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Sample records for polarised neutron diffraction

  1. Polarised neutron scattering from dynamic polarised targets in biology

    NASA Astrophysics Data System (ADS)

    Knop, W.; Hirai, M.; Olah, G.; Meerwinck, W.; Schink, H.-J.; Stuhrman, H. B.; Wagner, R.; Wenkow-EsSouni, M.; Zhao, J.; Schärpf, O.; Crichton, R. R.; Krumpolc, M.; Nierhaus, K. H.; Niinikoski, T. O.; Rijllart, A.

    1991-10-01

    The contrast giving rise to neutron small-angle scattering can be enhanced considerably by polarisation of the hydrogen nuclei [J. des Coizeaux and G. Jannink, Les Polymères en Solution, Les Editions de Physique, F-91944 Les Ulis, France (1987)]. Using polarised neutrons the scattering from protonated labels in a deuterated matrix will increase by an order of magnitude. This is the basis of nuclear spin contrast variation, a method which is of particular interest for the in situ structure determination of macromolecular components. A new polarised target for neutron scattering has been designed by CERN and tested successfully at FRG-1 of the GKSS research centre. For the purpose of thermal-neutron scattering the frozen solutions of biomolecules are immersed in liquid helium 4, which is thermally coupled to the cooling mixture of helium 3/helium 4 of the dilution refrigerator. The nuclear spins are aligned with respect to the external magnetic field-parallel or antiparallel-by dynamic nuclear polarisation (DNP). The gain in neutron scattering compared to earlier experiments using direct cooling of the sample by helium 3 is a factor of 30. Another factor of 30 arises from the installation of the cold source and the beryllium reflector in FRG-1 [W. Knop et al., J. Appl. Cryst. 22 (1989) 352]. Pure nuclear spin targets are produced from dynamic polarised targets by selective depolarisation. In biological material only the hydrogen isotopes contribute significantly to polarised neutron scattering. Thus, saturation of the proton NMR yields a deuteron target, provided the target material has been enriched by the latter isotope. A proton target is obtained from the dynamic polarised target by saturation of deuteron NMR. This leads to six additional scattering functions reflecting the proton and deuteron spin densities and the correlations between the polarised isotopes. Polarised neutron scattering from nuclear spin targets of apoferritin and various derivatives of the

  2. Polarised nuclei for neutron science: recent applications and perspectives

    NASA Astrophysics Data System (ADS)

    Glättli, Hans

    2004-08-01

    Neutron scattering on nuclei is spin dependent, particularly strongly for 1H. The means to achieve large nuclear polarisations and its use for structure analysis or as spin-handling device are reviewed. High resolution (diffraction) as well as low resolution (SANS) measurements can benefit from polarised nuclei by changing selectively the form factors of Bragg reflections or the contrasts (the scattering length density profiles) in SANS. The internal structure of ribosomes and the conformation of polymers in solution have been investigated by this method. A numerical simulation is presented to show the influence of steady-state polarisation of protons on the scattering from a protein-ARN model complex. In addition, a more recent technique, time-resolved SANS is described. It makes use of spatial polarisation gradients created around paramagnetic centres at the onset of nuclear polarisation. Such polarisation domains can enhance considerably the scattering amplitude of free radicals and thus contribute to determine their positions inside a complex protein. Examples of possible future experiments are proposed which combine simultaneously the selectivity of solid-state NMR techniques and neutron scattering.

  3. How to polarise all neutrons in one beam: a high performance polariser and neutron transport system

    NASA Astrophysics Data System (ADS)

    Rodriguez, D. Martin; Bentley, P. M.; Pappas, C.

    2016-09-01

    Polarised neutron beams are used in disciplines as diverse as magnetism,soft matter or biology. However, most of these applications often suffer from low flux also because the existing neutron polarising methods imply the filtering of one of the spin states, with a transmission of 50% at maximum. With the purpose of using all neutrons that are usually discarded, we propose a system that splits them according to their polarisation, flips them to match the spin direction, and then focuses them at the sample. Monte Carlo (MC) simulations show that this is achievable over a wide wavelength range and with an outstanding performance at the price of a more divergent neutron beam at the sample position.

  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. 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.

  6. Spin echo small angle neutron scattering using a continuously pumped {sup 3}He neutron polarisation analyser

    SciTech Connect

    Parnell, S. R.; Li, K.; Yan, H.; Stonaha, P.; Li, F.; Wang, T.; Baxter, D. V.; Snow, W. M.; Washington, A. L.; Walsh, A.; Chen, W. C.; Parnell, A. J.; Fairclough, J. P. A.; Pynn, R.

    2015-02-15

    We present a new instrument for spin echo small angle neutron scattering (SESANS) developed at the Low Energy Neutron Source at Indiana University. A description of the various instrument components is given along with the performance of these components. At the heart of the instrument are a series of resistive coils to encode the neutron trajectory into the neutron polarisation. These are shown to work well over a broad range of neutron wavelengths. Neutron polarisation analysis is accomplished using a continuously operating neutron spin filter polarised by Rb spin-exchange optical pumping of {sup 3}He. We describe the performance of the analyser along with a study of the {sup 3}He polarisation stability and its implications for SESANS measurements. Scattering from silica Stöber particles is investigated and agrees with samples run on similar instruments.

  7. Neutron diffraction studies of bacteriorhodopsin

    SciTech Connect

    Trewhella, J.; Popot, J.L.; Engelman, D.M.; Zaccai, G.

    1985-01-01

    Neutron diffraction studies of bacteriorhodopsin have utilized the entire range of deuterium labeling techniques that are commonly used in biological neutron scattering experiments. We will review the work published in this area and report on current projects. 10 refs., 1 fig.

  8. 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.

  9. 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.

  10. PASTIS2 and CROCODILE: XYZ-wide angle polarisation analysis for thermal neutrons

    NASA Astrophysics Data System (ADS)

    Enderle, Mechthild; Jullien, David; Petoukhov, Alexander; Mouveau, Pascal; Andersen, Ken; Courtois, Pierre

    2017-06-01

    We present a wide-angle device for inelastic neutron scattering with XYZ-polarisation analysis (PASTIS2). PASTIS2 employs a banana-shaped Si-walled 3He-filter for the polarisation analysis and allows pillar-free neutron scattering for horizontal scattering angles 0-100◦. The guide field direction at the sample can be chosen vertical or with 45◦ incremental steps in the horizontal scattering plane. When PASTIS2 is implemented on a polarised neutron beam, the incident neutron spin can be flipped with an easy-to-optimise broad-band adiabatic resonant flipper (CROCODILE) independent of the guide field direction at the sample position. We have tested the performance of this new device on the polarised thermal triple-axis spectrometer IN20 at the Institut Laue-Langevin, equipped with Heusler monochromator and the FlatCone multi-analyser, and discuss its potential for future instruments.

  11. 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.

  12. Structure of hydrogenous liquids: separation of coherent and incoherent cross sections using polarised neutrons

    NASA Astrophysics Data System (ADS)

    Stunault, A.; Vial, S.; Pusztai, L.; Cuello, G. J.; Temleitner, L.

    2016-04-01

    The determination of the coherent structure factor of hydrogenous liquids is very difficult: while X-rays are barely sensitive to hydrogen, neutrons results still lack accuracy due to the contamination of the scattering intensities by a huge spin-incoherent signal from the 1H atoms. Using polarised neutrons with polarisation analysis, one can experimentally separate the coherent and incoherent contributions to the scattered intensity. We present the upgrade of the D3 polarised hot neutron diffractometer at ILL to study hydrogenated liquids. We show first data obtained from a test sample of water and detail the data reduction leading to an unprecedented accuracy in the extraction of the coherent signal, representative of the structure.

  13. Optimizing Crystal Volume for Neutron Diffraction

    NASA Technical Reports Server (NTRS)

    Snell, Edward H.; vanderWoerd, Mark; Damon, Michael; Judge, Russell, A.; Myles, Dean; Meilleur, F.

    2006-01-01

    Neutron diffraction is uniquely sensitive to hydrogen positions and protonation state. In that context structural information from neutron data is complementary to that provided through X-ray diffraction. However, there are practical obstacles to overcome in fully exploiting the potential of neutron diffraction, Le. low flux and weak scattering. Several approaches are available to overcome these obstacles and we have investigated the simplest: increasing the diffracting volume of the crystals. Volume is a quantifiable metric that is well suited for experiment design and optimization techniques. By using response surface methods we have optimized xylose isomerase crystal volume, enabling neutron diffraction while we determined the crystallization parameters with the minimum of experiments. Our results suggest a systematic means of enabling neutron diffraction studies for a larger number of samples that require information on hydrogen position and/or protonation state.

  14. Optimizing Crystal Volume for Neutron Diffraction

    NASA Technical Reports Server (NTRS)

    Snell, Edward H.; vanderWoerd, Mark; Damon, Michael; Judge, Russell, A.; Myles, Dean; Meilleur, F.

    2006-01-01

    Neutron diffraction is uniquely sensitive to hydrogen positions and protonation state. In that context structural information from neutron data is complementary to that provided through X-ray diffraction. However, there are practical obstacles to overcome in fully exploiting the potential of neutron diffraction, Le. low flux and weak scattering. Several approaches are available to overcome these obstacles and we have investigated the simplest: increasing the diffracting volume of the crystals. Volume is a quantifiable metric that is well suited for experiment design and optimization techniques. By using response surface methods we have optimized xylose isomerase crystal volume, enabling neutron diffraction while we determined the crystallization parameters with the minimum of experiments. Our results suggest a systematic means of enabling neutron diffraction studies for a larger number of samples that require information on hydrogen position and/or protonation state.

  15. High-Accuracy Analysis of Compton Scattering in Chiral EFT: Proton and Neutron Polarisabilities

    NASA Astrophysics Data System (ADS)

    Griesshammer, Harald W.; Phillips, Daniel R.; McGovern, Judith A.

    2013-10-01

    Compton scattering from protons and neutrons provides important insight into the structure of the nucleon. A new extraction of the static electric and magnetic dipole polarisabilities αE 1 and βM 1 of the proton and neutron from all published elastic data below 300 MeV in Chiral Effective Field Theory shows that within the statistics-dominated errors, the proton and neutron polarisabilities are identical, i.e. no iso-spin breaking effects of the pion cloud are seen. Particular attention is paid to the precision and accuracy of each data set, and to an estimate of residual theoretical uncertainties. ChiEFT is ideal for that purpose since it provides a model-independent estimate of higher-order corrections and encodes the correct low-energy dynamics of QCD, including, for few-nucleon systems used to extract neutron polarisabilities, consistent nuclear currents, rescattering effects and wave functions. It therefore automatically respects the low-energy theorems for photon-nucleus scattering. The Δ (1232) as active degree of freedom is essential to realise the full power of the world's Compton data.Its parameters are constrained in the resonance region. A brief outlook is provided on what kind of future experiments can improve the database. Supported in part by UK STFC, DOE, NSF, and the Sino-German CRC 110.

  16. Neutron Reflectivity and Grazing Angle Diffraction

    PubMed Central

    Ankner, J. F.; Majkrzak, C. F.; Satija, S. K.

    1993-01-01

    Over the last 10 years, neutron reflectivity has emerged as a powerful technique for the investigation of surface and interfacial phenomena in many different fields. In this paper, a short review of some of the work on neutron reflectivity and grazing-angle diffraction as well as a description of the current and planned neutron rcflectometers at NIST is presented. Specific examples of the characterization of magnetic, superconducting, and polymeric surfaces and interfaces are included. PMID:28053457

  17. Probing the spiral magnetic phase in 6 nm textured erbium using polarised neutron reflectometry

    NASA Astrophysics Data System (ADS)

    Satchell, N.; Witt, J. D. S.; Burnell, G.; Curran, P. J.; Kinane, C. J.; Charlton, T. R.; Langridge, S.; Cooper, J. F. K.

    2017-02-01

    We characterise the magnetic state of highly-textured, sputter deposited erbium for a film of thickness 6 nm. Using polarised neutron reflectometry it is found that the film has a high degree of magnetic disorder, and we present some evidence that the film’s local magnetic state is consistent with bulk-like spiral magnetism. This, combined with complementary characterisation techniques, show that thin film erbium is a strong candidate material for incorporation into device structures.

  18. Spatial and spectral image distortions caused by diffraction of an ordinary polarised light beam by an ultrasonic wave

    SciTech Connect

    Machikhin, A S; Pozhar, V E

    2015-02-28

    We consider the problem of determining the spatial and spectral image distortions arising from anisotropic diffraction by ultrasonic waves in crystals with ordinary polarised light (o → e). By neglecting the small-birefringence approximation, we obtain analytical solutions that describe the dependence of the diffraction angles and wave mismatch on the acousto-optic (AO) interaction geometry and crystal parameters. The formulas derived allow one to calculate and analyse the magnitude of diffraction-induced spatial and spectral image distortions and to identify the main types of distortions: chromatic compression and trapezoidal deformation. A comparison of the values of these distortions in the diffraction of ordinary and extraordinary polarised light shows that they are almost equal in magnitude and opposite in signs, so that consistent diffraction (o → e → o or e → o → e) in two identical AO cells rotated through 180° in the plane of diffraction can compensate for these distortions. (diffraction of radiation)

  19. Neutron diffraction studies on single crystals in the NiAs-type system MnSb-CrSb

    NASA Astrophysics Data System (ADS)

    Reimers, W.; Hellner, E.; Treutmann, W.; Brown, P. J.; Heger, G.

    1980-01-01

    A more detailed magnetic phase diagram of the system MnSb-CrSb has been established. A polarised neutron diffraction study has been performed on a Mn 1.10Sb crystal. Some ideas on the electronic structure of the system Mn 1+σSb (0 ⩽ σ ⩽ 0.22) are given.

  20. 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.

  1. A New High-Accuracy Analysis of Compton Scattering in Chiral EFT: Neutron Polarisabilities

    NASA Astrophysics Data System (ADS)

    Griesshammer, Harald W.; McGovern, Judith A.; Phillips, Daniel R.

    2015-04-01

    Low-energy Compton scattering tests the symmetries and interaction strengths of a target's internal degrees of freedom in the electric and magnetic fields of a real, external photon. In the single-nucleon sector, information is often compressed into the static scalar dipole polarisabilities which are experimentally not directly accessible but encode information on the pion cloud and the Δ(1232) excitation. The interaction of the photon with the charged pion-exchange also provides a conceptually clean probe of few-nucleon binding. After demonstrating the statistical consistency of the world's γd dataset including the new data from the MAX-IV collaboration described in the preceding talk, we present a new extraction of the neutron polarisabilities in Chiral Effective Field Theory: αn = [ 11 . 55 +/- 1 . 25(stat) +/- 0 . 2(BSR) +/- 0 . 8(th) ] and βn = [ 3 . 65 -/+ 1 . 25(stat) +/- 0 . 2(BSR) -/+ 0 . 8(th) ] , in 10-4 fm3, with χ2 = 45 . 2 for 44 degrees of freedom. The new data reduced the statistical uncertainties by 30%. We discuss data accuracy and consistency, the role of the Δ(1232) , and an estimate of residual theoretical uncertainties. Within statistical and systematic errors, proton and neutron polarisabilities remain identical. Supported in part by UK STFC and US DOE.

  2. Construction of the new polarised hot neutrons single-crystal diffractometer POLI-HEiDi at FRM-II

    NASA Astrophysics Data System (ADS)

    Hutanu, Vladimir; Meven, Martin; Heger, Gernot

    2007-07-01

    A new hot neutrons single-crystal diffractometer for magnetic structure investigations with polarised neutrons is under construction now at FRM-II near Munich. The problems by implementing the polarised neutron option on the existing instrument HEiDi lead to the decision to build a parallel instrument especially designed for this purpose, called Polarisation Investigator-HEiDi (POLI-HEiDi). Both options, zero field for spherical polarisation analysis in complex magnetic structures and high magnetic field for flipping ratio measurements to study spin density distributions, should be available at the new instrument. We present the proposed design and construction of POLI-HEiDi. As neutron polarisation method, 3He spin filter cells (NSFC's) are planned to be used. Dedicated filter cell design as well as the results of the first experiments with a 3He NSFC, performed recently at the HEiDi diffractometer by means of compact magnetostatic cavities, are discussed. The novel multifunctional compact device Helium Rotating Polariser (HERO) is presented.

  3. Optimizing Crystal Volume for Neutron Diffraction Studies

    NASA Technical Reports Server (NTRS)

    Snell, E. H.

    2003-01-01

    For structural studies with neutron diffraction more intense neutron sources, improved sensitivity detector and larger volume crystals are all means by which the science is being advanced to enable studies on a wider range of samples. We have chosen a simplistic approach using a well understood crystallization method, with minimal amounts of sample and using design of experiment techniques to maximize the crystal volume all for minimum effort. Examples of the application are given.

  4. Optimizing Crystal Volume for Neutron Diffraction Studies

    NASA Technical Reports Server (NTRS)

    Snell, E. H.

    2003-01-01

    For structural studies with neutron diffraction more intense neutron sources, improved sensitivity detector and larger volume crystals are all means by which the science is being advanced to enable studies on a wider range of samples. We have chosen a simplistic approach using a well understood crystallization method, with minimal amounts of sample and using design of experiment techniques to maximize the crystal volume all for minimum effort. Examples of the application are given.

  5. 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

  6. Applications of TOF neutron diffraction in archaeometry

    NASA Astrophysics Data System (ADS)

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

    2006-05-01

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

  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. Unraveling protein catalysis through neutron diffraction

    NASA Astrophysics Data System (ADS)

    Myles, Dean

    Neutron scattering and diffraction are exquisitely sensitive to the location, concentration and dynamics of hydrogen atoms in materials and provide a powerful tool for the characterization of structure-function and interfacial relationships in biological systems. Modern neutron scattering facilities offer access to a sophisticated, non-destructive suite of instruments for biophysical characterization that provide spatial and dynamic information spanning from Angstroms to microns and from picoseconds to microseconds, respectively. Applications range from atomic-resolution analysis of individual hydrogen atoms in enzymes, through to multi-scale analysis of hierarchical structures and assemblies in biological complexes, membranes and in living cells. Here we describe how the precise location of protein and water hydrogen atoms using neutron diffraction provides a more complete description of the atomic and electronic structures of proteins, enabling key questions concerning enzyme reaction mechanisms, molecular recognition and binding and protein-water interactions to be addressed. Current work is focused on understanding how molecular structure and dynamics control function in photosynthetic, cell signaling and DNA repair proteins. We will highlight recent studies that provide detailed understanding of the physiochemical mechanisms through which proteins recognize ligands and catalyze reactions, and help to define and understand the key principles involved.

  9. Layer selective magnetometry in ultrathin magnetic structures by polarised neutron reflection

    NASA Astrophysics Data System (ADS)

    Bland, J. A. C.; Lee, J.; Hope, S.; Lauhoff, G.; Penfold, J.; Bucknall, D.

    1997-06-01

    We discuss the application of polarised neutron reflection to layer selective vector magnetometry measurements in thin magnetic films. To illustrate the application of PNR, we review recent measurements of the absolute moment in X/Fe/Ag(001) structures with X = Pd, Ag, Au and Cu and compare the results with the predictions based on theoretical calculations which take into account the measured interface roughness. For the case of strained fct Ni/Cu(001) structures we illustrate the use of PNR as a self-calibrating magnetometric technique in determining both the magnetic layer thickness and total sample moment for which a reduced moment per Ni atom is observed. Finally we present measurements of the layer dependent moments in FeNi/Cu/Co spin valve structures. We show that by comparing the PNR measurements with SQUID magnetometry measurements of the total sample moment we are able to determine the interface moments on an atomic scale.

  10. Layer selective magnetometry in ultrathin magnetic structures by polarised neutron reflection

    NASA Astrophysics Data System (ADS)

    Bland, J. A. C.; Lee, J.; Hope, S.; Lauhoff, G.; Penfold, J.; Bucknall, D.

    1997-01-01

    We discuss the application of polarised neutron reflection to layer selective vector magnetometry measurements in thin magnetic films. To illustrate the application of PNR, we review recent measurements of the absolute moment in X/Fe/Ag(001) structures with X = Pd, Ag, Au and Cu and compare the results with the predictions based on theoretical calculations which take into account the measured interface roughness. For the case of strained fct Ni/Cu(001) structures we illustrate the use of PNR as a self-calibrating magnetometric technique in determining both the magnetic layer thickness and total sample moment for which a reduced moment per Ni atom is observed. Finally we present measurements of the layer dependent moments in FeNi/Cu/Co spin valve structures. We show that by comparing the PNR measurements with SQUID magnetometry measurements of the total sample moment we are able to determine the interface moments on an atomic scale.

  11. 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.

  12. Neutron Diffraction Study of Silicate Perovskites

    NASA Astrophysics Data System (ADS)

    Mao, H. K.; van Orman, J.; Fei, Y.; Hemley, R. J.; Loveday, J.; Nelmes, R.; Smith, R. I.

    2002-12-01

    The oxygen deficiency and cation-site distribution of silicate perovskite control its physical and chemical properties, including density, bulk modulus, defect mobility, ionic transport, flow behavior, oxidation states, hydration, and minor-element solubility. These properties of perovskite, in turn control the geophysical and geochemical processes of the Earth. The possibility of oxygen deficiency was first recognized in perovskite with minor amounts of Al replacing Mg and Si [1, 2], and its significance is compared to the analogous defect perovskite in ceramics [3]. Basic crystallographic characteristics of the silicate perovskite, including the lattice parameters of the orthorhombic unit cell, the Pbmn space group, and atomic positions, were previously determined by x-ray diffraction [4]. The defect crystallography of silicate perovskite, however, cannot be measured by x-rays because the relevant ions (Mg2+, Al3+, Si4+ and O2-) are isoelectronic. These ions have very different neutron cross-section and can be readily resolved by neutron diffraction. Using multianvil apparatus, we synthesized perovskite samples at 1700°C and 25-28 GPa. We perform multiple runs to accumulate 3 mm3 sample each for the MgSiO3 end member and MgSiO3 plus 5 weight %\\ Al2O3 in perovskite structure. Excellent powder diffraction data were collected at the POLARIS Beamline of ISIS, Rutherford Appleton Lab, and were subjected to Rietveld analysis. Neutron derived information sheds light on the unusual effects found for Al3+ substitution on the compressibility of the silicate perovskite [1]. 1. J. Zhang and D. J. Weidner, Science 284, 782 (1999). 2. J. P. Brodholt, Nature 407, 620 (2000). 3. A. Navrotsky, Science 284, 1788 (1999). 4. N. L. Ross and R. M. Hazen, Phys. Chem. Minerals 17, 228 (1990).

  13. 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.

  14. 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.

  15. Neutron diffraction studies of thin film multilayer structures

    SciTech Connect

    Majkrzak, C.F.

    1985-01-01

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

  16. Microstructure of Horseshoe Nails Using Neutron Diffraction

    NASA Astrophysics Data System (ADS)

    Goossens, D. J.; Studer, A. J.; Stachurski, Z. H.

    2010-04-01

    Neutron diffraction allows nondestructive testing of the bulk microstructure of mechanical components. The microstructures of horseshoe nails made through three different processes have been explored as a function of position along the nail. Despite all nails being made of similar plain low-carbon steel and being process annealed after manufacture, the microstructures are far from the same. Nails made from strip, using a cold forging stamping process, show narrower diffraction peaks indicating a narrower distribution of lattice parameters and also show diffraction peak intensity ratios closer to those expected for unstrained steel. Thus, the distribution of the orientation of grains in these nails is closer to that of undistorted steel compared to nails made through the other two processes considered—one a drawing from wire and the other a combination of rolling and cold forging. The blades of the drawn nails showed little preferred orientation but the converse was true in the heads. Differing patterns of preferred orientation suggest that the various manufacturing approaches result in substantially different mechanical advantages for the three types of nails, a result in accord with mechanical testing.

  17. 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

  18. Pulsed Neutron Powder Diffraction for Materials Science

    SciTech Connect

    Kamiyama, T.

    2008-03-17

    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 {delta}d/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 A{sup -1}

  19. 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.

  20. 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.

  1. Feasibility of neutron diffraction on solid 3He

    NASA Astrophysics Data System (ADS)

    Siemensmeyer, K.; Schuberth, E. A.; Adams, E. D.; Takano, Y.; Guckelsberger, K.

    2000-07-01

    We have investigated the feasibility of neutron diffraction from solid 3He. The experiment will be performed at the HMI, first aiming for the properties of the antiferromagnetic ordering in the BCC phase and the ferromagnetic order in the HCP phase. Signal and beam heating considerations are essential to account for the enormous neutron absorption cross section of 3He. The study shows that neutron diffraction and transmission experiments are possible, relying on the experience gained from the neutron diffraction experiments on Cu and Ag at nanokelvin temperatures. A pressure cell has been developed which complies with the conflicting demands arising from the neutron and ultralow temperature aspects of the experiment. This work is a first step in an extensive effort to characterize 3He by neutron diffraction.

  2. High-precision neutron spectrometry, using diffraction focusing. Test experiment

    NASA Astrophysics Data System (ADS)

    Kuznetsov, I. A.; Berdnikov, Ya. A.; Berdnikov, A. Ya.; Borisov, Yu. V.; Braginetz, Yu. P.; Fedorov, V. V.; Lasitsa, M. V.; Semenikhin, S. Yu.; Khorina, M. L.; Voronin, V. V.

    2016-09-01

    The effect of double-crystal neutron focusing, using Laue diffraction in large perfect crystals was studied. The observed effect allows reach the angular resolution better than 0.03", that is ~ 10-2 of the Bragg reflection width. This fact makes it possible to create a new ultraprecise method for neutron spectrometry combining the spin-echo small angle neutron scattering with Laue diffraction.

  3. POLI-HEiDi: The new polarised neutron diffractometer at the hot source (SR9) at the FRM II—Project status

    NASA Astrophysics Data System (ADS)

    Huţanu, V.; Meven, M.; Lelièvre-Berna, E.; Heger, G.

    2009-09-01

    The project to upgrade the existing single-crystal diffractometer Heisses Einkristal Diffractometer (HEiDi) at FRM II with a polarised neutron option, enabling the investigation of magnetic ground states in single crystals has been ongoing since autumn 2004. After a detailed investigation of the possible options it has been decided to develop and rebuild the secondary spectrometer and keep the HEiDi monocromator. The new instrument has been named POLI-HEiDi as an abbreviation of Polarisation Investigator at HEiDi. Two different zero-field polarimeters will be made available for spherical neutron polarimetry, Cryoapad and MuPAD. Both, polarisation and analysis will be performed with polarised 3He spin filters. Several new and important components of the instrument have recently been commissioned. In this report we present these components and show how they fit with the design of the whole instrument.

  4. Neutron diffraction study of the zeolite edingtonite

    SciTech Connect

    Kvick, A.; Smith, J.V.

    1983-09-01

    A neutron diffraction study at 294 K of a single crystal of edingtonite (Ba/sub 2/Al/sub 4/Si/sub 6/O/sub 20/ x 7H/sub 2/O; a 9.537(3) b 9.651(2) c 6.509(2) A; P2/sub 1/2/sub 1/2) utilized 1876 diffraction intensities from the Brookhaven National Laboratory high-flux beam reactor. The agreement factor R(F/sup 2/) = 0.055 for conventional anisotropic refinement was reduced to 0.045 for a Gram--Charlier expansion up to fourth order for the thermal factors of the water atoms. The Si--O and Al--O distances correlate inversely with the Si--O--Al angle as in scolecite. There is no indication of substitutional disorder. The barium atom is coordinated to three pairs of framework oxygens (2.89, 2.96, and 3.04 A) and two pairs of water oxygens (2.79 and 2.79 A). Two framework oxygens have weak hydrogen bonds to both water molecules (O(4)--OW(1) 2.87, -OW(2) 2.96; O(5) -OW(1) 3.02, -OW(2) 3.02 A) and the other three framework oxygens are each bonded to a Ba atom. The OW--H xxx O angles (163.5/sup 0/, 165.1/sup 0/, 173.9/sup 0/, and 178.0/sup 0/) are fairly close to 180/sup 0/, the H xxx O distances are long (1.91, 2.02, 2.09, and 2.10 A) and the observed uncorrected OW--H distances range from 0.928(6) to 0.959(4) A. Only seven out of the eight water positions are occupied (W(1) 84% occupancy; W(2) 91%). The average rms displacement of each hydrogen (0.32, 0.29, 0.27, and 0.24 A) correlates approximately with the hydrogen bond length (2.09, 2.10, 2.02, and 1.91 A). Third- and fourth-order tensor components in the displacements of the water molecules may result from anharmonic or curvilinear vibrations; however, the effect of the static displacements of the center-of-motion from interaction with unoccupied water sites may also be important.

  5. Neutron Diffraction Investigation of Langanite Crystals

    SciTech Connect

    Kuz'micheva, G. M. Kaurova, I. A.; Rybakov, V. B.; Dubovsky, A. B.; Cousson, A.

    2010-11-15

    The upper and lower parts of a single crystal with a nominal composition La{sub 3}Ga{sub 5.5}Nb{sub 0.5}O{sub 14}grown by the Czochralski method (Ir crucible, 99%Ar + 1%O{sub 2}, growth direction) have been studied by neutron diffraction for the first time. The compositions of the upper and lower parts are found to differ ((La{sub 2.935(2)}{open_square}{sub 0.065})(Ga{sub 0.450}Nb{sub 0.550(3)})Ga{sub 3}(Ga{sub 1.965(4)} {open_square}{sub 0.035})(O{sub 13.90(1)} {open_square}{sub 0.10}) and (La{sub 2.940(1)} {open_square}{sub 0.060})(Ga{sub 0.590}Nb{sub 0.410(2)})Ga{sub 5}(O{sub 13.82(1)} {open_square}{sub 0.18}), respectively), and microtwin formation was observed in the upper part, with two unit cells related by the translation 1/2Z. Based on a comparison of the refined crystal composition and optical transmission spectra, the absorption bands at 30 000, 24 500, and 20 500 cm{sub -1} were assigned to divacancies (2 V{sub La}{sup '''}, 3 V{sub O}{sup ..}), oxygen vacancies, and color centers, respectively. A relationship between the crystal color and oxygen content is established.

  6. 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

  7. Cold neutron diffraction contrast tomography of polycrystalline material.

    PubMed

    Peetermans, S; King, A; Ludwig, W; Reischig, P; Lehmann, E H

    2014-11-21

    Traditional neutron imaging is based on the attenuation of a neutron beam through scattering and absorption upon traversing a sample of interest. It offers insight into the sample's material distribution at high spatial resolution in a non-destructive way. In this work, it is expanded to include the diffracted neutrons that were ignored so far and obtain a crystallographic distribution (grain mapping). Samples are rotated in a cold neutron beam of limited wavelength band. Projections of the crystallites formed by the neutrons they diffract are captured on a two dimensional imaging detector. Their positions on the detector reveal their orientation whereas the projections themselves are used to reconstruct the shape of the grains. Indebted to established synchrotron diffraction contrast tomography, this 'cold neutron diffraction contrast tomography' is performed on recrystallized aluminium for experimental comparison between both. Differences between set-up and method are discussed, followed by the application range in terms of sample properties (crystallite size and number, mosaicity and typical materials). Neutron diffraction contrast tomography allows to study large grains in bulky metallic structures.

  8. Future directions in high-pressure neutron diffraction

    NASA Astrophysics Data System (ADS)

    Guthrie, M.

    2015-04-01

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

  9. Neutron diffraction experiments with 40T pulsed magnets

    NASA Astrophysics Data System (ADS)

    Ohoyama, K.; Katoh, N.; Nojiri, H.; Matsuda, Y. H.; Hiraka, H.; Ikeda, K.; Shimizu, H. M.

    2006-11-01

    Aiming at realising neutron scattering experiments under B = 40T magnetic fields, we are developing diffusive techniques for neutron diffraction with a long pulse magnet. For the present experiments, we succeeded in observing the spin-flop transition of the antiferromagnet MnF2 around B = 10T using a 20T pulsed magnet on a neutron spectrometer installed at a reactor. 35T pulsed magnetic fields were also successfully generated.

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

    NASA Astrophysics Data System (ADS)

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

    2017-09-01

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

  11. 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

  12. Neutron diffraction optics of films with noncollinear magnetic depth structures

    NASA Astrophysics Data System (ADS)

    Korneev, Daniel A.; Chernenko, L. P.

    1992-11-01

    A model of a thin film with depth inhomogeneous or noncollinear magnetization is used to describe its neutron-optical, diffraction, and polarization properties. A quantum mechanical method of calculation is developed based on a numerical solution of the Pauli equation for a neutron in inhomogeneous matter with boundary conditions. This solution permits the uniform calculation of intensities and the polarization vector of the scattered beam over a wide range of conditions from specular reflection to neutron diffraction. The method is applied to certain model structures. Examples of its application to model structures (ferromagnetic spirals, long- period soliton) are given and the calculation can be programmed for a personal computer, taking a few seconds for each value of the incident neutron wave vector.

  13. High resolution neutron Larmor diffraction using superconducting magnetic Wollaston prisms.

    PubMed

    Li, Fankang; Feng, Hao; Thaler, Alexander N; Parnell, Steven R; Hamilton, William A; Crow, Lowell; Yang, Wencao; Jones, Amy B; Bai, Hongyu; Matsuda, Masaaki; Baxter, David V; Keller, Thomas; Fernandez-Baca, Jaime A; Pynn, Roger

    2017-04-13

    The neutron Larmor diffraction technique has been implemented using superconducting magnetic Wollaston prisms in both single-arm and double-arm configurations. Successful measurements of the coefficient of thermal expansion of a single-crystal copper sample demonstrates that the method works as expected. The experiment involves a new method of tuning by varying the magnetic field configurations in the device and the tuning results agree well with previous measurements. The difference between single-arm and double-arm configurations has been investigated experimentally. We conclude that this measurement benchmarks the applications of magnetic Wollaston prisms in Larmor diffraction and shows in principle that the setup can be used for inelastic phonon line-width measurements. The achievable resolution for Larmor diffraction is comparable to that using Neutron Resonance Spin Echo (NRSE) coils. The use of superconducting materials in the prisms allows high neutron polarization and transmission efficiency to be achieved.

  14. High resolution neutron Larmor diffraction using superconducting magnetic Wollaston prisms

    DOE PAGES

    Li, Fankang; Feng, Hao; Thaler, Alexander N.; ...

    2017-04-13

    The neutron Larmor diffraction technique has been implemented using superconducting magnetic Wollaston prisms in both single-arm and double-arm configurations. Successful measurements of the coefficient of thermal expansion of a single-crystal copper sample demonstrates that the method works as expected. Our experiment involves a new method of tuning by varying the magnetic field configurations in the device and the tuning results agree well with previous measurements. The difference between single-arm and double-arm configurations has been investigated experimentally. Here, we conclude that this measurement benchmarks the applications of magnetic Wollaston prisms in Larmor diffraction and shows in principle that the setup canmore » be used for inelastic phonon line-width measurements. The achievable resolution for Larmor diffraction is comparable to that using Neutron Resonance Spin Echo (NRSE) coils. Furthermore, the use of superconducting materials in the prisms allows high neutron polarization and transmission efficiency to be achieved.« less

  15. 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.

  16. 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.

  17. Dynamic theory of neutron diffraction from a moving grating

    SciTech Connect

    Bushuev, V. A.; Frank, A. I.; Kulin, G. V.

    2016-01-15

    A multiwave dynamic theory of diffraction of ultracold neutrons from a moving phase grating has been developed in the approximation of coupled slowly varying amplitudes of wavefunctions. The effect of the velocity, period, and height of grooves of the grating, as well as the spectral angular distribution of the intensity of incident neurons, on the discrete energy spectrum and the intensity of diffraction reflections of various orders has been analyzed.

  18. Physics and chemistry of materials from neutron diffraction and spectroscopy

    NASA Astrophysics Data System (ADS)

    Dahlborg, Ulf; Lovesey, Stephen W.

    1991-07-01

    A short introduction to the powerful techniques of neutron diffraction and spectroscopy is illustrated largely with achievements by Swedish researchers in the past few years. Background material on sources and instrumentation is included, together with a directory of facilities routinely available to the Swedish scientific community.

  19. 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.

  20. Extraction of polychromatic thermal neutrons by Bragg diffraction to use for prompt gamma neutron activation analysis

    NASA Astrophysics Data System (ADS)

    Byun, S. H.; Choi, H. D.; Jun, B. J.; Kim, M. S.

    2000-07-01

    Extraction method of thermal neutron beam by Bragg diffraction is investigated. A thermal neutron beam is used for the Prompt Gamma Neutron Activation Analysis system at HANARO, a 30 MW research reactor in the Korea Atomic Energy Research Institute. Polychromatic beam including all orders of diffraction is obtained by setting a pair of pyrolytic graphite crystals with a Bragg angle of 45° on a horizontal white beam line. Diffracted neutron flux at the sample position is calculated by considering the integrated reflectivity and mosaic spread of crystals. Due to the divergence effect, the mosaic spread of crystals is optimized to give the maximum and flat flux at the sample position. An experiment has been performed to verify the reflectivities for high order diffractions from pyrolytic graphite. When the focusing technique of bending the crystals is adopted, a design value of 1.0×108n/cm2s is expected at the sample position. Hence Bragg diffraction is a promising method of extracting thermal neutrons for PGNAA.

  1. Performance of a polarised neutron cryo-flipper using a high TcYBCO film

    NASA Astrophysics Data System (ADS)

    Parnell, S. R.; Washington, A. L.; Kaiser, H.; Li, F.; Wang, T.; Hamilton, W. A.; Baxter, D. V.; Pynn, R.

    2013-09-01

    It is well-known that the Meissner effect in superconducting materials can be used to provide a well-defined, non-adiabatic, magnetic-field transition. This can be utilised to produce a highly efficient neutron spin flipper that is suitable for use with neutrons of multiple wavelengths. Devices of this type using superconducting niobium have been deployed on neutron diffractometers for several decades but have required liquid helium to maintain the correct temperature. The use of high Tc materials, which removes the need for cryogens and simplifies the device, was first explored by Fitzsimmons et al. in [1]. In this communication, we describe a π flipper which uses commercially available films consisting of a 350-nm-thick YBCO film capped with 100 nm of gold on a 78×100×0.5 mm sapphire substrate. We discuss the design and performance of this device. The apparatus is compact (≈200 mm in length along the neutron beam), consisting of an oxygen-free high-conductivity copper frame, which holds the YBCO film and is mounted to the cold finger of a closed-cycle He refrigerator. The part of the vacuum chamber, where the YBCO film is located, is 5 cm wide, which allows us to minimise the distance from the film to the magnetic guide fields. Negligible small angle neutron scattering is observed from the flipper and its transmission is measured to be greater than 98.5% over a wide band of neutron wavelengths. In this design, the maximum neutron beam size that can be used is 42×42 mm2 and we can easily switch from a vertical to a horizontal guide field (both perpendicular to the neutron beam) on either side of the YBCO film. Data are reported for neutron wavelengths between 4 and 8.5 Å and flipping efficiencies under a variety of conditions are discussed. Under optimum conditions an efficiency of 99.5±0.3% was achieved for 4-8 Å neutrons on a pulsed source and 99.4±0.5% was achieved at a monochromatic source using a neutron wavelength of 4.2 Å.

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

    PubMed

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

    2017-09-27

    Polarised neutron diffraction measurements have been made on HoFeO3 single crystals magnetised in both the [0 0 1] and [1 0 0] directions (Pbnm setting). The polarisation dependencies of Bragg reflection intensities were measured both with a high field of [Formula: see text] T parallel to [0 0 1] at [Formula: see text] K and with the lower field [Formula: see text] T parallel to [1 0 0] at [Formula: see text] K. A Fourier projection of magnetization induced parallel to [0 0 1], made using the hk0 reflections measured in 9 T, indicates that almost all of it is due to alignment of Ho moments. Further analysis of the asymmetries of general reflections in these data showed that although, at 70 K, 9 T applied parallel to [0 0 1] hardly perturbs the antiferromagnetic order of the Fe sublattices, it induces significant antiferromagnetic order of the Ho sublattices in the [Formula: see text] plane, with the antiferromagnetic components of moment having the same order of magnitude as the induced ferromagnetic ones. Strong intensity asymmetries measured in the low temperature [Formula: see text] structure with a lower field, 0.5 T [Formula: see text] [1 0 0] allowed the variation of the ordered components of the Ho and Fe moments to be followed. Their absolute orientations, in the [Formula: see text] domain stabilised by the field were determined relative to the distorted perovskite structure. This relationship fixes the sign of the Dzyalshinski-Moriya (D-M) interaction which leads to the weak ferromagnetism. Our results indicate that the combination of strong y-axis anisotropy of the Ho moments and Ho-Fe exchange interactions breaks the centrosymmetry of the structure and could lead to ferroelectric polarization.

  3. 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.

  4. 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

  5. Characterization of pottery fragments by nondestructive neutron diffraction

    NASA Astrophysics Data System (ADS)

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

    2005-11-01

    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.

  6. Neutron diffraction study of α-iron titanium cerium hydride

    NASA Astrophysics Data System (ADS)

    Lin, Hong; Niu, Shiwen; Gou, Cheng; Jin, Longhuan; Tao, Fang; Bao, Deyou; Su, Lanying

    1987-03-01

    The results of the neutron scattering method shows that the crystal structure of Fe0.94TiCe0.06H0.03 is the same as that of the FeTiH0.02. However, its diffraction peak intensities drop by 47-58%, the background increased markedly about 2 times and the lattice constant increase by 5%.

  7. 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.

  8. Ellipsometric and neutron diffraction study of pentane physisorbed on graphite.

    PubMed

    Kruchten, Frank; Knorr, Klaus; Volkmann, Ulrich G; Taub, Haskell; Hansen, Flemming Y; Matthies, Blake; Herwig, Kenneth W

    2005-08-02

    High-resolution ellipsometry and neutron diffraction measurements have been used to investigate the structure, growth, and wetting behavior of fluid pentane (n-C(5)H(12)) films adsorbed on graphite substrates. We present isotherms of the thickness of pentane films adsorbed on the basal-plane surfaces of a pyrolytic graphite substrate as a function of the vapor pressure. These isotherms are measured ellipsometrically for temperatures between 130 and 190 K. We also describe neutron diffraction measurements in the temperature range 11-140 K on a deuterated pentane (n-C(5)D(12)) monolayer adsorbed on an exfoliated graphite substrate. Below a temperature of 99 K, the diffraction patterns are consistent with a rectangular centered structure. Above the pentane triple point at 143.5 K, the ellipsometric measurements indicate layer-by-layer adsorption of at least seven fluid pentane layers, each having the same optical thickness. Analysis of the neutron diffraction pattern of a pentane monolayer at a temperature of 130 K is consistent with small clusters having a rectangular-centered structure and an area per molecule of approximately 37 A(2) in coexistence with a fluid monolayer phase. Assuming values of the polarizability tensor from the literature and that the monolayer fluid has the same areal density as that inferred for the coexisting clusters, we calculate an optical thickness of the fluid pentane layers in reasonable agreement with that measured by ellipsometry. We discuss how these results support the previously proposed "footprint reduction" mechanism of alkane monolayer melting. In the hypercritical regime, we show that the layering behavior is consistent with the two-dimensional Ising model and determine the critical temperatures for layers n = 2-5.

  9. Examination of reactor grade graphite using neutron powder diffraction

    NASA Astrophysics Data System (ADS)

    DiJulio, D. D.; Hawari, A. I.

    2009-07-01

    Graphite is of principal interest in Generation IV nuclear reactor concepts. In particular, graphite will be the moderator for the Very High Temperature Reactor. In support of experimental and computational investigations that aim at understanding the behavior of reactor grade graphite under operating conditions, neutron powder diffraction experiments have been performed at the North Carolina State University PULSTAR reactor. The collected diffraction patterns exhibit intense broadening of several of the reflections, characteristic of turbostratic stacking. In order to quantify this disorder structurally, a model combined with a Rietveld-like refinement approach was implemented, which includes several refinable parameters that aim at describing this type of structure. Stacking parameters representing the probabilities of a random and registered shift between stacking packages were defined. The results indicate that the studied reactor grade graphite specimens contain a small fraction of layer disorder. The inferred interlayer spacing for the specimens is slightly larger than the theoretical value for graphite of 0.335 nm and the lattice constant is slightly less than 0.246 nm. The developed methodology is found to be successful in fitting the neutron diffraction patterns of reactor grade graphite.

  10. 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.

  11. Neutron diffraction measurements at the INES diffractometer using a neutron radiative capture based counting technique

    NASA Astrophysics Data System (ADS)

    Festa, G.; Pietropaolo, A.; Grazzi, F.; Barzagli, E.; Scherillo, A.; Schooneveld, E. M.

    2011-10-01

    The global shortage of 3He gas is an issue to be addressed in neutron detection. In the context of the research and development activity related to the replacement of 3He for neutron counting systems, neutron diffraction measurements performed on the INES beam line at the ISIS pulsed spallation neutron source are presented. For these measurements two different neutron counting devices have been used: a 20 bar pressure squashed 3He tube and a Yttrium-Aluminum-Perovskite scintillation detector. The scintillation detector was coupled to a cadmium sheet that registers the prompt radiative capture gamma rays generated by the ( n, γ) nuclear reactions occurring in cadmium. The assessment of the scintillator based counting system was done by performing a Rietveld refinement analysis on the diffraction pattern from an ancient Japanese blade and comparing the results with those obtained by a 3He tube placed at the same angular position. The results obtained demonstrate the considerable potential of the proposed counting approach based on the radiative capture gamma rays at spallation neutron sources.

  12. 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)

  13. 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.

  14. 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.

  15. 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.

  16. Neutron diffraction investigation of lattice microstrain in ferrite steel

    NASA Astrophysics Data System (ADS)

    Camanzi, A.; Moze, O.

    1992-06-01

    The degradation of carbon steels when exposed to H rich environments is well known to result in catastrophic failure. In order to characterize in a comprehensive manner the structural effects of hydrogenation, a series of high resolution neutron powder diffraction measurements were carried out on cross-sections of carbon steel segments used for gas pipelines. Peak positions were measured to an accuracy of 0.001%, whilst line broadening of individual peaks was measured to an accuracy of 0.1%. The ( h k l) dependent peak linewidths were fitted using a pseudo-Voigt peak shape function. Non-hydrogenated materials were found to display a different diffraction linewidth dependence on the crystal elastic anisotropy than hydrogenated materials.

  17. Palladium deuteride formation in the cathode of an electrochemical cell: An in situ neutron diffraction study

    SciTech Connect

    Rotella, F.J.; Richardson, J.W. Jr.; Redey, L.; Felcher, G.P.; Hitterman, R.L.; Kleb, R.

    1991-12-31

    In this report, neutron diffraction of palladium cathodes is utilized to reveal palladium deuteride formation within the crystal structure of the metal. The experiment described in this report demonstrates the efficacy of neutron powder diffraction as a tool for structural studies of metal deuterides/hydrides and the feasibility of in situ diffraction measurements from a working electrochemical cell. (JL)

  18. Palladium deuteride formation in the cathode of an electrochemical cell: An in situ neutron diffraction study

    SciTech Connect

    Rotella, F.J.; Richardson, J.W. Jr.; Redey, L.; Felcher, G.P.; Hitterman, R.L.; Kleb, R.

    1991-01-01

    In this report, neutron diffraction of palladium cathodes is utilized to reveal palladium deuteride formation within the crystal structure of the metal. The experiment described in this report demonstrates the efficacy of neutron powder diffraction as a tool for structural studies of metal deuterides/hydrides and the feasibility of in situ diffraction measurements from a working electrochemical cell. (JL)

  19. Neutron diffraction studies of welds of aerospace aluminum alloys

    SciTech Connect

    Martukanitz, R.P.; Howell, P.R.; Payzant, E.A.; Spooner, S.; Hubbard, C.R.

    1996-10-01

    Neutron diffraction and electron microscopy were done on residual stress in various regions comprising variable polarity plasma arc welds of alloys 2219 (Al-6.3Cu) and 2195 (Al-4.0Cu-1.0Li-0.5Mg-0.5Ag). Results indicate that lattice parameter changes in the various weld regions may be attributed to residual stresses generated during welding, as well as local changes in microstructure. Distribution of longitudinal and transverse stress of welded panels shows peaks of tension and compression, respectively, within the HAZ and corroborate earlier theoretical results. Position of these peaks are related to position of minimum strength within the HAZ, and the magnitude of these peaks are a fraction of the local yield strength in this region. Weldments of alloy 2195-T8 exhibited higher peak residual stress than alloy 2219-T87. Comparison of neutron diffraction and microstructural analysis indicate decreased lattice parameters associated with the solid solution of the near HAZ; this results in decreased apparent tensile residual stress within this region and may significantly alter interpretation of residual stress measurements of these alloys. Considerable relaxation of residual stress occurs during removal of specimens from welded panels and was used to aid in differentiating changes in lattice parameters attributed to residual stress from welding and modifications in microstructure.

  20. 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.

  1. Neutron and X-Ray Diffraction Studies of Advanced Materials

    SciTech Connect

    Barabash, Rozaliya; Tiley, Jaimie; Wang, Yandong; Liaw, Peter K

    2010-01-01

    The selection of articles in the special topic 'Neutron and X-Ray Studies of Advanced Materials' is based on the materials presented during the TMS 2009 annual meeting in San Francisco, CA, February 15-19, 2009. The development of ultrabrilliant third-generation synchrotron X-ray sources, together with advances in X-ray optics, has created intense X-ray microbeams, which provide the best opportunities for in-depth understanding of mechanical behavior in a broad spectrum of materials. Important applications include ultrasensitive elemental detection by X-ray fluorescence/absorption and microdiffraction to identify phase and strain with submicrometer spatial resolution. X-ray microdiffraction is a particularly exciting application compared with alternative probes of crystalline structure, orientation, and strain. X-ray microdiffraction is nondestructive with good strain resolution, competitive or superior spatial resolution in thick samples, and with the ability to probe below the sample surface. Moreover, the high-energy X-ray diffraction technique provides an effective tool for characterizing the mechanical and functional behavior in various environments (temperature, stress, and magnetic field). At the same time, some neutron diffraction instruments constructed mainly for the purpose of engineering applications can be found at nearly all neutron facilities. The first generation-dedicated instruments designed for studying in-situ mechanical behavior have been commissioned and used, and industrial standards for reliable and repeatable measurements have been developed. Furthermore, higher penetration of neutron beams into most engineering materials provides direct measurements on the distribution of various stresses (i.e., types I, II, and III) beneath the surface up to several millimeters, even tens of millimeters for important industrial components. With X-ray and neutron measurements, it is possible to characterize material behavior at different length scales. It

  2. 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.

  3. 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.

  4. A neutron diffraction study of ancient Greek ceramics

    NASA Astrophysics Data System (ADS)

    Siouris, I. M.; Walter, J.

    2006-11-01

    Non-destructive neutron diffraction studies were performed on three 2nd-century BC archaeological pottery fragments from the excavation site of Neos Scopos, Serres, in North Greece. In all the 273 K diagrams quartz and feldspars phase fractions are dominant. Diopside and iron oxide phases were also identifiable. The diopside content is found to decrease with increasing quartz-feldspar compositions. Iron oxides containing minerals were found to be present and the phase compositions reflect upon the coloring of the samples. However, the different content compositions of the phases may suggest different regions of the original clay materials as well as different preparation techniques. The firing temperatures were determined to be in the range of 900-1000 °C.

  5. Transmembrane location of retinal in bacteriorhodopsin by neutron diffraction

    SciTech Connect

    Hauss, T.; Grzesiek, S.; Otto, H.; Westerhausen, J.; Heyn, M.P. )

    1990-05-22

    The transmembrane location of the chromophore of bacteriorhodopsin was obtained by neutron diffraction on oriented stacks of purple membranes. Two selectively deuterated retinals were synthesized and incorporated in bacteriorhodopsin by using the retinal- mutant JW5: retinal-d11 (D11) contained 11 deuterons in the cyclohexene ring, and retinal-d5 (D5) had 5 deuterons as close as possible to the Schiff base end of the chromophore. The membrane stacks had a lamellar spacing of 53.1 A at 86% relative humidity. Five orders were observed in the lamellar diffraction pattern of the D11, D5, and nondeuterated reference samples. The reflections were phased by D2O-H2O exchange. The absolute values of the structure factors were nonlinear functions of the D2O content, suggesting that the coherently scattering domains consisted of asymmetric membrane stacks. The centers of deuteration were determined from the observed intensity differences between labeled and unlabeled samples by using model calculations and Fourier difference methods. With the origin of the coordinate system defined midway between consecutive intermembrane water layers, the coordinates of the center of deuteration of the D11 and D5 label are 10.5 +/- 1.2 and 3.8 +/- 1.5 A, respectively. Alternatively, the label distance may be measured from the nearest membrane surface as defined by the maximum in the neutron scattering length density at the water/membrane interface. With respect to this point, the D11 and D5 labels are located at a depth of 9.9 +/- 1.2 and 16.6 +/- 1.5 A, respectively. The chromophore is tilted with the Schiff base near the middle of the membrane and the ring closer to the membrane surface. The vector connecting the two label positions in the chromophore makes an angle of 40 +/- 12 degrees with the plane of the membrane.

  6. 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.

  7. 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.

  8. Novel diamond cells for neutron diffraction using multi-carat CVD anvils.

    PubMed

    Boehler, R; Molaison, J J; Haberl, B

    2017-08-01

    Traditionally, neutron diffraction at high pressure has been severely limited in pressure because low neutron flux required large sample volumes and therefore large volume presses. At the high-flux Spallation Neutron Source at the Oak Ridge National Laboratory, we have developed new, large-volume diamond anvil cells for neutron diffraction. The main features of these cells are multi-carat, single crystal chemical vapor deposition diamonds, very large diffraction apertures, and gas membranes to accommodate pressure stability, especially upon cooling. A new cell has been tested for diffraction up to 40 GPa with an unprecedented sample volume of ∼0.15 mm(3). High quality spectra were obtained in 1 h for crystalline Ni and in ∼8 h for disordered glassy carbon. These new techniques will open the way for routine megabar neutron diffraction experiments.

  9. Novel diamond cells for neutron diffraction using multi-carat CVD anvils

    NASA Astrophysics Data System (ADS)

    Boehler, R.; Molaison, J. J.; Haberl, B.

    2017-08-01

    Traditionally, neutron diffraction at high pressure has been severely limited in pressure because low neutron flux required large sample volumes and therefore large volume presses. At the high-flux Spallation Neutron Source at the Oak Ridge National Laboratory, we have developed new, large-volume diamond anvil cells for neutron diffraction. The main features of these cells are multi-carat, single crystal chemical vapor deposition diamonds, very large diffraction apertures, and gas membranes to accommodate pressure stability, especially upon cooling. A new cell has been tested for diffraction up to 40 GPa with an unprecedented sample volume of ˜0.15 mm3. High quality spectra were obtained in 1 h for crystalline Ni and in ˜8 h for disordered glassy carbon. These new techniques will open the way for routine megabar neutron diffraction experiments.

  10. Novel diamond cells for neutron diffraction using multi-carat CVD anvils

    DOE PAGES

    Boehler, R.; Molaison, J. J.; Haberl, Bianca

    2017-08-17

    Traditionally, neutron diffraction at high pressure has been severely limited in pressure because low neutron flux required large sample volumes and therefore large volume presses. At the high-flux Spallation Neutron Source at the Oak Ridge National Laboratory, we have developed new, large-volume diamond anvil cells for neutron diffraction. The main features of these cells are multi-carat, single crystal chemical vapor deposition diamonds, very large diffraction apertures, and gas membranes to accommodate pressure stability, especially upon cooling. A new cell has been tested for diffraction up to 40 GPa with an unprecedented sample volume of ~0.15 mm3. High quality spectra weremore » obtained in 1 h for crystalline Ni and in ~8 h for disordered glassy carbon. In conclusion, these new techniques will open the way for routine megabar neutron diffraction experiments.« less

  11. Novel diamond cells for neutron diffraction using multi-carat CVD anvils

    DOE PAGES

    Boehler, R.; Molaison, J. J.; Haberl, B.

    2017-08-17

    Traditionally, neutron diffraction at high pressure has been severely limited in pressure because low neutron flux required large sample volumes and therefore large volume presses. At the high-flux Spallation Neutron Source at the Oak Ridge National Laboratory, we have developed in this paper new, large-volume diamond anvil cells for neutron diffraction. The main features of these cells are multi-carat, single crystal chemical vapor deposition diamonds, very large diffraction apertures, and gas membranes to accommodate pressure stability, especially upon cooling. A new cell has been tested for diffraction up to 40 GPa with an unprecedented sample volume of ~0.15 mm3. Highmore » quality spectra were obtained in 1 h for crystalline Ni and in ~8 h for disordered glassy carbon. Finally, these new techniques will open the way for routine megabar neutron diffraction experiments.« less

  12. Novel diamond cells for neutron diffraction using multi-carat CVD anvils

    DOE PAGES

    Boehler, R.; Molaison, J. J.; Haberl, B.

    2017-08-17

    Traditionally, neutron diffraction at high pressure has been severely limited in pressure because low neutron flux required large sample volumes and therefore large volume presses. At the high-flux Spallation Neutron Source at the Oak Ridge National Laboratory, we have developed new, large-volume diamond anvil cells for neutron diffraction. Some main features of these cells are multi-carat, single crystal chemical vapor deposition diamonds, very large diffraction apertures, and gas membranes to accommodate pressure stability, especially upon cooling. A new cell has been tested for diffraction up to 40 GPa with an unprecedented sample volume of ~0.15 mm3. We obtained high qualitymore » spectra in 1 h for crystalline Ni and in ~8 h for disordered glassy carbon. These new techniques will open the way for routine megabar neutron diffraction experiments.« less

  13. 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.

  14. Large-volume diamond cells for neutron diffraction above 90GPa

    SciTech Connect

    Boehler, Reinhard; Guthrie, Malcolm; Molaison, Jamie J; Moreira Dos Santos, Antonio F; Sinogeikin, Stanislav; Machida, Shinichi; Pradhan, Neelam; Tulk, Christopher A

    2013-01-01

    Quantitative high pressure neutron-diffraction measurements have traditionally required large sample volumes of at least 25 mm3 due to limited neutron flux. Therefore, pressures in these experiments have been limited to below 25 GPa. In comparison, for X-ray diffraction, sample volumes in conventional diamond cells for pressures up to 100 GPa have been less than 1 10 4 mm3. Here, we report a new design of strongly supported conical diamond anvils for neutron diffraction that has reached 94 GPa with a sample volume of 2 10 2 mm3, a 100-fold increase. This sample volume is sufficient to measure full neutron-diffraction patterns of D2O ice to this pressure at the high flux Spallation Neutrons and Pressure beamline at the Oak Ridge National Laboratory. This provides an almost fourfold extension of the previous pressure regime for such measurements.

  15. 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

  16. Exploring the magnetic phase diagram of dysprosium with neutron diffraction

    NASA Astrophysics Data System (ADS)

    Yu, J.; LeClair, P. R.; Mankey, G. J.; Robertson, J. L.; Crow, M. L.; Tian, W.

    2015-01-01

    With one of the highest intrinsic magnetic moments (10.6 μB/atom ) among the heavy rare-earth elements, dysprosium exhibits a rich magnetic phase diagram, including several modulated magnetic phases. Aided by the Ruderman-Kittel-Kasuya-Yosida interaction, the magnetic modulations propagate coherently over a long range. Neutron diffraction experiments were performed to determine the microscopic magnetic origin of the field induced phases in bulk Dy as a function of temperature, covering regions of the well-known ferromagnetic, helical antiferromagnetic, fan phases, and several possible new phases suggested by previous studies. A short-range ordered fan phase was identified as the intermediate state between ferromagnetism and long-range ordered fan. In a field of 1 T applied along the a axis, the temperature range of a coexisting helix/fan phase was determined. The magnetic phase diagram of Dy was thus refined to include the detailed magnetic origin and the associated phase boundaries. Based on the period of the magnetic modulation and the average magnetization, the evolution of the spin arrangement upon heating was derived quantitatively for the modulated magnetic phases.

  17. Neutron diffraction observations of interstitial protons in dense Ice

    SciTech Connect

    Guthrie, Malcolm; Boehler, Reinhard; Tulk, Christopher A; Molaison, Jamie J; Moreira Dos Santos, Antonio F; Li, Kuo; Hemley, Russell

    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 similar to 13 GPa and cannot be described by the conventional network structure of ice VII above similar to 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.

  18. 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.

  19. 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.

  20. Neutron diffraction study of metal-matrix composite with fullerite

    NASA Astrophysics Data System (ADS)

    Borisova, P. A.; Blanter, M. S.; Brazhkin, VV; Somenkov, VA; Filonenko, V. P.

    2016-09-01

    Interaction of amorphous fullerite C60 with austenitic Fe-33.2 wt. % Ni alloy at pressures 0-8 GPa and temperatures 600-1100 °C was studied by neutron diffraction. The amorphous fullerite was obtained by ball milling and mixed with the powder of the crystalline alloy. The interaction at sintering led to the dissolution of carbon in fcc Fe-Ni solid solution and the formation of carbide (Fe, Ni)3C, but the Fe-Ni-C alloy did not undergo phase transformations and preserved the original fcc structure. As a result, the alloy hardened, we could also witness a clear barometric effect: at the pressure of 2 GPa the amount of the dissolved carbon and the microhardness turned out to be significantly higher than those at 8 GPa. During sintering amorphous fullerite is undergoing phase transitions and its microhardness is higher than the microhardness of the metal component. At high temperatures of interaction graphite appears. The presence of Fe-Ni alloy in the composite reduces the temperature of graphite formation in comparison with transformations in the pure amorphous fullerene.

  1. Magnetic susceptibility and neutron diffraction experiments on nuclear ordering in copper

    NASA Astrophysics Data System (ADS)

    Jyrkkio, Teppo

    Experimental curves of entropy and susceptibility versus temperature for copper nuclear spins down to the ordered state were obtained. Impurities and anomalous spin-lattice relaxation in copper at submilli-Kelvin temperatures were observed. Phase diagrams for spontaneous nuclear ordering in copper were derived. Nuclear antiferromagnetic ordering in copper was investigated. The feasibility of neutron diffraction experiments on ordered copper nuclei at nano-Kelvin temperature was studied. Neutron scattering experiments on nuclear magnets were carried out. Calibration and applications of polarized neutron thermometry at milli- and micro-Kelvin temperatures is described.Observation of nuclear antiferromagnetic order in copper by neutron diffraction at nano-Kelvin temparatures is reported.

  2. X-ray structure of perdeuterated diisopropyl fluorophosphatase (DFPase): perdeuteration of proteins for neutron diffraction

    PubMed Central

    Blum, Marc-Michael; Tomanicek, Stephen J.; John, Harald; Hanson, B. Leif; Rüterjans, Heinz; Schoenborn, Benno P.; Langan, Paul; Chen, Julian C.-H.

    2010-01-01

    The signal-to-noise ratio is one of the limiting factors in neutron macromolecular crystallography. Protein perdeuteration, which replaces all H atoms with deuterium, is a method of improving the signal-to-noise ratio of neutron crystallography experiments by reducing the incoherent scattering of the hydrogen isotope. Detailed analyses of perdeuterated and hydrogenated structures are necessary in order to evaluate the utility of perdeuterated crystals for neutron diffraction studies. The room-temperature X-ray structure of perdeuterated diisopropyl fluorophosphatase (DFPase) is reported at 2.1 Å resolution. Comparison with an independently refined hydrogenated room-temperature structure of DFPase revealed no major systematic differences, although the crystals of perdeuterated DFPase did not diffract neutrons. The lack of diffraction is examined with respect to data-collection and crystallo­graphic parameters. The diffraction characteristics of successful neutron structure determinations are presented as a guideline for future neutron diffraction studies of macromolecules. X-ray diffraction to beyond 2.0 Å resolution appears to be a strong predictor of successful neutron structures. PMID:20383004

  3. A neutron diffraction study of the zeolite edingtonitea)

    NASA Astrophysics Data System (ADS)

    Kvick, Åke; Smith, Joseph V.

    1983-09-01

    A neutron diffraction study at 294 K of a single crystal of edingtonite (Ba2Al4Si6O20 ṡ 7H2O; a 9.537(3) b 9.651(2) c 6.509(2) Å; P21212) utilized 1876 diffraction intensities from the Brookhaven National Laboratory high-flux beam reactor. The agreement factor R(F2)=0.055 for conventional anisotropic refinement was reduced to 0.045 for a Gram-Charlier expansion up to fourth order for the thermal factors of the water atoms. The Si-O and Al-O distances correlate inversely with the Si-O-Al angle as in scolecite. There is no indication of substitutional disorder. The barium atom is coordinated to three pairs of framework oxygens (2.89, 2.96, and 3.04 Å) and two pairs of water oxygens (2.79 and 2.79 Å). Two framework oxygens have weak hydrogen bonds to both water molecules [O(4)-OW(1) 2.87, -OW(2) 2.96; O(5) -OW(1) 3.02, -OW(2) 3.02 Å] and the other three framework oxygens are each bonded to a Ba atom. The OW-H ṡṡṡ O angles (163.5°, 165.1°, 173.9°, and 178.0°) are fairly close to 180°, the H ṡṡṡ O distances are long (1.91, 2.02, 2.09, and 2.10 Å) and the observed uncorrected OW-H distances range from 0.928(6) to 0.959(4) Å. Only seven out of the eight water positions are occupied [W(1) 84% occupancy; W(2) 91%]. The average rms displacement of each hydrogen (0.32, 0.29, 0.27, and 0.24 Å) correlates approximately with the hydrogen bond length (2.09, 2.10, 2.02, and 1.91 Å). Third- and fourth-order tensor components in the displacements of the water molecules may result from anharmonic or curvilinear vibrations; however, the effect of the static displacements of the center-of-motion from interaction with unoccupied water sites may also be important.

  4. Single crystal neutron diffraction refinement of bullvalene at 110 K

    SciTech Connect

    Luger, P.; Buschmann, J.; McMullan, R.K.; Ruble, J.R.; Matias, P.; Jeffrey, G.A.

    1986-11-26

    A low-temperature neutron diffraction refinement of the crystal structure of bullvalene, C/sub 10/H/sub 10/, tricyclo(3.3.2.0/sup 2.8/)deca-2,5,8-triene, shows that the molecule is distorted only very slightly from the C/sub 3 upsilon/ symmetry expected for the isolated molecule, although the crystal structure symmetry is monoclinic. There is a small but significant difference between the shortest and longest of the C-C bonds in the cyclopropane ring, which are 1.536 (1), 1.533 (1), and 1.530 (1) A. The three ethylenic wings of the molecule are virtually identical, except for small differences in planarity and C-C-H angles. One wing is exactly planar within 0.002 (3) A. In the other two, one of the hydrogen atoms in each is significantly displaced from the plane by 0.027 (3) and 0.023 (3) A. The mean bond lengths in the ethylenic wings are C/sub ring/-C, 1.4727 (7) A; C=C, 1.3423 (7) A; =C-C, 1.5163 (7) A. The C-H bond lengths range from 1.086 (2) to 1.092 (2) A. The thermal motion analysis gives an unusually good fit to the rigid-body model. Corrections for harmonic thermal motion lengthened all C-C and C=C bonds uniformly by 0.003 A. For the C-H bonds, the harmonic riding motion and anharmonicity corrections almost cancel, so that the thermally corrected bond lengths differ from those measured by +/- 0.001 A.

  5. 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.

  6. 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.

  7. Depolarization in the diffraction of polarized neutrons by a tungsten-186 single crystal

    SciTech Connect

    Aleksandrov, Y.A.; Vavra, J.; Vrana, M.; Goralik, L.; Kulda, I.; Lukash, P.; Mikula, P.; Chalupa, B.

    1985-09-10

    An observation of a depolarization of neutrons upon diffraction confirms that the paramagnetic phase of tungsten containing a microscopic cobalt impurity has regions in which the magnetic moments are ordered (magnetic clusters).

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

    NASA Astrophysics Data System (ADS)

    Branca, C.; Magazu', V.; Maisano, G.; Migliardo, F.; Soper, A. K.

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

  9. Investigation of Renal Stones by X-ray and Neutron Diffraction

    SciTech Connect

    Baeva, M.; Boianova, A.; Beskrovnyi, A. I.; Shelkova, I.

    2007-04-23

    Renal stones were investigated by X-ray diffraction. The obtained results showed only one crystal phase in every sample. With the aim to verify eventual availability of second phase (under 3 volume %) the same renal stones were investigated by neutron diffraction. The neutron spectra proved that additional crystal phase was absent in the renal stones. The obtained results are scientific-practical, in aid of the medicine, especially in the case of renal stone disease.

  10. Neutron Diffraction Investigations of Magnetism in BiFeO3 Epitaxial Films

    DTIC Science & Technology

    2011-01-01

    ordering temperatures are far too low for device applications. Perovskite-structured BiFeO 3 (BFO) with a rhom- bohedral distortion along the [111...where the magnetic moment lies in the HHL plane. Neutron Diffraction Investigations of Magnetism in BiFeO 3 Epitaxial Films The recovery of a...modulated magnetic structure in epitaxial BiFeO 3 thin fi lms as revealed by neutron diffraction is reported. The magnetic structure in thin fi lms is

  11. 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.

  12. 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.

  13. Neutron-diffraction characterization of tungsten-nickel-iron alloys. Preliminary technical report, 1984-1985

    SciTech Connect

    Prask, H.J.; Choi, C.S.

    1986-02-01

    Neutron diffraction and small-angle scattering were employed to elucidate the effect of strain aging on macroscopic properties of tungsten-nickel-iron (W-.07Ni-.03Fe) alloys. The neutron measurements indicate that strain aging causes reduction and redistribution of residual stresses induced by swaging, accompanied by void/precipitate evolution.

  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. 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.

  16. Verification of the weak equivalence principle with Laue diffracting neutrons: Test experiment

    NASA Astrophysics Data System (ADS)

    Vezhlev, E. O.; Voronin, V. V.; Kuznetsov, I. A.; Semenikhin, S. Yu.; Fedorov, V. V.

    2013-07-01

    We propose a novel experiment to test the weak equivalence principle (WEP) for the Laue diffracting neutron. Our experiment is based on an essential magnification of an external affect on neutron diffracting by Laue for the Bragg angles close to the right one in couple with additional enhancement factor which exists due to the delay of the Laue diffracting neutron at such Bragg angles. This enhancement phenomena is proposed to be utilized for measuring the force which deviates from zero if WEP is violated. The accuracy of measuring inertial to gravitational neutron masses ratio for the introduced setup can reach ˜10-5, which is more than one order superior to the best present-day result.

  17. Neutron diffraction and X-ray diffraction investigations of langasite crystals

    SciTech Connect

    Kuz'micheva, G. M.; Zakharko, O.; Tyunina, E. A.; Rybakov, V. B.; Domoroshchina, E. N.; Dubovskii, A. B.

    2008-11-15

    Crystals of langasite La{sub 3}Ga{sub 4}(GaSi)O{sub 14} grown by the Czochralski method are studied using neutron diffraction for the first time. It is established that the compositions of the upper and lower parts of an orange crystal grown from the La{sub 3}Ga{sub 5.14}Si{sub 0.86}O{sub 14} seed in an (Ar + O{sub 2}) atmosphere (the < 0001 > growth direction) can be written as(La{sub 2.85(2)}{open_square}{sub 0.15})(Ga{sub 0.95(2)}{open_square}{sub 0.05}) Ga{sub 3}(Ga{sub 1.15} Si{sub 0.85(5)})(O{sub 13.72}{open_square}{sub 0.28(7)}) and(La{sub 2.89(1)}{open_square}{sub 0.11}).(Ga{sub 0.98(1)}{open_square}{sub 0.02}) Ga{sub 3}(Ga{sub 1.06}Si{sub 0.94(4)})(O{sub 13.81}{open_square}{sub 0.19(9)}), respectively. The La content in the upper and lower parts of this crystal is lower and higher than the Ga content, respectively, and the Ga content exceeds the Si content in the (GaSi) position. By contrast, in a colorless crystal of the composition(La {sub 2.97(4)}{open_square}{sub 0.03}) Ga(1)(Ga{sub 2.94(9)}{open_square}{sub 0.06})(Ga{sub 0.7(1)} Si{sub 1.3})(O{sub 13.9}{open_square}{sub 0.1(1)}), which is grown from the La{sub 3} Ga{sub 5}SiO{sub 14} seed in an argon atmosphere (the < 011-bar1 Watch growth direction), the Ga content in the (GaSi) position is lower than the Si content. A relation between the Ga: Si ratio and the (Ga,Si)-3O interatomic distances is found.

  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. A preliminary neutron diffraction study of rasburicase, a recombinant urate oxidase enzyme, complexed with 8-azaxanthin

    SciTech Connect

    Budayova-Spano, Monika; Bonneté, Françoise; Ferté, Natalie; El Hajji, Mohamed; Meilleur, Flora; Blakeley, Matthew Paul; Castro, Bertrand

    2006-03-01

    Neutron diffraction data of hydrogenated recombinant urate oxidase enzyme (Rasburicase), complexed with a purine-type inhibitor 8-azaxanthin, was collected to 2.1 Å resolution from a crystal grown in D{sub 2}O by careful control and optimization of crystallization conditions via knowledge of the phase diagram. Deuterium atoms were clearly seen in the neutron-scattering density map. Crystallization and preliminary neutron diffraction measurements of rasburicase, a recombinant urate oxidase enzyme expressed by a genetically modified Saccharomyces cerevisiae strain, complexed with a purine-type inhibitor (8-azaxanthin) are reported. Neutron Laue diffraction data were collected to 2.1 Å resolution using the LADI instrument from a crystal (grown in D{sub 2}O) with volume 1.8 mm{sup 3}. The aim of this neutron diffraction study is to determine the protonation states of the inhibitor and residues within the active site. This will lead to improved comprehension of the enzymatic mechanism of this important enzyme, which is used as a protein drug to reduce toxic uric acid accumulation during chemotherapy. This paper illustrates the high quality of the neutron diffraction data collected, which are suitable for high-resolution structural analysis. In comparison with other neutron protein crystallography studies to date in which a hydrogenated protein has been used, the volume of the crystal was relatively small and yet the data still extend to high resolution. Furthermore, urate oxidase has one of the largest primitive unit-cell volumes (space group I222, unit-cell parameters a = 80, b = 96, c = 106 Å) and molecular weights (135 kDa for the homotetramer) so far successfully studied with neutrons.

  20. 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.

  1. in-situ chemistry mapping of hydrogen storage materials by neutron diffraction

    SciTech Connect

    Payzant, E Andrew; Bowman Jr, Robert C; Johnson, Terry A; Jorgensen, Scott W

    2013-01-01

    Neutron diffraction was used to nondestructively study the microstructures for two hydrogen storage media systems. In the first case, sodium alanate based hydrogen storage is a vehicle-scale candidate system developed by Sandia/GM. Neutron scattering was used to determine the distribution of phases in the storage media at different hydrogen loading levels, to help understand the absorption/desorption of hydrogen in large-scale systems. This study also included a 3D neutron tomographic study of the microstructure. In the second case, tin-doped lanthanum nickel alloys have been studied at JPL for space-based applications, for which the gradual degradation of the material due to segregation and disproportionation of phases is a known problem. A regenerative process developed to restore the storage properties of these alloys was studied, using in-situ neutron diffraction to relate the microstructure to the thermodynamic simulations.

  2. 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.

  3. 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.

  4. 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

  5. Adaptation of a neutron diffraction detector to coded aperture imaging

    SciTech Connect

    Vanier, P.E.; Forman, L.

    1997-02-01

    A coded aperture neutron imaging system developed at Brookhaven National Laboratory (BNL) has demonstrated that it is possible to record not only a flux of thermal neutrons at some position, but also the directions from whence they came. This realization of an idea which defied the conventional wisdom has provided a device which has never before been available to the nuclear physics community. A number of potential applications have been explored, including (1) counting warheads on a bus or in a storage area, (2) investigating inhomogeneities in drums of Pu-containing waste to facilitate non-destructive assays, (3) monitoring of vaults containing accountable materials, (4) detection of buried land mines, and (5) locating solid deposits of nuclear material held up in gaseous diffusion plants.

  6. 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.

  7. Neutron diffraction analysis of Pseudomonas aeruginosa peptidyl-tRNA hydrolase 1.

    PubMed

    McFeeters, Hana; Vandavasi, Venu Gopal; Weiss, Kevin L; Coates, Leighton; McFeeters, Robert L

    2016-03-01

    Perdeuterated peptidyl-tRNA hydrolase 1 from Pseudomonas aeruginosa was crystallized for structural analysis using neutron diffraction. Crystals of perdeuterated protein were grown to 0.15 mm(3) in size using batch crystallization in 22.5% polyethylene glycol 4000, 100 mM Tris pH 7.5, 10%(v/v) isopropyl alcohol with a 20-molar excess of trilysine as an additive. Neutron diffraction data were collected from a crystal at room temperature using the MaNDi single-crystal diffractometer at Oak Ridge National Laboratory.

  8. Observation of a strong interplanar electric field in a dynamical diffraction of polarized neutrons

    NASA Astrophysics Data System (ADS)

    Alexeev, V. L.; Fedorov, V. V.; Lapin, E. G.; Leushkin, E. K.; Rumiantsev, V. L.; Sumbaev, O. I.; Voronin, V. V.

    1989-11-01

    The first experimental study of the Schwinger interaction of polarized neutrons with an electric field of a noncentrosymmetric perfect crystal (α-quartz) was made for two wave dynamical diffraction. Phase shifts of Pendellösung fringes for two different spin to crystal field orientations were measured. The theory of the effect is given. The calculated value of SiO2 (11 overline20) interplanar electr field, seen by the diffracted neutron, is 2.1 × 10 8 V/cm. This is in good agreement with the experimental result: (1.8 ± 0.3) × 10 8 V/cm.

  9. Direct measurement of the quartz c-axis using neutron diffraction

    NASA Astrophysics Data System (ADS)

    Hunter, Nicholas J. R.; Luzin, Vladimir; Wilson, Christopher J. L.

    2017-08-01

    Quartz c-axis pole figures are widely used across structural geology and geophysics to gain insights into crustal properties, yet their direct measurement using bulk diffraction techniques has hitherto been unsuccessful. In this contribution, we present measurements of the quartz c-axis using neutron diffraction. This has been achieved by combining advances in neutron diffraction instrumentation, high neutron fluxes and fast data acquisition, with carefully performed diffraction pattern analysis to resolve low intensity diffractions on the (003) diffraction peak hidden in the shoulder of the higher intensity (112) peak. These measurements have allowed us to assess 'recalculated' c-axis pole figures (i.e. those predicted from ODF functions) against measured c-axis pole figures, and thus assess the reliability of quartz c-axis pole figures past and present. We find that measured and recalculated pole figures are generally in good agreement in both strongly and weakly textured rocks, and that inclusion of the (003) pole figure into quartz texture analysis routines improves ODF construction.

  10. 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}.

  11. Neutron diffraction study of the cube texture development in FeNi53% alloy

    NASA Astrophysics Data System (ADS)

    Branger, V.; Mathon, M. H.; Baudin, T.; Penelle, R.

    2000-03-01

    Crystallographic texture evolution during thermal annealing of the Fe-Ni53% alloy (94% rolled) has been characterized by “in situ” neutron diffraction. The texture components analysis, has allowed to follow the cube volume fraction component formation and its expansion to the wreckage of the deformation ones.

  12. Empirically testing vaterite structural models using neutron diffraction and thermal analysis

    NASA Astrophysics Data System (ADS)

    Chakoumakos, Bryan C.; Pracheil, Brenda M.; Koenigs, Ryan P.; Bruch, Ronald M.; Feygenson, Mikhail

    2016-11-01

    Otoliths, calcium carbonate (CaCO3) ear bones, are among the most commonly used age and growth structures of fishes. Most fish otoliths are comprised of the most dense CaCO3 polymorph, aragonite. Sturgeon otoliths, in contrast, have been characterized as the rare and structurally enigmatic polymorph, vaterite—a metastable polymorph of CaCO3. Vaterite is an important material ranging from biomedical to personal care applications although its crystal structure is highly debated. We characterized the structure of Lake Sturgeon otoliths using thermal analysis and neutron powder diffraction, which is used non-destructively. We confirmed that while Lake Sturgeon otoliths are primarily composed of vaterite, they also contain the denser CaCO3 polymorph, calcite. For the vaterite fraction, neutron diffraction data provide enhanced discrimination of the carbonate group compared to x-ray diffraction data, owing to the different relative neutron scattering lengths, and thus offer the opportunity to uniquely test the more than one dozen crystal structural models that have been proposed for vaterite. Of those, space group P6522 model, a = 7.1443(4)Å, c = 25.350(4)Å, V = 1121.5(2)Å3 provides the best fit to the neutron powder diffraction data, and allows for a structure refinement using rigid carbonate groups.

  13. Empirically testing vaterite structural models using neutron diffraction and thermal analysis

    DOE PAGES

    Chakoumakos, Bryan C.; Pracheil, Brenda M.; Koenigs, Ryan; ...

    2016-11-18

    Otoliths, calcium carbonate (CaCO3) ear bones, are among the most commonly used age and growth structures of fishes. Most fish otoliths are comprised of the most dense CaCO3 polymorph, aragonite. Sturgeon otoliths, in contrast, have been characterized as the rare and structurally enigmatic polymorph, vaterite a metastable polymorph of CaCO3. Vaterite is an important material ranging from biomedical to personal care applications although its crystal structure is highly debated. We characterized the structure of sturgeon otoliths using thermal analysis and neutron powder diffraction, which is used non-destructively. We confirmed that while sturgeon otoliths are primarily composed of vaterite, they alsomore » contain the denser CaCO3 polymorph, calcite. For the vaterite fraction, neutron diffraction data provide enhanced discrimination of the carbonate group compared to x-ray diffraction data, owing to the different relative neutron scattering lengths, and thus offer the opportunity to uniquely test the more than one dozen crystal structural models that have been proposed for vaterite. Of those, space group P6522 model, a = 7.1443(4)Å , c = 25.350(4)Å , V = 1121.5(2)Å3 provides the best fit to the neutron powder diffraction data, and allows for a structure refinement using rigid carbonate groups.« less

  14. Empirically testing vaterite structural models using neutron diffraction and thermal analysis

    SciTech Connect

    Chakoumakos, Bryan C.; Pracheil, Brenda M.; Koenigs, Ryan; Bruch, Ronald; Feygenson, Mikhail

    2016-11-18

    Otoliths, calcium carbonate (CaCO3) ear bones, are among the most commonly used age and growth structures of fishes. Most fish otoliths are comprised of the most dense CaCO3 polymorph, aragonite. Sturgeon otoliths, in contrast, have been characterized as the rare and structurally enigmatic polymorph, vaterite a metastable polymorph of CaCO3. Vaterite is an important material ranging from biomedical to personal care applications although its crystal structure is highly debated. We characterized the structure of sturgeon otoliths using thermal analysis and neutron powder diffraction, which is used non-destructively. We confirmed that while sturgeon otoliths are primarily composed of vaterite, they also contain the denser CaCO3 polymorph, calcite. For the vaterite fraction, neutron diffraction data provide enhanced discrimination of the carbonate group compared to x-ray diffraction data, owing to the different relative neutron scattering lengths, and thus offer the opportunity to uniquely test the more than one dozen crystal structural models that have been proposed for vaterite. Of those, space group P6522 model, a = 7.1443(4)Å , c = 25.350(4)Å , V = 1121.5(2)Å3 provides the best fit to the neutron powder diffraction data, and allows for a structure refinement using rigid carbonate groups.

  15. Empirically testing vaterite structural models using neutron diffraction and thermal analysis

    PubMed Central

    Chakoumakos, Bryan C.; Pracheil, Brenda M.; Koenigs, Ryan P.; Bruch, Ronald M.; Feygenson, Mikhail

    2016-01-01

    Otoliths, calcium carbonate (CaCO3) ear bones, are among the most commonly used age and growth structures of fishes. Most fish otoliths are comprised of the most dense CaCO3 polymorph, aragonite. Sturgeon otoliths, in contrast, have been characterized as the rare and structurally enigmatic polymorph, vaterite—a metastable polymorph of CaCO3. Vaterite is an important material ranging from biomedical to personal care applications although its crystal structure is highly debated. We characterized the structure of Lake Sturgeon otoliths using thermal analysis and neutron powder diffraction, which is used non-destructively. We confirmed that while Lake Sturgeon otoliths are primarily composed of vaterite, they also contain the denser CaCO3 polymorph, calcite. For the vaterite fraction, neutron diffraction data provide enhanced discrimination of the carbonate group compared to x-ray diffraction data, owing to the different relative neutron scattering lengths, and thus offer the opportunity to uniquely test the more than one dozen crystal structural models that have been proposed for vaterite. Of those, space group P6522 model, a = 7.1443(4)Å, c = 25.350(4)Å, V = 1121.5(2)Å3 provides the best fit to the neutron powder diffraction data, and allows for a structure refinement using rigid carbonate groups. PMID:27857219

  16. Protein crystallization and initial neutron diffraction studies of the photosystem II subunit PsbO.

    PubMed

    Bommer, Martin; Coates, Leighton; Dau, Holger; Zouni, Athina; Dobbek, Holger

    2017-09-01

    The PsbO protein of photosystem II stabilizes the active-site manganese cluster and is thought to act as a proton antenna. To enable neutron diffraction studies, crystals of the β-barrel core of PsbO were grown in capillaries. The crystals were optimized by screening additives in a counter-diffusion setup in which the protein and reservoir solutions were separated by a 1% agarose plug. Crystals were cross-linked with glutaraldehyde. Initial neutron diffraction data were collected from a 0.25 mm(3) crystal at room temperature using the MaNDi single-crystal diffractometer at the Spallation Neutron Source, Oak Ridge National Laboratory.

  17. 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.

  18. Neutron Radiography, Tomography, and Diffraction of Commercial Lithium-ion Polymer Batteries

    NASA Astrophysics Data System (ADS)

    Butler, Leslie G.; Lehmann, Eberhard H.; Schillinger, Burkhard

    Imaging an intact, commercial battery as it cycles and wears is proved possible with neutron imaging. The wavelength range of imaging neutrons corresponds nicely with crystallographic dimensions of the electrochemically active species and the metal elec- trodes are relatively transparent. The time scale of charge/discharge cycling is well matched to dynamic tomography as performed with a golden ratio based projection angle ordering. The hydrogen content does create scatter which tends to blur internal struc- ture. In this report, three neutron experiments will be described: 3D images of charged and discharged batteries were obtained with monochromatic neutrons at the FRM II reactor. 2D images (PSI) of fresh and worn batteries as a function of charge state may show a new wear pattern. In situ neutron diffraction (SNS) of the intact battery provides more information about the concentrations of electrochemical species within the battery as a function of charge state and wear. The combination of 2D imaging, 3D imaging, and diffraction data show how neutron imaging can contribute to battery development and wear monitoring.

  19. In-situ neutron diffraction measurements of temperature and stresses during friction stir welding of 6061-T6 aluminum alloy

    SciTech Connect

    Woo, Wan Chuck; Feng, Zhili; Wang, Xun-Li; Brown, D. W.; Clausen, B; An, Ke; Choo, Hahn; Hubbard, Camden R; David, Stan A

    2007-01-01

    The evolution of temperature and thermal stresses during friction stir welding of Al6061-T6 was investigated by means of in-situ, time-resolved neutron diffraction technique. A method is developed to deconvolute the temperature and stress from the lattice spacing changes measured by neutron diffraction. The deep penetration capability of neutrons made it possible for the first time to obtain the temperature and thermal stresses inside a friction stir weld.

  20. In-situ neutron diffraction measurements of temperature and stresses during friction stir welding of 6061-T6 aluminum alloy

    SciTech Connect

    Feng, Zhili; Wang, Xun-Li; David, Stan A; Choo, Hahn; Hubbard, Camden R; Woo, Wan Chuck; Brown, D. W.; Clausen, B; An, Ke

    2007-01-01

    The evolution of temperature and thermal stresses during friction stir welding of Al6061-T6 was investigated by means of in situ, time resolved neutron diffraction technique. A method was developed to deconvolute the temperature and stress from the lattice spacing changes measured by neutron diffraction. The deep penetration capability of neutrons made it possible for the first time to obtain the temperature and thermal stresses inside a friction stir weld.

  1. Neutron diffraction studies of magnetic-shape memory Ni-Mn-Ga single crystal

    NASA Astrophysics Data System (ADS)

    Heczko, Oleg; Prokes, Karel; Hannula, Simo-Pekka

    2007-09-01

    Neutron diffraction of single crystal of the typical example of magnetic-shape memory (MSM) alloy Ni 49.7Mn 29.3Ga 21 was carried out with a 2D position sensitive detector. The quality and inhomogeneity of the single crystal and martensite variant distribution was studied using ω-scan of selected nuclear Bragg reflections. The neutron diffraction reveals split of the (2 0 0) reflection of major martensite variant and large structural inhomogeneities in martensite phase. Using measurement in reciprocal space, we recorded a set of reflections that appear due to structural modulation (5 M) of the martensite, however, the set seems to be incomplete with missing or very weak reflections of second order compared with X-ray diffraction. The line of the magnetic reflection arising from the supposed antiferromagnetic ordering of the excess Mn atoms was very weak and it is difficult to discern from the background.

  2. 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).

  3. 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).

  4. 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.; Kelton, K. F.; Rustan, G. E.; Quirinale, D. G.; Goldman, A. I.; Kreyssig, A.; Lokshin, K. A.; Neuefeind, J. C.; An, Ke; Wang, Xun-Li; Egami, T.

    2016-01-15

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

  5. 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.; ...

    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

  6. 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).

  7. Preliminary time-of-flight neutron diffraction study on diisopropyl fluorophosphatase (DFPase) from Loligo vulgaris

    SciTech Connect

    Blum, Marc-Michael; Koglin, Alexander; Rüterjans, Heinz; Schoenborn, Benno; Langan, Paul; Chen, Julian C.-H.

    2007-01-01

    Diisopropyl fluorophosphatase (DFPase) effectively hydrolyzes a number of organophosphorus nerve agents, including sarin, cyclohexylsarin, soman and tabun. Neutron diffraction data have been collected from DFPase crystals to 2.2 Å resolution in an effort to gain further insight into the mechanism of this enzyme. The enzyme diisopropyl fluorophosphatase (DFPase) from Loligo vulgaris is capable of decontaminating a wide variety of toxic organophosphorus nerve agents. DFPase is structurally related to a number of enzymes, such as the medically important paraoxonase (PON). In order to investigate the reaction mechanism of this phosphotriesterase and to elucidate the protonation state of the active-site residues, large-sized crystals of DFPase have been prepared for neutron diffraction studies. Available H atoms have been exchanged through vapour diffusion against D{sub 2}O-containing mother liquor in the capillary. A neutron data set has been collected to 2.2 Å resolution on a relatively small (0.43 mm{sup 3}) crystal at the spallation source in Los Alamos. The sample size and asymmetric unit requirements for the feasibility of neutron diffraction studies are summarized.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Stress-induced martensite variant reorientation in magnetic shape memory Ni Mn Ga single crystal studied by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Molnar, P.; Sittner, P.; Lukas, P.; Hannula, S.-P.; Heczko, O.

    2008-06-01

    Stress-induced martensite variant reorientation in magnetic shape memory Ni-Mn-Ga single crystal was studied in situ by the neutron diffraction technique. Principles of determination of individual tetragonal martensitic variants in shape memory alloys are explained. Using neutron diffraction we show that the macroscopic strain originates solely from the martensite structure reorientation or variant redistribution. Neutron diffraction also reveals that the reorientation of martensite is not fully completed even at a stress value of 25 MPa, which is about 20 times larger than the mean stress needed for reorientation. Only one twinning system is active during the reorientation process.

  13. Neutron and X-ray Microbeam Diffraction Studies around a Fatigue-Crack Tip after Overload

    SciTech Connect

    Lee, Sooyeol; Barabash, Rozaliya; Chung, Jin-Seok; Liaw, Peter K; Choo, Hahn; Sun, Yinan; Fan, C; Li, Li; Brown, Donald; Ice, Gene E

    2008-01-01

    An in-situ neutron diffraction technique was used to investigate the lattice-strain distributions and plastic deformation around a crack tip after overload. The lattice-strain profiles around a crack tip were measured as a function of the applied load during the tensile loading cycles after overload. Dislocation densities calculated from the diffraction peak broadening were presented as a function of the distance from the crack tip. Furthermore, the crystallographic orientation variations were examined near a crack tip using polychromatic X-ray microdiffraction combined with differential aperture microscopy. Crystallographic tilts are considerably observed beneath the surface around a crack tip, and these are consistent with the high dislocation densities near the crack tip measured by neutron peak broadening.

  14. Structural analysis of a completely amorphous {sup 238}Pu-doped zircon by neutron diffraction.

    SciTech Connect

    Fortner, J. A.; Badyal, Y.; Price, D. C.; Hanchar, J. M.; Weber, W. J.; Materials Science Division; PNNL

    1999-01-01

    The structure of a completely amorphous zircon was determined by time-of-flight neutron diffraction at Argonne's Intense Pulsed Neutron Source (IPNS). The sample of metamict zircon (ZrSiO{sub 4}), initially doped to 8.85 weight percent {sup 238}Pu, had been completely amorphized by alpha-recoil damage since its synthesis in 1981 at the Pacific Northwest National Laboratory (PNNL). The measured diffraction structure factor, S(Q), indicated a completely amorphous sample, with no signs of residual zircon microcrystallinity. The pair distribution function obtained indicated that the structure was that of an oxide glass, retaining the Si-0, Zr-0, and O-O bond lengths of crystalline zircon.

  15. Structural analysis of a completely amorphous {sup 238}Pu-doped zircon by neutron diffraction.

    SciTech Connect

    Fortner, J. A.

    1998-12-16

    The structure of a completely amorphous zircon was determined by time-of-flight neutron diffraction at Argonne's Intense Pulsed Neutron Source (IPNS). The sample of metamict zircon (ZrSiO{sub 4}),initially doped to 8.85 weight percent {sup 238}Pi, had been completely amorphized by alpha-recoil damage since its synthesis in 1981 at the Pacific Northwest National Laboratory (PNNL). The measured diffraction structure factor, S(Q), indicated a completely amorphous sample, with no signs of residual zircon microcrystallinity. The pair distribution function obtained indicated that the structure was that of an oxide glass, retaining the Si-0, Zr-0, and O-O bond lengths of crystalline zircon.

  16. Numerical and neutron diffraction measurement of residual stress distribution in dissimilar weld

    DOE PAGES

    Eisazadeh, Hamid; Bunn, Jeffrey R.; Aidun, Daryush K.

    2017-01-01

    In this study, a model considering an asymmetric power heat distribution, temperature-dependent material properties, strain hardening and phase transformation was developed to predict temperature field and residual stress distribution in GTA dissimilar weld between austenitic stainless steel (304) and low carbon steel (1018). The effect of martensite formation on longitudinal and transverse residual stress distributions were investigated using both FE model and neutron diffraction measurement. The results indicate that martensitic phase has a significant influence on both residual stress components, i.e., transverse and longitudinal, and it not only can change the distribution shape of residual stress near the weld centermore » line but, also, can alter the peak value of the residual stresses. The calculated temperature and weld zone profile were in agreement with the experimental results. Favorable general agreement was also found between the calculated residual stress distribution and residual stress measurements by the neutron diffraction method.« less

  17. Numerical and neutron diffraction measurement of residual stress distribution in dissimilar weld

    SciTech Connect

    Eisazadeh, Hamid; Bunn, Jeffrey R.; Aidun, Daryush K.

    2017-01-01

    In this study, a model considering an asymmetric power heat distribution, temperature-dependent material properties, strain hardening and phase transformation was developed to predict temperature field and residual stress distribution in GTA dissimilar weld between austenitic stainless steel (304) and low carbon steel (1018). The effect of martensite formation on longitudinal and transverse residual stress distributions were investigated using both FE model and neutron diffraction measurement. The results indicate that martensitic phase has a significant influence on both residual stress components, i.e., transverse and longitudinal, and it not only can change the distribution shape of residual stress near the weld center line but, also, can alter the peak value of the residual stresses. The calculated temperature and weld zone profile were in agreement with the experimental results. Favorable general agreement was also found between the calculated residual stress distribution and residual stress measurements by the neutron diffraction method.

  18. 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).

  19. Lithium plating in lithium-ion batteries investigated by voltage relaxation and in situ neutron diffraction

    NASA Astrophysics Data System (ADS)

    von Lüders, Christian; Zinth, Veronika; Erhard, Simon V.; Osswald, Patrick J.; Hofmann, Michael; Gilles, Ralph; Jossen, Andreas

    2017-02-01

    In this work, lithium plating is investigated by means of voltage relaxation and in situ neutron diffraction in commercial lithium-ion batteries. We can directly correlate the voltage curve after the lithium plating with the ongoing phase transformation from LiC12 to LiC6 according to the neutron diffraction data during the relaxation. Above a threshold current of C/2 at a temperature of -2 °C, lithium plating increases dramatically. The results indicate that the intercalation rate of deposited lithium seems to be constant, independent of the deposited amount. It can be observed that the amount of plating correlates with the charging rate, whereas a charging current of C/2 leads to a deposited amount of lithium of 5.5% of the charge capacity and a current of 1C to 9.0%.

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

    NASA Astrophysics Data System (ADS)

    O'Neill, Brian; Tenailleau, Christophe; Nogthai, Yung; Studer, Andrew; Brugger, Joël; Pring, Allan

    2006-11-01

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

  1. 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.

  2. Crystallographic texture of straight-rolled ?-uranium foils via neutron and X-ray diffraction

    DOE PAGES

    Einhorn, J. R.; Steiner, M. A.; Vogel, S. C.; ...

    2017-05-25

    The texture of recrystallized straight-rolled ?-uranium foils, a component in prospective irradiation target designs for medical isotope production, has been measured by neutron diffraction, as well as X-ray diffraction using both Cu and Mo sources. Variations in the penetration depth of neutron and X-ray radiation allow for determination of both the bulk and surface textures. The bulk ?-uranium foil texture is similar to the warm straight-rolled plate texture, with the addition of a notable splitting of the (001) poles along the transverse direction. The surface texture of the foils is similar to the bulk, with an additional (001) texture componentmore » that is oriented between the rolling and normal directions. Differences between the surface and bulk textures are expected to arise from shear forces during the rolling process and the influence that distinct strain histories have on subsequent texture evolution during recrystallization.« less

  3. Testing energy quantization at the level of 100 kHz by neutron crystal diffraction

    NASA Astrophysics Data System (ADS)

    Summhammer, J.

    1996-10-01

    For the study of energy quantization in low-frequency potentials and the accompanying quantum effects we analyze a silicon double-crystal arrangement exploiting dynamical diffraction of neutrons to achieve the required extremely high energy resolution. The first crystal prepares a minimum-uncertainty beam that passes a potential region whose influence on the neutron energy is analyzed by the second crystal. With realistic parameters, changes of neutron energy below 0.5 neV can be resolved. This permits a test of quantized energy transfer in periodically time-dependent potentials of a frequency below 100 kHz. We also discuss three specific examples how to observe the quantum phenomena arising from the macroscopic wave packets thereby generated.

  4. 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.

  5. Residual stress measurements on a stress relieved Zircaloy-4 weld by neutron diffraction

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

    The macroscopic stress distribution across an annealed Zircaloy-4 gas tungsten arc weld was measured by neutron time-of-flight diffraction at the SMARTS diffractometer at Los Alamos National Laboratory. The stresses after annealing are about 40% lower than those in the same weld prior to heat treatment. The intergranular strains in the reference coupons, which give the macroscopic stress free lattice spacings, are consistent with the difference in cooling the strongly textured plate and the weakly textured weld.

  6. 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.

  7. 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.

  8. Residual strain scanning of alumina-based ceramic composites by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Ruiz-Hervias, J.; Bruno, G.; Bueno, S.; Gurauskis, J.; Baudín, C.; Fan, K. Y.

    2014-11-01

    Residual strain profiles were measured by neutron diffraction in alumina-aluminum titanate ceramic composites sintered at two different temperatures, namely 1450 and 1550°C. The results show that irrespective of the direction and the sintering temperature, the obtained profiles are almost flat, with very similar results for both temperatures. In addition, the results demonstrate that the alumina is in compression whereas the aluminium titanate is subjected to tensile residual stresses.

  9. 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.

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

    SciTech Connect

    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 cubic 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.

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

    DOE PAGES

    Wang, H.; Kirkham, M. J.; Watkins, T. R.; ...

    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

  12. A γ-ray detector with a silicon photomultiplier (SiPM) readout for neutron diffraction experiments at spallation neutron sources

    NASA Astrophysics Data System (ADS)

    Festa, G.; Pietropaolo, A.; Reali, E.; Grazzi, F.; Schooneveld, E. M.

    2010-03-01

    Standard detectors for neutron diffraction experiments are typically 3He filled proportional counters. Indeed, in the near future the 3He availability will be greatly reduced, so the R&D activity on alternative neutron counters is a very important issue to be addressed. Scintillator detectors could be considered as one of these alternatives. In this context, a prototype thermal neutron counter composed of a yttrium-aluminium-perovskite scintillator crystal coupled to a silicon photomultiplier (SiPM) and a standard photomultiplier tube (PMT) was used in time of flight neutron diffraction experiments on the INES spectrometer at the ISIS spallation neutron source. Neutron detection was realized by attaching the crystal to a natural cadmium sheet, used as a (n, γ) converter. Results show that the SiPM-based readout detection system has promising performances with respect to that based on a standard PMT. Diffraction patterns recorded with the 3He tubes' neutron counters in use on INES allowed a comparative assessment of the SiPM-based device for time of flight neutron diffraction experiments, with respect to the standard detection technique.

  13. An improved prompt gamma neutron activation analysis facility using a focused diffracted neutron beam

    NASA Astrophysics Data System (ADS)

    Riley, Kent J.; Harling, Otto K.

    1998-09-01

    The performance of the prompt gamma neutron activation analysis (PGNAA) facility at the MIT Research Reactor has been improved by a series of modifications. These modifications have increased the flux by a factor of three at the sample position to 1.7 × 10 7 n/cm 2 s, and have increased the sensitivity, on average, by a factor of 2.5. The background for many samples of interest is dominated by unavoidable neutron interactions that occur in or near the sample. Other background components comprise only 20% of the total background count rate. The implementation of fast electronics has helped to keep dead time reasonable, in spite of the increased count rates. The PGNAA facility at the MIT Research Reactor continues to serve as a major analytical tool for quantifying 10B in biological samples for Boron Neutron Capture Therapy (BNCT) research. The sensitivity for boron-10 in water is 18 750 cps/mg. The sensitivity for pure elements suitable for PGNAA analysis is reported. Possible further improvements are discussed.

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

    PubMed

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

    2012-12-01

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

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

    PubMed Central

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

    2012-01-01

    Inorganic pyrophosphatase (IPPase) from the archaeon Thermococcus thioreducens was cloned, overexpressed in Escherichia coli, purified and crystallized in restricted geometry, resulting in large crystal volumes exceeding 5 mm3. IPPase is thermally stable and is able to resist denaturation at temperatures above 348 K. Owing to the high temperature tolerance of the enzyme, the protein was amenable to room-temperature manipulation at the level of protein preparation, crystallization and X-ray and neutron diffraction analyses. A complete synchrotron X-ray diffraction data set to 1.85 Å resolution was collected at room temperature from a single crystal of IPPase (monoclinic space group C2, unit-cell parameters a = 106.11, b = 95.46, c = 113.68 Å, α = γ = 90.0, β = 98.12°). As large-volume crystals of IPPase can be obtained, preliminary neutron diffraction tests were undertaken. Consequently, Laue diffraction images were obtained, with reflections observed to 2.1 Å resolution with I/σ(I) greater than 2.5. The preliminary crystallographic results reported here set in place future structure–function and mechanism studies of IPPase. PMID:23192028

  16. 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.

  17. Magnetic structures of R(Cu, Ni)2 compounds (R = heavy rare earth) studied by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Smetana, Z.; Šíma, V.

    1985-11-01

    Magnetics structures of powdered orthorhombic R(Cu, Ni)2 compounds (R = heavy rare earth) determined by neutron diffraction are described. The influence of magnetocrystalline anisotropy and exchange interactions on the type of magnetic ordering is discussed.

  18. Disposition of ceramide in model lipid membranes determined by neutron diffraction.

    PubMed

    Groen, D; Gooris, G S; Barlow, D J; Lawrence, M J; van Mechelen, J B; Demé, B; Bouwstra, J A

    2011-03-16

    The lipid matrix present in the uppermost layer of the skin, the stratum corneum, plays a crucial role in the skin barrier function. The lipids are organized into two lamellar phases. To gain more insight into the molecular organization of one of these lamellar phases, we performed neutron diffraction studies. In the diffraction pattern, five diffraction orders were observed attributed to a lamellar phase with a repeat distance of 5.4 nm. Using contrast variation, the scattering length density profile could be calculated showing a typical bilayer arrangement. To obtain information on the arrangement of ceramides in the unit cell, a mixture that included a partly deuterated ceramide was also examined. The scattering length density profile of the 5.4-nm phase containing this deuterated ceramide demonstrated a symmetric arrangement of the ceramides with interdigitating acyl chains in the center of the unit cell.

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

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

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

  20. Influence of neutron irradiation on the microstructure of nuclear graphite: An X-ray diffraction study

    NASA Astrophysics Data System (ADS)

    Zhou, Z.; Bouwman, W. G.; Schut, H.; van Staveren, T. O.; Heijna, M. C. R.; Pappas, C.

    2017-04-01

    Neutron irradiation effects on the microstructure of nuclear graphite have been investigated by X-ray diffraction on virgin and low doses (∼ 1.3 and ∼ 2.2 dpa), high temperature (750° C) irradiated samples. The diffraction patterns were interpreted using a model, which takes into account the turbostratic disorder. Besides the lattice constants, the model introduces two distinct coherent lengths in the c-axis and the basal plane, that characterise the volumes from which X-rays are scattered coherently. The methodology used in this work allows to quantify the effect of irradiation damage on the microstructure of nuclear graphite seen by X-ray diffraction. The results show that the changes of the deduced structural parameters are in agreement with previous observations from electron microscopy, but not directly related to macroscopic changes.

  1. 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.

  2. Disposition of Ceramide in Model Lipid Membranes Determined by Neutron Diffraction

    PubMed Central

    Groen, D.; Gooris, G.S.; Barlow, D.J.; Lawrence, M.J.; van Mechelen, J.B.; Demé, B.; Bouwstra, J.A.

    2011-01-01

    The lipid matrix present in the uppermost layer of the skin, the stratum corneum, plays a crucial role in the skin barrier function. The lipids are organized into two lamellar phases. To gain more insight into the molecular organization of one of these lamellar phases, we performed neutron diffraction studies. In the diffraction pattern, five diffraction orders were observed attributed to a lamellar phase with a repeat distance of 5.4 nm. Using contrast variation, the scattering length density profile could be calculated showing a typical bilayer arrangement. To obtain information on the arrangement of ceramides in the unit cell, a mixture that included a partly deuterated ceramide was also examined. The scattering length density profile of the 5.4-nm phase containing this deuterated ceramide demonstrated a symmetric arrangement of the ceramides with interdigitating acyl chains in the center of the unit cell. PMID:21402030

  3. Polarisation vision: beetles see circularly polarised light.

    PubMed

    Warrant, Eric J

    2010-07-27

    It has long been known that the iridescent cuticle of many scarab beetles reflects circularly polarised light. It now turns out that scarabs can also see this light, potentially using it as a covert visual signal.

  4. 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

  5. Structure of molten Al and eutectic Al-Si alloy studied by neutron diffraction

    SciTech Connect

    Dahlborg, U.; Kramer, Matthew J.; Besser, M.; Morris, J. R.; Calvo-Dahlborg, M.

    2012-11-24

    The structure of molten eutectic Al87.8Si12.2 alloy has been studied by neutron diffraction during a temperature cycle. For comparison measurements were performed on pure molten Al. The measurements show that the alloy after heating above the liquidus contains particles of two kinds, aluminum-rich and silicon-rich. The silicon-rich particles are partly dissolved after a further heating. Earlier published data obtained by the γ-ray absorption technique of the density of the molten eutectic Al–Si alloy had demonstrated the existence of two temperatures above the liquidus temperature: A dissolution temperature Td, at which the microstructure of the melt inherited from the ingot starts to dissolve and a branching temperature, Tb, at which the melt reaches a fully mixed state. The highest temperature that was possible to reach during the neutron experiments lies between Td and Tb. The obtained results support these conclusions that molten alloys after melting are inhomogeneous up to a temperature well above the liquidus. Moreover, the difference in shape between the static structure factors measured by neutron and X-ray diffraction on molten aluminum is observed and is found to be more accentuated and to extend to larger wavevectors than in earlier works.

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

    PubMed Central

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

    2014-01-01

    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 mm3) 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. PMID:24699741

  7. 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.

  8. 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.

  9. Characterisation of Residual Stresses Generated by Laser Shock Peening by Neutron and Synchrotron Diffraction

    NASA Astrophysics Data System (ADS)

    Evans, Alexander Dominic; King, Andrew; Pirling, Thilo; Peyre, Patrice; Withers, Phillip John

    The fatigue behaviour of engineering alloys can be significantly improved through the application of mechanical surface treatments. These processes generate significant compressive residual stresses near surface by inhomogeneous plastic deformation. In the case of mechanical surface treatments such as laser shock peening, certain burnishing and rolling techniques and ultrasonic impact treatment (UIT), the compressive residual stress layer can extend to a depth of the order of millimeters, with balancing tensile stresses located deeper. Techniques to characterise the residual stresses generated by such mechanical surface treatments non-destructively are mainly limited to diffraction methods using penetrating neutron and synchrotron X-ray radiations. The application of these radiation sources is illustrated here by the characterisation of residual strain distributions in a two types of specimens treated with laser shock peening (LSP). Analyses of diffraction peak broadening provide qualitative information concerning the depth to which the plastic deformation of the treatments extends. Two case studies of laser shock peening of titanium and aluminium alloys is presented to demonstrate the capabilities of neutron and synchrotron diffraction techniques in the field of residual stress characterisation of surface engineered material non-destructively.

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

    PubMed

    Cereser, Alberto; Strobl, Markus; Hall, Stephen A; Steuwer, Axel; Kiyanagi, Ryoji; Tremsin, Anton S; Knudsen, Erik B; Shinohara, Takenao; Willendrup, Peter K; da Silva Fanta, Alice Bastos; Iyengar, Srinivasan; Larsen, Peter M; Hanashima, Takayasu; Moyoshi, Taketo; Kadletz, Peter M; Krooß, Philipp; Niendorf, Thomas; Sales, Morten; Schmahl, Wolfgang W; Schmidt, Søren

    2017-08-25

    The physical properties of polycrystalline materials depend on their microstructure, which is the nano- to centimeter scale arrangement of phases and defects in their interior. Such microstructure depends on the shape, crystallographic phase and orientation, and interfacing of the grains constituting the material. This article presents a new non-destructive 3D technique to study centimeter-sized bulk samples with a spatial resolution of hundred micrometers: time-of-flight three-dimensional neutron diffraction (ToF 3DND). Compared to existing analogous X-ray diffraction techniques, ToF 3DND enables studies of samples that can be both larger in size and made of heavier elements. Moreover, ToF 3DND facilitates the use of complicated sample environments. The basic ToF 3DND setup, utilizing an imaging detector with high spatial and temporal resolution, can easily be implemented at a time-of-flight neutron beamline. The technique was developed and tested with data collected at the Materials and Life Science Experimental Facility of the Japan Proton Accelerator Complex (J-PARC) for an iron sample. We successfully reconstructed the shape of 108 grains and developed an indexing procedure. The reconstruction algorithms have been validated by reconstructing two stacked Co-Ni-Ga single crystals, and by comparison with a grain map obtained by post-mortem electron backscatter diffraction (EBSD).

  11. 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.

  12. La structure des verres étudiée par diffraction des neutrons

    NASA Astrophysics Data System (ADS)

    Cormier, L.

    2003-09-01

    La diffraction des neutrons est une méthode largement utilisée pour déterminer la structure des matériaux amorphes et en particulier des verres. L'utilisation de la méthode de substitution isotopique permet d'extraire les fonctions de distribution de paires partielles centrées autour d'un élément choisi. Nous présentons quelques exemples récents d'études par diffraction des neutrons sur des verres qui ont permis de mieux comprendre à la fois le réseau polymérique de la matrice vitreuse et l'environnement local et à moyenne distance autour des cations. Ces études ont révélées un ordre structural s'étendant au delà des premiers voisins, jusque vers de distances d'environ 10Å. Le couplage avec d'autres méthodes expérimentales (diffraction anormale des rayons X) et des techniques de simulations (dynamique moléculaire, Monte Carlo Inverse ou RMC) sont indispensables pour affiner nos connaissances de la structure des verres.

  13. Polarisation analysis on the LET time-of-flight spectrometer

    NASA Astrophysics Data System (ADS)

    Nilsen, G. J.; Košata, J.; Devonport, M.; Galsworthy, P.; Bewley, R. I.; Voneshen, D. J.; Dalgliesh, R.; Stewart, J. R.

    2017-06-01

    We present a design for implementing uniaxial polarisation analysis on the LET cold neutron time-of-flight spectrometer, installed on the second target station at ISIS. The polarised neutron beam is to be produced by a transmission-based supermirror polariser with the polarising mirrors arranged in a “double-V” formation. This will be followed by a Mezei-type precession coil spin flipper, selected for its small spatial requirements, as well as a permanent magnet guide field to transport the beam polarisation to the sample position. The sample area will contain a set of holding field coils, whose purpose is to produce a highly homogenous magnetic field for the wide-angle 3He analyser cell. To facilitate fast cell changes and reduce the risk of cell failure, we intend to separate the cell and cryostat from the vacuum of the sample tank by installing both in a vessel at atmospheric pressure. When the instrument upgrade is complete, the performance of LET is expected to be commensurate with existing and planned polarised cold neutron spectrometers at other sources. Finally, we discuss the implications of performing uniaxial polarisation analysis only, and identify quasi-elastic neutron scattering (QENS) on ionic conducting materials as an interesting area to apply the technique.

  14. Measurement of residual strain in composites by means of time-of- flight neutron diffraction

    SciTech Connect

    Kupperman, D.S.; Majumdar, S.; Richardson, J.; Saigal, A.

    1993-05-01

    Neutron diffraction time-of-flight measurements using the Intense Pulsed Neutron Source at Argonne National Laboratory have been employed to study strain in various metal- and ceramic-matrix composites. For example, measurements carried out to 900 C on a composite composed of a titanium alloy matrix and silicon carbide fibers have been used to validate theoretical assumptions in the prediction of fabrication-induced residual stress. Sapphire reinforced nickel aluminide composites have also been studied. Studies of a high-temperature ceramic superconducting composite consisting of yttrium barium copper oxide and silver with various volume fractions of silver have also been carried out. The results of these studies have provided information on the effect of Ag content on interface bonding. In addition, ceramic-matrix composites with randomly dispersed ceramic whiskers with varying fiber content have been investigated.

  15. Measurement of residual strain in composites by means of time-of- flight neutron diffraction

    SciTech Connect

    Kupperman, D.S.; Majumdar, S.; Richardson, J. . Materials and Components Technology Div.); Saigal, A. . Dept. of Mechanical Engineering)

    1993-01-01

    Neutron diffraction time-of-flight measurements using the Intense Pulsed Neutron Source at Argonne National Laboratory have been employed to study strain in various metal- and ceramic-matrix composites. For example, measurements carried out to 900 C on a composite composed of a titanium alloy matrix and silicon carbide fibers have been used to validate theoretical assumptions in the prediction of fabrication-induced residual stress. Sapphire reinforced nickel aluminide composites have also been studied. Studies of a high-temperature ceramic superconducting composite consisting of yttrium barium copper oxide and silver with various volume fractions of silver have also been carried out. The results of these studies have provided information on the effect of Ag content on interface bonding. In addition, ceramic-matrix composites with randomly dispersed ceramic whiskers with varying fiber content have been investigated.

  16. Preliminary neutron diffraction analysis of challenging human manganese superoxide dismutase crystals.

    PubMed

    Azadmanesh, Jahaun; Trickel, Scott R; Weiss, Kevin L; Coates, Leighton; Borgstahl, Gloria E O

    2017-04-01

    Superoxide dismutases (SODs) are enzymes that protect against oxidative stress by dismutation of superoxide into oxygen and hydrogen peroxide through cyclic reduction and oxidation of the active-site metal. The complete enzymatic mechanisms of SODs are unknown since data on the positions of hydrogen are limited. Here, methods are presented for large crystal growth and neutron data collection of human manganese SOD (MnSOD) using perdeuteration and the MaNDi beamline at Oak Ridge National Laboratory. The crystal from which the human MnSOD data set was obtained is the crystal with the largest unit-cell edge (240 Å) from which data have been collected via neutron diffraction to sufficient resolution (2.30 Å) where hydrogen positions can be observed.

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

    SciTech Connect

    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-density elimination and tested with experimental powder and Laue single-crystal neutron data.

  18. Preliminary neutron diffraction analysis of challenging human manganese superoxide dismutase crystals

    PubMed Central

    Azadmanesh, Jahaun; Trickel, Scott R.; Borgstahl, Gloria E. O.

    2017-01-01

    Superoxide dismutases (SODs) are enzymes that protect against oxidative stress by dismutation of superoxide into oxygen and hydrogen peroxide through cyclic reduction and oxidation of the active-site metal. The complete enzymatic mechanisms of SODs are unknown since data on the positions of hydrogen are limited. Here, methods are presented for large crystal growth and neutron data collection of human manganese SOD (MnSOD) using perdeuteration and the MaNDi beamline at Oak Ridge National Laboratory. The crystal from which the human MnSOD data set was obtained is the crystal with the largest unit-cell edge (240 Å) from which data have been collected via neutron diffraction to sufficient resolution (2.30 Å) where hydrogen positions can be observed. PMID:28368283

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

    SciTech Connect

    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-density elimination and tested with experimental powder and Laue single-crystal neutron data.

  20. 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

  1. 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

  2. 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.

  3. Probing spin ordering in iron-platinum based antiferromagnetic films using neutron diffraction

    NASA Astrophysics Data System (ADS)

    Mani, Prakash

    The antiferromagnetic properties of chemically ordered and epitaxial films of FexPt100-x grown on MgO(111) & MgO(100) and Fe50Pt50- xRhx grown on MgO(100) have been studied with neutron diffraction. Epitaxial films of FexPt 100-x (x = 25, 30) have two kinds of antiferromagnetic ordering. The Neel temperature of spin wave vector QA = (1/2 1/2 0) is T N = 160 K and QB = (1/2 0 0) is TN = 100 K, respectively. Neutron diffraction is used to determine the phase diagram of the antiferromagnetic ordering as a function of composition and temperature. The nature of antiferromagnetic ordering was found to be strongly related to the lattice strain present in the system. Lattice-matched antiferromagnetic/ferromagnetic films offer an ideal layered system to study exchange bias. The loop shifts in FePt3(AF)/CoPt 3(F) multilayers are correlated with rocking curve peak widths, and it has been shown that films with a narrower full-width-half-maximum have a smaller exchange bias. Neutron reflectivity is also applied to CoPt 3/FePt3 multilayers in order to probe layer-specific magnetizations owing to the significant difference in neutron scattering length density between Fe and Co. Fe50Pt50-xRh x (x˜10) exhibits a temperature dependent antiferromagnetic-ferromagnetic-paramagnetic triple point near 400 K. The temperature and composition dependent spin structure of Fe50Pt 50-xRhx alloy films grown on MgO(100) have been determined for the first time with neutron diffraction. Three types of antiferromagnetic orderings were observed: (0 0 1/2), (1/2 1/2 1/2), and (1/2 1/2 3/2). Future studies have been planned to explore a magnetic field induced antiferromagnetic to ferromagnetic transition in Fe50Pt50-xRh x alloy films.

  4. 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.

  5. Neutron powder diffraction study on the iron-based nitride superconductor ThFeAsN

    NASA Astrophysics Data System (ADS)

    Mao, Huican; Wang, Cao; Maynard-Casely, Helen E.; Huang, Qingzhen; Wang, Zhicheng; Cao, Guanghan; Li, Shiliang; Luo, Huiqian

    2017-03-01

    We report neutron diffraction and transport results on the newly discovered superconducting nitride ThFeAsN with T_c= 30 \\text{K} . No magnetic transition, but a weak structural distortion around 160 K, is observed by cooling from 300 K to 6 K. Analysis on the resistivity, Hall transport and crystal structure suggests that this material behaves as an electron optimally doped pnictide superconductor due to extra electrons from nitrogen deficiency or oxygen occupancy at the nitrogen site, which, together with the low arsenic height, may enhance the electron itinerancy and reduce the electron correlations, thus suppressing the static magnetic order.

  6. Characterizing the dealumination of environmentally relevant zeolites using IR, NMR and neutron diffraction techniques

    SciTech Connect

    Paffett, M.T.; Szanyi, J.; Jacubinas, R.M.; Ott, K.C.; VonDreele, R.; Hughes, C.D.; Earl, W.L.

    1997-07-01

    Results of characterization studies monitoring the sequential chemical bond breaking events, local site symmetry, and long range structural modifications of specific zeolites (H-ZSM-5, TS-1) during hydrothermal treatment of these catalyst materials are described. These characterization techniques include infrared spectroscopy of selected probe molecules, magic angle spinning NMR spectroscopy, and powder neutron diffraction. Information regarding selected examples from each of these techniques is presented and the inherent strengths of each is discussed. The experimental insight into the chemical and structural modifications of high surface area microporous catalyst materials as a function of deactivation conditions (hydrothermal conditioning) is highlighted.

  7. Feasibility of thermal strain measurements during quasi-steady state using neutron diffraction

    SciTech Connect

    Woo, Wan Chuck; Feng, Zhili; Wang, Xun-Li; An, Ke; Bailey, William Barton; David, Stan A; Hubbard, Camden R; Choo, Hahn

    2006-01-01

    Localized heating was imposed on a 6061-T6 aluminum alloy plate to cause thermal strains, and simultaneously interplanar spacing changes were measured using in-situ time-resolved neutron diffraction techniques. Two different methods were used: (1) direct real-time measurements of the transient behavior and (2) a series of measurements based on the quasi-steady state (QSS) principle. A comparison of the two results shows that the QSS method can represent the transient behavior under the current experimental conditions.

  8. 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.

  9. 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.

  10. Interrupted Magnetic First Order Transitions and Kinetic Arrest probed with In-field Neutron Diffraction

    NASA Astrophysics Data System (ADS)

    Siruguri, V.; Kaushik, S. D.; Rayaprol, S.; Babu, P. D.; Chaddah, P.; Sampathkumaran, E. V.; Hoser, A.; Ritter, C.

    2016-09-01

    In-field neutron diffraction studies were carried out on two compounds that exhibit magnetic first order phase transitions (FOPT). It is shown that the FOPT can be interrupted by an external magnetic field, resulting in a coexistence of kinetically arrested metastable states and equilibrium phases. Use of a novel protocol CHUF (Cooling and Heating under Unequal Fields) helps to determine the coexisting phase fractions and also to observe the devitrification of the kinetically arrested phase into the equilibrium phase, in a manner similar to that found in structural glassy systems.

  11. Mössbauer spectroscopy and neutron diffraction studies of neptunium antimonide NpSb

    NASA Astrophysics Data System (ADS)

    Sanchez, J. P.; Burlet, P.; Quézel, S.; Bonnisseau, D.; Rossat-Mignod, J.; Spirlet, J. C.; Rebizant, J.; Vogt, O.

    1988-09-01

    NpSb has been studied by Mössbauer spectroscopy ( 237Np and 121Sb resonances) and by neutron diffraction using single crystals. Np 3+ magnetic moments order antiferromagnetically below TN = 200 K in a triple- k type I structure. A strong mixing of 5 f electrons with anion p states can be deduced from results of 121Sb resonance. This mixing is certainty at the origin of the interaction mechanism responsible of the coupling between the Fourier components leading to the triple- k multiaxial magnetic structure.

  12. Neutron diffraction study of the phase-specific stresses in graded alumina/zirconia ceramics

    NASA Astrophysics Data System (ADS)

    Lukáš, Petr; Vrána, Miroslav; Mikula, Pavel; Vleugels, J.; Anné, G.; van der Biest, O.

    2004-07-01

    New functionally graded Al2O3/Y-ZrO2 ceramics are developed as a new material for production of hip prosthesis, especially all-ceramic hip bearings. The used concept of graded ceramics is expected to provide better long-term performance based on improved mechanical properties and lower clinical risks. Mechanical properties are strongly dependent on distribution of residual stresses resulting mainly from phase specific stresses after cooling from sintering temperature. However, these stresses could be optimized by an appropriate selection of a concentration profile of constituent phases. The non-destructive neutron diffraction mapping of residual stresses has been used to investigate this problem experimentally.

  13. Neutron diffraction study of multiferroic Mo-doped CoFe2O4

    NASA Astrophysics Data System (ADS)

    Das, A.; Dwivedi, G. D.; Kumari, Poonam; Shahi, P.; Yang, H. D.; Ghosh, A. K.; Chatterjee, Sandip

    2015-04-01

    Neutron diffraction measurements have been carried out to study the coexistence of magnetic ordering and ferroelectricity at room temperature in CoFe1.8Mo0.2O4. It is observed from this study that the Mo6+ preferentially occupies the octahedral site and it converts some of the Fe3+ ions into Fe2+ ions in the tetrahedral site. The conversion of Fe3+ ions into Fe2+ ions modulate the Fe-Fe distances which in effect induce the ferroelectricity in magnetically ordered CoFe1.8Mo0.2O4.

  14. 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.

  15. Pulsed neutron powder diffraction at high pressure by a capacity-increased sapphire anvil cell

    NASA Astrophysics Data System (ADS)

    Okuchi, Takuo; Yoshida, Masashi; Ohno, Yoshiki; Tomioka, Naotaka; Purevjav, Narangoo; Osakabe, Toyotaka; Harjo, Stefanus; Abe, Jun; Aizawa, Kazuya; Sasaki, Shigeo

    2013-12-01

    A new design of opposed anvil cell for time-of-flight neutron powder diffraction was prepared for use at advanced pulsed sources. A couple of single-crystal sapphire sphere anvils and a gasket of fully hardened Ti-Zr null alloy were combined to compress 35 mm3 of sample volume to 1 GPa and 11 mm3 to 2 GPa of pressures, respectively. A very high-quality powder diffraction pattern was obtained at Japan Proton Accelerator Research Complex for a controversial high pressure phase of methane hydrate. The counting statistics, resolution, absolute accuracy and d-value range of the pattern were all improved to be best suitable for precise structure refinement. The sample is optically accessible to be measured by Raman and fluorescence spectroscopy during and after compression. The current cell will be an alternative choice to study hydrogenous materials of complex structures that are stable at the described pressure regime.

  16. REVIEW ARTICLE: Determination of residual stresses in materials and industrial components by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Albertini, Gianni; Bruno, Giovanni; Carradò, Adele; Fiori, Fabrizio; Rogante, Massimo; Rustichelli, Franco

    1999-03-01

    We present a review of the determination of residual stresses in materials and components of industrial interest by using the non-destructive technique of neutron diffraction. The fundamental aspects are discussed, together with a brief description of the experimental facilities. Several experimental results are then reported, particularly concerning applications to materials and components for power plants (CrMo steel, AISI304 stainless steel and 2.25Cr1Mo ferritic steel), aerospace and automotive technology (Al alloys, metal matrix composites, nickel superalloy gas-turbine components) and fusion-reactor technology (AISI316L for the first wall). A few thermomechanical treatments are considered, such as welding, cold-expanded holes, thermoelastic coupling and thermal and mechanical fatigue. Moreover, a few applications to general industrial problems are shown, namely brazed ceramic-steel components, coatings and fatigue-cracked samples. In some cases, experimental results are compared with numerical models or results from x-ray diffraction measurements.

  17. Neutron diffraction study of NiTi during compressive deformation and after shape-memory recovery

    SciTech Connect

    Dunand, D.C.; Mari, D.; Bourke, M.A.M.; Goldstone, J.A.

    1995-09-01

    Neutron diffraction measurements of internal elastic strains and texture were performed during compressive deformation of martensitic NiTi deforming by twinning. Rietveld refinement of the diffraction spectrum was performed in order to obtain lattice parameter variations and preferred orientation of martensitic variants. The elastic internal strains, are proportional to the externally applied stress but strongly dependent on crystallographic orientation. Plastic deformation by matrix twinning is consistent with type I (1-1-1) twinning, whereby (100) and (011) planes tend to align perpendicular and parallel to the stress axis, respectively. The preferred orientation ratio r according to the model by March and Dollase is proportional to the macroscopic plastic strain for (100) and (011) planes for loading, unloading and shape-memory recovery. To the best of our knowledge, this is the first in situ bulk measurement of reversible twinning in NiTi. Finally, shape-memory recovery results in a marked change of NiTi cell parameters.

  18. 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

  19. Direct determination of the calcium profile structure for dipalmitoyllecithin multilayers using neutron diffraction.

    PubMed Central

    Herbette, L; Napolitano, C A; McDaniel, R V

    1984-01-01

    The distribution of calcium in lamellar phases of dipalmitoyllecthin (DPPC) multilayers was directly determined by neutron diffraction and stable isotope substitution of 44Ca for 40Ca. A significant resonance effect on the intensities of the lamellar diffraction pattern was observed for millimolar concentrations of these calcium isotopes. The calcium difference profile indicated that calcium was localized in the phospholipid headgroup region, being excluded from the hydrocarbon core as was water separately determined from the water profile structure obtained by H2O/D2O exchange. A reciprocal space analysis of the difference structure factors indicated that calcium binds preferentially to within 1-2 A of the phosphate moiety of the phospholipid head groups of the DPPC bilayer. PMID:6549146

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  1. Determination of texture and estimation of anisotropie properties of metallic uranium rods by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Kim, Yong Che; Kim, Huhn Jun; Lee, Chang Hee; Seong, Baek Seok; Kim, Soon-Chul

    1998-12-01

    Textures of metallic uranium rods were measured by neutron diffraction. From experimentally measured single and composite pole figures, the crystallite orientation distribution function (ODF) was determined by the harmonic method using a computer program developed for the fiber texture with orthorhombic crystal symmetry. The composite pole figures measured at overlapped peak positions of the diffraction pattern were assumed to be a linear combination of several neighboring single pole figures. The calculated results show that the harmonic method based on this conjecture well recovers the experimentally measured composite pole figures. Anisotropie physical properties such as thermal expansion coefficients and elastic constants due to the texture were evaluated by numerically averaging the second and fourth rank tensors with the calculated ODF, respectively.

  2. 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.

  3. Isotope effects in water as investigated by neutron diffraction and path integral molecular dynamics

    NASA Astrophysics Data System (ADS)

    Zeidler, Anita; Salmon, Philip S.; Fischer, Henry E.; Neuefeind, Jörg C.; Simonson, J. Mike; Markland, Thomas E.

    2012-07-01

    The structures of heavy and light water at 300 K were investigated by using a joint approach in which the method of neutron diffraction with oxygen isotope substitution was complemented by path integral molecular dynamics simulations. The diffraction results, which give intra-molecular O-D and O-H bond distances of 0.985(5) and 0.990(5) Å, were found to be in best agreement with those obtained by using the flexible anharmonic TTM3-F water model. Both techniques show a difference of ≃ 0.5% between the O-D and O-H intra-molecular bond lengths, and the results support a competing quantum effects model for water in which its structural and dynamical properties are governed by an offset between intra-molecular and inter-molecular quantum contributions. Further consideration of the O-O correlations is needed in order to improve agreement with experiment.

  4. Water-DNA interactions as studied by X-ray and neutron fibre diffraction.

    PubMed Central

    Fuller, Watson; Forsyth, Trevor; Mahendrasingam, Arumugam

    2004-01-01

    X-ray fibre-diffraction studies indicate a high degree of stereochemical specificity in interactions between water and the DNA double helix. Evidence for this comes from data that show that the molecular conformations assumed by DNA in fibres are highly reproducible and that the hydration-driven transitions between these conformations are fully reversible. These conformational transitions are induced by varying the relative humidity of the fibre environment and hence its water content. Further evidence for stereochemical specificity comes from the observed dependence of the conformation assumed on the ionic content of the fibre and the nucleotide sequence of the DNA. For some transitions, information on stereochemical pathways has come from real-time X-ray fibre diffraction using synchrotron radiation; information on the location of water with respect to the double helix for a number of DNA conformations has come from neutron fibre diffraction. This structural information from fibre-diffraction studies of DNA is complemented by information from X-ray single-crystal studies of oligonucleotides. If the biochemical processes involving DNA have evolved to exploit the structural features observed in DNA fibres and oligonucleotide single crystals, the challenges in developing alternatives to a water environment can be expected to be very severe. PMID:15306379

  5. In Situ Neutron Diffraction Measurements During Annealing of Deformed Beryllium With Differing Initial Textures

    NASA Astrophysics Data System (ADS)

    Brown, Donald W.; Clausen, B.; Sisneros, T. A.; Balogh, L.; Beyerlein, I. J.

    2013-12-01

    The recovery of deformed beryllium was studied with mechanical testing and in situ neutron diffraction measurements. The initial texture of the material and the deformation rate were manipulated to produce four distinct deformation microstructures. The dislocation density was determined from line profile analysis of the neutron diffraction data collected as a function of temperature during annealing to a maximum homologous temperature of 0.53 following deformation. Mechanical testing was completed after the in situ annealing to determine the extent of the recovery of the flow stress. Both the dislocation density and flow stress recovered significantly by a relatively low homologous temperature of 0.3. A comparison with model calculations using a dislocation-based hardening law indicates that it is forest-type dislocations that annihilate during the relatively low temperature anneal; the dislocation substructure was stable at these temperatures. Finally, the motion of the dislocations during annealing prevented the development of intergranular thermal stresses due to the crystallographically anisotropic thermal expansion of beryllium.

  6. Biochemical profiles of membranes from x-ray and neutron diffraction

    SciTech Connect

    McCaughan, L.; Krimm, S.

    1982-02-01

    X-ray and neutron diffraction methods provide some information about the distribution of mass in biological membranes and lipid-water systems. Scattering density profiles obtained from thes systems, however, usually are not directly interpretable in terms of the relative amounts of chemical constituents (e.g., lipid, protein, and water) as a function of position in the membrane. We demonstrate here that the combined use of x-ray and neutron-scattering profiles, together with information on the total amounts of each of the major membrane components, are sufficient to calculate unambiguously the volume fractions of these components at well-defined regions of the lamellar unit. Three cases are considered: a calculated model membrane pair, dipalmitoylphosphatidyl-choline-water multilayers, and rabbit sciatic nerve myelin. For the model system, we discuss the limitations imposed by finite resolution in the diffraction patterns. For the lipid-water multilayers, we calculate water volume fractions in the hydrocarbon tail, lipid headgroup, and interlamellar regions; estimates of these values by various methods are in good agreement with our results. For the nerve myelin, we predict new results for the distribution of protein through the membrane.

  7. 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.

  8. 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.

  9. 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.

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

    PubMed

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

    2012-02-07

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

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

    DOE PAGES

    Keller, L.; White, J. S.; Babkevich, P.; ...

    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

  12. 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

  13. Magnetic Structure of Goethite α-FeOOH: A Neutron Diffraction Study

    NASA Astrophysics Data System (ADS)

    Zepeda-Alarcon, E.; Nakotte, H.; Vogel, S. C.; Wenk, H.

    2013-12-01

    Goethite (α-FeOOH) is found in diverse natural ecosystems, it is by far the most common oxyhydroxide in terrestrial soils, sediments and clays and an important mineral in the biogeochemical cycle of iron at the Earth's surface. Neutron diffraction studies have found that the iron magnetic moments are collinear in a two sublattice antiferromagnetic structure, aligned parallel to the c axis in space group Pbnm (Forsyth et. al. 1968). However, goethite shows superparamagnetic behavior and also a weak ferromagnetic component that has been attributed to the presence of lattice distortions. It is thought that these changes in magnetic ordering could be due to a 13° canting of the magnetic moment with respect to the c-axis, which enables the flipping of the spins due to small perturbations in the lattice (Coey et. al. 1995). In this study we used neutron diffraction at HIPPO and NPDF beamlines at LANSCE of Los Alamos National Laboratory on a powder of natural goethite provided by A. Gualtieri. The nuclear and magnetic structures were determined by means of a Rietveld refinement with GSAS and it was found that the spins of the iron atoms are aligned parallel to the c-axis, with no evidence of spin canting. The net magnetic moment is lower than what has previously been found. These results provide further insight into the magnetic ordering of this mineral and can be important in understanding the physical processes responsible for goethite's intriguing magnetic behavior.

  14. 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.

  15. 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.

  16. Localization of cholesterol and fatty acid in a model lipid membrane: a neutron diffraction approach.

    PubMed

    Mojumdar, E H; Groen, D; Gooris, G S; Barlow, D J; Lawrence, M J; Deme, B; Bouwstra, J A

    2013-08-20

    The intercellular lipid matrix of the skin's stratum corneum serves to protect the body against desiccation and simultaneously limits the passage of drugs and other xenobiotics into the body. The matrix is made up of ceramides, free fatty acids, and cholesterol, which are organized as two coexisting crystalline lamellar phases. In studies reported here, we sought to use the technique of neutron diffraction, together with the device of isotopic (H/D) substitution, to determine the molecular architecture of the lamellar phase having a repeat distance of 53.9 ± 0.3 Å. Using hydrogenous samples as well as samples incorporating perdeuterated (C24:0) fatty acids and selectively deuterated cholesterol, the diffraction data obtained were used to construct neutron scattering length density profiles. By this means, the locations within the unit cell were determined for the cholesterol and fatty acids. The cholesterol headgroup was found to lie slightly inward from the unit cell boundary and the tail of the molecule located 6.2 ± 0.2 Å from the unit cell center. The fatty acid headgroups were located at the unit cell boundary with their acyl chains straddling the unit cell center. Based on these results, a molecular model is proposed for the arrangement of the lipids within the unit cell.

  17. 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.

  18. 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)

  19. Neutron-diffraction measurement of residual stresses in Al-Cu cold-cut welding

    NASA Astrophysics Data System (ADS)

    Fiori, F.; Marcantoni, M.

    Usually, when it is necessary to join different materials with a large difference in their melting points, welding should be avoided. To overcome this problem we designed and built a device to obtain cold-cut welding, which is able to strongly decrease oxidation problems of the surfaces to be welded. Thanks to this device it is possible to achieve good joining between different pairs of materials (Al-Ti, Cu-Al, Cu-Al alloys) without reaching the material melting point. The mechanical and microstructural characterisation of the joining and the validation of its quality were obtained using several experimental methods. In particular, in this work neutron-diffraction experiments for the evaluation of residual stresses in Cu-Al junctions are described, carried out at the G5.2 diffractometer of LLB, Saclay. Neutron-diffraction results are presented and related to other experimental tests such as microstructural characterisation (through optical and scanning electron microscopy) and mechanical characterisation (tensile-strength tests) of the welded interface.

  20. 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.

  1. Neutron diffraction residual strain measurements in nanostructured hydroxyapatite coatings for orthopaedic implants.

    PubMed

    Ahmed, R; Faisal, N H; Paradowska, A M; Fitzpatrick, M E; Khor, K A

    2011-11-01

    The failure of an orthopaedic implant can be initiated by residual strain inherent to the hydroxyapatite coating (HAC). Knowledge of the through-thickness residual strain profile in the thermally sprayed hydroxyapatite coating/substrate system is therefore important in the development of a new generation of orthopaedic implants. As the coating microstructure is complex, non-destructive characterization of residual strain, e.g. using neutron diffraction, provides a useful measure of through thickness strain profile without altering the stress field. This first detailed study using a neutron diffraction technique, non-destructively evaluates the through thickness strain measurement in nanostructured hydroxyapatite plasma sprayed coatings on a titanium alloy substrate (as-sprayed, heat treated, and heat treated then soaked in simulated body fluid (SBF)). The influence of crystallographic plane orientation on the residual strain measurement is shown to indicate texturing in the coating. This texturing is expected to influence both the biological and fracture response of HA coatings. Results are discussed in terms of the influence of heat-treatment and SBF on the residual stress profile for these biomedical coatings. The results show that the through thickness residual strain in all three coatings was different for different crystallographic planes but was on average tensile. It is also concluded that the heat-treatment and simulated body fluid exposure had a significant effect on the residual strain profile in the top layers of HAC.

  2. Aging behavior of lithium iron phosphate based 18650-type cells studied by in situ neutron diffraction

    NASA Astrophysics Data System (ADS)

    Paul, Neelima; Wandt, Johannes; Seidlmayer, Stefan; Schebesta, Sebastian; Mühlbauer, Martin J.; Dolotko, Oleksandr; Gasteiger, Hubert A.; Gilles, Ralph

    2017-03-01

    The aging behavior of commercially produced 18650-type Li-ion cells consisting of a lithium iron phosphate (LFP) based cathode and a graphite anode based on either mesocarbon microbeads (MCMB) or needle coke (NC) is studied by in situ neutron diffraction and standard electrochemical techniques. While the MCMB cells showed an excellent cycle life with only 8% relative capacity loss (i.e., referenced to the capacity after formation) after 4750 cycles and showed no capacity loss on storage for two years, the needle coke cells suffered a 23% relative capacity loss after cycling and a 11% loss after storage. Based on a combination of neutron diffraction and electrochemical characterization, it is shown that the entire capacity loss for both cell types is dominated by the loss of active lithium; no other aging mechanisms like structural degradation of anode or cathode active materials or deactivation of active material could be found, highlighting the high structural stability of the active material and the excellent quality of the investigated cells.

  3. 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.

  4. 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.

  5. 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.

  6. Magnetic symmetries in neutron and resonant x-ray Bragg diffraction patterns of four iridium oxides.

    PubMed

    Lovesey, S W; Khalyavin, D D; Manuel, P; Chapon, L C; Cao, G; Qi, T F

    2012-12-12

    The magnetic properties of Sr(2)IrO(4), Na(2)IrO(3), Sr(3)Ir(2)O(7) and CaIrO(3) are discussed, principally in the light of experimental data in recent literature for Bragg intensities measured in x-ray diffraction with enhancement at iridium L-absorption edges. The electronic structure factors we report, which incorporate parity-even and acentric entities, serve the immediate purpose of making full use of crystal and magnetic symmetry to refine our knowledge of the magnetic properties of the four iridates from resonant x-ray diffraction data. They also offer a platform on which to interpret future investigations, using dichroic signals, resonant x-ray diffraction and neutron diffraction, for example, as well as ab initio calculations of electronic structure. Unit-cell structure factors, suitable for x-ray Bragg diffraction enhanced by an electric dipole-electric dipole (E1-E1) event, reveal exactly which iridium multipoles are visible, e.g., a magnetic dipole parallel to the crystal c-axis (z-axis) and an electric quadrupole with yz-like symmetry in the specific case of CaIrO(3). Magnetic space-groups are assigned to Sr(2)IrO(4), Sr(3)Ir(2)O(7) and CaIrO(3), namely, P(I)cca, P(A)ban and Cm'cm', respectively, in the Belov-Neronova-Smirnova notation. The assignment for Sr(2)IrO(4) is possible because of our new high-resolution neutron diffraction data, gathered on a powder sample. In addition, the new data are used to show that the ordered magnetic moment of an Ir(4+) ion in Sr(2)IrO(4) does not exceed 0.29(4) μ(B). Na(2)IrO(3) has two candidate magnetic space-groups that are not resolved with currently available resonant x-ray data.

  7. 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

  8. 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

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

    DOE PAGES

    Liao, Jian -Hong; Dhayal, Rajendra Singh; Wang, Xiaoping; ...

    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

  10. 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.

  11. 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

  12. Polarisation properties of pulsars at optical wavelengths

    NASA Astrophysics Data System (ADS)

    Mignani, Roberto; Marelli, Martino; Shearer, Andrew; Slowikowska, Agnieszka

    2016-07-01

    Polarisation measurements of pulsars offer unique insights into their highly-magnetised relativistic environments and represent a primary test for neutron star magnetosphere models and radiation emission mechanisms. Besides the radio band, optical observations have been, so far, best suited to these goals, with polarisation measurements in the X-rays becoming possible in the near future thanks to missions, such as XIPE and IXPE. In this talk, we review the status of the optical polarisation measurements of pulsars and we foresee possible synergies between X-ray polarimetry observations of selected pulsars with, e.g XIPE and IXPE, and optical observations with the next generation of extremely large telescope, such as the E-ELT.

  13. 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

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

    PubMed

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

    2015-12-01

    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.

  15. Measuring strain and stress distributions along rebar embedded in concrete using time-of-flight neutron diffraction

    NASA Astrophysics Data System (ADS)

    Suzuki, H.; Kusunoki, K.; Hatanaka, Y.; Mukai, T.; Tasai, A.; Kanematsu, M.; Kabayama, K.; Harjo, S.

    2014-02-01

    In modern society, architectural and civil engineering structures such as reinforced concrete buildings require high seismic performance to minimize the ‘megarisk’ exposed from urban earthquake hazards. In the reinforced concrete structures, the bond resistance between rebar and concrete is one important parameter for discussing its performance and it has been typically evaluated by measuring the strain distribution along the embedded rebar. Here, we present in-situ strain and stress measurements for the rebar in reinforced concrete using time-of-flight neutron diffraction as a novel alternative technique to typical strain gauges. It was demonstrated in this study that the three-dimensional deformation behavior of the embedded rebar in normal-strength concrete, cured in air, can be accurately measured under pull-out loading using time-of-flight neutron diffraction. Wider applications of neutron diffraction in the structural engineering field are expected for advanced understanding of actual phenomena on reinforced concrete structures.

  16. Defect dynamics in polycrystalline zirconium alloy probed in situ by primary extinction of neutron diffraction

    NASA Astrophysics Data System (ADS)

    Kabra, Saurabh; Yan, Kun; Carr, David G.; Harrison, Robert P.; Dippenaar, Rian J.; Reid, Mark; Liss, Klaus-Dieter

    2013-02-01

    After α + β-zirconium has fully transformed into β-phase upon heating, the intensities of all β-Zr Bragg reflections decrease simultaneously as a function of time. It is shown that this effect represents a transition from the kinematic to the dynamic theory of diffraction due to the ever increasing crystal perfection driven by thermal recovery of the system. The best fitting coherent crystallite size of 30 μm and other microstructural features are verified by in situ laser scanning confocal microscopy. This effect of primary extinction in neutron diffraction has been employed to further investigate the crystal perfection kinetics. Upon further heating, crystal recovery is identified as a process of dislocation annihilation, suffering from lattice friction. Upon cooling, precipitating α-Zr induces strain into the perfect β-crystallites, re-establishing the kinematic diffraction intensities. An Avrami analysis leads to the estimations of nucleation time, consumption of nucleation sites and lower-dimensional growth. Such technique bears great value for further investigation on all metal systems annealed close to the melting temperature.

  17. Effect of external stress on deuteride (hydride) precipitation in Zircaloy-4 using in situ neutron diffraction

    NASA Astrophysics Data System (ADS)

    Lin, Jun-li; An, Ke; Stoica, Alexandru D.; Heuser, Brent J.

    2017-04-01

    In situ neutron diffraction is utilized to study the deuteride (hydride) precipitation behavior in a cold-worked stress-relieved (CWSR) Zircaloy-4 material upon cooling from 420 °C to room temperature with a 78 MPa external stress applied along the rolling direction (RD) of the material. Two banks detector capture the diffraction signal from two principal directions of the specimen, the normal direction (ND) and the rolling direction (RD). The evolution of deuterium concentration in zirconium solid solution along the two specimen directions is measured by studying the δ-(220) peak intensity, applying the Rietveld refinement method to the diffraction data and using the measured zirconium c-axis lattice distortion. The deuterium concentration is observed to be higher for zirconium grains in the ND than the RD. The terminal solid solubility of precipitation (TSSp) for deuterium in the solution is then described using the Arrhenius equation. It is observed that the applied stress reduces the energy term Q in the Arrhenius equation when compared with the unstressed Q values from the work of others. A model by Puls is applied to study the effect of stress on deuterium solubility, with polycrystalline hydride precipitation strain calculated using the Kearns factor representative of the studied material. The experimental result does not agree with the model prediction of Puls.

  18. Analysis of the Tensile Behavior of 12 pct Mn Multi-phase ( α + γ) TWIP + TRIP Steel by Neutron Diffraction

    NASA Astrophysics Data System (ADS)

    Lee, Sangwon; Woo, Wanchuck; de Cooman, Bruno C.

    2016-05-01

    The tensile behavior of intercritically annealed Fe-12 pctMn-0.3 pctC-2 pctAl and Fe-12 pctMn-0.3 pctC-3 pctAl steel was studied by means of in situ neutron diffraction and microstructural analysis. The in situ neutron diffraction measurements showed that the ferrite had a much higher yield strength and lower work hardening rate as compared to the austenite. The strain hardening of the austenite was controlled by deformation twinning and strain-induced transformation, occurring in succession. This TWIP + TRIP effect acted as an effective plasticity-enhancing mechanism which increased the work hardening rate.

  19. In Situ Neutron Diffraction Study of NiTi-21Pt High-Temperature Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Benafan, O.; Gaydosh, D. J.; Noebe, R. D.; Qiu, S.; Vaidyanathan, R.

    2016-12-01

    In situ neutron diffraction was used to investigate the microstructural features of stoichiometric and Ti-rich NiTiPt high-temperature shape memory alloys with target compositions of Ni29Ti50Pt21 and Ni28.5Ti50.5Pt21 (in atomic percent), respectively. The alloys' isothermal and thermomechanical properties (i.e., moduli, thermal expansion, transformation strains, and dimensional stability) were correlated to the lattice strains, volume-averaged elastic moduli, and textures as determined by neutron diffraction. In addition, the unique aspects of this technique when applied to martensitic transformations in shape memory alloys are highlighted throughout the paper.

  20. 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].

  1. Comparison of quartz crystallographic preferred orientations identified with optical fabric analysis, electron backscatter and neutron diffraction techniques.

    PubMed

    Hunter, N J R; Wilson, C J L; Luzin, V

    2017-02-01

    Three techniques are used to measure crystallographic preferred orientations (CPO) in a naturally deformed quartz mylonite: transmitted light cross-polarized microscopy using an automated fabric analyser, electron backscatter diffraction (EBSD) and neutron diffraction. Pole figure densities attributable to crystal-plastic deformation are variably recognizable across the techniques, particularly between fabric analyser and diffraction instruments. Although fabric analyser techniques offer rapid acquisition with minimal sample preparation, difficulties may exist when gathering orientation data parallel with the incident beam. Overall, we have found that EBSD and fabric analyser techniques are best suited for studying CPO distributions at the grain scale, where individual orientations can be linked to their source grain or nearest neighbours. Neutron diffraction serves as the best qualitative and quantitative means of estimating the bulk CPO, due to its three-dimensional data acquisition, greater sample area coverage, and larger sample size. However, a number of sampling methods can be applied to FA and EBSD data to make similar approximations.

  2. 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.

  3. 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.

  4. 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.

  5. Texture studies of cold rolled steel, Cu and Ni by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Černík, M.; Neov, D.

    2000-03-01

    The submitted contribution deals with texture investigations of some polycrystalline materials subjected to cold rolling process. Using neutron diffraction the texture of rolled steel, Cu and electrolytic Ni having the cubic BCC or FCC lattices were studied. On the basis of pole figures for Fe(1 1 0), Fe(2 0 0), Fe(1 1 2), Cu(1 1 1), Cu(2 0 0), Cu(2 2 0) and Ni(1 1 1), Ni(2 0 0), Ni(2 20), orientation distribution function (ODF) fully describing the texture of individual samples, could be determined (Wenk and Kocks, Metall. Trans. Al8 (1987) 1083; Kallend et al. Mater. Sci. Eng. A132 (1991)). It has been found that cold rolling significantly changes the texture and a complete anisotropy of the original material. Cold rolling as a specific method of metal forming creates in the rolled material a fibrous structure with α and γ fibres.

  6. SURFING: A Program for Precise Determination of Sample Position in Stress Measurements Via Neutron Diffraction

    SciTech Connect

    Wang, D.-Q.

    2000-08-08

    Precise determination of the specimen position relative to the sampling volume for texture and stress measurements by neutron diffraction is difficult or sometimes impossible using only optical devices due to large or irregular sample dimensions and/or complicated shape of the sampling volume. The knowledge of the shape and size of the sampling volume allows development of a general mathematical model for the intensity variation with a parallelogram-shape sampling volume moving from outside to inside the specimen for both transmission and reflection geometric set-ups. Both fixed slits and radial collimators are options in defining the geometrical setup. The attenuation by the sample also has been taken into account in this model. Experimental results agree well with the model calculations. The program SURFING is based on the model calculation and was written in Labwindows/CVI{copyright}.

  7. A neutron diffraction and isotopic substitution measurement of the structure of liquid Cu2Se

    NASA Astrophysics Data System (ADS)

    Hamilton, M. A.; Barnes, A. C.; Beck, U.; Buchanan, P.; Howells, W. S.

    2000-11-01

    The partial structure factors and pair distribution functions of liquid Cu2Se have been determined by neutron diffraction with isotopic substitution. The structure shows characteristics typical of those of an ionic 2:1 melt consisting of Cu+ and Se2- ions with the cations moving through a more ordered Se2- sub-structure. A detailed comparison has been made with recent results obtained for liquid Ag2Se. The structure is similar although there is no evidence of the double peak structure in the cation-cation partial structure factor, SCuCu(Q), as has been found in SAgAg(Q) for liquid Ag2Se and, to a more limited extent, for liquid Ag2Te. There is also less order in the Se2- sub-structure based on a comparison of SSeSe(Q) and the Bhatia-Thornton concentration-concentration structure factor, SCC(Q), for the two liquids.

  8. Polarized Neutron Diffraction to discover symmetry breaking in pseudogap region of Y(123)-Cuprate

    NASA Astrophysics Data System (ADS)

    Bourges, Phiippe

    2006-03-01

    0.5 cm One of the leading issues in high-TC superconductors is the origin of the pseudogap phase in underdoped cuprates. Using polarized elastic neutron diffraction, we identify a novel magnetic order in the YBa2Cu3O6+x system^*. The observed magnetic order preserves translational symmetry as proposed for orbital moments in the circulating current theory of the pseudogap state (see C.M. Varma, at http://fr.arxiv.org/abs/cond-mat/0507214). To date, it is the first direct evidence of an hidden order parameter characterizing the pseudogap phase in high-TC cuprates. ^* B. Fauqu'e, Y. Sidis, V. Hinkov, S. Pailhès, C.T. Lin, X. Chaud and P. Bourges, at http://fr.arxiv.org/abs/cond- mat/0509210.

  9. Application of neutron diffraction technology to the determination of residual strain in engineering composites

    SciTech Connect

    Kupperman, D.S.

    1992-12-01

    Knowledge of fabrication induced residual stresses in the fiber and matrix of advanced engineering composites is important as these stresses can greatly influence the mechanical properties of these composites. In this paper, the application of neutron diffraction technology to the determination of thermal residual strains in the constituents of composites (from which stresses can be calculated) is discussed. Experimental determination of temperature dependent strain in the fiber and matrix of three composites compare favorably with the results of analytical and finite element methods used to predict strain. These composites (two ceramic matrix and one metal matrix) are materials of interest to a variety of industries. In this paper, the benefit of applying a National Laboratory developed technology to a problem of interest to industry, is shown.

  10. Application of neutron diffraction technology to the determination of residual strain in engineering composites

    SciTech Connect

    Kupperman, D.S.

    1992-01-01

    Knowledge of fabrication induced residual stresses in the fiber and matrix of advanced engineering composites is important as these stresses can greatly influence the mechanical properties of these composites. In this paper, the application of neutron diffraction technology to the determination of thermal residual strains in the constituents of composites (from which stresses can be calculated) is discussed. Experimental determination of temperature dependent strain in the fiber and matrix of three composites compare favorably with the results of analytical and finite element methods used to predict strain. These composites (two ceramic matrix and one metal matrix) are materials of interest to a variety of industries. In this paper, the benefit of applying a National Laboratory developed technology to a problem of interest to industry, is shown.

  11. Structural changes in bacteriorhodopsin during proton translocation revealed by neutron diffraction

    SciTech Connect

    Dencher, N.A.; Dresselhaus, D.; Zaccai, G.; Bueldt, G. )

    1989-10-01

    A neutron diffraction study of spectroscopic states for the light-energized proton pump bacteriorhodopsin (BR) is presented. The photocycle states BR-568 and M were generated at temperatures above 4 degrees C and were measured after trapping at--180{degree}C. In the BR-568 to M-state transition, which is known to be a key step in transmembrane proton pumping, reversible structural changes of the protein were detected. These structural alterations occur in the neighborhood of the cyclohexene ring and at the Schiff's base end of the chromophore retinal. They are interpreted as a 1-2 degree tilt of three or four of the transmembrane alpha-helices or as positional changes of four or five amino acids. The structural changes observed are inherent in the transport mechanism of bacteriorhodopsin.

  12. Neutron diffraction study of the BiFeO3 spin cycloid at low temperature

    NASA Astrophysics Data System (ADS)

    Herrero-Albillos, Julia; Catalan, Gustau; Rodriguez-Velamazan, José Alberto; Viret, Michel; Colson, Dorothée; Scott, James F.

    2010-06-01

    The reported observation of two anomalies in the intensity of the magnon Raman peaks of BiFeO3 at 140 and 200 K (Singh et al 2008 J. Phys.: Condens. Mater 20 252203; Cazayous et al 2008 Phys. Rev. Lett. 101 037601) led to the hypothesis that such anomalies might originate from a spin reorientation transition. In order to test this hypothesis, we have used temperature-dependent neutron diffraction to track the evolution of the magnetic configuration in single crystals of BiFeO3. Our results indicate that there is no average reorientation of the spins. This suggests that the magnon anomalies may instead be related to the freezing of modes that do not alter the average projection of the spins over the plane of the cycloid, as also reported for multiferroic TbMnO3 (Senff et al 2006 J. Phys.: Condens. Mater 18 2069).

  13. 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.

  14. 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.

  15. Solid-state synthesis of LiBD(4) observed by in situ neutron diffraction.

    PubMed

    Remhof, A; Friedrichs, O; Buchter, F; Mauron, Ph; Züttel, A; Wallacher, D

    2008-10-14

    The synthesis of Li[(11)BD(4)] from LiB and D(2) (p = 180 bar) is investigated by in situ neutron diffraction. The onset of the Li[(11)BD(4)] formation is observed far below the temperatures reported so far for the reaction from the pure elements, indicative of a lower activation barrier. We attribute the improved formation behavior to the breaking of the rigid boron lattice and intermixing of the elements on an atomic level when forming the binary compound LiB. The reaction starts with the decomposition of the initial LiB compound and the formation of LiD. At 623 K LiBD(4) starts to form. However, under the given experimental conditions (maximal temperature = 773 K) a complete reaction was not achieved; there is still residual LiD present.

  16. Neutron diffraction texture analysis and thermoelectric properties of BiCaCoO misfit compounds

    SciTech Connect

    Guilmeau, E. Pollet, M.; Grebille, D.; Chateigner, D.; Vertruyen, B.; Cloots, R.; Funahashi, R.; Ouladiaff, B.

    2008-02-05

    Sintered, textured and single crystal products of the layered misfit [Bi{sub 0.81}CaO{sub 2}]{sub 2}[CoO{sub 2}]{sub 1.69} cobaltite have been successfully synthesized and characterized. Based on structure and texture models, the orientation distribution of the hot-forged sample was successfully analysed by neutron diffraction. The results gave a clear description of the fiber texture with c-axes of the plate-like grains aligned parallel to the hot-forging direction. In terms of transport properties, the decrease of the electrical resistivity according to the degree of alignment and crystallinity of the materials evidenced the important role of the texturation and the strong anisotropy existing in these misfit layered cobaltites.

  17. 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.

  18. A neutron diffraction and computer modeling study of the interatomic structure of phosphoric acid

    NASA Astrophysics Data System (ADS)

    Tromp, R. Hans; Spieser, Stephane H.; Neilson, George W.

    1999-01-01

    Wide angle neutron diffraction in combination with H/D substitution was used to determine the inter- and intramolecular structure of 100% phosphoric acid (H3PO4, PA). From radial distribution functions gHH(r), gHX(r), and gXX(r) (where X is either O or P) the hydrogen bonds were found to be characterized by a very short O…H distance (1.54 Å). Within a molecule, the orientation of an OH group was found to be preferably in one of the three O-P-O planes. In the interpretation of the radial distribution functions, use was made of preliminary results of molecular dynamics simulations. Temperature effects on the structure of PA were only found in the hydrogen bond structure, which becomes somewhat less well defined when heating up from room temperature to 60 °C. Polyphosphates could not be detected, probably due to the small degree of polymerization.

  19. 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.

  20. 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.

  1. Neutron diffraction study of the magnetic structure of HoCu 2

    NASA Astrophysics Data System (ADS)

    Smetana, Z.; Šíma, V.; Lebech, B.

    1986-05-01

    Neutron diffraction measurements show that in the temperature range from 7.4 to TN=10.4 K the magnetic structure of HoCu 2 is a commensurably modulated a-axis collinear structure with a wave vector q1=1/3 a∗. Below 7.4 K an additional structure component develops and the low temperature magnetic structure of HoCu 2 is found to be an incommensurably modulated non-collinear structure characterized by wave vectors q 1=/13; a∗, q2= qcc∗ and 2 q2, where a∗ and c∗ are reciprocal lattice vectors of the orthorhombic structure and qc=0.300±0.005. The corresponding moment components μ- q1, μq2 and μ2q2 lie along the a, b and b directions of the orthorhombic crystal lattice, respectively.

  2. Uranium Hydridoborates: Synthesis, Magnetism, and X-ray/Neutron Diffraction Structures.

    PubMed

    Braunschweig, H; Gackstatter, A; Kupfer, T; Radacki, K; Franke, S; Meyer, K; Fucke, K; Lemée-Cailleau, M-H

    2015-08-17

    While uranium hydridoborate complexes containing the [BH4](-) moiety have been well-known in the literature for many years, species with functionalized borate centers remained considerably rare. We were now able to prepare several uranium hydridoborates (1-4) with amino-substituted borate moieties with high selectivity by smooth reaction of [Cp*2UMe2] (Cp* = C5Me5) and [Cp'2UMe2] (Cp' = 1,2,4-tBu3C5H2) with the aminoborane H2BN(SiMe3)2. A combination of nuclear magnetic resonance spectroscopy, deuteration experiments, magnetic SQUID measurements, and X-ray/neutron diffraction studies was used to verify the anticipated molecular structures and oxidation states of 1-4 and helped to establish a linear tridentate coordination mode of the borate anions.

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

    PubMed

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

    2017-08-01

    Neutron diffraction was employed to measure internal residual stresses at various locations along stainless steel (SS) 17-4 PH specimens additively manufactured via laser-powder bed fusion (L-PBF). Of these specimens, two were rods (diameter=8 mm, length=80 mm) built vertically upward and one a parallelepiped (8×80×9 mm(3)) built with its longest edge parallel to ground. One rod and the parallelepiped were left in their as-built condition, while the other rod was heat treated. Data presented provide insight into the microstructural characteristics of typical L-PBF SS 17-4 PH specimens and their dependence on build orientation and post-processing procedures such as heat treatment. Data have been deposited in the Data in Brief Dataverse repository (doi:10.7910/DVN/T41S3V).

  4. Application of neutron diffraction to measure residual strains in high temperature composites

    SciTech Connect

    Saigal, A. . Dept. of Mechanical Engineering); Kupperman, D.S. )

    1991-01-01

    An experimental neutron diffraction technique was used to measure residual thermal strains developed in high temperature composites during postfabrication cooling. Silicon carbide fiber-reinforced titanium aluminide (over the temperature range 20--950{degree}C) and tungsten and saphikon fiber-reinforced nickel aluminide composites (at room temperature) were investigated. As a result of thermal expansion mismatch, compressive residual strains and stresses were generated in the silicon carbide fibers during cooldown. The axial residual strains were tensile in the matrix and were lower in nickel aluminide matrix as compared to those in titanium aluminide matrix. The average transverse residual strains in the matrix were compressive. Liquid-nitrogen dipping and thermal-cycling tend to reduce the fabrication-induced residual strains in silicon carbide fiber-reinforced titanium aluminide matrix composite. However, matrix cracking can occur as a result of these processes. 10 refs., 5 figs., 2 tabs.

  5. 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.

  6. Neutron diffraction study of the BiFeO₃ spin cycloid at low temperature.

    PubMed

    Herrero-Albillos, Julia; Catalan, Gustau; Rodriguez-Velamazan, José Alberto; Viret, Michel; Colson, Dorothée; Scott, James F

    2010-06-30

    The reported observation of two anomalies in the intensity of the magnon Raman peaks of BiFeO₃ at 140 and 200 K (Singh et al 2008 J. Phys.: Condens. Mater 20 252203; Cazayous et al 2008 Phys. Rev. Lett. 101 037601) led to the hypothesis that such anomalies might originate from a spin reorientation transition. In order to test this hypothesis, we have used temperature-dependent neutron diffraction to track the evolution of the magnetic configuration in single crystals of BiFeO₃. Our results indicate that there is no average reorientation of the spins. This suggests that the magnon anomalies may instead be related to the freezing of modes that do not alter the average projection of the spins over the plane of the cycloid, as also reported for multiferroic TbMnO₃ (Senff et al 2006 J. Phys.: Condens. Mater 18 2069).

  7. Atomic displacements in BiFeO(3) as a function of temperature: neutron diffraction study.

    PubMed

    Palewicz, A; Przeniosło, R; Sosnowska, I; Hewat, A W

    2007-08-01

    The parameters of the crystal structure of BiFeO(3), described within the space group R3c, have been determined by high-resolution neutron powder diffraction for temperatures from 293 to 923 K. It was found that there is a local minimum for the rhombohedral angle alpha(rh), near the Néel temperature T(N) approximately 640 K, a gradual rotation of the FeO(6) octahedra and an increase of the Fe-O-Fe angle. The displacement of the Bi(3+) ions from the FeO(6) octahedra which influence the electric polarization decreases with temperature. One of the Bi-Fe distances also has a local maximum near T(N). The atomic vibrations of Bi(3+) and O(2-) ions show a significant anisotropy.

  8. On the numerical corrections of time-of-flight neutron powder diffraction data.

    SciTech Connect

    Avdeev, M.; Jorgensen, J.; Short, S.; Von Dreele, R.

    2007-08-01

    Time-of-flight neutron powder diffraction data for NIST Standard Reference Materials have been used to study the adequacy of the peak profile model obtained from a convolution of back-to-back exponentials with a pseudo-Voigt function that is widely used in Rietveld refinement. It is shown that, while the empirical models for d-spacing (wavelength) dependence of Gaussian and Lorentzian components of the pseudo-Voigt function and rise exponent are satisfactory, the behavior of the decay exponent and peak positions demonstrate significant deviations, which can be corrected by numerical methods. The practical side of this process as implemented in GSAS and FULLPROF and the effect of the corrections on the Rietveld analysis results are discussed.

  9. Neutron diffraction study of Li4Ti5O12 at low temperatures

    NASA Astrophysics Data System (ADS)

    Dolotko, Oleksandr; Senyshyn, Anatoliy; Mühlbauer, Martin J.; Boysen, Hans; Monchak, Mykhailo; Ehrenberg, Helmut

    2014-10-01

    The crystal structure of the "zero-strain" positive electrode material Li4Ti5O12 was characterized by neutron powder diffraction in the temperature range 3.4 K-300 K. No phase transition was detected, and the thermal evolution of lattice parameters has been evaluated by the 2nd order Grüneisen approximation using the Debye formalism for internal energy and intrinsic anharmonicity contributions. A relatively high Debye temperature θD = 689 ± 71 K was determined. The thermal behavior of cation-anion bond lengths in octahedral and tetrahedral environments is discussed. The lithium diffusion pathway in Li4Ti5O12 was discussed on the basis of bond-valence modeling.

  10. 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.

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

    PubMed

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

    2007-10-17

    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.

  12. Neutron diffraction as a tool in the study of reinforced concrete. Compilation of some cases

    NASA Astrophysics Data System (ADS)

    Castellote, M.

    2014-11-01

    Cementitious materials are much more complex than it seems at a first sight. On one hand, due to the excess of water needed to make the mix workable, a network of pores is generated, that puts in contact the material with the environment and allows their attack by aggressive agents that can be physical of chemical agents, producing the deterioration of the concrete itself and corrosion of the rebars. Then, it is necessary to study the transport properties and the chemical and physical interaction of aggressive agents with the solid and liquid phases of the cement paste the corrosion of the rebars, and the reparation processes. This is an approach concerning the service life of structures, however, we cannot forget an important chapter which is gaining much relevance in the last time: that of the special uses of concrete, for which, tailored concretes have to be designed. In order to undertake these problems, we need new analysis tools, different that the traditionally ones applied to study concrete, that allows the understanding of the mechanisms regulating the processes. One of these analysis tools is neutron diffraction that gives us the possibility of study the bulk of materials using a quite big specimen. In this work, 4 different problems undertaken with the help of neutrons in experiments carried out by the group of the author at the ILL, at the D1B and D20 instruments are presented.

  13. Residual stresses in a shape welded steel tube by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Taran, Yu V.; Balagurov, A. M.; Schreiber, J.; Stuhr, U.

    2008-03-01

    Measurements of the triaxial residual strains in a composite tube from an austenitic stainless steel as a parent material and a shape welded ferritic steel were carried out by the time-of-flight neutron diffraction method on the POLDI instrument at the PSI SINQ neutron pulsed facility. The shape weld is used to build compressive stresses and, as a result, to suppress stress corrosion. Investigations of the residual stresses in such composite tubes are important for developing optimal welding techniques. Calculation of the residual stresses was performed using measurement results with a comb-sample, machined from the tube by the electro-discharge method, as the stress free reference sample. The results of the POLDI measurements of the stress state in the composite tube are presented and compared to the results of the destructive turning out method and theoretical predictions of calculations by the finite element method. Semiquantitative agreement between all the used methods was only observed for the tangential component of the stress tensor. In this case, the ferrite cladding produced a tangential compressive stress of about 800 MPa on the austenitic tube.

  14. Neutron diffraction study of δ-alloy Pu242-Ga aging

    NASA Astrophysics Data System (ADS)

    Somenkov, V. A.; Blanter, M. S.; Glazkov, V. P.; Laushkin, A. V.; Orlov, V. K.

    2014-09-01

    In this paper, we report on a continuing neutron diffraction study of the mean-square atom displacements occurring during the long-term self-irradiation of a Pu-Ga alloy. The measurements were performed at room temperature using the sample based on the isotope Pu242 with low neutron absorption cross-section to which the short-lived isotope Pu238 (1.4 wt.%) was added to accelerate self-irradiation. We obtain the maximum self-irradiation equivalent time of 35.5 years, 12 years longer than in our previous papers. In the entire range of self-irradiation time a single fcc phase is preserved. It was found that after the two stages of change in the mean-square displacements we observed earlier (rapid growth up to ∼5-6 equivalent years and a slow decline in the range of ∼6-25 years), comes a stage of stabilization (after ∼25 years). The stabilization can be explained by the emergence of a balance between the formation of point defects and their absorption by helium bubbles and dislocation loops which accumulated over time.

  15. 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.

  16. The structure of phosphate glass biomaterials from neutron diffraction and (31)P nuclear magnetic resonance data.

    PubMed

    Pickup, D M; Ahmed, I; Guerry, P; Knowles, J C; Smith, M E; Newport, R J

    2007-10-17

    Neutron diffraction and (31)P nuclear magnetic resonance spectroscopy were used to probe the structure of phosphate glass biomaterials of general composition (CaO)0.5-x(Na2O)x(P2O5)0.5 (x = 0, 0.1 and 0.5). The results suggest that all three glasses have structures based on chains of Q(2) phosphate groups. Clear structural differences are observed between the glasses containing Na2O and CaO. The P-O bonds to bridging and non-bridging oxygens are less well resolved in the neutron data from the samples containing CaO, suggesting a change in the nature of the bonding as the field strength of the cation increases [Formula: see text]. In the (CaO)0.5(P2O5)0.5 glass most of the Ca(2+) ions are present in isolated CaOx polyhedra whereas in the (Na2O)0.5(P2O5)0.5 glass the NaOx polyhedra share edges leading to a Na-Na correlation. The results of the structural study are related to the properties of the (CaO)0.4(Na2O)0.1(P2O5)0.5 biomaterial.

  17. Neutron-diffraction study up to 1600 °C of 3:2 mullite

    NASA Astrophysics Data System (ADS)

    Brunauer, G.; Frey, F.; Boysen, H.; Schneider, H.; Fischer, P.; Hansen, Th.; Többens, D.; Ehrenberg, H.

    Neutron-diffraction studies were carried out on pure and Cr-doped 3:2 (`sinter') mullite. To learn about structure-property relationships of this refractory material, thermal expansion coefficients and structural parameters were determined by in situ high-temperature investigations. Neutron experiments were performed at the powder diffractometers D2B/ILL, E9/HMI, and HRPT/PSI. All data gave a rather uniform picture of the thermal expansion coefficients: a linear behaviour below 1000 °C and significantly increased (mean) expansion between 1000 and 1600 °C. There is a marked anisotropy of the highest values along the b-axis of the orthorhombic mullite structure. Concerning the structural parameters and the derived bond lengths, there is an expansion of the Al1O6 octahedra, whereas the cross-linking Al2SiO4 tetrahedra stay more or less rigid, but may slightly rotate. Thus a major expansion along the b direction may be qualitatively understood. A structural discussion, however, is affected by the presence of disorder in mullite, in particular in Cr-doped mullite, as it is also reflected by the presence of a modulated diffuse background in the powder patterns.

  18. A neutron diffraction study of chemisorbed methyl groups in the structure of Y zeolite

    NASA Astrophysics Data System (ADS)

    Vratislav, S.; Dlouhá, M.; Bosáček, V.

    A powder diffraction study of the structure of NaY zeolites with chemisorbed CD 3+ species created by a reaction of Na + cations with d-methyliodide show that chemisorbed methyl groups are preferentially located in alfa cages at O(1) oxygen sites. A complete set of the structural parameters in the frame of Fd3m space group for unperturbed NaY with NaY after the formation of surface methoxy groups were given and an influence of chemisorbed species on the distribution of Na + cations in the lattice was detected by neutron diffraction. Our results show that the population of cationic sites has been changed significantly after the chemisorption of methyl iodide. While the occupation of S II in NaY without adsorbate was 32 Na + per unit cell (i.e. 100%), after the chemisorption of CH 3I it was found to be 19.6 (61%) and in case of CD 3I 21.4 (67%). On the same samples also a significant decrease of population in S I‧ was detected accompanied by a slight increase of population in S I sites.

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

    SciTech Connect

    Cedervall, Johan; Kontos, Sofia; Hansen, Thomas C.; Balmes, Olivier; Martinez-Casado, Francisco Javier; Matej, Zdenek; Beran, Premysl; Svedlindh, Peter; Gunnarsson, Klas; Sahlberg, Martin

    2016-03-15

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

  20. Neutron diffraction studies on magnetic properties of Ca5Ni4V6O24

    NASA Astrophysics Data System (ADS)

    Sharma, Shivani; Singh, Kiran; Lalla, N. P.; Suard, E.; Simon, Ch.

    2017-01-01

    The temperature dependent neutron powder diffraction (NPD) and magnetization measurements of vanadium based garnet Ca5Ni4V6O24 (CNVO) have been performed to explore its crystal and magnetic structures. The magnetization results illustrate two magnetic anomalies at 7 and 4 K. The Rietveld analysis of room temperature x-ray diffraction and NPD data confirms its Ia-3d crystal structure. The temperature dependent NPD shows the emergence of magnetic reflections below 7 K whose intensity keeps on increasing with decreasing temperature down to 1.5 K. The crystal structure remains cubic down to 1.5 K. Rietveld analysis reveals that below 7 K, the Ni moments in CNVO undergo a commensurate collinear A-type antiferromagnetic ordering with propagation vector k=(0,0,0) and the per site ordered moment of Ni2+ is 1.69±0.05 μB. Absence of any additional magnetic or nuclear reflections below 4 K confirms that the nuclear and magnetic structures remain invariant across the 4 K magnetic anomaly.

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

    NASA Astrophysics Data System (ADS)

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

    2017-08-01

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

  2. Cold Drawn Steel Wires-Processing, Residual Stresses and Ductility Part II: Synchrotron and Neutron Diffraction

    SciTech Connect

    Phelippeau,A.; Pommier, S.; Zakharchenko, I.; Levy-Tubiana, R.; Tsakalakos, T.; Clavel, M.; Croft, M.; Zhong, Z.; Prioul, C.

    2006-01-01

    Cold drawing of steel wires leads to an increase of their mechanical strength and to a drop in their ductility. The increase of their mechanical strength has long been related to the reduction of the various material scales by an intense plastic deformation. Besides, it was discussed in the companion paper that large plastic deformation leads to the loss of the material hardening capabilities and that, in such a case, residual stresses preserve the elongation to failure of wires. Experimental measurements of residual stresses inside the wire have therefore been undertaken. In this paper, lattice parameters as measured using synchrotron diffraction are compared with those calculated using the residual stress fields as determined by the finite-element method. There is a major disagreement between experimental and numerical results that is too large to be attributed to the errors of the finite-element analyses. Therefore, neutron diffraction experiments have also been performed. These measurements show that there is a significant variation of the lattice parameter with the drawing level, which is not inherited from residual stresses, and that variation is very sensitive to the cooling rate after processing. It is therefore proposed that cold drawing would induce a phase transformation of the steel, possibly a martensitic transformation.

  3. A large volume cell for in situ neutron diffraction studies of hydrothermal crystallizations.

    PubMed

    Xia, Fang; Qian, Gujie; Brugger, Joël; Studer, Andrew; Olsen, Scott; Pring, Allan

    2010-10-01

    A hydrothermal cell with 320 ml internal volume has been designed and constructed for in situ neutron diffraction studies of hydrothermal crystallizations. The cell design adopts a dumbbell configuration assembled with standard commercial stainless steel components and a zero-scattering Ti-Zr alloy sample compartment. The fluid movement and heat transfer are simply driven by natural convection due to the natural temperature gradient along the fluid path, so that the temperature at the sample compartment can be stably sustained by heating the fluid in the bottom fluid reservoir. The cell can operate at temperatures up to 300 °C and pressures up to 90 bars and is suitable for studying reactions requiring a large volume of hydrothermal fluid to damp out the negative effect from the change of fluid composition during the course of the reactions. The capability of the cell was demonstrated by a hydrothermal phase transformation investigation from leucite (KAlSi(2)O(6)) to analcime (NaAlSi(2)O(6)⋅H(2)O) at 210 °C on the high intensity powder diffractometer Wombat in ANSTO. The kinetics of the transformation has been resolved by collecting diffraction patterns every 10 min followed by Rietveld quantitative phase analysis. The classical Avrami/Arrhenius analysis gives an activation energy of 82.3±1.1 kJ  mol(-1). Estimations of the reaction rate under natural environments by extrapolations agree well with petrological observations.

  4. A large volume cell for in situ neutron diffraction studies of hydrothermal crystallizations

    NASA Astrophysics Data System (ADS)

    Xia, Fang; Qian, Gujie; Brugger, Joël; Studer, Andrew; Olsen, Scott; Pring, Allan

    2010-10-01

    A hydrothermal cell with 320 ml internal volume has been designed and constructed for in situ neutron diffraction studies of hydrothermal crystallizations. The cell design adopts a dumbbell configuration assembled with standard commercial stainless steel components and a zero-scattering Ti-Zr alloy sample compartment. The fluid movement and heat transfer are simply driven by natural convection due to the natural temperature gradient along the fluid path, so that the temperature at the sample compartment can be stably sustained by heating the fluid in the bottom fluid reservoir. The cell can operate at temperatures up to 300 °C and pressures up to 90 bars and is suitable for studying reactions requiring a large volume of hydrothermal fluid to damp out the negative effect from the change of fluid composition during the course of the reactions. The capability of the cell was demonstrated by a hydrothermal phase transformation investigation from leucite (KAlSi2O6) to analcime (NaAlSi2O6ṡH2O) at 210 °C on the high intensity powder diffractometer Wombat in ANSTO. The kinetics of the transformation has been resolved by collecting diffraction patterns every 10 min followed by Rietveld quantitative phase analysis. The classical Avrami/Arrhenius analysis gives an activation energy of 82.3±1.1 kJ mol-1. Estimations of the reaction rate under natural environments by extrapolations agree well with petrological observations.

  5. Optimizations in angular dispersive neutron powder diffraction using divergent beam geometries

    NASA Astrophysics Data System (ADS)

    Buchsteiner, Alexandra; Stüßer, Norbert

    2009-01-01

    Angular dispersive neutron powder diffractometers are usually built using beam divergencies defined by Soller type collimators. To account for the needs of resolution for crystal structure refinement a good in-pile collimation α1, a high take-off angle above 90∘ at the monochromator and a good collimation α3 in front of the detector bank are chosen whereas the value of α2 for the collimation between monochromator and sample is less crucial. During the last years new strategies were developed at our institute using wide divergent beam geometries defined by fan collimators or slit-type diaphragms which correlate ray direction and wavelength within the beam. Here we present the performance of a newly developed fan collimator, which enables one to adjust the opening of the collimator channels on both sides independently. This fan collimator is positioned in front of the monochromator at the instrument E6 at the Helmholtz Centre Berlin (formerly Hahn-Meitner-Institut Berlin). It will be shown that control of the beam divergency allows optimization of the resolution in a large angular diffraction range. Hence the resolution and intensity can be adapted to the needs of powder diffraction. Monte Carlo simulations using McStas are used to check and prove the optimal setting of the instrument. We obtain a very good agreement between experimental and simulated data and demonstrate the superior outcome of the new instrument configuration with respect to Soller type instruments.

  6. 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).

  7. 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).

  8. 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

  9. 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

  10. 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)

  11. 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

  12. Single-crystal neutron diffraction studies on Ni-based metal-pnictide superconductor BaNi2As2

    SciTech Connect

    Kothapalli, Karunakar; Ronning, F; Bauer, E D; Schultz, A J; Nakotte, Heinz

    2009-01-01

    We report the results of single-crystal neutron diffraction studies of the superconductor BaNi{sub 2}As{sub 2}. The experiments were performed on a tiny crystal of mass 0.8 mg at several temperatures between 20 and 200 K using the Single Crystal Diffractometer, SCD, at the Los Alamos Neutron Science Center. Above 130 K, BaNi{sub 2}As{sub 2} crystallizes in the tetragonal ThCr{sub 2}Si{sub 2} structure. Our neutron diffraction data corroborate a first-order structural transition around 130 K with a relatively large hysteresis of about 10K, in agreement with observations from bulk studies. The anisotropic thermal displacement coefficients are enhanced along c-axis approaching the transition, and a splitting is observed for in-plane type reflections below the transition, which is evidence for a change in crystal structure.

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

    SciTech Connect

    Cummins, Dustin Ray; Vogel, Sven C.; Hollis, Kendall Jon; Brown, Donald William; Dombrowski, David E.

    2016-10-18

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

  14. An opposed-anvil-type apparatus with an optical window and a wide-angle aperture for neutron diffraction

    NASA Astrophysics Data System (ADS)

    Iizuka, Riko; Yagi, Takehiko; Gotou, Hirotada; Komatsu, Kazuki; Kagi, Hiroyuki

    2012-09-01

    We designed new anvil assemblies for acquiring high-quality neutron diffraction data and ruby fluorescence spectra inside a sample chamber. The conical aperture of Ni-binded WC anvils was expanded by a factor of two. A hybrid gasket made of TiZr- and Al-alloy was developed to prevent outward extrusion. A small and optically transparent window of moissanite was introduced to allow for the determination of pressure and hydrostaticity by measurement of ruby fluorescence spectra. High pressure-generation tests that make use of Bi electrical conductivity and ruby pressure markers revealed that pressure could be determined over 10 GPa. In situ synchrotron X-ray diffraction experiments were also carried out using NaCl as the pressure calibrants. The maximum pressure achieved was approximately 13 GPa. The neutron diffraction intensity from the newly generated anvil assemblies was 2.5-3.0 times greater than that using the standard toroidal anvil assemblies used previously.

  15. Using neutron diffraction to examine the onset of mechanical twinning in calcite rocks

    NASA Astrophysics Data System (ADS)

    Covey-Crump, S. J.; Schofield, P. F.; Oliver, E. C.

    2017-07-01

    Experimental calibration of the calcite twin piezometer is complicated by the difficulty of establishing the stresses at which the twins observed in the final deformation microstructures actually formed. In principle, this difficulty may be circumvented if the deformation experiments are performed in a polychromatic neutron beam-line because this allows the elastic strain (and hence stress) in differently oriented grains to be simultaneously monitored from diffraction patterns collected as the experiment is proceeding. To test this idea small strain (<0.3%), uniaxial compression experiments have been performed on Carrara marble (grain size 150 μm) and Solnhofen limestone (5 μm) at temperatures of 20°-600 °C using the ENGIN-X instrument at the ISIS neutron facility, UK. At the lowest temperatures (25 °C Carrara; 200 °C Solnhofen) the deformation response was purely elastic up to the greatest stresses applied (60 MPa Carrara; 175 MPa Solnhofen). The sign of the calcite elastic stiffness component c14 is confirmed to be positive when the obverse setting of the calcite rhombohedral lattice in hexagonal axes is used. In the Carrara marble samples deformed at higher temperatures, elastic twinning was initiated at small stresses (<15 MPa) in grains oriented such that the Schmid factor for twinning was positive on more than one e-twin system. At greater stresses (65 MPa at 200 °C decreasing to 41 MPa at 500 °C) there was an abrupt onset of permanent twinning in grains with large Schmid factors for twinning on any one e-twin system. No twinning was observed in the Solnhofen limestone samples deformed at 200° or 400 °C at applied stresses of <180 MPa. These results highlight the potential of this approach for detecting the onset of twinning and provide, through experiments on samples with different microstructures, a strategy for systematically investigating the effects of microstructural variables on crystallographically-controlled inelastic processes.

  16. Powder neutron diffraction of α-UB 2C (α-UB 2C-type)

    NASA Astrophysics Data System (ADS)

    Rogl, Peter; Fischer, Peter

    1991-02-01

    The crystal structure of α-UB 2C (low temperature modification below T = 1675(25)°C) was determined from powder X-ray data (RT) and powder neutron diffraction data (at 29 K) employing the Rietveld-Young-Wiles profile analysis method. α-UB 2C crystallizes in the orthorhombic space group Pmma with a = 0.60338(3), b = 0.35177(2), c = 0.41067(2) nm, V = 0.0872 nm 3, Z = 2. The residuals of the neutron refinement were R1 = 0.032 and RF = 0.043. The crystal structure of α-UB 2C is a new structure type where planar nonregular 6 3-U-metal layers alternate with planar nonmetal layers of the type (B 6C 2) 3. Boron atoms are in a typical triangular prismatic metal surrounding with a tetrakaidekahedral coordination B[U 6B 2C 1], whereas carbon atoms occupy the center points of rectangular bipyramids C[U 4B 2]. The crystal structure of α-UB 2C derives from the high temperature modification β-UB 2C (ThB 2C-type, R overline3m ), which reveals a similar stacking of slightly puckered metal layers 6 3, alternating with planar layers B 6 · (B 6C 3) 2. The phase transition from β-UB 2C to α-UB 2C is thus essentially generated by carbon diffusion within the limit∞2 B 6 · (B 6C 3) 2 layers to form limit∞2 (B 6C 2) 3 layers.

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

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

  18. BOOK REVIEW: Analysis of Residual Stress by Diffraction Using Neutron and Synchrotron Radiation

    NASA Astrophysics Data System (ADS)

    Fitzpatrick, ed M. E.; Lodini, A.

    2003-09-01

    The presence of residual stresses within engineering components is often a key feature in determining their usable lifetimes and failure characteristics. Residual surface compression can, for example, restrict the propagation of surface cracks through the bulk. As a consequence, it is essential to characterize the magnitude and spatial distribution of residual stresses and, at least for non-destructive testing, this is most widely achieved using diffraction of neutron and high energy synchrotron radiations. This book aims to provide a detailed description of the methodology used to determine residual stresses. The major emphasis is placed on the neutron method, this being the more widely established approach at present. It contains 20 chapters contributed by 23 authors, divided into five major parts. The overall layout is very logical, with the first part giving a general introduction to the use of neutrons and x-rays for materials research and summarizing the methods used for their production. Part 2 considers the more specific aspects of extracting the residual stress distribution within a bulk sample and includes some valuable comments on a number of potential experimental problems, such as the determination of the stress-free lattice parameter and the effects of broadening of the Bragg peaks. The experimental facilities currently available or under development are described in part 3, with the remaining two parts devoted to general and specific applications of the residual stress measurement technique. As expected with such a large number of different authors, there is some variation in style and quality. However, the text is generally easy to follow and, more importantly, it is largely free of the problems of inconsistent notation and dupication of material that can afflict multi-authored texts. My only negative comment concerns the latter portion of the book devoted to specific applications of the technique, which is illustrative rather than comprehensive. In

  19. Structure of zinc and niobium tellurite glasses by neutron and x-ray diffraction

    NASA Astrophysics Data System (ADS)

    Hoppe, U.; Yousef, E.; Rüssel, C.; Neuefeind, J.; Hannon, A. C.

    2004-03-01

    Neutron and x-ray diffraction experiments of high resolving power with neutrons from a spallation source and high-energy photons from a synchrotron have been performed on compositional series of binary Zn, Nb and on mixed Zn/Nb tellurite glasses. The Te-O, Zn-O and Nb-O coordination numbers are determined by Gaussian fitting of the first-neighbour peaks in the neutron and x-ray data simultaneously. The transition of TeO4 to TeO3 units with increasing fraction of a second component is indicated by decreasing total Te-O coordination numbers. This transition appears different for glasses with ZnO or Nb2O5 additions. Details of the Te-O peaks suggest there are two species of Te-O bonds with lengths of {\\sim }0.19 and {\\sim }0.21 nm. The change of their fractions shows excellent agreement with the existence of TeO4 trigonal bipyramids and TeO3 trigonal pyramids. All oxygen atoms from ZnO and Nb2O5 are used for rupture of Te-O-Te bridges, which is accompanied with a change of nearly all participating TeO4 to TeO3 groups. The tendency for a {\\mathrm {TeO}}_{4} \\to {\\mathrm {TeO}}_{3} change decreases for glasses of higher second component content which is accompanied by the occurrence of TeO4 groups with non-bridging oxygens. The Nb tellurite glasses show transition to network-forming behaviour with the formation of Nb-O-Nb bridges. The fractions of TeO3 units of ternary Zn/Nb tellurite glasses agree with an additivity behaviour of the modifying effects of ZnO and Nb2O5 additions. Some of these results have already been presented in thesis work: Yousef E 2003 A study of some physical properties of tellurite glass (Al-Azhar University, Assiut Egypt).

  20. Yttrium aluminum garnet Nanoparticles with low antisite Defects studied with neutron and X-ray diffraction

    SciTech Connect

    Sang Yuanhua; Yu Dehong; Avdeev, Maxim; Qin Haiming; Wang Jiyang; Liu Hong; Lv Yaohui

    2012-08-15

    The presence of cation antisite defects is considered to be one of the most important factors determining the fluorescence, laser, and scintillation properties of rare earth-doped yttrium aluminum garnet (YAG) materials. However, no direct evidence or systematic investigation of antisite defect evolution as a function of cation composition variation in YAG has been reported in the previous literature. In this paper, we report a combined neutron and X-ray diffraction investigation on cation antisite defects performed on specially synthesized nonstoichiometric yttrium aluminum garnet nanoparticles to try to understand the defect chemistry in the YAG system. No evidence was found for Y{sub Al,16a}, Y{sub Al,24d} and Al{sub Y,24c} antisite defects in these specially fabricated samples within the limit of diffraction techniques. The results suggest that YAG materials containing low level or no antisite defects can be achieved through low temperature synthesis process. - Graphical Abstract: Through combined Rietveld refinement against both the NPD and XRD data, no or low level antisite defect exists in the low temperature synthesized YAG powders, bond lengths are changeless as a function of the nominal Y/Al ratio, nonstoichiometry has little influence on antisite defect formation. Highlights: Black-Right-Pointing-Pointer Defects investigation with combined Rietveld refinement of NPD and XRD. Black-Right-Pointing-Pointer No or less than 2at% for Y{sub Al,16a} and Y{sub Al,24d} antisite defects. Black-Right-Pointing-Pointer Nonstoichiometry has little influence on antisite defect formation.

  1. 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.; ...

    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

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

    SciTech Connect

    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 literature 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.

  3. Tau polarisation at LEP

    NASA Astrophysics Data System (ADS)

    Alemany, Ricard

    1999-04-01

    The measurements of the tau polarisation at LEP I are reviewed. Special emphasis is given to the new preliminary results presented at this conference. The ALEPH collaboration has studied the polarisation as a function of the polar angle using a new method based on the tau direction reconstruction and fully exploiting the angular correlations. A second traditional approach, based on the single tau decays has been also developed. The DELPHI collaboration has also studied the full data sample using an individual tau decay method and an inclusive hadronic selection. The results from the four experiments are presented with discussion of the compatibility among the methods and experiments.

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

    PubMed

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

    2014-11-01

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

  5. Tensile deformation behaviors of Zircaloy-4 alloy at ambient and elevated temperatures: In situ neutron diffraction and simulation study

    NASA Astrophysics Data System (ADS)

    Li, Hongjia; Sun, Guangai; Woo, Wanchuck; Gong, Jian; Chen, Bo; Wang, Yandong; Fu, Yong Qing; Huang, Chaoqiang; Xie, Lei; Peng, Shuming

    2014-03-01

    Tensile stress-strain relationship of a rolled Zircaloy-4 (Zr-4) plate was examined in situ using a neutron diffraction method at room temperature (RT, 25 °C) and an elevated temperature (250 °C). Variations of lattice strains were obtained as a function of macroscopic bulk strains along prismatic (101¯0), basal (0 0 0 2) and pyramidal (101¯1) planes in the hexagonal close-packed structure of the Zr-4. The mechanisms of strain responses in these three major planes were simulated using elastic-plastic self-consistent (EPSC) model based on Hill-Hutchinson method, thus the inter-granular stresses and deformation systems of each individual grain under loading were obtained. Results show that there is a good agreement between the EPSC modeling and neutron diffraction measurements in terms of macroscopic stress-strain relationship and lattice strain evolutions of the planes at RT. However, there is a slight discrepancy in the lattice strains obtained from the EPSC modeling and neutron diffraction when the specimen was deformed at 250 °C. Analysis of grain structure and texture obtained using electron back-scattered diffraction suggests that dynamic recovery process is significant during the tensile deformation at the elevated temperature, which was not considered in the simulation.

  6. Understanding structural changes in NMC Li-ion cells by in situ neutron diffraction

    NASA Astrophysics Data System (ADS)

    Dolotko, O.; Senyshyn, A.; Mühlbauer, M. J.; Nikolowski, K.; Ehrenberg, H.

    2014-06-01

    Commercial NMC cells of 18650-type based on a Lix(Ni0.5Mn0.3Co0.2)O2 cathode and a graphitic anode were studied in situ using a combination of high-resolution monochromatic neutron powder diffraction and electrochemical analysis. The structural changes of the electrode materials during cell charge/discharge have been determined using Rietveld refinement and single profile decomposition techniques. A transformation of the graphitic anode to LiC12 and LiC6 through the formation of higher ordered lithium intercalated carbons was observed. A different behavior of electrochemically-driven lattice distortion was observed for NMC material in comparison to LixCoO2 and its influence on the overall cell performance has been discussed in brief. Detailed analysis of the structural changes in the Lix(Ni0.5Mn0.3Co0.2)O2 cathode material revealed reversible Li/Ni cation mixing (5.6(8)%), which is state-of-charge independent below 1600 mAh and vanishing above 1800 mAh (∼0.8Qmax).

  7. 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.

  8. Neutron diffraction studies of the hydrogen bonding and water molecules in zeolites

    SciTech Connect

    Artioli, G.; Smith, J.V.; Kvick, A.; Pluth, J.J.; Stahl, K.

    1984-01-01

    Neutron diffraction studies have been completed at different temperatures for all of the fibrous zeolites (natrolite, scolecite, edingtonite, thomsonite) and completed or in progress for several other zeolites with ordered or disordered frameworks (brewsterite, bikitaite, heulandite, yugawaralite). The evaluation of the data collected to date reveals the complexity of the interaction between cations, water molecules and framework atoms. The role of the water molecules is twofold: to complete the coordination of the cations in the cavities and to minimize the electrostatic repulsion between the framework oxygens. The hydrogen atom arrangement seems to be mainly influenced by the cation-hydrogen repulsion. A secondary effect on the hydrogen bonding system is played by the Si, Al distribution in the framework, that is the charge distribution around the acceptor oxygen atoms. The charge saturation of the framework oxygen atoms, the distance between pairs of available hydrogen bond acceptors and the flexibility of the water molecules determine the hydrogen bond geometry. The hydrogen bond lengths in zeolites are usually long in comparison with the range found in other crystalline hydrates.

  9. NEUTRON DIFFRACTION MEASUREMENT OF RESIDUAL STRESSES IN FRICTION STIR PROCESSED NANOCOMPOSITE SURFACE LAYER

    SciTech Connect

    Xu, Hanbing; Hubbard, Camden R; An, Ke; Wang, Xun-Li; Feng, Zhili; Qu, Jun

    2009-01-01

    Friction stir processing (FSP) was successfully used to stir and mix nano-sized Al2O3 particles into a Al6061-T6 aluminum plate to form a nanocomposite layer up to 3 mm thick. This nanocomposite surface has demonstrated significantly improved surface hardness, yield strength, and wear-resistance without sacrificing the substrate ductility and conductivity. Neutron diffraction analysis was conducted to determine the residual stress distribution in the nanocomposite surface layer. For comparison, the residual stress of the aluminum surface that was processed similarly but had no particle involved was also measured. Results showed that the macro-level residual stresses in the FSP zone without particles are low due to the annealing effect induced by the long heating time and large heat input. The macro-level residual stresses in the FSP-processed Al-Al2O3 nanocomposite zone are tensile up to 100 MPa in all three directions. The details of the results will be further discussed in the paper.

  10. 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.

  11. 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.

  12. Interaction of substance P with phospholipid bilayers: A neutron diffraction study.

    PubMed Central

    Bradshaw, J P; Davies, S M; Hauss, T

    1998-01-01

    Neutron diffraction has been used to study the membrane-bound structure of substance P (SP), a member of the tachykinin family of neuropeptides. The depth of penetration of its C-terminus in zwitterionic and anionic phospholipid bilayers was probed by specific deuteration of leucine 10, the penultimate amino acid residue. The results show that the interaction of SP with bilayers, composed of either dioleoylphosphatidylcholine (DOPC), or a 50:50 mixture of DOPC and the anionic phospholipid dioleoylphosphatidylglycerol (DOPG), takes place at two locations. One requires insertion of the peptide into the hydrophobic region of the bilayer, the other is much more peripheral. The penetration of the peptide into the hydrophobic region of the bilayer is reflected in a marked difference in the water distribution profiles. SP is seen to insert into DOPC bilayers, but a larger proportion of the peptide is found at the surface when compared to the anionic bilayers. The positions of the two label populations show only minor differences between the two types of bilayer. PMID:9675189

  13. Lattice thermal expansion effects in pure and doped cordierite by time-of-flight neutron diffraction

    SciTech Connect

    Predecki, P.K.; Haas, J.; Faber, J. Jr.; Hitterman, R.L.

    1985-10-01

    The thermal expansion behavior of pure, Ge-doped and Li-doped hexagonal cordierites with respective compositions: 2Mg0 2Al2O3 5SiO2, 2Mg0 2Al2O3 4SiO2 GeO2, and 2Mg0 (2+x)Al2O3 (5-2x)SiO2 xLi2O with x = .174, was investigated using time-of-flight neutron powder diffraction at temperatures from 22 to 750C in vacuum. The data were refined in space group P6/mcc using the Rietveld method. The lattice thermal expansion curves of all 3 samples were quite similar. The negative c axis expansion is asociated with (1) displacement of the T2 cations generally toward the c axis channels and (2) changes in the distortion of the coupled T1/M tetrahedra/octahedra in the structure. Both contributions were present in all 3 samples but the first was more dominant in the Ge doped sample. The nature and origin of the distortions in T1 and M are discussed.

  14. High-temperature single-crystal neutron diffraction study ofnatural chondrodite

    SciTech Connect

    Kunz, Martin; Lager, George A.; Burgi, Hans-Beat; Fernandez-Diaz,Maria Teresa

    2006-06-19

    The H-atom environment in a Tilly Foster chondrodite wasanalyzed using single-crystal neutron-diffraction data collected at 500,700 and 900 K and previously published low temperature data collected at10 K, 100 K and 300 K on the same crystal(Mg4.64Fe0.28Mn0.014Ti0.023(Si1.01O4)2F1.16OH0.84, Friedrich et al.2001). The full mean square displacement matrix S of the O-H pair wasdetermined from the temperature dependence of the anisotropicdisplacement parameters, enabling a proper correction of the O-H bond forthermal vibration without assumptions about the correlation of O and Hmovements. The results show that the perpendicular O-H motions inchondrodite are intermediate between the riding and the independentmotion models. The corrected O-H bond lengths do not change withtemperature whereas the corrected H...F distances show an increase of~;0.02 Angstrom with temperature, as do the Mg-O distances. This resultshows that spectroscopic observations on the strength of the covalent O-Hbond cannot be interpreted unambiguously in terms of a correspondingbehaviour of the associated H...O/F hydrogen bond.

  15. 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.

  16. In Situ Neutron Diffraction Studies of Large Monotonic Deformations of Superelastic Nitinol

    NASA Astrophysics Data System (ADS)

    Stebner, Aaron P.; Paranjape, Harshad M.; Clausen, Bjørn; Brinson, L. Catherine; Pelton, Alan R.

    2015-06-01

    Superelastic Nitinol micromechanics are studied well into plastic deformation regimes using neutron diffraction. Insights are made into the nature of initial transformation, bulk transformation, plastic deformation, and unloading. Schmid factor predictions based on habit plane variants are found to best describe the very first grains that transform, prior to the transformation plateaus. However, the bulk transformation behavior that gives rise to transformation plateaus violates single crystal Schmid factor analyses, indicating that in bulk polycrystals, it is the effect of grain neighborhoods, not the orientations of individual grains, that drives transformation behaviors. Beyond the plateaus, a sudden shift in micromechanical deformation mechanisms is observed at ~8.50 %/4.75 % tension/compression engineering strain. This mechanism results in reverse-phase transformation in both cases, indicating a strong relaxation in internal stresses of the samples. It is inferred that this mechanism is most likely initial bulk plastic flow, and postulated that it is the reason for a transition from fatigue life enhancement to detriment when pre-straining superelastic Nitinol. The data presented in this work provide critical datasets for development and verification of both phenomenological internal variable-driven and micromechanical theories of transformation-plasticity coupling in shape memory alloys.

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

  18. Correlating cycling history with structural evolution in commercial 26650 batteries using in operando neutron powder diffraction

    NASA Astrophysics Data System (ADS)

    Goonetilleke, Damian; Pramudita, James C.; Hagan, Mackenzie; Al Bahri, Othman K.; Pang, Wei Kong; Peterson, Vanessa K.; Groot, Jens; Berg, Helena; Sharma, Neeraj

    2017-03-01

    Ex situ and time-resolved in operando neutron powder diffraction (NPD) has been used to study the structural evolution of the graphite negative electrode and LiFePO4 positive electrode within ANR26650M1A commercial batteries from A123 Systems, in what to our knowledge is the first reported NPD study investigating a 26650-type battery. Batteries with different and accurately-known electrochemical and storage histories were studied, enabling the tell-tale signs of battery degradation to be elucidated using NPD. The ex-situ NPD data revealed that the intensity of the graphite/lithiated graphite (LixC6 or LiyC) reflections was affected by battery history, with lower lithiated graphite (LiC12) reflection intensities typically corresponding to more abused batteries. This indicates that the lithiation of graphite is less progressed in more abused batteries, and hence these batteries have lower capacities. In operando NPD allows the rate of structural evolution in the battery electrode materials to be correlated to the applied current. Interestingly, the electrodes exhibit different responses to the applied current that depend on the battery cycling history, with this particularly evident for the negative electrode. Therefore, this work illustrates how NPD can be used to correlate a battery history with electrode structure.

  19. 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.

  20. 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.

  1. Uranium surroundings in borosilicate glass from neutron and x-ray diffraction and RMC modelling.

    PubMed

    Fábián, M; Proffen, Th; Ruett, U; Veress, E; Sváb, E

    2010-10-13

    Neutron and high-energy x-ray diffraction measurements have been performed on multi-component 55SiO(2)·10B(2)O(3)·25Na(2)O·5BaO·ZrO(2) borosilicate host glass loaded with 30 wt% UO(3). Both the traditional Fourier transformation technique and the reverse Monte Carlo simulation of the experimental data have been applied to get structural information. It was established that the basic network structure consists of tetrahedral SiO(4) units and of mixed tetrahedral BO(4) and trigonal BO(3) units, similar to the corresponding host glass. Slight changes have been observed in the oxygen surroundings of the Na and Zr modifier cations; both the Na-O and Zr-O distances decrease and a more compact short-range structure has been obtained compared to the host glass. For the U-O correlations two distinct peaks were resolved at 1.84 and 2.24 Å, and for higher distances intermediate-range correlations were observed. Significant correlations have been revealed between U and the network former Si and B atoms. Uranium ions take part in the network forming, which may be the reason for the observed good glassy stability and hydrolytic properties.

  2. Neutron Powder Diffraction Study on the Magnetic Structure of NdPd 5 Al 2

    DOE PAGES

    Metoki, Naoto; Yamauchi, Hiroki; Kitazawa, Hideaki; ...

    2017-02-24

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

  3. 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.

  4. Neutron diffraction of titanium aluminides formed by continuous electron-beam treatment

    NASA Astrophysics Data System (ADS)

    Valkov, S.; Neov, D.; Luytov, D.; Petrov, P.

    2016-03-01

    Ti-Al-based alloys were produced by hybrid electron-beam technologies. A composite Ti-Al film was deposited on a Ti substrate by electron-beam evaporation (EBE), followed by electron-beam treatment (EBT) by a continuously scanned electron beam. The speed of the specimens motion during the EBT were V 1 = 1 cm/sec and V 2 = 5 cm/sec, in order to realize two different alloying mechanisms -- by surface melting and by electron-beam irradiation without melting the surface. The samples prepared were characterized by XRD and neutron diffraction to study the crystal structure on the surface and in depth. SEM/EDX analysis was conducted to explore the surface structure and analyze the chemical composition. Nanoindentation measurements were also carried out. No intermetallic phases were registered in the sample treated at velocity V 1, while the sample treated at V 2 exhibited a Ti3Al/TiAl structure on the surface, transformed to Ti/TiAl in depth. The nanoindentation test demonstrated a significant negative hardness gradient from the surface to the depth of the sample.

  5. Interaction of long-chain n-alcohols with fluid DOPC bilayers: a neutron diffraction study.

    PubMed

    Petrenko, Viktor I; Klacsova, Maria; Beskrovnyy, Anatoly I; Uhrikova, Daniela; Balgavy, Pavol

    2010-12-01

    Lamellar phases composed of fluid dioleoylphosphatidylcholine (DOPC) bilayers containing alkan-1-ols (CnOH, n = 8, 10, 14, 16, 18 is the number of carbon atoms) at CnOH : DOPC = 0.3 molar ratio and hydrated with heavy water at 20.2 ≥ D2O : DOPC ≥ 14.4 molar ratio were studied by neutron diffraction. The bilayer thickness d(L) and the bilayer surface area A(L) per DOPC at the bilayer-water interface were obtained from the lamellar repeat period d using molecular volumes of DOPC, CnOH and D2O, and the Luzatti's method. Both the d(L) and A(L) increase with the CnOH chain length n at CnOH : DOPC = 0.3 molar ratio: d(L) = (3.888 ± 0.066) + (0.016 ± 0.005)·n (in nm), A(L) = (0.6711 ± 0.0107) + (0.0012 ± 0.0008)·n (in nm²).

  6. Neutron Diffraction Study of 1,2,3-Trichlorobenzene-d3

    NASA Astrophysics Data System (ADS)

    Groke, Dirk; Heger, Gernot; Schweiss, Bernd Peter; Weiss, Alarich

    1994-05-01

    In order to explain the observed 35Cl-NQR anomaly of the title compound, a neutron diffraction study on single crystals was carried out at 295 K and 158 K. No significant structural changes concerning phase transitions or molecular disorder between the two experiments were observed. The space group is P21/c = C2h5 with 8 molecules per unit cell. The asymmetric unit contains 2 molecules. The cell parameters were determined to a = 1264(4) pm, b = 825(2) pm, c = 1503(3) pm, ß = 14.3(3)° at 295 K and a = 1243(2)pm, b = 815(1) pm, c = 1494(2) pm, ß = 114.3(1)° at 158 K. The molecules show rigid-body behaviour. No significant changes of the molecular geometry were observed. A strong variation of the temperature factors as function of the temperature was detected. An anharmonicity of the librational potential of the molecules was found by evaluation of the thermal parameters as function of temperature. For verifying the existence of dynamic processes which lead to a bleaching out of the 35Cl-NQR lines difference, Fourier syntheses were calculated. A reorientation or an order-disorder process as suggested by 35Cl-NQR spectroscopy above 230 K could not be confirmed within the error of the experiments. The degree of deuteration of the samples was determined by refinement of the occupation factors of the deuterium sites.

  7. 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.

  8. Single-crystal polarized FTIR spectroscopy and neutron diffraction refinement of cancrinite

    NASA Astrophysics Data System (ADS)

    Della Ventura, Giancarlo; Gatta, G. Diego; Redhammer, Gunter J.; Bellatreccia, Fabio; Loose, Anja; Parodi, Gian Carlo

    2009-04-01

    We relate a single-crystal FTIR (Fourier transform infrared) and neutron diffraction study of two natural cancrinites. The structural refinements show that the oxygen site of the H2O molecule lies off the triad axis. The water molecule is almost symmetric and slightly tilted from the (0001) plane. It is involved in bifurcated hydrogen bridges, with Ow···O donor-acceptor distances >2.7 Å. The FTIR spectra show two main absorptions. The first at 3,602 cm-1 is polarized for E ⊥ c and is assigned to the ν3 mode. The second, at 3,531 cm-1, is also polarized for E ⊥ c and is assigned to ν1 mode. A weak component at 4,108 cm-1 could possibly indicate the presence of additional OH groups in the structure of cancrinite. Several overlapping bands in the 1,300-1,500 cm-1 range are strongly polarized for E ⊥ c, and are assigned to the vibrations of the CO3 group.

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

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

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

  10. Equation of state of lithium deuteride from neutron diffraction under high pressure

    NASA Astrophysics Data System (ADS)

    Besson, J. M.; Weill, G.; Hamel, G.; Nelmes, R. J.; Loveday, J. S.; Hull, S.

    1992-02-01

    Time-of-flight neutron-diffraction spectra of powder samples of 7LiD have been recorded at 300 K, up to 10 GPa at the ISIS spallation source. The experimental setup consists of a 2.5-MN hydraulic press, 50 kg in mass, acting on a toroidal anvil cell. This allows compression of 100-mm3 samples to over 10 GPa, with better stress homogeneity than flat-anvil devices. The equation of state of 7LiD has been related to the NaCl pressure scale with a precision of 1.5×10-3 on the volume variation under pressure. Comparison of existing calculations with the present data shows variable agreement, depending on the calculational hypotheses. Reassessment of the divergent theoretical estimates for the pressure of band crossing in lithium hydrides reconciles them to a common prediction of about 180 GPa for the pressure of semi- metallization. However, the present work cannot reduce the wide separation of the estimates for the B1-->B2 structural-transition pressure.

  11. 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.

  12. Synthesis of specifically deuterated ceramide [AP]-C18 and its biophysical characterization using neutron diffraction.

    PubMed

    Sonnenberger, Stefan; Eichner, Adina; Hauß, Thomas; Schroeter, Annett; Neubert, Reinhard H H; Dobner, Bodo

    2017-04-01

    The very heterogeneous group of ceramides is known to be mandatory for proper barrier functions of the outermost layer of mammalian skin, referred to as stratum corneum (SC). The synthesis of a specifically deuterated ceramide [AP]-C18 variant is described. The synthesized ceramide contains the racemic forms of the α hydroxy fatty acid. For the biophysical implementation, the received diastereomeric ceramide was applied in a neutron diffraction experiment. Therefore, a SC lipid model membrane was prepared containing the described ceramide (CER), cholesterol (CHOL), stearic acid (SA), and cholesterol sulfate (ChS) in a ratio of 55/25/15/5wt%. Thus, we were able to localize the deuterated molecule part within the bilayers. In the process, a short-periodicity phase (SPP) was observed with a unit cell scale of about 44Å. For the first time, we were able to confirm former ideas concerning the arrangement of the CER within this quaternary lipid model membrane. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. High-temperature single-crystal neutron diffraction study of natural chondrodite

    NASA Astrophysics Data System (ADS)

    Kunz, Martin; Lager, George A.; Bürgi, Hans-Beat; Fernandez-Diaz, Maria Teresa

    2006-03-01

    The H-atom environment in a Tilly Foster chondrodite was analyzed using single-crystal neutron-diffraction data collected at 500, 700 and 900 K and previously published low temperature data collected at 10, 100 and 300 K on the same crystal (Mg4.64Fe0.28Mn0.014Ti0.023(Si1.01O4)2F1.16(OH)0.84; Friedrich et al. in Am Mineral 86:981-989, 2001). The full mean square displacement matrix Σ of the O-H pair was determined from the temperature dependence of the anisotropic displacement parameters, enabling a proper correction of the O-H bond for thermal vibration without assumptions about the correlation of O and H movements. The results show that the perpendicular O-H motions in chondrodite are intermediate between the riding and the independent motion models. The corrected O-H bond lengths do not change with temperature whereas the corrected H···F distances show an increase of ~0.02 Å with temperature, as do the Mg-O distances. This result shows that spectroscopic observations on the strength of the covalent O-H bond cannot be interpreted unambiguously in terms of a corresponding behaviour of the associated H···O/F hydrogen bond.

  14. Atomic structure of Mg-based metallic glasses from molecular dynamics and neutron diffraction.

    PubMed

    Gulenko, Anastasia; Forto Chungong, Louis; Gao, Junheng; Todd, Iain; Hannon, Alex C; Martin, Richard A; Christie, Jamieson K

    2017-03-13

    We use a combination of classical molecular dynamics simulation and neutron diffraction to identify the atomic structure of five different Mg-Zn-Ca bulk metallic glasses, covering a range of compositions with substantially different behaviour when implanted in vitro. There is very good agreement between the structures obtained from computer simulation and those found experimentally. Bond lengths and the total correlation function do not change significantly with composition. The zinc and calcium bonding shows differences between composition: the distribution of Zn-Ca bond lengths becomes narrower with increasing Zn content, and the preference for Zn and Ca to avoid bonding to themselves or each other becomes less strong, and, for Zn-Ca, transforms into a positive preference to bond to each other. This transition occurs at about the same Zn content at which the behaviour on implantation changes, hinting at a possible structural connection. A very broad distribution of Voronoi polyhedra are also found, and this distribution broadens with increasing Zn content. The efficient cluster packing model, which is often used to describe the structure of bulk metallic glasses, was found not to describe these systems well.

  15. 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

  16. Texture analysis of oxide dispersion strengthened (ODS) Fe alloys by X-ray and neutron diffraction

    NASA Astrophysics Data System (ADS)

    Béchade, J. L.; Mathon, M. H.; Branger, V.; Réglé, H.; Alamo, A.

    2002-07-01

    The ferritic ODS alloys studied were obtained by mechanical alloying. This strengthening method is very attractive, in particular for nuclear applications. In order to ensure the alloy a good compromise between mechanical resistance and ductility at high temperatures, it is necessary to control the microstructure and in particular the evolution during the recrystallization. First, a preliminary study, performed by X ray diffraction and optical microscopy, shows several grain growth mechanisms ; in particular, the “abnormal” grain growth mechanism which conducts to a large grain size [1], [2]. After annealing (3600s at 1470^{circ}C), the 30% cold-worked (swaging) alloys exhibit an heterogeneous microstructure with a large grains size ( 200 to 500 μm) in the heart and near the surface of the material when the intermediate zone is inhabited by small grains ( 1 μm). Fora higher cold-work level (60%), large size grains are only present in the periphery of the material. On account of the large grain size and strong heterogeneity of the microstructure, texture analysis using laboratory x-ray beam in not well adapted and so we have decided to use neutron beam. The neutron diffraction texture analysis has been performed at the Laboratoire Léon Brillouin on the 6T1 diffractometer on 2 different rods of the alloy (corresponding to the reduction ratios of 30% and 60%). Specific samples have been machined to characterise separately the zones with a different microstructure. After deformation, the alloys exhibit a typical α-fibre texture \\{ hkl \\} <1l0> whatever the area of the sample and the reduction ratio. After recrystallization, a very inhomogeneous texture is evidenced through the thickness of the sample, in particular for the rod deformed with a reduction ratio of 30% : in the heart and in the periphery of the rod, a “single-crystal” type texture is observed; the a fibre remains for the intermediate diameter of the rod. For the rod cold rolled with a

  17. Spin density in YTiO3: I. Joint refinement of polarized neutron diffraction and magnetic x-ray diffraction data leading to insights into orbital ordering

    NASA Astrophysics Data System (ADS)

    Kibalin, I. A.; Yan, Z.; Voufack, A. B.; Gueddida, S.; Gillon, B.; Gukasov, A.; Porcher, F.; Bataille, A. M.; Morini, F.; Claiser, N.; Souhassou, M.; Lecomte, C.; Gillet, J.-M.; Ito, M.; Suzuki, K.; Sakurai, H.; Sakurai, Y.; Hoffmann, C. M.; Wang, X. P.

    2017-08-01

    Orbital ordering below 30 K was previously observed in the ferromagnetic YTiO3 compound both by polarized neutron diffraction (PND) and x-ray magnetic diffraction (XMD). In this paper we report a procedure for the joint refinement of a unique spin-density model based on both PND and XMD data. The distribution of the unpaired 3 d electron of titanium is clearly seen on the magnetization density reconstructed by the maximum entropy method from the PND data collection at 5 K. The Ti3+ 3 d orbital populations obtained by joint model refinement are discussed in terms of the orbital ordering scheme. Small but significant magnetic moments on apical oxygen O1 and yttrium atoms are found. The agreement between experimental and theoretical spin densities obtained using density functional theory is discussed.

  18. 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

  19. 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.

  20. Synthesis and Neutron Diffraction Study of Na 3WN 3 and Na 3MoN 3

    NASA Astrophysics Data System (ADS)

    Rauch, P. E.; DiSalvo, F. J.; Brese, N. E.; Partin, D. E.; O'Keeffe, M.

    1994-05-01

    We have used our ambient pressure method for the synthesis of ternary alkali metal nitrides to synthesize a new class of nitrides, Na 3MN 3 ( M = Mo or W). These compounds were synthesized from the metal nitride and NaNH 2 at 500°C under flowing ammonia at atmospheric pressure. The structures were examined using X-ray powder diffraction and neutron powder diffraction and were found to be identical with that obtained from the single crystal prepared at high pressure by Ostermann, Zachwieja, and Jacobs.

  1. Neutron Diffraction Studies of the Atomic Vibrations of Bulk and Surface Atoms of Nanocrystalline SiC

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    Thermal atomic motions of nanocrystalline Sic were characterized by two temperature atomic factors B(sub core), and B(sub shell). With the use of wide angle neutron diffraction data it was shown that at the diffraction vector above 15A(exp -1) the Wilson plots gives directly the temperature factor of the grain interior (B(sub core)). At lower Q values the slope of the Wilson plot provides information on the relative amplitudes of vibrations of the core and shell atoms.

  2. Neutron Diffraction Studies of the Atomic Vibrations of Bulk and Surface Atoms of Nanocrystalline SiC

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    Thermal atomic motions of nanocrystalline Sic were characterized by two temperature atomic factors B(sub core), and B(sub shell). With the use of wide angle neutron diffraction data it was shown that at the diffraction vector above 15A(exp -1) the Wilson plots gives directly the temperature factor of the grain interior (B(sub core)). At lower Q values the slope of the Wilson plot provides information on the relative amplitudes of vibrations of the core and shell atoms.

  3. Quasi-steady state principle and in-situ real-time investigation of transient strains in 6061-T6 Al alloy using neutron diffraction

    SciTech Connect

    Woo, Wan Chuck; Brown, D. W.; Choo, Hahn; Clausen, B; David, Stan A; Feng, Zhili; Hubbard, Camden R; Wang, Xun-Li

    2007-01-01

    Neutron diffraction research has been limited to the "static" behavior of materials since the number of collected neutrons is insufficient to reach the adequate neutron counts in rapid changes of material state. In order to achieve the desired precision for the study of the transient material behavior, we propose an in-situ neutron-diffraction measurement method based on the quasi-steady state (QSS) phenomenon. The QSS principle was applied for the measurement of transient lattice spacing changes in a 6061-T6 aluminum alloy plate during thermo-mechanical processing.

  4. 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.

  5. Time-resolved proton polarisation (TPP) images tyrosyl radical sites in bovine liver catalase.

    NASA Astrophysics Data System (ADS)

    Zimmer, Oliver; Jouve, Hélène M.; Stuhrmann, Heinrich B.

    2017-05-01

    A differentiation between dynamic polarised protons close to tyrosyl radical sites in catalase and those of the bulk is achieved by time-resolved polarised neutron scattering. Three radical sites, all of them being close to the molecular centre and the heme, appear to be equally possible. Among these is tyr-369 the radial site of which had previously been proven by EPR.

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

    SciTech Connect

    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 °C 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.

  7. 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.

  8. 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.

  9. 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.

  10. In-situ neutron diffraction study on the tension-compression fatigue behavior of a twinning induced plasticity steel

    DOE PAGES

    Xie, Qingge; Liang, Jiangtao; Stoica, Alexandru Dan; ...

    2017-05-17

    Grain orientation dependent behavior during tension-compression type of fatigue loading in a TWIP steel was studied using in-situ neutron diffraction. Orientation zones with dominant behavior of (1) twinning-de-twinning, (2) twinning-re-twinning followed by twinning-de-twinning, (3) twinning followed by dislocation slip and (4) dislocation slip were identified. Jumps of the orientation density were evidenced in neutron diffraction peaks which explains the macroscopic asymmetric behavior. The asymmetric behavior in early stage of fatigue loading is mainly due to small volume fraction of twins in comparison with that at later stage. As a result, easy activation of the de-twin makes the macroscopically unloading behaviormore » nonlinear.« less

  11. 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.

  12. Crystalline, mixed-valence manganese analogue of prussian blue: magnetic, spectroscopic, X-ray and neutron diffraction studies.

    PubMed

    Franz, Patrick; Ambrus, Christina; Hauser, Andreas; Chernyshov, Dmitry; Hostettler, Marc; Hauser, Jürg; Keller, Lukas; Krämer, Karl; Stoeckli-Evans, Helen; Pattison, Philip; Bürgi, Hans-Beat; Decurtins, Silvio

    2004-12-22

    The compound of stoichiometry Mn(II)3[Mn(III)(CN)6]2.zH2O (z = 12-16) (1) forms air-stable, transparent red crystals. Low-temperature single crystal optical spectroscopy and single crystal X-ray diffraction provide compelling evidence for N-bonded high-spin manganese(II), and C-bonded low-spin manganese(III) ions arranged in a disordered, face-centered cubic lattice analogous to that of Prussian Blue. X-ray and neutron diffraction show structured diffuse scattering indicative of partially correlated (rather than random) substitutions of [Mn(III)(CN)6] ions by (H2O)6 clusters. Magnetic susceptibility measurements and elastic neutron scattering experiments indicate a ferrimagnetic structure below the critical temperature Tc = 35.5 K.

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

    SciTech Connect

    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 °C 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.

  14. 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.

  15. Single-Crystal Neutron Diffraction Study of the Heavy-Electron Superconductor CeNiGe3

    NASA Astrophysics Data System (ADS)

    Ikeda, Yoichi; Ueta, Daichi; Yoshizawa, Hideki; Nakao, Akiko; Munakata, Koji; Ohhara, Takashi

    2015-12-01

    A single-crystal neutron diffraction study was performed on anomalous antiferromagnetic ordering in the heavy-electron superconductor CeNiGe3. We observed incommensurate magnetic Bragg reflections characterized by the incommensurate propagation vector k2 = (0,0.41,1/2) below the Néel temperature of 5 K, but no significant magnetic reflection with the commensurate propagation vector k1 = (1,0,0), at which another magnetic reflection was observed in a previous neutron diffraction study with a polycrystalline sample. From the single-crystal study, we suggest that the magnetic phase of CeNiGe3 at ambient pressure is characterized only by the incommensurate propagation vector k2.

  16. 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.

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

    SciTech Connect

    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 magnetic 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.

  18. 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

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

    SciTech Connect

    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 magnetic 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.

  20. Crystal structure of YD/sub 1. 96/ and YH/sub 1. 98/ by neutron diffraction

    SciTech Connect

    Khatamian, D.; Kamitakahara, W.A.; Barnes, R.G.; Peterson, D.T.

    1980-03-15

    The crystal structure of YD/sub 1.96/ and YH/sub 1.98/ has been examined at room temperature and 11 K by neutron-diffraction techniques. Refinement of the data reveals the occupation of both tetrahedral and octahedral interstices of the fcc metal lattice. These results help to explain some features observed in the optical properties of YH/sub x/.

  1. Accuracy of determination of position and width of molecular groups in biological and lipid membranes via neutron diffraction.

    PubMed

    Gordeliy, V I; Chernov, N I

    1997-07-01

    Neutron diffraction combined with the deuterium-labelled molecular groups of biological and model membrane components allows one to detect with high accuracy the structure of these objects. Experiments of this kind are only possible at unique high-flux neutron sources, and the planning of neutron-diffraction experiments must take into account some special requirements primarily related to the duration of the experiment and the accuracy of estimation of membrane structure parameters as a result of finite time of the measurements. This paper deals with the question of statistical accuracy of the position x(0) and width v of the distribution of deuterium labels in membranes along the normal of their plane, which are determined in a neutron diffraction experiment. It is shown that the accuracy of x(0) and v estimation does not depend on membrane constitution. It is dependent only on the scattering amplitude of the deuterium label, the label position x(0) and the distribution width v. Analytic calculations show that the statistical errors Deltax(0) and Deltav are inversely proportional to the scattering amplitude of the label and, as usual, to the square root of measurement time. The question of Deltax0 and Deltav dependence on the number of structure factors used in the calculations of x(0) and v is also studied. It is shown that, the accuracy of x(0) estimation is approximately constant with down to four structure factors used, and, with the number of the factors below four, it deteriorates drastically. Analogous is the behaviour of Deltav(h(max)) relation with one exception: abrupt deterioration of the accuracy occurs beginning with five structure factors used. One does not have to measure the highest diffraction reflections which takes a much longer time compared with the first ones. It is an important result. All the problems mentioned above have also been considered for the case of two different deuterium labels in membranes.

  2. Neutron powder diffraction experiments on AMnF 4 (A=K, Rb): nuclear and magnetic structures

    NASA Astrophysics Data System (ADS)

    Morón, M. C.; Palacio, F.; Rodriguez-Carvajal, J.

    1992-06-01

    Neutron powder diffraction experiments show that KMnF 4 is monoclinic, space group P2 1/a, and RbMnF 4 orthorhombic, space group Pmab, between room temperature and 1.5K. The magnetic structure of both compounds is antiferromagnetic with Tc =6.6K for KMnF 4 and T = 3.9K for RbMnF 4.

  3. 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

  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. Martensitic transformation in a B2-containing CuZr-based BMG composite revealed by in situ neutron diffraction

    DOE PAGES

    Song, Gian; Lee, Chanho; Hong, Sung Hwan; ...

    2017-06-27

    Here, CuZr-based bulk-metallic-glass (BMG) composites reinforced by a B2-type CuZr crystalline-phase (CP) have been widely studied, and exhibit that the plastic deformation of the CP induces martensitic transformation from the B2 to B19', which plays a dominant role in the deformation behavior and mechanical properties. In the present study, 2.0% Co containing CuZr-based BMG composites were investigated using in-situ neutron-diffraction technique. The in-situ neutron-diffraction results reveal the continuous load transfer from the glass matrix to B2 CP and martensitic transformation from the B2 CP to B19' during the deformation of the composite. Moreover, it was found that the martensitic transformationmore » is initiated at the applied stress higher than 1500 MPa, and is significantly suppressed during the deformation, as compared to other 0.5% Co-containing CuZr-based BMG composites. Based on these in-situ neutron-diffraction results, the martensitic transformation is strongly affected by the amount of the addition of Co, which determines the mechanical properties of CP-reinforced BMG composites, such as ductility and hardening capability.« less

  6. Simultaneous X-ray and neutron diffraction Rietveld refinements of nanophase iron substituted hydroxyapatite

    NASA Astrophysics Data System (ADS)

    Kyriacou, Andreas

    The effect of Fe substitution on the crystal structure of hydroxyapatite (HAp) is studied by applying simultaneous Rietveld refinements of powder x-ray and neutron diffraction patterns. Fe is one of the trace elements replacing Ca in HAp, which is the major mineral phase in bones and teeth. The morphology and magnetic properties of the Fe-HAp system are also studied by transmission electron microscopy and magnetization measurements. Samples of Ca(5-x)Fex(PO4)3OH with 0 ≤ x ≤ 0.3 were prepared. Single phase HAp was identified in x-ray diffraction patterns (XRD) of samples with x < 0.1 inferring that the solubility limits are less than 0.1. Hematite (alpha-Fe2O3) is identified as a secondary phase for higher Fe content. The refined parameters show that Fe is incorporated in the HAp structure by replacing Ca in the two crystallographic sites with a preference at the Ca2 site. This preference explains the small effect of the Fe substitution on the lattice constants of HAp. The overall decrease of the lattice constants is explained by the ionic size difference of Ca and Fe. The increasing trend of the a-lattice constant with x in the Fe substituted samples is attributed to a lattice relaxation caused by the substitution of the 4- and 6-fold Fe at the 7- and 9-fold Ca1 and Ca2 sites. This Ca local geometry reduction is indicated by a slight increase of the Ca1-O3 and Ca2-O1 bond lengths. Above the solubility limit x = 0.05, the Fe is partitioned in and out of the HAp structure with increasing nominal Fe content x. The excess Fe is oxidized to hematite. The TEM analysis and magnetic measurements support the results of the simultaneous Rietveld refinements. The TEM images show no significant effect on the morphology and size of the HAp particles upon Fe incorporation. The particles are either spheres or short rods of dimensions 20--60 nm. Hematite particles are imaged in the samples with x exceeding the solubility limit. These particles are spheres, about 15 nm in

  7. In situ neutron diffraction studies of single crystals and powders during microwave irradiation.

    PubMed

    Harrison, Andrew; Ibberson, Richard; Robb, Graeme; Whittaker, Gavin; Wilson, Chick; Youngson, Douglas

    2003-01-01

    Microwave dielectric heating has become an important method in chemical synthesis and materials processing over the past 15 years, and in the case of the reactions in solutions, there is a well-developed understanding of heating mechanisms and their influence on reaction rate. In the solid-state however, there is much less clarity, despite the advantages to be gained from better insight into the way in which such electromagnetic radiation may couple directly to charge carriers, accelerating reactions in good conductors. The related issue of the influence of microwave irradiation on biological systems, in particular, proteins, and the way in which this may pose hazards to health is similarly poorly understood despite the obvious relevance this may have to the current debate on the influence of electromagnetic radiation, in particular, microwave transmission, on human health. One reason for the paucity of fundamental insight in both fields is because most work has been performed with microwave equipment whose design is derived from that of a domestic oven, and which is not ideal for in situ studies of microwave driven processes. We have been developing new methods of irradiating a variety of solid samples while measuring structural parameters through a range of diffraction techniques, and describe apparatus that will enable X-ray or neutron scattering measurements to be performed on powders or single crystals under microwave irradiation with controlled power level. We also describe preliminary studies of a single crystal of the molecular solid aspirin, and a powder of the microwave-susceptible ionic material BaTiO3, during microwave irradiation.

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

    SciTech Connect

    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 presence 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.

  9. Structure of Cu-As-Se glasses investigated by neutron diffraction with copper isotope substitution

    NASA Astrophysics Data System (ADS)

    Xin, Shuqin; Liu, Jian; Salmon, Philip S.

    2008-08-01

    Neutron diffraction with copper isotope substitution was used to study the structure of glassy Cu5As46.25Se48.75 , which lies at x=0.0513 on the (Cu2Se)x(AsSe)1-x pseudobinary tie line. The results are consistent with fourfold coordination of copper to matrix (As or Se) atoms at a mean distance of 2.40(2)Å and with threefold coordination of arsenic to one As and two Se atoms at a mean distance of 2.43(2)Å . A comparison is made with the structure of glassy AsSe and with the structure of a high-Cu content glass with x=0.25 . It is found that the short-range order of glassy AsSe is not changed when 5.13mol% of Cu2Se is added. However, the addition of 25mol% leads to a disruption of the intermediate-range order and to an alteration of the short-range order, which is consistent [within a scenario where arsenic remains threefold coordinated by matrix atoms at a mean distance of 2.42(2)Å ] with a substitution of As-As bonds by As-Se bonds. In the x=0.25 material, the Cu to matrix atom coordination number is ≃3 at 2.42(2)Å and the Cu-Cu nearest-neighbor coordination number is 1.0(3) at 2.70(4)Å . A comparison between (i) the measured structure of the glassy network formers AsSe and As2Se3 and (ii) the results obtained from first-principles molecular-dynamics methods points to a need for more accurate simulations in order to help elucidate the structure and properties of these materials.

  10. Variable temperature neutron diffraction and X-ray charge density studies of tetraacetylethane.

    PubMed

    Piccoli, Paula M B; Koetzle, Thomas F; Schultz, Arthur J; Zhurova, Elizabeth A; Stare, Jernej; Pinkerton, A Alan; Eckert, Juergen; Hadzi, Dusan

    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) A and the O1...H1 distance increases from 1.327(10) to 1.416(6) A. The convergence of the C-O bond lengths from inequivalent distances at low temperature to identical values (1.285(4) A) 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...O contacts may be responsible for the ordering at low temperature. The intramolecular O...O distance (2.432 +/- 0.006 A) 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.

  11. Neutron Powder Diffraction Study of CO2 Hydrate as a Function of Pressure

    NASA Astrophysics Data System (ADS)

    Rawn, C. J.; Chakoumakos, B. C.; Garlea, O.; Leeman, J. R.; Alford, J.; Elwood-Madden, M.; Phelps, T. J.

    2009-12-01

    A sample of structure type I gas hydrate was synthesized from pressuring D2O ice with CO2 and was subsequently studied at high pressure by neutron powder diffraction. Once the sample was loaded into a previously cooled TiZr null scattering pressure cell, the sample was pressurized to 0.1 kbar using He gas and was subsequently cooled to 225 K. Data were collected first at 0.1 kbar and then the cell was pressurized to 1 kbar while holding the temperature constant. Subsequent pressures for data collection were obtained by releasing pressure from the cell. The lattice parameters have been refined from the data using the Rietveld method and between 0.1 and 0.7 kbar the unit cell decreased in a linear fashion with a fairly large negative slope, however, between 0.7 and 1 kbar the unit cell changes are negligible and the slope becomes flat. A second sample was studied at ambient pressure and 175 K and initially showed a large amount of solid CO2 and a small amount of ice along with the CO2 hydrate, however, over time the solid CO2 decreased as it sublimed at that temperature. The average lattice parameter from ten data sets collected at this temperature was 11.890(4) Å agreeing well with previously reported lattice parameters. ACKNOWLEDGMENTS This work is sponsored by the Office of Fossil Energy under Field Work Proposal FEAB111 and access to Oak Ridge National Laboratory's High Flux Isotope Reactor was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences. Oak Ridge National Laboratory is managed by UT-Battelle LLC, for the U.S. Department of Energy.

  12. Structural characterization of titanium-doped Bioglass using isotopic substitution neutron diffraction.

    PubMed

    Martin, Richard A; Moss, Robert M; Lakhkar, Nilay J; Knowles, Jonathan C; Cuello, Gabriel J; Smith, Mark E; Hanna, John V; Newport, Robert J

    2012-12-05

    Melt quenched silicate glasses containing calcium, phosphorus and alkali metals have the ability to promote bone regeneration and to fuse to living bone. Of these glasses 45S5 Bioglass® is the most widely used being sold in over 35 countries as a bone graft product for medical and dental applications; particulate 45S5 is also incorporated into toothpastes to help remineralize the surface of teeth. Recently it has been suggested that adding titanium dioxide can increase the bioactivity of these materials. This work investigates the structural consequences of incorporating 4 mol% TiO(2) into Bioglass® using isotopic substitution (of the Ti) applied to neutron diffraction and X-ray Absorption Near Edge Structure (XANES). We present the first isotopic substitution data applied to melt quench derived Bioglass or its derivatives. Results show that titanium is on average surrounded by 5.2(1) nearest neighbor oxygen atoms. This implies an upper limit of 40% four-fold coordinated titanium and shows that the network connectivity is reduced from 2.11 to 1.97 for small quantities of titanium. Titanium XANES micro-fluorescence confirms the titanium environment is homogenous on the micron length scale within these glasses. Solid state magic angle spinning (MAS) NMR confirms the network connectivity model proposed. Furthermore, the results show the intermediate range order containing Na-O, Ca-O, O-P-O and O-Si-O correlations are unaffected by the addition of small quantities of TiO(2) into these systems.

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

    DOE PAGES

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

    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

  14. 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.

  15. Insertion of TAT peptide and perturbation of negatively charged model phospholipid bilayer revealed by neutron diffraction.

    PubMed

    Chen, Xiaochao; Sa'adedin, Farid; Deme, Bruno; Rao, Pingfan; Bradshaw, Jeremy

    2013-08-01

    TAT peptide is one of the best-characterized cell penetrating peptides derived from the transactivator of transcription protein from the human immunodeficiency virus 1. The aim of this study was to investigate the interaction between TAT peptide and partially negatively-charged phospholipid bilayer by using lamellar neutron diffraction. The main findings are the existence of a contiguous water channel across the bilayer in the presence of TAT peptide. Taken in combination with other observations, including thinning of the lipid bilayer, this unambiguously locates the peptide within the lipid bilayer. The interaction of TAT peptide with anionic lipid bilayer, composed of an 80:20 mixture of DOPC and DOPS, takes place at two locations. One is in the peripheral aqueous phase between adjacent bilayers and the second is below the glycerol backbone region of bilayer. A membrane thinning above a peptide concentration threshold (1mol%) was found, as was a contiguous transbilayer water channel at the highest peptide concentration (10mol%). This evidence leads to the suggestion that the toroidal pore model might be involved in the transmembrane of TAT peptide. We interpret the surface peptide distribution in the peripheral aqueous phase to be a massive exclusion of TAT peptide from its intrinsic location below the glycerol backbone region of the bilayer, due to the electrostatic attraction between the negatively-charged headgroups of phospholipids and the positively charged TAT peptides. Finally, we propose that the role that negatively-charged headgroups of DOPS lipids play in the transmembrane of TAT peptide is less important than previously thought. Copyright © 2013 Elsevier B.V. All rights reserved.

  16. Neutron diffraction study of the beta' and gamma phases of LiFeO{sub 2}

    SciTech Connect

    Barre, Maud; Catti, Michele

    2009-09-15

    The beta, beta', gamma and alpha phases of LiFeO{sub 2}, synthesized as powders, were annealed at different temperatures and characterized by X-ray measurements. The beta' and gamma modifications were also studied by time-of-flight neutron diffraction (ISIS Facility, UK). The structure of the beta' phase was refined in the monoclinic C2/c space group (a=8.566(1), b=11.574(2), c=5.1970(5) A, beta=146.064(5){sup o}) to wR{sub p}=0.071-0.080 (data from four counter banks). Fe and Li atoms are ordered over two of the four independent sites, and partially disordered over the other two. The ordered Li has a distorted tetrahedral coordination. The gamma structure was refined at RT (a=4.047(1), c=8.746(2) A) and at 570 deg. C (a=4.082(3), c=8.822(6) A) in the I4{sub 1}/amd symmetry, showing full order with Li in octahedral coordination at RT, and in a split-atom configuration at high temperature. On annealing, the beta' polymorph was found to transform to gamma at 550 deg. C, thus suggesting that it is a metastable phase. Electrostatics is discussed as the driving force for the alpha->beta'->gamma ordering process of LiFeO{sub 2}. - Graphical abstract: Crystal structure of beta'-LiFeO{sub 2} (monoclinic C2/c). Lithium and iron atoms are both ordered (blue and yellow balls) and partially disordered (green balls) over four independent sites. The beta' phase transforms to fully ordered gamma (tetragonal I4{sub 1}/amd) at 550 deg. C.

  17. Magnetic phase transitions of MnWO4 studied by the use of neutron diffraction

    NASA Astrophysics Data System (ADS)

    Lautenschläger, G.; Weitzel, H.; Vogt, T.; Hock, R.; Böhm, A.; Bonnet, M.; Fuess, H.

    1993-09-01

    Neutron-powder-diffraction data, collected with the D1B diffractometer, and single-crystal data, collected with the D10 four-circle diffractometer, both at the Institut Max von Laue-Paul Langevin, Grenoble, and single-crystal data, collected with the DN4 four-circle diffractometer at the Centre d'Etudes Nucléaires de Grenoble, show that MnWO4 (space group P2/c) undergoes three magnetic phase transitions below 14 K. The transition temperatures are 13.5 K (paramagnet-AF3), 12.3 K (AF3-AF2), and 8.0 K (AF2-AF1). Phases AF3 and AF2 are incommensurate with the crystallographic lattice. The propagation vector is k=(-0.214,1/2,0.457) in each case. In AF3 the magnetic moments order in the ac plane, whereas in AF2 an additional component in the [010] direction exists. The corresponding magnetic structures were found to be a sine wave in the case of AF3 and an elliptical spiral in the case of AF2. Other possibilities, like a simple spiral, a sine wave, and commensurate collinear spin arrangements, are also discussed for AF2. The magnetic structure in AF1 was refined based on a previously reported model. It is commensurate with a propagation vector k=(+/-1/4,1/2,1/2). The magnetic moments are again collinear in the ac plane as in AF3, forming an angle of 37° with the a axis.

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

    DOE PAGES

    Liu, Haodong; An, Ke; Venkatachalam, Subramanian; ...

    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

  19. Neutron Diffraction of Aqueous Tetramethylammonium Chloride (TMA) Solutions and TMA Intercalated Swelling Clays Under Burial Conditions

    NASA Astrophysics Data System (ADS)

    Patel, R.; Howard, C. A.; Greenwell, C.; Youngs, T.; Soper, A. K.; Skipper, N. T.

    2014-12-01

    There is a need for the improvement and optimisation of clay swelling inhibitors for the enhancement of oil and gas exploration. The hydration region of both ions and the possibility of ion pairing in 1 molar aqueous solution of clay swelling inhibitor, tetramethylammonium chloride (TMACl), in D2O, under elevated hydrostatic-pressures and temperatures has been determined with unprecedented detail using a combination of neutron diffraction and small-angle scattering in conjunction with hydrogen/deuterium isotopic labeling. The O-H correlation function (H-bonds) for the water in the 1.0M solution is measured and compared with that for pure D2O. Also investigated is the effect of burial conditions on the d-spacing of TMA-intercalated vermiculite. Contrary to expectations, no aggregation of TMA ions due to hydrophobic interactions is observed, nor are any ionic pairs of TMA+ and Cl- at these burial conditions. The data revealed a more ordered water-water structure with the addition of TMACl from bulk D2O. There is no change in the hydration structure measured at the applied elevated conditions. This is in remarkable contrast to pure water at the same conditions which is well known to be compressible. The dry d-spacing of the TMA-exchanged Eucatex vermiculite is measured at 13.66 Å which increases to 14.03 Å with the addition of D2O. Beyond this, there is no change in d-spacing with increasing pressure and temperature indicating the strength of the TMA ions binding to the clay interlayers and therefore its performance as a clay-swelling inhibitor.

  20. 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.

  1. Structure of Se-Te glasses studied using neutron, X-ray diffraction and reverse Monte Carlo modelling

    NASA Astrophysics Data System (ADS)

    Itoh, Keiji

    2017-02-01

    Pulsed neutron diffraction and synchrotron X-ray diffraction measurements were performed on Se100-xTex bulk glasses with x=10, 20, 30 and 40. The coordination numbers obtained from the diffraction results demonstrate that Se and Te atoms are twofold coordinated and the glass structure is formed by the chain network. The three-dimensional structure model for Se60Te40 glass obtained by using reverse Monte Carlo modelling shows that the alternating arrangements of Se and Te atoms compose the major part of the chain clusters but several other fragments such as Sen chains and Te-Te dimers are also present in large numbers. The chain clusters have geometrically disordered forms and the interchain atomic order is different from those in the crystal structures of trigonal Se and trigonal Te.

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

    NASA Astrophysics Data System (ADS)

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

    2017-09-01

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

  3. Hydrogen molecule binding to unsaturated metal sites in metal-organic frameworks studied by neutron powder diffraction and inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Liu, Yun; Brown, Craig; Neumann, Dan; Dinca, Mircea; Long, Jeffrey; Peterson, Vanessa; Kepert, Cameron

    2007-03-01

    Metal organic framework (MOF) materials have shown considerable potential for hydrogen storage arising from very large surface areas. However, the low binding energy of hydrogen molecules limits its storage capability to very low temperatures (< 77 K), which is impractical for industrial applications. Using neutron powder diffraction (NPD), we have characterized the hydrogen adsorption sites in a selected series of MOF materials with exposed unsaturated metal ions. Direct binding between the unsaturated metal ions and hydrogen molecules is observed and responsible for the enhanced initial hydrogen adsorption enthalpy. The different metals centers in these MOFs show different binding strength and interaction distances between the hydrogen molecule and metal ions. The organic linker also affects the overall H2 binding strength. Inelastic neutron scattering spectra of H2 in these MOFs are also discussed.

  4. 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.

  5. 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.

  6. 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.

  7. Double Polarisation Observables at Pax

    NASA Astrophysics Data System (ADS)

    Nekipelov, M.

    2009-04-01

    A polarised antiproton beam at the Facility for Antiproton and Ion Research, proposed by the PAX collaboration, will provide new physics possibilities, uniquely accessible at the planned High Energy Storage Ring at FAIR. Our proposal to realise an asymmetric collider, in which polarised antiprotons with momenta of about 3.5 GeV/c collide with polarised protons with momenta up to 15 GeV/c, is well suited to perform a direct measurement of the transversity distribution function h1.

  8. 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.

  9. Double polarisation experiments in meson photoproduction

    NASA Astrophysics Data System (ADS)

    Hartmann, Jan

    2016-11-01

    One of the remaining challenges within the standard model is to gain a good understanding of QCD in the non-perturbative regime. A key step towards this aim is baryon spectroscopy, investigating the spectrum and the properties of baryon resonances. To gain access to resonances with small πN partial width, photoproduction experiments provide essential information. Partial wave analyses need to be performed to extract the contributing resonances. Here, a complete experiment is required to unambiguously determine the contributing amplitudes. This involves the measurement of carefully chosen single and double polarisation observables. In a joint endeavour by MAMI, ELSA, and Jefferson Laboratory, a new generation of experiments with polarised beams, polarised proton and neutron targets, and 4π particle detectors have been performed in recent years. Many results of unprecedented quality were recently published by all three experiments, and included by the various partial wave analysis groups in their analyses, leading to substantial improvements, e.g. a more precise determination of resonance parameters. An overview of recent results is given, with an emphasis on results from the CBELSA/TAPS experiment, and their impact on our understanding of the nucleon excitation spectrum is discussed.

  10. 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.

  11. Characterization of neutron-irradiated HT-UPS steel by high-energy X-ray diffraction microscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Xuan; Park, Jun-Sang; Almer, Jonathan; Li, Meimei

    2016-04-01

    This paper presents the first measurement of neutron-irradiated microstructure using far-field high-energy X-ray diffraction microscopy (FF-HEDM) in a high-temperature ultrafine-precipitate-strengthened (HT-UPS) austenitic stainless steel. Grain center of mass, grain size distribution, crystallographic orientation (texture), diffraction spot broadening and lattice constant distributions of individual grains were obtained for samples in three different conditions: non-irradiated, neutron-irradiated (3dpa/500 °C), and irradiated + annealed (3dpa/500 °C + 600 °C/1 h). It was found that irradiation caused significant increase in grain-level diffraction spot broadening, modified the texture, reduced the grain-averaged lattice constant, but had nearly no effect on the average grain size and grain size distribution, as well as the grain size-dependent lattice constant variations. Post-irradiation annealing largely reversed the irradiation effects on texture and average lattice constant, but inadequately restored the microstrain.

  12. Crystal structure analysis of β-tricalcium phosphate Ca 3(PO 4) 2 by neutron powder diffraction

    NASA Astrophysics Data System (ADS)

    Yashima, Masatomo; Sakai, Atsushi; Kamiyama, Takashi; Hoshikawa, Akinori

    2003-11-01

    The crystal structure of sintered β-tricalcium phosphate, Ca 3(PO 4) 2, was refined using a high-resolution neutron powder diffraction data and the Rietveld method. This material was confirmed to have a rhombohedral structure (space group R3 c, Z=21). Unit-cell parameters with higher precision ( a= b=10.4352(2) Å, c=37.4029(5) Å, α= β=90°, and γ=120° in the hexagonal setting) and positional parameters for oxygen with equal precision were obtained by the neutron powder diffraction technique, compared with the single-crystal X-ray diffraction data by Dickens et al. (J. Solid State Chem. 10 (1974) 232). The site Ca(4) with atomic coordinates [0.0, 0.0, -0.0851(6)] was confirmed to be very different from the other four Ca sites: The position Ca(4) is three-fold coordinated with oxygen atoms, and has lower occupancy factor of 0.43(4), and a higher isotropic thermal parameter. On the contrary, each of the Ca(1), Ca(2), Ca(3), and Ca(5) is fully occupied by one Ca atom and these positions are coordinated with seven, eight, eight, and six oxygen atoms, respectively. The bond valence sums of Ca(4) and Ca(5) are lower (0.7) and higher (2.7), respectively, than the others (1.8-2.1).

  13. Path length dependent neutron diffraction peak shifts observed during residual strain measurements in U–8 wt% Mo castings

    DOE PAGES

    Steiner, M. A.; Bunn, J. R.; Einhorn, J. R.; ...

    2017-05-16

    This study reports an angular diffraction peak shift that scales linearly with the neutron beam path length traveled through a diffracting sample. This shift was observed in the context of mapping the residual stress state of a large U–8 wt% Mo casting, as well as during complementary measurements on a smaller casting of the same material. If uncorrected, this peak shift implies a non-physical level of residual stress. A hypothesis for the origin of this shift is presented, based upon non-ideal focusing of the neutron monochromator in combination with changes to the wavelength distribution reaching the detector due to factorsmore » such as attenuation. The magnitude of the shift is observed to vary linearly with the width of the diffraction peak reaching the detector. Consideration of this shift will be important for strain measurements requiring long path lengths through samples with significant attenuation. This effect can probably be reduced by selecting smaller voxel slit widths.« less

  14. In-Situ Neutron Diffraction Studies of Micromechanical Behavior in a Friction Stir Welded AA7475-T761

    NASA Astrophysics Data System (ADS)

    Liu, X. P.; Lin Peng, R.; Hofmann, M.; Johansson, S.; Wang, Y. D.

    2011-01-01

    An in-situ neutron diffraction technique was used to investigate the lattice strain distributions and micromechanical behavior in a friction stir welded (FSW) sheet of AA7475-T761. The neutron diffraction experiments were performed on the spectrometer for material research, STRESS-SPEC, at FRM II (Garching, Germany). The lattice strain profiles around the weld center were measured as a function of the applied strain during the tensile loading and unloading. The anisotropic elastic and plastic properties of the FSW aluminum alloy were simulated by elasto-plastic self-consistent (EPSC) model to predict the anisotropic deformation behaviors involving the grain-to-grain interactions. Material parameters used for describing the constitutive laws of each test position were determined from the measured lattice strain distributions for different diffraction hkl planes as well as the macroscopic stress-strain curve of the FSW aluminum alloy. A good agreement between experimental results and numerical simulations was obtained. The present investigations provided a reliable prediction of the anisotropic micromechanical behavior of the FSW aluminum alloy during tensile deformation.

  15. Perdeuteration, crystallization, data collection and comparison of five neutron diffraction data sets of complexes of human galectin-3C

    PubMed Central

    Manzoni, Francesco; Saraboji, Kadhirvel; Sprenger, Janina; Kumar, Rohit; Noresson, Ann-Louise; Nilsson, Ulf J.; Leffler, Hakon; Fisher, S. Zoë; Schrader, Tobias E.; Ostermann, Andreas; Coates, Leighton; Blakeley, Matthew P.; Oksanen, Esko; Logan, Derek T.

    2016-01-01

    Galectin-3 is an important protein in molecular signalling events involving carbohydrate recognition, and an understanding of the hydrogen-bonding patterns in the carbohydrate-binding site of its C-terminal domain (galectin-3C) is important for the development of new potent inhibitors. The authors are studying these patterns using neutron crystallography. Here, the production of perdeuterated human galectin-3C and successive improvement in crystal size by the development of a crystal-growth protocol involving feeding of the crystallization drops are described. The larger crystals resulted in improved data quality and reduced data-collection times. Furthermore, protocols for complete removal of the lactose that is necessary for the production of large crystals of apo galectin-3C suitable for neutron diffraction are described. Five data sets have been collected at three different neutron sources from galectin-3C crystals of various volumes. It was possible to merge two of these to generate an almost complete neutron data set for the galectin-3C–lactose complex. These data sets provide insights into the crystal volumes and data-collection times necessary for the same system at sources with different technologies and data-collection strategies, and these insights are applicable to other systems. PMID:27841752

  16. 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).

  17. 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.

  18. 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; ...

    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

  19. 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.

  20. In-situ neutron diffraction study of deformation behavior of a multi-component high-entropy alloy

    NASA Astrophysics Data System (ADS)

    Wu, Y.; Liu, W. H.; Wang, X. L.; Ma, D.; Stoica, A. D.; Nieh, T. G.; He, Z. B.; Lu, Z. P.

    2014-02-01

    Deformation behavior of a high-entropy alloy (HEA) was investigated by in situ tensile deformation with neutron diffraction. It was found that the face-centered cubic (FCC) HEA alloy showed strong crystal elastic and plastic anisotropy, and the evolution of its lattice strains and textures were similar to those observed in conventional FCC metals and alloys. Our results demonstrated that, in spite of chemical complexity, the multi-component HEA behaved like a simple FCC metal and the deformation was caused by the motion of mixed dislocations.

  1. 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.

  2. 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.

  3. Stress-induced martensitic transformations in NiTi and NiTi-TiC composites investigated by neutron diffraction

    SciTech Connect

    Vaidyanathan, R.; Bourke, M.A.M.; Dunand, D.C.

    1998-12-31

    Superelastic NiTi (51.0 at% Ni) with 0, 10 and 20 vol% TiC particles were deformed under uniaxial compression as neutron diffraction spectra were simultaneously obtained. The experiments yielded in-situ measurements of the thermoelastic stress-induced transformation. A detailed Rietveld determination is made of the phase fractions and the evolving strains in the reinforcing TiC particles and the austenite as it transforms to martensite on loading (and its subsequent back transformation on unloading). These strains are used to shed light on the phenomenon of load transfer in composites where the matrix undergoes a stress-induced phase transformation.

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

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

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

  5. Neutron powder diffraction studies of LiIO 3 and (HIO 3, 2LiIO 3)

    NASA Astrophysics Data System (ADS)

    Bouillot, J.; Coquet, E.; Pannetier, J.; Crettez, J.-M.

    1986-02-01

    A study of the kinetics of transition of powdered samples of LiIO 3 has been performed in order to determine the domain of stability of the γ-phase and to refine its structure. For a better undertanding of the transition mechanism which may involve the presence of proton impurities, the decomposition of (HIO 3, 2LiIO 3), while increasing the temperature, has been recorded continuously by means of neutron powder diffraction and the different features appearing in the observed patterns have been analyzed. A tentative interpretation is given.

  6. A 3D profile function suitable for integration of neutron time-of-flight single crystal diffraction peaks

    NASA Astrophysics Data System (ADS)

    Gutmann, Matthias J.

    2017-03-01

    A 3D profile function is presented suitable to integrate reflections arising in time-of-flight (TOF) single crystal neutron diffraction experiments. In order to account for the large asymmetry of the peak shape in the TOF direction, a 3D Gaussian ellipsoid in the pixel (x, z) and time-of-flight coordinates is convoluted with a rising and falling exponential along the time-of-flight direction. An analytic expression is derived, making it suitable for least-squares fitting. The application of this function in detector space or reciprocal space is straightforward.

  7. In-situ neutron diffraction study of deformation behavior of a multi-component high-entropy alloy

    SciTech Connect

    Wu, Y.; Liu, W. H.; He, Z. B.; Lu, Z. P.; Wang, X. L.; Ma, D.; Stoica, A. D.; Nieh, T. G.

    2014-02-03

    Deformation behavior of a high-entropy alloy (HEA) was investigated by in situ tensile deformation with neutron diffraction. It was found that the face-centered cubic (FCC) HEA alloy showed strong crystal elastic and plastic anisotropy, and the evolution of its lattice strains and textures were similar to those observed in conventional FCC metals and alloys. Our results demonstrated that, in spite of chemical complexity, the multi-component HEA behaved like a simple FCC metal and the deformation was caused by the motion of mixed dislocations.

  8. In situ neutron diffraction study of deformation behavior of a multi-component high-entropy alloy

    SciTech Connect

    Wu, Yuan; Liu, W H; Wang, Prof Xun-Li; Ma, Dong; Stoica, Alexandru Dan; Nieh, T. G.; He, Z b; Lu, Z.P.

    2014-01-01

    Deformation behavior of a high-entropy alloy (HEA) was investigated by in situ tensile deformation with neutron diffraction. It was found that the face-centered cubic (FCC) HEA alloy showed strong crystal elastic and plastic anisotropy, and the evolution of its lattice strains and textures were similar to those observed in conventional FCC metals and alloys. Our results demonstrated that, in spite of chemical complexity, the multi-component HEA behaved like a simple FCC metal and the deformation was caused by the motion of mixed dislocations.

  9. 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.

  10. Neutron Diffraction Study of Nonstoichiometry in Ba1.5La1.5Cu3Oy

    NASA Astrophysics Data System (ADS)

    Izumi, Fujio; Takayama-Muromachi, Eiji; Kobayashi, Michiko; Uchida, Yoshishige; Asano, Hajime; Ishigaki, Tōru; Watanabe, Noboru

    1988-05-01

    The structure parameters of annealed and quenched samples of Ba1.5La1.5Cu3Oy were refined by the Rietveld analysis of TOF neutron powder diffraction data. Partial occupation of an oxygen site at (0, 1/2, 0) causes nonstoichiometry in the oxide. The y values calculated from the occupation factors of oxygen at this site are 7.20 (annealed) and 6.76 (quenched), which are in fair agreement with those determined by iodometry: 7.15 (annealed) and 6.74 (quenched).

  11. Neutron diffraction, specific heat and magnetization studies on Nd{sub 2}CuTiO{sub 6}

    SciTech Connect

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

    2016-05-23

    Structural and physical properties of a double-perovskite compound, Nd{sub 2}CuTiO{sub 6} 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 300 K, 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.

  12. Estimation of residual stress in cold rolled iron-disks using magnetic and ultrasonic methods and neutron diffraction technique

    SciTech Connect

    Aksenov, V.L.; Balagurov, A.M.; Taran, Yu.V.; Bokuchava, G.D.; Schreiber, J.

    1995-12-31

    Variation of internal stress states in cold rolled sheet metal can essentially influence the result of forming processes. Therefore it is important to control the forming process by a practicable in line testing method. For this purpose magnetic and ultrasonic nondestructive methods are available. However, it is necessary to calibrate these techniques. This paper describes a first step of such a calibration procedure making use of the neutron diffraction method. On the basis of the diffraction results an assessment of the magnetic and ultrasonic methods for the estimation of residual stress in the cold rolled iron-disks was made. Reasonable measuring concepts for practical applications to forming processes with cold rolled sheet metal are discussed.

  13. 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.

  14. 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.

  15. Polarisation, key to good localisation.

    PubMed

    van Beest, Moniek; Robben, Joris H; Savelkoul, Paul J M; Hendriks, Giel; Devonald, Mark A J; Konings, Irene B M; Lagendijk, Anne K; Karet, Fiona; Deen, Peter M T

    2006-08-01

    Polarisation of cells is crucial for vectorial transport of ions and solutes. In literature, however, proteins specifically targeted to the apical or basolateral membrane are often studied in non-polarised cells. To investigate whether these data can be extrapolated to expression in polarised cells, we studied several membrane-specific proteins. In polarised MDCK cells, the Aquaporin-2 water channel resides in intracellular vesicles and apical membrane, while the vasopressin-type 2 receptor, anion-exchanger 1 (AE1) protein and E-Cadherin mainly localise to the basolateral membrane. In non-polarised MDCK cells, however, Aquaporin-2 localises, besides plasma membrane, mainly in the Golgi complex, while the others show a dispersed staining throughout the cell. Moreover, while AQP2 mutants in dominant nephrogenic diabetes insipidus are missorted to different organelles in polarised cells, they all predominantly localise to the Golgi complex in non-polarised MDCK cells. Additionally, the maturation of V2R, and likely its missorting, is affected in transiently-transfected compared to stably-transfected cells. In conclusion, we show that the use of stably-transfected polarised cells is crucial in interpreting the processing and the localisation of membrane targeted proteins.

  16. Hadron Contribution to Vacuum Polarisation

    NASA Astrophysics Data System (ADS)

    Davier, M.; Hoecker, A.; Malaescu, B.; Zhang, Z.

    2016-10-01

    Precision tests of the Standard Theory require theoretical predictions taking into account higher-order quantum corrections. Among these vacuum polarisation plays a predominant role. Vacuum polarisation originates from creation and annihilation of virtual particle-antiparticle states. Leptonic vacuum polarisation can be computed from quantum electrodynamics. Hadronic vacuum polarisation cannot because of the non-perturbative nature of QCD at low energy. The problem is remedied by establishing dispersion relations involving experimental data on the cross section for e+ e- annihilation into hadrons. This chapter sets the theoretical and experimental scene and reviews the progress achieved in the last decades thanks to more precise and complete data sets. Among the various applications of hadronic vacuum polarisation calculations, two are emphasised: the contribution to the anomalous magnetic moment of the muon, and the running of the fine structure constant α to the Z mass scale. They are fundamental ingredients to high precision tests of the Standard Theory.

  17. Crystal and magnetic structures of Cr{sub 1∕3}NbSe{sub 2} from neutron diffraction

    SciTech Connect

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

    2016-01-07

    Neutron diffraction measurements of the Cr intercalated niobium diselenide Cr{sub 1∕3}NbSe{sub 2} together with magnetization measurements have revealed that this compound exhibits ferromagnetic ordering below T{sub C} = 96 K unlike a chiral helimagnetic order observed in the sulfide compound Cr{sub 1∕3}NbS{sub 2}. As derived from neutron diffraction data, the Cr magnetic moments μ{sub Cr} = 2.83 ± 0.03 μ{sub B} in Cr{sub 1∕3}NbSe{sub 2} are aligned within basal plane. The discrepancy in the magnetic states of Cr{sub 1∕3}NbS{sub 2} and Cr{sub 1∕3}NbSe{sub 2} is ascribed to the difference in the preferential site occupation of Cr ions in crystal lattices. In Cr{sub 1∕3}NbSe{sub 2}, the Cr ions are predominantly distributed over 2b Wyckoff site, which determines a centrosymmetric character of the crystal structure unlike Cr{sub 1∕3}NbS{sub 2}, where the Cr ions are mainly located in 2c position and the crystal structure is non-centrosymmetric.

  18. Basic nanostructure of stratum corneum lipid matrices based on ceramides [EOS] and [AP]: a neutron diffraction study.

    PubMed

    Schröter, Annett; Kessner, Doreen; Kiselev, Mikhail A; Hauss, Thomas; Dante, Silva; Neubert, Reinhard H H

    2009-08-19

    The goal of this study was to investigate the nanostructure of SC lipid model membranes comprising the most relevant SC lipids such as the unique-structured omega-acylceramide [EOS] in a near natural ratio with neutron diffraction. In models proposed recently the presence of ceramide [EOS] and FFA are necessary for the formation of one of the two existent crystalline lamellar phases of the SC lipids, the long-periodicity phase as well as for the normal barrier function of the SC. The focus of this study was placed on the influence of the FFA BA on the membrane structure and its localization within the membrane based on the ceramides [EOS] and [AP]. The internal nanostructure of such membranes was obtained by Fourier synthesis from the experimental diffraction patterns. The resulting neutron scattering length density profiles showed that the exceptionally long ceramide [EOS] is arranged in a short-periodicity phase created by ceramide [AP] by spanning through the whole bilayer and extending even further into the adjacent bilayer. Specifically deuterated BA allowed us to determine the exact position of this FFA inside this SC lipid model membrane. Furthermore, hydration experiments showed that the presented SC mimic system shows an extremely small intermembrane hydration of approximately 1 A, consequently the headgroups of the neighboring leaflets are positioned close to each other.

  19. 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.; ...

    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

  20. 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.

  1. 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

  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. Visualizing the Structural Evolution of LSM/xYSZ Composite Cathodes for SOFC by in-situ Neutron Diffraction

    SciTech Connect

    Chen, Yan; Yang, Ling; Ren, Fei; An, Ke

    2014-01-01

    Composite cathodes for solid oxide fuel cells, the mixtures of (La0.8Sr0.2)0.95MnO3- (LSM) and (Y2O3)x(ZrO2)1-x (xYSZ, x = 3, 6, 8 and 10), have the thermal stability unraveled at elevated temperatures by using in-situ neutron diffraction. The Rietveld refinement analysis of neutron diffraction visualizes the phase evolutions and the ion activities in the material systems. The phase transition of tetragonal YSZ at T > 900 C leads to a heterogeneous redistribution of Mn ions. The reaction of LSM and YSZ occurring at T > 1100 C was revealed as a three-stage process, yielding La2Zr2O7, SrZrO3 and MnO. The activities of Y, Mn and La ions at elevated temperatures are derived by the structural analysis, and the three-stage reaction of YSZ and LSM was found strongly correlated to ions behaviors.

  4. Visualizing the chemistry and structure dynamics in lithium-ion batteries by in-situ neutron diffraction

    PubMed Central

    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.

    2012-01-01

    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. PMID:23087812

  5. 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.

  6. Procedure for Computing Residual Stresses from Neutron Diffraction Data and its Application to Multi-Pass Dissimilar Weld

    SciTech Connect

    Zhang, Wei; Feng, Zhili; Crooker, Paul

    2011-01-01

    Neutron diffraction is a powerful tool for non-destructive measurement of internal residual stresses of welded structures. The conventional approach for determination of residual stresses requires the knowledge of stress-free lattice spacing a priori. For multiple-pass dissimilar metal welds common to nuclear reactor pipeline systems, the stress-free lattice parameter is a complex function of position due to the chemistry inhomogeneity in the weld region and can be challenging to determine experimentally. This paper presents a new approach to calculate the residual stress field in dissimilar welds without the use of stress-free lattice parameter. The theoretical basis takes advantage of the fact that the normal component of welding residual stresses is typically small for thin plate or pipe welds. The applicability of the new approach is examined and justified in a multi-pass dissimilar metal weld consisting of a stainless steel plate and a nickel alloy filler metal. The level of uncertainties associated with this new approach is assessed. Neutron diffraction experiment is carried out to measure the lattice spacing at various locations in the dissimilar weld. A comb-shaped specimen, electro-discharge machined from a companion weld, is used to determine the stress-free lattice spacing. The calculated results from the new approach are consistent with those from the conventional approach. The new approach is found to be a practical method for determining the two in-plane residual stress components in thin plate or pipe dissimilar metal welds.

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

    PubMed Central

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

    2014-01-01

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

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

    PubMed

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

    2014-02-12

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

  9. Analysis of neutron diffraction spectra acquired [ital in situ] during stress-induced transformations in superelastic NiTi

    SciTech Connect

    Vaidyanathan, R. ); Bourke, M.A. ); Dunand, D.C. )

    1999-09-01

    Neutron diffraction spectra were obtained during various stages of a reversible stress-induced austenite to martensite phase transformation in superelastic NiTi. This was accomplished by neutron diffraction measurements on bulk polycrystalline NiTi samples simultaneously subjected to mechanical loading. Analysis of the data was carried out using individual lattice plane ([ital hkl]) reflections as well as by Rietveld refinement. In the Rietveld procedure, strains in austenite were described in terms of an isotropic ([ital hkl] independent) and an anisotropic ([ital hkl] dependent) component. At higher stresses, austenite lattice plane reflections exhibited nonlinear and dissimilar elastic responses which may be attributed to the transformation. The texture evolution is significant in both austenite and martensite phases during the transformation and two approaches were used to describe this evolving texture, i.e., an ellipsoidal model due to March[endash]Dollase and a generalized spherical-harmonic approach. The respective predictions of the phase fraction evolution as a function of applied stress were compared. A methodology is thus established to quantify the discrete phase strains, phase volume fractions, and texture during such transformations. [copyright] [ital 1999 American Institute of Physics.

  10. Neutron diffraction study of the Li-ion battery cathode Li2FeP2O7.

    PubMed

    Barpanda, Prabeer; Rousse, Gwenaëlle; Ye, Tian; Ling, Chris D; Mohamed, Zakiah; Klein, Yannick; Yamada, Atsuo

    2013-03-18

    With a combination of magnetic susceptibility measurements and low-temperature neutron diffraction analyses, the magnetic structure of Li2FeP2O7 cathode has been solved. This pyrophosphate Li2FeP2O7 compound stabilizes into a monoclinic framework (space group P2(1)/c), having a pseudolayered structure with the constituent Li/Fe sites distributed into MO6 and MO5 building units. The magnetic susceptibility follows a Curie-Weiss behavior above 50 K. Li2FeP2O7 shows a long-range antiferromagnetic ordering at T(N) = 9 K, as characterized by the appearance of distinct additional peaks in the neutron diffraction pattern below T(N). Its magnetic reflections can be indexed with a propagation vector k = (0,0,0). The magnetic moments inside the FeO6-FeO5 clusters are ferromagnetic, whereas these clusters are antiferromagnetic along the chains. The adjacent chains are in turn ferromagnetically arranged along the a-axis. The magnetic structure of Li2FeP2O7 cathode material is described focusing on their localized spin-spin exchange. The magnetic structure and properties have been generalized for Li2FeP2O7-Li2CoP2O7 binary solid solutions.

  11. 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.; ...

    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

  12. Neutron diffraction studies on the Heusler alloy Ni{sub 50}Mn{sub 37}Sb{sub 13}

    SciTech Connect

    Rama Rao, N. V.; Chelvane, J. Arout; Chandrasekaran, V.; Morozkin, A. V.; Lamsal, J.; Yelon, W. B.; Nirmala, R.; Suresh, K. G.; Malik, S. K.

    2011-04-01

    The evolution of martensitic to austenitic transformation in Ni{sub 50}Mn{sub 37}Sb{sub 13} has been studied usingtemperature dependent neutron diffraction, thermal property, and magnetization studies. Differential scanning calorimetric studies reveal a martensitic transformation T{sub M} around 291 K. The magnetization data yield a ferromagnetic ordering temperature of 329 K in the austenitic phase and 230 K in the martensitic phase. The analysis of the powder neutron diffraction data in the temperature range of 325-12 K indicates a structural transition from a high temperature cubic L2{sub 1} type structure to an orthorhombic structure. At 270 K, both cubic and orthorhombic phases coexist. Anisotropic unit cell changes are observed at the martensitic transformation: The unit cell expands by about 1.5% along the a axis, by about 2.5% along the c axis, and compresses by about 4.28% along the b axis. Both cubic and orthorhombic phases show commensurate collinear ferromagnetic ordering with a magnetic moment of {approx}3.67 {mu}{sub B}/Mn in Mn (2a and 2f) sites.

  13. 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.

  14. 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.

  15. A powder neutron diffraction study of the magnetic structure of FeV{sub 2}S{sub 4}

    SciTech Connect

    Powell, A.V.; Vaqueiro, P.; Ritter, C.

    1999-05-01

    Variable-temperature powder neutron diffraction data demonstrate that FeV{sub 2}S{sub 4} undergoes a transition to a long-range magnetically ordered state at 135(7) K, in agreement with magnetic susceptibility data. High-resolution neutron diffraction data collected at 1.9 K reveal that magnetic ordering results in a doubling of the crystallographic unit-cell dimensions (I2/m a = 5.8303(2), b = 3.2761(1), c = 11.2398(4) {angstrom}, {beta} = 92.046(2){degree}) in the a and c directions and that the magnetic structure is described by a propagation vector of ({1/2}, 0, {1/2}). Cations in an ordered defect layer, 76% of which are Fe(II), possess an average ordered moment of 1.86(5) {mu}{sub B}, which is directed at an angle of 75{degree} to the layer. Cation-cation interactions reduce the average moment of cations in the MS{sub 2} unit to 0.17(4) {mu}{sub B}. The complex magnetic structure involves essentially collinear antiferromagnetic ordering between nearest-neighbor cations.

  16. 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.

  17. Partitioning of Elastic, Transformation, and Plastic Strains Exhibited by Shape-Memory Nickel-Titanium through Modeling and Neutron Diffraction

    NASA Astrophysics Data System (ADS)

    Stebner, Aaron Paul

    Empirical investigations and first principles calculations performed in the years since shape memory alloy (SMA) model development efforts began have unveiled contradictions between the microstructural deformation mechanisms at play within these materials and the phenomenological appearance of SMA deformations, which are used to develop constitutive models. Thus, in this work theoretical calculations, numerical modeling, and neutron diffraction experiments were performed to elucidate relationships between phenomenological appearance and mechanistic activity of SMA deformations, in particular Nickel-Titanium. Numerical methods and improvements were derived to allow for robust finite element implementation of a phenomenological SMA constitutive model. New methodologies were also developed to verify and validate mechanistic SMA constitutive model predictions of microstructure evolution for the first time. In depth neutron diffraction empirical studies investigated in situ non-proportional compression as well as large-deformation uniaxial tension and compression of bulk martensitic NiTi. From these studies, insights were gained as to the partitioning of both macroscopic stresses and strains realized of elasticity, recoverable and deformation twinning, and slip within populations of orientation-specific martensite plates. The implications these empirical findings have toward both the models presented in this work as well as future development of SMA constitutive models are documented.

  18. 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

  19. 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.

  20. Basic Nanostructure of Stratum Corneum Lipid Matrices Based on Ceramides [EOS] and [AP]: A Neutron Diffraction Study

    PubMed Central

    Schröter, Annett; Kessner, Doreen; Kiselev, Mikhail A.; Hauß, Thomas; Dante, Silva; Neubert, Reinhard H.H.

    2009-01-01

    Abstract The goal of this study was to investigate the nanostructure of SC lipid model membranes comprising the most relevant SC lipids such as the unique-structured ω-acylceramide [EOS] in a near natural ratio with neutron diffraction. In models proposed recently the presence of ceramide [EOS] and FFA are necessary for the formation of one of the two existent crystalline lamellar phases of the SC lipids, the long-periodicity phase as well as for the normal barrier function of the SC. The focus of this study was placed on the influence of the FFA BA on the membrane structure and its localization within the membrane based on the ceramides [EOS] and [AP]. The internal nanostructure of such membranes was obtained by Fourier synthesis from the experimental diffraction patterns. The resulting neutron scattering length density profiles showed that the exceptionally long ceramide [EOS] is arranged in a short-periodicity phase created by ceramide [AP] by spanning through the whole bilayer and extending even further into the adjacent bilayer. Specifically deuterated BA allowed us to determine the exact position of this FFA inside this SC lipid model membrane. Furthermore, hydration experiments showed that the presented SC mimic system shows an extremely small intermembrane hydration of ∼1 Å, consequently the headgroups of the neighboring leaflets are positioned close to each other. PMID:19686658

  1. CO2 sorption to subsingle hydration layer montmorillonite clay studied by excess sorption and neutron diffraction measurements.

    PubMed

    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 CO(2) requires that the caprock sealing the storage rock is highly impermeable to CO(2). Swelling clays, which are important components of caprocks, may interact with CO(2) leading to volume change and potentially impacting the seal quality. The interactions of supercritical (sc) CO(2) 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 CO(2) densities of ≈ 0.15 g/cm(3), followed by an approximately linear decrease of excess sorption to zero and negative values with increasing CO(2) bulk density. Neutron diffraction experiments on the same clay sample measured interlayer spacing and composition. The results show that limited amounts of CO(2) 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 CO(2) in the clay pores is relatively stable over a wide range of CO(2) pressures at a given temperature, indicating the formation of a clay-CO(2) phase. At the excess sorption maximum, increasing CO(2) sorption with decreasing temperature is observed while the high-pressure sorption properties exhibit weak temperature dependence.

  2. Magnetic octupole order in Ce0.7La0.3B6: A polarized neutron diffraction study

    NASA Astrophysics Data System (ADS)

    Kuwahara, K.; Iwasa, K.; Kohgi, M.; Aso, N.; Sera, M.; Iga, F.; Matsuura, M.; Hirota, K.

    2009-09-01

    Recently, in phase IV of CexLa1-xB6, weak but distinct superlattice reflections from the order parameter of phase IV have been detected by our unpolarized neutron scattering experiment [K. Kuwahara, K. Iwasa, M. Kohgi, N. Aso, M. Sera, F. Iga, J. Phys. Soc. Japan 76 (2007) 093702]. The scattering vector dependence of the intensity of superlattice reflections is quite unusual; the intensity is stronger for high scattering vectors. This result strongly indicates that the order parameter of phase IV is the magnetic octupole. However, the possibility that the observed superlattice reflections are due to lattice distortions could not be completely ruled out only on the basis of the unpolarized neutron scattering experiment. To confirm that the superlattice reflections are magnetic, therefore, we have performed a single crystal polarized neutron diffraction experiment on Ce0.7La0.3B6. The obtained result has clearly shown that the time reversal symmetry is broken by the order parameter of phase IV. This is further evidence for the magnetic octupole order in CexLa1-xB6.

  3. Ancient and historic steel in Japan, India and Europe, a non-invasive comparative study using thermal neutron diffraction.

    PubMed

    Grazzi, F; Civita, F; Williams, A; Scherillo, A; Barzagli, E; Bartoli, L; Edge, D; Zoppi, M

    2011-05-01

    The production and refinement of steel has followed very different paths in different parts of the Eurasian continent. In aiming to characterize the similarities and differences between various smelting and smithing methods, we have analysed steel samples from four different areas and historic periods: the Kotō Age in Japan (twelfth-sixteenth century), the Moghul Empire in India (seventeenth-nineteenth century), the Ottoman Turkish Empire (seventeenth century) and the late Middle Ages (fifteenth century) in Italy. The best quality steel was employed for forging arms and armour of high quality, so that we have selected samples from Japan, India, the Middle East and Italy belonging to such a category. Traditional methods, such as metallography, used to characterize different steels in terms of their carbon contents, microconstituents and slag inclusions, entailed an invasive approach. Since many of the selected artefacts are in a very good state of conservation, a different and non-invasive approach was desirable. To this aim, we have used time of flight neutron diffraction on the Italian Neutron Experimental Station diffractometer, located at the pulsed neutron source ISIS in the United Kingdom. By this technique, we were able to quantify the phase distribution of the metal phases, the slag inclusion content, and the oxidation state of the samples, both as average concentration on the whole artefact and in selected gauge volumes. The results of the present investigation offer an interesting picture of the steel metallurgy in different areas of the world.

  4. 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.

  5. Arrangement of ceramide [EOS] in a stratum corneum lipid model matrix: new aspects revealed by neutron diffraction studies.

    PubMed

    Kessner, Doreen; Kiselev, Mikhail; Dante, Silvia; Hauss, Thomas; Lersch, Peter; Wartewig, Siegfried; Neubert, Reinhard H H

    2008-07-01

    The lipid matrix in stratum corneum (SC) plays a key role in the barrier function of the mammalian skin. The major lipids are ceramides (CER), cholesterol (CHOL) and free fatty acids (FFA). Especially the unique-structured omega-acylceramide CER[EOS] is regarded to be essential for skin barrier properties by inducing the formation of a long-periodicity phase of 130 angstroms (LPP). In the present study, the arrangement of CER[EOS], either mixed with CER[AP] and CHOL or with CER[AP], CHOL and palmitic acid (PA), inside a SC lipid model membrane has been studied for the first time by neutron diffraction. For a mixed CER[EOS]/CER[AP]/CHOL membrane in a partly dehydrated state, the internal membrane nanostructure, i.e. the neutron scattering length density profile in the direction normal to the surface, was obtained by Fourier synthesis from the experimental diffraction patterns. The membrane repeat distance is equal to that of the formerly used SC lipid model system composed of CER[AP]/CHOL/PA/ChS. By comparing both the neutron scattering length density profiles, a possible arrangement of synthetic long-chain CER[EOS] molecules inside a SC lipid model matrix is suggested. The analysis of the internal membrane nanostructure implies that one CER[EOS] molecule penetrates from one membrane layer into an adjacent layer. A 130 angstroms periodicity phase could not be observed under experimental conditions, either in CER/CHOL mixtures or in CER/CHOL/FFA mixture. CER[EOS] can be arranged inside a phase with a repeat unit of 45.2 angstroms which is predominately formed by short-chain CER[AP] with distinct polarity.

  6. Ferroelastic contribution to the piezoelectric response in lead zirconate titanate by in situ stroboscopic neutron diffraction

    NASA Astrophysics Data System (ADS)

    Jones, Jacob L.; Hoffman, Mark; Daniels, John E.; Studer, Andrew J.

    2006-11-01

    Ferroelastic domain switching during dynamic actuation is measured in situ for a piezoelectric lead zirconate titanate (PZT) ceramic utilizing a new capability developed on The Australian Strain Scanner (TASS) at ANSTO. Diffraction patterns are obtained as a function of time during a 1 Hz cycle. The change in the 0 0 2 and 2 0 0 diffraction intensities indicates there is ferroelastic domain switching at sub-coercive (weak) fields.

  7. Dynamical diffraction of neutrons and transition from beam splitter to phase shifter case

    SciTech Connect

    Lemmel, Hartmut

    2007-10-01

    This paper presents formulas for the transmission and the reflection of neutrons on a perfect crystal blade in symmetric Laue geometry. While the standard formulas are valid either for the situation very close to the Bragg condition or far off the Bragg condition (index of refraction model) the formulas presented here smoothly cover the whole range of transition. The paper concludes with experimental considerations.

  8. Polarisation of Planets and Exoplanets

    NASA Astrophysics Data System (ADS)

    Bailey, Jeremy; Kedziora-Chudczer, Lucyna; Bott, Kimberly; Cotton, Daniel V.

    2015-11-01

    We present observations of the linear polarisation of several hot Jupiter systems with our new high-precision polarimeter HIPPI (HIgh Precision Polarimetric Instrument). By looking at the combined light of the star and planet we aim to detect the polarised light reflected from the planet's atmosphere. This can provide information on the presence of, and nature of clouds in the atmosphere, and constrain the geometric albedo of the planet. The method is applicable to both transitting and non-transitting planets, and can also be used to determine the inclination of the system, and thus the true mass for radial velocity detected planets.To predict and interpret the polarisation from such observations, we have also developed an advanced polarimetric modelling capability, by incoroporating full polarised radiative transfer into our atmospheric modelling code VSTAR. This is done using the VLIDORT vector radiative transfer solver (Spurr, 2006). The resulting code allows us to predict disc-resolved, phase-resolved, and spectrally-resolved intensity and linear polarisation for any planet, exoplanet, brown dwarf or cool star atmosphere that can be modelled with VSTAR. We have tested the code by reproducing benchmark calculations in polarised radiative transfer, and by Solar System test cases, including reproducing the classic Hansen and Hovenier (1974) calculation of the polarisation phase curves of Venus.Hansen, J.E., & Hovenier, J.W., 1974, J. Atmos. Sci., 31, 1137Spurr, R., 2006, JQSRT, 102, 316.

  9. Determination of the absolute configuration of (+)-neopentyl-1-d alcohol by neutron and x-ray diffraction analysis

    SciTech Connect

    Yuan, H.S.H.; Stevens, R.C.; Bau, R. ); Mosher, H.S. ); Koetzle, T.F. )

    1994-12-20

    The absolute configuration of (+)-neopentyl-1-d alcohol, prepared by the reduction of 2,2-dimethylpropanol-1-d by actively fermenting yeast, has been determined to be S by neutron diffraction. The neutron study was carried out on the phthalate half ester of neopentyl-1-d alcohol, crystallized as its strychnine salt. The absolute configuration of the (-)-strychninium cation was first determined by an x-ray anomalous dispersion study of its iodide salt. The chiral skeleton of strychnine then served as a reference from which the absolute configuration of the -O-CHD-C(CH[sub 3])[sub 3] group of neopentyl phthalate was determined. Difference Fourier maps calculated from the neutron data showed unambiguously that the -O-CHD-C(CH[sub 3])[sub 3] groups of both independent molecules in the unit cell had the S configuration. This work proves conclusively that the yeast system reduces aldehydes by delivering hydrogen to the re face of the carbonyl group. Crystallographic details: (-)-strychninium (+)-neopentyl-1-d phthalate, space group P2[sub 1] (monoclinic), a = 18.564(6) [angstrom], b = 7.713(2) [angstrom], c = 23.361(8) [angstrom], [beta] = 94.18(4)[degrees], V = 3336.0(5) [angstrom][sup 3], Z = 2 (T = 100 K). Final agreement factors are R(F) = 0.073 for 2768 reflections collected at room temperature (x-ray analysis) and R(F) = 0.144 for 960 reflections collected at 100 K (neutron analysis). 49 refs., 7 figs., 2 tabs.

  10. Nanostructures of Mg0.65Ti0.35Dx studied with x-ray diffraction, neutron diffraction, and magic-angle-spinning H2 NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Srinivasan, S.; Magusin, P. C. M. M.; Kalisvaart, W. P.; Notten, P. H. L.; Cuevas, F.; Latroche, M.; van Santen, R. A.

    2010-02-01

    Magnesium transition-metal alloys have a high hydrogen-storage capacity and show improved hydrogen-uptake and -release kinetics compared to magnesium alone. In the present study we have investigated the structure of bulk magnesium-titanium deuteride Mg0.65Ti0.35Dx prepared via mechanical alloying and gas-phase deuterium absorption by combined use of x-ray diffraction (XRD), neutron diffraction, and magic-angle-spinning H2 nuclear magnetic resonance (NMR). The initial ball-milled alloy has two XRD-distinct Mg and Ti fcc phases. Even after prolonged exposure to deuterium gas at 75 bar and 175°C the materials with and without palladium catalyst are only partly deuterated. Deuterium loading causes the formation of, on the one hand, bct (rutile) MgD2 nanodomains with interdispersed TiDy layers and, on the other hand, a separate fcc (fluorite) TiDz phase. The TiDy phase is XRD invisible, but shows clearly up at a H2 NMR shift of -43ppm between the shift of MgD2 (3 ppm) and the Knight shift of the TiDz phase (-143ppm) . Exchange NMR indicates complete deuterium exchange at 25°C between the MgD2 and TiDy phase within 1 s, as consistent with intimate contacts between these phases. Combined analysis of the XRD and NMR peak areas suggests that the deuterium concentrations y and z in the TiDy and TiDz domains are about 1.5 and 2.0, respectively. Comparing the intrinsic cell parameters of rutile MgH2 and fluorite TiH2 , we propose that stabilization of the mixed nanocomposite may arise from a coherent coupling between the crystal structures of the rutile MgD2 nanodomains and the thin layers of fcc TiDy .

  11. The structure of calcium metaphosphate glass obtained from x-ray and neutron diffraction and reverse Monte Carlo modelling.

    PubMed

    Wetherall, K M; Pickup, D M; Newport, R J; Mountjoy, G

    2009-01-21

    The short range structure of (CaO)(0.5)(P(2)O(5))(0.5) glass has been studied using x-ray and neutron diffraction and modelled using the reverse Monte Carlo method. Using this combination of techniques has allowed six interatomic correlations to be distinguished and fitted to obtain a set of bond lengths and coordination numbers that describe the structure of the glass. The glass consists of metaphosphate chains of phosphate tetrahedra and each phosphate unit has two non-bridging oxygen atoms available for coordination with Ca. The Ca-O correlation was fitted with two peaks at 2.35 and 2.86 Å, representing a broad distribution of bond lengths. The total Ca-O coordination is 6.9 and is consistent with distorted polyhedral units such as capped octahedra or capped trigonal prisms. It is found that most non-bridging oxygen atoms are bonded to two calcium atoms. All of these observations are consistent with Hoppe's model for phosphate glasses. Furthermore, the medium range order is revealed to consist of phosphate chains intertwined with apparently elongated clusters of Ca ions, and the Ca-O and Ca-P correlations contributed significantly to the first sharp diffraction peak in x-ray diffraction.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Neutron diffraction study of. beta. -uranium pentafluoride between 77 and 403/sup 0/K

    SciTech Connect

    Taylor, J.C.; Waugh, A.B.

    1980-11-15

    The structure of ..beta..-UF/sub 5/ has been refined by neutron powder profile analyses at 77, 293, 348, and 403/sup 0/K. The structure is relatively temperature insensitive within this range and at 403/sup 0/K there is a slow conversion to ..cap alpha..-UF/sub 5/. The coordination polyhedron may be described as either a square antiprism or a dodecahedron, the former polyhedron giving the better fit with the observed atomic positions.

  17. 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.

  18. New neutron diffraction results on magnetic properties of the cubic rare earth compounds HoP and PrX2 (X=Ru, Rh, Ir, Pt)

    NASA Astrophysics Data System (ADS)

    Fischer, P.; Hälg, W.; Kaldis, E.; Greidanus, F. J. A. M.; Buschow, K. H. J.

    1982-09-01

    Neutron diffraction studies performed on polycrystalline, NaCl type HoP in external magnetic fields yield <100> as easy directions of magnetization in the ferromagnetic state. The magnetic ordering of the MgCu2 type Laves phase systems PrX2 (X=Ru, Rh, Ir, Pt) was investigated on powdered samples by means of neutron diffraction. Simple ferromagnetic structures were observed. The determined Curie temperatures confirm bulk measurements, and the values of the ordered magnetic moments indicate crystal field effects.

  19. Single phase synthesis and room temperature neutron diffraction studies on multiferroic PbFe{sub 0.5}Nb{sub 0.5}O{sub 3}

    SciTech Connect

    Matteppanavar, Shidaling; Angadi, Basavaraj; Rayaprol, Sudhindra

    2013-02-05

    The lead-iron-niobate, (PbFe{sub 0.5}Nb{sub 0.5}O{sub 3} or PFN) was synthesized by low temperature sintering Single Step / Solid State Reaction Method. The 700 Degree-Sign C/2 hrs. calcined powder was sintered at 1050 Degree-Sign C/1 hr. The sintered pellets were characterized through X-Ray Diffraction and Neutron Diffraction at room temperature. It is found from the XRD pattern that the materials is in single phase with no traces of pyrochlore phase. It was also confirmed from the neutron diffraction pattern, the structure of PFN to be monoclinic, space group Cm. Structural studies has been carried out by refining the obtained neutron diffraction data by Rietveld refinement method using Fullprof program. The neutron diffraction pattern at 300 K (room temperature) was selected to refine the structure. The lattice parameters obtained are; a = 5.6709 A, b = 5.6732 A, c = 4.0136 A, and {alpha}= 90, {beta}= 89.881, {gamma}= 90. The P-E measurements showed hysteretic behavior with high remnant polarization.

  20. La diffraction des neutrons et des rayons X pour l'étude structurale des liquides et des verres

    NASA Astrophysics Data System (ADS)

    Fischer, H. E.; Salmon, P. S.; Barnes, A. C.

    2003-02-01

    La compréhension de mainte propriété physique d'un verre ou d'un liquide nécessite la connaissance des facteurs de structure partiels (PSFs) qui décrivent chacun la distribution d'une espèce atomique autour d'une autre. La technique de diffraction des neutrons avec substitution isotopique (NDIS) [1,2,3], ayant bien réussi a déterminer les PSFs de certains composés [4,5], est pourtant restreinte aux isotopes présentant un contraste suffisant en longueur de diffusion. D'un autre cote, la technique de diffusion anomale des rayons X (AXS ou AXD) [6] permet de faire varier la longueur de diffusion d'une espèce atomique pourvu que son énergie d'absorption soit à la fois accessible et suffisamment élevée pour donner un assez grand transfert du moment. La combinaison des techniques de diffraction des neutrons (avec ou sans substitution isotopique) et de diffraction des rayons X (avec ou sans diffusion anomale) peut donc permettre d'obtenir un meilleur contraste en longueurs de diffusion pour un système donné, mais exige une analyse de données plus soignée pour pouvoir bien tenir compte des erreurs systématiques qui sont différentes pour les 2 techniques [7]. Pour les atomes ayant des distributions électroniques quasi-sphériques, e.g. dans le cas d'un alliage liquide, la combinaison des techniques de NDIS et de diffraction des rayons X s'est déjà montrée très avantageuse pour la détermination des PSFs [8,9]. Dans le cas des verres ayant d'importantes liaisons covalentes, l'effective combinaison des 2 techniques peut être moins directe mais facilitée lorsqu'il s'agit des atomes de grand Z [10,11]. Nous présentons ici un sommaire du méthode et quelques exemples des résultats.

  1. Pion-Mass Dependence of the Nucleon Polarisabilities: A Reappraisal

    NASA Astrophysics Data System (ADS)

    Phillips, Daniel R.; Griesshammer, Harald W.; McGovern, Judith A.

    2014-09-01

    The static electric and magnetic scalar dipole polarisabilities and the four spin polarisabilities parametrise the nucleon's two-photon response. At next-to-next-to-leading order in Chiral Effective Field Theory (χEFT) with dynamical Δ (1232) s, they have recently been extracted from Compton scattering data; ongoing experiments at HI γS, MAMI and MAXlab test proton-neutron differences and chiral symmetry breaking. Comparing lattice QCD simulations at pion masses mπ > 220 MeV to data and χEFT predictions requires a reliable extrapolation to the physical point. Since χEFT provides a systematically improvable, model-independent parametrisation of the polarisabilities, it is well-suited for that task. The relative theoretical uncertainties increase with increasing mπ: the magnitudes of the polarisabilities decrease; the χEFT expansion parameter itself increases; and the Δ (1232) becomes more important, leading to a re-ordering of contributions. After a review of χEFT, this presentation offers a method to quantitatively assess error-bands for chiral lattice extrapolations which can also be applied to other cases. Published errors appear to be underestimated. The static electric and magnetic scalar dipole polarisabilities and the four spin polarisabilities parametrise the nucleon's two-photon response. At next-to-next-to-leading order in Chiral Effective Field Theory (χEFT) with dynamical Δ (1232) s, they have recently been extracted from Compton scattering data; ongoing experiments at HI γS, MAMI and MAXlab test proton-neutron differences and chiral symmetry breaking. Comparing lattice QCD simulations at pion masses mπ > 220 MeV to data and χEFT predictions requires a reliable extrapolation to the physical point. Since χEFT provides a systematically improvable, model-independent parametrisation of the polarisabilities, it is well-suited for that task. The relative theoretical uncertainties increase with increasing mπ: the magnitudes of the

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

    SciTech Connect

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

    2014-01-28

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

  3. Residual Stress Analysis in Girth-welded Ferritic and Austenitic Steel Pipes Using Neutron and X-Ray Diffraction

    SciTech Connect

    Hempel, Nico; Bunn, Jeffrey R; Nitschke-Pagel, Thomas; Payzant, E Andrew; Dilger, Klaus

    2016-01-01

    This paper is dedicated to the thorough experimental analysis of the residual stresses in the vicinity of tubular welds and the mechanisms involved in their formation. Pipes made of a ferritic-pearlitic structural steel and an austenitic stainless steel are investigated in this study. The pipes feature a similar geometry and are MAG welded with two passes and comparable parameters. Residual strain mappings are carried out using X-ray and neutron diffraction. The combined use of both techniques permits both near-surface and through-wall analyses of the residual stresses. The findings allow for a consistent interpretation of the mechanisms accounting for the formation of the residual stress fields due to the welding process. Since the results are similar for both materials, it can be concluded that residual stresses induced by phase transformations, which can occur in the structural steel, play a minor role in this regard.

  4. 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.

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

    SciTech Connect

    Garlea, Vasile O; Darie, Celine; Isnard, Olivier; Bordet, Pierre

    2006-01-01

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

  6. Compressibility of copper-oxygen bonds: a high-pressure neutron powder diffraction study of CuO

    NASA Astrophysics Data System (ADS)

    Ehrenberg, H.; McAllister, J. A.; Marshall, W. G.; Attfield, J. P.

    1999-08-01

    A high-pressure neutron powder diffraction study has been performed on CuO at room temperature for nine different pressures up to 8.8 GPa. Rietveld refinement gives very precise atomic parameters, enabling the copper-oxygen bond compressibility to be determined accurately. The Jahn-Teller elongated bond distance obeys icons/Journals/Common/kappa" ALT="kappa" ALIGN="TOP"/>Cu-O(p) = 0.0710(55)/(p+3.15(55) GPa) and is compared with the Cu-O bond compressibility in other materials. A Birch equation of state fitted to the experimental cell volume data gives K0 = 72(2) GPa, K0´ = 8.7(1.2) and V0 = 80.89(5) Å3.

  7. A neutron diffraction study of oxygen and nitrogen ordering in a kinetically stable orthorhombic iron doped titanium oxynitride

    SciTech Connect

    Wu, On Ying; Parkin, Ivan P; Hyett, Geoffrey

    2012-06-15

    The synthesis of a polycrystalline powder sample of iron doped orthorhombic titanium oxynitride, Ti{sub 2.92}Fe{sub 0.01}O{sub 4.02}N{sub 0.98}, on the scale of 0.7 g has been achieved. This was conducted by the unusual route of delamination from a steel substrate of a thin film deposited using atmospheric pressure chemical vapour deposition. The structure of the titanium oxynitride is presented, determined from a combined analysis of X-ray and neutron powder diffraction data. The use of neutron diffraction allows the position of the oxygen and nitrogen ions in the material to be reported unambiguously for the first time. In this study Ti{sub 2.92}Fe{sub 0.01}O{sub 4.02}N{sub 0.98} is found to crystallise in the Cmcm space group, iso-structural pseudobrookite, with lattice parameters a=3.81080(6) A, b=9.6253(2) A, and c=9.8859(2) A, and contains partial oxygen-nitrogen ordering. Of the three anion sites in this structure one is exclusively occupied by oxygen, while the remaining two sites are occupied by oxygen and nitrogen in a disordered manner. Testing indicates that this iron doped titanium oxynitride is a metastable phase that decomposes above 700 Degree-Sign C into TiN and TiO{sub 2}, the thermodynamic products. - Graphical abstract: We report the synthesis of Ti{sub 2.92}Fe{sub 0.01}O{sub 4.02}N{sub 0.98} deposited as a thin film using atmospheric pressure chemical vapour deposition onto stainless steel, which is then delaminated to produce a polycrystalline powder sample. This powder sample was used in a neutron diffraction experiment, and analysis of this data has allowed the position of the oxygen and nitrogen ions in the material to be reported unambiguously for the first time. Ti{sub 2.92}Fe{sub 0.01}O{sub 4.02}N{sub 0.98} is found to crystallise in the Cmcm space group iso-structural pseudobrookite and contains partial oxygen-nitrogen ordering. Highlights: Black-Right-Pointing-Pointer Partial oxygen and nitrogen ordering has been observed using neutron

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

    SciTech Connect

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

    1987-05-01

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

  9. X-ray/neutron diffraction studies and ab initio electronic structure of CeMgNi 4 and its hydride

    NASA Astrophysics Data System (ADS)

    Roquefere, Jean-Gabriel; Matar, Samir F.; Huot, Jacques; Bobet, Jean-Louis

    2009-11-01

    The crystal structure of CeMgNi 4 intermetallic compound has been studied by both X-ray and neutron diffraction. Rietveld refinement shows that both 4a and 4c sites are occupied by Ce and Mg. The exchange has been evaluated to be about 15%. The hydrogenation of the sample leads to a decomposition and to the formation of CeH 2.52. Ab initio calculations using pseudo-potential and all-electron DFT methods are performed to explain such an unexpected behaviour. They predict a larger stability of the hydride system in the orthorhombic structure rather than in the cubic one. Anti-bonding Ce-H interactions within the hydride are proposed to assess the observed easy decomposition. Moreover, the metastability introduced by mechanosynthesis (i.e. exchange between Ce and Mg) was also evaluated.

  10. 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.

  11. Monoclinic β-Li2TiO3: Neutron diffraction study and estimation of Li diffusion pathways

    NASA Astrophysics Data System (ADS)

    Monchak, M.; Dolotko, O.; Mühlbauer, M. J.; Baran, V.; Senyshyn, A.; Ehrenberg, H.

    2016-11-01

    A neutron powder diffraction study on lithium titanate Li2TiO3 was performed at low temperatures. The monoclinic β-phase has been found to be stable over the whole investigated range of temperatures (4 K-300 K). A smooth and nonlinear increase of the lattice parameters has been observed upon heating and correlated to the behavior of interatomic distances. Lithium diffusion pathways in Li2TiO3 were estimated theoretically on the basis of the obtained structural data using bond-valence modeling. Experimentally diffusion pathways were evaluated by analysis of the negative nuclear scattering densities at 1073 K, which were reconstructed using a maximum entropy method. Although the bond-valence mismatch map indicated a possible Li diffusion either in ab plane or along c direction, analysis of the experimental data revealed that Li migration is thermodynamically less feasible in latter case.

  12. Determination of the magnetic structure of CePt2In7 by means of neutron diffraction

    NASA Astrophysics Data System (ADS)

    Raba, M.; Ressouche, E.; Qureshi, N.; Colin, C. V.; Nassif, V.; Ota, S.; Hirose, Y.; Settai, R.; Rodière, P.; Sheikin, I.

    2017-04-01

    The magnetic structure of the heavy fermion antiferromagnet CePt2In7 is determined using neutron diffraction. We find a magnetic wave vector qM=(1 /2 ,1 /2 ,1 /2 ) , which is temperature independent up to TN=5.5 K. A staggered moment of 0.45 (1 ) μB at 2 K resides on the Ce ion. The nearest-neighbor moments in the tetragonal basal plane are aligned antiferromagnetically. The moments rotate by 90∘ from one CeIn3 plane to another along the c axis. A much weaker satellite peak with an incommensurate magnetic wave vector qM=(1 /2 ,1 /2 ,0.47 ) seems to develop at low temperature. However, the experimental data available so far are not sufficient to draw a definitive conclusion about the possible coexistence of commensurate and incommensurate magnetic structures in this material.

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

    NASA Astrophysics Data System (ADS)

    Pramanick, Abhijit; Prewitt, Anderson D.; Cottrell, Michelle A.; Lee, Wayne; Studer, Andrew J.; An, Ke; Hubbard, Camden R.; Jones, Jacob L.

    2010-06-01

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

  14. Direct observation by neutron diffraction of antiferromagnetic ordering in s electrons confined in regular nanospace of sodalite.

    PubMed

    Nakano, Takehito; Matsuura, Masato; Hanazawa, Atsufumi; Hirota, Kazuma; Nozue, Yasuo

    2012-10-19

    Sodium clusters formed in the regular nanospace of sodalite (aluminosilicate zeolite) are known to show antiferromagnetic order without any magnetic elements. The clusters are arrayed in a body centered cubic structure. We have performed a neutron diffraction study and succeeded in detecting the magnetic Bragg peaks of the s-electron spins for the first time. The observation of both 001 and 111 magnetic reflections confirms the antiferromagnetic order with the antiparallel coupling between the nearest neighbor clusters. The magnetic form factor was examined by analyzing the intensity ratios of the magnetic and nuclear Bragg peaks. The result is in good agreement with the shape of the s-electron wave function derived from theoretical studies of the sodium nanoclusters in the cages.

  15. Neutron diffraction investigation of residual stresses in transverse/oblique rail slices subjected to different grinding strategies

    SciTech Connect

    Gnaeupel-Herold, T.; Brand, P.C.; Prask, H.J.

    1999-05-01

    Using the Double Axis system for Residual stress, Texture, and Single crystal analysis (DARTS) at NIST, neutron diffraction residual stress measurements were carried out in the head region of five pairs of transverse and oblique cut slices of railroad track, each having a thickness of 6.35 mm. The slices were taken from a 300 HB rail of CFI 136 RE size. All slices except one unworn reference piece had the same accumulated tonnage but were ground in different intervals. The measurements confirm the results previously found which indicated the existence of high sub-surface residual tensile stresses, while the regional close to the wheel-rail contact line shows high residual compressive stresses.

  16. Tetragonal magnetic phase in Ba1-xKxFe2As2 from x-ray and neutron diffraction

    DOE PAGES

    Allred, J. M.; Avci, S.; Chung, D. Y.; ...

    2015-09-28

    In this paper, combined neutron and x-ray diffraction experiments demonstrate the formation of a low-temperature minority magnetic tetragonal phase in Ba0.76K0.24Fe2As2 in addition to the majority magnetic, orthorhombic phase. The coincident enhancement in the magnetic (1/2 1/2 1) peaks shows that this minority phase is of the same type that was observed in Ba1-xNaxFe2As2 (0.24 ≤ x ≤ 0.28), in which the magnetic moments reorient along the c axis. This is evidence that the tetragonal magnetic phase is a universal feature of the hole-doped iron-based superconductors. Finally, the observations suggest that in this regime the energy levels of the C2more » and C4 symmetric magnetic phases are very close.« less

  17. Use of neutron and X-ray diffraction to study the precipitation mechanisms of oxides in ODS materials

    NASA Astrophysics Data System (ADS)

    Toualbi, L.; Ratti, M.; André, G.; Onimus, F.; de Carlan, Y.

    2011-10-01

    It is usually accepted that the formation of nano-clusters inside Oxide Dispersion Strengthened (ODS) materials is due to the dissolution of the yttrium oxide during the mechanical alloying and to the precipitation of the nano-oxides during the consolidation process. A study was conducted to follow the dissolution and the re-precipitation of the phases after mechanical alloying and different heat treatments. A Fe-9Cr powder was milled during different milling times with 10 wt.% of yttria and/or titanium in a planetary mill. Using neutron and X-ray diffractions and the Rietveld method, the dissolution and re-precipitation of yttria was investigated. Even with a content of 10 wt.%, the yttria particles disappear during milling to form a structure which can be described as Fe crystallites coexisting with amorphous domains composed of Y and O atoms. After annealing Y and O atoms re-precipitate into the matrix to form yttria crystallites.

  18. Direct Observation by Neutron Diffraction of Antiferromagnetic Ordering in s Electrons Confined in Regular Nanospace of Sodalite

    NASA Astrophysics Data System (ADS)

    Nakano, Takehito; Matsuura, Masato; Hanazawa, Atsufumi; Hirota, Kazuma; Nozue, Yasuo

    2012-10-01

    Sodium clusters formed in the regular nanospace of sodalite (aluminosilicate zeolite) are known to show antiferromagnetic order without any magnetic elements. The clusters are arrayed in a body centered cubic structure. We have performed a neutron diffraction study and succeeded in detecting the magnetic Bragg peaks of the s-electron spins for the first time. The observation of both 001 and 111 magnetic reflections confirms the antiferromagnetic order with the antiparallel coupling between the nearest neighbor clusters. The magnetic form factor was examined by analyzing the intensity ratios of the magnetic and nuclear Bragg peaks. The result is in good agreement with the shape of the s-electron wave function derived from theoretical studies of the sodium nanoclusters in the cages.

  19. Separate determination of the amplitude of thermal vibrations and static atomic displacements in titanium carbide by neutron diffraction

    SciTech Connect

    Khidirov, I. Parpiev, A. S.

    2011-05-15

    The amplitude of thermal (dynamic) atomic vibrations and meansquare static atomic displacements in titanium carbide TiC{sub x} (x = 0.97, 0.88, 0.70) have been separately determined by measuring neutron diffraction patterns at two temperatures (T{sub 1} = 300 K and T{sub 2} = 80 K). The static lattice distortions in stoichiometric titanium carbide are experimentally found to be negligible. In the TiC{sub x} homogeneity range, the amplitude {radical}u{sup 2}{sub dyn} of thermal atomic vibrations significantly increases with a decrease in the carbon concentration. The Debye temperature has been determined for the first time in the TiC{sub x} homogeneity range at both room and liquid-nitrogen temperatures.

  20. 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].