hydride emerging from the column by means of synchronized recorders. Separation of such mixtures has been tested with columns packed with palladium on silica, silica, alumina, and alumina coated with chromium oxide or ferric oxide. No effective separation was obtained with the palladium on silica column. Good separation was achieved with the plain silica column where hydrogen was employed as the carrier gas, but helium failed to elute the isotopes. Satisfactory results were obtained with the coated, partially deactivated alumina packing when helium or neon was the carrier gas, but the best separation was found with a column packing of uncoated activated alumina. Calibration with helium-tritium mixtures of known activity plus equilibrated hydrogen-tritium mixtures also of known activity allows quantitative estimation of tritium and tritium hydride. (author) [French] La separation de l'hydrogene, du deuterium et du deuterure d'hydrogene par chromatographic en phase gazeuse ayant ete realisee, on procede maintenant a des etudes semblables sur des melanges d'hydrogene de tritium et d'hydrure de tritium. Comme le tritium n'est present qu'en quantites infimes, on ne peut utiliser le catharometre ordinaire pour le detecter. On a surmonte cette difficulte en faisant suivre le catharometre d'un electrometre a lame vibrante, muni d'une fuite haute resistance, qui permet de mesurer, a l'aide d'enregistreurs synchronises, l'activite de

  5. Development of form stable Poly(methyl methacrylate) (PMMA) coated thermal phase change material for solar water heater applications

    Science.gov (United States)

    Munusamy, Y.; Shanmugam, S.; Shi-Ying, Kee

    2018-04-01

    Phase change material (PCM) is one of the most popular and widely used thermal energy storage material in solar water heater because it able to absorb and release a large amount of latent heat during a phase change process over a narrow temperature range. However the practical application of PCM is limited by two major issues; 1) leakage which leads to material loss and corrosion of tank and 2) large volume change during phase change process which cause pressure build up in the tank. In this work, form-stable PCM was prepared by coating myristic acid with Poly(methyl methacrylate) (PMMA) to prevent leakage of PCM. PMMA was mixed with different weight percentage (0.1, 0.2, 0.3, 0.4 and 0.5 wt%) of dicumyl peroxide (DCP). The purpose of adding DCP to PMMA is to crosslink the polymer and to increase the mechanical strength of PMMA to hold the myristic acid content inside the coating during the phase change process. Leakage test results showed that PMMA mixed with 0.1% DCP exhibit 0% leakage. This result is further supported by Field Emission Scanning Electron Microscopy (FESEM) images and Fourier transform infrared spectroscopy (FTIR) analysis results, where a compact and uniform coating without cracks were formed for PCM coated with PMMA with 0.1% DCP. Differential scanning calorimetry (DSC) results shows that the melting point of form-stable PCM is 55°C, freezing point is 50°C, the latent heat of melting and freezing is 67.59 J/g.

  6. Preparation and flammability of high density polyethylene/paraffin/organophilic montmorillonite hybrids as a form stable phase change material

    International Nuclear Information System (INIS)

    Cai, Yibing; Hu, Yuan; Song, Lei; Kong, Qinghong; Yang, Rui; Zhang, Yinping; Chen, Zuyao; Fan, Weicheng

    2007-01-01

    A kind of form stable phase change material (PCM) based on high density polyethylene (HDPE), paraffin, organophilic montmorillonite (OMT) and intumescent flame retardant (IFR) hybrids is prepared by using a twin screw extruder technique. This kind of form stable PCM is made of paraffin as a dispersed phase change material and HDPE as a supporting material. The structure of the montmorillonite (MMT) and OMT is characterized by X-ray diffraction (XRD) and high resolution electron microscopy (HREM). The analysis indicates that the MMT is a kind of lamellar structure, and the structure does not change after organic modification. However, the structure of the hybrid is evidenced by the XRD and scanning electronic microscope (SEM). Its thermal stability, latent heat and flame retardant properties are given by the Thermogravimetry analysis (TGA), differential scanning calorimeter (DSC) method and cone calorimeter, respectively. Synergy is observed between the OMT and IFR. The XRD result indicates that the paraffin intercalates into the silicate layers of the OMT, thus forming a typically intercalated hybrid. The SEM investigation and DSC result show that the additives of OMT and IFR have hardly any effect on the HDPE/paraffin three dimensional netted structure and the latent heat. In TGA curves, although the onset of weight loss of flame-retardant form stable PCMs occur at a lower temperature than that of form stable PCM, flame-retardant form stable PCMs produce a large amount of char residue at 700 o C. The synergy between OMT and IFR leads to the decrease of the heat release rate (HRR), contributing to improvement of the flammability performance

  7. The structural and phase state formed in construction titanium alloy by radial forging

    Energy Technology Data Exchange (ETDEWEB)

    Shlyakhova, Galina V.; Danilov, Vladimir I.; Orlova, Dina V.; Zuev, Lev B. [Institute of Strength Physics and Materials Science SB RAS, Tomsk (Russian Federation); Zavodchikov, Aleksandr S. [Perm State Technical University, Perm (Russian Federation)

    2011-07-01

    The feasibility of rod manufacture from construction titanium alloy using radial forging on a high duty machine SXK16 was investigated. The investigations were carried on for titanium rod samples using the methods of metallography, electron transmission microscophy and X-ray analysis. The results obtained are described herein. It is found that radial forging results in the formation of homogeneous fine-grained structure.Using radial forging process, high-quality items are produced. As-worked material has submicrocrystalline globular structure and an optimal α:β phase ratio. Besides, the technology is more cost-effective relative to conventional flow charts. Key words: forging, titanium alloy, fine-grain structure, substructure, pore size.

  8. Quantification by aberration corrected (S)TEM of boundaries formed by symmetry breaking phase transformations

    Energy Technology Data Exchange (ETDEWEB)

    Schryvers, D., E-mail: nick.schryvers@uantwerpen.be [EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp (Belgium); Salje, E.K.H. [Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ (United Kingdom); Nishida, M. [Department of Engineering Sciences for Electronics and Materials, Faculty of Engineering Sciences, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan); De Backer, A. [EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp (Belgium); Idrissi, H. [EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp (Belgium); Institute of Mechanics, Materials and Civil Engineering, Université Catholique de Louvain, Place Sainte Barbe, 2, B-1348, Louvain-la-Neuve (Belgium); Van Aert, S. [EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp (Belgium)

    2017-05-15

    The present contribution gives a review of recent quantification work of atom displacements, atom site occupations and level of crystallinity in various systems and based on aberration corrected HR(S)TEM images. Depending on the case studied, picometer range precisions for individual distances can be obtained, boundary widths at the unit cell level determined or statistical evolutions of fractions of the ordered areas calculated. In all of these cases, these quantitative measures imply new routes for the applications of the respective materials. - Highlights: • Quantification of picometer displacements at ferroelastic twin boundary in CaTiO{sub 3.} • Quantification of kinks in meandering ferroelectric domain wall in LiNbO{sub 3}. • Quantification of column occupation in anti-phase boundary in Co-Pt. • Quantification of atom displacements at twin boundary in Ni-Ti B19′ martensite.

  9. [DNA complexes, formed on aqueous phase surfaces: new planar polymeric and composite nanostructures].

    Science.gov (United States)

    Antipina, M N; Gaĭnutdinov, R V; Rakhnianskaia, A A; Sergeev-Cherenkov, A N; Tolstikhina, A L; Iurova, T V; Kislov, V V; Khomutov, G B

    2003-01-01

    The formation of DNA complexes with Langmuir monolayers of the cationic lipid octadecylamine (ODA) and the new amphiphilic polycation poly-4-vinylpyridine with 16% of cetylpyridinium groups (PVP-16) on the surface of an aqueous solution of native DNA of low ionic strength was studied. Topographic images of Langmuir-Blodgett films of DNA/ODA and DNA/PVP-16 complexes applied to micaceous substrates were investigated by the method of atomic force microscopy. It was found that films of the amphiphilic polycation have an ordered planar polycrystalline structure. The morphology of planar DNA complexes with the amphiphilic cation substantially depended on the incubation time and the phase state of the monolayer on the surface of the aqueous DNA solution. Complex structures and individual DNA molecules were observed on the surface of the amphiphilic monolayer. Along with quasi-linear individual bound DNA molecules, characteristic extended net-like structures and quasi-circular toroidal condensed conformations of planar DNA complexes were detected. Mono- and multilayer films of DNA/PVP-16 complexes were used as templates and nanoreactors for the synthesis of inorganic nanostructures via the binding of metal cations from the solution and subsequent generation of the inorganic phase. As a result, ultrathin polymeric composite films with integrated DNA building blocks and quasi-linear arrays of inorganic semiconductor (CdS) and iron oxide nanoparticles and nanowires were obtained. The nanostructures obtained were characterized by scanning probe microscopy and transmission electron microscopy techniques. The methods developed are promising for investigating the mechanisms of structural organization and transformation in DNA and polyelectrolyte complexes at the gas-liquid interface and for the design of new extremely thin highly ordered planar polymeric and composite materials, films, and coatings with controlled ultrastructure for applications in nanoelectronics and

  10. Development of delayed hydride cracking resistant-pressure tube

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Young Suk; Kwon, Sang Chul; Kim, S. S.; Yim, K. S

    2000-10-01

    For the first time, we demonstrate that the pattern of nucleation and growth of a DHC crack is governed by the precipitation of hydrides so that the DHC velocity and K{sub IH} are determined by an angle of the cracking plane and the hydride habit plane 10.7. Since texture controls the distribution of the 10.7 habit plane in Zr-2.5Nb pressure tube, we draw a conclusion that a textural change in Zr-2.5Nb tube from a strong tangential texture to the radial texture shall increase the threshold stress intensity factor, K{sub IH}, and decrease the delayed hydride cracking velocity. This conclusion is also verified by a complimentary experiment showing a linear dependence of DHCV and K{sub IH} with an increase in the basal component in the cracking plane. On the basis of the study on the DHC mechanism and the effect of manufacturing processes on the properties of Zr-2.5Nb tube, we have established a manufacturing procedure to make pressure tubes with improved DHC resistance. The main features of the established manufacturing process consist in the two step-cold pilgering process and the intermediate heat treatment in the {alpha} + {beta} phase for Zr-2.5Nb alloy and in the {alpha} phase for Zr-1Nb-1.2Sn-0.4Fe alloy. The manufacturing of DHC resistant-pressure tubes of Zr-2.5Nb and Zr-1N-1.2Sn-0.4Fe was made in the ChMP zirconium plant in Russia under a joint research with Drs. Nikulina and Markelov in VNIINM (Russia). Zr-2.5Nb pressure tube made with the established manufacturing process has met all the specification requirements put by KAERI. Chracterization tests have been jointly conducted by VNIINM and KAERI. As expected, the Zr-2.5Nb tube made with the established procedure has improved DHC resistance compared to that of CANDU Zr-2.5Nb pressure tube used currently. The measured DHC velocity of the Zr-2.5Nb tube meets the target value (DHCV <5x10{sup -8} m/s) and its other properties also were equivalent to those of the CANDU Zr-2.5Nb tube used currently. The Zr-1Nb-1

  11. Determination of hydrogen in zirconium hydride and uranium-zirconium hydride by inert gas exraction-gravimetric method

    International Nuclear Information System (INIS)

    Hoshino, Akira; Iso, Shuichi

    1976-01-01

    An inert gas extraction-gravimetric method has been applied to the determination of hydrogen in zirconium hydride and uranium-zirconium hydride which are used as neutron moderator and fuel of nuclear safety research reactor (NSRR), respectively. The sample in a graphite-enclosed quartz crucible is heated inductively to 1200 0 C for 20 min in a helium stream. Hydrogen liberated from the sample is oxidized to water by copper(I) oxide-copper(II) oxide at 400 0 C, and the water is determined gravimetrically by absorption in anhydrone. The extraction curves of hydrogen for zirconium hydride and uranium-zirconium hydride samples are shown in Figs. 2 and 3. Hydrogen in the samples is extracted quantitatively by heating at (1000 -- 1250) 0 C for (10 -- 40) min. Recoveries of hydrogen in the case of zirconium hydride were examined as follows: a weighed zirconium rod (5 phi x 6 mm, hydrogen -5 Torr. After the chamber was filled with purified hydrogen to 200 Torr, the rod was heated to 400 0 C for 15 h, and again weighed to determine the increase in weight. Hydrogen in the rod was then determined by the proposed method. The results are in excellent agreement with the increase in weight as shown in Table 1. Analytical results of hydrogen in zirconium hydride samples and an uranium-zirconium hydride sample are shown in Table 2. (auth.)

  12. Radionuclide Retention Mechanisms in Secondary Waste-Form Testing: Phase II

    Energy Technology Data Exchange (ETDEWEB)

    Um, Wooyong; Valenta, Michelle M.; Chung, Chul-Woo; Yang, Jungseok; Engelhard, Mark H.; Serne, R. Jeffrey; Parker, Kent E.; Wang, Guohui; Cantrell, Kirk J.; Westsik, Joseph H.

    2011-09-26

    This report describes the results from laboratory tests performed at Pacific Northwest National Laboratory (PNNL) for Washington River Protection Solutions (WRPS) to evaluate candidate stabilization technologies that have the potential to successfully treat liquid secondary waste stream effluents produced by the Hanford Tank Waste Treatment and Immobilization Plant (WTP). WRPS is considering the design and construction of a Solidification Treatment Unit (STU) for the Effluent Treatment Facility (ETF) at Hanford. The ETF, a multi-waste, treatment-and-storage unit that has been permitted under the Resource Conservation and Recovery Act (RCRA), can accept dangerous, low-level, and mixed wastewaters for treatment. The STU needs to be operational by 2018 to receive secondary liquid waste generated during operation of the WTP. The STU will provide the additional capacity needed for ETF to process the increased volume of secondary waste expected to be produced by WTP. This report on radionuclide retention mechanisms describes the testing and characterization results that improve understanding of radionuclide retention mechanisms, especially for pertechnetate, {sup 99}TcO{sub 4}{sup -} in four different waste forms: Cast Stone, DuraLith alkali aluminosilicate geopolymer, encapsulated fluidized bed steam reforming (FBSR) product, and Ceramicrete phosphate bonded ceramic. These data and results will be used to fill existing data gaps on the candidate technologies to support a decision-making process that will identify a subset of the candidate waste forms that are most promising and should undergo further performance testing.

  13. Comminution of the U-10Mo by hydriding cycles innovative process

    Energy Technology Data Exchange (ETDEWEB)

    Faeda, Kelly C.M.; Santos, Ana Maria M. dos; Paula, Joao B. de; Pereira, Edilson M.; Pedrosa, Tercio A.; Lameiras, Fernando S.; Ferraz, Wilmar B., E-mail: ferrazw@cdtn.br, E-mail: kelly.faeda@prof.una.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2013-07-01

    The research, test and producing radioisotopes compact reactors were developed with the use of high levels of enriched fuel of approximately 90% of the fissile isotope U-235. Since the 80s', a policy under the context of international program RERTR (Reduced Enrichment for Research and Test Reactors) encourages the fuel replacement of the high enriched fuel by the low one of about 20 % U-235. One way to compensate the substitution for the low enrichment fuel is to employ high density metal uranium alloys. The fabrication of compact reactor fuel uses the metal matrix dispersion and, for this, uranium alloys are used in the form of powders. Despite the high densities, the metallic uranium based alloys are ductile and therefore difficult to be comminuted. Among the different comminution processes, the hydriding-dehydriding process has proved most advantageous, primarily due to their relative simplicity of processing and low manufacturing cost. In this paper, we present the results of the development of the U-10Mo alloy comminution process by the hydriding-dehydriding method on a laboratory scale. Samples of the alloy were subjected to different hydriding cycle numbers in order to verify its influence in relation to the particle size distribution of powders. Powders of different particle sizes were obtained and characterized by the physical and morphological characteristics by optical microscopy, scanning electron microscopy and X ray diffraction. The obtained results are evaluated and discussed. (author)

  14. Process for production of a metal hydride

    Science.gov (United States)

    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.

  15. Hydrogen storage properties of metallic hydrides

    International Nuclear Information System (INIS)

    Latroche, M.; Percheron-Guegan, A.

    2005-01-01

    Nowadays, energy needs are mainly covered by fossil energies leading to pollutant emissions mostly responsible for global warming. Among the different possible solutions for greenhouse effect reduction, hydrogen has been proposed for energy transportation. Indeed, H 2 can be seen as a clean and efficient energy carrier. However, beside the difficulties related to hydrogen production, efficient high capacity storage means are still to be developed. Many metals and alloys are able to store large amounts of hydrogen. This latter solution is of interest in terms of safety, global yield and long term storage. However, to be suitable for applications, such compounds must present high capacity, good reversibility, fast reactivity and sustainability. In this paper, we will review the structural and thermodynamic properties of metallic hydrides. (authors)

  16. New Insights on the Creeping Phase of the Vajont Landslide form Rotary-Shear Experiments

    Science.gov (United States)

    Ferri, F.; Spagnuolo, E.; Di Felice, F.; Di Toro, G.

    2014-12-01

    It is well known that 1963 catastrophic Vajont landslide (NE Italy) was preceded by a creeping phase monitored over three years before the collapse and that water played a significant role in the instability of the rock sequence. However, the transition from the creeping phase to instability still remains elusive. Here we report experiments carried out in a rotary-shear friction apparatus (SHIVA at INGV, Rome, Italy) on smectite-rich gouges collected from the landslide surface (60-70% smectite, 20-30% calcite and minor quartz). Experiments were performed under shear stress controlled conditions at normal stress σnof 3-5 MPa in the presence of water (20% weight), and at room humidity. During the experiments, the shear stress τ was increased by a constant value Δτ and maintained for a fixed time Δt before applying the following shear stress step. When frictional instability was achieved, the machine started to rotate at an imposed velocity. In the first set of experiments, the initial τ (0.05 MPa) was increased by steps of Δτ = 0.25 MPa with Δt of 150 seconds. In the room humidity material, a series of spontaneous slip bursts occurred at τ = 2.5 MPa (at σn = 5MPa) until the shear stress reached 3.0 MPa. At this point, a large stress drop occurred with concomitant dilation. In the wet material, instability took place at τ= 0.3 MPa (at σn= 3 MPa). After forcing τ down, the material re-strengthened. A second main instability occurred when τ was restored to 0.3 MPa, with expulsion of water drops accompanied by an episode of dilation. At this point, the material spontaneously re-strengthened with a stick-slip behavior similar to that observed at room humidity conditions. In the second set of experiments, Δτ was reduced to 0.05 MPa and Δt increased up to 360 seconds producing a general enhancement of the shear stress required to generate unstable sliding. Instability took place at very high τ (3.12 MPa at σn= 3 MPa) at room-humidity conditions, and at

  17. IAEA co-ordinated research program. 'Round Robin' on measuring the velocity of delayed hydride cracking (DHC)

    International Nuclear Information System (INIS)

    Grigoriev, V.; Jakobsson, R.

    1999-09-01

    The International Atomic Agency (IAEA) has initiated a new Co-ordinated Research Programme (CRP) on Hydrogen and hydride induced degradation of the mechanical and physical properties of Zirconium-based alloys. In the first phase of this CRP the methodology for measuring the velocity of Delayed Hydride Cracking (DHC) should be established and participating laboratories from about nine countries around the world carry out identical tests in 'round robin'. The objective of the present work is to establish at Studsvik laboratory the method of a constant load cracking test on unirradiated Zr-2.5Nb and attain a comparison of results between laboratories. Constant load tests are performed on specimens cut from unirradiated CANDU Zr-2.5Nb pressure tube and the rate of crack propagation is determined in each test. Pre-hydrided specimens for testing are supplied from the host laboratory. Six specimens have been tested for delayed hydride cracking (DHC) at 250 deg C. The axial crack growth velocities measured in the tests are within the interval of 8.62x10 -8 - 1.06x10 -7 m/s. The results obtained agree well with the earlier published data for similar materials and test conditions

  18. Phase equilibrium condition measurements in nitrogen and air clathrate hydrate forming systems at temperatures below freezing point of water

    International Nuclear Information System (INIS)

    Yasuda, Keita; Oto, Yuya; Shen, Renkai; Uchida, Tsutomu; Ohmura, Ryo

    2013-01-01

    Highlights: • Phase equilibrium conditions in the nitrogen and modelled air hydrate forming systems are measured. • Measurements are conducted at temperatures below the freezing point of water. • Results have relevance to the air hydrate formation in the ice sheets. • Measured data are quantitatively compared with the previously reported values. • Range of the equilibrium measurements was from (242 to 268) K. -- Abstract: Contained in this paper are the three phase equilibrium conditions of the (ice + clathrate hydrate + guest-rich) vapour in the (nitrogen + water) and the modelled (air + water) systems at temperatures below the freezing point of water. The precise determination of the equilibrium conditions in those systems are of importance for the analysis of the past climate change using the cored samples from the ice sheets at Antarctica and Greenland because the air hydrates keep the ancient climate signals. The mole ratio of the modelled air composed of nitrogen and oxygen is 0.790:0.210. The equilibrium conditions were measured by the batch, isochoric procedure. The temperature range of the measurements in the nitrogen hydrate forming system is (244.05 < T < 266.55) K and the corresponding equilibrium pressure range is (7.151 < p < 12.613) MPa. The temperature range of the measurements in the modelled air hydrate forming system is (242.55 < T < 267.85) K, and the corresponding equilibrium pressure range is (6.294 < p < 12.144) MPa. The data obtained quantitatively compared with the previously reported data

  19. Oxidation state specific generation of arsines from methylated arsenicals based on L-cysteine treatment in buffered media for speciation analysis by hydride generation-automated cryotrapping-gas chromatography-atomic absorption spectrometry with the multiatomizer

    Energy Technology Data Exchange (ETDEWEB)

    Matousek, Tomas [Institute of Analytical Chemistry of the ASCR, v.v.i., Videnska 1083, 14220 Prague (Czech Republic)], E-mail: matousek@biomed.cas.cz; Hernandez-Zavala, Araceli [Center for Environmental Medicine, Asthma, and Lung Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7310 (United States); Svoboda, Milan; Langrova, Lenka [Institute of Analytical Chemistry of the ASCR, v.v.i., Videnska 1083, 14220 Prague (Czech Republic); Charles University, Faculty of Science, Albertov 8, 12840 Prague 2 (Czech Republic); Adair, Blakely M. [Pharmacokinetics Branch, Experimental Toxicology Division, National Health and Environmental Effects Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711 (United States); Drobna, Zuzana [Department of Nutrition, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7461 (United States); Thomas, David J. [Pharmacokinetics Branch, Experimental Toxicology Division, National Health and Environmental Effects Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711 (United States); Styblo, Miroslav [Center for Environmental Medicine, Asthma, and Lung Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7310 (United States); Department of Nutrition, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7461 (United States); Dedina, Jiri [Institute of Analytical Chemistry of the ASCR, v.v.i., Videnska 1083, 14220 Prague (Czech Republic)

    2008-03-15

    An automated system for hydride generation-cryotrapping-gas chromatography-atomic absorption spectrometry with the multiatomizer is described. Arsines are preconcentrated and separated in a Chromosorb filled U-tube. An automated cryotrapping unit, employing nitrogen gas formed upon heating in the detection phase for the displacement of the cooling liquid nitrogen, has been developed. The conditions for separation of arsines in a Chromosorb filled U-tube have been optimized. A complete separation of signals from arsine, methylarsine, dimethylarsine, and trimethylarsine has been achieved within a 60 s reading window. The limits of detection for methylated arsenicals tested were 4 ng l{sup -1}. Selective hydride generation is applied for the oxidation state specific speciation analysis of inorganic and methylated arsenicals. The arsines are generated either exclusively from trivalent or from both tri- and pentavalent inorganic and methylated arsenicals depending on the presence of L-cysteine as a prereductant and/or reaction modifier. A TRIS buffer reaction medium is proposed to overcome narrow optimum concentration range observed for the L-cysteine modified reaction in HCl medium. The system provides uniform peak area sensitivity for all As species. Consequently, the calibration with a single form of As is possible. This method permits a high-throughput speciation analysis of metabolites of inorganic arsenic in relatively complex biological matrices such as cell culture systems without sample pretreatment, thus preserving the distribution of tri- and pentavalent species.

  20. Positron bound states on hydride ions in thermochemically reduced MgO single crystals

    International Nuclear Information System (INIS)

    Monge, M.A.; Pareja, R.; Gonzalez, R.; Chen, Y.

    1996-01-01

    Positron-lifetime and Doppler-broadening techniques were used to unambiguously identify positronium hydrides in thermochemically reduced MgO crystals at low temperatures. Positrons trapped at H - ions, forming PsH, yield a lifetime of (640±40) ps, independent of temperature. Complementary evidence for this identification was provided by Doppler-broadening experiments, in which positrons were trapped at H 2- sites at low temperatures. The H 2- ions were formed via H - +e - →H 2- by the capturing of an electron released from Fe + impurity under blue-light stimulation. copyright 1996 The American Physical Society

  1. Nano-scale clusters formed in the early stage of phase decomposition of Al-Mg-Si alloys

    Energy Technology Data Exchange (ETDEWEB)

    Hirosawa, S.; Sato, T. [Dept. of Metallurgy and Ceramics Science, Tokyo Inst. of Tech. (Japan)

    2005-07-01

    The formation of nano-scale clusters (nanoclusters) prior to the precipitation of the strengthening {beta}'' phase significantly influences two-step aging behavior of Al-Mg-Si alloys. In this work, the existence of two kinds of nanoclusters has been verified in the early stage of phase decomposition by differential scanning calorimetry (DSC) and three-dimensional atom probe (3DAP). Pre-aging treatment at 373 K before natural aging was also found to form preferentially one of the two nanoclusters, resulting in the remarkable restoration of age-hardenability at paint-bake temperatures. Such microstructural control by means of optimized heat-treatments; i.e. nanocluster assist processing (NCAP), possesses great potential for enabling Al-Mg-Si alloys to be used more widely as a body-sheet material of automobiles. (orig.)

  2. Impact of Intragranular Substructure Parameters on the Forming Limit Diagrams of Single-Phase B.C.C. Steels

    Directory of Open Access Journals (Sweden)

    Gérald Franz

    2013-11-01

    Full Text Available An advanced elastic-plastic self-consistent polycrystalline model, accounting for intragranular microstructure development and evolution, is coupled with a bifurcation-based localization criterion and applied to the numerical investigation of the impact of microstructural patterns on ductility of single-phase steels. The proposed multiscale model, taking into account essential microstructural aspects, such as initial and induced textures, dislocation densities, and softening mechanisms, allows us to emphasize the relationship between intragranular microstructure of B.C.C. steels and their ductility. A qualitative study in terms of forming limit diagrams for various dislocation networks, during monotonic loading tests, is conducted in order to analyze the impact of intragranular substructure parameters on the formability of single-phase B.C.C. steels.

  3. Artificial exomuscle investigations for applications-metal hydride

    International Nuclear Information System (INIS)

    Crevier, Marie-Charlotte; Richard, Martin; Rittenhouse, D Matheson; Roy, Pierre-Olivier; Bedard, Stephane

    2007-01-01

    In pursuing the development of bionic devices, Victhom identified a need for technologies that could replace current motorized systems and be better integrated into the human body motion. The actuators used to obtain large displacements are noisy, heavy, and do not adequately reproduce human muscle behavior. Subsequently, a project at Victhom was devoted to the development of active materials to obtain an artificial exomuscle actuator. An exhaustive literature review was done at Victhom to identify promising active materials for the development of artificial muscles. According to this review, metal hydrides were identified as a promising technology for artificial muscle development. Victhom's investigations focused on determining metal hydride actuator potential in the context of bionics technology. Based on metal hydride properties and artificial muscle requirements such as force, displacement and rise time, an exomuscle was built. In addition, a finite element model, including heat and mass transfer in the metal hydride, was developed and implemented in FEMLAB software. (review article)

  4. Ductile zirconium powder by hydride-dehydride process

    Energy Technology Data Exchange (ETDEWEB)

    Krishnan, T S [BHABHA ATOMIC RESEARCH CENTRE, BOMBAY (INDIA); CHAUDHARY, S [NUCLEAR FUEL COMPLEX, HYDERABAD (INDIA)

    1976-09-01

    The preparation of ductile zirconium powder by the hydride-dehydride process has been described. In this process massive zirconium obtained from Kroll reduction of ZrCl/sub 4/ is first rendered brittle by hydrogenation and the hydride crushed and ground in a ball mill to the required particle size. Hydrogen is then hot vacuum extracted to yield the metal powder. The process has been successfully employed for the production of zirconium powders with low oxygen content and having hardness values in the range of 115-130 BHN, starting from a zirconium sponge of 100-120 BHN hardness. Influence of surface characteristics of the starting metal on its hydriding behaviour has been studied and the optimum hydriding-dehydriding conditions established.

  5. Development of zirconium hydride highly effective moderator materials

    International Nuclear Information System (INIS)

    Yin Changgeng

    2005-10-01

    The zirconium hydride with highly content of hydrogen and low density is new efficient moderator material for space nuclear power reactor. Russia has researched it to use as new highly moderator and radiation protection materials. Japanese has located it between the top of pressure vessel and the main protection as a shelter, the work temperature is rach to 220 degree C. The zirconium hydride moderator blocks are main parts of space nuclear power reactor. Development of zirconium hydride moderator materials have strength research and apply value. Nuclear Power Research and Design Instituteoh China (NPIC) has sep up the hydrogenation device and inspect systems, and accumurate a large of experience about zirconium hydride, also set up a strict system of QA and QC. (authors)

  6. Precipitation of hydrides in high purity niobium after different treatments

    Energy Technology Data Exchange (ETDEWEB)

    Barkov, F.; Romanenko, A.; Trenikhina, Y.; Grassellino, A.

    2013-01-01

    Precipitation of lossy non-superconducting niobium hydrides represents a known problem for high purity niobium in superconducting applications. Using cryogenic optical and laser confocal scanning microscopy we have directly observed surface precipitation and evolution of niobium hydrides in samples after different treatments used for superconducting RF cavities for particle acceleration. Precipitation is shown to occur throughout the sample volume, and the growth of hydrides is well described by the fast diffusion-controlled process in which almost all hydrogen is precipitated at $T=140$~K within $\\sim30$~min. 120$^{\\circ}$C baking and mechanical deformation are found to affect hydride precipitation through their influence on the number of nucleation and trapping centers.

  7. Reactions of zinc hydride and magnesium hydride with pyridine; synthesis and characterization of 1,4-dihydro-1-pyridylzinc and -magnesium complexes

    NARCIS (Netherlands)

    Koning, A.J. de; Boersma, J.; Kerk, G.J.M. van der

    1980-01-01

    The synthesis and characterization of 1,4-dihydro-1-pyridylzinc and -magnesium complexes are described. Zinc hydride and magnesium hydride dissolve in and react with pyridine, and the reaction has been studied in detail in the case of zinc hydride. Evaporation of the solvent after 1–2 hours at 0°C

  8. Electronic structure of ternary hydrides based on light elements

    Energy Technology Data Exchange (ETDEWEB)

    Orgaz, E. [Departamento de Fisica y Quimica Teorica, Facultad de Quimica, Universidad Nacional Autonoma de Mexico, CP 04510 Coyoacan, Mexico, D.F. (Mexico)]. E-mail: orgaz@eros.pquim.unam.mx; Membrillo, A. [Departamento de Fisica y Quimica Teorica, Facultad de Quimica, Universidad Nacional Autonoma de Mexico, CP 04510 Coyoacan, Mexico, D.F. (Mexico); Castaneda, R. [Departamento de Fisica y Quimica Teorica, Facultad de Quimica, Universidad Nacional Autonoma de Mexico, CP 04510 Coyoacan, Mexico, D.F. (Mexico); Aburto, A. [Departamento de Fisica, Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, CP 04510 Coyoacan, Mexico, D.F. (Mexico)

    2005-12-08

    Ternary hydrides based on light elements are interesting owing to the high available energy density. In this work we focused into the electronic structure of a series of known systems having the general formula AMH{sub 4}(A=Li,Na,M=B,Al). We computed the energy bands and the total and partial density of states using the linear-augmented plane waves method. In this report, we discuss the chemical bonding in this series of complex hydrides.

  9. Spectroscopy of helium hydride and triatomic hydrogen molecules

    International Nuclear Information System (INIS)

    Ketterle, W.

    1986-07-01

    Helium hydride and triatomic hydrogen has been produced by charge exchange between fast mass selected beams of molecular ions and alkali vapor. Using this method, the first discrete spectra of helium hydride were obtained. Fine electronic transitions with resolved rotational structure were observed in the visible and near infrared. Four isotopic mixtures were studied. Furthermore the first lifetime measurement of triatomic hydrogen states were performed and compared to theoretical predictions. (orig.)

  10. Proton location in metal hydrides using electron spin resonance

    International Nuclear Information System (INIS)

    Venturini, E.L.

    1979-01-01

    Electron spin resonance (ESR) of dilute paramagnetic ions establishes the site symmetry of these ions. In the case of metal hydrides the site symmetry is determined by the number and location of neighboring protons. Typical ESR spectra for trivalent erbium in scandium and yttrium hydrides are presented and analyzed, and this technique is shown to be a versatile microscopic probe of the location, net charge and occupation probability of nearby protons

  11. The Production of Uranium Metal by Metal Hydrides Incorporated

    Energy Technology Data Exchange (ETDEWEB)

    Alexander, P. P.

    1943-01-01

    Metal Hydrides Incorporated was a pioneer in the production of uranium metal on a commercial scale and supplied it to all the laboratories interested in the original research, before other methods for its production were developed. Metal Hydrides Inc. supplied the major part of the metal for the construction of the first experimental pile which, on December 2, 1942, demonstrated the feasibility of the self-sustaining chain reaction and the release of atomic energy.

  12. Atomistic simulation of hydrogen dynamics near dislocations in vanadium hydrides

    International Nuclear Information System (INIS)

    Ogawa, Hiroshi

    2015-01-01

    Highlights: • Hydrogen–dislocation interaction was simulated by molecular dynamics method. • Different distribution of H atoms were observed at edge and screw dislocation. • Planner distribution of hydrogen may be caused by partialized edge dislocation. • Hydrogen diffusivity was reduced in both edge and screw dislocation models. • Pipe diffusion was observed for edge dislocation but not for screw dislocation. - Abstract: Kinetics of interstitial hydrogen atoms near dislocation cores were analyzed by atomistic simulation. Classical molecular dynamics method was applied to model structures of edge and screw dislocations in α-phase vanadium hydride. Simulation showed that hydrogen atoms aggregate near dislocation cores. The spatial distribution of hydrogen has a planner shape at edge dislocation due to dislocation partialization, and a cylindrical shape at screw dislocation. Simulated self-diffusion coefficients of hydrogen atoms in dislocation models were a half- to one-order lower than that of dislocation-free model. Arrhenius plot of self-diffusivity showed slightly different activation energies for edge and screw dislocations. Directional dependency of hydrogen diffusion near dislocation showed high and low diffusivity along edge and screw dislocation lines, respectively, hence so called ‘pipe diffusion’ possibly occur at edge dislocation but does not at screw dislocation

  13. Hydrogen storage in lithium hydride: A theoretical approach

    Science.gov (United States)

    Banger, Suman; Nayak, Vikas; Verma, U. P.

    2018-04-01

    First principles calculations have been carried out to analyze structural stability of lithium hydride (LiH) in NaCl phase using the full potential linearized augmented plane wave (FP-LAPW) method within the framework of density functional theory (DFT). Calculations have been extended to physiosorbed H-atom compounds LiH·H2, LiH·3H2 and LiH·4H2. The obtained results are discussed in the paper. The results for LiH are in excellent agreement with earlier reported data. The obtained direct energy band gap of LiH is 3.0 eV which is in excellent agreement with earlier reported theoretical band gap. The electronic band structure plots of the hydrogen adsorbed compounds show metallic behavior. The elastic constants, anisotropy factor, shear modulus, Young's modulus, Poisson's ratio and cohesive energies of all the compounds are calculated. Calculation of the optical spectra such as the real and imaginary parts of dielectric function, optical reflectivity, absorption coefficient, optical conductivity, refractive index, extinction coefficient and electron energy loss are performed for the energy range 0-15 eV. The obtained results for LiH·H2, LiH·3H2 and LiH·4H2, are reported for the first time. This study has been made in search of materials for hydrogen storage. It is concluded that LiH is a promising material for hydrogen storage.

  14. Matched-filtering generalized phase contrast using LCoS pico-projectors for beam-forming

    OpenAIRE

    Bañas, Andrew Rafael; Palima, Darwin; Glückstad, Jesper

    2012-01-01

    We report on a new beam-forming system for generating high intensity programmable optical spikes using so-called matched-filtering Generalized Phase Contrast (mGPC) applying two consumer handheld pico-projectors. Such a system presents a low-cost alternative for optical trapping and manipulation, optical lattices and other beam-shaping applications usually implemented with high-end spatial light modulators. Portable pico-projectors based on liquid crystal on silicon (LCoS) devices are used as...

  15. Preparation and chemical crystallographic study of new hydrides and hydro-fluorides of ionic character; Preparation et etude cristallochimique de nouveaux hydrures et fluorohydrures a caractere ionique

    Energy Technology Data Exchange (ETDEWEB)

    Park, Hyung-Ho

    1988-07-22

    Within the context of a growing interest in the study of reversible hydrides with the perspective of their application in hydrogen storage, this research thesis more particularly addressed the case of ternary hydrides and fluorides, and of hydro-fluorides. The author reports the development of a method of preparation of alkaline hydrides, of alkaline earth hydrides and of europium hydride, and then the elaboration of ternary hydrides. He addresses the preparation of caesium fluorides and of calcium or nickel fluorides, of Europium fluorides, and of ternary fluorides. Then, he addresses the preparation of hydro-fluorides (caesium, calcium, europium fluorides, and caesium and nickel fluorides). The author presents the various experimental techniques: chemical analysis, radio-crystallographic analysis, volumetric mass density measurement, magnetic measurements, ionic conductivity measurements, Moessbauer spectroscopy, and nuclear magnetic resonance. He reports the crystallographic study of some ternary alkaline and alkaline-earth hydrides (KH-MgH{sub 2}, RbH-CaH{sub 2}, CsH-CaH{sub 2}, RbH-MgH{sub 2} and CsH-MgH{sub 2}) and of some hydro-fluorides (CsCaF{sub 2}H, EuF{sub 2}H, CsNiF{sub 2}H) [French] Dans une premiere partie, de nouveaux hydrures ternaires ont ete prepares et caracterises. Les systemes etudies sont AH-MH 2 (A = K, Rb, Cs et M = Mg, Ca). Dans les systemes AH-MgH 2 l'evolution structurale a ete discutee en fonction du caractere iono-covalent de la liaison magnesium-hydrogene. Dans une deuxieme partie, plusieurs nouveaux fluorohydrures ont ete mis en evidence. L'effet de la substitution de l'hydrogene au fluor dans ces phases a ete etudiee en utilisant la RMN, la spectroscopie Moessbauer, la conductivite ionique et les mesures magnetiques.

  16. The use of metal hydrides in fuel cell applications

    Directory of Open Access Journals (Sweden)

    Mykhaylo V. Lototskyy

    2017-02-01

    Full Text Available This paper reviews state-of-the-art developments in hydrogen energy systems which integrate fuel cells with metal hydride-based hydrogen storage. The 187 reference papers included in this review provide an overview of all major publications in the field, as well as recent work by several of the authors of the review. The review contains four parts. The first part gives an overview of the existing types of fuel cells and outlines the potential of using metal hydride stores as a source of hydrogen fuel. The second part of the review considers the suitability and optimisation of different metal hydrides based on their energy efficient thermal integration with fuel cells. The performances of metal hydrides are considered from the viewpoint of the reversible heat driven interaction of the metal hydrides with gaseous H2. Efficiencies of hydrogen and heat exchange in hydrogen stores to control H2 charge/discharge flow rates are the focus of the third section of the review and are considered together with metal hydride – fuel cell system integration issues and the corresponding engineering solutions. Finally, the last section of the review describes specific hydrogen-fuelled systems presented in the available reference data.

  17. Metal hydrides based high energy density thermal battery

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Zhigang Zak, E-mail: zak.fang@utah.edu [Department of Metallurgical Engineering, The University of Utah, 135 South 1460 East, Room 412, Salt Lake City, UT 84112-0114 (United States); Zhou, Chengshang; Fan, Peng [Department of Metallurgical Engineering, The University of Utah, 135 South 1460 East, Room 412, Salt Lake City, UT 84112-0114 (United States); Udell, Kent S. [Department of Metallurgical Engineering, The University of Utah, 50 S. Central Campus Dr., Room 2110, Salt Lake City, UT 84112-0114 (United States); Bowman, Robert C. [Department of Metallurgical Engineering, The University of Utah, 135 South 1460 East, Room 412, Salt Lake City, UT 84112-0114 (United States); Vajo, John J.; Purewal, Justin J. [HRL Laboratories, LLC, 3011 Malibu Canyon Road, Malibu, CA 90265 (United States); Kekelia, Bidzina [Department of Metallurgical Engineering, The University of Utah, 50 S. Central Campus Dr., Room 2110, Salt Lake City, UT 84112-0114 (United States)

    2015-10-05

    Highlights: • The principle of the thermal battery using advanced metal hydrides was demonstrated. • The thermal battery used MgH{sub 2} and TiMnV as a working pair. • High energy density can be achieved by the use of MgH{sub 2} to store thermal energy. - Abstract: A concept of thermal battery based on advanced metal hydrides was studied for heating and cooling of cabins in electric vehicles. The system utilized a pair of thermodynamically matched metal hydrides as energy storage media. The pair of hydrides that was identified and developed was: (1) catalyzed MgH{sub 2} as the high temperature hydride material, due to its high energy density and enhanced kinetics; and (2) TiV{sub 0.62}Mn{sub 1.5} alloy as the matching low temperature hydride. Further, a proof-of-concept prototype was built and tested, demonstrating the potential of the system as HVAC for transportation vehicles.

  18. Epoxy-Based Organogels for Thermally Reversible Light Scattering Films and Form-Stable Phase Change Materials.

    Science.gov (United States)

    Puig, Julieta; Dell' Erba, Ignacio E; Schroeder, Walter F; Hoppe, Cristina E; Williams, Roberto J J

    2017-03-29

    Alkyl chains of β-hydroxyesters synthesized by the capping of terminal epoxy groups of diglycidylether of bisphenol A (DGEBA) with palmitic (C16), stearic (C18), or behenic (C22) fatty acids self-assemble forming a crystalline phase. Above a particular concentration solutions of these esters in a variety of solvents led to supramolecular (physical) gels below the crystallization temperature of alkyl chains. A form-stable phase change material (FS-PCM) was obtained by blending the ester derived from behenic acid with eicosane. A blend containing 20 wt % ester was stable as a gel up to 53 °C and exhibited a heat storage capacity of 161 J/g, absorbed during the melting of eicosane at 37 °C. Thermally reversible light scattering (TRLS) films were obtained by visible-light photopolymerization of poly(ethylene glycol) dimethacrylate-ester blends (50 wt %) in the gel state at room temperature. The reaction was very fast and not inhibited by oxygen. TRLS films consisted of a cross-linked methacrylic network interpenetrated by the supramolecular network formed by the esters. Above the melting temperature of crystallites formed by alkyl chains, the film was transparent due to the matching between refractive indices of the methacrylic network and the amorphous ester. Below the crystallization temperature, the film was opaque because of light dispersion produced by the organic crystallites uniformly dispersed in the material. Of high significance for application was the fact that the contrast ratio did not depend on heating and cooling rates.

  19. Kinetics of hydrogen evolution in the thermal dissociation of the hydride ZrNiH /SUB 2.8/

    International Nuclear Information System (INIS)

    Chernavskii, P.A.; Lunin, V.V.

    1985-01-01

    The kinetics of hydrogen evolution in the thermal decomposition of ZrNiH /SUB 2.8/ has been studied. The kinetic curve has two rate maxima. It is presumed that the second maximum is related to the phenomenon of critical inhibition that accompanies the phase transition. Apparent activation energies were determined for hydrogen evolution in argon and argon-ethylene atmospheres. The apparent energy increases in the argon-ethylene mixture. On the basis of the activation energy measurements it is presumed that the rate-determining step in hydrogen evolution is either the formation of hydrogen molecules from atoms on the surface of the lateral diffusion of atomic hydrogen. In the region of hydrogen concentration in the hydride corresponding to the phase transition, the rate-determining step is hydrogen diffusion in the hydride

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

    Science.gov (United States)

    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

  1. Influence of disorder on phonon resistivity of ion-implanted nickel hydride

    International Nuclear Information System (INIS)

    Brossard, L.; Bernas, H.; Thome, L.; Traverse, A.; Nedellec, P.

    1982-01-01

    Metastable nickel hydride NiHsub(1.00) is produced by low energy proton implantation into thin nickel films at 6 K. After annealing at different temperatures (125, 185 K), the sample resistivity-temperature dependence is studied by cycling between 4.2 K and the annealing temperature. The temperature-dependent term in the resistivity is thus determined - for the first time - in an implanted system. A T 3 -dependence is found, in contrast to the T 5 -dependence of the ordered NiH β-phase obtained by electrolytic charging. This result is ascribed to implantation induced disorder. Isochronal annealing experiments are discussed elsewhere. (author)

  2. Control of microstructure to increase the tolerance of zirconium alloys to hydride cracking

    International Nuclear Information System (INIS)

    Coleman, C.E.; Sagat, S.; Amouzouvi, K.F.

    1987-12-01

    The microstructure of Zr-2.5 Nb has been altered in three ways in attempts to increase the alloy's tolerance to delayed hydride cracking, namely by breaking up the β-phase which reduces diffusivity of hydrogen and decreases crack velocity, by means of a gettering element (yttrium) which reduces susceptibility to cracking although the yttrium alloy has low toughness and poor corrosion resistance, and by reducing the number of basal plane normals in the main stressing direction which improves resistance to crack growth

  3. Oriented xenon hydride molecules in the gas phase

    Czech Academy of Sciences Publication Activity Database

    Buck, U.; Fárník, Michal

    2006-01-01

    Roč. 25, č. 4 (2006), s. 583-612 ISSN 0144-235X Grant - others:Deutsche Forschungsgemeinschaft(DE) SFB 357 Institutional research plan: CEZ:AV0Z40400503 Keywords : photofragment translational spectroscopy * charge transfer molecules * low temperature matrices * neutral rare-gas Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 6.036, year: 2006

  4. Reaction of plutonium with water kinetic and equilibrium behavior of binary and ternary phases in the Pu + O + H system

    International Nuclear Information System (INIS)

    Haschke, J.M.; Hodges, A.E. III; Bixby, G.E.; Lucas, R.L.

    1983-01-01

    The kinetic and equilibrium behavior of the Pu + O + H system has been studied by measuring the production of hydrogen gas formed by a sequence of hydrolysis reactions. The kinetic dependence of the Pu + H 2 O reaction on salt concentration and temperature has been defined. The metal is quantitatively converted to a fine black powder which has been identified as plutonium monoxide monohydride, PuOH. Other hydrolysis products formed in aqueous media include a second oxide hydride, Pu 7 O 9 H 3 , and the oxides Pu 2 O 3 , Pu 7 O 12 , Pu 9 O 16 , Pu 10 O 18 , Pu 12 O 22 , and PuO 2 . Thermal decomposition products of PuOH include Pu 2 O 2 H and PuO. A tentative phase diagram for Pu + O + H is presented and structural relationships of the oxide hydrides and oxides are discussed. 10 figures, 5 tables

  5. The phases formed by the dehydration of disodium zirconium (IV) bis(orthophosphate) trihydrate and their ion-exchange behavior

    International Nuclear Information System (INIS)

    Inoue, Yasushi; Yamada, Yoshimune

    1982-01-01

    The phase transformation of Na 2 Zr(PO 4 ) 2 .3H 2 O which had been obtained from zirconium (IV) bis(hydrogenphosphate) monohydrate(α-zirconium phosphate), prepared by the direct precipitation method, was studied by means of gravimetry, X-ray analysis, and acid-base titration. When the material was heated for 2d, it was transformed to a monohydrate at 80 0 C and then successively to three anhydrous phases, depending on the temperature. The monohydrate was also formed by letting the trihydrate stand over P 2 O 5 at room temperature for longer than two weeks. The processes were confirmed to be irreversible by an examination of the rehydration behavior, from which the conditions of the storage of five modifications of disodium zirconium (IV) bis(orthophosphate) were established. It is of special interest that the second anhydrous phase reverted to the first one when it was allowed to stand at room temperature in air or in a desiccator. The rate of the reversion decreased with the temperature of heat-treatment and with a decrease in the relative humidity of the surroundings. The difference between the present results and Clearfield's was clarified and attributed mainly to the difference in the crystallinity of the starting α-zirconium phosphate. (author)

  6. Electrolytic hydriding of LaFe{sub 13-x}Si{sub x} alloys for energy efficient magnetic cooling

    Energy Technology Data Exchange (ETDEWEB)

    Lyubina, Julia; Hannemann, Ullrich; Ryan, Mary P. [Department of Materials, Imperial College London (United Kingdom); Cohen, Lesley F. [Department of Physics, Imperial College London (United Kingdom)

    2012-04-17

    An effective, low-temperature and readily available electrochemical method for tuning the operation temperature of LaFe{sub 13-x}Si{sub x}-type alloys is demonstrated. Electrolytically hydrided materials have the same high level magnetic properties as in high temperature gas-phase processed materials and offer an advantage of higher hydrogen absorption rate in the ferromagnetic state. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Effect of electronegativity on the mechanical properties of metal hydrides with a fluorite structure

    International Nuclear Information System (INIS)

    Ito, Masato; Setoyama, Daigo; Matsunaga, Junji; Muta, Hiroaki; Kurosaki, Ken; Uno, Masayoshi; Yamanaka, Shinsuke

    2006-01-01

    Bulk titanium, yttrium, and zirconium hydrides, which have the same structure as that of fluorite-type fcc C 1, were produced and their mechanical properties were investigated. With an increase in the hydrogen content, the lattice parameters of titanium and zirconium hydrides increased, whereas those of yttrium hydride decreased. The elastic moduli of titanium and zirconium hydrides decreased by hydrogen addition, whereas those of yttrium hydride increased. There are linear relations between the electronegativities and hydrogen content dependence of the properties. Therefore, the mechanical properties of the metal hydrides are considered to be determined by a common rule based on the electronegativity

  8. Fullerene hydride - A potential hydrogen storage material

    International Nuclear Information System (INIS)

    Nai Xing Wang; Jun Ping Zhang; An Guang Yu; Yun Xu Yang; Wu Wei Wang; Rui long Sheng; Jia Zhao

    2005-01-01

    Hydrogen, as a clean, convenient, versatile fuel source, is considered to be an ideal energy carrier in the foreseeable future. Hydrogen storage must be solved in using of hydrogen energy. To date, much effort has been put into storage of hydrogen including physical storage via compression or liquefaction, chemical storage in hydrogen carriers, metal hydrides and gas-on-solid adsorption. But no one satisfies all of the efficiency, size, weight, cost and safety requirements for transportation or utility use. C 60 H 36 , firstly synthesized by the method of the Birch reduction, was loaded with 4.8 wt% hydrogen indicating [60]fullerene might be as a potential hydrogen storage material. If a 100% conversion of C 60 H 36 is achieved, 18 moles of H 2 gas would be liberated from each mole of fullerene hydride. Pure C 60 H 36 is very stable below 500 C under nitrogen atmosphere and it releases hydrogen accompanying by other hydrocarbons under high temperature. But C 60 H 36 can be decomposed to generate H 2 under effective catalyst. We have reported that hydrogen can be produced catalytically from C 60 H 36 by Vasks's compound (IrCl(CO)(PPh 3 ) 2 ) under mild conditions. (RhCl(CO)(PPh 3 ) 2 ) having similar structure to (IrCl(CO)(PPh 3 ) 2 ), was also examined for thermal dehydrogenation of C 60 H 36 ; but it showed low catalytic activity. To search better catalyst, palladium carbon (Pd/C) and platinum carbon (Pt/C) catalysts, which were known for catalytic hydrogenation of aromatic compounds, were tried and good results were obtained. A very big peak of hydrogen appeared at δ=5.2 ppm in 1 H NMR spectrum based on Evans'work (fig 1) at 100 C over a Pd/C catalyst for 16 hours. It is shown that hydrogen can be produced from C 60 H 36 using a catalytic amount of Pd/C. Comparing with Pd/C, Pt/C catalyst showed lower activity. The high cost and limited availability of Vaska's compounds, Pd and Pt make it advantageous to develop less expensive catalysts for our process based on

  9. The reaction process of the Bi-Sr-Ca-Cu-O system and the forming mechanism of the 2212 superconducting phase

    International Nuclear Information System (INIS)

    Xiong Guohong; Wang Minquan; Fan Xianping; Tang Xiaoming

    1993-01-01

    The reaction process and the reaction behavior of each component in the Bi-Sr-Ca-Cu-O system are presented in this paper. It reveals that the reaction is carried out in three different stages: forming of an insulating interphase at 680 C-790 C, forming of the 2212 superconducting phase at 790 C-860 C and forming of semiconducting phases in the presence of the liquid phase at 860 C-970 C. It is also confirmed that the 2212 superconducting phase (T c =85 K) is formed by the reaction of a trinary interphase together with CuO, SrO and CaO. A new two-step method is presented to prepare the 2212 superconducting phase by a presynthesized interphase. (orig.)

  10. The reaction process of the Bi-Sr-Ca-Cu-O system and the forming mechanism of the 2212 superconducting phase

    Science.gov (United States)

    Xiong, Guohong; Wang, Minquan; Fan, Xianping; Tang, Xiaoming

    1993-02-01

    The reaction process and the reaction behavior of each component in the Bi-Sr-Ca-Cu-O system are presented in this paper. It reveals that the reaction is carried out in three different stages: forming of an insulating interphase at 680°C 790°C, forming of the 2212 superconducting phase at 790°C 860°C and forming often semiconducting phases in the presence of the liquid phase at 860°C 970°C. It is also confirmed that the 2212 superconducting phase ( T c=85 K) is formed by the reaction of a trinary interphase together with CuO, SrO and CaO. A new two-step method is presented to prepare the 2212 superconducting phase by a presynthesized interphase.

  11. The reaction process of the Bi-Sr-Ca-Cu-O system and the forming mechanism of the 2212 superconducting phase

    Energy Technology Data Exchange (ETDEWEB)

    Xiong Guohong (Zhejiang Univ., Hangzhou (China). Dept. of Materials Science and Engineering); Wang Minquan (Zhejiang Univ., Hangzhou (China). Dept. of Materials Science and Engineering); Fan Xianping (Zhejiang Univ., Hangzhou (China). Dept. of Materials Science and Engineering); Tang Xiaoming (Zhejiang Univ., Hangzhou (China). Center for Analysis and Measurement)

    1993-02-01

    The reaction process and the reaction behavior of each component in the Bi-Sr-Ca-Cu-O system are presented in this paper. It reveals that the reaction is carried out in three different stages: forming of an insulating interphase at 680 C-790 C, forming of the 2212 superconducting phase at 790 C-860 C and forming of semiconducting phases in the presence of the liquid phase at 860 C-970 C. It is also confirmed that the 2212 superconducting phase (T[sub c]=85 K) is formed by the reaction of a trinary interphase together with CuO, SrO and CaO. A new two-step method is presented to prepare the 2212 superconducting phase by a presynthesized interphase. (orig.)

  12. Effect of hydridation on structure of amorphous and amorphous-crystalline Fe40Ni40B20 and Co70Fe5Si15B10 bands

    International Nuclear Information System (INIS)

    Il'inskij, A.G.; Brovko, A.P.; Zelinskaya, G.M.; Kosenko, N.S.; Khristenko, T.M.; Kobzenko, G.F.; Shkola, A.A.

    1988-01-01

    The structure of amorphous and amorphous-crystaliline Fe 40 Ni 40 B 20 and Co 70 Fe 5 Si-1 5 B 10 alloys, exposed to hydridation at different temperatures, is studied by X-ray diffraction technique. The presence of crystalline constituent in amorphous bands was determined on DRON-3 device and by method of small-angle scattering. The experimental data obtained verify, that hydridation does not only prevent the formation of crystalline phases at annealing, but leads, as well, to disappearance of band crystalline constituent in case of its presence

  13. Dehydriding and re-hydriding properties of high-energy ball milled LiBH{sub 4}+MgH{sub 2} mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Crosby, Kyle; Shaw, Leon L. [Department of Chemical, Materials and Biomolecular Engineering, University of Connecticut, 97 North Eagleville Road, U-3136, Storrs, CT 06269 (United States)

    2010-07-15

    Here we report the first investigation of the dehydriding and re-hydriding properties of 2LiBH{sub 4} + MgH{sub 2} mixtures in the solid state. Such a study is made possible by high-energy ball milling of 2LiBH{sub 4}+MgH{sub 2} mixtures at liquid nitrogen temperature with the addition of graphite. The 2LiBH{sub 4}+MgH{sub 2} mixture ball milled under this condition exhibits a 5-fold increase in the released hydrogen at 265 C when compared with ineffectively ball milled counterparts. Furthermore, both LiBH{sub 4} and MgH{sub 2} contribute to hydrogen release in the solid state. The isothermal dehydriding/re-hydriding cycles at 265 C reveal that re-hydriding is dominated by re-hydriding of Mg. These unusual phenomena are explained based on the formation of nanocrystalline and amorphous phases, the increased defect concentration in crystalline compounds, and possible catalytic effects of Mg,MgH{sub 2} and LiBH{sub 4} on their dehydriding and re-hydriding properties. (author)

  14. Preparation and thermal energy storage properties of paraffin/calcined diatomite composites as form-stable phase change materials

    International Nuclear Information System (INIS)

    Sun, Zhiming; Zhang, Yuzhong; Zheng, Shuilin; Park, Yuri; Frost, Ray L.

    2013-01-01

    Highlights: ► Composite phase change material (PCM) was prepared by blending composite paraffin and calcined diatomite. ► The optimum mixed proportion was obtained through differential scanning calorimetry. ► Thermal energy storage properties of the composite PCMs were determined by DSC. ► Thermal cycling test showed that the prepared PCMs are thermally reliable and chemically stable. - Abstract: A composite paraffin-based phase change material (PCM) was prepared by blending composite paraffin and calcined diatomite through the fusion adsorption method. In this study, raw diatomite was purified by thermal treatment in order to improve the adsorption capacity of diatomite, which acted as a carrier material to prepare shape-stabilized PCMs. Two forms of paraffin (paraffin waxes and liquid paraffin) with different melting points were blended together by the fusion method, and the optimum mixed proportion with a suitable phase-transition temperature was obtained through differential scanning calorimetry (DSC) analysis. Then the prepared composite paraffin was adsorbed in calcined diatomite. The prepared paraffin/calcined diatomite composites were characterized by the scanning electron microscope (SEM) and Fourier transformation infrared (FT-IR) analysis techniques. Thermal energy storage properties of the composite PCMs were determined by DSC method. DSC results showed that there was an optimum adsorption ratio between composite paraffin and calcined diatomite and the phase-transition temperature and the latent heat of the composite PCMs were 33.04 °C and 89.54 J/g, respectively. Thermal cycling test of composite PCMs showed that the prepared material is thermally reliable and chemically stable. The obtained paraffin/calcined diatomite composites have proper latent heat and melting temperatures, and show practical significance and good potential application value

  15. Preparation and thermal energy storage properties of paraffin/calcined diatomite composites as form-stable phase change materials

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Zhiming [School of Chemical and Environmental Engineering, China University of Mining and Technology, Beijing 100083 (China); Chemistry Discipline, Faculty of Science and Technology, Queensland University of Technology, 2 George Street, GPO Box 2434, Brisbane, Queensland 4001 (Australia); Zhang, Yuzhong [School of Chemical and Environmental Engineering, China University of Mining and Technology, Beijing 100083 (China); Zheng, Shuilin, E-mail: shuilinzh@yahoo.com.cn [School of Chemical and Environmental Engineering, China University of Mining and Technology, Beijing 100083 (China); Park, Yuri [Chemistry Discipline, Faculty of Science and Technology, Queensland University of Technology, 2 George Street, GPO Box 2434, Brisbane, Queensland 4001 (Australia); Frost, Ray L., E-mail: r.frost@qut.edu.au [Chemistry Discipline, Faculty of Science and Technology, Queensland University of Technology, 2 George Street, GPO Box 2434, Brisbane, Queensland 4001 (Australia)

    2013-04-20

    Highlights: ► Composite phase change material (PCM) was prepared by blending composite paraffin and calcined diatomite. ► The optimum mixed proportion was obtained through differential scanning calorimetry. ► Thermal energy storage properties of the composite PCMs were determined by DSC. ► Thermal cycling test showed that the prepared PCMs are thermally reliable and chemically stable. - Abstract: A composite paraffin-based phase change material (PCM) was prepared by blending composite paraffin and calcined diatomite through the fusion adsorption method. In this study, raw diatomite was purified by thermal treatment in order to improve the adsorption capacity of diatomite, which acted as a carrier material to prepare shape-stabilized PCMs. Two forms of paraffin (paraffin waxes and liquid paraffin) with different melting points were blended together by the fusion method, and the optimum mixed proportion with a suitable phase-transition temperature was obtained through differential scanning calorimetry (DSC) analysis. Then the prepared composite paraffin was adsorbed in calcined diatomite. The prepared paraffin/calcined diatomite composites were characterized by the scanning electron microscope (SEM) and Fourier transformation infrared (FT-IR) analysis techniques. Thermal energy storage properties of the composite PCMs were determined by DSC method. DSC results showed that there was an optimum adsorption ratio between composite paraffin and calcined diatomite and the phase-transition temperature and the latent heat of the composite PCMs were 33.04 °C and 89.54 J/g, respectively. Thermal cycling test of composite PCMs showed that the prepared material is thermally reliable and chemically stable. The obtained paraffin/calcined diatomite composites have proper latent heat and melting temperatures, and show practical significance and good potential application value.

  16. Computer x-ray powder diffraction patterns and densities for corundum, aluminium, zirconium, delta-UZr2 and the zirconium hydrides

    International Nuclear Information System (INIS)

    Ferguson, I.F.

    1976-11-01

    The computer-calculated X-ray powder diffraction patterns and theoretical densities of α-Al 2 O 3 ; Al; α-Zr; β-Zr; delta-UZr 2 ; γ, delta - and epsilon-zirconium hydrides are presented. Brief comments are given on some of the published X-ray powder diffraction data on these phases. (author)

  17. New Promising Hydride Based on the Cu-Li-Mg System

    Energy Technology Data Exchange (ETDEWEB)

    Braga, M H; Acatrinei, A; Hartl, M; Vogel, S; Proffen, Th; Daemen, L, E-mail: mbraga@lanl.gov

    2010-11-01

    We investigated the ternary Cu-Li-Mg system, in particular the CuLi{sub x}Mg{sub 2-x} (x = 0.08) for hydrogen storage. Instead of crystallizing in an orthorhombic phase, as CuMg2, this phase presents a hexagonal structure very similar to that of NiMg{sub 2} and NiMg{sub 2}H{sub 0.3}. In this work we will discuss the structure of CuLi{sub x}Mg{sub 2-x} by the analysis of the neutron scattering data and first principles calculations. The first results for a hydride (deuteride) phase will also mentioned since preliminary studies at LANSCE showed that CuLi{sub x}Mg{sub 2-x} might absorb approximately 5.3 to 6 wt% of H at an equilibrium pressure of approximately 27 bar at 200 deg. C. If these results are confirmed in future work, this will mean that, not only CuLi{sub x}Mg{sub 2-x} absorbs a considerable amount of hydrogen (close to DOE's expectations for hydrogen storage materials), but also will probably release it at a temperature in the range of 50 to 150 deg. C, where applications are easier to develop. Hence it should be possible to use this alloy with fuel cells or in batteries. Another important observation is that cycling has a strong effect on the structure of the hydride.

  18. Gas-phase complexes formed between amidoxime ligands and vanadium or iron investigated using electrospray ionization mass spectrometry.

    Science.gov (United States)

    Mustapha, Adetayo M; Pasilis, Sofie P

    2016-08-15

    Amidoxime-functionalized sorbents can be used to extract uranium from seawater. Iron(III) and vanadium(V) may compete with uranium for adsorption sites. We use 2,6-dihydroxyiminopiperidine (DHIP) and N(1) ,N(5) -dihydroxypentanediimidamide (DHPD) to model amidoxime functional groups and characterize the vanadium(V) and iron(III) complexes with these ligands. We also examine the effect of iron(III) and vanadium(V) on uranyl(VI) complexation by DHIP and DHPD. The experiments were carried out in positive ion mode using a quadrupole ion trap mass spectrometer equipped with an electrospray ionization source. The effect on the mass spectra of changes in ligand, metal:ligand mole ratio, and pH was examined. Iron(III) formed a 1:2 metal:ligand complex with DHIP at all metal:ligand mole ratios and pH values investigated; it formed both 1:2 and 1:3 metal:ligand complexes with DHPD. Vanadium(V) formed 1:1 and 1:2 metal:ligand complexes with DHIP. A 1:2 metal:ligand complex was formed with DHPD at all vanadium(V):DHPD mole ratios investigated. Changes in solution pH did not affect the ions observed. The relative binding affinities of the metal ions towards DHIP followed the order iron(III) > vanadium(V) > uranyl(VI). This study presents a first look at the gas-phase vanadium(V)- and iron(III)-DHIP and -DHPD complexes using electrospray ionization mass spectrometry. These metals form stronger complexes with amidoxime ligands than uranyl(VI), and will affect uranyl(VI) adsorption to amidoxime-based sorbents. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  19. Hydrogen in niobium, tantalum, and vanadium: Structures, phase diagrams, and morphologies

    International Nuclear Information System (INIS)

    Schober, T.

    1978-07-01

    The paper discusses basic aspects of the reactions between the metals niobium, tantalum, vanadium, and hydrogen or deuterium. After an introduction to problems of preparation experimental technqiues for the investigation of hydrides are presented. The possible hydride structures are discussed. With vanadium, there are great differences between the structures of hydrides and deuterides. Detailed mention is also made of recent measurements of the NGH, TaH, VH, and VD phase diagrams. (orig./WBU) [de

  20. Influence of uranium hydride oxidation on uranium metal behaviour

    International Nuclear Information System (INIS)

    Patel, N.; Hambley, D.; Clarke, S.A.; Simpson, K.

    2013-01-01

    This work addresses concerns that the rapid, exothermic oxidation of active uranium hydride in air could stimulate an exothermic reaction (burning) involving any adjacent uranium metal, so as to increase the potential hazard arising from a hydride reaction. The effect of the thermal reaction of active uranium hydride, especially in contact with uranium metal, does not increase in proportion with hydride mass, particularly when considering large quantities of hydride. Whether uranium metal continues to burn in the long term is a function of the uranium metal and its surroundings. The source of the initial heat input to the uranium, if sufficient to cause ignition, is not important. Sustained burning of uranium requires the rate of heat generation to be sufficient to offset the total rate of heat loss so as to maintain an elevated temperature. For dense uranium, this is very difficult to achieve in naturally occurring circumstances. Areas of the uranium surface can lose heat but not generate heat. Heat can be lost by conduction, through contact with other materials, and by convection and radiation, e.g. from areas where the uranium surface is covered with a layer of oxidised material, such as burned-out hydride or from fuel cladding. These rates of heat loss are highly significant in relation to the rate of heat generation by sustained oxidation of uranium in air. Finite volume modelling has been used to examine the behaviour of a magnesium-clad uranium metal fuel element within a bottle surrounded by other un-bottled fuel elements. In the event that the bottle is breached, suddenly, in air, it can be concluded that the bulk uranium metal oxidation reaction will not reach a self-sustaining level and the mass of uranium oxidised will likely to be small in relation to mass of uranium hydride oxidised. (authors)

  1. Influence of uranium hydride oxidation on uranium metal behaviour

    Energy Technology Data Exchange (ETDEWEB)

    Patel, N.; Hambley, D. [National Nuclear Laboratory (United Kingdom); Clarke, S.A. [Sellafield Ltd (United Kingdom); Simpson, K.

    2013-07-01

    This work addresses concerns that the rapid, exothermic oxidation of active uranium hydride in air could stimulate an exothermic reaction (burning) involving any adjacent uranium metal, so as to increase the potential hazard arising from a hydride reaction. The effect of the thermal reaction of active uranium hydride, especially in contact with uranium metal, does not increase in proportion with hydride mass, particularly when considering large quantities of hydride. Whether uranium metal continues to burn in the long term is a function of the uranium metal and its surroundings. The source of the initial heat input to the uranium, if sufficient to cause ignition, is not important. Sustained burning of uranium requires the rate of heat generation to be sufficient to offset the total rate of heat loss so as to maintain an elevated temperature. For dense uranium, this is very difficult to achieve in naturally occurring circumstances. Areas of the uranium surface can lose heat but not generate heat. Heat can be lost by conduction, through contact with other materials, and by convection and radiation, e.g. from areas where the uranium surface is covered with a layer of oxidised material, such as burned-out hydride or from fuel cladding. These rates of heat loss are highly significant in relation to the rate of heat generation by sustained oxidation of uranium in air. Finite volume modelling has been used to examine the behaviour of a magnesium-clad uranium metal fuel element within a bottle surrounded by other un-bottled fuel elements. In the event that the bottle is breached, suddenly, in air, it can be concluded that the bulk uranium metal oxidation reaction will not reach a self-sustaining level and the mass of uranium oxidised will likely to be small in relation to mass of uranium hydride oxidised. (authors)

  2. Permeation rates for RTF metal hydride vessels

    International Nuclear Information System (INIS)

    Klein, J.E.

    1992-01-01

    Contamination rates have been estimated for the RTF nitrogen heating and cooling system (NH and CS) due to tritium permeation through the walls of metal hydride vessels. Tritium contamination of the NH and CS will be seen shortly after start-up of the RTF with the majority of it coming from the TCAP units. Contamination rates of the NH and CS are estimated to exceed 400 Ci/year after three years of operation and will elevate tritium concentrations in the NH and CS above 6 x 10 -3 μCi/cc. To reduce tritium activity in the NH and CS, a stripper or ''getter'' bed may need to be installed in the NH and CS. Increasing the purge rate of nitrogen from the NH and CS is shown to be an impractical method for reducing tritium activity due to the high purge rates required. Stripping of the NH and CS nitrogen in the glove box stripper system will give a temporary lowering of tritium activity in the NH and CS, but tritium activity will return to its previous level in approximately two weeks

  3. Hydriding and neutron irradiation in zircaloy-4

    International Nuclear Information System (INIS)

    Ramos, Ruben Fortunato; Martin, Juan Ezequiel; Orellano, Pablo; Dorao, Carlos; Analia Soldati; Ghilarducci, Ada Albertina; Corso, Hugo Luis; Peretti, Hernan Americo; Bolcich, Juan Carlos

    2003-01-01

    The composition of Zircaloy-4 for nuclear applications is specified by the ASTM B350 Standard, that fixes the amount of alloying elements (Sn, Fe, Cr) and impurities (Ni, Hf, O, N, C, among others) to optimize good corrosion and mechanical behavior.The recycling of zircaloy-4 scrap and chips resulting from cladding tube fabrication is an interesting issue.However, changes in the final composition of the recycled material may occur due to contamination with tool pieces, stainless steel chips, turnings, etc. while scrap is stored and handled. Since the main components of the possible contaminants are Fe, Cr and Ni, it arises the interest in studying up to what limit the Fe, Ni and Cr contents could be exceeded beyond the standard specification without affecting significantly the alloy properties.Zircaloy-4 alloys elaborated with Fe, Cr and Ni additions and others of standard composition in use in nuclear plants are studied by tensile tests, SEM observations and EDS microanalysis.Some samples are tested in the initial condition and others after hydriding treatments and neutron irradiation in the RA6

  4. Optical and photoemission studies of lanthanum hydrides

    International Nuclear Information System (INIS)

    Peterman, D.J.; Peterson, D.T.; Weaver, J.H.

    1980-01-01

    The results of optical absorptivity and photoemission measurements on lanthanum hydrides, LaH/sub x/ (1.98 less than or equal to x less than or equal to 2.89) are reported. The low energy (hν less than or equal to 0.5 eV) optical features in LaH/sub x/ are attributed to the filling of octahedral sites. Higher energy interband absorption involves states within the d-band complex, analogous to other dihydrides. As x increases above 2.0, the optical features change rapidly due to the increase in the number of occupied octahedral sites. Various band structure studies suggest that LaH 3 might be a semiconductor. Photoemission results show that as x increases, the d-derived states at E/sub F/ are drawn down and that for LaH 2 89 only very weak valence band emission is observed. The hydrogen-derived bonding bands are shown centered approx. 5 eV below E/sub F/. Observed chemical shifts in the La 5p/sub 1/2 3/2/ cores are discussed for 1.98 less than or equal to x less than or equal to 2.89

  5. Heat pretreatment-induced activation of gadolinium surfaces towards the initial precipitation of hydrides

    International Nuclear Information System (INIS)

    Benamar, G.; Schweke, D.; Shamir, N.; Zalkind, S.; Livneh, T.; Danon, A.; Kimmel, G.; Mintz, M.H.

    2010-01-01

    A vacuum heat pretreatment is applied, in order to enhance the reactivity of hydride-forming metals towards hydrogen reaction. For gadolinium, as for other rare-earth metals and some actinides, pretreatment temperatures of about 470 K are sufficient to induce such activation. The different factors that may be involved in that activation mechanism are identified and analyzed for gadolinium and their role is evaluated. It is concluded that the most prominent effect is desorption of surface hydroxyl groups, which impede the dissociative chemisorptions of hydrogen.

  6. Measurements of ionic structure in shock compressed lithium hydride from ultrafast x-ray Thomson scattering.

    Science.gov (United States)

    Kritcher, A L; Neumayer, P; Brown, C R D; Davis, P; Döppner, T; Falcone, R W; Gericke, D O; Gregori, G; Holst, B; Landen, O L; Lee, H J; Morse, E C; Pelka, A; Redmer, R; Roth, M; Vorberger, J; Wünsch, K; Glenzer, S H

    2009-12-11

    We present the first ultrafast temporally, spectrally, and angularly resolved x-ray scattering measurements from shock-compressed matter. The experimental spectra yield the absolute elastic and inelastic scattering intensities from the measured density of free electrons. Laser-compressed lithium-hydride samples are well characterized by inelastic Compton and plasmon scattering of a K-alpha x-ray probe providing independent measurements of temperature and density. The data show excellent agreement with the total intensity and structure when using the two-species form factor and accounting for the screening of ion-ion interactions.

  7. Analysis of Hazards Associated with a Process Involving Uranium Metal and Uranium Hydride Powders

    Energy Technology Data Exchange (ETDEWEB)

    Bullock, J.S.

    2000-05-01

    An analysis of the reaction chemistry and operational factors associated with processing uranium and uranium hydride powders is presented, focusing on a specific operation in the Development Division which was subjected to the Job Hazard Analysis (JHA) process. Primary emphasis is on the thermodynamic factors leading to pyrophoricity in common atmospheres. The discussion covers feed powders, cold-pressed and hot-pressed materials, and stray material resulting from the operations. The sensitivity of the various forms of material to pyrophoricity in common atmospheres is discussed. Operational recommendations for performing the work described are given.

  8. Determination of glibenclamide, metformin hydrochloride and rosiglitazone maleate by reversed phase liquid chromatographic technique in tablet dosage form

    Directory of Open Access Journals (Sweden)

    Havele Shweta S.

    2014-01-01

    Full Text Available A simple, precise and accurate high performance liquid chromatography (HPLC method was developed for the simultaneous estimation of metformin hydrochloride, rosiglitazone maleate, glibenclamide present in multicomponent dosage forms. Chromatography was performed on a 25 cm × 4.6 mm i.d., 5-μm particle, C18 column with 78:22 (v/v methanol: 20 mM potassium dihydrogen phosphate buffer as mobile phase at a flow rate of 1.0 ml/min and UV detection at 238 nm for metformin hydrochloride, rosiglitazone maleate, and glibenclamide. The total elution time was shorter than 9 min. This method was found to be precise and reproducible. This proposed method was successfully applied for the analysis of metformin hydrochloride, rosiglitazone maleate, glibenclamide as a bulk drug and in pharmaceutical formulation without any interference from the excipients.

  9. Estimation of Rabeprazole Sodium and Itopride Hydrochloride in Tablet Dosage Form Using Reverse Phase High Performance Liquid Chromatography

    Directory of Open Access Journals (Sweden)

    Shaik Harum Rasheed

    2011-01-01

    Full Text Available A reversed phase high performance liquid chromatography (RP-HPLC method was developed, validated and used for the quantitative determination of rabeprazole sodium (RP and itopride hydrochloride (IH, from its tablet dosage form. Chromatographic separation was performed on a Phenomenex C18 column (250 mm × 4.6 mm, 5 μm, with a mobile phase comprising of a mixture of 50 mM ammonium acetate buffer and methanol (20:80v/v, pH 4.5 adjusted with acetic acid, at a flow rate of 1.3 mL/min with detection at 286 nm. Separation was completed in less than 10 min. As per International Conference on Harmonization (ICH guidelines the method was validated for linearity, accuracy, precision, limit of quantitation and limit of detection. Linearity of RP was found to be in the range of 37.5-375 μg/mL and IH was found to be in the range of 5-50 μg/mL. The correlation coefficients were 0.9997 and 0.9995 for RB and IH respectively. The accuracy of the developed method was found to be 98.6-100.7 for RP and 99.42 -100.81 for IH. The experiment shows the developed method is free from interference of excipients. It indicates the developed RP-HPLC method is simple, linear, precise and accurate and it can be conveniently adopted for the routine quality control analysis of the tablet dosage form.

  10. Oxidation-induced phase transformations and lifetime limits of chromia-forming nickel-base alloy 625

    Energy Technology Data Exchange (ETDEWEB)

    Chyrkin, Anton

    2011-12-05

    For its high creep resistance the commercial nickel-base alloy 625 relies on solid solution strengthening in combination with precipitation hardening by formation of δ-Ni{sub 3}Nb and (Ni,Mo,Si){sub 6}C precipitates during high-temperature service. In oxidizing environments the alloy forms a slow growing, continuous chromia layer on the material surface which protects the alloy against rapid oxidation attack. The growth of the chromia base oxide scale results during exposure at 900-1000 C in oxidation-induced chromium depletion in the subsurface zone of the alloy. Microstructural analyses of the cross-sectioned specimens revealed that this process results in formation of a wide subsurface zone in which the mentioned strengthening phases are dissolved, in spite of the fact that both phases do not contain substantial amounts of the scale-forming element chromium. The cross-sectional analyses revealed that, in parallel to the formation of a precipitate depleted zone, a thin, continuous layer of niobium-rich intermetallic precipitates formed in the immediate vicinity of the scale/alloy interface. The Subsurface Phase Enrichment (abbreviated as SPE) was shown to be the result of an uphill-diffusion of niobium, i.e. the element stabilizing the strengthening precipitates δ-Ni{sub 3}Nb, in the chromium activity gradient and is thus a natural consequence of the oxidation-induced chromium depletion beneath the chromia scale. The thermodynamic calculations carried out using the Thermo-Calc/DICTRA software packages revealed that in alloy 625 the chemical activity of niobium decreases with decreasing chromium content. As chromium is being continuously removed from the alloy as the result of the chromia scale growth, the zone of lowest Nb-activity is formed in the location with the lowest chromium concentration, i.e. the scale/alloy interface. This creates a driving force for Nb to diffuse towards the scale/alloy interface against its own concentration gradient, which is known

  11. A closed-form solution for moving source localization using LBI changing rate of phase difference only

    Directory of Open Access Journals (Sweden)

    Zhang Min

    2014-04-01

    Full Text Available Due to the deficiencies in the conventional multiple-receiver localization systems based on direction of arrival (DOA such as system complexity of interferometer or array and amplitude/phase unbalance between multiple receiving channels and constraint on antenna configuration, a new radiated source localization method using the changing rate of phase difference (CRPD measured by a long baseline interferometer (LBI only is studied. To solve the strictly nonlinear problem, a two-stage closed-form solution is proposed. In the first stage, the DOA and its changing rate are estimated from the CRPD of each observer by the pseudolinear least square (PLS method, and then in the second stage, the source position and velocity are found by another PLS minimization. The bias of the algorithm caused by the correlation between the measurement matrix and the noise in the second stage is analyzed. To reduce this bias, an instrumental variable (IV method is derived. A weighted IV estimator is given in order to reduce the estimation variance. The proposed method does not need any initial guess and the computation is small. The Cramer–Rao lower bound (CRLB and mean square error (MSE are also analyzed. Simulation results show that the proposed method can be close to the CRLB with moderate Gaussian measurement noise.

  12. Hydrogen storage as a hydride. Citations from the International Aerospace Abstracts data base

    Science.gov (United States)

    Zollars, G. F.

    1980-01-01

    These citations from the international literature concern the storage of hydrogen in various metal hydrides. Binary and intermetallic hydrides are considered. Specific alloys discussed are iron titanium, lanthanium nickel, magnesium copper and magnesium nickel among others.

  13. Sodium-based hydrides for thermal energy applications

    Science.gov (United States)

    Sheppard, D. A.; Humphries, T. D.; Buckley, C. E.

    2016-04-01

    Concentrating solar-thermal power (CSP) with thermal energy storage (TES) represents an attractive alternative to conventional fossil fuels for base-load power generation. Sodium alanate (NaAlH4) is a well-known sodium-based complex metal hydride but, more recently, high-temperature sodium-based complex metal hydrides have been considered for TES. This review considers the current state of the art for NaH, NaMgH3- x F x , Na-based transition metal hydrides, NaBH4 and Na3AlH6 for TES and heat pumping applications. These metal hydrides have a number of advantages over other classes of heat storage materials such as high thermal energy storage capacity, low volume, relatively low cost and a wide range of operating temperatures (100 °C to more than 650 °C). Potential safety issues associated with the use of high-temperature sodium-based hydrides are also addressed.

  14. Group 13 β-ketoiminate compounds: gallium hydride derivatives as molecular precursors to thin films of Ga2O3.

    Science.gov (United States)

    Pugh, David; Marchand, Peter; Parkin, Ivan P; Carmalt, Claire J

    2012-06-04

    Bis(β-ketoimine) ligands, [R{N(H)C(Me)-CHC(Me)═O}(2)] (L(1)H(2), R = (CH(2))(2); L(2)H(2), R = (CH(2))(3)), linked by ethylene (L(1)) and propylene (L(2)) bridges have been used to form aluminum, gallium, and indium chloride complexes [Al(L(1))Cl] (3), [Ga(L(n))Cl] (4, n = 1; 6, n = 2) and [In(L(n))Cl] (5, n = 1; 7, n = 2). Ligand L(1) has also been used to form a gallium hydride derivative [Ga(L(1))H] (8), but indium analogues could not be made. β-ketoimine ligands, [Me(2)N(CH(2))(3)N(H)C(R')-CHC(R')═O] (L(3)H, R' = Me; L(4)H, R' = Ph), with a donor-functionalized Lewis base have also been synthesized and used to form gallium and indium alkyl complexes, [Ga(L(3))Me(2)] (9) and [In(L(3))Me(2)] (10), which were isolated as oils. The related gallium hydride complexes, [Ga(L(n))H(2)] (11, n = 3; 12, n = 4), were also prepared, but again no indium hydride species could be made. The complexes were characterized mainly by NMR spectroscopy, mass spectrometry, and single crystal X-ray diffraction. The β-ketoiminate gallium hydride compounds (8 and 11) have been used as single-source precursors for the deposition of Ga(2)O(3) by aerosol-assisted (AA)CVD with toluene as the solvent. The quality of the films varied according to the precursor used, with the complex [Ga(L(1))H] (8) giving by far the best quality films. Although the films were amorphous as deposited, they could be annealed at 1000 °C to form crystalline Ga(2)O(3). The films were analyzed by powder XRD, SEM, and EDX.

  15. Calorimetric determination of the δ hydride dissolution enthalpy in Zircaloy-4

    International Nuclear Information System (INIS)

    Vizcaino, Pablo; Banchik, Abraham D.

    2003-01-01

    In this work, the dissolution enthalpy, ΔH δ→α , of the δ hydride phase in the αZr matrix in Zircaloy-4 has been determined with a differential scanning calorimeter (DSC) in two different ways: by means of a vant Hoff equation, measuring the terminal solubility temperature in dissolution, TSSd, and by direct measurement of the dissolution heat, Q δ→α , as the area between the base line and the calorimetric curve. The application of the DSC technique to the hydride dissolution heat measurements, a transformation which covers an extended temperature range, is completely original and requires a special treatment of the calorimetric curve. These measurements were done on samples, which practically cover the whole solubility range of hydrogen in αZr phase (80-640 ppm). The values obtained, 36.9 kJ/mol H and 39.3 kJ/mol H respectively, are self-consistent and in good agreement with the values of the more recent revisions, but reduces considerably the scatter of the literature data. (author)

  16. Zr - based alloys as hydride electrodes in Ni-MH batteries

    International Nuclear Information System (INIS)

    Biris, A.R.; Biris, A.S.; Misan, I.; Lupu, D.

    1999-01-01

    Hydrogen storage alloys, MH, are already used in Ni-MH alkaline batteries conquering an important share of the rechargeable nickel-cadmium battery market. This remarkable success is due not only to the replacement of the toxic material, cadmium, by metal hydrides but also to an increased specific energy, which makes them attractive for electric vehicles. Many research groups are concerned in the improvement of the hydride electrode characteristics: hydrogen storage capacity, high-rate discharge ability, increased cycle life. These properties can be modified by substitution of the base components of a given alloy. A comparison of two types of alloys suitable for MH electrodes LaNi 5 able to store 1.36 w/o hydrogen with Zr(Ti)-Ni alloys of the AB 2 Laves phase type structure showed that the latter could absorb higher amounts of hydrogen. We report part of studies on Zr-V-Cr-Ni of the 15 C type Laves phase structure using our original procedure for pasted electrodes. The substitution of Cr for V atoms in ZrV 0.5 Ni 1 . 5 did not increase the discharge capacity. However, it proved to have a remarkable effect on the discharge capacity C at low temperatures. C at - 12 deg. C as compared to 20 deg.C increases up to ∼ 65 % for Cr containing alloys. (authors)

  17. Etude de la transition ferroelectrique-ferroelastique du KD2PO4 forme du front de phase en fonction du gradient thermique

    OpenAIRE

    Kvítek, Zdeněk

    2010-01-01

    Etude de la transition ferroelectrique-ferroelastique du KD2PO4 forme du front de phase en fonction du gradient thermique The thesis explores complex process of first order transition of KD2PO4 crystal from tetragonal phase to ferroelectric - ferroelastic orthorhombic phase and back at temperature 209 K. The experimental set up of nitrogeneous cryostat allowes temperature and temperature gradient variations during simultaneous three axes optical sample observations, dielectric measurements. T...

  18. Polymer-induced liquid precursor (PILP) phases of calcium carbonate formed in the presence of synthetic acidic polypeptides - relevance to biomineralization

    NARCIS (Netherlands)

    Schenk, A.S.; Zope, H.; Kim, Y.; Kros, A.; Sommerdijk, N.A.J.M.; Meldrum, F.C.

    2012-01-01

    Polymer-induced liquid precursor (PILP) phases of calcium carbonate have attracted significant interest due to possible applications in materials synthesis, and their resemblance to intermediates seen in biogenic mineralisation processes. Further, these PILP phases have been formed in vitro using

  19. Infrared diode laser spectroscopy of lithium hydride

    International Nuclear Information System (INIS)

    Yamada, C.; Hirota, E.

    1988-01-01

    The fundamental and hot bands of the vibration--rotation transitions of 6 LiH, 7 LiH, 6 LiD, and 7 LiD were observed by infrared diode laser spectroscopy at Doppler-limited resolution. Lithium hydride molecules were produced by the reaction of the Li vapor with hydrogen at elevated temperatures. Some 40 transitions were observed and, after combined with submillimeter-wave spectra reported by G. M. Plummer et al. [J. Chem. Phys. 81, 4893 (1984)], were analyzed to yield Dunham-type constants with accuracies more than an order of magnitude higher than those published in the literature. It was clearly demonstrated that the Born--Oppenheimer approximation did not hold, and some parameters representing the breakdown were evaluated. The Born--Oppenheimer internuclear distance r/sup BO//sub e/ was derived to be 1.594 914 26 (59) A, where a new value of Planck's constant recommended by CODATA was employed. The relative intensity of absorption lines was measured to determine the ratio of the permanent dipole moment to its first derivative with respect to the internuclear distance: μ/sub e/ [(partialμpartialr)/sub e/ r/sub e/ ] = 1.743(86). The pressure broadening parameter Δν/sub p/ P was determined to be 6.40 (22) MHzTorr by measuring the linewidth dependence on the pressure of hydrogen, which was about four times larger than the value for the dipole--quadrupole interaction estimated by Kiefer and Bushkovitch's theory

  20. A fractographic distinction between hydride cracking and stress corrosion cracking in zircaloys

    International Nuclear Information System (INIS)

    Cox, B.

    1978-06-01

    The fractographic details of SCC and delayed hydride failures are compared by scanning and replica electron microscopy. It is shown that there are distinct features ascribable to the fracture of hydride platelets which are absent from SCC fractures and which distinguish them from fractures produced by delayed hydride cracking. (author)