WorldWideScience

Sample records for ni k-edge xas

  1. Metal and ligand K-edge XAS of organotitanium complexes: metal 4p and 3d contributions to pre-edge intensity and their contributions to bonding.

    Science.gov (United States)

    George, Serena DeBeer; Brant, Patrick; Solomon, Edward I

    2005-01-19

    Titanium cyclopentadienyl (Cp) complexes play important roles as homogeneous polymerization catalysts and have recently received attention as potential anticancer agents. To systematically probe the contribution of the Cp to bonding in organotitanium complexes, Ti K-edge XAS has been applied to TiCl(4) and then to the mono- and bis-Cp complexes, TiCpCl(3) and TiCp(2)Cl(2). Ti K-edge XAS is used as a direct probe of metal 3d-4p mixing and provides insight into the contribution of the Cp to bonding. These data are complimented by Cl K-edge XAS data, which provide a direct probe of the effect of the Cp on the bonding to the spectator chloride ligand. The experimental results are correlated to DFT calculations. A model for metal 3d-4p mixing is proposed, which is based on covalent interactions with the ligands and demonstrates that metal K-pre-edge intensities may be used as a measure of ligand-metal covalency in molecular Ti(IV) systems in noncentrosymmetric environments.

  2. Ligand K-edge XAS, DFT, and TDDFT analysis of pincer linker variations in Rh(i) PNP complexes: reactivity insights from electronic structure.

    Science.gov (United States)

    Lee, Kyounghoon; Wei, Haochuan; Blake, Anastasia V; Donahue, Courtney M; Keith, Jason M; Daly, Scott R

    2016-06-14

    Here we report P K-edge, Cl K-edge, and Rh L3-edge X-ray absorption spectroscopy (XAS) data for Rh[C5H3N-2,6-(XP(t)Bu2)2]Cl, where X = O ((tBu)PONOP; ) or CH2 ((tBu)PNP; ). Solid-state XAS data for and were compared to density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations to identify how changing the PNP pincer linker from O to CH2 affected electronic structure and bonding at Rh(i). Pronounced differences in XAS peak intensities and energies were observed. The P K-edge XAS data revealed a large increase in Rh 4dx(2)-y(2) and P 3p orbital-mixing (Rh-P σ*) in compared to , and pronounced transition energy variations reflected marked differences in orbital energies and compositions. By comparison, the Cl K-edge XAS data revealed only subtle differences in Rh-Cl covalency, although larger splitting between the Rh-Cl π* and σ* transitions was observed in . Analysis of the occupied MOs from DFT (HOMO, HOMO-1, HOMO-2, and HOMO-3) and comparison to the unoccupied MOs involved in XAS revealed a relatively uniform energy increase (ca. 0.3-0.5 eV) for all five 4d-derived molecular orbitals in Rh((tBu)PNP)Cl () compared to Rh((tBu)PONOP)Cl (). The energy shift was relatively invariant with respect to differences in orbital symmetry, bonding type (σ or π), and orbital mixing, which suggested that the increase could be attributed to electrostatic effects. The change in d-orbital energies are consistent with known reactivity differences of Rh((tBu)PONOP)(+) and Rh((tBu)PNP)(+) towards CO, H2, and CH2Cl2, and are explained here by considering how d-orbital energies affect covalent L → M σ bonding and M → L π backbonding.

  3. Effects of higher-coordination shells in garnets detected by XAS at the Al K-edge

    International Nuclear Information System (INIS)

    Marcelli, A.; Wu, Z.; Mottana, A.; Giuli, G.; Paris, E.; Seifert, F.

    1996-03-01

    The aluminium 1 s x-ray-absorption spectra of a series of garnets, pyrope, almandine, spessartine and grossular, are compared to full multiple-scattering calculation using cluster models. An overall good agreement between experiment and calculation, extended also to the edge region,is obtained in the energy range in up to 60 e V above the threshold, provided cluster containing at least 40 atoms are used. The analysis of these garnet XAS spectra provides clear evidence on the effect of probe, XANES spectroscopy at the edge of low Z elements appears to be a perfect tool to investigate the role played by atoms located in higher-coordination shells

  4. Effects of higher-coordination shells in garnets detected by XAS at the Al K-edge

    Energy Technology Data Exchange (ETDEWEB)

    Marcelli, A. [Istituto Nazionale di Fisica Nucleare, Frascati (Italy). Lab. Nazionale di Frascati; Wu, Z. [CNRS UMR 110, Laboratoire de Chimie des Solides, Nantes Cedex (France). Institut de materiaux de Nantes; Mottana, A. [Roma III Univ., Rome (Italy). Dipartimento di Scienze Geologiche; Giuli, G.; Paris, E. [Camerino Univ., Camerino (Italy).Diparimento di Scienze della Terra; Seifert, F [Univ. Bayreuth, Bayreuth (Italy). Bayerisches Geoinstitut (Germany)

    1996-03-01

    The aluminium 1 s x-ray-absorption spectra of a series of garnets, pyrope, almandine, spessartine and grossular, are compared to full multiple-scattering calculation using cluster models. An overall good agreement between experiment and calculation, extended also to the edge region,is obtained in the energy range in up to 60 e V above the threshold, provided cluster containing at least 40 atoms are used. The analysis of these garnet XAS spectra provides clear evidence on the effect of probe, XANES spectroscopy at the edge of low Z elements appears to be a perfect tool to investigate the role played by atoms located in higher-coordination shells.

  5. K-edge resonant x-ray magnetic scattering from a transition-metal oxide: NiO

    DEFF Research Database (Denmark)

    Hill, J.P.; Kao, C.C.; McMorrow, D.F.

    1997-01-01

    We report the observation of resonant x-ray magnetic scattering in the vicinity of the Ni K edge in the antiferromagnet NiO. An approximately twofold increase in the scattering is observed as the incident photon energy is tuned through a pre-edge feature in the absorption spectrum, associated wit...... with quadrupolar (1s-->3d) transitions. No enhancement is observed at the dipolar (1s-->4p) maximum. The quadrupolar resonant scattering amplitude is estimated to be similar to 0.01r(0)....

  6. Identification of Ni2C electronic states in graphene-Ni(111) growth through resonant and dichroic angle-resolved photoemission at the C K -edge

    Science.gov (United States)

    Drera, G.; Cepek, C.; Patera, L. L.; Bondino, F.; Magnano, E.; Nappini, S.; Africh, C.; Lodi-Rizzini, A.; Joshi, N.; Ghosh, P.; Barla, A.; Mahatha, S. K.; Pagliara, S.; Giampietri, A.; Pintossi, C.; Sangaletti, L.

    2017-10-01

    The graphene-Ni(111) (GrNi) growth via chemical vapor deposition has been explored by resonant, angle-resolved, and dichroic photoemission spectroscopy (soft x-ray Res-ARPES) in order to identify the possible contributions to the electronic structure deriving from different phases that can coexist in this complex system. We provide evidences of electronic states so far unexplored at the Γ ¯ point of GrNi, appearing at the C K -edge resonance. These states show both circular dichroism (CD) and k dependence, suggesting a long-range orbital ordering, as well as a coherent matching with the underlying lattice. Through a comparison of core-level photoemission, valence band resonances, and constant initial-state spectroscopy, we demonstrate that these states are actually induced by a low residual component of nickel carbide (Ni2C ). These results also show that caution must be exercised while interpreting x-ray magnetic circular dichroism collected on C K -edge with Auger partial yield method, due to the presence of CD in photoelectron spectra unrelated to magnetic effects.

  7. Difference between Cr and Ni K-edge XANES spectra of rust layers formed on Fe-based binary alloys exposed to Cl-rich environment

    International Nuclear Information System (INIS)

    Konishi, Hiroyuki; Mizuki, Jun'ichiro; Yamashita, Masato; Uchida, Hitoshi

    2005-01-01

    The rust layer formed on weathering steel possesses a strong protective ability against corrosives in an atmospheres. This ability is related to the structure of the rust layer. The difference in the protective ability of a rust layer. The difference in the protective ability of a rust layer in a Cl-rich environment between conventional weathering steel containing Cr and advanced weathering steel containing Ni is believed to be caused by the differences in local structural and chemical properties between alloying elements. Cr and Ni, in the rust layer. In order to examine the effect of these alloying elements on the structure of the rust layer formed on steel in a Cl-rich environment, we have performed Cr and Ni K-edge X-ray absorption near-edge structure (XANES) measurements for the rust layer of Fe-Cr and Fe-Ni binary alloys exposed to a Cl-rich atmosphere using synchrotron radiation. The results of the Cr K-edge XANES measurements for the rust layer of Fe-Cr binary alloys show that the atomic geometry around Cr depends on the concentration of Cr. Therefore, it is expected that the local structure around Cr in the rust layer is unstable. On the other hand, from the results of the Ni K-edge XANES measurements for the rust layer of Fe-Ni binary alloys. Ni is considered to be positioned at a specific site in the crystal structure of a constituent of the rust layer, such as akaganeite or magnetite. As a consequence, Ni negligibly interacts with Cl - ions in the rust layer. (author)

  8. Cl K-edge XANES spectra of atmospheric rust on Fe, Fe-Cr and Fe-Ni alloys exposed to saline environment

    International Nuclear Information System (INIS)

    Konishi, Hiroyuki; Mizuki, Jun'ichiro; Yamashita, Masato; Uchida, Hitoshi

    2004-01-01

    Cl K-edge XANES measurements of atmospheric corrosion products (rust) formed on Fe, Fe-Ni and Fe-Cr alloys in chloride pollution have been performed using synchrotron radiation in order to clarify roles of anticorrosive alloying elements and of Cl in the corrosion resistance of weathering steel. The spectra of binary alloys show a shoulder structure near the absorption edge. The intensity of the shoulder peak depends on the kind and amount of the alloying element, whereas the energy position is invariant. This indicates that Cl is not combined directly with alloying elements in the rust. (author)

  9. Structural disorder and electronic hybridization in Ni{sub c}Mg{sub 1-c}O solid solutions probed by XANES at the oxygen K edge

    Energy Technology Data Exchange (ETDEWEB)

    Chen Dongliang [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Zhong Jun [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Chu Wangsheng [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Wu Ziyu [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Kuzmin, Alexei [Institute of Solid State Physics, University of Latvia, Kengaraga 8, LV-1063 Riga (Latvia); Mironova-Ulmane, Nina [Institute of Solid State Physics, University of Latvia, Kengaraga 8, LV-1063 Riga (Latvia); Marcelli, Augusto [Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare, PO Box 13, 00044 Frascati (Italy)

    2007-09-05

    A series of Ni{sub c}Mg{sub 1-c}O solid solutions has been studied for the first time looking at the structural disorder by means of x-ray absorption near-edge-structure (XANES) spectroscopy at the oxygen K edge. The experimental XANES signals were analysed within the full multiple scattering formalism and were interpreted taking into account clusters of up to 15 coordination shells around an absorbing oxygen atom. The substitution of nickel atoms by magnesium atoms results in a dramatic decrease of the empty density of states in the conduction band close to the Fermi level due to an exchange of the 3d(Ni)-2p(O) interaction with 3p(Mg)-2p(O). Besides, a simultaneous small decrease of the 3d(Ni)-2p(O) hybridization is also induced by the lattice expansion, determined by the difference in ionic radii between nickel and magnesium ions.

  10. K-edge densitometer (KED)

    Energy Technology Data Exchange (ETDEWEB)

    Sprinkle, J.K.; Hansen, W.J.

    1993-02-11

    In 1979, a K-edge densitometer (KED) was installed by the Safeguards Assay group from Los Alamos National Laboratory in the PNC reprocessing plant at Tokai-mura, Japan. It uses an active nondestructive assay technique, KED, to measure the plutonium concentration of the product solution. The measurement uncertainty of an assay depends on the count time chosen, but can be 0.5% or better. The computer hardware and software were upgraded in 1992. This manual describes the operation of the instrument, with an emphasis on the user interface to the software.

  11. Characterization of rust layer formed on Fe, Fe-Ni and Fe-Cr alloys exposed to Cl-rich environment by Cl and Fe K-edge XANES measurements

    International Nuclear Information System (INIS)

    Konishi, Hiroyuki; Mizuki, Jun'ichiro; Yamashita, Masato; Uchida, Hitoshi

    2005-01-01

    Chloride in atmosphere considerably reduces the corrosion resistance of conventional weathering steel containing a small amount of Cr. Ni is an effective anticorrosive element for improving the corrosion resistance of steel in a Cl-rich environment. In order to clarify the structure of the protective rust layer of weathering steel, Cl and Fe K-edge X-ray absorption near edge structure (XANES) spectra of atmospheric corrosion products (rust) formed on Fe, Fe-Ni and Fe-Cr alloys exposed to Cl-rich atmosphere were measured. The Fe K-XANES measurements enable the characterization of mixture of iron oxides such as rust. The chemical composition of the rust was determined by performing pattern fitting of the measured spectra. All the rust is composed mainly of goethite, akaganeite, lepidocrocite and magnetite. Among these iron oxides, akaganeite in particular is the major component in the rust. Additionally, the amount of akaganeite in the rust of Fe-Ni alloy is much greater than that in rust of Fe-Cr alloy. Akaganeite is generally considered to facilitate the corrosion of steel, but our results indicate that akaganeite in the rust of Fe-Ni alloy is quantitatively different from that in rust of Fe-Cr alloy and does not facilitate the corrosion of steel. The shoulder peak observed in Cl K-XANES spectra reveals that the rust contains a chloride other than akaganeite. The energy of the shoulder peak does not correspond to that of any well-known chlorides. In the measured spectra, there is no proof that Cl, by combining with the alloying element, inhibits the alloying element from acting in corrosion resistance. The shoulder peak appears only when the content of the alloying element is lower than a certain value. This suggests that the generation of the unidentified chloride is related to the corrosion rate of steel. (author)

  12. LUCIA, a microfocus soft XAS beamline

    Energy Technology Data Exchange (ETDEWEB)

    Flank, A.-M. [LURE, Bat. 209D, Centre Universitaire, BP 34, F-91898 Orsay (France)]. E-mail: anne-marie.flank@psi.ch; Cauchon, G. [LURE, Bat. 209D, Centre Universitaire, BP 34, F-91898 Orsay (France); Lagarde, P. [LURE, Bat. 209D, Centre Universitaire, BP 34, F-91898 Orsay (France); Bac, S. [Paul Scherrer Institut, SLS, Villigen-PSI, CH 5232 (Switzerland); Janousch, M. [Paul Scherrer Institut, SLS, Villigen-PSI, CH 5232 (Switzerland); Wetter, R. [Paul Scherrer Institut, SLS, Villigen-PSI, CH 5232 (Switzerland); Dubuisson, J.-M. [SOLEIL, BP 48, F-91192 Gif-sur-Yvette (France); Idir, M. [SOLEIL, BP 48, F-91192 Gif-sur-Yvette (France); Langlois, F. [SOLEIL, BP 48, F-91192 Gif-sur-Yvette (France); Moreno, T. [SOLEIL, BP 48, F-91192 Gif-sur-Yvette (France); Vantelon, D. [SOLEIL, BP 48, F-91192 Gif-sur-Yvette (France)

    2006-05-15

    The beamline 'LUCIA' (line for ultimate characterization by imaging and absorption) is a 'tender' (0.8-8 keV) X-ray microprobe with capabilities for chemical speciation by micro-X-ray absorption spectroscopy ({mu}-XAS) and for elemental mapping by X-ray micro-fluorescence ({mu}-XRF). It allows the possibility to study heterogeneous samples at a micrometer scale and to combine these two element-specific and non-destructive techniques. A monochromatic beam of a few micrometer in size is incident on a sample which is mounted on a scanning x-y-z stage. {mu}-XRF shows the location of the elements, their relative abundances, and their association with other elements. One can take advantage of the monochromatic beam which allows separating out different elements by their absorption edges. After mapping the fluorescence, spots of interest can be analysed by XAS to determine the speciation (local chemistry, quantitative determination of the local geometric structure around the absorbing atom) of the elements and how they depend on the different components. Installed at first at the SLS of the Paul Scherrer Institute (Switzerland), the LUCIA beamline will be transferred to SOLEIL by the beginning of 2008. The energy range offered by the beamline corresponds to the best performances of SLS and SOLEIL in terms of brightness. It allows XAS experiments at the K edge of elements ranging from Na to Fe, L edges from Ni to Gd, and M edges of rare earths and actinides.

  13. Vanadium K-edge x-ray absorption spectroscopy reveals species differences within the same ascidian genera. A comparison of whole blood from Ascidia nigra and Ascidia ceratodes.

    Science.gov (United States)

    Frank, P; Hodgson, K O; Kustin, K; Robinson, W E

    1998-09-18

    Vanadium K-edge x-ray absorption spectroscopy (XAS) was used to examine whole blood preparations from the tunicates Ascidia nigra and Ascidia ceratodes. Each XAS spectrum exhibits a rising edge inflection near 5480 eV characteristic of vanadium(III) and an intensity maximum at 5484.0 eV. In A. ceratodes blood cells, intrinsic aquo-VSO4+ complex ion is indicated by an inflection feature at 5476 eV in the first derivative of the vanadium K-edge XAS spectrum, but this feature is notably absent from the first derivative of the vanadium K-edge spectrum of blood cells from A. nigra. A strong pre-edge feature at 5468.6 eV also uniquely distinguishes the vanadium K-edge XAS spectrum of A. nigra blood cells, implying that vanadyl ion represents approximately 25% of the endogenous vanadium. However, the energy position of the rising edge inflection of the vanadium K-edge XAS spectrum of A. nigra (5479.5 eV) is 1 eV lower than that of A. ceratodes (5480.5 eV), the reverse of any expected shift arising from the endogenous vanadyl ion. Thus, in contrast to A. ceratodes, a significant fraction of the blood cell vanadium(III) in A. nigra is apparently in a ligation environment substantially different from that provided by water. These novel species-related differences may have taxonomic significance.

  14. Photoelectric interaction around the K edge

    International Nuclear Information System (INIS)

    Murty, V.R.K.; Rao, K.S.; Parthasaradhi, K.; Rao, J.R.; Lakshminarayana, V.

    1977-01-01

    Total photon cross sections are determined around the K edges of four elements Cu, Sn, Pb and U using a Ge(Li) detector, argon and krypton proportional counters on a 'good geometry' set-up. The total photoelectric cross sections are extracted by subtracting the small scattering contribution from the total photon cross sections. Total-to-K-shell photoelectric cross section ratios (K-jump ratios) are evaluated by extrapolating the total photon cross section data to the K edge. An analysis of the data is presented. (author)

  15. Photoelectric interaction below the K edge

    International Nuclear Information System (INIS)

    Reddy, D.K.S.; Premachand, K.; Radha Krishna Murty, V.; Rama Rao, J.; Lakshminarayana, V.

    1976-01-01

    Total photon cross sections are measured, using the transmission method in the heavy elements U, Th, Pb, and Au at energies of 30.9, 35.9, and 55.4 keV, to study the photoelectric interaction below the K edges of these elements. A krypton-filled proportional counter with a 512-channel analyzer is used as the detector of photons. The photoelectric cross sections, obtained by subtracting the small scattering contributions from the total cross section, are compared with theoretical predictions of Scofield and of Storm and Israel. General agreement is obtained, except for U and Th at 30.9 keV where the present experimental values show a slight preference to the calculations of Storm and Israel rather than the theoretical ones used by Scofield

  16. Sulfur K-edge X-ray absorption spectroscopy and time-dependent density functional theory of arsenic dithiocarbamates.

    Science.gov (United States)

    Donahue, Courtney M; Pacheco, Juan S Lezama; Keith, Jason M; Daly, Scott R

    2014-06-28

    S K-edge X-ray absorption spectroscopy (XAS) and time-dependent density functional theory (TDDFT) calculations were performed on a series of As[S2CNR2]3 complexes, where R2 = Et2, (CH2)5 and Ph2, to determine how dithiocarbamate substituents attached to N affect As[S2CNR2]3 electronic structure. Complimentary [PPh4][S2CNR2] salts were also studied to compare dithiocarbamate bonding in the absence of As. The XAS results indicate that changing the orientation of the alkyl substituents from trans to cis (R2 = Et2vs. (CH2)5) yields subtle variations whereas differences associated with a change from alkyl to aryl are much more pronounced. For example, despite the differences in As 4p mixing, the first features in the S K-edge XAS spectra of [PPh4][S2CNPh2] and As[S2CNPh2]3 were both shifted by 0.3 eV compared to their alkyl-substituted derivatives. DFT calculations revealed that the unique shift observed for [PPh4][S2CNPh2] is due to phenyl-induced splitting of the π* orbitals delocalized over N, C and S. A similar phenomenon accounts for the shift observed for As[S2CNPh2]3, but the presence of two unique S environments (As-S and As···S) prevented reliable analysis of As-S covalency from the XAS data. In the absence of experimental values, DFT calculations revealed a decrease in As-S orbital mixing in As[S2CNPh2]3 that stems from a redistribution of electron density to S atoms participating in weaker As···S interactions. Simulated spectra obtained from TDDFT calculations reproduce the experimental differences in the S K-edge XAS data, which suggests that the theory is accurately modeling the experimental differences in As-S orbital mixing. The results highlight how S K-edge XAS and DFT can be used cooperatively to understand the electronic structure of low symmetry coordination complexes containing S atoms in different chemical environments.

  17. Investigation of Prussian Blue Analogs by XMCD at the K-edge of transition metals

    International Nuclear Information System (INIS)

    Bordage, A; Bleuzen, A; Nataf, L; Baudelet, F

    2016-01-01

    Despite transition metal (TM) K-edge x-ray magnetic circular dichroism (XMCD) seems an interesting tool to get magnetic and structural information at the atomic scale, the effects originating this signal are still poorly understood. We thus initiated a deep investigation of the TM K-edge XMCD using Prussian Blue analogs (PBA) as model-compounds. In a recent study of the NiFe PBA family, we demonstrated that the XMCD signals at the TM K-edges strongly vary with external (mechanical) or internal (chemical) pressure and so that they are highly sensitive to small structural distortions. Following these first results, we extended this approach to the MnFe and CoFe families to evaluate the effect of electronic parameters (number of unpaired electrons of the M II TM) on the XMCD signal. All the results set milestones in the disentanglement of the components originating the XMCD signals at the K-edge of TM and will eventually help in a better understanding of the photomagnetic properties of PBAs. (paper)

  18. Experimental and theoretical correlations between vanadium K-edge X-ray absorption and Kβ emission spectra.

    Science.gov (United States)

    Rees, Julian A; Wandzilak, Aleksandra; Maganas, Dimitrios; Wurster, Nicole I C; Hugenbruch, Stefan; Kowalska, Joanna K; Pollock, Christopher J; Lima, Frederico A; Finkelstein, Kenneth D; DeBeer, Serena

    2016-09-01

    A series of vanadium compounds was studied by K-edge X-ray absorption (XAS) and K[Formula: see text] X-ray emission spectroscopies (XES). Qualitative trends within the datasets, as well as comparisons between the XAS and XES data, illustrate the information content of both methods. The complementary nature of the chemical insight highlights the success of this dual-technique approach in characterizing both the structural and electronic properties of vanadium sites. In particular, and in contrast to XAS or extended X-ray absorption fine structure (EXAFS), we demonstrate that valence-to-core XES is capable of differentiating between ligating atoms with the same identity but different bonding character. Finally, density functional theory (DFT) and time-dependent DFT calculations enable a more detailed, quantitative interpretation of the data. We also establish correction factors for the computational protocols through calibration to experiment. These hard X-ray methods can probe vanadium ions in any oxidation or spin state, and can readily be applied to sample environments ranging from solid-phase catalysts to biological samples in frozen solution. Thus, the combined XAS and XES approach, coupled with DFT calculations, provides a robust tool for the study of vanadium atoms in bioinorganic chemistry.

  19. Time-Dependent Density Functional Calculations of Ligand K-Edge X-Ray Absorption Spectra

    Energy Technology Data Exchange (ETDEWEB)

    DeBeer George, S.; /SLAC, SSRL; Petrenko, T.; Neese, F.

    2007-07-10

    X-ray absorption spectra (XAS) at the Cl and S K edge and Mo L edge have been calculated at the TDDFT level for a series of dioxomolybdenum complexes LMoO{sub 2}X (L = hydrotris(3,5-dimethyl-1-pyrazolyl)borate, X = Cl, SCH{sub 2}Ph, OPh), which play an important role in modeling the catalytic cycle of the sulfite oxidase enzyme. Also, the XAS spectra of model molecules of the Mo complexes have been simulated and interpreted in terms of the Mo 4d orbital splitting, in order to find possible correlations with the spectral pattern of the complexes. Comparison with the available experimental data allows us to assess the performances of the present computational scheme to describe the core excitations in large bioinorganic systems. The theoretical interpretation of the spectral features of both the metal and ligand core excitations in terms of the oscillator strength distribution provides important insight into the covalency of the metal-ligand bond.

  20. Defining chemical species in complex environments using K-edge X-ray absorption spectroscopy: vanadium in intact blood cells and Henze solution from the tunicate Ascidia ceratodes.

    Science.gov (United States)

    Frank, P; Hodgson, K O

    2000-12-25

    A K-edge X-ray absorption spectrum (XAS) fitting approach has been developed to speciate elements of interest in complex materials and used here to model the storage of biological vanadium within whole blood cells from the tunicate Ascidia ceratodes. The response of the K-edge XAS of solution-phase V(III) to increasing c(sulfate) at constant pH 1.8 produced specific and systematic effects in the preedge transition at 5468.8 eV (preedge transitions: 1s-->4A2 at 5464.9 +/- 0.1 eV, 1s-->4T2 at 5466.9 +/- 0.1 eV, and 1s-->4T1 at 5468.8 +/- 0.1 eV for 11 different V(III)/sulfate solutions). In contrast, variations in acidity (as pH) at constant c(sulfate) systematically modified the V(III) preedge XAS at 5466.9 eV. The energy position of the K-edge absorption maximum also serially shifted -0.32 eV/pH unit, from 5483.7 eV (pH 3.0) to 5484.7 eV (pH 0.3). Fits to the V-K XAS of two samples of A. ceratodes whole blood cells representing dozens of animals implied storage of V(III) ions in four predominant solution regimes: approximately 10% high sulfate/pH 0 acid; approximately 40% high sulfate/pH 1.8 acid; approximately 40% moderate sulfate/pH 1.8 acid; approximately 10% moderate sulfate/pH 3 acid. For lysed blood cells, the best fit represented 63% of the V(III) in a pH 1.6 sulfate-free environment and a further 16% in acidic sulfate solution. Nearly 18% of lysed cells vanadium(III) appeared in a tris(catecholate)-like environment. A detailed speciation of biological vanadium complex ions was calculated from these fits by application of the known equilibrium constants governing V(III) and sulfate in acidic aqueous solution. The utility of blood cell V(III) to ascidians is discussed. Fits to K-edge XAS spectra using the XAS spectra of appropriate models are suggested to be generally applicable to elucidating the state of metal ions in a wide variety of complex environments.

  1. Material Discrimination Based on K-edge Characteristics

    Directory of Open Access Journals (Sweden)

    Peng He

    2013-01-01

    Full Text Available Spectral/multienergy CT employing the state-of-the-art energy-discriminative photon-counting detector can identify absorption features in the multiple ranges of photon energies and has the potential to distinguish different materials based on K-edge characteristics. K-edge characteristics involve the sudden attenuation increase in the attenuation profile of a relatively high atomic number material. Hence, spectral CT can utilize material K-edge characteristics (sudden attenuation increase to capture images in available energy bins (levels/windows to distinguish different material components. In this paper, we propose an imaging model based on K-edge characteristics for maximum material discrimination with spectral CT. The wider the energy bin width is, the lower the noise level is, but the poorer the reconstructed image contrast is. Here, we introduce the contrast-to-noise ratio (CNR criterion to optimize the energy bin width after the K-edge jump for the maximum CNR. In the simulation, we analyze the reconstructed image quality in different energy bins and demonstrate that our proposed optimization approach can maximize CNR between target region and background region in reconstructed image.

  2. Electronic and crystallographic properties of the system CeY2Ni9Dx (0-bar x-bar 8.7) measured by X-ray absorption spectroscopy

    International Nuclear Information System (INIS)

    Latroche, M.; Paul-Boncour, V.; Percheron-Guegan, A.

    2005-01-01

    The electronic and crystallographic properties of CeY 2 Ni 9 D x (0-bar x-bar 8.7D/f.u.) have been investigated by X-ray absorption spectroscopy (XAS). The PuNi 3 -type structure (space group R3-bar m) is described as a stacking of RM 2 and RM 5 units (R: Y, Ce; M: Ni). Hydrogen occupies the RM 2 units only. The Ce-L III and Ni-K edges have been measured by XAS as a function of hydrogen uptake. A heterogeneous mixed valence state is reported for Ce in the hydride and related to differences in deuterium site occupancies. Huge anisotropic volume expansion is observed and is related to hydrogen absorption and valence change of Ce

  3. Direct observation of the pressure-induced charge redistribution in BiNiO3 by x-ray absorption spectroscopy

    Science.gov (United States)

    Mizumaki, Masaichiro; Ishimatsu, Naoki; Kawamura, Naomi; Azuma, Masaki; Shimakawa, Yuichi; Takano, Mikio; Uozumi, Takayuki

    2009-12-01

    To investigate the change in the electronic structure of BiNiO3 accompanied by metal-insulator (MI) transition, we measured x-ray absorption spectroscopy (XAS) spectra at the NiK and BiL edges under various pressures up to 6 GPa. Both BiL3 and NiK edge XAS spectra clearly change at 4 GPa, indicating the electronic state in Bi and Ni ion changes. A quantitative analysis of the NiK edge spectra in the pre-edge region based on the charge-transfer cluster model including multiplet terms revealed that the electronic configuration changes from d8 in the insulating phase to 56%d7+44%d8Ḻ in the metal phase. From these results, we concluded that the MI transition in BiNiO3 is induced by the collapse of charge-transfer gap and is governed by the redistribution of O2p ligand holes.

  4. Zn K-edge XANES in nanocrystalline ZnO

    International Nuclear Information System (INIS)

    Kuzmin, A; Larcheri, S; Rocca, F

    2007-01-01

    Zn K-edge XANES in ZnO has been calculated within the full-multiple-scattering (FMS) and finite difference method (FDM) formalism using the ab initio FDMNES code. The influence of non-muffin-tin potential, bulk defects, surface termination and polarization effects on XANES has been analysed. The obtained theoretical results are compared with available experimental data for polycrystalline and nanocrystalline zinc oxide systems

  5. Zn K-edge XANES in nanocrystalline ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Kuzmin, A [Institute of Solid State Physics, University of Latvia, Riga (Latvia); Larcheri, S [IFN-CNR, Istituto di Fotonica e Nanotecnologie del Consiglio Nazionale delle Ricerche, Sezione di Trento, Povo (Trento) (Italy); Rocca, F [IFN-CNR, Istituto di Fotonica e Nanotecnologie del Consiglio Nazionale delle Ricerche, Sezione di Trento, Povo (Trento) (Italy)

    2007-12-15

    Zn K-edge XANES in ZnO has been calculated within the full-multiple-scattering (FMS) and finite difference method (FDM) formalism using the ab initio FDMNES code. The influence of non-muffin-tin potential, bulk defects, surface termination and polarization effects on XANES has been analysed. The obtained theoretical results are compared with available experimental data for polycrystalline and nanocrystalline zinc oxide systems.

  6. K-edge radiography: Comparison of two detectors

    International Nuclear Information System (INIS)

    Albertin, F.

    2011-01-01

    Non-invasive and non-destructive diagnostics represent an important resource for historians and conservators for a deep knowledge of cultural heritage materials. K-edge radiography allows to obtain an elemental mapping of painting layers. It is performed at Larix laboratory, in Ferrara, by quasi-monochromatic X-ray beams obtained via Bragg diffraction. This technique takes advantage of the sharp rise of X-ray absorption coefficient of the elements, the K-edge discontinuity. Working at different energies, below and above the K-edge peak, allows to make the recognition of the target element. Each pigment is characterized by one or more elements; mapping an element means finding the spatial distribution of that pigment. Two different detectors have been used to perform an efficiency comparison at different energies. A commercial Front Illuminated CCD, 3075 x 128 pixels by Hamamatsu and an Edge-on SSD detector, designed by the Department of Science and Advanced Technology of Piemonte Orientale University, 512 Si-strip, 300 x 100 μm 2 , 1 cm thick. In this paper the elemental distributions on canvas test objects with different pigment layers are presented.

  7. Unexpected covalency from actinide 5f orbital interactions (An = Th, U, Np, Pu) determined from chlorine K-edge X-ray absorption spectroscopy and electronic structure theory

    International Nuclear Information System (INIS)

    Clark, D.L.; Batista, E.R.; Boland, K.S.

    2010-01-01

    We have employed Cl K-edge XAS and multiple levels of sophisticated electronic structure calculations on a series of simple octahedral light actinide (Th, U, Np, Pu) chloride salts, AnCl 6 n- in order to assess the relative roles of the valence 5f and 6d orbitals in chemical bonding. Chlorine K-edge X-ray absorption spectroscopy on AnCl 6 n- (An = Th, U, Np, Pu) systems indicates the presence of covalent interactions between both Cl 3p and An 5f and 6d orbitals, with the relative contributions changing across the series. Electronic structure calculations indicate the predominant covalent interactions are expected to occur through An-Cl bonding via t 1u and t 2u interactions with the An 5f orbitals, and through t 2g and e g interactions with An 6d orbitals. For the Cl K-edge data therefore, we expect bound state transitions from Cl 1s → e g (σ), t 2g (π), and t 1u (σ + π) orbitals. Qualitatively, the Cl K-edge data fulfills these expectations

  8. Probing covalency in halogen bonds through donor K-edge X-ray absorption spectroscopy: polyhalides as coordination complexes.

    Science.gov (United States)

    Mustoe, Chantal L; Gunabalasingam, Mathusan; Yu, Darren; Patrick, Brian O; Kennepohl, Pierre

    2017-10-13

    The properties of halogen bonds (XBs) in solid-state I 2 X - and I 4 X - materials (where X = Cl, Br) are explored using donor K-edge X-ray absorption spectroscopy (XAS) to experimentally determine the degree of charge transfer in such XB interactions. The degree of covalency in these bonds is substantial, even in cases where significantly weaker secondary interactions are observed. These data, in concert with previous work in this area, suggests that certain halogen bonds have covalent contributions to bonding that are similar to, and even exceed, those observed in transition metal coordinate bonds. For this reason, we suggest that XB interactions of this type be denoted in a similar way to coordination bonds (X → Y) as opposed to using a representation that is the same as for significantly less covalent hydrogen bonds (XY).

  9. Investigating the interstellar dust through the Fe K-edge

    Science.gov (United States)

    Rogantini, D.; Costantini, E.; Zeegers, S. T.; de Vries, C. P.; Bras, W.; de Groot, F.; Mutschke, H.; Waters, L. B. F. M.

    2018-01-01

    Context. The chemical and physical properties of interstellar dust in the densest regions of the Galaxy are still not well understood. X-rays provide a powerful probe since they can penetrate gas and dust over a wide range of column densities (up to 1024 cm-2). The interaction (scattering and absorption) with the medium imprints spectral signatures that reflect the individual atoms which constitute the gas, molecule, or solid. Aims: In this work we investigate the ability of high resolution X-ray spectroscopy to probe the properties of cosmic grains containing iron. Although iron is heavily depleted into interstellar dust, the nature of the Fe-bearing grains is still largely uncertain. Methods: In our analysis we use iron K-edge synchrotron data of minerals likely present in the ISM dust taken at the European Synchrotron Radiation Facility. We explore the prospects of determining the chemical composition and the size of astrophysical dust in the Galactic centre and in molecular clouds with future X-ray missions. The energy resolution and the effective area of the present X-ray telescopes are not sufficient to detect and study the Fe K-edge, even for bright X-ray sources. Results: From the analysis of the extinction cross sections of our dust models implemented in the spectral fitting program SPEX, the Fe K-edge is promising for investigating both the chemistry and the size distribution of the interstellar dust. We find that the chemical composition regulates the X-ray absorption fine structures in the post edge region, whereas the scattering feature in the pre-edge is sensitive to the mean grain size. Finally, we note that the Fe K-edge is insensitive to other dust properties, such as the porosity and the geometry of the dust. The absorption, scattering, and extinction cross sections of the compounds are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/609/A22

  10. Phosphorus K-edge XANES spectroscopy of mineral standards

    International Nuclear Information System (INIS)

    Ingall, Ellery D.; Brandes, Jay A.; Diaz, Julia M.; Jonge, Martin D. de; Paterson, David; McNulty, Ian; Elliott, W. Crawford; Northrup, Paul

    2011-01-01

    Phosphorus K-edge XANES spectra are presented for a diverse set of 44 phosphate minerals. Phosphorus K-edge X-ray absorption near-edge structure (XANES) spectroscopy was performed on phosphate mineral specimens including (a) twelve specimens from the apatite group covering a range of compositional variation and crystallinity; (b) six non-apatite calcium-rich phosphate minerals; (c) 15 aluminium-rich phosphate minerals; (d) ten phosphate minerals rich in either reduced iron or manganese; (e) four phosphate minerals rich in either oxidized iron or manganese; (f) eight phosphate minerals rich in either magnesium, copper, lead, zinc or rare-earth elements; and (g) four uranium phosphate minerals. The identity of all minerals examined in this study was independently confirmed using X-ray powder diffraction. Minerals were distinguished using XANES spectra with a combination of pre-edge features, edge position, peak shapes and post-edge features. Shared spectral features were observed in minerals with compositions dominated by the same specific cation. Analyses of apatite-group minerals indicate that XANES spectral patterns are not strongly affected by variations in composition and crystallinity typical of natural mineral specimens

  11. Thermodynamic Modeling of Poorly Complexing Metals in Concentrated Electrolyte Solutions: An X-Ray Absorption and UV-Vis Spectroscopic Study of Ni(II) in the NiCl2-MgCl2-H2O System

    Science.gov (United States)

    Zhang, Ning; Brugger, Joël; Etschmann, Barbara; Ngothai, Yung; Zeng, Dewen

    2015-01-01

    Knowledge of the structure and speciation of aqueous Ni(II)-chloride complexes is important for understanding Ni behavior in hydrometallurgical extraction. The effect of concentration on the first-shell structure of Ni(II) in aqueous NiCl2 and NiCl2-MgCl2 solutions was investigated by Ni K edge X-ray absorption (XAS) and UV-Vis spectroscopy at ambient conditions. Both techniques show that no large structural change (e.g., transition from octahedral to tetrahedral-like configuration) occurs. Both methods confirm that the Ni(II) aqua ion (with six coordinated water molecules at RNi-O = 2.07(2) Å) is the dominant species over the whole NiCl2 concentration range. However, XANES, EXAFS and UV-Vis data show subtle changes at high salinity (> 2 mol∙kg-1 NiCl2), which are consistent with the formation of small amounts of the NiCl+ complex (up to 0.44(23) Cl at a Ni-Cl distance of 2.35(2) Å in 5.05 mol∙kg-1 NiCl2) in the pure NiCl2 solutions. At high Cl:Ni ratio in the NiCl2-MgCl2-H2O solutions, small amounts of [NiCl2]0 are also present. We developed a speciation-based mixed-solvent electrolyte (MSE) model to describe activity-composition relationships in NiCl2-MgCl2-H2O solutions, and at the same time predict Ni(II) speciation that is consistent with our XAS and UV-Vis data and with existing literature data up to the solubility limit, resolving a long-standing uncertainty about the role of chloride complexing in this system. PMID:25885410

  12. Thermodynamic modeling of poorly complexing metals in concentrated electrolyte solutions: an X-ray absorption and UV-Vis spectroscopic study of Ni(II in the NiCl2-MgCl2-H2O system.

    Directory of Open Access Journals (Sweden)

    Ning Zhang

    Full Text Available Knowledge of the structure and speciation of aqueous Ni(II-chloride complexes is important for understanding Ni behavior in hydrometallurgical extraction. The effect of concentration on the first-shell structure of Ni(II in aqueous NiCl2 and NiCl2-MgCl2 solutions was investigated by Ni K edge X-ray absorption (XAS and UV-Vis spectroscopy at ambient conditions. Both techniques show that no large structural change (e.g., transition from octahedral to tetrahedral-like configuration occurs. Both methods confirm that the Ni(II aqua ion (with six coordinated water molecules at RNi-O = 2.07(2 Å is the dominant species over the whole NiCl2 concentration range. However, XANES, EXAFS and UV-Vis data show subtle changes at high salinity (> 2 mol∙kg(-1 NiCl2, which are consistent with the formation of small amounts of the NiCl+ complex (up to 0.44(23 Cl at a Ni-Cl distance of 2.35(2 Å in 5.05 mol∙kg(-1 NiCl2 in the pure NiCl2 solutions. At high Cl:Ni ratio in the NiCl2-MgCl2-H2O solutions, small amounts of [NiCl2]0 are also present. We developed a speciation-based mixed-solvent electrolyte (MSE model to describe activity-composition relationships in NiCl2-MgCl2-H2O solutions, and at the same time predict Ni(II speciation that is consistent with our XAS and UV-Vis data and with existing literature data up to the solubility limit, resolving a long-standing uncertainty about the role of chloride complexing in this system.

  13. K-Edge Subtraction Angiography with Synchrotron X-Rays

    International Nuclear Information System (INIS)

    Giacomini, John C.

    1996-01-01

    The purpose of this project was to utilize dual energy, monochromatic X-rays produced from synchrotrons radiation in order to obtain noninvasive medical imaging. The application of synchrotrons radiation to medical imaging is based on the principle of iodine dichromography, first described by Bertil Jacobson of the Karolinska Institute in 1953. Medical imaging using synchrotrons radiation and K-edge dichromography was pioneered at Stanford University under the leadership of Dr. Ed Rubenstein, and the late Nobel Laureate in Physics, Dr. Robert Hofstadter. With progressive refinements in hardware, clinical-quality images were obtained of human coronary arteries utilizing peripheral injections of iodinated contrast agent. These images even now are far superior to those being presented by investigators using MRI as an imaging tool for coronary arteries. However, new supplies and instruments in the cardiac catheterization laboratory have served to transform coronary angiography into an outpatient procedure, with relatively little morbidity. We extended the principles learned with coronary angiography to noninvasive imaging of the human bronchial tree. For these images, we utilized xenon as the contrast agent, as it has a K-edge very similar to that of iodine. In this case, there is no true competing diagnostic test, and pulmonary neoplasm is an enormous public health concern. In early experiments, we demonstrated remarkably clear images of the human bronchial tree. These images have been shown internationally; however, funding difficulties primarily with the Department of Energy have not allowed for progression of this promising avenue of research. One potential criticism of the project is that in order to obtain these images, we utilized national laboratories. Some have questioned whether this would lead to a practical imaging modality. However, we have shown that the technology exists to allow for construction of a miniature storage ring, with a superconducting

  14. Portable X-Ray, K-Edge Heavy Metal Detector

    Energy Technology Data Exchange (ETDEWEB)

    Fricke, V.

    1999-10-25

    The X-Ray, K-Edge Heavy Metal Detection System was designed and built by Ames Laboratory and the Center for Nondestructive Evaluation at Iowa State University. The system uses a C-frame inspection head with an X-ray tube mounted on one side of the frame and an imaging unit and a high purity germanium detector on the other side. the inspection head is portable and can be easily positioned around ventilation ducts and pipes up to 36 inches in diameter. Wide angle and narrow beam X-ray shots are used to identify the type of holdup material and the amount of the contaminant. Precise assay data can be obtained within minutes of the interrogation. A profile of the containerized holdup material and a permanent record of the measurement are immediately available.

  15. Portable X-Ray, K-Edge Heavy Metal Detector

    International Nuclear Information System (INIS)

    Fricke, V.

    1999-01-01

    The X-Ray, K-Edge Heavy Metal Detection System was designed and built by Ames Laboratory and the Center for Nondestructive Evaluation at Iowa State University. The system uses a C-frame inspection head with an X-ray tube mounted on one side of the frame and an imaging unit and a high purity germanium detector on the other side. the inspection head is portable and can be easily positioned around ventilation ducts and pipes up to 36 inches in diameter. Wide angle and narrow beam X-ray shots are used to identify the type of holdup material and the amount of the contaminant. Precise assay data can be obtained within minutes of the interrogation. A profile of the containerized holdup material and a permanent record of the measurement are immediately available

  16. K-Edge Subtraction Angiography with Synchrotron X-Rays

    CERN Document Server

    Giacomini, J C

    1996-01-01

    The purpose of this project was to utilize dual energy, monochromatic X-rays produced from synchrotrons radiation in order to obtain noninvasive medical imaging. The application of synchrotrons radiation to medical imaging is based on the principle of iodine dichromography, first described by Bertil Jacobson of the Karolinska Institute in 1953. Medical imaging using synchrotrons radiation and K-edge dichromography was pioneered at Stanford University under the leadership of Dr. Ed Rubenstein, and the late Nobel Laureate in Physics, Dr. Robert Hofstadter. With progressive refinements in hardware, clinical-quality images were obtained of human coronary arteries utilizing peripheral injections of iodinated contrast agent. These images even now are far superior to those being presented by investigators using MRI as an imaging tool for coronary arteries. However, new supplies and instruments in the cardiac catheterization laboratory have served to transform coronary angiography into an outpatient procedure, with r...

  17. Covalency Trends in Group IV Metallocene Dichlorides. Chlorine K-Edge X-Ray Absorption Spectroscopy And Time Dependent-Density Functional Theory

    Energy Technology Data Exchange (ETDEWEB)

    Kozimor, S.A.; Yang, P.; Batista, E.R.; Boland, K.S.; Burns, C.J.; Christensen, C.N.; Clark, D.L.; Conradson, S.D.; Hay, P.J.; Lezama, J.S.; Martin, R.L.; Schwarz, D.E.; Wilkerson, M.P.; Wolfsberg, L.E.

    2009-05-20

    For 3-5d transition-metal ions, the (C{sub 5}R{sub 5}){sub 2}MCl{sub 2} (R = H, Me for M = Ti, Zr, Hf) bent metallocenes represent a series of compounds that have been central in the development of organometallic chemistry and homogeneous catalysis. Here, we evaluate how changes in the principal quantum number for the group IV (C{sub 5}H{sub 5}){sub 2}MCl{sub 2} (M = Ti, Zr, Hf; 1-3, respectively) complexes affects the covalency of M-Cl bonds through application of Cl K-edge X-ray Absorption Spectroscopy (XAS). Spectra were recorded on solid samples dispersed as a thin film and encapsulated in polystyrene matrices to reliably minimize problems associated with X-ray self-absorption. The data show that XAS pre-edge intensities can be quantitatively reproduced when analytes are encapsulated in polystyrene. Cl K-edge XAS data show that covalency in M-Cl bonding changes in the order Ti > Zr > Hf and demonstrates that covalency slightly decreases with increasing principal quantum number in 1-3. The percent Cl 3p character was experimentally determined to be 26, 23, and 18% per M-Cl bond in the thin-film samples for 1-3 respectively and was indistinguishable from the polystyrene samples, which analyzed as 25, 25, and 19% for 1-3, respectively. To aid in interpretation of Cl K-edge XAS, 1-3 were also analyzed by ground-state and time-dependent density functional theory (TD-DFT) calculations. The calculated spectra and percent chlorine character are in close agreement with the experimental observations, and show 20, 18, and 17% Cl 3p character per M-Cl bond for 1-3, respectively. Polystyrene matrix encapsulation affords a convenient method to safely contain radioactive samples to extend our studies to include actinide elements, where both 5f and 6d orbitals are expected to play a role in M-Cl bonding and where transition assignments must rely on accurate theoretical calculations.

  18. XAS study of V2O5/Al2O3 catalysts doped with rare earth oxides

    International Nuclear Information System (INIS)

    Centeno, M.A.; Malet, P.; Capitan, M.J.; Benitez, J.J.; Carrizosa, I.; Odriozola, J.A.

    1995-01-01

    This paper reports on XAS studies of well dispersed V 2 O 5 /Al 2 O 3 and V 2 O 5 /Sm 2 O 3 /Al 2 O 3 samples. XAS spectra at V-K and Sm-L III edges show that the rare earth oxide favours the formation of regular tetrahedral units, [VO 4 ], over the surface of the support. Positions of the preedge peak at the V-K edge, and intensities of the white line at the Sm-L III edge also suggest modifications in the electronic density around V and Sm atoms when they are simultaneously supported over Al 2 O 3 . ((orig.))

  19. Sulfur K-edge absorption spectroscopy on selected biological systems

    International Nuclear Information System (INIS)

    Lichtenberg, Henning

    2008-07-01

    Sulfur is an essential element in organisms. In this thesis investigations of sulfur compounds in selected biological systems by XANES (X-ray Absorption Near Edge Structure) spectroscopy are reported. XANES spectroscopy at the sulfur K-edge provides an excellent tool to gain information about the local environments of sulfur atoms in intact biological samples - no extraction processes are required. Spatially resolved measurements using a Kirkpatrick-Baez mirror focusing system were carried out to investigate the infection of wheat leaves by rust fungi. The results give information about changes in the sulfur metabolism of the host induced by the parasite and about the extension of the infection into visibly uninfected plant tissue. Furthermore, XANES spectra of microbial mats from sulfidic caves were measured. These mats are dominated by microbial groups involved in cycling sulfur. Additionally, the influence of sulfate deprivation and H 2 S exposure on sulfur compounds in onion was investigated. To gain an insight into the thermal degradation of organic material the influence of roasting of sulfur compounds in coffee beans was studied. (orig.)

  20. Fragmentation of HCl following excitation at the chlorine K edge

    International Nuclear Information System (INIS)

    Hansen, D.L.; Arrasate, M.E.; Cotter, J.P.

    1997-01-01

    A space-focused time-of-flight (TOF) mass spectrometer was used to study the relaxation dynamics of HCl following excitation in the vicinity of the Cl-K edge (∼2.8 keV) using x-rays from B.L. 9.3.1. At the lowest resonant excitation to a σ * antibonding orbital (1σ → 6σ), a significant fraction of the excited molecules decay by emission of a neutral H atom. While neutral-H emission has been observed for shallow core levels (e.g., Cl 2p in HCl), the authors believe this to be the first observation of neutral-atom emission as a significant decay channel following resonant excitation of a deep core hole. The dissociation of neutral hydrogen atoms raises the issue of how effectively dissociation competes with Auger decay in the relaxation of these deep core levels (i.e., Cl 1s). Graphical evidence is presented to support the dissociation agrument. In addition, trends in fractional ion yields from Photo-Ion Photo-Ion COincidence (PIPICO) spectra suggest the presence of post-collision interaction (PCI). While, electron spectroscopy studies are required to confirm the observation of this effect, the authors believe this to be the first evidence of PCI moderated dissociation in molecules

  1. Fe K-edge XANES of Maya blue pigment

    International Nuclear Information System (INIS)

    Rio, M. Sanchez del; Sodo, A.; Eeckhout, S.G.; Neisius, T.; Martinetto, P.; Dooryhee, E.; Reyes-Valerio, C.

    2005-01-01

    The utilization of techniques used in Materials Science for the characterization of artefacts of interest for cultural heritage is getting more and more attention nowadays. One of the products of the ancient Maya chemistry is the 'Maya blue' pigment, made with natural indigo and palygorskite. This pigment is different from any other pigment used in other parts of the world. It is durable and acid-resistant, and still keeps many secrets to scientists even though it has been studied for more than 50 years. Although the pigment is basically made of palygorskite Si 8 (Mg 2 Al 2 )O 20 (OH) 2 (OH 2 ) 4 .4H 2 O and an organic colourant (indigo: C 16 H 10 N 2 O 2 ), a number of other compounds have been found in previous studies on archaeological samples, like other clays and minerals, iron nanoparticles, iron oxides, impurities of transition metals (Cr, Mn, Ti, V), etc. We measured at the ESRF ID26 beamline the Fe K-edge XANES spectra of the blue pigment in ancient samples. They are compared to XANES spectra of Maya blue samples synthesized under controlled conditions, and iron oxides usually employed as pigments (hematite and goethite). Our results show that the iron found in ancient Maya blue pigment is related to the Fe exchanged in the palygorskite clay. We did not find iron in metallic form or goethite in archaeological Maya blue

  2. Fragmentation of HCl following excitation at the chlorine K edge

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, D.L.; Arrasate, M.E. [Univ. of Nevada, Las Vegas, NV (United States); Cotter, J.P. [Univ. of Nevada, Reno, NV (United States)] [and others

    1997-04-01

    A space-focused time-of-flight (TOF) mass spectrometer was used to study the relaxation dynamics of HCl following excitation in the vicinity of the Cl-K edge ({approximately}2.8 keV) using x-rays from B.L. 9.3.1. At the lowest resonant excitation to a {sigma}{sup *} antibonding orbital (1{sigma} {r_arrow} 6{sigma}), a significant fraction of the excited molecules decay by emission of a neutral H atom. While neutral-H emission has been observed for shallow core levels (e.g., Cl 2p in HCl), the authors believe this to be the first observation of neutral-atom emission as a significant decay channel following resonant excitation of a deep core hole. The dissociation of neutral hydrogen atoms raises the issue of how effectively dissociation competes with Auger decay in the relaxation of these deep core levels (i.e., Cl 1s). Graphical evidence is presented to support the dissociation agrument. In addition, trends in fractional ion yields from Photo-Ion Photo-Ion COincidence (PIPICO) spectra suggest the presence of post-collision interaction (PCI). While, electron spectroscopy studies are required to confirm the observation of this effect, the authors believe this to be the first evidence of PCI moderated dissociation in molecules.

  3. A new high temperature reactor for operando XAS: Application for the dry reforming of methane over Ni/ZrO2 catalyst

    Science.gov (United States)

    Aguilar-Tapia, Antonio; Ould-Chikh, Samy; Lahera, Eric; Prat, Alain; Delnet, William; Proux, Olivier; Kieffer, Isabelle; Basset, Jean-Marie; Takanabe, Kazuhiro; Hazemann, Jean-Louis

    2018-03-01

    The construction of a high-temperature reaction cell for operando X-ray absorption spectroscopy characterization is reported. A dedicated cell was designed to operate as a plug-flow reactor using powder samples requiring gas flow and thermal treatment at high temperatures. The cell was successfully used in the reaction of dry reforming of methane (DRM). We present X-ray absorption results in the fluorescence detection mode on a 0.4 wt. % Ni/ZrO2 catalyst under realistic conditions at 750 °C, reproducing the conditions used for a conventional dynamic microreactor for the DRM reaction. The setup includes a gas distribution system that can be fully remotely operated. The reaction cell offers the possibility of transmission and fluorescence detection modes. The complete setup dedicated to the study of catalysts is permanently installed on the Collaborating Research Groups French Absorption spectroscopy beamline in Material and Environmental sciences (CRG-FAME) and French Absorption spectroscopy beamline in Material and Environmental sciences at Ultra-High Dilution (FAME-UHD) beamlines (BM30B and BM16) at the European Synchrotron Radiation Facility in Grenoble, France.

  4. A new high temperature reactor for operando XAS: Application for the dry reforming of methane over Ni/ZrO2 catalyst

    KAUST Repository

    Aguilar Tapia, Antonio

    2018-03-22

    The construction of a high-temperature reaction cell for operando X-ray absorption spectroscopy characterization is reported. A dedicated cell was designed to operate as a plug-flow reactor using powder samples requiring gas flow and thermal treatment at high temperatures. The cell was successfully used in the reaction of dry reforming of methane (DRM). We present X-ray absorption results in the fluorescence detection mode on a 0.4 wt. % Ni/ZrO2 catalyst under realistic conditions at 750 °C, reproducing the conditions used for a conventional dynamic microreactor for the DRM reaction. The setup includes a gas distribution system that can be fully remotely operated. The reaction cell offers the possibility of transmission and fluorescence detection modes. The complete setup dedicated to the study of catalysts is permanently installed on the Collaborating Research Groups French Absorption spectroscopy beamline in Material and Environmental sciences (CRG-FAME) and French Absorption spectroscopy beamline in Material and Environmental sciences at Ultra-High Dilution (FAME-UHD) beamlines (BM30B and BM16) at the European Synchrotron Radiation Facility in Grenoble, France.

  5. A new high temperature reactor for operando XAS: Application for the dry reforming of methane over Ni/ZrO2catalyst.

    Science.gov (United States)

    Aguilar-Tapia, Antonio; Ould-Chikh, Samy; Lahera, Eric; Prat, Alain; Delnet, William; Proux, Olivier; Kieffer, Isabelle; Basset, Jean-Marie; Takanabe, Kazuhiro; Hazemann, Jean-Louis

    2018-03-01

    The construction of a high-temperature reaction cell for operando X-ray absorption spectroscopy characterization is reported. A dedicated cell was designed to operate as a plug-flow reactor using powder samples requiring gas flow and thermal treatment at high temperatures. The cell was successfully used in the reaction of dry reforming of methane (DRM). We present X-ray absorption results in the fluorescence detection mode on a 0.4 wt. % Ni/ZrO 2 catalyst under realistic conditions at 750 °C, reproducing the conditions used for a conventional dynamic microreactor for the DRM reaction. The setup includes a gas distribution system that can be fully remotely operated. The reaction cell offers the possibility of transmission and fluorescence detection modes. The complete setup dedicated to the study of catalysts is permanently installed on the Collaborating Research Groups French Absorption spectroscopy beamline in Material and Environmental sciences (CRG-FAME) and French Absorption spectroscopy beamline in Material and Environmental sciences at Ultra-High Dilution (FAME-UHD) beamlines (BM30B and BM16) at the European Synchrotron Radiation Facility in Grenoble, France.

  6. Chemical shift of Mn and Cr K-edges in X-ray absorption ...

    Indian Academy of Sciences (India)

    The above chemical effect has been quantitatively described by determining the effective charges on Mn and Cr cations in the above compounds. Keywords. Mn K edge; Cr K edge; EXAFS; synchrotron radiation; energy shift; oxidation state; effective charge. 1. Introduction. It is well known that the X-ray absorption edge of a ...

  7. Ca L2,3-edge XANES and Sr K-edge EXAFS study of hydroxyapatite and fossil bone apatite.

    Science.gov (United States)

    Zougrou, I M; Katsikini, M; Brzhezinskaya, M; Pinakidou, F; Papadopoulou, L; Tsoukala, E; Paloura, E C

    2016-08-01

    Upon burial, the organic and inorganic components of hard tissues such as bone, teeth, and tusks are subjected to various alterations as a result of interactions with the chemical milieu of soil, groundwater, and presence of microorganisms. In this study, simulation of the Ca L 2,3-edge X-ray absorption near edge structure (XANES) spectrum of hydroxyapatite, using the CTM4XAS code, reveals that the different symmetry of the two nonequivalent Ca(1) and Ca(2) sites in the unit cell gives rise to specific spectral features. Moreover, Ca L 2,3-edge XANES spectroscopy is applied in order to assess variations in fossil bone apatite crystallinity due to heavy bacterial alteration and catastrophic mineral dissolution, compared to well-preserved fossil apatite, fresh bone, and geologic apatite reference samples. Fossilization-induced chemical alterations are investigated by means of Ca L 2,3-edge XANES and scanning electron microscopy (SEM) and are related to histological evaluation using optical microscopy images. Finally, the variations in the bonding environment of Sr and its preference for substitution in the Ca(1) or Ca(2) sites upon increasing the Sr/Ca ratio is assessed by Sr K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy.

  8. Strong excitonic interactions in the oxygen K-edge of perovskite oxides

    Energy Technology Data Exchange (ETDEWEB)

    Tomita, Kota; Miyata, Tomohiro [Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan); Olovsson, Weine [Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden); Mizoguchi, Teruyasu, E-mail: teru@iis.u-tokyo.ac.jp [Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan)

    2017-07-15

    Excitonic interactions of the oxygen K-edge electron energy-loss near-edge structure (ELNES) of perovskite oxides, CaTiO{sub 3}, SrTiO{sub 3}, and BaTiO{sub 3}, together with reference oxides, MgO, CaO, SrO, BaO, and TiO{sub 2}, were investigated using a first-principles Bethe–Salpeter equation calculation. Although the transition energy of oxygen K-edge is high, strong excitonic interactions were present in the oxygen K-edge ELNES of the perovskite oxides, whereas the excitonic interactions were negligible in the oxygen K-edge ELNES of the reference compounds. Detailed investigation of the electronic structure suggests that the strong excitonic interaction in the oxygen K-edge ELNES of the perovskite oxides is caused by the directionally confined, low-dimensional electronic structure at the Ti–O–Ti bonds. - Highlights: • Excitonic interaction in oxygen-K edge is investigated. • Strong excitonic interaction is found in the oxygen-K edge of perovskite oxides. • The strong excitonic interaction is ascribed to the low-dimensional and confined electronic structure.

  9. Trends in Covalency for d- and f-Element Metallocene Dichlorides Identified Using Chlorine K-Edge X-Ray Absorption Spectroscopy and Time Dependent-Density Functional Theory

    Energy Technology Data Exchange (ETDEWEB)

    Kozimor, Stosh A.; Yang, Ping; Batista, Enrique R.; Boland, Kevin S.; Burns, Carol J.; Clark, David L.; Conradson, Steven D.; Martin, Richard L.; Wikerson, Marianne P.; Wolfsberg, Laura E.

    2009-09-02

    We describe the use of Cl K-edge X-ray Absorption Spectroscopy (XAS) and both ground state and time-dependent hybrid density functional theory (DFT) to probe electronic structure and determine the degree of orbital mixing in M-Cl bonds for (C5Me5)2MCl2 (M = Ti, 1; Zr, 2; Hf, 3; Th, 4; and U, 5), where we can directly compare a class of structurally similar compounds for d- and f-elements. We report direct experimental evidence for covalency in M-Cl bonding, including actinides, and offer insight into the relative roles of the valence f- and dorbitals in these systems. The Cl K-edge XAS data for the group IV transition metals, 1 – 3, show slight decreases in covalency in M-Cl bonding with increasing principal quantum number, in the order Ti > Zr > Hf. The percent Cl 3p character per M-Cl bond was experimentally determined to be 25, 23, and 22% per M-Cl bond for 1-3, respectively. For actinides, we find a shoulder on the white line for (C5Me5)2ThCl2, 4, and distinct, but weak pre-edge features for 2 (C5Me5)2UCl2, 5. The percent Cl 3p character in Th-Cl bonds in 4 was determined to be 14 %, with high uncertainty, while the U-Cl bonds in 5 contains 9 % Cl 3p character. The magnitudes of both values are approximately half what was observed for the transition metal complexes in this class of bent metallocene dichlorides. Using the hybrid DFT calculations as a guide to interpret the experimental Cl K-edge XAS, these experiments suggest that when evaluating An- Cl bonding, both 5f- and 6d-orbitals should be considered. For (C5Me5)2ThCl2, the calculations and XAS indicate that the 5f- and 6d-orbitals are nearly degenerate and heavily mixed. In contrast, the 5f- and 6d-orbitals in (C5Me5)2UCl2 are no longer degenerate, and fall in two distinct energy groupings. The 5f-orbitals are lowest in energy and split into a 5-over-2 pattern with the high lying U 6d-orbitals split in a 4-over-1 pattern, the latter of which is similar to the dorbital splitting in group IV transition

  10. Application of X-ray K-edge densitometry in D and D operations

    International Nuclear Information System (INIS)

    Jensen, T.; Aljundi, T.; Gray, J.N.; Iowa State Univ., Ames, IA

    1998-01-01

    K-edge densitometry is a nondestructive assay technique which provides accurate measurement of heavy metal contamination in pipes, containers, and other items encountered in D and D operations. A prototype mobile K-edge instrument has been built and demonstrated in several applications. Results from measurements of uranium in pipes and spent reactor fuel plates, and quantification of mercury and lead in waste drums are presented. In this report the authors briefly describe the theory behind K-edge densitometry. They follow that with a description of the prototype system they have developed, and a presentation of results from demonstrations of this system. They conclude with a discussion of the potential for application of K-edge analysis in D and D operations

  11. Evaluation of high-rate pulse processing in K-edge densitometry

    International Nuclear Information System (INIS)

    Eberle, H.; Matussek, P.; Michel-Piper, I.; Ottmar, H.

    1987-08-01

    Different pulse processing systems have been tested at high counting rates for K-edge densitometry measurements with a continuous X-ray beam. The total input counting rates presented to the gamma detector have been varied between 10 kcps and 100 kcps. This paper describes the results of the measurements, in particular the influence of high counting rates on the spectral resolution, on the pile-up behaviour, on the throughput rate, and on the K-edge densitometry results. (orig.) [de

  12. Interpretation of O K-edge EELS in zircon using a structural variation approach.

    Science.gov (United States)

    Jiang, Nan; Spence, John C H

    2009-12-01

    This work describes an approach to interpret the near-edge fine structure of electron energy-loss spectroscopy (EELS) of O K-edge in zircon using a structural variation method. The positions and intensities of several peaks in the O K-edge EELS spectrum are assigned to specific structural parameters. It suggests that the near-edge structures in EELS can be used to measure atomic structure changes.

  13. Chemical shift of Mn and Cr K-edges in X-ray absorption ...

    Indian Academy of Sciences (India)

    ... observed for Mn K edge in the Mn-compounds while a shift of 13–20 eV was observed for Cr K edge in Cr-compounds compared to values in elementalMn and Cr, respectively. The different chemical shifts observed for compounds having the same oxidation state of the cation but different anions or ligands show the effect ...

  14. Ion charge-state production and photoionization near the K edge in argon and potassium

    International Nuclear Information System (INIS)

    Berry, H.G.; Azuma, Y.; Cowan, P.L.; Gemmell, D.S.; LeBrun, T.; Amusia, M.Y.

    1994-01-01

    We have measured the time-of-flight charge distributions of ions of argon and potassium following x-ray absorption at energies near their respective K edges. We confirm previously observed enhancements of the higher charge states at energies up to 100 eV below the K edge in argon. The measurements confirm recent calculations suggesting excitation of a virtual 1s state in this energy range

  15. Carbon K-edge X-ray absorption spectroscopy and time-dependent density functional theory examination of metal-carbon bonding in metallocene dichlorides.

    Science.gov (United States)

    Minasian, Stefan G; Keith, Jason M; Batista, Enrique R; Boland, Kevin S; Kozimor, Stosh A; Martin, Richard L; Shuh, David K; Tyliszczak, Tolek; Vernon, Louis J

    2013-10-02

    Metal-carbon covalence in (C5H5)2MCl2 (M = Ti, Zr, Hf) has been evaluated using carbon K-edge X-ray absorption spectroscopy (XAS) as well as ground-state and time-dependent hybrid density functional theory (DFT and TDDFT). Differences in orbital mixing were determined experimentally using transmission XAS of thin crystalline material with a scanning transmission X-ray microscope (STXM). Moving down the periodic table (Ti to Hf) has a marked effect on the experimental transition intensities associated with the low-lying antibonding 1a1* and 1b2* orbitals. The peak intensities, which are directly related to the M-(C5H5) orbital mixing coefficients, increase from 0.08(1) and 0.26(3) for (C5H5)2TiCl2 to 0.31(3) and 0.75(8) for (C5H5)2ZrCl2, and finally to 0.54(5) and 0.83(8) for (C5H5)2HfCl2. The experimental trend toward increased peak intensity for transitions associated with 1a1* and 1b2* orbitals agrees with the calculated TDDFT oscillator strengths [0.10 and 0.21, (C5H5)2TiCl2; 0.21 and 0.73, (C5H5)2ZrCl2; 0.35 and 0.69, (C5H5)2HfCl2] and with the amount of C 2p character obtained from the Mulliken populations for the antibonding 1a1* and 1b2* orbitals [8.2 and 23.4%, (C5H5)2TiCl2; 15.3 and 39.7%, (C5H5)2ZrCl2; 20.1 and 50.9%, (C5H5)2HfCl2]. The excellent agreement between experiment, theory, and recent Cl K-edge XAS and DFT measurements shows that C 2p orbital mixing is enhanced for the diffuse Hf (5d) and Zr (4d) atomic orbitals in relation to the more localized Ti (3d) orbitals. These results provide insight into how changes in M-Cl orbital mixing within the metallocene wedge are correlated with periodic trends in covalent bonding between the metal and the cyclopentadienide ancillary ligands.

  16. XAS spectroscopy, sulfur, and the brew within blood cells from Ascidia ceratodes.

    Science.gov (United States)

    Frank, Patrick; Hedman, Britt; Hodgson, Keith O

    2014-02-01

    We report the first use of K-edge X-ray absorption spectroscopy (XAS) as a direct spectroscopic probe of pH and cytosolic emf within living cells. A new accuracy metric of model-based fits to K-edge spectra is further developed. Sulfur functional groups in three collections of living blood cells and one sample of cleared blood plasma from the tunicate Ascidia ceratodes were speciated using K-edge XAS. Cysteine and cystine, the preferred thiol-disulfide model, averaged about 12% of total sulfur. Sulfate monoesters and cyclic diesters unexpectedly constituted 36% of blood cell sulfur. Soluble sulfate averaged about 25% across the three blood cell samples, while the ratio of SO4(2-) to HSO4(-) implied average signet ring vacuolar pH values of 0.85, 1.4, or 3.1. Intracellular (VSO4)(+) was unobserved, while [V(RSO3)n]((3-n)+) was detected in the two lowest pH blood cell samples. About 5% of sulfur was distributed as mono- or dibenzothiophene or ethylene-epi-sulfide, or as a thiadiazole reminiscent of the polycarpathiamines. Blood plasma was dominated by sulfate (83%), but with 15% of an alkylsulfate ester and about 2% of low-valent sulfur. Gravimetric analysis of soluble sulfate yielded average concentrations of blood cell sulfur. Average [cysteine] and [cystine] (ranging ~10-30 mM and ~20-90 mM, respectively) implied blood-cell cytosolic emf values of approximately -0.20 V. High cellular [cysteine] is consistent with the proposed model for enzymatic reduction of vanadate by endogenous thiol, wherein the trajectory of metal site-symmetry is controlled and directed through to a thermodynamically favored 7-coordinate V(III) product. Copyright © 2013. Published by Elsevier Inc.

  17. X-ray K-edge analysis of drain lines in Wilhelm Hall, Ames Laboratory

    International Nuclear Information System (INIS)

    Jensen, T.; Whitmore, C.; Iowa State Univ., Ames, IA

    1999-01-01

    From August 12--27, 1998 X-ray K-edge measurements were made on drain lines in seven rooms in Wilhelm Hall, Ames Laboratory. The purpose of these measurements was to determine the extent of thorium (and other heavy metal) contamination inside these pipes. The K-edge method is a noninvasive inspection technique that can provide accurate quantification of heavy metal contamination interior to an object. Of the seven drain lines inspected, one was found to have no significant contamination, three showed significant thorium deposits, two showed mercury contamination, and one line was found to contain mercury, thorium and uranium. The K-edge measurements were found to be consistent with readings from hand-held survey meters, and provided much greater detail on the location and amount of heavy metal contamination

  18. Inversed linear dichroism in F K-edge NEXAFS spectra of fluorinated planar aromatic molecules

    DEFF Research Database (Denmark)

    de Oteyza, D. G.; Sakko, A.; El-Sayed, A.

    2012-01-01

    The symmetry and energy distribution of unoccupied molecular orbitals is addressed in this work by means of NEXAFS and density functional theory calculations for planar, fluorinated organic semiconductors (perfluorinated copper phthalocyanines and perfluoropentacene). We demonstrate how molecular...... orbitals with significant density of states on the fluorine atoms show different symmetry from those mainly located on C and N atoms. As a result, the angle-dependent linear dichroism in NEXAFS F K-edge spectra is inversed with respect to that in the C and N K-edges. In addition, the significant overlap...

  19. Plutonium isotopic assay of reprocessing product solutions in the KfK K-edge densitometer

    International Nuclear Information System (INIS)

    Eberle, H.; Ottmar, H.; Matussek, P.

    1985-04-01

    The KfK K-edge densiometer, designed for accurate element concentration measurements using the technique of X-ray absorptiometry at the K absorption edge, provides as an additional option the possibility to determine the isotopic composition of freshly separated plutonium from an gamma-spectrometric analysis of its self-radiation. This report describes the underlying methodology and experimental procedures for the isotopic analysis in the K-edge densitometer. The paper also presents and discusses the experimental results so far obtained from routine measurements on reprocessing product solutions. (orig.)

  20. Theoretical Mn K-edge XANES for Li2MnO3: DFT + U study

    International Nuclear Information System (INIS)

    Tamura, Tomoyuki; Ohwaki, Tsukuru; Ito, Atsushi; Ohsawa, Yasuhiko; Kobayashi, Ryo; Ogata, Shuji

    2012-01-01

    Spectral features of Mn K-edge x-ray absorption near-edge structure (XANES) for Li 2 MnO 3 were calculated using the first-principles full projector augmented wave method with the general gradient approximation plus U method. We demonstrated that the U parameter affects the spectral features in the pre-edge region while it does not affect those in the major absorption region. From the comparison with the experimental spectra and those of reference compounds, we showed that the spectral features of Mn K-edge XANES and the differences in the valence state can be reproduced well. (paper)

  1. A PEM fuel cell for in situ XAS studies

    International Nuclear Information System (INIS)

    Wiltshire, Richard J.K.; King, Colin R.; Rose, Abigail; Wells, Peter P.; Hogarth, Martin P.; Thompsett, David; Russell, Andrea E.

    2005-01-01

    A miniature proton exchange membrane (PEM) fuel cell has been designed to enable in situ XAS investigations of the anode catalyst using fluorescence detection. The development of the cell is described, in particular the modifications required for elevated temperature operation and humidification of the feed gasses. The impact of the operating conditions is observed as an increase in the catalyst utilisation, which is evident in the EXAFS collected at the Pt L III and Ru K edges for a PtRu/C catalyst. The Pt component of the catalyst was found to be readily reduced by hydrogen in the fuel, while the Ru was only fully reduced under conditions of good gas flow and electrochemical contact. Under such conditions no evidence of O neighbours were found at the Ru edge. The results are interpreted in relation to the lack of surface sensitivity of the EXAFS method and indicate that the equilibrium coverage of O species on the Ru surface sites is too low to be observed using EXAFS

  2. Functional Groups and Sulfur K-Edge XANES Spectra : Divalent Sulfur and Disulfides

    NARCIS (Netherlands)

    Mijovilovich, A.E.; Pettersson, Lars G. M.; de Groot, Frank M. F.; Weckhuysen, Bert M.

    2010-01-01

    Sulfur K-edge XANES was measured for two divalent sulfurs (dibenzyl and benzyl phenyl) and two disulfides (dibenzyl and diphenyl). The absorption spectra could be assigned using density functional theory with the "half core hole" approximation for the core hole including relaxation of selected

  3. K- and L-edge X-ray Absorption Spectroscopy (XAS) and Resonant Inelastic X-ray Scattering (RIXS) Determination of Differential Orbital Covalency (DOC) of Transition Metal Sites.

    Science.gov (United States)

    Baker, Michael L; Mara, Michael W; Yan, James J; Hodgson, Keith O; Hedman, Britt; Solomon, Edward I

    2017-08-15

    Continual advancements in the development of synchrotron radiation sources have resulted in X-ray based spectroscopic techniques capable of probing the electronic and structural properties of numerous systems. This review gives an overview of the application of metal K-edge and L-edge X-ray absorption spectroscopy (XAS), as well as K resonant inelastic X-ray scattering (RIXS), to the study of electronic structure in transition metal sites with emphasis on experimentally quantifying 3d orbital covalency. The specific sensitivities of K-edge XAS, L-edge XAS, and RIXS are discussed emphasizing the complementary nature of the methods. L-edge XAS and RIXS are sensitive to mixing between 3d orbitals and ligand valence orbitals, and to the differential orbital covalency (DOC), that is, the difference in the covalencies for different symmetry sets of the d orbitals. Both L-edge XAS and RIXS are highly sensitive to and enable separation of and donor bonding and back bonding contributions to bonding. Applying ligand field multiplet simulations, including charge transfer via valence bond configuration interactions, DOC can be obtained for direct comparison with density functional theory calculations and to understand chemical trends. The application of RIXS as a probe of frontier molecular orbitals in a heme enzyme demonstrates the potential of this method for the study of metal sites in highly covalent coordination sites in bioinorganic chemistry.

  4. Structural disorder and electronic hybridization in NicMg1-cO solid solutions probed by XANES at the oxygen K edge

    International Nuclear Information System (INIS)

    Chen Dongliang; Zhong Jun; Chu Wangsheng; Wu Ziyu; Kuzmin, Alexei; Mironova-Ulmane, Nina; Marcelli, Augusto

    2007-01-01

    A series of Ni c Mg 1-c O solid solutions has been studied for the first time looking at the structural disorder by means of x-ray absorption near-edge-structure (XANES) spectroscopy at the oxygen K edge. The experimental XANES signals were analysed within the full multiple scattering formalism and were interpreted taking into account clusters of up to 15 coordination shells around an absorbing oxygen atom. The substitution of nickel atoms by magnesium atoms results in a dramatic decrease of the empty density of states in the conduction band close to the Fermi level due to an exchange of the 3d(Ni)-2p(O) interaction with 3p(Mg)-2p(O). Besides, a simultaneous small decrease of the 3d(Ni)-2p(O) hybridization is also induced by the lattice expansion, determined by the difference in ionic radii between nickel and magnesium ions

  5. Probing ultrafast ππ*/nπ* internal conversion in organic chromophores via K-edge resonant absorption

    DEFF Research Database (Denmark)

    Wolf, T. J. A.; Myhre, Rolf H.; Cryan, J. P.

    2017-01-01

    -edge soft X-ray absorption spectroscopy. As a hole forms in the n orbital during ππ*/nπ* internal conversion, the absorption spectrum at the heteroatom K-edge exhibits an additional resonance. We demonstrate the concept using the nucleobase thymine at the oxygen K-edge, and unambiguously show that ππ...

  6. Visualization of pigment distributions in paintings using synchrotron K-edge imaging

    Energy Technology Data Exchange (ETDEWEB)

    Krug, K.; Dik, J. [TU Delft, Department of Materials Science and Engineering, Delft (Netherlands); Leeuw, M. [Atelier for Restoration and Research of Paintings, The Hague (Netherlands); Whitson, A. den [L3 Communications, Woburn, MA (United States); Tortora, J. [JK Consulting, Sudbury, MA (United States); Coan, P.; Nemoz, C.; Bravin, A. [European Synchrotron Radiation Facility, Grenoble (France)

    2006-05-15

    X-ray radiography plays an important role in the study of artworks and archaeological artifacts. The internal structure of objects provides information on genesis, authenticity, painting technique, material condition and conservation history. Transmission radiography, however, does not provide information on the exact elemental composition of objects and heavy metal layers can shadow or obscure the ones including lighter elements. This paper presents the first application of synchrotron-based K-edge absorption imaging applied to paintings. Using highly monochromatic radiation, K-edge imaging is used to obtain elemental distribution images over large areas. Such elemental maps visualize the distribution of an individual pigment throughout the paint stratigraphy. This provides color information on hidden paint layers, which is of great relevance to art historians and painting conservators. The main advantage is the quick data acquisition time and the sensitivity to elements throughout the entire paint stratigraphy. The examination of a test painting is shown and further instrumental developments are discussed. (orig.)

  7. Oxygen K-edge electron energy loss spectra of hydrous and anhydrous compounds

    Science.gov (United States)

    Winkler, B.; Avalos-Borja, M.; Milman, V.; Perlov, A.; Pickard, C. J.; Yates, J. R.

    2013-12-01

    First-principles calculations have been employed to examine the possible use of electron energy loss spectroscopy (EELS) as a tool for determining the presence of OH groups and hence hydrogen content in compounds. Our density functional theory (DFT) based calculations describe accurately the experimental EELS results for forsterite (Mg2SiO4), hambergite (Be2BO3(OH)), brucite (Mg(OH)2) and diaspore (α-AlOOH). DFT calculations were complemented by an experimental time resolved study of the oxygen K-edge in diaspore. The results show unambiguously that there is no connection between a pre-edge feature in the oxygen K-edge spectrum of diaspore and the presence of OH groups in the structure. Instead, the experimental study shows that the pre-edge feature in diaspore is transient. It can be explained by the presence of molecular O2, which is produced as a result of the electron irradiation.

  8. Visualization of pigment distributions in paintings using synchrotron K-edge imaging

    International Nuclear Information System (INIS)

    Krug, K.; Dik, J.; Leeuw, M.; Whitson, A. den; Tortora, J.; Coan, P.; Nemoz, C.; Bravin, A.

    2006-01-01

    X-ray radiography plays an important role in the study of artworks and archaeological artifacts. The internal structure of objects provides information on genesis, authenticity, painting technique, material condition and conservation history. Transmission radiography, however, does not provide information on the exact elemental composition of objects and heavy metal layers can shadow or obscure the ones including lighter elements. This paper presents the first application of synchrotron-based K-edge absorption imaging applied to paintings. Using highly monochromatic radiation, K-edge imaging is used to obtain elemental distribution images over large areas. Such elemental maps visualize the distribution of an individual pigment throughout the paint stratigraphy. This provides color information on hidden paint layers, which is of great relevance to art historians and painting conservators. The main advantage is the quick data acquisition time and the sensitivity to elements throughout the entire paint stratigraphy. The examination of a test painting is shown and further instrumental developments are discussed. (orig.)

  9. X-ray attenuation around K-edge of Zr, Nb, Mo and Pd: A ...

    Indian Academy of Sciences (India)

    Abstract. Mass attenuation coefficients (µ/ρ) for Zr, Nb, Mo and Pd elements around their K-edges are measured at 14 energies in the range 15.744–28.564 keV using secondary excitation from thin Zr, Nb, Mo, Rh, Pd, Cd and Sn foils. The measurements were carried out at the Kα and Kβ energy values of the target elements ...

  10. Phosphorus Speciation of Forest-soil Organic Surface Layers using P K-edge XANES Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    J Prietzel; J Thieme; D Paterson

    2011-12-31

    The phosphorus (P) speciation of organic surface layers from two adjacent German forest soils with different degree of water-logging (Stagnosol, Rheic Histosol) was analyzed by P K-edge XANES and subsequent Linear Combination Fitting. In both soils, {approx}70% of the P was inorganic phosphate and {approx}30% organic phosphate; reduced P forms such as phosphonate were absent. The increased degree of water-logging in the Histosol compared to the Stagnosol did not affect P speciation.

  11. Doping and bond length contributions to Mn K-edge shift in La1 ...

    Indian Academy of Sciences (India)

    of La1−xSrxMnO3 (x = 0–0.7) are compared with the band structure calculations using spin polarized density functional .... and electronic structure calculations that shift in Mn K-edge position on Sr doping in LaMnO3 corresponds to ... three directions for the tetrahedron integration were used to calculate the density of states.

  12. Standard Protocol and Quality Assessment of Soil Phosphorus Speciation by P K-Edge XANES Spectroscopy.

    Science.gov (United States)

    Werner, Florian; Prietzel, Jörg

    2015-09-01

    Phosphorus (P) in soils is most often bound as phosphate to one or more of the following four elements or compounds: calcium, aluminum, iron, and soil organic matter. A promising method for direct P speciation in soils is synchrotron-based X-ray absorption near edge structure (XANES) spectroscopy at the K-edge of P. However, the quality of this method is debated controversially, partly because a standard protocol for reproducible spectrum deconvolution is lacking and minor modifications of the applied deconvolution procedure can lead to considerable changes in the P speciation results. On the basis of the observation that appropriate baseline correction and edge-step normalization are crucial for correct linear combination (LC) fitting results, we established a standard protocol for the deconvolution and LC fitting of P K-edge XANES spectra. We evaluated the quality of LC fits obtained according to this standard protocol with 16 defined dilute (2 mg P g(-1)) ternary mixtures of aluminum phosphate, iron phosphate, hydroxyapatite, and phytic acid in a quartz matrix. The LC fitting results were compared with the contribution of the different P compounds to total P in the various mixtures. Compared to using a traditional LC fitting procedure, our standard protocol reduced the fitting error by 6% (absolute). However, P portions smaller than 5% should be confirmed with other methods or excluded from the P speciation results. A publicly available database of P K-edge XANES reference spectra was initiated.

  13. X-ray absorption spectroscopic studies of the blue copper site: Metal and ligand K-edge studies to probe the origin of the EPR hyperfine splitting in plastocyanin

    International Nuclear Information System (INIS)

    Shadle, S.E.; Penner-Hahn, J.E.; Schugar, H.J.; Hedman, B.; Hodgson, K.O.; Solomon, E.I.

    1993-01-01

    X-ray absorption spectra for the oxidized blue copper protein plastocyanin and several Cu(II) model complexes have been measured at both the Cu K-edge and the ligand K-edges (Cl and S) in order to elucidate the source of the small parallel hyperfine splitting in the EPR spectra of blue copper centers. Assignment and analysis of a feature in the Cu K-edge X-ray absorption spectrum at ∼8,987 eV as the Cu 1s → 4p + ligand-to-metal charge-transfer shakedown transition has allowed for quantitation of 4p mixing into the ground-state wave function as reflected in the 1s →3d (+4p) intensity at ∼8,979 eV. The results show that distorted tetrahedral (D 2d )CuCl 4 2- is characterized by z mixing, while plastocyanin has only Cu 4p xy mixing. Thus, the small parallel hyperfine splitting in the EPR spectra of D 2d CuCl 4 2- and of oxidized plastocyanin cannot be explained by 12% 4p z mixing into the 3d x 2 -y 2 orbital as had been previously postulated. Data collected at the Cl K-edge for CuCl 4 2- show that the intensity of the ligand pre-edge feature at ∼2,820 eV reflects the degree of covalency between the metal half-occupied orbital and the ligands. The data show that D 2d CuCl 4 2- is not unusually covalent. The source of the small parallel splitting in the EPR of D 2d CuCl 4 2- is discussed. Experiments at the S K-edge (∼2,470 eV) show that plastocyanin is characterized by a highly covalent Cu-S(cysteine) bond relative to the cupric-thiolate model complex [Cu(tet b)(o-SC 6 H 4 CO 2 )]·H 2 O. The XAS results demonstrate that the small parallel hyperfine splitting in the EPR spectra of blue copper sites reflects the high degree of covalency of the copper-thiolate bond. 34 refs., 12 figs., 3 tabs

  14. Parameters Influencing Sulfur Speciation in Environmental Samples Using Sulfur K-Edge X-Ray Absorption Near-Edge Structure

    Directory of Open Access Journals (Sweden)

    Siwatt Pongpiachan

    2012-01-01

    Full Text Available This paper aims to enhance the credibility of applying the sulfur K-edge XANES spectroscopy as an innovative “fingerprint” for characterizing environmental samples. The sensitivities of sulfur K-edge XANES spectra of ten sulfur compound standards detected by two different detectors, namely, Lytle detector (LyD and Germanium detector (GeD, were studied and compared. Further investigation on “self-absorption” effect revealed that the maximum sensitivities of sulfur K-edge XANES spectra were achieved when diluting sulfur compound standards with boron nitride (BN at the mixing ratio of 0.1%. The “particle-size” effect on sulfur K-edge XANES spectrum sensitivities was examined by comparing signal-to-noise ratios of total suspended particles (TSP and particulate matter of less than 10 millionths of a meter (PM10 collected at three major cities of Thailand. The analytical results have demonstrated that the signal-to-noise ratios of sulfur K-edge XANES spectra were positively correlated with sulfate content in aerosols and negatively connected with particle sizes. The combination of hierarchical cluster analysis (HCA and principal component analysis (PCA has proved that sulfur K-edge XANES spectrum can be used to characterize German terrestrial soils and Andaman coastal sediments. In addition, this study highlighted the capability of sulfur K-edge XANES spectra as an innovative “fingerprint” to distinguish tsunami backwash deposits (TBD from typical marine sediments (TMS.

  15. Combined non-destructive XRF and SR-XAS study of archaeological artefacts.

    Science.gov (United States)

    Bardelli, Fabrizio; Barone, Germana; Crupi, Vincenza; Longo, Francesca; Majolino, Domenico; Mazzoleni, Paolo; Venuti, Valentina

    2011-03-01

    We report on a non-destructive study of Sicilian ceramic fragments of cultural heritage interest, classified as "proto-majolica" pottery and dating back to the twelfth to thirteen centuries AD. The analytical approach used is based on the employment of two totally non-invasive spectroscopic techniques: X-ray fluorescence (XRF), using a portable energy-dispersive XRF analyser, and X-ray absorption spectroscopy, using synchrotron radiation as a probe (SR-XAS). XRF measurements allowed us to collect elemental and spatially resolved information on major and minor constituents of the decorated coating of archaeological pottery fragments, so providing preliminary results on the main components characterizing the surface. In particular, we assigned to Fe and Mn the role of key elements of the colouring agent. With the aim of obtaining more detailed information, we performed SR-XAS measurements at the Fe and Mn K-edges at the Italian BM08 beamline at the European Synchrotron Radiation Facility (Grenoble, France). The experimental data were analysed by applying principal component analysis and least-squares fitting to the near-edge part of the spectra (X-ray absorption near-edge structure) to determine the samples' speciation. From the overall results, umber, a class of brownish pigments characterized by a mixture of hydrated iron and manganese oxides, has been ascribed as a pigmenting agent.

  16. Spectral K-edge subtraction imaging of experimental non-radioactive barium uptake in bone.

    Science.gov (United States)

    Panahifar, Arash; Samadi, Nazanin; Swanston, Treena M; Chapman, L Dean; Cooper, David M L

    2016-12-01

    To evaluate the feasibility of using non-radioactive barium as a bone tracer for detection with synchrotron spectral K-edge subtraction (SKES) technique. Male rats of 1-month old (i.e., developing skeleton) and 8-month old (i.e., skeletally mature) were orally dosed with low dose of barium chloride (33mg/kg/day Ba 2+ ) for 4weeks. The fore and hind limbs were dissected for imaging in projection and computed tomography modes at 100μm and 52μm pixel sizes. The SKES method utilizes a single bent Laue monochromator to prepare a 550eV energy spectrum to encompass the K-edge of barium (37.441keV), for collecting both 'above' and 'below' the K-edge data sets in a single scan. The SKES has a very good focal size, thus limits the 'crossover' and motion artifacts. In juvenile rats, barium was mostly incorporated in the areas of high bone turnover such as at the growth plate and the trabecular surfaces, but also in the cortical bone as the animals were growing at the time of tracer administration. However, the adults incorporated approximately half the concentration and mainly in the areas where bone remodeling was predominant and occasionally in the periosteal and endosteal layers of the diaphyseal cortical bone. The presented methodology is simple to implement and provides both structural and functional information, after labeling with barium, on bone micro-architecture and thus has great potential for in vivo imaging of pre-clinical animal models of musculoskeletal diseases to better understand their mechanisms and to evaluate the efficacy of pharmaceuticals. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

  17. XANES at the silicon k-edge in the kaolin-meta kaolin-geopolymer system

    International Nuclear Information System (INIS)

    Lima, F.T.; Silva, F.J.; Thaumaturgo, C.

    2005-01-01

    The geo polymer synthesis process optimization pretends to control the re logical and mechanical properties. The Al/Si ratio is the main variable that governs the geo polymerization process. This control occurs by changing temperature, pressure and chemical composition of the geo polymer. Thermal analysis (DTA/DSC), microscopic (SEM/TEM) and spectroscopic (FTIR, XRD, SAXS, EXAFS and XANES) techniques have been used to characterize these inorganic systems. In this work, XANES spectra of the k-edge silicon (Si) of the kaolin-meta kaolin-geo polymer are presented. The XANES spectra provides the oxidation state and structural information about the present studied atom: Silicon (Si). (author)

  18. Maximal $k$-Edge-Colorable Subgraphs, Vizing's Theorem, and Tuza's Conjecture

    OpenAIRE

    Puleo, Gregory J.

    2015-01-01

    We prove that if $M$ is a maximal $k$-edge-colorable subgraph of a multigraph $G$ and if $F = \\{v \\in V(G) : d_M(v) \\leq k-\\mu(v)\\}$, then $d_F(v) \\leq d_M(v)$ for all $v \\in F$. (When $G$ is a simple graph, the set $F$ is just the set of vertices having degree less than $k$ in $M$.) This implies Vizing's Theorem as well as a special case of Tuza's Conjecture on packing and covering of triangles. A more detailed version of our result also implies Vizing's Adjacency Lemma for simple graphs.

  19. The hybrid K-edge/K-XRF densitometer: Principles - design - performance

    International Nuclear Information System (INIS)

    Ottmar, H.; Eberle, H.

    1991-02-01

    The Euratom Safeguards Directorate (ESD) has recently installed a hybrid K-edge/K-XRF densitometer in a commerical reprocessing plant for the safeguarding of nuclear materials. This instrument, developed at KfK Karlsruhe, offers for the first time analytical measurement capabilities for timely on-site input accountancy verification. Lectures providing informations on measurement principles, instrument design features and performance data have been given to inspectors of ESD to make them familiar with the new instrument. This report summarizes the essential materials presented during these courses. (orig.) [de

  20. K-edge energy-based calibration method for photon counting detectors

    Science.gov (United States)

    Ge, Yongshuai; Ji, Xu; Zhang, Ran; Li, Ke; Chen, Guang-Hong

    2018-01-01

    In recent years, potential applications of energy-resolved photon counting detectors (PCDs) in the x-ray medical imaging field have been actively investigated. Unlike conventional x-ray energy integration detectors, PCDs count the number of incident x-ray photons within certain energy windows. For PCDs, the interactions between x-ray photons and photoconductor generate electronic voltage pulse signals. The pulse height of each signal is proportional to the energy of the incident photons. By comparing the pulse height with the preset energy threshold values, x-ray photons with specific energies are recorded and sorted into different energy bins. To quantitatively understand the meaning of the energy threshold values, and thus to assign an absolute energy value to each energy bin, energy calibration is needed to establish the quantitative relationship between the threshold values and the corresponding effective photon energies. In practice, the energy calibration is not always easy, due to the lack of well-calibrated energy references for the working energy range of the PCDs. In this paper, a new method was developed to use the precise knowledge of the characteristic K-edge energy of materials to perform energy calibration. The proposed method was demonstrated using experimental data acquired from three K-edge materials (viz., iodine, gadolinium, and gold) on two different PCDs (Hydra and Flite, XCounter, Sweden). Finally, the proposed energy calibration method was further validated using a radioactive isotope (Am-241) with a known decay energy spectrum.

  1. A Li K-edge XANES study of salts and minerals.

    Science.gov (United States)

    O'Shaughnessy, Cedrick; Henderson, Grant S; Moulton, Benjamin J A; Zuin, Lucia; Neuville, Daniel R

    2018-03-01

    The first comprehensive Li K-edge XANES study of a varied suite of Li-bearing minerals is presented. Drastic changes in the bonding environment for lithium are demonstrated and this can be monitored using the position and intensity of the main Li K-absorption edge. The complex silicates confirm the assignment of the absorption edge to be a convolution of triply degenerate p-like states as previously proposed for simple lithium compounds. The Li K-edge position depends on the electronegativity of the element to which it is bound. The intensity of the first peak varies depending on the existence of a 2p electron and can be used to evaluate the degree of ionicity of the bond. The presence of a 2p electron results in a weak first-peak intensity. The maximum intensity of the absorption edge shifts to lower energy with increasing SiO 2 content for the lithium aluminosilicate minerals. The bond length distortion of the lithium aluminosilicates decreases with increasing SiO 2 content, thus increased distortion leads to an increase in edge energy which measures lithium's electron affinity.

  2. K-Edge Subtraction Angiography with Synchrotron X-Rays; TOPICAL

    International Nuclear Information System (INIS)

    Giacomini, John C.

    1996-01-01

    The purpose of this project was to utilize dual energy, monochromatic X-rays produced from synchrotrons radiation in order to obtain noninvasive medical imaging. The application of synchrotrons radiation to medical imaging is based on the principle of iodine dichromography, first described by Bertil Jacobson of the Karolinska Institute in 1953. Medical imaging using synchrotrons radiation and K-edge dichromography was pioneered at Stanford University under the leadership of Dr. Ed Rubenstein, and the late Nobel Laureate in Physics, Dr. Robert Hofstadter. With progressive refinements in hardware, clinical-quality images were obtained of human coronary arteries utilizing peripheral injections of iodinated contrast agent. These images even now are far superior to those being presented by investigators using MRI as an imaging tool for coronary arteries. However, new supplies and instruments in the cardiac catheterization laboratory have served to transform coronary angiography into an outpatient procedure, with relatively little morbidity. We extended the principles learned with coronary angiography to noninvasive imaging of the human bronchial tree. For these images, we utilized xenon as the contrast agent, as it has a K-edge very similar to that of iodine. In this case, there is no true competing diagnostic test, and pulmonary neoplasm is an enormous public health concern. In early experiments, we demonstrated remarkably clear images of the human bronchial tree. These images have been shown internationally; however, funding difficulties primarily with the Department of Energy have not allowed for progression of this promising avenue of research. One potential criticism of the project is that in order to obtain these images, we utilized national laboratories. Some have questioned whether this would lead to a practical imaging modality. However, we have shown that the technology exists to allow for construction of a miniature storage ring, with a superconducting

  3. Solid energy calibration standards for P K-edge XANES: electronic structure analysis of PPh4Br.

    Science.gov (United States)

    Blake, Anastasia V; Wei, Haochuan; Donahue, Courtney M; Lee, Kyounghoon; Keith, Jason M; Daly, Scott R

    2018-03-01

    P K-edge X-ray absorption near-edge structure (XANES) spectroscopy is a powerful method for analyzing the electronic structure of organic and inorganic phosphorus compounds. Like all XANES experiments, P K-edge XANES requires well defined and readily accessible calibration standards for energy referencing so that spectra collected at different beamlines or under different conditions can be compared. This is especially true for ligand K-edge X-ray absorption spectroscopy, which has well established energy calibration standards for Cl (Cs 2 CuCl 4 ) and S (Na 2 S 2 O 3 ·5H 2 O), but not neighboring P. This paper presents a review of common P K-edge XANES energy calibration standards and analysis of PPh 4 Br as a potential alternative. The P K-edge XANES region of commercially available PPh 4 Br revealed a single, highly resolved pre-edge feature with a maximum at 2146.96 eV. PPh 4 Br also showed no evidence of photodecomposition when repeatedly scanned over the course of several days. In contrast, we found that PPh 3 rapidly decomposes under identical conditions. Density functional theory calculations performed on PPh 3 and PPh 4 + revealed large differences in the molecular orbital energies that were ascribed to differences in the phosphorus oxidation state (III versus V) and molecular charge (neutral versus +1). Time-dependent density functional theory calculations corroborated the experimental data and allowed the spectral features to be assigned. The first pre-edge feature in the P K-edge XANES spectrum of PPh 4 Br was assigned to P 1s → P-C π* transitions, whereas those at higher energy were P 1s → P-C σ*. Overall, the analysis suggests that PPh 4 Br is an excellent alternative to other solid energy calibration standards commonly used in P K-edge XANES experiments.

  4. K-edge x-ray-absorption spectroscopy of laser-generated Kr+ and Kr2+

    International Nuclear Information System (INIS)

    Southworth, S. H.; Arms, D. A.; Dufresne, E. M.; Dunford, R. W.; Ederer, D. L.; Hoehr, C.; Kanter, E. P.; Kraessig, B.; Landahl, E. C.; Peterson, E. R.; Rudati, J.; Santra, R.; Walko, D. A.; Young, L.

    2007-01-01

    Tunable, polarized, microfocused x-ray pulses were used to record x-ray absorption spectra across the K edges of Kr + and Kr 2+ produced by laser ionization of Kr. Prominent 1s→4p and 5p excitations are observed below the 1s ionization thresholds in accord with calculated transition energies and probabilities. Due to alignment of 4p hole states in the laser-ionization process, the Kr + 1s→4p cross section varies with respect to the angle between the laser and x-ray polarization vectors. This effect is used to determine the Kr + 4p 3/2 and 4p 1/2 quantum state populations, and these are compared with results of an adiabatic strong-field ionization theory that includes spin-orbit coupling

  5. Determination of the calcium species in coal chars by Ca K-edge XANES analysis

    Science.gov (United States)

    Liu, Li-Juan; Liu, Hui-Jun; Cui, Ming-Qi; Hu, Yong-Feng; Zheng, Lei; Zhao, Yi-Dong; Ma, Chen-Yan; Xi, Shi-Bo; Yang, Dong-Liang; Guo, Zhi-Ying; Wang, Jie

    2013-02-01

    Ca-based additives have been widely used as a sulfur adsorbent during coal pyrolysis and gasification. The Ca speciation and evolution during the pyrolysis of coal with Ca additives have attracted great attention. In this paper, Ca species in the coal chars prepared from the pyrolysis of Ca(OH)2 or CaCO3-added coals are studied by using Ca K-edge X-ray absorption near-edge structural spectroscopy. The results demonstrate that Ca(OH)2, CaSO4, CaS and CaO coexist in the Ca(OH)2-added chars, while Ca(OH)2 and CaSO4 are the main species in the Ca(OH)2-added chars. Besides, a carboxyl-bound Ca is also formed during both the pyrolysis for the Ca(OH)2-added and the CaCO3-added coals. A detailed discussion about the Ca speciation is given.

  6. Measurement of areal density modulation of laser-imploded shells through K-edge imaging

    International Nuclear Information System (INIS)

    Yaakobi, B.; Smalyuk, V. A.; Delettrez, J. A.; Marshall, F. J.; Meyerhofer, D. D.; Seka, W.

    2000-01-01

    A new method for studying the modulations in the ρΔR of imploded shells is introduced: using a recently developed pinhole-array x-ray spectrometer, core images are obtained at energies below and above the K-edge energy of a titanium dopant. The ratio of these images reflects the nonuniformity of the cold shell around the time of peak compression, independently of modulation in core emission. The two-dimensional images of ρΔR modulations are of interest in laser fusion because they show the final result of unstable implosion evolution. The measured average ρΔR of the cold shell and the amplitude and spectrum of its modulations are in agreement with the results of two-dimensional code simulations that include imprinting of laser nonuniformity on the target. (c) 2000 American Institute of Physics

  7. Three dimensional mapping of strontium in bone by dual energy K-edge subtraction imaging

    International Nuclear Information System (INIS)

    Cooper, D M L; Chapman, L D; Carter, Y; Zhouping, W; Wu, Y; Panahifar, A; Duke, M J M; Doschak, M; Britz, H M; Bewer, B

    2012-01-01

    The bones of many terrestrial vertebrates, including humans, are continually altered through an internal process of turnover known as remodeling. This process plays a central role in bone adaptation and disease. The uptake of fluorescent tetracyclines within bone mineral is widely exploited as a means of tracking new tissue formation. While investigation of bone microarchitecture has undergone a dimensional shift from 2D to 3D in recent years, we lack a 3D equivalent to fluorescent labeling. In the current study we demonstrate the ability of synchrotron radiation dual energy K-edge subtraction (KES) imaging to map the 3D distribution of elemental strontium within rat vertebral samples. This approach has great potential for ex vivo analysis of preclinical models and human tissue samples. KES also represents a powerful tool for investigating the pharmokinetics of strontium-based drugs recently approved in many countries around the globe for the treatment of osteoporosis. (paper)

  8. The potential for neurovascular intravenous angiography using K-edge digital subtraction angiography

    International Nuclear Information System (INIS)

    Schueltke, E.; Fiedler, S.; Kelly, M.; Griebel, R.; Juurlink, B.; LeDuc, G.; Esteve, F.; Le Bas, J.-F.; Renier, M.; Nemoz, C.; Meguro, K.

    2005-01-01

    Background: Catheterization of small-caliber blood vessels in the central nervous system can be extremely challenging. Alternatively, intravenous (i.v.) administration of contrast agent is minimally invasive and therefore carries a much lower risk for the patient. With conventional X-ray equipment, volumes of contrast agent that could be safely administered to the patient do not allow acquisition of high-quality images after i.v. injection, because the contrast bolus is extremely diluted by passage through the heart. However, synchrotron-based digital K-edge subtraction angiography does allow acquisition of high-quality images after i.v. administration of relatively small doses of contrast agent. Materials and methods: Eight adult male New Zealand rabbits were used for our experiments. Animals were submitted to both angiography with conventional X-ray equipment and synchrotron-based digital subtraction angiography. Results: With conventional X-ray equipment, no contrast was seen in either cerebral or spinal blood vessels after i.v. injection of iodinated contrast agent. However, using K-edge digital subtraction angiography, as little as 1 ml iodinated contrast agent, when administered as i.v. bolus, yielded images of small-caliber blood vessels in the central nervous system (both brain and spinal cord). Conclusions: If it would be possible to image blood vessels of the same diameter in the central nervous system of human patients, the synchrotron-based technique could yield high-quality images at a significantly lower risk for the patient than conventional X-ray imaging. Images could be acquired where catheterization of feeding blood vessels has proven impossible

  9. Stability of Working Reference Standards for Hybrid K-Edge Densitometer Quality Assurance

    International Nuclear Information System (INIS)

    Guzzardo, T.; Pickett, C.A.; McElroy, R.; Croft, S.; Garrison, J.; Venkataraman, R.

    2015-01-01

    The relatively short working life of aqueous solution standards of actinides for the calibration and quality control of Hybrid K-Edge Densitometer (HKED) measurements necessitates the development of a stable matrix material less susceptible to degradation. Degradation in the form of evaporation, radiolysis, settling, sloshing, and sediment formation can all reduce the reliability and working life of an aqueous standard. These factors make aqueous solutions inadequate for long-term quality assurance measurements designed to detect weak or subtle trends in system performance. Epoxy, studied here, is an alternative matrix material that may be less vulnerable to degradation. An additional benefit of epoxy is that standards can easily be characterized as sealed sources which allows for simplified administrative controls during shipping and storage. The stability of working reference standards consisting of U 3 O 8 in an epoxy matrix for use in the HKED has been tracked for over three years through repeated X-ray Fluorescence (XRF) and K-Edge (KED) measurements. A set of six epoxy standards ranging in concentration from 1 g/l to 76 g/l uranium were determined to be stable, within the expected accuracy of the system, over the period of analysis. During this time, no effort was made to enhance the stability of the epoxy standards; the radial measurement position was not controlled and in the middle of the analysis period the HKED system and standards were shipped from the vendor's factory to the customer. Epoxy standards afford numerous benefits over those created from aqueous solutions and should be considered when developing HKED standards for quality assurance measurements. The stability of the epoxy allows the development of working standards of a stability and robustness sufficient for use in a proposed international round-robin exercise based on the exchange of such standards. (author)

  10. The potential for neurovascular intravenous angiography using K-edge digital subtraction angiography

    Energy Technology Data Exchange (ETDEWEB)

    Schueltke, E. [University of Saskatchewan, Saskatoon, SK (Canada) and Walton Medical Centre, University of Liverpool (United Kingdom)]. E-mail: els433@duke.usask.ca; Fiedler, S. [EMBL, Hamburg (Germany); Kelly, M. [University of Saskatchewan, Saskatoon, SK (Canada); Griebel, R. [University of Saskatchewan, Saskatoon, SK (Canada); Juurlink, B. [University of Saskatchewan, Saskatoon, SK (Canada); LeDuc, G. [ESRF, Grenoble (France); Esteve, F. [INSERM U647-ESRF, Grenoble (France); Le Bas, J.-F. [INSERM U647-ESRF, Grenoble (France); Renier, M. [ESRF, Grenoble (France); Nemoz, C. [ESRF, Grenoble (France); Meguro, K. [University of Saskatchewan, Saskatoon, SK (Canada)

    2005-08-11

    Background: Catheterization of small-caliber blood vessels in the central nervous system can be extremely challenging. Alternatively, intravenous (i.v.) administration of contrast agent is minimally invasive and therefore carries a much lower risk for the patient. With conventional X-ray equipment, volumes of contrast agent that could be safely administered to the patient do not allow acquisition of high-quality images after i.v. injection, because the contrast bolus is extremely diluted by passage through the heart. However, synchrotron-based digital K-edge subtraction angiography does allow acquisition of high-quality images after i.v. administration of relatively small doses of contrast agent. Materials and methods: Eight adult male New Zealand rabbits were used for our experiments. Animals were submitted to both angiography with conventional X-ray equipment and synchrotron-based digital subtraction angiography. Results: With conventional X-ray equipment, no contrast was seen in either cerebral or spinal blood vessels after i.v. injection of iodinated contrast agent. However, using K-edge digital subtraction angiography, as little as 1 ml iodinated contrast agent, when administered as i.v. bolus, yielded images of small-caliber blood vessels in the central nervous system (both brain and spinal cord). Conclusions: If it would be possible to image blood vessels of the same diameter in the central nervous system of human patients, the synchrotron-based technique could yield high-quality images at a significantly lower risk for the patient than conventional X-ray imaging. Images could be acquired where catheterization of feeding blood vessels has proven impossible.

  11. Preliminary study of an angiographic and angio-tomographic technique based on K-edge filters

    Energy Technology Data Exchange (ETDEWEB)

    Golosio, Bruno; Brunetti, Antonio [Dipartimento POLCOMING, Istituto di Matematica e Fisica, Università di Sassari, 07100 Sassari (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Cagliari (Italy); Oliva, Piernicola; Carpinelli, Massimo [Dipartimento di Chimica e Farmacia, Università di Sassari, 07100 Sassari (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Cagliari (Italy); Luca Masala, Giovanni [Dipartimento di Chimica e Farmacia, Università di Sassari, 07100 Sassari (Italy); Meloni, Francesco [Unità operativa di Diagnostica per immagini Asl n. 1, Ospedale Civile SS Annunziata, 07100 Sassari (Italy); Battista Meloni, Giovanni [Istituto di Scienze Radiologiche, Università di Sassari, 07100 Sassari (Italy)

    2013-08-14

    Digital Subtraction Angiography is commonly affected by artifacts due to the patient movements during the acquisition of the images without and with the contrast medium. This paper presents a preliminary study on an angiographic and angio-tomographic technique based on the quasi-simultaneous acquisition of two images, obtained using two different filters at the exit of an X-ray tube. One of the two filters (K-edge filter) contains the same chemical element used as a contrast agent (gadolinium in this study). This filter absorbs more radiation with energy just above the so called K-edge energy of gadolinium than the radiation with energy just below it. The other filter (an aluminium filter in this study) is simply used to suppress the low-energy contribution to the spectrum. Using proper calibration curves, the two images are combined to obtain an image of the contrast agent distribution. In the angio-tomographic application of the proposed technique two images, corresponding to the two filter types, are acquired for each viewing angle of the tomographic scan. From the two tomographic reconstructions, it is possible to obtain a three-dimensional map of the contrast agent distribution. The technique was tested on a sample consisting of a rat skull placed inside a container filled with water. Six small cylinders with 4.7 mm internal diameter containing the contrast medium at different concentrations were placed inside the skull. In the plain angiographic application of the technique, five out of six cylinders were visible, with gadolinium concentration down to 0.96%. In the angio-tomographic application, all six cylinders were visible, with gadolinium concentration down to 0.49%. This preliminary study shows that the proposed technique can provide images of the contrast medium at low concentration without most of the artifacts that are present in images produced by conventional techniques. The results encourage further investigation on the feasibility of a clinical

  12. Cation occupancy sites in synthetic Co-doped magnetites as determined with X-ray absorption (XAS) and Moessbauer spectroscopies

    International Nuclear Information System (INIS)

    Lelis, M.F.F.; Porto, A.O.; Goncalves, C.M.; Fabris, J.D.

    2004-01-01

    In the present work, cobalt-doped magnetites, prepared by the co-precipitation method, were mainly studied by X-ray absorption and Moessbauer spectroscopies. From the chemical analysis, it was observed that the continuous increase of Co 2+ is followed by a simultaneous decrease of the Fe 2+ contents, in the spinel structure. Room temperature Moessbauer parameters indicate that samples are formed by single crystallographic phases of pure magnetite or its Co-substituted analogs. Basing on the inversion of intensities of the Moessbauer lines 1 (leftmost, in the negative Doppler velocity scale) and 2, it is assumed that the Co-substitution occurs essentially, if not only, at octahedral sites of the spinel structure. XAS results obtained at Co K-edge confirm that the Co-substitution occurs preferentially at octahedral coordination sites

  13. Structure of spinel at high temperature using in-situ XANES study at the Al and Mg K-edge

    Energy Technology Data Exchange (ETDEWEB)

    Ligny, D de [Universite Claude Bernard Lyon 1, LPCML, 69622 Villeurbanne (France); Neuville, D R [Physique des Mineraux et Magmas, Geochimie-Cosmochimie, CNRS-IPGP, 4 place Jussieu, 75005 Paris (France); Flank, A-M; Lagarde, P, E-mail: deligny@pcml.univ-lyon1.f [Synchrotron SOLEIL, L' Orme des Merisiers, Saint Aubin, 91192 France (France)

    2009-11-15

    We present structural information obtained on spinel at high temperature (298-2400 K) using in situ XANES at the Mg and Al K-edge. Spinel, {sup [4]}(Al{sub x},Mg{sub 1-x}){sup [6]}(Al{sub 2-x},Mg{sub x})O{sub 4}, with increasing temperature, show a substitution of Mg by Al and Al by Mg in their respective sites. This substitution corresponds to an inversion of the Mg and Al sites. Furthermore, both experiments at the Al and Mg K-edges are in good agreement with XANES calculation made using FDMNES code.

  14. Electronic structure of Ni/sub 3/Al and Ni/sub 3/Ga alloys

    CERN Document Server

    Pong, W F; Chang, Y K; Tsai, M H; Hsieh, H H; Pieh, J Y; Tseng, P K; Lee, J F; Hsu, L S

    1999-01-01

    This work investigates the charge transfer and Al(Ga) p-Ni d hybridization effects in the intermetallic Ni/sub 3/Al(Ni/sub 3/Ga) alloy using the NiL/sub 3.2/- and K-edge and Al(Ga)K X-ray absorption near edge structure (XANES) measurements. We find that the intensity of white-line features at the NiL/sub 3.2/-edge in the Ni/sub 3/Al(Ni /sub 3/Ga) alloy decreased in comparison with that of pure Ni, which can be attributed to the enhancement of Ni3d states filling and the depletion of the density of Ni 3d unoccupied states in the Ni/sub 3 /Al(Ni/sub 3/Ga) alloy. Two clear features are also observed in the Ni/sub 3/Al(Ni/sub 3/Ga) XANES spectrum at the Al(Ga) K-edge, which can be assigned to the Al(Ga) unoccupied 3p (4p) states and their hybridized states with the Ni 3d/4sp states above the Fermi level in Ni/sub 3/Al(Ni/sub 3/Ga). The threshold at Al K-edge XANES for Ni/sub 3/Al clearly shifts towards higher photon energies relative to that of pure Al, indicating that Al loses charges upon forming Ni/sub 3 /Al. ...

  15. Variations in cerium X-ray spectra and enhanced K-edge angiography

    International Nuclear Information System (INIS)

    Sato, Eiichi; Tanaka, Etsuro; Mori, Hidezo

    2005-01-01

    A cerium-target X-ray tube is useful in performing cone-beam K-edge angiography because K-series characteristic X-rays from the cerium target are absorbed effectively by iodine-based contrast media. The X-ray generator consists of a main controller and a unit with a high-voltage circuit and a fixed anode X-ray tube. The tube is a 1.0-mm-focus diode with a cerium target and a 0.5-mm-thick beryllium window. The maximum tube voltage and current were 65 kV and 0.4 mA, respectively. Cerium Kα rays were selected out using a barium sulfate filter, and the X-ray intensities without filtering and with a barium sulfate filter were 209 and 16.8 μGy/s, respectively, at 1.0 m from the source with a tube voltage of 60 kV and a current of 0.40 mA. Angiography was performed with an X-ray film using the filter and iodine-based microspheres 15 μm in diameter. In the angiography of nonliving animals, we observed fine blood vessels approximately 100 μm in diameter with high contrasts. (author)

  16. New K-edge-balanced contrast phantom for image quality assurance in projection radiography

    Science.gov (United States)

    Cresens, Marc; Schaetzing, Ralph

    2003-06-01

    X-ray-absorber step-wedge phantoms serve in projection radiography to assess a detection system's overall exposure-related signal-to-noise ratio performance and contrast response. Data derived from a phantom image, created by exposing a step-wedge onto the image receptor, are compared with predefined acceptance criteria during periodic image quality assurance (QA). For contrast-related measurements, in particular, the x-ray tube potential requires accurate setting and low ripple, since small deviations from the specified kVp, causing energy spectrum changes, lead to significant image signal variation at high contrast ratios. A K-edge-balanced, rare-earth-metal contrast phantom can generate signals that are significantly more robust to the spectral variability and instability of exposure equipment in the field. The image signals from a hafnium wedge, for example, are up to eight times less sensitive to spectral fluctuations than those of today"s copper phantoms for a 200:1 signal ratio. At 120 kVp (RQA 9), the hafnium phantom still preserves 70% of the subject contrast present at 75 kVp (RQA 5). A copper wedge preserves only 7% of its contrast over the same spectral range. Spectral simulations and measurements on prototype systems, as well as potential uses of this new class of phantoms (e.g., QA, single-shot exposure response characterization) are described.

  17. Molecular anisotropy effects in carbon K-edge scattering: depolarized diffuse scattering and optical anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Stone, Kevin H.

    2014-07-14

    Some polymer properties, such as conductivity, are very sensitive to short- and intermediate-range orientational and positional ordering of anisotropic molecular functional groups, and yet means to characterize orientational order in disordered systems are very limited. We demonstrate that resonant scattering at the carbon K-edge is uniquely sensitive to short-range orientation correlations in polymers through depolarized scattering at high momentum transfers, using atactic polystyrene as a well-characterized test system. Depolarized scattering is found to coexist with unpolarized fluorescence, and to exhibit pronounced anisotropy. We also quantify the spatially averaged optical anisotropy from low-angle reflectivity measurements, finding anisotropy consistent with prior visible, x-ray absorption, and theoretical studies. The average anisotropy is much smaller than that in the depolarized scattering and the two have different character. Both measurements exhibit clear spectral signatures from the phenyl rings and the polyethylene-like backbone. Discussion focuses on analysis considerations and prospects for using this depolarized scattering for studies of disorder in soft condensed matter.

  18. Photoabsorption spectra of potassium and rubidium near the K-edge

    International Nuclear Information System (INIS)

    Azuma, Y.; Berry, H.G.; Cowan, P.L.

    1995-01-01

    We have used a high-temperature circulating heat-pipe absorption cell together with monochromatized X-ray beams at the X24A and X23A2 beam lines at the NSLS to obtain photoabsorption spectra of potassium and rubidium at their K- and KM-edges. The photon-energy ranges lay near 3600 eV and 15200 eV, respectively. We have also obtained first measurements of the LII and LIII edges in cesium. Although the K-edge photoabsorptions of the rare gases have been studied, there is little previous work on other atomic vapors. Most of the edges and resonance peaks that we observed have now been identified using Dirac Hartree-Fock calculations. As a check, we have compared these results with those obtained previously in closed-shell rare-gas absorption spectra. The absolute energies were obtained through a calibration of the X24A systems using measurements of several metal L-edges in the 3200-5000 eV energy range. We found that the 4p resonance in potassium is significantly enhanced compared with the corresponding situation in argon. Likewise, the 5p resonance in krypton is unresolved from the background ionization cross section, whereas it is well resolved in rubidium. As suggested by Amusia, these enhancements may be due to the enhanced potential seen in the excited state of the alkali systems as a result of the presence of an s-electron which reduces the nuclear shielding

  19. Using solution- and solid-state S K-edge X-ray absorption spectroscopy with density functional theory to evaluate M-S bonding for MS4(2-) (M = Cr, Mo, W) dianions.

    Science.gov (United States)

    Olson, Angela C; Keith, Jason M; Batista, Enrique R; Boland, Kevin S; Daly, Scott R; Kozimor, Stosh A; MacInnes, Molly M; Martin, Richard L; Scott, Brian L

    2014-12-14

    Herein, we have evaluated relative changes in M-S electronic structure and orbital mixing in Group 6 MS4(2-) dianions using solid- and solution-phase S K-edge X-ray absorption spectroscopy (XAS; M = Mo, W), as well as density functional theory (DFT; M = Cr, Mo, W) and time-dependent density functional theory (TDDFT) calculations. To facilitate comparison with solution measurements (conducted in acetonitrile), theoretical models included gas-phase calculations as well as those that incorporated an acetonitrile dielectric, the latter of which provided better agreement with experiment. Two pre-edge features arising from S 1s → e* and t electron excitations were observed in the S K-edge XAS spectra and were reasonably assigned as (1)A1 → (1)T2 transitions. For MoS4(2-), both solution-phase pre-edge peak intensities were consistent with results from the solid-state spectra. For WS4(2-), solution- and solid-state pre-edge peak intensities for transitions involving e* were equivalent, while transitions involving the t orbitals were less intense in solution. Experimental and computational results have been presented in comparison to recent analyses of MO4(2-) dianions, which allowed M-S and M-O orbital mixing to be evaluated as the principle quantum number (n) for the metal valence d orbitals increased (3d, 4d, 5d). Overall, the M-E (E = O, S) analyses revealed distinct trends in orbital mixing. For example, as the Group 6 triad was descended, e* (π*) orbital mixing remained constant in the M-S bonds, but increased appreciably for M-O interactions. For the t orbitals (σ* + π*), mixing decreased slightly for M-S bonding and increased only slightly for the M-O interactions. These results suggested that the metal and ligand valence orbital energies and radial extensions delicately influenced the orbital compositions for isoelectronic ME4(2-) (E = O, S) dianions.

  20. Dispersive magnetic and electronic excitations in iridate perovskites probed by oxygen K -edge resonant inelastic x-ray scattering

    Science.gov (United States)

    Lu, Xingye; Olalde-Velasco, Paul; Huang, Yaobo; Bisogni, Valentina; Pelliciari, Jonathan; Fatale, Sara; Dantz, Marcus; Vale, James G.; Hunter, E. C.; Chang, Johan; Strocov, Vladimir N.; Perry, R. S.; Grioni, Marco; McMorrow, D. F.; Rønnow, Henrik M.; Schmitt, Thorsten

    2018-01-01

    Resonant inelastic x-ray scattering (RIXS) experiments performed at the oxygen K edge on the iridate perovskites Sr2IrO4 and Sr3Ir2O7 reveal a sequence of well-defined dispersive modes over the energy range up to ˜0.8 eV . The momentum dependence of these modes and their variation with the experimental geometry allows us to assign each of them to specific collective magnetic and/or electronic excitation processes, including single and bimagnons, and spin-orbit and electron-hole excitons. We thus demonstrate that dispersive magnetic and electronic excitations are observable at the O K edge in the presence of the strong spin-orbit coupling in the 5 d shell of iridium and strong hybridization between Ir 5 d and O 2 p orbitals, which confirm and expand theoretical expectations. More generally, our results establish the utility of O K -edge RIXS for studying the collective excitations in a range of 5 d materials that are attracting increasing attention due to their novel magnetic and electronic properties. Especially, the strong RIXS response at O K edge opens up the opportunity for investigating collective excitations in thin films and heterostructures fabricated from these materials.

  1. Blueprint XAS: a Matlab-based toolbox for the fitting and analysis of XAS spectra.

    Science.gov (United States)

    Delgado-Jaime, Mario Ulises; Mewis, Craig Philip; Kennepohl, Pierre

    2010-01-01

    Blueprint XAS is a new Matlab-based program developed to fit and analyse X-ray absorption spectroscopy (XAS) data, most specifically in the near-edge region of the spectrum. The program is based on a methodology that introduces a novel background model into the complete fit model and that is capable of generating any number of independent fits with minimal introduction of user bias [Delgado-Jaime & Kennepohl (2010), J. Synchrotron Rad. 17, 119-128]. The functions and settings on the five panels of its graphical user interface are designed to suit the needs of near-edge XAS data analyzers. A batch function allows for the setting of multiple jobs to be run with Matlab in the background. A unique statistics panel allows the user to analyse a family of independent fits, to evaluate fit models and to draw statistically supported conclusions. The version introduced here (v0.2) is currently a toolbox for Matlab. Future stand-alone versions of the program will also incorporate several other new features to create a full package of tools for XAS data processing.

  2. Synthesis of nanocrystalline NiO/ZnO heterostructured composite powders by sol-gel auto combustion method and their characterizations

    Science.gov (United States)

    Tangcharoen, Thanit; Klysubun, Wantana; Kongmark, Chanapa

    2018-03-01

    Nanocrystalline NiO/ZnO heterostructured composite powders were prepared by the sol-gel auto combustion method, based on nickel and zinc nitrate precursors and using diethanolamine (DEA) as novel fuel. The composition of different NiO and ZnO ratios, ranging from 100/0, 95/5, 90/10, 80/20, 60/40, 50/50, 40/60, 20/80, 10/90, 5/95 to 0/100, were studied. The structural, chemical bonding, morphological, optical, and fluorescence properties including the local atomic structure of each calcined sample were systematically investigated by means of X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), UV-visible diffuse reflectance spectroscopy (UV-DRS), photoluminescence (PL) spectroscopy, and synchrotron X-ray absorption spectroscopy (XAS), respectively. For the ZnO concentration below 20%, both XRD and Raman spectroscopy results revealed only the NiO phase. This conformed to the observation of Zn K-edge and Ni K-edge X-ray absorption near edge structure (XANES). The Zn ions found in the samples of low ZnO concentration exhibited six-fold coordination with oxygen atoms rather than the four-fold coordination found in the wurtzite (WZ) structure of ZnO. In contrast, the Ni ions which are found in the samples of low NiO concentration (≤10%) are coordinated both tetrahedrally and octahedrally by four or six oxygen atoms, respectively, rather than the six-fold coordination which is usually observed for Ni ions in the rock salt (RS) form of NiO. All analytical results obtained from experimental XANES spectra were verified by the theoretical calculation of absorption spectra using the FEFF9.7 code. The UV-DRS results showed that there was an increase in the reflectance efficiency for both infrared and visible light conditions as the content of ZnO increases; meanwhile, the values for the energy gap (Eg) of all composite samples were higher than that of pure NiO and ZnO. In addition, the PL spectra revealed major blue emission bands observed at 490

  3. Off-line NDA measurement of actinides in reprocessing solution using hybrid K-edge/K-XRF densitometer

    International Nuclear Information System (INIS)

    Bootharajan, M.; Swaminathan, K.; Venkata Subramani, C.R.; Kumar, R.

    2015-01-01

    A versatile, nondestructive assay (NDA) system of a hybrid K-edge/K-XRF facility adapted to a glove box facility has been developed at RCL, IGCAR for the analysis of U and Pu in process solutions obtained from the reprocessing of spent nuclear fuels. This paper describes i) The development of a hybrid K-edge/K-XRF facility adapted to a glove box system ii) The results obtained using conditioner solution of burn up 155 GWd/t with a dose of 20 R/h and iii) Comparison of the results with the parallel analyses of the same by Isotope dilution mass spectrometry. The hybrid K-edge cum K-XRF densitometer is ideally suited for dissolver solutions as well as U and Pu product solutions from reprocessing plant. This method can be useful in the analysis of mixed solution of Special Nuclear Materials (SNM) without chemical separation. To assay solutions with high radiation background, the hybrid K-edge/K-XRF system is designed and fabricated inside a glove box with adequate shielding from both source X-rays and the sample radiation. The theory and preliminary experiments are described elsewhere. Around 5 mL of the conditioner solution (burn up of 155 GWd/t with a dose of 20 R/h) was taken in a poly propylene vial placed concentrically in to another poly propylene vial. The concentration was estimated by K-edge densitometry with X-ray tube operated with 150 kV and 1 mA and counting period of 3000s. Background correction was obtained with the X-ray tube in OFF condition. The solution was analysed parallelly using isotopic dilution mass spectrometry

  4. Structural and chemical reactivity modifications of a cobalt perovskite induced by Sr-substitution. An in situ XAS study

    International Nuclear Information System (INIS)

    Hueso, Jose L.; Holgado, Juan P.; Pereñíguez, Rosa; Gonzalez-DelaCruz, V.M.; Caballero, Alfonso

    2015-01-01

    LaCoO 3 and La 0.5 Sr 0.5 CoO 3−δ perovskites have been studied by in situ Co K-edge XAS. Although the partial substitution of La(III) by Sr(II) species induces an important increase in the catalytic oxidation activity and modifies the electronic state of the perovskite, no changes could be detected in the oxidation state of cobalt atoms. So, maintaining the electroneutrality of the perovskite requires the generation of oxygen vacancies in the network. The presence of these vacancies explains that the substituted perovskite is now much more reducible than the original LaCoO 3 perovskite. As detected by in situ XAS, after a consecutive reduction and oxidation treatment, the original crystalline structure of the LaCoO 3 perovskite is maintained, although in a more disordered state, which is not the case for the Sr doped perovskite. So, the La 0.5 Sr 0.5 CoO 3−δ perovskite submitted to the same hydrogen reduction treatment produces metallic cobalt, while as determined by in situ XAS spectroscopy the subsequent oxidation treatment yields a Co(III) oxide phase with spinel structure. Surprisingly, no Co(II) species are detected in this new spinel phase. - Highlights: • A Sr-substituted lanthanum cobalt perovskite has been prepared by spray pyrolysis. • It has been established that Co(III) cations are present in both perovskites. • LaCoO 3 is a less reducible phase than the substituted La 0.5 Sr 0.5 CoO 3−δ . • After reoxidation of reduced La 0.5 Sr 0.5 CoO 3−δ , a 100% Co(III) spinel is obtained

  5. XAS Investigation of bio-relevant cobalt complexes in aqueous media

    International Nuclear Information System (INIS)

    Bresson, C.; Lamouroux, C.; Esnouf, S.; Solari, P.L.; Den Auwer, C.

    2006-01-01

    Cobalt is an essential element of biological cycles involved in numerous metallo-biomolecules, but it becomes a toxic element at high concentration or a radio-toxic element because of its use in the nuclear industry. 'Molecular speciation' in biological media is an essential prerequisite to evaluate its chemical behaviour as well as its toxic or beneficial effects. In this scheme, we have focused on the coordination properties of the thiol-containing amino acid cysteine (Cys) and the pseudo-peptide N-(2-mercapto-propionyl) glycine (MPG) towards the Co 2+ cation in aqueous media. XAS at the Co K edge and traditional spectroscopic techniques have been coupled in order to structurally characterize the cobalt coordination sphere. Oxidation states and geometries of the bis- and tris-cysteinato Co(III) complexes are in agreement with the literature data. In addition, bond lengths between the metallic centre and the donor atoms have been determined. The structure of a new dimeric N-(2-mercapto-propionyl) glycinato Co(II) complex in solution is also reported. The coordination of MPG to Co(II) through the thiolate and carboxylate functions is ascertained. This work provides fundamental structural information about bio-relevant complexes of cobalt, which will contribute to our understanding of the chemical behaviour and the biological role of this radionuclide. (authors)

  6. X-ray spectroscopy at the Mn K edge in LaMnO3 : An ab initio study

    NARCIS (Netherlands)

    Hozoi, L.; Vries, A.H. de; Broer, R.

    2001-01-01

    We present ab initio quantum chemical embedded cluster calculations of Mn core-valence and d-d transitions in LaMnO3. The results are also important for the analysis of recent x-ray absorption and x-ray scattering experiments at the Mn K edge in LaMnO3. We find that the first two peaks of the

  7. Feasibility study of X-ray K-edge analysis of RCRA heavy metal contamination of sludge packaged in drums

    International Nuclear Information System (INIS)

    Jensen, T.

    1999-01-01

    A study has been completed to assess the capabilities of X-ray K-edge analysis in the measurement of RCRA metal contamination of sludge packaged in drums. Results were obtained for mercury and lead contamination. It was not possible to measure cadmium contamination using this technique. No false positive signals were observed. In cases where uniformity of the sludge can be assumed, this analysis can provide a quick, accurate measurement of heavy-metal contamination

  8. K-edge XANES analysis of sulfur compounds: an investigation of the relative intensities using internal calibration.

    Science.gov (United States)

    Almkvist, Gunnar; Boye, Kristin; Persson, Ingmar

    2010-09-01

    Sulfur K-edge XANES (X-ray absorption near-edge structure) spectroscopy is an excellent tool for determining the speciation of sulfur compounds in complex matrices. This paper presents a method to quantitatively determine the kinds of sulfur species in natural samples using internally calibrated reference spectra of model compounds. Owing to significant self-absorption of formed fluorescence radiation in the sample itself the fluorescence signal displays a non-linear correlation with the sulfur content over a wide concentration range. Self-absorption is also a problem at low total absorption of the sample when the sulfur compounds are present as particles. The post-edge intensity patterns of the sulfur K-edge XANES spectra vary with the type of sulfur compound, with reducing sulfur compounds often having a higher post-edge intensity than the oxidized forms. In dilute solutions (less than 0.3-0.5%) it is possible to use sulfur K-edge XANES reference data for quantitative analysis of the contribution from different species. The results show that it is essential to use an internal calibration system when performing quantitative XANES analysis. Preparation of unknown samples must take both the total absorption and possible presence of self-absorbing particles into consideration.

  9. Interpolation of Gamma-ray buildup Factors for Arbitrary Source Energies in the Vicinity of the K-edge

    International Nuclear Information System (INIS)

    Michieli, I.

    1998-01-01

    Recently, a new buildup factors approximation formula based on the expanded polynomial set (E-P function) was successfully introduced (Michieli 1994.) with the maximum approximation error below 4% throughout the standard data domain. Buildup factors interpolation in E-P function parameters for arbitrary source energies, near the K-edge in lead, was satisfactory. Maximum interpolation error, for lead, lays within 12% what appears to be acceptable for most Point Kernel application. 1991. Harima at. al., showed that, near the K-edge, fluctuation in energy of exposure rate attenuation factors i.e.: D(E)B(E, μ E r)exp(-μ E r), given as a function of penetration depth (r) in ordinary length units (not mfps.), is not nearly as great as that of buildup factors. That phenomenon leads to the recommendation (ANSI/ANS-6.4.3) that interpolations in that energy range should be made in the attenuation factors B(E, μ E r)exp(-μ E r) rather than in the buildup factors alone. In present article, such interpolation approach is investigated by applying it to the attenuation factors in lead, with E-P function representation of exposure buildup factors. Simple form of the E-P function leads to strait calculation of new function parameters for arbitrary source energy near the K-edge and thus allowing the same representation form of buildup factors as in the standard interpolation procedure. results of the interpolation are discussed and compared with those from standard approach. (author)

  10. A theoretical study on the selective oxygen K-edge soft X-ray emission spectroscopy of liquid acetic acid

    Science.gov (United States)

    Nishida, Naohiro; Kanai, Seiji; Tokushima, Takashi; Horikawa, Yuka; Takahashi, Osamu

    2015-11-01

    We have performed theoretical calculations to reproduce the site-selective X-ray emission spectroscopy (XES) spectra of liquid acetic acid at the oxygen K-edge (OCdbnd O,1s and OOH,1s). Structure sampling of an acetic acid cluster model was performed from the ab initio molecular dynamics trajectory. Relative XES intensities for the core-hole excited state dynamics simulations were calculated using density functional theory. We found that the theoretical XES spectra reproduced well the experimental spectra and that these calculations gave us electronic and molecular structure information about liquid acetic acid.

  11. Isotope effects in liquid water probed by transmission mode x-ray absorption spectroscopy at the oxygen K-edge.

    Science.gov (United States)

    Schreck, Simon; Wernet, Philippe

    2016-09-14

    The effects of isotope substitution in liquid water are probed by x-ray absorption spectroscopy at the O K-edge as measured in transmission mode. Confirming earlier x-ray Raman scattering experiments, the D2O spectrum is found to be blue shifted with respect to H2O, and the D2O spectrum to be less broadened. Following the earlier interpretations of UV and x-ray Raman spectra, the shift is related to the difference in ground-state zero-point energies between D2O and H2O, while the difference in broadening is related to the difference in ground-state vibrational zero-point distributions. We demonstrate that the transmission-mode measurements allow for determining the spectral shapes with unprecedented accuracy. Owing in addition to the increased spectral resolution and signal to noise ratio compared to the earlier measurements, the new data enable the stringent determination of blue shift and broadening in the O K-edge x-ray absorption spectrum of liquid water upon isotope substitution. The results are compared to UV absorption data, and it is discussed to which extent they reflect the differences in zero-point energies and vibrational zero-point distributions in the ground-states of the liquids. The influence of the shape of the final-state potential, inclusion of the Franck-Condon structure, and differences between liquid H2O and D2O resulting from different hydrogen-bond environments in the liquids are addressed. The differences between the O K-edge absorption spectra of water from our transmission-mode measurements and from the state-of-the-art x-ray Raman scattering experiments are discussed in addition. The experimentally extracted values of blue shift and broadening are proposed to serve as a test for calculations of ground-state zero-point energies and vibrational zero-point distributions in liquid H2O and D2O. This clearly motivates the need for new calculations of the O K-edge x-ray absorption spectrum of liquid water.

  12. On the origin of the differences in the Cu K-edge XANES of isostructural and isoelectronic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Sipr, O [Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnicka 10, CZ-162 53 Prague (Czech Republic); Rocca, F [IFN-CNR, Istituto di Fotonica e Nanotecnologie del Consiglio Nazionale delle Ricerche, Sezione ' FBK-CeFSA' di Trento, Via alla Cascata 56/C, I-38123 Povo (Trento) (Italy); Fornasini, P [Dipartimento di Fisica, Universita di Trento, Via Sommarive 14, I-38123 Povo (Trento) (Italy)], E-mail: sipr@fzu.cz

    2009-06-24

    Cu K-edge x-ray absorption near-edge structure (XANES) spectra of trigonal (3R) CuScO{sub 2} and CuLaO{sub 2} and of hexagonal (2H) CuScO{sub 2} were investigated experimentally and theoretically, in order to study differences between spectra of isostructural and isoelectronic compounds. Significant differences were found in the Cu K-edge XANES of 3R CuScO{sub 2} and 3R CuLaO{sub 2}; these differences can be understood by considering the calculated polarization dependence of the XANES spectra and the differences between the phaseshifts of Sc and La. Spectra of the 3R and 2H polytypes of CuScO{sub 2} differ only weakly and the difference originates from the long-range order. The pre-edge peak around 8980 eV is generated by the same mechanism as the pre-edge peak in Cu{sub 2}O, i.e. involving scattering by the Cu atoms in the plane which is perpendicular to the O-Cu-O axis.

  13. Novel digital K-edge imaging system with transition radiation from an 855-MeV electron beam

    CERN Document Server

    Hagenbuck, F; Clawiter, N; Euteneuer, H; Görgen, F; Holl, P; Johann, K; Kiser, K H; Kemmer, J; Kerschner, T; Kettig, O; Koch, H; Kube, G; Lauth, W; Mauhay, H; Schütrumpf, M; Stotter, R; Strüder, L; Walcher, T; Wilms, A; von Zanthier, C; Zemter, M

    2001-01-01

    A novel K-edge imaging method has been developed at the Mainz Microtron MAMI aiming at a very efficient use of the transition radiation (TR) flux generated by the external 855-MeV electron beam in a foil stack. A fan-like quasi-monochromatic hard X-ray beam is produced from the +or-1-mrad-wide TR cone with a highly oriented pyrolytic graphite (HOPG) crystal. The absorption of the object in front of a 30 mm*10 mm pn charge-coupled device (pn-CCD) photon detector is measured at every pixel by a broad-band energy scan around the K-absorption edge. This is accomplished by a synchronous variation of the lateral crystal position and the electron beam direction which defines also the direction of the TR cone. The system has been checked with a phantom consisting of a 2.5- mu m thick molybdenum sample embedded in a 136- or 272- mu m-thick copper bulk foil. A numerical analysis of the energy spectrum for every pixel demonstrates that data as far as +or-0.75 keV away from the K edge of molybdenum at 20 keV still improv...

  14. Mn K-edge X-ray absorption studies of oxo- and hydroxo-manganese(IV) complexes: experimental and theoretical insights into pre-edge properties.

    Science.gov (United States)

    Leto, Domenick F; Jackson, Timothy A

    2014-06-16

    Mn K-edge X-ray absorption spectroscopy (XAS) was used to gain insights into the geometric and electronic structures of [Mn(II)(Cl)2(Me2EBC)], [Mn(IV)(OH)2(Me2EBC)](2+), and [Mn(IV)(O)(OH)(Me2EBC)](+), which are all supported by the tetradentate, macrocyclic Me2EBC ligand (Me2EBC = 4,11-dimethyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane). Analysis of extended X-ray absorption fine structure (EXAFS) data for [Mn(IV)(O)(OH)(Me2EBC)](+) revealed Mn-O scatterers at 1.71 and 1.84 Å and Mn-N scatterers at 2.11 Å, providing the first unambiguous support for the formulation of this species as an oxohydroxomanganese(IV) adduct. EXAFS-determined structural parameters for [Mn(II)(Cl)2(Me2EBC)] and [Mn(IV)(OH)2(Me2EBC)](2+) are consistent with previously reported crystal structures. The Mn pre-edge energies and intensities of these complexes were examined within the context of data for other oxo- and hydroxomanganese(IV) adducts, and time-dependent density functional theory (TD-DFT) computations were used to predict pre-edge properties for all compounds considered. This combined experimental and computational analysis revealed a correlation between the Mn-O(H) distances and pre-edge peak areas of Mn(IV)═O and Mn(IV)-OH complexes, but this trend was strongly modulated by the Mn(IV) coordination geometry. Mn 3d-4p mixing, which primarily accounts for the pre-edge intensities, is not solely a function of the Mn-O(H) bond length; the coordination geometry also has a large effect on the distribution of pre-edge intensity. For tetragonal Mn(IV)═O centers, more than 90% of the pre-edge intensity comes from excitations to the Mn═O σ* MO. Trigonal bipyramidal oxomanganese(IV) centers likewise feature excitations to the Mn═O σ* molecular orbital (MO) but also show intense transitions to 3dx(2)-y(2) and 3dxy MOs because of enhanced 3d-4px,y mixing. This gives rise to a broader pre-edge feature for trigonal Mn(IV)═O adducts. These results underscore the importance of

  15. Quantification of chemical sulphur species in bulk soil and organic sulphur fractions by S K-edge Xanes spectroscopy

    DEFF Research Database (Denmark)

    Boye, K; Almkvist, G; Nilsson, S I

    2011-01-01

    residue (CR) incorporation and farmyard manure (FYM) application, with equal applications of mineral nutrients were included in the study. In the new data treatment method, internally calibrated spectra of dilute solutions (30 mm) of model compounds were used to fit the sample spectra. This greatly...... the opposite trend was observed. Sulphur XANES spectroscopy of acetylacetone extracts of physically protected and unprotected organic S in two of the soils revealed that physical protection was not related to S speciation; however, intermediate forms of oxidized S species appeared to accumulate in the residual......A new data treatment method for fitting spectra obtained by sulphur (S) K-edge X-ray absorption near-edge structure (XANES) spectroscopy was used to quantify the chemical S speciation at three experimental sites with arable soils receiving the same long-term field treatments. Two treatments, crop...

  16. Vulcanization reaction of squalene and S8 powder studied by Sulfur K-edge NEXAFS under liquid phase

    Science.gov (United States)

    Yagi, S.; Menjo, Y.; Tsukada, C.; Ogawa, S.; Kutluk, G.; Namatame, H.; Taniguchi, M.

    2015-03-01

    Vulcanized rubber materials are useful in our surroundings. However, detail structure and reaction are not revealed even in present. Since squalene molecule possesses some same properties compared with natural rubber, we have prepared the samples of vulcanized squalene at 140 °C for several hours. To understand the vulcanization reaction,sulfur K-edge NEXAFS measurements have been carried out for the vulcanized squalene under liquid phase with He-path system and fluorescence detection mode. Moreover, we have tried curve fitting analysis of NEXAFS spectra. The results indicate that the squalene has been vulcanized by the S8 molecule at 140 °C and the S8 molecule length is shortened from 8 to 5-6 after the vulcanization reaction.

  17. Automated chemical analysis of internally mixed aerosol particles using X-ray spectromicroscopy at the carbon K-edge.

    Science.gov (United States)

    Moffet, Ryan C; Henn, Tobias; Laskin, Alexander; Gilles, Mary K

    2010-10-01

    We have developed an automated data analysis method for atmospheric particles using scanning transmission X-ray microscopy coupled with near edge X-ray fine structure spectroscopy (STXM/NEXAFS). This method is applied to complex internally mixed submicrometer particles containing organic and inorganic material. Several algorithms were developed to exploit NEXAFS spectral features in the energy range from 278 to 320 eV for quantitative mapping of the spatial distribution of elemental carbon, organic carbon, potassium, and noncarbonaceous elements in particles of mixed composition. This energy range encompasses the carbon K-edge and potassium L2 and L3 edges. STXM/NEXAFS maps of different chemical components were complemented with a subsequent analysis using elemental maps obtained by scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM/EDX). We demonstrate the application of the automated mapping algorithms for data analysis and the statistical classification of particles.

  18. Local structure of LiCoO2 nanoparticles studied by Co K-edge x-ray absorption spectroscopy

    Science.gov (United States)

    Maugeri, L.; Iadecola, A.; Joseph, B.; Simonelli, L.; Olivi, L.; Okubo, M.; Honma, I.; Wadati, H.; Mizokawa, T.; Saini, N. L.

    2012-08-01

    We have studied the local structure of LiCoO2 nanoparticles by Co K-edge x-ray absorption spectroscopy as a function of particle size. Extended x-ray absorption fine structure data reveal substantial changes in the near neighbor distances and the associated mean square relative displacements with decreasing particle size. X-ray absorption near edge structure spectra show clear local geometrical changes with decreasing particle size, similar to those that appear in the charging (delithiation) process. The results suggest that the LiCoO2 nanoparticles are characterized by a large atomic disorder confined to the Co-O octahedra, similar to the distortions generated during the delithiation, and this disorder should be the primary limiting factor for a reversible diffusion of Li ions when nanoparticles of LiCoO2 are used as cathode material in rechargeable Li ion batteries.

  19. The local structure of Ca-Na pyroxenes. 2-Xanes studies at the Mg and A1 K edges

    International Nuclear Information System (INIS)

    Mottana, A.; Cibin, G.; Paris, E.; Giuli, G.; Florence Univ., Florence

    1999-01-01

    X-ray absorption spectra at the Mg and A1 K edges have been recorded on synthetic endmember diopside (Di) and jadeite (Jd) and on a series of natural Fe-poor Ca-Na clinopyroxenes compositionally straddling the Jd-Di join. The spectra of C2/c members of the series (C-omphacites) are different from having P2/n symmetry (P-omphacites). Differences can be explained by theoretical spectra calculated via the multiple-scattering formalism on atomic clusters with at least 89 atoms, extending to a. 0.62 nm away from the Mg viz. A1 absorber: Xanes detects in these systems medium- rather than short-range order-disorder relationships. Near-edge features of C-omphacites reflect the single-type of octahedral arrangement of the back scattering nearest-neighbours (six O atoms) around the absorber (Mg resp. A1) at the centre of the cluster (site M1). Others arise again from medium-range order. P-omphacites show more complicated spectra than C-omphacites. Their additional features reflect the increased local disorder around the probed atom (Mg resp. A1) induced by the two alternative M1, M11 configurations of the six O atoms forming the first co-ordination spheres. Mg and A1 are confirmed to be preferentially partitioned in the M1 resp. M11 site of the P-omphacite crystal structure, however never exclusively, but in a ratio close to 85:15 (plus or minus 10%) that implies a certain degree of local disorder. Changes in the relative heights of some prominent features are more evident in the A1 than in the Mg K-edge spectra. They are diagnostic to qualitatively distinguish C-from P-omphacites

  20. The local structure of Ca-Na pyroxenes. 2-Xanes studies at the Mg and A1 K edges

    Energy Technology Data Exchange (ETDEWEB)

    Mottana, A. [Rome Univ. Roma Tre, Rome (Italy). Dipt. di Scienze Geologiche; Murata, T. [Kyoto University of Education, Kyoto (Japan). Dept. of Physics; Marcelli, A. [Istituto Nazionale di Fisica Nucleare, Frascati, RM (Italy). Laboratori Nazionali di Frascati; Wu, Z.Y. [Istituto Nazionale di Fisica Nucleare, Frascati, RM (Italy). Laboratori Nazionali di Frascati]|[Laboratoire Piere Suee, Gif-sur Yvette Cedex, (France); Cibin, G. [Istituto Nazionale di Fisica Nucleare, Frascati, RM (Italy). Laboratori Nazionali di Frascati; Paris, E. [Camerino Univ., Camerino, MC (Italy). Dipt. di Scienze della Terra; Giuli, G. [Camerino Univ., Camerino, MC (Italy). Dipt. di Scienze della Terra]|[Florence Univ., Florence (Italy). Dipt. di Scienze della Terra

    1999-07-01

    X-ray absorption spectra at the Mg and A1 K edges have been recorded on synthetic end member diopside (Di) and jadeite (Jd) and on a series of natural Fe-poor Ca-Na clinopyroxenes compositionally straddling the Jd-Di join. The spectra of C2/c members of the series (C-omphacites) are different from having P2/n symmetry (P-omphacites). Differences can be explained by theoretical spectra calculated via the multiple-scattering formalism on atomic clusters with at least 89 atoms, extending to a. 0.62 nm away from the Mg viz. A1 absorber: Xanes detects in these systems medium- rather than short-range order-disorder relationships. Near-edge features of C-omphacites reflect the single-type of octahedral arrangement of the back scattering nearest-neighbours (six O atoms) around the absorber (Mg resp. A1) at the centre of the cluster (site M1). Others arise again from medium-range order. P-omphacites show more complicated spectra than C-omphacites. Their additional features reflect the increased local disorder around the probed atom (Mg resp. A1) induced by the two alternative M1, M11 configurations of the six O atoms forming the first co-ordination spheres. Mg and A1 are confirmed to be preferentially partitioned in the M1 resp. M11 site of the P-omphacite crystal structure, however never exclusively, but in a ratio close to 85:15 (plus or minus 10%) that implies a certain degree of local disorder. Changes in the relative heights of some prominent features are more evident in the A1 than in the Mg K-edge spectra. They are diagnostic to qualitatively distinguish C-from P-omphacites.

  1. The vanadium environment in blood cells of Ascidia ceratodes is divergent at all organismal levels: an XAS and EPR spectroscopic study.

    Science.gov (United States)

    Frank, Patrick; Carlson, Robert M K; Carlson, Elaine J; Hodgson, Keith O

    2003-02-01

    K-edge X-ray absorption and EPR spectroscopies were used to test the variation in blood cell vanadium between and within specimens of the tunicate Ascidia ceratodes from Bodega Bay, California. Intracellular vanadium was speciated by fitting the XAS spectra of whole blood cells with linear combinations of the XAS spectra of models. Blood cell samples representing one specimen each, respectively, revealed 92.5 and 38.7% of endogenous vanadium as [V(H(2)O)(6)](3+), indicating dissimilar distributions. Conversely, vanadium distributions within blood cell samples respectively representing one and six specimens proved very similar. The derived array of V(III) complexes was consistent with multiple intracellular regions that differ both in pH and c(sulfate), both within and between specimens. No systematic effect on vanadium distribution was apparent on mixing blood cells. EPR and XAS results indicated at least three forms of endogenous vanadyl ion, two of which may be dimeric. An inverse linear correlation was found between soluble and complexed forms of vanadyl ion, implying co-regulation. The EPR A value of endogenous vanadyl ion [A(0)=(1.062+/-0.008)x10(-2) cm(-1)] was marginally different from that representing Monterey Bay A. ceratodes [A(0)=(1.092+/-0.006) x10(-2) cm(-1)]. Comparisons indicate that Bodega Bay A. ceratodes maintain V(III) in a more acidic intracellular environment on average than do those from Monterey Bay, showing variation across populations. Blood cell vanadium thus noticeably diverges at all organismal levels among A. ceratodes.

  2. The structure of ZrO{sub 2} phases and deviltrification processes in a Ca-Zr-Si-O-based glass ceramic: a combined a-XRD and XAS study

    Energy Technology Data Exchange (ETDEWEB)

    Meneghini, C. [Rome-3 Univ. (Italy). Dipt. di Fisica; INFM-OGG, 38 - Grenoble (France); Mobilio, S. [Rome-3 Univ. (Italy). Dipt. di Fisica; Lusvarghi, L.; Bondioli, F.; Ferrari, A.M.; Manfredini, T.; Siligardi, C. [Dipt. Ingegneria dei Materiali e dell' Ambiente, Modena (Italy)

    2004-12-01

    The structure of Zr atomic environment in a CaO-ZrO{sub 2}-Si{sub 2} glass ceramic as a function of thermal treatments has been studied, combining X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD) and anomalous XRD (a-XRD) techniques. The analysis of XRD patterns demonstrates that the devitrification process proceeds through the partial segregation of Zr-depleted phases (wollastonite-like) and Zr-rich phases (Zr oxides). The XAS and a-XRD measurements at the Zr K-edge have been exploited in order to obtain a closer insight into the atomic structure around the Zr atoms. In the as-quenched glass the Zr atom is sixfold coordinated to O atoms in an amorphous environment rich in Ca and Si. Thermal treatment firstly (T=1273-1323 K) causes partial segragation of Zr in the form of an oxide with a tetragonal zirconia (t-ZrO{sub 2}) crystalline structure. Raising the temperature (T=1373 K) causes the formation of ZrO{sub 2} crystallites in the monoclinic crystallographic phase (baddeleyite, m-ZrO{sub 2}). Analysis of the XAS data shows that a considerable amount of Zr remains in an amorphous calcium silicate phase. (orig.)

  3. Changes in the As solid speciation during weathering of volcanic ashes: A XAS study on Patagonian ashes and Chacopampean loess

    Science.gov (United States)

    Bia, G.; García, M. G.; Borgnino, L.

    2017-09-01

    X-ray absorption spectroscopy (XAS) was used to determine the oxidation state of As, local chemical coordination and the relative proportion of different As species in recent and ancient Andean volcanic ashes, as well as in Chaco Pampean loess. As K edge XANES analysis indicates that in loess sediments the dominant species is As(V) (i.e., >91%). Conversely, As(III) is dominant in all ash samples. In the Puyehue sample, only As(III) species were determined, while in both, the Chaitén and the ancient tephra samples, As(III) species accounts for 66% of the total As. The remaining 34% corresponds to As(-1) in the Chaitén sample and to As(V) in the weathered tephra. The proposed EXAFS models fit well with the experimental data, suggesting that in ancient and recent volcanic ashes, As(III) is likely related to As atoms present as impurities within the glass structure, forming hydroxide species bound to the Al-Si network. In addition, the identified As(-1) species is related to arsenian pyrite, while in the ancient volcanic ash, As(V) was likely a product of incipient weathering. In loess sediments, the identified As(V) species represents arsenate ions adsorbed onto Fe oxy(hydr)oxides, forming inner-sphere surface complexes, in a bidentate binuclear configuration.

  4. Atomistic simulation and XAS investigation of Mn induced defects in Bi{sub 12}TiO{sub 20}

    Energy Technology Data Exchange (ETDEWEB)

    Rezende, Marcos V dos S. [Functional Nanomaterials Group, Physics Department, Federal University of Sergipe, Campus Universitário Professor Alberto Carvalho, 49500-000 Itabaiana-SE (Brazil); Santos, Denise J. [Physics Department, Federal University of Sergipe, São Cristovão, 49000-000 SE (Brazil); Jackson, Robert A. [School of Physical and Geographical Sciences, Keele University, Keele, Staffordshire ST5 5BG (United Kingdom); Valerio, Mário E.G.; Macedo, Zélia S. [Physics Department, Federal University of Sergipe, São Cristovão, 49000-000 SE (Brazil)

    2016-06-15

    This work reports an investigation of the valence and site occupancy of Mn dopants in Bi{sub 12}TiO{sub 20} (BTO: Mn) host using X-ray Absorption (XAS) and atomistic simulation techniques based on energy minimisation. X-ray Absorption Near Edge Structure (XANES) at the Mn K-edges gave typical results for Mn ions with mixed valences of 3+ and 4+. Extended X-ray Absorption Fine Structure (EXAFS) results indicated that Mn ions are probably substituted at Ti sites. Atomistic simulation was performed assuming the incorporation of Mn{sup 2+}, Mn{sup 3+} and Mn{sup 4+} ions at either Bi{sup 3+} or Ti{sup 4+} sites, and the results were compared to XANES and EXAFS measurements. Electrical conductivity for pure and doped samples was used to evaluate the consistency of the proposed model. - Graphical abstract: The structure of Bi{sub 12}TiO{sub 20} (BTO). Display Omitted - Highlights: • Pure and Mn-doped Bi{sub 12}TiO{sub 20} samples were studied by experimental techniques combined with atomistic simulation. • Good agreement between experimental and simulation results was obtained. • XANES results suggest a mixture of 3+ and 4+ valences for Mn, occupying the Ti4+ site in both cases. • Charge compensation by holes is most energetically favoured, explaining the enhancement observed in AC dark conductivity.

  5. Circular magnetic X-ray dichroism at the K-absorption edge in Fe-Ni alloys

    International Nuclear Information System (INIS)

    Sakurai, Hiroshi; Itoh, Fumitake; Maruyama, Hiroshi; Koizumi, Akihisa; Kobayashi, Kenji; Yamazaki, Hitoshi; Tanji, Yasunori; Kawata, Hiroshi.

    1993-01-01

    The first systematic measurements of circular magnetic X-ray dichroism (CMXD) effects at the K-edge in 3d-transition metal alloys have been made in Fe-Ni alloy over a wide composition range. It has been found that the CMXD spectrum at the Fe K-edge is similar to that at the Ni K-edge in each alloy, indicating that the CMXD spectra at the K-edge mainly reflect an itinerant character of 4q-states. The features of the CMXD spectra correspond to those of X-ray absorption near-edge structure (XANES) spectra, reflecting the change of crystal structure. The signal intensities around the absorption edge energy, E 0 , have strong Ni concentration dependence, suggesting a close relationship between the CMXD effects around E 0 and the spin polarization of 3d-states. (author)

  6. Synchrotron-based intra-venous K-edge digital subtraction angiography in a pig model: A feasibility study

    Energy Technology Data Exchange (ETDEWEB)

    Schueltke, Elisabeth [Departments of Surgery, University of Saskatchewan, Saskatoon, SK (Canada); Anatomy and Cell Biology, University of Saskatchewan, Saskatoon, SK (Canada); Department of Neurological Sciences, Walton Medical Centre, University of Liverpool, Liverpool L97 LJ (United Kingdom)], E-mail: e.schultke@usask.ca; Fiedler, Stefan [European Molecular Biology Laboratory (EMBL), Nottkestrasse 85, 22603 Hamburg (Germany); Nemoz, Christian [European Synchrotron Radiation Facility (ESRF), 6 rue Horowitz, 38043 Grenoble (France); Ogieglo, Lissa [Departments of Surgery, University of Saskatchewan, Saskatoon, SK (Canada); Kelly, Michael E. [Departments of Surgery, University of Saskatchewan, Saskatoon, SK (Canada); Department of Neurosurgery, Section of Cerebrovascular and Endovascular Neurosurgery, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH (United States); Crawford, Paul [Royal Veterinary College, Hawkshead Lane, North Mymms, Hatfield, Herfordshire AL9 7TA (United Kingdom); Esteve, Francois [INSERM U836-ESRF, 6 rue Horowitz, 38043 Grenoble (France); Brochard, Thierry; Renier, Michel; Requardt, Herwig; Le Duc, Geraldine [European Synchrotron Radiation Facility (ESRF), 6 rue Horowitz, 38043 Grenoble (France); Juurlink, Bernhard [Anatomy and Cell Biology, University of Saskatchewan, Saskatoon, SK (Canada); Meguro, Kotoo [Departments of Surgery, University of Saskatchewan, Saskatoon, SK (Canada)

    2010-03-15

    Background: K-edge digital subtraction angiography (KEDSA) combined with the tunability of synchrotron beam yields an imaging technique that is highly sensitive to low concentrations of contrast agents. Thus, contrast agent can be administered intravenously, obviating the need for insertion of a guided catheter to deliver a bolus of contrast agent close to the target tissue. With the high-resolution detectors used at synchrotron facilities, images can be acquired at high spatial resolution. Thus, the KEDSA appears particularly suited for studies of neurovascular pathology in animal models, where the vascular diameters are significantly smaller than in human patients. Materials and methods: This feasibility study was designed to test the suitability of KEDSA after intravenous injection of iodine-based contrast agent for use in a pig model. Four adult male pigs were used for our experiments. Neurovascular angiographic images were acquired using KEDSA with a solid state Germanium (Ge) detector at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. Results: After intravenous injection of 0.9 ml/kg iodinated contrast agent (Xenetix), the peak iodine concentrations in the internal carotid and middle cerebral arteries reached 35 mg/ml. KEDSA images in radiography mode allowed the visualization of intracranial arteries of less than 1.5 mm diameter.

  7. Sulfur K-edge absorption spectroscopy on selected biological systems; Schwefel-K-Kanten-Absorptionsspektroskopie an ausgewaehlten biologischen Systemen

    Energy Technology Data Exchange (ETDEWEB)

    Lichtenberg, Henning

    2008-07-15

    Sulfur is an essential element in organisms. In this thesis investigations of sulfur compounds in selected biological systems by XANES (X-ray Absorption Near Edge Structure) spectroscopy are reported. XANES spectroscopy at the sulfur K-edge provides an excellent tool to gain information about the local environments of sulfur atoms in intact biological samples - no extraction processes are required. Spatially resolved measurements using a Kirkpatrick-Baez mirror focusing system were carried out to investigate the infection of wheat leaves by rust fungi. The results give information about changes in the sulfur metabolism of the host induced by the parasite and about the extension of the infection into visibly uninfected plant tissue. Furthermore, XANES spectra of microbial mats from sulfidic caves were measured. These mats are dominated by microbial groups involved in cycling sulfur. Additionally, the influence of sulfate deprivation and H{sub 2}S exposure on sulfur compounds in onion was investigated. To gain an insight into the thermal degradation of organic material the influence of roasting of sulfur compounds in coffee beans was studied. (orig.)

  8. Origin of the pre-edge structure at the Al K-edge: The role of atomic vibrations

    Science.gov (United States)

    Cabaret, Delphine; Brouder, Christian

    2009-11-01

    We present a detailed analysis of the pre-edge peak present in the Al K-edge XANES spectra of corundum (α-Al2O3) and diaspore (α-AlOOH), as measured at room temperature. This is achieved by XANES and DOS calculations performed using the density functional theory in a pseudopotential plane-wave framework. The XANES calculations carried out for the equilibrium atomic positions do not reproduce the pre-edge of corundum and partially reproduce it in the case of diaspore. It is shown that the electronic transitions occuring in the pre-edge involves the 3s empty states of the aluminium absorbing atom. The Al 3s states can be probed in the electric dipole approximation via a p-s mixing, which is possible only if the Al site is not centrosymmetric. Although Al does not occupy an inversion center in the two minerals under study, the p-s mixing is too weak to provide a pre-edge feature in good agreement with experiment. The deviation from centrosymmetry can be enhanced by the atomic vibrations. We develop a theory that takes into account the atomic vibrations directly in the calculation of the absorption cross section, based on the Born-Oppenheimer approximation. This theory is applied to corundum and diaspore and yields satisfactory results in the pre-edge region.

  9. Resonant soft x-ray reflectivity of Me/B(4)C multilayers near the boron K edge.

    Science.gov (United States)

    Ksenzov, Dmitriy; Schlemper, Christoph; Pietsch, Ullrich

    2010-09-01

    Energy dependence of the optical constants of boron carbide in the short period Ru/B(4)C and Mo/B(4)C multilayers (MLs) are evaluated from complete reflectivity scans across the boron K edge using the energy-resolved photon-in-photon-out method. Differences between the refractive indices of the B(4)Cmaterial inside and close to the surface are obtained from the peak profile of the first order ML Bragg peak and the reflection profile near the critical angle of total external reflection close to the surface. Where a Mo/B(4)C ML with narrow barrier layers appears as a homogeneous ML at all energies, a Ru/B(4)C ML exhibits another chemical nature of boron at the surface compared to the bulk. From evaluation of the critical angle of total external reflection in the energy range between 184 and 186eV, we found an enriched concentration of metallic boron inside the Ru-rich layer at the surface, which is not visible in other energy ranges.

  10. Origin of the chemical shift in X-ray absorption near-edge spectroscopy at the Mn K-Edge in manganese oxide compounds

    NARCIS (Netherlands)

    de Vries, AH; Hozoi, L.; Broer, R.

    2003-01-01

    The absorption edge in Mn K-edge X-ray absorption spectra of manganese oxide compounds shows a shift of several electronvolts in going from MnO through LaMnO3 to CaMnO3. On the other hand, in X-ray photoelectron spectra much smaller shifts are observed. To identify the mechanisms that cause the

  11. Influence of Steam Activation on Pore Structure and Acidity of Zeolite Beta: An Al K Edge XANES Study of Aluminum Coordination

    NARCIS (Netherlands)

    Koningsberger, D.C.; Bokhoven, J.A. van; Kunkeler, P.J.; Bekkum, H. van

    2002-01-01

    The effect of steam activation on the aluminum coordination in zeolite NH{4}-beta was investigated by means of quantitative analysis of Al K edge XANES spectra. Framework tetrahedral aluminum is converted to octahedral aluminum after calcination and steaming, a process that, at the same time,

  12. The local structure of Ca{sub N}a pyroxenes. I. XANES study at the Na K-edge

    Energy Technology Data Exchange (ETDEWEB)

    Mottana, Annibale [Rome, Univ. III (Italy). Dipt. di Scienze Geologiche; Murata, T. [Kyoto, Univ. of Education (Japan). Dept. of Physics; Wu, Ziyu; Marcelli, Augusto [INFN, Frascati (Italy). Laboratori Nazionali di Frascati; Paris, E. [Camerino, Univ. (Italy). Dipt. di Scienze della Terra

    1996-07-01

    X-ray absorption Na K-edge spectra have been recorded on synthetic end member jadeite and on a series of natural Ca-Na pyroxenes compositionally straddling the Jd-Di. The disordered C2/c members of the series are systematically different from the ordered P2/n members. These differences can be interpreted and explained by comparing the experimental spectra with theoretical spectra. These have been calculated by the multiple-scattering formalism from the atomic positional parameters determined by single-crystal X-ray diffraction structure refinement on the same samples. In the full multiple scattering region of the spectrum (1075 to 1095 eV) C-pyroxenes exhibit three features which reflect the 6-2 configuration of the O back-scattering atoms around the Na absorber located at the center of the cluster (site M2 of the jadeite structure). P-pyroxenes show more complicated spectra in which at least four features can be recognized; they reflect the two types of the configuration (6-2 and 4-2-2) of the oxygens around Na in the two independent M2 and M21 eight-fold coordinated sites of the omphacite structure. A weak, sometimes poorly resolved peak at 1079 eV diagnostic and discriminates C- from P-pyroxenes. The Garnet Ridge C2/c impure jadeite exhibits a spectrum which is intermediate between those of jadeite and omphacite. The Hedin-Lundqist potential proves best for these insulating materials and allows multiple-scattering calculations agreeing well with experiments. The assessment of the local electronic properties of compositionally and structurally complex minerals such as clinopyroxenes is thus enhanced.

  13. Nitrogen K-edge X-ray absorption near edge structure (XANES) spectra of purine-containing nucleotides in aqueous solution

    International Nuclear Information System (INIS)

    Shimada, Hiroyuki; Fukao, Taishi; Minami, Hirotake; Ukai, Masatoshi; Fujii, Kentaro; Yokoya, Akinari; Fukuda, Yoshihiro; Saitoh, Yuji

    2014-01-01

    The N K-edge X-ray absorption near edge structure (XANES) spectra of the purine-containing nucleotide, guanosine 5 ′ -monophosphate (GMP), in aqueous solution are measured under various pH conditions. The spectra show characteristic peaks, which originate from resonant excitations of N 1s electrons to π* orbitals inside the guanine moiety of GMP. The relative intensities of these peaks depend on the pH values of the solution. The pH dependence is explained by the core-level shift of N atoms at specific sites caused by protonation and deprotonation. The experimental spectra are compared with theoretical spectra calculated by using density functional theory for GMP and the other purine-containing nucleotides, adenosine 5 ′ -monophosphate, and adenosine 5 ′ -triphosphate. The N K-edge XANES spectra for all of these nucleotides are classified by the numbers of N atoms with particular chemical bonding characteristics in the purine moiety

  14. Optical properties of boron carbide near the boron K edge evaluated by soft-x-ray reflectometry from a Ru/B(4)C multilayer.

    Science.gov (United States)

    Ksenzov, Dmitriy; Panzner, Tobias; Schlemper, Christoph; Morawe, Christian; Pietsch, Ullrich

    2009-12-10

    Soft-x-ray Bragg reflection from two Ru/B(4)C multilayers with 10 and 63 periods was used for independent determination of both real and imaginary parts of the refractive index n = 1 - delta + ibeta close to the boron K edge (approximately 188 eV). Prior to soft x-ray measurements, the structural parameters of the multilayers were determined by x-ray reflectometry using hard x rays. For the 63-period sample, the optical properties based on the predictions made for elemental boron major deviations were found close to the K edge of boron for the 10-period sample explained by chemical bonding of boron to B(4)C and various boron oxides.

  15. Sn-L3 EDGE and Fe K edge XANES spectra of the surface layer of ancient Chinese black mirror Heiqigu

    International Nuclear Information System (INIS)

    Gaowei Mengjia; Liu Yuzhen; Chu Wangsheng; Wu Ziyu; Wang Changsui

    2009-01-01

    The Chinese ancient black mirror known as Heiqigu was studied by x-ray-absorption near-edge structure spectroscopy and results were reported. The Sn-L 3 edge and Fe K edge spectra further confirmed the Schottky-type defect model in the Heiqigu surface system. And it was suggested that the surface layer of the mirror was a combined structure of oxidation of Sn(IV) and Sn(II). (authors)

  16. Activation of [CrCl3{PPh2N(Pr-i)PPh2}] for the selective oligomerisation of ethene: a Cr K-edge XAFS study

    NARCIS (Netherlands)

    Bartlett, S.A.; Moulin, J.; Tromp, M.; Reid, G.; Dent, A.J.; Cibin, G.; McGuinness, D.S.; Evans, J.

    2016-01-01

    The activation of the ethene tetramerisation catalyst system based upon [CrCl3(THF)(3)] and N(Pr-i)(PPh2)(2) has been investigated in situ via the reaction of [CrCl3{PPh2N(R)PPh2}(THF)] 1a (R = Pr-i) with excess AlMe3 in toluene. The Cr K-edge XAFS spectrum of the solution freeze quenched after 1

  17. Investigation of carbon-coated silicon oxide phase changes during charge/discharge by oxygen and lithium K-Edge X-ray absorption fine structure spectroscopy

    Science.gov (United States)

    Hirose, Takakazu; Morishita, Masanori; Yoshitake, Hideya; Sakai, Tetsuo

    2018-01-01

    To understand the phase changes associated with the charge/discharge mechanism during cycling, we evaluated the electronic states of oxygen and lithium atoms in the high-capacity anode material SiO-C using O and Li K-edge X-ray absorption fine structure (XAFS) spectroscopy. Multiple peaks observed in the O K-edge spectrum in the 532-548 eV range were likely related to Osbnd Si bonds. During the initial charge, when SiO-C occludes Li, a new peak related to Lisbnd O bonds appeared at 534 eV. During the initial discharge, this peak was maintained at potentials below 0.7 V vs. Li/Li+, but decreased at higher potentials, suggesting the presence of a phase change point near 0.7 V vs. Li/Li+. This change was also supported by the Li K-edge spectrum. An examination of the phase change after charge/discharge cycling at negative electrode termination potentials of 0.66 and 1.1 V vs. Li/Li+ confirmed that the phase structure was stable when cycling at potentials below the phase change point, but unstable at higher potentials. Thus, stable charge/discharge cycling can be achieved by designing batteries with negative electrode termination potentials that are lower than the potential at which the phase change occurs.

  18. In situ removal of carbon contamination from a chromium-coated mirror: ideal optics to suppress higher-order harmonics in the carbon K-edge region.

    Science.gov (United States)

    Toyoshima, Akio; Kikuchi, Takashi; Tanaka, Hirokazu; Mase, Kazuhiko; Amemiya, Kenta

    2015-11-01

    Carbon-free chromium-coated optics are ideal in the carbon K-edge region (280-330 eV) because the reflectivity of first-order light is larger than that of gold-coated optics while the second-order harmonics (560-660 eV) are significantly suppressed by chromium L-edge and oxygen K-edge absorption. Here, chromium-, gold- and nickel-coated mirrors have been adopted in the vacuum ultraviolet and soft X-ray branch beamline BL-13B at the Photon Factory in Tsukuba, Japan. Carbon contamination on the chromium-coated mirror was almost completely removed by exposure to oxygen at a pressure of 8 × 10(-2) Pa for 1 h under irradiation of non-monochromated synchrotron radiation. The pressure in the chamber recovered to the order of 10(-7) Pa within a few hours. The reflectivity of the chromium-coated mirror of the second-order harmonics in the carbon K-edge region (560-660 eV) was found to be a factor of 0.1-0.48 smaller than that of the gold-coated mirror.

  19. Local environment of zirconium in nuclear gels studied by XAS

    International Nuclear Information System (INIS)

    Pelegrin, E.; Ildefonse, Ph.; Calas, G.; Ricol, St.; Flank, A.M.

    1997-01-01

    During lixiviation experiments, nuclear gels are formed and heavy metals are retained. In order to understand this retardation mechanisms, we performed an analysis of the local environment of Zr in parent glasses and derived alteration gels both at the Zr-L II,III , and Zr-K edges. Calibration of the method was conducted through the analysis of model compounds with known coordination number (CN): catapleite Na 2 ZrSi 3 O 9 ,2H 2 O (CN=6), baddeleyite ZrO 2 (CN=7) and zircon SiZrO 4 (CN=8). Nuclear glasses (R7T7, and a simplified nuclear glass V 1) and gels obtained at 90 deg C, with leaching times from 7 to 12 months and with solution renewal. were also investigated (GR7T7R and GV1). Zr-L II,III XANES spectra evidenced that zirconium is 6-fold coordinated in R7T7 and V1 nuclear glasses. For GR7T7R and GV1 gels, Zr local environment is significantly changed, and a mixture of CN (6 and 7J has been evidenced. Quantitative structural results were derived from EXAFS analysis at Zr-K edge. In parent glasses, derived Zr-O distance is 2.10±0.01 10 -10 m, and is in the range Zr-O distances for octahedral coordination in model compounds. In both gels studied, Zr-O distances increase significantly up to 2.15 ±0.01 10 -10 m. This distance is close to that known in baddeleyite (2,158 10 -10 m). A better understanding of the Zr retention mechanism has to be made by studying the second neighbors contributions. (authors)

  20. XAS study of the local environment of impurities in doped TiO{sub 2} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez Torres, C.E. [Departamento de Fisica e IFLP (CONICET), Facultad de Ciencias Exactas, Universidad Nacional de La Plata (Argentina)]. E-mail: torres@fisica.unlp.edu.ar; Cabrera, A.F. [Departamento de Fisica e IFLP (CONICET), Facultad de Ciencias Exactas, Universidad Nacional de La Plata (Argentina); Errico, L.A. [Departamento de Fisica e IFLP (CONICET), Facultad de Ciencias Exactas, Universidad Nacional de La Plata (Argentina); Duhalde, S. [Lab. de Ablacion Laser, FI-UBA (Argentina); Renteria, M. [Departamento de Fisica e IFLP (CONICET), Facultad de Ciencias Exactas, Universidad Nacional de La Plata (Argentina); Golmar, F. [Lab. de Ablacion Laser, FI-UBA (Argentina); Sanchez, F.H. [Departamento de Fisica e IFLP (CONICET), Facultad de Ciencias Exactas, Universidad Nacional de La Plata (Argentina)

    2007-09-01

    In this work, we present an X-ray absorption spectroscopy (XAS) characterization of the local environment of the impurity in room temperature ferromagnetic (RTF) anatase TiO{sub 2} thin films doped with Co, Ni, Cu, or Zn, deposited on LaAlO{sub 3} substrate by pulsed laser deposition (PLD). It was found that there is a considerable amount of impurity atoms substituting Ti in TiO{sub 2} anatase, although the presence of metal transition monoxide clusters can not be discarded. From our results, we infer that the observed RT ferromagnetism of the samples could be assigned to the metal transition atoms replacing Ti in TiO{sub 2} anatase.

  1. Matrix effect corrections for the uranium assay with a 57Co-153Gd isotopic source-based K-edge densitometer

    International Nuclear Information System (INIS)

    Abousahl, S.; Ottmar, H.; Matussek, P.

    2001-01-01

    Full text: A combined K-edge densitometer/ 235 U-enrichment meter known as 'COMPUCEA' is now successfully used for several years at the Institute for Transuranium Elements (ITU) and by the Euratom Safeguards Directorate for the determination of the uranium element content and 235 U enrichment in uranium samples. The device is utilised as stationary equipment at ITU and in the Euratom On-Site Laboratories at La Hague and Sellafield, and as mobile instrument for in- field measurements in uranium fuel fabrication plants during inventory verification campaigns. The actual measurements are performed on samples in liquid form, requiring a prior sample dissolution for the analysis powder and pellet samples. The K-edge densitometer in COMPUCEA has been originally equipped with a single isotopic source ( 57 Co), which in conjunction with a uranium converter foil provided the necessary radiations on both sides of the uranium K-edge energy at 115.6 keV. This type of radiation source was recently replaced by a mixed 57 Co- 153 Gd source because of the added advantage of providing a perfectly linear instrument response as a function of the measured uranium concentration. The major radiations from this mixed source offer two pairs of gamma rays (103/122 keV and 97/136 keV), which both bracket the uranium K-edge energy but differ in their energy difference by about a factor of 2. A total of five COMPUCEA instruments are now operated with this type of source. Variations in the matrix composition of the analysed samples represent the main parameter influencing the accuracy of the uranium element assay with this kind of K-edge densitometry. The dependence on the sample matrix is related to the energy difference of the photon energies used for the transmission measurements. The magnitude of a possible measurement bias is dependent on the magnitude of this energy difference and on the nature of the matrix composition. The presence of a higher Z element, and the resulting bias effect

  2. Experimental versus ab initio x-ray absorption of iron-doped zirconia: Trends in O K -edge spectra as a function of iron doping

    Science.gov (United States)

    Douma, D. H.; Ciprian, R.; Lamperti, A.; Lupo, P.; Cianci, E.; Sangalli, D.; Casoli, F.; Nasi, L.; Albertini, F.; Torelli, P.; Debernardi, A.

    2014-11-01

    We present an experimental study of x-ray absorption near edge structure (XANES) at L2 ,3,M2 ,3, and K edges of, respectively, Fe, Zr, and O in iron-doped zirconia (ZrO2:Fe ) for different Fe dopant concentrations x (from x ˜6 % to x ˜25 % at.) and make the comparison with ab initio simulations at the O K -edge. The x-ray magnetic circular dichroism (XMCD) measurements show no evidence of ferromagnetic (FM) order for all the analyzed samples in agreement with our ab initio simulations, which show an antiferromagnetic (AFM) order. We found that substituting Zr with Fe atoms leads to a radical change in the O K -edge XANES spectrum, especially in the pre-edge region where a pre-edge peak appears. This pre-edge peak is ascribed to dipole transitions from O 1 s to O 2 p states that are hybridized with the unoccupied Fe 3 d states. Both theoretical and experimental results reveal that the intensity of the pre-edge peak increases with Fe concentration, suggesting the increase of unoccupied Fe 3 d states. The increase of Fe concentration increases oxygen vacancies as required for charge neutrality and consequently improves AFM ordering. According to our first-principles calculations, the effect of one Fe atom is mostly localized in the first oxygen shell and vanishes as one moves far from it. Thus the increase of the O K -pre-edge peak with increasing Fe concentration is due to the increase of percentage of oxygen atoms that are near neighbors to Fe atoms.

  3. K-edge x-ray dichroism investigation of Fe1-xCoxSi: Experimental evidence for spin polarization crossover

    Science.gov (United States)

    Hearne, G. R.; Diguet, G.; Baudelet, F.; Itié, J.-P.; Manyala, N.

    2015-04-01

    Both Fe and Co K-edge x-ray magnetic circular dichroism (XMCD) have been employed as element-specific probes of the magnetic moments in the composition series of the disordered ferromagnet Fe1-xCoxSi (for x=0.2, 0.3, 0.4, 0.5). A definitive single peaked XMCD profile occurs for all compositions at both Fe and Co K-edges. The Fe 4p orbital moment, deduced from the integral of the XMCD signal, has a steep dependence on x at low doping levels and evolves to a different (weaker) dependence at x≥0.3, similar to the behavior of the magnetization in the Co composition range studied here. It is systematically higher, by at least a factor of two, than the corresponding Co orbital moment for most of the composition series. Fine structure beyond the K-edge absorption (limited range EXAFS) suggests that the local order (atomic environment) is very similar across the series, from the perspective of both the Fe and Co absorbing atom. The variation in the XMCD integral across the Co composition range has two regimes, that which occurs below x=0.3 and then evolves to different behavior at higher doping levels. This is more conspicuously present in the Fe contribution. This is rationalized as the evolution from a half-metallic ferromagnet at low Co doping to that of a strong ferromagnet at x>0.3 and as such, spin polarization crossover occurs. The Fermi level is tuned from the majority spin band for x<0.3 where a strongly polarized majority spin electron gas prevails, to a regime where minority spin carriers dominate at higher doping. The evolution of the Fe-derived spin polarized (3d) bands, indirectly probed here via the 4p states, is the primary determinant of the doping dependence of the magnetism in this alloy series.

  4. MO-FG-CAMPUS-IeP1-01: Alternative K-Edge Filters for Low-Energy Image Acquisition in Contrast Enhanced Spectral Mammography

    Energy Technology Data Exchange (ETDEWEB)

    Shrestha, S; Vedantham, S; Karellas, A [University of Massachusetts Medical School, Worcester, MA (United States)

    2016-06-15

    Purpose: In Contrast Enhanced Spectral Mammography (CESM), Rh filter is often used during low-energy image acquisition. The potential for using Ag, In and Sn filters, which exhibit K-edge closer to, and just below that of Iodine, instead of the Rh filter, was investigated for the low-energy image acquisition. Methods: Analytical computations of the half-value thickness (HVT) and the photon fluence per mAs (photons/mm2/mAs) for 50µm Rh were compared with other potential K-edge filters (Ag, In and Sn), all with K-absorption edge below that of Iodine. Two strategies were investigated: fixed kVp and filter thickness (50µm for all filters) resulting in HVT variation, and fixed kVp and HVT resulting in variation in Ag, In and Sn thickness. Monte Carlo simulations (GEANT4) were conducted to determine if the scatter-to-primary ratio (SPR) and the point spread function of scatter (scatter PSF) differed between Rh and other K-edge filters. Results: Ag, In and Sn filters (50µm thick) increased photon fluence/mAs by 1.3–1.4, 1.8–2, and 1.7–2 at 28-32 kVp compared to 50µm Rh, which could decrease exposure time. Additionally, the fraction of spectra closer to and just below Iodine’s K-edge increased with these filters, which could improve post-subtraction image contrast. For HVT matched to 50µm Rh filtered spectra, the thickness range for Ag, In, and Sn were (41,44)µm, (49,55)µm and (45,53)µm, and increased photon fluence/mAs by 1.5–1.7, 1.6–2, and 1.6–2.2, respectively. Monte Carlo simulations showed that neither the SPR nor the scatter PSF of Ag, In and Sn differed from Rh, indicating no additional detriment due to x-ray scatter. Conclusion: The use of Ag, In and Sn filters for low-energy image acquisition in CESM is potentially feasible and could decrease exposure time and may improve post-subtraction image contrast. Effect of these filters on radiation dose, contrast, noise and associated metrics are being investigated. Funding Support: Supported in

  5. Determination of the products from the oxidation of aqueous hydrogen sulfide by sulfur K-edge XANES spectroscopy

    International Nuclear Information System (INIS)

    Vairavamurthy, A.; Manowitz, B.; Jeon, Yongseog; Zhou, Weiqing.

    1993-01-01

    The application of synchrotron radiation based XANES spectroscopy is described for determining the products formed from oxidation of aqueous sulfide.This technique allows simultaneous characterization of all the different forms of sulfur both qualitatively and quantitatively. Thus, it is superior to other commonly used techniques, such as chromatography, which are usually targeted at specific compounds. Since the use of XANES-based technique is relatively new in geochemistry, we present here an overview of the principles of the technique as well as the approach used for quantitative analysis. We studied the sulfide oxidation under conditions of high sulfide to oxygen ratio using 0.1 M sulfide solutions and the catalytic effects of sea sand, Fe 2+ , and Ni 2+ , were also examined. Significant results obtained from this study are presented to illustrate the value of the XANES technique for the determination of the products formed from the oxidation of sulfide at high concentrations

  6. Composite Ni/NiO-Cr2O3 Catalyst for Alkaline Hydrogen Evolution Reaction

    OpenAIRE

    Bates, Michael K.; Jia, Qingying; Ramaswamy, Nagappan; Allen, Robert J.; Mukerjee, Sanjeev

    2015-01-01

    We report a Ni–Cr/C electrocatalyst with unprecedented mass-activity for the hydrogen evolution reaction (HER) in alkaline electrolyte. The HER kinetics of numerous binary and ternary Ni-alloys and composite Ni/metal-oxide/C samples were evaluated in aqueous 0.1 M KOH electrolyte. The highest HER mass-activity was observed for Ni–Cr materials which exhibit metallic Ni as well as NiOx and Cr2O3 phases as determined by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) analysis. Th...

  7. Composite Ni/NiO-Cr2O3Catalyst for Alkaline Hydrogen Evolution Reaction.

    Science.gov (United States)

    Bates, Michael K; Jia, Qingying; Ramaswamy, Nagappan; Allen, Robert J; Mukerjee, Sanjeev

    2015-03-12

    We report a Ni-Cr/C electrocatalyst with unprecedented mass-activity for the hydrogen evolution reaction (HER) in alkaline electrolyte. The HER kinetics of numerous binary and ternary Ni-alloys and composite Ni/metal-oxide/C samples were evaluated in aqueous 0.1 M KOH electrolyte. The highest HER mass-activity was observed for Ni-Cr materials which exhibit metallic Ni as well as NiO x and Cr 2 O 3 phases as determined by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) analysis. The onset of the HER is significantly improved compared to numerous binary and ternary Ni-alloys, including Ni-Mo materials. It is likely that at adjacent Ni/NiO x sites, the oxide acts as a sink for OH ads , while the metallic Ni acts as a sink for the H ads intermediate of the HER, thus minimizing the high activation energy of hydrogen evolution via water reduction. This is confirmed by in situ XAS studies that show that the synergistic HER enhancement is due to NiO x content and that the Cr 2 O 3 appears to stabilize the composite NiO x component under HER conditions (where NiO x would typically be reduced to metallic Ni 0 ). Furthermore, in contrast to Pt, the Ni(O x )/Cr 2 O 3 catalyst appears resistant to poisoning by the anion exchange ionomer (AEI), a serious consideration when applied to an anionic polymer electrolyte interface. Furthermore, we report a detailed model of the double layer interface which helps explain the observed ensemble effect in the presence of AEI.

  8. Composite Ni/NiO-Cr2O3 Catalyst for Alkaline Hydrogen Evolution Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Bates, MK; Jia, QY; Ramaswamy, N; Allen, RJ; Mukerjee, S

    2015-03-12

    We report a Ni-Cr/C electrocatalyst with unpreeedented massactivity for the hydrogen evolution reaction (HER). in alkaline electrolyte. The HER Oietics of numerous binary and ternary Ni-alloys and composite Ni/metal-euride/C samples were evaluated in aquebus 0.1 M KOH electrolyte. The highest HER mass-activity was observed for Ni-Cr materials which exhibit metallic Ni as well as NiOx and Cr2O3 phases as determined by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) analysis. The onset of the HER is significantly improved compared to munerous binary dor ternary Ni-alloys, inCluding Ni Mg materials. It is likely that at adjacent Ni/NiOx sites, the oxide acts as a sink for OHads, while the metallic Ni acts as a, sink for the H-ads, intermediate of the HER, thus minimizing the high activation energy of hydrogen evolution via water reduction. This is confirmed by in situ XAS studies that show that the synergistic HER enhancement is due to NiO content and that the Cr2O3 appears to stabilize the composite NiO component-under HER conditions (where NiOx would typically be reduced to metallic Ni-0). Furthermore, in contrast to Pt, the Ni(O-x)/Cr2O3 catalyst appears resistant to poisoning by the anion.exchange ionomer (AEI), a serloua consideration when applied to an anionic polymer electrolyte interface. Furthermore, we report a: detailed model of the double layer interface which helps explain the observed ensemble effect in the presence of AEI.

  9. A Monte Carlo simulation study of an improved K-edge log-subtraction X-ray imaging using a photon counting CdTe detector

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Youngjin, E-mail: radioyoungj@gmail.com [Department of Radiological Science, Eulji University, 553, Sanseong-daero, Sujeong-gu, Seongnam-si, Gyeonggi-do (Korea, Republic of); Lee, Amy Candy [Department of Mathematics and Statistics, McGill University (Canada); Kim, Hee-Joung [Department of Radiological Science and Radiation Convergence Engineering, Yonsei University (Korea, Republic of)

    2016-09-11

    Recently, significant effort has been spent on the development of photons counting detector (PCD) based on a CdTe for applications in X-ray imaging system. The motivation of developing PCDs is higher image quality. Especially, the K-edge subtraction (KES) imaging technique using a PCD is able to improve image quality and useful for increasing the contrast resolution of a target material by utilizing contrast agent. Based on above-mentioned technique, we presented an idea for an improved K-edge log-subtraction (KELS) imaging technique. The KELS imaging technique based on the PCDs can be realized by using different subtraction energy width of the energy window. In this study, the effects of the KELS imaging technique and subtraction energy width of the energy window was investigated with respect to the contrast, standard deviation, and CNR with a Monte Carlo simulation. We simulated the PCD X-ray imaging system based on a CdTe and polymethylmethacrylate (PMMA) phantom which consists of the various iodine contrast agents. To acquired KELS images, images of the phantom using above and below the iodine contrast agent K-edge absorption energy (33.2 keV) have been acquired at different energy range. According to the results, the contrast and standard deviation were decreased, when subtraction energy width of the energy window is increased. Also, the CNR using a KELS imaging technique is higher than that of the images acquired by using whole energy range. Especially, the maximum differences of CNR between whole energy range and KELS images using a 1, 2, and 3 mm diameter iodine contrast agent were acquired 11.33, 8.73, and 8.29 times, respectively. Additionally, the optimum subtraction energy width of the energy window can be acquired at 5, 4, and 3 keV for the 1, 2, and 3 mm diameter iodine contrast agent, respectively. In conclusion, we successfully established an improved KELS imaging technique and optimized subtraction energy width of the energy window, and based on

  10. A Monte Carlo simulation study of an improved K-edge log-subtraction X-ray imaging using a photon counting CdTe detector

    International Nuclear Information System (INIS)

    Lee, Youngjin; Lee, Amy Candy; Kim, Hee-Joung

    2016-01-01

    Recently, significant effort has been spent on the development of photons counting detector (PCD) based on a CdTe for applications in X-ray imaging system. The motivation of developing PCDs is higher image quality. Especially, the K-edge subtraction (KES) imaging technique using a PCD is able to improve image quality and useful for increasing the contrast resolution of a target material by utilizing contrast agent. Based on above-mentioned technique, we presented an idea for an improved K-edge log-subtraction (KELS) imaging technique. The KELS imaging technique based on the PCDs can be realized by using different subtraction energy width of the energy window. In this study, the effects of the KELS imaging technique and subtraction energy width of the energy window was investigated with respect to the contrast, standard deviation, and CNR with a Monte Carlo simulation. We simulated the PCD X-ray imaging system based on a CdTe and polymethylmethacrylate (PMMA) phantom which consists of the various iodine contrast agents. To acquired KELS images, images of the phantom using above and below the iodine contrast agent K-edge absorption energy (33.2 keV) have been acquired at different energy range. According to the results, the contrast and standard deviation were decreased, when subtraction energy width of the energy window is increased. Also, the CNR using a KELS imaging technique is higher than that of the images acquired by using whole energy range. Especially, the maximum differences of CNR between whole energy range and KELS images using a 1, 2, and 3 mm diameter iodine contrast agent were acquired 11.33, 8.73, and 8.29 times, respectively. Additionally, the optimum subtraction energy width of the energy window can be acquired at 5, 4, and 3 keV for the 1, 2, and 3 mm diameter iodine contrast agent, respectively. In conclusion, we successfully established an improved KELS imaging technique and optimized subtraction energy width of the energy window, and based on

  11. X-ray absorption spectroscopy by full-field X-ray microscopy of a thin graphite flake: Imaging and electronic structure via the carbon K-edge

    Directory of Open Access Journals (Sweden)

    Carla Bittencourt

    2012-04-01

    Full Text Available We demonstrate that near-edge X-ray-absorption fine-structure spectra combined with full-field transmission X-ray microscopy can be used to study the electronic structure of graphite flakes consisting of a few graphene layers. The flake was produced by exfoliation using sodium cholate and then isolated by means of density-gradient ultracentrifugation. An image sequence around the carbon K-edge, analyzed by using reference spectra for the in-plane and out-of-plane regions of the sample, is used to map and spectrally characterize the flat and folded regions of the flake. Additional spectral features in both π and σ regions are observed, which may be related to the presence of topological defects. Doping by metal impurities that were present in the original exfoliated graphite is indicated by the presence of a pre-edge signal at 284.2 eV.

  12. Assignment of Pre-Edge Features in the Ru K-Edge X-Ray Absorption Spectra of Organometallic Ruthenium Complexes

    Energy Technology Data Exchange (ETDEWEB)

    Getty, K.; Delgado-Jaime, M.U.; Kennepohl, P.

    2009-05-18

    The nature of the lowest energy bound-state transition in the Ru K-edge X-ray absorption spectra for a series of Grubbs-type ruthenium complexes was investigated. The pre-edge feature was unambiguously assigned as resulting from formally electric dipole forbidden Ru 4d {l_arrow} 1s transitions. The intensities of these transitions are extremely sensitive to the ligand environment and the symmetry of the metal centre. In centrosymmetric complexes the pre-edge is very weak since it is limited by the weak electric quadrupole intensity mechanism. By contrast, upon breaking centrosymmetry, Ru 5p-4d mixing allows for introduction of electric dipole allowed character resulting in a dramatic increase in the pre-edge intensity. The information content of this approach is explored as it relates to complexes of importance in olefin metathesis and its relevance as a tool for the study of reactive intermediates.

  13. Ion time-of-flight spectroscopy: krypton charge-state spectra as a function of photon excitation energy near the K edge

    International Nuclear Information System (INIS)

    Hastings, J.B.; Kostroun, V.O.

    1982-01-01

    In this experiment, we have recorded the charge state distribution resulting from atomic rearrangement following the creation of the inner shell vacancies in krypton atoms. Intense, highly collimated, monochromatic and tunable x-ray radiation available at the CHESS synchrotron radiation facility at Cornell was used to photoionize krypton atoms in a gas jet target, and a time-of-flight spectrometer was used to record the ions in different charge states formed after photoionization. Charge state spectra were recorded at below, at the peak in the K edge and above the edge. Below the edge, charge states +4 to +7 were observed with appreciable intensity, while at, and above the edge, the charge states ranged from +4 to +10

  14. Order-disorder in olivine minerals by synchrotron X-ray absorption near-edge structure (Xane) spectroscopy at the Mg, Fe and Ca K edges

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Z.; Marcelli, A.; Cibin, G. [Istituto Nazionale di Fisica Nucleare, Frascati, RM (Italy). Laboratori Nazionali di Frascati; Mottana, A. [Istituto Nazionale di Fisica Nucleare, Frascati, RM (Italy). Laboratori Nazionali di Frascati; Rome Univ. Roma Tre, Rome (Italy). Dipt. di Scienze Geologiche; Paris, E.; Giuli, G [INFM, Camerino Univ., Camerino, MC (Italy). Dipt. di Scienze della Terra

    1999-07-01

    In this paper, are presented new, high-resolution experimental spectra at the Mg and Fe K edges for the two Fe-Mg end members F o and F a, and for three other olivines. Two are the Ca end members of the family, namely monticellite (Mtc: CaMgSiO4) and kirschsteinite (Krs: CaFeSiO4). The main purpose of this work is to investigate the effects of Mg, Fe, and Ca partition in the Pbnm (or {alpha}) olivine structure on the electronic properties, as well as the relationships that exist between chemical substitutions and features occurring in Xanes spectra. One wants to explore the relationships that intervene between LRO, as determined by XRD, and SRO, as determined by Xanes, on the endmembers and on a well-known intermediate member as well, and deduce from it a model for the behavior of the entire olivine solid-solution system.

  15. Order-disorder in olivine minerals by synchrotron X-ray absorption near-edge structure (Xane) spectroscopy at the Mg, Fe and Ca K edges

    International Nuclear Information System (INIS)

    Wu, Z.; Marcelli, A.; Cibin, G.; Mottana, A.; Rome Univ. Roma Tre, Rome; Paris, E.; Giuli, G.

    1999-01-01

    In this paper, are presented new, high-resolution experimental spectra at the Mg and Fe K edges for the two Fe-Mg endmembers F o and F a, and for three other olivines. Two are the Ca endmembers of the family, namely monticellite (Mtc: CaMgSiO4) and kirschsteinite (Krs: CaFeSiO4). The main purpose of this work is to investigate the effects of Mg, Fe, and Ca partition in the Pbnm (or α) olivine structure on the electronic properties, as well as the relationships that exist between chemical substitutions and features occurring in Xanes spectra. One wants to explore the relationships that intervene between LRO, as determined by XRD, and SRO, as determined by Xanes, on the endmembers and on a well-known intermediate member as well, and deduce from it a model for the behavior of the entire olivine solid-solution system

  16. Effect of atomic vibrations in XANES: polarization-dependent damping of the fine structure at the Cu K-edge of (creat)2CuCl4.

    Science.gov (United States)

    Šipr, Ondřej; Vackář, Jiří; Kuzmin, Alexei

    2016-11-01

    Polarization-dependent damping of the fine structure in the Cu K-edge spectrum of creatinium tetrachlorocuprate [(creat) 2 CuCl 4 ] in the X-ray absorption near-edge structure (XANES) region is shown to be due to atomic vibrations. These vibrations can be separated into two groups, depending on whether the respective atoms belong to the same molecular block; individual molecular blocks can be treated as semi-rigid entities while the mutual positions of these blocks are subject to large mean relative displacements. The effect of vibrations can be efficiently included in XANES calculations by using the same formula as for static systems but with a modified free-electron propagator which accounts for fluctuations in interatomic distances.

  17. Near K-edge measurement of the X-ray attenuation coefficient of heavy elements using a tuneable X-ray source based on an electron LINAC

    CERN Document Server

    Materna, T; Mondelaers, W; Masschaele, B

    2000-01-01

    The X-ray attenuation coefficients of bismuth and of uranium were measured in the regions of 40-240 and 70-240 keV, respectively, using a tuneable hard X-ray source based on the linear electron accelerator at the University of Ghent. Results were compared with the semi-empirical values of Storm and Israel and to the theoretical values of Berger and Hubbell. We also propose a simple function for the attenuation coefficient in the vicinity of the K-edge for uranium and in an extended range of energy for bismuth. The set-up of the source at Ghent is described and the future improvements are explained.

  18. Degradation of Bimetallic Model Electrocatalysts ___ an in situ XAS Study

    Energy Technology Data Exchange (ETDEWEB)

    Friebel, Daniel

    2011-06-22

    One of the major challenges in the development of clean energy fuel cells is the performance degradation of the electrocatalyst, which, apart from poisoning effects, can suffer from corrosion due to its exposure to a harsh environment under high potentials. In this communication, we demonstrate how interactions of Pt with a transition metal support affect not only, as commonly intended, the catalytic activity, but also the reactivity of Pt towards oxide formation or dissolution. We use two well-defined single-crystal model systems, Pt/Rh(111) and Pt/Au(111) and a unique x-ray spectroscopy technique with enhanced energy resolution to monitor the potential-dependent oxidation state of Pt, and find two markedly different oxidation mechanisms on the two different substrates. This information can be of great significance for future design of more active and more stable catalysts. We have studied the potential-induced degradation of Pt monolayer model electrocatalysts on Rh(111) and Au(111) single-crystal substrates. The anodic formation of Pt oxides was monitored using in situ high energy resolution fluorescence detection x-ray absorption spectroscopy (HERFD XAS). Although Pt was deposited on both substrates in a three-dimensional island growth mode, we observed remarkable differences during oxide formation that can only be understood in terms of strong Pt-substrate interactions throughout the Pt islands. Anodic polarization of Pt/Rh(111) up to +1.6 V vs. RHE (reversible hydrogen electrode) leads to formation an incompletely oxidized passive layer, whereas formation of PtO2 and partial Pt dissolution is observed for Pt/Au(111).

  19. Composite Ni/NiO-Cr2O3 Catalyst for Alkaline Hydrogen Evolution Reaction

    Science.gov (United States)

    Bates, Michael K.; Jia, Qingying; Ramaswamy, Nagappan; Allen, Robert J.; Mukerjee, Sanjeev

    2015-01-01

    We report a Ni–Cr/C electrocatalyst with unprecedented mass-activity for the hydrogen evolution reaction (HER) in alkaline electrolyte. The HER kinetics of numerous binary and ternary Ni-alloys and composite Ni/metal-oxide/C samples were evaluated in aqueous 0.1 M KOH electrolyte. The highest HER mass-activity was observed for Ni–Cr materials which exhibit metallic Ni as well as NiOx and Cr2O3 phases as determined by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) analysis. The onset of the HER is significantly improved compared to numerous binary and ternary Ni-alloys, including Ni–Mo materials. It is likely that at adjacent Ni/NiOx sites, the oxide acts as a sink for OHads, while the metallic Ni acts as a sink for the Hads intermediate of the HER, thus minimizing the high activation energy of hydrogen evolution via water reduction. This is confirmed by in situ XAS studies that show that the synergistic HER enhancement is due to NiOx content and that the Cr2O3 appears to stabilize the composite NiOx component under HER conditions (where NiOx would typically be reduced to metallic Ni0). Furthermore, in contrast to Pt, the Ni(Ox)/Cr2O3 catalyst appears resistant to poisoning by the anion exchange ionomer (AEI), a serious consideration when applied to an anionic polymer electrolyte interface. Furthermore, we report a detailed model of the double layer interface which helps explain the observed ensemble effect in the presence of AEI. PMID:26191118

  20. XPS and XAS investigation of condensed and adsorbed n-octane on a Cu(110) surface

    International Nuclear Information System (INIS)

    Weiss, K.; Oestroem, H.; Triguero, L.; Ogasawara, H.; Garnier, M.G.; Pettersson, L.G.M.; Nilsson, A.

    2003-01-01

    The electronic structure of n-octane adsorbed on Cu(110) is studied by using X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) in combination with cluster model calculations in the framework of density functional theory (DFT). The molecule is found to be well oriented on the surface, which is seen from the high degree of XAS dichroism. Saturated hydrocarbons are commonly considered to physisorb on metals such as Cu(110), but still the C 1s XAS spectra reveal large changes in the electronic structure of the adsorbed octane relative to the free molecule. We find that the XAS resonances corresponding to the molecular Rydberg-valence states are strongly quenched upon adsorption and that there is a significant hybridization of the molecular valence orbitals with the metal bands. In addition to a precise interpretation of the XAS spectra, we present details on the molecular orbital structure of the adsorbed octane molecule. We also discuss shifts in the relative binding energies of the chemically inequivalent carbon atoms in octane upon adsorption, which lead to a narrower XPS spectrum for the adsorbate than the condensed phase spectrum due to the existence of a new relaxation channel

  1. XPS and XAS investigation of condensed and adsorbed n-octane on a Cu(110) surface

    CERN Document Server

    Weiss, K; Triguero, L; Ogasawara, H; Garnier, M G; Pettersson, L G M; Nilsson, A

    2003-01-01

    The electronic structure of n-octane adsorbed on Cu(110) is studied by using X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) in combination with cluster model calculations in the framework of density functional theory (DFT). The molecule is found to be well oriented on the surface, which is seen from the high degree of XAS dichroism. Saturated hydrocarbons are commonly considered to physisorb on metals such as Cu(110), but still the C 1s XAS spectra reveal large changes in the electronic structure of the adsorbed octane relative to the free molecule. We find that the XAS resonances corresponding to the molecular Rydberg-valence states are strongly quenched upon adsorption and that there is a significant hybridization of the molecular valence orbitals with the metal bands. In addition to a precise interpretation of the XAS spectra, we present details on the molecular orbital structure of the adsorbed octane molecule. We also discuss shifts in the relative binding energies of the ...

  2. Understanding the Intrinsic Electrochemistry of Ni-Rich Layered Cathodes

    Science.gov (United States)

    Sallis, Shawn

    The demand for energy is continually increasing overtime and the key to meeting future demand in a sustainable way is with energy storage. Li-ion batteries employing layered transition metal oxide cathodes are one of the most technologically important energy storage technologies. However, current Li-ion batteries are unable to access their full theoretical capacity and suffer from performance limiting degradation over time partially originating from the cathode and partially from the interface with the electrolyte. Understanding the fundamental limitations of layered transition metal oxide cathodes requires a complete understanding of the surface and bulk of the materials in their most delithiated state. In this thesis, we employ LiNi0.8Co0.15Al 0.05O2 (NCA) as a model system for Ni-rich layered oxide cathodes. Unlike its parent compound, LiCoO2, NCA is capable of high states of delithiation with minimal structural transitions. Furthermore, commercially available NCA has little to no transition metals in the Li layer. X-ray spectroscopies are an ideal tool for studying cathodes at high states of delithiation due their elemental selectivity, range of probing depths, and sensitivity to both chemical and electronic state information. The oxidation state of the transition metals at the surface can be probed via X-ray photoelectron spectroscopy (XPS) while both bulk and surface oxidation states as well as changes in metal oxygen bonding can be probed using X-ray absorption spectroscopy (XAS). Using X-ray spectroscopy in tandem with electrochemical, transport and microscopy measurements of the same materials, the impedance growth with increasing delithiation was correlated with the formation of a disordered NiO phase on the surface of NCA which was precipitated by the release of oxygen. Furthermore, the surface degradation was strongly impacted by the type of Li salt used in the electrolyte, with the standard commercial salt LiPF6 suffering from exothermic decomposition

  3. Retention Mechanisms of Citric Acid in Ternary Kaolinite-Fe(III)-Citrate Acid Systems Using Fe K-edge EXAFS and L3,2-edge XANES Spectroscopy

    Science.gov (United States)

    Yang, Jianjun; Wang, Jian; Pan, Weinan; Regier, Tom; Hu, Yongfeng; Rumpel, Cornelia; Bolan, Nanthi; Sparks, Donald

    2016-01-01

    Organic carbon (OC) stability in tropical soils is strongly interlinked with multivalent cation interaction and mineral association. Low molecular weight organic acids (LMWOAs) represent the readily biodegradable OC. Therefore, investigating retention mechanisms of LMWOAs in mineral-cation-LMWOAs systems is critical to understanding soil C cycling. Given the general acidic conditions and dominance of kaolinite in tropical soils, we investigated the retention mechanisms of citric acid (CA) in kaolinite-Fe(III)-CA systems with various Fe/CA molar ratios at pH ~3.5 using Fe K-edge EXAFS and L3,2-edge XANES techniques. With Fe/CA molar ratios >2, the formed ferrihydrite mainly contributed to CA retention through adsorption and/or coprecipitation. With Fe/CA molar ratios from 2 to 0.5, ternary complexation of CA to kaolinite via a five-coordinated Fe(III) bridge retained higher CA than ferrihydrite-induced adsorption and/or coprecipitation. With Fe/CA molar ratios ≤0.5, kaolinite-Fe(III)-citrate complexation preferentially occurred, but less CA was retained than via outer-sphere kaolinite-CA complexation. This study highlighted the significant impact of varied Fe/CA molar ratios on CA retention mechanisms in kaolinite-Fe(III)-CA systems under acidic conditions, and clearly showed the important contribution of Fe-bridged ternary complexation on CA retention. These findings will enhance our understanding of the dynamics of CA and other LMWOAs in tropical soils. PMID:27212680

  4. Organometallic model complexes elucidate the active gallium species in alkane dehydrogenation catalysts based on ligand effects in Ga K-edge XANES

    Energy Technology Data Exchange (ETDEWEB)

    Getsoian, Andrew “Bean”; Das, Ujjal; Camacho-Bunquin, Jeffrey; Zhang, Guanghui; Gallagher, James R.; Hu, Bo; Cheah, Singfoong; Schaidle, Joshua A.; Ruddy, Daniel A.; Hensley, Jesse E.; Krause, Theodore R.; Curtiss, Larry A.; Miller, Jeffrey T.; Hock, Adam S.

    2016-01-01

    Gallium-modified zeolites are known catalysts for the dehydrogenation of alkanes, reactivity that finds industrial application in the aromatization of light alkanes by Ga-ZSM5. While the role of gallium cations in alkane activation is well known, the oxidation state and coordination environment of gallium under reaction conditions has been the subject of debate. Edge shifts in Ga K-edge XANES spectra acquired under reaction conditions have long been interpreted as evidence for reduction of Ga(III) to Ga(I). However, a change in oxidation state is not the only factor that can give rise to a change in the XANES spectrum. In order to better understand the XANES spectra of working catalysts, we have synthesized a series of molecular model compounds and grafted surface organometallic Ga species and compared their XANES spectra to those of gallium-based catalysts acquired under reducing conditions. We demonstrate that changes in the identity and number of gallium nearest neighbors can give rise to changes in XANES spectra similar to those attributed in literature to changes in oxidation state. Specifically, spectral features previously attributed to Ga(I) may be equally well interpreted as evidence for low-coordinate Ga(III) alkyl or hydride species. These findings apply both to gallium-impregnated zeolite catalysts and to silica-supported single site gallium catalysts, the latter of which is found to be active and selective for dehydrogenation of propane and hydrogenation of propylene.

  5. First-Principles Fe L 2,3 -Edge and O K-Edge XANES and XMCD Spectra for Iron Oxides

    Energy Technology Data Exchange (ETDEWEB)

    Sassi, Michel [Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Pearce, Carolyn I. [Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Bagus, Paul S. [Department; Arenholz, Elke [Advanced; Rosso, Kevin M. [Pacific Northwest National Laboratory, Richland, Washington 99352, United States

    2017-10-02

    X-ray absorption near-edge structure (XANES) and X-ray magnetic circular dichroism (XMCD) spectroscopies are tools in widespread use for providing detailed local atomic structure, oxidation state, and magnetic structure information for materials and organometallic complexes. The analysis of these spectra for transition-metal L-edges is routinely performed on the basis of ligand-field multiplet theory because one- and two-particle mean-field ab initio methods typically cannot describe the multiplet structure. Here we show that multireference configuration interaction (MRCI) calculations can satisfactorily reproduce measured XANES spectra for a range of complex iron oxide materials including hematite and magnetite. MRCI Fe L2,3-edge XANES and XMCD spectra of Fe(II)O6, Fe(III)O6, and Fe(III)O4 in magnetite are found to be in very good qualitative agreement with experiment and multiplet calculations. Point-charge embedding and small distortions of the first-shell oxygen ligands have only small effects. Oxygen K-edge XANES/XMCD spectra for magnetite investigated by a real-space Green’s function approach complete the very good qualitative agreement with experiment. Material-specific differences in local coordination and site symmetry are well reproduced, making the approach useful for assigning spectral features to specific oxidation states and coordination environments.

  6. Surface structure of alpha-Fe sub 2 O sub 3 nanocrystal observed by O K-edge X-ray absorption spectroscopy

    CERN Document Server

    Zhang, J; Ibrahim, K; Abbas, M I; Ju, X

    2003-01-01

    X-ray absorption near edge structure (XANES) spectra is used as a probe of surface structure of alpha-Fe sub 2 O sub 3 nanocrystal, prepared by sol-gel method. We present O K-edge XANES of alpha-Fe sub 2 O sub 3 in nanocrystal and bulk by total electron yield at the photoemission station of Beijing Synchrotron Radiation Facility. The spectrum of alpha-Fe sub 2 O sub 3 shows a splitting of the pre-edge structure, which is interpreted as two subsets of Fe 3d t sub 2 sub g and e sub g orbitals in oxygen octahedral (O sub h) crystal field, and is also sensitive to long-range order effects. However, no distinguishable splitting of the pre-edge peak of nanocrystal alpha-Fe sub 2 O sub 3 is observed. This suggests that there exists the distorted octahedral coordination around Fe sites and also the long-range disorder due to the surface as compared with bulk alpha-Fe sub 2 O sub 3.

  7. Total electron yield measurements of extended x-ray absorption fine structures (EXAFS) of Ni and Fe thin foils, and adsorption of Ni on polycrystalline Fe substrates

    International Nuclear Information System (INIS)

    Sham, T.K.; Carr, R.G.

    1985-01-01

    X-ray absorption spectra of Fe and Ni K edges have been obtained at room temperature by means of a total electron yield technique for a clean Fe foil on which Ni was subsequently deposited, and a Ni foil. This technique involves the measurement of the specimen current. The total yield is found to be approx.1 x 10 -2 electron per photon absorbed at the Fe K edge for a 1/4 mil foil. Dramatic increase in surface sensitivity is gained over transmission EXAFS by using this technique to study Ni overlayers on Fe surface. The EXAFS of the deposited Ni overlayers (several monolayer coverage) are compared with those of the pure elements and of Ni/Fe alloys in the α(bcc) and γ(fcc) phases. The results indicate that the average Ni--Ni bond in the deposited Ni overlayers does not contract relative to that in the bulk in contrast to previously observed contraction of Ni deposition on carbon substrates. The feasibility of this technique and its application are discussed

  8. Valence changes associated with the metal-insulator transition in Bi1-xLaxNiO3

    Science.gov (United States)

    Wadati, H.; Takizawa, M.; Tran, T. T.; Tanaka, K.; Mizokawa, T.; Fujimori, A.; Chikamatsu, A.; Kumigashira, H.; Oshima, M.; Ishiwata, S.; Azuma, M.; Takano, M.

    2005-10-01

    Perovskite-type BiNiO3 is an insulating antiferromagnet in which a charge disproportionation occurs at the Bi site. La substitution for Bi suppresses the charge disproportionation and makes the system metallic. We have measured the photoemission and x-ray-absorption (XAS) spectra of Bi1-xLaxNiO3 to investigate how the electronic structure changes with La doping. From Ni 2p XAS, we observed an increase of the valence of Ni from 2+ toward 3+ . Combined with the core-level photoemission study, it was found that the average valence of Bi remains ˜4+ and that the Ni valence behaves as ˜(2+x)+ , that is, La substitution results in a hole doping at the Ni sites. In the valence-band photoemission spectra, we observed a Fermi cutoff for x>0 , consistent with the metallic behavior of the La-doped compounds. The Ni 2p XAS, Ni 2p core-level photoemission, and valence-band photoemission spectra were analyzed by configuration-interaction cluster-model calculation, and the spectral line shapes were found to be consistent with the gradual Ni2+→Ni3+ valence change.

  9. In-operando synchronous time-multiplexed O K-edge x-ray absorption spectromicroscopy of functioning tantalum oxide memristors

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Suhas [Hewlett-Packard Laboratories, 1501 Page Mill Road, Palo Alto, California 94304 (United States); Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States); Graves, Catherine E.; Strachan, John Paul, E-mail: john-paul.strachan@hp.com; Williams, R. Stanley [Hewlett-Packard Laboratories, 1501 Page Mill Road, Palo Alto, California 94304 (United States); Kilcoyne, A. L. David; Tyliszczak, Tolek [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Nishi, Yoshio [Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States)

    2015-07-21

    Memristors are receiving keen interest because of their potential varied applications and promising large-scale information storage capabilities. Tantalum oxide is a memristive material that has shown promise for high-performance nonvolatile computer memory. The microphysics has been elusive because of the small scale and subtle physical changes that accompany conductance switching. In this study, we probed the atomic composition, local chemistry, and electronic structure of functioning tantalum oxide memristors through spatially mapped O K-edge x-ray absorption. We developed a time-multiplexed spectromicroscopy technique to enhance the weak and possibly localized oxide modifications with spatial and spectral resolutions of <30 nm and 70 meV, respectively. During the initial stages of conductance switching of a micrometer sized crosspoint device, the spectral changes were uniform within the spatial resolution of our technique. When the device was further driven with millions of high voltage-pulse cycles, we observed lateral motion and separation of ∼100 nm-scale agglomerates of both oxygen interstitials and vacancies. We also demonstrate a unique capability of this technique by identifying the relaxation behavior in the material during electrical stimuli by identifying electric field driven changes with varying pulse widths. In addition, we show that changes to the material can be localized to a spatial region by modifying its topography or uniformity, as against spatially uniform changes observed here during memristive switching. The goal of this report is to introduce the capability of time-multiplexed x-ray spectromicroscopy in studying weak-signal transitions in inhomogeneous media through the example of the operation and temporal evolution of a memristor.

  10. Comparison of Hybrid K-Edge Densitometer (HKED) Performance Operating with the Canberra Lynx MCA and the Canberra ICB-NIM Electronics

    Energy Technology Data Exchange (ETDEWEB)

    McElroy, Robert Dennis [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-10-01

    From the 1991 until 2008 the Canberra Hybrid K-Edge Densitometer systems were provided with ICB-NIM (Integrated Control Bus – Nuclear Instrument Module) acquisition electronics. Newer electronics modules, such as the Lynx, were not supported under the VMS based operating system. The LYNX module was provided as the standard acquisition electronics following the release of the Windows based CHKED software. This report compares the electronics dead-time, gain shifts, detector resolution and measurement performance of the HKED system operated with the two types of acquisition modules. The comparison was performed using measurements obtained with the ORNL HKED system. The original intent of this study was to take advantage of both the timing and energy outputs from the HPGE detector to acquire data with both sets of electronics in parallel. Although this approach has been applied successfully with other systems, in this case we found the timing output produced a significant amount of noise such that a comparison between the electronics would be invalid. So the comparative measurements were performed sequentially. The ICB-NIM data was acquired over the course of 12 months with 255 measurements while the LYNX data was acquired over a period of 10 months with 75 measurements. To simplify the comparison, all data used in this study was acquired using the Canberra CHKED (V1.0) software package. The performance analysis was based primarily on the peak locations, peak widths and concentration values reported by the CHKED software. The raw spectra from the XRF measurements were also examined to extract additional 109Cd peak location and width data for the hybrid measurements (the standard hybrid report template does not report these values).

  11. X-ray absorption near edge spectroscopy at the Mn K-edge in highly homogeneous GaMnN diluted magnetic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Sancho-Juan, O.; Cantarero, A.; Garro, N.; Cros, A. [Materials Science Institute, University of Valencia, PO Box 22085, 46071 Valencia (Spain); Martinez-Criado, G.; Salome, M.; Susini, J. [ESRF, Polygone Scientifique Louis Neel, 6 rue Jules Horowitz, 38000 Grenoble (France); Olguin, D. [Dept. de Fisica, CINVESTAV-IPN, 07300 Mexico D.F. (Mexico); Dhar, S.; Ploog, K. [Paul Drude Institute, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2006-06-15

    We have studied by X-ray absorption spectroscopy the local environment of Mn in highly homogeneous Ga{sub 1-x}Mn{sub x}N (0.06K-edges. In this report, we focus our attention to the X-ray absorption near edge spectroscopy (XANES) results. The comparison of the XANES spectra corresponding to the Ga and Mn edges indicates that Mn is substitutional to Ga in all samples studied. The XANES spectra measured at the Mn absorption edge shows in the near-edge region a double peak and a shoulder below the absorption edge and the main absorption peak after the edge, separated around 15 eV above the pre-edge structure. We have compared the position of the edge with that of MnO (Mn{sup 2+}) and Mn{sub 2}O{sub 3} (Mn{sup 3+}). All samples studied present the same Mn oxidation state, 2{sup +}. In order to interprete the near-edge structure, we have performed ab initio calculations with a 2 x 2 x 1supercell ({proportional_to}6% Mn) using the full potential linear augmented plane wave method as implemented in the Wien2k code. The calculations show the appearance of Mn anti-bonding t{sub 2g} bands, which are responsible for the pre-edge absorption. The shoulder and main absorption peaks are due to transitions from the valence band 1s-states of Mn to the p-contributions of the conduction bands. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Trace metal analysis by laser ablation-inductively coupled plasmamass spectrometry and x-ray K-edge densitometry of forensic samples

    Energy Technology Data Exchange (ETDEWEB)

    Berry, Jonna Elizabeth [Iowa State Univ., Ames, IA (United States)

    2016-10-25

    This dissertation describes a variety of studies on the determination of trace elements in samples with forensic importance. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was used to determine the trace element composition of numerous lipstick samples. Lipstick samples were determined to be homogeneous. Most lipstick samples of similar colors were readily distinguishable at a 95% confidence interval based on trace element composition. Numerous strands of a multi-strand speaker cable were analyzed by LA-ICP-MS. The strands in this study are spatially heterogeneous in trace element composition. In actual forensic applications, the possibility of spatial heterogeneity must be considered, especially in cases where only small samples (e.g., copper wire fragments after an explosion) are available. The effects of many unpredictable variables, such as weather, temperature, and human activity, on the retention of gunshot residue (GSR) around projectile wounds were assessed with LAICP- MS. Skin samples around gunshot and stab wounds and larvae feeding in and around the wounds on decomposing pig carcasses were analyzed for elements consistent with GSR (Sb, Pb, Ba, and Cu). These elements were detected at higher levels in skin and larvae samples around the gunshot wounds compared to the stab wounds for an extended period of time throughout decomposition in both a winter and summer study. After decomposition, radiographic images of the pig bones containing possible damage from bullets revealed metallic particles embedded within a number of bones. Metallic particles within the bones were analyzed with x-ray, K-edge densitometry and determined to contain lead, indicating that bullet residue can be retained throughout decomposition and detected within bones containing projectile trauma.

  13. Imaging Taurine in the Central Nervous System Using Chemically Specific X-ray Fluorescence Imaging at the Sulfur K-Edge

    Energy Technology Data Exchange (ETDEWEB)

    Hackett, Mark J.; Paterson, Phyllis G.; Pickering, Ingrid J.; George, Graham N. (Curtin U.); (Saskatchewan)

    2016-11-15

    A method to image taurine distributions within the central nervous system and other organs has long been sought. Since taurine is small and mobile, it cannot be chemically “tagged” and imaged using conventional immuno-histochemistry methods. Combining numerous indirect measurements, taurine is known to play critical roles in brain function during health and disease and is proposed to act as a neuro-osmolyte, neuro-modulator, and possibly a neuro-transmitter. Elucidation of taurine’s neurochemical roles and importance would be substantially enhanced by a direct method to visualize alterations, due to physiological and pathological events in the brain, in the local concentration of taurine at or near cellular spatial resolution in vivo or in situ in tissue sections. We thus have developed chemically specific X-ray fluorescence imaging (XFI) at the sulfur K-edge to image the sulfonate group in taurine in situ in ex vivo tissue sections. To our knowledge, this represents the first undistorted imaging of taurine distribution in brain at 20 μm resolution. We report quantitative technique validation by imaging taurine in the cerebellum and hippocampus regions of the rat brain. Further, we apply the technique to image taurine loss from the vulnerable CA1 (cornus ammonis 1) sector of the rat hippocampus following global brain ischemia. The location-specific loss of taurine from CA1 but not CA3 neurons following ischemia reveals osmotic stress may be a key factor in delayed neurodegeneration after a cerebral ischemic insult and highlights the significant potential of chemically specific XFI to study the role of taurine in brain disease.

  14. Cu K-edge X-ray Absorption Spectroscopy Reveals Differential Copper Coordimation Within Amyloid-beta Oligomers Compared to Amyloid-beta Monomers

    Energy Technology Data Exchange (ETDEWEB)

    J Shearer; P Callan; T Tran; V Szalai

    2011-12-31

    The fatal neurodegenerative disorder Alzheimer's disease (AD) has been linked to the formation of soluble neurotoxic oligomers of amyloid-{beta} (A{beta}) peptides. These peptides have high affinities for copper cations. Despite their potential importance in AD neurodegeneration few studies have focused on probing the Cu{sup 2+/1+} coordination environment within A{beta} oligomers. Herein we present a Cu K-edge X-ray absorption spectroscopic study probing the copper-coordination environment within oligomers of A{beta}(42) (sequence: DAEFRHDSGYEVHHQKLVFFAEDVGSNKGAIIGLMVGGVVIA). We find that the Cu{sup 2+} cation is contained within a square planar mixed N/O ligand environment within A{beta}(42) oligomers, which is similar to the copper coordination environment of the monomeric forms of {l_brace}Cu{sup II}A{beta}(40){r_brace} and {l_brace}Cu{sup II}A{beta}(16){r_brace}. Reduction of the Cu{sup 2+} cation within the A{beta}(42) oligomers to Cu{sup 1+} yields a highly dioxygen sensitive copper-species that contains Cu{sup 1+} in a tetrahedral coordination geometry. This can be contrasted with monomers of {l_brace}Cu{sup I}A{beta}(40){r_brace} and {l_brace}Cu{sup I}A{beta}(16){r_brace}, which contain copper in a dioxygen inert linear bis-histidine ligand environment [Shearer and Szalai, J. Am. Chem. Soc., 2008, 130, 17826]. The biological implications of these findings are discussed.

  15. Kinetics of formation of NiO nanoparticles by X-ray absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Meneses, C.T. [Departamento de Fisica, Universidade Federal do Ceara, Campus do Pici, CP 6030, 60455-760 Fortaleza, CE (Brazil)], E-mail: cristiano@fisica.ufc.br; Flores, W.H. [Centro de Ciencias Exatas e Tecnologicas, Universidade Federal de Pelotas, Campus de Bage, 96412-420 Bage, RS (Brazil); Sasaki, J.M. [Departamento de Fisica, Universidade Federal do Ceara, Campus do Pici, CP 6030, 60455-760 Fortaleza, CE (Brazil)

    2007-05-15

    We report the in situ X-ray absorption investigations to study kinetic formation on NiO nanoparticles growth. The effects caused in the initial stage of particles growth by different heating rates are investigated. XAS results show that the particles disorder appears for high heating rates and growth process is faster for low heating rates.

  16. An in situ EXAFS study of the influence of the H2S/H2 ratio and the temperature on the local order of palladium, nickel and molybdenum atoms in the case of a highly dispersed multimetallic catalyst: Pd-Ni-Mo/Al2O3

    Science.gov (United States)

    Maire, F.; Bazin, D.

    2002-07-01

    Hydrotreating catalysts for efficient upgrading of crude oil fractions are made of a mixed- sulphide phase supported on oxidic carriers. More precisely, MoS2 promoted with Ni or Co is an important hydrodesulfurization (HDS) catalyst used to remove sulfur from petroleum feedstoock. The usual characterisation techniques, such as transmission electron microscopy help to restrict the problem but do not precisely show the structure of the metallic particles. A more appropriate technique, such as X-ray absorption spectroscopy is thus necessary. Here, in situ Xas experiments have been performed on a PdO/Ni-Mo/Al2O3 catalyst at the Mo K, Ni K and Pd K edge in order to understand the possible interaction between the components. Two parameters are considered : the H2S/H2 ratio and the temperature. Finally, a structural model is proposed. L'optimisation d'un catalyseur dédié à la diminution de la teneur en soufre des pétroles “bruts” conduit à un matériau composé d'un sulfure de molybdène (MoS2) déposé sur une alumine sur lequel sont placés en outre différents métaux (nickel, cobalt, palladium). Cet ajout se présente sous la forme d'entités de dimension nanométrique, cette particularité structurale rendant inopérante les techniques de caractérisation classiques (Diffraction des rayons X, microscopie électronique notamment). Dans cette étude, la spectroscopie d'absorption X permet une détermination structurale fine du système catalytique Pd/Ni-Mo/Al2O3. Mené aux seuils K des différents métaux (Mo, Ni, Pd) et considérant deux paramètres significatifs, le rapport H2S/H2 et la température, ce travail nous permet de proposer un modèle structural.

  17. An XAS experimental approach to study low Pt content electrocatalysts operating in PEM fuel cells.

    Science.gov (United States)

    Principi, Emiliano; Witkowska, Agnieszka; Dsoke, Sonia; Marassi, Roberto; Di Cicco, Andrea

    2009-11-21

    We present an X-ray absorption spectroscopy (XAS) study of a low Pt content catalyst layer (Pt loading 0.1 mg cm(-2)) operating at the cathode of a proton exchange membrane fuel cell (PEMFC). This catalyst is based on the use of a mesoporous inorganic matrix as a support for the catalyst Pt nanoparticles. Due to the high Pt dilution, in situ measurements of its structural properties by XAS are challenging and suitable experimental strategies must be devised for this purpose. In particular, we show that accurate XAS in situ fluorescence measurements can be obtained using an optimized fuel cell, suitable protocols for alignment of a focused X-ray beam and an appropriate filter for the background signal of the other atomic species contained in the electrodes. Details, advantages and limitations of the XAS technique for in situ measurements are discussed. Analysis of the near-edge XAS and EXAFS (extended X-ray absorption fine structure) data, corroborated by a HRTEM (high-resolution transmission electron microscopy) study, shows that the Pt particles have a local structure compatible with that of bulk Pt (fcc) and coordination numbers match those expected for particles with typical sizes in the 1.5-2.0 nm range. Substantial changes in the oxidation state and in local atomic arrangement of the Pt particles are found for different applied potentials. The catalyst support, containing W atoms, exhibits a partial reduction upon PEMFC activation, thus mimicking the catalyst behavior. This indicates a possible role of the mesoporous matrix in favouring the oxygen reduction reaction (ORR) and stimulates further research on active catalyst supports.

  18. Spatial distribution of transferred charges across the heterointerface between perovskite transition metal oxides LaNiO{sub 3} and LaMnO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Kitamura, Miho [Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801 (Japan); Horiba, Koji; Kobayashi, Masaki; Sakai, Enju; Minohara, Makoto; Mitsuhashi, Taichi; Kumigashira, Hiroshi, E-mail: hiroshi.kumigashira@kek.jp [Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801 (Japan); Fujimori, Atsushi [Department of Physics, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Nagai, Takuro [National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba 305-0044 (Japan); Fujioka, Hiroshi [Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan)

    2016-03-14

    To investigate the interfacial charge-transfer phenomena between perovskite transition metal oxides LaNiO{sub 3} (LNO) and LaMnO{sub 3} (LMO), we have performed in situ x-ray absorption spectroscopy (XAS) measurements on LNO/LMO multilayers. The Ni-L{sub 2,3} and Mn-L{sub 2,3} XAS spectra clearly show the occurrence of electron transfer from Mn to Ni ions in the interface region. Detailed analysis of the thickness dependence of these XAS spectra has revealed that the spatial distribution of the transferred charges across the interface is significantly different between the two constituent layers. The observed spatial distribution is presumably described by the charge spreading model that treats the transfer integral between neighboring transition metal ions and the Coulomb interaction, rather than the Thomas–Fermi screening model.

  19. High-flux table-top soft x-ray source driven by sub-2-cycle, CEP stable, 1.85-μm 1-kHz pulses for carbon K-edge spectroscopy.

    Science.gov (United States)

    Cousin, S L; Silva, F; Teichmann, S; Hemmer, M; Buades, B; Biegert, J

    2014-09-15

    We report on the first table-top high-flux source of coherent soft x-ray radiation up to 400 eV, operating at 1 kHz. This source covers the carbon K-edge with a beam brilliance of (4.3±1.2)×10(15) photons/s/mm(2)/strad/10% bandwidth and a photon flux of (1.85±0.12)×10(7) photons/s/1% bandwidth. We use this source to demonstrate table-top x-ray near-edge fine-structure spectroscopy at the carbon K-edge of a polyimide foil and retrieve the specific absorption features corresponding to the binding orbitals of the carbon atoms in the foil.

  20. Structure and atomic correlations in molecular systems probed by XAS reverse Monte Carlo refinement

    Science.gov (United States)

    Di Cicco, Andrea; Iesari, Fabio; Trapananti, Angela; D'Angelo, Paola; Filipponi, Adriano

    2018-03-01

    The Reverse Monte Carlo (RMC) algorithm for structure refinement has been applied to x-ray absorption spectroscopy (XAS) multiple-edge data sets for six gas phase molecular systems (SnI2, CdI2, BBr3, GaI3, GeBr4, GeI4). Sets of thousands of molecular replicas were involved in the refinement process, driven by the XAS data and constrained by available electron diffraction results. The equilibrated configurations were analysed to determine the average tridimensional structure and obtain reliable bond and bond-angle distributions. Detectable deviations from Gaussian models were found in some cases. This work shows that a RMC refinement of XAS data is able to provide geometrical models for molecular structures compatible with present experimental evidence. The validation of this approach on simple molecular systems is particularly important in view of its possible simple extension to more complex and extended systems including metal-organic complexes, biomolecules, or nanocrystalline systems.

  1. Noncollinear Spin Structure in Fe--Ni Invar Alloy Probed by Magnetic EXAFS at High Pressure

    Science.gov (United States)

    Matsumoto, Ken; Maruyama, Hiroshi; Ishimatsu, Naoki; Kawamura, Naomi; Mizumaki, Masaichiro; Irifune, Tetsuo; Sumiya, Hitoshi

    2011-02-01

    To examine theoretical models of the Invar effect, X-ray magnetic circular dichroism and magnetic extended X-ray absorption fine structure (MEXAFS) measurements are performed under high pressures at the Fe and Ni K-edges in 35.4 at. % Ni--Fe alloy. An oscillatory MEXAFS signal is observed up to 6 GPa. Its amplitude significantly decreases with increasing pressure. The magnetic component of the radial distribution function, obtained by taking the Fourier transform, shows a different reduction in the ferromagnetic correlations of Fe and Ni absorbing atoms. The present results are favorable to the noncollinear spin structure picture rather than the Fe 2γ-state model.

  2. ALD Zn(O,S) Thin Films’ Interfacial Chemical and Structural Configuration Probed by XAS

    OpenAIRE

    Dadlani, Anup; Acharya, Shinjita; Trejo, Orlando; Fritz, Prinz; Torgersen, Jan

    2016-01-01

    The ability to precisely control interfaces of atomic layer deposited (ALD) zinc oxysulfide (Zn(O,S)) buffer layers to other layers allows precise tuning of solar cell performance. The O K- and S K-edge X-ray absorption near edge structure (XANES) of ∼2–4 nm thin Zn(O,S) films reveals the chemical and structural influences of their interface with ZnO, a common electrode material and diffusion barrier in solar cells. We observe that sulfate formation at oxide/sulfide interfaces is independent ...

  3. Iron speciation in human cancer cells by K-edge total reflection X-ray fluorescence-X-ray absorption near edge structure analysis

    Energy Technology Data Exchange (ETDEWEB)

    Polgari, Zs. [Eoetvoes Lorand University, Institute of Chemistry, Department of Analytical Chemistry, Laboratory of Environmental Chemistry and Bioanalytics, P.O. Box 32, H-1518, Budapest (Hungary); Meirer, F. [Institute of Atomic and Subatomic Physics, Vienna University of Technology, Vienna (Austria); MiNALab, CMM-irst, Fondazione Bruno Kessler, Povo, Trento (Italy); Sasamori, S.; Ingerle, D. [Institute of Atomic and Subatomic Physics, Vienna University of Technology, Vienna (Austria); Pepponi, G. [MiNALab, CMM-irst, Fondazione Bruno Kessler, Povo, Trento (Italy); Streli, C. [Institute of Atomic and Subatomic Physics, Vienna University of Technology, Vienna (Austria); Rickers, K. [Hamburger Synchrotronstrahlungslabor at DESY, Hamburg (Germany); Reti, A.; Budai, B. [Department of Clinical Research, National Institute of Oncology, Budapest (Hungary); Szoboszlai, N. [Eoetvoes Lorand University, Institute of Chemistry, Department of Analytical Chemistry, Laboratory of Environmental Chemistry and Bioanalytics, P.O. Box 32, H-1518, Budapest (Hungary); Zaray, G., E-mail: zaray@ludens.elte.hu [Eoetvoes Lorand University, Institute of Chemistry, Department of Analytical Chemistry, Laboratory of Environmental Chemistry and Bioanalytics, P.O. Box 32, H-1518, Budapest (Hungary)

    2011-03-15

    X-ray absorption near edge structure (XANES) analysis in combination with synchrotron radiation induced total reflection X-ray fluorescence (SR-TXRF) acquisition was used to determine the oxidation state of Fe in human cancer cells and simultaneously their elemental composition by applying a simple sample preparation procedure consisting of pipetting the cell suspension onto the quartz reflectors. XANES spectra of several inorganic and organic iron compounds were recorded and compared to that of different cell lines. The XANES spectra of cells, independently from the phase of cell growth and cell type were very similar to that of ferritin, the main Fe store within the cell. The spectra obtained after CoCl{sub 2} or NiCl{sub 2} treatment, which could mimic a hypoxic state of cells, did not differ noticeably from that of the ferritin standard. After 5-fluorouracil administration, which could also induce an oxidative-stress in cells, the absorption edge position was shifted toward higher energies representing a higher oxidation state of Fe. Intense treatment with antimycin A, which inhibits electron transfer in the respiratory chain, resulted in minor changes in the spectrum, resembling rather the N-donor Fe-{alpha},{alpha}'-dipyridyl complex at the oxidation energy of Fe(III), than ferritin. The incorporation of Co and Ni in the cells was followed by SR-TXRF measurements.

  4. Mn K-edge XANES and Kbeta XES studies of two Mn-oxo binuclear complexes: investigation of three different oxidation states relevant to the oxygen-evolving complex of photosystem II.

    Science.gov (United States)

    Visser, H; Anxolabéhère-Mallart, E; Bergmann, U; Glatzel, P; Robblee, J H; Cramer, S P; Girerd, J J; Sauer, K; Klein, M P; Yachandra, V K

    2001-07-25

    Two structurally homologous Mn compounds in different oxidation states were studied to investigate the relative influence of oxidation state and ligand environment on Mn K-edge X-ray absorption near-edge structure (XANES) and Mn Kbeta X-ray emission spectroscopy (Kbeta XES). The two manganese compounds are the di-mu-oxo compound [L'2Mn(III)O2Mn(IV)L'2](ClO4)3, where L' is 1,10-phenanthroline (Cooper, S. R.; Calvin, M. J. Am. Chem. Soc. 1977, 99, 6623-6630) and the linear mono-mu-oxo compound [LMn(III)OMn(III)L](ClO4)2, where L- is the monoanionic N,N-bis(2-pyridylmethyl)-N'-salicylidene-1,2-diaminoethane ligand (Horner, O.; Anxolabéhère-Mallart, E.; Charlot, M. F.; Tchertanov, L.; Guilhem, J.; Mattioli, T. A.; Boussac, A.; Girerd, J.-J. Inorg. Chem. 1999, 38, 1222-1232). Preparative bulk electrolysis in acetonitrile was used to obtain higher oxidation states of the compounds: the Mn(IV)Mn(IV) species for the di-mu-oxo compound and the Mn(III)Mn(IV) and Mn(IV)Mn(IV) species for the mono-mu-oxo compound. IR, UV/vis, EPR, and EXAFS spectra were used to determine the purity and integrity of the various sample solutions. The Mn K-edge XANES spectra shift to higher energy upon oxidation when the ligand environment remains similar. However, shifts in energy are also observed when only the ligand environment is altered. This is achieved by comparing the di-mu-oxo and linear mono-mu-oxo Mn-Mn moieties in equivalent oxidation states, which represent major structural changes. The magnitude of an energy shift due to major changes in ligand environment can be as large as that of an oxidation-state change. Therefore, care must be exercised when correlating the Mn K-edge energies to manganese oxidation states without taking into account the nature of the ligand environment and the overall structure of the compound. In contrast to Mn K-edge XANES, Kbeta XES spectra show less dependence on ligand environment. The Kbeta1,3 peak energies are comparable for the di-mu-oxo and mono

  5. Resonant inelastic x-ray scattering on iso-C{sub 2}H{sub 2}Cl{sub 2} around the chlorine K-edge: Structural and dynamical aspects

    Energy Technology Data Exchange (ETDEWEB)

    Kawerk, Elie, E-mail: eliekawerk@hotmail.com, E-mail: ekawerk@units.it [CNRS, UMR 7614, Laboratoire de Chimie Physique-Matière et Rayonnement, F-75005 Paris (France); Sorbonne Universités, UPMC Université Paris 06, UMR 7614, Laboratoire de Chimie Physique-Matière et Rayonnement, F-75005 Paris (France); Laboratoire de Physique Appliquée, Faculté des Sciences II, Université Libanaise, 90656 Jdeidet el Metn, Liban (Libya); Dipartimento di Scienze Chimiche, Università di Trieste, Via L. Giorgieri 1, I-34127 Trieste (Italy); Carniato, Stéphane; Journel, Loïc; Marchenko, Tatiana; Simon, Marc [CNRS, UMR 7614, Laboratoire de Chimie Physique-Matière et Rayonnement, F-75005 Paris (France); Sorbonne Universités, UPMC Université Paris 06, UMR 7614, Laboratoire de Chimie Physique-Matière et Rayonnement, F-75005 Paris (France); Piancastelli, Maria Novella [CNRS, UMR 7614, Laboratoire de Chimie Physique-Matière et Rayonnement, F-75005 Paris (France); Sorbonne Universités, UPMC Université Paris 06, UMR 7614, Laboratoire de Chimie Physique-Matière et Rayonnement, F-75005 Paris (France); Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala (Sweden); Žitnik, Matjaž; Bučar, Klemen; Bohnic, Rok [Jožef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana (Slovenia); and others

    2014-10-14

    We report a theoretical and experimental study of the high resolution resonant K{sub α} X-ray emission lines around the chlorine K-edge in gas phase 1,1-dichloroethylene. With the help of ab initio electronic structure calculations and cross section evaluation, we interpret the lowest lying peak in the X-ray absorption and emission spectra. The behavior of the K{sub α} emission lines with respect to frequency detuning highlights the existence of femtosecond nuclear dynamics on the dissociative Potential Energy Surface of the first K-shell core-excited state.

  6. Mn K-Edge XANES and Kβ XES Studies of Two Mn–Oxo Binuclear Complexes: Investigation of Three Different Oxidation States Relevant to the Oxygen-Evolving Complex of Photosystem II

    Science.gov (United States)

    Visser, Hendrik; Anxolabéhère-Mallart, Elodie; Bergmann, Uwe; Glatzel, Pieter; Robblee, John H.; Cramer, Stephen P.; Girerd, Jean-Jacques; Sauer, Kenneth; Klein, Melvin P.; Yachandra, Vittal K.

    2014-01-01

    Two structurally homologous Mn compounds in different oxidation states were studied to investigate the relative influence of oxidation state and ligand environment on Mn K-edge X-ray absorption near-edge structure (XANES) and Mn Kβ X-ray emission spectroscopy (Kβ XES). The two manganese compounds are the di-μ-oxo compound [L′2MnIIIO2MnIVL′2](ClO4)3, where L′ is 1,10-phenanthroline (Cooper, S. R.; Calvin, M. J. Am. Chem. Soc. 1977, 99, 6623–6630) and the linear mono-μ-oxo compound [LMnIIIOMnIIIL](ClO4)2, where L− is the monoanionic N,N-bis(2-pyridylmethyl)-N′-salicylidene-1,2-diaminoethane ligand (Horner, O.; Anxolabéhère-Mallart, E.; Charlot, M. F.; Tchertanov, L.; Guilhem, J.; Mattioli, T. A.; Boussac, A.; Girerd, J.-J. Inorg. Chem. 1999, 38, 1222–1232). Preparative bulk electrolysis in acetonitrile was used to obtain higher oxidation states of the compounds: the MnIVMnIV species for the di-μ-oxo compound and the MnIIIMnIV and MnIVMnIV species for the mono-μ-oxo compound. IR, UV/vis, EPR, and EXAFS spectra were used to determine the purity and integrity of the various sample solutions. The Mn K-edge XANES spectra shift to higher energy upon oxidation when the ligand environment remains similar. However, shifts in energy are also observed when only the ligand environment is altered. This is achieved by comparing the di-μ-oxo and linear mono-μ-oxo Mn–Mn moieties in equivalent oxidation states, which represent major structural changes. The magnitude of an energy shift due to major changes in ligand environment can be as large as that of an oxidation-state change. Therefore, care must be exercised when correlating the Mn K-edge energies to manganese oxidation states without taking into account the nature of the ligand environment and the overall structure of the compound. In contrast to Mn K-edge XANES, Kβ XES spectra show less dependence on ligand environment. The Kβ1,3 peak energies are comparable for the di-μ-oxo and mono

  7. Influence of Ni doping on PtNi nanoparticles: Synthesis, electronic/atomic structure and photocatalyst investigations

    Science.gov (United States)

    Varshney, Mayora; Sharma, Aditya; Shin, Hyun-Joon; Lee, Hyun Hwi; Jeon, Tae-Yeol; Lee, Byeong-Hyeon; Chae, Keun-Hwa; Won, Sung Ok

    2017-11-01

    Carbon-supported Pt and PtNi nanoparticles (NPs) were synthesized using a borohydride reduction method. Structural properties were studied by synchrotron X-ray diffraction (XRD) and the size/shape of the NPs was determined by transmission electron microscope (TEM). X-ray absorption spectroscopy with its two amendments; X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), has been employed to investigate the local electronic/atomic structure surrounding the Pt and Ni atoms. XANES results, at Pt L3-edge and Ni K-edge, have shown fractional oxidation of Pt and Ni atoms. The Pt3Ni1NPs have exhibited a lower bond distance of Pt-Ni shell and higher coordination number of Pt-Ni shells, indicating the alloy formation between Pt and Ni. We further have demonstrated that the Pt and PtNi NPs can serve as effective photocatalysts towards the degradation of water pollutant dye (methyl orange (MO)). By considering the interband charge-transfer of Pt (5d →6sp), a tentative mechanism is proposed to understand the photocatalytic degradation of MO dye molecules by Pt/PtNi NPs under the light irradiation.

  8. Axial Ligation and Redox Changes at the Cobalt Ion in Cobalamin Bound to Corrinoid Iron-Sulfur Protein (CoFeSP) or in Solution Characterized by XAS and DFT.

    Science.gov (United States)

    Schrapers, Peer; Mebs, Stefan; Goetzl, Sebastian; Hennig, Sandra E; Dau, Holger; Dobbek, Holger; Haumann, Michael

    2016-01-01

    A cobalamin (Cbl) cofactor in corrinoid iron-sulfur protein (CoFeSP) is the primary methyl group donor and acceptor in biological carbon oxide conversion along the reductive acetyl-CoA pathway. Changes of the axial coordination of the cobalt ion within the corrin macrocycle upon redox transitions in aqua-, methyl-, and cyano-Cbl bound to CoFeSP or in solution were studied using X-ray absorption spectroscopy (XAS) at the Co K-edge in combination with density functional theory (DFT) calculations, supported by metal content and cobalt redox level quantification with further spectroscopic methods. Calculation of the highly variable pre-edge X-ray absorption features due to core-to-valence (ctv) electronic transitions, XANES shape analysis, and cobalt-ligand bond lengths determination from EXAFS has yielded models for the molecular and electronic structures of the cobalt sites. This suggested the absence of a ligand at cobalt in CoFeSP in α-position where the dimethylbenzimidazole (dmb) base of the cofactor is bound in Cbl in solution. As main species, (dmb)CoIII(OH2), (dmb)CoII(OH2), and (dmb)CoIII(CH3) sites for solution Cbl and CoIII(OH2), CoII(OH2), and CoIII(CH3) sites in CoFeSP-Cbl were identified. Our data support binding of a serine residue from the reductive-activator protein (RACo) of CoFeSP to the cobalt ion in the CoFeSP-RACo protein complex that stabilizes Co(II). The absence of an α-ligand at cobalt not only tunes the redox potential of the cobalamin cofactor into the physiological range, but is also important for CoFeSP reactivation.

  9. Axial Ligation and Redox Changes at the Cobalt Ion in Cobalamin Bound to Corrinoid Iron-Sulfur Protein (CoFeSP or in Solution Characterized by XAS and DFT.

    Directory of Open Access Journals (Sweden)

    Peer Schrapers

    Full Text Available A cobalamin (Cbl cofactor in corrinoid iron-sulfur protein (CoFeSP is the primary methyl group donor and acceptor in biological carbon oxide conversion along the reductive acetyl-CoA pathway. Changes of the axial coordination of the cobalt ion within the corrin macrocycle upon redox transitions in aqua-, methyl-, and cyano-Cbl bound to CoFeSP or in solution were studied using X-ray absorption spectroscopy (XAS at the Co K-edge in combination with density functional theory (DFT calculations, supported by metal content and cobalt redox level quantification with further spectroscopic methods. Calculation of the highly variable pre-edge X-ray absorption features due to core-to-valence (ctv electronic transitions, XANES shape analysis, and cobalt-ligand bond lengths determination from EXAFS has yielded models for the molecular and electronic structures of the cobalt sites. This suggested the absence of a ligand at cobalt in CoFeSP in α-position where the dimethylbenzimidazole (dmb base of the cofactor is bound in Cbl in solution. As main species, (dmbCoIII(OH2, (dmbCoII(OH2, and (dmbCoIII(CH3 sites for solution Cbl and CoIII(OH2, CoII(OH2, and CoIII(CH3 sites in CoFeSP-Cbl were identified. Our data support binding of a serine residue from the reductive-activator protein (RACo of CoFeSP to the cobalt ion in the CoFeSP-RACo protein complex that stabilizes Co(II. The absence of an α-ligand at cobalt not only tunes the redox potential of the cobalamin cofactor into the physiological range, but is also important for CoFeSP reactivation.

  10. Electronic structure of benzene adsorbed on Ni and Cu surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Weinelt, M.; Nilsson, A.; Wassdahl, N. [Uppsala Univ. (Sweden)] [and others

    1997-04-01

    Benzene has for a long time served as a prototype adsorption system of large molecules. It adsorbs with the molecular plane parallel to the surface. The bonding of benzene to a transition metal is typically viewed to involve the {pi} system. Benzene adsorbs weakly on Cu and strongly on Ni. It is interesting to study how the adsorption strength is reflected in the electronic structure of the adsorbate-substrate complex. The authors have used X-ray Emission (XE) and X-ray Absorption (XA) spectroscopies to selectively study the electronic states localized on the adsorbed benzene molecule. Using XES the occupied states can be studies and with XAS the unoccupied states. The authors have used beamline 8.0 and the Swedish endstation equipped with a grazing incidence x-ray spectrometer and a partial yield absorption detector. The resolution in the XES and XAS were 0.5 eV and 0.05 eV, respectively.

  11. The relationship between Al and Si in biogenic silica as determined by PIXE and XAS

    International Nuclear Information System (INIS)

    Beck, L.; Gehlen, M.; Flank, A.-M.; Bennekom, A.J. van; Beusekom, J.E.E. van

    2002-01-01

    Biogenic silica, one of the major constituents of marine sediments, is a potentially powerful paleoceanographic tool, revealing information on past productivity. Interpreting the sedimentary records of the biogenic silica requires, however, an understanding of its preservation. Dissolution of biogenic silica is controlled by the presence of trace elements such as Al. The work in this paper focuses on the association of Al and Si in biogenic silica. The composition and the atomic structure of cultured and natural diatoms were determined by using PIXE and XAS techniques. This study provides the first evidence for a structural association of Al and Si in biogenic silica

  12. A dispenser-reactor apparatus applied for in situ XAS monitoring of Pt nanoparticle formation.

    Science.gov (United States)

    Boita, Jocenir; Castegnaro, Marcus Vinicius; Alves, Maria do Carmo Martins; Morais, Jonder

    2015-05-01

    In situ time-resolved X-ray absorption spectroscopy (XAS) measurements collected at the Pt L3-edge during the synthesis of Pt nanoparticles (NPs) in aqueous solution are reported. A specially designed dispenser-reactor apparatus allowed for monitoring changes in the XAS spectra from the earliest moments of Pt ions in solution until the formation of metallic nanoparticles with a mean diameter of 4.9 ± 1.1 nm. By monitoring the changes in the local chemical environment of the Pt atoms in real time, it was possible to observe that the NPs formation kinetics involved two stages: a reduction-nucleation burst followed by a slow growth and stabilization of NPs. Subsequently, the synthesized Pt NPs were supported on activated carbon and characterized by synchrotron-radiation-excited X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS). The supported Pt NPs remained in the metallic chemical state and with a reduced size, presenting slight lattice parameter contraction in comparison with the bulk Pt values.

  13. A combined in situ XAS-XRPD-Raman study of Fischer-Tropsch synthesis over a carbon supported Co catalyst

    DEFF Research Database (Denmark)

    Tsakoumis, Nikolaos E.; Dehghan, Roya; Johnsen, Rune

    2013-01-01

    A cobalt based Fischer-Tropsch synthesis (FTS) catalyst, supported on a carbon nanofibers/carbon felt composite (Co/CNF/CF) was studied in situ at realistic conditions. The catalyst was monitored by Xray absorption spectroscopy (XAS), high-resolution X-ray powder diffraction (HR-XRPD) and Raman...

  14. Comparison between XAS, AWAXS and DAFS applied to nanometer scale supported metallic clusters. Pt.1; monometallic clusters

    International Nuclear Information System (INIS)

    Bazin, D.C.; Sayers, D.A.

    1993-01-01

    The structural information found using three techniques related to synchrotron radiation are compared. XAS (X-ray Absorption Spectroscopy), AWAXS (Anomalous Wide Angle X-ray Scattering) and DAFS (Diffraction Anomalous Fine Structure) are applied to nanometer scale metallic clusters. (author)

  15. Comparison between XAS, AWAXS and DAFS applied to nanometer scale supported metallic clusters. Pt.2; bimetallic clusters

    International Nuclear Information System (INIS)

    Bazin, D.; Sayers, D.

    1993-01-01

    The structural information obtained using three techniques related to synchrotron radiation are compared. XAS (X-ray Absorption Spectroscopy), AWAXS (Anomalous Wide Angle X-ray Scattering) and DAFS (Diffraction Anomalous Fine Structure) are applied to the study of nanometer scale bimetallic clusters. (author)

  16. In situ measurement of ferric iron in lunar glass beads using Fe-XAS

    Energy Technology Data Exchange (ETDEWEB)

    McCanta, Molly C.; Dyar, M. Darby; Rutherford, Malcolm J.; Lanzirotti, Antonio; Sutton, Stephen R.; Thomson, Bradley J.

    2017-03-01

    Through use of a new X-ray Absorption Spectroscopy (XAS) calibration for Fe3+ analysis in silicate glasses, the first direct measurements of ferric iron in natural lunar picritic glasses are presented. Lunar glass beads from the Apollo sample collection contain up to 60.0% Fe3+. No correlation with melt chemical properties, such as Mg# or weight % TiO2, or physical properties, such as bead diameter, was observed. Fe3+/ΣFe is negatively correlated with NBO/T. These elevated Fe3+/ΣFe values reflect eruption and post-eruption oxidation due to magmatic degassing of H or OH. Glass beads observed to be zoned to lower Fe3+/ΣFe rims may represent a subsequent reduction in the lunar vacuum prior to cooling through the glass transition temperature.

  17. In situ measurement of ferric iron in lunar glass beads using Fe-XAS

    Energy Technology Data Exchange (ETDEWEB)

    McCanta, Molly C.; Dyar, M. Darby; Rutherford, Malcolm J.; Lanzirotti, Antonio; Sutton, Stephen R.; Thomson, Bradley J.

    2017-03-01

    Through use of a new X-ray Absorption Spectroscopy (XAS) calibration for Fe3+ analysis in silicate glasses, the first direct measurements of ferric iron in natural lunar picritic glasses are presented. Lunar glass beads from the Apollo sample collection contain up to 60.0% Fe3+. No correlation with melt chemical properties, such as Mg# or weight % TiO2, or physical properties, such as bead diameter, was observed. Fe3+/ΣFe is negatively correlated with NBO/T. These elevated Fe3+/ΣFe values reflect eruption and post-eruption oxidation due to magmatic degassing of H or OH. Glass beads observed to be zoned to lower Fe3+/ΣFe rims may represent a subsequent reduction in the lunar vacuum prior to cooling through the glass transition temperature

  18. EXAFS study of the aging of LaNi5 and LaNi4.5Mn0.5 compounds during tritium storage

    International Nuclear Information System (INIS)

    Paul-Boncour, V.; Percheron-Guegan, A.; Achard, J.C.; Gasnier, P.; Carriat, J.Y.; Limacher, B.; Leroy, D.

    1994-01-01

    The modification of the thermodynamic and structural properties of LaNi 5 and LaNi 4.5 Mn 0.5 tritides, due to the presence of helium coming from the radioactive decay of tritium is studied by pressure-composition-temperature (P-C-T) isotherms determination, X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) experiments. For high He content a loss of long range order is observed and Extended X-ray Absorption Fine Structure (EXAFS) study show a small increase of the static disorder around Ni and Mn atoms and a larger one around La atoms. The assumption that a great part of the helium is located in the largest interstitial sites of the LaNi 5 or LaNi 5-x M x cell, leading to a cell distortion for high He content, allows to explain both thermodynamic and structural results. (orig.)

  19. Consequences of realistic embedding for the L 2,3 edge XAS of α-Fe 2 O 3

    Energy Technology Data Exchange (ETDEWEB)

    Bagus, Paul S. [Department of Chemistry; University of North Texas; Denton; USA; Nelin, Connie J. [Consultant; Austin; USA; Sassi, Michel [Pacific Northwest National Laboratory; Richland; USA; Ilton, Eugene S. [Pacific Northwest National Laboratory; Richland; USA; Rosso, Kevin M. [Pacific Northwest National Laboratory; Richland; USA

    2018-01-01

    Cluster models of condensed systems are often used to simulate the core-level spectra obtained with X-ray Photoelectron Spectroscopy, XPS, or with X-ray Absorption Spectroscopy, XAS, especially for near edge features.

  20. ALD Zn(O,S) Thin Films’ Interfacial Chemical and Structural Configuration Probed by XAS

    Science.gov (United States)

    2016-01-01

    The ability to precisely control interfaces of atomic layer deposited (ALD) zinc oxysulfide (Zn(O,S)) buffer layers to other layers allows precise tuning of solar cell performance. The O K- and S K-edge X-ray absorption near edge structure (XANES) of ∼2–4 nm thin Zn(O,S) films reveals the chemical and structural influences of their interface with ZnO, a common electrode material and diffusion barrier in solar cells. We observe that sulfate formation at oxide/sulfide interfaces is independent of film composition, a result of sulfur diffusion toward interfaces. Leveraging sulfur’s diffusivity, we propose an alternative ALD process in which the zinc precursor pulse is bypassed during H2S exposure. Such a process yields similar results to the nanolaminate deposition method and highlights mechanistic differences between ALD sulfides and oxides. By identifying chemical species and structural evolution at sulfide/oxide interfaces, this work provides insights into increasing thin film solar cell efficiencies. PMID:27223620

  1. ALD Zn(O,S) Thin Films' Interfacial Chemical and Structural Configuration Probed by XAS.

    Science.gov (United States)

    Dadlani, Anup L; Acharya, Shinjita; Trejo, Orlando; Prinz, Fritz B; Torgersen, Jan

    2016-06-15

    The ability to precisely control interfaces of atomic layer deposited (ALD) zinc oxysulfide (Zn(O,S)) buffer layers to other layers allows precise tuning of solar cell performance. The O K- and S K-edge X-ray absorption near edge structure (XANES) of ∼2-4 nm thin Zn(O,S) films reveals the chemical and structural influences of their interface with ZnO, a common electrode material and diffusion barrier in solar cells. We observe that sulfate formation at oxide/sulfide interfaces is independent of film composition, a result of sulfur diffusion toward interfaces. Leveraging sulfur's diffusivity, we propose an alternative ALD process in which the zinc precursor pulse is bypassed during H2S exposure. Such a process yields similar results to the nanolaminate deposition method and highlights mechanistic differences between ALD sulfides and oxides. By identifying chemical species and structural evolution at sulfide/oxide interfaces, this work provides insights into increasing thin film solar cell efficiencies.

  2. XAS studies of the effectiveness of iron chelating treatments of Mary Rose timbers

    Energy Technology Data Exchange (ETDEWEB)

    Berko, A; Schofield, E J; Chadwick, A V [School of Physical Sciences, University of Kent, CT2 7NR (United Kingdom); Smith, A D [STFC Daresbury Laboratory, Warrington, Cheshire, WA4 4AD (United Kingdom); Jones, A M [The Mary Rose Trust, HM Naval Base, Portsmouth, PO1 3LX (United Kingdom); Mosselmans, J F W, E-mail: a.berko@kent.ac.u [Diamond Light Source, Didcot, OX11 0DE (United Kingdom)

    2009-11-15

    The oxidation of sulfur in marine archaeological timbers under museum storage conditions is a recently identified problem, particularly for major artefacts such as historic ships excavated from the seabed. Recent work on the Vasa has stressed the role of iron in catalysing the oxidative degradation of the wood cellulose and the polyethylene glycols used to restore mechanical integrity to the timbers. In developing new treatment protocols for the long term preservation of Henry VIII of England's flagship, the Mary Rose, we are investigating the potential of chelating agents to neutralise and remove the iron products from the ships timbers. We have explored the use of aqueous solutions of chelating agents of calcium phytate, ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA) and ammonium citrate to extract the iron compounds. All of these solutions exhibit some level of iron removal; however the key is to find the most effective concentration at pH of around 7 of the reagent solution, to minimise the treatment time and find the most cost-effective treatment for the whole of the Mary Rose hull. Fe K-edge XAFS data from samples of Mary Rose timbers, before and after treatment by the chelating agents mentioned has been collected. The data collected provide valuable insights into the effectiveness of the treatment solutions.

  3. Photoelectric cross sections around the K edge

    International Nuclear Information System (INIS)

    Lingam, S.C.; Babu, K.S.; Reddy, D.V.K.

    1983-01-01

    Total attenuation cross sections for four elements, Ta, W, Au and Pb, were measured at the photon energies 32.1, 52, 72.1, 84.3, 145.4 and 279.2 keV. A good narrow beam geometry with two NaI (Tl) scintillation counters in conjunction with a single-channel analyser was used for the detection of low and medium energy photons. The measured total attenuation cross sections are compared with the theoretical compilations of Storm and Israel and the available earlier investigations. The scattering cross sections obtained by interpolation using the atomic data tables of Storm and Israel were subtracted from the measured total cross sections to obtain the photoelectric cross sections. The photoelectric cross sections thus derived are compared with the latest theoretical values of Scofield. (orig.)

  4. A solid-state NMR and DFT study of compositional modulations in AlxGa1-xAs

    NARCIS (Netherlands)

    Knijn, Paulus J.; Bentum, P. Jan M. van; Eck, Ernst R.H. van; Fang, Changming; Grimminck, Dennis L.A.G.; Groot, Robert A. de; Havenith, Remco W.A.; Marsman, Martijn; Meerts, W. Leo; Wijs, Gilles A. de; Kentgens, Arno P.M.

    2010-01-01

    We have conducted 75As and 69Ga Nuclear Magnetic Resonance (NMR) experiments to investigate order/disorder in AlxGa1-xAs lift-off films with x ~ 0.297 and 0.489. We were able to identify all possible As(AlnGa4-n) sites with n = 0–4 coordinations in 75As NMR spectra using spin-echo experiments at

  5. Study of temperature dependent local structure by polarized Cu K-edge EXAFS measurements on La sub 2 sub - sub x Sr sub x CuO sub 4 (x=0.105, 0.13, 0.20)

    CERN Document Server

    Saini, N L; Bianconi, A; Oyanagi, H; Ito, T; Oka, K

    2003-01-01

    We have studied temperature dependent local structure of superconducting La sub 2 sub - sub x Sr sub x CuO sub 4 (0.105, 0.13, 0.20) single crystals by Cu K-edge extended x-ray absorption fine structure (EXAFS) measurements with polarization parallel to the in-plane Cu-O bonds. We find that, while underdoped crystals (x=0.105, 0.13) show anomalous temperature dependence, similar to the case of optimally doped system (x=0.15), overdoped crystal (x=0.20) does not reveal such anomaly. Correlated Debye-Waller factor (DWF) of the Cu-O bonds (distance broadening) has been used as an order parameter to determine characteristic local displacements in the CuO sub 2 plane. The amplitude of temperature dependent step-like increase in the DWF at low temperature decreases with increasing doping. It has been discussed that decreasing electron-lattice interaction with increasing doping, shown by angle resolved photoemission measurements, is closely related to the evolving anomalous local CuO sub 2 distortion and charge inho...

  6. Chemical kinetics of Cs species in an alkali-activated municipal solid waste incineration fly ash and pyrophyllite-based system using Cs K-edge in situ X-ray absorption fine structure analysis

    Science.gov (United States)

    Shiota, Kenji; Nakamura, Takafumi; Takaoka, Masaki; Nitta, Kiyofumi; Oshita, Kazuyuki; Fujimori, Takashi; Ina, Toshiaki

    2017-05-01

    We conducted in situ X-ray absorption fine structure (in situ XAFS) analysis at the Cs K-edge to investigate the chemical kinetics of Cs species during reaction in an alkali-activated municipal solid waste incineration fly ash (MSWIFA) and pyrophyllite-based system. Understanding the kinetics of Cs is essential to the design of appropriate conditions for Cs stabilization. In situ XAFS analysis of four pastes, prepared from NaOHaq, sodium silicate solution, pyrophyllite, and MSWIFA with the addition of CsCl, was conducted in custom-built reaction cells at four curing temperatures (room temperature, 60 °C, 80 °C, 105 °C) for approximately 34 h. The results indicated that the change in Cs species during reaction at room temperature was small, while changes at higher temperatures were faster and more extreme, with the fastest conversion to pollucite occurring at 105 °C. Further analysis using a leaching test and a simple reaction model for Cs species during reaction showed that the pollucite formation rate was dependent on the curing temperature and had a significant negative correlation with Cs leaching. The activation energy of pollucite formation was estimated to be 31.5 kJ/mol. These results revealed that an important change in the chemical state of Cs occurs during reaction in the system.

  7. XAS study of mercury(II) ions trapped in mercaptan-functionalized mesostructured silicate with a wormhole framework structure.

    Science.gov (United States)

    Chen, Chia-Chen; McKimmy, Emily J; Pinnavaia, Thomas J; Hayes, Kim F

    2004-09-15

    Directly assembled wormhole mesostructures with high level functionalized mercaptan (MP-HMS) have been shown to be effective mercury(II) (Hg2+) trapping agents. Sorption of Hg2+ onto MP-HMS was investigated using X-ray absorption spectroscopy (XAS) to identify the structural coordination of the adsorbed Hg. Samples with different fractions of mercaptan functionalized groups (i.e., x = 0.1 and 0.5) with various Hg/S molar ratios ranging from 0.05 to 1.4 were investigated. XAS analysis indicates that adsorbed Hg first coordination shell is best fitted with an Hg-O path and an Hg-S path. The Hg-S atomic distance (R(Hg-S)) remained relatively constant while the Hg-S coordination numbers (CN) decreased as Hg/S loading increased. For the Hg-O path, both the CN and the R(Hg-O) increased with increasing Hg loading. XAS results suggest that at low Hg loadings, adsorbed Hg2+ forms mostly monodentate sulfur complexes (-S-Hg-OH) with the sulfur functional groups on the MP-HMS surfaces. At high Hg loadings, the Hg coordination environment is consistent with the formation of a double-layer structure of Hg attached to sulfur binding sites (-S-Hg-O-Hg-OH).

  8. Characterization of Monodispersed Iron Oxide Nanocrystals by XAS and MCD measurement

    International Nuclear Information System (INIS)

    Kim, J.-Y.; Noh, H.-J.; Park, B.-G.; Kim, T.-Y.; Park, J.-H.; Hyeon, T.; Park, J.; Kang, E.

    2004-01-01

    Full text: Nanoparticles have attracted so much attention because of their potential technological applications and abundance of scientifically interesting issues. In particular, magnetic nanoparticles are considered to be applicable to various magnetic devices such as terabit memory, ferrofluids, magnetocaloric refrigeration systems, blood cells, etc. With the development of nano-technology, variation of physical properties as a function of particle size is one of the most important issues, but has been rarely explored because of difficulty of the size control in synthesizing nanoparticles. Recently, some of us successfully synthesized high crystalline and monodisperse maghemite nanoparticles without a size selection process and research in this field seems to be promoted by one step. In this report, we present a systematic characterization of the monodispersed nanocrystalline γ - Fe 2 O 3 with the diameter of 13, 8 and 4 nm by measuring the x-ray absorption spectroscopy (XAS) and the x-ray magnetic circular dichroism(XMCD) spectra on Fe L edge. The spectra of the 4 nm nanoparticles are very similar to those of maghemite (γ - Fe 2 O 3 ). However, the spectra become close to those of magnetite (Fe 3 O 4 ) as the particle size becomes 8 and 13 nm. Considering that the maghemite and magnetite have the same spinel structure with different Fe vacancies, these results can be explained that the surface of nanoparticles has more vacancies than the core part, indicating that surface disorder increases as the particle size decreases

  9. Understanding the biomimetic properties of gallium in Pseudomonas aeruginosa: an XAS and XPS study.

    Science.gov (United States)

    Porcaro, F; Bonchi, C; Ugolini, A; Frangipani, E; Polzonetti, G; Visca, P; Meneghini, C; Battocchio, C

    2017-05-30

    Pyochelin (PCH) is a siderophore (extracellular chelator) produced by the pathogenic bacterium Pseudomonas aeruginosa (PAO). PCH is implicated in iron (Fe 3+ ) transport to PAO, and is crucial for its metabolism and pathogenicity. Due to the chemical similarity with Fe 3+ , gallium (Ga 3+ ) interferes with vital iron-dependent processes in bacterial cells, thereby opening new perspectives for the design of specific metal-based antibacterial drugs. However, the structural basis for the Fe 3+ -mimetic properties of Ga 3+ complexed with the PCH siderophore is still lacking. A precise knowledge of the coordination chemistry at the metal site is one of the topmost issues in the production of novel biomimetic metal-based drugs. Elucidation of this issue by means of a deep structural spectroscopic investigation could lead to an improved interference with, or a specific inhibition of, relevant biological pathways. For this reason, we applied Synchrotron Radiation induced X-ray Photoelectron Spectroscopy (SR-XPS) and X-ray Absorption Spectroscopy (XAS) to probe the electronic nature and coordination chemistry of Fe 3+ and Ga 3+ coordinative sites in PCH metal complexes. Combined XAFS and SR-XPS studies allow us to demonstrate that both Fe and Ga have the same valence state in Fe-PCH and Ga-PCH, and have the same octahedral coordination geometry. Moreover, a similar next neighbour distribution for Fe and Ga, resulting from the EXAFS data analysis, strongly supports similar coordination chemistry at the origin of the biomimetic behaviour of Ga.

  10. A nanostructured Ni/graphene hybrid for enhanced electrochemical hydrogen storage

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Moon-Hyung; Min, Young-Je [Department of Chemistry and Green-Nano Materials Research Center, Kyungpook National University, Taegu 702-701 (Korea, Republic of); Gwak, Gyeong-Hyeon [Department of Chemistry and Medical Chemistry, College of Science and Technology, Yonsei University, Wonju, Gangwondo 220-710 (Korea, Republic of); Paek, Seung-Min, E-mail: smpaek@knu.ac.kr [Department of Chemistry and Green-Nano Materials Research Center, Kyungpook National University, Taegu 702-701 (Korea, Republic of); Oh, Jae-Min, E-mail: jaemin.oh@yonsei.ac.kr [Department of Chemistry and Medical Chemistry, College of Science and Technology, Yonsei University, Wonju, Gangwondo 220-710 (Korea, Republic of)

    2014-10-15

    Highlights: • Graphene oxide(GO) was hybridized with the Ni(OH){sub 2}. • The Ni(OH){sub 2}/GO was reduced to Ni/graphene. • XRD, TEM, and X-ray absorption spectroscopy were examined. • The hydrogen storage property of Ni/graphene was significantly enhanced. - Abstract: To fabricate electrochemical hydrogen storage materials with delaminated structure, the graphene oxide (GO) in the ethylene glycol solution was reassembled in the presence of the precursor of Ni nanoparticles, and then, the reassembled hybrid was reduced under hydrogen atmosphere to obtain Ni/graphene hybrid. X-ray diffraction patterns and X-ray absorption spectscopic (XAS) analysis clearly show that Ni nanoparticles in Ni/graphene hybrid maintain its nanosized nature even after hybridization with graphene nanosheet (GNS). According to the TEM analysis, the Ni nanoparticles with an average size of 5.2 nm are homogeneously distributed onto the GNS in such a way that the nanoporous structure with much amount of void spaces could be fabricated. The obtained Ni/GNS exhibits a hydrogen storage capacity of 160 mA h/g, while the specific capacity of the graphene nanosheet was only 21 mA h/g. A flexible delaminated structure of Ni/GNS nanocomposite could provide additional intercalation sites for accommodation of hydrogen, leading to the enhancement of hydrogen storage capacity.

  11. Ni cycling in mangrove sediments from New Caledonia

    Science.gov (United States)

    Noël, Vincent; Morin, Guillaume; Juillot, Farid; Marchand, Cyril; Brest, Jessica; Bargar, John R.; Muñoz, Manuel; Marakovic, Grégory; Ardo, Sandy; Brown, Gordon E.

    2015-11-01

    Covering more than 70% of tropical and subtropical coastlines, mangrove intertidal forests are well known to accumulate potentially toxic trace metals in their sediments, and thus are generally considered to play a protective role in marine and lagoon ecosystems. However, the chemical forms of these trace metals in mangrove sediments are still not well known, even though their molecular-level speciation controls their long-term behavior. Here we report the vertical and lateral changes in the chemical forms of nickel, which accumulates massively in mangrove sediments downstream from lateritized ultramafic deposits from New Caledonia, where one of nature's largest accumulations of nickel occurs. To accomplish this we used Ni K-edge Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy data in combination with microscale chemical analyses using Scanning Electron Microscopy coupled with Energy-Dispersive X-ray Spectroscopy (SEM-EDXS). After Principal Component and Target Transform analyses (PCA-TT), the EXAFS data of the mangrove sediments were reliably least-squares fitted by linear combination of 3-components chosen from a large model compound spectral database including synthetic and natural Ni-bearing sulfides, clay minerals, oxyhydroxides, and organic complexes. Our results show that in the inland salt flat Ni is hosted in minerals inherited from the eroded lateritic materials, i.e. Ni-poor serpentine (44-58%), Ni-rich talc (20-31%), and Ni-goethite (18-24%). In contrast, in the hydromorphic sediments beneath the vegetated Avicennia and Rhizophora stands, a large fraction of Ni is partly redistributed into a neoformed smectite pool (20-69% of Ni-montmorillonite), and Ni speciation significantly changes with depth in the sediment. Indeed, Ni-rich talc (25-56%) and Ni-goethite (15-23%) disappear below ∼15 cm depth in the sediment and are replaced by Ni-sorbed pyrite (23-52%) in redox-active intermediate depth layers and by pyrite (34-55%) in the deepest

  12. Sulfur K-edge XANES and acid volatile sulfide analyses of changes in chemical speciation of S and Fe during sequential extraction of trace metals in anoxic sludge from biogas reactors.

    Science.gov (United States)

    Shakeri Yekta, Sepehr; Gustavsson, Jenny; Svensson, Bo H; Skyllberg, Ulf

    2012-01-30

    The effect of sequential extraction of trace metals on sulfur (S) speciation in anoxic sludge samples from two lab-scale biogas reactors augmented with Fe was investigated. Analyses of sulfur K-edge X-ray absorption near edge structure (S XANES) spectroscopy and acid volatile sulfide (AVS) were conducted on the residues from each step of the sequential extraction. The S speciation in sludge samples after AVS analysis was also determined by S XANES. Sulfur was mainly present as FeS (≈ 60% of total S) and reduced organic S (≈ 30% of total S), such as organic sulfide and thiol groups, in the anoxic solid phase. Sulfur XANES and AVS analyses showed that during first step of the extraction procedure (the removal of exchangeable cations), a part of the FeS fraction corresponding to 20% of total S was transformed to zero-valent S, whereas Fe was not released into the solution during this transformation. After the last extraction step (organic/sulfide fraction) a secondary Fe phase was formed. The change in chemical speciation of S and Fe occurring during sequential extraction procedure suggests indirect effects on trace metals associated to the FeS fraction that may lead to incorrect results. Furthermore, by S XANES it was verified that the AVS analysis effectively removed the FeS fraction. The present results identified critical limitations for the application of sequential extraction for trace metal speciation analysis outside the framework for which the methods were developed. Copyright © 2011 Elsevier B.V. All rights reserved.

  13. Full-Field Calcium K-Edge X-ray Absorption Near-Edge Structure Spectroscopy on Cortical Bone at the Micron-Scale: Polarization Effects Reveal Mineral Orientation.

    Science.gov (United States)

    Hesse, Bernhard; Salome, Murielle; Castillo-Michel, Hiram; Cotte, Marine; Fayard, Barbara; Sahle, Christoph J; De Nolf, Wout; Hradilova, Jana; Masic, Admir; Kanngießer, Birgit; Bohner, Marc; Varga, Peter; Raum, Kay; Schrof, Susanne

    2016-04-05

    Here, we show results on X-ray absorption near edge structure spectroscopy in both transmission and X-ray fluorescence full-field mode (FF-XANES) at the calcium K-edge on human bone tissue in healthy and diseased conditions and for different tissue maturation stages. We observe that the dominating spectral differences originating from different tissue regions, which are well pronounced in the white line and postedge structures are associated with polarization effects. These polarization effects dominate the spectral variance and must be well understood and modeled before analyzing the very subtle spectral variations related to the bone tissue variations itself. However, these modulations in the fine structure of the spectra can potentially be of high interest to quantify orientations of the apatite crystals in highly structured tissue matrices such as bone. Due to the extremely short wavelengths of X-rays, FF-XANES overcomes the limited spatial resolution of other optical and spectroscopic techniques exploiting visible light. Since the field of view in FF-XANES is rather large the acquisition times for analyzing the same region are short compared to, for example, X-ray diffraction techniques. Our results on the angular absorption dependence were verified by both site-matched polarized Raman spectroscopy, which has been shown to be sensitive to the orientation of bone building blocks and by mathematical simulations of the angular absorbance dependence. As an outlook we further demonstrate the polarization based assessment of calcium-containing crystal orientation and specification of calcium in a beta-tricalcium phosphate (β-Ca3(PO4)2 scaffold implanted into ovine bone. Regarding the use of XANES to assess chemical properties of Ca in human bone tissue our data suggest that neither the anatomical site (tibia vs jaw) nor pathology (healthy vs necrotic jaw bone tissue) affected the averaged spectral shape of the XANES spectra.

  14. Structural characterization of half-metallic Heusler compound NiMnSb

    Energy Technology Data Exchange (ETDEWEB)

    Nowicki, L. E-mail: lech.nowicki@fuw.edu.pl; Abdul-Kader, A.M.; Bach, P.; Schmidt, G.; Molenkamp, L.W.; Turos, A.; Karczewski, G

    2004-06-01

    High resolution X-ray diffraction (HRXRD) and Rutherford backscattering/channeling (RBS/c) techniques were used to characterize layers of NiMnSb grown by molecular beam epitaxy (MBE) on InP with a In{sub x}Ga{sub 1-x}As buffer. Angular scans in the channeling mode reveal that the crystal structure of NiMnSb is tetragonally deformed with c/a=1.010{+-}0.002, in agreement with HRXRD data. Although HRXRD demonstrates the good quality of the pseudomorphic NiMnSb layers the channeling studies show that about 20% of atoms in the layers do not occupy lattice sites in the [0 0 1] rows of NiMnSb. The possible mechanisms responsible for the observed disorder are discussed.

  15. Electrochemical cycling effect on structural parameters and electron density of Li1-xNi0.5Mn1.5O4 using synchrotron X-ray analyses

    Science.gov (United States)

    Itoh, Takanori; Imai, Hideto

    2018-03-01

    We investigated the electrochemical cycling effects on the average, local, and electronic structures of 1st and 28th cycled Li1-xNi0.5Mn1.5O4 (LNMO) by Rietveld refinements, the maximum entropy method (MEM) for synchrotron X-ray, and X-ray absorption spectroscopy (XAS) using unexposed cathode materials. The results obtained with Rietveld refinements and XAS showed that the electrochemical cycling increases the transition metal valences, distorts the (Ni, Mn)-O6 octahedral, and decreases the Ni content in LNMO. Through MEM analyses we found that Li ions were stabilized by the electrochemical cycling. We also used synchrotron X-ray analyses to ascertain the correlation among specific capacity degradation, average and local structures, and the electron density before and after cycled LNMO.

  16. Spectral studies on sulfur poisoning of Pd/Mg{sub 6}Ni by NEXAFS and XPS

    Energy Technology Data Exchange (ETDEWEB)

    Yagi, S., E-mail: s-yagi@nucl.nagoya-u.ac.jp [Department of Quantum Engineering, School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Synchrotron Radiation Center, Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-0046 (Japan); Nambu, M.; Tsukada, C.; Ogawa, S. [Department of Quantum Engineering, School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Kutluk, G.; Namatame, H.; Taniguchi, M. [Synchrotron Radiation Center, Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-0046 (Japan)

    2013-02-15

    We have studied on the hydrogen storage materials based on Mg–Ni alloy and fabricated the sample constructed with the Pd thin layer (TL) on Mg{sub 6}Ni alloy substrate. The adsorption behavior of the dimethyl disulfide (DMS) molecules on the sample has been measured to reveal the sulfur poisoning of the Pd TL/Mg{sub 6}Ni by means of XPS and Sulfur K-edge NEXAFS techniques. The chemisorbed DMS, methanethiolate (MT) and atomic S have been observed on the surface. Especially, it is clear that some atomic S has been oxidized by air and detected the adsorbate of the SO{sub 3}{sup 2−} and SO{sub 4}{sup 2−} species. During exposure to the atmosphere, most of the adsorbed DMS and MT adsorbates desorb from the Pd TL surface. We thus conclude the Pd TL might be able to prevent the hydrogen storage materials from the sulfur poisoning.

  17. Spectral studies on sulfur poisoning of Pd/Mg6Ni by NEXAFS and XPS

    International Nuclear Information System (INIS)

    Yagi, S.; Nambu, M.; Tsukada, C.; Ogawa, S.; Kutluk, G.; Namatame, H.; Taniguchi, M.

    2013-01-01

    We have studied on the hydrogen storage materials based on Mg–Ni alloy and fabricated the sample constructed with the Pd thin layer (TL) on Mg 6 Ni alloy substrate. The adsorption behavior of the dimethyl disulfide (DMS) molecules on the sample has been measured to reveal the sulfur poisoning of the Pd TL/Mg 6 Ni by means of XPS and Sulfur K-edge NEXAFS techniques. The chemisorbed DMS, methanethiolate (MT) and atomic S have been observed on the surface. Especially, it is clear that some atomic S has been oxidized by air and detected the adsorbate of the SO 3 2− and SO 4 2− species. During exposure to the atmosphere, most of the adsorbed DMS and MT adsorbates desorb from the Pd TL surface. We thus conclude the Pd TL might be able to prevent the hydrogen storage materials from the sulfur poisoning.

  18. The Effect of Electrical Polarization on Electronic Structure in LSM Electrodes: An Operando XAS, RIXS and XES Study

    DEFF Research Database (Denmark)

    Traulsen, Marie Lund; Carvalho, H.W.P.; Zielke, Philipp

    2017-01-01

    in the Mn K edge energy towards lower energies. The shift is assigned to a decrease in the average Mn oxidation state, which based on Kβ XES changes from 3.4 at open circuit voltage to 3.2 at −800 mV applied potential. Furthermore, RIXS rendered pronounced changes in the population of the Mn 3d orbitals...... (RIXS) at the Mn K-edge. The study of polarization induced changes in the electronic properties and structure has been carried out at 500°C in 10–20% O2 with electrical polarization applied in the range from −850 mV to 800 mV. Cathodic polarizations in the range −600 mV to −850 mV induced a shift......, due to filling of the Mn d-orbitals during the cathodic polarization. Overall, the study experimentally links the electrical polarization of LSM electrodes to the structural and electronic properties of Mn - these properties are expected to be of major importance for the electrocatalytic performance...

  19. Characterization of chemical bonding in low-k dielectric materialsfor interconnect isolation: a xas and eels study

    Energy Technology Data Exchange (ETDEWEB)

    Hoffmann, P.; Schmeisser, D.; Engelmann, H.-J.; Zschech, E.; Stegmann, H.; Himpsel, F.; Denlinger, J.

    2006-04-10

    The use of low dielectric constant materials in the on-chipinterconnect process reduces interconnect delay, power dissipation andcrosstalk noise. To achieve the requirements of the ITRS for 2007-2009minimal sidewall damage from etch, ash or cleans is required. In chemicalvapor deposited (CVD) organo-silicate glass (OSG) which are used asintermetal dielectric (IMD) materials the substitution of oxygen in SiO2by methyl groups (-CH3) reduces the permittivity significantly (from 4.0in SiO2 to 2.6-3.3 in the OSG), since the electronic polarizability islower for Si-C bonds than for Si-O bonds. However, plasma processing forresist stripping, trench etching and post-etch cleaning removes C and Hcontaining molecular groups from the near-surface layer of OSG.Therefore, compositional analysis and chemical bonding characterizationof structured IMD films with nanometer resolution is necessary forprocess optimization. OSG thin films as-deposited and after plasmatreatment are studied using X-ray absorption spectroscopy (XAS) andelectron energy loss spectroscopy (EELS). In both techniques, the finestructure near the C1s absorption or energy loss edge, respectively,allows to identify C-H, C-C, and C-O bonds. This gives the opportunity todifferentiate between individual low-k materials and their modifications.The O1s signal is less selective to individual bonds. XAS spectra havebeen recorded for non-patterned films and EELS spectra for patternedstructures. The chemical bonding is compared for as-deposited andplasma-treated low-k materials. The Fluorescence Yield (FY) and the TotalElectron Yield (TEY) recorded while XAS measurement are compared.Examination of the C 1s near-edge structures reveal a modified bonding ofthe remaining C atoms in the plasma-treated sample regions.

  20. Predicted electronic and structural properties of B{sub x}In{sub 1-x}As

    Energy Technology Data Exchange (ETDEWEB)

    Tayebi, N. [Laboratory of Applied Materials, University of Sidi Bel Abbes, 31 rue de Madagascar, Sidi Bel Abbes (Algeria); Benkabou, K., E-mail: kbenkabou@yahoo.fr [Laboratory of Applied Materials, University of Sidi Bel Abbes, 31 rue de Madagascar, Sidi Bel Abbes (Algeria); Aoumeur-Benkabou, F.Z. [Laboratory of Applied Materials, University of Sidi Bel Abbes, 31 rue de Madagascar, Sidi Bel Abbes (Algeria)

    2012-07-15

    Structural and electronic properties of the B{sub x}In{sub 1-x}As ternary alloy are studied using the tight binding method. The optical band gap bowing is calculated for the first time in the full range of Boron composition x. It is found to be strong. A small deviation from virtual crystal approximation is found for the bond length. New results on elastic constants are reported. The obtained results are in good agreement with the available data in the literature.

  1. Spin excitation and band-narrowing in Al{sub x}Ga{sub 1-x}As heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Miah, M. Idrish, E-mail: m.miah@griffith.edu.au [Department of Physics, University of Chittagong, Chittagong 4331 (Bangladesh)

    2010-11-01

    We studied the spin excitation in dependences of the applied electric field and lattice temperature (LT) via the measurements of the circularly polarized photoluminescence (CPPL) in Al{sub x}Ga{sub 1-x}As heterostructures (HSs). The intensity of CPPL was found to strongly depend on the electric field applied to the HSs. The CPPL was also found to enhance with decreasing LT. It was demonstrated that the observed LT dependence might be due to the LT-dependent band-gap shift of the HS materials.

  2. Structural alteration of hexagonal birnessite by aqueous Mn(II): Impacts on Ni(II) sorption

    Energy Technology Data Exchange (ETDEWEB)

    Lefkowitz, Joshua P.; Elzinga, Evert J.

    2017-09-01

    We studied the impacts of aqueous Mn(II) (1 mM) on the sorption of Ni(II) (200 μM) by hexagonal birnessite (0.1 g L- 1) at pH 6.5 and 7.5 with batch experiments and XRD, ATR-FTIR and Ni K-edge EXAFS analyses. In the absence of Mn(II)aq, sorbed Ni(II) was coordinated predominantly as triple corner-sharing complexes at layer vacancies at both pH values. Introduction of Mn(II)aq into Ni(II)-birnessite suspensions at pH 6.5 caused Ni(II) desorption and led to the formation of edge-sharing Ni(II) complexes. This was attributed to competitive displacement of Ni(II) from layer vacancies by either Mn(II) or by Mn(III) formed through interfacial Mn(II)-Mn(IV) comproportionation, and/or incorporation of Ni(II) into the birnessite lattice promoted by Mn(II)-catalyzed recrystallization of the sorbent. Similar to Mn(II)aq, the presence of HEPES or MES caused the formation of edge-sharing Ni(II) sorption complexes in Ni(II)-birnessite suspensions, which was attributed to partial reduction of the sorbent by the buffers. At pH 7.5, interaction with aqueous Mn(II) caused reductive transformation of birnessite into secondary feitknechtite that incorporated Ni(II), enhancing removal of Ni(II) from solution. These results demonstrate that reductive alteration of phyllomanganates may significantly affect the speciation and solubility of Ni(II) in anoxic and suboxic environments.

  3. XMCD and XAS examination of cation ordering in synthetic Mg- and Al-substituted titanomagnetites

    Science.gov (United States)

    Lappe, S. C. L. L.; Bowles, J.; Jackson, M.; Arenholz, E.

    2015-12-01

    composition. X-ray absorption spectra (XAS) of the Ti, Mg and Al show no significant differences for samples of different anneal stages, suggesting no reordering of the Ti4+, Al3+ and Mg2+. The lack of observed (re)ordering between A and B lattice sites suggests the process may be vacancy mediated or there might be short-range cation (re)ordering within the lattice sites.

  4. Growth of block copolymer stabilized metal nanoparticles probed simultaneously by in situ XAS and UV-Vis spectroscopy.

    Science.gov (United States)

    Nayak, C; Bhattacharyya, D; Jha, S N; Sahoo, N K

    2016-01-01

    The growth of Au and Pt nanoparticles from their respective chloride precursors using block copolymer-based reducers has been studied by simultaneous in situ measurement of XAS and UV-Vis spectroscopy at the energy-dispersive EXAFS beamline (BL-08) at INDUS-2 SRS at RRCAT, Indore, India. While the XANES spectra of the precursor give real-time information on the reduction process, the EXAFS spectra reveal the structure of the clusters formed at the intermediate stages of growth. The growth kinetics of both types of nanoparticles are found to be almost similar and are found to follow three stages, though the first stage of nucleation takes place earlier in the case of Au than in the case of Pt nanoparticles due to the difference in the reduction potential of the respective precursors. The first two stages of the growth of Au and Pt nanoparticles as obtained by in situ XAS measurements could be corroborated by simultaneous in situ measurement of UV-Vis spectroscopy also.

  5. Temperature dependence of the minimum V/III ratio for the growth of In xGa 1-xAs

    Science.gov (United States)

    Riechert, H.; Averbeck, R.; Bernklau, D.

    1993-02-01

    We have quantitatively determined the minimum V/III ratios for the growth of In xGa 1- xAs ( x = 0, 0.1, 0.2 and 0.53) on GaAs and InP. Minimum As 4 fluxes were measured for a wide range of growth temperatures using a transition of the surface reconstruction. Their temperature dependence can be fitted very well by thetypical curve for thermally activated behavior. We find that the basic reaction kinetics of As 4 with In xGa 1- xAs are the same as with GaAs. The activation energies for As desorption from In xGa 1- xAs and GaAs are found to be similar (1.9 and 2.1 eV, respectively) but the rates of As- In xGa 1- xAs. This may be seen as evidence for a less effective dissociative reaction of As 4 with In than with Ga.

  6. Electron microscopic and optical investigations of the indium distribution GaAs capped InxGa1-xAs islands

    DEFF Research Database (Denmark)

    Woggon, U.; Langbein, Wolfgang Werner; Hvam, Jørn Märcher

    1997-01-01

    Results from a structural and optical analysis of buried InxGa1-xAs islands carried out after the process of GaAs overgrowth are presented. It is found that during the growth process, the indium concentration profile changes and the thickness of the wetting layer emanating from a Stranski...

  7. An assessment of some theoretical models used for the calculation of the refractive index of InXGa1-xAs

    Science.gov (United States)

    Engelbrecht, J. A. A.

    2018-04-01

    Theoretical models used for the determination of the refractive index of InXGa1-XAs are reviewed and compared. Attention is drawn to some problems experienced with some of the models. Models also extended to the mid-infrared region of the electromagnetic spectrum. Theoretical results in the mid-infrared region are then compared to previously published experimental results.

  8. Stress-induced Curie temperature increase in the Fe{sub 64}Ni{sub 36} invar alloy

    Energy Technology Data Exchange (ETDEWEB)

    Gorria, Pedro; Martinez-Blanco, David; Blanco, Jesus A. [Departamento de Fisica, Universidad de Oviedo (Spain); Boada, Roberto; Chaboy, Jesus [ICMA and Departamento de Fisica de la Materia Condensada, CSIC - Universidad de Zaragoza (Spain); Fernandez-Martinez, Alejandro [LGIT, University of Grenoble and CNRS, Maison des Geosciences, Grenoble (France); Institut Laue-Langevin, Grenoble (France); Garbarino, Gaston; Castro, German R.; Mezouar, Mohamed [European Synchrotron Radiation Facility (ESRF), Grenoble (France); Smith, Ronald I. [ISIS Facility, RAL, Chilton, Didcot, Oxon (United Kingdom); Alonso, J.I.G. [Department of Physical and Analytical Chemistry, University of Oviedo (Spain); Hernando, Antonio [Instituto de Magnetismo Aplicado, UCM-ADIF-CSIC, Madrid (Spain)

    2009-05-15

    Structural and magnetic changes on invar Fe{sub 64}Ni{sub 36} alloy (T{sub C}=500 K) produced by mechanical milling followed by heating up to 1073 K, were investigated by neutron diffraction, magnetization measurements, X-ray diffraction under high pressures and X-ray absorption at both Fe and Ni K-edges. We argue that the strain induced in the Fe{sub 64}Ni{sub 36} material after this treatment mainly affects the Fe sites due to the magnetovolume coupling, the most notorious feature being the increase of the Curie temperature ({delta}T{sub C}=70 K). (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Parametrization of an anharmonic Kirkwood-Keating potential for AlxGa1-xAs alloys.

    Science.gov (United States)

    Sim, Eunji; Beckers, Joost; de Leeuw, Simon; Thorpe, Michael; Ratner, Mark A

    2005-05-01

    We introduce a simple semiempirical anharmonic Kirkwood-Keating potential to model A(x)B(1-x)C-type semiconductors. The potential consists of the Morse strain energy and Coulomb interaction terms. The optical constants of pure components, AB and BC, were employed to fit the potential parameters such as bond-stretching and -bending force constants, dimensionless anharmonicity parameter, and charges. We applied the potential to finite temperature molecular-dynamics simulations on Al(x)Ga(1-x)As for which there is no lattice mismatch. The results were compared with experimental data and those of harmonic Kirkwood-Keating model and of equation-of-motion molecular-dynamics technique. Since the Morse strain potential effectively describes finite temperature damping, we have been able to numerically reproduce experimentally obtained optical properties such as dielectric functions and reflectance. This potential model can be readily generalized for strained alloys.

  10. Mutual alloying of XAs (X=Ga, In, Al) materials: Tuning the optoelectronic and thermodynamic properties for solar energy applications

    KAUST Repository

    Haq, Bakhtiar Ul

    2014-02-01

    In the present work we did mutual alloying of the versatile XAs (X=Ga, In, Al) materials in order to improve their efficiency and enhance their range of technological applications using state of the art first principles method. We investigate the structural, electronic and thermodynamic properties of Ga1-xAlxAs, Ga1-xInxAs and In1-xAlxAs for x=0.25, 0.50, and 0.75. Calculations have been performed using the density functional theory (DFT) as implemented within the full potential linearized augmented plane wave plus local orbital (FP-LAPW+lo) method. For exchange and correlation energy treatment, we employed the local density approximations (LDA) as proposed by Wang and Perdew and the generalized gradient approximation (GGA) from Perdew et al. proposed. To calculate the accurate band structure, recently modified Becke Johnson (mBJ) potential was suggested as an alternative. Our calculations show a linear fall in the lattice constant in contrast to linear rise in bulk moduli of Ga1-xAlxAs and In1-xAlxAs with the increase of Al concentration. However the change of indium concentration in Ga1-xInxAs is displaying a reverse effect. The energy band gap of Ga1-xAlxAs and In1-xAlxAs was found to be increased, where a crossover from direct to indirect band gap has been observed with the increase of Al concentration. This direct to indirect crossover was found at 93.4% of Al concentration for Ga1-xAlxAs and at 84.63% of Al concentration for In1-xAlxAs. The effect of the mutual alloying of XAs materials on the thermodynamic properties is comprehensively reported. © 2013 Elsevier Ltd.

  11. Analysis of the suitability of Al{sub x}Ga{sub 1-x}As as active material in III-V multiple-junction solar cells; Analyse zur Eignung von Al{sub x}Ga{sub 1-x}As als aktives Material in III-V Mehrfachsolarzellen

    Energy Technology Data Exchange (ETDEWEB)

    Heckelmann, Stefan

    2017-05-01

    In the past, Al{sub x}Ga{sub 1-x}As single and multiple-junction solar cells have been manufactured and tested. Although the ternary Al{sub x}Ga{sub 1-x}As is one of the most studied semiconductor systems, the results have often lagged behind expectations. In the thesis presented here, for the first time, the deep understanding of the Al{sub x}Ga{sub 1-x}As material system resulting from material analysis was linked with its application in solar cells. As has been shown, many cell results can only be explained if the peculiarities of the material, in particular the formation of DX centers and the transition from direct to indirect semiconductor, are also included. From this purposeful consideration of the material in terms of its usefulness in the semiconductor device and the technological significance of individual properties, not only high-quality solar cells based on Al{sub x}Ga{sub 1-x}As were produced but also new insights into the material properties of (Al{sub y}Ga{sub 1-y}){sub 1-z}In{sub z}As and the information gain from photoluminescence measurements can be significantly increased. [German] In der Vergangenheit wurden bereits Einfach- und Mehrfachsolarzellen aus Al{sub x}Ga{sub 1-x}As hergestellt und untersucht. Obwohl das ternaere Al{sub x}Ga{sub 1-x}As eines der meist untersuchten Halbleitersysteme ist, blieben die Ergebnisse oft hinter den Erwartungen zurueck. In der hier vorgestellten Dissertation wurde zum ersten Mal das aus der Materialanalytik heraus entstandene, tiefe Verstaendnis ueber das AlxGa1-xAs Materialsystem mit seiner Anwendung in Solarzellen verknuepft. Wie sich gezeigt hat, werden viele Zellergebnisse erst erklaerbar, wenn auch die Besonderheiten des Materials, insbesondere die Bildung von DX-Zentren und der Uebergang vom direkten zum indirekten Halbleiter, mit einbezogen werden. Aus dieser zielgerichteten Betrachtung des Materials im Hinblick auf seinen Nutzen im Halbleiterbauelement und der technologischen Bedeutung einzelner

  12. Temperature dependence of the minimum V/III ratio for the growth of In[sub x]Ga[sub 1-x]As

    Energy Technology Data Exchange (ETDEWEB)

    Riechert, H. (Siemens Corporate Research and Development, Muenchen (Germany)); Averbeck, R. (Siemens Corporate Research and Development, Muenchen (Germany)); Bernklau, D. (Siemens Corporate Research and Development, Muenchen (Germany))

    1993-02-01

    We have quantitatively determined the minimum V/III ratios for the growth of In[sub x]Ga[sub 1-x]As(x=0, 0.1, 0.2 and 0.53) on GaAs and InP. Minimum As[sub 4] fluxes were measured for a wide range of growth temperatures using a transition of the surface reconstruction. Their temperature dependence can be fitted very well by the typical curve for thermally activated behavior. We find In[sub x]Ga[sub 1-x]As and GaAs are found to be similar (1.9 and 2.1 eV, respectively) but the rates of As-desorption are much higher for In[sub x]Ga[sub 1-x]As. This may be seen as evidence for a less effective dissociative reaction of As[sub 4] with In than with Ga. (orig.)

  13. The time-resolved and extreme conditions XAS (TEXAS) facility at the European Synchrotron Radiation Facility: the general-purpose EXAFS bending-magnet beamline BM23.

    Science.gov (United States)

    Mathon, O; Beteva, A; Borrel, J; Bugnazet, D; Gatla, S; Hino, R; Kantor, I; Mairs, T; Munoz, M; Pasternak, S; Perrin, F; Pascarelli, S

    2015-11-01

    BM23 is the general-purpose EXAFS bending-magnet beamline at the ESRF, replacing the former BM29 beamline in the framework of the ESRF upgrade. Its mission is to serve the whole XAS user community by providing access to a basic service in addition to the many specialized instruments available at the ESRF. BM23 offers high signal-to-noise ratio EXAFS in a large energy range (5-75 keV), continuous energy scanning for quick-EXAFS on the second timescale and a micro-XAS station delivering a spot size of 4 µm × 4 µm FWHM. It is a user-friendly facility featuring a high degree of automation, online EXAFS data reduction and a flexible sample environment.

  14. Real-Time Observation of Platinum Redispersion on Ceria-Based Oxide by In-situ Turbo-XAS in Fluorescence Mode

    International Nuclear Information System (INIS)

    Nagai, Yasutaka; Dohmae, Kazuhiko; Tanabe, Toshitaka; Shinjoh, Hirofumi; Takagi, Nobuyuki; Ikeda, Yasuo; Guilera, Gemma; Pascarelli, Sakura; Newton, Mark; Matsumoto, Shin'ichi

    2007-01-01

    A real-time observation of the redispersion behavior of sintered Pt on ceria-based oxide was made possible by in-situ time-resolved Turbo-XAS in fluorescence mode. 2 wt% Pt/Ce-Zr-Y mixed oxide samples were prepared, and then treated under an aging condition. The average Pt particle size measured by CO absorption method after aging was 7 nm. Redispersion treatments of the previously aged catalyst were carried out at 600 deg. C within an in-situ XAS cell in a cyclical flow of reducing/oxidizing gases. Pt L3-edge XANES spectra were collected every 1.1 second under in-situ conditions. From a change in the XANES spectra, we observed that the Pt particle size of the aged catalyst decreased from 7 to 5 nm after 60 seconds and then to 3 nm after 1000 seconds

  15. Some properties of Ga-As-Alsub(x)Gasub(1-x)As heterojunction grown by low temperature liquid phase epitaxy

    International Nuclear Information System (INIS)

    Yu Lisheng; Liu Hongxun; Zhang Bei; Wang Shumin

    1986-03-01

    GaAs-Alsub(x)Gasub(1-x)As heterojunction was grown by liquid phase epitaxy at low growth temperature 650-700 deg. C. The series resistance of heterojunction with DH laser structure was measured. Doping properties of Mg in GaAs and Alsub(x)Gasub(1-x)As were investigated. It is found that impurity concentration of Mg as high as 10 18 cm -3 can be doped easily. The Shubnikov-de-Haas oscillation was observed in GaAs-N Alsub(0.35)Gasub(0.65)As heterointerface. It is demonstrated that in these heterointerfaces there exists 2DEG with some contribution from 3D electron of N-AlGaAs layer. (author)

  16. Direct measurement of DX-centre related lattice relaxations in Al$_{x}$Ga$_{1-x}$As compounds

    CERN Multimedia

    2002-01-01

    Donor impurities from elements of group IV and VI form localized electronic states, so-called DX-centers, in AlGaAs and other semiconductors. One of the well known effects related to DX-centers is the persistent photoconductivity. In spite of extensive studies, the microscopic structure of the DX-center is still a matter of controversy. The direct determination of the donor lattice sites and their microscopical surrounding is a crucial point in understanding the relation of microscopic structure to the localized electronic state of the DX-center.\\\\ It is proposed to implant radioactive group VI elements $^{73}$Se (from $^{73}$Br) and $^{118}$Te (from $^{118}$Xe) into Al$_{x}$Ga$_{1-x}$As of different mole fractions ${x}$ and to determine (i) the lattice site of Te and Se impurities by emission channeling of decay positrons and electrons (ii) the local structure of Se impurities using the perturbed $\\gamma$-$\\gamma$-angular correlation technique (PAC). The appearance of the DX-center shall be check...

  17. XAS and XRF investigation of an actual HAWC glass fragment obtained from the Karlsruhe vitrification plant (VEK)

    Science.gov (United States)

    Dardenne, K.; González-Robles, E.; Rothe, J.; Müller, N.; Christill, G.; Lemmer, D.; Praetorius, R.; Kienzler, B.; Metz, V.; Roth, G.; Geckeis, H.

    2015-05-01

    Several sections of HAWC glass rods remaining at the end of glass pouring at the Karlsruhe Vitrification Plant (VEK) were retained during vitrification operation in 2009-2010 and transferred to the KIT-INE shielded box line for later glass product characterization. A mm sized fragment with a contact dose rate of ∼590 μSv/h was selected for pilot XAS/XRF investigations at the INE-Beamline for actinide science at the ANKA synchrotron radiation source. The experiment was aimed at elucidating the potential of direct radionuclide speciation with an emphasis on the fission products Se and Tc in highly active nuclear materials and at assessing the possible influence of the γ-radiation field surrounding highly active samples on the beamline instrumentation. While the influence of γ-radiation turned out to be negligible, initial radionuclide speciation studies by XAFS were most promising. In addition to Se and Tc speciation, the focus of these initial investigations was on the possibility for direct actinide speciation by recording corresponding L3-edge XAFS data. The registration of high quality XANES data was possible for the actinide elements U, Np, Pu and Am, as well as for Zr.

  18. Structural and Electrochemical Investigation of Li(Ni0.4Co0.2-yAlyMn0.4)O2 Cathode Material

    Energy Technology Data Exchange (ETDEWEB)

    Rumble, C.; Conry, T.E.; Doeff, Marca; Cairns, Elton J.; Penner-Hahn, James. E.; Deb, Aniruddha

    2010-02-02

    Li(Ni{sub 0.4}Co{sub 0.2-y}Al{sub y}Mn{sub 0.4})O{sub 2} with y=0.05 was investigated to understand the effect of replacement of the cobalt by aluminum on the structural and electrochemical properties. The effect of the substitution was studied by in-situ X-ray absorption spectroscopy (XAS), utilizing a novel in situ electrochemical cell, specifically designed for long-term X-ray experiments. The cell was cycled at a moderate rate through a typical Li-ion battery operating voltage range (1.0-4.7 V). XAS measurements were performed at different states-of-charge (SOC) during cycling, at the Ni, Co, and the Mn edges, revealing details about the response of the cathode to Li insertion and extraction processes. The extended X-ray absorption fine structure region of the spectra revealed the changes of bond distance and coordination number of Ni, Co, and Mn absorbers as a function of the SOC of the material. The oxidation states of the transition metals in the system are Ni{sup 2+}, Co{sup 3+}, and Mn{sup 4+} in the as-made material (fully discharged), while during charging the Ni{sup 2+} is oxidized to Ni{sup 4+} through an intermediate stage of Ni{sup 3+}, Co{sup 3+} is oxidized towards Co{sup 4+} and Mn was found to be electrochemically inactive and remains as Mn{sup 4+}. The EXAFS results during cycling show that the Ni-O changes the most, followed by Co-O and Mn-O varies the least. These measurements on this cathode material confirmed that the material retains its symmetry and good structural short-range order leading to the superior cycling reported earlier.

  19. Temperature-dependent photoemission and x-ray absorption studies of the metal-insulator transition in Bi1-xLaxNiO3

    Science.gov (United States)

    Wadati, Hiroki; Tanaka, Kiyohisa; Fujimori, Atsushi; Mizokawa, Takashi; Kumigashira, Hiroshi; Oshima, Masaharu; Ishiwata, Shintaro; Azuma, Masaki; Takano, Mikio

    2007-11-01

    Perovskite-type BiNiO3 is an insulating antiferromagnet in which a charge disproportionation occurs at the Bi site. La substitution for Bi suppresses the charge disproportionation and makes the system metallic, and for 0.05≤x≤0.1 a broad metal-insulator transition (MIT) occurs as a function of temperature. We have measured the temperature dependence of the photoemission and x-ray absorption (XAS) spectra of Bi1-xLaxNiO3 to investigate how the electronic structure changes across the MIT. From the Ni2p XAS spectra of x=0.05 , we found almost no change in the valence of Ni across the MIT. In the valence-band photoemission spectra, the Fermi cutoff disappeared for x=0.05 at a low temperature, whereas for x=0.1 and 0.2, it remained at all temperatures but the intensity at the Fermi level decreased gradually with decreasing temperature. Our experimental results suggest that the MIT is caused by the localization of holes in the O2p band and that the “insulating” phase below the MIT is indeed a mixture of insulating and metallic regions.

  20. Effect of Molecular Guest Binding on the d-d Transitions of Ni2+of CPO-27-Ni: A Combined UV-Vis, Resonant-Valence-to-Core X-ray Emission Spectroscopy, and Theoretical Study.

    Science.gov (United States)

    Gallo, Erik; Gorelov, Evgeny; Guda, Alexander A; Bugaev, Aram L; Bonino, Francesca; Borfecchia, Elisa; Ricchiardi, Gabriele; Gianolio, Diego; Chavan, Sachin; Lamberti, Carlo

    2017-12-04

    We used Ni K-edge resonant-valence-to-core X-ray emission spectroscopy (RVtC-XES, also referred to as direct RIXS), an element-selective bulk-sensitive synchrotron-based technique, to investigate the electronic structure of the CPO-27-Ni metal-organic framework (MOF) upon molecular adsorption of significant molecular probes: H 2 O, CO, H 2 S, and NO. We compare RVtC-XES with UV-vis spectroscopy, and we show that the element selectivity of RVtC-XES is of strategic significance to observe the full set of d-d excitations in Ni 2+ , which are partially overshadowed by the low-energy π-π* transitions of the Ni ligands in standard diffuse-reflectance UV-vis experiments. Our combined RVtC-XES/UV-vis approach provides access to the whole set of d-d excitations, allowing us a complete discussion of the changes undergone by the electronic configuration of the Ni 2+ sites hosted within the MOF upon molecular adsorption. The experimental data have been interpreted by multiplet ligand-field theory calculations based on Wannier orbitals. This study represents a step further in understanding the ability of the CPO-27-Ni MOFs in molecular sorption and separation applications.

  1. Solid-Phase Fe Speciation along the Vertical Redox Gradients in Floodplains using XAS and Mössbauer Spectroscopies

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Chunmei [Department; Kukkadapu, Ravi K. [Environmental; Lazareva, Olesya [Department; Sparks, Donald L. [Department

    2017-06-30

    Properties of Fe minerals are poorly understood in natural soils and sediments with variable redox conditions. In this study, we combined 57Fe Mössbauer and Fe K-edge X-ray absorption spectroscopic techniques to assess solid-phase Fe speciation along the vertical redox gradients of floodplain profiles, which exhibited a succession of oxic, anoxic and suboxic-oxic zones with increasing depth along the vertical profiles. The anoxic conditions at the intermediate horizon (55-80 cm) of the eastern floodplain resulted in extensive depletion of Fe(III)-oxides including both ferrihydrite and goethite, concurrent with a corresponding reduction of phyllosilicates(PS)-Fe(III) to PS-Fe(II). In addition, the anoxic conditions increased the crystallinity of Fe(III)-oxides in this reduced zone, relative to the oxic zones. In the most reduced intermediate sediments at 80-120cm of the western floodplain, the anoxic conditions drove the complete reductive dissolution of Fe(III) oxides, as well as the greatest reduction (48-55%) in PS-Fe(III). In both oxic near-surface horizon and oxic-suboxic gravel aquifers beneath the soil horizons, Fe(III)-oxides were mainly present as ferrihydrite with a less amount of goethite, which preferentially occurred as nanogoethite or Al/Si-substituted goethite. Ferrihydrite with varying crystallinity or impurities such as organic matter, Al or Si, persisted under suboxic-oxic conditions in the floodplain. This study indicates that vertical redox gradients exert a major control on the quantity and speciation of Fe(III) oxides as well as the oxidation state of structural Fe in PS, which could significantly affect nutrient cycling and carbon (de)stabilization.

  2. In situ XAS study of the Mn(III)(salen)Br catalyzed synthesis of cyclic organic carbonates from epoxides and CO2

    DEFF Research Database (Denmark)

    Jutz, Fabian; Grunwaldt, Jan-Dierk; Baiker, Alfons

    2009-01-01

    In situ X-ray absorption spectroscopy at the Mn K- and Br K-edge was employed to study the cycloaddition of carbon dioxide to propylene oxide and styrene oxide, catalyzed by Mn(III) salen bromide complexes. Three homogeneous complexes with varying salen ligand structure and one complex immobilized...... conditions. This was the case for all three homogeneous catalysts with varying salen ligand structure as well as for the heterogeneous catalyst. In case of the heterogeneous catalyst bromide also went into the solution whereas most of the manganese remained on the solid support. The loss of the direct...

  3. Effect of Cu insertion on structural, local electronic/atomic structure and photocatalyst properties of TiO{sub 2}, ZnO and Ni(OH){sub 2} nanostructures: XANES-EXAFS study

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Aditya; Varshney, Mayora [Advanced Analysis Centre, Korea Institute of Science and Technology, Seoul, 02792 (Korea, Republic of); Shin, Hyun Joon, E-mail: shj001@postech.ac.kr [Pohang Accelerator Laboratory (POSTECH), Pohang, 37673 (Korea, Republic of); Lee, Byeong-Hyeon [Advanced Analysis Centre, Korea Institute of Science and Technology, Seoul, 02792 (Korea, Republic of); Chae, Keun Hwa, E-mail: khchae@kist.re.kr [Advanced Analysis Centre, Korea Institute of Science and Technology, Seoul, 02792 (Korea, Republic of); Won, Sung Ok, E-mail: sowon@kist.re.kr [Advanced Analysis Centre, Korea Institute of Science and Technology, Seoul, 02792 (Korea, Republic of)

    2017-04-15

    We report detailed investigations on the synthesis, structural, morphology, electronic/atomic structure and photocatalyst properties of Cu doped TiO{sub 2}, ZnO and Ni(OH){sub 2} nanostructures. All of the samples were synthesized by using the chemical precipitation method. Samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS) and photocatalyst measurements. XRD studies revealed single phase nature of the samples and omitted the presence of trivial metallic or binary oxide phases. TiO{sub 2} set of samples have shown nanorod kind of morphology, however TEM images of ZnO and Ni(OH){sub 2} set of samples depicted the spherical morphology of particles. XANES spectra at the Cu K-edge and Cu L-edge, along with the atomic multiplet calculations, revealed the predominance of Cu{sup 2+} ions in all of the samples, within the entire doping range. Ti L-edge and Ti K-edge XANES confirmed the existence of Ti{sup 4+} ions in the pure and Cu doped TiO{sub 2} samples with anatase local structure. Zn L-edge XANES results confirmed the divalent character of Zn ions in the pure and Cu doped ZnO, which is further validated by the Zn K-edge XANES. Ni L-edge and Ni K-edge XANES conveyed the +2 valence state of Ni ions in the pure and Cu doped Ni (OH){sub 2} samples. EXAFS analysis at the Cu K-edge nullifies the formation of Cu metallic clusters and other trivial phases, suggesting random distribution of Cu atoms in the oxide materials. Though, local atomic arrangement of Cu ions is disparate in the different oxide compounds. As an application of the pure and Cu doped TiO{sub 2}, ZnO and Ni(OH){sub 2} nanostructures, towards the degradation of water pollutant dyes, we demonstrate that all of the samples can serve as effective photocatalyst materials towards the degradation of methyl orange aqueous pollutant dye under the UV-light irradiation

  4. Automatic reduction of large X-ray fluorescence data-sets applied to XAS and mapping experiments

    International Nuclear Information System (INIS)

    Martin Montoya, Ligia Andrea

    2017-02-01

    In this thesis two automatic methods for the reduction of large fluorescence data sets are presented. The first method is proposed in the framework of BioXAS experiments. The challenge of this experiment is to deal with samples in ultra dilute concentrations where the signal-to-background ratio is low. The experiment is performed in fluorescence mode X-ray absorption spectroscopy with a 100 pixel high-purity Ge detector. The first step consists on reducing 100 fluorescence spectra into one. In this step, outliers are identified by means of the shot noise. Furthermore, a fitting routine which model includes Gaussian functions for the fluorescence lines and exponentially modified Gaussian (EMG) functions for the scattering lines (with long tails at lower energies) is proposed to extract the line of interest from the fluorescence spectrum. Additionally, the fitting model has an EMG function for each scattering line (elastic and inelastic) at incident energies where they start to be discerned. At these energies, the data reduction is done per detector column to include the angular dependence of scattering. In the second part of this thesis, an automatic method for texts separation on palimpsests is presented. Scanning X-ray fluorescence is performed on the parchment, where a spectrum per scanned point is collected. Within this method, each spectrum is treated as a vector forming a basis which is to be transformed so that the basis vectors are the spectra of each ink. Principal Component Analysis is employed as an initial guess of the seek basis. This basis is further transformed by means of an optimization routine that maximizes the contrast and minimizes the non-negative entries in the spectra. The method is tested on original and self made palimpsests.

  5. Automatic reduction of large X-ray fluorescence data-sets applied to XAS and mapping experiments

    Energy Technology Data Exchange (ETDEWEB)

    Martin Montoya, Ligia Andrea

    2017-02-15

    In this thesis two automatic methods for the reduction of large fluorescence data sets are presented. The first method is proposed in the framework of BioXAS experiments. The challenge of this experiment is to deal with samples in ultra dilute concentrations where the signal-to-background ratio is low. The experiment is performed in fluorescence mode X-ray absorption spectroscopy with a 100 pixel high-purity Ge detector. The first step consists on reducing 100 fluorescence spectra into one. In this step, outliers are identified by means of the shot noise. Furthermore, a fitting routine which model includes Gaussian functions for the fluorescence lines and exponentially modified Gaussian (EMG) functions for the scattering lines (with long tails at lower energies) is proposed to extract the line of interest from the fluorescence spectrum. Additionally, the fitting model has an EMG function for each scattering line (elastic and inelastic) at incident energies where they start to be discerned. At these energies, the data reduction is done per detector column to include the angular dependence of scattering. In the second part of this thesis, an automatic method for texts separation on palimpsests is presented. Scanning X-ray fluorescence is performed on the parchment, where a spectrum per scanned point is collected. Within this method, each spectrum is treated as a vector forming a basis which is to be transformed so that the basis vectors are the spectra of each ink. Principal Component Analysis is employed as an initial guess of the seek basis. This basis is further transformed by means of an optimization routine that maximizes the contrast and minimizes the non-negative entries in the spectra. The method is tested on original and self made palimpsests.

  6. Orbital-Specific observation of O2p and Ni3d electrons in LiNi0.5Mn0.5O2, a cathode material for lithium-ion batteries

    Directory of Open Access Journals (Sweden)

    Yoshinori Satou

    2017-09-01

    Full Text Available Cathode materials for lithium-ion batteries containing Ni2+ have attracted much interest because of their high theoretical capacity. However, the precise electronic structures of these cathode materials have not yet been clearly observed, especially the energy positions of the O2p and Ni3d orbitals and the shape of the density of states. The aim of this study was to investigate the relative energy positions and shape of the density of states of O2p and Ni3d for LiNi0.5Mn0.5O2 experimentally. We cleaved a LiNi0.5Mn0.5O2 pellet in an Ar-filled glove box and performed synchrotron ultraviolet photoelectron spectroscopy for different photon energies, which enabled us to investigate the relative cross-section intensity of O2p and Ni3d. As a result, the valence-band structure was determined. We found that O2p electrons are itinerant and exist in the vicinity of the Fermi energy more than Ni3d electrons. Ni3d electrons are more localized and spread mainly from 1.2–1.5 eV below the Fermi energy. To validate the electronic structure, we measured the synchrotron O K-edge X-ray absorption fine structure of electrochemically lithium-extracted LiNi0.5Mn0.5O2. The electronic structure demonstrated that ligand holes in the oxygen atoms form below the Fermi level during the initial stage of Li extraction and that the formation rate of the holes decreases with Li extraction.

  7. Orbital-Specific observation of O2p and Ni3d electrons in LiNi0.5Mn0.5O2, a cathode material for lithium-ion batteries

    Science.gov (United States)

    Satou, Yoshinori; Komine, Shigeki; Shimizu, Sumera

    2017-09-01

    Cathode materials for lithium-ion batteries containing Ni2+ have attracted much interest because of their high theoretical capacity. However, the precise electronic structures of these cathode materials have not yet been clearly observed, especially the energy positions of the O2p and Ni3d orbitals and the shape of the density of states. The aim of this study was to investigate the relative energy positions and shape of the density of states of O2p and Ni3d for LiNi0.5Mn0.5O2 experimentally. We cleaved a LiNi0.5Mn0.5O2 pellet in an Ar-filled glove box and performed synchrotron ultraviolet photoelectron spectroscopy for different photon energies, which enabled us to investigate the relative cross-section intensity of O2p and Ni3d. As a result, the valence-band structure was determined. We found that O2p electrons are itinerant and exist in the vicinity of the Fermi energy more than Ni3d electrons. Ni3d electrons are more localized and spread mainly from 1.2-1.5 eV below the Fermi energy. To validate the electronic structure, we measured the synchrotron O K-edge X-ray absorption fine structure of electrochemically lithium-extracted LiNi0.5Mn0.5O2. The electronic structure demonstrated that ligand holes in the oxygen atoms form below the Fermi level during the initial stage of Li extraction and that the formation rate of the holes decreases with Li extraction.

  8. X-ray Absorption Spectroscopy Reveals an Organometallic Ni-C Bond in the CO-Treated Form of Acetyl-CoA Synthase.

    Science.gov (United States)

    Can, Mehmet; Giles, Logan J; Ragsdale, Stephen W; Sarangi, Ritimukta

    2017-03-07

    Acetyl-CoA synthase (ACS) is a key enzyme in the Wood-Ljungdahl pathway of anaerobic CO 2 fixation, which has long been proposed to operate by a novel mechanism involving a series of protein-bound organometallic (Ni-CO, methyl-Ni, and acetyl-Ni) intermediates. Here we report the first direct structural evidence of the proposed metal-carbon bond. We describe the preparation of the highly active metal-replete enzyme and near-quantitative generation of the kinetically competent carbonylated intermediate. This advance has allowed a combination of Ni and Fe K-edge X-ray absorption spectroscopy and extended X-ray absorption fine structure experiments along with density functional theory calculations. The data reveal that CO binds to the proximal Ni of the six-metal metallocenter at the active site and undergoes dramatic structural and electronic perturbation in forming this organometallic Ni-CO intermediate. This direct identification of a Ni-carbon bond in the catalytically competent CO-bound form of the A cluster of ACS provides definitive experimental structural evidence supporting the proposed organometallic mechanism of anaerobic acetyl-CoA synthesis.

  9. Modeling the amorphous structure of mechanically alloyed Ti{sub 50}Ni{sub 25}Cu{sub 25} using anomalous wide-angle x-ray scattering and reverse Monte Carlo simulation

    Energy Technology Data Exchange (ETDEWEB)

    Lima, J.C. de, E-mail: fsc1jcd@fisica.ufsc.br [Departamento de Física, Universidade Federal de Santa Catarina, Campus Universitário Trindade, S/N, C.P. 476, 88040-900 Florianópolis, Santa Catarina (Brazil); Poffo, C.M. [Departamento de Engenharia Mecânica, Universidade Federal de Santa Catarina, Campus Universitário Trindade, S/N, C.P. 476, 88040-900 Florianópolis, Santa Catarina (Brazil); Departamento de Física, Universidade Federal do Amazonas, 3000 Japiim, 69077-000 Manaus, Amazonas (Brazil); Souza, S.M. [Departamento de Física, Universidade Federal do Amazonas, 3000 Japiim, 69077-000 Manaus, Amazonas (Brazil); Machado, K.D. [Departamento de Física, Centro Politécnico, Universidade Federal do Paraná, 81531-990 Curitiba, Paraná (Brazil); Trichês, D.M. [Departamento de Física, Universidade Federal do Amazonas, 3000 Japiim, 69077-000 Manaus, Amazonas (Brazil); Grandi, T.A. [Departamento de Física, Universidade Federal de Santa Catarina, Campus Universitário Trindade, S/N, C.P. 476, 88040-900 Florianópolis, Santa Catarina (Brazil); Biasi, R.S. de [Seção de Engenharia Mecânica e de Materiais, Instituto Militar de Engenharia, 22290-270 Rio de Janeiro, RJ (Brazil)

    2013-09-01

    An amorphous Ti{sub 50}Ni{sub 25}Cu{sub 25} alloy was produced by 19 h of mechanical alloying. Anomalous wide angle x-ray scattering data were collected at six energies and six total scattering factors were obtained. By considering the data collected at two energies close to the Ni and Cu K edges, two differential anomalous scattering factors about the Ni and Cu atoms were obtained, showing that the chemical environments around these atoms are different. Eight factors were used as input data to the reverse Monte Carlo method used to compute the partial structure factors S{sub Ti3Ti}(K), S{sub Ti–Cu}(K), S{sub Ti–Ni}(K), S{sub Cu3Cu}(K), S{sub Cu–Ni}(K) and S{sub Ni–Ni}(K) and the partial pair distribution functions G{sub Ti3Ti}(r), G{sub Ti–Cu}(r), G{sub Ti–Ni}(r), G{sub Cu3Cu}(r), G{sub Cu–Ni}(r) and G{sub Ni–Ni}(r). From the RMC final atomic configuration and G{sub ij}(r) functions, the coordination numbers and interatomic atomic distances for the first neighbors were determined.

  10. Towards accurate structural characterization of metal centres in protein crystals: the structures of Ni and Cu T6 bovine insulin derivatives

    DEFF Research Database (Denmark)

    Frankær, Christian Grundahl; Mossin, Susanne; Ståhl, Kenny

    2014-01-01

    of the copper insulin derivative was deteriorated as a consequence of radiation damage. To provide more detail, X-ray absorption spectroscopy (XAS) was used to improve the information level about metal coordination in each derivative. The nickel derivative contains hexacoordinated Ni2+ with trigonal symmetry...... towards lower coordination numbers. Primary damage, i.e. photoreduction, was followed directly by XANES as a function of radiation dose, while secondary damage in the form of structural changes around the Cu atoms after exposure to different radiation doses was studied by crystallography using...

  11. Climate Literacy Initiatives as part of the TXESS (TeXas Earth and Space Science) Revolution Program

    Science.gov (United States)

    Olson, H. C.; Ellins, K. K.; Snow, E.; Bryant, S. L.; Olson, J. E.; Castillo Comer, C. A.; Willis, M.; Odell, M.; Stocks, E.

    2010-12-01

    For four years the National Science Foundation (NSF)-sponsored TeXas Earth and Space Science (TXESS) Revolution professional development program has helped teachers build a solid foundation in the geosciences through guided inquiry activities and lectures delivered by science experts. The professional development program comprises eight professional development academies and two summer institutes. Climate literacy has been a cross-cutting theme throughout the series of academies and institutes. Although we present a special emphasis on climate literacy in the 7th academy on Climate Change, the 8th academy on Humans at the Helm and the 2nd summer institute module on climate mitigation technology, activities related to climate literacy are woven into each academy. Examples of climate as a cross-cutting theme include a module on water and drought, including research on climate change through the analysis of deep-sea cores, and the effects on the Mayan population. Our distinguished lecturers bring in climate literacy as part of their presentations and programs: our Poking Holes into the Planet and Team Science professional development academy included two distinguished lecturers who brought current research results and educational materials from the ANDRILL (Antarctic Geological Drilling) program and the Integrated Ocean Drilling Program. Our Earth as a Habitable Planet professional development academy featured an activity on corals that used data to explore how higher than normal sea surface temperatures contribute to coral bleaching events. TXESS Revolution also works with our teachers to link them with other opportunities aligned with our professional development goals. With our assistance, one of our TXESS Revolution teachers sailed as part of the science team on Integrated Ocean Drilling Program expedition 317 to investigate sea level fluctuations in the Canterbury Basin offshore New Zealand, creating various resources (e.g., podcasts, blogs) to multiply the

  12. Electrical transport mechanisms and structure of hydrogenated and non-hydrogenated nanocrystalline Ga{sub 1−x}Mn{sub x}As films

    Energy Technology Data Exchange (ETDEWEB)

    Angelico, João C., E-mail: jcangelico@facol.br [Universidade Estadual Paulista, UNESP, Bauru, SP 17033-360 (Brazil); Pereira, André L.J. [Instituto Tecnológico de Aeronáutica ITA, 12228-900 São José dos Campos, SP (Brazil); Arruda, Larisa B. de; Dias da Silva, José H. [Universidade Estadual Paulista, UNESP, Bauru, SP 17033-360 (Brazil)

    2015-05-05

    Highlights: • Ga{sub 1−x}Mn{sub x}As films were produced by the RF magnetron sputtering technique. • The structures of the films were analyzed by Rietveld refinement. • Electrical conductivity was analyzed with basis on the structure and morphology. • Space charge limited current regime was identified in the films without manganese. • The electrical transport of the sample with manganese showed only “Ohmic regime”. - Abstract: The mechanisms of electrical conductivity in hydrogenated and non-hydrogenated nanocrystalline Ga{sub 1−x}Mn{sub x}As (0.000 ⩽ x ⩽ 0.081) films were analyzed, first from a macroscopic perspective, followed by microscopic analysis to investigate the energy levels for trapping electric charges. The analysis of the current–voltage and resistivity–temperature characteristics allowed the development of a model based on the morphology and structure of the films. This model takes into account the main aspects of the transport above 300 K. Space charge limited current (SCLC) mechanism was observed in Mn-free films and is associated with deep trap states located at 0.10 and 0.22 eV below the conduction band. In samples containing Mn, the dark conductivity is highly dependent on the presence of hydrogen. This effect was related to the grain boundaries and interstitial regions of the films, in which the density of gap states is expected to be reduced by the presence of hydrogen.

  13. Identification of the chemical form of sulfur compounds in the Japanese pink coral (Corallium elatius) skeleton using μ-XRF/XAS speciation mapping.

    Science.gov (United States)

    Tamenori, Yusuke; Yoshimura, Toshihiro; Luan, Nguyen Trong; Hasegawa, Hiroshi; Suzuki, Atsushi; Kawahata, Hodaka; Iwasaki, Nozomu

    2014-05-01

    The distributions and chemical forms of sulfur compounds in the skeleton of Japanese pink coral (Corallium elatius) were investigated using X-ray spectroscopic techniques combined with micro-focused soft X-ray radiation. Microscopic X-ray fluorescence/soft X-ray photoabsorption (μ-XRF/XAS) speciation mapping clarified that sulfate is the primary species in the coral skeleton, with minor amounts of organic sulfur, whereas both sulfate and organic sulfur coexist in coenenchyme. Analysis of the post-edge region of the XAS spectra confirmed that sulfate ions in the coral skeleton are mainly in the form of gypsum-like inorganic sulfate substituting for the carbonate ions in the calcite skeleton. The sulfate concentration was negatively correlated with the magnesium concentration and positively correlated with that of phosphorus. Speciation mapping of sulfate in the coral skeleton showed clear fluctuations with sulfate concentrations being higher at dark bands, whereas the small amount of organic sulfur had unclear dark/bright bands. These results suggest that the little organic sulfur that is present is contained in the organic matter embedded in the biocrystal of coral skeleton. Copyright © 2014 Elsevier Inc. All rights reserved.

  14. Mechanistic insights into the interaction between energetic oxygen ions and nanosized ZnFe2O4: XAS-XMCD investigations.

    Science.gov (United States)

    Singh, Jitendra Pal; Kaur, Baljeet; Sharma, Aditya; Kim, So Hee; Gautam, Sanjeev; Srivastava, Ramesh Chandra; Goyal, Navdeep; Lim, Weol Cheol; Lin, H-J; Chen, J M; Asokan, K; Kanjilal, D; Won, Sung Ok; Lee, Ik-Jae; Chae, Keun Hwa

    2018-04-20

    The interactions of energetic ions with multi-cation compounds and their consequences in terms of changes in the local electronic structure, which may facilitate intriguing hybridization between O 2p and metal d orbitals and magnetic ordering, are the subject of debate and require a deep understanding of energy transfer processes and magnetic exchange mechanisms. In this study, nanocrystals of ZnFe2O4 were exposed to O7+ ions with an energy of 100 MeV to understand, qualitatively and quantitatively, the metal-ligand field interactions, cation migration and magnetic exchange interactions by employing X-ray absorption fine structure measurements and X-ray magnetic circular dichroism to get deeper mechanistic insights. Nanosized zinc ferrite nanoparticles (NPs) with a size of ∼16 nm synthesized in the cubic spinel phase exhibited deterioration of the crystalline phase when 100 MeV O7+ ions passed through them. However, the size of these NPs remained almost the same. The behaviour of crystal deterioration is associated with the confinement of heat in this interaction. The energy confined inside the nanoparticles promotes cation redistribution as well as the modification of the local electronic structure. Prior to this interaction, almost 42% of Zn2+ ions occupied AO4 tetrahedra; however, this value increased to 63% after the interaction. An inverse effect was observed for metal ion occupancies in BO6 octahedra. The L-edge spectra of Fe and Zn reveal that the spin and valence states of the metal ions were not affected by this interaction. This effect is also supported by K-edge measurements for Fe and Zn. The t2g/eg intensity ratio in the O K-edge spectra decreased after this interaction, which is associated with detachment of Zn2+ ions from the lattice. The extent of hybridization, as estimated from the ratio of the post-edge to the pre-edge region of the O K-edge spectra, decreased after this interaction. The metal-oxygen and metal-metal bond lengths were modified

  15. Inelastic scattering at the B K edge of hexagonal BN

    Energy Technology Data Exchange (ETDEWEB)

    Jia, J.J.; Callcott, T.A.; Zhou, L. [Univ. of Tennessee, Knoxville, TN (United States)] [and others

    1997-04-01

    Many recent soft x-ray fluorescence (SXF) studies have shown that inelastic scattering processes make important contributions to the observed spectra for excitation near the x-ray threshold. These effects are all attributed to a process, usually called an electronic Raman scattering (ERS) process, in which energy is lost to an electronic excitation. The theory has been described using second order perturbation theory by Tulkki and Aberg. In different materials, the detailed nature of the electronic excitation producing the energy loss may be very different. In crystalline Si, diamond and graphite, changes in spectral shape and dispersion of spectral features with variation of the excitation energy are observed, which are attributed to k conservation between the photoelectron generated in the excitation process and the valence hole remaining after the coupled emission process. Hence the process is strongly localized in k-space. In haxagonal boron nitride, which has a lattice and band structure very similar to graphite, inelastic scattering produces very different effects on the observed spectra. Here, the inelastic losses are coupled to a strong resonant elastic scattering process, in which the intermediate state is a localized core exciton and the final state is a localized valence exciton, so that the electronic excitation is strongly localized in real rather than reciprocal space.

  16. F K-edge soft X-ray absorption spectroscopy

    International Nuclear Information System (INIS)

    Sugimura, Tetsuro; Kawai, Jun; Maeda, Kuniko; Fukushima, Akiko; Shin, S.; Motoyama, Muneyuki; Nakajima Tsuyoshi

    2001-01-01

    We measured F X-ray absorption spectra of various fluorine compounds using a synchrotron radiation at KEK-PF. The absorption spectra were measured using X-ray fluorescence yield (XFY) and total electron yield (TEY) methods. Change of the spectral shape has a relation to the metal-fluorine bond distance. By comparing with the experimental spectrum and calculated spectrum, F 2p state density is divined into up and down states. (author)

  17. New analysis technique for K-edge densitometry spectra

    International Nuclear Information System (INIS)

    Hsue, Sin-Tao; Collins, M.L.

    1995-01-01

    A method for simulating absorption edge densitometry has been developed. This program enables one to simulate spectra containing any combination of special nuclear materials (SNM) in solution. The method has been validated with an analysis method using a single SNM in solution or a combination of two types of SNM separated by a Z of 2. A new analysis technique for mixed solutions has been developed. This new technique has broader applications and eliminates the need for bias correction

  18. Double-electron excitation above Xe K-edge

    International Nuclear Information System (INIS)

    Ito, Y.; Tochio, T.; Vlaicu, A.M.; Mutaguchi, K.; OhHashi, H.; Shigeoka, N.; Nakata, Y.; Akahama, Y.; Uruga, T.; Emura, Sh.

    2000-01-01

    When X-rays fall on any substance, whether solid, liquid, or gaseous, a photoabsorption occurs. Photoabsorption in atoms has been generally treated as a single-electron excitation process. However, the existence of the multi-electron excitation process, where the removal of a core electron by photoabsorption causes excitation of additional electrons in the same atoms, has been known in x-ray absorption spectra for a long time. In x-ray absorption spectra, experimental investigations of the shake processes in inner-shell ionization phenomena have been performed by detecting discontinuities. The shake effect which is a consequence of rearrangement of the atomic electrons, occurs in association with inner-shell excitation and ionization phenomena in x-ray absorption. The shake process has been studied extensively in various gases, because it is usually considered that the measurement of the multi-electron excitation is only possible for monatomic gases or vapors. The x-ray absorption spectra in Kr gas were measured by Ito et al. in order to observe precisely x-ray absorption spectra and to investigate the multi-electron excitation cross sections in Kr as a function of photon energy using synchrotron radiation. However, no suitable measured K x-ray absorption spectra was available to elucidate the shake processes. In the present work, the photoabsorption cross sections in Xe have been precisely measured in order to determine the features on the shake processes resulting from multiple electron excitations as a function of photon energy. Double-electron transitions of [1s4d], [1s4p], [1s4s], and [1s3d] are first detected. (author)

  19. Chemical shifts of K-X-ray absorption edges on copper in different compounds by X-ray absorption spectroscopy (XAS) with Synchrotron radiation

    Science.gov (United States)

    Joseph, D.; Basu, S.; Jha, S. N.; Bhattacharyya, D.

    2012-03-01

    Cu K X-ray absorption edges were measured in compounds such as CuO, Cu(CH3CO2)2, Cu(CO3)2, and CuSO4 where Cu is present in oxidation state of 2+, using the energy dispersive EXAFS beamline at INDUS-2 Synchrotron radiation source at RRCAT, Indore. Energy shifts of ˜4-7 eV were observed for Cu K X-ray absorption edge in the above compounds compared to its value in elemental copper. The difference in the Cu K edge energy shifts in the different compounds having same oxidation state of Cu shows the effect of different chemical environments surrounding the cation in the above compounds. The above chemical effect has been quantitatively described by determining the effective charges on Cu cations in the above compounds.

  20. First-principles calculations of the structural, electronic and optical properties of cubic B{sub x}Ga{sub 1-x}As alloys

    Energy Technology Data Exchange (ETDEWEB)

    Guemou, M., E-mail: guemoumhamed7@gmail.com [Engineering Physics Laboratory, University Ibn Khaldoun of Tiaret, BP 78-Zaaroura, Tiaret 14000 (Algeria); Bouhafs, B. [Modelling and Simulation in Materials Science Laboratory, Physics Department, University of Sidi Bel-Abbes, 22000 Sidi Bel-Abbes (Algeria); Abdiche, A. [Applied Materials Laboratory, Research Center, University of Sidi Bel Abbes, 22000 Sidi Bel Abbes (Algeria); Khenata, R. [Laboratoire de Physique Quantique et de Modelisation Mathematique (LPQ3M), Departement de Technologie, Universite de Mascara, 29000 Mascara (Algeria); Al Douri, Y. [Institute of Nano Electronic Engineering, Universiti Malaysia Perlis, Perlis (Malaysia); Bin Omran, S. [Department of Physics and Astronomy, Faculty of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia)

    2012-04-15

    Density functional calculations are performed to study the structural, electronic and optical properties of technologically important B{sub x}Ga{sub 1-x}As ternary alloys. The calculations are based on the total-energy calculations within the full-potential augmented plane-wave (FP-LAPW) method. For exchange-correlation potential, local density approximation (LDA) and the generalized gradient approximation (GGA) have been used. The structural properties, including lattice constants, bulk modulus and their pressure derivatives, are in very good agreement with the available experimental and theoretical data. The electronic band structure, density of states for the binary compounds and their ternary alloys are given. The dielectric function and the refractive index are also calculated using different models. The obtained results compare very well with previous calculations and experimental measurements.

  1. Photoluminescence energy transitions in GaAs-Ga{sub 1-x}Al{sub x}As double quantum wells: Electric and magnetic fields and hydrostatic pressure effects

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, S.Y. [Grupo de Educacion en Ciencias Experimentales y Matematicas-GECEM, Facultad de Educacion, Universidad de Antioquia, AA 1226 Medellin (Colombia); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autonoma del Estado de Morelos, Av. Universidad 1001, CP 62209, Cuernavaca, Morelos (Mexico); Duque, C.A., E-mail: cduque@fisica.udea.edu.c [Instituto de Fisica, Universidad de Antioquia, AA 1226 Medellin (Colombia)

    2009-12-15

    The photoluminescence energy transitions in GaAs-Ga{sub 1-x}Al{sub x}As coupled double quantum wells are presented by considering the simultaneous effects of applied electric and magnetic fields and hydrostatic pressure. Calculations have been made in the framework of the effective mass and parabolic band approximations and using a variational procedure. The electric field is taken to be oriented along the growth direction of the heterostructure whereas for the magnetic field both in-plane and in-growth directions have been considered. The results show that the hydrostatic pressure and the applied electric field are two useful tools to tune the direct and indirect exciton transitions in such heterostructures. Our results are in good agreement with previous experimental findings in double quantum wells under applied electric field and hydrostatic pressure.

  2. Structural study of ZnSe films grown on substrate with In{sub x}Ga{sub 1-x}As and Al{sub 1-x}Ga{sub x}As buffer layers: strain, relaxation and lattice parameter

    Energy Technology Data Exchange (ETDEWEB)

    Perez Ladron de Guevara, H.; Gaona-Couto, A.; Vidal, M.A. [Instituto de Investigacion En Comunicacion Optica (IICO), Universidad Autonoma de San Luis Potosi, San Luis Potosi (Mexico)]. E-mail: mavidal@cactus.iico.uaslp.mx; Luyo Alvarado, J.; Melendez Lira, M.; Lopez-Lopez, M. [Departamento de Fisica, Centro de Investigacion y Estudios Avanzados del IPN, Mexico DF (Mexico)

    2002-06-21

    ZnSe layers of various thickness were grown on (001) GaAs substrates, using In{sub x}Ga{sub 1-x}As or Al{sub 1-x}Ga{sub x}As as buffer layers by molecular beam epitaxy and were studied by high-resolution x-ray diffraction. The principal structural characteristics of ZnSe layer and buffer layer were determined using several reflections, such as (004) and two pairs of coupled asymmetric reflections, namely (224), (-2-24) and (115) (-1-15). In order to evaluate their validity, the experimental data obtained from these reflections were handled by means of two known expressions found in the literature. We have found the relaxation process of ZnSe layers is well described by a geometrical model including the thermal strain and small strain due to work hardening. The relaxation process is faster for ZnSe grown on ternary buffer layers despite the fact that, some buffer layers are pseudomorphically grown to the substrate; therefore we conclude that not only the lattice mismatches have effect on the relaxation process but also the surface state of the buffer layer has an influence in this process. (author)

  3. and ni(ii)

    African Journals Online (AJOL)

    userpc

    NI(II) COMPLEXES WITH SCHIFF BASE DERIVED FROM SULPHANILAMINE AND. SALICYLALDEHYDE. ⃰Siraj, I. T. and ... with nickel(II) and cobalt(II) chloride in 2:1 mole ratio yielded Ni(II) and Co(II) complexes respectively. The synthesized .... coordinated ligand (coordination number) was determined using the relation ...

  4. Ultrafine and highly disordered Ni 2 Fe 1 nanofoams enabled highly efficient oxygen evolution reaction in alkaline electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Shaofang; Song, Junhua; Zhu, Chengzhou; Xu, Gui-Liang; Amine, Khalil; Sun, Chengjun; Li, Xiaolin; Engelhard, Mark H.; Du, Dan; Lin, Yuehe

    2018-02-01

    Nickel iron hydroxides are the most promising non-noble electrocatalysts for oxygen evolution reaction (OER) in alkaline media. By in situ reduction of metal precursors, compositionally controlled three-dimensional (3D) NixFeyB nanofoams (NFs) are synthesized with high surface area and uniformly distributed bimetallic networks. The resultant ultrafine amorphous Ni2Fe1B NFs exhibit extraordinary electrocatalytic performance toward OER and overall water splitting in alkaline media. At a potential as low as 1.42 V (vs. RHE), Ni2Fe1B NFs can deliver a current density of 10 mA/cm2 and show negligible activity loss after 12 hours’ stability test. Even at large current flux of 100 mA/cm2, an ultralow overpotential of 0.27 V is achieved, which is about 0.18 V more negative than benchmark RuO2. Both ex-situ Mӧssbauer spectroscopy and X-ray Absorption Spectroscopy (XAS) reveal a phase separation and transformation for the Ni2Fe1B catalyst during OER process. The evolution of oxidation state and disordered structure of Ni2Fe1B might be a key to the high catalytic performance for OER.

  5. Decay of 57Ni

    International Nuclear Information System (INIS)

    Santos Scardino, A.M. dos.

    1987-01-01

    The decay of 57 Ni to 57 Co was studied by gamma ray spectroscopy using both singles and coincidence spectra. The sources were obtained with the 58 Ni (Y,n) 57 Ni reaction. Natural metallic nickel was irradiated in the bremsstrahluhng beam of the linear accelerator of the Instituto de Fisica da Universidade de Sao Paulo with 30 MeV electrons. The singles espectra were taken with 104 cc HPGe detector and the coincidences espectra with 27 and 53cc Ge(Li) and 104 cc. HPGe detectors. The energies of transitions that follow the 57 Ni decay were measured using 56 Co as standard (which was obtained by (Y,np) reaction in 58 Ni) and taking into account the cascade cross-over relations. (author) [pt

  6. Submicron particles of Co, Ni and Co–Ni alloys

    Indian Academy of Sciences (India)

    Unknown

    meter (VSM). It may be noted that Co and Ni form a solid solution in the bulk, CoxNi1–x. For x 0⋅7, the alloy has a fcc structure, with a mixed regime in the intermediate compositions. The atomic moments in Co–Ni alloys increase linearly with Ni content (Tebble and Craik.

  7. Bridging exchange bias effect in NiO and Ni(core)@NiO(shell) nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Rinaldi-Montes, Natalia, E-mail: nataliarin@gmail.com [Departamento de Física, Universidad de Oviedo, E-33007 Oviedo (Spain); Gorria, Pedro [Departamento de Física & IUTA, EPI, Universidad de Oviedo, E-33203 Gijón (Spain); Martínez-Blanco, David [Servicios Científico-Técnicos, Universidad de Oviedo, E-33006 Oviedo (Spain); Fuertes, Antonio B. [Instituto Nacional del Carbón, CSIC, E-33080 Oviedo (Spain); Fernández Barquín, Luis [CITIMAC, Facultad de Ciencias, Universidad de Cantabria, E-39005 Santander (Spain); Puente-Orench, Inés [Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza and Institut Laue-Langevin, BP 156, F-38042 Grenoble Cedex 9 (France); Blanco, Jesús A. [Departamento de Física, Universidad de Oviedo, E-33007 Oviedo (Spain)

    2016-02-15

    Among all bi-magnetic core(transition metal)@shell(transition metal oxide) nanoparticles (NPs), Ni@NiO ones show an onset temperature for the exchange bias (EB) effect far below the Néel temperature of bulk antiferromagnetic NiO. In this framework, the role played by the magnetism of NiO at the nanoscale is investigated by comparing the microstructure and magnetic properties of NiO and Ni@NiO NPs. With the aim of bridging the two systems, the diameter of the NiO NPs (~4 nm) is chosen to be comparable to the shell thickness of Ni@NiO ones (~2 nm). The EB effect in Ni@NiO NPs is attributed to the exchange coupling between the core and the shell, with an interfacial exchange energy of ΔE~0.06 erg cm{sup −2}, thus comparable to previous reports on Ni/NiO interfaces both in thin film and NP morphologies. In contrast, the EB detected in NiO NPs is explained in a picture where uncompensated spins located on a magnetically disordered surface shell are exchange coupled to the antiferromagnetic core. In all the studied NPs, the variation of the EB field as a function of temperature is described according to a negative exponential law with a similar decay constant, yielding a vanishing EB effect around T~40–50 K. In addition, the onset temperature for the EB effect in both NiO and Ni@NiO NPs seems to follow a universal dependence with the NiO crystallite size. - Highlights: • Comparison of the exchange bias effect in NiO and Ni(core)@NiO(shell) nanoparticles. • Universal temperature dependence of the exchange bias effect. • Suggested similar physical origin of the effect in both systems. • Size and crystallinity of the NiO shell hold the key for exchange bias properties.

  8. OpenNI cookbook

    CERN Document Server

    Falahati, Soroush

    2013-01-01

    This is a Cookbook with plenty of practical recipes enriched with explained code and relevant screenshots to ease your learning curve. If you are a beginner or a professional in NIUI and want to write serious applications or games, then this book is for you. Even OpenNI 1 and OpenNI 1.x programmers who want to move to new versions of OpenNI can use this book as a starting point. This book uses C++ as the primary language but there are some examples in C# and Java too, so you need to have about a basic working knowledge of C or C++ for most cases.

  9. ENERGÍA DE ENLACE DE EXCITONES EN POZOS CUÁNTICOS DE GaAs/Ga1-xAl xAs

    Directory of Open Access Journals (Sweden)

    Parménides Aristizábal

    2007-06-01

    Full Text Available El uso de las estructuras de baja dimensionalidad es un elemento tecnológico clave en la creación de nuevos dispositivos cuánticos funcionales de la siguiente generación de circuitos integrados electrónicos, fotónicos y espintrónicos y muchos otros dispositivos nanotecnológicos que son necesarios para la sociedad de la información del siglo XXI. Una de las propiedades ópticas más importante es la fotoluminiscencia producida por agentes tales como impurezas y excitones en pozos, hilos y puntos cuánticos de arseniuro de galio GaAs con dimensiones nanométricas bajo la influencia de campos eléctricos y magnéticos y presiones externas. Se presenta la energía de enlace para los tres primeros estados excitónicos en pozos cuánticos de GaAs/Ga1-xAl xAs describiendo el sistema por medio de la teoría cuántica, en la aproximación de masa efectiva y usando el método variacional.The use of low dimensional structures is a key technological element in the creation of new quantum functional devices in the development of the next generation of the electronic, photonic, and spintronic integrated circuits and many other nanoscaled devices that are necessary for the information society of 21st century. One of the most important optical properties is the photoluminescence produced by agents as impurities and excitons in GaAs quantum wells, wires, and dots with nanometric dimensions under the influence of electric and magnetic fields and external pressures. The binding energy for the first three excitonic states in GaAs/Ga1-xA1xAs quantum wells describing the system through quantum theory in the effective mass approximation and using the variational method is presented.

  10. Local atomic characterization of LiCo1/3Ni1/3Mn1/3O2 cathode material

    International Nuclear Information System (INIS)

    Nedoseykina, Tatiana; Kim, Sung-Soo; Nitta, Yoshiaki

    2006-01-01

    Co, Ni and Mn K-edge XAFS investigation of LiCo 1/3 Ni 1/3 Mn 1/3 O 2 as alternative cathode material to commercially used LiCoO 2 in lithium rechargeable battery has been performed. Parameters of a local atomic structure such as radii of metal-oxygen and metal-metal coordination shells and disorder in those shells have been determined. It has been found that the radius of the first coordination shell (metal-oxygen) as well as a local disorder in the second shell (metal-metal) around each of the 3d-metals are in a good agreement with obtained for superlattice model of √3 x √3] R30 o type in triangular lattice of sites by first principle calculation. Other parameters of the local atomic structure around Co, Ni and Mn atoms do not provide evidence for presence of superstructure in LiCo 1/3 Ni 1/3 Mn 1/3 O 2

  11. Capping layer modulation of composition of GaAs/In0.15Ga0.75As/InXGa1-XAs/GaAs quantum wells and InAs QD's emission

    Science.gov (United States)

    Vega-Macotela, L. G.; Torchynska, T.; Polupan, G.; Muñiz-García, P. I.

    2018-02-01

    The GaAs/In0.15Ga0.85As/InxGa1-xAs /GaAs quantum wells (QWs) with the InAs quantum dots (QDs) have been studied by means of photoluminescence and high resolution X ray diffraction (HR-XRD) methods. The QW structures are characterized by the different compositions of capping InxGa1-xAs layers with the parameter x from the range 0.10-0.25. The InxGa1-xAs composition varying is accompanied by the change non-monotonously of the PL intensity and peak positions of InAs QD emission. HR-XRD results have been used for the control the QW compositions. Numerical simulations of HR-XRD results have shown that the composition of quantum layers vary none monotonously in studied QD structures as well. The physical reasons of the mentioned optical and structural effects and their dependence on capping layer compositions have been discussed.

  12. Energy-filtered environmental transmission electron microscopy for the assessment of solid-gas reactions at elevated temperature: NiO/YSZ-H2 as a case study.

    Science.gov (United States)

    Jeangros, Q; Hansen, T W; Wagner, J B; Dunin-Borkowski, R E; Hébert, C; Van Herle, J; Hessler-Wyser, A

    2016-10-01

    A novel approach, which is based on the analysis of sequences of images recorded using energy-filtered transmission electron microscopy and can be used to assess the reaction of a solid with a gas at elevated temperature, is illustrated for the reduction of a NiO/ceramic solid oxide fuel cell anode in 1.3mbar of H2. Three-window elemental maps and jump-ratio images of the O K edge and total inelastic mean free path images are recorded as a function of temperature and used to provide local and quantitative information about the reaction kinetics and the volume changes that result from the reaction. Under certain assumptions, the speed of progression of the reaction front in all three dimensions is obtained, thereby providing a three-dimensional understanding of the reaction. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Intermediate band formation in a δ-doped like QW superlattices of GaAs/AlxGa1-xAs for solar cell design

    Science.gov (United States)

    Del Río-De Santiago, A.; Martínez-Orozco, J. C.; Rodríguez-Magdaleno, K. A.; Contreras-Solorio, D. A.; Rodríguez-Vargas, I.; Ungan, F.

    2018-03-01

    It is reported a numerical computation of the local density of states for a δ-doped like QW superlattices of AlxGa1-xAs, as a possible heterostructure that, being integrated into a solar cell device design, can provide an intermediate band of allowed states to assist the absorption of photons with lower energies than that of the energy gap of the solar-cell constituent materials. This work was performed using the nearest neighbors sp3s* tight-binding model including spin. The confining potential caused by the ionized donor impurities in δ-doped impurities seeding that was obtained analytically within the lines of the Thomas-Fermi approximation was reproduced here by the Al concentration x variation. This potential is considered as an external perturbation in the tight-binding methodology and it is included in the diagonal terms of the tight-binding Hamiltonian. Special attention is paid to the width of the intermediate band caused by the change in the considered aluminium concentration x, the inter-well distance between δ-doped like QW wells and the number of them in the superlattice. In general we can conclude that this kind of superlattices can be suitable for intermediate band formation for possible intermediate-band solar cell design.

  14. First-principle calculations of structural, electronic, optical, elastic and thermal properties of MgXAs2 (X=Si, Ge) compounds

    Science.gov (United States)

    Cheddadi, S.; Boubendira, K.; Meradji, H.; Ghemid, S.; Hassan, F. El Haj; Lakel, S.; Khenata, R.

    2017-12-01

    First-principle calculations on the structural, electronic, optical, elastic and thermal properties of the chalcopyrite MgXAs2 (X=Si, Ge) have been performed within the density functional theory (DFT) using the full-potential linearized augmented plane wave (FP-LAPW) method. The obtained equilibrium structural parameters are in good agreement with the available experimental data and theoretical results. The calculated band structures reveal a direct energy band gap for the interested compounds. The predicted band gaps using the modified Becke-Johnson (mBJ) exchange approximation are in fairly good agreement with the experimental data. The optical constants such as the dielectric function, refractive index, and the extinction coefficient are calculated and analysed. The independent elastic parameters namely, C_{11}, C_{12}, C_{13}, C_{33}, C_{44} and C_{66 } are evaluated. The effects of temperature and pressure on some macroscopic properties of MgSiAs2 and MgGeAs2 are predicted using the quasiharmonic Debye model in which the lattice vibrations are taken into account.

  15. Study on the reversible electrode reaction of Na(1-x)Ni(0.5)Mn(0.5)O2 for a rechargeable sodium-ion battery.

    Science.gov (United States)

    Komaba, Shinichi; Yabuuchi, Naoaki; Nakayama, Tetsuri; Ogata, Atsushi; Ishikawa, Toru; Nakai, Izumi

    2012-06-04

    Layered NaNi(0.5)Mn(0.5)O(2) (space group: R ̅3m), having an O3-type (α-NaFeO(2) type) structure according to the Delmas' notation, is prepared by a solid-state method. The electrochemical reactivity of NaNi(0.5)Mn(0.5)O(2) is examined in an aprotic sodium cell at room temperature. The NaNi(0.5)Mn(0.5)O(2) electrodes can deliver ca. 105-125 mAh g(-1) at rates of 240-4.8 mA g(-1) in the voltage range of 2.2-3.8 V and show 75% of the initial reversible capacity after 50 charge/discharge cycling tests. In the voltage range of 2.2-4.5 V, a higher reversible capacity of 185 mAh g(-1) is achieved; however, its reversibility is insufficient because of the significant expansion of interslab space by charging to 4.5 V versus sodium. The reversbility is improved by adding fluoroethylene carbonate into the electrolyte solution. The structural transition mechanism of Na(1-x)Ni(0.5)Mn(0.5)O(2) is also examined by an ex situ X-ray diffraction method combined with X-ray absorption spectroscopy (XAS). The staking sequence of the [Ni(0.5)Mn(0.5)]O(2) slabs changes progressively as sodium ions are extracted from the crystal lattice. It is observed that the original O3 phase transforms into the O'3, P3, P'3, and P3" phases during sodium extraction. XAS measurement proves that NaNi(0.5)Mn(0.5)O(2) consists of divalent nickel and tetravalent manganese ions. As sodium ions are extracted from the oxide to form Na(1-x)Ni(0.5)Mn(0.5)O(2), nickel ions are oxidized to the trivalent state, while the manganese ions are electrochemically inactive as the tetravalent state.

  16. Study of local disorder in LiMn(Cr,Ni)O2 compounds by extended X-ray absorption fine structure measurements

    Science.gov (United States)

    Maugeri, L.; Iadecola, A.; Simonelli, L.; Chen, G.; Wadati, H.; Mizokawa, T.; Saini, N. L.

    2013-11-01

    We have studied local structure of LiMnO2, LiMn0.65Cr0.35O2 and LiMn0.5Ni0.5O2 compounds by Mn K-edge extended X-ray absorption fine structure measurements. The local structure of LiMnO2 is found to be consistent with Jahn-Teller distorted MnO6 octahedra characterized by two different Mn-O bond distances. The Jahn-Teller distortions are suppressed in the Cr and Ni substituted compounds, resulting a single Mn-O distance. However, the Cr atoms tend to occupy a site at a longer distance from Mn in the host lattice (Mn-Cr distance is longer than Mn-Mn distance), unlike the Ni atoms which prefer a site closer to the Mn atoms (Mn-Ni distance is shorter than Mn-Mn distance). Incidentally, Mn-O and Mn-Mn bonds are substantially stiffer in the Cr and Ni substituted compounds. In addition, the static atomic disorder is confined around Cr atoms in the LiMn0.65Cr0.35O2, that is different from the case of LiMn0.5Ni0.5O2 in which larger static disorder appears in the proximity of the Mn atoms. The results suggest that the differences in the local structure of different compounds should be the likely reason for their differing battery characteristics.

  17. Use of Hydrogen Chemisorption and Ethylene Hydrogenation as Predictors for Aqueous Phase Reforming of Lactose over Ni@Pt and Co@Pt Bimetallic Overlayer Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Lai, Qinghua; Skoglund, Michael D.; Zhang, Chen; Morris, Allen R.; Holles, Joseph H.

    2016-10-20

    Overlayer Pt on Ni (Ni@Pt) or Co (Co@Pt) were synthesized and tested for H2 generation from APR of lactose. H2 chemisorption descriptor showed that Ni@Pt and Co@Pt overlayer catalysts had reduced H2 adsorption strength compared to a Pt only catalyst, which agree with computational predictions. The overlayer catalysts also demonstrated lower activity for ethylene hydrogenation than the Pt only catalyst, which likely resulted from decreased H2 binding strength decreasing the surface coverage of H2. XAS results showed that overlayer catalysts exhibited higher white line intensity than the Pt catalyst, which indicates a negative d-band shift for the Pt overlayer, further providing evidence for overlayer formation. Lactose APR studies showed that lactose can be used as feedstock to produce H2 and CO under desirable reaction conditions. The Pt active sites of Ni@Pt and Co@Pt overlayer catalysts showed significantly enhanced H2 production selectivity and activity when compared with that of a Pt only catalyst. The single deposition overlayer with the largest d-band shift showed the highest H2 activity. The results suggest that overlayer formation using directed deposition technique could modify the behavior of the surface metal and ultimately modify the APR activity.

  18. Revealing the atomic and electronic structure of a SrTiO3/LaNiO3/SrTiO3 heterostructure interface

    International Nuclear Information System (INIS)

    Zhang, Zaoli; Soltan, S.; Schmid, H.; Habermeier, H.-U.; Keimer, B.; Kaiser, U.

    2014-01-01

    The atomic structures of SrTiO 3 (STO)/LaNiO 3 (LNO)/STO heterostructure interfaces were investigated by spherical aberration-corrected (C S ) (scanning) transmission electron microscopy. Atomic displacement and lattice distortion measurements and electron energy loss spectroscopy (EELS) were used to quantitatively analyze the distortion of the interfacial octahedra and the bond length at the interfaces. Combined with high-resolution transmission electron microscopy (HRTEM) and scanning transmission electron microscopy analyses, two distinct interfacial atomic terminating layers are unambiguously determined. Ensuing quantitative HRTEM measurements revealed that the Ni-O bond length in the interfacial octahedral is elongated at the bottom interface (–NiO 2 -SrO–). Atomic displacement shows structural relaxation effects when crossing the interfaces and lattice distortions across the interface is more pronounced in LNO than in STO. The Ti/O atomic ratio, La and Ti relative atomic ratio as derived by EELS quantification indicate non-stoichiometric composition at the interfaces. Distinct fine structures of Ti-L 2,3 edge and O-K edge at the bottom and top interfaces are observed. By comparison, we are able to estimate Ti valency at both interfaces. Combining the structural distortions and Ti valency, the polar discontinuity and charge transfer at the interfaces are discussed

  19. In-operando elucidation of bimetallic CoNi nanoparticles during high-temperature CH 4 /CO 2 reaction

    KAUST Repository

    Al-Sabban, Bedour

    2017-05-02

    Dry reforming of methane (DRM) proceeds via CH4 decomposition to leave surface carbon species, followed by their removal with CO2-derived species. Reactivity tuning for stoichiometric CH4/CO2 reactants was attempted by alloying the non-noble metals Co and Ni, which have high affinity with CO2 and high activity for CH4 decomposition, respectively. This study was focused on providing evidence of the capturing surface coverage of the reactive intermediates and the associated structural changes of the metals during DRM at high temperature using in-operando X-ray absorption spectroscopy (XAS). On the Co catalysts, the first-order effects with respect to CH4 pressure and negative-order effects with respect to CO2 pressure on the DRM rate are consistent with the competitive adsorption of the surface oxygen species on the same sites as the CH4 decomposition reaction. The Ni surface provides comparatively higher rates of CH4 decomposition and the resultant DRM than the Co catalyst but leaves some deposited carbon on the catalyst surface. In contrast, the bimetallic CoNi catalyst exhibits reactivity towards the DRM but with kinetic orders resembling Co catalyst, producing negligible carbon deposition by balancing CH4 and CO2 activation. The in-operando X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements confirmed that the Co catalyst was progressively oxidized from the surface to the bulk with reaction time, whereas CoNi and Ni remained relatively reduced during DRM. Density functional theory (DFT) calculation considering the high reaction temperature for DRM confirmed the unselective site arrangement between Co and Ni atoms in both the surface and bulk of the alloy nanoparticle (NP). The calculated heat of oxygen chemisorption became more exothermic in the order of Ni, CoNi, Co, consistent with the catalytic behavior. The comprehensive experimental and theoretical evidence provided herein clearly suggests

  20. Donor impurity-related optical absorption spectra in GaAs-Ga{sub 1-x}Al{sub x}As quantum wells: hydrostatic pressure and {gamma}-X conduction band mixing effects

    Energy Technology Data Exchange (ETDEWEB)

    Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autonoma del Estado de Morelos, Av. Universidad 1001, C.P. 62209, Cuernavaca, MOR (Mexico); Inst. de Ciencia de Materiales de Madrid, CSIC, Sor Juana Ines de la Cruz 3, 28049 Madrid (Spain); Lopez, S.Y. [Fac. de Educacion, Universidad de Antioquia, AA 1226, Medellin (Colombia); Duque, C.A. [Inst. de Fisica, Universidad de Antioquia, AA 1226, Medellin (Colombia); Velasco, V.R. [Inst. de Ciencia de Materiales de Madrid, CSIC, Sor Juana Ines de la Cruz 3, 28049 Madrid (Spain)

    2007-07-01

    Using a variational procedure within the effective mass approximation, the mixing between the {gamma} and X conduction band valleys in GaAs-Ga{sub 1-x}Al{sub x}As quantum wells is investigated by taking into account the effect of applied hydrostatic pressure. Some optical properties such as donor and/or acceptor binding energy and impurity-related transition energies are calculated and comparisons with available experimental data are presented. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Impurity-related optical properties in rectangular-transverse section GaAs-Ga{sub 1-x}Al{sub x}As quantum well wires: Hydrostatic pressure and electric field effects

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, J.W.; Duque, C.A. [Instituto de Fisica, Universidad de Antioquia, AA 1226, Medellin (Colombia); Lopez, S.Y. [Facultad de Educacion, Universidad de Antioquia, AA 1226, Medellin (Colombia); Rodriguez, A.H. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico (UNAM), Apdo. Postal 20-364, San Angel 01000, Mexico DF (Mexico); Porras-Montenegro, N. [Departamento de Fisica, Universidad del Valle, AA 25360, Cali (Colombia)

    2007-01-15

    Using a variational procedure within the effective mass approximation, we have calculated the influence of an applied electric field and hydrostatic pressure on the shallow-impurity-related optical properties in a rectangular-transverse section GaAs-Ga{sub 1-x}Al{sub x}As quantum well wire. The electric field is applied in the plane of the transverse section of the wire and different angular directions have been considered. The results presented are for the impurity binding energy, its corresponding density of impurity states, and impurity-related transition energy and polarizability. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Comparative study of the hydrostatic pressure and temperature effects on the impurity-related optical properties in single and double GaAs-Ga{sub 1-x}Al{sub x}As quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Odhiambo Oyoko, H. [Department of Physics, Westville Campus, University of KwaZulu-Natal, Private Bag X 54001, Durban 4000 (South Africa); Porras-Montenegro, N. [Departamento de Fisica, Universidad del Valle, AA 25360, Cali (Colombia); Lopez, S.Y. [Facultad de Educacion, Universidad de Antioquia, AA 1226, Medellin (Colombia); Duque, C.A. [Instituto de Fisica, Universidad de Antioquia, AA 1226, Medellin (Colombia)

    2007-07-01

    Using a variational technique within the effective mass approximation we have carried out a comparative study of the effect of hydrostatic pressure and temperature on the shallow-impurity related optical absorption spectra in GaAs-Ga{sub 1-x}Al{sub x}As single and double quantum wells. The results show a pressure dependent read-shift and a temperature dependent blue-shift in the optical absorption spectra. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. Iron Transformation Pathways and Redox Micro-Environments in Seafloor Sulfide-Mineral Deposits: Spatially Resolved Fe XAS and δ(57/54)Fe Observations.

    Science.gov (United States)

    Toner, Brandy M; Rouxel, Olivier J; Santelli, Cara M; Bach, Wolfgang; Edwards, Katrina J

    2016-01-01

    Hydrothermal sulfide chimneys located along the global system of oceanic spreading centers are habitats for microbial life during active venting. Hydrothermally extinct, or inactive, sulfide deposits also host microbial communities at globally distributed sites. The main goal of this study is to describe Fe transformation pathways, through precipitation and oxidation-reduction (redox) reactions, and examine transformation products for signatures of biological activity using Fe mineralogy and stable isotope approaches. The study includes active and inactive sulfides from the East Pacific Rise 9°50'N vent field. First, the mineralogy of Fe(III)-bearing precipitates is investigated using microprobe X-ray absorption spectroscopy (μXAS) and X-ray diffraction (μXRD). Second, laser-ablation (LA) and micro-drilling (MD) are used to obtain spatially-resolved Fe stable isotope analysis by multicollector-inductively coupled plasma-mass spectrometry (MC-ICP-MS). Eight Fe-bearing minerals representing three mineralogical classes are present in the samples: oxyhydroxides, secondary phyllosilicates, and sulfides. For Fe oxyhydroxides within chimney walls and layers of Si-rich material, enrichments in both heavy and light Fe isotopes relative to pyrite are observed, yielding a range of δ(57)Fe values up to 6‰. Overall, several pathways for Fe transformation are observed. Pathway 1 is characterized by precipitation of primary sulfide minerals from Fe(II)aq-rich fluids in zones of mixing between vent fluids and seawater. Pathway 2 is also consistent with zones of mixing but involves precipitation of sulfide minerals from Fe(II)aq generated by Fe(III) reduction. Pathway 3 is direct oxidation of Fe(II) aq from hydrothermal fluids to form Fe(III) precipitates. Finally, Pathway 4 involves oxidative alteration of pre-existing sulfide minerals to form Fe(III). The Fe mineralogy and isotope data do not support or refute a unique biological role in sulfide alteration. The findings

  4. Nickel speciation in cement-stabilized/solidified metal treatment filtercakes

    Energy Technology Data Exchange (ETDEWEB)

    Roy, Amitava, E-mail: reroy@lsu.edu [J. Bennett Johnston, Sr., Center for Advanced Microstructures and Devices, Louisiana State University, Baton Rouge, LA 70806, USA (United States); Stegemann, Julia A., E-mail: j.stegemann@ucl.ac.uk [Centre for Resource Efficiency & the Environment, Department of Civil, Environmental & Geomatic Engineering, University College London, Chadwick Building, Gower Street, London WC1E 6BT, UK (United Kingdom)

    2017-01-05

    Highlights: • XAS shows the same Ni speciation in untreated and stabilized/solidified filtercake. • Ni solubility is the same for untreated and stabilized/solidified filtercake. • Leaching is controlled by pH and physical encapsulation for all binders. - Abstract: Cement-based stabilization/solidification (S/S) is used to decrease environmental leaching of contaminants from industrial wastes. In this study, two industrial metal treatment filtercakes were characterized by X-ray diffractometry (XRD), thermogravimetric and differential thermogravimetric analysis (TG/DTG) and Fourier transform infrared (FTIR); speciation of nickel was examined by X-ray absorption (XAS) spectroscopy. Although the degree of carbonation and crystallinity of the two untreated filtercakes differed, α-nickel hydroxide was identified as the primary nickel-containing phase by XRD and nickel K edge XAS. XAS showed that the speciation of nickel in the filtercake was unaltered by treatment with any of five different S/S binder systems. Nickel leaching from the untreated filtercakes and all their stabilized/solidified products, as a function of pH in the acid neutralization capacity test, was essentially complete below pH ∼5, but was 3–4 orders of magnitude lower at pH 8–12. S/S does not respeciate nickel from metal treatment filtercakes and any reduction of nickel leaching by S/S is attributable to pH control and physical mechanisms only. pH-dependent leaching of Cr, Cu and Ni is similar for the wastes and s/s products, except that availability of Cr, Cu and Zn at decreased pH is reduced in matrices containing ground granulated blast furnace slag.

  5. Reduction mechanism of Ni2+ into Ni nanoparticles prepared from ...

    Indian Academy of Sciences (India)

    journal of. March 2009 physics pp. 577–586. Reduction mechanism of Ni2+ into Ni nanoparticles prepared from different precursors: Magnetic studies ... 2Department of Chemistry, Indian Institute of Technology, Kanpur 208 016, India ..... this work and Avanti, Analytical Chemistry Division, BARC for her help in cyclic.

  6. Charge density studies of 3 d metal (Ni/Cu) complexes with a non-innocent ligand

    Energy Technology Data Exchange (ETDEWEB)

    Chuang, Yu-Chun; Sheu, Chou-Fu; Lee, Gene-Hsiang; Chen, Yu-Sheng; Wang, Yu (NTU); (UC)

    2017-07-25

    High-resolution X-ray diffraction experiments and atom-specific X-ray absorption experiments are applied to investigate a series of square planar complexes with the non-innocent ligand of maleonitriledithiolate (mnt), [S2C2(CN)2]z-, containingM—S bonds. Four complexes of (PyH)z[M(mnt)2]z-, whereM= Ni or Cu,z= 2 or 1 and PyH+= C5NH6+, were studied in order to clarify whether such one-electron oxidation–reduction, [M(mnt)2]2-/[M(mnt)2]1-, is taking place at the metal or the ligand site. Combining the techniques of metalK-,L-edge and SK-edge X-ray absorption spectroscopy with high-resolution X-ray charge density studies, it is unambiguously demonstrated that the electron redox reaction is ligand based and metal based for Ni and Cu pairs, respectively. The bonding characters in terms of topological properties associated with the bond critical points are compared between the oxidized form [ML]-and the reduced form [ML]2-. In the case of Ni complexes, the formal oxidation state of Ni remains as Ni2+and each mnt ligand carries a 2- charge in [Ni(mnt)2]2-, but only one of the ligands is formally oxidized in [Ni(mnt)2]1-. In contrast, in the case of Cu complexes, the mnt remains as 2- in both complexes, but the formal oxidation states of the metal are Cu2+and Cu3+. Bond characterizations andd-orbital populations will be presented. The complementary results of XAS, XRD and DFT calculations will be discussed. The conclusion on the redox reactions in these

  7. Reactive Ni/Ti nanolaminates

    International Nuclear Information System (INIS)

    Adams, D. P.; Bai, M. M.; Rodriguez, M. A.; McDonald, J. P.; Jones, E. Jr.; Brewer, L.; Moore, J. J.

    2009-01-01

    Nickel/titanium nanolaminates fabricated by sputter deposition exhibited rapid, high-temperature synthesis. When heated locally, self-sustained reactions were produced in freestanding Ni/Ti multilayer foils characterized by average propagation speeds between ∼0.1 and 1.4 m/s. The speed of a propagating reaction front was affected by total foil thickness and bilayer thickness (layer periodicity). In contrast to previous work with compacted Ni-Ti powders, no preheating of Ni/Ti foils was required to maintain self-propagating reactions. High-temperature synthesis was also stimulated by rapid global heating demonstrating low ignition temperatures (T ig )∼300-400 deg. C for nanolaminates. Ignition temperature was influenced by bilayer thickness with more coarse laminate designs exhibiting increased T ig . Foils reacted in a vacuum apparatus developed either as single-phase B2 cubic NiTi (austenite) or as a mixed-phase structure that was composed of monoclinic B19 ' NiTi (martensite), hexagonal NiTi 2 , and B2 NiTi. Single-phase, cubic B2 NiTi generally formed when the initial bilayer thickness was made small.

  8. Importance of reduced sulfur for the equilibrium chemistry and kinetics of Fe(II), Co(II) and Ni(II) supplemented to semi-continuous stirred tank biogas reactors fed with stillage.

    Science.gov (United States)

    Shakeri Yekta, Sepehr; Lindmark, Amanda; Skyllberg, Ulf; Danielsson, Asa; Svensson, Bo H

    2014-03-30

    The objective of the present study was to assess major chemical reactions and chemical forms contributing to solubility and speciation of Fe(II), Co(II), and Ni(II) during anaerobic digestion of sulfur (S)-rich stillage in semi-continuous stirred tank biogas reactors (SCSTR). These metals are essential supplements for efficient and stable performance of stillage-fed SCSTR. In particular, the influence of reduced inorganic and organic S species on kinetics and thermodynamics of the metals and their partitioning between aqueous and solid phases were investigated. Solid phase S speciation was determined by use of S K-edge X-ray absorption near-edge spectroscopy. Results demonstrated that the solubility and speciation of supplemented Fe were controlled by precipitation of FeS(s) and formation of the aqueous complexes of Fe-sulfide and Fe-thiol. The relatively high solubility of Co (∼ 20% of total Co content) was attributed to the formation of compounds other than Co-sulfide and Co-thiol, presumably of microbial origin. Nickel had lower solubility than Co and its speciation was regulated by interactions with FeS(s) (e.g. co-precipitation, adsorption, and ion substitution) in addition to precipitation/dissolution of discrete NiS(s) phase and formation of aqueous Ni-sulfide complexes. Copyright © 2014 Elsevier B.V. All rights reserved.

  9. Bisamidate and mixed amine/amidate NiN2S2 complexes as models for nickel-containing acetyl coenzyme A synthase and superoxide dismutase: an experimental and computational study.

    Science.gov (United States)

    Mathrubootham, Vaidyanathan; Thomas, Jason; Staples, Richard; McCraken, John; Shearer, Jason; Hegg, Eric L

    2010-06-21

    The distal nickel site of acetyl-CoA synthase (Ni(d)-ACS) and reduced nickel superoxide dismutase (Ni-SOD) display similar square-planar Ni(II)N(2)S(2) coordination environments. One difference between these two sites, however, is that the nickel ion in Ni-SOD contains a mixed amine/amidate coordination motif while the Ni(d) site in Ni-ACS contains a bisamidate coordination motif. To provide insight into the consequences of the different coordination environments on the properties of the Ni ions, we systematically examined two square-planar Ni(II)N(2)S(2) complexes, one with bisthiolate-bisamidate ligation (Et(4)N)(2)(Ni(L1)).2H(2)O (2) [H(4)L1 = N-(2-mercaptoacetyl)-N'-(2-mercaptoethyl)glycinamide] and another with bisthiolate-amine/amidate ligation K(Ni(HL2)) (3) [H(4)L2 = N-(2''-mercaptoethyl)-2-((2'-mercaptoethyl)amino)acetamide]. Although these two complexes differ only by a single amine versus amidate ligand, their chemical properties are quite different. The stronger in-plane ligand field in the bisamidate complex (Ni(II)(L1))(2-) (2) results in an increase in the energies of the d --> d transitions and a considerably more negative oxidation potential. Furthermore, while the bisamidate complex (Ni(II)(L1))(2-) (2) readily forms a trinuclear species (Et(4)N)(2)({Ni(L1)}(2)Ni).H(2)O (1) and reacts rapidly with O(2), presumably via sulfoxidation, the mixed amine/amidate complex (Ni(II)(HL2))(-) (3) remains monomeric and is stable for days in air. Interestingly, the Ni(III) species of the bisamidate complex formed by chemical oxidation with I(2) can be detected by electron paramagnetic resonance (EPR) spectroscopy while the mixed amine/amidate complex immediately decomposes upon oxidation. To explain these experimentally observed properties, we performed S K-edge X-ray absorption spectroscopy and low-temperature (77 K) electronic absorption measurements as well as both hybrid density functional theory (hybrid-DFT) and spectroscopy oriented configuration

  10. Hydrostatic pressure effects on the {gamma}-X conduction band mixing and the binding energy of a donor impurity in GaAs-Ga{sub 1-x}Al{sub x}As quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Duque, C.A. [Instituto de Fisica, Universidad de Antioquia, AA 1226, Medellin (Colombia); Lopez, S.Y. [Facultad de Educacion, Universidad de Antioquia, AA 1226, Medellin (Colombia); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autonoma del Estado de Morelos, Av. Universidad 1001, C.P. 62210, Cuernavaca (Mexico)

    2007-06-15

    Mixing between {gamma} and X valleys of the conduction band in GaAs-Ga{sub 1-x}Al{sub x}As quantum wells is investigated taken into account the effect of applied hydrostatic pressure. This effect is introduced via the pressure-dependent values of the corresponding energy gaps and the main band parameters. The mixing is considered along the lines of a phenomenological model. Variation of the confined ground state in the well as a function of the pressure is reported. The dependencies of the variationally calculated binding energy of a donor impurity with the hydrostatic pressure and well width are also presented. It is shown that the inclusion of the {gamma}-X mixing explains the non-linear behavior in the photoluminescence peak of confined exciton states that has been observed for pressures above 20 kbar. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Excitations of the unstable nuclei 48Ni and 49Ni

    International Nuclear Information System (INIS)

    Kamerdzhiev, S.P.; Tselyaev, V.I.

    2002-01-01

    The isoscalar E1 and E2 resonances in the proton-rich nuclei 48,49 Ni and the {f 7/2 x3 - } multiplet in 49 Ni have been calculated taking into account the single-particle continuum exactly. The analogous calculations for the mirror nuclei 48 Ca and 49 Sc are presented. The models used are the continuum random-phase approximation (RPA) for 48 Ni, 48 Ca and the odd RPA for 49 Ni, 49 Sc, where the latter has been developed recently and describes both single particle and collective excitations of an odd nucleus on a common basis. In all four nuclei, we obtained a distinct splitting of the isoscalar E1 resonance into 1(ℎ/2π)ω and 3(ℎ/2π)ω peaks at about 11 MeV and 30 MeV, respectively. The main part of the isoscalar E1 energy-weighted sum rule (EWSR) is exhausted by the 3(ℎ/2π)ω resonances. The 1(ℎ/2π)ω resonances exhaust about 35% of this EWSR in 48,49 Ni and about 22% in 48 Ca and 49 Sc. All seven {f 7/2 x3 - } multiplet members in 49 Ni are calculated to be in the 6-8 MeV energy region and have noticeable escape widths

  12. Nitriding behavior of Ni and Ni-based binary alloys

    Energy Technology Data Exchange (ETDEWEB)

    Fonovic, Matej

    2015-01-15

    Gaseous nitriding is a prominent thermochemical surface treatment process which can improve various properties of metallic materials such as mechanical, tribological and/or corrosion properties. This process is predominantly performed by applying NH{sub 3}+H{sub 2} containing gas atmospheres serving as the nitrogen donating medium at temperatures between 673 K and 873 K (400 C and 600 C). NH{sub 3} decomposes at the surface of the metallic specimen and nitrogen diffuses into the surface adjacent region of the specimen whereas hydrogen remains in the gas atmosphere. One of the most important parameters characterizing a gaseous nitriding process is the so-called nitriding potential (r{sub N}) which determines the chemical potential of nitrogen provided by the gas phase. The nitriding potential is defined as r{sub N} = p{sub NH{sub 3}}/p{sub H{sub 2}{sup 3/2}} where p{sub NH{sub 3}} and p{sub H{sub 2}} are the partial pressures of the NH{sub 3} and H{sub 2} in the nitriding atmosphere. In contrast with nitriding of α-Fe where the nitriding potential is usually in the range between 0.01 and 1 atm{sup -1/2}, nitriding of Ni and Ni-based alloys requires employing nitriding potentials higher than 100 atm{sup -1/2} and even up to ∞ (nitriding in pure NH{sub 3} atmosphere). This behavior is compatible with decreased thermodynamic stability of the 3d-metal nitrides with increasing atomic number. Depending on the nitriding conditions (temperature, nitriding potential and treatment time), different phases are formed at the surface of the Ni-based alloys. By applying very high nitriding potential, formation of hexagonal Ni{sub 3}N at the surface of the specimen (known as external nitriding) leads to the development of a compound layer, which may improve tribological properties. Underneath the Ni{sub 3}N compound layer, two possibilities exist: (i) alloying element precipitation within the nitrided zone (known as internal nitriding) and/or (ii) development of metastable and

  13. 111Cd PAC Study of Gd-Ni Intermetallic Compounds

    International Nuclear Information System (INIS)

    Presa, P. de la; Forker, M.

    2004-01-01

    This paper presents a perturbed angular correlation study of the magnetic and electric hyperfine interactions of 111 Cd on Gd sites of the Gd-Ni intermetallic compounds GdNi, GdNi 2 , GdNi 3 , Gd 2 Ni 7 , GdNi 5 and Gd 2 Ni 17 .

  14. Measurement of 59Ni and 63Ni by accelerator mass spectrometry at CIAE

    Science.gov (United States)

    Wang, Xiaoming; He, Ming; Ruan, Xiangdong; Xu, Yongning; Shen, Hongtao; Du, Liang; Xiao, Caijin; Dong, Kejun; Jiang, Shan; Yang, Xuran; Lan, Xiaoxi; Wu, Shaoyong; Zhao, Qingzhang; Cai, Li; Pang, Fangfang

    2015-10-01

    The long lived isotopes 59Ni and 63Ni can be used in many areas such as radioactive waste management, neutron dosimetry, cosmic radiation study, and so on. Based on the large accelerator and a big Q3D magnetic spectrometer, the measurement method for 59Ni and 63Ni is under development at the AMS facility at China Institute of Atomic Energy (CIAE). By using the ΔE-Q3D technique with the Q3D magnetic spectrometer, the isobaric interferences were greatly reduced in the measurements of 59Ni and 63Ni. A four anode gas ionization chamber was then used to further identify isobars. With these techniques, the abundance sensitivities of 59Ni and 63Ni measurements are determined as 59Ni/Ni = 1 × 10-13 and 63Ni/Ni = 2 × 10-12, respectively.

  15. Measurement of {sup 59}Ni and {sup 63}Ni by accelerator mass spectrometry at CIAE

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiaoming [China Institute of Atomic Energy, P.O. Box 275(50), Beijing 102413 (China); He, Ming, E-mail: minghe@ciae.ac.cn [China Institute of Atomic Energy, P.O. Box 275(50), Beijing 102413 (China); Ruan, Xiangdong [College of Physics and Technology, Guangxi University, Nanning 530004 (China); Xu, Yongning [China Institute of Atomic Energy, P.O. Box 275(50), Beijing 102413 (China); Shen, Hongtao [College of Physics and Technology, Guangxi Normal University, Guilin 541004 (China); Du, Liang; Xiao, Caijin; Dong, Kejun; Jiang, Shan; Yang, Xuran [China Institute of Atomic Energy, P.O. Box 275(50), Beijing 102413 (China); Lan, Xiaoxi [College of Physics and Technology, Guangxi University, Nanning 530004 (China); Wu, Shaoyong; Zhao, Qingzhang [China Institute of Atomic Energy, P.O. Box 275(50), Beijing 102413 (China); Cai, Li [College of Physics and Technology, Guangxi University, Nanning 530004 (China); Pang, Fangfang [College of Physics and Technology, Guangxi Normal University, Guilin 541004 (China)

    2015-10-15

    The long lived isotopes {sup 59}Ni and {sup 63}Ni can be used in many areas such as radioactive waste management, neutron dosimetry, cosmic radiation study, and so on. Based on the large accelerator and a big Q3D magnetic spectrometer, the measurement method for {sup 59}Ni and {sup 63}Ni is under development at the AMS facility at China Institute of Atomic Energy (CIAE). By using the ΔE-Q3D technique with the Q3D magnetic spectrometer, the isobaric interferences were greatly reduced in the measurements of {sup 59}Ni and {sup 63}Ni. A four anode gas ionization chamber was then used to further identify isobars. With these techniques, the abundance sensitivities of {sup 59}Ni and {sup 63}Ni measurements are determined as {sup 59}Ni/Ni = 1 × 10{sup −13} and {sup 63}Ni/Ni = 2 × 10{sup −12}, respectively.

  16. Ni4Ti3 precipitate structures in Ni-rich NiTi shape memory alloys

    Czech Academy of Sciences Publication Activity Database

    Holec, David; Bojda, Ondřej; Dlouhý, Antonín

    2008-01-01

    Roč. 481, Sp. Iss. (2008), s. 462-465 ISSN 0921-5093. [ESOMAT 2006. Bochum, 10.09.2006-15.09.2006] R&D Projects: GA ČR(CZ) GA106/05/0918 Institutional research plan: CEZ:AV0Z20410507 Keywords : NiTi shape memory alloys * Ni4Ti3 precipitates * Multi-step martensitic transformations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.806, year: 2008

  17. Relation between shape of Ni-particles and Ni migration in Ni-YSZ electrodes – a hypothesis

    DEFF Research Database (Denmark)

    Mogensen, Mogens Bjerg; Hauch, Anne; Sun, Xiufu

    2016-01-01

    pressure (pH2O) gradient as previously observed [1], but in the present cases Ni seems to migrate up the pH2O gradient. However, it is also observed that there is a preceding phase in this Ni-YSZ electrode degradation, namely that the Ni-particles closest to the YSZ electrolyte loose contact to each other......This is an attempt to explain a phenomenon of total depletion of Ni next to the electrolyte in Ni-YSZ cermet electrodes in solid oxide electrolysis cells during electrolysis at high current density/overpotential. Intuitively, we would think that Ni would always migrate down the steam partial...

  18. Hexanuclear [Ni6L12] metallacrown framework consisting of NiS4 square-planar and NiS5 square-pyramidal building blocks

    NARCIS (Netherlands)

    Angamuthu, R.; Kooijman, H.; Lutz, M.; Spek, A.L.; Bouwman, E.

    2007-01-01

    The hexanuclear [Ni6L12] (2) wheel-type cluster adopts an unusual structural motif whereby four NiS4 square-planar and two NiS5 square-pyramidal units are conjoined by edge sharing; the NiS5 units resemble the Ni centre of the inactive state in the [NiFe] hydrogenase.

  19. Superstructure of NiAs

    International Nuclear Information System (INIS)

    Nozue, Tatsuhiro; Kobayashi, Hisao; Kamimura, Takashi; Yamaguchi, Yasuo

    2001-01-01

    The structural transition in NiAs was studied by neutron diffraction on the single crystalline sample. The crystal structure of NiAs has been reported to be bottom-centered orthorhombic with Cmc2 1 symmetry (niccolite-type). The measurement of temperature dependence of the powder X-ray diffraction revealed that NiAs undergoes a structural transition to the NiAs-type at T t =335 K. In present neutron diffraction experiment at room temperature, we observed the reflections indexed on the basis of the orthorhombic unit cell. The intensities of these reflections are qualitatively explained in terms of the niccolite-type structure with taking account of three domain structures, except for the weak reflections indexed as (001), (003) and (012). Then, the intensities of (001), (002) and (004) reflections were measured in temperature range of 20 to 420 K. The temperature dependences of (002) and (004) reflections qualitatively agree with those of the calculated intensities using the atomic positions of niccolite-type structure. However, the temperature dependence of (001) reflection shows the anomaly around T t , which suggests the symmetry of crystal structure of NiAs is not the Cmc2 1 symmetry. (author)

  20. Giant magnetoimpedance effect in sputtered single layered NiFe film and meander NiFe/Cu/NiFe film

    International Nuclear Information System (INIS)

    Chen, L.; Zhou, Y.; Lei, C.; Zhou, Z.M.; Ding, W.

    2010-01-01

    Giant magnetoimpedance (GMI) effect on NiFe thin film is very promising due to its application in developing the magnetic field sensors with highly sensitivity and low cost. In this paper, the single layered NiFe thin film and NiFe/Cu/NiFe thin film with a meander structure are prepared by the MEMS technology. The influences of sputtering parameters, film structure and conductor layer width on GMI effect in NiFe single layer and meander NiFe/Cu/NiFe film are investigated. Maximum of the GMI ratio in single layer and sandwich film is 5% and 64%, respectively. The results obtained are useful for developing the high-performance magnetic sensors based on NiFe thin film.

  1. The Ni-YSZ interface

    DEFF Research Database (Denmark)

    Jensen, Karin Vels

    content (99.8% Ni and 99.995% Ni) were used to examine the impact of impurities on the polarisation resistance and contact area morphology. The electropolished nickel wires were pressed against a polished 8 mol% YSZ surface. Extensive structural changes from a flat interface to a hill and valley structure...... between polarised and non-polarised samples. With pure nickel wires, however, the microstructures depended on the polarisation/non-polarisation conditions. At non-polarised conditions a hill and valley type structure was found. Anodic polarisation produced an up to 1 μm thick interface layer consisting...... of nano-sized YSZ particles with some Ni present. At cathodic polarisation both a granulated structure and a hill and valley structure resembling the structure of non-polarised samples were found. Small impurity ridges were surrounding the contact areas on non-polarised and cathodically polarised samples...

  2. Umreti ni mogla stara Sibila

    Directory of Open Access Journals (Sweden)

    Matej Hriberšek

    2001-07-01

    Full Text Available Izid omenjene knjige prof. Jožeta Kastelica predstavlja še enega od dogodkov v sklopu proslave 200-letnice Prešernovega rojstva. Delo je nastalo na osnovi njegove (kot sam pravi »Že davno napisane in neobjavljene« doktorske disertacije, ki jo je za izdajo v knjižni obliki dopolnil in obogatil ne le vsebinsko, ampak tudi oblikovno. Naslov sam skriva v sebi globoko simboliko; na eni strani kaže na simbolično povezavo med Sibilo, ki ni mogla umreti prej, dokler se ni dotaknila prsti iz svoje domovine (zgodba je povzeta po Serviju in Prešernom kot prvim imenom slovenskega parnasa ter aludira na njuno nesmrtnost, po drugi pa že sam po sebi kaže na Prešernovo izjemno poznavanje antike.

  3. ni potni list

    Directory of Open Access Journals (Sweden)

    Ana Krajnc

    1996-12-01

    Full Text Available Decembra 1994 je bila v Rimu velika mednarodna konferenca o permanentnem ali vse življenje trajajočem izobraževanju. Široki strokovni javnosti sta bila takrat prvič predstavljena tudi dva nova pojma: osebni učni načrt in učni potni list. Pri priči sta se prijela v teoriji in praksi - očitno sta bila oba predloga odsev potreb.

  4. Submicron particles of Co, Ni and Co–Ni alloys

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 24; Issue 5. Submicron particles of Co, Ni and ... bulk values. The alloy particles follow a trend similar to the bulk alloys. ... G U Kulkarni1. Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560 064, India ...

  5. Revisiting El Niño Modokis

    Science.gov (United States)

    Marathe, Shamal; Ashok, Karumuri; Swapna, P.; Sabin, T. P.

    2015-12-01

    The suggestion that there exist two types of El Niño in the tropical Pacific has generated a debate in the community. Applying various linear and non-linear approaches and composite analysis technique on observed and reanalyzed climate datasets primarily for the 1950-2010 period, we revisit the variability of the tropical Pacific in the light of this debate. Our objective is to examine whether the proposed El Niño Modokis need a classification distinct from canonical El Niños. Even if the distinction is subject to short data records, we demonstrate that the El Niño Modoki events indeed display a seasonal evolution and teleconnections different from the canonical El Niños, and that the distinction is not subject to inclusion of the two extreme El Niños 1982 and 1997 as canonical El Niños. We show that the El Niño Modoki events are not an artifact associated with the orthogonality constraint associated with the EOF technique. Our cluster analysis shows that evolutions of the canonical El Niño and El Niño Modokis through various seasons differ from one another. Importantly, the dynamic and thermodynamic air-sea coupling strength is distinctly different between the El Niño Modoki and the canonical El Niño events. We find that, dynamic feedback intensity is stronger for El Niño Modoki (canonical El Niño) during boreal summer (winter); though the air-sea coupling strength, a major contributor to Bjerknes feedback, is maximum for Modokis during the developing stages, it decreases thereafter. In case of thermodynamic feedback intensity, SST-wind-evaporation feedback is dominant for El Niños while SST-SHF feedback is important during El Niño Modokis. However, we find that the thermodynamic feedback values significantly differ across the flux datasets.

  6. Laser alloyed Al-Ni-Fe coatings

    CSIR Research Space (South Africa)

    Pityana, SL

    2008-10-01

    Full Text Available The aim of this work was to produce crack-free thin surface layers consisting of binary (Al-Ni, Al-Fe) and ternary (Al-Ni-Fe) intermetallic phases by means of a high power laser beam. The laser surface alloying was carried out by melting Fe and Ni...

  7. A hybrid method using the widely-used WIEN2k and VASP codes to calculate the complete set of XAS/EELS edges in a hundred-atoms system.

    Science.gov (United States)

    Donval, Gaël; Moreau, Philippe; Danet, Julien; Larbi, Séverine Jouanneau-Si; Bayle-Guillemaud, Pascale; Boucher, Florent

    2017-01-04

    Most of the recent developments in EELS modelling has been focused on getting a better agreement with measurements. Less work however has been dedicated to bringing EELS calculations to larger structures that can more realistically describe actual systems. The purpose of this paper is to present a hybrid approach well adapted to calculating the whole set of localised EELS core-loss edges (at the XAS level of theory) on larger systems using only standard tools, namely the WIEN2k and VASP codes. We illustrate the usefulness of this method by applying it to a set of amorphous silicon structures in order to explain the flattening of the silicon L 2,3 EELS edge peak at the onset. We show that the peak flattening is actually caused by the collective contribution of each of the atoms to the average spectrum, as opposed to a flattening occurring on each individual spectrum. This method allowed us to reduce the execution time by a factor of 3 compared to a usual-carefully optimised-WIEN2k calculation. It provided even greater speed-ups on more complex systems (interfaces, ∼300 atoms) that will be presented in a future paper. This method is suited to calculate all the localized edges of all the atoms of a structure in a single calculation for light atoms as long as the core-hole effects can be neglected.

  8. Nanostructure analysis of friction welded Pd-Ni-P/Pd-Cu-Ni-P metallic glass interface

    International Nuclear Information System (INIS)

    Ohkubo, T.; Shoji, S.; Kawamura, Y.; Hono, K.

    2005-01-01

    Friction welded Pd 40 Ni 40 P 20 /Pd 40 Cu 30 Ni 10 P 20 metallic glass interface has been characterized by energy filtering transmission electron microscopy. The interface is fully amorphous with a gradual compositional change of Cu and Ni in the range of 30 nm. By annealing above T g , the interdiffusion of Cu and Ni progressed in the supercooled liquid region, and the crystallization occurred from the Pd 40 Ni 40 P 20 glass

  9. Characterization of Boroaluminosilicate Glass Surface Structures by B k-edge NEXAFS

    Energy Technology Data Exchange (ETDEWEB)

    R Schaut; R Lobello; K Mueller; C Pantano

    2011-12-31

    Techniques traditionally used to characterize bulk glass structure (NMR, IR, etc.) have improved significantly, but none provide direct measurement of local atomic coordination of glass surface species. Here, we used Near-Edge X-ray Absorption Fine Structure (NEXAFS) as a direct measure of atomic structure at multicomponent glass surfaces. Focusing on the local chemical structure of boron, we address technique-related issues of calibration, quantification, and interactions of the beam with the material. We demonstrate that beam-induced adsorption and structural damage can occur within the timeframe of typical measurements. The technique is then applied to the study of various fracture surfaces where it is shown that adsorption and reaction of water with boroaluminosilicate glass surfaces induces structural changes in the local coordination of boron, favoring B{sup IV} species after reaction.

  10. Doping and bond length contributions to Mn K-edge shift in La1 ...

    Indian Academy of Sciences (India)

    ... corresponds to the shift in the center of gravity of the unoccupied Mn 4-band contributing to the Mn K-absorption edge region. This correspondence is then used to separate the doping and size contributions to the edge shift due to variation in the number of electrons in valence band and Mn-O bond lengths, respectively, ...

  11. Demonstration of flash K-edge angiography utilizing gadolinium-based contrast medium

    Science.gov (United States)

    Sato, Eiichi; Sagae, Michiaki; Obara, Haruo; Germer, Rudolf; Tanaka, Etsuro; Mori, Hidezo; Kawai, Toshiaki; Ichimaru, Toshio; Sato, Shigehiro; Ojima, Hidenori; Takayama, Kazuhiro; Ido, Hideaki

    2005-03-01

    The high-voltage condensers in a polarity-inversion two-stage Marx surge generator are charged from -50 to -70 kV by a power supply, and the electric charges in the condensers are discharged to an x-ray tube after closing gap switches in the surge generator with a trigger device. The x-ray tube is a demountable diode, and the turbomolecular pump evacuates air from the tube with a pressure of approximately 1 mPa. Tungsten characteristic x rays can be produced, since the tube utilizes a disk cathode and a rod target, and bremsstrahlung rays are not emitted in the opposite direction to that of electron acceleration. At a charging voltage of -70 kV, the instantaneous tube voltage and current were 140 kV and 1.0 kA, respectively. The x-ray pulse widths were approximately 90 ns, and the estimated number of K photons was approximately 5×108 photons/cm2 per pulse at 0.5 m from the source of 3.0 mm in diameter.

  12. Doping and bond length contributions to Mn K-edge shift in La1 ...

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 70; Issue 2 ... Contributed papers Volume 70 Issue 2 February 2008 pp 359-366 ... School of Physics, Devi Ahilya University, Khandwa Road, Indore 452 017, India; Department of Physics, Institute of Science and Laboratory Education, IPS Academy, Indore 452 012, ...

  13. On the Minimum Number of Spanning Trees in k-Edge-Connected Graphs

    DEFF Research Database (Denmark)

    Ok, Seongmin; Thomassen, Carsten

    2017-01-01

    >2.75. Not surprisingly, c3 is smaller than the corresponding number for 4-edge-connected graphs. Examples show that c3≤ √2+√3≈1.93. However, we have no examples of 5-edge-connected graphs with fewer spanning trees than the n-cycle with all edge multiplicities (except one) equal to 3, which is almost 6-regular. We have...... no examples of 5-regular 5-edge-connected graphs with fewer than 3.09n-1 spanning trees, which is more than the corresponding number for 6-regular 6-edge-connected graphs. The analogous surprising phenomenon occurs for each higher odd edge connectivity and regularity....

  14. X-ray attenuation around K-edge of Zr, Nb, Mo and Pd: A ...

    Indian Academy of Sciences (India)

    coefficients with which the experimental values can be compared. The XCOM pack- age [24–26] is a very powerful and useful computer program and database which can be used to calculate, with a personal computer, photon cross-sections for scattering, photoelectric absorption and pair production. Total attenuation ...

  15. X-Ray Absorption in Carbon Ions Near the K-Edge

    Science.gov (United States)

    Hasoglu, M. F.; Abdel-Naby, Sh. A.; Nikolic, D.; Gorczyca, T. W.; McLaughlin, B. M.

    2007-06-01

    K-shell photoabsorption calculations are important for determining the elemental abundances of the interstellar medium (ISM) from observed X-ray absorption spectra. Previously, we performed reliable K-shell photoabsorption calculations for oxygen [1-3] and neon [4,5] ions. We have executed detailed R-matrix calculations for carbon ions, including Auger broadening, by using an optical potential, and relaxation effects, by using pseudoorbitals with the necessary pseudoresonance elimination. This work was funded by NASA's Astronomy Physics Research and Analysis (APRA) and Solar and Heliospheric Physics (SHP) Supporting Research and Technology (SR&T) programs. References: [1] T. W. Gorczyca and B. M. McLaughlin. J Phys. B. 33 L859 (2000) [2] A. M. Juett, et al., Astrophys. J. 612, 308 (2004) [3] J. Garcia et al., Astrophys. J. Supp. S. 158, 68 (2005) [4] T. W. Gorczyca., Phys. Rev. A. 61, 024702 (2000) [5] A. M. Juett, et al., Astrophys. J. 648, 1066 (2006)

  16. Polarized Cu K edge XANES spectra of CuO - theory and experiment

    Czech Academy of Sciences Publication Activity Database

    Šipr, Ondřej; Šimůnek, Antonín; Bocharov, S.; Kirchner, T.; Dräger, G.

    2001-01-01

    Roč. 8, - (2001), s. 235-237 ISSN 0909-0495 R&D Projects: GA ČR GA202/99/0404 Institutional research plan: CEZ:A02/98:Z1-010-914 Keywords : polarized Cu K XANES * CuO Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.519, year: 2001

  17. Chemical shift of Mn and Cr K-edges in X-ray absorption ...

    Indian Academy of Sciences (India)

    increases, since the metal atom transforms to a positive ion while participating in the formation of a chemical bond and this energy shift ( E) increases with an increase in the oxi- dation state or positive charge on the metal ions. Thus, as the valency ... the bond, electronegativity of the anion etc or in other words, the chemical ...

  18. Electronic structure effects on B K-edge XANES of minerals

    Czech Academy of Sciences Publication Activity Database

    Šipr, Ondřej; Rocca, F.

    2010-01-01

    Roč. 17, č. 3 (2010), s. 367-373 ISSN 0909-0495 R&D Projects: GA ČR GA202/08/0106 Institutional research plan: CEZ:AV0Z10100521 Keywords : structure * potentials * boron Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.335, year: 2010

  19. X-ray attenuation around K-edge of Zr, Nb, Mo and Pd: A ...

    Indian Academy of Sciences (India)

    The measurements were carried out at the and energy values of the target elements by two techniques: (1) Proton-induced X-ray emission (PIXE) and (2) 241Am (300 mCi) source. In PIXE, 2 MeV proton-excited X-rays were detected by a Si(Li) detector. In the second case, X-rays excited by 59.54 keV photons from ...

  20. Determination of Cr(VI) in wood specimen: A XANES study at the Cr K edge

    International Nuclear Information System (INIS)

    Strub, E.; Plarre, R.; Radtke, M.; Reinholz, U.; Riesemeier, H.; Schoknecht, U.; Urban, K.; Juengel, P.

    2008-01-01

    The content of chromium in different oxidation states in chromium-treated wood was studied with XANES (X-ray absorption near-edge structure) measurements at the Cr K absorption edge. It could be shown that wood samples treated with Cr(VI) (pine and beech) did still contain a measurable content of Cr(VI) after four weeks conditioning. If such wood samples were heat exposed for 2 h with 135 deg. C prior conditioning, Cr(VI) was no longer detected by XANES, indicating a complete reduction to chromium (III)

  1. Ca and S K-edge XANES studies of calcite-acid mine water interactions

    Energy Technology Data Exchange (ETDEWEB)

    Myneni, S.C.B.; Perera, R.C.C. [Lawrence Berkeley National Lab., CA (United States)

    1997-04-01

    Heavy metal-rich acidic waters (SO{sub 4}{sup 2{minus}}, AsO{sub 4}{sup 3{minus}}, SeO{sub 4}{sup 2{minus}}, Fe{sup 2+}, Fe{sup 3+}, Al{sup 3+}, Cu{sup 2+}, Zn{sup 2+}, Cd{sup 2+}) and related ochreous coatings are common around abandoned sulfide and coal mine sites. This is mainly caused by the natural weathering of pyrite (FeS{sub 2}), arsenopyrite (FeAsS), and other metal sulfide containing shales. Acid generation in the case of pyrite can be explained by a general reaction: FeS{sub 2} + 3.5 O{sub 2} + H{sub 2}O {leftrightarrow} Fe{sup 2+} + SO{sub 4}{sup 2{minus}} + 2H{sup +}. Also, these low pH waters interact with the soils, and mobilize their soluble elements. One of the common remediation strategies is to allow these acid waters to react with limestone (CaCO{sub 3}-rich rock) and neutralize the pH and precipitate out soluble metals. Yet, the associated problem is the precipitation of Fe and Al oxides and hydroxy sulfate coatings on limestone surfaces, which block calcite reactive sites, and make them ineffective a few hours after initiation of treatment. The main objectives of this research are to examine: (1) the chemistry of limestone surface coatings, and (2) their toxic metal uptake and the conditions that inhibit their formation. Previous molecular studies using X-ray diffraction, and vibrational spectroscopy on limestone surface coatings (sampled from Athens, OH) indicate that the surface-most layer (the layer in contact with water) is composed of schwertmannite (Fe(III)-hydroxy sulfate) like phases. However, white, X-ray amorphous; Al-, sulfate- and carbonate-rich; and Ca-poor phases appeared at the interface between the limestone and the iron oxide coatings. The structure, morphology, and coordination chemistry of component major and trace elements of these white precipitate phases have not previously been examined.

  2. Spatially resolved sulfur K-edge XANES spectroscopy of wheat leaves infected by Puccinia triticina

    Energy Technology Data Exchange (ETDEWEB)

    Lichtenberg, H; Prange, A; Hormes, J [CAMD, Louisiana State University, 6980 Jefferson Hwy, Baton Rouge, LA 70806 (United States); Steiner, U; Oerke, E-C, E-mail: lichtenberg@lsu.ed [INRES-Phytomedicine, University of Bonn, Nussallee 9, 53115 Bonn (Germany)

    2009-11-15

    In this study, wheat leaves infected with brown rust, a plant disease of serious economic concern caused by the fungus Puccinia triticina, were investigated using spatially resolved XANES (X-ray Absorption Near Edge Structure) spectroscopy at the sulfur K-absorption edge.

  3. Chemical shift of Mn and Cr K-edges in X-ray absorption ...

    Indian Academy of Sciences (India)

    ... but different anions or ligands show the effect of different chemical environments surrounding the cations in determining their X-ray absorption edges in the above compounds. The above chemical effect has been quantitatively described by determining the effective charges on Mn and Cr cations in the above compounds.

  4. Niños investigadores

    OpenAIRE

    Manfred Liebel

    2007-01-01

    EN LA SOCIOLOGÍA INFANTIL, EL PRINCIPIO DE HACER PARTICIPAR A NIÑAS Y NIÑOS en los procesos de investigación está ampliamente reconocido. Tomando como punto de partida ese principio de participación, el presente aporte analiza la pregunta de en qué medida y de qué manera los niños mismos pueden actuar como investigadores. A fin de apreciar en lo justo la perspectiva de los niños, el presente trabajo aboga por que –con el debido acompañamiento de personas adultas– la investigación esté en mano...

  5. Flowsheet for 63Ni production

    International Nuclear Information System (INIS)

    Williams, D.F.; Knauer, J.B.; O'Kelley, G.D.; Wiggins, J.T.; Porter, C.E.

    1992-01-01

    The production of large quantities of high specific activity 63 Ni (>10Ci/g) requires both a highly enriched 62 Ni target and a long irradiation period at high neutron flux. Trace impurities in the nickel and associated target materials are also activated and account for a significant fraction of the discharged activity and essentially all of the gamma activity. While most of these undesirable activation products (mainly transition metals) can be easily removed as chloride complexes during anion exchange, chromium, present as 51 Cr, and manganese, present as 54 Mn, are exceptions and require solvent extraction of the in-cell product to achieve the desired purity. In addition to summarizing the current development and production experience, optimized flowsheets are discussed

  6. niños preescolares

    Directory of Open Access Journals (Sweden)

    Claudia Rosario Portilla Ramírez

    2007-01-01

    Full Text Available Este estudio explora la relación entre la escritura y la comprensión de la referencia a través de una tarea de sinonimia en niños entre 5 y 6 años de edad, de origen latinoamericano, escolarizados en Barcelona (España. Las variables relacionadas con la tarea de sinonimia fueron (a la comprensión de la entidad lingüística nombre y (b el nivel de conceptualización de la escritura de los niños y la presencia de etiquetas escritas durante la tarea. Para la tarea de sinonimia se utilizaron pares de sinónimos dialectales del español (de Latinoamérica y de la Península Ibérica. Los resultados mostraron una diferenciación en el razonamiento de los niños, la cual dependía de la comparación entre lenguaje oral y lenguaje escrito en el desarrollo de la tarea, evidenciando una mayor aceptación de la sinonimia en la modalidad de lenguaje oral que en la modalidad de lenguaje escrito.

  7. Exclusive study of Ni+Ni and Ni+Au central collisions: phase coexistence and spinodal decomposition; Etude exclusive des collisions centrales Ni+Ni et Ni+Au: coexistence de phase et decomposition spinodale

    Energy Technology Data Exchange (ETDEWEB)

    Guiot, B

    2002-12-01

    The INDRA multidetector allowed us to study the Ni+Ni collisions at 32A MeV and the Ni+Au collisions at 52,4 MeV. Central collisions leading to 'quasi-fused' systems were isolated using multidimensional analysis techniques: the Discriminant Analysis and the Principal Component Analysis. Comparison with a statistical model shows that the selected events are compatible with thermodynamical equilibrium. The average thermal excitation energy is 5A MeV for both systems. Calculations of heat capacities show that the deexcitation of the hot sources are akin to a liquid-gas phase transition of nuclear matter. Indeed heat capacities exhibit a negative branch as expected for a phase transition of a finite system. The dynamics of this phase transition has been investigated by applying the charge correlation method. An enhanced production of events with equal-sized fragments has been evidenced for Ni+Au at 52A MeV. No signal was found for Ni+Ni at 32A MeV. Finally this method was improved by taking into account the total charge conservation. The signal is seen more clearly for Ni+Au at 52A MeV, but is ambiguous for Ni+Ni at 32A MeV. The path followed in the state diagram, or the involved time scales, seem to be different for these systems. (authors)

  8. Processing and Mechanical Properties of Directionally Solidified NiAl/NiAlTa Alloys

    Science.gov (United States)

    Johnson, D. R.; Oliver, B. F.; Noebe, R. D.; Whittenberger, J. D.

    1994-01-01

    Promising creep strengths were found for a directionally solidified NiAl-NiAlTa alloy when compared to other NiAl based intermetallics. The directionally solidified alloy had an off-eutectic composition that resulted in microstructures consisting of NiAl dendrites surrounded by aligned eutectic regions. The room temperature toughness of the two phase alloy was similar to that of polycrystalline NiAl even with the presence of the brittle Laves phase NiAlTa. Alloying additions that may improve the room temperature toughness by producing multiphase alloys are discussed.

  9. Transparent nanostructured electrodes: Electrospun NiO nanofibers/NiO films

    Energy Technology Data Exchange (ETDEWEB)

    Lamastra, F.R. [Italian Interuniversity Consortium on Materials Science and Technology (INSTM), Research Unit Roma Tor Vergata, Via del Politecnico 1, 00133 Rome (Italy); Nanni, F. [Italian Interuniversity Consortium on Materials Science and Technology (INSTM), Research Unit Roma Tor Vergata, Via del Politecnico 1, 00133 Rome (Italy); Department of Enterprise Engineering, University of Rome Tor Vergata, Via del Politecnico 1, 00133 Rome (Italy); Menchini, F. [ENEA, CR Casaccia, Via Anguillarese 301, 00123 Rome (Italy); Nunziante, P. [Italian Interuniversity Consortium on Materials Science and Technology (INSTM), Research Unit Roma Tor Vergata, Via del Politecnico 1, 00133 Rome (Italy); Department of Chemical Sciences and Technologies, University of Rome Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome (Italy); Grilli, M.L., E-mail: marialuisa.grilli@enea.it [ENEA, CR Casaccia, Via Anguillarese 301, 00123 Rome (Italy)

    2016-02-29

    Polyvinylpyrrolidone (PVP)/nickel(II) acetate precursor fibers were deposited by electrospinning directly on radio frequency sputtered thin Ni and NiO films grown on quartz substrate, starting from Ni(II) acetate and PVP solution in ethanol. The samples were calcined in air in the temperature range 400–500 °C to obtain transparent and conductive p-type NiO nanofibers on NiO films. A higher density of nanofibers was obtained on Ni/quartz substrates, as compared to NiO/quartz ones, demonstrating the feasibility of fiber adhesion directly to an insulating substrate previously coated by a thin Ni layer. Samples were characterized by field emission-scanning electron microscopy, X-ray diffraction, spectrophotometric and resistance measurements. - Highlights: • Nanostructured electrodes: electrospun NiO nanofibers/NiO films were fabricated. • NiO fibers were directly grown on insulating substrate coated by thin Ni or NiO films. • Good quality crystalline fibers were obtained at low calcination temperatures. • Transparent and conductive p-type electrodes were fabricated.

  10. Atomistic calculations of hydrogen interactions with Ni3Al grain boundaries and Ni/Ni3Al interfaces

    International Nuclear Information System (INIS)

    Baskes, M.I.; Angelo, J.E.; Moody, N.R.

    1995-01-01

    Embedded Atom Method (EAM) potentials have been developed for the Ni/Al/H system. The potentials have been fit to numerous properties of this system. For example, these potentials represent the structural and elastic properties of bulk Ni, Al, Ni 3 Al, and NiAl quite well. In addition the potentials describe the solution and migration behavior of hydrogen in both nickel and aluminum. A number of calculations using these potentials have been performed. It is found that hydrogen strongly prefers sites in Ni 3 Al that are surrounded by 6 Ni atoms. Calculations of the trapping of hydrogen to a number of grain boundaries in Ni 3 Al have been performed as a function of hydrogen chemical potential at room temperature. The failure of these bicrystals under tensile stress has been examined and will be compared to the failure of pure Ni 3 Al boundaries. Boundaries containing a preponderance of nickel are severely weakened by hydrogen. In order to investigate the potential embrittlement of γ/γ' alloys, trapping of hydrogen to a spherical Ni 3 Al precipate in nickel as a function of chemical potential at room temperature has been calculated. It appears that the boundary is not a strong trap for hydrogen, hence embrittlement in these alloys is not primarily due to interactions of hydrogen with the γ/γ interface

  11. Exclusive study of Ni+Ni and Ni+Au central collisions: phase coexistence and spinodal decomposition

    International Nuclear Information System (INIS)

    Guiot, B.

    2002-12-01

    The INDRA multidetector allowed us to study the Ni+Ni collisions at 32A MeV and the Ni+Au collisions at 52,4 MeV. Central collisions leading to 'quasi-fused' systems were isolated using multidimensional analysis techniques: the Discriminant Analysis and the Principal Component Analysis. Comparison with a statistical model shows that the selected events are compatible with thermodynamical equilibrium. The average thermal excitation energy is 5A MeV for both systems. Calculations of heat capacities show that the deexcitation of the hot sources are akin to a liquid-gas phase transition of nuclear matter. Indeed heat capacities exhibit a negative branch as expected for a phase transition of a finite system. The dynamics of this phase transition has been investigated by applying the charge correlation method. An enhanced production of events with equal-sized fragments has been evidenced for Ni+Au at 52A MeV. No signal was found for Ni+Ni at 32A MeV. Finally this method was improved by taking into account the total charge conservation. The signal is seen more clearly for Ni+Au at 52A MeV, but is ambiguous for Ni+Ni at 32A MeV. The path followed in the state diagram, or the involved time scales, seem to be different for these systems. (authors)

  12. Microstructural investigations of Ni and Ni2Al3 coatings exposed in biomass power plants

    DEFF Research Database (Denmark)

    Wu, D. L.; Dahl, K. V.; Christiansen, T. L.

    2018-01-01

    temperature pack cementation. After exposure, microstructural investigations were performed by light optical and electron microscopy (SEM-EDS). Electroplated Ni coatings were not protective in straw firing power plants and exhibited similar corrosion morphology as uncoated tubes. For Ni2Al3 coatings......The present work investigates the corrosion resistance of Ni and Ni2Al3 coated austenitic stainless steel (TP347H) tubes, which were exposed in a biomass-fired boiler with an outlet steam temperature of 540 °C for 6757 h. The Ni2Al3 coating was produced by electroplating Ni followed by low......, the nickel aluminide layer was no longer adherent to the tube and was only found within the deposit. However, Ni2Al3 coatings had provided some protection compared to uncoated and Ni coated tubes. The formation of nickel chloride binds aggressive chlorine and slows down the active oxidation mechanism...

  13. Analisis Interferensi dalam Kelas Kata Keishiki Meishi Khususnya Penggunaan Tame Ni dan You Ni

    Directory of Open Access Journals (Sweden)

    Nalti Novianti

    2008-05-01

    Full Text Available Article aimed to find out the amount of interference in the translation using tame ni and you ni. The research used analysis description. Data were taken by giving a test to 20 student from the Japanese Department, Bina Nusantara University. The result showed that there is some interference in the exercises in the test given to the respondents. It is concluded that the interference occurs because many students do not understand the differences in using tame ni anda you ni.

  14. Formation enthalpy of NiBe and Ni5Be21

    International Nuclear Information System (INIS)

    Ivanov, M.I.; Karpova, T.F.; Dalago, N.Yu.

    1981-01-01

    The method of dissolution calorimetry is used to determine standard enthalpies of NiBe and Ni 5 Be 21 formation, which are 84.8+-2.2 and (-669+-37)kJ/mol. The enthalpy values of NiBe and Ni 5 Be 21 at 331 K are shown to coincide (within the limits of errors of these values) with the values at the standard temperature of 298.15 K [ru

  15. The Ni-Al-Hf Multiphase Diffusion

    Directory of Open Access Journals (Sweden)

    Romanowska J.

    2016-06-01

    Full Text Available The generalized Darken method was applied to simulate the diffusion between γ-Ni| γ’-Ni3Al and γ’-Ni3Al|β-NiAl interfaces. The results of calculations were compared with the experimental concentration’s profiles of nickel, aluminum and hafnium in aluminide and hafnium doped aluminide coatings deposited by the CVD and PVD methods on pure nickel. The method deals with the Wagner’s integral diffusion coefficients and thermodynamic data - activities of components. The experimental results agree with the simulated ones.

  16. Probing The Electrode/Electrolyte Interface in The Lithium Excess Layered Oxide Li1.2Ni0.2Mn0.6O2

    Energy Technology Data Exchange (ETDEWEB)

    Carroll, Kyler J [University of California, San Diego; Qian, Danna [University of California, San Diego; Fell, Chris [University of Florida, Gainesville; Calvin, Scott [Sarah Lawrence College; Veith, Gabriel M [ORNL; Chi, Miaofang [ORNL; Dudney, Nancy J [ORNL; Meng, Ying Shirley [University of California, San Diego

    2013-01-01

    A detailed surface investigation of the lithium-excess nickel manganese layered oxide Li1.2Ni0.2Mn0.6O2 structure was carried out using x-ray photoelectron spectroscopy (XPS), total electron yield and transmission x-ray absorption spectroscopy (XAS), and electron energy loss spectroscopy (EELS) during the first two electrochemical cycles. All spectroscopy techniques consistently showed the presence of Mn4+ in the pristine material and a surprising reduction of Mn at the voltage plateau during the first charge. The Mn reduction is accompanied by the oxygen loss revealed by EELS. Upon the first discharge, the Mn at the surface never fully returns back to Mn4+. The electrode/electrolyte interface of this compound consists of the reduced Mn at the crystalline defect-spinel inner layer and an oxidized Mn species simultaneously with the presence of a superoxide species in amorphous outer layer. This proposed model signifies that oxygen vacancy formation and lithium removal result in electrolyte decomposition and superoxide formation, leading to Mn activation/dissolution and surface layer-spinel phase transformation. The results also indicate that the role of oxygen is complex and significant in contributing to the extra capacity of this class of high energy density cathode materials.

  17. Effects of Ni vacancy, Ni antisite, Cr and Pt on the third-order elastic constants and mechanical properties of NiAl

    KAUST Repository

    Wu, Shaohua

    2014-12-01

    Effects of Ni vacancy, Ni antisite in Al sublattice, Cr in Al sublattice, Pt in Ni sublattice on the second-order elastic constants (SOECs) and third-order elastic constants (TOECs) of the B2 NiAl have been investigated using the first-principles methods. Lattice constant and the SOECs of NiAl are in good agreement with the previous results. The brittle/ductile transition map based on Pugh ratio G/B and Cauchy pressure Pc shows that Ni antisite, Cr, Pt and pressure can improve the ductility of NiAl, respectively. Ni vacancy and lower pressure can enhance the Vickers hardness Hv of NiAl. The density of states (DOS) and the charge density difference are also used to analysis the effects of vacancy, Ni antisite, Cr and Pt on the mechanical properties of NiAl, and the results are in consistent with the transition map. © 2014 Elsevier Ltd. All rights reserved.

  18. Contexto Familiar: Diferencias Conductuales entre Niños y Niñas

    Directory of Open Access Journals (Sweden)

    María Aurelia Ramírez Castillo

    2005-01-01

    Full Text Available En este trabajo se investigan las diferencias por género en problemas de conducta. En una muestra de 200 sujetos (niños y niñas en tre 5 y 18 años de Granada (España, los resultados concluyen que los niños tienen más problemas de conducta delictiva que las niñas. Cuando existen conflictos matrimoniales y prácticas de crianza negativas, de nuevo los niños tienen más problemas externos que las niñas. En este trabajo se investigan las diferencias por género en problemas de conducta. En una muestra de 200 sujetos (niños y niñas en tre 5 y 18 años de Granada (España, los resultados concluyen que los niños tienen más problemas de conducta delictiva que las niñas. Cuando existen conflictos matrimoniales y prácticas de crianza negativas, de nuevo los niños tienen más problemas externos que las niñas.

  19. Porous NiTi shape memory alloys produced by SHS: microstructure and biocompatibility in comparison with Ti2Ni and TiNi3.

    Science.gov (United States)

    Bassani, Paola; Panseri, Silvia; Ruffini, Andrea; Montesi, Monica; Ghetti, Martina; Zanotti, Claudio; Tampieri, Anna; Tuissi, Ausonio

    2014-10-01

    Shape memory alloys based on NiTi have found their main applications in manufacturing of new biomedical devices mainly in surgery tools, stents and orthopedics. Porous NiTi can exhibit an engineering elastic modulus comparable to that of cortical bone (12-17 GPa). This condition, combined with proper pore size, allows good osteointegration. Open cells porous NiTi was produced by self propagating high temperature synthesis (SHS), starting from Ni and Ti mixed powders. The main NiTi phase is formed during SHS together with other Ni-Ti compounds. The biocompatibility of such material was investigated by single culture experiment and ionic release on small specimen. In particular, NiTi and porous NiTi were evaluated together with elemental Ti and Ni reference metals and the two intermetallic TiNi3, Ti2Ni phases. This approach permitted to clearly identify the influence of secondary phases in porous NiTi materials and relation with Ni-ion release. The results indicated, apart the well-known high toxicity of Ni, also toxicity of TiNi3, whilst phases with higher Ti content showed high biocompatibility. A slightly reduced biocompatibility of porous NiTi was ascribed to combined effect of TiNi3 presence and topography that requires higher effort for the cells to adapt to the surface.

  20. Dynamic recovery in nanocrystalline Ni

    International Nuclear Information System (INIS)

    Sun, Z.; Van Petegem, S.; Cervellino, A.; Durst, K.; Blum, W.; Van Swygenhoven, H.

    2015-01-01

    The constant flow stress reached during uniaxial deformation of electrodeposited nanocrystalline Ni reflects a quasi-stationary balance between dislocation slip and grain boundary (GB) accommodation mechanisms. Stress reduction tests allow to suppress dislocation slip and bring recovery mechanisms into the foreground. When combined with in situ X-ray diffraction it can be shown that grain boundary recovery mechanisms play an important role in producing plastic strain while hardening the microstructure. This result has a significant consequence for the parameters of thermally activated glide of dislocations, such as athermal stress and activation volume, which are traditionally derived from stress/strain rate change tests

  1. Morphological control of Ni/NiO core/shell nanoparticles and production of hollow NiO nanostructures

    International Nuclear Information System (INIS)

    Chopra, Nitin; Claypoole, Leslie; Bachas, Leonidas G.

    2010-01-01

    Chemical synthesis coupled with a microwave irradiation process allowed for the control of size (6-40 nm), shape, and shell thickness of Ni/NiO core/shell nanoparticles. In this unique synthetic route, the size of Ni nanoparticles (NiNPs) was strongly influenced by the nickel salt-to-stabilizer ratio and the amount of the stabilizer. Interestingly, it was observed that the shape of the nanoparticles was altered by varying the reaction time, where longer reaction times resulted in annealing effects and rupture of the stabilizer micelle leading to distinct shapes of Ni/NiO core/shell nanostructures. Product cooling rate was another important parameter identified in this study that not only affected the shape, but also the crystal structure of the core/shell nanoparticles. In addition, a simple and cost-effective method of microwave irradiation of NiNPs led to the formation of distinctly shaped hollow NiO nanoparticles. These high surface area core/shell nanoparticles with well-controlled morphologies are important and can lead to significant advancement in the design of improved fuel cells, electrochromic display devices, and catalysis systems.

  2. .';.:NI~

    African Journals Online (AJOL)

    He mentions, inter alia, the share he had in the passing of Defence Act no 44 of 1957 and expresses his gratitude to God for saving his life and allowing him to ...... gevolg dat vier van ons seniors, brigadiers rang behou het. Een offisier, wat betreklik junior was voor die oorlog, is ook brigadiersrang toegeken, sodat hy in een ...

  3. Estilos de vida saludables de niños, niñas y adolescentes

    OpenAIRE

    Lilia Campo-Ternera; Yaneth Herazo-Beltrán; Floralinda García-Puello; Mariela Suarez-Villa; Orlando Méndez; Francisco Vásquez-De la Hoz

    2017-01-01

    Objetivo: Describir los estilos de vida saludables de niños, niñas y adolescentes de Barranquilla. Materiales y métodos: Estudio descriptivo de corte transversal en 991 niños, niñas y ado - lescentes. Se evaluó la actividad física mediante los cuestionarios de Actividad Física para Adolescentes y para niños escolares; se aplicó una encuesta que midió los conocimientos y prácticas de los escolares sobre salud bucal, lavado de manos, consumo de frutas y verduras y ...

  4. Creatividad en niños superdotados

    OpenAIRE

    González Román, María del Pilar

    1992-01-01

    Se ha realizado un estudio sobre la creatividad en los niños superdotados. Analizándose los diferentes modelos de creatividad y superdotacion avalados por un estudio empírico, en el cual se han valorado las diferencial que existen entre los niños superdotados y contraste a nivel verbal y grafico-espacial.

  5. Who is El Niño?

    Science.gov (United States)

    Philander, S. George

    It is a curious story, about a phenomenon we first welcomed as a blessing but now view with dismay, if not horror [Philander, 1998]. We named it El Niño for the child Jesus, provided it with relatives—La Niña and ENSO—and are devoting innumerable studies to the description and idealization of this family. These scriptures provide such a broad spectrum of historical, cultural, and scientific perspectives that there is now confusion about the identity of El Niño. Trenberth [1997] summarizes the situation as follows.The atmospheric component tied to El Niño is termed the “Southern Oscillation.” Scientists often call the phenomenon where the atmosphere and ocean collaborate ENSO, short for El Niño-Southern Oscillation. El Niño then corresponds to the warm phase of ENSO. The opposite “La Niña” (“the girl” in Spanish) phase consists of a basinwide cooling of the tropical Pacific and thus the cold phase of ENSO. However, for the public, the term for the whole phenomenon is “El Niño.”

  6. Preparation of one-step NiO/Ni-CGO composites using factorial design

    International Nuclear Information System (INIS)

    Araujo, A.J.M. de; Sousa, A R.O. de; Camposa, L.F.A.; Macedo, D.A.; Loureiro, F. J.A.; Fagg, D.P.

    2016-01-01

    This work deals with the synthesis, processing and characterization of NiO/Ni- CGO composite materials as potential solid oxide fuel cell (SOFC) anodes. The particulate materials were obtained by a one-step synthesis method and characterized by thermal analysis (prior to calcination) and X-ray diffraction (calcined powder). The ceramic processing of samples containing from 30 to 70 wt.% NiO was carried out by factorial design. Besides the NiO content controlled during the chemical synthesis, the impacts of the pore-former content (citric acid, used in proportions of 0, 7.5 and 15 wt.%) and the sintering temperature (1300, 1350 and 1400 °C) were also investigated. The open porosity of NiO-CGO composites and reduced Ni-CGO cermets was modeled as a function of factors (NiO content, citric acid content and sintering temperature) and interaction of factors. (author)

  7. Torsional superelasticity of NiTi archwires.

    Science.gov (United States)

    Bolender, Yves; Vernière, Anne; Rapin, Christophe; Filleul, Marie-Pierryle

    2010-11-01

    To reproduce and compare the intraoral torsional behavior of 10 commonly used preformed upper NiTi 0.017 x 0.025 archwires in 0.018-slot brackets at 20 degrees C, 35 degrees C, and 55 degrees C. Ten upper preformed NiTi archwires were compared to a multibraided stainless steel wire. An original testing bench was used to reproduce palatal root torque applied onto an upper central incisor with a maximum value of 1540 g x mm. Ten samples of each wire type were tested at 20 degrees C, 35 degrees C, and 55 degrees C each. Loading and unloading at 20 degrees C revealed three categories of wires: a group of four NiTi wires of relative stiffness bereft of any superelasticity, a group of six NiTi wires displaying some horizontal plateau, and finally the stainless steel wire of lesser stiffness. Testing at the average oral temperature of 35 degrees C produced the same three categories of wires, with only 2 of 10 NiTi wires displaying a superelastic effect (Copper NiTi 35 degrees C and 40 degrees C). None of the NiTi wires was superelastic at 55 degrees C. Moments increased with temperature as the martensite was replaced by the more rigid austenite. This study showed that most NiTi wires did not exhibit in torsion the superelastic effect traditionally described in bending. The combination of straight-wire prescriptions and rectangular superelastic NiTi archwires did not provide optimal constant moments necessary to gain third-order control of tooth movement early in treatment. A braided stainless steel rectangular archwire displayed better torsional behavior at 35 degrees C than most NiTi archwires of the same dimensions.

  8. Influence of annealing temperature on the microstructure and magnetic properties of Ni/NiO core-shell nanowires

    Science.gov (United States)

    Xiang, Wenfeng; Liu, Yuan; Yao, Jiangfeng; Sun, Rui

    2018-03-01

    Ni/NiO core-shell nanowires (NWs) were synthesized by thermal annealing of Ni NWs and variations in the microstructure, surface morphology, and magnetic properties of the NWs as a function of annealing temperature were investigated. The results showed that the grain size and crystal quality of NiO increased with an increasing annealing temperature. Specially, the effect of annealing temperature was much greater than annealing time for the formation of Ni/NiO NWs during the oxidization process. The total weight gain of the Ni/NiO NWs continuously increased when the annealing temperature was lower than 400 °C and the annealing time was more than 2 h; however, the weight gain of the Ni/NiO NWs was almost constant after annealing for 40 min when the annealing temperature was higher than 500 °C. The thorns on the surface of the Ni/NiO NWs gradually passivated and magnetic properties declined when the annealing temperature was increased from 300 °C to 400 °C. Smooth Ni/NiO NWs with no magnetic properties were prepared when the annealing temperature was over 500 °C. The detail study regarding the formation and evolution of Ni/NiO NWs is of considerable value and may provide useful information regarding the choice of post-treatment parameters for different applications of Ni/NiO NWs.

  9. Niño maltratado

    Directory of Open Access Journals (Sweden)

    Ana Ivis Crespo Barrios

    1996-12-01

    Full Text Available Se presentan 200 niños maltratados que acuden al Hospital Pediátrico Docente "Juan Manuel Márquez" en el período comprendido de diciembre de 1990 a enero de 1992; éstos fueron seleccionados teniendo en cuenta los criterios de maltrato, y era el objetivo fundamental del estudio conocer cómo se comporta en nuestro medio. En los resultados se muestra que la forma más frecuente fue el tipo no intencional; la ingestión de tóxicos fue la forma de negligencia física más frecuente dentro del maltrato no intencional, ésta es más usual en los niños menores de 5 años; los trastornos psiquiátricos y el alcoholismo son favorecedores del maltrato intencional, la madre es la que más maltrata; la mortalidad por esta causa no fue elevada (5 fallecidos y los criterios de riesgo de maltrato tienen utilidad para su identificación.200 mistreated children who were seen at the "Juan Manual Márquez" Pediatric Teaching Hospital from December, 1990 to January, 1992, are presented. These patients were selected taking into consideration the abuse criteria. The main objective of this paper was to know how these criteria behave in our enviroment. According to the results, the most common form was the non-intentional type. The ingestion of toxic agents was the most frequent form of physical neglect within the non-intentional mistreatment, and it is the most usual among children under 5. Psychiatric disorders and alcoholism favor the intentional mistreatment, and the mother mistreats the most. Mortality due to this cause was not high (5 deaths, and the abuse risk criteria are useful for its identification.

  10. Nonenzymatic Glucose Sensor Based on In Situ Reduction of Ni/NiO-Graphene Nanocomposite

    Directory of Open Access Journals (Sweden)

    Xiaohui Zhang

    2016-10-01

    Full Text Available Ni/NiO nanoflower modified reduced graphene oxide (rGO nanocomposite (Ni/NiO-rGO was introduced to screen printed electrode (SPE for the construction of a nonenzymatic electrochemical glucose biosensor. The Ni/NiO-rGO nanocomposite was synthesized by an in situ reduction process. Graphene oxide (GO hybrid Nafion sheets first chemical adsorbed Ni ions and assembled on the SPE. Subsequently, GO and Ni ions were reduced by hydrazine hydrate. The electrochemical properties of such a Ni/NiO-rGO modified SPE were carefully investigated. It showed a high activity for electrocatalytic oxidation of glucose in alkaline medium. The proposed nonenzymatic sensor can be utilized for quantification of glucose with a wide linear range from 29.9 μM to 6.44 mM (R = 0.9937 with a low detection limit of 1.8 μM (S/N = 3 and a high sensitivity of 1997 μA/mM∙cm−2. It also exhibited good reproducibility as well as high selectivity.

  11. Asymmetry of inter-El Niño and -La Niña diversity

    Science.gov (United States)

    Kim, S.; Kug, J. S.

    2016-12-01

    Over the North Pacific, there is a distinctive asymmetry of inter-El Niño and -La Niña diversity in atmospheric teleconnection patterns, indicating a strong diversity during La Niña events. Recent studies suggested that the typical patterns of the extratopical teleconnections associated with El Niño-Southern Oscillation (ENSO) are predominantly explained by the relative roles of the equatorial central Pacific (CP) and western North Pacific (WNP) precipitation anomalies. We find that the diversity of WNP precipitation anomalies is greater during La Niña events than during El Niño events. It also implies that the diversity of WNP precipitation anomalies during La Niña events is responsible for the diversity in the extratropical teleconnection. Since the relationship of anomalous sea surface temperature (SST) to precipitation is quite sensitive for SST in the range of 27-28°C, the WNP precipitation differences located over the warm pool among La Niña events lead to considerable teleconnection changes. In addition, we find here that the CMIP5 models well simulate the overall diversity in the tropical precipitation and extratropical teleconnection patterns during La Niña events, but it fails to reproduce a detailed pattern difference of atmospheric teleconnection in inter-La Niña events.

  12. Enthalpy of mixing of liquid Ni-Zr and Cu-Ni-Zr alloys

    International Nuclear Information System (INIS)

    Witusiewicz, V.T.; Sommer, F.

    2000-01-01

    Since the Al-Cu-Ni-Zr system is a basis for the production of bulk amorphous materials by rapid solidification techniques from the liquid state, it is of great scientific interest to determine the partial and the integral thermodynamic functions of liquid and undercooled liquid alloys. Such data, as was pointed out previously, are important in order to understand their extremely good glass-forming ability in multicomponent metallic systems as well as for processing improvements. In order to measure the thermodynamic properties of the Al-Cu-Ni-Zr quaternary, it is necessary to have reliable thermochemical data for its constituent canaries and ternaries first. In a series of articles, the authors have reported in detail the thermodynamic properties of liquid Al-Cu, Al-Ni, Cu-Ni, Cu-Zr, Al-Zr, Al-Cu-Ni, and Al-Cu-Zr alloys. This article deals with the direct calorimetric measurements of the partial and the integral enthalpies of mixing of liquid Ni-Zr and Cu-Ni-Zr alloys and the heat capacity of liquid Ni 26 Zr 74 . In a subsequent article, the authors will present similar data for the liquid ternary Al-Ni-Zr and for the liquid quaternary Al-Cu-Ni-Zr alloys

  13. Study of the central collisions in the reactions Ni + Al and Ni + Ni at 28 A.MeV; Etude des collisions centrales dans les reactions Ni + Al et Ni + Ni a 28 A.MeV

    Energy Technology Data Exchange (ETDEWEB)

    Lebreton, L.

    1995-12-01

    The work is in characterisation of mechanisms in the energy range of onset of multifragmentation (excitation energy of composed nucleus around 4 - 5 AMeV). This work focused on an experiment performed at the SARA facility, in Grenoble, using the AMPHORA multi detection array. I have been particularly interested in central collisions in the Ni + Al and Ni + Ni systems. The possibility to detect complete events for Ni + Al, and quasi-complete events for the Ni + Ni case, is the reason of this choice. Furthermore Ni + Ni presents the interest of a symmetrical system, for which the excitation energy per nucleon is maximum. The study of these reactions has been focused on the quasi-complete events (events for which at least 80 % of the total charge has been detected). Heavy ions produced in peripheral collisions are very likely emitted along the beam line or stopped in the plastic detectors, energy thresholds are too high for the quasi-target products detection, consequently by requiring complete or quasi-complete measurement of the total charge, we are able to detect mostly central events. The knowledge of informations like charge, energy or detection angles allows to isolate the source(s) and to reconstruct the size and the excitation energy of the source(s). Comparisons with simulations like sequential emission (GEMINI code), very deep inelastic collision or instantaneous emission (Berliner code) allows to characterise the first stage of the collision (binary collisions or central collisions) and the type of deexcitation of the source(s). Some calculations was also performed with the statistical model code MODGAN. Indeed azimuthal correlations seem to be a good tool in getting more information about involved reaction mechanisms. Comparisons with MODGAN provide information about angular momentum of the source and time delay between emissions of the two particles (separation between sequential or instantaneous process). (author). 69 refs.

  14. Nanostructures of Boron, Carbon and Magnesium Diboride for High Temperature Superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Pfefferle, Lisa [Yale Univ., New Haven, CT (United States); Fang, Fang [Yale Univ., New Haven, CT (United States); Iyyamperumal, Eswarmoorthi [Yale Univ., New Haven, CT (United States); Keskar, Gayatri [Yale Univ., New Haven, CT (United States)

    2013-12-23

    Direct fabrication of MgxBy nanostructures is achieved by employing metal (Ni,Mg) incorporated MCM-41 in the Hybrid Physical-Chemical Vapor Deposition (HPCVD) reaction. Different reaction conditions are tested to optimize the fabrication process. TEM analysis shows the fabrication of MgxBy nanostructures starting at the reaction temperature of 600oC, with the yield of the nanostructures increasing with increasing reaction temperature. The as-synthesized MgxBy nanostructures have the diameters in the range of 3-5nm, which do not increase with the reaction temperature consistent with templated synthesis. EELS analysis of the template removed nanostructures confirms the existence of B and Mg with possible contamination of Si and O. NEXAFS and Raman spectroscopy analysis suggested a concentric layer-by-layer MgxBy nanowire/nanotube growth model for our as-synthesized nanostructures. Ni k-edge XAS indicates that the formation of MgNi alloy particles is important for the Vapor-Liquid-Solid (VLS) growth of MgxBy nanostructures with fine diameters, and the presence of Mg vapor not just Mg in the catalyst is crucial for the formation of Ni-Mg clusters. Physical templating by the MCM-41 pores was shown to confine the diameter of the nanostructures. DC magnetization measurements indicate possible superconductive behaviors in the as-synthesized samples.

  15. niños pre-escolares

    Directory of Open Access Journals (Sweden)

    Sandra León Muñoz

    2006-01-01

    Full Text Available Este estudio tuvo como objetivo caracterizar las producciones narrativas orales de niños de pre-escolar y relacionar estos desempeños con la lectura de imágenes. Se conformó una muestra de 9 niños entre 4 y 6 años que pertenecían a instituciones de educación formal. Se realizó un análisis de tarea de la historieta presentada y la aplicación de ésta fue de manera individual en el contexto familiar del niño. Los resultados mostraron que los niños identificaban la situación inicial de la narración, en la cual relacionaban personajes principales, actividades propias de ellos y del espacio donde sucedían sin embargo, a medida que se avanzaban en el procedimiento, se observó cómo se dificultaba para los niños la elaboración de las otras categorías que estructuran la narración como la complicación, la reacción, la resolución y la situación final. En relación con las estrategias cognitivas se observó que cuatro niños se encuentra en un nivel cognitivo bajo, cuatro se encuentra en un nivel cognitivo medio y un niño, en un nivel cognitivo alto. En cuanto a los procesos de lectura de imágenes se encontró que sólo dos niños utilizaron la referencia y dos niños usaron conectores temporales

  16. Electrochemical preparation and characteristics of Ni-Co-LaNi5 composite coatings as electrode materials for hydrogen evolution

    International Nuclear Information System (INIS)

    Wu Gang; Li Ning; Dai Changsong; Zhou Derui

    2004-01-01

    Electrocatalytic activity for the hydrogen evolution reaction on Ni-Co-LaNi 5 composite electrodes prepared by electrochemical codeposition technique was evaluated. The relationship between the current density for hydrogen evolution reaction and the amount of LaNi 5 particles in Ni-Co baths is like the well-known 'volcano plot'. The Surface morphology and microstructure of Ni-Co-LaNi 5 coatings were determined by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). The kinetic parameters were determined from electrochemical steady-state Tafel polarization and electrochemical impedance spectroscopy technology in 1 M NaOH solution. The values obtained for the apparent energies of activation are 32.48, 46.29 and 57.03 kJ mol -1 for the Ni-Co-LaNi 5 , Ni-Co and Ni electrodes, respectively. The hydrogen evolution reaction on Ni-Co-LaNi 5 proceeds via Volmer-Tafel reaction route with the mixed rate determining characteristics. The composite coating Ni-Co-LaNi 5 is catalytically more active than Ni and Ni-Co electrodes due to the increase in its real surface areas and the decrease in the apparent free energy of activation caused by the electrocatalytic synergistic effect of the Ni-Co alloys and the hydrogen storage intermetallic particles on the electrode surface

  17. De niños e infancias

    OpenAIRE

    Camenen, Gersende; Liendo, Victoria

    2014-01-01

    A Sarmiento, el niño sabio, lo llevan de casa en casa como al prodigio del pueblo para oírlo leer en voz alta. Norah Lange, la niña excéntrica, grita desaforada en distintos idiomas y finge carcajadas enloquecidas desde el techo de su casa hasta gastar la voz. Reinaldo Arenas, el niño salvaje, escribe, como Celestino, poemas con un cuchillo en el tronco los árboles para que no amanezca. Borges, el traductor precoz, lee a los seis años el Quijote en inglés sin tener la menor sospecha de que el...

  18. New developments in Ni/Ti multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, I.; Hoghoj, P. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)

    1997-04-01

    It is now 20 years since super-mirrors were first used as a neutron optical element. Since then the field of multilayer neutron-optics has matured with multilayers finding their way to application in many neutron scattering instruments. However, there is still room for progress in terms of multilayer quality, performance and application. Along with work on multilayers for neutron polarisation Ni/Ti super-mirrors have been optimised. The state-of-the-art Ni/Ti super-mirror performance and the results obtained in two neutron-optics applications of Ni/Ti multilayers are presented. (author).

  19. Nickel Release, ROS Generation and Toxicity of Ni and NiO Micro- and Nanoparticles.

    Science.gov (United States)

    Latvala, Siiri; Hedberg, Jonas; Di Bucchianico, Sebastiano; Möller, Lennart; Odnevall Wallinder, Inger; Elihn, Karine; Karlsson, Hanna L

    2016-01-01

    Occupational exposure to airborne nickel is associated with an elevated risk for respiratory tract diseases including lung cancer. Therefore, the increased production of Ni-containing nanoparticles necessitates a thorough assessment of their physical, chemical, as well as toxicological properties. The aim of this study was to investigate and compare the characteristics of nickel metal (Ni) and nickel oxide (NiO) particles with a focus on Ni release, reactive oxygen species (ROS) generation, cellular uptake, cytotoxicity and genotoxicity. Four Ni-containing particles of both nano-size (Ni-n and NiO-n) and micron-size (Ni-m1 and Ni-m2) were tested. The released amount of Ni in solution was notably higher in artificial lysosomal fluid (e.g. 80-100 wt% for metallic Ni) than in cell medium after 24h (ca. 1-3 wt% for all particles). Each of the particles was taken up by the cells within 4 h and they remained in the cells to a high extent after 24 h post-incubation. Thus, the high dissolution in ALF appeared not to reflect the particle dissolution in the cells. Ni-m1 showed the most pronounced effect on cell viability after 48 h (alamar blue assay) whereas all particles showed increased cytotoxicity in the highest doses (20-40 μg cm2) when assessed by colony forming efficiency (CFE). Interestingly an increased CFE, suggesting higher proliferation, was observed for all particles in low doses (0.1 or 1 μg cm-2). Ni-m1 and NiO-n were the most potent in causing acellular ROS and DNA damage. However, no intracellular ROS was detected for any of the particles. Taken together, micron-sized Ni (Ni-m1) was more reactive and toxic compared to the nano-sized Ni. Furthermore, this study underlines that the low dose effect in terms of increased proliferation observed for all particles should be further investigated in future studies.

  20. Exchange bias variations of the seed and top NiFe layers in NiFe/FeMn/NiFe trilayer as a function of seed layer thickness

    International Nuclear Information System (INIS)

    Sankaranarayanan, V.K.; Yoon, S.M.; Kim, C.G.; Kim, C.O.

    2005-01-01

    Development of exchange bias at the seed and top NiFe layers in the NiFe (t nm)/FeMn(10 nm)/NiFe(5 nm) trilayer structure is investigated as a function of seed layer thickness, in the range of 2-20 nm. The seed NiFe layer shows maximum exchange bias at 4 nm seed layer thickness. The bias shows inverse thickness dependence with increasing thickness. The top NiFe layer on the other hand shows only half the bias of the seed layer which is retained even after the sharp fall in seed layer bias. The much smaller bias for the top NiFe layer is related to the difference in crystalline texture and spin orientations at the top FeMn/NiFe interface, in comparison to the bottom NiFe/FeMn interface which grows on a saturated NiFe layer with (1 1 1) orientation

  1. Synthesis of Supported NiPt Bimetallic Nanoparticles, Methods for Controlling the Surface Coverage of Ni Nanoparticles With Pt, Methods Of Making NiPt Multilayer Core-Shell Structures and Application of the Supported Catalysts for CO2 Reforming

    KAUST Repository

    Li, Lidong

    2015-06-25

    Embodiments of the present disclosure provide for supported Ni/Pt bimetallic nanoparticles, compositions including supported NiPt nanoparticles, methods of making supported NiPt nanoparticles, methods of using supported NiPt nanoparticles, and the like.

  2. Free-energies of the Ti-Ni, Fe-Ni and Mo-Ni alloys in relation to their behaviour under particle irradiation

    International Nuclear Information System (INIS)

    De Tendler, R.H.; Rodriguez, C.; Gallego, L.J.; Alonso, J.A.

    1996-01-01

    The metastable free-energy diagrams of the Ti-Ni, Fe-Ni and Mo-Ni systems were calculated at room temperature using a semiempirical theory based on thermodynamic considerations. Ti-Ni and Mo-Ni form equilibrium-ordered compounds that are destabilized by particle irradiation. Effectively, Ti 2 Ni, TiNi, MoNi and MoNi 3 amorphize after irradiation. In the present work, this experimental behaviour is understood by considering the modification of the free-energy diagrams after particle irradiation. Conversely, in the Fe-Ni system, a metastable f c c solid solution evolves under irradiation towards ordered FeNi. In this system, according to our calculation, the free-energy of the amorphous phase is much higher than the free-energy of any other competing phase, so the amorphous phase cannot be produced. Each selected alloy has an intermetallic compound (TiNi 3 , FeNi 3 and MoNi 4 ) which does not amorphize by particle irradiation and whose composition is close to the nickel-rich end of the phase diagram. According to the calculated free-energy diagrams, the reason for this impossibility of amorphization would be the competition of the terminal solid solution with the amorphous phase. (Author)

  3. Precipitation of Ni4Ti3-variants in a polycrystalline Ni-rich NiTi shape memory alloy

    Czech Academy of Sciences Publication Activity Database

    Bojda, Ondřej; Eggeler, G.; Dlouhý, Antonín

    2005-01-01

    Roč. 53, č. 1 (2005), s. 99-104 ISSN 1359-6462 R&D Projects: GA ČR(CZ) GA106/05/0918 Institutional research plan: CEZ:AV0Z20410507 Keywords : NiTi shape memory alloys * Ni4Ti3 precipitation * Transmission electron microscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.228, year: 2005

  4. Influence of Ni Solute segregation on the intrinsic growth stresses in Cu(Ni) thin films

    International Nuclear Information System (INIS)

    Kaub, T.M.; Felfer, P.; Cairney, J.M.; Thompson, G.B.

    2016-01-01

    Using intrinsic solute segregation in alloys, the compressive stress in a series of Cu(Ni) thin films has been studied. The highest compressive stress was noted in the 5 at.% Ni alloy, with increasing Ni concentration resulting in a subsequent reduction of stress. Atom probe tomography quantified Ni's Gibbsian interfacial excess in the grain boundaries and confirmed that once grain boundary saturation is achieved, the compressive stress was reduced. This letter provides experimental support in elucidating how interfacial segregation of excess adatoms contributes to the post-coalescence compressive stress generation mechanism in thin films. - Graphical abstract: Cu(Ni) film stress relationship with Ni additions. Atom probe characterization confirms solute enrichment in the boundaries, which was linked to stress response.

  5. Continuum mechanics simulations of NiO/Ni-YSZ composites during reduction and re-oxidation

    DEFF Research Database (Denmark)

    Pihlatie, Mikko; Frandsen, Henrik Lund; Kaiser, Andreas

    2010-01-01

    Repeated reduction–oxidation (redox) cycles on Ni-based solid oxide fuel cells (SOFC) have been experimentally well investigated and are known to be detrimental to the thermomechanical stability of the composites, especially on anode supported structures. In the present work the mechanistic...... for the dimensional change arises from the volumetric change related to the phase change NiO ↔ Ni. The measurable change in bulk length is given by the ceramic YSZ backbone as a response to the stress created by the chemical strain. The different subprocesses described in the model for YSZ were elastic and anelastic...... expansion, diffusional creep, grain boundary sliding (GBS) and microcracking due to excessive stress. In the Ni/NiO phase, nonelastic strains in terms of diffusional and power law creep were implemented, and additionally for NiO deformation due to microcracking and/or pseudoplasticity. Semi...

  6. Site occupancy of Fe in ternary Ni 75-x

    Indian Academy of Sciences (India)

    The results of a detailed structural and magnetic study clearly indicate that regardless of the thermal history of the samples, Fe has a strong preference for the Ni sites in Ni-poor (non-stoichiometric) Ni75Al25 alloys. Fe substitution has a profound effect on the nature of magnetism in Ni75Al25.

  7. Reduction of a Ni/Spinel Catalyst for Methane Reforming

    DEFF Research Database (Denmark)

    Kehres, Jan; Andreasen, Jens Wenzel; Fløystad, Jostein Bø

    2015-01-01

    microscopy (HRTEM) was performed on the fresh catalyst sample. The Ni particles in the fresh catalyst sample were observed to exhibit a Ni/NiO core/shell structure. A decrease of the Ni lattice parameter is observed during the reduction in a temperature interval from 413 – 453 K, which can be related...

  8. Electronic structure of graphene on Ni surfaces with different orientation

    International Nuclear Information System (INIS)

    Pudikov, D.A.; Zhizhin, E.V.; Rybkin, A.G.; Rybkina, A.A.; Zhukov, Y.M.; Vilkov, O. Yu.; Shikin, A.M.

    2016-01-01

    An experimental study of the graphene, synthesized by propylene cracking on Ni surfaces with different orientation: (100) and (111), using angle-resolved photoemission, has been performed. It has been shown that graphene on Ni(111) had a perfect lateral structure due to consistency of their lattices, whereas graphene/Ni(100) consisted of a lot of domains. For both systems electronic structure was quite similar and demonstrated a strong bonding of graphene to the underlying Ni surface. After Au intercalation the electronic structure of graphene in both systems was shifted to the Fermi level and became linear in the vicinity of the K point of the Brillouin zone. - Highlights: • Graphene on Ni(111) is well-ordered, whereas on Ni(100) – multi-domain. • Graphene on Ni(111) and Ni(100) is strongly bonded with substrate. • Intercalation of Au atoms restores the linearity in dispersion and makes graphene quasi-free on both Ni(100) and Ni(111).

  9. Modeling and simulation of NiO dissolution and Ni deposition in molten carbonate fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Nam, Suk Woo; Choi, Hyung-Joon; Lim, Tae Hoon [Korea Institute of Science & Technology, Seoul (Korea, Republic of)] [and others

    1996-12-31

    Dissolution of NiO cathode into the electrolyte matrix is an important phenomena limiting the lifetime of molten carbonate fuel cell (MCFC). The dissolved nickel diffuses into the matrix and is reduced by dissolved hydrogen leading to the formation of metallic nickel films in the pores of the matrix. The growth of Ni films in the electrolyte matrix during the continuous cell operation results eventually in shorting between cathode and anode. Various mathematical and empirical models have been developed to describe the NiO dissolution and Ni deposition processes, and these models have some success in estimating the lifetime of MCFC by correlating the amount of Ni deposited in the matrix with shorting time. Since the exact mechanism of Ni deposition was not well understood, deposition reaction was assumed to be very fast in most of the models and the Ni deposition region was limited around a point in the matrix. In fact, formation of Ni films takes place in a rather broad region in the matrix, the location and thickness of the film depending on operating conditions as well as matrix properties. In this study, we assumed simple reaction kinetics for Ni deposition and developed a mathematical model to get the distribution of nickel in the matrix.

  10. Directional Solidification and Mechanical Properties of NiAl-NiAlTa Alloys

    Science.gov (United States)

    Johnson, D. R.; Chen, X. F.; Oliver, B. F.; Noebe, R. D.; Whittenberger, J. D.

    1995-01-01

    Directional solidification of eutectic alloys is a promising technique for producing in-situ composite materials exhibiting a balance of properties. Consequently, the microstructure, creep strength and fracture toughness of directionally solidified NiAl-NiAlTa alloys were investigated. Directional solidification was performed by containerless processing techniques to minimize alloy contamination. The eutectic composition was found to be NiAl-15.5 at% Ta and well-aligned microstructures were produced at this composition. A near-eutectic alloy of NiAl-14.5Ta was also investigated. Directional solidification of the near-eutectic composition resulted in microstructures consisting of NiAl dendrites surrounded by aligned eutectic regions. The off-eutectic alloy exhibited promising compressive creep strengths compared to other NiAl-based intermetallics, while preliminary testing indicated that the eutectic alloy was competitive with Ni-base single crystal superalloys. The room temperature toughness of these two-phase alloys was similar to that of polycrystalline NiAl even with the presence of the brittle Laves phase NiAlTa.

  11. The magnetic moment of Ni in the Laves phase compound GdNi2

    International Nuclear Information System (INIS)

    Yano, Kazuo; Umehara, Izuru; Miyazawa, Tomoaki; Adachi, Yoshiya; Sato, Kiyoo

    2005-01-01

    Magnetization and inverse susceptibility of the Laves phase compound GdNi 2 were investigated and analyzed in detail by employing molecular-field analysis. Both the temperature dependence of the magnetization and the Curie-Weiss (C-W) law-like linear relationship of inverse susceptibility are reproduced in terms of a two-sublattice model and it is seen that the magnetic structure of GdNi 2 is ferrimagnetic and Ni in GdNi 2 retains a magnetic moment of about 0.24μ B

  12. Polymer stabilized Ni-Ag and Ni-Fe alloy nanoclusters: Structural and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Kabir, L.; Mandal, A.R. [Department of Physics, Visva-Bharati, Santiniketan-731 235 (India); Mandal, S.K., E-mail: sk_mandal@hotmail.co [Department of Physics, Visva-Bharati, Santiniketan-731 235 (India)

    2010-04-15

    We report here the structural and magnetic behaviors of nickel-silver (Ni-Ag) and nickel-iron (Ni-Fe) nanoclusters stabilized with polymer (polypyrrole). High resolution transmission electron microscopy (HRTEM) indicates Ni-Ag nanoclusters to stabilize in core-shell configuration while that of Ni-Fe nanoclusters in a mixed type of geometry. Structural characterizations by X-ray diffraction (XRD) reveal the possibility of alloying in such bimetallic nanoclusters to some extent even at temperatures much lower than that of bulk alloying. Electron paramagnetic resonance (EPR) spectra clearly reveal two different absorption behaviors: one is ascribed to non-isolated Ni{sup 2+} clusters surrounded by either silver or iron giving rise to a broad signal, other (very narrow signal) being due to the isolated superparamagnetic Ni{sup 2+} clusters or bimetallic alloy nanoclusters. Results obtained for Ni-Ag and Ni-Fe nanoclusters have been further compared with the behavior exhibited by pure Ni nanoclusters in polypyrrole host. Temperature dependent studies (at 300 and 77 K) of EPR parameters, e.g. linewidth, g-value, line shape and signal intensity indicating the significant influence of surrounding paramagnetic silver or ferromagnetic iron within polymer host on the EPR spectra have been presented.

  13. Polymer stabilized Ni-Ag and Ni-Fe alloy nanoclusters: Structural and magnetic properties

    Science.gov (United States)

    Kabir, L.; Mandal, A. R.; Mandal, S. K.

    2010-04-01

    We report here the structural and magnetic behaviors of nickel-silver (Ni-Ag) and nickel-iron (Ni-Fe) nanoclusters stabilized with polymer (polypyrrole). High resolution transmission electron microscopy (HRTEM) indicates Ni-Ag nanoclusters to stabilize in core-shell configuration while that of Ni-Fe nanoclusters in a mixed type of geometry. Structural characterizations by X-ray diffraction (XRD) reveal the possibility of alloying in such bimetallic nanoclusters to some extent even at temperatures much lower than that of bulk alloying. Electron paramagnetic resonance (EPR) spectra clearly reveal two different absorption behaviors: one is ascribed to non-isolated Ni 2+ clusters surrounded by either silver or iron giving rise to a broad signal, other (very narrow signal) being due to the isolated superparamagnetic Ni 2+ clusters or bimetallic alloy nanoclusters. Results obtained for Ni-Ag and Ni-Fe nanoclusters have been further compared with the behavior exhibited by pure Ni nanoclusters in polypyrrole host. Temperature dependent studies (at 300 and 77 K) of EPR parameters, e.g. linewidth, g-value, line shape and signal intensity indicating the significant influence of surrounding paramagnetic silver or ferromagnetic iron within polymer host on the EPR spectra have been presented.

  14. Polymer stabilized Ni-Ag and Ni-Fe alloy nanoclusters: Structural and magnetic properties

    International Nuclear Information System (INIS)

    Kabir, L.; Mandal, A.R.; Mandal, S.K.

    2010-01-01

    We report here the structural and magnetic behaviors of nickel-silver (Ni-Ag) and nickel-iron (Ni-Fe) nanoclusters stabilized with polymer (polypyrrole). High resolution transmission electron microscopy (HRTEM) indicates Ni-Ag nanoclusters to stabilize in core-shell configuration while that of Ni-Fe nanoclusters in a mixed type of geometry. Structural characterizations by X-ray diffraction (XRD) reveal the possibility of alloying in such bimetallic nanoclusters to some extent even at temperatures much lower than that of bulk alloying. Electron paramagnetic resonance (EPR) spectra clearly reveal two different absorption behaviors: one is ascribed to non-isolated Ni 2+ clusters surrounded by either silver or iron giving rise to a broad signal, other (very narrow signal) being due to the isolated superparamagnetic Ni 2+ clusters or bimetallic alloy nanoclusters. Results obtained for Ni-Ag and Ni-Fe nanoclusters have been further compared with the behavior exhibited by pure Ni nanoclusters in polypyrrole host. Temperature dependent studies (at 300 and 77 K) of EPR parameters, e.g. linewidth, g-value, line shape and signal intensity indicating the significant influence of surrounding paramagnetic silver or ferromagnetic iron within polymer host on the EPR spectra have been presented.

  15. Pressure dependence on the remanent magnetization of Fe-Ni alloys and Ni metal

    Science.gov (United States)

    Wei, Qingguo; Gilder, Stuart Alan; Maier, Bernd

    2014-10-01

    We measured the acquisition of magnetic remanence of iron-nickel alloys (Fe64Ni36, Fe58Ni42, and Fe50Ni50) and pure Ni under pressures up to 23 GPa at room temperature. Magnetization decreases markedly for Fe64Ni36 between 5 and 7 GPa yet remains ferromagnetic until at least 16 GPa. Magnetization rises by a factor of 2-3 for the other compositions during compression to the highest applied pressures. Immediately upon decompression, magnetic remanence increases for all Fe-Ni alloys while magnetic coercivity remains fairly constant at relatively low values (5-20 mT). The amount of magnetization gained upon complete decompression correlates with the maximum pressure experienced by the sample. Martensitic effects best explain the increase in remanence rather than grain-size reduction, as the creation of single domain sized grains would raise the coercivity. The magnetic remanence of low Ni Invar alloys increases faster with pressure than for other body-centered-cubic compositions due to the higher magnetostriction of the low Ni Invar metals. Thermal demagnetization spectra of Fe64Ni36 measured after pressure release broaden as a function of peak pressure, with a systematic decrease in Curie temperature. Irreversible strain accumulation from the martensitic transition likely explains the broadening of the Curie temperature spectra, consistent with our x-ray diffraction analyses.

  16. Grain boundaries in Ni3Al. 2

    International Nuclear Information System (INIS)

    Kung, H.; Sass, S.L.

    1992-01-01

    This paper discusses the dislocation structure of small angle tilt and twist boundaries in ordered Ni 3 Al, with and without boron, investigated using transmission electron microscopy. Dislocation with Burgers vectors that correspond to anti-phase boundary (APB)-coupled superpartials were found in small angle twist boundaries in both boron-free and boron-doped Ni 3 Al, and a small angle tilt boundary in boron-doped Ni 3 Al. The boundary structures are in agreement with theoretical models proposed by Marcinkowski and co-workers. The APB energy determined from the dissociation of the grain boundary dislocations was lower than values reported for isolated APBs in Ni 3 Al. For small angle twist boundaries the presence of boron reduced the APB energy at the interface until it approached zero. This is consistent with the structure of these boundaries containing small regions of increased compositional disorder in the first atomic plane next to the interface

  17. Niños y Violencia

    OpenAIRE

    International Child Development Centre

    1997-01-01

    Este Innocenti Digest explora la violencia de los niños y hacia los niños, usando el marco de la Convención de los Derechos del Niño de las Naciones Unidas. Se centra en la violencia interpersonal, tanto intrafamiliar como extrafamiliar. Se incluye el abuso sexual y la explotación ya que a pesar de no implicar obligatoriamente violencia o coerción, la mayor parte de la evidencia demuestra su efectos dañinos tanto físicos como psicológicos. También se discute la implicación de los niños en los...

  18. Root morphology of Ni-treated plants

    International Nuclear Information System (INIS)

    Leskova, A.; Fargasova, A.; Giehl, R. F. H.; Wiren, N. von

    2015-01-01

    Plant roots are very important organs in terms of nutrient and water acquisition but they also serve as anchorages for the aboveground parts of the plants. The roots display extraordinary plasticity towards stress conditions as a result of integration of environmental cues into the developmental processes of the roots. Our aim was to investigate the root morphology of Arabidopsis thaliana plants exposed to a particular stress condition, excess Ni supply. We aimed to find out which cellular processes - cell division, elongation and differentiation are affected by Ni, thereby explaining the seen root phenotype. Our results reveal that a distinct sensitivity exists between roots of different order and interference with various cellular processes is responsible for the effects of Ni on roots. We also show that Ni-treated roots have several auxin-related phenotypes. (authors)

  19. Ni adsorption and Ni-Al LDH precipitation in a sandy aquifer: An experimental and mechanistic modeling study

    NARCIS (Netherlands)

    Regelink, I.C.; Temminghoff, E.J.M.

    2011-01-01

    Mining activities and industries have created nickel (Ni) contaminations in many parts of the world. The objective of this study is to increase our understanding of Ni adsorption and Nickel-Aluminium Layered Double Hydroxide (Ni-Al LDH) precipitation to reduce Ni mobility in a sandy soil aquifer. At

  20. Fe-Cr-Ni system alloys

    International Nuclear Information System (INIS)

    Levin, F.L.

    1986-01-01

    Phase diagram of Fe-Cr-Ni system, which is the basic one for production of corrosion resistant alloys, is considered. Data on corrosion resistance of such alloys are correlated depending on a number of factors: quality and composition of modifying elements, corrosion medium, temperature, alloy structure, mechanical and thermal treatment. Grades of Fe-Ni-Cr alloys are presented, and fields of their application are pointed out

  1. Heteromorphic NiCo2S4/Ni3S2/Ni Foam as a Self-Standing Electrode for Hydrogen Evolution Reaction in Alkaline Solution.

    Science.gov (United States)

    Liu, Hui; Ma, Xiao; Rao, Yuan; Liu, Yang; Liu, Jialiang; Wang, Luyang; Wu, Mingbo

    2018-04-04

    Considerable works have been devoted on developing high-efficiency nonplatinum electrocatalysts for hydrogen evolution reaction (HER). Herein, 3D heteromorphic NiCo 2 S 4 /Ni 3 S 2 nanosheets network has been constructed on Ni foam (denoted as NiCo 2 S 4 /Ni 3 S 2 /NF) serving as a self-standing electrocatalyst through directly thermal sulfurization of a single-source NiCo-layered double hydroxide precursor. The resultant NiCo 2 S 4 /Ni 3 S 2 /NF electrode exhibits outstanding electrocatalytic HER performance with an extremely low onset overpotential of 15 mV and long-term durability in alkaline solution. Such enhanced HER performance can be credited to (1) the massive exposed active sites provided by mixed transition metal chalcogenides (NiCo 2 S 4 and Ni 3 S 2 ), (2) the strong interfacial interaction at NiCo 2 S 4 /Ni 3 S 2 heterojunction interfaces with the strengthened H binding, and (3) the porous highly conductive Ni foam substrate with accelerated electron transfer. This work opens up a new direction to fabricate effective and non-noble-metal electrodes for water splitting and hydrogen generation.

  2. Effects of crystallite size on the structure and magnetism of ferrihydrite

    NARCIS (Netherlands)

    Wang, Xiaoming; Zhu, Mengqiang; Koopal, L.K.; Li, Wei; Xu, Wenqian; Liu, Fan; Zhang, Jing; Liu, Qingsong; Feng, Xionghan; Sparks, D.L.

    2016-01-01

    The structure and magnetic properties of nano-sized (1.6 to 4.4 nm) ferrihydrite samples are systematically investigated through a combination of X-ray diffraction (XRD), X-ray pair distribution function (PDF), X-ray absorption spectroscopy (XAS) and magnetic analyses. The XRD, PDF and Fe K-edge

  3. Heavy metal environmental impact. Nickel (Ni); Impatto ambientale da metalli pesanti. Il Nichel (Ni)

    Energy Technology Data Exchange (ETDEWEB)

    Bressa, G. [Padua Univ. Padua (Italy). Dipt. di Farmacologia, Lab. di Tossicologia

    2001-02-01

    Nickel (Ni) is a heavy metal in over 3.000 different alloys used to produce kitchen utensils, batteries, coins, etc.. Human extractive and industrial activities are therefore a cause for environmental dispersion of this metal into the biosphere. This shows how in urban areas car traffic and house-heating are the main sources of nickel pollution. Nickel is relatively non-toxic, such as iron, cobalt, copper and zinc; nevertheless prolonged inhalation of dust containing such compounds as Ni O or NiCl{sub 2} concurs in the outbreak of respiratory pathologies. The carcinogenic effect of such compounds as Ni S, Ni O and Ni(CO){sub 4} has been confirmed by experiments on laboratory animals. Ni potentially toxic concentrations, and as a consequence of potential environmental impact, are to be mainly found in populated areas where the main sources are represented by industries and landfills. [Italian] Il nichel (Ni) e' un metallo presente in oltre 3.000 differenti leghe che vengono utilizzate per la produzione di utensili da cucina, batterie, monete, ecc.. Le attivita' estrattive ed industriali dell'uomo sono quindi causa di una dispersione del metallo nella biosfera. Sono stati riscontrati elevati tassi di Ni nell'atmosfera di aree urbane. Cio' sta a dimostrare che nelle aree urbane il traffico automobilistico e il riscaldamento domestico sono le fonti principali di inquinamento da tale metallo. Il nichel e' relativamente atossico, analogamente a ferro, cobalto, rame e zinco, tuttavia l'inalazione protratta di polveri contenenti composti come il NiO o il NiCl{sub 2} contribuisce al manifestarsi di patologie dell'apparato respiratorio. E' stato confermato sperimentalmente su animali da laboratorio l'effetto cancerogeno di alcuni composti quali NiS, NiO e Ni(CO){sub 4}. Concentrazioni potenzialmente tossiche di Ni, e quindi di probabile impatto ambientale, sono maggiormente da ricercare nelle zone antropizzate dove le fonti

  4. Moessbauer analysis and magnetic properties of Invar Fe-Ni-C and Fe-Ni-Mn-C alloys

    International Nuclear Information System (INIS)

    Nadutov, V. M.; Svystunov, Ye. O.; Kosintsev, S. G.; Tatarenko, V. A.

    2006-01-01

    The saturation magnetization and the hyperfine magnetic field of different f.c.c. Fe-Ni based alloys containing nearby 29 at .% Ni were studied as a function of temperature and for different Carbon and Manganese contents. We have observed abnormal behaviors that are explained in terms of mixed exchange interactions between atomic spins: J NiNi (r i ) FeFe (r i ) > 0, J NiFe (r i ) < 0.

  5. Influence of H2O and H2S on the Composition, Activity, and Stability of Sulfided Mo, CoMo, and NiMo Supported on MgAl2O4 for Hydrodeoxygenation of Ethylene Glycol

    DEFF Research Database (Denmark)

    Dabros, Trine Marie Hartmann; Gaur, Abhijeet; Pintos, Delfina Garcia

    2018-01-01

    variation of the partial pressures of H2O and H2S. The results show high water tolerance of the catalysts and highlight the importance of promotion and H2S level during HDO. DFT calculations unraveled that the active edge of MoS2 could be stabilized against S-O exchanges by increasing the partial pressure...... that the catalysts were tolerant towards water when exposed to increasing water concentration with H2O/H2S ratios up to 300 at 400-450 °C. Raman spectroscopy and XAS showed that MoS2 was present in the prepared catalysts as small and highly dispersed particles, probably owing to a strong interaction with the support...... showed the presence of MoS2 in all sulfided catalysts. Sulfided CoMo was present as a mixture of CoMoS and Co9S8, whereas sulfided NiMo was present as NiMoS....

  6. Influence of Amide/Amine vs Nis-Amide Coordination in Nickel Superoxide Dismutase

    Energy Technology Data Exchange (ETDEWEB)

    Neupane,K.; Shearer, J.

    2006-01-01

    Nickel superoxide dismutase (NiSOD) is a mononuclear nickel-containing metalloenzyme that catalyzes the disproportionation of superoxide by cycling between Ni{sup II} and Ni{sup III} oxidation states. In the reduced Ni{sup II} oxidation state, the metal center is ligated by two cysteinate sulfurs, one amide nitrogen, and one amine nitrogen (from the N-terminus), while in the oxidized Ni{sup III} state, an imidazole nitrogen coordinates to the metal center. Herein, we expand on a previous report in which we described a functional metallopeptide-based NiSOD model compound [Ni{sup II}(SOD{sup M1})] (SOD{sup M1} = H{sub 2}N-HCDLPCGVYDPA-COOH) by exploring how acylation of the N-terminus (producing [Ni{sup II}(SOD{sup M1}-Ac)]) influences the properties of the metallopeptide. Titration results, GPC data, and mass-spectrometry data demonstrate that Ni{sup II} coordinates to SOD{sup M1}-Ac in a 1:1 ratio, while variable pH studies show that Ni{sup II} coordination is strong at a pH of 7.5 and above but not observed below a pH of 6.2. This is higher than [Ni{sup II}(SOD{sup M1})] by {approx}1.0 pH unit consistent with bisamide ligation. Ni K-edge XAS demonstrates that the Ni{sup II} center is coordinated in a square-planar NiN{sub 2}S{sub 2} coordination environment with Ni-N distances of 1.846(4) {angstrom} and Ni-S distances of 2.174(3) {angstrom}. Comparison of the electronic absorption and CD spectrum of [Ni{sup II}(SOD{sup M1})] versus [Ni{sup II}(SOD{sup M1}-Ac)] in conjunction with time-dependent DFT calculations suggests a decrease in Ni covalency in the acylated versus unacylated metallopeptide. This decrease in covalency was also supported by DFT calculations and Ni L-edge XAS. [Ni{sup II}(SOD{sup M1}-Ac)] has a quasireversible Ni{sup II}/Ni{sup III} redox couple of 0.49(1) V vs Ag/AgCl, which represents a -0.2 V shift compared with [Ni{sup II}(SOD{sup M1})], while the peak separation suggests a change in the coordination environment upon oxidation (i.e., axial

  7. Single-crystalline Ni2Ge/Ge/Ni2Ge nanowire heterostructure transistors.

    Science.gov (United States)

    Tang, Jianshi; Wang, Chiu-Yen; Xiu, Faxian; Hong, Augustin J; Chen, Shengyu; Wang, Minsheng; Zeng, Caifu; Yang, Hong-Jie; Tuan, Hsing-Yu; Tsai, Cho-Jen; Chen, Lih Juann; Wang, Kang L

    2010-12-17

    In this study, we report on the formation of a single-crystalline Ni(2)Ge/Ge/Ni(2)Ge nanowire heterostructure and its field effect characteristics by controlled reaction between a supercritical fluid-liquid-solid (SFLS) synthesized Ge nanowire and Ni metal contacts. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies reveal a wide temperature range to convert the Ge nanowire to single-crystalline Ni(2)Ge by a thermal diffusion process. The maximum current density of the fully germanide Ni(2)Ge nanowires exceeds 3.5 × 10(7) A cm(-2), and the resistivity is about 88 μΩ cm. The in situ reaction examined by TEM shows atomically sharp interfaces for the Ni(2)Ge/Ge/Ni(2)Ge heterostructure. The interface epitaxial relationships are determined to be [Formula: see text] and [Formula: see text]. Back-gate field effect transistors (FETs) were also fabricated using this low resistivity Ni(2)Ge as source/drain contacts. Electrical measurements show a good p-type FET behavior with an on/off ratio over 10(3) and a one order of magnitude improvement in hole mobility from that of SFLS-synthesized Ge nanowire.

  8. Synthesis and magnetic properties of multilayer Ni/Cu and NiFe/Cu ...

    Indian Academy of Sciences (India)

    (EV5 VSM, ADE Technologies) and MFM (D3100, Digital Instrument) were used to characterize the magnetic properties of these nanowires. 3. Discussion. The bamboo-like structure of Ni/Cu nanowires is shown in figure 1. From the. TEM micrograph the thickness of Ni layer and Cu layer are 400 nm and 50 nm, respectively.

  9. Eutectic superalloys strengthened by delta Ni3Cb lamellae, and gamma prime, Ni3Al precipitates.

    Science.gov (United States)

    Lemkey, F. D.; Thompson, E. R.

    1972-01-01

    Bivariant eutectic alloys, located on a liquidus surface within the Ni-Cb-Cr-Al quaternary, were identified which permitted the production of aligned delta Ni3Cb lamellae within a nichrome matrix containing the fcc precipitate gamma prime Ni3Al. The volume fraction of delta and gamma prime could be varied significantly by compositional changes. After directional solidification certain alloys possessed improved ductility and corrosion resistance with respect to the Ni3Al-Ni3Cb eutectic, while their values of tensile and creep strength approached or exceeded those for the Ni3Al-Ni3Cb pseudobinary system. The mechanical properties of the directionally solidified alloy, Ni-19.7 wt % Cb-6.0 wt % Cr-2.5 wt % Al, were evaluated. Its longitudinal strength in tension and creep was found to be superior to all advanced nickel base superalloys. It is thus demonstrated that useful properties for gas turbine airfoil applications can be achieved by reinforcing a strong and tough gamma nichrome matrix containing precipitated gamma prime by a strong lamellar intermetallic compound having greater strength at elevated temperature.

  10. Enhanced Electrocatalytic Activity for Water Splitting on NiO/Ni/Carbon Fiber Paper

    Directory of Open Access Journals (Sweden)

    Ruoyu Zhang

    2016-12-01

    Full Text Available Large-scale growth of low-cost, efficient, and durable non-noble metal-based electrocatalysts for water splitting is crucial for future renewable energy systems. Atomic layer deposition (ALD provides a promising route for depositing uniform thin coatings of electrocatalysts, which are useful in many technologies, including the splitting of water. In this communication, we report the growth of a NiO/Ni catalyst directly on carbon fiber paper by atomic layer deposition and report subsequent reduction and oxidation annealing treatments. The 10–20 nm NiO/Ni nanoparticle catalysts can reach a current density of 10 mA·cm−2 at an overpotential of 189 mV for hydrogen evolution reactions and 257 mV for oxygen evolution reactions with high stability. We further successfully achieved a water splitting current density of 10 mA·cm−2 at 1.78 V using a typical NiO/Ni coated carbon fiber paper two-electrode setup. The results suggest that nanoparticulate NiO/Ni is an active, stable, and noble-metal-free electrocatalyst, which facilitates a method for future water splitting applications.

  11. Adherencia al tratamiento en niñas y niños con VIH

    Directory of Open Access Journals (Sweden)

    Ana María Ruiz Navia

    2009-01-01

    Full Text Available Este artículo describe y determina el grado de adherencia al tratamiento en niños y niñas con VIH/ SIDA teniendo en cuenta los comportamientos y las variables asociadas a ésta. La muestra estuvo conformada por 1 niño y 5 niñas, diagnosticados con VIH, y su respectivo cuidador primario, quienes respondieron a la entrevista semiestructurada de evaluación de adherencia para niños y niñas con VIH/ SIDA ad hoc y a la entrevista semiestructurada de evaluación de adherencia para niños y niñas con VIH/SIDA versión cuidador primario ad hoc, respectivamente. Los resultados muestran la presencia de conductas de adherencia en los participantes del estudio, evidenciando la influencia de una serie de variables determinantes para este comportamiento. Cinco de los participantes cumplieron más del 95% de adherencia, mientras que uno se ubicó por debajo de este porcentaje. Como aspectos centrales se destacan la influencia de los estados emocionales en la toma del medicamento y la importancia del rol del cuidador primario en la adherencia.

  12. Probing the semi-magicity of $^{68}$Ni via the $^{3}$H($^{66}$Ni,$^{68}$Ni)p two-neutron transfer reaction in inverse kinematics

    CERN Multimedia

    Reiter, P; Blazhev, A A; Kruecken, R; Franchoo, S; Mertzimekis, T; Darby, I G; Van de walle, J; Raabe, R; Elseviers, J; Gernhaeuser, R A; Sorlin, O H; Georgiev, G P; Bree, N C F; Habs, D; Chapman, R; Gaudefroy, L; Diriken, J V J; Jenkins, D G; Kroell, T; Axiotis, M; Huyse, M L; Patronis, N

    We propose to perform the two-neutron transfer reaction $^{3}$H($^{66}$Ni, $^{68}$Ni)$p$ using the ISOLDE radioactive ion beam at 2.7 $A$ MeV and the MINIBALL + T-REX setup to characterize the 0$^{+}$ and 2$^{+}$ states in $^{68}$Ni.

  13. First-Principles Study of Substitution of Au for Ni in Ni3Sn4

    Science.gov (United States)

    Tian, Yali; Wu, Ping

    2018-02-01

    First-principles calculations were performed to investigate the effects of substitution of Au for Ni on the structural, elastic, thermodynamic and electronic properties of Ni3Sn4. The calculated lattice constants for the pure phase are consistent with the reported values. Substitution of Au for Ni results in a stable thermodynamic structure. The bulk modulus, shear modulus, Young's modulus, hardness and thermal conductivity are decreased and the relative brittleness is improved after substitution. A three-dimensional graphic representation of the anisotropy of Young's modulus indicates that substitution of Au for Ni increases the anisotropy. All of the compound compositions examined are metallic and nonmagnetic. The electronic density of states manifests a conjoined peak between - 6 eV and - 4 eV hybridized by Au-d electrons and Sn-p electrons when the fraction of Au atom is above 14.29 at.% in Ni3Sn4.

  14. Ni(OH){sub 2} and NiO nano structures: Synthesis, characterization and electrochemical performance

    Energy Technology Data Exchange (ETDEWEB)

    Saghatforoush, Lotf Ali; Sanati, Soheila; Mehdizadeh, Robabeh [Payam Noor Univ., Tehran (Iran, Islamic Republic of); Hasanzadeh, Mohammad [Tabriz Univ. of Medical Sciences, Tabriz (Iran, Islamic Republic of)

    2012-04-15

    Hydrothermal route have been used in different conditions for preparation of Ni(OH){sub 2} nano structures. The NiO nanoparticles were obtained by calcining the Ni(OH){sub 2} precursor at 450 .deg. C for 2 h. The effect of sodium dodecyl sulfonate (SDS) as surfactant on the morphology and size of Ni(OH){sub 2} nanoparticles were discussed in detail. X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) spectroscopy were used to characterize the products. The growth mechanism of the as-synthesized nano structures was also discussed in detail based on the experimental results. Coming up, the NiO nanoparticle modified carbon paste electrode was applied to the determination of captopril in aqueous solution.

  15. Effect of amount of glycine as fuel in obtaining nanocomposite Ni/NiO

    International Nuclear Information System (INIS)

    Simoes, A.N.; Simoes, V.N.; Neiva, L.S.; Quirino, M.R.; Vieira, D.A.; Gama, L.

    2010-01-01

    This paper proposes to investigate the effect of the amount of glycine in obtaining nanocomposite Ni/NiO synthesized by combustion reaction technique. The amount of glycine used was calculated on the stoichiometric composition of 50% and 100%. Characterizations by X-ray diffraction (XRD), N2 adsorption by the BET method and scanning electron microscopy (SEM) were performed with powder of Ni/NiO result. The analysis of X-ray diffraction showed the presence of crystalline NiO phase in the presence of nickel as a secondary phase, whose amount increased with the amount of glycine. Increasing the concentration of glycine also caused an increase in surface area, which ranged from 1.1 to 1.4 m 2 /g. The micrographs revealed the formation of soft agglomerates with porous appearance and easy dispersions. It can be concluded that the synthesis is effective to obtain nanosized powders. (author)

  16. Mechanical alloying of the FeNi-Ag system

    International Nuclear Information System (INIS)

    Gonzalez, G.; Ibarra, D.; Ochoa, J.; Villalba, R.; Sagarzazu, A.

    2007-01-01

    The Fe-Ni-Ag system is of particular interest for its potential applications as soft magnetic granular material with small magnetic grains embedded in a non-magnetic metal matrix. Under equilibrium conditions: Fe-Ag and Ni-Ag are immiscible and Fe-Ni shows complete solubility. These materials are particularly important for magnetoresistivity properties. The properties of these alloys are closely related to their microstructure; therefore, a detailed study of the transformations occurring during milling was undertaken using pre-alloyed Fe x Ni 100-x (x = 30, 50 and 70) further milled with different Ag content to give the following alloys compositions (Fe x -Ni 100-x ) 100-y Ag y (y = 5, 20, 60). Consolidation of the mechanically alloyed powders by sintering at 950 o C was performed. Morphological and structural characterization of the sintered powders was carried out by scanning and transmission electron microscopy and X-ray diffraction. Fe 30 Ni 70 and Fe 50 Ni 50 formed ordered FeNi 3 compound. Fe 70 Ni 30 showed the formation of a mixture of γ-(Fe,Ni) and α-Fe(Ni) solid solutions. The mixture of these systems with Ag showed the metal solid solutions surrounded by Ag islands of Fe x Ni y -Ag, There was also evidence of Ag diffusing into the γ-(Fe,Ni). High Ag content (60%) shows formation of islands of FeNi surrounded by Ag. Sintering is always improved with the Ag content

  17. Magnetoresistance of nanogranular Ni/NiO controlled by exchange anisotropy

    International Nuclear Information System (INIS)

    Del Bianco, L.; Spizzo, F.; Tamisari, M.; Allia, P.

    2013-01-01

    A link between exchange anisotropy and magnetoresistance has been found to occur in a Ni/NiO sample consisting of Ni nanocrystallites (mean size ∼13 nm, Ni content ∼33 vol%) dispersed in a NiO matrix. This material shows metallic-type electric conduction and isotropic spin-dependent magnetoresistance as well as exchange bias effect. The latter is the outcome of an exchange anisotropy arising from the contact interaction between the Ni phase and the NiO matrix. Combined analysis of magnetization M(H) and magnetoresistance MR(H) loops measured in the 5–250 K temperature range after zero-field-cooling (ZFC) and after field-cooling (FC) from 300 K reveals that the magnetoresistance is influenced by exchange anisotropy, which is triggered by the FC process and can be modified in strength by varying the temperature. Compared to the ZFC case, the exchange anisotropy produces a horizontal shift of the FC MR(H) loop along with a reduction of the MR response associated to the reorientation of the Ni moments. A strict connection between magnetoresistance and remanent magnetization of FC loops on one side and the exchange field on the other, ruled by exchange anisotropy, is indicated. - Highlights: • Nanogranular Ni/NiO with giant magnetoresistance (MR) and exchange bias effect. • Exchange anisotropy produces a shift of the field-cooled MR(H) loop and reduces MR. • MR, remanence of field-cooled loops and exchange field are three correlated quantities. • It is possible to control MR of nanogranular systems through the exchange anisotropy

  18. Oxide Scales Formed on NiTi and NiPtTi Shape Memory Alloys

    Science.gov (United States)

    Smialek, James L.; Garg, Anita; Rogers, Richard B.; Noebe, Ronald D.

    2011-01-01

    Ni-49Ti and Ni-30Pt-50Ti (at.%) shape memory alloys were oxidized isothermally in air over the temperature range of 500 to 900 C. The microstructure, composition, and phase content of the scales were studied by SEM, EDS, XRD, and metallography. Extensive plan view SEM/EDS identified various features of intact or spalled scale surfaces. The outer surface of the scale was a relatively pure TiO2 rutile structure, typified by a distinct highly striated and faceted crystal morphology. Crystal size increased significantly with temperature. Spalled regions exhibited some porosity and less distinct features. More detailed information was obtained by correlation of SEM/EDS studies of 700 C/100 hr cross-sections with XRD analyses of serial or taper-polishing of plan surfaces. Overall, multiple layers exhibited graded mixtures of NiO, TiO2, NiTiO3, Ni(Ti) or Pt(Ni,Ti) metal dispersoids, Ni3Ti or Pt3Ti depletion zones, and substrate, in that order. The NiTi alloy contained a 3 at.% Fe impurity that appeared in embedded localized Fe-Ti-rich oxides, while the NiPtTi alloy contained a 2 v/o dispersion of TiC that appeared in lower layers. The oxidation kinetics of both alloys (in a previous report) indicated parabolic growth and an activation energy (250 kJ/mole) near those reported in other Ti and NiTi studies. This is generally consistent with TiO2 existing as the primary scale constituent, as described here.

  19. Hydrothermal synthesis of α-Ni(OH){sub 2} and its conversion to NiO with electrochemical properties

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Yong; Ma, Jianmin, E-mail: nanoelechem@hnu.edu.cn; Wang, Taihong, E-mail: thwang@hnu.edu.cn

    2014-01-05

    Highlights: • α-Ni(OH){sub 2} microspheres have been synthesized with triethanolamine. • The formation mechanism of α-Ni(OH){sub 2} microspheres is suggested. • NiO deriving from α-Ni(OH){sub 2} microspheres exhibits better electrochemical performances. -- Abstract: The paper reports the fabrication of microscale NiO matrixes with enhanced electrochemical properties through annealing the corresponding chrysanthemum-like α-Ni(OH){sub 2} microspheres. The precursor α-Ni(OH){sub 2} can be synthesized by a hydrothermal method using triethanolamine as the alkaline source. The formation mechanism of chrysanthemum-like α-Ni(OH){sub 2} microspheres is properly discussed. Furthermore, the electrochemical experiments demonstrate that the microscale NiO matrixes show superior electrochemical behavior in lithium-ion batteries due to their unique structures.

  20. Hydrogen absorption kinetics and structural properties of Mg85Ni10Ca5 and Mg90Ni10

    International Nuclear Information System (INIS)

    Aoki, Masakazu; Saito, Katsushi; Towata, Shin-ichi

    2005-01-01

    Mg 85 Ni 10 Ca 5 and Mg 90 Ni 10 were prepared by melting mixtures of the elements in mild steel crucibles and pouring them into copper molds. Hydrogen absorption kinetics and structural properties of the alloys were characterized by the volumetric method using a Sievert's apparatus, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The crystallite size of Mg in Mg 85 Ni 10 Ca 5 , which is evaluated by XRD peak broadening, is about 50% smaller than that in Mg 90 Ni 10 . In addition, the nanometer-scale structure composed of Mg, Mg 2 Ni, Mg 2 Ca was observed in Mg 85 Ni 10 Ca 5 . Mg 85 Ni 10 Ca 5 shows better hydrogen absorption kinetics than Mg 90 Ni 10 in the temperature range of room temperature to 573 K. The better absorption kinetics of Mg 85 Ni 10 Ca 5 is mainly attributed to the nanometer-scale structure

  1. Evolution of Ni nanofilaments and electromagnetic coupling in the resistive switching of NiO

    Science.gov (United States)

    Luo, Yuxiang; Zhao, Diyang; Zhao, Yonggang; Chiang, Fu-Kuo; Chen, Pengcheng; Guo, Minghua; Luo, Nannan; Jiang, Xingli; Miao, Peixian; Sun, Ying; Chen, Aitian; Lin, Zhu; Li, Jianqi; Duan, Wenhui; Cai, Jianwang; Wang, Yayu

    2014-12-01

    Resistive switching effect in conductor/insulator/conductor thin-film stacks is promising for resistance random access memory with high-density, fast speed, low power dissipation and high endurance, as well as novel computer logic architectures. NiO is a model system for the resistive switching effect and the formation/rupture of Ni nanofilaments is considered to be essential. However, it is not clear how the nanofilaments evolve in the switching process. Moreover, since Ni nanofilaments should be ferromagnetic, it provides an opportunity to explore the electromagnetic coupling in this system. Here, we report a direct observation of Ni nanofilaments and their specific evolution process for the first time by a combination of various measurements and theoretical calculations. We found that multi-nanofilaments are involved in the low resistance state and the nanofilaments become thin and rupture separately in the RESET process with subsequent increase of the rupture gaps. Theoretical calculations reveal the role of oxygen vacancy amount in the evolution of Ni nanofilaments. We also demonstrate electromagnetic coupling in this system, which opens a new avenue for multifunctional devices.Resistive switching effect in conductor/insulator/conductor thin-film stacks is promising for resistance random access memory with high-density, fast speed, low power dissipation and high endurance, as well as novel computer logic architectures. NiO is a model system for the resistive switching effect and the formation/rupture of Ni nanofilaments is considered to be essential. However, it is not clear how the nanofilaments evolve in the switching process. Moreover, since Ni nanofilaments should be ferromagnetic, it provides an opportunity to explore the electromagnetic coupling in this system. Here, we report a direct observation of Ni nanofilaments and their specific evolution process for the first time by a combination of various measurements and theoretical calculations. We found

  2. Exchange bias beyond the superparamagnetic blocking temperature of the antiferromagnet in a Ni-NiO nanoparticulate system

    Science.gov (United States)

    Roy, Aparna; De Toro, J. A.; Amaral, V. S.; Muniz, P.; Riveiro, J. M.; Ferreira, J. M. F.

    2014-02-01

    We report magnetic and exchange bias studies on Ni-NiO nanoparticulate systems synthesized by a two-step process, namely, chemical reduction of a Ni salt followed by air annealing of the dried precipitate in the temperature range 400-550 °C. Size of Ni and NiO crystallites as estimated from X-ray diffraction line broadening ranges between 10.5-13.5 nm and 2.3-4 nm, respectively. The magneto-thermal plots (M-T) of these bi-magnetic samples show a well developed peak in the vicinity of 130 K. This has been identified as the superparamagnetic blocking temperature "TB" of NiO. Interestingly, all samples exhibit exchange bias even above their respective NiO blocking temperatures, right up to 300 K, the maximum temperature of measurement. This is in contrast to previous reports since exchange bias requires the antiferromagnetic NiO to have a stable direction of its moment in order to pin the ferromagnet (Ni) magnetization, whereas such stability is unlikely above TB since the NiO is superparamagnetic, its moment flipping under thermal activation. Our observation is elucidated by taking into account the core-shell morphology of the Ni-NiO nanoparticles whereby clustering of some of these nanoparticles connects their NiO shells to form extended continuous regions of NiO, which because of their large size remain blocked at T > TB, with thermally stable spins capable of pinning the Ni cores and giving rise to exchange bias. The investigated samples may thus be envisaged as being constituted of both isolated core-shell Ni-NiO nanoparticles as well as clustered ones, with TB denoting the blocking temperature of the NiO shell of the isolated particles.

  3. La niña proletaria

    Directory of Open Access Journals (Sweden)

    Cartabia, Sabrina A.

    2011-12-01

    Full Text Available El presente trabajo se propone trazar un paralelo entre el cuento de Osvaldo Lamborghini “El niño proletario”, el cual, según la autora del ensayo, introduce al lector en la lucha de clases y el sometimiento de los/as proletarios/as, que sufren las mujeres, en particular a través de la violencia sexual. De esa forma la autora se pregunta si el poder que ciertas clases detentan sobre otras no influye también sobre el sometimiento de la mujer. El ensayo analiza además cómo la violencia sexual es una herramienta que constituye la base de la desigualdad, el sometimiento y la degradación de la mujer, al igual que constituye una herramienta de opresión de otros grupos vulnerables como los niños y niñas.

  4. Analisis Kesalahan Penggunaan Partikel Ni dan De

    Directory of Open Access Journals (Sweden)

    Elisa Carolina Marion

    2008-05-01

    Full Text Available Articel clasified the type and cause of mistake done by Bina Nusantara Japanese student of six and eight semesters on the use of ni (に and de (で particles indicating place in the exam. Data were collected from library research and distributed questionnaires to 79 student of the 6th and 8th semester, Japanese departement. The result showed that the student of Japanese language did not make the same mistake in using the ni (に and de (で particles having the some function in indicating place. It is concluded that the respondents are able to use the ni (に and de (で particles.       

  5. Advances in developing TiNi nanoparticles

    International Nuclear Information System (INIS)

    Castro, A. Torres; Cuellar, E. Lopez; Mendez, U. Ortiz; Yacaman, M. Jose

    2006-01-01

    The elaboration of nanoparticles has become a field of great interest for many scientists. Nanoparticles possess different properties than those ones shown in bulk materials. Shape memory alloys have the exceptional ability to recuperate its original shape by simple heating after being 'plastically' deformed. When this process is originated, important changes in properties, as mechanical and electrical, are developed in bulk material. If there is possible to obtain nanoparticles with shape memory effects, these nanoparticles could be used in the elaboration of nanofluids with the ability to change their electrical and thermal conductivity with temperature changes, i.e., smart nanofluids. In this work, some recent results and discussion of TiNi nanoparticles obtained by ion beam milling directly from a TiNi wire with shape memory are presented. The nanoparticles obtained by this process are about 2 nm of diameter with a composition of Ti-41.0 at.% Ni. Synthesized nanoparticles elaborated by this method have an ordered structure

  6. Dynamical effects in x-ray absorption spectra of graphene and monolayered h-BN on Ni(111)

    Czech Academy of Sciences Publication Activity Database

    Rusz, Ján; Preobrajenski, A.B.; Ling, M.L.; Vinogradov, N.A.; Martensson, N.; Wessely, O.; Sanyal, B.; Eriksson, O.

    2010-01-01

    Roč. 81, č. 7 (2010), 073402/1-073402/4 ISSN 1098-0121 Institutional research plan: CEZ:AV0Z10100520 Keywords : fine-structure * boron-nitride * hegxagonal BN * K- edge * graphite * excitations * excitons Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.772, year: 2010

  7. Effects of phase transformation and interdiffusion on the exchange bias of NiFe/NiMn

    International Nuclear Information System (INIS)

    Lai, Chih-Huang; Lien, W. C.; Chen, F. R.; Kai, J. J.; Mao, S.

    2001-01-01

    The correlation between the exchange field of NiFe/NiMn and the phase transformation of NiMn was investigated. Transmission electron microscopy (TEM) dark-field images, contributed by the order phase of NiMn, were used to identify the location and volume fraction of the order phase. TEM selected area diffraction patterns showed the (110) superlattice diffraction rings of NiMn, verifying the existence of the order phase in the annealed samples. The order volume fraction can be calculated by the dark field image contributed by the (110) diffraction. The exchange field increased almost linearly with increasing order volume fraction. Energy dispersive x-ray spectroscopy attached to TEM indicated that Mn diffused into NiFe for annealing at 280 degreeC, leading to a larger coercivity and small coercivity squareness. Part of the NiMn still maintains the paramagnetic phase even after annealing at 280 degreeC. [copyright] 2001 American Institute of Physics

  8. Corrosion and wear resistance study of Ni-P and Ni-P-PTFE nanocomposite coatings

    Science.gov (United States)

    Ankita, Sharma; Singh, Ajay

    2011-09-01

    This article reports on the corrosion and wear resistance of Ni-P and Ni-P-PTFE nanocomposite coatings deposited on mild steel substrates using the electroless plating technique. The coatings were characterized by scanning electron microscopy (SEM), energy dispersive analysis of X-Ray (EDAX), and X-ray diffractometry (XRD). The coatings were smooth and had thicknesses between 7 and 23 µm. They contained Ni, P, and additionally, F, in the case of the Ni-P-PTFE films. A broadening of the Ni peak in XRD was attributed to the amorphous nature and/or fine grain size of the films. Corrosion resistance was measured using immersion and electrochemical polarization tests in 3.5% NaCl solution whereas wear resistance was determined by the pin-on-disc method. Both Ni-P and Ni-P-PTFE coatings exhibited significant improvement in corrosion (in salty media) and wear behavior. Furthermore, the addition of PTFE in the coatings showed improvement in their corrosion resistance as well as a reduction in friction coefficient. Our testing revealed that the coatings' wore out following the "adhesive type" mechanism.

  9. Exchange bias in finite sized NiO nanoparticles with Ni clusters

    Energy Technology Data Exchange (ETDEWEB)

    Gandhi, Ashish Chhaganlal; Lin, Jauyn Grace, E-mail: jglin@ntu.edu.tw

    2017-02-15

    Structural and magnetic properties of finite sized NiO nanoparticles are investigated with synchrotron X-ray diffraction (XRD), transmission electron microscopy, magnetometer and ferromagnetic resonance (FMR) spectroscopy. A minor Ni phase is detected with synchrotron XRD, attributed to the oxygen defects in the NiO core. A considerable exchange bias of ~100 Oe is observed at 50 K and it drops abruptly and vanishes above 150 K, in association with the reduction of frozen spins. FMR data indicate a strong interaction between ferromagnetic (FM) and antiferromagnetic (AFM) phases below 150 K, consistent with the picture of isolated FM clusters in AFM matrix. - Highlights: • Structural and magnetic properties of finite sized NiO nanoparticles are systematically investigated with several advanced techniques. • A strong interaction between ferromagnetic and antiferromagnetic phases is found below 150 K. • Exchange bias field in finite sized NiO nanoparticles is due to anisotropy energy of Ni clusters over riding the domain wall energy of NiO.

  10. Exchange bias in finite sized NiO nanoparticles with Ni clusters

    International Nuclear Information System (INIS)

    Gandhi, Ashish Chhaganlal; Lin, Jauyn Grace

    2017-01-01

    Structural and magnetic properties of finite sized NiO nanoparticles are investigated with synchrotron X-ray diffraction (XRD), transmission electron microscopy, magnetometer and ferromagnetic resonance (FMR) spectroscopy. A minor Ni phase is detected with synchrotron XRD, attributed to the oxygen defects in the NiO core. A considerable exchange bias of ~100 Oe is observed at 50 K and it drops abruptly and vanishes above 150 K, in association with the reduction of frozen spins. FMR data indicate a strong interaction between ferromagnetic (FM) and antiferromagnetic (AFM) phases below 150 K, consistent with the picture of isolated FM clusters in AFM matrix. - Highlights: • Structural and magnetic properties of finite sized NiO nanoparticles are systematically investigated with several advanced techniques. • A strong interaction between ferromagnetic and antiferromagnetic phases is found below 150 K. • Exchange bias field in finite sized NiO nanoparticles is due to anisotropy energy of Ni clusters over riding the domain wall energy of NiO.

  11. Bone Cell–materials Interactions and Ni Ion Release of Anodized Equiatomic NiTi Alloy

    Science.gov (United States)

    Bernard, Sheldon A.; Balla, Vamsi Krishna; Davies, Neal M.; Bose, Susmita; Bandyopadhyay, Amit

    2011-01-01

    Laser processed NiTi alloy was anodized for different durations in H2SO4 electrolyte with varying pH to create biocompatible surfaces with low Ni ion release as well as bioactive surfaces to enhance biocompatibility and bone cell-materials interactions. The anodized surfaces were assessed for their in vitro cell-materials interactions using human fetal osteoblast (hFOB) cells for 3, 7 and 11 days, and Ni ion release up to 8 weeks in simulated body fluids. The results were correlated with surface morphologies of anodized surfaces characterized using field-emission scanning electron microscopy (FESEM). The results show that the anodization creates a surface with nano/micro roughness depending on anodization conditions. The hydrophilicity of NiTi surface was found to improve after anodization due to lower contact angles in cell media, which dropped from 32° to NiTi surfaces after anodization. This work indicates that anodization of NiTi alloy has a positive influence on the surface energy and surface morphology, which in turn improve bone cell-materials interactions and reduce Ni ion release in vitro. PMID:21232641

  12. Tipos especiales de niños

    Directory of Open Access Journals (Sweden)

    Mercedes Rodrigo Bellido

    1946-09-01

    Full Text Available En las tres últimas lecciones han sido expuestas algunas consideraciones referentes a niños y adolescentes desde el nacimiento hasta el dintel de la juventud. En todas ellas hemos procurado poner de relieve la necesidad de individualizar el conocimiento de cada niño para obtener mejores resultados en su adaptación a su futura vida de adultos, En todas ellas  nos hemos referido al llamado niño normal. Nos corresponde en la lección de hoy ocuparnos can la superficialidad característica de estas charlas tipo-muestrario, de otras categorías de niños muy dignos de interés.. quienes unas por exceso, otros por defecto, otros por dificultades de adaptación por diferentes causas, se desvían de la línea media de la normalidad. Consideramos que no está fuera del lugar, aquí, el tema de los niños excepcionales y por el contrario que es necesario intensificar el estudio de los trastornos de la vida mental y emocional de los niños en la preparación de los estudiantes de Medicina. Y no es nuestra solo esta opinión; no hace mucho tiempo en la Medical School de Ia Universidad de Minnessota hemos sabido que se ha hecho un intento de considerar y evaluar factores emocionales ambientales sobre las mismas bases que los descubrimientos fisiológicos.

  13. Generation and Decay Mechanisms of Ningaloo Niño/Niña

    Science.gov (United States)

    Kataoka, Takahito; Tozuka, Tomoki; Yamagata, Toshio

    2017-11-01

    Using an ocean model, generation and decay mechanisms of warm/cool sea surface temperature anomalies (SSTAs) off Western Australia, or Ningaloo Niño/Niña, are investigated through the calculation of a mixed-layer temperature (MLT) balance taking the mixed-layer depth (MLD) variation into account. Since Ningaloo Niño/Niña develops owing to local air-sea interaction and/or remote forcing, events are classified into two cases based on alongshore wind anomalies and analyzed separately. It is revealed that the anomalous meridional advection associated with the stronger Leeuwin Current and the enhanced warming by the climatological shortwave radiation because of the shallower MLD generate warm SSTAs in the coastal region for both cases of Ningaloo Niño. On the other hand, the latent heat flux damps SSTAs only in a case without northerly alongshore wind anomalies. In the decay, larger sensible heat loss is important. Because of the reduced meridional temperature gradient, the meridional advection eventually damps SSTAs. The sensitivity change to the climatological shortwave radiation owing to MLD anomalies explains offshore MLT tendency anomalies for both cases throughout the events. The mechanisms for Ningaloo Niña are close to a mirror image of Ningaloo Niño but differ in that the latent heat flux damps offshore SSTAs. The seasonal phase-locking nature of Ningaloo Niño/Niña is related to the seasonal variations of MLD and surface heat fluxes, which regulate the amplitude and sign of the sensitivity change to surface heat fluxes. It is also related to the seasonal variations of the Leeuwin Current and meridional temperature gradient through advection anomalies.

  14. Ionizing Radiation Effects in Ni Nanotubes

    Science.gov (United States)

    Shlimas, D.; Kozlovsky, A.; Shumskaya, A.; Kaniukov, E.; Ibragimova, M.; Zdorovets, M.; Kadyrzhanov, K.

    2017-01-01

    Polycrystalline nickel nanotubes with diameter of 380 nm and wall thickness 95 nm were synthesized by electrochemical method using PET track-etched membranes with thickness of 12 μm. A comprehensive study of the structural, morphological and electrical characteristics of Ni nanotubes irradiated with C+13 ions with energy 1.75 MeV/nucleon and fluence ranging from 109 to 5 × 1011 cm-2 was carried out. The ability of modification of structural parameters such as lattice parameter and the average size of crystallites and conductivity of Ni nanotubes by irradiation was shown.

  15. Salud mental del niño

    OpenAIRE

    Ospina de González, Bernarda

    1987-01-01

    Es ya reconocida por todos las importancia de los primeros años de vida en la estructutración de la personalidad y, por consiguiente, en la salud mental del niño. En este artículo se hace una síntesis de los diferentes aspectos del desarrollo de la personalidad infanltil que seben ser conocidos por el personal de salud para estar en condiciones de brindar una atención integral a la madre y al niño. Con igual propósito se señalan algunos patrones de tipo psicosocial que influyen en la estabili...

  16. Magnetic anisotropy of Ni/Cr multilayers

    International Nuclear Information System (INIS)

    Kang, S.; Xia, H.

    1997-01-01

    The magnetic anisotropy of Ni/Cr multilayers has been investigated by using vibrating sample magnetometer (VSM) and ferromagnetic resonance techniques (FMR). The FMR spectra are obtained as a function of the orientation of the applied magnetic field from in-plane to out-of-plane. The results are fitted theoretically to determine the magnetic anisotropy. From VSM and FMR, a positive value for Ni/Cr interface anisotropy is obtained, which favours a perpendicular easy axis. The possible mechanism for the perpendicular anisotropy has been discussed and it may be attributed to the magnetostriction, caused by intrinsic stress due to lattice mismatch. (orig.). With 005 figs., 001 tabs

  17. The structure of extruded NiAl

    Science.gov (United States)

    Baker, I.; Schulson, E. M.

    1984-01-01

    The deformation structure of Ni-rich NiAl extruded at 550 C has been characterized by transmission electron microscopy and by optical microscopy. Dislocations having a(100) Burgers vectors were found as complex networks, tangles, and prismatic loops. a(110) dislocations, which were rare, were concluded to arise from reactions of a(100) dislocations. Evidence of recovery and recrystallization was obtained. Extrusion was deemed to have been possible by the operation of (hko)(001) slip systems (often in plane strain flow) plus diffusion-assisted processes.

  18. Comparative effectiveness of NiCl2, Ni- and NiO-NPs in controlling oral bacterial growth and biofilm formation on oral surfaces.

    Science.gov (United States)

    Khan, Shams Tabrez; Ahamed, Maqusood; Alhadlaq, Hisham A; Musarrat, Javed; Al-Khedhairy, Abdulaziz

    2013-12-01

    Oral ailments are often treated with antibiotics, which are rendered ineffective as bacteria continue to develop resistance against them. It has been suggested that the nanoparticles (NPs) approach may provide a safer and viable alternative to traditional antibacterial agents. Therefore, nickel (Ni)- and nickel oxide (NiO)-NPs were synthesized, characterized and assessed for their efficacy in reducing oral bacterial load in vitro. Also, the effects of bulk compound NiCl2 (Ni ions), along with the Ni- and NiO-NPs on bacterial exopolysaccharide (EPS) production and biofilm formation on the surface of artificial teeth, and acrylic dentures, were investigated. Total bacteria from a healthy male were collected and adjusted to 4×109cells/ml for all the tests. Effect of the NPs on growth, biofilm formation, EPS production and acid production from glucose was tested using standard protocols. Data revealed that the Ni-NPs (average size 41.23nm) exhibited an IC50 value of 73.37μg/ml against total oral bacteria. While, NiO-NPs (average size 35.67nm) were found less effective with much higher IC50 value of 197.18μg/ml. Indeed, the Ni ions exhibited greater biocidal activity with an IC50 value of 70μg/ml. Similar results were obtained with biofilm inhibition on the surfaces of dental prostheses. The results explicitly suggested the effectiveness of tested Ni compounds on the growth of oral bacteria and biofilm formation in the order as NiCl2>Ni-NPs>NiO-NPs. The results elucidated that Ni-NPs could serve as effective nanoantibiotics against oral bacteria. Copyright © 2013 Elsevier Ltd. All rights reserved.

  19. Thermodynamics of disaggregated polymer composites based on nanosized powders of Ni and NiO

    Directory of Open Access Journals (Sweden)

    N. S. Volodina

    2015-03-01

    Full Text Available Technique to obtain disaggregated composites with uniform distribution of the Ni nanoparticles in a polymer matrix was developed on the example of epoxy resin. Disaggregated and aggregated composites based on butyl methacrylate copolymer with 5 wt% methacrylic acid and Ni and NiO nanoparticles were obtained. Enthalpies of mixing the components compositions in a wide range of compositions were defined using isothermal calorimetry. Parameters adhesive interaction at the interface and glassy polymer structure changes were calculated. The influence of the chemical nature of nanosized filler on interfacial energy was found.

  20. IMPURITY CENTRES.Ni+ and Ni3+ centers in X-irradiated CaF2

    OpenAIRE

    Casas, J.; Den Hartog, H.; Alcalá, R.

    1980-01-01

    Optical and EPR measurements of CaF2 : Ni before and after X-irradiation are reported. An absorption band at 255 nm grows during X-irradiation. The thermal evolution of this band and some bleaching experiments in 15 K X-irradiated samples containing Vk centers indicate that the 255 nm band is due to Ni+ centers. Some EPR signals associated with the Ni+ centers are also observed. Low temperature measurements show that there are two slightly different kinds of centers one of them having tetrago...

  1. Structure characterization of Ni/NiO and Ti/TiO2 interfaces

    International Nuclear Information System (INIS)

    Lamine, Brahim

    1983-01-01

    This research thesis reports the structure characterization of Ni-NiO and Ti-TiO 2 interfaces through an in-situ investigation of thin blade oxidation, of oxide germination and growth, and through a determination of mutual metal/oxide orientation relationships. Thin films of TiO 2 have also been characterized and the study of the influence of vacuum annealing on TiO 2 layer structure and morphology has been attempted. The examination of metal-oxide interface reveals a duplex structure of NiO and TiO 2 layers, and a preferential grain boundary oxidation of the underlying metal [fr

  2. X-ray fluorescence analysis of Fe - Ni - Mo systems

    International Nuclear Information System (INIS)

    Belyaev, E.E.; Ershov, A.V.; Mashin, A.I.; Mashin, N.I.; Rudnevskij, N.K.

    1998-01-01

    Procedures for the X-ray fluorescence determination of the composition and thickness of Fe - Ni - Mo thin films and the concentration of elements in thick films of the Fe - Ni - Mo alloy are developed [ru

  3. Enhancement of porous silicon photoluminescence using (Ni) treatment

    Science.gov (United States)

    Nabil, M.; Elnouby, M.; Gayeh, N.; Sakr, A. H.; Motaweh, H. A.

    2017-10-01

    A new method has been developed to improve the photoluminescence intensity of porous silicon (PS). Self-organized (PS) can be used in various fields. The deposition of metal nanoparticles (Ni) allows utilizing the obtained nano-composite for numerous applications such as sensor technology, biomedicine, and many more. (Ni/PS) nano-composite powders are prepared using Ni deposition on the PS powder surface. The (Ni/PS) powders became hydrophilic by the deposited Ni nanoparticles. At the different percentages of (Ni: PS), at a higher percentage than (3:1) the values of the crystallite size of Ni and PS are nearly equivalent which suggests the saturation case of PS surface by Ni particles. It also depends on the deposition time value. In this study, that is the commercialization of nanostructured materials, it is important that the manufacturing costs are appropriate and inexpensive for large scale production, in addition, the enhancement of the photoluminescence intensity of (PS).

  4. Effect of thermomechanical pre-treatment on short- and long-term Ni release from biomedical NiTi.

    Science.gov (United States)

    Freiberg, Katharina E; Bremer-Streck, Sibylle; Kiehntopf, Michael; Rettenmayr, Markus; Undisz, Andreas

    2014-05-01

    The effect of annealing and deformation on short-term (21days) and long-term (8months) Ni release from biomedical NiTi wires is studied. The deformation of annealed NiTi wires causes cracking and flaking of the surface oxide layer. Flaking of oxide particles does not uncover the Ni-rich layer underneath the surface oxide layer, since at sites where flaking occurs, a thin (∼25nm) layer of oxide remains on top of this Ni-rich layer. The number of cracks in the oxide and Ni-rich layer, respectively, increases with deformation, and intercrystalline crack propagation into the Ni-rich layer and the NiTi bulk is observed. In plastically deformed wires, the cracks may remain opened, providing access of immersion liquid to these zones. Characteristics and quantity of short-term Ni release are significantly affected by the pre-deformation, resulting in an up to 2 times higher total Ni release within the first 21days of deformed compared to annealed wires. Pre-deformation does not significantly influence long-term Ni release; all annealed and deformed samples exhibit similar long-term Ni release rates. The source of Ni during short-term release is the Ni contained in the surface zone of the oxide layer. For high pre-deformation, the Ni-rich layer is a second source for Ni. This second source is also the cause for Ni release in long-term immersion experiments. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  5. Simple solution-combustion synthesis of Ni-NiO@C nanocomposites with highly electrocatalytic activity for methanol oxidation

    Science.gov (United States)

    Yu, Jie; Ni, Yonghong; Zhai, Muheng

    2018-01-01

    Transition metal and its oxide composite nanomaterials are attracting increasing research interest due to their superior properties and extensive applications in many fields. In this paper, Ni-NiO@C nanocomposites were successfully synthesized in one step via a simple solution-combustion route, employing NiCl2 as the Ni source, oxygen in the atmosphere as the oxygen source, and ethanol as the solvent. The final product was characterized by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), (high resolution) transmission electron microscopy (TEM/HRTEM), and Raman spectra. N2 gas sorption-desorption experiments uncovered that the BET surface area of Ni-NiO@C nanocomposites reached 161.9 m2 g-1, far higher than 34.2 m2 g-1 of Ni-NiO. The electrochemical measurement showed that the as-produced Ni-NiO@C nanocomposites presented better catalytic activity for the electro-oxidation of methanol than Ni-NiO and NiO, which provides a new catalyst selection for the electro-oxidation of methanol.

  6. Fabrication of CdTe/NiTe films on Ni foils by radio-frequency magnetron sputtering method

    International Nuclear Information System (INIS)

    Mu, Yannan; Zhou, Xiaoming; Yao, Huizhen; Su, Shi; Lv, Pin; Chen, Yanli; Wang, Jun; Fu, Wuyou; Song, Wenxu; Yang, Haibin

    2015-01-01

    Highlights: • The effects of T s on CdTe deposited on Ni by magnetron sputtering is investigated. • An effective method is studied of making CdTe/NiTe without post-treatment. • As-prepared CdTe/NiTe raised optical absorption and PEC properties. • Pre-deposited Te can react with Ni to generate NiTe at T s = 350 °C. - Abstract: Cadmium Telluride (CdTe) semiconductor thin films are fabricated on flexible Ni foil substrates using radio-frequency (RF) magnetron sputtering under different substrate temperatures. The crystal structure and properties of the prepared functional thin films were characterized with series analysis technologies. The characterization results revealed that Nickel Telluride (NiTe) phase formatted at the interface of CdTe and Ni substrate when substrate temperature (T s ) is 450 °C. Specially, XRD results demonstrated that CdTe/NiTe films could also be obtained by pre-depositing Te film on Ni and reducing T s to 350 °C. The investigation on optical and photoelectrochemical (PEC) properties of the products illustrated that compact CdTe/NiTe films had improved the absorption in the visible region. Furthermore, PEC measurements indicated that CdTe/NiTe/Ni photoelectrode can have a promising application in photovoltaic devices

  7. Effect of Synthetic Levers on Nickel Phosphide Nanoparticle Formation: Ni5P4 and NiP2.

    Science.gov (United States)

    Li, Da; Senevirathne, Keerthi; Aquilina, Lance; Brock, Stephanie L

    2015-08-17

    Due to their unique catalytic, electronic, and redox processes, Ni5P4 and NiP2 nanoparticles are of interest for a wide-range of applications from the hydrogen evolution reaction to energy storage (batteries); yet synthetic approaches to these materials are limited. In the present work, a phase-control strategy enabling the arrested-precipitation synthesis of nanoparticles of Ni5P4 and NiP2 as phase-pure samples using different Ni organometallic precursors and trioctylphosphine (TOP) is described. The composition and purity of the product can be tuned by changing key synthetic levers, including the Ni precursor, the oleylamine (OAm) coordinating solvent and TOP concentrations, temperature, time, and the presence or absence of a moderate temperature soak step to facilitate formation of Ni and/or Ni-P amorphous nanoparticle intermediates. Notably, the 230 °C intermediate step favors the ultimate formation of Ni2P and hinders further phosphidation to form Ni5P4 or NiP2 as phase-pure products. In the absence of this step, increasing the P/Ni ratio (13-20), reaction temperature (350-385 °C), and time (10-48 h) favors more P-rich phases, and these parameters can be adjusted to generate either Ni5P4 or NiP2. The phase of the obtained particles can also be tuned between pure Ni2P to Ni5P4 and NiP2 by simply decreasing the OAm/TOP ratio and/or changing the nickel precursor (nickel(II)acetylacetonate, nickel(II)acetate tetrahydrate, or bis(cyclooctadiene)nickel(0)). However, at high concentrations of OAm, the product formed is the same regardless of Ni precursor, suggesting the formation of a uniform Ni intermediate (an Ni-oleylamine complex) under these conditions that is responsible for product distribution. Intriguingly, under the extreme phosphidation conditions required to favor Ni5P4 and NiP2 over Ni2P (large excess of TOP), the 20-30 nm crystallites assemble into supraparticles with diameters of 100-500 nm. These factors are discussed in light of a comprehensive

  8. Oxidation of hydrogen peroxide by [Ni (cyclam)] in aqueous acidic ...

    Indian Academy of Sciences (India)

    e-mail: smradha73@gmail.com; viju47@yahoo.co.in. MS received 29 August 2012; revised 9 February 2013; accepted 8 March 2013. Abstract. The kinetics of oxidation of H2O2 by [NiIII(cyclam)]3+, [NiIIIL1], was studied in aqueous acidic media at 25. ◦. C and I = 0.5 M (NaClO4). The [NiIIIL1] to [NiIIL1] reduction was found ...

  9. New route for synthesis of electrocatalytic Ni (OH) 2 modified ...

    Indian Academy of Sciences (India)

    Immobilization of redox species like Ni(OH)2 onto the electrode surface is important in the application areas such as super capacitor, electrochromic displays and electrocatalysis. Nickel hexacyanoferrate (NiHCF) modified glassy carbon could be further derivatized with Ni(OH)2 by electrochemical cycling in alkali.

  10. Phytoremediation technologies for Ni ++ by water hyacinth | Hussain ...

    African Journals Online (AJOL)

    In the second experiment, Ni++ contaminated Hoagland's solution was used for the hydroponic growth of water hyacinth. The result of hydroponic experiment showed the phytoremoval of Ni++ from Ni++ contaminated wastewater; maximum removal was 1.954 μg/g of dry weight. In third experiment, ash of water hyacinth ...

  11. Large scale synthesis and characterization of Ni nanoparticles by ...

    Indian Academy of Sciences (India)

    WINTEC

    energy absorption, fuel cell electrodes, catalysts etc. So the synthesis of Ni nanoparticles has attracted considerable attention. Although many methods are used to prepare Ni particles (Pfeil and Leonard 1987; Degen and Matek. 1999; Zheng et al 2001; Ni et al 2003; Syukri et al 2003;. Hou and Gao 2004; Kumar et al 2004; ...

  12. Fabrication of micro-Ni arrays by electroless and electrochemical ...

    Indian Academy of Sciences (India)

    Administrator

    Abstract. Nickel micro-arrays were fabricated by electroless and electrochemical deposition in an etched porous aluminum membrane. The aluminum membrane with metal characteristic could be fabricated from high-purity aluminium by electrochemical method. The aluminum reduced Ni. 2+ into Ni and the formed Ni.

  13. Morphological and compositional engineering of Ni/carbon ...

    Indian Academy of Sciences (India)

    Ni/multi-walled carbon nanotubes (MWCNTs) composite films were deposited on the glassy carbon electrode (GCE) by a Ni plating bath containing homogeneously dispersed MWCNTs using polyvinylpyrrolidone (PVP) as dispersion additive. Incorporation of MWCNTs into Ni matrix was greatly enhanced by the application ...

  14. Optimization of process parameters for synthesis of silica–Ni ...

    Indian Academy of Sciences (India)

    The optimumcombination of experimental variable, temperature, time of heat treatment under nitrogen atmosphere and amount of Ni-salt was delineated to find out the maximum yield of nanophase Ni in the silica gel matrix. The size of Ni in the silica gel was found to be 34 and 45 nm for the two chosen compositions, ...

  15. Optimization of process parameters for synthesis of silica–Ni ...

    Indian Academy of Sciences (India)

    Abstract. The optimum combination of experimental variable, temperature, time of heat treatment under nitrogen atmosphere and amount of Ni-salt was delineated to find out the maximum yield of nanophase Ni in the silica gel matrix. The size of Ni in the silica gel was found to be 34 and 45 nm for the two chosen ...

  16. Irradiation induced defects in deformed $Ni_{3}Ge$ and $Ni_{3}Al$ single crystals

    CERN Document Server

    Murakumo, T; Miyahara, A; Hannuki, T; Sato, A

    2000-01-01

    The effect of plastic deformation on the formation of point defects and defect clusters by electron irradiation has been studied in Ll /sub 2/ ordered Ni/sub 3/Ge and Ni/sub 3/Al by high voltage electron microscopy. It is found that defects are formed preferentially along the Burgers vector directions as linear lines and grow into linear chains of clusters by electron irradiation. This phenomenon is explained by preferential generation of the defects along the antiphase boundary (APE) tubes, in specimens deformed both below and above the peak temperature T/sub p/. Based on three-dimensional analyses of the defect distribution, the formation mechanism of the APE tubes is discussed with particular reference to superdislocation motion and the strengthening of the Ll/sub 2/ ordered compounds of Ni /sub 3/Ge and Ni/sub 3/Al. (44 refs).

  17. Evolution of collectivity in the 78Ni region: Coulomb excitation of 74Ni at intermediate energies.

    Directory of Open Access Journals (Sweden)

    Marchi T.

    2014-03-01

    Full Text Available The study of the collective properties of nuclear excitations far from stability provides information about the shell structure at extreme conditions. Spectroscopic observables such as the energy or the transition probabilities of the lowest states, in nuclei with large neutron excess, allow to probe the density and isospin dependence of the effective interaction. Indeed, it was recently shown that tensor and three-body forces play an important role in breaking and creating magic numbers. Emblematic is the case of the evolution of the Ni isotopic chain where several features showed up moving from the most neutron rich stable isotope (64Ni towards the 78Ni nucleus where the large neutron excess coincides with a double shell closure. In this framework, we have recently performed an experiment with the goal to extract the B(E2; 0+ → 2+ value for the 74Ni nucleus in an intermediate-energy Coulomb excitation experiment: preliminary results are discussed.

  18. Mechanical properties of NiO/Ni-YSZ composites depending on temperature, porosity and redox cycling

    DEFF Research Database (Denmark)

    Pihlatie, Mikko; Kaiser, Andreas; Mogensen, Mogens Bjerg

    2009-01-01

    %. For all samples a linear relation between Young's modulus and porosity was found. The temperature dependency of the mechanical properties of both as-sintered and reduced composites was investigated by IET up to 1200 degrees C. In the as-sintered state, first an increase and peak of stiffness coinciding......The Impulse Excitation Technique (IET) was used to determine the elastic modulus and specific damping of different Ni/NiO-YSZ composites suitable for use in solid oxide fuel cells (SOFC). The porosity of the as-sintered samples varied from 9 to 38% and that of the reduced ones from 31 to 52...... with the Neel temperature, 250 degrees C, of NiO was observed. Above this temperature, a linear decrease occurred. Specific damping showed a peak at 170-180 degrees C and increased above ca. 1000 degrees C in NiO-YSZ. In the reduced state the elastic modulus decreased linearly with temperature; specific damping...

  19. Synthesis and Magnetic Properties of Ni and Carbon Coated Ni by Levitational Gas Condensation (LGC

    Directory of Open Access Journals (Sweden)

    Young Rang Uhm

    2013-01-01

    Full Text Available The nickel (Ni, and carbon coated nickel (Ni@C nanoparticles were synthesized by levitaional gas condensation (LGC methods using a micron powder feeding (MPF system. Both metal and carbon coated metal nano powders include a magnetic ordered phase. The synthesis by LGC yields spherical particles with a large coercivity. The abnormal initial magnetization curve for Ni indicates a non-collinear magnetic structure between the core and surface layer of the particles. The carbon coated particles had a core structure diameter at and below 10 nm and were covered by 2-3 nm thin carbon layers. The hysteresis loop of the as-prepared Ni@Cs materials with unsaturated magnetization shows a superparamagnetic state at room temperature.

  20. Thermal stability of electrodeposited Ni and Ni-Co layers; an EBSD-study

    DEFF Research Database (Denmark)

    Rasmussen, Anette Alsted; Gholinia, A.; Trimby, P.W.

    2004-01-01

    The influence of heat treatment on the microstructure and the microtexture of electrodeposited Ni and Ni-Co layers was investigated with Electron Backscatter Diffraction (EBSD) with high resolution. Samples were annealed for 1 hour at 523 K and 673 K, the temperature region wherein recrystallisat......The influence of heat treatment on the microstructure and the microtexture of electrodeposited Ni and Ni-Co layers was investigated with Electron Backscatter Diffraction (EBSD) with high resolution. Samples were annealed for 1 hour at 523 K and 673 K, the temperature region wherein...... recrystallisation occurs. The results are discussed in relation to the resolution of EBSD for the very fine grained electrodeposits and previous X-ray diffracton investigations....

  1. Bottom and top AF/FM interfaces of NiFe/FeMn/NiFe trilayers

    Energy Technology Data Exchange (ETDEWEB)

    Nascimento, V.P. [Universidade Federal Rural do Rio de Janeiro, Instituto Multidisciplinar, Rua Professor Paris, s/n Centro, 26221-150 Nova Iguacu, RJ (Brazil)], E-mail: valberto@cbpf.br; Passamani, E.C. [Universidade Federal do Espirito Santo, Depto. Fisica, Avenida Fernando Ferrari, 514 Goiabeiras, 29075-910 Vitoria, ES (Brazil); Alvarenga, A.D. [Instituto Nacional de Metrologia, Normalizacao e Qualidade Industrial, Avenida Nossa Senhora das Gracas, 50 Duque de Caxias, 25250-020 Rio de Janeiro, RJ (Brazil); Biondo, A. [Universidade Federal do Espirito Santo, Depto. Fisica, Avenida Fernando Ferrari, 514 Goiabeiras, 29075-910 Vitoria, ES (Brazil); Pelegrini, F. [Universidade Federal de Goias, Instituto de Fisica, Campus Samambaia, 74001-970 Goiania, GO (Brazil); Saitovitch, E. Baggio [Centro Brasileiro de Pesquisas Fisicas, Rua Dr. Xavier Sigaud, 150 Urca, 22290-180 Rio de Janeiro, RJ (Brazil)

    2008-01-30

    X-ray reflectivity analyses were performed in the Si/WTi (7 nm)/NiFe (30 nm)/FeMn (13 nm)/NiFe (10 nm)/WTi (7 nm) exchange-biased system prepared by magnetron sputtering under three different argon working pressures. Layer-by-layer analyses were realized in order to obtain the interfacial roughness parameters quantitatively. For a fixed argon pressure, the root-mean-square roughness (including the atomic grading) of the upper (FeMn/NiFe) interface are greater than that for the lower one in all studied samples. Argon working pressure also has severe influence over the NiFe/FeMn interfaces, being more pronounced at the upper interfaces.

  2. Ni MINERALIZATION AND PGE CHARACTERIZATION IN THE ...

    African Journals Online (AJOL)

    Mgina

    fractionation, (2) the IPGEs are often associated with chromites as alloys or sulfides in dunites whilst the PPGEs are often ... al. 2001, Maier et al. 2001). Several factors affect the Ni, Cu and PGE grades of the sulfides of the magmatic sulfide deposits, the most important of which include: concentration of these elements in the.

  3. Collision strengths for transitions in Ni XIX

    Indian Academy of Sciences (India)

    atomic data (namely energy levels, radiative rates, collision strengths, excitation rates, etc.) are required in order to estimate the power loss from the walls of the reactors. Furthermore, Ni XIX, a neon-like ion, is also very useful in lasing plas- mas. Similarly many transitions, particularly within the n = 3 configurations, have.

  4. Ni (II) complexes of dithiophosphonic acids

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 126; Issue 4. Ni(II) complexes of dithiophosphonic acids ... Gholivand Ali Asghar Ebrahimi Valmoozi. Volume 126 Issue 4 July 2014 pp 1125-1133 ... The new compounds were additionally tested in view of their anti-bacterial properties. The ligands containing amine ...

  5. CLASSICAL AREAS OF PHENOMENOLOGY: First-principles calculations for the elastic properties of Ni-base model superalloys: Ni/Ni3Al multilayers

    Science.gov (United States)

    Wang, Yun-Jiang; Wang, Chong-Yu

    2009-10-01

    A model system consisting of Ni[001](100)/Ni3Al[001](100) multi-layers are studied using the density functional theory in order to explore the elastic properties of single crystal Ni-based superalloys. Simulation results are consistent with the experimental observation that rafted Ni-base superalloys virtually possess a cubic symmetry. The convergence of the elastic properties with respect to the thickness of the multilayers are tested by a series of multilayers from 2γ'+2γ to 10γ'+10γ atomic layers. The elastic properties are found to vary little with the increase of the multilayer's thickness. A Ni/Ni3Al multilayer with 10γ'+10γ atomic layers (3.54 nm) can be used to simulate the mechanical properties of Ni-base model superalloys. Our calculated elastic constants, bulk modulus, orientation-dependent shear modulus and Young's modulus, as well as the Zener anisotropy factor are all compatible with the measured results of Ni-base model superalloys R1 and the advanced commercial superalloys TMS-26, CMSX-4 at a low temperature. The mechanical properties as a function of the γ' phase volume fraction are calculated by varying the proportion of the γ and γ' phase in the multilayers. Besides, the mechanical properties of two-phase Ni/Ni3Al multilayer can be well predicted by the Voigt-Reuss-Hill rule of mixtures.

  6. Microporous Ni@NiO nanoparticles prepared by chemically dealloying Al{sub 3}Ni{sub 2}@Al nanoparticles as a high microwave absorption material

    Energy Technology Data Exchange (ETDEWEB)

    Pang, Yu; Xie, Xiubo; Li, Da [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, No.37 Xueyuan Road, Beijing 100191 (China); Chou, Wusheng [School of Mechanical Engineering and Automation, Beihang University, Beijing 100191 (China); Liu, Tong, E-mail: tongliu@buaa.edu.cn [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, No.37 Xueyuan Road, Beijing 100191 (China)

    2017-03-15

    The Al{sub 3}Ni{sub 2}@Al nanoparticles (NPs) were prepared from Ni{sub 45}Al{sub 55} master alloy by hydrogen plasma-metal reaction method, and were subsequently dealloyed to produce porous Ni@NiO NPs of 36 nm. The pore size ranges from 0.7 to 1.6 nm, leading to large specific surface area of 69.5 m{sup 2}/g and big pore volume of 0.507 cc/g. The saturation magnetization (M{sub S}) and coercivity (H{sub C}) of the microporous Ni@NiO NPs are 11.5 emu/g and 5.2 Oe. They exhibit high microwave absorption performance with a minimum reflection coefficient (RC) of −86.9 dB and an absorption bandwidth of 2.6 GHz (RC≤−10 dB) at thickness of 4.5 mm. The enhanced microwave absorption properties are attributed to the synergistic effect of the magnetic Ni core and dielectric NiO shell, and the micropore architecture. The NPs with micropore morphology and core/shell structure open a new way to modify the microwave absorption performance. - Graphical abstract: The microporous Ni/NiO nanoparticles prepared by chemically dealloying Al{sub 3}Ni{sub 2}@Al NPs exhibit high microwave absorption intensity (−86.9 dB) and wide absorption bandwidth (2.6 GHz for RC≤−10 dB). - Highlights: • Microporous Ni/NiO nanoparticals were prepared by chemically dealloying method. • They possessed micropores of 0.7–1.6 nm with a surface area of 69.5 m{sup 2}/g. • They showed high microwave absorption intensity and wide absorption bandwidth. • Microwave absorption mechanism was explained by micropore and core/shell structures.

  7. Electroplating condition for Ni nanocrystalline on metal (Ni and Cu) plates

    Energy Technology Data Exchange (ETDEWEB)

    Park, Keun Yung; Uhm, Young Rang; Son, Kwang Jae; Shim, Young Ho; Choi, Sun Ju [KAERI, Daejeon (Korea, Republic of)

    2012-10-15

    Ni 63, a beta radiation source, is prepared by the electrical deposition of radioactive Ni 63 ions on a thin non radioactive nickel foil or Cu plate. Given a half life of 100 years, a nuclear battery will still produce half of its initial starting power after 100 years. A speck of a radioisotope like nickel 63, for example, contains enough energy to power a nano nuclear battery for decades, and to do so safely. Ni 63 plating is similar to other electroplating processes that employ soluble metal anodes. It requires the passage of a direct current between two electrodes that are immersed in a conductive, aqueous solution of nickel salts. The charged Ni ions are formed by sulfate, sulfamate, chloride, and a Watts bath. However, the charged Ni 63 ions are formed by dissolving metal Ni 63. To established the coating condition of Ni 63, non radioactive metal Ni particles are dissolved an acid solution and electroplated on a Ni sheet. The nickel plating process is used extensively for decorative, engineering and electro forming purposes because the appearance and other properties of electrodeposited nickel can be varied over a wide range by controlling the composition and operating parameters of the plating solution. A continuous increase in the grain size versus current density has also been recognized in the direct current electrodeposition of nickel coating. On the other hand, A runa et al. reported that the current density has no significant effect on the grain size of nickel electro deposits. A review of the literature shows that saccharin has often been added to a nickel plating bath since the 1980s to improve the ductility and brightness, and in later periods as a grain refiner agent. In the present paper, not only the preparation of a Ni plating solution prepared by dissolving metal particles, but also an optimization of the deposition conditions, such as the current density, saccharin concentration in the bath, and different metal substrates were investigated

  8. Electroplating condition for Ni nanocrystalline on metal (Ni and Cu) plates

    International Nuclear Information System (INIS)

    Park, Keun Yung; Uhm, Young Rang; Son, Kwang Jae; Shim, Young Ho; Choi, Sun Ju

    2012-01-01

    Ni 63, a beta radiation source, is prepared by the electrical deposition of radioactive Ni 63 ions on a thin non radioactive nickel foil or Cu plate. Given a half life of 100 years, a nuclear battery will still produce half of its initial starting power after 100 years. A speck of a radioisotope like nickel 63, for example, contains enough energy to power a nano nuclear battery for decades, and to do so safely. Ni 63 plating is similar to other electroplating processes that employ soluble metal anodes. It requires the passage of a direct current between two electrodes that are immersed in a conductive, aqueous solution of nickel salts. The charged Ni ions are formed by sulfate, sulfamate, chloride, and a Watts bath. However, the charged Ni 63 ions are formed by dissolving metal Ni 63. To established the coating condition of Ni 63, non radioactive metal Ni particles are dissolved an acid solution and electroplated on a Ni sheet. The nickel plating process is used extensively for decorative, engineering and electro forming purposes because the appearance and other properties of electrodeposited nickel can be varied over a wide range by controlling the composition and operating parameters of the plating solution. A continuous increase in the grain size versus current density has also been recognized in the direct current electrodeposition of nickel coating. On the other hand, A runa et al. reported that the current density has no significant effect on the grain size of nickel electro deposits. A review of the literature shows that saccharin has often been added to a nickel plating bath since the 1980s to improve the ductility and brightness, and in later periods as a grain refiner agent. In the present paper, not only the preparation of a Ni plating solution prepared by dissolving metal particles, but also an optimization of the deposition conditions, such as the current density, saccharin concentration in the bath, and different metal substrates were investigated

  9. Effects of Ni concentration on structural, magnetic and optical properties of Ni-doped ZnO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yang [Institute of Condensed State Physics, Jilin Normal University, Siping 136000 (China); Institute of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Department of Chemistry, Purdue University, West Lafayette 47907 (United States); Liu, Hongbo [Institute of Condensed State Physics, Jilin Normal University, Siping 136000 (China); Institute of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Chen, Zhenguo; Kadasala, Naveen; Mao, Chenyi [Department of Chemistry, Purdue University, West Lafayette 47907 (United States); Wang, Yaxin; Zhang, Yongjun; Liu, Huilian; Liu, Yanqing [Institute of Condensed State Physics, Jilin Normal University, Siping 136000 (China); Yang, Jinghai, E-mail: jhyang1@jlnu.edu.cn [Institute of Condensed State Physics, Jilin Normal University, Siping 136000 (China); Yan, Yongsheng [Institute of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China)

    2014-08-01

    Graphical abstract: With increase of Ni concentration, the saturated magnetization increases firstly and then decreases, which results from the competition between oxygen vacancies and antiferromagnetic coupling between Ni{sup 2+} in NiO. - Highlights: • Ni-doped zinc oxide nanoparticles (NPs) were synthesized by sol–gel method. • Ni ions are substitutionally incorporated into the crystal lattice of ZnO. • Saturated solubility of Ni in ZnO is 2%. • Oxygen vacancies are the origin of ferromagnetism in Ni-doped ZnO NPs. - Abstract: Ni-doped zinc oxide (Zn{sub 1−x}Ni{sub x}O, 0 ⩽ x ⩽ 0.08) diluted magnetic semiconductors have been synthesized by the using a sol–gel method. Structural, magnetic and optical properties of the samples have been studied. The results of X-ray diffraction (XRD), transmission electron microscope (TEM) and X-ray absorption fine structure (XAFS) indicated that Ni ions were substitutionally incorporated into the crystal lattice of ZnO. With Ni concentration increasing up to 2 at.%, all diffraction peaks corresponded to wurtzite structure of ZnO, but for Zn{sub 0.97}Ni{sub 0.03}O, secondary phase of NiO emerged. Based on the results of X-ray photoelectron spectroscopy (XPS), Ni incorporated into the ZnO lattice as Ni{sup 2+}. The produced samples showed good high-Tc (Curie temperature) ferromagnetism. The results of vibrating sample magnetometer (VSM) and photoluminescence (PL) showed that ferromagnetism (FM) of the Ni-doped ZnO nanoparticles originated from the presence of the O vacancy.

  10. Superconductivity in Bi/Ni bilayer system: Clear role of superconducting phases found at Bi/Ni interface

    Science.gov (United States)

    Liu, L. Y.; Xing, Y. T.; Merino, I. L. C.; Micklitz, H.; Franceschini, D. F.; Baggio-Saitovitch, E.; Bell, D. C.; Solórzano, I. G.

    2018-01-01

    Bi/Ni bilayers with varying Bi and Ni layer thicknesses have been prepared by (a) pulsed-laser deposition (PLD) at 300 K and (b) thermal evaporation at 4.2 K. A two-step superconducting transition appears on the electrical transport measurements in the samples prepared by PLD. High-resolution transmission and scanning transmission electron microscopy, supported by energy-dispersive x-ray spectroscopy (EDXS) analysis, reveal that two superconducting intermetallic alloys, namely NiBi and NiBi3, are formed by interdiffusion, if the bilayers are prepared at 300 K. The Tc of the two phases behaves very differently in an external magnetic field and the upper critical magnetic fields at zero temperature [Bc 2(0 ) ] were estimated as 1.1 and 7.4 T, respectively. The lower value corresponds to the Bc 2(0) of NiBi3 phase and the higher one is supposed to be of NiBi. These alloys are responsible for the superconductivity and the two-step transition appearing in the Bi/Ni bilayer system. Surprisingly, the Bi-rich phase (NiBi3) is formed near the Ni layer, while the Ni-rich phase (NiBi) is formed far from the Ni layer. The EDXS analysis at nanometer scale clearly shows an unusual increase of Ni concentration near the interface of Bi/substrate. The limited thickness of Bi layer in the interdiffusion process results in an unexpected distribution of Ni concentration. Samples prepared at 4.2 K after annealing at 300 K do not show any superconductivity, which indicates that a nonepitaxial Bi/Ni interface does not induce superconductivity in the case interdiffusion does not occur. These results offer a deeper understanding of the superconductivity in the Bi/Ni bilayer system.

  11. Geometric structures of thin film: Pt on Pd(110) and NiO on Ni(100)

    Energy Technology Data Exchange (ETDEWEB)

    Warren, Oden L. [Iowa State Univ., Ames, IA (United States)

    1993-07-01

    This thesis is divided into 3 papers: dynamical low-energy electron- diffraction investigation of lateral displacements in topmost layer of Pd(110); determination of (1x1) and (1x2) structures of Pt thin films on Pd(110) by dynamical low-energy electron-diffraction analysis; and structural determination of a NiO(111) film on Ni(100) by dynamical low-energy electron-diffraction analysis.

  12. Electrodeposited nanocrystalline Ni-Co and Co-Ni-P coatings for hard chromium replacement

    OpenAIRE

    Ma, Chao

    2013-01-01

    This thesis describes the preparation and characterisation of environmentally friendly and low-cost nanocrystalline Ni-Co coatings and Co-Ni-P coatings to replace hard chromium coatings for anti-wear and anti-corrosion applications. nanocrystalline Ni–Co coatings with different cobalt contents were electrodeposited.The investigation on the role of tribofilms and wear debris in the tribological behavior sliding against AISI-52100 stainless steel under unlubricated conditions shows that the tri...

  13. 3D Computer Models of T- x- y Diagrams, Forming the Fe-Ni-Co-FeS-NiS-CoS Subsystem

    Science.gov (United States)

    Lutsyk, V. I.; Vorob'eva, V. P.

    2017-12-01

    3D computer models of Fe-Ni-Co, Fe-Ni-FeS-NiS, Fe-Co-FeS-CoS, Ni-Co-NiS-CoS T- x- y diagrams have been designed. The geometric structure (35 surfaces, two-phase surface of the reaction type change, 17 phase regions) of the Fe-Ni-FeS-NiS T- x- y diagram is investigated in detail. The liquidus hypersurfaces prediction of the Fe-Ni-Co-FeS-NiS-CoS subsystem is represented.

  14. Weldability of spheroidal graphite ductile cast iron using Ni / Ni-Fe electrodes

    Directory of Open Access Journals (Sweden)

    Pascual, M.

    2009-10-01

    Full Text Available Weldability of spheroidal graphite ductile cast iron was established using a cheap Ni-Fe and a high purity Ni electrode. A preheating treatment at 350 °C and an annealing treatment at 850 °C were carried out to improve mechanical properties of welded pieces. The pure Ni electrode showed graphite diffusion in the bead with a uniform distribution of phases, improving weldability and decreasing fragility. Preheating and annealing treatments increased ductility and improved weldability.

    Se establece la soldabilidad de funciones dúctiles de grafito según las características mecánicas alcanzadas, utilizando un electrodo puro de Ni mientras se compara con uno más económico de Ni-Fe. Diferentes tratamientos t��rmicos son propuestos y analizados. El electrodo de Ni puro mostró difusión de grafito desde el material original al cordón de soldadura, dando como resultado una fase homogénea que mejoró la soldabilidad y redujo la fragilidad. Un pre tratamiento a 350 °C y un recocido a 850 °C incrementaron la ductilidad y mejoró la soldabilidad.

  15. Effect of Ni4Ti3 precipitation on martensitic transformation in Ti-Ni

    International Nuclear Information System (INIS)

    Zhou, N.; Shen, C.; Wagner, M.F.-X.; Eggeler, G.; Mills, M.J.; Wang, Y.

    2010-01-01

    Precipitation of Ni 4 Ti 3 plays a critical role in determining the martensitic transformation path and temperature in Ni-Ti shape memory alloys. In this study, the equilibrium shape of a coherent Ni 4 Ti 3 precipitate and the concentration and stress fields around it are determined quantitatively using the phase field method. Most recent experimental data on lattice parameters, elastic constants, precipitate-matrix orientation relationship and thermodynamic database are used as model inputs. The effects of the concentration and stress fields on subsequent martensitic transformations are analyzed through interaction energy between a nucleating martensitic particle and the existing microstructure. Results indicate that R-phase formation prior to B19' phase could be attributed to both direct elastic interaction and stress-induced spatial variation in concentration near Ni 4 Ti 3 precipitates. The preferred nucleation sites for the R-phase are close to the broad side of the lenticular-shaped Ni 4 Ti 3 precipitates, where tension normal to the habit plane is highest, and Ni concentration is lowest.

  16. Phase transformation and deformation behavior of NiTi-Nb eutectic joined NiTi wires.

    Science.gov (United States)

    Wang, Liqiang; Wang, Cong; Zhang, Lai-Chang; Chen, Liangyu; Lu, Weijie; Zhang, Di

    2016-04-06

    NiTi wires were brazed together via eutectic reaction between NiTi and Nb powder deposited at the wire contact region. Phase transformation and deformation behavior of the NiTi-Nb eutectic microstructure were investigated using transmission electron microscopy (TEM) and cyclic loading-unloading tests. Results show that R phase and B19' martensite transformation are induced by plastic deformation. R phase transformation, which significantly contributes to superelasticity, preferentially occurs at the interfaces between NiTi and eutectic region. Round-shaped Nb-rich phase with rod-like and lamellar-type eutectics are observed in eutectic regions. These phases appear to affect the deformation behavior of the brazed NiTi-Nb region via five distinct stages in stress-strain curves: (I) R phase reorientation, (II) R phase transformation from parent phase, (III) elastic deformation of reoriented martensite accompanied by the plastic deformation of Nb-rich phase and lamellar NiTi-Nb eutectic, (IV) B19' martensitic transformation, and (V) plastic deformation of the specimen.

  17. Fabrication of metallic alloy powder (Ni{sub 3}Fe) from Fe–77Ni scrap

    Energy Technology Data Exchange (ETDEWEB)

    Seo, Inseok [ES Materials Research Center, Research Institute of Industrial Science and Technology, Incheon 406-840 (Korea, Republic of); Shin, Shun-Myung [Extractive Metallurgy Department, Korea Institute of Geoscience and Mineral Resources, Deajeon 305-350 (Korea, Republic of); Ha, Sang-An [Department of Environmental Engineering, Silla University, Busan 46958 (Korea, Republic of); Wang, Jei-Pil, E-mail: jpwang@pknu.ac.kr [Department of Metallurgical Engineering, Pukyong National University, Busan 608-739 (Korea, Republic of)

    2016-06-15

    The oxidation behavior of Fe–77Ni alloy scrap was investigated at an oxygen partial pressure of 0.2 atm and temperatures ranging from 400 °C to 900 °C. The corresponding oxidation rate increased with increasing temperature and obeyed the parabolic rate law, as evidenced by its linear proportionality to the temperature. In addition, surface morphologies, cross-sectional views, compositions, structural properties were examined by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Diffusion through either the spinel structure or the NiO layer, which were both present in the alloy during oxidation at elevated temperatures, was deemed the rate-limiting step of the reaction. The oxide powder less than 10 μm was obtained from Fe–77Ni alloy scrap was obtained using ball-milling and sieving processes. In fact, 15 h of milling yielded a recovery ratio of 97%. Using hydrogen gas, the oxide powder was successfully reduced to an alloy powder of Ni{sub 3}Fe and reduction rates of ∼97% were achieved after 3 h at 1000 °C. - Highlights: • The oxidation behavior of Fe–77Ni alloy scrap was investigated. • The oxide powder less than 10 μm was obtained from Fe–77Ni alloy scrap. • Using hydrogen gas, the oxide powder was successfully reclaimed. • Reduction rates of ∼97% were achieved after 3 h at 1000 °C.

  18. Epitaxial NiWO4 films on Ni(110): Experimental and theoretical study of surface stability

    Science.gov (United States)

    Doudin, N.; Pomp, S.; Blatnik, M.; Resel, R.; Vorokhta, M.; Goniakowski, J.; Noguera, C.; Netzer, F. P.; Surnev, S.

    2017-05-01

    Despite the application potential of nickel tungstate (NiWO4) in heterogeneous catalysis, humidity and gas sensing, etc, its surfaces have essentially remained unexplored. In this work, NiWO4 nanoparticles and films with the wolframite structure have been grown via a solid-state reaction of (WO3)3 clusters and a NiO(100) film on a Ni(110) crystal surface and characterized by a variety of experimental techniques, including x-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy (STM) and x-ray diffraction (XRD), combined with ab-initio density functional theory (DFT) calculations. NiWO4 grows initially as three-dimensional (3D) crystalline nanoparticles displaying mainly two crystalline facets vicinal to the (100) surface, which merge with increasing the (WO3)3 coverage into a quasi-continuous epitaxial film. The DFT results provide an account of the energetics of NiWO4 low index surfaces and highlight the role of faceting in the stabilization of extended polar (100) terraces. These combined experimental and theoretical results show that interaction with a metal substrate and vertical confinement may stabilize oxide nano-objects with high energy facets, able to enhance their reactivity.

  19. Studies on the valence electronic structure of Fe and Ni in FexNi1−x ...

    Indian Academy of Sciences (India)

    sults of MCDF calculations performed for various valence electronic configurations [2] of. Fe and Ni. The 3d electron populations, thus obtained, for pure Fe and Ni metals (table 2) are found to be in close agreement with the results of band structure calculations of Papa- constantopoulos [9] (6.93 for Fe and 8.97 for Ni) and ...

  20. Synthesis and catalytic activity of electrospun NiO/NiCo2O4 nanotubes for CO and acetaldehyde oxidation

    Science.gov (United States)

    Kim, Il Hee; Lee, Hyerim; Yu, Areum; Jeong, Jae Hwan; Lee, Youngmi; Kim, Myung Hwa; Lee, Chongmok; Dok Kim, Young

    2018-04-01

    NiO/NiCo2O4 nanotubes with a diameter of approximately 100 nm are synthesized using Ni and Co precursors via electro-spinning and subsequent calcination processes. The tubular structure is confirmed via transmission electron microscopy imaging, whereas the structures and elemental compositions of the nanotubes are determined using x-ray diffraction, energy dispersive x-ray spectroscopy, and x-ray photoelectron spectroscopy. N2 adsorption isotherm data reveal that the surface of the nanotubes consists of micropores, thereby resulting in a significantly higher surface area (˜20 m2 g-1) than expected for a flat-surface structure (present a study of the catalytic activity of our novel NiO/NiCo2O4 nanotubes for CO and acetaldehyde oxidation. The catalytic activity of NiO/NiCo2O4 is superior to Pt below 100 °C for CO oxidation. For acetaldehyde oxidation, the total oxidation activity of NiO/NiCo2O4 for acetaldehyde is comparable with that of Pt. Coexistence of many under-coordinated Co and Ni active sites in our structure is suggested be related to the high catalytic activity. It is suggested that our novel NiO/NiCo2O4 tubular structures with surface microporosity can be of interest for a variety of applications, including the catalytic oxidation of harmful gases.

  1. Interfacial reaction of Ni{sub 3}Sn{sub 4} intermetallic compound in Ni/SnAg solder/Ni system under thermomigration

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Yi-Shan; Yang, Chia-Jung; Ouyang, Fan-Yi, E-mail: fyouyang@ess.nthu.edu.tw

    2016-07-25

    The growth of Ni{sub 3}Sn{sub 4} intermetallic compound (IMC) between liquid–solid interface in micro-scale Ni/SnAg/Ni system was investigated under a temperature gradient of 160 °C/cm at 260 °C on a hot plate. In contrast to a symmetrical growth of Ni{sub 3}Sn{sub 4} on both interfaces under isothermally annealed at 260 °C, the interfacial Ni{sub 3}Sn{sub 4} IMC exhibited asymmetric growth under a temperature gradient; the growth of Ni{sub 3}Sn{sub 4} at cold interface was faster than that at hot side because of temperature gradient induced mass migration of Ni atoms from the hot end toward the cold end. It was found that two-stage growth behavior of Ni{sub 3}Sn{sub 4} IMC under a temperature gradient. A growth model was established and growth kinetic analysis suggested that the chemical potential gradient controlled the growth of Ni{sub 3}Sn{sub 4} at stage I (0–120 min) whereas the dynamic equilibrium between chemical potential gradient and temperature gradient forces was attained at the hot end at stage II (120–210 min). When dynamic equilibrium was achieved at 260 °C, the critical length-temperature gradient product at the hot end was experimentally estimated to be 489.18 μm × °C/cm and the moving velocity of Ni{sub 3}Sn{sub 4} interface due to Ni consumption was calculated to be 0.134 μm/h. The molar heat of transport (Q*) of Ni atoms in molten SnAg solder was calculated to be +0.76 kJ/mol. - Highlights: • Interfacial reaction in Ni/SnAg solder/Ni system under thermal gradient. • Growth rate of Ni{sub 3}Sn{sub 4} at cold end is faster than that at hot end. • Critical length-temperature gradient product at hot end is 489.2 μm°C/cm at 260 °C. • Velocity of Ni{sub 3}Sn{sub 4} moving interface is 0.134 μm/h during dynamic equilibrium. • Molar heat of transport (Q*) of Ni in molten SnAg was +0.76 kJ/mol.

  2. La2MnVO6 Double Perovskite: A Structural, Magnetic and X-Ray Absorption Investigation

    International Nuclear Information System (INIS)

    Mandal, T.; Croft, M.; Hadermann, J.; Van Tendeloo, G.; Stephens, P.; Greenblatt, M.

    2009-01-01

    The synthesis, electron diffraction (ED), synchrotron X-ray and neutron structure, X-ray absorption spectroscopy (XAS) and magnetic property studies of La2MnVO6 double perovskite are described. Analysis of the synchrotron powder X-ray diffraction data for La2MnVO6 indicates a disordered arrangement of Mn and V at the B-site of the perovskite structure. Absence of super-lattice reflections in the ED patterns for La2MnVO6 supports the disordered cation arrangement. Room temperature time-of-flight (TOF) neutron powder diffraction (NPD) data show no evidence of cation ordering, in corroboration with the ED and synchrotron studies (orthorhombic Pnma, a = 5.6097(3), b = 7.8837(5) and c = 5.5668(3); 295 K, NPD). A comparison of XAS analyses of La2TVO6 with T = Ni and Co shows T2+ formal oxidation state while the T = Mn material evidences a Mn3+ admixture into a dominantly Mn2+ ground state. V-K edge measurements manifest a mirror image behavior with a V4+ state for T = Ni and Co with a V3+ admixture arising in the T = Mn material. The magnetic susceptibility data for La2MnVO6 show ferromagnetic correlations; the observed effective moment, μeff (5.72 μB) is much smaller than the calculated moment (6.16 μμB) based on the spin-only formula for Mn2+ (d5, HS)/V4+ (d1), supportive of the partly oxidized Mn and reduced V scenario (Mn3+/V3+).

  3. Thin NiTi Films Deposited on Graphene Substrates

    Science.gov (United States)

    Hahn, S.; Schulze, A.; Böhme, M.; Hahn, T.; Wagner, M. F.-X.

    2017-03-01

    We present experimental results on the deposition of Nickel Titanium (NiTi) films on graphene substrates using a PVD magnetron sputter process. Characterization of the 2-4 micron thick NiTi films by electron microscopy, electron backscatter diffraction, and transmission electron microscopy shows that grain size and orientation of the thin NiTi films strongly depend on the type of combination of graphene and copper layers below. Our experimental findings are supported by density functional theory calculations: a theoretical estimation of the binding energies of different NiTi-graphene interfaces is in line with the experimentally determined microstructural features of the functional NiTi top layer.

  4. Evaluation of the Antitumor Activity by Ni Nanoparticles with Verbascoside

    Directory of Open Access Journals (Sweden)

    Mingyue Chen

    2013-01-01

    Full Text Available Verbascoside (VB has attracted a great deal of attention due to ITS pharmacological properties. In our study, we synthesized a multifunctional verbascoside coated Ni nanoparticles (VB-Ni. Transmission electron microscopy (TEM and high performance liquid chromatography (HPLC display the characteristics of VB-Ni nanoparticles. Compared with VB, VB-Ni has been proven to induce apoptosis and resist the growth of doxorubicin-resistant K562 cells in vitro and in vivo. Thus, VB-Ni nanoparticles can be thought of as an ideal mode of cancer treatment.

  5. Atomistic modeling of ternary additions to NiTi and quaternary additions to Ni-Ti-Pd, Ni-Ti-Pt and Ni-Ti-Hf shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Mosca, H.O., E-mail: hmosca@cnea.gov.ar [Gcia. Investigacion y Aplicaciones, CNEA, Av. Gral Paz 1499, B1650KNA San Martin (Argentina); GCMM, UTN, FRG Pacheco, Av. H. Yrigoyen 288, Gral. Pacheco (Argentina); Bozzolo, G. [Loyola University Maryland, 4501 N. Charles St., Baltimore, MD 21210 (United States); Grosso, M.F. del [Gcia. Investigacion y Aplicaciones, CNEA, Av. Gral Paz 1499, B1650KNA San Martin (Argentina); GCMM, UTN, FRG Pacheco, Av. H. Yrigoyen 288, Gral. Pacheco (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas, CONICET (Argentina)

    2012-08-15

    The behavior of ternary and quaternary additions to NiTi shape memory alloys is investigated using a quantum approximate method for the energetics. Ternary additions X to NiTi and quaternary additions to Ni-Ti-Pd, Ni-Ti-Pt, and Ni-Ti-Hf alloys, for X=Au, Pt, Ir, Os, Re, W, Ta,Ag, Pd, Rh, Ru, Tc, Mo, Nb, Zr, Zn, Cu, Co, Fe, Mn, V, Sc, Si, Al and Mg are considered. Bulk properties such as lattice parameter, energy of formation, and bulk modulus of the B2 alloys are studied for variations due to the presence of one or two simultaneous additives.

  6. Kinetic study of hydrogen evolution reaction on Ni30 Mo70, Co30Mo70, Co30Ni70 and Co10Ni20Mo70 alloy electrodes

    International Nuclear Information System (INIS)

    Dominguez-Crespo, M.A.; Plata-Torres, M.; Torres-Huerta, A.M.; Arce-Estrada, E.M.; Hallen-Lopez, J.M.

    2005-01-01

    The hydrogen evolution reaction on nanocrystalline Ni 30 Mo 70 , Co 30 Mo 70 , Co 30 Ni 70 , and Co 10 Ni 20 Mo 70 , metallic powders prepared by mechanical alloying was investigated with linear polarization and ac impedance methods, in 30 wt.% KOH aqueous solution at room temperature. The formation process and structural properties of these nanocrystalline materials were characterized by X-ray diffraction and transmission electron microscopy. Alloyed powders showed the presence of two phases: an fcc solid solution and intermetallic compounds of Ni, Co and Mo. Based on polarization and ac impedance measurements, an improved electrocatalytic activity for hydrogen evolution reaction was observed in mechanically alloyed Co 30 Ni 70 powders, which is slightly higher than milled metallic Ni powders

  7. Structural evaluation and nonlinear optical properties of Ni/NiO, Ni/NiCo{sub 2}O{sub 4} and Co/Co{sub 3}O{sub 4} nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Rahulan, K. Mani, E-mail: krahul.au@gmail.com [Department of Chemistry, SRM Valliammai Engineering College, Chennai 603203 (India); Padmanathan, N. [Department of Physics, Anna University, Guindy, Chennai 600025 (India); Philip, Reji [Light and Matter Physics Group, Raman Research Institute, Bangalore 560080 (India); Balamurugan, S. [Liquid Crystal Research Laboratory, School of Chemical Sciences, Universiti Sains Malaysia, 11800 Minden, Penang (Malaysia); Kanakam, Charles C., E-mail: charlesckin@yahoo.com [Department of Chemistry, SRM Valliammai Engineering College, Chennai 603203 (India)

    2013-10-01

    Nanocomposites of Ni/NiO, Ni/NiCo{sub 2}O{sub 4} and Co/Co{sub 3}O{sub 4} have been synthesized by a chemical reduction technique. X-ray diffraction (XRD) and transmission electron microscopy (TEM) images confirm the mixed composite nature of the sample and uniform particle size of approximately 13 nm. Formation of Ni/NiCo{sub 3}O{sub 4} solid solution or NiCo{sub 2}O{sub 4} spinel phase in the mixed composite is confirmed by energy dispersive X-ray (EDX) spectrum. Magnetic hysteresis (M–H) curves of the nanocomposites show excellent ferromagnetic (FM) nature at room temperature. Nonlinear optical transmission of the nanocomposites is measured using the open aperture Z-scan technique employing 7 nanosecond laser pulses at 532 nm. Experimental results show that NiO/NiO–Co{sub 3}O{sub 4}/Co{sub 3}O{sub 4} nanocomposites exhibit good optical limiting performance. From the measurements and numerical fitting of the data to theory, it is found that nonlinear absorption has contributions from excited state absorption and two-photon absorption. Optical limiting is enhanced in Co{sub 3}O{sub 4} and Ni/NiCo{sub 2}O{sub 4} in which the Co{sub 3}O{sub 4} content has a larger volume ratio.

  8. CO2 activation on bimetallic CuNi nanoparticles

    Directory of Open Access Journals (Sweden)

    Natalie Austin

    2016-10-01

    Full Text Available Density functional theory calculations have been performed to investigate the structural, electronic, and CO2 adsorption properties of 55-atom bimetallic CuNi nanoparticles (NPs in core-shell and decorated architectures, as well as of their monometallic counterparts. Our results revealed that with respect to the monometallic Cu55 and Ni55 parents, the formation of decorated Cu12Ni43 and core-shell Cu42Ni13 are energetically favorable. We found that CO2 chemisorbs on monometallic Ni55, core-shell Cu13Ni42, and decorated Cu12Ni43 and Cu43Ni12, whereas, it physisorbs on monometallic Cu55 and core-shell Cu42Ni13. The presence of surface Ni on the NPs is key in strongly adsorbing and activating the CO2 molecule (linear to bent transition and elongation of C˭O bonds. This activation occurs through a charge transfer from the NPs to the CO2 molecule, where the local metal d-orbital density localization on surface Ni plays a pivotal role. This work identifies insightful structure-property relationships for CO2 activation and highlights the importance of keeping a balance between NP stability and CO2 adsorption behavior in designing catalytic bimetallic NPs that activate CO2.

  9. Changing effect of El Niño on Antarctic iceberg distribution: From canonical El Niño to El Niño Modoki

    Science.gov (United States)

    Romanov, Yury A.; Romanova, Nina A.; Romanov, Peter

    2014-01-01

    Earlier studies indicate that during El Niño events the iceberg concentration increases in the east of the Pacific sector and in the west of the Atlantic sector of Southern Ocean, but decreases in the center of the Pacific sector. During La Niña the pattern of the iceberg concentration anomalies in these regions reverses. This iceberg redistribution is explained by anomalous winds and currents around an extensive positive atmospheric pressure anomaly that typically develops in the South-East Pacific during the warm El Niño-Southern Oscillation (ENSO) phase. In this study, the results of iceberg observations during two cruises of the r/v "Akademik Fedorov" in Antarctica in January-February 2008 (La Niña) and 2010 (El Niño) have been used to examine the consistency of changes in the iceberg distribution in the Southern Ocean related to El Niño events. The analysis of these observations has shown that in the Pacific Sector of Antarctica changes in the iceberg distribution between 2008 and 2010 followed the scenario outlined above and thus could be associated with the ENSO phase change. Contrary to earlier observations, the iceberg concentration in the Atlantic sector of Antarctica did not increase during 2010 El Niño. The latter is explained by a noncanonical type of 2010 El Niño, El Niño Modoki, and associated atmospheric circulation pattern different from the canonical El Niño. Further analysis has shown that a more frequent occurrence of El Niño Modoki in recent years have resulted in weaker links between El Niño events and the Antarctic iceberg distribution.

  10. NiCo2S4nanosheet-decorated 3D, porous Ni film@Ni wire electrode materials for all solid-state asymmetric supercapacitor applications.

    Science.gov (United States)

    Saravanakumar, Balasubramaniam; Jayaseelan, Santhana Sivabalan; Seo, Min-Kang; Kim, Hak-Yong; Kim, Byoung-Suhk

    2017-12-07

    Wire type supercapacitors with high energy and power densities have generated considerable interest in wearable applications. Herein, we report a novel NiCo 2 S 4 -decorated 3D, porous Ni film@Ni wire electrode for high performance supercapacitor application. In this work, a facile method is introduced to fabricate a 3D, porous Ni film deposited on a Ni wire as a flexible electrode, followed by decoration with NiCo 2 S 4 as an electroactive material. The fabricated NiCo 2 S 4 -decorated 3D, porous Ni film@Ni wire electrode displays a superior performance with an areal and volumetric capacitance of 1.228 F cm -2 and 199.74 F cm -3 , respectively, at a current density of 0.2 mA cm -1 with a maximum volumetric energy and power density (E V : 6.935 mW h cm -3 ; P V : 1.019 W cm -3 ). Finally, the solid state asymmetric wire type supercapacitor is fabricated using the fabricated NiCo 2 S 4 -decorated 3D, porous Ni film@Ni wire as a positive electrode and N-doped reduced graphene oxide (N-rGO) as a negative electrode and this exhibits good areal and volumetric capacitances of C A : 0.12 F cm -2 and C V : 19.57 F cm -2 with a higher rate capability (92%). This asymmetric wire type supercapacitor demonstrates a low leakage current and self-discharge with a maximum volumetric energy (E V : 5.33 mW h cm -3 ) and power (P V : 855.69 mW cm -3 ) density.

  11. Structural and magnetic properties of Ni-Zn and Ni-Zn-Co ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Knyazev, A.V., E-mail: knyazevav@gmail.com [N.I. Lobachevsky State University of Nizhni Novgorod, Gagarin Prospekt 23/2, 603950 Nizhni Novgorod (Russian Federation); Zakharchuk, I.; Lähderanta, E. [Lappeenranta University of Technology, P.O. Box 20, FI-53851 Lappeenranta (Finland); Baidakov, K.V.; Knyazeva, S.S. [N.I. Lobachevsky State University of Nizhni Novgorod, Gagarin Prospekt 23/2, 603950 Nizhni Novgorod (Russian Federation); Ladenkov, I.V. [Joint-stock Company “Research and Production Company “Salut”, Nizhni Novgorod (Russian Federation)

    2017-08-01

    Highlights: • Ni-Zn and Ni-Zn-Co ferrite powders were prepared by the solid-state reaction at 1073 K. • The room temperature saturation magnetizations are 59.7 emu/g for Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} and 57.1 emu/g for Ni{sub 0.5}Zn{sub 0.3}Co{sub 0.2}Fe{sub 2}O{sub 4}. • The coercivity of the samples is found to be much larger than that of bulk ferrites and increases with Co introduction. • The temperature dependences of magnetization exhibit large spin frustration and spin-glass-like behavior. - Abstract: Ni-Zn and Ni-Zn-Co ferrite powders with nominal compositions Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} and Ni{sub 0.5}Zn{sub 0.3}Co{sub 0.2}Fe{sub 2}O{sub 4} were prepared by the solid-state reaction synthesis with periodic regrinding during the calcination at 1073 K. The structure of Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} and Ni{sub 0.5}Zn{sub 0.3}Co{sub 0.2}Fe{sub 2}O{sub 4} was refined assuming space group F d-3m. Scanning electron microscopy revealed the average sizes of the crystalline ferrite particles are 130–630 nm for Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} and 140–350 nm for Ni{sub 0.5}Zn{sub 0.3}Co{sub 0.2}Fe{sub 2}O{sub 4}. The room temperature saturation magnetizations are 59.7 emu/g for Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} and 57.1 emu/g for Ni{sub 0.5}Zn{sub 0.3}Co{sub 0.2}Fe{sub 2}O{sub 4}. The coercivity of the samples is found to be much larger than that of bulk ferrites and increases with Co introduction. The Curie temperature tends to increase upon Zn substitution by Co, as well. The temperature dependences of magnetization measured using zero-field cooled and field cooled protocols exhibit large spin frustration and spin-glass-like behavior.

  12. Effects of Bond Coating on NiCrBSi-Mo Composite Functional Coating Properties in Plasma Spraying NiCrBSi-Mo/Ni Coating

    OpenAIRE

    DU Ji-yu; LI Fang-yi; LU Hai-yang; SHANG Jian-tong; LI Zhen

    2017-01-01

    Nickel-based bond coating and composite functional coating were sprayed on leaf blade steel material FV520B successively by using air plasma spraying system. NiCrBSi-Mo powder deposition rate, coating porosity, bonding strength and surface hardness were tested. The results indicate that, for the NiCrBSi-Mo/Ni coating, bond coating with 180-220μm thickness can improve NiCrBSi-Mo powder deposition rate while the surface coating with lower porosity, higher bonding strength and high hardness is p...

  13. Thermodynamic characterization of Ni3TeO6, Ni2Te3O8 and NiTe2O5

    Science.gov (United States)

    Dawar, Rimpi; Babu, R.; Ananthasivan, K.; Anthonysamy, S.

    2017-09-01

    Measurement of vapour pressure of TeO2(g) over the biphasic mixture Ni3TeO6 (s) + NiO(s) in the temperature range 1143-1272 K was carried out using transpiration-thermogravimetric technique (TTG). Gibbs energy of formation of Ni3TeO6 was obtained from the temperature dependence of vapour pressure of TeO2 (g) generated by the incongruent vapourisation reaction, Ni3TeO6 (s) → NiO(s) + TeO2 (g) + 1/2 O2 in the temperature range 1143-1272 K. An isoperibol type drop calorimeter was used to measure the enthalpy increments of Ni3TeO6, Ni2Te3O8 and NiTe2O5. Thermodynamic functions viz., heat capacity, entropy and Gibbs energy functions of these compounds were derived from the experimentally measured enthalpy increment values. Third-law analysis was carried out to ascertain absence of temperature dependent systematic errors in the measurement of vapour pressure of TeO2 (g). A value of -1265.1 ± 1.5 kJ mol-1 was obtained for Δ Hf,298K o (Ni3TeO6) using third-law analysis.

  14. Estilos de vida saludables de niños, niñas y adolescentes

    Directory of Open Access Journals (Sweden)

    Lilia Campo-Ternera

    2017-01-01

    Full Text Available Objetivo: Describir los estilos de vida saludables de niños, niñas y adolescentes de Barranquilla. Materiales y métodos: Estudio descriptivo de corte transversal en 991 niños, niñas y ado - lescentes. Se evaluó la actividad física mediante los cuestionarios de Actividad Física para Adolescentes y para niños escolares; se aplicó una encuesta que midió los conocimientos y prácticas de los escolares sobre salud bucal, lavado de manos, consumo de frutas y verduras y cuidado postural; la Lista de Chequeo “Mi Vida en la Escuela”, la cual evalúa los índices de “bullying” y agresión; y la inteligencia emocional a través dela escala TMMS -24. Resultados: El 65,4 % se categoriza como inactivos físicamente. Solo el 14,7% de los estudiantes reconoce que el peso máximo del bolso es el 10 % de su peso corporal; el 34,1 % cambia el cepillo de dientes cada 3 meses, como lo recomiendan los expertos, y 48,4 % se cepilla los dientes entre 2 y 3 veces al día. El 16,6 % no se lava las manos antes y después de ir al baño y 9,4 % no lo hace antes y después de las comidas; el 17,5 % no tiene un buen consumo de verduras y frutas; y se encontró un Índice de “bullying” en el 55,6 % de los participantes. Conclusión: Los anteriores resultados obligan a plantear intervenciones que incrementen las prácticas saludables en niños, niñas y adolescentes.

  15. Evaluation of structure and mechanical properties of Ni-rich NiTi/Kapton composite film

    Energy Technology Data Exchange (ETDEWEB)

    Mohri, Maryam [Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT), Karlsruhe (Germany); School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Nili-Ahmadabadi, Mahmoud [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); PouryazdanPanah, Mohsen; Hahn, Horst [Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT), Karlsruhe (Germany); Joint Research Labaratory Nanomaterials, Technische Universität Darmstadt, Darmstadt (Germany)

    2016-06-21

    NiTi thin films are usually sputtered on silicon wafers by magnetron sputtering. But the systems composed of thin film on flexible polymeric substrate are used in many applications such as micro electro-mechanical systems (MEMS). Investigation on mechanical properties of thin films has attracted much attention due to their widespread applications. In this paper, the mechanical properties of 1 µm-thick crystallized Ni-49.2 at%Ti thin film alloy deposited by DC magnetron sputtering on Kapton substrate are investigated by using tensile test. The as-deposited thin films are in amorphous state, then for crystallization, the thin film was annealed at 450 °C for 30 min. Formation of the austenite phase after annealing was confirmed by X-ray diffractometry (XRD) and differential scanning calorimetry (DSC). The surface morphology of as deposited and crystallized thin films were examined by scanning electron microscopy (SEM). Stress-strain curves of the NiTi alloy thin film were obtained by subtracting of the stress-strain Kapton curves from the corresponding curves of the NiTi/Kapton composite. The XRD results revealed that the NiTi thin film deposited on the Kapton is austenitic and presents super-elastic effect at room temperature. This pseudo elastic effect leads to more recoverable strain in NiTi/Kapton composite film compared with Kapton foils on loading/unloading test. Furthermore, it was concluded that nanostructure of the NiTi thin film is responsible for remarkable improvement of ultimate tensile strength (1.4 GPa) at a strain of 30% compared with the bulk material.

  16. High Damping of Lightweight TiNi-Ti2Ni Shape Memory Composites for Wide Temperature Range Usage

    Science.gov (United States)

    Yang, Bing; Luo, Zheng; Yuan, Bin; Liu, Jiangwen; Gao, Yan

    2017-10-01

    A bimodal porous TiNi-Ti2Ni shape memory alloy composite (SMAC) with 59% porosity was fabricated by sintering Ti-46at.%Ni elemental powders with pore-forming agent. The porous TiNi-Ti2Ni SMAC contains two irregular pores of about 400 and 120 μm. We investigated the microstructure and pore morphology correlated with the mechanical properties and damping capacities of the SMAC. Ti2Ni intermetallic phases with size of 1-3 μm were homogeneously distributed in the TiNi matrix. The porous TiNi-Ti2Ni SMAC exhibits exceptionally high inverse mechanical quality factor ( Q -1) of 0.25 at SMAC at relatively low strain amplitude can exhibit considerable high Q -1 of 0.06 0.11 for a wide range of temperature between - 90 and 200 °C, which is attributed to the stress concentration distribution provided by the bimodal structure of pores and the massive interfaces between pore/matrix and TiNi/Ti2Ni. These porous SMACs can be an ideal candidate for using as a lightweight damping material in the energy-saving applications.

  17. Preparation of Ni-YSZ Cermet through Reduction of NiO-YSZ Ceramic for SOFC Anode

    Science.gov (United States)

    Baity, P. S. N.; Budiana, B.; Suasmoro, S.

    2017-07-01

    Research on the synthesis of Nickel-Yttria Stabilized Zirconia (Ni-YSZ) cermet for Solid Oxide Fuel Cell (SOFC) anode has been performed. The preparation was carried out through the reduction process of the Nickel Oxide-Yttria stabilized Zirconia (NiO-YSZ) ceramic. NiO and YSZ were prepared separately, the NiO powder was prepared by calcination of CH4Ni3O7.xH2O at 500°C for 3 hours, while YSZ powder was prepared by calcination of 7mol% Y2O3 and 93mol% ZrO2 mixture at 1350°C for an hour. The NiO-YSZ ceramic preparation was carried outby mixing of YSZ and NiO powder with natural white starch by weight ratio NiO: YSZ: natural white starch = 4:6:1 followed by sintering at 1200°C for 4 hours. The completion of reduction process of NiO-YSZ ceramic was performed at 1000°C in flowing Argon (Ar) containing 10% Hydrogen (H2) up to 4 hours. The characterisations include thermogravimetric analysis (TGA), XRD, SEM-EDX and Impedance Analyzer meter. The synthesised Ni-YSZ cermet at composition 33wt% Ni and 67wt% YSZ, shows relative density 70% and electrical conductivity 10-2 S/cm at 700°C, it qualifies as anode for SOFC.

  18. Role of Ni-tolerant Bacillus spp. and Althea rosea L. in the phytoremediation of Ni-contaminated soils.

    Science.gov (United States)

    Khan, Waheed Ullah; Yasin, Nasim Ahmad; Ahmad, Sajid Rashid; Ali, Aamir; Ahmed, Shakil; Ahmad, Aqeel

    2017-05-04

    In our current study, four nickel-tolerant (Ni-tolerant) bacterial species viz, Bacillus thuringiensis 002, Bacillus fortis 162, Bacillus subtilis 174, and Bacillus farraginis 354, were screened using Ni-contaminated media. The screened microbes exhibited positive results for synthesis of indole acetic acid (IAA), siderophore production, and phosphate solubilization. The effects of these screened microbes on Ni mobility in the soil, root elongation, plant biomass, and Ni uptake in Althea rosea plants grown in Ni-contaminated soil (200 mg Ni kg -1 ) were evaluated. Significantly higher value for water-extractable Ni (38 mg kg -1 ) was observed in case of Ni-amended soils inoculated with B. subtilis 174. Similarly, B. thuringiensis 002, B. fortis 162, and B. subtilis 174 significantly enhanced growth and Ni uptake in A. rosea. The Ni uptake in the shoots and roots of B. subtilis 174-inoculated plants enhanced up to 1.7 and 1.6-fold, respectively, as compared to that in the un-inoculated control. Bacterial inoculation also significantly improved the root and shoot biomass of treated plants. The current study presents a novel approach for bacteria-assisted phytoremediation of Ni-contaminated areas.

  19. Microwave assisted synthesis and characterization of Ni/NiO nanoparticles as electrocatalyst for methanol oxidation in alkaline solution

    Science.gov (United States)

    Arunachalam, Prabhakarn; Ghanem, Mohamed A.; Al-Mayouf, Abdullah M.; Al-shalwi, Matar; Hamed Abd-Elkader, Omar

    2017-02-01

    Nickel/Nickel oxide (Ni/NiO) nanoparticles catalyst is prepared by microwave-assisted liquid-phase deposition using ethylene glycol (EG) and water mixture under atmospheric conditions. The physicochemical characterizations of the catalyst carried out by surface area analyzer, x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), electron microscopes measurements suggest the formation of crystalline nanoparticles structure of NiO. The surface area of Ni/NiO prepared using EG/water mixture reaches 70 m2 g-1 which is 2-fold enhsancement in surface area in comparison with NiO prepared in pure EG and an order of magnitude higher than that of bulk nickel prepared in pure water. The methanol electro-oxidation activity of the Ni/NiO nanoparticles obtained in EG/water mixture displayed more than 4-fold increase in oxidation current at 1.7 V versus RHE in comparison with NiO nanoparticles obtained in EG and 20-fold increase compared to bulk nickel catalyst concord with the enhancement of electro-active surface area. The results show the Ni/NiO nanoparticles produced by microwave assisted synthesis has superior activity for methanol oxidation in alkaline solution over the other nickel based catalysts and has potential for mass production.

  20. Anti-corrosive and anti-microbial properties of nanocrystalline Ni-Ag coatings

    Energy Technology Data Exchange (ETDEWEB)

    Raghupathy, Y.; Natarajan, K.A.; Srivastava, Chandan, E-mail: csrivastava@materials.iisc.ernet.in

    2016-04-15

    Graphical abstract: - Highlights: • Electrodeposition yielded phase-segregated, nanocrystalline Ni-Ag coatings. • Ni-Ag alloys exhibited smaller Ni crystals compared to pure Ni. • Ultra fine Ni grains of size 12–14 nm favoured Ni-Ag solid solution. • Nanocrystalline Ag resisted bio-fouling by Sulphate Reducing bacteria. • Ni-Ag outperformed pure Ni in corrosion and bio-corrosion tests. - Abstract: Anti-corrosive and anti-bacterial properties of electrodeposited nanocrystalline Ni-Ag coatings are illustrated. Pure Ni, Ni-7 at.% Ag, & Ni-14 at.% Ag coatings were electrodeposited on Cu substrate. Coating consisted of Ni-rich and Ag-rich solid solution phases. With increase in the Ag content, the corrosion resistance of the Ni-Ag coating initially increased and then decreased. The initial increase was due to the Ni-Ag solid solution. The subsequent decrease was due to the increased galvanic coupling between the Ag-rich and Ni-rich phases. For all Ag contents, the corrosion resistance of the Ni-Ag coating was higher than the pure Ni coating. Exposure to Sulphate Reducing Bacteria (SRB) revealed that the extent of bio-fouling decreased with increase in the Ag content. After 2 month exposure to SRB, the Ni-Ag coatings demonstrated less loss in corrosion resistance (58% for Ni-7 at.% Ag and 20% for Ni-14 at.% Ag) when compared pure Ni coating (115%).

  1. Anti-corrosive and anti-microbial properties of nanocrystalline Ni-Ag coatings

    International Nuclear Information System (INIS)

    Raghupathy, Y.; Natarajan, K.A.; Srivastava, Chandan

    2016-01-01

    Graphical abstract: - Highlights: • Electrodeposition yielded phase-segregated, nanocrystalline Ni-Ag coatings. • Ni-Ag alloys exhibited smaller Ni crystals compared to pure Ni. • Ultra fine Ni grains of size 12–14 nm favoured Ni-Ag solid solution. • Nanocrystalline Ag resisted bio-fouling by Sulphate Reducing bacteria. • Ni-Ag outperformed pure Ni in corrosion and bio-corrosion tests. - Abstract: Anti-corrosive and anti-bacterial properties of electrodeposited nanocrystalline Ni-Ag coatings are illustrated. Pure Ni, Ni-7 at.% Ag, & Ni-14 at.% Ag coatings were electrodeposited on Cu substrate. Coating consisted of Ni-rich and Ag-rich solid solution phases. With increase in the Ag content, the corrosion resistance of the Ni-Ag coating initially increased and then decreased. The initial increase was due to the Ni-Ag solid solution. The subsequent decrease was due to the increased galvanic coupling between the Ag-rich and Ni-rich phases. For all Ag contents, the corrosion resistance of the Ni-Ag coating was higher than the pure Ni coating. Exposure to Sulphate Reducing Bacteria (SRB) revealed that the extent of bio-fouling decreased with increase in the Ag content. After 2 month exposure to SRB, the Ni-Ag coatings demonstrated less loss in corrosion resistance (58% for Ni-7 at.% Ag and 20% for Ni-14 at.% Ag) when compared pure Ni coating (115%).

  2. Covalency in Metal-Oxygen Multiple Bonds Evaluated Using Oxygen K-edge Spectroscopy and Electronic Structure Theory

    Energy Technology Data Exchange (ETDEWEB)

    Minasian, Stefan G.; Keith, Jason M.; Batista, Enrique R.; Boland, Kevin S.; Bradley, Joseph A.; Daly, Scott R.; Kozimor, Stosh A.; Lukens, Wayne W.; Martin, Richard L.; Nordlund, Dennis; Seidler, Gerald T.; Shuh, David K.; Sokaras, Dimosthenis; Tyliszczak, Tolek; Wagner, Gregory L.; Weng, Tsu-Chein; Yang, Ping

    2014-01-01

    Advancing theories of how metal oxygen bonding influences metal oxo properties can expose new avenues for innovation in materials science, catalysis, and biochemistry. Historically, spectroscopic analyses of the transition metal peroxyanions, MO4x-, have formed the basis for new M O bonding theories. Herein, relative changes in M O orbital mixing in MO42- (M = Cr, Mo, W) and MO41- (M = Mn, Tc, Re) are evaluated for the first time by non-resonant inelastic X-ray scattering, X-ray absorption spectroscopy using fluorescence and transmission (via a scanning transmission X-ray microscope), and linear-response density functional theory. The results suggest that moving from Group 6 to Group 7 or down the triads increases M O e () mixing. Meanwhile, t2 mixing ( + ) remains relatively constant within the same Group. These unexpected changes in frontier orbital energy and composition are evaluated in terms of periodic trends in d orbital energy and radial extension.

  3. High-resolution study of x-ray resonant Raman scattering at the k edge of silicon

    OpenAIRE

    Szlachetko, Jakub; Dousse, Jean-Claude; Hoszowska, J.; Pajek, M.; Barrett, R.; Berset, Michel; Fennane, Karima; Kubala-Kukus, A.; Szlachetko, Monika

    2007-01-01

    We report on the first high-resolution measurements of the K x-ray resonant Raman scattering (RRS) in Si. The measured x-ray RRS spectra, interpreted using the Kramers-Heisenberg approach, revealed spectral features corresponding to electronic excitations to the conduction and valence bands in silicon. The total cross sections for the x-ray RRS at the 1s absorption edge and the 1s-3p excitation were derived. The Kramers-Heisenberg formalism was found to reproduce quite well the x-ray RRS spec...

  4. Effect of Ni Core Structure on the Electrocatalytic Activity of Pt-Ni/C in Methanol Oxidation

    Science.gov (United States)

    Kang, Jian; Wang, Rongfang; Wang, Hui; Liao, Shijun; Key, Julian; Linkov, Vladimir; Ji, Shan

    2013-01-01

    Methanol oxidation catalysts comprising an outer Pt-shell with an inner Ni-core supported on carbon, (Pt-Ni/C), were prepared with either crystalline or amorphous Ni core structures. Structural comparisons of the two forms of catalyst were made using transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and methanol oxidation activity compared using CV and chronoamperometry (CA). While both the amorphous Ni core and crystalline Ni core structures were covered by similar Pt shell thickness and structure, the Pt-Ni(amorphous)/C catalyst had higher methanol oxidation activity. The amorphous Ni core thus offers improved Pt usage efficiency in direct methanol fuel cells. PMID:28811402

  5. Effect of Ni Core Structure on the Electrocatalytic Activity of Pt-Ni/C in Methanol Oxidation

    Directory of Open Access Journals (Sweden)

    Vladimir Linkov

    2013-07-01

    Full Text Available Methanol oxidation catalysts comprising an outer Pt-shell with an inner Ni-core supported on carbon, (Pt-Ni/C, were prepared with either crystalline or amorphous Ni core structures. Structural comparisons of the two forms of catalyst were made using transmission electron microscopy (TEM, X-ray diffraction (XRD and X-ray photoelectron spectroscopy (XPS, and methanol oxidation activity compared using CV and chronoamperometry (CA. While both the amorphous Ni core and crystalline Ni core structures were covered by similar Pt shell thickness and structure, the Pt-Ni(amorphous/C catalyst had higher methanol oxidation activity. The amorphous Ni core thus offers improved Pt usage efficiency in direct methanol fuel cells.

  6. Resiliencia en Niños

    OpenAIRE

    Norma Ivonne González Arratia Lopez Fuentes

    2007-01-01

    Con el objetivo de acercarse al constructo teórico de resiliencia, y desde la propuesta de Grotberg (1995a) y Melillo (2003), del modelo donde es posible caracterizar a un niño resiliente a través de la posesión de condiciones que en el lenguaje se expresan diciendo: "Yo tengo", "Yo soy", "Yo estoy", "Yo puedo", es que se procedió a hacer la aplicación de la técnica de Redes Semánticas Naturales a 400 niños de ambos sexos, de 6° año de primaria de escuelas públicas y privadas de la ciudad de ...

  7. Ni ion damage in Cu and Nb

    International Nuclear Information System (INIS)

    Roberto, J.B.; Narayan, J.

    1975-01-01

    Ni ion damage in Cu was studied using x-ray diffuse scattering and transmission electron microscopy, and in Nb using x-ray diffuse scattering. Single crystals of Cu and Nb were irradiated at room temperature to a fluence of 1.2 x 10 13 /cm 2 at 60 MeV, and Cu was also irradiated to 5 x 10 12 /cm 2 at 4 MeV. The x-ray diffuse scattering from loop-type defect clusters in the crystals was measured near several Bragg reflections in order to probe the depth distributions of the damage. In Cu, cluster size distributions derived from the x-ray measurements agreed well with TEM results. Comparison with fission reactor irradiations using the damage energy concept suggests similarities in retained damage between the neutron and Ni ion irradiations

  8. Internal chlorination of Ni-Cr alloys

    Energy Technology Data Exchange (ETDEWEB)

    Berztiss, D.; Hennesen, K.; Grabke, H.J. [Max-Planck-Institut fuer Eisenforschung GmbH, Duesseldorf (Germany)

    1998-12-31

    In contrast to internal oxidation, sulfidation and carburization, very little information is available regarding internal chlorination, especially diffusion of chlorine in metallic alloys. This paper describes results of experiments on Ni-Cr alloys (<10 wt% Cr) exposed in an atmosphere containing radioactive HCl. The diffusion of chlorine in the alloy can be determined by measurement of residual {beta}-activity from the sample surface. Successively thin layers (0.5-10 {mu}m) of the alloy were removed by lapping and the surface activity was measured to obtain a depth profile. Both single and polycrystalline materials were tested. Through this work it should be determined if there is in fact solubility and diffusion of chlorine in Ni-based alloys as some authors have proposed or if the ingress of chlorine is mainly a grain boundary phenomenon. (orig.)

  9. Fe-Ni-bearing serpentines from the saprolite horizon of Caribbean Ni-laterite deposits: new insights from thermodynamic calculations

    Science.gov (United States)

    Villanova-de-Benavent, Cristina; Domènech, Cristina; Tauler, Esperança; Galí, Salvador; Tassara, Santiago; Proenza, Joaquín A.

    2017-10-01

    Fe-Ni-bearing serpentine from the saprolite horizon is the main Ni ores in hydrous silicate-type Ni laterites and formed by chemical weathering of partially serpentinized ultramafic rocks under tropical conditions. During lateritization, Mg, Si, and Ni are leached from the surface and transported downwards. Fe2+ is oxidized to Fe3+ and fixed as insoluble Fe-oxyhydroxides (mostly goethite) that incorporate Ni. This Ni is later leached from goethite and incorporated in secondary serpentine and garnierite. As a result, a serpentine-dominated saprolite horizon forms over the ultramafic protolith, overlapped by a Fe-oxyhydroxide-dominated limonite horizon. The serpentine from the protolith (serpentine I) is of hydrothermal origin and yields similar Ni (0.10-0.62 wt.% NiO) and lower Fe (mostly 1.37-5.81 wt.% FeO) concentrations than the primary olivine. In contrast, Fe-Ni-bearing serpentine from the saprolite (serpentine II) shows significantly higher and variable Fe and Ni contents, typically ranging from 2.23 to 15.59 wt.% Fe2O3 and from 1.30 to 7.67 wt.% NiO, suggesting that serpentine get enriched in Fe and Ni under supergene conditions. This study presents detailed mineralogical, textural, and chemical data on this serpentine II, as well as new insights by thermodynamic calculations assuming ideal solution between Fe-, Ni- and Mg-pure serpentines. The aim is to assess if at atmospheric pressure and temperature Fe-Ni-bearing serpentine can be formed by precipitation. Results indicate that the formation of serpentine II under atmospheric pressure and temperature is thermodynamically supported, and pH, Eh, and the equilibrium constant of the reaction are the parameters that affect the results more significantly.

  10. Electrochemically induced transformation of NiS nanoparticles into Ni(OH)2 in KOH aqueous solution toward electrochemical capacitors

    International Nuclear Information System (INIS)

    Hou Linrui; Yuan Changzhou; Li Diankai; Yang Long; Shen Laifa; Zhang Fang; Zhang Xiaogang

    2011-01-01

    Highlights: → NiS is synthesized by means of the H 2 O/CS 2 interface under hydrothermal treatment. → NiS itself owns poor electrochemical capacitance in 2 M KOH solution. → NiS is electrochemically induced and transformed into electroactive Ni(OH) 2 . → Ni(OH) 2 is responsible for good energy storage of the NiS in the KOH solution. → The new formed Ni(OH) 2 delivers large energy density at high rates. - Abstract: Nickel sulfide nanoparticles (NPs) are first synthesized by virtue of a unique H 2 O/CS 2 interface under mild hydrothermal treatment. Electrochemical data reveals that the as-synthesized NiS NPs themselves own poor supercapacitive behavior at initial cyclic voltammetry (CV) cycles in 2 M KOH solution, while a specific capacitance of 893 F g -1 can be surprisingly obtained at a current density of 5 A g -1 just after continuous 320 CV cycles. X-ray diffraction and Fourier transform infrared techniques demonstrate that what is really responsible for the good electrochemical capacitance in the KOH aqueous solution is the new electrochemically formed Ni(OH) 2 phase, rather than NiS NPs themselves. The Ni(OH) 2 is slowly formed during the continuous CV cycling process, in which the electrochemically induced phase transformation from NiS to Ni(OH) 2 phase takes place. Furthermore, the new Ni(OH) 2 phase demonstrates the great ability of delivering large specific capacitance at high rates.

  11. Marca personal: Niña Pinturera

    OpenAIRE

    Cordero González, Bella

    2017-01-01

    En el siguiente trabajo fin de grado se expone el proceso del Personal Branding o creación de marca personal de “Niña Pinturera”. Se desarrolla desde los inicios de su historia, el diseño de la identidad corporativa hasta la estrategia a seguir y su plan de comunicación, enfocado al entorno digital y las redes sociales. Grado en Publicidad y Relaciones Públicas

  12. Imaging magnetic domains in Ni nanostructures

    International Nuclear Information System (INIS)

    Asenjo, A.; Jaafar, M.; Gonzalez, E.M.; Martin, J.I.; Vazquez, M.; Vicent, J.L.

    2007-01-01

    The study of nanomagnets is the subject of increasing scientific effort. The size, the thickness and the geometric shape of the elements determine the magnetic properties and then the domain configuration. In this work, we fabricated by electron-beam lithography the three different arrays of Ni nanostructures keeping the size, the thickness and also the distance constant between the elements but varying the geometry: square, triangular and circular. The domain structure of the nanomagnets is studied by magnetic force microscopy

  13. Breakdown of antiferromagnet order in polycrystalline NiFe/NiO bilayers probed with acoustic emission

    Science.gov (United States)

    Lebyodkin, M. A.; Lebedkina, T. A.; Shashkov, I. V.; Gornakov, V. S.

    2017-07-01

    Magnetization reversal of polycrystalline NiFe/NiO bilayers was investigated using magneto-optical indicator film imaging and acoustic emission techniques. Sporadic acoustic signals were detected in a constant magnetic field after the magnetization reversal. It is suggested that they are related to elastic waves excited by sharp shocks in the NiO layer with strong magnetostriction. Their probability depends on the history and number of repetitions of the field cycling, thus testifying the thermal-activation nature of the long-time relaxation of an antiferromagnetic order. These results provide evidence of spontaneous thermally activated switching of the antiferromagnetic order in NiO grains during magnetization reversal in ferromagnet/antiferromagnet (FM/AFM) heterostructures. The respective deformation modes are discussed in terms of the thermal fluctuation aftereffect in the Fulcomer and Charap model which predicts that irreversible breakdown of the original spin orientation can take place in some antiferromagnetic grains with disordered anisotropy axes during magnetization reversal of exchange-coupled FM/AFM structures. The spin reorientation in the saturated state may induce abrupt distortion of isolated metastable grains because of the NiO magnetostriction, leading to excitation of shock waves and formation of plate (or Lamb) waves.

  14. Structural, electrical and magnetic properties of evaporated Ni/Cu and Ni/glass thin films

    International Nuclear Information System (INIS)

    Nacereddine, C.; Layadi, A.; Guittoum, A.; Cherif, S.-M.; Chauveau, T.; Billet, D.; Youssef, J. Ben; Bourzami, A.; Bourahli, M.-H.

    2007-01-01

    The structural, electrical and magnetic properties of Ni thin films evaporated onto glass and polycrystalline Cu substrates have been investigated. The Ni thickness ranges from 31 to 165 nm. X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) have been used to study the structure and morphology of these systems. The Ni/Cu and Ni/glass thin films are found to be polycrystalline with a (1 1 1) texture. There is an overall increase of the grain size with increasing thickness. A negative strain was noted indicating that all the samples are under a compressive stress. Diffusion at the grain boundaries seems to be a major contribution to the electrical resistivity in this thickness range. Study of the hysteresis curves, obtained by vibrating sample magnetometer (VSM), indicates that all samples are characterized by an in-plane magnetization easy axis. Higher in-plane coercive fields seem to be associated with higher grain size, indicating that coercivity may be due to nucleation of reverse domains rather than pinning of domain walls. The saturation field and the squareness have been studied as a function of the Ni thickness

  15. Participar como niña o niño en el mundo social

    Directory of Open Access Journals (Sweden)

    Silvia Paulina Díaz

    2010-01-01

    Full Text Available En este artículo presento la participación como resultado de un trabajo investigativo realizado durante el año 2007, con niños y niñas escolarizados habitantes de la ciudad de Medellín, Colombia, cuyo objetivo fue analizar las representaciones sociales que ellos y ellas comparten sobre el ejercicio ciudadano. El análisis de la información tiene como ejes fundamentales, la salud colectiva, la sociología de la infancia y la participación en la niñez, en una aproximación que se realiza desde un enfoque cualitativo y etnográfico. En los hallazgos, sobresale cómo las niñas y niños se muestran preparados para ejercer su derecho a la participación como aspecto de sus vidas que se haría posible dentro del marco normativo existente, pero que aún no es asumido en prácticas sociales que los incluyan.

  16. High resolution TEM study of Ni4Ti3 precipitates in austenitic Ni51Ti49

    International Nuclear Information System (INIS)

    Tirry, Wim; Schryvers, Dominique

    2003-01-01

    Binary NiTi with a composition of 51 at.% Ni was heat treated to form lens-shaped Ni 4 Ti 3 precipitates that are coherent or semi-coherent with the B2 matrix. High resolution transmission electron microscopy (HRTEM) was used to study the internal structure of the precipitates, precipitate-precipitate and matrix-precipitate interfaces and the deformation of the B2 matrix near a precipitate. Observations were made in the B2 and B2 zones and compared with computer simulated high resolution images. The B2 observations made it possible to study the [0 0 1] H zone orientation of Ni 4 Ti 3 (direction defined according to the hexagonal unit cell of Ni 4 Ti 3 ) which corresponds to the normal of the central plane of the discs. In these images the superperiodicity of the 4:3 ordering is clearly visible confirming the known atomic structure. Close to the precipitate the B2 matrix is deformed, as determined by measuring the interplanar spacing from the HRTEM images. The observed deformations are compared with theoretical models for the stress field

  17. Coarsening kinetics of coherent precipitates in Ni-Al-Mo and Fe-Ni-Al alloys

    International Nuclear Information System (INIS)

    Calderon, H.A.; Dorantes, H.J.; Cruz, J.J.; Cabanas-Moreno, J.G.

    1997-01-01

    The late stage coarsening kinetics of coherent γ' and β' have been investigated in single crystalline specimens of Ni-14.5 at.% Al-5.9 at.% Mo and Fe-10 at.% Ni-15 at.% Al after aging at 1453 K for the Ni alloy and 1233 K for the Fe alloy. Scanning electron microscopy (SEM) shows that early in the coarsening regime there is particle splitting in the Ni-base alloy. Continued aging changes the spatial distribution of particles giving rise to the formation of groups of many particles. In the Fe-base alloy, formation of particle groups is seen earlier. Longer aging treatments produce large particles that split forming plate like precipitates. Particle migration is evident in both alloys. The coarsening kinetics of particles in the Ni-base alloy show deviations from the usual linear behavior between the cube of the average particle radius and the aging time. There is a reduction of the coarsening rate and in addition broader particle size distributions are obtained. In the Fe-base alloy, direct measurements of particle areas on SEM images show a linear dependence of the cube of the average particle radius with the aging time. However, after correcting for particle shape an increase of the coarsening rate is suggested. (orig.)

  18. Coarsening kinetics of coherent precipitates in Ni-Al-Mo and Fe-Ni-Al alloys

    Energy Technology Data Exchange (ETDEWEB)

    Calderon, H.A.; Dorantes, H.J.; Cruz, J.J.; Cabanas-Moreno, J.G. [ESIQIE-IPN, Mexico (Mexico). Dept. de Ingenieria Metalurgica; Kostorz, G.; Qu, Y.Y. [ETH Zuerich, Institut fuer Angewandte Physik, Zuerich CH-8093 (Switzerland)

    1997-10-30

    The late stage coarsening kinetics of coherent {gamma}` and {beta}` have been investigated in single crystalline specimens of Ni-14.5 at.% Al-5.9 at.% Mo and Fe-10 at.% Ni-15 at.% Al after aging at 1453 K for the Ni alloy and 1233 K for the Fe alloy. Scanning electron microscopy (SEM) shows that early in the coarsening regime there is particle splitting in the Ni-base alloy. Continued aging changes the spatial distribution of particles giving rise to the formation of groups of many particles. In the Fe-base alloy, formation of particle groups is seen earlier. Longer aging treatments produce large particles that split forming plate like precipitates. Particle migration is evident in both alloys. The coarsening kinetics of particles in the Ni-base alloy show deviations from the usual linear behavior between the cube of the average particle radius and the aging time. There is a reduction of the coarsening rate and in addition broader particle size distributions are obtained. In the Fe-base alloy, direct measurements of particle areas on SEM images show a linear dependence of the cube of the average particle radius with the aging time. However, after correcting for particle shape an increase of the coarsening rate is suggested. (orig.) 19 refs.

  19. Participar como niña o niño en el mundo social

    Directory of Open Access Journals (Sweden)

    Silvia Paulina Díaz

    2010-10-01

    Full Text Available En este artículo presento la participación como resultado de un trabajo investigativo realizado durante el año 2007, con niños y niñas escolarizados habitantes de la ciudad de Medellín, Colombia, cuyo objetivo fue analizar las representaciones sociales que ellos y ellas comparten sobre el ejercicio ciudadano. El análisis de la información tiene como ejes fundamentales, la salud colectiva, la sociología de la infancia y la participación en la niñez, en una aproximación que se realiza desde un enfoque cualitativo y etnográfico. En los hallazgos, sobresale cómo las niñas y niños se muestran preparados para ejercer su derecho a la participación como aspecto de sus vidas que se haría posible dentro del marco normativo existente, pero que aún no es asumido en prácticas sociales que los incluyan.

  20. Carbon dioxide hydrogenation on Ni(110).

    Science.gov (United States)

    Vesselli, Erik; De Rogatis, Loredana; Ding, Xunlei; Baraldi, Alessandro; Savio, Letizia; Vattuone, Luca; Rocca, Mario; Fornasiero, Paolo; Peressi, Maria; Baldereschi, Alfonso; Rosei, Renzo; Comelli, Giovanni

    2008-08-27

    We demonstrate that the key step for the reaction of CO 2 with hydrogen on Ni(110) is a change of the activated molecule coordination to the metal surface. At 90 K, CO 2 is negatively charged and chemically bonded via the carbon atom. When the temperature is increased and H approaches, the H-CO 2 complex flips and binds to the surface through the two oxygen atoms, while H binds to the carbon atom, thus yielding formate. We provide the atomic-level description of this process by means of conventional ultrahigh vacuum surface science techniques combined with density functional theory calculations and corroborated by high pressure reactivity tests. Knowledge about the details of the mechanisms involved in this reaction can yield a deeper comprehension of heterogeneous catalytic organic synthesis processes involving carbon dioxide as a reactant. We show why on Ni the CO 2 hydrogenation barrier is remarkably smaller than that on the common Cu metal-based catalyst. Our results provide a possible interpretation of the observed high catalytic activity of NiCu alloys.