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Sample records for techniques xanes exafs

  1. EXAFS and XANES analysis of oxides at the nanoscale

    Directory of Open Access Journals (Sweden)

    Alexei Kuzmin

    2014-11-01

    Full Text Available Worldwide research activity at the nanoscale is triggering the appearance of new, and frequently surprising, materials properties in which the increasing importance of surface and interface effects plays a fundamental role. This opens further possibilities in the development of new multifunctional materials with tuned physical properties that do not arise together at the bulk scale. Unfortunately, the standard methods currently available for solving the atomic structure of bulk crystals fail for nanomaterials due to nanoscale effects (very small crystallite sizes, large surface-to-volume ratio, near-surface relaxation, local lattice distortions etc.. As a consequence, a critical reexamination of the available local-structure characterization methods is needed. This work discusses the real possibilities and limits of X-ray absorption spectroscopy (XAS analysis at the nanoscale. To this end, the present state of the art for the interpretation of extended X-ray absorption fine structure (EXAFS is described, including an advanced approach based on the use of classical molecular dynamics and its application to nickel oxide nanoparticles. The limits and possibilities of X-ray absorption near-edge spectroscopy (XANES to determine several effects associated with the nanocrystalline nature of materials are discussed in connection with the development of ZnO-based dilute magnetic semiconductors (DMSs and iron oxide nanoparticles.

  2. EXAFS and XANES analysis of plutonium and cerium edges from titanate ceramics for fissile materials disposal

    International Nuclear Information System (INIS)

    Fortner, J. A.; Kropf, A. J.; Bakel, A. J.; Hash, M. C.; Aase, S. B.; Buck, E. C.; Chamerlain, D. B.

    1999-01-01

    We report x-ray absorption near edge structure (XANES) and extended x-ray absorption fine structure (EXAFS) spectra from the plutonium L III edge and XANES from the cerium L II edge in prototype titanate ceramic hosts. The titanate ceramics studied are based upon the hafnium-pyrochlore and zirconolite mineral structures and will serve as an immobilization host for surplus fissile materials, containing as much as 10 weight % fissile plutonium and 20 weight % (natural or depleted) uranium. Three ceramic formulations were studied: one employed cerium as a ''surrogate'' element, replacing both plutonium and uranium in the ceramic matrix, another formulation contained plutonium in a ''baseline'' ceramic formulation, and a third contained plutonium in a formulation representing a high-impurity plutonium stream. The cerium XANES from the surrogate ceramic clearly indicates a mixed III-IV oxidation state for the cerium. In contrast, XANES analysis of the two plutonium-bearing ceramics shows that the plutonium is present almost entirely as Pu(IV) and occupies the calcium site in the zirconolite and pyrochlore phases. The plutonium EXAFS real-space structure shows a strong second-shell peak, clearly distinct from that of PuO 2 , with remarkably little difference in the plutonium crystal chemistry indicated between the baseline and high-impurity formulations

  3. X-ray absorption spectroscopy: EXAFS and XANES - A versatile tool to study the atomic and electronic structure of materials

    International Nuclear Information System (INIS)

    Alp, E.E.; Mini, S.M.; Ramanathan, M.

    1990-01-01

    X-ray absorption spectroscopy (XAS) had been an essential tool to gather spectroscopic information about atomic energy level structure in the early decades of this century. The correct interpretation of the oscillatory structure in the x-ray absorption cross-section above the absorption edge has transformed XAS from a spectroscopic tool to a structural technique. EXAFS (Extended X-ray Absorption Fine Structure) yields information about the interatomic distances, near neighbor coordination numbers, and lattice dynamics. XANES (X-ray Absorption Near Edge Structure), on the other hand, gives information about the valence state, energy bandwidth and bond angles. Today, there are about 50 experimental stations in various synchrotrons around the world dedicated to collecting x-ray absorption data from the bulk and surfaces of solids and liquids. In this chapter, they will give the basic principles of XAS, explain the information content of essentially two different aspects of the absorption process leading to EXAFS and XANES, and discuss the source and sample limitations

  4. Polarized XANES and EXAFS spectroscopic investigation into copper(II) complexes on vermiculite

    Science.gov (United States)

    Furnare, Luca J.; Vailionis, Arturas; Strawn, Daniel G.

    2005-11-01

    Interaction of heavy metals with clay minerals can dominate solid-solution reactions in soil, controlling the fate of the metals in the environment. In this study we used powdered and polarized extended X-ray absorption fine structure (EXAFS) spectroscopy and X-ray absorption near edge spectroscopy (XANES) to investigate Cu sorbed on Llano vermiculite and compare the results to reported Cu sorption mechanism on Wyoming (WY) smectite and reduced South African (SA) vermiculite. Analysis of the Cu K-edge spectra revealed that Cu sorbed on Llano vermiculite at high ionic strength ( I) has the greatest degree of covalent bond character, followed by Cu sorbed on montmorillonite at high I, and Cu sorbed on reduced SA vermiculite at high I. Cu sorbed on clay minerals at low I has the least covalent character. EXAFS data from Cu sorbed Ca- and K-equilibrated Llano vermiculites showed the presence of a second-shell Al, Si, or Mg backscatterer at 3.02 Å. This distance is consistent with Cu sorbing via a corner-sharing monodentate or bidentate bond. Polarized XANES and EXAFS results revealed that the angle between the Cu atom and the mineral sorption sites is 68° with respect to the [001] direction. From the bond angle and the persistence of the second-shell backscatterer when the interlayer is collapsed (K-equilibration), we conclude that Cu adsorption on the Llano vermiculite is not occurring in the interlayer but rather Cu is adsorbing onto the edges of the vermiculite. Results from this research provide evidence that Cu forms inner-sphere and outer-sphere complexes on clay minerals, and does not form the vast multinuclear surface precipitates that have been observed for Co, Zn, and Ni.

  5. The geochemical behaviour of selenium in the Boom Clay system - a XANES and EXAFS study

    International Nuclear Information System (INIS)

    2S, KULeuven, B-3001Leuven (Belgium))" data-affiliation=" (Center for surface Chemistry and Catalysis - M2S, KULeuven, B-3001Leuven (Belgium))" >Breynaert, Eric; 2S, KULeuven, B-3001Leuven (Belgium))" data-affiliation=" (Center for surface Chemistry and Catalysis - M2S, KULeuven, B-3001Leuven (Belgium))" >Dom, Dirk; 2S, KULeuven, B-3001Leuven (Belgium))" data-affiliation=" (Center for surface Chemistry and Catalysis - M2S, KULeuven, B-3001Leuven (Belgium))" >Vancluysen, Jacqueline; 2S, KULeuven, B-3001Leuven (Belgium))" data-affiliation=" (Center for surface Chemistry and Catalysis - M2S, KULeuven, B-3001Leuven (Belgium))" >Kirschhock, Christine E.A.; 2S, KULeuven, B-3001Leuven (Belgium))" data-affiliation=" (Center for surface Chemistry and Catalysis - M2S, KULeuven, B-3001Leuven (Belgium))" >Maes, Andre; Scheinost, Andreas C.

    2010-01-01

    Document available in extended abstract form only. In Belgium, the Boom Clay formation is studied as a reference host formation for the geological disposal of high-level and long-lived radioactive waste for more than 30 years. This formation mainly consists of mixed clay minerals (illite, inter-stratified illite-smectite), pyrite and immobile and dissolved natural organic matter. Since it provides good sorption capacities, very low permeability, and chemically reducing conditions due to the presence of pyrite (FeS 2 ), the Boom clay formation itself is considered to be the main barrier preventing radionuclide migration from the geological repository. Within this concept for geological storage Se 79 has been identified as one of the critical elements contributing to the final dose to man. Although the sorption and migration behaviour of Se in the Boom Clay system has been thoroughly studied, the speciation of Se in the Boom Clay system has never been identified spectroscopically. In all previous studies, the interpretation of the behaviour of Se in Boom Clay conditions has always been based on circumstantial evidence such as solubility measurements or comparison with the spectroscopically identified speciation of Se in model systems. Based on the XANES analysis, selenite is transformed into Se 0 confirming the previously proposed reduction of selenite in the Boom Clay system. Combination of the mass-balance for Se with the results from linear combination analysis of the XANES spectra provided new evidence for the sorption-reduction mechanism proposed to explain the interaction between Se(IV) and the BC solid phase. In addition, evidence was found that that the fate of Se(IV) in the BC system is completely dominated by its interaction with pyrite present in the Boom Clay. The combined EXAFS analysis of Se in Se 0 reference phases (hexagonal, monoclinic, Se-loaded pyrite) allowed to elucidate further details on the short-range structure of the reaction products formed

  6. XANES, EXAFS and Kbeta spectroscopic studies of the oxygen-evolving complex in Photosystem II

    Energy Technology Data Exchange (ETDEWEB)

    Robblee, John Henry [Univ. of California, Berkeley, CA (United States)

    2000-12-01

    A key question for the understanding of photosynthetic water oxidation is whether the four oxidizing equivalents necessary to oxidize water to dioxygen are accumulated on the four Mn ions of the oxygen evolving complex (OEC), or whether some ligand-centered oxidations take place before the formation and release of dioxygen during the S3 → [S4] → S0 transition. Progress in instrumentation and flash sample preparation allowed us to apply Mn Kβ X-ray emission spectroscopy (Kb XES) to this problem for the first time. The Kβ XES results, in combination with Mn X-ray absorption near-edge structure (XANES) and electron paramagnetic resonance (EPR) data obtained from the same set of samples, show that the S2 → S3 transition, in contrast to the S0 → S1 and S1 → S2 transitions, does not involve a Mn-centered oxidation. This is rationalized by manganese μ-oxo bridge radical formation during the S2 → S3 transition. Using extended X-ray absorption fine structure (EXAFS) spectroscopy, the local environment of the Mn atoms in the S0 state has been structurally characterized. These results show that the Mn-Mn distance in one of the di-μ-oxo-bridged Mn-Mn moieties increases from 2.7 Å in the S1} state to 2.85 Å in the S0 state. Furthermore, evidence is presented that shows three di-μ-oxo binuclear Mn2 clusters may be present in the OEC, which is contrary to the widely held theory that two such clusters are present in the OEC. The EPR properties of the S0 state have been investigated and a characteristic ''multiline'' signal in the S0 state has been discovered in the presence of methanol. This provides the first direct confirmation that the native S0 state is paramagnetic. In addition, this signal was simulated using parameters derived from three

  7. Reduction and re-oxidation of Cu/Al{sub 2}O{sub 3} catalysts investigated with quick-scanning XANES and EXAFS

    Energy Technology Data Exchange (ETDEWEB)

    Stoetzel, J; Luetzenkirchen-Hecht, D; Frahm, R [Department of Physics, University of Wuppertal, Gaussstr. 20, D-42097 Wuppertal (Germany); Kimmerle, B; Baiker, A [Department of Chemistry and Applied Biosciences, ETH Zuerich, CH-8093 Zuerich (Switzerland); Nachtegaal, M [Paul Scherrer Institut, CH-5232 Villigen (Switzerland); Beier, M J; Grunwaldt, J-D, E-mail: j.stoetzel@uni-wuppertal.d, E-mail: jdg@kt.dtu.d [Department of Chemical and Biochemical Engineering, Technical University of Denmark, Building 229, DK-2800 Kgs. Lyngby (Denmark)

    2009-11-15

    In the present study the structure of copper catalysts on alumina support were investigated in situ and time resolved during reduction and re-oxidation at different temperatures with the quick-scanning EXAFS (QEXAFS) technique. Different impregnation times (2 min and 90 min) were chosen for the preparation which resulted in different copper species that show a strong variation in the reduction/re-oxidation behaviour. These dynamic changes as well as possible intermediate phases during the gas atmospheres changes were followed with up to 20 EXAFS spectra per second at the copper K-edge covering an energy range of 450 eV. The high time resolution provided new insights into the dynamics of the catalysts e.g. revealing Cu(I) as intermediate state during re-oxidation. Latest advances in the data acquisition hardware are leading to an improved data quality of spectra collected at the SuperXAS beamline. Thus, not only accurate analysis of the catalysts via XANES but also by EXAFS was possible. This is also due to the recent upgrade to monitor the Bragg angle directly with an encoder during the experiments.

  8. Shape resonances and EXAFS scattering in the $Pt L_{2,3}$ XANES from a Pt electrode

    CERN Document Server

    O'Grady, W E

    1999-01-01

    Atomic hydrogen and oxygen adsorption on a platinum electrode in H /sub 2/SO/sub 4/ and HClO/sub 4/ electrolytes were studied by Pt L /sub 23/ XANES. The Pt electrode was formed of highly dispersed 1.5-3.0 nm particles supported on $9 carbon. A difference procedure utilizing the L/sub 2/ and L/sub 3/ spectra at various applied voltages was used to isolate the electronic and geometric effects in the XANES spectra. At 0.54 V (relative to RHE) the Pt electrode in $9 HClO/sub 4/ is assumed to be "clean". By taking the difference between the spectra at 0.0 and 0.54 V, the Pt-H antibonding state (electronic effect) is isolated and found to have a Fano-resonance line shape. In addition, a $9 significant Pt-H EXAFS scattering (geometric effect) was found for photon energies 0 to 20 eV above the edge. The difference between the spectra at 1.14 and 0.54 V allows isolation of the Pt-O antibonding state and the Pt-O EXAFS $9 scattering. (7 refs).

  9. Alternative difference analysis scheme combining R-space EXAFS fit with global optimization XANES fit for X-ray transient absorption spectroscopy.

    Science.gov (United States)

    Zhan, Fei; Tao, Ye; Zhao, Haifeng

    2017-07-01

    Time-resolved X-ray absorption spectroscopy (TR-XAS), based on the laser-pump/X-ray-probe method, is powerful in capturing the change of the geometrical and electronic structure of the absorbing atom upon excitation. TR-XAS data analysis is generally performed on the laser-on minus laser-off difference spectrum. Here, a new analysis scheme is presented for the TR-XAS difference fitting in both the extended X-ray absorption fine-structure (EXAFS) and the X-ray absorption near-edge structure (XANES) regions. R-space EXAFS difference fitting could quickly provide the main quantitative structure change of the first shell. The XANES fitting part introduces a global non-derivative optimization algorithm and optimizes the local structure change in a flexible way where both the core XAS calculation package and the search method in the fitting shell are changeable. The scheme was applied to the TR-XAS difference analysis of Fe(phen) 3 spin crossover complex and yielded reliable distance change and excitation population.

  10. EXAFS analysis of uranium speciation in plants using the difference technique

    International Nuclear Information System (INIS)

    Rossberg, A.; Reich, T.; Guenther, A.; Bernhard, G.

    2002-01-01

    An EXAFS spectrum is the sum of the signals of scattering contributions from single atoms and multiple scattering (MS) between atoms. The scattering contributions with high intensity are the major and such with low intensity are the minor components in an EXAFS spectrum. A chi-squared fit algorithm is not sensitive enough to the minor components. A difference technique has been developed /1/ to isolate the minor components from the whole EXAFS spectrum to increase the accuracy in determinating of their EXAFS structural parameters. (orig.)

  11. Mercury speciation on three European mining districts by XANES techniques

    Science.gov (United States)

    Esbri, J. M.; Garcia-Noguero, E. M.; Guerrero, B.; Kocman, D.; Bernaus, A.; Gaona, X.; Higueras, P.; Alvarez, R.; Loredo, J.; Horvat, M.; Ávila, M.

    2009-04-01

    The mobility, bioavailability and toxicity of mercury in the environment depend on the chemical species in which is present in soil, sediments, water or air. In this work we used synchrotron radiation to determine mercury species in geological samples of three mercury mining districts: Almadén (Spain), Idria (Slovenia) and Asturias (Spain). The aim of this study was to find differences on mobility and bioavailability of mercury on three mining districts with different type of mineralization. For this porpoises we selected samples of ore, calcines, soils and stream sediments from the three sites, completely characterized by the Almadén School of Mines, Josef Stefan Institute of Ljubljana and Oviedo School of Mines. Speciation of mercury was carried out on Synchrotron Laboratories of Hamburg (HASYLAB) by XANES techniques. Spectra of pure compounds [HgCl2, HgSO4, HgO, CH3HgCl, Hg2Cl2 (calomel), HgSred (cinnabar), HgSblack (metacinnabar), Hg2NCl0.5(SO4)0.3(MoO4)0.1(CO3)0.1(H2O) (mosesite), Hg3S2Cl2 (corderoite), Hg3(SO4)O2 (schuetteite) y Hg2ClO (terlinguaite)] were obtained on transmittance mode. The number and type of the compounds required to reconstruct experimental spectra for each sample was obtained by PCA analysis and linear fitting of minimum quadratics of the pure compounds spectra. This offers a semiquantitative approach to the mineralogical constitution of each analyzed sample. The results put forward differences on the efficiency of roasting furnaces from the three studied sites, evidenced by the presence of metacinnabar on the less efficient (Almadén and Asturias) and absence on the most efficient (Idria). For the three studied sites, sulfide species (cinnabar and metacinnabar) were largely more abundant than soluble species (chlorides and sulfates). On the other hand, recent results on the mobility of both Hg and As on the target sites will be presented. These results correlate with the related chemical species found by XANES techniques.

  12. 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

  13. 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)

  14. Effect of Fe(II)/Ce(III) dosage ratio on the structure and anion adsorptive removal of hydrothermally precipitated composites: Insights from EXAFS/XANES, XRD and FTIR

    KAUST Repository

    Chubar, Natalia

    2016-10-24

    In this work, we present material chemistry in the hydrothermal synthesis of new complex structure materials based on various dosage ratios of Fe and Ce (1:0, 2:1, 1:1, 1:2, 0:1), characterize them by the relevant methods that allow characterization of both crystalline and amorphous phases and correlate their structure/surface properties with the adsorptive performance of the five toxic anions. The applied synthesis conditions resulted in the formation of different compounds of Fe and Ce components. The Fe-component was dominated by various phases of Fe hydrous oxides, whereas the Ce-component was composed of various phases of Ce carbonates. The presence of two metal salts in raw materials resulted in the formation of a mesoporous structure and averaged the surface area compared to one metal-based material. The surface of all Fe-Ce composites was abundant in Fe component phases. Two-metal systems showed stronger anion removal performance than one-metal materials. The best adsorption was demonstrated by Fe-Ce based materials that had low crystallinity, that were rich in phases and that exhibited surfaces were abundant in greater number of surface functional groups. Notably, Fe extended fine structures simulated by EXAFS in these better adsorbents were rich from oscillations from both heavy and light atoms. This work provides new insights on the structure of composite inorganic materials useful to develop their applications in adsorption and catalysis. It also presents new inorganic anion exchangers with very high removal potential to fluoride and arsenate.

  15. Effect of Fe(II)/Ce(III) dosage ratio on the structure and anion adsorptive removal of hydrothermally precipitated composites: Insights from EXAFS/XANES, XRD and FTIR

    KAUST Repository

    Chubar, Natalia; Gerda, Vasyl; Banerjee, Dipanjan; Yablokova, Ganna

    2016-01-01

    In this work, we present material chemistry in the hydrothermal synthesis of new complex structure materials based on various dosage ratios of Fe and Ce (1:0, 2:1, 1:1, 1:2, 0:1), characterize them by the relevant methods that allow characterization of both crystalline and amorphous phases and correlate their structure/surface properties with the adsorptive performance of the five toxic anions. The applied synthesis conditions resulted in the formation of different compounds of Fe and Ce components. The Fe-component was dominated by various phases of Fe hydrous oxides, whereas the Ce-component was composed of various phases of Ce carbonates. The presence of two metal salts in raw materials resulted in the formation of a mesoporous structure and averaged the surface area compared to one metal-based material. The surface of all Fe-Ce composites was abundant in Fe component phases. Two-metal systems showed stronger anion removal performance than one-metal materials. The best adsorption was demonstrated by Fe-Ce based materials that had low crystallinity, that were rich in phases and that exhibited surfaces were abundant in greater number of surface functional groups. Notably, Fe extended fine structures simulated by EXAFS in these better adsorbents were rich from oscillations from both heavy and light atoms. This work provides new insights on the structure of composite inorganic materials useful to develop their applications in adsorption and catalysis. It also presents new inorganic anion exchangers with very high removal potential to fluoride and arsenate.

  16. Investigation of the Role of Hole Doping in Different High Temperature Superconducting Systems Using XANES Technique

    International Nuclear Information System (INIS)

    Hamdan, N.M.; Hasan, A.; Faiz, M.; Salim, M.A.; Hussain, Z.

    2004-01-01

    X-ray Absorption Near edge Structure (XANES) technique was used to study the role of hole doping in F-doped Hg-1223 and the Ce-doped Tl-1223. Oxygen k-edge and Cu L2,3-edge structures were thoroughly investigated. The pre-edge features of O k-edge spectra, as a function of doping, reveal important information about the projected local density of unoccupied states on the O sites in the region close to the absorption edge, which is a measure of O 2p hole concentration in the valance band. Furthermore, the Cu L2,3 absorption edge provides useful information about the valance state of Cu which is also related to the hole state in the CuO 2 planes. In this work, we will discuss these XANES results in these systems and correlate the observed improvements in the superconducting properties to the electronic structure in the CuO2 planes

  17. A study on the structures of hemoglobin of diabetic patients by EXAFS technique

    International Nuclear Information System (INIS)

    Wang Yinsong; Tan Mingguang; Zhang Guilin

    2001-01-01

    Hemoglobin was the carrier of oxygen in blood circulation. For the patients with diabetes mellitus the enhancement of glycidate hemoglobin in blood causes the decrease of oxygen transmission function. The local atomic structures of iron in hemoglobin were determined by EXAFS techniques. The relationship between diabetes mellitus and hemoglobin structures was observed. The blood samples were taken from normal people, slight and serious diabetic patients. The results show that the coordination number of iron atoms and Fe-O bond length were almost the same for the three samples. However, for the samples of serious diabetic patients the Fe-N bond length increases by about 0.002 nm, the possible reasons were the increase of deoxyhemoglobin contents in their blood

  18. Can we trust mass spectrometry for determination of arsenic peptides in plants: comparison of LC-ICP-MS and LC-ES-MS/ICP-MS with XANES/EXAFS in analysis of Thunbergia alata.

    Science.gov (United States)

    Bluemlein, Katharina; Raab, Andrea; Meharg, Andrew A; Charnock, John M; Feldmann, Jörg

    2008-04-01

    The weakest step in the analytical procedure for speciation analysis is extraction from a biological material into an aqueous solution which undergoes HPLC separation and then simultaneous online detection by elemental and molecular mass spectrometry (ICP-MS/ES-MS). This paper describes a study to determine the speciation of arsenic and, in particular, the arsenite phytochelatin complexes in the root from an ornamental garden plant Thunbergia alata exposed to 1 mg As L(-1) as arsenate. The approach of formic acid extraction followed by HPLC-ES-MS/ICP-MS identified different As(III)-PC complexes in the extract of this plant and made their quantification via sulfur (m/z 32) and arsenic (m/z 75) possible. Although sulfur sensitivity could be significantly increased when xenon was used as collision gas in ICP-qMS, or when HR-ICP-MS was used in medium resolution, the As:S ratio gave misleading results in the identification of As(III)-PC complexes due to the relatively low resolution of the chromatography system in relation to the variety of As-peptides in plants. Hence only the parallel use of ES-MS/ICP-MS was able to prove the occurrence of such arsenite phytochelatin complexes. Between 55 and 64% of the arsenic was bound to the sulfur of peptides mainly as As(III)(PC(2))(2), As(III)(PC(3)) and As(III)(PC(4)). XANES (X-ray absorption near-edge spectroscopy) measurement, using the freshly exposed plant root directly, confirmed that most of the arsenic is trivalent and binds to S of peptides (53% As-S) while 38% occurred as arsenite and only 9% unchanged as arsenate. EXAFS data confirmed that As-S and As-O bonds occur in the plants. This study confirms, for the first time, that As-peptides can be extracted by formic acid and chromatographically separated on a reversed-phase column without significant decomposition or de-novo synthesis during the extraction step.

  19. Composition-driven Cu-speciation and reducibility in Cu-CHA zeolite catalysts: a multivariate XAS/FTIR approach to complexity† †Electronic supplementary information (ESI) available: Sample description and synthesis details, experimental setup for in situ XAS and FTIR spectroscopy, details on the MCR-ALS method, details on DFT-assisted XANES simulations, details on the determination of N pure by PCA, MCR-ALS results for downsized and upsized component spaces, additional information to support the assignment of theoretical XANES curves, details on EXAFS analysis, details on IR spectral deconvolution. See DOI: 10.1039/c7sc02266b Click here for additional data file.

    Science.gov (United States)

    Martini, A.; Lomachenko, K. A.; Pankin, I. A.; Negri, C.; Berlier, G.; Beato, P.; Falsig, H.; Bordiga, S.; Lamberti, C.

    2017-01-01

    The small pore Cu-CHA zeolite is attracting increasing attention as a versatile platform to design novel single-site catalysts for deNOx applications and for the direct conversion of methane to methanol. Understanding at the atomic scale how the catalyst composition influences the Cu-species formed during thermal activation is a key step to unveil the relevant composition–activity relationships. Herein, we explore by in situ XAS the impact of Cu-CHA catalyst composition on temperature-dependent Cu-speciation and reducibility. Advanced multivariate analysis of in situ XANES in combination with DFT-assisted simulation of XANES spectra and multi-component EXAFS fits as well as in situ FTIR spectroscopy of adsorbed N2 allow us to obtain unprecedented quantitative structural information on the complex dynamics during the speciation of Cu-sites inside the framework of the CHA zeolite. PMID:29147509

  20. Macroscopic and microscopic investigation of Ni(II) sequestration on diatomite by batch, XPS, and EXAFS techniques.

    Science.gov (United States)

    Sheng, Guodong; Yang, Shitong; Sheng, Jiang; Hu, Jun; Tan, Xiaoli; Wang, Xiangke

    2011-09-15

    Sequestration of Ni(II) on diatomite as a function of time, pH, and temperature was investigated by batch, XPS, and EXAFS techniques. The ionic strength-dependent sorption at pH < 7.0 was consistent with outer-sphere surface complexation, while the ionic strength-independent sorption at pH = 7.0-8.6 was indicative of inner-sphere surface complexation. EXAFS results indicated that the adsorbed Ni(II) consisted of ∼6 O at R(Ni-O) ≈ 2.05 Å. EXAFS analysis from the second shell suggested that three phenomena occurred at the diatomite/water interface: (1) outer-sphere and/or inner-sphere complexation; (2) dissolution of Si which is the rate limiting step during Ni uptake; and (3) extensive growth of surface (co)precipitates. Under acidic conditions, outer-sphere complexation is the main mechanism controlling Ni uptake, which is in good agreement with the macroscopic results. At contact time of 1 h or 1 day or pH = 7.0-8.0, surface coprecipitates occur concurrently with inner-sphere complexes on diatomite surface, whereas at contact time of 1 month or pH = 10.0, surface (co)precipitates dominate Ni uptake. Furthermore, surface loading increases with temperature increasing, and surface coprecipitates become the dominant mechanism at elevated temperature. The results are important to understand Ni interaction with minerals at the solid-water interface, which is helpful to evaluate the mobility of Ni(II) in the natural environment.

  1. Laser EXAFS

    International Nuclear Information System (INIS)

    Mallozzi, P.J.; Epstein, H.M.; Schwenzel, R.E.; Campbell, B.E.

    1983-01-01

    Apparatus for obtaining EXAFS data of a material, comprising means for directing radiant energy from a laser onto a target in such manner as to produce X-rays at the target of a selected spectrum and intensity, suitable for obtaining the EXAFS spectrum of the material, means for directing X-rays from the target onto spectral dispersive means so located as to direct the spectrally resolved X-rays therefrom onto recording means, and means for positioning a sample of material in the optical path of the X-rays, the recording means providing a reference spectrum of X-rays not affected by the sample and absorption spectrum of X-rays modified by transmission through the sample

  2. Local structure in LaMnO3 and CaMnO3 perovskites: A quantitative structural refinement of Mn K-edge XANES data

    International Nuclear Information System (INIS)

    Monesi, C.; Meneghini, C.; Bardelli, F.; Benfatto, M.; Mobilio, S.; Manju, U.; Sarma, D.D.

    2005-01-01

    Hole-doped perovskites such as La 1-x Ca x MnO 3 present special magnetic and magnetotransport properties, and it is commonly accepted that the local atomic structure around Mn ions plays a crucial role in determining these peculiar features. Therefore experimental techniques directly probing the local atomic structure, like x-ray absorption spectroscopy (XAS), have been widely exploited to deeply understand the physics of these compounds. Quantitative XAS analysis usually concerns the extended region [extended x-ray absorption fine structure (EXAFS)] of the absorption spectra. The near-edge region [x-ray absorption near-edge spectroscopy (XANES)] of XAS spectra can provide detailed complementary information on the electronic structure and local atomic topology around the absorber. However, the complexity of the XANES analysis usually prevents a quantitative understanding of the data. This work exploits the recently developed MXAN code to achieve a quantitative structural refinement of the Mn K-edge XANES of LaMnO 3 and CaMnO 3 compounds; they are the end compounds of the doped manganite series La x Ca 1-x MnO 3 . The results derived from the EXAFS and XANES analyses are in good agreement, demonstrating that a quantitative picture of the local structure can be obtained from XANES in these crystalline compounds. Moreover, the quantitative XANES analysis provides topological information not directly achievable from EXAFS data analysis. This work demonstrates that combining the analysis of extended and near-edge regions of Mn K-edge XAS spectra could provide a complete and accurate description of Mn local atomic environment in these compounds

  3. Influence of 300°C thermal conversion of Fe-Ce hydrous oxides prepared by hydrothermal precipitation on the adsorptive performance of five anions: Insights from EXAFS/XANES, XRD and FTIR (companion paper)

    KAUST Repository

    Chubar, Natalia; Gerda, Vasyl; Banerjee, Dipanjan

    2016-01-01

    In this work, we report atomic-scale reconstruction processes in Fe-Ce oxide-based composites (hydrothermally precipitated at Fe-to-Ce dosage ratios of 1:0, 2:1, 1:1, 1:2, and 0:1), upon treatment at 300 °C. The structural changes are correlated with the adsorptive removal of arsenate, phosphate, fluoride, bromide, and bromate. The presence of the carbonate-based Ce-component and surface sulfate in precursor samples creates favorable conditions for phase transformation, resulting in the formation of novel (unknown) layered compounds of Fe and Ce. These compounds are of the layered double hydroxide type, with sulfate in the interlayer space. In spite of general awareness of the importance of surface area in adsorptive removal, the increase in surface area upon thermal treatment did not increase adsorption of the studied anions. However, EXAFS simulations and the adsorption tests provided evidence of regularities between local structures of Fe in composites obtained at 80 and 300 °C and adsorption performance of most studied anions. The best adsorption of tetrahedral anions was demonstrated by samples whose simulated outer Fe shells resulted from oscillations from both O and Fe atoms. In contrast, the loss of extended x-ray absorption fine structure was correlated with the decrease of adsorptive removal. Both Fe K-edge and Ce L3 -edge EXAFS suggested the formation of solid solutions. For the first time, the utilization of extended x-ray absorption fine structure is suggested as a methodological approach (first expressed in the companion paper) to estimate the surface reactivity of inorganic materials intended for use as anion exchange adsorbents.

  4. Influence of 300°C thermal conversion of Fe-Ce hydrous oxides prepared by hydrothermal precipitation on the adsorptive performance of five anions: Insights from EXAFS/XANES, XRD and FTIR (companion paper)

    KAUST Repository

    Chubar, Natalia

    2016-12-07

    In this work, we report atomic-scale reconstruction processes in Fe-Ce oxide-based composites (hydrothermally precipitated at Fe-to-Ce dosage ratios of 1:0, 2:1, 1:1, 1:2, and 0:1), upon treatment at 300 °C. The structural changes are correlated with the adsorptive removal of arsenate, phosphate, fluoride, bromide, and bromate. The presence of the carbonate-based Ce-component and surface sulfate in precursor samples creates favorable conditions for phase transformation, resulting in the formation of novel (unknown) layered compounds of Fe and Ce. These compounds are of the layered double hydroxide type, with sulfate in the interlayer space. In spite of general awareness of the importance of surface area in adsorptive removal, the increase in surface area upon thermal treatment did not increase adsorption of the studied anions. However, EXAFS simulations and the adsorption tests provided evidence of regularities between local structures of Fe in composites obtained at 80 and 300 °C and adsorption performance of most studied anions. The best adsorption of tetrahedral anions was demonstrated by samples whose simulated outer Fe shells resulted from oscillations from both O and Fe atoms. In contrast, the loss of extended x-ray absorption fine structure was correlated with the decrease of adsorptive removal. Both Fe K-edge and Ce L3 -edge EXAFS suggested the formation of solid solutions. For the first time, the utilization of extended x-ray absorption fine structure is suggested as a methodological approach (first expressed in the companion paper) to estimate the surface reactivity of inorganic materials intended for use as anion exchange adsorbents.

  5. Spatial structure of transition metal complexes in solution determined by EXAFS spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Erenburg, S.B. E-mail: simon@che.nsk.su; Bausk, N.V.; Zemskova, S.M.; Mazalov, L.N

    2000-06-21

    CdK EXAFS, ZnK and CuK EXAFS and XANES spectra were measured for solutions of cadmium, zinc and copper dialkyldithiocarbamates in organic solvents with varying donating abilities: tributylphosphine, methylene chloride, benzene, dibutylsulfide, pyridine, dimethylsulfoxide and for some model compounds. The parameters of the local surroundings of the Cd, Zn and Cu atoms for complex forms in solutions were determined using EXAFS spectroscopy. Spatial structure models of the complex forms in a metal chelate - nonaqueous solvent system are suggested.

  6. Spatial structure of transition metal complexes in solution determined by EXAFS spectroscopy

    International Nuclear Information System (INIS)

    Erenburg, S.B.; Bausk, N.V.; Zemskova, S.M.; Mazalov, L.N.

    2000-01-01

    CdK EXAFS, ZnK and CuK EXAFS and XANES spectra were measured for solutions of cadmium, zinc and copper dialkyldithiocarbamates in organic solvents with varying donating abilities: tributylphosphine, methylene chloride, benzene, dibutylsulfide, pyridine, dimethylsulfoxide and for some model compounds. The parameters of the local surroundings of the Cd, Zn and Cu atoms for complex forms in solutions were determined using EXAFS spectroscopy. Spatial structure models of the complex forms in a metal chelate - nonaqueous solvent system are suggested

  7. EXAFS studies of metamict materials

    International Nuclear Information System (INIS)

    Greegor, R.B.; Lytle, F.W.; Ewing, R.C.; Haaker, R.F.

    1984-01-01

    An important approach in the evaluation of crystalline wasteforms for nuclear waste storage is to study the long term stabilities of closely related radioactive mineral species which have become metamict (radiation damaged) and have been exposed to weathering processes for geologic periods of time. The metamictization and alteration effects can then be used for comparison with the results of short term laboratory leaching and irradiation experiments which have been designed to simulate long term effects. Phosphates, the Ti-Nb-Ta complex oxide minerals and various selected silicates are natural analogues for phases in proposed radioactive wasteforms. Because of the geochemical similarities with wasteforms, a study of the metamict state and annealing in complex mineral phosphates, silicates and oxides will yield data that is important in evaluating the long term stability of radioactive wasteforms. The investigation reported here is an application of EXAFS and XANES spectroscopy to the study of the structure of the metamict state. The nearest neighbor environment of Ti and Ca in metamict AB 2 O 6 -type complex oxides has been examined using SSRL Beam Line VII-3 in order to evaluate the effect of alpha-recoil damage on these structures. Comparison of the EXAFS/XANES data for metamict samples with data for annealed and crystalline samples suggests minor changes in the first coordination sphere, Ca-O or Ti-O, (a slight decrease in coordination number and bond lengths, and increased distortion of the coordination polyhedron), but major disruption of the second coordination sphere, for the material in the metamict state. These data suggest a mechanism for the transition from the crystalline to the metamict state in which tilting of cation coordiantion polyhedra is a possible effect of damage caused by alpha-recoil events

  8. Structure of Rhodium in an Ultradispersed Rhodium/Alumina Catalyst as Studied by EXAFS and Other Technique

    NARCIS (Netherlands)

    Koningsberger, D.C.; Blik, H.F.J. van 't; Zon, J.B.A.D. van; Huizinga, T.; Vis, J.C.; Prins, R.

    1985-01-01

    The structure of rhodium in an ultradispersed 0.57 wt % Rh/y-Al,O, catalyst before and after CO adsorption was studied with extended X-ray absorption fine structure (EXAFS), X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR), temperature programmed reduction (TPR), CO infrared

  9. (EXAFS) X-ray absorption spectroscopy

    International Nuclear Information System (INIS)

    Craievich, A.F.

    1983-01-01

    The technique EXAFS (Extended X-Ray Absorption Fine Structure) is presented and its applications using the synchrotron radiation as an incidente beam in Science of Materials and Biophysics are shown. (L.C.) [pt

  10. EX6AFS: A data acquisition system for high-speed dispersive EXAFS measurements implemented using object-oriented programming techniques

    International Nuclear Information System (INIS)

    Jennings, G.; Lee, P.L.

    1995-01-01

    In this paper we describe the design and implementation of a computerized data-acquisition system for high-speed energy-dispersive EXAFS experiments on the X6A beamline at the National Synchrotron Light Source. The acquisition system drives the stepper motors used to move the components of the experimental setup and controls the readout of the EXAFS spectra. The system runs on a Macintosh IIfx computer and is written entirely in the object-oriented language C++. Large segments of the system are implemented by means of commercial class libraries, specifically the MacApp application framework from Apple, the Rogue Wave class library, and the Hierarchical Data Format datafile format library from the National Center for Supercomputing Applications. This reduces the amount of code that must be written and enhances reliability. The system makes use of several advanced features of C++: Multiple inheritance allows the code to be decomposed into independent software components and the use of exception handling allows the system to be much more reliable in the event of unexpected errors. Object-oriented techniques allow the program to be extended easily as new requirements develop. All sections of the program related to a particular concept are located in a small set of source files. The program will also be used as a prototype for future software development plans for the Basic Energy Science Synchrotron Radiation Center Collaborative Access Team beamlines being designed and built at the Advanced Photon Source

  11. Magnetic properties and EXAFS study of nanocrystalline Fe2Mn0.5Cu0.5Al synthesized using mechanical alloying technique

    International Nuclear Information System (INIS)

    Nanto, Dwi; Yang, Dong-Seok; Yu, Seong-Cho

    2014-01-01

    Nanocrystalline Fe 2 Mn 0.5 Cu 0.5 Al has been synthesized by the mechanical alloying technique and studied as a function of milling time. Alloy nature of Fe 2 Mn 0.5 Cu 0.5 Al was observed in a sample milled for 96 h. The magnetic saturation is 4.0 μ B /f.u., which coincidently follows Slater–Pauling rule at 5 K. Nanocrystalline Fe 2 Mn 0.5 Cu 0.5 Al has enhanced saturate magnetization compared to any other fabrication of Fe 2 MnAl reported. Cu element plays an important role in site competes with other elements and may result in the enhancement of saturate magnetization. In accordance to the magnetic results and EXAFS pattern, it was revealed that the dynamics of magnetic properties were confirmed as structural changes of nanocrystalline Fe 2 Mn 0.5 Cu 0.5 Al

  12. EXAFS as a tool for catalyst characterization: a review of the data analysis methods

    Directory of Open Access Journals (Sweden)

    NORONHA F. B.

    1999-01-01

    Full Text Available A review of the EXAFS data analysis methods is presented. A detailed description of the EXAFS signal extraction and the Fourier transform of the data are discussed. The procedure for determining interatomic distances, coordination numbers and disorder effects from EXAFS data is described. This paper also discusses the data analysis statistics. Finally, one example of catalyst characterization by the EXAFS technique is reported.

  13. Surface EXAFS - A mathematical model

    International Nuclear Information System (INIS)

    Bateman, J.E.

    2002-01-01

    Extended X-ray absorption fine structure (EXAFS) studies are a powerful technique for studying the chemical environment of specific atoms in a molecular or solid matrix. The study of the surface layers of 'thick' materials introduces special problems due to the different escape depths of the various primary and secondary emission products which follow X-ray absorption. The processes are governed by the properties of the emitted fluorescent photons or electrons and of the material. Their interactions can easily destroy the linear relation between the detected signal and the absorption cross-section. Also affected are the probe depth within the surface and the background superimposed on the detected emission signal. A general mathematical model of the escape processes is developed which permits the optimisation of the detection modality (X-rays or electrons) and the experimental variables to suit the composition of any given surface under study

  14. EXAFS study of plutonium sorption onto kaolinite

    International Nuclear Information System (INIS)

    Reich, T.Y.; Banik, L.; Buda, R.A.; Amayri, S.; Drebert, J.; Kratz, J.V.; Trautmann, N.; Reich, T.; Ageev, A.L.; Korshunov, M.E.

    2007-01-01

    The uptake mechanism of plutonium by kaolinite was investigated by applying X-ray absorption spectroscopy to batch sorption samples (total Pu concentrations 1 and 10 μM; 4 g kaolinite/L in 0.1 M NaClO 4 ; 1 ≤ pH ≤ 9; presence and absence of ambient CO 2 ). For XAFS measurements, one sample was prepared from a Pu(III) solution at pH 6 under argon atmosphere. Three samples were obtained by sorption of Pu(IV) at pH I, 4, and 9 in an air-equilibrated system. The Pu L III -edge XANES spectra indicated that in all samples, including the Pu(III) sample, plutonium is sorbed at the kaolinite surface as Pu(IV). The Pu L III -edge k 3 -weighted EXAFS spectra showed eight oxygen atoms at an average Pu-O distance of 2.3 angstrom. Two Pu atoms were detected at ∼ 3.7 angstrom in all spectra, indicating the formation of polynuclear Pu(IV) species at the kaolinite surface. For the sample prepared from Pu(III) solution, an additional Pu-O shell at 3.2 angstrom was observed. The spectra of samples prepared from Pu(IV) included a Pu-Al/Si co-ordination shell at approximately 3.6 angstrom, indicating formation of inner-sphere sorption complexes. The structural models used in the least-squares fits were confirmed by an alternative EXAFS data analysis approach based on a modified Tikhonov regularization method. (authors)

  15. Laboratory EXAFS using photographic method

    International Nuclear Information System (INIS)

    Joshi, S K; Gaur, A; Johari, A; Shrivastava, B D

    2009-01-01

    Laboratory EXAFS facilities have been used since long. However, EXAFS data analysis has not been reported as yet for the spectra recorded photographically. Though from our laboratory we have been reporting various studies employing X-ray spectrographs using the photographic method of registration of EXAFS spectra, but the data has never been analyzed using the Fourier transformation method and fitting with standards. This paper reports the study of copper metal EXAFS spectra at the K-edge recorded photographically employing a 400 mm curved mica crystal Cauchois type spectrograph with 0.5 kW tungsten target X-ray tube. The data obtained in digital form with the help of a microphotometer has been processed using EXAFS data analysis programs Athena and Artemis. The experimental data for copper metal foil have been fitted with the theoretical standards. The results have been compared with those obtained from another laboratory EXAFS set up employing 12 kW Rigaku rotating anode, Johansson-type spectrometer with Si(311) monochromator crystal and scintillation counter. The results have also been compared with those obtained from SSRL. The parameters obtained for the first two shells from the photographic method are comparable with those obtained from the other two methods. The present work shows that the photographic method of registering EXAFS spectra in laboratory set up using fixed target X-ray tubes can also be used for getting structural information at least for the first two coordination shells.

  16. Laboratory EXAFS using photographic method

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, S K [Government College, Badnawar (Dhar)-454660 (India); Gaur, A; Johari, A; Shrivastava, B D, E-mail: joshisantoshk@yahoo.co [School of Studies in Physics, Vikram University, Ujjain-456010 (India)

    2009-11-15

    Laboratory EXAFS facilities have been used since long. However, EXAFS data analysis has not been reported as yet for the spectra recorded photographically. Though from our laboratory we have been reporting various studies employing X-ray spectrographs using the photographic method of registration of EXAFS spectra, but the data has never been analyzed using the Fourier transformation method and fitting with standards. This paper reports the study of copper metal EXAFS spectra at the K-edge recorded photographically employing a 400 mm curved mica crystal Cauchois type spectrograph with 0.5 kW tungsten target X-ray tube. The data obtained in digital form with the help of a microphotometer has been processed using EXAFS data analysis programs Athena and Artemis. The experimental data for copper metal foil have been fitted with the theoretical standards. The results have been compared with those obtained from another laboratory EXAFS set up employing 12 kW Rigaku rotating anode, Johansson-type spectrometer with Si(311) monochromator crystal and scintillation counter. The results have also been compared with those obtained from SSRL. The parameters obtained for the first two shells from the photographic method are comparable with those obtained from the other two methods. The present work shows that the photographic method of registering EXAFS spectra in laboratory set up using fixed target X-ray tubes can also be used for getting structural information at least for the first two coordination shells.

  17. EXAFS spectroscopy of quasicrystals

    International Nuclear Information System (INIS)

    Menushenkov, A. P.; Rakshun, Ya. V.

    2007-01-01

    The results of the investigation of the features of the local structure of quasicrystalline materials by extended X-ray absorption fine structure (EXAFS) spectroscopy with the use of synchrotron radiation are analyzed. The advantages of this method from the point of view of deriving information about the local shifts of the atoms forming an icosahedral structure are demonstrated. The rearrangement of the local environment of copper and iron in Al-Fe-Cu ternary alloys at a transition from the crystalline to the quasicrystalline phase has been investigated. It is established that the nearest copper coordination retains the symmetry characteristic of the crystal; however, rotation and small displacements of copper matrix atoms lead to significant rearrangement of aluminum atoms around iron atoms. As a result, icosahedral clusters with pentagonal symmetry are formed around iron atoms and violation of the translational symmetry is accompanied by the transition of Al-Fe-Cu to the quasicrystalline state

  18. X-ray absorption near edge structure (XANES) study of some hydroxamic mixed ligand copper complexes

    International Nuclear Information System (INIS)

    Mishra, A; Parsai, N; Shrivastava, B D; Soni, N

    2012-01-01

    With the advent of modern bright synchrotron radiation sources, X-ray absorption spectra has emerged as a powerful technique for local structure determination, which can be applied to any type of material. The X-ray absorption measurements of four hydroxamic mixed ligand copper complexes have been performed at the recently developed BL-8 Dispersive EXAFS beamline at 2.5 GeV Indus-2 synchrotron at RRCAT, Indore, India. The X-ray absorption near edge structure (XANES) data obtained has been processed using data analysis program Athena. The energies of the K absorption edge, chemical shifts, edge-widths, shifts of the principal absorption maximum in the complexes have been determined. The values of the chemical shift suggest that copper is in oxidation state +2 in all of the complexes. The chemical shift data has been utilized to estimate effective nuclear charge on copper atom. The order of the chemical shifts has been correlated to the relative ionic character of the bonding in these complexes.

  19. Moessbauer and EXAFS spectroscopy investigation of iron and arsenic adsorption to lettuce leaves

    International Nuclear Information System (INIS)

    Vasconcelos, Igor F.; Silva, Gabriela C.; Carvalho, Regina P.; Dantas, Maria Sylvia S.; Ciminelli, Virginia S. T.

    2010-01-01

    The accumulation of iron and arsenic from aqueous solution by lettuce leaves biomass was investigated using Moessbauer and EXAFS spectroscopic techniques. Moessbauer spectroscopy results show that iron is oxidized during sorption while EXAFS results indicate that iron is coordinated by approximately 6 oxygen and 2 carbon atoms while arsenic is coordinated by approximately 4 oxygen atoms with iron as a second neighbor.

  20. Moessbauer and EXAFS spectroscopy investigation of iron and arsenic adsorption to lettuce leaves

    Energy Technology Data Exchange (ETDEWEB)

    Vasconcelos, Igor F., E-mail: ifvasco@ufc.br [Universidade Federal do Ceara, Dep. Eng. Metalurgica e de Materiais (Brazil); Silva, Gabriela C.; Carvalho, Regina P.; Dantas, Maria Sylvia S.; Ciminelli, Virginia S. T. [Universidade Federal de Minas Gerais, Dep. Eng. Metalurgica e de Materiais (Brazil)

    2010-01-15

    The accumulation of iron and arsenic from aqueous solution by lettuce leaves biomass was investigated using Moessbauer and EXAFS spectroscopic techniques. Moessbauer spectroscopy results show that iron is oxidized during sorption while EXAFS results indicate that iron is coordinated by approximately 6 oxygen and 2 carbon atoms while arsenic is coordinated by approximately 4 oxygen atoms with iron as a second neighbor.

  1. Modeling of XANES-spectra with the FEFF-program

    Energy Technology Data Exchange (ETDEWEB)

    Bosman, E; Thieme, J, E-mail: e.bosman@gmx.d, E-mail: jthieme@gwdg.d [Institute for X-Ray Physics, Georg-August-University Gottingen, Friedrich-Hund-Platz 1, 37077 Gottingen (Germany)

    2009-09-01

    The aim of this project is the calculation of the absorption coefficient {mu} of x-ray absorption spectra as a function of energy and a comparison with experimental data. A characteristic fine structure can be found in x-ray absorption spectra (XAS) consisting of the XANES (X-Ray Absorption Near Edge Structure) and the EXAFS (Extended X-Ray Absorption Fine Structure) region. XANES is characterized by multiple scattering and provides information about coordination chemistry and bonding angles of the irradiated sample. The program FEFF 8.4 was used for the calculations of the absorption K-edge spectra. FEFF was generated for ab initio multiple scattering calculations of X-ray Absorption Fine Structure (XAFS) of atom-clusters. The code yields scattering amplitudes, phases and other quantities. We computed {mu} at the K-edge of several elements like Ti, S and Fe. For this purpose, clusters of Na{sub 2}SO{sub 4}, Ba{sub 2}TiO{sub 4}, FeS{sub 2}, CaSO{sub 2} 2(H {sub 2}O) were used, working with several space groups. Some of the calculations are consistent with the results of the experiments, but others show energy shifts in the range of some eV. In summary, the FEFF calculations and the experimental data exhibit similarities as well as deviations. By using trimming parameters, deviations could be eliminated to a certain extent, which will be presented.

  2. Chemistry of uranium in evaporation pond sediment in the San Joaquin Valley, California, USA, using x-ray fluorescence and XANES techniques

    International Nuclear Information System (INIS)

    Duff, M.C.; Amrhein, C.; Bertsch, P.M.; Hunter, D.B.

    1997-01-01

    Evaporation ponds in the San Joaquin Valley (SJV), CA, used for the disposal of irrigation drainage waters, contain elevated levels of uranium. The ponds are filled periodically and support algae which upon evaporation become incorporated in the sediments as layers of decaying organic matter. This rich source of organic matter promotes reducing conditions in the sediments. Our research was conducted to characterize oxidation/reduction reactions that affect soluble and sediment U(IV)/U(VI) concentrations in the SJV ponds. Studies were done to (1) determine soluble U(Vl)/U(IV) in waters in contact with a pond sediment subjected to changes in redox status, (2) observe U solid oxidation state as a reducing pond sediment underwent (in vitro) oxidation, and (3) determine U solid oxidation state with respect to depth in pond surface sediment layers. Low pressure ion-exchange chromatography with an eluent of 0.125 M H 2 C 2 O 4 /0.25 M HNO 3 was used for the separation of U(IV) and U(VI) oxidation states in the drainage waters. Soluble U(VI) and U(IV) coexisted in sediment suspensions exposed to changes in redox potential (Eh) (-260 mV to +330 mV), and U(VI) was highly soluble in the oxidized, surface pond sediments. X-ray near edge absorption spectroscopy (XANES) showed that the U solid phases were 25% U(IV) and 75% U(VI) and probably a mixed solid [U 3 O 8(s) ] in highly reducing pond sediments. Sediment U(IV) increased slightly with depth in the surface pond sediment layers suggesting a gradual reduction of U(VI) to U(IV) with time. Under oxidized conditions, this mixed oxidation-state solid was highly soluble. 59 refs., 6 figs., 1 tab

  3. Location of rare-earth dopants on LiCAF and LiSAF laser hosts via XRD, EXAFS and computer modeling technique

    International Nuclear Information System (INIS)

    Valerio, Mario Ernesto Giroldo; Amaral, Jomar Batista de; Baldochi, Sonia Licia Vera; Mazzocchi, L.; Sasaki, Jose Marcos; Jackson, Robert A.

    2004-01-01

    , SP, Brazil (project No 938-01). Standard procedures were used for data reduction and analyses using the WinXAS package. The EXAFS simulations were carried out using the FEFF8 packages and the calculated paths were used within the WinXAS program for the fitting procedure of the spectra. All fittings were performed in k-space. The results indicates that depending on the size of the dopant ion, either the M 2+ site or the Al 3+ was preferred. The coordination number and average neighbouring distances were in agreement with the computer simulations carried out on the crystalline systems. (author)

  4. EXAFS of dilute systems: fluorescence detection

    International Nuclear Information System (INIS)

    Hastings, J.B.

    1979-01-01

    Since the first observations of the variation of the absorption coefficient for x-rays above the energy thresholds in the thirties until the early seventies, measurements and analysis of these variations were merely intended for the understanding of the underlying physics. Recently, with the understanding of the information available about the local atomic structure in the neighborhood of the absorbing species and the availability of high intensity synchrotron radiation sources, EXAFS has become a powerful structural tool. In these discussions, the details of the measurements for very dilute species are presented. It is shown that for the more dilute systems the measurement of the emission rather than the direct absorption is a more favorable technique

  5. XANES- and EXAFS-Investigations on Chromium-Doped Mullite Precursors

    OpenAIRE

    Arzberger , I.; Küper , G.; Pantelouris , A.; Peitz , B.; Hormes , J.; Schneider , H.; Saruhan , B.

    1997-01-01

    Chromium-doped non-crystalline mullite precursors for ceramics were investigated with x-ray absorption spectroscopy at the Cr K edge. They were prepared using a sol-gel-route. 3 wt% Cr2O3 were added to partially substitute aluminium by chromium in the aluminosilicate network. The aim of the study was to characterize the development of the electronic and geometric structure of the precursor at different temperatures prior to its crystallization to mullite. The x-ray absorption spectra of the p...

  6. Determination of Chemical States of Mercury on Activated Carbon Using XANES

    International Nuclear Information System (INIS)

    Takaoka, Masaki; Takeda, Nobuo; Oshita, Kazuyuki; Yamamoto, Takashi; Tanaka, Tsunehiro; Uruga, Tomoya

    2007-01-01

    Although the adsorption of mercury vapor onto activated carbon is a widely used technology to prevent environmental release, the adsorption mechanism is not clearly understood. In this study, we determined the chemical states of mercury on two kinds of activated carbon using X-ray absorption near-edge spectroscopy (XANES) to elucidate the adsorption mechanism. The adsorption experiments of elemental mercury onto activated carbon were conducted under air and nitrogen atmospheres at temperatures of 20 and 160 deg. C. Two types of activated carbon were prepared. X-ray absorption fine structure (XAFS) measurements were carried out on beamline BL01B1 at SPring-8. Hg-LIII edge XANES spectra suggested that chemical adsorption of elemental mercury on the activated carbon occurred in the 20-160 deg. C temperature range. According to the XANES spectra, a difference occurred in the chemical states of mercury between AC no. 1 and AC no. 2. The Hg XANES spectra on AC no. 1 were similar to those of Hg2Cl2 and HgS, and the Hg XANES spectra on AC no. 2 were similar to that of HgO, which suggested that nitric acid treatment removed sulfur from AC no. 1 and functional groups that were strong oxidizers on the surface of AC no. 2 created HgO. According to the EXAFS oscillation, a difference occurred in the chemical states of mercury on AC no. 1 between 20 and 160 deg. C. We found that impurities and oxidant functional groups on activated carbon play key roles in mercury adsorption

  7. New insight on the local structure of Cu2+ ion in the solution of CuBr2 by EXAFS studies

    International Nuclear Information System (INIS)

    Yu Meijuan; Chu Wangsheng; Chen Xing; Wu Ziyu

    2009-01-01

    CuBr 2 solutions at different concentrations were studied by extended X-ray absorption fine structure (EXAFS) at the Cu K edge. In the saturated solution Cu 2+ ions have chemical bonds with 3.0 oxygen atoms and 0.9 Br ion at about 1.96 A and 2.42 A, respectively. It indicates that the CuBr 4 -2 configuration exists with a ratio of 25% under this condition. In the dilute solutions no evidence of Br ions contributions in the first shell around Cu 2+ ions occurs. The almost identical X-ray absorption near edge structure (XANES) and EXAFS characters address similar local environments around Cu 2+ in agreement with results of the EXAFS fit taking into account only the contributions of Cu-O bonds.

  8. New insight on the local structure of Cu{sup 2+} ion in the solution of CuBr{sub 2} by EXAFS studies

    Energy Technology Data Exchange (ETDEWEB)

    Yu Meijuan; Chu Wangsheng; Chen Xing; Wu Ziyu, E-mail: wuzy@ustc.edu.c [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049 (China)

    2009-11-15

    CuBr{sub 2} solutions at different concentrations were studied by extended X-ray absorption fine structure (EXAFS) at the Cu K edge. In the saturated solution Cu{sup 2+} ions have chemical bonds with 3.0 oxygen atoms and 0.9 Br ion at about 1.96 A and 2.42 A, respectively. It indicates that the CuBr{sub 4}{sup -2} configuration exists with a ratio of 25% under this condition. In the dilute solutions no evidence of Br ions contributions in the first shell around Cu{sup 2+} ions occurs. The almost identical X-ray absorption near edge structure (XANES) and EXAFS characters address similar local environments around Cu{sup 2+} in agreement with results of the EXAFS fit taking into account only the contributions of Cu-O bonds.

  9. Exafs studies of coprecipitation and adsorption reactions of Tc

    Energy Technology Data Exchange (ETDEWEB)

    Bunker, D.J.; Jones, M.J.; Livens, F.R.; Collison, D. [Manchester Univ. (United Kingdom). Dept. of Chemistry; Pattrick, R.A.D. [Manchester Univ., Dept. of Earth Sciences (United Kingdom); Charnock, J.M. [CLRC Daresbury Laboratoire, Warrington Cheshire (United Kingdom)

    2000-07-01

    Adsorption and coprecipitation reactions may be a simple way of removing [TcO{sub 4}]{sup -} from aqueous solution. The effectiveness of a range of potential adsorbents and precipitants has been evaluated and some are capable of near quantitative (>98%) removal of [TcO{sub 4}){sup -} from solution. X-ray absorption near edge structure (XANES) has been used to determine Tc oxidation states and extended X-ray absorption fine structure spectroscopy (EXAFS) has been used to identify the local environment of Tc. The absorption edge position has been determined, using [PPh{sub 4}][TcO{sub 4}], TcS{sub 2} and Tc{sub 2}S{sub 7} as model compounds, and is diagnostic of Tc oxidation state. In a series of experiments investigating FeS coprecipitation, Tc was reduced to oxidation state (IV) and its local environment resembled that in TcO{sub 2} (6 O atoms at approximately 2.0 Angstrom). (authors)

  10. EXAFS-spectroscopy on synchrotron radiation beam

    CERN Document Server

    Aksenov, V L; Kuzmin, A Y; Purans, Y

    2001-01-01

    In the review the basis theoretical principles of EXAFS spectroscopy are given, as one of principal directions of an absorption spectroscopy permitting with a high accuracy to gain parameters of the short-range order in multicomponent amorphous and quasi-crystal mediums. The methods of the analysis of EXAFS spectra with allowance of effects of multiply scattering are featured. The exposition of the experimental set-ups, which realize the method of EXAFS spectroscopy on beams of SR, requirement of the monochromatization of radiation beams are given. For investigation of phase transition and external effects the energy-dispersive EXAFS spectrometer is creating at the National center of SR Kurchatov Institute which can measure the EXAFS spectrum with a time resolution 3-5 ms. The experimental results on investigation (by the EXAFS spectroscopy method) of oxides of tungsten and molybdenum are given, which have unique property: the variable valence of an ion of metal is depending on external action. The most inter...

  11. Interpretation of the U L3-edge EXAFS in uranium dioxide using molecular dynamics and density functional theory simulations

    International Nuclear Information System (INIS)

    Bocharov, Dmitry; Chollet, Melanie; Krack, Matthias; Bertsch, Johannes; Grolimund, Daniel; Martin, Matthias; Kuzmin, Alexei; Purans, Juris; Kotomin, Eugene

    2016-01-01

    X-ray absorption spectroscopy is employed to study the local structure of pure and Cr-doped UO 2 at 300 K. The U L 3 -edge EXAFS spectrum is interpreted within the multiplescattering (MS) theory using the results of the classical and ab initio molecular dynamics simulations, allowing us to validate the accuracy of theoretical models. The Cr K-edge XANES is simulated within the full-multiple-scattering formalism considering a substitutional model (Cr at U site). It is shown that both unrelaxed and relaxed structures, produced by ab initio density functional theory (DFT) calculations, fail to describe the experiment. (paper)

  12. Temperature-dependent magnetic EXAFS investigation of Gd

    CERN Document Server

    Wende, H; Poulopoulos, P N; Rogalev, A; Goulon, J; Schlagel, D L; Lograsso, T A; Baberschke, K

    2001-01-01

    Magnetic EXAFS (MEXAFS) is the helicity-dependent counterpart of the well-established EXAFS technique. By means of MEXAFS it is possible not only to analyze the local magnetic structure but also to learn about magnetic fluctuations. Here we present the MEXAFS of a Gd single crystal at the L sub 3 sub , sub 2 -edges in the temperature range of 10-250 K. For the first time MEXAFS was probed over a large range in reduced temperature of 0.04<=T/T sub C<=0.85 with T sub C =293 K. We show that the vibrational damping described by means of a Debye temperature of theta sub D =160 K must be taken into account for the spin-dependent MEXAFS before analyzing magnetic fluctuations. For a detailed analysis of the MEXAFS and the EXAFS, the experimental data are compared to ab initio calculations. This enables us to separate the individual single- from the multiple-scattering contributions. The MEXAFS data have been recorded at the ID 12A beamline of the European Synchrotron Radiation Facility (ESRF). To ensure that th...

  13. EXAFS cumulants of CdSe

    International Nuclear Information System (INIS)

    Diop, D.

    1997-04-01

    EXAFS functions had been extracted from measurements on the K edge of Se at different temperatures between 20 and 300 K. The analysis of the EXAFS of the filtered first two shells has been done in the wavevector range laying between 2 and 15.5 A -1 in terms of the cumulants of the effective distribution of distances. The cumulants C 3 and C 4 obtained from the phase difference and the amplitude ratio methods have shown the anharmonicity in the vibrations of atoms around their equilibrium position. (author). 13 refs, 3 figs

  14. DFT and EXAFS, mutually enhancing tools for structure elucidation of Tc complexes

    International Nuclear Information System (INIS)

    Breynaert, E.; Bruggeman, C.; Maes, A.

    2005-01-01

    Full text of publication follows: The redox-sensitive fission product technetium-99 (Tc) is of great interest in nuclear waste disposal studies because of its potential for contaminating the geosphere due to its very long half-life (2.13 x 10 5 year) and high mobility under oxidising conditions, where technetium forms pertechnetate (TcO 4 - ). Under suitable reducing conditions, e.g. in the presence of an iron(II) containing solid phase which can act as an electron donor, the solubility can be limited by the reduction of pertechnetate followed by the formation of a surface precipitate [1]. However, by association with mobile humic substances (HS) or other associating/complexing species, the solubility of reduced Tc species may be drastically enhanced [2]. The elucidation of the identity and geometrical structure of the species causing this enhanced solubility often remains a difficult issue. Extended X-Ray Absorption Fluorescence Spectroscopy/ X-Ray Absorption Near Edge Spectroscopy (EXAFS/XANES) analysis can be very helpful to determine the molecular surroundings of reduced Tc organic complexes of Tc(IV) colloid-HS-associations. The interpretation of the EXAFS spectra is however not a straightforward process due to the possibly strong influence of multiple scattering paths on the spectra. Contrary to single scattering analysis which can be easily performed on the experimental EXAFS spectra, multiple scattering analysis can only be done, based on good approximations of the possible geometrical structures of the species under consideration. It has been shown that the Density Functional Theory (DFT) can be used to perform geometry optimizations of technetium species and therefore can be utilized to predict the structure of technetium complexes [3]. The success and computational effort needed for such structure predictions are however highly dependant on the quality of the initial structure from which the geometry optimization is started. Single scattering analysis of

  15. Development of XAFS Into a Structure Determination Technique

    Science.gov (United States)

    Stern, E. A.

    After the detection of diffraction of x-rays by M. Laue in 1912, the technique was soon applied to structure determination by Bragg within a year. On the other hand, although the edge steps in X-Ray absorption were discovered even earlier by Barkla and both the near edge (XANES) and extended X-Ray fine structure (EXAFS) past the edge were detected by 1929, it still took over 40 years to realize the structure information contained in this X-Ray absorption fine structure (XAFS). To understand this delay a brief historical review of the development of the scientific ideas that transformed XAFS into the premiere technique for local structure determination is given. The development includes both advances in theoretical understanding and calculational capabilities, and in experimental facilities, especially synchrotron radiation sources. The present state of the XAFS technique and its capabilities are summarized.

  16. High resolution x-ray fluorescence spectroscopy - a new technique for site- and spin-selectivity

    International Nuclear Information System (INIS)

    Wang, Xin

    1996-12-01

    X-ray spectroscopy has long been used to elucidate electronic and structural information of molecules. One of the weaknesses of x-ray absorption is its sensitivity to all of the atoms of a particular element in a sample. Through out this thesis, a new technique for enhancing the site- and spin-selectivity of the x-ray absorption has been developed. By high resolution fluorescence detection, the chemical sensitivity of K emission spectra can be used to identify oxidation and spin states; it can also be used to facilitate site-selective X-ray Absorption Near Edge Structure (XANES) and site-selective Extended X-ray Absorption Fine Structure (EXAFS). The spin polarization in K fluorescence could be used to generate spin selective XANES or spin-polarized EXAFS, which provides a new measure of the spin density, or the nature of magnetic neighboring atoms. Finally, dramatic line-sharpening effects by the combination of absorption and emission processes allow observation of structure that is normally unobservable. All these unique characters can enormously simplify a complex x-ray spectrum. Applications of this novel technique have generated information from various transition-metal model compounds to metalloproteins. The absorption and emission spectra by high resolution fluorescence detection are interdependent. The ligand field multiplet model has been used for the analysis of Kα and Kβ emission spectra. First demonstration on different chemical states of Fe compounds has shown the applicability of site selectivity and spin polarization. Different interatomic distances of the same element in different chemical forms have been detected using site-selective EXAFS

  17. X-ray absorption spectroscopy (EXAFS)

    International Nuclear Information System (INIS)

    Craievich, A.F.

    1983-01-01

    The experimental technics of Extended X-ray Absorption Fine Structure (EXAFS) is presented and several uses of it in atomic, molecular and bio physics are shown. The recent progresses of this technics, both theoretical and experimental, are discussed and the future perspectives on this subject are commented. (L.C.) [pt

  18. In situ EXAFS study of Ru-containing electrocatalysts of oxygen reduction

    International Nuclear Information System (INIS)

    Malakhov, I.V.; Nikitenko, S.G.; Savinova, E.R.; Kochubey, D.I.; Alonso-Vante, N.

    2000-01-01

    The series of Ru chalcogenide compounds is obtained by varying the nature of the chalcogen with the transition metal (Ru) matrix. The EXAFS technique reveals that the electrocatalytic centre is Ru in a cluster matrix. Furthermore, a reversible change in the structure of the active centre as a function of the applied electrode potential appears

  19. EXAFS: New tool for study of battery and fuel cell materials

    Science.gov (United States)

    Mcbreen, James; Ogrady, William E.; Pandya, Kaumudi I.

    1987-01-01

    Extended X ray absorption fine structure (EXAFS) is a powerful technique for probing the local atomic structure of battery and fuel cell materials. The major advantages of EXAFS are that both the probe and the signal are X rays and the technique is element selective and applicable to all states of matter. This permits in situ studies of electrodes and determination of the structure of single components in composite electrodes, or even complete cells. EXAFS specifically probes short range order and yields coordination numbers, bond distances, and chemical identity of nearest neighbors. Thus, it is ideal for structural studies of ions in solution and the poorly crystallized materials that are often the active materials or catalysts in batteries and fuel cells. Studies on typical battery and fuel cell components are used to describe the technique and the capability of EXAFS as a structural tool in these applications. Typical experimental and data analysis procedures are outlined. The advantages and limitations of the technique are also briefly discussed.

  20. EXAFS, Determination of Short Range Order and Local Structures in Materials

    NARCIS (Netherlands)

    Koningsberger, D.C.; Prins, R.

    1981-01-01

    Extended X-ray Absorption Fine Structure (EXAFS) is a powerful method of determining short range order and local structures in materials using X-ray photons produced by a synchrotron light source, or in-house by a high intensity rotating anode X-ray generator. The technique has provided valuable

  1. EXAFS Studies of Ga Doped Pb1-xMnxTe

    International Nuclear Information System (INIS)

    Radisavljevic, I.; Ivanovic, N.; Novakovic, N.; Romcevic, N.; Mahnke, H.-E.

    2007-01-01

    We have employed the X-Rays Absorption Fine Structure (EXAFS) technique to resolve the local structure of Pb1-xMnxTe (Ga) in order to provide answers on questions concerning the exact positions and charge states of constitutive and impurity atoms, possibilities and features of their ordering and (or) clustering, as well as configurational and thermal disorder in the system

  2. Theoretical XANES Study of the Activated Nickel (t-Amylisocyanide) Molecule

    International Nuclear Information System (INIS)

    Glover, J. L.; Chantler, C. T.; Soldatov, A. V.; Smolentsev, G.; Feiters, M. C.

    2007-01-01

    XANES is one of the most powerful techniques for investigating the active centres of non-crystalline systems such as synthetic catalysts and enzymes. We have investigated XANES for an active species in the Ni-catalyzed polymerization of isocyanides, the activated Ni (t-amylisocyanide) complex, using two of the most popular theoretical approaches. This is a very large cluster for which it is extremely difficult to derive a converged solution using the Finite Difference Method. The cluster has been linked to important chemical developments for catalysts for isocyanide polymerization. Predicted XANES for the nano-cluster are compared with experimental data, providing an important test for different theoretical approaches. Developments of a finite element method gave excellent agreement with the experimental data, while simpler models were relatively unsuccessful

  3. A structural study of bone changes in knee osteoarthritis by synchrotron-based X-ray fluorescence and X-ray absorption spectroscopy techniques

    Science.gov (United States)

    Sindhupakorn, Bura; Thienpratharn, Suwittaya; Kidkhunthod, Pinit

    2017-10-01

    Osteoarthritis (OA) is characterized by degeneration of articular cartilage and thickening of subchondral bone. The present study investigated the changing of biochemical components of cartilage and bone compared between normal and OA people. Using Synchrotron-based X-ray fluorescence (SR-XRF) and X-ray absorption spectroscopy (XAS) techniquesincluding X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) were employed for the bone changes in kneeosteoarthritisstudies. The bone samples were collected from various osteoarthritis patients with both male and female in the ages range between 20 and 74 years old. SR-XRF results excited at 4240 eV for Ca elements show a majority three main groups, based on their XRF intensities, 20-36 years, 40-60 years and over 70 years, respectively. By employing XAS techniques, XANES features can be used to clearly explain in term of electronic transitions occurring in bone samples which are affected from osteoarthritis symptoms. Moreover, a structural change around Ca ions in bone samples is obviously obtained by EXAFS results indicating an increase of Ca-amorphous phase when the ages increase.

  4. EXAFS and principal component analysis : a new shell game

    International Nuclear Information System (INIS)

    Wasserman, S.

    1998-01-01

    The use of principal component (factor) analysis in the analysis EXAFS spectra is described. The components derived from EXAFS spectra share mathematical properties with the original spectra. As a result, the abstract components can be analyzed using standard EXAFS methodology to yield the bond distances and other coordination parameters. The number of components that must be analyzed is usually less than the number of original spectra. The method is demonstrated using a series of spectra from aqueous solutions of uranyl ions

  5. Fe K-edge XANES of Maya blue pigment

    Science.gov (United States)

    Río, M. Sánchez del; Sodo, A.; Eeckhout, S. G.; Neisius, T.; Martinetto, P.; Dooryhée, E.; Reyes-Valerio, C.

    2005-08-01

    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 Si8(Mg2Al2)O20(OH)2(OH2)4.4H2O and an organic colourant (indigo: C16H10N2O2), 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.

  6. 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

  7. 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

  8. EXAFS analysis of a human Cu,Zn SOD isoform focused using non-denaturing gel electrophoresis

    Energy Technology Data Exchange (ETDEWEB)

    Chevreux, Sylviane; Roudeau, Stephane; Deves, Guillaume; Ortega, Richard [Laboratoire de Chimie Nucleaire Analytique et Bioenvironnementale, CNRS UMR5084, Universite Bordeaux 1, Chemin du Solarium, F-33175 Gradignan cedex (France); Solari, Pier Lorenzo [Synchrotron SOLEIL, L' Orme des Merisiers, BP 48, F-91192 Gif-sur-Yvette cedex, Saint-Aubin (France); Alliot, Isabelle; Testemale, Denis; Hazemann, Jean Louis, E-mail: ortega@cenbg.in2p3.f [FAME, ESRF, 6 rue Jules Horowitz, BP220, F-38043 Grenoble cedex (France)

    2009-11-15

    Isoelectric point isoforms of a metalloprotein, copper-zinc superoxide dismutase (CuZnSOD), separated on electrophoresis gels were analyzed using X-ray Absorption Spectroscopy. Mutations of this protein are involved in familial cases of amyotrophic lateral sclerosis. The toxicity of mutants could be relied to defects in the metallation state. Our purpose is to establish analytical protocols to study metallation state of protein isoforms such as those from CuZnSOD. We previously highlighted differences in the copper oxidation state between CuZnSOD isoforms using XANES. Here, we present the first results for EXAFS analyses performed at Cu and Zn K-edge on the majoritary expressed isoform of human CuZnSOD separated on electrophoresis gels.

  9. EXAFS analysis of a human Cu,Zn SOD isoform focused using non-denaturing gel electrophoresis

    Science.gov (United States)

    Chevreux, Sylviane; Solari, Pier Lorenzo; Roudeau, Stéphane; Deves, Guillaume; Alliot, Isabelle; Testemale, Denis; Hazemann, Jean Louis; Ortega, Richard

    2009-11-01

    Isoelectric point isoforms of a metalloprotein, copper-zinc superoxide dismutase (CuZnSOD), separated on electrophoresis gels were analyzed using X-ray Absorption Spectroscopy. Mutations of this protein are involved in familial cases of amyotrophic lateral sclerosis. The toxicity of mutants could be relied to defects in the metallation state. Our purpose is to establish analytical protocols to study metallation state of protein isoforms such as those from CuZnSOD. We previously highlighted differences in the copper oxidation state between CuZnSOD isoforms using XANES. Here, we present the first results for EXAFS analyses performed at Cu and Zn K-edge on the majoritary expressed isoform of human CuZnSOD separated on electrophoresis gels.

  10. EXAFS analysis of a human Cu,Zn SOD isoform focused using non-denaturing gel electrophoresis

    International Nuclear Information System (INIS)

    Chevreux, Sylviane; Roudeau, Stephane; Deves, Guillaume; Ortega, Richard; Solari, Pier Lorenzo; Alliot, Isabelle; Testemale, Denis; Hazemann, Jean Louis

    2009-01-01

    Isoelectric point isoforms of a metalloprotein, copper-zinc superoxide dismutase (CuZnSOD), separated on electrophoresis gels were analyzed using X-ray Absorption Spectroscopy. Mutations of this protein are involved in familial cases of amyotrophic lateral sclerosis. The toxicity of mutants could be relied to defects in the metallation state. Our purpose is to establish analytical protocols to study metallation state of protein isoforms such as those from CuZnSOD. We previously highlighted differences in the copper oxidation state between CuZnSOD isoforms using XANES. Here, we present the first results for EXAFS analyses performed at Cu and Zn K-edge on the majoritary expressed isoform of human CuZnSOD separated on electrophoresis gels.

  11. The local structure of U(VI)-ferri-hydrite sorption complexes revisited: EXAFS spectroscopy and Monte-Carlo simulations

    International Nuclear Information System (INIS)

    Rossberg, A.; Ulrich, K.U.; Scheinost, A.C.

    2005-01-01

    Full text of publication follows: EXAFS analysis of actinyl sorption complexes is a complicated task due to the presence of overlapping shells, structural disorder and the presence of multiple scattering paths due to the specific actinyl structure. Hence often controversial interpretations arise from conventional shell fitting. A typical example is the proposed formation of ternary uranyl carbonato surface complexes on ferri-hydrite, where a peak at ∼2.4 Angstrom in the Fourier transform is explained by backscattering carbon atoms at 2.86-2.94 Angstrom. While such ternary carbonate complexes have been confirmed by complementary techniques like FTIR and electrophoretic mobility measurements, the EXAFS peak shows even up in those uranyl ferri-hydrite systems, where great care has been taken to keep the system carbonate-free, rendering an EXAFS fit with carbon meaningless. To overcome this common problem of EXAFS shell fitting, we developed a new analysis approach based on Monte-Carlo simulations coupled to theoretical EXAFS modeling using FEFF. Here, the position of the uranyl atom is first refined in relation to a given ferri-hydrite surface structure. In a second step, the whole complex structure is refined to allow for e.g. surface relaxation effects. Using this approach, a match to the experimental EXAFS spectra of U(VI) ferri-hydrite complexes without carbonate could be achieved. The local structure indicates a mononuclear bidentate (edge-sharing) surface complex, which was identified for the first time by EXAFS spectroscopy. Further fits were performed to elucidate the influence of carbonate and other anions on the structure of the surface complex. The results demonstrate the potential of the Monte-Carlo approach for determining the structure of actinyl surface complexes. (authors)

  12. Chemical state analysis of conversion coatings by SR-XPS and TEY-XANES

    CERN Document Server

    Noro, H; Nagoshi, M

    2002-01-01

    Chromate coatings on galvanized steel have been studied by Synchrotron Radiation (SR) based techniques that include X-ray Photoelectron Spectroscopy (XPS) and Total-Electron-Yield X-ray Absorption Near Edge Structure (TEY-XANES). Non-destructive depth profiling of the coatings by SR-XPS reveals the enhancement of Cr sup 6 sup + in the outer surface. TEY-XANES spectroscopy based on simple specimen current measurement is demonstrated as an effective technique for analyzing chemical states of conversion coatings on general bulk substrates. The sampling depth of this technique, which exceeds several tens of nanometer, is determined by the penetration length of Auger electrons excited by X-ray and the inelastic mean free path of secondary electrons excited by inelastically scattered Auger electrons. The chemical states of phosphoric acid added chromate coatings are studied using this technique. The phosphoric acid is taken into the chromate coatings as partially changed into zinc and chromium phosphates, and the r...

  13. Characterisation of zinc in slags originated from a contaminated sediment by coupling /μ-PIXE, /μ-RBS, /μ-EXAFS and powder EXAFS spectroscopy

    Science.gov (United States)

    Isaure, M. P.; Laboudigue, A.; Manceau, A.; Sarret, G.; Tiffreau, C.; Trocellier, P.

    2001-07-01

    Depositing dredged sediments on soils is usual but it is a hazardous practice for the local environment when these sediments are polluted by heavy metals. This chemical hazard can be assessed by determining the speciation of metals. In this study, slags highly polluted with Zn and originated from a contaminated dredged sediment were investigated. Zn speciation was studied by laterally resolved techniques such as μ-particle induced X-ray emission (μ-PIXE), μ-Rutherford backscattering spectrometry (μ-RBS), μ-extended X-ray absorption fine structure (μ-EXAFS), and bulk analyses such as powder EXAFS spectroscopy. μ-PIXE and μ-RBS results showed that high concentrations of Zn were associated with S in localised areas at the surface of the slags while moderate amounts of Zn were mainly associated with Fe in the matrix. EXAFS results allowed to identify ZnS and Zn sorbed on ferrihydrite (5Fe 2O 3·9H 2O), proxy for iron oxy-hydroxides, as the main Zn-bearing phases. The occurrence of this Zn-iron oxy-hydroxide is interpreted as a mobilisation of Zn released from ZnS oxidation.

  14. Characterisation of zinc in slags originated from a contaminated sediment by coupling μ-PIXE, μ-RBS, μ-EXAFS and powder EXAFS spectroscopy

    International Nuclear Information System (INIS)

    Isaure, M.P.; Laboudigue, A.; Manceau, A.; Sarret, G.; Tiffreau, C.; Trocellier, P.

    2001-01-01

    Depositing dredged sediments on soils is usual but it is a hazardous practice for the local environment when these sediments are polluted by heavy metals. This chemical hazard can be assessed by determining the speciation of metals. In this study, slags highly polluted with Zn and originated from a contaminated dredged sediment were investigated. Zn speciation was studied by laterally resolved techniques such as μ-particle induced X-ray emission (μ-PIXE), μ-Rutherford backscattering spectrometry (μ-RBS), μ-extended X-ray absorption fine structure (μ-EXAFS), and bulk analyses such as powder EXAFS spectroscopy. μ-PIXE and μ-RBS results showed that high concentrations of Zn were associated with S in localised areas at the surface of the slags while moderate amounts of Zn were mainly associated with Fe in the matrix. EXAFS results allowed to identify ZnS and Zn sorbed on ferrihydrite (5Fe 2 O 3 ·9H 2 O), proxy for iron oxy-hydroxides, as the main Zn-bearing phases. The occurrence of this Zn-iron oxy-hydroxide is interpreted as a mobilisation of Zn released from ZnS oxidation

  15. XANES analysis of dried and calcined bones

    International Nuclear Information System (INIS)

    Rajendran, Jayapradhi; Gialanella, Stefano; Aswath, Pranesh B.

    2013-01-01

    The structure of dried and calcined bones from chicken, bovine, deer, pig, sheep and chamois was examined using X-ray Absorption Near Edge Structure (XANES) spectroscopy. The oxygen K-edge absorption edge indicates that the surface of dried bone has a larger proportion of carbonate than the interior that is made up of phosphates. The phosphorus L and K edge clearly indicate that pyrophosphates, α-tricalcium phosphate (α-TCP) and hydrogen phosphates of Ca do not exist in either the dried bone or calcined bone and phosphorus exists as either β-tricalcium phosphate (β-TCP) or hydroxyapatite, both in the dried and calcined conditions. The Ca K-edge analysis indicates that β-TCP is the likely form of phosphate in both the dried and calcined conditions. - Highlights: • For the first time bones of five different species of vertebrates have been compared in both the dried and calcined states. • O, P and Ca edges detail the local coordination of these atoms in dried and calcined bone. • O K-edge shows that the surface of bone has more CO 3 while the interior has more PO 4 . • P and Ca edges eliminate the presence of pyrophosphates and confirmed the presence of HA and β-TCP. • The stability of these phosphates on calcination has been examined using XANES

  16. XANES analysis of dried and calcined bones

    Energy Technology Data Exchange (ETDEWEB)

    Rajendran, Jayapradhi [Materials Science and Engineering Department, University of Texas at Arlington (United States); Gialanella, Stefano [Materials Science and Industrial Technology Department, University of Trento (Italy); Aswath, Pranesh B., E-mail: aswath@uta.edu [Materials Science and Engineering Department, University of Texas at Arlington (United States)

    2013-10-15

    The structure of dried and calcined bones from chicken, bovine, deer, pig, sheep and chamois was examined using X-ray Absorption Near Edge Structure (XANES) spectroscopy. The oxygen K-edge absorption edge indicates that the surface of dried bone has a larger proportion of carbonate than the interior that is made up of phosphates. The phosphorus L and K edge clearly indicate that pyrophosphates, α-tricalcium phosphate (α-TCP) and hydrogen phosphates of Ca do not exist in either the dried bone or calcined bone and phosphorus exists as either β-tricalcium phosphate (β-TCP) or hydroxyapatite, both in the dried and calcined conditions. The Ca K-edge analysis indicates that β-TCP is the likely form of phosphate in both the dried and calcined conditions. - Highlights: • For the first time bones of five different species of vertebrates have been compared in both the dried and calcined states. • O, P and Ca edges detail the local coordination of these atoms in dried and calcined bone. • O K-edge shows that the surface of bone has more CO{sub 3} while the interior has more PO{sub 4}. • P and Ca edges eliminate the presence of pyrophosphates and confirmed the presence of HA and β-TCP. • The stability of these phosphates on calcination has been examined using XANES.

  17. A multi-technique approach to assess chemical speciation of phosphate in soils

    Science.gov (United States)

    Belchior Abdala, Dalton; Rodrigues, Marcos; Herrera, Wilfrand; Pavinato, Paulo Sergio

    2017-04-01

    different P pools considered in the fractionation protocol, (ii) two synchrotron-based X-ray absorption spectroscopic techniques, XANES and EXAFS, for chemical characterization of the P forms and mineralogy of Fe-(hydr)oxides present in a sample, and (iii) Scanning Electron Microscopy and Energy-Dispersive spectroscopy, SEM/EDS, to provide complimentary information to corroborate and aid in the interpretation of our P XANES data. It was shown that the combination of techniques can assist us not only in the determination of the P chemical species present in a given material, but also to better understand the complex and dynamic processes to which P is subjected in soils. The association of spectroscopy (XANES and EXAFS) and microscopy (SEM/EDS) with wet chemistry data in this study was key to shift our understanding of the relationship between P and other soil mineral components from a macroscopic into a microscopic one. This represents a strong driving force to integrate the results of multi-analytical techniques into a more complete understanding of the systems under study. In addition, we provide a library of reference spectra for P K-edge XANES containing P sorbed to single and binary mixtures of mineral analogues intended to assist in the identification of P sorbed species commonly found in soils and sediments. Key-words: P K-edge XANES, Fe K-edge EXAFS, sequential chemical fractionation, soil phosphorus

  18. Extended x-ray absorption fine structure (EXAFS): a novel probe for local structure of glassy solids

    International Nuclear Information System (INIS)

    Wong, J.

    1979-01-01

    The extended x-ray absorption fine structure (EXAFS) is the oscillation in the absorption coefficient extending a few hundred eVs on the high energy side of an x-ray absorption edge. This mode of spectroscopy has recently been realized to be a powerful tool in probing the local atomic structure of all states of matter, particularly with the advent of intense synchrotron radiation. More importantly is the unique ability of EXAFS to probe the structure and dynamics around individual atomic species in a multi-atomic system. In this paper, the physical processes associated with the EXAFS phenomenon will be discussed. Experimental results obtained at the Stanford Synchrotron Radiation Laboratory on some oxide and metallic glasses will be presented. The local structure in these materials are elucidated using a Fourier transform technique

  19. Towards advanced structural analysis of iron oxide clusters on the surface of γ-Al{sub 2}O{sub 3} using EXAFS

    Energy Technology Data Exchange (ETDEWEB)

    Boubnov, Alexey [Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology, Kaiserstr. 12, D-76131 Karlsruhe (Germany); Institute of Catalysis Research and Technology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany); Roppertz, Andreas [Institute of Energy Process Engineering and Chemical Engineering, Chair of Reaction Engineering, Technical University of Freiberg, Fuchsmuehlenweg 9, D-09599 Freiberg (Germany); Kundrat, Matthew D. [Center for Functional Nanostructures and Institute of Physical Chemistry, Karlsruhe Institute of Technology, Kaiserstr. 12, D-76131 Karlsruhe (Germany); Mangold, Stefan [Institut für Beschleunigerphysik und Technologie (IBPT), Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany); Reznik, Boris [Institute of Applied Geosciences, Karlsruhe Institute of Technology, Kaiserstr. 12, D-76131 Karlsruhe (Germany); Jacob, Christoph R. [Center for Functional Nanostructures and Institute of Physical Chemistry, Karlsruhe Institute of Technology, Kaiserstr. 12, D-76131 Karlsruhe (Germany); Institute of Physical and Theoretical Chemistry, TU Braunschweig, Hans-Sommer-Str. 10, D-38106 Braunschweig (Germany); Kureti, Sven [Institute of Energy Process Engineering and Chemical Engineering, Chair of Reaction Engineering, Technical University of Freiberg, Fuchsmuehlenweg 9, D-09599 Freiberg (Germany); Grunwaldt, Jan-Dierk, E-mail: grunwaldt@kit.edu [Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology, Kaiserstr. 12, D-76131 Karlsruhe (Germany); Institute of Catalysis Research and Technology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany)

    2016-11-15

    Highlights: • Analysis of isolated and oligomeric FeOx (x = 4, 5) on Al{sub 2}O{sub 3} by XANES and EXAFS. • Iron is trivalent and is mainly located at octahedral lattice sites of Al{sub 2}O{sub 3}. • Low Fe loading (0.1%) guarantees high dispersion of catalytically active iron sites. • Surface Fe-cluster on Al{sub 2}O{sub 3} and DFT-optimised Fe-doped Al{sub 2}O{sub 3} as input models for EXAFS. • Interactions of iron with support are well-accounted for using realistic models. - Abstract: Iron oxide centres are structurally investigated in 0.1% Fe/γ-Al{sub 2}O{sub 3}, which is known as highly active catalyst, for instance in the oxidation of CO. The sample was characterised by using X-ray absorption spectroscopy (XAS) in terms of X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), Mössbauer spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). These analyses evidenced high dispersion of the iron oxide entities without significant presence of bulk-like aggregates associated with the low Fe content of the catalyst. A library of structural models of Al{sub 2}O{sub 3}-supported surface Fe was created as input for EXAFS fitting. Additionally, several model structures of Fe substituting Al ions in bulk γ-Al{sub 2}O{sub 3} were created with optimised geometry based on density-functional theory (DFT) calculations. From EXAFS refinement of the best 8 out of 24 models, it was found that the trivalent Fe ions are coordinated by 4–5 oxygen atoms and are located on octahedral lattice sites of the exposed surfaces of γ-Al{sub 2}O{sub 3}. These iron oxide species exist mainly as a mixture of monomeric and binuclear species and due to the low concentration represent suitable model systems as alternative to single crystal systems for structure-function relationships.

  20. Fe K-edge XANES of Maya blue pigment

    Energy Technology Data Exchange (ETDEWEB)

    Rio, M. Sanchez del [ESRF, Experiments Division, B.P. 220, F-38043, Grenoble Cedex (France)]. E-mail: srio@esrf.fr; Sodo, A. [ESRF, Experiments Division, B.P. 220, F-38043, Grenoble Cedex (France); Eeckhout, S.G. [ESRF, Experiments Division, B.P. 220, F-38043, Grenoble Cedex (France); Neisius, T. [ESRF, Experiments Division, B.P. 220, F-38043, Grenoble Cedex (France); Martinetto, P. [Laboratoire de Cristallographie, CNRS, Grenoble B.P. 166, F-38042, Grenoble Cedex 09 (France); Dooryhee, E. [Laboratoire de Cristallographie, CNRS, Grenoble B.P. 166, F-38042, Grenoble Cedex 09 (France); Reyes-Valerio, C. [INAH, Mexico DF (Mexico)

    2005-08-15

    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{sub 8}(Mg{sub 2}Al{sub 2})O{sub 20}(OH){sub 2}(OH{sub 2}){sub 4}.4H{sub 2}O and an organic colourant (indigo: C{sub 16}H{sub 10}N{sub 2}O{sub 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.

  1. Augmentation of Quick-EXAFS measurement facility at the energy scanning EXAFS beamline at INDUS-2 SRS

    Energy Technology Data Exchange (ETDEWEB)

    Poswal, A. K., E-mail: poswalashwini@gmail.com; Agrawal, Ankur; Bhattachryya, D.; Jha, S. N.; Sahoo, N. K. [Atomic and Molecular Physics Division, Bhabha Atomic Research Centre, Mumbai -400085 (India)

    2015-06-24

    In this paper implementation of Quick-EXAFS data acquisition facility at the Energy Scanning EXAFS beamline(BL-09) at INDUS-2 synchrotron source, Indore is presented. By adopting a continuous-scan mode in the Double Crystal monochromator (DCM), a high signal-to-noise ratio is maintained and the acquisition time is reduced to few seconds. The quality of spectra and repeatability is checked by measuring standards. The present mode of data acquisition would enable EXAFS measurement for in-situ studies even in fluorescence mode.

  2. Comparison of EXAFS Foil Spectra from Around the World

    International Nuclear Information System (INIS)

    Kelly, S.D.; Bare, S.R.; Greenlay, N.; Azevedo, G.; Balasubramanian, M.; Barton, D.; Chattopadhyay, S.; Fakra, S.; Johannessen, B.; Newville, M.; Pena, J.; Pokrovski, G.S; Proux, O.; Priolkar, K.; Ravel, B.; Webb, S.M.

    2010-01-01

    The EXAFS spectra of Cu and Pd foil from many different beamlines and synchrotrons are compared to address the dependence of the amplitude reduction factor (S 0 2 ) on beamline specific parameters. Even though S 0 2 is the same parameter as the EXAFS coordination number, the value for S 0 2 is given little attention, and is often unreported. The S 0 2 often differs for the same material due to beamline and sample attributes, such that no importance is given to S 0 2 -values within a general range of 0.7 to 1.1. EXAFS beamlines have evolved such that it should now be feasible to use standard S 0 2 values for all EXAFS measurements of a specific elemental environment. This would allow for the determination of the imaginary energy (Ei) to account for broadening of the EXAFS signal rather than folding these errors into an effective S 0 2 -value. To test this concept, we model 11 Cu-foil and 6 Pd-foil EXAFS spectra from around the world to compare the difference in S 0 2 - and Ei-values.

  3. XANES and XMCD studies of FeRh and CoRh nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Smekhova, A; Wilhelm, F; Rogalev, A [European Synchrotron Radiation Facility, Grenoble Cedex 9, 38043 (France); Atamena, N; Ciuculescu, D; Amiens, C [Laboratoire de Chimie de Coordination, UPR 8241-CNRS, Toulouse Cedex 04, 31077 (France); Lecante, P, E-mail: smeal@esrf.f [Centre d' Elaboration de Materiaux et d' Etudes Structurales, UPR 8011-CNRS, Toulouse Cedex 04, 31055 (France)

    2010-01-01

    Element-selective magnetic properties of new core-shell bimetallic MRh (M=Fe or Co) nanoparticles (NP{sub S}) of 50/50 composition with either M-Rh or Rh-M core/shell order and an average diameter of {approx}2 nm have been investigated by X-ray Absorption Spectroscopy (XANES) and X-Ray Magnetic Circular Dichroism (XMCD) technique. XANES spectra at the Rh L{sub 2,3} edges exhibit the same characteristic features for all systems having the Rh metal enriched shell. XMCD experiments at the same edges have shown that 4d states of Rh atoms acquire a magnetic moment as a result of hybridization with iron or cobalt 3d states. As expected the value of this induced moment depends on the 3d transition metal and on the core/shell chemical order in the nanoparticle.

  4. The Difficult Chore of Measuring Coordination by EXAFS

    International Nuclear Information System (INIS)

    Ravel, B.; Kelly, S. D.

    2007-01-01

    Neither the theory nor the interpretation of Extended X-Ray-Absorption Fine-Structure (EXAFS) spectroscopy requires assumptions of crystalline symmetry or periodicity. As a result, EXAFS is a tool applied to a wide range of scientific disciplines and to a wide variety of experimental systems. A simple enumeration of the atoms in the coordination environment of the absorber is often the primary goal of an EXAFS experiment. There are, however, a number of pitfalls in the way of an accurate determination of coordination number (CN). These include statistical limitations of the EXAFS fitting problem, empirical effects due to sample preparation, and the assumptions made about the physical structure surrounding the absorber in the course of data analysis. In this paper we examine several of these pitfalls and their effects upon the determination of CN. Where possible, we offer suggestions for avoiding or mitigating the pitfalls. We hope this paper will help guide the general EXAFS practitioner through the difficult chore of accurately determining CN

  5. Composing complex EXAFS problems with severe information constraints

    International Nuclear Information System (INIS)

    Ravel, B

    2009-01-01

    In recent work, a model for the structural environment of Hg bound to a catalytic DNA sensor was proposed on the basis of EXAFS data analysis. Although severely constrained by limited data quality and scant supporting structural data, a compelling structural model was found which agreed with a similar but less detailed model proposed on the basis on NMR data. I discuss in detail the successes and limitations of the analytical strategy that were implemented in the earlier work. I then speculate on future software requirements needed to make this and similarly complex analytical strategies more available to the wider audience of EXAFS practitioners.

  6. Automating an EXAFS facility: hardware and software considerations

    International Nuclear Information System (INIS)

    Georgopoulos, P.; Sayers, D.E.; Bunker, B.; Elam, T.; Grote, W.A.

    1981-01-01

    The basic design considerations for computer hardware and software, applicable not only to laboratory EXAFS facilities, but also to synchrotron installations, are reviewed. Uniformity and standardization of both hardware configurations and program packages for data collection and analysis are heavily emphasized. Specific recommendations are made with respect to choice of computers, peripherals, and interfaces, and guidelines for the development of software packages are set forth. A description of two working computer-interfaced EXAFS facilities is presented which can serve as prototypes for future developments. 3 figures

  7. EXAFS determination of cation local order in layered perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Montero C, M. E.; Fuentes M, L.; Duarte M, J. A.; Fuentes C, L. [Centro de Investigacion en Materiales Avanzados S. C., Miguel de Cervantes Saavedra 120, Complejo Industrial Chihuahua, 31109 Chihuahua (Mexico); Garcia G, M. [Instituto de Fisica, UNAM, Ciudad Universitaria, 04510 Mexico D. F. (Mexico); Mehta, A.; Webb, S. [Stanford Synchrotron Radiation Laboratory, CA (United States)

    2008-02-15

    EXAFS analysis of Bi{sub 6}Ti{sub 3}Fe{sub 2}O{sub 18} Aurivillius ceramic was performed to elucidate the local environment of Fe cations. Experiments were performed at Stanford Synchrotron Radiation Laboratory, at T = 10, 30, 50, 75, 100 and 298 K, in fluorescence regime. EXAFS spectra were processed using the ab initio multiple scattering program FEFF6. Distances among representative atomic pairs were refined. As a basic result, the previous hypothesis suggested by X-ray diffraction experiments, regarding a preference of iron atoms for the centered perovskite layer of the unit cell, was confirmed. (Author)

  8. Development of synchrotron x-ray micro-spectroscopic techniques and application to problems in low temperature geochemistry. Progress report

    Energy Technology Data Exchange (ETDEWEB)

    1993-10-01

    The focus of the technical development effort has been the development of apparatus and techniques for the utilization of X-ray Fluorescence (XRF), Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Absorption Near Edge Structure (XANES) spectroscopies in a microprobe mode. The present XRM uses white synchrotron radiation (3 to 30 keV) from a bending magnet for trace element analyses using the x-ray fluorescence technique Two significant improvements to this device have been recently implemented. Focusing Mirror: An 8:1 ellipsoidal mirror was installed in the X26A beamline to focus the incident synchrotron radiation and thereby increase the flux on the sample by about a factor of 30. Incident Beam Monochromator: The monochromator has been successfully installed and commissioned in the X26A beamline upstream of the mirror to permit analyses with focused monochromatic radiation. The monochromator consists of a channel-cut silicon (111) crystal driven by a Klinger stepping motor translator. We have demonstrated the operating range of this instrument is 4 and 20 keV with 0.01 eV steps and produces a beam with a {approximately}10{sup {minus}4} energy bandwidth. The primary purpose of the monochromator is for x-ray absorption spectroscopy (XAS) measurements but it is also used for selective excitation in trace element microanalysis. To date, we have conducted XANES studies on Ti, Cr, Fe, Ce and U, spanning the entire accessible energy range and including both K and L edge spectra. Practical detection limits for microXANES are 10--100 ppM for 100 {mu}m spots.

  9. Multifunctional synchrotron spectrometer of NRC Kurchatov Institute. Part 1. EXAFS in dispersive mode

    International Nuclear Information System (INIS)

    Aksenov, V.L.; Tyutyunnikov, S.I.; Shalyapin, V.N.; Belyaev, A.D.; Artem'ev, A.N.; Kirillov, B.F.; Demkiv, A.A.; Knyazev, G.A.; Koval'chuk, M.V.; Artem'ev, N.A.

    2017-01-01

    The improved X-ray optical scheme, the system of registration and measurement procedure of multifunctional synchrotron radiation spectrometer in dispersive EXAFS mode are described. The results of the energy permission measurements of spectrometer are given. The advantages and disadvantages in the traditional and dispersion schematics of spectrometers EXAFS are analyzed. Examples of the EXAFS spectra measured in the dispersion mode are given.

  10. Pressure effects in Debye-Waller factors and in EXAFS

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen Van Hung, E-mail: hungnv@vnu.edu.v [University of Science, VNU Hanoi, 334 Nguyen Trai, Thanh Xuan, Hanoi (Viet Nam); Vu Van Hung [Hanoi National University of Education, 136 Xuan Thuy, Cau Giay, Hanoi (Viet Nam); Ho Khac Hieu [University of Science, VNU Hanoi, 334 Nguyen Trai, Thanh Xuan, Hanoi (Viet Nam); National University of Civil Engineering, 55 Giai Phong, Hai Ba Trung, Hanoi (Viet Nam); Frahm, Ronald R. [Bergische Universitaet-Gesamthochschule Wuppertal, FB: 8-Physik, Gauss Strasse 20, 42097 Wuppertal (Germany)

    2011-02-01

    Anharmonic correlated Einstein model (ACEM) and statistical moment method (SMM) have been developed to derive analytical expressions for pressure dependence of the lattice bond length, effective spring constant, correlated Einstein frequency and temperature, Debye-Waller factors (DWF) or second cumulant, first and third cumulants in Extended X-ray Absorption Fine Structure (EXAFS) at a given temperature. Numerical results for pressure-dependent DWF of Kr and Cu agree well with experiment and other theoretical values. Simulated EXAFS of Cu and its Fourier transform magnitude using our calculated pressure-induced change in the 1st shell are found to be in a reasonable agreement with those using X-ray diffraction (XRD) experimental results. -- Research Highlights: {yields} We have developed anharmonic correlated Einstein model and statistical moment method. {yields} The pressure effects in cumulants including DWF and in EXAFS has been investigated. {yields} Calculated pressure-dependent DWF for Kr, Cu agree with experiment and other results. {yields} Simulated EXAFS and Fourier transform magnitude of Cu agree with those using XRD data.

  11. Pressure effects in Debye-Waller factors and in EXAFS

    International Nuclear Information System (INIS)

    Nguyen Van Hung; Vu Van Hung; Ho Khac Hieu; Frahm, Ronald R.

    2011-01-01

    Anharmonic correlated Einstein model (ACEM) and statistical moment method (SMM) have been developed to derive analytical expressions for pressure dependence of the lattice bond length, effective spring constant, correlated Einstein frequency and temperature, Debye-Waller factors (DWF) or second cumulant, first and third cumulants in Extended X-ray Absorption Fine Structure (EXAFS) at a given temperature. Numerical results for pressure-dependent DWF of Kr and Cu agree well with experiment and other theoretical values. Simulated EXAFS of Cu and its Fourier transform magnitude using our calculated pressure-induced change in the 1st shell are found to be in a reasonable agreement with those using X-ray diffraction (XRD) experimental results. -- Research Highlights: → We have developed anharmonic correlated Einstein model and statistical moment method. → The pressure effects in cumulants including DWF and in EXAFS has been investigated. → Calculated pressure-dependent DWF for Kr, Cu agree with experiment and other results. → Simulated EXAFS and Fourier transform magnitude of Cu agree with those using XRD data.

  12. Investigation of radiation defects in solids using the EXAFS method

    International Nuclear Information System (INIS)

    Eritsyan, G.N.

    1983-01-01

    The exafs method is proposed as a more informative, universal one to investigate the radiation defects in solids. The successful results as obtained by the author using the synchrotron radiation source are reported for the first time. The measurements were carried out in GaAsP crystals irradiated with 50 MeV electrons

  13. XRF and XANES Data for Kaplan U Paper

    Science.gov (United States)

    The dataset contains two XRF images of iron and uranium distribution on plant roots and a database of XANES data used to produce XANES spectra figure for Figure 7 in the published paper.This dataset is associated with the following publication:Kaplan, D., R. Kukkadapu, J. Seaman, B. Arey, A. Dohnalkova, S. Buettner, D. Li, T. Varga, K. Scheckel, and P. Jaffe. Iron Mineralogy and Uranium-Binding Environment in the Rhizosphere of a Wetland Soil. D. Barcelo SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier BV, AMSTERDAM, NETHERLANDS, 569: 53-64, (2016).

  14. EXAFS: Possibilities, advantages and limitations for the investigation of local order in metallic glasses

    International Nuclear Information System (INIS)

    Haensel, R.; Rabe, P.; Tolkiehn, G.; Werner, A.

    1980-06-01

    Throughout this book many examples for the close relationship between the macroscopic properties and the local structure of liquid and amorphous metals and alloys are given. Complementing the conventional X-ray, electron and neutron scattering techniques the analysis of the Extended X-ray Absorption Fine Structure (EXAFS) has been developed to a reliable method for structural analysis. Although the phenomenon is known since the thirties of the century, its application for the determination of local geometrical parameters has only been introduced about ten years ago. The development of the method has been greatly stimulated by extensive theoretical work, e.g. more refined calculations of complex scattering amplitudes and by the availability of synchrotron radiation as an intense X-ray continuum source. Two aspects are discussed in this paper: i) the basic principles of EXAFS and the usual data evaluation techniques demonstrated for crystalline Fe; ii) Applications on amorphous systems, the modifications of the data evaluation due to nonsymmetric pair distributions and the comparison with other methods for structure determination. (orig.)

  15. Electron microscopy and EXAFS studies on oxide-supported gold-silver nanoparticles prepared by flame spray pyrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Hannemann, Stefan [Institute of Chemical and Bioengineering, Swiss Federal Institute of Technology, ETH Hoenggerberg, CH-8093 Zurich (Switzerland); Grunwaldt, Jan-Dierk [Institute of Chemical and Bioengineering, Swiss Federal Institute of Technology, ETH Hoenggerberg, CH-8093 Zurich (Switzerland)]. E-mail: grunwaldt@chem.ethz.ch; Krumeich, Frank [Laboratory of Inorganic Chemistry, Swiss Federal Institute of Technology, ETH Hoenggerberg, CH-8093 Zurich (Switzerland); Kappen, Peter [Department of Physics, La Trobe University, Victoria 3086 (Australia); Baiker, Alfons [Institute of Chemical and Bioengineering, Swiss Federal Institute of Technology, ETH Hoenggerberg, CH-8093 Zurich (Switzerland)

    2006-09-15

    Gold and gold-silver nanoparticles prepared by flame spray pyrolysis (FSP) were characterized by electron microscopy, in situ X-ray absorption spectroscopy (XANES and EXAFS), X-ray diffraction (XRD) and their catalytic activity in CO oxidation. Within this one-step flame-synthesis procedure, precursor solutions of dimethyl gold(III) acetylacetonate and silver(I) benzoate together with the corresponding precursor of the silica, iron oxide or titania support, were sprayed and combusted. In order to prepare small metal particles, a low noble metal loading was required. A loading of 0.1-1 wt.% of Au and Ag resulted in 1-6 nm particles. The size of the noble metal particles increased with higher loadings of gold and particularly silver. Both scanning transmission electron microscopy (STEM) combined with energy dispersive X-ray spectroscopy (EDXS) and X-ray absorption spectroscopy (XAS) studies proved the formation of mixed Au-Ag particles. In case of 1% Au-1% Ag/SiO{sub 2}, TEM combined with electron spectroscopic imaging (ESI) using an imaging filter could be used in addition to prove the presence of silver and gold in the same noble metal particle. CO oxidation in the presence of hydrogen was chosen as a test reaction sensitive to small gold particles. Both the influence of the particle size and the alloying of gold and silver were reflected in the CO oxidation activity.

  16. Electron microscopy and EXAFS studies on oxide-supported gold-silver nanoparticles prepared by flame spray pyrolysis

    International Nuclear Information System (INIS)

    Hannemann, Stefan; Grunwaldt, Jan-Dierk; Krumeich, Frank; Kappen, Peter; Baiker, Alfons

    2006-01-01

    Gold and gold-silver nanoparticles prepared by flame spray pyrolysis (FSP) were characterized by electron microscopy, in situ X-ray absorption spectroscopy (XANES and EXAFS), X-ray diffraction (XRD) and their catalytic activity in CO oxidation. Within this one-step flame-synthesis procedure, precursor solutions of dimethyl gold(III) acetylacetonate and silver(I) benzoate together with the corresponding precursor of the silica, iron oxide or titania support, were sprayed and combusted. In order to prepare small metal particles, a low noble metal loading was required. A loading of 0.1-1 wt.% of Au and Ag resulted in 1-6 nm particles. The size of the noble metal particles increased with higher loadings of gold and particularly silver. Both scanning transmission electron microscopy (STEM) combined with energy dispersive X-ray spectroscopy (EDXS) and X-ray absorption spectroscopy (XAS) studies proved the formation of mixed Au-Ag particles. In case of 1% Au-1% Ag/SiO 2 , TEM combined with electron spectroscopic imaging (ESI) using an imaging filter could be used in addition to prove the presence of silver and gold in the same noble metal particle. CO oxidation in the presence of hydrogen was chosen as a test reaction sensitive to small gold particles. Both the influence of the particle size and the alloying of gold and silver were reflected in the CO oxidation activity

  17. Functional Groups Quantification of Chondritic Organics by XANES Spectroscopy

    Science.gov (United States)

    Le Guillou, C.; Bernard, S.

    2017-07-01

    We have developed a new method to quantify the functional group concentration of organics using STXM-XANES. Applied to IOM and in situ FIB sections measurement, it reveals a lower aromaticity than expected from previous NMR results (35% vs. 60%).

  18. X-ray photoemission spectroscopy (XPS) and extended x-ray absorption fine structure (EXAFS) studies of silicate based glasses

    International Nuclear Information System (INIS)

    Karim, D.; Lam, D.J.

    1979-01-01

    The application of the x-ray photoemission spectroscopy (XPS) technique to study the electronic structure and bonding of heavy metal oxides in alkali- and alkali-earth-silicate glasses had been demonstrated. The bonding characteristics of the iron oxide and uranium oxide in sodium silicate glasses were deduced from the changes in the oxygen 1s levels and the heavy metal core levels. It is reasonable to expect that the effect of leaching on the heavy metal ions can be monitored using the appropriate core levels of these ions. To study the effect of leaching on the glass forming network, the valence band structure of the bridging and nonbridging oxygens in sodium silicate glasses were investigated. The measurement of extended x-ray absorption fine-structure (EXAFS) is a relatively new analytical technique for obtaining short range (<5 A) structural information around atoms of a selected species in both solid and fluid systems. Experiments have recently begun to establish the feasibility of using EXAFS to study the bonding of actinides in silicate glasses. Because of the ability of EXAFS to yield specific structural data even in complex multicomponent systems, it could prove to be an invaluable tool in understanding glass structure

  19. Silicon Detector System for High Rate EXAFS Applications.

    Science.gov (United States)

    Pullia, A; Kraner, H W; Siddons, D P; Furenlid, L R; Bertuccio, G

    1995-08-01

    A multichannel silicon pad detector for EXAFS (Extended X-ray Absorption Fine Structure) applications has been designed and built. The X-ray spectroscopic measurements demonstrate that an adequate energy resolution of 230 eV FWHM (corresponding to 27 rms electrons in silicon) can be achieved reliably at -35 °C. A resolution of 190 eV FWHM (corresponding to 22 rms electrons) has been obtained from individual pads at -35 °C. At room temperature (25 °C) an average energy resolution of 380 eV FWHM is achieved and a resolution of 350 eV FWHM (41 rms electrons) is the best performance. A simple cooling system constituted of Peltier cells is sufficient to reduce the reverse currents of the pads and their related shot noise contribution, in order to achieve resolutions better than 300 eV FWHM which is adequate for the EXAFS applications.

  20. In-situ EXAFS study on the thermal decomposition of TiH2

    International Nuclear Information System (INIS)

    Zhou Yingli; Wu Min; An Pengfei; Zheng Lirong; Chu Shengqi; Zhang Jing; Hu Tiandou

    2014-01-01

    Thermal decomposition behaviors of TiH 2 powder under a flowing helium atmosphere and in a low vacuum condition have been studied using an in situ EXAFS technique. By an EXAFS analysis containing the multiple scattering paths including H atoms, the changes of the hydrogen stoichiometric ratio and the phase transformation sequence are obtained. The results demonstrate that the initial decomposition temperature is dependent on experimental conditions, which occurs, respectively, at about 300 and 400 °C in a low vacuum condition and under a flowing helium atmosphere. During the decomposition process of TiH 2 in a low vacuum condition, the sample experiences a phase change process: δ(TiH 2 ) → δ (TiH x ) → δ(TiH x )+ β(TiH x ) → δ(TiH x )+ β(TiH x ) + α(Ti) → β(TiH x ) + α(Ti) → α(Ti) + β(Ti). This study offers a way to detect the structural information of hydrogen. A detailed discussion about the decomposition process of TiH 2 is given in this paper. (authors)

  1. Characterization of U(VI)-carbonato ternary complexes on hematite: EXAFS and electrophoretic mobility measurements

    Science.gov (United States)

    Bargar, John R.; Reitmeyer, Rebecca; Lenhart, John J.; Davis, James A.

    2000-01-01

    We have measured U(VI) adsorption on hematite using EXAFS spectroscopy and electrophoresis under conditions relevant to surface waters and aquifers (0.01 to 10 μM dissolved uranium concentrations, in equilibrium with air, pH 4.5 to 8.5). Both techniques suggest the existence of anionic U(VI)-carbonato ternary complexes. Fits to EXAFS spectra indicate that U(VI) is simultaneously coordinated to surface FeO6 octahedra and carbonate (or bicarbonate) ligands in bidentate fashions, leading to the conclusion that the ternary complexes have an inner-sphere metal bridging (hematite-U(VI)-carbonato) structure. Greater than or equal to 50% of adsorbed U(VI) was comprised of monomeric hematite-U(VI)-carbonato ternary complexes, even at pH 4.5. Multimeric U(VI) species were observed at pH ≥ 6.5 and aqueous U(VI) concentrations approximately an order of magnitude more dilute than the solubility of crystalline β-UO2(OH)2. Based on structural constraints, these complexes were interpreted as dimeric hematite-U(VI)-carbonato ternary complexes. These results suggest that Fe-oxide-U(VI)-carbonato complexes are likely to be important transport-limiting species in oxic aquifers throughout a wide range of pH values.

  2. Silver and copper nanoclusters in the lustre decoration of Italian Renaissance pottery: an EXAFS study

    Science.gov (United States)

    Padovani, S.; Borgia, I.; Brunetti, B.; Sgamellotti, A.; Giulivi, A.; D'Acapito, F.; Mazzoldi, P.; Sada, C.; Battaglin, G.

    Lustre is one of the most important decorative techniques of the Medieval and Renaissance pottery of the Mediterranean basin, capable of producing brilliant metallic reflections and iridescence. Following the recent finding that the colour of lustre decorations is mainly determined by copper and silver nanoclusters dispersed in the glaze layer, the local environment of copper and silver atoms has been studied by extended X-ray absorption fine structure (EXAFS) spectroscopy on original samples of gold and red lustre. It has been found that, in gold lustre, whose colour is attributed mainly to the silver nanocluster dispersion, silver is only partially present in the metallic form and copper is almost completely oxidised. In the red lustre, whose colour is attributed mainly to the copper nanocluster dispersion, only a fraction of copper is present in the metallic form. EXAFS measurements on red lustre, carried out in the total electron yield mode to probe only the first 150 nm of the glaze layer, indicated that in some cases lustre nanoclusters may be confined in a very thin layer close to the surface.

  3. EXAFS and XPS Study of Rutile-Type Difluorides of First-Row Transition Metals

    International Nuclear Information System (INIS)

    Murai, Kei-ichiro; Suzuki, Yohei; Moriga, Toshihiro; Yoshiasa, Akira

    2007-01-01

    Although most rutile-type difluorides (MnF2, CoF2 and NiF2) have a positive thermal expansion coefficient, FeF2 has a negative thermal expansion (NTE) along the c-axis in the high temperature region. In this study, we give an explanation of that behavior with Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Photoelectron Spectroscopy (XPS) techniques. From EXAFS results, it has become apparent that the length of the share-edge (Fe-Fe) of FeF6 octahedra increased with the rise of temperature in the high temperature region. We have revealed that the force constant between nearest neighbor atoms (Fe-F) was much larger than that between second-nearest neighbor atoms (Fe-Fe) in FeF2. In XPS measurements, it was discovered that the peak of F 1s of FeF2 was located at the lowest binding energy position as compared to that of other difluorides. This means that the charge density around the F atom in FeF2 was higher than that in other difluorides. It follows from this that the share-edge repulsive force in FeF2 is larger than that in other difluorides. On account of the large repulsive force and the large force constant between nearest neighbor atoms, Fe atoms are attracted to share-edge with the rise of temperature

  4. EXAFS investigation on microstructure of La-based alloy deuteride

    CERN Document Server

    Chen Bo Fei; Xie Chao Mei; Chen Xi Ping; Liu Li Juan; Xie Ya Ning; Hu Tian Dou; Zhang Jing

    2002-01-01

    Extended X-ray absorption fine structure (EXAFS) spectra were measured to investigate the microstructure of La-based alloy deuteride. The radial structural functions of LaNi sub 4 sub . sub 2 sub 5 Al sub 0 sub . sub 7 sub 5 D sub x samples were obtained and the comparisons among different samples were performed. The results show that removal of deuterium is fast in La-Ni-Al hydrogen storage alloys under non-airtight condition

  5. EXAFS investigations of Cu-Mg-O compound

    CERN Document Server

    Sidorenko, A F; Babanov, Y A; Naumov, S V; Samokhvalov, A A

    2001-01-01

    The interest to systems containing copper oxide is connected with the problem of high-temperature superconductivity because of the closeness of its basic physical properties and properties of superconductor mother Cu-compounds. In this work, EXAFS study of the Cu sub 0 sub . sub 2 Mg sub 0 sub . sub 8 O compound is presented. A new iterative algorithm of the solution of ill-posed problem on determining three partial pair correlation functions from one EXAFS-data set near the Cu K-edge is described. The results of X-ray scattering study of a given sample show a presence of a single phase with the MgO structure and a lattice parameter of 4.219 A instead of 4.208 A for pure MgO. From the EXAFS investigations, we find the local distortion of the lattice. We revealed that the short range order differs both from a hypothetical alloy with the MgO structure and from copper oxide.

  6. Aqueous U(VI) interaction with magnetite nanoparticles in a mixed flow reactor system: HR-XANES study

    International Nuclear Information System (INIS)

    Pidchenko, I; Heberling, F; Finck, N; Schild, D; Bohnert, E; Schäfer, T; Rothe, J; Geckeis, H; Vitova, T; Kvashnina, KO

    2016-01-01

    The redox variations and changes in local atomic environment of uranium (U) interacted with the magnetite nanoparticles were studied in a proof of principle experiment by the U L 3 and M 4 edges high energy resolution X-ray absorption near edge structure (HR-XANES) technique. We designed and applied a mixed flow reactor (MFR) set-up to maintain dynamic flow conditions during U-magnetite interactions. Formation of hydrolyzed, bi- and poly-nuclear U species were excluded by slow continuous injection of U(VI) (10 -6 M) and pH control integrated in the MFR set-up. The applied U HR-XANES technique is more sensitive to minor changes in the U redox states and bonding compared to the conventional XANES method. Major U(VI) contribution in uranyl type of bonding is found in the magnetite nanoparticles after three days operation time of the MFR. Indications for shortening of the U-O axial bond length for the magnetite compared to the maghemite system are present too. (paper)

  7. XPS and XANES studies of biomimetic composites based on B-type nano-hydroxyapatite

    Science.gov (United States)

    Goloshchapov, D. L.; Gushchin, M. S.; Kashkarov, V. M.; Seredin, P. V.; Ippolitov, Y. A.; Khmelevsky, N. O.; Aksenenko, A. Yu.

    2018-06-01

    The paper presents an investigation of the local atomic structure of nanocrystalline carbonate-substituted hydroxyapatite (CHAP) contained in biomimetic composites - analogues of intact human tooth tissues. Using the XPS technique, the presence of impurity Mg and F atoms and structurally bound carbon in CHAP, at the concentrations typical of apatite enamel and dentine was determined. The XANES method was used to study the changes occurring in P L2,3 spectra of biocomposites with CHAP, depending on the percentage of the amino acid matrix. The appearance of maxima in the spectra of XANES P L2,3 near 135.7 eV for the samples with the composition of amino acid complex/hydroxyapatite - 5/95, 25/75 and the splitting of a broad peak of 146.9 eV in the spectrum of a biocomposite with a composition of 40/60 indicates at the interaction of molecular complex of amino acids with atomic environment of phosphorus. This fact can be used in the fundamental medicine for synthesizing of new biomaterials in dentistry.

  8. Transfer characterization of sulfur from coal-burning emission to plant leaves by PIXE and XANES

    Energy Technology Data Exchange (ETDEWEB)

    Bao, L.M.; Zhang, G.L.; Zhang, Y.X.; Li, Y.; Lin, J.; Liu, W.; Cao, Q.C.; Zhao, Y.D.; Ma, C.Y.; Han, Y. [Chinese Academy of Sciences, Shanghai (China). Shanghai Institute of Applied Physics

    2009-11-15

    The impact of coal-burning emission on sulfur in camphor leaves was investigated using Proton Induced X-ray Emission (PIXE) and synchrotron radiation technique X-ray Absorption Near-Edge Structure (XANES) spectroscopy. The PIXE results show that the sulfur concentrations in the leaves collected at the polluted site are significantly higher than those in controls. The sulfur XANES spectra show the presence of organic (disulfides, thiols, thioethers, sulfonates and sulfoxides) and inorganic sulfur (sulfates) in the leaves. The inorganic sulfur in the leaves of camphor tree polluted by coal combustion is 15% more than that of the control site. The results suggest that the long-term coal-burning pollution resulted in an enhanced content of the total sulfur and sulfate in the leaves, and the uptake of sulfur by leaves had exceeded the metabolic requirement of plants and the excess of sulfur was stored as SO{sub 4}2{sup -}. It can monitor the sulfur pollution in atmosphere.

  9. The application of iterative transformation factor analysis to resolve multi-component EXAFS spectra of uranium(6) complexes with acetic acid as a function of pH

    International Nuclear Information System (INIS)

    Robberg, A.; Reich, T.

    2002-01-01

    Synchrotron-based EXAFS spectroscopy is a powerful technique to obtain structural information on radionuclide complexes in solution. Depending on the chemical conditions of the samples several radionuclide species can coexist in the solution as is often the case for environmentally related samples. All radionuclide species, which may have different near-neighbour environments, contribute to the measured EXAFS signal. In order to isolate the EXAFS spectra of the individual species (pure spectral components), it is necessary, in a first step, to measure a series of samples where their composition is changed by variation of one physico-chemical parameter (e.g. pH, concentration, etc.). For the spectral decomposition it is necessary that the EXAFS signal change as a function of the chosen physico-chemical parameter. In a second step, the series of EXAFS spectra is analysed with Eigen analysis and Iterative Transformation Factor Analysis (ITFA). As a result of the ITFA one obtains: a) for each sample the relative concentration of the structural distinguishable species and b) their corresponding pure spectral components. From the information obtained in a), one can construct a speciation diagram. The pure spectral components contain the structural information of the individual species, which can be extracted by conventional EXAFS analysis. To evaluate our ITFA algorithm for EXAFS analysis of mixtures, we prepared a series of eight solution samples of 0.05 M uranium(VI) and 1 M acetate (Ac) in the pH range of 0.1 to 4.5. From thermodynamic constants it is known that under these conditions up to four species can occur: uranyl hydrate, and the 1:1, 1:2 and 1:3 complexes of uranyl acetate. The uranium L III -edge EXAFS spectra were measured at room temperature in transmission mode at the Rossendorf Beamline (ROBL) at the ESRF. The average bond length between uranium and the equatorial oxygen atoms (O eq ) increases from 2.40 to 2.46 angstrom with increasing pH. This increase

  10. Silicon Detector System for High Rate EXAFS Applications

    OpenAIRE

    Pullia, A.; Kraner, H. W.; Siddons, D. P.; Furenlid, L. R.; Bertuccio, G.

    1995-01-01

    A multichannel silicon pad detector for EXAFS (Extended X-ray Absorption Fine Structure) applications has been designed and built. The X-ray spectroscopic measurements demonstrate that an adequate energy resolution of 230 eV FWHM (corresponding to 27 rms electrons in silicon) can be achieved reliably at −35 °C. A resolution of 190 eV FWHM (corresponding to 22 rms electrons) has been obtained from individual pads at −35 °C. At room temperature (25 °C) an average energy resolution of 380 eV FWH...

  11. EXAFS investigations on PbMoO4 single crystals grown under ...

    Indian Academy of Sciences (India)

    Abstract. Extended X-ray absorption fine structure (EXAFS) measurements on PbMoO4 (LMO) crystals have been performed at the recently-commissioned dispersive EXAFS beamline (BL-8) of INDUS-2 Synchrotron facility at Indore, India. The LMO samples were prepared under three different conditions viz. (i) grown from ...

  12. Manganese speciation in Diplodon chilensis patagonicus shells: a XANES study

    Science.gov (United States)

    Soldati, A. L.; Vicente-Vilas, V.; Goettlicher, J.; Jacob, D. E.

    2009-04-01

    century, resolving the environmental signal annually and even seasonally (Soldati et al., 2008b). High resolution trace elemental analysis by LA-ICPMS and EPMA in the shells show that elements like Mg and Mn are related to the seasonal pattern and can be enriched along the organic-rich annual shell growth lines. Thus, these elements could possibly be bound organically instead of occupying a defined site in the crystal lattice of the calcium carbonate phase. LA-ICP-MS results show that Mn concentrations in these Diplodon shells range between 1000-300 g/g and 100-10 g/g and that the areas of enrichment are in the micrometer range. Raman and XRD measurements at high spatial resolution failed in recognizing whether the Mn is in carbonate solid solution or not. Therefore, speciation techniques like X-ray absorption fine structure (XAFS) spectroscopy with a high lateral resolution are required to address this question. Prior to XAFS spectroscopy the samples were mapped with the intensity of the Mn Kα fluorescence emission line in order to locate the Mn rich areas of interest. Because of the Mn concentrations in the sub % range the XAFS spectra at the positions of interest have been recorded in fluorescence mode using a 7 element Si(Li) detector. This study focuses on the near edge (XANES: X-ray absorption near edge structure) part of the spectra. For data evaluation, XANES spectra of reference substances were additionally measured in order to get first hints to Mn valence and bonding. As standards were used Mn and Mn rich carbonates, Mn oxides with Mn in different oxidation states, and Mn in organic compounds (Mn-porphyrin and Mn-acetate). The XAFS measurements have been carried out at the SUL-X beamline of the synchrotron radiation source ANKA of the Forschungszentrum Karlsruhe. Data evaluation is ongoing. References MEIBOM, A., CUIF, J.P., HOULBREQUE, F., MOSTEFAOUI, S., DAUPHIN, Y., MEIBOM; K.L. & DUNBAR, R. (2008). Compositional variations at ultra-structure length scales

  13. Zn-K edge EXAFS study of human nails

    Energy Technology Data Exchange (ETDEWEB)

    Katsikini, M; Mavromati, E; Pinakidou, F; Paloura, E C [School of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Gioulekas, D, E-mail: katsiki@auth.g [Medical School, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece)

    2009-11-15

    Extended X-ray absorption fine structure (EXAFS) spectroscopy at the Zn - K edge is applied for the study of the bonding geometry of Zn in human nails. The studied nail clippings belong to healthy donors and donors who suffer from lung diseases. Fitting of the first nearest neighboring shell of Zn reveals that it is bonded with N and S, at distances that take values in the ranges 2.00-2.04 A and 2.23-2.28A, respectively. Zn is four - fold coordinated and the ratio of the number of sulfur and nitrogen atoms (N{sub S}/N{sub N}) in the first coordination shell ranges from 0.52 to 1. The sample that belongs to the donor who suffers from lung fibrosis, a condition that is related to keratinization of the lung tissue, is characterized by the highest number of N{sub S}/N{sub N}. Simulation, using the FEFF8 code, of the Zn - K edge EXAFS spectra with models of tetrahedrally coordinated Zn with 1 (or 2) cysteine and 3 (or 2) histidines is satisfactory.

  14. Manganese in photosynthetic oxygen evolution: An edge and EXAFS study

    International Nuclear Information System (INIS)

    Yachandra, V.K.; Guiles, R.D.; McDermott, A.; Britt, R.D.; Dexheimer, S.L.; Saver, K.; Klein, M.P.

    1985-01-01

    The authors edge studies have previously shown that the Mn edges in photosynthetic samples in the S 1 and S 2 states fall into the range for Mn III and Mn IV complexes, and that the K-edge energy increases appreciably on advancing S 1 to S 2 . This was the first evidence that manganese is directly involved in the storage of oxidizing equivalents. More recently, they have extended this result with better quality data from both spinach and a thermophilic cyanobacterium. The newer results show an interesting structure to the edges, including a 1s to 3d transition. The EXAFS results for spinach membranes show that the salient features of the Mn structure are the same in the S 1 and S 2 states. These features are a Mn neighbor at approx. =2.7 A and O or N neighbors at approx. =1.75 A and approx. =2.0 A. The EXAFS spectrum of the S 1 state of the thermophilic blue green algae are strikingly similar to that of spinach

  15. SAXS and EXAFS studies of ion beam synthesized Au nanocrystals

    International Nuclear Information System (INIS)

    Kluth, P.; Johannessen, B.; Cookson, D.J.; Foran, G.J.; Ridgway, M.C.

    2006-01-01

    We have used small-angle X-ray scattering (SAXS) and extended X-ray absorption fine structure (EXAFS) spectroscopy to investigate Au nanocrystals (NCs) fabricated by high dose ion implantation into thin SiO 2 and subsequent annealing at different temperatures. Size distributions were determined from SAXS and structural parameters were extracted from EXAFS measurements, the latter analyzed as a function of NC size. Increasing implantation dose leads to an increasing average NC size and broadening of the size distribution. A significant size-dependent bond length contraction with respect to bulk material was observed. For samples annealed at 1100 deg. C our analysis suggests that an increased structural disorder is predominantly located at the NC surface. Post-implantation annealing at temperatures of 500 deg. C and 800 deg. C for 1 h in forming gas had no detectable influence on the NC size distribution, however, a significant influence on the structural parameters, in particular increased disorder was observed. This is potentially the result of stress induced disorder due to the different thermal expansion of the NC and matrix materials

  16. Convergence of the multiple scattering expansion in XAFS and XANES

    International Nuclear Information System (INIS)

    Rehr, J.J.

    1992-01-01

    The convergence of the multiple-scattering expansion of XAFS and XANES by explicit path-bypath calculations. The approach is based on the fast scattering matrix formalism of Rehr and Albers, together with an automated path finder and filters that exclude negligible paths. High-order scattering terms are found to be essential, especially at low energies. Several factors including the magnitude of curved wave scattering amplitudes, inelastic losses and multiple-scattering Debye-Waller factors control convergence of the expansion. The convergence is illustrated explicitly for the case of diatomic molecules

  17. Combined mineralogical and EXAFS characterization of polluted sediments for the definition of technological variables and constraints

    Science.gov (United States)

    Brigatti, M. F.; Elmi, C.; Laurora, A.; Malferrari, D.; Medici, L.

    2009-04-01

    An extremely severe aspect, both from environmental and economic viewpoint, is the management of polluted sediments removed from drainage and irrigation canals. Canals, in order to retain their functionality over the time, need to have their beds, periodically cleaned from sediments there accumulating. The management of removed sediments is extremely demanding, also from an economical perspective, if these latter needs to be treated as dangerous waste materials, as stated in numerous international standards. Furthermore the disposal of such a large amount of material may introduce a significant environmental impact as well. An appealing alternative is the recovery or reuse of these materials, for example in brick and tile industry, after obviously the application of appropriate techniques and protocols that could render these latter no longer a threat for human health. The assessment of the effective potential danger for human health and ecosystem of sediments before and after treatment obviously requires both a careful chemical and mineralogical characterization and, even if not always considered in the international standards, the definition of the coordination shell of heavy metals dangerous for human health, as a function of their oxidation state and coordination (e.g. Cr and Pb), and introducing technological constraints or affecting the features of the end products. Fe is a good representative for this second category, as the features of the end product, such as color, strongly depend not only from Fe concentration but also from its oxidation state, speciation and coordination. This work will first of all provide mineralogical characterization of sediments from various sampling points of irrigation and drainage canals of Po river region in the north-eastern of Italy. Samples were investigated with various approaches including X-ray powder diffraction under non-ambient conditions, thermal analysis and EXAFS spectroscopy. Obtained results, and in particular

  18. Combining µXANES and µXRD mapping to analyse the heterogeneity in calcium carbonate granules excreted by the earthworm Lumbricus terrestris

    International Nuclear Information System (INIS)

    Brinza, Loredana; Schofield, Paul F.; Hodson, Mark E.; Weller, Sophie; Ignatyev, Konstantin; Geraki, Kalotina; Quinn, Paul D.; Mosselmans, J. Frederick W.

    2014-01-01

    A new experimental set-up enabling microfocus fluorescence XANES mapping and microfocus XRD mapping on the same sample at beamline I18 at Diamond Light Source is described. To demonstrate this set-up the heterogeneous mineralogy in calcium carbonate granules excreted by the earthworm Lumbricus terrestris has been analysed. Data analysis methods have been developed which enable µXRD and µXANES two-dimensional maps to be compared. The use of fluorescence full spectral micro-X-ray absorption near-edge structure (µXANES) mapping is becoming more widespread in the hard energy regime. This experimental method using the Ca K-edge combined with micro-X-ray diffraction (µXRD) mapping of the same sample has been enabled on beamline I18 at Diamond Light Source. This combined approach has been used to probe both long- and short-range order in calcium carbonate granules produced by the earthworm Lumbricus terrestris. In granules produced by earthworms cultured in a control artificial soil, calcite and vaterite are observed in the granules. However, granules produced by earthworms cultivated in the same artificial soil amended with 500 p.p.m. Mg also contain an aragonite. The two techniques, µXRD and µXANES, probe different sample volumes but there is good agreement in the phase maps produced

  19. Combining µXANES and µXRD mapping to analyse the heterogeneity in calcium carbonate granules excreted by the earthworm Lumbricus terrestris

    Energy Technology Data Exchange (ETDEWEB)

    Brinza, Loredana [Diamond Light Source, Harwell Campus, Didcot, Oxon OX11 0DE (United Kingdom); Schofield, Paul F. [Natural History Museum, Cromwell Road, London SW7 5BD (United Kingdom); Hodson, Mark E. [University of York, York YO10 5DD (United Kingdom); Weller, Sophie [University of Oxford, South Parks Road, Oxford OX1 3QR (United Kingdom); Ignatyev, Konstantin; Geraki, Kalotina; Quinn, Paul D.; Mosselmans, J. Frederick W., E-mail: fred.mosselmans@diamond.ac.uk [Diamond Light Source, Harwell Campus, Didcot, Oxon OX11 0DE (United Kingdom)

    2014-01-01

    A new experimental set-up enabling microfocus fluorescence XANES mapping and microfocus XRD mapping on the same sample at beamline I18 at Diamond Light Source is described. To demonstrate this set-up the heterogeneous mineralogy in calcium carbonate granules excreted by the earthworm Lumbricus terrestris has been analysed. Data analysis methods have been developed which enable µXRD and µXANES two-dimensional maps to be compared. The use of fluorescence full spectral micro-X-ray absorption near-edge structure (µXANES) mapping is becoming more widespread in the hard energy regime. This experimental method using the Ca K-edge combined with micro-X-ray diffraction (µXRD) mapping of the same sample has been enabled on beamline I18 at Diamond Light Source. This combined approach has been used to probe both long- and short-range order in calcium carbonate granules produced by the earthworm Lumbricus terrestris. In granules produced by earthworms cultured in a control artificial soil, calcite and vaterite are observed in the granules. However, granules produced by earthworms cultivated in the same artificial soil amended with 500 p.p.m. Mg also contain an aragonite. The two techniques, µXRD and µXANES, probe different sample volumes but there is good agreement in the phase maps produced.

  20. Soft X-ray excited colour-centre luminescence and XANES studies of calcium oxide

    International Nuclear Information System (INIS)

    Ko, J.Y.P.; Heigl, F.; Yiu, Y.M.; Zhou, X.-T.; Regier, T.; Blyth, R.I.R.; Sham, T.-K.

    2007-01-01

    In this study, we show that colour centres can be produced by irradiating calcium oxide with soft X-rays from a synchrotron radiation source. Using the X-ray excited optical Iuminescence (XEOL) technique, two colour centres, F-centre, and F + -centre can be identified. These colour centres emit photons at characteristic wavelengths. In addition, by performing time-resolved XEOL (TRXEOL), we are able to reveal timing and decay characteristics of the colour centres. We also present X-ray absorption near-edge structure (XANES) spectra collected across oxygen K-edge, calcium L 3,2 -edge, and calcium K-edge. Experimental results are compared with density functional theory (DFT) calculations. (author)

  1. XANES study on the electronic states of carbon nanotube and related materials

    Energy Technology Data Exchange (ETDEWEB)

    Imamura, M [National Inst. of Mater. and Chem. Res., Ibaraki (Japan); Shimada, H [National Inst. of Mater. and Chem. Res., Ibaraki (Japan); Matsubayashi, H [National Inst. of Mater. and Chem. Res., Ibaraki (Japan); Yumura, M [National Inst. of Mater. and Chem. Res., Ibaraki (Japan); Uchida, K [National Inst. of Mater. and Chem. Res., Ibaraki (Japan); Oshima, S [National Inst. of Mater. and Chem. Res., Ibaraki (Japan); Kuriki, Y [National Inst. of Mater. and Chem. Res., Ibaraki (Japan); Yoshimura, Y [National Inst. of Mater. and Chem. Res., Ibaraki (Japan); Sato, T [National Inst. of Mater. and Chem. Res., Ibaraki (Japan); Nishijima, A [National Inst. of Mater. and Chem. Res., Ibaraki (Japan)

    1995-03-01

    The C K-edge XANES spectra of carbon nanotubes and two fullerenes are presented . The XANES of the nanotubes is quite different from those of fullerenes, but analogous to that of HOPG. The difference in the 1s{yields}{pi}{sup *} transition is discussed in conjunction with the structural features. ((orig.)).

  2. Speciation of uranium after microbial action by XANES and XPS

    International Nuclear Information System (INIS)

    Dodge, C.J.; Francis, A.J.; Lu, F.; Halada, G.P.; Kagwade, S.V.; Clayton, C.R.

    1993-01-01

    The speciation of radionuclides and toxic metals in wastes subjected to microbial action is important in determining the extent of stabilization in a disposal environment. As part of an ongoing study, we investigated the reduction of uranium by a Clostridium sp. using X-ray absorption neat edge spectroscopy (XANES) at the National Synchrotron Light Source (NSLS) and X-ray photoelectron spectroscopy (XPS). XPS analysis of uranyl acetate containing hexavalent uranium exhibited a binding energy of 382.0eV at the U 4f 7/2 peak. The sample incubated in the presence of bacteria was shifted to lower binding energy (380.6eV), confirming the reduction of U 6+ to U 4+ at the bacterial surface. XANES analysis, using an electron yield detector, was performed at the M v absorption edge (3d-->5f). The absorption peak energy of the sample exhibited a shift from 3551.1eV to 3550.1eV which is higher than uranium metal (3549.6eV ) but lower than U 4+ (3550.4eV). This indicates the presence of U 3+ which is probably located beneath the surface within the biomass. Anaerobic bacterial treatment of wastes containing uranyl ion can result in the stabilization of uranium

  3. MULTI ELEMENT SI SENSOR WITH READOUT ASIC FOR EXAFS SPECTROSCOPY.

    Energy Technology Data Exchange (ETDEWEB)

    DE GERONIMO,G.; O CONNOR,P.; BEUTTENMULLER,R.H.; LI,Z.; KUCZEWSKI,A.J.; SIDDONS,D.P.

    2002-09-09

    Extended X-ray Absorption Fine Structure (EXAFS) experiments impose stringent requirements on a detection system, due to the need for processing ionizing events at a high rate, typically above of 10Mcps/cm{sup 2}, and with a high resolution, typically better than 300eV. The detection system here presented is being developed targeting these stringent requirements. It is the result of a cooperation between the Instrumentation Division and the National Synchrotron Light Source (NSLS) of the Brookhaven National Laboratory (BNL). The system is composed of a multi-element Si sensor with dedicated per pixel electronics. The combination of high rate, high resolution and moderate complexity makes this system attractive when compared to other multi-element solutions. In sections 2, 3 and 4 the sensor, the interconnect and the electronics are briefly described. Section 5 reports on the first experimental results.

  4. Radiation damage in A-15 materials: EXAFS studies

    International Nuclear Information System (INIS)

    Knapp, G.S.; Kampwirth, R.T.; Georgopoulos, P.; Brown, B.S.

    1980-01-01

    EXAFS measurements are useful in determining the local atomic environment of a particular element in a solid. Since there has been some controversy about the nature of the defects produced in A-15 materials by radiation damage, such studies were carried out on some A-15 compounds, V 3 Ga which was damaged by neutrons, as well as Nb 3 Ge damaged by 2.5 MeV a particles. In the V 3 Ga sample, site exchange disorder seems to be the most important result of the neutron damage with less than 20% of the vanadium atoms on wrong sites. However, in the Nb 3 Ge samples in addition to site exchange disorder, an unusual splitting of the first near-neighbor distance between the Ge and Nb is found. This splitting, approximately 0.2 A, may explain the large Debye Waller factors observed by Burbank et al

  5. Vanadium K Xanes Studies of EET79001 Impact-Melt Glasses Revisited

    Science.gov (United States)

    Sutton, S. R.; Rao, M. N.; Nyquist, L. E.; Ross, D. K.

    2016-01-01

    Some impact-melt glasses in shergottites are rich in Martian atmospheric noble gases and sulfur suggesting a possible association with regolith-derived secondary mineral assemblages in the shocked samples. Previously, we studied two glasses, # 506 (Lith C in Lith A) and # 507 (Lith C in Lith B) from EET79001 [1,2] and suggested that sulfur initially existed as sulfate in the glass precursor materials and, on shock-melting of the precursors, the sulfate was reduced to sulfides in the shock glasses. To examine the validity of this hypothesis, we used V K microXANES techniques to measure the valence states of vanadium in the Lith C glasses from Lith A and Lith B in EET79001 [3] to complement and com-pare with previous analogous measurements on,78 glass (Lith C in Lith A) [4,5]. We reported the preliminary results in [3]. Vanadium is ideal for addressing the redox issue because it has multiple valence states and is a well-studied element. Vanadium in basalts exists mostly as V(sup 3+), V(sup 4+) and V(sup 5+) in terrestrial samples, mainly as V(sup 3+) with minor V(sup 2+) and minor V(sup 4+) in lunar samples and as roughly equal mixtures of V(sup 3+) and V(sup 4+) in Martian meteorites. In this report, we discuss the application of the V K XANES results to decipher the nature of shock reduction occurring in the silicate glasses during the impact process.

  6. Solution Structures of Highly Active Molecular Ir Water-Oxidation Catalysts from Density Functional Theory Combined with High-Energy X-ray Scattering and EXAFS Spectroscopy.

    Science.gov (United States)

    Yang, Ke R; Matula, Adam J; Kwon, Gihan; Hong, Jiyun; Sheehan, Stafford W; Thomsen, Julianne M; Brudvig, Gary W; Crabtree, Robert H; Tiede, David M; Chen, Lin X; Batista, Victor S

    2016-05-04

    The solution structures of highly active Ir water-oxidation catalysts are elucidated by combining density functional theory, high-energy X-ray scattering (HEXS), and extended X-ray absorption fine structure (EXAFS) spectroscopy. We find that the catalysts are Ir dimers with mono-μ-O cores and terminal anionic ligands, generated in situ through partial oxidation of a common catalyst precursor. The proposed structures are supported by (1)H and (17)O NMR, EPR, resonance Raman and UV-vis spectra, electrophoresis, etc. Our findings are particularly valuable to understand the mechanism of water oxidation by highly reactive Ir catalysts. Importantly, our DFT-EXAFS-HEXS methodology provides a new in situ technique for characterization of active species in catalytic systems.

  7. EXAFS analysis of the L3 edge of Ce in CeO2: effects of multielectron excitations and final-state mixed valence

    International Nuclear Information System (INIS)

    Fonda, E.; Andreatta, D.; Colavita, P.E.; Vlaic, G.

    1999-01-01

    Cerium oxide (IV) (CeO 2 ) is extensively employed in heterogeneous catalysis, particularly as a promoter of noble metal action in three-way catalysts. For this reason there is a great scientific and economical interest in the development of any possible chemical or structural analysis technique that could provide information on these systems. EXAFS spectroscopy has revealed itself as a powerful technique for structural characterization of such catalysts. Unfortunately, good quality K-edge spectra of cerium are not yet easily obtainable because of the high photon energy required (>40 keV). On the other hand, at lower energies it is easy to collect very good spectra of the L 3 edge (5.5 keV), but L 3 -edge spectra of cerium (IV) are characterized by the presence of two undesired additional phenomena that interfere with EXAFS analysis: final-state mixed-valence behaviour and intense multi-electron excitations. Here, a comparative analysis of the K, L 3 , L 2 and L 1 edges of Ce in CeO 2 has been made and a procedure for obtaining structural parameters from L 3 -edge EXAFS, even in the presence of these features, has been developed. This procedure could allow further studies of catalytic compounds containing tetravalent cerium surrounded by oxygen ligands. (au)

  8. Application of a high intensity laboratory X-ray source to EXAFS spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, G G; Deslattes, R D [National Bureau of Standards, Washington, DC (USA)

    1982-02-15

    A practically oriented summary for the design and operation of a high-performance laboratory EXAFS system is presented. Emphasis is on an evaluation of total system performance, including both geometrical and crystal diffraction effects.

  9. Predetermining acceptable noise limits of EXAFS spectra in the limit of stochastic noise

    International Nuclear Information System (INIS)

    Hu, Yung-Jin; Booth, Corwin H

    2009-01-01

    The effect of stochastic noise on Extended X-ray Absorption Fine Structure (EXAFS) data measurement, analysis, and fitting is discussed. Stochastic noise reduces the ability to uniquely fit a calculated model to measured EXAFS data. Such noise can be reduced by common methods that increase the signal-to-noise ratio; however, these methods are not always practical. Therefore, predetermined, quantitative knowledge of the level of acceptable stochastic noise when fitting for a particular model system is essential in maximizing the chances of a successful EXAFS experiment and minimizing wasted beamtime. This paper outlines a method to estimate, through simulation, the acceptable level of stochastic noise in EXAFS spectra that still allows a successful test of a proposed model compound.

  10. Behavior and mechanism of Ni(II) uptake on MnO2 by a combination of macroscopic and EXAFS investigation

    International Nuclear Information System (INIS)

    Guodong Sheng; Jiang Sheng; Shitong Yang; Ju Hu; Xiangke Wang

    2011-01-01

    The effects of pH, ionic strength, competing ions and initial metal concentrations on the uptake behavior and mechanism of radioactive Ni(II) onto MnO 2 was investigated using a combination of classical macroscopic methods and the extended X-ray absorption fine structure (EXAFS) spectroscopy technique. The results indicated that the uptake of Ni(II) on MnO 2 is obviously dependent on pH but independent of ionic strength, which suggested that the uptake of Ni(II) onto MnO 2 is attributed to an inner-sphere surface complex rather than an outer-sphere surface complex. EXAFS analysis shows that the hydrated Ni(II) is adsorbed through six-fold coordination with an average Ni-O interatomic distance of 2.04 ± 0.01 A. It can be inferred from the EXAFS analysis that the inner-sphere surface complex of Ni(II) onto MnO 2 is involved in both edge-sharing and corner-sharing linkages. Both the macroscopic uptake data and the molecular level evidence of Ni(II) surface speciation at the MnO 2 -water interfaces should be factored into better prediction of the bioavailability and mobility of Ni(II) in soil and water environment. (author)

  11. Combining µXANES and µXRD mapping to analyse the heterogeneity in calcium carbonate granules excreted by the earthworm Lumbricus terrestris.

    Science.gov (United States)

    Brinza, Loredana; Schofield, Paul F; Hodson, Mark E; Weller, Sophie; Ignatyev, Konstantin; Geraki, Kalotina; Quinn, Paul D; Mosselmans, J Frederick W

    2014-01-01

    The use of fluorescence full spectral micro-X-ray absorption near-edge structure (µXANES) mapping is becoming more widespread in the hard energy regime. This experimental method using the Ca K-edge combined with micro-X-ray diffraction (µXRD) mapping of the same sample has been enabled on beamline I18 at Diamond Light Source. This combined approach has been used to probe both long- and short-range order in calcium carbonate granules produced by the earthworm Lumbricus terrestris. In granules produced by earthworms cultured in a control artificial soil, calcite and vaterite are observed in the granules. However, granules produced by earthworms cultivated in the same artificial soil amended with 500 p.p.m. Mg also contain an aragonite. The two techniques, µXRD and µXANES, probe different sample volumes but there is good agreement in the phase maps produced.

  12. Microanalysis of iron oxidation state in iron oxides using X Ray Absorption Near Edge Structure (XANES)

    Science.gov (United States)

    Sutton, S. R.; Delaney, J.; Bajt, S.; Rivers, M. L.; Smith, J. V.

    1993-01-01

    An exploratory application of x ray absorption near edge structure (XANES) analysis using the synchrotron x ray microprobe was undertaken to obtain Fe XANES spectra on individual sub-millimeter grains in conventional polished sections. The experiments concentrated on determinations of Fe valence in a suite of iron oxide minerals for which independent estimates of the iron speciation could be made by electron microprobe analysis and x ray diffraction.

  13. First Ti-XANES analyses of refractory inclusions from Murchison

    International Nuclear Information System (INIS)

    Simon, S.B.; Sutton, S.R.; Grossman, L.

    2009-01-01

    Ti valence in refractory phases is an important recorder of redox conditions in the early solar nebula. We report the valence of Ti in pyroxene, spinel and hibonite in spinel-hibonite and spinel-pyroxene inclusions and in a coarse hibonite grain. A system of solar composition is so reducing that Ti 3+ and Ti 4+ can coexist, making the valence of Ti a valuable indicator of f O2 conditions during formation of nebular materials. The Ti 3+ /Ti 4+ ratios observed in the Ti-rich phases fassaite and rhoenite in coarse-grained refractory inclusions from CV3 chondrites have been shown to be quantitatively consistent with formation in a gas of solar composition (log f O2 = IW-6.8), but these are the only objects in chondrites for which this is the case. Here, we report the valence of Ti in various phases in refractory inclusions from the Murchison CM2 chondrite. The second-highest temperature, major-element-bearing phase predicted to condense from a gas of solar composition, hibonite (ideally CaAl 12 O 19 ), can contain significant amounts of Ti, but the hibonite structure can have oxygen vacancies, so calculation of Ti valence from stoichiometry of electron probe analyses is not recommended for hibonite. To date, the only reported measurement of Ti valence in meteoritic hibonite was done by electron spin resonance, on coarse crystals from a Murchison hibonite-perovskite-melilite inclusion. Spinel and most of the pyroxene in CM inclusions contain too little Ti for derivation of Ti 3+ /Ti 4+ ratios from electron probe analyses. X-ray absorption near edge spectroscopy (XANES), however, allows determination of Ti valence in relatively Ti-poor phases. In the present work, we apply synchrotron microXANES to a large hibonite grain from Murchison and to spinel-hibonite (sp-hib) and spinel-pyroxene (sp-pyx) inclusions from Murchison, refractory materials whose Ti 3+ /Ti 4+ ratios have not been previously measured. Analysis of these samples allows comparison of Ti valence of (1

  14. Polychrome glass from Etruscan sites: first non-destructive characterization with synchrotron μ-XRF, μ-XANES and XRPD

    International Nuclear Information System (INIS)

    Arletti, R.; Vezzalini, G.; Quartieri, S.; Ferrari, D.; Merlini, M.; Cotte, M.

    2008-01-01

    This work is devoted to the characterization of a suite of very rare, highly decorated and coloured glass vessels and beads from the VII to the IV century BC. The most serious difficulty in developing this study was that any sampling - even micro-sampling - was absolutely forbidden. As a consequence, the mineralogical and chemical nature of chromophores and opacifiers present in these Iron Age finds were identified by means of the following synchrotron-based, strictly non-destructive, techniques: micro X-ray fluorescence (μ-XRF), Fe K-edge micro X-ray absorption near edge spectroscopy (μ-XANES) and X-ray powder diffraction (XRPD). The μ-XRF mapping evidenced high levels of Pb and Sb in the yellow decorations and the presence of only Sb in the white and light-blue ones. Purple and black glass show high amounts of Mn and Fe, respectively. The XRPD analyses confirmed the presence of lead and calcium antimonates in yellow, turquoise and white decorations. Fe K-edge μ-XANES spectra were collected in different coloured parts of the finds, thus enabling the mapping of the oxidation state of these elements across the samples. In most of the samples iron is present in the reduced form Fe 2+ in the bulk glass of the vessels, and in the oxidized form Fe 3+ in the decorations, indicating that these glass artefacts were produced in at least two distinct processing steps under different furnace conditions. (orig.)

  15. First approach to studies of sulphur electron DOS in prostate cancer cell lines and tissues studied by XANES

    International Nuclear Information System (INIS)

    Kwiatek, Wojciech M.; Czapla, Joanna; Podgorczyk, Magdalena; Kisiel, Andrzej; Konior, Jerzy; Balerna, Antonella

    2011-01-01

    Urological cancers comprise approximately one-third of all cancers diagnosed in men worldwide and out of these, prostate cancer is the most common one (). Several risk factors such as age, hormone levels, environmental conditions and family history are suspected to play a role in the onset of this disease of otherwise obscure aetiology. It is therefore the medical need that drives multidisciplinary research in this field, carried out by means of various experimental and theoretical techniques. Out of many relevant factors, it is believed that sulphur can take an important part in cancer transformations. We have investigated the prostate cancer cell lines and tissues, along with selected organic and inorganic compounds used as references, by the X-ray absorption fine structure spectroscopy near the sulphur edge energy region. Particularly, the comparison of the experimental results collected during XANES measurements and theoretical calculations of electron density of states with use of the FEFF8 code and LAPW (linearised augmented plane-wave) method has been performed and in this work the first results of our studies are presented. - Highlights: → Different forms of sulphur has been found in prostate cancer cells. → FEFF8 code and LAPW method gave fairly good correspondence with the experiment. → LAPW is able to reproduce the fine structure of the absorption spectra. → Calculated DOS showed the influence of core atom on the shape of XANES spectra.

  16. Localization and Speciation of Arsenic in Soil and Desert Plant Parkinsonia florida using μXRF and μXANES

    Science.gov (United States)

    Castillo-Michel, Hiram; Hernandez-Viezcas, Jose; Dokken, Kenneth M.; Marcus, Matthew A.; Peralta-Videa, Jose R.; Gardea-Torresdey, Jorge L.

    2011-01-01

    Parkinsonia florida is a plant species native to the semi-desert regions of North America. The cultivation characteristics of this shrub/tree suggest that it could be used for phytoremediation purposes in semiarid regions. This work describes, through the use of synchrotron μXRF and μXANES techniques and ICP-OES, the arsenic (As) accumulation and distribution in P. florida plants grown in two soils spiked with As at 20 mg kg-1. Plants grown in a sandy soil accumulated at least twice more As in the roots compared to plants grown in a loamy soil. The lower As accumulation in plants grown in the loamy soil corresponded to a lower concentration of As in the water soluble fraction (WSF) of this soil. LC-ICP-MS speciation analysis showed only As(V) in the WSF from all treatments. In contrast, linear combination XANES speciation analysis from the root tissues showed As mainly present in the reduced As(III) form. Moreover, a fraction of the reduced As was found coordinating to S in a form consistent with As-Cys3. The percentage of As coordinated to sulfur was smaller for plants grown in the loamy soil when compared to the sandy soil. PMID:21842861

  17. Localization and speciation of arsenic in soil and desert plant Parkinsonia florida using μXRF and μXANES.

    Science.gov (United States)

    Castillo-Michel, Hiram; Hernandez-Viezcas, Jose; Dokken, Kenneth M; Marcus, Matthew A; Peralta-Videa, Jose R; Gardea-Torresdey, Jorge L

    2011-09-15

    Parkinsonia florida is a plant species native to the semidesert regions of North America. The cultivation characteristics of this shrub/tree suggest that it could be used for phytoremediation purposes in semiarid regions. This work describes, through the use of synchrotron μXRF and μXANES techniques and ICP-OES, the arsenic (As) accumulation and distribution in P. florida plants grown in two soils spiked with As at 20 mg kg(-1). Plants grown in a sandy soil accumulated at least twice more As in the roots compared to plants grown in a loamy soil. The lower As accumulation in plants grown in the loamy soil corresponded to a lower concentration of As in the water-soluble fraction (WSF) of this soil. LC-ICP-MS speciation analysis showed only As(V) in the WSF from all treatments. In contrast, linear combination XANES speciation analysis from the root tissues showed As mainly present in the reduced As(III) form. Moreover, a fraction of the reduced As was found coordinating to S in a form consistent with As-Cys(3). The percentage of As coordinated to sulfur was smaller for plants grown in the loamy soil when compared to the sandy soil.

  18. Silicon K-edge XANES spectra of silicate minerals

    Science.gov (United States)

    Li, Dien; Bancroft, G. M.; Fleet, M. E.; Feng, X. H.

    1995-03-01

    Silicon K-edge x-ray absorption near-edge structure (XANES) spectra of a selection of silicate and aluminosilicate minerals have been measured using synchrotron radiation (SR). The spectra are qualitatively interpreted based on MO calculation of the tetrahedral SiO{4/4-}cluster. The Si K-edge generally shifts to higher energy with increased polymerization of silicates by about 1.3 eV, but with considerable overlap for silicates of different polymerization types. The substitution of Al for Si shifts the Si K-edge to lower energy. The chemical shift of Si K-edge is also sensitive to cations in more distant atom shells; for example, the Si K-edge shifts to lower energy with the substitution of Al for Mg in octahedral sites. The shifts of the Si K-edge show weak correlation with average Si-O bond distance (dSi-O), Si-O bond valence (sSi-O) and distortion of SiO4 tetrahedra, due to the crystal structure complexity of silicate minerals and multiple factors effecting the x-ray absorption processes.

  19. Determination of two- and three-body correlation functions in ionic solutions by means of MD and EXAFS investigations

    International Nuclear Information System (INIS)

    D'Angelo, P.; Pavel, N.V.

    1999-01-01

    The solvation structure of Sr 2+ ions in acetonitrile has been studied by x-ray absorption spectroscopy (XAS) and molecular dynamics (MD) simulations. The extended x-ray absorption fine structure (EXAFS) above the Sr K-edge has been interpreted in the framework of the multiple scattering (MS) formalism and, for the first time, clear evidence of MS contributions has been found for non-complexing ions in solution. Molecular dynamics has been used to generate the partial pair g(r) and the three-body g(r 1 , r 2 , θ) distribution functions from which a model χ(k) has been constructed. An excellent agreement has been found between the theoretical and experimental data. This result demonstrates the ability of the XAS technique in probing three-body correlation functions in solutions. (au)

  20. The thermal behaviour of cuprite: An XRD-EXAFS combined approach

    International Nuclear Information System (INIS)

    Dapiaggi, M.; Tiano, W.; Artioli, G.; Sanson, A.; Fornasini, P.

    2003-01-01

    Cuprite (Cu 2 O) is a low thermal expansion material with a negative thermal expansion coefficient below room temperature. Its peculiar thermal behaviour encompasses the increase of the shear modulus with increasing temperature, and the presence of rather intense symmetry-forbidden eeo reflections below room temperature. The thermal expansion of cuprite was studied at low temperature (between 5 and 298 K) by means of high-resolution (10 -5 A) X-ray powder diffraction at European Synchrotron Radiation Facility (Grenoble, BM16) and extended X-ray absorption fine structure (EXAFS) (BM29). Negative thermal expansion is confirmed up to 200 K, by EXAFS as well as by XRD measurements, and no sign of transition was found in XRD data. The comparison between EXAFS and XRD results provides a valuable insight into vibrational behaviour of cuprite at low temperature

  1. Uranium speciation in 30-year old Freital mine tailings: an EXAFS, {mu}-XRD, and {mu}-XRF study

    Energy Technology Data Exchange (ETDEWEB)

    Scheinost, A.C.; Hennig, C. [Institute of Radiochemistry, FZR, D-01314 Dresden (Germany); Somogyi, A. [Synchrotron Soleil, F-91192 Gif-sur-Yvette (France); Martinez-Criado, G. [ESRF, ID-22, F-38043 Grenoble (France); Knappik, R. [VKTA Rossendorf, D-01314 Dresden (Germany)

    2005-07-01

    Full text of publication follows: Risk assessments of actinide-contaminated soils and sediments require detailed knowledge of actinide speciation and its long-term kinetics. Former Saxonian mine tailings, which have been covered but else left undisturbed, are ideally suited to study changes in uranium speciation over timescales of decades. We investigated the major uranium species in two samples from buried mine tailings using a combination of Synchrotron-based microfocus-techniques ({mu}-XRF, {mu}-XRD with micrometer resolution), bulk EXAFS spectroscopy, and chemical extractions. In sample F1 (5 m depth, oxic, pH 8, U = 440 mg/kg, high Ca, S, Pb, Cu, Zn concentrations), uranium is diffusely distributed among aggregates of layer silicates (muscovite, illite and kaolinite). The chemical extractions and EXAFS results confirm that uranium is sorbed to these minerals, but is not incorporated into their crystal structure. Sorption is also in line with the high pH and low carbonate concentrations in pore water. In sample F3 (12 m depth, oxic, pH 4, U = 430 mg/kg), the combination of {mu}-XRF and {mu}-XRD enabled us to identify several U(IV) and U(VI) containing minerals like coffinite, uraninite, uranyl hydroxide, and vanuralite. Only a minor part of U is sorbed to layer silicates as confirmed by chemical extractions and EXAFS spectroscopy. At smaller depth (F1, 5 m), sulfuric acid from the ore extraction procedure was completely neutralized by the construction waste used as cover material, resulting in precipitation of jarosite and gypsum. Even 30 years after the ore extraction, uranium remains highly soluble. At greater depth (F3, 12 m), the low pH from ore extraction was conserved. The presence of U(IV) minerals suggest either precipitation of secondary (IV) minerals due to microbial redox activity, or incomplete dissolution of primary (IV) minerals due to ore processing inefficiency of these older sediments. The U(IV) minerals were recalcitrant during chemical

  2. Uranium speciation in 30-year old Freital mine tailings: an EXAFS, μ-XRD, and μ-XRF study

    International Nuclear Information System (INIS)

    Scheinost, A.C.; Hennig, C.; Somogyi, A.; Martinez-Criado, G.; Knappik, R.

    2005-01-01

    Full text of publication follows: Risk assessments of actinide-contaminated soils and sediments require detailed knowledge of actinide speciation and its long-term kinetics. Former Saxonian mine tailings, which have been covered but else left undisturbed, are ideally suited to study changes in uranium speciation over timescales of decades. We investigated the major uranium species in two samples from buried mine tailings using a combination of Synchrotron-based microfocus-techniques (μ-XRF, μ-XRD with micrometer resolution), bulk EXAFS spectroscopy, and chemical extractions. In sample F1 (5 m depth, oxic, pH 8, U = 440 mg/kg, high Ca, S, Pb, Cu, Zn concentrations), uranium is diffusely distributed among aggregates of layer silicates (muscovite, illite and kaolinite). The chemical extractions and EXAFS results confirm that uranium is sorbed to these minerals, but is not incorporated into their crystal structure. Sorption is also in line with the high pH and low carbonate concentrations in pore water. In sample F3 (12 m depth, oxic, pH 4, U = 430 mg/kg), the combination of μ-XRF and μ-XRD enabled us to identify several U(IV) and U(VI) containing minerals like coffinite, uraninite, uranyl hydroxide, and vanuralite. Only a minor part of U is sorbed to layer silicates as confirmed by chemical extractions and EXAFS spectroscopy. At smaller depth (F1, 5 m), sulfuric acid from the ore extraction procedure was completely neutralized by the construction waste used as cover material, resulting in precipitation of jarosite and gypsum. Even 30 years after the ore extraction, uranium remains highly soluble. At greater depth (F3, 12 m), the low pH from ore extraction was conserved. The presence of U(IV) minerals suggest either precipitation of secondary (IV) minerals due to microbial redox activity, or incomplete dissolution of primary (IV) minerals due to ore processing inefficiency of these older sediments. The U(IV) minerals were recalcitrant during chemical extractions

  3. EXAFS study on dynamic structural property of porous morph-genetic SiC

    International Nuclear Information System (INIS)

    Ding, J.; Sun, B.H.; Fan, T.X.; Zhang, D.; Kamada, M.; Ogawa, H.; Guo, Q.X.

    2005-01-01

    Novel porous morph-genetic silicon carbide has been fabricated through sintering treatment, after infiltrating the methyl organic silicone resin to the bio-template. Its dynamic transition of structure during sintering process is investigated by extended X-ray absorption fine structure (EXAFS) for the first time. By analyzing Si K-edge EXAFS, it is found that the coordination number of the nearest C shell remains almost unchanged while that of the nearest Si shell dramatically changes when the structure is transformed from amorphous into crystalline state

  4. Fischer-Tropsch synthesis: study of the promotion of Pt on the reduction property of Co/Al2O3 catalysts by in situ EXAFS of Co K and Pt LIII edges and XPS

    International Nuclear Information System (INIS)

    Jacobs, G.; Chaney, J.A.; Patterson, P.M.; Das, T.K.; Maillot, J.C.; Davis, B.H.

    2004-01-01

    The addition of platinum metal to cobalt/alumina-based Fischer-Tropsch synthesis (FTS) catalysts increases both the reduction rate and, consequently, the density of active cobalt sites. Platinum also lowers the temperature of the two-step conversion of cobalt oxide to cobalt metal observed in temperature programmed reduction (TPR) as Co 3 O 4 to CoO and CoO to Co 0 . The interaction of the alumina support with cobalt oxide ultimately determines the active site density of the catalyst surface. This interaction can be controlled by varying the cobalt loading and dispersion, selecting supports with differing surface areas or pore sizes, or changing the noble metal promoter. However, the active site density is observed to depend primarily on the cluster size and extent of reduction, and there is a direct relationship between site density and FTS rate. In this work, in situ extended X-ray absorption fine structure (EXAFS) at the L III edge of Pt was used to show that isolated Pt atoms interact with supported cobalt clusters without forming observable Pt-Pt bonds. K-edge EXAFS was also used to verify that the cobalt cluster size increases slightly for those systems with Pt promotion. X-ray absorption near-edge spectroscopy (XANES) was used to examine the remaining cobalt clusters after the first stage of TPR, and it revealed that the species were almost entirely cobalt (II) oxide. After the second stage of TPR to form cobalt metal, a residual oxide persists in the sample, and this oxide has been identified as cobalt (II) aluminate using X-ray photoelectron spectroscopy (XPS). Sequential in situ reduction of promoted and unpromoted systems was also monitored through XPS, and Pt was seen to increase the extent of cobalt reduction by a factor of two. (orig.)

  5. Reactions of SO 2 on hydrated cement particle system for atmospheric pollution reduction: A DRIFTS and XANES study

    Energy Technology Data Exchange (ETDEWEB)

    Ramakrishnan, Girish; Wu, Qiyuan; Moon, Juhyuk; Orlov, Alexander

    2017-07-01

    An investigation of the adsorptive property of hydrated cement particle system for sulfur dioxide (SO2) removal was conducted. In situ and ex situ experiments using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) and X-ray Absorption Near Edge Spectroscopy (XANES) characterization techniques were employed to identify surface species formed during the exposure to SO2. Oxidation of SO2 to sulfate and sulfite species observed during these experiments indicated dominant reaction pathways for SO2 reaction with concrete constituents, such as calcium hydroxide, which were also moderated by adsorption on porous surfaces of crushed aggregates. The impact of variable composition of concrete on its adsorption capacity and reaction mechanisms was also proposed in this work.

  6. PREFACE: Proceedings of the First International Workshop on the Theoretical Calculation of ELNES and XANES (TEX2008) (Nagoya, Japan, 2-4 July 2008) Proceedings of the First International Workshop on the Theoretical Calculation of ELNES and XANES (TEX2008) (Nagoya, Japan, 2-4 July 2008)

    Science.gov (United States)

    Tanaka, Isao; Mizoguchi, Teruyasu; Yamamoto, Tomoyuki

    2009-03-01

    -or-less independently by the two communities. The three-day workshop on the Theoretical Calculation of ELNES and XANES (TEX2008) was planned to help remedy this situation. It aimed to demonstrate capability of state-of-the-art theoretical techniques to explain and predict ELNES and XANES spectra, and to allow deep discussion between scientists in the two communities. It also provided an excellent opportunity to introduce experimentalists to the computational techniques available. Invited talks and poster presentations by leading scientists were given on the first day, which was followed by tutorial sessions for five computer programs on the second and third days. Excellent lectures were given by Peter Blaha (Vienna, Austria) on the WIEN2k code, Chris J Pickard (St Andrews, UK) on the CASTEP code, John J Rehr (Seattle, USA) on the FEFF8 code, Frank de Groot (Utrecht, The Netherlands) on the CTM4XAS code, and Hidekazu Ikeno (Kyoto, Japan) on the first-principles CI-multiplet code. Thanks to the enthusiastic participation of more than 100 scientists from around the world, the workshop was a complete success. The aim of this special issue in Journal of Physics: Condensed Matter is to share with the readers the most up-to-date knowledge presented at the workshop. We believe this will prove useful as a reference for researchers in many different fields, as well as an overview of the current status and future directions of theoretical calculations for ELNES and XANES. TEX2008 was a satellite meeting of the First International Symposium on Advanced Microscopy and Theoretical Calculations (AMTC1) (Nagoya, Japan, 29-30 June 2008), which was held in commemoration of the establishment of the Nanostuctures Research Laboratory (NSRL) at the Japan Fine Ceramics Center (JFCC) and as a daughter event of EXPO 2005, Aichi, Japan. A Grant-in-Aid for Scientific Research on Priority Areas 'Nano Materials Science for Atomic-Scale Modification' from the Ministry of Education, Culture, Sports and Technology

  7. Structural characterization of Am(III) formate complexes. Combining EXAFS spectroscopy with DFT and thermodynamical calculations

    Energy Technology Data Exchange (ETDEWEB)

    Rossberg, Andre [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Molecular Structures; Froehlich, D.R. [Heidelberg Univ. (Germany). Physikalisch-Chemisches Inst.

    2017-06-01

    We used iterative transformation factor analysis (ITFA) in order to isolate the EXAFS spectral contributions of the complexing ligand from a Am(III)/formate pH-series. Thermodynamic calculations were used as constraint for ITFA and for density functional theory (DFT) calculations to identify the coordination mode within the formed complexes.

  8. EXAFS study of Mo2N and Mo nitrides supported on zeolites

    International Nuclear Information System (INIS)

    Liu Zhenlin; Meng Ming; Fu Yilu; Jiang Ming; Hu Tiandou; Xie Yaning; Liu Tao

    2002-01-01

    In the present study, the reaction is applied to prepare molybdenum nitrides with high surface area, and zeolites are used as supports. The EXAFS of the Mo K-absorption edge is measured and the change of coordination environment of Mo atoms before and after the nitridation is revealed

  9. The structural analysis of zinc borate glass by laboratory EXAFS and X-ray diffraction measurements

    International Nuclear Information System (INIS)

    Kajinami, Akihiko; Harada, Yasushi; Inoue, Shinsuke; Deki, Shigehito; Umesaki, Norimasa

    1999-01-01

    The structure of zinc borate glass has been investigated by laboratory EXAFS and X-ray diffraction measurement as preliminary investigations for the detailed study in SPring-8. The zinc borate glass was prepared in the range from 40 to 65 mol% of zinc oxide content. The X-ray diffraction was measured by horizontal θ-θ goniometer with 60 kV and 300 mA output of Mo target. The EXAFS of zinc borate glass was measured by laboratory EXAFS system with 20 kV, 100 mA output of Mo target for the K absorption edge of zinc atom. From the X-ray diffraction and the EXAFS measurements, it is found that the zinc ion is surrounded by four oxygen atoms and formed a tetrahedral structure whose (Zn-O) distance is about 2 A and that the structure is unchanged with the zinc oxide content. The diffraction data show that the neighboring structure of boron atom transforms from BO 4 tetrahedra to BO 3 tetragonal planar structure with increasing of the zinc oxide content. (author)

  10. 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)

  11. 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)

  12. Pressure-induced coordination change of Ti in silicate glass: a XANES study

    OpenAIRE

    Paris, Eleonora; Dingwell, Donald B.; Seifert, Friedrich; Mottana, Annibale; Romano, Claudia

    1994-01-01

    The effect of pressure on titanium coordination in glasses, with composition K2TiSi4O11, quenched isobarically from liquids equilibrated at high pressure (5, 10, 15, 20, 25, 30 kbar respectively) and T=1600° C has been investigated by X-ray absorption spectroscopy (XAS). The XANES spectra collected at the Ti K-edge clearly show a variation with pressure that is related to changes in the geometrical environment around the Ti atoms. By comparison with spectra of standard materials, the XANES sp...

  13. Europium-151 Moessbauer spectroscopic and XANES investigation of europium-exchanged Y-zeolite

    International Nuclear Information System (INIS)

    Berry, F.J.; Marco, J.F.; Steel, A.T.

    1994-01-01

    Eu 3+ in ca. 10 wt% europium-exchanged Y-zeolite is partially reduced by treatment in hydrogen at 600 C to Eu 2+ . The reduction of Eu 3+ is more readily achieved in Y-zeolite than in europium(III) oxide. The discrepancy in the extent of reduction as revealed by 151 Eu Moessbauer spectroscopy and near edge X-ray absorption fine structure (XANES) is associated with any difference in the recoil free fractions of Eu 2+ and Eu 3+ which may exist at 298 K and the enhanced sensitivity of the XANES to changes in the europium oxidation state. (orig.)

  14. PySpline: A Modern, Cross-Platform Program for the Processing of Raw Averaged XAS Edge and EXAFS Data

    International Nuclear Information System (INIS)

    Tenderholt, Adam; Hedman, Britt; Hodgson, Keith O.

    2007-01-01

    PySpline is a modern computer program for processing raw averaged XAS and EXAFS data using an intuitive approach which allows the user to see the immediate effect of various processing parameters on the resulting k- and R-space data. The Python scripting language and Qt and Qwt widget libraries were chosen to meet the design requirement that it be cross-platform (i.e. versions for Windows, Mac OS X, and Linux). PySpline supports polynomial pre- and post-edge background subtraction, splining of the EXAFS region with a multi-segment polynomial spline, and Fast Fourier Transform (FFT) of the resulting k3-weighted EXAFS data

  15. Spatially resolved sulfur K-edge XANES spectroscopy of wheat leaves infected by Puccinia triticina

    International Nuclear Information System (INIS)

    Lichtenberg, H; Prange, A; Hormes, J; Steiner, U; Oerke, E-C

    2009-01-01

    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.

  16. 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.

  17. Probability density of wave function of excited photoelectron: understanding XANES features

    Czech Academy of Sciences Publication Activity Database

    Šipr, Ondřej

    2001-01-01

    Roč. 8, - (2001), s. 232-234 ISSN 0909-0495 R&D Projects: GA ČR GA202/99/0404 Institutional research plan: CEZ:A02/98:Z1-010-914 Keywords : XANES * PED - probability density of wave function Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.519, year: 2001

  18. Universal energy-dispersive EXAFS spectrometer based on SR beam of `Kurchatovskij Institute` and scientific program of investigations; Universal`nyj ehnergodispersionnyj EXAFS-spektrometr v Natsional`nom tsentre sinkhrotronnogo izlucheniya (`Kurchatovskij institut`) i nauchnaya programma issledovanij

    Energy Technology Data Exchange (ETDEWEB)

    Aksenov, V L; Ivanov, I N [Laboratory of Particle Physics, Joint Institute for Nuclear Research, Dubna (Russian Federation); Koval` chuk, M V [Institut Kristallografii, RAN, Moscow (Russian Federation); and others

    1997-12-31

    The scheme of the energy-dispersive EXAFS spectrometer is discussed. The spectrometer will be used for the solid state investigations on the Kurchatov Synchrotron Radiation Source KSRS. The main elements of the universal station are described, including the results of the positive-sensitive X-ray detector testing. The experimental investigations are presented which are supposed to be carried out with this EXAFS spectrometer. (author). 4 refs., 14 figs., 1 tab. Submitted to Poverkhnost`. Rentgenovskie, Sinkhrotronnye i Nejtronnye Issledovaniya.

  19. Correlated XANES, TEM, and NanoSIMS of presolar graphite grains

    Science.gov (United States)

    Groopman, Evan E.; Nittler, Larry R.

    2018-01-01

    We report correlated XANES, TEM, and NanoSIMS measurements of twelve presolar graphite grains extracted from primitive meteorites and for which isotopic data indicate predominantly Type-II supernovae origins. We find continued evidence for isotopic heterogeneities in presolar graphite grains, including the first observation of a radial gradient in the inferred initial 26Al/27Al within a presolar graphite grain. The XANES spectra of these samples show a variety of minor absorbances near the C K-edge, attributable to vinyl-keto, aliphatic, carboxyl, and carbonate molecules, as well as possible damage during sample preparation. Each sample exhibits homogeneous C K-edge XANES spectra within the graphite, however, showing no correlation with isotopic heterogeneities. Gradients in the isotope ratios of C, N, O, and Al could be due to both processes during condensation, e.g., mixing in stellar ejecta and granular transport, and post-condensation effects, such as isotope dilution and exchange with isotopically normal material in the early Solar System or laboratory, the latter of which is a significant issue for high-density presolar graphite grains. It remains unknown whether the mechanisms behind isotope exchange would also affect the local chemistry and therefore the XANES spectra. Ti L-edge XANES from most Ti-rich subgrains match standard spectra for TiC and potentially TiCN. A rare rutile (TiO2) subgrain has been identified, though it lacks the lowest energy L3 peak typically seen in standard spectra. Ca has also been identified by EDXS in TiC subgrains, likely due to the decay of live 44Ti at the time of formation. Future NanoSIMS measurements will determine the variability of initial 44Ti in TiC subgrains, an important constraint on mixing in the ejecta of the grains' parent supernovae.

  20. Diamond xenolith and matrix organic matter in the Sutter's Mill meteorite measured by C-XANES

    Science.gov (United States)

    Kebukawa, Yoko; Zolensky, Michael E.; Kilcoyne, A. L. David; Rahman, Zia; Jenniskens, Peter; Cody, George D.

    2014-11-01

    The Sutter's Mill (SM) meteorite fell in El Dorado County, California, on April 22, 2012. This meteorite is a regolith breccia composed of CM chondrite material and at least one xenolithic phase: oldhamite. The meteorite studied here, SM2 (subsample 5), was one of three meteorites collected before it rained extensively on the debris site, thus preserving the original asteroid regolith mineralogy. Two relatively large (10 μm sized) possible diamond grains were observed in SM2-5 surrounded by fine-grained matrix. In the present work, we analyzed a focused ion beam (FIB) milled thin section that transected a region containing these two potential diamond grains as well as the surrounding fine-grained matrix employing carbon and nitrogen X-ray absorption near-edge structure (C-XANES and N-XANES) spectroscopy using a scanning transmission X-ray microscope (STXM) (Beamline 5.3.2 at the Advanced Light Source, Lawrence Berkeley National Laboratory). The STXM analysis revealed that the matrix of SM2-5 contains C-rich grains, possibly organic nanoglobules. A single carbonate grain was also detected. The C-XANES spectrum of the matrix is similar to that of insoluble organic matter (IOM) found in other CM chondrites. However, no significant nitrogen-bearing functional groups were observed with N-XANES. One of the possible diamond grains contains a Ca-bearing inclusion that is not carbonate. C-XANES features of the diamond-edges suggest that the diamond might have formed by the CVD process, or in a high-temperature and -pressure environment in the interior of a much larger parent body.

  1. Characterization of iron speciation in urban and rural single particles using XANES spectroscopy and micro X-ray fluorescence measurements: investigating the relationship between speciation and fractional iron solubility

    OpenAIRE

    Oakes, M.; Weber, R. J.; Lai, B.; Russell, A.; Ingall, E. D.

    2012-01-01

    Soluble iron in fine atmospheric particles has been identified as a public health concern by participating in reactions that generate reactive oxygen species (ROS). The mineralogy and oxidation state (speciation) of iron have been shown to influence fractional iron solubility (soluble iron/total iron). In this study, iron speciation was determined in single particles at urban and rural sites in Georgia USA using synchrotron-based techniques, such as X-ray Absorption Near-Edge Structure (XANES...

  2. Use of X-ray absorption near edge structure (XANES) to identify physisorption and chemisorption of phosphate onto ferrihydrite-modified diatomite.

    Science.gov (United States)

    Xiong, Wenhui; Peng, Jian; Hu, Yongfeng

    2012-02-15

    This paper presents a novel technique integrating bulk-sensitive and surface-sensitive XANES methods to distinguish between physisorption and chemisorption for phosphate adsorption onto ferrihydrite-modified diatomite (FHMD). XANES P K-edge, L-edge, and Fe M-edge spectra were obtained for reference samples (K(2)HPO(4) and FePO(4)·2H(2)O) and test samples (phosphate adsorbed onto FHMD (FHMD-Ps) and Si-containing ferrihydrite (FHYD-Ps)). A resolvable pre-edge peak in the P K-edge spectra of FHMD-Ps and FHYD-Ps provided direct evidence for the formation of P-O-Fe(III) coordination and the occurrence of chemisorption. The resemblance between the P L-edge spectra of K(2)HPO(4) and FHMD-Ps and the marked difference between the spectra of FHMD-Ps and FePO(4)·2H(2)O indicated the intact existence of the adsorbate and the adsorbent. The similarity between Fe M-edge spectra of FHMD and FHMD-Ps and the difference between the spectra of FHMD-Ps and FePO(4)·2H(2)O confirmed the findings from P L-edge analyses. Therefore, chemisorption and physisorption coexisted during phosphate adsorption onto FHMD. Phosphate chemisorption occurred in the deeper zone of FHMD (from 50 nm to 5 μm); whereas physisorption occurred in the zone of FHMD shallower than 50 nm since the probing depth of XANES P K-edge method is 5 μm and that of P L-edge and Fe M-edge methods is 50 nm. Copyright © 2011 Elsevier Inc. All rights reserved.

  3. Iodine K-edge EXAFS analysis of iodide ion-cyclodextrin inclusion complexes in aqueous solution

    International Nuclear Information System (INIS)

    Kaneko, T; Ueda, M; Nagamatsu, S; Konishi, T; Fujikawa, T; Mizumaki, M

    2009-01-01

    We study the structure of inclusion complexes of α-, β-, γ-cyclodextrin with mono-iodide ion in aqueous solution by means of iodine K-edge EXAFS spectroscopy. The analysis is based on the assumption that two kinds of iodide ions exist in KI-cyclodextrin aqueous solution i.e. hydrated mono-iodide ions and one-one mono-iodide-cyclodextrin inclusion complexes. In KI-α-cyclodextrin system, iodine K-edge EXAFS analyse show that the average coordination number of the oxygen atoms in water molecules in the first hydration shell decreases as the fraction of included ions increases. This result suggests that dehydration process accompanies the formation of the inclusion complex. This is not found in the case of β-cyclodextrin, indicating that in this case the iodide ions are included together with the whole first hydration shell.

  4. EXAFS study influence of pH on microscopic structure of zinc

    International Nuclear Information System (INIS)

    Li Xianliang; Chongqing Entry-Exit Inspection and Quarantine Bureau, Chongqing; Pan Gang; Zhu Mengqiang; Chen Hao; Hu Tiandou; Wu Ziyu; Xie Yaning; Du Yonghua

    2004-01-01

    Microscopic local structures of Zn(II) were studied using extended X-ray absorption fine structure (EXAFS) spectroscopy under different pH conditions. When pH 2+ (aq) was coordinated with six water molecules and the average Zn-O distance was measured to be 2.08 Angstrom, which indicated that hydrated Zn 2+ (aq) ions were in octahedral geometry under acid conditions. Under alkaline conditions, Zn 2+ (aq) was coordinated with four water molecules and the average Zn-O distance was measured to be 1.96 Angstrom, which indicated that hydrated Zn 2+ (aq) ions were in tetrahedral geometry. EXAFS results provided detailed information on the form and microscopic structure of hydrated Zn(II) ions under different pH conditions, which were fundamental for understanding the reactivity of Zn(II) in solutions and at particle-water interfaces. (authors)

  5. Commissioning and first results of scanning type EXAFS beamline (BL-09) at INDUS-2 synchrotron source

    Energy Technology Data Exchange (ETDEWEB)

    Poswal, A. K., E-mail: poswalashwini@gmail.com; Agrawal, A., E-mail: poswalashwini@gmail.com; Yadav, A. K., E-mail: poswalashwini@gmail.com; Nayak, C., E-mail: poswalashwini@gmail.com; Basu, S., E-mail: poswalashwini@gmail.com; Bhattachryya, D.; Jha, S. N.; Sahoo, N. K. [Atomic and Molecular Physics Division, Bhabha Atomic Research Centre, Mumbai -400085 (India); Kane, S. R.; Garg, C. K. [Indus Synchrotrons Utilization Division, Raja Ramanna Centre for Advanced Technology, Indore- 452013 (India)

    2014-04-24

    An Energy Scanning X-ray Absorption Fine Structure spectroscopy beamline has recently been installed and commissioned at BL-09 bending magnet port of INDUS-2 synchrotron source, Indore. The beamline uses an UHV compatible fixed exit double crystal monochromator (DCM) with two Si (111) crystals. Two grazing incidence cylindrical mirrors are also used in this beamline; the pre-mirror is used as a collimating mirror while the post mirror is used for vertical focusing and higher harmonic rejection. In this beamline it is possible to carry out EXAFS measurements both in transmission and fluorescence mode on various types of samples, using Ionization chamber detectors and solid state drift detector respectively. In this paper, results from first experiments of the Energy Scanning EXAFS beamline are presented.

  6. Removal of Cu from aqueous solutions by synthetic hydroxyapatite: EXAFS investigation

    International Nuclear Information System (INIS)

    Corami, Alessia; D'Acapito, Francesco; Mignardi, Silvano; Ferrini, Vincenzo

    2008-01-01

    The sorption of aqueous Cu on synthetic hydroxyapatite has been investigated by means of the results of a combined structural simulation and extended X-ray absorption fine structure (EXAFS) analysis. The removal of Cu was studied in batch experiments at 25 ± 2 deg. C. The sorption of Cu follows Langmuir behaviour and was attributed to a two-step mechanism involving surface complexation and ion exchange with Ca resulting in the formation of a copper-containing hydroxyapatite. EXAFS results suggest that the heavy metal is present in the Cu 2+ form. The structural experimental and theoretical analysis shows that Cu is bond to about four O atoms at a distance of about 1.95 A. In all the studied cases the immobilization site of Cu is the same. The fixation of Cu occurs in the surface sites of hydroxyapatite whereas the sorption in the Ca sites in the inner part of the structure is unlikely

  7. A gas microstrip X-ray detector for soft energy fluorescence EXAFS

    CERN Document Server

    Smith, A D; Derbyshire, G E; Duxbury, D M; Lipp, J; Spill, E J; Stephenson, R

    2001-01-01

    Gas microstrip detectors have been previously developed by the particle physics community, where their robustness, compactness and high counting speed have been recognised. These features are particularly attractive to synchrotron radiation use. In this paper, we describe a gas microstrip detector employing multi-element readout and specifically developed for high count rate fluorescence EXAFS at soft X-ray energies below 4 keV.

  8. EXAFS and RDF studies of Ge27S53I20 glass

    International Nuclear Information System (INIS)

    Nasu, H.; Myoren, H.; Makida, S.; Imura, T.; Osaka, Y.

    1988-01-01

    Detailed X-ray diffraction measurements and extended X-ray absorption fine structure (EXAFS) have been applied to Ge 23 S 57 I 20 glass as a typical chalcohalide glass and to GeS 2 glass for comparison, in order to investigate the structure of Ge-S-I glass system. From the derived curves against atomic distance, the formation of Ge-I bonds is evidenced in the glass structure. (author) 4 refs., 2 figs., 1 tab

  9. Interaction between crystal lattice and mobile ions in copper selenides studied by EXAFS spectroscopy

    International Nuclear Information System (INIS)

    Asylgushina, G.N.; Bikkulova, N.N.; Titova, S.G.; Kochubey, D.I.

    2005-01-01

    Interaction between crystal lattice and mobile Cu ions has been studied in Cu 2- x Se in superionic and in normal state using EXAFS-spectroscopy. It has been found that the transition from normal to superionic state and change of mobile Cu ion concentration practically do not have an influence on local state of Cu atoms, but change of both these parameters is accompanied by a change of Se-sublattice state

  10. EXAFS study of the stability of amorphous TbFe thin films

    International Nuclear Information System (INIS)

    Samant, M.G.; Marinero, E.E.; Robinson, C.; Cargill, G.S.

    1989-01-01

    This paper discusses the measurement of the local atomic structure of Fe in Au doped Tb-Fe thin film alloys by the use of EXAFS. The as deposited sample shows structural features which are essentially identical to those of the undoped films. Au additions stabilizes the amorphous structure against recrystallization, however, the loss of magnetic anisotropy under thermal annealing is not reduced. This demonstrates that magnetic relaxation in these alloys does not involve crystallization of the amorphous structure

  11. Selenium Sequestration in a Cationic Layered Rare Earth Hydroxide: A Combined Batch Experiments and EXAFS Investigation.

    Science.gov (United States)

    Zhu, Lin; Zhang, Linjuan; Li, Jie; Zhang, Duo; Chen, Lanhua; Sheng, Daopeng; Yang, Shitong; Xiao, Chengliang; Wang, Jianqiang; Chai, Zhifang; Albrecht-Schmitt, Thomas E; Wang, Shuao

    2017-08-01

    Selenium is of great concern owing to its acutely toxic characteristic at elevated dosage and the long-term radiotoxicity of 79 Se. The contents of selenium in industrial wastewater, agricultural runoff, and drinking water have to be constrained to a value of 50 μg/L as the maximum concentration limit. We reported here the selenium uptake using a structurally well-defined cationic layered rare earth hydroxide, Y 2 (OH) 5 Cl·1.5H 2 O. The sorption kinetics, isotherms, selectivity, and desorption of selenite and selenate on Y 2 (OH) 5 Cl·1.5H 2 O at pH 7 and 8.5 were systematically investigated using a batch method. The maximum sorption capacities of selenite and selenate are 207 and 124 mg/g, respectively, both representing the new records among those of inorganic sorbents. In the low concentration region, Y 2 (OH) 5 Cl·1.5H 2 O is able to almost completely remove selenium from aqueous solution even in the presence of competitive anions such as NO 3 - , Cl - , CO 3 2- , SO 4 2- , and HPO 4 2- . The resulting concentration of selenium is below 10 μg/L, well meeting the strictest criterion for the drinking water. The selenate on loaded samples could be desorbed by rinsing with concentrated noncomplexing NaCl solutions whereas complexing ligands have to be employed to elute selenite for the material regeneration. After desorption, Y 2 (OH) 5 Cl·1.5H 2 O could be reused to remove selenate and selenite. In addition, the sorption mechanism was unraveled by the combination of EDS, FT-IR, Raman, PXRD, and EXAFS techniques. Specifically, the selenate ions were exchanged with chloride ions in the interlayer space, forming outer-sphere complexes. In comparison, besides anion exchange mechanism, the selenite ions were directly bound to the Y 3+ center in the positively charged layer of [Y 2 (OH) 5 (H 2 O)] + through strong bidentate binuclear inner-sphere complexation, consistent with the observation of the higher uptake of selenite over selenate. The results presented in

  12. Self-consistent EXAFS PDF Projection Method by Matched Correction of Fourier Filter Signal Distortion

    International Nuclear Information System (INIS)

    Lee, Jay Min; Yang, Dong-Seok

    2007-01-01

    Inverse problem solving computation was performed for solving PDF (pair distribution function) from simulated data EXAFS based on data FEFF. For a realistic comparison with experimental data, we chose a model of the first sub-shell Mn-0 pair showing the Jahn Teller distortion in crystalline LaMnO3. To restore the Fourier filtering signal distortion, involved in the first sub-shell information isolated from higher shell contents, relevant distortion matching function was computed initially from the proximity model, and iteratively from the prior-guess during consecutive regularization computation. Adaptive computation of EXAFS background correction is an issue of algorithm development, but our preliminary test was performed under the simulated background correction perfectly excluding the higher shell interference. In our numerical result, efficient convergence of iterative solution indicates a self-consistent tendency that a true PDF solution is convinced as a counterpart of genuine chi-data, provided that a background correction function is iteratively solved using an extended algorithm of MEPP (Matched EXAFS PDF Projection) under development

  13. EXAFS Study on LiFePO4 Powders Produced From Two Sol-Gel Routes

    Science.gov (United States)

    Negara, V. S. I.; Latif, C.; Wongtepa, W.; Pratapa, S.

    2018-04-01

    The local structure of LiFePO4 powders has been investigated using Fe K-edge Extended X-Ray Absorption Fine Structure (EXAFS) Spectroscopy data. The synthesis of LFP powders was carried out using two different sol-gel methods. The raw materials for Fe source were ironstone and commercial precursor of FeCl2·4H2O. Synthesis using natural materials produced two phases, namely LiFePO4 olivine and Li3Fe2(PO4)3 nasicon, whereas that using a commercial product produced a single phase of LiFePO4 olivine. The EXAFS data for both samples were collected at Synchrotron Light Research Institute (SLRI), Thailand. Fitting of the model on the experimental curve provided parameters that can be interpreted as the distance between Fe as the absorber and the nearest atoms on the LFP materials. The EXAFS data analysis has shown that synthesis of LFPs using different Fe sources gives slightly different nearest-neighbor distances, namely Fe-O of 0.21% -0.23%, Fe-P of 0.14% - 0.16%, Fe-Fe of 0.12% for both samples, respectively.

  14. Diversity in C-Xanes Spectra Obtained from Carbonaceous Solid Inclusions from Monahans Halite

    Science.gov (United States)

    Kebukawa, Y.; Zolensky, M. E.; Fries, M.; Kilcoyne, A. L. D.; Rahman, Z.; Cody, G. D.

    2014-01-01

    Monahans meteorite (H5) contains fluid inclusion- bearing halite (NaCl) crystals [1]. Microthermometry and Raman spectroscopy showed that the fluid in the inclusions is an aqueous brine and they were trapped near 25degC [1]. Their continued presence in the halite grains requires that their incorporation into the H chondrite asteroid was post metamorphism [2]. Abundant solid inclusions are also present in the halites. The solid inclusions include abundant and widely variable organics [2]. Analyses by Raman microprobe, SEM/EDX, synchrotron X-ray diffraction and TEM reveal that these grains include macromolecular carbon similar in structure to CV3 chondrite matrix carbon, aliphatic carbon compounds, olivine (Fo99-59), high- and low-Ca pyroxene, feldspars, magnetite, sulfides, lepidocrocite, carbonates, diamond, apatite and possibly the zeolite phillipsite [3]. Here we report organic analyses of these carbonaceous residues in Monahans halite using C-, N-, and O- X-ray absorption near edge structure (XANES). Samples and Methods: Approximately 100 nm-thick sections were extracted with a focused ion beam (FIB) at JSC from solid inclusions from Monahans halite. The sections were analyzed using the scanning transmission X-ray microscope (STXM) on beamline 5.3.2.2 at the Advanced Light Source, Lawrence Berkeley National Laboratory for XANES spectroscopy. Results and Discussion: C-XANES spectra of the solid inclusions show micrometer-scale heterogeneity, indicating that the macromolecular carbon in the inclusions have complex chemical variations. C-XANES features include 284.7 eV assigned to aromatic C=C, 288.4-288.8 eV assigned to carboxyl, and 290.6 eV assigned to carbonate. The carbonyl features obtained by CXANES might have been caused by the FIB used in sample preparation. No specific N-XANES features are observed. The CXANES spectra obtained from several areas in the FIB sections include type 1&2 chondritic IOM like, type 3 chondritic IOM like, and none of the above

  15. K-XANES study of YBa2Cu3O6.96 system

    International Nuclear Information System (INIS)

    Mishra, A.; Varshney, D.; Shivkumar, K.M.; Pandey, D.

    1998-01-01

    The copper K-edge x-ray absorption near edge structure (XANES) has been recorded in both CuO and YBaCuO samples on Cauchois type spectrograph with 0.4 m radius of curvature and a laboratory source of x-rays. The sample of YBa 2 Cu 3 ) 6.96 (T c =91K) were prepared by solid state route. The Cu K-XANES measurements were made on the powdered sample. The x-ray parameters, e.g., K-edge shift (ΔE k ), shift of principal absorption maximum (δE K ) and edge-width (δE A ) with reference to metal K-edge have been reported. The value of edge-shift of YBaCuO is larger than parent CuO. Also the smaller value of edge-width in YBaCuO is indicative of its ionic character. (author)

  16. Spectral Analysis by XANES Reveals that GPNMB Influences the Chemical Composition of Intact Melanosomes

    Energy Technology Data Exchange (ETDEWEB)

    T Haraszti; C Trantow; A Hedberg-Buenz; M Grunze; M Anderson

    2011-12-31

    GPNMB is a unique melanosomal protein. Unlike many melanosomal proteins, GPNMB has not been associated with any forms of albinism, and it is unclear whether GPNMB has any direct influence on melanosomes. Here, melanosomes from congenic strains of C57BL/6J mice mutant for Gpnmb are compared to strain-matched controls using standard transmission electron microscopy and synchrotron-based X-ray absorption near-edge structure analysis (XANES). Whereas electron microscopy did not detect any ultrastructural changes in melanosomes lacking functional GPNMB, XANES uncovered multiple spectral phenotypes. These results directly demonstrate that GPNMB influences the chemical composition of melanosomes and more broadly illustrate the potential for using genetic approaches in combination with nano-imaging technologies to study organelle biology.

  17. Local structural disorder in REFeAsO oxypnictides by RE L3 edge XANES

    International Nuclear Information System (INIS)

    Xu, W; Chu, W S; Wu, Z Y; Marcelli, A; Di Gioacchino, D; Joseph, B; Iadecola, A; Bianconi, A; Saini, N L

    2010-01-01

    The REFeAsO (RE = La, Pr, Nd and Sm) system has been studied by RE L 3 x-ray absorption near edge structure (XANES) spectroscopy to explore the contribution of the REO spacers between the electronically active FeAs slabs in these materials. The XANES spectra have been simulated by full multiple scattering calculations to describe the different experimental features and their evolution with the RE size. The near edge feature just above the L 3 white line is found to be sensitive to the ordering/disordering of oxygen atoms in the REO layers. In addition, shape resonance peaks due to As and O scattering change systematically, indicating local structural changes in the FeAs slabs and the REO spacers due to RE size. The results suggest that interlayer coupling and oxygen order/disorder in the REO spacers may have an important role in the superconductivity and itinerant magnetism of the oxypnictides.

  18. 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.

  19. Indium local geometry in In-Sb-Te thin films using XANES and DFT calculations

    Science.gov (United States)

    Bilovol, V.; Gil Rebaza, A. V.; Mudarra Navarro, A. M.; Errico, L.; Fontana, M.; Arcondo, B.

    2017-12-01

    In-Sb-Te when is a thin film presents a huge difference in its electrical resistivity when transform from the amorphous (insulating) to the crystalline (conducting) phase. This property made this system one of the main phase-change materials used in the data storage industry. The change in the electrical conductivity is probably associated to a change in the bonding geometry of some of its constituents. To explore this point, we present in this work an study of the bonding geometry of In atoms in In-Sb-Te films by means of In K-edge X-ray absorption near edge structure (XANES) spectroscopy using synchrotron radiation in both as deposited (amorphous) and crystalline thin films obtained as a result of resistance (R) vs temperature (T) measurements. Comparison of the XANES spectra obtained for ternary amorphous films and binary crystalline reference films suggests that in amorphous films the bonding geometry of In atoms is tetrahedral-like. After the thermal annealing has been carried out the differences in the XANES spectra of the as deposited and the annealed films indicate that the bonding geometry of In atoms changes. Based on X-ray diffraction results and ab initio calculations in the framework of the Density Functional Theory (DFT) we show that the new coordination geometry is associated with a tendency of In atoms towards octahedral-like.

  20. EXAFS investigation of uranium(6) complexes formed at Acidithiobacillus ferro oxidans types

    International Nuclear Information System (INIS)

    Merroun, M.; Reich, T.; Hennig, Ch.; Selenska-Pobell, S.

    2002-01-01

    Mining activities have brought excessive amounts of uranium into the environment. In uranium deposits a number of acidophilic chemo-litho-autotrophic bacteria have been identified which are able to oxidize sulphide minerals, elemental sulphur, ferrous iron and also (in the presence of uranium mineral) U(IV). In particular, the interaction of one representative of the group Acidithiobacillus ferro oxidans (new designation of Thiobacillus ferro oxidans) with uranium has been investigated. Uranium(VI) complex formations at the surfaces of Acidithiobacillus ferro oxidans were studied using uranium L III -edge extended X-ray absorption fine structure (EXAFS) spectroscopy. In all samples uranium is co-ordinated by two axial oxygen atoms (O ax ) at a distance of 1.77-1.78 angstrom. The average distance between uranium and the equatorial oxygen atoms (O eq ) is 2.35 angstrom. The co-ordination number for O eq is 5-6. In comparison to the uranium crystal structure data, the U-O eq distance indicates a co-ordination number of the equatorial oxygen of 5. Within the experimental error, there are no differences in the U-O bond distances between samples from the three types of A. ferro oxidans investigated. The fit to the EXAFS data of samples measured as wet pastes gave the same results as for dried samples. No significant structural differences were observed for the uranium complexes formed by the eco-types of A. ferro oxidans. However, the EXAFS spectra do indicate a formation of uranium complexes which are different from those formed by Bacilli where the bond length of 2.28 angstrom indicates a co-ordination number of 4 for the equatorial oxygen atoms. (authors)

  1. A new cell for high temperature EXAFS measurements in molten rare earth fluorides

    International Nuclear Information System (INIS)

    Rollet, Anne-Laure; Bessada, Catherine; Auger, Yannick; Melin, Philippe; Gailhanou, Marc; Thiaudiere, Dominique

    2004-01-01

    A new cell with simple design has been developed for high temperature X-rays absorption measurements in both solid and molten lanthanide fluorides. Two plates of pyrolitic boron nitride are fixed hermetically together around the samples in order to avoid any evaporation and atmosphere interaction. EXAFS spectra of molten mixtures of LiF-LaF 3 measured at the La L III absorption edge are reported up to 900 deg C, and show the ability of this cell to keep the salt and to perform long time acquisition improving the signal to noise ratio

  2. Local structure and speciation of uranium in strontium orthosilicate: TRFS and EXAFS studies

    International Nuclear Information System (INIS)

    Gupta, Santosh K.; Thulasidas, S.K.; Natarajan, V.; Yadav, A.K.; Bhattacharya, D.

    2015-01-01

    TRFS is used to investigate the valence state and coordination behavior of uranium in strontium orthosilicate. From TRFS measurement it was observed that uranium exists as U(VI) in the form of UO 2 2+ in Sr 2 SiO 4 . Based on life time measurement and EXAFS studies it was inferred that uranyl is stabilized on both 9- and 10- coordinated strontium polyhedra. Majority of uranyl ion occupy relatively asymmetric site in strontium silicate most probably 9-coordinated Sr sites. (author)

  3. Extended X-ray absorption fine structure (EXAFS) studies of supported catalysts

    International Nuclear Information System (INIS)

    Joyner, R.W.

    1979-01-01

    Since the rebirth of interest in extended X-ray absorption fine structure there have been several studies of systems of catalytic interest. This note is a preliminary account of an investigation of supported platinum catalysts and NiO/Al 2 O 3 catalysts. Experiments were performed on pressed disc samples at the DESY synchrotron, Hamburg, using the EXAFS spectrometer. The synchrotron operated at 7 GeV energy with a circulating current of approximately 4 mA; spectrum accumulation time was typically 45 minutes. (author)

  4. An EXAFS spectrometer on beam line 10B at the Photon Factory

    International Nuclear Information System (INIS)

    Oyanagi, Hiroyuki; Matsushita, Tadashi; Ito, Masahisa; Kuroda, Haruo.

    1984-03-01

    An EXAFS spectrometer installed on the beam line 10B at the Photon Factory is designed to cover the photon energy between 4 and 30 keV. Utilizing either a channel-cut or two flat silicon crystals as a monochromator, a beam intensity between 10 8 and 10 9 photons/sec is obtained at 9 keV with a resolution of 1 eV. The performance of the spectrometer, such as a signal-to-noise ratio or an energy resolution is demonstrated with examples of K edge absorption spectra of bromine, germanium, gallium arsenide, and zinc selenide. (author)

  5. EXAFS Study of Disorder in SrTiO3 Perovskite

    International Nuclear Information System (INIS)

    Kodre, Alojz; Arcon, Iztok; Gomilsek, Jana Padeznik; Zalar, Bostjan

    2007-01-01

    Ti K-edge EXAFS spectra of SrTiO3 at room temperature and at N2 boiling point are measured to detect the Ti ion displacement above and below the antiferrodistortive phase transition occurring at Tc = 105 K. The data yield a definite value of the displacement, only slightly dependent on the temperature. The sensitive dependence of the amplitude of Ti-O-Ti focusing paths on the scattering angle is used to infer the correlation of Ti displacements. A preference to alternating displacements is indicated

  6. 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.

  7. STRUCTURAL STUDY OF BIS(2,6-BIS(PYRAZOL-3-YLPYRIDINENICKEL(II BY CALORIMETRY AND EXAFS SPECTROMETRY

    Directory of Open Access Journals (Sweden)

    Kristian H Sugiyarto

    2010-06-01

    Full Text Available The main aim of this work is to reveal the complex formation of 2,6-bis(pyrazol-3-ylpyridine, bpp, with nickel(II perchlorate in DMF by calorimetric stepwise complex formation and then followed by EXAFS spectrometry. It was found that the complex formation follows two stepwise pathways namely the formation of mono pyrazolyl-pyridine, [Ni(DMF3 bpp]2+, and bis pyrazolyl-pyridine, [Ni(bpp2]2+;  the formation constants being  log β1 = 6.57, and log β2 = 5.02, and the total value of log β  = 11.58. The final formation of six-coordinated compound was confirmed by EXAFS analysis with the mean Ni-Nbpp bond length of 2.0646(0.0014 Å.   Keywords: nickel(II, bpp, EXAFS

  8. Characterization of isolated Ag cations in homoionic Ag-Y zeolites: A combined anomalous XRPD and EXAFS study

    International Nuclear Information System (INIS)

    Lamberti, C.; Prestipino, C.; Bordiga, S.; Fitch, A.N.; Marra, G.L.

    2003-01-01

    In this contribution we report a structural characterization of a homoionic Ag-Y zeolite (Si/Al=2.63) on both short (EXAFS) and long range (XRD) scales. Our study shows that the zeolite is a near-100% exchanged silver faujasite, showing almost isolated Ag + counterions (EXAFS estimates that clustered species represent less than 2% of the whole silver). Synchrotron radiation XRPD measurements (ESRF, BM16), performed at the Ag-K edge (λ=0.486103(2) A), just before (λ=0.486093(2) A) and far away (λ=0.491153(2) A), allowed us to locate the near totality of the expected Ag + counterions: 51.9(4) out of 52.9 per unit cell, located in five different sites. The output of the Rietveld refinement has been used successfully to simulate the Ag-K edge EXAFS spectra (ESRF, BM29)

  9. Calcium EXAFS establishes the Mn-Ca cluster in the oxygen-evolving complex of Photosystem II

    Energy Technology Data Exchange (ETDEWEB)

    Cinco, Roehl M.; McFarlane Holman, Karen L.; Robblee, John H.; Yano, Junko; Pizarro, Shelly A.; Bellacchio, Emanuele; Sauer, Kenneth; Yachandra, Vittal K.

    2002-08-02

    The proximity of Ca to the Mn cluster of the photosynthetic water-oxidation complex is demonstrated by X-ray absorption spectroscopy. We have collected EXAFS data at the Ca K-edge using active PS II membrane samples that contain approximately 2 Ca per 4 Mn. These samples are much less perturbed than previously investigated Sr-substituted samples, which were prepared subsequent to Ca depletion. The new Ca EXAFS clearly shows backscattering from Mn at 3.4 angstroms, a distance that agrees with that surmised from previously recorded Mn EXAFS. This result is also consistent with earlier related experiments at the Sr K-edge, using samples that contained functional Sr, that show Mn is {approx}; 3.5 angstroms distant from Sr. The totality of the evidence clearly advances the notion that the catalytic center of oxygen evolution is a Mn-Ca heteronuclear cluster.

  10. Controlled Oxygen Chemisorption on an Alumina Supported Rhodium Catalyst. The Formation of a New Metal-Metal Oxide Interface Determined with EXAFS.

    NARCIS (Netherlands)

    Koningsberger, D.C.; Martens, J.H.A.; Prins, R.

    1989-01-01

    An alumina-supported rhodium catalyst has been studied with EXAFS. After reduction and evacuation, oxygen was admitted at 100 and 300 K. EXAFS spectra of the catalyst after oxygen admission at 100 K indicated the beginning of oxidation. At 300 K only a small part of the rhodium particles remained

  11. Multiple Scattering Analysis of Cu - K EXAFS in Bi2Sr1.5 Cu2O8+δ

    International Nuclear Information System (INIS)

    Roehler, J.; Cruesemann, R.

    1995-01-01

    We have analyzed the Cu K-EXAFS of Bi 2 Sr 1.5 Ca 1.5 Cu 2 O 8+δ using a full multiple scattering analysis in a cluster with diameter d∼ 7.6 A. The layered structure has numerous quasi one-dimensional structural elements which give rise to significant multiple scattering contributions in the EXAFS. We confirm the Sr/Ca ratio of the sample is 1:1, and one Ca atom is located close to a nominal Sr-site. At 40 K the dimpling angle in the CuO 2 -plane is found to be ≤ 3.5 . (author)

  12. EXAFS measurements under high pressure conditions using a combination of a diamond anvil cell and synchrotron radiation

    International Nuclear Information System (INIS)

    Sueno, Shigeho; Nakai, Izumi; Imafuku, Masayuki; Morikawa, Hideki; Kimata, Mitsuyoshi; Ohsumi, Kazumasa; Nomura, Masaharu; Shimomura, Osamu.

    1986-01-01

    EXAFS spectra for Fe, Co, Ni K-edges were successfully measured under high pressure conditions using a combination of a set of normal 1/8 carat diamond anvils, synchrotron radiation and a scintillation counter. A newly developed motor controlled goniometer stage was used for adjusting the position of a miniature diamond anvil cell. On the measurement of Cr and Mn spectra, specially designed thinner diamond anvil was necessary. EXAFS analysis of bis(dimethylglyoximato)nickel(II) at pressures from 1 atm to 5.6 GPa was made. (author)

  13. An EXAFS study of the structure of Co-Mo hydrodesulfurization catalysts

    International Nuclear Information System (INIS)

    Clausen, B.S.; Topsoe, H.; Candia, R.; Villadsen, J.; Lengeler, B.

    1981-05-01

    By analysing the extended X-ray absorption fine structure (EXAFS) of the Mo absorption edge, structural information about both calcined and sulfided Mo/Al 2 O 3 and Co-Mo/Al 2 O 3 catalysts has been obtained. The calcined catalysts show only one strong backscatterer peak in the radial distribution function, which indicates that molybdenum is present in a highly disordered structure. For the Co-Mo/Al 2 O 3 catalyst the presence of cobalt seems to have some effect on the immediate surroundings of molybdenum. Upon sulfiding the catalysts, an ordering of the molybdenum-containing phase takes place as evidenced by the observation of a contribution from the second coordination shell. From a comparison with EXAFS data obtained on well-crystallized MoS 2 it is concluded that the molybdenum atoms in the catalysts are present in MoS 2 -like structures. Furthermore, from a comparison of the amplitude of the Mo-backscatterer peak it is found that these MoS 2 -like structures are ordered in very small domains. (orig.)

  14. Sorption Speciation of Lanthanides/Actinides on Minerals by TRLFS, EXAFS and DFT Studies: A Review

    Directory of Open Access Journals (Sweden)

    Xiaoli Tan

    2010-11-01

    Full Text Available Lanthanides/actinides sorption speciation on minerals and oxides by means of time resolved laser fluorescence spectroscopy (TRLFS, extended X-ray absorption fine structure spectroscopy (EXAFS and density functional theory (DFT is reviewed in the field of nuclear disposal safety research. The theoretical aspects of the methods are concisely presented. Examples of recent research results of lanthanide/actinide speciation and local atomic structures using TRLFS, EXAFS and DFT are discussed. The interaction of lanthanides/actinides with oxides and minerals as well as their uptake are also of common interest in radionuclide chemistry. Especially the sorption and inclusion of radionuclides into several minerals lead to an improvement in knowledge of minor components in solids. In the solid-liquid interface, the speciation and local atomic structures of Eu(III, Cm(III, U(VI, and Np(IV/VI in several natural and synthetic minerals and oxides are also reviewed and discussed. The review is important to understand the physicochemical behavior of lanthanides/actinides at a molecular level in the natural environment.

  15. Experimental evidence of six-fold oxygen coordination for phosphorus and XANES calculations

    Energy Technology Data Exchange (ETDEWEB)

    Flank, A-M; Trcera, N; Itie, J-P; Lagarde, P [Synchrotron Soleil, L' Orme des Merisiers, BP 48, 91192 Gif sur Yvette (France); Brunet, F [Laboratoire de Geologie, CNRS-ENS-UMR8538, 24 rue Lhommond, 75005 Paris (France); Irifune, T [Geodynamics Research Center, Ehime University, Matsuyama 790-8577 (Japan)

    2009-11-15

    Phosphorus, a group V element, has always been found so far in minerals, biological systems and synthetic compounds with an oxygen coordination number of four (i.e, PO{sub 4} groups). We demonstrate here using phosphorus K-edge XANES spectroscopy that this element can also adopt a six-fold oxygen coordination (i.e, PO{sub 6} groups). This new coordination was achieved in AlPO{sub 4} doped SiO{sub 2} stishovite synthesized at 18 GPa and 1873 K and quenched down to ambient conditions. The well-crystallized P-bearing stishovite grains (up to 100{mu}m diameter) were embedded in the back-transformation products of high pressure form of AlPO{sub 4} matrix. They were identified by elemental mapping ({mu}-XRF). {mu}-XANES spectra collected at the Si and P K edges in the Si rich region with a very low concentration of P present striking resemblance, Si itself being characteristic of pure stishovite. We can therefore infer that phosphorus in the corresponding stishovite crystal is involved in an octahedral coordination made of six oxygen atoms. First principle XANES calculations using a plane-wave density functional formalism with core-hole effects treated in a supercell approach at the P K edge for a P atom substituting an Si one in the stishovite structure confirm this assertion. This result shows that in the lower-mantle where all silicon is six-fold coordinated, phosphorus has the crystal-chemical ability to remain incorporated into silicate structures.

  16. Experimental evidence of six-fold oxygen coordination for phosphorus and XANES calculations

    Science.gov (United States)

    Flank, A.-M.; Trcera, N.; Brunet, F.; Itié, J.-P.; Irifune, T.; Lagarde, P.

    2009-11-01

    Phosphorus, a group V element, has always been found so far in minerals, biological systems and synthetic compounds with an oxygen coordination number of four (i.e, PO4 groups). We demonstrate here using phosphorus K-edge XANES spectroscopy that this element can also adopt a six-fold oxygen coordination (i.e, PO6 groups). This new coordination was achieved in AlPO4 doped SiO2 stishovite synthesized at 18 GPa and 1873 K and quenched down to ambient conditions. The well-crystallized P-bearing stishovite grains (up to 100μm diameter) were embedded in the back-transformation products of high pressure form of AlPO4 matrix. They were identified by elemental mapping (μ-XRF). μ-XANES spectra collected at the Si and P K edges in the Si rich region with a very low concentration of P present striking resemblance, Si itself being characteristic of pure stishovite. We can therefore infer that phosphorus in the corresponding stishovite crystal is involved in an octahedral coordination made of six oxygen atoms. First principle XANES calculations using a plane-wave density functional formalism with core-hole effects treated in a supercell approach at the P K edge for a P atom substituting an Si one in the stishovite structure confirm this assertion. This result shows that in the lower-mantle where all silicon is six-fold coordinated, phosphorus has the crystal-chemical ability to remain incorporated into silicate structures.

  17. Experimental evidence of six-fold oxygen coordination for phosphorus and XANES calculations

    International Nuclear Information System (INIS)

    Flank, A-M; Trcera, N; Itie, J-P; Lagarde, P; Brunet, F; Irifune, T

    2009-01-01

    Phosphorus, a group V element, has always been found so far in minerals, biological systems and synthetic compounds with an oxygen coordination number of four (i.e, PO 4 groups). We demonstrate here using phosphorus K-edge XANES spectroscopy that this element can also adopt a six-fold oxygen coordination (i.e, PO 6 groups). This new coordination was achieved in AlPO 4 doped SiO 2 stishovite synthesized at 18 GPa and 1873 K and quenched down to ambient conditions. The well-crystallized P-bearing stishovite grains (up to 100μm diameter) were embedded in the back-transformation products of high pressure form of AlPO 4 matrix. They were identified by elemental mapping (μ-XRF). μ-XANES spectra collected at the Si and P K edges in the Si rich region with a very low concentration of P present striking resemblance, Si itself being characteristic of pure stishovite. We can therefore infer that phosphorus in the corresponding stishovite crystal is involved in an octahedral coordination made of six oxygen atoms. First principle XANES calculations using a plane-wave density functional formalism with core-hole effects treated in a supercell approach at the P K edge for a P atom substituting an Si one in the stishovite structure confirm this assertion. This result shows that in the lower-mantle where all silicon is six-fold coordinated, phosphorus has the crystal-chemical ability to remain incorporated into silicate structures.

  18. Combined application of XANES and XPS to study oxygen species adsorbed on Ag foil

    CERN Document Server

    Bukhtiyarov, V I; Kaichev, V V; Knop-Gericke, A; Mayer, R W; Schloegl, R

    2001-01-01

    Adsorbed oxygen species realized in the course of ethylene epoxidation over polycrystalline silver have been characterized by X-ray absorption near the edge structure and X-ray photoelectron spectroscopy. Namely, the combined application of XANES and XPS in similar UHV conditions using the same sample allowed us to assign an XAS feature to the nucleophilic and electrophilic oxygen. This is of great significance, since these species are suggested to be included into the active center for ethylene epoxidation. The differences in the oxygen-silver bonding of these oxygen species are discussed.

  19. EXAFS and FTIR studies of selenite and selenate sorption by alkoxide-free sol–gel generated Mg–Al–CO 3 layered double hydroxide with very labile interlayer anions

    KAUST Repository

    Chubar, Natalia

    2014-01-01

    © the Partner Organisations 2014. Current research on Layered Double Hydroxides (LDHs, also known as hydrotalcites, HTs) is predominantly focused on their intercalations, but the industrial application of LDHs for anion exchange adsorption has not yet been achieved. It was recently recognized that, to develop LDH applications, these materials should be produced using methods other than direct co-precipitation. Mg-Al-CO3LDH produced using an alkoxide-free sol-gel synthesis showed exceptional removal properties for aqueous selenium species. Se K-edge EXAFS/XANES and FTIR studies (supporting the data by XRD patterns) were performed to explain the unusual adsorptive performance of Mg-Al LDH by revealing the molecular-level mechanism of HSeO3 -, SeO4 2-and {HSeO3 -+ SeO4 2-} uptake at pH 5, 7 and 8.5. The role of inner-sphere complexation (exhibited by inorganic adsorbents with good performance) in adsorption of both selenium aqueous species was not confirmed. However, Mg-Al LDH fully met the other expectations regarding the involvement of the interlayer anions. The interlayer carbonate (due to its favorable speciation and generous HT hydration) gave a "second breath" to selenite sorption and was the only mechanism that controlled the removal of Se(vi). Because inner sphere complexation was the leading mechanism for selenite removal, ion exchange via surface OH-and interlayer CO3 2-species was the only mechanism for selenate removal; both of these species were easily bound to Mg-Al LDH (on its surface and gently parked into the interlayer forming a multilayer without violation of the structure of Mg-Al-CO3LDH). This work provides the first theoretical explanation of why it is more difficult to sorb selenate than selenite and which material should be used for this purpose. This journal is

  20. EXAFS and FTIR studies of selenite and selenate sorption by alkoxide-free sol–gel generated Mg–Al–CO 3 layered double hydroxide with very labile interlayer anions

    KAUST Repository

    Chubar, Natalia

    2014-08-08

    © the Partner Organisations 2014. Current research on Layered Double Hydroxides (LDHs, also known as hydrotalcites, HTs) is predominantly focused on their intercalations, but the industrial application of LDHs for anion exchange adsorption has not yet been achieved. It was recently recognized that, to develop LDH applications, these materials should be produced using methods other than direct co-precipitation. Mg-Al-CO3LDH produced using an alkoxide-free sol-gel synthesis showed exceptional removal properties for aqueous selenium species. Se K-edge EXAFS/XANES and FTIR studies (supporting the data by XRD patterns) were performed to explain the unusual adsorptive performance of Mg-Al LDH by revealing the molecular-level mechanism of HSeO3 -, SeO4 2-and {HSeO3 -+ SeO4 2-} uptake at pH 5, 7 and 8.5. The role of inner-sphere complexation (exhibited by inorganic adsorbents with good performance) in adsorption of both selenium aqueous species was not confirmed. However, Mg-Al LDH fully met the other expectations regarding the involvement of the interlayer anions. The interlayer carbonate (due to its favorable speciation and generous HT hydration) gave a "second breath" to selenite sorption and was the only mechanism that controlled the removal of Se(vi). Because inner sphere complexation was the leading mechanism for selenite removal, ion exchange via surface OH-and interlayer CO3 2-species was the only mechanism for selenate removal; both of these species were easily bound to Mg-Al LDH (on its surface and gently parked into the interlayer forming a multilayer without violation of the structure of Mg-Al-CO3LDH). This work provides the first theoretical explanation of why it is more difficult to sorb selenate than selenite and which material should be used for this purpose. This journal is

  1. REDOX state analysis of platinoid elements in simulated high-level radioactive waste glass by synchrotron radiation based EXAFS

    Energy Technology Data Exchange (ETDEWEB)

    Okamoto, Yoshihiro, E-mail: okamoto.yoshihiro@jaea.go.jp [Condensed Matter Chemistry Group, Quantum Beam Science Center, Japan Atomic Energy Agency, Shirakata 2-4, Tokai-mura, Ibaraki 319-1195 (Japan); Shiwaku, Hideaki [Quantum Beam Science Center, Japan Atomic Energy Agency, Kouto 1-1-1, Sayo-cho, Hyogo 679-5143 (Japan); Nakada, Masami [Nuclear Engineering Science Center, Japan Atomic Energy Agency, Shirakata 2-4, Tokai-mura, Ibaraki 319-1195 (Japan); Komamine, Satoshi; Ochi, Eiji [Japan Nuclear Fuel Limited, 4-108 Aza Okitsuke, Oaza Obuchi, Rokkasho-mura, Aomori 030-3212 (Japan); Akabori, Mitsuo [Nuclear Engineering Science Center, Japan Atomic Energy Agency, Shirakata 2-4, Tokai-mura, Ibaraki 319-1195 (Japan)

    2016-04-01

    Extended X-ray Absorption Fine Structure (EXAFS) analyses were performed to evaluate REDOX (REDuction and OXidation) state of platinoid elements in simulated high-level nuclear waste glass samples prepared under different conditions of temperature and atmosphere. At first, EXAFS functions were compared with those of standard materials such as RuO{sub 2}. Then structural parameters were obtained from a curve fitting analysis. In addition, a fitting analysis used a linear combination of the two standard EXAFS functions of a given elements metal and oxide was applied to determine ratio of metal/oxide in the simulated glass. The redox state of Ru was successfully evaluated from the linear combination fitting results of EXAFS functions. The ratio of metal increased at more reducing atmosphere and at higher temperatures. Chemical form of rhodium oxide in the simulated glass samples was RhO{sub 2} unlike expected Rh{sub 2}O{sub 3}. It can be estimated rhodium behaves according with ruthenium when the chemical form is oxide.

  2. 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.

  3. Vanadium K XANES of synthetic olivine: Valence determinations and crystal orientation effects

    International Nuclear Information System (INIS)

    Sutton, S.R.; Newville, M.

    2005-01-01

    Vanadium can exist in a large number of valence states in nature (2+?, 3+, 4+ and 5+) and determinations of V valence is therefore valuable in defining the oxidation states of earth and planetary materials over a large redox range. Synchrotron-based x-ray absorption near edge structure (XANES) spectroscopy is well-suited for measurements of V valence with ∼micrometer spatial resolution and ∼ppm elemental sensitivity. Applications of microXANES have been demonstrated for basaltic glasses. Applications to minerals are feasible but complicated by orientation effects (e.g. due to polarization of the synchrotron x-ray beam) and some results for spinel have been reported. Here we report initial results for olivine from laboratory crystallization ex-periments. The goal is to define the valence partition-ing between olivine and melt and quantify the magnitude of orientation effects, the latter tested by measuring grains at a variety of orientations in the same charge.

  4. The Electronic Properties and L3 XANES of Au and Nano-Au

    International Nuclear Information System (INIS)

    Yiu, Y.M.; Zhang, P.; Sham, T.K.

    2004-01-01

    The electronic properties of Au crystal and nano Au have been investigated by theory and experiment. Molecularly capped nano-Au was synthesized using the two-phase method. Au nano-particles have been characterized by X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). They retain the fcc crystal structure. Their sizes have been determined to be in a range from 5.5 nm to 1.7 nm. The L3 X-ray Absorption Near Edge Structure (XANES) of nano-Au and Au foil have been recorded using synchrotron radiation, and examined by theoretical calculation based on the first principles. Both theory and experiment show that the nano-Au particles have essentially all the Au L3 XANES features of bulk Au in the near edge region with less pronounced resonance peaks. It is also shown that nano Au exhibits lower 4f binding energy than bulk Au in good agreement with quantum confined Au systems reported previously.

  5. Valence determination of rare earth elements in lanthanide silicates by L 3-XANES spectroscopy

    International Nuclear Information System (INIS)

    Kravtsova, Antonina N; Guda, Alexander A; Soldatov, Alexander V; Goettlicher, Joerg; Taroev, Vladimir K; Suvorova, Lyudmila F; Tauson, Vladimir L; Kashaev, Anvar A

    2016-01-01

    Lanthanide silicates have been hydrothermally synthesized using Cu and Ni containers. Chemical formulae of the synthesized compounds correspond to K 3 Eu[Si 6 O 15 ] 2H 2 O, HK 6 Eu[Si 10 O 25 ], K 7 Sm 3 [Si 12 O 32 ], K 2 Sm[AlSi 4 O 12 ] 0.375H 2 O, K 4 Yb 2 [Si 8 O 21 ], K 4 Ce 2 [Al 2 Si 8 O 24 ]. The oxidation state of lanthanides (Eu, Ce, Tb, Sm, Yb) in these silicates has been determined using XANES spectroscopy at the Eu, Ce, Tb, Sm, Yb, L 3 - edges. The experimental XANES spectra were recorded using the synchrotron radiation source ANKA (Karlsruhe Institute of Technology) and the X-ray laboratory spectrometer Rigaku R- XAS. By comparing the absorption edge energies and white line intensities of the silicates with the ones of reference spectra the oxidation state of lanthanides Eu, Ce, Tb, Sm, Yb has been found to be equal to +3 in all investigated silicates except of the Ce-containing silicate from the run in Cu container where the cerium oxidation state ranges from +3 (Ce in silicate apatite and in a KCe silicate with Si 12 O 32 layers) to +4 (starting CeO 2 or oxidized Ce 2 O 3 ). (paper)

  6. XANES studies of titanium dioxide nanoparticles synthesized by using Peltophorum pterocarpum plant extract

    Energy Technology Data Exchange (ETDEWEB)

    Saravanan, S. [Centre for Photonics and Nanotechnology, Sona College of Technology, Salem 636005, Tamilnadu (India); Balamurugan, M., E-mail: chem.muruga@gmail.com [Centre for Photonics and Nanotechnology, Sona College of Technology, Salem 636005, Tamilnadu (India); Lippitz, A. [Bundesanstalt für Materialforschung und -prüfung, 6.8 Oberflächenanalytik und Grenzflächenchemie Unter den Eichen 44 – 46, 12203, Berlin (Germany); Fonda, E.; Swaraj, S. [Synchrotron SOLEIL, L’ormes des merisiers, Saint Aubin BP-48, 91192, Gif-Sur-Yvette Cedex (France)

    2016-12-15

    The preparation and characterization of a Titanium dioxide (TiO{sub 2}) by a simple, cost effective, facile and eco-friendly green synthesis method using Peltophorum pterocarpum plant extract is presented. The green synthesized nanoparticles were characterized using X-ray diffraction (XRD), Raman spectroscopy, High-resolution transmission electron microscopy (HR-TEM) and X-ray absorption near edge spectroscopy (XANES). XRD results show that the prepared TiO{sub 2} NPs were significantly crystalline with various percentages of anatase and rutile phases. The nanoparticles were found to have different diameters ranging from 20 to 80 nm. No evidence of any intermediate or different TiO{sub 2} phases were found in XANES measurements performed at the Ti K- and L-edge. It is shown that the TiO{sub 2} NPs with high uniformity, high surface area and minimum aggregation can be prepared with relative ease and the desired anatase: rutile phase ratio can be obtained by controlling the experimental conditions.

  7. A XANES Study of Sulfur Speciation and Reactivity in Cokes for Anodes Used in Aluminum Production

    Science.gov (United States)

    Jahrsengene, Gøril; Wells, Hannah C.; Rørvik, Stein; Ratvik, Arne Petter; Haverkamp, Richard G.; Svensson, Ann Mari

    2018-06-01

    Availability of anode raw materials in the growing aluminum industry results in a wider range of petroleum cokes being used to produce carbon anodes. The boundary between anode grade cokes and what previously was considered non-anode grades are no longer as distinct as before, leading to introduction of cokes with higher sulfur and higher trace metal impurity content in anode manufacturing. In this work, the chemical nature of sulfur in five industrial cokes, ranging from 1.42 to 5.54 wt pct S, was investigated with K-edge XANES, while the reactivity of the cokes towards CO2 was measured by a standard mass loss test. XANES identified most of the sulfur as organic sulfur compounds. In addition, a significant amount is identified (16 to 53 pct) as S-S bound sulfur. A strong inverse correlation is observed between CO2-reactivity and S-S bound sulfur in the cokes, indicating that the reduction in reactivity is more dependent on the amount of this type of sulfur compound rather than the total amount of sulfur or the amount of organic sulfur.

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

    Energy Technology Data Exchange (ETDEWEB)

    Mathon, O., E-mail: mathon@esrf.fr; Beteva, A.; Borrel, J.; Bugnazet, D.; Gatla, S.; Hino, R.; Kantor, I.; Mairs, T. [European Synchrotron Radiation Facility, CS 40220, 38043 Grenoble Cedex 9 (France); Munoz, M. [European Synchrotron Radiation Facility, CS 40220, 38043 Grenoble Cedex 9 (France); Université Joseph Fourier, 1381 rue de la Piscine, BP 53, 38041 Grenoble Cedex 9 (France); Pasternak, S.; Perrin, F.; Pascarelli, S. [European Synchrotron Radiation Facility, CS 40220, 38043 Grenoble Cedex 9 (France)

    2015-10-17

    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. 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.

  9. Comparative EXAFS study of uranium(VI) and neptunium(V) sorption onto kaolinite

    International Nuclear Information System (INIS)

    Reich, T.; Amayri, S.; Reich, Ta.; Jermolajev, J.

    2005-01-01

    Full text of publication follows: We investigated the surface sorption process of U(VI) and Np(V) on kaolinite by extended X-ray absorption fine structure (EXAFS) spectroscopy in the 10 μM concentration range. Batch experiments with kaolinite in CO 2 -equilibrated systems showed that the adsorption edge of U(VI) occurs at pH 5.5, i.e., near the pH PZC of kaolinite. The adsorption edge of Np(V) occurs well above the pH PZC value at pH 8.5. This may indicate that the bonds between Np(V) and the surface functional groups of kaolinite are not as strong as in the case of U(VI). U(VI) and Np(V) have in common that the amount which is adsorbed decreases when the pH is increased beyond the absorption maximum. This behavior can be attributed to the formation of U(VI) and Np(V) carbonato complexes in the aqueous solutions. The aim of this comparative EXAFS study was to investigate the reason for the different affinities of U(VI) and Np(V) for kaolinite by measuring their local environments at the clay surface. Samples were prepared from 4 g/L kaolinite, 0.1 M NaClO 4 , pH 3.0 - 10.5, presence and absence of ambient CO 2 . The U L 3 - and Np L 2 -edge EXAFS spectra of the wet paste samples were measured at room temperature in fluorescence mode at the Rossendorf Beamline (ROBL) at the European Synchrotron Radiation Facility. The measured U-O and U-Al/Si distances indicate inner-sphere sorption of U(VI) on kaolinite. There was no evidence of uranium neighbors in the EXAFS spectra, suggesting that the adsorbed U(VI) complexes were predominantly monomeric. The average distance between uranium and its equatorial oxygen atoms, O eq , increased from 2.32 to 2.38 Angstrom in the presence of atmospheric CO 2 when the pH was increased from 5.0 to 8.5. In the CO 2 -free system, the U-O eq distance was independent from pH and equal to 2.32 Angstrom. The lengthening of the average U-O eq distance in the presence of carbonate (or bicarbonate) suggests the formation of ternary U

  10. The Mn site in Mn-doped GaAs nanowires: an EXAFS study

    International Nuclear Information System (INIS)

    D’Acapito, F; Rovezzi, M; Boscherini, F; Jabeen, F; Bais, G; Piccin, M; Rubini, S; Martelli, F

    2012-01-01

    We present an EXAFS study of the Mn atomic environment in Mn-doped GaAs nanowires. Mn doping has been obtained either via the diffusion of the Mn used as seed for the nanowire growth or by providing Mn during the growth of Au-induced wires. As a general finding, we observe that Mn forms chemical bonds with As but is not incorporated in a substitutional site. In Mn-induced GaAs wires, Mn is mostly found bonded to As in a rather disordered environment and with a stretched bond length, reminiscent of that exhibited by MnAs phases. In Au-seeded nanowires, along with stretched MnAs coordination, we have found the presence of Mn in a MnAu intermetallic compound. (paper)

  11. EXAFS Phase Retrieval Solution Tracking for Complex Multi-Component System: Synthesized Topological Inverse Computation

    International Nuclear Information System (INIS)

    Lee, Jay Min; Yang, Dong-Seok; Bunker, Grant B

    2013-01-01

    Using the FEFF kernel A(k,r), we describe the inverse computation from χ(k)-data to g(r)-solution in terms of a singularity regularization method based on complete Bayesian statistics process. In this work, we topologically decompose the system-matched invariant projection operators into two distinct types, (A + AA + A) and (AA + AA + ), and achieved Synthesized Topological Inversion Computation (STIC), by employing a 12-operator-closed-loop emulator of the symplectic transformation. This leads to a numerically self-consistent solution as the optimal near-singular regularization parameters are sought, dramatically suppressing instability problems connected with finite precision arithmetic in ill-posed systems. By statistically correlating a pair of measured data, it was feasible to compute an optimal EXAFS phase retrieval solution expressed in terms of the complex-valued χ(k), and this approach was successfully used to determine the optimal g(r) for a complex multi-component system.

  12. Characterization of mercury based Indian herbomineral drug by radioisotope induced EDXRF and synchrotron based EXAFS

    International Nuclear Information System (INIS)

    Joseph, Daisy; Saxena, A.; Joseph, Rajeeta; Rajput, P.; Nayak, C.; Bhattacharya, D.; Jha, S.N.; Natrajan, V.

    2014-01-01

    An Indian herbomineral drug was characterized for its trace elements by radioisotope induced EDXRF. The drug contains minerals like mercury, sulfur and arsenic disulfide, along with herbs such as dhaturra, bhrami, vacha etc. All the above ingredients were processed together in a step wise manner (6 steps). Hence the motive was to expect some change in the drug molecule at every step of processing it. The 6 samples are the samples collected at every step of drug preparation. These 6 samples which are collected as intermediatary samples would be then evaluated for its role in various neuropsychological (psychosis, depression etc) disorders in experimental animals such as rats/mice. Hence it was required to find the elements/trace elements composition, details of chemical components present in the drug samples. It was seen that using EDXRF it was possible to determine As and Hg. The EXAFS results also showed the presence of As in their sulphide form. (author)

  13. High pressure and high temperature EXAFS and diffraction study of AgI

    International Nuclear Information System (INIS)

    Yoshiasa, Akira; Arima, Hiroshi; Fukui, Hiroshi; Okube, Maki; Katayama, Yoshinori; Ohtaka, Osamu

    2009-01-01

    We have determined the precise P-T phase diagram of AgI by in-situ high-pressure high-temperature synchrotron experiments. X-ray diffraction and XAFS measurements were performed up to 6.0 GPa and 1100 K using a multi-anvil high-pressure device and synchrotron radiation from SPring-8. In the disordered rock-salt phase, Ag ions occupy both octahedral and tetrahedral sites and twenty percent of Ag ions occupy the tetrahedral site as a maximum value at 2 GPa. From the viewpoint of the local structure analyses, some sudden changes are recognized near broad phase transition point. Analysis of EXAFS Debye-Waller factor is useful because the force constant can be decided directly even at high pressure and high temperature. Pressure influences greatly the effective potential and anharmonicity decreases with increasing pressure. (author)

  14. Colloidal diatomite, radionickel, and humic substance interaction: a combined batch, XPS, and EXAFS investigation.

    Science.gov (United States)

    Sheng, Guodong; Shen, Runpu; Dong, Huaping; Li, Yimin

    2013-06-01

    This work determined the influence of humic acid (HA) and fulvic acid (FA) on the interaction mechanism and microstructure of Ni(II) onto diatomite by using batch experiments, X-ray photoelectron spectroscopy (XPS), and extended X-ray absorption fine structure (EXAFS) methods. Macroscopic and spectroscopic experiments have been combined to see the evolution of the interaction mechanism and microstructure of Ni(II) in the presence of HA/FA as compared with that in the absence of HA/FA. The results indicated that the interaction of Ni(II) with diatomite presents the expected solution pH edge at 7.0, which is modified by addition of HA/FA. In the presence of HA/FA, the interaction of Ni(II) with diatomite increased below solution pH 7.0, while Ni(II) interaction decreased above solution pH 7.0. XPS analysis suggested that the enrichment of Ni(II) onto diatomite may be due to the formation of (≡SO)2Ni. EXAFS results showed that binary surface complexes and ternary surface complexes of Ni(II) can be simultaneously formed in the presence of HA/FA, whereas only binary surface complexes of Ni(II) are formed in the absence of HA/FA, which contribute to the enhanced Ni(II) uptake at low pH values. The results observed in this work are important for the evaluation of Ni(II) and related radionuclide physicochemical behavior in the natural soil and water environment.

  15. Xanes and SR-XRF Study of Skin as a Barrier to Ultra-Fine Nanocrystals of TiO2

    International Nuclear Information System (INIS)

    Kwiatek, W.M.; Lekki, J.; Stachura, Z.; Hanson, A.; Ablett, J.

    2007-01-01

    Nanocrystalline TiO 2 is commonly used in cosmetic industry as a photoprotective agent. With recent advances in nanomaterial processing, the size of TiO 2 crystals decreased into the nanometre regime. There is no satisfactory evidence that crystals of such small size are harmless to the human population. An EU project NANODERM has been launched where several techniques have been applied to investigate the possibility of particle penetration through the protective horny layer into vital skin regions. Skin biopsies of the animal and human skin have been collected after exposition to formulations containing TiO 2 nanocrystals. The Ti depth distributions were measured by electron and ion microscopy. The microscopy studies did not detect penetration into vital tissue of healthy skin what does not exclude a possibility that TiO 2 could penetrate pathological skin with lowered barrier efficiency. Due to literature the physical effect of the UV irradiation of the TiO 2 nanoparticle is the shift from 4 th to 3 rd oxidation state of the Ti. Titanium at 3 rd oxidation state interact with environment producing free radicals and Reactive Oxygen Species. In order to quantify the oxidation state shift, XANES experiments were carried out with commercially available TiO 2 nanocrystals (6 - 100 nm size), both in anatase and rutile phase. The samples were irradiated with X-rays with, and without accompanying UV illumination at the NSLS X27A beam line. The corresponding XANES spectra were registered and the absorption edge was compared in UV - illuminated and not illuminated spectra. A shift of about 1 eV in the absorption edge position of the rutile sample exposed to UVA light (365 nm, 20 mW/cm 2 ) has been measured and attributed to the changed electron configuration. However, the direction of the shift detected in measured samples was opposite to the expected. (author)

  16. Speciation of magnesium in monohydrocalcite: XANES, ab initio and geochemical modeling

    Science.gov (United States)

    Fukushi, Keisuke; Suzuki, Yuma; Kawano, Jun; Ohno, Takeshi; Ogawa, Masahiro; Yaji, Toyonari; Takahashi, Yoshio

    2017-09-01

    Monohydrocalcite (MHC: CaCO3·H2O), a rare carbonate mineral formed under surface conditions, is usually observed in nature as containing a variable amount of Mg, with a 0.007-0.45 Mg/Ca mole ratio. The variable Mg composition in MHC is anticipated as a promising proxy to assess paleo-hydrochemistry especially in saline lakes. Although the roles of Mg on the formation and stability of MHC have been studied intensively, the Mg speciation in MHC has remained unclear and controversial. This study examined Mg speciation in MHC using X-ray absorption near edge structure (XANES), ab initio molecular simulation, and geochemical modeling. Mg-XANES spectra of MHC with different Mg/Ca ratios prepared from mixing solutions of Na2CO3, CaCl2 and MgCl2 revealed that the Mg in MHC is a mixture of amorphous Mg carbonate (AMC) and other Mg containing phase. The contribution of AMC to total Mg is negatively correlated to the crystallinity of MHC. Results show that AMC might play a protective role in the crystallization and the transformation to stable calcium carbonates. Ab initio calculation of Mg2+ substitution into MHC showed that a limited amount of Mg2+ can be incorporated into the MHC structure. Six-fold coordination of Mg2+ is substituted for eight-fold coordination of Ca2+ in the MHC structure. The other type of Mg in MHC revealed from the XANES analyses most likely corresponds to the structural Mg in MHC. The contribution of the structural Mg is almost constant at 0.06 in Mg/Ca, representing the limit of solid solubility of Mg in MHC. The solubility products of the MHC with the limit of solid solubility of Mg and the AMC associated with MHC were estimated from the reacted solution compositions. Prediction of the Mg/Ca ratio as a function of the initial solution conditions using solubility reasonably reproduces the observed apparent Mg/Ca ratios in MHC from the present study and earlier studies. The apparent Mg/Ca ratio of MHC is useful to elucidate water chemistry

  17. Detection of Pb-LIII edge XANES spectra of urban atmospheric particles combined with simple acid extraction

    International Nuclear Information System (INIS)

    Funasaka, K.; Tojo, T.; Katahira, K.; Shinya, M.; Miyazaki, T.; Kamiura, T.; Yamamoto, O.; Moriwaki, H.; Tanida, H.; Takaoka, M.

    2008-01-01

    Pb-LIII edge XANES spectra of atmospheric particles are directly obtained by fluorescent XAFS spectroscopy using a 19-element solid state detector (SSD). Particulate sample was collected on a quartz fiber filter using a high-volume air sampler, and the filter was cut into small pieces (25 x 25 mm). Then, surface layer of the filter piece was scaled and accumulated in order to enhance the particle density per filter unit. Use of 10 pieces of the surface layer enables the measurement of Pb-LIII edge XANES spectra on beamline BL01B1 at SPring-8, Hyogo, Japan. The shape of the Pb-LIII edge XANES spectra of the particulate sample is similar to the shapes of the spectra for PbS, PbCO 3 , PbSO 4 and/or PbCl 2 . Additionally, the filter sample is also divided into water-soluble, 0.1 M HCl-extractable, and residual fractions of Pb compounds by a simple acid extraction procedure. We discuss the possibility of Pb speciation in the particulate samples with combination of highly sensitive XANES spectroscopy and simple acid extraction

  18. A Mexican kaolin deposit: XANES characterization, mineralogical phase analysis and applications

    Directory of Open Access Journals (Sweden)

    Martínez, A.

    2009-06-01

    Full Text Available A kaolin obtained from Villa de Reyes, a region near to San Luis Potosí (México was characterized by means of X-ray powder diffraction (XRD, optical microscopy (OM, scanning electron microscopy (SEM, X-ray fluorescence (XRF, X-Ray Absorption Near Edge Spectroscopy (XANES, thermal analysis (DTA/TGA, dilatometry (DIL, and chemical analysis. Mineralogical and morphological characteristics of the mineral are presented. The kaolin sample was formed mainly by kaolinite, but other minor phases were also detected such as quartz, cristobalite, tridymite, and dolomite. The high content of volcanic glass detected, by optical microscopy, revealed an incomplete kaolinization process of the raw material. The reddish color of the kaolin was associated with the free iron content in the form of limonite [FeO(OH], which was determined by XANES. The influence of the particle size on the whiteness of kaolin was evaluated. Dilatometric analysis revealed a strong thermal expansion between 110 y 240 °C, which would difficult the use of this material in traditional ceramic applications. On the other hand the presence of glass and high temperature phases of SiO2, such as cristobalite and tridymite will favor its use in the cement industry.El caolín obtenido de Villa de Reyes, una región cercana a San Luis Potosí, México, fue caracterizado por las siguientes técnicas: difracción de rayos-X en polvos (DRX, microscopía óptica (MO, microscopía electrónica de barrido (MEB, fluorescencia de rayos-X (FRX, espectroscopía de absorción de rayos-X (XANES, análisis térmico (DTA/TGA, dilatometría (DIL y análisis químico. Los resultados del análisis mineralógico mediante DRX mostraron un mineral constituido principalmente de caolinita, con una contribución minoritaria de cuarzo, cristobalita, tridimita y dolomita. El análisis por microscopía óptica reveló un alto contenido de material amorfo volcánico, indicando una caolinización incompleta del material v

  19. XPS and Ag L3-edge XANES characterization of silver and silver-gold sulfoselenides

    Science.gov (United States)

    Mikhlin, Yuri L.; Pal'yanova, Galina A.; Tomashevich, Yevgeny V.; Vishnyakova, Elena A.; Vorobyev, Sergey A.; Kokh, Konstantin A.

    2018-05-01

    Gold and silver sulfoselenides are of interest as materials with high ionic conductivity and promising magnetoresistive, thermoelectric, optical, and other physico-chemical properties, which are strongly dependent on composition and structure. Here, we applied X-ray photoelectron spectroscopy and Ag L3 X-ray absorption near-edge structure (XANES) to study the electronic structures of low-temperature compounds and solid solutions Ag2SxSe1-x (0 compounds; in particular, the Ag L3-edge peak is about 35% lower for AgAuS relative to Ag2S. At the same time, the Au 4f binding energy and, therefore, charge at Au(I) sites increase with increasing S content due to the transfer of electron density from Au to Ag atoms. It was concluded that the effects mainly originate from shortening of the metal-chalcogen and especially the Ausbnd Ag interatomic distances in substances having similar coordination geometry.

  20. TEM and XANES study of MOVPE grown InAIN layers with different indium content

    International Nuclear Information System (INIS)

    Kret, S; Wolska, A; Klepka, M T; Letrouit, A; Ivaldi, F; Szczepańska, A; Carlin, J-F; Kaufmann, N A K; Grandjean, N

    2011-01-01

    We present structure and spatially resolved composition studies by TEM (Transmission Electron Microscopy) and XANES (X-ray Absorption Near Edge Structure) of InAIN MOVPE (Metal-Organic Vapor Phase Epitaxy) epilayers containing 16-27 at% of indium. Investigations of the In L 3 edge by synchrotron radiation absorption show a significant change of the post-edge structure depending on the indium content. We attribute this to the solubility limit and phase separation in this system. Our measurements suggest that the critical composition is 18% for our growth conditions. HRTEM cross-sectional and EDX investigations confirm such phase separation as well as the changing of the structure from 2D growth to columnar like growth for the sample with the highest indium content.

  1. Time resolved XANES illustrates a substrate-mediated redox process in Prussian blue cultural heritage materials

    International Nuclear Information System (INIS)

    Gervais, Claire; Moretti, Giulia; Lanquille, Marie-Angélique; Réguer, Solenn

    2016-01-01

    The pigment Prussian blue is studied in heritage science because of its capricious fading behavior under light exposure. We show here that XANES can be used to study the photosensitivity of Prussian blue heritage materials despite X-ray radiation damage. We used an original approach based on X-ray photochemistry to investigate in depth the redox process of Prussian blue when it is associated with a cellulosic substrate, as in cyanotypes and watercolors. By modifying cation and proton contents of the paper substrate, we could tune both rate and extent of Prussian blue reduction. These results demonstrate that the photoreduction and fading of Prussian blue is principally mediated by the substrate and its interaction with the oxygen of the environment. (paper)

  2. 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.

  3. Limitations on the extent of off-center displacements in TbMnO3 from EXAFS measurements

    International Nuclear Information System (INIS)

    Bridges, F.; Downs, C.; O'Brien, T.; Jeong, Il-K; Kimura, T.

    2007-01-01

    We present extended x-ray-absorption fine structure (EXAFS) data at the Mn K and Tb L 3 edges that provide upper limits on the possible displacements of any atoms in TbMnO 3 . The displacements must be less than 0.005-0.01 A for all atoms, which eliminates the possibility of moderate distortions (0.02 A) with a small c-axis component, but for which the displacements in the ab plane average to zero. Assuming the polarization arises from a displacement of the O2 atoms along the c axis, the measured polarization then leads to an O2 displacement that is at least 6x10 -4 A, well below our experimental limit. Thus, a combination of the EXAFS and the measured electrical polarization indicate that the atomic displacements likely lie in the range 6x10 -4 -5x10 -3 A

  4. Local atomic structure of Zr-Cu and Zr-Cu-Al amorphous alloys investigated by EXAFS method

    International Nuclear Information System (INIS)

    Antonowicz, J.; Pietnoczka, A.; Zalewski, W.; Bacewicz, R.; Stoica, M.; Georgarakis, K.; Yavari, A.R.

    2011-01-01

    Research highlights: → Coordination number, interatomic distances and mean square atomic displacement in Zr-Cu and Zr-Cu-Al glasses. → Icosahedral symmetry in local atomic structure. → Deviation from random mixing behavior resulting from Al addition. - Abstract: We report on extended X-ray absorption fine structure (EXAFS) study of rapidly quenched Zr-Cu and Zr-Cu-Al glassy alloys. The local atomic order around Zr and Cu atoms was investigated. From the EXAFS data fitting the values of coordination number, interatomic distances and mean square atomic displacement were obtained for wide range of compositions. It was found that icosahedral symmetry rather than that of corresponding crystalline analogs dominates in the local atomic structure of Zr-Cu and Zr-Cu-Al amorphous alloys. Judging from bonding preferences we conclude that addition of Al as an alloying element results in considerable deviation from random mixing behavior observed in binary Zr-Cu alloys.

  5. Relationship between the adsorption species of cesium and radiocesium interception potential in soils and minerals: an EXAFS study

    International Nuclear Information System (INIS)

    Fan, Qiaohui; Yamaguchi, Noriko; Tanaka, Masato; Tsukada, Hirofumi; Takahashi, Yoshio

    2014-01-01

    This study examined the radiocesium (RCs) interception potential (RIP), cation exchange capacity (CEC), total organic carbon (TOC) content, and adsorption species in soils and minerals by using extended X-ray absorption fine structure (EXAFS) spectroscopy. The RIP related to Cs + adsorption by frayed-edge site (FES) has often been used to measure the mobility and bioavailability of RCs in the environment. This study found that the presence of organic matter (OM) can reduce RIP to a certain extent. The adsorption amount (=Q T ) in soil was obviously correlated to RIP at a small [Cs + ] region, whereas a linear relationship between Q T and CEC was observed at a large [Cs + ] region. Both the inner-sphere (IS) and outer-sphere (OS) complexes of Cs + were observed through EXAFS at a molecular scale. The linear correlation between log (RIP/CEC) and the ratio of the coordination number (CN) of IS (=CN IS ) and OS (=CN OS ) complexes noted as CN IS /(CN IS + CN OS ) suggested that the ratio of CN is very sensitive to Cs + adsorption species with variable RIP and CEC. The adsorption species of Cs + in soil was mainly dependent on the clay mineral content of soil. RIP was affected not only by FES but also by other strong adsorption sites, such as the interlayers and cavities identified as the IS complex in EXAFS analysis. Findings indicated that the EXAFS approach is a powerful and efficient tool to explore the behavior of Cs + in a given environment. - Highlights: • The relationship of Cs + species on soils and minerals and RIP was firstly clarified in this study. • Coordination number of Cs + was very sensitive to Cs + adsorption species with variable RIP and CEC. • This finding can be used as a basis for understanding of Cs + behavior in nature

  6. Structure of bimetallic clusters. Extended x-ray absorption fine structure (EXAFS) studies of Rh--Cu clusters

    International Nuclear Information System (INIS)

    Meitzner, G.; Via, G.H.; Lytle, F.W.; Sinfelt, J.H.

    1983-01-01

    An investigation of the structure of the bimetallic clusters present in rhodium--copper catalysts was conducted with the use of extended x-ray absorption fine structure (EXAFS) measurements. Two catalysts were studied, both employing silica as a support for the clusters and both containing 1 wt. % rhodium. In one catalyst the Cu:Rh atomic ratio was 1:2 and in the other 1:1. Studies were made of the EXAFS associated with the K absorption edges of the rhodium and copper. The results of the EXAFS studies indicate that copper concentrates at the surface of the rhodium--copper clusters. In this regard the results are similar to our earlier reported results on ruthenium--copper clusters. However, the extent of surface segregation of the copper appears to be less pronounced for rhodium--copper clusters. This result is reasonable on the basis that rhodium and copper, unlike ruthenium and copper, exhibit at least some miscibility in the bulk

  7. EXAFS as a tool for investigation of the local environment of Ge atoms in buried low-dimensional structures

    International Nuclear Information System (INIS)

    Demchenko, I.N.; Lawniczak-Jablonska, K.; Liliental-Weber, Z.; Zakharov, D.N.; Zhuravlev, K.S.

    2005-01-01

    In spite of large number of articles dedicated to the investigation of GeSi islands, a lot of problems concerning growth mechanism and island composition, as well as elastic strains inside the QDs, are still unsolved. To solve such problems, the GeSi low dimensional structures were studied by Extended X-Ray Absorption Fine Structure (EXAFS). The aim of this investigation was to get knowledge about the local structure around Ge atoms inside formed quantum dots. The paper presents a series of measurements performed for a single Ge layer buried in the silicon matrix at A1 station at the HASYLAB/DESY (Germany) with the angle of 45 o between the incident beam and sample surface. The fluorescence, total electron yield and the transmission modes of detection were used. To confirm the EXAFS analysis conclusion more measurements were performed using transmission electron microscopy (TEM). The low temperature samples with 8-20 ML of Ge were investigated by cross-section and plan-view TEM. The reported results of TEM studies of the local structure of germanium quantum dots (QDs) in Si/Ge/Si '' sandwich '' structures are in good correlation with EXAFS conclusion

  8. Quick EXAFS experiments using a now GDA eclipse RCP GUI with EPICS hardware control

    International Nuclear Information System (INIS)

    Woolliscroft, R.J.; Coles, C.; Gerring, M.; Pearson, M.

    2012-01-01

    The Generic Data Acquisition (GDA) framework is an open source, Java and Eclipse RCP based, data acquisition software framework for synchrotron and neutron facilities. A new implementation of the GDA on the B18 X-ray beamline at the Diamond synchrotron will be discussed. This beamline performs energy scanning Xray Absorption Spectroscopy (XAS) experiments. It includes a continuous-scan mode of the monochromator synchronized with various detectors for Quick EXAFS (QEXAFS) experiments. XAS energy scans may now be performed in 30 s, where the equivalent step scans take approximately 40 minutes. A new generic perspective for the GDA client has been developed in which graphical editors are used to write XML files which hold experimental parameters. The XML files are marshalled by the GDA server to create Java beans used by Jython scripts which run on the GDA server. Underlying this, a new generic continuous scanning mechanism for the GDA has been developed. The new Eclipse RCP UI, the new continuous scanning mechanism, new hardware development and integration between the two systems shall be covered. (authors)

  9. EXAFS and XRD studies of nanocrystalline cerium oxide: the effect of preparation method on the microstructure

    International Nuclear Information System (INIS)

    Savin, S.L.P.; Chadwick, A.V.; Smith, M.E.; O'Dell, L.A.

    2007-01-01

    There is considerable interest in nanocrystalline materials due to their unusual properties, such as enhanced ionic conductivity in the case of nanocrystalline ionic solids. This has potential commercial applications, particularly for oxide ion conductors. However, a detailed knowledge of the microstructure is important in fully understanding the novel properties exhibited by nanocrystalline materials. The final microstructure of a material is dependent on the preparation method used, for example, sol-gel and ball-milling methods are commonly used in the preparation of nanocrystalline oxides. Additionally, there is a problem in maintaining the materials in nanocrystalline form when they are subjected to elevated temperatures. We have been exploring strategies to restrict the growth of nanocrystalline oxides and have found that adding a small amount of an inert material, e.g. SiO 2 or Al 2 O 3 , is particularly effective. We will report XRD and EXAFS studies of nanocrystalline ceria prepared by sol-gel, sol-gel pinned and ball-milling methods and the effect of preparation method on the final microstructure. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Zinc adsorption on clays inferred from atomistic simulations and EXAFS spectroscopy

    International Nuclear Information System (INIS)

    Churakov, S.V.; Daehn, R.

    2012-01-01

    Document available in extended abstract form only. Clay minerals such as illite and montmorillonite are ubiquitous in the environment. Because of their large specific area and high structural charge, they control the migration of heavy metals in the geosphere via different uptake mechanisms. The main processes for the sequestration of trace concentrations of heavy metals are sorption to clay edge sites and incorporation into clay structures. Whereas, sorption is a fast process occurring nearly instantaneously, the incorporation of metal ions into clay minerals occurs over geological time scales. Zn is a divalent transition metal, which shows similar chemical behavior to Ni and Co and can thus also be considered as a natural analogue for radioactive Ni and Co arising from nuclear fuel and radioactive waste from the decommissioning of nuclear power plants. The release of radionuclides from a repository can be considerably retarded due to interactions with clay minerals. For example, bentonite containing >70 wt% di-octahedral alumino-silicate clays is foreseen as a backfill material in the Swiss concept for a high level radioactive waste repository (NAGRA, 2002). Knowing the uptake mechanism of these elements on clays can help to protect the natural environment. In this study ab initio molecular dynamics (MD) calculations were applied to simulate the molecular mechanism of Zn uptake on the edge surfaces of montmorillonite, a di-octahedral clay, and to explain the measured K-edge extended X-ray absorption fine structure (EXAFS) spectra of Zn adsorbed on montmorillonite at different loadings. Two different montmorillonites were chosen for the experimental part of this study: Milos (Island of Milos, Greece) and STx-1 (Gonzales County, Texas, USA) (VANTELON et al., 2003). As a reference for Zn substituted for Al in the clay octahedral sheet a MILOS sample was prepared without adding any Zn. Milos was chosen because it contains 1.8 [mmol/kg] Zn incorporated into the

  11. DEVELOPMENT OF A HIGH RATE HIGH RESOLUTION DETECTOR FOR EXAFS EXPERIMENTS.

    Energy Technology Data Exchange (ETDEWEB)

    DE GERONIMO,G.; O CONNOR,P.; BEUTTENMULLER,R.H.; LI,Z.; KUCZEWSKI,A.J.; SIDDONS,D.P.

    2002-11-10

    A new detector for EXAFS experiments is being developed. It is based on a multi-element Si sensor and dedicated readout ASICs. The sensor is composed of 384 pixels, each having 1 mm{sup 2} area, arranged in four quadrants of 12 x 8 elements, and wire-bonded to 32-channel front-end ASICs. Each channel implements low noise preamplification with self-adaptive continuous reset, high order shaper, band-gap referenced baseline stabilizer, one threshold comparator and two DAC adjustable window comparators, each followed by a 24-bit counter. Fabricated in 0.35{micro}m CMOS dissipates about 8mW per channel. First measurements show at room temperature a resolution of 14 rms electrons without the detector and of 40 rms electrons (340eV) with the detector connected and biased. Cooling at -35C a FWHM of 205eV (167eV from electronics) was measured at the Mn-K{alpha} line. A resolution of about 300eV was measured for rates approaching 100kcps/cm{sup 2} per channel, corresponding to an overall rate in excess of 10MHz/cm{sup 2}. A channel-to-channel threshold dispersion after DACs adjustment of 2.5 rms electrons was also measured.

  12. EXAFS studies on the reaction of gold (III) chloride complex ions with sodium hydroxide and glucose.

    Science.gov (United States)

    Pacławski, K; Zajac, D A; Borowiec, M; Kapusta, Cz; Fitzner, K

    2010-11-11

    EXAFS and QEXAFS experiments were carried out at Hasylab laboratory in DESY center (X1 beamline, Hamburg, Germany) to monitor the course of the hydrolysis reactions of [AuCl(4)](-) complex ions as well as their reduction using glucose. As a result, changes in the spectra of [AuCl(4)](-) ions and disappearance of absorption Au-L(3) edge were registered. From the results of the experiments we have carried out, the changes in bond lengths between Au(3+) central ion and Cl(-) ligands as well as the reduction of Au(3+) to metallic form (colloidal gold was formed in the system) are evident. Good quality spectra obtained before and after the reactions gave a chance to determine the bond length characteristic of Au-Cl, Au-OH and Au-Au pairs. Additionally, the obtained results were compared with the simulated spectra of different gold (III) complex ions, possibly present in the solution. Finally, the mechanism of these reactions was suggested. Unfortunately, it was not possible to detect the changes in the structure of gold (III) complex ions within the time of reaction, because of too high rates of both processes (hydrolysis and reduction) as compared with the detection time.

  13. Synchrotron Micro-XANES Measurements of Vanadium Oxidation State in Glasses as a Function of Oxygen Fugacity: Experimental Calibration of Data Relevant to Partition Coefficient Determination

    Science.gov (United States)

    Delaney, J. S.; Sutton, S. R.; Newville, M.; Jones, J. H.; Hanson, B.; Dyar, M. D.; Schreiber, H.

    2000-01-01

    Oxidation state microanalyses for V in glass have been made by calibrating XANES spectral features with optical spectroscopic measurements. The oxidation state change with fugacity of O2 will strongly influence partitioning results.

  14. μ-XRF and μ-XANES at calcification fronts of human articular cartilage

    International Nuclear Information System (INIS)

    Streli, C.; Zoeger, N.; Wobrauschek, P.; Jokubonis, C.; Pepponi, G.; Falkenberg, G.; Simon, P.; Roschger, P.; Tampieri, A.

    2006-01-01

    fronts of human calcified tissue. The finding of elevated Pb levels in cartilage compared to the subchondral region of the bone (about 10 times higher) motivated a study on the chemical speciation of Pb in both compartments of calcified human tissue. Comparing results from micro x-ray Absorption Near Edge Structure (μXANES) measurements in the tidemark with the ones from adequate standard materials gives information on the chemical bond of Pb in human cartilage. Results from a first μ-XANES experiment carried out at HASYLAB beamline L will be presented in this paper. μ-XANES scans at the tidemark of a femoral head and patella, and on a set of standard materials namely Pb-hydroxyapatite, PbO, PbS, PbCO 3 , and PbSO 4 have been compared and will be presented. Although suffering from weak counting statistics one could estimate from the results, that most of the accumulated Pb in the tidemark is bound to hydroxyapatite. (author)

  15. Kinetics of iron redox reaction in silicate melts: A high temperature Xanes study on an alkali basalt

    Energy Technology Data Exchange (ETDEWEB)

    Cochain, B; Neuville, D R; Roux, J; Strukelj, E; Richet, P [Physique des Mineraux et Magmas, Geochimie-Cosmochimie, CNRS-IPGP, 4 place Jussieu, 75005 Paris (France); Ligny, D de [Universite Claude Bernard Lyon 1, LPCML, F-69622 Villeurbanne (France); Baudelet, F, E-mail: cochain@ipgp.jussieu.f [Synchrotron SOLEIL, L' Orme des Merisiers, Saint Aubin (France)

    2009-11-15

    In Earth and Materials sciences, iron is the most important transition element. Glass and melt properties are strongly affected by iron content and redox state with the consequence that some properties (i.e. viscosity, heat capacity, crystallization...) depend not only on the amounts of Fe{sup 2+} and Fe{sup 3+}, but also on the coordination state of these ions. In this work we investigate iron redox reactions through XANES experiments at the K-edge of iron. Using a high-temperature heating device, pre-edge of XANES spectra exhibits definite advantages to make in-situ measurements and to determine the evolution of redox state with time, temperature and composition of synthetic silicate melts. In this study, new kinetics measurements are presented for a basalt melt from the 31,000-BC eruption of the Puy de Lemptegy Volcano in France. These measurements have been made between 773 K and at superliquidus temperatures up to 1923 K.

  16. Kinetics of iron redox reaction in silicate melts: A high temperature Xanes study on an alkali basalt

    International Nuclear Information System (INIS)

    Cochain, B; Neuville, D R; Roux, J; Strukelj, E; Richet, P; Ligny, D de; Baudelet, F

    2009-01-01

    In Earth and Materials sciences, iron is the most important transition element. Glass and melt properties are strongly affected by iron content and redox state with the consequence that some properties (i.e. viscosity, heat capacity, crystallization...) depend not only on the amounts of Fe 2+ and Fe 3+ , but also on the coordination state of these ions. In this work we investigate iron redox reactions through XANES experiments at the K-edge of iron. Using a high-temperature heating device, pre-edge of XANES spectra exhibits definite advantages to make in-situ measurements and to determine the evolution of redox state with time, temperature and composition of synthetic silicate melts. In this study, new kinetics measurements are presented for a basalt melt from the 31,000-BC eruption of the Puy de Lemptegy Volcano in France. These measurements have been made between 773 K and at superliquidus temperatures up to 1923 K.

  17. A XANES and Raman investigation of sulfur speciation and structural order in Murchison and Allende meteorites

    Science.gov (United States)

    Bose, M.; Root, R. A.; Pizzarello, S.

    2017-03-01

    Insoluble organic matter (IOM) and hydrothermally treated IOM extracted from two carbonaceous chondrites, Murchison and Allende, was studied using sulfur K-edge XANES (X-ray absorption near edge structure) and μ-Raman spectroscopy, with the aim to understand their IOM's sulfur speciation and structural order, and how aqueous alteration or thermal metamorphism may have transformed these materials. We found that the sulfur-functional group chemistry of both the Murchison IOM and hydrothermally treated IOM samples have a large chemical variability ranging from oxidation states of S-2 to S+6, and exhibit a transformation in their oxidation state after the hydrothermal treatment (HT) to produce thiophenes and thiol compounds. Sulfoxide and sulfite peaks are also present in Murchison. Sulfates considered intrinsic to Murchison are most likely preaccretionary in nature, and not a result of reactions with water at high temperatures on the asteroid parent body. We argue that the reduced sulfides may have formed in the CM parent body, while the thiophenes and thiol compounds are a result of the HT. Micro-Raman spectra show the presence of aliphatic and aromatic moieties in Murchison's material as observed previously, which exhibits no change after HT. Because the Murchison IOM was modified, as seen by XANES analysis, absence of a change observed using micro-Raman indicated that although the alkyl carbons of IOM were cleaved, the aromatic network was not largely modified after HT. By contrast, Allende IOM contains primarily disulfide and elemental sulfur, no organic sulfur, and shows no transformation after HT. This nontransformation of Allende IOM after HT would indicate that parent body alteration of sulfide to sulfate is not feasible up to temperatures of 300°C. The reduced sulfur products indicate extreme secondary chemical processing from the precursor compounds in its parent body at temperatures as high as 624°C, as estimated from μ-Raman D band parameters. The

  18. Hg L3 XANES Study of Mercury Methylation in Shredded Eichhornia Crassipes

    International Nuclear Information System (INIS)

    Rajan, M.; Darrow, J.; Hua, M.; Barnett, B.; Mendoza, M.; Greenfield, B.K.; Andrews, J.C.

    2008-01-01

    Eichhornia crassipes (water hyacinth) is a non-native plant found in abundance in the Sacramento-San Joaquin River Delta (hereafter called Delta). This species has become a problem, clogging waterways and wetlands. Water hyacinth are also known to accumulate mercury. Recent attempts to curb its proliferation have included shredding with specialized boats. The purpose of this research is to better understand the ability of water hyacinth to phytoremediate mercury and to determine the effect of shredding and anoxic conditions on mercury speciation in plant tissue. In the field assessment, total mercury levels in sediment from the Dow Wetlands in the Delta were found to be 0.273 ± 0.070 ppm Hg, and levels in hyacinth roots and shoots from this site were 1.17 ± 0.08 ppm and 1.03 ± 0.52 ppm, respectively, indicating bioaccumulation of mercury. Plant samples collected at this site were also grown in nutrient solution with 1 ppm HgCl 2 under (1) aerobic conditions, (2) anaerobic conditions, and (3) with shredded plant material only. The greatest accumulation was found in the roots of whole plants. Plants grown in these conditions were also analyzed at Stanford Synchrotron Radiation Laboratory using Hg L 3 X-ray Absorption Near Edge Spectroscopy (XANES), a method to examine speciation that is element-specific and noninvasive. Least-squares fitting of the XANES data to methylated and inorganic mercury(II) model compounds revealed that in plants grown live and aerobically, 5 ± 3% of the mercury was in the form of methylmercury, in a form similar to methylmercury cysteine. This percentage increased to 16 ± 4% in live plants grown anaerobically and to 22 ± 6% in shredded anaerobic plants. We conclude that shredding of the hyacinth plants and, in fact, subjection of plants to anaerobic conditions (e.g., as in normal decay, or in crowded growth conditions) increases mercury methylation. Mechanical removal of the entire plant is significantly more expensive than shredding

  19. Synchrotron WAXS and XANES studies of silica (SiO2) powders synthesized from Indonesian natural sands

    International Nuclear Information System (INIS)

    Muchlis, Khairanissa; Fauziyah, Nur Aini; Pratapa, Suminar; Soontaranon, Siriwat; Limpirat, Wanwisa

    2017-01-01

    In this study, we have investigated polymorphic silica (SiO 2 ) powders using, Wide Angle X-ray Scattering (WAXS) and X-Ray Absorption Near Edge Spectroscopy (XANES), laboratory X-Ray Diffraction (XRD) instruments. The WAXS and XANES spectra were collected using synchrotron radiation at Synchrotron Light Research Institute (SLRI), Nakhon Ratchasima, Thailand. The silica powders were obtained by processing silica sand from Tanah Laut, South Kalimantan, Indonesia. Purification process of silica sand was done by magnetic separation and immersion with HCl. The purification step was needed to reduce impurity or undesirable non Si elements. Three polymorphs of silica were produced, i.e. amorphous phase (A), quartz (B), and cristobalite (C). WAXS profile for each phase was presented in terms of intensity vs. 2θ prior to analyses. Both XRD (λ CuKα =1.54056 Å) and WAXS (λ=1.09 Å) patttern show that (1) A sample contains no crystallites, (2) B sample is monophasic, contains only quartz, and (3) C sample contains cristobalite and trydimite. XRD quantitative analysis using Rietica gave 98,8 wt% cristobalite, while the associated WAXS data provided 98.7 wt% cristobalite. Si K-edge XANES spectra were measured at energy range 1840 to 1920 eV. Qualitatively, the pre-edge and edge features for all phases are similar, but their main peaks in the post-edge region are different. (paper)

  20. Environmental impacts of steel slag reused in road construction: A crystallographic and molecular (XANES) approach

    Energy Technology Data Exchange (ETDEWEB)

    Chaurand, Perrine [CEREGE, UMR 6635 CNRS, University Paul Cezanne, IFR 112 PMSE, Europole Mediterraneen de l' Arbois, BP 80, 13545 Aix en Provence Cedex 04 (France)]. E-mail: chaurand@cerege.fr; Rose, Jerome [CEREGE, UMR 6635 CNRS, University Paul Cezanne, IFR 112 PMSE, Europole Mediterraneen de l' Arbois, BP 80, 13545 Aix en Provence Cedex 04 (France); Briois, Valerie [LURE Laboratoire pour l' Utilisation du Rayonnement Electromagnetique, Universite Paris-Sud, Orsay (France); Olivi, Luca [Sincrotrone Trieste S.C.p.A. S.S., 14 Km 163.5, 34012 Basovizza Trieste (Italy); Hazemann, Jean-Louis [Laboratoire de Cristallographie, BP 166, 38042 Grenoble Cedex 09 (France); Proux, Olivier [Laboratoire de Geophysique Interne et de Tectonophysique, UMR CNRS Universite Joseph Fourier, 1381 rue de la piscine, Domaine Universitaire, 38400 St Martin d' Heres (France); Domas, Jeremie [INERIS, Domaine du petit Arbois, Batiment Laennec, BP 33, 13545 Aix en Provence Cedex 04 (France); Bottero, Jean-Yves [CEREGE, UMR 6635 CNRS, University Paul Cezanne, IFR 112 PMSE, Europole Mediterraneen de l' Arbois, BP 80, 13545 Aix en Provence Cedex 04 (France)

    2007-01-31

    Basic oxygen furnace (BOF) steel slag is a residue from the basic oxygen converter in steel-making operations, and is partially reused as an aggregate for road constructions. Although BOF slag is an attractive building material, its long-term behaviour and the associated environmental impacts must be taken into account. Indeed BOF slag is mainly composed of calcium, silicon and iron but also contains trace amounts of potential toxic elements, specifically chromium and vanadium, which can be released. The present research focuses (i) on the release of Cr and V during leaching and (ii) on their speciation within the bearing phase. Indeed the mobility and toxicity of heavy metals strongly depend on their speciation. Leaching tests show that only low amounts of Cr, present at relatively high concentration in steel slag, are released while the release of V is significantly high. X-ray absorption near-edge structure (XANES) spectroscopy indicates that Cr is present in the less mobile and less toxic trivalent form and that its speciation does not evolve during leaching. On the contrary, V which is predominantly present in the 4+ oxidation state seems to become oxidized to the pentavalent form (the most toxic form) during leaching.

  1. Environmental impacts of steel slag reused in road construction: A crystallographic and molecular (XANES) approach

    International Nuclear Information System (INIS)

    Chaurand, Perrine; Rose, Jerome; Briois, Valerie; Olivi, Luca; Hazemann, Jean-Louis; Proux, Olivier; Domas, Jeremie; Bottero, Jean-Yves

    2007-01-01

    Basic oxygen furnace (BOF) steel slag is a residue from the basic oxygen converter in steel-making operations, and is partially reused as an aggregate for road constructions. Although BOF slag is an attractive building material, its long-term behaviour and the associated environmental impacts must be taken into account. Indeed BOF slag is mainly composed of calcium, silicon and iron but also contains trace amounts of potential toxic elements, specifically chromium and vanadium, which can be released. The present research focuses (i) on the release of Cr and V during leaching and (ii) on their speciation within the bearing phase. Indeed the mobility and toxicity of heavy metals strongly depend on their speciation. Leaching tests show that only low amounts of Cr, present at relatively high concentration in steel slag, are released while the release of V is significantly high. X-ray absorption near-edge structure (XANES) spectroscopy indicates that Cr is present in the less mobile and less toxic trivalent form and that its speciation does not evolve during leaching. On the contrary, V which is predominantly present in the 4+ oxidation state seems to become oxidized to the pentavalent form (the most toxic form) during leaching

  2. EXAFS analysis of full color glasses and glass ceramics: local order and color

    International Nuclear Information System (INIS)

    Santa Cruz, Petrus A.; Sa, Gilberto F. de; Malta, Oscar L.; Silva, Jose expedito Cavalcante

    1996-01-01

    The generation and control of the relative intensities of the primary additive colors in solid state light emitters is very important to the development of higher resolution media, used in color monitors, solid state sensors, large area and flat displays and other optoelectronic devices. We have developed a multi-doped glassy material named FCG (full color glass, to generate and to control the primary light colors, allowing the simulation of any color of light by additive synthesis. Tm(III), Tb(III) and Eu(III) ions were used (0.01 to 5.0 mol%) as blue, green and red narrow emitters. A wide color gamut was obtained under ultraviolet excitation by varying the material composition. The chromaticity diagram is covered, including the white simulation. We proposed a mechanism to control the chromaticity of a fixed composition of the material, using the Er (III) as a selective quencher that may be deactivated by infrared excitation. Although this new material presents at this time a high efficiency, it may be improved because the energy transfer between the rare earth triad may be still reduced. Optical spectroscopy measurements confirms that it is still possible to improve the efficiency of the FCC material. EXAFS analysis will be used to probe the local environment around the triad of rare earth that generates the primary colors. For this purpose we have prepared single doped glasses with each component of the triad with the same concentration than FCG. The devitrification of these glasses will be analyzed in order to produce glassceramics with ion segregation. (author)

  3. Geological and anthropogenic factors influencing mercury speciation in mine wastes: An EXAFS spectroscopy study

    Science.gov (United States)

    Kim, C.S.; Rytuba, J.J.; Brown, Gordon E.

    2004-01-01

    The speciation of Hg is a critical determinant of its mobility, reactivity, and potential bioavailability in mine-impacted regions. Furthermore, Hg speciation in these complex natural systems is influenced by a number of physical, geological, and anthropogenic variables. In order to investigate the degree to which several of these variables may affect Hg speciation, extended X-ray absorption fine structure (EXAFS) spectroscopy was used to determine the Hg phases and relative proportions of these phases present in Hg-bearing wastes from selected mine-impacted regions in California and Nevada. The geological origin of Hg ore has a significant effect on Hg speciation in mine wastes. Specifically, samples collected from hot-spring Hg deposits were found to contain soluble Hg-chloride phases, while such phases were largely absent in samples from silica-carbonate Hg deposits; in both deposit types, however, Hg-sulfides in the form of cinnabar (HgS, hex.) and metacinnabar (HgS, cub.) dominate. Calcined wastes in which Hg ore was crushed and roasted in excess of 600??C, contain high proportions of metacinnabar while the main Hg-containing phase in unroasted waste rock samples from the same mines is cinnabar. The calcining process is thought to promote the reconstructive phase transformation of cinnabar to metacinnabar, which typically occurs at 345??C. The total Hg concentration in calcines is strongly correlated with particle size, with increases of nearly an order of magnitude in total Hg concentration between the 500-2000 ??m and process, identified the presence of Hg-sulfides and schuetteite (Hg3O2SO4), which may have formed as a result of long-term Hg(0) burial in reducing high-sulfide sediments. ?? 2003 Elsevier Ltd. All rights reserved.

  4. EXAFS Characterization of Dendrimer-Derived Pt/γ-Al2O3

    International Nuclear Information System (INIS)

    Siani, A.; Alexeev, O. S.; Williams, C. T.; Ploehn, H. J.; Amiridis, M. D.

    2007-01-01

    The various steps involved in the preparation of a Pt/γ-Al2O3 material using hydroxyl-terminated generation four (G4OH) PAMAM dendrimers as templates were monitored by EXAFS. The results indicate that Cl ligands in the Pt precursors (H2PtCl6 and K2PtCl4) were partially replaced by aquo ligands upon hydrolysis to form [PtCl3(H2O)3]+ and [PtCl2(H2O)2] species. After interaction of such species with G4OH, Cl ligands from the first coordination shell of Pt were further replaced by nitrogen atoms from the dendrimer interior, indicating the complexation of Pt with the dendrimer. This process was accompanied by a transfer of the electron density from the dendrimer to Pt, indicating that the former plays the role of a ligand. Following treatment of the H2PtCl6/G4OH and K2PtCl4/G4OH composites with NaBH4, no substantial changes were detecteded in the electronic or coordination environment of Pt, and no formation of metal nanoparticles was observed. However, when the reduction treatment was performed with H2, the formation of extremely small Pt clusters incorporating no more than 4 Pt atoms was observed. These Pt species remained strongly bonded to the dendrimer and their nuclearity depends on the length of the H2 treatment. Formation of Pt nanoparticles with an average diameter of approximately 10 A was finally observed after the deposition of H2PtCl6/G4OH on γ-Al2O3 and drying, suggesting that their formation may be related to the collapse of the dendrimer structure. The Pt nanoparticles formed appear to have high mobility, since subsequent thermal treatment in O2/H2 led to further sintering

  5. Comparative study of the electronic structure of natural and synthetic ...

    Indian Academy of Sciences (India)

    ... have studied the Cr–K-edge XANES and EXAFS in natural Indian rubies from two sources and a synthetic ruby at ESRF. Weight % of various constituents in them is determined using EDAX measurements. Taking the results from the three techniques together we are able to demonstrate their feasibility in quantitative study ...

  6. Evolution of phosphorus complexation and mineralogy during (hydro)thermal treatments of activated and anaerobically digested sludge: Insights from sequential extraction and P K-edge XANES.

    Science.gov (United States)

    Huang, Rixiang; Tang, Yuanzhi

    2016-09-01

    (Hydro)thermal treatments of sewage sludge is a promising option that can simultaneously target safe waste disposal, energy recovery, and nutrient recovery/recycling. The speciation of phosphorus (P) in sludge is of great relevance to P reclamation/recycling and soil application of sludge-derived products, thus it is critical to understand the effects of different treatment techniques and conditions on P speciation. This study systematically characterized P speciation (i.e. complexation and mineral forms) in chars derived from pyrolysis and hydrothermal carbonization (HTC) of municipal sewage sludges. Combined sequential extraction and P K-edge X-ray absorption near edge structure (XANES) spectroscopy analysis revealed the dependence of P transformation on treatment conditions and metal composition in the feedstocks. Pyrolysis of sludges decreased the relative abundance of phytic acid while increased the abundance of Al-associated P. HTC thoroughly homogenized and exposed P for interaction with various metals/minerals, with the final P speciation closely related to the composition/speciation of metals and their affinities to P. Results from this study revealed the mechanisms of P transformation during (hydro)thermal treatments of sewage sludges, and might be applicable to other biosolids. It also provided fundamental knowledge basis for the design and selection of waste management strategies for better P (re)cycling and reclamation. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. In situ Ru K-edge EXAFS of CO adsorption on a Ru modified Pt/C fuel cell catalyst

    International Nuclear Information System (INIS)

    Rose, Abigail; Bilsborrow, Robert; King, Colin R.; Ravikumar, M.K.; Qian Yangdong; Wiltshire, Richard J.K.; Crabb, Eleanor M.; Russell, Andrea E.

    2009-01-01

    The Ru-CO bond of CO adsorbed on a Ru modified Pt/C fuel cell catalyst has been directly probed by in situ EXAFS at the Ru K-edge, providing evidence of a CO:metal surface atom ratio greater than 1:1 and that CO is adsorbed at bridging sites associated with Ru atoms at the surface of the catalyst nanoparticles. This result illustrates the limitations of single crystal models as representations of the bonding of adsorbed species at nanoparticle surfaces.

  8. Spin Equilibria in Monomeric Manganocenes: Solid State Magnetic and EXAFS Studies

    Energy Technology Data Exchange (ETDEWEB)

    Walter, M. D.; Sofield, C. D.; Booth, C. H.; Andersen, R. A.

    2009-02-09

    Magnetic susceptibility measurements and X-ray data confirm that tert-butyl-substituted manganocenes [(Me{sub 3}C){sub n}C{sub 5}H{sub 5?n}]{sub 2}Mn (n = 1, 2) follow the trend previously observed with the methylated manganocenes; that is, electron-donating groups attached to the Cp ring stabilize the low-spin (LS) electronic ground state relative to Cp{sub 2}Mn and exhibit higher spin-crossover (SCO) temperatures. However, introducing three CMe{sub 3} groups on each ring gives a temperature-invariant high-spin (HS) state manganocene. The origin of the high-spin state in [1,2,4-(Me{sub 3}C){sub 3}C{sub 5}H{sub 2}]{sub 2}Mn is due to the significant bulk of the [1,2,4-(Me{sub 3}C){sub 3}C{sub 5}H{sub 2}]{sup -} ligand, which is sufficient to generate severe inter-ring steric strain that prevents the realization of the low-spin state. Interestingly, the spin transition in [1,3-(Me{sub 3}C){sub 2}C{sub 5}H{sub 3}]{sub 2}Mn is accompanied by a phase transition resulting in a significant irreversible hysteresis ({Delta}T{sub c} = 16 K). This structural transition was also observed by extended X-ray absorption fine-structure (EXAFS) measurements. Magnetic susceptibility studies and X-ray diffraction data on SiMe{sub 3}-substituted manganocenes [(Me{sub 3}Si){sub n}C{sub 5}H{sub 5-n}]{sub 2}Mn (n = 1, 2, 3) show high-spin configurations in these cases. Although tetra- and hexasubstituted manganocenes are high-spin at all accessible temperatures, the disubstituted manganocenes exhibit a small low-spin admixture at low temperature. In this respect it behaves similarly to [(Me{sub 3}C)(Me{sub 3}Si)C{sub 5}H{sub 3}]{sub 2}Mn, which has a constant low-spin admixture up to 90 K and then gradually converts to high-spin. Thermal spin-trapping can be observed for [(Me{sub 3}C)(Me{sub 3}Si)C{sub 5}H{sub 3}]{sub 2}Mn on rapid cooling.

  9. Techniques for materials research with synchrotron radiation x-rays

    International Nuclear Information System (INIS)

    Bowen, D.K.

    1983-01-01

    A brief introductory survey is presented of the properties and generation of synchrotron radiation and the main techniques developed so far for its application to materials problems. Headings are:synchrotron radiation; X-ray techniques in synchrotron radiation (powder diffraction; X-ray scattering; EXAFS (Extended X-ray Absorption Fine Structure); X-ray fluorescent analysis; microradiography; white radiation topography; double crystal topography); future developments. (U.K.)

  10. 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.

  11. 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...

  12. Multiple Scattering Approach to Polarization Dependence of F K-Edge XANES Spectra for Highly Oriented Polytetrafluoroethylene (PTFE) Thin Film

    International Nuclear Information System (INIS)

    Nagamatsu, S.; Ono, M.; Kera, S.; Okudaira, K. K.; Fujikawa, T.; Ueno, N.

    2007-01-01

    The polarization dependence of F K-edge X-ray absorption near edge structure (XANES) spectra of highly-oriented thin-film of polytetrafluoroethylene (PTFE) has been analyzed by using multiple scattering theory. The spectra show clear polarization dependence due to the highly-oriented structure. The multiple scattering calculations reflects a local structure around an absorbing atom. The calculated results obtained by considering intermolecular-interactions are in good agreement with the observed polarization-dependence. We have also analyzed structural models of the radiation damaged PTFE films

  13. Solvent phase characterisation of lanthanide(3) and americium(3) complexes with malonamide (tema) and ter-pyridine ligands by EXAFS: comparison with single crystals

    International Nuclear Information System (INIS)

    Den Auwer, C.; Presson, M.T.; Grigoriev, M.; Madic, C.; Nierlich, M.; Thuery, P.; David, F.; Hubert, S.; Drew, M.G.B.; Hudson, M.J.; Iveson, P.B.; Russell, M.L.

    2002-01-01

    In order to develop molecules that will be good candidates for the extractive separation of the various elements contained within nuclear fuels, 4f and 5f molecular chemistry has been the subject of numerous studies. Thus, to better understand the ligand to cation interaction and to fine tune the theoretical models, precise knowledge about the cation co-ordination sphere must be obtained. More precisely, both structural and electronic data must be acquired in order to define the role of the cation frontier orbitals within the complex. To do so, various structural probes must be used, from vibrational and nuclear techniques to X-ray spectroscopies. In the field of actinide solvent extraction, the species of interest are in the solvent phase and both solid state diffraction methods and solvent phase X-ray absorption spectroscopy have become of primary importance lately. A number of Ln(III) and Am(III) complexes of the type M(NO 3 ) 3 L 1,2 (where M is either Ln 3+ or Am 3+ and L is either the 2,2',6',2 - ter-pyridine (Tpy) or the N,N,N',N' tetraethyl-malonamide (TEMA) ligand) have been crystallographically characterised in the solid state. In order to obtain structural information in the solvent phase, EXAFS L III edge measurements have been performed on the cation (DCI ring at the LURE facility). The overall contraction (-0.05 Angstrom) of the cation co-ordination sphere from Nd 3+ to Lu 3+ reflects the decrease in the lanthanide ionic radii. With the TEMA ligand, this steric constraint generates the elongation of one nitrate bond, leading to one formally monodendate nitrate for the late Ln ions. Comparison is made with the Tpy ligand. In the case of Am 3+ cation, comparison with isostructural Nd 3+ shows that similar co-ordination spheres are obtained, either with the TEMA or the Tpy ligands. (authors)

  14. Fate and chemical speciation of antimony (Sb) during uptake, translocation and storage by rye grass using XANES spectroscopy.

    Science.gov (United States)

    Ji, Ying; Sarret, Géraldine; Schulin, Rainer; Tandy, Susan

    2017-12-01

    Antimony (Sb) is a contaminant of increased prevalence in the environment, but there is little knowledge about the mechanisms of its uptake and translocation within plants. Here, we applied for the synchrotron based X-ray absorption near-edge structure (XANES) spectroscopy to analyze the speciation of Sb in roots and shoots of rye grass (Lolium perenne L. Calibra). Seedlings were grown in nutrient solutions to which either antimonite (Sb(III)), antimonate (Sb(V)) or trimethyl-Sb(V) (TMSb) were added. While exposure to Sb(III) led to around 100 times higher Sb accumulation in the roots than the other two treatments, there was no difference in total Sb in the shoots. Antimony taken up in the Sb(III) treatment was mainly found as Sb-thiol complexes (roots: >76% and shoots: 60%), suggesting detoxification reactions with compounds such as glutathione and phytochelatins. No reduction of accumulated Sb(V) was found in the roots, but half of the translocated Sb was reduced to Sb(III) in the Sb(V) treatment. Antimony accumulated in the TMSb treatment remained in the methylated form in the roots. By synchrotron based XANES spectroscopy, we were able to distinguish the major Sb compounds in plant tissue under different Sb treatments. The results help to understand the translocation and transformation of different Sb species in plants after uptake and provide information for risk assessment of plant growth in Sb contaminated soils. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Hydration effects on the molecular structure of silica-supported vanadium oxide catalysts: A combined IR, Raman, UV–vis and EXAFS study

    NARCIS (Netherlands)

    Keller, D.E.; Visser, T.; Soulimani, F.; Koningsberger, D.C.; Weckhuysen, B.M.

    2007-01-01

    The effect of hydration on the molecular structure of silica-supported vanadium oxide catalysts with loadings of 1–16 wt.% V has been systematically investigated by infrared, Raman, UV–vis and EXAFS spectroscopy. IR and Raman spectra recorded during hydration revealed the formation of V–OH groups,

  16. Determination of sorption mechanisms of radionuclides onto clay minerals using extended x-ray absorption fine structure (EXAFS) spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Daehn, R.; Scheidegger, A.; Baeyens, B.; Bradbury, M.H

    2001-03-01

    Much of the experimental work in the Waste Management Laboratory at PSI concentrates on trying to understand the processes and mechanisms which govern the release of safety-relevant radionuclides from waste matrices, and their transport through engineered barrier systems and the surrounding geosphere. For this reason, detailed sorption studies of radionuclides (Cs, Sr, Ni, Zn, Eu, Am, Th and Se) in clay and cement systems are being conducted. The sorption and modelling studies are combined with kinetic investigations and advanced spectroscopic and microscopic methods in order to understand the sorption mechanism on an atomic level. This approach is part of a new multidisciplinary research field called Molecular Environmental Science (MES). In this paper, a case study of Ni sorption on montmorillonite is presented to illustrate how EXAFS can be used successfully to better understand sorption processes. (author)

  17. Determination of sorption mechanisms of radionuclides onto clay minerals using extended x-ray absorption fine structure (EXAFS) spectroscopy

    International Nuclear Information System (INIS)

    Daehn, R.; Scheidegger, A.; Baeyens, B.; Bradbury, M.H.

    2001-01-01

    Much of the experimental work in the Waste Management Laboratory at PSI concentrates on trying to understand the processes and mechanisms which govern the release of safety-relevant radionuclides from waste matrices, and their transport through engineered barrier systems and the surrounding geosphere. For this reason, detailed sorption studies of radionuclides (Cs, Sr, Ni, Zn, Eu, Am, Th and Se) in clay and cement systems are being conducted. The sorption and modelling studies are combined with kinetic investigations and advanced spectroscopic and microscopic methods in order to understand the sorption mechanism on an atomic level. This approach is part of a new multidisciplinary research field called Molecular Environmental Science (MES). In this paper, a case study of Ni sorption on montmorillonite is presented to illustrate how EXAFS can be used successfully to better understand sorption processes. (author)

  18. EXAFS study on the neptunium(V) complexation by various humic acids under neutral pH conditions

    Energy Technology Data Exchange (ETDEWEB)

    Sachs, S.; Schmeide, K.; Brendler, V.; Heise, K.H.; Bernhard, G. [Forschungszentrum Rossendorf e.V., Inst. of Radiochemistry, Dresden (Germany); Reich, T. [Forschungszentrum Rossendorf e.V., Inst. of Radiochemistry, Dresden (Germany); Univ. Mainz, Inst. of Nuclear Chemistry (Germany)

    2005-07-01

    The structure of Np(V) humic acid (HA) complexes at pH 7 was studied by extended X-ray absorption fine structure analysis (EXAFS). For the first time, the influence of phenolic OH groups on the complexation of HA and Np(V) in the neutral pH range was investigated using modified HAs with blocked phenolic OH groups and Bio-Rex70, a cation exchange resin having only carboxyl groups as proton exchanging sites. The formation of Np(V) humate complexes was verified by near-infrared (NIR) spectroscopy. Axial Np-O bond distances of 1.84-1.85 Aa were determined for the studied Np(V) humate complexes and the Np(V)-Bio-Rex70 sorbate. In the equatorial plane Np(V) is surrounded by about 3 oxygen atoms with bond lengths of 2.48-2.49 Aa. The comparison of the structural parameters of the Np(V) humates with those of Np(V)-Bio-Rex70 points to the fact that the interaction between HA and Np(V) in the neutral pH range is dominated by carboxylate groups. However, up to now a contribution of phenolic OH groups to the interaction process cannot be excluded completely. The comparison of the obtained structural data for the Np(V) humates to those of Np(V) carboxylates and Np(V) aquo ions reported in the literature indicates that humic acid carboxylate groups predominantly act as monodentate ligands. A differentiation between equatorial coordinated carboxylate groups and water molecules using EXAFS spectroscopy is impossible. (orig.)

  19. Diurnal Variation and Spatial Distribution Effects on Sulfur Speciation in Aerosol Samples as Assessed by X-Ray Absorption Near-Edge Structure (XANES

    Directory of Open Access Journals (Sweden)

    Siwatt Pongpiachan

    2012-01-01

    Full Text Available This paper focuses on providing new results relating to the impacts of Diurnal variation, Vertical distribution, and Emission source on sulfur K-edge XANES spectrum of aerosol samples. All aerosol samples used in the diurnal variation experiment were preserved using anoxic preservation stainless cylinders (APSCs and pressure-controlled glove boxes (PCGBs, which were specially designed to prevent oxidation of the sulfur states in PM10. Further investigation of sulfur K-edge XANES spectra revealed that PM10 samples were dominated by S(VI, even when preserved in anoxic conditions. The “Emission source effect” on the sulfur oxidation state of PM10 was examined by comparing sulfur K-edge XANES spectra collected from various emission sources in southern Thailand, while “Vertical distribution effects” on the sulfur oxidation state of PM10 were made with samples collected from three different altitudes from rooftops of the highest buildings in three major cities in Thailand. The analytical results have demonstrated that neither “Emission source” nor “Vertical distribution” appreciably contribute to the characteristic fingerprint of sulfur K-edge XANES spectrum in PM10.

  20. 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.

  1. SORPTION OF ARSENATE AND ARSENITE ON RUO2 X H2O: ANALYSIS OF SORBED PHASE OXIDATION STATE BY XANES IN ADVANCED PHOTON SOURCE ACTIVITY REPORT 2002

    Science.gov (United States)

    The sorption reactions of arsenate (As(V)) and arsenite (As(III)) on RuO2 x H2O were examined by X-ray Absorption Near Edge Spectroscopy (XANES) to elucidate the solid state speciation of sorbed As. At all pH values studied (pH 4-8), RuO2 x H

  2. XANES study on Ruddlesdan-Popper phase, Lan+1NinO3n+1 (n = 1, 2 and ∞)

    International Nuclear Information System (INIS)

    Park, Jung-Chul; Kim, Dong-Kuk; Byeon, Song-Hu; Kim, Don

    2001-01-01

    Ruddlesden-Popper phase, La n+1 Ni n O 3n+ 1 (n = 1, 2, and ∞) compounds were prepared by citrate sol-gel method. We revealed the origin of the variation of the electrical conductivities in La n+1 Ni n O 3n+1 (n= 1, 2, and ∞) using resistivity measurements, Rietveld analysis, and X-ray absorption spectroscopy. According to the XANES spectra, it is found that the degree of 4pπ - 4pσ energy splitting between 8345 eV and 8350 eV is qualitatively proportional to the elongation of the out-of-plane Ni-O bond length. With the decrease of 4pπ-4pσ splitting, the strong hybridization of the σ-bonding between Ni-3d and O-2p orbitals creates narrow antibonding σ bands, which finally results in the lower electrical resistivity. (au)

  3. Following the Formation of Active Co(III) Sites in Cobalt Substituted Aluminophosphates Catalysts by In-Situ Combined UV-VIS/XAFS/XRD Technique

    International Nuclear Information System (INIS)

    Sankar, Gopinathan; Fiddy, Steven; Harvey, Ian; Hayama, Shusaku; Bushnell-Wye, Graham; Beale, Andrew M.

    2007-01-01

    Cobalt substituted aluminophosphates, CoAlPO-34 (Chabazite structure) and DAF-8 (Phillipsite structure) were investigated by in situ combined XRD/EXAFS/UV-VIS technique. In-situ combined XRD, Co K-edge EXAFS and UV-Vis measurements carried out during the calcination process reveal that CoAlPO-34 containing 10 wt percent cobalt is stable and the cobalt ions are converted from Co(II) in the as synthesised form to Co(III); DAF-8 containing about 25 percent cobalt is not stable and does not show change in oxidation state

  4. The structure of well defined SiO2 supported MoO3 clusters during sulfidation : an in situ EXAFS-study

    NARCIS (Netherlands)

    Boer, de M.; Dillen, van A.J.; Koningsberger, D.C.; Geus, J.W.; Kuroda, H.; Ohta, T.

    1993-01-01

    The sulfidation of a well defined MoO3/SiO2 catalyst has been examd. by means of TPS, EXAFS, and TEM. The oxidic clusters in a 5.6 wt% MoO3/SiO2 catalyst are transformed into almost completely sulfided particles (MoOxSy) by O-S exchange at RT. A molybdenum-sulfido particle that resembles the MoS3

  5. In-Plane Structure of Underpotentially Deposited Copper on Gold (111) Determined by Surface EXAFS (Extended X-Ray Absorption Fine Structure).

    Science.gov (United States)

    1988-01-28

    EXAFS is the inverse transform of the two peaks in the RSF using a filtering a12 function to isolate the range between I and 4A. Both the frequency...backscattering of different neighbors. This inverse transform contains only one frequency and its envelope of intensity is the backscattering amplitude function...and the inverse transform of the RSF using a fourier filter between 1 and 4A (Solid line). Insert: Radial Structure Function (RSF) analyzed between

  6. Lanthanide complexes of macrocyclic polyoxovanadates by VO4 units: synthesis, characterization, and structure elucidation by X-ray crystallography and EXAFS spectroscopy.

    Science.gov (United States)

    Nishio, Masaki; Inami, Shinnosuke; Katayama, Misaki; Ozutsumi, Kazuhiko; Hayashi, Yoshihito

    2012-01-16

    Reactions of a tetravanadate anion, [V(4)O(12)](4-), with a series of lanthanide(III) salts yield three types of lanthanide complexes of macrocyclic polyoxovanadates: (Et(4)N)(6)[Ln(III)V(9)O(27)] [Ln = Nd (1), Sm (2), Eu (3), Gd (4), Tb (5), Dy (6)], (Et(4)N)(5)[(H(2)O)Ho(III)(V(4)O(12))(2)] (7), and (Et(4)N)(7)[Ln(III)V(10)O(30)] [Ln = Er (8), Tm (9), Yb (10), Lu (11)]. Lanthanide complexes 1-11 are isolated and characterized by IR, elemental analysis, single-crystal X-ray diffraction, and extended X-ray absorption fine structure spectroscopy (EXAFS). Lanthanide complexes 1-6 are composed of a square-antiprism eight-coordinated Ln(III) center with a macrocyclic polyoxovanadate that is constructed from nine VO(4) tetrahedra through vertex sharing. The structure of 7 is composed of a seven-coordinated Ho(III) center, which exhibits a capped trigonal-prism coordination environment by the sandwiching of two cyclic tetravanadates with a capping H(2)O ligand. Lanthanide complexes 8-11 have a six-coordinated Ln(III) center with a 10-membered vanadate ligand. The structural trend to adopt a larger coordination number for a larger lanthanide ion among the three types of structures is accompanied by a change in the vanadate ring sizes. These lanthanide complexes are examined by EXAFS spectroscopies on lanthanide L(III) absorption edges, and the EXAFS oscillations of each of the samples in the solid state and in acetonitrile are identical. The Ln-O and Ln···V bond lengths obtained from fits of the EXAFS data are consistent with the data from the single-crystal X-ray studies, reflecting retention of the structures in acetonitrile.

  7. EXAFS analysis of intermediate phases in the synthesis of the YBa2Cu3O7-x high-Tc superconductor from xerogel

    International Nuclear Information System (INIS)

    Arcon, I.; Bele, M.; Hribar, M.; Kodre, A.; Pejovnik, S.; Stuhec, M.; Drube, W.

    1994-01-01

    In the synthesis of superconducting cuprate ceramics starting from gels, the advantage of stoichiometric homogeneity of the constituent atoms on the molecular level is exploited. However, x-ray diffraction analysis of samples taken in consecutive temperature points in the process of calcination shows formation of a number of well-crystalized intermediary products. EXAFS spectrometry gives additional insight into the process, providing the information on the neighborhood of constituent atoms in the crystalline as well as amorphous phase. (orig.)

  8. Characterization of structural properties of U and Pu in model systems by advanced synchrotron based X-ray spectroscopy

    International Nuclear Information System (INIS)

    Pidchenko, Ivan

    2016-01-01

    This dissertation presents the investigations of different U and Pu model systems relevant for safety assessment studies of nuclear waste repositories using the X-ray based synchrotron techniques: U and Pu L_3/M_4_,_5 edges HR-XANES, L_3 edge EXAFS and 3d4f RIXS as well as other complementary techniques, including XPS, XRD, SEM, TEM and UV-Vis-NIR techniques.

  9. Evidence from EXAFS for Different Ta/Ti Site Occupancy in High Critical Current Density Nb3Sn Superconductor Wires.

    Science.gov (United States)

    Heald, Steve M; Tarantini, Chiara; Lee, Peter J; Brown, Michael D; Sung, ZuHawn; Ghosh, Arup K; Larbalestier, David C

    2018-03-19

    To meet critical current density, J c , targets for the Future Circular Collider (FCC), the planned replacement for the Large Hadron Collider (LHC), the high field performance of Nb 3 Sn must be improved, but champion J c values have remained static for the last 10 years. Making the A15 phase stoichiometric and enhancing the upper critical field H c2 by Ti or Ta dopants are the standard strategies for enhancing high field performance but detailed recent studies show that even the best modern wires have broad composition ranges. To assess whether further improvement might be possible, we employed Extended X-ray Absorption Fine Structure (EXAFS) to determine the lattice site location of dopants in modern high-performance Nb 3 Sn strands with J c values amongst the best so far achieved. Although Ti and Ta primarily occupy the Nb sites in the A15 structure, we also find significant Ta occupancy on the Sn site. These findings indicate that the best performing Ti-doped stand is strongly sub-stoichiometric in Sn and that antisite disorder likely explains its high average H c2 behavior. These new results suggest an important role for dopant and antisite disorder in minimizing superconducting property distributions and maximizing high field J c properties.

  10. Hard real-time quick EXAFS data acquisition with all open source software on a commodity personal computer

    International Nuclear Information System (INIS)

    So, I.; Siddons, D.P.; Caliebe, W.A.; Khalid, S.

    2007-01-01

    We describe here the data acquisition subsystem of the Quick EXAFS (QEXAFS) experiment at the National Synchrotron Light Source of Brookhaven National Laboratory. For ease of future growth and flexibility, almost all software components are open source with very active maintainers. Among them, Linux running on x86 desktop computer, RTAI for real-time response, COMEDI driver for the data acquisition hardware, Qt and PyQt for graphical user interface, PyQwt for plotting, and Python for scripting. The signal (A/D) and energy-reading (IK220 encoder) devices in the PCI computer are also EPICS enabled. The control system scans the monochromator energy through a networked EPICS motor. With the real-time kernel, the system is capable of deterministic data-sampling period of tens of micro-seconds with typical timing-jitter of several micro-seconds. At the same time, Linux is running in other non-real-time processes handling the user-interface. A modern Qt-based controls-frontend enhances productivity. The fast plotting and zooming of data in time or energy coordinates let the experimenters verify the quality of the data before detailed analysis. Python scripting is built-in for automation. The typical data-rate for continuous runs are around 10 M bytes/min

  11. Micro-XANES Determination Fe Speciation in Natural Basalts at Mantle-Relevant fO2

    Science.gov (United States)

    Fischer, R.; Cottrell, E.; Lanzirotti, A.; Kelley, K. A.

    2007-12-01

    We demonstrate that the oxidation state of iron (Fe3+/ΣFe) can be determined with a precision of ±0.02 (10% relative) on natural basalt glasses at mantle-relevant fO2 using Fe K-edge X-ray absorption near edge structure (XANES) spectroscopy. This is equivalent to ±0.25 log unit resolution relative to the QFM buffer. Precise determination of the oxidation state over this narrow range (Fe3+/ΣFe=0.06-0.30) and at low fO2 (down to QFM-2) relies on appropriate standards, high spectral resolution, and highly reproducible methods for extracting the pre-edge centroid position. We equilibrated natural tholeiite powder in a CO/CO2 gas mixing furnace at 1350°C from QFM-3 to QFM+2 to create six glasses of known Fe3+/ΣFe, independently determined by Mössbauer spectroscopy. XANES spectra were collected at station X26A at NSLS, Brookhaven Natl. Lab, in fluorescence mode (9 element Ge array detector) using both Si(111) and Si(311) monochromators. Generally, the energy position of the 1s→3d (pre-edge) transition centroid is the most sensitive monitor of Fe oxidation state using XANES. For the mixture of Fe oxidation states in these glasses and the resulting coordination geometries, the pre-edge spectra are best defined by two multiple 3d crystal field transitions. The Si(311) monochromator, with higher energy resolution, substantially improved spectral resolution for the 1s→3d transition. Dwell times of 5s at 0.1eV intervals across the pre-edge region yielded spectra with the 1s→3d transition peaks clearly resolved. The pre-edge centroid position is highly sensitive to the background subtraction and peak fitting procedures. Differences in fitting models result in small but significant differences in the calculated peak area of each pre-edge multiplet, and the relative contribution of each peak to the calculated centroid. We assessed several schemes and obtained robust centroid positions by simultaneously fitting the background with a damped harmonic oscillator (DHO

  12. The O2-Evolving Complex of Photosystem II: Recent Insights from Quantum Mechanics/Molecular Mechanics (QM/MM), Extended X-ray Absorption Fine Structure (EXAFS), and Femtosecond X-ray Crystallography Data.

    Science.gov (United States)

    Askerka, Mikhail; Brudvig, Gary W; Batista, Victor S

    2017-01-17

    Efficient photoelectrochemical water oxidation may open a way to produce energy from renewable solar power. In biology, generation of fuel due to water oxidation happens efficiently on an immense scale during the light reactions of photosynthesis. To oxidize water, photosynthetic organisms have evolved a highly conserved protein complex, Photosystem II. Within that complex, water oxidation happens at the CaMn 4 O 5 inorganic catalytic cluster, the so-called oxygen-evolving complex (OEC), which cycles through storage "S" states as it accumulates oxidizing equivalents and produces molecular oxygen. In recent years, there has been significant progress in understanding the OEC as it evolves through the catalytic cycle. Studies have combined conventional and femtosecond X-ray crystallography with extended X-ray absorption fine structure (EXAFS) and quantum mechanics/molecular mechanics (QM/MM) methods and have addressed changes in protonation states of μ-oxo bridges and the coordination of substrate water through the analysis of ammonia binding as a chemical analog of water. These advances are thought to be critical to understanding the catalytic cycle since protonation states regulate the relative stability of different redox states and the geometry of the OEC. Therefore, establishing the mechanism for substrate water binding and the nature of protonation/redox state transitions in the OEC is essential for understanding the catalytic cycle of O 2 evolution. The structure of the dark-stable S 1 state has been a target for X-ray crystallography for the past 15 years. However, traditional X-ray crystallography has been hampered by radiation-induced reduction of the OEC. Very recently, a revolutionary X-ray free electron laser (XFEL) technique was applied to PSII to reveal atomic positions at 1.95 Å without radiation damage, which brought us closer than ever to establishing the ultimate structure of the OEC in the S 1 state. However, the atom positions in this crystal

  13. 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

  14. 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.

  15. 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.

  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. 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

  18. Change in Localizations of Arsenic in Rice Grains After Cooking with High Arsenic Waters - µXRF and XANES studies

    Science.gov (United States)

    Datta, S.; Ryan, B.; Kumar, N.; Bortz, T.; Bolen, Z. T.

    2016-12-01

    Threats of Arsenic (As) through food uptake, via consumption of rice, is a potential pathway that presents a concern not only for the millions of inhabitants who reside in river valleys and irrigate their soil with contaminated water, but the global rice market as well. This study focuses on high As rice from India and Bangladesh grown in such soils, and the effect of boiling rice with As-contaminated water in preparation for dietary intake. Husked and unhusked rice grains were boiled with >500 µg/L As-bearing water from the field to simulate local cooking methods. The resulting cooked water was analyzed using iCAP low limit detection via ICP-MS to understand the changes in dissolved elemental concentrations before and after cooking, and HPLC was introduced to measure for changes in As speciation in the waters. Using spectroscopic methods such as µXRF mapping associated with µXANES, distribution/localization and speciation changes of As in rice grains were identified. Further, with Linear Combination Fitting (LCF) of XANES spectra utilizing relevant reference compounds (As-S, AsIII, AsV, MMA and DMA), organic and inorganic As species were able to be mapped within rice grains. The results for uncooked/raw grains showed that predominantly As-S combined with AsIII and AsV accounted for 90% of speciation in most samples, localized in areas such as the outer aleurone layer. When analyzing cooked rice grains, the speciation appears to be an unidentified As species while the best LCF shows between 63-93% of As as MMA. Arsenic was found less localized throughout the cooked grains but rather heterogeneously distributed when compared to the uncooked/raw samples. The analyses of boiled/cooked water resulted in a significant decrease in dissolved As post-cooking (90%), but a subsequent increase in elements such as K, La, Li, Mo, Na, Ni, and Zr was observed; As-V was shown to be the main in-As species in the cooked water. The impact that this study portrays is consuming rice

  19. Local Environment Sensitivity of the Cu K-Edge XANES Features in Cu-SSZ-13: Analysis from First-Principles.

    Science.gov (United States)

    Zhang, Renqin; McEwen, Jean-Sabin

    2018-05-22

    Cu K-edge X-ray absorption near-edge spectra (XANES) have been widely used to study the properties of Cu-SSZ-13. In this Letter, the sensitivity of the XANES features to the local environment for a Cu + cation with a linear configuration and a Cu 2+ cation with a square-linear configuration in Cu-SSZ-13 is reported. When a Cu + cation is bonded to H 2 O or NH 3 in a linear configuration, the XANES has a strong peak at around 8983 eV. The intensity of this peak decreases as the linear configuration is broken. As for the Cu 2+ cations in a square-planar configuration with a coordination number of 4, two peaks at around 8986 and 8993 eV are found. An intensity decrease for both peaks at around 8986 and 8993 eV is found in an NH 3 _4_Z 2 Cu model as the N-Cu-N angle changes from 180 to 100°. We correlate these features to the variation of the 4p state by PDOS analysis. In addition, the feature peaks for both the Cu + cation and Cu 2+ cation do not show a dependence on the Cu-N bond length. We further show that the feature peaks also change when the coordination number of the Cu cation is varied, while these feature peaks are independent of the zeolite topology. These findings help elucidate the experimental XANES features at an atomic and an electronic level.

  20. Mn K-edge XANES spectroscopy of photosynthetic water oxidation enzyme in the S0-, S1-, S2- and S3-states induced by flash excitation

    International Nuclear Information System (INIS)

    Ono, Taka-aki; Noguchi, Takumi; Inoue, Yorinao; Kusunoki, Masami; Matsushita, Tadashi; Oyanagi, Hiroyuki.

    1993-01-01

    Electronic and structural rearrangement of the Mn-cluster during the four step oxidation of water in photosynthetic oxygen evolution was studied by XANES spectroscopy. The Mn K-edge energy of the spectrum was changed with flash number to show a clear quadruple oscillation, indicating a periodic change in oxidation and electronic state of the Mn-cluster depending on Joliot and Kok's oxygen clock. (author)

  1. Local structure information by EXAFS analysis using two algorithms for Fourier transform calculation

    International Nuclear Information System (INIS)

    Aldea, N; Pintea, S; Rednic, V; Matei, F; Hu Tiandou; Xie Yaning

    2009-01-01

    The present work is a comparison study between different algorithms of Fourier transform for obtaining very accurate local structure results using Extended X-ray Absorption Fine Structure technique. In this paper we focus on the local structural characteristics of supported nickel catalysts and Fe 3 O 4 core-shell nanocomposites. The radial distribution function could be efficiently calculated by the fast Fourier transform when the coordination shells are well separated while the Filon quadrature gave remarkable results for close-shell coordination.

  2. New insights into the role of Mn and Fe in coloring origin of blue decorations of blue-and-white porcelains by XANES spectroscopy

    International Nuclear Information System (INIS)

    Zhu, Jian; Luo, Wugan; Ming, Chaofang; Wang, Changsui; Chen, Dongliang; Xu, Wei; Wang, Lihua

    2013-01-01

    Blue and white porcelain is one of the most valuable ancient ceramics varieties in ancient China. It is well known for its beautiful blue decorations. However, the origin of its blue color has not been very clear till now. In this research, two blue and white porcelains from Jingdezhen, Jiangxi province were selected and Mn and Fe K-edge XANES spectra were recorded from blue decorations with or without transparent glaze. Results showed that Mn K-edge XANES features were almost identical between different samples while that of iron changed. The above findings indicated the positive role of iron in the variation of blue decorations. As for manganese, although more system researches were need, its negative role on the variations of the tone of blue decorations was obtained. On the other hand, the paper also revealed the XAFS results will be affect by the glaze layer above the pigment. These findings provided us more information to understand the coloring origin of blue decorations of blue-and-white porcelain by means of XANES spectroscopy.

  3. Comparison of Nickel XANES Spectra and Elemental Maps from a Ureilite, a LL3.8 Ordinary Chondrite, Two Carbonaceous Chondrites and Two Large Cluster IDPs

    Science.gov (United States)

    Wirick, S.; Flynn, G. J.; Sutton, S.; Zolensky, M. E.

    2014-01-01

    Nickel in the extraterrestrial world is commonly found in both Fe-Ni sulfide and Fe-Ni met-al forms [1] and in the pure metal state in the interior of iron meteorites where it is not easily oxidized. Ni is also found in olivine, pyroxene and glasses and in some melts the partitioning of Ni between the olivines and glass is controlled by the amount of S in the melt [2]. Its most common valence state is Ni(2+) but Ni also occurs as Ni(0), Ni(+), and Ni(3+) and rarely as Ni(2-), Ni(1-) and Ni(4+) [3]. It's valence state in olivines is Ni(2+) in octa-hedral coordination on the M1 site and rarely on the M2 site.[4]. The chemical sensitivity of X-ray absorp-tion near-edge structure (XANES) spectroscopy is well established and can be used to determine not only va-lence states but also coordination sites [5]. We report here Ni XANES spectroscopy and elemental maps collected from 2 carbonaceous chondrites, 2 large clus-ter IDPs, 1 ureilite and 1 LL3 orginary chondrite.Using XANES it may be possible to find a common trait in the large cluster IDPs that will also be found in mete-orite samples.

  4. An X-ray absorption near-edge structure (XANES) study of the Sn L_3 edge in zirconium alloy oxide films formed during autoclave corrosion

    International Nuclear Information System (INIS)

    Hulme, Helen; Baxter, Felicity; Babu, R. Prasath; Denecke, Melissa A.; Gass, Mhairi; Steuwer, Axel; Norén, Katarina; Carlson, Stefan; Preuss, Michael

    2016-01-01

    Highlights: • Characterisation of tin speciation in zirconium alloy metal and oxide films using Sn L_3-XANES. • Chemical environment of tin in Zircaloy-4 and ZIRLO™ oxide films shown to be similar. • Tin in the oxide films is present in both the di- and tetravalent states and oxidises progressively with oxide-layer growth. - Abstract: Application of Sn L_3-XANES to study the oxidation state of alloying additions of tin (1–1.2 wt%) in <2 μm oxide layers formed on nuclear grade zirconium alloy has been demonstrated. Data obtained for metallic and corroded ZIRLO™ (1 wt% Sn) and Zircaloy-4 (1.2 wt% Sn) indicate tin has a similar chemical speciation in both metal alloys but this differs in the oxidised surface layers. By recording XANES at various incident angles to vary the photon penetration depth and amount of the oxide layer probed in the measurement, the authors found evidence that the oxidation of tin progresses with increasing oxide thickness.

  5. New insights into the role of Mn and Fe in coloring origin of blue decorations of blue-and-white porcelains by XANES spectroscopy

    Science.gov (United States)

    Zhu, Jian; Luo, Wugan; Chen, Dongliang; Xu, Wei; Ming, Chaofang; Wang, Changsui; Wang, Lihua

    2013-04-01

    Blue and white porcelain is one of the most valuable ancient ceramics varieties in ancient China. It is well known for its beautiful blue decorations. However, the origin of its blue color has not been very clear till now. In this research, two blue and white porcelains from Jingdezhen, Jiangxi province were selected and Mn and Fe K-edge XANES spectra were recorded from blue decorations with or without transparent glaze. Results showed that Mn K-edge XANES features were almost identical between different samples while that of iron changed. The above findings indicated the positive role of iron in the variation of blue decorations. As for manganese, although more system researches were need, its negative role on the variations of the tone of blue decorations was obtained. On the other hand, the paper also revealed the XAFS results will be affect by the glaze layer above the pigment. These findings provided us more information to understand the coloring origin of blue decorations of blue-and-white porcelain by means of XANES spectroscopy.

  6. Ce-doped nanoparticles of TiO2: Rutile-to-brookite phase transition and evolution of Ce local-structure studied with XRD and XANES

    International Nuclear Information System (INIS)

    Kityakarn, Sutasinee; Worayingyong, Attera; Suramitr, Anwaraporn; Smith, M.F.

    2013-01-01

    The crystal and electronic structural changes undergone by TiO 2 nanoparticles when Ce is introduced were studied using X-ray diffraction (XRD) and X-ray absorption near-edge spectroscopy (XANES). A small amount of Ce (less than 1% molar concentration) resulted in i/a significant reduction of the average size of the TiO 2 nanoparticles and ii/a phase transition in which brookite replaced rutile as the minority phase component (anatase was the majority phase component at all Ce concentrations studied up to 10% molar concentration). The Ce L3 edge XANES revealed changes in the local environment of Ce impurities. As Ce concentration was increased the fraction of Ce that have formal valence of +3 decreased and, for the remaining Ce with valence +4, the 4f orbitals became less-strongly hybridized with the p-orbitals of oxygen neighbors. The results have implications for photocatalytic and gas sensing properties of Ce-doped TiO 2 . - Highlights: ► Ce-doping: TiO 2 nanoparticles shrink and minority phase changes rutile-> brookite. ► XANES reveals phase change for arbitrarily small particles (while XRD fails). ► As Ce added: fraction of Ce +3 dopants falls, hybridization of Ce +4 with O weakens

  7. STXM-XANES Analysis of Organic Matter in Dark Clasts and Halite Crystals in Zag and Monahans Meteorites

    Science.gov (United States)

    Kebukawa, Y.; Zolensky, M. E.; Fries, M.; Nakato, A.; Kilcoyne, A. L. D.; Takeichi, Y.; Suga, H.; Miyamoto, C.; Rahman, Z.; Kobayashi, K.; hide

    2016-01-01

    Zag and Monahans meteorites (H5) contains xenolithic dark clasts and halite (NaCl) crystals [e.g., 1]. The proposed source of the H chondrites is asteroid 6 Hebe [2]. The modern orbits of 1 Ceres and 6 Hebe essentially cross, with aphelion/perihelion of Ceres and Hebe of 2.99/2.55 and 2.91/1.94 AU (Astronomical Units), respectively. Therefore, Ceres might be the source of the clasts and halite in Zag and Monahans meteorites. Recent results from NASA's Dawn mission shows that bright spots in Ceres's crater may be hydrated magnesium sulfate with some water ice, and an average global surface contains ammoniated phyllosilicates that is likely of outer Solar System origin. One dark clast and all halite crystals in Zag and Monahans meteorites contain carbon-rich particles. We report organic analyses of these carbon-rich particles using carbon, nitrogen, and oxygen X-ray absorption near edge structure (C-, N-, and O-XANES), in order to constrain the origin of the clast and halite crystals.

  8. Determination of localized Fe2+/Fe3+ ratios in inks of historic documents by means of μ-XANES

    International Nuclear Information System (INIS)

    Proost, K.; Janssens, K.; Wagner, B.; Bulska, E.; Schreiner, M.

    2004-01-01

    An important part of the European cultural heritage is composed of hand-written documents. Many of these documents were drawn up with iron-gall ink. This type of ink present a serious conservation problem, as it slowly oxidizes ('burns') the paper it is written on, thereby gradually disintegrating the historic document. Acid hydrolysis of the cellulose and/or the oxidation of organic compounds promoted by radical intermediates that are formed due to the presence of Fe 2+ ions are considered to be the cause of the disintegration. μ-XANES measurements were performed with a lateral resolution of 30-50 μm in order to determine the local Fe 2+ /Fe 3+ ratio in 19th C. documents from the Austrian National Archives and fragments of 16th C documents from the Polish National Library. In the 19th C documents, no significant amount of Fe 2+ was detected. On the other hand, in the 16th C fragments, significant amounts of Fe 2+ and appreciable differences in distribution of Fe 2+ and Fe 3+ within individual letters/ink stains were observed

  9. The valence state of Yb metal under high pressure determined by XANES measurement up to 34.6 GPa

    International Nuclear Information System (INIS)

    Fuse, Akinori; Nakamoto, Go; Kurisu, Makio; Ishimatsu, Naoki; Tanida, Hajime

    2004-01-01

    The purpose of this study was to accurately determine the valency of Yb at high pressure and room temperature and to clarify the relation between the valence state and the crystal structure of Yb metal. L III -edge X-ray absorption near-edge structure (XANES) spectra were measured to determine the valence state of Yb metal in the pressure range from 0 to 34.6 GPa at room temperature, using a diamond anvil cell (DAC) and synchrotron radiation at SPring-8. In the fcc phase, Yb metal exhibits mixed valence (the mean valence ν-bar >2.1). At the fcc-to-bcc phase transition, a 0.1 jump is found in ν-bar. In the bcc phase, ν-bar(P) is an increasing function of pressure with downward curvature, reaching only 2.55 at 26 GPa. The ν-bar is only 2.65 in the hcp phase at 34.6 GPa. A tendency for saturation in ν-bar(P) to values smaller than 3.0 is found

  10. The darkening of zinc yellow: XANES speciation of chromium in artist;s paints after light and chemical exposures

    Energy Technology Data Exchange (ETDEWEB)

    Zanella, Luciana; Casadio, Francesca; Gray, Kimberly A.; Warta, Richard; Ma, Qing; Gaillard, Jean-François

    2012-03-14

    The color darkening of selected brushstrokes of the masterpiece A Sunday on La Grande Jatte - 1884 (by Georges Seurat) has been attributed to the alteration of the chromate pigment zinc yellow. The pigment originally displays a bright greenish-yellow color but may undergo, after aging, darkening to a dull, ocher tone. We used XANES to probe the oxidation state of Cr on paint reconstructions, and show that color changes are associated with the reduction of Cr(VI) to Cr(III). Paint mixtures containing the pigment and linseed oil to mimic mixtures used in La Grande Jatte were subjected to artificial aging in the presence of light, SO{sub 2}, and variable air humidity - 50 and 90% relative humidity. High relative humidity led to the largest degree of Cr(VI) reduction whereas low relative humidity promoted light-induced alterations. These results are corroborated by visible reflectance measurements on the same laboratory samples and contribute to a better understanding of the chemical reactivity of chromate pigments, which are present in many historical works of art.

  11. Characterization of the impregnated iron based catalyst for direct coal liquefaction by EXAFS

    International Nuclear Information System (INIS)

    Yang Jianli; Zhun Jisheng; Liu Zhenyu; Zhong Bing

    2002-01-01

    Catalyst plays an important role in direct coal liquefaction (DCL). Iron catalysts are regarded as the most attractive catalysts for DCL. To maximize catalytic effect and minimize catalysts usage, ultra-fine size catalysts are preferred. The most effective catalysts are found to be those impregnated onto coal because of their high dispersion on coal surface and intimate contact with coal particles. Besides the physical size, chemical form of a catalyst or a catalyst precursor is also important in determination of DCL activity. The expended X-ray absorption fine structure spectroscopy technique were used in this study. It was shown that the catalysts tested are in nanomater range and have structure mainly in the form of γ-FeOOH and FeS, or possibly of Fe/O/S. The presence of γ-FeOOH can be attributed to the interaction between Fe and the oxygen containing groups of coal or oxygen from moisture

  12. An EXAFS Study on the Local Structure Around Iron in Atmospheric Aerosols Collected in the Qingdao Area

    Directory of Open Access Journals (Sweden)

    Tiandou Hu

    2003-01-01

    Full Text Available The existing forms of Fe are of great interest since they have a profound effect on the biological availability of Fe. In this work, aerosol samples collected in different seasons and at different locations in the Qingdao region were examined by means of extended X-ray absorption fine structure (EXAFS K-edge analysis of Fe, X-ray diffraction (XRD and Fe content analysis. The results showed that an iron ion in aerosol particles is surrounded on average by 5.8 (coordinated O ions. For the six samples examined, the coordination number of the first Fe-O coordination subshell is always 3 with a coordination distance (with O in the range of 1.952~1.966±0.002 Å, while the coordination number of the second subshell varies from 2.2 to 3.0 with a coordination distance of 2.108±0.002 Å. The coordination is approximately consistent with that of a-Fe2O3, suggesting that iron in aerosol samples is mainly present in the form of a-Fe2O3. The fact that the coordination number in the second subshell is smaller than that of a-Fe2O3 might be an indication that there is a small amount of FeO mixed with a-Fe2O3 in aerosol particles. Existence of FeO is confirmed by a later XRD experiment.

  13. Origin of Blue-Green Emission in α-Zn2P2O7 and Local Structure of Ln3+ Ion in α-Zn2P2O7:Ln3+ (Ln = Sm, Eu): Time-Resolved Photoluminescence, EXAFS, and DFT Measurements.

    Science.gov (United States)

    Gupta, Santosh Kumar; Ghosh, Partha Sarathi; Yadav, Ashok Kumar; Jha, Shambhu Nath; Bhattacharyya, Dibyendu; Kadam, Ramakant Mahadeo

    2017-01-03

    Considering the fact that pyrophosphate-based hosts are in high demand for making highly efficient luminescence materials, we doped two visible lanthanide ions, viz. Sm 3+ and Eu 3+ , in Zn 2 P 2 O 7 . Interestingly, it was oberved that pure Zn 2 P 2 O 7 displayed blue-green dual emission on irradiation with ultraviolet light. Emission and lifetime spectroscopy shows the presence of defects in pyrophosphate samples which are responsible for such emission. DFT calculations clearly pinpointed that the electronic transitions between defect states located at just below the conduction band minimum (arises due to V O 1+ and V O 2+ defects) and valence band maximum, as well as impurity states situated in the band gap, can lead to dual emission in the blue-green region, as is also indicated by emission and lifetime spectra. X-ray absorption near edge spectroscopy (XANES) shows the stabilization of europium as well as samarium ion in the +3 oxidation state in α-Zn 2 P 2 O 7 . The fact that α-Zn 2 P 2 O 7 has two different coordination numbers for zinc ions, i.e. five- and six-coordinate, the study of dopant ion distribution in this particular matrix will be an important step in realizing a highly efficient europium- and samarium-based red-emitting phosphor. Time resolved photoluminescence (TRPL) shows that both of these ions are heterogeneously distributed between five- and six-coordinated Zn 2+ sites and it is the six-coordinated Zn 2+ site which is the most favorable for lanthanide ion doping. Extended X-ray absorption fine structure (EXAFS) measurements also suggested that a six-coordinated zinc ion is the preferred site occupied by trivalent lanthanide ions, which is in complete agreement with TRPL results. It was observed that there is almost complete transfer of photon energy from Zn 2 P 2 O 7 to Eu 3+ , whereas this transfer is inefficient and almost incomplete in case of Sm 3+ , which is indeed important information for the realization of pyrophosphate

  14. Uranium-bearing francolites present in organic-rich limestones of NW Greece: a preliminary study using synchrotron radiation and fission track techniques

    DEFF Research Database (Denmark)

    Tzifas, I. T.; Glasmacher, U. A.; Misaelides, P.

    2017-01-01

    Synchrotron radiation techniques (μ-XRF and μ-XANES) were applied to the study of organic-rich phosphatized limestones of NW Greece (Epirus). The results revealed uranium accumulation in areas of the material containing, among others, carbonate apatite (francolite) and organic matter. The UL3-edge...

  15. Investigation of Technetium Redox Cycling in FRC Background Sediments using EXAFS and Gamma Camera Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Lloyd, J.R.; McBeth, J.M.; Lear, G.; Morris, K.; Burke, I.T.; Livens, F.R.; Ellis, B.; Lawson, R.

    2006-04-05

    Technetium-99 is a priority pollutant at numerous DOE sites, due to its long half-life (2.1 x 105 years), high mobility as Tc(VII) in oxic waters, and bioavailability as a sulfate analogue. {sup 99}Tc is far less mobile under anaerobic conditions, forming insoluble Tc(IV) precipitates. As anaerobic microorganisms can reduce soluble Tc(VII) to insoluble Tc(IV), microbial metabolism may have the potential to treat sediments and waters contaminated with Tc. Baseline studies of fundamental mechanisms of Tc(VII) bioreduction and precipitation (reviewed by Lloyd et al., 2005, in press) have generally used pure cultures of metal-reducing bacteria, in order to develop conceptual models for the biogeochemical cycling of {sup 99}Tc. There is, however, comparatively little known about interactions of metal-reducing bacteria with environmentally relevant trace concentrations of {sup 99}Tc, against a more complex biogeochemical background provided by mixed microbial communities in aquifer sediments. The objective of this project is to probe the site specific biogeochemical conditions that control the mobility of {sup 99}Tc at the US DOE Field Research Center Site (FRC; Oak Ridge, Tennessee). This information is required for the rational design of in situ bioremediation strategies for technetium-contaminated subsurface environments. We are using a combination of geochemical, mineralogical, microbiological and spectroscopic techniques to determine the solubility and phase associations of {sup 99}Tc in FRC sediments, and characterize the underpinning biogeochemical controls.

  16. Microscanning XRF, Xanes, And XRD Studies Of The decorated Surface Of Roman Terra Sigillata Ceramics

    International Nuclear Information System (INIS)

    Mirguet, C.; Sciau, P.; Goudeau, P.; Mehta, A.; Pianetta, P.; Liu, Z.; Tamura, N.

    2008-01-01

    Different microscanning synchrotron techniques were used to better understand the elaboration process and origins of Terra Sigillata potteries from the Roman period. A mixture Gallic slip sample cross-section showing red and yellow colors was studied. The small (micron) size of the X-ray beam available at Stanford Synchrotron Radiation Laboratory (SSRL) and Advanced Light Source (ALS) synchrotron sources, coupled with the use of a sample scanning stage allowed us to spatially resolve the distribution of the constitutive mineral phases related to the chemical composition. Results show that red color is a result of iron-rich hematite crystals and the yellow part is a result of the presence of Ti-rich rutile-type phase (brookite). Volcanic-type clay is at the origin of these marble Terra Sigillata.

  17. A combined wet chemistry and EXAFS study of U(VI) uptake by cementitious materials

    International Nuclear Information System (INIS)

    Wieland, E.; Harfouche, M.; Tits, J.; Kunz, D.; Daehn, R.; Fujita, T.; Tsukamoto, M.

    2006-01-01

    The sorption behaviour and speciation of U(VI) in cementitious systems was investigated by a combination of wet chemistry experiments and synchrotron-based X-ray absorption spectroscopy (XAS) measurements. Radiotracer studies using 233 U were carried out on hardened cement paste (HCP) and calcium silicate hydrates (C-S-H), which are the major constituents of HCP, to determine the uptake kinetics and sorption isotherms. C-S-H phases were synthesized using different methods for solid phase preparation, which enabled us to study the U(VI) uptake by different types of C-S-H phases and a wide range of Ca/Si compositions, and to distinguish U(VI) sorption on the surface of C-S-H from U(VI) incorporation into the structure. XAS measurements were performed using U(VI) loaded HCP and C-S-H materials (sorption and co-precipitation samples) to gain structural information on the U(VI) speciation in these systems, i.e., the type and number of neighbouring atoms, and bond distances. Examples of studies that have utilized XAS to characterize U(VI) speciation in cementitious systems are still rare, and to the best of our knowledge, detailed XAS investigations of the U(VI)/C-S-H system are lacking. The results obtained from the combined use of wet chemical and spectroscopic techniques allow mechanistic models of the immobilization process to be proposed for cementitious waste forms containing low and high U(VI) inventories. In the latter case U(VI) immobilization is controlled by a solubility-limiting process with the U(VI) mineral predominantly formed under the conditions prevailing in cementitious systems. At low U(VI) concentrations, however, U(VI) appears to be predominantly bound onto C-S-H phases. The coordination environment of U(VI) taken up by C-S-H was found to resemble that of U(VI) in uranophane. A mechanistic understanding of the U(VI) binding by cementitious materials will allow more detailed and scientifically well founded predictions of the retention of

  18. THE STATE OF MANGANESE IN THE PHOTOSYNTHETIC APPARATUS. I. EXAFS STUDIES ON CHLOROPLASTS AND di-u-oxo BRIDGED di-MANGANESE MODEL COMPOUNDS

    Energy Technology Data Exchange (ETDEWEB)

    Kirby, J. A.; Robertson, A. S.; Smith, J. P.; Thompson, A. C.; Thompson, A. C.; Klein, M. P.

    1980-11-01

    Extended X-ray Absorption Fine Structure (EXAFS) studies on the manganese contained in spinach chloroplasts and on certain di-u-oxo bridged manganese dimers of the form (X{sub 2}Mn)O{sub 2}(MnX{sub 2} (X=2,2'-bypyridine and 1,10-phenanthroline) are reported. From these studies, the manganese associated with photosynthetic oxygen evolution is suggested to occur as a bridged transition metal dimer with most likely another manganese. Extensive details on the analysis are included.

  19. Micro-XANES measurements on experimental spinels and the oxidation state of vanadium in coexisting spinel and silicate melt

    International Nuclear Information System (INIS)

    Righter, K.; Sutton, S.R.; Newville, M.; Le, L.; Schwandt, C.S.

    2006-01-01

    We show that experimental spinels coexisting with silicate melt always have lower valence vanadium, and that spinels typically have 3+, whereas the coexisting melt has 4+ or 5+. Implications of these results for planetary basalts will be discussed. Spinel can be a significant host phase for V which has multiple oxidation states V 2+ , V 3+ , V 4+ or V 5+ at oxygen fugacities relevant to natural systems. The magnitude of D(V) spinel/melt is known to be a function of composition, temperature and fO 2 , but the uncertainty of the oxidation state under the range of natural conditions has made elusive a thorough understanding of D(V) spinel/melt. For example, V 3+ is likely to be stable in spinels, based on exchange with Al in experiments in the CaO-MgO-Al 2 O 3 -SiO 2 system. On the other hand, it has been argued that V 4+ will be stable across the range of natural oxygen fugacities in nature. In order to build on our previous work in more oxidized systems, we have carried out experiments at relatively reducing conditions from the FMQ buffer to 2 log fO 2 units below the IW buffer. These spinel-melt pairs, where V is present in the spinel at natural levels (∼300 ppm V), were analyzed using an electron microprobe at NASA-JSC and mi-cro-XANES at the Advanced Photon Source at Argonne National Laboratory. The new results will be used together with previous results to understand the valence of V in spinel-melt systems across 12 orders of magnitude of oxygen fugacity, and with application to natural systems.

  20. 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

  1. 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.

  2. Non-equilibrium solid-to-plasma transition dynamics using XANES diagnostic

    Energy Technology Data Exchange (ETDEWEB)

    Dorchies, F., E-mail: dorchies@celia.u-bordeaux1.fr [Univ. Bordeaux, CNRS, CEA, CELIA (Centre Lasers Intenses et Applications), UMR 5107, F-33400 Talence (France); Recoules, V. [CEA-DAM-DIF, F-91297 Arpajon (France)

    2016-10-31

    The advent of femtosecond lasers has shed new light on non-equilibrium high energy density physics. The ultrafast energy absorption by electrons and the finite rate of their energy transfer to the lattice creates non-equilibrium states of matter, triggering a new class of non-thermal processes from the ambient solid up to extreme conditions of temperature and pressure, referred as the warm dense matter regime. The dynamical interplay between electron and atomic structures is the key issue that drives the ultrafast phase transitions dynamics. Bond weakening or bond hardening are predicted, but strongly depends on the material considered. Many studies have been conducted but this physics is still poorly understood. The experimental tools used up-to-now have provided an incomplete insight. Pure optical techniques measure only indirectly atomic motion through changes in the dielectric function whereas X-ray or electron diffraction only probes the average long-range order. This review is dedicated to recent developments in time-resolved X-ray absorption near-edge spectroscopy, which is expected to give a more complete picture by probing simultaneously the modifications of the near-continuum electron and local atomic structures. Results are reported for three different types of metals (simple, transition and noble metals) in which a confrontation has been carried out between measurements and ab initio simulations.

  3. Characterization of electron beam deposited thin films of HfO2 and binary thin films of (HfO2:SiO2) by XRD and EXAFS measurements

    International Nuclear Information System (INIS)

    Das, N.C.; Sahoo, N.K.; Bhattacharyya, D.; Thakur, S.; Kamble, N.M.; Nanda, D.; Hazra, S.; Bal, J.K.; Lee, J.F.; Tai, Y.L.; Hsieh, C.A.

    2009-10-01

    In this report, we have discussed the microstructure and the local structure of composite thin films having varying hafnia and silica compositions and prepared by reactive electron beam evaporation. XRD and EXAFS studies have confirmed that the pure hafnium oxide thin film has crystalline microstructure whereas the films with finite hafnia and silica composition are amorphous. The result of EXAFS analysis has shown that the bond lengths as well as coordination numbers around hafnium atom change with the variation of hafnia and silica compositions in the thin film. Finally, change of bond lengths has been correlated with change of refractive index and band gap of the composite thin films. (author)

  4. 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)

  5. Structural and thermal investigations of an amorphous GaSe9 alloy using EXAFS, cumulant expansion, and reverse Monte Carlo simulations

    International Nuclear Information System (INIS)

    Siqueira, M. C.; Maia, R. N. A.; Araujo, R. M. T.; Machado, K. D.; Stolf, S. F.

    2015-01-01

    In this article, we investigated structural and thermal properties of an amorphous alloy of the Ga–Se system. The amorphous GaSe 9 alloy was produced by mechanical alloying and it was studied using EXAFS spectroscopy and cumulant expansion method. We also made reverse Monte Carlo simulations using the total structure factor S(K) obtained from x-ray diffraction and the EXAFS χ(k) oscillations on Se and Ga K edges as input data. Several parameters, such as average coordination numbers and interatomic distances, structural and thermal disorders, asymmetry of the partial distribution functions g ij (r), and Einstein and Debye temperatures, were determined. The g ij E (r) functions were reconstructed from the cumulants C 1 , C 2 , and C 3 obtained from the Einstein model, and they were compared to the g ij RMC (r) functions obtained from the simulations. The simulations also furnished the partial bond angle distribution functions Θ ijℓ (cosθ), which describe the angular distribution of bonds between first neighbors, and give information about the kind of structural units present in the alloy

  6. Structure of a Rh/TiO2 catalyst in the strong metal-support interaction state as determined by EXAFS

    International Nuclear Information System (INIS)

    Koningsberger, D.C.; Martens, J.H.A.; Prins, R.; Short, D.R.; Sayers, D.E.

    1986-01-01

    Reduction of a highly dispersed 2.85 wt% Rh/TiO 2 catalyst at 473 K after previous calcination at 623 K resulted in EXAFS whose primary contributions are due to nearest rhodium (average coordination number of 3.1 and distance of 2.67 A) and oxygen neighbors (coordination 2.5 and distance 2.71 A). These oxygen neighbors originated at the metal-support interface. The average rhodium-rhodium coordination number did not change in the SMSI state produced by reducing the catalyst at 673 K. However, the average coordination distance contracted by 0.04 A with an accompanying decrease of the Debye-Waller factor of the Rh-Rh bond of 0.0012 A 2 . This is due to the fact that in the SMSI state the surface of the metal particles is not covered with chemisorbed hydrogen. The SMSI state leads to a structural reorganization of the support in the vicinity of the rhodium metal particles. This can be concluded from the appearance of a Rh-Ti bond at 3.42 A in the SMSI state coupled with the fact that the average coordination number of the rhodium-support oxygen bonds does not increase. Other types of rhodium-oxygen bonds could not be detected with EXAFS in this state. Thus, these results provide no evidence for coverage of the metal particle by a suboxide of TiO 2 in the SMSI state

  7. 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)

  8. Using Fluorescence XANES Measurement to Correct the Content of Hexavalent Chromium in Chromate Conversion Coatings Determined by Diphenyl Carbazide Color Test

    International Nuclear Information System (INIS)

    Nishino, Junichi; Ofuchi, Hironori; Taniguchi, Yosuke; Honma, Tetsuo; Sekikawa, Toshikazu; Otani, Haruka; Bando, Akio

    2007-01-01

    The Restriction of the use of certain Hazardous Substances (RoHS) directive will take effect on July 1 of this year. From that date, the use of chromate conversion coatings containing hexavalent chromium will not be permitted. By comparing the concentration of Cr6+ determined by the diphenyl carbazide color test and by fluorescence XANES (X-Ray Absorption Near Edge Structure) measurement, we can correct for the Cr6+ content of the color test. This will enable the use of the diphenyl carbazide color test to check product shipments in compliance with the RoHS directive

  9. Assessment of uranium and selenium speciation in human and bacterial biological models to probe changes in their structural environment

    Energy Technology Data Exchange (ETDEWEB)

    Avoscan, L.; Milgram, S.; Untereiner, G.; Collins, R.; Khodja, H.; Carriere, M.; Gouget, B. [Lab. Pierre Sue, CEA-CNRS UMR 9956, CEA/Saclay, Gif-sur-Yvette (France); Coves, J. [Inst. de Biologie Structurale - J.-P. Ebel, Lab. des Proteines Membranaires, Grenoble (France); Hazemann, J.L. [Lab. de Geophysique Interne et Tectonopbysique, UMR CNRS/Univ. Joseph Fourier, Saint-Martin-D' Heres (France)

    2009-07-01

    This study illustrates the potential of physicochemical techniques to speciate uranium (U) and selenium (Se) in biological samples. Speciation, defined he0re as the study of structural environment, of both toxic elements, was characterized at several levels in biological media and directly in human cells or bacteria once the metal(loid)s were internalized. External speciation that is extracellular speciation in culture media was predicted by thermodynamic equilibrium computer modelling using the JChess software and validated by spectroscopic measurements (XANES and EXAFS). Internal speciation that is intracellular speciation in eukaryotic and prokaryotic cells was studied in vitro with a soil bacterium Cupriavidus metallidurans CH34 and ROS 17/2.8 osteoblasts, human cells responsible for bone formation. XANES, EXAFS, HPLC-ICP-MS and SDS-PAGE coupled to particle induced X-ray emission (PIXE) permitted the identification and quantification of complexes formed with organic or inorganic molecules and/or larger proteins. (orig.)

  10. Assessment of uranium and selenium speciation in human and bacterial biological models to probe changes in their structural environment

    International Nuclear Information System (INIS)

    Avoscan, L.; Milgram, S.; Untereiner, G.; Collins, R.; Khodja, H.; Carriere, M.; Gouget, B.; Coves, J.; Hazemann, J.L.

    2009-01-01

    This study illustrates the potential of physicochemical techniques to speciate uranium (U) and selenium (Se) in biological samples. Speciation, defined he0re as the study of structural environment, of both toxic elements, was characterized at several levels in biological media and directly in human cells or bacteria once the metal(loid)s were internalized. External speciation that is extracellular speciation in culture media was predicted by thermodynamic equilibrium computer modelling using the JChess software and validated by spectroscopic measurements (XANES and EXAFS). Internal speciation that is intracellular speciation in eukaryotic and prokaryotic cells was studied in vitro with a soil bacterium Cupriavidus metallidurans CH34 and ROS 17/2.8 osteoblasts, human cells responsible for bone formation. XANES, EXAFS, HPLC-ICP-MS and SDS-PAGE coupled to particle induced X-ray emission (PIXE) permitted the identification and quantification of complexes formed with organic or inorganic molecules and/or larger proteins. (orig.)

  11. In situ XANES studies of TiO{sub 2}/Fe{sub 3}O{sub 4}-C during photocatalytic degradation of trichloroethylene

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, T.-F.; Hsiung, T.-L. [Department of Environmental Engineering, National Cheng Kung University, Tainan 70101, Taiwan (China); Wang, James [Department of Biomedical Engineering, University of Southern California, Los Angeles 90007 (United States); Huang, C.-H. [Department of Environmental Engineering, National Cheng Kung University, Tainan 70101, Taiwan (China); Paul Wang, H., E-mail: wanghp@mail.ncku.edu.t [Department of Environmental Engineering, National Cheng Kung University, Tainan 70101, Taiwan (China); Sustainable Environmental Research Center, National Cheng Kung University, Tainan 70101, Taiwan (China)

    2010-07-21

    Mainly anatase and Fe{sub 3}O{sub 4} in the magnetic photocatalysts (TiO{sub 2} on Fe{sub 3}O{sub 4}-C core-shell nanoparticles (TiO{sub 2}/Fe{sub 3}O{sub 4}-C)) are observed by X-ray powder diffraction (XRD) spectroscopy. The Ti K-edge least-square fitted XANES spectra of the TiO{sub 2}/Fe{sub 3}O{sub 4}-C photocatalyst indicate that the main titanium species are nanosize TiO{sub 2} (9 nm) (77%) and bulky TiO{sub 2} (23%). Speciation of titanium in the TiO{sub 2}/Fe{sub 3}O{sub 4}-C during photocatalytic degradation of 100 ppm of trichloroethylene (TCE) has also been studied by in situ X-ray absorption near-edge structural (XANES) spectroscopy. TiO{sub 2} is not perturbed during the course of photocatalysis. However, it is worth to note that during photocatalytic degradation of TCE, about 33% of FeO and 67% of Fe{sub 3}O{sub 4} are observed in the photocatalyst. It seems that the carbon layer on the TiO{sub 2}/Fe{sub 3}O{sub 4}-C photocatalysts can reduce the possibility for photoexcited electron-hole recombination as usually found on the relatively narrow bandgap of ferric oxide during photocatalysis.

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

    Energy Technology Data Exchange (ETDEWEB)

    Shimada, Hiroyuki; Fukao, Taishi; Minami, Hirotake; Ukai, Masatoshi [Department of Applied Physics, Tokyo University of Agriculture and Technology, Koganei-shi, Tokyo 184-8588 (Japan); Fujii, Kentaro; Yokoya, Akinari [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Fukuda, Yoshihiro; Saitoh, Yuji [Synchrotron Radiation Research Center, Japan Atomic Energy Agency, Sayo-gun, Hyougo 679-5148 (Japan)

    2014-08-07

    The N K-edge X-ray absorption near edge structure (XANES) spectra of the purine-containing nucleotide, guanosine 5{sup ′}-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{sup ′}-monophosphate, and adenosine 5{sup ′}-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.

  13. μ-XRF imaging and μ-XANES analysis of root of arsenic hyperaccumulator fern (Pteris vittata L.) by using synchrotron radiation

    International Nuclear Information System (INIS)

    Kitajima, Nobuyuki; Onuma, Ryoko; Hokura, Akiko; Nakai, Izumi; Terada, Yasuko

    2006-01-01

    Pteris vittata L. is known as a peculiar fern which have high performance to accumulate arsenic, a toxic heavy metal, in its plant body. This fern is expected as a strong candidate plant for a technology of phytoremediation due to its hyperaccumulation ability (over 2% arsenic concentration with dry weight basis). In this study, the distribution of arsenic in a horizontal cross-section of root was examined by μ-SR-XRF imaging, and a valence change from surface to centre of the root was revealed by the As-K edge μ-XANES spectra. All the measurements were carried out utilizing X-ray microbeam (1.1 μm x 1.3 μm) from the undulator source at BL37XU in SPring-8 (JASRI, Japan). Arsenic was detected on whole area of root tissue from surface to centre, and mainly distributed within the structure through a cell wall. A comparison of XANES spectra of the 8 points in the root tissue at high As level with those of the reference compounds (As 2 O 3 and H 3 AsO 4 ), revealed that As (V) uptaken by root was reduced to As (III) immediately, and existed as a mixture of As (III) and As (V). Furthermore, it was indicated that their ratios As (III)/As (V) increased remarkably at the boundary area between the cortex and the central cylinder. (author)

  14. The interaction of copper ions with Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli: an X-ray absorption near-edge structure (XANES) spectroscopy study.

    Science.gov (United States)

    Zanzen, Ulrike; Bovenkamp-Langlois, Lisa; Klysubun, Wantana; Hormes, Josef; Prange, Alexander

    2018-04-01

    The antimicrobial properties of copper ions have been known for a long time. However, the exact mechanism of action of the transition metal on microorganisms has long been unclear. X-ray absorption near-edge structure (XANES) spectroscopy at the Cu K edge allows the determination of copper speciation in Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa that have been treated with Cu(II) and Cu(I) solutions. The death/inactivation of the bacteria was observed using plate counting and light microscopy. The Cu K-XANES spectra of the two Gram-negative bacteria are different than those of the Gram-positive strain. The results clearly show that the Cu + -S bond contributes to the antibacterial activity of copper, as in the case of silver. The detailed evaluation of the differentiated absorption spectra shows that Cu + (not Cu 2+ ) is the dominant ion that binds to the bacteria. Because Cu + is not the most common copper ion, copper is not as effective an antibacterial agent as silver, whose common valency is actually + 1. Any reaction of copper with phosphorus from the bacteria can be excluded after the evaluation of the absorption spectra.

  15. Evidence of a splitting of the Mn-O distance and of a large lattice disorder in the charge-ordered phase of LiMn2O4 obtained by EXAFS

    International Nuclear Information System (INIS)

    Paolone, A.; Castellano, C.; Cantelli, R.; Rousse, G.; Masquelier, C.

    2003-01-01

    We measured the extended x-ray-absorption fine-structure (EXAFS) spectrum of LiMn 2 O 4 below room temperature in the charge-ordered phase and for comparison at room temperature in the cubic phase. By means of a standard fit procedure we verified that, as reported by neutron-scattering experiments, also at the local level there are two different Mn-O distances below room temperature, which correspond to the surroundings of well-defined Mn 3+ and Mn 4+ ions. This result is different from the ones obtained from previous EXAFS measurements and confirms the physical picture of the phase transition caused by the ordering of charges in contrast to a cooperative Jahn-Teller phenomenon. Moreover a large lattice disorder in the charge-ordered state, which determines a significant static contribution to the EXAFS Debye-Waller factor, has been found. This last result can be considered as the EXAFS spectral mark of charge-order transitions, even in those materials in which there is no clear evidence of the splitting of bond lengths

  16. Interaction of Zn(II) with hematite nanoparticles and microparticles: Part 2. ATR-FTIR and EXAFS study of the aqueous Zn(II)/oxalate/hematite ternary system.

    Science.gov (United States)

    Ha, Juyoung; Trainor, Thomas P; Farges, François; Brown, Gordon E

    2009-05-19

    Sorption of Zn(II) to hematite nanoparticles (HN) (av diam=10.5 nm) and microparticles (HM) (av diam=550 nm) was studied in the presence of oxalate anions (Ox2-(aq)) in aqueous solutions as a function of total Zn(II)(aq) to total Ox2-(aq) concentration ratio (R=[Zn(II)(aq)]tot/[Ox2-(aq)]tot) at pH 5.5. Zn(II) uptake is similar in extent for both the Zn(II)/Ox/HN and Zn(II)/Ox/HM ternary systems and the Zn(II)/HN binary system at [Zn(II)(aq)](tot)system than for the Zn(II)/Ox/HM ternary and the Zn(II)/HN and Zn(II)/HM binary systems at [Zn(II)(aq)]tot>4 mM. In contrast, Zn(II) uptake for the Zn(II)/HM binary system is a factor of 2 greater than that for the Zn(II)/Ox/HM and Zn(II)/Ox/HN ternary systems and the Zn(II)/HN binary system at [Zn(II)(aq)]totternary system at both R values examined (0.16 and 0.68), attenuated total reflectance Fourier transform infrared (ATR-FTIR) results are consistent with the presence of inner-sphere oxalate complexes and outer-sphere ZnOx(aq) complexes, and/or type A ternary complexes. In addition, extended X-ray absorption fine structure (EXAFS) spectroscopic results suggest that type A ternary surface complexes (i.e., >O2-Zn-Ox) are present. In the Zn(II)/Ox/HN ternary system at R=0.15, ATR-FTIR results indicate the presence of inner-sphere oxalate and outer-sphere ZnOx(aq) complexes; the EXAFS results provide no evidence for inner-sphere Zn(II) complexes or type A ternary complexes. In contrast, ATR-FTIR results for the Zn/Ox/HN sample with R = 0.68 are consistent with a ZnOx(s)-like surface precipitate and possibly type B ternary surface complexes (i.e., >O2-Ox-Zn). EXAFS results are also consistent with the presence of ZnOx(s)-like precipitates. We ascribe the observed increase of Zn(II)(aq) uptake in the Zn(II)/Ox/HN ternary system at [Zn(II)(aq)]tot>or=4 mM relative to the Zn(II)/Ox/HM ternary system to formation of a ZnOx(s)-like precipitate at the hematite nanoparticle/water interface.

  17. Structural studies using X-ray absorption and scattering techniques

    International Nuclear Information System (INIS)

    Ericson, Agneta.

    1989-01-01

    The thesis presents extended X-ray absorption fine structure, EXAFS, and large angle X-ray scattering, LAXS, techniques; instrumentation, data collection and reduction, and applications. These techniques have been used to determine the structures of magnesium halides and organomagnesium halides in diethyl ether and tetrahydrofuran solution. The iodides were used for the LAXS measurements and Br K edge EXAFS data were collected for the corresponding bromides. Two different complexes are present in the diethyl ether solution of magnesium iodide; a polymeric chain-type structure where magnesium is tetrahedrally coordinated, as well as dimeric complex with octahedrally coordinated magnesium. Solvated MgI + is the dominating species in tetrahydrofuran solution. The organomagnesium halides are present in diethyl ether solution as both solvated monomeric and dimeric complexes. Magnesium coordinates a halide ion, an alkyl or aryl group and four solvent molecules octahedrally in the monomeric complex. In the dimeric complex magnesium is octahedrally coordinated by two bridging halide ions, an alkyl or aryl group and three solvent molecules. The distribution of monomeric and dimeric complexes in various solutions are given by a dimerisation constant, K dl . The results indicate that the Schlenk equilibrium is present in these solutions, however, in an extended form. In diethyl ether solution, where MgX 2 does not dissociate, no MgX 2 complex and thereby no Schlenk equilibrium has been observed. In tetrahydrofuran solution MgI 2 has dissociated into mainly MgI + and I - . This indicates that the concentration of MgI 2 is low and that the Schlenk equilibrium should be expanded even further to include the dissociation equilibrium of the magnesium halide. In the thesis Fe K edge EXAFS data collected for the semireduced form of protein A of methane monooxygenase from Methylococcus capsulatus, are also presented. (139 refs.)

  18. Angle and Polarization Dependent Fluorescence EXAFS Measurements on Al-doped Single Crystal V_2O3 Above and Below the Transition Temperature

    Science.gov (United States)

    Müller, O.; Pfalzer, P.; Schramme, M.; Urbach, J.-P.; Klemm, M.; Horn, S.; Frenkel, A. I.; Denboer, M. L.

    1998-03-01

    We present angle and polarisation dependent flourescence EXAFS measured on Al-doped single crystal V_2O3 below and above the structural phase transition from monoclinic to trigonal. Strong self-absorption distorted the spectra; this was corrected by using the procedure described by Tröger et al. (L. Tröger, D. Arvantis, K. Baberschke, H. Michaelis, U. Grimm, and E. Zschech, Phys. Rev. B,.46), 3238 (1992), generalized to the Lytle detector employed in our work. The spectra show pronounced dependence on the angle between the threefold symmetry axes and the polarization of the incident photons, making it possible to measure the local atomic distances in different directions. We compare our results with the measurements of Frenkel et al. (A. I. Frenkel, E. A. Stern, and F. A. Chudnovsky, Sol. State Comm.102), 637 (1997) on pure V_2O3 They found that locally the monoclinic distortion persists in the trigonal metallic phase.

  19. Study of oxidation states of the transition metals in a series of Prussian blue analogs using x-ray absorption near edge structure (XANES) spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Adak, S. [Department of Physics, New Mexico State University, Las Cruces, NM, 88003 (United States); Hartl, M., E-mail: monika.hartl@esss.se [European Spallation Source ESS AB, 22100, Lund (Sweden); Manuel Lujan Jr. Neutron Scattering Center (LANSCE-LC), Los Alamos National Laboratory, Los Alamos, NM, 87545 (United States); Daemen, L. [Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN, 37830 (United States); Manuel Lujan Jr. Neutron Scattering Center (LANSCE-LC), Los Alamos National Laboratory, Los Alamos, NM, 87545 (United States); Fohtung, E.; Nakotte, H. [Department of Physics, New Mexico State University, Las Cruces, NM, 88003 (United States)

    2017-01-15

    Highlights: • Systematic XANES measurements on Prussian blue analogs shows oxidation state of transition metals. • Cobal-iron bimetallic hexacyanometallates show unexpected oxidation states. • Iron(II) ions in hexacyanometallates(III) show varying spin state depending on their bond to the “N” end or “C” end of the cyanide ligand. • Thermal expansion coefficients have been linked to the XANES results. - Abstract: There have been renewed interests in metal-organic framework classes of materials such as Prussian blue analogues (PBAs) due to their potential usage in energy storage applications. In particular, due to their high surface areas, controllable structures and excellent electrochemical properties, PBAs such as hexacyanometalates M{sup II}{sub 3}[A{sup III}(CN){sub 6}]{sub 2*}nH{sub 2}O (M = Mn, Fe, Co, Ni, Cu, Zn; A = Co, Fe, Cr; n = no. of water molecules present), M{sup II}{sub 2}[Fe{sup II}(CN){sub 6}]{sub 2*}nH{sub 2}O (M = Mn, Co, Ni, Cu, Zn) and mixed hexacyanometalates(III) (Fe{sub 1-x}Co{sub x}){sub 3}[B{sup III}(CN){sub 6}]{sub 2}·nH{sub 2}O (x = 0.25, 0.5, 0.75; B = Co, Fe) could have possible usage as a new class of cathode and even anode materials for rechargeable batteries. Detailed knowledge of the oxidation states of the transition metals in PBAs is required to improve efficiency and durability of such devices. Furthermore, a link between the thermal expansion observed in these materials and the oxidation state of the transition metal is of interest to synthesize materials with a desired thermal expansion behavior, Here we demonstrate the use of Synchrotron based X-ray absorption near-edge structure (XANES) spectra to identify transition metal oxidation states. Our analysis reveals the presence of divalent, trivalent and/or mixed valence transition metals in the materials as well as high-spin and low-spin complexes.

  20. Origin of improved scintillation efficiency in (Lu,Gd).sub.3./sub.(Ga,Al).sub.5./sub.O.sub.12./sub.:Ce multicomponent garnets: an X-ray absorption near edge spectroscopy (XANES) study

    Czech Academy of Sciences Publication Activity Database

    Wu, Y.; Luo, J.; Nikl, Martin; Ren, G.

    2014-01-01

    Roč. 2, č. 1 (2014), "012101-1"-"012101-8" ISSN 2166-532X R&D Projects: GA MŠk LH12185 Institutional support: RVO:68378271 Keywords : scintillator * multicomponent garnet * Ce 4+ * XANES Subject RIV: BM - Solid Matter Physics ; Magnetism

  1. Temperature dependent changes of the Mn 3d and 4p bands near $T_{c}$ in Colossal Magnetoresistance systems : a XANES study of $La_{1-x}Ca_{x}MnO_{3}$

    NARCIS (Netherlands)

    Bridges, F; Booth, C. H.; Kwei, G. H.; Neumeier, J. J.; Sawatzky, G. A.

    2000-01-01

    Abstract: We report high-resolution X-ray Absorption Near Edge Structure (XANES)measurements at the Mn K-edge as a function of temperature, forLa$_{1-x}$Ca$_x$MnO$_3$ samples, with a focus mainly on the pre-edge region.Small peaks labeled A$_1$-A$_3$ are observed which corresponds to

  2. Effect of atomic vibrations in XANES: polarization-dependent damping of the fine structure at the Cu K-edge of (creat).sub.2./sub.CuCl.sub.4./sub.

    Czech Academy of Sciences Publication Activity Database

    Šipr, Ondřej; Vackář, Jiří; Kuzmin, A.

    2016-01-01

    Roč. 23, č. 6 (2016), s. 1433-1439 ISSN 1600-5775 R&D Projects: GA MŠk LD15097 Institutional support: RVO:68378271 Keywords : XANES * vibrations * multiple-scattering formalism Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.011, year: 2016

  3. Time-dependent uptake, distribution and biotransformation of chromium(VI) in individual and bulk human lung cells : application of synchrotron radiation techniques

    International Nuclear Information System (INIS)

    Harris, H. H.; Levina, A.; Dillon, C. T.; Mulyani, I.; Lai, B.; Cai, Z.; Lay, P.

    2005-03-01

    Chromium(VI) is a human carcinogen, primarily affecting the respiratory tract probably via active transport into cells, followed by the reduction to Cr(III) with the formation of DNA-damaging intermediates. Distribution of Cr and endogenous elements within A549 human lung adenocarcinoma epithelial cells, following treatment with Cr(VI) (100 (micro)M, 20 min or 4 h) were studied by synchrotron-radiation-induced X-ray emission (SRIXE) of single freeze-dried cells. After the 20-min treatment, Cr was confined to a small area of the cytoplasm and strongly co-localized with S, Cl, K, and Ca. After the 4-h treatment, Cr was distributed throughout the cell, with higher concentrations in the nucleus and the cytoplasmic membrane. This time-dependence corresponded to ∼100% or 0% clonogenic survival of the cells following the 20-min or 4-h treatments, respectively, and could potentially be explained by a new cellular protective mechanism. Such processes may also be important in reducing the potential hazards of Cr(III) dietary supplements, for which there is emerging evidence that they exert their anti-diabetic effects via biological oxidation to Cr(VI). The predominance of Cr(III) was confirmed by micro-XANES spectroscopy of intracellular Cr hotspots. X-ray absorption spectroscopy (XANES and EXAFS, using freeze-dried cells after the 0-4-h treatments) was used to gain insight into the chemical structures of Cr(III) complexes formed during the intracellular reduction of Cr(VI). The polynuclear nature of such complexes (probably with a combination of carboxylato and hydroxo bridging groups and O-donor atoms of small peptides or proteins) was established by XAFS data analyses

  4. The structure of nano-palladium deposited on carbon-based supports

    International Nuclear Information System (INIS)

    Pikna, Ľubomír; Milkovič, Ondrej; Saksl, Karel; Heželová, Mária; Smrčová, Miroslava; Puliš, Pavel; Michalik, Štefan; Gamcová, Jana

    2014-01-01

    Nano-palladium catalysts, prepared using the same procedure with the same metal content (3 wt%) and two different supports, activated carbon (Pd/C) and activated carbon—multiwalled carbon nanotubes (Pd/C/CNT), are discussed. The simple technique of deposition reduction was applied in the preparation of these two types of Pd catalysts. TEM, XRD analysis, EXAFS signal analysis, and XANES were used for sample characterization. In both samples, transmission electron microscopy identified nanosized Pd particles with nearly spherical morphology but different sizes. The mean diameters of the particles on Pd/C and Pd/C/CNT were estimated to be 5.4 nm and 7.8 nm, respectively. The EXAFS signal analysis showed that Pd atoms on the particle surfaces were coordinated by 4 oxygens to form a PdO monolayer covering a metallic core. The XANES signal analysis indicated a smaller particle size for Pd/C (∅ 5 nm) than for Pd/C/CNT (∅ 10 nm), in good agreement with the TEM observations. - Graphical abstract: Visualization of metallic core (left), oxide monolayer (middle) and nanoparticle of diameter 5 nm (right). - Highlights: • Pd catalysts were prepared on two types of supports: carbon and carbon nanotubes. • BET, TEM, XRD characterization of prepared catalysts. • XAFS: Concentration of Pd in samples Pd/C and Pd/C/CNT. • EXAFS and XANES signal analysis of catalysts. • Visualisation of atoms arrangement at the Pd nanoparticle surface

  5. Effect of metal ion on the structure and function of LiPDF: The study of the fine structure around the metal site using XANES

    International Nuclear Information System (INIS)

    Wang Yu; Chu Wangsheng; Yang Feifei; Yu Meijuan; Zhao Haifeng; Gong Weimin; Dong Yuhui; Xie Yaning; Wu, Ziyu

    2010-01-01

    We used X-ray absorption near edge structure (XANES) spectroscopy to investigate the metal-dependent enzymatic activity of the peptide deformylase from Leptospira interrogans (LiPDF). Ab initio full multiple scattering calculations performed by MXAN are applied to obtain the local structure of the cobalt-containing LiPDF (Co-LiPDF) and zinc-containing LiPDF (Zn-LiPDF) around the metal sites in pH9.0 buffer solution. The result shows the cobalt-wat1 (the bond water molecule) distance of Co-LiPDF is 1.89 A, much shorter than that of Zn-LiPDF, 2.50 A. That is an essential factor for its low catalytic activity.

  6. Effect of metal ion on the structure and function of LiPDF: The study of the fine structure around the metal site using XANES

    Energy Technology Data Exchange (ETDEWEB)

    Wang Yu [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China); Chu Wangsheng, E-mail: cws@ihep.ac.c [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Yang Feifei; Yu Meijuan; Zhao Haifeng [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Gong Weimin [National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101 (China); Dong Yuhui; Xie Yaning [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Wu, Ziyu, E-mail: wuzy@ustc.edu.c [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China); Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)

    2010-07-21

    We used X-ray absorption near edge structure (XANES) spectroscopy to investigate the metal-dependent enzymatic activity of the peptide deformylase from Leptospira interrogans (LiPDF). Ab initio full multiple scattering calculations performed by MXAN are applied to obtain the local structure of the cobalt-containing LiPDF (Co-LiPDF) and zinc-containing LiPDF (Zn-LiPDF) around the metal sites in pH9.0 buffer solution. The result shows the cobalt-wat1 (the bond water molecule) distance of Co-LiPDF is 1.89 A, much shorter than that of Zn-LiPDF, 2.50 A. That is an essential factor for its low catalytic activity.

  7. Chemical state analysis of heat-treated 6, 13-bis(triisopropylsilylethynyl) pentacene investigated by XPS valence band spectra, XANES spectra and first-principles calculation

    International Nuclear Information System (INIS)

    Muro, Maiko; Natsume, Yutaka; Kikuma, Jun; Setoyama, Hiroyuki

    2014-01-01

    X-ray photoelectron spectroscopy (XPS) valence band spectra reflect the chemical bonding states. To take this advantage, we tried to interpret experimental spectra by the occupied density of states (DOS) based on first principles calculation. In this work, we discussed XPS and X-ray Absorption Near Edge Structure (XANES) spectra of 6, 13-bis(triisopropylsilylethynyl) pentacene (TIPS-Pen), which is well known as an organic semiconductor. We studied chemical structure change of TIPS-Pen caused by heat-treatment at 300degC under nitrogen and under the air. It has been suggested that the structural change of pentacene skeleton by Diels-Alder type reaction occurs in both cases. In addition, the sample heat-treated under the air showed desorption of the isopropyl group and increase of oxygen concentration. (author)

  8. XANES analysis of calcium and sodium phosphates and silicates and hydroxyapatite-Bioglass (registered) 45S5 co-sintered bioceramics

    International Nuclear Information System (INIS)

    Demirkiran, Hande; Hu Yongfeng; Zuin, Lucia; Appathurai, Narayana; Aswath, Pranesh B.

    2011-01-01

    Bioglass (registered) 45S5 was co-sintered with hydroxyapatite at 1200 deg. C. When small amounts ( 5 (PO 4 ) 2 SiO 4 and Na 3 Ca 6 (PO 4 ) 5 in an amorphous silicate matrix respectively. These chemistries show improved bioactivity compared to hydroxyapatite and are the subject of this study. The structure of several crystalline calcium and sodium phosphates and silicates as well as the co-sintered hydroxyapatite-Bioglass (registered) 45S5 bioceramics were examined using XANES spectroscopy. The nature of the crystalline and amorphous phases were studied using silicon (Si) and phosphorus (P) K- and L 2,3 -edge and calcium (Ca) K-edge XANES. Si L 2,3 -edge spectra of sintered bioceramic compositions indicates that the primary silicates present in these compositions are sodium silicates in the amorphous state. From Si K-edge spectra, it is shown that the silicates are in a similar structural environment in all the sintered bioceramic compositions with 4-fold coordination. Using P L 2,3 -edge it is clearly shown that there is no evidence of sodium phosphate present in the sintered bioceramic compositions. In the P K-edge spectra, the post-edge shoulder peak at around 2155 eV indicates that this shoulder to be more defined for calcium phosphate compounds with decreasing solubility and increasing thermodynamic stability. This shoulder peak is more noticeable in hydroxyapatite and β-TCP indicating greater stability of the phosphate phase. The only spectra that does not show a noticeable peak is the composition with Na 3 Ca 6 (PO 4 ) 5 in a silicate matrix indicating that it is more soluble compared to the other compositions.

  9. XANES investigation of Chinese faience excavated from Peng State Cemetery site in Western Zhou Period (BC1046–BC771)

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Wentao; Yang, Yimin [Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044 (China); Department of Scientific History and Archaeometry, University of Chinese Academy of Sciences, Beijing 100049 (China); Zhu, Jian, E-mail: jzhu@ucas.ac.cn [Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044 (China); Department of Scientific History and Archaeometry, University of Chinese Academy of Sciences, Beijing 100049 (China); Gu, Zhou [Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044 (China); Department of Scientific History and Archaeometry, University of Chinese Academy of Sciences, Beijing 100049 (China); Xie, Yaoting [Institute of Archaeology of Shanxi Province, Taiyuan 030001 (China); Zhang, Jing [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Wang, Lihua [Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204 (China)

    2014-10-15

    Highlights: • We analyzed faience of Peng State archaeological cemetery site in Western Zhou Dynasty (BC1046–BC771). • We investigated the chemical composition and oxidation state by energy dispersive X-ray fluorescence (EDXRF) and X-ray absorption near edge spectroscopy (XANES), respectively. • The coloring element in both beads is copper in +2 valence, and the color divergence of these two beads may originate from different local chemical environments of Cu{sup 2+}. • Chinese faience in this period is the earliest glaze with copper colorant. - Abstract: As a special kind of glazed ceramic, faience has an important role to play in the technological trajectory that eventually leads to the development of ancient glass. In China, faience products first emerged in early Western Zhou Dynasty (1046BC–771BC), and their great significance as well as brilliant colors varying between blue and green attracted a lot of scholars. However, scientific researches on the color source of Chinese faience in view of microstructure characterization are quite few. In the present work, analyses by energy dispersive X-ray fluorescence (EDXRF) and X-ray absorption near edge spectroscopy (XANES) were carried out on two faience beads with relatively blue and green color, respectively, both of which were excavated from Peng State archaeological cemetery site in Western Zhou Dynasty. The results show that the coloring element in both beads is copper with +2 valence, and the color divergence of these two beads may originate from different local chemical environments of Cu{sup 2+}. It is suggested that the faience in this period is the earliest glaze with copper colorant in China.

  10. Olivine-melt relationships and syneruptive redox variations in the 1959 eruption of K$\\bar{i}$lauea Volcano as revealed by XANES

    Energy Technology Data Exchange (ETDEWEB)

    Helz, R. T.; Cottrell, E.; Brounce, M. N.; Kelley, K. A.

    2017-03-01

    The 1959 summit eruption of K$\\bar{i}$lauea Volcano exhibited high lava fountains of gas-rich, primitive magma, containing olivine + chromian spinel in highly vesicular brown glass. Microprobe analysis of these samples shows that euhedral rims on olivine phenocrysts, in direct contact with glass, vary significantly in forsterite (Fo) content, at constant major-element melt composition, as do unzoned groundmass olivine crystals. Ferric/total iron (Fe+ 3/FeT)ratios for matrix and interstitial glasses, plus olivine-hosted glass inclusions in eight 1959 scoria samples have been determined by micro X-ray absorption near-edge structure spectroscopy (μ-XANES). These data show that much of the variation in Fo content reflects variation in oxidation state of iron in the melt, which varies with sulfur concentration in the glass and (locally) with proximity to scoria edges in contact with air. Data for 24 olivine-melt pairs in the better-equilibrated samples from later in the eruption show KD averaging 0.280 ± 0.03 for the exchange of Fe and Mg between olivine and melt, somewhat displaced from the value of 0.30 ± 0.03 given by Roeder and Emslie (1970). This may reflect the low SiO2 content of the 1959 magmas, which is lower than that in most K$\\bar{i}$lauea tholeiites. More broadly, we show the potential of μ-XANES and electron microprobe to revisit and refine the value of KD in natural systems.

  11. XANES investigation of Chinese faience excavated from Peng State Cemetery site in Western Zhou Period (BC1046–BC771)

    International Nuclear Information System (INIS)

    Hao, Wentao; Yang, Yimin; Zhu, Jian; Gu, Zhou; Xie, Yaoting; Zhang, Jing; Wang, Lihua

    2014-01-01

    Highlights: • We analyzed faience of Peng State archaeological cemetery site in Western Zhou Dynasty (BC1046–BC771). • We investigated the chemical composition and oxidation state by energy dispersive X-ray fluorescence (EDXRF) and X-ray absorption near edge spectroscopy (XANES), respectively. • The coloring element in both beads is copper in +2 valence, and the color divergence of these two beads may originate from different local chemical environments of Cu 2+ . • Chinese faience in this period is the earliest glaze with copper colorant. - Abstract: As a special kind of glazed ceramic, faience has an important role to play in the technological trajectory that eventually leads to the development of ancient glass. In China, faience products first emerged in early Western Zhou Dynasty (1046BC–771BC), and their great significance as well as brilliant colors varying between blue and green attracted a lot of scholars. However, scientific researches on the color source of Chinese faience in view of microstructure characterization are quite few. In the present work, analyses by energy dispersive X-ray fluorescence (EDXRF) and X-ray absorption near edge spectroscopy (XANES) were carried out on two faience beads with relatively blue and green color, respectively, both of which were excavated from Peng State archaeological cemetery site in Western Zhou Dynasty. The results show that the coloring element in both beads is copper with +2 valence, and the color divergence of these two beads may originate from different local chemical environments of Cu 2+ . It is suggested that the faience in this period is the earliest glaze with copper colorant in China

  12. Chemical Heterogeneity of a Large Cluster IDP: Clues to its Formation History Using X-ray Fluorescence Mapping and XANES Spectroscopy

    Science.gov (United States)

    Wirick, S.; Flynn, G. J.; Sutton, S.; Zolensky, M. E.

    2013-01-01

    Chondritic porous IDPs may be among the most primitive objects found in our solar system [1]. They consist of many micron to submicron minerals, glasses and carbonaceous matter [2,3,4,5,6,7] with > 10(exp 4) grains in a 10 micron cluster [8]. Speculation on the environment where these fine grained, porous IDPs formed varies with possible sources being presolar dusty plasma clouds, protostellar condensation, solar asteroids or comets [4,6,9]. Also, fine grained dust forms in our solar system today [10,11]. Isotopic anomalies in some particles in IDPs suggest an interstellar source[4,7,12]. IDPs contain relic particles left from the dusty plasma that existed before the protostellar disk formed and other grains in the IDPs formed later after the cold dense nebula cloud collapsed to form our protostar and other grains formed more recently. Fe and CR XANES spectroscopy is used here to investigate the oxygen environment in a large (>50 10 micron or larger sub-units) IDP. Conclusions: Analyzing large (>50 10 micron or larger sub-units) CP IDPs gives one a view on the environments where these fine dust grains formed which is different from that found by only analyzing the small, 10 micron IDPs. As with cluster IDP L2008#5 [3], L2009R2 cluster #13 appears to be an aggregate of grains that sample a diversity of solar and perhaps presolar environments. Sub-micron, grain by grain measurement of trace element contents and elemental oxidation states determined by XANES spectroscopy offers the possibility of understanding the environments in which these grains formed when compared to standard spectra. By comparing thermodynamic modeling of condensates with analytical data an understanding of transport mechanisms operating in the early solar system may be attained.

  13. P-EXAFS investigations of Zn uptake by montmorillonite. The strong and weak sites concept in the 2SPNE SC/CE sorption model

    International Nuclear Information System (INIS)

    Daehn, R.; Baeyens, B.; Bradbury, M.H.

    2012-01-01

    Document available in extended abstract form only. The sorption of radioactive elements on the immobile components in the near- and far-fields of a deep geological radioactive waste repository is a significant process in retarding their aqueous phase transport and an important component in safety assessment studies. The development of robust and well-founded mechanistic sorption models to predict the uptake of radionuclides under different geochemical conditions would enhance the justification and defensibility of the sorption values used in safety studies and thereby represent a considerable contribution to the scientific basis for radioactive waste disposal. The 2 site proto-lysis non electrostatic surface complexation and cation exchange (2SPNE SC/CE) sorption model has been used over the past decade or so to quantitatively describe the uptake of metals with oxidation states from II to VI on 2:1 clay minerals; montmorillonite and illite (Bradbury and Baeyens, 1997). One of the main features in this model is that there are two broad categories of amphoteric edge sorption sites; the so called strong (≡SSOH) and weak (≡SW1OH) sites. Because of their different sorption characteristics, it was expected that the coordination environments of the surface complexes on the two site types would be different. Although the 2SPNE SC/CE model uses different mechanistic uptake processes to describe sorption, it can only be described as a 'quasi mechanistic' model because the exact nature of the surface binding sites and surface complexes is not known. In order to check the 'strong site / weak site' sorption sites hypothesis in the 2SPNE SC/CE sorption model, it was essential to perform polarised extended X-ray absorption fine structure (P-EXAFS) measurements on an uptake system, in which it was possible to obtain good spectra particularly at the low metal loadings (∼2 mmol kg-1 or less) corresponding to occupancies dominated by strong sites. The Zn-montmorillonite system

  14. Binuclear Pt-Tl bonded complex with square pyramidal coordination around Pt: a combined multinuclear NMR, EXAFS, UV-Vis, and DFT/TDDFT study in dimethylsulfoxide solution.

    Science.gov (United States)

    Purgel, Mihály; Maliarik, Mikhail; Glaser, Julius; Platas-Iglesias, Carlos; Persson, Ingmar; Tóth, Imre

    2011-07-04

    The structure and bonding of a new Pt-Tl bonded complex formed in dimethylsulfoxide (dmso), (CN)(4)Pt-Tl(dmso)(5)(+), have been studied by multinuclear NMR and UV-vis spectroscopies, and EXAFS measurements in combination with density functional theory (DFT) and time dependent density functional theory (TDDFT) calculations. This complex is formed following the equilibrium reaction Pt(CN)(4)(2-) + Tl(dmso)(6)(3+) ⇆ (CN)(4)Pt-Tl(dmso)(5)(+) + dmso. The stability constant of the Pt-Tl bonded species, as determined using (13)C NMR spectroscopy, amounts to log K = 2.9 ± 0.2. The (NC)(4)Pt-Tl(dmso)(5)(+) species constitutes the first example of a Pt-Tl bonded cyanide complex in which the sixth coordination position around Pt (in trans with respect to the Tl atom) is not occupied. The spectral parameters confirm the formation of the metal-metal bond, but differ substantially from those measured earlier in aqueous solution for complexes (CN)(5)Pt-Tl(CN)(n)(H(2)O)(x)(n-) (n = 0-3). The (205) Tl NMR chemical shift, δ = 75 ppm, is at extraordinary high field, while spin-spin coupling constant, (1)J(Pt-Tl) = 93 kHz, is the largest measured to date for a Pt-Tl bond in the absence of supporting bridging ligands. The absorption spectrum is dominated by two strong absorption bands in the UV region that are assigned to MMCT (Pt → Tl) and LMCT (dmso → Tl) bands, respectively, on the basis of MO and TDDFT calculations. The solution of the complex has a bright yellow color as a result of a shoulder present on the low energy side of the band at 355 nm. The geometry of the (CN)(4)Pt-Tl core can be elucidated from NMR data, but the particular stoichiometry and structure involving the dmso ligands are established by using Tl and Pt L(III)-edge EXAFS measurements. The Pt-Tl bond distance is 2.67(1) Å, the Tl-O bond distance is 2.282(6) Å, and the Pt-C-N entity is linear with Pt-C and Pt···N distances amounting to 1.969(6) and 3.096(6) Å, respectively. Geometry optimizations on

  15. Gd doping induced weak ferromagnetic ordering in ZnS nanoparticles synthesized by low temperature co-precipitation technique

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Palvinder [Department of Physics, Punjabi University, Patiala, Punjab, 147002 (India); Kumar, Sanjeev, E-mail: sanjeev04101977@gmail.com [Applied Science Department, PEC University of Technology, Chandigarh, 160012 (India); Chen, Chi-Liang, E-mail: chen.cl@nsrrc.org.tw [National Synchrotron Radiation Research Center (NSRRC), Hsinchu, 30076, Taiwan (China); Yang, Kai-Siang [National Synchrotron Radiation Research Center (NSRRC), Hsinchu, 30076, Taiwan (China); Department of Mechanical Engineering, National Taipei University of Technology, Taipei, Taiwan (China); Wei, Da-Hua [Department of Mechanical Engineering, National Taipei University of Technology, Taipei, Taiwan (China); Dong, Chung-Li [Department of Physics, Tamkang University, Tamsui, Taiwan (China); Srivastava, C. [Materials Engineering Department, Indian Institute of Science, Bangalore, 560012 (India); Rao, S.M. [Department of Physics, Punjabi University, Patiala, Punjab, 147002 (India); Institute of Physics, Academia Sinica, Taipei, 11529, Taiwan (China)

    2017-01-15

    Zn{sub 1−x}Gd{sub x}S nanoparticles with Gd concentration x = 0.00, 0.02 and 0.04 were synthesized by the chemical co-precipitation technique using thioglycerol as capping agent. X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL) spectroscopy, X-ray absorption near-edge structure (XANES) and vibrating sample magnetometer (VSM) were employed to characterize the as synthesized Gd doped ZnS nanoparticles. XRD and TEM studies show the formation of cubic ZnS nanoparticles with an average size in the range 5–10 nm. The doping did not alter the phase of the ZnS. The PL spectra of doped ZnS nanoparticles showed the presence of sulphur vacancies in the lattice. XANES of Gd doped ZnS nanoparticles depicts spectral changes may arise from charge transfer between host Zn and dopant Gd ions. A VSM study shows that the weak ferromagnetic behaviour increases with increase in Gd doping ZnS nanoparticles. - Highlights: • Gd doped ZnS nanoparticles synthesized using co-precipitation technique. • PL studies depict sulphur and zinc vacancies in Gd doped ZnS nanoparticles. • XANES studies depict the charge transfer between host Zn and dopant Gd ions. • Room temperature weak ferromagnetism is observed in Gd doped ZnS nanoparticles.

  16. Gd doping induced weak ferromagnetic ordering in ZnS nanoparticles synthesized by low temperature co-precipitation technique

    International Nuclear Information System (INIS)

    Kaur, Palvinder; Kumar, Sanjeev; Chen, Chi-Liang; Yang, Kai-Siang; Wei, Da-Hua; Dong, Chung-Li; Srivastava, C.; Rao, S.M.

    2017-01-01

    Zn_1_−_xGd_xS nanoparticles with Gd concentration x = 0.00, 0.02 and 0.04 were synthesized by the chemical co-precipitation technique using thioglycerol as capping agent. X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL) spectroscopy, X-ray absorption near-edge structure (XANES) and vibrating sample magnetometer (VSM) were employed to characterize the as synthesized Gd doped ZnS nanoparticles. XRD and TEM studies show the formation of cubic ZnS nanoparticles with an average size in the range 5–10 nm. The doping did not alter the phase of the ZnS. The PL spectra of doped ZnS nanoparticles showed the presence of sulphur vacancies in the lattice. XANES of Gd doped ZnS nanoparticles depicts spectral changes may arise from charge transfer between host Zn and dopant Gd ions. A VSM study shows that the weak ferromagnetic behaviour increases with increase in Gd doping ZnS nanoparticles. - Highlights: • Gd doped ZnS nanoparticles synthesized using co-precipitation technique. • PL studies depict sulphur and zinc vacancies in Gd doped ZnS nanoparticles. • XANES studies depict the charge transfer between host Zn and dopant Gd ions. • Room temperature weak ferromagnetism is observed in Gd doped ZnS nanoparticles.

  17. Iron environment in ferritin with large amounts of phosphate, from Azotobacter vinelandii and horse spleen, analyzed using Extended X-ray Absorption fine Structure (EXAFS)

    International Nuclear Information System (INIS)

    Rohrer, J.S.; Islam, Q.T.; Sayes, D.E.; Theil, E.C.; Watt, G.D.

    1990-01-01

    The iron core of proteins in the ferritin family displays structural variations that includes phosphate content was well as the number and the degree of ordering of the iron atoms. Earlier studies had shown that ferritin iron cores naturally high in phosphate, e.g., Azotobacter vinelandii (AV) ferritin had decreased long-range order. Here, the influence of phosphate on the local structure around iron in ferritin cores is reported, comparing the EXAFS of AV ferritin, reconstituted ferritin and native horse spleen ferritin. In contrast, when the phosphate content was high in AV ferritin and horse spleen ferritin reconstituted with phosphate, the average iron atom had five to six phosphorus neighbors at 3.17 angstrom. Moreover, the number of detectable iron neighbors was lower when phosphate was high or present during reconstitution and the interatomic distance was longer indicating that some phosphate bridges neighboring iron atoms. However, the decrease in the number of detectable iron-iron neighbors compared to HSF and the higher number of Fe-P interactions relative to Fe-Fe interactions suggest that some phosphate ligands were chain termini, or blocked crystal growth, and/or introduced defects which contributed both to the long-range disorder and to altered redox properties previously observed in AV ferritin

  18. The double-well oscillating potential of oxygen atoms in perovskite system Ba(K)BiO sub 3 : EXAFS - analysis results

    CERN Document Server

    Menushenkov, A P; Konarev, P V; Meshkov, A A; Benazeth, S; Purans, J

    2000-01-01

    Temperature-dependent X-ray absorption investigations were made on the Bi L sub 3 -edge in Ba sub 1 sub - sub x K sub x BiO sub 3 with x=0.0, 0.4 and 0.5. For the superconducting samples (x=0.4 and 0.5) it has been found that the local structure differs from the ideal cubic in contrast to the neutron and X-ray diffraction data. The provided analysis of the EXAFS spectra indicates that the oxygen atoms move in double-well potential produced by the existence of two non-equivalent octahedral types of the oxygen environment of bismuth. The vibrations in such a potential lead to modulations of the Bi-O lengths with low frequency which is determined by the soft oxygen octahedron rotation mode frequency. This induces strong electron-phonon interaction and may be the reason for relatively high-temperature transition (T sub c approx 30 K) to the superconducting state.

  19. EXAFS analysis of cations distribution in structure of Co1-xNixFe2O4 nanoparticles obtained by hydrothermal method in aloe vera extract solution

    Science.gov (United States)

    Wongpratat, Unchista; Maensiri, Santi; Swatsitang, Ekaphan

    2016-09-01

    Effect of cations distribution upon EXAFS analysis on magnetic properties of Co1-xNixFe2O4 (x = 0, 0.25, 0.50, 0.75 and 1.0) nanoparticles prepared by the hydrothermal method in aloe vera extract solution were studied. XRD analysis confirmed a pure phase of cubic spinel ferrite of all samples. Changes in lattice parameter and particle size depended on the Ni content with partial substitution and site distributions of Co2+, Ni2+ ions of different ionic radii at both tetrahedral and octahedral sites in the crystal structure. Particle sizes of samples estimated by TEM images were found to be in the range of 10.87-62.50 nm. The VSM results at room temperature indicated the ferrimagnetic behavior of all samples. Superparamagnetic behavior was observed in NiFe2O4 sample. The coercivity (Hc) and remanance (Mr) values were related to the particle sizes of samples. The saturation magnetization (Ms) was increased by a factor of 1.4 to a value of 57.57 emu/g, whereas the coercivity (Hc) was decreased by a factor of 20 to a value of 63.15 Oe for a sample with x = 0.75. In addition to the cations distribution, the increase of aspect ratio (surface to volume ratio) due to the decrease of particle size could significantly affect the magnetic properties of the materials.

  20. Structure of the Hydrated Platinum(II) Ion And the Cis-Diammine-Platinum(II) Complex in Acidic Aqueous Solution: An EXAFS Study

    Energy Technology Data Exchange (ETDEWEB)

    Jalilehvand, F.; Laffin, L.J.

    2009-05-18

    Careful analysis of Pt L{sub 3}-edge extended X-ray absorption fine structure (EXAFS) spectra shows that the hydrated platinum(II) ion in acidic (HClO{sub 4}) aqueous solution binds four water molecules with the Pt-O bond distance 2.01(2) {angstrom} and one (or two) in the axial position at 2.39(2) {angstrom}. The weak axial water coordination is in accordance with the unexpectedly small activation volume previously reported for water exchange in an interchange mechanism with associative character. The hydrated cis-diammineplatinum(II) complex has a similar coordination environment with two ammine and two aqua ligands strongly bound with Pt-O/N bond distances of 2.01(2) {angstrom} and, in addition, one (or two) axial water molecule at 2.37(2) {angstrom}. This result provides a new basis for theoretical computational studies aiming to connect the function of the anticancer drug cis-platin to its ligand exchange reactions, where usually four-coordinated square planar platinum(II) species are considered as the reactant and product. {sup 195}Pt NMR spectroscopy has been used to characterize the Pt(II) complexes.

  1. Optical and mechanical design of the extended x-ray absorption fine structure (EXAFS) beam-line at Indus-II synchrotron source

    International Nuclear Information System (INIS)

    Das, N.C.; Jha, S.N.; Bhattacharyya, D.; Sinha, A.K.; Mishra, V.K.; Verma, Vishnu; Ghosh, A.K.

    2002-11-01

    An extended x-ray absorption fine structure (EXAFS) beam line for x-ray absorption studies using energy dispersive geometry and position sensitive detector is being designed for the INDUS-II Synchrotron source. The beam line would be used for doing x-ray absorption experiments involving measurements of fme structures above the absorption edge of different species of atoms in a material The results of the above experiments would lead to the determination of different important structural parameters of materials viz.. inter-atomic distance. co-ordination number, degree of disorder and radial distribution function etc. The optical design of the beam line has been completed based on the working principle that a single crystal bent in the shape of an ellipse by a crystal bender would act as a dispersing as well as focusing element. The mechanical design of the beam line including the crystal bender has also been completed and discussed here. Calculations have been done to detennine the temperature profile on the different components of the beam line under exposure to synchrotron radiation and proper cooling channels have been designed to bring down the heat load on the components. (author)

  2. Olivine-melt relationships and syneruptive redox variations in the 1959 eruption of Kīlauea Volcano as revealed by XANES

    Science.gov (United States)

    Helz, Rosalind L.; Cottrell, Elizabeth; Brounce, Maryjo N.; Kelley, Katherine A.

    2017-01-01

    The 1959 summit eruption of Kīlauea Volcano exhibited high lava fountains of gas-rich, primitive magma, containing olivine + chromian spinel in highly vesicular brown glass. Microprobe analysis of these samples shows that euhedral rims on olivine phenocrysts, in direct contact with glass, vary significantly in forsterite (Fo) content, at constant major-element melt composition, as do unzoned groundmass olivine crystals. Ferric/total iron (Fe+ 3/FeT)ratios for matrix and interstitial glasses, plus olivine-hosted glass inclusions in eight 1959 scoria samples have been determined by micro X-ray absorption near-edge structure spectroscopy (μ-XANES). These data show that much of the variation in Fo content reflects variation in oxidation state of iron in the melt, which varies with sulfur concentration in the glass and (locally) with proximity to scoria edges in contact with air. Data for 24 olivine-melt pairs in the better-equilibrated samples from later in the eruption show KD averaging 0.280 ± 0.03 for the exchange of Fe and Mg between olivine and melt, somewhat displaced from the value of 0.30 ± 0.03 given by Roeder and Emslie (1970). This may reflect the low SiO2 content of the 1959 magmas, which is lower than that in most Kīlauea tholeiites. More broadly, we show the potential of μ-XANES and electron microprobe to revisit and refine the value of KD in natural systems.The observed variations of Fe+ 3/FeT ratios in the glasses reflect two distinct processes. The main process, sulfur degassing, produces steady decrease of the Fe+ 3/FeT ratio. Melt inclusions in olivine are high in sulfur (1060–1500 ppm S), with Fe+ 3/FeT = 0.160–0.175. Matrix glasses are degassed (mostly S eruption and (2) the melts originally had Fe+ 3/FeT ≥ 0.175, consistent with oxygen fugacity (fO2) at least 0.4 log units above the fayalite-magnetite-quartz (FMQ) buffer at 1 atm and magmatic temperature of 1200 °C.The second process is interaction between the

  3. XANES analysis of calcium and sodium phosphates and silicates and hydroxyapatite-Bioglass (registered) 45S5 co-sintered bioceramics

    Energy Technology Data Exchange (ETDEWEB)

    Demirkiran, Hande [Graduate Student, Materials Science and Engineering Department, University of Texas at Arlington, Arlington, TX (United States); Hu Yongfeng; Zuin, Lucia [Beamline Scientist, Canadian Light Source, Saskatoon, SK (Canada); Appathurai, Narayana [Beamline Scientist, Synchrotron Radiation Center, Madison, WI (United States); Aswath, Pranesh B., E-mail: aswath@uta.edu [Materials Science and Engineering Department, University of Texas at Arlington, Arlington, TX (United States)

    2011-03-12

    Bioglass (registered) 45S5 was co-sintered with hydroxyapatite at 1200 deg. C. When small amounts (< 5 wt.%) of Bioglass (registered) 45S5 was added it behaved as a sintering aid and also enhanced the decomposition of hydroxyapatite to {beta}-tricalcium phosphate. However when 10 wt.% and 25 wt.% Bioglass (registered) 45S5 was used it resulted in the formation of Ca{sub 5}(PO{sub 4}){sub 2}SiO{sub 4} and Na{sub 3}Ca{sub 6}(PO{sub 4}){sub 5} in an amorphous silicate matrix respectively. These chemistries show improved bioactivity compared to hydroxyapatite and are the subject of this study. The structure of several crystalline calcium and sodium phosphates and silicates as well as the co-sintered hydroxyapatite-Bioglass (registered) 45S5 bioceramics were examined using XANES spectroscopy. The nature of the crystalline and amorphous phases were studied using silicon (Si) and phosphorus (P) K- and L{sub 2,3}-edge and calcium (Ca) K-edge XANES. Si L{sub 2,3}-edge spectra of sintered bioceramic compositions indicates that the primary silicates present in these compositions are sodium silicates in the amorphous state. From Si K-edge spectra, it is shown that the silicates are in a similar structural environment in all the sintered bioceramic compositions with 4-fold coordination. Using P L{sub 2,3}-edge it is clearly shown that there is no evidence of sodium phosphate present in the sintered bioceramic compositions. In the P K-edge spectra, the post-edge shoulder peak at around 2155 eV indicates that this shoulder to be more defined for calcium phosphate compounds with decreasing solubility and increasing thermodynamic stability. This shoulder peak is more noticeable in hydroxyapatite and {beta}-TCP indicating greater stability of the phosphate phase. The only spectra that does not show a noticeable peak is the composition with Na{sub 3}Ca{sub 6}(PO{sub 4}){sub 5} in a silicate matrix indicating that it is more soluble compared to the other compositions.

  4. A XANES study of cobalt speciation state in blue-and-white glazes from 16th to 17th century Chinese porcelains

    Energy Technology Data Exchange (ETDEWEB)

    Figueiredo, M.O., E-mail: ondina.figueiredo@lneg.pt [CENIMAT/I3N, Faculty Sciences and Technology, New University of Lisbon, Campus da Caparica, 2829-516 Caparica (Portugal); National Laboratory of Energy and Geology (LNEG), Apartado 7586, 2721-866 Alfragide (Portugal); Silva, T.P. [National Laboratory of Energy and Geology (LNEG), Apartado 7586, 2721-866 Alfragide (Portugal); CENIMAT/I3N, Faculty Sciences and Technology, New University of Lisbon, Campus da Caparica, 2829-516 Caparica (Portugal); Veiga, J.P. [CENIMAT/I3N, Faculty Sciences and Technology, New University of Lisbon, Campus da Caparica, 2829-516 Caparica (Portugal)

    2012-04-15

    Highlights: Black-Right-Pointing-Pointer Speciation of cobalt in ancient Chinese porcelain glazes studied by X-ray absorption near-edge spectroscopy. Black-Right-Pointing-Pointer Blue pigmenting role of tetrahedral Co{sup 2+} ions. Black-Right-Pointing-Pointer Uncertainties in deducing a formal valence state for cobalt ions from the edge energy. - Abstract: The composition of cobalt blue pigments used in ancient blue-and-white Chinese glazes is known to have changed between the 14th and the 17th century and ratios of some main chemical components plus trace elements are relevant guide-lines to establish the porcelain manufacture period. Once archaeological findings of Chinese porcelains can contribute to set up dating processes, a study of blue-and-white porcelain shards recovered during recent excavations in Lisbon Old-City was carried out by non-destructive laboratory X-ray fluorescence spectrometry for chemical characterization, combined with X-ray absorption spectroscopy (XAS) using synchrotron radiation to ascertain the formal valence and coordination of pigmenting cobalt ions. Following a preliminary extended X-ray absorption fine-structure study that revealed a coordination of divalent cobalt ions slightly above four, a detailed analysis of the near-edge region of Co 1s X-ray absorption spectra (XANES) was carried out on the blue-and-white glazes from those archaeological Chinese porcelain fragments. Pre-edge features and edge details are discussed in comparison with XANES spectra obtained from model compounds with well known crystal structure - Co{sub 3}O{sub 4}, CoAl{sub 2}O{sub 4} and Co{sub 2}SiO{sub 4}, plus a cobalt-based blue pigment (cerulean). Present chemical data validate the manufacture period of studied Chinese porcelains advanced by Art Historians on the single basis of stylistic features (late 16th and medium 17th century). Spectroscopic results confirm a coordination environment of pigmenting Co{sup 2+} ions close to tetrahedral and

  5. A XANES study of cobalt speciation state in blue-and-white glazes from 16th to 17th century Chinese porcelains

    International Nuclear Information System (INIS)

    Figueiredo, M.O.; Silva, T.P.; Veiga, J.P.

    2012-01-01

    Highlights: ► Speciation of cobalt in ancient Chinese porcelain glazes studied by X-ray absorption near-edge spectroscopy. ► Blue pigmenting role of tetrahedral Co 2+ ions. ► Uncertainties in deducing a formal valence state for cobalt ions from the edge energy. - Abstract: The composition of cobalt blue pigments used in ancient blue-and-white Chinese glazes is known to have changed between the 14th and the 17th century and ratios of some main chemical components plus trace elements are relevant guide-lines to establish the porcelain manufacture period. Once archaeological findings of Chinese porcelains can contribute to set up dating processes, a study of blue-and-white porcelain shards recovered during recent excavations in Lisbon Old-City was carried out by non-destructive laboratory X-ray fluorescence spectrometry for chemical characterization, combined with X-ray absorption spectroscopy (XAS) using synchrotron radiation to ascertain the formal valence and coordination of pigmenting cobalt ions. Following a preliminary extended X-ray absorption fine-structure study that revealed a coordination of divalent cobalt ions slightly above four, a detailed analysis of the near-edge region of Co 1s X-ray absorption spectra (XANES) was carried out on the blue-and-white glazes from those archaeological Chinese porcelain fragments. Pre-edge features and edge details are discussed in comparison with XANES spectra obtained from model compounds with well known crystal structure – Co 3 O 4 , CoAl 2 O 4 and Co 2 SiO 4 , plus a cobalt-based blue pigment (cerulean). Present chemical data validate the manufacture period of studied Chinese porcelains advanced by Art Historians on the single basis of stylistic features (late 16th and medium 17th century). Spectroscopic results confirm a coordination environment of pigmenting Co 2+ ions close to tetrahedral and substantiate the dual role of cobalt as network former plus modifier in the glaze of ancient Chinese porcelains.

  6. The origin of luminescence from di[4-(4-diphenylaminophenyl)phenyl]sulfone (DAPSF), a blue light emitter: an X-ray excited optical luminescence (XEOL) and X-ray absorption near edge structure (XANES) study.

    Science.gov (United States)

    Zhang, Duo; Zhang, Hui; Zhang, Xiaohong; Sham, Tsun-Kong; Hu, Yongfeng; Sun, Xuhui

    2016-03-07

    The electronic structure and optical properties of di[4-(4-diphenylaminophenyl)phenyl]sulfone (denoted as DAPSF), a highly efficient fluorophor, have been investigated using X-ray excited optical luminescence (XEOL) and X-ray absorption near edge structure (XANES) spectroscopy at excitation energies across the C, N, O K-edges and the sulfur K-edge. The results indicate that the blue luminescence is mainly related to the sulfur functional group.

  7. Fe K-Edge X-ray absorption near-edge spectroscopy (XANES) and X-ray diffraction (XRD) analyses of LiFePO4 and its base materials

    Science.gov (United States)

    Latif, C.; Negara, V. S. I.; Wongtepa, W.; Thamatkeng, P.; Zainuri, M.; Pratapa, S.

    2018-03-01

    XANES analysis has been performed with the aim of knowing the Fe oxidation state in a synthesized LiFePO4 and its base materials. XANES measurements were performed at SLRI on energy around Fe K-edge. An XRD analysis has also been performed with the aim of knowing the phase composition, lattice parameters and crystallite size of the LiFePO4 as well as the base materials. From the XRD analysis, it was found that the dominating phase in the iron sand sample was Fe3O4 and the only phase found after calcination was LiFePO4. The latter phase exhibited crystallite size of 100 nm and lattice parameters a = 10.169916 Å, b = 5.919674 Å, c = 4.627893 Å. Qualitative analysis of XANES data revealed that the oxidation number of Fe in the sample before calcination was greater than that after calcination and Fe in the natural iron sand, indicated by the E0 values of 7129.2 eV, 7120.6 eV and 7124.4 eV respectively.

  8. MS-XANES studies on the interface effect of semiconductor InSb nanoparticles embedded in a-SiO2 matrix

    International Nuclear Information System (INIS)

    Chen Dongliang; Wu Ziyu; Wei Shiqiang

    2006-01-01

    The interface effect of semiconductor InSb nanoparticles (NPs) embedded in a-SiO 2 matrix was investigated via multi-scattering XANES simulations. The results show that the white line increase and broadening to higher energies of InSb NPs embedded in a-SiO 2 host matrix are mainly due to the interaction of InSb NPs and a-SiO 2 matrix. It can be interpreted as both a local single-site effect on μ 0 (E) due to the effect of a-SiO 2 matrix on Sb intra-atomic potential and the increase in 5p-hole population due to 5p-electron depletion in Sb for the InSb NPs embedded in SiO 2 matrix. On the other hand, our result reveals evidently that it is not reasonable to estimate the 5p-hole counts only according to the intensity of the white line due to the interface effect of nanoparticles. (authors)

  9. Redox Reaction in Silicate Melts Monitored by ''Static'' In-Situ Fe K-Edge XANES up to 1180 deg. C

    International Nuclear Information System (INIS)

    Wilke, Max; Partzsch, Georg M.; Welter, Edmund; Farges, Francois

    2007-01-01

    A new experimental setup to measure in-situ kinetics of redox reactions in silicate melts is presented. To study the progress of the Fe-redox reaction, the variation of the signal is recorded at an energy, where the difference between the spectra of the oxidized and reduced Fe in the melt is largest (''static XANES''). To control the redox conditions, the gas atmosphere could be changed between to types of gases using computer-controlled valves (N2:H2 and air, respectively). In this way, a number of reduction/oxidation cycles can be monitored in-situ and continuously. Applied at the Fe K-edge in molten silicates, we obtained a set of high quality data, which includes the very first steps of the redox reaction. An Avrami-type equation is used to investigate rate-controlling parameters for the iron oxidation/reduction kinetics for two melts (basaltic and Na trisilicate) for temperatures up to 1180 deg. C

  10. Hydrous ferric oxide: evaluation of Cd-HFO surface complexation models combining Cd(K) EXAFS data, potentiometric titration results, and surface site structures identified from mineralogical knowledge.

    Science.gov (United States)

    Spadini, Lorenzo; Schindler, Paul W; Charlet, Laurent; Manceau, Alain; Vala Ragnarsdottir, K

    2003-10-01

    The surface properties of ferrihydrite were studied by combining wet chemical data, Cd(K) EXAFS data, and a surface structure and protonation model of the ferrihydrite surface. Acid-base titration experiments and Cd(II)-ferrihydrite sorption experiments were performed within 3titration data could be adequately modeled by triple bond Fe- OH(2)(+1/2)-H(+)triple bond Fe-OH(-1/2),logk((int))=-8.29, assuming the existence of a unique intrinsic microscopic constant, logk((int)), and consequently the existence of a single significant type of acid-base reactive functional groups. The surface structure model indicates that these groups are terminal water groups. The Cd(II) data were modeled assuming the existence of a single reactive site. The model fits the data set at low Cd(II) concentration and up to 50% surface coverage. At high coverage more Cd(II) ions than predicted are adsorbed, which is indicative of the existence of a second type of site of lower affinity. This agrees with the surface structure and protonation model developed, which indicates comparable concentrations of high- and low-affinity sites. The model further shows that for each class of low- and high-affinity sites there exists a variety of corresponding Cd surface complex structure, depending on the model crystal faces on which the complexes develop. Generally, high-affinity surface structures have surface coordinations of 3 and 4, as compared to 1 and 2 for low-affinity surface structures.

  11. XAFS study on silica glasses irradiated in a nuclear reactor

    International Nuclear Information System (INIS)

    Yoshida, Tomoko; Yoshida, Hisao; Hara, Takanobu; Ii, Tatsuya; Okada, Tomohisa; Tanabe, Tetsuo

    2000-01-01

    X-ray absorption technique (XANES and EXAFS) was applied to study the local structures of silica glasses before and after the irradiation in a nuclear reactor. Although our separate photoluminescence (PL) measurements clearly showed the different aspects about oxygen vacancies in these samples, i.e., at least the B 2β type oxygen-deficient center exists as an intrinsic defect in the fused silica glass while another type B 2α center is formed in the synthesized silica glass, such differences did not directly reflect on the X-ray absorption spectra (XANES and EXAFS). However, the curve-fitting analysis of EXAFS showed that the number of oxygen atoms coordinated to Si relatively increased after the irradiation. This result may indicate the occurrence of the structural relaxation in the irradiated samples, that is, a slightly distorted SiO 4 tetrahedra in silica glasses relaxed to the regular SiO 4 tetrahedra due to the break of some connections between SiO 4 units in the silica glasses. Thus, the X-ray absorption technique gave the important information of the in-reactor irradiated silica glasses which complements the results obtained from PL measurements

  12. Papers from U.S. Department of Energy Science Undergraduate Laboratory Internship Program (SULI) 2010

    Energy Technology Data Exchange (ETDEWEB)

    2011-06-22

    The solvation sphere of halides in water has been investigated using a combination of extended x-ray absorption fine structure (EXAFS) and x-ray absorption near-edge structure (XANES) analysis techniques. The results have indicated that I{sup -} and Br{sup -} both have an asymmetric, 8 water molecule primary solvation spheres. These spheres are identical, with the Br{sup -} sphere about .3 {angstrom} smaller than the I{sup -} sphere. This study utilized near-edge analysis to supplement EXAFS analysis which suffers from signal dampening/broadening due to thermal noise. This paper has reported on the solvation first sphere of I{sup -} and Br{sup -} in water. Using EXAFS and XANES analysis, strong models which describe the geometric configuration of water molecules coordinated to a central anion have been developed. The combination of these techniques has provided us with a more substantiated argument than relying solely on one or the other. An important finding of this study is that the size of the anion plays a smaller role than previously assumed in determining the number of coordinating water molecules. Further experimental and theoretical investigation is required to understand why the size of the anion plays a minor role in determining the number of water molecules bound.

  13. Quantitative investigation of two metallohydrolases by X-ray absorption spectroscopy near-edge spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, W. [Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230027 (China); Chu, W.S.; Yang, F.F.; Yu, M.J.; Chen, D.L.; Guo, X.Y. [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Zhou, D.W.; Shi, N. [Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230027 (China); Marcelli, A. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, P.O. Box 13, Frascati 00044 (Italy); Niu, L.W.; Teng, M.K. [Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230027 (China); Gong, W.M. [Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101 (China); Benfatto, M. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, P.O. Box 13, Frascati 00044 (Italy); Wu, Z.Y. [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, P.O. Box 13, Frascati 00044 (Italy)], E-mail: wuzy@ihep.ac.cn

    2007-09-21

    The last several years have witnessed a tremendous increase in biological applications using X-ray absorption spectroscopy (BioXAS), thanks to continuous advancements in synchrotron radiation (SR) sources and detector technology. However, XAS applications in many biological systems have been limited by the intrinsic limitations of the Extended X-ray Absorption Fine Structure (EXAFS) technique e.g., the lack of sensitivity to bond angles. As a consequence, the application of the X-ray absorption near-edge structure (XANES) spectroscopy changed this scenario that is now continuously changing with the introduction of the first quantitative XANES packages such as Minut XANES (MXAN). Here we present and discuss the XANES code MXAN, a novel XANES-fitting package that allows a quantitative analysis of experimental data applied to Zn K-edge spectra of two metalloproteins: Leptospira interrogans Peptide deformylase (LiPDF) and acutolysin-C, a representative of snake venom metalloproteinases (SVMPs) from Agkistrodon acutus venom. The analysis on these two metallohydrolases reveals that proteolytic activities are correlated to subtle conformation changes around the zinc ion. In particular, this quantitative study clarifies the occurrence of the LiPDF catalytic mechanism via a two-water-molecules model, whereas in the acutolysin-C we have observed a different proteolytic activity correlated to structural changes around the zinc ion induced by pH variations.

  14. Quantitative investigation of two metallohydrolases by X-ray absorption spectroscopy near-edge spectroscopy

    International Nuclear Information System (INIS)

    Zhao, W.; Chu, W.S.; Yang, F.F.; Yu, M.J.; Chen, D.L.; Guo, X.Y.; Zhou, D.W.; Shi, N.; Marcelli, A.; Niu, L.W.; Teng, M.K.; Gong, W.M.; Benfatto, M.; Wu, Z.Y.

    2007-01-01

    The last several years have witnessed a tremendous increase in biological applications using X-ray absorption spectroscopy (BioXAS), thanks to continuous advancements in synchrotron radiation (SR) sources and detector technology. However, XAS applications in many biological systems have been limited by the intrinsic limitations of the Extended X-ray Absorption Fine Structure (EXAFS) technique e.g., the lack of sensitivity to bond angles. As a consequence, the application of the X-ray absorption near-edge structure (XANES) spectroscopy changed this scenario that is now continuously changing with the introduction of the first quantitative XANES packages such as Minut XANES (MXAN). Here we present and discuss the XANES code MXAN, a novel XANES-fitting package that allows a quantitative analysis of experimental data applied to Zn K-edge spectra of two metalloproteins: Leptospira interrogans Peptide deformylase (LiPDF) and acutolysin-C, a representative of snake venom metalloproteinases (SVMPs) from Agkistrodon acutus venom. The analysis on these two metallohydrolases reveals that proteolytic activities are correlated to subtle conformation changes around the zinc ion. In particular, this quantitative study clarifies the occurrence of the LiPDF catalytic mechanism via a two-water-molecules model, whereas in the acutolysin-C we have observed a different proteolytic activity correlated to structural changes around the zinc ion induced by pH variations

  15. Stability of mineral fibres in contact with human cell cultures. An in situ μXANES, μXRD and XRF iron mapping study.

    Science.gov (United States)

    Pollastri, Simone; Gualtieri, Alessandro F; Vigliaturo, Ruggero; Ignatyev, Konstantin; Strafella, Elisabetta; Pugnaloni, Armanda; Croce, Alessandro

    2016-12-01

    Relevant mineral fibres of social and economic importance (chrysotile UICC, crocidolite UICC and a fibrous erionite from Jersey, Nevada, USA) were put in contact with cultured diploid human non-tumorigenic bronchial epithelial (Beas2B) and pleural transformed mesothelial (MeT5A) cells to test their cytotoxicity. Slides of each sample at different contact times up to 96 h were studied in situ using synchrotron XRF, μ-XRD and μ-XAS (I18 beamline, Diamond Light Source, UK) and TEM investigations. XRF maps of samples treated for 96 h evidenced that iron is still present within the chrysotile and crocidolite fibres and retained at the surface of the erionite fibres, indicating its null to minor mobilization in contact with cell media; this picture was confirmed by the results of XANES pre-edge analyses. μ-XRD and TEM data indicate greater morphological and crystallinity modifications occurring in chrysotile, whereas crocidolite and erionite show to be resistant in the biological environment. The contact of chrysotile with the cell cultures seems to lead to earlier amorphization, interpreted as the first dissolution step of these fibres. The formation of such silica-rich fibre skeleton may prompt the production of HO in synergy with surface iron species and could indicate that chrysotile may be much more reactive and cytotoxic in vitro in the (very) short term whereas the activity of crocidolite and erionite would be much more sluggish but persistent in the long term. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Correlation of the oxidation state of cerium in sol-gel glasses as a function of thermal treatment via optical spectroscopy and XANES studies.

    Science.gov (United States)

    Assefa, Zerihun; Haire, R G; Caulder, D L; Shuh, D K

    2004-07-01

    Sol-gel glass matrices containing lanthanides have numerous technological applications and their formation involves several chemical facets. In the case of cerium, its ability to exist in two different oxidation states or in mixed valence state provides additional complexities for the sol-gel process. The oxidation state of cerium present during different facets of preparation of sol-gel glasses, and also as a function of the starting oxidation state of cerium added, were studied both by optical spectroscopy and X-ray absorption near-edge structures (XANES). The findings acquired by each approach were compared. The primary focus was on the redox chemistries associated with sample preparation, gelation, and thermal treatment. When Ce3+ is introduced into the starting sols, the trivalent state normally prevails in the wet and room temperature-dried gels. Heating in air at >100 degrees C can generate a light yellow coloration with partial oxidation to the tetravalent state. Above 200 degrees C and up to approximately 1000 degrees C, cerium is oxidized to its tetravalent state. In contrast, when tetravalent cerium is introduced into the sol, both the wet and room temperature-dried gels lose the yellow-brown color of the initial ceric ammonium nitrate solution. When the sol-gel is heated to 110 degrees C it turns yellowish as the cerium tends to be re-oxidized. The yellow color is believed to represent the effect of oxidation and oligomerization of the cerium-silanol units in the matrix. The luminescence properties are also affected by these changes, the details of which are reported herein.

  17. 3D local structure around copper site of rabbit prion-related protein: Quantitative determination by XANES spectroscopy combined with multiple-scattering calculations

    International Nuclear Information System (INIS)

    Cui, P.X.; Lian, F.L.; Wang, Y.; Wen, Yi; Chu, W.S.; Zhao, H.F.; Zhang, S.; Li, J.; Lin, D.H.; Wu, Z.Y.

    2014-01-01

    Prion-related protein (PrP), a cell-surface copper-binding glycoprotein, is considered to be responsible for a number of transmissible spongiform encephalopathies (TSEs). The structural conversion of PrP from the normal cellular isoform (PrP C ) to the post-translationally modified form (PrP Sc ) is thought to be relevant to Cu 2+ binding to histidine residues. Rabbits are one of the few mammalian species that appear to be resistant to TSEs, because of the structural characteristics of the rabbit prion protein (RaPrP C ) itself. Here we determined the three-dimensional local structure around the C-terminal high-affinity copper-binding sites using X-ray absorption near-edge structure combined with ab initio calculations in the framework of the multiple-scattering (MS) theory. Result shows that two amino acid resides, Gln97 and Met108, and two histidine residues, His95 and His110, are involved in binding this copper(II) ion. It might help us understand the roles of copper in prion conformation conversions, and the molecular mechanisms of prion-involved diseases. - Highlights: ► The first structure of the metal ion binding site in RaPrP fifth copper-binding site. ► Quantitative determination by XANES spectroscopy combined with ab initio calculations. ► Provide a proof of the roles of copper in prion conformation conversions. ► Provide a proof of the molecular mechanisms of prion-involved diseases

  18. The hydrolysis and precipitation of Pd(II) in 0.6 mol kg-1 NaCl: A potentiometric, spectrophotometric, and EXAFS study

    International Nuclear Information System (INIS)

    Boily, Jean-Francois F.; Seward, Terry M.; Charnock, John M.

    2007-01-01

    The hydrolysis of palladium was investigated in 0.6 mol kg -1 NaCl at 298.2 K. Potentiometric titrations of solutions at various total concentrations of palladium(II) revealed that dilute (millimolar) conditions can be used to monitor the proton release due to hydrolysis reactions up to 2 protons per palladium(II) as long as the equilibration time is kept small. Spectrophotometric titrations were used to corroborate the homogeneous changes in speciation for the PdCl 3 OH 2- species and to extract its correlative molar absorption coefficients in the 210-320 nm range. The molar absorption coefficients are similar to those of PdCl42- but exhibit a broader distribution of excitation energies resulting from the blue shift of the dominant charge transfer bands due to the presence of OH-. The longer-term potentiometric titrations systematically yielded, on the other hand, precipitates which matured over a period of 6 weeks and resulted in a more extensive release of protons to the solution. Precipitation experiments at six different total palladium(II) concentrations in the 3-11 pH range showed the dominant precipitating phase as Pd(OH)1.72Cl0.28. The coordination environment of Pd in this solid was investigated by extended X-ray absorption fine structure spectroscopy (EXAFS) and yielded an average 1.75 O and 0.25 Cl per Pd atoms with a Pd-O distance of 2.0 (angstrom) and Pd-Cl of 2.1 (angstrom). Finally, the precipitation experiments showed the final products to be of larger solubility than a literature Pd(OH)2 solubility study in which the KCl media induced a solid phase transformation to Pd(OH)1.72Cl0.28. Polynuclear complexes Pdq(OH)r2q-r with q=r=[3,9] explain the combined precipitation and hydrolysis data and may represent subsets of [Pd(OH)2]n and/or [Pd(OH)1.72Cl0.28]n chains coiled into nanometer-sized spheroids previously described in the literature

  19. 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)

  20. EXAFS and EPR study of La0.6Sr0.2Ca0.2MnO3 and La0.6Sr0.2Ba0.2MnO3

    International Nuclear Information System (INIS)

    Yang, D.-K.Dong-Seok; Ulyanov, A.N.; Phan, Manh-Huong; Kim, Ikgyun; Ahn, Byong-Keun; Rhee, Jang Roh; Kim, Jung Sun; Nguyen, Chau; Yu, Seong-Cho

    2003-01-01

    Extended X-ray absorption fine structure (EXAFS) analysis and electron-paramagnetic resonance (EPR) have been used to examine the local structure and the internal dynamics of La 0.6 Sr 0.2 Ca 0.2 MnO 3 and La 0.6 Sr 0.2 Ba 0.2 MnO 3 lanthanum manganites. The Mn-O bond distance (∼1.94 Angst for both samples) and the Debye-Waller factors (0.36x10 -2 and 0.41x10 -2 Angst 2 for La 0.6 Sr 0.2 Ca 0.2 MnO 3 and for La 0.6 Sr 0.2 Ba 0.2 MnO 3 , respectively) were obtained from the EXAFS analysis. The dependence of the EPR line width on dopant kind (Ca or Ba) showed a decrease of the spin-lattice interaction with an increase of the Curie temperature. For both compositions, the EPR line intensity followed the exponential law I(T)=I 0 exp(E a /k B T), deduced on the basis of the adiabatic polaron hopping model

  1. Structure-conductivity studies in polymer electrolytes containing multivalent cations

    International Nuclear Information System (INIS)

    Aziz, M.

    1996-05-01

    Understanding the structure - conductivity relationship is of paramount importance for the development of polymer electrolytes. The present studies present the techniques found useful in the elucidation of structure - conductivity relationship in PEO n :ZnBr 2 (n = 8, 1000, 2000, 3000, 4000 and 5000) and PEO n :FeBr x (n= 8, 20 and 50; x = 2 and 3). Local structural studies have been undertaken using X-ray absorption fine structures (XAFS) which includes extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES). EXAFS provides interatomic distance and coordination numbers of the nearest neighbours and results from the EXAFS studies showed that high conductivity is associated with stretched M - O interatomic distance. In the studies on ultra dilute Zn samples it was found that the cation is highly solvated by the heteroatom forming a tightly bound environment which inhibits local segmental motion thus impeding ion migration. XANES studies on the PEO and modified PEO complexes of NiBr 2 revealed the sensitivity of XANES to the structural differences. XANES on Zn and Fe samples also revealed the sensitivity to changes in interatomic distances reflected in shifts of the white line. The complementary nature of EXAFS and XANES was reflected in the studies conducted. Morphological studies were undertaken employing differential scanning calorimetry (DSC), variable temperature polarising microscopy (VTPM) and atomic force microscopy (AFM). DSC evidences helped to explain the texture of the iron samples during the drying process, and showed transitions between low melting, PEO and high melting spherulites, and VTPM is able to visualise the spherulites present in the samples. AFM has successfully imaged the as cast PEO 8 :FeBr 2 sample and the surface effect causing extra resistance in the impedance spectra could be seen. Conductivity studies were carried out using a.c. impedance spectra. Fe(ll) samples exhibit the typical semicircle

  2. Development and applications of microanalytical techniques

    International Nuclear Information System (INIS)

    Cholewa, M.

    2005-05-01

    The development of new analytical techniques is an essential part of our everyday life and is dictated by strong progress in modern science and technology. Both these areas require more precise information about materials and processes involved. Due to these requirements we have been observing a rapid growth in the development of techniques that require both a high spatial resolution and high sensitivity. Modern analytical techniques provide an important interface between science and applications. The works presented in this habilitation thesis span the period of almost 20 years. During this time the author has been leading the development and applications of several new analytical and micro analytical techniques which have been documented in this thesis. This development has required development of ideas, strong leadership, organisational skills, organisation of funds and groups to carry out the necessary work. In chapter 3 the use of the PIXE and XANES techniques described an investigation of permeability for selected elements inside cells. It was important to develop new protocols for sample preparation and analysis and a large number of cells were necessary in order to obtain meaningful data. This development was closely associated with work presented in chapter 4 where the role of sample damage under the MeV ion beam bombardment was investigated. At that time we were the leading group in the world to perform such studies. Chapter 5 describes development of new analytical techniques and its possible applications. Development of the SIHF has been probably the most demanding and difficult project and was described in chapter 6 and it was closely related with development of a diamond detector described in chapter 7. A great part of these works were performed by the author at the Micro Analytical Research Centre (MARC) in the School of Physics at the University of Melbourne in Australia. However, some works were performed at GSI in Germany and BNL in USA. (author)

  3. Experimental techniques; Techniques experimentales

    Energy Technology Data Exchange (ETDEWEB)

    Roussel-Chomaz, P. [GANIL CNRS/IN2P3, CEA/DSM, 14 - Caen (France)

    2007-07-01

    This lecture presents the experimental techniques, developed in the last 10 or 15 years, in order to perform a new class of experiments with exotic nuclei, where the reactions induced by these nuclei allow to get information on their structure. A brief review of the secondary beams production methods will be given, with some examples of facilities in operation or under project. The important developments performed recently on cryogenic targets will be presented. The different detection systems will be reviewed, both the beam detectors before the targets, and the many kind of detectors necessary to detect all outgoing particles after the reaction: magnetic spectrometer for the heavy fragment, detection systems for the target recoil nucleus, {gamma} detectors. Finally, several typical examples of experiments will be detailed, in order to illustrate the use of each detector either alone, or in coincidence with others. (author)

  4. Synchrotron-based P K-edge XANES spectroscopy reveals rapid changes of phosphorus speciation in the topsoil of two glacier foreland chronosequences

    Science.gov (United States)

    Prietzel, Jörg; Dümig, Alexander; Wu, Yanhong; Zhou, Jun; Klysubun, Wantana

    2013-05-01

    Phosphorus (P) is a crucial element for life on Earth, and the bioavailability of P in terrestrial ecosystems, which is dependent on the soil P stock and its speciation, may limit ecosystem productivity and succession. In our study, for the first time a direct speciation of soil P in two glacier foreland chronosequences has been conducted using synchrotron-based X-ray Absorption Near-Edge Structure (XANES) spectroscopy. The chronosequences are located in the forefields of Hailuogou Glacier (Gongga Shan, China) and Damma Glacier (Swiss Alps). The age since deglaciation of the investigated soils ranges from 0 to 120 years at Hailuogou, and from 15 to >700 years at Damma. Differences in climate conditions (cooler at Damma, in contrast to Hailuogou precluding the establishment of forest in advanced ecosystem succession stages) and in the chemical composition of the parent material result in different soil contents of total P and Fe/Al oxyhydroxides, which are much smaller at Damma than at Hailuogou. Nevertheless, both chronosequences show similar trends of their topsoil P status with increasing soil age. Our study reveals a rapid change of topsoil P speciation in glacier retreat areas already during initial stages of pedogenesis: Initially dominating bedrock-derived apatite-P and Al-bound P is depleted; Fe-bound P and particularly organically-bound P is accumulated. Organic P strongly dominates in the topsoil of the mature soils outside the proglacial area of Damma Glacier (age 700-3000 years), and already 50 years after deglacation in the topsoil of the retreat area of Hailuogou Glacier. A key factor for the change in topsoil P speciation is the establishment of vegetation, resulting in soil organic matter (SOM) accumulation as well as accelerated soil acidification and apatite dissolution by organic acids, which are produced by SOM-degrading micro-organisms, mykorrhiza fungi, and plant roots. Particularly the succession of grassland to forest seems to accelerate the

  5. On the molecular basis of the activity of the antimalarial drug chloroquine: EXAFS-assisted DFT evidence of a direct Fe–N bond with free heme in solution

    International Nuclear Information System (INIS)

    Macetti, Giovanni; Rizzato, Silvia; Beghi, Fabio; Presti, Leonardo Lo; Silvestrini, Lucia

    2016-01-01

    4-aminoquinoline antiplasmodials interfere with the biocrystallization of the malaria pigment, a key step of the malaria parasite metabolism. It is commonly believed that these drugs set stacking π···π interactions with the Fe-protoporphyrin scaffold of the free heme, even though the details of the heme:drug recognition process remain elusive. In this work, the local coordination of Fe(III) ions in acidic solutions of hematin at room temperature was investigated by extended x-ray absorption fine structure (EXAFS) spectroscopy in the 4.0–5.5 pH range, both in the presence and in the absence of the antimalarial drug chloroquine. EXAFS results were complemented by DFT simulations in polarizable continuum media to model solvent effects. We found evidence that a complex where the drug quinoline nitrogen is coordinated with the iron center might coexist with formerly proposed adduct geometries, based on stacking interactions. Charge-assisted hydrogen bonds among lateral chains of the two molecules play a crucial role in stabilizing this complex, whose formation is favored by the presence of lipid micelles. The direct Fe–N bond could reversibly block the axial position in the Fe 1st coordination shell in free heme, acting as an inhibitor for the crystallization of the malaria pigment without permanently hampering the catalytic activity of the redox center. These findings are discussed in the light of possible implications on the engineering of drugs able to thwart the adaptability of the malaria parasite against classical aminoquinoline-based therapies. (invited comment)

  6. On the molecular basis of the activity of the antimalarial drug chloroquine: EXAFS-assisted DFT evidence of a direct Fe-N bond with free heme in solution

    Science.gov (United States)

    Macetti, Giovanni; Rizzato, Silvia; Beghi, Fabio; Silvestrini, Lucia; Lo Presti, Leonardo

    2016-02-01

    4-aminoquinoline antiplasmodials interfere with the biocrystallization of the malaria pigment, a key step of the malaria parasite metabolism. It is commonly believed that these drugs set stacking π···π interactions with the Fe-protoporphyrin scaffold of the free heme, even though the details of the heme:drug recognition process remain elusive. In this work, the local coordination of Fe(III) ions in acidic solutions of hematin at room temperature was investigated by extended x-ray absorption fine structure (EXAFS) spectroscopy in the 4.0-5.5 pH range, both in the presence and in the absence of the antimalarial drug chloroquine. EXAFS results were complemented by DFT simulations in polarizable continuum media to model solvent effects. We found evidence that a complex where the drug quinoline nitrogen is coordinated with the iron center might coexist with formerly proposed adduct geometries, based on stacking interactions. Charge-assisted hydrogen bonds among lateral chains of the two molecules play a crucial role in stabilizing this complex, whose formation is favored by the presence of lipid micelles. The direct Fe-N bond could reversibly block the axial position in the Fe 1st coordination shell in free heme, acting as an inhibitor for the crystallization of the malaria pigment without permanently hampering the catalytic activity of the redox center. These findings are discussed in the light of possible implications on the engineering of drugs able to thwart the adaptability of the malaria parasite against classical aminoquinoline-based therapies.

  7. X-ray spectroscopic studies of microbial transformations of uranium

    International Nuclear Information System (INIS)

    Dodge, C.J.; Francis, A.J.; Clayton, C.R.

    1995-10-01

    Several uranium compounds U-metal (α-phase), UO 2 , U 3 O 8 , γ-UO 3 , uranyl acetate, uranyl nitrate, uranyl sulfate, aqueous and solid forms of 1:1 U:citric acid and 1:1:2 U:Fe:citric acid mixed-metal complexes, and a precipitate obtained by photodegradation of the U-citrate complex were characterized by X-ray spectroscopy using XPS, XANES, and EXAFS. XPS and XANES were used to determine U oxidation states. Spectral shifts were obtained at the U 4f 7/2 and U 4f 5/2 binding energies using XPS, and at the uranium M V absorption edge using XANES. The magnitude of the energy shift with oxidation state, and the ability to detect mixed-valent forms make these ideal techniques for determining uranium speciation in wastes subjected to bacterial action. The structure of 1:1 U:citric acid complex in both the aqueous and solid state was determined by EXAFS analysis of hexavalent uranium at the L M absorption edge and suggests the presence of a binuclear complex with a (UO 2 ) 2 (μ,η 2 -citrato) 2 core with a U-U distance of 5.2 angstrom. The influence of Fe on the structure of U-citrate complex was determined by EXAFS and the presence of a binuclear mixed-metal citrate complex with a U-Fe distance of 4.8 angstrom was confirmed. The precipitate resulting from photodegradation of U-citrate complex was identified as an amorphous form of uranium trioxide by XPS and EXAS

  8. On the use of the spectroscopic techniques to model the interactions between radionuclides and solid minerals

    Energy Technology Data Exchange (ETDEWEB)

    Simoni, E. [IPN, Paris XI University, 91406 Orsay (France)]. e-mail: simoni@ipno.in2p3.fr

    2004-07-01

    In order to determine the radionuclides sorption constants on solid natural minerals, both thermodynamic and structural investigations, using spectroscopic techniques, are presented. The natural clays, that could be used as engineering barrier in the nuclear waste geological repository, are rather complex minerals. Therefore, in order to understand how these natural materials retain the radionuclides, it is necessary first to perform these studies on simple substrates such as phosphates, oxides and silicates (as powder and single crystal as well) and then extrapolate the obtained results on the natural minerals. As examples, the main results on the sorption processes of the hexavalent uranium onto zircon (ZrSiO{sub 4}) and lanthanum phosphate (LaPO{sub 4}) are presented. The corresponding sorption curves are simulated using the results obtained with the following spectroscopic techniques: laser induced spectro fluorimetry, X-ray photoelectron spectroscopy (XP S), X-ray absorption spectroscopy (Exafs). Finally, the thermodynamic sorption constants are calculated. (Author)

  9. X-ray Absorption Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Yano, Junko; Yachandra, Vittal K.

    2009-07-09

    This review gives a brief description of the theory and application of X-ray absorption spectroscopy, both X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), especially, pertaining to photosynthesis. The advantages and limitations of the methods are discussed. Recent advances in extended EXAFS and polarized EXAFS using oriented membranes and single crystals are explained. Developments in theory in understanding the XANES spectra are described. The application of X-ray absorption spectroscopy to the study of the Mn4Ca cluster in Photosystem II is presented.

  10. Characterization techniques for graphene-based materials in catalysis

    Directory of Open Access Journals (Sweden)

    Maocong Hu

    2017-06-01

    Full Text Available Graphene-based materials have been studied in a wide range of applications including catalysis due to the outstanding electronic, thermal, and mechanical properties. The unprecedented features of graphene-based catalysts, which are believed to be responsible for their superior performance, have been characterized by many techniques. In this article, we comprehensively summarized the characterization methods covering bulk and surface structure analysis, chemisorption ability determination, and reaction mechanism investigation. We reviewed the advantages/disadvantages of different techniques including Raman spectroscopy, X-ray photoelectron spectroscopy (XPS, Fourier transform infrared spectroscopy (FTIR and Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS, X-Ray diffraction (XRD, X-ray absorption near edge structure (XANES and X-ray absorption fine structure (XAFS, atomic force microscopy (AFM, scanning electron microscopy (SEM, transmission electron microscopy (TEM, high-resolution transmission electron microscopy (HRTEM, ultraviolet-visible spectroscopy (UV-vis, X-ray fluorescence (XRF, inductively coupled plasma mass spectrometry (ICP, thermogravimetric analysis (TGA, Brunauer–Emmett–Teller (BET, and scanning tunneling microscopy (STM. The application of temperature-programmed reduction (TPR, CO chemisorption, and NH3/CO2-temperature-programmed desorption (TPD was also briefly introduced. Finally, we discussed the challenges and provided possible suggestions on choosing characterization techniques. This review provides key information to catalysis community to adopt suitable characterization techniques for their research.

  11. Dismantling techniques

    International Nuclear Information System (INIS)

    Wiese, E.

    1998-01-01

    Most of the dismantling techniques used in a Decontamination and Dismantlement (D and D) project are taken from conventional demolition practices. Some modifications to the techniques are made to limit exposure to the workers or to lessen the spread of contamination to the work area. When working on a D and D project, it is best to keep the dismantling techniques and tools as simple as possible. The workers will be more efficient and safer using techniques that are familiar to them. Prior experience with the technique or use of mock-ups is the best way to keep workers safe and to keep the project on schedule

  12. Dismantling techniques

    Energy Technology Data Exchange (ETDEWEB)

    Wiese, E.

    1998-03-13

    Most of the dismantling techniques used in a Decontamination and Dismantlement (D and D) project are taken from conventional demolition practices. Some modifications to the techniques are made to limit exposure to the workers or to lessen the spread of contamination to the work area. When working on a D and D project, it is best to keep the dismantling techniques and tools as simple as possible. The workers will be more efficient and safer using techniques that are familiar to them. Prior experience with the technique or use of mock-ups is the best way to keep workers safe and to keep the project on schedule.

  13. Zn speciation in a soil contaminated by the deposition of a dredged sediment by synchrotron X-ray techniques

    International Nuclear Information System (INIS)

    Isaure, Marie-Pierre; Manceau, Alain; Laboudigue, Agnes; Tamura, Nobumichi; Marcus, Matthew A.

    2003-09-01

    The nature and proportion of Zn species present in an agricultural soil overlaid by a dredged contaminated sediment have been untangled by the novel combination of three non-invasive synchrotron-based x-ray techniques: x-ray microfluorescence (μSXRF), microdiffraction (μXRD), and absorption spectroscopy (EXAFS). One primary (franklinite) and two secondary (phyllomanganate and phyllosilicate) Zn-containing minerals were identified in the initial soil, and another primary (ZnS) and a new secondary (Fe-(oxyhydr)oxide) Zn species in the covered soil. The quantitative analysis of EXAFS spectra recorded on bulk samples indicated that ZnS and Zn-Fe (oxyhydr)oxides amounted to 71+-10 percent and 27+-10 percent, respectively, and the other Zn species to less than 10 percent. The two new Zn species found in the covered soil result from the gravitational migration of ZnS particles initially present in the sediment, and from their further oxidative dissolution and fixation of leached Zn on F e (oxyhydr) oxides

  14. The role of the A ion in the Fe local structure of the AFe{sub 2}As{sub 2} systems (A=Sr, Eu, Ba): an EXAFS study

    Energy Technology Data Exchange (ETDEWEB)

    Tobia, Dina; Radaelli, Matheus; Piva, Mario Moda; Lesseux, Guilherme Gorgen; Jesus, Camilo Bruno Ramos; Urbano, Ricardo Rodrigues; Granado, Eduardo; Pagliuso, Pascoal G., E-mail: ifitobia@ifi.unicamp.br [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Instituto de Fisica Gleb Wataghin; Saleta, Martin Eduardo [Laboratorio Nacional de Luz Sincrotron (LNLS), Campinas, SP (Brazil)

    2016-07-01

    Full text: The recent discovery of high-T{sub C} superconductivity on Fe-based intermetallic materials has motivated an extensive research in this area due to the rich phase diagrams that they present. The non-doped AFe{sub 2}As{sub 2} compounds (named A122) are oxygen free iron arsenides (with A= Ba, Sr, Ca, Eu). At room temperature they are paramagnetic and crystallize in a tetragonal structure. At low temperature they exhibit a spin-density-wave (SDW) ordering transition (typically 100 K < T{sub SDW} < 200 K), connected with a structural phase transition to an orthorhombic structure. These transitions are reflected as anomalies in the electric resistivity, magnetic susceptibility and specific heat data. Although the pure A122 compounds are not superconductors, in these systems, it was observed that the SDW phase can be destabilized through chemical substitution or external applied pressure, leading to the emergence of superconductivity. In particular, the atomic substitution of the alkali atoms with different ionic radii in the A site results in a change of the cell parameters and, consequently, these systems experience effects of chemical pressure. In this context, it is of great interest to investigate the role of the local distortion on the Fe-As bonds for temperatures above and below T{sub SDW}, as the Fe-As bond distance controls directly the chemical pressure on Fe and ultimately the orbital differentiation of the Fe 3d bands on the Fermi Surface of these compounds. Extended X-ray absorption fine structure (EXAFS) measurements are ideal to obtain information about the relationship between local structural distortions and the system spin dynamics. In this work we present a study of the As local environment in AFe{sub 2}As{sub 2} (for A=Eu, Sr, Ba) as a function of temperature through EXAFS measurements in the As K absorption edge. We have investigated the effects of each particular A-site ion on the Fe-As bond from a local point of view. In all cases, high

  15. Translation Techniques

    OpenAIRE

    Marcia Pinheiro

    2015-01-01

    In this paper, we discuss three translation techniques: literal, cultural, and artistic. Literal translation is a well-known technique, which means that it is quite easy to find sources on the topic. Cultural and artistic translation may be new terms. Whilst cultural translation focuses on matching contexts, artistic translation focuses on matching reactions. Because literal translation matches only words, it is not hard to find situations in which we should not use this technique.  Because a...

  16. X-ray absorption edges and E.X.A.F.S.: application to the study of electronic and atomic structures of titanium and vanadium carbides TiC(1-x) and VC(1-x)

    International Nuclear Information System (INIS)

    Moisy-Maurice, Virginie.

    1980-09-01

    This text presents a systematic study of the X-ray absorption fine structures evolution, at the K edge of titanium, with vacancy concentration in TiC(1-x). The absorption edges are situated in the 50 eV following the coefficient discontinuity: from the evaluation of their general aspect, it is deduced that the positive charge of titanium atoms decreases when vacancy concentration increases in TiC(1-x). This allowed us to determine the best band structure calculation model. The interpretation of EXAFS spectra (modulation of the absorption coefficient until 1500 eV above the edge) gives indications about the local atomic structure. Here, the contraction of the average titanium-carbon interatomic distances compared to the distances between crystallographic sites is of the order of the experimental resolution 0.02 A for Ti C(0.8). The study of the damping of the spectra in terms of Debye-Waller factors gave an evaluation of the relative static atomic mean square displacements between first neighbours. Last, it has been established that the disordering of vacancies in the order-disorder transition of V 8 C 7 is an atomic scale phenomenon [fr

  17. Phase diagram and EXAFS study of La sub 0 sub . sub 7 Ca sub 0 sub . sub 3 sub - sub x Ba sub x MnO sub 3 manganites

    CERN Document Server

    Ulyanov, A N; Yang, D S

    2003-01-01

    The phase diagram and local structure of La sub 0 sub . sub 7 Ca sub 0 sub . sub 3 sub - sub x Ba sub x MnO sub 3 (x=0; 0.03; 0.06; ... 0.3) lanthanum manganites were studies. The Curie temperature, T sub c , of the compositions showed a sharp change near the concentrational structural orthorhombic-rhombohedral phase transition. Maximums of dispersion, sigma sub M sub n sub - sub O sup 2 , and asymmetry, sigma M sub n sub - sub O sup 3 , of pair distribution function for the Mn-O bond distances of MnO sub 6 octahedron on x-dependence were observed by extended X-ray absorption fine structure (EXAFS) analysis. The maximum of sigma sub M sub n sub - sub O sup 2 is caused by increase of dynamic rms displacements of Mn-O bond distances near the T sub c. The observed x dependence of sigma sub M sub n sub - sub O sup 3 reflects the reduction of charge carriers mobility at approaching to T sub c. (author)

  18. Local structural changes in paramagnetic and charge-ordered phases of Sm0.2Pr0.3Sr0.5MnO3: an EXAFS study

    International Nuclear Information System (INIS)

    Priolkar, K R; Kulkarni, Vishwajeet; Sarode, P R; Emura, S

    2008-01-01

    Sm 0.5-x Pr x Sr 0.5 MnO 3 exhibits a variety of ground states as x is varied from 0 to 0.5. At an intermediate doping of x = 0.3 a charge-ordered CE-type antiferromagnetic insulating (AFI) ground state is seen. The transition to this ground state is from a paramagnetic-insulating (PMI) phase through a ferromagnetic-metallic phase (FMM). Local structures in PMI and AFI phases of the x = 0.3 sample have been investigated using Pr K-edge and Sm K-edge extended x-ray absorption fine structure (EXAFS). It can be seen that the tilting and rotation of the MnO 6 octahedra about the b-axis are responsible for the charge-ordered CE-type antiferromagnetic ground state at low temperatures. In addition a shift in the position of the rare-earth ion along the c-axis has to be considered to account for observed distribution of bond distances around the rare-earth ion

  19. Diagnostic techniques

    International Nuclear Information System (INIS)

    Berquist, T.H.; Bender, C.E.; James, E.M.; Brown, M.L.; McLeod, R.A.; Broderick, D.F.; Welch, T.J.

    1989-01-01

    Proper application of imaging procedures is essential to obtain needed information for diagnosis and therapy planning in patients with suspected foot and/or ankle pathology. This paper provides basic background data for the numerous imaging techniques

  20. Speciation of trace elements in biological samples by nuclear analytical and related techniques coupled with chemical and biochemical separation

    International Nuclear Information System (INIS)

    Chen, C.Y.; Gao, Y.X.; Li, B.; Yu, H.W.; Li, Y.F.; Sun, J.; Chai, Z.F.

    2005-01-01

    In the past, most analytical problems relating to biological systems were addressed by measuring the total concentrations of elements. Now there is increasing interest of the importance of their chemical forms, in which an element is present in biological systems, e.g., the oxidation state, the binding state with macromolecules, or even the molecular structure. The biological effects of chromium, which is classified as an essential nutrient, are dependent upon its oxidation. state. In general, trivalent chromium is biochemically active, whereas hexavalent chromium is considered to be toxic. Mercury is one of serious environmental persistent pollutants. However, organic forms of mercury are known to possess much higher toxicity than inorganic mercury. Therefore, information on speciation is critically required in order to better understanding of their bioavailability, metabolism, transformation, and toxicity in vivo. Recently, chemical speciation of selenium, mercury, copper, zinc, iron, and so on, has been investigated by INAA, ICP-MS, XRF, EXAFS and related techniques combined with chemical and biochemical separation (extraction, chromatography, gel electrophoresis, etc.). INAA, XRF, and ICP-MS have superior advantages in aspect of multielemental analysis with high accuracy and sensitivity, which render the possibility of analyzing various elements of interest simultaneously. These offline or online techniques have been flexibly applied to different biological matrixes, such as human hair, serum, urine, various tissues and organs in our researches. In addition, EXAFS provides structural information about the moiety of metal centers up to a distance of approximately 4-5 Anstrom. For instance, hepatocellular carcinoma (HCC) is one of the most common cancers worldwide. Imbalance of elements, such as Se, Zn, Fe, Cu, Cd, Ca, etc., has been found in the whole blood or serum of patients with HCC. We found that the profiles of Se, Cd, Fe, Zn and Cu-containing proteins

  1. Decomposition techniques

    Science.gov (United States)

    Chao, T.T.; Sanzolone, R.F.

    1992-01-01

    Sample decomposition is a fundamental and integral step in the procedure of geochemical analysis. It is often the limiting factor to sample throughput, especially with the recent application of the fast and modern multi-element measurement instrumentation. The complexity of geological materials makes it necessary to choose the sample decomposition technique that is compatible with the specific objective of the analysis. When selecting a decomposition technique, consideration should be given to the chemical and mineralogical characteristics of the sample, elements to be determined, precision and accuracy requirements, sample throughput, technical capability of personnel, and time constraints. This paper addresses these concerns and discusses the attributes and limitations of many techniques of sample decomposition along with examples of their application to geochemical analysis. The chemical properties of reagents as to their function as decomposition agents are also reviewed. The section on acid dissolution techniques addresses the various inorganic acids that are used individually or in combination in both open and closed systems. Fluxes used in sample fusion are discussed. The promising microwave-oven technology and the emerging field of automation are also examined. A section on applications highlights the use of decomposition techniques for the determination of Au, platinum group elements (PGEs), Hg, U, hydride-forming elements, rare earth elements (REEs), and multi-elements in geological materials. Partial dissolution techniques used for geochemical exploration which have been treated in detail elsewhere are not discussed here; nor are fire-assaying for noble metals and decomposition techniques for X-ray fluorescence or nuclear methods be discussed. ?? 1992.

  2. Nanoscale Phase Separation and Lattice Complexity in VO2: The Metal–Insulator Transition Investigated by XANES via Auger Electron Yield at the Vanadium L23-Edge and Resonant Photoemission

    Directory of Open Access Journals (Sweden)

    Augusto Marcelli

    2017-12-01

    Full Text Available Among transition metal oxides, VO2 is a particularly interesting and challenging correlated electron material where an insulator to metal transition (MIT occurs near room temperature. Here we investigate a 16 nm thick strained vanadium dioxide film, trying to clarify the dynamic behavior of the insulator/metal transition. We measured (resonant photoemission below and above the MIT transition temperature, focusing on heating and cooling effects at the vanadium L23-edge using X-ray Absorption Near-Edge Structure (XANES. The vanadium L23-edges probe the transitions from the 2p core level to final unoccupied states with 3d orbital symmetry above the Fermi level. The dynamics of the 3d unoccupied states both at the L3- and at the L2-edge are in agreement with the hysteretic behavior of this thin film. In the first stage of the cooling, the 3d unoccupied states do not change while the transition in the insulating phase appears below 60 °C. Finally, Resonant Photoemission Spectra (ResPES point out a shift of the Fermi level of ~0.75 eV, which can be correlated to the dynamics of the 3d// orbitals, the electron–electron correlation, and the stability of the metallic state.

  3. Towards a comprehensive X-ray approach for studying the photosynthetic manganese complex-XANES, K{alpha}/K{beta}/K{beta}-satellite emission lines, RIXS, and comparative computational approaches for selected model complexes

    Energy Technology Data Exchange (ETDEWEB)

    Zaharieva, I; Chernev, P; Risch, M; Gerencser, L; Haumann, M; Dau, H [Free University Berlin, FB Physik, Arnimallee 14, D-14195 Berlin (Germany); Berggren, G; Shevchenko, D; Anderlund, M [Dept. of Photochemistry and Molecular Science, Uppsala University, Box 523, S-751 20 Uppsala (Sweden); Weng, T C, E-mail: holger.dau@fu-berlin.d, E-mail: michael.haumann@fu-berlin.d [European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex (France)

    2009-11-15

    Advanced X-ray spectroscopy experiments can contribute to elucidation of the mechanism of water oxidation in biological (tetra-manganese complex of Photosystem II) and artificial systems. Although the electronic structure of the catalytic metal site is of high interest, it is experimentally not easily accessible. Therefore, we and other researchers are working towards a comprehensive approach involving a combination of methods, namely (1) quantitative analysis of X-ray absorption near-edge structure (XANES) spectra collected at the K-edge and, in the long run, at the L-edge of manganese; (2) high-resolution X-ray emission spectroscopy (XES) of K{alpha} and K{beta} lines, (3) two-dimensional resonant inelastic X-ray scattering (RIXS) spectra. Collection of these spectroscopic data sets requires state-of-the-art synchrotron radiation facilities as well as experimental strategies to minimize the radiation-induced modifications of the samples. Data analysis requires the use and development of appropriate theoretical tools. Here, we present exemplary data collected for three multi-nuclear synthetic Mn complexes with the Mn ions in the oxidation states II, III, and IV, and for Mn{sup VII} of the permanganate ion. Emission spectra are calculated for the Mn{sup VII} ion using both multiple-scattering (MS) approach and time-dependent density functional theory (TDDFT).

  4. Atomic structure of glassy Mg60Cu30Y10 investigated with EXAFS, x-ray and neutron diffraction, and reverse Monte Carlo simulations

    DEFF Research Database (Denmark)

    Jovari, P.; Saksl, K.; Pryds, Nini

    2007-01-01

    Short range order of amorphous Mg60Cu30Y10 was investigated by x-ray and neutron diffraction, Cu and Y K-edge x-ray absorption fine structure measurements, and the reverse Monte Carlo simulation technique. We found that Mg-Mg and Mg-Cu nearest neighbor distances are very similar to values found...... in crystalline Mg2Cu. The Cu-Y coordination number is 1.1 +/- 0.2, and the Cu-Y distance is similar to 4% shorter than the sum of atomic radii, suggesting that attraction between Cu and Y plays an important role in stabilizing the glassy state. Thermal stability and structure evolution upon annealing were also...

  5. Crystal and electronic structure study of AgAu and AgCu bimetallic alloy thin films by X-ray techniques

    Energy Technology Data Exchange (ETDEWEB)

    Ozkendir, O. Murat, E-mail: ozkendir@gmail.com [Mersin University, Faculty of Technology, Energy Systems Engineering, Tarsus (Turkey); Mersin University, Institute of Natural Science, Department of Nanotechnology and Advanced Materials, Mersin (Turkey); Cengiz, E. [Karadeniz Technical University, Faculty of Science, Department of Physics, Trabzon (Turkey); Yalaz, E. [Mersin University, Institute of Natural Science, Department of Nanotechnology and Advanced Materials, Mersin (Turkey); Söğüt, Ö.; Ayas, D.H. [Kahramanmaraş Sütçü İmam Üniversitesi, Faculty of Science and Letters, Department of Physics, Kahramanmaraş (Turkey); Thammajak, B. Nirawat [Synchrotron Light Research Institute (Public Organisation), 111 University Avenue, T. Suranaree, A. Muang, Nakhon Ratchasima 30000 (Thailand)

    2016-05-15

    Highlights: • Crystal and electronic properties of bimetallic AgCu and AgAu alloy thin films were studied. • Both AgCu and AgAu bimetallic samples were determined to have cubic crystal geometry. • Strong influence of Cu and Au atoms on the electronic structure of the Ag atoms were determined. - Abstract: Crystal and electronic structure properties of bimetallic AgAu and AgCu alloy thin films were investigated by X-ray spectroscopic techniques. The aim of this study is to probe the influence of Au or Cu atoms on the electronic behaviors of Ag ions in bimetallic alloy materials that yields different crystal properties. To identify the mechanisms causing crystal phase transitions, study were supported by the collected EXAFS (Extended X-ray Absorption Fine Structure) data. Crystal structures of both Cu and Au doped bimetallic Ag samples were determined mainly in cubic geometry with “Fm3m” space group. Through the Ag–Au and Ag–Cu molecular interactions during bimetallic alloy formations, highly overlapped electronic levels that supports large molecular band formations were observed with different ionization states. Besides, traces of the d–d interactions in Au rich samples were determined as the main interplay in the broad molecular bond formations. The exact atomic locations and types in the samples were determined by EXAFS studies and supported by the performed calculations with FEFF scientific code.

  6. Neutron techniques

    International Nuclear Information System (INIS)

    Charlton, J.S.

    1986-01-01

    The way in which neutrons interact with matter such as slowing-down, diffusion, neutron absorption and moderation are described. The use of neutron techniques in industry, in moisture gages, level and interface measurements, the detection of blockages, boron analysis in ore feedstock and industrial radiography are discussed. (author)

  7. Astrophysical techniques

    CERN Document Server

    Kitchin, CR

    2013-01-01

    DetectorsOptical DetectionRadio and Microwave DetectionX-Ray and Gamma-Ray DetectionCosmic Ray DetectorsNeutrino DetectorsGravitational Radiation Dark Matter and Dark Energy Detection ImagingThe Inverse ProblemPhotographyElectronic ImagingScanningInterferometrySpeckle InterferometryOccultationsRadarElectronic ImagesPhotometryPhotometryPhotometersSpectroscopySpectroscopy SpectroscopesOther TechniquesAstrometryPolarimetrySolar StudiesMagnetometryComputers and The Internet.

  8. Presentation Technique

    International Nuclear Information System (INIS)

    Froejmark, M.

    1992-10-01

    The report presents a wide, easily understandable description of presentation technique and man-machine communication. General fundamentals for the man-machine interface are illustrated, and the factors that affect the interface are described. A model is presented for describing the operators work situation, based on three different levels in the operators behaviour. The operator reacts routinely in the face of simple, known problems, and reacts in accordance with predetermined plans in the face of more complex, recognizable problems. Deep fundamental knowledge is necessary for truly complex questions. Today's technical status and future development have been studied. In the future, the operator interface will be based on standard software. Functions such as zooming, integration of video pictures, and sound reproduction will become common. Video walls may be expected to come into use in situations in which several persons simultaneously need access to the same information. A summary of the fundamental rules for the design of good picture ergonomics and design requirements for control rooms are included in the report. In conclusion, the report describes a presentation technique within the Distribution Automation and Demand Side Management area and analyses the know-how requirements within Vattenfall. If different systems are integrated, such as geographical information systems and operation monitoring systems, strict demands are made on the expertise of the users for achieving a user-friendly technique which is matched to the needs of the human being. (3 figs.)

  9. Synthesis and detection the oxidization of Co cores of Co@SiO2 core-shell nanoparticles by in situ XRD and EXAFS.

    Science.gov (United States)

    Zhang, Kunhao; Zhao, Ziyan; Wu, Zhonghua; Zhou, Ying

    2015-01-01

    In this paper, the Co@SiO2 core-shell nanoparticles were prepared by the sol-gel method. The oxidization of Co core nanoparticles was studied by the synchrotron radiation-based techniques including in situ X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS) up to 800°C in air and N2 protection conditions, respectively. It was found that the oxidization of Co cores is undergoing three steps regardless of being in air or in N2 protection condition. In the first step ranging from room temperature to 200°C, the Co cores were dominated by Co(0) state as well as small amount of Co(2+) ions. When temperature was above 300°C, the interface between Co cores and SiO2 shells was gradually oxidized into Co(2+), and the CoO layer was observed. As the temperature increasing to 800°C, the Co cores were oxidized to Co3O4 or Co3O4/CoO. Nevertheless, the oxidization kinetics of Co cores is different for the Co@SiO2 in air and N2 gas conditions. Generally, the O2 in the air could get through the SiO2 shells easily onto the Co core surface and induce the oxidization of the Co cores due to the mesoporous nature of the SiO2 shells. However, in N2 gas condition, the O atoms can only be from the SiO2 shells, so the diffusion effect of O atoms in the interface between Co core and SiO2 shell plays a key role.

  10. Astrophysical techniques

    Energy Technology Data Exchange (ETDEWEB)

    Kitchin, C R

    1984-01-01

    The subject is covered in chapters, entitled: detectors (optical and infrared detection; radio and microwave detection; X-ray and gamma-ray detection; cosmic ray detectors; neutrino detectors; gravitational radiation); imaging (photography; electronic imaging; scanning; interferometry; speckle interferometry; occultations; radar); photometry and photometers; spectroscopy and spectroscopes; other techniques (astrometry; polarimetry; solar studies; magnetometry). Appendices: magnitudes and spectral types of bright stars; north polar sequence; standard stars for the UBV photometric system; standard stars for the UVBY photometric system; standard stars for MK spectral types; standard stars for polarimetry; Julian date; catalogues; answers to the exercises.

  11. Llizarov technique

    International Nuclear Information System (INIS)

    Shankman, S.; Rosenberg, Z.S.; Frankel, V.; Golyakhovsky, V.

    1990-01-01

    This paper illustrates the radiographic manifestations of the Ilizarov distraction technique for the correction of short and deformed limbs. The radiographs of 130 patients who underwent Ilizarov distraction at 160 sites since December 1986 were reviewed retrospectively. Reasons for correction included fracture nonunion and malunion idiopathic leg length discrepancy, achondroplasia, and neurofibromatosis with tibial pseudarthrosis. Ninety patients were adults, and 40 were children. In order to assess cortical bone development during the fixation phase, CT of the regenerate bone was performed in 17 patients. Conventional tomograms were obtained in 20 patients for the evaluation of delayed or hypoplastic union at the distraction site

  12. Experimental Techniques

    International Nuclear Information System (INIS)

    Fournier, D.; Serin, L.

    1995-01-01

    Experimental techniques to be used in the new generation of high energy physics are presented. The emphasis is put on the new ATLAS and CMS detectors for the CERN LHC. For the most important elements of these detectors, a description of the underlying physics processes is given, sometimes with reference to comparable detectors used in the past. Some comparative global performances of the two detectors are also given, with reference to benchmark physics processes (detection of the Higgs boson in various mass regions, etc). (author)

  13. In situ characterization of uranium and americium oxide solid solution formation for CRMP process: first combination of in situ XRD and XANES measurements.

    Science.gov (United States)

    Caisso, Marie; Picart, Sébastien; Belin, Renaud C; Lebreton, Florent; Martin, Philippe M; Dardenne, Kathy; Rothe, Jörg; Neuville, Daniel R; Delahaye, Thibaud; Ayral, André

    2015-04-14

    Transmutation of americium in heterogeneous mode through the use of U1-xAmxO2±δ ceramic pellets, also known as Americium Bearing Blankets (AmBB), has become a major research axis. Nevertheless, in order to consider future large-scale deployment, the processes involved in AmBB fabrication have to minimize fine particle dissemination, due to the presence of americium, which considerably increases the risk of contamination. New synthesis routes avoiding the use of pulverulent precursors are thus currently under development, such as the Calcined Resin Microsphere Pelletization (CRMP) process. It is based on the use of weak-acid resin (WAR) microspheres as precursors, loaded with actinide cations. After two specific calcinations under controlled atmospheres, resin microspheres are converted into oxide microspheres composed of a monophasic U1-xAmxO2±δ phase. Understanding the different mechanisms during thermal conversion, that lead to the release of organic matter and the formation of a solid solution, appear essential. By combining in situ techniques such as XRD and XAS, it has become possible to identify the key temperatures for oxide formation, and the corresponding oxidation states taken by uranium and americium during mineralization. This paper thus presents the first results on the mineralization of (U,Am) loaded resin microspheres into a solid solution, through in situ XAS analysis correlated with HT-XRD.

  14. Synchrotron light techniques for the investigation of advanced nuclear reactor structural materials

    International Nuclear Information System (INIS)

    Pouchon, M.A.; Froideval, A.; Degueldre, C.; Gavillet, D.; Hoffelner, W.

    2008-01-01

    In the frame of the Generation IV initiative, different structural material candidates are investigated at the Paul Scherrer Institute. These are oxide dispersion strengthened (ODS) steels, intermetallic materials and ceramic composite materials. The response of the material to different potential loads (irradiation, temperature...) is addressed in a multi-scale approach, both, modelling wise and also experimentally. The investigation of each scale delivers at least a qualitative understanding of possibly evolving damage in the material and also delivers a validation of the corresponding scale on the modelling side. From the experimental side, the lower end of the scale, the atomistic and structural level, can be investigated by conventional techniques, as for example transmission electron microscopy (TEM) and X-ray diffraction (XRD). However, the use of synchrotron radiation techniques offers an ideal, complementary way to investigate the material structure and other properties. This paper presents applications in the field of the ODS research, where the structural behaviour of the nano-scopic dispersoids can selectively be investigated, although only being present with roughly 5 wt % in the matrix. A study showing the structural behaviour of these oxide particles as a function of irradiation illustrates the potential of the extended X-ray absorption fine structure (EXAFS) technique. Using X-ray magnetic circular dichroism (XMCD), which is a difference-signal of two X-ray absorption spectra recorded for positive and negative helicities of the beam, the magnetic structure and some magnetic parameters, can be resolved. An example shows, how this can be applied to understand (Fe,Cr) systems, which is the base alloy of the investigated ODS steel. The results deliver an important cross-check for modelling. Beside the presentation of these techniques, this paper shows how beamline techniques can serve nuclear research, with possibly activated materials. At the Paul

  15. Industrial technique

    International Nuclear Information System (INIS)

    Robertson, D.H.

    1975-01-01

    Techniques for selectively extracting and storing only krypton and xenon in the waste gases that are released from a pressurized water nuclear power reactor are described. The illustrative fluorocarbon absorption system has three separation stages: an initial gas-fluorocarbon absorber, a flash chamber and fractionator for segregating all of the absorbed gases from the loaded absorber stage fluorocarbon (save for the krypton and xenon), and a stripper that receives the partially loaded fluorocarbon liquid directly from the fractionator in order to separate only the krypton and xenon. A molecular sieve filter dries the input process gas, a cartridge type solvent filter is used to remove radiation degradation products from the loaded liquid that flows from the absorber, a cold trap gas drier is provided to remove residual solvent vapor from the separated krypton and xenon, and radiation detectors automatically activate valves to establish safe conditions in the event of an accident or plant failure. (U.S.)

  16. Experimental techniques

    International Nuclear Information System (INIS)

    Roussel-Chomaz, P.

    2007-01-01

    This lecture presents the experimental techniques, developed in the last 10 or 15 years, in order to perform a new class of experiments with exotic nuclei, where the reactions induced by these nuclei allow to get information on their structure. A brief review of the secondary beams production methods will be given, with some examples of facilities in operation or under project. The important developments performed recently on cryogenic targets will be presented. The different detection systems will be reviewed, both the beam detectors before the targets, and the many kind of detectors necessary to detect all outgoing particles after the reaction: magnetic spectrometer for the heavy fragment, detection systems for the target recoil nucleus, γ detectors. Finally, several typical examples of experiments will be detailed, in order to illustrate the use of each detector either alone, or in coincidence with others. (author)

  17. Combinatorial techniques

    CERN Document Server

    Sane, Sharad S

    2013-01-01

    This is a basic text on combinatorics that deals with all the three aspects of the discipline: tricks, techniques and theory, and attempts to blend them. The book has several distinctive features. Probability and random variables with their interconnections to permutations are discussed. The theme of parity has been specially included and it covers applications ranging from solving the Nim game to the quadratic reciprocity law. Chapters related to geometry include triangulations and Sperner's theorem, classification of regular polytopes, tilings and an introduction to the Eulcidean Ramsey theory. Material on group actions covers Sylow theory, automorphism groups and a classification of finite subgroups of orthogonal groups. All chapters have a large number of exercises with varying degrees of difficulty, ranging from material suitable for Mathematical Olympiads to research.

  18. Industrial technique

    International Nuclear Information System (INIS)

    Jabsen, F.S.

    1975-01-01

    An illustrative embodiment of the invention discloses a technique for disassembling a nuclear reactor fuel element without destroying the individual fuel pins and other structural components from which the element is assembled. A traveling bridge and trolley that span a water-filled spent fuel storage pool support a strongback. The strongback is under water and provides a working surface on which the spent fuel element is placed for inspection and for the manipulation that is associated with disassembly and assembly. To remove, in a non-destructive manner, the grids that hold the fuel pins in the proper relative positions within the element, bars are inserted through apertures in the grids with the aid of special tools. These bars are rotated to flex the adjacent grid walls and, in this way relax the physical engagement between protruding portions of the grid walls and the associated fuel pins. With the grid structure so flexed to relax the physical grip on the individual fuel pins, these pins can be withdrawn for inspection or replacement as necessary without imposing a need to destroy fuel element components. (U.S.)

  19. X-ray spectroscopy of solids under pressure. Annual progress report, August 1983-July 1984

    International Nuclear Information System (INIS)

    Ingalls, R.L.

    1984-01-01

    X-ray absorption studies of several materials as a function of pressure have been performed. Of particular interest has been the EXAFS (extended x-ray absorption fine structure) and XANES (x-ray absorption near edge structure). Materials studied include the alkali halides, NaBr and RbCl, zinc blend semiconductors ZnSe and CuBr and mixed-valence materials SmS and SmSe. In the former, the volume dependence of bond lengths and their mean square fluctuations were determined from the EXAFS. In the latter materials the XANES exhibited the pressure induced change from the Sm 2+ configuration to Sm 3+

  20. Molecular characterization of copper in soils using X-ray absorption spectroscopy

    International Nuclear Information System (INIS)

    Strawn, Daniel G.; Baker, Leslie L.

    2009-01-01

    Bioavailability of Cu in the soil is a function of its speciation. In this paper we investigated Cu speciation in six soils using X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS), and synchrotron-based micro X-ray fluorescence (μ-XRF). The XANES and EXAFS spectra in all of the soils were the same. μ-XRF results indicated that the majority of the Cu particles in the soils were not associated with calcium carbonates, Fe oxides, or Cu sulfates. Principal component analysis and target transform of the XANES and EXAFS spectra suggested that Cu adsorbed on humic acid (HA) was an acceptable match. Thus it appears that Cu in all of the soils is primarily associated with soil organic matter (SOM). Theoretical fitting of the molecular structure in the soil EXAFS spectra revealed that the Cu in the soils existed as Cu atoms bound in a bidentate complex to O or N functional groups. - Copper speciation in six soils was investigated using XANES, EXAFS, and μ-XRF.

  1. Techniques de combustion Combustin Techniques

    Directory of Open Access Journals (Sweden)

    Perthuis E.

    2006-11-01

    Full Text Available L'efficacité d'un processus de chauffage par flamme est étroitement liée à la maîtrise des techniques de combustion. Le brûleur, organe essentiel de l'équipement de chauffe, doit d'une part assurer une combustion complète pour utiliser au mieux l'énergie potentielle du combustible et, d'autre part, provoquer dans le foyer les conditions aérodynamiques les plus propices oux transferts de chaleur. En s'appuyant sur les études expérimentales effectuées à la Fondation de Recherches Internationales sur les Flammes (FRIF, au Groupe d'Étude des Flammes de Gaz Naturel (GEFGN et à l'Institut Français du Pétrole (IFP et sur des réalisations industrielles, on présente les propriétés essentielles des flammes de diffusion aux combustibles liquides et gazeux obtenues avec ou sans mise en rotation des fluides, et leurs répercussions sur les transferts thermiques. La recherche des températures de combustion élevées conduit à envisager la marche à excès d'air réduit, le réchauffage de l'air ou son enrichissement à l'oxygène. Par quelques exemples, on évoque l'influence de ces paramètres d'exploitation sur l'économie possible en combustible. The efficiency of a flame heating process is closely linked ta the mastery of, combustion techniques. The burner, an essential element in any heating equipment, must provide complete combustion sa as to make optimum use of the potential energy in the fuel while, at the same time, creating the most suitable conditions for heat transfers in the combustion chamber. On the basis of experimental research performed by FRIF, GEFGN and IFP and of industrial achievements, this article describesthe essential properties of diffusion flames fed by liquid and gaseous fuels and produced with or without fluid swirling, and the effects of such flames on heat transfers. The search for high combustion temperatures means that consideration must be given to operating with reduced excess air, heating the air or

  2. Irregular distribution of metal ions in ferrites prepared by co-precipitation technique structure analysis of Mn-Zn ferrite using extended X-ray absorption fine structure

    International Nuclear Information System (INIS)

    Jeyadevan, B.; Tohji, K.; Nakatsuka, K.; Narayanasamy, A.

    2000-01-01

    The tetrahedral/octahedral site occupancy of non-magnetic zinc ion, added to maximize the net magnetic moment of mixed ferrites has been found to depend on the method of preparation. In this paper, we qualitatively analyze the metal ion distribution in Mn-Zn ferrite particles prepared by co-precipitation and ceramic methods using extended X-ray absorption fine structure (EXAFS) technique. The results suggest that the differences observed in the magnetic properties of the samples prepared by different methods are not only due to the difference in particle size but also due to the difference in cation distribution. The difference in cation distributions between ferrites of similar composition prepared differently has been found to depend on the crystal field stability energies of the metal ion of interest and associated cations

  3. Structural changes of noble metal catalysts during ignition and extinction of the partial oxidation of methane studied by advanced QEXAFS techniques

    DEFF Research Database (Denmark)

    Grunwaldt, Jan-Dierk; Beier, M.; Kimmerle, B.

    2009-01-01

    The dynamics of the ignition and extinction of the catalytic partial oxidation (CPO) of methane to hydrogen and carbon monoxide over Pt-Rh/Al2O3 and Pt/Al2O3 were studied in the subsecond timescale using quick-EXAFS with a novel cam-driven X-ray monochromator employing Si(111) and Si(311) crystals...... to discuss the potential and limitation of this technique in catalysis and related areas. With respect to the noble metal catalysed partial oxidation of methane, several interesting observations were made: structural changes during ignition were-independent of the chosen reaction conditions......-significantly faster than during the extinction of the reaction. The dynamic behavior of the catalysts was dependent on the flow conditions and the respective noble metal component(s). Higher reaction gas flow led to a faster ignition process. While the ignition over Pt-Rh/Al2O3 occurred at lower temperature than over...

  4. EXAFS analysis of cations distribution in structure of Co{sub 1−x}Ni{sub x}Fe{sub 2}O{sub 4} nanoparticles obtained by hydrothermal method in aloe vera extract solution

    Energy Technology Data Exchange (ETDEWEB)

    Wongpratat, Unchista [Materials Science and Nanotechnology Program, Faculty of Science, Khon Kaen University, Khon Kaen 40002 (Thailand); Maensiri, Santi [School of Physics, Institute of Science, Suranaree University, Nakhonratchasima 30000 (Thailand); Swatsitang, Ekaphan, E-mail: ekaphan@kku.ac.th [Materials Science and Nanotechnology Program, Faculty of Science, Khon Kaen University, Khon Kaen 40002 (Thailand); Integrated Nanotechnology Research Center, Department of Physics, Faculty of Science, Khon Kaen University, Khon Kaen 40002 Thailand (Thailand)

    2016-09-01

    Graphical abstract: It is obvious from the M–H curves at room temperature of Co{sub 1−x}Ni{sub x}Fe{sub 2}O{sub 4} (x = 0, 0.25, 0.50, 0.75 and 1.0) nanoparticles that partially substitution of the lower Bohr magneton (2 μ{sub B}) and smaller atomic radii (0.55 Å at A site, 0.69 Å at B site) of Ni{sup 2+} ions on the higher Bohr magneton (3 μ{sub B}) and larger atomic radii (0.58 Å at A site, 0.74 Å at B site) of Co{sup 2+} ions can increase the saturation magnetization (M{sub s}) of sample with x = 0.75 to approximately 1.4 times of sample with x = 0, due to the increase of the aspect ratio (surface to volume) of nanoparticles, as a result of particle size decreasing from 37.03 to 12.63 nm. In addition to this, the ferrimagnetic behavior of CoFe{sub 2}O{sub 4} has been changed to superparamagnetic behavior with the dramatic decrease of the coercivity from 1365.60 to 63.15 Oe. - Highlights: • Magnetic behavior of Co{sub 1−x}Ni{sub x}Fe{sub 2}O{sub 4} NPs depends on Ni content and size of NPs. • Distribution of Co{sup 2+} and Ni{sup 2+} ions in the structure results in the increase of M{sub s}. • Superparamagnetic behavior is observed with increasing of the aspect ratio. • M{sub s} is increased by a factor 1.4 to a value of 57.57 emu/g in Co{sub 0.25}Ni{sub 0.75}Fe{sub 2}O{sub 4}. • H{sub c} is decreased by a factor 20 to a value of 63.15 Oe in Co{sub 0.25}Ni{sub 0.75}Fe{sub 2}O{sub 4}. - Abstract: Effect of cations distribution upon EXAFS analysis on magnetic properties of Co{sub 1−x}Ni{sub x}Fe{sub 2}O{sub 4} (x = 0, 0.25, 0.50, 0.75 and 1.0) nanoparticles prepared by the hydrothermal method in aloe vera extract solution were studied. XRD analysis confirmed a pure phase of cubic spinel ferrite of all samples. Changes in lattice parameter and particle size depended on the Ni content with partial substitution and site distributions of Co{sup 2+}, Ni{sup 2+} ions of different ionic radii at both tetrahedral and octahedral sites in the

  5. EXAFS analysis of cations distribution in structure of Co_1_−_xNi_xFe_2O_4 nanoparticles obtained by hydrothermal method in aloe vera extract solution

    International Nuclear Information System (INIS)

    Wongpratat, Unchista; Maensiri, Santi; Swatsitang, Ekaphan

    2016-01-01

    Graphical abstract: It is obvious from the M–H curves at room temperature of Co_1_−_xNi_xFe_2O_4 (x = 0, 0.25, 0.50, 0.75 and 1.0) nanoparticles that partially substitution of the lower Bohr magneton (2 μ_B) and smaller atomic radii (0.55 Å at A site, 0.69 Å at B site) of Ni"2"+ ions on the higher Bohr magneton (3 μ_B) and larger atomic radii (0.58 Å at A site, 0.74 Å at B site) of Co"2"+ ions can increase the saturation magnetization (M_s) of sample with x = 0.75 to approximately 1.4 times of sample with x = 0, due to the increase of the aspect ratio (surface to volume) of nanoparticles, as a result of particle size decreasing from 37.03 to 12.63 nm. In addition to this, the ferrimagnetic behavior of CoFe_2O_4 has been changed to superparamagnetic behavior with the dramatic decrease of the coercivity from 1365.60 to 63.15 Oe. - Highlights: • Magnetic behavior of Co_1_−_xNi_xFe_2O_4 NPs depends on Ni content and size of NPs. • Distribution of Co"2"+ and Ni"2"+ ions in the structure results in the increase of M_s. • Superparamagnetic behavior is observed with increasing of the aspect ratio. • M_s is increased by a factor 1.4 to a value of 57.57 emu/g in Co_0_._2_5Ni_0_._7_5Fe_2O_4. • H_c is decreased by a factor 20 to a value of 63.15 Oe in Co_0_._2_5Ni_0_._7_5Fe_2O_4. - Abstract: Effect of cations distribution upon EXAFS analysis on magnetic properties of Co_1_−_xNi_xFe_2O_4 (x = 0, 0.25, 0.50, 0.75 and 1.0) nanoparticles prepared by the hydrothermal method in aloe vera extract solution were studied. XRD analysis confirmed a pure phase of cubic spinel ferrite of all samples. Changes in lattice parameter and particle size depended on the Ni content with partial substitution and site distributions of Co"2"+, Ni"2"+ ions of different ionic radii at both tetrahedral and octahedral sites in the crystal structure. Particle sizes of samples estimated by TEM images were found to be in the range of 10.87–62.50 nm. The VSM results at room

  6. Crystal structure and properties of tetragonal EuAg4In8 grown by metal flux technique

    International Nuclear Information System (INIS)

    Subbarao, Udumula; Sarkar, Sumanta; Peter, Sebastian C.

    2015-01-01

    The compound EuAg 4 In 8 has been obtained as single crystals in high yield from reactions run in liquid indium. X-ray diffraction on single crystals suggests that EuAg 4 In 8 crystallizes in the CeMn 4 Al 8 structure type, tetragonal space group I4/mmm with lattice constants a=b=9.7937(2) Å and c=5.7492(2) Å. Crystal structure of EuAg 4 In 8 is composed of pseudo Frank–Kasper cages occupied by one europium atom in each ring, which are shared through the corner along the ab plane resulting in a three dimensional network. The magnetic susceptibility of EuAg 4 In 8 was measured in the temperature range 2–300 K, which obeyed Curie–Weiss law above 50 K. Magnetic moment value calculated from the fitting indicates the presence of divalent europium, which was confirmed by X-ray absorption near edge spectroscopy. Electrical resistivity measurements suggest that EuAg 4 In 8 is metallic in nature with a probable Fermi liquid behavior at low temperature. - Graphical abstract: The tetragonal EuAg 4 In 8 has been grown as single crystals from reactions run in liquid indium. Magnetic and XANES measurements suggest divalent nature of Eu and resistivity measurements suggest metallic nature. - Highlights: • EuAg 4 In 8 phase having tetragonal phase is grown by metal flux technique. • Magnetic and XANES measurements exhibit divalent nature of Eu in EuAg 4 In 8 . • Resistivity measurement suggests metallic nature and probable Fermi liquid behavior

  7. New Technique for Speciation of Uranium in Sediments Following Acetate-Stimulated Bioremediation

    Energy Technology Data Exchange (ETDEWEB)

    2011-06-22

    Acetate-stimulated bioremediation is a promising new technique for sequestering toxic uranium contamination from groundwater. The speciation of uranium in sediments after such bioremediation attempts remains unknown as a result of low uranium concentration, and is important to analyzing the stability of sequestered uranium. A new technique was developed for investigating the oxidation state and local molecular structure of uranium from field site sediments using X-Ray Absorption Spectroscopy (XAS), and was implemented at the site of a former uranium mill in Rifle, CO. Glass columns filled with bioactive Rifle sediments were deployed in wells in the contaminated Rifle aquifer and amended with a hexavalent uranium (U(VI)) stock solution to increase uranium concentration while maintaining field conditions. This sediment was harvested and XAS was utilized to analyze the oxidation state and local molecular structure of the uranium in sediment samples. Extended X-Ray Absorption Fine Structure (EXAFS) data was collected and compared to known uranium spectra to determine the local molecular structure of the uranium in the sediment. Fitting was used to determine that the field site sediments did not contain uraninite (UO{sub 2}), indicating that models based on bioreduction using pure bacterial cultures are not accurate for bioremediation in the field. Stability tests on the monomeric tetravalent uranium (U(IV)) produced by bioremediation are needed in order to assess the efficacy of acetate-stimulation bioremediation.

  8. Solving mercury (Hg) speciation in soil samples by synchrotron X-ray microspectroscopic techniques.

    Science.gov (United States)

    Terzano, Roberto; Santoro, Anna; Spagnuolo, Matteo; Vekemans, Bart; Medici, Luca; Janssens, Koen; Göttlicher, Jörg; Denecke, Melissa A; Mangold, Stefan; Ruggiero, Pacifico

    2010-08-01

    Direct mercury (Hg) speciation was assessed for soil samples with a Hg concentration ranging from 7 up to 240 mg kg(-1). Hg chemical forms were identified and quantified by sequential extractions and bulk- and micro-analytical techniques exploiting synchrotron generated X-rays. In particular, microspectroscopic techniques such as mu-XRF, mu-XRD and mu-XANES were necessary to solve bulk Hg speciation, in both soil fractions soil samples were metacinnabar (beta-HgS), cinnabar (alpha-HgS), corderoite (Hg(3)S(2)Cl(2)), and an amorphous phase containing Hg bound to chlorine and sulfur. The amount of metacinnabar and amorphous phases increased in the fraction soil components was observed. All the observed Hg-species originated from the slow weathering of an inert Hg-containing waste material (K106, U.S. EPA) dumped in the area several years ago, which is changing into a relatively more dangerous source of pollution. Copyright 2010 Elsevier Ltd. All rights reserved.

  9. Solving mercury (Hg) speciation in soil samples by synchrotron X-ray microspectroscopic techniques

    International Nuclear Information System (INIS)

    Terzano, Roberto; Santoro, Anna; Spagnuolo, Matteo; Vekemans, Bart; Medici, Luca; Janssens, Koen; Goettlicher, Joerg; Denecke, Melissa A.; Mangold, Stefan; Ruggiero, Pacifico

    2010-01-01

    Direct mercury (Hg) speciation was assessed for soil samples with a Hg concentration ranging from 7 up to 240 mg kg -1 . Hg chemical forms were identified and quantified by sequential extractions and bulk- and micro-analytical techniques exploiting synchrotron generated X-rays. In particular, microspectroscopic techniques such as μ-XRF, μ-XRD and μ-XANES were necessary to solve bulk Hg speciation, in both soil fractions 3 S 2 Cl 2 ), and an amorphous phase containing Hg bound to chlorine and sulfur. The amount of metacinnabar and amorphous phases increased in the fraction <2 μm. No interaction among Hg-species and soil components was observed. All the observed Hg-species originated from the slow weathering of an inert Hg-containing waste material (K106, U.S. EPA) dumped in the area several years ago, which is changing into a relatively more dangerous source of pollution. - Direct mercury (Hg) speciation in chlor-alkali plant contaminated soils enabled the identification of potentially dangerous Hg-S/Cl amorphous species.

  10. Crystal and electronic structure study of Mn doped wurtzite ZnO nanoparticles

    Directory of Open Access Journals (Sweden)

    O.M. Ozkendir

    2016-08-01

    Full Text Available The change in the crystal and electronic structure properties of wurtzite ZnO nanoparticles was studied according to Mn doping in the powder samples. The investigations were conducted by X-ray Absorption Fine Structure Spectroscopy (XAFS technique for the samples prepared with different heating and doping processes. Electronic analysis was carried out by the collected data from the X-ray Absorption Near-Edge Structure Spectroscopy (XANES measurements. Additional crystal structure properties were studied by Extended-XAFS (EXAFS analysis. Longer heating periods for the undoped wurtzite ZnO samples were determined to own stable crystal geometries. However, for some doped samples, the distortions in the crystal were observed as a result of the low doping amounts of Mn which was treated as an impurity. Besides, the changes in oxygen locations were determined to create defects and distortions in the samples.

  11. X-ray Absorption Spectroscopy Characterization of Electrochemical Processes in Renewable Energy Storage and Conversion Devices

    Energy Technology Data Exchange (ETDEWEB)

    Farmand, Maryam [George Washington Univ., Washington, DC (United States)

    2013-05-19

    The development of better energy conversion and storage devices, such as fuel cells and batteries, is crucial for reduction of our global carbon footprint and improving the quality of the air we breathe. However, both of these technologies face important challenges. The development of lower cost and better electrode materials, which are more durable and allow more control over the electrochemical reactions occurring at the electrode/electrolyte interface, is perhaps most important for meeting these challenges. Hence, full characterization of the electrochemical processes that occur at the electrodes is vital for intelligent design of more energy efficient electrodes. X-ray absorption spectroscopy (XAS) is a short-range order, element specific technique that can be utilized to probe the processes occurring at operating electrode surfaces, as well for studying the amorphous materials and nano-particles making up the electrodes. It has been increasingly used in recent years to study fuel cell catalysts through application of the and #916; and mgr; XANES technique, in combination with the more traditional X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) techniques. The and #916; and mgr; XANES data analysis technique, previously developed and applied to heterogeneous catalysts and fuel cell electrocatalysts by the GWU group, was extended in this work to provide for the first time space resolved adsorbate coverages on both electrodes of a direct methanol fuel cell. Even more importantly, the and #916; and mgr; technique was applied for the first time to battery relevant materials, where bulk properties such as the oxidation state and local geometry of a cathode are followed.

  12. Active Ti Species in TiCl3-Doped NaAlH4. Mechanism for Catalyst Deactivation

    NARCIS (Netherlands)

    Balde, C.P.; Stil, H.A.; van der Eerden, A.M.J.; de Jong, K.P.; Bitter, J.H.

    2007-01-01

    The nature of the active Ti species in TiCl3-doped NaAlH4, a promising hydrogen storage material, was studied as a function of the desorption temperature with Ti K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy, Ti K-edge X-ray absorption near-edge structure (XANES) spectroscopy,

  13. Synchrotron x-ray sources and new opportunities in the soil and environmental sciences

    International Nuclear Information System (INIS)

    Schulze, D.; Anderson, S.; Mattigod, S.

    1990-07-01

    This report contains the following papers: characteristics of the advanced photon source and comparison with existing synchrotron facilities; x-ray absorption spectroscopy: EXAFS and XANES -- A versatile tool to study the atomic and electronic structure of materials; applications of x-ray spectroscopy and anomalous scattering experiments in the soil and environmental sciences; X-ray fluorescence microprobe and microtomography

  14. Comparative study of the electronic structure of natural and synthetic ...

    Indian Academy of Sciences (India)

    Unknown

    We have studied the Cr–K-edge XANES and EXAFS in natural Indian rubies from two sources and a synthetic ... mineral in a wide variety of quality spread all over the world e.g. Burma ... using Si diode pairs oriented toward the sample. The.

  15. In situ, Cr K-edge XAS study on the Phillips catalyst : activation and ethylene polymerization

    NARCIS (Netherlands)

    Groppo, E.; Prestipino, C.; Cesano, F.; Bonino, F.; Bordiga, S.; Lamberti, C.; Thuene, P.C.; Niemantsverdriet, J.W.; Zecchina, A.

    2005-01-01

    In this in situ EXAFS and XANES study on the Phillips ethylene-polymerization Cr/SiO2 catalyst, two polymerization routes are investigated and compared. The first mimics that adopted in industrial plants, where ethylene is dosed directly on the oxidized catalyst, while in the second the oxidized

  16. Unusual Coordination Behavior of Cr3+ in Microporous Aluminophosphates

    NARCIS (Netherlands)

    Beale, AM; Grandjean, D; Kornatowski, J; Glatzel, P; de Groot, FMF; Weckhuysen, BM

    2006-01-01

    A CrAPO-5 molecular sieve has been investigated with X-ray absorption spectroscopy (EXAFS-XANES) as dehydrated material and after loading with water and ammonia to unravel the coordination geometries of Cr3+ in the framework of a microporous crystalline aluminophosphate, more particularly of the

  17. Cogeneration techniques; Les techniques de cogeneration

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-10-01

    This dossier about cogeneration techniques comprises 12 parts dealing successively with: the advantages of cogeneration (examples of installations, electrical and thermal efficiency); the combustion turbine (principle, performances, types); the alternative internal combustion engines (principle, types, rotation speed, comparative performances); the different configurations of cogeneration installations based on alternative engines and based on steam turbines (coal, heavy fuel and natural gas-fueled turbines); the environmental constraints of combustion turbines (pollutants, techniques of reduction of pollutant emissions); the environmental constraints of alternative internal combustion engines (gas and diesel engines); cogeneration and energy saving; the techniques of reduction of pollutant emissions (pollutants, unburnt hydrocarbons, primary and secondary (catalytic) techniques, post-combustion); the most-advanced configurations of cogeneration installations for enhanced performances (counter-pressure turbines, massive steam injection cycles, turbo-chargers); comparison between the performances of the different cogeneration techniques; the tri-generation technique (compression and absorption cycles). (J.S.)

  18. The Reduction of Cr(VI) to Cr(III) by Natural Fe-Bearing Minerals: A Synchrotron XAS Study

    Science.gov (United States)

    Xu, H.; Guo, X.; Ding, M.; Migdissov, A. A.; Boukhalfa, H.; Sun, C.; Roback, R. C.; Reimus, P. W.; Katzman, D.

    2017-12-01

    Cr(VI) in the form of CrO42- is a pollutant species in groundwater and soils that can pose health and environmental problems. Cr(VI) associated with use as a corrosion inhibitor at a power plant from 1956-1972 is present in a deep groundwater aquifer at Los Alamos National Laboratory. A potential remediation strategy for the Cr contamination is reduction of Cr(VI) to Cr(III) via the acceptance of electrons from naturally occurring or induced Fe(II) occurring in Fe-bearing minerals. In this work, using synchrotron-based X-ray techniques, we investigated the Cr reduction behavior by Fe-bearing minerals from outcrop and core samples representative of the contaminated portion of the aquifer. Samples were exposed to solutions with a range of known Cr (VI) concentrations. XANES and EXAFS spectra showed that all the Cr(VI) had been reduced to Cr(III), and micro XRF mapping revealed close correlation of Cr and Fe distribution, implying that Fe(II) in minerals reduced Cr(VI) in the solution. Similar behavior was observed from in-situ XANES measurements on Cr reduction and adsorption by mineral separates from the rock samples in Cr(VI)-bearing solutions. In addition, to obtain reference parameters for interpreting the data of natural samples, we collected Cr and Fe EXAFS spectra of Cr(III)-Fe(III) hydroxide solid solutions, which show progressive changes in the local structure around Cr and Fe over the whole series.

  19. Incorporation of Uranium into Hematite during Crystallization from Ferrihydrite

    Science.gov (United States)

    2014-01-01

    Ferrihydrite was exposed to U(VI)-containing cement leachate (pH 10.5) and aged to induce crystallization of hematite. A combination of chemical extractions, TEM, and XAS techniques provided the first evidence that adsorbed U(VI) (≈3000 ppm) was incorporated into hematite during ferrihydrite aggregation and the early stages of crystallization, with continued uptake occurring during hematite ripening. Analysis of EXAFS and XANES data indicated that the U(VI) was incorporated into a distorted, octahedrally coordinated site replacing Fe(III). Fitting of the EXAFS showed the uranyl bonds lengthened from 1.81 to 1.87 Å, in contrast to previous studies that have suggested that the uranyl bond is lost altogether upon incorporation into hematite. The results of this study both provide a new mechanistic understanding of uranium incorporation into hematite and define the nature of the bonding environment of uranium within the mineral structure. Immobilization of U(VI) by incorporation into hematite has clear and important implications for limiting uranium migration in natural and engineered environments. PMID:24580024

  20. Surface science techniques

    CERN Document Server

    Bracco, Gianangelo

    2013-01-01

    The book describes the experimental techniques employed to study surfaces and interfaces. The emphasis is on the experimental method. Therefore all chapters start with an introduction of the scientific problem, the theory necessary to understand how the technique works and how to understand the results. Descriptions of real experimental setups, experimental results at different systems are given to show both the strength and the limits of the technique. In a final part the new developments and possible extensions of the techniques are presented. The included techniques provide microscopic as well as macroscopic information. They cover most of the techniques used in surface science.

  1. Training techniques for industry

    International Nuclear Information System (INIS)

    Jones, D.W.

    1978-01-01

    The advantages and disadvantages of commonly used training techniques in relation to cost-effective, prevention-oriented Quality Assurance are examined. Important questions are whether training techniques teach cost effectiveness and whether the techniques are, themselves, cost effective. To answer these questions, criteria for evaluating teaching techniques for cost effectiveness were developd, and then commonly used techniques are evaluated in terms of specific training program objectives. Motivation of personnel is also considered important to the success of a training program, and methods are outlined by which recognition of the academic quality of industrial training can be used as a motivational technique

  2. Characterization of yellow and colorless decorative glasses from the Temple of the Emerald Buddha, Bangkok, Thailand

    Science.gov (United States)

    Klysubun, Wantana; Ravel, Bruce; Klysubun, Prapong; Sombunchoo, Panidtha; Deenan, Weeraya

    2013-06-01

    Yellow and colorless ancient glasses, which were once used to decorate the Temple of the Emerald Buddha, Bangkok, Thailand, around 150 years ago, are studied to unravel the long-lost glass-making recipes and manufacturing techniques. Analyses of chemical compositions, using synchrotron x-ray fluorescence (SRXRF), indicate that the Thai ancient glasses are soda lime silica glasses (60 % SiO2; 10 % Na2O; 10 % CaO) bearing lead oxide between 2-16 %. Iron (1.5-9.4 % Fe2O3) and manganese (1.7 % MnO) are present in larger abundance than the other 3 d transition metals detected (0.04-0.2 %). K-edge x-ray absorption near edge spectroscopy (XANES) and extended x-ray absorption fine structure spectroscopy (EXAFS) provide conclusive evidence on the oxidation states of Fe being 3+ and Mn being 2+ and on short-length tetrahedral structures around the cations. This suggests that iron is used as a yellow colorant with manganese as a decolorant. L 3-edge XANES results reveal the oxidation states of lead as 2+. The results from this work provide information crucial for replicating these decorative glasses for the future restoration of the Temple of the Emerald Buddha.

  3. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... to loosen mucus from airway walls. See how different airway clearance techniques work to help you clear the thick, sticky mucus ... Offer their tips for fitting ACTs into daily life Airway Clearance Techniques | Webcast ... Facebook Twitter ...

  4. Nuclear techniques in industry

    International Nuclear Information System (INIS)

    Hammad, F.H.

    1994-01-01

    Nuclear techniques are utilized in almost every industry. The discussion in this paper includes discussions on tracer methods and uses nucleonic control systems technology; non-destructive testing techniques and radiation technology. 1 fig., 2 tabs

  5. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... decisions about your health care. CF Genetics: The Basics CF Mutations Video Series Find Out More About ... of Breathing Technique Airway Clearance Techniques Autogenic Drainage Basics of Lung Care Chest Physical Therapy Coughing and ...

  6. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... Active Cycle of Breathing Technique Airway Clearance Techniques Autogenic Drainage Basics of Lung Care Chest Physical Therapy ... clearance. Facebook Twitter Email More Related Content Medications Autogenic Drainage Positive Expiratory Pressure High-Frequency Chest Wall ...

  7. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... a range of treatment options. Airway Clearance Active Cycle of Breathing Technique Airway Clearance Techniques Autogenic Drainage ... LEGACY GIFT Sponsor a Participant CF Climb CF Cycle for Life Great Strides Xtreme Hike Participate In ...

  8. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... many challenges, including medical, social, and financial. By learning more about how you can manage your disease every day, you can ultimately help find a ... Cycle of Breathing Technique Airway Clearance Techniques Autogenic ...

  9. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... Cycle of Breathing Technique Airway Clearance Techniques Autogenic Drainage Basics of Lung Care Chest Physical Therapy Coughing ... Facebook Twitter Email More Related Content Medications Autogenic Drainage Positive Expiratory Pressure High-Frequency Chest Wall Oscillation ( ...

  10. Radiation scattering techniques

    International Nuclear Information System (INIS)

    Edmonds, E.A.

    1986-01-01

    Radiation backscattering techniques are useful when access to an item to be inspected is restricted to one side. These techniques are very sensitive to geometrical effects. Scattering processes and their application to the determination of voids, thickness measuring, well-logging and the use of x-ray fluorescence techniques are discussed. (U.K.)

  11. Point of Technique

    African Journals Online (AJOL)

    .

    Minimally invasive techniques are becoming popular choice for the recent times. These techniques are lowering the cost and giving the best cosmetic results. For cardiovascular surgery these techniques are much more newer and much more unknown. Open lumbar sympathectomy for certain indications is a very well ...

  12. Nuclear techniques in hydrology

    International Nuclear Information System (INIS)

    Moser, H.

    1976-01-01

    The nuclear techniques used in hydrology are usually tracer techniques based on the use of nuclides either intentionally introduced into, or naturally present in the water. The low concentrations of these nuclides, which must be detected in groundwater and surface water, require special measurement techniques for the concentrations of radioactive or of stable nuclides. The nuclear techniques can be used most fruitfully in conjunction with conventional methods for the solution of problems in the areas of hydrology, hydrogeology and glacier hydrology. Nuclear techniques are used in practice in the areas of prospecting for water, environment protection and engineering hydrogeology. (orig.) [de

  13. Specific radiography technique

    International Nuclear Information System (INIS)

    Abdul Nassir Ibrahim; Azali Muhammad; Ab. Razak Hamzah; Abd. Aziz Mohamed; Mohamad Pauzi Ismail

    2008-01-01

    Beside radiography testing using x-ray machine and gamma source, there are several technique that developed specifically to complete the testing that cannot be done with the two earlier. This technique was specific based on several factor, for the example, the advantages of neutron and electron using to show the image was unique compare to x-ray and gamma. Besides that, these special radiography techniques maybe differ in how to detect the radiation get through the object. These technique can used to inspect thin or specimen that contained radioactive material. There are several technique will discussed in this chapter such as neutron radiography, electron radiography, fluoroscopy and also autoradiography.

  14. Low current beam techniques

    Energy Technology Data Exchange (ETDEWEB)

    Saint, A; Laird, J S; Bardos, R A; Legge, G J.F. [Melbourne Univ., Parkville, VIC (Australia). School of Physics; Nishijima, T; Sekiguchi, H [Electrotechnical Laboratory, Tsukuba (Japan).

    1994-12-31

    Since the development of Scanning Transmission Microscopy (STIM) imaging in 1983 many low current beam techniques have been developed for the scanning (ion) microprobe. These include STIM tomography, Ion Beam Induced Current, Ion Beam Micromachining and Microlithography and Ionoluminense. Most of these techniques utilise beam currents of 10{sup -15} A down to single ions controlled by beam switching techniques This paper will discuss some of the low beam current techniques mentioned above, and indicate, some of their recent applications at MARC. A new STIM technique will be introduced that can be used to obtain Z-contrast with STIM resolution. 4 refs., 3 figs.

  15. Low current beam techniques

    Energy Technology Data Exchange (ETDEWEB)

    Saint, A.; Laird, J.S.; Bardos, R.A.; Legge, G.J.F. [Melbourne Univ., Parkville, VIC (Australia). School of Physics; Nishijima, T.; Sekiguchi, H. [Electrotechnical Laboratory, Tsukuba (Japan).

    1993-12-31

    Since the development of Scanning Transmission Microscopy (STIM) imaging in 1983 many low current beam techniques have been developed for the scanning (ion) microprobe. These include STIM tomography, Ion Beam Induced Current, Ion Beam Micromachining and Microlithography and Ionoluminense. Most of these techniques utilise beam currents of 10{sup -15} A down to single ions controlled by beam switching techniques This paper will discuss some of the low beam current techniques mentioned above, and indicate, some of their recent applications at MARC. A new STIM technique will be introduced that can be used to obtain Z-contrast with STIM resolution. 4 refs., 3 figs.

  16. Nickel speciation in several serpentine (ultramafic) topsoils via bulk synchrotron-based techniques

    Energy Technology Data Exchange (ETDEWEB)

    Siebecker, Matthew G.; Chaney, Rufus L.; Sparks, Donald L.

    2017-07-01

    Serpentine soils have elevated concentrations of trace metals including nickel, cobalt, and chromium compared to non-serpentine soils. Identifying the nickel bearing minerals allows for prediction of potential mobility of nickel. Synchrotron-based techniques can identify the solid-phase chemical forms of nickel with minimal sample treatment. Element concentrations are known to vary among soil particle sizes in serpentine soils. Sonication is a useful method to physically disperse sand, silt and clay particles in soils. Synchrotron-based techniques and sonication were employed to identify nickel species in discrete particle size fractions in several serpentine (ultramafic) topsoils to better understand solid-phase nickel geochemistry. Nickel commonly resided in primary serpentine parent material such as layered-phyllosilicate and chain-inosilicate minerals and was associated with iron oxides. In the clay fractions, nickel was associated with iron oxides and primary serpentine minerals, such as lizardite. Linear combination fitting (LCF) was used to characterize nickel species. Total metal concentration did not correlate with nickel speciation and is not an indicator of the major nickel species in the soil. Differences in soil texture were related to different nickel speciation for several particle size fractionated samples. A discussion on LCF illustrates the importance of choosing standards based not only on statistical methods such as Target Transformation but also on sample mineralogy and particle size. Results from the F-test (Hamilton test), which is an underutilized tool in the literature for LCF in soils, highlight its usefulness to determine the appropriate number of standards to for LCF. EXAFS shell fitting illustrates that destructive interference commonly found for light and heavy elements in layered double hydroxides and in phyllosilicates also can occur in inosilicate minerals, causing similar structural features and leading to false positive results in

  17. Pulse holographic measurement techniques

    International Nuclear Information System (INIS)

    Kim, Cheol Jung; Baik, Seong Hoon; Hong, Seok Kyung; Kim, Jeong Moog; Kim, Duk Hyun

    1992-01-01

    With the development of laser, remote inspection techniques using laser have been growing on. The inspection and measurement techniques by pulse holography are well-established technique for precise measurement, and widely used in various fields of industry now. In nuclear industry, this technology is practically used because holographic inspection is remote, noncontact, and precise measurement technique. In relation to remote inspection technology in nuclear industry, state-of-the art of pulse HNDT (Holographic non-destructive testing) and holographic measurement techniques are examined. First of all, the fundamental principles as well as practical problems for applications are briefly described. The fields of pulse holography have been divided into the HNDT, flow visualization and distribution study, and other application techniques. Additionally holographic particle study, bubble chamber holography, and applications to other visualization techniques are described. Lastly, the current status for the researches and applications of pulse holography to nuclear industry which are carried out actively in Europe and USA, is described. (Author)

  18. Quality Attribute Techniques Framework

    Science.gov (United States)

    Chiam, Yin Kia; Zhu, Liming; Staples, Mark

    The quality of software is achieved during its development. Development teams use various techniques to investigate, evaluate and control potential quality problems in their systems. These “Quality Attribute Techniques” target specific product qualities such as safety or security. This paper proposes a framework to capture important characteristics of these techniques. The framework is intended to support process tailoring, by facilitating the selection of techniques for inclusion into process models that target specific product qualities. We use risk management as a theory to accommodate techniques for many product qualities and lifecycle phases. Safety techniques have motivated the framework, and safety and performance techniques have been used to evaluate the framework. The evaluation demonstrates the ability of quality risk management to cover the development lifecycle and to accommodate two different product qualities. We identify advantages and limitations of the framework, and discuss future research on the framework.

  19. Development of an x-ray beam line at the NSLS for studies in materials science using x-ray absorption spectroscopy: Annual progress report

    International Nuclear Information System (INIS)

    Sayers, D.E.

    1987-01-01

    The research programs reported span virtually the entire range of condensed matter studies involving the fields of solid state physics, chemistry, electrochemistry, materials science and biochemistry. Results are discussed for various groups. Topics reported include work on amorphous chalcogenide semiconductors, particularly photostructural changes, kinetics of structural changes and rapid quenching, bond strengths, force constants and phonons. Also reported are temperature dependent EXAFS studies of bonding in high temperature alloys, amorphous systems, disordered alloys and studies of resolve electronic structure, EXAFS and XANES studies of permanent magnet systems based on Nd 2 Fe 14 B, glancing angle EXAFS study of Nb/Al and Nb/Si interfacial systems, x-ray absorption of krypton-implanted solids and high dose implants into silicon, and x-ray absorption and EXAFS studies of superconducting oxide compounds of Cu and related magnetic systems. Work is also reported on XAFS measurements on the icosahedral phase

  20. Tracer techniques in microelectronics

    International Nuclear Information System (INIS)

    Flachowsky, J.; Freyer, K.

    1981-01-01

    Tracer technique and neutron activation analysis are capable of measuring impurities in semiconductor material or on the semiconductor surface in a very low concentration range. The methods, combined with autoradiography, are also suitable to determine dopant distributions in silicon. However, both techniques suffer from certain inherent experimental difficulties and/or limitations which are discussed. Methods of tracer technique practicable in the semiconductor field are described. (author)

  1. Materials characterization techniques

    National Research Council Canada - National Science Library

    Zhang, Sam; Li, L; Kumar, Ashok

    2009-01-01

    "With an emphasis on practical applications and real-world case studies, Materials Characterization Techniques presents the principles of widely used advanced surface and structural characterization...

  2. Persian fencing techniques

    Directory of Open Access Journals (Sweden)

    Manouchehr Moshtagh Khorasani

    2012-07-01

    Full Text Available There are numerous manuscripts, poems and stories that describe, specifically and in detail, the different techniques used in Persian swordsmanship. The present article explains the origins and the techniques of Persian swordsmanship. The article also describes the traditional code of conduct for Persian warriors. Additionally, it describes an array of techniques that were deployed in actual combat in Iran’s history. Some of these techniques are represented via the miniatures that are reproduced herein. This is the first article on Persian swordsmanship published in any periodical.

  3. Uranium exploration techniques

    International Nuclear Information System (INIS)

    Nichols, C.E.

    1984-01-01

    The subject is discussed under the headings: introduction (genetic description of some uranium deposits; typical concentrations of uranium in the natural environment); sedimentary host rocks (sandstones; tabular deposits; roll-front deposits; black shales); metamorphic host rocks (exploration techniques); geologic techniques (alteration features in sandstones; favourable features in metamorphic rocks); geophysical techniques (radiometric surveys; surface vehicle methods; airborne methods; input surveys); geochemical techniques (hydrogeochemistry; petrogeochemistry; stream sediment geochemistry; pedogeochemistry; emanometry; biogeochemistry); geochemical model for roll-front deposits; geologic model for vein-like deposits. (U.K.)

  4. Principles of fluorescence techniques

    CERN Document Server

    2016-01-01

    Fluorescence techniques are being used and applied increasingly in academics and industry. The Principles of Fluorescence Techniques course will outline the basic concepts of fluorescence techniques and the successful utilization of the currently available commercial instrumentation. The course is designed for students who utilize fluorescence techniques and instrumentation and for researchers and industrial scientists who wish to deepen their knowledge of fluorescence applications. Key scientists in the field will deliver theoretical lectures. The lectures will be complemented by the direct utilization of steady-state and lifetime fluorescence instrumentation and confocal microscopy for FLIM and FRET applications provided by leading companies.

  5. Laser induced pyrolysis techniques

    International Nuclear Information System (INIS)

    Vanderborgh, N.E.

    1976-01-01

    The application of laser pyrolysis techniques to the problems of chemical analysis is discussed. The processes occurring during laser pyrolysis are first briefly reviewed. The problems encountered in laser pyrolysis gas chromatography are discussed using the analysis of phenanthrene and binary hydrocarbons. The application of this technique to the characterization of naturally occurring carbonaceous material such as oil shales and coal is illustrated

  6. A Technique: Exposure Therapy

    Directory of Open Access Journals (Sweden)

    Serkan AKKOYUNLU

    2013-08-01

    Conclusion: Exposure with response prevention is a basic and effective technique. Every cognitive behavior therapist must be able to implement this technique and be cognizant of pearls of this procedure. (Journal of Cognitive Behavioral Psychotherapy and Research 2013, 2: 121-128 [JCBPR 2013; 2(2.000: 121-128

  7. Analytical system availability techniques

    NARCIS (Netherlands)

    Brouwers, J.J.H.; Verbeek, P.H.J.; Thomson, W.R.

    1987-01-01

    Analytical techniques are presented to assess the probability distributions and related statistical parameters of loss of production from equipment networks subject to random failures and repairs. The techniques are based on a theoretical model for system availability, which was further developed

  8. Glycoprotein and proteoglycan techniques

    International Nuclear Information System (INIS)

    Beeley, J.G.

    1985-01-01

    The aim of this book is to describe techniques which can be used to answer some of the basic questions about glycosylated proteins. Methods are discussed for isolation, compositional analysis, and for determination of the primary structure of carbohydrate units and the nature of protein-carbohydrate linkages of glycoproteins and proteoglycans. High resolution NMR is considered, as well as radioactive labelling techniques. (Auth.)

  9. Lymphography - an outdated technique

    International Nuclear Information System (INIS)

    Peters, P.E.

    1982-01-01

    The indications for lymphography have changed with the availability of non-invasive techniques like ultrasonic techniques and computerized tomography. This review discusses: Recent results of lymphography in histologically verified patient collectives with lymphatic systemic diseases and lymphatic metastizing tumors. The present role of lymphography is derived from this status report as well as the future perspectives. (orig.) [de

  10. Techniques of radiation dosimetry

    International Nuclear Information System (INIS)

    Mahesk, K.

    1985-01-01

    A text and reference with an interdisciplinary approach to physics, atomic energy, radiochemistry, and radiobiology. Chapters examine basic principles, experimental techniques, the methodology of dose experiments, and applications. Treats 14 different dosimetric techniques, including ionization chamber, thermoluminescence, and lyoluminescence. Considers the conceptual aspects and characteristic features of radiation

  11. Contamination Control Techniques

    Energy Technology Data Exchange (ETDEWEB)

    EBY, J.L.

    2000-05-16

    Welcome to a workshop on contamination Control techniques. This work shop is designed for about two hours. Attendee participation is encouraged during the workshop. We will address different topics within contamination control techniques; present processes, products and equipment used here at Hanford and then open the floor to you, the attendees for your input on the topics.

  12. Contamination Control Techniques

    International Nuclear Information System (INIS)

    EBY, J.L.

    2000-01-01

    Welcome to a workshop on contamination Control techniques. This work shop is designed for about two hours. Attendee participation is encouraged during the workshop. We will address different topics within contamination control techniques; present processes, products and equipment used here at Hanford and then open the floor to you, the attendees for your input on the topics

  13. Relaxation techniques for stress

    Science.gov (United States)

    ... raise your heart rate. This is called the stress response. Relaxation techniques can help your body relax and lower your blood pressure ... also many other types of breathing techniques you can learn. In many cases, you do not need much ... including those that cause stress. Meditation has been practiced for thousands of years, ...

  14. Emerging optical nanoscopy techniques

    Directory of Open Access Journals (Sweden)

    Montgomery PC

    2015-09-01

    Full Text Available Paul C Montgomery, Audrey Leong-Hoi Laboratoire des Sciences de l'Ingénieur, de l'Informatique et de l'Imagerie (ICube, Unistra-CNRS, Strasbourg, France Abstract: To face the challenges of modern health care, new imaging techniques with subcellular resolution or detection over wide fields are required. Far field optical nanoscopy presents many new solutions, providing high resolution or detection at high speed. We present a new classification scheme to help appreciate the growing number of optical nanoscopy techniques. We underline an important distinction between superresolution techniques that provide improved resolving power and nanodetection techniques for characterizing unresolved nanostructures. Some of the emerging techniques within these two categories are highlighted with applications in biophysics and medicine. Recent techniques employing wider angle imaging by digital holography and scattering lens microscopy allow superresolution to be achieved for subcellular and even in vivo, imaging without labeling. Nanodetection techniques are divided into four subcategories using contrast, phase, deconvolution, and nanomarkers. Contrast enhancement is illustrated by means of a polarized light-based technique and with strobed phase-contrast microscopy to reveal nanostructures. Very high sensitivity phase measurement using interference microscopy is shown to provide nanometric surface roughness measurement or to reveal internal nanometric structures. Finally, the use of nanomarkers is illustrated with stochastic fluorescence microscopy for mapping intracellular structures. We also present some of the future perspectives of optical nanoscopy. Keywords: microscopy, imaging, superresolution, nanodetection, biophysics, medical imaging

  15. Disagreements around techniques

    International Nuclear Information System (INIS)

    Sachsse, H.

    The modern man lives in disagreement with its techniques. Technical progress is the foundation of its material and spiritual existence, but he does not like it. Specialization, difficult understanding of the technical procedures and the price that has to be paid for technical progress, have led to a deep-going enstrangement. Therefore the question: What kind of human function has our technique. It is understood as an extension and perfection of our bodily organs, in order to increase our ability to see and to hear enormously, and to intervene formatively in the existing reality. Technique is therefore an instrument of comprehensive self-realization of man. (orig./GL) [de

  16. Spectrometric techniques 3

    CERN Document Server

    Vanasse, George A

    2013-01-01

    Spectrometric Techniques, Volume III presents the applications of spectrometric techniques to atmospheric and space studies. This book reviews the spectral data processing and analysis techniques that are of broad applicability.Organized into five chapters, this volume begins with an overview of the instrumentation used for obtaining field data. This text then reviews the contribution that space-borne spectroscopy in the thermal IR has made to the understanding of the planets. Other chapters consider the instruments that have recorded the planetary emission spectra. This book discusses as well

  17. Spectrometric techniques 4

    CERN Document Server

    Vanasse, George A

    2013-01-01

    Spectrometric Techniques, Volume IV discusses three widely diversified areas of spectrometric techniques. The book focuses on three spectrometric methods. Chapter 1 discusses the phenomenology and applications of Coherent Anti-Stokes Raman Spectroscopy (CARS), the most commonly used optical technique that exploit the Raman effect. The second chapter is concerned with diffraction gratings and mountings for the Vacuum Ultraviolet Spectral Region. Chapter 3 accounts the uses of mass spectrometry, detectors, types of spectrometers, and ion sources. Physicists and chemists will find the book a go

  18. Separation techniques: Chromatography

    Science.gov (United States)

    Coskun, Ozlem

    2016-01-01

    Chromatography is an important biophysical technique that enables the separation, identification, and purification of the components of a mixture for qualitative and quantitative analysis. Proteins can be purified based on characteristics such as size and shape, total charge, hydrophobic groups present on the surface, and binding capacity with the stationary phase. Four separation techniques based on molecular characteristics and interaction type use mechanisms of ion exchange, surface adsorption, partition, and size exclusion. Other chromatography techniques are based on the stationary bed, including column, thin layer, and paper chromatography. Column chromatography is one of the most common methods of protein purification. PMID:28058406

  19. Spectrometric techniques 2

    CERN Document Server

    Vanasse, George A

    2013-01-01

    Spectrometric Techniques, Volume II provides information pertinent to vacuum ultraviolet techniques to complete the demonstration of the diversity of methods available to the spectroscopist interested in the ultraviolet visible and infrared spectral regions. This book discusses the specific aspects of the technique of Fourier transform spectroscopy.Organized into five chapters, this volume begins with an overview of the large number of systematic effects in the recording of an interferogram. This text then examines the design approach for a Fourier transform spectrometer with focus on optics.

  20. Advanced analytical techniques

    International Nuclear Information System (INIS)

    Mrochek, J.E.; Shumate, S.E.; Genung, R.K.; Bahner, C.T.; Lee, N.E.; Dinsmore, S.R.

    1976-01-01

    The development of several new analytical techniques for use in clinical diagnosis and biomedical research is reported. These include: high-resolution liquid chromatographic systems for the early detection of pathological molecular constituents in physiologic body fluids; gradient elution chromatography for the analysis of protein-bound carbohydrates in blood serum samples, with emphasis on changes in sera from breast cancer patients; electrophoretic separation techniques coupled with staining of specific proteins in cellular isoenzymes for the monitoring of genetic mutations and abnormal molecular constituents in blood samples; and the development of a centrifugal elution chromatographic technique for the assay of specific proteins and immunoglobulins in human blood serum samples

  1. Adaptive algebraic reconstruction technique

    International Nuclear Information System (INIS)

    Lu Wenkai; Yin Fangfang

    2004-01-01

    Algebraic reconstruction techniques (ART) are iterative procedures for reconstructing objects from their projections. It is proven that ART can be computationally efficient by carefully arranging the order in which the collected data are accessed during the reconstruction procedure and adaptively adjusting the relaxation parameters. In this paper, an adaptive algebraic reconstruction technique (AART), which adopts the same projection access scheme in multilevel scheme algebraic reconstruction technique (MLS-ART), is proposed. By introducing adaptive adjustment of the relaxation parameters during the reconstruction procedure, one-iteration AART can produce reconstructions with better quality, in comparison with one-iteration MLS-ART. Furthermore, AART outperforms MLS-ART with improved computational efficiency

  2. Approximation techniques for engineers

    CERN Document Server

    Komzsik, Louis

    2006-01-01

    Presenting numerous examples, algorithms, and industrial applications, Approximation Techniques for Engineers is your complete guide to the major techniques used in modern engineering practice. Whether you need approximations for discrete data of continuous functions, or you''re looking for approximate solutions to engineering problems, everything you need is nestled between the covers of this book. Now you can benefit from Louis Komzsik''s years of industrial experience to gain a working knowledge of a vast array of approximation techniques through this complete and self-contained resource.

  3. X-Ray Absorption Near-Edge Structure (XANES) of Calcium L3,2 Edges of Various Calcium Compounds and X-Ray Excited Optical Luminescence (XEOL) Studies of Luminescent Calcium Compounds

    International Nuclear Information System (INIS)

    Ko, J. Y. Peter; Zhou Xingtai; Sham, T.-K.; Heigl, Franziskus; Regier, Tom; Blyth, Robert

    2007-01-01

    X-ray absorption at calcium L3,2 edges of various calcium compounds were measured using a high resolution Spherical Grating Monochromator (SGM) at the Canadian Light Source (CLS). We observe that each compound has its unique fine structure of L3,2 edges. This uniqueness is due to differences in local structure of compounds. We also performed (X-ray Excited Optical Luminescence) XEOL of selected luminescent calcium compounds to investigate their optical properties. XEOL is a photon-in-photon-out technique in which the optical luminescence that is excited by tunable x-rays from a synchrotron light source is monitored. Depending on excitation energy of the x-ray, relative intensities of luminescence peaks vary. Recent findings of the results will be presented here

  4. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... specialized CF care and a range of treatment options. Airway Clearance Active Cycle of Breathing Technique Airway ... on their own. Share Facebook Twitter Email More options Print Share Facebook Twitter Email Print Permalink All ...

  5. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... Techniques Autogenic Drainage Basics of Lung Care Chest Physical Therapy Coughing and Huffing High-Frequency Chest Wall ... Care Guidelines Newborn Screening Clinical Care Guidelines Sweat Test Clinical Care Guidelines Infection Prevention and Control Care ...

  6. Plant tissue culture techniques

    Directory of Open Access Journals (Sweden)

    Rolf Dieter Illg

    1991-01-01

    Full Text Available Plant cell and tissue culture in a simple fashion refers to techniques which utilize either single plant cells, groups of unorganized cells (callus or organized tissues or organs put in culture, under controlled sterile conditions.

  7. RFCM Techniques Chamber Facility

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Provides the capability to develop radio-frequency countermeasure (RFCM) techniques in a controlled environment from 2.0 to 40.0 GHz. The configuration of...

  8. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... Treatments and Therapies Airway Clearance Airway Clearance Techniques (ACTs) There are different ways to clear your airways. ... or caregiver. Older kids and adults can choose ACTs that they can do on their own. Share ...

  9. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... a Family Parenting as an Adult With CF Treatments and Therapies People with cystic fibrosis are living ... to specialized CF care and a range of treatment options. Airway Clearance Active Cycle of Breathing Technique ...

  10. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... a Family Parenting as an Adult With CF Treatments and Therapies People with cystic fibrosis are living longer and ... to specialized CF care and a range of treatment options. Airway Clearance Active Cycle of Breathing Technique ...

  11. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... Make a Charitable Gift Our Corporate Supporters Workplace Engagement DONATE YOUR PROPERTY eCards for a Cure About ... airway walls. See how different airway clearance techniques work to help you clear the thick, sticky mucus ...

  12. Lightweight Cryptographic Techniques

    National Research Council Canada - National Science Library

    Yuen, Horace

    2004-01-01

    The objective of this project was to develop new cryptographic techniques, and to modify the important existing ones, for applications to encryption and authentication in energy-constrained sensors...

  13. Variational Monte Carlo Technique

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 19; Issue 8. Variational Monte Carlo Technique: Ground State Energies of Quantum Mechanical Systems. Sukanta Deb. General Article Volume 19 Issue 8 August 2014 pp 713-739 ...

  14. Alternative Assessment Techniques.

    Science.gov (United States)

    Lowenthal, Barbara

    1988-01-01

    Maintaining the precision necessary for administering norm referenced tests can be a problem for the special education teacher who is trained to assist the student. Criterion-referenced tests, observations, and interviews are presented as effective alternative assessment techniques. (JDD)

  15. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... Techniques Autogenic Drainage Basics of Lung Care Chest Physical Therapy Coughing and Huffing High-Frequency Chest Wall ... Clinical Care Guidelines Chronic Medications to Maintain Lung Health Clinical Care Guidelines Lung Transplants Clinical Care Guidelines ...

  16. Healthy Cooking Techniques

    Science.gov (United States)

    Healthy Lifestyle Nutrition and healthy eating Healthy-cooking techniques capture the flavor and nutrients of food without extra fat or salt. By Mayo Clinic Staff Healthy cooking doesn't mean that ...

  17. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... today. ANNUAL FUND Become a Corporate Supporter Cause Marketing Make a Charitable Gift Our Corporate Supporters Workplace ... Clearance Airway Clearance Techniques (ACTs) There are different ways to clear your airways. Most are easy to ...

  18. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... ACTs involve coughing or huffing . Many of them use percussion (clapping) or vibration to loosen mucus from airway walls. See how different airway clearance techniques work to help you clear the thick, sticky mucus ...

  19. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... Physical Therapy Coughing and Huffing High-Frequency Chest Wall Oscillation Positive Expiratory Pressure Clinical Trials Clinical Trials ... clapping) or vibration to loosen mucus from airway walls. See how different airway clearance techniques work to ...

  20. Airway Clearance Techniques (ACTs)

    Medline Plus

    Full Text Available ... D Structure Consortium CFTR Folding Consortium Epithelial Stem Cell Consortium Mucociliary Clearance Consortium SUCCESS WITH THERAPIES RESEARCH ... clapping) or vibration to loosen mucus from airway walls. See how different airway clearance techniques work to ...

  1. Materials characterization techniques

    National Research Council Canada - National Science Library

    Zhang, Sam; Li, L; Kumar, Ashok

    2009-01-01

    ... techniques for quality assurance, contamination control, and process improvement. The book reviews the most popular and powerful analysis and quality control tools, explaining the appropriate uses and related technical requirements...

  2. Radiochemical procedures and techniques

    International Nuclear Information System (INIS)

    Flynn, K.

    1975-04-01

    A summary is presented of the radiochemical procedures and techniques currently in use by the Chemistry Division Nuclear Chemistry Group at Argonne National Laboratory for the analysis of radioactive samples. (U.S.)

  3. Airway Clearance Techniques (ACTs)

    Science.gov (United States)

    ... infant or child manage their lung health, watch parents of children with CF and a respiratory therapist talk about the different techniques they use for airway ... Positive Expiratory Pressure High-Frequency Chest Wall Oscillation (the Vest) Follow ...

  4. Radon survey techniques

    International Nuclear Information System (INIS)

    Anon.

    1976-01-01

    The report reviews radon measurement surveys in soils and in water. Special applications, and advantages and limitations of the radon measurement techniques are considered. The working group also gives some directions for further research in this field

  5. Stargate: Energy Management Techniques

    OpenAIRE

    Vijay Raghunathan; Mani Srivastava; Trevor Pering; Roy Want

    2004-01-01

    This poster presents techniques for energy efficient operation of the Stargate wireless platform. In addition to conventional power management techniques such as dynamic voltage and scaling and processor shutdown, the Stargate features several mechanisms for energy efficient operation of the communication subsystem, such as support for hierarchical radios, Bluetooth based remote wakeup, mote based wakeup, etc. Finally, design optimizations including the use of power gating, and provision for ...

  6. Applying contemporary statistical techniques

    CERN Document Server

    Wilcox, Rand R

    2003-01-01

    Applying Contemporary Statistical Techniques explains why traditional statistical methods are often inadequate or outdated when applied to modern problems. Wilcox demonstrates how new and more powerful techniques address these problems far more effectively, making these modern robust methods understandable, practical, and easily accessible.* Assumes no previous training in statistics * Explains how and why modern statistical methods provide more accurate results than conventional methods* Covers the latest developments on multiple comparisons * Includes recent advanc

  7. Next generation initiation techniques

    Science.gov (United States)

    Warner, Tom; Derber, John; Zupanski, Milija; Cohn, Steve; Verlinde, Hans

    1993-01-01

    Four-dimensional data assimilation strategies can generally be classified as either current or next generation, depending upon whether they are used operationally or not. Current-generation data-assimilation techniques are those that are presently used routinely in operational-forecasting or research applications. They can be classified into the following categories: intermittent assimilation, Newtonian relaxation, and physical initialization. It should be noted that these techniques are the subject of continued research, and their improvement will parallel the development of next generation techniques described by the other speakers. Next generation assimilation techniques are those that are under development but are not yet used operationally. Most of these procedures are derived from control theory or variational methods and primarily represent continuous assimilation approaches, in which the data and model dynamics are 'fitted' to each other in an optimal way. Another 'next generation' category is the initialization of convective-scale models. Intermittent assimilation systems use an objective analysis to combine all observations within a time window that is centered on the analysis time. Continuous first-generation assimilation systems are usually based on the Newtonian-relaxation or 'nudging' techniques. Physical initialization procedures generally involve the use of standard or nonstandard data to force some physical process in the model during an assimilation period. Under the topic of next-generation assimilation techniques, variational approaches are currently being actively developed. Variational approaches seek to minimize a cost or penalty function which measures a model's fit to observations, background fields and other imposed constraints. Alternatively, the Kalman filter technique, which is also under investigation as a data assimilation procedure for numerical weather prediction, can yield acceptable initial conditions for mesoscale models. The

  8. Speciation of plutonium during sorption and diffusion in Opalinus clay

    International Nuclear Information System (INIS)

    Kaplan, Ugras

    2013-01-01

    The presented work was carried out in the framework of the BMWi-project ''Interaction and migration of actinides in natural clay rocks taking into account humic substances and clay organic matter - Interactions of neptunium and plutonium with natural clay rocks''. For the long-term safety assessments of nuclear repositories, the possible migration of the radiotoxic wastes into the environment must be considered. Due to its long half-life (T 1/2 = 24000 y) 239 Pu has a significant contribution to the radiotoxicity of spent nuclear fuel in a repository after long periods of storage. The redox-sensitive plutonium has a very complicated chemical behavior. In aqueous solution under environmental relevant conditions Pu can exist in oxidation states +III to +VI and it can exist in up to four oxidation states simultaneously in a solution. Clays are considered as a possible host rock formation for of high-level radioactive waste disposal. Therefore, detailed information on the mobilization and immobilization of plutonium through / into the groundwater from a repository are of special interest. In this work new insights into the interaction between Pu and natural Opalinus clay (OPA, Mont Terri, Switzerland) are obtained with regard to the disposal of heat-generating radioactive waste in a deep geological repository.rnThe focus of this work was on the determination of the speciation of Pu on the mineral surface after sorption and diffusion process by different synchrotron based techniques (μ-XRF, μ-XANES/-EXAFS, μ-XRD, and EXAFS/XANES). The interaction between Pu and OPA was studied in batch sorption and diffusion experiments in dependence of various experimental parameters (e.g. pH, Pu oxidation state). Sorption experiments showed that some experimental parameters (e.g. temperature, humic acid) have a significant impact on the sorption of Pu on OPA. Speciation studies were performed as a function of various chemical parameters on powder samples form batch experiments as

  9. Protaper--hybrid technique.

    Science.gov (United States)

    Simon, Stephane; Lumley, Philip; Tomson, Phillip; Pertot, Wilhelm-Joseph; Machtou, Pierre

    2008-03-01

    Crown down preparation is the most known and described technique since the introduction of Nickel Titanium (NiTi) rotary instruments in endodontics. This technique gives good results but has limitations, such as not addressing the initial anatomy of oval or dumb-bell shaped canals. The specific design of the Protaper instruments allows use of them with a different technique and, specifically, with a brushing motion in the body of the canal. The recent introduction of hand Protaper files has expanded the range of application of this system, especially in curved canals. The 'hybrid technique', using rotary and hand files, and the advantages of the combination of both instruments, are clearly described in this article. Used with this technique, the Protaper is a very safe system to use, and more controllable, for both inexperienced and experienced practitioners alike, than other systems. To understand the precautions needed with rotary files, and how to use them to preserve the anatomy of the canal and get a tapered shaping, even in severely curved canals.

  10. Handbook of laboratory techniques

    International Nuclear Information System (INIS)

    2002-01-01

    The Nuclear Regulatory Authority in Argentina have laboratories of support to regulations functions on radiological and nuclear safety, safeguards and physical protection, that have a surface of 2950 m 2 in the Ezeiza Atomic Center. The manual describes in seven chapters the different techniques developed and applied in the laboratories along four decades of existence. The chapter 1: Dedicated to the treatment of environmental samples, described the procedures associated with the different types of samples: deposits, waters, sediments, vegetables, milk, fish and diet. The chapter 2: Details 48 radiochemical techniques associated to the measurements of americium 241, carbon 16, strontium 90, iodine 129, plutonium, radium 226, radon, uranium, nickel and actinides. The chapter 3: Describes the measurements techniques of alpha and gamma spectrometry. The different techniques of biological and physical dosimetry are described in the chapters 5 and 6 respectively. The final chapter is dedicated the techniques of external and internal contamination. It s important to emphasize that this manual contains the standardized technologies that the Nuclear Regulatory Authority of Argentina submits regularly to international comparisons

  11. Telescopes and Techniques

    CERN Document Server

    Kitchin, C R

    2013-01-01

    Telescopes and Techniques has proved itself in its first two editions, having become probably one of the most widely used astronomy texts, both for amateur astronomers and astronomy and astrophysics undergraduates. Both earlier editions of the book were widely used for introductory practical astronomy courses in many universities. In this Third Edition the author guides the reader through the mathematics, physics and practical techniques needed to use today's telescopes (from the smaller models to the larger instruments installed in many colleges) and how to find objects in the sky. Most of the physics and engineering involved is described fully and requires little prior knowledge or experience. Both visual and electronic imaging techniques are covered, together with an introduction to how data (measurements) should be processed and analyzed. A simple introduction to radio telescopes is also included. Brief coverage of the more advanced topics of photometry and spectroscopy are included, but mainly to enable ...

  12. Radiation techniques for acromegaly

    Directory of Open Access Journals (Sweden)

    Minniti Giuseppe

    2011-12-01

    Full Text Available Abstract Radiotherapy (RT remains an effective treatment in patients with acromegaly refractory to medical and/or surgical interventions, with durable tumor control and biochemical remission; however, there are still concerns about delayed biochemical effect and potential late toxicity of radiation treatment, especially high rates of hypopituitarism. Stereotactic radiotherapy has been developed as a more accurate technique of irradiation with more precise tumour localization and consequently a reduction in the volume of normal tissue, particularly the brain, irradiated to high radiation doses. Radiation can be delivered in a single fraction by stereotactic radiosurgery (SRS or as fractionated stereotactic radiotherapy (FSRT in which smaller doses are delivered over 5-6 weeks in 25-30 treatments. A review of the recent literature suggests that pituitary irradiation is an effective treatment for acromegaly. Stereotactic techniques for GH-secreting pituitary tumors are discussed with the aim to define the efficacy and potential adverse effects of each of these techniques.

  13. Radiation techniques for acromegaly

    International Nuclear Information System (INIS)

    Minniti, Giuseppe; Scaringi, Claudia; Enrici, Riccardo Maurizi

    2011-01-01

    Radiotherapy (RT) remains an effective treatment in patients with acromegaly refractory to medical and/or surgical interventions, with durable tumor control and biochemical remission; however, there are still concerns about delayed biochemical effect and potential late toxicity of radiation treatment, especially high rates of hypopituitarism. Stereotactic radiotherapy has been developed as a more accurate technique of irradiation with more precise tumour localization and consequently a reduction in the volume of normal tissue, particularly the brain, irradiated to high radiation doses. Radiation can be delivered in a single fraction by stereotactic radiosurgery (SRS) or as fractionated stereotactic radiotherapy (FSRT) in which smaller doses are delivered over 5-6 weeks in 25-30 treatments. A review of the recent literature suggests that pituitary irradiation is an effective treatment for acromegaly. Stereotactic techniques for GH-secreting pituitary tumors are discussed with the aim to define the efficacy and potential adverse effects of each of these techniques

  14. Non-platinum nanocatalyst on porous nitrogen-doped carbon fabricated by cathodic vacuum arc plasma technique

    Energy Technology Data Exchange (ETDEWEB)

    Sirirak, Reungruthai [Material Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Department of Chemistry and Center of Excellence for Innovation in Chemistry (PERCH-CIC), Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Sarakonsri, Thapanee, E-mail: tsarakonsri@gmail.com [Material Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Department of Chemistry and Center of Excellence for Innovation in Chemistry (PERCH-CIC), Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Medhesuwakul, Min [Plasma & Beam Physics Research Facility, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand)

    2015-11-30

    the iron nitride and the carbon nitride phases. The SEM images in the backscattered electron mode (BSE) reveal good dispersion of very small metal particles (bright spots) on the highly porous coral-like carbon film. The TEM images clearly show the spherical Fe nanoparticles (64 nm) dispersed on the porous carbon film. However, the XANES (X-ray absorption near edge structure) analysis specifies that the prepared Fe is in the form of iron(III). As a result of no FeN standard for confirmation, both the XRD and the XANES results are used to confirm the Fe(III) compound. In preparing the catalyst as FeN, all these results specify that the CVAP technique can be used to produce the catalyst on the membrane.

  15. Non-platinum nanocatalyst on porous nitrogen-doped carbon fabricated by cathodic vacuum arc plasma technique

    International Nuclear Information System (INIS)

    Sirirak, Reungruthai; Sarakonsri, Thapanee; Medhesuwakul, Min

    2015-01-01

    the iron nitride and the carbon nitride phases. The SEM images in the backscattered electron mode (BSE) reveal good dispersion of very small metal particles (bright spots) on the highly porous coral-like carbon film. The TEM images clearly show the spherical Fe nanoparticles (64 nm) dispersed on the porous carbon film. However, the XANES (X-ray absorption near edge structure) analysis specifies that the prepared Fe is in the form of iron(III). As a result of no FeN standard for confirmation, both the XRD and the XANES results are used to confirm the Fe(III) compound. In preparing the catalyst as FeN, all these results specify that the CVAP technique can be used to produce the catalyst on the membrane.

  16. Novel food processing techniques

    Directory of Open Access Journals (Sweden)

    Vesna Lelas

    2006-12-01

    Full Text Available Recently, a lot of investigations have been focused on development of the novel mild food processing techniques with the aim to obtain the high quality food products. It is presumed also that they could substitute some of the traditional processes in the food industry. The investigations are primarily directed to usage of high hydrostatic pressure, ultrasound, tribomechanical micronization, microwaves, pulsed electrical fields. The results of the scientific researches refer to the fact that application of some of these processes in particular food industry can result in lots of benefits. A significant energy savings, shortening of process duration, mild thermal conditions, food products with better sensory characteristics and with higher nutritional values can be achieved. As some of these techniques act also on the molecular level changing the conformation, structure and electrical potential of organic as well as inorganic materials, the improvement of some functional properties of these components may occur. Common characteristics of all of these techniques are treatment at ambient or insignificant higher temperatures and short time of processing (1 to 10 minutes. High hydrostatic pressure applied to various foodstuffs can destroy some microorganisms, successfully modify molecule conformation and consequently improve functional properties of foods. At the same time it acts positively on the food products intend for freezing. Tribomechanical treatment causes micronization of various solid materials that results in nanoparticles and changes in structure and electrical potential of molecules. Therefore, the significant improvement of some rheological and functional properties of materials occurred. Ultrasound treatment proved to be potentially very successful technique of food processing. It can be used as a pretreatment to drying (decreases drying time and improves functional properties of food, as extraction process of various components

  17. Surface science techniques

    CERN Document Server

    Walls, JM

    2013-01-01

    This volume provides a comprehensive and up to the minute review of the techniques used to determine the nature and composition of surfaces. Originally published as a special issue of the Pergamon journal Vacuum, it comprises a carefully edited collection of chapters written by specialists in each of the techniques and includes coverage of the electron and ion spectroscopies, as well as the atom-imaging methods such as the atom probe field ion microscope and the scanning tunnelling microscope. Surface science is an important area of study since the outermost surface layers play a crucial role

  18. Millimicrosecond pulse techniques

    CERN Document Server

    Lewis, Ian A D

    1959-01-01

    Millimicrosecond Pulse Techniques, Second Edition focuses on millimicrosecond pulse techniques and the development of devices of large bandwidth, extending down to comparatively low frequencies (1 Mc/s). Emphasis is on basic circuit elements and pieces of equipment of universal application. Specific applications, mostly in the field of nuclear physics instrumentation, are considered. This book consists of eight chapters and opens with an introduction to some of the terminology employed by circuit engineers as well as theoretical concepts, including the laws of circuit analysis, Fourier analysi

  19. Single well techniques

    International Nuclear Information System (INIS)

    Drost, W.

    1983-01-01

    The single well technique method includes measurement of parameters of groundwater flow in saturated rock. For determination of filtration velocity the dilution of radioactive tracer is measured, for direction logging the collimeter is rotated in the probe linked with the compass. The limiting factor for measurement of high filtration velocities is the occurrence of turbulent flow. The single well technique is used in civil engineering projects, water works and subsurface drainage of liquid waste from disposal sites. The radioactive tracer method for logging the vertical fluid movement in bore-holes is broadly used in groundwater survey and exploitation. (author)

  20. Stochastic Feedforward Control Technique

    Science.gov (United States)

    Halyo, Nesim

    1990-01-01

    Class of commanded trajectories modeled as stochastic process. Advanced Transport Operating Systems (ATOPS) research and development program conducted by NASA Langley Research Center aimed at developing capabilities for increases in capacities of airports, safe and accurate flight in adverse weather conditions including shear, winds, avoidance of wake vortexes, and reduced consumption of fuel. Advances in techniques for design of modern controls and increased capabilities of digital flight computers coupled with accurate guidance information from Microwave Landing System (MLS). Stochastic feedforward control technique developed within context of ATOPS program.