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Sample records for high-pressure neutron diffraction

  1. Future directions in high-pressure neutron diffraction

    Science.gov (United States)

    Guthrie, M.

    2015-04-01

    The ability to manipulate structure and properties using pressure has been well known for many centuries. Diffraction provides the unique ability to observe these structural changes in fine detail on lengthscales spanning atomic to nanometre dimensions. Amongst the broad suite of diffraction tools available today, neutrons provide unique capabilities of fundamental importance. However, to date, the growth of neutron diffraction under extremes of pressure has been limited by the weakness of available sources. In recent years, substantial government investments have led to the construction of a new generation of neutron sources while existing facilities have been revitalized by upgrades. The timely convergence of these bright facilities with new pressure-cell technologies suggests that the field of high-pressure (HP) neutron science is on the cusp of substantial growth. Here, the history of HP neutron research is examined with the hope of gleaning an accurate prediction of where some of these revolutionary capabilities will lead in the near future. In particular, a dramatic expansion of current pressure-temperature range is likely, with corresponding increased scope for extreme-conditions science with neutron diffraction. This increase in coverage will be matched with improvements in data quality. Furthermore, we can also expect broad new capabilities beyond diffraction, including in neutron imaging, small angle scattering and inelastic spectroscopy.

  2. Investigation of Methacrylic Acid at High Pressure Using Neutron Diffraction

    DEFF Research Database (Denmark)

    Marshall, William G.; Urquhart, Andrew; Oswald, Iain D. H.

    2015-01-01

    This article shows that pressure can be a low-intensity route to the synthesis of polymethacrylic acid. The exploration of perdeuterated methacrylic acid at high pressure using neutron diffraction reveals that methacrylic acid exhibits two polymorphic phase transformations at relatively low...... pressures. The first is observed at 0.39 GPa, where both phases were observed simultaneously and confirm our previous observations. This transition is followed by a second transition at 1.2 GPa to a new polymorph that is characterized for the first time. On increasing pressure, the diffraction pattern...

  3. Investigation of Acrylic Acid at High Pressure using Neutron Diffraction

    DEFF Research Database (Denmark)

    Johnston, Blair F.; Marshall, William G.; Parsons, Simon

    2014-01-01

    This article details the exploration of perdeuterated acrylic acid at high pressure using neutron diffraction. The structural changes that occur in acrylic acid-d4 are followed via diffraction and rationalised using the Pixel method. Acrylic acid undergoes a reconstructive phase transition to a new...... phase at ~0.8 GPa and remains molecular to 7.2 GPa before polymerising on decompression to ambient pressure. The resulting product is analysed via Raman, FT-IR spectroscopy and Differential Scanning Calorimetry and found to possess a different molecular structure compared with polymers produced via...

  4. Neutron Diffraction Investigation of MnAs under High Pressure

    DEFF Research Database (Denmark)

    Andresen, A.F; Fjellvag, H; Lebech, Bente

    1984-01-01

    Powdered MnAs has been investigated by neutron diffraction in a pressure cryostat, at hydrostatic pressures up to 13 kbar and temperatures down to 4.2 K. It has been found that in the orthorhombic MnP type structure, which under pressure is retained at low temperature, a spiral magnetic structure...

  5. High-pressure studies on Ba-doped cobalt perovskites by neutron diffraction

    Science.gov (United States)

    Cao, Huibo; Garlea, Vasile; Wang, Fangwei; Dos Santos, Antonio; Cheng, Zhaohua

    2012-02-01

    Cobalt perovskite possess rich structural, magnetic and electrical properties depending on the subtle balance of the interactions among the spin, charge, and orbital degrees of freedom. Divalent hole-doped cobalt perovskites LaA^2+CoO3 exhibit structural phase transitions, metal-insulator transitions, and multi-magnetic phase transitions. High-pressure measurement is believed to mimic the size effects of the doped ions. We performed neutron diffraction experiments on selected Ba-doped LaCoO3 under pressures up to 6.3 GPa at SNAP at Spallation Neutron Source of ORNL. This work focuses on the high-pressure effects of the selected Ba-doped samples and the change of the phase diagram with pressure.

  6. One picture says it all-high-pressure cells for neutron Laue diffraction on VIVALDI

    Energy Technology Data Exchange (ETDEWEB)

    McIntyre, G J [Institut Laue-Langevin, BP156, 38042 Grenoble Cedex 9 (France); Melesi, L [Institut Laue-Langevin, BP156, 38042 Grenoble Cedex 9 (France); Guthrie, M [CSEC, School of Physics, University of Edinburgh, Edinburgh EH9 3JZ (United Kingdom); Tulk, C A [Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831 (United States); Xu, J [Geophysical Laboratory, Carnegie Institute of Washington, 5251 Broad Branch Rd, NW, Washington, DC 20015 (United States); Parise, J B [Department of Geosciences, State University of New York, Stony Brook, NY 11749-2100 (United States); Department of Chemistry, State University of New York, Stony Brook, NY 11749-2100 (United States)

    2005-10-12

    Possible applications of the neutron single-crystal Laue diffraction technique with a large image-plate detector to high-pressure studies are examined. One opposed-piston cell with a Ti-Zr casing is shown to be acceptable for medium pressures. For higher pressures a moissanite-anvil cell with reasonably large accessibility is shown to offer impressive gains in data collection rate as compared to the monochromatic technique. Moreover, the projected forms of the reflections from the sample and anvils facilitate alignment, and the wide wavelength band of the Laue technique allows recovery of reflections masked by the cell pillars, simply by rotation of the cell.

  7. Probing the Hydrogen Sublattice of FeHx with High-Pressure Neutron Diffraction

    Science.gov (United States)

    Murphy, C. A.; Guthrie, M.; Boehler, R.; Somayazulu, M.; Fei, Y.; Molaison, J.; dos Santos, A. M.

    2013-12-01

    The combination of seismic, cosmochemical, and mineral physics observations have revealed that Earth's iron-rich core must contain some light elements, such as hydrogen, carbon, oxygen, silicon, and/or sulfur. Therefore, understanding the influence of these light elements on the structural, thermoelastic, and electronic properties of iron is important for constraining the composition of this remote layer of the Earth and, in turn, providing constraints on planetary differentiation and core formation models. The high-pressure structural and magnetic properties of iron hydride (FeHx) have previously been studied using synchrotron x-ray diffraction and Mössbauer spectroscopy. Such experiments revealed that the double hexagonal close-packed (dhcp) structure of FeHx is stable above a pressure of ~5 GPa and up to at least 80 GPa at 300 K [1]. In addition, dhcp-FeHx is ferromagnetic at low-pressures, but undergoes a magnetic collapse around 22 GPa [2]. X-ray experiments provide valuable insight into the properties of FeHx, but such techniques are largely sensitive to the iron component because it is difficult to detect the hydrogen sublattice with x-rays. Therefore, neutron diffraction has been used to investigate metastable FeHx, which is formed by quenching the high-pressure phase to liquid nitrogen temperatures and probing the sample at ambient pressure [3]. However, such neutron experiments have been limited to formation pressures below 10 GPa, and cannot be performed at ambient temperature. Here we present the first in-situ investigation of FeHx at 300 K using high-pressure neutron diffraction experiments performed at the Spallation Neutrons and Pressure Diffractometer (SNAP) instrument at the Spallation Neutron Source, Oak Ridge National Laboratory. In order to achieve pressures of ~50 GPa, we loaded iron samples with a hydrogen gas pressure medium into newly designed large-volume panoramic diamond-anvil cells (DACs) for neutron diffraction experiments [4; 5]. We

  8. High pressure behavior of phlogopite using neutron diffraction and first principle simulations

    Science.gov (United States)

    Chheda, T. D.; Mookherjee, M.; dos Santos, A. M.; Molaison, J.; Manthilake, G. M.; Chantel, J.; Mainprice, D.

    2013-12-01

    Hydrous phases play an important role in the deep water cycle by transporting water into the Earth's interior. Upon, reaching their thermodynamic stability, these hydrous phases decompose and release the water. A part of the water is cycled back to the arc, thus completing the deep water cycle, the remaining water is partitioned into dense hydrous phases and nominally anhydrous phases. Hence, in order to understand the role the hydrous phases in the deep water cycle, it is important to constrain the effect of pressure, temperature, and chemistry on the thermodynamic stability of the hydrous phases. In addition, it is important to constrain the elasticity of these hydrous phases to test whether they can explain the distinct geophysical observations such as lower bulk sound velocities and elastic anisotropy. Phlogopite is a potassium bearing mica that is stable in the hydrated crust and metasomatized mantle up to pressures of ~9 GPa, i.e., base of the upper mantle. We investigated the response of the crystal structure, lattice parameters and unit-cell volume of a natural phlogopite upon compression. We conducted in situ neutron diffraction studies at high-pressures using Paris-Edinburgh press at the Spallation Neutrons and Pressure Diffractometer (SNAP), Oak Ridge National Laboratory. All the experiments were conducted at room temperatures and pressures up to 10 GPa were explored. The equation of state parameters from our experiments could be explained by a finite strain formulation with V0= 487 Å3, K0 = 49 GPa, K' = 4.1. In addition, we have used first principle simulations based on density functional theory to calculate the equation of state and elasticity. The predicted equation of state is in good agreement with the experiments, with V0= 519 Å3, K0 = 45.8 GPa and K'= 6.9. The full elastic constant tensor shows significant anisotropy with the principal elastic constants at theoretical V0: C11= 181 GPa, C22= 185 GPa, C33= 62 GPa, the shear elastic constants- C44

  9. Neutron and high-pressure X-ray diffraction study of hydrogen-bonded ferroelectric rubidium hydrogen sulfate.

    Science.gov (United States)

    Binns, Jack; McIntyre, Garry J; Parsons, Simon

    2016-12-01

    The pressure- and temperature-dependent phase transitions in the ferroelectric material rubidium hydrogen sulfate (RbHSO4) are investigated by a combination of neutron Laue diffraction and high-pressure X-ray diffraction. The observation of disordered O-atom positions in the hydrogen sulfate anions is in agreement with previous spectroscopic measurements in the literature. Contrary to the mechanism observed in other hydrogen-bonded ferroelectric materials, H-atom positions are well defined and ordered in the paraelectric phase. Under applied pressure RbHSO4 undergoes a ferroelectric transition before transforming to a third, high-pressure phase. The symmetry of this phase is revised to the centrosymmetric space group P21/c, resulting in the suppression of ferroelectricity at high pressure.

  10. Six-axis multi-anvil press for high-pressure, high-temperature neutron diffraction experiments

    Energy Technology Data Exchange (ETDEWEB)

    Sano-Furukawa, A., E-mail: sano.asami@jaea.go.jp; Hattori, T. [Quantum Beam Science Center, Japan Atomic Energy Agency, Ibaraki 319-1195 (Japan); J-PARC Center, Japan Atomic Energy Agency, Ibaraki 319-1195 (Japan); Arima, H. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Yamada, A. [The University of Shiga Prefecture, Shiga 522-8533 (Japan); Tabata, S.; Kondo, M.; Nakamura, A. [Sumitomo Heavy Industries Co., Ltd., Ehime 792-0001 (Japan); Kagi, H.; Yagi, T. [Geochemical Research Center, Graduate School of Science, The University of Tokyo, Tokyo 113-0033 (Japan)

    2014-11-15

    We developed a six-axis multi-anvil press, ATSUHIME, for high-pressure and high-temperature in situ time-of-flight neutron powder diffraction experiments. The press has six orthogonally oriented hydraulic rams that operate individually to compress a cubic sample assembly. Experiments indicate that the press can generate pressures up to 9.3 GPa and temperatures up to 2000 K using a 6-6-type cell assembly, with available sample volume of about 50 mm{sup 3}. Using a 6-8-type cell assembly, the available conditions expand to 16 GPa and 1273 K. Because the six-axis press has no guide blocks, there is sufficient space around the sample to use the aperture for diffraction and place an incident slit, radial collimators, and a neutron imaging camera close to the sample. Combination of the six-axis press and the collimation devices realized high-quality diffraction pattern with no contamination from the heater or the sample container surrounding the sample. This press constitutes a new tool for using neutron diffraction to study the structures of crystals and liquids under high pressures and temperatures.

  11. Six-axis multi-anvil press for high-pressure, high-temperature neutron diffraction experiments.

    Science.gov (United States)

    Sano-Furukawa, A; Hattori, T; Arima, H; Yamada, A; Tabata, S; Kondo, M; Nakamura, A; Kagi, H; Yagi, T

    2014-11-01

    We developed a six-axis multi-anvil press, ATSUHIME, for high-pressure and high-temperature in situ time-of-flight neutron powder diffraction experiments. The press has six orthogonally oriented hydraulic rams that operate individually to compress a cubic sample assembly. Experiments indicate that the press can generate pressures up to 9.3 GPa and temperatures up to 2000 K using a 6-6-type cell assembly, with available sample volume of about 50 mm(3). Using a 6-8-type cell assembly, the available conditions expand to 16 GPa and 1273 K. Because the six-axis press has no guide blocks, there is sufficient space around the sample to use the aperture for diffraction and place an incident slit, radial collimators, and a neutron imaging camera close to the sample. Combination of the six-axis press and the collimation devices realized high-quality diffraction pattern with no contamination from the heater or the sample container surrounding the sample. This press constitutes a new tool for using neutron diffraction to study the structures of crystals and liquids under high pressures and temperatures.

  12. Cage occupancies in the high pressure structure H methane hydrate: a neutron diffraction study.

    Science.gov (United States)

    Tulk, C A; Klug, D D; dos Santos, A M; Karotis, G; Guthrie, M; Molaison, J J; Pradhan, N

    2012-02-07

    A neutron diffraction study was performed on the CD(4) : D(2)O structure H clathrate hydrate to refine its CD(4) fractional cage occupancies. Samples of ice VII and hexagonal (sH) methane hydrate were produced in a Paris-Edinburgh press and in situ neutron diffraction data collected. The data were analyzed with the Rietveld method and yielded average cage occupancies of 3.1 CD(4) molecules in the large 20-hedron (5(12)6(8)) cages of the hydrate unit cell. Each of the pentagonal dodecahedron (5(12)) and 12-hedron (4(3)5(6)6(3)) cages in the sH unit cell are occupied with on average 0.89 and 0.90 CD(4) molecules, respectively. This experiment avoided the co-formation of Ice VI and sH hydrate, this mixture is more difficult to analyze due to the proclivity of ice VI to form highly textured crystals, and overlapping Bragg peaks of the two phases. These results provide essential information for the refinement of intermolecular potential parameters for the water-methane hydrophobic interaction in clathrate hydrates and related dense structures.

  13. Use of a miniature diamond-anvil cell in high-pressure single-crystal neutron Laue diffraction

    Directory of Open Access Journals (Sweden)

    Jack Binns

    2016-05-01

    Full Text Available The first high-pressure neutron diffraction study in a miniature diamond-anvil cell of a single crystal of size typical for X-ray diffraction is reported. This is made possible by modern Laue diffraction using a large solid-angle image-plate detector. An unexpected finding is that even reflections whose diffracted beams pass through the cell body are reliably observed, albeit with some attenuation. The cell body does limit the range of usable incident angles, but the crystallographic completeness for a high-symmetry unit cell is only slightly less than for a data collection without the cell. Data collections for two sizes of hexamine single crystals, with and without the pressure cell, and at 300 and 150 K, show that sample size and temperature are the most important factors that influence data quality. Despite the smaller crystal size and dominant parasitic scattering from the diamond-anvil cell, the data collected allow a full anisotropic refinement of hexamine with bond lengths and angles that agree with literature data within experimental error. This technique is shown to be suitable for low-symmetry crystals, and in these cases the transmission of diffracted beams through the cell body results in much higher completeness values than are possible with X-rays. The way is now open for joint X-ray and neutron studies on the same sample under identical conditions.

  14. Use of a miniature diamond-anvil cell in high-pressure single-crystal neutron Laue diffraction.

    Science.gov (United States)

    Binns, Jack; Kamenev, Konstantin V; McIntyre, Garry J; Moggach, Stephen A; Parsons, Simon

    2016-05-01

    The first high-pressure neutron diffraction study in a miniature diamond-anvil cell of a single crystal of size typical for X-ray diffraction is reported. This is made possible by modern Laue diffraction using a large solid-angle image-plate detector. An unexpected finding is that even reflections whose diffracted beams pass through the cell body are reliably observed, albeit with some attenuation. The cell body does limit the range of usable incident angles, but the crystallographic completeness for a high-symmetry unit cell is only slightly less than for a data collection without the cell. Data collections for two sizes of hexamine single crystals, with and without the pressure cell, and at 300 and 150 K, show that sample size and temperature are the most important factors that influence data quality. Despite the smaller crystal size and dominant parasitic scattering from the diamond-anvil cell, the data collected allow a full anisotropic refinement of hexamine with bond lengths and angles that agree with literature data within experimental error. This technique is shown to be suitable for low-symmetry crystals, and in these cases the transmission of diffracted beams through the cell body results in much higher completeness values than are possible with X-rays. The way is now open for joint X-ray and neutron studies on the same sample under identical conditions.

  15. Neutron Diffraction and Electrical Transport Studies on Magnetic Transition in Terbium at High Pressures and Low Temperatures

    Science.gov (United States)

    Thomas, Sarah; Montgomery, Jeffrey; Tsoi, Georgiy; Vohra, Yogesh; Weir, Samuel; Tulk, Christopher; Moreira Dos Santos, Antonio

    2013-06-01

    Neutron diffraction and electrical transport measurements have been carried out on the heavy rare earth metal terbium at high pressures and low temperatures in order to elucidate its transition from a helical antiferromagnetic to a ferromagnetic ordered phase as a function of pressure. The electrical resistance measurements using designer diamonds show a change in slope as the temperature is lowered through the ferromagnetic Curie temperature. The temperature of the ferromagnetic transition decreases at a rate of -16.7 K/GPa till 3.6 GPa, where terbium undergoes a structural transition from hexagonal close packed (hcp) to an α-Sm phase. Above this pressure, the electrical resistance measurements no longer exhibit a change in slope. In order to confirm the change in magnetic phase suggested by the electrical resistance measurements, neutron diffraction measurements were conducted at the SNAP beamline at the Oak Ridge National Laboratory. Measurements were made at pressures to 5.3 GPa and temperatures as low as 90 K. An abrupt increase in peak intensity in the neutron diffraction spectra signaled the onset of magnetic order below the Curie temperature. A magnetic phase diagram of rare earth metal terbium will be presented to 5.3 GPa and 90 K based on these studies.

  16. Neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Heger, G. [Rheinisch-Westfaelische Technische Hochschule Aachen, Inst. fuer Kristallographie, Aachen (Germany)

    1996-12-31

    X-ray diffraction using conventional laboratory equipment and/or synchrotron installations is the most important method for structure analyses. The purpose of this paper is to discuss special cases, for which, in addition to this indispensable part, neutrons are required to solve structural problems. Even though the huge intensity of modern synchrotron sources allows in principle the study of magnetic X-ray scattering the investigation of magnetic structures is still one of the most important applications of neutron diffraction. (author) 15 figs., 1 tab., 10 refs.

  17. Techniques in high pressure neutron scattering

    CERN Document Server

    Klotz, Stefan

    2013-01-01

    Drawing on the author's practical work from the last 20 years, Techniques in High Pressure Neutron Scattering is one of the first books to gather recent methods that allow neutron scattering well beyond 10 GPa. The author shows how neutron scattering has to be adapted to the pressure range and type of measurement.Suitable for both newcomers and experienced high pressure scientists and engineers, the book describes various solutions spanning two to three orders of magnitude in pressure that have emerged in the past three decades. Many engineering concepts are illustrated through examples of rea

  18. Inelastic neutron scattering to very high pressures

    Science.gov (United States)

    Klotz, S.; Braden, M.; Besson, J. M.

    2000-11-01

    Progress in high-pressure and neutron scattering methods has recently allowed measurements of phonon dispersion curves of simple solids at high pressures to 10 GPa. In this technique single crystals of 10 25 mm3 volume are compressed by the Paris-Edinburgh cell and the phonon frequencies are measured on high-flux triple axis spectrometers. Detailed studies of the lattice dynamics of low-compressible systems are feasible, including measurements of mode Grüneisen parameters, elastic constants, and precursor effects of phase transitions. We describe the experimental set-up and illustrate its potential by results on semiconductors (Ge and GaSb) and metals (Fe and Zn) obtained at the LLB (Saclay) and ILL (Grenoble) reactor sources.

  19. Magnetic-crystallographic p,T-phase diagram of Fe{sub 1.141}Te: A high-pressure neutron diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Joergensen, Jens-Erik [Department of Chemistry, Aarhus University (Denmark); Hansen, Thomas Christian [Institute Max von Laue-Paul Langevin, Grenoble (France)

    2016-11-15

    The crystal and magnetic structures of Fe{sub 1.141}Te have been studied by neutron powder diffraction in the temperature range from 5 to 106 K and pressures in the range from ambient to ∼2.7 GPa. The p,T-phase diagram contains three phases with monoclinic, orthorhombic, and tetragonal symmetry. The monoclinic phase was found to be stable for T 2.16 GPa. The monoclinic phase shows commensurate bicollinear antiferromagnetic order with propagation vector k = (1/2 0 1/2), while the orthorhombic phase is incommensurately antiferromagnetically ordered with propagation vector k = (1/2-δ 0 1/2). The δ-parameter increases linearly with the pressure for 0.4 or similar 2.1 GPa and temperatures less than ∝68 K, depending on the pressure. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. SINGLE CRYSTAL NEUTRON DIFFRACTION.

    Energy Technology Data Exchange (ETDEWEB)

    KOETZLE,T.F.

    2001-03-13

    Single-crystal neutron diffraction measures the elastic Bragg reflection intensities from crystals of a material, the structure of which is the subject of investigation. A single crystal is placed in a beam of neutrons produced at a nuclear reactor or at a proton accelerator-based spallation source. Single-crystal diffraction measurements are commonly made at thermal neutron beam energies, which correspond to neutron wavelengths in the neighborhood of 1 Angstrom. For high-resolution studies requiring shorter wavelengths (ca. 0.3-0.8 Angstroms), a pulsed spallation source or a high-temperature moderator (a ''hot source'') at a reactor may be used. When complex structures with large unit-cell repeats are under investigation, as is the case in structural biology, a cryogenic-temperature moderator (a ''cold source'') may be employed to obtain longer neutron wavelengths (ca. 4-10 Angstroms). A single-crystal neutron diffraction analysis will determine the crystal structure of the material, typically including its unit cell and space group, the positions of the atomic nuclei and their mean-square displacements, and relevant site occupancies. Because the neutron possesses a magnetic moment, the magnetic structure of the material can be determined as well, from the magnetic contribution to the Bragg intensities. This latter aspect falls beyond the scope of the present unit; for information on magnetic scattering of neutrons see Unit 14.3. Instruments for single-crystal diffraction (single-crystal diffractometers or SCDs) are generally available at the major neutron scattering center facilities. Beam time on many of these instruments is available through a proposal mechanism. A listing of neutron SCD instruments and their corresponding facility contacts is included in an appendix accompanying this unit.

  1. X-ray Diffraction Study of Arsenopyrite at High Pressure

    Energy Technology Data Exchange (ETDEWEB)

    D Fan; M Ma; W Zhou; S Wei; Z Chen; H Xie

    2011-12-31

    The high-pressure X-ray diffraction study of a natural arsenopyrite was investigated up to 28.2 GPa using in situ angle-dispersive X-ray diffraction and a diamond anvil cell at National Synchrotron Light Source, Brookhaven National Laboratory. The 16:3:1 methanol-ethanol-water mixture was used as a pressure-transmitting medium. Pressures were measured using the ruby-fluorescence method. No phase change has been observed up to 28.2 GPa. The isothermal equation of state (EOS) was determined. The values of K{sub 0}, and K'{sub 0} refined with a third-order Birch-Murnaghan EOS are K{sub 0} = 123(9) GPa, and K'{sub 0} = 5.2(8). Furthermore, we confirm that the linear compressibilities ({beta}) along a, b and c directions of arsenopyrite is elastically isotropic ({beta}{sub a} = 6.82 x 10{sup -4}, {beta}{sub b} = 6.17 x 10{sup -4} and {beta}{sub c} = 6.57 x 10{sup -4} GPa{sup -1}).

  2. Phonons from neutron powder diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Dimitrov, D.A.; Louca, D.; Roeder, H. (Los Alamos National Laboratory, Los Alamos, New Mexico 87544 (United States))

    1999-09-01

    The spherically averaged structure function S([vert bar][bold q][vert bar]) obtained from pulsed neutron powder diffraction contains both elastic and inelastic scattering via an integral over energy. The Fourier transformation of S([vert bar][bold q][vert bar]) to real space, as is done in the pair density function (PDF) analysis, regularizes the data, i.e., it accentuates the diffuse scattering. We present a technique which enables the extraction of off-center ([vert bar][bold q][vert bar][ne]0) phonon information from powder diffraction experiments by comparing the experimental PDF with theoretical calculations based on standard interatomic potentials and the crystal symmetry. This procedure [dynamics from powder diffraction] has been [ital successfully] implemented as demonstrated here for two systems, a simple metal fcc Ni and an ionic crystal CaF[sub 2]. Although computationally intensive, this data analysis allows for a phonon based modeling of the PDF, and additionally provides off-center phonon information from neutron powder diffraction. [copyright] [ital 1999] [ital The American Physical Society

  3. Recent advances in high pressure neutron scattering at the Spallation Neutron Source at Oak Ridge National Laboratory

    Science.gov (United States)

    Tulk, C.; dos Santos, A.; Klug, D.; Guthrie, M.; Machida, S.; Molaison, J.

    2012-12-01

    There have been significant improvements in the operation of the high pressure diffractometer, SNAP, at the Spallation Neutron Source over the past two years. This talk will highlight the current capacities which include low temperature systems, high temperature systems, and the introduction of new pressure cell technology that is based on supported diamond anvils and, with advances in software, is particularly suited for powder diffraction. Specific examples of our recent research will focus on high pressure transitions in hydrogen bonded systems such as methane and CO2 hydrate. The high pressure hexagonal phase of methane hydrate is studied to determine the nature of the hydrate cage loading, this provides detailed experimental data that will lead to better intermolecular potentials for methane - methane interactions, particularly when methane molecules are in close contact and strongly repelling. The high pressure structural systematics of carbon dioxide hydrate is reported. While the structural transformation sequence of most hydrates progress from sI (or sII) to the hexagonal form then to a flied ice structure, CO2 hydrate is an example of a system that skips the hexagonal phase and transforms directly into the filled ice structure. Finally examples of using SNAP to study disorder in amorphous systems will be given. Particularly amorphous vapor co-deposits of water, known as amorphous solid water, and clathrate forming molecules such as CO2, and the structural response of these systems to increased pressure at low temperature.

  4. Pulsed Neutron Powder Diffraction for Materials Science

    Science.gov (United States)

    Kamiyama, T.

    2008-03-01

    The accelerator-based neutron diffraction began in the end of 60's at Tohoku University which was succeeded by the four spallation neutron facilities with proton accelerators at the High Energy Accelerator Research Organization (Japan), Argonne National Laboratory and Los Alamos Laboratory (USA), and Rutherford Appleton Laboratory (UK). Since then, the next generation source has been pursued for 20 years, and 1MW-class spallation neutron sources will be appeared in about three years at the three parts of the world: Japan, UK and USA. The joint proton accelerator project (J-PARC), a collaborative project between KEK and JAEA, is one of them. The aim of the talk is to describe about J-PARC and the neutron diffractometers being installed at the materials and life science facility of J-PARC. The materials and life science facility of J-PARC has 23 neutron beam ports and will start delivering the first neutron beam of 25 Hz from 2008 May. Until now, more than 20 proposals have been reviewed by the review committee, and accepted proposal groups have started to get fund. Those proposals include five polycrystalline diffractometers: a super high resolution powder diffractometer (SHRPD), a 0.2%-resolution powder diffractometer of Ibaraki prefecture (IPD), an engineering diffractometers (Takumi), a high intensity S(Q) diffractometer (VSD), and a high-pressure dedicated diffractometer. SHRPD, Takumi and IPD are being designed and constructed by the joint team of KEK, JAEA and Ibaraki University, whose member are originally from the KEK powder group. These three instruments are expected to start in 2008. VSD is a super high intensity diffractometer with the highest resolution of Δd/d = 0.3%. VSD can measure rapid time-dependent phenomena of crystalline materials as well as glass, liquid and amorphous materials. The pair distribution function will be routinely obtained by the Fourier transiformation of S(Q) data. Q range of VSD will be as wide as 0.01 Å-1science and

  5. High-pressure x-ray diffraction of icosahedral Zr-Al-Ni-Cu-Ag quasicrystals

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Saksl, Karel; Rasmussen, Helge Kildahl

    2001-01-01

    The effect of pressure on the structural stability of icosahedral Zr-Al-Ni-Cu-Ag quasicrystals forming from a Zr65Al7.5Ni10Cu7.5Ag10 metallic glass with a supercooled liquid region of 44 K has been investigated by in situ high-pressure angle-dispersive x-ray powder diffraction at ambient temperat...

  6. Neutron diffraction from superparamagnetic colloidal crystals

    Science.gov (United States)

    Ličen, M.; Drevenšek-Olenik, I.; Čoga, L.; Gyergyek, S.; Kralj, S.; Fally, M.; Pruner, C.; Geltenbort, P.; Gasser, U.; Nagy, G.; Klepp, J.

    2017-11-01

    We fabricated a superparamagnetic ordered structure via self-assembly of a colloidal crystal from a suspension of maghemite nanoparticles and polystyrene beads. Such crystals are potential candidates for novel polarizing beam-splitters for cold neutrons, complementing the available methods of neutron polarization. Different bead sizes and nanoparticle concentrations were tested to obtain a crystal of reasonable quality. Neutron diffraction experiments in the presence of an external magnetic field were performed on the most promising sample. We demonstrate that the diffraction efficiency of such crystals can be controlled by the magnetic field. Our measurements also indicate that the Bragg diffraction regime can be reached with colloidal crystals.

  7. Automated high pressure cell for pressure jump x-ray diffraction.

    Science.gov (United States)

    Brooks, Nicholas J; Gauthe, Beatrice L L E; Terrill, Nick J; Rogers, Sarah E; Templer, Richard H; Ces, Oscar; Seddon, John M

    2010-06-01

    A high pressure cell for small and wide-angle x-ray diffraction measurements of soft condensed matter samples has been developed, incorporating a fully automated pressure generating network. The system allows both static and pressure jump measurements in the range of 0.1-500 MPa. Pressure jumps can be performed as quickly as 5 ms, both with increasing and decreasing pressures. Pressure is generated by a motorized high pressure pump, and the system is controlled remotely via a graphical user interface to allow operation by a broad user base, many of whom may have little previous experience of high pressure technology. Samples are loaded through a dedicated port allowing the x-ray windows to remain in place throughout an experiment; this facilitates accurate subtraction of background scattering. The system has been designed specifically for use at beamline I22 at the Diamond Light Source, United Kingdom, and has been fully integrated with the I22 beamline control systems.

  8. High-pressure powder x-ray diffraction experiments on Zn at low temperature

    CERN Document Server

    Takemura, K; Fujihisa, H; Kikegawa, T

    2002-01-01

    High-pressure powder x-ray diffraction experiments have been performed on Zn with a He-pressure medium at low temperature. When the sample was compressed in the He medium at low temperature, large nonhydrostaticity developed, yielding erroneous lattice parameters. On the other hand, when the pressure was changed at high temperatures, good hydrostaticity was maintained. No anomaly in the volume dependence of the c/a axial ratio has been found.

  9. High pressure x-ray diffraction study of nickel-copper chromites solid solutions

    Science.gov (United States)

    Mikheykin, A. S.; Torgashev, V. I.; Talanov, V. M.; Bush, A. A.; Chernyshov, D.; Yuzyuk, I. Yu; Dmitriev, V. P.

    2014-12-01

    A high-pressure synchrotron radiation diffraction study has been carried out on Ni1-xCuxCr2O4 solid solutions. Observed pressure-controlled phase transitions, along with data previously collected for temperature-induced phase transitions, are analyzed in the framework of the unified phenomenological model that results in mapping of the generic phase diagram for the whole family of Ni1-xCuxCr2O4 solid solutions.

  10. Feasibility study neutron diffraction at IRI

    Energy Technology Data Exchange (ETDEWEB)

    Haan, V.O. de

    1995-06-01

    Although neutron diffraction is a basic and relatively simple technique and should be available at a neutron source, it is not possible to perform neutron diffraction measurements at IRI at this moment. Until recently a neutron diffractometer with a relatively small flux at the sample position and a relaxed resolution (designed for liquid diffraction) was operated at IRI. Due to the modest neutron source intensity and the relatively old design (flat monochromator and single detector) this diffractometer was outdated. However, at a contemporary reactor source an instrument to perform neutron diffraction experiments cannot be missed. This study shows that thanks to recent developments in neutron diffraction optics it is possible to increase the flux, to enhance the resolution and to get a better flexibility. If also the number of detectors is increased or a position-sensitive detector is used to performance can be increased at least a thousand fold. A preliminary design is given to indicate how this gain can be realized. (orig.).

  11. Neutron forward diffraction by single crystal prisms

    Indian Academy of Sciences (India)

    Abstract. We have derived analytic expressions for the deflection as well as transmitted fraction of monochromatic neutrons forward diffracted by a single crystal prism. In the vicinity of a Bragg reflection, the neutron deflection deviates sharply from that for an amorphous prism, exhibiting three orders of magnitude greater ...

  12. High pressure in situ diffraction studies of metal-hydrogen systems

    Energy Technology Data Exchange (ETDEWEB)

    Yartys, V.A., E-mail: volodymyr.yartys@ife.no [Institute for Energy Technology, Kjeller NO 2027 (Norway); Norwegian University of Science and Technology, Trondheim NO 7491 (Norway); Denys, R.V. [Institute for Energy Technology, Kjeller NO 2027 (Norway); Karpenko Physico-Mechanical Institute, NAS of Ukraine, Lviv 79601 (Ukraine); Webb, C.J. [Queensland Micro- and Nanotechnology Centre, Griffith University (Australia); Maehlen, J.P. [Institute for Energy Technology, Kjeller NO 2027 (Norway); Gray, E. MacA.; Blach, T. [Queensland Micro- and Nanotechnology Centre, Griffith University (Australia); Isnard, O. [Institute Neel, CNRS/UJF, 38042 Grenoble (France); Barnsley, L.C. [Queensland Micro- and Nanotechnology Centre, Griffith University (Australia)

    2011-09-15

    Research highlights: > CeNi{sub 5}-D{sub 2} and Zr(Fe,Al){sub 2}-D{sub 2} systems were studied by in situ NPD at P up to 1000 bar. > In the hexagonal CeNi{sub 5}D{sub 6.3} deuterium atoms fill three types of interstices. > In the Zr(Fe,Al){sub 2}-based deuterides D atoms occupy the Zr(Fe,Al){sub 2} tetrahedra only D/Zr(Fe,Al){sub 2}, hysteresis and hydrides stability systematically change with Al content. - Abstract: 'Hybrid' hydrogen storage, where hydrogen is stored in both the solid material and as a high pressure gas in the void volume of the tank can improve overall system efficiency by up to 50% compared to either compressed hydrogen or solid materials alone. Thermodynamically, high equilibrium hydrogen pressures in metal-hydrogen systems correspond to low enthalpies of hydrogen absorption-desorption. This decreases the calorimetric effects of the hydride formation-decomposition processes which can assist in achieving high rates of heat exchange during hydrogen loading-removing the bottleneck in achieving low charging times and improving overall hydrogen storage efficiency of large hydrogen stores. Two systems with hydrogenation enthalpies close to -20 kJ/mol H{sub 2} were studied to investigate the hydrogenation mechanism and kinetics: CeNi{sub 5}-D{sub 2} and ZrFe{sub 2-x}Al{sub x} (x = 0.02; 0.04; 0.20)-D{sub 2}. The structure of the intermetallics and their hydrides were studied by in situ neutron powder diffraction at pressures up to 1000 bar and complementary X-ray diffraction. The deuteration of the hexagonal CeNi{sub 5} intermetallic resulted in CeNi{sub 5}D{sub 6.3} with a volume expansion of 30.1%. Deuterium absorption filled three different types of interstices, Ce{sub 2}Ni{sub 2} and Ni{sub 4} tetrahedra, and Ce{sub 2}Ni{sub 3} half-octahedra and was accompanied by a valence change for Ce. Significant hysteresis was observed between deuterium absorption and desorption which profoundly decreased on a second absorption cycle. For the Al

  13. Quantitative phase analysis by neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Chang Hee; Song, Su Ho; Lee, Jin Ho; Shim, Hae Seop [Korea Atomic Energy Research Institute, Taejon (Korea)

    1999-06-01

    This study is to apply quantitative phase analysis (QPA) by neutron diffraction to the round robin samples provided by the International Union of Crystallography(IUCr). We measured neutron diffraction patterns for mixed samples which have several different weight percentages and their unique characteristic features. Neutron diffraction method has been known to be superior to its complementary methods such as X-ray or Synchrotron, but it is still accepted as highly reliable under limited conditions or samples. Neutron diffraction has strong capability especially on oxides due to its scattering cross-section of the oxygen and it can become a more strong tool for analysis on the industrial materials with this quantitative phase analysis techniques. By doing this study, we hope not only to do one of instrument performance tests on our HRPD but also to improve our ability on the analysis of neutron diffraction data by comparing our QPA results with others from any advanced reactor facilities. 14 refs., 4 figs., 6 tabs. (Author)

  14. High Pressure X-ray Diffraction Study on Icosahedral Boron Arsenide (B12As2)

    Energy Technology Data Exchange (ETDEWEB)

    J Wu; H Zhu; D Hou; C Ji; C Whiteley; J Edgar; Y Ma

    2011-12-31

    The high pressure properties of icosahedral boron arsenide (B12As2) were studied by in situ X-ray diffraction measurements at pressures up to 25.5 GPa at room temperature. B12As2 retains its rhombohedral structure; no phase transition was observed in the pressure range. The bulk modulus was determined to be 216 GPa with the pressure derivative 2.2. Anisotropy was observed in the compressibility of B12As2-c-axis was 16.2% more compressible than a-axis. The boron icosahedron plays a dominant role in the compressibility of boron-rich compounds.

  15. High-pressure cell for neutron reflectometry of supercritical and subcritical fluids at solid interfaces.

    Science.gov (United States)

    Carmichael, Justin R; Rother, Gernot; Browning, James F; Ankner, John F; Banuelos, Jose L; Anovitz, Lawrence M; Wesolowski, David J; Cole, David R

    2012-04-01

    A new high-pressure cell design for use in neutron reflectometry (NR) for pressures up to 50 MPa and a temperature range of 300-473 K is described. The cell design guides the neutron beam through the working crystal without passing through additional windows or the bulk fluid, which provides for a high neutron transmission, low scattering background, and low beam distortion. The o-ring seal is suitable for a wide range of subcritical and supercritical fluids and ensures high chemical and pressure stability. Wafers with a diameter of 5.08 cm (2 in.) and 5 mm or 10 mm thickness can be used with the cells, depending on the required pressure and momentum transfer range. The fluid volume in the sample cell is very small at about 0.1 ml, which minimizes scattering background and stored energy. The cell design and pressure setup for measurements with supercritical fluids are described. NR data are shown for silicon/silicon oxide and quartz wafers measured against air and subsequently within the high-pressure cell to demonstrate the neutron characteristics of the high-pressure cell. Neutron reflectivity data for supercritical CO(2) in contact with quartz and Si/SiO(2) wafers are also shown. © 2012 American Institute of Physics

  16. High-pressure cell for neutron reflectometry of supercritical and subcritical fluids at solid interfaces

    Science.gov (United States)

    Carmichael, Justin R.; Rother, Gernot; Browning, James F.; Ankner, John F.; Banuelos, Jose L.; Anovitz, Lawrence M.; Wesolowski, David J.; Cole, David R.

    2012-04-01

    A new high-pressure cell design for use in neutron reflectometry (NR) for pressures up to 50 MPa and a temperature range of 300-473 K is described. The cell design guides the neutron beam through the working crystal without passing through additional windows or the bulk fluid, which provides for a high neutron transmission, low scattering background, and low beam distortion. The o-ring seal is suitable for a wide range of subcritical and supercritical fluids and ensures high chemical and pressure stability. Wafers with a diameter of 5.08 cm (2 in.) and 5 mm or 10 mm thickness can be used with the cells, depending on the required pressure and momentum transfer range. The fluid volume in the sample cell is very small at about 0.1 ml, which minimizes scattering background and stored energy. The cell design and pressure setup for measurements with supercritical fluids are described. NR data are shown for silicon/silicon oxide and quartz wafers measured against air and subsequently within the high-pressure cell to demonstrate the neutron characteristics of the high-pressure cell. Neutron reflectivity data for supercritical CO2 in contact with quartz and Si/SiO2 wafers are also shown.

  17. Cryogenic x-ray diffraction microscopy utilizing high-pressure cryopreservation

    Science.gov (United States)

    Lima, Enju; Chushkin, Yuriy; van der Linden, Peter; Kim, Chae Un; Zontone, Federico; Carpentier, Philippe; Gruner, Sol M.; Pernot, Petra

    2014-10-01

    We present cryo x-ray diffraction microscopy of high-pressure-cryofixed bacteria and report high-convergence imaging with multiple image reconstructions. Hydrated D. radiodurans cells were cryofixed at 200 MPa pressure into ˜10-μm-thick water layers and their unstained, hydrated cellular environments were imaged by phasing diffraction patterns, reaching sub-30-nm resolutions with hard x-rays. Comparisons were made with conventional ambient-pressure-cryofixed samples, with respect to both coherent small-angle x-ray scattering and the image reconstruction. The results show a correlation between the level of background ice signal and phasing convergence, suggesting that phasing difficulties with frozen-hydrated specimens may be caused by high-background ice scattering.

  18. Neutron Powder Diffraction and Constrained Refinement

    DEFF Research Database (Denmark)

    Pawley, G. S.; Mackenzie, Gordon A.; Dietrich, O. W.

    1977-01-01

    The first use of a new program, EDINP, is reported. This program allows the constrained refinement of molecules in a crystal structure with neutron diffraction powder data. The structures of p-C6F4Br2 and p-C6F4I2 are determined by packing considerations and then refined with EDINP. Refinement...

  19. Strength and structural phase transitions of gadolinium at high pressure from radial X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Xiong, Lun, E-mail: xionglun@ihep.ac.cn; Liu, Jing; Bai, Ligang; Li, Xiaodong; Lin, Chuanlong [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Lin, Jung-Fu [Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Texas 78712 (United States)

    2014-12-28

    Lattice strength and structural phase transitions of gadolinium (Gd) were determined under nonhydrostatic compression up to 55 GPa using an angle-dispersive radial x-ray diffraction technique in a diamond-anvil cell at room temperature. Three new phases of fcc structure, dfcc structure, and new monoclinic structure were observed at 25 GPa, 34 GPa, and 53 GPa, respectively. The radial x-ray diffraction data yield a bulk modulus K{sub 0} = 36(1) GPa with its pressure derivate K{sub 0}′ = 3.8(1) at the azimuthal angle between the diamond cell loading axis and the diffraction plane normal and diffraction plane ψ = 54.7°. With K{sub 0}′ fixed at 4, the derived K{sub 0} is 34(1) GPa. In addition, analysis of diffraction data with lattice strain theory indicates that the ratio of differential stress to shear modulus (t/G) ranges from 0.011 to 0.014 at pressures of 12–55 GPa. Together with estimated high-pressure shear moduli, our results show that Gd can support a maximum differential stress of 0.41 GPa, while it starts to yield to plastic deformation at 16 GPa under uniaxial compression. The yield strength of Gd remains approximately a constant with increasing pressure, and reaches 0.46 GPa at 55 GPa.

  20. Scientific Advancements and Technological Developments of High P-T Neutron Diffraction at LANSCE, Los Alamos

    Science.gov (United States)

    Zhao, Y.; Daemen, L. L.; Zhang, J.

    2003-12-01

    In-situ high P-T neutron diffraction experiments provide unique opportunities to study the crystal structure, hydrogen bonding, magnetism, and thermal parameters of light elements (eg. H, Li, B) and heavy elements (eg. Ta, U, Pu,), that are virtually impossible to determine with x-ray diffraction techniques. For example, thermoelasticity and Debye-Waller factor as function of pressure and temperature can be derived using in-situ high P-T neutron diffraction techniques. These applications can also be extended to a much broader spectrum of scientific problems. For instance, puzzles in Earth science such as the carbon cycle and the role of hydrous minerals for water exchange between lithosphere and biosphere can be directly addressed. Moreover, by introducing in-situ shear, texture of metals and minerals accompanied with phase transitions at high P-T conditions can also be studied by high P-T neutron diffraction. We have successfully conducted high P-T neutron diffraction experiments at LANSCE and achieved simultaneous high pressures and temperatures of 10 GPa and 1500 K. With an average 3-6 hours of data collection, the diffraction data are of sufficiently high quality for the determination of structural parameters and thermal vibrations. We have studied hydrous mineral (MgOD), perovskite (K.15,Na.85)MgF3, clathrate hydrates (CH4-, CO2-, and H2-), metals (Mo, Al, Zr), and amorphous materials (carbon black, BMG). The aim of our research is to accurately map bond lengths, bond angles, neighboring atomic environments, and phase stability in P-T-X space. Studies based on high-pressure neutron diffraction are important for multi-disciplinary science and we welcome researchers from all fields to use this advanced technique. We have developed a 500-ton toroidal press, TAP-98, to conduct simultaneous high P-T neutron diffraction experiments inside of HIPPO (High-Pressure and Preferred-Orientation diffractometer). We have also developed a large gem-crystal anvil cell, ZAP-01

  1. High-pressure X-ray diffraction study of bulk- and nanocrystalline GaN

    DEFF Research Database (Denmark)

    Jorgensen, J.E.; Jakobsen, J.M.; Jiang, Jianzhong

    2003-01-01

    Bulk- and nanocrystalline GaN have been studied by high-pressure energy-dispersive X-ray diffraction. Pressure-induced structural phase transitions from the wurtzite to the NaCl phase were observed in both materials. The transition pressure was found to be 40 GPa for the bulk-crystalline GaN, while...... the wurtzite phase was retained up to 60 GPa in the case of nanocrystalline GaN. The bulk moduli for the wurtzite phases were determined to be 187 ( 7) and 319 ( 10) GPa for the bulk- and nanocrystalline phases, respectively, while the respective NaCl phases were found to have very similar bulk moduli [ 208...

  2. Applications of TOF neutron diffraction in archaeometry

    Science.gov (United States)

    Kockelmann, W.; Siano, S.; Bartoli, L.; Visser, D.; Hallebeek, P.; Traum, R.; Linke, R.; Schreiner, M.; Kirfel, A.

    2006-05-01

    Neutron radiation meets the demand for a versatile diagnostic probe for collecting information from the interior of large, undisturbed museum objects or archaeological findings. Neutrons penetrate through coatings and corrosion layers deep into centimetre-thick materials, a property that makes them ideal for non-destructive examination of objects for which sampling is impractical or unacceptable. A particular attraction of neutron techniques for archaeologists and conservation scientists is the prospect of locating hidden materials and structures inside objects. Time-of-flight (TOF) neutron diffraction allows for the examination of mineral and metal phase contents, crystal structures, grain orientations, and microstructures as well as micro- and macro strains. A promising application is texture analysis which may provide clues to the deformation history of the material, and hence to specific working processes. Here we report on instructive examples of TOF neutron diffraction, including phase analyses of medieval Dutch tin-lead spoons, texture analyses of bronze specimens as well as of 16th-century silver coins.

  3. Data processing method for neutron diffraction experiments

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez Palomino, L.A. [Consejo Nacional de Investigaciones Cientificas y Tecnicas, Centro Atomico Bariloche, Instituto Balseiro, Comision Nacional de Energia Atomica, Universidad Nacional de Cuyo, 8400 Bariloche (Argentina); Dawidowski, J. [Consejo Nacional de Investigaciones Cientificas y Tecnicas, Centro Atomico Bariloche, Instituto Balseiro, Comision Nacional de Energia Atomica, Universidad Nacional de Cuyo, 8400 Bariloche (Argentina)]. E-mail: javier@cab.cnea.gov.ar; Blostein, J.J. [Consejo Nacional de Investigaciones Cientificas y Tecnicas, Centro Atomico Bariloche, Instituto Balseiro, Comision Nacional de Energia Atomica, Universidad Nacional de Cuyo, 8400 Bariloche (Argentina); Cuello, G.J. [Institut Laue Langevin, Boite Postale 156, F-38042 Grenoble Cedex 9 (France)

    2007-05-15

    We present a procedure to perform multiple scattering, attenuation and efficiency corrections in reactor neutron diffraction experiments, based on a Monte Carlo code applied iteratively. We discuss the application of two procedures, the first based on Granada's synthetic model, useful for incoherent scatterers, and the second, based on the measured experimental distributions for coherent scatterers. Experiments on samples of polyethylene, light water, heavy water and Teflon of different sizes were performed and the correction procedures are tested. The problem of normalization in an absolute scale in diffraction experiments is addressed and results obtained from the present procedure are shown.

  4. DNA hydration studied by neutron fiber diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Fuller, W.; Forsyth, V.T.; Mahendrasingam, A.; Langan, P.; Pigram, W.J. [Keele Univ. (United Kingdom)] [and others

    1994-12-31

    The development of neutron high angle fiber diffraction to investigate the location of water around the deoxyribonucleic acid (DNA) double-helix is described. The power of the technique is illustrated by its application to the D and A conformations of DNA using the single crystal diffractometer, D19, at the Institute Laue-Langevin, Grenoble and the time of flight diffractometer, SXD, at the Rutherford Appleton ISIS Spallation Neutron Source. These studies show the existence of bound water closely associated with the DNA. The patterns of hydration in these two DNA conformations are quite distinct and are compared to those observed in X-ray single crystal studies of two-stranded oligodeoxynucleotides. Information on the location of water around the DNA double-helix from the neutron fiber diffraction studies is combined with that on the location of alkali metal cations from complementary X-ray high angle fiber diffraction studies at the Daresbury Laboratory SRS using synchrotron radiation. These analyses emphasize the importance of viewing DNA, water and ions as a single system with specific interactions between the three components and provide a basis for understanding the effect of changes in the concentration of water and ions in inducing conformations] transitions in the DNA double-helix.

  5. Workshop on industrial application of neutron diffraction. Stress measurement by neutron diffraction

    CERN Document Server

    Minakawa, N; Morii, Y; Oyama, Y

    2002-01-01

    This workshop was planned to make use of the neutron from the reactor and the pulse neutron source JSNS for the industrial world. Especially, this workshop focused on the stress measurement by the neutron diffraction and it was held on the Tokai JAERI from October 15 to 16, 2001. The participant total was 93 and 40 participated from the industrial world. The introduction of the residual stress development of measurement technique by the neutron diffraction method and a research of the measurement of the residual stress such as the nuclear reactor material, the ordinary structure material, the composite material, the quenching steel, the high strength material were presented and discussed in this workshop. Moreover, it was introduced for the industrial world that an internal stress measurement is important for development of new product or an improvement of a manufacturing process. The question from the industrial world about which can be measured the product form, the size, the measurement precision, the reso...

  6. Safety analysis of high pressure 3He-filled micro-channels for thermal neutron detection.

    Energy Technology Data Exchange (ETDEWEB)

    Ferko, Scott M.; Galambos, Paul C.; Derzon, Mark Steven; Renzi, Ronald F.

    2008-11-01

    This document is a safety analysis of a novel neutron detection technology developed by Sandia National Laboratories. This technology is comprised of devices with tiny channels containing high pressure {sup 3}He. These devices are further integrated into large scale neutron sensors. Modeling and preliminary device testing indicates that the time required to detect the presence of special nuclear materials may be reduced under optimal conditions by several orders of magnitude using this approach. Also, these devices make efficient use of our {sup 3}He supply by making individual devices more efficient and/or extending the our limited {sup 3}He supply. The safety of these high pressure devices has been a primary concern. We address these safety concerns for a flat panel configuration intended for thermal neutron detection. Ballistic impact tests using 3 g projectiles were performed on devices made from FR4, Silicon, and Parmax materials. In addition to impact testing, operational limits were determined by pressurizing the devices either to failure or until they unacceptably leaked. We found that (1) sympathetic or parasitic failure does not occur in pressurized FR4 devices (2) the Si devices exhibited benign brittle failure (sympathetic failure under pressure was not tested) and (3) the Parmax devices failed unacceptably. FR4 devices were filled to pressures up to 4000 + 100 psig, and the impacts were captured using a high speed camera. The brittle Si devices shattered, but were completely contained when wrapped in thin tape, while the ductile FR4 devices deformed only. Even at 4000 psi the energy density of the compressed gas appears to be insignificant compared to the impact caused by the incoming projectile. In conclusion, the current FR4 device design pressurized up to 4000 psi does not show evidence of sympathetic failure, and these devices are intrinsically safe.

  7. Neutron diffraction studies of thin film multilayer structures

    Energy Technology Data Exchange (ETDEWEB)

    Majkrzak, C.F.

    1985-01-01

    The application of neutron diffraction methods to the study of the microscopic chemical and magnetic structures of thin film multilayers is reviewed. Multilayer diffraction phenomena are described in general and in particular for the case in which one of the materials of a bilayer is ferromagnetic and the neutron beam polarized. Recent neutron diffraction measurements performed on some interesting multilayer systems are discussed. 70 refs., 5 figs.

  8. A cryogenic high pressure cell for inelastic neutron scattering measurements of quantum fluids and solids.

    Science.gov (United States)

    Carmichael, J R; Diallo, S O

    2013-01-01

    We present our new development of a high pressure cell for inelastic neutron scattering measurements of helium at ultra-low temperatures. The cell has a large sample volume of ~140 cm(3) and a working pressure of ~7 MPa, with a relatively thin wall-thickness (1.1 mm)--thanks to the high yield strength aluminum used in the design. Two variants of this cell have been developed. The first cell is permanently joined components using electron-beam welding and explosion welding, methods that have little or no impact on the global heat treatment of the cell. The second cell discussed has modular and interchangeable components, which includes a capacitance pressure gauge, that can be sealed using the traditional indium wire technique. The performance of the cells have been tested in recent measurements on superfluid liquid helium near the solidification line.

  9. A high-pressure vessel for X-ray diffraction experiments for liquids in a wide temperature range

    CERN Document Server

    Hosokawa, S

    2001-01-01

    An internally heated high-pressure vessel was developed for angle-dispersive X-ray scattering experiments on liquids at high-temperatures and high-pressures. It consists of a closed-end Al cylinder and a steel flange. Continuous windows made of Be cover a scattering angle range up to 55 deg. In combination with a single-crystal sapphire cell and a small heating system inside the vessel, we were able to carry out diffraction measurements for liquids in a wide temperature range up to 2000 K at high pressures up to 150 bars. Some of our recent X-ray scattering experiments using synchrotron radiation, such as inelastic scattering, high-energy elastic scattering, and anomalous scattering, are also reported.

  10. The dynamic response of high pressure phase of Si using phase contrast imaging and X-ray diffraction

    Science.gov (United States)

    Lee, H. J.; Galtier, E.; Xing, Z.; Gleason, A.; Granados, E.; Tavella, F.; Schropp, A.; Seiboth, F.; Schroer, C.; Higginbotham, A.; Brown, S.; Arnold, B.; Curiel, R.; Peterswright, D.; Fry, A.; Nagler, B.

    2015-11-01

    Static compression studies have revealed that crystalline silicon undergoes phase transitions from a cubic diamond structure to a variety of phases including body-centered tetragonal phase, an orthorhombic phase, and a hexagonal primitive phase. However, the dynamic response of silicon at high pressure is not well understood. Phase contrast imaging has proven to be a powerful tool for probing density changes caused by the shock propagation into a material. With respect to the elastic and plastic compression, we image shock waves in Si with high spatial resolution using the LCLS X-ray free electron laser and Matter in Extreme Conditions instrument. In this study, the long pulse optical laser with pseudoflat top shape creates high pressures up to 60 GPa. We also measure the crystal structure by observing the X-ray diffraction orthogonal to the shock propagation direction over a range of pressure. In this talk, we will present the capability of simultaneously performing phase contrast imaging and in situ X-ray diffraction during shock loading and will discuss the dynamic response of Si in high pressure phases

  11. A new bridge technique for neutron tomography and diffraction measurements

    Energy Technology Data Exchange (ETDEWEB)

    Burca, G., E-mail: G.Burca@open.ac.uk [Materials Engineering, Open University, Milton Keynes, MK7 6AA (United Kingdom); James, J.A. [Materials Engineering, Open University, Milton Keynes, MK7 6AA (United Kingdom); Kockelmann, W. [ISIS Facility, STFC, Rutherford Appleton Laboratory, Chilton, OX11 0QX (United Kingdom); Fitzpatrick, M.E. [Materials Engineering, Open University, Milton Keynes, MK7 6AA (United Kingdom); Zhang, S.Y. [ISIS Facility, STFC, Rutherford Appleton Laboratory, Chilton, OX11 0QX (United Kingdom); Hovind, J. [Paul Scherrer Institute (PSI), CH-5232, Villigen (Switzerland); Langh, R. van [Delft University of Technology, Department of Materials Science, Faculty 3mE, Mekelweg 2, 2628 CD Delft (Netherlands); Rijksmuseum Amsterdam, P.O. Box 74888, 1070 DN Amsterdam (Netherlands)

    2011-09-21

    An attractive feature of neutron techniques is the ability to identify hidden materials and structures inside engineering components and objects of art and archaeology. Bearing this in mind we are investigating a new technique, 'Tomography Driven Diffraction' (TDD), that exploits tomography data to guide diffraction experiments on samples with complex structures and shapes. The technique can be used utilising combinations of individual tomography and diffraction instruments, such as NEUTRA (PSI, CH) and ENGIN-X (ISIS, UK), but is also suitable for new combined imaging and diffraction instruments such as the JEEP synchrotron engineering instrument (DIAMOND, UK) and the proposed IMAT neutron imaging and diffraction instrument (ISIS, UK).

  12. X-ray diffraction and electroresistance measurements under high pressure and temperature using a large-volume cell

    Energy Technology Data Exchange (ETDEWEB)

    Principi, E; Minicucci, M [CNISM, CNR-INFM SOFT and Dipartimento di Fisica Universita degli Studi di Camerino via Madonna delle Carceri 62032, Camerino (Italy); Di Cicco, A

    2008-07-15

    In this communication we report about original experimental techniques for in-house x-ray diffraction and electrical resistance measurements under high-temperature and high pressure conditions, using large volume cells in the opposite anvil recessed geometry. The high-pressure devices we are currently using are a compact Paris-Edinburgh (PE) V5 150 Tons press and a 50 Tons standard hydraulic press, coupled usually with WC anvils and 10 mm or 7 mm boron-epoxy or pyrophyllite biconical gaskets for x-ray diffraction and resistance measurements respectively. Limiting pressures, using such a non-toroidal sample assembly and WC anvils, are about 10 GPa on samples of large sizes (10-20 mm{sup 3}). Samples can be heated using an hollow graphite cylinder as a crucible reaching temperatures as high as 2300 K, while the temperature can be measured up to 1300 K by using a K-type thermocouple. The highly automated setup developed for resistance measurements is described in details. In particular, we present electroresistance measurements of Bi melting under pressure and measurements of the Ge and LiF EOS (equation of state) at high temperature and pressure obtained using x-ray diffraction showing the sensitivity of the techniques. The relevance of these experiments to the exploitation of the potential of equipments available at synchrotron radiation facilities is emphasized.

  13. A CCD area detector for X-ray diffraction under high pressure for ...

    Indian Academy of Sciences (India)

    Details of a two-dimensional X-ray area detector developed using a charge coupled device, a image intensifier and a fibre optic taper are given. The detector system is especially optimized for angle dispersive X-ray diffraction set up using rotating anode generator as X-ray source. The performance of this detector was ...

  14. A CCD area detector for X-ray diffraction under high pressure for ...

    Indian Academy of Sciences (India)

    Unknown

    Abstract. Details of a two-dimensional X-ray area detector developed using a charge coupled device, a image intensifier and a fibre optic taper are given. The detector system is especially optimized for angle dispersive X-ray diffraction set up using rotating anode generator as X-ray source. The performance of this detector ...

  15. High-pressure X-ray diffraction of L-ALANINE crystal

    DEFF Research Database (Denmark)

    Olsen, J.S.; Gerward, Leif; Souza, A.G.

    2006-01-01

    L-ALANINE has been studied by X-ray diffraction at ambient temperature and pressure up to 10.3 GPa. The material is found to transform to a tetragonal structure between 2 and 3 GPa. and to a monoclinic structure between 8 and 10 GPa. The experimental bulk modulus is 25(5) GPa for the orthorhombic...

  16. High-pressure X-ray diffraction and Raman scattering of LiTaO sub 3

    CERN Document Server

    Zhang Wei; Pan Yue Wu; Dong Shu Shan; Zou Guang Tian; Liu Jing

    2002-01-01

    The authors study the energy-dispersive x-ray diffraction and Raman scattering of LiTaO sub 3 at high pressure. The result remains stable up to 36 GPa. The average isothermal bulk modulus and its pressure derivative are obtained to be k sub 0 =(225 +- 6) GPa and k sub 0 '=1.3 +- 0.5 at zero pressure by the Birch-Murnaghan equation of state and the 'universal' equation of state. The linear incompressibility of LiTaO sub 3 between the a- and c-directions differs by a factor of four, which shows that the compression is anisotropic

  17. High pressure Laue diffraction and its application to study microstructural changes during the α → β phase transition in Si.

    Science.gov (United States)

    Popov, D; Park, C; Kenney-Benson, C; Shen, G

    2015-07-01

    An approach using polychromatic x-ray Laue diffraction is described for studying pressure induced microstructural changes of materials under pressure. The advantages of this approach with respect to application of monochromatic x-ray diffraction and other techniques are discussed. Experiments to demonstrate the applications of the method have been performed on the α → β phase transition in Si at high pressures using a diamond anvil cell. We present the characterization of microstructures across the α-β phase transition, such as morphology of both the parent and product phases, relative orientation of single-crystals, and deviatoric strains. Subtle inhomogeneous strain of the single-crystal sample caused by lattice rotations becomes detectable with the approach.

  18. Prospect for application of compact accelerator-based neutron source to neutron engineering diffraction

    Science.gov (United States)

    Ikeda, Yoshimasa; Taketani, Atsushi; Takamura, Masato; Sunaga, Hideyuki; Kumagai, Masayoshi; Oba, Yojiro; Otake, Yoshie; Suzuki, Hiroshi

    2016-10-01

    A compact accelerator-based neutron source has been lately discussed on engineering applications such as transmission imaging and small angle scattering as well as reflectometry. However, nobody considers using it for neutron diffraction experiment because of its low neutron flux. In this study, therefore, the neutron diffraction experiments are carried out using Riken Accelerator-driven Compact Neutron Source (RANS), to clarify the capability of the compact neutron source for neutron engineering diffraction. The diffraction pattern from a ferritic steel was successfully measured by suitable arrangement of the optical system to reduce the background noise, and it was confirmed that the recognizable diffraction pattern can be measured by a large sampling volume with 10 mm in cubic for an acceptable measurement time, i.e. 10 min. The minimum resolution of the 110 reflection for RANS is approximately 2.5% at 8 μs of the proton pulse width, which is insufficient to perform the strain measurement by neutron diffraction. The moderation time width at the wavelength corresponding to the 110 reflection is estimated to be approximately 30 μs, which is the most dominant factor to determine the resolution. Therefore, refinements of the moderator system to decrease the moderation time by decreasing a thickness of the moderator or by applying the decoupler system or application of the angular dispersive neutron diffraction technique are important to improve the resolution of the diffraction experiment using the compact neutron source. In contrast, the texture evolution due to plastic deformation was successfully observed by measuring a change in the diffraction peak intensity by RANS. Furthermore, the volume fraction of the austenitic phase in the dual phase mock specimen was also successfully evaluated by fitting the diffraction pattern using a Rietveld code. Consequently, RANS has been proved to be capable for neutron engineering diffraction aiming for the easy access

  19. Prospect for application of compact accelerator-based neutron source to neutron engineering diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Ikeda, Yoshimasa, E-mail: yoshimasa.ikeda@riken.jp [Center for Advanced Photonics, RIKEN, Wako, Saitama 351-0198 (Japan); Taketani, Atsushi; Takamura, Masato; Sunaga, Hideyuki [Center for Advanced Photonics, RIKEN, Wako, Saitama 351-0198 (Japan); Kumagai, Masayoshi [Faculty of Engineering, Tokyo City University, Setagaya, Tokyo 158-8857 (Japan); Oba, Yojiro [Research Reactor Institute, Kyoto University, Kumatori, Osaka 590-0494 (Japan); Otake, Yoshie [Center for Advanced Photonics, RIKEN, Wako, Saitama 351-0198 (Japan); Suzuki, Hiroshi [Materials Sciences Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan)

    2016-10-11

    A compact accelerator-based neutron source has been lately discussed on engineering applications such as transmission imaging and small angle scattering as well as reflectometry. However, nobody considers using it for neutron diffraction experiment because of its low neutron flux. In this study, therefore, the neutron diffraction experiments are carried out using Riken Accelerator-driven Compact Neutron Source (RANS), to clarify the capability of the compact neutron source for neutron engineering diffraction. The diffraction pattern from a ferritic steel was successfully measured by suitable arrangement of the optical system to reduce the background noise, and it was confirmed that the recognizable diffraction pattern can be measured by a large sampling volume with 10 mm in cubic for an acceptable measurement time, i.e. 10 min. The minimum resolution of the 110 reflection for RANS is approximately 2.5% at 8 μs of the proton pulse width, which is insufficient to perform the strain measurement by neutron diffraction. The moderation time width at the wavelength corresponding to the 110 reflection is estimated to be approximately 30 μs, which is the most dominant factor to determine the resolution. Therefore, refinements of the moderator system to decrease the moderation time by decreasing a thickness of the moderator or by applying the decoupler system or application of the angular dispersive neutron diffraction technique are important to improve the resolution of the diffraction experiment using the compact neutron source. In contrast, the texture evolution due to plastic deformation was successfully observed by measuring a change in the diffraction peak intensity by RANS. Furthermore, the volume fraction of the austenitic phase in the dual phase mock specimen was also successfully evaluated by fitting the diffraction pattern using a Rietveld code. Consequently, RANS has been proved to be capable for neutron engineering diffraction aiming for the easy access

  20. In situ X-ray diffraction environments for high-pressure reactions

    DEFF Research Database (Denmark)

    R. S. Hansen, Bjarne; Møller, Kasper Trans; Paskevicius, Mark

    2015-01-01

    New sample environments and techniques specifically designed for in situ powder X-ray diffraction studies up to 1000 bar (1 bar = 105 Pa) gas pressure are reported and discussed. The cells can be utilized for multiple purposes in a range of research fields. Specifically, investigations of gas......–solid reactions and sample handling under inert conditions are undertaken here. Sample containers allowing the introduction of gas from one or both ends are considered, enabling the possibility of flow-through studies. Various containment materials are evaluated, e.g. capillaries of single-crystal sapphire (Al2O3...

  1. Innovative high pressure gas MEM's based neutron detector for ICF and active SNM detection.

    Energy Technology Data Exchange (ETDEWEB)

    Martin, Shawn Bryan; Derzon, Mark Steven; Renzi, Ronald F.; Chandler, Gordon Andrew

    2007-12-01

    An innovative helium3 high pressure gas detection system, made possible by utilizing Sandia's expertise in Micro-electrical Mechanical fluidic systems, is proposed which appears to have many beneficial performance characteristics with regards to making these neutron measurements in the high bremsstrahlung and electrical noise environments found in High Energy Density Physics experiments and especially on the very high noise environment generated on the fast pulsed power experiments performed here at Sandia. This same system may dramatically improve active WMD and contraband detection as well when employed with ultrafast (10-50 ns) pulsed neutron sources.

  2. A high pressure cell for simultaneous osmotic pressure and x-ray diffraction measurements

    Science.gov (United States)

    Gauthé, Béatrice L. L. E.; Heron, Andrew J.; Seddon, John M.; Ces, Oscar; Templer, Richard H.

    2009-03-01

    In this paper, we report on a novel osmotic cell, developed to simultaneously subject a sample to osmotic stress and measure structural changes by small angle x-ray diffraction. The osmotic cell offers many advantages over more conventional methods of osmotically stressing soft materials to measure their structural response. In particular, a full osmotic analysis can be performed with a single small sample (25 μl). This reduces sample handling and the associated systematic errors, as well as enabling tight control and monitoring of the thermodynamic environment during osmosis, thereby increasing measurement precision. The cell design enables control of osmotic pressure to ±0.04 bar over a pressure range of 1-100 bar, and temperature control to ±0.05 °C. Under these conditions, the lattice spacing in lyotropic structures was resolved to better than ±0.005 Å. Using the osmotic cell, we demonstrate good agreement with previous conventional measurements on the energy of dehydrating the fluid lamellar phase of dioleoylphosphatidylcholine in water.

  3. Experimental determination of bulk modulus of 14Å tobermorite using high pressure synchrotron X-ray diffraction

    KAUST Repository

    Oh, Jae Eun

    2012-02-01

    Using a diamond anvil cell, 14 Å tobermorite, a structural analogue of calcium silicate hydrates (C-S-H), was examined by high-pressure synchrotron X-ray diffraction up to 4.8 GPa under hydrostatic conditions. The bulk modulus of 14 Å tobermorite was calculated, K o = 47 GPa. Comparison of the current results with previous high pressure studies on C-S-H(I) indicates that: (1) the compression behavior of the lattice parameters a and b of 14 Å tobermorite and C-S-H(I) are very similar, implying that both materials may have very similar Ca-O layers, and also implying that an introduction of structural defects into the Ca-O layers may not substantially change in-plane incompressibility of the ab plane of 14 Å tobermorite; and (2) the bulk modulus values of 14 Å tobermorite and C-S-H(I) are dominated by the incompressibility of the lattice parameter c, which is directly related to the interlayer spacing composed of dreierketten silicate chains, interlayer Ca, and water molecules. © 2011 Elsevier Ltd. All rights reserved.

  4. Diffraction on disordered materials using 'neutron-like' photons

    DEFF Research Database (Denmark)

    Neuefeind, J.; Poulsen, H.F.

    1995-01-01

    In the past photon diffraction has been carried out mainly using the characteristic radiation from X-ray tubes in the energy range from about 8-20 keV. Comparison of these experiments with neutron diffraction results is difficult since in this energy range the photoelectric absorption is the pred......In the past photon diffraction has been carried out mainly using the characteristic radiation from X-ray tubes in the energy range from about 8-20 keV. Comparison of these experiments with neutron diffraction results is difficult since in this energy range the photoelectric absorption...... is the predominant process. The photoelectric absorption decreases with lambda(3), so increasing the energy to about 100 keV has a drastic effect on the absorption coefficient. Photons in the high energy rang can be obtained conveniently from modern synchrotron sources. High energy photon diffraction has additional...

  5. Examination of the Atomic Pair Distribution Function (PDF) of SiC Nanocrystals by In-situ High Pressure Diffraction

    Science.gov (United States)

    Grzanka, E.; Stelmakh, S.; Gierlotka, S.; Zhao, Y.; Palosz, B.; Palosz, W.

    2003-01-01

    Key properties of nanocrystals are determined by their real atomic structure, therefore a reasonable understanding and meaningful interpretation of their properties requires a realistic model of the structure. In this paper we present an evidence of a complex response of the lattice distances to external pressure indicating a presence of a complex structure of Sic nanopowders. The experiments were performed on nanocrystalline Sic subjected to hydrostatic or isostatic pressure using synchrotron and neutron powder diffraction. Elastic properties of the samples were examined based on X-ray diffraction data using a Diamond Anvil Cell (DAC) in HASYLAB at DESY. The dependence'of the lattice parameters and of the Bragg reflections width with pressure exhibits a ha1 nature of the properties (compressibilities) of the powders and indicates a complex structure of the grains. We interpreted tws behaviour as originating from different elastic properties of the grain interior and surface. Analysis of the dependence of individual interatomic distances on pressure was based on in-situ neutron diffraction measurements done with HbD diffractometer at LANSCE in Los Alamos National Laboratory with the Paris-Edinburgh cell under pressures up to 8 GPa (Qmax = 26/A). Interatomic distances were obtained by PDF analysis using the PDFgetN program. We have found that the interatomic distances undergo a complex, non-monotonic changes. Even under substantial pressures a considerable relaxation of the lattice may take place: some interatomic distances increase with an increase in pressure. We relate this phenomenon to: (1), changes of the microstructure of the densified material, in particular breaking of its fractal chain structure and, (2), its complex structure resembling that of a material composed of two phases, each with its distinct elastic properties.

  6. Maximizing Macromolecule Crystal Size for Neutron Diffraction Experiments

    Science.gov (United States)

    Judge, R. A.; Kephart, R.; Leardi, R.; Myles, D. A.; Snell, E. H.; vanderWoerd, M.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    A challenge in neutron diffraction experiments is growing large (greater than 1 cu mm) macromolecule crystals. In taking up this challenge we have used statistical experiment design techniques to quickly identify crystallization conditions under which the largest crystals grow. These techniques provide the maximum information for minimal experimental effort, allowing optimal screening of crystallization variables in a simple experimental matrix, using the minimum amount of sample. Analysis of the results quickly tells the investigator what conditions are the most important for the crystallization. These can then be used to maximize the crystallization results in terms of reducing crystal numbers and providing large crystals of suitable habit. We have used these techniques to grow large crystals of Glucose isomerase. Glucose isomerase is an industrial enzyme used extensively in the food industry for the conversion of glucose to fructose. The aim of this study is the elucidation of the enzymatic mechanism at the molecular level. The accurate determination of hydrogen positions, which is critical for this, is a requirement that neutron diffraction is uniquely suited for. Preliminary neutron diffraction experiments with these crystals conducted at the Institute Laue-Langevin (Grenoble, France) reveal diffraction to beyond 2.5 angstrom. Macromolecular crystal growth is a process involving many parameters, and statistical experimental design is naturally suited to this field. These techniques are sample independent and provide an experimental strategy to maximize crystal volume and habit for neutron diffraction studies.

  7. Internal strain measurement using pulsed neutron diffraction at LANSCE

    Energy Technology Data Exchange (ETDEWEB)

    Goldstone, J.A.; Bourke, M.A.M.; Shi, N. [Los Alamos National Lab., NM (United States). Manuel Lujan Jr. Neutron Scattering Center

    1994-12-01

    The presence of residual stress in engineering components can effect their mechanical properties and structural integrity. Neutron diffraction in the only technique that can make nondestructive measurements in the interior of components. By recording the change in crystalline lattice spacings, elastic strains can be measured for individual lattice reflections. Using a pulsed neutron source, all lattice reflections are recorded in each measurement, which allows for easy examination of heterogeneous materials such as metal matrix composites. Measurements made at the Manuel Lujan Jr. Neutron Scattering Center (LANSCE) demonstrate the potential at pulsed sources for in-situ stress measurements at ambient and elevated temperatures.

  8. Rotary and High-Pressure Nozzle Spray Plume Droplet Analysis For Aerially Applied Mosquito Adulticides: Laser Diffraction Characterization.

    Science.gov (United States)

    Hornby, Jonathan A; Robinson, Jim; Sterling, Milton

    2017-03-01

    The droplet spectrum of a mosquito adulticide spray plume determines its ability to drift through the target area, impinge on the mosquito, deliver a toxic dose, and the risk of environmental contamination. This paper provides data on droplet spectra produced from 6 nozzles in a high-pressure nozzle spray system and 5 rotary nozzle systems for common mosquito adulticides. Spray plume spectra were measured by laser diffraction. High-pressure nozzles were evaluated at pressures ranging from 500 psi to 6,000 psi. Rotary nozzles were evaluated at rotational speeds ranging from 500 rpm to 24,000 rpm. Measurements were made at wind speeds of 129 km/h (80 mph) to 225 km/h (140 mph). Adulticides included were Fyfanon®, Aqua-Reslin®, Dibrom®, Duet®, Permanone®, and the inert mineral oil, Orchex® 796. High-pressure nozzles produced spray plumes within the US Environmental Protection Agency (EPA) label requirements for all configurations tested except for one at a wind speed of 225 km/h, BETE® MW125. Air speed had no significant effect on the spray plume volume median diameter (Dv(0.5)) at the speeds tested with Fyfanon®. The spray plume 90% drop volume diameter (Dv(0.9)) significantly decreased, 13% at the higher wind speed of 225 km/h. Drop size was inversely related to pressure. Dilution of the product formulations increased the Dv(0.5) of the spray plume but it did not exceed the label requirements. For the PJ15 nozzle, orientation of the nozzle into the wind of up to 135° showed a significant increase in Dv(0.5) at 500 psi, 750 psi, and 1,500 psi. The Dv(0.5) varied Rotary nozzles produced spray plumes within the EPA label requirements for all test configurations examined. Air speed had no significant effect on Dv(0.5) or Dv(0.9) of the plume at speeds tested with Fyfanon for the ASC A20 nozzle. The rotary AU5000 nozzle using Orchex 796 produced plumes of larger drops in all configurations than any of the rotary nozzles of similar configurations using active

  9. Phase modulation of a neutron wave and diffraction of ultracold neutrons on a moving grating

    Energy Technology Data Exchange (ETDEWEB)

    Frank, A.I.; Balashov, S.N.; Bondarenko, I.V.; Geltenbort, P.; Hoeghoej, P.; Masalovich, S.V.; Nosov, V.G

    2003-05-05

    We report the result of the experiment of UCN diffraction on a moving grating. The resulting spectrum is found to be discrete in good agreement with theory. This purely quantum effect may be interpret as a result of phase modulation of the neutron wave or as diffraction in time. Also, this experiment demonstrates the validity of the Galilean transformation of the neutron wave function in a new and very clear way.

  10. Zinc (tris) thiourea sulphate (ZTS): A single crystal neutron diffraction ...

    Indian Academy of Sciences (India)

    2015-11-27

    Nov 27, 2015 ... The crystal structure of ZTS has been determined by neutron diffraction with a final -value of 0.026. Using the structural parameters, the contributions from the structural groups to the linear optical susceptibility and linear electro-optic coefficients have been evaluated. Results showed a significant ...

  11. Zinc (tris) thiourea sulphate (ZTS): A single crystal neutron diffraction ...

    Indian Academy of Sciences (India)

    tal which is used for electro-optical (EO) applications and frequency doubling of near IR laser radiations. In this study, the crystal structure of ZTS has been ob- tained in detail by single crystal neutron diffraction technique. Using the structural parameters and an existing formalism [1] based on the theory of bond polarizability,.

  12. High-speed neutron Laue diffraction comes of age

    Energy Technology Data Exchange (ETDEWEB)

    McIntyre, Garry J. [Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9 (France)]. E-mail: mcintyre@ill.fr; Lemee-Cailleau, Marie-Helene [Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9 (France); Wilkinson, Clive [Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9 (France): Department of Chemistry, University of Durham, Durham DH1 3LE (United Kingdom)

    2006-11-15

    The first years of operation of the Laue diffractometer VIVALDI at the ILL are reviewed. Neutron Laue diffraction with image-plate detection on a thermal beam is now a high-performance technique especially well suited to small crystals, rapid chemical crystallography, reciprocal-space surveys and studies of structural and magnetic phase transitions.

  13. A preliminary neutron diffraction study of γ-­chymotrypsin

    Science.gov (United States)

    Novak, Walter R. P.; Moulin, Aaron G.; Blakeley, Matthew P.; Schlichting, Ilme; Petsko, Gregory A.; Ringe, Dagmar

    2009-01-01

    The crystal preparation and preliminary neutron diffraction analysis of γ-­chymotrypsin are presented. Large hydrogenated crystals of γ-chymotrypsin were exchanged into deuterated buffer via vapor diffusion in a capillary and neutron Laue diffraction data were collected from the resulting crystal to 2.0 Å resolution on the LADI-III diffractometer at the Institut Laue–Langevin (ILL) at room temperature. The neutron structure of a well studied protein such as γ-­chymotrypsin, which is also amenable to ultrahigh-resolution X-ray crystallo­graphy, represents the first step in developing a model system for the study of H atoms in protein crystals. PMID:19255494

  14. Performance evaluation of high-pressure MWPC with individual line readout under Cf-252 neutron irradiation

    Science.gov (United States)

    Toh, K.; Nakamura, T.; Sakasai, K.; Soyama, K.; Yamagishi, H.

    2014-07-01

    A multiwire proportional chamber (MWPC) neutron detector system was developed for the Materials and Life Science Experimental Facility at the Japan Proton Accelerator Research Complex. Its basic performance was evaluated by an irradiation experiment using a Cf-252 neutron source. A short response time and high spatial resolution can be obtained using an individual line readout method. The detector system exhibited a one-dimensional uniformity of response of 4.8% and 3.8% in the x- and y-directions, respectively. The uniformity of all pixels in the two-dimensional image was 7.9%. The average intrinsic spatial resolution was 1.55 mm full width at half maximum in the sensitive region calculated by taking into account the track lengths of secondary particles. The signal intensity of the system remained constant during the operation for 500 min under Cf-252 neutron irradiation.

  15. Small-size hydraulic press for application in high-pressure installations for neutron investigations

    CERN Document Server

    Stishov, S M

    2002-01-01

    Paper describes design of small-size hydraulic press enabling to minimize shielding of neutron beam by press substantial elements. Press frame and power cylinder are made of alloyed steel. The performances of hydraulic press are as follows: rotated gain - 200 t, maximum piston run - 10 mm, height - 305 mm, maximum diameter - 210 mm, weight - 60 kg

  16. Neutron Diffraction Studies of Nuclear Magnetic Ordering in Copper

    DEFF Research Database (Denmark)

    Jyrkkiö, T.A.; Huiku, M.T.; Siemensmeyer, K.

    1989-01-01

    to depend strongly on the external magnetic field between zero and the critical fieldB c=0.25 mT, indicating the existence of at least two antiferromagnetic phases. The results are compared to previous measurements of the magnetic susceptibility. Theoretical calculations do not provide a full explanation......We have constructed a two-stage nuclear demagnetization cryostat for neutron diffraction studies of nuclear magnetism in copper. The cryostat is combined with a two-axis neutron spectrometer which can use both polarized and unpolarized neutrons. By demagnetizing highly polarized copper nuclear...... for measurements in the ordered state; both our calculations and the experiments yield 1 nW beam heating. Polarized neutron experiments show that the scattered intensities from the strong fcc reflections are severely reduced by extinction. This makes the sample not very suitable for further studies with polarized...

  17. The accuracy of the crystal chemical parameters at high-pressure conditions from single-crystal X-ray diffraction in diamond-anvil cell

    DEFF Research Database (Denmark)

    Periotto, Benedetta

    applications also in the materials science as it can provide useful information about the properties and performance of new materials. Over the past decades, the research in this field has been strongly developed due to the advances in computer capabilities and to the technological improvements of X-ray...... instruments. At the same time, the high-pressure experiments have benefited by the strong improvements on the high-pressure devices, in particular the diamond-anvil cell (DAC). The aim of this research project is to assess the quality of the data obtained by means of the single-crystal X-ray diffraction...... technique through the study of different mineral phases. The procedure for setting up an experiment under high-pressure conditions, using a single crystal as sample held within a DAC, are presented here with all the details of the in situ measurements at high-pressure conditions. The research project...

  18. Oxides neutron and synchrotron X-ray diffraction studies

    CERN Document Server

    Sosnowska, I M

    1999-01-01

    We review some results from several areas of oxide science in which neutron scattering and X-ray synchrotron scattering exercise a complementary role to high-resolution transmission electron microscopy. The very high-resolution time-of-flight neutron diffraction technique and its role in studies of the magnetic structure of oxides is especially reviewed. The selected topics of structural studies for the chosen oxides are: crystal and magnetic structure of the so-called cellular random systems, magnetic structure and phase transitions in ferrites and the behaviour of water in non-stoichiometric protonic conductors and in the opal silica-water system. (40 refs).

  19. 3DXRD microscopy - a comparison with neutron diffraction

    DEFF Research Database (Denmark)

    Poulsen, H.F.

    2002-01-01

    3DXRD microscopy is a novel tool for fast and non-destructive characterisation of the individual grains and sub-grains inside bulk materials (powders or polycrystals). The method is based on diffraction with hard X-rays (E > 50 keV), enabling 3D studies of millimeter to centimeter-thick specimens...... of the technique is presented and the potential for in situ processing studies illustrated. The hard-X-ray method is compared to conventional neutron-diffraction techniques: texture and strain measurements, small-angle scattering, and in situ powder diffraction.......3DXRD microscopy is a novel tool for fast and non-destructive characterisation of the individual grains and sub-grains inside bulk materials (powders or polycrystals). The method is based on diffraction with hard X-rays (E > 50 keV), enabling 3D studies of millimeter to centimeter-thick specimens...

  20. Structure of amorphous selenium studied by neutron diffraction

    DEFF Research Database (Denmark)

    Hansen, Flemming Yssing; Knudsen, Torben Steen; Carneiro, K.

    1975-01-01

    Neutron diffraction measurements on amorphous selenium have been performed at 293 and 80 K. Careful analyses of the instrumental corrections were made to avoid systematic errors in the measured structure factor S (kappa) in the wave vector region 0 ? kappa ? 12 Å−1. As a result of the data...... treatment, the neutron scattering cross sections of selenium are determined to be sigmacoh = 8.4±0.1 b and sigmainc = 0.1±0.1 b. Using the fact that S (kappa) for large kappa's is determined by the short distances in the sample, a new method for extrapolation of the experimental S (kappa) until convergence....... Finally, we give a brief discussion of the different models for the structure of amorphous selenium, taking both diffraction measurements and thermodynamic considerations into account. The Journal of Chemical Physics is copyrighted by The American Institute of Physics....

  1. Synchrotron X-ray diffraction studies of phase transitions and mechanical properties of nanocrystalline materials at high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Prilliman, Stephen Gerald [Univ. of California, Berkeley, CA (United States)

    2003-01-01

    The behavior of nanocrystals under extreme pressure was investigated using synchrotron x-ray diffraction. A major part of this investigation was the testing of a prototype synchrotron endstation on a bend magnet beamline at the Advanced Light Source for high pressure work using a diamond anvil cell. The experiments conducted and documented here helped to determine issues of efficiency and accuracy that had to be resolved before the construction of a dedicated ''super-bend'' beamline and endstation. The major conclusions were the need for a cryo-cooled monochromator and a fully remote-controllable pressurization system which would decrease the time to change pressure and greatly reduce the error created by the re-placement of the diamond anvil cell after each pressure change. Two very different types of nanocrystal systems were studied, colloidal iron oxide (Fe2O3) and thin film TiN/BN. Iron oxide nanocrystals were found to have a transition from the γ to the α structure at a pressure strongly dependent on the size of the nanocrystals, ranging from 26 GPa for 7.2 nm nanocrystals to 37 GPa for 3.6 nm nanocrystals. All nanocrystals were found to remain in the α structure even after release of pressure. The transition pressure was also found, for a constant size (5.7 nm) to be strongly dependent on the degree of aggregation of the nanocrystals, increasing from 30 GPa for completely dissolved nanocrystals to 45 GPa for strongly aggregated nanocrystals. Furthermore, the x-ray diffraction pattern of the pressure induced α phase demonstrated a decrease in intensity for certain select peaks. Together, these observations were used to make a complete picture of the phase transition in nanocrystalline systems. The size dependence of the transition was interpreted as resulting from the extremely high surface energy of the α phase which would increase the thermodynamic offset and thereby increase the kinetic barrier to transition

  2. Origin of Negative Thermal Expansion in Cubic ZrW2O8 Revealed by High Pressure Inelastic Neutron Scattering

    Science.gov (United States)

    Mittal, R.; Chaplot, S. L.; Schober, H.; Mary, T. A.

    2001-05-01

    Isotropic negative thermal expansion has been reported in cubic ZrW2O8 over a wide range of temperatures (0-1050 K). Here we report the direct experimental determination of the Grüneisen parameters of phonon modes as a function of their energy, averaged over the whole Brillouin zone, by means of high pressure inelastic neutron scattering measurements. We observe a pronounced softening of the phonon spectrum at P = 1.7 kbar compared to that at ambient pressure by about 0.1-0.2 meV for phonons of energy below 8 meV. This unusual phonon softening on compression, corresponding to large negative Grüneisen parameters, is able to account for the observed large negative thermal expansion.

  3. Magnetization and neutron diffraction studies on FeCrP

    Indian Academy of Sciences (India)

    thorhombic FeZrP type structure (Pnma space group, Z = 4) in which Cr atoms occupy ... Magnetization measurements have been made on a vibrating sample ... Results of profile refinement of neutron diffraction data on FeCrP at 300 K. Space group = Pnma; a = 5.833(1) Å, b = 3.569(1) Å and c = 6.658(1) Å. Atom. Position.

  4. Engineering related neutron diffraction measurements probing strains, texture and microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Clausen, Bjorn [Los Alamos National Laboratory; Brown, Donald W [Los Alamos National Laboratory; Tome, Carlos N [Los Alamos National Laboratory; Balogh, Levente [Los Alamos National Laboratory; Vogel, Sven C [Los Alamos National Laboratory

    2010-01-01

    Neutron diffraction has been used for engineering applications for nearly three decades. The basis of the technique is powder diffraction following Bragg's Law. From the measured diffraction patterns information about internal, or residual, strain can be deduced from the peak positions, texture information can be extracted from the peak intensities, and finally the peak widths can provide information about the microstructure, e.g. dislocation densities and grain sizes. The strains are measured directly from changes in lattice parameters, however, in many cases it is non-trivial to determine macroscopic values of stress or strain from the measured data. The effects of intergranular strains must be considered, and combining the neutron diffraction measurements with polycrystal deformation modeling has proven invaluable in determining the overall stress and strain values of interest in designing and dimensioning engineering components. Furthelmore, the combined use of measurements and modeling has provided a tool for elucidating basic material properties, such as critical resolved shear stresses for the active deformation modes and their evolution as a function of applied deformation.

  5. New developments in laser-heated diamond anvil cell with in situ synchrotron x-ray diffraction at High Pressure Collaborative Access Team.

    Science.gov (United States)

    Meng, Yue; Hrubiak, Rostislav; Rod, Eric; Boehler, Reinhard; Shen, Guoyin

    2015-07-01

    An overview of the in situ laser heating system at the High Pressure Collaborative Access Team, with emphasis on newly developed capabilities, is presented. Since its establishment at the beamline 16-ID-B a decade ago, laser-heated diamond anvil cell coupled with in situ synchrotron x-ray diffraction has been widely used for studying the structural properties of materials under simultaneous high pressure and high temperature conditions. Recent developments in both continuous-wave and modulated heating techniques have been focusing on resolving technical issues of the most challenging research areas. The new capabilities have demonstrated clear benefits and provide new opportunities in research areas including high-pressure melting, pressure-temperature-volume equations of state, chemical reaction, and time resolved studies.

  6. Stabilized voltage sources for a slow neutron diffraction analyzer

    Energy Technology Data Exchange (ETDEWEB)

    Plyusnin, N.I.; Lobachev, S.A.; Galkin, N.G.

    An unified voltage source (UVS) and filament voltage source (FVS) are described' The sources are used for a slow neutron diffraction analyzer. FVS supplies the filament of a gun cathode and provides beam currents upto 2 mA at electric currents upto 5A and voltages upto 8V. FVS is built by a compensation scheme with continuous control. It possesses a control element with high output power and trigger protection. The range of the EVS protection circuit operation threshold control is 1-5 A, instability of output voltage doesn't exceed 1 mV, the load power consumption doesn't exceed 40 W. UVS is also built according to compensation principle with continuous control and non-regulated power supply of a negative feedback amplifier. The output voltage is controlled within the limits of 5-250 V, maximum load current is 5 mA, instability of output voltage doesn't exceed 50 mV, maximum power consumption is 1.5 W. Simplicity of the UVS circuit is reached by application of the minimum number of active and passive elements, and reliability - by the circuit protection from overloads. Operation of the slow neutron diffraction analyzer, a control unit of which is built on the base of the above voltage sources, proves their reliability and convenience. Diffraction patterns of good quality are obtained.

  7. Neutron diffraction study of unusual phase separation in the antiperovskite nitride Mn3ZnN.

    Science.gov (United States)

    Sun, Ying; Wang, Cong; Huang, Qingzhen; Guo, Yanfeng; Chu, Lihua; Arai, Masao; Yamaura, Kazunari

    2012-07-02

    The antiperovskite Mn(3)ZnN is studied by neutron diffraction at temperatures between 50 and 295 K. Mn(3)ZnN crystallizes to form a cubic structure at room temperature (C1 phase). Upon cooling, another cubic structure (C2 phase) appears at around 177 K. Interestingly, the C2 phase disappears below 140 K. The maximum mass concentration of the C2 phase is approximately 85% (at 160 K). The coexistence of C1 and C2 phase in the temperature interval of 140-177 K implies that phase separation occurs. Although the C1 and C2 phases share their composition and lattice symmetry, the C2 phase has a slightly larger lattice parameter (Δa ≈ 0.53%) and a different magnetic structure. The C2 phase is further investigated by neutron diffraction under high-pressure conditions (up to 270 MPa). The results show that the unusual appearance and disappearance of the C2 phase is accompanied by magnetic ordering. Mn(3)ZnN is thus a valuable subject for study of the magneto-lattice effect and phase separation behavior because this is rarely observed in nonoxide materials.

  8. Crystal structure of human tooth enamel studied by neutron diffraction

    Science.gov (United States)

    Ouladdiaf, Bachir; Rodriguez-Carvajal, Juan; Goutaudier, Christelle; Ouladdiaf, Selma; Grosgogeat, Brigitte; Pradelle, Nelly; Colon, Pierre

    2015-02-01

    Crystal structure of human tooth enamel was investigated using high-resolution neutron powder diffraction. Excellent agreement between observed and refined patterns is obtained, using the hexagonal hydroxyapatite model for the tooth enamel, where a large hydroxyl deficiency ˜70% is found in the 4e site. Rietveld refinements method combined with the difference Fourier maps have revealed, however, that the hydroxyl ions are not only disordered along the c-axis but also within the basal plane. Additional H ions located at the 6h site and forming HPO42- anions were found.

  9. Neutron diffraction characterization of Japanese artworks of Tokugawa age.

    Science.gov (United States)

    Grazzi, F; Bartoli, L; Civita, F; Zoppi, M

    2009-12-01

    Neutron time-of-flight diffraction technique has been used to characterize some Japanese historical artifacts. With this method, metal samples can be analyzed in their bulk properties without need of sampling. Results shown here were obtained at the Italian Neutron Experimental Station (INES@ISIS) located at the pulsed neutron source ISIS (UK). The parallel use of a scanning electron microscope equipped with an energy-dispersive X-ray fluorescence device (SEM-EDX) permitted a full quantitative characterization of the investigated samples, namely four hand-guards (Tsubas) of Japanese swords attributed to the Tokugawa age. In particular, we were able to obtain, in a totally non-invasive non-destructive way, a full quantitative phase characterization of the samples, a detailed Bragg peak broadening analysis, and a quantitative texture determination. These results, complemented with those obtained via the traditional analysis method of SEM-EDX, allowed a full characterization of both the bulk and the surface of the artifacts.

  10. Magnetostructural transition in Fe5SiB2 observed with neutron diffraction

    Czech Academy of Sciences Publication Activity Database

    Cedervall, J.; Kontos, S.; Hansen, T. C.; Balmes, O.; Martinez-Casado, F. J.; Matěj, Z.; Beran, Přemysl; Svedlindh, P.; Gunnarsson, K.; Sahlberg, M.

    2016-01-01

    Roč. 235, MAR (2016), s. 113-118 ISSN 0022-4596 Institutional support: RVO:61389005 Keywords : magnetism * X-ray diffraction * neutron diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.299, year: 2016

  11. Variable temperature and high-pressure crystal chemistry of perovskite formamidinium lead iodide: a single crystal X-ray diffraction and computational study.

    Science.gov (United States)

    Sun, Shijing; Deng, Zeyu; Wu, Yue; Wei, Fengxia; Halis Isikgor, Furkan; Brivio, Federico; Gaultois, Michael W; Ouyang, Jianyong; Bristowe, Paul D; Cheetham, Anthony K; Kieslich, Gregor

    2017-07-04

    We investigate the variable temperature (100-450 K) and high-pressure (p = ambient - 0.74 GPa) crystal chemistry of the black perovskite formamidinium lead iodide, [(NH2)2CH]PbI3, using single crystal X-ray diffraction. In both cases we find a phase transition to a tetragonal phase. Our experimental results are combined with first principles calculations, providing information about the electronic properties of [(NH2)2CH]PbI3 as well as the most probable orientation of the [(NH2)2CH](+) cations.

  12. Neutron diffraction studies of amphipathic helices in phospholipid bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Bradshaw, J.P.; Gilchrist, P.J. [Univ. of Edinburgh (United Kingdom); Duff, K.C. [Univ. of Edinburgh Medical School (United Kingdom); Saxena, A.M. [Brookhaven National Laboratory, Upton, NY (United States)

    1994-12-31

    The structural feature which is thought to facilitate the interaction of many peptides with phospholipid bilayers is the ability to fold into an amphipathic helix. In most cases the exact location and orientation of this helix with respect to the membrane is not known, and may vary with factors such as pH and phospholipid content of the bilayer. The growing interest in this area is stimulated by indications that similar interactions can contribute to the binding of certain hormones to their cell-surface receptors. We have been using the techniques of neutron diffraction from stacked phospholipid bilayers in an attempt to investigate this phenomenon with a number of membrane-active peptides. Here we report some of our findings with three of these: the bee venom melittin; the hormone calcitonin; and a synthetic peptide representing the ion channel fragment of influenza A M2 protein.

  13. Principles of the measurement of residual stress by neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Webster, G.A.; Ezeilo, A.N. [Imperial Coll. of Science and Technology, London (United Kingdom). Dept. of Mechanical Engineering

    1996-11-01

    The presence of residual stresses in engineering components can significantly affect their load carrying capacity and resistance to fracture. In order to quantify their effect it is necessary to know their magnitude and distribution. Neutron diffraction is the most suitable method of obtaining these stresses non-destructively in the interior of components. In this paper the principles of the technique are described. A monochromatic beam of neutrons, or time of flight measurements, can be employed. In each case, components of strain are determined directly from changes in the lattice spacings between crystals. Residual stresses can then be calculated from these strains. The experimental procedures for making the measurements are described and precautions for achieving reliable results discussed. These include choice of crystal planes on which to make measurements, extent of masking needed to identify a suitable sampling volume, type of detector and alignment procedure. Methods of achieving a stress free reference are also considered. A selection of practical examples is included to demonstrate the success of the technique. (author) 14 figs., 1 tab., 18 refs.

  14. Multiferroic CuCrO₂ under high pressure: In situ X-ray diffraction and Raman spectroscopic studies

    Energy Technology Data Exchange (ETDEWEB)

    Garg, Alka B., E-mail: alkagarg@barc.gov.in; Mishra, A. K.; Pandey, K. K.; Sharma, Surinder M. [High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)

    2014-10-07

    The compression behavior of delafossite compound CuCrO₂ has been investigated by in situ x-ray diffraction (XRD) and Raman spectroscopic measurements up to 23.2 and 34 GPa, respectively. X-ray diffraction data show the stability of ambient rhombohedral structure up to ~23 GPa. Material shows large anisotropy in axial compression with c-axis compressibility, κ{sub c} = 1.26 × 10⁻³(1) GPa⁻¹ and a-axis compressibility, κ{sub a} = 8.90 × 10⁻³(6) GPa⁻¹. Our XRD data show an irreversible broadening of diffraction peaks. Pressure volume data when fitted to 3rd order Birch-Murnaghan equation of state give the value of bulk modulus, B₀ = 156.7(2.8) GPa with its pressure derivative, B₀{sup ’} as 5.3(0.5). All the observed vibrational modes in Raman measurements show hardening with pressure. Appearance of a new mode at ~24 GPa indicates the structural phase transition in the compound. Our XRD and Raman results indicate that CuCrO{sub 2} may be transforming to an ordered rocksalt type structure under compression.

  15. Neutrons in studies of phospholipid bilayers and bilayer–drug interaction. I. Basic principles and neutron diffraction

    Directory of Open Access Journals (Sweden)

    Belička M.

    2014-12-01

    Full Text Available In our paper, we demonstrate several possibilities of using neutrons in pharmaceutical research with the help of examples of scientific results achieved at our University. In this first part, basic properties of neutrons and elementary principles of elastic scattering of thermal neutrons are described. Results of contrast variation neutron diffraction on oriented phospholipid bilayers with intercalated local anaesthetic or cholesterol demonstrate the potential of this method at determination of their position in bilayers. Diffraction experiments with alkan-1-ols located in the bilayers revealed their influence on bilayer thickness as a function of their alkyl chain length.

  16. Mapping residual and internal stress in materials by neutron diffraction

    Science.gov (United States)

    Withers, Philip J.

    2007-09-01

    Neutron diffraction provides one of the few means of mapping residual stresses deep within the bulk of materials and components. This article reviews the basic scientific methodology by which internal strains and stresses are inferred from recorded diffraction peaks. Both conventional angular scans and time-of-flight measurements are reviewed and compared. Their complementarity with analogous synchrotron X-ray methods is also highlighted. For measurements to be exploited in structural integrity calculations underpinning the safe operation of engineering components, measurement standards have been defined and the major findings are summarised. Examples are used to highlight the unique capabilities of the method showing how it can provide insights ranging from the basic physics of slip mechanisms in hexagonal polycrystalline materials, through the materials optimisation of stress induced transformations in smart nanomaterials, to the industrial introduction of novel friction welding processes exploiting stress residual measurements transferred from prototype sub-scale tests to the joining of full-scale aeroengine assemblies. To cite this article: P.J. Withers, C. R. Physique 8 (2007).

  17. High-pressure and high-temperature powder diffraction on molybdenum diphosphide, MoP{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Soto, V. [Centro de Investigacion Cientifica y de Educacion Superior de Ensenada, Esenada (Mexico); Knorr, K.; Ehm, L. [Christian-Albrechts-Univ. zu Kiel, Inst. fuer Geowissenschaften, Mineralogie/Kristallographie, Kiel (Germany); Baehtz, C. [HASYLAB Hamburg and TU Darmstadt, Materialwissenschaften, Darmstadt (Germany); Winkler, B. [Johann-Wolfgang-Goethe Univ. Frankfurt-Main, Mineralogie, Frankfurt/M. (Germany); Avalos-Borja, M. [Centro de Ciencias de la Materia Condensada, Univ. Nacional Autonoma de Mexico, Ensenada, BC (Mexico)

    2004-07-01

    The isothermal compressibility and bulk thermal expansion of molybdenum diphosphide, MoP{sub 2}, were measured by in-situ X-ray powder diffraction from ambient conditions to 6.8 GPa and 839 K, respectively. A small anisotropy of the compressibilities in MoP{sub 2} appears to be governed by non-bonding interactions in this layer-like material. The thermal expansion data are compared to molybdenum phosphide, MoP, which was measured to 1262 K. (orig.)

  18. Three-port beam splitter for slow neutrons using holographic nanoparticle-polymer composite diffraction gratings

    Energy Technology Data Exchange (ETDEWEB)

    Klepp, J.; Fally, M. [Faculty of Physics, University of Vienna, 1090 Wien (Austria); Tomita, Y. [Department of Engineering Science, University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo 182 (Japan); Pruner, C. [Department of Materials Science and Physics, University of Salzburg, 5020 Salzburg (Austria); Kohlbrecher, J. [Laboratory for Neutron Scattering, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland)

    2012-10-08

    Diffraction of slow neutrons by nanoparticle-polymer composite gratings has been observed. By carefully choosing grating parameters such as grating thickness and spacing, a three-port beam splitter operation for slow neutrons - splitting the incident neutron intensity equally into the {+-}1st and the 0th diffraction orders - has been realized. As a possible application, a Zernike three-path interferometer is briefly discussed.

  19. Neutron diffraction study of quasi-one-dimensional spin-chain ...

    Indian Academy of Sciences (India)

    Abstract. We report the results of the DC magnetization, neutron powder diffraction and neutron depolarization studies on the spin-chain compounds Ca3Co2−xFexO6 (x = 0,. 0.1, 0.2 and 0.4). Rietveld refinement of neutron powder diffraction patterns at room temperature confirms the single-phase formation for all the ...

  20. Combined resistive and laser heating technique for in situ radial X-ray diffraction in the diamond anvil cell at high pressure and temperature

    Energy Technology Data Exchange (ETDEWEB)

    Miyagi, Lowell [Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112 (United States); Department of Earth Sciences, Montana State University, Bozeman, Montana 59717 (United States); Kanitpanyacharoen, Waruntorn; Kaercher, Pamela; Wenk, Hans-Rudolf; Alarcon, Eloisa Zepeda [Department of Earth and Planetary Science, University of California, Berkeley, California 94720 (United States); Raju, Selva Vennila [Advanced Light Source, Lawrence Berkeley Laboratory, Berkeley, California 94720 (United States); HiPSEC, Department of Physics, University of Nevada, Las Vegas, Nevada 89154 (United States); Knight, Jason; MacDowell, Alastair [Advanced Light Source, Lawrence Berkeley Laboratory, Berkeley, California 94720 (United States); Williams, Quentin [Department of Earth and Planetary Science, University of California, Santa Cruz, California 95064 (United States)

    2013-02-15

    To extend the range of high-temperature, high-pressure studies within the diamond anvil cell, a Liermann-type diamond anvil cell with radial diffraction geometry (rDAC) was redesigned and developed for synchrotron X-ray diffraction experiments at beamline 12.2.2 of the Advanced Light Source. The rDAC, equipped with graphite heating arrays, allows simultaneous resistive and laser heating while the material is subjected to high pressure. The goals are both to extend the temperature range of external (resistive) heating and to produce environments with lower temperature gradients in a simultaneously resistive- and laser-heated rDAC. Three different geomaterials were used as pilot samples to calibrate and optimize conditions for combined resistive and laser heating. For example, in Run1, FeO was loaded in a boron-mica gasket and compressed to 11 GPa then gradually resistively heated to 1007 K (1073 K at the diamond side). The laser heating was further applied to FeO to raise temperature to 2273 K. In Run2, Fe-Ni alloy was compressed to 18 GPa and resistively heated to 1785 K (1973 K at the diamond side). The combined resistive and laser heating was successfully performed again on (Mg{sub 0.9}Fe{sub 0.1})O in Run3. In this instance, the sample was loaded in a boron-kapton gasket, compressed to 29 GPa, resistive-heated up to 1007 K (1073 K at the diamond side), and further simultaneously laser-heated to achieve a temperature in excess of 2273 K at the sample position. Diffraction patterns obtained from the experiments were deconvoluted using the Rietveld method and quantified for lattice preferred orientation of each material under extreme conditions and during phase transformation.

  1. Combined resistive and laser heating technique for in situ radial X-ray diffraction in the diamond anvil cell at high pressure and temperature.

    Science.gov (United States)

    Miyagi, Lowell; Kanitpanyacharoen, Waruntorn; Raju, Selva Vennila; Kaercher, Pamela; Knight, Jason; MacDowell, Alastair; Wenk, Hans-Rudolf; Williams, Quentin; Alarcon, Eloisa Zepeda

    2013-02-01

    To extend the range of high-temperature, high-pressure studies within the diamond anvil cell, a Liermann-type diamond anvil cell with radial diffraction geometry (rDAC) was redesigned and developed for synchrotron X-ray diffraction experiments at beamline 12.2.2 of the Advanced Light Source. The rDAC, equipped with graphite heating arrays, allows simultaneous resistive and laser heating while the material is subjected to high pressure. The goals are both to extend the temperature range of external (resistive) heating and to produce environments with lower temperature gradients in a simultaneously resistive- and laser-heated rDAC. Three different geomaterials were used as pilot samples to calibrate and optimize conditions for combined resistive and laser heating. For example, in Run#1, FeO was loaded in a boron-mica gasket and compressed to 11 GPa then gradually resistively heated to 1007 K (1073 K at the diamond side). The laser heating was further applied to FeO to raise temperature to 2273 K. In Run#2, Fe-Ni alloy was compressed to 18 GPa and resistively heated to 1785 K (1973 K at the diamond side). The combined resistive and laser heating was successfully performed again on (Mg0.9Fe0.1)O in Run#3. In this instance, the sample was loaded in a boron-kapton gasket, compressed to 29 GPa, resistive-heated up to 1007 K (1073 K at the diamond side), and further simultaneously laser-heated to achieve a temperature in excess of 2273 K at the sample position. Diffraction patterns obtained from the experiments were deconvoluted using the Rietveld method and quantified for lattice preferred orientation of each material under extreme conditions and during phase transformation.

  2. Derivation of radiation quality average parameters in neutron-gamma radiation fields with the high-pressure ionization chamber: theory and practice.

    Science.gov (United States)

    Makrigiorgos, G M

    1989-06-01

    The established radiation quality parameters in mixed neutron-gamma radiation fields may be measured by applying the initial (columnar) recombination of ions in tissue-equivalent (TE) high-pressure ionization chambers (recombination chambers). The mean quality factor can be determined to within 10-15% for mixed fields with neutrons ranging from thermal to 10 MeV, and the dose mean LET of the proton component can be determined to within 10-15% if the gamma-ray absorbed dose fraction is known. These average parameters are derived by measuring the ratio of the ionization currents collected at two high-field strengths and constant gas pressure applied to the ionization chamber. By utilizing approximate correlations between physical parameters in the neutron energy region from thermal to 10 MeV, the dose mean LET of the heavy ion component, the overall dose mean LET, and the microdosimetric parameter y0,D of the mixed field can also be derived. Experimental verification of the method is presented for various neutron-gamma radiation spectra in air and in water by comparison to theoretical calculations and results from low-pressure proportional counter measurements. Good agreement is shown. The TE high-pressure ionization chamber appears to have wide potential for use as a dose-equivalent meter in radiation protection or as a beam characterization device in radiobiology.

  3. White-Beam X-ray Diffraction and Radiography Studies on High-Boron Containing Borosilicate Glass at High Pressures

    Science.gov (United States)

    Ham, Kathryn; Vohra, Yogesh; Kono, Yoshio; Wereszczak, Andrew; Patel, Parimal

    Multi-angle energy-dispersive x-ray diffraction studies and white-beam x-ray radiography were conducted with a cylindrically shaped (1 mm diameter and 0.7 mm high) high-boron content borosilicate glass sample (17.6% B2O3) to a pressure of 13.7 GPa using a Paris-Edinburgh (PE) press at Beamline 16-BM-B, HPCAT of the Advanced Photon Source. The measured structure factor S(q) to large q = 19 Å-1, is used to determine information about the internuclear bond distances between various species of atoms within the glass sample. Sample pressure was determined with gold as a pressure standard. The sample height as measured by radiography showed an overall uniaxial compression of 22.5 % at 13.7 GPa with 10.6% permanent compaction after decompression to ambient conditions. The reduced pair distribution function G(r) was extracted and Si-O, O-O, and Si-Si bond distances were measured as a function of pressure. Raman spectroscopy of pressure recovered sample as compared to starting material showed blue-shift and changes in intensity and widths of Raman bands associated with silicate and B3O6 boroxol rings. US Army Research Office under Grant No. W911NF-15-1-0614.

  4. High-pressure, high-temperature deformation of dunite, eclogite, clinopyroxenite and garnetite using in situ X-ray diffraction

    Science.gov (United States)

    Farla, R.; Rosenthal, A.; Bollinger, C.; Petitgirard, S.; Guignard, J.; Miyajima, N.; Kawazoe, T.; Crichton, W. A.; Frost, D. J.

    2017-09-01

    The rheology of eclogite, garnetite and clinopyroxenite in the peridotitic upper mantle was experimentally investigated in a large volume press combined with in situ synchrotron X-ray diffraction techniques to study the impact on mantle convection resulting from the subduction of oceanic lithosphere. Experiments were carried out over a range of constant strain rates (2 ×10-6- 3 ×10-5 s-1), pressures (4.3 to 6.7 GPa) and temperatures (1050 to 1470 K). Results show substantial strength variations among eclogitic garnet and clinopyroxene and peridotitic olivine. At low temperatures (1400 K) eclogite is weaker than dunite by 0.2 GPa or more. Garnetite and clinopyroxenite exhibit higher strength than dunite at approximately 1200 K. However, at higher temperature (1370 K), clinopyroxenite is significantly weaker than garnetite (and dunite) by more than a factor of five. We explain these observations by transitions in deformation mechanisms among the mineral phases. In clinopyroxene, high temperature dislocation creep resulting in a strength reduction replaces low temperature twinning. Whereas garnet remains very rigid at all experimental conditions when nominally anhydrous ('dry'). Microstructural observations show phase segregation of clinopyroxene and garnet, development of a crystallographic and shape preferred orientation in the former but not in the latter, suggesting an overall weak seismic anisotropy. Detection of eclogite bodies in the peridotite-dominated mantle may only be possible via observation of high VP /VS1 ratios. A comparable or weaker rheology of eclogite to dunite suggests effective stirring and mixing of eclogite in the convecting mantle.

  5. High-pressure X-ray diffraction and Raman spectroscopy of CaFe2O4-type β-CaCr2O4

    Science.gov (United States)

    Zhai, Shuangmeng; Yin, Yuan; Shieh, Sean R.; Shan, Shuangming; Xue, Weihong; Wang, Ching-Pao; Yang, Ke; Higo, Yuji

    2016-04-01

    In situ high-pressure synchrotron X-ray diffraction and Raman spectroscopic studies of orthorhombic CaFe2O4-type β-CaCr2O4 chromite were carried out up to 16.2 and 32.0 GPa at room temperature using multi-anvil apparatus and diamond anvil cell, respectively. No phase transition was observed in this study. Fitting a third-order Birch-Murnaghan equation of state to the P-V data yields a zero-pressure volume of V 0 = 286.8(1) Å3, an isothermal bulk modulus of K 0 = 183(5) GPa and the first pressure derivative of isothermal bulk modulus K 0' = 4.1(8). Analyses of axial compressibilities show anisotropic elasticity for β-CaCr2O4 since the a-axis is more compressible than the b- and c-axis. Based on the obtained and previous results, the compressibility of several CaFe2O4-type phases was compared. The high-pressure Raman spectra of β-CaCr2O4 were analyzed to determine the pressure dependences and mode Grüneisen parameters of Raman-active bands. The thermal Grüneisen parameter of β-CaCr2O4 is determined to be 0.93(2), which is smaller than those of CaFe2O4-type CaAl2O4 and MgAl2O4.

  6. Time-of-flight 3D Neutron Diffraction for Multigrain Crystallography

    DEFF Research Database (Denmark)

    Cereser, Alberto

    This thesis presents a new technique for measuring spatially resolved microstructures in crystalline materials using pulsed neutron beams. The method, called Time-of-Flight Three Dimensional Neutron Diffraction (ToF 3DND), identifies the position, shape and crystallographic orientation of the ind......This thesis presents a new technique for measuring spatially resolved microstructures in crystalline materials using pulsed neutron beams. The method, called Time-of-Flight Three Dimensional Neutron Diffraction (ToF 3DND), identifies the position, shape and crystallographic orientation...

  7. Refractive and diffractive neutron optics with reduced chromatic aberration

    DEFF Research Database (Denmark)

    Poulsen, Stefan Othmar; Poulsen, Henning Friis; Bentley, P.M.

    2014-01-01

    Thermal neutron beams are an indispensable tool in physics research. The spatial and the temporal resolution attainable in experiments are dependent on the flux and collimation of the neutron beam which remain relatively poor, even for modern neutron sources. These difficulties may be mitigated...

  8. Neutron scattering and diffraction instrument for structural study on biology in Japan

    Energy Technology Data Exchange (ETDEWEB)

    Niimura, Nobuo [Japan Atomic Energy Research Inst., Ibaraki-ken (Japan)

    1994-12-31

    Neutron scattering and diffraction instruments in Japan which can be used for structural studies in biology are briefly introduced. Main specifications and general layouts of the instruments are shown.

  9. Study on Destructuring effect of trehalose on water by neutron diffraction

    CERN Document Server

    Branca, C; Migliardo, F; Magazù, V; Soper, A K

    2002-01-01

    In this work results on trehalose/water solutions by neutron diffraction are reported. The study of the partial structure factors and spatial distribution functions gives evidence of a decreasing tetrahedrality degree of water and justifies its cryoprotectant effectiveness. (orig.)

  10. High-resolution neutron diffraction studies of biological and industrial fibres

    Energy Technology Data Exchange (ETDEWEB)

    Langan, P.; Mason, S.A. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France); Fuller, W.; Forsyth, V.T.; Mahendrasingam, A.; Shotton, M.; Simpson, L. [Keele Univ. (United Kingdom); Grimm, H. [FZ, Juelich (Germany); Leberman, R. [EMBL, (Country Unknown)

    1997-04-01

    Neutron diffraction is becoming an important tool for studying fibres due to its complementarity to X-ray diffraction. Unlike X-rays, scattering of neutrons by polymer atoms is not a function of their atomic number. In high-resolution studies (1.5-3 A) on D19 deuteration (replacing H by D) is being used to change the relative scattering power of chosen groups making them easier to locate. Recent studies on DNA and cellulose are described. (author). 6 refs.

  11. Longe-Range Order in beta-Brass Studied by Neutron Diffraction

    DEFF Research Database (Denmark)

    Rathmann, Ole; Als-Nielsen, Jens Aage

    1974-01-01

    The long-range order, M(T), in β-brass has been measured by neutron diffraction from a small extinction-free crystal. The results agree with those obtained recently by x-ray diffraction. Near Tc our data are in accordance with a power law M(T)=D(1-T/Tc)β with the critical exponent β=0...

  12. Work hardening mechanism in high nitrogen austenitic steel studied by in situ neutron diffraction and in situ electron backscattering diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Ojima, M., E-mail: 07nd602g@hcs.ibaraki.ac.jp [Graduate School of Science and Engineering, Ibaraki University, Nakanarusawa, 316-8511 Hitachi, Ibaraki (Japan); Adachi, Y. [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Tomota, Y. [Graduate School of Science and Engineering, Ibaraki University, Nakanarusawa, 316-8511 Hitachi, Ibaraki (Japan); Ikeda, K. [Sumitomo Metal Industries, Ltd., Hikari, Kashima, Ibaraki 314-0014 (Japan); Kamiyama, T. [Institute of Material Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Katada, Y. [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan)

    2009-12-15

    With a focus on microstructural hierarchy, work hardening behaviour in high nitrogen-bearing austenitic steel (HNS) was investigated mainly by a combined technique of in situ neutron diffraction and in situ electron backscattering diffraction (EBSD). Stress partitioning due to difference in deformability among grains is enhanced in HNS. The larger stress partitioning among [h k l]-oriented family grains seems to realize high work hardening at a small strain. At a larger strain, dislocation density is higher in HNS than in low nitrogen austenitic steel (LNS), which is a possible reason for high work hardening after straining proceeds, resulting in large uniform elongation.

  13. Structural Transitions in Nanosized Zn0.97Al0.03O Powders under High Pressure Analyzed by in Situ Angle-Dispersive X-ray Diffraction

    Directory of Open Access Journals (Sweden)

    Chih-Ming Lin

    2016-07-01

    Full Text Available Nanosized aluminum-doped zinc oxide Zn1−xAlxO (AZO powders (AZO-NPs with x = 0.01, 0.03, 0.06, 0.09 and 0.11 were synthesized by chemical precipitation method. The thermogravimetric analysis (TGA indicated that the precursors were converted to oxides from hydroxides near 250 °C, which were then heated to 500 °C for subsequent thermal processes to obtain preliminary powders. The obtained preliminary powders were then calcined at 500 °C for three hours. The structure and morphology of the products were measured and characterized by angle-dispersive X-ray diffraction (ADXRD and scanning electron microscopy (SEM. ADXRD results showed that AZO-NPs with Al content less than 11% exhibited würtzite zinc oxide structure and there was no other impurity phase in the AZO-NPs, suggesting substitutional doping of Al on Zn sites. The Zn0.97Al0.03O powders (A3ZO-NPs with grain size of about 21.4 nm were used for high-pressure measurements. The in situ ADXRD measurements revealed that, for loading run, the pressure-induced würtzite (B4-to-rocksalt (B1 structural phase transition began at 9.0(1 GPa. Compared to the predicted phase-transition pressure of ~12.7 GPa for pristine ZnO nanocrystals of similar grain size (~21.4 nm, the transition pressure for the present A3ZO-NPs exhibited a reduction of ~3.7 GPa. The significant reduction in phase-transition pressure is attributed to the effects of highly selective site occupation, namely Zn2+ and Al3+, were mainly found in tetrahedral and octahedral sites, respectively.

  14. Structural Transitions in Nanosized Zn0.97Al0.03O Powders under High Pressure Analyzed by in Situ Angle-Dispersive X-ray Diffraction

    Science.gov (United States)

    Lin, Chih-Ming; Liu, Hsin-Tzu; Zhong, Shi-Yao; Hsu, Chia-Hung; Chiu, Yi-Te; Tai, Ming-Fong; Juang, Jenh-Yih; Chuang, Yu-Chun; Liao, Yen-Fa

    2016-01-01

    Nanosized aluminum-doped zinc oxide Zn1−xAlxO (AZO) powders (AZO-NPs) with x = 0.01, 0.03, 0.06, 0.09 and 0.11 were synthesized by chemical precipitation method. The thermogravimetric analysis (TGA) indicated that the precursors were converted to oxides from hydroxides near 250 °C, which were then heated to 500 °C for subsequent thermal processes to obtain preliminary powders. The obtained preliminary powders were then calcined at 500 °C for three hours. The structure and morphology of the products were measured and characterized by angle-dispersive X-ray diffraction (ADXRD) and scanning electron microscopy (SEM). ADXRD results showed that AZO-NPs with Al content less than 11% exhibited würtzite zinc oxide structure and there was no other impurity phase in the AZO-NPs, suggesting substitutional doping of Al on Zn sites. The Zn0.97Al0.03O powders (A3ZO-NPs) with grain size of about 21.4 nm were used for high-pressure measurements. The in situ ADXRD measurements revealed that, for loading run, the pressure-induced würtzite (B4)-to-rocksalt (B1) structural phase transition began at 9.0(1) GPa. Compared to the predicted phase-transition pressure of ~12.7 GPa for pristine ZnO nanocrystals of similar grain size (~21.4 nm), the transition pressure for the present A3ZO-NPs exhibited a reduction of ~3.7 GPa. The significant reduction in phase-transition pressure is attributed to the effects of highly selective site occupation, namely Zn2+ and Al3+, were mainly found in tetrahedral and octahedral sites, respectively. PMID:28773683

  15. The use of pulsed neutron diffraction to measure strain in composites

    Energy Technology Data Exchange (ETDEWEB)

    Bourke, M.A.M.; Goldstone, J.A.; Shi, N.; Gray, G.T. III [Los Alamos National Lab., NM (United States); James, M.R. [Rockwell Intl., Thousand Oaks, CA (United States). Science Center; Todd, R.I. [Oxford Univ. (United Kingdom)

    1994-03-01

    Neutron diffraction is a technique for measuring strain in crystalline materials. It is non destructive, phase discriminatory and more penetrating than X rays. Pulsed neutron sources (in contrast with steady state reactor sources) are particularly appropriate for examining heterogeneous materials or for recording the polycrystalline response of all lattice reflections. Several different aspects of composite behavior can be characterized and examples are given of residual strain measurements, strain relaxation during heating, applied loading, and determination of the strain distribution function.

  16. In situ neutron diffraction study of the nickel oxihydroxide electrode upon discharge

    Energy Technology Data Exchange (ETDEWEB)

    Barde, F.; Palacin, M.R.; Chabre, Y.; Isnard, O.; Tarascon, J.-M

    2004-07-15

    The redox discharge process of the nickel oxihydroxide electrode (NOE) were followed by in situ neutron diffraction with the aim of getting a deeper insight into the phases and mechanisms involved, paying special attention to the second plateau. A set of deuterated samples was prepared to be used as a reference for the interpretation of the in situ patterns. Neutron diffraction experiments indicate that redox process is the same over both the first and second plateaus and corresponds to a phase transformation over the main part of the oxidation/reduction range and hence indicates that this phenomenon should not be associated to a structural transformation.

  17. Real Structure and Resudal Stresses in Advanced Welds Determined by X-ray and Neutron Diffraction

    Czech Academy of Sciences Publication Activity Database

    Trojan, K.; Hervoches, Charles; Ganev, N.; Mikula, Pavol; Čapek, J.

    2017-01-01

    Roč. 9, SEP (2017), s. 32-38 E-ISSN 2336-5382 R&D Projects: GA MŠk LM2015056; GA ČR GB14-36566G Institutional support: RVO:61389005 Keywords : laser and MAG welding * residual stresses * X-ray diffraction * neutron diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism https://ojs.cvut.cz/ojs/index.php/APP/article/view/4401/4298

  18. Neutron Powder Diffraction Analysis and Constrained Refinement of Per-Fluorodiphenyl

    DEFF Research Database (Denmark)

    Mackenzie, Gordon A.; Pawley, G. S.; Dietrich, O. W.

    1975-01-01

    It is shown that with the small amount of data available in the neutron powder diffraction method, it is possible, by means of reasonable constraints, to refine a molecular structure involving a large number of atoms. The method has been used to refine the crystal structure of perfluorodiphenyl...

  19. Localization of ferrocene in NaY zeolite by powder x-ray and neutron diffraction

    NARCIS (Netherlands)

    Kemner, E.; Overweg, A.R.; Van Eijck, L.; Fitch, A.N.; Suard, E.; De Schepper, I.M.; Kearley, G.J.

    2002-01-01

    We study the inclusion of the metallocene ferrocene Fe(C5H5)2 molecules in the supercages of NaY zeolite. To find the exact location of the ferrocene molecules within the supercages we perform neutron and powder x-ray diffraction on bare NaY zeolite, and on NaY zeolite loaded with one or two

  20. Neutron diffraction study of the magnetic structure of HoCu2

    DEFF Research Database (Denmark)

    Smetana, Z.; Sima, V.; Lebech, Bente

    1986-01-01

    Neutron diffraction measurements show that in the temperature range from 7.4 to TN=10.4 K the magnetic structure of HoCu2 is a commensurably modulated a-axis collinear structure with a wave vector q1=1/3a*. Below 7.4 K an additional structure component develops and the low temperature magnetic...

  1. Neutron diffraction investigation of liquid alkali metal-gallium alloys. Giant cluster formation?

    NARCIS (Netherlands)

    Alvarez, M; Lomba, E; Verkerk, P; van der Aart, SA; Bionducci, M; Mirebeau, [No Value; van der Lugt, W

    Neutron diffraction experiments were performed on the liquid alloys NaGa, NaGa3, KGa3 and CsGa3. The structure factors of KGa3 and CsGa3 display prepeaks at small wavenumbers (0.64 and 0.61 (A) over circle -1, respectively). This may indicate the existence of extremely large aggregates of atoms in

  2. Neutron diffraction studies of the magnetic structures of TbRu2Si2

    DEFF Research Database (Denmark)

    Kawano, S.; Lebech, B.; Shigeoka, T.

    2000-01-01

    We have confirmed by neutron diffraction that the high-temperature phase of TbRu2Si2 exhibits a magnetic one-dimensional modulation with Q=(3/13 0 0), while for the intermediate phase the modulation becomes two-dimensional with many satellites. At low-temperature the magnetic structure changes...

  3. Neutron diffraction studies of Ho1-xYxNi2B2C compounds

    DEFF Research Database (Denmark)

    Chang, L.J.; Tomy, C.V.; Paul, D.M.K.

    1996-01-01

    Neutron diffraction measurements have been carried out to investigate the nature of magnetic ordering in Ho(1-x)Y(x)Ni(2)B(2)C (x = 0, 0.1 and 0.2) compounds. HoNi(2)B(2)C shows a complex type of magnetic ordering below the superconducting transition, with a commensurate antiferromagnetic ordering...

  4. Neutron Diffraction Studies of Dilute Cr-Re Single Crystal Alloys

    DEFF Research Database (Denmark)

    Lebech, Bente; Mikke, K.

    1972-01-01

    Neutron diffraction studies have been performed on five Cr-Re single crystal alloys with a Re content from 0 to 0·8 at. %. It was found that the wave vector of the sinusoidally modulated spin arrangement increases uniformly with temperature and concentration until a critical value of about 0·97. (2...

  5. Neutron diffraction from the vortex lattice in the heavy-fermion superconductor UPt3

    DEFF Research Database (Denmark)

    Kleiman, R.N.; Broholm, C.; Aeppli, G.

    1992-01-01

    We have used neutron diffraction to observe the vortex lattice of UPt3. This is the first such measurement in a heavy-fermion system, a superconductor below 1 K, or in a system with such a long magnetic penetration depth (6000 +/- 75 angstrom). It also provides the first value for the pair...

  6. A single crystal neutron diffraction study on mixed crystal (K)0.25 ...

    Indian Academy of Sciences (India)

    2018-02-02

    Feb 2, 2018 ... https://doi.org/10.1007/s12034-017-1514-x. A single crystal neutron diffraction study on mixed crystal. (K)0.25(NH4)0.75H2PO4: tuning of short strong hydrogen bonds by ionic interactions. RAJUL RANJAN CHOUDHURY. ∗ and R CHITRA. Solid State Physics Division, Bhabha Atomic Research Center, ...

  7. Recrystallization kinetics in copper investigated by in situ texture measurements by neutron diffraction

    DEFF Research Database (Denmark)

    Leffers, Torben; Hansen, Niels; Kjems, Jørgen

    1981-01-01

    The potential of neutron-diffraction texture measurement as a tool for accurate investigations of recrystallization kinetics is demonstrated by the application of the method to the recrystallization of heavily rolled copper (99.98% purity). The present investigation demonstrates that this technique...

  8. Experimental evaluation of a polycrystal deformation modeling scheme using neutron diffraction measurements

    DEFF Research Database (Denmark)

    Clausen, Bjørn; Lorentzen, Torben

    1997-01-01

    The uniaxial behavior of aluminum polycrystals is simulated using a rate-independent incremental self-consistent elastic-plastic polycrystal deformation model, and the results are evaluated by neutron diffraction measurements. The elastic strains deduced from the model show good agreement with th...

  9. Optimization of spring exchange coupled ferrites, studied by in situ neutron diffraction

    DEFF Research Database (Denmark)

    Ahlburg, Jakob; Christensen, Mogens; Granados-Miralles, Cecilia

    ) is reduced to a metallic alloy CoFe (soft magnet) by heating the sample and flowing it with hydrogen gas. It is studied in situ using neutron powder diffraction with a time resolution of 12 min. The transition from spinel to pure metal goes through an intermediate step of a metal oxide before being fully...... reduced. These metal oxides are antiferromagnetically ordered an is therefore considered a parasitic phase. However by fine-tuning the reaction temperature and hydrogen flow rate the occurrence of the phase can be minimized. In order to distinguish between Co and Fe Neutrons are chosen. Since neutrons...... have a spin it will also be possible to measure a magnetic signal and investigate the exchange-coupling. After the reduction the samples was furthermore investigated using powder x-ray diffraction and VSM (vibrating sample magnetometer). To understand the reaction mechanism, a series of experiments...

  10. Neutron diffraction and gravimetric study of the iron nitriding reaction under ammonia decomposition conditions.

    Science.gov (United States)

    Wood, Thomas J; Makepeace, Joshua W; David, William I F

    2017-10-18

    Ammonia decomposition over iron catalysts is known to be affected by whether the iron exists in elemental form or as a nitride. In situ neutron diffraction studies with simultaneous gravimetric analysis were performed on the nitriding and denitriding reactions of iron under ammonia decomposition conditions. The gravimetric analysis agrees well with the Rietveld analysis of the neutron diffraction data, both of which confirm that the form of the iron catalyst is strongly dependent on ammonia decomposition conditions. Use of ammonia with natural isotopic abundance as the nitriding agent means that the incoherent neutron scattering of any hydrogen within the gases present is able to be correlated to how much ammonia had decomposed. This novel analysis reveals that the nitriding of the iron occurred at exactly the same temperature as ammonia decomposition started. The iron nitriding and denitriding reactions are shown to be related to steps that take place during ammonia decomposition and the optimum conditions for ammonia decomposition over iron catalysts are discussed.

  11. In-Situ Neutron Diffraction Study of the Deformation Mechanisms in Solutionized Mg-Zn Alloys

    Science.gov (United States)

    Mulay, R. P.; Agnew, S. R.; Caceres, C. H.

    In-situ neutron diffraction experiments were carried out on solutionized and randomly textured Mg-Zn alloy castings with similar grain sizes but variation in Zn content from 1.7 to 6.6 wt %. The evolution in internal elastic strains and diffraction peak intensities with increasing load were analyzed. The macroscopic stress strain curve shows an increase in yield strength with an increase in zinc content. Neutron diffraction results indicate that the strength of basal slip, tension twinning and slip/compression twinning modes increases with increase in zinc content. However, the strength of prismatic slip appears to be unaffected by zinc content at lower concentrations and increases with zinc content only at higher concentrations. These results are discussed in light of prior work on the Mg-Zn system.

  12. High-resolution neutron powder-diffraction in CMR manganates

    Energy Technology Data Exchange (ETDEWEB)

    Suard, E.; Radaelli, P.G. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)

    1997-04-01

    Manganese-oxide materials have recently been the subject of renewed attention, due to the `colossal` magnetoresistance (CMR) displayed near the spin-ordering temperature T{sub c} by some of these compounds. CMR has been evidenced in at least three families of manganese oxides. In most cases, the CMR compounds behave as paramagnetic semiconductors at high temperatures, and as ferromagnetic metals below T{sub c}. The study of this metallization process has lead some theorists to challenge its traditional interpretation in terms of the so-called double-exchange mechanism, and to propose alternative scenarios in which the coupling of the charge carriers with the lattice plays a paramount role. Powder diffraction method, being at the forefront of CMR research is presented. (author). 4 refs.

  13. Electrostatic levitation facility optimized for neutron diffraction studies of high temperature liquids at a spallation neutron source

    Energy Technology Data Exchange (ETDEWEB)

    Mauro, N. A., E-mail: namauro@noctrl.edu [Department of Physics, North Central College, Naperville, Illinois 60540 (United States); Vogt, A. J. [Instrument and Source Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Derendorf, K. S. [Mechanical Engineering and Materials Science, Washington University, St. Louis, Missouri 63130 (United States); Johnson, M. L.; Kelton, K. F. [Department of Physics and Institute of Materials Science and Engineering, Washington University, 1 Brookings Drive, St. Louis, Missouri 63130 (United States); Rustan, G. E.; Quirinale, D. G.; Goldman, A. I. [Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States); Kreyssig, A. [Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States); Division of Materials Sciences and Engineering, Ames Laboratory, Ames, Iowa 50011 (United States); Lokshin, K. A. [Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996 (United States); Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Neuefeind, J. C.; An, Ke [Chemical and Engineering Materials Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Wang, Xun-Li [Department of Physics and Materials Science, City University of Hong Kong, 83 Tat Chee Ave., Kowloon (Hong Kong); Egami, T. [Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996 (United States); Department of Physics and Astronomy, Joint Institute for Neutron Sciences, University of Tennessee, Knoxville, Tennessee 37996 (United States)

    2016-01-15

    Neutron diffraction studies of metallic liquids provide valuable information about inherent topological and chemical ordering on multiple length scales as well as insight into dynamical processes at the level of a few atoms. However, there exist very few facilities in the world that allow such studies to be made of reactive metallic liquids in a containerless environment, and these are designed for use at reactor-based neutron sources. We present an electrostatic levitation facility, NESL (for Neutron ElectroStatic Levitator), which takes advantage of the enhanced capabilities and increased neutron flux available at spallation neutron sources (SNSs). NESL enables high quality elastic and inelastic neutron scattering experiments to be made of reactive metallic and other liquids in the equilibrium and supercooled temperature regime. The apparatus is comprised of a high vacuum chamber, external and internal neutron collimation optics, and a sample exchange mechanism that allows up to 30 samples to be processed between chamber openings. Two heating lasers allow excellent sample temperature homogeneity, even for samples approaching 500 mg, and an automated temperature control system allows isothermal measurements to be conducted for times approaching 2 h in the liquid state, with variations in the average sample temperature of less than 0.5%. To demonstrate the capabilities of the facility for elastic scattering studies of liquids, a high quality total structure factor for Zr{sub 64}Ni{sub 36} measured slightly above the liquidus temperature is presented from experiments conducted on the nanoscale-ordered materials diffractometer (NOMAD) beam line at the SNS after only 30 min of acquisition time for a small sample (∼100 mg)

  14. Final Technical Report: Application of in situ Neutron Diffraction to Understand the Mechanism of Phase Transitions

    Energy Technology Data Exchange (ETDEWEB)

    Chandran, Ravi

    2018-02-09

    In this research, phase transitions in the bulk electrodes for Li-ion batteries were investigated using neutron diffraction (ND) as well as neutron imaging techniques. The objectives of this research is to design of a novel in situ electrochemical cell to obtain Rietveld refinable neutron diffraction experiments using small volume electrodes of various laboratory/research-scale electrodes intended for Li-ion batteries. This cell is also to be used to investigate the complexity of phase transitions in Li(Mg) alloy electrodes, either by diffraction or by neutron imaging, which occur under electrochemical lithiation and delithiation, and to determine aspects of phase transition that enable/limit energy storage capacity. Additional objective is to investigate the phase transitions in electrodes made of etched micro-columns of silicon and investigate the effect of particle/column size on phase transitions and nonequilibrium structures. An in situ electrochemical cell was designed successfully and was used to study the phase transitions under in-situ neutron diffraction in both the electrodes (anode/cathode) simultaneously in graphite/LiCoO2 and in graphite/LiMn2O4 cells each with two cells. The diffraction patterns fully validated the working of the in situ cell. Additional experimental were performed using the Si micro-columnar electrodes. The results revealed new lithiation phenomena, as evidenced by mosaicity formation in silicon electrode. These experiments were performed in Vulcan diffractometer at SNS, Oak Ridge National Laboratory. In parallel, the spatial distribution of Li during lithiation and delithiation processes in Li-battery electrodes were investigated. For this purpose, neutron tomographic imaging technique has been used for 3D mapping of Li distribution in bulk Li(Mg) alloy electrodes. It was possible to observe the phase boundary of Li(Mg) alloy indicating phase transition from Li-rich BCC β-phase to Li-lean

  15. Neutron diffraction study of LnBaCuFeO5+#delta#, (Ln=Y,Pr)

    DEFF Research Database (Denmark)

    Ruiz-Aragón, M.J.; Amador, U.; Morán, E.

    1994-01-01

    Neutron diffraction studies of the title materials have been performed at 600K, R.T. and 8K. Copper and iron ions are randomly distributed in two equivalent MO2 planes being the symmetry P4/mmm for all the samples and temperatures. Some extra oxygen has been found in PrBaCuFeO5+δ destroying the AF...... ordering, present at R. T. in YBaCuFeO5. Besides this, at low temperature a magnetic phase transition has been found. On the other hand, both materials show a complex micro-structure as determined by electron diffraction....

  16. Path Dependency of High Pressure Phase Transformations

    Science.gov (United States)

    Cerreta, Ellen

    2017-06-01

    At high pressures titanium and zirconium are known to undergo a phase transformation from the hexagonal close packed (HCP), alpha-phase to the simple-hexagonal, omega-phase. Under conditions of shock loading, the high-pressure omega-phase can be retained upon release. It has been shown that temperature, peak shock stress, and texture can influence the transformation. Moreover, under these same loading conditions, plastic processes of slip and twinning are also affected by similar differences in the loading path. To understand this path dependency, in-situ velocimetry measurements along with post-mortem metallographic and neutron diffraction characterization of soft recovered specimens have been utilized to qualitatively understand the kinetics of transformation, quantify volume fraction of retained omega-phase and characterize the shocked alpha and omega-phases. Together the work described here can be utilized to map the non-equilibrium phase diagram for these metals and lend insight into the partitioning of plastic processes between phases during high pressure transformation. In collaboration with: Frank Addesssio, Curt Bronkhorst, Donald Brown, David Jones, Turab Lookman, Benjamin Morrow, Carl Trujillo, Los Alamos National Lab.; Juan Pablo Escobedo-Diaz, University of New South Wales; Paulo Rigg, Washington State University.

  17. Neutron diffraction measurements and modeling of residual strains in metal matrix composites

    Science.gov (United States)

    Saigal, A.; Leisk, G. G.; Hubbard, C. R.; Misture, S. T.; Wang, X. L.

    1996-01-01

    Neutron diffraction measurements at room temperature are used to characterize the residual strains in tungsten fiber-reinforced copper matrix, tungsten fiber-reinforced Kanthal matrix, and diamond particulate-reinforced copper matrix composites. Results of finite element modeling are compared with the neutron diffraction data. In tungsten/Kanthal composites, the fibers are in compression, the matrix is in tension, and the thermal residual strains are a strong function of the volume fraction of fibers. In copper matrix composites, the matrix is in tension and the stresses are independent of the volume fraction of tungsten fibers or diamond particles and the assumed stress free temperature because of the low yield strength of the matrix phase.

  18. Time-of-Flight Three Dimensional Neutron Diffraction in Transmission Mode for Mapping Crystal Grain Structures

    DEFF Research Database (Denmark)

    Cereser, Alberto; Strobl, Markus; Hall, Stephen A.

    2017-01-01

    -of-flight neutron beamline. The technique was developed and tested with data collected at the Materials and Life Science Experimental Facility of the Japan Proton Accelerator Complex (J-PARC) for an iron sample. We successfully reconstructed the shape of 108 grains and developed an indexing procedure...... constituting the material. This article presents a new non-destructive 3D technique to study centimeter-sized bulk samples with a spatial resolution of hundred micrometers: time-of-flight three-dimensional neutron diffraction (ToF 3DND). Compared to existing analogous X-ray diffraction techniques, ToF 3DND...... enables studies of samples that can be both larger in size and made of heavier elements. Moreover, ToF 3DND facilitates the use of complicated sample environments. The basic ToF 3DND setup, utilizing an imaging detector with high spatial and temporal resolution, can easily be implemented at a time...

  19. In Situ Studies of Intercritically Austempered Ductile Iron Using Neutron Diffraction

    Science.gov (United States)

    Druschitz, Alan P.; Aristizabal, Ricardo E.; Druschitz, Edward; Hubbard, C. R.; Watkins, Thomas R.; Walker, L.; Ostrander, Mel

    2012-05-01

    Intercritically austempered ductile irons hold promise for applications requiring fatigue durability, excellent castability, low production energy requirements, reduced greenhouse gas emissions, and excellent machinability. In the present study, four different ductile iron alloys, containing manganese and nickel as the primary austenite-stabilizing elements, were heat treated to obtain different quantities of austenite in the final microstructure. This article reports the microstructures and phases present in these alloys. Furthermore, lattice strains and diffraction elastic constants in various crystallographic directions and the transformation characteristics of the austenite were determined as a function of applied stress using in situ loading during neutron diffraction at the second generation Neutron Residual Stress Facility at the High Flux Isotope Reactor at Oak Ridge National Laboratory.

  20. Neutron Diffraction from the Second Layer of 4He on Graphite

    DEFF Research Database (Denmark)

    da Costa Carneiro, Kim; Passell, L.; Thomlinson, W.

    1981-01-01

    Neutron diffraction has been used to study the second atomic layer of **4He adsorbed on graphite. As the **4He-coverage exceeds the first layer, the second initially forms a fluid phase. But when there is enough **4He in the third layer to compress the second, this layer solidifies. The structure...... of the second layer as well as the distances between layers are discussed.......Neutron diffraction has been used to study the second atomic layer of **4He adsorbed on graphite. As the **4He-coverage exceeds the first layer, the second initially forms a fluid phase. But when there is enough **4He in the third layer to compress the second, this layer solidifies. The structure...

  1. Time-of-Flight Three Dimensional Neutron Diffraction in Transmission Mode for Mapping Crystal Grain Structures

    DEFF Research Database (Denmark)

    Cereser, Alberto; Strobl, Markus; Hall, Stephen A.

    2017-01-01

    constituting the material. This article presents a new non-destructive 3D technique to study centimeter-sized bulk samples with a spatial resolution of hundred micrometers: time-of-flight three-dimensional neutron diffraction (ToF 3DND). Compared to existing analogous X-ray diffraction techniques, ToF 3DND...... enables studies of samples that can be both larger in size and made of heavier elements. Moreover, ToF 3DND facilitates the use of complicated sample environments. The basic ToF 3DND setup, utilizing an imaging detector with high spatial and temporal resolution, can easily be implemented at a time......-of-flight neutron beamline. The technique was developed and tested with data collected at the Materials and Life Science Experimental Facility of the Japan Proton Accelerator Complex (J-PARC) for an iron sample. We successfully reconstructed the shape of 108 grains and developed an indexing procedure...

  2. Neutron diffraction on CeMnAlD{sub x} (0{<=}x{<=}2.5)

    Energy Technology Data Exchange (ETDEWEB)

    Spatz, P.; Gross, K.; Schlapbach, L. [Fribourg Univ. (Switzerland); Fischer, P.; Fauth, F. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-09-01

    CeMnAl was found to absorb considerable amounts of hydrogen. Part of the totally stored hydrogen is absorbed at low pressures (< 10 mbar). Additional hydrogen can be absorbed and desorbed reversible in a wide pressure range (10 mbar to 10 bar) at room temperature. In order to a better understanding of this new metal-hydride system, we performed neutron diffraction on deuterated CeMnAl samples with different D-concentrations. (author) 1 fig., 2 refs.

  3. Optimisation of post-drawing treatments by means of neutron diffraction

    OpenAIRE

    Ruiz Hervías, Jesús; Atienza Riera, José Miguel; Elices Calafat, Manuel; Oliver, E.C

    2008-01-01

    The mechanical properties and the durability of cold-drawn eutectoid wires (especially in aggressive environments) are influenced by the residual stresses generated during the drawing process. Steelmakers have devised procedures (thermomechanical treatments after drawing) attempting to relieve them in order to improve wire performance. In thiswork neutron diffraction measurements have been used to ascertain the role of temperature and applied force – during post-drawing treatments – on the re...

  4. Neutron Diffraction Study of Magnetic Ordering in Cd1-xMnxTe

    DEFF Research Database (Denmark)

    Giebultowicz, T.; Kepa, H.; Buras, B.

    1981-01-01

    Neutron diffraction experiments were performed on Cd1−xMnxTe crystals for x=0.40, 0.60, 0.63, 0.65 and 0.70. Magnetic Bragg scattering was observed at low temperatures for xgreater-or-equal, slanted0.60 corresponding to the Type III antiferromagnetic ordering of a f.c.c. sub-lattice. The Néel...

  5. Neutron Diffraction Evaluation of Near Surface Residual Stresses at Welds in 1300 MPa Yield Strength Steel

    Science.gov (United States)

    Harati, Ebrahim; Karlsson, Leif; Svensson, Lars-Erik; Pirling, Thilo; Dalaei, Kamellia

    2017-01-01

    Evaluation of residual stress in the weld toe region is of critical importance. In this paper, the residual stress distribution both near the surface and in depth around the weld toe was investigated using neutron diffraction, complemented with X-ray diffraction. Measurements were done on a 1300 MPa yield strength steel welded using a Low Transformation Temperature (LTT) consumable. Near surface residual stresses, as close as 39 µm below the surface, were measured using neutron diffraction and evaluated by applying a near surface data correction technique. Very steep surface stress gradients within 0.5 mm of the surface were found both at the weld toe and 2 mm into the heat affected zone (HAZ). Neutron results showed that the LTT consumable was capable of inducing near surface compressive residual stresses in all directions at the weld toe. It is concluded that there are very steep stress gradients both transverse to the weld toe line and in the depth direction, at the weld toe in LTT welds. Residual stress in the base material a few millimeters from the weld toe can be very different from the stress at the weld toe. Care must, therefore, be exercised when relating the residual stress to fatigue strength in LTT welds. PMID:28772953

  6. Neutron Diffraction Evaluation of Near Surface Residual Stresses at Welds in 1300 MPa Yield Strength Steel

    Directory of Open Access Journals (Sweden)

    Ebrahim Harati

    2017-05-01

    Full Text Available Evaluation of residual stress in the weld toe region is of critical importance. In this paper, the residual stress distribution both near the surface and in depth around the weld toe was investigated using neutron diffraction, complemented with X-ray diffraction. Measurements were done on a 1300 MPa yield strength steel welded using a Low Transformation Temperature (LTT consumable. Near surface residual stresses, as close as 39 µm below the surface, were measured using neutron diffraction and evaluated by applying a near surface data correction technique. Very steep surface stress gradients within 0.5 mm of the surface were found both at the weld toe and 2 mm into the heat affected zone (HAZ. Neutron results showed that the LTT consumable was capable of inducing near surface compressive residual stresses in all directions at the weld toe. It is concluded that there are very steep stress gradients both transverse to the weld toe line and in the depth direction, at the weld toe in LTT welds. Residual stress in the base material a few millimeters from the weld toe can be very different from the stress at the weld toe. Care must, therefore, be exercised when relating the residual stress to fatigue strength in LTT welds.

  7. Neutron diffraction and quasielastic neutron scattering studies of films of intermediate-length alkanes adsorbed on a graphite surface

    Science.gov (United States)

    Diama, Armand

    Over the past several years, we have conducted a variety of elastic neutron diffraction and quasielastic neutron scattering experiments to study the structure and the dynamics of films of two intermediate-length alkane molecules (C nH2n+2), adsorbed on a graphite basal-plane surface. The two molecules are the normal alkane n-tetracosane [n-CH 3(CH2)22CH3] and the branched alkane squalane (C30H62 or 2, 6, 10, 15, 19, 23-hexamethyltetracosane) whose carbon backbone is the same length as teteracosane. The temperature dependence of the monolayer structure of tetracosane and squalane was investigated using elastic neutron diffraction and evidence of two phase transitions was observed. Both the low-coverage tetracosane (C 24H50) and squalane (C30H62) monolayers have crystalline-to-"smectic" and "smectic"-to-isotropic fluid phase transitions upon heating. The diffusive motion in the tetracosane and squalane monolayers has been investigated by quasielastic neutron scattering. Two different quasielastic neutron scattering spectrometers at the Center for Neutron Research, National Institute of Standards and Technology (NIST) have been used. The spectrometers differ in both their dynamic range and energy resolution allowing molecular motions to be investigated on time scales in the range 10-13--10 -9 s. On these time scales, we observe evidence of translational, rotational, and intermolecular diffusive motions in the tetracosane and squalane monolayers. We conclude that the molecular diffusive motion in the two monolayers is qualitatively similar. Thus, despite the three methyl sidegroups at each end of the squalane molecule, its monolayer structure, phase transitions, and dynamics are qualitatively similar to that of a monolayer of the unbranched tetracosane molecules. With the higher resolution spectrometer at NIST, we have also investigated the molecular diffusive motion in multilayer tetracosane films. The analysis of our measurements indicates slower diffusive motion in

  8. Raman scattering and x-ray diffraction studies of polycrystalline CaCu3Ti4O12 under high-pressure

    DEFF Research Database (Denmark)

    Valim, D.; Filho, A. G. S.; Freire, P. T. C.

    2004-01-01

    remains stable up to the maximum pressure (5.3 GPa) we reached in this experiment. The pressure coefficients for the observed Raman modes were determined. This set of parameters was used for evaluating the stress developed in CCTO thin films. The high-pressure x-ray studies were extended up to 46 GPa...... and the data confirmed that the T-h structure remains stable up to this pressure. The pressure-volume data are well described by the Birch's equation of state. The experimental value of the zero pressure bulk modulus is B-0=212+/-2 GPa. Gruneisen parameters of CCTO were also determined....

  9. Inorganic pyrophosphatase crystals from Thermococcus thioreducens for X-ray and neutron diffraction.

    Science.gov (United States)

    Hughes, Ronny C; Coates, Leighton; Blakeley, Matthew P; Tomanicek, Steve J; Langan, Paul; Kovalevsky, Andrey Y; García-Ruiz, Juan M; Ng, Joseph D

    2012-12-01

    Inorganic pyrophosphatase (IPPase) from the archaeon Thermococcus thioreducens was cloned, overexpressed in Escherichia coli, purified and crystallized in restricted geometry, resulting in large crystal volumes exceeding 5 mm3. IPPase is thermally stable and is able to resist denaturation at temperatures above 348 K. Owing to the high temperature tolerance of the enzyme, the protein was amenable to room-temperature manipulation at the level of protein preparation, crystallization and X-ray and neutron diffraction analyses. A complete synchrotron X-ray diffraction data set to 1.85 Å resolution was collected at room temperature from a single crystal of IPPase (monoclinic space group C2, unit-cell parameters a=106.11, b=95.46, c=113.68 Å, α=γ=90.0, β=98.12°). As large-volume crystals of IPPase can be obtained, preliminary neutron diffraction tests were undertaken. Consequently, Laue diffraction images were obtained, with reflections observed to 2.1 Å resolution with I/σ(I) greater than 2.5. The preliminary crystallographic results reported here set in place future structure-function and mechanism studies of IPPase.

  10. Sample positioning in neutron diffraction experiments using a multi-material fiducial marker

    Energy Technology Data Exchange (ETDEWEB)

    Marais, D., E-mail: Deon.Marais@necsa.co.za [Research and Development Division, South African Nuclear Energy Corporation (Necsa) SOC Limited, PO Box 582, Pretoria 0001 (South Africa); School of Mechanical and Nuclear Engineering, North-West University, Potchefstroom 2520 (South Africa); Venter, A.M., E-mail: Andrew.Venter@necsa.co.za [Research and Development Division, South African Nuclear Energy Corporation (Necsa) SOC Limited, PO Box 582, Pretoria 0001 (South Africa); Faculty of Agriculture Science and Technology, North-West University, Mahikeng 2790 (South Africa); Markgraaff, J., E-mail: Johan.Markgraaff@nwu.ac.za [School of Mechanical and Nuclear Engineering, North-West University, Potchefstroom 2520 (South Africa); James, J., E-mail: Jon.James@open.ac.uk [Faculty of Mathematics, Computing and Technology, The Open University, Milton Keynes, MK76AA England (United Kingdom)

    2017-01-01

    An alternative sample positioning method is reported for use in conjunction with sample positioning and experiment planning software systems deployed on some neutron diffraction strain scanners. In this approach, the spherical fiducial markers and location trackers used with optical metrology hardware are replaced with a specifically designed multi-material fiducial marker that requires one diffraction measurement. In a blind setting, the marker position can be determined within an accuracy of ±164 µm with respect to the instrument gauge volume. The scheme is based on a pre-determined relationship that links the diffracted peak intensity to the absolute positioning of the fiducial marker with respect to the instrument gauge volume. Two methods for establishing the linking relationship are presented, respectively based on fitting multi-dimensional quadratic functions and a cross-correlation artificial neural network.

  11. Sample positioning in neutron diffraction experiments using a multi-material fiducial marker

    Science.gov (United States)

    Marais, D.; Venter, A. M.; Markgraaff, J.; James, J.

    2017-01-01

    An alternative sample positioning method is reported for use in conjunction with sample positioning and experiment planning software systems deployed on some neutron diffraction strain scanners. In this approach, the spherical fiducial markers and location trackers used with optical metrology hardware are replaced with a specifically designed multi-material fiducial marker that requires one diffraction measurement. In a blind setting, the marker position can be determined within an accuracy of ±164 μm with respect to the instrument gauge volume. The scheme is based on a pre-determined relationship that links the diffracted peak intensity to the absolute positioning of the fiducial marker with respect to the instrument gauge volume. Two methods for establishing the linking relationship are presented, respectively based on fitting multi-dimensional quadratic functions and a cross-correlation artificial neural network.

  12. Urea and deuterium mixtures at high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Donnelly, M., E-mail: m.donnelly-2@sms.ed.ac.uk; Husband, R. J.; Frantzana, A. D.; Loveday, J. S. [Centre for Science at Extreme Conditions and School of Physics and Astronomy, The University of Edinburgh, Erskine Williamson Building, Peter Guthrie Tait Road, The King’s Buildings, Edinburgh EH9 3FD (United Kingdom); Bull, C. L. [ISIS, Rutherford Appleton Laboratory, Oxford Harwell, Didcot OX11 0QX (United Kingdom); Klotz, S. [IMPMC, CNRS UMR 7590, Université P and M Curie, 4 Place Jussieu, 75252 Paris (France)

    2015-03-28

    Urea, like many network forming compounds, has long been known to form inclusion (guest-host) compounds. Unlike other network formers like water, urea is not known to form such inclusion compounds with simple molecules like hydrogen. Such compounds if they existed would be of interest both for the fundamental insight they provide into molecular bonding and as potential gas storage systems. Urea has been proposed as a potential hydrogen storage material [T. A. Strobel et al., Chem. Phys. Lett. 478, 97 (2009)]. Here, we report the results of high-pressure neutron diffraction studies of urea and D{sub 2} mixtures that indicate no inclusion compound forms up to 3.7 GPa.

  13. Methane storage mechanism in the metal-organic framework Cu3(btc)2: An in situ neutron diffraction study

    NARCIS (Netherlands)

    Getzschmann, J.; Senkovska, I.; Wallacher, D.; Tovar, M.; Fairen-Jimenez, D.; Düren, T.; van Baten, J.M.; Krishna, R.; Kaskel, S.

    2010-01-01

    The adsorption of deutero-methane (CD4) in Cu3(btc)2 (HKUST-1) was investigated at 77 K using high-resolution neutron powder diffraction. Rietveld refinement of the neutron data revealed a sequential filling of the rigid framework at distinct preferred adsorption sites, and showed the importance of

  14. Magnetic Phase Transition in Rare Earth Metal Holmium at Low Temperatures and High Pressures

    Science.gov (United States)

    Thomas, Sarah; Uhoya, Walter; Wenger, Lowell; Vohra, Yogesh

    2012-02-01

    The heavy rare earth metal Holmium has been studied under high pressures and low temperatures using a designer diamond anvil cell and neutron diffraction using a Paris-Edinburgh Cell at the Spallation Neutrons and Pressure (SNAP) Diffractometer. The electrical resistance measurement using designer diamond shows a change in slope at the Neel temperature as the temperature is lowered at high pressures. At atmospheric pressure TN=120 K and decreases with a slope of -4.7 K/GPa as pressure is increased, until reaching 9 GPa, at which pressure the magnetic ordering is lost. This correlates to the pressure at which there is a structural change from an hcp phase to an α-Sm structure. Neutron diffraction measurements made above and below the Neel temperature at increasing pressures show the reversibility of the change between the paramagnetic and antiferromagnetic states. The parameters of the low temperature incommensurate magnetic phase will be reported at various pressures.

  15. X-ray Diffraction and Neutron Scattering Analysis of Natural and Synthetic Spider Silk Fibers

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, Randolph [Utah State Univ., Logan, UT (United States)

    2013-11-11

    Spider silks have the potential to provide new bio-inspired materials for numerous applications in bioenergetics and products ranging from protective clothing to artificial ligaments and tendons. A number of spider silk genes have been cloned and sequenced by the Lewis laboratory revealing the basis for understanding the key elements of spider silk proteins with respect to their materials performance. In particular, specific amino acid motifs have been identified which have been conserved for over 125 million years in all spiders that use their silk to physically trap prey. The key element in taking the next step toward generating bio-based materials from spider silks will be to move from the current descriptive data to predictive knowledge. Current efforts are focused on mimicking spider silk through synthetic proteins. In developing synthetic silk fibers, we first need to understand the complete secondary and tertiary structure of natural silk so that we can compare synthetic constructs to the natural material. Being able to compare the structure on a single fiber level is critical to the future of molecular directed mimic development because we can vary mechanical properties by different spinning methods. The new generation of synchrotron x-ray diffraction and neutron beamlines will allow, for the first time, determination of the molecular structure of silk fibers and synthetic mimics. We propose an exciting new collaborative research team working jointly between Argonne National Laboratory, Arizona State U. and the University of Wyoming to address the ?characterization of synthetic and natural spider silk fibers using x-ray and neutron diffraction.? Thus these new methodologies will provide understanding of current fibers and determine changes needed to produce fibers with specific properties. The following specific aims are proposed: ? Synthesize spider silk fibers with molecular structures mimicking that of natural silks. Test the mechanic properties of these

  16. Production, crystallization and neutron diffraction of fully deuterated human myelin peripheral membrane protein P2.

    Science.gov (United States)

    Laulumaa, Saara; Blakeley, Matthew P; Raasakka, Arne; Moulin, Martine; Härtlein, Michael; Kursula, Petri

    2015-11-01

    The molecular details of the formation of the myelin sheath, a multilayered membrane in the nervous system, are to a large extent unknown. P2 is a peripheral membrane protein from peripheral nervous system myelin, which is believed to play a role in this process. X-ray crystallographic studies and complementary experiments have provided information on the structure-function relationships in P2. In this study, a fully deuterated sample of human P2 was produced. Crystals that were large enough for neutron diffraction were grown by a ten-month procedure of feeding, and neutron diffraction data were collected to a resolution of 2.4 Å from a crystal of 0.09 mm(3) in volume. The neutron crystal structure will allow the positions of H atoms in P2 and its fatty-acid ligand to be visualized, as well as shedding light on the fine details of the hydrogen-bonding networks within the P2 ligand-binding cavity.

  17. Structure of deuterated liquid n-butanol by neutron diffraction and molecular dynamics simulations

    Science.gov (United States)

    Cristiglio, Viviana; Gonzalez, Miguel Angel; Cuello, Gabriel Julio; Cabrillo, Carlos; Pardo, Luis Carlos; Silva-Santisteban, Alvaro

    Aliphatic alcohols are the simpler molecular liquids possessing a polar hydroxylic group and a nonpolar alkyl tail. While the structure of the smallest alcohols has been relatively well studied, no much attention has been paid to the temperature dependence of the pre-peak observed before the main diffraction peak. The role of H-bonding in causing this feature and the direct relation between the number of C atoms and their distance were discovered very early, suggesting a liquid picture constituted of straight chains joined by H-bonds with the formation of mesoscopic size clusters. X-rays and neutron diffraction measurements showed that the height of the pre-peak associated with the formation of H-bonds increases with temperature. To explain this counterintuitive effect, a complete diffraction study using two neutron diffractometers D4 and D16 (ILL, Grenoble, France) allowing to cover the range 0.01-23 Å t1 and exploring a temperature range from 100 K (glassy butanol) to 400 K (moderately supercritical conditions) has been conducted. Molecular Dynamics simulations using the OPLS-AA potential were also carried out as a function of temperature and compared to experiment. Experimental and numerical results of liquid n-butanol and its glassy transition will be presented.

  18. Neutron diffraction analysis of residual strain/stress distribution in the vicinity of high strength welds

    Directory of Open Access Journals (Sweden)

    Hamák I.

    2010-06-01

    Full Text Available Residual stresses resulting from non homogeneous heat distribution during welding process belong to most significant factor influencing behavior of welded structures. These stresses are responsible for defect occurrence during welding and they are also responsible for crack initiation and propagation at the either static or dynamic load. The significant effect of weld metal chemical composition as well as the effect of fatigue load and local plastic deformation on residual stress distribution and fatigue life have been recognized for high strength steels welds. The changes in residual stress distribution have then positive effect on cold cracking behavior and also on fatigue properties of the welds [1-3]. Several experimental methods, both destructive and non-destructive, such as hole drilling method, X-ray diffraction, neutron diffraction and others, have been used to examine residual stress distribution in all three significant orientations in the vicinity of the welds. The present contribution summarizes the results of neutron diffraction measurements of residual stress distribution in the vicinity of single-pass high-strength-steel welds having different chemical composition as well as the influence of fatigue load and local plastic deformation. It has been observed that the chemical composition of the weld metal has a significant influence on the stress distribution around the weld. Similarly, by aplying both cyclic load or pre-stress load on the specimens, stress relaxation was observed even in the region of approximately 40 mm far from the weld toe.

  19. Structural characterization of substituted lanthanum tungstates with X-ray and neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Fantin, Andrea; Scherb, Tobias; Schumacher, Gerhard [Helmholtz-Zentrum Berlin fuer Materialen und Energie (Germany); Seeger, Janka; Meulenberg, Wilhelm A. [Forschungszentrum Juelich (Germany)

    2015-07-01

    Our work on proton conducting materials deals with structural characterization of two different series of substituted lanthanum tungstates: La5.4W(1-x)MxO12-delta with M=Mo,Re and 0<=x<=0.2. The main methods used to understand their crystal structure are Neutron Diffraction (ND) and High-Resolution X-Ray Diffraction (HRXRD). Experiments were carried at ILL (Grenoble, France) and PSI (Villigen, Switzerland). Different elemental contrast is reached with these complementary diffraction techniques. Our specimens consist of three cations (La, W, Mo or Re) and oxygen anions. In order to distinguish W (Z=74, b=4.86fm) and Re (Z=75, b=9.2fm) neutrons are needed, while for La (Z=57, b=8.2fm), W(Z=74, b=4.86fm) and Mo (Z=42, b=6.7fm) good contrast is also given by X-Rays. Combined refinements to model accurately anti-site disorder, position of the substituted elements and oxygen (Z=8, b=5.8fm) positions in this highly disordered material are mandatory. Measurements in dependence of temperature down to 1.5K confirm the structural model suggested by one of the coauthors without any unmodeled static disorder. Substitution and deuteration/humidification show no relevant structural changes.

  20. First experimental implementation of pulse shaping for neutron diffraction on pulsed sources

    Energy Technology Data Exchange (ETDEWEB)

    Russina, M. [Helmholtz-Zentrum-Berlin, Hahn-Meitner Platz 1, 14109 Berlin (Germany); Kali, Gy.; Santa, Zs. [HAS Research Institute for Solid State Physics, Konkoly Thege ut. 29-33, 1121 Budapest (Hungary); Mezei, F., E-mail: f.mezei@esshungary.eu [HAS Research Institute for Solid State Physics, Konkoly Thege ut. 29-33, 1121 Budapest (Hungary); European Spallation Source ESS AB, P.O. Box 176, 22100 Lund (Sweden)

    2011-10-21

    One of the central issues in the design and the use of pulsed neutron sources is the control of pulse length in elastic scattering experiments, most significantly diffraction on crystalline matter. On the existing short pulse spallation sources the strongly wavelength dependent source pulse length that determines the resolution is permanently fixed on each beam line by the type of the moderator it faces. We have experimentally implemented for the first time the wavelength frame multiplication (WFM) multiplexing chopper method, an earlier proposed variant of the by now fully tested repetition rate multiplication technique for inelastic scattering spectroscopy on pulsed neutron sources. We have operated the time-of-flight diffractometer at the continuous reactor source at BNC in an unconventional multiplexing mode that emulates a pulsed source. As a full proof of principle of the WFM method we have experimentally demonstrated the extraction from each source pulse a series of polychromatic, chopper shaped neutron pulses, which can continuously cover any wavelength band. The achieved 25 {mu}s FWHM pulse length is shorter than that can be obtained at all at short pulse spallation sources for cold neutrons. The method allows us to build efficient, high and variable resolution diffractometers at long pulse spallation sources.

  1. Residual stress determination in an overlay dissimilar welded pipe by neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Woo, Wan Chuck [ORNL; Em, Vyacheslav [Korea Atomic Energy Research Institute; Hubbard, Camden R [ORNL; Lee, Ho-Jin [Korea Atomic Energy Research Institute; Park, Kwang Soo [Doosan Heavy Industries & Construction

    2011-01-01

    Residual stresses were determined through the thickness of a dissimilar weld overlay pipe using neutron diffraction. The specimen has a complex joining structure consisting of a ferritic steel (SA508), austenitic steel (F316L), Ni-based consumable (Alloy 182), and overlay of Ni-base superalloy (Alloy 52M). It simulates pressurized nozzle components, which have been a critical issue under the severe crack condition of nuclear power reactors. Two neutron diffractometers with different spatial resolutions have been utilized on the identical specimen for comparison. The macroscopic 'stress-free' lattice spacing (d{sub o}) was also obtained from both using a 2-mm width comb-like coupon. The results show significant changes in residual stresses from tension (300-400 MPa) to compression (-600 MPa) through the thickness of the dissimilar weld overlay pipe specimen.

  2. Neutron Diffraction Characterization of C–H···Li Interactions in a Lithium Aluminate Polymer

    Energy Technology Data Exchange (ETDEWEB)

    Cole, Jacqueline M.; Waddell, Paul G.; Wheatley, Andrew E. H.; McIntyre, Garry J.; Peel, Andrew J.; Tate, Christopher W.; Linton, David J.

    2014-08-11

    The reaction of AlMe3 with tBuLi in the presence of trimethylacetonitrile affords the bimetallic complex [tBu(Me)Al(μ-Me)2Li·NC(tBu)]∞ (1). Pseudotetrahedral Al centers form by the nucelophilic addition of tBuLi to AlMe3.The alkali-metal center is stabilized through coordination of the unreacted nitrile and polymer formation via the construction of Al(μ-Me)nLi (n = 1, 2) motifs. Neutron diffraction evidences agostic interactions in the bridging methyl group to give further stabilization. There is only one previous report of a neutron structure of a lithium aluminate compound. This work therefore offers an important structural example of agostic interactions and the precise nature of Al(μ-Me)2Li bridging.

  3. Neutron diffraction studies on a system with a 4-coordinate hydrogen atom in an yttrium cluster

    Energy Technology Data Exchange (ETDEWEB)

    Yousufuddin, Muhammed [Department of Chemistry, University of Southern California, Los Angeles, CA 90089 (United States); Baldamus, Jens [RIKEN - Institute of Physical and Chemical Research, Hirosawa 2-1, Wako, Saitama 351-0198 (Japan); Tardif, Olivier [RIKEN - Institute of Physical and Chemical Research, Hirosawa 2-1, Wako, Saitama 351-0198 (Japan); Hou Zhaomin [RIKEN - Institute of Physical and Chemical Research, Hirosawa 2-1, Wako, Saitama 351-0198 (Japan); Mason, Sax A. [Institut Laue Langevin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9 (France); McIntyre, Garry J. [Institut Laue Langevin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9 (France); Bau, Robert [Department of Chemistry, University of Southern California, Los Angeles, CA 90089 (United States)]. E-mail: bau@usc.edu

    2006-11-15

    A 4-coordinate H atom has been unambiguously located, by single-crystal neutron diffraction for the first time, in the center of the tetrahedral metal complex Y{sub 4}H{sub 8}(Cp''){sub 4}(THF) [Cp''=C{sub 5}Me{sub 4}(SiMe{sub 3})]. The core of the molecule consists of a tetranuclear cluster with one interstitial, one face-bridging and six edge-bridging hydride ligands. The four individual Y-H distances to the unique interstitial hydride ligand are 2.184(16), 2.189(16), 2.221(13) and 2.168(12) A. Neutron data were collected on a 4-mm{sup 3} crystal at the Quasi-Laue diffractometer VIVALDI at ILL (Grenoble), and the present agreement factor is R=12.2% for 3566 reflections.

  4. Single-crystal diffraction at the Extreme Conditions beamline P02.2: procedure for collecting and analyzing high-pressure single-crystal data.

    Science.gov (United States)

    Rothkirch, André; Gatta, G Diego; Meyer, Mathias; Merkel, Sébastien; Merlini, Marco; Liermann, Hanns Peter

    2013-09-01

    Fast detectors employed at third-generation synchrotrons have reduced collection times significantly and require the optimization of commercial as well as customized software packages for data reduction and analysis. In this paper a procedure to collect, process and analyze single-crystal data sets collected at high pressure at the Extreme Conditions beamline (P02.2) at PETRA III, DESY, is presented. A new data image format called `Esperanto' is introduced that is supported by the commercial software package CrysAlis(Pro) (Agilent Technologies UK Ltd). The new format acts as a vehicle to transform the most common area-detector data formats via a translator software. Such a conversion tool has been developed and converts tiff data collected on a Perkin Elmer detector, as well as data collected on a MAR345/555, to be imported into the CrysAlis(Pro) software. In order to demonstrate the validity of the new approach, a complete structure refinement of boron-mullite (Al5BO9) collected at a pressure of 19.4 (2) GPa is presented. Details pertaining to the data collections and refinements of B-mullite are presented.

  5. Determination of the bulk modulus of hydroxycancrinite, a possible zeolitic precursor in geopolymers, by high-pressure synchrotron X-ray diffraction

    KAUST Repository

    Oh, Jae Eun

    2011-11-01

    Crystalline zeolitic materials, such as hydroxycancrinite, hydroxysodalite, herschelite and nepheline, are often synthesized from geopolymerization using fly-ash and solutions of NaOH at high temperatures. Comprised mainly of 6-membered aluminosilicate rings that act as basic building units, their crystal structures may provide insight into the reaction products formed in NaOH-activated fly ash-based geopolymers. Recent research indicates that the hydroxycancrinite and hydroxysodalite may play an important role as possible analogues of zeolitic precursor in geopolymers. Herein is reported a high pressure synchrotron study of the behavior of hydroxycancrinite exposed to pressures up to 6.1 GPa in order to obtain its bulk modulus. A refined equation of state for hydroxycancrinite yielded a bulk modulus of Ko = 46 ± 5 GPa (assuming Ko′ = 4.0) for a broad range of applied pressure. When low pressure values are excluded from the fit and only the range of 2.5 and 6.1 GPa is considered, the bulk modulus of hydroxycancrinite was found to be Ko = 46.9 ± 0.9 GPa (Ko′ = 4.0 ± 0.4, calculated). Comparison with the literature shows that all zeolitic materials possessing single 6-membered rings (i.e., hydroxycancrinite, sodalite and nepheline) have similar bulk moduli. © 2011 Elsevier Ltd. All rights reserved.

  6. Assessment of Shape Memory Alloys - From Atoms To Actuators - Via In Situ Neutron Diffraction

    Science.gov (United States)

    Benafan, Othmane

    2014-01-01

    As shape memory alloys (SMAs) become an established actuator technology, it is important to identify the fundamental mechanisms responsible for their performance by understanding microstructure performance relationships from processing to final form. Yet, microstructural examination of SMAs at stress and temperature is often a challenge since structural changes occur with stress and temperature and microstructures cannot be preserved through quenching or after stress removal, as would be the case for conventional materials. One solution to this dilemma is in situ neutron diffraction, which has been applied to the investigation of SMAs and has offered a unique approach to reveal the fundamental micromechanics and microstructural aspects of bulk SMAs in a non-destructive setting. Through this technique, it is possible to directly correlate the micromechanical responses (e.g., internal residual stresses, lattice strains), microstructural evolutions (e.g., texture, defects) and phase transformation properties (e.g., phase fractions, kinetics) to the macroscopic actuator behavior. In this work, in situ neutron diffraction was systematically employed to evaluate the deformation and transformation behavior of SMAs under typical actuator conditions. Austenite and martensite phases, yield behavior, variant selection and transformation temperatures were characterized for a polycrystalline NiTi (49.9 at. Ni). As the alloy transforms under thermomechanical loading, the measured textures and lattice plane-level variations were directly related to the cyclic actuation-strain characteristics and the dimensional instability (strain ratcheting) commonly observed in this alloy. The effect of training on the shape memory characteristics of the alloy and the development of two-way shape memory effect (TWSME) were also assessed. The final conversion from a material to a useful actuator, typically termed shape setting, was also investigated in situ during constrained heatingcooling and

  7. Convergent beam neutron crystallography

    Science.gov (United States)

    Gibson, Walter M.; Schultz, Arthur J.; Richardson, James W.; Carpenter, John M.; Mildner, David F. R.; Chen-Mayer, Heather H.; Miller, M. E.; Maxey, E.; Prask, Henry J.; Gnaeupel-Herold, Thomas H.; Youngman, Russell

    2004-01-01

    Applications of neutron diffraction for small samples (small fiducial areas are limited by the available neutron flux density. Recent demonstrations of convergent beam electron and x-ray diffraction and focusing of cold (λ>1 Å) neutrons suggest the possibility to use convergent beam neutron diffraction for small sample crystallography. We have carried out a systematic study of diffraction of both monoenergetic and broad bandwidth neutrons at the NIST Research Reactor and at the Intense Pulsed Neutron Source (IPNS) at Argonne National Laboratory. Combining convergent beams with time-of-flight Laue diffraction is particularly attractive for high efficiency small sample diffraction studies. We have studied single crystal and powder diffraction of neutrons with convergence angles as large as 15° and have observed diffracted peak intensity gains greater than 20. The convergent beam method (CBM) shows promise for crystallography on small samples of small to medium size molecules (potentially even for proteins), ultra-high pressure samples, and for mapping of strain and texture distributions in larger samples.

  8. Neutron powder diffraction studies as a function of temperature of structure II hydrate formed from propane

    Science.gov (United States)

    Rawn, C.J.; Rondinone, A.J.; Chakoumakos, B.C.; Circone, S.; Stern, L.A.; Kirby, S.H.; Ishii, Y.

    2003-01-01

    Neutron powder diffraction data confirm that hydrate samples synthesized with propane crystallize as structure type II hydrate. The structure has been modeled using rigid-body constraints to describe C3H8 molecules located in the eight larger polyhedral cavities of a deuterated host lattice. Data were collected at 12, 40, 100, 130, 160, 190, 220, and 250 K and used to calculate the thermal expansivity from the temperature dependence of the lattice parameters. The data collected allowed for full structural refinement of atomic coordinates and the atomic-displacement parameters.

  9. Residual stress measurements via neutron diffraction of additive manufactured stainless steel 17-4 PH

    OpenAIRE

    Mohammad Masoomi; Nima Shamsaei; Winholtz, Robert A.; Milner, Justin L.; Thomas Gnäupel-Herold; Alaa Elwany; Mohamad Mahmoudi; Thompson, Scott M.

    2017-01-01

    Neutron diffraction was employed to measure internal residual stresses at various locations along stainless steel (SS) 17-4 PH specimens additively manufactured via laser-powder bed fusion (L-PBF). Of these specimens, two were rods (diameter=8 mm, length=80 mm) built vertically upward and one a parallelepiped (8×80×9 mm3) built with its longest edge parallel to ground. One rod and the parallelepiped were left in their as-built condition, while the other rod was heat treated. Data presented pr...

  10. The structure of polyunsaturated lipid bilayers important for rhodopsin function: a neutron diffraction study.

    Science.gov (United States)

    Mihailescu, Mihaela; Gawrisch, Klaus

    2006-01-01

    The structure of oriented 1-stearoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine bilayers with perdeuterated stearoyl- or docosahexaenoyl hydrocarbon chains was investigated by neutron diffraction. Experiments were conducted at two different relative humidities, 66 and 86%. At both humidities we observed that the polyunsaturated docosahexaenoyl chain has a preference to reside near the lipid water interface. That leaves voids in the bilayer center that are occupied by saturated stearoyl chain segments. This uneven distribution of saturated- and polyunsaturated chain densities is likely to result in membrane elastic stress that modulates function of integral receptor proteins like rhodopsin.

  11. Neutron diffraction studies of structural phase transformations for water-ice in confined geometry

    OpenAIRE

    Dore, John C.; J. Beau W. WEBBER; Hartl, Monika; Behrens, Peter; Hansen, Thomas

    2002-01-01

    Neutron diffraction measurements have been made for D2O water in\\ud the confined geometry of various mesoporous silicas over a wide temperature range. The data have been taken for cooling and heating runs incorporating the nucleation and melting of the crystalline phases and the super-cooled liquid phase. The crystalline forms and the temperatures at which they change are shown to be strongly dependent on the pore size and type of silica used as the confining medium and relate to the phase re...

  12. Neutron diffraction measurements for the determination of residual stresses in MMC tensile and fatigue specimens

    DEFF Research Database (Denmark)

    Fiori, F.; Girardin, E.; Giuliani, A.

    2000-01-01

    The experiments here described have been carried out in the framework of a more general research, aiming to develop a set of complementary models to predict the in-service performances of particle reinforced MMC automotive and aeronautical components. As MMCs are highly heterogeneous materials......, residual stresses are present in both the matrix and the particles microstructure, prior to any macroscopic loading. They vary with the temperature and with the type and level of loading imposed to the material, having a strong influence on the mechanical behaviour of MMCs. Neutron diffraction measurements...

  13. Neutron-Diffraction Study of the Phase Transition in Stannous Chloride Dihydrate

    DEFF Research Database (Denmark)

    Youngblood, R.; Kjems, Jørgen

    1979-01-01

    of the system does not change. We present neutron-diffraction results which show that the temperature dependence of the hydrogen-site occupancies is also highly symmetric around the phase-transition temperature. These results are discussed in terms of a lattice statistical model which was proposed and solved......The order-disorder phase transition in two-dimensional hydrogen-bonded layers of water molecules in SnCl2·2D2O is remarkable in several respects. It has been shown that the peak in the specific heat is highly symmetric around the phase-transition temperature, and that the crystallographic symmetry...

  14. 5-A Fourier map of gramicidin A phased by deuterium-hydrogen solvent difference neutron diffraction

    OpenAIRE

    Koeppe 2nd, R.E.; Schoenborn, B. P.

    1984-01-01

    Crystals of ion-free gramicidin A (P212121: a = 24.61, b = 32.28, c = 32.52) have been investigated using neutron diffraction. A difference analysis of crystals soaked in ethanol/H2O as opposed to ethanol-d6/D2O has led to single isomorphous replacement Fourier projections of the structure at 5-A resolution. The gramicidin dimer appears to be a 32-A-long cylinder oriented parallel to the c-axis in these crystals.

  15. 5-A Fourier map of gramicidin A phased by deuterium-hydrogen solvent difference neutron diffraction.

    Science.gov (United States)

    Koeppe, R E; Schoenborn, B P

    1984-03-01

    Crystals of ion-free gramicidin A (P212121: a = 24.61, b = 32.28, c = 32.52) have been investigated using neutron diffraction. A difference analysis of crystals soaked in ethanol/H2O as opposed to ethanol-d6/D2O has led to single isomorphous replacement Fourier projections of the structure at 5-A resolution. The gramicidin dimer appears to be a 32-A-long cylinder oriented parallel to the c-axis in these crystals.

  16. Residual stress in sprayed Ni+5%Al coatings determined by neutron diffraction

    CERN Document Server

    Matejicek, J; Gnaeupel-Herold, T; Prask, H J

    2002-01-01

    Coatings of nickel-based alloys are used in numerous high-performance applications. Their properties and lifetimes are influenced by factors such as residual stress. Neutron diffraction is a powerful tool for nondestructive residual stress determination. In this study, through-thickness residual stress profiles in Ni+5%Al coatings on steel substrates were determined. Two examples of significantly different spraying techniques - plasma spraying and cold spraying - are highlighted. Different stress-generation mechanisms are discussed with respect to process parameters and material properties. (orig.)

  17. In situ observation of high-pressure phase transition in silicon carbide under shock loading using ultrafast x-ray diffraction

    Science.gov (United States)

    Tracy, Sally June

    2017-06-01

    SiC is an important high-strength ceramic material used for a range of technological applications, including lightweight impact shielding and abrasives. SiC is also relevant to geology and planetary science. It may be a host of reduced carbon in the Earth's interior and also occurs in meteorites and impact sites. SiC has also been put forward as a possible major constituent in the proposed class of extra-solar planets known as carbon planets. Previous studies have used wave profile measurements to identify a phase transition under shock loading near 1 Mbar, but lattice-level structural information was not obtained. Here we present the behavior of silicon carbide under shock loading as investigated through a series of time-resolved pump-probe x-ray diffraction measurements up to 200 GPa. Our experiments were conducted at the Materials in Extreme Conditions beamline of the Linac Coherent Light Source. In situ x-ray diffraction data on shock-compressed SiC was collected using a free electron laser source combined with a pulsed high-energy laser. These measurements allow for the determination of time-dependent atomic arrangements, demonstrating that the wurtzite phase of SiC transforms directly to the B1 structure. Our measurements also reveal details of the material texture evolution under shock loading and release.

  18. Neutron Diffraction Study on the Magnetic Structure of Pr6Fe13Sn

    Directory of Open Access Journals (Sweden)

    Suharyana

    2010-04-01

    Full Text Available We have successfully prepared a Pr6Fe13Sn sample by employing argon arc melting. The crystal structure of the sample has been examined by an x-ray diffraction. The x-ray pattern reveals that the sample crystallize in the tetragonal Nd6Fe13Si structure type with space group I4/mcm. Neutron diffraction at 150K performed on a powder sample shows a collinear antiferromagnetic ordering of the Fe and Pr sublattices with the wave vector (0, 0, 1 and an Ip type magnetic lattice with anti-centering translation. The main axis of antiferromagnetism is restricted to the (0 0 1 plane. The average refined Fe moments at 150 K is (2.0±0.4 µB whereas the Pr moments are (2.1±0.4 and (1.9±0.4 µB for the 8f and 16l sites, respectively

  19. Real-time observations of lithium battery reactions—operando neutron diffraction analysis during practical operation

    Science.gov (United States)

    Taminato, Sou; Yonemura, Masao; Shiotani, Shinya; Kamiyama, Takashi; Torii, Shuki; Nagao, Miki; Ishikawa, Yoshihisa; Mori, Kazuhiro; Fukunaga, Toshiharu; Onodera, Yohei; Naka, Takahiro; Morishima, Makoto; Ukyo, Yoshio; Adipranoto, Dyah Sulistyanintyas; Arai, Hajime; Uchimoto, Yoshiharu; Ogumi, Zempachi; Suzuki, Kota; Hirayama, Masaaki; Kanno, Ryoji

    2016-01-01

    Among the energy storage devices for applications in electric vehicles and stationary uses, lithium batteries typically deliver high performance. However, there is still a missing link between the engineering developments for large-scale batteries and the fundamental science of each battery component. Elucidating reaction mechanisms under practical operation is crucial for future battery technology. Here, we report an operando diffraction technique that uses high-intensity neutrons to detect reactions in non-equilibrium states driven by high-current operation in commercial 18650 cells. The experimental system comprising a time-of-flight diffractometer with automated Rietveld analysis was developed to collect and analyse diffraction data produced by sequential charge and discharge processes. Furthermore, observations under high current drain revealed inhomogeneous reactions, a structural relaxation after discharge, and a shift in the lithium concentration ranges with cycling in the electrode matrix. The technique provides valuable information required for the development of advanced batteries. PMID:27357605

  20. Real-time observations of lithium battery reactions—operando neutron diffraction analysis during practical operation

    Science.gov (United States)

    Taminato, Sou; Yonemura, Masao; Shiotani, Shinya; Kamiyama, Takashi; Torii, Shuki; Nagao, Miki; Ishikawa, Yoshihisa; Mori, Kazuhiro; Fukunaga, Toshiharu; Onodera, Yohei; Naka, Takahiro; Morishima, Makoto; Ukyo, Yoshio; Adipranoto, Dyah Sulistyanintyas; Arai, Hajime; Uchimoto, Yoshiharu; Ogumi, Zempachi; Suzuki, Kota; Hirayama, Masaaki; Kanno, Ryoji

    2016-06-01

    Among the energy storage devices for applications in electric vehicles and stationary uses, lithium batteries typically deliver high performance. However, there is still a missing link between the engineering developments for large-scale batteries and the fundamental science of each battery component. Elucidating reaction mechanisms under practical operation is crucial for future battery technology. Here, we report an operando diffraction technique that uses high-intensity neutrons to detect reactions in non-equilibrium states driven by high-current operation in commercial 18650 cells. The experimental system comprising a time-of-flight diffractometer with automated Rietveld analysis was developed to collect and analyse diffraction data produced by sequential charge and discharge processes. Furthermore, observations under high current drain revealed inhomogeneous reactions, a structural relaxation after discharge, and a shift in the lithium concentration ranges with cycling in the electrode matrix. The technique provides valuable information required for the development of advanced batteries.

  1. X-ray, synchrotron, and neutron diffraction analysis of Roman cavalry parade helmet fragment

    Energy Technology Data Exchange (ETDEWEB)

    Smrcok, L' . [Institute of Inorganic Chemistry, Slovak Academy of Sciences, Dubravska cesta 9, 84536 Bratislava (Slovakia); Petrik, I. [Geological Institute, Slovak Academy of Sciences, Dubravska cesta 9, 84005 Bratislava (Slovakia); Langer, V. [Environmental Inorganic Chemistry, Chalmers University of Technology, 412 96 Gothenburg (Sweden); Filinchuk, Y. [Swiss-Norwegian Beam Lines, European Synchrotron Radiation Facility, 6 rue Jules Horowitz, BP-220, 38043 Grenoble CEDEX (France); Beran, P. [Nuclear Physics Institute ASCR v.v.i. and Research Centre Rez Ltd., 25068 Rez (Czech Republic)

    2010-10-15

    A partially corroded fragment of the neck guard of a Roman cavalry helmet excavated in the former military camp of Gerulata, a part of the Limes Romanus on the River Danube, was analysed by laboratory X-ray, synchrotron and neutron powder diffraction. The approximate phase composition determined by the neutron diffraction of the bulk, 82% (wt) of the copper alloy phase, 12 % (wt) of cuprite and 6% of nantokite indicate a significant degree of corrosion of the artefact. Elemental EDX analysis of cleaned surface showed that the chemical composition of the original alloy is 78 to 82 % (wt) of Cu and 21.4 to 16.5 % of Zn with minute amounts of Sn, Si and S. High contents of Cu and Zn with the negligible amount of Sn showed that the body of the helmet was made of brass and not of bronze as expected before. The amount of zinc in the copper alloy calculated from the refined lattice parameter agrees fairly well with the value determined by EDX. The most abundant phase in the synchrotron powder diffraction pattern of the corrosion products scrapped from the artefact is cuprite, but presence of atacamite, malachite, brochantite, nantokite, mixed Cu-Zn hydroxyl carbonates and probably also of simonkolleite (Zn{sub 5}(OH){sub 8}Cl{sub 2}.H{sub 2}O) have been detected. In contrast, the X-ray pattern taken directly from the surface of the artefact is dominated by atacamite with some traces of malachite and quartz. Because the penetration depth of laboratory X-rays is in order of tens of microns, the phase analysis based only on a diffraction pattern taken from a surface can lead to erroneous conclusions concerning the phase composition of the patina. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Perdeuteration, purification, crystallization and preliminary neutron diffraction of an ocean pout type III antifreeze protein

    Science.gov (United States)

    Petit-Haertlein, Isabelle; Blakeley, Matthew P.; Howard, Eduardo; Hazemann, Isabelle; Mitschler, Andre; Haertlein, Michael; Podjarny, Alberto

    2009-01-01

    The highly homologous type III antifreeze protein (AFP) subfamily share the capability to inhibit ice growth at subzero temperatures. Extensive studies by X-­ray crystallography have been conducted, mostly on AFPs from polar fishes. Although interactions between a defined flat ice-binding surface and a particular lattice plane of an ice crystal have now been identified, the fine structural features underlying the antifreeze mechanism still remain unclear owing to the intrinsic difficulty in identifying H atoms using X-ray diffraction data alone. Here, successful perdeuteration (i.e. complete deuteration) for neutron crystallo­graphic studies of the North Atlantic ocean pout (Macrozoarces americanus) AFP in Escherichia coli high-density cell cultures is reported. The perdeuterated protein (AFP D) was expressed in inclusion bodies, refolded in deuterated buffer and purified by cation-exchange chromatography. Well shaped perdeuterated AFP D crystals have been grown in D2O by the sitting-drop method. Preliminary neutron Laue diffraction at 293 K using LADI-III at ILL showed that with a few exposures of 24 h a very low background and clear small spots up to a resolution of 1.85 Å were obtained using a ‘radically small’ perdeuterated AFP D crystal of dimensions 0.70 × 0.55 × 0.35 mm, corresponding to a volume of 0.13 mm3. PMID:19342793

  3. The chemical reactivity and structure of collagen studied by neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Wess, T.J.; Wess, L.; Miller, A. [Univ. of Stirling (United Kingdom)

    1994-12-31

    The chemical reactivity of collagen can be studied using neutron diffraction (a non-destructive technique), for certain reaction types. Collagen contains a number of lysine and hydroxylysine side chains that can react with aldehydes and ketones, or these side chains can themselves be converted to aldehydes by lysyl oxidase. The reactivity of these groups not only has an important role in the maintenance of mechanical strength in collagen fibrils, but can also manifest pathologically in the cases of aging, diabetes (reactivity with a variety of sugars) and alcoholism (reactivity with acetaldehyde). The reactivity of reducing groups with collagen can be studied by neutron diffraction, since the crosslink formed in the adduction process is initially of a Schiff base or keto-imine nature. The nature of this crosslink allows it to be deuterated, and the position of this relatively heavy scattering atom can be used in a process of phase determination by multiple isomorphous replacement. This process was used to study the following: the position of natural crosslinks in collagen; the position of adducts in tendon from diabetic rats in vivo and the in vitro position of acetaidehyde adducts in tendon.

  4. A flow-through hydrothermal cell for in situ neutron diffraction studies of phase transformations

    Energy Technology Data Exchange (ETDEWEB)

    O' Neill, Brian [School of Chemical Engineering, The University of Adelaide, South Australia 5005 (Australia); Tenailleau, Christophe [Department of Mineralogy, South Australian Museum, North Terrace, Adelaide, South Australia 5000 (Australia); Nogthai, Yung [School of Chemical Engineering, The University of Adelaide, South Australia 5005 (Australia); Studer, Andrew [Bragg Institute, ANSTO, PMB 1 Menai, New South Wales 2234 (Australia); Brugger, Joel [Department of Mineralogy, South Australian Museum, North Terrace, Adelaide, South Australia 5000 (Australia): Department of Geology and Geophysics, The University of Adelaide, North Terrace, Adelaide, South Australia 5005 (Australia); Pring, Allan [Department of Mineralogy, South Australian Museum, North Terrace, Adelaide, South Australia 5000 (Australia): Department of Geology and Geophysics, The University of Adelaide, North Terrace, Adelaide, South Australia 5005 (Australia)]. E-mail: pring.allan@saugov.sa.gov.au

    2006-11-15

    A flow-through hydrothermal cell for the in situ neutron diffraction study of crystallisation and phase transitions has been developed. It can be used for kinetic studies on materials that exhibit structural transformations under hydrothermal conditions. It is specifically designed for use on the medium-resolution powder diffractometer (MRPD) at ANSTO, Lucas Heights, Sydney. But it is planned to adapt the design for the Polaris beamline at ISIS and the new high-intensity powder diffractometer (Wombat) at the new Australian reactor Opal. The cell will operate in a flow-through mode over the temperature range from 25-300 deg. C and up to pressures of 100 bar. The first results of a successful transformation of pentlandite (Fe,Ni){sub 9}S{sub 8} to violarite (Fe,Ni){sub 3}S{sub 4} under mild conditions (pH{approx}4) at 120 deg. C and 3 bar using in situ neutron diffraction measurements are presented.

  5. Neutron diffraction and micro-Raman scattering studies on rare-earth carbide halides

    Science.gov (United States)

    Henn, R. W.; Strach, T.; Kremer, R. K.; Simon, A.

    1998-12-01

    Neutron-diffraction experiments on powder samples and micro-Raman scattering investigations on single crystals of the layered compounds R2CxHal2, (R=Y, Gd, x=1,2, and Hal=Br, I) have been performed in order to study their static and dynamic lattice properties. For the superconductors Y2C2I2 (Tc=9.97 K) and Y2C2Br2 (Tc=5.04 K), the C-C atomic distances were obtained with high accuracy from neutron-diffraction experiments between T=1.5 and 270 K. The expected Raman-active phonons were determined from a factor-group analysis of the crystal structures. In the monocarbide Y2CBr2, the Raman-active phonons of the heavy-ion sublattices have been observed. In the dicarbide compounds R2C2Hal2, additionally, the stretching and tilting modes of the dimeric C2 units were clearly identified by analyzing spectra from natC and 13C substituted samples. The influence of the quasimolecular C2 unit on the electronic properties in the R2C2Hal2 compounds and its interaction with the surrounding metal atom octahedra is discussed.

  6. Diffraction des neutrons : principe, dispositifs expérimentaux et applications

    Science.gov (United States)

    Muller, C.

    2003-02-01

    La diffraction de neutrons, sur monocristal ou sur échantillon polycristallin (ou poudre), est une technique très largement utilisée, en science des matériaux comme en biologie, lorsque l'on souhaite déterminer la structure cristalline d'un composé ou d'une molécule. Toutefois, le degré de précision de la détermination structurale est très corrélé au choix de l'instrument utilisé. Il s'en suit que la question “comment choisir l'instrument le mieux adapté au composé et à la problématique ?" apparaît comme fondamentale. L'objectif de ce cours est de tenter de répondre à cette question en décrivant brièvement les caractéristiques instrumentales de différents diffractomètres, en exposant les avantages spécifiques des expériences de diffraction de neutrons et en donnant quelques exemples d'application.

  7. Post-spinel transformations and equation of state in ZnGa2O4 : Determination at high pressure by in situ x-ray diffraction

    Science.gov (United States)

    Errandonea, D.; Kumar, Ravhi S.; Manjón, F. J.; Ursaki, V. V.; Rusu, E. V.

    2009-01-01

    Room-temperature angle-dispersive x-ray diffraction measurements on spinel ZnGa2O4 up to 56 GPa show evidence of two structural phase transformations. At 31.2 GPa, ZnGa2O4 undergoes a transition from the cubic spinel structure to a tetragonal spinel structure similar to that of ZnMn2O4 . At 55 GPa, a second transition to the orthorhombic marokite structure ( CaMn2O4 -type) takes place. The equation of state of cubic spinel ZnGa2O4 is determined: V0=580.1(9)Å3 , B0=233(8)GPa , B0'=8.3(4) , and B0″=-0.1145GPa-1 (implied value); showing that ZnGa2O4 is one of the less compressible spinels studied to date. For the tetragonal structure an equation of state is also determined: V0=287.8(9)Å3 , B0=257(11)GPa , B0'=7.5(6) , and B0″=-0.0764GPa-1 (implied value). The reported structural sequence coincides with that found in NiMn2O4 and MgMn2O4 .

  8. High-pressure investigations on Piplia Kalan eucrite meteorite using in-situ X-ray diffraction and 57Fe Mössbauer spectroscopic technique up to 16 GPa

    Directory of Open Access Journals (Sweden)

    Usha Chandra

    2016-03-01

    Full Text Available We report here high-pressure investigations on Piplia Kalan eucrite–a member of HED (Howardite–Eucrite–Diogenite family from asteroid 4-Vesta based on synchrotron X-ray diffraction (up to 16 GPa and 57Fe Mössbauer spectroscopy (up to 8 GPa. Dominant with anorthite-rich plagioclase, pigeonite-rich pyroxene and clino-ferrosilite, the sample displayed various phase transitions attaining amorphous character at 16 GPa. These phase transitions of individual components could be explained simultaneously through variations in high-pressure XRD patterns and the Mössbauer parameters. Most prominent P21/c to C2/c transition of pigeonite and ferrosilite was exhibited both as sudden variation in Mössbauer parameters and population inversion of Fe2+ in M1 and M2 sites between 2.9 and 3.8 GPa and variation in intensity profile in XRD patterns at 3.56 GPa. Anorthite seemed to respond more to such impact than other components in the sample. Complete amorphization in anorthite which occurred at lower pressure of ∼12 GPa implied residual stress experienced due to shock impact. The presence of high pressure (monoclinic phase of pigeonite and ferrosilite at ambient condition in this eucrite sample confirmed earlier suggestions of an early shock event. This report is an attempt to emphasize the role of anorthite in the determination of the residual stress due to impact process in the parent body thus to understand the behavioral differences amongst HED members.

  9. Intermolecular Interactions at high pressure

    DEFF Research Database (Denmark)

    Eikeland, Espen Zink

    2016-01-01

    In this project high-pressure single crystal X-ray diffraction has been combined with quantitative energy calculations to probe the energy landscape of three hydroquinone clathrates enclosing different guest molecules. The simplicity of the hydroquinone clathrate structures together with their st......In this project high-pressure single crystal X-ray diffraction has been combined with quantitative energy calculations to probe the energy landscape of three hydroquinone clathrates enclosing different guest molecules. The simplicity of the hydroquinone clathrate structures together....... High-pressure crystallography is the perfect method for studying intermolecular interactions, by forcing the molecules closer together. In all three studied hydroquinone clathrates, new pressure induced phase transitions have been discovered using a mixture of pentane and isopentane as the pressure...... transmitting medium. Through careful structural analysis combined with theoretical calculations, the structures of all the new high-pressure phases identified herein were determined. In the hydroquinone - methanol and hydroquinone - acetonitrile clathrate structures the phase transitions break the host...

  10. In situ neutron diffraction study of twin reorientation and pseudoplastic strain in Ni-Mn-Ga single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Stoica, Alexandru Dan [ORNL

    2011-01-01

    Twin variant reorientation in single-crystal Ni-Mn-Ga during quasi-static mechanical compression was studied using in situ neutron diffraction. The volume fraction of reoriented twin variants for different stress amplitudes were obtained from the changes in integrated intensities of high-order neutron diffraction peaks. It is shown that, during compressive loading, {approx}85% of the twins were reoriented parallel to the loading direction resulting in a maximum pseudoplasticstrain of {approx}5.5%, which is in agreement with measured macroscopic strain.

  11. Neutron Scattering and Diffraction Studies of Fluids and Fluid-Solid Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Cole, David R [ORNL; Herwig, Kenneth W [ORNL; Mamontov, Eugene [ORNL; Larese, John Z [ORNL

    2006-01-01

    There can be no disputing the fact that neutron diffraction and scattering have made a clear contribution to our current understanding of the structural and dynamical characteristics of liquid water and water containing dissolved ions at ambient conditions and to a somewhat lesser degree other state conditions involving a change in temperature and pressure. Indeed, a molecular-level understanding of how fluids (e.g., water, CO{sub 2}, CH{sub 4}, higher hydrocarbons, etc.) interact with and participate in reactions with other solid earth materials are central to the development of predictive models that aim to quantify a wide array of geochemical processes. In the context of natural systems, interrogation of fluids and fluid-solid interactions at elevated temperatures and pressures is an area requiring much more work, particularly for complex solutions containing geochemically relevant cations, anions, and other important dissolved species such as CO{sub 2} or CH{sub 4}. We have tried to describe a series of prototypical interfacial and surface problems using neutron scattering to stimulate the thinking of earth scientists interested applying some of these approaches to confined systems of mineralogical importance. Our ability to predict the molecular-level properties of fluids and fluid-solid interactions relies heavily on the synergism between experiments such as neutron diffraction or inelastic neutron scattering and molecular-based simulations. Tremendous progress has been made in closing the gap between experimental observations and predicted behavior based on simulations due to improvements in the experimental methodologies and instrumentation on the one hand, and the development of new potential models of water and other simple and complex fluids on the other. For example there has been an emergence of studies taking advantage of advanced computing power that can accommodate the demands of ab initio molecular dynamics. On the neutron instrumentation side

  12. Neutron-diffraction measurement of the evolution of strain for non-uniform plastic deformation

    CERN Document Server

    Rogge, R B; Boyce, D

    2002-01-01

    Neutrons are particularly adept for the validation of modeling predictions of stress and strain. In recent years, there has been a significant effort to model the evolution of both the macroscopic stresses and the intergranular stress during plastic deformation. These have had broad implications with regard to understanding the evolution of residual stress and to diffraction-based measurements of strain. Generally the modeling and associated measurements have been performed for simple uniaxial tension, leaving questions with regard to plastic deformation under multi-axial stress and non-uniform stress. Extensive measurements of the strain profile across a plastic hinge for each of a series of loading and unloading cycles to progressively higher degrees of plastic deformation are presented. These measurements are used to assess multiple-length-scale finite-element modeling (FEM) of the plastic hinge, in which the elements will range in size from single crystallites (as used in successful simulations of uniaxia...

  13. Determination of the Crystal Structure of Lead Tungstate by Neutron Diffraction

    CERN Document Server

    Cousson, A; Paulus, W

    1999-01-01

    The crystal structure of lead tungstate, PbWO4, is tetragonal, scheelite type, space group I4/a. This compound, due to the difference in the vapour pressure of the two raw oxides, WO3 and PbO, used in the crystal growth, is frequently subjected to lead deficiency. It has been reported by one group that lead vacancies can order in a crystal structure derived from the scheelite type, but of lower symmetry and described by the space group P4/nnc or P-4. We report here on neutron diffraction measurements performed on three different single crystals, two of them being presented to us as possibly presenting the lead deficient phase. Our measurements do not show any indication of structural distortion, even at 70 K for one of the samples. The existence of a lead deficient structure remains unconfirmed.

  14. Neutron diffraction stress determination in W-laminates for structural divertor applications

    Directory of Open Access Journals (Sweden)

    R. Coppola

    2015-07-01

    Full Text Available Neutron diffraction measurements have been carried out to develop a non-destructive experimental tool for characterizing the crystallographic structure and the internal stress field in W foil laminates for structural divertor applications in future fusion reactors. The model sample selected for this study had been prepared by brazing, at 1085 °C, 13 W foils with 12 Cu foils. A complete strain distribution measurement through the brazed multilayered specimen and determination of the corresponding stresses has been obtained, assuming zero stress in the through-thickness direction. The average stress determined from the technique across the specimen (over both ‘phases’ of W and Cu is close to zero at −17 ± 32 MPa, in accordance with the expectations.

  15. Neutron diffraction study of the magnetic-field-induced transition in Mn3GaC

    Science.gov (United States)

    Ćakιr, Ö.; Acet, M.; Farle, M.; Senyshyn, A.

    2014-01-01

    The antiperovskite Mn3GaC undergoes an isostructural cubic-cubic first order transition from a low-temperature, large-cell-volume antiferromagnetic state to a high-temperature, small-cell-volume ferromagnetic state at around 160 K. The transition can also be induced by applying a magnetic field. We study here the isothermal magnetic-field-evolution of the transition as ferromagnetism is stabilized at the expense of antiferromagnetism. We make use of the presence of the two distinct cell volumes of the two magnetic states as a probe to observe by neutron diffraction the evolution of the transition, as the external magnetic field carries the system from the antiferromagnetic to the ferromagnetic state. We show that the large-volume antiferromagnetic and the small-volume ferromagnetic states coexist in the temperature range of the transition. The ferromagnetic state is progressively stabilized as the field increases.

  16. Neutron diffraction studies of the low-temperature magnetic structure of hexagonal FeGe

    DEFF Research Database (Denmark)

    Bernhard, J.; Lebech, Bente; Beckman, O.

    1984-01-01

    The magnetic structure of the hexagonal polymorph of FeGe has been investigated by means of neutron diffraction on single crystals at low temperature and for magnetic fields applied perpendicular to the c axis. Between 410 and approximately 55K the magnetic structure is collinear c......-axis antiferromagnetic. Below approximately 55K the structure changes to c-axis double-cone antiferromagnetic with an inter-layer turn angle for the basal-plane moment component of 194.4 degrees , independent of temperature and applied field. The cone half-angle increases with decreasing temperature to approximately 14...... degrees at 4.2K, but its temperature dependence shows a pronounced kink at 30K, indicating a phase change at this temperature. At 4.2K the authors observe an anomalous decrease of the basal-plane moment component at a critical field (B perpendicular to c) of 1.4 T. As the temperature is increased...

  17. Neutron diffraction investigation of water on MgO(001) surfaces, from monolayer to bulk condensation

    Science.gov (United States)

    Demirdjian, B.; Suzanne, J.; Ferry, D.; Coulomb, J. P.; Giordano, L.

    2000-08-01

    The structure of D 2O molecules adsorbed on MgO(001) surfaces has been studied by neutron diffraction within the 200-273 K temperature range and at coverages ( θ) of 0.93, 1.5, 4 and 20 monolayers (ML). At low coverage ( θ≤1.5 ML) and whatever the temperature, the two-dimensional (2D) analysis of the monolayer structure is compatible with the previously observed p(3×2) commensurate phase, but presenting a short coherence length of 35±5 Å. At higher coverages, we show that this 2D ordered phase coexists with the bulk phase. These results confirm the outstanding stability of the water monolayer adsorbed on MgO(001) found by recent molecular dynamics calculations.

  18. Residual stress measurements via neutron diffraction of additive manufactured stainless steel 17-4 PH

    Directory of Open Access Journals (Sweden)

    Mohammad Masoomi

    2017-08-01

    Full Text Available Neutron diffraction was employed to measure internal residual stresses at various locations along stainless steel (SS 17-4 PH specimens additively manufactured via laser-powder bed fusion (L-PBF. Of these specimens, two were rods (diameter=8 mm, length=80 mm built vertically upward and one a parallelepiped (8×80×9 mm3 built with its longest edge parallel to ground. One rod and the parallelepiped were left in their as-built condition, while the other rod was heat treated. Data presented provide insight into the microstructural characteristics of typical L-PBF SS 17-4 PH specimens and their dependence on build orientation and post-processing procedures such as heat treatment. Data have been deposited in the Data in Brief Dataverse repository (doi:10.7910/DVN/T41S3V.

  19. Laue diffraction: The key to neutron crystallography from submillimetric-volume single crystals

    Science.gov (United States)

    Lemée-Cailleau, M.-H.; McIntyre, G. J.; Wilkinson, C.

    2005-12-01

    For several decades, chemists and physicists have been fascinated by molecular compounds rich in delocalized electrons. In the solid state these compounds may offer a very rich fan of properties: optical, conduction and dielectric, magneticldots Each state is the result of a delicate balance amongst intra- and/or intermolecular interactions which can be controlled, not just by direct chemical substitution, but also by external parameters such as temperature, pressure, continuous electric or magnetic fields, or by light. The recent evolution of this field of science towards more and more sophisticated materials makes also more and more difficult their crystal growth. While neutron scattering is an extremely powerful technique to get precise structural information, it is also often disregarded in this field because usually large single crystals are required. With the recent renaissance of Laue techniques using the very intense flux provided by the reactor of the Institut Laue-Langevin (ILL), accurate structural and/or magnetic information can be now extracted routinely from molecular crystals of volume 0.1 mm3 or smaller, with easy possibilities of high pressure (up to 3 GPa) down to 0.2 K. A general survey of these new possibilities is illustrated by an example taken from the field of low-dimensional organic complexes.

  20. Characterisation of polycrystal deformation by numerical modelling and neutron diffraction measurements

    Energy Technology Data Exchange (ETDEWEB)

    Clausen, B.

    1997-09-01

    The deformation of polycrystals are modelled using three micron mechanic models; the Taylor model, the Sachs model and Hutchinson`s self-consistent (SC) model. The predictions of the rigid plastic Taylor and Sachs models are compared with the predictions of the SC model. As expected, the results of the SC model is about half-way between the upper- and lower-bound models. The influence of the elastic anisotropy is investigated by comparing the SC predictions for aluminium, copper and a hypothetical material (Hybrid) with the elastic anisotropy of copper and the Young`s modulus and hardening behaviour of aluminium. It is concluded that the effect of the elastic anisotropy is limited to the very early stages of plasticity, as the deformation pattern is almost identical for the three materials at higher strains. The predictions of the three models are evaluated by neutron diffraction measurements of elastic lattice strains in grain sub-sets within the polycrystal. The two rigid plastic models do not include any material parameters and therefore the predictions of the SC model is more accurate and more detailed than the predictions of the Taylor and Sachs models. The SC model is used to determine the most suitable reflection for technological applications of neutron diffraction, where focus is on the volume average stress state in engineering components. To be able to successfully to convert the measured elastic lattice strains for a specific reflection into overall volume average stresses, there must be a linear relation between the lattice strain of the reflection and the overall stress. According to the model predictions the 311-reflection is the most suitable reflection as it shows the smallest deviations from linearity and thereby also the smallest build-up of residual strains. The model predictions have pin pointed that the selection of the reflection is crucial for the validity of stresses calculated from the measured elastic lattice strains. (au) 14 tabs., 41

  1. Study of phase development in alumina-spodumene ceramics by high temperature neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Gan, B.K. [University of Technology, Sydney, NSW (Australia). Microstructural Analysis Unit; Latella, B.A.; Hunter, B.A. [Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW (Australia); O`Connor, B.H. [Curtin University of Technology, Perth, WA (Australia). Department of Applied Physics

    1999-12-01

    Full text: Melting and crystallisation of minor phases are important in many material systems which contain impurities and/or grain boundary liquid phases. Grain boundary glassy phases are generally not thermodynamically stable, and can devitrify during the sintering process or from other high temperature exposure. Characterising the minor phase assemblage in these types of materials has implications in processing, microstructural design and in-service use, particularly fluctuating thermal environments. An in situ high temperature neutron diffraction (ND) technique was used to follow the phase dynamics on sintering an alumina-spodumene ceramic as well as the crystallisation kinetics of the evolving crystalline phase in real time. The main benefit of using ND analysis in the present work is that it provides bulk specimen character of the material which is important in quantitatively extracting phase composition information. Likewise, most diffraction measurements are conducted with ambient or static temperature data, collected after specimens have been heat-treated and then cooled. Such data may yield misleading information particularly in relation to non-equilibrium phases. Hence dynamic measurements are clearly preferable as a direct means of confirming sintering processes. ND measurements were performed using the High Flux Australian Reactor (HIFAR) neutron source operated by the Australian Nuclear Science and Technology Organisation (ANSTO) at Lucas Heights, NSW, Australia. The ND patterns collected on heating the compacts provided relevant information for optimising materials processing and sintering protocols. Similarly, the ND patterns collected for three specific cooling schemes yielded significant details of evolution and crystallisation of the minor phase. The principal aim was to demonstrate the fundamental influence of the minor crystalline phase (and hence glassy phase) on properties and to manipulate and tailor the phase structure by controlled

  2. The high pressure structure and equation of state of 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) up to 20 GPa: X-ray diffraction measurements and first principles molecular dynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Stavrou, Elissaios, E-mail: stavrou1@llnl.gov; Riad Manaa, M., E-mail: manaa1@llnl.gov; Zaug, Joseph M.; Kuo, I-Feng W.; Pagoria, Philip F.; Crowhurst, Jonathan C.; Armstrong, Michael R. [Lawrence Livermore National Laboratory, Physical and Life Sciences Directorate, P.O. Box 808 L-350, Livermore, California 94550 (United States); Kalkan, Bora [Advanced Light Source, Lawrence Berkeley Laboratory, Berkeley, California 94720 (United States); Advanced Materials Research Laboratory, Department of Physics Engineering, Hacettepe University 06800, Beytepe, Ankara (Turkey)

    2015-10-14

    Recent theoretical studies of 2,6-diamino-3,5-dinitropyrazine-1-oxide (C{sub 4}H{sub 4}N{sub 6}O{sub 5} Lawrence Livermore Molecule No. 105, LLM-105) report unreacted high pressure equations of state that include several structural phase transitions, between 8 and 50 GPa, while one published experimental study reports equation of state (EOS) data up to a pressure of 6 GPa with no observed transition. Here we report the results of a synchrotron-based X-ray diffraction study and also ambient temperature isobaric-isothermal atomistic molecular dynamics simulations of LLM-105 up to 20 GPa. We find that the ambient pressure phase remains stable up to 20 GPa; there is no indication of a pressure induced phase transition. We do find a prominent decrease in b-axis compressibility starting at approximately 13 GPa and attribute the stiffening to a critical length where inter-sheet distance becomes similar to the intermolecular distance within individual sheets. The ambient temperature isothermal equation of state was determined through refinements of measured X-ray diffraction patterns. The pressure-volume data were fit using various EOS models to yield bulk moduli with corresponding pressure derivatives. We find very good agreement between the experimental and theoretically derived EOS.

  3. The high pressure structure and equation of state of 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) up to 20 GPa: X-ray diffraction measurements and first principles molecular dynamics simulations

    Science.gov (United States)

    Stavrou, Elissaios; Riad Manaa, M.; Zaug, Joseph M.; Kuo, I.-Feng W.; Pagoria, Philip F.; Kalkan, Bora; Crowhurst, Jonathan C.; Armstrong, Michael R.

    2015-10-01

    Recent theoretical studies of 2,6-diamino-3,5-dinitropyrazine-1-oxide (C4H4N6O5 Lawrence Livermore Molecule No. 105, LLM-105) report unreacted high pressure equations of state that include several structural phase transitions, between 8 and 50 GPa, while one published experimental study reports equation of state (EOS) data up to a pressure of 6 GPa with no observed transition. Here we report the results of a synchrotron-based X-ray diffraction study and also ambient temperature isobaric-isothermal atomistic molecular dynamics simulations of LLM-105 up to 20 GPa. We find that the ambient pressure phase remains stable up to 20 GPa; there is no indication of a pressure induced phase transition. We do find a prominent decrease in b-axis compressibility starting at approximately 13 GPa and attribute the stiffening to a critical length where inter-sheet distance becomes similar to the intermolecular distance within individual sheets. The ambient temperature isothermal equation of state was determined through refinements of measured X-ray diffraction patterns. The pressure-volume data were fit using various EOS models to yield bulk moduli with corresponding pressure derivatives. We find very good agreement between the experimental and theoretically derived EOS.

  4. X-ray diffraction and Raman spectroscopy on Gd{sub 2}(Ti{sub 2-y}Te{sub y})O{sub 7} prepared at high pressure and high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Heredia, A.R. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, A. Postal 70-360, Mexico D.F. 04510 (Mexico); Garcia, M. Quintana; Mazariego, J.L. Perez [Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, A. Postal 70-360, Mexico D.F. 04510 (Mexico); Escamilla, R., E-mail: rauleg@servidor.unam.m [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, A. Postal 70-360, Mexico D.F. 04510 (Mexico)

    2010-08-20

    A series of Te-substituted pyrochlores of stoichiometry Gd{sub 2}(Ti{sub 2-y}Te{sub y})O{sub 7} (y {<=} 0.2) were prepared under high-pressure and high-temperature conditions and characterized by X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy. X-ray diffraction and X-ray photoelectron spectroscopy studies revealed that the Te{sup 4+} and Te{sup 6+} ions occupy the Ti{sup 4+}sites; the percentage of the contribution of Te{sup 6+} increases as tellurium content. These substitutions induce an increase of the volume of the TiO{sub 6} octahedron due to the increase in the Ti-O(2) bond length, which preserves the oxygen positional parameter (x{sub 48f}) and the Gd-O(1) bond length. Results of Raman spectroscopy showed a significant shift to higher frequencies of the E{sub g} mode associated to the O(2) sublattice, as well an increase in the full-width-at-half-maximum intensity (FWHM) of the F{sub 2g} mode (O-Gd-O bending) as the level of Te substitution for Ti increases. These results are discussed and compared with those reported in the literature.

  5. Polymorphism in Photoluminescent KNdW2O8: Synthesis, Neutron Diffraction, and Raman Study

    Energy Technology Data Exchange (ETDEWEB)

    S. M. Bhat, Swetha [Materials Science Division, Poornaprajna Institute of Scientific Research, Bidalur Near Devanahalli,; Swain, Diptikanta [CPMU, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru, Karnataka, India; Feygenson, Mikhail [ORNL; Neuefeind, Joerg C [ORNL; Sundaram, Nalini [Materials Science Division, Poornaprajna Institute of Scientific Research, Bidalur Near Devanahalli,

    2014-01-01

    Polymorphs of KNdW2O8 ( -KNdW2O8 and -KNdW2O8) phosphors were synthesized by an efficient solution combustion technique for the first time. The crystal structure of the polymorphs analyzed from Rietveld refinement of neutron diffraction data confirms that -KNdW2O8 crystallizes in the tetragonal system (space group I4 ), and -KNdW2O8 crystallizes in the monoclinic system (space group C2/m). The local structure of both polymorphs was elucidated using combined neutron pair distribution function (PDF) and Raman scattering techniques. Photoluminescence measurements of the polymorphs showed broadened emission line width and increased intensity for -KNdW2O8 in the visible region compared to -KNdW2O8. This phenomenon is attributed to the increased distortion in the coordination environment of the luminescing Nd3+ ion. Combined PDF, Rietveld, and Raman measurements reveal distortions of the WO6 octahedra and NdO8 polyhedra in -KNdW2O8. This crystal structure photoluminescence study suggests that this class of tungstates can be exploited for visible light emitting devices by tuning the crystal symmetry.

  6. Residual stress determination in a dissimilar weld overlay pipe by neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Woo, Wanchuck, E-mail: chuckwoo@kaeri.re.kr [Neutron Science Division, Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Em, Vyacheslav [Neutron Science Division, Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Hubbard, Camden R. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Lee, Ho-Jin [Nuclear Materials Research Center, Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Park, Kwang Soo [Corporate R and D Institute, Doosan Heavy Industries and Construction, Changwon 641-792 (Korea, Republic of)

    2011-10-15

    Highlights: {yields} Determined residual stress distribution in a dissimilar weld overlay pipe. {yields} Consists of a ferritic (SA508), austenitic (F316L) steels, Alloy 182 consumable. {yields} Measured significant compression (-600 MPa) near the inner wall of overlay. {yields} Validate integrity of the inner wall for the pressurized nozzle nuclear structure. - Abstract: Residual stresses were determined through the thickness of a dissimilar weld overlay pipe using neutron diffraction. The specimen has a complex joining structure consisting of a ferritic steel (SA508), austenitic steel (F316L), Ni-based consumable (Alloy 182), and overlay of Ni-base superalloy (Alloy 52M). It simulates pressurized nozzle components, which have been a critical issue under the severe crack condition of nuclear power reactors. Two neutron diffractometers with different spatial resolutions have been utilized on the identical specimen for comparison. The macroscopic 'stress-free' lattice spacing (d{sub o}) was also obtained from both using a 2-mm width comb-like coupon. The results show significant changes in residual stresses from tension (300-400 MPa) to compression (-600 MPa) through the thickness of the dissimilar weld overlay pipe specimen.

  7. Magnetostructural transition in Fe{sub 5}SiB{sub 2} observed with neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Cedervall, Johan, E-mail: johan.cedervall@kemi.uu.se [Department of Chemistry - Ångström Laboratory, Uppsala University, Box 538, 751 21 Uppsala (Sweden); Kontos, Sofia [Department of Engineering Sciences, Uppsala University, Box 534, 751 21 Uppsala (Sweden); Hansen, Thomas C. [Institut Laue-Langevin, B.P. 156, 38042 Grenoble Cedex 9 (France); Balmes, Olivier; Martinez-Casado, Francisco Javier; Matej, Zdenek [MAX IV Laboratory, Lund University, Box 118, 221 00 Lund (Sweden); Beran, Premysl [Nuclear Physics Institute, Academy of Sciences of the Czech Republic, 25068 Rez (Czech Republic); Svedlindh, Peter; Gunnarsson, Klas [Department of Engineering Sciences, Uppsala University, Box 534, 751 21 Uppsala (Sweden); Sahlberg, Martin [Department of Chemistry - Ångström Laboratory, Uppsala University, Box 538, 751 21 Uppsala (Sweden)

    2016-03-15

    The crystal and magnetic structure of Fe{sub 5}SiB{sub 2} has been studied by a combination of X-ray and neutron diffraction. Also, the magnetocrystalline anisotropy energy constant has been estimated from magnetisation measurements. High quality samples have been prepared using high temperature synthesis and subsequent heat treatment protocols. The crystal structure is tetragonal within the space group I4/mcm and the compound behaves ferromagnetically with a Curie temperature of 760 K. At 172 K a spin reorientation occurs in the compound and the magnetic moments go from aligning along the c-axis (high T) down to the ab-plane (low T). The magnetocrystalline anisotropy energy constant has been estimated to 0.3 MJ/m{sup 3} at 300 K. - Highlights: • The crystal and magnetic structure of Fe{sub 5}SiB{sub 2} has been studied by diffraction. • At 172 K a spin reorientation occurs in the compound. • The magnetic moments are aligned along the c-axis at high T. • The magnetic moments are aligned in the ab-plane at low T. • The magnetocrystalline anisotropy energy constant has been estimated to 0.3 MJ/m{sup 3}.

  8. Structure of naturally hydrated ferrihydrite revealed through neutron diffraction and first-principles modeling

    Science.gov (United States)

    Chappell, Helen F.; Thom, William; Bowron, Daniel T.; Faria, Nuno; Hasnip, Philip J.; Powell, Jonathan J.

    2017-08-01

    Ferrihydrite, with a ``two-line'' x-ray diffraction pattern (2L-Fh), is the most amorphous of the iron oxides and is ubiquitous in both terrestrial and aquatic environments. It also plays a central role in the regulation and metabolism of iron in bacteria, algae, higher plants, and animals, including humans. In this study, we present a single-phase model for ferrihydrite that unifies existing analytical data while adhering to fundamental chemical principles. The primary particle is small (20-50 Å) and has a dynamic and variably hydrated surface, which negates long-range order; collectively, these features have hampered complete characterization and frustrated our understanding of the mineral's reactivity and chemical/biochemical function. Near and intermediate range neutron diffraction (NIMROD) and first-principles density functional theory (DFT) were employed in this study to generate and interpret high-resolution data of naturally hydrated, synthetic 2L-Fh at standard temperature. The structural optimization overcomes transgressions of coordination chemistry inherent within previously proposed structures, to produce a robust and unambiguous single-phase model.

  9. Potassium Disorder in the Defect Pyrochlore KSbTeO6: A Neutron Diffraction Study

    Directory of Open Access Journals (Sweden)

    José Antonio Alonso

    2017-01-01

    Full Text Available KSbTeO6 defect pyrochlore has been prepared from K2C2O4, Sb2O3, and 15% excess TeO2 by solid-state reaction at 850 °C. Direct methods implemented in the software EXPO2013 allowed establishing the basic structural framework. This was followed by a combined Rietveld refinement from X-ray powder diffraction (XRD and neutron powder diffraction (NPD data, which unveiled additional structural features. KSbTeO6 is cubic, a = 10.1226(7 Å, space group F d 3 ¯ m , Z = 8 and it is made of a mainly covalent framework of corner-sharing (Sb,TeO6 octahedra, with weakly bonded K+ ions located within large cages. The large K-O distances, 3.05(3–3.07(3 Å, and quite large anisotropic atomic displacement parameters account for the easiness of K+ exchange for other cations of technological importance.

  10. The storage degradation of an 18650 commercial cell studied using neutron powder diffraction

    Science.gov (United States)

    Lee, Po-Han; Wu, She-huang; Pang, Wei Kong; Peterson, Vanessa K.

    2018-01-01

    Commercial 18650 lithium ion cells containing a blended positive electrode of layered LiNi0.5Mn0.3Co0.2O2 and spinel Li1.1Mn1.9O4 alongside a graphite negative electrode were stored at various depth-of-discharge (DoD) at 60 °C for 1, 2, 4, and 6 months. After storage, the cells were cycled at C/25 at 25 °C between 2.75 and 4.2 V for capacity determination and incremental capacity analysis (ICA). In addition to ICA analysis, the mechanism for capacity fade was investigated by combining the results of neutron powder diffraction under in-situ and operando conditions, in conjunction with post-mortem studies of the electrodes using synchrotron X-ray powder diffraction and inductively-coupled plasma optical emission spectroscopy. Among the cells, those stored at 25% DoD suffered the highest capacity fade due to their higher losses of active Li, NMC, and LMO than cells stored at other DoD. The cells stored at 0% DoD shows second high capacity fade because they exhibit the highest of active LMO and graphite anode among the stored cells and higher losses of active Li and NMC than cells stored at 50% DoD.

  11. Magnetic ordering in electronically phase-separated La2-xSrxCuO4+y: Neutron diffraction experiments

    DEFF Research Database (Denmark)

    Udby, Linda; Andersen, Niels Hessel; Chou, F.C.

    2009-01-01

    We present results of magnetic neutron diffraction experiments on the codoped superoxygenated La2-xSrxCuO4+y (LSCO+O) system with x=0.09. We find that the magnetic phase is long-range ordered incommensurate antiferromagnetic with a Neacuteel temperature T-N coinciding with the superconducting...

  12. Tunable high pressure lasers

    Science.gov (United States)

    Hess, R. V.

    1976-01-01

    Atmospheric transmission of high energy CO2 lasers is considerably improved by high pressure operation which, due to pressure broadening, permits tuning the laser lines off atmospheric absorption lines. Pronounced improvement is shown for horizontal transmission at altitudes above several kilometers and for vertical transmission through the entire atmosphere. Applications of tunable high pressure CO2 lasers to energy transmission and to remote sensing are discussed along with initial efforts in tuning high pressure CO2 lasers.

  13. Non-destructive Quantitative Phase Analysis and Microstructural Characterization of Zirconium Coated U-10Mo Fuel Foils via Neutron Diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Cummins, Dustin Ray [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Vogel, Sven C. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hollis, Kendall Jon [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Brown, Donald William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dombrowski, David E. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-10-18

    This report uses neutron diffraction to investigate the crystal phase composition of uranium-molybdenum alloy foils (U-10Mo) for the CONVERT MP-1 Reactor Conversion Project, and determines the effect on alpha-uranium contamination following the deposition of a Zr metal diffusion layer by various methods: plasma spray deposition of Zr powders at LANL and hot co-rolling with Zr foils at BWXT. In summary, there is minimal decomposition of the gamma phase U-10Mo foil to alpha phase contamination following both plasma spraying and hot co-rolling. The average unit cell volume, i.e. lattice spacing, of the Zr layer can be mathematically extracted from the diffraction data; co-rolled Zr matches well with literature values of bulk Zr, while plasma sprayed Zr shows a slight increase in the lattice spacing, indicative of interstitial oxygen in the lattice. Neutron diffraction is a beneficial alternative to conventional methods of phase composition, i.e. x ray diffraction (XRD) and destructive metallography. XRD has minimal penetration depth in high atomic number materials, particularly uranium, and can only probe the first few microns of the fuel plate; neutrons pass completely through the foil, allowing for bulk analysis of the foil composition and no issues with addition of cladding layers, as in the final, aluminum-clad reactor fuel plates. Destructive metallography requires skilled technicians, cutting of the foil into small sections, hazardous etching conditions, long polishing and microscopy times, etc.; the neutron diffraction system has an automated sample loader and can fit larger foils, so there is minimal analysis preparation; the total spectrum acquisition time is ~ 1 hour per sample. The neutron diffraction results are limited by spectra refinement/calculation times and the availability of the neutron beam source. In the case of LANSCE at Los Alamos, the beam operates ~50% of the year. Following the lessons learned from these preliminary results, optimizations to

  14. Neutron diffraction study of La 4LiAuO 8: Understanding Au 3+ in an oxide environment

    Science.gov (United States)

    Kurzman, Joshua A.; Moffitt, Stephanie L.; Llobet, Anna; Seshadri, Ram

    2011-06-01

    Owing to gold's oxophobicity, its oxide chemistry is rather limited, and elevated oxygen pressures are usually required to prepare ternary and quaternary oxide compounds with gold ions. The Au 3+ oxide, La 4LiAuO 8, is remarkable both because it can be prepared at ambient pressure in air, and because of its unusual stability toward thermal decomposition and reduction. The structure of La 4LiAuO 8 was established by Pietzuch et al. using single crystal X-ray diffraction [1]. The compound adopts an ordered modification of the Nd 2CuO 4 structure, containing two-dimensional sheets in which AuO 4 square planes are separated from one another by LiO 4 square planes. In light of the meager X-ray scattering factors of Li and O, relative to La and Au, we report here a neutron powder diffraction study of La 4LiAuO 8, definitively confirming the structure. To our knowledge, this is the first reported neutron diffraction study of any stoichiometric oxide compound of gold. X- N maps, which make use of nuclear positions obtained from Rietveld refinement of time-of-flight neutron diffraction data and electron densities obtained from synchrotron X-ray powder diffraction data, point to the highly covalent nature of the Au-O bonding in La 4LiAuO 8. This is in good agreement with charge densities and Bader charges obtained from full density functional relaxation of the structure.

  15. Carbonado revisited: Insights from neutron diffraction, high resolution orientation mapping and numerical simulations

    Science.gov (United States)

    Piazolo, Sandra; Kaminsky, Felix V.; Trimby, Patrick; Evans, Lynn; Luzin, V.

    2016-11-01

    One of the most controversial diamond types is carbonado, as its origin and geological history are still under debate. Here, we investigate selected carbonado samples using neutron diffraction and high resolution orientation mapping in combination with numerical simulations. Neutron diffraction analyses show that fine grained carbonado samples exhibit a distinct lack of crystallographic preferred orientation. Quantitative crystallographic orientation analyses performed on transmission electron microscope (TEM) sections reveal that the 2-10 μm grains exhibit locally significant internal deformation. Such features are consistent with crystal plastic deformation of a grain aggregate that initially formed by rapid nucleation, characterized by a high number of nucleation sites and no crystallographic preferred orientation. Crystal plastic deformation resulted in high stress heterogeneities close to grain boundaries, even at low bulk strains, inducing a high degree of lattice distortion without significant grain size reduction and the development of a crystallographic preferred orientation. Observed differences in the character of the grain boundary network and internal deformation structures can be explained by significant post-deformation annealing occurring to variable degrees in the carbonado samples. Differences in intensity of crystal bending and subgrain boundary sharpness can be explained by dislocation annihilation and rearrangement, respectively. During annealing grain energy is reduced resulting in distinct changes to the grain boundary geometry. Grain scale numerical modelling shows that anisotropic grain growth, where grain boundary energy is determined by the orientation of a boundary segment relative to the crystallographic orientation of adjacent grains results in straight boundary segments with abrupt changes in orientation even if the boundary is occurring between two triple junctions forming a ;zigzag; pattern. In addition, in diamond anisotropic

  16. High-resolution inelastic neutron scattering and neutron powder diffraction study of the adsorption of dihydrogen by the Cu(II) metal-organic framework material HKUST-1

    Science.gov (United States)

    Callear, Samantha K.; Ramirez-Cuesta, Anibal J.; David, William I. F.; Millange, Franck; Walton, Richard I.

    2013-12-01

    We present new high-resolution inelastic neutron scattering (INS) spectra (measured using the TOSCA and MARI instruments at ISIS) and powder neutron diffraction data (measured on the diffractometer WISH at ISIS) from the interaction of the prototypical metal-organic framework HKUST-1 with various dosages of dihydrogen gas. The INS spectra show direct evidence for the sequential occupation of various distinct sites for dihydrogen in the metal-organic framework, whose population is adjusted during increasing loading of the guest. The superior resolution of TOSCA reveals subtle features in the spectra, not previously reported, including evidence for split signals, while complementary spectra recorded on MARI present full information in energy and momentum transfer. The analysis of the powder neutron patterns using the Rietveld method shows a consistent picture, allowing the crystallographic indenisation of binding sites for dihydrogen, thus building a comprehensive picture of the interaction of the guest with the nanoporous host.

  17. High-resolution inelastic neutron scattering and neutron powder diffraction study of the adsorption of dihydrogen by the Cu(II) metal–organic framework material HKUST-1

    Energy Technology Data Exchange (ETDEWEB)

    Callear, Samantha K.; Ramirez-Cuesta, Anibal J.; David, William I.F. [ISIS Facility, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, OX11 0QX (United Kingdom); Millange, Franck [Institut Lavoisier Versailles (CNRS UMR 8180), Université de Versailles, 78035 Versailles (France); Walton, Richard I., E-mail: r.i.walton@warwick.ac.uk [Department of Chemistry, University of Warwick, CV4 7AL, Coventry (United Kingdom)

    2013-12-12

    Highlights: • Binding sites for dihydrogen in a metal–organic framework have been identified. • The combination of diffraction and spectroscopy shows competitive filling of various adsorption sites. • Inelastic neutron scattering over wide-momentum transfer reveals new models for hydrogen-framework interactions. - Abstract: We present new high-resolution inelastic neutron scattering (INS) spectra (measured using the TOSCA and MARI instruments at ISIS) and powder neutron diffraction data (measured on the diffractometer WISH at ISIS) from the interaction of the prototypical metal–organic framework HKUST-1 with various dosages of dihydrogen gas. The INS spectra show direct evidence for the sequential occupation of various distinct sites for dihydrogen in the metal–organic framework, whose population is adjusted during increasing loading of the guest. The superior resolution of TOSCA reveals subtle features in the spectra, not previously reported, including evidence for split signals, while complementary spectra recorded on MARI present full information in energy and momentum transfer. The analysis of the powder neutron patterns using the Rietveld method shows a consistent picture, allowing the crystallographic indenisation of binding sites for dihydrogen, thus building a comprehensive picture of the interaction of the guest with the nanoporous host.

  18. Neutron diffraction studies of magnetic ordering in Ni-doped LaCoO3

    Science.gov (United States)

    Rajeevan, N. E.; Kumar, Vinod; Kumar, Rajesh; Kumar, Ravi; Kaushik, S. D.

    2015-11-01

    Research in rare earth cobaltite has recently been intensified due to its fascinating magnetic properties. LaCoO3, an important cobaltite, exhibits two prominent susceptibility features at 90 K and 500 K in low field measurement. The magnetic behavior below 100 K is predominantly antiferromagnetic (AFM), but absence of pure AFM ordering and emergence of ferromagnetic coupling on further decreasing temperature made situation more intricate. The present work of studying the effect of Ni substitution at Co site in polycrystalline LaCo1-xNixO3 (0≤x≤0.3) is motivated by the interesting changes in magnetic and electronic properties. For lucid understanding, temperature dependent neutron diffraction (ND) study was carried out. ND patterns fitted with rhombohedral structure in perovskite form with R-3c space group, elucidated information on phase purity. Further temperature dependent cell parameter, Co-O bond-length and Co-O-Co bond angle were calculated for the series of Ni doped LaCoO3. The results are explained in terms of decrease in the crystal field energy which led to the transition of cobalt from low Spin (LS) state to intermediate spin state (IS).

  19. Structural refinement of delithiated LiVO/sub 2/ by neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Thackeray, M.M.; de Picciotto, L.A.; David, W.I.F.; Bruce, P.G.; Goodenough, J.B.

    1987-04-01

    Lithium has been extracted from the layered compound LiVO/sub 2/ by chemical oxidation with bromine. Previous X-ray data have shown that in Li/sub 1-x/VO/sub 2/ lithium extraction beyond x approx. = 0.33 is accompanied by migration of one-third of the vanadium ions into the lithium-deficient layer to stabilize the structure; little information about the location of the lithium ions could be gathered from this data. The neutron diffraction data presented in this paper show that at a composition Li/sub 0.22/VO/sub 2/, determined by atomic absorption spectroscopy, the residual lithium ions are distributed over the octahedral sites of the original lithium layer; the possibility that a small fraction of the lithium ions partially occupy the tetrahedral istes in this layer cannot be discounted. No significant occupation by lithium of the tetrahedral or octahedral vacancies in the vanadium-rich layer could be detected.

  20. Structure and dynamics of cholesterol-containing polyunsaturated lipid membranes studied by neutron diffraction and NMR.

    Science.gov (United States)

    Mihailescu, Mihaela; Soubias, Olivier; Worcester, David; White, Stephen H; Gawrisch, Klaus

    2011-01-01

    A direct and quantitative analysis of the internal structure and dynamics of a polyunsaturated lipid bilayer composed of 1-stearoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine (18:0-22:6n3-PC) containing 29 mol% cholesterol was carried out by neutron diffraction, (2)H-NMR and (13)C-MAS NMR. Scattering length distribution functions of cholesterol segments as well as of the sn-1 and sn-2 hydrocarbon chains of 18:0-22:6n3-PC were obtained by conducting experiments with specifically deuterated cholesterol and lipids. Cholesterol orients parallel to the phospholipids, with the A-ring near the lipid glycerol and the terminal methyl groups 3 Å away from the bilayer center. Previously, we reported that the density of polyunsaturated docosahexaenoic acid (DHA, 22:6n3) chains was higher near the lipid-water interface. Addition of cholesterol partially redistributes DHA density from near the lipid-water interface to the center of the hydrocarbon region. Cholesterol raises chain-order parameters of both stearic acid and DHA chains. The fractional order increase for stearic acid methylene carbons C(8)-C(18) is larger, reflecting the redistribution of DHA chain density toward the bilayer center. The correlation times of DHA chain isomerization are short and mostly unperturbed by the presence of cholesterol. The uneven distribution of saturated and polyunsaturated chain densities and the cholesterol-induced balancing of chain distributions may have important implications for the function and integrity of membrane receptors, such as rhodopsin.

  1. In situ observation of the reaction of scandium and carbon by neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Juarez-Arellano, Erick A., E-mail: eajuarez@unpa.edu.m [Institut fuer Geowissenschaften, Universitaet Frankfurt, Altenhoeferallee 1, 60438 Frankfurt a.M. (Germany); Universidad del Papaloapan, Circuito Central 200, Parque Industrial, Tuxtepec 68301 (Mexico); Winkler, Bjorn [Institut fuer Geowissenschaften, Universitaet Frankfurt, Altenhoeferallee 1, 60438 Frankfurt a.M. (Germany); Vogel, Sven C. [Los Alamos National Laboratory, Lujan Center. Mail Stop H805, Los Alamos, NM 87545 (United States); Senyshyn, Anatoliy [Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), Technische Universitaet Muenchen, Lichtenbergstr. 1, D-85747 Garching (Germany); Materialwissenschaft, TU Darmstadt, Petersensstr. 23, D-64287 Darmstadt (Germany); Kammler, Daniel R. [Sandia National Laboratories, Albuquerque, NM 87185 (United States); Avalos-Borja, Miguel [CNyN, UNAM, A. Postal 2681, Ensenada, B.C. (Mexico)

    2011-01-05

    Research highlights: {yields} Exist two ScC cubic phases with B1-structure type differing in site occupancy of C. {yields} A new orthorhombic scandium carbide phase is formed at 1473(50) K. {yields} The recrystallization of alpha-Sc occurs between 1000 and 1223 K. - Abstract: The formation of scandium carbides by reaction of the elements has been investigated by in situ neutron diffraction up to 1823 K. On heating, the recrystallization of {alpha}-Sc occurs between 1000 and 1223 K. The formation of Sc{sub 2}C and ScC (NaCl-B1 type structure) phases has been detected at 1323 and 1373 K, respectively. The formation of a new orthorhombic scandium carbide phase was observed at 1473(50) K. Once the scandium carbides are formed they are stable upon heating or cooling. No other phases were detected in the present study, in which the system was always carbon saturated. The thermal expansion coefficients of all phases have been determined, they are constant throughout the temperature interval studied.

  2. Distribution of Drug Molecules in Lipid Membranes: Neutron Diffraction and MD Simulations.

    Science.gov (United States)

    Boggara, Mohan; Mihailescu, Ella; Krishnamoorti, Ramanan

    2009-03-01

    Non-steroidal anti-inflammatory drugs (NSAIDs) e.g. Aspirin and Ibuprofen, with chronic usage cause gastro intestinal (GI) toxicity. It has been shown experimentally that NSAIDs pre-associated with phospholipids reduce the GI toxicity and also increase the therapeutic activity of these drugs compared to the unmodified ones. In this study, using neutron diffraction, the DOPC lipid bilayer structure (with and without drug) as well as the distribution of a model NSAID (Ibuprofen) as a function of its position along the membrane normal was obtained at sub-nanometer resolution. It was found that the bilayer thickness reduces as the drug is added. Further, the results are successfully compared with atomistic Molecular Dynamics simulations. Based on this successful comparison and motivated by atomic details from MD, quasi-molecular modeling of the lipid membrane is being carried out and will be presented. The above study is expected to provide an effective methodology to design drug delivery nanoparticles based on a variety of soft condensed matter such as lipids or polymers.

  3. Neutron diffraction studies of the interaction between amphotericin B and lipid-sterol model membranes

    Science.gov (United States)

    Foglia, Fabrizia; Lawrence, M. Jayne; Demeė, Bruno; Fragneto, Giovanna; Barlow, David

    2012-10-01

    Over the last 50 years or so, amphotericin has been widely employed in treating life-threatening systemic fungal infections. Its usefulness in the clinic, however, has always been circumscribed by its dose-limiting side-effects, and it is also now compromised by an increasing incidence of pathogen resistance. Combating these problems through development of new anti-fungal agents requires detailed knowledge of the drug's molecular mechanism, but unfortunately this is far from clear. Neutron diffraction studies of the drug's incorporation within lipid-sterol membranes have here been performed to shed light on this problem. The drug is shown to disturb the structures of both fungal and mammalian membranes, and co-localises with the membrane sterols in a manner consistent with trans-membrane pore formation. The differences seen in the membrane lipid ordering and in the distributions of the drug-ergosterol and drug-cholesterol complexes within the membranes are consistent with the drug's selectivity for fungal vs. human cells.

  4. Residual stress determination in thermally sprayed metallic deposits by neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Keller, Thomas; Margadant, Nikolaus; Pirling, Thilo; Riegert-Escribano, Maria J.; Wagner, Werner

    2004-05-25

    Neutron diffraction was used to obtain spatially resolved strain and stress profiles in thermally sprayed metallic 'NiCrAlY' deposits (chemical composition 67 wt.% Ni, 22 wt.% Cr, 10 wt.% Al, 1 wt.% Y) and the underlying steel substrates. Samples of four different spray techniques were analyzed: atmospheric and water stabilized plasma spraying (APS and WSP), flame spraying (FS) and wire arc spraying (WAS). The results are quantitatively compared with the average in-plane residual stress determined by complementary bending tests and the hole drilling technique. While the stress profiles from the surface to the interface in the deposits are similar for all investigated spray techniques, their absolute values and gradients vary strongly. This is attributed to different quenching stresses from the impinging particles, different thermal histories the deposit/substrate systems undergo during the spraying and subsequent cooling, and also to different coating properties. In the water stabilized plasma sprayed and the wire arc sprayed deposits, a gradient in the stress-free lattice parameter was observed. Crack formation is found to be a dominant mechanism for stress relaxation in the surface plane.

  5. Neutron-diffraction studies of the nuclear magnetic phase diagram of copper

    DEFF Research Database (Denmark)

    Annila, A.J.; Clausen, Kurt Nørgaard; Oja, A.S.

    1992-01-01

    -field phase and the intermediate-field structure is of first order. The change from (0 2/3 2/3) at intermediate fields to (100) at zero field is associated with a large region (0.02 less-than-or-equal-to B less-than-or-equal-to 0.06 mT) of coexisting-(100) and (0 2/3 2/3)-type Bragg peaks, and can......We have studied the spontaneous antiferromagnetic (AF) order in the nuclear spin system of copper by use of neutron-diffraction experiments at nanokelvin temperatures. Copper is an ideal model system as a nearest-neighbor-dominated spin-3/2 fcc antiferromagnet. The phase diagram has been...... investigated by measuring the magnetic-field dependence of the (100) reflection, characteristic of a type-I AF structure, and of a Bragg peak at (0 2/3 2/3). The results suggest the presence of high-field (100) phases at 0.12 less-than-or-equal-to B less-than-or-equal-to B(c) almost-equal-to 0.26 mT, for B...

  6. Neutron Powder Diffraction Study on the Magnetic Structure of NdPd5Al2

    Science.gov (United States)

    Metoki, Naoto; Yamauchi, Hiroki; Kitazawa, Hideaki; Suzuki, Hiroyuki S.; Hagihala, Masato; Frontzek, Matthias D.; Matsuda, Masaaki; Fernandez-Baca, Jaime A.

    2017-03-01

    The magnetic structure of NdPd5Al2 has been studied by neutron powder diffraction. We observed the magnetic reflections with the modulation vector q = (1/2,0,0) below the ordering temperature TN. We found a collinear magnetic structure with a Nd moment of 2.7(3) μB at 0.5 K parallel to the c-axis, where the ferromagnetically ordered a-planes stack with a four-Nd-layer period having a ++- sequence along the a-direction with the distance between adjacent Nd layers equal to a/2 (magnetic space group Panma). This "stripe"-like modulation is very similar to that in CePd5Al2 with q = (0.235,0.235,0) with the Ce moment parallel to the c-axis. These structures with in-plane modulation are a consequence of the two-dimensional nature of the Fermi surface topology in this family, originating from the unique crystal structure with a very long tetragonal unit cell and a large distance of >7 Å between the rare-earth layers separated by two Pd and one Al layers.

  7. Thermal expansion and decomposition of jarosite: a high-temperature neutron diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Hongwu [Los Alamos National Laboratory; Zhao, Yusheng [Los Alamos National Laboratory; Vogel, Sven C [Los Alamos National Laboratory; Hickmott, Donald D [Los Alamos National Laboratory; Daemen, Luke L [Los Alamos National Laboratory; Hartl, Monika A [Los Alamos National Laboratory

    2009-01-01

    The structure of deuterated jarosite, KFe{sub 3}(SO{sub 4}){sub 2}(OD){sub 6}, was investigated using time-of-flight neutron diffraction up to its dehydroxylation temperature. Rietveld analysis reveals that with increasing temperature, its c dimension expands at a rate {approx}10 times greater than that for a. This anisotropy of thermal expansion is due to rapid increase in the thickness of the (001) sheet of [Fe(O,OH){sub 6}] octahedra and [SO{sub 4}] tetrahedra with increasing temperature. Fitting of the measured cell volumes yields a coefficient of thermal expansion, a = a{sub 0} + a{sub 1} T, where a{sub 0} = 1.01 x 10{sup -4} K{sup -1} and a{sub 1} = -1.15 x 10{sup -7} K{sup -2}. On heating, the hydrogen bonds, O1{hor_ellipsis}D-O3, through which the (001) octahedral-tetrahedral sheets are held together, become weakened, as reflected by an increase in the D{hor_ellipsis}O1 distance and a concomitant decrease in the O3-D distance with increasing temperature. On further heating to 575 K, jarosite starts to decompose into nanocrystalline yavapaiite and hematite (as well as water vapor), a direct result of the breaking of the hydrogen bonds that hold the jarosite structure together.

  8. X-Ray and Neutron Diffraction Study of CaBi 2O 4

    Science.gov (United States)

    Sora, I. Natali; Wong-Ng, W.; Huang, Q.; Roth, R. S.; Rawn, C. J.; Burton, B. P.; Santoro, A.

    1994-04-01

    The crystal structure of the 1:1 CaO-Bi 2O 3 compound (CaBi 2O 4) has been determined by single crystal X-ray and neutron powder diffraction techniques. The compound crystallizes with the symmetry of the monoclinic space group C2/ c and lattice parameters a = 16.6130(5) Å, b = 11.5900(4) Å, c = 13.9939(4) Å, β = 134.048(1)°. The structure consists of sheets parallel to the b-c plane and connected by Ca-O bonds. There is a structural unit in each layer consisting of four Bi atoms, ten oxygen atoms, and two calcium atoms. The Bi atoms are fourfold coordinated and the coordination polyhedron may be described as a short distorted pyramid, open on one end to accommodate the lone-pair electrons of the bismuth atoms. Calcium is seven-coordinated and the coordination polyhedron may be described as a monocapped trigonal prism.

  9. Single crystal polarized neutron diffraction study of the magnetic structure of HoFeO3

    Science.gov (United States)

    Chatterji, T.; Stunault, A.; Brown, P. J.

    2017-09-01

    Polarised neutron diffraction measurements have been made on HoFeO3 single crystals magnetised in both the [0 0 1] and [1 0 0] directions (Pbnm setting). The polarisation dependencies of Bragg reflection intensities were measured both with a high field of H = 9 T parallel to [0 0 1] at T = 70 K and with the lower field H = 0.5 T parallel to [1 0 0] at T = 5, 15, 25 K. A Fourier projection of magnetization induced parallel to [0 0 1], made using the hk0 reflections measured in 9 T, indicates that almost all of it is due to alignment of Ho moments. Further analysis of the asymmetries of general reflections in these data showed that although, at 70 K, 9 T applied parallel to [0 0 1] hardly perturbs the antiferromagnetic order of the Fe sublattices, it induces significant antiferromagnetic order of the Ho sublattices in the x-y plane, with the antiferromagnetic components of moment having the same order of magnitude as the induced ferromagnetic ones. Strong intensity asymmetries measured in the low temperature Γ2 structure with a lower field, 0.5 T \\Vert [1 0 0] allowed the variation of the ordered components of the Ho and Fe moments to be followed. Their absolute orientations, in the \

  10. Neutron diffraction residual stress analysis of Al2O3/Y-TZP ceramic composites

    Directory of Open Access Journals (Sweden)

    Kunyang Fan

    2016-01-01

    Full Text Available Residual stress measurements were conducted by time-of-flight neutron diffraction and Rietveld analysis method in Al2O3/Y-TZP ceramic composites fabricated by different green processing techniques (a novel tape casting and conventional slip casting and with different Y-TZP content (5 and 40 vol.% Y-TZP. The results show that the residual stresses in Y-TZP particulates are tensile and the ones in Al2O3 matrix are compressive, with almost flat through-thickness residual stress profiles in all bulk samples. As Y-TZP content increased, tension in Y-TZP phase was decreased but compression in Al2O3 matrix was increased (in absolute value. The values of residual stresses for both phases were mainly dependent on the Y-TZP content in the studied Al2O3/Y-TZP composites, irrespective of sample orientation and fabrication processes (a novel tape casting and conventional slip casting.

  11. Optimization of spring exchange coupled ferrites, studied by in situ neutron diffraction

    DEFF Research Database (Denmark)

    Ahlburg, Jakob; Christensen, Mogens; Granados-Miralles, Cecilia

    the 3d orbitals but these can only contain up to 10 electrons. This means that other measures have to be done in order to compete with the REM magnets. One prominent method is mixing a hard and a soft magnetic phase, on the nanoscale, to achieve an exchange coupling between the phases and enhancing...... the magnetic energy product. For the exchange coupling to happen it is crucial to have the right ratio between the hard and the soft phase but also to control the size of the particles since exchange coupling is a very small range effect. In this study, nanoparticles of the spinel CoFe2O4 (hard magnet......) is reduced to a metallic alloy CoFe (soft magnet) by heating the sample and flowing it with hydrogen gas. It is studied in situ using neutron powder diffraction with a time resolution of 12 min. The transition from spinel to pure metal goes through an intermediate step of a metal oxide before being fully...

  12. Determination of crystallographic young’s modulus for sheet metals by in situ neutron diffraction

    Science.gov (United States)

    Vitzthum, S. J.; Hartmann, C.; Weiss, H. A.; Baumgartner, G.; Hofmann, M.; Volk, W.

    2017-09-01

    Elastic recovery is an important issue in sheet metal forming, especially in the context of the upcoming use of high strength steels due to shifted relations between Young’s modulus and strength. One important factor when it comes to elastic recovery prediction is a deep understanding for the elasto-plastic characteristics of the material. Today in general simple elastic behavior with constant Young’s modulus and Poisson’s ratio is assumed. Macroscopic analysis in standard tests shows that these assumptions are insufficient for an appropriate prediction of elastic recovery in sheet metal forming, which is why different phenomenological correlation models are derived. An experimental setup and microscopic investigation to further prove these models and to verify the approaches on another scale for sheet metals is presented within this paper. In the study microscopic deformation behavior of loading and unloading of a HC260LA sheet metal is analysed using in-situ neutron diffraction. Based on the lattice plane strains an orientation specific crystallographic Young’s modulus for different rolling directions is determined.

  13. Residual stress in a laser welded EUROFER blanket module assembly using non-destructive neutron diffraction techniques

    CERN Document Server

    Hughes, D J; Heeley, E L

    2014-01-01

    Whilst the structural integrity and lifetime considerations in welded joints for blanket modules can be predicted using finite element software, it is essential to prove the validity of these simulations. This paper provides detailed analysis for the first time, of the residual stress state in a laser-welded sample with integral cooling channels. State-of-the-art non-destructive neutron diffraction was employed to determine the triaxial stress state and to understand microstructural changes around the heat affected zone. Synchrotron X-ray diffraction was used to probe the variation of strain-free lattice reference parameter around the weld zone allowing correction of the neutron measurements. This paper details an important experimental route to validation of predicted stresses in complex safety-critical reactor components for future applications.

  14. Residual stress characterization of steel TIG welds by neutron diffraction and by residual magnetic stray field mappings

    Energy Technology Data Exchange (ETDEWEB)

    Stegemann, Robert, E-mail: Robert.Stegemann@bam.de [Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, 12200 Berlin (Germany); Cabeza, Sandra; Lyamkin, Viktor; Bruno, Giovanni; Pittner, Andreas [Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, 12200 Berlin (Germany); Wimpory, Robert; Boin, Mirko [HZB Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); Kreutzbruck, Marc [Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, 12200 Berlin (Germany); IKT, University of Stuttgart, Pfaffenwaldring 32, 70569 Stuttgart (Germany)

    2017-03-15

    The residual stress distribution of tungsten inert gas welded S235JRC+C plates was determined by means of neutron diffraction (ND). Large longitudinal residual stresses with maxima around 600 MPa were found. With these results as reference, the evaluation of residual stress with high spatial resolution GMR (giant magneto resistance) sensors was discussed. The experiments performed indicate a correlation between changes in residual stresses (ND) and the normal component of local residual magnetic stray fields (GMR). Spatial variations in the magnetic field strength perpendicular to the welds are in the order of the magnetic field of the earth. - Highlights: • Comparison of magnetic microstructure with neutron diffraction stress analysis. • High spatial resolution magnetic stray field images of hypereutectoid TIG welds. • Spatial variations of the stray fields are below the magnetic field of the earth. • GMR spin valve gradiometer arrays adapted for the evaluation of magnetic microstructures. • Magnetic stray fields are closely linked to microstructure of the material.

  15. Fluid bilayer structure determination: Joint refinement in composition space using X-ray and neutron diffraction data

    Energy Technology Data Exchange (ETDEWEB)

    White, S.H. [Univ. of California, Irvine, CA (United States); Wiener, M.C. [Univ. of California, San Francisco, CA (United States)

    1994-12-31

    Experimentally-determined structural models of fluid lipid bilayers are essential for verifying molecular dynamics simulations of bilayers and for understanding the structural consequences of peptide interactions. The extreme thermal motion of bilayers precludes the possibility of atomic-level structural models. Defining {open_quote}the structure{close_quote} of a bilayer as the time-averaged transbilayer distribution of the water and the principal lipid structural groups such as the carbonyls and double-bonds (quasimolecular fragments), one can represent the bilayer structure as a sum of Gaussian functions referred to collectively as the quasimolecular structure. One method of determining the structure is by neutron diffraction combined with exhaustive specific deuteration. This method is impractical because of the expense of the chemical syntheses and the limited amount of neutron beam time currently available. We have therefore developed the composition space refinement method for combining X-ray and minimal neutron diffraction data to arrive at remarkably detailed and accurate structures of fluid bilayers. The composition space representation of the bilayer describes the probability of occupancy per unit length across the width of the bilayer of each quasimolecular component and permits the joint refinement of X-ray and neutron lamellar diffraction data by means of a single quasimolecular structure that is fitted simultaneously to both data sets. Scaling of each component by the appropriate neutron or X-ray scattering length maps the composition-space profile to the appropriate scattering length space for comparison to experimental data. The difficulty with the method is that fluid bilayer structures are generally only marginally determined by the experimental data. This means that the space of possible solutions must be extensively explored in conjunction with a thorough analysis of errors.

  16. High-pressure stability and compressibility of APO[subscript 4] (A=La, Nd, Eu, Gd, Er, and Y) orthophosphates: An x-ray diffraction study using synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Lacomba-Perales, R.; Errandonea, D.; Meng, Y.; Bettinelli, M. (Verona); (Valencia); (CIW)

    2010-03-16

    Room-temperature angle-dispersive x-ray diffraction measurements on zircon-type YPO{sub 4} and ErPO{sub 4}, and monazite-type GdPO{sub 4}, EuPO{sub 4}, NdPO{sub 4}, and LaPO{sub 4} were performed in a diamond-anvil cell up to 30 GPa using neon as pressure-transmitting medium. In the zircon-structured oxides we found evidence of a reversible pressure-induced structural phase transformation from zircon to a monazite-type structure. The onset of the transition is at 19.7 GPa in YPO{sub 4} and 17.3 GPa in ErPO{sub 4}. In LaPO{sub 4} a nonreversible transition is found at 26.1 GPa and a barite-type structure is proposed for the high-pressure phase. For the other three monazites studied, their structures were found to be stable up to 30 GPa. Evidence for additional phase transitions or chemical decomposition of the materials was not found in the experiments. The equations of state and axial compressibility for the different phases are also determined. In particular, we found that in a given compound the monazite structure is less compressible than the zircon structure. This fact is attributed to the higher packing efficiency of monazite versus zircon. The differential bond compressibility of different polyhedra is also reported and related to the anisotropic compressibility of both structures. Finally, the sequence of structural transitions and compressibilities are discussed in comparison with other orthophosphates.

  17. High-pressure microfluidics

    Science.gov (United States)

    Hjort, K.

    2015-03-01

    When using appropriate materials and microfabrication techniques, with the small dimensions the mechanical stability of microstructured devices allows for processes at high pressures without loss in safety. The largest area of applications has been demonstrated in green chemistry and bioprocesses, where extraction, synthesis and analyses often excel at high densities and high temperatures. This is accessible through high pressures. Capillary chemistry has been used since long but, just like in low-pressure applications, there are several potential advantages in using microfluidic platforms, e.g., planar isothermal set-ups, large local variations in geometries, dense form factors, small dead volumes and precisely positioned microstructures for control of reactions, catalysis, mixing and separation. Other potential applications are in, e.g., microhydraulics, exploration, gas driven vehicles, and high-pressure science. From a review of the state-of-art and frontiers of high pressure microfluidics, the focus will be on different solutions demonstrated for microfluidic handling at high pressures and challenges that remain.

  18. Temperature evolution of magnetic structure of HoFeO3 by single crystal neutron diffraction

    Directory of Open Access Journals (Sweden)

    T. Chatterji

    2017-04-01

    Full Text Available We have investigated the temperature evolution of the magnetic structures of HoFeO3 by single crystal neutron diffraction. The three different magnetic structures werevfound as a function of temperature for HoFeO3. In all three phases the fundamental coupling between the Fe sub-lattices remains the same and only their orientation and the degree of canting away from the ideal axial direction varies. The magnetic polarisation of the Ho sub-lattices in these two higher temperature regions, in which the major components of the Fe moment lie along x and y, is very small. The canting of the moments from the axial directions is attributed to the antisymmetric interactions allowed by the crystal symmetry. In the low temperature phase two further structural transitions are apparent in which the spontaneous magnetisation changes sign with respect to the underlying antiferromagnetic configuration. In this temperature range the antisymmetric exchange energy varies rapidly as the the Ho sub-lattices begin to order. So long as the ordered Ho moments are small the antisymmetric exchange is due only to Fe-Fe interactions, but as the degree of Ho order increases the Fe-Ho interactions take over whilst at the lowest temperatures, when the Ho moments approach saturation the Ho-Ho interactions dominate. The reversals of the spontaneous magnetisation found in this study suggest that in HoFeO3 the sums of the Fe-Fe and Ho-Ho antisymmetric interactions have the same sign as one another, but that of the Ho-Fe terms is opposite.

  19. Antiferroelastic structural transitions in PrAlO{sub 3} by means of neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, S. [Department of Physics, Graduate School of Sciences, Kyushu University, 33, Fukuoka 812-8581 (Japan); Neutron Scattering Laboratory, ISSP, University of Tokyo, Tokai, Ibaraki, 319-1106 (Japan); Hidaka, M. [Department of Physics, Graduate School of Sciences, Kyushu University, 33, Fukuoka 812-8581 (Japan); Yoshizawa, H. [Neutron Scattering Laboratory, ISSP, University of Tokyo, Tokai, Ibaraki, 319-1106 (Japan); Wanklyn, B.M. [Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, OX1 3PU (United Kingdom)

    2006-02-01

    Structural phase transitions of the perovskite-type PrAlO{sub 3} have been studied by using neutron diffraction. The results show that, on cooling, the structures are successively transformed from R anti 3c (Phase II) to Imma (Phase III), Imma (Phase IV), I4/mcm (Phase V) by the 215-K, 153-K, and 122-K transitions. The tilting schemes in Phase III, IV and V are mainly characterized by ({psi}{sub a} = {psi}{sub c}, {psi}{sub b} = 0), ({psi}{sub a} {ne} {psi}{sub c}, {psi}{sub b} = 0), and ({psi}{sub c}, {psi}{sub a} = {psi}{sub b} = 0), respectively, where {psi}{sub a}, {psi}{sub b} and {psi}{sub c} are rotational angles around a-, b-, and c-primitive axes of the AlO{sub 6} octahedron. The refreezes of the condensed R{sub 25} {sub {sup y}} and R {sub 25} {sub {sup x}} optical soft modes occurring at about 215 K and 122 K are interpreted by correlation with the cooperative Jahn-Teller distortion (JTD) of the Pr {sup 3+}-4f orbitals in the PrO {sub 12} polyhedra. The phase IV is characterized as an intermediate state, in which the {psi}{sub a} tilts are continuously reduced by the JTD and disappear just above the 122-K transition. The easy mobility of the domain walls suggests the PrAlO {sub 3} crystal to be of antiferroelastic nature, an unusual property that results from the cooperative displacements of O ions induced by the correlation between the antiphase tilts along primitive axes of the AlO {sub 6} octahedra and the JTD around Pr {sup +3} ions in PrO {sub 12} polyhedra. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Neutron diffraction reveals the existence of confined water in triangular and hexagonal channels of modified YPO4 at elevated temperatures

    Science.gov (United States)

    Mishra, S. K.; Ningthoujam, R. S.; Mittal, R.; Vatsa, R. K.; Zbiri, M.; Sharma, K. Shitaljit; Singh, B. P.; Sastry, P. U.; Hansen, T.; Schober, H.; Chaplot, S. L.

    2017-09-01

    We provide experimental evidence for confinement of water molecules in the pores of hexagonal structure of YPO4 at elevated temperatures up to 600 K using powder neutron diffraction. In order to avoid the large incoherent scattering from the hydrogen, deuterated samples of doped YPO4:Ce-Eu were used for diffraction measurements. The presence of water molecules in the triangular and hexagonal pores in the hexagonal structure was established by detailed simulation of the diffraction pattern and Rietveld refinement of the experimental data. It was observed that the presence of water leads specifically to suppression of the intensity of a peak around Q = 1.04 Å-1 while the intensity of peaks around Q = 1.83 Å-1 is enhanced in the neutron-diffraction pattern. We estimate the number of water molecules as 2.36 (6) per formula units at 300 K and the sizes of the hexagonal and triangular pores as 7.2 (1) and 4.5 (1) Å, respectively. With an increase in temperature, the water content in both pores decreases above 450 K and vanishes around 600 K. Analysis of the powder-diffraction data reveals that the hexagonal structure with the pores persist up to 1273 K, and transforms to another structure at 1323 K. The high-temperature phase is not found to have the zircon- or monazite-type structure, but a monoclinic structure (space group P 2 /m ) with lattice parameters am= 6.826 (4 ) Å ,bm= 6.645 (4 ) Å ,cm= 10.435 (9 ) Å , and β = 107.21 (6) ∘ . The monoclinic structure has about 14% smaller volume than the hexagonal structure which essentially reflects the collapse of the pores. The phase transition and the change in the volume are also confirmed by x-ray-diffraction measurements. The hexagonal-to-monoclinic phase transition is found to be irreversible on cooling to room temperature.

  1. Neutron diffraction and μ SR studies of two polymorphs of nickel niobate NiNb2O6

    Science.gov (United States)

    Munsie, T. J. S.; Wilson, M. N.; Millington, A.; Thompson, C. M.; Flacau, R.; Ding, C.; Guo, S.; Gong, Z.; Aczel, A. A.; Cao, H. B.; Williams, T. J.; Dabkowska, H. A.; Ning, F.; Greedan, J. E.; Luke, G. M.

    2017-10-01

    Neutron diffraction and muon spin relaxation (μ SR ) studies are presented for the newly characterized polymorph of NiNb2O6 (β -NiNb2O6) with space group P4 2/n and μ SR data only for the previously known columbite structure polymorph with space group P b c n . The magnetic structure of the P4 2/n form was determined from neutron diffraction using both powder and single-crystal data. Powder neutron diffraction determined an ordering wave vector k ⃗=(1/2 ,1/2 ,1/2 ) . Single-crystal data confirmed the same k ⃗ vector and showed that the correct magnetic structure consists of antiferromagnetically coupled chains running along the a or b axis in adjacent Ni2 + layers perpendicular to the c axis, which is consistent with the expected exchange interaction hierarchy in this system. The refined magnetic structure is compared with the known magnetic structures of the closely related trirutile phases, NiSb2O6 and NiTa2O6 . μ SR data finds a transition temperature of TN˜15 K for this system, while the columbite polymorph exhibits a lower TN=5.7 (3 ) K. Our μ SR measurements also allowed us to estimate the critical exponent of the order parameter β for each polymorph. We found β =0.25 (3 ) and 0.16(2) for the β and columbite polymorphs, respectively. The single-crystal neutron scattering data give a value for the critical exponent β =0.28 (3 ) for β -NiNb2O6 , in agreement with the μ SR value. While both systems have β values less than 0.3, which is indicative of reduced dimensionality, this effect appears to be much stronger for the columbite system. In other words, although both systems appear to be well described by S =1 spin chains, the interchain interactions in the β polymorph are likely much larger.

  2. High Pressure Biomass Gasification

    Energy Technology Data Exchange (ETDEWEB)

    Agrawal, Pradeep K [Georgia Tech Research Corporation, Atlanta, GA (United States)

    2016-07-29

    According to the Billion Ton Report, the U.S. has a large supply of biomass available that can supplement fossil fuels for producing chemicals and transportation fuels. Agricultural waste, forest residue, and energy crops offer potential benefits: renewable feedstock, zero to low CO2 emissions depending on the specific source, and domestic supply availability. Biomass can be converted into chemicals and fuels using one of several approaches: (i) biological platform converts corn into ethanol by using depolymerization of cellulose to form sugars followed by fermentation, (ii) low-temperature pyrolysis to obtain bio-oils which must be treated to reduce oxygen content via HDO hydrodeoxygenation), and (iii) high temperature pyrolysis to produce syngas (CO + H2). This last approach consists of producing syngas using the thermal platform which can be used to produce a variety of chemicals and fuels. The goal of this project was to develop an improved understanding of the gasification of biomass at high pressure conditions and how various gasification parameters might affect the gasification behavior. Since most downstream applications of synags conversion (e.g., alcohol synthesis, Fischer-Tropsch synthesis etc) involve utilizing high pressure catalytic processes, there is an interest in carrying out the biomass gasification at high pressure which can potentially reduce the gasifier size and subsequent downstream cleaning processes. It is traditionally accepted that high pressure should increase the gasification rates (kinetic effect). There is also precedence from coal gasification literature from the 1970s that high pressure gasification would be a beneficial route to consider. Traditional approach of using thermogravimetric analyzer (TGA) or high-pressure themogravimetric analyzer (PTGA) worked well in understanding the gasification kinetics of coal gasification which was useful in designing high pressure coal gasification processes. However

  3. Cu-Zn disorder in Cu2ZnGeSe4: A complementary neutron diffraction and Raman spectroscopy study

    Science.gov (United States)

    Gurieva, G.; Többens, D. M.; Valakh, M. Ya.; Schorr, S.

    2016-12-01

    The crystal structure of the quaternary compound semiconductor Cu2ZnGeSe4 (CZGSe) was investigated by the complementary use of neutron diffraction, and Raman spectroscopy. The powder sample, which resulting from wavelength dispersive X-ray spectroscopy (WDX) turned out to be single phase Cu-rich CZGSe, was synthesized by solid state reaction of the pure elements in an evacuated silica tube at 700 °C. Raman spectroscopy confirmed the homogeneity and phase purity of the sample, in addition, the kesterite type structure was suggested. Rietveld analysis of the neutron diffraction data confirmed that the compound crystallizes in the tetragonal kesterite type structure. The refined site occupancy factors were used to determine the average neutron scattering lengths of the cation sites, giving insights into cation distribution and finally point defect types. Thus it has been shown, that additional to the CuZn-ZnCu anti-site defects in the lattice planes at z=¼ and ¾ (Cu-Zn disorder) also the off-stoichiometry type related point defects like Cui and CuZn occur in Cu-rich CZGSe.

  4. Hemoglobin redux: combining neutron and X-ray diffraction with mass spectrometry to analyse the quaternary state of oxidized hemoglobins

    Energy Technology Data Exchange (ETDEWEB)

    Mueser, Timothy C., E-mail: timothy.mueser@utoledo.edu; Griffith, Wendell P. [Department of Chemistry, University of Toledo, Toledo, OH 43606 (United States); Kovalevsky, Andrey Y. [Bioscience Division, MS M888, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Guo, Jingshu; Seaver, Sean [Department of Chemistry, University of Toledo, Toledo, OH 43606 (United States); Langan, Paul [Department of Chemistry, University of Toledo, Toledo, OH 43606 (United States); Bioscience Division, MS M888, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Hanson, B. Leif [Department of Chemistry, University of Toledo, Toledo, OH 43606 (United States)

    2010-11-01

    X-ray and neutron diffraction studies of cyanomethemoglobin are being used to evaluate the structural waters within the dimer–dimer interface involved in quaternary-state transitions. Improvements in neutron diffraction instrumentation are affording the opportunity to re-examine the structures of vertebrate hemoglobins and to interrogate proton and solvent position changes between the different quaternary states of the protein. For hemoglobins of unknown primary sequence, structural studies of cyanomethemoglobin (CNmetHb) are being used to help to resolve sequence ambiguity in the mass spectra. These studies have also provided additional structural evidence for the involvement of oxidized hemoglobin in the process of erythrocyte senescence. X-ray crystal studies of Tibetan snow leopard CNmetHb have shown that this protein crystallizes in the B state, a structure with a more open dyad, which possibly has relevance to RBC band 3 protein binding and erythrocyte senescence. R-state equine CNmetHb crystal studies elaborate the solvent differences in the switch and hinge region compared with a human deoxyhemoglobin T-state neutron structure. Lastly, comparison of histidine protonation between the T and R state should enumerate the Bohr-effect protons.

  5. High pressure synthesis of bismuth disulfide

    DEFF Research Database (Denmark)

    Søndergaard-Pedersen, Simone; Nielsen, Morten Bormann; Bremholm, Martin

    In this research the BiS2 compound was synthesized by a high pressure and high temperature method using a multi-anvil large volume press and the structure was solved by single crystal diffraction. The structure contains Bi atoms in distorted square-based pyramidal coordination to five surrounding...

  6. High pressure and synchrotron radiation satellite workshop

    Energy Technology Data Exchange (ETDEWEB)

    Bass, J.; Guignot, N.; Morard, G.; Mezouar, M.; Andrault, D.; Bolfan-Casanova, N.; Sturhahn, W.; Daniel, I.; Reynard, B.; Simionovici, A.; Sanchez Valle, C.; Martinez, I.; Kantor, I.; Dubrovinsky, I.; Mccammon, C.; Dubrovinskaia, N.; Kurnosiv, A.; Kuznetsov, A.; Goncharenko, I.; Loubeyre, P.; Desgreniers, S.; Weck, G.; Yoo, C.S.; Iota, V.; Park, J.; Cynn, H.; Gorelli, F.; Toulemonde, P.; Machon, D.; Merlen, A.; San Miguel, A.; Amboage, M.; Aquilanti, G.; Mathon, O.; Pascarelli, S.; Itie, J.P.; Mcmillan, P.F.; Trapananti, A.; Di Cicco, A.; Panfilis, S. de; Filipponi, A.; Kreisel, J.; Bouvier, P.; Dkhil, B.; Chaabane, B.; Rosner, H.; Koudela, D.; Schwarz, U.; Handestein, A.; Hanfland, M.; Opahle, I.; Koepernik, K.; Kuzmin, M.; Mueller, K.H.; Mydosh, J.; Richter, M.; Hejny, C.; Falconi, S.; Lundegaard, L.F.; Mcmahon, M.I; Loa, I.; Syassen, K.; Wang, X.; Roth, H.; Lorenz, T.; Farber Daniel, I.; Antonangeli Daniele, I.; Krisch, M.; Badro, J.; Fiquet, G.; Occelli, F.; Mao, W.L.; Mao, H.K.; Eng, P.; Kao, C.C.; Shu, J.F.; Hemley, R.J.; Tse, J.S.; Yao, Y.; Deen, P.P.; Paolasini, I.; Braithwaite, D.; Kernavanois, N.; Lapertot, G.; Rupprecht, K.; Leupold, O.; Ponkratz, U.; Wortmann, G.; Beraud, A.; Krisch, M.; Farber, D.; Antonangeli, D.; Aracne, C.; Zarestky, J.L.; Mcqueeney, R.; Mathon, O.; Baudelet, F.; Decremps, F.; Itie, J.P.; Nataf, I.; Pascarelli, S.; Polian, A

    2006-07-01

    The workshop is dedicated to recent advances on science at high pressure at third generation synchrotron sources. A variety of experiments using synchrotron radiation techniques including X-ray diffraction, EXAFS (extended X-ray absorption fine structure), inelastic X-ray scattering, Compton scattering and Moessbauer spectroscopy of crystalline, liquid or amorphous samples, are reported. This document gathers the abstracts of the presentations.

  7. Structural studies of lithium zinc borohydride by neutron powder diffraction, Raman and NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ravnsbaek, D.B. [Center for Materials Crystallography (CMC), Interdisciplinary Nanoscience Center (iNANO), Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C (Denmark); Frommen, C. [Institute for Energy Technology, P.O. Box 40, N-2027 Kjeller (Norway); Reed, D. [School of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham, B15 2TT (United Kingdom); Filinchuk, Y. [Center for Materials Crystallography (CMC), Interdisciplinary Nanoscience Center (iNANO), Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C (Denmark); Swiss-Norwegian Beam Lines at ESRF, BP-220, 38043 Grenoble (France); Institute of Condensed Matter and Nanosciences, Universite Catholique de Louvain, 1 Place L. Pasteur, B-1348, Louvain-la-Neuve (Belgium); Sorby, M.; Hauback, B.C. [Institute for Energy Technology, P.O. Box 40, N-2027 Kjeller (Norway); Jakobsen, H.J. [Instrument Centre for Solid-State NMR Spectroscopy and Interdisciplinary Nanoscience Center (iNANO), Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C (Denmark); Book, D. [School of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham, B15 2TT (United Kingdom); Besenbacher, F. [Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C (Denmark); Skibsted, J. [Instrument Centre for Solid-State NMR Spectroscopy and Interdisciplinary Nanoscience Center (iNANO), Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C (Denmark); Jensen, T.R., E-mail: trj@chem.au.dk [Center for Materials Crystallography (CMC), Interdisciplinary Nanoscience Center (iNANO), Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C (Denmark)

    2011-09-15

    Research highlights: > Structural study of the first interpenetrated framework hydride, LiZn{sub 2}(BH{sub 4}){sub 5} > Determination of deuterium positions and revision of crystal structure by PND. > Raman spectroscopy confirms the presence of isolated [Zn{sub 2}(BD{sub 4}){sub 5}]-bar complex anions. > Determination of quadrupole coupling parameters and chemical shifts by {sup 11}B MAS NMR. - Abstract: The crystal structure of LiZn{sub 2}(BH{sub 4}){sub 5} is studied in detail using a combination of powder neutron diffraction (PND), Raman spectroscopy, and {sup 11}B MAS NMR spectroscopy on LiZn{sub 2}(BH{sub 4}){sub 5} and LiZn{sub 2}({sup 11}BD{sub 4}){sub 5}. The aim is to obtain detailed structural knowledge of the first interpenetrated framework hydride compound, LiZn{sub 2}(BD{sub 4}){sub 5} which consists of doubly interpenetrated 3D frameworks built from dinuclear complex ions [Zn{sub 2}(BD{sub 4}){sub 5}]{sup -} and lithium ions. The positions of the deuterium atoms are determined using Rietveld refinement of the PND data and the orientation of one of the four independent BD{sub 4}{sup -} groups is revised. The current data reveal that the structure of [Zn{sub 2}(BD{sub 4}){sub 5}]{sup -} is more regular than previously reported, as are also the coordinations around the Zn and Li atoms. Both Zn and Li atoms are found to coordinate to the BD{sub 4}{sup -} units via the tetrahedral edges. Some distortion of the angles within the BD{sub 4} units is observed, relative to the expected angles of 109.4 for the ideal tetrahedral coordination. Raman spectroscopy confirms bending and stretching modes from the expected terminal and bridging bidentate BH{sub 4}{sup -} and BD{sub 4}{sup -} units. The {sup 11}B MAS NMR spectrum of the satellite transitions resolves two distinct manifolds of spinning sidebands, which allows estimation of the {sup 11}B quadrupole coupling parameters and isotropic chemical shifts for the four distinct {sup 11}B sites of [Zn{sub 2}(BD

  8. Residual stress in a laser welded EUROFER blanket module assembly using non-destructive neutron diffraction techniques

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, D.J., E-mail: d.hughes@warwick.ac.uk [WMG, University of Warwick, Coventry CV4 7AL (United Kingdom); Koukovini-Platia, E. [CERN, CH-1211 Geneva 23 (Switzerland); Heeley, E.L. [Department of Physical Sciences, Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom)

    2014-02-15

    Highlights: • Residual stresses were determined in a welded EUROFER blanket assembly with integrated cooling channels. • Good agreement was seen between experimentally determined and predicted stresses. • We show that microstructure changes that occur in EUROFER steels during welding must be considered for residual stress determination. • An experimental route is proposed for validation of predicted stresses in reactor components using non-destructive diffraction techniques. - Abstract: Whilst the structural integrity and lifetime considerations in welded joints for blanket modules can be predicted using finite element software, it is essential to prove the validity of these simulations. This paper provides detailed analysis for the first time, of the residual stress state in a laser-welded sample with integral cooling channels. State-of-the-art non-destructive neutron diffraction was employed to determine the triaxial stress state and to understand microstructural changes around the heat affected zone. Synchrotron X-ray diffraction was used to probe the variation of strain-free lattice reference parameter around the weld zone allowing correction of the neutron measurements. This paper details an important experimental route to validation of predicted stresses in complex safety-critical reactor components for future applications.

  9. Neutron diffraction study of the inverse spinels Co2TiO4 and Co2SnO4

    Science.gov (United States)

    Thota, S.; Reehuis, M.; Maljuk, A.; Hoser, A.; Hoffmann, J.-U.; Weise, B.; Waske, A.; Krautz, M.; Joshi, D. C.; Nayak, S.; Ghosh, S.; Suresh, P.; Dasari, K.; Wurmehl, S.; Prokhnenko, O.; Büchner, B.

    2017-10-01

    We report a detailed single-crystal and powder neutron diffraction study of Co2TiO4 and Co2SnO4 between the temperature 1.6 and 80 K to probe the spin structure in the ground state. For both compounds the strongest magnetic intensity was observed for the (111)M reflection due to ferrimagnetic ordering, which sets in below TN=48.6 and 41 K for Co2TiO4 and Co2SnO4 , respectively. An additional low intensity magnetic reflection (200)M was noticed in Co2TiO4 due to the presence of an additional weak antiferromagnetic component. Interestingly, from both the powder and single-crystal neutron data of Co2TiO4 , we noticed a significant broadening of the magnetic (111)M reflection, which possibly results from the disordered character of the Ti and Co atoms on the B site. Practically, the same peak broadening was found for the neutron powder data of Co2SnO4 . On the other hand, from our single-crystal neutron diffraction data of Co2TiO4 , we found a spontaneous increase of particular nuclear Bragg reflections below the magnetic ordering temperature. Our data analysis showed that this unusual effect can be ascribed to the presence of anisotropic extinction, which is associated to a change of the mosaicity of the crystal. In this case, it can be expected that competing Jahn-Teller effects acting along different crystallographic axes can induce anisotropic local strain. In fact, for both ions Ti3 + and Co3 +, the 2 tg levels split into a lower dx y level yielding a higher twofold degenerate dx z/dy z level. As a consequence, one can expect a tetragonal distortion in Co2TiO4 with c /a work.

  10. A Neutron Diffraction Study of the Nuclear and Magnetic Structure of MnNb2O6

    DEFF Research Database (Denmark)

    Nielsen, Oliver Vindex; Lebech, Bente; Krebs Larsen, F.

    1976-01-01

    A neutron diffraction study was made of the nuclear and the magnetic structure of MnNb2O6 single crystals. The thirteen nuclear parameters (space group Pbcn) were determined from 304 reflections at room temperature. The antiferromagnetic structure (Neel temperature=4.4K), determined at 1.2K......, is a superposition of G- and A-type structures of the form 0.90 Gx+0.34 Gy+0.28 Az. The corresponding magnetic space group is P2'1/c....

  11. Baromagnetic Effect in Antiperovskite Mn3 Ga0.95 N0.94 by Neutron Powder Diffraction Analysis.

    Science.gov (United States)

    Shi, Kewen; Sun, Ying; Yan, Jun; Deng, Sihao; Wang, Lei; Wu, Hui; Hu, Pengwei; Lu, Huiqing; Malik, Muhammad Imran; Huang, Qingzhen; Wang, Cong

    2016-05-01

    A baromagnetic effect in a novel tetragonal magnetic structure is introduced by vacancies in Mn3 Ga0.95 N0.94 , due to the change of the Mn-Mn distance and their spin re-orientation induced by a pressure field. This effect is proven for the first time in antiperovskite compounds by neutron powder diffraction analysis. This feature will enable wide applications in magnetoelectric devices and intelligent instruments. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Residual stress characterization of steel TIG welds by neutron diffraction and by residual magnetic stray field mappings

    Science.gov (United States)

    Stegemann, Robert; Cabeza, Sandra; Lyamkin, Viktor; Bruno, Giovanni; Pittner, Andreas; Wimpory, Robert; Boin, Mirko; Kreutzbruck, Marc

    2017-03-01

    The residual stress distribution of tungsten inert gas welded S235JRC+C plates was determined by means of neutron diffraction (ND). Large longitudinal residual stresses with maxima around 600 MPa were found. With these results as reference, the evaluation of residual stress with high spatial resolution GMR (giant magneto resistance) sensors was discussed. The experiments performed indicate a correlation between changes in residual stresses (ND) and the normal component of local residual magnetic stray fields (GMR). Spatial variations in the magnetic field strength perpendicular to the welds are in the order of the magnetic field of the earth.

  13. Neutron and X-ray diffraction and empirical potential structure refinement modelling of magnesium stabilised amorphous calcium carbonate

    DEFF Research Database (Denmark)

    Cobourne, G.; Mountjoy, G.; Rodriguez Blanco, Juan Diego

    2014-01-01

    Amorphous calcium carbonate (ACC) plays a key role in biomineralisation processes in sea organisms. Neutron and X-ray diffraction have been performed for a sample of magnesium-stabilised ACC, which was prepared with a Mg:Ca ratio of 0.05:1 and 0.25 H2O molecules per molecule of CO3. The empirical...... potential structure refinement method has been used to make a model of magnesium-stabilised ACC and the results revealed a fair agreement with the experimental diffraction data. The model has well-defined CO3 and H2O molecules. The average coordination number of Ca is 7.4 and is composed of 6.8 oxygen atoms...

  14. Neutron powder diffraction study on Mg sup 1 sup 1 B sub 2 synthesized by different procedures

    CERN Document Server

    Oikawa, K; Arai, M; Mochiku, T; Takeya, H; Furuyama, M; Kamisawa, S; Kadowaki, K

    2002-01-01

    The crystal structure of a new superconducting material, MgB sub 2 , was studied by high-resolution neutron powder diffraction as a function of temperature from 8K to 305K. Two samples of Mg sup 1 sup 1 B sub 2 were measured; one was synthesized for 2d at 1050degC, and the other one was done for 1d at 1100degC. All of the diffraction data were precisely refined by the Rietveld method, and we confirmed that there was no clear anomaly on the temperature dependence of the lattice constants around T sub c for both samples. The difference in sample synthesis procedures affects the profile shapes of the 001 reflections, whereas the hh0 lines are almost the same.

  15. Superconductivity under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Amaya, K.; Shimizu, K.; Takeda, K.; Tateiwa, N.; Muramatsu, T.; Ishizuka, M.; Kobayashi, T.C

    2003-05-01

    In part 1, we review techniques developed in our laboratory for producing the complex extreme condition of very low temperature and ultra-high pressure and those for measuring electrical resistance and magnetization of the sample confined in the extremely small space of the used pressure cell. In part 2, we review our experimental results in search for pressure-induced superconductivity, which have been obtained by the use of developed techniques. Typical examples are shown in the case of simple inorganic and organic molecular crystals, ionic crystals, and magnetic metals.

  16. High pressure induced superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Amaya, K.; Shimizu, K

    2003-10-15

    We have developed complex extreme condition of very low temperature down to 30 mK and ultra high pressure exceeding 200 GPa by assembling compact diamond anvil cell (DAC) on a powerful {sup 3}He/{sup 4}He dilution refrigerator. We have also developed measuring techniques of electrical resistance, magnetization and optical measurement for the sample confined in the sample space of the DAC. Using the newly developed apparatus and techniques, we have searched for superconductivity in various materials under pressure. In this paper, we will shortly review our newly developed experimental apparatus and techniques and discuss a few examples of pressure induced superconductivity which were observed recently.

  17. In situ Neutron Diffraction during Casting: Determination of Rigidity Point in Grain Refined Al-Cu Alloys

    Directory of Open Access Journals (Sweden)

    Jean-Marie Drezet

    2014-02-01

    Full Text Available The rigidity temperature of a solidifying alloy is the temperature at which the solid plus liquid phases are sufficiently coalesced to transmit long range tensile strains and stresses. It determines the point at which thermally induced deformations start to generate internal stresses in a casting. As such, it is a key parameter in numerical modelling of solidification processes and in studying casting defects such as solidification cracking. This temperature has been determined in Al-Cu alloys using in situ neutron diffraction during casting in a dog bone shaped mould. In such a setup, the thermal contraction of the solidifying material is constrained and stresses develop at a hot spot that is irradiated by neutrons. Diffraction peaks are recorded every 11 s using a large detector, and their evolution allows for the determination of the rigidity temperatures. We measured rigidity temperatures equal to 557 °C and 548 °C, depending on cooling rate, for a grain refined Al-13 wt% Cu alloy. At high cooling rate, rigidity is reached during the formation of the eutectic phase and the solid phase is not sufficiently coalesced, i.e., strong enough, to avoid hot tear formation.

  18. In situ Neutron Diffraction during Casting: Determination of Rigidity Point in Grain Refined Al-Cu Alloys

    Science.gov (United States)

    Drezet, Jean-Marie; Mireux, Bastien; Szaraz, Zoltan; Pirling, Thilo

    2014-01-01

    The rigidity temperature of a solidifying alloy is the temperature at which the solid plus liquid phases are sufficiently coalesced to transmit long range tensile strains and stresses. It determines the point at which thermally induced deformations start to generate internal stresses in a casting. As such, it is a key parameter in numerical modelling of solidification processes and in studying casting defects such as solidification cracking. This temperature has been determined in Al-Cu alloys using in situ neutron diffraction during casting in a dog bone shaped mould. In such a setup, the thermal contraction of the solidifying material is constrained and stresses develop at a hot spot that is irradiated by neutrons. Diffraction peaks are recorded every 11 s using a large detector, and their evolution allows for the determination of the rigidity temperatures. We measured rigidity temperatures equal to 557 °C and 548 °C, depending on cooling rate, for a grain refined Al-13 wt% Cu alloy. At high cooling rate, rigidity is reached during the formation of the eutectic phase and the solid phase is not sufficiently coalesced, i.e., strong enough, to avoid hot tear formation. PMID:28788507

  19. Characterisation of polycrystal deformation by numerical modelling and neutron diffraction measurements

    DEFF Research Database (Denmark)

    Clausen, Bjørn

    , that the effect of the elastic anisotropy is limited to the very early stages of plasticity (εP neutron diffraction mea-surements of elastic lattice strains...... reflections. The self-consistent model is used to determine the most suitable reflection for technological applications of neutron diffraction, where focus is on the volume av-erage stress state in engineering components. To be able to successfully convert the measured elastic lattice strains for a specific...... the smallest build-up of residual lattice strains. Below 5% deforma-tion the deviations from linearity and the residual strains are below the normal strain resolution of a neutron diffraction measurement. The model predictions have pinpointed, that the selection of the reflection is crucial for the validity...

  20. Characterisation of a neutron diffraction detector prototype based on the Trench-MWPC technology

    Science.gov (United States)

    Buffet, J. C.; Clergeau, J. F.; Cuccaro, S.; Guérard, B.; Mandaroux, N.; Marchal, J.; Pentenero, J.; Platz, M.; Van Esch, P.

    2017-12-01

    The Trench Multi-Wire-Proportional-Chamber is a new type of MWPC which has been designed to fulfill the requirements of the 2D curved neutron detector under development for the XtremeD neutron diffractometer, under construction at ILL. In this design, anode wires are mounted orthogonally to a stack of metallic cathode plates which are insulated from each other by ceramic spacers. A row of teeth is spark-eroded along the edge of the cathode plates so that anode wires appear to be stretched along trenches machined across a segmented cathode plane. This design was tested on a prototype detector module mounted in a vessel filled with a mixture of 3He-Ar-CO2 at 7 bar. The detector configuration as well as measurements performed on this prototype at ILL neutron test beam line are presented. Results show that the Trench-MWPC design provides uniform amplification gain across the detection area despite the absence of the top cathode wires used to balance the electric field in standard Cathode-Anode-Cathode MWPC configurations. The presence of cathode trench side-walls surrounding anode wires minimises the spread of neutron-induced charge across electrodes, allowing for detector operation at reduced amplification gain without compromising the signal to noise per electrode. Pulse-height spectra acquired under various neutron flux conditions demonstrated that the Trench-MWPC design minimises space-charge effects, thanks to its low amplification gain combined with the fast collection of ions by cathode trench side-walls surrounding anode wires. Measurements also showed that this space-charge effect reduction results in a high local count-rate of ~100 kHz at 10% count loss when irradiating the detector with a small 5 mm × 5 mm neutron beam.

  1. First spin-resolved electron distributions in crystals from combined polarized neutron and X-ray diffraction experiments

    Directory of Open Access Journals (Sweden)

    Maxime Deutsch

    2014-05-01

    Full Text Available Since the 1980s it has been possible to probe crystallized matter, thanks to X-ray or neutron scattering techniques, to obtain an accurate charge density or spin distribution at the atomic scale. Despite the description of the same physical quantity (electron density and tremendous development of sources, detectors, data treatment software etc., these different techniques evolved separately with one model per experiment. However, a breakthrough was recently made by the development of a common model in order to combine information coming from all these different experiments. Here we report the first experimental determination of spin-resolved electron density obtained by a combined treatment of X-ray, neutron and polarized neutron diffraction data. These experimental spin up and spin down densities compare very well with density functional theory (DFT calculations and also confirm a theoretical prediction made in 1985 which claims that majority spin electrons should have a more contracted distribution around the nucleus than minority spin electrons. Topological analysis of the resulting experimental spin-resolved electron density is also briefly discussed.

  2. Development of a prompt gamma activation analysis facility using diffracted polychromatic neutron beam

    CERN Document Server

    Byun, S H; Choi, H D

    2002-01-01

    A prompt gamma activation analysis facility has recently been developed at Hanaro, the 24 MW research reactor in the Korea Atomic Energy Research Institute. Polychromatic thermal neutrons are extracted by setting pyrolytic graphite crystals at a Bragg angle of 45 deg. . The detection system comprises a large single n-type HPGe detector, signal electronics and a fast ADC. Neutron beam characterization was performed both theoretically and experimentally. The neutron flux was measured to be 7.9x10 sup 7 n/cm sup 2 s in a 1x1 cm sup 2 beam area at the sample position with a uniformity of 12%. The corresponding Cd-ratio for gold was found to be 266. The beam quality was compared with other representative thermal neutron prompt gamma activation analysis. The detection efficiency was calibrated up to 11 MeV using a set of radionuclides and the (n,gamma) reactions of N and Cl. Finally, the sensitivities and the detection limits were obtained for several elements.

  3. The effect of experimental resolution on crystal reflectivity and secondary extinction in neutron diffraction

    DEFF Research Database (Denmark)

    Dietrich, O.W.; Als-Nielsen, Jens Aage

    1965-01-01

    The reflectivity for neutrons of a plane slab crystal is calculated in the transmission case when the crystal is placed between two Seller collimators. The calculations indicate that the crystal reflectivity, as well as the secondary extinction coefficient, depends signicantly on the angular...... resolution of the collimators. Curves are given for the extinction of the crystal with different crystal and collimator parameters....

  4. Pair-correlation function in disordered β-brass as studied by neutron diffraction

    DEFF Research Database (Denmark)

    Als-Nielsen, Jens Aage; Dietrich, O.W.

    1967-01-01

    Critical neutron scattering around a superlattice reflection above Tc yields information on the pair correlation function for occupation of lattice sites. The Ornstein-Zernike correlation function e-k 1 r/r is proved to fit the data excellently, and at 8.9deg K above Tc the inverse correlation...

  5. Magnetic Structure of Tb-Tm Alloys Studied by Neutron Diffraction

    DEFF Research Database (Denmark)

    Hansen, P.; Lebech, Bente

    1976-01-01

    Single crystals of Tb-Tm alloys with Tm contents of 12%, 40%, 55% and 65% were investigated by neutron diffractometry over the temperature range 4.2-300K. All these alloys order magnetically to a basal plane spiral below the Neel temperature. Below the Curie temperature the magnetic ordering...

  6. Neutron diffraction studies on La2−xDyxCa2xBa2Cu4+2xOz ...

    Indian Academy of Sciences (India)

    Abstract. Structural studies on Dy-substituted La-2125 type superconductors have been carried out by neutron diffraction experiments at room temperature using a monochromatic neutron beam of wavelength (λ) = 1.249 Å. A series of samples with. La2−xDyxCa2xBa2Cu4+2xOz stoichiometric composition, for x = 0.1–0.5, ...

  7. The high-pressure behavior of bloedite

    DEFF Research Database (Denmark)

    Comodi, Paola; Nazzareni, Sabrina; Balic Zunic, Tonci

    2014-01-01

    High-pressure single-crystal synchrotron X‑ray diffraction was carried out on a single crystal of bloedite [Na2Mg(SO4)24H2O] compressed in a diamond-anvil cell. The volume-pressure data, collected up to 11.2 GPa, were fitted by a second- and a third-order Birch-Murnaghan equation of state (EOS), ...

  8. The structure of NH4F as determined by neutron and X-ray diffraction

    NARCIS (Netherlands)

    Adrian, H.W.W.; Feil, D.

    1969-01-01

    Neutron and X-ray intensities of NH4F were measured at -196°C and -155°C respectively. The wurtzite type structure and space group P63mc were confirmed. The displacement of the two h.c.p. sublattices, formed by each of the F-- and NH+4- ions, is such that all bond-distances are equivalent. The N-H

  9. Thermodynamic properties and neutron diffraction studies of silver ferrite AgFeO2

    Science.gov (United States)

    Vasiliev, A.; Volkova, O.; Presniakov, I.; Baranov, A.; Demazeau, G.; Broto, J.-M.; Millot, M.; Leps, N.; Klingeler, R.; Büchner, B.; Stone, M. B.; Zheludev, A.

    2010-01-01

    We present thermodynamic and neutron scattering data on silver ferrite AgFeO2. The data imply that strong magnetic frustration Θ/TN~10 and magnetic ordering arise via two successive phase transitions at T2 = 7 K and T1 = 16 K. At Tdelafossite CuFeO2, the wavevector of the magnetic structure is independent of temperature both at T

  10. Correlation of Magnetic Properties and Residual Stress Distribution Monitored by X-Ray and Neutron Diffraction in Welded AISI 1008 Steel Sheets

    Czech Academy of Sciences Publication Activity Database

    Vourna, P.; Hervoches, Charles; Vrána, Miroslav; Ktena, A.; Hristoforou, E.

    2015-01-01

    Roč. 51, č. 1 (2015), s. 6200104 ISSN 0018-9464 R&D Projects: GA ČR GB14-36566G; GA MŠk LM2011019 EU Projects: European Commission(XE) 283883 - NMI3-II Institutional support: RVO:61389005 Keywords : Magnetic Barkhausen noise (MBN) * neutron diffraction (ND) * residual stress * X-ray diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.277, year: 2015

  11. In-situ neutron diffraction of LaCoO3 perovskite under uniaxial compression. II. Elastic properties

    Science.gov (United States)

    Lugovy, Mykola; Aman, Amjad; Chen, Yan; Orlovskaya, Nina; Kuebler, Jakob; Graule, Thomas; Reece, Michael J.; Ma, Dong; Stoica, Alexandru D.; An, Ke

    2014-07-01

    Calculations of elastic constants and development of elastic anisotropy under uniaxial compression in originally isotropic polycrystalline LaCoO3 perovskite are reported. The lattice strains in individual (hkl) planes as well as average lattice strain were determined both for planes oriented perpendicular and parallel to the loading direction using in-situ neutron diffraction. Utilizing average lattice strains as well as lattice strains along the a and c crystallographic directions, an attempt was made to determine Poisson's ratio of LaCoO3, which was then compared with that measured using an impulse excitation technique. The elastic constants were calculated and Young's moduli of LaCoO3 single crystal in different crystallographic directions were estimated.

  12. Neutron diffraction and thermal studies of amorphous CS{sub 2} realised by low-temperature vapour deposition

    Energy Technology Data Exchange (ETDEWEB)

    Yamamuro, O.; Matsuo, T. [Osaka Univ., Dept. of Chemistry, Graduate School of Sciences (Japan); Onoda-Yamamuro, N. [Tokyo Denki Univ., College of Sciences and Technology (Japan); Takeda, K. [Naruto Univ., Dept. of Chemistry, Tokushima (Japan); Munemura, H.; Tanaka, S.; Misawa, M. [Niigata Univ. (Japan). Faculty of Science

    2003-08-01

    We have succeeded in preparing amorphous carbon disulphide (CS{sub 2}) by depositing its vapour on a cold substrate at 10 K. Complete formation of the amorphous state has been confirmed by neutron diffraction and differential thermal analysis (DTA). The amorphous sample crystallized at ca. 70 K, which is lower than the hypothetical glass transition temperature (92 K) estimated from the DTA data of the (CS{sub 2}){sub x}(S{sub 2}Cl{sub 2}){sub 1-x} binary mixture. CS{sub 2}, a symmetric linear tri-atomic molecule, is the simplest of the amorphized molecular substances whose structural and thermal information has been reported so far. Comparison of the static structure factors S(Q) has shown that the orientational correlation of CS{sub 2} molecules may be much stronger in the amorphous state than in the liquid state at higher temperature. (authors)

  13. FEA predictions of residual stress in stainless steel compared to neutron and x-ray diffraction measurements. [Finite element analysis

    Energy Technology Data Exchange (ETDEWEB)

    Flower, E.C.; MacEwen, S.R.; Holden, T.M.

    1987-05-01

    Residual stresses in a body arise from nonuniform plastic deformation and continue to be an important consideration in the design and the fabrication of metal components. The finite element method offers a potentially powerful tool for predicting these stresses. However, it is important to first verify this method through careful analysis and experimentation. This paper describes experiments using neutron and x-ray diffraction to provide quantitative data to compare to finite element analysis predictions of deformation induced residual stress in a plane stress austenitic stainless steel ring. Good agreement was found between the experimental results and the numerical predictions. Effects of the formulation of the finite element model on the analysis, constitutive parameters and effects of machining damage in the experiments are addressed.

  14. Structure Refinement of (Sr,BaNb2O6 Ceramic Powder from Neutron and X-Rays Diffraction Data

    Directory of Open Access Journals (Sweden)

    J.G. Carrio

    2002-03-01

    Full Text Available The structure of polycrystalline strontium barium niobate at room temperature was refined by the Rietveld method. Sintered ceramic samples were used to collect powder neutron and X-ray diffraction data. The ratio Sr/Ba ~ 64/36 was found from the initial batch composition Sr0.61Ba0.39Nb2O6, corroborating with the quantitative X-ray dispersive spectroscopy (EDS measurements. The structure is tetragonal with cell parameters a, b = 12.4504(3 Å and c = 3.9325(1 Å and space group P4bm. It was not necessary to introduce any positional disorder for the oxygen atoms. Cation Nb+5 displacements not parallel to the c direction are presented, which can influence the behavior of the ferroelectric properties.

  15. In-situ neutron diffraction of LaCoO{sub 3} perovskite under uniaxial compression. II. Elastic properties

    Energy Technology Data Exchange (ETDEWEB)

    Lugovy, Mykola [Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, Florida 32816 (United States); Institute for Problems of Materials Science, Kiev 03142 (Ukraine); Aman, Amjad; Orlovskaya, Nina, E-mail: Nina.Orlovskaya@ucf.edu [Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, Florida 32816 (United States); Chen, Yan [Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, Florida 32816 (United States); Chemical and Engineering Materials Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Kuebler, Jakob; Graule, Thomas [Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for High Performance Ceramics, Ueberlandstrasse 129, 8600 Duebendorf (Switzerland); Reece, Michael J. [The School of Engineering and Materials Science, Queen Mary, University of London, London E1 4NS (United Kingdom); Ma, Dong; Stoica, Alexandru D.; An, Ke [Chemical and Engineering Materials Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

    2014-07-07

    Calculations of elastic constants and development of elastic anisotropy under uniaxial compression in originally isotropic polycrystalline LaCoO{sub 3} perovskite are reported. The lattice strains in individual (hkl) planes as well as average lattice strain were determined both for planes oriented perpendicular and parallel to the loading direction using in-situ neutron diffraction. Utilizing average lattice strains as well as lattice strains along the a and c crystallographic directions, an attempt was made to determine Poisson's ratio of LaCoO{sub 3}, which was then compared with that measured using an impulse excitation technique. The elastic constants were calculated and Young's moduli of LaCoO{sub 3} single crystal in different crystallographic directions were estimated.

  16. Neutron diffraction study of the magnetic-field-induced transition in Mn{sub 3}GaC

    Energy Technology Data Exchange (ETDEWEB)

    Çakir, Ö. [Physics Department, Yildiz Technical University, TR-34220 Esenler, Istanbul (Turkey); Physics Engineering Department, Ankara University, TR-06100 Ankara (Turkey); Acet, M.; Farle, M. [Faculty of Physics and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany); Senyshyn, A. [Forschungsneutronenquelle Heinz Maier-Leibnitz FRM-II, Technische Universität München, D-85747 Garching bei München (Germany)

    2014-01-28

    The antiperovskite Mn{sub 3}GaC undergoes an isostructural cubic–cubic first order transition from a low-temperature, large-cell-volume antiferromagnetic state to a high-temperature, small-cell-volume ferromagnetic state at around 160 K. The transition can also be induced by applying a magnetic field. We study here the isothermal magnetic-field-evolution of the transition as ferromagnetism is stabilized at the expense of antiferromagnetism. We make use of the presence of the two distinct cell volumes of the two magnetic states as a probe to observe by neutron diffraction the evolution of the transition, as the external magnetic field carries the system from the antiferromagnetic to the ferromagnetic state. We show that the large-volume antiferromagnetic and the small-volume ferromagnetic states coexist in the temperature range of the transition. The ferromagnetic state is progressively stabilized as the field increases.

  17. In situ neutron diffraction studies of a commercial, soft lead zirconate titanate ceramic: Response to electric fields and mechanical stress

    Energy Technology Data Exchange (ETDEWEB)

    Pramanick, Abhijit [University of Florida; Prewitt, Anderson [University of Florida; Cottrell, Michelle [University of Florida; Lee, Wayne [ITT Corporation Acoustic Sensors; Studer, Andrew J. [Bragg Institute, ANSTO; An, Ke [ORNL; Hubbard, Camden R [ORNL; Jones, Jacob [University of Florida

    2010-01-01

    Structural changes in commercial lead zirconate titanate (PZT) ceramics (EC-65) under the application of electric fields and mechanical stress were measured using neutron diffraction instruments at the Australian Nuclear Science and Technology Organisation (ANSTO) and the Oak Ridge National Laboratory (ORNL). The structural changes during electric-field application were measured on the WOMBAT beamline at ANSTO and include non-180{sup o} domain switching, lattice strains and field-induced phase transformations. Using time-resolved data acquisition capabilities, lattice strains were measured under cyclic electric fields at times as short as 30 {mu}s. Structural changes including the (002) and (200) lattice strains and non-180{sup o} domain switching were measured during uniaxial mechanical compression on the NRSF2 instrument at ORNL. Contraction of the crystallographic polarization axis, (002), and reorientation of non-180{sup o} domains occur at lowest stresses, followed by (200) elastic strains at higher stresses.

  18. Synthesis and Neutron Powder Diffraction Structural Analysis of Oxidized Delafossite YCuO2.5

    Energy Technology Data Exchange (ETDEWEB)

    Garlea, Vasile O [ORNL; Darie, Celine [Laboratoire of Cristallographie, Grenoble; Isnard, Olivier [Laboratoire of Cristallographie, Grenoble; Bordet, Pierre [Laboratoire of Cristallographie, Grenoble

    2006-01-01

    We report a study of the evolution of the structure of the delafossite-derived compounds YCuO{sub 2+{delta}} as a function of oxygen stoichiometry. The structural details of the oxygenated material YCuO{sub 2.5} were examined by means of high-resolution neutron powder diffraction. We confirmed that YCuO{sub 2.5} adopts an orthorhombic superstructure (a = {radical}3a{sub H}, b=c{sub H}, c=2a{sub H}) in which the anions are located at the center of corner-sharing triangles to form undulating chains of Cu{sup 2+} (s=1/2), running along a-axis direction.

  19. The metal-insulator transition of RNiO{sub 3} perovskites. What can we learn from neutron diffraction?

    Energy Technology Data Exchange (ETDEWEB)

    Medarde, M.L. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1996-11-01

    RNiO{sub 3} perovskites (R = rare earth) provide a remarkable opportunity to study the relationship between structural and physical properties since by moving along the 4f rare earth series, the evolution of several transport and magnetic properties can be nicely correlated to the steric effects associated with the lanthanide contraction. The most appealing example is probably the metal-insulator transition discovered for the compounds with R{ne}La, whose critical temperature T{sub M-I} increases with decreasing size of the rare earth ion. In this lecture, a summary of the most relevant neutron diffraction results on this system is presented. Moreover, the nickelates are used as an example to illustrate the performance of the diffractometers HRPT and DMCG to be installed at the SINQ. (author) 12 figs., 2 tabs., 17 refs.

  20. Anomalous magnetic ordering phenomena in tetragonal TbB sub 2 C sub 2 observed by neutron diffraction

    CERN Document Server

    Kaneko, K; Onodera, H; Yamaguchi, Y; Katano, S; Matsuda, M

    2002-01-01

    Detailed neutron diffraction measurements on a single crystalline TbB sub 2 C sub 2 in which magnetic field induced antiferroquadrupolar orderings are realised have been performed to understand characteristics of the transition under zero magnetic field. The results indicate that the magnetic transition phenomena consist of development of at least three magnetic components: (1) a dominant antiferromagentic component which develops below T sub N = 21.7 K, (2) a weak long periodic component which develops below about 18 K, and (3) anomalous components with broad magnetic scatterings which develop below about 50 K, which can not be understood by only a short range magnetic ordering. Since these three components develop independently, the transition phenomena in TbB sub 2 C sub 2 are much more complicated than expected from a typical lambda-type anomaly at T sub N in the temperature dependence of magnetic specific heat. (author)

  1. Resolution of crystal structures by X-ray and neutrons powder diffraction using global optimisation methods; Resolution des structures cristallines par diffraction des rayons X et neutrons sur poudres en utilisant les methodes d'optimisation globale

    Energy Technology Data Exchange (ETDEWEB)

    Palin, L

    2005-03-15

    We have shown in this work that X-ray diffraction on powder is a powerful tool to analyze crystal structure. The purpose of this thesis is the resolution of crystal structures by X-ray and neutrons diffraction on powder using global optimisation methods. We have studied 3 different topics. The first one is the order-disorder phenomena observed in some globular organic molecular solids. The second is the opiate family of neuropeptides. These neurotransmitters regulate sensory functions including pain and control of respiration in the central nervous system. The aim of our study was to try to determine the crystal structure of Leu-enkephalin and some of its sub-fragments. The determination of the crystal structures has been done performing Monte Carlo simulations. The third one is the location of benzene in a sodium-X zeolite. The zeolite framework was already known and the benzene has been localized by simulated annealing and by the use of maximum entropy maps.

  2. Small angle neutron diffraction studies of vortex structures in high temperature superconductors

    DEFF Research Database (Denmark)

    Cubitt, R.; Forgan, E.M.; Wylie, M.T.

    1994-01-01

    We have used neutron scattering to provide direct information about flux structures in the bulk of crystals of the superconductor Bi2Sr2CaCu2O8. Its extremely high effective mass anisotropy, makes the flux lattice susceptable to melting and also to decomposition into 'pancake' vortices, which would...... give a more two-dimensional vortex structure. At low temperatures and fields the scattered intensity is consistent with a three dimensional flux-line structure. At higher fields and temperatures, the scattering from the flux lattice dissapears well below T-c. We can associate this dissappearance...

  3. Structure of Calcium Aluminate Decahydrate (CaAl2O4.10D2O) from Neutron and X-ray Powder Diffraction Data

    Energy Technology Data Exchange (ETDEWEB)

    Christensen,A.; Lebech, B.; Sheptyakov, D.; Hanson, J.

    2007-01-01

    Calcium aluminate decahydrate is hexagonal with the space group P63/m and Z = 6. The compound has been named CaAl2O4{center_dot}10H2O (CAH10) for decades and is known as the product obtained by hydration of CaAl2O4 (CA) in the temperature region 273-288 K - one of the main components in high-alumina cements. The lattice constants depend on the water content. Several sample preparations were used in this investigation: one CAH10, three CAD10 and one CA(D/H)10, where the latter is a zero-matrix sample showing no coherent scattering contribution from the D/H atoms in a neutron diffraction powder pattern. The crystal structure including the positions of the H/D atoms was determined from analyses of four neutron diffraction powder patterns by means of the ab initio crystal structure determination program FOX and the FULLPROF crystal structure refinement program. Additionally, eight X-ray powder diffraction patterns (Cu K[alpha]1 and synchrotron X-rays) were used to establish phase purity. The analyses of these combined neutron and X-ray diffraction data clearly show that the previously published positions of the O atoms in the water molecules are in error. Thermogravimetric analysis of the CAD10 sample preparation used for the neutron diffraction studies gave the composition CaAl2(OD)8(D2O)2{center_dot}2.42D2O. Neutron and X-ray powder diffraction data gave the structural formula CaAl2(OX)8(X2O)2{center_dot}[gamma]X2O (X = D, H and D/H), where the [gamma] values are sample dependent and lie between 2.3 and 3.3.

  4. Investigation on the Residual Stress State of Drawn Tubes by Numerical Simulation and Neutron Diffraction Analysis

    Directory of Open Access Journals (Sweden)

    Adele Carradò

    2013-11-01

    Full Text Available Cold drawing is widely applied in the industrial production of seamless tubes, employed for various mechanical applications. During pre-processing, deviations in tools and their adjustment lead to inhomogeneities in the geometry of the tubes and cause a gradient in residuals. In this paper a three dimensional finite element (3D-FE-model is presented which was developed to calculate the change in wall thickness, eccentricity, ovality and residual macro-stress state of the tubes, produced by cold drawing. The model simulates the drawing process of tubes, drawn with and without a plug. For finite element modelling, the commercial software package Abaqus was used. To validate the model, neutron strain imaging measurements were performed on the strain imaging instrument SALSA at the Institute Laue Langevin (ILL, Grenoble, France on a series of SF-copper tubes, drawn under controlled laboratory conditions, varying the drawing angle and the plug geometry. It can be stated that there is sufficient agreement between the finite element method (FEM-calculation and the neutron stress determination.

  5. Investigation on the Residual Stress State of Drawn Tubes by Numerical Simulation and Neutron Diffraction Analysis.

    Science.gov (United States)

    Palkowski, Heinz; Brück, Sebastian; Pirling, Thilo; Carradò, Adele

    2013-11-08

    Cold drawing is widely applied in the industrial production of seamless tubes, employed for various mechanical applications. During pre-processing, deviations in tools and their adjustment lead to inhomogeneities in the geometry of the tubes and cause a gradient in residuals. In this paper a three dimensional finite element (3D-FE)-model is presented which was developed to calculate the change in wall thickness, eccentricity, ovality and residual macro-stress state of the tubes, produced by cold drawing. The model simulates the drawing process of tubes, drawn with and without a plug. For finite element modelling, the commercial software package Abaqus was used. To validate the model, neutron strain imaging measurements were performed on the strain imaging instrument SALSA at the Institute Laue Langevin (ILL, Grenoble, France) on a series of SF-copper tubes, drawn under controlled laboratory conditions, varying the drawing angle and the plug geometry. It can be stated that there is sufficient agreement between the finite element method (FEM)-calculation and the neutron stress determination.

  6. Evolution of magnetic phases in SmCrO3: A neutron diffraction and magnetometric study

    Science.gov (United States)

    Tripathi, Malvika; Choudhary, R. J.; Phase, D. M.; Chatterji, T.; Fischer, H. E.

    2017-11-01

    The classical belief about the mechanism of spin reorientation phase transition (SRPT) and ground-state magnetic structure in SmCrO3 has become intriguing because of inconsistent bulk magnetization observations. The presence of highly neutron-absorbing Sm atom has so far evaded the determination of microscopic magnetic structure. In the present report, we have utilized very high-energy "hot neutrons" to overcome the Sm absorption and to determine the thermal evolution of magnetic configurations. Unambiguously, three distinct phases are observed: the uncompensated canted antiferromagnetic structure Γ4(Gx,Ay,Fz;FzR) occurring below the Néel temperature (TN=191 K), the collinear antiferromagnetic structure Γ1(Ax,Gy,Cz;CzR) occurring below 10 K, and a nonequilibrium configuration with cooccurring Γ1 and Γ4 phases in the neighborhood of the SRPT (10 K ≤T ≤ 40 K). In differing to the earlier predictions, we divulge the SRPT to be a discontinuous transition where chromium spins switch from the a -b crystallographic plane to the b -c crystallographic plane in a discrete manner with no allowed intermediate configuration. The canting angle of chromium ions in the a -b plane is unusually not a thermal constant, rather it is empirically discerned to follow exponential behavior. The competition between magnetocrystalline anisotropy and free energy derived by isotropic and antisymmetric exchange interactions between different pairs of magnetic ions is observed to govern the mechanism of SRPT.

  7. High pressure direct injection

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, J. [Cummins Westport Inc., Vancouver, BC (Canada)

    2002-07-01

    A brief overview of Cummins Westport was provided, indicating that Westport originated in the 1980s through a research team at the University of British Columbia, and the hiring of the first employees began in 1996. The joint venture between Cummins and Westport was formed in March 2001. Cummins is the largest builder of commercial diesels in the world, and Westport is a small incubation technology company with emphasis on natural gas. The contribution of each company benefits the joint venture. Cummins brings traditional expertise in product and process development and distribution system, while Westport contributes new high pressure direct injection (HPDI) technology, funding and enthusiasm. The same base engine is kept and only the fuel system is changed. HPDI uses diesel cycle combustion and diesel pilot ignites natural gas. It allows for low emissions, high performance, high efficiency and economic payback. The pilot-ignited HPDI technology was explained, and its application to large class-8 trucks was discussed. The efficiency and performance of diesel engines is maintained by HPDI technology, there are 40 per cent reductions in nitrous oxide emissions, particulate matter emissions are reduced by 60 per cent, and carbon dioxide emissions are reduced by 20 per cent. A field demonstration was reviewed, and the major test at Norcal in San Francisco was discussed. The key success factors were found to be: formalized customer support plan, on-site technical support, parts availability, driver support and interaction, and training. Liquid natural gas fuel contamination was found to cause component wear. The emphasis has now been placed on three issues: injector life improvements, fuel debris and liquid natural gas pump/dome regulator life, and fuel economy improvements. The accomplishments for 2001 were identified, such as rapidly improving reliability, 17 HPDI trucks are upfit and in-service to name a few. The goals for 2002 include the placement of permanent fuel

  8. Glycine zinc sulfate pentahydrate: redetermination at 10 K from time-of-flight neutron Laue diffraction

    Directory of Open Access Journals (Sweden)

    A. Dominic Fortes

    2016-10-01

    Full Text Available Single crystals of glycine zinc sulfate pentahydrate [systematic name: hexaaquazinc tetraaquadiglycinezinc bis(sulfate], [Zn(H2O6][Zn(C2H5NO22(H2O4](SO42, have been grown by isothermal evaporation from aqueous solution at room temperature and characterized by single-crystal neutron diffraction. The unit cell contains two unique ZnO6 octahedra on sites of symmetry -1 and two SO4 tetrahedra with site symmetry 1; the octahedra comprise one [tetraaqua-diglycine zinc]2+ ion (centred on one Zn atom and one [hexaaquazinc]2+ ion (centred on the other Zn atom; the glycine zwitterion, NH3+CH2COO−, adopts a monodentate coordination to the first Zn atom. All other atoms sit on general positions of site symmetry 1. Glycine forms centrosymmetric closed cyclic dimers due to N—H...O hydrogen bonds between the amine and carboxylate groups of adjacent zwitterions and exhibits torsion angles varying from ideal planarity by no more than 1.2°, the smallest values for any known glycine zwitterion not otherwise constrained by a mirror plane. This work confirms the H-atom locations estimated in three earlier single-crystal X-ray diffraction studies with the addition of independently refined fractional coordinates and Uij parameters, which provide accurate internuclear X—H (X = N, O bond lengths and consequently a more accurate and precise depiction of the hydrogen-bond framework.

  9. Work Hardening, Dislocation Structure, and Load Partitioning in Lath Martensite Determined by In Situ Neutron Diffraction Line Profile Analysis

    Science.gov (United States)

    Harjo, Stefanus; Kawasaki, Takuro; Tomota, Yo; Gong, Wu; Aizawa, Kazuya; Tichy, Geza; Shi, Zengmin; Ungár, Tamas

    2017-09-01

    A lath martensite steel containing 0.22 mass pct carbon was analyzed in situ during tensile deformation by high-resolution time-of-flight neutron diffraction to clarify the large work-hardening behavior at the beginning of plastic deformation. The diffraction peaks in plastically deformed states exhibit asymmetries as the reflection of redistributions of the stress and dislocation densities/arrangements in two lath packets: soft packet, where the dislocation glides are favorable, and hard packet, where they are unfavorable. The dislocation density was as high as 1015 m-2 in the as-heat-treated state. During tensile straining, the load and dislocation density became different between the two lath packets. The dislocation character and arrangement varied in the hard packet but hardly changed in the soft packet. In the hard packet, dislocations that were mainly screw-type in the as-heat-treated state became primarily edge-type and rearranged towards a dipole character related to constructing cell walls. The hard packet played an important role in the work hardening in martensite, which could be understood by considering the increase in dislocation density along with the change in dislocation arrangement.

  10. Neutron diffraction study of quadruple perovskite SrCu{sub 3}Fe{sub 3}O{sub 12}

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, Ikuya, E-mail: i-yamada@21c.osakafu-u.ac.jp [Nanoscience and Nanotechnology Research Center, Osaka Prefecture University, 1-2 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8570 (Japan); Murakami, Makoto; Mori, Shigeo [Department of Materials Science, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531 (Japan); Irifune, Tetsuo [Geodynamics Research Center, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime 790-8577 (Japan)

    2016-08-26

    The magnetic structure of the quadruple perovskite SrCu{sub 3}Fe{sub 4}O{sub 12} is studied by means of neutron powder diffraction. The magnetic diffraction peaks are observed at low temperatures below 200 K. The Rietveld refinement result suggests an antiferromagnetic alignment of Fe spin magnetic moments for SrCu{sub 3}Fe{sub 4}O{sub 12} at low temperature. The refined magnetic moment at 4 K is ∼3.5 µ{sub B}, which is larger than that of that of CeCu{sub 3}Fe{sub 4}O{sub 12} (2.3 µ{sub B}). The increase in the magnetic moment is attributed to the larger Fe{sup 3+}:Fe{sup 5+} ratio for SrCu{sub 3}Fe{sub 4}O{sub 12} (∼4:1) compared with that of CeCu{sub 3}Fe{sub 4}O{sub 12} (∼3:1).

  11. 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...

  12. In situ shape and distance measurements in neutron scattering and diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Fujiwara, Satoru; Mendelson, R.A. [Univ. of California, San Francisco, CA (United States)

    1994-12-31

    Neutron scattering combined with selective isotopic labeling and contrast matching is useful for obtaining in situ structural information about a selected particle, or particles, in a macromolecular complex. The observed intensities, however, may be distorted by inter-complex interference and by scattering-length-density fluctuations of the (otherwise) contrast-matched portions. Methods have been proposed to cancel out such distortions (Hoppe`s method, the Statistical Labeling Method, and the Triple Isotopic Substitution Method). With these methods as well as related unmixed-sample methods, structural information about the selected particles can be obtained without these distortions. We have generalized these methods so that, in addition to globular particles in solution, they can be applied to in situ structures of systems having underlying symmetry and/or net orientation as well. The information obtainable from such experiments is discussed.

  13. Charge localization in oxidized Pb2Sr2Y0.5Cu308+8 studies by electron and neutron powder diffraction

    DEFF Research Database (Denmark)

    Iversen, M.H.; Jørgensen, J.E.; Andersen, N.H.

    1998-01-01

    Oxidized Pb2Sr2Y0.5Ca0.5Cu3O8+delta was studied by electron diffraction and neutron powder diffraction. The electron diffraction diagrams showed a doubling along the b-axis and a quadruplication along the a-axis indicating that the excess oxygen is incorporated into the structure in an ordered way....... The oxygen content was determined from refinement of the neutron data and delta = 1.2(1) was obtained. Calculation of bond valency sums for the cations shows that the bond valency sum for Cu in the CuO2 layers in Pb2Sr2Y0.5Ca0.5Cu3O8 decreases when the compound is oxidized, thereby explaining the lack...

  14. High Pressure Research on Materials

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 12; Issue 6. High Pressure Research on Materials - Production and Measurement of High Pressures in the Laboratory. P Ch Sahu N V Chandra Shekar. General Article Volume 12 Issue 6 June 2007 pp 10-23 ...

  15. Frustrated magnetic structure of Y-substituted CePdAl studied by powder neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Cermak, Petr; Javorsky, Pavel [Charles University, Faculty of Mathematics and Physics, Department of Condensed Matter Physics, Ke Karlovu 5, 121 16 Prague 2 (Czech Republic); Hofmann, Tommy, E-mail: cermak@mag.mff.cuni.cz [Helmholtz-Zentrum Berlin, Lise-Meitner Campus, Glienicker Str. 100, 14109 Berlin (Germany)

    2011-07-06

    CePdAl is a heavy-fermion antiferromagnet with T{sub N} = 2.7 K, crystallizing in the ZrNiAl-type structure. The magnetic structure is described by the propagation vector k = (1/2, 0, {tau}), {tau} = 0.35, with the cerium magnetic moments aligned along the c-axis. One third of magnetic moments remains disordered due to the geometrical frustration. Specific heat measurements on substituted Ce{sub 1-x}Y{sub x}PdAl compounds revealed strong reduction of T{sub N} with Y substitution and the antiferromagnetic order vanishes around x = 0.2. To investigate the microscopic details of the changes in the magnetic structure evoked by nonmagnetic ion substitution, we have performed an experiment on the powder neutron diffractometer E6 at HZB on the samples with x = 0.02, 0.06 and 0.1. Measurements showed the magnitude reduction of the ordered cerium moments with Y substitution while the propagation vector and other magnetic structure characteristics remain unchanged.

  16. Polarized neutron powder diffraction studies of antiferromagnetic order in bulk and nanoparticle NiO

    DEFF Research Database (Denmark)

    Brok, Erik; Lefmann, Kim; Deen, Pascale P.

    2015-01-01

    NiO and platelet-shaped NiO nanoparticles with thickness from greater than 200 nm down to 2.0 nm. The advantage of the applied method is that it is able to clearly separate the structural, the magnetic, and the spin-incoherent scattering signals for all particle sizes. For platelet-shaped particles...... with thickness from greater than 200 nm down to 2.2 nm we find that the spin orientation deviates about 16° from the primary (111) plane of the platelet-shaped particles. In the smallest particles (2.0 nm thick) we find the spins are oriented with a 30° average angle to the primary (111) plane of the particles...... at the particle surfaces and by the broadening of diffraction peaks due to the finite crystallite size. Moreover, the spin structure in magnetic nanoparticles may deviate significantly from that of the corresponding bulk material because of the low-symmetry surroundings of surface atoms and the large relative...

  17. Glycine zinc sulfate penta-hydrate: redetermination at 10 K from time-of-flight neutron Laue diffraction.

    Science.gov (United States)

    Fortes, A Dominic; Howard, Christopher M; Wood, Ian G; Gutmann, Matthias J

    2016-10-01

    Single crystals of glycine zinc sulfate penta-hydrate [systematic name: hexa-aqua-zinc tetra-aquadiglycinezinc bis-(sulfate)], [Zn(H2O)6][Zn(C2H5NO2)2(H2O)4](SO4)2, have been grown by isothermal evaporation from aqueous solution at room temperature and characterized by single-crystal neutron diffraction. The unit cell contains two unique ZnO6 octa-hedra on sites of symmetry -1 and two SO4 tetra-hedra with site symmetry 1; the octa-hedra comprise one [tetra-aqua-diglycine zinc]2+ ion (centred on one Zn atom) and one [hexa-aqua-zinc]2+ ion (centred on the other Zn atom); the glycine zwitterion, NH3+CH2COO-, adopts a monodentate coordination to the first Zn atom. All other atoms sit on general positions of site symmetry 1. Glycine forms centrosymmetric closed cyclic dimers due to N-H⋯O hydrogen bonds between the amine and carboxyl-ate groups of adjacent zwitterions and exhibits torsion angles varying from ideal planarity by no more than 1.2°, the smallest values for any known glycine zwitterion not otherwise constrained by a mirror plane. This work confirms the H-atom locations estimated in three earlier single-crystal X-ray diffraction studies with the addition of independently refined fractional coordinates and Uij parameters, which provide accurate inter-nuclear X-H (X = N, O) bond lengths and consequently a more accurate and precise depiction of the hydrogen-bond framework.

  18. Single-crystal neutron diffraction study of Nd magnetic ordering in NdFeO{sub 3} at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Bartolome, J.; Palacios, E.; Kuzmin, M.D.; Bartolome, F. [Instituto de Ciencia de Materiales de Aragon, CSIC-Universidad de Zaragoza, 50009 Zaragoza (Spain); Sosnowska, I.; Przenioslo, R. [Institute of Experimental Physics, Warsaw University, PL-00 681 Warsaw (Poland); Sonntag, R. [Hahn-Meitner-Institut, D-14109 Berlin (Germany); Lukina, M.M. [Department of Physics, Moscow State University, Leninskie Gory, 119899 Moscow (Russia)

    1997-05-01

    The temperature variation of the (100) and (010) neutron diffraction peak intensities, related only to the Nd magnetic moments, have been measured on a NdFeO{sub 3} single crystal, at temperatures down to 70 mK. The (100) peak becomes noticeable below 25 K while the (010) peak only gives an appreciable contribution below 1 K. Above T{sub N2}{approx}1K the (100) peak intensity is accounted for by the electronic magnetic moments polarized by the Nd-Fe exchange field. Near T{sub N2} a change of slope is observed in the temperature dependence of the (100) reflection intensity, demonstrating the crossover from the above polarization of Nd under the Nd-Fe exchange to proper long-range ordering due to Nd-Nd interaction. Below {approximately}0.4K another mechanism, polarization of Nd nuclear moments by hyperfine field, contributes to the intensity of the (100) and (010) peaks. A simple mean-field model explains consistently the observed temperature dependence of the diffraction intensities as well as earlier specific-heat data. The main feature of this model is allowance for Van Vleck susceptibility, which appears to play an important role in the overall polarization of Nd. The values of the hyperfine field at the Nd nuclei H{sub hf}=1.0{plus_minus}0.15MOe and of the Nd electronic magnetic moment {mu}{sub Nd}=0.9{mu}{sub B} are deduced, the ratio H{sub hf}/{mu}{sub Nd} being the same as in other Nd compounds. {copyright} {ital 1997} {ital The American Physical Society}

  19. A Novel In-situ Electrochemical Cell for Neutron Diffraction Studies of Phase Transitions in Small Volume Electrodes of Li-ion Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Vadlamani, Bhaskar S [ORNL; An, Ke [ORNL; Jagannathan, M. [University of Utah; Ravi Chandran, K. [University of Utah

    2014-01-01

    The design and performance of a novel in-situ electrochemical cell that greatly facilitates the neutron diffraction study of complex phase transitions in small volume electrodes of Li-ion cells, is presented in this work. Diffraction patterns that are Rietveld-refinable could be obtained simultaneously for all the electrodes, which demonstrates that the cell is best suited to explore electrode phase transitions driven by the lithiation and delithiation processes. This has been facilitated by the use of single crystal (100) Si sheets as casing material and the planar cell configuration, giving improved signal-to-noise ratio relative to other casing materials. The in-situ cell has also been designed for easy assembly and to facilitate rapid experiments. The effectiveness of cell is demonstrated by tracking the neutron diffraction patterns during the charging of graphite/LiCoO2 and graphite/LiMn2O4 cells. It is shown that good quality neutron diffraction data can be obtained and that most of the finer details of the phase transitions, and the associated changes in crystallographic parameters in these electrodes, can be captured.

  20. Analyze of phase's mechanical behaviour of a multiphase polycrystalline alloy by X-ray and neutron diffraction; Analyse du comportement mecanique des constituants d'un alliage polycristallin multiphase par diffraction des rayons X et neutronique

    Energy Technology Data Exchange (ETDEWEB)

    Dakhlaoui, R

    2006-12-15

    The aim of this work is to propose a methodology using diffraction methods and theoretical approaches of self-consistent modeling in order to analyze and better understand the mechanical behavior of each phase of hot-rolled duplex stainless steel. The purpose of the experimental study is to characterize the local mechanical behavior of phases under uniaxial loading. X-ray and neutron diffraction which enable to measure strains in each phase separately were used in this aim. Austenitic and ferritic phase stresses are determined by X-ray diffraction during tensile tests. Evolution of the elastic strains in each phase was measured by neutron diffraction using 'time-of-flight' method during tensile and compression tests. Elastic constants were given using the self-consistent model for a purely elastic deformation. To reproduce the mechanical behaviour of the studied material, self-consistent polycrystalline micro-mechanical model for elastoplastic deformation has been adapted and confronted to experimental results. Crystallographic texture and initial residual stresses were considered in this analysis. Critical shear stresses and hardening parameters of each phase of the studied duplex steel have been identified. Results of this study showed that the austenitic phase represents the softest and the most hardenable phase. Taking into account in calculations the initial residual stresses in the non deformed sample leads to the conclusion that the initial stresses modify considerably the values of phase's yield stresses. Good agreement has been noted comparing results obtained by XRD to those obtained by neutron diffraction. The problem of relaxation of normal stresses in the analysed layer by X-rays was analysed and discussed. Using XRD and self-consistent modelling, the effect of the chemical composition of the duplex stainless steel and the influence of ageing at 400 C degrees for 1000 h on the mechanical behaviour of austenitic and ferritic phases have

  1. A new high pressure form of Ba{sub 3}NiSb{sub 2}O{sub 9}

    Energy Technology Data Exchange (ETDEWEB)

    Darie, Céline; Lepoittevin, Christophe; Klein, Holger; Kodjikian, Stéphanie; Bordet, Pierre; Colin, Claire V. [Institut Néel, Université Grenoble-Alpes, and Institut Néel, CNRS, Grenoble F−38042 (France); Lebedev, Oleg I. [Laboratoire CRISMAT, ENSICAEN UMR6508, 6 Bd Maréchal Juin, Caen Cedex 4 F−14050 (France); Deudon, Catherine; Payen, Christophe [Institut des Matériaux Jean Rouxel (IMN), UMR 6502, Université de Nantes, CNRS, Nantes Cedex 3 F−44322 (France)

    2016-05-15

    In the search of an experimental realization of quantum spin liquid phases we have synthesized polycrystalline samples of Ba{sub 3}NiSb{sub 2}O{sub 9} under high pressure–high temperature conditions. Combining X-ray powder diffraction, neutron powder diffraction and precession electron diffraction we show that the obtained phase isn't hexagonal as reported in the literature, but trigonal. This new structure shows triangular Ni planes, but only in domains of sizes of the order of 10 nm. It therefore is still interesting as a potential candidate for a quantum spin liquid. - Graphical abstract: Synthesis under high pressure of a new form of Ba{sub 3}NiSb{sub 2}O{sub 9} : a promising candidate for a quantum spin liquid. Triangular Ni-planes can effectively be present in this structure but only in domains of up to 10 nm in size.

  2. Neutron diffraction residual stress analysis of Al{sub 2}O{sub 3}/Y-TZP ceramic composites

    Energy Technology Data Exchange (ETDEWEB)

    Fan, K.; Ruiz-Hervias, J.; Gurauskis, J.; Sanchez-Herencia, A. J.; Baudin, C.

    2016-05-01

    Residual stress measurements were conducted by time-of-flight neutron diffraction and Rietveld analysis method in Al{sub 2}O{sub 3}/Y-TZP ceramic composites fabricated by different green processing techniques (a novel tape casting and conventional slip casting) and with different Y-TZP content (5 and 40 vol.% Y-TZP). The results show that the residual stresses in Y-TZP particulates are tensile and the ones in Al{sub 2}O{sub 3} matrix are compressive, with almost flat through-thickness residual stress profiles in all bulk samples. As Y-TZP content increased, tension in Y-TZP phase was decreased but compression in Al{sub 2}O{sub 3} matrix was increased (in absolute value). The values of residual stresses for both phases were mainly dependent on the Y-TZP content in the studied Al{sub 2}O{sub 3}/Y-TZP composites, irrespective of sample orientation and fabrication processes (a novel tape casting and conventional slip casting). (Author)

  3. The application of neutron diffraction to a study of phases in type 316 stainless steel weld metals

    Science.gov (United States)

    Slattery, G. F.; Windsor, C. G.

    1983-10-01

    Neutron diffraction techniques have been utilised to study the phases in type 316 austenitic stainless steel weld metal, both in the as-welded condition and after stress-relieving and ageing heat-treatments. The amounts of the principal crystallographic phases present in bulk specimens have been measured. Two compositions of weld metal were selected to provide a "low" (6%) and "high" (16%) initial ferrite level and the subsequent volume fractions of transformation products were measured after heat-treatment. Some retained ferrite was observed in all the heat-treated specimens, ranging from 4% for specimens of both initial ferrite levels treated at 625°C for 1000 h, to around 1% for the specimens treated at 850°C for 6 h. The high initial ferrite specimen produced 0.9% of sigma phase after the 850°C treatment and 0.2% sigma after the 625°C treatment. The low initial ferrite specimen produced 1.5% M 23C 6 carbide after both heat-treatments. The results compare well with previous findings on similar samples of weld metal using optical and electron microscopy.

  4. The crystal structure of superconducting FeSe{sub 1-x}Te{sub x} by pulsed neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Lehman, M C; Llobet, A; Horigane, K; Louca, D, E-mail: mcl4v@virginia.edu

    2010-11-01

    A transition to a superconducting state was recently observed in the binary alloy of FeSe{sub 1-x}Te{sub x} system where TC rises with increasing x. The substitution of the larger Te for Se ion results in no additional charges but increases the internal chemical pressure. Earlier studies suggested that the crystal structure maintains the tetragonal P4/nmm symmetry with the substitution of Te where the average bond angle, {alpha}, decreases considerably from {approx} 104{sup 0} in FeSe to 100.5{sup 0} in the mixed phase of FeSe{sub 0.5}Te{sub 0.5}. With the use of pulsed neutron power diffraction and the Rietveld analysis, the crystal structure refinement for FeSe{sub 0.5}Te{sub 0.5} yielded very large thermal factors in the superconducting phase indicative of the presence of structural distortions that may be significant in understanding the electronic and magnetic properties of this system.

  5. Comparison between Neutron Diffraction measurements and numerical simulation of residual stresses of a Wire-Drawing process

    Directory of Open Access Journals (Sweden)

    Tomaz Fantin de Souza

    2013-04-01

    Full Text Available In this work, a drawing processed was simulated to calculate forces and the resulting residual stresses in the material. The calculated residual stresses were compared with experimentally measured residual stresses by the Neutron Diffraction Method. The modeled process was the Wire Drawing. The necessary parameters to model the process were taken from an industrial currently used process. Rods of an AISI 1045 steel with nominal diameters of 21.46 mm were reduced to 20.25 mm by drawing with an drawing angle of 15°. Compression tests were used to determinate flow curves of the real material an used in the simulation models. The possibility to estimate drawing forces by numerical simulation was evaluated by comparing simulated results with values from empirical equations given by the literature. The results have shown a sufficient accuracy for the calculation of forces, but the comparison of residual stresses has shown differences to the experimentally determined ones that can be minimized by the consideration of high strain rates in the compression tests, anisotropy of the material and kinematic hardening.

  6. A high-pressure MWPC detector for crystallography

    DEFF Research Database (Denmark)

    Ortuno-Prados, F.; Bazzano, A.; Berry, A.

    1999-01-01

    The application of the Multi-Wire Proportional Counter (MWPC) as a potential detector for protein crystallography and other wide-angle diffraction experiments is presented. Electrostatic problems found with our large area MWPC when operated at high pressure are discussed. We suggest that a soluti...... to these problems is to use a glass micro-strip detector in place of the wire frames. The characteristics of a high-pressure Micro-Strip Gas Chamber (MSGC) tested in the laboratory are presented....

  7. Phase Evolution of Hydrous Enstatite at High Pressures and Temperatures

    Science.gov (United States)

    Xu, J.; Zhang, D.; Dera, P.; Zhang, J.; Fan, D.

    2016-12-01

    Pyroxenes, including Mg-rich orthopyroxene and Ca-rich clinopyroxene, are among the most important minerals in the Earth's upper mantle (account for 20% by volume). Pyroxenes are major phases of harzburgite and lherzolite, which are important components of subducting slabs, so the high pressure behavior of pyroxenes should influence the physical properties of the subducted slabs. Therefore, understanding the phase evolution and thermal equations of state and of pyroxenes at elevated pressure and temperature is crucial to model theupper mantle and subduction zones. On the other hand, water is expected to be incorporated into pyroxene minerals in the upper mantle environments, yet the effect of water on the high pressure behavior of pyroxene has not been fully explored. In this study, we conducted high-pressure single-crystal X-ray diffraction study on hydrous enstatite sample (Mg2Si2O6) at ambient and high temperatures. High-pressure single-crystal diffraction experiments at ambient temperature were performed to 30 GPa at the experimental station 13BMC of the Advanced Photon Source. Two phase transformations were detected within the pressure range. High-pressure and high-temperature single crystal diffraction experiments were conducted to 27 GPa and 700 K also at 13BMC. From the experimental data, we derived the thermoelastic parameters of enstatite and performed structural refinements of enstatite at high pressures and temperatures, which is of implication for understanding of geophysics and geochemistry of subducting slabs.

  8. High-level expression and deuteration of sperm whale myoglobin: A study of its solvent structure by X-ray and neutron diffraction methods

    Energy Technology Data Exchange (ETDEWEB)

    Shu, F. [State Univ. of New York, Stony Brook, NY (United States); Ramakrishnan, V. [Brookhaven National Laboratory, Upton, NY (United States); Schoenborn, B.P. [Los Alamos National Laboratory, NM (United States)

    1994-12-31

    Neutron diffraction has become one of the best ways to study light atoms, such as hydrogens. Hydrogen however has a negative coherent scattering factor, and a large incoherent scattering factor, while deuterium has virtually no incoherent scattering, but a large positive coherent scattering factor. Beside causing high background due to its incoherent scattering, the negative coherent scattering of hydrogen tends to cancel out the positive contribution from other atoms in a neutron density map. Therefore a fully deuterated sample will yield better diffraction data with stronger density in the hydrogen position. On this basis, a sperm whale myoglobin gene modified to include part of the A cII protein gene has been cloned into the T7 expression system. Milligram amounts of fully deuterated holo-myoglobin have been obtained and used for crystallization. The synthetic sperm whale myoglobin crystallized in P2{sub 1} space group isomorphous with the native protein crystal. A complete X-ray diffraction dataset at 1.5{Angstrom} has been collected. This X-ray dataset, and a neutron data set collected previously on a protonated carbon-monoxymyoglobin crystal have been used for solvent structure studies. Both X-ray and neutron data have shown that there are ordered hydration layers around the protein surface. Solvent shell analysis on the neutron data further has shown that the first hydration layer behaves differently around polar and apolar regions of the protein surface. Finally, the structure of per-deuterated myoglobin has been refined using all reflections to a R factor of 17%.

  9. Assessment of firing conditions in old fired-clay bricks. The contribution of X-ray powder diffraction with the Rietveld method and small angle neutron scattering

    Czech Academy of Sciences Publication Activity Database

    Viani, Alberto; Sotiriadis, Konstantinos; Len, A.; Šašek, Petr; Ševčík, Radek

    2016-01-01

    Roč. 116, June (2016), s. 33-43 ISSN 1044-5803 R&D Projects: GA MŠk(CZ) LO1219 Keywords : fired- clay brick * Rietveld method * small angle neutron scattering * X-ray diffraction * firing temperature Subject RIV: AL - Art, Architecture, Cultural Heritage Impact factor: 2.714, year: 2016 http://www.sciencedirect.com/science/article/pii/S1044580316300870

  10. Performance studies on high pressure 1-D position sensitive ...

    Indian Academy of Sciences (India)

    Performance studies on high pressure 1-D position sensitive neutron detectors. S S DESAI and A M SHAIKH∗. Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085, India. *Corresponding author. E-mail: shaikham@barc.gov.in. Abstract. The powder diffractometer and Hi-Q diffractometer at ...

  11. Neutron powder thermo-diffraction in mechanically alloyed Fe{sub 64}Ni{sub 36} invar alloy

    Energy Technology Data Exchange (ETDEWEB)

    Gorria, Pedro, E-mail: pgorria@uniovi.e [Departamento de Fisica, Universidad de Oviedo, Avda. Calvo Sotelo s/n, Oviedo 33007, Asturias (Spain); Martinez-Blanco, David [Unidad de Magnetometria, SCT' s, Universidad de Oviedo, Julian Claveria 8, 33006 Oviedo (Spain); Blanco, Jesus A. [Departamento de Fisica, Universidad de Oviedo, Avda. Calvo Sotelo s/n, Oviedo 33007, Asturias (Spain); Smith, Ronald I. [ISIS Facility, RAL, Chilton, Didcot, Oxon OX11 0QX (United Kingdom)

    2010-04-16

    Nanostructured Fe{sub 64}Ni{sub 36} alloy has been obtained using high-energy ball milling for 35 h of milling time, Fe{sub 64}Ni{sub 36} MA-35 h. The initial as-milled Fe{sub 64}Ni{sub 36} MA-35 h powders are inhomogeneous, showing a majority phase with a face-centred cubic (fcc) crystal structure [88(2)%] and a minority phase with body-centred cubic (bcc) crystal structure [7(2)%]. The evolution of the microstructure with temperature between 300 K and 1100 K has been followed by means of in situ neutron powder thermo-diffraction experiments. The room temperature values for the mean crystalline size and the mechanical-induced microstrain of the fcc phase in the as-milled sample are {approx}10 nm and {approx}0.7%, respectively. Moreover, after heating the Fe{sub 64}Ni{sub 36} MA-35 h powders up to 1100 K, an increase of around 65 K in the Curie temperature respect to that of the commercial coarse-grained alloy of the same composition is observed. The latter together with the observed temperature dependence of the lattice parameter suggests that the Fe{sub 64}Ni{sub 36} MA-35 h sample subjected to the heating process exhibits invar behaviour. On heating up to 1100 K thermal relaxation of the microstructure occurs giving rise to grain growth above 100 nm, nearly vanishing values for the maximum strain, and the transformation of the bcc phase into the fcc one above 800 K, being the latter stable in subsequent heating-cooling processes.

  12. X-Ray and Neutron Diffraction Measurements of Dislocation Density and Subgrain Size in a Friction-Stir-Welded Aluminum Alloy

    Science.gov (United States)

    Woo, Wanchuck; Ungár, Tamás; Feng, Zhili; Kenik, Edward; Clausen, Bjørn

    2010-05-01

    The dislocation density and subgrain size were determined in the base material and friction-stir welds of 6061-T6 aluminum alloy. High-resolution X-ray diffraction measurement was performed in the base material. The result of the line profile analysis of the X-ray diffraction peak shows that the dislocation density is about 4.5 × 1014 m-2 and the subgrain size is about 200 nm. Meanwhile, neutron diffraction measurements have been performed to observe the diffraction peaks during friction-stir welding (FSW). The deep penetration capability of the neutron enables us to measure the peaks from the midplane of the Al plate underneath the tool shoulder of the friction-stir welds. The peak broadening analysis result using the Williamson-Hall method shows the dislocation density of about 3.2 × 1015 m-2 and subgrain size of about 160 nm. The significant increase of the dislocation density is likely due to the severe plastic deformation during FSW. This study provides an insight into understanding the transient behavior of the microstructure under severe thermomechanical deformation.

  13. Electrokinetic high pressure hydraulic system

    Science.gov (United States)

    Paul, Phillip H.; Rakestraw, David J.; Arnold, Don W.; Hencken, Kenneth R.; Schoeniger, Joseph S.; Neyer, David W.

    2001-01-01

    An electrokinetic high pressure hydraulic pump for manipulating fluids in capillary-based systems. The pump uses electro-osmotic flow to provide a high pressure hydraulic system, having no moving mechanical parts, for pumping and/or compressing fluids, for providing valve means and means for opening and closing valves, for controlling fluid flow rate, and manipulating fluid flow generally and in capillary-based systems (Microsystems), in particular. The compact nature of the inventive high pressure hydraulic pump provides the ability to construct a micro-scale or capillary-based HPLC system that fulfills the desire for small sample quantity, low solvent consumption, improved efficiency, the ability to run samples in parallel, and field portability. Control of pressure and solvent flow rate is achieved by controlling the voltage applied to an electrokinetic pump.

  14. A Neutron-Diffraction Study of the Solid Layers at the Liquid Solid Boundary in 4He-Films Adsorbed on Graphite

    DEFF Research Database (Denmark)

    da Costa Carneiro, Kim; Passell, L.; Thomlinson, W.

    1981-01-01

    A neutron scattering study of the structure of 4He films adsorbed on graphite is reported. Diffraction from helium monolayers at a temperature of 1.2K shows the formation of an incommensurate, triangular-lattice solid of high density. As the coverage is increased above two layers, the diffraction...... precise identification. A measurement of the height of the first helium layer above the graphite basal plane was also made. This was done by determining the coverage-dependent shift in the position of the graphite (002) diffraction peak (assumed to arise from interference between film and substrate...... scattering) and fitting it to a simple structural model. Values for the monolayer height above the graphite plane and for the lattice constants of the possible bilayer structures are given....

  15. Electrokinetic high pressure hydraulic system

    Science.gov (United States)

    Paul, Phillip H.; Rakestraw, David J.

    2000-01-01

    A compact high pressure hydraulic pump having no moving mechanical parts for converting electric potential to hydraulic force. The electrokinetic pump, which can generate hydraulic pressures greater than 2500 psi, can be employed to compress a fluid, either liquid or gas, and manipulate fluid flow. The pump is particularly useful for capillary-base systems. By combining the electrokinetic pump with a housing having chambers separated by a flexible member, fluid flow, including high pressure fluids, is controlled by the application of an electric potential, that can vary with time.

  16. NEUTRON POWDER DIFFRACTION TECHNIQUE '

    African Journals Online (AJOL)

    2006-05-04

    May 4, 2006 ... (paramagnetic), whereas it varies irregularly with temperature in the low temperature region, due to the small Co moment. Thetefpte, in our model, the value of BCO at low temperature is estimated by extrapolating thatj in iicubic structure. Then 8Tb can be deriveciirandshows an almost linear variation.

  17. High pressure neon arc lamp

    Science.gov (United States)

    Sze, Robert C.; Bigio, Irving J.

    2003-07-15

    A high pressure neon arc lamp and method of using the same for photodynamic therapies is provided. The high pressure neon arc lamp includes a housing that encloses a quantity of neon gas pressurized to about 500 Torr to about 22,000 Torr. At each end of the housing the lamp is connected by electrodes and wires to a pulse generator. The pulse generator generates an initial pulse voltage to breakdown the impedance of the neon gas. Then the pulse generator delivers a current through the neon gas to create an electrical arc that emits light having wavelengths from about 620 nanometers to about 645 nanometers. A method for activating a photosensitizer is provided. Initially, a photosensitizer is administered to a patient and allowed time to be absorbed into target cells. Then the high pressure neon arc lamp is used to illuminate the target cells with red light having wavelengths from about 620 nanometers to about 645 nanometers. The red light activates the photosensitizers to start a chain reaction that may involve oxygen free radicals to destroy the target cells. In this manner, a high pressure neon arc lamp that is inexpensive and efficiently generates red light useful in photodynamic therapy is provided.

  18. High Pressure Research on Materials

    Indian Academy of Sciences (India)

    basic types of apparatus that are now being used throughout the world. He was awarded the Nobel Prize in Physics in 1946. The static high pressure generating devices can be divided into two categories: piston-cylinder and opposed anvil devices. These devices with their pressure capabilities are listed in Figure 4.

  19. Nested neutron microfocusing optics on SNAP

    Science.gov (United States)

    Ice, G. E.; Choi, J.-Y.; Takacs, P. Z.; Khounsary, A.; Puzyrev, Y.; Molaison, J. J.; Tulk, C. A.; Andersen, K. H.; Bigault, T.

    2010-06-01

    The high source intensity of the Spallation Neutron Source (SNS), together with efficient detectors and large detector solid angles, now makes possible neutron experiments with much smaller sample volumes than previously were practical. Nested Kirkpatrick-Baez supermirror optics provide a promising and efficient way to further decrease the useable neutron sample size by focusing polychromatic neutrons into microbeams. Because the optics are nondispersive, they are ideal for spallation sources and for polychromatic and wide bandpass experiments on reactor sources. Theoretical calculations indicate that nested mirrors can preserve source brilliance at the sample for small beams and for modest divergences that are appropriate for diffraction experiments. Although the flux intercepted by a sample can be similar with standard beam-guided approaches, the signal-to-background is much improved with small beams on small samples. Here we describe the design, calibration and performance of a nested neutron mirror pair for the Spallation Neutrons At Pressure (SNAP) beamline at the SNS. High-pressure neutron diffraction is but one example of a large class of neutron experiments that will benefit from spatially-resolved microdiffraction.

  20. Magnetic structures of erbium under high pressure

    DEFF Research Database (Denmark)

    Kawano, S.; Lebech, B.; Achiwa, N.

    1993-01-01

    Neutron diffraction studies of the magnetic structures of erbium metal at 4.5 K and 11.5 kbar hydrostatic pressure have revealed that the transition to a conical structure at low temperatures is suppressed and that the cycloidal structure, with modulation vector Q congruent-to (2/7 2pi/c)c persists...... between 4.5 K and approximately 50 K, where it tends to increase. The intensities of the magnetic satellites originating from higher-order harmonics of the c-axis-moment component observed at 4.5 K decrease slowly with increasing temperature, but persist up to approximately 60 K....

  1. Quantum interferences revealed by neutron diffraction accord with a macroscopic-scale quantum-theory of ferroelectrics KH2(1- ρ)D2 ρ PO4

    Science.gov (United States)

    Fillaux, François; Cousson, Alain

    2016-03-01

    Neutron diffraction by single-crystals KH2(1- ρ)D2 ρ PO4 at 293 K reveal quantum interferences consistent with a static lattice of entangled proton-deuteron scatterers. These crystals are represented by a macroscopic-scale condensate of phonons with continuous space-time-translation symmetry and zero-entropy. This state is energetically favored and decoherence-free over a wide temperature-range. Projection of the crystal state onto a basis of four electrically- and isotopically-distinct state-vectors accounts for isotope and pressure effects on the temperature of the ferroelectric-dielectric transition, as well as for the latent heat. At the microscopic level, an incoming wave realizes a transitory state either in the space of static positional parameters (elastic scattering) or in that of the symmetry species (energy transfer). Neutron diffraction, vibrational spectroscopy, relaxometry and neutron Compton scattering support the conclusion that proton and deuteron scatterers are separable exclusively through resonant energy-transfer.

  2. Two-dimensional position-sensitive gaseous detectors for high-resolution neutron and X-ray diffraction

    CERN Document Server

    Marmotti, M; Kampmann, R

    2002-01-01

    Two-dimensional position-sensitive gaseous detectors have been developed at the Geesthacht Neutron Facility (GeNF) for high-resolution neutron and X-ray diffractometry. They are multi-wire proportional counters with delay-line readout and sensitive areas of 300 mm x 300 mm or 500 mm x 500 mm. For detecting X-rays, neutrons and hard X-rays the counters are filled with Ar/CO sub 2 , sup 3 He/CF sub 4 and Xe/CO sub 2 , respectively. One neutron detector is used at the ARES diffractometer at GKSS, which is dedicated to the analysis of residual stresses. Further ones are used for analysing textures and residual stresses at the hard-X-ray beamline PETRA-2 at HASYLAB, and one detector is being developed for the neutron reflectometer REFSANS at the research reactor FRM-II in Munich, Germany. (orig.)

  3. Screening of hydrogen storage media applying high pressure thermogravimetry

    DEFF Research Database (Denmark)

    Bentzen, J.J.; Pedersen, Allan Schrøder; Kjøller, J.

    2001-01-01

    A number of commercially available hydride-forming alloys of the MmNi5–xSnx (Mm=mischmetal, a mixture of lanthanides) type were examined using a high pressure, high temperature microbalance,scanning electron microscopy and X-ray diffraction. Activation conditions, reversible storage capacity, wor...

  4. Texture Analysis using The Neutron Diffraction Method on The Non Standardized Austenitic Steel Process by Machining,Annealing, and Rolling

    Directory of Open Access Journals (Sweden)

    Tri Hardi Priyanto

    2016-04-01

    Full Text Available Austenitic steel is one type of stainless steel which is widely used in the industry. Many studies on  austenitic stainless steel have been performed to determine the physicalproperties using various types of equipment and methods. In this study, the neutron diffraction method is used to characterize the materials which have been made from  minerals extracted from the mines in Indonesia. The materials consist of a granular ferro-scrap, nickel, ferro-chrome, ferro-manganese, and ferro-silicon added with a little titanium. Characterization of the materials was carried out in threeprocesses, namely: machining, annealing, and rolling. Experimental results obtained from the machining process generally produces a texture in the 〈100〉direction. From the machining to annealing process, the texture index decreases from 3.0164 to 2.434.Texture strength in the machining process (BA2N sample is  8.13 mrd and it then decreases to 6.99 in the annealing process (A2DO sample. In the annealing process the three-component texture appears, cube-on-edge type texture{110}〈001〉, cube-type texture {001}〈100〉, and brass-type {110}〈112〉. The texture is very strong leading to the direction of orientation {100}〈001〉, while the {011}〈100〉is weaker than that of the {001}, and texture withorientation {110}〈112〉is weak. In the annealing process stress release occurred, and this was shown by more randomly pole compared to stress release by the machining process. In the rolling process a brass-type texture{110}〈112〉with a spread towards the goss-type texture {110}〈001〉 appeared,  and  the  brass  component  is markedly  reinforced  compared  to  the undeformed state (before rolling. Moreover, the presence of an additional {110} component was observed at the center of the (110 pole figure. The pole density of three components increases withthe increasing degree of thickness reduction. By increasing degrees

  5. An in situ powder neutron diffraction study of nano-precipitate formation during processing of oxide-dispersion-strengthened ferritic steels

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hongtao, E-mail: hongtao.zhang@materials.ox.ac.uk [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Gorley, Michael J. [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Chong, Kok Boon; Fitzpatrick, Michael E. [Materials Engineering, The Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Roberts, Steve G.; Grant, Patrick S. [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom)

    2014-01-05

    Highlights: • In situ powder neutron diffraction to study precipitate formation in ODS steel. • First real time observation of nano-precipitate formation during processing. • Y{sub 2}O{sub 3} particles were fully dissolved into steel matrix during mechanical alloy. • The precipitation occurred during annealing of as-milled powder above 900 °C. -- Abstract: The evolution of phases in a Fe–14Cr–10Y{sub 2}O{sub 3} (wt%) oxide-dispersion-strengthened ferritic steel during mechanical alloying (MA) and subsequent annealing was studied by high resolution powder neutron diffraction, with emphasis on the kinetics of oxide-based nano-precipitate formation. Y{sub 2}O{sub 3} particles were completely dissolved into the ferritic matrix during MA. The formation of nano-precipitates was then observed by in situ thermo-diffraction experiments during annealing of as-milled powder above 900 °C, supported by scanning electron microscopy. This revealed nano-precipitate coarsening with increasing annealing temperature. Powder microhardness was measured at various processing stages, and hardness changes are discussed in terms of the measured phase fractions, crystallite size and lattice strain at different temperatures and times.

  6. Structural study of the apatite Nd₈Sr₂Si₆O₂₆ by Laue neutron diffraction and single-crystal Raman spectroscopy.

    Science.gov (United States)

    An, Tao; Orera, Alodia; Baikie, Tom; Herrin, Jason S; Piltz, Ross O; Slater, Peter R; White, Tim J; Sanjuán, María L

    2014-09-02

    A single-crystal structure determination of Nd8Sr2Si6O26 apatite, a prototype intermediate-temperature electrolyte for solid oxide fuel cells grown by the floating-zone method, was completed using the combination of Laue neutron diffraction and Raman spectroscopy. While neutron diffraction was in good agreement with P6₃/m symmetry, the possibility of P6₃ could not be convincingly excluded. This ambiguity was removed by the collection of orientation-dependent Raman spectra that could only be consistent with P6₃/m. The composition of Nd8Sr2Si6O26 was independently verified by powder X-ray diffraction in combination with electron probe microanalysis, with the latter confirming a homogeneous distribution of Sr and the absence of chemical zonation commonly observed in apatites. This comprehensive crystallochemical description of Nd8Sr2Si6O26 provides a baseline to quantify the efficacy of cation vacancies, oxygen superstoichiometry, and symmetry modification for promoting oxygen-ion mobility.

  7. Blue emitting organic semiconductors under high pressure

    DEFF Research Database (Denmark)

    Knaapila, Matti; Guha, Suchismita

    2016-01-01

    highlighted by high pressure optical spectroscopy whilst analogous x-ray diffraction experiments remain less frequent. By focusing on a class of blue-emitting π-conjugated polymers, polyfluorenes, this article reviews optical spectroscopic studies under hydrostatic pressure, addressing the impact of molecular......This review describes essential optical and emerging structural experiments that use high GPa range hydrostatic pressure to probe physical phenomena in blue-emitting organic semiconductors including π-conjugated polyfluorene and related compounds. The work emphasizes molecular structure...... and intermolecular self-organization that typically determine transport and optical emission in π-conjugated oligomers and polymers. In this context, hydrostatic pressure through diamond anvil cells has proven to be an elegant tool to control structure and interactions without chemical intervention. This has been...

  8. High pressure chemistry of substituted acetylenes

    Energy Technology Data Exchange (ETDEWEB)

    Chellappa, Raja [Los Alamos National Laboratory; Dattelbaum, Dana [Los Alamos National Laboratory; Sheffield, Stephen [Los Alamos National Laboratory; Robbins, David [Los Alamos National Laboratory

    2011-01-25

    High pressure in situ synchrotron x-ray diffraction experiments were performed on substituted polyacetylenes: tert-butyl acetylene [TBA: (CH{sub 3}){sub 3}-C{triple_bond}CH] and ethynyl trimethylsilane [ETMS: (CH{sub 3}){sub 3}-Si{triple_bond}CH] to investigate pressure-induced chemical reactions. The starting samples were the low temperature crystalline phases which persisted metastably at room temperature and polymerized beyond 11 GPa and 26 GPa for TBA and ETMS respectively. These reaction onset pressures are considerably higher than what we observed in the shockwave studies (6.1 GPa for TBA and 6.6 GPa for ETMS). Interestingly, in the case of ETMS, it was observed with fluid ETMS as starting sample, reacts to form a semi-crystalline polymer (crystalline domains corresponding to the low-T phase) at pressures less than {approx}2 GPa. Further characterization using vibrational spectroscopy is in progress.

  9. Polymerization of Formic Acid under High Pressure

    Energy Technology Data Exchange (ETDEWEB)

    Goncharov, A F; Manaa, M R; Zaug, J M; Fried, L E; Montgomery, W B

    2004-08-23

    We report combined Raman, infrared (IR) and x-ray diffraction (XRD) measurements, along with ab initio calculations on formic acid under pressure up to 50 GPa. Contrary to the report of Allan and Clark (PRL 82, 3464 (1999)), we find an infinite chain low-temperature Pna2{sub 1} structure consisting of trans molecules to be a high-pressure phase at room temperature. Our data indicate the symmetrization and a partially covalent character of the intra-chain hydrogen bonds above approximately 20 GPa. Raman spectra and XRD patterns indicate a loss of the long-range order at pressures above 40 GPa with a large hysteresis at decompression. We attribute this behavior to a three-dimensional polymerization of formic acid.

  10. Formation of incommensurate long-range magnetic order in the Dzyaloshinskii-Moriya antiferromagnet Ba2CuGe2O7 studied by neutron diffraction

    Science.gov (United States)

    Mühlbauer, S.; Brandl, G.; Mânsson, M.; Garst, M.

    2017-10-01

    Neutron diffraction on a triple-axis spectrometer and a small-angle neutron scattering instrument is used to study the magnetic phase transition in tetragonal Ba2CuGe2O7 at zero magnetic field. In addition to the incommensurate cycloidal antiferromagnetic (AFM) long-range order, we establish that weak incommensurate ferromagnetism (FM) also arises below the transition temperature TN identified by sharp Bragg peaks close to the Γ point. The intensities of both the incommensurate AFM and FM Bragg peaks vanish abruptly at TN, which is indicative of a weak first-order transition. Above TN, evidence is presented that the magnetic intensity within the tetragonal (a ,b ) plane is distributed on a ring in momentum space whose radius is determined by the incommensurate wave vector of the cycloidal order. We speculate that the associated soft fluctuations are at the origin of the weak first-order transition in the spirit of a scenario proposed by Brazovskii.

  11. Weld residual stresses near the bimetallic interface in clad RPV steel: A comparison between deep-hole drilling and neutron diffraction data

    Energy Technology Data Exchange (ETDEWEB)

    James, M.N., E-mail: mjames@plymouth.ac.uk [School of Marine Science and Engineering, University of Plymouth, Drake Circus, Plymouth (United Kingdom); Department of Mechanical Engineering, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Newby, M.; Doubell, P. [Eskom Holdings SOC Ltd, Lower Germiston Road, Rosherville, Johannesburg (South Africa); Hattingh, D.G. [Department of Mechanical Engineering, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Serasli, K.; Smith, D.J. [Department of Mechanical Engineering, University of Bristol, Queen' s Building, University Walk, Bristol (United Kingdom)

    2014-07-01

    Highlights: • Identification of residual stress trends across bimetallic interface in stainless clad RPV. • Comparison between deep hole drilling (DHD – stress components in two directions) and neutron diffraction (ND – stress components in three directions). • Results indicate that both techniques can assess the trends in residual stress across the interface. • Neutron diffraction gives more detailed information on transient residual stress peaks. - Abstract: The inner surface of ferritic steel reactor pressure vessels (RPV) is clad with strip welded austenitic stainless steel primarily to increase the long-term corrosion resistance of the ferritic vessel. The strip welding process used in the cladding operation induces significant residual stresses in the clad layer and in the RPV steel substrate, arising both from the thermal cycle and from the very different thermal and mechanical properties of the austenitic clad layer and the ferritic RPV steel. This work measures residual stresses using the deep hole drilling (DHD) and neutron diffraction (ND) techniques and compares residual stress data obtained by the two methods in a stainless clad coupon of A533B Class 2 steel. The results give confidence that both techniques are capable of assessing the trends in residual stresses, and their magnitudes. Significant differences are that the ND data shows greater values of the tensile stress peaks (∼100 MPa) than the DHD data but has a higher systematic error associated with it. The stress peaks are sharper with the ND technique and also differ in spatial position by around 1 mm compared with the DHD technique.

  12. Anomalous Depletion of Pore-Confined Carbon Dioxide upon Cooling below the Bulk Triple Point: An In Situ Neutron Diffraction Study

    Science.gov (United States)

    Stefanopoulos, K. L.; Katsaros, F. K.; Steriotis, Th. A.; Sapalidis, A. A.; Thommes, M.; Bowron, D. T.; Youngs, T. G. A.

    2016-01-01

    The phase behavior of sorbed CO2 in an ordered mesoporous silica sample (SBA-15) was studied by neutron diffraction. Surprisingly, upon cooling our sample below the bulk critical point, confined CO2 molecules neither freeze nor remain liquid as expected, but escape from the pores. The phenomenon has additionally been confirmed gravimetrically. The process is reversible and during heating CO2 refills the pores, albeit with hysteresis. This depletion was for the first time observed in an ordered mesoporous molecular sieve and provides new insight on the phase behavior of nanoconfined fluids.

  13. Strain Mapping and Nanocrystallite Size Determination by Neutron Diffraction in an Aluminum Alloy (AA5083 Severely Plastically Deformed through Equal Channel Angular Pressing

    Directory of Open Access Journals (Sweden)

    P. A. González Crespo

    2013-01-01

    Full Text Available Six specimens of an aluminum alloy (AA-5083 extruded by Equal Channel Angular Pressing following two different routes plus a blank sample were examined with a neutron radiation of 1.5448 Å. Macrostrain maps from the (311 reflection were obtained. A clear difference about accumulated macrostrain with the extrusion cycles between the two routes is shown. The diffraction data of annealed specimens did permit to estimate crystallite sizes that range between 89 nm and 115 nm depending on the routes.

  14. In-situ neutron diffraction study of martensitic variant redistribution in polycrystalline Ni-Mn-Ga alloy under cyclic thermo-mechanical treatment

    Science.gov (United States)

    Li, Zongbin; Zhang, Yudong; Esling, Claude; Gan, Weimin; Zou, Naifu; Zhao, Xiang; Zuo, Liang

    2014-07-01

    The influences of uniaxial compressive stress on martensitic transformation were studied on a polycrystalline Ni-Mn-Ga bulk alloy prepared by directional solidification. Based upon the integrated in-situ neutron diffraction measurements, direct experimental evidence was obtained on the variant redistribution of seven-layered modulated (7M) martensite, triggered by external uniaxial compression during martensitic transformation. Large anisotropic lattice strain, induced by the cyclic thermo-mechanical treatment, has led to the microstructure modification by forming martensitic variants with a strong ⟨0 1 0⟩7M preferential orientation along the loading axis. As a result, the saturation of magnetization became easier to be reached.

  15. Neutron diffraction studies of Ho sub 2 Fe sub 9 Ga sub 8 sub - sub x Al sub x (x=2, 4) at 50 K and 300 K

    CERN Document Server

    Chen, D F; Sun, K; Ridwan; Mujamilah, A; Marsongkohadi; Yan, Q W; Zhang, P L; Shen, B G; Gong, H Y

    1998-01-01

    The crystallographic and magnetic structures of Ho sub 2 Fe sub 9 Ga sub 8 sub - sub x Al sub x (x=2, 4) were studied by powder neutron diffraction at 50 K and 300 K. The atom fractional occupancies of gallium and aluminium and the magnetic moments of Ho and Fe atoms were obtained by a Rietveld analysis program. The gallium atoms occupy preferentially 18f sites, but aluminium atoms prefer to occupy 6c sites. The magnetic moments of the phase with the x=2, 4 at 50 K and x=2 at 300 K show uniaxial anisotropy. A qualitative explanation for this result is given. (author)

  16. Twin-domain size and bulk oxygen in-diffusion kinetics of YBa2Cu3O6+x studied by neutron powder diffraction and gas volumetry

    DEFF Research Database (Denmark)

    Poulsen, H.F.; Andersen, N.H.; Lebech, B.

    1991-01-01

    We report experimental results of twin-domain size and bulk oxygen in-diffusion kinetics of YBa2Cu3O6+x, which supplement a previous and simultaneous study of the structural phase diagram and oxygen equilibrium partial pressure. Analysis of neutron powder diffraction peak broadening show features...... which are identified to result from temperature independent twin-domain formation in to different orthorhombic phases with domain sizes 250 and 350 angstrom, respectively. The oxygen in-diffusion flow shows simple relaxation type behaviour J = J0 exp(-t/tau) despite a rather broad particle size...

  17. Neutron diffraction investigation for possible anisotropy within monolithic Al{sub 2}O{sub 3}/Y-TZP composites fabricated by stacking together cast tapes

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz-Hervias, J. [Departamento de Ciencia de Materiales, UPM, E.T.S.I. Caminos, Canales y Puertos, C/Profesor Aranguren s/n, E-28040 Madrid (Spain); Bruno, G. [Institut Max von Laue-Paul Langevin, BP 156, F-38042 Grenoble (France); Gurauskis, J. [Instituto de Ceramica y Vidrio (CSIC), Department of Ceramics, C/Kelsen 5, E-28049 Madrid (Spain); Sanchez-Herencia, A.J. [Instituto de Ceramica y Vidrio (CSIC), Department of Ceramics, C/Kelsen 5, E-28049 Madrid (Spain); Baudin, C. [Instituto de Ceramica y Vidrio (CSIC), Department of Ceramics, C/Kelsen 5, E-28049 Madrid (Spain)]. E-mail: cbaudin@icv.csic.es

    2006-03-15

    development of residual stresses in two Al{sub 2}O{sub 3} + 5 vol.% yttria-tetragonal zirconia polycrystal (Y-TZP) ceramic composites fabricated by conventional slip casting and by joining green cast tapes was investigated. Neutron diffraction profiles revealed compressive microstresses (-200 MPa) in the Al{sub 2}O{sub 3} matrix and tensile ones (2200 MPa) in the Y-TZP particles, irrespective of the processing route and the direction of measurement, which demonstrates the lack of residual macrostresses due to the joining procedure.

  18. The asymmetric interface structure of bcc Fe{sub 82}Ni{sub 18}/Co superlattices as revealed by neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Bjoerck, M. [Department of Physics, Uppsala Universitet, Box 530, SE-751 21 Uppsala (Sweden)]. E-mail: Matts.Bjorck@fysik.uu.se; Soroka, I.L. [Department of Physics, Uppsala Universitet, Box 530, SE-751 21 Uppsala (Sweden); Atomic Physics Department, Stockholm University, AlbaNova University Centrum, 106 91 Stockholm (Sweden); Chacon-Carillo, C. [Department of Physics, Uppsala Universitet, Box 530, SE-751 21 Uppsala (Sweden); Laboratoire Materiaux et Phenomenes Quantiques, Universite Paris 7, CNRS, UMR 7162, 2 Place Jussieu, 75251 Paris Cedex (France); Andersson, G. [Department of Physics, Uppsala Universitet, Box 530, SE-751 21 Uppsala (Sweden)

    2007-02-26

    The interface structure of Fe{sub 82}Ni{sub 18}/Co (001) superlattices has been studied with a combination of X-ray and neutron diffraction. The analysis reveals highly asymmetric interfaces with total interface widths of 10 {+-} 1 ML(monolayers) for Fe{sub 82}Ni{sub 18} on Co and a maximum interface width of 1 ML for Co on Fe{sub 82}Ni{sub 18}. In addition it is concluded that there is no detectable long range B2-type chemical order occurring in the interface region. These results are also discussed in the context of previously measured magnetic moments of the same system.

  19. Resonant x-ray and neutron diffraction study of USb0.8Te0.2

    DEFF Research Database (Denmark)

    Nuttall, W.J.; Langridge, S.; Stirling, W.G.

    1995-01-01

    Complementary neutron and magnetic x-ray scattering experiments have been performed on the pseudobinary compound USb0.8Te0.2. Both techniques reveal a succession of magnetic phases on cooling. On passing through the Neel temperature (T-N similar to 205 K), the system enters an antiferromagnetic (AF...... in the neutron and x-ray experiments are compared and discussed....

  20. Synthesis and magnetic properties of the high-pressure scheelite-type GdCrO{sub 4} polymorph

    Energy Technology Data Exchange (ETDEWEB)

    Dos santos-Garcia, A.J., E-mail: adossant@quim.ucm.es [Departamento de Quimica Inorganica I, Facultad de Ciencias Quimicas, Universidad Complutense de Madrid, 28040 Madrid (Spain); Climent-Pascual, E.; Gallardo-Amores, J.M.; Rabie, M.G. [Departamento de Quimica Inorganica I, Facultad de Ciencias Quimicas, Universidad Complutense de Madrid, 28040 Madrid (Spain); Doi, Y. [Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan); Romero de Paz, J. [CAI Tecnicas Fisicas, Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Beuneu, B. [Laboratoire Leon Brillouin (CEA-CNRS), CEA/Saclay-91191 Gif-sur-Yvette cedex (France); Saez-Puche, R. [Departamento de Quimica Inorganica I, Facultad de Ciencias Quimicas, Universidad Complutense de Madrid, 28040 Madrid (Spain)

    2012-10-15

    The scheelite-type polymorph of GdCrO{sub 4} has been obtained from the corresponding zircon-type compound under high pressure and temperature conditions, namely 4 GPa and 803 K. The crystal structure has been determined by X-ray powder diffraction. This GdCrO{sub 4} scheelite crystallizes in a tetragonal symmetry with space group I4{sub 1}/a (No. 88, Z=4), a=5.0501(1) A, c=11.4533(2) A and V=292.099(7) A{sup 3}. The thermal decomposition leads to the formation of the zircon-polymorph as intermediate phase at 773 K to end in the corresponding GdCrO{sub 3} distorted perovskite-structure at higher temperatures. Magnetic susceptibility and magnetization measurements suggest the existence of long-range antiferromagnetic interactions which have been also confirmed from specific heat measurements. Neutron powder diffraction data reveal the simultaneous antiferromagnetic Gd{sup 3+} and Cr{sup 5+} ordering in the scheelite-type GdCrO{sub 4} with a T{sub N}{approx}20 K. The magnetic propagation vector was found to be k=(0 0 0). Combined with group theory analysis, the best neutron powder diffraction fit was obtained with a collinear antiferromagnetic coupling in which the m{sub Cr{sup 5}{sup +}} and m{sub Gd{sup 3}{sup +}} magnetic moments are confined in the tetragonal basal plane according to the mixed representation {Gamma}{sub 6} Circled-Plus {Gamma}{sub 8}. Thermal decomposition of the GdCrO{sub 4} high pressure polymorph, from the scheelite-type through the zircon-type structure as intermediate to end in the GdCrO{sub 3} perovskite. Highlights: Black-Right-Pointing-Pointer New high pressure GdCrO{sub 4} polymorph crystallizing in the scheelite type structure. Black-Right-Pointing-Pointer It is an antiferromagnet with a metamagnetic transition at low magnetic fields. Black-Right-Pointing-Pointer We have determined its magnetic structure from powder neutron diffraction data. Black-Right-Pointing-Pointer Otherwise, the room pressure zircon-polymorph is a ferromagnet

  1. Carbon nanostructures under high pressure

    CERN Document Server

    Sundqvist, B

    2002-01-01

    Results from recent high-pressure experiments in the field of fullerenes are briefly reviewed. In particular, new results on one-, two- and three-dimensional polymerized C sub 6 sub 0 and C sub 7 sub 0 are discussed. Results discussed include the first synthesis of a well defined, one-dimensional polymer based on C sub 7 sub 0 , transformations from two-dimensional (2D) to three-dimensional phases in C sub 6 sub 0 , and doping of 2D C sub 6 sub 0 polymers.

  2. High-pressure synthesis of tantalum dihydride

    Science.gov (United States)

    Kuzovnikov, Mikhail A.; Tkacz, Marek; Meng, Haijing; Kapustin, Dmitry I.; Kulakov, Valery I.

    2017-10-01

    The reaction of tantalum with molecular hydrogen was studied by x-ray diffraction in a diamond-anvil cell at room temperature and pressures from 1 to 41 GPa. At pressures up to 5.5 GPa, a substoichiometric tantalum monohydride with a distorted bcc structure was shown to be stable. Its hydrogen content gradually increased with the pressure increase, reaching H /Ta =0.92 (5 ) at 5 GPa. At higher pressures, a new dihydride phase of tantalum was formed. This phase had an hcp metal lattice, and its hydrogen content was virtually independent of pressure. When the pressure was decreased, the tantalum dihydride thus obtained transformed back to the monohydride at P =2.2 GPa . Single-phase samples of tantalum dihydride also were synthesized at a hydrogen pressure of 9 GPa in a toroid-type high-pressure apparatus, quenched to the liquid-N2 temperature, and studied at ambient pressure. X-ray diffraction showed them to have an hcp metal lattice with a =3.224 (3 ) and c =5.140 (5 )Å at T =85 K . The hydrogen content determined by thermal desorption was H /Ta =2.2 (1 ) .

  3. High-pressure crystallography of periodic and aperiodic crystals

    Directory of Open Access Journals (Sweden)

    Clivia Hejny

    2015-03-01

    Full Text Available More than five decades have passed since the first single-crystal X-ray diffraction experiments at high pressure were performed. These studies were applied historically to geochemical processes occurring in the Earth and other planets, but high-pressure crystallography has spread across different fields of science including chemistry, physics, biology, materials science and pharmacy. With each passing year, high-pressure studies have become more precise and comprehensive because of the development of instrumentation and software, and the systems investigated have also become more complicated. Starting with crystals of simple minerals and inorganic compounds, the interests of researchers have shifted to complicated metal–organic frameworks, aperiodic crystals and quasicrystals, molecular crystals, and even proteins and viruses. Inspired by contributions to the microsymposium `High-Pressure Crystallography of Periodic and Aperiodic Crystals' presented at the 23rd IUCr Congress and General Assembly, the authors have tried to summarize certain recent results of single-crystal studies of molecular and aperiodic structures under high pressure. While the selected contributions do not cover the whole spectrum of high-pressure research, they demonstrate the broad diversity of novel and fascinating results and may awaken the reader's interest in this topic.

  4. In-situ neutron diffraction of LaCoO3 perovskite under uniaxial compression. I. Crystal structure analysis and texture development

    Science.gov (United States)

    Aman, Amjad; Chen, Yan; Lugovy, Mykola; Orlovskaya, Nina; Reece, Michael J.; Ma, Dong; Stoica, Alexandru D.; An, Ke

    2014-07-01

    The dynamics of texture formation, changes in crystal structure, and stress accommodation mechanisms have been studied in perovskite-type R3¯c rhombohedral LaCoO3 during uniaxial compression using in-situ neutron diffraction. The in-situ neutron diffraction revealed the complex crystallographic changes causing the texture formation and significant straining along certain crystallographic directions during compression, which are responsible for the appearance of hysteresis and non-linear ferroelastic deformation in the LaCoO3 perovskite. The irreversible strain after the first loading was connected with the appearance of non-recoverable changes in the intensity ratio of certain crystallographic peaks, causing non-reversible texture formation. However, in the second loading/unloading cycle, the hysteresis loop was closed and no further irrecoverable strain appeared after deformation. The significant texture formation is responsible for an increase in the Young's modulus of LaCoO3 at high compressive stresses, ranging from 76 GPa at the very beginning of the loading to 194 GPa at 900 MPa at the beginning of the unloading curve.

  5. In-situ neutron diffraction of LaCoO3 perovskite under uniaxial compression. I. Crystal structure analysis and texture development

    Energy Technology Data Exchange (ETDEWEB)

    Aman, Amjad [ORNL; Chen, Yan [ORNL; Lugovy, Mykola [University of Central Florida; Orlovskaya, Nina [ORNL; Reece, Michael John [University of London; Ma, Dong [ORNL; Stoica, Alexandru Dan [ORNL; An, Ke [ORNL

    2014-01-01

    The dynamics of texture formation, changes in crystal structure and stress accommodation mechanisms are studied in R3c rhombohedral LaCoO3 perovskite during in-situ uniaxial compression experiment by neutron diffraction. The neutron diffraction revealed the complex crystallographic changes causing the texture formation and significant straining along certain crystallographic directions during in-situ compression, which are responsible for the appearance of hysteresis and non-linear ferroelastic deformation in LaCoO3 perovskite. The irreversible strain after the first loading was connected with the appearance of non-recoverable changes in the intensity ratio of certain crystallographic peaks, causing non-reversible texture formation. However in the second loading/unloading cycle the hysteresis loop was closed and no irreversible strain appears after deformation. The significant texture formation is responsible for increase in the Young s modulus of LaCoO3 at high compressive loads, where the reported values of Young s modulus increase from 76 GPa measured at the very beginning of the loading to 194 GPa at 900 MPa applied compressive stress measured at the beginning of the unloading curve.

  6. Crystal structure relation between tetragonal and orthorhombic CsAlD{sub 4}: DFT and time-of-flight neutron powder diffraction studies

    Energy Technology Data Exchange (ETDEWEB)

    Bernert, Thomas; Krech, Daniel; Felderhoff, Michael; Weidenthaler, Claudia [Department of Heterogeneous Catalysis, Max-Planck-Institut fuer Kohlenforschung, Muelheim/Ruhr (Germany); Kockelmann, Winfried [Rutherford Appleton Laboratory, Harwell Oxford, Didcot (United Kingdom); Frankcombe, Terry J. [Research School of Chemistry, The Australian National University, Canberra, ACT (Australia); School of Physical, Environmental and Mathematic Sciences, The University of New South Wales, Canberra, ACT (Australia)

    2015-11-15

    The crystal structures of orthorhombic and tetragonal CsAlD{sub 4} were refined from time-of-flight neutron powder diffraction data starting from atomic positions predicted from DFT calculations. The earlier proposed crystal structure of orthorhombic CsAlH{sub 4} is confirmed. For tetragonal CsAlH{sub 4}, DFT calculations predicted a crystal structure in I4{sub 1}/amd as potential minimum structure, while from neutron diffraction studies of CsAlD{sub 4} best refinement is obtained for a disordered structure in the space group I4{sub 1}/a, with a = 5.67231(9) Aa, c = 14.2823(5) Aa. While the caesium atoms are located on the Wyckoff position 4b and aluminium at Wyckoff position 4a, there are two distinct deuterium positions at the Wyckoff position 16f with occupancies of 50 % each. From this structure, the previously reported phase transition between the orthorhombic and tetragonal polymorphs could be explained. (Copyright copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Combined X-ray and neutron diffraction study of vacancies and disorder in the dimorphic clathrate Ba8Ga16Sn30 of type I and VIII.

    Science.gov (United States)

    Christensen, Sebastian; Avila, Marcos A; Suekuni, Koichiro; Piltz, Ross; Takabatake, Toshiro; Christensen, Mogens

    2013-10-01

    We report detailed structural investigations of the dimorphic clathrate Ba8Ga16Sn30 that crystallizes in both type I and VIII clathrate structures. Single crystals of type I and VIII have been examined using single crystal X-ray and Laue neutron diffraction in the temperature range T = 10 K-500 K. The utilization of both X-ray and neutron diffraction gives a unique ability to reveal the occurrence of minute vacancy occupancies in the host structure. The vacancies are shown to be located on the 6c (type I) and 24g (type VIII) framework sites. Largest vacancy densities are observed for type I p-Ba8Ga16Sn30, 1.3(4)%, and type VIII n-Ba8Ga16Sn30, 0.7(2)%. The relation between guest atom disorder and occurrence of glasslike thermal conductivity in intermetallic clathrates was also investigated. In type VIII Ba8Ga16Sn30 neither n-type (crystalline thermal conductivity) nor p-type (glasslike thermal conductivity) showed any significant disorder of the guest atoms; they do however show anharmonic motion. The glasslike thermal conductivity of p-type Ba8Ga16Sn30 is interpretable as a result of higher effective mass of p-type charge-carriers affecting phonon scattering. In type I Ba8Ga16Sn30 guest atoms are highly disordered for both carrier types and samples of both charge carrier types have glasslike thermal conductivity.

  8. In-Situ High Temperature Neutron Diffraction Study of Bi,Pb(2223) Phase Formation in Ag-Sheathed Monofilamentary Tapes

    Science.gov (United States)

    Giannini, E.; Bellingeri, E.; Passerini, R.; Flükiger, R.

    High temperature neutron diffraction measurements were performed on Bi(2223)/Ag-sheathed monofilamentary tapes at the ILL high-flux reactor in Grenoble. Reactions leading to the conversion from Bi(2212) to Bi,Pb(2223), as well as other transformations involving secondary phases, were directly observed during the reaction heat treatment. The heating ramp and annealing conditions were exactly the same as those used for standard high-performance tapes processing. A quantitative analysis was carried out by means of a full-pattern profile refinement technique: up to 7 phases were simultaneously detected and successfully refined. An increase of the Bi(2212) phase during a slow cooling was found not to be related to a decomposition of Bi,Pb(2223), which remained stable during cooling. The role of secondary cuprates, in particular (Ca,Sr)14Cu24 O41, was investigated. Since neutron diffraction allows for an absolute measurement of the weight of crystalline matter inside the sample, it was possible to measure the total crystalline matter amount as a function of temperature and time during processing. Evidence of partial melting at high temperature was found strongly supporting the Bi,Pb(2223) formation via a nucleation-and-growth mechanism at the early stage of the process.

  9. The influence of peak shock stress on the high pressure phase transformation in zirconium

    Directory of Open Access Journals (Sweden)

    Brown D.W.

    2012-08-01

    Full Text Available At high pressures zirconium is known to undergo a phase transformation from the hexagonal close packed (HCP alpha phase to the simple hexagonal omega phase. Under conditions of shock loading, the high-pressure omega phase is retained upon release. However, the hysteresis in this transformation is not well represented by equilibrium phase diagrams and currently models that accurately represent such a solid-solid phase transformation coupled with the multi-phase plasticity likely under shock conditions do not exist. For this reason, the influence of peak shock stress on the retention of omega phase in Zr is explored in this study. In-situ VISAR measurements along with post-mortem metallographic and neutron diffraction characterization of soft recovered specimens have been utilized to quantify the volume fraction of retained omega phase, morphology of the shocked alpha and omega phases, and qualitatively understand the kinetics of this transformation. This understanding of the role of peak shock stress will be utilized to address physics to be encoded in our present macro-scale models.

  10. Application of neutron diffraction in characterization of texture evolution during high-temperature creep in magnesium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Vogel, Sven C [Los Alamos National Laboratory; Sediako, Dimitry [CANADIAN NEUTRON BEAM; Shook, S [APPLIED MAGNESIUM INTERNATIONAL; Sediako, A [MCGILL UNIV

    2010-01-01

    A good combination of room-temperature and elevated temperature strength and ductility, good salt-spray corrosion resistance and exceUent diecastability are frequently among the main considerations in development of a new alloy. Unfortunately, there has been much lesser effort in development of wrought-stock alloys for high temperature applications. Extrudability and high temperature performance of wrought material becomes an important factor in an effort to develop new wrought alloys and processing technologies. This paper shows some results received in creep testing and studies of in-creep texture evolution for several wrought magnesium alloys developed for use in elevated-temperature applications. These studies were performed using E3 neutron spectrometer of the Canadian Neutron Beam Centre in Chalk River, ON, and HIPPO time-of-flight (TOF) spectrometer at Los Alamos Neutron Science Center, NM.

  11. Neutron diffraction and TSDC on Ba1−xUxF2+2x solid electrolytes

    DEFF Research Database (Denmark)

    Ouwerkerk, M.; Andersen, N. H.; Veldkamp, F. F.

    1986-01-01

    The defect structure of fluorite-type Ba1−xUxF2+2x solid solutions, which exhibit fast fluoride ion conductivity, has been investigated by quasi-elastic diffuse neutron scattering (QDNS) experiments, and thermally stimulated depolarisation current (TSDC) measurements. A comparison with model...

  12. High pressure processing of meat

    DEFF Research Database (Denmark)

    Grossi, Alberto; Christensen, Mette; Ertbjerg, Per

    Abstract Background: The research of high pressure (HP) processing of meat based foods needs to address how pressure affects protein interactions, aggregation and/or gelation. The understanding of the gel forming properties of myofibrillar components is fundamental for the development of muscle...... based products (Chapleau et al., 2004;Colmenero, 2002). Object: The aim was to study the rheological properties of pork meat emulsion exposed to HP and the effect of HP on the aggregation state of myofibrillar proteins. To address the role of cathepsin in myofibrillar protein degradation the changes...... in the myofibrillar protein pattern and HP-induced change in activity of cathepsin B and L were investigated. Results: In this study we showed that HP treatment of pork meat emulsion, ranging from 0.1 to 800 MPa, induced protein gel formation as shown by the increased Young’s modulus (Fig.1). Analysis of SDS...

  13. Deformation Twinning of a Silver Nanocrystal under High Pressure

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Xiaojing; Yang, Wenge; Harder, Ross; Sun, Yugang; Liu, Ming; Chu, Yong S.; Robinson, Ian K.; Mao, Ho-kwang

    2015-11-01

    Within a high-pressure environment, crystal deformation is controlled by complex processes such as dislocation motion, twinning, and phase transitions, which change materials' microscopic morphology and alter their properties. Understanding a crystal's response to external stress provides a unique opportunity for rational tailoring of its functionalities. It is very challenging to track the strain evolution and physical deformation from a single nanoscale crystal under high-pressure stress. Here, we report an in situ three-dimensional mapping of morphology and strain evolutions in a single-crystal silver nanocube within a high-pressure environment using the Bragg Coherent Diffractive Imaging (CDI) method. We observed a continuous lattice distortion, followed by a deformation twining process at a constant pressure. The ability to visualize stress-introduced deformation of nanocrystals with high spatial resolution and prominent strain sensitivity provides an important route for interpreting and engineering novel properties of nanomaterials.

  14. Deformation Twinning of a Silver Nanocrystal under High Pressure

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Xiaojing; Yang, Wenge; Harder, Ross; Sun, Yugang; Lu, Ming; Chu, Yong S.; Robinson, Ian K.; Mao, Ho-kwang

    2015-10-20

    Within a high-pressure environment, crystal deformation is controlled by complex processes such as dislocation motion, twinning, and phase transitions, which change materials’ microscopic morphology and alter their properties. Understanding a crystal’s response to external stress provides a unique opportunity for rational tailoring of its functionalities. It is very challenging to track the strain evolution and physical deformation from a single nanoscale crystal under high-pressure stress. Here, we report an in situ three-dimensional mapping of morphology and strain evolutions in a single-crystal silver nanocube within a high-pressure environment using the Bragg Coherent Diffractive Imaging (CDI) method. We observed a continuous lattice distortion, followed by a deformation twining process at a constant pressure. The ability to visualize stress-introduced deformation of nanocrystals with high spatial resolution and prominent strain sensitivity provides an important route for interpreting and engineering novel properties of nanomaterials.

  15. Crystallization of a fungal lytic polysaccharide monooxygenase expressed from glycoengineered Pichia pastoris for X-ray and neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    O; Dell, William B.; Swartz, Paul D.; Weiss, Kevin L.; Meilleur, Flora (ORNL); (NCSU)

    2017-01-19

    Lytic polysaccharide monooxygenases (LPMOs) are carbohydrate-disrupting enzymes secreted by bacteria and fungi that break glycosidic bondsviaan oxidative mechanism. Fungal LPMOs typically act on cellulose and can enhance the efficiency of cellulose-hydrolyzing enzymes that release soluble sugars for bioethanol production or other industrial uses. The enzyme PMO-2 fromNeurospora crassa(NcPMO-2) was heterologously expressed inPichia pastoristo facilitate crystallographic studies of the fungal LPMO mechanism. Diffraction resolution and crystal morphology were improved by expressingNcPMO-2 from a glycoengineered strain ofP. pastorisand by the use of crystal seeding methods, respectively. These improvements resulted in high-resolution (1.20 Å) X-ray diffraction data collection at 100 K and the production of a largeNcPMO-2 crystal suitable for room-temperature neutron diffraction data collection to 2.12 Å resolution.

  16. High pressure studies on uranium and thorium silicide compounds: Experiment and theory

    DEFF Research Database (Denmark)

    Yagoubi, S.; Heathman, S.; Svane, A.

    2013-01-01

    The actinide silicides ThSi, USi and USi2 have been studied under high pressure using both theory and experiment. High pressure synchrotron X-ray diffraction experiments were performed on polycrystalline samples in diamond anvil cells at room temperature and for pressures up to 54, 52 and 26 GPa,...

  17. Suppression of magnetic order in CaCo1.86As2 with Fe substitution: Magnetization, neutron diffraction, and x-ray diffraction studies of Ca (Co1-xFex) yAs2

    Science.gov (United States)

    Jayasekara, W. T.; Pandey, Abhishek; Kreyssig, A.; Sangeetha, N. S.; Sapkota, A.; Kothapalli, K.; Anand, V. K.; Tian, W.; Vaknin, D.; Johnston, D. C.; McQueeney, R. J.; Goldman, A. I.; Ueland, B. G.

    2017-02-01

    Magnetization, neutron diffraction, and high-energy x-ray diffraction results for Sn-flux grown single-crystal samples of Ca (Co1-xFex) yAs2 , 0 ≤x ≤1 , 1.86 ≤y ≤2 , are presented and reveal that A-type antiferromagnetic order, with ordered moments lying along the c axis, persists for x ≲0.12 (1 ) . The antiferromagnetic order is smoothly suppressed with increasing x , with both the ordered moment and Néel temperature linearly decreasing. Stripe-type antiferromagnetic order does not occur for x ≤0.25 , nor does ferromagnetic order for x up to at least x =0.104 , and a smooth crossover from the collapsed-tetragonal (cT) phase of CaCo1.86As2 to the tetragonal (T) phase of CaFe2As2 occurs. These results suggest that hole doping CaCo1.86As2 has a less dramatic effect on the magnetism and structure than steric effects due to substituting Sr for Ca.

  18. Decomposition of silicon carbide at high pressures and temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Daviau, Kierstin; Lee, Kanani K. M.

    2017-11-01

    We measure the onset of decomposition of silicon carbide, SiC, to silicon and carbon (e.g., diamond) at high pressures and high temperatures in a laser-heated diamond-anvil cell. We identify decomposition through x-ray diffraction and multiwavelength imaging radiometry coupled with electron microscopy analyses on quenched samples. We find that B3 SiC (also known as 3C or zinc blende SiC) decomposes at high pressures and high temperatures, following a phase boundary with a negative slope. The high-pressure decomposition temperatures measured are considerably lower than those at ambient, with our measurements indicating that SiC begins to decompose at ~ 2000 K at 60 GPa as compared to ~ 2800 K at ambient pressure. Once B3 SiC transitions to the high-pressure B1 (rocksalt) structure, we no longer observe decomposition, despite heating to temperatures in excess of ~ 3200 K. The temperature of decomposition and the nature of the decomposition phase boundary appear to be strongly influenced by the pressure-induced phase transitions to higher-density structures in SiC, silicon, and carbon. The decomposition of SiC at high pressure and temperature has implications for the stability of naturally forming moissanite on Earth and in carbon-rich exoplanets.

  19. Temperature induced phase transformations and microstructural changes in nanostructured FeCu solid solutions using in situ neutron powder thermo-diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Blanco, D. [Unidad de Magnetometria, SCT' s, Universidad de Oviedo, Julian Claveria, 8, 33006 Oviedo (Spain); Departamento de Fisica, Universidad de Oviedo, Calvo Sotelo s/n, Oviedo 33007 (Spain); Gorria, P., E-mail: pgorria@uniovi.e [Departamento de Fisica, Universidad de Oviedo, Calvo Sotelo s/n, Oviedo 33007 (Spain); Blanco, J.A. [Departamento de Fisica, Universidad de Oviedo, Calvo Sotelo s/n, Oviedo 33007 (Spain); Smith, R.I. [ISIS facility, RAL, Chilton, Didcot, Oxon OX11 0QX (United Kingdom)

    2009-08-26

    In situ neutron powder thermo-diffraction experiments in the temperature range from 300 K to 1170 K have been carried out in nanostructured and metastable Fe{sub 15}Cu{sub 85} and Fe{sub 85}Cu{sub 15} solid solutions, which were synthesized by means of a mechanical alloying technique. We report on the microstructural changes and the phase transformations that take place during controlled heating and cooling processes. The average crystalline grain size is similar for both samples in the as-milled state (approx16-20 nm) while the induced strain is 2.5 times higher in the Fe-rich powders, reaching 1%. Moreover, the alpha-gamma transformation for Fe{sub 15}Cu{sub 85} starts at temperatures lower (approx900 K) than that expected for pure Fe (1183 K) due likely to the existence of local inhomogeneities in the composition of the ball milled material.

  20. Neutron diffraction study of the formation kinetics of ordered antiphase domains in titanium carbohydride TiC{sub x}H{sub y}

    Energy Technology Data Exchange (ETDEWEB)

    Khidirov, I., E-mail: khidirov@inp.uz [Uzbekistan Academy of Sciences, Institute of Nuclear Physics (Uzbekistan)

    2015-09-15

    The kinetics of formation and growth of ordered antiphase domains (APDs) in titanium carbohydride TiC{sub 0.50}H{sub 0.21} has been investigated by neutron diffraction. A model of ordered APDs is proposed. It is established that the pronounced ordering of interstitial atoms and APDs begin at 450°C. It is shown that the period of ordered APDs (P ≈ 10–12) is independent of the exposure time at a constant temperature. It is found that the temperature of ordered APDs, T{sub OAPD}, increases nonlinearly with an increase in the carbon concentration in the range 0.50 ≤ C/Ti ≤ 0.70. The formation temperature of ordered APDs is found to correlate with the concentration dependence of the order–disorder transition temperature and be 0.60 of the order–disorder transition temperature: T{sub APD} = 0.60Τ{sub C}.

  1. Local Jahn-Teller distortion in La{sub 1{minus}x}Sr{sub x}MnO{sub 3} observed by pulsed neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Louca, D.; Egami, T. [Department of Materials Science and Engineering and Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States); Brosha, E.L.; Roeder, H.; Bishop, A.R. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    1997-10-01

    The atomic pair-density function of La{sub 1{minus}x}Sr{sub x}MnO{sub 3} (0{le}x{le}0.4) obtained by pulsed neutron diffraction indicates that their local atomic structure significantly deviates from the average structure, and that the local Jahn-Teller (JT) distortion persists even when the crystallographic structure shows no JT distortion. In the paramagnetic insulating phase doped holes form one-site small polarons, represented by the local absence of JT distortion. The polarons become more extended at low temperatures, but local distortions are found even in the metallic phase. The role of polarons in the phase transitions in transport and magnetic properties are discussed. {copyright} {ital 1997} {ital The American Physical Society}

  2. Evidence for incomplete martensitic transformation in Ni{sub 0.62}Al{sub 0.38} by neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Kelley, Darren [Department of Physics, University of Virginia, 382 McCormick Road, P.O. Box 400714, Charlottesville, VA 22904 (United States); Louca, Despina [Department of Physics, University of Virginia, 382 McCormick Road, P.O. Box 400714, Charlottesville, VA 22904 (United States)]. E-mail: louca@virginia.edu

    2005-09-15

    High-resolution neutron powder diffraction was used to investigate the evolution of the crystal structure of Ni{sub 0.62}Al{sub 0.38} with a martensitic transformation temperature, M {sub S}, of 65 K as a function of temperature. Although the {beta}{sub 2} parent phase has the propensity to nucleation instability, no precursor effects are observed until {approx}40 deg. above M {sub S}. Below M {sub S}, the transition does not occur homogeneously and it is shown that the martensite coexists with the austenite over a wide temperature range. The low temperature phase seems to be largely described by the 7R structure that accomodates the transition from the parent to the martensite and minimizes the lattice mismatch between the two.

  3. In Situ Neutron Diffraction Study of the Influence of Microstructure on the Mechanical Response of Additively Manufactured 304L Stainless Steel

    Science.gov (United States)

    Brown, D. W.; Adams, D. P.; Balogh, L.; Carpenter, J. S.; Clausen, B.; King, G.; Reedlunn, B.; Palmer, T. A.; Maguire, M. C.; Vogel, S. C.

    2017-12-01

    In situ neutron diffraction measurements were completed during tensile and compressive deformation of stainless steel 304L additively manufactured (AM) using a high power directed energy deposition process. Traditionally produced wrought 304L material was also studied for comparison. The AM material exhibited roughly 200 MPa higher flow stress relative to the wrought material. Crystallite size, crystallographic texture, dislocation density, and lattice strains were all characterized to understand the differences in the macroscopic mechanical behavior. The AM material's initial dislocation density was about 10 times that of the wrought material, and the flow strength of both materials obeyed the Taylor equation, indicating that the AM material's increased yield strength was primarily due to greater dislocation density. Also, a 50 MPa flow strength tension/compression asymmetry was observed in the AM material, and several potential causes were examined.

  4. Sodium Ion Transport Mechanisms in Antiperovskite Electrolytes Na3OBr and Na4OI2: An in Situ Neutron Diffraction Study.

    Science.gov (United States)

    Zhu, Jinlong; Wang, Yonggang; Li, Shuai; Howard, John W; Neuefeind, Jörg; Ren, Yang; Wang, Hui; Liang, Chengdu; Yang, Wenge; Zou, Ruqiang; Jin, Changqing; Zhao, Yusheng

    2016-06-20

    Na-rich antiperovskites are recently developed solid electrolytes with enhanced sodium ionic conductivity and show promising functionality as a novel solid electrolyte in an all solid-state battery. In this work, the sodium ionic transport pathways of the parent compound Na3OBr, as well as the modified layered antiperovskite Na4OI2, were studied and compared through temperature-dependent neutron diffraction combined with the maximum entropy method. In the cubic Na3OBr antiperovskite, the nuclear density distribution maps at 500 K indicate that sodium ions hop within and among oxygen octahedra, and Br(-) ions are not involved. In the tetragonal Na4OI2 antiperovskite, Na ions, which connect octahedra in the ab plane, have the lowest activation energy barrier. The transport of sodium ions along the c axis is assisted by I(-) ions.

  5. Novel Pr-Cu magnetic phase at low temperature in PrBa2Cu3O6+x observed by neutron diffraction

    DEFF Research Database (Denmark)

    Boothroyd, A.T.; Longmore, A.; Andersen, N.H.

    1997-01-01

    We have studied by neutron diffraction the magnetic ordering in Al-free crystals of PrBa2Cu3O6+x (x = 0.35 and 0.92) that do not display the AFII Cu magnetic phase. Wt find that the Pr ordering below 20 K is accompanied by a counterrotation of the Cu antiferromagnetism on each plane of the bilayer....... The maximum turn angle between the two planes is 60 degrees +/- 9 degrees for the x = 0.92 crystal, and 40 degrees +/- 11 degrees for the x = 0.35 crystal. This is the first observation of a noncollinear ordering of Cu moments in the bilayer, and is evidence for significant magnetic coupling between the Cu...

  6. In Situ Neutron Diffraction Study of the Influence of Microstructure on the Mechanical Response of Additively Manufactured 304L Stainless Steel

    Science.gov (United States)

    Brown, D. W.; Adams, D. P.; Balogh, L.; Carpenter, J. S.; Clausen, B.; King, G.; Reedlunn, B.; Palmer, T. A.; Maguire, M. C.; Vogel, S. C.

    2017-10-01

    In situ neutron diffraction measurements were completed during tensile and compressive deformation of stainless steel 304L additively manufactured (AM) using a high power directed energy deposition process. Traditionally produced wrought 304L material was also studied for comparison. The AM material exhibited roughly 200 MPa higher flow stress relative to the wrought material. Crystallite size, crystallographic texture, dislocation density, and lattice strains were all characterized to understand the differences in the macroscopic mechanical behavior. The AM material's initial dislocation density was about 10 times that of the wrought material, and the flow strength of both materials obeyed the Taylor equation, indicating that the AM material's increased yield strength was primarily due to greater dislocation density. Also, a 50 MPa flow strength tension/compression asymmetry was observed in the AM material, and several potential causes were examined.

  7. Crystal structure of acetanilide at 15 and 295 K by neutron diffraction. Lack of evidence for proton transfer along the N-H...O hydrogen bond

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, S.W.; Eckert, J. [Los Alamos National Lab., NM (United States); Barthes, M. [Universite Montpellier II (France); McMullan, R.K. [Brookhaven National Lab., Upton, NY (United States); Muller, M. [Universite Lille I, Villeneuve d`Ascq (France)

    1995-11-02

    The crystal structure of acetanilide C{sub 8}H{sub 9}NO, M{sub r} = 135.17, orthorhombic, space group Pbca, Z=8, has been determined from neutron diffraction data at 15 and 295 K. The crystal data obtained are presented. This new investigation of the structure of acetanilide has been undertaken in order to assess a recent suggestion that confirmational substates in the amide proton position may be responsible for the vibrational anomalies. We found no evidence for multiple conformations or transfer along the N-H...O hydrogen bond of the amide proton at either temperature. However the intramolecular O...H6 distance from O to the nearest phenyl ring proton is unusually short and the amide proton has relatively close contacts with one of the phenyl and one of the methyl protons, which may well affect the vibrational parameters of the respective molecular groups. 44 refs., 6 figs., 5 tabs.

  8. Characterization of white poplar and eucalyptus after ionic liquid pretreatment as a function of biomass loading using X-ray diffraction and small angle neutron scattering

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Xueming [Beijing Univ. of Chemical Technology (China); Duan, Yonghao [Beijing Univ. of Chemical Technology (China); He, Lilin [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Singh, Seema [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Joint BioEnergy Inst. (JBEI), Emeryville, CA (United States); Simmons, Blake [Joint BioEnergy Inst. (JBEI), Emeryville, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Cheng, Gang [Beijing Univ. of Chemical Technology (China); Joint BioEnergy Inst. (JBEI), Emeryville, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2017-02-08

    A systematic study was done to understand interactions among biomass loading during ionic liquid (IL) pretreatment, biomass type and biomass structures. White poplar and eucalyptus samples were pretreated using 1-ethyl-3-methylimidazolium acetate (EmimOAc) at 110 °C for 3 h at biomass loadings of 5, 10, 15, 20 and 25 wt%. All of the samples were chemically characterized and tested for enzymatic hydrolysis. Physical structures including biomass crystallinity and porosity were measured by X-ray diffraction (XRD) and small angle neutron scattering (SANS), respectively. SANS detected pores of radii ranging from ~25 to 625 Å, enabling assessment of contributions of pores with different sizes to increased porosity after pretreatment. Contrasting dependences of sugar conversion on white poplar and eucalyptus as a function of biomass loading were observed and cellulose crystalline structure was found to play an important role.

  9. In-situ time-of-flight neutron diffraction of ErD2 (beta phase) formation during D2 loading.

    Energy Technology Data Exchange (ETDEWEB)

    Browning, James Frederick (Oak Ridge National Laboratory, Oak Ridge, TN); Llobet, Anna (Los Alamos National Laboratory, Los Alamos, NM); Snow, Clark Sheldon; Rodriguez, Mark Andrew; Wixom, Ryan R.

    2008-06-01

    In an effort to better understand the structural changes occurring during hydrogen loading of erbium target materials, we have performed D{sub 2} loading of erbium metal (powder) with simultaneous neutron diffraction analysis. This experiment tracked the conversion of Er metal to the {alpha} erbium deuteride (solid-solution) phase and then on to the {beta} (fluorite) phase. Complete conversion to ErD{sub 2.0} was accomplished at 10 Torr D{sub 2} pressure with deuterium fully occupying the tetrahedral sites in the fluorite lattice. Increased D{sub 2} pressure (up to 500 Torr at 450 C) revealed {approx}10 % deuterium occupation of the octahedral sites. Subsequent vacuum pumping of the sample at 450 C removed octahedral site occupancy while maintaining tetrahedral deuterium occupancy, thereby yielding stoichiometric ErD{sub 2.0} {beta} phase.

  10. Hydrogen molecule binding to unsaturated metal sites in metal-organic frameworks studied by neutron powder diffraction and inelastic neutron scattering

    Science.gov (United States)

    Liu, Yun; Brown, Craig; Neumann, Dan; Dinca, Mircea; Long, Jeffrey; Peterson, Vanessa; Kepert, Cameron

    2007-03-01

    Metal organic framework (MOF) materials have shown considerable potential for hydrogen storage arising from very large surface areas. However, the low binding energy of hydrogen molecules limits its storage capability to very low temperatures (hydrogen adsorption sites in a selected series of MOF materials with exposed unsaturated metal ions. Direct binding between the unsaturated metal ions and hydrogen molecules is observed and responsible for the enhanced initial hydrogen adsorption enthalpy. The different metals centers in these MOFs show different binding strength and interaction distances between the hydrogen molecule and metal ions. The organic linker also affects the overall H2 binding strength. Inelastic neutron scattering spectra of H2 in these MOFs are also discussed.

  11. Cation distribution and crystallographic characterization of the spinel oxides MgCr{sub x}Fe{sub 2−x}O{sub 4} by neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Zakaria, A.K.M., E-mail: zakaria6403@yahoo.com [Institute of Nuclear Science & Technology, Bangladesh Atomic Energy Commission, Dhaka (Bangladesh); Nesa, Faizun [Department of Natural Science, Daffodil International University, Dhaka (Bangladesh); Department of Physics, Jahangirnagar University, Savar, Dhaka (Bangladesh); Saeed Khan, M.A. [Department of Physics, Jahangirnagar University, Savar, Dhaka (Bangladesh); Datta, T.K.; Aktar, Sanjida; Liba, Samia Islam; Hossain, Shahzad; Das, A.K.; Kamal, I.; Yunus, S.M. [Institute of Nuclear Science & Technology, Bangladesh Atomic Energy Commission, Dhaka (Bangladesh); Eriksson, S.-G. [Department of Chemical and Biological Engineering, Chalmers University of Technology, Gothenburg (Sweden)

    2015-06-05

    Highlights: • MgCr{sub x}Fe{sub 2−x}O{sub 4} ferrites crystallize at 1300 °C and possess cubic symmetry. • Cation distribution and crystallographic parameters have been determined precisely. • Cell parameter decreases with increasing Cr content in the system. • Ferrimagnetic ordering was found at room temperature for all the samples. - Abstract: The spinel system MgCr{sub x}Fe{sub 2−x}O{sub 4} (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) has been prepared by solid state sintering method in air at 1573 K. X-ray and neutron powder diffraction experiments have been performed on the samples at room temperature for structural characterization. Rietveld refinement of the neutron diffraction data reveals that all the samples of the series possess cubic symmetry corresponding to the space group F d-3m. The distribution of the three cations Mg, Fe and Cr over the two sublattices and other crystallographic parameters has been determined precisely. The results reveal that Cr has been substituted for Fe selectively. Cr ions invariably occupy the octahedral (B) site for all values of x. Mg and Fe ions are distributed over both A and B sites for all x values. With increasing x the occupation of Mg increases in the A site and decreases in the B site for all the samples, while the Fe ions gradually decreases in both the sites for all values of x. The lattice constant decreases with increasing Cr content in the system. The magnetic structure at room temperature was ferrimagnetic for all the samples.

  12. Metal ion roles and the movement of hydrogen during the reaction catalyzed by d-xylose isomerase: a joint X-ray and neutron diffraction study

    Science.gov (United States)

    Kovalevsky, Andrey Y.; Hanson, Leif; Fisher, S. Zoe; Mustyakimov, Marat; Mason, Sax; Forsyth, Trevor; Blakeley, Matthew P.; Kean, David. A.; Wagner, Trixie; Carrell, H. L.; Katz, Amy K.; Glusker, Jenny P.; Langan, Paul

    2010-01-01

    SUMMARY Conversion of aldo to keto sugars by the metalloenzyme d-xylose isomerase (XI) is a multi-step reaction involving hydrogen transfer. We have determined the structure of this enzyme by neutron diffraction in order to locate H atoms (or their isotope D). Two studies are presented, one of XI containing cadmium and cyclic d-glucose (before sugar ring opening has occurred), and the other containing nickel and linear d-glucose (after ring opening has occurred but before isomerization). Previously we reported the neutron structures of ligand-free enzyme and enzyme with bound product. Data show that His54 is doubly protonated on the ring N in all four structures. Lys289 is neutral before ring opening, and gains a proton after this, the catalytic metal-bound water is deprotonated to hydroxyl during isomerization and O5 is deprotonated. These results lead to new suggestions as to how changes might take place over the course of the reaction. PMID:20541506

  13. Assessment of firing conditions in old fired-clay bricks: The contribution of X-ray powder diffraction with the Rietveld method and small angle neutron scattering

    Energy Technology Data Exchange (ETDEWEB)

    Viani, Alberto, E-mail: viani@itam.cas.cz [Institute of Theoretical and Applied Mechanics AS CR, Centre of Excellence Telč, Batelovská 485, CZ-58856 Telč (Czech Republic); Sotiriadis, Konstantinos [Institute of Theoretical and Applied Mechanics AS CR, Centre of Excellence Telč, Batelovská 485, CZ-58856 Telč (Czech Republic); Len, Adél [Wigner Research Centre for Physics HAS, Konkoly-Thege 29-33, 1121 Budapest (Hungary); Šašek, Petr; Ševčík, Radek [Institute of Theoretical and Applied Mechanics AS CR, Centre of Excellence Telč, Batelovská 485, CZ-58856 Telč (Czech Republic)

    2016-06-15

    Full characterization of fired-clay bricks is crucial for the improvement of process variables in manufacturing and, in case of old bricks, for restoration/replacement purposes. To this aim, five bricks produced in a plant in Czech Republic in the past have been investigated with a combination of analytical techniques in order to derive information on the firing process. An additional old brick from another brickyard was also used to study the influence of different raw materials on sample microstructure. The potential of X-ray diffraction with the Rietveld method and small angle neutron scattering technique has been exploited to describe the phase transformations taking place during firing and characterize the brick microstructure. Unit-cell parameter of spinel and amount of hematite are proposed as indicators of the maximum firing temperature, although for the latter, limited to bricks produced from the same raw material. The fractal quality of the surface area of pores obtained from small angle neutron scattering is also suggested as a method to distinguish between bricks produced from different raw clays. - Highlights: • Rietveld method helps in describing microstructure and physical properties of bricks. • XRPD derived cell parameter of spinel is proposed as an indicator of firing temperature. • SANS effectively describes brick micro and nanostructure, including closed porosity. • Fractal quality of pore surface is proposed as ‘fingerprint’ of brick manufacturing.

  14. Reply to ``Comment on `Magnetic field effects on neutron diffraction in the antiferromagnetic phase of $UPt_3$'''

    OpenAIRE

    Moreno, Juana; Sauls, J A

    2002-01-01

    Fak, van Dijk and Wills (FDW) question our interpretation of elastic neutron-scattering experiments in the antiferromagnetic phase of UPt_3. They state that our analysis is incorrect because we average over magnetic structures that are disallowed by symmetry. We disagree with FDW and reply to their criticism. FDW also point out that we have mistaken the magnetic field direction in the experiment reported by N. H. van Dijk et al. [Phys. Rev. B 58, 3186 (1998)]. We correct this error and note t...

  15. Residual stress state in an induction hardened steel bar determined by synchrotron- and neutron diffraction compared to results from lab-XRD

    Energy Technology Data Exchange (ETDEWEB)

    Holmberg, Jonas, E-mail: jonas.holmberg@swerea.se [Swerea IVF AB, Argongatan 30, 431 22 Mölndal (Sweden); University West, 461 86 Trollhättan (Sweden); Steuwer, Axel [Nelson Mandela Metropolitan University, Gardham Avenue, 6031 Port Elizabeth (South Africa); Stormvinter, Albin; Kristoffersen, Hans [Swerea IVF AB, Argongatan 30, 431 22 Mölndal (Sweden); Haakanen, Merja [Stresstech OY, Tikkutehtaantie 1, 40 800 Vaajakoski (Finland); Berglund, Johan [Swerea IVF AB, Argongatan 30, 431 22 Mölndal (Sweden)

    2016-06-14

    Induction hardening is a relatively rapid heat treatment method to increase mechanical properties of steel components. However, results from FE-simulation of the induction hardening process show that a tensile stress peak will build up in the transition zone in order to balance the high compressive stresses close to the surface. This tensile stress peak is located in the transition zone between the hardened zone and the core material. The main objective with this investigation has been to non-destructively validate the residual stress state throughout an induction hardened component. Thereby, allowing to experimentally confirming the existence and magnitude of the tensile stress peak arising from rapid heat treatment. For this purpose a cylindrical steel bar of grade C45 was induction hardened and characterised regarding the microstructure, hardness, hardening depth and residual stresses. This investigation shows that a combined measurement with synchrotron/neutron diffraction is well suited to non-destructively measure the strains through the steel bar of a diameter of 20 mm and thereby making it possible to calculate the residual stress profile. The result verified the high compressive stresses at the surface which rapidly changes to tensile stresses in the transition zone resulting in a large tensile stress peak. Measured stresses by conventional lab-XRD showed however that at depths below 1.5 mm the stresses were lower compared to the synchrotron and neutron data. This is believed to be an effect of stress relaxation from the layer removal. The FE-simulation predicts the depth of the tensile stress peak well but exaggerates the magnitude compared to the measured results by synchrotron/neutron measurements. This is an important knowledge when designing the component and the heat treatment process since this tensile stress peak will have great impact on the mechanical properties of the final component.

  16. Pargasite at high pressure and temperature

    Science.gov (United States)

    Comboni, Davide; Lotti, Paolo; Gatta, G. Diego; Merlini, Marco; Liermann, Hanns-Peter; Frost, Daniel J.

    2017-08-01

    The P-T phase stability field, the thermoelastic behavior and the P-induced deformation mechanisms at the atomic scale of pargasite crystals, from the "phlogopite peridotite unit" of the Finero mafic-ultramafic complex (Ivrea-Verbano Formation, Italy), have been investigated by a series of in situ experiments: (a) at high pressure (up to 20.1 GPa), by single-crystal synchrotron X-ray diffraction with a diamond anvil cell, (b) at high temperature (up to 823 K), by powder synchrotron X-ray diffraction using a hot air blower device, and (c) at simultaneous HP-HT conditions, by single-crystal synchrotron X-ray diffraction with a resistive-heated diamond anvil cell (P max = 16.5 GPa, T max = 1200 K). No phase transition has been observed within the P-T range investigated. At ambient T, the refined compressional parameters, calculated by fitting a second-order Birch-Murnaghan Equation of State (BM-EoS), are: V 0 = 915.2(8) Å3 and K P0,T0 = 95(2) GPa (β P0,T0 = 0.0121(2) GPa-1) for the unit-cell volume; a 0 = 9.909(4) Å and K(a) P0,T0 = 76(2) GPa for the a-axis; b 0 = 18.066(7) Å and K(b) P0,T0 = 111(2) GPa for the b-axis; c 0 = 5.299(5) Å and K(c) P0,T0 = 122(12) GPa for the c-axis [K(c) P0,T0 K(b) P0,T0 > K(a) P0,T0]. The high-pressure structure refinements (at ambient T) show a moderate contraction of the TO4 double chain and a decrease of its bending in response to the hydrostatic compression, along with a pronounced compressibility of the A- and M(4)-polyhedra [K P0, T0(A) = 38(2) GPa, K P0, T0(M4) = 79(5) GPa] if compared to the M(1)-, M(2)-, M(3)-octahedra [K P0, T0(M1,2,3) ≤ 120 GPa] and to the rigid tetrahedra [K P0, T0(T1,T2) 300 GPa]. The thermal behavior, at ambient pressure up to 823 K, was modelled with Berman's formalism, which gives: V 0 = 909.1(2) Å3, α0 = 2.7(2)·10-5 K-1 and α1 = 1.4(6)·10-9 K-2 [with α0(a) = 0.47(6)·10-5 K-1, α0(b) = 1.07(4)·10-5 K-1, and α0(c) = 0.97(7)·10-5 K-1]. The petrological implications for the experimental

  17. Bond lengths in organic and metal-organic compounds revisited: X-H bond lengths from neutron diffraction data.

    Science.gov (United States)

    Allen, Frank H; Bruno, Ian J

    2010-06-01

    The number of structures in the Cambridge Structural Database (CSD) has increased by an order of magnitude since the preparation of two major compilations of standard bond lengths in mid-1985. It is now of interest to examine whether this huge increase in data availability has implications for the mean bond-length values published in the late 1980s. Those compilations reported mean X-H bond lengths derived from rather sparse information and for rather few chemical environments. During the intervening years, the number of neutron studies has also increased, although only by a factor of around 2.25, permitting a new analysis of X-H bond-length distributions for (a) organic X = C, N, O, B, and (b) a variety of terminal and homometallic bridging transition metal hydrides. New mean values are reported here and are compared with earlier results. These new overall means are also complemented by an analysis of X-H distances at lower temperatures (T chemical environments for which statistically acceptable mean X-H bond lengths can be obtained, although values from individual structures are also collated to further extend the chemical range of this compilation. Updated default 'neutron-normalization' distances for use in hydrogen-bond and deformation-density studies are also proposed for C-H, N-H and O-H, and the low-temperature analysis provides specific values for certain chemical environments and hybridization states of X.

  18. Quasi-Laue neutron-diffraction study of the water arrangement in crystals of triclinic hen egg-white lysozyme.

    Science.gov (United States)

    Bon, C; Lehmann, M S; Wilkinson, C

    1999-05-01

    Triclinic crystals of lysozyme, hydrogen-deuterium exchanged in deuterated solvent, have been studied using neutron quasi-Laue techniques and a newly developed cylinder image-plate detector. The wavelength range employed was from 2.7 to 3.5 A, which gave 9426 significant reflections [F >/= 2sigma(F)] to a resolution limit of 1. 7 A. The deuteration states of the H atoms in the protein molecule were identified, followed by an extensive analysis of the water structure surrounding the protein. The final R factor was 20.4% (Rfree = 22.1%). In total, the 244 observed water molecules form approximately one layer of water around the protein with far fewer water molecules located further away. Water molecules covering the apolar patches make tangential layers at 4-5 A from the surface or form C-H...O contacts, and several water-molecule sites can be identified in the apolar cavities. Many of the water molecules are apparently orientationally disordered, and only 115 out of the 244 water molecules sit in mean single orientations. Comparison of these results with quasi-elastic neutron scattering observations of the water dynamics leads to a picture of the water molecules forming an extended constantly fluctuating network covering the protein surface.

  19. A-site order–disorder in the NdBaMn2O5+δ SOFC electrode material monitored in situ by neutron diffraction under hydrogen flow

    KAUST Repository

    Tonus, Florent

    2017-05-11

    The A-site disordered perovskite manganite, Nd0.5Ba0.5MnO3, has been obtained by heating the A-site-ordered and vacancy ordered layered double perovskite, NdBaMn2O5, in air at 1300 °C for 5 h. Combined transmission electron microscopy (TEM) images and neutron powder diffraction (NPD) analysis at 25 °C revealed that Nd0.5Ba0.5MnO3 has a pseudotetragonal unit cell with orthorhombic symmetry (space group Imma, √2ap × 2ap × √2ap) at 20 °C with the cell dimensions a = 5.503(1) Å, b = 7.7962(4) Å, c = 5.502(1) Å, in contrast to Pm[3 with combining macron]m or Cmcm that have been previously stated from X-ray diffraction studies. The in situ neutron diffraction study carried out on Nd0.5Ba0.5MnO3 in hydrogen flow up to T ∼ 900 °C, allows monitoring the A-site cation disorder–order structural phase transition of this representative member of potential SOFC anode materials between air sintering conditions and hydrogen working conditions. Oxygen loss from Nd0.5Ba0.5MnO3 proceeds with retention of A-site disorder until the oxygen content reaches the Nd0.5Ba0.5MnO2.5 composition at 600 °C. The phase transition to layered NdBaMn2O5 and localization of the oxygen vacancies in the Nd layer proceeds at 800 °C with retention of the oxygen content. Impedance spectroscopy measurements for the oxidized A-site ordered electrode material, NdBaMn2O6, screen printed on a Ce0.9Gd0.1O2−δ (CGO) electrolyte showed promising electrochemical performance in air at 700 °C with a polarization resistance of 1.09 Ω cm2 without any optimization.

  20. Neutron powder diffraction investigation of magnetic structure and spin reorientation transition of HoFe{sub 1-x}Cr{sub x}O{sub 3} solid solutions

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xinzhi [Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413 (China); Hao, Lijie, E-mail: haolijie@ciae.ac.cn [Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413 (China); Liu, Yuntao; Ma, Xiaobai; Meng, Siqin; Li, Yuqing; Gao, Jianbo; Guo, Hao; Han, Wenze; Sun, Kai; Wu, Meimei [Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413 (China); Chen, Xiping; Xie, Lei [Institute of Nuclear Physics and Chemistry, CAEP, Mianyang 621900 (China); Klose, Frank [Australian Nuclear Science and Technology Organization, Lucas Heights, New South Wales 2234 (Australia); Department of Physics and Materials Science, The City University of Hong Kong, Hong Kong (China); Chen, Dongfeng, E-mail: dongfeng@ciae.ac.cn [Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413 (China)

    2016-11-01

    Orthoferrite solid solution HoFe{sub 1−x}Cr{sub x}O{sub 3} (x=0, 0.2,…,1.0) was synthesized via solid state reaction methods. The crystal structure, magnetism and spin reorientation properties of this system were investigated by X-ray diffraction, neutron powder diffraction and magnetic measurements. For compositions of x≤0.6, the system exhibits similar magnetic properties to HoFeO{sub 3}. With increasing Cr-doping, the system adopts a Γ{sub 4}(G{sub x}A{sub y}F{sub z}) magnetic configuration with a decreased Neel temperature from 640 K to 360 K. A Γ{sub 42} spin reorientation of Fe(Cr){sup 3+} was also observed in this system with an increase in transition temperature from 56 K to about 200 K due to competition between the Fe(Cr)–Fe(Cr) and Ho–Fe(Cr) interactions. For the x≥0.8, the system behaves more like HoCrO{sub 3} which adopts a Γ{sub 2}(F{sub x}C{sub y}G{sub z}) configuration with no spin reorientation below the Neel temperature T{sub N}. Throughout the whole substitution range, we found that the saturated moment of Fe(Cr) was less than the ideal value for a free ion, which implies the existence of spin fluctuation in this system. A systematic magnetic structure variation with Cr-substitution is revealed by Rietveld refinement. A phase diagram combining the results of the magnetic measurements and neutron powder diffraction results was obtained. - Highlights: • With Cr-substitution in the HoFe{sub 1−x}Cr{sub x}O{sub 3} system, A Γ{sub 42} spin reorientation of Fe(Cr){sup 3+} was observed with an increase in transition temperature from 56 K to about 200 K for x=0−0.6. • The saturated moment of Fe(Cr) position was found to be systematically less than the ideal value of free ion, and thus implies the presence of spin quantum fluctuation. • A composition–temperature phase diagram throughout x=0–1 for HoFe{sub 1−x}Cr{sub x}O{sub 3} system was established.

  1. Progress report on neutron scattering at JAERI

    Energy Technology Data Exchange (ETDEWEB)

    Morii, Yukio [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-10-01

    In the first half of fiscal year 1997, JRR-3M was operated for 97 days followed by a long term shut down for its annual maintenance. Three days were lost out of 100 scheduled operation days, due to a trouble in irradiation facility. Neutron scattering research activities at the JRR-3M have been extended from that of fiscal year 1996. In the Research Group for Quantum Condensed Matter System, experimental study under high pressures, low temperatures and high fields as well as coupling of these conditions were planned to find new quantum condensed matter systems. And, obtained experimental results were immediately provided to theorists for their investigations. In cooperation with new group, Research Group for Neutron Scattering of Strongly Correlated Electron Systems and Research Group for Neutron Scattering at Ultralow Temperatures were carrying neutron scattering experiments at JRR-3M. Research Group for Neutron Crystallography in Biology had opened a way for investigating biomatter neutron diffraction research with high experimental accuracy by growing a millimeter-class large single crystal. In fiscal year 1997, 39 research projects were conducted by these four groups and other staffs in JAERI, 27 projects collaborated with university researchers and 3 projects collaborated with private enterprises were also conducted as complementary researches. 2117 days of machine times were requested to use 8 neutron scattering instruments this year, which corresponded to 1.51 times larger than those planned at its beginning. (G.K.)

  2. A search for disorder in the spin glass double perovskites Sr(2)CaReO(6) and Sr(2)MgReO(6) using neutron diffraction and neutron pair distribution function analysis.

    Science.gov (United States)

    Greedan, J E; Derakhshan, Shahab; Ramezanipour, F; Siewenie, J; Proffen, Th

    2011-04-27

    The geometrically frustrated, B-site ordered, S = 1/2, double perovskites Sr(2)CaReO(6) and Sr(2)MgReO(6), which show spin frozen magnetic ground states, have been investigated using neutron powder diffraction (ND) and neutron pair distribution function (NPDF) analysis in a search for evidence for atomic positional disorder. For both materials, data were taken above and below the spin freezing temperatures of ∼ 14 K and ∼ 45 K for the CaRe and MgRe phases, respectively. In both cases the fully B-site ordered model was in excellent agreement with the data, both ND and NPDF, at all temperatures studied. Thus, the structure of these materials, from the average and the local perspectives, is very well described by the fully B-site ordered model, which raises questions concerning the origin of the spin glass ground state. These results are compared with those for the spin glass pyrochlore Y(2)Mo(2)O(7) and other B-site ordered double perovskites.

  3. Neutron diffraction study of anomalous high-field magnetic phases in TmNi2B2C

    DEFF Research Database (Denmark)

    Toft, K.N.; Abrahamsen, A.B.; Eskildsen, M.R.

    2004-01-01

    We present a (B,T)-phase diagram of the magnetic superconductor TmNi2B2C obtained by neutron scattering. The measurements were performed in magnetic fields up to 6 T applied along the crystalline a axis. The observed phases are characterized by three ordering vectors, Q(F)=(0.094,0.094,0),Q(AI)=(0.......90Yb0.10)Ni2B2C the Q(F)-->Q(AI) phase transition is also observed but at a larger transition field compared to the undoped compound. In (Tm0.85Yb0.15)Ni2B2C the Q(F) phase persists up to at least 1.8 T. The magnetic correlation length of the Q(AI) phase in TmNi2B2C measured parallel and perpendicular...

  4. High-Pressure Lightweight Thrusters

    Science.gov (United States)

    Holmes, Richard; McKechnie, Timothy; Shchetkovskiy, Anatoliy; Smirnov, Alexander

    2013-01-01

    Returning samples of Martian soil and rock to Earth is of great interest to scientists. There were numerous studies to evaluate Mars Sample Return (MSR) mission architectures, technology needs, development plans, and requirements. The largest propulsion risk element of the MSR mission is the Mars Ascent Vehicle (MAV). Along with the baseline solid-propellant vehicle, liquid propellants have been considered. Similar requirements apply to other lander ascent engines and reaction control systems. The performance of current state-ofthe- art liquid propellant engines can be significantly improved by increasing both combustion temperature and pressure. Pump-fed propulsion is suggested for a single-stage bipropellant MAV. Achieving a 90-percent stage propellant fraction is thought to be possible on a 100-kg scale, including sufficient thrust for lifting off Mars. To increase the performance of storable bipropellant rocket engines, a high-pressure, lightweight combustion chamber was designed. Iridium liner electrodeposition was investigated on complex-shaped thrust chamber mandrels. Dense, uniform iridium liners were produced on chamber and cylindrical mandrels. Carbon/carbon composite (C/C) structures were braided over iridium-lined mandrels and densified by chemical vapor infiltration. Niobium deposition was evaluated for forming a metallic attachment flange on the carbon/ carbon structure. The new thrust chamber was designed to exceed state-of-the-art performance, and was manufactured with an 83-percent weight savings. High-performance C/Cs possess a unique set of properties that make them desirable materials for high-temperature structures used in rocket propulsion components, hypersonic vehicles, and aircraft brakes. In particular, more attention is focused on 3D braided C/Cs due to their mesh-work structure. Research on the properties of C/Cs has shown that the strength of composites is strongly affected by the fiber-matrix interfacial bonding, and that weakening

  5. Structural and energetical studies of the adsorption of para and meta-isomers of xylene on pre-hydrated zeolite BaX. Characterization by neutron diffraction and temperature programmed desorption; Etude structurale et energetique de l'adsorption des isomeres para- et meta- du xylene dans la zeolithe BaX prehydratee. Caracterisation par diffraction des neutrons et thermodesorption programmee

    Energy Technology Data Exchange (ETDEWEB)

    Pichon, Ch.

    1999-10-19

    The separation of p-xylene from C{sub 8} aromatics is performed industrially by selective adsorption on zeolitic materials. FAU-type zeolites are currently used for this separation and especially the partially hydrated BaX. The aim of this work is to characterize from a structural (by low temperature neutron powder diffraction) and an energetical (by temperature programmed desorption) point of view, the adsorption of para- and meta- isomers of xylene, for different fillings, as pure substances as well as mixtures, on pre-hydrated zeolite BaX. The influence of the water pre-adsorption on xylene adsorption selectivity is carefully discussed. The crystalline structure of the zeolite BaX (framework and compensation of charge cations) and of the adsorbed phase (water, p- and m-xylene molecules) are completely characterized by neutron diffraction. The location and the distribution of water and xylene molecules on their adsorption sites is especially followed as a function of the filling of the zeolite and of the composition of the adsorbed phase. Microscopic measurements were correlated to the energetical analysis (at a macroscopic level) in order to obtain a consistent description of adsorption phenomenon and to propose a possible origin for adsorption selectivity.

  6. REFRACTIVE NEUTRON LENS

    OpenAIRE

    Petrov, P. V.; Kolchevsky, N. N.

    2013-01-01

    Compound concave refractive lenses are used for focusing neutron beam. Investigations of spectral and focusing properties of a refractive neutron lens are presented. Resolution of the imaging system on the base of refractive neutron lenses depends on material properties and parameters of neutron source. Model of refractive neutron lens are proposed. Results of calculation diffraction resolution and focal depth of refractive neutron lens are discussed.

  7. Cobalt ferrite nanoparticles under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Saccone, F. D.; Ferrari, S.; Grinblat, F.; Bilovol, V. [Instituto de Tecnologías y Ciencias de la Ingeniería, “Ing. H. Fernández Long,” Av. Paseo Colón 850 (1063), Buenos Aires (Argentina); Errandonea, D., E-mail: daniel.errandonea@uv.es [Departamento de Fisica Aplicada, Institut Universitari de Ciència dels Materials, Universitat de Valencia, c/ Doctor Moliner 50, E-46100 Burjassot, Valencia (Spain); Agouram, S. [Departamento de Física Aplicada y Electromagnetismo, Universitat de València, 46100 Burjassot, Valencia (Spain)

    2015-08-21

    We report by the first time a high pressure X-ray diffraction and Raman spectroscopy study of cobalt ferrite (CoFe{sub 2}O{sub 4}) nanoparticles carried out at room temperature up to 17 GPa. In contrast with previous studies of nanoparticles, which proposed the transition pressure to be reduced from 20–27 GPa to 7.5–12.5 GPa (depending on particle size), we found that cobalt ferrite nanoparticles remain in the spinel structure up to the highest pressure covered by our experiments. In addition, we report the pressure dependence of the unit-cell parameter and Raman modes of the studied sample. We found that under quasi-hydrostatic conditions, the bulk modulus of the nanoparticles (B{sub 0} = 204 GPa) is considerably larger than the value previously reported for bulk CoFe{sub 2}O{sub 4} (B{sub 0} = 172 GPa). In addition, when the pressure medium becomes non-hydrostatic and deviatoric stresses affect the experiments, there is a noticeable decrease of the compressibility of the studied sample (B{sub 0} = 284 GPa). After decompression, the cobalt ferrite lattice parameter does not revert to its initial value, evidencing a unit cell contraction after pressure was removed. Finally, Raman spectroscopy provides information on the pressure dependence of all Raman-active modes and evidences that cation inversion is enhanced by pressure under non-hydrostatic conditions, being this effect not fully reversible.

  8. Powder diffraction at ALBA synchrotron

    OpenAIRE

    Aranda, Miguel A. G.

    2017-01-01

    This talk is devoted to explain the uses of powder diffraction at MSPD (material science and powder diffraction) of ALBA synchrotron light source. General characteristics of the beamline are: Station 1 - High Pressure Diffraction on powders with diamond anvil cell (DAC) and CCD detector. Microdiffraction; and Station 2 - High Resolution Powder Diffraction with Multicrystal- and Silicon-Strip detector. Energy Range: 8-50keV; Typical beam size: 4x1mm; all typical sample geometries possible: cap...

  9. Neutron scattering. Lectures

    Energy Technology Data Exchange (ETDEWEB)

    Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)

    2010-07-01

    The following topics are dealt with: Neutron sources, symmetry of crystals, diffraction, nanostructures investigated by small-angle neutron scattering, the structure of macromolecules, spin dependent and magnetic scattering, structural analysis, neutron reflectometry, magnetic nanostructures, inelastic scattering, strongly correlated electrons, dynamics of macromolecules, applications of neutron scattering. (HSI)

  10. World of high pressure. Koatsuryoku no sekai

    Energy Technology Data Exchange (ETDEWEB)

    Moritoki, M.; Kanda, T. (Kobe Steel, Ltd., Kobe (Japan))

    1993-05-01

    The present article describes development and current status of high pressure technology. It introduces applications of high pressure technology to chemical reactions and processings, utilizations of phase changes and supercritical fluids, and applications of high pressure to food processings. Contributions of high pressure technology to synthetic chemistry are mentioned as for industrialization of syntheses of ammonia, urea and methanol, and invention of synthesis of polyethylene. Processing technologies utilizing high pressure are also mentioned as for cold isostatic pressing, hot isostatic pressing, hydrostatic extrusion technique, water jet working technique, and explosive forming technique. Introduced are application of phase changes under high pressure, such as high pressure synthesis of diamond and pressurized crystallization technology, and supercritical extraction technology using water and carbon dioxide. Pressurized food processings of mandarin orange, jam, and grapefruit are described. Furthermore, current status of fundamental technologies of high pressure installations is provided as for pressure vessel technology, pressure generation and control technology, and pressure sealing technology. 12 refs., 15 figs., 1 tab.

  11. High pressure studies of molecular lumenescence

    Energy Technology Data Exchange (ETDEWEB)

    Drickamer, H.G.

    1982-01-01

    The studies of high pressure molecular luminescence reviewed, along with results for inorganic systems discussed elsewhere, provide evidence about the versatility and power of high pressure as a tool for characterizing electronic states, testing theories concerning electronic phenomena, and generally obtaining a better understanding of electronic behavior in condensed systems. 16 figures.

  12. High pressure effects on fruits and vegetables

    NARCIS (Netherlands)

    Timmermans, R.A.H.; Matser, A.M.

    2016-01-01

    The chapter provides an overview on different high pressure based treatments (high pressure pasteurization, blanching, pressure-assisted thermal processing, pressure-shift freezing and thawing) available for the preservation of fruits and vegetable products and extending their shelf life. Pressure

  13. Coal swelling and thermoplasticity under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Ndaji, F.E.; Butterfield, I.M.; Thomas, K.M. (Newcastle upon Tyne University, Newcastle upon Tyne (United Kingdom). Northern Carbon Research Labs., Dept. of Chemistry)

    1992-01-01

    The literature on the following topics is reviewed: swelling and agglomeration of coal; measurements of swelling index and dilatometric and plastometric properties at high pressures; and the effects of oxidation, tar addition and minerals on high-pressure thermoplastic properties. 34 refs., 6 figs.

  14. Depth Gauge for Liquids Under High Pressure

    Science.gov (United States)

    Zuckerwar, A. J.; Mazel, D. S.

    1987-01-01

    Piezoelectric element mounted in hole drilled in high-pressure plug. Transducer used to measure depth of liquid when pressure in vessel high. New configuration transmits ultrasonic vibration directly into liquid, enhancing signal strength, accuracy, and range, yet piezoelectric element protected from high-pressure liquid.

  15. Shock Recovery of the High Pressure Phase Bismuth III

    Science.gov (United States)

    Fussell, Zachary; Tschauner, Oliver; Hawkins, Cameron; Ma, Chi; Smith, Jesse; Advanced Photon Source Team; California Institution of Technology Team; National Security Technologies Team; University of Nevada, Las Vegas Team

    2017-06-01

    Between 0 and 10 GPa there are five different bismuth phases. High-pressure bismuth (Bi) phases have been examined in static compression experiments; however, none could be recovered to ambient conditions. Here we report Bi-III recovery (stable above 3 GPa) to ambient conditions from a shock compression experiment to 5.7 GPa. Bi-III was identified by synchrotron micro-diffraction and backscatter electron imaging. Our work shows shock-compression provides a tool for recovering high-pressure phases that otherwise elude decompression. This work supported by National Security Technologies, LLC, under Contract No. DE-AC52-06NA25946 with the U.S. Department of Energy and by the Site-Directed Research and Development Program. DOE/NV/25946-3070.

  16. Phase diagram of Nitrogen at high pressures and temperatures

    Science.gov (United States)

    Jenei, Zsolt; Lin, Jung-Fu; Yoo, Choong-Shik

    2007-03-01

    Nitrogen is a typical molecular solid with relatively weak van der Waals intermolecular interactions but strong intramolecular interaction arising from the second highest binding energy of all diatomic molecules. The phase diagram of solid nitrogen is, however, complicated at high pressures, as inter-molecular interaction becomes comparable to the intra-molecular interaction. In this paper, we present an updated phase diagram of the nitrogen in the pressure-temperature region of 100 GPa and 1000 K, based on in-situ Raman and synchrotron x-ray diffraction studies using externally heated membrane diamond anvil cells. While providing an extension of the phase diagram, our results indicate a ``steeper'' slope of the δ/ɛ phase boundary than previously determined^1. We also studied the stability of the ɛ phase at high pressures and temperatures. Our new experimental results improve the understanding of the Nitrogen phase diagram. 1. Gregoryanz et al, Phys. Rev. B 66, 224108 (2002)

  17. Magnetic ordering of Mo2NiB2-type {Gd, Tb, Dy)2Co2Al compounds by magnetization and neutron diffraction study

    Science.gov (United States)

    Morozkin, A. V.; Genchel, V. K.; Garshev, A. V.; Yapaskurt, V. O.; Isnard, O.; Yao, Jinlei; Nirmala, R.; Quezado, S.; Malik, S. K.

    2017-11-01

    The magnetic ordering of Mo2NiB2-type {Gd, Tb, Dy}2Co2Al (Immm, No. 71, oI10) compounds has been established using bulk magnetic measurements and neutron diffraction study. Polycrystalline Gd2Co2Al, Tb2Co2Al and Dy2Co2Al undergo ferrimagnetic transitions (TC) at 78 K, 98 K and 58 K, respectively, and low-temperature field induced transition (Tm) around 15 K, 20 K and 15 K, respectively. Between Tm and TC Gd2Co2Al, Tb2Co2Al and Dy2Co2Al are soft ferrimagnets. Below Tm Gd2Co2Al is soft ferrimagnet, whereas Tb2Co2Al and Dy2Co2Al exhibit permanent magnet properties with residual magnetization per rare earth of 4.95 B and 4.8 B, respectively, and large coercive field of 72 kOe and 22 kOe, respectively, at 2 K. The magnetocaloric effects of Gd2Co2Al, Tb2Co2Al and Dy2Co2Al were calculated in terms of isothermal magnetic entropy change and they reach maximum values of -10.4 J/kg K, -7.6 J/kg K and -6.6 J/kg K for a field change of 50 kOe near 75 K, 98 K and 58 K, respectively. Low-temperature transition of Gd2Co2Al is followed by the magnetic entropy change of -2.9 J/kg K in a field change of 50 kOe at 15 K. Low temperature magnetic ordering with enhanced anisotropic effects in Tb2Co2Al and Dy2Co2Al is accompanied by a positive magnetocaloric effect with isothermal magnetic entropy changes of +19.9 J/kg K at 20 K (field change 0-50 kOe) and +2.7 J/kg K at 15 K (field change 0-10 kOe), respectively. Neutron diffraction study shows that, in zero applied field, Tb2Co2Al exhibits c-axis ferrimagnetic ordering with magnetic space group Immm‧ and propagation vector K0 = [0, 0, 0] below TCND ∼ 111 K with MTb = 8.86(15) B and MCo = 0.26(2) B at 2 K.

  18. A neutron diffraction study of the crystal of benzoic acid from 6 to 293 K and a macroscopic-scale quantum theory of the lattice of hydrogen-bonded dimers

    Energy Technology Data Exchange (ETDEWEB)

    Fillaux, François, E-mail: francois.fillaux@upmc.fr [Sorbonne Universités, UPMC Univ Paris 06, UMR 8233, MONARIS, F-7505 Paris (France); Cousson, Alain, E-mail: alain-f.cousson@cea.fr [Laboratoire Léon Brillouin (CEA-CNRS), C.E. Saclay, 91191 Gif-sur-Yvette cedex (France)

    2016-11-10

    Highlights: • Proton transfer and tautomerism are revisited from quantum viewpoint. • Neutron-diffraction gives evidence for long-range correlations for protons. • We introduce a decoherence-free macroscopic-scale crystal-state. • All observations accord with the principle of complementarity. • Computational-chemistry models are inappropriate. - Abstract: Measurements via different techniques of the crystal of benzoic acid have led to conflicting conceptions of tautomerism: statistical disorder for diffraction; semiclassical jumps for relaxometry; quantum states for vibrational spectroscopy. We argue that these conflicts follow from the prejudice that nuclear positions and eigenstates are pre-existing to measurements, what is at variance with the principle of complementarity. We propose a self-contained quantum theory. First of all, new single-crystal neutron-diffraction data accord with long-range correlation for proton-site occupancies. Then we introduce a macroscopic-scale quantum-state emerging from phonon condensation, for which nuclear positions and eigenstates are indefinite. As to quantum-measurements, an incoming wave (neutron or photon) entangled with the condensate realizes a transitory state, either in the space of static nuclear-coordinates (diffraction), or in that of the symmetry coordinates (spectroscopy and relaxometry). We derive temperature-laws for proton-site occupancies and for the relaxation rate, which compare favorably with measurements.

  19. Heterolytic cleavage of hydrogen by an iron hydrogenase model: an Fe-H⋅⋅⋅H-N dihydrogen bond characterized by neutron diffraction.

    Science.gov (United States)

    Liu, Tianbiao; Wang, Xiaoping; Hoffmann, Christina; DuBois, Daniel L; Bullock, R Morris

    2014-05-19

    Hydrogenase enzymes in nature use hydrogen as a fuel, but the heterolytic cleavage of H-H bonds cannot be readily observed in enzymes. Here we show that an iron complex with pendant amines in the diphosphine ligand cleaves hydrogen heterolytically. The product has a strong Fe-H⋅⋅⋅H-N dihydrogen bond. The structure was determined by single-crystal neutron diffraction, and has a remarkably short H⋅⋅⋅H distance of 1.489(10) Å between the protic N-H(δ+) and hydridic Fe-H(δ-) part. The structural data for [Cp(C5F4N)FeH(P(tBu)2N(tBu)2H)](+) provide a glimpse of how the H-H bond is oxidized or generated in hydrogenase enzymes. These results now provide a full picture for the first time, illustrating structures and reactivity of the dihydrogen complex and the product of the heterolytic cleavage of H2 in a functional model of the active site of the [FeFe] hydrogenase enzyme. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Effect of Extrusion Temperature on the Plastic Deformation of an Mg-Y-Zn Alloy Containing LPSO Phase Using In Situ Neutron Diffraction

    Science.gov (United States)

    Garces, G.; Perez, P.; Cabeza, S.; Kabra, S.; Gan, W.; Adeva, P.

    2017-11-01

    The evolution of the internal strains during in situ tension and compression tests has been measured in an MgY2Zn1 alloy containing long-period stacking ordered (LPSO) phase using neutron diffraction. The alloy was extruded at two different temperatures to study the influence of the microstructure and texture of the magnesium and the LPSO phases on the deformation mechanisms. The alloy extruded at 623 K (350 °C) exhibits a strong fiber texture with the basal plane parallel to the extrusion direction due to the presence of areas of coarse non-recrystallised grains. However, at 723 K (450 °C), the magnesium phase is fully recrystallised with grains randomly oriented. On the other hand, at the two extrusion temperatures, the LPSO phase orients their basal plane parallel to the extrusion direction. Yield stress is always slightly higher in compression than in tension. Independently on the stress sign and the extrusion temperature, the beginning of plasticity is controlled by the activation of the basal slip system in the dynamic recrystallized grains. Therefore, the elongated fiber-shaped LPSO phase which behaves as the reinforcement in a metal matrix composite is responsible for this tension-compression asymmetry.

  1. Electronic, spin-state, and magnetic transitions in B a2C o9O14 investigated by x-ray spectroscopies and neutron diffraction

    Science.gov (United States)

    Herrero-Martín, J.; Padilla-Pantoja, J.; Lafuerza, S.; Romaguera, A.; Fauth, F.; Reparaz, J. S.; García-Muñoz, J. L.

    2017-06-01

    The mixed B a2C o9O14C o2 +/C o3 + system undergoes an insulator-insulator transition at TSS˜567 K that arises from a spin-state transition at trivalent cobalt sites. Below this temperature, Co1, Co2, and Co4 are nonmagnetic (S =0 , low spin). Ferromagnetically aligned Co5 spins are sandwiched between antiparallel planes of Co3 spins below TN≈41 K . The successive antiferromagnetic trilayers are inverted along the c axis (compatible with Cc2 /c ,Cc2 /m , or PS-1 magnetic space groups, depending on the moment orientation in the a b plane). The origin of the resistivity drop on warming was investigated by means of neutron and x-ray diffraction, x-ray absorption and emission spectroscopies, and x-ray magnetic circular dichroism. Charge-transfer multiplet calculations confirm that the divalent Co sites are both in an S =3 /2 high spin state. Independently, the analysis of measured Co Kβ x-ray emission spectroscopy spectra agrees with this model. The magnetic moment from divalent Co5 ions is not fully ordered, likely due to the competition between magnetic anisotropy and weak supersuperexchange interactions, but not to covalency effects. Results agree with the spin blockade of electronic transport being partially removed at the octahedral trimers and also at the Co 4 O6 units within the Cd I2 -type layer.

  2. Crystal structures of spinel-type Na2MoO4 and Na2WO4 revisited using neutron powder diffraction

    Directory of Open Access Journals (Sweden)

    A. Dominic Fortes

    2015-06-01

    Full Text Available Time-of-flight neutron powder diffraction data have been collected from Na2MoO4 and Na2WO4 to a resolution of sin (θ/λ = 1.25 Å−1, which is substantially better than the previous analyses using Mo Kα X-rays, providing roughly triple the number of measured reflections with respect to the previous studies [Okada et al. (1974. Acta Cryst. B30, 1872–1873; Bramnik & Ehrenberg (2004. Z. Anorg. Allg. Chem. 630, 1336–1341]. The unit-cell parameters are in excellent agreement with literature data [Swanson et al. (1962. NBS Monograph No. 25, sect. 1, pp. 46–47] and the structural parameters for the molybdate agree very well with those of Bramnik & Ehrenberg (2004. However, the tungstate structure refinement of Okada et al. (1974 stands apart as being conspicuously inaccurate, giving significantly longer W—O distances, 1.819 (8 Å, and shorter Na—O distances, 2.378 (8 Å, than are reported here or in other simple tungstates. As such, this work represents an order-of-magnitude improvement in precision for sodium molybdate and an equally substantial improvement in both accuracy and precision for sodium tungstate. Both compounds adopt the spinel structure type. The Na+ ions have site symmetry .-3m and are in octahedral coordination while the transition metal atoms have site symmetry -43m and are in tetrahedral coordination.

  3. Neutron diffraction study of the crystal structure of BaMoO{sub 4}: A suitable precursor for metallic BaMoO{sub 3} perovskite

    Energy Technology Data Exchange (ETDEWEB)

    Nassif, V.; Carbonio, R.E. [Univ. Nacional de Cordoba (Argentina). Inst. de Investigaciones en Fisicoquimica; Alonso, J.A. [C.S.I.C., Madrid (Spain). Inst. de Ciencia de Materiales

    1999-08-01

    BaMoO{sub 3}, metallic and Pauli paramagnetic, has been prepared by controlled reduction of BaMoO{sub 4}. This precursor, containing Mo(VI), is unusually stable against reduction, due to structural factors. The crystal structure of BaMoO{sub 4} has been refined from neutron powder diffraction data: space group I4{sub 1}/a (no. 88), Z = 4, a = 5.5479(9), and c = 12.743(2) {angstrom}. A bond-valence study allowed the authors to detect the presence of slight tensile and compressive stresses in the crystal structure of BaMoO{sub 4}, in which Ba is overbonded and Mo is underbonded. However, this effect is less pronounced than in other AMO{sub 4} oxides with a scheelite structure (A = Ca, Sr, Ba; M = Mo, W): BaMoO{sub 4} contains the M cation exhibiting the closest valence to the nominal value of 6+, suggesting a large covalent contribution to the Mo-O bonds. This observation is coherent with the large thermal stability of this compound against reduction, taking place at temperatures above 920 C in H{sub 2} flow.

  4. Neutron diffraction investigation of the H -T phase diagram above the longitudinal incommensurate phase of BaCo2V2O8

    Science.gov (United States)

    Grenier, B.; Simonet, V.; Canals, B.; Lejay, P.; Klanjšek, M.; Horvatić, M.; Berthier, C.

    2015-10-01

    The quasi-one-dimensional antiferromagnetic Ising-like compound BaCo2V2O8 has been shown to be describable by the Tomonaga-Luttinger liquid theory in its gapless phase induced by a magnetic field applied along the Ising axis. Above 3.9 T, this leads to an exotic field-induced low-temperature magnetic order, made of a longitudinal incommensurate spin-density wave, stabilized by weak interchain interactions. By single-crystal neutron diffraction we explore the destabilization of this phase at a higher magnetic field. We evidence a transition at around 8.5 T towards a more conventional magnetic structure with antiferromagnetic components in the plane perpendicular to the magnetic field. The phase diagram boundaries and the nature of this second field-induced phase are discussed with respect to previous results obtained by means of nuclear magnetic resonance and electron spin resonance, and in the framework of the simple model based on the Tomonaga-Luttinger liquid theory, which obviously has to be refined in this complex system.

  5. Neutron-Diffraction Measurements of an Antiferromagnetic Semiconducting Phase in the Vicinity of the High-Temperature Superconducting State of KxFe2-ySe2

    Science.gov (United States)

    Zhao, Jun; Cao, Huibo; Bourret-Courchesne, E.; Lee, D.-H.; Birgeneau, R. J.

    2012-12-01

    The recently discovered K-Fe-Se high-temperature superconductor has caused heated debate regarding the nature of its parent compound. Transport, angle-resolved photoemission spectroscopy, and STM measurements have suggested that its parent compound could be insulating, semiconducting, or even metallic [M. H. Fang, H.-D. Wang, C.-H. Dong, Z.-J. Li, C.-M. Feng, J. Chen, and H. Q. Yuan, Europhys. Lett. 94, 27009 (2011)EULEEJ0295-507510.1209/0295-5075/94/27009; F. Chen , Phys. Rev. X 1, 021020 (2011)PRXHAE2160-330810.1103/PhysRevX.1.021020; and W. Li , Phys. Rev. Lett. 109, 057003 (2012)PRLTAO0031-900710.1103/PhysRevLett.109.057003]. Because the magnetic ground states associated with these different phases have not yet been identified and the relationship between magnetism and superconductivity is not fully understood, the real parent compound of this system remains elusive. Here, we report neutron-diffraction experiments that reveal a semiconducting antiferromagnetic (AFM) phase with rhombus iron vacancy order. The magnetic order of the semiconducting phase is the same as the stripe AFM order of the iron pnictide parent compounds. Moreover, while the 5×5 block AFM phase coexists with superconductivity, the stripe AFM order is suppressed by it. This leads us to conjecture that the new semiconducting magnetic ordered phase is the true parent phase of this superconductor.

  6. Neutron Diffraction Measurement of Residual Stresses, Dislocation Density and Texture in Zr-bonded U-10Mo ''Mini'' Fuel Foils and Plates

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Donald W. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Okuniewski, M. A. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Sisneros, Thomas A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Clausen, Bjorn [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Moore, G. A. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Balogh, L [Queen' s Univ., Kingston, ON (Canada)

    2014-08-07

    Aluminum clad monolithic uranium 10 weight percent molybdenum (U-10Mo) fuel plates are being considered for conversion of several research and test nuclear reactors from high-enriched to low-enriched uranium fuel due to the inherently high density of fissile material. Comprehensive neutron diffraction measurements of the evolution of the textures, residual phase stresses, and dislocation densities in the individual phases of the mini-foils throughout several processing steps and following hot-isostatic pressing to the Al cladding, have been completed. Recovery and recrystallization of the bare U-10Mo fuel foil, as indicated by the dislocation density and texture, are observed depending on the state of the material prior to annealing and the duration and temperature of the annealing process. In general, the HIP procedure significantly reduces the dislocation density, but the final state of the clad plate, both texture and dislocation density, depends strongly on the final processing step of the fuel foil. In contrast, the residual stresses in the clad fuel plate do not depend strongly on the final processing step of the bare foil prior to HIP bonding. Rather, the residual stresses are dominated by the thermal expansion mismatch of the constituent materials of the fuel plate.

  7. Visualizing oxygen anion transport pathways in NdBaCo2O5+δ by in situ neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Cox-Galhotra, Rosemary A. [Univ. of Virginia, Charlottesville, VA (United States). Dept. of Chemical Engineering; Huq, Ashfia [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source; Hodges, Jason P. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source; Kim, Jung-Hyun [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source; Yu, Chengfei [Univ. of Houston, TX (United States). Dept. of Chemistry; Wang, Xiqu [Univ. of Houston, TX (United States). Dept. of Chemistry; Jacobson, Allan J. [Univ. of Houston, TX (United States). Dept. of Chemistry; McIntosh, Steven [Univ. of Virginia, Charlottesville, VA (United States). Dept. of Chemical Engineering; Lehigh Univ., Bethlehem, PA (United States). Dept. of Chemical Engineering

    2013-01-14

    We characterized the layered perovskite NdBaCo2O5+δ (NBCO) using neutron powder diffraction under in situ conditions from 577–852 °C and in 10-1 to 10-4 atm oxygen. The best fit to the data was obtained in the tetragonal (P4/mmm) space group. No oxygen atom vacancy ordering was observed that warranted a lowering of the symmetry to orthorhombic (Pmmm). Two P4/mmm structural models were investigated: Model 1 (no split sites) and Model 2 (split Nd and O2 sites). Furthermore, transport of oxygen through the material via the vacancy hopping mechanism will likely involve the nearest-neighbor oxygen atom sites in the Nd layer. Total oxygen stoichiometry values were in the range 5.51 ≤ δ ≤ 5.11. The tetragonal lattice parameters increased with temperature as expected. But, the a-axis expands while the c-axis contracts with decreasing pO2 at a given temperature due to increasing vacancy concentration in the Nd layer.

  8. Polarised neutron diffraction measurements of PrBa sub 2 Cu sub 3 O sub 6 sub + X and Bayesian statistical analysis of such data

    CERN Document Server

    Markvardsen, A J

    2000-01-01

    sub 2 Cu sub 3 O sub 6 sub + sub x and leaving room for more questions to be answered. The physics of the series Pr sub y Y sub 1 sub - sub y Ba sub 2 CU sub 3 O sub 6 sub + sub x , and ability of Pr to suppress superconductivity, has been a subject of frequent discussions in the literature for more than a decade. This thesis describes a polarised neutron diffraction (PND) experiment performed on PrBa sub 2 Cu sub 3 O sub 6 sub . sub 2 sub 4 designed to find out something about the electron structure. This experiment pushed the limits of what can be done using the PND technique. The problem is one of a limited number of measured Fourier components that need to be inverted to form a real space image. To accomplish this inversion the maximum entropy technique has been employed. In some cases, the maximum entropy technique has the ability to increase the resolution of 'inverted' data immensely, but this ability is found to depend critically on the choice of constants used in the method. To investigate this a Bay...

  9. Application of High Pressure in Food Processing

    Directory of Open Access Journals (Sweden)

    Herceg, Z.

    2011-01-01

    Full Text Available In high pressure processing, foods are subjected to pressures generally in the range of 100 – 800 (1200 MPa. The processing temperature during pressure treatments can be adjusted from below 0 °C to above 100 °C, with exposure times ranging from a few seconds to 20 minutes and even longer, depending on process conditions. The effects of high pressure are system volume reduction and acceleration of reactions that lead to volume reduction. The main areas of interest regarding high-pressure processing of food include: inactivation of microorganisms, modification of biopolymers, quality retention (especially in terms of flavour and colour, and changes in product functionality. Food components responsible for the nutritive value and sensory properties of food remain unaffected by high pressure. Based on the theoretical background of high-pressure processing and taking into account its advantages and limitations, this paper aims to show its possible application in food processing. The paper gives an outline of the special equipment used in highpressure processing. Typical high pressure equipment in which pressure can be generated either by direct or indirect compression are presented together with three major types of high pressure food processing: the conventional (batch system, semicontinuous and continuous systems. In addition to looking at this technology’s ability to inactivate microorganisms at room temperature, which makes it the ultimate alternative to thermal treatments, this paper also explores its application in dairy, meat, fruit and vegetable processing. Here presented are the effects of high-pressure treatment in milk and dairy processing on the inactivation of microorganisms and the modification of milk protein, which has a major impact on rennet coagulation and curd formation properties of treated milk. The possible application of this treatment in controlling cheese manufacture, ripening and safety is discussed. The opportunities

  10. Forge-Hardened TiZr Null-Matrix Alloy for Neutron Scattering under Extreme Conditions

    Directory of Open Access Journals (Sweden)

    Takuo Okuchi

    2015-12-01

    Full Text Available For neutron scattering research that is performed under extreme conditions, such as high static pressures, high-strength metals that are transparent to the neutron beam are required. The diffraction of the neutron beam by the metal, which follows Bragg’s law, can be completely removed by alloying two metallic elements that have coherent scattering lengths with opposite signs. An alloy of Ti and Zr, which is known as a TiZr null-matrix alloy, is an ideal combination for such purposes. In this study, we increased the hardness of a TiZr null-matrix alloy via extensive mechanical deformation at high temperatures. We successfully used the resulting product in a high-pressure cell designed for high-static-pressure neutron scattering. This hardened TiZr null-matrix alloy may play a complementary role to normal TiZr alloy in future neutron scattering research under extreme conditions.

  11. Straightforward high-pressure synthesis and characterization of indium-based thiospinels: photocatalytic potential for hydrogen production

    Energy Technology Data Exchange (ETDEWEB)

    Falcon, Horacio [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco (Spain); NANOTEC (Centro de Investigacion en Nanociencia y Nanotecnologia), Universidad Tecnologica Nacional-Facultad Regional Cordoba, Cordoba (Argentina); Tartaj, Pedro; Alonso, Jose Antonio [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco (Spain); Vaquero, Fernando; Navarro, Rufino M.; Fierro, Jose Luis G. [Instituto de Catalisis y Petroleoquimica, CSIC, Cantoblanco, Madrid (Spain); Bolletta, Juan P.; Paoli, Juan M. de; Carbonio, Raul E. [INFIQC - CONICET, Departamento de Fisicoquimica, Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba (Argentina); Fernandez-Diaz, Maria Teresa [Institut Laue Langevin, Grenoble (France)

    2016-04-15

    Ternary chalcogenides (AB{sub 2}X{sub 4}) based on the spinel structure are gaining a great deal of attention because of the possibility of tuning their magnetic and optoelectronic properties not only by changing chemical composition but also by altering their degree of inversion. Here we report a rapid high-pressure synthetic method for the synthesis of MIn{sub 2}S{sub 4} powders starting from commercially available solid sulfides. We prove the versatility of our method by reporting the synthesis of six members of the MIn{sub 2}S{sub 4} family (M = Mn, Fe, Co, Ni, Zn, and Cd) under high-pressure conditions (3.5 GPa); these compounds show complete to moderate degrees of inversion. Furthermore, this family covers a spectral region that includes visible band gaps. Interestingly, the structural refinement carried out by X-ray and neutron diffraction allows one to establish positive correlations between the gap and different parameters, including the degree of inversion. Finally, as a proof-of-concept, these ternary chalcogenides show moderate photocatalytic hydrogen production from aqueous solutions. (Copyright copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. Novel stable structure of Li3PS4 predicted by evolutionary algorithm under high-pressure

    Directory of Open Access Journals (Sweden)

    S. Iikubo

    2018-01-01

    Full Text Available By combining theoretical predictions and in-situ X-ray diffraction under high pressure, we found a novel stable crystal structure of Li3PS4 under high pressures. At ambient pressure, Li3PS4 shows successive structural transitions from γ-type to β-type and from β-type to α type with increasing temperature, as is well established. In this study, an evolutionary algorithm successfully predicted the γ-type crystal structure at ambient pressure and further predicted a possible stable δ-type crystal structures under high pressure. The stability of the obtained structures is examined in terms of both static and dynamic stability by first-principles calculations. In situ X-ray diffraction using a synchrotron radiation revealed that the high-pressure phase is the predicted δ-Li3PS4 phase.

  13. Exploring charge density analysis in crystals at high pressure: data collection, data analysis and advanced modelling.

    Science.gov (United States)

    Casati, Nicola; Genoni, Alessandro; Meyer, Benjamin; Krawczuk, Anna; Macchi, Piero

    2017-08-01

    The possibility to determine electron-density distribution in crystals has been an enormous breakthrough, stimulated by a favourable combination of equipment for X-ray and neutron diffraction at low temperature, by the development of simplified, though accurate, electron-density models refined from the experimental data and by the progress in charge density analysis often in combination with theoretical work. Many years after the first successful charge density determination and analysis, scientists face new challenges, for example: (i) determination of the finer details of the electron-density distribution in the atomic cores, (ii) simultaneous refinement of electron charge and spin density or (iii) measuring crystals under perturbation. In this context, the possibility of obtaining experimental charge density at high pressure has recently been demonstrated [Casati et al. (2016). Nat. Commun. 7, 10901]. This paper reports on the necessities and pitfalls of this new challenge, focusing on the species syn-1,6:8,13-biscarbonyl[14]annulene. The experimental requirements, the expected data quality and data corrections are discussed in detail, including warnings about possible shortcomings. At the same time, new modelling techniques are proposed, which could enable specific information to be extracted, from the limited and less accurate observations, like the degree of localization of double bonds, which is fundamental to the scientific case under examination.

  14. High-pressure study on some superconductors

    CERN Document Server

    Li, K Q; Yao, Y S; Che, G C; Zhao, Z X

    2002-01-01

    High-pressure study has played an important role in the investigation of conventional superconductors. Since the discovery of cuprate superconductors, high-pressure study has become even more important, especially as regards high-pressure synthesis and the effect of pressure. In this report, the new materials Ca-doped Pr-123, (Fe, Cu)-1212, and MgB sub 2 - a very new and interesting system synthesized under high pressure with good quality - will be discussed. Chemical inner pressure has been thought to explain the high T sub c of Ca-doped Pr-123. As another possibility, the replacement of the physical pressure effect by a chemical effect will be discussed.

  15. An experimental apparatus for EDXD of high pressure specimens using synchrotron radiation at BSRF

    CERN Document Server

    Liu Jing; Zhao, J; Jing, Y H; Yang, Y; Ju, X

    2001-01-01

    A high pressure energy dispersive X-ray diffraction apparatus on 3W1A beamline, at BSRF, is described. A ten-poles permanent magnetic wiggler provided white X-ray beam. The extreme high pressure up to 115 GPa has been obtained by a modified Mao-Bell diamond anvil cell. A motorized loading system with strain sensor can finely control the pressure change. The in situ experimental procedures are described. Some applications are also presented.

  16. High pressure structural studies of conjugated molecules

    DEFF Research Database (Denmark)

    Knaapila, Matti; Torkkeli, Mika; Scherf, Ullrich

    2018-01-01

    This chapter highlights high pressure GPa level structural studies of conjugated polymers and their analogues: conjugated oligomers and molecules, and rigid rod polymers. Attention is placed on our recent studies of polyfluorenes.......This chapter highlights high pressure GPa level structural studies of conjugated polymers and their analogues: conjugated oligomers and molecules, and rigid rod polymers. Attention is placed on our recent studies of polyfluorenes....

  17. High-pressure minerals in shocked meteorites

    Science.gov (United States)

    Tomioka, Naotaka; Miyahara, Masaaki

    2017-09-01

    Heavily shocked meteorites contain various types of high-pressure polymorphs of major minerals (olivine, pyroxene, feldspar, and quartz) and accessory minerals (chromite and Ca phosphate). These high-pressure minerals are micron to submicron sized and occur within and in the vicinity of shock-induced melt veins and melt pockets in chondrites and lunar, howardite-eucrite-diogenite (HED), and Martian meteorites. Their occurrence suggests two types of formation mechanisms (1) solid-state high-pressure transformation of the host-rock minerals into monomineralic polycrystalline aggregates, and (2) crystallization of chondritic or monomineralic melts under high pressure. Based on experimentally determined phase relations, their formation pressures are limited to the pressure range up to 25 GPa. Textural, crystallographic, and chemical characteristics of high-pressure minerals provide clues about the impact events of meteorite parent bodies, including their size and mutual collision velocities and about the mineralogy of deep planetary interiors. The aim of this article is to review and summarize the findings on natural high-pressure minerals in shocked meteorites that have been reported over the past 50 years.

  18. High-pressure structural behavior of nanocrystalline Ge

    DEFF Research Database (Denmark)

    Wang, H.; Liu, J. F.; Yan, H.

    2007-01-01

    The equation of state and the pressure of the I-II transition have been studied for nanocrystalline Ge using synchrotron x-ray diffraction. The bulk modulus and the transition pressure increase with decreasing particle size for both Ge-I and Ge-II, but the percentage volume collapse at the transi......The equation of state and the pressure of the I-II transition have been studied for nanocrystalline Ge using synchrotron x-ray diffraction. The bulk modulus and the transition pressure increase with decreasing particle size for both Ge-I and Ge-II, but the percentage volume collapse...... at the transition remains constant. Simplified models for the high-pressure structural behaviour are presented, based on the assumption that a large fraction of the atoms reside in grain boundary regions of the nanocrystalline material. The interface structure plays a significant role in affecting the transition...

  19. Oxygen stoichiometry and chemical expansion of Ba0.5Sr0.5Co0.8Fe0.2O3-d measured by in-situ neutron diffraction

    NARCIS (Netherlands)

    McIntosh, S.; McIntosh, Steven; Vente, Jaap F.; Haije, Wim G.; Blank, David H.A.; Bouwmeester, Henricus J.M.

    2006-01-01

    The structure, oxygen stoichiometry, and chemical and thermal expansion of Ba0.5Sr0.5Co0.8Fe0.2O3-ä (BSCF) between 873 and 1173 K and oxygen partial pressures of 1 10-3 to 1 atm were determined by in situ neutron diffraction. BSCF has a cubic perovskite structure, space group Pm3hm, across the whole

  20. Neutron Powder Diffraction Measurements of the Spinel MgGa 2 O 4 :Cr 3+ - A Comparative Study between the High Flux Diffractometer D2B at the ILL and the High Resolution Powder Diffractometer Aurora at IPEN

    DEFF Research Database (Denmark)

    Silva, M A F M da; Sosman, L P; Yokaichiya, F

    2012-01-01

    and MgGa 2 O 4 and relate structural changes observed in MgGa 2 O 4 -Ga 2 O 3 system to the optical properties, and secondly, to compare the neutron powder diffraction results obtained using two diffractometers: D2B located at the ILL (Grenoble, France) and Aurora located at IPEN (São Paulo, Brazil......). In the configuration chosen, Aurora shows an improved resolution, which is related to the design of its silicon focusing monochromator....

  1. Synthesis and stability of hydrogen selenide compounds at high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Pace, Edward J.; Binns, Jack; Alvarez, Miriam Pena; Dalladay-Simpson, Philip; Gregoryanz, Eugene; Howie, Ross T. (Edinburgh); (CHPSTAR- China)

    2017-11-14

    The observation of high-temperature superconductivity in hydride sulfide (H2S) at high pressures has generated considerable interest in compressed hydrogen-rich compounds. High-pressure hydrogen selenide (H2Se) has also been predicted to be superconducting at high temperatures; however, its behaviour and stability upon compression remains unknown. In this study, we synthesize H2Se in situ from elemental Se and molecular H2 at pressures of 0.4 GPa and temperatures of 473 K. On compression at 300 K, we observe the high-pressure solid phase sequence (I-I'-IV) of H2Se through Raman spectroscopy and x-ray diffraction measurements, before dissociation into its constituent elements. Through the compression of H2Se in H2 media, we also observe the formation of a host-guest structure, (H2Se)2H2, which is stable at the same conditions as H2Se, with respect to decomposition. These measurements show that the behaviour of H2Se is remarkably similar to that of H2S and provides further understanding of the hydrogen chalcogenides under pressure.

  2. High pressure synthesis of amorphous TiO2 nanotubes

    Directory of Open Access Journals (Sweden)

    Quanjun Li

    2015-09-01

    Full Text Available Amorphous TiO2 nanotubes with diameters of 8-10 nm and length of several nanometers were synthesized by high pressure treatment of anatase TiO2 nanotubes. The structural phase transitions of anatase TiO2 nanotubes were investigated by using in-situ high-pressure synchrotron X-ray diffraction (XRD method. The starting anatase structure is stable up to ∼20GPa, and transforms into a high-density amorphous (HDA form at higher pressure. Pressure-modified high- to low-density transition was observed in the amorphous form upon decompression. The pressure-induced amorphization and polyamorphism are in good agreement with the previous results in ultrafine TiO2 nanoparticles and nanoribbons. The relationship between the LDA form and α-PbO2 phase was revealed by high-resolution transmission electron microscopy (HRTEM study. In addition, the bulk modulus (B0 = 158 GPa of the anatase TiO2 nanotubes is smaller than those of the corresponding bulks and nanoparticles (180-240 GPa. We suggest that the unique open-ended nanotube morphology and nanosize play important roles in the high pressure phase transition of TiO2 nanotubes.

  3. Reinvestigation of high pressure polymorphism in hafnium metal

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, K. K., E-mail: kkpandey@barc.gov.in; Sharma, Surinder M. [High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Mumbai-400 085 (India); Gyanchandani, Jyoti; Dey, G. K. [Materials Science Division, Bhabha Atomic Research Centre, Mumbai-400 085 (India); Somayazulu, M. [Geophysical Laboratory, Carnegie Institution of Washington, Washington, D.C. 20015 (United States); Sikka, S. K. [Indian National Science Academy, New Delhi-110 002 (India)

    2014-06-21

    There has been a recent controversy about the high pressure polymorphism of Hafnium (Hf). Unlike, the earlier known α→ω structural transition at 38 ± 8 GPa, at ambient temperature, Hrubiak et al. [J. Appl. Phys. 111, 112612 (2012)] did not observe it till 51 GPa. They observed this transition only at elevated temperatures. We have reinvestigated the room temperature phase diagram of Hf, employing x-ray diffraction (XRD) and DFT based first principles calculations. Experimental investigations have been carried out on several pure and impure Hf samples and also with different pressure transmitting media. Besides demonstrating the significant role of impurity levels on the high pressure phase diagram of Hf, our studies re-establish room temperature α→ω transition at high pressures, even in quasi-hydrostatic environment. We observed this transition in pure Hf with equilibrium transition pressure P{sub o} = 44.5 GPa; however, with large hysteresis. The structural sequence, transition pressures, the lattice parameters, the c/a ratio and its variation with compression for the α and ω phases as predicted by our ab-initio scalar relativistic (SR) calculations are found to be in good agreement with our experimental results of pure Hf.

  4. Elasticity of methane hydrate phases at high pressure.

    Science.gov (United States)

    Beam, Jennifer; Yang, Jing; Liu, Jin; Liu, Chujie; Lin, Jung-Fu

    2016-04-21

    Determination of the full elastic constants (cij) of methane hydrates (MHs) at extreme pressure-temperature environments is essential to our understanding of the elastic, thermodynamic, and mechanical properties of methane in MH reservoirs on Earth and icy satellites in the solar system. Here, we have investigated the elastic properties of singe-crystal cubic MH-sI, hexagonal MH-II, and orthorhombic MH-III phases at high pressures in a diamond anvil cell. Brillouin light scattering measurements, together with complimentary equation of state (pressure-density) results from X-ray diffraction and methane site occupancies in MH from Raman spectroscopy, were used to derive elastic constants of MH-sI, MH-II, and MH-III phases at high pressures. Analysis of the elastic constants for MH-sI and MH-II showed intriguing similarities and differences between the phases' compressional wave velocity anisotropy and shear wave velocity anisotropy. Our results show that these high-pressure MH phases can exhibit distinct elastic, thermodynamic, and mechanical properties at relevant environments of their respective natural reservoirs. These results provide new insight into the determination of how much methane exists in MH reservoirs on Earth and on icy satellites elsewhere in the solar system and put constraints on the pressure and temperature conditions of their environment.

  5. Elasticity of methane hydrate phases at high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Beam, Jennifer; Yang, Jing; Liu, Jin [Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78712 (United States); Liu, Chujie [Laboratory of Seismology and Physics of Earth’s Interior, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026 (China); Lin, Jung-Fu, E-mail: afu@jsg.utexas.edu [Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78712 (United States); Center for High Pressure Science and Advanced Technology Research (HPSTAR), Shanghai 201203 (China)

    2016-04-21

    Determination of the full elastic constants (c{sub ij}) of methane hydrates (MHs) at extreme pressure-temperature environments is essential to our understanding of the elastic, thermodynamic, and mechanical properties of methane in MH reservoirs on Earth and icy satellites in the solar system. Here, we have investigated the elastic properties of singe-crystal cubic MH-sI, hexagonal MH-II, and orthorhombic MH-III phases at high pressures in a diamond anvil cell. Brillouin light scattering measurements, together with complimentary equation of state (pressure-density) results from X-ray diffraction and methane site occupancies in MH from Raman spectroscopy, were used to derive elastic constants of MH-sI, MH-II, and MH-III phases at high pressures. Analysis of the elastic constants for MH-sI and MH-II showed intriguing similarities and differences between the phases′ compressional wave velocity anisotropy and shear wave velocity anisotropy. Our results show that these high-pressure MH phases can exhibit distinct elastic, thermodynamic, and mechanical properties at relevant environments of their respective natural reservoirs. These results provide new insight into the determination of how much methane exists in MH reservoirs on Earth and on icy satellites elsewhere in the solar system and put constraints on the pressure and temperature conditions of their environment.

  6. Neutron diffraction and neutron depolarization study

    Indian Academy of Sciences (India)

    S Rößler, U K Rößler, K Nenkov, D Eckert, S M Yusuf, K Dörr and K-H Müller,. Phys. Rev. B70, 104417 (2004). D K Aswal, A Singh, C Thinaharan, S M Yusuf, C S Viswanatham, G L Goswami, L. C Gupta, S K Gupta, J V Yakhmi and V C Sahni, Philos. Magn. B83, 3181 (2003). Pramana – J. Phys., Vol. 71, No. 4, October 2008.

  7. Synthesis and morphology of iron-iron oxide core-shell nanoparticles produced by high pressure gas condensation

    NARCIS (Netherlands)

    Xing, Lijuan; ten Brink, Gert H.; Chen, Bin; Schmidt, Franz P.; Haberfehlner, Georg; Hofer, Ferdinand; Kooi, Bart J.; Palasantzas, Georgios

    2016-01-01

    Core-shell structured Fe nanoparticles (NPs) produced by high pressure magnetron sputtering gas condensation were studied using transmission electron microscopy (TEM) techniques, electron diffraction, electron energy-loss spectroscopy (EELS), tomographic reconstruction, and Wulff shape construction

  8. High pressure processing for food safety.

    Science.gov (United States)

    Fonberg-Broczek, Monika; Windyga, B; Szczawiński, J; Szczawińska, M; Pietrzak, D; Prestamo, G

    2005-01-01

    Food preservation using high pressure is a promising technique in food industry as it offers numerous opportunities for developing new foods with extended shelf-life, high nutritional value and excellent organoleptic characteristics. High pressure is an alternative to thermal processing. The resistance of microorganisms to pressure varies considerably depending on the pressure range applied, temperature and treatment duration, and type of microorganism. Generally, Gram-positive bacteria are more resistant to pressure than Gram-negative bacteria, moulds and yeasts; the most resistant are bacterial spores. The nature of the food is also important, as it may contain substances which protect the microorganism from high pressure. This article presents results of our studies involving the effect of high pressure on survival of some pathogenic bacteria -- Listeria monocytogenes, Aeromonas hydrophila and Enterococcus hirae -- in artificially contaminated cooked ham, ripening hard cheese and fruit juices. The results indicate that in samples of investigated foods the number of these microorganisms decreased proportionally to the pressure used and the duration of treatment, and the effect of these two factors was statistically significant (level of probability, P monocytogenes and A. hydrophila. Mathematical methods were applied, for accurate prediction of the effects of high pressure on microorganisms. The usefulness of high pressure treatment for inactivation of microorganisms and shelf-life extention of meat products was also evaluated. The results obtained show that high pressure treatment extends the shelf-life of cooked pork ham and raw smoked pork loin up to 8 weeks, ensuring good micro-biological and sensory quality of the products.

  9. A neutron diffraction study of crystal and low-temperature magnetic structures within the (Na,Li)FeGe2O6 pyroxene-type solid solution series

    Science.gov (United States)

    Redhammer, Günther J.; Senyshyn, Anatoliy; Lebernegg, Stefan; Tippelt, Gerold; Dachs, Edgar; Roth, Georg

    2017-10-01

    Solid solution compounds along the Li1- x Na x FeGe2O6 clinopyroxene series have been prepared by solid state ceramic sintering and investigated by bulk magnetic and calorimetric methods; the Na-rich samples with x(Na) > 0.7 were also investigated by low-temperature neutron diffraction experiments in a temperature range of 4-20 K. For samples with x(Na) > 0.76 the crystal structure adopts the C2/ c symmetry at all measuring temperatures, while the samples display P21/ c symmetry for smaller Na contents. Magnetic ordering is observed for all samples below 20 K with a slight decrease of T N with increasing Na content. The magnetic spin structures change distinctly as a function of chemical composition: up to x(Na) = 0.72 the magnetic structure can be described by a commensurate arrangement of magnetic spins with propagation vector k = (½, 0 0), an antiferromagnetic (AFM) coupling within the Fe3+O6 octahedra zig-zag chains and an alternating AFM and ferromagnetic (FM) interaction between the chains, depending on the nature of the tetrahedral GeO4 chains. The magnetic structure can be described in magnetic space group P a21/ c. Close to the structural phase transition for sample with x(Na) = 0.75, magnetic ordering is observed below 15 K; however, it becomes incommensurately modulated with k = (0.344, 0, 0.063). At 4 K, the magnetic spin structure best can be described by a cycloidal arrangement within the M1 chains, the spins are within the a- c plane. Around 12 K the cycloidal structure transforms to a spin density wave (SDW) structure. For the C2/ c structures, a coexistence of a simple collinear and an incommensurately modulated structure is observed down to lowest temperatures. For 0.78 ≤ x(Na) ≤ 0.82, a collinear magnetic structure with k = (0 1 0), space group P C21/ c and an AFM spin structure within the M1 chains and an FM one between the spins is dominating, while the incommensurately modulated structure becomes dominating the collinear one in the

  10. High-pressure behavior of CaMo O4

    Science.gov (United States)

    Panchal, V.; Garg, N.; Poswal, H. K.; Errandonea, D.; Rodríguez-Hernández, P.; Muñoz, A.; Cavalli, E.

    2017-09-01

    We report a high-pressure study of tetragonal scheelite-type CaMo O4 up to 29 GPa. In order to characterize its high-pressure behavior, we have combined Raman and optical-absorption measurements with density functional theory calculations. We have found evidence of a pressure-induced phase transition near 15 GPa. Experiments and calculations agree in assigning the high-pressure phase to a monoclinic fergusonite-type structure. The reported results are consistent with previous powder x-ray-diffraction experiments, but are in contradiction with the conclusions obtained from earlier Raman measurements, which support the existence of more than one phase transition in the pressure range covered by our studies. The observed scheelite-fergusonite transition induces significant changes in the electronic band gap and phonon spectrum of CaMo O4 . We have determined the pressure evolution of the band gap for the low- and high-pressure phases as well as the frequencies and pressure dependencies of the Raman-active and infrared-active modes. In addition, based on calculations of the phonon dispersion of the scheelite phase, carried out at a pressure higher than the transition pressure, we propose a possible mechanism for the reported phase transition. Furthermore, from the calculations we determined the pressure dependence of the unit-cell parameters and atomic positions of the different phases and their room-temperature equations of state. These results are compared with previous experiments showing a very good agreement. Finally, information on bond compressibility is reported and correlated with the macroscopic compressibility of CaMo O4 . The reported results are of interest for the many technological applications of this oxide.

  11. On the Sr1−xBaxFeO2F Oxyfluoride Perovskites: Structure and Magnetism from Neutron Diffraction and Mössbauer Spectroscopy

    Directory of Open Access Journals (Sweden)

    Crisanto A. García-Ramos

    2016-11-01

    Full Text Available Four oxyfluorides of the title series (x = 0.00, 0.25, 0.50, 0.75 have been stabilized by topotactic treatment of perovskite precursors Sr1−xBaxFeO3−δ prepared by soft-chemistry procedures, yielding reactive materials that can easily incorporate a substantial amount of F atoms at moderate temperatures, thus avoiding the stabilization of competitive SrF2 and BaF2 parasitic phases. XRD and Neutron Powder Diffraction (NPD measurements assess the phase purity and yield distinct features concerning the unit cell parameters’ variation, the Sr and Ba distribution, the stoichiometry of the anionic sublattice and the anisotropic displacement factors for O and F atoms. The four oxyfluorides are confirmed to be cubic in all of the compositional range, the unit cell parameters displaying Vergard’s law. All of the samples are magnetically ordered above room temperature; the magnetic structure is always G-type antiferromagnetic, as shown from NPD data. The ordered magnetic moments are substantially high, around 3.5 μB, even at room temperature (RT. Temperature-dependent Mössbauer data allow identifying Fe3+ in all of the samples, thus confirming the Sr1−xBaxFeO2F stoichiometry. The fit of the magnetic hyperfine field vs. temperature curve yields magnetic ordering TN temperatures between 740 K (x = 0.00 and 683 K (x = 0.75. These temperatures are substantially higher than those reported before for some of the samples, assessing for stronger Fe-Fe superexchange interactions for these specimens prepared by fluorination of citrate precursors in mild conditions.

  12. Crystal Structural Determination of SrAlD5 with Corner-Sharing AlD6 Octahedron Chains by X-ray and Neutron Diffraction

    Directory of Open Access Journals (Sweden)

    Toyoto Sato

    2018-02-01

    Full Text Available Aluminium-based complex hydrides (alanates composed of metal cation(s and complex anion(s, [AlH4]− or [AlH6]3− with covalent Al–H bonds, have attracted tremendous attention as hydrogen storage materials since the discovery of the reversible hydrogen desorption and absorption reactions on Ti-enhanced NaAlH4. In cases wherein alkaline-earth metals (M are used as a metal cation, MAlH5 with corner-sharing AlH6 octahedron chains are known to form. The crystal structure of SrAlH5 has remained unsolved although two different results have been theoretically and experimentally proposed. Focusing on the corner-sharing AlH6 octahedron chains as a unique feature of the alkaline-earth metal, we here report the crystal structure of SrAlD5 investigated by synchrotron radiation powder X-ray and neutron diffraction. SrAlD5 was elucidated to adopt an orthorhombic unit cell with a = 4.6226(10 Å, b = 12.6213(30 Å and c = 5.0321(10 Å in the space group Pbcm (No. 57 and Z = 4. The Al–D distances (1.77–1.81 Å in the corner-sharing AlD6 octahedra matched with those in the isolated [AlD6]3− although the D–Al–D angles in the penta-alanates are significantly more distorted than the isolated [AlD6]3−.

  13. Silicon supported lipid-DNA thin film structures at varying temperature studied by energy dispersive X-ray diffraction and neutron reflectivity.

    Science.gov (United States)

    Domenici, F; Castellano, C; Dell'Unto, F; Albinati, A; Congiu, A

    2011-11-01

    Non-viral gene transfection by means of lipid-based nanosystems, such as solid supported lipid assemblies, is often limited due to their lack of stability and the consequent loss of efficiency. Therefore not only a detailed thermo-lyotropic study of these DNA-lipid complexes is necessary to understand their interaction mechanisms, but it can also be considered as a first step in conceiving and developing new transfection biosystems. The aim of our study is a structural characterization of 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC)-dimethyl-dioctadecyl-ammonium bromide (DDAB)-DNA complex at varying temperature using the energy dispersive X-ray diffraction (EDXD) and neutron reflectivity (NR) techniques. We have shown the formation of a novel thermo-lyotropic structure of DOPC/DDAB thin film self-organized in multi-lamellar planes on (100)-oriented silicon support by spin coating, thus enlightening its ability to include DNA strands. Our NR measurements indicate that the DOPC/DDAB/DNA complex forms temperature-dependent structures. At 65°C and relative humidity of 100% DNA fragments are buried between single lamellar leaflets constituting the hydrocarbon core of the lipid bilayers. This finding supports the consistency of the hydrophobic interaction model, which implies that the coupling between lipid tails and hypo-hydrated DNA single strands could be the driving force of DNA-lipid complexation. Upon cooling to 25°C, EDXD analysis points out that full-hydrated DOPC-DDAB-DNA can switch in a different metastable complex supposed to be driven by lipid heads-DNA electrostatic interaction. Thermotropic response analysis also clarifies that DOPC has a pivotal role in promoting the formation of our observed thermophylic silicon supported lipids-DNA assembly. Copyright © 2011 Elsevier B.V. All rights reserved.

  14. The crystal structure, electrostatic properties, and thermal vibrations of some hydrated spermine compounds using neutron and x-ray diffraction data

    Science.gov (United States)

    Cohen, Aina Elizabeth

    Spermine phosphate hexahydrate crystallizes in space group P21/a with unit cell dimensions a = 7.931(1) A, b = 23.158(5) A, c = 6.856(2) A, and b = 113.44(2)° at 125 K with unit cell contents ([C10H 30N4]2+4 4[HPO4] -2·12H2O). The packing of spermines and monohydrogen phosphates in this crystal structure has features which may be relevant to the binding of spermine to DNA. Another important structural feature is the presence of channels containing water that is H-bonded as in ice-Ih with disordered protons. The channels occur between sheets of spermine long chains and are also bordered by H-bonded monohydrogen phosphate chains. Using neutron diffraction data, the H-bonding scheme of these water chains proposed on the basis of an earlier X-ray study is now confirmed. Nuclear positions, anisotropic m.s. displacements, an overall scale factor, and two extinction parameters ( r and g) were refined using full-matrix least-squares giving values of R(Fo2) = 0.09, Rw(Fo 2) = 0.11 and S = 1.02. Thermal vibrational analysis revealed that the backbone of the spermine cation can be described as a single rigid segment with a substantial libration of 27 deg2 around the spermine molecular long axis. The charge density distribution in the crystal structure of spermine phosphate hexahydrate ([C10H30N4] +4 2[HPO4]-2·6H2O) has been determined from X-ray diffraction data MoKa at 125 K using 13,984 reflections with sin/l≤1. 51 A-1. Least-squares structure refinement assuming Stewart's rigid pseudoatom model (variables included electron populations for multipole terms extending to octapoles for C, N, O, and P and up to dipoles for H) gave R(F2) = 0.042, Rw(F2) = 0.071 and S = 1.06. The electron density and its Laplacian have been determined at the (3, -1) or bond-critical points. The crystal structure of spermine dihydrate (C10H26N 4·2H2O), or possibly sperminium dihydroxide, has been determined for the non-hydrogen atoms. Spermine dihydrate crystallizes in space group P1¯ with

  15. High pressure water jet mining machine

    Science.gov (United States)

    Barker, Clark R.

    1981-05-05

    A high pressure water jet mining machine for the longwall mining of coal is described. The machine is generally in the shape of a plowshare and is advanced in the direction in which the coal is cut. The machine has mounted thereon a plurality of nozzle modules each containing a high pressure water jet nozzle disposed to oscillate in a particular plane. The nozzle modules are oriented to cut in vertical and horizontal planes on the leading edge of the machine and the coal so cut is cleaved off by the wedge-shaped body.

  16. NATO Advanced Study Institute on High-Pressure Crystallography

    CERN Document Server

    Boldyreva, Elena; High-Pressure Crystallography

    2010-01-01

    This book is devoted to the theme of crystallographic studies at high pressure, with emphasis on the phenomena characteristic to the compressed state of matter, as well as experimental and theoretical techniques used to study these phenomena. As a thermodynamic parameter, pressure is remarkable in many ways. In the visible universe its value spans over sixty orders of magnitude, from the non-equilibrium pressure of hydrogen in intergalactic space, to the kind of pressure encountered within neutron stars. In the laboratory, it provides the unique possibility to control the structure and properties of materials, to dramatically alter electronic properties, and to break existing, or form new chemical bonds. This agenda naturally encompasses elements of physics (properties, structure and transformations), chemistry (reactions, transport), materials science (new materials) and engineering (mechanical properties); in addition it has direct applications and implications for geology (minerals in deep Earth environmen...

  17. Determination of the cell parameters of {beta}-quartz at 1003 K by neutron multiple diffraction; Parametros de rede do quartzo-{beta} a 1003 K determinados por difracao multipla de neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Campos, Luiz Carlos de

    2002-07-01

    In this work, neutron multiple diffraction (NMD) data was employed for the determination of the parameters a and c of the {beta}-quartz hexagonal cell at 1003 K. An experimental 00.1 {beta}-quartz NMD 'Umweg' pattern has been used for the determinations. During the indexing of the {beta}-quartz pattern it was verified that most of the peaks could be classified as either 'good for the determination of the parameter a' or 'good for the determination of the parameter c'. With such a classification, it became possible to employ an iterative process for the determination of both parameters. To attain this purpose, two methods were developed. The first one, named 'absolute method', used angular azimuthal positions of the peaks, related to the origin of the experimental diagram. The second method, named 'relative method', used azimuthal angular differences between two selected peaks. The values obtained for both parameters, in the two methods employed, were found by applying the angular azimuthal positions, for the first method, and the azimuthal angular differences, for the second method, upon appropriate theoretical indexing diagrams. An iterative process was applied in order to obtain the values of the parameters. In this process, the value obtained for one of the parameters was used in the determination of the other parameter. The process continues until both parameters converge. The iterative process was used in both methods. The relative method proved to be better than the absolute method. The best values of the parameters obtained by the relative method were: a 4.99638 {+-} 0.00057 angstrom and c = 5.46119 {+-} 0.00044 angstrom. (author)

  18. Development of high pressure proportional counters

    Energy Technology Data Exchange (ETDEWEB)

    Oddone, P.; Smith, G.; Green, A.; Nemethy, P.; Baksay, L.; Schick, L.; Heflin, E.G.

    1986-12-01

    We have begun to investigate the possibility of operating gas counters at high pressures. In a first step we were able to operate cylindrical chambers up to 430 atm with a gas gain of about 300 using a mixture of 92% Ar and 8% CH/sub 4/.

  19. High-field/high-pressure ESR.

    Science.gov (United States)

    Sakurai, T; Okubo, S; Ohta, H

    2017-07-01

    We present a historical review of high-pressure ESR systems with emphasis on our recent development of a high-pressure, high-field, multi-frequency ESR system. Until 2000, the X-band system was almost established using a resonator filled with dielectric materials or a combination of the anvil cell and dielectric resonators. Recent developments have shifted from that in the low-frequency region, such as X-band, to that in multi-frequency region. High-pressure, high-field, multi-frequency ESR systems are classified into two types. First are the systems that use a vector network analyzer or a quasi-optical bridge, which have high sensitivity but a limited frequency region; the second are like our system, which has a very broad frequency region covering the THz region, but lower sensitivity. We will demonstrate the usefulness of our high-pressure ESR system, in addition to its experimental limitations. We also discuss the recent progress of our system and future plans. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. High-pressure oxidation of methane

    NARCIS (Netherlands)

    Hashemi, Hamid; Christensen, Jakob M.; Gersen, Sander; Levinsky, Howard; Klippenstein, Stephen J.; Glarborg, Peter

    2016-01-01

    Methane oxidation at high pressures and intermediate temperatures was investigated in a laminar flow reactor and in a rapid compression machine (RCM). The flow-reactor experiments were conducted at 700–900 K and 100 bar for fuel-air equivalence ratios (Φ) ranging from 0.06 to 19.7, all highly

  1. High pressure metrology for industrial applications

    Science.gov (United States)

    Sabuga, Wladimir; Rabault, Thierry; Wüthrich, Christian; Pražák, Dominik; Chytil, Miroslav; Brouwer, Ludwig; Ahmed, Ahmed D. S.

    2017-12-01

    To meet the needs of industries using high pressure technologies, in traceable, reliable and accurate pressure measurements, a joint research project of the five national metrology institutes and the university was carried out within the European Metrology Research Programme. In particular, finite element methods were established for stress–strain analysis of elastic and nonlinear elastic–plastic deformation, as well as of contact processes in pressure-measuring piston-cylinder assemblies, and high-pressure components at pressures above 1 GPa. New pressure measuring multipliers were developed and characterised, which allow realisation of the pressure scale up to 1.6 GPa. This characterisation is based on research including measurements of material elastic constants by the resonant ultrasound spectroscopy, hardness of materials of high pressure components, density and viscosity of pressure transmitting liquids at pressures up to 1.4 GPa and dimensional measurements on piston-cylinders. A 1.6 GPa pressure system was created for operation of the 1.6 GPa multipliers and calibration of high pressure transducers. A transfer standard for 1.5 GPa pressure range, based on pressure transducers, was built and tested. Herewith, the project developed the capability of measuring pressures up to 1.6 GPa, from which industrial users can calibrate their pressure measurement devices for accurate measurements up to 1.5 GPa.

  2. A structural study of the pseudo-binary mercury chalcogenide alloy HgSe sub 0 sub . sub 7 S sub 0 sub . sub 3 at high pressure

    CERN Document Server

    Kozlenko, D P; Hull, S; Knorr, K; Savenko, B N; Shchennikov, V V; Voronin, V I

    2002-01-01

    The structure of the pseudo-binary mercury chalcogenide alloy HgSe sub 0 sub . sub 7 S sub 0 sub . sub 3 has been studied by means of X-ray and neutron powder diffraction at pressure up to 8.5 GPa. A phase transition from the cubic zinc blende structure to the hexagonal cinnabar structure was observed at P approx 1 GPa. The obtained structural parameters were used for the analysis of the geometrical relationship between the zinc blende and the cinnabar phases. The zinc blende-cinnabar phase transition is discussed in the framework of the Landau theory of phase transitions. It was found that the possible order parameter for the structural transformation is the spontaneous strain e sub 4. This assignment agrees with previously observed high pressure behaviour of the elastic constants of other mercury chalcogenides

  3. A Structural Study of the Pseudo-Binary Mercury Chalcogenide Alloy HgSe_{0.7}S_{0.3} at High Pressure

    CERN Document Server

    Kozlenko, D P; Ehm, L; Knorr, K; Hull, S; Shchennikov, V V; Voronin, V I

    2002-01-01

    The structure of the pseudo-binary mercury chalcogenide alloy HgSe_{0.7}S_{0.3} has been studied by means of X-ray and neutron powder diffraction at pressure up to 8.5 GPa. A phase transition from the cubic zinc blende structure to the hexagonal cinnabar structure was observed at P{\\sim}1 GPa. The obtained structural parameters were used for the analysis of the geometrical relationship between the zinc blende and the cinnabar phases. The zinc blende-cinnabar phase transition is discussed in the framework of Landau theory of the phase transitions. It was found that the possible order parameter for the structural transformation is the spontaneous strain e_{4}. This assignment agrees with previously observed high pressure behaviour of the elastic constants of other mercury chalcogenides.

  4. Advanced Diagnostics for High Pressure Spray Combustion.

    Energy Technology Data Exchange (ETDEWEB)

    Skeen, Scott A.; Manin, Julien Luc; Pickett, Lyle M.

    2014-06-01

    The development of accurate predictive engine simulations requires experimental data to both inform and validate the models, but very limited information is presently available about the chemical structure of high pressure spray flames under engine- relevant conditions. Probing such flames for chemical information using non- intrusive optical methods or intrusive sampling techniques, however, is challenging because of the physical and optical harshness of the environment. This work details two new diagnostics that have been developed and deployed to obtain quantitative species concentrations and soot volume fractions from a high-pressure combusting spray. A high-speed, high-pressure sampling system was developed to extract gaseous species (including soot precursor species) from within the flame for offline analysis by time-of-flight mass spectrometry. A high-speed multi-wavelength optical extinction diagnostic was also developed to quantify transient and quasi-steady soot processes. High-pressure sampling and offline characterization of gas-phase species formed following the pre-burn event was accomplished as well as characterization of gas-phase species present in the lift-off region of a high-pressure n-dodecane spray flame. For the initial samples discussed in this work several species were identified, including polycyclic aromatic hydrocarbons (PAH); however, quantitative mole fractions were not determined. Nevertheless, the diagnostic developed here does have this capability. Quantitative, time-resolved measurements of soot extinction were also accomplished and the novel use of multiple incident wavelengths proved valuable toward characterizing changes in soot optical properties within different regions of the spray flame.

  5. Properties of planetary ices in the NH3 + CO2 ± H2O ternary system using neutron diffraction and ab initio calculations

    Science.gov (United States)

    Howard, C. M.; Wood, I. G.; Fortes, A. D.; Vocadlo, L.

    2016-12-01

    BackgroundInteractions between simple molecules are of fundamental interest across diverse areas of the physical sciences, and the ternary system NH3 + CO2 ± H2O is no exception. In the outer solar system, interaction of CO2 with aqueous ammonia is likely to occur, synthesizing `rock-forming' minerals [1], with CO2 perhaps playing a role in ammonia-water oceans and cryomagmas inside icy planetary bodies - the discovery of ammonium carbonates in a crater of Pluto's moon Charon [2] adds weight to CO2 occuring in these planetary environments. In the same context, ammonium carbonates may have some astrobiological relevance, since removal of water leads to the formation of urea. On Earth, combination of CO2 with aqueous ammonia has relevance to carbon capture schemes [3], and there is interest in using such materials for hydrogen storage in fuel cells [4]. Consequently, from earthly matters of climate change to the study of extraterrestrial ices, understanding the structures and properties of ammonium carbonates are important. Despite this, our knowledge of ammonium carbonates is limited under ambient conditions of pressure and temperature and is entirely absent at the higher pressures, severely limiting our ability to model the behaviour of NH3 + CO2 ± H2O solids and fluids in planetary environments. ResultsWe report the results of several experiments using variable pressure and temperature neutron diffraction work on ammonium carbonate monohydrate, ammonium bicarbonate and ammonium carbamate, with complementary Density Functional Theory (DFT) calculations. The excellent agreement between experiments and DFT calculations obtained so far adds weight to the accuracy of calculated material properties of ammonium sesquicarbonate monohydrate and several polymorphs of urea where little empirical data exists. These experimental and computational studies provide the structural, thermoelastic and vibrational information required for accurate planetary modelling and remote

  6. High-pressure synthesis of Na{sub 1-x}Li{sub x}MgH{sub 3} perovskite hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Coronado, R., E-mail: rmartinez@icmm.csic.es [Instituto de Ciencia de Materiales de Madrid, C.S.I.C., Cantoblanco, E-28049 Madrid (Spain); Sanchez-Benitez, J. [Instituto de Ciencia de Materiales de Madrid, C.S.I.C., Cantoblanco, E-28049 Madrid (Spain); Dpto. Quimica Fisica I, Facultad de Ciencias Quimicas, Universidad Complutense de Madrid, 28040 Madrid (Spain); Retuerto, M. [Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, 610 Taylor Road, Piscataway, NJ 08854-808 (United States); Fernandez-Diaz, M.T. [Institut Laue Langevin, BP 156X, Grenoble F-38042 (France); Alonso, J.A. [Instituto de Ciencia de Materiales de Madrid, C.S.I.C., Cantoblanco, E-28049 Madrid (Spain)

    2012-05-05

    Highlights: Black-Right-Pointing-Pointer New synthesis method for the ternary metal hydride perovskite system Na{sub 1-x}Li{sub x}MgH{sub 3}. Black-Right-Pointing-Pointer Direct reaction of simple hydrides under high-pressure and high-temperature conditions. Black-Right-Pointing-Pointer X-ray and Neutron Powder Diffraction analysis were used to identify the purity of the samples. Black-Right-Pointing-Pointer Perovskite hydride structure; more distorted and unstable as Li is introduced (smaller ionic size of Li{sup +}vs Na{sup +}). Black-Right-Pointing-Pointer Hydrogen desorption temperature much reduced respect to MgH{sub 2}; useful as hydrogen storage materials. - Abstract: Magnesium base alloys are very attractive for hydrogen storage due to their large hydrogen capacity, small weight and low-cost. We have designed a new synthesis method for the ternary metal hydride perovskite system Na{sub 1-x}Li{sub x}MgH{sub 3}, based on the direct reaction of simple hydrides under high-pressure and moderate-temperature conditions. Well-crystallized samples were obtained in a piston-cylinder hydrostatic press at moderate pressures of 2 GPa and temperatures around 750 Degree-Sign C from mixtures of MgH{sub 2}, NaH and LiH enclosed in gold capsules. X-ray and neutron powder diffraction analysis were used to identify the purity of the samples and provide an accurate description of the crystal structure features (GdFeO{sub 3} type). Na{sub 1-x}Li{sub x}MgH{sub 3} hydrides series (0 {<=} x {<=} 0.18) show an orthorhombic symmetry with space group Pnma (No. 62). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) have been carried out to determine the hydrogen desorption temperatures.

  7. High-pressure studies of cycloheptane up to 30 GPa

    Science.gov (United States)

    Ma, Chunli; Cui, Qiliang; Liu, Zhenxian

    2013-06-01

    High-pressure synchrotron angle dispersive x-ray diffraction, Raman scattering and infrared absorption studies have been performed on cycloheptane (C7H14) up to 30 GPa at room temperature by using diamond anvil cell techniques. The synchrotron x-ray diffraction results indicate that the liquid cyclopentane undergoes two phase transitions at around 0.5 and 1.0 GPa, respectively. Then, it gradually turns into glass state starting from 3.0 GPa. The features of the Raman scattering and infrared absorption show no significant changes with increasing pressure below 3 GPa. This implies that the two phases observed by the x-ray diffraction can be attributed to plastic phases in which the cycloheptane molecules are held in an ordered structure while the molecular orientation is disordered. Up on further compression, all Raman and infrared bands begin broadening around 3.0 GPa that provide further evidence on the transition to glass state. Our results also suggest different paths on phase transitions under isothermal compression at room temperature compare to that previously reported under isobaric cooling at ambient pressure. This work was supported by the NSF of China (91014004, 11004074,11074089), the specialized Research Fund for the Doctoral Program of Higher Education (20110061110011, 20100061120093), and the National Basic Research Program of China (2011CB808200).

  8. Enhancement of magnetoresistance and ferromagnetic coupling in the complex perovskites CaCu{sub 3}(Mn{sub 4−x}Al{sub x})O{sub 12} (x = 0, 0.2, 0.4, and 0.6): A neutron diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Ben Hassine, R.; Cherif, W. [Faculty of Sciences, Sfax University, Sfax, B.P. 1171-3000 (Tunisia); Sánchez-Benítez, J. [Departamento de Química Física I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Mompean, F. J.; Alonso, J. A., E-mail: ja.alonso@icmm.csic.es [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, E-28049 Madrid (Spain); Fernández-Díaz, M. T. [Institut Laue-Langevin, B.P. 156, F-38042 Grenoble Cedex 9 (France); Elhalouani, F. [National School of Engineers, Sfax University, Sfax, B.P. W 3038 (Tunisia)

    2015-09-14

    New compounds of the series CaCu{sub 3}(Mn{sub 4−x}Al{sub x})O{sub 12} have been prepared under high pressure conditions (2 GPa), in the presence of KClO{sub 4} as oxidizing agent to stabilize Mn{sup 3+,4+} mixed valence. The polycrystalline samples have been characterized by x-ray diffraction, neutron powder diffraction (NPD), magnetic, and magnetotransport measurements. All the samples are cubic, space group Im-3. These oxides adopt a superstructure of ABO{sub 3} perovskite given by the long-range 1:3 ordering of Ca{sup 2+} and Cu{sup 2+} ions at the A sublattice. The NPD study for x = 0.4 shows that Al{sup 3+} ions are statistically distributed at the octahedral positions, being the (Mn,Al)O{sub 6} octahedra strongly tilted, with superexchange (Mn,Al)-O-(Mn,Al) angles of 142.1°. Also, neutron data clearly show that some Mn{sup 3+} ions (0.65(2) per formula) are located together with Cu{sup 2+} at the square-planar 6b positions. Regarding the magnetic properties, all the compounds present a spontaneous increase of the magnetization below T{sub C}, typical of ferro-or ferrimagnetic materials, with T{sub C} decreasing upon Al introduction. The magnetic structure determined from low-temperature NPD data unveils a ferromagnetic coupling between (Cu{sup 2+}, Mn{sup 3+}){sub 6b} spins and Mn{sub 8c} spins at octahedral positions; this is in contrast with the ferrimagnetic structure observed for RCu{sub 3}Mn{sub 4}O{sub 12} and CaCu{sub 3}Mn{sub 4}O{sub 12}, where an AFM coupling is observed between both magnetic sublattices. Interestingly, an enhancement of the magnetoresistance effect is observed for x = 0.2, well beyond that found for the parent compound. This effect, in materials subtly doped with non-magnetic elements at the Mn positions, may be of interest for applications.

  9. High pressure study of high-temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Souliou, Sofia-Michaela

    2014-09-29

    The current thesis studies experimentally the effect of high external pressure on high-T{sub c} superconductors. The structure and lattice dynamics of several members of the high-T{sub c} cuprate and Fe-based superconductors families were investigated by means of Raman spectroscopy and X-ray diffraction under well-controlled, hydrostatic high pressure and low temperature conditions. The lattice dynamics of the high-T{sub c} superconductor YBa{sub 2}Cu{sub 3}O{sub 6+x} have been investigated systematically by Raman spectroscopy as a function of doping (x = 0.95, 0.75, 0.60, 0.55, and 0.45) and external pressure. Under ambient pressure conditions, in addition to the Raman modes expected from group theory, we observe new Raman active phonons upon cooling the underdoped samples, at temperatures well above the superconducting transition temperature. The doping dependence and the onset temperatures of the new Raman features suggest that they are associated with the incommensurate charge density wave (CDW) state recently discovered in underdoped cuprates using synchrotron X-ray scattering techniques. Under high pressure conditions (from 2 to 12 GPa), our Raman measurements on highly ordered underdoped YBa{sub 2}Cu{sub 3}O{sub 6.55} samples do not show any of the new Raman phonons seen at ambient pressure. High pressure and low temperature Raman measurements have been performed on the underdoped superconductor YBa{sub 2}Cu{sub 4}O{sub 8}. A clear renormalization of some of the Raman phonons is seen below T{sub c} as a result of the changes in the phonon self-energy upon the opening of the superconducting gap, with the most prominent one being that of the B{sub 1g}-like buckling phonon mode. The amplitude of this renormalization strongly increases with pressure, resembling the effect of hole doping in YBa{sub 2}Cu{sub 3}O{sub 6+x}. At ∝ 10 GPa, the system undergoes a reversible pressure-induced structural phase transition to a non-centrosymmmetric structure (space group

  10. Re-investigation of the crystal structure of enstatite under high-pressure conditions

    DEFF Research Database (Denmark)

    Periotto, Benedetta; Balic Zunic, Tonci; Nestola, Fabrizio

    2012-01-01

    A synthetic single crystal of pure orthoenstatite (MgSiO3, space group Pbca) has been investigated at high pressure for structural determinations by in situ single-crystal X‑ray diffraction using a diamond-anvil cell. Ten complete intensity data collections were performed up to 9.36 GPa. This stu...

  11. Structural stability of binary CdCa quasicrystal under high pressure

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Gerward, Leif; Olsen, J. S.

    2001-01-01

    The structural stability of a binary CdCa quasicrystal with a primitive icosahedral structure has been investigated by in situ high-pressure x-ray powder diffraction at an ambient temperature using synchrotron radiation. It is demonstrated that the icosahedral quasicrystalline structure of the sa...

  12. Anomalous compressive behavior in CeO2 nanocubes under high pressure

    DEFF Research Database (Denmark)

    Ge, M. Y.; Fang, Y. Z.; Wang, H.

    2008-01-01

    High-pressure angle-dispersive x-ray diffraction measurements have been performed on bulk and nanocrystalline cubic CeO2 with mean sizes of 4.7 and 5.6 nm. It is found that the compressibility of the nanocrystals is lower than the bulk when a threshold pressure is reached. This critical pressure ...

  13. High Pressure investigations of some exotic materials

    Indian Academy of Sciences (India)

    Co-filled tubes (PRB, 73, 184119, 2006) · Variation of the FWHM of the MWCNTs' diffraction line for cobalt-filled MWCNTs. The linewidth for Au 220 is also plotted for comparison. The increase in FWHM of the diffraction peak of MWCNTs is apparent from the solid line drawn as a guide to the eye. Slide 36 · Slide 37 · Slide 38.

  14. Magnetic and Superconducting Materials at High Pressures

    Energy Technology Data Exchange (ETDEWEB)

    Struzhkin, Viktor V. [Carnegie Inst. of Washington, Washington, DC (United States)

    2015-03-24

    The work concentrates on few important tasks in enabling techniques for search of superconducting compressed hydrogen compounds and pure hydrogen, investigation of mechanisms of high-Tc superconductivity, and exploring new superconducting materials. Along that route we performed several challenging tasks, including discovery of new forms of polyhydrides of alkali metal Na at very high pressures. These experiments help us to establish the experimental environment that will provide important information on the high-pressure properties of hydrogen-rich compounds. Our recent progress in RIXS measurements opens a whole field of strongly correlated 3d materials. We have developed a systematic approach to measure major electronic parameters, like Hubbard energy U, and charge transfer energy Δ, as function of pressure. This technique will enable also RIXS studies of magnetic excitations in iridates and other 5d materials at the L edge, which attract a lot of interest recently. We have developed new magnetic sensing technique based on optically detected magnetic resonance from NV centers in diamond. The technique can be applied to study superconductivity in high-TC materials, to search for magnetic transitions in strongly correlated and itinerant magnetic materials under pressure. Summary of Project Activities; development of high-pressure experimentation platform for exploration of new potential superconductors, metal polyhydrides (including newly discovered alkali metal polyhydrides), and already known superconductors at the limit of static high-pressure techniques; investigation of special classes of superconducting compounds (high-Tc superconductors, new superconducting materials), that may provide new fundamental knowledge and may prove important for application as high-temperature/high-critical parameter superconductors; investigation of the pressure dependence of superconductivity and magnetic/phase transformations in 3d transition metal compounds, including

  15. Diffraction: Principles and application

    Directory of Open Access Journals (Sweden)

    Hansen Thomas C.

    2015-01-01

    Full Text Available We introduce here diffraction in general, as well as neutron and powder diffraction in particular as a tool to study the structure of condensed matter, crystalline solids in particular. Diffraction is a crucial experimental technique of extraordinary potential to elucidate the structure and its evolution of materials important for all domains in the production, conversion, storage and transport of energy. It allows therefore establishing structure-property relationships, which need to be understood in order to develop new and better performing materials.

  16. Cementing liners through deep high pressure ones

    Energy Technology Data Exchange (ETDEWEB)

    Mahony, B.J.; Barrios, J.R.

    1974-03-01

    Entry of gas into the liner-hole annulus during and after cementing liners though deep high pressure zones, generally results in a gas cut cement column from depth of gas entry to top of liner. Prior to undertaking design of liner cementation, it is necessary to know fracture pressure limits of the formations. It is also necessary to know the formation pore pressure or the pressure required to hold gas in the formation and precisely the depth of formation from which gas emerges. This knowledge may be gained from a study of formation pressure gradients of nearby wells or from sonic log analysis of the interval being readied for cementation. Both single-stage and 2-stage techniques are used to solve liner cementing problems in these high pressure zones. An example sets out conditions which are more or less typical and demonstrates how the problem may be considered and solved.

  17. Inspection technology for high pressure pipes

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jae H.; Lee, Jae C.; Eum, Heung S.; Choi, Yu R.; Moon, Soon S.; Jang, Jong H

    2000-02-01

    Various kinds of defects are likely to be occurred in the welds of high pressure pipes in nuclear power plants. Considering the recent accident of Zuruga nuclear power plant in Japan, reasonable policy is strongly requested for the high pressure pipe integrity. In this study, we developed the technologies to inspect pipe welds automatically. After development of scanning robot prototype in the first research year, we developed and implemented the algorithm of automatic tracking of the scanning robot along the weld line of the pipes. We use laser slit beam on weld area and capture the image using digital camera. Through processing of the captures image, we finally determine the weld line automatically. In addition, we investigated a new technology on micro systems for developing micro scanning robotic inspection of the pipe welds. The technology developed in this study is being transferred to the industry. (author)

  18. High-pressure oxidation of methane

    DEFF Research Database (Denmark)

    Hashemi, Hamid; Christensen, Jakob Munkholt; Gersen, Sander

    2016-01-01

    Methane oxidation at high pressures and intermediate temperatures was investigated in a laminar flow reactor and in a rapid compression machine (RCM). The flow-reactor experiments were conducted at 700–900 K and 100 bar for fuel-air equivalence ratios (Φ) ranging from 0.06 to 19.7, all highly...... diluted in nitrogen. It was found that under the investigated conditions, the onset temperature for methane oxidation ranged from 723 K under reducing conditions to 750 K under stoichiometric and oxidizing conditions. The RCM experiments were carried out at pressures of 15–80 bar and temperatures of 800......–1250 K under stoichiometric and fuel-lean (Φ=0.5) conditions. Ignition delays, in the range of 1–100 ms, decreased monotonically with increasing pressure and temperature. A chemical kinetic model for high-pressure methane oxidation was established, with particular emphasis on the peroxide chemistry...

  19. Melting point of polymers under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Seeger, Andreas [Technische Universitaet Darmstadt, Ernst Berl-Institut fuer Technische und Makromolekulare Chemie, Petersenstr. 20, D-64287 Darmstadt (Germany)], E-mail: seeger@chemie.tu-darmstadt.de; Freitag, Detlef [Friedrich-Alexander-Universitaet, Erlangen-Nuernberg (Germany); Freidel, Frank [Technische Universitaet Darmstadt, Ernst Berl-Institut fuer Technische und Makromolekulare Chemie, Petersenstr. 20, D-64287 Darmstadt (Germany); Luft, Gerhard [Technische Universitaet Darmstadt, Ernst Berl-Institut fuer Technische und Makromolekulare Chemie, Petersenstr. 20, D-64287 Darmstadt (Germany)], E-mail: luft@bodo.ct.chemie.tu-darmstadt.de

    2009-03-20

    The influence of highly compressed gases on the melting of polyethylene was investigated for nitrogen, helium and ethylene. The impact of the particle size of the polymer and the heating rate on the melting point were also analysed. The melting points were determined with a high pressure differential thermal analysis (HPDTA) apparatus. These measurements were compared with independent measurements, done by high pressure differential scanning calorimetry (HPDSC), without gas. From this experimental data it was possible to calculate the concentration of the gas in the molten polymer phase based on equilibrium thermodynamics. For high density polyethylene (HDPE), a concentration of nitrogen at the polymer melting point of 10.4-35.7 mL(SATP) g(polymer){sup -1}, in the pressure interval of 65-315 MPa, was calculated.

  20. Stability of xenon oxides at high pressures.

    Science.gov (United States)

    Zhu, Qiang; Jung, Daniel Y; Oganov, Artem R; Glass, Colin W; Gatti, Carlo; Lyakhov, Andriy O

    2013-01-01

    Xenon, which is quite inert under ambient conditions, may become reactive under pressure. The possibility of the formation of stable xenon oxides and silicates in the interior of the Earth could explain the atmospheric missing xenon paradox. Using an ab initio evolutionary algorithm, we predict the existence of thermodynamically stable Xe-O compounds at high pressures (XeO, XeO(2) and XeO(3) become stable at pressures above 83, 102 and 114 GPa, respectively). Our calculations indicate large charge transfer in these oxides, suggesting that large electronegativity difference and high pressure are the key factors favouring the formation of xenon compounds. However, xenon compounds cannot exist in the Earth's mantle: xenon oxides are unstable in equilibrium with the metallic iron occurring in the lower mantle, and xenon silicates are predicted to decompose spontaneously at all mantle pressures (xenon atoms may be retained at defects in mantle silicates and oxides.

  1. Linear ruby scale and one megabar. [high pressure fluorescence

    Science.gov (United States)

    Ruoff, A. L.

    1979-01-01

    The accuracy and validity of certain techniques used in studying high-pressure transitions have been investigated. Experiments which place upper limits of about 20 GPa and about 50 GPa on pressures practically attainable using uniaxial supported opposed anvil devices with tungsten carbide pistons and uniaxial opposed flat anvil diamond devices, respectively, are reported. Direct static determinations of the transition pressures of GaP by two different methods are described. The values obtained indicate that the linear ruby scale increasingly overestimates the transition pressure as the pressure rises above 10 GPa. It is further shown that the use of shock-based marker materials, such as silver, as the basis of pressure measurement in X-ray diffraction studies leads to bulk moduli of cubic carbides which are in extreme disagreement with expected values.

  2. The high-pressure phase of CePtAl

    Energy Technology Data Exchange (ETDEWEB)

    Heymann, Gunter [Univ. Innsbruck (Austria). Inst. fuer Allgemeine, Anorganische und Theoretische Chemie; Heying, Birgit; Rodewald, Ute C. [Univ. Muenster (Germany). Inst. fuer Anorganische und Analytische Chemie; Janka, Oliver [Univ. Muenster (Germany). Inst. fuer Anorganische und Analytische Chemie; Univ. Oldenburg (Germany). Inst. fuer Chemie

    2017-03-01

    The intermetallic aluminum compound HP-CePtAl was synthesized by arc melting of the elements with subsequent high-pressure/high-temperature treatment at 1620 K and 10.5 GPa in a multianvil press. The compound crystallizes in the hexagonal MgZn{sub 2}-type structure (P6{sub 3}/mmc) with lattice parameters of a=552.7(1) and c=898.8(2) pm refined from powder X-ray diffraction data. With the help of single crystal investigations (wR=0.0527, 187 F{sup 2} values, 13 variables), the proposed structure type was confirmed and the mixed Pt/Al site occupations could be refined. Magnetic susceptibility measurements showed a disappearance of the complex magnetic ordering phenomena, which are observed in NP-CePtAl.

  3. Structural Phase Transition of ThC Under High Pressure.

    Science.gov (United States)

    Yu, Cun; Lin, Jun; Huai, Ping; Guo, Yongliang; Ke, Xuezhi; Yu, Xiaohe; Yang, Ke; Li, Nana; Yang, Wenge; Sun, Baoxing; Xie, Ruobing; Xu, Hongjie

    2017-03-07

    Thorium monocarbide (ThC) as a potential fuel for next generation nuclear reactor has been subjected to its structural stability investigation under high pressure, and so far no one reported the observation of structure phase transition induced by pressure. Here, utilizing the synchrotron X-ray diffraction technique, we for the first time, experimentally revealed the phase transition of ThC from B1 to P4/nmm at pressure of ~58 GPa at ambient temperature. A volume collapse of 10.2% was estimated during the phase transition. A modulus of 147 GPa for ThC at ambient pressure was obtained and the stoichiometry was attributed to the discrepancy of this value to the previous reports.

  4. High pressure layered structure of carbon disulfide

    OpenAIRE

    Naghavi, S. Shahab; Crespo, Yanier; Martonak, Roman; Tosatti, Erio

    2015-01-01

    Solid CS$_{2}$ is superficially similar to CO$_{2}$, with the same $Cmca$ molecular crystal structure at low pressures, which has suggested similar phases also at high pressures. We carried out an extensive first principles evolutionary search in order to identify the zero temperature lowest enthalpy structures of CS$_{2}$ for increasing pressure up to 200\\,GPa. Surprisingly, the molecular $Cmca$ phase does not evolve into $\\beta$-cristobalite as in CO$_{2}$, but transforms instead into phase...

  5. High Pressure Multicomponent Adsorption in Porous Media

    DEFF Research Database (Denmark)

    Shapiro, Alexander; Stenby, Erling Halfdan

    1999-01-01

    We analyse adsorption of a multicomponent mixture at high pressure on the basis of the potential theory of adsorption. The adsorbate is considered as a segregated mixture in the external field produced by a solid adsorbent. we derive an analytical equation for the thickness of a multicomponent film...... close to a dew point. This equation (asymptotic adsorption equation, AAE) is a first order approximation with regard to the distance from a phase envelope....

  6. observed by high pressure NMR and NQR

    Indian Academy of Sciences (India)

    Abstract. NMR and NQR studies on two interesting systems (URu2Si2, CeTIn5) were performed under high pressure. (1) URu2Si2: In the pressure range 3.0 to 8.3 kbar, we have observed new 29Si. NMR signals arising from the antiferromagnetic (AF) region besides the previously observed 29Si. NMR signals which come ...

  7. CRRT Connected to ECMO: Managing High Pressures.

    Science.gov (United States)

    de Tymowski, Christian; Augustin, Pascal; Houissa, Hamda; Allou, Nicolas; Montravers, Philippe; Delzongle, Alienor; Pellenc, Quentin; Desmard, Mathieu

    Metabolic disorders and fluid overload are indications of continuous renal replacement therapy (CRRT) including continuous venovenous hemofiltration in patients on extracorporeal membrane oxygenation (ECMO). Direct connection of CRRT machine to the ECMO circuit provides many advantages. Nevertheless, because pressures in CRRT lines relate to ECMO blood flow, high ECMO blood flow may be associated with high pressures in CRRT lines. Thus, management of CRRT pressure lines becomes challenging. We evaluated a protocol for managing high CRRT pressures. Connections were performed according to a standardized protocol to maintain CRRT lines in the correct pressure ranges without modifying ECMO settings or inhibiting pressure alarms. To achieve this goal, the way of connecting of CRRT lines was adapted following a standardized protocol. Connection was first attempted between pump and oxygenator in the 12 patients. In five cases, high pressures in CRRT lines were successfully managed by changing the connection segment. Continuous renal replacement therapy parameters were within target levels and reduction of serum creatinine was 37%. In conclusion, management of high pressures in CRRT lines induced by ECMO could be achieved without modifying ECMO blood flow or inhibiting CRRT alarms. Iterative stops were avoided allowing efficient procedures.

  8. High pressure synthesis gas conversion. Final report

    Energy Technology Data Exchange (ETDEWEB)

    1993-05-01

    The purpose of this research project is to build and test a high pressure fermentation system for the production of ethanol from synthesis gas. The fermenters, pumps, controls, and analytical system were procured or fabricated and assembled in our laboratory. This system was then used to determine the effects of high pressure on growth and ethanol production by Clostridium ljungdahlii. The limits of cell concentration and mass transport relationships were found in CSTR and immobilized cell reactors (ICR). The minimum retention times and reactor volumes were found for ethanol production in these reactors. A maximum operating pressure of 150 psig has been shown to be possible for C. ljungdahlli with the medium of Phillips et al. This medium was developed for atmospheric pressure operation in the CSTR to yield maximum ethanol concentrations and thus is not best for operation at elevated pressures. It is recommended that a medium development study be performed for C. ljungdahlii at increased pressure. Cell concentration, gas conversion and product concentration profiles were presented for C. ljungdahlii as a function of gas flow rate, the variable which affects bacterium performance the most. This pressure was chosen as a representative pressure over the 0--150 psig operating pressure range for the bacterium. Increased pressure negatively affected ethanol productivity probably due to the fact that medium composition was designed for atmospheric pressure operation. Medium development at increased pressure is necessary for high pressure development of the system.

  9. Cubic-tetragonal phase transition in Ca sub 0 sub . sub 0 sub 4 Sr sub 0 sub . sub 9 sub 6 TiO sub 3 a combined specific heat and neutron diffraction study

    CERN Document Server

    Gallardo, M C; Romero, F J; Cerro, J D; Seifert, F; Redfern, S A T

    2003-01-01

    The specific heat corresponding to the tetragonal-to-cubic transition in Ca sub 0 sub . sub 0 sub 4 Sr sub 0 sub . sub 9 sub 6 TiO sub 3 perovskite has been measured by conduction calorimetry. The order parameter of the transition has been obtained by means of neutron diffraction at low temperatures. Comparison of calorimetric data with the evolution of the order parameter indicates that this transition seems to follow a mean field Landau potential as in SrTiO sub 3. The linear behaviour of the excess of entropy versus temperature suggests that a 2-4 Landau potential is sufficient to describe the transition.

  10. Neutron diffraction evidence of microscopic charge inhomogeneities in the CuO2 plane of superconducting La2-xSrxCuO4 (0

    Science.gov (United States)

    Bozin, E S; Kwei, G H; Takagi, H; Billinge, S J

    2000-06-19

    High-resolution atomic pair distribution functions have been obtained using neutron powder diffraction data from La2-xSrxCuO4 over the range of doping 0distribution as a function of doping up to optimal doping. Thereafter the peak abruptly sharpens. The peak broadening can be well explained by a local microscopic coexistence of doped and undoped material. This suggests a crossover from a charge inhomogeneous state at and below optimal doping to a homogeneous charge state above optimal doping.

  11. Neutron Diffraction Evidence of Microscopic Charge Inhomogeneities in the CuO2 Plane of Superconducting La2-xSrxCuO4 ( 0 <= x <= 0.30)

    Science.gov (United States)

    Božin, E. S.; Kwei, G. H.; Takagi, H.; Billinge, S. J. L.

    2000-06-01

    High-resolution atomic pair distribution functions have been obtained using neutron powder diffraction data from La2-xSrxCuO4 over the range of doping 0distribution as a function of doping up to optimal doping. Thereafter the peak abruptly sharpens. The peak broadening can be well explained by a local microscopic coexistence of doped and undoped material. This suggests a crossover from a charge inhomogeneous state at and below optimal doping to a homogeneous charge state above optimal doping.

  12. Recent Developments in High-Pressure Research at GSECARS (Invited)

    Science.gov (United States)

    Rivers, M. L.; Prakapenka, V.; Wang, Y.; Dera, P. K.; Eng, P.; Newville, M.; Sutton, S. R.

    2009-12-01

    GeoSoilEnviroCARS (GSECARS) is a national user facility for geoscience research at sector 13 of the Advanced Photon Source, Argonne National Laboratory. GSECARS provides the scientific community with access to high-brightness x-rays and supports a wide range of experimental techniques. Approximately 50% of the research conducted at GSECARS involves high-pressure, both in the diamond anvil cell, and in 250-ton and 1000-ton multi-anvil presses. The other 50% of the research includes x-ray microprobe, microtomography, surface scattering and spectroscopy. The high-pressure experimental techniques provided at the facility include: - Diamond Anvil Cell: Monochromatic diffraction and spectroscopy. Online laser heating is available on the undulator beamline, and external heating is available on the bending magnet beamline. The online laser heating includes two 100W 1060nm fiber lasers and a 200W CO2 laser. - Multi-anvil Press: energy-dispersive and monochromatic diffraction and imaging. There is a 250 ton press on the bending magnet beamline, and a 1000 ton press on the undulator beamline; deformation experiments, acoustic velocity measurements, and computed tomography can all be performed in the press. An addition coming soon is the D-DIA30 module, which is a large multi-stage module for deformation experiments in the 1000-ton press. This device should also permit multi-anvil experiments to approach the megabar pressure range. - Inelastic scattering (X-ray Raman) in the diamond anvil cell. This is performed on a large 6-circle diffractometer in the 13-ID-C station. It is used to determine the electronic structure of low-Z elements, such as B, C, N, and O at high pressure. - Brillouin spectroscopy in the diamond anvil cell. This facility is located on the bending magnet beamline, and allows simultaneous measurement of density (by x-ray diffraction of the sample), pressure (by x-ray diffraction of standard materials), and sound speeds (by Brillouin spectroscopy). Offline

  13. HIGH PRESSURE COAL COMBUSTON KINETICS PROJECT

    Energy Technology Data Exchange (ETDEWEB)

    Stefano Orsino

    2005-03-30

    As part of the U.S. Department of Energy (DoE) initiative to improve the efficiency of coal-fired power plants and reduce the pollution generated by these facilities, DOE has funded the High-Pressure Coal Combustion Kinetics (HPCCK) Projects. A series of laboratory experiments were conducted on selected pulverized coals at elevated pressures with the specific goals to provide new data for pressurized coal combustion that will help extend to high pressure and validate models for burnout, pollutant formation, and generate samples of solid combustion products for analyses to fill crucial gaps in knowledge of char morphology and fly ash formation. Two series of high-pressure coal combustion experiments were performed using SRI's pressurized radiant coal flow reactor. The first series of tests characterized the near burner flame zone (NBFZ). Three coals were tested, two high volatile bituminous (Pittsburgh No.8 and Illinois No.6), and one sub-bituminous (Powder River Basin), at pressures of 1, 2, and 3 MPa (10, 20, and 30 atm). The second series of experiments, which covered high-pressure burnout (HPBO) conditions, utilized a range of substantially longer combustion residence times to produce char burnout levels from 50% to 100%. The same three coals were tested at 1, 2, and 3 MPa, as well as at 0.2 MPa. Tests were also conducted on Pittsburgh No.8 coal in CO2 entrainment gas at 0.2, 1, and 2 MPa to begin establishing a database of experiments relevant to carbon sequestration techniques. The HPBO test series included use of an impactor-type particle sampler to measure the particle size distribution of fly ash produced under complete burnout conditions. The collected data have been interpreted with the help of CFD and detailed kinetics simulation to extend and validate devolatilization, char combustion and pollutant model at elevated pressure. A global NOX production sub-model has been proposed. The submodel reproduces the performance of the detailed chemical

  14. Heterogeneous flow during high-pressure torsion

    Directory of Open Access Journals (Sweden)

    Roberto B. Figueiredo

    2013-06-01

    Full Text Available High-Pressure Torsion (HPT has attracted significant attention in recent years as an effective technique to process ultrafine and nanostructured materials. The hydrostatic pressure developed during processing prevents the occurrence of cracks and the low thickness to diameter ratio provides the opportunity for developing high strains at low numbers of rotations. The present work analyses the plastic flow during HPT. Experimental results and computer modeling are used to describe heterogeneous plastic flow. It is shown that variations in structure, hardness and in the distribution of strain are observed along the disc thickness. The sources of these heterogeneities are discussed.

  15. Foaming Glass Using High Pressure Sintering

    DEFF Research Database (Denmark)

    Østergaard, Martin Bonderup; Petersen, Rasmus Rosenlund; König, Jakob

    Foam glass is a high added value product which contributes to waste recycling and energy efficiency through heat insulation. The foaming can be initiated by a chemical or physical process. Chemical foaming with aid of a foaming agent is the dominant industrial process. Physical foaming has two...... variations. One way is by saturation of glass melts with gas. The other involves sintering of powdered glass under a high gas pressure resulting in glass pellets with high pressure bubbles entrapped. Reheating the glass pellets above the glass transition temperature under ambient pressure allows the bubbles...

  16. High pressure hydroformylation in the chemical industry

    Energy Technology Data Exchange (ETDEWEB)

    Paciello, R. [BASF Aktiengesellschaft, Ludwigshafen (Germany)

    2006-07-01

    Higher oxo alcohols are intermediates for large-scale applications, such as plasticizers, detergents and fuel additives, as well as being useful in the synthesis of fine chemicals such as vitamins or flavors and fragrances. Many of these alcohols are still made using high pressure technologies. Advantages and disadvantages of different technologies presently in use or being developed are discussed. In particular, efforts to decrease raw material costs, e.g. by increasing yield, or investment, e.g. by decreasing pressure, will be highlighted. (orig.)

  17. Neutron structural biology

    Energy Technology Data Exchange (ETDEWEB)

    Niimura, Nobuo [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-03-01

    Neutron diffraction provides an experimental method of directly locating hydrogen atoms in protein which play important roles in physiological functions. However, there are relatively few examples of neutron crystallography in biology since it takes a lot of time to collect a sufficient number of Bragg reflections due to the low flux of neutrons illuminating the sample. In order to overcome the flux problem, we have successfully developed the neutron IP, where the neutron converter, {sup 6}Li or Gd, was mixed with a photostimulated luminescence material on flexible plastic support. Neutron Laue diffraction 2A data from tetragonal lysozyme were collected for 10 days with neutron imaging plates, and 960 hydrogen atoms in the molecule and 157 bound water molecules were identified. These results explain the proposed hydrolysis mechanism of the sugar by the lysozyme molecule and that lysozyme is less active at pH7.0. (author)

  18. The use of neutron diffraction for the determination of the in-depth residual stresses profile in weld coatings; A utilizacao da difracao de neutroes na determinacao do perfil de tensoes residuais em revestimentos por soldadura

    Energy Technology Data Exchange (ETDEWEB)

    Marques, Maria Jose; Batista, A.C.; Nobre, J.P. [Universidade de Coimbra (Portugal). Dept. de Fisica. Centro de Estudos de Materiais por Difraccao de Raios X (CEMDRX); Loureiro, Altino [Universidade de Coimbra (Portugal). Dept. de Engenharia Mecanica. Centro de Engenharia Mecanica (CEMUC); Kornmeier, Joana R., E-mail: mjvaz@fe.up.pt [Technische Universitaet Muenchen, Garching (Germany). FRM II

    2013-04-15

    The neutron diffraction is a non-destructive technique, particularly suitable for the analysis of residual stress fields in welds. The technique is used in this article to study ferritic samples, coated by submerged arc welding using stainless steel filler metals. This procedure is often used for manufacturing process equipment for chemical and nuclear industries, for ease of implementation and economic reasons. The main disadvantage of that processes is the cracking phenomenon that often occurs at the interface between the base material and coatings, which can be minimized by performing post-weld stress relief heat treatments. The samples analyzed in this study were made of carbon steel plates, coated by submerged arc welding two types of stainless steel filler metals. For the first layer was used one EN 12 072 - S 2 U 23 12 electrode, while for the second and third layers were used an EN 12 072 - 19 12 3 S L electrode. After cladding, the samples were submitted to a post-weld heat treatment for 1 hour at 620 deg C. The residual stress profiles obtained by neutron diffraction evidence the relaxation of residual stress given by the heat treatment. (author)

  19. Structural study of CaMn{sub 1−x}Mo{sub x}O{sub 3} (0.08 ≤ x ≤ 0.12) system by neutron powder diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Supelano, G.I., E-mail: ivan.supelano@uptc.edu.co [Grupo Física de Materiales, Escuela de Física, Universidad Pedagógica y Tecnológica de Colombia, Tunja (Colombia); Parra Vargas, C.A.; Barón-González, A.J. [Grupo Física de Materiales, Escuela de Física, Universidad Pedagógica y Tecnológica de Colombia, Tunja (Colombia); Sarmiento Santos, A. [Grupo Superficies Electroquímica y Corrosión, Escuela de Física, Universidad Pedagógica y Tecnológica de Colombia, Tunja (Colombia); Frontera, C. [Institut de Ciència de Materials de Barcelona, CSIC, Campus Universitari de Bellaterra, E-08193, Bellaterra, Barcelona (Spain)

    2016-08-15

    Neutron powder diffraction experiments and magnetic measurements in polycrystalline CaMn{sub 1−x}Mo{sub x}O{sub 3} (x = 0.08, 0.10, 0.12) point towards a possible charge and orbital order in this system. The analysis of structural and magnetic data show that the samples present structural phase transformation from Pnma to P2{sub 1}/m space group and the system has a C-type antiferromagnetic configuration at low temperature. A detailed analysis of the bond distances signals a small Jahn-Teller distortion of only one (x = 0.08) or of the two Mn ions (x = 0.10, 0.12). We identify the partially occupied e{sub g} orbitals and this explains the C-type magnetic structure. - Highlights: • CaMn{sub 1−x}Mo{sub x}O{sub 3} (x = 0.08, 0.10, 0.12) is investigated by neutron powder diffraction. • Analysis of individual Mn-O distances demonstrates the apparition of orbital order. • By symmetry analysis, we find that the low temperature magnetic structure is C-type. • Magnetic interactions foreseen by the orbital order explain the magnetic structure.

  20. Structural investigation of ribonuclease A conformational preferences using high pressure protein crystallography

    Energy Technology Data Exchange (ETDEWEB)

    Kurpiewska, Katarzyna, E-mail: kurpiews@chemia.uj.edu.pl [Jagiellonian University, Faculty of Chemistry, Department of Crystal Chemistry and Crystal Physics, Protein Crystallography Group, Ingardena 3, 30-060 Kraków (Poland); Dziubek, Kamil; Katrusiak, Andrzej [Adam Mickiewicz University, Faculty of Chemistry, Department of Materials Chemistry, Umultowska 89b, 61-61 Poznań (Poland); Font, Josep [School of Medical Science, University of Sydney, NSW 2006 (Australia); Ribò, Marc; Vilanova, Maria [Universitat de Girona, Laboratorid’Enginyeria de Proteïnes, Departament de Biologia, Facultat de Ciències, Campus de Montilivi, 17071 Girona (Spain); Lewiński, Krzysztof [Jagiellonian University, Faculty of Chemistry, Department of Crystal Chemistry and Crystal Physics, Protein Crystallography Group, Ingardena 3, 30-060 Kraków (Poland)

    2016-04-01

    Highlights: • A unique crystallographic studies of wild-type and mutated form of the same protein under high pressure. • Compressibility of RNase A molecule is significantly affected by a single amino acid substitution. • High pressure protein crystallography helps understanding protein flexibility and identify conformational substrates. - Abstract: Hydrostatic pressure in range 0.1–1.5 GPa is used to modify biological system behaviour mostly in biophysical studies of proteins in solution. Due to specific influence on the system equilibrium high pressure can act as a filter that enables to identify and investigate higher energy protein conformers. The idea of the presented experiments is to examine the behaviour of RNase A molecule under high pressure before and after introduction of destabilizing mutation. For the first time crystal structures of wild-type bovine pancreatic ribonuclease A and its markedly less stable variant modified at position Ile106 were determined at different pressures. X-ray diffraction experiments at high pressure showed that the secondary structure of RNase A is well preserved even beyond 0.67 GPa at room temperature. Detailed structural analysis of ribonuclease A conformation observed under high pressure revealed that pressure influences hydrogen bonds pattern, cavity size and packing of molecule.

  1. A high-pressure van der Waals compound in solid nitrogen-helium mixtures

    Science.gov (United States)

    Vos, W. L.; Finger, L. W.; Hemley, R. J.; Hu, J. Z.; Mao, H. K.; Schouten, J. A.

    1992-01-01

    A detailed diamond anvil-cell study using synchrotron X-ray diffraction, Raman scattering, and optical microscopy has been conducted for the He-N system, with a view to the weakly-bound van der Waals molecule interactions that can be formed in the gas phase. High pressure is found to stabilize the formation of a stoichiometric, solid van der Waals compound of He(N2)11 composition which may exemplify a novel class of compounds found at high pressures in the interiors of the outer planets and their satellites.

  2. The present status of high-pressure research at Beijing Synchrotron Radiation Facility

    CERN Document Server

    Liu, J; Li, Y C

    2002-01-01

    The present status of high-pressure research at Beijing Synchrotron Radiation Facility is reported. A ten-poles wiggler beamline provides a white beam for investigating samples using a diamond anvil cell. In situ energy-dispersive diffraction is used to determine the pressure-induced phase transitions and equations of state. High pressure can be stably applied by a stepper-motorized loading system with a strain sensor. Some megabar experiments have been carried out without damage on diamonds. Improved beam collimation reduces the background and eliminates gasket scatter. Some research and future developments are also presented.

  3. Phase transitions in Cd3P2 at high pressures and high temperatures

    DEFF Research Database (Denmark)

    Yel'kin, F.S.; Sidorov, V.A.; Waskowska, A.

    2008-01-01

    The high-pressure, high-temperature structural behaviour of Cd3P2 has been studied using electrical resistance measurements, differential thermal analysis, thermo baric analysis and X-ray diffraction. At room temperature, a phase transformation is observed at 4.0 GPa in compression....... The experimental zero-pressure bulk modulus of the low-pressure phase is 64.7(7) GPa, which agrees quite well with the calculated value of 66.3 GPa using the tight-binding linear muffin-tin orbital method within the local density approximation. Tentatively, the high-pressure phase has an orthorhombic crystal...

  4. High Pressure and Temperature Effects in Polymers

    Science.gov (United States)

    Bucknall, David; Arrighi, Valeria; Johnston, Kim; Condie, Iain

    Elastomers are widely exploited as the basis for seals in gas and fluid pipelines. The underlying behaviour of these elastomer at the high pressure, elevated temperatures they experience in operation is poorly understood. Consequently, the duty cycle of these materials is often deliberately limited to a few hours, and in order to prevent failure, production is stopped in order to change the seals in critical joints. The result is significant time lost due to bringing down production to change the seals as well as knock on financial costs. In order to address the fundamental nature of the elastomers at their intended operating conditions, we are studying the gas permeation behaviour of hydrogenated natural butyl rubber (HNBR) and fluorinated elastomers (FKM) at a high pressure and elevated temperature. We have developed a pressure system that permits gas permeation studies at gas pressures of up to 5000 psi and operating temperatures up to 150° C. In this paper, we will discuss the nature of the permeation behaviour at these extreme operating conditions, and how this relates to the changes in the polymer structure. We will also discuss the use of graphene-polymer thin layer coatings to modify the gas permeation behaviour of the elastomers.

  5. High Pressure Hydrogen from First Principles

    Science.gov (United States)

    Morales, M. A.

    2014-12-01

    Typical approximations employed in first-principles simulations of high-pressure hydrogen involve the neglect of nuclear quantum effects (NQE) and the approximate treatment of electronic exchange and correlation, typically through a density functional theory (DFT) formulation. In this talk I'll present a detailed analysis of the influence of these approximations on the phase diagram of high-pressure hydrogen, with the goal of identifying the predictive capabilities of current methods and, at the same time, making accurate predictions in this important regime. We use a path integral formulation combined with density functional theory, which allows us to incorporate NQEs in a direct and controllable way. In addition, we use state-of-the-art quantum Monte Carlo calculations to benchmark the accuracy of more approximate mean-field electronic structure calculations based on DFT, and we use GW and hybrid DFT to calculate the optical properties of the solid and liquid phases near metallization. We present accurate predictions of the metal-insulator transition on the solid, including structural and optical properties of the molecular phase. This work was supported by the U.S. Department of Energy at the Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and by LDRD Grant No. 13-LW-004.

  6. Is sodium a superconductor under high pressure?

    Science.gov (United States)

    Tutchton, Roxanne; Chen, Xiaojia; Wu, Zhigang

    2017-01-07

    Superconductivity has been predicted or measured for most alkali metals under high pressure, but the computed critical temperature (T c ) of sodium (Na) at the face-centered cubic (fcc) phase is vanishingly low. Here we report a thorough, first-principles investigation of superconductivity in Na under pressures up to 260 GPa, where the metal-to-insulator transition occurs. Linear-response calculations and density functional perturbation theory were employed to evaluate phonon distributions and the electron-phonon coupling for bcc, fcc, cI16, and tI19 Na. Our results indicate that the maximum electron-phonon coupling parameter, λ, is 0.5 for the cI16 phase, corresponding to a theoretical peak in the critical temperature at T c ≈1.2 K. When pressure decreases or increases from 130 GPa, T c drops quickly. This is mainly due to the lack of p-d hybridization in Na even at 260 GPa. Since current methods based on the Eliashberg and McMillian formalisms tend to overestimate the T c (especially the peak values) of alkali metals, we conclude that under high pressure-before the metal-to-insulator transition at 260 GPa-superconductivity in Na is very weak, if it is measurable at all.

  7. New developments in high pressure x-ray spectroscopy beamline at High Pressure Collaborative Access Team.

    Science.gov (United States)

    Xiao, Y M; Chow, P; Boman, G; Bai, L G; Rod, E; Bommannavar, A; Kenney-Benson, C; Sinogeikin, S; Shen, G Y

    2015-07-01

    The 16 ID-D (Insertion Device - D station) beamline of the High Pressure Collaborative Access Team at the Advanced Photon Source is dedicated to high pressure research using X-ray spectroscopy techniques typically integrated with diamond anvil cells. The beamline provides X-rays of 4.5-37 keV, and current available techniques include X-ray emission spectroscopy, inelastic X-ray scattering, and nuclear resonant scattering. The recent developments include a canted undulator upgrade, 17-element analyzer array for inelastic X-ray scattering, and an emission spectrometer using a polycapillary half-lens. Recent development projects and future prospects are also discussed.

  8. Neutron Diffraction Studies of a Class A beta-Lactamase Toho-1 E166A/R274N/R276N Triple Mutant

    Energy Technology Data Exchange (ETDEWEB)

    Blakeley, Matthew P. [Institut Laue-Langevin (ILL); Chen, Yu [ORNL; Afonine, Pavel [Lawrence Berkeley National Laboratory (LBNL)

    2010-01-01

    beta-Lactam antibiotics have been used effectively over several decades against many types of bacterial infectious diseases. However, the most common cause of resistance to the beta-lactam antibiotics is the production of beta-lactamase enzymes that inactivate beta-lactams by rapidly hydrolyzing the amide group of the beta-lactam ring. Specifically, the class A extended-spectrum beta-lactamases (ESBLs) and inhibitor-resistant enzymes arose that were capable of hydrolyzing penicillins and the expanded-spectrum cephalosporins and monobactams in resistant bacteria, which lead to treatment problems in many clinical settings. A more complete understanding of the mechanism of catalysis of these ESBL enzymes will impact current antibiotic drug discovery efforts. Here, we describe the neutron structure of the class A, CTX-M-type ESBL Toho-1 E166A/R274N/R276N triple mutant in its apo form, which is the first reported neutron structure of a beta-lactamase enzyme. This neutron structure clearly reveals the active-site protonation states and hydrogen-bonding network of the apo Toho-1 ESBL prior to substrate binding and subsequent acylation. The protonation states of the active-site residues Ser70, Lys73, Ser130, and Lys234 in this neutron structure are consistent with the prediction of a proton transfer pathway from Lys73 to Ser130 that is likely dependent on the conformation of Lys73, which has been hypothesized to be coupled to the protonation state of Glu166 during the acylation reaction. Thus, this neutron structure is in agreement with a proposed mechanism for acylation that identifies Glu166 as the general base for catalysis.

  9. High pressure photophysics of organic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Brey, L. A.

    1979-01-01

    High pressure spectroscopic studies on several classes of organic compounds were made both in fluid solution (to 10 kbar) and in polymeric media (to 40 kbar). The first three studies were conducted in fluid solution and concern the effect of solvent viscosity on the nonradiative deactivation rates from electronically excited states. Pressure was utilized to attain high viscosities in organic solvents at room temperature. The primary experimental technique used was fluorescence emission spectroscopy. In the fourth and last study observations were made both in fluid solution and in plastic films. The focus of this study was the effect of pressure on the solvent-chromophore dispersion interaction in several polyenes and the concomitant changes in both the radiative and non-radiative rates from the excited states. Extensive use was made of fluorescence lifetime measurements and excitation spectra. 105 references.

  10. Superconductivity from magnetic elements under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu, Katsuya [KYOKUGEN, Research Center for Materials Science at Extreme Conditions, Osaka University, Osaka 560-8531 (Japan)]. E-mail: shimizu@rcem.osaka-u.ac.jp; Amaya, Kiichi [Toyota Physical and Chemical Research Institute, Aichi 480-1192 (Japan); Suzuki, Naoshi [Graduate School of Engineering Science, Osaka University, Osaka 560-8531 (Japan); Onuki, Yoshichika [Graduate School of Science, Osaka University, Osaka 560-0043 (Japan)

    2006-05-01

    Can we expect the appearance of superconductivity from magnetic elements? In general, superconductivity occurs in nonmagnetic metal at low temperature and magnetic impurities destroy superconductivity; magnetism and superconductivity are as incompatible as oil and water. Here, we present our experimental example of superconducting elements, iron and oxygen. They are magnetic at ambient pressure, however, they become nonmagnetic under high pressure, then superconductor at low temperature. What is the driving force of the superconductivity? Our understanding in the early stages was a simple scenario that the superconductive state was obtained as a consequence of an emergence of the nonmagnetic states. In both cases, we may consider another scenario for the appearance of superconductivity; the magnetic fluctuation mechanism in the same way as unconventional superconductors.

  11. High pressure Raman scattering of silicon nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Khachadorian, Sevak; Scheel, Harald; Thomsen, Christian [Institut fuer Festkoerperphysik, Technische Universitaet Berlin, 10623 Berlin (Germany); Papagelis, Konstantinos [Materials Science Department, University of Patras, 26504 Patras (Greece); Colli, Alan [Nokia Research Centre, 21 J J Thomson Avenue, Cambridge CB3 0FA (United Kingdom); Ferrari, Andrea C, E-mail: khachadorian@physik.tu-berlin.de [Department of Engineering, University of Cambridge, Cambridge CB3 0FA (United Kingdom)

    2011-05-13

    We study the high pressure response, up to 8 GPa, of silicon nanowires (SiNWs) with {approx} 15 nm diameter, by Raman spectroscopy. The first order Raman peak shows a superlinear trend, more pronounced compared to bulk Si. Combining transmission electron microscopy and Raman measurements we estimate the SiNWs' bulk modulus and the Grueneisen parameters. We detect an increase of Raman linewidth at {approx} 4 GPa, and assign it to pressure induced activation of a decay process into LO and TA phonons. This pressure is smaller compared to the {approx} 7 GPa reported for bulk Si. We do not observe evidence of phase transitions, such as discontinuities or change in the pressure slopes, in the investigated pressure range.

  12. High-pressure structures of methane hydrate

    CERN Document Server

    Hirai, H; Fujihisa, H; Sakashita, M; Katoh, E; Aoki, K; Yamamoto, Y; Nagashima, K; Yagi, T

    2002-01-01

    Three high-pressure structures of methane hydrate, a hexagonal structure (str. A) and two orthorhombic structures (str. B and str. C), were found by in situ x-ray diffractometry and Raman spectroscopy. The well-known structure I (str. I) decomposed into str. A and fluid at 0.8 GPa. Str. A transformed into str. B at 1.6 GPa, and str. B further transformed into str. C at 2.1 GPa which survived above 7.8 GPa. The fluid solidified as ice VI at 1.4 GPa, and the ice VI transformed to ice VII at 2.1 GPa. The bulk moduli, K sub 0 , for str. I, str. A, and str. C were calculated to be 7.4, 9.8, and 25.0 GPa, respectively.

  13. A pseudo-tetragonal tungsten bronze superstructure: a combined solution of the crystal structure of K6.4(Nb,Ta)(36.3)O94 with advanced transmission electron microscopy and neutron diffraction.

    Science.gov (United States)

    Paria Sena, Robert; Babaryk, Artem A; Khainakov, Sergiy; Garcia-Granda, Santiago; Slobodyanik, Nikolay S; Van Tendeloo, Gustaaf; Abakumov, Artem M; Hadermann, Joke

    2016-01-21

    The crystal structure of the K6.4Nb28.2Ta8.1O94 pseudo-tetragonal tungsten bronze-type oxide was determined using a combination of X-ray powder diffraction, neutron diffraction and transmission electron microscopy techniques, including electron diffraction, high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), annular bright field STEM (ABF-STEM) and energy-dispersive X-ray compositional mapping (STEM-EDX). The compound crystallizes in the space group Pbam with unit cell parameters a = 37.468(9) Å, b = 12.493(3) Å, c = 3.95333(15) Å. The structure consists of corner sharing (Nb,Ta)O6 octahedra forming trigonal, tetragonal and pentagonal tunnels. All tetragonal tunnels are occupied by K(+) ions, while 1/3 of the pentagonal tunnels are preferentially occupied by Nb(5+)/Ta(5+) and 2/3 are occupied by K(+) in a regular pattern. A fractional substitution of K(+) in the pentagonal tunnels by Nb(5+)/Ta(5+) is suggested by the analysis of the HAADF-STEM images. In contrast to similar structures, such as K2Nb8O21, also parts of the trigonal tunnels are fractionally occupied by K(+) cations.

  14. Amorphouslike diffraction pattern in solid metallic titanium

    DEFF Research Database (Denmark)

    Wang, Y.; Fang, Y.Z.; Kikegawa, T.

    2005-01-01

    Amorphouslike diffraction patterns of solid elemental titanium have been detected under high pressure and high temperature using in situ energy-dispersive x-ray diffraction and a multianvil press. The onset pressure and the temperature of formation of amorphous titanium is found to be close to th...

  15. Reactivity, structure and physical properties of SrCo{sub 2.5+{delta}} and La{sub 2}CoO{sub 4.0+{delta}}. In situ X-ray diffraction and neutrons study; Reactivite, structure et proprietes physiques de SrCoO{sub 2.5+{delta}} et La{sub 2}CoO{sub 4.0+{delta}}. Etude par diffraction des rayons X et des neutrons in situ

    Energy Technology Data Exchange (ETDEWEB)

    Le Toquin, R.

    2003-11-15

    This work was devoted to the study of the reactivity and more specifically the influence of the intercalated oxygen amount {delta} on the structure and physical properties of SrCoO{sub 2.5+{delta}} et La{sub 2}CoO{sub 4.0+{delta}} We controlled the oxidation level by means of reversible electrochemical red ox reaction at room temperature. Structural modifications, especially disorder, and electronic properties were studied for the first time on large orientated single crystal. In the SrCoO{sub 2.5+{delta}} system, after structural and electronic characterisation of the end phases, we studied the real structure of the brownmillerite SrCoO{sub 2.5} phase using single crystal. Moreover, we investigated structural and magnetic evolution upon red ox cycle using X-ray diffraction on 6 times twinned single crystal and in situ neutron powder diffraction. Two intermediate SrCoO{sub 2.75} and SrCoO{sub 2.82} phases have been observed. The reaction on single crystal has evidenced the evolution of domain structure. For the La{sub 2}CoO{sub 4+{delta}} system, we synthesised a large variety of single crystal with stoichiometry {delta} 0.0, 0.09, 0.12, 0.16, 0.20 and 0.25. Using single crystal X-ray and neutron diffraction, we showed a disorder-order transition of the apical and interstitial oxygen for the higher {delta} values. (author)

  16. Novel High Pressure Pump-on-a-Chip Technology Project

    Data.gov (United States)

    National Aeronautics and Space Administration — HJ Science & Technology, Inc. proposes to develop a novel high pressure "pump-on-a-chip" (HPPOC) technology capable of generating high pressure and flow rate on...

  17. The piston-cylinder apparatus for in-situ structural investigations of high-pressure phases of gas hydrates with the use of synchrotron radiation

    CERN Document Server

    Mirinski, D S; Larionova, E G; Kurnosov, A V; Ancharov, A I; Dyadin, Y A; Tolochko, B P; Sheromov, M A

    2001-01-01

    The piston-cylinder apparatus for the investigation of high-pressure gas hydrate phases by the powder diffraction method is presented. The first results concerning the nature of the high-pressure gas hydrate phase in the sulfur hexafluoride-water system are reported.

  18. Phase transitions in delafossite CuLaO{sub 2} at high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Salke, Nilesh P.; Rao, Rekha, E-mail: rekhar@barc.gov.in; Gupta, M. K.; Mittal, R. [Solid State Physics Division, Bhabha Atomic Research Center, Mumbai 400 085 (India); Garg, Alka B. [High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Center, Mumbai 400 085 (India); Achary, S. N.; Tyagi, A. K. [Chemistry Division, Bhabha Atomic Research Center, Mumbai 400 085 (India)

    2014-04-07

    Structural stability of a transparent conducting oxide CuLaO{sub 2} at high pressures is investigated using in-situ Raman spectroscopy, electrical resistance, and x-ray diffraction techniques. The present Raman investigations indicate a sequence of structural phase transitions at 1.8 GPa and 7 GPa. The compound remains in the first high pressure phase when pressure is released. Electrical resistance measurements carried out at high pressures confirm the second phase transition. These observations are further supported by powder x-ray diffraction at high pressures which also showed that a-axis is more compressible than c-axis in this compound. Fitting the pressure dependence of unit cell volume to 3{sup rd} order Birch-Murnaghan equation of state, zero pressure bulk modulus of CuLaO{sub 2} is determined to be 154(25) GPa. The vibrational properties in the ambient delafossite phase of CuLaO{sub 2} are investigated using ab-initio calculations of phonon frequencies to complement the Raman spectroscopic measurements. Temperature dependence of the Raman modes of CuLaO{sub 2} is investigated to estimate the anharmonicity of Raman modes.

  19. Synthesis of well-aligned boron nanowires and their structural stability under high pressure

    CERN Document Server

    Cao Li Min; Gao Cun Xiao; Li Yan Cun; Li Xiao Dong; Wang, Y Q; Zhang, Z; Cui Qi Liang; Zou Guang Tian; Sun Li; Wang Wen Kui

    2002-01-01

    Owing to its unusual bonding and vast variety of unique crystal structures, boron is one of the most fascinating elements in the periodic table. Here we report the large-scale synthesis of well-ordered boron nanowires and their structural stability at high pressure. Boron nanowires with uniform diameter and length grown vertically on silicon substrates were synthesized by radio-frequency magnetron sputtering with a target of pure boron using argon as the sputtering atmosphere without involvement of templates and catalysts. Detailed characterization by high-resolution transmission electron microscopy and electron diffraction indicates that the boron nanowires are amorphous. Structural stability of the boron nanowires at room temperature has been investigated by means of in situ high-pressure energy-dispersive x-ray powder diffraction using synchrotron radiation in a diamond anvil cell. No crystallization was observed up to a pressure of 103.5 GPa, suggesting that the amorphous structure of boron nanowires is s...

  20. 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

    studied by differential scanning calorimetry and in situ x-ray powder diffraction. The alloy shows a glass transition and three crystallization events, the first and dominant one at 456 K corresponding to eutectic crystallization of at least three phases: Mg2Cu and most likely cubic MgY and CuMgY....