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Sample records for neutron diffraction investigation

  1. Levitation apparatus for neutron diffraction investigations on high temperature liquids

    SciTech Connect

    Hennet, Louis; Pozdnyakova, Irina; Bytchkov, Aleksei; Cristiglio, Viviana; Palleau, Pierre; Fischer, Henry E.; Cuello, Gabriel J.; Johnson, Mark; Melin, Philippe; Zanghi, Didier; Brassamin, Severine; Brun, Jean-Francois; Price, David L.; Saboungi, Marie-Louise

    2006-05-15

    We describe a new high temperature environment based on aerodynamic levitation and laser heating designed for neutron scattering experiments up to 3000 deg. C. The sample is heated to the desired temperature with three CO{sub 2} lasers from different directions in order to obtain a homogeneous temperature distribution. The apparent temperature of the sample is measured with an optical pyrometer, and two video cameras are employed to monitor the sample behavior during heating. The levitation setup is enclosed in a vacuum-tight chamber, enabling a high degree of gas purity and a reproducible sample environment for structural investigations on both oxide and metallic melts. High-quality neutron diffraction data have been obtained on liquid Y{sub 3}Al{sub 5}O{sub 12} and ZrNi alloy for relatively short counting times (1.5 h)

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

    PubMed Central

    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 rationalized 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 polymerizing on decompression to ambient pressure. The resulting product is analyzed via Raman and FT-IR spectroscopy and differential scanning calorimetry and found to possess a different molecular structure compared with polymers produced via traditional routes. PMID:24650085

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

    PubMed

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

    2015-09-10

    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 of phase III deteriorates significantly. On decompression phase III persists to 0.54 GPa before transformation to the ambient pressure phase. There is significant loss of signal after decompression, signifying that there has been a loss of material through polymerization. The orientation of the molecules in phase III provides insight into the possible polymerization reaction. PMID:26289930

  4. SINGLE CRYSTAL NEUTRON DIFFRACTION.

    SciTech Connect

    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.

  5. Investigation on Deformation Behavior of Nickel Aluminum Bronze by Neutron Diffraction and Transmission Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Xu, Xiaoyan; Wang, Hong; Lv, Yuting; Lu, Weijie; Sun, Guangai

    2016-05-01

    The deformation behavior, deformation microstructures, and generated inter-phase stresses of nickel aluminum bronze were investigated by in situ neutron diffraction instrument and transmission electron microscopy in this paper. Lattice strains calculated by both peak shifting and broadening by Gaussian fitting of α and κ phase neutron diffraction peak profiles at both holding stress conditions and unloaded stress conditions were compared. Twining and stacking faults in α matrix were observed after deformed by different tensile stresses. Compressive internal/residual stress in α matrix and tensile internal stress in κ phase in elasto-plastic region were calculated based on neutron diffraction analysis. The piled-up dislocations around hard κ phases increase with increasing the deformation degree, which raise the stress concentration near α/ κ interface and increase the internal stresses.

  6. Neutron diffraction investigation of an in-plane biaxial fatigued stainless steel sample of cruciform geometry

    NASA Astrophysics Data System (ADS)

    Taran, Yu V.; Balagurov, A. M.; Sheverev, S. G.; Schreiber, J.; Korsunsky, A. M.; Vorster, W. J. J.; Bomas, H.; Stoeberl, C.

    2008-03-01

    Fatigue and fracture under multiaxial stresses are among the most important current research topics aimed at ensuring improved reliability of industrial components. An ex situ in-plane biaxial low cycle fatigued sample of cruciform geometry from austenitic stainless steel AISI 321 H was investigated on the FSD stress-diffractometer at the IBR-2 pulsed nuclear reactor by using the neutron strain scanner and the uniaxial stress rig. The phase composition of fatigued material was determined and the residual macrostresses and phase microstresses were measured. To the best of our knowledge, no neutron diffraction investigations of materials subjected to biaxial loading have been previously carried out. The first results of the neutron diffraction experiment are presented and discussed.

  7. Deformation mechanisms of a 20Mn TWIP steel investigated by in situ neutron diffraction and TEM

    SciTech Connect

    Shen, Yongfeng; Wang, Y. D.; Liu, Xiaopeng; Sun, Xin; Peng, R. Lin; Zhang, S. Y.; Zuo, Liang; Liaw, Peter K.

    2013-07-25

    The deformation mechanisms and associated microstructure changes during tensile loading of an annealed twinning-induced plasticity (TWIP) steel with the chemical composition of Fe–20Mn–3Si–3Al–0.045C (wt.%) were systematically investigated using in situ time-of-flight (TOF) neutron diffraction in combination with postmortem transmission electron microscopy (TEM). The initial microstructure of the investigated alloy consists of equiaxed austenitic grains with the initial α´-phase of ~7% in volume. In addition to dislocation slip, twinning and two kinds of martensitic transformations from the austenite to α´- and epsilon martensites were observed as the main deformation modes during the tensile deformation. In situ neutron diffraction provides a powerful tool to establish the deformation mode map for elucidating the role of different deformation modes in different strain regions. The critical stress is 520 MPa for the martensitic transformation from the austenite to α´-martensite, whereas a higher stress (>600 MPa) is required for actuating the deformation twin and/or the martensitic transformation from -martensite. Both epsilon- and α´-martensites act as the hard phases whereas mechanical twinning contributes to both strength and ductility of the studied steel. TEM observations confirmed that the twinning process was facilitated by the parent grains orientated with <111> or <110> parallel to the loading direction. The nucleation and growth of twins are attributed to the pole and self-generation formation mechanisms, as well as the stair-rod cross-slip mechanism.

  8. Complex investigation of deformation twinning in γ-TiAl by TEM and neutron diffraction

    NASA Astrophysics Data System (ADS)

    Beran, Premysl; Heczko, Milan; Kruml, Tomas; Panzner, Tobias; van Petegem, Steven

    2016-10-01

    A near-γ TiAl based alloy with 2 at% of Nb was investigated by means of collaborative research based on transmission electron microscopy and in-situ neutron diffraction techniques with the aim to study mechanical twinning and its role within the mechanisms governing fatigue response and material properties. In-situ neutron diffraction measurements were performed during low cycle fatigue straining at room temperature. Induced lattice strain related to the formation of deformation twins was detected and used to follow changes in the macroscopic material response caused by the twinning process during cycling. A microscopic insight was realised by using several transmission electron microscopy techniques to reveal in detail an internal deformation microstructure of the material at the beginning as well as at the end of the fatigue life. The study was focused on the first loading cycles where the material shows intense cyclic hardening. The effect of mechanical twinning on the material behaviour at several stages of the fatigue life is discussed for two different total strain amplitudes of 0.2% and 0.4%.

  9. Fatigue investigations of autofrettaged steel cylinders based on neutron-diffraction measurements

    NASA Astrophysics Data System (ADS)

    de Swardt, R. R.; Venter, A. M.; van der Watt, M. W.

    A series of cyclic internal pressurization fatigue experiments was conducted on partially autofrettaged cylinders with multiple internal radial elliptic shaped cracks covering a wide range of possible configurations. A theoretical model was developed to predict the theoretical fatigue life using as input data the actual measured position of the plastic boundary from neutron-diffraction measurements on the failed specimens, as well as a position calculated analytically from the autofrettage pressure. The theoretical fatigue-life predictions based on the neutron-diffraction results were found to give the best correlation with experimental fatigue results.

  10. At-temperature neutron diffraction investigation of the aging process in magnesia-partially-stabilized zirconia

    SciTech Connect

    Argyriou, D.N. Univ. of Technology, Sydney ); Howard, C.J. ); Smith, R.I. . ISIS Facility)

    1994-12-01

    A time-resolved neutron powder diffraction technique has been used to follow the changes occurring during the aging of magnesia-partially-stabilized zirconia at 1,100 C. Through quantitative phase analyses it has been possible to follow the development with aging time of tetragonal zirconia and of the [delta]-phase (Mg[sub 2]Zr[sub 5]O[sub 12], related to cubic, but with ordered anion vacancies), both at the expense of cubic zirconia. Changes in lattice parameters have been attributed to the expulsion of MgO stabilizer from the tetragonal zirconia precipitates as the aging proceeds. The broadening of peaks in the neutron diffraction pattern suggests there is considerable strain in the tetragonal precipitates in the c-direction, which is the short dimension in these lenticular precipitates. On cooling, there is some transformation of tetragonal zirconia to the monoclinic and orthorhombic phases.

  11. High resolution neutron diffraction crystallographic investigation of Oxide Dispersion Strengthened steels of interest for fusion technology

    NASA Astrophysics Data System (ADS)

    Coppola, R.; Rodriguez-Carvajal, J.; Wang, M.; Zhang, G.; Zhou, Z.

    2014-12-01

    High resolution neutron diffraction measurements have been carried out to characterize the crystallographic phases present in different Oxide Dispersion Strengthened (ODS) steels of interest for fusion technology. The different lattice structures, Im3m for the ferritic ODS and Fm3m for the austenitic ODS, are resolved showing line anisotropy effects possibly correlated with differences in dislocation densities and texture. Many contributions from minority phases are detected well above the background noise; none of the expected crystallographic phases, such as M23C6 and including Y2O3, fits them, but the TiN phase is identified in accordance with results of other microstructural techniques.

  12. Pressure dependence of the magnetic order in CrAs: a neutron diffraction investigation

    SciTech Connect

    Keller, L.; White, J. S.; Babkevich, P.; Susner, Michael A.; Sims, Zachary C; Safa-Sefat, Athena; Ronnow, H. M.; Ruegg, Ch.

    2015-01-29

    The suppression of magnetic order with pressure concomitant with the appearance of pressure-induced superconductivity was recently discovered in CrAs. Here we present a neutron diffraction study of the pressure evolution of the helimagnetic ground-state towards and in the vicinity of the superconducting phase. Neutron diffraction on polycrystalline CrAs was employed from zero pressure to 0.65 GPa and at various temperatures. The helimagnetic long-range order is sustained under pressure and the magnetic propagation vector does not show any considerable change. The average ordered magnetic moment is reduced from 1.73(2) μB at ambient pressure to 0.4(1) μB close to the critical pressure Pc ≈ 0.7 GPa, at which magnetic order is completely suppressed. The width of the magnetic Bragg peaks strongly depends on temperature and pressure, showing a maximum in the region of the onset of superconductivity. In conclusion, we interpret this as associated with competing ground-states in the vicinity of the superconducting phase.

  13. Pressure dependence of the magnetic order in CrAs: a neutron diffraction investigation

    DOE PAGES

    Keller, L.; White, J. S.; Babkevich, P.; Susner, Michael A.; Sims, Zachary C; Safa-Sefat, Athena; Ronnow, H. M.; Ruegg, Ch.

    2015-01-29

    The suppression of magnetic order with pressure concomitant with the appearance of pressure-induced superconductivity was recently discovered in CrAs. Here we present a neutron diffraction study of the pressure evolution of the helimagnetic ground-state towards and in the vicinity of the superconducting phase. Neutron diffraction on polycrystalline CrAs was employed from zero pressure to 0.65 GPa and at various temperatures. The helimagnetic long-range order is sustained under pressure and the magnetic propagation vector does not show any considerable change. The average ordered magnetic moment is reduced from 1.73(2) μB at ambient pressure to 0.4(1) μB close to the critical pressuremore » Pc ≈ 0.7 GPa, at which magnetic order is completely suppressed. The width of the magnetic Bragg peaks strongly depends on temperature and pressure, showing a maximum in the region of the onset of superconductivity. In conclusion, we interpret this as associated with competing ground-states in the vicinity of the superconducting phase.« less

  14. Pressure dependence of the magnetic order in CrAs: A neutron diffraction investigation

    NASA Astrophysics Data System (ADS)

    Keller, L.; White, J. S.; Frontzek, M.; Babkevich, P.; Susner, M. A.; Sims, Z. C.; Sefat, A. S.; Rønnow, H. M.; Rüegg, Ch.

    2015-01-01

    The suppression of magnetic order with pressure concomitant with the appearance of pressure-induced superconductivity was recently discovered in CrAs. Here we present a neutron diffraction study of the pressure evolution of the helimagnetic ground state towards and in the vicinity of the superconducting phase. Neutron diffraction on polycrystalline CrAs was employed from zero pressure to 0.65 GPa and at various temperatures. The helimagnetic long-range order is sustained under pressure and the magnetic propagation vector does not show any considerable change. The average ordered magnetic moment is reduced from 1.73(2) μB at ambient pressure to 0.4(1) μB close to the critical pressure Pc≈0.7 GPa, at which magnetic order is completely suppressed. The width of the magnetic Bragg peaks strongly depends on temperature and pressure, showing a maximum in the region of the onset of superconductivity. We interpret this as associated with competing ground states in the vicinity of the superconducting phase.

  15. Phase development of Bi-2212 superconductor: A time-resolved neutron powder diffraction investigation

    SciTech Connect

    Argyriou, D.N.; Garcia, J.A.; Mitchell, J.F.; Jorgensen, J.D.; Hinks, D.G.

    1996-02-01

    Time-resolved {ital in} {ital situ} neutron powder diffraction and Rietveld refinement have been used to study the synthesis of Bi-2212 from hydroxide precursors in a 2{percent} O{sub 2} atmosphere. Bi-2212 was found to form within the temperature range 770{endash}800{degree}C. Studies at 800{degree}C show that Bi-2212 grows rapidly at the expense of Bi-2201. Upon lowering the temperature to 500{degree}C and changing the atmosphere to Ar, a rapid increase in the lattice parameters was observed. We attribute this change to the loss of oxygen from the Bi-2212 lattice. The final material exhibited a {ital T}{sub {ital c}} of 94 K. {copyright} {ital 1996 Materials Research Society.}

  16. Texture Evolution and Phase Transformation in Titanium Investigated by In-Situ Neutron Diffraction

    SciTech Connect

    Ma, Dong; Stoica, Alexandru Dan; An, Ke; Yang, Ling; Bei, Hongbin; Mills, Rebecca A; Skorpenske, Harley David; Wang, Xun-Li

    2011-01-01

    We report in-situ neutron diffraction studies of texture evolution and the (hcp) (bcc) phase transformation in commercially pure cold-drawn titanium upon continuous heating and cooling, complemented by differential scanning calorimetry (DSC) measurements. We show that the recrystallization of the phase at elevated temperature enhanced the preexisting fiber texture, which eventually facilitated the nucleation and growth of the phase favored by the Burgers orientation relationship, i.e., {0001} //{110} . More strikingly, upon completion of the transformation, the {110} texture (or preferred orientation) in was eliminated immediately by the rapid grain growth of intergranular allotriomorphs. This resulted in the loss of the original -texture when Ti was transformed back to from to upon subsequent cooling, distinct from the known texture memory effect for rolling textures in titanium. Our present work provides useful experimental results for understanding the mechanisms of texture evolution and phase transformation in titanium and its alloys and, by and large, low-symmetry alloys such as zirconium.

  17. Investigation of an unusual low-temperature phase transformation in RbBH{sub 4} by neutron diffraction

    SciTech Connect

    Kitchen, Brian B.; Verdal, Nina; Udovic, Terrence J.; Rush, John J.; Hartman, Michael R.; DeVries, Daniel J.

    2013-07-15

    To investigate the previously reported low-temperature phase transition in rubidium borohydride (RbBH{sub 4}) near 48.5 K, we carried out neutron powder diffraction and vibrational spectroscopy measurements both above and below this temperature on an isotopically-enriched sample of Rb{sup 11}BD{sub 4}. Our diffraction data reflected an average cubic Fm3{sup ¯}m structure with BD{sub 4}{sup −} anion orientational disorder at all temperatures, with no hint of extra Bragg peaks due to long-range orientational order below the transition temperature as reported by others. These structural results and careful analysis of torsional vibrations in RbBD{sub 4} corroborate the results of prior neutron vibrational spectroscopy measurements suggesting that the low-temperature RbBH{sub 4} structure indeed possesses some orientational ordering of the BH{sub 4}{sup −} anions, but of a shorter-ranged nature insensitive to powder diffraction methods. - The neutron powder diffraction pattern of RbBD{sub 4} below the phase transition temperature (shown here in black) is indistinguishable from that collected above the phase transition temperature. The inset depicts the cubic structure that fits the data at both temperatures. - Highlights: • We investigated the nature of the RbBD{sub 4} phase transition using NVS and NPD. • A change in shape of the RbBD{sub 4} torsion mode was observed across the transition. • The RbBD{sub 4} diffraction pattern across this phase transition was unchanged. • The phase transition in RbBD{sub 4} appears to produce only short-range ordering of BD{sub 4}{sup −}.

  18. Neutron diffraction investigations of L- and D-alanine at different temperatures: The search for structural evidence for parity violation

    SciTech Connect

    Wilson, Chick C.; Ghosh, Minakshi; Johnson, Louise N.; Wang, Wenging

    2005-09-01

    Single crystal neutron diffraction has been used in an investigation of the structures of the amino acids L- and D-alanine. The aim of the study was to look for proposed phase transitions around T{sub c} {approx} 270 K. Measurements of both structures at 295 K and 60 K - the neutron structure of D-alanine being determined for the first time - show no significant structural basis for this phase transition in alanine. Further, confirmatory, investigation of the structure of D-alanine at temperatures of 240, 250, 260 and 300 K also showed no significant changes in bond lengths or angles. We can thus offer no structural support to other physical measurements, which are indicative of the observable effect of parity violation of the electroweak force in these phase transitions.

  19. Industrial applications of neutron diffraction

    SciTech Connect

    Felcher, G.P.

    1989-01-01

    Neutron diffraction (or, to be more general, neutron scattering) is a most versatile and universal tool, which has been widely employed to probe the structure, the dynamics and the magnetism of condensed matter. Traditionally used for fundamental research in solid state physics, this technique more recently has been applied to problems of immediate industrial interest, as illustrated in examples covering the main fields of endeavour. 14 refs., 14 figs.

  20. High-pressure neutron diffraction

    SciTech Connect

    Xu, Hongwu

    2011-01-10

    This lecture will cover progress and prospect of applications of high-pressure neutron diffraction techniques to Earth and materials sciences. I will first introduce general high-pressure research topics and available in-situ high-pressure techniques. Then I'll talk about high-pressure neutron diffraction techniques using two types of pressure cells: fluid-driven and anvil-type cells. Lastly, I will give several case studies using these techniques, particularly, those on hydrogen-bearing materials and magnetic transitions.

  1. A neutron diffraction and molecular dynamics investigation of the environment of Dy3+ ions in a fluoroberyllate glass

    NASA Astrophysics Data System (ADS)

    Clare, Alexis G.; Etherington, George; Wright, Adrian C.; Weber, Marvin J.; Brawer, Steven A.; Kingman, Donald D.; Sinclair, Roger N.

    1989-11-01

    A combined neutron diffraction and molecular dynamics study is reported of the Dy3+ ion environment in vitreous NaF-DyF3-BeF2, using a special version of the isotopic substitution procedure known as the null technique. To investigate the effects of both NaF and DyF3 on the basic beryllium fluoride glass network, complementary measurements and simulations have been performed for vitreous NaF-BeF2, with the same NaF:BeF2 ratio as the DyF3 containing glass, and also for pure vitreous BeF2. The neutron diffraction data indicate that for glasses simulated using pair potentials the BeF4 tetrahedra are much more distorted than those in the real materials and the mean Be-F-Be angle is too high. Both of these deficiencies in the simulations are attributed to the use of simple ionic potentials with no bond angle restoring forces. Experimentally, the distribution of Dy-F first neighbor distances is found to be narrow, having a root mean square deviation of 0.110±0.003 Å about the mean value of 2.290±0.003 Å. The Dy(F) coordination number is 7.3±0.2 which is slightly less than that in crystalline DyF3.

  2. A structural investigation of the alkali metal site distribution within bioactive glass using neutron diffraction and multinuclear solid state NMR.

    PubMed

    Martin, Richard A; Twyman, Helen L; Rees, Gregory J; Smith, Jodie M; Barney, Emma R; Smith, Mark E; Hanna, John V; Newport, Robert J

    2012-09-21

    The atomic-scale structure of Bioglass and the effect of substituting lithium for sodium within these glasses have been investigated using neutron diffraction and solid state magic angle spinning (MAS) NMR. Applying an effective isomorphic substitution difference function to the neutron diffraction data has enabled the Na-O and Li-O nearest-neighbour correlations to be isolated from the overlapping Ca-O, O-(P)-O and O-(Si)-O correlations. These results reveal that Na and Li behave in a similar manner within the glassy matrix and do not disrupt the short range order of the network former. Residual differences are attributed solely to the variation in ionic radius between the two species. Successful simplification of the 2 < r (Å) < 3 region via the difference method has enabled all the nearest neighbour correlations to be deconvolved. The diffraction data provides the first direct experimental evidence of split Na-O nearest-neighbour correlations in these melt quench bioactive glasses, and an analogous splitting of the Li-O correlations. The observed correlations are attributed to the metal ions bonded either to bridging or to non-bridging oxygen atoms. (23)Na triple quantum MAS (3QMAS) NMR data corroborates the split Na-O correlations. The structural sites present will be intimately related to the release properties of the glass system in physiological fluids such as plasma and saliva, and hence to the bioactivity of the material. Detailed structural knowledge is therefore a prerequisite for optimizing material design. PMID:22868255

  3. Neutron diffraction and Vitamin E

    NASA Astrophysics Data System (ADS)

    Harroun, T. A.

    2010-11-01

    It is generally accepted that neutron diffraction from model membrane systems is an effective biophysical technique for determining membrane structure. Here we describe an example of how deuterium labelling can elucidate the location of specific membrane soluble molecules, including a brief discussion of the technique itself. We show that deuterium labelled α-tocopherol sits upright in the bilayer, as might be expected, but at very different locations within the bilayer, depending on the degree of lipid chain unsaturation.

  4. Micromechanical Behavior of Solid-Solution-Strengthened Mg-1wt.%Al Alloy Investigated by In-Situ Neutron Diffraction

    SciTech Connect

    Lee, Sooyeol; Woo, Wanchuck; Gharghouri, Michael; Yoon, Cheol; An, Ke

    2014-01-01

    In-situ neutron-diffraction experiments were employed to investigate the micromechanical behavior of solid-solution-strengthened Mg-1wt.%Al alloy. Two starting textures were used: 1) as-extruded then solutionized texture, T1, in which the basal poles of most grains are tilted around 70~85 from the extrusion axis, and 2) a reoriented texture, T2, in which the basal poles of most grains are tilted around 10~20 from the extrusion axis. Lattice strains and diffraction peak intensity variations were measured in situ during loading-unloading cycles in uniaxial tension. Twinning activities and stress states for various grain orientations were revealed. The results show that the soft grain orientations, favorably oriented for either extension twinning or basal slip, exhibit the stress relaxation, resulting in the compressive residual strain after unloading. On the other hand, the hard grain orientations, unfavorably oriented for both extension twinning and basal slip, carry more applied load, leading to much higher lattice strains during loading followed by tensile residual strains upon unloading.

  5. Phonons from neutron powder diffraction

    SciTech Connect

    Dimitrov, D.A.; Louca, D.; Roeder, H. )

    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

  6. Investigation of the reduction of NiAl{sub 2}O{sub 4}. 1: Neutron diffraction studies

    SciTech Connect

    Uestuendag, E.; Hanan, J.C.; Clausen, B.; Bourke, M.A.M.; Sass, S.L.; Barbieri, T.J.

    1998-09-01

    In-situ metal-ceramic composites consisting of Ni particles embedded in alumina matrices were obtained by the partial reduction of NiAl{sub 2}O{sub 4}. The volume shrinkage that accompanies the reduction reaction generates residual stresses. Neutron diffraction studies were performed for the first time at various temperatures to study the evolution of phases in situ during reduction and to determine their stress state. It was determined that compressive stresses of several hundred MPa in magnitude can be generated inside the unreduced part of spinel. It was also found that the stress generation is strongly influenced by material and processing variables such as reduction temperature and the initial density of spinel. The diffraction results were then compared to finite element calculations and a reasonable agreement was obtained.

  7. DNA hydration studied by neutron fiber diffraction

    SciTech Connect

    Fuller, W.; Forsyth, V.T.; Mahendrasingam, A.; Langan, P.; Pigram, W.J.

    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.

  8. Development of a Neutron Diffraction Based Experiemental Capability for Investigating Hydraulic Fracturing for EGS-like Conditions

    SciTech Connect

    Polsky, Yarom; Anovitz, Lawrence {Larry} M; An, Ke; Carmichael, Justin R; Bingham, Philip R; Dessieux Jr, Luc Lucius

    2013-01-01

    Hydraulic fracturing to enhance formation permeability is an established practice in the Oil & Gas (O&G) industry and is expected to be an enabler for EGS. However, it is rarely employed in conventional geothermal systems and there are significant questions regarding the translation of practice from O&G to both conventional geothermal and EGS applications. Lithological differences(sedimentary versus crystalline rocks, significantly greater formation temperatures and different desired fracture characteristics are among a number of factors that are likely to result in a gap of understanding of how to manage hydraulic fracturing practice for geothermal. Whereas the O&G community has had both the capital and the opportunity to develop its understanding of hydraulic fracturing operations empirically in the field as well through extensive R&D efforts, field testing opportunities for EGS are likely to be minimal due to the high expense of hydraulic fracturing field trials. A significant portion of the knowledge needed to guide the management of geothermal/EGS hydraulic fracturing operations will therefore likely have to come from experimental efforts and simulation. This paper describes ongoing efforts at Oak Ridge National Laboratory (ORNL) to develop an experimental capability to map the internal stresses/strains in core samples subjected to triaxial stress states and temperatures representative of EGS-like conditions using neutron diffraction based strain mapping techniques. This capability is being developed at ORNL\\'s Spallation Neutron Source, the world\\'s most powerful pulsed neutron source and is still in a proof of concept phase. A specialized pressure cell has been developed that permits independent radial and axial fluid pressurization of core samples, with axial flow through capability and a temperature rating up to 300 degrees C. This cell will ultimately be used to hydraulically pressurize EGS-representative core samples to conditions of imminent fracture

  9. Thermal-expansion behavior of a directionally solidified NiAl-Mo composite investigated by neutron diffraction and dilatometry

    SciTech Connect

    Bei, H.; George, E.P.; Brown, D.W.; Pharr, G.M.; Choo, H.; Porter, W.D.; Bourke, M.A.M.

    2005-06-15

    The thermal expansion of directionally solidified NiAl-Mo eutectic alloys consisting of nanoscale Mo fibers embedded in a NiAl matrix was analyzed by neutron diffraction and dilatometry. From room temperature to 800 deg. C, perpendicular to the fiber direction, the NiAl and Mo phases expand independently with average coefficients of thermal expansion (CTEs) of 16.0x10{sup -6} deg. C{sup -1} and 5.8x10{sup -6} deg. C{sup -1}, respectively. Parallel to the fiber direction, they coexpand up to 650 deg. C with an average CTE of 12.8x10{sup -6} deg. C{sup -1}, but above this temperature the Mo fibers expand more than the NiAl matrix. This anomalous behavior is the result of the load transfer to the Mo fibers when the NiAl matrix softens. The average CTE of the composite parallel to the fiber direction was determined by dilatometry to be 13.0x10{sup -6} deg. C{sup -1}, which is approximately 11% lower than the value predicted by a simple rule of mixtures using the CTEs of the constituent phases.

  10. Neutron powder diffraction investigation of magnetic structure and spin reorientation transition of HoFe1-xCrxO3 solid solutions

    NASA Astrophysics Data System (ADS)

    Liu, Xinzhi; Hao, Lijie; Liu, Yuntao; Ma, Xiaobai; Meng, Siqin; Li, Yuqing; Gao, Jianbo; Guo, Hao; Han, Wenze; Sun, Kai; Wu, Meimei; Chen, Xiping; Xie, Lei; Klose, Frank; Chen, Dongfeng

    2016-11-01

    Orthoferrite solid solution HoFe1-xCrxO3 (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 HoFeO3. With increasing Cr-doping, the system adopts a Γ4(GxAyFz) magnetic configuration with a decreased Neel temperature from 640 K to 360 K. A Γ42 spin reorientation of Fe(Cr)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 HoCrO3 which adopts a Γ2(FxCyGz) configuration with no spin reorientation below the Neel temperature TN. 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.

  11. Measurement of neutron diffraction with compact neutron source RANS

    NASA Astrophysics Data System (ADS)

    Ikeda, Y.; Takamura, M.; Taketani, A.; Sunaga, H.; Otake, Y.; Suzuki, H.; Kumagai, M.; Oba, Y.; Hama, T.

    2016-11-01

    Diffraction is used as a measurement technique for crystal structure. X-rays or electron beam with wavelength that is close to the lattice constant of the crystal is often used for the measurement. They have sensitivity in surface (0.01mm) of heavy metals due to the mean free path for heavy ions. Neutron diffraction has the probe of the internal structure of the heavy metals because it has a longer mean free path than that of the X-rays or the electrons. However, the neutron diffraction measurement is not widely used because large facilities are required in the many neutron sources. RANS (Riken Accelerator-driven Compact Neutron Source) is developed as a neutron source which is usable easily in laboratories and factories. In RANS, fast neutrons are generated by 7MeV protons colliding on a Be target. Some fast neutrons are moderated with polyethylene to thermal neutrons. The thermal neutrons of 10meV which have wavelength of 10nm can be used for the diffraction measurement. In this study, the texture evolution in steels was measured with RANS and the validity of the compact neutron source was proved. The texture of IF steel sheets with the thickness of 1.0mm was measured with 10minutes run. The resolution is 2% and is enough to analyze a evolution in texture due to compression/tensile deformation or a volume fraction of two phases in the steel sample. These results have proven the possibility to use compact neutron source for the analysis of mesoscopic structure of metallic materials.

  12. Neutron diffraction studies of natural glasses

    SciTech Connect

    Wright, A.C.; Erwin Desa, J.A.; Weeks, R.A.; Sinclair, R.N.; Bailey, D.K.

    1983-08-01

    A neutron diffraction investigation has been carried out of the structures of several naturally occurring glasses, viz. Libyan Desert glass, a Fulgurite, Wabar glass, Lechatelierite from Canon Diablo, a Tektite, Obsidian (3 samples), and Macusani glass. Libyan Desert sand has also been examined, together with crystalline ..cap alpha..-quartz and ..cap alpha..-cristobalite. A comparison of data for the natural glasses and synthetic vitreous silica (Spectrosil B) in both reciprocal and real space allows a categorisation into Silicas, which closely resemble synthetic vitreous silica, and Silicates, for which the resemblance to silica is consistently less striking. The data support the view that Libyan Desert glass and sand have a common origin, while the Tektite has a structure similar to that of volcanic glasses.

  13. Maximizing Macromolecule Crystal Size for Neutron Diffraction Experiments

    NASA Technical Reports Server (NTRS)

    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.

  14. Magnetic structures of actinide materials by pulsed neutron diffraction

    SciTech Connect

    Lawson, A.C.; Goldstone, J.A.; Huber, J.G.; Giorgi, A.L.; Conant, J.W.; Severing, A.; Cort, B.; Robinson, R.A.

    1990-01-01

    We describe some attempts to observe magnetic structure in various actinide (5f-electron) materials. Our experimental technique is neutron powder diffraction as practiced at a spallation (pulsed) neutron source. We will discuss our investigations of {alpha}-Pu, {delta}-Pu, {alpha}-UD{sub 3} and {beta}-UD{sub 3}. {beta}-UD{sub 3} is a simple ferromagnet: surprisingly, the moments on the two non-equivalent uranium atoms are the same within experimental error. {alpha}-UD{sub 3}, {alpha}-Pu and {delta}-Pu are non-magnetic, within the limits of our observations. Our work with pulsed neutron diffraction shows that it is a useful technique for research on magnetic materials.

  15. Single crystal neutron diffraction for the inorganic chemist - a practical guide.

    SciTech Connect

    Piccoli, P.; Koetzle, T. F.; Schultz, A. J.; Intense Pulsed Neutron Source

    2007-01-01

    Advances and upgrades in neutron sources and instrumentation are poised to make neutron diffraction more accessible to inorganic chemists than ever before. These improvements will pave the way for single crystal investigations that currently may be difficult, for example due to small crystal size or large unit cell volume. This article aims to highlight what can presently be achieved in neutron diffraction and looks forward toward future applications of neutron scattering in inorganic chemistry.

  16. Status of the Neutron Imaging and Diffraction Instrument IMAT

    NASA Astrophysics Data System (ADS)

    Kockelmann, Winfried; Burca, Genoveva; Kelleher, Joe F.; Kabra, Saurabh; Zhang, Shu-Yan; Rhodes, Nigel J.; Schooneveld, Erik M.; Sykora, Jeff; Pooley, Daniel E.; Nightingale, Jim B.; Aliotta, Francesco; Ponterio, Rosa C.; Salvato, Gabriele; Tresoldi, Dario; Vasi, Cirino; McPhate, Jason B.; Tremsin, Anton S.

    A cold neutron imaging and diffraction instrument, IMAT, is currently being constructed at the ISIS second target station. IMAT will capitalize on time-of-flight transmission and diffraction techniques available at a pulsed neutron source. Analytical techniques will include neutron radiography, neutron tomography, energy-selective neutron imaging, and spatially resolved diffraction scans for residual strain and texture determination. Commissioning of the instrument will start in 2015, with time-resolving imaging detectors and two diffraction detector prototype modules. IMAT will be operated as a user facility for material science applications and will be open for developments of time-of-flight imaging methods.

  17. Growing Larger Crystals for Neutron Diffraction

    NASA Technical Reports Server (NTRS)

    Pusey, Marc

    2003-01-01

    Obtaining crystals of suitable size and high quality has been a major bottleneck in macromolecular crystallography. With the advent of advanced X-ray sources and methods the question of size has rapidly dwindled, almost to the point where if one can see the crystal then it was big enough. Quality is another issue, and major national and commercial efforts were established to take advantage of the microgravity environment in an effort to obtain higher quality crystals. Studies of the macromolecule crystallization process were carried out in many labs in an effort to understand what affected the resultant crystal quality on Earth, and how microgravity improved the process. While technological improvements are resulting in a diminishing of the minimum crystal size required, neutron diffraction structural studies still require considerably larger crystals, by several orders of magnitude, than X-ray studies. From a crystal growth physics perspective there is no reason why these 'large' crystals cannot be obtained: the question is generally more one of supply than limitations mechanism. This talk will discuss our laboratory s current model for macromolecule crystal growth, with highlights pertaining to the growth of crystals suitable for neutron diffraction studies.

  18. Low temperature nickel titanium iron shape memory alloys: Actuator engineering and investigation of deformation mechanisms using in situ neutron diffraction at Los Alamos National Laboratory

    NASA Astrophysics Data System (ADS)

    Krishnan, Vinu B.

    Shape memory alloys are incorporated as actuator elements due to their inherent ability to sense a change in temperature and actuate against external loads by undergoing a shape change as a result of a temperature-induced phase transformation. The cubic so-called austenite to the trigonal so-called R-phase transformation in NiTiFe shape memory alloys offers a practical temperature range for actuator operation at low temperatures, as it exhibits a narrow temperature-hysteresis with a desirable fatigue response. Overall, this work is an investigation of selected science and engineering aspects of low temperature NiTiFe shape memory alloys. The scientific study was performed using in situ neutron diffraction measurements at the newly developed low temperature loading capability on the Spectrometer for Materials Research at Temperature and Stress (SMARTS) at Los Alamos National Laboratory and encompasses three aspects of the behavior of Ni46.8Ti50Fe3.2 at 92 K (the lowest steady state temperature attainable with the capability). First, in order to study deformation mechanisms in the R-phase in NiTiFe, measurements were performed at a constant temperature of 92 K under external loading. Second, with the objective of examining NiTiFe in one-time, high-stroke, actuator applications (such as in safety valves), a NiTiFe sample was strained to approximately 5% (the R-phase was transformed to B19' phase in the process) at 92 K and subsequently heated to full strain recovery under a load. Third, with the objective of examining NiTiFe in cyclic, low-stroke, actuator applications (such as in cryogenic thermal switches), a NiTiFe sample was strained to 1% at 92 K and subsequently heated to full strain recovery under load. Neutron diffraction spectra were recorded at selected time and stress intervals during these experiments. The spectra were subsequently used to obtain quantitative information related to the phase-specific strain, texture and phase fraction evolution using the

  19. Dynamics of anions and cations in cesium hydrogensulfide (CsHS, CsDS): Neutron and x-ray diffraction, calorimetry and proton NMR investigations

    NASA Astrophysics Data System (ADS)

    Haarmann, F.; Jacobs, H.; Kockelmann, W.; Senker, J.; Muller, P.; Kennedy, C. A.; Marriott, R. A.; Qiu, L.; White, M. A.

    2002-09-01

    Protonated and deuterated samples of the hydrogensulfide of cesium were studied by high-resolution neutron powder diffraction, calorimetry and proton NMR investigations in a wide temperature range. Primarily due to reorientational disorder of the anions, three modifications of the title compounds are known: an ordered low-temperature modification--LTM (tetragonal, I4/m, Z=8), a dynamically disordered middle-temperature modification--MTM (tetragonal, P4/mbm, Z=2), and a high-temperature modification--HTM (cubic, Pm3m, Z=1). The LTM[rightleft arrows]MTM phase transition is continuous. Its order parameter, related to an order/disorder and to a displacive part of the phase transition, coupled bilinearly, follows a critical law. The critical temperature TC=123.2plus-or-minus0.5 K determined by neutron diffraction of CsDS is in good agreement with TC=121plus-or-minus2 K obtained by calorimetric investigations. For the protonated title compound a shift to TC=129plus-or-minus2 K was observed by calorimetric measurements. The entropy change of this transition is (0.24plus-or-minus0.04) R and (0.27plus-or-minus0.04) R for CsHS and CsDS, respectively. The MTM[rightleft arrows]HTM phase transition is clearly of first order. The transition temperatures of CsHS and CsDS are T=207.9plus-or-minus0.3 K and T=213.6plus-or-minus0.3 K with entropy changes of (0.86plus-or-minus0.01) R and (0.81plus-or-minus0.01) R, respectively. Second moments (M2) of the proton NMR absorption signal of MTM and HTM are in reasonable agreement with M2 calculated for the known crystal structures. A minimum in spin-lattice relaxation times (T1) in the MTM could not be assigned by dipolar coupling to a two-site 180deg reorientation of the anions, a model of motion presumed by the knowledge of the crystal structure. The activation enthalpies determined by fits of T1 presuming a thermal activated process are in the order of molecular reorientations (Ea=13.5plus-or-minus0.5 kJ mol-1 for the MTM and Ea=9.3plus

  20. Characterization of pottery fragments by nondestructive neutron diffraction

    SciTech Connect

    Barilaro, Donatella; Crupi, Vincenza; Majolino, Domenico; Venuti, Valentina; Barone, Germana; Kockelmann, Winfried

    2005-11-15

    The aim of the present work is the characterization of pottery fragments coming from the town of Caltagirone (Sicily, Italy). The samples belong to very different historical periods, from 18th century B.C. to 16th century A.D., and have finely decorated surfaces. Time-of-flight neutron-diffraction measurements were performed in order to obtain a quantitative identification of the mineralogical composition of the samples. A good determination of the relative weight fractions of the phases was obtained using the Rietveld analysis method. The application of neutron-diffraction technique allowed us to carry out a detailed analysis in a nondestructive way, so intact large fragments were investigated without damaging the precious decoration on the surface.

  1. Pressure-induced structural changes in the network-forming isostatic glass GeSe4: An investigation by neutron diffraction and first-principles molecular dynamics

    NASA Astrophysics Data System (ADS)

    Bouzid, Assil; Pizzey, Keiron J.; Zeidler, Anita; Ori, Guido; Boero, Mauro; Massobrio, Carlo; Klotz, Stefan; Fischer, Henry E.; Bull, Craig L.; Salmon, Philip S.

    2016-01-01

    The changes to the topological and chemical ordering in the network-forming isostatic glass GeSe4 are investigated at pressures up to ˜14.4 GPa by using a combination of neutron diffraction and first-principles molecular dynamics. The results show a network built from corner- and edge-sharing Ge(Se1 /2)4 tetrahedra, where linkages by Se2 dimers or longer Sen chains are prevalent. These linkages confer the network with a local flexibility that helps to retain the network connectivity at pressures up to ˜8 GPa, corresponding to a density increase of ˜37 % . The network reorganization at constant topology maintains a mean coordination number n ¯≃2.4 , the value expected from mean-field constraint-counting theory for a rigid stress-free network. Isostatic networks may therefore remain optimally constrained to avoid stress and retain their favorable glass-forming ability over a large density range. As the pressure is increased to around 13 GPa, corresponding to a density increase of ˜49 % , Ge(Se1 /2)4 tetrahedra remain as the predominant structural motifs, but there is an appearance of 5-fold coordinated Ge atoms and homopolar Ge-Ge bonds that accompany an increase in the fraction of 3-fold coordinated Se atoms. The band gap energy decreases with increasing pressure, and midgap states appear at pressures beyond ˜6.7 GPa. The latter originate from undercoordinated Se atoms that terminate broken Sen chains.

  2. Neutron powder diffraction study of perdeuterodimethyl sulfone.

    PubMed

    Ibberson, R M

    2007-05-01

    The crystal structure of perdeuterodimethyl sulfone, (CD(3))(2)SO(2) or C(2)D(6)O(2)S, has been refined at 4.5 K against high-resolution neutron powder diffraction data. The structure determined previously by Sands [Z. Kristallogr. (1963), 119, 245-251] at ambient temperature is shown to remain down to liquid helium temperature, and at 4.5 K the S-C and S-O bond distances are 1.441 (2) and 1.760 (2) A, respectively. The molecules are distorted tetrahedra with C(2v) point symmetry (crystallographic symmetry m2m for S and m for C, O and one D atom) and are linked through a network of weak hydrogen bonds in the C-centred orthorhombic structure.

  3. Pulsed Neutron Powder Diffraction for Materials Science

    NASA Astrophysics Data System (ADS)

    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-1

  4. Neutron diffraction studies of viral fusion peptides

    NASA Astrophysics Data System (ADS)

    Bradshaw, Jeremy P.; J. M. Darkes, Malcolm; Katsaras, John; Epand, Richard M.

    2000-03-01

    Membrane fusion plays a vital role in a large and diverse number of essential biological processes. Despite this fact, the precise molecular events that occur during fusion are still not known. We are currently engaged on a study of membrane fusion as mediated by viral fusion peptides. These peptides are the N-terminal regions of certain viral envelope proteins that mediate the process of fusion between the viral envelope and the membranes of the host cell during the infection process. As part of this study, we have carried out neutron diffraction measurements at the ILL, BeNSC and Chalk River, on a range of viral fusion peptides. The peptides, from simian immunodeficiency virus (SIV), influenza A and feline leukaemia virus (FeLV), were incorporated into stacked phospholipid bilayers. Some of the peptides had been specifically deuterated at key amino acids. Lamellar diffraction data were collected and analysed to yield information on the peptide conformation, location and orientation relative to the bilayer.

  5. The early development of neutron diffraction: science in the wings of the Manhattan Project.

    PubMed

    Mason, T E; Gawne, T J; Nagler, S E; Nestor, M B; Carpenter, J M

    2013-01-01

    Although neutron diffraction was first observed using radioactive decay sources shortly after the discovery of the neutron, it was only with the availability of higher intensity neutron beams from the first nuclear reactors, constructed as part of the Manhattan Project, that systematic investigation of Bragg scattering became possible. Remarkably, at a time when the war effort was singularly focused on the development of the atomic bomb, groups working at Oak Ridge and Chicago carried out key measurements and recognized the future utility of neutron diffraction quite independent of its contributions to the measurement of nuclear cross sections. Ernest O. Wollan, Lyle B. Borst and Walter H. Zinn were all able to observe neutron diffraction in 1944 using the X-10 graphite reactor and the CP-3 heavy water reactor. Subsequent work by Wollan and Clifford G. Shull, who joined Wollan's group at Oak Ridge in 1946, laid the foundations for widespread application of neutron diffraction as an important research tool.

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

    NASA Astrophysics Data System (ADS)

    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.

  7. On the ammonolysis of Ga{sub 2}O{sub 3}: An XRD, neutron diffraction and XAS investigation of the oxygen-rich part of the system Ga{sub 2}O{sub 3}-GaN

    SciTech Connect

    Roehrens, D.; Brendt, J.; Samuelis, D.; Martin, M.

    2010-03-15

    We investigated the ammonolysis of beta-Ga{sub 2}O{sub 3} at elevated temperatures by means of ex situ X-ray diffraction, ex situ neutron diffraction and in situ X-ray absorption spectroscopy. Within the detection limits of these methods, we can rule out the existence of a crystalline or amorphous oxynitride phase that is not derived from wurtzite-type GaN. No evidence for a beta-Ga{sub 2}O{sub 3} related oxynitride phase was found, and the nitrogen solubility in beta-Ga{sub 2}O{sub 3} was found to be below the detection limit of about 2-3 at% in the anionic sublattice. These findings were obtained by monitoring the anionic occupancy factors and the lattice parameters of the beta-Ga{sub 2}O{sub 3} phase obtained from total diffraction pattern refinement with the Rietveld method and by linear combination fitting of the X-ray absorption spectra that were recorded during the ammonolysis. - Graphical abstract: The ammonolysis of beta-Ga{sub 2}O{sub 3} powders forming GaN at temperatures of 600-780 deg. C was monitored by means of XRD, neutron diffraction and X-ray absorption spectroscopy in order to identify the possible intermediates and the solubility limit of nitrogen in the oxide lattice.

  8. High-pressure neutron diffraction studies at LANSCE

    NASA Astrophysics Data System (ADS)

    Zhao, Yusheng; Zhang, Jianzhong; Xu, Hongwu; Lokshin, Konstantin A.; He, Duanwei; Qian, Jiang; Pantea, Cristian; Daemen, Luke L.; Vogel, Sven C.; Ding, Yang; Xu, Jian

    2010-06-01

    The development of neutron diffraction under extreme pressure ( P) and temperature ( T) conditions is highly valuable to condensed matter physics, crystal chemistry, materials science, and earth and planetary sciences. We have incorporated a 500-ton press TAP-98 into the HiPPO diffractometer at the Los Alamos Neutron Science Center (LANSCE) to conduct in situ high- P- T neutron diffraction experiments. We have developed a large gem-crystal anvil cell, ZAP, to conduct neutron diffraction experiments at high P. The ZAP cell can be used to integrate multiple experimental techniques such as neutron diffraction, laser spectroscopy, and ultrasonic interferometery. More recently, we have developed high- P low- T gas/liquid cells in conjunction with neutron diffraction. These techniques enable in situ and real-time examination of gas uptake/release processes and allow accurate, time-dependent determination of changes in crystal structure and related reaction kinetics. We have successfully used these techniques to study the equations of state, structural phase transitions, and thermo-mechanical properties of metals, ceramics, and minerals. We have conducted researches on the formation/decomposition kinetics of methane, CO2 and hydrogen hydrate clathrates, and hydrogen/CO2 adsorption of inclusion compounds such as metal-organic frameworks (MOFs). The aim of our research is to accurately map out phase relations and determine structural parameters (lattice constants, atomic positions, atomic thermal parameters, bond lengths, bond angles, etc.) in the P- T- X space. We are developing further high- P- T technology with a new 2000-ton press, TAPLUS-2000, and a ZIA (Deformation-DIA type) cubic anvil package to routinely achieve pressures up to 20 GPa and temperatures up to 2000 K. The design of a dedicated high- P neutron beamline, LAPTRON, is also underway for simultaneous high- P- T neutron diffraction, ultrasonic, calorimetry, radiography, and tomography studies. Studies based

  9. Oxygen as a site specific structural probe in neutron diffraction

    SciTech Connect

    Neuefeind, Joerg C; Simonson, J Michael {Mike}; Salmon, Phil; Zeidler, Anita; Fischer, Henry E; Rauch, Helmut; Markland, Thomas; Lemmel, Hartmut

    2011-01-01

    Oxygen is a ubiquitous element, playing an essential role in most scientific and technological disciplines, and is often incorporated within a structurally disordered material where examples include molten silicates in planetary science, glasses used for lasers and optical communication, and water in biological processes. Establishing the structure of a liquid or glassy oxide and thereby its relation to the functional properties of a material is not, however, a trivial task owing to the complexity associated with atomic disorder. Here we approach this challenge by measuring the bound coherent neutron scattering lengths of the oxygen isotopes with the sensitive technique of neutron interferometry. We find that there is a small but finite contrast of 0.204(6) fm between the scattering lengths of the isotope 18O and oxygen of natural isotopic abundance natO, contrary to tables of recommended values. This has enabled us to investigate the structure of both light and heavy water by exploiting, for the first time, the method of oxygen isotope substitution in neutron diffraction, thus circumventing many of the significant problems associated with more traditional methods in which hydrogen is substituted by deuterium. We find a difference of ~0.5% between the O-H and O-D intra-molecular bond distances which is much smaller than recent estimates based on diffraction data and is found to be in excellent agreement with path integral molecular dynamics simulations made with a flexible polarisable water model. Our results demonstrate the potential for using oxygen isotope substitution as a powerful and effective site specific probe in a plethora of materials, of pertinence as instrumentation at next generation neutron sources comes online

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

    NASA Astrophysics Data System (ADS)

    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

  11. The early development of neutron diffraction: Science in the wings of the Manhattan Project

    SciTech Connect

    Mason, Thom; Gawne, Timothy J; Nagler, Stephen E; Nestor, Margaret Boone {Bonnie}; Carpenter, John M

    2012-01-01

    Although neutron diffraction was first observed using radioactive decay sources shortly after the discovery of the neutron, it was only with the availability of higher intensity neutron beams from the first nuclear reactors, constructed as part of the Manhattan project, that systematic investigation of Bragg scattering became possible. Remarkably, at a time when the war effort was singularly focused on the development of the atomic bomb, groups working at Oak Ridge and Chicago carried out key measurements and recognized the future utility of neutron diffraction quite independent of its contributions to the measurements of nuclear cross sections. Ernest O. Wollan, Lyle B. Borst, and Walter H. Zinn were all able to observe neutron diffraction in 1944 using the X-10 graphite reactor and the CP-3 heavy water reactor.

  12. Neutron diffraction study of U-10 wt% Mo alloy

    NASA Astrophysics Data System (ADS)

    Seong, Baek-Seok; Lee, Chang-Hee; Lee, Jeong-Soo; Shim, Hae-Seop; Lee, Jin-Ho; Kim, Ki Hwan; Kim, Chang Kyu; Em, Vyacheslav

    2000-01-01

    The structural properties of a U-10 wt% Mo powder sample prepared by the centrifugal atomization method were investigated by the Rietveld total profile analysis method. The high resolution neutron powder diffractometer at the HANARO research reactor in Taejon, Korea, was used for a series of neutron diffraction pattern measurements for the study. The sample was synthesized by the centrifugal atomization method and was found to consist of two γ-U solid solution phases having identical bcc structures, but slightly different lattice dimensions, and accordingly different Mo content. When the sample was annealed for 10 h at 600°C, the two solid solution phases with different Mo contents merged into a uniform single phased γ-U solid solution. The diffraction pattern of the annealed sample showed two additional weak reflections, which could be indexed as a super lattice structure U 3Mo derived from the bcc cell by a /1 1 0/-1 1 0/0 0 1/ type lattice transformation. The disorder-order phase transition leading to the formation of ordered metastable phase U 3Mo should be of the first-order.

  13. The early development of neutron diffraction: science in the wings of the Manhattan Project

    SciTech Connect

    Mason, T. E. Gawne, T. J.; Nagler, S. E.; Nestor, M. B.; Carpenter, J. M.

    2013-01-01

    Early neutron diffraction experiments performed in 1944 using the first nuclear reactors are described. Although neutron diffraction was first observed using radioactive decay sources shortly after the discovery of the neutron, it was only with the availability of higher intensity neutron beams from the first nuclear reactors, constructed as part of the Manhattan Project, that systematic investigation of Bragg scattering became possible. Remarkably, at a time when the war effort was singularly focused on the development of the atomic bomb, groups working at Oak Ridge and Chicago carried out key measurements and recognized the future utility of neutron diffraction quite independent of its contributions to the measurement of nuclear cross sections. Ernest O. Wollan, Lyle B. Borst and Walter H. Zinn were all able to observe neutron diffraction in 1944 using the X-10 graphite reactor and the CP-3 heavy water reactor. Subsequent work by Wollan and Clifford G. Shull, who joined Wollan’s group at Oak Ridge in 1946, laid the foundations for widespread application of neutron diffraction as an important research tool.

  14. Macromolecular structure phasing by neutron anomalous diffraction

    PubMed Central

    Cuypers, Maxime G.; Mason, Sax A.; Mossou, Estelle; Haertlein, Michael; Forsyth, V. Trevor; Mitchell, Edward P.

    2016-01-01

    In this report we show for the first time that neutron anomalous dispersion can be used in a practical manner to determine experimental phases of a protein crystal structure, providing a new tool for structural biologists. The approach is demonstrated through the use of a state-of-the-art monochromatic neutron diffractometer at the Institut Laue-Langevin (ILL) in combination with crystals of perdeuterated protein that minimise the level of hydrogen incoherent scattering and enhance the visibility of the anomalous signal. The protein used was rubredoxin in which cadmium replaced the iron at the iron-sulphur site. While this study was carried out using a steady-state neutron beam source, the results will be of major interest for capabilities at existing and emerging spallation neutron sources where time-of-flight instruments provide inherent energy discrimination. In particular this capability may be expected to offer unique opportunities to a rapidly developing structural biology community where there is increasing interest in the identification of protonation states, protein/water interactions and protein-ligand interactions – all of which are of central importance to a wide range of fundamental and applied areas in the biosciences. PMID:27511806

  15. Lithium insertion properties of Li{sub x}TiNb{sub 2}O{sub 7} investigated by neutron diffraction and first-principles modelling

    SciTech Connect

    Catti, Michele; Pinus, Ilya; Knight, Kevin

    2015-09-15

    TiNb{sub 2}O{sub 7}, a good candidate as anode in lithium batteries, was treated with n-butyllithium to synthesize Li{sub x}TiNb{sub 2}O{sub 7} phases similar to those formed during electrochemical reactions. The Li{sub 2.67}TiNb{sub 2}O{sub 7} and Li{sub 3.33}TiNb{sub 2}O{sub 7} compounds, monoclinic C2/m, were studied by time-of-flight powder neutron diffraction. Their crystal structures, containing 3×3 blocks of (Ti,Nb)O{sub 6} octahedra, were Rietveld refined including Li positions. The Li atoms are distributed in similar amounts over sites with (Li–O) Coordination Numbers 5 and 4, although CN=5 should be preferred for having lower energy. Quantum-mechanical calculations were also performed, determining the average charge–discharge voltages to be 1.415 and 1.571 V for Li{sub 3.33}TiNb{sub 2}O{sub 7} and Li{sub 2.67}TiNb{sub 2}O{sub 7}, respectively, in good agreement with experimental results. An analysis of the theoretical charge distribution shows that, on lithiation, the chemical reduction of Ti and Nb atoms concentrates in the more condensed peripheral octahedra of the 3×3 block. This corresponds to electrons moving into a partly spin-polarized small band which gives rise to semi-metallic conductivity. - Graphical abstract: Structure of monoclinic Li{sub 3.33}TiNb{sub 2}O{sub 7}, and corresponding electron density of states. - Highlights: • Lithium was chemically inserted into the battery anode material TiNb{sub 2}O{sub 7}. • Li atoms are distributed over four- and fivefold oxygen coordinated sites. • On lithiation Nb and Ti atoms are reduced according to a peculiar structural pattern. • Theoretically predicted charge–discharge voltages fit experiments very well.

  16. Neutron diffraction studies of amphipathic helices in phospholipid bilayers

    SciTech Connect

    Bradshaw, J.P.; Gilchrist, P.J.; Duff, K.C.; Saxena, A.M.

    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.

  17. Neutron powder diffraction study of sulfated zirconia catalysts

    SciTech Connect

    Li, X.; Lager, G.A.; Loong, C.K.

    1997-07-01

    In situ neutron powder diffraction method was used to investigate the crystal structures, phase abundance and thermal stability of sulfated zirconia catalysts prepared by impregnation of hydrous zirconium oxide gels with 0.5 M H{sub 2}SO{sub 4} solutions. The sample studied was precipitated at pH = 10 and dried for 5 h at 493 K, and then calcined at 853 K for 3 h. Diffraction data were collected in the temperature range 295-1273 K in an Ar atmosphere and analyzed using the Rietveld method. Only the metastable tetragonal phase was observed below 673 K. Above this temperature, the sample consisted of a mixture of tetragonal (T) and monoclinic (M) phases in the proportions (T:M wt%) 85:15 (1073 K) and 61:39 (1273 K). Surface modification by sulfation was found to retard the onset of the tetragonal-to-monoclinic transformation relative to pure zirconia. The decrease in peak-broadening at the higher temperatures reflects both an increase in crystallite size and a decrease in microstrain.

  18. The early development of neutron diffraction: science in the wings of the Manhattan Project

    PubMed Central

    Mason, T. E.; Gawne, T. J.; Nagler, S. E.; Nestor, M. B.; Carpenter, J. M.

    2013-01-01

    Although neutron diffraction was first observed using radioactive decay sources shortly after the discovery of the neutron, it was only with the availability of higher intensity neutron beams from the first nuclear reactors, constructed as part of the Manhattan Project, that systematic investigation of Bragg scattering became possible. Remarkably, at a time when the war effort was singularly focused on the development of the atomic bomb, groups working at Oak Ridge and Chicago carried out key measurements and recognized the future utility of neutron diffraction quite independent of its contributions to the measurement of nuclear cross sections. Ernest O. Wollan, Lyle B. Borst and Walter H. Zinn were all able to observe neutron diffraction in 1944 using the X-10 graphite reactor and the CP-3 heavy water reactor. Subsequent work by Wollan and Clifford G. Shull, who joined Wollan’s group at Oak Ridge in 1946, laid the foundations for widespread application of neutron diffraction as an important research tool. PMID:23250059

  19. X-ray and neutron diffraction determination of residual stresses in a pressed and welded component

    NASA Astrophysics Data System (ADS)

    Albertini, G.; Bruno, G.; Fiori, F.; Girardin, E.; Giuliani, A.; Quadrini, E.

    2000-03-01

    X-ray and neutron diffraction experiments have been carried out, in order to determine the residual stress (RS) field in a pressed and welded mock-up of an engine support for motor-bike technology. Such investigation is suggested by the need to know the stress state of the component after forming and welding. This allows to assess the quality of the first machining and further to theoretically simulate its performances under operation. Results are presented below, showing a good agreement between X-ray and neutron diffraction experiments.

  20. Effect of Cu{sup 2+} and Ni{sup 2+} substitution at the Mn site in (La{sub 0.63}Ca{sub 0.37})MnO{sub 3}: A neutron powder diffraction investigation

    SciTech Connect

    Martinelli, A.; Ferretti, M.; Castellano, C.; Cimberle, M.R.; Ritter, C.

    2013-04-15

    The crystal and magnetic structures of the (La{sub 0.63}Ca{sub 0.37})(Mn{sub 1−x}TM{sub x})O{sub 3} compounds (x=0.00, 0.03, 0.08; TM=Cu{sup 2+}, Ni{sup 2+}) were investigated between 5 K and 300 K by means of dc magnetic measurements and neutron powder diffraction analysis followed by Rietveld refinement. Both substituting cations lead to a reduction of the long range ferromagnetic ordering temperature; ferromagnetism is strongly suppressed in the 8% Cu-substituted sample, where long- and short-range FM magnetic orders coexist together with short-range A-type AFM order. This particular feature can be related to the Jahn–Teller character of Cu{sup 2+}, absent in Ni{sup 2+}, and suggests the occurrence of a quantum critical point in the (La{sub 0.63}Ca{sub 0.37})(Mn{sub 1−x}Cu{sub x})O{sub 3} system. - Graphical abstract: Rietveld refinement plot of (La{sub 0.63}Ca{sub 0.37})(Mn{sub 0.92}Cu{sub 0.08})O{sub 3} showing in the inset the coexistence of broad A-type AFM peaks with FM ones. Highlights: ► (La{sub 0.63}Ca{sub 0.37})MnO{sub 3} was substituted with Ni and Cu. ► Neutron powder diffraction and Rietveld refinement were carried out. ► A quantum critical point possibly occurs in the (La{sub 0.63}Ca{sub 0.37})(Mn{sub 1−x}Cu{sub x})O{sub 3} system.

  1. Atomic structure of glassy Mg{sub 60}Cu{sub 30}Y{sub 10} investigated with EXAFS, x-ray and neutron diffraction, and reverse Monte Carlo simulations

    SciTech Connect

    Jovari, Pal; Saksl, Karel; Pryds, Nini; Lebech, Bente; Bailey, Nicholas P.; Mellerga ring rd, Anders; Delaplane, Robert G.; Franz, Hermann

    2007-08-01

    Short range order of amorphous Mg{sub 60}Cu{sub 30}Y{sub 10} was investigated by x-ray and neutron diffraction, Cu and Y K-edge x-ray absorption fine structure measurements, and the reverse Monte Carlo simulation technique. We found that Mg-Mg and Mg-Cu nearest neighbor distances are very similar to values found in crystalline Mg{sub 2}Cu. The Cu-Y coordination number is 1.1{+-}0.2, and the Cu-Y distance is {approx}4% shorter than the sum of atomic radii, suggesting that attraction between Cu and Y plays an important role in stabilizing the glassy state. Thermal stability and structure evolution upon annealing were also 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: Mg{sub 2}Cu and most likely cubic MgY and CuMgY.

  2. Morin transition in Hematite nanoparticles analyzed by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Pérez-Landazábal, J. I.; Gómez-Polo, C.; Recarte, V.; Larumbe, S.; Sánchez-Alarcos, V.; Fernandes Silva, M.; Gómez Pineda, E. A.; Winkler Hechenleitner, A. A.; Lima, M. K.; Rodriguez-Velamazán, J. A.

    2015-11-01

    Hematite (α-Fe2O3) undergoes a first order spin reorientation transition called the Morin transition: upon cooling, the moments align antiferromagnetically along the rhombohedral axis, and the net magnetic moment goes to zero. Morin transition temperature is around to 260K in bulk materials and depends on the mean particle size. In this work, the Morin transition has been studied by neutron diffraction as function of temperature and applied magnetic field in 47 nm nanoparticles. The Rietveld analysis of the diffraction spectra around the Morin transition shows a similar behavior to that found in bulk samples. On the other side, the magnetic field induced phase transformation has been analyzed.

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

    SciTech Connect

    Clausen, Bjorn; Brown, Donald W; Tome, Carlos N; Balogh, Levente; Vogel, Sven C

    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.

  4. Similar quartz crystallographic textures in rocks of continental earth's crust (by neutron diffraction data): I. Quartz textures in monomineral rocks

    SciTech Connect

    Nikitin, A. N. Ivankina, T. I.; Ullemeyer, K.; Vasin, R. N.

    2008-09-15

    Quartz crystallographic textures in different rocks have been investigated by neutron diffraction. Various types of crystallographic textures of quartz-bearing mineral associations in monomineral and multiphase rocks from a representative collection of samples have been revealed and classified. Experimental investigations have been performed on special neutron texture diffractometers designed at the Frank Laboratory of Neutron Physics and mounted in the seventh channel of the IBR-2 reactor at the Joint Institute for Nuclear Research (Dubna).

  5. Refractive and diffractive neutron optics with reduced chromatic aberration

    NASA Astrophysics Data System (ADS)

    Poulsen, S. O.; Poulsen, H. F.; Bentley, P. M.

    2014-12-01

    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 by the use of optics for focusing and imaging. Refractive and diffractive optical elements, e.g. compound refractive lenses and Fresnel zone plates, are attractive due to their low cost, and simple alignment. These optical elements, however, suffer from chromatic aberration, which limit their effectiveness to highly monochromatic beams. This paper presents two novel concepts for focusing and imaging non-monochromatic thermal neutron beams with well-known optical elements: (1) a fast mechanical transfocator based on a compound refractive lens, which actively varies the number of individual lenses in the beam path to focus and image a time-of-flight beam, and (2) a passive optical element consisting of a compound refractive lens, and a Fresnel zone plate, which may focus and image both continuous and pulsed neutron beams.

  6. The structure of tellurite glass: A combined NMR, neutron diffraction, and x-ray diffraction study

    SciTech Connect

    McLaughlin, J. C.; Tagg, S. L.; Zwanzier, J. W.; Shastri, S. D.; Haeffner, D. R.

    2000-04-04

    Models are presented of sodium tellurite glasses in the composition range (Na{sub 2}0){sub x}-(TeO{sub 2}){sub 1{minus}x}. 0.1 < x < 0.3. The models combine self-consistently data from three different and complementary sources: sodium-23 nuclear magnetic resonance (NMR), neutron diffraction, and x-ray diffraction. The models were generated using the Reverse Monte Carlo algorithm, modified to include NMR data in addition to diffraction data. The presence in the models of all five tellurite polyhedra consistent with the Te{sup +4} oxidation state were found to be necessary to achieve agreement with the data. The distribution of polyhedra among these types varied from a predominance of highly bridged species at low sodium content, to polyhedra with one or zero bridging oxygen at high sodium content. The models indicate that the sodium cations themselves form sodium oxide clusters particularly at the x = 0.2 composition.

  7. Carbonation profiles in cement paste analyzed by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Galan, I.; Sanchez, J.; Andrade, C.; Evans, A.

    2012-02-01

    The present work deals with the carbonation process in cement based materials such as concrete. In order to clarify the evolution of the two main phases involved in the process, portlandite and calcium carbonate as a function of depth, spatially resolved neutron diffraction experiments have been performed at SALSA diffractometer at ILL in carbonated cement paste samples. Specimens submitted to different carbonation processes, both natural and accelerated, have been analyzed with this non destructive technique. The evolution of the main diffraction peaks of portlandite and calcite has been followed by means of neutron diffraction patterns measured at different depths. The results indicate that, in specimens subjected to CO2 atmospheres for 24 and 48 hours, the amount of calcite increases from the centre of the specimen to the surface. In both type of specimens calcite is formed at all depths analyzed, with higher quantities for the ones submitted to the longest carbonation period. Regarding the evolution of portlandite in these specimens, it almost completely disappeared, with only a low amount of the phase constant throughout the sample. In specimens subjected to air in a closed chamber for 21 months, higher amounts of portlandite were observed throughout the sample and little increase of calcite in the outer part, pointing out a much less severe reaction. The absorption effects are characterized by measuring in perpendicular directions and an absorption coefficient is calculated for portlandite.

  8. A neutron diffraction study of RMn2O5 multiferroics

    NASA Astrophysics Data System (ADS)

    Radaelli, P. G.; Chapon, L. C.

    2008-10-01

    The magnetic properties of RMn2O5 multiferroics as obtained by unpolarized and polarized neutron diffraction experiments are reviewed. We discuss the qualitative features of the magnetic phase diagram in both zero magnetic field and in field and analyze the commensurate magnetic structure and its coupling to an applied electric field. The origin of ferroelectricity is discussed based on calculations of the ferroelectric polarization predicted by different microscopic coupling mechanisms (exchange-striction and cycloidal spin-orbit models). A minimal model containing a small set of parameters is also presented in order to understand the propagation of the magnetic structure along the c-direction.

  9. Bayesian Library for the Analysis of Neutron Diffraction Data

    NASA Astrophysics Data System (ADS)

    Ratcliff, William; Lesniewski, Joseph; Quintana, Dylan

    During this talk, I will introduce the Bayesian Library for the Analysis of Neutron Diffraction Data. In this library we use of the DREAM algorithm to effectively sample parameter space. This offers several advantages over traditional least squares fitting approaches. It gives us more robust estimates of the fitting parameters, their errors, and their correlations. It also is more stable than least squares methods and provides more confidence in finding a global minimum. I will discuss the algorithm and its application to several materials. I will show applications to both structural and magnetic diffraction patterns. I will present examples of fitting both powder and single crystal data. We would like to acknowledge support from the Department of Commerce and the NSF.

  10. Crystallization of porcine pancreatic elastase and a preliminary neutron diffraction experiment

    SciTech Connect

    Kinoshita, Takayoshi; Tamada, Taro; Imai, Keisuke; Kurihara, Kazuo; Ohhara, Takashi; Tada, Toshiji; Kuroki, Ryota

    2007-04-01

    To investigate the structural characteristics of a covalent inhibitor bound to porcine pancreatic elastase (PPE), including H atoms and hydration by water, a crystal of porcine pancreatic elastase with its inhibitor was grown to a size of 1.6 mm{sup 3} for neutron diffraction study. The crystal diffracted to 2.3 Å resolution with sufficient quality for further structure determination owing to the similar atomic scattering properties of deuterium and carbon. Porcine pancreatic elastase (PPE) resembles the attractive drug target leukocyte elastase, which has been implicated in a number of inflammatory disorders. In order to investigate the structural characteristics of a covalent inhibitor bound to PPE, including H atoms and the hydration by water, a single crystal of PPE for neutron diffraction study was grown in D{sub 2}O containing 0.2 M sodium sulfate (pD 5.0) using the sitting-drop vapour-diffusion method. The crystal was grown to a size of 1.6 mm{sup 3} by repeated macroseeding. Neutron diffraction data were collected at room temperature using a BIX-3 diffractometer at the JRR-3 research reactor of the Japan Atomic Energy Agency (JAEA). The data set was integrated and scaled to 2.3 Å resolution in space group P2{sub 1}2{sub 1}2{sub 1}, with unit-cell parameters a = 51.2, b = 57.8, c = 75.6 Å.

  11. Neutron diffraction measurements of time-dependent residual stresses generated by severe thermomechanical deformation

    SciTech Connect

    Woo, Wan Chuck; Feng, Zhili; Wang, Xun-Li; Hubbard, Camden R

    2009-01-01

    Residual stresses were generated by severe thermomechanical deformation in an aluminum alloy plate. The evolution of the residual stresses during natural aging was investigated by neutron diffraction up to 10,000h. A data reduction method was developed to eliminate microstructure influences (solute variations) on the lattice spacing changes, thereby allowing the determination of the long-range macroscopic residual stresses. The residual stress decreased ({approx}25MPa) with time due to the microstructural modification within the deformed region during natural aging.

  12. Powder neutron diffraction studies of a carbonate fluorapatite

    SciTech Connect

    Leventouri, Th.; Chakoumakos, B. C.; Moghaddam, H. Y.; Perdikatsis, V.

    2000-02-01

    Atomic positional disorder of a single-phase natural carbonate fluorapatite (francolite) is revealed from analysis of the atomic displacement parameters (ADPs) refined from neutron powder diffraction data as a function of temperature and carbonate content. The ADPs of the francolite show a strong disturbance at the P, O3, and F sites. When it is heat treated to partially or completely remove the carbonate, the ADPs as well as the other structural parameters resemble those of a fluorapatite (Harding pegmatite) that was measured under the same conditions. The various structural changes are consistent with a substitution mechanism whereby the planar carbonate group replaces a phosphate group and lies on the mirror plane of the apatite structure. (c) 2000 Materials Research Society.

  13. Neutron diffraction study of aluminous hydroxide δ-AlOOD

    NASA Astrophysics Data System (ADS)

    Vanpeteghem, C. B.; Sano, A.; Komatsu, K.; Ohtani, E.; Suzuki, A.

    2007-11-01

    We have determined the position of deuterium atoms in δ-AlOOD by neutron powder diffraction at ambient pressure. As previously reported by theoretical and experimental studies, the deuterium atoms are located in the tunnel formed by the chains of AlO6 octahedra. The data are best fit with the P21 nm structure, producing bond lengths of D O1 of 1.552(2) Å, O2 D of 1.020(2) Å and O1 O2 of 2.571(2). This study confirms that the hydrogen bond is asymmetric at ambient conditions in agreement with recent single-crystal synchrotron study for δ-AlOOH.

  14. Diffraction of slow neutrons by holographic SiO{sub 2} nanoparticle-polymer composite gratings

    SciTech Connect

    Klepp, J.; Fally, M.; Pruner, C.; Tomita, Y.; Plonka-Spehr, C.; Geltenbort, P.; Ivanov, S.; Manzin, G.; Andersen, K. H.; Kohlbrecher, J.; Ellabban, M. A.

    2011-07-15

    Diffraction experiments with holographic gratings recorded in SiO{sub 2} nanoparticle-polymer composites have been carried out with slow neutrons. The influence of parameters such as nanoparticle concentration, grating thickness, and grating spacing on the neutron-optical properties of such materials has been tested. Decay of the grating structure along the sample depth due to disturbance of the recording process becomes an issue at grating thicknesses of about 100 microns and larger. This limits the achievable diffraction efficiency for neutrons. As a solution to this problem, the Pendelloesung interference effect in holographic gratings has been exploited to reach a diffraction efficiency of 83% for very cold neutrons.

  15. In situ neutron diffraction under high pressure—Providing an insight into working catalysts

    NASA Astrophysics Data System (ADS)

    Kandemir, Timur; Wallacher, Dirk; Hansen, Thomas; Liss, Klaus-Dieter; Naumann d'Alnoncourt, Raoul; Schlögl, Robert; Behrens, Malte

    2012-05-01

    In the present work the construction and application of a continuous flow cell is presented, from which neutron diffraction data could be obtained during catalytic reactions at high pressure. By coupling an online gas detection system, parallel structure and activity investigations of working catalysts under industrial relevant conditions are possible. The flow cell can be operated with different feed gases in a wide range from room temperature to 603 K. Pressures from ambient up to 6 MPa are applicable. An exchangeable sample positioning system makes the flow cell suitable for several different goniomter types on a variety of instrument beam lines. Complementary operational test measurements were carried out monitoring reduction of and methanol synthesis over a Cu/ZnO/Al2O3 catalyst at the high-flux powder diffraction beamline D1B at ILL and high-resolution diffraction beamline Echidna at ANSTO.

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

    SciTech Connect

    Klepp, J.; Fally, M.; Tomita, Y.; Pruner, C.; Kohlbrecher, J.

    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.

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

    NASA Astrophysics Data System (ADS)

    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

  18. Zeeman spectrum, magnetic neutron diffraction pattern, and Dirac multipoles for a multiferroic material Cu B2O4

    NASA Astrophysics Data System (ADS)

    Lovesey, S. W.

    2016-09-01

    Zeeman spectra, dichroic signals, and neutron Bragg diffraction patterns generated by copper ions in magnetically ordered copper metaborate (Cu B2O4 ) are investigated within a minimal model of Cu atomic states. A theory platform, common to understanding optical spectra and neutron diffraction patterns, affords the immediate benefit of a unified description of the experimental probes in terms of electronic multipoles. Results for dichroic signals illustrate a nontrivial use of a general, quantum mechanical theory of photon absorption couched in terms of Dirac multipoles that are magnetic and polar. Anapoles (Dirac dipoles) are predicted to generate Bragg spots in magnetic neutron diffraction that are not indexed by the motif of conventional (axial) magnetic-dipole moments. The minimal model of Cu states is informed by magnetic symmetry, derived from an established commensurate antiferromagnetic order, with a sparse number of parameters that comply with available empirical evidence.

  19. Neutron diffraction studies for realtime leaching of catalytic Ni.

    PubMed

    Iles, Gail N; Devred, François; Henry, Paul F; Reinhart, Guillaume; Hansen, Thomas C

    2014-07-21

    The leaching of Al from intermetallic samples of Nickel Aluminium alloys to form Raney-type nickel catalysts is widely used in the hydrogenation industry, however, little is known of the leaching process itself. In this study, the leaching of Al was measured in realtime, in situ, using the high-flux powder neutron diffractometer, D20, at the Institut Laue-Langevin. Despite the liberation of hydrogen and effervescent nature of the reaction the transformation of the dry powder phases into Raney-type Ni was determined. Samples produced by gas-atomisation were found to leach faster than those produced using the cast and crushed technique. Regardless of processing route of the precursor powder, the formation of spongy-Ni occurs almost immediately, while Ni2Al3 and NiAl3 continue to transform over longer periods of time. Small-angle scattering and broadening of the diffraction peaks is an evidence for the formation of the smaller Ni particles. Understanding the kinetics of the leaching process will allow industry to refine production of catalysts for optimum manufacturing time while knowledge of leaching dynamics of powders produced by different manufacturing techniques will allow further tailoring of catalytic materials. PMID:25053313

  20. Neutron diffraction studies for realtime leaching of catalytic Ni

    SciTech Connect

    Iles, Gail N. Reinhart, Guillaume; Devred, François; Henry, Paul F. Hansen, Thomas C.

    2014-07-21

    The leaching of Al from intermetallic samples of Nickel Aluminium alloys to form Raney-type nickel catalysts is widely used in the hydrogenation industry, however, little is known of the leaching process itself. In this study, the leaching of Al was measured in realtime, in situ, using the high-flux powder neutron diffractometer, D20, at the Institut Laue-Langevin. Despite the liberation of hydrogen and effervescent nature of the reaction the transformation of the dry powder phases into Raney-type Ni was determined. Samples produced by gas-atomisation were found to leach faster than those produced using the cast and crushed technique. Regardless of processing route of the precursor powder, the formation of spongy-Ni occurs almost immediately, while Ni{sub 2}Al{sub 3} and NiAl{sub 3} continue to transform over longer periods of time. Small-angle scattering and broadening of the diffraction peaks is an evidence for the formation of the smaller Ni particles. Understanding the kinetics of the leaching process will allow industry to refine production of catalysts for optimum manufacturing time while knowledge of leaching dynamics of powders produced by different manufacturing techniques will allow further tailoring of catalytic materials.

  1. Density functional and neutron diffraction studies of lithium polymer electrolytes.

    SciTech Connect

    Baboul, A. G.

    1998-06-26

    The structure of PEO doped with lithium perchlorate has been determined using neutron diffraction on protonated and deuterated samples. The experiments were done in the liquid state. Preliminary analysis indicates the Li-O distance is about 2.0 {angstrom}. The geometries of a series of gas phase lithium salts [LiCF{sub 3}SO{sub 3}, Li(CF{sub 3}SO{sub 2}){sub 2}N, Li(CF{sub 3}SO{sub 2}){sub 2}CH, LiClO{sub 4}, LiPF{sub 6}, LiAsF{sub 6}] used in polymer electrolytes have been optimized at B3LYP/6-31G(d) density functional level of theory. All local minima have been identified. For the triflate, imide, methanide, and perchlorate anions, the lithium cation is coordinated to two oxygens and have binding energies of ca 141 kcal/mol at the B3LYP/6-311+G(3df,2p)/B3LYP/6-31G* level of theory. For the hexafluoroarsenate and hexafluorophosphate the lithium cation is coordinated to three oxygens and have binding energies of ca. 136 kcal/mol.

  2. Neutron diffraction studies for realtime leaching of catalytic Ni

    NASA Astrophysics Data System (ADS)

    Iles, Gail N.; Devred, François; Henry, Paul F.; Reinhart, Guillaume; Hansen, Thomas C.

    2014-07-01

    The leaching of Al from intermetallic samples of Nickel Aluminium alloys to form Raney-type nickel catalysts is widely used in the hydrogenation industry, however, little is known of the leaching process itself. In this study, the leaching of Al was measured in realtime, in situ, using the high-flux powder neutron diffractometer, D20, at the Institut Laue-Langevin. Despite the liberation of hydrogen and effervescent nature of the reaction the transformation of the dry powder phases into Raney-type Ni was determined. Samples produced by gas-atomisation were found to leach faster than those produced using the cast and crushed technique. Regardless of processing route of the precursor powder, the formation of spongy-Ni occurs almost immediately, while Ni2Al3 and NiAl3 continue to transform over longer periods of time. Small-angle scattering and broadening of the diffraction peaks is an evidence for the formation of the smaller Ni particles. Understanding the kinetics of the leaching process will allow industry to refine production of catalysts for optimum manufacturing time while knowledge of leaching dynamics of powders produced by different manufacturing techniques will allow further tailoring of catalytic materials.

  3. Neutron diffraction observations of interstitial protons in dense ice

    PubMed Central

    Guthrie, Malcolm; Boehler, Reinhard; Tulk, Christopher A.; Molaison, Jamie J.; dos Santos, António M.; Li, Kuo; Hemley, Russell J.

    2013-01-01

    The motif of distinct H2O molecules in H-bonded networks is believed to persist up to the densest molecular phase of ice. At even higher pressures, where the molecule dissociates, it is generally assumed that the proton remains localized within these same networks. We report neutron-diffraction measurements on D2O that reveal the location of the D atoms directly up to 52 GPa, a pressure regime not previously accessible to this technique. The data show the onset of a structural change at ∼13 GPa and cannot be described by the conventional network structure of ice VII above ∼26 GPa. Our measurements are consistent with substantial deuteron density in the octahedral, interstitial voids of the oxygen lattice. The observation of this “interstitial” ice VII form provides a framework for understanding the evolution of hydrogen bonding in ice that contrasts with the conventional picture. It may also be a precursor for the superionic phase reported at even higher pressure with important consequences for our understanding of dense matter and planetary interiors. PMID:23757495

  4. Lattice collapse and quenching of magnetism in CaFe[subscript 2]As[subscript 2] under pressure: A single-crystal neutron and x-ray diffraction investigation

    SciTech Connect

    Goldman, A.I.; Kreyssig, A.; Prokeš, K.; Pratt, D.K.; Argyriou, D.N.; Lynn, J.W.; Nandi, S.; Kimber, S.A.J.; Chen, Y.; Lee, Y.B.; Samolyuk, G.; Leão, J.B.; Poulton, S.J.; Bud'ko, S.L.; Ni, N.; Canfield, P.C.; Harmon, B.N.; McQueeney, R.J.

    2009-06-12

    Single-crystal neutron and high-energy x-ray diffraction measurements have identified the phase lines corresponding to transitions among the ambient-pressure paramagnetic tetragonal (T), the antiferromagnetic orthorhombic (O), and the nonmagnetic collapsed tetragonal (cT) phases of CaFe{sub 2}As{sub 2}. We find no evidence of additional structures for pressures of up to 2.5 GPa (at 300 K). Both the T-cT and O-cT transitions exhibit significant hysteresis effects, and we demonstrate that coexistence of the O and cT phases can occur if a nonhydrostatic component of pressure is present. Measurements of the magnetic diffraction peaks show no change in the magnetic structure or ordered moment as a function of pressure in the O phase, and we find no evidence of magnetic ordering in the cT phase. Band-structure calculations show that the transition into the cT phase results in a strong decrease in the iron 3d density of states at the Fermi energy, consistent with a loss of the magnetic moment.

  5. Residual Stress Analysis in Deep Drawn Twinning Induced Plasticity (TWIP) Steels Using Neutron Diffraction Method

    NASA Astrophysics Data System (ADS)

    Hong, Seokmin; Lee, Junghoon; Lee, Sunghak; Woo, Wanchuck; Kim, Sung-Kyu; Kim, Hyoung Seop

    2014-04-01

    In Twinning Induced Plasticity (TWIP) steels, delayed fracture occurs due to residual stresses induced during deep drawing. In order to investigate the relation between residual stresses and delayed fracture, in the present study, residual stresses of deep drawn TWIP steels (22Mn-0.6C and 18Mn-2Al-0.6C steels) were investigated using the finite element method (FEM) and neutron diffraction measurements. In addition, the delayed fracture properties were examined by dipping tests of cup specimens in the boiled water. In the FEM analysis, the hoop direction residual stress was highly tensile at cup edge, and the delayed fracture was initiated by the separation of hoop direction and propagated in an axial direction. According to the neutron diffraction analysis, residual stresses in 18Mn-2Al-0.6C steel were about half the residual stresses in 22Mn-0.6C steel. From the residual strain measurement using electron back-scatter diffraction, formation of deformation twins caused a lot of grain rotation and local strain at the grain boundaries and twin boundaries. These local residual strains induce residual stress at boundaries. Al addition in TWIP steels restrained the formation of deformation twins and dynamic strain aging, resulting in more homogeneous stress and strain distributions in cup specimens. Thus, in Al-added TWIP steels, residual stress of cup specimen considerably decreased, and delayed fracture resistance was remarkably improved by the addition of Al in TWIP steels.

  6. Neutron diffraction study of hydrogen-bond symmetrization in δ-AlOOD

    NASA Astrophysics Data System (ADS)

    Sano-Furukawa, A.; Hattori, T.; Kuribayashi, T.

    2013-12-01

    δ-AlOOH, a high-pressure polymorph of diaspore, is an important hydrous mineral in the deep earth that has the ability to transport hydrogen into the lower mantle. Theoretical studies have pointed out that hydrogen would locate at the center between two oxygen atoms at high pressure, which is so called hydrogen-bond symmetrization [1]. It was also suggested that the symmetrization would trigger the increase of bulk modulus, which is one of the important parameters of minerals at high pressure. The transition of δ-AlOOH(D) at high pressure has been suggested by X-ray and neutron diffraction [2, 3]. X-ray diffraction study found that the axes a and b where the hydrogen bond is oriented become less compressible above 12 GPa in δ-AlOOD. Neutron diffraction study on δ-AlOOD up to 9.2 GPa showed the increase of O-D bond distance, that is considered as a precousor phenomena of the symmetrization. However, the pressure was insufficient to observe the symmetrization. To investigate the symmetrization of hydrogen bond directly, we conducted neutron diffraction experiments to 16.7 GPa at PLANET, MLF in J-PARC. Powder sample of δ-AlOOD was loaded in Paris-Edinburgh press with double-toroid sintered diamond anvils with methanol-ethanol mixture of pressure medium. In the experiments, the disappearance of 120 refrection was observed at 12.1 GPa, indicating the transition from P21nm to Pnnm, which can be attributed to the disorder of hydrogen bond or the symmtrization. Results of Rietveld refienment will be shown in the presentation. [1] Tsuchiya et al., Geophys. Res. Lett., 29, 1909, 2002. [2] Sano-Furukawa et al., Am. Mineral., 93, 1558-1567, 2008. [3] Sano-Furukawa et al., Am. Mineral., 94, 1255-1261, 2009.

  7. Nanoscale characterisation by SANS and residual stresses determination by neutron diffraction related to materials and components of technological interest

    NASA Astrophysics Data System (ADS)

    Rogante, Massimo; Rosta, Laszlo

    2005-06-01

    Neutron techniques, among the other non-destructive diagnostics, are becoming more and more relevant in investigating materials and components of industrial interest. In this paper, Small Angle Neutron Scattering (SANS) for microstructural characterisation-especially related to the nanoscale-and Neutron Diffraction for Residual Stresses (RS) measurements are considered. The basic theoretical aspects and some industrial applications of each technique are described. In particular, RS determination in welding, in extruded specimens and in components for energy industry is reported. SANS measurements concerning materials and components for energy and automotive industry are finally presented.

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

    NASA Technical Reports Server (NTRS)

    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

  9. 5-A Fourier map of gramicidin A phased by deuterium-hydrogen solvent difference neutron diffraction

    SciTech Connect

    Koeppe, R.E. II; Schoenborn, B.P.

    1984-03-01

    Crystals of ion-free gramicidin A (P2/sub 1/2/sub 1/2/sub 1/: a = 24.61, b = 32.28, c = 32.52) have been investigated using neutron diffraction. A difference analysis of crystals soaked in ethanol/H/sub 2/O as opposed to ethanol-d/sub 6//D/sub 2/O has lead 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.

  10. Intergranular Strain Evolution in Titanium During Tensile Loading: Neutron Diffraction and Polycrystalline Model

    NASA Astrophysics Data System (ADS)

    Gloaguen, David; Oum, Guy; Legrand, Vincent; Fajoui, Jamal; Moya, Marie-José; Pirling, Thilo; Kockelmann, Winfried

    2015-11-01

    Intergranular strains due to tensile plastic deformation were investigated in a commercially pure Ti. Neutron diffraction has been used to characterize the evolution of residual elastic strain in grains with different crystallographic orientations. Experimental data have been obtained for the macroscopic stress-strain curve and the intergranular strain evolution in the longitudinal and transverse direction relative to the uniaxial loading axis. The elasto-plastic self-consistent (EPSC) approach was used to model the deformation behavior of the studied material. Comparison between the neutron measurements and the model predictions shows that in most cases the EPSC approach can predict the lattice strain evolution and capture the plastic anisotropy observed in the experiments.

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

    SciTech Connect

    Niimura, Nobuo

    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.

  12. Analysis of neutron diffraction profiles in bronze archaeological statuettes produced by solid lost wax casting

    NASA Astrophysics Data System (ADS)

    Giuliani, Alessandra; Fiori, Fabrizio; Gysens, Jacqueline; Manescu, Adrian; Rustichelli, Franco

    2008-03-01

    In the framework of a research aiming to assess the suitability of neutron/x-ray non-destructive techniques for the characterization of archaeological objects, two bronze items were studied by neutron diffraction. The origins of two small statues are, respectively, Egyptian (XXI-XXX Dynasties, c1070-343 B.C.) and Etruscan (IV-III centuries B.C.), belonging to a private collection. By hard x-ray diffraction we previously verified that both statuettes have a coarse microstructure (big grains). From historical considerations we believe that both items were produced by solid lost wax processes of casting. This processing technique does not completely justify the presence of microstrains; as a consequence, due to unexpected neutron diffraction peak broadening, a non-uniform Sn wt% is suspected. In the present work we discuss this deduction by means of Rietveld analysis of the neutron diffraction profiles.

  13. Neutron irradiated uranium silicides studied by neutron diffraction and Rietveld analysis

    SciTech Connect

    Birtcher, R.C.; Mueller, M.H.; Richardson, J.W. Jr.

    1990-11-01

    The irradiation behavior of high-density uranium silicides has been a matter of interest to the nuclear industry for use in high power or low enrichment applications. Transmission electron microscopy studies have found that heavy ion bombardment renders U{sub 3}Si and U{sub 3}Si{sub 2} amorphous at temperatures below about 250 C and that U{sub 3}Si becomes mechanically unstable suffering rapid growth by plastic flow. In this present work, crystallographic changes preceding amorphization by fission fragment damage have been studied by high-resolution neutron diffraction as a function of damage produced by uranium fission at room temperature. Initially, both silicides had tetragonal crystal structures. Crystallographic and amorphous phases were studied simultaneously by combining conventional Rietveld refinement of the crystallographic phases with Fourier-filtering analysis of the non-crystalline scattering component. 13 refs., 5 figs.

  14. Proceedings of the 1986 workshop on advanced time-of-flight neutron powder diffraction

    SciTech Connect

    Lawson, A.C.; Smith, K.

    1986-09-01

    This report contains abstracts of talks and summaries of discussions from a small workshop held to discuss the future of time-of-flight neutron powder diffraction and its implementation at the Los Alamos Neutron Scattering Center. 47 refs., 3 figs.

  15. Neutron diffraction measurements of residual stresses in friction stir welding: a review

    SciTech Connect

    Woo, Wan Chuck; Feng, Zhili; Wang, Xun-Li; David, Stan A

    2011-01-01

    Significant amounts of residual stresses are often generated during welding and result in critical degradation of the structural integrity and performance of components. Neutron diffraction has become a well established technique for the determination of residual stresses in welds because of the unique deep penetration, three-dimensional mapping capability, and volume averaged bulk measurements characteristic of the scattering neutron beam. Friction stir welding has gained prominence in recent years. The authors reviewed a number of neutron diffraction measurements of residual stresses in friction stir welds and highlighted examples addressing how the microstructures and residual stresses are correlated with each other. An example of in situ neutron diffraction measurement result shows the evolution of the residual stresses during welding.

  16. Unraveling cyclic deformation mechanisms of a rolled magnesium alloy using in situ neutron diffraction

    SciTech Connect

    Wu, Wei; An, Ke; Liaw, Peter K.

    2014-12-23

    In the current study, the deformation mechanisms of a rolled magnesium alloy were investigated under cyclic loading using real-time in situ neutron diffraction under a continuous-loading condition. The relationship between the macroscopic cyclic deformation behavior and the microscopic response at the grain level was established. The neutron diffraction results indicate that more and more grains are involved in the twinning and detwinning deformation process with the increase of fatigue cycles. The residual twins appear in the early fatigue life, which is responsible for the cyclic hardening behavior. The asymmetric shape of the hysteresis loop is attributed to the early exhaustion of the detwinning process during compression, which leads to the activation of dislocation slips and rapid strain-hardening. The critical resolved shear stress for the activation of tensile twinning closely depends on the residual strain developed during cyclic loading. In the cycle before the sample fractured, the dislocation slips became active in tension, although the sample was not fully twinned. The increased dislocation density leads to the rise of the stress concentration at weak spots, which is believed to be the main reason for the fatigue failure. Furthermore, the deformation history greatly influences the deformation mechanisms of hexagonal-close-packed-structured magnesium alloy during cyclic loading.

  17. Unraveling cyclic deformation mechanisms of a rolled magnesium alloy using in situ neutron diffraction

    DOE PAGES

    Wu, Wei; An, Ke; Liaw, Peter K.

    2014-12-23

    In the current study, the deformation mechanisms of a rolled magnesium alloy were investigated under cyclic loading using real-time in situ neutron diffraction under a continuous-loading condition. The relationship between the macroscopic cyclic deformation behavior and the microscopic response at the grain level was established. The neutron diffraction results indicate that more and more grains are involved in the twinning and detwinning deformation process with the increase of fatigue cycles. The residual twins appear in the early fatigue life, which is responsible for the cyclic hardening behavior. The asymmetric shape of the hysteresis loop is attributed to the early exhaustionmore » of the detwinning process during compression, which leads to the activation of dislocation slips and rapid strain-hardening. The critical resolved shear stress for the activation of tensile twinning closely depends on the residual strain developed during cyclic loading. In the cycle before the sample fractured, the dislocation slips became active in tension, although the sample was not fully twinned. The increased dislocation density leads to the rise of the stress concentration at weak spots, which is believed to be the main reason for the fatigue failure. Furthermore, the deformation history greatly influences the deformation mechanisms of hexagonal-close-packed-structured magnesium alloy during cyclic loading.« less

  18. In situ synthesis and characterization of uranium carbide using high temperature neutron diffraction

    NASA Astrophysics Data System (ADS)

    Reiche, H. Matthias; Vogel, Sven C.; Tang, Ming

    2016-04-01

    We investigated the formation of UCx from UO2+x and graphite in situ using neutron diffraction at high temperatures with particular focus on resolving the conflicting reports on the crystal structure of non-quenchable cubic UC2. The agents were UO2 nanopowder, which closely imitates nano grains observed in spent reactor fuels, and graphite powder. In situ neutron diffraction revealed the onset of the UO2 + 2C → UC + CO2 reaction at 1440 °C, with its completion at 1500 °C. Upon further heating, carbon diffuses into the uranium carbide forming C2 groups at the octahedral sites. This resulting high temperature cubic UC2 phase is similar to the NaCl-type structure as proposed by Bowman et al. Our novel experimental data provide insights into the mechanism and kinetics of formation of UC as well as characteristics of the high temperature cubic UC2 phase which agree with proposed rotational rehybridization found from simulations by Wen et al.

  19. Structure and dynamics of aqueous 2-propanol: a THz-TDS, NMR and neutron diffraction study.

    PubMed

    McGregor, James; Li, Ruoyu; Zeitler, J Axel; D'Agostino, Carmine; Collins, James H P; Mantle, Mick D; Manyar, Haresh; Holbrey, John D; Falkowska, Marta; Youngs, Tristan G A; Hardacre, Christopher; Stitt, E Hugh; Gladden, Lynn F

    2015-11-11

    Aqueous liquid mixtures, in particular, those involving amphiphilic species, play an important role in many physical, chemical and biological processes. Of particular interest are alcohol/water mixtures; however, the structural dynamics of such systems are still not fully understood. Herein, a combination of terahertz time-domain spectroscopy (THz-TDS) and NMR relaxation time analysis has been applied to investigate 2-propanol/water mixtures across the entire composition range; while neutron diffraction studies have been carried out at two specific concentrations. Excellent agreement is seen between the techniques with a maximum in both the relative absorption coefficient and the activation energy to molecular motion occurring at ∼90 mol% H2O. Furthermore, this is the same value at which well-established excess thermodynamic functions exhibit a maximum/minimum. Additionally, both neutron diffraction and THz-TDS have been used to provide estimates of the size of the hydration shell around 2-propanol in solution. Both methods determine that between 4 and 5 H2O molecules per 2-propanol are found in the 2-propanol/water clusters at 90 mol% H2O. Based on the acquired data, a description of the structure of 2-propanol/water across the composition range is presented.

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

    NASA Astrophysics Data System (ADS)

    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

  1. Neutron diffraction on polymer nanocomposites - A tool for structural and orientation studies

    NASA Astrophysics Data System (ADS)

    Sapalidis, A. A.; Katsaros, F. K.; Steriotis, Th A.; Kanellopoulos, N. K.; Dante, S.; Hauss, T.

    2012-02-01

    A series of Polyvinyl alcohol (Mowiol 5-88) - Bentonite nanocomposite films with predefined clay loading (up to 0-20%), were prepared via solvent casting technique. The developed films, due to the favourable polymer-particle interactions, revealed excellent dispersion of the clay particles in the polymer matrix and improved properties. Furthermore, the properties of PVA/clay nanocomposites as well as their structural changes as a function of the relative humidity were thoroughly investigated using neutron membrane diffraction experiments. The samples prior their measurement were equilibrated at different relative humidity levels (%RH) using either H2O or D2O. The application of contrast variation technique enabled us to investigate the contribution of both the polymer and the clay particles to the diffraction spectra. Thus, the use of H2O enlightened the low Q region, providing information about the structure of the inorganic phase and specifically the stacking of the clay platelets. The diffraction patterns in this region obtained from perpendicular and in-plane sample positions revealed that there is a specific orientation of bentonite plates, parallel to the film surface. This conclusion is in agreement with the results obtained from XRD and gas permeability technique, in which the well organized and dispersed impermeable inorganic layers, increase the resistance in flow through the nanocomposites film, acting as gas barriers. On the other hand, diffraction experiments on pre-equilibrated with D2O samples revealed the structural changes in polymeric matrix, due to hydration. The obtained peak revealed the presence of a new crystalline phase, presumably induced by the presence of the silicates, which is in agreement with DSC data reported in previous studies.

  2. Area detectors in single-crystal neutron diffraction

    NASA Astrophysics Data System (ADS)

    McIntyre, Garry J.

    2015-12-01

    The introduction of area detectors has brought about a gentle revolution in the routine application of single-crystal neutron diffractometry. Implemented first for macromolecular crystallography, electronic detectors subsequently gradually spread to chemical and physics-oriented crystallography at steady-state sources. The volumetric surveying of reciprocal space implicit in the Laue technique has required area detectors right from the start, whether using film and more recently image plates and CCD-based detectors at reactors, or scintillation detectors at spallation sources. Wide-angle volumetric data collection has extended application of neutron single-crystal diffractometry to chemical structures, sample volumes, and physical phenomena previously deemed impossible. More than 30 of the dedicated single-crystal neutron diffractometers at steady-state reactor and neutron spallation sources worldwide and accessible via peer-review proposal mechanisms are currently equipped with area detectors. Here we review the historical development of the various types of area detectors used for single crystals, discuss experimental aspects peculiar to experiments with such detectors, highlight the scientific fields where the use of area detectors has had a special impact, and forecast future developments in hardware, implementation, and software.

  3. Lithium Ion Materials for Energy Applications: Structural Properties from Neutron Diffraction

    NASA Astrophysics Data System (ADS)

    Catti, Michele

    Cathode materials and solid electrolytes to be used in lithium batteries require a high ionic mobility of Li^+ species in their crystal structures. This in turn depends on the order-disorder state of lithium and on its bonding environment. Neutron diffraction is the choice technique to study the structural features of polycrystalline lithium materials that control their performance in ion transport processes. The basic principles of ionic mobility in solids and of the Rietveld refinement methods for neutron diffraction data are briefly reviewed. Then two important families of lithium conductors are selected from the literature and thoroughly discussed: the LLTO perovskite-type Li_xLa_{2/3-x/3}TiO_3 system and the Li_{1+x}Me_2(PO_4)_3 Nasicon phases. Accurate neutron diffraction determinations of the corresponding crystal structures have been shown to provide a considerable insight into the mechanisms of Li^+ ion transfer in such materials.

  4. An Approach to Model Neutron Diffraction Pattern of Uniaxial Deformed Sandstone Using Elastic Properties of Quartz

    NASA Astrophysics Data System (ADS)

    Breuer, S.; Schilling, F. R.; Mueller, B.; Scheffzuek, C.

    2015-12-01

    Mechanical properties of sedimentary rocks such as stress-strain-relations are essential for understanding dynamic processes within the Earth's crust. The measurement of in-situ lattice strain in bulk samples is possible with diffraction methods, e.g. with neutrons. The advantage of neutron diffraction is their high penetration depth, which enables to gather a statistically relevant number of grains by diffraction. The neutron time-of-flight diffraction at the strain diffractometer EPSILON which is located at the pulsed neutron source IBR-2M (JINR Dubna, RUS) enables the detection of the complete diffraction pattern up to λ = 7.1 Å (d = 5.1 Å). Uniaxial cyclic deformation experiments were carried out up to 50 MPa (three steps) on a macroscopically isotropic sandstone from Kuhbach / Lahr (Germany). The aim of the present study is to model diffraction patterns for different applied stress-levels, based on the zero-stress diffraction pattern and known elastic properties of Quartz single crystals. The as received model-predictions are compared to observations, both, in the direction of maximum stress (along the cylindric axis) and perpendicular to it. The results show that the shape of the grains has an influence on the macroscopic elastic behavior of the rock whereas the microscopic strain is affected in a different manner. The model is based on spherical quartz grains. The spheres are divided into slices. By removing some slices, the shape of sand grains is approximated. The reaction of each slice through the applied stress is modelled. Together with the relative volume of each slice and it´s elastic behavior, the diffraction pattern is predicted for different applied loads. Measured and modelled diffraction-patterns at different applied loads are in good agreement.

  5. Development of MnBi permanent magnet: Neutron diffraction of MnBi powder

    SciTech Connect

    Cui, J.; Choi, J. P.; Li, G.; Polikarpov, E.; Darsell, J.; Kramer, M. J.; Zarkevich, N. A.; Wang, L. L.; Johnson, D. D.; Marinescu, M.; Huang, Q. Z.; Wu, H.; Vuong, N. V.; Liu, J. P.

    2014-05-07

    MnBi attracts great attention in recent years for its great potential as permanent magnet materials. MnBi phase is difficult to obtain because of the rather drastic peritectic reaction between Mn and Bi. In this paper, we report our effort on synthesizing high purity MnBi compound using conventional powder metallurgical approaches. Neutron diffraction was carried out to investigate the crystal and nuclear structure of the obtained powder. The result shows that the purity of the obtained powder is about 91 wt. % at 300 K, and the magnetic moment of the Mn atom in MnBi lattice is 4.424 and 4.013 μB at 50 K and 300 K, respectively.

  6. Development of MnBi permanent magnet: Neutron diffraction of MnBi powder

    SciTech Connect

    Cui, J. Choi, J. P.; Li, G.; Polikarpov, E.; Darsell, J.; Kramer, M. J.; Zarkevich, N. A.; Wang, L. L.; Johnson, D. D.; Marinescu, M.; Huang, Q. Z.; Wu, H.; Vuong, N. V.; Liu, J. P.

    2014-05-07

    MnBi attracts great attention in recent years for its great potential as permanent magnet materials. MnBi phase is difficult to obtain because of the rather drastic peritectic reaction between Mn and Bi. In this paper, we report our effort on synthesizing high purity MnBi compound using conventional powder metallurgical approaches. Neutron diffraction was carried out to investigate the crystal and nuclear structure of the obtained powder. The result shows that the purity of the obtained powder is about 91 wt. % at 300 K, and the magnetic moment of the Mn atom in MnBi lattice is 4.424 and 4.013 μ{sub B} at 50 K and 300 K, respectively.

  7. Development of MnBi permanent magnet: neutron diffraction of MnBi powder

    SciTech Connect

    Cui, Jun; Choi, Jung-Pyung; Li, Guosheng; Polikarpov, Evgueni; Darsell, Jens T.; Kramer, Matthew J.; Zarkevich, Nikolai; Wang, L. L.; Johnson, D. D.; Marinescu, Melania; Huang, Qingzhen; Wu, Hui; Vuong, Nguyen V.; Liu, J.Ping

    2014-03-05

    MnBi attracts great attention in recent years for its great potential as permanent magnet materials. MnBi phase is difficult to obtain because of the rather drastic peritectic reaction between Mn and Bi. In this paper, we report our effort on synthesizing high purity MnBi compound using conventional powder metallurgical approaches. Neutron diffraction was carried out to investigate the crystal and nuclear structure of the obtained power. The result shows that the purity of the obtained powder is about 91wt.% at 300K, and the magnetic moment of the Mn atom in MnBi lattice is 4.424 and 4.013 μB at 50 K and 300 K respectively.

  8. Neutron Diffraction Characterization of Residual Strain in Welded Inconel 718 for NASA Space Shuttle Flow Liners

    SciTech Connect

    Rathod, C.R.; Vaidyanathan, R.; Livescu, V.; Clausen, B.; Bourke, M. A. M.; Notardonato, W.U.; Femminineo, M.

    2004-06-28

    This work quantitatively assesses residual strains and stresses associated with the weld repair process used to repair cracks on NASA's space shuttle flow liners. The coupons used in this investigation were made of the same INCONEL 718 alloy used for the flow liners. They were subjected to identical welding and certification procedures that were carried out on the space shuttle. Neutron diffraction measurements at Los Alamos National Laboratory determined residual strains at selected locations in a welded coupon at 293 K and 135 K. The weld repair process introduced Mises effective residual stresses of up to 555 MPa. On comparing the measurements at 293 K and 135 K, no significant change to the residual strain profile was noted at the low temperature. This indicated minimal mismatch in the coefficients of thermal expansion between the base metal and the weld.

  9. Development of MnBi permanent magnet: Neutron diffraction of MnBi powder

    SciTech Connect

    Cui, J; Choi, JP; Li, G; Polikarpov, E; Darsell, J; Kramer, MJ; Zarkevich, NA; Wang, LL; Johnson, DD; Marinescu, M; Huang, QZ; Wu, H; Vuong, NV; Liu, JP

    2014-05-07

    MnBi attracts great attention in recent years for its great potential as permanent magnet materials. MnBi phase is difficult to obtain because of the rather drastic peritectic reaction between Mn and Bi. In this paper, we report our effort on synthesizing high purity MnBi compound using conventional powder metallurgical approaches. Neutron diffraction was carried out to investigate the crystal and nuclear structure of the obtained powder. The result shows that the purity of the obtained powder is about 91 wt. % at 300 K, and the magnetic moment of the Mn atom in MnBi lattice is 4.424 and 4.013 mu(B) at 50 K and 300 K, respectively. (C) 2014 AIP Publishing LLC.

  10. Neutron Diffraction Characterization of Residual Strain in Welded Inconel 718 for NASA Space Shuttle Flow Liners

    NASA Astrophysics Data System (ADS)

    Rathod, C. R.; Livescu, V.; Clausen, B.; Bourke, M. A. M.; Notardonato, W. U.; Femminineo, M.; Vaidyanathan, R.

    2004-06-01

    This work quantitatively assesses residual strains and stresses associated with the weld repair process used to repair cracks on NASA's space shuttle flow liners. The coupons used in this investigation were made of the same INCONEL 718 alloy used for the flow liners. They were subjected to identical welding and certification procedures that were carried out on the space shuttle. Neutron diffraction measurements at Los Alamos National Laboratory determined residual strains at selected locations in a welded coupon at 293 K and 135 K. The weld repair process introduced Mises effective residual stresses of up to 555 MPa. On comparing the measurements at 293 K and 135 K, no significant change to the residual strain profile was noted at the low temperature. This indicated minimal mismatch in the coefficients of thermal expansion between the base metal and the weld.

  11. A preliminary neutron diffraction analysis of Achromobacter protease I

    NASA Astrophysics Data System (ADS)

    Ohnishi, Yuki; Masaki, Takeharu; Yamada, Taro; Kurihara, Kazuo; Tanaka, Ichiro; Niimura, Nobuo

    2010-11-01

    Achromobacter protease I (API, E.C. 3.4.21.50) is one of the serine proteases produced by Achromobacter lyticus M497-1. API is distinct from the other tripsin type protease in its lysine specificity. The neutron structure analysis of catalytic triad with Trp169 and His210 was presented. His57 was double protonated and formed hydrogen bonds to Ser194Oγ and Asp113Oδ1, Oδ2.

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

    SciTech Connect

    Bourke, M.A.M.; Goldstone, J.A.; Shi, N.; Gray, G.T. III; James, M.R.; Todd, R.I.

    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.

  13. High-Pressure Neutron Diffraction Studies for Materials Sciences and Energy Sciences

    NASA Astrophysics Data System (ADS)

    Zhao, Y.; Los Alamos High Pressure Materials Research Team

    2013-05-01

    The development of neutron diffraction under extreme pressure (P) and temperature (T) conditions is highly valuable to condensed matter physics, crystal chemistry, materials sciences, as well as earth and planetary sciences. We have incorporated a 500-ton press TAP-98 into the HiPPO diffractometer at LANSCE to conduct in situ high P-T neutron diffraction experiments. We have worked out a large gem-crystal anvil cell, ZAP, to conduct neutron diffraction experiments at high-P and low-T. The ZAP cell can be used to integrate multiple experimental techniques such as neutron diffraction, laser spectroscopy, and ultrasonic interferometery. Recently, we have developed high-P low-T gas/fluid cells in conjunction with neutron diffraction and inelastic neutron scattering instruments. These techniques enable in-situ and real-time examination of gas uptake/release processes and allow high-resolution time-dependent determination of changes in crystal structure and related reaction kinetics. We have successfully used these techniques to study the equation of state, structural phase transition, and thermo-mechanical properties of metals, ceramics, and minerals. We have conducted researches on the formation of methane and hydrogen clathrates, and hydrogen adsorption of the inclusion compounds such as the recently discovered metal-organic frameworks (MOFs). The aim of our research is to accurately map phase diagram, lattice parameters, thermal parameters, bond lengths, bond angles, neighboring atomic environments, and phase stability in P-T-X space. We are currently developing further high P-T technology with a new "true" triaxial loading press, TAP_6x, to compress cubic sample package to achieve pressures up to 20 GPa and temperatures up to 2000 K in routine experiments. The implementation of TAP_6x300 with high-pressure neutron beamlines is underway for simultaneous high P-T neutron diffraction, ultrasonic, calorimetry, radiography, and tomography studies. Studies based on high

  14. Ferroelectric glycine silver nitrate: a single-crystal neutron diffraction study.

    PubMed

    Choudhury, R R; Chitra, R; Aliouane, N; Schefer, J

    2013-12-01

    Protonated crystals of glycine silver nitrate (C4H10Ag2N4O10) undergo a displacive kind of structural phase transition to a ferroelectric phase at 218 K. Glycine silver nitrate (GSN) is a light-sensitive crystal. Single-crystal X-ray diffraction investigations are difficult to perform on these crystals due to the problem of crystal deterioration on prolonged exposure to X-rays. To circumvent this problem, single-crystal neutron diffraction investigations were performed. We report here the crystal structure of GSN in a ferroelectric phase. The final R value for the refined structure at 150 K is 0.059. A comparison of the low-temperature structure with the room-temperature structure throws some light on the mechanism of the structural phase change in this crystal. We have attempted to explain the structural transition in GSN within the framework of the vibronic theory of ferroelectricity, suggesting that the second-order Jahn-Teller (pseudo-Jahn-Teller) behavior of the Ag(+) ion in GSN leads to structural distortion at low temperature (218 K). PMID:24253085

  15. Ferroelectric glycine silver nitrate: a single-crystal neutron diffraction study.

    PubMed

    Choudhury, R R; Chitra, R; Aliouane, N; Schefer, J

    2013-12-01

    Protonated crystals of glycine silver nitrate (C4H10Ag2N4O10) undergo a displacive kind of structural phase transition to a ferroelectric phase at 218 K. Glycine silver nitrate (GSN) is a light-sensitive crystal. Single-crystal X-ray diffraction investigations are difficult to perform on these crystals due to the problem of crystal deterioration on prolonged exposure to X-rays. To circumvent this problem, single-crystal neutron diffraction investigations were performed. We report here the crystal structure of GSN in a ferroelectric phase. The final R value for the refined structure at 150 K is 0.059. A comparison of the low-temperature structure with the room-temperature structure throws some light on the mechanism of the structural phase change in this crystal. We have attempted to explain the structural transition in GSN within the framework of the vibronic theory of ferroelectricity, suggesting that the second-order Jahn-Teller (pseudo-Jahn-Teller) behavior of the Ag(+) ion in GSN leads to structural distortion at low temperature (218 K).

  16. Thermodynamic and neutron diffraction studies on multiferroic NdMn2O5

    NASA Astrophysics Data System (ADS)

    Chattopadhyay, S.; Balédent, V.; Auban-Senzier, P.; Pasquier, C.; Doubrovsky, C.; Greenblatt, M.; Foury-Leylekian, P.

    2015-03-01

    Magnetically frustrated RMn2O5 oxides have attracted considerable attention in recent years, because most of the members of this family show spin ordering induced dielectric polarization along with strong magneto-electric coupling. Although the true origin of the ferroelectricity is still a matter of debate, it has been observed that the magneto-electric phase diagram can be substantially tuned with the variation of rare earth elements. In this work, we have chosen NdMn2O5 as the compound of our interest since it lies exactly in between the ferroelectric and non-ferroelectric members of this family and also, because there are few investigations performed on RMn2O5 systems with large rare earth atoms . With the combination of heat capacity, magnetic susceptibility, dielectric permittivity, powder X-ray diffraction, and powder neutron diffraction measurements, it has been found that NdMn2O5 undergoes an incommensurate magnetic ordering around 30 K followed by a possible ferroelectric-like transition at ∼26 K. Another lock-in kind of magnetic transition appears when the temperature is decreased to ∼15 K. With further lowering of temperature, an antiferromagnetic ordering, which is presumably associated with the Nd3+, is achieved near 4 K. This study thus sheds light on a new compound of the RMn2O5 series presenting different multiferroic properties.

  17. Lamellar spacing of photosystem II membrane fragments upon dehydration studied by neutron membrane diffraction

    NASA Astrophysics Data System (ADS)

    Pieper, Jörg; Rusevich, Leonid; Hauß, Thomas; Renger, Gernot

    2015-12-01

    The effect of dehydration on the lamellar spacing of photosystem II (PS II) membrane fragments from spinach has been investigated using neutron membrane diffraction at room temperature. The diffraction data reveal a major peak at a scattering vector Q of 0.049 Å-1 at a relative humidity (r.h.) of 90% corresponding to a repeat distance D of about 129 Å. Upon dehydration to 44% r.h., this peak shifts to about 0.060 Å-1 corresponding to a distance of 104.7±2.5 Å. Within experimental error, the latter repeat distance remains almost the same at hydration levels below 44% r.h. indicating that most of the hydration water is removed. This result is consistent with the earlier finding that hydration-induced conformational protein motions in PS II membrane fragments are observed above 44% r.h. and correlated with the onset electron transfer in PS II (Pieper et al. 2008, Eur. Biophys. J. 37: 657-663).

  18. Lamellar spacing of photosystem II membrane fragments upon dehydration studied by neutron membrane diffraction

    NASA Astrophysics Data System (ADS)

    Pieper, Jörg; Rusevich, Leonid; Hauß, Thomas; Renger, Gernot

    2016-02-01

    The effect of dehydration on the lamellar spacing of photosystem II (PS II) membrane fragments from spinach has been investigated using neutron membrane diffraction at room temperature. The diffraction data reveal a major peak at a scattering vector Q of 0.049 Å-1 at a relative humidity (r.h.) of 90% corresponding to a repeat distance D of about 129 Å. Upon dehydration to 44% r.h., this peak shifts to about 0.060 Å-1 corresponding to a distance of 104.7±2.5 Å. Within experimental error, the latter repeat distance remains almost the same at hydration levels below 44% r.h. indicating that most of the hydration water is removed. This result is consistent with the earlier finding that hydration-induced conformational protein motions in PS II membrane fragments are observed above 44% r.h. and correlated with the onset electron transfer in PS II (Pieper et al. 2008, Eur. Biophys. J. 37: 657-663).

  19. The structure of fluid fluoroform, chlorodifluoromethane, and dichlorodifluoromethane by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Hall, C. D.; Johnson, K. A.; Burgess, A. N.; Winterton, N.; Howells, W. S.

    Neutron diffraction has been used to study the structure of liquid fluoroform, dichlorodifluoromethane, and chlorodifluoromethane at 153 K. Accurate values of the intramolecular atomic separations have been found from the radial distribution functions. In addition, information regarding the intermolecular liquid structure of the three fluids has been obtained. Molecular dynamics simulations are underway to interpret these observations.

  20. Combined X-ray and neutron fibre diffraction studies of biological and synthetic polymers.

    SciTech Connect

    Parrot, I. M.; Urban, Volker S; Gardner, K. H.; Forsyth, V. T.

    2005-04-01

    The fibrous state is a natural one for polymer molecules which tend to assume regular helical conformations rather than the globular structures characteristic of many proteins. Fibre diffraction therefore has broad application to the study of a wide range of biological and synthetic polymers. The purpose of this paper is to illustrate the general scope of the method and in particular to demonstrate the impact of a combined approach involving both X-ray and neutron diffraction methods. While the flux of modern X-ray synchrotron radiation sources allows high quality datasets to be recorded with good resolution within a very short space of time, neutron studies can provide unique information through the ability to locate hydrogen or deuterium atoms that are often difficult or impossible to locate using X-ray methods. Furthermore, neutron fibre diffraction methods can, through the ability to selectively label specific parts of a structure, be used to highlight novel aspects of polymer structure that can not be studied using X-rays. Two examples are given. The first describes X-ray and neutron diffraction studies of conformational transitions in DNA. The second describes structural studies of the synthetic high-performance polymer poly(p-phenylene terephthalamide) (PPTA), known commercially as Kevlar{reg_sign} or Twaron{reg_sign}.

  1. Neutron diffraction residual stress studies for aero-engine component applications

    NASA Astrophysics Data System (ADS)

    Clay, K.; Small, C.

    1991-12-01

    Computer graphics for a presentation describing how Rolls-Royce is refining the method of residual stress measurement by neutron diffraction to suit the characteristic stress fields of components are presented. Results to date are given. An outline of how this residual stress data is to be used in developing stress models for critical rotating components is given.

  2. Observation of an intermediate phase in dysprosium near the Neel point by neutron diffraction

    SciTech Connect

    Bessergenev, V.G.; Gogava, V.V.; Kovalevskaya, Y.A.; Mandzhavidze, A.G.; Fedorov, V.M.; Shilo, S.I.

    1985-11-25

    The magnetic structure of dysprosium near the point of magnetic disordering has been studied as a function of the thermal history of the sample by neutron diffraction. An intermediate vortex phase appears during cooling from the paramagnetic phase and then converts into a helicoidal phase.

  3. Enhanced crystal fabric analysis of a lava flow sample by neutron texture diffraction: A case study from the Castello d'Ischia dome

    NASA Astrophysics Data System (ADS)

    Walter, Jens M.; Iezzi, Gianluca; Albertini, Gianni; Gunter, Mickey E.; Piochi, Monica; Ventura, Guido; Jansen, Ekkehard; Fiori, Fabrizio

    2013-01-01

    The crystal fabric of a lava has been analyzed for the first time by neutron texture diffraction. In this study we quantitatively investigate the crystallographic preferred orientation of feldspars in the Castello d'Ischia (Ischia Island, Italy) trachytic exogenous dome. The crystallographic preferred orientation was measured with the monochromatic neutron texture diffractometer SV7 at the Forschungszentrum Jülich in Germany and a Rietveld refinement was applied to the sum diffraction pattern. The complementary thin section analysis showed that the three-dimensional crystal shape and the corresponding shape preferred orientation are in agreement with the quantitative orientation distributions of the neutron texture data. The (0k0) crystallographic planes of the feldspars are roughly parallel to the local flow bands, whereas the other corresponding pole figures show that a pivotal rotation of the anorthoclase and sanidine crystals was active during the emplacement of this lava dome. In combination with scanning electron microscopy investigations, electron probe microanalysis, XRF, and X-ray diffraction, the Rietveld refinement of the neutron diffraction data indicates a slow cooling dynamic on the order of several months during their crystallization under subaerial conditions. Results attained here demonstrate that neutron texture diffraction is a powerful tool that can be applied to lava flows.

  4. An In Situ Study of Sintering Behavior and Phase Transformation Kinetics in NiTi Using Neutron Diffraction

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Liss, Klaus-Dieter; Cao, Peng

    2015-12-01

    The powder sintering behavior of NiTi from an elemental powder mixture of Ni/Ti has been investigated, using an in situ neutron diffraction technique. In the sintered alloys, the overall porosity ranges from 9.2 to 15.6 pct, while the open-to-overall porosity ratio is between 8.3 and 63.7 pct and largely depends on the sintering temperature. In comparison to powder compacts sintered at 1223 K and 1373 K (950 °C and 1100 °C), the powder compact sintered at 1153 K (880 °C) shows a much smaller pore size, a higher open-to-overall porosity ratio but smaller shrinkage and a lower density. Direct evidence of eutectoid transformation in the binary Ni-Ti system during furnace cooling to ca. 890 K (617 °C) is provided by in situ neutron diffraction. The intensities of the B2-NiTi reflections decrease during the holding stage at 1373 K (1100 °C), which has been elaborated as an extinction effect according to the dynamical theory of neutron diffraction, when distorted crystallites gradually recover to perfect crystals. The analysis on the first five reflections clarifies the non-existence of any order-disorder transition in the NiTi phase from B2-to-BCC structure.

  5. Processing of Neutron Diffraction Data for Strain Measurement in Geological Materials

    SciTech Connect

    Polsky, Yarom; An, Ke; Anovitz, Lawrence {Larry} M; Bingham, Philip R; Carmichael, Justin R; Dessieux Jr, Luc Lucius

    2014-01-01

    : Conventional rock mechanics testing techniques typically involve the loading of samples and measurement of displacements or strains on the outer boundary of the specimen surface. Neutron diffraction based strain measurement techniques represent a unique and powerful tool for measuring the strain within geological materials under load. The structural variability and non-uniform crystallinity of geological materials, however, create many complexities in the intensity patterns that must be analyzed to quantify strains within the material. The attenuating and scattering properties of the pressure cell housing the sample further add difficulties to the data analysis. This paper describes the methods and processes used to process neutron scattering data for strain measurement in geological materials. It is intended to provide a primer for those in the rock mechanics community that are interested in utilizing this technique along with additional discussion of neutron diffraction experimental factors that may affect data quality.

  6. Investigations of stone consolidants by neutron imaging

    NASA Astrophysics Data System (ADS)

    Hameed, F.; Schillinger, B.; Rohatsch, A.; Zawisky, M.; Rauch, H.

    2009-06-01

    The chemical preservation and structural reintegration of natural stones applied in historical buildings is carried out by the use of different stone strengtheners. As these agents contain hydrogen, they offer good properties for neutron imaging. The main interest in the restoration process is the development of a suitable stone consolidant. In cooperation with the St. Stephans Cathedral and the geologists at Vienna University of Technology, we are investigating the penetration depth and distribution of different stone consolidants. These studies are being carried out with different stone samples, mostly porous natural building stones, limestones and sandstones. The two strengtheners used in this study are ethyl silicate ester (Wacker OH100) and dissolved polymethylmetacrylate (PMMA, Paraloid B72). Neutron radiography and neutron tomography can be used successfully to visualize the distribution of consolidants both in two and three dimensions.

  7. In-Situ Neutron Diffraction Studies of Complex Hydrogen Storage Materials

    SciTech Connect

    Yelon, William B.

    2013-05-13

    The thrust of this project was to investigate the structures of important materials with potential application to hydrogen storage, in an effort to meet the DOE goals for 2010 and 2015, namely 9% (wt) and 15% (wt) respectively. Unfortunately, no material has been found, despite the efforts of many laboratories, including our own, that achieves these goals in a reversible complex hydride such as ammonia borane (NH{sub 4}BH{sub 4}), and other ammonia based compounds, or with light hydrides such as LiBH{sub 4}, due either to their irreversibility or to the high decomposition temperatures and residual simple hydrides such as LiH from the decomposition of the last named compound. Nevertheless, several important technical goals have been accomplished that could be valuable to other DOE programs and would be available for collaborative research. These include the development of a high quality glove box with controlled (low) oxygen and water content, which we continue to employ for the synthesis of potential new materials (unfunded research) and the development of a high quality neutron diffraction furnace with controlled gas environment for studies of hydrogen uptake and loss as well as for studies with other gasses. This furnace was initially constructed with an alumina (Al{sub 2}O{sub 3}) center tube to contain the sample and the flowing gas. The heaters are located in the vacuum space outside the tube and it was found that, for the low temperatures required for the study of hydrogen storage materials, the heat transfer was too poor to allow good control. At temperatures in excess of about 400C (and up to more than 1200C) the heat transfer and control are excellent. For the lower temperatures, however, the center tube was replaced by stainless steel and temperature control to 1C became possible. The paired heaters, above and below the neutron beam window allowed control of the temperature gradient to a similar precision. The high temperature capability of the furnace

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

    PubMed

    Mauro, N A; Vogt, A J; Derendorf, K S; Johnson, M L; Rustan, G E; Quirinale, D G; Kreyssig, A; Lokshin, K A; Neuefeind, J C; An, Ke; Wang, Xun-Li; Goldman, A I; Egami, T; Kelton, K F

    2016-01-01

    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 Zr64Ni36 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).

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

    SciTech Connect

    Mauro, N. A.; Vogt, A. J.; Derendorf, K. S.; Johnson, M. L.; Rustan, G. E.; Quirinale, D. G.; Kreyssig, A.; Lokshin, K. A.; Neuefeind, J. C.; An, Ke; Wang, Xun-Li; Goldman, A. I.; Egami, T.; Kelton, K. F.

    2016-01-01

    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. But, 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%. Furthermore, to demonstrate the capabilities of the facility for elastic scattering studies of liquids, a high quality total structure factor for Zr64Ni36 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).

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

    PubMed

    Mauro, N A; Vogt, A J; Derendorf, K S; Johnson, M L; Rustan, G E; Quirinale, D G; Kreyssig, A; Lokshin, K A; Neuefeind, J C; An, Ke; Wang, Xun-Li; Goldman, A I; Egami, T; Kelton, K F

    2016-01-01

    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 Zr64Ni36 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). PMID:26827330

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

    NASA Astrophysics Data System (ADS)

    Mauro, N. A.; Vogt, A. J.; Derendorf, K. S.; Johnson, M. L.; Rustan, G. E.; Quirinale, D. G.; Kreyssig, A.; Lokshin, K. A.; Neuefeind, J. C.; An, Ke; Wang, Xun-Li; Goldman, A. I.; Egami, T.; Kelton, K. F.

    2016-01-01

    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 Zr64Ni36 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).

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

    DOE PAGES

    Mauro, N. A.; Vogt, A. J.; Derendorf, K. S.; Johnson, M. L.; Rustan, G. E.; Quirinale, D. G.; Kreyssig, A.; Lokshin, K. A.; Neuefeind, J. C.; An, Ke; et al

    2016-01-01

    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. But, 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 elasticmore » 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%. Furthermore, to demonstrate the capabilities of the facility for elastic scattering studies of liquids, a high quality total structure factor for Zr64Ni36 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).« less

  13. Microscopic structure factor of liquid hydrogen by neutron-diffraction measurements

    SciTech Connect

    Celli, M.; Bafile, U.; Zoppi, M.; Cuello, G.J.; Formisano, F.; Magli, R.; Neumann, M.

    2005-01-01

    The center-of-mass structure factor of liquid para hydrogen has been measured, using neutron diffraction, in four thermodynamic states close to the triple point. Path integral Monte Carlo simulations have been carried out at the same temperatures and densities. The present experimental data are in reasonable quantitative agreement with the simulations and closer to these results than previous neutron determinations available in the literature. The thermodynamic derivatives of the structure factor, from both experiment and simulation, have been compared to previous measurements obtaining a quantitative consistency.

  14. On the reliability of neutron diffraction for residual stress measurement in cold-drawn steels

    NASA Astrophysics Data System (ADS)

    Ruiz-Hervias, J.; Mompean, F.; Hofmann, M.; Atienza, J. M.

    2011-10-01

    Residual strains were measured in the ferrite phase of pearlitic steel rods along the radial, axial and hoop directions. Two samples with different initial diameters were subjected to one drawing pass (using same drawing parameters) with 20% section reduction and measured in two different neutron diffraction instruments. The results show that the residual strain state is very similar in both cases, regardless of the diameter of the initial rod. This means that the final residual strain-stress state is unique and it is related to the cold-drawing process parameters. In addition, the results show the reliability of strain scanning with different neutron instruments and experimental conditions.

  15. MnO spin-wave dispersion curves from neutron powder diffraction

    SciTech Connect

    Goodwin, Andrew L.; Dove, Martin T.; Tucker, Matthew G.; Keen, David A.

    2007-02-15

    We describe a model-independent approach for the extraction of spin-wave dispersion curves from powder neutron total scattering data. Our approach is based on a statistical analysis of real-space spin configurations to calculate spin-dynamical quantities. The RMCPROFILE implementation of the reverse Monte Carlo refinement process is used to generate a large ensemble of supercell spin configurations from MnO powder diffraction data collected at 100 K. Our analysis of these configurations gives spin-wave dispersion curves for MnO that agree well with those determined independently using neutron triple-axis spectroscopic techniques.

  16. Ionization Chamber for Prompt Fission Neutron Investigations

    NASA Astrophysics Data System (ADS)

    Zeynalov, Sh.; Zeynalova, O.; Hambsch, F.-J.; Sedyshev, P.; Shvetsov, V.

    In this work we report recent achievements in design of twin back-to-back ionization chamber (TIC) for fission fragment (FF) mass and kinetic energy measurement. Correlated FF kinetic energies, their masses and the angle of FF in respect to the axes in 3D Cartesian coordinates can be determined from analysis of the heights and shapes of the pulses induced by the fission fragments on the anodes of TIC. Anodes of TIC were designed as consisting of isolated strips each having independent electronic circuitry and special multi-channel pulse processing apparatus. Mathematical formulae provided for FF angles measured in respect to the coordinate axes. It was shown how the point of fission fragments origin on the target plane may be determined using the same measured data. The last feature made the TIC a rather powerful tool for prompt fission neutron (PFN) emission investigation in event-by-event analysis of individual fission reactions from non- point fissile source. Position sensitive neutron induced fission detector for neutron-imaging applications with both thermal and low energy neutrons was found as another possible implementation of the designed TIC.

  17. Spinel materials for Li-ion batteries: new insights obtained by operando neutron and synchrotron X-ray diffraction.

    PubMed

    Bianchini, Matteo; Fauth, François; Suard, Emmanuelle; Leriche, Jean Bernard; Masquelier, Christian; Croguennec, Laurence

    2015-12-01

    In the last few decades Li-ion batteries changed the way we store energy, becoming a key element of our everyday life. Their continuous improvement is tightly bound to the understanding of lithium (de)intercalation phenomena in electrode materials. Here we address the use of operando diffraction techniques to understand these mechanisms. We focus on powerful probes such as neutrons and synchrotron X-ray radiation, which have become increasingly familiar to the electrochemical community. After discussing the general benefits (and drawbacks) of these characterization techniques and the work of customization required to adapt standard electrochemical cells to an operando diffraction experiment, we highlight several very recent results. We concentrate on important electrode materials such as the spinels Li1 + xMn2 - xO4 (0 ≤ x ≤ 0.10) and LiNi0.4Mn1.6O4. Thorough investigations led by operando neutron powder diffraction demonstrated that neutrons are highly sensitive to structural parameters that cannot be captured by other means (for example, atomic Debye-Waller factors and lithium site occupancy). Synchrotron radiation X-ray powder diffraction reveals how LiMn2O4 is subject to irreversibility upon the first electrochemical cycle, resulting in severe Bragg peak broadening. Even more interestingly, we show for the first time an ordering scheme of the elusive composition Li0.5Mn2O4, through the coexistence of Mn(3+):Mn(4+) 1:3 cation ordering and lithium/vacancy ordering. More accurately written as Li0.5Mn(3+)0.5Mn(4+)1.5O4, this intermediate phase loses the Fd\\overline 3m symmetry, to be correctly described in the P213 space group.

  18. Heterogeneous Catalysis under pressure - In-situ neutron diffraction under industrial conditions

    NASA Astrophysics Data System (ADS)

    Kandemir, Timur; Girgsdies, Frank; Kasatkin, Igor; Kunkes, Edward; Liss, Klaus-Dieter; Peterson, Vanessa K.; Schlögl, Robert; Behrens, Malte

    2012-02-01

    The present work describes the application of a tubular reactor that allows in-situ neutron diffraction on working catalysts at high pressures. The designed reactor enables the application to a sample of industrially-relevant reaction conditions, i.e., in a temperature range up to 330° C and 60 bar pressure, coupled with online gas-analysis. Application of the cell is demonstrated by ammonia synthesis over a commercial catalyst with diffraction data obtained from the high-resolution powder diffractometer, Echidna, at the Australian Nuclear Science and Technology Organisation, ANSTO.

  19. Neutron diffraction in a model itinerant metal near aquantum critical point

    SciTech Connect

    Sokolov, D A; Aronson, Meigan C.; Erwin, R; Lynn, J. W.; Lumsden, Mark D; Nagler, Stephen E

    2009-01-01

    Neutron diffraction measurements on single crystals of Cr1−xVx (x=0, 0.02, 0.037) show that the ordering moment and the Neel temperature are continuously suppressed as x approaches 0.037, a proposed Quantum Critical Point (QCP). The wave vector Q of the spin density wave (SDW) becomes more incommensurate as x increases in accordance with the two band model. At xC=0.037 we have found temperature dependent, resolution limited elastic scattering at 4 incommensurate wave vectors Q=(1 1,2, 0, 0)*2/a, which correspond to 2 SDWs with Neel temperatures of 19 K and 300 K. Our neutron diffraction measurements indicate that the electronic structure of Cr is robust, and that tuning Cr to its QCP results not in the suppression of antiferromagnetism, but instead enables new spin ordering due to novel nesting of the Fermi surface of Cr.

  20. Neutron-diffraction study of the magnetic structure of PrCoAl 4

    NASA Astrophysics Data System (ADS)

    Schobinger-Papamantellos, P.; Wilkinson, C.; Tung, L. D.; Buschow, K. H. J.; McIntyre, G. J.

    2004-12-01

    The magnetic structure of PrCoAl4 has been studied by neutron diffraction from a single crystal. The Pr moments order at a temperature near to 20 K with a sine-wave longitudinal amplitude-modulated structure. The length of the wave vector q = (0 0qz) is almost temperature independent with qz = 0.4087 (5) , and only the first harmonic was observed down to 2 K. The amplitude of the wave, 2.05(3) μB/Pr atom at 2 K, is reduced compared to the Pr3+ free-ion moment value g JμB = 3.2μB , due to strong crystal-field effects. One difference between the present and previously reported neutron powder-diffraction results concerns the wave vector length. The reason for this may lie in the different magnetic microstructure (stacking faults) of the material depending on the thermochemical history of each sample.

  1. α-Phase transformation kinetics of U - 8 wt% Mo established by in situ neutron diffraction

    NASA Astrophysics Data System (ADS)

    Steiner, M. A.; Calhoun, C. A.; Klein, R. W.; An, K.; Garlea, E.; Agnew, S. R.

    2016-08-01

    The α-phase transformation kinetics of as-cast U - 8 wt% Mo below the eutectoid temperature have been established by in situ neutron diffraction. α-phase weight fraction data acquired through Rietveld refinement at five different isothermal hold temperatures can be modeled accurately utilizing a simple Johnson-Mehl-Avrami-Kolmogorov impingement-based theory, and the results are validated by a corresponding evolution in the γ-phase lattice parameter during transformation that follows Vegard's law. Neutron diffraction data is used to produce a detailed Time-Temperature-Transformation diagram that improves upon inconsistencies in the current literature, exhibiting a minimum transformation start time of 40 min at temperatures between 500 °C and 510 °C. The transformation kinetics of U - 8 wt% Mo can vary significantly from as-cast conditions after extensive heat treatments, due to homogenization of the typical dendritic microstructure which possesses non-negligible solute segregation.

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

    SciTech Connect

    Druschitz, Alan; Aristizabal, Ricardo; Druschitz, Edward; Hubbard, Camden R; Watkins, Thomas R; Walker, Larry R; Ostrander, M

    2012-01-01

    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 paper reports the microstructures and phases present in these alloys. Further, lattice strains and diffraction elastic constants in various crystallographic directions and the transformation characteristics of the austenite as a function of applied stress were determined using in-situ loading with neutron diffraction at the second generation Neutron Residual Stress Facility (NRSF2) at the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL).

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

    SciTech Connect

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

    1996-04-01

    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.

  4. Bauschinger Effect in an Austenitic Steel: Neutron Diffraction and a Multiscale Approach

    NASA Astrophysics Data System (ADS)

    Fajoui, Jamal; Gloaguen, David; Legrand, Vincent; Oum, Guy; Kelleher, Joe; Kockelmann, Winfried

    2016-05-01

    The generation of internal stresses/strains arising from mechanical deformations in single-phase engineering materials was studied. Neutron diffraction measurements were performed to study the evolution of intergranular strains in austenitic steel during sequential loadings. Intergranular strains expand due to incompatibilities between grains and also resulting from single-crystal elastic and plastic anisotropy. A two-level homogenization approach was adopted in order to predict the mechanical state of deformed polycrystals in relation to the microstructure during Bauschinger tests. A mechanical description of the grain was developed through a micro-meso transition based on the Kröner model. The meso-macro transition using a self-consistent approach was applied to deduce the global behavior. Mechanical tests and neutron diffraction measurements were used to validate and assess the model.

  5. Crystallisation behaviour of bulk metallic glasses by in-situ neutron diffraction

    NASA Astrophysics Data System (ADS)

    Soubeyroux, J. L.; Claret, N.

    Crystallisation behaviour of some bulk metallic glasses has been studied by neutron diffraction and by differential scanning calorimetry (DSC) performed at the same heating rate. The alloys Zr51Ti2.5Al11.5Cu22Ni13 (F35) and Zr41.25Ti13.75Cu8Ni14.5Be22.5 (Vit1*) present a first crystallisation corresponding to the first peak in the DSC experiments, this first phase being different in each system and corresponding to intermediate phases. The Pd43Cu27Ni10P20 alloy crystallises by forming, in a very narrow interval of temperature, binary and ternary phosphides, all stable up to the melting temperature. The combination of in-situ neutron-diffraction and DSC experiments has proved to be a powerful technique to study the crystallisation of bulk metallic glasses.

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

    NASA Technical Reports Server (NTRS)

    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.

  7. The temperature dependent structure of liquid 1-propanol as studied by neutron diffraction and EPSR simulations

    NASA Astrophysics Data System (ADS)

    Sillrén, Per; Swenson, Jan; Mattsson, Johan; Bowron, Daniel; Matic, Aleksandar

    2013-06-01

    The structure of liquid 1-propanol is investigated as a function of temperature using neutron diffraction together with Empirical Potential Structure Refinement modelling. The combined diffraction and computer modelling analysis demonstrates that propanol molecules form hydrogen bonded clusters with a relatively wide size distribution, which broadens at lower temperatures. We find that the cluster size distribution is well described by a recently proposed statistical model for branched H-bonded networks [P. Sillrén, J. Bielecki, J. Mattsson, L. Börjesson, and A. Matic, J. Chem. Phys. 136, 094514 (2012)], 10.1063/1.3690137. The average cluster size increases from ˜3 to 7 molecules, whilst the standard deviation of the size distribution increases from 3.3 to 8.5 as the temperature is decreased from 293 to 155 K. The clusters are slightly branched, with a higher degree of branching towards lower temperatures. An analysis of the cluster gyration tensor (Rmn) reveals an average elongated ellipsoidal shape with axes having proportions 1:1.4:1.9. We find that the average radius of gyration has a cluster size dependence consistent with that of fractal clusters, Rg ∝ n1/D, with a fractal dimension D ≈ 2.20, which is close to D = 2.00 expected for an ideal random walk or D = 2.11 expected for reaction limited aggregation. The characteristic angles between the H-bonded OH-groups that constitute the clusters show only a weak temperature dependence with O-H⋯O angles becoming more narrowly distributed around 180° at lower temperatures.

  8. Revealing cyclic hardening mechanism of a TRIP steel by real-time in situ neutron diffraction

    SciTech Connect

    Yu, Dunji; An, Ke; Chen, Yan; Chen, Xu

    2014-01-01

    Real-time in situ neutron diffraction was performed on a transformation-induced plasticity (TRIP) steel under cyclic loading at room temperature. By Rietveld refinement and single peak analysis, the volume fraction and average stress estimates as well as dislocation density of individual phases (austenite and martensite phase) were derived. The results reveal that the volume fraction of martensite phase, instead of individual phase strengthening, should be accounted for the remarkable secondary cyclic hardening.

  9. Monte-Carlo sorption and neutron diffraction study of the filling isotherm in clathrate hydrates

    SciTech Connect

    Klapproth, Alice; Kuhs, Werner F.; Chazallon, Bertrand

    1999-06-15

    We are interested in the thermodynamics of the gas filling of clathrate hydrates. In order to determine the pressure-dependent filling of the cages, neutron powder diffraction experiments on N{sub 2} and CO{sub 2} clathrates were performed. Interaction potentials were refined by comparing the experimentally determined fillings with those generated by MC-sorption calculations. Unsatisfactory agreement between experiment and simulation is observed when using the widely employed SPC water-water interaction potential.

  10. Texture analysis of bulk YBa sub 2 Cu sub 3 O sub x by neutron diffraction

    SciTech Connect

    Kallend, J.S. ); Biondo, A.C.; Schultz, A.J.; Goretta, K.C. )

    1990-09-01

    Neutron diffraction has been used to generate Orientation Distribution Functions for two sinter-forged YBa{sub 2}Cu{sub 3}O{sub x} specimens. Sinter forging imparted a strong texture, with c axes of crystals preferentially aligned parallel to the forging direction. The distribution of a and b axes was not uniform, which may have implications to critical current density. 14 refs., 6 figs.

  11. Neutron diffraction analysis of residual stresses near unannealed welds in anhydrous ammonia nurse tanks.

    PubMed

    Becker, A T; Chumbley, L S; Goettee, D; Russell, A M

    2014-01-01

    Neutron diffraction analysis was employed to measure residual stresses near welds in used anhydrous ammonia nurse tanks. Tensile residual stresses contribute to stress corrosion cracking of nurse tanks, which can cause tanks to release toxic ammonia vapor. The analysis showed that tensile residual stresses were present in the tanks measured, and the magnitudes of these stresses approached the yield strength of the steel. Implications for agricultural safety and health are discussed.

  12. Investigation of hydrogen bonded molecular solids by diffraction, spectroscopy, and computational chemistry

    NASA Astrophysics Data System (ADS)

    Hudson, Matthew R.

    The nature of hydrogen-bonding interactions in the solid state is examined through the investigation of molecular crystals by incoherent inelastic neutron scattering (INS) spectroscopy, Raman spectroscopy, X-ray and neutron diffraction, and computational chemistry. The molecular solids studied range from small organic molecules to larger inorganic acid salts. Hydrogen bonding is the primary mode of interaction in the solid state for each of the systems studied. INS spectra were collected at 25 K for each molecular solid and the motions of the hydrogen atoms assigned. Raman spectra were collected at 78 and 298 K to aid in the molecular mode assignments of the INS spectra and to examine possible phase changes as a function of temperature. Neutron diffraction was employed, when possible, to accurately locate the hydrogen atom positions, and X-ray diffraction was performed to obtain accurate unit cell dimensions and to obtain initial characterizations of the samples. The diffraction structures served as the basis for solid-state density functional theory (DFT) calculations. DFT simulations were used to aid in the vibrational normal mode assignments, to investigate possible solid-phase transitions, and as a test of the limits of basis sets and the available DFT theory. Of the six molecular solids studied, several important observations were made: (1) the determination of a structural phase transition in L-alanine alaninium nitrate by both spectroscopic and theoretical methods, (2) the structure of picolinic acid was elucidated at 25 K and room-temperature by the combination of INS and theory, (3) glycine lithium sulfate was found to be a useful test of DFT to accurately optimize the structure and calculate the normal modes of a complex 3D network of hydrogen-bonding interactions, (4) nicotinic acid was found to be a useful test of one dimensional hydrogen-bonding interactions with pi-stacking interactions dominating the orthogonal directions, and (5) parabanic acid

  13. Neutron and X-ray powder diffraction study of skutterudite thermoelectrics

    DOE PAGES

    Wang, H.; Kirkham, M. J.; Watkins, T. R.; Payzant, E. A.; Salvador, J. R.; Thompson, A. J.; Sharp, J.; Brown, D.; Miller, D.

    2016-02-17

    N- and p-type filled-skutterudite materials prepared for thermoelectric power generation modules were analyzed by neutron diffraction at the POWGEN beam line of the Spallation Neutron Source (SNS) and X-ray diffraction (XRD). The skutterudite powders were processed by melt spinning, followed by ball milling and annealing. The n-type material consists of Ba–Yb–Co–Sb and the p-type material consists of Di–Fe–Ni–Sb or Di–Fe–Co–Sb (Di = didymium, an alloy of Pr and Nd). Powders for prototype module fabrication from General Motors and Marlow Industries were analyzed in this study. XRD and neutron diffraction studies confirm that both the n- and p-type materials have cubicmore » symmetry. Structural Rietveld refinements determined the lattice parameters and atomic parameters of the framework and filler atoms. The cage filling fraction was found to depend linearly on the lattice parameter, which in turn depends on the average framework atom size. Ultimately, this knowledge may allow the filling fraction of these skutterudite materials to be purposefully adjusted, thereby tuning the thermoelectric properties.« less

  14. Verification of residual stresses in flash-butt-weld rails using neutron diffraction

    NASA Astrophysics Data System (ADS)

    Tawfik, David; Kirstein, Oliver; Mutton, Peter John; Chiu, Wing Kong

    2006-11-01

    Residual stresses developed during flash-butt welding may play a crucial role in prolonging the fatigue life of the welded tracks under service loading conditions. The finished welds typically exhibit high levels of tensile residual stresses in the web region of the weld. Moreover, the surface condition of the web may contain shear drag or other defects resulting from the shearing process which may lead to the initiation and propagation of fatigue cracks in a horizontal split web failure mode under high axle loads. However, a comprehensive understanding into the residual stress behaviour throughout the complex weld geometry remains unclear and is considered necessary to establish the correct localised post-weld heat treatment modifications intended to lower tensile residual stresses. This investigation used the neutron diffraction technique to analyse residual stresses in an AS60 flash-butt-welded rail cooled under normal operating conditions. The findings will ultimately contribute to developing modifications to the flash-butt-welding procedure to lower tensile residual stresses which may then improve rail performance under high axle load.

  15. Neutron diffraction measurements of residual strains in tungsten fiber-reinforced Kanthal composites

    SciTech Connect

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

    1996-04-15

    FeAl and FeCrAl alloys containing small quantities of Y, such as Kanthal, have been shown to exhibit outstanding high-temperature oxidation/corrosion resistance and therefore have great potential for use as corrosion-resistant cladding in a variety of high-temperature structural applications. Recently, several such FeAl alloys have been developed with improved mechanical behavior and weldability. In order to further enhance strength, tungsten fiber-reinforced Kanthal metal matrix composites have been developed for possible applications in space structures. However, thermal residual stresses are developed as a result of the mismatch of the coefficients of thermal expansion between those of the tungsten fibers and the Kanthal matrix during post-fabrication cooldown. These stresses can lead to matrix cracking, thereby deteriorating the aggregate mechanical properties of the composites. To develop composites with reliable and enhanced properties, it is necessary to understand the nature and the magnitude of these residual stresses. High-resolution neutron powder diffraction was used in this study to investigate the residual strains and stresses at room temperature in W/Kanthal composites containing different volume fractions of tungsten fibers.

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

    SciTech Connect

    Xu, Hongwu; Zhao, Yusheng; Vogel, Sven C; Hickmott, Donald D; Daemen, Luke L; Hartl, Monika A

    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.

  17. Neutron diffraction and the electronic properties of BaFe2Se3

    NASA Astrophysics Data System (ADS)

    Lovesey, S. W.; Khalyavin, D. D.; van der Laan, G.

    2016-01-01

    It is argued on the basis of previously published experimental data that, the magnetic space-group Cac (#9.41) is the correct description of magnetically ordered BaFe2Se3. The corresponding crystal class m1‧ allows axial and polar dipoles and forbids bulk ferromagnetism. Magneto-electric multipoles that are both time-odd and parity-odd are allowed, e.g., a magnetic charge (monopole) and an anapole (magnetic toroidal dipole). The experimental observation of magneto-electric multipoles must shed light on valence electrons involved in bonding, including charge transfer using 3d(Fe) and p-states of ligand ions. We provide the appropriate structure factors for the Bragg diffraction neutrons, together with estimates of atomic form factors. Structure factors for resonant x-ray Bragg diffraction are also considered, because the analysis of successful experiments will yield complementary information about electronic properties. Magneto-electric multipoles, over and above those that contribute to magnetic neutron diffraction, include the magnetic monopole. A time-odd, parity-even monopole created from the magnetic dipole and an electric toroidal dipole, which is a manifestation of a structural rotation, is allowed in BaFe2Se3 but it is not visible in diffraction, nor is the corresponding dipole.

  18. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: Neutron Diffraction Measurements of a Thermally Fatigued Single Crystal Superalloy

    NASA Astrophysics Data System (ADS)

    Sun, Guang-Ai; Chen, Bo; Wu, Er-Dong; Li, Jin-Chao; Pirling, T.; Hughes, D.

    2009-08-01

    The thermally fatigued single crystal superalloy DZ125L is investigated by neutron diffraction measurements. The measurements, made using the phi angle oscillating method, provide more detailed and reliable data than those with the phi angle fixed. Diffraction studies show that the influence of thermal fatigue on the lattice parameters of the alloy is very limited. The stress analysis reveals that triaxial elastic hydrostatic stress plays a major role during thermal fatigue. The magnitude of the macrostress increases with the fatigue cycles, with the stress of the γ phase increasing more significantly than that of the γ' phase, and becoming fragile after many cycles. The changes in the microstrain are dependent on the reflection planes. The microstrains at the center of the sample are released by the thermal fatigue in comparison with those at the outlying locations, which has been attributed to the advance of the dislocation slips.

  19. X-ray Laue micro diffraction and neutron diffraction analysis of residual elastic strains and plastic deformation in a 1% uniaxial tensile tested nickel alloy 600 sample

    SciTech Connect

    Chao, Jing; Mark, Alison; Fuller, Marina; Barabash, Rozaliya; McIntyre, Stewart; Holt, Richard A.; Klassen, Robert; Liu, W.

    2009-01-01

    The magnitude and distribution of elastic strain for a nickel alloy 600 (A600) sample that had been subjected to uniaxial tensile stress were measured by micro Laue diffraction (MLD) and neutron diffraction techniques. For a sample that had been dimensionally strained by 1%, both MLD and neutron diffraction data indicated that the global residual elastic strain was on the order of 10{sup -4}, however the micro-diffraction data indicated considerable grain-to-grain variability amongst individual components of the residual strain tensor. A more precise comparison was done by finding those grains in the MLD map that had appropriate oriented in the specific directions matching those used in the neutron measurements and the strains were found to agree within the uncertainty. Large variations in strain values across the grains were noted during the MLD measurements which are reflected in the uncertainties. This is a possible explanation for the large uncertainty in the average strains measured from multiple grains during neutron diffraction.

  20. Advanced sample environments for in situ neutron diffraction studies of nuclear materials

    NASA Astrophysics Data System (ADS)

    Reiche, Helmut Matthias

    Generation IV nuclear reactor concepts, such as the supercritical-water-cooled nuclear reactor (SCWR), are actively researched internationally. Operating conditions above the critical point of water (374°C, 22.1 MPa) and fuel core temperature that potentially exceed 1850°C put a high demand on the surrounding materials. For their safe application, it is essential to characterize and understand the material properties on an atomic scale such as crystal structure and grain orientation (texture) changes as a function of temperature and stress. This permits the refinement of models predicting the macroscopic behavior of the material. Neutron diffraction is a powerful tool in characterizing such crystallographic properties due to their deep penetration depth into condensed matter. This leads to the ability to study bulk material properties, as opposed to surface effects, and allows for complex sample environments to study e.g. the individual contributions of thermo-mechanical processing steps during manufacturing, operating or accident scenarios. I present three sample environments for in situ neutron diffraction studies that provide such crystallographic information and have been successfully commissioned and integrated into the user program of the High Pressure -- Preferred Orientation (HIPPO) diffractometer at the Los Alamos Neutron Science Center (LANSCE) user facility. I adapted a sample changer for reliable and fast automated texture measurements of multiple specimens. I built a creep furnace combining a 2700 N load frame with a resistive vanadium furnace, capable of temperatures up to 1000°C, and manipulated by a pair of synchronized rotation stages. This combination allows following deformation and temperature dependent texture and strain evolutions in situ. Utilizing the presented sample changer and creep furnace we studied pressure tubes made of Zr-2.5wt%Nb currently employed in CANDURTM nuclear reactors and proposed for future SCWRs, acting as the primary

  1. First principles calculations, neutron, and x-ray diffraction investigation of Y{sub 3}Ni{sub 13}B{sub 2}, Y{sub 3}Co{sub 13}B{sub 2}, and Y{sub 3}Ni{sub 10}Co{sub 3}B{sub 2}

    SciTech Connect

    Plugaru, N.; Valeanu, M.; Plugaru, R.; Campo, J.

    2014-01-14

    Fully relativistic calculations within the local spin density approximation and the generalized gradient approximation were performed to determine the local spin and orbital magnetic moments, as well as the magnetocrystalline anisotropy energy of Y{sub 3}Ni{sub 13}B{sub 2}, Y{sub 3}Co{sub 13}B{sub 2}, and Y{sub 3}Ni{sub 10}Co{sub 3}B{sub 2} compounds. A weak in-plane magnetic anisotropy is determined for Y{sub 3}Ni{sub 13}B{sub 2}, under the assumption of a crystallographic-like magnetic unit cell and collinear magnetic moments. The calculations predict considerable c-axis anisotropy for Y{sub 3}Co{sub 13}B{sub 2} and Y{sub 3}Ni{sub 10}Co{sub 3}B{sub 2}, but smaller than that of YCo{sub 5}. The values of the magnetocrystalline anisotropy energy correlate well with both the magnitude of the orbital magnetic moment and the orbital magnetic moment anisotropy. The mixing between Co or Ni 3d states and B 2p states, observable at the bottom of the valence band of the 3d metal having a boron atom nearest neighbor, decreases the 3d spin and especially, the 3d orbital magnetic moments. Y{sub 3}Ni{sub 13}B{sub 2} and Y{sub 3}Ni{sub 10}Co{sub 3}B{sub 2} were also investigated by powder neutron diffraction experiments, at temperatures between 1.8 and 249 K. The Co and Ni site averaged magnetic moments calculated in the mixed compound are in fair agreement with the values obtained by the refinement of the magnetic contribution to the diffraction pattern.

  2. Neutron scatter and diffraction techniques applied to nucleosome and chromatin structure.

    PubMed

    Bradbury, E M; Baldwin, J P

    1986-12-01

    Neutron scatter and diffraction techniques have made substantial contributions to our understanding of the structure of the nucleosome, the structure of the 10-nm filament, the "10-nm----30-nm" filament transition, and the structure of the "34-nm" supercoil or solenoid of nucleosomes. Neutron techniques are unique in their properties, which allows for the separation of the spatial arrangements of histones and DNA in nucleosomes and chromatin. They have equally powerful applications in structural studies of any complex two-component biological system. A major success for the application of neutron techniques was the first clear proof that DNA was located on the outside of the histone octamer in the core particle. A full analysis of the neutron-scatter data gave the parameters of Table 3 and the low-resolution structure of the core particle in solution shown in Fig. 6. Initial low-resolution X-ray diffraction studies of core particle crystals gave a model with a lower DNA pitch of 2.7 nm. Higher-resolution X-ray diffraction studies now give a structure with a DNA pitch of 3.0 nm and a hole of 0.8 nm along the axis of the DNA supercoil. The neutron-scatter solution structure and the X-ray crystal structure of the core particle are thus in full agreement within the resolution of the neutron-scatter techniques. The model for the chromatosome is largely based on the structural parameters of the DNA supercoil in the core particle, nuclease digestion results showing protection of a 168-bp DNA length by histone H1 and H1 peptide, and the conformational properties of H1. The path of the DNA outside the chromatosome is not known, and this information is crucial for our understanding of higher chromatin structure. The interactions of the flexible basic and N- and C-terminal regions of H1 within chromatin and how these interactions are modulated by H1 phosphorylation are not known. The N- and C-terminal regions of H1 represent a new type of protein behavior, i.e., extensive

  3. Crystallization and preliminary neutron diffraction experiment of human farnesyl pyrophosphate synthase complexed with risedronate.

    PubMed

    Yokoyama, Takeshi; Ostermann, Andreas; Mizuguchi, Mineyuki; Niimura, Nobuo; Schrader, Tobias E; Tanaka, Ichiro

    2014-04-01

    Nitrogen-containing bisphosphonates (N-BPs), such as risedronate and zoledronate, are currently used as a clinical drug for bone-resorption diseases and are potent inhibitors of farnesyl pyrophosphate synthase (FPPS). X-ray crystallographic analyses of FPPS with N-BPs have revealed that N-BPs bind to FPPS with three magnesium ions and several water molecules. To understand the structural characteristics of N-BPs bound to FPPS, including H atoms and hydration by water, neutron diffraction studies were initiated using BIODIFF at the Heinz Maier-Leibnitz Zentrum (MLZ). FPPS-risedronate complex crystals of approximate dimensions 2.8 × 2.5 × 1.5 mm (∼3.5 mm(3)) were obtained by repeated macro-seeding. Monochromatic neutron diffraction data were collected to 2.4 Å resolution with 98.4% overall completeness. Here, the first successful neutron data collection from FPPS in complex with N-BPs is reported.

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

    PubMed

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  6. Neutron and X-ray diffraction of plasma-sprayed zirconia-yttria thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Shankar, N. R.; Herman, H.; Singhal, S. P.; Berndt, C. C.

    1984-01-01

    ZrO2-7.8mol. pct. YO1.5, a fused powder, and ZrO2-8.7mol. pct. YO1.5, a prereacted powder, were plasma-sprayed onto steel substrates. Neutron diffraction and X-ray diffraction of the as-received powder, the powder plasma sprayed into water, as-sprayed coatings, and coatings heat-treated for 10 and 100 h were carried out to study phase transformations and ordering of the oxygen ions on the oxygen sublattice. The as-received fused powder has a much lower monoclinic percentage than does the pre-reacted powder, this resulting in a much lower monoclinic percentage in the coating. Heat treatment increases the percentages of the cubic and monoclinic phases, while decreasing the tetragonal content. An ordered tetragonal phase is detected by the presence of extra neutron diffraction peaks. These phase transformations and ordering will result in volume changes. The implications of these transformations on the performance of partially stabilized zirconia thermal barrier coatings is discussed.

  7. On the magnetic structure of Er3Co: single-crystal neutron diffraction study

    SciTech Connect

    Gubkin, Andrey; Podlesnyak, Andrey A; Baranov, Nikolai

    2010-01-01

    The effect of the magnetic field applied along the main crystallographic directions on the magnetic structure of Er{sub 3}Co has been studied by means of single-crystal neutron diffraction technique. At zero field the compound exhibits a noncoplanar commensurate magnetic structure with ferromagnetic alignment of the Er magnetic-moment projections along the b axis in an orthorhombic unit cell. The present measurements revealed that the application of the magnetic field along the c direction [c {perpendicular} (ab)] leads to the pronounced metamagneticlike transition in the low-field region {mu}{sub 0}H < 1.2 T, although, the magnetization curve does not exhibit any anomalies. Combining the present single-crystal diffraction and magnetization data with the results of the previous powder neutron diffraction study [Gignoux et al., Solid State Commun. 8, 391 (1970)], we conclude that the nature of the magnetic ion, whether Kramers or non-Kramers, has a decisive effect on the commensurability of the magnetic structure of R{sub 3}Co. In particular, the commensurate magnetic structure observed in Er{sub 3}Co originate from the Kramers character of Er{sup 3+} ion in contrast to the incommensurate structures found earlier in R{sub 3}Co with R = Tb and Ho.

  8. Structural factors that enhance lithium mobility in fast-ion Li(1+x)Ti(2-x)Al(x)(PO4)3 (0 ≤ x ≤ 0.4) conductors investigated by neutron diffraction in the temperature range 100-500 K.

    PubMed

    Arbi, K; Hoelzel, M; Kuhn, A; García-Alvarado, F; Sanz, J

    2013-08-19

    Structural features responsible for lithium conductivity in Li(1+x)Ti(2-x)Al(x)(PO4)3 (x = 0, 0.2, and 0.4) samples have been investigated by Rietveld analysis of high-resolution neutron diffraction (ND) patterns. From structural analysis, variation of the Li site occupancies and atomic thermal factors have been deduced as a function of aluminum doping in the temperature range 100-500 K. Fourier map differences deduced from ND patterns revealed that Li ions occupy M1 sites and, to a lower extent, M3 sites, disposed around ternary axes. The occupation of M1 sites by Li ions is responsible for the preferential expansion of the rhombohedral R3c unit cell along the c axis with temperature. The occupation of less symmetric M3 sites decreases electrostatic repulsions among Li cations, favoring ion conductivity in Li(1+x)Ti(2-x)Al(x)(PO4)3 compounds. The variations detected on long-range lithium motions have been related to variations of the oxygen thermal factors with temperature. The information deduced by ND explains two lithium motion regimes deduced previously by (7)Li NMR and impedance spectroscopy. PMID:23898863

  9. Numerical investigation of diffraction of acoustic waves by phononic crystals

    NASA Astrophysics Data System (ADS)

    Moiseyenko, Rayisa P.; Declercq, Nico F.; Laude, Vincent

    2012-05-01

    Diffraction as well as transmission of acoustic waves by two-dimensional phononic crystals (PCs) composed of steel rods in water are investigated in this paper. The finite element simulations were performed in order to compute pressure fields generated by a line source that are incident on a finite size PC. Such field maps are analyzed based on the complex band structure for the infinite periodic PC. Finite size computations indicate that the exponential decrease of the transmission at deaf frequencies is much stronger than that in Bragg band gaps.

  10. Neutron diffraction study of a nitrogen martensitic steel 0Kh16N4AB under load

    NASA Astrophysics Data System (ADS)

    Sumin, V. V.; Papushkin, I. V.; Bannykh, O. A.; Blinov, V. M.; Lukáš, P.

    2008-01-01

    An austenitic-martensitic nitrogen steel 0Kh16N4AB has been studied under load using high-resolution neutron diffraction analysis on an FSD neutron diffractometer at an IBR-2 reactor (Dubna) and on a diffractometer with a focusing monochromator on a reactor of the Nuclear Physics Institute (Czech Republic). Young's moduli calculated from different reflections of the martensite and austenite phases have been obtained. It has been found that the yield strength σ0.2 corresponding to the slip plane (111) of the austenite phase is anomalously low and that with increasing degree of uniaxial tension the width of lines (111)γ strongly grows. In the steel under consideration the plane (111) of the austenite phase appears to be an easy-slip plane that ensures the enhanced properties of the steel, i.e., the combination of a high ultimate strength (1600 MPa) with a high plasticity (δ = 16%).

  11. Asymmetric band flipping for time-of-flight neutron diffraction data

    DOE PAGES

    Whitfield, Pamela S.; Coelho, Alan A.

    2016-08-24

    Charge flipping with powder diffraction data is known to produce a result more reliably with high-resolution data,i.e.visible reflections at smalldspacings. This data are readily accessible with the neutron time-of-flight technique but the assumption that negative scattering density is nonphysical is no longer valid where elements with negative scattering lengths are present. The concept of band flipping was introduced in the literature, where a negative threshold is used in addition to a positive threshold during the flipping. But, it was not tested with experimental data at the time. Finallly, band flipping has been implemented inTOPAStogether with the band modification of low-densitymore » elimination and tested with experimental powder and Laue single-crystal neutron data.« less

  12. Determination of the residual stress tensor in textured zirconium alloy by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Sumin, V. V.; Papushkin, I. V.; Vasin, R. N.; Venter, А. M.; Balagurov, А. М.

    2012-02-01

    Results of neutron diffraction studies of crystallographic texture and residual stress tensor components in cold-worked and annealed cylindrical components made from E-110 zirconium alloy are presented. Those components are used as plugs in the fuel elements of the VVER-type reactors; the resident residual stresses influence the durability and safety of the fuel elements. The experiments were carried out on the neutron diffractometers at Dubna (the IBR-2 pulsed reactor) and Berlin Helmholtz-Zentrum (the BER II research reactor). It is shown that the samples have fiber texture that is changed considerably with annealing. The type I residual stress tensors for both samples were calculated by the BulkPathGEO model. The cold worked component has 136-166 MPa tensile residual stress in the radial direction and zero stress along the axial direction. Residual stress values in the annealed component are close to zero.

  13. Neutron diffraction and reflectivity studies of the Cr Neel transition in Fe/Cr(001) superlatices

    SciTech Connect

    Fullerton, E.E.; Adenwalla, S.; Felcher, G.P.

    1995-12-31

    The effects on the interlayer coupling of the Cr Neel transition is studied in Fe/Cr(001) superlattices. The Neel transition is suppressed for Cr layer thickness < 42 {angstrom}. For > 42{angstrom} of Cr, the Neel temperature TN initially increases rapidly and then asymptotically approaches its bulk value with a three-dimensional transition-temperature shift exponent value of {lambda}=1.4{+-}0.3. Neutron diffraction confirms both the Cr antiferromagnetic order and the existence of the incommensurate, transverse spin density wave whose nesting wavevector is the same as that of bulk Cr. The ordering of the Cr dramatically alters the coupling of the Fe layers. The biquadratic Fe interlayer coupling observed for T>T{sub N} vanishes below T{sub N} as confirmed by polarized neutron reflectivity. The behavior can be understood in terms of finite-size and spin frustration effects at rough Fe-Cr interfaces.

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

    SciTech Connect

    Woo, Wan Chuck; Em, Vyacheslav; Hubbard, Camden R; Lee, Ho-Jin; Park, Kwang Soo

    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.

  15. The magnetic structure of Co(NCNH)₂ as determined by (spin-polarized) neutron diffraction

    SciTech Connect

    Jacobs, Philipp; Houben, Andreas; Senyshyn, Anatoliy; Müller, Paul; Dronskowski, Richard

    2013-06-01

    The magnetic structure of Co(NCNH)₂ has been studied by neutron diffraction data below 10 K using the SPODI and DNS instruments at FRM II, Munich. There is an intensity change in the (1 1 0) and (0 2 0) reflections around 4 K, to be attributed to the onset of a magnetic ordering of the Co²⁺ spins. Four different spin orientations have been evaluated on the basis of Rietveld refinements, comprising antiferromagnetic as well as ferromagnetic ordering along all three crystallographic axes. Both residual values and supplementary susceptibility measurements evidence that only a ferromagnetic ordering with all Co²⁺ spins parallel to the c axis is a suitable description of the low-temperature magnetic ground state of Co(NCNH)₂. The deviation of the magnetic moment derived by the Rietveld refinement from the expectancy value may be explained either by an incomplete saturation of the moment at temperatures slightly below the Curie temperature or by a small Jahn–Teller distortion. - Graphical abstract: The magnetic ground state of Co(NCNH)₂ has been clarified by (spin-polarized) neutron diffraction data at low temperatures. Intensity changes below 4 K arise due to the onset of ferromagnetic ordering of the Co²⁺ spins parallel to the c axis, corroborated by various (magnetic) Rietveld refinements. Highlights: • Powderous Co(NCNH)₂ has been subjected to (spin-polarized) neutron diffraction. • Magnetic susceptibility data of Co(NCNH)₂ have been collected. • Below 4 K, the magnetic moments align ferromagnetically with all Co²⁺ spins parallel to the c axis. • The magnetic susceptibility data yield an effective magnetic moment of 4.68 and a Weiss constant of -13(2) K. • The ferromagnetic Rietveld refinement leads to a magnetic moment of 2.6 which is close to the expectancy value of 3.

  16. Mechanochemical synthesis in the Li-Mg-N-D system under deuterium gas: a neutron diffraction study.

    PubMed

    Li, Z; Zhang, J; Latroche, M; Wang, S; Jiang, L; Du, J; Cuevas, F

    2016-09-14

    The Mg(NH2)2/2LiH mixture is considered as one of the most valuable reversible hydrogen storage systems for feeding PEM fuel cells. In this paper, we investigate the mechanochemical synthesis in the Li-Mg-N-H system under deuterium gas, using Li3N and Mg as reactants, and the structural and sorption properties of the intermediate and final products mainly by means of neutron powder diffraction. Mechanochemistry leads to the end formation of amorphous Mg(ND2)2, which crystallizes upon heating above 425 K. During synthesis, a novel cation-mixed nitride/imide phase of simplified composition Li3MgN2D has been unveiled as the intermediate phase. It crystallizes in the cubic disordered anti-fluorite type structure (S.G. Fm3[combining macron]m) with a lattice parameter of 4.996 Å at room temperature. Deuterium absorption in this compound occurs through an original solid solution type mechanism ending with the imide compound β-Li2MgN2D2. The conjoint use of mechanochemistry under deuterium gas and in situ neutron diffraction techniques offers new avenues for better characterization of the efficient hydrogen storage materials. In particular, this work highlights the unexpected role of intermediate nitride/imide phases in the Li-Mg-N-H system. PMID:27523164

  17. Temperature-dependent neutron diffraction measurements from D2O hydrating single-supported lipid bilayers of DMPC

    NASA Astrophysics Data System (ADS)

    Buck, Z. N.; Torres, J.; Mazza, A.; Kaiser, H.; Taub, H.; Hansen, F. Y.; Miskowiec, A.; Tyagi, M.

    The freezing point depression of water associated with biological membranes, studied principally by NMR, has been of interest for decades. Here we have used neutron diffraction measurements at the University of Missouri Research Reactor (MURR) to investigate the freezing behavior of water associated with single-supported zwitterionic lipid bilayers composed of DMPC. Diffraction patterns obtained as a function of temperature reveal that water freezes abruptly into its hexagonal phase at 270 K with no evidence of amorphous ice. Following the initial crystallization of the membrane-associated water there is a region of continuous hexagonal crystal growth, which is believed to occur in the interfacial water closest to the membrane. The temperature-dependent intensity of the observed Bragg peaks have been compared with that of incoherently elastically-scattered neutrons collected on the High-Flux Backscattering Spectrometer at NIST from an identical sample hydrated with H2O [2]. We find excellent agreement between the two data sets, suggesting the absence of amorphous solid water and that all the water hydrating a DMPC membrane eventually freezes into the hexagonal crystalline phase. 2 M. Bai et al., Europhys. Lett. 98, 48006 (2012). Supported by NSF Grant Nos. DMR-0944772 and DGE-1069091.

  18. Mechanochemical synthesis in the Li-Mg-N-D system under deuterium gas: a neutron diffraction study.

    PubMed

    Li, Z; Zhang, J; Latroche, M; Wang, S; Jiang, L; Du, J; Cuevas, F

    2016-09-14

    The Mg(NH2)2/2LiH mixture is considered as one of the most valuable reversible hydrogen storage systems for feeding PEM fuel cells. In this paper, we investigate the mechanochemical synthesis in the Li-Mg-N-H system under deuterium gas, using Li3N and Mg as reactants, and the structural and sorption properties of the intermediate and final products mainly by means of neutron powder diffraction. Mechanochemistry leads to the end formation of amorphous Mg(ND2)2, which crystallizes upon heating above 425 K. During synthesis, a novel cation-mixed nitride/imide phase of simplified composition Li3MgN2D has been unveiled as the intermediate phase. It crystallizes in the cubic disordered anti-fluorite type structure (S.G. Fm3[combining macron]m) with a lattice parameter of 4.996 Å at room temperature. Deuterium absorption in this compound occurs through an original solid solution type mechanism ending with the imide compound β-Li2MgN2D2. The conjoint use of mechanochemistry under deuterium gas and in situ neutron diffraction techniques offers new avenues for better characterization of the efficient hydrogen storage materials. In particular, this work highlights the unexpected role of intermediate nitride/imide phases in the Li-Mg-N-H system.

  19. Neutron diffraction studies and magnetism in Ti doped SrFeO{sub 3−δ} systems

    SciTech Connect

    Sendil Kumar, A.; Srinath, S.; Babu, P. D.

    2014-03-14

    The magnetic ground state of single phase tetragonal crystal structure with I4/mmm space group SrFe{sub 1−x}Ti{sub x}O{sub 3−δ} (x = 0.2 and 0.3) is investigated from 2 K to 300 K. Strong irreversibility is observed in zero-field-cooled (ZFC) and field-cooled DC magnetization curves. Arrott plots show the absence of spontaneous magnetization (M{sub S}) down to 2 K, ruling out the possibility of long range ferromagnetic order. Neutron diffraction measurements carried out at H = 0, 7 T (field cooled) at several temperatures above and below the T* (temperature at which M{sub ZFC}(T) is maximum) do not show any additional peaks and also no difference in intensity rules out, both the long range antiferromagnetic and ferromagnetic orders. Hence, the combined study of dc magnetization and neutron diffraction results reveals cluster spin glass behavior in SrFe{sub 1−x}Ti{sub x}O{sub 3−δ} (x = 0.2 and 0.3)

  20. Neutron diffraction texture analysis for α-Al2O3 oriented by high magnetic field and sintering

    NASA Astrophysics Data System (ADS)

    Terada, N.; Suzuki, H. S.; Suzuki, T. S.; Kitazawa, H.; Sakka, Y.; Kaneko, K.; Metoki, N.

    2009-05-01

    We have performed neutron diffraction experiments on highly oriented α-Al2O3, obtained by slip casting under a magnetic field and sintering. In order to investigate the magnetic field, B, and sintering temperature, Tsint, dependence of the degree of alignment of the orientation, we used samples treated with systematically varied B up to 12 T and Tsint up to 1600 °C. The degree of alignment of the magnetic easy axis (the hexagonal c-axis) is rapidly enhanced by sintering above 1200 °C, which is coincident with the temperature at which crystal grains start to grow. The angular distribution of the c-axis for the sample sintered at 1600 °C, obtained by ω-scan neutron diffraction profiles, is almost coincident with the probability distribution calculated for the particle size two times larger than that in the starting material. We discuss the orientation process mechanism with sintering in light of the results of this analysis.

  1. In Situ Neutron and Synchrotron X-ray Diffraction Studies of Jarosite at High-Temperature High-Pressure Conditions

    NASA Astrophysics Data System (ADS)

    Xu, H.; Zhao, Y.; Hickmott, D.; Zhang, J.; Vogel, S.; Daemen, L.; Hartl, M.

    2011-03-01

    Jarosite (KFe 3 (SO4)2 (OH)6) occurs in acid mine drainage and epithermal environments and hot springs associated with volcanic activity. Jarosite is also of industrial interest as an iron-impurity extractor from zinc sulfide ores. In 2004, jarosite was detected by the Mars Exploration Rover Mössbauer spectrometer, which has been interpreted as a strong evidence for the existence of water (and possibly life) on ancient Mars. This discovery has spurred considerable interests in stability and structural behavior of jarosite and related phases at various temperature, pressure, and aqueous conditions. In this work, we have investigated the crystal structure and phase stability of jarosite at temperatures up to 900 K and/or pressures up to 9 GPa using in situ neutron and synchrotron X-ray diffraction. To avoid the large incoherent scattering of neutrons by hydrogen, a deuterated sample was synthesized and characterized. Rietveld analysis of the obtained diffraction data allowed determination of unit-cell parameters, atomic positions and atomic displacement parameters as a function of temperature and pressure. In addition, the coefficients of thermal expansion, bulk moduli and pressure-temperature stability regions of jarosite were determined.

  2. Structure of 2 molar NaOH in aqueous solution from neutron diffraction and empirical potential structure refinement

    SciTech Connect

    McLain, Sylvia E.; Imberti, Silvia; Soper, Alan K.; Botti, Alberto; Bruni, Fabio; Ricci, Maria Antonietta

    2006-09-01

    Neutron diffraction with isotopic substitution has been used to investigate aqueous solutions of 2M NaOH in the liquid state. The data were modeled using empirical potential structure refinement which allows for the extraction of the ion-water and water-water correlations. The data show that the ion-water radial distribution functions are in accordance with those found by previous studies on NaOH solutions and follow a trend which is dependent on the concentration of the solute. In particular, the shape of the hydroxide hydration shell is found to be concentration independent, but the number of water molecules occupying this shell increases with dilution. Additionally, the water-water correlations show that there is still a measurable effect on water structure with the addition of ions at this concentration, as the second shell in the water oxygen radial distribution function is compressed relative to the first shell. The data are also used to discuss the recent claims that the published radial distribution functions of water are unreliable, showing that data taken at different neutron sources, with different diffraction geometry and systematic errors lead to the same structural information when analyzed via a realistic modeling regime.

  3. Residual stress measurements in a zircaloy-4 weld by neutron diffraction

    SciTech Connect

    Carr, D.G.; Ripley, M.I.; Holden, T.M.; Brown, D.W.; Vogel, S.C

    2004-08-16

    The macroscopic stress distribution across a Zircaloy-4 gas tungsten arc weld was measured by time-of-flight neutron diffraction at the SMARTS diffractometer at Los Alamos National Laboratory. The method enabled the measurement of strain for all the available reflections permitted by the rolling texture of the plate and the modified texture in the weld-metal and heat affected zone. A maximum longitudinal stress of 220 {+-} 40 MPa was observed in the weld compared with the 0.2% yield stress of 390 MPa of the plate. A maximum transverse stress of 60 {+-} 40 MPa was observed in the weld. Textures were measured at the HIPPO diffractometer.

  4. Neutron diffraction, specific heat and magnetization studies on Nd2CuTiO6

    NASA Astrophysics Data System (ADS)

    Rayaprol, S.; Kaushik, S. D.; Kumar, Naresh; Singh, K.; Guillou, F.; Simon, C.

    2016-05-01

    Structural and physical properties of a double-perovskite compound, Nd2CuTiO6 have been studied using neutron diffraction, magnetization and specific heat measurements. The compound crystallizes in an orthorhombic structure in space group Pnma. The interesting observation we make here is that, though no long range magnetic order is observed between 2 and 300K, the low temperature specific heat and magnetic susceptibility behavior exhibits non-Fermi liquid like behavior in this insulating compound. The magnetization and specific heat data are presented and discussed in light of these observations.

  5. Neutron-diffraction approach to the atomic decoration of the Al-Mn icosahedral quasicrystal

    NASA Astrophysics Data System (ADS)

    Janot, Chr.; Pannetier, J.; Dubois, J. M.; de Boissieu, M.

    1989-01-01

    Neutron-diffraction data were obtained from single-phase icosahedral powder of the system Al74Si5Mn21 and its modification by isomorphous substitution on the Mn sites. Amplitudes and phase differences of partial structure factors were determined. Within a strip-projection approach, phases were reconstructed. Atomic densities calculated in the physical three-dimensional space show that Mackay (1981) icosahedra, the structural units usually invoked for quasi-crystal models, do not emerge as the basic ingredients of the atomic arrangements.

  6. Molecular-dynamics modelling and neutron diffraction study of the site disorder in air clathrate hydrates

    SciTech Connect

    Chazallon, Bertrand; Klapproth, Alice; Kuhs, Werner F.

    1999-06-15

    We present the results of MD-simulation runs with subsequent quenches for clathrate hydrates using SPC water in order to model properly the crystallographic site disorder of the guest molecules in the water cages. A procedure is described to transform the results of the quench (symmetry P1) into the proper space-time averaged space group (Fd3-bar m) of the clathrate hydrate. The resulting disorder models are compared with the outcome of crystallographic structure refinements (R-factors, Fourier maps) from our neutron powder diffraction data. A correct description of the disorder is important for a reliable determination of the pressure-dependent cage filling.

  7. Neutron Diffraction as a Tool to Explore the Free Energy Landscape in Orientationally Disordered Phases

    NASA Astrophysics Data System (ADS)

    Rovira-Esteva, Muriel; Pardo, Luis C.; Tamarit, Josep LL.; Bermejo, F. Javier

    The temperature dependence of structural parameters of orientational glasses of the halogenomethane family, Freon 112 (FCl2C)-(CCl2F)) and Freon 112a (F2ClC)-(CCl3)) are studied at short- (molecular) intermediate- (orientational correlations) and long-range (lattice parameters) scales by means of neutron diffraction. The two materials which are chemical isomers display strikingly different properties in their ordering patterns resulting from a shift in balance between electrostatic and excluded-volume interaction. The relevance of these findings to our understanding of glassy phenomena is discussed.

  8. The Crystal Structure of Thorium and Zirconium Dihydrides by X-ray and Neutron Diffraction

    DOE R&D Accomplishments Database

    Rundle, R.E.; Shull, C.G.; Wollan, E.O.

    1951-04-20

    Thorium forms a tetragonal lower hydride of composition ThH{sub 2}. The hydrides ThH{sub 2}, ThD{sub 2}, and ZrD{sub 2} have been studied by neutron diffraction in order that hydrogen positions could be determined. The hydrides are isomorphous, and have a deformed fluorite structure. Metal-hydrogen distances in thorium hydride are unusually large, as in UH{sub 3}. Thorium and zirconium scattering amplitudes and a revised scattering amplitude for deuterium are reported.

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

    USGS Publications Warehouse

    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.

  10. In situ observation of ErD2 formation during D-2 loading via neutron diffraction

    SciTech Connect

    Browning, Jim; Snow, Clark; Wixom, Ryan R; Llobet, Anna; Rodriguez, Mark

    2011-01-01

    In an effort to better understand the structural changes occurring during hydrogen loading of erbium target materials, we have performed in situ D{sub 2} loading of erbium metal (powder) at temperature (450 C) with simultaneous neutron diffraction analysis. This experiment tracked the conversion of Er metal to the {alpha} erbium deuteride (solid-solution) phase and then into 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.

  11. Anomalous structural feature of LiNbO{sub 3} observed using neutron diffraction

    SciTech Connect

    Fernandez-Ruiz, R.; Bermudez, V.; Martin y Marero, D.

    2005-11-01

    An anomalous structural effect has been observed and analyzed on LiNbO{sub 3} at low temperature by neutron-diffraction experiments. Two minima in the unit-cell volume at 55 and 100 K related with maxima and minima in the volume vibrational isotropic factors of Li and Nb atoms, respectively, and a change in the curve slope of the spontaneous stress at 55 K have been identified. This fact, together with the shortening in distance of the Li and O layers at 55 K, has been related with variations in the Ps factor through the secondary pyroelectric effect.

  12. Structural Study of Liquid Se-Te Alloys by Neutron Diffraction

    NASA Astrophysics Data System (ADS)

    Takeda, Shin'ichi; Tamaki, Shigeru; Waseda, Yoshio

    1986-12-01

    The neutron diffraction study of liquid Se-Te system has been carried out to reveal the origin of characteristic temperature dependence of various properties related to the structural order in atomic scale. The temperature dependence of measured structural functions of liquid SexTe1-x system could be explained by a gradual transition from two-fold coordinated component (non-metallic) to the three-fold coordinated one (metallic). The partial structure factors of these two-fold and three-fold coordinations are separated with the help of the thermodynamic data. A configurational model satisfying these situations is also presented.

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

    NASA Astrophysics Data System (ADS)

    Dore, John; Webber, Beau; Hartl, Monika; Behrens, Peter; Hansen, Thomas

    2002-11-01

    Neutron diffraction measurements have been made for D 2O water in 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 relationship between hexagonal ice [ Ih] and cubic ice [ Ic].

  14. Structural characterization of phosphatidylcholine-diacylglycerol system by neutron scattering and X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Takahashi, H.; Nagura, K.; Imai, M.; Matsushita, Y.; Hatta, I.

    Diacylglycerol (DAG) is recognized as one of the most important lipids for biological functions of cell membranes. In order to understand the functions of DAG, it is indispensable to study the effect of DAG on phosphatidylcholine (PC), which is a main lipid component of biomembranes. Here we report neutron-scattering data of sonicated PC/DAG vesicles and X-ray-diffraction data of oriented PC/DAG multilamellar systems. These data imply that addition of DAG induces a change in the tilt angle of lipid molecules and that, as a result, an increase of the membrane thickness is induced.

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

    PubMed

    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

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

    PubMed Central

    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

  17. Topological characterization of metallic glasses by neutron diffraction and RMC modeling

    NASA Astrophysics Data System (ADS)

    Fukunaga, Toshiharu; Itoh, Keiji; Otomo, Toshiya; Mori, Kazuhiro; Sugiyama, Masaaki; Kato, Hidemi; Hasegawa, Masashi; Hirata, Akihiko; Hirotsu, Yoshihiko; Aoki, Kiyoshi

    2006-11-01

    TbFe 2D 3.8, TbNi 2D 2.4, CuZr 2 and NiZr 2 metallic glasses have been studied to elucidate the structural characteristics by taking advantage of neutron and X-ray diffraction and using the reverse Monte Carlo (RMC) modeling based on the diffraction data. Topologically, about 98% of D atoms occupy tetrahedral sites formed by metal atoms for TbFe 2D 3.8 and TbNi 2D 2.4 metallic glasses. The Volonoi analysis of the structure of CuZr 2 and NiZr 2 metallic glasses was carried out to elucidate the relationship between the stability of glassy state and the atomic configuration. The prismatic-like polyhedra dominate in NiZr 2 metallic glass. In contrast, the icosahedron-like polyhedra faces are preferred for constructing the structure of CuZr 2 metallic glass.

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

    PubMed

    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

    2016-06-30

    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.

  19. A short note on physical properties to irradiated nuclear fuel by means of X-ray diffraction and neutron scattering techniques

    NASA Astrophysics Data System (ADS)

    Abdullah, Yusof; Husain, Hishamuddin; Hak, Cik Rohaida Che; Alias, Nor Hayati; Yusof, Mohd Reusmaazran; Kasim, Norasiah Ab; Zali, Nurazila Mat; Mohamed, Abdul Aziz

    2015-04-01

    For nuclear reactor applications, understanding the evolution of the fuel materials microstructure during irradiation are of great importance. This paper reviews the physical properties of irradiated nuclear fuel analysis which are considered to be of most importance in determining the performance behavior of fuel. X-rays diffraction was recognize as important tool to investigate the phase identification while neutron scattering analyses the interaction between uranium and other materials and also investigation of the defect structure.

  20. Neutron and X-ray single-crystal diffraction from protein microcrystals via magnetically oriented microcrystal arrays in gels.

    PubMed

    Tsukui, Shu; Kimura, Fumiko; Kusaka, Katsuhiro; Baba, Seiki; Mizuno, Nobuhiro; Kimura, Tsunehisa

    2016-07-01

    Protein microcrystals magnetically aligned in D2O hydrogels were subjected to neutron diffraction measurements, and reflections were observed for the first time to a resolution of 3.4 Å from lysozyme microcrystals (∼10 × 10 × 50 µm). This result demonstrated the possibility that magnetically oriented microcrystals consolidated in D2O gels may provide a promising means to obtain single-crystal neutron diffraction from proteins that do not crystallize at the sizes required for neutron diffraction structure determination. In addition, lysozyme microcrystals aligned in H2O hydrogels allowed structure determination at a resolution of 1.76 Å at room temperature by X-ray diffraction. The use of gels has advantages since the microcrystals are measured under hydrated conditions.

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

    SciTech Connect

    Wess, T.J.; Wess, L.; Miller, A.

    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.

  2. Magnetic neutron diffraction and pressure studies on CeRuSn

    NASA Astrophysics Data System (ADS)

    Hartwig, Steffen; Prokeš, Karel; Huang, Yingkai; Pöttgen, Rainer

    2015-03-01

    We have determined the influence of magnetic fields on the crystal and magnetic structures of CeRuSn using single crystal neutron diffraction and susceptibility measurements at various pressures up to 7.4 kbar and temperatures down to 1.6 K. CeRuSn adopts below 160 K an incommensurately modulated crystal structure. It orders antiferromagnetically below TN=2.8 K in an incommensurate manner as well. This Néel-temperature is pressure independent up to 7.4 kbar. The neutron diffraction experiments detected a magnetic modulation vector qmag = (0, 0, 0.175), however, it is commensurate with the incommensurate crystal structure with qnuc = (0, 0, 0.35). At 0.6 T as well as at 0.9 T metamagnetic transitions have been observed via magnetic property measurements. The magnetic field of 0.9 T applied along the c-axis suppresses the magnetic reflections. The moments align ferromagnetically along the modulated crystal structure. Up to 3 T no change of the wavelength of the crystal structure modulations could be detected.

  3. Structure, magnetic properties, polarized neutron diffraction, and theoretical study of a copper(II) cubane.

    PubMed

    Aronica, Christophe; Chumakov, Yurii; Jeanneau, Erwann; Luneau, Dominique; Neugebauer, Petr; Barra, Anne-Laure; Gillon, Béatrice; Goujon, Antoine; Cousson, Alain; Tercero, Javier; Ruiz, Eliseo

    2008-01-01

    The paper reports the synthesis, X-ray and neutron diffraction crystal structures, magnetic properties, high field-high frequency EPR (HF-EPR), spin density and theoretical description of the tetranuclear CuII complex [Cu4L4] with cubane-like structure (LH2=1,1,1-trifluoro-7-hydroxy-4-methyl-5-aza-hept-3-en-2-one). The simulation of the magnetic behavior gives a predominant ferromagnetic interaction J1 (+30.5 cm(-1)) and a weak antiferromagnetic interaction J2 (-5.5 cm(-1)), which correspond to short and long Cu-Cu distances, respectively, as evidence from the crystal structure [see formulate in text]. It is in agreement with DFT calculations and with the saturation magnetization value of an S=2 ground spin state. HF-EPR measurements at low temperatures (5 to 30 K) provide evidence for a negative axial zero-field splitting parameter D (-0.25+/-0.01 cm(-1)) plus a small rhombic term E (0.025+/-0.001 cm(-1), E/D = 0.1). The experimental spin distribution from polarized neutron diffraction is mainly located in the basal plane of the CuII ion with a distortion of yz-type for one CuII ion. Delocalization on the ligand (L) is observed but to a smaller extent than expected from DFT calculations. PMID:18792037

  4. Neutron diffraction study of water freezing on aircraft engine combustor soot.

    PubMed

    Tishkova, V; Demirdjian, B; Ferry, D; Johnson, M

    2011-12-14

    The study of the formation of condensation trails and cirrus clouds on aircraft emitted soot particles is important because of its possible effects on climate. In the present work we studied the freezing of water on aircraft engine combustor (AEC) soot particles under conditions of pressure and temperature similar to the upper troposphere. The microstructure of the AEC soot was found to be heterogeneous containing both primary particles of soot and metallic impurities (Fe, Cu, and Al). We also observed various surface functional groups such as oxygen-containing groups, including sulfate ions, that can act as active sites for water adsorption. Here we studied the formation of ice on the AEC soot particles by using neutron diffraction. We found that for low amount of adsorbed water, cooling even up to 215 K did not lead to the formation of hexagonal ice. Whereas, larger amount of adsorbed water led to the coexistence of liquid water (or amorphous ice) and hexagonal ice (I(h)); 60% of the adsorbed water was in the form of ice I(h) at 255 K. Annealing of the system led to the improvement of the crystal quality of hexagonal ice crystals as demonstrated from neutron diffraction.

  5. Crystal and magnetic structures of Cr1/3NbSe2 from neutron diffraction

    NASA Astrophysics Data System (ADS)

    Gubkin, A. F.; Proskurina, E. P.; Kousaka, Y.; Sherokalova, E. M.; Selezneva, N. V.; Miao, P.; Lee, S.; Zhang, J.; Ishikawa, Y.; Torii, S.; Kamiyama, T.; Campo, J.; Akimitsu, J.; Baranov, N. V.

    2016-01-01

    Neutron diffraction measurements of the Cr intercalated niobium diselenide Cr1/3NbSe2 together with magnetization measurements have revealed that this compound exhibits ferromagnetic ordering below TC = 96 K unlike a chiral helimagnetic order observed in the sulfide compound Cr1/3NbS2. As derived from neutron diffraction data, the Cr magnetic moments μCr = 2.83 ± 0.03 μB in Cr1/3NbSe2 are aligned within basal plane. The discrepancy in the magnetic states of Cr1/3NbS2 and Cr1/3NbSe2 is ascribed to the difference in the preferential site occupation of Cr ions in crystal lattices. In Cr1/3NbSe2, the Cr ions are predominantly distributed over 2b Wyckoff site, which determines a centrosymmetric character of the crystal structure unlike Cr1/3NbS2, where the Cr ions are mainly located in 2c position and the crystal structure is non-centrosymmetric.

  6. Neutron diffraction structure study of Er and Yb doped YAl3(BO3)4

    NASA Astrophysics Data System (ADS)

    Sváb, E.; Beregi, E.; Fábián, M.; Mészáros, Gy.

    2012-06-01

    Neutron diffraction structure study has been performed on YAl3(BO3)4 (YAB), on doped Y0.88Er0.12Al3(BO3)4, Y0.5Er0.5Al3(BO3)4, Y0.5Yb0.5Al3(BO3)4 and on co-doped Y0.84Er0.01Yb0.15Al3(BO3)4 compositions. It was established that the doped compounds are isostructural to YAB. The neutron diffraction pattern have been be fitted in space group R32 using the triple hexagonal Wyckoff notation. Both Er3+ and Yb3+ ions occupy the Y3+ (3a) sites and not the Al3+ (9d) sites, as it was suggested previously. The lattice parameters are decreasing with increasing amount of the dopant elements. Slight changes are revealed in the positional parameters and interatomic distances with increasing concentration of the dopant ions. For the co-doped Y0.84Er0.01Yb0.15Al3(BO3)4 the changes are more significant than for the doped YAB compounds with only one type of dopant element, Er or Yb.

  7. Cage occupancies in the high pressure structure H methane hydrate: A neutron diffraction study

    SciTech Connect

    Tulk, Christopher A; Klug, Dennis D; Moreira Dos Santos, Antonio F; Karotsis, Georgios; Guthrie, Malcolm; Molaison, Jamie J; Pradhan, Neelam

    2012-01-01

    A neutron diffraction study was performed on the CD{sub 4}: D{sub 2}O structure H clathrate hydrate to refine its CD{sub 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{sub 4} molecules in the large 20-hedron (5{sup 12}6{sup 8}) cages of the hydrate unit cell. Each of the pentagonal dodecahedron (5{sup 12}) and 12-hedron (4{sup 3}5{sup 6}6{sup 3}) cages in the sH unit cell are occupied with on average 0.89 and 0.90 CD{sub 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.

  8. Validation of neutron texture data on GEM at ISIS using electron backscattered diffraction

    NASA Astrophysics Data System (ADS)

    Davies, Peter; Kockelmann, Winfried; Wynne, Brad; Eccleston, Roger; Hutchinson, Bevis; Rainforth, W. Mark

    2008-03-01

    The high solid angular coverage of the general materials (GEM) diffractometer at the ISIS pulsed neutron source located at the UK Rutherford Appleton Laboratory offers the capability of obtaining quantitative bulk crystallographic texture data in a 'single shot' within a matter of minutes. This enables the possibility of in situ texture measurements to be made as a function of temperature to monitor and quantify texture changes during phase transformation or microstructure restoration processes like recrystallization. The purpose of this paper is to determine the quality of the texture data produced from GEM in order to define a level of confidence for subsequent texture model validation. This has been achieved by comparing textures of sections of a 200 mm diameter titanium alloy billet using data obtained from GEM with data obtained using electron backscattered diffraction (EBSD). In both cases, the data were obtained at room temperature. EBSD, unlike time-of-flight neutron diffraction analysis, obtains texture data directly from orientation measurements via backscattered Kikuchi patterns in the scanning electron microscope. In all analysed locations, both methods show near-identical textures, with regard to both the general orientation distributions and the levels of intensity of the distributions. This shows that the GEM diffractometer is capable of accurately determining bulk textures in a single shot, thus confirming its suitability for in situ high temperature experiments.

  9. Neutron diffraction and ferromagnetic resonance studies on plasma-sprayed MnZn ferrite films

    SciTech Connect

    Yan, Q.Y.; Gambino, R.J.; Sampath, S.; Huang, Q.

    2005-02-01

    The magnetic properties of MnZn ferrites are affected by the plasma spray process. It is found that improvements can be made by annealing the ferrite films at 500 deg. C - 800 deg. C. The annealing induced magnetic property changes are studied by neutron diffraction and ferromagnetic resonance techniques. The increase of the saturation magnetization is attributed to the cation ordering within the spinel lattice, which increases the magnetic moment per ferrite formula. The refinements on the neutron diffraction data suggest that the redistribution of the cation during annealing neither starts from a fully disordered state nor ends to a fully ordered state. The decrease of the coercivity is analyzed with the domain wall pinning model. The measurements on the magnetostriction and residual stress indicate that coercive mechanisms arising from the magnetoelastic energy term are not dominant in these ferrite films. The decrease of the coercivity for annealed ferrite films is mainly attributed to the decrease of the effective anisotropic field, which may result from the homogenization of the film composition and the reduction of the microstructural discontinuity (e.g., cracks, voids, and splat boundaries)

  10. High-pressure neutron diffraction study on H D isotope effects in brucite

    SciTech Connect

    Horita, Juske; Moreira Dos Santos, Antonio F; Tulk, Christopher A; Chakoumakos, Bryan C; Polyakov, Dr. V. B.

    2010-01-01

    A neutron powder diffraction study of hydrogenated and deuterated brucite was conducted at ambient temperature and at pressures up to 9 GPa, using a Paris Edinburgh high-pressure cell at the WAND instrument of the ORNL High Flux Isotope Reactor. The two materials were synthesized by the same method and companion measurements of neutron diffraction were conducted under the same conditions. Our refinement results show that the lattice-parameters of the a axis, parallel to the sheets of Mg O octahedra, decrease only slightly with pressure with no effect of H D substitution. However, the c axis of Mg(OD)2 is shorter and may exhibit greater compressibility with pressure than that of Mg(OH)2. Consequently, the unit-cell volume of deuterated brucite is slightly, but systematically smaller than that of hydrogenated brucite. When fitted to a third-order Birch Murnaghan equation in terms of the normalized unit-cell volume, values of the bulk modulus for hydrogenated and deuterated brucite (K0 = 39.0 2.8 and 40.4 1.3 GPa, respectively) are, however, indistinguishable from each other within the experimental errors. The measured effect of H D substitution on the unit-cell volume also demonstrates that brucite (and other hydrous minerals) preferentially incorporate deuterium over hydrogen under pressure, suggesting that the distribution of hydrogen isotopes in deep-earth conditions may differ significantly from that in near-surface environments.

  11. Cage occupancies in the high pressure structure H methane hydrate: A neutron diffraction study

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

    A neutron diffraction study was performed on the CD4 : D2O structure H clathrate hydrate to refine its CD4 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 CD4 molecules in the large 20-hedron (51268) cages of the hydrate unit cell. Each of the pentagonal dodecahedron (512) and 12-hedron (435663) cages in the sH unit cell are occupied with on average 0.89 and 0.90 CD4 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  13. Numerical investigations on reignition behavior of detonation diffraction

    NASA Astrophysics Data System (ADS)

    Wang, Cheng; Han, Wen-Hu; Bi, Yong; Ding, Jian-Xu

    2016-02-01

    In this paper, by adopting a fifth-order weighted essentially non-oscillatory (WENO) scheme with a third-order TVD Runge-Kutta time stepping method for two-dimensional reactive Euler equations, a parallel code is developed, and reignition behavior after a self-sustaining detonation from the tube into free space filled with H2/O2 mixtures is investigated. The numerical results show that the initial pressure has a great influence on the detonation cellular width, and that as the initial pressure increases, the cellular width gradually decreases and the cellular shape changes from irregular structure to regular structure, demonstrating the detonation instability to stability transition. When the initial pressure is larger than 1.2 atm, the detonation wave expands over the edge of the splitter plate, reignition can come into being because enough transverse waves collide with each other at the leading edge of the expanding front. When the initial pressure is 1.2 atm, hot spots appear on the front, and ignite the combustible gas near the hot spots after detonation diffraction. When the initial pressure is 1.0 atm, reignition fails. These findings hint that a critical initial pressure exists between 1.0-1.2 atm for direct reignition after detonation diffraction.

  14. Using Neutron Diffraction to Determine the Low-Temperature Behavior of Pb2+ in Lead Feldspar

    NASA Astrophysics Data System (ADS)

    Kolbus, L. M.; Anovitz, L. M.; Chakoumackos, B. C.; Wesolowski, D. J.

    2014-12-01

    Feldspar minerals comprise 60% of the Earth's crust, so it imperative that the properties of feldspar be well understood for seismic modeling. The structure of feldspar consists of a three-dimensional framework of strongly-bonded TO4 tetrahedra formed by the sharing of oxygen atoms between tetrahedra. The main solid solution series found in natural feldspars are alkali NaAlSi3O8 -KAlSi3O8 and plagioclase CaAl2Si2O8-NaAlSi3O8. Recently, efforts have been made to systematically quantify feldspars structural change at non-ambient temperatures by considering only the relative tilts of the tetrahedral framework [1]. This serves as a tool to predict various behaviors of the structure such as the relative anisotropy of unit cell parameters and volume evolution with composition and temperature. Monoclinic feldspars are well predicted by the model [1], but discrepancies still remain between the model predictions and real structures with respect to absolute values of the unit cell parameters. To improve the existing model, a modification must be made to account for the M-cation interaction with its surrounding oxygen atoms. We have, therefore, chosen to study the structure of Pb-feldspar (PbAl2Si2O8), which provides the opportunity to characterize a monoclinic Al2Si2 feldspar containing a large M-site divalent cation using neutron diffraction. Neutron diffraction allows for the characterization of the M-site cation interaction between the oxygen atoms in the polyhedral cage by providing information to accurately determine the atomic displacement parameters.. Lead feldspar was synthesized for this study using the method described in [2], and confirmed to have a monoclinic C2/m space group. In this talk we will present structural determinations and atomic displacement parameters of Pb-feldspar from 10 - 300K generated from Neutron diffraction at the POWGEN beamline at the Spallation Neutron Source at Oak Ridge National lab, and compare our results to those predicted by the

  15. Non destructive neutron diffraction measurements of cavities, inhomogeneities, and residual strain in bronzes of Ghiberti's relief from the Gates of Paradise

    SciTech Connect

    Festa, G.; Senesi, R.; Alessandroni, M.; Andreani, C.; Vitali, G.; Porcinai, S.; Giusti, A. M.; Materna, T.; Paradowska, A. M.

    2011-03-15

    Quantitative neutron studies of cultural heritage objects provide access to microscopic, mesoscopic, and macroscopic structures in a nondestructive manner. In this paper we present a neutron diffraction investigation of a Ghiberti Renaissance gilded bronze relief devoted to the measurement of cavities and inhomogeneities in the bulk of the sample, along with the bulk phase composition and residual strain distribution. The quantitative measurements allowed the determination of the re-melting parts extension, as well as improving current knowledge about the manufacturing process. The study provides significant and unique information to conservators and restorators about the history of the relief.

  16. Neutron diffraction studies of a four-coordinated hydride in near square-planar geometry

    SciTech Connect

    Liao, Jian -Hong; Dhayal, Rajendra Singh; Wang, Xiaoping; Kahlal, Samia; Saillard, Jean -Yves; Liu, C. W.

    2014-10-07

    The structure of a nanospheric polyhydrido copper cluster, [Cu20(H)11{S2P(OiPr)2}9], was determined by single-crystal neutron diffraction. Cu20 cluster consists of an elongated triangular orthobicupola constructed from 18 Cu atoms that encapsulate a [Cu2H5}3- ion in the center with an exceptionally short Cu-Cu distance. The eleven hydrides in the cluster display three different coordination modes to the Cu atoms: Six μ3-hydrides in pyramidal geometry, two μ4-hydrides in tetrahedral cavity, and three μ4-hydrides in an unprecedented near square-planar geometry. The neutron data set was collected on a small crystal of the size 0.20 mm x 0.50 mm x 0.65 mm for seven days using the Spallation Neutron Source TOPAZ single-crystal time-of-flight Laue diffractometer at the Oak Ridge National Laboratory. Furthermore, the final R-factor is 8.64% for 16014 reflections.

  17. Neutron diffraction studies of a four-coordinated hydride in near square-planar geometry

    DOE PAGES

    Liao, Jian -Hong; Dhayal, Rajendra Singh; Wang, Xiaoping; Kahlal, Samia; Saillard, Jean -Yves; Liu, C. W.

    2014-10-07

    The structure of a nanospheric polyhydrido copper cluster, [Cu20(H)11{S2P(OiPr)2}9], was determined by single-crystal neutron diffraction. Cu20 cluster consists of an elongated triangular orthobicupola constructed from 18 Cu atoms that encapsulate a [Cu2H5}3- ion in the center with an exceptionally short Cu-Cu distance. The eleven hydrides in the cluster display three different coordination modes to the Cu atoms: Six μ3-hydrides in pyramidal geometry, two μ4-hydrides in tetrahedral cavity, and three μ4-hydrides in an unprecedented near square-planar geometry. The neutron data set was collected on a small crystal of the size 0.20 mm x 0.50 mm x 0.65 mm for seven daysmore » using the Spallation Neutron Source TOPAZ single-crystal time-of-flight Laue diffractometer at the Oak Ridge National Laboratory. Furthermore, the final R-factor is 8.64% for 16014 reflections.« less

  18. Neutron diffraction studies of a four-coordinated hydride in near square-planar geometry.

    PubMed

    Liao, Jian-Hong; Dhayal, Rajendra Singh; Wang, Xiaoping; Kahlal, Samia; Saillard, Jean-Yves; Liu, C W

    2014-10-20

    The structure of a nanospheric polyhydrido copper cluster, [Cu20(H)11{S2P(O(i)Pr)2}9], was determined by single-crystal neutron diffraction. The Cu20 cluster consists of an elongated triangular orthobicupola constructed from 18 Cu atoms that encapsulate a [Cu2H5](3-) ion with an exceptionally short Cu-Cu distance. The 11 hydrides in the cluster display three different coordination modes to the Cu atoms: six μ3-hydrides in a pyramidal geometry, two μ4-hydrides in a tetrahedral cavity, and three μ4-hydrides in an unprecedented near square-planar geometry. The neutron data set was collected for 7 days on a small crystal with dimensions of 0.20 mm × 0.50 mm × 0.65 mm using the Spallation Neutron Source TOPAZ single-crystal time-of-flight Laue diffractometer at Oak Ridge National Laboratory. The final R-factor was 8.63% for 16,014 reflections. PMID:25290745

  19. Texture and anisotropy analysis of a laminated lower crust: a neutron diffraction study of felsic granulites

    NASA Astrophysics Data System (ADS)

    Benitez Perez, J.; Gomez Barreiro, J.; Martinez-Catalan, J. R.; Castiñeiras Garcia, P.; Vogel, S. C.; Wenk, H.; Alvarez Valero, A.

    2013-12-01

    Quantitative fabric analyses of high-P and high-T tectonites were done with HIPPO, a Time-Of-Flight (TOF) neutron diffractometer at Los Alamos National Lab. Samples were collected in the Sobrado unit (NW Spain), a tectonic stack of highly deformed slices of metabasites, paragneisses and ultramafic rocks. Metamorphism ranges from granulites on top, to eclogites at the bottom of the unit. The ensemble represents and excellent example of laminated lower crust. The alternation of mechanically contrasted lithologies and/or the development of crystal preferred orientation might result into anisotropy. We explore the contribution of crystallographic preferred orientation or texture to the seismic anisotropy of the lower crust. Since strain partitioning occurred between mechanically strong and weak lithologies, a higher crystal preferred orientation is expected along the weak levels: the metasediments. TOF neutron diffraction experiments were conducted in HIPPO (LANSCE) with high-P and high-T mylonitic felsic paragneisses. Quantitative texture analysis of neutron data was accomplished by using the Rietveld method, with E-WIMW algorithm, implemented in the program package MAUD (Material Analysis Using Diffraction; Lutterotti, 1999). The orientation distribution function (ODF) for each mineral was calculated in MAUD and then processed in BEARTEX (Wenk et al. 1998). Selected pole figures were plotted for major components, quartz, plagioclase and biotite (first setting in monoclinic crystals). Texture patterns are compatible with non-coaxial progressive deformation and discussed accordingly in terms of dislocation activity. Besides, seismic waves velocities were computed from the texture data in BEARTEX. Calculated velocities and anisotropy were based on ODF, volume fraction of each mineral and their single-crystal elastic constant. Kinematic and mechanical implications are discussed in terms of the regional geology. The correlation of texture, mineral composition and seismic

  20. A revised structure and hydrogen bonding system in cellulose II from a neutron fiber diffraction analysis

    SciTech Connect

    Langan, P.; Nishiyama, Y.; Chanzy, H.

    1999-11-03

    The crystal and molecular structure and hydrogen bonding system in cellulose II have been revised using new neutron diffraction data extending to 1.2 {angstrom} resolution collected from two highly crystalline fiber samples of mercerized flax. Mercerization was achieved in NaOH/H{sub 2}O for one sample and in NaOD/D{sub 2}O for the other, corresponding to the labile hydroxymethyl moieties being hydrogenated and deuterated, respectively. Fourier difference maps were calculated in which neutron difference amplitudes were combined with phases calculated from two revised X-ray models of cellulose II. The revised phasing models were determined by refinement against the X-ray data set of Kolpak and Blackwell, using the LALS methodology. Both models have two antiparallel chains organized in a P2{sub 1} space group and unit cell parameters: a = 8.01 {angstrom}, b = 9.04 {angstrom}, c = 10.36 {angstrom}, and {gamma} = 117.1{degree}. One has equivalent backbone conformations for both chains but different conformations for the hydroxymethyl moieties: gt for the origin chain and tg for the center chain. The second model based on the recent crystal structures of cellotetraose, has different conformations for the two chains but nearly equivalent conformations for the hydroxymethyl moieties. On the basis of the X-ray data alone, the models could not be differentiated. From the neutron Fourier difference maps, possible labile hydrogen atom positions were identified for each model and refined using LALS. The second model is significantly different from previous proposals based on the crystal structures of cellotetraose, MD simulations of cellulose II, and any potential hydrogen-bonding network in the structure of cellulose II determined in earlier X-ray fiber diffraction studies. The exact localization of the labile hydrogen atoms involved in this bonding, together with their donor and acceptor characteristics, is presented and discussed. This study provides, for the first time

  1. A Rietveld refinement method for angular- and wavelength-dispersive neutron time-of-flight powder diffraction data

    PubMed Central

    Jacobs, Philipp; Houben, Andreas; Schweika, Werner; Tchougréeff, Andrei L.; Dronskowski, Richard

    2015-01-01

    This paper introduces a two-dimensional extension of the well established Rietveld refinement method for modeling neutron time-of-flight powder diffraction data. The novel approach takes into account the variation of two parameters, diffraction angle 2θ and wavelength λ, to optimally adapt to the varying resolution function in diffraction experiments. By doing so, the refinement against angular- and wavelength-dispersive data gets rid of common data-reduction steps and also avoids the loss of high-resolution information typically introduced by integration. In a case study using a numerically simulated diffraction pattern of Rh0.81Fe3.19N taking into account the layout of the future POWTEX instrument, the profile function as parameterized in 2θ and λ is extracted. As a proof-of-concept, the resulting instrument parameterization is then utilized to perform a typical refinement of the angular- and wavelength-dispersive diffraction pattern of CuNCN, yielding excellent residuals within feasible computational efforts. Another proof-of-concept is carried out by applying the same approach to a real neutron diffraction data set of CuNCN obtained from the POWGEN instrument at the Spallation Neutron Source in Oak Ridge. The paper highlights the general importance of the novel approach for data analysis at neutron time-of-flight diffractometers and its possible inclusion within existing Rietveld software packages. PMID:26664340

  2. Non-destructive magneto-strain analysis of YB2Cu3Oy superconducting magnets using neutron diffraction in the time-of-flight mode

    NASA Astrophysics Data System (ADS)

    Tomita, M.; Muralidhar, M.; Suzuki, K.; Ishihara, A.; Fukumoto, Y.; Osamura, K.; Machiya, S.; Harjo, S.

    2012-09-01

    In general, neutron diffraction allows a non-destructive investigation of bulk samples. In this study, a magneto-strain analysis of the trapped field in YB2Cu3Oy "YBCO" superconducting bulks was carried out at 45 K using neutron diffraction time-of-flight (TOF) method. The TAKUMI TOF neutron diffractometer offers unique advantages, including accommodation of large objectives, control of the experimental set-up using a 4-axial goniometer (XYZθ), and a positional resolution of 0.01 mm allowing an accurate sample positioning. As a result, the lattice strain in the YB2Cu3Oy material could be estimated in both radial and hoop directions by estimating the difference of plane spacing with/without the trapped magnetic field. The results indicate that the samples with a low trapped field values have smaller magnetic strain than those with a high trapped field. Further, the strain in the hoop direction is higher than that in the radial direction. The present results indicate that neutron diffraction measurements are an effective method for evaluating the bulk residual strains in a non-destructive manner.

  3. Neutron diffraction study of the formation kinetics of ordered antiphase domains in titanium carbohydride TiC x H y

    NASA Astrophysics Data System (ADS)

    Khidirov, I.

    2015-09-01

    The kinetics of formation and growth of ordered antiphase domains (APDs) in titanium carbohydride TiC0.50H0.21 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 ( Р ≈ 10-12) is independent of the exposure time at a constant temperature. It is found that the temperature of ordered APDs, T 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 APD = 0.60 Т С.

  4. Powder neutron diffraction study of quasi-one-dimensional Li0.9Mo6O17

    NASA Astrophysics Data System (ADS)

    da Luz, Mario S.; Dos Santos, C. A. M.; White, B. D.; Neumeier, J. J.; Huang, Q.; Leao, J. B.; Lynn, J. W.

    2008-03-01

    The crystallographic structure of quasi-one-dimensional Li0.9Mo6O17 was investigated by Rietveld refinement of powder neutron diffraction data at temperatures in the range 5 K < T < 295 K. Structural parameters, atomic positions, occupation numbers, and isotropic thermal parameter Biso will be reported. The occupancy was refined revealing a Li occupancy greater than 0.9. Bond valences sums will also be reported for various Li and Mo sites. At room temperature, the crystal was found to exhibit monoclinic symmetry with space group P21/m and lattice parameters a =12.7506(1) ,b = 5.5242(1) ,c = 9.4913(2) å,nd β = 90.593(1)^o. Good agreement between the temperature dependence of lattice parameters and high resolution thermal expansion results^* was obtained. ^*C. A. M. dos Santos, B. D. White, Yi-Kuo Yu, J. J. Neumeier, and J.A. Souza, Phys. Rev. Lett. 98, 266405 (2007).

  5. Investigations on interfacial dynamics with ultrafast electron diffraction

    NASA Astrophysics Data System (ADS)

    Murdick, Ryan A.

    An ultrafast electron diffractive voltammetry (UEDV) technique is introduced, extended from ultrafast electron diffraction, to investigate the ultrafast charge transport dynamics at interfaces and in nanostructures. Rooted in Coulomb-induced refraction, formalisms are presented to quantitatively deduce the transient surface voltages (TSVs), caused by photoinduced charge redistributions at interfaces, and are applied to examine a prototypical Si/SiO2 interface, known to be susceptible to photoinduced interfacial charging The ultrafast time resolution and high sensitivity to surface charges of this electron diffractive approach allows direct elucidation of the transient effects of photoinduced hot electron transport at nanometer (˜2 nm) interfaces. Two distinctive regimes are uncovered, characterized by the time scales associated with charge separation. At the low fluence regime, the charge transfer is described by a thermally-mediated process with linear dependence on the excitation fluence. Theoretical analysis of the transient thermal properties of the carriers show that it is well-described by a direct tunneling of the laser heated electrons through the dielectric oxide layer to surface states. At higher fluences, a coherent multiphoton absorption process is invoked to directly inject electrons into the conduction band of SiO2, leading to a more efficient surface charge accumulation. A quadratic fluence dependence on this coherent, 3-photon lead electron injection is characterized by the rapid dephasing of the intermediately generated hot electrons from 2-photon absorption, limiting the yield of the consecutive 1-photon absorption by free carriers. The TSV formalism is extended beyond the simple slab geometry associated with planar surfaces (Si/SiO2), to interfaces with arbitrary geometrical features, by imposing a corrective scheme to the slab model. The validity of this treatment is demonstrated in an investigation of the charge transfer dynamics at a metal

  6. Applications of Neutron Diffraction Measurements in the Characterization of the Mechanical Properties of Polycrystalline Geological Materials

    NASA Astrophysics Data System (ADS)

    Schofield, P. F.; Covey-Crump, S. J.; Stretton, I. C.; Knight, K. S.; Daymond, M. R.; Holloway, R. F.

    2002-12-01

    Conventional deformation experiments on polycrystalline materials are restricted to measurements of whole sample properties. This is a significant limitation for problems where it is important to know how the deformation is accommodated at the grain scale in order to interpret the experimental results and compare them with theoretical treatments. Such problems include (a) characterizing the properties of elastically anisotropic materials, where it is helpful to know the elastic strain in different lattice directions of the constituent minerals, and how this varies with microstructural variables such as the lattice preferred orientation of those minerals; (b) characterizing the mechanical properties of polymineralic materials in terms of the properties of their constituent minerals, where it is helpful to know the contribution which each mineral phase makes to the whole rock properties during deformation and how this varies with microstructural variables such as the spatial distribution of those phases; (c) calibrating stress-induced crystallographic transformations (e.g., mechanical twinning) where it is important to monitor closely the initiation and progress of the transformation as a function of applied stress. By performing deformation experiments in-situ within neutron beam-lines and collecting neutron diffraction patterns at different applied loads, the lattice parameters of all the constituent minerals in the sample may be determined as a function of load. All the requisite information required to address the three problems above may then be obtained. The value of such an approach is much diminished if in obtaining the data, compromises have to be made in the quality of the mechanical measurements. This is particularly so if the diffraction data have to be collected either from small samples or from near surface parts of the sample because the interpretation of the mechanical data in such circumstances is notoriously difficult. In this respect, the

  7. Thermal neutron diffraction determination of the magnetic structure of EuCu{sub 2}Ge{sub 2}

    SciTech Connect

    Rowan-Weetaluktuk, W. N.; Ryan, D. H.; Lemoine, P.; Cadogan, J. M.

    2014-05-07

    The magnetic structure of EuCu{sub 2}Ge{sub 2} has been determined by flat-plate neutron powder diffraction. Two magnetic phases are present in the neutron diffraction pattern at 3.5 K. They have the same moment, within error, and a common transition temperature. Both {sup 151}Eu and {sup 153}Eu Mössbauer spectroscopy show that the two magnetic phases belong to the same crystallographic phase. Both phases can be modelled by planar helimagnetic structures: one with a propagation vector of [0.654(1), 0, 0], the other with a propagation vector of [0.410(1), 0.225(1), 0].

  8. Neutron scattering investigations of frustated magnets

    NASA Astrophysics Data System (ADS)

    Fennell, Tom

    This thesis describes the experimental investigation of frustrated magnetic systems based on the pyrochlore lattice of corner-sharing tetrahedra. Ho2Ti207 and Dy2Ti207 are examples of spin ices, in which the manifold of disordered magnetic groundstates maps onto that of the proton positions in ice. Using single crystal neutron scattering to measure Bragg and diffuse scattering, the effect of applying magnetic fields along different directions in the crystal was investigated. Different schemes of degeneracy removal were observed for different directions. Long and short range order, and the coexistence of both could be observed by this technique.The field and temperature dependence of magnetic ordering was studied in Ho2Ti207 and Dy2Ti207. Ho2Ti2()7 has been more extensively investigated. The field was applied on [00l], [hh0], [hhh] and [hh2h]. Dy2Ti207 was studied with the field applied on [00l] and [hho] but more detailed information about the evolution of the scattering pattern across a large area of reciprocal space was obtained.With the field applied on [00l] both materials showed complete degeneracy removal. A long range ordered structure was formed. Any magnetic diffuse scattering vanished and was entirely replaced by strong magnetic Bragg scattering. At T =0.05 K both materials show unusual magnetization curves, with a prominent step and hysteresis. This was attributed to the extremely slow dynamics of spin ice materials at this temperature.Both materials were studied in greatest detail with the field applied on [hh0]. The coexistence of long and short range order was observed when the field was raised at T = 0.05 K. The application of a field in this direction separated the spin system into two populations. One could be ordered by the field, and one remained disordered. However, via spin-spin interactions, the field restricted the degeneracy of the disordered spin population. The neutron scattering pattern of Dy2Ti207 shows that the spin system was separated

  9. Investigation of condensed matter by means of elastic thermal-neutron scattering

    NASA Astrophysics Data System (ADS)

    Abov, Yu. G.; Dzheparov, F. S.; Elyutin, N. O.; Lvov, D. V.; Tyulyusov, A. N.

    2016-07-01

    The application of elastic thermal-neutron scattering in investigations of condensed matter that were performed at the Institute for Theoretical and Experimental Physics is described. An account of diffraction studies with weakly absorbing crystals, including studies of the anomalous-absorption effect and coherent effects in diffuse scattering, is given. Particular attention is given to exposing the method of multiple small-angle neutron scattering (MSANS). It is shown how information about matter inhomogeneities can be obtained by this method on the basis of Molière's theory. Prospects of the development of this method are outlined, and MSANS theory is formulated for a high concentration of matter inhomogeneities.

  10. Local magnetic moments in a dinuclear Co{sup 2+} complex as seen by polarized neutron diffraction:Beyond the effective spin-(1/2) model

    SciTech Connect

    Borta, Ana; Luneau, Dominique; Jeanneau, Erwann; Gillon, Beatrice; Gukasov, Arsen; Cousson, Alain; Ciumacov, Iurii; Sakiyama, Hiroshi; Tone, Katsuya; Mikuriya, Masahiro

    2011-05-01

    Polarized neutron diffraction investigations of a paramagnetic molecular dinuclear Co{sup 2+} complex, using the local site susceptibility method, show that the Co{sup 2+} ions carry opposite magnetic moments of 3.1(1) and 3.2(1) {mu}{sub B}, making an angle of 37(1) deg. which is in agreement with the value (39 deg.) provided by the theoretical analysis of the magnetic susceptibility using the model of effective spin 1/2. Polarized neutron diffraction (PND) shows that this dinuclear Co{sup 2+} complex behaves more like a system of two antiferromagnetically coupled ions with spin 3/2, the directions of which are imposed by the distortion axis of the octahedra around each Co{sup 2+} ion due to ligand field. This first application of the local susceptibility tensor method to a molecular compound demonstrates the efficiency of the PND method as a tool for exploring magnetic anisotropy in molecular paramagnets.

  11. Study of tempering behavior of lath martensite using in situ neutron diffraction

    SciTech Connect

    Shi, Z.M.; Gong, W.; Tomota, Y.; Harjo, S.; Li, J.; Chi, B.; Pu, J.

    2015-09-15

    To elucidate changes in the density and substructure of dislocations during tempering of lath martensite steel, a convolutional multiple whole-profile fitting method was applied to in situ neutron diffraction profiles. With increasing tempering temperature, the dislocation density scarcely changed in the beginning and then decreased at temperatures above 473 K, whereas the dislocation arrangement drastically changed at temperatures above 673 K. The strength of the steel is speculated to depend on the density and arrangement of dislocations. - Highlights: • A convolutional multiple whole-profile fitting method was applied. • Dislocation density and dislocation arrangement changing with tempering were discussed. • Dislocation density scarcely changed in the beginning. • And then dislocation density decreased at temperatures above 473 K. • The dislocation arrangement drastically changed at temperatures above 673 K.

  12. Neutron diffraction determination of the residual stress redistribution in cracked autofrettaged tubing

    SciTech Connect

    Bourke, M.A. ); McGillivray, H.J.; Webster, G.A. . Dept. of Mechanical Engineering); Webster, P.J. . Dept. of Civil Engineering)

    1991-01-01

    Neutron diffraction has been used to measure the residual stress distributions in uncracked and fatigue cracked rings taken from a high strength, low alloy steel autofrettage tube with a bore diameter of 60mm and a wall thickness of 32mm. Stresses were determined to a precision of {plus minus} 10MPa. Three crack sixes were examines. No appreciable stress redistribution was observed until the crack was grown into a region which originally contained tensile residual hoop stress. When this occurred an increase in residual hoop tension was observed ahead of the crick tip. Qualitative agreement was achieved between the measured hoop stress distribution and values predicted using a boundary element method. 9 refs., 12 figs.

  13. Degradation analysis of 18650-type lithium-ion cells by operando neutron diffraction

    NASA Astrophysics Data System (ADS)

    Shiotani, Shinya; Naka, Takahiro; Morishima, Makoto; Yonemura, Masao; Kamiyama, Takashi; Ishikawa, Yoshihisa; Ukyo, Yoshio; Uchimoto, Yoshiharu; Ogumi, Zempachi

    2016-09-01

    In-situ and operando neutron diffraction are used to analyze the degradation of 18650-type Li-ion cells. Structural characterization of the electrode materials is performed by applying the Rietveld refinement technique to the in-situ data. The structural refinement of both electrodes in the degraded cells indicates that the amount of active Li-ions is reduced by 14.4% and 13.7% in the cathode and anode, respectively. This reduction is good in agreement with the capacity loss determined electrochemically. The results suggest that capacity loss might be mainly caused by loss of active Li-ions due to side reactions such as solid electrolyte interface (SEI) growth. Furthermore, operando measurements are performed to examine the deterioration of the electrode and active materials. Because the structural evolution depending on capacity is increased in the cathode of degraded cells, it is presumed that the cathode active material has deteriorated due to phase transitions.

  14. Strontium environment transition in tin silicate glasses by neutron and x-ray diffraction.

    SciTech Connect

    Johnson, J. A.; Urquidi, D.; Holland, D.; Johnson, C. E.; Appelyard, P. G.; New Mexico State Univ.; LANL; Warwick Univ.; Northern Illinois Univ.; Cranfield Univ.

    2007-11-15

    The effect of Sr modifier atoms on the structure of stannosilicate glasses of composition (Sr0){sub x}(SnO){sub 0.5-x}(SiO{sub 2}){sub 0.5}, with 0 {le} x {le} 0.15, has been studied using Moessbauer spectroscopy and neutron and X-ray diffraction. The tin is mostly in the Sn{sup 2+} state. The Sr-O bond length undergoes a step decrease from (2.640 {+-} 0.005) {angstrom} to (2.585 {+-} 0.005) {angstrom} as x increases from 0.10 to 0.15, indicating a decrease in co-ordination number from 8 to 7. A Sn-Sn distance of 3.507 {+-} 0.005 {angstrom} is revealed by a first-order difference calculation from the x = 0 sample. This is too short to be consistent with significant edge sharing of [SnO{sub 3}] trigonal pyramids.

  15. Neutron diffraction analysis of Nd3Fe29 - xTx (T=Ti, Cr, Mn)

    NASA Astrophysics Data System (ADS)

    Yelon, W. B.; Hu, Z.

    1996-02-01

    Rietveld analysis of neutron-diffraction data from Nd3Fe29-xTx (T=Ti, Cr, and Mn) has been used to determine the location of the substitutional atoms and the magnetic moments. Reanalysis of the T=Ti data confirms that the space group A2/m is a better choice than P21/c, which had previously been used to describe the structure. The Ti atom locations and concentrations remain unaffected in the two space groups, but for the other substituents the refined concentrations are well behaved in A2/m, whereas in P21/c the refinements were unstable due to the symmetry relations between certain substituted sites. The site occupancies are analyzed in terms of steric and environment effects. A possible explanation for the high Curie temperature of the Cr compound is proposed.

  16. Neutron diffraction measurement of internal strain in the first Japanese ITER CS conductor sample

    NASA Astrophysics Data System (ADS)

    Hemmi, T.; Harjo, S.; Nunoya, Y.; Kajitani, H.; Koizumi, N.; Aizawa, K.; Machiya, S.; Osamura, K.

    2013-08-01

    Several conductor samples were fabricated and tested in the SULTAN facility at CRPP for ITER Central Solenoid (CS) conductor qualification. From the result of the cyclic testing on the first and second conductor samples named CSJA01 and CSJA02, continuous linear degradation of the current sharing temperature (Tcs) was found. From the result of the visual inspection, a large deflection on the lower loading side (LLS) in the high field zone (HFZ) was observed. The bending strain of the strands cannot be evaluated from only the deflection obtained visually. To evaluate the strain of strands in CSJA01 quantitatively, a neutron diffraction measurement of the CSJA01 left leg was performed using the engineering materials diffractometer ‘Takumi’ in J-PARC. From the result, the large bending strain at the LLS in the HFZ was found. Therefore, the Tcs degraded position in the conductor sample due to the cyclic testing can be determined.

  17. In-situ monitoring the realkalisation process by neutron diffraction: Electroosmotic flux and portlandite formation

    SciTech Connect

    Castellote, Marta . E-mail: martaca@ietcc.csic.es; Llorente, Irene; Andrade, Carmen; Turrillas, Xavier; Alonso, Cruz; Campo, Javier

    2006-05-15

    Even though the electroosmotic flux through hardened cementitious materials during laboratory realkalisation trials had been previously noticed, it has never been in-situ monitored, analysing at the same time the establishment of the electroosmotic flux and the microstructure changes in the surroundings of the rebar. In this paper, two series of cement pastes, cast with CEM I and CEM I substituted in a 35% by fly ash, previously carbonated at 100% CO{sub 2}, were submitted to realkalisation treatments followed on line by simultaneous acquisition of neutron diffraction data. As a result, it has been possible to confirm the electroosmosis as the driving force of carbonates towards the rebar and to determine the range of pH in the anolyte in which most of the relevant electroosmotic phenomena takes place. On the other hand, the behaviour of the main crystalline phases involved in the process has been monitored during the treatment, with the precipitation of portlandite as main result.

  18. Neutron diffraction on porin, a channel-forming protein in the outer membrane of Escherichia coli

    NASA Astrophysics Data System (ADS)

    Mischel, Maja; Hentschel, Manfred; Rosenbusch, Jüirg P.; BÜldt, Georg

    1986-02-01

    It is known from planar lipid membrane experiments that matrix porin from E. coli outer membrane forms large channels of about 10 Å diameter which open and close dependent on the trans-membrane potential. Transmission electron microscopy on negatively stained two-dimensional porin lattices showed a trimer in the elementary cell. A 3D analysis of these membranes suggests that the three channels per trimer converge as they traverse the membrane. The aim of our neutron diffraction experiments was to locate the channels independently using H 2O/D 2O exchange experiments and model calculations. The common feature of the best fits shows that the main part of the channels is concentrated at the centre of the trimer, in agreement with the EM result.

  19. Neutron diffraction study of U-5.4 wt% Mo alloy

    NASA Astrophysics Data System (ADS)

    Lee, Jeong-Soo; Lee, Chang-Hee; Kim, Ki Hwan; Em, Vyacheslav

    2000-06-01

    The structure of U-5.4 wt% Mo alloy prepared by the centrifugal atomization method and the decomposition of the alloy at elevated temperature were studied. The single uniform γ-phase was obtained after annealing the synthesized alloy at 700°C for 48 h. The homogenized alloy was annealed at 400°C and 500°C to search for an ordered phase and study the decomposition process. No ordered phase in U-5.4 wt% Mo alloy after annealing was observed. With the result from the Rietveld refinement of the neutron diffraction patterns it was concluded that the b parameter of the α-phase is contracted like metastable α'-phase and phase boundary of the α-phase region at 500°C lies near 2.6 at.% Mo.

  20. Accelerated carbonation of cement pastes in situ monitored by neutron diffraction

    SciTech Connect

    Castellote, M. Andrade, C.; Turrillas, X.; Campo, J.; Cuello, G.J.

    2008-12-15

    In-situ monitoring of the changes that take place in the phase composition of cement pastes during accelerated carbonation (100% CO{sub 2}) for different binders, has been carried out, by taking Neutron Diffraction patterns in parallel with the carbonation experiments. The variation of the intensity of chosen reflections for each phase along the experiment has been used to monitor concentration changes and has supplied data, in real time, for fractional conversion of different phases (Portlandite, Ettringite and CSH gel) of the hydrated cement pastes. Fitting of these results has allowed to make a qualitative approach to the kinetics of the carbonation of the different phases and extracting conclusions on the microstructural changes that takes place during the carbonation of cement pastes.

  1. Applications of pulsed neutron powder diffraction to actinide elements. [Pu-Al

    SciTech Connect

    Lawson, A.C.; Richardson, J.W.; Mueller, M.H.; Lander, G.H.; Goldstone, J.A.; Williams, A.; Kwei, G.H.; Von Dreele, R.B.; Faber, J. Jr.; Hitterman, R.L.

    1987-11-01

    We have been using the technique of pulsed neutron powder diffraction to study several problems in the physics and chemistry of the actinide elements. In these elements one often encounters very complex structures resulting from polymorphic transformations presumably induced by the presence of 5f-electrons. For example, at least five distinct structures of plutonium metal are found between room temperature and its melting point of 640/sup 0/C, and two of the structures are monoclinc. The determination of the crystal structure of beta-uranium (tetragonal, 30 atoms per unit cell) which has finnaly been shown to be centrosymmetric, after decades of uncertainty is discussed. Some preliminary results on the structure of alpha-plutonium (which confirm Zachariasen's original determination of the monoclinic structure) are presented. Pu-Al alloys were also studied. 12 refs., 18 figs.

  2. Fast and simple method for Goss texture evaluation by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Kucerakova, M.; Kolařík, K.; Čapek, J.; Vratislav, S.; Kalvoda, L.

    2016-09-01

    Requirement of low power losses is one of the crucial demands laid on properties of electric steel sheets used in construction of various magnetic circuits. For cold-rolled grain- oriented (CRGO) Fe-3%Si sheets used in majority of power distribution transformers, the Goss texture {110}<001> is known to provide the best utility properties (low power loses, high magnetic permeability). Due to the coarse grain size of CRGO steel, neutron diffraction (ND) is dominantly used to characterize the sheets' texture in order to achieve statistically significant data. In this paper, we present a fast and simple method for characterization of Goss texture perfection level in CRGO steel sheets based on monochromatic ND. The method is tested on 8 samples differing in fabrication technology and magnetic properties. Satisfactory performance of the method and its suitability for a detail texture analyses is tested by juxtaposition of the obtained textural and the magnetic characteristics measured by Barkhausen method.

  3. Prompt gamma activation analysis of boron in reference materials using diffracted polychromatic neutron beam

    NASA Astrophysics Data System (ADS)

    Byun, S. H.; Sun, G. M.; Choi, H. D.

    2004-01-01

    Boron concentrations were analyzed for standard reference materials by prompt gamma activation analysis (PGAA). The measurements were performed at the SNU-KAERI PGAA facility installed at Hanaro, the research reactor of Korea Atomic Energy Research Institute (KAERI). The facility uses a diffracted polychromatic beam with a neutron flux of 7.9 × 10 7 n/cm 2 s. Elemental sensitivity for boron was calibrated from the prompt gamma-ray spectra of boric acid samples containing 2-45 μg boron. The sensitivity of 2131 cps/mg-B was obtained from the linearity of the boron peak count rate versus the boron mass. The detection limit for boron was estimated to be 67 ng from an empty sample bag spectrum for a counting time of 10,000 s. The measured boron concentrations for standard reference materials showed good consistency with the certified or information values.

  4. Plastic ice in confined geometry: the evidence from neutron diffraction and NMR relaxation

    NASA Astrophysics Data System (ADS)

    Webber, J. Beau W.; Dore, John C.; Strange, John H.; Anderson, Ross; Tohidi, Bahman

    2007-10-01

    Neutron diffraction and nuclear magnetic resonance (NMR) relaxation studies have been made of water/ice in mesoporous SBA-15 silica with ordered structures of cylindrical mesopores with a pore diameter ~8.6 nm, over the temperature range 180-300 K. Both measurements show similar depressed freezing and melting points due to the Gibb-Thomson effect. The neutron diffraction measurements for fully filled pores show, in addition to cubic and hexagonal crystalline ice, the presence of a disordered water/ice component extending a further 50-80 K, down to around or below 200 K. NMR relaxation measurements over the same temperature range show a free induction decay that is partly Gaussian and characteristic of brittle ice but that also exhibits a longer exponential relaxation component. An argument has been made (Liu et al 2006 J. Phys:. Condens. Matter 18 10009-28 Webber et al 2007 Magn. Reson. Imag. 25 533-6) to suggest that this is an observation of ice in a plastic or rotationally mobile state, and that there is a fully reversible inter-conversion between brittle and plastic states of ice as the temperature is lowered or raised. More recent detailed NMR measurements are also discussed that allow the extraction of activation enthalpies and an estimate to be made of the equilibrium thickness, as a function of temperature, if the the assumption is made that the plastic component is in the form of a layer at the silica interface. The two different techniques suggest a maximum layer thickness of about 1.0-1.5 nm.

  5. High-Pressure Neutron Diffraction Study on H-D Isotope Effects in Brucite

    SciTech Connect

    Horita, Juske; Chakoumakos, Bryan C; dos Santos, Antonio M.; Tulk, Christopher A; Polyakov, Dr. Veniamin B

    2010-01-01

    A neutron powder diffraction study of hydrogenated and deuterated brucite was conducted at ambient temperature and at pressures to 9 GPa, using a Paris-Edinburgh high-pressure cell at the WAND instrument of ORNL High Flux Isotope Reactor. The two materials were synthesized by the same method and companion measurements of neutron diffraction were conducted under the same conditions. Our refinement results show that the lattice-parameters of the a axis, parallel to the sheets of Mg-O octahedra, decreases only slightly with pressure with no effect of H-D substitution. However, the c axis of Mg(OD)2 is shorter and decreases more rapidly than that of Mg(OH)2 with increasing pressure. Consequently, the unit-cell volume of deuterated brucite is slightly, but systematically smaller than that of normal brucite, which were fitted to third-order Birch-Murnaghan equation: K0=41.46 0.52 and 39.04 0.30 GPa for Mg(OH)2 and Mg(OD)2, respectively with a fixed K0 value of 10. Our results suggest that H-D substitution of brucite and other hydrous minerals with H-bonding likely influences their structural and dynamic properties under pressure, including the position of hydrogen atoms. The measured effect of H-D substitution on the unit-cell volume also demonstrates that brucite (and other hydrous minerals) preferentially incorporate deuterium over hydrogen under pressure, suggesting that the distribution of hydrogen isotopes in deep-earth conditions may differ significantly from that in near-surface environments.

  6. Neutron and X-ray diffraction study on the hydrous SiO2 glass under pressure

    NASA Astrophysics Data System (ADS)

    Urakawa, S.; Inoue, T.; Hattori, T.; Sano, A.; Kikegawa, T.; Funakoshi, K. I.; Mibe, K.; Kohara, S.

    2015-12-01

    Water has significant effects on the physical properties and the structure of silicate melts. Studies on hydrous silicate melts are, therefore, important to understand the magma-related phenomena of the planetary interior. Neutron has an advantage over X-ray to study the structure of hydrous melts. We have developed the high-pressure neutron diffraction method on the amorphous silicates with water at the PLANTE beamline of MLF, J-PARC. Here we report the results of in-situ neutron diffraction experiments on the hydrous silica glass at room temperature up to 10 GPa as well as X-ray diffraction study. Hydrous silica glass was synthesized by quenching from liquid at 3 GPa, in which D2O content is 13 wt.%. Neutron diffraction experiments were carried out at BL11 of MLF, J-PARC and X-ray studies were done at BL04B2 of SPring-8 and AR-NE5 of Photon Factory. On the neutron and X-ray spectra, the FSDP of hydrous glass locates at the higher Q-side than dry one, indicating the breakdown of network structure of silica glass by an addition of water. The FSDP shifts toward higher-Q side with increasing pressure parallel to that of dry silica glass. The radial distribution functions shows that the SiO4 unit does not change up to 10 GPa but the Si-Si-distance decreases with pressure. These show that the intermediate range order, which consists of the network of SiO4 tetrahedra, shrinks with increasing pressure. The changes of silica framework with pressure in hydrous silica glass are similar to those in dry silica glass. On the other hand, neutron diffraction shows the D-O distance in hydrous silica glass is nearly constant up to 10 GPa.

  7. Rearrangement of twin variants in ferromagnetic shape memory alloy polyurethane composites studied by stroboscopic neutron diffraction

    NASA Astrophysics Data System (ADS)

    Feuchtwanger, J.; Lázpita, P.; Vidal, N.; Barandiaran, J. M.; Gutiérrez, J.; Hansen, T.; Peel, M.; Mondelli, C.; O'Handley, R. C.; Allen, S. M.

    2008-03-01

    The use of ferromagnetic shape memory alloy (FSMA) particles as fillers in polymeric matrix composites has been proposed for vibration damping. The large pseudo-plastic recoverable deformation of the FSMA particles due to the rearrangement of twin variants can dissipate a large amount of energy, both under compression and tension. The composites studied are made by mixing particles of NiMnGa with a polyurethane matrix. A magnetic field is applied to the composite while the matrix sets, to achieve a strong [112] texture in the field direction. In situ strobed neutron diffraction measurements were carried out while the composites were subjected to a cyclic deformation. They show that the intensity of certain peaks varies during the deformation cycle. All the peaks that show this behavior can be grouped into pairs that stem from a single austenitic peak. The (020) and (112) martensite peaks correspond to the splitting of the (220) austenite peak, and the intensity of one increases as that of the other decreases. The neutron measurements show directly that there is a change in the texture of the composite during the stress cycle applied to the composite and confirm that the large mechanical loss observed in the stress-strain cycles is in good part due to the rearrangement of twin variants in the FSMA filler used in the composites.

  8. The intermolecular hydrogen-hydrogen structure of chain-molecule liquids from neutron diffraction

    NASA Astrophysics Data System (ADS)

    Londono, J. D.; Annis, B. K.; Turner, J. Z.; Soper, A. K.

    1994-11-01

    Neutron diffraction isotopic substitution experiments on liquid n-decane (C10H22) and n-eicosane (C20H42) are described. The intermolecular H-H structure function hHH(Q) and the intermolecular H-H correlation function ginterHH(r) are obtained without recourse to models of the intramolecular structure. The structure of the ginterHH(r) found at 2.5, 5.0, and 7.0 Å corresponds to different shells in the H-H pair correlation function. In addition, ginterHH(r)<1 for a considerable range, due to the screening of intermolecular correlations by intramolecular correlations. This ``correlation hole'' effect is accentuated by extrapolation of the structure functions to the expected infinite wavelength limit, and shows good agreement with values determined from small-angle neutron scattering (SANS) data. All of these features are in good agreement with the results of molecular dynamics simulations for the closely related system C13H28.

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

    SciTech Connect

    S. M. Bhat, Swetha; Swain, Diptikanta; Feygenson, Mikhail; Neuefeind, Joerg C; Sundaram, Nalini

    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.

  10. Neutron diffraction study of a non-strichiometric Ni-Mn-Ga MSM alloy

    SciTech Connect

    Ari-Gur, Pnina; Garlea, Vasile O

    2013-01-01

    The structure and chemical order of a Heusler alloy of non-stoichiometric composition Ni-Mn-Ga were studied using constant-wavelength (1.538 ) neutron diffraction at 363K and the diffraction pattern was refined using the FullProf software. At this temperature the structure is austenite (cubic) with Fm-3m space group and lattice constant of a = 5.83913(4) [ ]. The chemical order is of critical importance in these alloys, as Mn becomes antiferromagnetic when the atoms are closer than the radius of the 3d shell. In the studied alloy the refinement of the site occupancy showed that the 4b (Ga site) contained as much as 22% Mn; that significantly alters the distances between the Mn atoms in the crystal and, as a result, also the exchange energy between some of the Mn atoms. Based on the refinement, the composition was determined to be Ni1.91Mn1.29Ga0.8

  11. Uranium and thorium hydride complexes as multielectron reductants: a combined neutron diffraction and quantum chemical study.

    PubMed

    Grant, Daniel J; Stewart, Timothy J; Bau, Robert; Miller, Kevin A; Mason, Sax A; Gutmann, Matthias; McIntyre, Garry J; Gagliardi, Laura; Evans, William J

    2012-03-19

    The unusual uranium reaction system in which uranium(4+) and uranium(3+) hydrides interconvert by formal bimetallic reductive elimination and oxidative addition reactions, [(C(5)Me(5))(2)UH(2)](2) (1) ⇌ [(C(5)Me(5))(2)UH](2) (2) + H(2), was studied by employing multiconfigurational quantum chemical and density functional theory methods. 1 can act as a formal four-electron reductant, releasing H(2) gas as the byproduct of four H(2)/H(-) redox couples. The calculated structures for both reactants and products are in good agreement with the X-ray diffraction data on 2 and 1 and the neutron diffraction data on 1 obtained under H(2) pressure as part of this study. The interconversion of the uranium(4+) and uranium(3+) hydride species was calculated to be near thermoneutral (~-2 kcal/mol). Comparison with the unknown thorium analogue, [(C(5)Me(5))(2)ThH](2), shows that the thorium(4+) to thorium(3+) hydride interconversion reaction is endothermic by 26 kcal/mol.

  12. A comparison of dilatometry and in-situ neutron diffraction in tracking bulk phase transformations in a martensitic stainless steel

    SciTech Connect

    Christien, F.; Telling, M.T.F.; Knight, K.S.

    2013-08-15

    Phase transformations in the 17-4PH martensitic stainless steel have been studied using different in-situ techniques, including dilatometry and high resolution neutron diffraction. Neutron diffraction patterns were quantitatively processed using the Rietveld refinement method, allowing the determination of the temperature-dependence of martensite (α′, bcc) and austenite (γ, fcc) phase fractions and lattice parameters on heating to 1000 °C and then cooling to room temperature. It is demonstrated in this work that dilatometry doesn't permit an accurate determination of the end temperature (Ac3) of the α′ → γ transformation which occurs upon heating to high temperature. The analysis of neutron diffraction data has shown that the respective volumes of the two phases become very close to each other at high temperature, thus making the dilatometric technique almost insensitive in that temperature range. However, there is a very good agreement between neutron diffraction and dilatometry at lower temperature. The martensitic transformation occurring upon cooling has been analysed using the Koistinen–Marburger equation. The thermal expansion coefficients of the two phases have been determined in addition. A comparison of the results obtained in this work with data from literature is presented. - Highlights: • Martensite is still present at very high temperature (> 930 °C) upon heating. • The end of austenitisation cannot be accurately monitored by dilatometry. • The martensite and austenite volumes become similar at high temperature (> ∼ 850 °C)

  13. Determination and mitigation of the uncertainty of neutron diffraction measurements of residual strain in large-grained polycrystalline material

    PubMed Central

    Holden, Tom M.; Traore, Yeli; James, Jon; Kelleher, Joe; Bouchard, P. John

    2015-01-01

    For large-grained samples it is advantageous to perform pairs of neutron diffraction measurements at the same spatial location but rotated 180° around the geometric centre of the gauge volume as a means of minimizing the scatter coming from the random positioning of grains within the gauge volume. PMID:25844082

  14. Hippo/crates-in-situ deformation strain and testure studies using neutron time-of-flight diffraction.

    SciTech Connect

    Vogel, S. C.; Hartig, C.; Brissier, T. D.; Mecking, H.

    2005-01-01

    In situ deformation studies by diffraction allow studying of deformation mechanisms and provide valuable data to validate and improve deformation models. In particular, deformation studies using time-of-flight neutrons provide averages over large numbers of grains and allow to probing the response of lattice planes parallel and perpendicular to the applied load simultaneously. In this paper we describe the load-frame CRATES, designed for the HIPPO neutron time-of-flight diffractometer at LANSCE. The HIPPO/CRATES combination allows probing up to 20 diffraction vectors simultaneously and provides rotation of the sample in the beam while under load. With this, deformation texture, i.e. the change of grain orientation due to plastic deformation, or strain pole figures may be measured. We report initial results of a validation experiment, comparing deformation of a Zircaloy specimen measured using the NPD neutron diffractometer with results obtained for the same material using HIPPO/CRATES.

  15. Investigating the Defect Structures in Transparent Conducting Oxides Using X-ray and Neutron Scattering Techniques

    SciTech Connect

    González, Gabriela B.

    2012-10-23

    Transparent conducting oxide (TCO) materials are implemented into a wide variety of commercial devices because they possess a unique combination of high optical transparency and high electrical conductivity. Created during the processing of the TCOs, defects within the atomic-scale structure are responsible for their desirable optical and electrical properties. Therefore, studying the defect structure is essential to a better understanding of the behavior of transparent conductors. X-ray and neutron scattering techniques are powerful tools to investigate the atomic lattice structural defects in these materials. This review paper presents some of the current developments in the study of structural defects in n-type TCOs using x-ray diffraction (XRD), neutron diffraction, extended x-ray absorption fine structure (EXAFS), pair distribution functions (PDFs), and x-ray fluorescence (XRF).

  16. Fatigue-induced Reversible/Irreversible Structural-transformation Study of a Ni-based Superalloy Using Combined In-situ Neutron-Diffraction and Thermal Approaches

    SciTech Connect

    Huang, E-Wen; Barabash, Rozaliya; Clausen, Bjorn; Liu, Yee-Lang; Kai, Ji-Jung; Ice, Gene E; Woods, Kyle P.; Liaw, Peter K

    2010-01-01

    Cyclic loading and the subsequent fatigue damage have been investigated with the in-situ neutron-diffraction and thermal characterization for a single-phase, polycrystal nickel-based alloy. The lattice-strain evolution is compared with the bulk parameters, such as the applied stress and the thermal response as a function of the fatigue cycles. The in-situ neutron-diffraction and thermal-evolution results identify the development of the five fatigue-damage stages. Fatigue damage is observed with bulk hardening, softening, and eventual saturation evident in both the diffraction patterns and the thermal-evolution features. An increase in the dislocation density and the formation of the patterned-dislocation structure are responsible for hardening within the early cycles. With further cyclic loading, the rearrangements of the dislocations result in the cyclic softening. The transition to saturation cycles is characterized by the anisotropy of the lattice strain evolution. The nonmonotonic thermal response and the irreversible anisotropy of the lattice-strain evolution are observed in the final saturation fatigue cycles. The fatigue-damage microstructure and dislocation-substructure evolution are studied with diffraction-profile analyses and complemented by the transmission-electron microscopy. The fluctuations of the differential dislocation density and size of the patterned substructure along with the in-situ thermal measurements reveal a second-order-kind structural transition and indicate the development of the irreversible fatigue-induced microstructure.

  17. Neutron diffraction measurements and micromechanical modelling of temperature-dependent variations in TATB lattice parameters

    DOE PAGES

    Yeager, John D.; Luscher, Darby J.; Vogel, Sven C.; Clausen, Bjorn; Brown, Donald W.

    2016-02-02

    Triaminotrinitrobenzene (TATB) is a highly anisotropic molecular crystal used in several plastic-bonded explosive (PBX) formulations. TATB-based explosives exhibit irreversible volume expansion (“ratchet growth”) when thermally cycled. A theoretical understanding of the relationship between anisotropy of the crystal, crystal orientation distribution (texture) of polycrystalline aggregates, and the intergranular interactions leading to this irreversible growth is necessary to accurately develop physics-based predictive models for TATB-based PBXs under various thermal environments. In this work, TATB lattice parameters were measured using neutron diffraction during thermal cycling of loose powder and a pressed pellet. The measured lattice parameters help clarify conflicting reports in the literaturemore » as these new results are more consistent with one set of previous results than another. The lattice parameters of pressed TATB were also measured as a function of temperature, showing some differences from the powder. This data is used along with anisotropic single-crystal stiffness moduli reported in the literature to model the nominal stresses associated with intergranular constraints during thermal expansion. The texture of both specimens were characterized and the pressed pellet exhibits preferential orientation of (001) poles along the pressing direction, whereas no preferred orientation was found for the loose powder. Lastly, thermal strains for single-crystal TATB computed from lattice parameter data for the powder is input to a self-consistent micromechanical model, which predicts the lattice parameters of the constrained TATB crystals within the pellet. The agreement of these model results with the diffraction data obtained from the pellet is discussed along with future directions of research.« less

  18. Investigations on landmine detection by neutron-based techniques.

    PubMed

    Csikai, J; Dóczi, R; Király, B

    2004-07-01

    Principles and techniques of some neutron-based methods used to identify the antipersonnel landmines (APMs) are discussed. New results have been achieved in the field of neutron reflection, transmission, scattering and reaction techniques. Some conclusions are as follows: The neutron hand-held detector is suitable for the observation of anomaly caused by a DLM2-like sample in different soils with a scanning speed of 1m(2)/1.5 min; the reflection cross section of thermal neutrons rendered the determination of equivalent thickness of different soil components possible; a simple method was developed for the determination of the thermal neutron flux perturbation factor needed for multi-elemental analysis of bulky samples; unfolded spectra of elastically backscattered neutrons using broad-spectrum sources render the identification of APMs possible; the knowledge of leakage spectra of different source neutrons is indispensable for the determination of the differential and integrated reaction rates and through it the dimension of the interrogated volume; the precise determination of the C/O atom fraction requires the investigations on the angular distribution of the 6.13MeV gamma-ray emitted in the (16)O(n,n'gamma) reaction. These results, in addition to the identification of landmines, render the improvement of the non-intrusive neutron methods possible.

  19. Phase transitions and hydrogen bonding in deuterated calcium hydroxide: High-pressure and high-temperature neutron diffraction measurements

    SciTech Connect

    Iizuka, Riko; Komatsu, Kazuki; Kagi, Hiroyuki; Nagai, Takaya; Sano-Furukawa, Asami; Hattori, Takanori; Gotou, Hirotada; Yagi, Takehiko

    2014-10-15

    In situ neutron diffraction measurements combined with the pulsed neutron source at the Japan Proton Accelerator Research Complex (J-PARC) were conducted on high-pressure polymorphs of deuterated portlandite (Ca(OD){sub 2}) using a Paris–Edinburgh cell and a multi-anvil press. The atomic positions including hydrogen for the unquenchable high-pressure phase at room temperature (phase II′) were first clarified. The bent hydrogen bonds under high pressure were consistent with results from Raman spectroscopy. The structure of the high-pressure and high-temperature phase (Phase II) was concordant with that observed previously by another group for a recovered sample. The observations elucidate the phase transition mechanism among the polymorphs, which involves the sliding of CaO polyhedral layers, position modulations of Ca atoms, and recombination of Ca–O bonds accompanied by the reorientation of hydrogen to form more stable hydrogen bonds. - Graphical abstract: Crystal structures of high-pressure polymorphs of Ca(OD){sub 2}, (a) at room temperature (phase II′) and (b) at high temperature (phase II), were obtained from in situ neutron diffraction measurements. - Highlights: • We measured in situ neutron diffraction of high-pressure polymorphs of Ca(OD){sub 2}. • Hydrogen positions of the high-pressure phase are first determined. • The obtained hydrogen bonds reasonably explain Raman peaks of OH stretching modes. • A phase transition mechanism among the polymorphs is proposed.

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

    SciTech Connect

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

    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.

  1. In-situ neutron diffraction analysis of deformation behavior of ductile rare-earth intermetallic yttrium-copper

    NASA Astrophysics Data System (ADS)

    Williams, Scott H.

    Intermetallic compounds exhibit favorable properties for numerous diverse engineering applications. Many intermetallic compounds possess high strength and high stiffness at elevated temperature, excellent corrosion resistance, and low density, making them potentially useful in a wide range of applications. However, several drawbacks, limited ductility in particular, have prevented these compounds from achieving wide-spread application. In order to make full use of potential of intermetallic compounds, these limitations must be better understood and overcome. In the search for improved ductility in intermetallics, recent findings from an Ames Laboratory research group have uncovered an entire family of compounds possessing the B2 structure which exhibit room temperature tensile ductility. These materials do not require third-element additions, off-stoichiometric chemistry, disordering, or elaborate environmental testing conditions to enhance ductility. Previous studies have investigated various structural and physical properties of this family of compounds, yet the mechanisms for ductility remain uncertain. Low temperature phase transformations are known to occur in several of these compounds. Suggestions for possible mechanisms have included stress-induced phase transformation, as well as the deformation accommodated through crystallographic twinning. In-situ neutron diffraction allows for observations of structural changes and the relationship to macroscopic physical properties. Using this investigation technique, experiments have been conducted to examine rare-earth intermetallic YCu for evidence of phase transformation, twinning, or indications of other deformation behavior. Results give insight into the crystal structure of the compound, indicating a high degree of crystal lattice coherency, and resulting dynamical diffraction behavior not commonly observed in engineering materials.

  2. Magnetostructural phase transitions in NiO and MnO: Neutron diffraction data

    NASA Astrophysics Data System (ADS)

    Balagurov, A. M.; Bobrikov, I. A.; Sumnikov, S. V.; Yushankhai, V. Yu.; Mironova-Ulmane, N.

    2016-07-01

    Structural and magnetic phase transitions in NiO and MnO antiferromagnets have been studied by high-precision neutron diffraction. The experiments have been performed on a high-resolution Fourier diffractometer (pulsed reactor IBR-2), which has the record resolution for the interplanar distance and a high intensity in the region of large interplanar distances; as a result, the characteristics of both transitions have been determined simultaneously. It has been shown that the structural and magnetic transitions in MnO occur synchronously and their temperatures coincide within the experimental errors: T str ≈ T mag ≈ (119 ± 1) K. The measurements for NiO have been performed with powders with different average sizes of crystallites (~1500 nm and ~138 nm). It has been found that the transition temperatures differ by ~50 K: T str = (471 ± 3) K, T mag = (523 ± 2) K. It has been argued that a unified mechanism of the "unsplit" magnetic and structural phase transition at a temperature of T mag is implemented in MnO and NiO. Deviation from this scenario in the behavior of NiO is explained by the quantitative difference—a weak coupling between the magnetic and secondary structural order parameters.

  3. Residual Stresses in DC cast Aluminum Billet: Neutron Diffraction Measurements and Thermomechanical Modeling

    SciTech Connect

    Drezet, J.-M.; Evans, A.; Pirling, T.

    2011-05-04

    Thermally-induced residual stresses, generated during the industrial Direct Chill casting process of aluminum alloys, can cause both significant safety concerns as well as the formation of defects during down-stream processing. Although these thermally induced strains can be partially relieved by permanent deformation, cracks will be generated either during solidification (hot tears) or post-solidification cooling (cold cracks) when stresses exceed the deformation limit of the alloy. Furthermore, the thermally induced strains result in the presence of large internal stresses within the billet before further processing steps. Although numerical models have been previously developed to compute these residual stresses, most of the computations have been validated only against measured surface distortions. In the present work, the variation in residual elastic strains and stresses in the steady state regime of casting has been measured as a function of radial position using neutron diffraction in an AA6063 grain-refined cylindrical billet. These measurements have been carried out on the same billet section at Poldi at PSI-Villigen and at Salsa at ILL-Grenoble and compare favorably. The results are used to validate a thermo-mechanical finite element casting model and to assess the level of stored elastic energy within the billet.

  4. Submarine lava flow direction revealed by neutron diffraction analysis in mineral lattice orientation

    NASA Astrophysics Data System (ADS)

    Zucali, M.; Fontana, E.; Panseri, M.; Tartarotti, P.; Capelli, S.; Ouladdiaf, B.

    2014-03-01

    ocean crust is formed by the rising of magma from mid-ocean ridges and voluminous (1-30 km3) flows of lava away from ridge axes. However, our understanding of the emplacement kinematics of submarine lava is often limited to plan view geometries of near-axis lava. Drilled cores provide in situ access to the intact internal structure of submarine lavas. We used neutron diffraction to study off-axis lava flows drilled into the uppermost crust of ODP/IODP-Site 1256 (Cocos Plate). We provide quantitative insights into submarine lava microstructures and strong evidence for a secondary lava injection into the interior of a solidifying flow of lava along the NW-SE direction parallel to the paleo-ridge axis of the East Pacific Rise. The dynamics of lava inflow are controlled by crystal abundance and the temperature of the lava-crystal mixture rather than by local seafloor topography. We provide a description of an in situ shear within submarine lavas revealed by composite shape and lattice preferred orientations, accounting for a dominant laminar nonuniform-type flow.

  5. Monitoring in situ stress/strain behaviour during plastic yielding in polymineralic rocks using neutron diffraction

    NASA Astrophysics Data System (ADS)

    Covey-Crump, S. J.; Schofield, P. F.; Stretton, I. C.; Daymond, M. R.; Knight, K. S.; Tant, J.

    2013-02-01

    Attempts to use rock deformation experiments to examine the elastic and plastic behaviour of polymineralic rocks are hampered by the fact that usually only whole sample properties can be monitored as opposed to the separate contribution of each phase. To circumvent this difficulty, room-temperature, uniaxial compression experiments were performed in a neutron beam-line on a suite of calcite + halite samples with different phase volume proportions. By collecting diffraction data during loading, the elastic strain and hence stress in each phase was determined as a function of load to bulk strains of 1-2%. In all cases, the calcite behaved elastically while the halite underwent plastic yielding. During the fully elastic part of the deformation, the composite elastic properties and the within-phase stresses are well-described both by recent shear lag models and by analyses based on Eshelby's solution for the elastic field around an ellipsoidal inclusion in a homogeneous medium. After the onset of yielding, the halite in situ stress/total strain curve may be reconstructed using the rule of mixtures. At calcite contents of greater than 30%, the in situ halite response may be significantly weaker or stronger than that obtained at lesser calcite contents. The results highlight the potential that such techniques offer for developing an explicitly experimental approach for determining the influence of microstructural variables on the mechanical properties of polymineralic rocks.

  6. Neutron diffraction study of MnNiGa{sub 2}—Structural and magnetic behaviour

    SciTech Connect

    Wang, J. L.; Ma, L.; Wu, G. H.; Hofmann, M.; Avdeev, M.; Kennedy, S. J.; Campbell, S. J.; Md Din, M. F.; Dou, S. X.; Hoelzel, M.

    2014-05-07

    MnNiGa{sub 2} crystallizes in the L21 (Heusler) structure and has a ferromagnetic ordering temperature T{sub C} ∼ 192 K. Rietveld refinement of the neutron diffraction patterns indicates that the Ga atoms occupy the equivalent 8c position, while Mn and Ni share the 4a (0, 0, 0) and 4b (0.5, 0.5, 0.5) sites with a mixed occupancy of Mn and Ni atoms. It is found that that ∼83% of Mn and ∼17% Ni are located at the 4a site while ∼83% of Ni and ∼17% Mn occupy the 4b site. There is no evidence of a magneto-volume effect around T{sub C}. In agreement with this finding, our detailed critical exponent analyses of isothermal magnetization curves and the related Arrott plots confirm that the magnetic phase transition at T{sub C} is second order.

  7. Neon Hydrate at High Pressure: an in-situ Neutron Diffraction Study

    NASA Astrophysics Data System (ADS)

    Yu, Xiaohui

    2013-03-01

    Clathrate hydrates are a group of ice-like, crystalline inclusion compounds which form through the combination of water and suitably sized ``guest'' molecules. There are mainly three crystallographic structures of the hydrate clathrate: SI, SII and SH, which are determined by the shape and size of the included gas molecular. However, when the neon gas pressure got increased to 0.48 GPa, we found that the neon gas could be enclathrate in the ice II frameworks which is totally different structure from the traditional cubic clathrate. Through the in-situ neutron diffraction study, the detail structure of Ne hydrate, including the atom positions, can be derived using the Rietveld refinements. The Ne atoms are just in the middle of H2O channels and sandwiches by two H2O rings The thermal equation of state was calculated and compared with pure ice II. We found that inclusion of Ne atoms could enlarge the ice II H2O hexagonal rings, however, shortened the H2O channels. Although the Ne atoms crystallized in ice II frameworks, the thermal vibration is significant compared to the host atoms. The distribution of Ne atoms are presented by MD simulations.

  8. Collinear antiferromagnetism in trigonal SrMn2As2 revealed by single crystal neutron diffraction

    NASA Astrophysics Data System (ADS)

    Kreyssig, A.; Das, P.; Sangeetha, N. S.; Benson, Z. A.; Heitman, T.; Johnston, D. C.; Goldman, A. I.

    FeAs-based compounds and related materials have been an area of intense research in understanding the complex interplay between magnetism and superconductivity. Here we report on the magnetic structure of SrMn2As2 that crystallizes in a trigonal structure (P 3 m1) and undergoes an antiferromagnetic (AFM) transition at TN ~ 120 K. The temperature dependence of the magnetic susceptibility remains nearly constant below TN with H ∥ c while it decreases significantly with H ∥ ab . This shows that the local Mn moments order and lie in the ab plane instead of aligning along the c axis as in BaMn2As2. Single crystal neutron diffraction measurements on SrMn2As2 determined that the Mn moments are collinearly aligned in a G-type AFM order with AFM alignments between a moment and all nearest neighbors in the basal plane and also perpendicular to it. This manifests that G-type AFM order is robust for Mn122 systems despite different symmetries, i.e. tetragonal for BaMn2As2 and trigonal for SrMn2As2.Work at Ames Laboratory was supported by the DOE, BES, Division of Materials Sciences & Engineering, through DE-AC02-07CH11358. This research used resources at University of Missouri Research Reactor.

  9. A new layered perovskite, KSrNb2O6F, by powder neutron diffraction.

    PubMed

    Yoo, Chung Yul; Hong, Kun Pyo; Kim, Seung Joo

    2007-08-01

    The structure of a new layered oxyfluoride, viz. potassium strontium diniobium hexaoxide fluoride, KSrNb(2)O(6)F, was refined from powder neutron diffraction data in the orthorhombic space group Immm. The oxyfluoride compound is an n = 2 member of the Dion-Jacobson-type family of general formula A[A'(n-1)B(n)X(3n+1)], which consists of double layered perovskite slabs, [SrNb(2)O(6)F](-), between which K(+) ions are located. Within the perovskite slabs, the NbO(5)F octahedra are significantly distorted and tilted about the a axis. A bond-valence-sum calculation gives evidence for O/F ordering in KSrNb(2)O(6)F, with the F(-) ions located in the central sites of the corner-sharing NbO(5)F octahedra along the b axis. All atoms lie on special positions, namely Nb on m, Sr on mmm, K on m2m, F on mm2, and O on sites of symmetry m and m2m.

  10. Three-Orthogonal-Direction Stress Mapping around a Fatigue-Crack Tip Using Neutron Diffraction

    NASA Astrophysics Data System (ADS)

    Huang, E.-Wen; Lee, Soo Yeol; Woo, Wanchuck; Lee, Kuan-Wei

    2012-08-01

    Quantitative determination of the stress fields around the crack tip is a challenging and important subject to understand the fatigue crack-growth mechanism. In the current study, we measured the distribution of residual stresses and the evolution of the stress fields around a fatigue crack tip subjected to the constant-amplitude cyclic loading in a 304L stainless steel compact-tension (CT) specimen. The three orthogonal stress components ( i.e., crack growth, crack opening, and through thickness) of the CT specimen were determined as a function of distance from the crack tip with 1-mm spatial resolution along the crack-propagation direction. In-situ neutron-diffraction results show that the enlarged tensile stresses were developed during loading along the through-thickness direction at a localized volume close to the crack tip, resulting in the lattice expansion in all three orthogonal directions during P max. The current study suggests that the atypical plane strainlike behavior observed at the midthickness position might be the reason for the mechanism of the faster crack-growth rate inside the interior than that near the surface.

  11. Residual Stresses in DC cast Aluminum Billet: Neutron Diffraction Measurements and Thermomechanical Modeling

    NASA Astrophysics Data System (ADS)

    Drezet, J.-M.; Evans, A.; Pirling, T.

    2011-05-01

    Thermally-induced residual stresses, generated during the industrial Direct Chill casting process of aluminum alloys, can cause both significant safety concerns as well as the formation of defects during down-stream processing. Although these thermally induced strains can be partially relieved by permanent deformation, cracks will be generated either during solidification (hot tears) or post-solidification cooling (cold cracks) when stresses exceed the deformation limit of the alloy. Furthermore, the thermally induced strains result in the presence of large internal stresses within the billet before further processing steps. Although numerical models have been previously developed to compute these residual stresses, most of the computations have been validated only against measured surface distortions. In the present work, the variation in residual elastic strains and stresses in the steady state regime of casting has been measured as a function of radial position using neutron diffraction in an AA6063 grain-refined cylindrical billet. These measurements have been carried out on the same billet section at Poldi at PSI-Villigen and at Salsa at ILL-Grenoble and compare favorably. The results are used to validate a thermo-mechanical finite element casting model and to assess the level of stored elastic energy within the billet.

  12. Residual stress measurements in forced convective quenched steel bars by means of neutron diffraction

    SciTech Connect

    Hernandez-Morales, B.; Hawbolt, B.E.; Brimacombe, J.K.

    1996-12-31

    The residual stress distributions in 38.1 mm-dia., forced convective quenched bars of interstitial-free (IF), 1045 carbon, and alloyed steels were determined by neutron diffraction. The IF and 1045 carbon steel quenched bars exhibited compressive axial and circumferential (hoop) residual stresses near the surface and tensile values at the center. The radial residual stresses were tensile at all radial positions, decreasing towards zero near the surface. In contrast, the measured axial and circumferential components of the residual stress tensor in the alloyed eutectoid steel quenched bar were tensile near the surface and decreased to compressive values at the center. The radial component showed a maximum compressive value at the center and approached zero close to the surface. Metallographic analysis and hardness testing of the three steel specimens, revealed that the IF steel had transformed completely to ferrite, while the 1045 carbon steel bar transformed to martensite near the surface and a mixture of pearlite, ferrite and martensite at the center. On the other hand, the alloyed eutectoid steel specimen transformed entirely to martensite with small amounts of bainite near the center of the rod. The observed differences in the residual stress distributions in the three steels were explained based on the sequence of phase transformations that took place during quenching.

  13. Spin and orbital ordering in TlMnO3: Neutron diffraction study

    NASA Astrophysics Data System (ADS)

    Khalyavin, Dmitry D.; Manuel, Pascal; Yi, Wei; Belik, Alexei A.

    2016-10-01

    Crystal and magnetic structures of the high-pressure stabilized perovskite phase of TlMnO3 have been studied by neutron powder diffraction. The crystal structure involves two types of primary structural distortions: a+b-b- octahedral tilting and antiferrodistortive type of orbital ordering, whose common action reduces the symmetry down to triclinic P 1 ¯ . The orbital pattern and the way it is combined with the octahedral tilting are different from the family of LnMnO3 (Ln = lanthanide or Y) manganites who share with TlMnO3 the same tilting scheme. The experimentally determined magnetic structure with the k =(1 /2 ,0 ,1 /2 ) propagation vector and PS1 ¯ symmetry implies anisotropic exchange interactions with a ferromagnetic coupling within the (1 ,0 ,1 ¯) planes and an antiferromagnetic one between them (A type). The spins in the primary magnetic mode were found to be confined close to the (1 ,0 ,1 ¯) plane, which underlines the predominant role of the single ion anisotropy with the local easy axes of Mn3 + following the Jahn-Teller distortions of the octahedra. In spite of the same octahedral tilting scheme in the perovskite structures of both LnMnO3 and TlMnO3 manganites, a coupling of the secondary ferromagnetic component to the primary A-type spin configuration through antisymmetric exchange interaction is allowed in the former and forbidden in the latter cases.

  14. Location of chlorhexidine in DMPC model membranes: a neutron diffraction study.

    PubMed

    Komljenović, Ivana; Marquardt, Drew; Harroun, Thad A; Sternin, Edward

    2010-06-01

    Chlorhexidine (CHX) is an effective anti-bacterial agent whose mode of action is thought to be the disruption of the cell membrane. It is known to partition into phospholipid bilayers of aqueous model-membrane preparations. Neutron diffraction data taken at 36 degrees C on the location of CHX in phosphatidylcholine (PC) bilayers is presented. The center of mass of the deuterated hydrocarbon chain of CHX is found to reside 16A from the center of the bilayer in 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (14:0-14:0PC). This places the drug near the glycerol backbone of the lipid, and suggests a mode of action whereby the molecule is bent in half and inserts wedge-like into the lipid matrix. This mechanism is distinct from detergent-like mechanisms of membrane disruption and more similar to some anti-microbial peptide action, where peptides insert obliquely into the bilayer headgroup region to disrupt its structure. PMID:20359468

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

    NASA Astrophysics Data System (ADS)

    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.

  16. Neutron diffraction study of the magnetic structure of Na2 RuO 4

    NASA Astrophysics Data System (ADS)

    Mogare, K. M.; Sheptyakov, D. V.; Bircher, R.; Güdel, H.-U.; Jansen, M.

    2006-08-01

    Nuclear and magnetic structures of sodium ruthenate (VI) have been studied by neutron powder diffraction in the temperature range 1.5 200 K. Na2RuO4 crystallizes in the monoclinic structure, with space group P 21/c. The structure consists of apical corner sharing RuO5 trigonal bipyramids forming infinite chains running along the b axis. These infinite [ RuO3O2/2] chains form a pseudo hexagonal close packing of rods with Ru Ru distances of 3.51 Å within the chains and 5.30 5.47 Å between the chains. At TN=37.2 K a magnetic transition leads to an antiferromagnetic state. The Ru6+ magnetic moments are ordered antiferromagnetically along the chains (b-axis), while the inter-chain interaction is ferromagnetic. A classical infinite chain model was fitted to the magnetic susceptibility data in order to estimate the strength of the nearest-neighbor exchange interactions along and between the chains, resulting in an intrachain coupling parameter of 2J=-86 K, and an interchain parameter J⊥ with \\vert 2J⊥ \\vert = 3 K.

  17. Joint structure refinement of x-ray and neutron diffraction data on disordered materials: application to liquid water.

    PubMed

    Soper, A K

    2007-08-22

    X-ray diffraction data on liquids and disordered solids often provide useful complementary structural information to neutron diffraction data. Interpretation of the x-ray diffraction pattern, which is produced by scattering from the atomic electrons rather than from the atomic nuclei as in the case of neutron diffraction, is, however, complicated by the Q-dependent electronic form factors, which cause the x-ray diffraction signal to decline rapidly with increasing Q, where Q is the wave vector change in the diffraction experiment. The problem is particularly important in cases such as water where there is a significant molecular polarization caused by charge transfer within the molecule. This means that the electron form factors applicable to the molecule in the condensed environment often deviate from their free atom values. The technique of empirical potential structure refinement (EPSR) is used here to focus on the problem of forming a single atomistic structural model which is simultaneously consistent with both x-ray and neutron diffraction data. The case of liquid water is treated explicitly. It is found that x-ray data for water do indeed provide a powerful constraint on possible structural models, but that the Q-range of the different x-ray data sets (maximum Q ranges from 10.8 to ∼17.0 Å(-1) for different x-ray experiments), combined with variations between different data sets, means that it is not possible to rigorously define the precise position and height of the first peak in the OO radial distribution function. Equally, it is found that two different neutron datasets on water, although measured to a maximum Q of at least 30 Å(-1), give rise to further small uncertainties in the position of the hydrogen bond peaks. One general conclusion from the combined use of neutron and x-ray data is that many of the classical water potentials may have a core which is too repulsive at short distances. This produces too sharp a peak in r-space at too short a

  18. Identification of phases in gas-atomised droplets by combination of neutron and X-ray diffraction techniques with atom probe tomography.

    PubMed

    Calvo-Dahlborg, M; Chambreland, S; Bao, C M; Quelennec, X; Cadel, E; Cuvilly, F; Dahlborg, U

    2009-04-01

    Powders of Al(68.5)Ni(31.5) alloy have been produced by gas atomisation and sieved in different grain size families. The resulting families have been analysed by combined neutron and X-ray diffraction in order to investigate the structure and identify the existing phases at the surface and in the bulk of the grains. The weight fraction of the identified phases (Al(3)Ni(2), Al(3)Ni and Al) has been estimated from a profile refinement with the FULLPROF computer codes. An additional phase was observed but could not be identified in the diffraction patterns. Starting from grains less than 5mum in diameter, samples have been shaped by annular focused ion beam into needles that were suitable for atom probe investigations. The structure and morphologies observed by different techniques are compared and discussed. It has also been possible to estimate the crystallite sizes and the strains corresponding to the different phases present in the powders from the refinement of the ND patterns. In addition to Al(3)Ni(2) and Al(3)Ni, a phase of composition close to the nominal one of the alloy was observed in the atom probe measurements. This phase could be one of the decagonal ones referred to in the literature. Small particles of composition close to Al(82)Ni(18) are attributed to the metastable Al(9)Ni(2) phase. The achieved conclusions demonstrate the complementarity of X-ray and neutron diffraction techniques and atom probe tomography to analyse complex structures.

  19. Microdosimetric investigations at the fast neutron therapy facility at Fermilab

    SciTech Connect

    Langen, K.M.

    1997-12-01

    Microdosimetry was used to investigate three issues at the neutron therapy facility (NTF) at Fermilab. Firstly, the conversion factor from absorbed dose in A-150 tissue equivalent plastic to absorbed dose in ICRU tissue was determined. For this, the effective neutron kerma factor ratios, i.e., oxygen tissue equivalent plastic and carbon to A-150 tissue equivalent plastic, were measured in the neutron beam. An A-150 tissue equivalent plastic to ICRU tissue absorbed dose conversion factor of 0.92 {+-} 0.04 was determined. Secondly, variations in the radiobiological effectiveness (RBE) in the beam were mapped by determining variations in two related quantities, e{sup *} and R, with field size and depth in tissue. Maximal variation in e{sup *} and R of 9% and 15% respectively were determined. Lastly, the feasibility of utilizing the boron neutron capture reaction on boron-10 to selectively enhance the tumor dose in the NTF beam was investigated.

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

    PubMed

    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.

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

    PubMed Central

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

    2016-01-01

    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. PMID:27158503

  2. Effect of microstructure anisotropy on the deformation of MAX polycrystals studied by in-situ compression combined with neutron diffraction

    SciTech Connect

    Guitton, A.; Joulain, A.; Thilly, L.; Van Petegem, S.; Tromas, C.; Van Swygenhoven, H.

    2014-06-16

    In situ compression tests combined with neutron diffraction were performed on Ti{sub 2}AlN MAX polycrystals with lamellar anisotropic microstructure: the diffraction peak evolution (position and profile) with applied stress reveals that lamellar grains parallel to compression axis remain elastic while lamellar grains perpendicular to compression plastify, both families being subjected to strong variations of heterogeneous strains (types II and III). We demonstrate that this behavior originates from the complex response of the very anisotropic lamellar microstructure and explains the observation of reversible hysteretic loops when cycling MAX polycrystals even in the elastic regime.

  3. High-resolution neutron diffraction study of CuNCN: New evidence of structure anomalies at low temperature

    SciTech Connect

    Jacobs, Philipp; Houben, Andreas; Dronskowski, Richard; Tchougréeff, Andrei L.

    2013-12-14

    Copper carbodiimide (CuNCN) is the nitrogen-containing analogue of cupric oxide. Based on high-resolution neutron-diffraction data, CuNCN's lattice parameters are derived as a function of the temperature. In accordance with a recent synchrotron study, a clear trend in the cell parameter a is observed accompanying the changing magnetic behavior. With decreasing temperature, a slowly decreases to a minimum at ∼100 K after which it rises again. The same trend—albeit more pronounced—is observed for the c lattice parameter at ∼35 K. The herein presented neutron powder-diffraction data also support the conjectured sequence of transitions from the high-temperature one-dimensional resonating valence-bond (RVB) state to a transient two-dimensional RVB state and eventually, at lowest temperatures, into another two-dimensional RVB state, presumably the ground state.

  4. Neutron diffraction and electrical transport studies on the incommensurate magnetic phase transition in holmium at high pressures

    SciTech Connect

    Thomas, Sarah; Uhoya, Walter; Tsoi, Georgiy; Wenger, Lowell E; Vohra, Yogesh; Chesnut, Gary Neal; Weir, S. T.; Tulk, Christopher A; Moreira Dos Santos, Antonio F

    2012-01-01

    Neutron diffraction and electrical transport measurements have been made on the heavy rare earth metal holmium at high pressures and low temperatures in order to elucidate its transition from a paramagnetic (PM) to a helical antiferromagnetic (AFM) ordered phase as a function of pressure. The electrical resistance measurements show a change in the resistance slope as the temperature is lowered through the antiferromagnetic Neel temperature. The temperature of this antiferromagnetic transition decreases from approximately 122 K at ambient pressure at a rate of -4.9 K GPa(-1) up to a pressure of 9 GPa, whereupon the PM-to-AFM transition vanishes for higher pressures. Neutron diffraction measurements as a function of pressure at 89 and 110 K confirm the incommensurate nature of the phase transition associated with the antiferromagnetic ordering of the magnetic moments in a helical arrangement and that the ordering occurs at similar pressures as determined from the resistance results for these temperatures.

  5. Neutron diffraction and electrical transport studies on the incommensurate magnetic phase transition in holmium at high pressures.

    PubMed

    Thomas, Sarah A; Uhoya, Walter O; Tsoi, Georgiy M; Wenger, Lowell E; Vohra, Yogesh K; Chesnut, Gary N; Weir, Samuel T; Tulk, Christopher A; dos Santos, Antonio M

    2012-05-30

    Neutron diffraction and electrical transport measurements have been made on the heavy rare earth metal holmium at high pressures and low temperatures in order to elucidate its transition from a paramagnetic (PM) to a helical antiferromagnetic (AFM) ordered phase as a function of pressure. The electrical resistance measurements show a change in the resistance slope as the temperature is lowered through the antiferromagnetic Néel temperature. The temperature of this antiferromagnetic transition decreases from approximately 122 K at ambient pressure at a rate of -4.9 K GPa(-1) up to a pressure of 9 GPa, whereupon the PM-to-AFM transition vanishes for higher pressures. Neutron diffraction measurements as a function of pressure at 89 and 110 K confirm the incommensurate nature of the phase transition associated with the antiferromagnetic ordering of the magnetic moments in a helical arrangement and that the ordering occurs at similar pressures as determined from the resistance results for these temperatures.

  6. The application of neutron diffraction to stress mapping in pipeline steels: Measurement of residual, applied, and defect-induced stresses

    SciTech Connect

    Clapham, L.; Krause, T.W.; Olsen, H.; Atherton, D.L.; Holden, T.M.

    1996-12-31

    Gas pipelines are inspected for defects including generalized corrosion, localized corrosion and environmentally-induced cracking. The most common in-line corrosion inspection tools utilize the magnetic flux leakage (MFL) technique, which is also sensitive to the pipeline stress state. Accurate determination of the residual, applied (bulk) and local defect-induced stresses is therefore essential to understand how stress affects MFL signals. This paper summarizes the results of the following work: (1) Measurement of residual stresses in a section of X70 pipe, using neutron diffraction. (2) Examination with neutron diffraction of the local stresses surrounding a blind (i.e., 50% through-wall) hole defect in the X70 pipe wall section, when the section is subjected to a bending stress in the hoop direction.

  7. Neutron diffraction study of Bi doped cubic spinel Co{sub 2}MnO{sub 4}

    SciTech Connect

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

    2015-06-24

    Polycrystalline Bi doped spinel Bi{sub x}Co{sub 2-x}MnO{sub 4} compounds were prepared by solid state reaction route. Room temperature neutron diffraction study reveals that all the compounds are formed in cubic phase and there is no change in the crystal structure due to Bi doping and the compound has cubic structure with Fd-3m space group. Cell parameter found to increase with respect to Bi doping and ferrimagnetic nature is established through magnetization. Low temperature neutron diffraction is carried out and emphasis the ferrimagnetic ordering in the samples of Bi{sub x}Co{sub 2-x}MnO{sub 4} series.

  8. Neutron diffraction and electrical transport studies on the incommensurate magnetic phase transition in holmium at high pressures

    NASA Astrophysics Data System (ADS)

    Thomas, Sarah A.; Uhoya, Walter O.; Tsoi, Georgiy M.; Wenger, Lowell E.; Vohra, Yogesh K.; Chesnut, Gary N.; Weir, Samuel T.; Tulk, Christopher A.; dos Santos, Antonio M.

    2012-05-01

    Neutron diffraction and electrical transport measurements have been made on the heavy rare earth metal holmium at high pressures and low temperatures in order to elucidate its transition from a paramagnetic (PM) to a helical antiferromagnetic (AFM) ordered phase as a function of pressure. The electrical resistance measurements show a change in the resistance slope as the temperature is lowered through the antiferromagnetic Néel temperature. The temperature of this antiferromagnetic transition decreases from approximately 122 K at ambient pressure at a rate of -4.9 K GPa-1 up to a pressure of 9 GPa, whereupon the PM-to-AFM transition vanishes for higher pressures. Neutron diffraction measurements as a function of pressure at 89 and 110 K confirm the incommensurate nature of the phase transition associated with the antiferromagnetic ordering of the magnetic moments in a helical arrangement and that the ordering occurs at similar pressures as determined from the resistance results for these temperatures.

  9. High-resolution neutron diffraction study of CuNCN: new evidence of structure anomalies at low temperature.

    PubMed

    Jacobs, Philipp; Houben, Andreas; Tchougréeff, Andrei L; Dronskowski, Richard

    2013-12-14

    Copper carbodiimide (CuNCN) is the nitrogen-containing analogue of cupric oxide. Based on high-resolution neutron-diffraction data, CuNCN's lattice parameters are derived as a function of the temperature. In accordance with a recent synchrotron study, a clear trend in the cell parameter a is observed accompanying the changing magnetic behavior. With decreasing temperature, a slowly decreases to a minimum at ~100 K after which it rises again. The same trend-albeit more pronounced-is observed for the c lattice parameter at ~35 K. The herein presented neutron powder-diffraction data also support the conjectured sequence of transitions from the high-temperature one-dimensional resonating valence-bond (RVB) state to a transient two-dimensional RVB state and eventually, at lowest temperatures, into another two-dimensional RVB state, presumably the ground state.

  10. Investigation of diffractive optical element femtosecond laser machining

    NASA Astrophysics Data System (ADS)

    Chabrol, Grégoire R.; Ciceron, Adline; Twardowski, Patrice; Pfeiffer, Pierre; Flury, Manuel; Mermet, Frédéric; Lecler, Sylvain

    2016-06-01

    This paper presents an explorative study on the machining of diffractive optical elements (DOEs) in transparent materials using a femtosecond laser source. A simple form of DOE, a binary phase grating with a period of 20.85 μm (σ = 0.5 μm), a groove depth and width of 0.7 μm (σ = 0.2 μm) and 8.8 μm (σ = 0.5 μm) respectively, was successfully machined in BK7. The topographic characteristics were measured by white light interferometry and scanning electron microscopy (SEM). The processing was carried out on high precision stages with an ultrafast fibre laser (350 fs) emitting a 343 nm pulse focused onto the sample with a stationary microscope objective. A diffracted efficiency of 27%, obtained with a spectro goniometer, was corroborated by the theoretical results obtained by the Fourier modal method (FMM), taking into account the measured topographic values. These encouraging results demonstrate that high-speed femtosecond laser manufacturing of DOE in bulk glasses can be achieved, opening the way to rapid prototyping of multi-layered-DOEs.

  11. Methods for lipid nanostructure investigation at neutron and synchrotron sources

    NASA Astrophysics Data System (ADS)

    Kiselev, M. A.

    2011-03-01

    A lipid membrane is a main component of biological membranes. Contemporary bionanotechnologies use phospholipids and ceramides as basic components of drugs and cosmetic preparations. Phospholipids-based nanoparticles are used as drug carriers. Effective development of bionanotechnologies in Russia calls for creation of physical methods to diagnose the particle nanostructure which would be promising for application in pharmacology. Radiation with wavelengths of 1-10 Å is an adequate instrument for detecting the nanostructure of lipid bi- and monolayers. The review deals with methods that apply neutron scattering and synchrotron radiation for studying nanostructures of lipid membranes, phospholipid nanoparticles, and phospholipid monolayers on a water surface by techniques of diffraction, small-angle scattering, and reflectometry. The importance of the mutually complementary application of neutron and synchrotron radiation for solving urgent problems of membrane biophysics, microbiology, dermapharmacology, and bionanotechnologies is demonstrated by particular examples of studies of phospholipid membranes and ceramide-based membranes. The efficiency of development and application of new methods for solving urgent problems of biophysics is shown. The review is written on the basis of results obtained over the period of 1999-2010 at the Joint Institute for Nuclear Research (JINR) Laboratory of Neutron Physics in collaboration with the Pharmaceutical Departments of universities of France (Paris-Sud, Chatenay Malabry) and Germany (Martin Luther University, Halle). The experiments were performed at various European and Russian neutron and synchrotron sources.

  12. Neutron Diffraction Residual Strain Tensor Measurements Within The Phase IA Weld Mock-up Plate P-5

    SciTech Connect

    Hubbard, Camden R

    2011-09-01

    Oak Ridge National Laboratory (ORNL) has worked with NRC and EPRI to apply neutron and X-ray diffraction methods to characterize the residual stresses in a number of dissimilar metal weld mockups and samples. The design of the Phase IA specimens aimed to enable stress measurements by several methods and computational modeling of the weld residual stresses. The partial groove in the 304L stainless steel plate was filled with weld beads of Alloy 82. A summary of the weld conditions for each plate is provided in Table 1. The plates were constrained along the long edges during and after welding by bolts with spring-loaded washers attached to the 1-inch thick Al backing plate. The purpose was to avoid stress relief due to bending of the welded stainless steel plate. The neutron diffraction method was one of the methods selected by EPRI for non-destructive through thickness strain and stress measurement. Four different plates (P-3 to P-6) were studied by neutron diffraction strain mapping, representing four different welding conditions. Through thickness neutron diffraction strain mappings at NRSF2 for the four plates and associated strain-free d-zero specimens involved measurement along seven lines across the weld and at six to seven depths. The mountings of each plate for neutron diffraction measurements were such that the diffraction vector was parallel to each of the three primary orthogonal directions of the plate: two in-plane directions, longitudinal and transverse, and the direction normal to the plate (shown in left figure within Table 1). From the three orthogonal strains for each location, the residual stresses along the three plate directions were calculated. The principal axes of the strain and stress tensors, however, need not necessarily align with the plate coordinate system. To explore this, plate P-5 was selected for examination of the possibility that the principal axes of strain are not along the sample coordinate system axes. If adequate data could

  13. Energy-dispersive neutron imaging and diffraction of magnetically driven twins in a Ni2MnGa single crystal magnetic shape memory alloy

    NASA Astrophysics Data System (ADS)

    Kabra, Saurabh; Kelleher, Joe; Kockelmann, Winfried; Gutmann, Matthias; Tremsin, Anton

    2016-09-01

    Single crystals of a partially twinned magnetic shape memory alloy, Ni2MnGa, were imaged using neutron diffraction and energy-resolved imaging techniques at the ISIS spallation neutron source. Single crystal neutron diffraction showed that the crystal produces two twin variants with a specific crystallographic relationship. Transmission images were captured using a time of flight MCP/Timepix neutron counting detector. The twinned and untwinned regions were clearly distinguishable in images corresponding to narrow-energy transmission images. Further, the spatially-resolved transmission spectra were used to elucidate the orientations of the crystallites in the different volumes of the crystal.

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

    SciTech Connect

    White, S.H.; Wiener, M.C.

    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.

  15. Quantitative phase analysis of challenging samples using neutron powder diffraction. Sample #4 from the CPD QPA round robin revisited

    DOE PAGES

    Whitfield, Pamela S.

    2016-04-29

    Here, quantitative phase analysis (QPA) using neutron powder diffraction more often than not involves non-ambient studies where no sample preparation is possible. The larger samples and penetration of neutrons versus X-rays makes neutron diffraction less susceptible to inhomogeneity and large grain sizes, but most well-characterized QPA standard samples do not have these characteristics. Sample #4 from the International Union of Crystallography Commission on Powder Diffraction QPA round robin was one such sample. Data were collected using the POWGEN time-of-flight (TOF) neutron powder diffractometer and analysed together with historical data from the C2 diffractometer at Chalk River. The presence of magneticmore » reflections from Fe3O4 (magnetite) in the sample was an additional consideration, and given the frequency at which iron-containing and other magnetic compounds are present during in-operando studies their possible impact on the accuracy of QPA is of interest. Additionally, scattering from thermal diffuse scattering in the high-Qregion (<0.6 Å) accessible with TOF data could impact QPA results during least-squares because of the extreme peak overlaps present in this region. Refinement of POWGEN data was largely insensitive to the modification of longer d-spacing reflections by magnetic contributions, but the constant-wavelength data were adversely impacted if the magnetic structure was not included. A robust refinement weighting was found to be effective in reducing quantification errors using the constant-wavelength neutron data both where intensities from magnetic reflections were ignored and included. Results from the TOF data were very sensitive to inadequate modelling of the high-Q (lowd-spacing) background using simple polynomials.« less

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

    NASA Astrophysics Data System (ADS)

    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.

  17. A neutron diffraction study and mode analysis of compounds of the system La{sub 1−x}Sr{sub x}FeO{sub 3−x}F{sub x} (x=1, 0.8, 0.5, 0.2) and an investigation of their magnetic properties

    SciTech Connect

    Clemens, Oliver; Berry, Frank J.; Wright, Adrian J.; Knight, Kevin S.; Perez-Mato, J.M.; Igartua, J.M.; Slater, Peter R.

    2013-10-15

    We report here a detailed study of the system La{sub 1−x}Sr{sub x}FeO{sub 3−x}F{sub x}, by neutron powder diffraction- and magnetic-measurements. All the compounds are robust antiferromagnetics with ordering temperatures well above room temperature. Magnetic moments are shown to align parallel to the c-axis. FC-ZFC measurements indicate a small canting of the magnetic moments, resulting in a ferromagnetic component with a maximum for La{sub 0.5}Sr{sub 0.5}FeO{sub 2.5}F{sub 0.5}. We show that the system exhibits a composition-driven transition from a phase, for low fluorination levels (x≤0.5), with Pnma symmetry and the usual system of octahedral tiltings, to a phase with space group Imma for higher fluorine contents, where a correlated distortion of the oxygen octahedra plays a significant role. The consistency of the structural models, with respect to the expected continuity of the amplitudes of the different distortion modes and the invariance of their internal form, was monitored through the symmetry mode decomposition of the structures. - Graphical abstract: The crystal and magnetic structure of La{sub 0.5}Sr{sub 0.5}FeO{sub 2.5}F{sub 0.5}. Display Omitted - Highlights: • The compounds La{sub 1−x}Sr{sub x}FeO{sub 3−x}F{sub x} (x=1, 0.8, 0.5, 0.2) were studied by neutron diffraction. • A mode analysis shows lower symmetry for Sr rich compounds than previously reported. • SrFeO{sub 2}F crystallizes in the orthorhombic space group Imma. • Magnetic moments resulting from canting depend on metric distortion. • The magnetic structure was determined for La{sub 0.5}Sr{sub 0.5}FeO{sub 2.5}F{sub 0.5}.

  18. In-situ neutron diffraction study of cathode/electrolyte interactions under electrical load and elevated temperature

    NASA Astrophysics Data System (ADS)

    Tonus, F.; Skinner, S. J.

    2016-05-01

    Fuel cells are proposed as a future energy conversion technology that will reduce greenhouse gas emissions at the point of operation due to their ability to produce electrical energy from non-hydrocarbon fuel sources. The Solid Oxide Fuel Cell (SOFC) is amongst the most efficient fuel cell types, however, due to the high cell operating temperature cation diffusion occurs between the different components of the cell, resulting in rapid degradation of the power output. In this paper we investigate cation migration between the promising intermediate temperature-SOFC cathode La1-xSrxCo1-yFeyO3-δ (LSCF) and a fluorite type electrolyte Ce1-xPrxO2-δ (CPO). The crystallographic structure evolution and degradation of the materials were studied by neutron diffraction in-situ under pseudo-operating conditions, i.e. at 600 °C under air and under electrical polarisation. The lattice parameter and cation occupancy evolution were analysed by Rietveld refinement as a function of time and applied potential. The materials were found to be stable, as no impurity formation, lattice parameter or site occupancy evolution was observed during the experiment. However La migration prior to the experiment from LSCF to CPO was observed as well as B-site vacancies in LSCF.

  19. As-Cast Residual Stresses in an Aluminum Alloy AA6063 Billet: Neutron Diffraction Measurements and Finite Element Modeling

    NASA Astrophysics Data System (ADS)

    Drezet, J.-M.; Phillion, A. B.

    2010-12-01

    The presence of thermally induced residual stresses, created during the industrial direct chill (DC) casting process of aluminum alloys, can cause both significant safety concerns and the formation of defects during downstream processing. Although numerical models have been previously developed to compute these residual stresses, most of the computations have been validated only against measured surface distortions. Recently, the variation in residual elastic strains in the steady-state regime of casting has been measured as a function of radial position using neutron diffraction (ND) in an AA6063 grain-refined cylindrical billet. In the present study, these measurements are used to show that a well-designed thermomechanical finite element (FE) process model can reproduce relatively well the experimental results. A sensitivity analysis is then carried out to determine the relative effect of the various mechanical parameters when computing the as-cast residual stresses in a cylindrical billet. Two model parameters have been investigated: the temperature when the alloy starts to thermally contract and the plasticity behavior. It is shown that the mechanical properties at low temperatures have a much larger influence on the residual stresses than those at high temperatures.

  20. Network structure of molybdate glasses by neutron and X-ray diffraction and reverse Monte Carlo modelling

    NASA Astrophysics Data System (ADS)

    Fabian, M.; Svab, E.; Krezhov, K.

    2016-09-01

    Rare-earth molybdate glasses have been prepared by rapid quench technique, the network structure was investigated by neutron and high-energy X-ray diffraction. For data evaluation the reverse Monte Carlo simulation technique was applied to obtain a possible 3dimensional network configuration, which is consistent with the experimental data. From the modelling the partial atomic correlation functions giJ(r) and the coordination number distributions CNij have been revealed. Formation of MoO4 (55%) and MoO6 (25%) units was established for the binary 90MoO3-10Nd2O3 glass. The B-O first neighbour distribution show a relatively broad first neighbour distance at 1.40A, the average coordination numbers show the presents of trigonal BO3 and tetrahedral BO4 groups. For 50MoO3-25Nd2O3-25B2O3 sample mixed MoO4-BO4 and MoO4-BO3 linkages form pronounced intermediate-range order.

  1. Neutron diffraction study on very high elastic strain of 6% in an Fe{sub 3}Pt under compressive stress

    SciTech Connect

    Yamaguchi, Takashi; Fukuda, Takashi Kakeshita, Tomoyuki; Harjo, Stefanus; Nakamoto, Tatsushi

    2014-06-09

    An Fe{sub 3}Pt alloy with degree of order 0.75 exhibits a second-order-like martensitic transformation from a cubic structure to a tetragonal one at about 90 K; its tetragonality c/a changes nearly continuously from 1 to 0.945 on cooling from 90 K to 14 K. We have investigated the change in lattice parameters in a single crystal of the Fe{sub 3}Pt alloy at 93 K under compressive stresses, σ, applied in the [001] direction by neutron diffraction. The tetragonality c/a has decreased continuously from 1 to 0.907 with an increase in |σ| up to |σ| = 280 MPa; the corresponding lattice strain in the [001] direction, due to the continuous structure change, increases from 0% to 6.1%. When the stress of 300 MPa is reached, c/a has changed abruptly from 0.907 to 0.789 due to a first-order martensitic transformation.

  2. Deformation mechanisms in a precipitation-strengthened ferritic superalloy revealed by in situ neutron diffraction studies at elevated temperatures

    DOE PAGES

    Huang, Shenyan; Gao, Yanfei; An, Ke; Zheng, Lili; Wu, Wei; Teng, Zhenke; Liaw, Peter K

    2014-10-22

    In this study, the ferritic superalloy Fe–10Ni–6.5Al–10Cr–3.4Mo strengthened by ordered (Ni,Fe)Al B2-type precipitates is a candidate material for ultra-supercritical steam turbine applications above 923 K. Despite earlier success in improving its room-temperature ductility, the creep resistance of this material at high temperatures needs to be further improved, which requires a fundamental understanding of the high-temperature deformation mechanisms at the scales of individual phases and grains. In situ neutron diffraction has been utilized to investigate the lattice strain evolution and the microscopic load-sharing mechanisms during tensile deformation of this ferritic superalloy at elevated temperatures. Finite-element simulations based on the crystal plasticitymore » theory are employed and compared with the experimental results, both qualitatively and quantitatively. Based on these interphase and intergranular load-partitioning studies, it is found that the deformation mechanisms change from dislocation slip to those related to dislocation climb, diffusional flow and possibly grain boundary sliding, below and above 873 K, respectively. Insights into microstructural design for enhancing creep resistance are also discussed.« less

  3. Deformation mechanisms in a precipitation-strengthened ferritic superalloy revealed by in situ neutron diffraction studies at elevated temperatures

    SciTech Connect

    Huang, Shenyan; Gao, Yanfei; An, Ke; Zheng, Lili; Wu, Wei; Teng, Zhenke; Liaw, Peter K

    2014-10-22

    In this study, the ferritic superalloy Fe–10Ni–6.5Al–10Cr–3.4Mo strengthened by ordered (Ni,Fe)Al B2-type precipitates is a candidate material for ultra-supercritical steam turbine applications above 923 K. Despite earlier success in improving its room-temperature ductility, the creep resistance of this material at high temperatures needs to be further improved, which requires a fundamental understanding of the high-temperature deformation mechanisms at the scales of individual phases and grains. In situ neutron diffraction has been utilized to investigate the lattice strain evolution and the microscopic load-sharing mechanisms during tensile deformation of this ferritic superalloy at elevated temperatures. Finite-element simulations based on the crystal plasticity theory are employed and compared with the experimental results, both qualitatively and quantitatively. Based on these interphase and intergranular load-partitioning studies, it is found that the deformation mechanisms change from dislocation slip to those related to dislocation climb, diffusional flow and possibly grain boundary sliding, below and above 873 K, respectively. Insights into microstructural design for enhancing creep resistance are also discussed.

  4. Refinement of atomic and magnetic structures using neutron diffraction for synthesized bulk and nano-nickel zinc gallate ferrite

    NASA Astrophysics Data System (ADS)

    Ata-Allah, S. S.; Balagurov, A. M.; Hashhash, A.; Bobrikov, I. A.; Hamdy, Sh.

    2016-01-01

    The parent NiFe2O4 and Zn/Ga substituted spinel ferrite powders have been prepared by solid state reaction technique. As a typical example, the Ni0.7Zn0.3Fe1.5Ga0.5O4 sample has been prepared by sol-gel auto combustion method with the nano-scale crystallites size. X-ray and Mössbauer studies were carried out for the prepared samples. Structure and microstructure properties were investigated using the time-of-flight HRFD instrument at the IBR-2 pulsed reactor, at a temperatures range 15-473 K. The Rietveld refinement of the neutron diffraction data revealed that all samples possess cubic symmetry corresponding to the space group Fd3m. Cations distribution show that Ni2+ is a complete inverse spinel ion, while Ga3+ equally distributed between the two A and B-sublattices. The level of microstrains in bulk samples was estimated as very small while the size of coherently scattered domains is quite large. For nano-structured sample the domain size is around 120 Å.

  5. Neutron Diffraction Study Oxygen Dissolution Alpha(sub 2)-Ti3Al

    NASA Technical Reports Server (NTRS)

    Jones, Camille Y.; Luecke, William E.; Copland, Evan

    2005-01-01

    Rietveld refinements of neutron powder diffraction data on alpha(sub 2)-Ti3Al have been performed to determine the crystal structure as a function of interstitial oxygen (O) concentration for three alloys with a Ti/Al ratio of approximately equal to 2.34 and O concentrations of 0.25%, 3.99% and 7.71%. The structures of the allows are hexagonal in space group P6(sub 3)/mmc where Ti and Al atoms populate unique sites with excess Al at the Ti site and O atoms occupy octahedral interstitial sites surrounded by six Ti sites. The length of the c-axis was found to increase linearly as the O occupancy of the interstitial sites increased; this lattice lengthening effect was much less pronounced along the alpha axis. Correspondingly, the increases in the lengths of Ti-Al and Ti-Ti bonds with a major component of their direction parallel to the c-axis were roughly an order of magnitude greater than the increases in the lengths of Ti-al and Ti-Ti bonds more closely aligned with the alpha-axis. Densities calculated form the lattice parameters and occupancy factors fall in the range (4.118 plus or minus 0.004) grams per cubic centimeter to (4.194 plus or minus 0.004) grams per cubic centimeter, and exhibit a nearly linear increase with oxygen concentration. Measured densities of (4.113 plus or minus 0.001) grams per cubic centimeter, (4.146 plus or minus 0.009) grams per cubic centimeter, and (4.191 plus or minus 0.002) grams per cubic centimeter for these alloys agree with the results of the refinements.

  6. Operando Lithium Dynamics in the Li-Rich Layered Oxide Cathode Material via Neutron Diffraction

    DOE PAGES

    Liu, Haodong; An, Ke; Venkatachalam, Subramanian; Qian, Danna; Zhang, Minghao; Meng, Ying Shirley

    2016-04-06

    Neutron diffraction under operando battery cycling is used to study the lithium and oxygen dynamics of high Li-rich Li(Lix/3Ni(3/8-3x/8)Co(1/4-x/4)Mn(3/8+7x/24)O2 (x = 0.6, HLR) and low Li-rich Li(Lix/3Ni(1/3-x/3)Co(1/3-x/3)Mn(1/3+x/3)O2 (x = 0.24, LLR) compounds that exhibit different degrees of oxygen activation at high voltage. The measured lattice parameter changes and oxygen position show largely contrasting changes for the two cathodes where the LLR exhibits larger movement of oxygen and lattice contractions in comparison to the HLR that maintains relatively constant lattice parameters and oxygen position during the high voltage plateau until the end of charge. Density functional theory calculations show the presencemore » of oxygen vacancy during the high voltage plateau; changes in the lattice parameters and oxygen position are consistent with experimental observations. Lithium migration kinetics for the Li-rich material is observed under operando conditions for the first time to reveal the rate of lithium extraction from the lithium layer, and transition metal layer is related to the different charge and discharge characteristics. At the beginning of charging, the lithium extraction predominately occurs within the lithium layer. The lithium extraction from the lithium layer slows down and extraction from the transition metal layer evolves at a faster rate once the high voltage plateau is reached.« less

  7. X-ray and neutron diffraction studies of syntactic metal foams and metal matrix composites

    NASA Astrophysics Data System (ADS)

    Balch, Dorian Kenneth

    2002-11-01

    Synchrotron x-ray and neutron diffraction can provide both the in-situ elastic phase strains and the phases present in metal matrix composites subjected to thermo-mechanical loading by measuring the lattice spacings parallel and perpendicular to the loading axis, as well as changes in the crystalline structure of the composite constituents. Such measurements can give insight into load transfer between phases, the onset of matrix or reinforcement plasticity or damage, and thermally or mechanically induced phase transformations. Four composite systems are presented: (a) bulk metallic glass composites containing low volume fractions of tungsten and tantalum particles, (b) bulk metallic composites containing low volume fractions of both tantalum particles and crystallized matrix inclusions, (c) copper composites containing high volume fractions of particles of the negative thermal expansion ceramic zirconium tungstate, and (d) aluminum matrix syntactic foams containing high volume fractions of hollow ceramic spheres. In the bulk metallic glass composites, plasticity of the metallic reinforcement was observed during mechanical cycling, leading to residual stresses that may alter the subsequent composite behavior. The zirconium tungstate present in the low thermal expansion copper composites was observed to undergo both thermal and stress induced transformations during thermal cycling, confirming the interpretation of ex-situ thermal expansion measurements. In the aluminum syntactic foams, matrix plasticity and ceramic microsphere damage were seen, as well as relative unloading of the matrix during mechanical testing and an improvement in elastic properties due to presence of the hollow spheres. For all systems, continuum mechanical modeling using the Eshelby method was performed, with good agreement found between predictions and measurements.

  8. Oxygen transport pathways in Ruddlesden–Popper structured oxides revealed via in situ neutron diffraction

    DOE PAGES

    Tomkiewicz, Alex C.; Tamimi, Mazin; Huq, Ashfia; McIntosh, Steven

    2015-09-21

    Ruddlesden-Popper structured oxides, general form An+1BnO3n+1, consist of n-layers of the perovskite structure stacked in between rock-salt layers, and have potential application in solid oxide electrochemical cells and ion transport membrane reactors. Three materials with constant Co/Fe ratio, LaSrCo0.5Fe0.5O4-δ (n = 1), La0.3Sr2.7CoFeO7-δ (n = 2), and LaSr3Co1.5Fe1.5O10-δ (n = 3) were synthesized and studied via in situ neutron powder diffraction between 765 K and 1070 K at a pO2 of 10-1 atm. Then, the structures were fit to a tetragonal I4/mmm space group, and were found to have increased total oxygen vacancy concentration in the order La0.3Sr2.7CoFeO7-δ > LaSr3Co1.5Fe1.5O10-δmore » > LaSrCo0.5Fe0.5O4-δ, following the trend predicted for charge compensation upon increasing Sr2+/La3+ ratio. The oxygen vacancies within the material were almost exclusively located within the perovskite layers for all of the crystal structures with only minimal vacancy formation in the rock-salt layer. Finally, analysis of the concentration of these vacancies at each distinct crystallographic site and the anisotropic atomic displacement parameters for the oxygen sites reveals potential preferred oxygen transport pathways through the perovskite layers.« less

  9. Variable temperature neutron diffraction and x-ray charge density studies of tetraacetylethane.

    SciTech Connect

    Piccoli, P. M. B.; Koetzle, T. F.; Schultz, A. J.; Zhurova, E. A.; Stare, J.; Pinkerton, A. A.; Eckert, J.; Hadzi, D.; Univ. of Toledo; National Inst. of Chemistry; Univ. of California at Santa Barbara

    2008-07-24

    Single crystal neutron diffraction data have been collected on a sample of enolized 3,4-diacetyl-2,5-hexanedione (tetraacetylethane, TAE) at five temperatures between 20 and 298 K to characterize the temperature-dependent behavior of the short, strong, intramolecular hydrogen bond. Upon decreasing the temperature from 298 K to 20 K, the O2-H1 distance decreases from 1.171(11) to 1.081(2) {angstrom} and the O1 {hor_ellipsis} H1 distance increases from 1.327(10) to 1.416(6) {angstrom}. The convergence of the C?O bond lengths from inequivalent distances at low temperature to identical values (1.285(4) {angstrom}) at 298 K is consistent with a resonance-assisted hydrogen bond. However, a rigid bond analysis indicates that the structure at 298 K is disordered. The disorder vanishes at lower temperatures. Short intermolecular C?H {hor_ellipsis} O contacts may be responsible for the ordering at low temperature. The intramolecular O {hor_ellipsis} O distance (2.432 0.006 {angstrom}) does not change with temperature. X-ray data at 20 K were measured to analyze the charge density and to gain additional insight into the nature of the strong hydrogen bond. Quantum mechanical calculations demonstrate that periodic boundary conditions provide significant enhancement over gas phase models in that superior agreement with the experimental structure is achieved when applying periodicity. One-dimensional potential energy calculations followed by quantum treatment of the proton reproduce the location of the proton nearer to the O2 site reasonably well, although they overestimate the O?H distance at low temperatures. The choice of the single-point energy calculation strategy for the proton potential is justified by the fact that the proton is preferably located nearer to O2 rather than being equally distant to O1 and O2 or evenly distributed (disordered) between them.

  10. X-ray and neutron diffraction measurements of dislocation density and subgrain size in a friction stir welded aluminum alloy

    SciTech Connect

    Claussen, Bjorn; Woo, Wanchuck; Zhili, Feng; Edward, Kenik; Ungar, Tamas

    2009-01-01

    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 x 10{sup 14} m{sup 02} 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 x 10{sup 15} m{sup -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.

  11. Simultaneous neutron diffraction and microwave dielectric characterisation of ammine materials - a non-destructive, non-contact characterisation tool for determining ammonia content in solids.

    PubMed

    Jones, Martin Owen; Hartley, Jon; Porch, Adrian

    2016-08-17

    We have investigated ammonia adsorption in group two halides (MgI2 and CaBr2) using custom-built apparatus that permits simultaneous neutron diffraction, microwave dielectric characterisation and out-gas mass spectroscopy of solid state materials during ammonia adsorption. Deuterated ammonia was flowed over the sample and the uptake - as measured by mass flow meters, mass spectroscopy and structure - compared with the change in dielectric constant. An excellent correlation between ammonia content and dielectric property was observed and, when linked to diffraction, mass flow and mass spectroscopy data, could be used to determine the amount of ammonia present within the solid. The combination of these techniques could also be used to differentiate physisorbed and metal-coordinated ammonia and explain subtleties in the observed structural transformations. PMID:27498837

  12. Further investigations on CR-39 fast neutron personal dosemeter

    NASA Astrophysics Data System (ADS)

    Djeffal, S.; Lounis, Z.; Allab, M.; Izerrouken, M.

    1997-02-01

    A fast neutron personal dosemeter based on CR-39 nuclear track detectors has been developed in as simple a form as possible to be used in routine monitoring. It has been investigated during the last joint irradiation exposures to neutrons organised by EURADOS-CENDOS committee on the application of track detectors in neutron dosimetry. The energy response and the angle dependence of two types of CR-39 material, produced by Pershore Mouldings Ltd (as standard grade material) and American Acrylics (as dosimetry grade material), have been studied using neutron energies ranging from 144 keV up to 66 MeV and the 252Cf neutron spectrum at different angles of incidence, i.e. 0°, 30°, 60° and 85°. Irradiated detectors have been processed using a conventional chemical etching (CE) and a two-step electrochemical etching at low (200 Hz) and high (2 kHz) frequencies (ECE). Under the ECE etching conditions a 80 μSv minimum dose equivalent value is achieved. The response of these detectors to the ambient dose equivalent in the range 0.4-13 mSv has also been studied for monoenergetic neutron beams of 1.2, 5.3 and 15.1 MeV. The dosimetric characteristics of the proposed dosemeter have been much improved by using the ECE conditions. The variations and values of these characteristics approach the required ones in a better way than that given till now in previous works.

  13. Neutron scattering investigation of the magnetic order in single crystalline BaFe2As2

    SciTech Connect

    Bao, Wei; Qiu, Y; Kofu, M; Lee, S - H; Chang, S; Wu, T; Wu, G; Chen, X H

    2008-01-01

    The magnetic structure of BaFe{sub 2}As{sub 2} was determined from polycrystalline neutron diffraction measurements soon after the ThCr{sub 2}Si{sub 2}-type FeAs-based superconductors were discovered. Both the moment direction and the in-plane antiferromagnetic wavevector are along the longer a-axis of the orthorhombic unit cell. There is only one combined magnetostructural transition at {approx}140 K. However, a later single-crystal neutron diffraction work reported contradicting results. Here, we show neutron diffraction results from a single-crystal sample, grown by a self-flux method, that support the original polycrystalline work.

  14. A neutron diffraction and magnetic Barkhausen noise evaluation of defect-induced stress concentrations

    NASA Astrophysics Data System (ADS)

    Sabet-Sharghi, Riaz

    This thesis studies the effect of altering both the drilling technique (mechanical drilling vs. Electro-Chemical Milling) and the sequence of defect introduction and load application on the defect-induced stress distributions in sections of line pipe steel material. The defect-induced stress concentrations in loaded samples with defects introduced whilst loaded (in-situ) and prior to the application of load (pre-drilled) were examined using both neutron diffraction and Magnetic Barkhausen Noise (MBN). These results indicated the presence of potentially large levels of residual stress particularly in the in-situ sample. This is believed to be a result of plastic deformation being introduced by the mechanical drilling process. Similar studies on ECM defects showed no signs of drilling-induced stresses. Experimental stress distribution results from the in-situ and pre-drilled samples were compared to those predicted using a three-dimensional finite element model solution. The overall level of agreement was found to be best for the pre-drilled sample case. The study also aimed to determine the effectiveness of MBN as a non-destructive method for characterizing line pipe samples. Results of an initial experiment are presented showing the effectiveness of MBN for performing quantitative strain analysis on samples. This was determined by comparing MBN-measured stress concentrations with those predicted by theory and reported in the literature. Magnetic Flux Leakage (MFL) tests were also performed on the samples in order to examine any stress-induced differences in MFL response. It was found that the differences in stress distribution between the in-situ and pre-drilled samples were also reflected in the trend of the MFL signal amplitude and shape as a function of applied stress. The original work in this thesis includes the first definitive test of the effects of the order of load application and defect introduction on the resulting stress distributions around through

  15. Oxygen transport pathways in Ruddlesden–Popper structured oxides revealed via in situ neutron diffraction

    SciTech Connect

    Tomkiewicz, Alex C.; Tamimi, Mazin; Huq, Ashfia; McIntosh, Steven

    2015-09-21

    Ruddlesden-Popper structured oxides, general form An+1BnO3n+1, consist of n-layers of the perovskite structure stacked in between rock-salt layers, and have potential application in solid oxide electrochemical cells and ion transport membrane reactors. Three materials with constant Co/Fe ratio, LaSrCo0.5Fe0.5O4-δ (n = 1), La0.3Sr2.7CoFeO7-δ (n = 2), and LaSr3Co1.5Fe1.5O10-δ (n = 3) were synthesized and studied via in situ neutron powder diffraction between 765 K and 1070 K at a pO2 of 10-1 atm. Then, the structures were fit to a tetragonal I4/mmm space group, and were found to have increased total oxygen vacancy concentration in the order La0.3Sr2.7CoFeO7-δ > LaSr3Co1.5Fe1.5O10-δ > LaSrCo0.5Fe0.5O4-δ, following the trend predicted for charge compensation upon increasing Sr2+/La3+ ratio. The oxygen vacancies within the material were almost exclusively located within the perovskite layers for all of the crystal structures with only minimal vacancy formation in the rock-salt layer. Finally, analysis of the concentration of these vacancies at each distinct crystallographic site and the anisotropic atomic displacement parameters for the oxygen sites reveals potential preferred oxygen transport pathways through the perovskite layers.

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

    SciTech Connect

    Mueser, Timothy C. Griffith, Wendell P.; Kovalevsky, Andrey Y.; Guo, Jingshu; Seaver, Sean; Langan, Paul; Hanson, B. Leif

    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.

  17. In Situ Tensile Deformation and Residual Stress Measurement by Neutron Diffraction in Modified 9Cr-1Mo Steel

    NASA Astrophysics Data System (ADS)

    Shrestha, Triratna; Charit, Indrajit; Potirniche, Gabriel

    2015-12-01

    The deformation behavior of monolithic modified 9Cr-1Mo (Grade 91) steel during uniaxial tensile loading was studied using the in situ neutron diffraction technique. The residual stress distribution across gas tungsten arc welds in the Grade 91 steel was measured by the time-of-flight neutron diffraction method using the SMARTS diffractometer at Lujan Neutron Scattering Center, Los Alamos National Laboratory. Grade 91 plates were welded using the gas tungsten arc welding (GTAW) technique. The load sharing by different grain orientations was observed during the tensile loading. The residual stresses along three orthogonal directions were determined at the mid-thickness, 4.35 and 2.35 mm below the surface of both the as-welded and post-weld heat-treated plates. The residual stresses of the as-welded plates were compared with those of the post-weld heat-treated plates. The post-weld heat treatment significantly reduced the residual stress level in the base metal, the heat-affected zone, and the weld zone. Vickers microhardness across the weld zone of the as-welded and post-weld heat-treated specimens was evaluated and correlated with the observed residual stress profile and microstructure.

  18. Neutron production and time resolution of a new class moderator for pulsed neutron diffraction. Measurements and transport calculations

    NASA Astrophysics Data System (ADS)

    Mayer, R. E.; Florido, P. C.; Granada, J. R.; Dawidowski, J.; Gillette, V. H.

    1992-06-01

    Measurements of neutron pulse time-width and intensity have been carried out on grids of small moderators placed side by side and decoupled by cadium strips; a moderator concept introduced by the authors through previous publications. Transport calculations are based on the standard reactor code DOT 3.5 with the ENDF-B IV nuclear data library.

  19. Diffraction pattern from thermal neutron incoherent elastic scattering and the holographic reconstruction of the coherent scattering length distribution

    SciTech Connect

    Sur, B.; Anghel, V.N.P.; Rogge, R.B.; Katsaras, J.

    2005-01-01

    The diffraction of spherical waves (S waves) interacting with a periodic scattering length distribution produces characteristic intensity patterns known as Kossel and Kikuchi lines (collectively called K lines). The K-line signal can be inverted to give the three-dimensional structure of the coherent scattering length distribution surrounding the source of S waves - a process known as 'Gabor holography' or, simply, 'holography'. This paper outlines a kinematical formulation for the diffraction pattern of monochromatic plane waves scattering from a mixed incoherent and coherent S-wave scattering length distribution. The formulation demonstrates that the diffraction pattern of plane waves incident on a sample with a uniformly random distribution of incoherent scatterers is the same as that from a sample with a single incoherent scatterer per unit cell. In practice, one can therefore reconstruct the holographic data from samples with numerous incoherent S-wave scatterers per unit cell. Thus atomic resolution thermal neutron holography is possible for materials naturally rich in incoherent thermal neutron scatterers, such as hydrogen (e.g., biological and polymeric materials). Additionally, holographic inversions from single-wavelength data have suffered from the so-called conjugate or twin-image problem. The formulation presented for holographic inversion - different from those used previously [e.g., T. Gog et al., Phys. Rev. Lett. 76, 3132 (1996)] - eliminates the twin-image problem for single-wavelength data.

  20. Diffraction pattern from thermal neutron incoherent elastic scattering and the holographic reconstruction of the coherent scattering length distribution

    NASA Astrophysics Data System (ADS)

    Sur, B.; Anghel, V. N. P.; Rogge, R. B.; Katsaras, J.

    2005-01-01

    The diffraction of spherical waves ( S waves) interacting with a periodic scattering length distribution produces characteristic intensity patterns known as Kossel and Kikuchi lines (collectively called K lines). The K -line signal can be inverted to give the three-dimensional structure of the coherent scattering length distribution surrounding the source of S waves—a process known as “Gabor holography” or, simply, “holography.” This paper outlines a kinematical formulation for the diffraction pattern of monochromatic plane waves scattering from a mixed incoherent and coherent S -wave scattering length distribution. The formulation demonstrates that the diffraction pattern of plane waves incident on a sample with a uniformly random distribution of incoherent scatterers is the same as that from a sample with a single incoherent scatterer per unit cell. In practice, one can therefore reconstruct the holographic data from samples with numerous incoherent S -wave scatterers per unit cell. Thus atomic resolution thermal neutron holography is possible for materials naturally rich in incoherent thermal neutron scatterers, such as hydrogen (e.g., biological and polymeric materials). Additionally, holographic inversions from single-wavelength data have suffered from the so-called conjugate or twin-image problem. The formulation presented for holographic inversion—different from those used previously [e.g., T. Gog , Phys. Rev. Lett. 76, 3132 (1996)]—eliminates the twin-image problem for single-wavelength data.

  1. Neutron scattering investigation of a macroscopic single crystal of a lyotropic Lα phase

    NASA Astrophysics Data System (ADS)

    Goecking, K. D.; Monkenbusch, M.

    1998-07-01

    Water-rich lamellar samples of the quaternary microemulsion SDS-pentanol-water-dodecane have been prepared in form of 1 mm×10 mm×20 mm macroscopic mono domains. The shape is given by the quartz cuvette containing the sample, the layer planes are parallel to the cuvette walls. Diffraction patterns and "rocking curves" have been obtained by neutron diffraction using a triple-axis spectrometer. Three "pseudo-Bragg peaks" have been observed, their (relative) intensities yield a new experimental access to estimate the product of the elastic constants η-2 propto Bκ resulting in a lower value than obtained from synchrotron investigation using peak shape fitting (Roux D. et al., Micelles, Membranes, Microemulsions and Monolayers (Springer, New York, Berlin) 1994).

  2. Radiation-induced stress relaxation in high temperature water of type 316L stainless steel evaluated by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Ishiyama, Y.; Rogge, R. B.; Obata, M.

    2011-01-01

    Weld beads on plate specimens made of type 316L stainless steel were neutron-irradiated up to about 2.5 × 10 25 n/m 2 ( E > 1 MeV) at 561 K in the Japan Material Testing Reactor (JMTR). Residual stresses of the specimens were measured by the neutron diffraction method, and the radiation-induced stress relaxation was evaluated. The values of σ x residual stress (transverse to the weld bead) and σ y residual stress (longitudinal to the weld bead) decreased with increasing neutron dose. The tendency of the stress relaxation was almost the same as previously published data, which were obtained for type 304 stainless steel. From this result, it was considered that there was no steel type dependence on radiation-induced stress relaxation. The neutron irradiation dose dependence of the stress relaxation was examined using an equation derived from the irradiation creep equation. The coefficient of the stress relaxation equation was obtained, and the value was 1.4 (×10 -6/MPa/dpa). This value was smaller than that of nickel alloy.

  3. Structure of molten CaSiO3: neutron diffraction isotope substitution with aerodynamic levitation and molecular dynamics study.

    PubMed

    Skinner, L B; Benmore, C J; Weber, J K R; Tumber, S; Lazareva, L; Neuefeind, J; Santodonato, L; Du, J; Parise, J B

    2012-11-15

    We have performed neutron diffraction isotopic substitution experiments on aerodynamically levitated droplets of CaSiO(3), to directly extract intermediate and local structural information on the Ca environment. The results show a substantial broadening of the first Ca-O peak in the pair distribution function of the melt compared to the glass, which comprises primarily of 6- and 7-fold coordinated Ca-polyhedra. The broadening can be explained by a redistribution of Ca-O bond lengths, especially toward longer distances in the liquid. The first order neutron difference function provides a test of recent molecular dynamics simulations and supports the MD model which contains short chains or channels of edge shared Ca-octahedra in the liquid state. It is suggested that the polymerization of Ca-polyhedra is responsible for the fragile viscosity behavior of the melt and the glass forming ability in CaSiO(3). PMID:23106223

  4. The structure of molten CaSiO3: A neutron diffraction isotope substitution and aerodynamic levitation study.

    SciTech Connect

    Skinner, Lawrie; Benmore, Chris J; Weber, Richard; Santodonato, Louis J; Tumber, Sonia; Neuefeind, Joerg C; Lazareva, Lena; Du, Jincheng; Parise, John B

    2012-01-01

    We have performed neutron diffraction isotopic substitution experiments on aerodynamically levitated droplets of CaSiO3, to directly extract intermediate and local structural information on the Ca environment. The results show a substantial broadening of the Ca-O peak in the pair distribution function of the melt compared to the glass, which comprises primarily of 6- and 7-fold coordinated Ca-polyhedra. The broadening can be explained by a re-distribution of Ca-O bond lengths, especially towards longer distances in the liquid. The first order neutron difference function provides a rigorous test of recent molecular dynamics simulations and supports the model of the presence of short chains or channels of edge shared Ca-octahedra in the liquid state. It is suggested that the polymerization of Ca-polyhedra is responsible for the fragile viscosity behavior of the melt and the glass forming ability in CaSiO3.

  5. Extracting grain-orientation-dependent data from in situ time-of-flight neutron diffraction. I. Inverse pole figures

    DOE PAGES

    Stoica, Grigoreta M.; Stoica, Alexandru Dan; An, Ke; Ma, Dong; Vogel, S. C.; Carpenter, J. S.; Wang, Xun-Li

    2014-11-28

    The problem of calculating the inverse pole figure (IPF) is analyzed from the perspective of the application of time-of flight neutron diffraction toin situmonitoring of the thermomechanical behavior of engineering materials. On the basis of a quasi-Monte Carlo (QMC) method, a consistent set of grain orientations is generated and used to compute the weighting factors for IPF normalization. The weighting factors are instrument dependent and were calculated for the engineering materials diffractometer VULCAN (Spallation Neutron Source, Oak Ridge National Laboratory). The QMC method is applied to face-centered cubic structures and can be easily extended to other crystallographic symmetries. Examples includemore » 316LN stainless steelin situloaded in tension at room temperature and an Al–2%Mg alloy, substantially deformed by cold rolling and in situannealed up to 653 K.« less

  6. A Multi-Anode Photomultiplier Tube Based Wavelength-Shifting-Fiber Detector for neutron diffraction

    SciTech Connect

    Berry, Kevin D; Clonts, Lloyd G; Crow, Lowell; Diawara, Yacouba; Funk, Loren L; Hannan, Bruce W; Hodges, Jason P; Riedel, Richard A; Wang, Cai-Lin

    2012-01-01

    The wavelength-shifting (WLS) fiber scintillator neutron detectors were developed for two time-of-flight (TOF) neutron powder diffractometers (POWGEN, VULCAN) at Spallation Neutron Source (SNS). In a recent module (v3.0), however, there are 32 1-inch-diameter photomultiplier tubes (PMTs) which are bulky and expensive. We built a new detector module (v3.1) based on four multi-anode (MA) PMTs, and tested its performance including detection efficiency, count rate capability, spatial resolution, ghosting properties, and gamma-ray sensitivity. The v3.1 module was compared with two prior v3.0 modules, and 3He tube detectors.

  7. Exploring the complex magnetic phase diagram of Ce2PdGe3 : A neutron powder diffraction and μ SR study

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, A.; Ritter, C.; Adroja, D. T.; Coomer, F. C.; Strydom, A. M.

    2016-07-01

    The magnetic state of the tetragonal compound Ce2PdGe3 , which crystallizes in the space group P 42/m m c , a derivative of the α -ThSi2 structure, has been investigated by magnetic susceptibility, heat capacity, muon spin relaxation (μ SR ), and neutron diffraction measurements. Heat capacity data indicate two separate magnetic phase transitions at TN1=10.7 K and TN 2=2.3 K. The presence of bulk long-range magnetic order is confirmed by our μ SR study below 11 K, where a drop of nearly 2/3 in the muon initial asymmetry and a sharp increase in the muon depolarization rate were observed. Neutron powder diffraction reveals that only one out of two Ce sites becomes magnetically ordered with magnetic propagation vector κ =(0 ) at TN1,adopting an antiferromagnetic arrangement of magnetic moments μCe3+=1.78 (1 ) μB along the c axis. At TN 2 the second Ce site orders similarly, following the same magnetic propagation vector κ =(0 ) , showing, however, at the same time a significant ferromagnetic component within the tetragonal basal plane. A second propagation vector, κ =(1/2 ,0 ,1/2 ) , appears concomitantly at TN 2.

  8. High-resolution neutron powder diffraction study on the phase transitions in BaPbO{sub 3}

    SciTech Connect

    Fu, W.T. Visser, D.; Knight, K.S.; IJdo, D.J.W.

    2007-05-15

    Phase transitions that occurred in perovskite BaPbO{sub 3} have been investigated using high-resolution time-of-flight neutron powder diffraction. The structure at room temperature is orthorhombic (space group Imma), which is derived from the cubic aristotype by tilting the PbO{sub 6} octahedra around the two-fold axis (tilt system a {sup 0} b {sup -} b {sup -}). The orthorhombic structure shows anisotropic line broadening attributed to the presence of micro twins. At above about 573 K, BaPbO{sub 3} undergoes a discontinuous phase transition to a tetragonal structure (space group I4/mcm) with the tilting of the PbO{sub 6} octahedra being about the four-fold axis of the cubic aristotype (tilt system a {sup 0} a {sup 0} c {sup -}). With further increasing the temperature, BaPbO{sub 3} experiences a continuous phase transition to a simple cubic structure (space group Pm3-barm) at above about 673 K. The later phase transition is characterised by a critical exponent of {beta}=0.36, depicted by the three-dimensional Heisenberg universality class. The earlier reported Imma{sup {yields}}I2/m phase transition above room temperature has not been observed. - Graphical abstract: Temperature dependence of the octahedral tilting angles in BaPbO{sub 3}. The continuous line in tetragonal phase region is the fit to the expression: {phi}=A(T {sub c}-T) {sup {beta}} with the fitted values of T {sub c}=658(1) K, {beta}=0.36(2) and A=1.1(1). The shaded area indicates the possible two-phase region.

  9. Magnetic Barkhausen Noise and Neutron Diffraction Techniques for the Study of Intergranular Residual Strains in Mild Steel

    SciTech Connect

    Hutanu, Roxana; Clapham, Lynann; Rogge, Ronald

    2004-02-26

    Intergranular residual stresses (IS) are microscopic residual stresses which have been found to accumulate along the <100> direction in steels. The <100> direction is also the magnetic easy axis direction in steel. This work involved Magnetic Barkhausen Noise (MBN) studies on steel samples, deformed uniaxially to increasing levels of strain. The MBN results indicated that a bulk magnetic easy axis was produced by the deformation process, and neutron diffraction experiments showed that this easy axis was correlated with the tensile strain in grains oriented in the <100> direction.

  10. Neutron-Diffraction Evidence for the Ferrimagnetic Ground State of a Molecule-Based Magnet with Weakly Coupled Sublattices

    SciTech Connect

    Fishman, Randy Scott; Campo, Javier; Vos, Thomas E.; Miller, Joel S.

    2012-01-01

    The diruthenium compound [Ru2(O2CMe)4]3[Cr(CN)6] contains two weakly coupled, ferrimag- netically ordered sublattices occupying the same volume. The magnetic field Hc 800 Oe required to align the two sublattice moments is proportional to the antiferromagnetic dipolar interaction Kc B Hc 5 10 3 meV between sublattices. Powder neutron-diffraction measurements on a deuterated sample reveal that the sublattice moments are restricted by the anisotropy of the diruthenium paddle-wheel complexes to the cubic diagonals. Those measurements also suggest that the quantum corrections to the ground state are significant.

  11. In-situ observation of ErD2 formation during D2 loading via neutron diffraction.

    SciTech Connect

    Browning, James Frederick; Llobet, Anna; Snow, Clark Sheldon; Rodriguez, Mark Andrew; Wixom, Ryan R.

    2010-09-01

    In an effort to better understand the structural changes occurring during hydrogen loading of erbium target materials, we have performed in situ D{sub 2} loading of erbium metal (powder) at temperature (450 C) with simultaneous neutron diffraction analysis. This experiment tracked the conversion of Er metal to the {alpha} erbium deuteride (solid-solution) phase and then into 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.

  12. Complete crystal structure of decafluorocyclohex-1-ene at 4.2 K from original neutron diffraction data.

    PubMed

    Solovyov, Leonid A; Fedorov, Alexandr S; Kuzubov, Aleksandr A

    2014-04-01

    The crystal structure model of decafluorocyclohex-1-ene at 4.2 K derived from simulated powder diffraction data and solid-state energy minimization [Smrčok et al. (2013). Acta Cryst. B69, 395-404] is found to be incomplete. In this study it is completed by an additional alternative molecular orientation revealed from the difference density analysis and direct space search. The structure is refined by the derivative difference method in the rigid-body approximation leading to perfect agreement between observed and calculated neutron powder patterns. PMID:24675609

  13. In situ x-ray and neutron powder diffraction study of LaNi5-xSnx-H systems

    NASA Technical Reports Server (NTRS)

    Bowman, Robert C., Jr.; Nakamara, Yumiko; Akiba, Etsuo

    2004-01-01

    This paper will present results of in situ XRD measurements of LaNi4.75Sn0.25 .during the initial absorption-desorption cycle, These measurements were performed under a similar condition to that for LaNi4.75Al0.25 previously reported [1]. The data were analyzed by the Rietveld method. Lattice parameter change and strain formation accompanying hydride phase formation and decomposition will be discussed. In addition, results of in situ neutron diffraction of LaNi4.78Sn0.22, focusing on hydrogen occupation in the hydride phase, will be presented.

  14. Microdosimetric investigations at the Fast Neutron Therapy Facility at Fermilab

    SciTech Connect

    Langen, K.M.

    1997-12-31

    Microdosimetry was used to investigate three issues at the neutron therapy facility (NTF) at Fermilab. Firstly, the conversion factor from absorbed dose in A-150 tissue equivalent plastic to absorbed dose in ICRU tissue was determined. For this, the effective neutron kerma factor ratios, i.e. oxygen tissue equivalent plastic and carbon to A-150 tissue equivalent plastic, were measured in the neutron beam. An A-150 tissue equivalent plastic to ICRU tissue absorbed dose conversion factor of 0.92 {+-} 0.04 determined. Secondly, variations in the radiobiological effectiveness (RBE) in the beam were mapped by determining variations in two related quantities, e{sup *} and R, with field size and depth in tissue. Maximal variation in e{sup *} and R of 9% and 15% respectively were determined. Lastly, the feasibility of utilizing the boron neutron capture reaction on boron-10 to selectively enhance the tumor dose in the NTF beam was investigated. In the unmodified beam, a negligible enhancement for a 50 ppm boron loading was measured. To boost the boron dose enhancement to 3% it was necessary to change the primary proton energy from 66 MeV and to filter the beam by 90 mm of tungsten.

  15. In situ neutron diffraction of heavily drawn steel wires with ultra-high strength under tensile loading

    SciTech Connect

    Tomota, Y. . E-mail: tomota@mx.ibaraki.ac.jp; Suzuki, T.; Kanie, A.; Shiota, Y.; Uno, M.; Moriai, A.; Minakawa, N.; Morii, Y.

    2005-01-10

    To make clear the strengthening mechanism of heavily drawn steel wires exhibiting ultra-high strength, in situ neutron diffraction during tensile loading was performed. A ferrite steel (FK) subjected to a true strain of 6.6 and a pearlite steel (PS) subjected to 4.0 were extended on a tensile tester and (1 1 0) diffraction profiles were measured at various holding stresses. Tensile strengths of steel FK and PS are 1.7 and 3.7 GPa, respectively. The change in (1 1 0) spacing with tensile stress is reversible, i.e., elastic, close to the relevant tensile strength. A stress versus (1 1 0) lattice plane strain is linear for steel FK while evidently nonlinear at higher stresses for steel PS. In steel PS in which cementite peaks were hardly observed, the strengthening mechanism is postulated to be different from that for as-patented pearlite steels.

  16. Characterization of residual stresses in Eurofer welded specimens: Measurements by neutron diffraction and comparison with weld modeling

    NASA Astrophysics Data System (ADS)

    Coppola, R.; Asserin, O.; Aubert, P.; Braham, C.; Monnier, A.; Valli, M.; Diegele, E.

    2011-10-01

    The stress field of a dual-beam laser weld on a Eurofer-97 model plate has been experimentally determined by neutron diffraction measurements. The measurements were carried out at the ILL-Grenoble, in the three principal directions, at different distances from the weld and inside the weld itself. In the longitudinal direction, the most relevant for technical applications, there is good agreement between these experimental results and results obtained by finite element numerical methods: tensile stresses as high as 750 MPa are found inside the weld, rapidly decreasing with increasing distance from the weld centre. In the two other directions the agreement between experimentally determined and calculated stresses is still good far from the weld; inside the weld the experimental data are affected by the strong texture detected by X-ray diffraction, possibly produced by the heating and subsequent cooling of the structure.

  17. Neutron diffraction analyses of U-(6-10 wt.%)Mo alloy powders fabricated by centrifugal atomization

    NASA Astrophysics Data System (ADS)

    Park, Jong Man; Ryu, Ho Jin; Kim, Ki Hwan; Lee, Don Bae; Lee, Yoon Sang; Lee, Jeong Soo; Seong, Baek Seok; Kim, Chang Kyu; Cornen, Marilyne

    2010-02-01

    Lattice parameters of U-(6-10 wt.%)Mo alloy powders fabricated by a centrifugal atomization technique were measured by neutron diffraction analyses. A micro-segregation of Mo at cell boundaries was observed in the centrifugally atomized U-Mo alloy powders with varying Mo content. Lattice parameters of gamma phases decrease linearly with the increasing Mo content. By separating the overlapped diffraction peaks from cell boundaries and cell interior, lattice parameters and Mo contents of each region were calculated. The Mo content at cell boundaries is about 2-5 at.% lower than that in the cell interior and the lattice parameters for the cell boundaries are higher than those for the cell interior of the atomized U-Mo powder.

  18. Neutron diffraction and electrical transport studies on magnetic ordering in terbium at high pressures and low temperatures

    SciTech Connect

    Thomas, Sarah A.; Montgomery, Jeffrey M.; Tsoi, Georgiy M.; Vohra, Yogesh K.; Chesnut, Gary N.; Weir, Samuel T.; Tulk, Christopher A.; dos Santos, Antonio M.

    2013-06-11

    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 the onset of ferromagnetic order as a function of pressure. The electrical resistance measurements show a change in slope as the temperature is lowered through the ferromagnetic Curie temperature. The temperature of this ferromagnetic transition decreases from approximately 240 K at ambient pressure at a rate of –16.7 K/GPa up to a pressure of 3.6 GPa, at which point the onset of ferromagnetic order is suppressed. Neutron diffraction measurements as a function of pressure at temperatures ranging from 90 K to 290 K confirm that the change of slope in the resistance is associated with the ferromagnetic ordering, since this occurs at pressures similar to those determined from the resistance results at these temperatures. Furthermore, a change in ferromagnetic ordering as the pressure is increased above 3.6 GPa is correlated with the phase transition from the ambient hexagonal close packed (hcp) structure to an α-Sm type structure at high pressures.

  19. Quantitative analysis of hydrogen sites and occupancy in deep mantle hydrous wadsleyite using single crystal neutron diffraction

    PubMed Central

    Purevjav, Narangoo; Okuchi, Takuo; Tomioka, Naotaka; Wang, Xiaoping; Hoffmann, Christina

    2016-01-01

    Evidence from seismological and mineralogical studies increasingly indicates that water from the oceans has been transported to the deep earth to form water-bearing dense mantle minerals. Wadsleyite [(Mg, Fe2+)2SiO4] has been identified as one of the most important host minerals incorporating this type of water, which is capable of storing the entire mass of the oceans as a hidden reservoir. To understand the effects of such water on the physical properties and chemical evolution of Earth’s interior, it is essential to determine where in the crystal structure the hydration occurs and which chemical bonds are altered and weakened after hydration. Here, we conduct a neutron time-of-flight single-crystal Laue diffraction study on hydrous wadsleyite. Single crystals were grown under pressure to a size suitable for the experiment and with physical qualities representative of wet, deep mantle conditions. The results of this neutron single crystal diffraction study unambiguously demonstrate the method of hydrogen incorporation into the wadsleyite, which is qualitatively different from that of its denser polymorph, ringwoodite, in the wet mantle. The difference is a vital clue towards understanding why these dense mantle minerals show distinctly different softening behaviours after hydration. PMID:27725749

  20. Neutron diffraction and electrical transport studies on magnetic ordering in terbium at high pressures and low temperatures

    SciTech Connect

    Thomas, Sarah; Montgomery, Jeffrey M; Tsoi, Georgiy; Vohra, Yogesh; Chesnut, Gary Neal; Weir, S. T.; Tulk, Christopher A; Moreira Dos Santos, Antonio F

    2013-01-01

    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 the onset of ferromagnetic (FM) order as a function of pressure. The electrical resistance measurements show a change in slope as the temperature is lowered through the FM Curie temperature. The temperature of this FM transition decreases at a rate of-16.7 K/GPa up to a pressure of 3.6 GPa, at which point the onset of FM order is suppressed. The neutron diffraction measurements as a function of pressure at temperatures ranging from 90 to 290 K confirm that the change of slope in the resistance is associated with the FM ordering, since this occurs at pressures similar to those determined from the resistance results at these temperatures. A disappearance of FM ordering was observed as the pressure is increased above 3.6 GPa and is correlated with the phase transition from the ambient hexagonal close packed structure to an -Sm-type structure at high pressures.

  1. Neutron diffraction and electrical transport studies on magnetic ordering in terbium at high pressures and low temperatures

    DOE PAGES

    Thomas, Sarah A.; Montgomery, Jeffrey M.; Tsoi, Georgiy M.; Vohra, Yogesh K.; Chesnut, Gary N.; Weir, Samuel T.; Tulk, Christopher A.; dos Santos, Antonio M.

    2013-06-11

    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 the onset of ferromagnetic order as a function of pressure. The electrical resistance measurements show a change in slope as the temperature is lowered through the ferromagnetic Curie temperature. The temperature of this ferromagnetic transition decreases from approximately 240 K at ambient pressure at a rate of –16.7 K/GPa up to a pressure of 3.6 GPa, at which point the onset of ferromagnetic order is suppressed. Neutron diffraction measurements as a function ofmore » pressure at temperatures ranging from 90 K to 290 K confirm that the change of slope in the resistance is associated with the ferromagnetic ordering, since this occurs at pressures similar to those determined from the resistance results at these temperatures. Furthermore, a change in ferromagnetic ordering as the pressure is increased above 3.6 GPa is correlated with the phase transition from the ambient hexagonal close packed (hcp) structure to an α-Sm type structure at high pressures.« less

  2. CO2 Sorption to Subsingle Hydration Layer Montmorillonite Clay Studied by Excess Sorption and Neutron Diffraction Measurements

    SciTech Connect

    Rother, Gernot; Ilton, Eugene S.; Wallacher, Dirk; Hauβ, Thomas; Schaef, Herbert T.; Qafoku, Odeta; Rosso, Kevin M.; Felmy, Andrew R.; Krukowski, Elizabeth G.; Stack, Andrew G.; Grimm, Nico; Bodnar, Robert J.

    2013-01-02

    Geologic storage of CO2 requires that the caprock sealing the storage rock is highly impermeable to CO2. Swelling clays, which are important components of caprocks, may interact with CO2 leading to volume change and potentially impacting the seal quality. The interactions of supercritical (sc) CO2 with Na saturated montmorillonite clay containing a subsingle layer of water in the interlayer region have been studied by sorption and neutron diffraction techniques. The excess sorption isotherms show maxima at bulk CO2 densities of ≈0.15 g/cm3, followed by an approximately linear decrease of excess sorption to zero and negative values with increasing CO2 bulk density. Neutron diffraction experiments on the same clay sample measured interlayer spacing and composition. The results show that limited amounts of CO2 are sorbed into the interlayer region, leading to depression of the interlayer peak intensity and an increase of the d(001) spacing by ca. 0.5 Å. The density of CO2 in the clay pores is relatively stable over a wide range of CO2 pressures at a given temperature, indicating the formation of a clay-CO2 phase. Finally, at the excess sorption maximum, increasing CO2 sorption with decreasing temperature is observed while the high-pressure sorption properties exhibit weak temperature dependence.

  3. CO2 Adsorption to Sub-Single Hydration Layer Montmorillonite Clay Studied by Excess Sorption and Neutron Diffraction

    SciTech Connect

    Rother, Gernot; Ilton, Eugene; Wallacher, Dirk; Hauss, Thomas; Schaef, Herbert; Qafoku, Odeta; Rosso, Kevin M.; Felmy, Andrew; Krukowski, Elizabeth G; Stack, Andrew G; Bodnar, Robert J

    2013-01-01

    Geologic storage of CO2 requires that the caprock sealing the storage rock is highly impermeable by CO2. Swelling clays, which are important components of caprocks, may react with CO2 under volume change, potentially impacting the seal quality. The interactions of scCO2 with Na saturated montmorillonite clay containing a sub-single layer of water in the interlayer region have been studied by sorption and neutron diffraction techniques. The excess sorption isotherms show maxima at bulk CO2 densities of 0.15 g/cm3, followed by an approximately linear decrease of excess sorption to zero and negative values with increasing CO2 bulk density. Neutron diffraction experiments on the same clay sample measured interlayer spacing and composition. The results show that limited amounts of CO2 are sorbed into the interlayer region, leading to depression of the interlayer peak intensity and an increase of the d(001) spacing by ca. 0.5 . The density of CO2 in the clay pores is relatively stable over a wide range of CO2 pressures at a given temperature, indicating the formation of a clay-CO2 phase. At low pressure increasing CO2 adsorption with decreasing temperature is observed while the high-pressure sorption properties exhibit weak or no temperature dependence. Supercritical fluids, sorption phenomena, carbon dioxide, carbon sequestration, caprock integrity

  4. α-Phase transformation kinetics of U – 8 wt% Mo established by in situ neutron diffraction

    DOE PAGES

    Garlea, Elena; Steiner, M. A.; Calhoun, C. A.; Klein, R. W.; An, K.; Agnew, S. R.

    2016-05-08

    The α-phase transformation kinetics of as-cast U - 8 wt% Mo below the eutectoid temperature have been established by in situ neutron diffraction. α-phase weight fraction data acquired through Rietveld refinement at five different isothermal hold temperatures can be modeled accurately utilizing a simple Johnson-Mehl-Avrami-Kolmogorov impingement-based theory, and the results are validated by a corresponding evolution in the γ-phase lattice parameter during transformation that follows Vegard’s law. Neutron diffraction data is used to produce a detailed Time-Temperature-Transformation diagram that improves upon inconsistencies in the current literature, exhibiting a minimum transformation start time of 40 min at temperatures between 500 °Cmore » and 510 °C. Lastly, the transformation kinetics of U – 8 wt% Mo can vary significantly from as-cast conditions after extensive heat treatments, due to homogenization of the typical dendritic microstructure which possesses non-negligible solute segregation.« less

  5. Quantitative analysis of hydrogen sites and occupancy in deep mantle hydrous wadsleyite using single crystal neutron diffraction

    NASA Astrophysics Data System (ADS)

    Purevjav, Narangoo; Okuchi, Takuo; Tomioka, Naotaka; Wang, Xiaoping; Hoffmann, Christina

    2016-10-01

    Evidence from seismological and mineralogical studies increasingly indicates that water from the oceans has been transported to the deep earth to form water-bearing dense mantle minerals. Wadsleyite [(Mg, Fe2+)2SiO4] has been identified as one of the most important host minerals incorporating this type of water, which is capable of storing the entire mass of the oceans as a hidden reservoir. To understand the effects of such water on the physical properties and chemical evolution of Earth’s interior, it is essential to determine where in the crystal structure the hydration occurs and which chemical bonds are altered and weakened after hydration. Here, we conduct a neutron time-of-flight single-crystal Laue diffraction study on hydrous wadsleyite. Single crystals were grown under pressure to a size suitable for the experiment and with physical qualities representative of wet, deep mantle conditions. The results of this neutron single crystal diffraction study unambiguously demonstrate the method of hydrogen incorporation into the wadsleyite, which is qualitatively different from that of its denser polymorph, ringwoodite, in the wet mantle. The difference is a vital clue towards understanding why these dense mantle minerals show distinctly different softening behaviours after hydration.

  6. Crystal structure of magnesium dichloride decahydrate determined by X-ray and neutron diffraction under high pressure.

    PubMed

    Komatsu, Kazuki; Shinozaki, Ayako; Machida, Shinichi; Matsubayashi, Takuto; Watanabe, Mao; Kagi, Hiroyuki; Sano-Furukawa, Asami; Hattori, Takanori

    2015-02-01

    Magnesium dichloride decahydrate (MgCl2·10H2O) and its deuterated counterpart (MgCl2·10D2O) are identified for the first time by in-situ powder synchrotron X-ray and spallation neutron diffraction. These substances are crystallized from a previously unidentified nanocrystalline compound, which originates from an amorphous state at low temperature. A combination of a recently developed autoindexing procedure and the charge-flipping method reveals that the crystal structure of MgCl2·10H2O consists of an ABCABC··· sequence of Mg(H2O)6 octahedra. The Cl(-) anions and remaining water molecules unconnected to the Mg(2+) cations bind the octahedra, similar to other water-rich magnesium dichloride hydrates. The D positions in MgCl2·10D2O, determined by the difference Fourier methods using the neutron powder diffraction patterns at 2.5 GPa, show the features such as bifurcated hydrogen bonds and tetrahedrally coordinated O atoms, which were not found in other forms of magnesium chloride hydrates.

  7. Neutron diffraction evidence for kinetic arrest of first order magneto-structural phase transitions in some functional magnetic materials.

    PubMed

    Siruguri, V; Babu, P D; Kaushik, S D; Biswas, Aniruddha; Sarkar, S K; Krishnan, Madangopal; Chaddah, P

    2013-12-11

    Neutron diffraction measurements, performed in the presence of an external magnetic field, have been used to show structural evidence for the kinetic arrest of the first order phase transition from (i) the high temperature austenite phase to the low temperature martensite phase in the magnetic shape memory alloy Ni37Co11Mn42.5Sn9.5, (ii) the higher temperature ferromagnetic phase to the lower temperature antiferromagnetic phase in the half-doped charge ordered compound La0.5Ca0.5MnO3 and (iii) the formation of glass-like arrested states in both compounds. The cooling and heating under unequal fields protocol has been used to establish phase coexistence of metastable and equilibrium states, and also to demonstrate the devitrification of the arrested metastable states in the neutron diffraction patterns. We also explore the field–temperature dependent kinetic arrest line TK(H), through the transformation of the arrested phase to the equilibrium phase. This transformation has been observed isothermally in reducing H, as also on warming in constant H. TK is seen to increase as H increases in both cases, consistent with the low-T equilibrium phase having lower magnetization.

  8. Neutron diffraction and electrical transport studies on magnetic ordering in terbium at high pressures and low temperatures

    NASA Astrophysics Data System (ADS)

    Thomas, Sarah A.; Montgomery, Jeffrey M.; Tsoi, Georgiy M.; Vohra, Yogesh K.; Chesnut, Gary N.; Weir, Samuel T.; Tulk, Christopher A.; dos Santos, Antonio M.

    2013-08-01

    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 the onset of ferromagnetic (FM) order as a function of pressure. The electrical resistance measurements show a change in slope as the temperature is lowered through the FM Curie temperature. The temperature of this FM transition decreases at a rate of-16.7 K/GPa up to a pressure of 3.6 GPa, at which point the onset of FM order is suppressed. The neutron diffraction measurements as a function of pressure at temperatures ranging from 90 to 290 K confirm that the change of slope in the resistance is associated with the FM ordering, since this occurs at pressures similar to those determined from the resistance results at these temperatures. A disappearance of FM ordering was observed as the pressure is increased above 3.6 GPa and is correlated with the phase transition from the ambient hexagonal close packed structure to an α-Sm-type structure at high pressures.

  9. Visualizing the chemistry and structure dynamics in lithium-ion batteries by in-situ neutron diffraction

    SciTech Connect

    Wang, Xun-Li; An, Ke; Cai, Lu; Feng, Zhili; Nagler, Stephen E.; Daniel, Claus; Rhodes, Kevin J.; Stoica, Alexandru D.; Skorpenske, Harley D.; Liang, Chengdu; Zhang, Wei; Kim, Joon; Qi, Yue; Harris, Stephen J.

    2012-10-19

    We report an in-situ neutron diffraction study of a large format pouch battery cell. The succession of Li-Graphite intercalation phases was fully captured under an 1C charge-discharge condition (i.e., charge to full capacity in 1 hour). However, the lithiation and dilithiation pathways are distinctively different and, unlike in slowing charging experiments with which the Li-Graphite phase diagram was established, no LiC24 phase was found during charge at 1C rate. Approximately 75 mol. % of the graphite converts to LiC6 at full charge, and a lattice dilation as large as 4% was observed during a charge-discharge cycle. Our work demonstrates the potential of in-situ, time and spatially resolved neutron diffraction study of the dynamic chemical and structural changes in “real-world” batteries under realistic cycling conditions, which should provide microscopic insights on degradation and the important role of diffusion kinetics in energy storage materials.

  10. A combined diffraction (XRD, electron and neutron) and electrical study of Na 3MoO 3F 3

    NASA Astrophysics Data System (ADS)

    Brink, Frank J.; Norén, Lasse; Goossens, Darren J.; Withers, Ray L.; Liu, Yun; Xu, Chao-Nan

    2003-09-01

    Na 3MoO 3F 3, a member of the A2BMVIO 3F 3 family of elpasolite-related oxyfluorides, has been prepared by the reaction of NaF with MoO 3 at 650°C. It is shown by a combined X-ray, electron and neutron diffraction study, that the true symmetry of Na 3MoO 3F 3 is not monoclinic (pseudo-orthorhombic) as previously reported but instead triclinic (metrically rhombohedral) P1. The superstructure unit cell is given by a=- aR+ bR, b= cR, c=( aR+ bR+ cR), when expressed with respect to the underlying rhombohedral parent structure. Neutron diffraction refinement of the rhombohedral sub-structure shows O and F to be fully ordered with alternate (111) R planes being occupied by O and then F. The nature of the distortion away from the high temperature Fm 3¯m parent structure is consistent with a combination of φφφ type rotations of the octahedral framework together with ppp type displacements of the octahedral cations, which is not observed in any of the closely related A2BMVIO 3F 3 family members. Bond valence arguments are used to give a plausible explanation for this difference in behavior.

  11. Structural and magnetic behavior of the cubic oxyfluoride SrFeO{sub 2}F studied by neutron diffraction

    SciTech Connect

    Thompson, Corey M.; Blakely, Colin K.; Flacau, Roxana; Greedan, John E.; Poltavets, Viktor V.

    2014-11-15

    The oxyfluoride SrFeO{sub 2}F has been prepared via a low temperature route involving the infinite-layer SrFeO{sub 2} and XeF{sub 2}. SrFeO{sub 2}F crystallizes in the cubic space group Pm-3m with disordered oxygen and fluorine atoms on the anion site. Recent reports demonstrated that SrFeO{sub 2}F is antiferromagnetic at room temperature and the zero field cooled and field cooled curves diverge at ∼150 K and ∼60 K, suggesting that the material has a spin glassy magnetic state at low temperatures. In this article, variable-temperature neutron diffraction (4–723 K) was performed to clarify the magnetic behavior observed in this material. Neutron powder diffraction measurements confirmed the antiferromagnetic (AFM) ordering of the system at room temperature. Below 710(1) K, the magnetic structure is a G-type AFM structure characterized by a propagation vector k=(1/2 , 1/2 , 1/2 ). The ordered moments on Fe{sup 3+} are 4.35(6)µ{sub B} at 4 K and 4.04(5)µ{sub B} at 290 K. Our results indicate that the cubic structure is retained all the way to base temperature (4 K) in contrast to PbFeO{sub 2}F. These results are compared with those of Pb and Ba analogs which exhibit very similar magnetic behavior. Furthermore, the observation of magnetic reflections at 4 K in the diffraction pattern shows the absence of the previously proposed spin glassy behavior at low temperatures. Previous proposals to explain the ZFC/FC divergences are examined. - Graphical abstract: Variable temperature powder neutron diffraction was employed to follow the evolution of the long range antiferromagnetic state in SrFeO{sub 2}F. - Highlights: • SrFeO{sub 2}F prepared via low temperature route involving SrFeO{sub 2} and XeF{sub 2}. • The cubic structure, Pm-3m, is retained at low temperatures, 4 K. • The magnetic structure is G-type AFM with T{sub N}=710 K and Fe{sup 3+} moment of 4.35µ{sub B}. • A small volume, bulk decoupled, spin glassy domain/cluster mechanism is proposed.

  12. Complementarity of real-time neutron and synchrotron radiation structural investigations in molecular biology

    SciTech Connect

    Aksenov, V. L.; Kiselev, M. A.

    2010-12-15

    General problems of the complementarity of different physical methods and specific features of the interaction between neutron and matter and neutron diffraction with respect to the time of flight are discussed. The results of studying the kinetics of structural changes in lipid membranes under hydration and self-assembly of the lipid bilayer in the presence of a detergent are reported. The possibilities of the complementarity of neutron diffraction and X-ray synchrotron radiation and developing a free-electron laser are noted.

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

    PubMed Central

    Deutsch, Maxime; Gillon, Béatrice; Claiser, Nicolas; Gillet, Jean-Michel; Lecomte, Claude; Souhassou, Mohamed

    2014-01-01

    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. PMID:25075338

  14. Combined high-pressure neutron and X-ray diffraction study of H-D substitution effects on brucite

    SciTech Connect

    dos Santos, Antonio M.; Horita, Juske; Tulk, Christopher A; Chakoumakos, Bryan C; Polyakov, Dr. Veniamin B

    2010-01-01

    The high-pressure behavior of the mineral brucite, Mg(OH)2, is of great geochemical and geophysical interest, because brucite-type minerals serve as a simple analog for more complex, hydrogen-bearing oxide and silicate minerals in the deep-earth. A combined neutron and synchrotron x-ray powder diffraction study of hydrogenated and deuterated brucite was conducted at ambient temperature and at pressures to 9 and 20 GPa, using a Paris-Edinburgh (neutron diffraction) and a diamond anvil cell (synchrotron x-ray radiation), respectively. The two materials were synthesized by the same method and companion diffraction measurements of the two materials were conducted under the same conditions. Our experimental results show that the lattice-parameters of the a axis, parallel to the sheets of Mg-O octahedra, decrease only slightly with pressure with no effect of H-D substitution. However, the c axis of Mg (OD)2 is shorter and may exhibit greater compressibility with pressure than that of Mg (OH)2. Consequently, the unit-cell volume of deuterated brucite is slightly, but systematically smaller than that of hydrogenated brucite. Fitting to a third-order Birch-Murnaghan equation shows that values of the bulk modulus for hydrogenated and deuterated brucite are indistinguishable from each other within the experimental errors. The measured effect of H-D substitution on the unit-cell volume demonstrates that brucite (and other hydrous minerals) preferentially incorporate deuterium over hydrogen under pressure, suggesting that the distribution of hydrogen isotopes in deep-earth conditions may differ significantly from that in near-surface environments.

  15. Combined high-pressure neutron and X-ray diffraction study of H-D substitution effects on brucite

    SciTech Connect

    Moreira Dos Santos, Antonio F; Horita, Juske; Tulk, Christopher A; Chakoumakos, Bryan C; Polyakov, Dr. V. B.

    2010-01-01

    The high-pressure behavior of the mineral brucite, Mg(OH){sub 2}, is of great geochemical and geophysical interest, because brucite-type minerals serve as a simple analog for more complex, hydrogen-bearing oxide and silicate minerals in the deep-earth. A combined neutron and synchrotron x-ray powder diffraction study of hydrogenated and deuterated brucite was conducted at ambient temperature and at pressures to 9 and 20 GPa, using a Paris-Edinburgh (neutron diffraction) and a diamond anvil cell (synchrotron x-ray radiation), respectively. The two materials were synthesized by the same method and companion diffraction measurements of the two materials were conducted under the same conditions. Our experimental results show that the lattice-parameters of the a axis, parallel to the sheets of Mg-O octahedra, decrease only slightly with pressure with no effect of H-D substitution. However, the c axis of Mg (OD){sub 2} is shorter and may exhibit greater compressibility with pressure than that of Mg (OH){sub 2}. Consequently, the unit-cell volume of deuterated brucite is slightly, but systematically smaller than that of hydrogenated brucite. Fitting to a third-order Birch-Murnaghan equation shows that values of the bulk modulus for hydrogenated and deuterated brucite are indistinguishable from each other within the experimental errors. The measured effect of H-D substitution on the unit-cell volume demonstrates that brucite (and other hydrous minerals) preferentially incorporate deuterium over hydrogen under pressure, suggesting that the distribution of hydrogen isotopes in deep-earth conditions may differ significantly from that in near-surface environments.

  16. Density-driven structural transformations in network forming glasses: a high-pressure neutron diffraction study of GeO2 glass up to 17.5 GPa

    NASA Astrophysics Data System (ADS)

    Salmon, Philip S.; Drewitt, James W. E.; Whittaker, Dean A. J.; Zeidler, Anita; Wezka, Kamil; Bull, Craig L.; Tucker, Matthew G.; Wilding, Martin C.; Guthrie, Malcolm; Marrocchelli, Dario

    2012-10-01

    The structure of GeO2 glass was investigated at pressures up to 17.5(5) GPa using in situ time-of-flight neutron diffraction with a Paris-Edinburgh press employing sintered diamond anvils. A new methodology and data correction procedure were developed, enabling a reliable measurement of structure factors that are largely free from diamond Bragg peaks. Calibration curves, which are important for neutron diffraction work on disordered materials, were constructed for pressure as a function of applied load for both single and double toroid anvil geometries. The diffraction data are compared to new molecular-dynamics simulations made using transferrable interaction potentials that include dipole-polarization effects. The results, when taken together with those from other experimental methods, are consistent with four densification mechanisms. The first, at pressures up to ≃ 5 GPa, is associated with a reorganization of GeO4 units. The second, extending over the range from ≃ 5 to 10 GPa, corresponds to a regime where GeO4 units are replaced predominantly by GeO5 units. In the third, as the pressure increases beyond ˜10 GPa, appreciable concentrations of GeO6 units begin to form and there is a decrease in the rate of change of the intermediate-range order as measured by the pressure dependence of the position of the first sharp diffraction peak. In the fourth, at about 30 GPa, the transformation to a predominantly octahedral glass is achieved and further densification proceeds via compression of the Ge-O bonds. The observed changes in the measured diffraction patterns for GeO2 occur at similar dimensionless number densities to those found for SiO2, indicating similar densification mechanisms for both glasses. This implies a regime from about 15 to 24 GPa where SiO4 units are replaced predominantly by SiO5 units, and a regime beyond ˜24 GPa where appreciable concentrations of SiO6 units begin to form.

  17. Neutrons and music: Imaging investigation of ancient wind musical instruments

    NASA Astrophysics Data System (ADS)

    Festa, G.; Tardino, G.; Pontecorvo, L.; Mannes, D. C.; Senesi, R.; Gorini, G.; Andreani, C.

    2014-10-01

    A set of seven musical instruments and two instruments cares from the 'Fondo Antico della Biblioteca del Sacro Convento' in Assisi, Italy, were investigated through neutron and X-ray imaging techniques. Historical and scientific interests around ancient musical instruments motivate an intense research effort for their characterization using non-destructive and non-invasive techniques. X-ray and neutron tomography/radiography were applied to the study of composite material samples containing wood, hide and metals. The study was carried out at the NEUTRA beamline, PSI (Paul Scherrer Institute, Switzerland). Results of the measurements provided new information on the composite and multi-scale structure, such as: the internal structure of the samples, position of added materials like metals, wood fiber displays, deformations, presence of adhesives and their spatial distribution and novel insight about construction methods to guide the instruments' restoration process.

  18. Investigation of neutron converters for production of optically stimulated luminescence (OSL) neutron dosimeters using Al 2O 3:C

    NASA Astrophysics Data System (ADS)

    Mittani, J. C. R.; da Silva, A. A. R.; Vanhavere, F.; Akselrod, M. S.; Yukihara, E. G.

    2007-07-01

    This paper presents the optically stimulated luminescence (OSL) properties of neutron dosimeters in powder and in the form of pellets prepared with a mixture of Al 2O 3:C and neutron converters. The neutron converters investigated were high density polyethylene (HDPE), lithium fluoride (LiF), lithium fluoride 95% enriched with 6Li ( 6LiF), lithium carbonate 95% enriched with 6Li ( 6Li 2CO 3), boric acid enriched with 99% of 10B (H310BO) and gadolinium oxide (Gd 2O 3). The proportion of Al 2O 3:C and neutron converter in the mixture was varied to optimize the total OSL signal and neutron sensitivity. The neutron sensitivity and dose-response were determined for the OSL dosimeters using a bare 252Cf source and compared to the response of Harshaw TLD-600 and TLD-700 dosimeters ( 6LiF:Mg,Ti and 7LiF:Mg,Ti). The results demonstrate the possibility of developing an OSL dosimeter made of Al 2O 3:C powder and neutron converter with a neutron sensitivity (defined as the ratio between the 60Co equivalent gamma dose and the reference neutron absorbed dose) and neutron-gamma discrimination comparable to the TLD-600/TLD-700 combination. It was shown that the shape of the OSL decay curves varied with the type of the neutron converter, demonstrating the influence of the energy deposition mechanism and ionization density on the OSL process in Al 2O 3:C.

  19. Are geological media homogeneous or heterogeneous for neutron investigations?

    PubMed

    Woźnicka, U; Drozdowicz, K; Gabańska, B; Krynicka, E; Igielski, A

    2003-01-01

    The thermal neutron absorption cross section of a heterogeneous material is lower than that of the corresponding homogeneous one which contains the same components. When rock materials are investigated the sample usually contains grains which create heterogeneity. The heterogeneity effect depends on the mass contribution of highly and low-absorbing centers, on the ratio of their absorption cross sections, and on their sizes. An influence of the granulation of silicon and diabase samples on the absorption cross section measured with Czubek's method has been experimentally investigated. A 20% underestimation of the absorption cross section has been observed for diabase grains of sizes from 6.3 to 12.8 mm.

  20. Neutron diffraction study of the formation kinetics of ordered antiphase domains in titanium carbohydride TiC{sub x}H{sub y}

    SciTech Connect

    Khidirov, I.

    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. [Cu32(H)20{S2P(O i Pr)2 }12 ]: The Largest Number of Hydrides Recorded in a Molecular Nanocluster by Neutron Diffraction

    DOE PAGES

    Dhayal, Rajendra S.; Liao, Jian-Hong; Kahlal, Samia; Wang, Xiaoping; Liu, Yu-Chiao; Chiang, Ming-Hsi; van Zyl, Werner E.; Saillard, Jean-Yves; Liu, C. W.

    2015-04-20

    An air- and moisture-stable nanoscale polyhydrido copper cluster [Cu32(H)20{S2P(O i Pr)2 }12 ] (1H) was synthesized and structurally characterized. The molecular structure of 1H exhibits a hexacapped pseudo-rhombohedral core of 14 Cu atoms sandwiched between two nestlike triangular cupola fragments of (2x9) Cu atoms in an elongated triangular gyrobicupola polyhedron. The discrete Cu32 cluster is stabilized by 12 dithiophosphate ligands and a record number of 20 hydride ligands, which were found by high-resolution neutron diffraction to exhibit tri-, tetra-, and pentacoordinated hydrides in capping and interstitial modes. We conclude that this result was further supported by a density functional theorymore » investigation on the simplified model [Cu32(H)20(S2PH2)12].« less

  2. 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

    SciTech Connect

    Johnson, S.W.; Eckert, J.; Barthes, M.; McMullan, R.K.; Muller, M.

    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.

  3. Phase separation and ordering process in Al-Li alloys studied by small-angle neutron scattering and neutron diffraction

    SciTech Connect

    Furusaka, M.; Fujikawa, S.I.; Tranquada, J.M.

    1993-07-01

    To study phase separation kinetics of Al-9.5at.%Li polycrystalline alloys in which precipitates have ordered Al{sub 3}Li ({delta}{prime}) structure, profile analysis of small-angle neutron scattering and superlattice reflections (100) and (110) were done. A small-angle scattering instrument and a triple-axis spectrometer in elastic mode were used in the measurements. Strong texture was observed in the reflections. Therefore, measurements were done using the crystal orientation where the intensity of the reflection was at the maximum. Profiles of small-angle scattering and superlattice reflections were almost identical at higher momentum transfer side. At lower momentum transfer side, small-angle scattering showed interference effects, but superlattice reflection did not show any sign of interference. Integrated intensities of superlattice reflections were obtained and compared with small-angle scattering intensity. The order parameter was not saturated in the {delta}{prime} precipitates at the early stage of the phase separation process.

  4. New neutron small-angle diffraction instrument at the Brookhaven High Flux Beam Reactor

    SciTech Connect

    Schneider, D.K.; Schoenborn, B.P.

    1982-01-01

    The new instrument utilizes cold neutrons emerging from a series of straight neutron guides. A multilayered monochromator is used in combination with a short collimator to obtain a monochromatized beam with a wavelength between 4 and 10 A and a wavelength spread of about 10%. The flux at 5 A exceeds 10/sup 6/ ns/sup -1/ cm/sup -2/ in a typical beam of 6-mm diameter at the sample. The spectrometer itself incorporates provisions for computer-controlled positioning of samples and a two-dimensional detector. At a sample-detector distance between 50 and 200 cm the detector can be centered at scattering angles of up to 45/sup 0/. The beam-defining components, the monochromator, the collimator, and various slits, are easily accessible and exchangeable for alternative devices. These features make the instrument modular and give it flexibility approaching that of standard x-ray equipment.

  5. High-pressure cell for neutron diffraction with in situ pressure control at cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Jacobsen, Matthew K.; Ridley, Christopher J.; Bocian, Artur; Kirichek, Oleg; Manuel, Pascal; Khalyavin, Dmitry; Azuma, Masaki; Attfield, J. Paul; Kamenev, Konstantin V.

    2014-04-01

    Pressure generation at cryogenic temperatures presents a problem for a wide array of experimental techniques, particularly neutron studies due to the volume of sample required. We present a novel, compact pressure cell with a large sample volume in which load is generated by a bellow. Using a supply of helium gas up to a pressure of 350 bar, a load of up to 78 kN is generated with leak-free operation. In addition, special fiber ports added to the cryogenic center stick allow for in situ pressure determination using the ruby pressure standard. Mechanical stability was assessed using finite element analysis and the dimensions of the cell have been optimized for use with standard cryogenic equipment. Load testing and on-line experiments using NaCl and BiNiO3 have been done at the WISH instrument of the ISIS pulsed neutron source to verify performance.

  6. High-pressure cell for neutron diffraction with in situ pressure control at cryogenic temperatures

    SciTech Connect

    Jacobsen, Matthew K.; Ridley, Christopher J.; Bocian, Artur; Kamenev, Konstantin V.; Kirichek, Oleg; Manuel, Pascal; Khalyavin, Dmitry; Azuma, Masaki; Attfield, J. Paul

    2014-04-15

    Pressure generation at cryogenic temperatures presents a problem for a wide array of experimental techniques, particularly neutron studies due to the volume of sample required. We present a novel, compact pressure cell with a large sample volume in which load is generated by a bellow. Using a supply of helium gas up to a pressure of 350 bar, a load of up to 78 kN is generated with leak-free operation. In addition, special fiber ports added to the cryogenic center stick allow for in situ pressure determination using the ruby pressure standard. Mechanical stability was assessed using finite element analysis and the dimensions of the cell have been optimized for use with standard cryogenic equipment. Load testing and on-line experiments using NaCl and BiNiO{sub 3} have been done at the WISH instrument of the ISIS pulsed neutron source to verify performance.

  7. High-pressure cell for neutron diffraction with in situ pressure control at cryogenic temperatures.

    PubMed

    Jacobsen, Matthew K; Ridley, Christopher J; Bocian, Artur; Kirichek, Oleg; Manuel, Pascal; Khalyavin, Dmitry; Azuma, Masaki; Attfield, J Paul; Kamenev, Konstantin V

    2014-04-01

    Pressure generation at cryogenic temperatures presents a problem for a wide array of experimental techniques, particularly neutron studies due to the volume of sample required. We present a novel, compact pressure cell with a large sample volume in which load is generated by a bellow. Using a supply of helium gas up to a pressure of 350 bar, a load of up to 78 kN is generated with leak-free operation. In addition, special fiber ports added to the cryogenic center stick allow for in situ pressure determination using the ruby pressure standard. Mechanical stability was assessed using finite element analysis and the dimensions of the cell have been optimized for use with standard cryogenic equipment. Load testing and on-line experiments using NaCl and BiNiO3 have been done at the WISH instrument of the ISIS pulsed neutron source to verify performance. PMID:24784623

  8. Investigations of fundamental phenomena in quantum mechanics with neutrons

    NASA Astrophysics Data System (ADS)

    Hasegawa, Yuji

    2014-04-01

    Neutron interferometer and polarimeter are used for the experimental investigations of quantum mechanical phenomena. Interferometry exhibits clear evidence of quantum-contextuality and polarimetry demonstrates conflicts of a contextual model of quantum mechanics á la Leggett. In these experiments, entanglements are achieved between degrees of freedom in a single-particle: spin, path and energy degrees of freedom are manipulated coherently and entangled. Both experiments manifest the fact that quantum contextuality is valid for phenomena with matter waves with high precision. In addition, another experiment is described which deals with error-disturbance uncertainty relation: we have experimentally tested error-disturbance uncertainty relations, one is derived by Heisenberg and the other by Ozawa. Experimental results confirm the fact that the Heisenberg's uncertainty relation is often violated and that the new relation by Ozawa is always larger than the limit. At last, as an example of a counterfactual phenomenon of quantum mechanics, observation of so-called quantum Cheshire Cat is carried out by using neutron interferometer. Experimental results suggest that pre- and post-selected neutrons travel through one of the arms of the interferometer while their magnetic moment is located in the other arm.

  9. Structural and magnetic phase transitions in the synthetic clinopyroxene LiCrGe2O6: a neutron diffraction study between 0.5 and 1473 K

    NASA Astrophysics Data System (ADS)

    Redhammer, Günther J.; Senyshyn, Anatoliy; Tippelt, Gerold; Prinz, Sebastian; Roth, Georg

    2015-06-01

    The pyroxene-type compound LiCrGe2O6, the Li- and Ge-analogue to the silicate mineral kosmochlor, has been synthesized at 1373 K and investigated by neutron diffraction between 0.5 and 1473 K in order to investigate the variation in magnetic and crystal structure with temperature. A structural phase transition from a low-temperature P21/ c to a high-temperature C2/ c structure was found around 1140 K. The two different structures exhibit different thermal expansion behavior with temperature with a reversal of the largest thermal expansion from the c-axis to the b-axis in the P21/ c and C2/ c phase, respectively. The structural phase transition is accompanied by a large volume increase of 1.9 % and sharp discontinuities in bond lengths, especially for the Li-O and—to a lesser extent—for the Cr-O bonds. At low temperature, some additional nonlinear changes in lattice parameters occur, which are associated with a magnetoelastic couplings of the lattice. Magnetic ordering is observed below 6 K in the neutron diffraction data. Data could be indexed with k = (0 0 0), giving rise to magnetic space group P21'/ c. This model of the magnetic structure has a pure antiferromagnetic arrangement of spins, both within and between the M1 chains. The spins are oriented within the a- c plane with an almost nil component along [0 1 0]. A shift of the Cr atom out of the center in the equatorial plane of the octahedron is observed below 6 K and is associated with the magnetic phase transition.

  10. Absolute configuration of a chiral CHD group via neutron diffraction: confirmation of the absolute stereochemistry of the enzymatic formation of malic acid

    SciTech Connect

    Bau, R.; Brewer, I.; Chiang, M.Y.; Fujita, S.; Hoffman, J.; Watkins, M.I.; Koetzle, T.F.

    1983-09-30

    Neutron diffraction has been used to monitor the absolute stereochemistry of an enzymatic reaction. (-)(2S)malic-3-d acid was prepared by the action of fumarase on fumaric acid in D/sub 2/O. After a large number of cations were screened, it was found that (+)(R)..cap alpha..-phenylethylamine forms the large crystals necessary for a neutron diffraction analysis. The subsequent structure determination showed that (+)(R)..cap alpha..-phenylethylammonium (-)(2S)malate-3-d has an absolute configuration of R at the CHD site. This result confirms the absolute stereochemistry of fumarate-to-malate transformation as catalyzed by the enzyme fumarase.

  11. High pressure single crystal x-ray and neutron powder diffraction study of the ferroelectric-paraelectric phase transition in PbTiO3

    NASA Astrophysics Data System (ADS)

    Al-Zein, A.; Bouvier, P.; Kania, A.; Levelut, C.; Hehlen, B.; Nassif, V.; Hansen, T. C.; Fertey, P.; Haines, J.; Rouquette, J.

    2015-12-01

    The results obtained by high pressure neutron powder diffraction and single-crystal x-ray diffraction for the P4mm-Pm \\bar{3} m phase transition in the prototype ferroelectric perovskite lead titanate are shown. Neutron diffraction is found to be strongly sensitive to the dipolar moment in the PbTiO3 unit cell due to the gradual reduction of the displacement of the Ti and O atoms from centrosymmetric positions in the cubic perovskite structure which exhibits anti-phase scattering of Pb, Ti and O atoms. From applying both techniques, the anomalously high Debye-Waller factor for the lead atoms confirms the disordered character of the cubic phase. High pressure single crystal x-ray diffraction also perfectly describes the ferroelectric-paraelectric transition and will be the technique of choice to solve higher pressure structures for PbTiO3.

  12. Electronically- and crystal-structure-driven magnetic structures and physical properties of RScSb (R = rare earth) compounds. A neutron diffraction, magnetization and heat capacity study

    SciTech Connect

    Ritter, C; Dhar, S K; Kulkarni, R; Provino, A; Paudyal, Durga; Manfrinetti, Pietro; Gschneidner, Karl A

    2014-08-14

    The synthesis of the new equiatomic RScSb ( R = La-Nd, Sm, Gd-Tm, Lu, Y) compounds has been recently reported. These rare earth compounds crystallize in two different crystal structures, adopting the CeScSi-type ( I 4/ mmm) for the lighter R (La-Nd, Sm) and the CeFeSi-type (P4 /nmm) structure for the heavier R ( R = Gd-Tm, Lu, Y). Here we report the results of neutron diffraction, magnetization and heat capacity measurements on some of these compounds ( R = Ce, Pr, Nd, Gd and Tb). Band structure calculations have also been performed on CeScSb and GdScGe (CeScSi-type), and on GdScSb and TbScSb (CeFeSi-type) to compare and understand the exchange interactions in CeScSi and CeFeSi structure types. The neutron diffraction investigation shows that all five compounds order magnetically, with the highest transition temperature of 66 K in TbScSb and the lowest of about 9 K in CeScSb. The magnetic ground state is simple ferromagnetic (τ = [0 0 0]) in CeScSb, as well in NdScSb for 32 >T > 22 K. Below 22 K a second magnetic transition, with propagation vector τ = [¼ ¼ 0], appears in NdScSb. PrScSb has a magnetic structure within, determined by mostly ferromagnetic interactions and antiferromagnetic alignment of the Pr-sites connected through the I-centering ( τ = [1 0 0]). A cycloidal spiral structure with a temperature dependent propagation vector τ = [δ δ ½] is found in TbScSb. The results of magnetization and heat capacity lend support to the main conclusions derived from neutron diffraction. As inferred from a sharp peak in magnetization, GdScSb orders antiferromagnetically at 56 K. First principles calculations show lateral shift of spin split bands towards lower energy from the Fermi level as the CeScSi-type structure changes to the CeFeSi-type structure. This rigid shift may force the system to transform from exchange split ferromagnetic state to the antiferromagnetic state in RScSb compounds (as seen for example in GdScSb and TbScSb) and is proposed to

  13. In situ neutron diffraction study of the low cycle fatigue of the α-γ duplex stainless steel

    NASA Astrophysics Data System (ADS)

    Jenčuš, Peter; Polák, Jaroslav; Lukáš, Petr; Muránsky, Ondrej

    2006-11-01

    In duplex stainless steels, significant thermal stresses are generated during the cooling from the homogenization temperature due to different thermal expansion coefficients of the austenitic and ferritic phases. The results of the in situ neutron diffraction examination of the evolution of the internal stresses during the low cycle fatigue in the SAF 2507 duplex stainless steel are reported. Stress response of both constituent components resulting from the load sharing between austenitic and ferritic grains was measured. It was found that the initial thermal residual stresses were relaxed rapidly at the beginning of the cyclic loading. Whereas initial hardening was identified in both phases, the subsequent fatigue softening was fully attributed to the austenitic phase.

  14. Studies of V, Nb, Cr, and Zr substituted 2:17 compounds and their carbides using neutron diffraction

    NASA Astrophysics Data System (ADS)

    Luo, H.; Hu, Z.; Chen, M.; Yelon, W. B.; Marasinghe, G. K.; Ezekwenna, P. C.; James, W. J.; Chang, W. C.; Tsai, S. H.

    1997-04-01

    Samples of Nd2Fe17-xTxCy with T=V, Nb, Cr, and Zr were prepared by melting of the constituent elements including C and studied by neutron diffraction. Comparing with their uncarbided counterparts, we found that the substituents transfer, more or less, from the 6c site to the 18f and 18h sites with the introduction of C atoms. This behavior appears to relate to the electronegativities between the C atoms and the early transition series elements because the 18f and 18h sites are near neighbors of the interstitial C site. However, the C effects in the V, Nb, Cr, and Zr samples are not as strong as those in Ti samples. SQUID measurements show that the Curie temperatures of these samples depend on both the interstitial C atoms and the substituents.

  15. Polarized-neutron-diffraction study of the microscopic magnetic structure in α''-Fe 16N2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Hiraka, H.; Ohoyama, K.; Ogata, Y.; Ogawa, T.; Gallage, R.; Kobayashi, N.; Takahashi, M.; Gillon, B.; Gukasov, A.; Yamada, K.

    2014-10-01

    Polarized-neutron-diffraction (PND) measurements were carried out using a pseudo-single-phase powder sample of ferromagnetic α''-Fe16N2 nanoparticles. For the well-identified α''-Fe16N2 phase, sizes of the magnetic moments at the three crystallographic Fe sites were determined in the absolute scale. The agreement between the magnetization value deduced from the present PND and that measured by a magnetometer (MVSM) supports the hypothesis that MVSM is primarily caused by the magnetization value in the target α''-Fe16N2 ; thus there is no evidence for macroscopic giant saturation magnetization, at least for α''-Fe16N2 nanoparticles. On the basis of the large magnetic moment size at one of the Fe sites, a possible coexisting state of localized spins and itinerant electron spins is inferred. Drawing a distinction between thin films and nanoparticles is currently necessary because of their divergent magnetic evolutions.

  16. Neutron powder diffraction study of phase transitions in Sr{sub 2}SnO{sub 4}

    SciTech Connect

    Fu, W.T. . E-mail: w.fu@chem.leidenuniv.nl; Visser, D.; Knight, K.S.; IJdo, D.J.W.

    2004-11-01

    The phase transitions in Sr{sub 2}SnO{sub 4} at high temperature have been studied using high resolution time-of-flight powder neutron diffraction. The room temperature structure of Sr{sub 2}SnO{sub 4} is orthorhombic (Pccn), which can be derived from the tetragonal K{sub 2}NiF{sub 4} structure by tilting the SnO{sub 6} octahedra along the tetragonal [100]{sub T}- and [010]{sub T}-axes with non-equal tilts. At the temperature of about 423K, it transforms to another orthorhombic structure (Bmab) characterized by the SnO{sub 6} octahedral tilt around the [110]{sub T}-axis. At still higher temperatures ({approx}573K) the structure was found to be tetragonal K{sub 2}NiF{sub 4}-type (I4/mmm)

  17. Neutron Diffraction Study On Gamma To Alpha Phase Transition In Ce0.9th0.1 Alloy

    SciTech Connect

    Lashley, Jason C1; Heffner, Robert H; Llobet, A; Darling, T W; Jeong, I K

    2008-01-01

    Comprehensive neutron diffraction measurements were performed to study the isostructural {gamma} {leftrightarrow} {alpha} phase transition in Ce{sub 0.9}Th{sub 0.1} alloy. Using Rietveld refinements, we obtained lattice and thermal parameters as a function of temperature. From the temperature slope of the thermal parameters, we determined Debye temperatures {Theta}{sup {gamma}}{sub D} = 133(1) K and {Theta}{sup {alpha}}{sub D} = 140(1) K for the {gamma} phase and the {alpha} phase, respectively. This result implies that the vibrational entropy change is not significant at the {gamma} {leftrightarrow} {alpha} transition, contrary to that from elemental Cerium [Phys. Rev. Lett. 92, 105702, 2004].

  18. Kagome staircase compound Co3V2O8 in an applied magnetic field: Single-crystal neutron diffraction study

    NASA Astrophysics Data System (ADS)

    Petrenko, O. A.; Wilson, N. R.; Balakrishnan, G.; Paul, D. Mck; McIntyre, G. J.

    2010-09-01

    The magnetic properties of Co3V2O8 have been studied by single-crystal neutron diffraction. In zero magnetic field, the observed broadening of the magnetic Bragg peaks suggests the presence of disorder both in the low-temperature ferromagnetic and in the higher temperature antiferromagnetic state. The field dependence of the intensity and position of the magnetic reflections in Co3V2O8 reveals a complex sequence of phase transitions in this Kagome staircase compound. For H∥a , a commensurate-incommensurate-commensurate transition is found in a field of 0.072 T in the antiferromagnetic phase at 7.5 K. For H∥c at low temperature, an applied field induces an unusual transformation from a ferromagnetic to an antiferromagnetic state at about 1 T accompanied by a sharp increase in magnetization.

  19. In-situ observation of inhomogeneous degradation in large format Li-ion cells by neutron diffraction

    SciTech Connect

    Cai, Lu; An, Ke; Feng, Zhili; Liang, Chengdu; Harris, Stephen J.

    2013-08-01

    This work presents a non-destructive in-situ method for probing degradation mechanisms in large format, operating, commercial lithium-ion batteries by neutron diffraction. A fresh battery (15 Ah capacity) was shown to have a uniform (homogeneous) local state of charge (SOC) at 4.0 V (9 Ah SOC) and 4.2 V (15 Ah SOC), with 1.33 C and 2.67 C charging rates, respectively. This battery was then aggressively cycled until it retained only a 9 Ah capacity, 60% of its original value. Inhomogeneous deterioration in the battery was observed: near the edges, both the graphite anode and the spinel-based cathode showed a significant loss of capacity, while near the central area, both electrodes functioned properly. An SOC mapping measurement of the degraded battery in the fully charged state (4.2 V) indicated that the loss of local capacity of the anode and cathode is coupled.

  20. Locating Active-site Hydrogen Atoms in D-Xylose Isomerase: Time-of-Flight Neutron Diffraction.

    SciTech Connect

    Bunick, G J

    2006-01-01

    Time-of-flight neutron diffraction has been used to locate hydrogen atoms that define the ionization states of amino acids in crystals of D-xylose isomerase. This enzyme, from Streptomyces rubiginosus, is one of the largest enzymes studied to date at high resolution (1.8 ) by this method. We have determined the position and orientation of a metal ion-bound water molecule that is located in the active site of the enzyme; this water has been thought to be involved in the isomerization step in which D-xylose is converted to D-xylulose or D-glucose to D-fructose. It is shown to be water (rather than a hydroxyl group) under the conditions of measurement (pH 8.0). Our analyses also reveal that one lysine probably has an -NH2 terminal group (rather than NH3+). The ionization state of each histidine residue was also determined.

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

    SciTech Connect

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

    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.

  2. In situ neutron diffraction and Elastic-Plastic Self-Consistent polycrystal modeling of HT-9

    NASA Astrophysics Data System (ADS)

    Clausen, B.; Brown, D. W.; Bourke, M. A. M.; Saleh, T. A.; Maloy, S. A.

    2012-06-01

    Qualifying materials for use in reactors with fluences greater than 200 dpa (displacements per atom) requires development of advanced alloys and irradiations in fast reactors to test these alloys. Research into the mechanical behavior of these materials under reactor conditions is ongoing. In order to probe changes in deformation mechanisms due to radiation in these materials, samples of HT-9 were tested in tension in situ on the SMARTS instrument at Los Alamos Neutron Science Center. Experimental results, confirmed with modeling, show significant load sharing between the carbides and parent phase of the steel beyond yield, displaying the critical role of carbides during deformation, along with basic texture development.

  3. A neutron diffraction study of hydrogen positions at 13 K, domain model, and chemical composition of staurolite

    NASA Astrophysics Data System (ADS)

    Ståhl, K.; Kvick, Å.; Smith, J. V.

    1988-04-01

    Comparison of new neutron and old X-ray diffraction data for single crystals of staurolite from Pizzo Forno yielded unique answers to some, but not all, outstanding structural questions. Neutron data were collected at 13(1) K for a crystal with assumed composition Li 0.07Mg 0.87Ti 0.14V 0.01Cr 0.01Mn 0.04Fe 2+3.00 Fe 3+0.06Co 0.01Zn 0.05Al 17.69Si 7.67O 48H 3.41F 0.01, Mw = 1671, a = 7.8639(10), b = 16.625(2), c = 5.651(2) Å, β = 90.015(14)°, {C2}/{m}, Z = 1, D x = 3.75 g cm-3; 1874 (1024 unique) reflections, λ = 1.1598(1) Å, R( F) = 3.3%. The diffraction evidence is consistent with full occupancy of the Si, Al(1), Al(2), and Al(3) sites, but not of the other ones. Detailed assignment of atoms is based on diffraction evidence and crystal-chemical arguments, but some uncertainties remain; thus exchange of (Li + Fe) by two Mg would have little effect on diffraction data. A structural model with three types of domains is proposed: ˜63% type 1, (Fe, etc.) + H(1); ˜22% type 2, (Mg, etc.) + H(2); ˜15% type 3, (Fe, etc.) without hydrogen. For the orthorhombic pseudostructure, the occupancies of the two hydrogen sites place strong restrictions on the other site occupancies. The 25(4)% observed occupancy of H(2) limits the occupancy of the nearby (Fe, etc.) site to a maximum of 75(4)%. To explain the neutron scattering, the Fe site must be occupied mainly by Fe; Li, Mn, Zn, and Mg may also occupy this site. A good ionic balance is attained for the type 2 domain if the U site from the old X-ray work is occupied simultaneously with H(2). To match the neutron data, assignment of 21(2)% Mg to the U site is plausible, but other substituents are possible. H(2) lies directly between two O(1) atoms at ˜0.9 and 2.3 Å, and H(1) is displaced away from the Fe site so that it is bonded to one O(1) at 1.01 Å and one O(3) at 2.07 Å. Four-fifths of the Fe atoms should be displaced from z = 0.25 because of electrostatic repulsion from H(1), and one-fifth should not be. This is

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

    PubMed Central

    Mueser, Timothy C.; Griffith, Wendell P.; Kovalevsky, Andrey Y.; Guo, Jingshu; Seaver, Sean; Langan, Paul; Hanson, B. Leif

    2010-01-01

    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. PMID:21041946

  5. Neutron Diffraction on NaNi2 BiO6 : Complex Interactions on a Honeycomb Lattice

    NASA Astrophysics Data System (ADS)

    Scheie, Allen; Ross, Kate; Seibel, Elizabeth; Rodriguez-Rivera, Jose; Broholm, Collin; Cava, Robert; Institute for Quantum Matter Collaboration

    Magnetic crystals with a honeycomb lattice can have a very high degree of frustration when next-nearest neighbor interactions are strong. Such complex interactions can lead to Kitaev model physics, including a proposed spin liquid phase. Using neutron scattering, we studied the magnetic properties of a new spin-1/2 honeycomb compound, NaNi2BiO6, which was known to have heat capacity peaks indicative of a phase transition at 5 K. The magnetic order indicates beyond nearest-neighbor exchange as well as significant inter-plane interaction, which allows for a study of rich and complex structure. In this talk I report the magnetic structure of the compound as found with neutron powder diffraction, and discuss the exchanges necessary to lead to such a complex order. The work at IQM was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Material Sciences and Engineering, under Grant No. DEFG02-08ER46544.

  6. Visualizing the Structural Evolution of LSM/xYSZ Composite Cathodes for SOFC by in-situ Neutron Diffraction

    PubMed Central

    Chen, Yan; Yang, Ling; Ren, Fei; An, Ke

    2014-01-01

    Thermal stability of composite cathodes for solid oxide fuel cells, the mixtures of (La0.8Sr0.2)0.95MnO3−δ (LSM) and (Y2O3)x(ZrO2)1−x (xYSZ, x = 3, 6, 8 and 10), is determined using in-situ neutron diffraction. Thanks to the most advanced high flux neutron source, our work highlights the visualization of the phase evolutions in heterogeneous material systems at high temperatures, along with the analysis of the diffusion activities of transition metal ions that reveal the reaction mechanism and kinetics. It is found that the tetragonal-to-cubic phase transition in YSZ at T > 900°C leads to a heterogeneous redistribution of Mn ions. The subsequent reaction of LSM and YSZ occurring at T > 1100°C is revealed as a three-stage kinetic process, yielding La2Zr2O7, SrZrO3 and MnO. The diffusion activities of Y, Mn and La ions in the heterogeneous systems at elevated temperatures are derived by the structural analysis, and the three-stage reaction of YSZ and LSM is found strongly correlated to ions' behaviors as functions of temperature. PMID:24899139

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

    PubMed

    Mueser, Timothy C; Griffith, Wendell P; Kovalevsky, Andrey Y; Guo, Jingshu; Seaver, Sean; Langan, Paul; Hanson, B Leif

    2010-11-01

    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.

  8. Magnetic phases in the Kagomé staircase compound Co3V2O8 studied using powder neutron diffraction

    NASA Astrophysics Data System (ADS)

    Wilson, N. R.; Petrenko, O. A.; Chapon, L. C.

    2007-03-01

    The low temperature properties of the Kagomé-type system Co3V2O8 have been studied by powder neutron diffraction both in zero field and in applied magnetic fields of up to 8T . Below 6K , the zero-field ground state is ferromagnetic with the magnetic moments aligned along the a axis. The size of the moment on one of the two Co sites, the so-called cross-tie site, is considerably reduced compared to the fully polarized state. The application of a magnetic field in this phase is found to rapidly enhance the cross-tie site magnetic moment, which reaches the expected value of ˜3μB by the maximum applied field of 8T . Different reorientation behaviors are found for the Co cross-tie and spine sites, suggesting a more pronounced easy-axis anisotropy for moments on the spine sites. Rietveld refinements reveal that a simple model, where the spins on both cross-tie and spine sites rotate in the ac plane in a magnetic field, reproduces the experimental diffraction patterns well. In addition, it is found that at higher temperatures and moderate magnetic fields, the incommensurate antiferromagnetic order, corresponding to a transverse sinusoidal modulation above 8K , is suppressed to be replaced by ferromagnetic order.

  9. Single crystal neutron diffraction study of the magnetic structure of TmNi{sub 2}B{sub 2}C

    SciTech Connect

    Sternlieb, B.; Shapiro, S.; Stassis, C.; Goldman, A.I.; Canfield, P.

    1997-02-01

    Neutron diffraction techniques have been used to study the magnetic structure of single crystals of the magnetic superconductor (T{sub c} {congruent} 11K) TmNi{sub 2}B{sub 2}C. We find that below approximately 1.5K the magnetic moments order in an incommensurate spin wave with propagation vector q{sub m} = q{sub m} (a* +b*) (or q{sub m} = q{sub m} (a* + b*)) with q{sub m} = 0.094 {+-} 0.001. The spin wave is transverse with the moments aligned along the c-axis, and the observation of relatively intense higher order harmonics shows that the modulation is not purely sinusoidal but considerably squared. This incommensurate magnetic structure, which coexists with superconductivity below T{sub N} {congruent} 1.5K, is quite different from those observed in the magnetic superconductors HoNi{sub 2}B{sub 2}C and ErNi{sub 2}B{sub 2}C. The origin of diffraction peaks observed in scans parallel to a* is briefly discussed.

  10. Structure of amorphous GeSe9 by neutron diffraction and first-principles molecular dynamics: Impact of trajectory sampling and size effects

    NASA Astrophysics Data System (ADS)

    Le Roux, Sébastien; Bouzid, Assil; Kim, Kye Yeop; Han, Seungwu; Zeidler, Anita; Salmon, Philip S.; Massobrio, Carlo

    2016-08-01

    The structure of glassy GeSe9 was investigated by combining neutron diffraction with density-functional-theory-based first-principles molecular dynamics. In the simulations, three different models of N = 260 atoms were prepared by sampling three independent temporal trajectories, and the glass structures were found to be substantially different from those obtained for models in which smaller numbers of atoms or more rapid quench rates were employed. In particular, the overall network structure is based on Sen chains that are cross-linked by Ge(Se4)1/2 tetrahedra, where the latter are predominantly corner as opposed to edge sharing. The occurrence of a substantial proportion of Ge-Se-Se connections does not support a model in which the material is phase separated into Se-rich and GeSe2-rich domains. The appearance of a first-sharp diffraction peak in the Bhatia-Thornton concentration-concentration partial structure factor does, however, indicate a non-uniform distribution of the Ge-centered structural motifs on an intermediate length scale.

  11. High temperature phase stability in Li0.12Na0.88NbO3: A combined powder X-ray and neutron diffraction study

    NASA Astrophysics Data System (ADS)

    Mishra, S. K.; Krishna, P. S. R.; Shinde, A. B.; Jayakrishnan, V. B.; Mittal, R.; Sastry, P. U.; Chaplot, S. L.

    2015-09-01

    The phase stabilities of ecofriendly piezoelectric material of lithium doped sodium niobate for composition Li0.12Na0.88NbO3 (LNN12) have been investigated by a combination of powder X-ray and neutron diffraction techniques in the temperature range of 300-1100 K. We observed interesting changes with appearance or disappearance of the super-lattice reflections in the powder diffraction patterns. Unambiguous experimental evidence is shown for coexistence of paraelectric and ferroelectric orthorhombic phases in the temperature range of 525 K to 675 K. We identified the correct crystal structure of LNN12 with temperature and correlated it with observed anomaly in the physical properties. Identification of crystal structure also helps in the mode assignments in Raman and infrared spectroscopies. We argued that application of chemical pressure as a result of Li substitution in NaNbO3 matrix favors the freezing of zone centre phonons in contrast to the freezing of zone boundary phonons in pure NaNbO3 with the variation of temperature.

  12. Structural phase transition and magnetism in hexagonal SrMnO{sub 3} by magnetization measurements and by electron, x-ray, and neutron diffraction studies

    SciTech Connect

    Daoud-Aladine, A.; Chapon, L. C.; Knight, K. S.; Martin, C.; Hervieu, M.; Brunelli, M.; Radaelli, P. G.

    2007-03-01

    The structural and magnetic properties of the hexagonal four-layer form of SrMnO{sub 3} have been investigated by combining magnetization measurements, electron diffraction, and high-resolution synchrotron x-ray and neutron powder diffraction. Below 350 K, there is subtle structural phase transition from hexagonal symmetry (space group P6{sub 3}/mmc) to orthorhombic symmetry (space group C222{sub 1}) where the hexagonal metric is preserved. The second-order phase transition involves a slight tilting of the corner-sharing Mn{sub 2}O{sub 9} units composed of two face-sharing MnO{sub 6} octahedra and the associated displacement of Sr{sup 2+} cations. The phase transition is described in terms of symmetry-adapted displacement modes of the high symmetry phase. Upon further cooling, long range magnetic order with propagation vector k=(0,0,0) sets in below 300 K. The antiferromagnetic structure, analyzed using representation theory, shows a considerably reduced magnetic moment indicating the crucial role played by direct exchange between Mn centers of the Mn{sub 2}O{sub 9} units.

  13. Structure of amorphous GeSe9 by neutron diffraction and first-principles molecular dynamics: Impact of trajectory sampling and size effects.

    PubMed

    Le Roux, Sébastien; Bouzid, Assil; Kim, Kye Yeop; Han, Seungwu; Zeidler, Anita; Salmon, Philip S; Massobrio, Carlo

    2016-08-28

    The structure of glassy GeSe9 was investigated by combining neutron diffraction with density-functional-theory-based first-principles molecular dynamics. In the simulations, three different models of N = 260 atoms were prepared by sampling three independent temporal trajectories, and the glass structures were found to be substantially different from those obtained for models in which smaller numbers of atoms or more rapid quench rates were employed. In particular, the overall network structure is based on Sen chains that are cross-linked by Ge(Se4)1/2 tetrahedra, where the latter are predominantly corner as opposed to edge sharing. The occurrence of a substantial proportion of Ge-Se-Se connections does not support a model in which the material is phase separated into Se-rich and GeSe2-rich domains. The appearance of a first-sharp diffraction peak in the Bhatia-Thornton concentration-concentration partial structure factor does, however, indicate a non-uniform distribution of the Ge-centered structural motifs on an intermediate length scale. PMID:27586930

  14. Cryostat system for investigation on new neutron moderator materials at reactor TRIGA PUSPATI

    NASA Astrophysics Data System (ADS)

    Dris, Zakaria bin; Mohamed, Abdul Aziz bin; Hamid, Nasri A.; Azman, Azraf; Ahmad, Megat Harun Al Rashid Megat; Jamro, Rafhayudi; Yazid, Hafizal

    2016-01-01

    A simple continuous flow (SCF) cryostat was designed to investigate the neutron moderation of alumina in high temperature co-ceramic (HTCC) and polymeric materials such as Teflon under TRIGA neutron environment using a reflected neutron beam from a monochromator. Cooling of the cryostat will be carried out using liquid nitrogen. The cryostat will be built with an aluminum holder for moderator within stainless steel cylinder pipe. A copper thermocouple will be used as the temperature sensor to monitor the moderator temperature inside the cryostat holder. Initial measurements of neutron spectrum after neutron passing through the moderating materials have been carried out using a neutron spectrometer.

  15. Synthesis, x-ray, and low-temperature neutron diffraction study of a rhodium (V) complex: dihydridobis(triethylsilyl)-pentamethylcyclopentadienylrhodium

    SciTech Connect

    Fernandez, M.J.; Bailey, P.M.; Bentz, P.O.; Ricci, J.S.; Koetzle, T.F.; Maitlis, P.M.

    1984-09-19

    Reaction of (C/sub 5/ qentamethyl Rh)/sub 2/Cl/sub 4/) (1) with triethylsilane leads to the novel rhodium(V) complex (eta/sup 5/-C/sub 5/Me/sub 5/Rh(H)/sub 2/(SiE-triethyl/sub 3/)/sub 2/) (2) characterized by NMR spectra (/sup 1/H, /sup 13/C, /sup 29/Si, and /sup 103/Rh), X-ray diffraction, and neutron diffraction at 20 K. The complex shows a four-legged piano stool geometry with the pentamethylcyclopentadienyl eta/sub 5/-bonded to the rhodium (average Rh-C, 2.283 (9) A) on top and the two triethylsilyl ligands trans in the basal plane (Rh-Si, 2.379 (2) A). The neutron diffraction analysis located the two hydrides, which are trans to each other and cis to the triethylsilyls in the basal plane. The mean Rh-H distance is 1.581 (3) A, and the H-Rh-H angle is 94.8 (2)/sup 0/. Complex 2 is rather stable, but it reacts under forcing conditions with neutral ligands (triphenylphosphine, CO, or maleic anhydride) to give (C/sub 5/Me/sub 5/Rh(PPh/sub 3/)H(SiEt/sub 3/)), (C/sub 5/Me/sub 5/Rh(CO)/sub 2/), or (C/sub 5/M3/5Rh(maleic anhydride)/sup 2/). It reacts more easily with electrophiles such as HBF/sub 4/ to give (C/sub 5/Me/sub 5/Rh)/sub 4/H/sub 4/)/sup 2 +/, with HCl to give 1, with AgBF/sub 4/ in MeCN to give (C/sub 5/Me/sub 5/Rh(MeCN)/sub 3/)/sup 2 +/, and with I/sub 2/ to give ((C/sub 5/Me/sub 5/Rh)/sub 2/I/sub 4/). The predominant mode of reaction involves reductive elimination of Et/sub 3/Si-H, which can be strongly promoted by an electrophile. 43 references, 3 figures, 3 tables.

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

    SciTech Connect

    Fujiwara, Satoru; Mendelson, R.A.

    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.

  17. Assessment of residual strain in zirconia-toughened alumina using neutron diffraction

    SciTech Connect

    Riessen, A. van; O'Connor, B.H. . Dept. of Applied Physics)

    1993-08-01

    Substantial strains may be generated in [alpha]-alumina (Al[sub 2]O[sub 3]) matrix ceramics by including zirconia (ZrO[sub 2]) second-phase particles, the material being known as zirconia-toughened alumina (ZTA). These strains arise from the expansion in unit cell volume resulting from tetragonal-to-monoclinic transformation in the ZrO[sub 2] particles and from thermal contraction mismatch (TCM) caused by differences between the expansion coefficients of the Al[sub 2]O[sub 3] and ZrO[sub 2] phases. Neutron powder diffractometry has been used to examine bulk, volume-averaged, microstrain character for each of the crystalline phases in a suite of zirconia-toughened alumina ceramics. Line-broadening estimates and cell parameter shifts, determined by the Rietveld method, have provided microstrain assessments of the nonuniform and uniform types, respectively.

  18. Are geological media homogeneous or heterogeneous for neutron investigations?

    PubMed

    Woźnicka, U; Drozdowicz, K; Gabańska, B; Krynicka, E; Igielski, A

    2003-01-01

    The thermal neutron absorption cross section of a heterogeneous material is lower than that of the corresponding homogeneous one which contains the same components. When rock materials are investigated the sample usually contains grains which create heterogeneity. The heterogeneity effect depends on the mass contribution of highly and low-absorbing centers, on the ratio of their absorption cross sections, and on their sizes. An influence of the granulation of silicon and diabase samples on the absorption cross section measured with Czubek's method has been experimentally investigated. A 20% underestimation of the absorption cross section has been observed for diabase grains of sizes from 6.3 to 12.8 mm. PMID:12485675

  19. Compact turnkey focussing neutron guide system for inelastic scattering investigations

    NASA Astrophysics Data System (ADS)

    Brandl, G.; Georgii, R.; Dunsiger, S. R.; Tsurkan, V.; Loidl, A.; Adams, T.; Pfleiderer, C.; Böni, P.

    2015-12-01

    We demonstrate the performance of a compact neutron guide module which boosts the intensity in inelastic neutron scattering experiments by approximately a factor of 40. The module consists of two housings containing truly curved elliptic focussing guide elements, positioned before and after the sample. The advantage of the module lies in the ease with which it may be reproducibly mounted on a spectrometer within a few hours, on the same timescale as conventional sample environments. It is particularly well suited for samples with a volume of a few mm3, thus enabling the investigation of materials which to date would have been considered prohibitively small or samples exposed to extreme environments, where there are space constraints. We benchmark the excellent performance of the module by measurements of the structural and magnetic excitations in single crystals of model systems. In particular, we report the phonon dispersion in the simple element lead. We also determine the magnon dispersion in the spinel ZnCr2Se4 (V = 12.5 mm3), where strong magnetic diffuse scattering at low temperatures evolves into distinct helical order.

  20. Compact turnkey focussing neutron guide system for inelastic scattering investigations

    SciTech Connect

    Brandl, G.; Georgii, R.; Dunsiger, S. R.; Tsurkan, V.; Loidl, A.; Adams, T.; Pfleiderer, C.; Böni, P.

    2015-12-21

    We demonstrate the performance of a compact neutron guide module which boosts the intensity in inelastic neutron scattering experiments by approximately a factor of 40. The module consists of two housings containing truly curved elliptic focussing guide elements, positioned before and after the sample. The advantage of the module lies in the ease with which it may be reproducibly mounted on a spectrometer within a few hours, on the same timescale as conventional sample environments. It is particularly well suited for samples with a volume of a few mm{sup 3}, thus enabling the investigation of materials which to date would have been considered prohibitively small or samples exposed to extreme environments, where there are space constraints. We benchmark the excellent performance of the module by measurements of the structural and magnetic excitations in single crystals of model systems. In particular, we report the phonon dispersion in the simple element lead. We also determine the magnon dispersion in the spinel ZnCr{sub 2}Se{sub 4} (V = 12.5 mm{sup 3}), where strong magnetic diffuse scattering at low temperatures evolves into distinct helical order.

  1. Neutron diffraction studies on structural and magnetic properties of RE{sub 2}NiGe{sub 3} (RE=La, Ce)

    SciTech Connect

    Kalsi, Deepti; Rayaprol, S.; Siruguri, V.; Peter, Sebastian C.

    2014-09-15

    We report the crystallographic properties of RE{sub 2}NiGe{sub 3} (RE=La, Ce) synthesized by arc melting. Rietveld refinement on the powder neutron diffraction (ND) data suggest both compounds are isostructural and crystallize in the non-centrosymmetric Er{sub 2}RhSi{sub 3} type structure having hexagonal space group P6{sup ¯}2c. In the crystal structure of RE{sub 2}NiGe{sub 3}, two dimensional arrangements of nickel and germanium atoms lead to the formation of hexagonal layers with rare earth atoms sandwiched between them. Magnetic susceptibility measurements performed in low fields exhibit antiferromagnetic ordering in cerium compound around (T{sub o}=) 3.2 K. Neutron diffraction measurements at 2.8 K (i.e., at Tdiffraction lines nor indicate the appearance of any new diffraction lines in the Q-range of 0.47–7.34 Å{sup −1}, thus ruling out any long-range magnetic order. - Graphical abstract: The compounds La{sub 2}NiGe{sub 3} and Ce{sub 2}NiGe{sub 3} crystallize in the Er{sub 2}RhSi{sub 3} type. Magnetic susceptibility show antiferromagnetic ordering for Ce{sub 2}NiGe{sub 3} at 3.2 K and neutron diffraction confirms the absence of long range ordering. - Highlights: RE{sub 2}NiGe{sub 3} (RE=La, Ce) crystallize in the ordered superstructure of the AlB{sub 2} type. Magnetic susceptibility measurements exhibit antiferromagnetic ordering in Ce{sub 2}NiGe{sub 3}. Structure and magnetism of RE{sub 2}NiGe{sub 3} (RE=La, Ce) are studied by neutron diffraction.

  2. Neutron-diffraction studies of the crystal structure and the color enhancement in γ-irradiated tourmaline

    NASA Astrophysics Data System (ADS)

    Maneewong, Apichate; Seong, Baek Seok; Shin, Eun Joo; Kim, Jeong Seog; Kajornrith, Varavuth

    2016-01-01

    Tourmaline gemstones have an extremely complex composition and show great variety in color. Most color centers are related to transition-metal ions. Oxidation/reduction of these ions is known to be related with the color enhancement of tourmaline caused by gamma-ray ( γ)-irradiation and/or thermal treatment. However, the current understanding of the microscopic structure of the color centers remains weak. In this work, γ-irradiation was performed on three types of tourmaline gemstones to enhance the colors of the gemstones: two pink from Afghanistan and one green from Nigeria. All three samples were irradiated at 600 and 800 kGy. Their crystal structural and chemical behaviors have been investigated by using a Rietveld refinement analysis of neutron diffraction data, Energy Dispersive X-ray Fluorescence (EDXRF), Ultraviolet-visible Spectroscopy (UV-Vis) and X-ray Photoelectron Spectroscopy (XPS), and the results were compared with data obtained for samples in the natural state. Pink tourmaline of a high number of Mn ions (T2, 0.24 wt%) showed significant improvement in the quality of the pink color (rubellite) after irradiation of 800 kGy while the pink tourmaline of low MnO content (T1, 0.08 wt%) showed color adulteration. Pink color enhancement in T2, responding to darker pink, was associated with increases in the two absorption bands, one peaking at 396 and the other at 522 nm, after irradiation. These absorption bands are ascribed to d-d transitions of divalent manganese. T1 with color enhancement due to oxidation of Mn2+ showed a slightly larger < Y- O> distance. The green tourmaline containing much higher amounts of both Mn (T3) and Fe ions, 2.59 wt% and 5.7 wt%, respectively, changed to a yellow color after irradiation at 800 kGy. The refined structural parameters of this sample revealed distortions in the Z site. The < Z- O> distance decreased from 2.033 to 2.0192 Å. In addition, the unit-cell parameter was decreased after irradiation. The color change

  3. A high-temperature neutron diffraction study of Nb2AlC and TiNbAlC

    DOE PAGES

    Bentzel, Grady W.; Lane, Nina J.; Vogel, Sven C.; An, Ke; Barsoum, Michel W.; Caspi, El'ad N.

    2014-12-16

    In this paper, we report on the crystal structures of Nb2AlC and TiNbAlC actual composition (Ti0.45,Nb0.55)2AlC compounds determined from Rietveld analysis of neutron diffraction patterns in the 300-1173 K temperature range. The average linear thermal expansion coefficients of a Nb2AlC sample in the a and c directions are, respectively, 7.9(5)x10-6 K-1 and 7.7(5)x10-6 K-1 on one neutron diffractometer and 7.3(3)x10-6 K-1 and 7.0(2)x10-6 K-1 on a second diffractometer. The respective values for the (Ti0.45,Nb0.55)2AlC composition - only tested on one diffractometer - are 8.5(3)x10-6 K-1 and 7.5(5)x10-6 K-1. These values are relatively low compared to other MAX phases. Like othermore » MAX phases, however, the atomic displacement parameters show that the Al atoms vibrate with higher amplitudes than the Ti and C atoms, and 1 more along the basal planes than normal to them. In addition, when the predictions of the atomic displacement parameters obtained from density functional theory are compared to the experimental results, good quantitative agreement is found for the Al atoms. In case of the Nb and C atoms, the agreement was more qualitative.« less

  4. Neutron diffraction study of monoclinic brannerite-type CoV{sub 2}O{sub 6}

    SciTech Connect

    Markkula, Mikael; Arevalo-Lopez, Angel M.; Paul Attfield, J.

    2012-08-15

    A variable-temperature powder neutron diffraction study of the monoclinic brannerite-type CoV{sub 2}O{sub 6} (space group C2/m, a=9.2531(2), b=3.5040(1), c=6.6201(1) A and {beta}=111.617(1) Degree-Sign at 300 K) is reported. No structural transition is observed down to 4 K, but a magnetostriction accompanying antiferromagnetic order at T{sub N}=15 K is discovered. Antiferromagnetic order observed below T{sub N} has an a Multiplication-Sign b Multiplication-Sign 2c supercell in which Co{sup 2+} moments of magnitude 4.77(4) {mu}{sub B} at 4 K lie in the ac plane and are ferromagnetically coupled within chains of edge-sharing CoO{sub 6} octahedra parallel to b. Ferromagnetic chains are coupled antiferromagnetically to neighbouring chains in the a and c directions, and a model for the interchain order in the reported 1/3 magnetization plateau region is proposed. - Graphical abstract: Antiferromagnetic order of Co{sup 2+} moments in monoclinic brannerite type CoV2O6 results in a magnetostriction at the 15 K Neel transition. An alternative coupling between ferromagnetic chains is proposed to account for a 1/3 magnetization plateau in this material. Highlights: Black-Right-Pointing-Pointer Variable-temperature powder neutron diffraction study of the monoclinic brannerite-type CoV{sub 2}O{sub 6} is reported. Black-Right-Pointing-Pointer Magnetostriction accompanying antiferromagnetic order at T{sub N}=15 K in monoclinic CoV{sub 2}O{sub 6} is discovered. Black-Right-Pointing-Pointer Antiferromagnetic order in a Multiplication-Sign b Multiplication-Sign 2c supercell of CoV{sub 2}O{sub 6} is determined. Black-Right-Pointing-Pointer Model for spin order in the reported 1/3 magnetization plateau of CoV{sub 2}O{sub 6} is proposed.

  5. Neutron and X-Ray Diffraction Studies of Magnetic Order in Uranium-Based Heavy Fermion Superconductors

    NASA Astrophysics Data System (ADS)

    Lussier, Jean-Guy

    UPt_3, URu_2 Si_2, UNi_2 Al_3 and UPd_2 Al_3 form a special group among the uranium alloys because they exhibit heavy fermion character, magnetic order and superconductivity. This main interest in the study of this group of compounds resides in the simultaneous occurrence of magnetism and superconductivity at low temperature. Such a state could potentially involve an unconventional superconducting pairing mechanism, different from that contained in standard BCS theory. In this thesis, the magnetic states of three of these materials (URu_2Si _2, UNi_2Al _3 and UPd_2Al _3) is investigated with neutron and the relatively new resonant magnetic X-ray scattering techniques. The work presented here on URu_2Si _2 follows an earlier effort that demonstrated the applicabililty of the resonant X-ray technique to this weak magnetic system. Access to reciprocal space was extended in order to confirm the multipolar form of the resonant X-ray cross-section and to explore the limits of the technique compared to neutron scattering. The situation with the newly discovered UNi_2Al _3 and UPd_2Al _3 was different since their magnetic structure and phases needed first to be established. This task was achieved using two magnetic probes (neutron and X-ray scattering). Several magnetic order parameters in the normal and in the superconducting phase were also measured. The incommensurate magnetic order found in UNi_2Al_3 by neutron scattering constitutes the first observation of long range order in this compound. Other measurements on this compound provided some clues about the evolution of the magnetic structure in high magnetic fields.

  6. The phase diagram of BaFe2(As1-xPx)2 as determined by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Allred, Jared; Taddei, Keith; Bugaris, Daniel; Avci, Sevda; Chmaissem, Omar; Dela Cruz, Clarina; Chung, Duck Young; Kanatzidis, Mercouri; Rosenkranz, Stephan; Osborn, Ray

    2013-03-01

    The iron-arsenides are a now famous family of high-Tc superconductors where the superconducting state is stabilized by suppressing a magnetic ground state in a parent compound. The phenomenon is quite robust, and BaFe2As2, for example, can be made superconducting either by applying pressure or by electron, hole, or isovalent doping. The isovalently doped BaFe2(As1-xPx)2 materials are particularly interesting because it is not obvious what is driving the suppression of the SDW and enhancing Tc. The driving force has been variously ascribed to chemical pressure, changes in polarity of the Fe-(As,P) bond, and other even more subtle chemical effects. Moreover, reports on various general features in the iron-arsenide phase diagram--such as short-range nematic order and the separation of the Néel transition (TN) and the structural transition (Ts) --remain contradictory and underexplored. We have undertaken a detailed neutron diffraction study of the phase diagram in order to clarify some of the ambiguities. We find that Ts = TN and that the superconducting dome rises more sharply than for the aliovalently doped materials. Moreover, the T dependence of the structural and magnetic order parameters and a discontinuous increase in c/ a below TN suggest a first order phase transition.

  7. Neutron diffraction measurements for the determination of heat treatment effectiveness in generating compressive residual stress in an automotive crown gear

    NASA Astrophysics Data System (ADS)

    Albertini, G.; Bruno, G.; Fiori, F.; Girardin, E.; Giuliani, A.; Quadrini, E.; Romani, F.

    2000-03-01

    Thermal austenitizing and tempering treatments are being developed in automotive industry to prevent crack initiation and propagation, especially in components where stress intensity factors influence the stress field and ultimately the fatigue life of the component. This is the case of crown gears, where the tooth root typically undergoes impulsive and very high loads which frequently cause cracking if tensile residual stresses are present at the surface. The sign reversal of these stresses is the aim of austenitizing and tempering treatments. In this work neutron diffraction measurements of residual stress (RS) on a UNI55Cr3 steel crown gear, carried out at HMI-BENSC , are presented. The sample was submitted to a new multi-frequency induction technique whose effectiveness was checked. Comparisons with X-ray measurements are shown, and RS measured by X-rays on a similar shot-peened sample are also mentioned. Experiments at HMI-BENSC have received financial support by the European Commission under the TMR/LSF Access Programme (contract no. ERBFMGE CT950060).

  8. Phase coexistence in NaTaO3 at room temperature; a high resolution neutron powder diffraction study

    NASA Astrophysics Data System (ADS)

    Knight, Kevin S.; Kennedy, Brendan J.

    2015-05-01

    Room temperature high resolution neutron powder diffraction data, measured in time-of-flight, from two independent samples of NaTaO3 shows the presence of phase coexistence of two orthorhombic structures with space groups Pbnm, and Cmcm. The failure of earlier work to recognise the extent of the hysteresis associated with the high temperature (∼763 K on heating) Cmcm - Pbnm phase transition, that extends down to room temperature, and probably to 0 K, is due to data having been collected at too low a real-space resolution to characterise the diagnostic pseudocubic fundamental and superlattice reflection multiplicities. The phase fraction of the Cmcm phase increases with increasing temperature from 45 weight % at 298 K, to 74 weight % at 758 K. Throughout the whole temperature interval 298 K-758 K, the volume per formula unit of the Cmcm phase exceeds that of the Pbnm phase by an almost constant ∼0.01 Å3 suggesting the addition of pressure would supress the volume fraction of the higher temperature phase. The crystal structure of both phases, determined from data collected at 298 K, are reported, with the atomic displacement parameters of the Cmcm phase being significantly larger than those associated with the Pbnm phase, probably reflecting a high degree of thermal and static disorder.

  9. Direct determination of the spin structure of Nd2Ir2O7 by means of neutron diffraction

    NASA Astrophysics Data System (ADS)

    Guo, H.; Ritter, C.; Komarek, A. C.

    2016-10-01

    We report on the spin structure of the pyrochlore iridate Nd2Ir2O7 that could be directly determined by means of powder neutron diffraction. Our magnetic structure refinement unravels a so-called all-in/all-out magnetic structure that appears in both the Nd and the Ir sublattice. The ordered magnetic moments at 1.8 K amount to 0.34 (1 )μB/Ir4 + and 1.27 (1 )μB/Nd3 +. The Nd3 + moment size at 1.8 K is smaller than that expected for the Nd3 + ground state doublet. On the other hand, the size of the ordered moments of the Ir4 + ions at 1.8 K agrees very well with the value expected for a Jeff=1 /2 state based on the presence of strong spin-orbit coupling in this system. Finally, our measurements reveal a parallel alignment of the Nd3 + moments with the net moment of its six nearest neighboring Ir4 + ions.

  10. Neutron diffraction determination of hydrogen atom locations in the α(TiCrSiO) 1/1 crystal approximant

    NASA Astrophysics Data System (ADS)

    Kim, J. Y.; Kim, W. J.; Gibbons, P. C.; Kelton, K. F.; Yelon, W. B.

    1999-08-01

    Titanium/zirconium-based quasicrystals and their related crystal approximants have been identified as potential new materials for hydrogen storage applications. To better understand the local chemistry and atomic ordering in these phases, preferential interstitial sites for hydrogen/deuterium were determined for α(TiCrSiO). This is a bcc 1/1 crystal approximant to the icosahedral quasicrystal phase that contains a two-shell, Mackay-icosahedral cluster of atoms at each bcc site. It absorbs hydrogen or deuterium, without formation of other hydride phases, to a maximum hydrogen to metal atom ratio (H/M) of 0.26. For fully deuterated samples, both tetrahedral and octahedral interstitial sites are occupied with fractions of 0.14 and 0.12, respectively. Here, the hydrogen/deuterium sites are determined from a Rietveld analysis of x-ray and neutron powder diffraction data taken from samples of α(TiCrSiO) loaded with deuterium. Only the octahedral sites are occupied in the partially deuterated samples (D/M=0.11). A decrease in the oxygen concentration below the stoichiometric value for α(TiCrSiO) leads to an increase in the total amount of hydrogen that can be absorbed, suggesting that these interstitial atoms are competing for the same octahedral interstitial sites.

  11. Commensurate magnetic structures of RMn2O5 (R=Y,Ho,Bi) determined by single-crystal neutron diffraction

    NASA Astrophysics Data System (ADS)

    Vecchini, C.; Chapon, L. C.; Brown, P. J.; Chatterji, T.; Park, S.; Cheong, S.-W.; Radaelli, P. G.

    2008-04-01

    Precise magnetic structures of RMn2O5 , with R=Y,Ho,Bi in the commensurate and/or ferroelectric regime, have been determined by single-crystal neutron diffraction. For each system, the integrated intensities of a large number of independent magnetic Bragg reflections have been measured, allowing unconstrained least-squares refinement of the structures. The analysis confirms the previously reported magnetic configuration in the ab plane, in particular, the existence of zigzag antiferromagnetic chains. For the Y and Ho compounds, additional weak magnetic components parallel to the c axis were detected, which are modulated in phase quadrature with the a-b components. This component is extremely small in the BiMn2O5 sample, therefore supporting symmetric exchange as the principal mechanism inducing ferroelectricity. For HoMn2O5 , a magnetic ordering of the Ho moments was observed, which is consistent with a superexchange interaction through the oxygens. For all three compounds, the point symmetry in the magnetically ordered state is m2m , allowing the polar b axis found experimentally.

  12. Quantum entanglement in manganese(II) hexakisimidazole nitrate: on electronic structure imaging - A polarized neutron diffraction and DFT study

    NASA Astrophysics Data System (ADS)

    Wallace, Warren A.

    2016-04-01

    Quantum entanglement has been visualized for the first time, in view of the spin density distribution and electronic structure for manganese in manganese(II)hexakisimidazole nitrate. Using polarized neutron diffraction and density functional theory modelling we have found for the complex, which crystallizes in the R3¯ spacegroup, a = b = 12.4898(3) Å, c = 14.5526(4) Å, α = γ = 90°, β = 120°, Z = 3, that spatially antisymmetric and spatially symmetric shaped regions of negative spin density, in the spin density map for manganese, are a result of quantum entanglement of the high spin d5 configuration due to dative imidazole- manganese π- donation and σ-bonding interactions respectively. We have found leakage of the entangled states for manganese observed as regions of positive spin density with spherical (3.758(2) μB) and non-spherical (1.242(3) μB) contributions. Our results, which are supportive of Einstein's theory of general relativity, provide evidence for the existence of a black hole spin density distribution at the origin of an electronic structure and also address the paradoxical views of entanglement and quantum mechanics. We have also found the complex, which is an insulator, to be suitable for spintronic studies.

  13. High pressure phase transformations in α-AlPO4: an x-ray diffraction investigation

    NASA Astrophysics Data System (ADS)

    Sharma, Surinder M.; Garg, Nandini; Sikka, S. K.

    2000-07-01

    We have re-investigated the high pressure behaviour of berlinite AlPO4 (α-AlPO4) with x-ray diffraction using a powerful synchrotron x-ray source SPring-8. Our results show that it transforms to a crystalline phase beyond ~13 GPa. Our data seem to be consistent with a CrVO4 type of structure in the Cmcm space group, similar to the high pressure phase observed in some isostructural phosphate compounds. The persistence of the diffraction pattern up to 40 GPa establishes that the previously accepted amorphization of AlPO4 around 12-18 GPa is incorrect. Experimental results suggest that the so-called memory glass effect observed earlier may in fact be the reversibility of the α-phase←⇔crystalline phase transformation. Comparisons of our experimental and theoretical results raise serious doubts about the theoretical understanding of the high pressure behaviour of α-AlPO4.

  14. Computation of diffuse scattering arising from one-phonon excitations in a neutron time-of-flight single-crystal Laue diffraction experiment

    PubMed Central

    Gutmann, Matthias J.; Graziano, Gabriella; Mukhopadhyay, Sanghamitra; Refson, Keith; von Zimmerman, Martin

    2015-01-01

    Direct phonon excitation in a neutron time-of-flight single-crystal Laue diffraction experiment has been observed in a single crystal of NaCl. At room temperature both phonon emission and excitation leave characteristic features in the diffuse scattering and these are well reproduced using ab initio phonons from density functional theory (DFT). A measurement at 20 K illustrates the effect of thermal population of the phonons, leaving the features corresponding to phonon excitation and strongly suppressing the phonon annihilation. A recipe is given to compute these effects combining DFT results with the geometry of the neutron experiment. PMID:26306090

  15. Study of the magnetic and electronic properties of nanocrystalline PrCo3 by neutron powder diffraction and density functional theory.

    PubMed

    Younsi, Khedidja; Crivello, Jean-Claude; Paul-Boncour, Valérie; Bessais, Lotfi; Porcher, Florence; André, Gilles

    2013-03-20

    Nanocrystalline PrCo(3) powder has been synthesized by high-energy milling and was subsequently annealed from 873 to 1273 K for 30 min to optimize the extrinsic properties. The structure and magnetic properties of the nanocrystalline PrCo(3) have been investigated by means of x-ray and neutron diffraction as well as magnetization measurements. All compounds crystallize in the same PuNi(3) type structure, with grain sizes between 28 and 47 nm. As the annealing temperature increases, a maximum coercive field of 12 kOe at 300 K (55 kOe at 10 K) was obtained by annealing at 1023 K for a grain size of 35 nm. The refinement of the neutron powder diffraction patterns (NPD) of PrCo(3) from 1.8 to 300 K shows an expansion of the parameter a and a contraction of the parameter c, leading to a decrease of the ratio c/a. The evolution of the Co and Pr magnetic sublattices measured by NPD indicates that this compound is a highly anisotropic uniaxial ferromagnet with the easy magnetization axis parallel to c(-->). This experimental study has been completed by a theoretical investigation of the electronic structure of the PrCo(x) (x = 2, 3 and 5) compounds. Band structure calculations with collinear spin polarization were performed by using the local approximation of the density functional theory scheme implemented in the projector-augmented wave method. The electronic structure of PrCo(3) compound in both directions of spin shows that the majority of occupied states are dominated by the 3d states of Co, with a strong electronic charge transfer from Pr to Co. The PrCo(3) electronic structure can be explained by a superimposition of those of PrCo(2) and PrCo(5), as expected from its crystal structure. The magnetic anisotropy has been confirmed for PrCo(3), as a non-collinear spin calculation with the polarization along the c axis is shown to be more stable than with the polarization in the (a(-->),b(-->)) plane.

  16. The commensurate spin excitation in chromium: A polarised neutron investigation

    SciTech Connect

    Pynn, R. ); Stirling, W.G. . Dept. of Physics); Severing, A. )

    1991-01-01

    A polarised neutron experiment with neutron energy analysis has been performed with a single-Q sample of chromium in a large magnetic field. The 4-meV commensurate'' mode is found to involve spin fluctuations parallel to the ordered chromium moments. 8 refs., 3 figs.

  17. Amorphous polymorphis in ice investigated by inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Schober, H.; Koza, M.; Tölle, A.; Fujara, F.; Angell, C. A.; Böhmer, R.

    High-density I lda and low-density I lda amorphous have been investigated by inelastic neutron scattering (INS) with emphasis on the energy window from 0.5 to 20 meV. At variance with earlier measurements the spectra in the I lda phase show a simple ω2 behaviour in the acoustic region and the temperature dependence is found to be harmonic. I lda converts with a strongly temperature-dependent rate towards I lda ice. We have investigated in detail the time evolution of both the static and dynamic response functions at several temperatures. Elastic small-angle signals indicate the presence of strong heterogeneties at the early stages of the conversion process. At least two different time scales are present in the transition. The structural changes are reflected in the frequency distribution. The first peak in the phonon density-of-states softens appreciably when going from I lda to I lda. In the acoustic region there is evidence that I lda is softer than both I lda and crystalline cubic ice I c. No signs of a fast ps process related to melting can be detected in the dynamics.

  18. New insights into the compressibility and high-pressure stability of Ni(CN)2: a combined study of neutron diffraction, Raman spectroscopy, and inelastic neutron scattering.

    PubMed

    Mishra, Sanjay K; Mittal, Ranjan; Zbiri, Mohamed; Rao, Rekha; Goel, Prabhatasree; Hibble, Simon J; Chippindale, Ann M; Hansen, Thomas; Schober, Helmut; Chaplot, Samrath L

    2016-02-01

    Nickel cyanide is a layered material showing markedly anisotropic behaviour. High-pressure neutron diffraction measurements show that at pressures up to 20.1 kbar, compressibility is much higher in the direction perpendicular to the layers, c, than in the plane of the strongly chemically bonded metal-cyanide sheets. Detailed examination of the behaviour of the tetragonal lattice parameters, a and c, as a function of pressure reveal regions in which large changes in slope occur, for example, in c(P) at 1 kbar. The experimental pressure dependence of the volume data is fitted to a bulk modulus, B0, of 1050 (20) kbar over the pressure range 0-1 kbar, and to 124 (2) kbar over the range 1-20.1 kbar. Raman spectroscopy measurements yield additional information on how the structure and bonding in the Ni(CN)2 layers change with pressure and show that a phase change occurs at about 1 kbar. The new high-pressure phase, (Phase PII), has ordered cyanide groups with sheets of D4h symmetry containing Ni(CN)4 and Ni(NC)4 groups. The Raman spectrum of phase PII closely resembles that of the related layered compound, Cu1/2Ni1/2(CN)2, which has previously been shown to contain ordered C≡N groups. The phase change, PI to PII, is also observed in inelastic neutron scattering studies which show significant changes occurring in the phonon spectra as the pressure is raised from 0.3 to 1.5 kbar. These changes reflect the large reduction in the interlayer spacing which occurs as Phase PI transforms to Phase PII and the consequent increase in difficulty for out-of-plane atomic motions. Unlike other cyanide materials e.g. Zn(CN)2 and Ag3Co(CN)6, which show an amorphization and/or a decomposition at much lower pressures (~100 kbar), Ni(CN)2 can be recovered after pressurising to 200 kbar, albeit in a more ordered form. PMID:26751175

  19. An investigation into the use of electron back scattered diffraction to measure recrystallized fraction

    SciTech Connect

    Black, M.P.; Higginson, R.L. . Dept. of Engineering Materials)

    1999-06-18

    The Electron Back-Scattered Diffraction (EBSD) technique is in its infancy and is a highly promising area of development. Use of EBSD has been predominantly for the determination of crystallographic textures. Other applications have also been considered, which include: crystal structure determination, phase determination, grain boundary studies and both elastic and plastic deformation measurement. Although it has been acknowledged that an important use of the EBSD could be in the measurement of recrystallization and its kinetics there are a number of inherent problems with such measurements using EBSD. These problems include the ability of the system to index deformed microstructures even those on a fine scale, the difficulties of analyzing patterns in the region of grain boundaries and the problems of sample preparation which is critical in the quality of the diffraction patterns obtained. The aim of the present study is to determine whether it is possible to measure the volume fraction recrystallized using EBSP of partially recrystallized stainless steel. This has been done by investigation of the quality of matching between the observed and calculated diffraction patterns, and the quality of the observed patterns measured in terms of their contrast. The material used was stainless steel 316L.

  20. Residual stress profiling in the ferrite and cementite phases of cold-drawn steel rods by synchrotron X-ray and neutron diffraction

    SciTech Connect

    Martinez-Perez, M.L.; Mompean, F.J.; Ruiz-Hervias, J.; Atienza, J.M.; Elices, M.; Peng Rulin; Buslaps, T.

    2004-10-18

    Residual stress profiles have been measured in the ferrite and cementite phases of a cold-drawn eutectoid steel rod by neutron and synchrotron X-ray diffraction in three orientations (axial, radial and hoop). Neutron diffraction was employed to measure the ferrite stresses, whereas synchrotron radiation was used for ferrite and cementite stresses. Experimental results in the ferrite phase showed excellent agreement between both experimental techniques when gauge volume effects were accounted for. Axial cementite stresses were always tensile, with a maximum value close to 1700 MPa at the rod surface. Radial and hoop cementite stresses were compressive along the diameter of the rod, with a minimum of -1900 MPa at the rod center. A 3D-finite element simulation of the macro residual stresses resulting from cold-drawing showed remarkable agreement with those determined from the experimental measurements in the ferrite and cementite phases.

  1. Neutron diffraction study of the formation of ordered antiphase domains in cubic titanium carbide TiC{sub 0.60}

    SciTech Connect

    Khidirov, I. Parpiev, A. S.

    2013-05-15

    A series of superstructural reflections (described within the sp. gr. Fd3m) are found to be split into three symmetric parts in the neutron powder diffraction pattern of titanium carbide TiC{sub 0.60} annealed at a temperature of 600 Degree-Sign C. No splitting of superstructural reflections is observed in the neutron diffraction pattern of TiC{sub 0.60} annealed at relatively high temperatures (780 Degree-Sign C). This phenomenon can be explained by that fact that the ordering of carbon atoms at relatively high temperatures (780 Degree-Sign C) is accompanied by the formation of randomly oriented rather large antiphase domains (APDs) (450 A). At relatively low temperatures (600 Degree-Sign C), stacking faults arise in the arrangement of partially ordered carbon atoms. In this case, relatively small ordered APDs (290 A) are formed, along with disordered ones.

  2. A method for the monitoring of metal recrystallization based on the in-situ measurement of the elastic energy release using neutron diffraction.

    PubMed

    Christien, F; Telling, M T F; Knight, K S; Le Gall, R

    2015-05-01

    A method is proposed for the monitoring of metal recrystallization using neutron diffraction that is based on the measurement of stored energy. Experiments were performed using deformed metal specimens heated in-situ while mounted at the sample position of the High Resolution Powder Diffractometer, HRPD (ISIS Facility), UK. Monitoring the breadth of the resulting Bragg lines during heating not only allows the time-dependence (or temperature-dependence) of the stored energy to be determined but also the recrystallized fraction. The analysis method presented here was developed using pure nickel (Ni270) specimens with different deformation levels from 0.29 to 0.94. In situ temperature ramping as well as isothermal annealing was undertaken. The method developed in this work allows accurate and quantitative monitoring of the recrystallization process. The results from neutron diffraction are satisfactorily compared to data obtained from calorimetry and hardness measurements.

  3. Structural analysis of PrBaMn2O5+δ under SOFC anode conditions by in-situ neutron powder diffraction

    NASA Astrophysics Data System (ADS)

    Tomkiewicz, Alex C.; Tamimi, Mazin A.; Huq, Ashfia; McIntosh, Steven

    2016-10-01

    The crystal structure and oxygen stoichiometry of the proposed double perovskite solid oxide fuel cell (SOFC) anode material PrBaMn2O5+δ were determined under SOFC anode conditions via in-situ neutron diffraction. Measurements were performed in reducing atmospheres between 692 K and 984 K. The structure was fit to a tetragonal (space group P4/mmm) layered double perovskite structure with alternating Pr and Ba A-site cation layers. Under all conditions examined, the oxygen sites in the Ba and Mn layers were fully occupied, while the sites in the Pr layer were close to completely vacant. The results of the neutron diffraction experiments are compared to previous thermogravimetric analysis experiments to verify the accuracy of both experiments. PrBaMn2O5+δ was shown to be stable over a wide range of reducing atmospheres similar to anode operating conditions in solid oxide fuel cells without significant structural changes.

  4. Magnetization distribution in the tetragonal Ba(Fe1-xCox)2As2, x=0.066 probed by polarized neutron diffraction

    NASA Astrophysics Data System (ADS)

    Prokeš, K.; Gukasov, A.; Argyriou, D. N.; Bud'ko, S. L.; Canfield, P. C.; Kreyssig, A.; Goldman, A. I.

    2011-02-01

    Polarized neutron diffraction has been performed on a tetragonal Ba(Fe1-xCox)2As2, x=0.066 single crystal under an applied magnetic field of 6 T directed along the [\\overline{1}10 ] direction to determine the magnetic structure factors of various Bragg reflections. The maximum entropy reconstruction based on bulk magnetization measurements and polarized neutron diffraction data reveal a small induced magnetic moment residing on the 4d Wyckoff site that is occupied by Fe/Co atoms. No significant magnetization density has been found on the Ba and As atomic positions. The small polarizability of Fe/Co sites leads to flipping ratios very close to 1.00. Our data suggest a non-zero orbital contribution to the Fe/Co magnetic form factor in good agreement with recent theoretical and experimental studies.

  5. NEUTRON-DIFFRACTION STUDY ON PLASTIC BEHAVIOR OF A NICKEL-BASED ALLOY UNDER THE MONOTONIC-TENSION AND THE LOW-CYCLE-FATIGUE EXPERIMENTS

    SciTech Connect

    Huang, E-Wen; Barabash, Rozaliya; Clausen, Bjorn; Wang, Yandong; Yang, Dr Ren; Li, Li; Choo, Hahn; Liaw, Peter K

    2007-01-01

    The plastic behavior of an annealed HASTELLOY C-22HS alloy, a face-centered cubic (FCC), nickel-based superalloy, was examined by in-situ neutron-diffraction measurements at room temperature. Both monotonic-tension and low-cycle-fatigue experiments were conducted. Monotonic-tension straining and cyclic-loading deformation were studied as a function of stress. The plastic behavior during deformation is discussed in light of the relationship between the stress and dislocation-density evolution. The calculated dislocation-density evolution within the alloy reflects the strain hardening and cyclic hardening/softening. Experimentally determined lattice strains are compared to verify the hardening mechanism at selected stress levels for tension and cyclic loadings. Combined with calculations of the dislocation densities, the neutron-diffraction experiments provide direct information about the strain and cyclic hardening of the alloy.

  6. Neutron Diffraction Study on Plastic behavior of a Nickel-Based Alloy Under the Monotonic-Tension and the Low-Cyclic-Fatigue Experiments

    SciTech Connect

    Huang, E.-W.; Barabash, R.; Clausen, B.; Wang, Y.; Yang, R.; Li, L.; Choo, H.; Liaw, P.K.

    2007-11-02

    The plastic behavior of an annealed HASTELLOY C-22HS alloy, a face-centered cubic (FCC), nickel-based superalloy, was examined by in-situ neutron-diffraction measurements at room temperature. Both monotonic-tension and low-cycle-fatigue experiments were conducted. Monotonic-tension straining and cyclic-loading deformation were studied as a function of stress. The plastic behavior during deformation is discussed in light of the relationship between the stress and dislocation-density evolution. The calculated dislocation-density evolution within the alloy reflects the strain hardening and cyclic hardening/softening. Experimentally determined lattice strains are compared to verify the hardening mechanism at selected stress levels for tension and cyclic loadings. Combined with calculations of the dislocation densities, the neutron-diffraction experiments provide direct information about the strain and cyclic hardening of the alloy.

  7. A method for the monitoring of metal recrystallization based on the in-situ measurement of the elastic energy release using neutron diffraction

    SciTech Connect

    Christien, F. Le Gall, R.; Telling, M. T. F.; Knight, K. S.

    2015-05-15

    A method is proposed for the monitoring of metal recrystallization using neutron diffraction that is based on the measurement of stored energy. Experiments were performed using deformed metal specimens heated in-situ while mounted at the sample position of the High Resolution Powder Diffractometer, HRPD (ISIS Facility), UK. Monitoring the breadth of the resulting Bragg lines during heating not only allows the time-dependence (or temperature-dependence) of the stored energy to be determined but also the recrystallized fraction. The analysis method presented here was developed using pure nickel (Ni270) specimens with different deformation levels from 0.29 to 0.94. In situ temperature ramping as well as isothermal annealing was undertaken. The method developed in this work allows accurate and quantitative monitoring of the recrystallization process. The results from neutron diffraction are satisfactorily compared to data obtained from calorimetry and hardness measurements.

  8. A method for the monitoring of metal recrystallization based on the in-situ measurement of the elastic energy release using neutron diffraction

    NASA Astrophysics Data System (ADS)

    Christien, F.; Telling, M. T. F.; Knight, K. S.; Le Gall, R.

    2015-05-01

    A method is proposed for the monitoring of metal recrystallization using neutron diffraction that is based on the measurement of stored energy. Experiments were performed using deformed metal specimens heated in-situ while mounted at the sample position of the High Resolution Powder Diffractometer, HRPD (ISIS Facility), UK. Monitoring the breadth of the resulting Bragg lines during heating not only allows the time-dependence (or temperature-dependence) of the stored energy to be determined but also the recrystallized fraction. The analysis method presented here was developed using pure nickel (Ni270) specimens with different deformation levels from 0.29 to 0.94. In situ temperature ramping as well as isothermal annealing was undertaken. The method developed in this work allows accurate and quantitative monitoring of the recrystallization process. The results from neutron diffraction are satisfactorily compared to data obtained from calorimetry and hardness measurements.

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

    SciTech Connect

    Shu, F.; Ramakrishnan, V.; Schoenborn, B.P.

    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%.

  10. X-ray diffraction investigation of 1-phenyl-3-isopropyl-5-(benzothiazol-2-yl)formazan

    SciTech Connect

    Slepukhin, P. A. Pervova, I. G.; Rezinskikh, Z. G.; Lipunova, G. N.; Gorbatenko, Yu. A.; Lipunov, I. N.

    2008-01-15

    The crystal structure of 1-phenyl-3-isopropyl-5-(benzothiazol-2-yl)formazan is investigated using X-ray diffraction. The compound crystallizes in the form of two crystallographically independent molecules (A and B) in identical conformations that are stabilized by intermolecular hydrogen bonds. The intermolecular hydrogen bonds N-H-N (N-N, 2.892 and 2.939 A) link molecules into AB dimers. Both molecules have a flattened structure, except for the isopropyl fragment. The bonds in the formazan chains are delocalized. Molecules A and B have close geometric characteristics.

  11. Deformation Behavior of Solid-Solution-Strengthened Mg-9wt%Al Alloy: In-Situ Neutron Diffraction and Elastic-Viscoplastic Self-Consistent Modeling

    SciTech Connect

    Lee, Sooyeol; Wang, H; Gharghouri, Michael; Nayyeri, G.; Woo, Wan; Shin, E; Wu, Peidong; Poole, W. J.; Wu, Wei; An, Ke

    2014-01-01

    In situ neutron diffraction and elastic viscoplastic self-consistent (EVPSC) modeling have been employed to understand the deformation mechanisms of the loading unloading process under uniaxial tension in a solid-solution-strengthened extruded Mg 9 wt.% Al alloy. The initial texture measured by neutron diffraction shows that the {00.2} basal planes in most grains are tilted around 20 30 from the extrusion axis, indicating that basal slip should be easily activated in a majority of grains under tension. Non-linear stress strain responses are observed during unloading and reloading after the material is fully plastically deformed under tension. In situ neutron diffraction measurements have also demonstrated the non-linear behavior of lattice strains during unloading and reloading, revealing that load redistribution continuously occurs between soft and hard grain orientations. The predicted macroscopic stress strain curve and the lattice strain evolution by the EVPSC model are in good agreement with the experimental data. The EVPSC model provides the relative activities of the available slip and twinning modes, as well as the elastic and plastic strains of the various grain families. It is suggested that the non-linear phenomena in the macroscopic stress strain responses and microscopic lattice strains during unloading and reloading are due to plastic deformation by the operation of basal a slip in the soft grain orientations (e.g. {10.1}, {11.2} and {10.2} grain families).

  12. Preliminary neutron and ultrahigh-resolution X-ray diffraction studies of the aspartic proteinase endothiapepsin cocrystallized with a gem-diol inhibitor

    SciTech Connect

    Tuan, Han-Fang; Erskine, Peter; Langan, Paul; Cooper, Jon; Coates, Leighton

    2007-12-01

    Three data sets have been collected on endothiapepsin complexed with the gem-diol inhibitor PD-135,040: a high-resolution synchrotron X-ray data set, a room-temperature X-ray data set and a neutron diffraction data set. Until recently, it has been impossible to grow large protein crystals of endothiapepsin with any gem-diol inhibitor that are suitable for neutron diffraction. Endothiapepsin has been cocrystallized with the gem-diol inhibitor PD-135,040 in a low solvent-content (39%) unit cell, which is unprecedented for this enzyme–inhibitor complex and enables ultrahigh-resolution (1.0 Å) X-ray diffraction data to be collected. This atomic resolution X-ray data set will be used to deduce the protonation states of the catalytic aspartate residues. A room-temperature neutron data set has also been collected for joint refinement with a room-temperature X-ray data set in order to locate the H/D atoms at the active site.

  13. H-bonding scheme and cation partitioning in axinite: a single-crystal neutron diffraction and Mössbauer spectroscopic study

    NASA Astrophysics Data System (ADS)

    Gatta, G. Diego; Redhammer, Günther J.; Guastoni, Alessandro; Guastella, Giorgio; Meven, Martin; Pavese, Alessandro

    2016-05-01

    The crystal chemistry of a ferroaxinite from Colebrook Hill, Rosebery district, Tasmania, Australia, was investigated by electron microprobe analysis in wavelength-dispersive mode, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), 57Fe Mössbauer spectroscopy and single-crystal neutron diffraction at 293 K. The chemical formula obtained on the basis of the ICP-AES data is the following: ^{X1,X2} {{Ca}}_{4.03} Y ( {{{Mn}}_{0.42} {{Mg}}_{0.23} {{Fe}}^{2 + }_{1.39} } )_{Σ 2.04} ^{Z1,Z2} ( {{{Fe}}^{3 + }_{0.15} {{Al}}_{3.55} {{Ti}}_{0.12} } )_{Σ 3.82} ^{T1,T2,T3,T4} ( {{{Ti}}_{0.03} {{Si}}_{7.97} } )_{Σ 8} ^{T5} {{B}}_{1.96} {{O}}_{30} ( {{OH}} )_{2.18} . The 57Fe Mössbauer spectrum shows unambiguously the occurrence of Fe2+ and Fe3+ in octahedral coordination only, with Fe2+/Fe3+ = 9:1. The neutron structure refinement provides a structure model in general agreement with the previous experimental findings: the tetrahedral T1, T2, T3 and T4 sites are fully occupied by Si, whereas the T5 site is fully occupied by B, with no evidence of Si at the T5, or Al or Fe3+ at the T1- T5 sites. The structural and chemical data of this study suggest that the amount of B in ferroaxinite is that expected from the ideal stoichiometry: 2 a.p.f.u. (for 32 O). The atomic distribution among the X1, X2, Y, Z1 and Z2 sites obtained by neutron structure refinement is in good agreement with that based on the ICP-AES data. For the first time, an unambiguous localization of the H site is obtained, which forms a hydroxyl group with the oxygen atom at the O16 site as donor. The H-bonding scheme in axinite structure is now fully described: the O16- H distance (corrected for riding motion effect) is 0.991(1) Å and an asymmetric bifurcated bonding configuration occurs, with O5 and O13 as acceptors [i.e. with O16··· O5 = 3.096(1) Å, H··· O5 = 2.450(1) Å and O16- H··· O5 = 123.9(1)°; O16··· O13 = 2.777(1) Å, H··· O13 = 1.914(1) Å and O16- H··· O13 = 146

  14. Neutron Diffraction Study of Parasitic Nd-Moment Order in the Checkerboard-Type Phase Nd1.3Sr0.7NiO4

    DOE PAGES

    Kobayashi, Riki; Yoshizawa, Hideki; Matsuda, Masaaki; Kajimoto, Ryoichi; Ishizaka, Kyoko; Tokura, Yoshinori

    2015-05-25

    In this paper, the Nd-moment order in the layered nickelate Nd2-xSrxNiO4 (x = 0.7) has been investigated by performing a neutron diffraction experiment using a single crystal sample. First, the checkerboard (CB)-type charge order was confirmed by observing the temperature dependence of the nuclear superlattice peak at Q=(5,0,0) between 1.9 and 300 K, which indicates that the transition temperature of the CB-type charge order is above 300 K. Magnetic superlattice peaks with the propagation vector k=(1-ε,0,1) appear below 67 K, and the value of ε was determined to be 0.455 in good agreement with previous studies. The intensity of themore » magnetic superlattice peaks appearing below 67 K shows a sharp increase below ≈20 K. This behavior indicates that the Nd moments freeze under the influence of the Ni ordering. The CB-type antiferromagnetic (AFM) Ni order in the NiO2 layers is stacked antiferromagnetically in the c-axis direction, while the Nd moments in the Nd/SrO2 layers are coupled antiferromagnetically with the Ni moments. Finally, the Nd moments are parallel to the c-axis, while the Ni moments are canted towards the c-axis direction from the basal ab-plane at low temperatures where the Nd moments are well ordered.« less

  15. Characterization of the intermediate-range order in new superionic conducting AgI-Ag2S-AgPO3 glasses by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Kartini, E.; Kennedy, S. J.; Itoh, K.; Fukunaga, T.; Suminta, S.; Kamiyama, T.

    Superionic conducting glasses are of considerable technological interest because of their use in batteries, sensors, and displays. We have investigated the new ternary systems AgI-Ag2S-AgPO3 where the ratio AgI:Ag2S is 1:1. The system (AgI)x(Ag2S)x(AgPO3)1-2x, for a AgI+Ag2S fraction less than 82mol%, yields glasses. We have used a neutron-diffraction technique to obtain the total scattering structure factor S(Q) of this system at room temperature by using the HIT spectrometer at the High Energy Accelerator (KEK), Tsukuba, Japan. As for AgI-AgPO3 glasses, S(Q) shows a peak at anomalously low Q in the range from 0.6 to 0.9 Å-1. This peak is not observed in the corresponding glass Ag2S-AgPO3 or pure AgPO3. The peak depends strongly on the dopant salt. Its intensity increases as the amount of (AgI+Ag2S) increases and its position shifts to lower Q, while the number density of the glasses decreases with x. This peak can be associated with an intermediate structure of particles lying inside a continuous host with the characteristic length between 5 and 10 Å [1].

  16. Mechanisms of network collapse in GeO2 glass: high-pressure neutron diffraction with isotope substitution as arbitrator of competing models.

    PubMed

    Wezka, Kamil; Salmon, Philip S; Zeidler, Anita; Whittaker, Dean A J; Drewitt, James W E; Klotz, Stefan; Fischer, Henry E; Marrocchelli, Dario

    2012-12-19

    The structure of the network forming glass GeO(2) is investigated by making the first application of the method of in situ neutron diffraction with isotope substitution at pressures increasing from ambient to 8 GPa. Of the various models, the experimental results are in quantitative agreement only with molecular dynamics simulations made using interaction potentials that include dipole-polarization effects. When the reduced density ρ/ρ(0) > or approximately equal to 1.16, where ρ(0) is the value at ambient pressure, network collapse proceeds via an interplay between the predominance of distorted square pyramidal GeO(5) units versus octahedral GeO(6) units as they replace tetrahedral GeO(4) units. This replacement necessitates the formation of threefold coordinated oxygen atoms and leads to an increase with density in the number of small rings, where a preference is shown for sixfold rings when ρ/ρ(0) = 1 and fourfold rings when ρ/ρ(0) = 1.64.

  17. Mechanisms of network collapse in GeO2 glass: high-pressure neutron diffraction with isotope substitution as arbitrator of competing models

    NASA Astrophysics Data System (ADS)

    Wezka, Kamil; Salmon, Philip S.; Zeidler, Anita; Whittaker, Dean A. J.; Drewitt, James W. E.; Klotz, Stefan; Fischer, Henry E.; Marrocchelli, Dario

    2012-12-01

    The structure of the network forming glass GeO2 is investigated by making the first application of the method of in situ neutron diffraction with isotope substitution at pressures increasing from ambient to 8 GPa. Of the various models, the experimental results are in quantitative agreement only with molecular dynamics simulations made using interaction potentials that include dipole-polarization effects. When the reduced density ρ/ρ0 ≳ 1.16, where ρ0 is the value at ambient pressure, network collapse proceeds via an interplay between the predominance of distorted square pyramidal GeO5 units versus octahedral GeO6 units as they replace tetrahedral GeO4 units. This replacement necessitates the formation of threefold coordinated oxygen atoms and leads to an increase with density in the number of small rings, where a preference is shown for sixfold rings when ρ/ρ0 = 1 and fourfold rings when ρ/ρ0 = 1.64.

  18. In operando neutron diffraction study of a commercial graphite/(Ni, Mn, Co) oxide-based multi-component lithium ion battery

    NASA Astrophysics Data System (ADS)

    Nazer, N. S.; Yartys, V. A.; Azib, T.; Latroche, M.; Cuevas, F.; Forseth, S.; Vie, P. J. S.; Denys, R. V.; Sørby, M. H.; Hauback, B. C.; Arnberg, L.; Henry, P. F.

    2016-09-01

    In situ neutron diffraction was employed to investigate the structural evolution of the electrode materials in an ICR 10440 commercial cylindrical lithium-ion battery, which has a discharge capacity of 360 mAh and a nominal voltage of 3.7 V. A three-phase mixture of Li(Ni,Mn,Co)O2, LiCoO2 and LiMn2O4 was identified as the active material of the cathode, with graphite acting as the anode material. The study revealed that the graphite anode underwent structural changes to form a series of insertion-type lithiated derivatives, with up to 12.7% volume expansion for the Li-saturated compound LiC6. The charge-discharge behavior was more complex for the cathode. Here, the charge process was associated with partial lithium depletion from the initially Li-saturated compounds, leading to volume shrinkage for Li(Ni,Mn,Co)O2, in contrast to (Ni,Mn)-free LiCoO2. Electrochemical discharge experiments performed under a fast regime (2 C) at 5, 25 and 45 °C revealed that the discharge capacity followed the trend of an increased diffusion rate of Li+ ions in the electrolyte and Li atoms in both electrodes, being highest for 45 °C. At the lowest tested temperature (5 °C), a rapid drop in the discharge capacity took place using the same kinetic regime.

  19. Magnetic ground state of superconducting Eu (Fe 0.88Ir 0.12)2As 2: A combined neutron diffraction and first-principles calculation study

    NASA Astrophysics Data System (ADS)

    Jin, W. T.; Li, Wei; Su, Y.; Nandi, S.; Xiao, Y.; Jiao, W. H.; Meven, M.; Sazonov, A. P.; Feng, E.; Chen, Yan; Ting, C. S.; Cao, G. H.; Brückel, Th.

    2015-02-01

    The magnetic order of the localized Eu2 + spins in optimally doped Eu (Fe1 -xIrx )2As2 (x =0.12 ) with superconducting transition temperature TSC=22 K was investigated by single-crystal neutron diffraction. The Eu2 + moments were found to be ferromagnetically aligned along the c direction with an ordered moment of 7.0(1) μB well below the magnetic phase transition temperature TC=17 K. No evidence of the tetragonal-to-orthorhombic structural phase transition was found in this compound within the experimental uncertainty, in which the spin-density-wave (SDW) order of the Fe sublattice is supposed to be completely suppressed and the superconductivity gets fully developed. The ferromagnetic ground state of the Eu2 + spins in Eu (Fe0.88Ir0.12 )2As2 was supported by the first-principles density functional calculation. In addition, comparison of the electronic structure calculations between Eu (Fe0.875Ir0.125 )2As2 and the parent compound EuFe2As2 indicates stronger hybridization and more expanded bandwidth due to the Ir substitution, which together with the introduction of electrons might work against the Fe-SDW in favor of the superconductivity.

  20. A Single-Crystal Neutron Diffraction Study on Magnetic Structure of the Quasi-One-Dimensional Antiferromagnet SrCo2V2O8

    NASA Astrophysics Data System (ADS)

    Juan-Juan, Liu; Jin-Chen, Wang; Wei, Luo; Jie-Ming, Sheng; Zhang-Zhen, He; A. Danilkin, S.; Wei, Bao

    2016-03-01

    The magnetic structure of the spin-chain antiferromagnet SrCo2V2O8 is determined by single-crystal neutron diffraction experiment. The system undergoes magnetic long range order below T_N = 4.96 K. The moment of 2.16{\\mu}_B per Co at 1.6 K in the screw chain running along the c axis alternates in the c-axis. The moments of neighboring screw chains are arranged antiferromagnetically along one in-plane axis and ferromagnetically along the other in-plane axis. This magnetic configuration breaks the 4-fold symmetry of the tetragonal crystal structure and leads to two equally populated magnetic twins with antiferromagnetic vector in the a or b axis. The very similar magnetic state to the isostructural BaCo2V2O8 warrants SrCo2V2O8 another interesting half-integer spin-chain antiferromagnet for investigation on quantum antiferromagnetism.

  1. High-sensitivity neutron diffraction of membranes: Location of the Schiff base end of the chromophore of bacteriorhodopsin

    SciTech Connect

    Heyn, M.P.; Westerhausen, J.; Wallat, I.; Seiff, F. )

    1988-04-01

    Three important events in the functional cycle of bacteriorhodopsin occur at the chromophore: the primary absorption of light, the isomerization from the all-trans to the 13-cis form, and the deprotonation and reprotonation of its Schiff base. The protonated Schiff base linkage of the chromophore with lysine-216 plays an essential role in the color regulation of the pigment and is most likely directly involved in the charge translocation of this light-driven proton pump. Although much is known about the structure of the protein, the position of this key functional group has not yet been determined. The authors have synthesized a retinal in which the five protons closest to the Schiff base are replaced by deuterons. The labeled retinal was spontaneously incorporated into bacteriorhodopsin by using a mutant of Halobacterium halobium that is deficient in the synthesis of retinal. The position of the labeled Schiff base end of the chromophore was determined in the two-dimensional projected density of dark-adapted bacteriorhodopsin by neutron diffraction. The result fits very well with their previous work using retinals that were selectively deuterated in the middle of the polyene chain or in the cyclohexene ring. A coherent structure emerges with the three labeled positions on one line, separated by distances that are in good agreement with the tilt angle of the polyene chain (about 20{degree}). The results show that it is possible to locate a small group containing as few as five deuterons in a membrane protein of molecular weight 27,000.

  2. The magnetic phase diagram of the UAs 1- xSe x system studied by neutron diffraction from single crystals

    NASA Astrophysics Data System (ADS)

    Kuznietz, M.; Burlet, P.; Rossat-Mignod, J.; Vogt, O.

    1987-10-01

    The magnetic phase diagram of the UAs 1- xSe x system (temperature versus composition) has been determined from neutron diffraction measurements in zero applied magnetic field on single crystals with x=0.03, 0.05, 0.10, 0.20, 0.25, 0.30, 0.40 and 0.50, as well as from measurements in finite applied magnetic fields on single crystals with x=0.10, 0.20, 0.25 and 0.30. For x⩽0.40 an incommensurate magnetic ordering ( k=[0,0, k]; mk ∥ k) develops below TN down to TIC. The k- value at TN decreases with the increase of x; in decreasing temperatures the k-value approaches the commensurate value below TIC. At TIC an incommensurate-commensurate transition leads to the type-I phase ( k=1) for x ⩽0.05 (with a subsequent transition to type-IA at TO), to the type-IA phase ( k= {1}/{2}) for 0.05 ⩽ x⩽ 0.30, and to the squaring-up of the (5+,4-) phase ( k≈0.244) for x=0.40 below T≈90 K. For x⩽0.50 the ordering is ferromagnetic. The nature of the multi- k structure is determined from measurements in finite fields. With the previously established single- k structure of type-I (in UAs), the UAs 1- xSe x system exhibits single- k, double- k and triple- k structures. A double- k-triple- k transition occurs for x ≈0.15 in the type-IA phase and for x≈0.22 in the incommensurate phase. The ordered magnetic moment at T=4.2 K is practically independent of the ordering ( m≈2μ B).

  3. Neutron diffraction and electrochemical studies of Na0.79(Co,Mn)O2 cathodes for sodium-ion batteries

    SciTech Connect

    Beck, Faith R; Cheng, Yongqiang; Feygenson, Mikhail; Bridges, Craig A; Moorhead-Rosenberg, Z; Manthiram, Arumugam; Goodenough, J. B.; Paranthaman, Mariappan Parans; Manivannan, A.

    2014-01-01

    Na0.79CoO2 and Na0.79Co0.7Mn0.3O2 with a layered hexagonal structure (P2-type) were synthesized by the Pechini process followed by heat treatment at elevated temperatures in order to achieve the crystalline phases. The samples were characterized with x-ray diffraction, neutron diffraction, magnetic measurements and electrochemical charge-discharge cycling. X-ray diffraction confirmed the P2 layered hexagonal structure after heat treatment at 900 C in air. Neutron diffraction patterns confirm Mn doping on Co sites without forming pronounced Mn-Co ordering. Cyclic voltammetry showed the oxidation and reduction peaks of Co and Mn, indicating the intercalation and de-intercalation behavior of the Na ions. A discharge capacity of 60 mAh/g was achieved for both the compositions, with the Na0.79Co0.70Mn0.3O2 composition showing a more stable discharge capacity up to 60 cycles.

  4. Investigation of Plutonium and Uranium Precipitation Behavior with Gadolinium as a Neutron Poison

    SciTech Connect

    Visser, A.E.

    2003-10-17

    The caustic precipitation of plutonium (Pu)-containing solutions has been investigated to determine whether the presence of 3:1 uranium (U):Pu in solutions stored in the H-Canyon Facility at the U.S. Department of Energy's (DOE) Savannah River Site (SRS) would adversely impact the use of gadolinium nitrate (Gd(NO3)3) as a neutron poison. In the past, this disposition strategy has been successfully used to discard solutions containing approximately 100 kg of Pu to the SRS high level waste (HLW) system. In the current experiments, gadolinium (as Gd(NO3)3) was added to samples of a 3:1 U:Pu solution, a surrogate 3 g/L U solution, and a surrogate 3 g/L U with 1 g/L Pu solution. A series of experiments was then performed to observe and characterize the precipitate at selected pH values. Solids formed at pH 4.5 and were found to contain at least 50 percent of the U and 94 percent of the Pu, but only 6 percent of the Gd. As the pH of the solution increased (e.g., pH greater than 14 with 1.2 or 3.6 M sodium hydroxide (NaOH) excess), the precipitate contained greater than 99 percent of the Pu, U, and Gd. After the pH greater than 14 systems were undisturbed for one week, no significant changes were found in the composition of the solid or supernate for each sample. The solids were characterized by X-ray diffraction (XRD) which found sodium diuranate (Na2U2O7) and gadolinium hydroxide (Gd(OH)3) at pH 14. Thermal gravimetric analysis (TGA) indicated sufficient water molecules were present in the solids to thermalize the neutrons, a requirement for the use of Gd as a neutron poison. Scanning electron microscopy (SEM) was also performed and the accompanying back-scattering electron analysis (BSE) found Pu, U, and Gd compounds in all pH greater than 14 precipitate samples. The rheological properties of the slurries at pH greater than 14 were also investigated by performing precipitate settling rate studies and measuring the viscosity and density of the materials. Based on the

  5. A-site deficient perovskites in the SrO-ZrO{sub 2}-Nb{sub 2}O{sub 5} system: Composition dependent structures from neutron powder diffraction data

    SciTech Connect

    Schmid, Siegbert; Withers, Ray L.

    2012-07-15

    A series of A-site deficient perovskite-type phases was synthesised and characterised in the SrO-ZrO{sub 2}-Nb{sub 2}O{sub 5} system. The composition range was established as Sr{sub 0.70+x}Zr{sub 0.40+2x}Nb{sub 0.60-2x}O{sub 3}, {approx}0.02{<=}x{<=}0.30, and the resulting structures refined using high resolution neutron powder diffraction data. While structures in this composition range are closely related to the cubic perovskite parent, the symmetry for all investigated compositions is lowered to tetragonal or orthorhombic. For x<0.15 the resulting space group is tetragonal I4/mcm, for x>0.15 it is orthorhombic Pnma and for x=0.15 two phases co-exist, in space groups I4/mcm and Pnma. - Graphical abstract: Structured diffuse intensity indicating additional short range order in the defect perovskite Sr{sub 0.72}Zr{sub 0.44}Nb{sub 0.56}O{sub 3}. Highlights: Black-Right-Pointing-Pointer A-site deficient perovskites synthesised in Sr{sub 0.70+x}Zr{sub 0.40+2x}Nb{sub 0.60-2x}O{sub 3}, {approx}0.02 {<=}x{<=}0.30. Black-Right-Pointing-Pointer Space groups established from X-ray, electron and neutron powder diffraction. Black-Right-Pointing-Pointer Structures refined and phase transition established from neutron diffraction data.

  6. INVESTIGATING SUPERCONDUCTIVITY IN NEUTRON STAR INTERIORS WITH GLITCH MODELS

    SciTech Connect

    Haskell, B.; Pizzochero, P. M.; Seveso, S.

    2013-02-20

    The high-density interior of a neutron star is expected to contain superconducting protons and superfluid neutrons. Theoretical estimates suggest that the protons will form a type II superconductor in which the stellar magnetic field is carried by flux tubes. The strong interaction between the flux tubes and the neutron rotational vortices could lead to strong ''pinning'', i.e., vortex motion could be impeded. This has important implications especially for pulsar glitch models as it would lead to a large part of the vorticity of the star being decoupled from the ''normal'' component to which the electromagnetic emission is locked. In this Letter, we explore the consequences of strong pinning in the core on the ''snowplow'' model for pulsar glitches, making use of realistic equations of state and relativistic background models for the neutron star. We find that, in general, a large fraction of the pinned vorticity in the core is not compatible with observations of giant glitches in the Vela pulsar. Thus, the conclusion is that either most of the core is in a type I superconducting state or the interaction between vortices and flux tubes is weaker than previously assumed.

  7. Investigating Prompt Fission Neutron Emission from 235U(n,f) in the Resolved Resonance Region

    NASA Astrophysics Data System (ADS)

    Göök, Alf; Hambsch, Franz-Josef; Oberstedt, Stephan

    2016-03-01

    Investigations of prompt emission in fission is of importance in understanding the fission process in general and the sharing of excitation energy among the fission fragments in particular. Experimental activities at IRMM on prompt neutron emission from fission in response to OECD/NEA nuclear data requests is presented in this contribution. Main focus lies on currently on-going investigations of prompt neutron emission from the reaction 235U(n,f) in the region of the resolved resonances. For this reaction strong fluctuations of fission fragment mass distributions and mean total kinetic energy have been observed [Nucl. Phys. A 491, 56 (1989)] as a function of incident neutron energy in the resonance region. In addition fluctuations of prompt neutron multiplicities were also observed [Phys. Rev. C 13, 195 (1976)]. The goal of the present study is to verify the current knowledge of prompt neutron multiplicity fluctuations and to study correlations with fission fragment properties.

  8. Structure of GeO(2)-P(2)O(5) glasses studied by x-ray and neutron diffraction.

    PubMed

    Hoppe, U; Brow, R K; Tischendorf, B C; Jóvári, P; Hannon, A C

    2006-02-15

    The structures of three xGeO(2)-(1- x)P(2)O(5) glasses, where x = 0.98,0.88, and 0.81, have been studied by neutron and x-ray diffraction experiments that yield well resolved P-O and Ge-O bond distances. The Ge-O coordination number (N(GeO)) increased from 4.0 ± 0.2 to 4.5 ± 0.2 with the decrease in x from 0.98 to 0.81. The increase in N(GeO) is consistent with a structural model that assumes that all oxygen form Ge-O-Ge and P-O-Ge linkages between Ge polyhedra and P tetrahedra and that new GeO(5) or GeO(6) polyhedra are formed with isolated PO(4) units when P(2)O(5) is added to GeO(2). The bond valencies in the P-O bonds of the PO(4) tetrahedra are greater than unity and are balanced in P-O-Ge bridges with underbonded Ge-O links in the GeO(5) or GeO(6) polyhedra. Mixed site connections are expected for the GeO(5) (or GeO(6)) and PO(4) units in glasses with relatively low (<20 mol%) P(2)O(5) content due to the overwhelming fraction of GeO(4) tetrahedra. The structural changes are compared with those reported for alkali germanate glasses. Several features indicate different characteristics for the compositional dependence of N(GeO) for the GeO(2)-P(2)O(5) and alkali germanate glasses. However, the distributions of the first-neighbour Ge-O distances are found to be nearly identical for the GeO(2)-P(2)O(5) and K(2)O-GeO(2) glasses of equimolar K(2)O and P(2)O(5) content.

  9. Crystal structure and magnetism of YbFeMnO 5: A neutron diffraction and Mössbauer spectroscopy study

    NASA Astrophysics Data System (ADS)

    Martínez-Lope, M. J.; Retuerto, M.; Alonso, J. A.; García-Hernández, M.; Krezhov, K.; Spirov, I.; Ruskov, T.; Fernández-Díaz, M. T.

    2009-04-01

    We have studied the crystal structure and magnetic properties of Y bFeMnO 5 obtained by substituting Fe 3+ for Mn 3+ in the parent Y bMn 2O 5 compound, through x-ray (XRD) and neutron (NPD) powder diffraction, magnetometry and Mössbauer spectroscopy. The samples were prepared in polycrystalline form by a soft chemistry route, followed by thermal treatments under high-oxygen pressure. The Rietveld analysis of diffraction data shows that Y bFeMnO 5 is isostructural with the oxides of stoichiometry RMn 2O 5 (R=rare earth, Y or Bi); the crystal structure is orthorhombic, Pbam space group, formed by chains of edge-sharing Mn 4+O 6 octahedra linked together by dimer groups of square pyramids Fe 3+O 5 and Y b 3+O 8 scalenohedra. A low level of disorder was established between the two transition metal positions 4 f and 4 h, occupied ideally by Mn 4+ and by Fe 3+: about 6% of Mn cations is replaced by Fe and 16% of Fe by Mn. Mössbauer spectroscopy data confirm the existence of two distinct crystallographic sites for Fe 3+. One of them corresponds to almost regular octahedra (at 4 f positions), characterized by nearly equal Mn/Fe-O distances of 1.890 Å at RT (from NPD data), giving a quadrupole doublet in the Mössbauer spectra at RT, broadened by the Fe/Mn disorder over this site. The second environment for Fe 3+ contributes to a less broadened, but more intensive doublet in the Mössbauer spectra, which corresponds to a distorted square pyramid Fe 3+O 5 (at 4h sites), for which NPD data demonstrates an axial distortion with three sets of Fe-O distances at 2.010(2) Å, 1.859(5) Å and 1.925(3) Å. Magnetic studies and the thermal evolution of the NPD patterns show that below a transition temperature Tc˜178 K a long-range magnetic order is developed, resolved from NPD data as a ferrimagnetic structure with propagation vector k=0. The spin arrangements for the Mn 4+ ions ( 4f site) and Fe 3+ ions ( 4h site) are given by the basis vectors ( 0,0,Fz) and ( 0,0,Fz

  10. Phase Transition and Texture Evolution in the Ni-Mn-Ga Ferromagnetic Shape-Memory Alloys Studied by a Neutron Diffraction Technique

    NASA Astrophysics Data System (ADS)

    Nie, Z. H.; Wang, Y. D.; Wang, G. Y.; Richardson, J. W.; Wang, G.; Liu, Y. D.; Liaw, P. K.; Zuo, L.

    2008-12-01

    The phase transition and influence of the applied stress on the texture evolution in the as-cast Ni-Mn-Ga ferromagnetic shape-memory alloys were studied by the time-of-flight (TOF) neutron diffraction technique. The neutron diffraction experiments were performed on the General Purpose Powder Diffractometer (Argonne National Laboratory). Inverse pole figures were determined from the neutron data for characterizing the orientation distributions and variant selections of polycrystalline Ni-Mn-Ga alloys subjected to different uniaxial compression deformations. Texture analyses reveal that the initial texture for the parent phase in the as-cast specimen was composed of {left\\{ {{text{001}}} right\\}}{left< {{text{100}}} rightrangle } , {left\\{ {{text{001}}} right\\}}{left< {{text{110}}} rightrangle } , {left\\{ {{text{011}}} right\\}}{left< {{text{100}}} rightrangle } , and {left\\{ {{text{011}}} right\\}}{left< {{text{110}}} rightrangle } , which was weakened after the compression deformation. Moreover, a strong preferred selection of martensitic-twin variants ( {left\\{ {{text{110}}} right\\}}{left< {{text{001}}} rightrangle } and {left\\{ {{text{100}}} right\\}}{left< {{text{001}}} rightrangle } ) was observed in the transformed martensite after a compression stress applied on the parent phase along the cyclindrical axis of the specimens. The preferred selection of variants can be well explained by considering the grain/variant-orientation-dependent Bain-distortion energy.

  11. Superstructure of a phosphor material Ba{sub 3}MgSi{sub 2}O{sub 8} determined by neutron diffraction data

    SciTech Connect

    Park, Cheol-Hee Hong, Seung-Tae; Keszler, Douglas A.

    2009-03-15

    Ba{sub 3}MgSi{sub 2}O{sub 8}, a phosphor host examined for use in white-light devices and plant-growth lamps, was synthesized at 1225 deg. C in air. Its crystal structure has been determined and refined by a combined powder X-ray and neutron Rietveld method (P3-bar, Z=3, a=9.72411(3) A, c=7.27647(3) A, V=595.870(5) A{sup 3}; R{sub p}/R{sub wp}=3.79%/5.03%, {chi}{sup 2}=4.20). Superstructure reflections, observed only in the neutron diffraction data, provided the means to establish the true unit cell and a chemically reasonable structure. The structure contains three crystallographically distinct Ba atoms-Ba1 resides in a distorted octahedral site with S{sub 6} (3-bar) symmetry, Ba2 in a nine-coordinate site with C{sub 3} (3) symmetry, and Ba3 in a ten-coordinate site with C{sub 1} (1) symmetry. The Mg atoms occupy distorted octahedral sites, and the Si atom occupies a distorted tetrahedral site. - Graphical Abstract: Crystal structure of Ba{sub 3}MgSi{sub 2}O{sub 8} viewed along the c direction. Superstructure reflections, observed only in the neutron diffraction data, provided the means to establish the true unit cell and a chemically reasonable structure.

  12. Neutron diffraction study of the martensitic transformation and chemical order in Heusler alloy Ni1.91Mn1.29Ga0.8

    DOE PAGES

    Ari-Gur, Pnina; Garlea, Vasile O.; Cao, Huibo; Ge, Y.; Aaltio, I.; Hannula, S. P.; Koledov, V.

    2015-11-05

    In this study, Heusler alloys of Ni-Mn-Ga compositions demonstrate ferromagnetic shape memory effect in the martensitic state. The transformation temperature and the chemical order depend strongly on the composition. In the current work, the structure and chemical order of the martensitic phase of Ni1.91Mn1.29Ga0.8 were studied using neutron diffraction; the diffraction pattern was refined using the FullProf software. It was determined that the structural transition occurs around 330 K. At room temperature, 300 K, which is below the martensite transformation temperature, all the Bragg reflections can be described by a monoclinic lattice with a symmetry of space group P 1more » 2/m 1 and lattice constants of a = 4.23047(7) [Å], b = 5.58333(6) [Å], c = 21.0179(2) [Å], beta = 90.328(1). The chemical order is of critical importance in these alloys, and it was previously studied at 363 K. Analysis of the neutron diffraction in the monoclinic phase shows that the chemical order is maintained during the martensitic transformation.« less

  13. Neutron diffraction study of the La1-xPrxMn2Si2 ( x=0.4, 0.7 and 1) compounds and the general description of the magnetic behavior of Mn in RMn2Ge2 and RMn2Si2

    NASA Astrophysics Data System (ADS)

    Dincer, I.; Elerman, Y.; Elmali, A.; Ehrenberg, H.; André, G.

    2007-06-01

    The magnetic structures of the La1-xPrxMn2Si2 ( x=0.4, 0.7 and 1) have been investigated by powder neutron diffraction between 2 and 308 K. According to magnetic measurements, the x=0.4 sample shows a typical SmMn2Ge2-like magnetic behavior. Neutron diffraction indicates a canted antiferromagnetic structure below 130 K and a canted ferromagnetic structure above 240 K. Between 130 and 240 K, the canted ferromagnetic and antiferromagnetic structures coexist. Since the magnetic moments of Mn atoms, the unit cell parameters and the scale parameters of the canted antiferromagnetism and canted ferromagnetism are highly correlated between 130 and 240 K, a special refinement procedure was introduced. The critical Mn-Mn value was determined as 2.87 A˚, and the spontaneous volume change and linear magnetostriction are derived. Neutron diffraction revealed a canted antiferromagnetic structure for La0.3Pr0.7Mn2Si2. A canted antiferromagnetic structure was also detected for PrMn2Si2 by neutron diffraction in contrast to previous reports of a collinear arrangement. The present results are compiled together with previous ones on RMn2Ge2 and RMn2Si2 (R: Y, La and rare-earth) compounds in two magnetic phase diagrams. These two graphics summarize the general magnetic behavior of Mn in the RMn2Ge2 and RMn2Si2 compounds.

  14. AND/R: Advanced neutron diffractometer/reflectometer for investigation of thin films and multilayers for the life sciences

    PubMed Central

    Dura, Joseph A.; Pierce, Donald J.; Majkrzak, Charles F.; Maliszewskyj, Nicholas C.; McGillivray, Duncan J.; Lösche, Mathias; O'Donovan, Kevin V.; Mihailescu, Mihaela; Perez-Salas, Ursula; Worcester, David L.; White, Stephen H.

    2011-01-01

    An elastic neutron scattering instrument, the advanced neutron diffractometer/reflectometer (AND/R), has recently been commissioned at the National Institute of Standards and Technology Center for Neutron Research. The AND/R is the centerpiece of the Cold Neutrons for Biology and Technology partnership, which is dedicated to the structural characterization of thin films and multilayers of biological interest. The instrument is capable of measuring both specular and nonspecular reflectivity, as well as crystalline or semicrystalline diffraction at wave-vector transfers up to approximately 2.20 Å−1. A detailed description of this flexible instrument and its performance characteristics in various operating modes are given. PMID:21892232

  15. Data processing of the active neutron experiment DAN for a Martian regolith investigation

    NASA Astrophysics Data System (ADS)

    Sanin, A. B.; Mitrofanov, I. G.; Litvak, M. L.; Lisov, D. I.; Starr, R.; Boynton, W.; Behar, A.; DeFlores, L.; Fedosov, F.; Golovin, D.; Hardgrove, C.; Harshman, K.; Jun, I.; Kozyrev, A. S.; Kuzmin, R. O.; Malakhov, A.; Milliken, R.; Mischna, M.; Moersch, J.; Mokrousov, M. I.; Nikiforov, S.; Shvetsov, V. N.; Tate, C.; Tret'yakov, V. I.; Vostrukhin, A.

    2015-07-01

    Searching for water in the soil of Gale Crater is one of the primary tasks for the NASA Mars Science Laboratory rover named Curiosity. The primary task of the Dynamic Albedo of Neutrons (DAN) experiment on board the rover is to investigate and qualitatively characterize the presence of water along the rover's traverse across Gale Crater. The water depth distribution may be found from measurements of neutrons generated by the Pulsing Neutron Generator (PNG) included in the DAN instrument, scattered by the regolith and returned back to the detectors. This paper provides a description of the data processing of such measurements and data products of DAN investigation.

  16. Preliminary time-of-flight neutron diffraction studies of Escherichia coli ABC transport receptor phosphate-binding protein at the Protein Crystallography Station

    PubMed Central

    Sippel, K. H.; Bacik, J.; Quiocho, F. A.; Fisher, S. Z.

    2014-01-01

    Inorganic phosphate is an essential molecule for all known life. Organisms have developed many mechanisms to ensure an adequate supply, even in low-phosphate conditions. In prokaryotes phosphate transport is instigated by the phosphate-binding protein (PBP), the initial receptor for the ATP-binding cassette (ABC) phosphate transporter. In the crystal structure of the PBP–phosphate complex, the phosphate is completely desolvated and sequestered in a deep cleft and is bound by 13 hydrogen bonds: 12 to protein NH and OH donor groups and one to a carboxylate acceptor group. The carboxylate plays a key recognition role by accepting a phosphate hydrogen. PBP phosphate affinity is relatively consistent across a broad pH range, indicating the capacity to bind monobasic (H2PO4 −) and dibasic (HPO4 2−) phosphate; however, the mechanism by which it might accommodate the second hydrogen of monobasic phosphate is unclear. To answer this question, neutron diffraction studies were initiated. Large single crystals with a volume of 8 mm3 were grown and subjected to hydrogen/deuterium exchange. A 2.5 Å resolution data set was collected on the Protein Crystallography Station at the Los Alamos Neutron Science Center. Initial refinement of the neutron data shows significant nuclear density, and refinement is ongoing. This is the first report of a neutron study from this superfamily. PMID:24915101

  17. Negative thermal expansion in the Russian blue analog Zn3[Fe(CN)6]2: x-ray diffraction and neutron vibrational studies

    SciTech Connect

    Nakotte, Heinz; Daemen, Luke; Adak, Sourav

    2009-01-01

    The cubic Prussian Blue (PB) analog, Zn{sub 3} [Fe(CN){sub 6}]{sub 2}, has been studied by X-ray powder diffraction and inelastic neutron scattering (INS). X-ray data collected at 300 and 84 K revealed negative thermal expansion (NTE) behavior for this material. The NTE coefficient was found to be -31.1 x 10{sup -6} K{sup -1}. The neutron vibrational spectrum for Zn{sub 3}[Fe(CN){sub 6}]{sub 2}.xH{sub 2}O, was studied in detail. The INS spectrum showed well-defined, well-separated bands corresponding to the stretching of and deformation modes of the Fe and Zn octahedra, all below 800 cm{sup -1}.

  18. Extracting grain-orientation-dependent data from in situ time-of-flight neutron diffraction. I. Inverse pole figures

    SciTech Connect

    Stoica, Grigoreta M.; Stoica, Alexandru Dan; An, Ke; Ma, Dong; Vogel, S. C.; Carpenter, J. S.; Wang, Xun-Li

    2014-11-28

    The problem of calculating the inverse pole figure (IPF) is analyzed from the perspective of the application of time-of flight neutron diffraction toin situmonitoring of the thermomechanical behavior of engineering materials. On the basis of a quasi-Monte Carlo (QMC) method, a consistent set of grain orientations is generated and used to compute the weighting factors for IPF normalization. The weighting factors are instrument dependent and were calculated for the engineering materials diffractometer VULCAN (Spallation Neutron Source, Oak Ridge National Laboratory). The QMC method is applied to face-centered cubic structures and can be easily extended to other crystallographic symmetries. Examples include 316LN stainless steelin situloaded in tension at room temperature and an Al–2%Mg alloy, substantially deformed by cold rolling and in situannealed up to 653 K.

  19. The magnetic and neutron diffraction studies of La{sub 1−x}Sr{sub x}MnO{sub 3} nanoparticles prepared via molten salt synthesis

    SciTech Connect

    Kačenka, M.; Kaman, O.; Jirák, Z.; Maryško, M.; Veverka, P.; Veverka, M.; Vratislav, S.

    2015-01-15

    Series of single-phase La{sub 1−x}Sr{sub x}MnO{sub 3} nanoparticles (x=0.25−0.47) with the size of about 50 nm was prepared in molten NaNO{sub 2}. TEM evidenced well dispersed particles that are not interconnected by sintering bridges in contrast to traditional products. Interestingly, some reduction of the perovskite cell volume, particularly at higher Sr-contents, was detected by XRD. Moreover, reduced magnetization and decreased Curie temperature in comparison to sol–gel samples were observed. Neutron diffraction analysis of the as-prepared nanoparticles and several comparative samples with x=0.37 indicated that the anomalous behavior of studied particles probably originate in the overdoped outer shell. The overdoping might result from both the surface oxygen chemisorption and from an increased Sr concentration in the shell. By all means, the overdoping would lead to compressive surface stress, driving the x=0.37 ground state toward a mixture of FM and A-type AFM ordering as observed by neutron diffraction. - Graphical abstract: La{sub 1−x}Sr{sub x}MnO{sub 3} nanoparticles with the size of about 50 nm were prepared by newly established method in molten NaNO{sub 2}. TEM proved the formation of well-separated particles without sintering bridges, the major advantage over traditional preparation methods. - Highlights: • Series of La{sub 1−x}Sr{sub x}MnO{sub 3} nanoparticles was prepared by novel method in NaNO{sub 2} melt. • Lower magnetization and Curie temperature in comparison to sol–gel nanoparticles was observed. • Overdoping of outer shell was indicated by neutron diffraction and cerimetric titration. • Overdoping shifts La{sub 0.37}Sr{sub 0.63}MnO{sub 3} ground state to a mixture of FM and A-type AFM ordering.

  20. Investigation of the Statistical Properties of Stable Eu Nuclei using Neutron-Capture Reactions

    SciTech Connect

    Agvaanluvsan, U; Alpizar-Vicente, A; Becker, J A; Becvar, F; Bredeweg, T A; Clement, R; Esch, E; Folden, III, C M; Hatarik, R; Haight, R C; Hoffman, D C; Krticka, M; Macri, R A; Mitchell, G E; Nitsche, H; O'Donnell, J M; Parker, W; Reifarth, R; Rundberg, R S; Schwantes, J M; Sheets, S A; Ullmann, J L; Vieira, D J; Wilhelmy, J B; Wilk, P; Wouters, J M; Wu, C Y

    2005-10-04

    Neutron capture for incident neutron energies <1eV up to 100 keV has been measured for {sup 151,153}Eu targets. The highly efficient DANCE (Detector for Advanced Neutron Capture Experiments) array coupled with the intense neutron beam at Los Alamos Neutron Science Center is used for the experiment. Stable Eu isotopes mass separated and electroplated on Be backings were used. Properties of well-resolved, strong resonances in two Eu nuclei are examined. The parameters for most of these resonances are known. Detailed multiplicity information for each resonance is obtained employing the high granularity of the DANCE array. The radiative decay cascades corresponding to each resonance are obtained in the experiment. The measurements are compared to simulation of these cascades which calculated with various models for the radiative strength function. Comparison between the experimental data and simulation provides an opportunity to investigate the average quantities.

  1. Feasibility study for the investigation of Nitinol self-expanding stents by neutron techniques

    NASA Astrophysics Data System (ADS)

    Rogante, M.; Pasquini, U.; Rosta, L.; Lebedev, V.

    2011-02-01

    In this paper, neutron techniques - in particular, small angle neutron scattering (SANS) and neutron diffraction (ND) - are considered for the non-destructive characterization of Nitinol artery stents. This roughly equiatomic (50Ni-50Ti at%) shape memory alloy (SMA) exhibits significant properties of superelasticity and biocompatibility that make it suitable to be typically used as smart material for medical implants and devices. Nitinol self-expanding artery stents, as permanent vascular support structures, supply an ideal option to bypass surgery, but they are submitted for the whole of patient's life to the dynamical stress of the artery pulsation and the aggression from the biological environment. These stents, consequently, can suffer from wear and fracture occurrence likely due to a variety of cyclic fatigue, overload conditions and residual stresses. Neutrons have recently become a progressively more important probe for various materials and components and they allow achieving information complementary to those obtained from the traditional microstructural analyses. The outputs from the preliminary works already carried out in this field consent to consider neutron techniques capable to contribute to the development of these crucial medical implants. The achievable results can yield trends adoptable in monitoring of the stent features.

  2. Dimethylamine borane dehydrogenation chemistry: syntheses, X-ray and neutron diffraction studies of 18-electron aminoborane and 14-electron aminoboryl complexes.

    PubMed

    Tang, Christina Y; Phillips, Nicholas; Bates, Joshua I; Thompson, Amber L; Gutmann, Matthias J; Aldridge, Simon

    2012-08-21

    The reactions of Me(2)NH·BH(3) with cationic Rh(III) and Ir(III) complexes have been shown to generate the 18-electron aminoborane adduct [Ir(IMes)(2)(H)(2){κ(2)-H(2)BNMe(2))](+) and the remarkable 14-electron aminoboryl complex [Rh(IMes)(2)(H)-{B(H)NMe(2))](+). Neutron diffraction studies have been used for the first time to define H-atom locations in metal complexes of this type formed under catalytic conditions. PMID:22781307

  3. Anomalous Depletion of Pore-Confined Carbon Dioxide upon Cooling below the Bulk Triple Point: An In Situ Neutron Diffraction Study.

    PubMed

    Stefanopoulos, K L; Katsaros, F K; Steriotis, Th A; Sapalidis, A A; Thommes, M; Bowron, D T; Youngs, T G A

    2016-01-15

    The phase behavior of sorbed CO{2} in an ordered mesoporous silica sample (SBA-15) was studied by neutron diffraction. Surprisingly, upon cooling our sample below the bulk critical point, confined CO{2} 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 CO{2} 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. PMID:26824548

  4. Selective Synthesis of Cyclooctanoids by Radical Cyclization of Seven-Membered Lactones: Neutron Diffraction Study of the Stereoselective Deuteration of a Chiral Organosamarium Intermediate.

    PubMed

    Just-Baringo, Xavier; Clark, Jemma; Gutmann, Matthias J; Procter, David J

    2016-09-26

    Seven-membered lactones undergo selective SmI2 -H2 O-promoted radical cyclization to form substituted cyclooctanols. The products arise from an exo-mode of cyclization rather than the usual endo-attack employed in the few radical syntheses of cyclooctanes. The process is terminated by the quenching of a chiral benzylic samarium. A labeling experiment and neutron diffraction study have been used for the first time to probe the configuration and highly diastereoselective deuteration of a chiral organosamarium intermediate. PMID:27600354

  5. Analysis of the Plasticity-Enhancing Mechanisms in 12 pctMn Austeno-ferritic Steel by In Situ Neutron Diffraction

    NASA Astrophysics Data System (ADS)

    Lee, Sangwon; Woo, Wanchuck; De Cooman, Bruno C.

    2014-12-01

    The tensile behavior of ductile ultra-high strength Fe-12 pctMn-0.3 pctC-2 pctAl austeno-ferritic steel was studied by in situ neutron diffraction measurement of the elastic lattice strains, dislocation density, stacking fault probability, and strain-induced transformation kinetics. Micro-yielding was observed in austenite, and the plastic deformation of ferrite remained very limited throughout the deformation. The analysis identified three contributions to the strain hardening: twinning-induced plasticity, transformation-induced plasticity, and the accumulation of a high density of geometrically necessary dislocations accommodating the strain mismatch at the phase boundaries.

  6. Zigzag type magnetic structure of the spin J eff = ½ compound α-RuCl3 as determined by neutron powder diffraction

    NASA Astrophysics Data System (ADS)

    Ritter, C.

    2016-09-01

    Using high intensity powder neutron diffraction the magnetic structure of a-RuCl3 has been determined. Following the magnetic propagation vector κ = (½, 0, ½) the J eff = ½ spins of Ru3+ adopt a Zigzag type arrangement on the honeycomb lattice of the layered P3112 structure. The magnetic moments are oriented perpendicular to the trigonal axis. Similarities and differences to previously published single crystal data are discussed. The low value of the magnetic moments, μRu = 0.5(1) μB indicates a possible closeness of α-RuCl3 to the Kitaev spin liquid state.

  7. Neutron diffraction study of magnetic field induced behavior in the heavy Fermion Ce3Co4Sn13

    SciTech Connect

    Christianson, Andrew D; Goremychkin, E. A.; Gardner, J. S.; Kang, H. J.; Chung, J.-H.; Manuel, P.; Thompson, J. D.; Sarrao, J. L.; Lawrence, J. M.

    2008-01-01

    The specific heat of Ce3Co4Sn13 exhibits a crossover from heavy Fermion behavior with antiferromagnetic correlations at low field to single impurity Kondo behavior above 2 T. We have performed neutron diffraction measurements in magnetic fields up to 6 Tesla on single crystal samples. The (001) position shows a dramatic increase in intensity in field which appears to arise from static polarization of the 4f level and which at 0.14 K also exhibits an anomaly near 2T reflecting the crossover to single impurity behavior.

  8. Change in the magnetic structure of (Bi,Sm)FeO{sub 3} thin films at the morphotropic phase boundary probed by neutron diffraction

    SciTech Connect

    Maruyama, Shingo; Anbusathaiah, Varatharajan; Takeuchi, Ichiro; Fennell, Amy; Enderle, Mechthild; Ratcliff, William D.

    2014-11-01

    We report on the evolution of the magnetic structure of BiFeO{sub 3} thin films grown on SrTiO{sub 3} substrates as a function of Sm doping. We determined the magnetic structure using neutron diffraction. We found that as Sm increases, the magnetic structure evolves from a cycloid to a G-type antiferromagnet at the morphotropic phase boundary, where there is a large piezoelectric response due to an electric-field induced structural transition. The occurrence of the magnetic structural transition at the morphotropic phase boundary offers another route towards room temperature multiferroic devices.

  9. Structure of a fluid dioleoylphosphatidylcholine bilayer determined by joint refinement of x-ray and neutron diffraction data. I. Scaling of neutron data and the distributions of double bonds and water.

    PubMed Central

    Wiener, M. C.; King, G. I.; White, S. H.

    1991-01-01

    We described in two previous papers a method for the joint refinement of the structure of fluid bilayers using neutron and x-ray diffraction data (Wiener, M. C., and S. H. White 1991a, b. Biophys. J. 59: 162-173 and 174-185). An essential part of the method is the appropriate scaling of the diffraction data. Here we describe the scaling of the neutron data and the determination of the transbilayer distribution of double bonds in liquid-crystalline (L alpha phase) phospholipid bilayers of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). The distribution was determined by neutron diffraction of oriented multilayers (66% RH) of DOPC specifically deuterated at the 9- and 10-position of both acyl chains. The double-bond distribution is described accurately by a pair of Gaussian functions each located at a position Zcc = 7.88 +/- 0.09 A from the bilayer center with 1/e-halfwidths of Acc = 4.29 +/- 0.16 A. Previously, we determined the transbilayer distribution of bromine atoms in a specifically halogenated lipid, 1-oleoyl-2-9,10-dibromostearoyl-sn-glycero-3-phosphocholine (OBPC), and showed it to be an isomorphous replacement for DOPC (Wiener, M. C., and S. H. White, 1991c. Biochemistry. In press). A comparison of the double-bond and bromine profiles indicates that the positions of the centers of the deuterated double bond and the brominated methylene Gaussian distributions are equal within experimental error and that each label undergoes similar average thermal motions with respect to the bilayer normal. The observation that the average position of a label on both acyl chains (the deuterated double bonds) is similar to the average position of a label on the 2-chain alone (the brominated methylenes) indicates that the maximum separation along the bilayer normal between the double bonds of the acyl chains is 1 A or less. The fully-resolved transbilayer water distribution, previously determined at lower resolution (Jacobs, R. E., and S. H. White. 1989. Biochemistry. 28

  10. Unconventional magnetic order in the frustrated diamond-lattice antiferromagnet CoAl2O4 studied by neutron diffraction and classical Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Zaharko, O.; Tóth, S.; Sendetskyi, O.; Cervellino, A.; Wolter-Giraud, A.; Dey, T.; Maljuk, A.; Tsurkan, V.

    2014-10-01

    CoAl2O4 spinel with magnetic Co2+ ions on the diamond lattice is known to be magnetically frustrated. We compare neutron single-crystal diffraction patterns measured in zero and applied magnetic fields with the ones obtained from classical Monte Carlo models. In simulations we test the influence of various parameters on diffraction patterns: the ratio of nearest-, J1, and next-nearest-, J2, neighbor interactions, magnetic field applied along the principal crystallographic directions, and random disorder on the A (Co2+) and B (Al3+) sites. We conclude that the models considered so far explain the broadening of magnetic Bragg peaks in zero magnetic field and their anisotropic response to applied magnetic field only partly. As bulk properties of our single crystal are isotropic, we suggest that its microstructure, specifically <111>-twin boundaries, could be a reason for the nonconventional magnetic order in CoAl2O4.

  11. X-ray and Neutron Diffraction Studies of Rb{sub 4}LiH{sub 3}(XO{sub 4}){sub 4} (X = S, Se) Single Crystals

    SciTech Connect

    Troyanov, S.I.; Snigireva, E.M.; Ling, C.D.

    2004-11-01

    Rb{sub 4}LiH{sub 3}(SeO{sub 4}){sub 4} single crystals (1) are studied by the X-ray diffraction method at 180 K and Rb{sub 4}LiH{sub 3}(SO{sub 4}){sub 4} single crystals (2a-2c) are studied by the neutron diffraction method at 298 K (2a and 2b) and 480 K (2c). It is established that isostructural single crystals 1 and 2 (sp. gr. P4{sub 1}) have analogous systems of hydrogen bonds: chains of four XO{sub 4} tetrahedra linked by three H bonds with the central bond (2.49 A) being somewhat shorter than the terminal ones (2.52-2.54 A). In the high-temperature 2c phase, the amplitudes of atomic thermal vibrations and the degree of proton disorder in the central hydrogen bond have somewhat elevated values.

  12. X-ray Diffraction Investigations of Shape Memory NiTi Wire

    NASA Astrophysics Data System (ADS)

    Honarvar, Mohammad; Konh, Bardia; Podder, Tarun K.; Dicker, Adam P.; Yu, Yan; Hutapea, Parsaoran

    2015-08-01

    Outstanding properties of nitinol, known as shape memory and superelasticity, make them suitable alternatives in several biomedical, aerospace, and civil applications. For instance, nitinol wires have been used as the actuator components in many innovative medical devices aiming to make surgical tasks less invasive and more efficient. In most of these applications, it is desired to have a consistent strain response of nitinol wires; therefore, it is necessary to investigate the internal phase transformations from microstructural point of view. In this study, the effect of influencing factors such as biased stress during thermal cycle, the maximum temperature wires experienced during heating part of thermal cycle, and also wire diameters on the amount of unrecovered strain occurred between the first and the second thermal cycles has been investigated. The generation of different phase compositions in the same thermomechanical condition for different wire diameters has been discussed using x-ray diffraction (XRD) method. The location and intensity of characteristic peaks were studied prior and after the loading cycles. It was observed that nitinol wires of diameters less than 0.19 mm exhibit unrecovered strain while heated to the range of 70-80 °C in a thermal cycle, whereas no unrecovered strain was found in wires with larger diameter. The observation was supported by the XRD patterns where the formation of R-phase instead of martensite was shown in wire diameters of less than 0.19 mm after cooling back to room temperature.

  13. A Hybrid Reflective/Refractive/Diffractive Achromatic Fiber-Coupled Radiation Resistant Imaging System for Use in the Spallation Neutron Source (SNS)

    SciTech Connect

    Maxey, L Curt; Ally, Tanya R; Brunson, Aly; Garcia, Frances; Goetz, Kathleen C; Hasse, Katelyn E; McManamy, Thomas J; Shea, Thomas J; Simpson, Marc Livingstone

    2011-01-01

    A fiber-coupled imaging system for monitoring the proton beam profile on the target of the Spallation Neutron Source was developed using reflective, refractive and diffractive optics to focus an image onto a fiber optic imaging bundle. The imaging system monitors the light output from a chromium-doped aluminum oxide (Al{sub 2}0{sub 3}:Cr) scintillator on the nose of the target. Metal optics are used to relay the image to the lenses that focus the image onto the fiber. The material choices for the lenses and fiber were limited to high-purity fused silica, due to the anticipated radiation dose of 10{sup 8} R. In the first generation system (which had no diffractive elements), radiation damage to the scintillator on the nose of the target significantly broadened the normally monochromatic (694 nm) spectrum. This created the need for an achromatic design in the second generation system. This was achieved through the addition of a diffractive optic for chromatic correction. An overview of the target imaging system and its performance, with particular emphasis on the design and testing of a hybrid refractive/diffractive high-purity fused silica imaging triplet, is presented.

  14. Neutron and X-ray diffraction analysis of the effect of irradiation dose and temperature on microstructure of irradiated HT-9 steel

    NASA Astrophysics Data System (ADS)

    Mosbrucker, P. L.; Brown, D. W.; Anderoglu, O.; Balogh, L.; Maloy, S. A.; Sisneros, T. A.; Almer, J.; Tulk, E. F.; Morgenroth, W.; Dippel, A. C.

    2013-11-01

    Material harvested from several positions within a nuclear fuel duct (the ACO-3 duct) used in a 6-year irradiation of a fuel assembly in the Fast Flux Test Reactor Facility (FFTF) was examined using neutron and high-energy X-ray diffraction. Samples with a wide range of irradiation dose and irradiation temperature history, reaching doses of up to 147 dpa and temperatures of up to 777 K, were examined. The response of various microstructural characteristics such as the weight fraction of M23C6 carbides, the dislocation density and character, and the crystallographic texture were determined using whole profile analysis of the diffraction data and related to the macroscopic mechanical behavior. For instance, the dislocation density was observed to be intimately linked with observed flow strength of the irradiated materials, following the Taylor law. In general, at the high doses studied in this work, the irradiation temperature is the predominant controlling factor of the dislocation density and, thus, the flow strength of the irradiated material. The results, representing some of the first diffraction work done on samples exposed to such a high received dose, demonstrate how non-destructive and stand-off diffraction techniques can be used to characterize irradiation induced microstructure and at least estimate mechanical properties in irradiated materials without exposing workers to radiation hazards.

  15. Investigation of the neutron activation of endohedral rare earth metallofullerenes

    SciTech Connect

    Shilin, V. A. Lebedev, V. T.; Kolesnik, S. G.; Kozlov, V. S.; Grushko, Yu. S.; Sedov, V. P.; Kukorenko, V. V.

    2011-12-15

    Endohedral lanthanide metallofullerenes and their water-soluble biocompatible derivatives have been synthesized. The effect that fast-neutron irradiation has on the stability and nuclear physical properties of endohedral metallofullerenes that are used as magnetocontrast materials ({sup 46}Sc, {sup 140}La, {sup 141}Nd, {sup 153}Sm, {sup 152}Eu, {sup 154}Eu, {sup 153}Sm, {sup 160}Tb, {sup 169}Yb, {sup 170}Tm (isomers I and III), and {sup 177}Lu) is studied. Our hypothesis, according to which carbon-shell relaxation is based on the fast nonradiative processes of an electron shake-off type, is confirmed.

  16. Neutronics investigation of advanced self-cooled liquid blanket systems in the helical reactor

    NASA Astrophysics Data System (ADS)

    Tanaka, T.; Sagara, A.; Muroga, T.; Youssef, M. Z.

    2008-03-01

    Neutronics investigations have been conducted in the design activity of the helical-type reactor Force Free Helical Reactor (FFHR2) adopting Flibe-cooled and Li-cooled advanced liquid blanket systems. In this study, comprehensive investigations and geometry modifications related to the tritium breeding ratios (TBRs), neutron shielding performance and neutron wall loading on the first walls in FFHR2 have been performed by improving the three-dimensional (3D) neutronics calculation system developed for non-axisymmetric helical designs. The total TBRs obtained after modifying the blanket dimensions indicated that all the advanced blanket systems proposed for FFHR2 would achieve adequate tritium self-sufficiency by dimension adjustment and optimization of structures in the breeder layers. However, it appeared that the most important neutronics issue in the present helical blanket configuration was suppression of neutron streaming through the divertor pumping areas and reflection from support structures for protection of poloidal and helical coils. Evaluation of neutron wall loading on the first walls indicated that the peaking factor would be moderated as low as 1.2 by the toroidal and helical effect of the helical-shaped plasma distribution in the helical reactor.

  17. A physics investigation of deadtime losses in neutron counting at low rates with Cf252

    SciTech Connect

    Evans, Louise G; Croft, Stephen

    2009-01-01

    {sup 252}Cf spontaneous fission sources are used for the characterization of neutron counters and the determination of calibration parameters; including both neutron coincidence counting (NCC) and neutron multiplicity deadtime (DT) parameters. Even at low event rates, temporally-correlated neutron counting using {sup 252}Cf suffers a deadtime effect. Meaning that in contrast to counting a random neutron source (e.g. AmLi to a close approximation), DT losses do not vanish in the low rate limit. This is because neutrons are emitted from spontaneous fission events in time-correlated 'bursts', and are detected over a short period commensurate with their lifetime in the detector (characterized by the system die-away time, {tau}). Thus, even when detected neutron events from different spontaneous fissions are unlikely to overlap in time, neutron events within the detected 'burst' are subject to intrinsic DT losses. Intrinsic DT losses for dilute Pu will be lower since the multiplicity distribution is softer, but real items also experience self-multiplication which can increase the 'size' of the bursts. Traditional NCC DT correction methods do not include the intrinsic (within burst) losses. We have proposed new forms of the traditional NCC Singles and Doubles DT correction factors. In this work, we apply Monte Carlo neutron pulse train analysis to investigate the functional form of the deadtime correction factors for an updating deadtime. Modeling is based on a high efficiency {sup 3}He neutron counter with short die-away time, representing an ideal {sup 3}He based detection system. The physics of dead time losses at low rates is explored and presented. It is observed that new forms are applicable and offer more accurate correction than the traditional forms.

  18. Low-energy electron diffraction investigation of epitaxial growth: Pt and Pd on Pd(100)

    SciTech Connect

    Flynn-Sanders, D.

    1990-09-21

    We investigate the epitaxial growth of Pt and Pd and Pd(100) via spot profile analysis using conventional low-energy electron diffraction (LEED). We resolve a central-spike and diffuse component in the spot profiles, reflecting the layer-occupations and pair-correlations, respectively. Kinetic limitations inhibit layer-by-layer growth at low temperatures. Our data suggest diffusion switches on at ca. 150 K for Pt and ca. 170 K for Pd indicating activation barriers to surface diffusion of ca. 10 and ca. 13 kcal/mol, respectively. To clarify the role of diffusion in determining the resulting film morphology, we develop a growth model that incorporates the adsorption-site requirement and predicts intensity oscillations. We present a new procedure to experimentally determine out-of-phase scattering conditions. At these energies, ring-structure is evident in the profiles during Pd growth between ca. 200 and 400 K. We report ring intensity oscillations as a function of coverage, which demonstrate the filling of individual layers.

  19. Investigation of shock focusing in a cavity with incident shock diffracted by an obstacle

    NASA Astrophysics Data System (ADS)

    Zhang, Q.; Chen, X.; He, L.-M.; Rong, K.; Deiterding, R.

    2016-05-01

    Experiments and numerical simulations were carried out in order to investigate the focusing of a shock wave in a test section after the incident shock has been diffracted by an obstacle. A conventional shock tube was used to generate the planar shock. Incident shock Mach numbers of 1.4 and 2.1 were tested. A high-speed camera was employed to obtain schlieren photos of the flow field in the experiments. In the numerical simulations, a weighted essentially non-oscillatory (WENO) scheme of third-order accuracy supplemented with structured dynamic mesh adaptation was adopted to simulate the shock wave interaction. Good agreement between experiments and numerical results is observed. The configurations exhibit shock reflection phenomena, shock-vortex interaction and—in particular—shock focusing. The pressure history in the cavity apex was recorded and compared with the numerical results. A quantitative analysis of the numerically observed shock reflection configurations is also performed by employing a pseudo-steady shock transition boundary calculation technique. Regular reflection, single Mach reflection and transitional Mach reflection phenomena are observed and are found to correlate well with analytic predictions from shock reflection theory.

  20. X-ray diffraction from shocked materials: investigating solid-solid phase transitions

    NASA Astrophysics Data System (ADS)

    Wark, Justin

    2008-04-01

    X-ray diffraction on nanosecond and sub-nanosecond time-scales has proven to be a useful tool in investigating the transient response of shocked crystals. Perhaps the most notable success in this area has been the direct observation of the α- ɛ transition in laser-shocked single crystals of [001] iron. [1,2] The information extracted from the diffraction patterns has been shown to be in remarkable agreement with multi-million atom molecular dynamics calculations. [3] Having successfully observed the transition in single crystals shocked along the principal axis, several further challenges remain. Amongst these are the exploration of the response of single crystals to shocks propagating along other crystallographic directions (where significantly different response is predicted [4]) the role of pre-existing defects in the time-scale of the elastic/plastic response of the material, and any differences that may occur in polycrystalline compared with single crystal samples.[5] A further challenge will be the development of rapid compression techniques that take samples to off-Hugoniot states (for example so-called quasi-isentropic compression). If such states can be produced in a controlled way, much could potentially be learnt about the state of certain planetary cores, including our own. [1] D.H. Kalantar, J.F. Belak, G.W. Collins, J.D. Colvin, H.M. Davies, J.H. Eggert, T.C. Germann, J. Hawreliak, B.L. Holian, K. Kadau, P.S. Lomdahl, H.E. Lorenzana, M.A. Meyers, K. Rosolankova, M.S. Schneider, J. Sheppard, J.S. Stolken and J.S. Wark, Phys. Rev. Lett., 95 075502, 2005 [2] J. Hawreliak, J.D. Colvin, J.H.Eggert, D. Kalantar, H.E. Lorenzana, J.S. Stölken, H.M. Davies, T.C. Germann, B.L. Holian, K. Kadau, P.S. Lomdahl, A. Higginbotham, K. Rosolankova, J. Sheppard, and J.S. Wark, Phys. Rev. B, 74, 184107, 2006 [3] K. Kadau, Timothy C. Germann, Peter S. Lomdahl, and Brad Lee Holian, Science, 296, 1681, 2002 [4] Kai Kadau, Timothy C. Germann, Peter S. Lomdahl, and Brad

  1. Investigation of the tungsten isotopes via thermal neutron capture

    NASA Astrophysics Data System (ADS)

    Hurst, A. M.; Firestone, R. B.; Sleaford, B. W.; Summers, N. C.; Révay, Zs.; Szentmiklósi, L.; Basunia, M. S.; Belgya, T.; Escher, J. E.; Krtička, M.

    2014-01-01

    Total radiative thermal neutron-capture γ-ray cross sections for the 182,183,184,186W isotopes were measured using guided neutron beams from the Budapest Research Reactor to induce prompt and delayed γ rays from natural and isotopically-enriched tungsten targets. These cross sections were determined from the sum of measured γ-ray cross sections feeding the ground state from low-lying levels below a cutoff energy, Ecrit, where the level scheme is completely known, and continuum γ rays from levels above Ecrit, calculated using the Monte Carlo statistical-decay code dicebox. The new cross sections determined in this work for the tungsten nuclides are σ0(182W)=20.5(14) b and σ11/2+(183Wm,5.2s )=0.177(18) b; σ0(183W)=9.37(38) b and σ5-(184Wm,8.33μs )=0.0247(55) b; σ0(184W)=1.43(10) b and σ11/2+(185Wm,1.67min)=0.0062(16) b; and, σ0(186W)=33.33(62) b and σ9/2+(187Wm,1.38μs)=0.400(16) b. These results are consistent with earlier measurements in the literature. The 186W cross section was also independently confirmed from an activation measurement, following the decay of 187W, yielding values for σ0(186W) that are consistent with our prompt γ-ray measurement. The cross-section measurements were found to be insensitive to choice of level density or photon strength model and only weakly dependent on Ecrit. Total radiative-capture widths calculated with dicebox showed much greater model dependence; however, the recommended values could be reproduced with selected model choices. The decay schemes for all tungsten isotopes were improved in these analyses. We were also able to determine new neutron-separation energies from our primary γ-ray measurements for the respective (n ,γ) compounds: 183W [Sn=6190.88(6) keV]; 184W [Sn=7411.11(13) keV]; 185W [Sn=5753.74(5) keV]; and, 187W [Sn=5466.62(7) keV].

  2. In-situ neutron diffraction of LaCoO₃ perovskite under uniaxial compression. I. Crystal structure analysis and texture development

    SciTech Connect

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

    2014-07-07

    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.

  3. Spin reorientation in Ba0.65Na0.35Fe2As2 studied by single-crystal neutron diffraction

    NASA Astrophysics Data System (ADS)

    Waßer, F.; Schneidewind, A.; Sidis, Y.; Wurmehl, S.; Aswartham, S.; Büchner, B.; Braden, M.

    2015-02-01

    We have studied the magnetic ordering in Ba1 -xNaxFe2As2 with 0.25 ≤x ≤0.4 by unpolarized and polarized neutron diffraction using single crystals. Unlike most FeAs-based compounds that magnetically order, Na-doped BaFe2As2 exhibits two successive magnetic transitions: For x =0.35 , upon cooling, magnetic order occurs at ˜70 K with in-plane magnetic moments being arranged as in pure or Ni-, Co-, or K-doped BaFe2As2 samples. At a temperature of ˜46 K a second phase transition occurs, which the single-crystal neutron-diffraction experiments can unambiguously identify as a spin reorientation. At low temperatures, the ordered magnetic moments in Ba0.65Na0.35Fe2As2 point along the c direction. The two nearly degenerate magnetic states document orbital degeneracy to persist in the superconducting phase.

  4. Contributions of the electronic spin and orbital current to the CoCl{sub 4}{sup 2-} magnetic field probed in polarised neutron diffraction experiments

    SciTech Connect

    Cassam-Chenaie, Patrick; Jayatilaka, Dylan

    2012-08-14

    Polarised neutron diffraction experiments conducted at 4.2 K on Cs{sub 3}CoCl{sub 5} crystals have been analysed by using a four-dimensional model Hilbert space made of ab initio n-electron wave functions of the CoCl{sub 4}{sup 2-} molecular ion. Two spin-orbit mixing coefficients and several configuration interaction coefficients have been optimized by fitting calculated magnetic structure factors to experimental ones, to obtain the best ensemble density operator that is representable in the model space. A goodness of fit, {chi}{sup 2}, less then 1 has been obtained for the first time for the two experimental data sets available. In the present article, the optimized density operators are used to calculate the magnetic field densities that are the genuine observables probed in neutron diffraction experiments. Density maps of such observables are presented for the first time and numerical details are provided. The respective contributions of spin density and orbital current to the magnetic field density are analyzed.

  5. A high temperature neutron diffraction study of the double perovskite Ba{sub 2}{sup 154}SmMoO{sub 6}

    SciTech Connect

    Wallace, Thomas K.; Ritter, Clemens; Mclaughlin, Abbie C.

    2012-12-15

    Ba{sub 2}LnMoO{sub 6} double perovskites have been recently shown to display a wide range of interesting magnetic and structural properties; Ba{sub 2}{sup 154}SmMoO{sub 6} exhibits simultaneous antiferromagnetic order and a Jahn-Teller distortion. Here we report a high temperature neutron diffraction study of Ba{sub 2}{sup 154}SmMoO{sub 6} from 353 to 877 K. The results evidence a tetragonal to cubic phase transition at 423 K. Above this temperature the thermal displacement parameters of the oxygen atoms are modelled anisotropically as a result of a transverse vibration of the bridging oxygen. A smooth increase in the cell parameter a is observed with temperature for Ba{sub 2}{sup 154}SmMoO{sub 6}. - Graphical abstract: The high temperature crystal structure of Ba{sub 2}{sup 154}SmMoO{sub 6} evidencing a transverse oxygen vibration. Highlights: Black-Right-Pointing-Pointer A high temperature neutron diffraction study has been performed on an isotopically enriched sample of Ba{sub 2}{sup 154}SmMoO{sub 6}. Black-Right-Pointing-Pointer A cubic-tetragonal phase transition occurs below 423 K. Black-Right-Pointing-Pointer The thermal displacement parameters of the bridging oxygens are modelled anisotropically. Black-Right-Pointing-Pointer There is a transverse vibration of the bridging oxygen.

  6. In-situ neutron diffraction of LaCoO3 perovskite under uniaxial compression. I. Crystal structure analysis and texture development

    SciTech Connect

    Aman, Amjad; Chen, Yan; Lugovy, Mykola; Orlovskaya, Nina; Reece, Michael John; Ma, Dong; Stoica, Alexandru Dan; An, Ke

    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.

  7. Application of neutron diffraction in characterization of texture evolution during high-temperature creep in magnesium alloys

    SciTech Connect

    Vogel, Sven C; Sediako, Dimitry; Shook, S; Sediako, A

    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.

  8. Diffusion, diffraction des neutrons en temps réel et études réalisées in situ

    NASA Astrophysics Data System (ADS)

    Isnard, O.

    2003-02-01

    La diffusion des neutrons est une technique particulièrement efficace pour l'analyse en temps réel des processus réactionnels dans la matière. La diffraction de neutrons in situ a été développée très tôt sur les sources à haut flux tel que l'Institut Laue Langevin. Ces études nécessitent un flux de neutrons important et un détecteur couvrant un domaine angulaire le plus grand possible. Les neutrons offrent la spécificité d'être très peu absorbés par nombre de matériaux, cette faible absorption fait de la diffusion neutronique un excellent outil pour sonder la matière en volume et de manière non destructive. Cela permet en particulier d'utiliser des environnements d'échantillons complexes tout en conservant un flux raisonnable. La diffusion de neutrons en temps réel est donc très largement utilisée par diverses communautés scientifiques : sciences des matériaux, physiciens, chimistes... L'objet de ce cours est de donner les paramètres importants pour ce type d'étude et d'illustrer le propos à l'aide d'exemples pris dans des domaines scientifiques divers : électrochimie, magnétisme, métallurgie, chimie du solide. Après avoir présenté quelques repères méthodologiques sur les méthodes d'acquisition de données, des exemples montreront le fort potentiel de la diffusion neutronique en temps réel pour l'étude de la matière dans des conditions dynamiques. Enfin, nous donnerons aussi quelques conseils pour la visualisation, le dépouillement et l'analyse de ce type d'expérience. La diffusion des neutrons sur poudre est actuellement très bien adaptée aux études réalisées in situ. Cependant, nous verrons que la faisabilité d'études in situ s'étend à d'autres techniques expérimentales telles que la diffusion des neutrons aux petits angles et même la diffusion sur monocristal qui est en plein renouveau.

  9. The order-disorder transition in Cu2ZnSnS4 - A neutron scattering investigation

    NASA Astrophysics Data System (ADS)

    Ritscher, A.; Hoelzel, M.; Lerch, M.

    2016-06-01

    In this work a series of stoichiometric Cu2ZnSnS4 (CZTS) samples annealed at different temperatures in the range of 473-623 K were investigated. The temperature dependence of the Cu/Zn-order-disorder behavior was analyzed by neutron powder diffraction measurements. Cu fully occupies the 2a and Sn the 2b position within the whole temperature range. For Zn and the remaining Cu on sites 2d and 2c, a clear change from ordered to disordered kesterite structure is found. The critical temperature Tc for this Landau-type second order transition was determined as 552±2 K. It was found that in Cu2ZnSnS4 very long annealing times are necessary to reach equilibrium at low temperatures.

  10. Further investigation of an integrated picture of photon diffraction described by virtual particle momentum exchange

    NASA Astrophysics Data System (ADS)

    Mobley, Michael J.

    2013-10-01

    An alternative picture for photon diffraction had been proposed describing diffraction by a distribution of photon paths determined through a Fourier analysis of a scattering lattice. The momentum exchange probabilities are defined at the location of scattering, not the point of detection. This contrasts with the picture from classical optical wave theory that describes diffraction in terms of the Huygens-Fresnel principle and sums the phased contributions of electromagnetic waves to determine probabilities at detection. This revised picture, termed "Momentum Exchange Theory," can be derived through a momentum representation of the diffraction formulas of optical wave theory, replacing the concept of Huygens wavelets with photon scattering through momentum exchange with the lattice. Starting with the Rayleigh-Sommerfeld and Fresnel-Kirchoff formulas, this paper demonstrates that diffraction results from positive and negative photon dispersions through virtual particle exchange probabilities that depend on the lattice geometry and are constrained by the Heisenberg uncertainty principle. The positive and negative increments of momentum exchange exhibit harmonic probability distributions characteristic of a "random walk," dependent on the distance of momentum exchange. The analysis produces a simplified prediction for the observed intensity profile for a collimated laser beam diffracted by a long, straight edge that lends conceptual support for this alternative picture.

  11. Neutron diffraction study and superparamagnetic behavior of ZnFe{sub 2}O{sub 4} nanoparticles obtained with different conditions

    SciTech Connect

    Blanco-Gutierrez, V.; Climent-Pascual, E.; Torralvo-Fernandez, M.J.; Saez-Puche, R.; Fernandez-Diaz, M.T.

    2011-07-15

    Spinel-type (S.G.= Fd3-bar m) ZnFe{sub 2}O{sub 4} fine particles with sizes from 4 to 19 nm prepared by solvothermal and microwave-assisted solvothermal methods have been studied by neutron powder diffraction at room temperature. The cation distribution corresponding to mixed spinel structure (Zn{sup 2+}{sub 1-x}Fe{sup 3+}{sub x})[Fe{sup 3+}{sub 2-x}Zn{sup 2+}{sub x}]O{sub 4} along with the unit cell parameter has been estimated after Rietveld refinement of the obtained neutron diffraction data for all the samples. It has been found that the inversion degree parameter (x) takes values between 0.11 and 0.20 depending not only on the particle size but also on the synthesis conditions as well. All the samples behave as superparamagnetic with an effective magnetic moment per particle ({mu}{sub SP}) from 7.0x10{sup 2} to 7.7x10{sup 3} {mu}{sub B}. The sample obtained by microwave assistance displays a different magnetic behavior as the ZFC and FC magnetic susceptibility and the magnetization versus applied field hysteresis loop measured at 5 K suggest. This is related with the dipole interactions that are a consequence of the higher inversion degree and {mu}{sub SP}. - Graphical abstract: ZnFe{sub 2}O{sub 4} nanoparticles of 19 nm obtained by the solvotermal method together with its Rietveld refined pattern. Highlights: > Solvothermally prepared ZnFe{sub 2}O{sub 4} nanoparticles.{yields} Inversion degree obtained after Rietveld refinement of neutron data.{yields} Superparamagnetic behavior.{yields} Dependence with the synthesis conditions.

  12. Illuminating the Past: The Neutron as a Tool in Archaeology

    ERIC Educational Resources Information Center

    Kockelmann, W.; Kirfel, A.; Siano, S.; Frost, C. D.

    2004-01-01

    Neutrons can be produced in nuclear reactions and used as very versatile probes for condensed matter research. Since their introduction in the 1950s neutron scattering techniques have evolved to be very powerful tools for investigating the properties of condensed matter. Here we present the concept of neutron diffraction and how this technique can…

  13. X-ray diffraction study of BaTiO3 single crystals before and after fast-neutron irradiation

    NASA Astrophysics Data System (ADS)

    Stash, A. I.; Ivanov, S. A.; Stefanovich, S. Yu.; Mosunov, A. V.; Boyko, V. M.; Ermakov, V. S.; Korulin, A. V.; Kalyukanov, A. I.; Isakova, N. N.

    2015-09-01

    The neutron irradiation of ferroelectrics is efficiently used to form structural states that cannot be obtained by conventional technologies. To date, the effect of neutron irradiation on the structure and properties of BaTiO3 has been studied for only ceramic materials. We have considered the influence of fast-neutron irradiation ( F = 1 × 1017 cm-2) on the structure and properties of BaTiO3 single crystals for the first time. The structural changes occurring in irradiated BaTiO3 and their correlation with the behavior of dielectric and nonlinear optical characteristics are analyzed with the aid of a specially developed method for taking into account the experimental correction to diffuse scattering. Neutron irradiation to the aforementioned dose retains the polar structure of the material and only slightly changes atomic displacements. The radiationinduced structural changes occur according to the high-temperature type to form a structure similar to the cubic modification of unirradiated BaTiO3 crystal.

  14. Effects of temperature on the crystal structure of epidote: a neutron single-crystal diffraction study at 293 and 1,070 K

    NASA Astrophysics Data System (ADS)

    Gatta, G. Diego; Meven, Martin; Bromiley, Geoffrey

    2010-07-01

    The effects of temperature on the crystal structure of a natural epidote [Ca1.925 Fe0.745Al2.265Ti0.004Si3.037O12(OH), a = 8.890(6), b = 5.630(4), c = 10.150(6) Å and β = 115.36(5)°, Sp. Gr. P21 /m] have been investigated by means of neutron single-crystal diffraction at 293 and 1,070 K. At room conditions, the structural refinement confirms the presence of Fe3+ at the M3 site [%Fe(M3) = 73.1(8)%] and all attempts to refine the amount of Fe at the M(1) site were unsuccessful. Only one independent proton site was located. Two possible hydrogen bonds, with O(2) and O(4) as acceptors [i.e. O(10)-H(1)···O(2) and O(10)-H(1)···O(4)], occur. However, the topological configuration of the bonds suggests that the O(10)-H(1)···O(4) is energetically more favourable, as H(1)···O(4) = 1.9731(28) Å, O(10)···O(4) = 2.9318(22) Å and O(10)-H(1)···O4 = 166.7(2)°, whereas H(1)···O(2) = 2.5921(23) Å, O(10)···O(2) = 2.8221(17) Å and O(10)-H(1)···O2 = 93.3(1)°. The O(10)-H(1) bond distance corrected for “riding motion” is 0.9943 Å. The diffraction data at 1,070 K show that epidote is stable within the T-range investigated, and that its crystallinity is maintained. A positive thermal expansion is observed along all the three crystallographic axes. At 1,070 K the structural refinement again shows that Fe3+ share the M(3) site along with Al3+ [%Fe(M3)1,070K = 74(2)%]. The refined amount of Fe3+ at the M(1) is not significant [%Fe(M1)1,070K = 1(2)%]. The tetrahedral and octahedral bond distances and angles show a slight distortion of the polyhedra at high- T, but a significant increase of the bond distances compared to those at room temperature is observed, especially for bond distances corrected for “rigid body motions”. The high- T conditions also affect the inter-polyhedral configurations: the bridging angle Si(2)-O(9)-Si(1) of the Si2O7 group increases significantly with T. The high- T structure refinement shows that no dehydration effect

  15. The application of inelastic neutron scattering to investigate the interaction of methyl propanoate with silica.

    PubMed

    McFarlane, Andrew R; Geller, Hannah; Silverwood, Ian P; Cooper, Richard I; Watkin, David J; Parker, Stewart F; Winfield, John M; Lennon, David

    2016-06-29

    A modern industrial route for the manufacture of methyl methacrylate involves the reaction of methyl propanoate and formaldehyde over a silica-supported Cs catalyst. Although the process has been successfully commercialised, little is known about the surface interactions responsible for the forward chemistry. This work concentrates upon the interaction of methyl propanoate over a representative silica. A combination of infrared spectroscopy, inelastic neutron scattering, DFT calculations, X-ray diffraction and temperature-programmed desorption is used to deduce how the ester interacts with the silica surface. PMID:27182815

  16. Symmetry lowering in crystalline solid solutions: A study of cinnamamide-thienylacrylamide by x-ray and neutron diffraction and solid-state photochemistry

    SciTech Connect

    Shimon, L.J.W.; Weissinger-Lewin, Y.; McMullan, R.K.; Vaida, M.; Frolow, F.; Lahav, M.; Leiserowitz, L.

    1993-04-01

    Principles are outlined for symmetry lowering of a mixed crystal. A survey is given of methods used to detect reduced symmetry: changes in crystal morphology, detection of enantiomeric segregation of chiral additives in ``centrosymmetric`` crystals, generation of second harmonic optical signals, optical birefringence, asymmetric photoreactions in the crystalline state and X-ray and neutron diffraction. The last two methods are applied to mixed crystals of cinnamamide host and thienylacrylamide. Diffraction demonstrated that the mixed crystals are composed of six sectors of reduced symmetry, from monoclinic centrosymmetric P2{sub 1}/c to triclinic P1 in four sectors and possibly Pc in the remaining two. The X-ray diffraction data were not sufficiently accurate for assigning the absolute structures of the PI sectors of anomalous X-ray scattering. Thus, by this method one could not ascertain the absolute orientation of the guest molecules on the surface sites through which they were selectively occluded. This ambiguity was resolved by assignment of the absolute configuration of the chiral heterophotodimers, between host and guest, in enantiomeric excess in the PI sectors, after irradiation with UV light. This leads to the conclusion that the selective occlusion of thienylacrylamide arises from replacement of attractive C-H{pi} (electron) interactions between host molecules by a repulsive sulfur (lone pair electron){pi}(electron) interactions between guest and host at the crystal surfaces.

  17. Symmetry lowering in crystalline solid solutions: A study of cinnamamide-thienylacrylamide by x-ray and neutron diffraction and solid-state photochemistry

    SciTech Connect

    Shimon, L.J.W.; Weissinger-Lewin, Y.; McMullan, R.K. ); Vaida, M.; Frolow, F.; Lahav, M.; Leiserowitz, L. . Dept. of Materials and Interfaces)

    1993-01-01

    Principles are outlined for symmetry lowering of a mixed crystal. A survey is given of methods used to detect reduced symmetry: changes in crystal morphology, detection of enantiomeric segregation of chiral additives in centrosymmetric'' crystals, generation of second harmonic optical signals, optical birefringence, asymmetric photoreactions in the crystalline state and X-ray and neutron diffraction. The last two methods are applied to mixed crystals of cinnamamide host and thienylacrylamide. Diffraction demonstrated that the mixed crystals are composed of six sectors of reduced symmetry, from monoclinic centrosymmetric P2[sub 1]/c to triclinic P1 in four sectors and possibly Pc in the remaining two. The X-ray diffraction data were not sufficiently accurate for assigning the absolute structures of the PI sectors of anomalous X-ray scattering. Thus, by this method one could not ascertain the absolute orientation of the guest molecules on the surface sites through which they were selectively occluded. This ambiguity was resolved by assignment of the absolute configuration of the chiral heterophotodimers, between host and guest, in enantiomeric excess in the PI sectors, after irradiation with UV light. This leads to the conclusion that the selective occlusion of thienylacrylamide arises from replacement of attractive C-H[pi] (electron) interactions between host molecules by a repulsive sulfur (lone pair electron)[pi](electron) interactions between guest and host at the crystal surfaces.

  18. Investigation of piezoelectric softening mechanisms in lead zirconate titanate using diffraction and property measurements

    NASA Astrophysics Data System (ADS)

    Seshadri, Shruti B.

    Lead zirconate titanate (PZT) is a well-known piezoelectric ceramic of commercial and scientific importance. Typically, PZT is used in its doped form as doping allows its properties to be tailored for specific applications. Donor doping turns PZT into a "soft" ferroelectric. One of the characteristics of soft ferroelectrics is an increase in their longitudinal piezoelectric coefficient. Softening is currently attributed to an increase in the concentration of lead vacancies and the associated effect on the behavior of ferroelectric domain walls. However, the exact mechanism by which donor doping enhances the longitudinal piezoelectric coefficient is still not understood. In this work, the crystallographic response of donor-doped PZT is studied in situ during the application of electric fields in order to deduce the strain mechanisms which contribute to ferroelectric softening. X-ray diffraction from a synchrotron source is employed for this investigation. It was found that the use of different donor dopants results in distinctive, characteristic strain mechanisms that soften PZT. Sm and Nd aid in the softening of PZT solely by enhancing 90° domain wall mobility. However, La and Nb doping results in a material with coexisting ferroelectric phases. It was further found that Nb doping results in at least two additional strain mechanisms including interphase boundary motion and a large strain in the (200) rhombohedral lattice plane. As piezoelectrics are also used in high temperature applications, the temperature dependence of the piezoelectric coefficient in soft doped PZT was also investigated. It was found that Sm doping leads to a high temperature (≈300°C) piezoelectric coefficient that is substantially greater than that found in La and Nb-doped PZT. In some cases, the coefficient in Sm-doped PZT is greater than that of La and Nd-doped PZT by a factor of two. Conventionally, the largest piezoelectric coefficient values are obtained in soft doped PZT by using a

  19. Crystal structure of α- and β-Na{sub 2}U{sub 2}O{sub 7}: From Rietveld refinement using powder neutron diffraction data

    SciTech Connect

    IJdo, D.J.W. Akerboom, S.; Bontenbal, A.

    2015-01-15

    The crystal structures of α- and β-Na{sub 2}U{sub 2}O{sub 7} have been determined from neutron powder diffraction. At 293 K, the compound α-Na{sub 2}U{sub 2}O{sub 7} has a monoclinic unit cell, space group P2{sub 1}/a, with a=12.7617(14) Å, b=7.8384(10) Å, c=6.8962(9) Å, β=111.285(9)°, and Z=4. At 773 K, β-Na{sub 2}U{sub 2}O{sub 7} is also monoclinic, space group C2/m, with a=12.933(1) Å, b=7.887(1) Å, c=6.9086(8) Å, β=110.816(10)°, and Z=4. The structures can be described by layers U{sub 2}O{sub 7}{sup 2−} built from corner linked deformed UO{sub 6} octahedra with pentagonal UO{sub 7} bipyramids in between linked with common edges to each other and to the octahedra. The Na atoms occupy the interlayer space. The Na{sub 2}U{sub 2}O{sub 7} layers are similar as in K{sub 2}U{sub 2}O{sub 7}, but with a different stacking sequence of the layers. The layers in β-Na{sub 2}U{sub 2}O{sub 7} are more symmetric. The relationship with the compounds A{sub 2}U{sub 2}O{sub 7} (A=K, Rb, and Cs) is discussed. - Graphical abstract: The U{sub 2}O{sub 7} layer of α-Na{sub 2}U{sub 2}O{sub 7} (left) at 293 K and of β-Na{sub 2}U{sub 2}O{sub 7} (right) at 773 K determined by neutron diffraction. Some Na atoms between the layers are visible. - Highlights: • Na{sub 2}U{sub 2}O{sub 7} has been prepared by means of a solid state reaction. • The structure has been determined using neutron diffraction. • At 293 K, the compound adopts a monoclinic structure with space group P2{sub 1}/a. • The structure at 773 K is closely related, and is described in the space group C2/m.

  20. Investigation and application of neutron damage to bipolar transistors in light water reactor dosimetry

    SciTech Connect

    Roknizadeh, M.

    1987-01-01

    A method of fast neutron metrology and a basis for prediction of changes in performance parameters of semiconductor devices in power plant radiation environments has been established using Cf-252 sources. Three general purpose NPN bipolar transistors (PN2222A, ECG-196, and ECG-184) were chosen as the neutron damage monitors and the change in inverse d.c. current gain before and after irradiation was chosen as the damage parameter for the measurement. The main findings of the investigation were as follows: the change in inverse d.c. current gain for PN2222A transistors was approximately a linear function of the neutron fluence up to 2.0E15 n(1MeV)/cm/sup 2/. The concept of 1-MeV equivalent neutron fluence which characterizes an incident energy-fluence spectrum in terms of the fluence of monoenergetic neutrons at 1 MeV, is in error for application to common transistors in a typical power plant environment. Finally, the normalized damage coefficient which is the ratio of damage to 1-MeV equivalent neutron fluence divided by the measured base transit time of individual transistors, for all three types of transistors is nearly the same with an average value of 1.27E - 7 +/- 15.0% cm/sup 2//m(1 MeV).Sec.