Science.gov

Sample records for resolved powder diffraction

  1. X-ray characterization by energy-resolved powder diffraction

    NASA Astrophysics Data System (ADS)

    Cheung, G.; Hooker, S. M.

    2016-08-01

    A method for single-shot, nondestructive characterization of broadband x-ray beams, based on energy-resolved powder diffraction, is described. Monte-Carlo simulations are used to simulate data for x-ray beams in the keV range with parameters similar to those generated by betatron oscillations in a laser-driven plasma accelerator. The retrieved x-ray spectra are found to be in excellent agreement with those of the input beams for realistic numbers of incident photons. It is demonstrated that the angular divergence of the x rays can be deduced from the deviation of the detected photons from the Debye-Scherrer rings which would be produced by a parallel beam. It is shown that the angular divergence can be measured as a function of the photon energy, yielding the angularly resolved spectrum of the input x-ray beam.

  2. In-situ time resolved synchrotron powder diffraction studies of synthesis and chemical reactions

    SciTech Connect

    Norby, P.

    1995-09-01

    Equipment for time and temperature dependent powder diffraction has been developed, especially in order to be able to study hydrothermal syntheses of zeolites. The system is very versatile and has so far been used to study e.g. hydrothermal syntheses of zeolites and aluminophosphates, syntheses of layered phosphates, formation of Sorel cements, dehydration and phase transformations of zeolites, solid state synthesis of lanthanum manganites, ion exchange of zeolites using molten salt, and oxidation/reduction of lanthanum manganites at high temperatures. The sample is contained in quartz capillaries and is heated using a stream of hot air. External pressure can be applied allowing hydrothermal syntheses at temperatures up to 200 C to be performed. Controlled atmosphere is obtained by flowing gas or a mixture of gases through the capillary.

  3. Powder Diffraction: By Decades

    NASA Astrophysics Data System (ADS)

    David, William I. F.

    This introductory chapter reviews the first 100 years of powder diffraction, decade by decade, from the earliest X-ray powder diffraction measurements of the crystal structure of graphite through to the diversity and complexity of twenty-first century powder diffraction. Carbon features as an illustrative example throughout the discussion of these ten decades from graphite and the disorder of carbon black through to lonsdaleite, the elusive hexagonal polymorph of diamond, and C60, the most symmetrical of molecules. Electronics and computing have played a leading role in the development of powder diffraction, particularly over the past 60 years, and the Moore's Law decade-by-decade rise in computing power is clear in the increasing complexity of powder diffraction experiments and material systems that can be studied. The chapter concludes with a final discussion of decades - the four decades of length-scale from the ångstrom to the micron that not only represent the domain of powder diffraction but are also the distances that will dominate twenty-first century science and technology.

  4. Devitrification of Mechanically Alloyed Zr-Ti-Nb-Cu-Ni-Al Glassy Powders Studied by Time-Resolved X-ray Diffraction

    SciTech Connect

    Scudino, S.; Sordelet, D.J.; Eckert, J.

    2009-04-13

    The crystallization of mechanically alloyed Zr{sub 67}Ti{sub 6.14}Nb{sub 1.92}Cu{sub 10.67}Ni{sub 8.52}Al{sub 5.75} glassy powder is investigated by time-resolved X-ray diffraction. The powder displays a multi-step crystallization behavior characterized by the formation of a metastable nanoscale quasicrystalline phase during the first stage of the crystallization process. At higher temperatures, coinciding with the second crystallization event, the amorphous-to-quasicrystalline transformation is followed by the precipitation of the tetragonal Zr{sub 2}Cu phase (space group I4/mmm) and the tetragonal Zr{sub 2}Ni phase (space group I4/mcm). The transformations are gradual and the quasicrystals and the subsequent phases coexist over a temperature interval of about 25K.

  5. Time-resolved X-ray powder diffraction on a three-way catalyst at the GILDA beamline.

    PubMed

    Martorana, A; Deganello, G; Longo, A; Deganello, F; Liotta, L; Macaluso, A; Pantaleo, G; Balerna, A; Meneghini, C; Mobilio, S

    2003-03-01

    Time-resolved X-ray diffraction experiments carried out at the beamline BM08-GILDA of ESRF allowed a study of the structural modifications taking place in a Pt/ceria-zirconia catalyst while the CO oxidation reaction was in progress. The capillary tube in which the sample is stored acts effectively as a chemical microreactor that ensures homogeneity of the sample treatments and minimization of diffusion effects. During the flowing of the reactant CO/He mixture, the investigated catalyst undergoes a fast Ce(IV)-Ce(III) partial reduction that involves the release of one O atom for every two reduced Ce cations. Because Ce(III) has a larger ionic radius than Ce(IV), the structural modification produces an increase of the lattice constant of the ceria-zirconia mixed oxide, and this increase is monitored by the translating imaging-plate device implemented at GILDA. The CO(2) resulting from the oxidation of the fluxed CO is monitored by a quadrupole mass spectrometer during the recording of the time-resolved X-ray diffraction pattern. The chemical and structural information was combined to show that the CO(2) yield is nearly constant until the catalytic system can provide oxygen for the reaction, while the structural rearrangement of the catalyst is delayed with respect to the switching on of the CO/He flux. After this induction time, during which CO(2) is produced with no structural modification of the catalyst, a fast increase of the lattice constant takes place. PMID:12606797

  6. High Resolution Powder Diffraction and Structure Determination

    SciTech Connect

    Cox, D. E.

    1999-04-23

    It is clear that high-resolution synchrotrons X-ray powder diffraction is a very powerful and convenient tool for material characterization and structure determination. Most investigations to date have been carried out under ambient conditions and have focused on structure solution and refinement. The application of high-resolution techniques to increasingly complex structures will certainly represent an important part of future studies, and it has been seen how ab initio solution of structures with perhaps 100 atoms in the asymmetric unit is within the realms of possibility. However, the ease with which temperature-dependence measurements can be made combined with improvements in the technology of position-sensitive detectors will undoubtedly stimulate precise in situ structural studies of phase transitions and related phenomena. One challenge in this area will be to develop high-resolution techniques for ultra-high pressure investigations in diamond anvil cells. This will require highly focused beams and very precise collimation in front of the cell down to dimensions of 50 {micro}m or less. Anomalous scattering offers many interesting possibilities as well. As a means of enhancing scattering contrast it has applications not only to the determination of cation distribution in mixed systems such as the superconducting oxides discussed in Section 9.5.3, but also to the location of specific cations in partially occupied sites, such as the extra-framework positions in zeolites, for example. Another possible application is to provide phasing information for ab initio structure solution. Finally, the precise determination of f as a function of energy through an absorption edge can provide useful information about cation oxidation states, particularly in conjunction with XANES data. In contrast to many experiments at a synchrotron facility, powder diffraction is a relatively simple and user-friendly technique, and most of the procedures and software for data analysis

  7. Macromolecular Powder Diffraction: Ready for genuine biological problems.

    PubMed

    Karavassili, Fotini; Margiolaki, Irene

    2016-01-01

    Knowledge of 3D structures of biological molecules plays a major role in both understanding important processes of life and developing pharmaceuticals. Among several methods available for structure determination, macromolecular X-ray powder diffraction (XRPD) has transformed over the past decade from an impossible dream to a respectable method. XRPD can be employed in biosciences for various purposes such as observing phase transitions, characterizing bulk pharmaceuticals, determining structures via the molecular replacement method, detecting ligands in protein-ligand complexes, as well as combining micro-sized single crystal crystallographic data and powder diffraction data. Studies using synchrotron and laboratory sources in some standard configuration setups are reported in this review, including their respective advantages and disadvantages. Methods presented here provide an alternative, complementary set of tools to resolve structural problems. A variety of already existing software packages for powder diffraction data processing and analysis, some of which have been adapted to large unit cell studies, are briefly described. This review aims to provide necessary elements of theory and current methods, along with practical explanations, available software packages and highlighted case studies. PMID:26786768

  8. X-ray diffraction investigation of ultrafine boron nitride powders

    SciTech Connect

    Gurov, S.V.; Chukalin, V.I.; Rezchikova, T.V.; Torbov, V.J.; Troitskii, V.N.

    1986-01-01

    This paper presents an x-ray diffraction analysis of ultrafine boron nitride powders of different mean particle sizes. Diffraction spectra of the ultrafine boron nitride powders were obtained using a DRON-1 apparatus. The experimental facts are indicative of a turbostratic character of deformation of the hexagonal lattice of ultrafinely divided boron nitride.

  9. 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}

  10. 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

  11. Powder diffraction from a continuous microjet of submicrometer protein crystals.

    PubMed

    Shapiro, D A; Chapman, H N; Deponte, D; Doak, R B; Fromme, P; Hembree, G; Hunter, M; Marchesini, S; Schmidt, K; Spence, J; Starodub, D; Weierstall, U

    2008-11-01

    Atomic-resolution structures from small proteins have recently been determined from high-quality powder diffraction patterns using a combination of stereochemical restraints and Rietveld refinement [Von Dreele (2007), J. Appl. Cryst. 40, 133-143; Margiolaki et al. (2007), J. Am. Chem. Soc. 129, 11865-11871]. While powder diffraction data have been obtained from batch samples of small crystal-suspensions, which are exposed to X-rays for long periods of time and undergo significant radiation damage, the proof-of-concept that protein powder diffraction data from nanocrystals of a membrane protein can be obtained using a continuous microjet is shown. This flow-focusing aerojet has been developed to deliver a solution of hydrated protein nanocrystals to an X-ray beam for diffraction analysis. This method requires neither the crushing of larger polycrystalline samples nor any techniques to avoid radiation damage such as cryocooling. Apparatus to record protein powder diffraction in this manner has been commissioned, and in this paper the first powder diffraction patterns from a membrane protein, photosystem I, with crystallite sizes of less than 500 nm are presented. These preliminary patterns show the lowest-order reflections, which agree quantitatively with theoretical calculations of the powder profile. The results also serve to test our aerojet injector system, with future application to femtosecond diffraction in free-electron X-ray laser schemes, and for serial crystallography using a single-file beam of aligned hydrated molecules. PMID:18955765

  12. Quality experimental and calculated powder x-ray diffraction

    SciTech Connect

    Sullenger, D.B.; Cantrell, J.S.; Beiter, T.A.; Tomlin, D.W.

    1996-08-01

    For several years, we have submitted quality powder XRD patterns to the International Centre for Diffraction Data for inclusion as reference standards in their Powder Diffraction File. The procedure followed is described; examples used are {beta}-UH{sub 3}, {alpha}- BaT{sub 2}, alpha-lithium disilicate ({alpha}-Li{sub 2}Si{sub 2}O{sub 5}), and 2,2`,4,4`,6,6`hexanitroazobenzene-III (HNAB-III).

  13. Total-scattering pair-distribution function of organic material from powder electron diffraction data.

    PubMed

    Gorelik, Tatiana E; Schmidt, Martin U; Kolb, Ute; Billinge, Simon J L

    2015-04-01

    This paper shows that pair-distribution function (PDF) analyses can be carried out on organic and organometallic compounds from powder electron diffraction data. Different experimental setups are demonstrated, including selected area electron diffraction and nanodiffraction in transmission electron microscopy or nanodiffraction in scanning transmission electron microscopy modes. The methods were demonstrated on organometallic complexes (chlorinated and unchlorinated copper phthalocyanine) and on purely organic compounds (quinacridone). The PDF curves from powder electron diffraction data, called ePDF, are in good agreement with PDF curves determined from X-ray powder data demonstrating that the problems of obtaining kinematical scattering data and avoiding beam damage of the sample are possible to resolve. PMID:25510245

  14. Total-scattering pair-distribution function of organic material from powder electron diffraction data

    SciTech Connect

    Gorelik, Tatiana E.; Billinge, Simon J. L.; Schmidt, Martin U.; Kolb, Ute

    2015-04-01

    This paper shows for the first time that pair-distribution function analyses can be carried out on organic and organo-metallic compounds from powder electron diffraction data. Different experimental setups are demonstrated, including selected area electron diffraction (SAED) and nanodiffraction in transmission electron microscopy (TEM) or nanodiffraction in scanning transmission electron microscopy (STEM) modes. The methods were demonstrated on organo-metallic complexes (chlorinated and unchlorinated copper-phthalocyanine) and on purely organic compounds (quinacridone). The PDF curves from powder electron diffraction data, called ePDF, are in good agreement with PDF curves determined from X-ray powder data demonstrating that the problems of obtaining kinematical scattering data and avoiding beam-damage of the sample are possible to resolve.

  15. Total-scattering pair-distribution function of organic material from powder electron diffraction data

    DOE PAGESBeta

    Gorelik, Tatiana E.; Billinge, Simon J. L.; Schmidt, Martin U.; Kolb, Ute

    2015-04-01

    This paper shows for the first time that pair-distribution function analyses can be carried out on organic and organo-metallic compounds from powder electron diffraction data. Different experimental setups are demonstrated, including selected area electron diffraction (SAED) and nanodiffraction in transmission electron microscopy (TEM) or nanodiffraction in scanning transmission electron microscopy (STEM) modes. The methods were demonstrated on organo-metallic complexes (chlorinated and unchlorinated copper-phthalocyanine) and on purely organic compounds (quinacridone). The PDF curves from powder electron diffraction data, called ePDF, are in good agreement with PDF curves determined from X-ray powder data demonstrating that the problems of obtaining kinematical scattering datamore » and avoiding beam-damage of the sample are possible to resolve.« less

  16. Idealized powder diffraction patterns for cellulose polymorphs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cellulose samples are routinely analyzed by X-ray diffraction to determine their crystal type (polymorph) and crystallinity. However, the connection is seldom made between those efforts and the crystal structures of cellulose that have been determined with synchrotron X-radiation and neutron diffrac...

  17. Single Hit Energy-resolved Laue Diffraction

    SciTech Connect

    Patel, Shamim; Suggit, Matthew J.; Stubley, Paul G.; Ciricosta, Orlando; Wark, Justin S.; Higginbotham, Andrew; Hawreliak, James A.; Collins, Gilbert W.; Eggert, Jon H.; Comley, Andrew J.; Foster, John M.

    2015-05-15

    In situ white light Laue diffraction has been successfully used to interrogate the structure of single crystal materials undergoing rapid (nanosecond) dynamic compression up to megabar pressures. However, information on strain state accessible via this technique is limited, reducing its applicability for a range of applications. We present an extension to the existing Laue diffraction platform in which we record the photon energy of a subset of diffraction peaks. This allows for a measurement of the longitudinal and transverse strains in situ during compression. Consequently, we demonstrate measurement of volumetric compression of the unit cell, in addition to the limited aspect ratio information accessible in conventional white light Laue. We present preliminary results for silicon, where only an elastic strain is observed. VISAR measurements show the presence of a two wave structure and measurements show that material downstream of the second wave does not contribute to the observed diffraction peaks, supporting the idea that this material may be highly disordered, or has undergone large scale rotation.

  18. Scanning CCD Detector for X-ray Powder Diffraction

    NASA Astrophysics Data System (ADS)

    Madden, T.; Baldwin, J.; Von Dreele, R.; Suchomel, M.; Toby, B. H.

    2014-03-01

    We discuss the design, fabrication and use of a custom CCD detector for x-ray powder diffraction measurements. The detector is mounted on a diffractometer arm, where line-by-line readout of the CCD is coupled to continuous motion of the arm. As the arm moves, the data from the CCD detector are accumulated and can be viewed as if it were a "film strip" with partial powder diffraction rings. Because of the unique design of the camera, both high-resolution and rapid measurements can be performed. Powder diffraction patterns are collected with speeds of a few minutes, or less, with many of the advantages of large area position-sensitive detectors, for example amorphous silicon flat panels, such as high sensitivity, direct evidence of grainy samples and freedom from low-angle asymmetry, but with resolution better than linear position-sensitive detectors and nearly as good as the ultimate in resolution, analyser-crystal detection [2,3].

  19. Ultrafast Time-Resolved Electron Diffraction with Megavolt Electron Beams

    SciTech Connect

    Hastings, J.B.; Rudakov, F.M.; Dowell, D.H.; Schmerge, J.F.; Cardoza, J.D.; Castro, J.M.; Gierman, S.M.; Loos, H.; Weber, P.M.; /Brown U.

    2006-10-24

    An rf photocathode electron gun is used as an electron source for ultrafast time-resolved pump-probe electron diffraction. We observed single-shot diffraction patterns from a 160 nm Al foil using the 5.4 MeV electron beam from the Gun Test Facility at the Stanford Linear Accelerator. Excellent agreement with simulations suggests that single-shot diffraction experiments with a time resolution approaching 100 fs are possible.

  20. Ab Initio Structure Analysis Using Laboratory Powder Diffraction Data

    NASA Astrophysics Data System (ADS)

    Sasaki, Akito

    Today, laboratory X-ray diffractometers are seeing increasingly wide use in the ab initio crystal structure analysis of organic powder samples. This is because optics and optical devices have been improved, making it possible to obtain precise integrated intensities of reflections in high 2-theta ranges. Another reason is that one can use direct-space methods, which do not require “high-resolution diffraction data”, much more easily than before. Described here are some key points to remember when performig ab initio crystal structure analysis using powder diffraction data from organic compounds.

  1. Powder diffraction studies using anomalous dispersion

    SciTech Connect

    Cox, D.E.; Wilkinson, A.P.

    1993-05-01

    With the increasing availability and accessibility of high resolution powder diffractometers at many synchrotron radiation sources throughout the world, there is rapidly-growing interest in the exploitation of anomalous dispersion techniques for structural studies of polycrystalline materials. In conjunction with the Rietveld profile method for structure refinement, such studies are especially useful for the determination of the site distributions of two or more atoms which are near neighbors in the periodic table, or atoms which are distributed among partially occupied sites. Additionally, it is possible to (1) determine the mean-square displacements associated with different kinds of atoms distributed over a single set of sites, (2) distinguish between different oxidation states and coordination geometries of a particular atom in a compound and (3) to determine f` for a wide range of atomic species as a function of energy in the vicinity of an absorption edge. Experimental methods for making anomalous dispersion measurements are described in some detail, including data collection strategies, data analysis and correlation problems, possible systematic errors, and the accuracy of the results. Recent work in the field is reviewed, including cation site-distribution studies (e.g. doped high {Tc} superconductors, ternary alloys, FeCo{sub 2}(PO{sub 4}){sub 3}, FeNi{sub 2}BO{sub 5}), oxidation-state contrast (e.g. YBa{sub 2}Cu{sub 3}O{sub 6+x}, Eu{sub 3}O{sub 4}, GaCl{sub 2}, Fe{sub 2}PO{sub 5}), and the effect of coordination geometry (e.g. Y{sub 3}Ga{sub 5}O{sub l2}).

  2. Powder diffraction studies using anomalous dispersion

    SciTech Connect

    Cox, D.E. ); Wilkinson, A.P. . Dept. of Materials)

    1993-01-01

    With the increasing availability and accessibility of high resolution powder diffractometers at many synchrotron radiation sources throughout the world, there is rapidly-growing interest in the exploitation of anomalous dispersion techniques for structural studies of polycrystalline materials. In conjunction with the Rietveld profile method for structure refinement, such studies are especially useful for the determination of the site distributions of two or more atoms which are near neighbors in the periodic table, or atoms which are distributed among partially occupied sites. Additionally, it is possible to (1) determine the mean-square displacements associated with different kinds of atoms distributed over a single set of sites, (2) distinguish between different oxidation states and coordination geometries of a particular atom in a compound and (3) to determine f' for a wide range of atomic species as a function of energy in the vicinity of an absorption edge. Experimental methods for making anomalous dispersion measurements are described in some detail, including data collection strategies, data analysis and correlation problems, possible systematic errors, and the accuracy of the results. Recent work in the field is reviewed, including cation site-distribution studies (e.g. doped high [Tc] superconductors, ternary alloys, FeCo[sub 2](PO[sub 4])[sub 3], FeNi[sub 2]BO[sub 5]), oxidation-state contrast (e.g. YBa[sub 2]Cu[sub 3]O[sub 6+x], Eu[sub 3]O[sub 4], GaCl[sub 2], Fe[sub 2]PO[sub 5]), and the effect of coordination geometry (e.g. Y[sub 3]Ga[sub 5]O[sub l2]).

  3. Powder Diffraction Simulated by a Polycrystalline Film of Spherical Colloids

    ERIC Educational Resources Information Center

    Campbell, Dean J.; Xia, Younan

    2006-01-01

    This article describes a simple way to demonstrate powder diffraction in a classroom setting using a dry film of spherical colloids on a glass substrate. Use of transparent, elastomeric poly(dimethylsiloxane) as a supporting substrate for the spheres rather than glass enables demonstration of the reciprocal lattice effect. (Contains 4 figures and…

  4. Angle-resolved diffraction grating biosensor based on porous silicon

    NASA Astrophysics Data System (ADS)

    Lv, Changwu; Jia, Zhenhong; Liu, Yajun; Mo, Jiaqing; Li, Peng; Lv, Xiaoyi

    2016-03-01

    In this study, an optical biosensor based on a porous silicon composite structure was fabricated using a simple method. This structure consists of a thin, porous silicon surface diffraction grating and a one-dimensional porous silicon photonic crystal. An angle-resolved diffraction efficiency spectrum was obtained by measuring the diffraction efficiency at a range of incident angles. The angle-resolved diffraction efficiency of the 2nd and 3rd orders was studied experimentally and theoretically. The device was sensitive to the change of refractive index in the presence of a biomolecule indicated by the shift of the diffraction efficiency spectrum. The sensitivity of this sensor was investigated through use of an 8 base pair antifreeze protein DNA hybridization. The shifts of the angle-resolved diffraction efficiency spectrum showed a relationship with the change of the refractive index, and the detection limit of the biosensor reached 41.7 nM. This optical device is highly sensitive, inexpensive, and simple to fabricate. Using shifts in diffraction efficiency spectrum to detect biological molecules has not yet been explored, so this study establishes a foundation for future work.

  5. The MYTHEN detector for X-ray powder diffraction experiments at the Swiss Light Source

    PubMed Central

    Bergamaschi, Anna; Cervellino, Antonio; Dinapoli, Roberto; Gozzo, Fabia; Henrich, Beat; Johnson, Ian; Kraft, Philipp; Mozzanica, Aldo; Schmitt, Bernd; Shi, Xintian

    2010-01-01

    The MYTHEN single-photon-counting silicon microstrip detector has been developed at the Swiss Light Source for time-resolved powder diffraction experiments. An upgraded version of the detector has been installed at the SLS powder diffraction station allowing the acquisition of diffraction patterns over 120° in 2θ in fractions of seconds. Thanks to the outstanding performance of the detector and to the calibration procedures developed, the quality of the data obtained is now comparable with that of traditional high-resolution point detectors in terms of FWHM resolution and peak profile shape, with the additional advantage of fast and simultaneous acquisition of the full diffraction pattern. MYTHEN is therefore optimal for time-resolved or dose-critical measurements. The characteristics of the MYTHEN detector together with the calibration procedures implemented for the optimization of the data are described in detail. The refinements of two known standard powders are discussed together with a remarkable application of MYTHEN to organic compounds in relation to the problem of radiation damage. PMID:20724787

  6. Multiple powder diffraction data for an accurate charge density study using synchrotron radiation x-ray

    NASA Astrophysics Data System (ADS)

    Kasai, Hidetaka; Nishibori, Eiji

    2016-04-01

    In recent years multiple synchrotron radiation (SR) powder x-ray diffraction profiles have been successfully applied to advanced structural studies such as an accurate charge density study and a structure determination from powder diffraction. The results have been presented with several examples. Abilities and future prospects have been discussed using state of the art powder diffraction data.

  7. Feasibility studies for high pressure neutron powder diffraction experiments

    SciTech Connect

    Von Dreele, R.B. ); Parise, J. )

    1990-01-01

    We recently performed two neutron powder diffraction experiments on very small samples on the High Intensity Powder Diffractometer (HIPD). These were done to determine the feasibility of performing in situ high pressure/high temperature neutron diffraction experiments on HIPD at pressures which would exceed the previous limit of {approximately}50 kbar achievable in a neutron diffraction experiment. The first experiment consisted of examining the product from a high pressure preparation done at Stony Brook. The sample, which had been prepared at 65 kbar and 1000{degree}C, consisted of a small platinum capsule filled with CaGeO{sub 3} perovskite. The weights of the capsule included 225 mg of platinum and 49 mg of the germanate. A diffraction experiment taking {approximately}8.6 hrs at a LANSCE proton beam current of {approximately}53 {mu}A gave peaks of good intensity from both Pt and CaGeO{sub 3}; we could begin to see them after only 20 min of beam time. The second experiment was to test the possibility of diffraction from a high pressure apparatus. We placed in the HIPD sample position the central assembly from a 100 kbar octahedral press. Four tungsten carbide anvils and a copper block previously pressed to 65 kbar were held in an aluminum frame. The sample consisted of a small bit of nickel foil (175 mg) placed in a 3 mm hole in the copper block. The active sample volume is defined by the gap between the anvils and the length of the sample. A small portion of the copper block is also seen in this arrangement. This is viewed at 90{degree} 2{Theta} through a similar gap between the anvils by 4 1/2 in. {times} 12 in. {sup 3}He counter tubes. This arrangement simulates the operating conditions of a high pressure run at 100 kbar and takes advantage of the fixed instrument geometry possible in time-of-flight neutron diffraction experiments.

  8. A compact electron gun for time-resolved electron diffraction

    SciTech Connect

    Robinson, Matthew S.; Lane, Paul D.; Wann, Derek A.

    2015-01-15

    A novel compact time-resolved electron diffractometer has been built with the primary goal of studying the ultrafast molecular dynamics of photoexcited gas-phase molecules. Here, we discuss the design of the electron gun, which is triggered by a Ti:Sapphire laser, before detailing a series of calibration experiments relating to the electron-beam properties. As a further test of the apparatus, initial diffraction patterns have been collected for thin, polycrystalline platinum samples, which have been shown to match theoretical patterns. The data collected demonstrate the focusing effects of the magnetic lens on the electron beam, and how this relates to the spatial resolution of the diffraction pattern.

  9. A compact electron gun for time-resolved electron diffraction

    NASA Astrophysics Data System (ADS)

    Robinson, Matthew S.; Lane, Paul D.; Wann, Derek A.

    2015-01-01

    A novel compact time-resolved electron diffractometer has been built with the primary goal of studying the ultrafast molecular dynamics of photoexcited gas-phase molecules. Here, we discuss the design of the electron gun, which is triggered by a Ti:Sapphire laser, before detailing a series of calibration experiments relating to the electron-beam properties. As a further test of the apparatus, initial diffraction patterns have been collected for thin, polycrystalline platinum samples, which have been shown to match theoretical patterns. The data collected demonstrate the focusing effects of the magnetic lens on the electron beam, and how this relates to the spatial resolution of the diffraction pattern.

  10. Advanced Structural Analyses by Third Generation Synchrotron Radiation Powder Diffraction

    SciTech Connect

    Sakata, M.; Aoyagi, S.; Ogura, T.; Nishibori, E.

    2007-01-19

    Since the advent of the 3rd generation Synchrotron Radiation (SR) sources, such as SPring-8, the capabilities of SR powder diffraction increased greatly not only in an accurate structure refinement but also ab initio structure determination. In this study, advanced structural analyses by 3rd generation SR powder diffraction based on the Large Debye-Scherrer camera installed at BL02B2, SPring-8 is described. Because of high angular resolution and high counting statistics powder data collected at BL02B2, SPring-8, ab initio structure determination can cope with a molecular crystals with 65 atoms including H atoms. For the structure refinements, it is found that a kind of Maximum Entropy Method in which several atoms are omitted in phase calculation become very important to refine structural details of fairy large molecule in a crystal. It should be emphasized that until the unknown structure is refined very precisely, the obtained structure by Genetic Algorithm (GA) or some other ab initio structure determination method using real space structural knowledge, it is not possible to tell whether the structure obtained by the method is correct or not. In order to determine and/or refine crystal structure of rather complicated molecules, we cannot overemphasize the importance of the 3rd generation SR sources.

  11. The High Resolution Powder Diffraction Beam Line at ESRF

    PubMed Central

    Fitch, A. N.

    2004-01-01

    The optical design and performance of the high-resolution powder diffraction beam line BM16 at ESRF are discussed and illustrated. Some recent studies carried out on BM16 are described, including crystal structure solution and refinement, anomalous scattering, in situ measurements, residual strain in engineering components, investigation of microstructure, and grazing-incidence diffraction from surface layers. The beam line is built on a bending magnet, and operates in the energy range from 5 keV to 40 keV. After the move to an undulator source in 2002, it will benefit from an extented energy range up to 60 keV and increased flux and resolution. It is anticipated that enhancements to the data quality will be achieved, leading to the solution of larger crystal structures, and improvements in the accuracy of refined structures. The systematic exploitation of anisotropic thermal expansion will help reduce the effects of peak overlap in the analysis of powder diffraction data. PMID:27366602

  12. Structural studies of magnesium nitride fluorides by powder neutron diffraction

    SciTech Connect

    Brogan, Michael A.; Hughes, Robert W.; Smith, Ronald I.; Gregory, Duncan H.

    2012-01-15

    Samples of ternary nitride fluorides, Mg{sub 3}NF{sub 3} and Mg{sub 2}NF have been prepared by solid state reaction of Mg{sub 3}N{sub 2} and MgF{sub 2} at 1323-1423 K and investigated by powder X-ray and powder neutron diffraction techniques. Mg{sub 3}NF{sub 3} is cubic (space group: Pm3m) and has a structure related to rock-salt MgO, but with one cation site vacant. Mg{sub 2}NF is tetragonal (space group: I4{sub 1}/amd) and has an anti-LiFeO{sub 2} related structure. Both compounds are essentially ionic and form structures in which nitride and fluoride anions are crystallographically ordered. The nitride fluorides show temperature independent paramagnetic behaviour between 5 and 300 K. - Graphical abstract: Definitive structures of the ternary magnesium nitride fluorides Mg{sub 3}NF{sub 3} and the lower temperature polymorph of Mg{sub 2}NF have been determined from powder neutron diffraction data. The nitride halides are essentially ionic and exhibit weak temperature independent paramagnetic behaviour. Highlights: Black-Right-Pointing-Pointer Definitive structures of Mg{sub 3}NF{sub 3} and Mg{sub 2}NF were determined by neutron diffraction. Black-Right-Pointing-Pointer Nitride and fluoride anions are crystallographically ordered in both structures. Black-Right-Pointing-Pointer Both compounds exhibit weak, temperature independent paramagnetic behaviour. Black-Right-Pointing-Pointer The compounds are essentially ionic with ionicity increasing with F{sup -} content.

  13. Transient electron density maps of ionic materials from femtosecond x-ray powder diffraction

    NASA Astrophysics Data System (ADS)

    Elsaesser, Thomas

    2014-05-01

    X-ray diffraction represents a key method for spatially resolving electron distributions in crystalline materials. So far, electron density maps have been derived from stationary diffraction patterns, providing detailed insight into the equilibrium charge distribution and crystal geometry. Functional processes in condensed matter are frequently connected with nonequilibrium excitations resulting in atomic motions and charge relocations on ultrashort time scales. Transient structures are resolved in space and time by novel x-ray diffraction methods with a femtosecond time resolution, giving access to the driving mechanisms and underlying interactions. In this talk, new results are presented on transient electron distributions of ionic materials mapped with the help of femtosecond x-ray powder diffraction. Experiments are based on a pump-probe approach in which an optical pulse initiates structural dynamics and a hard x-ray pulse from a synchronized laser-driven plasma source is diffracted from the excited powder sample. Such measurements reveal the interplay of lattice and charge motions in the photoexcited prototype material KDP (KH2PO4) which occur on distinctly different length scales. As a second topic, electron relocations induced by strong external optical fields will be discussed. This interaction mechanism allows for generating coherent superpositions of valence and conduction band quantum states and inducing fully reversible charge dynamics. While the materials LiBH4 and NaBH4 display electron relocations from the (BH4)- ions to the neighboring Li+ and Na+ ions, LiH exhibits an electron transfer from Li to H. The latter is a manifestation of electron correlations and in agreement with theoretical calculations.

  14. Spatially resolved scatter measurement of diffractive micromirror arrays.

    PubMed

    Sicker, Cornelius; Heber, Jörg; Berndt, Dirk

    2016-06-01

    Spatial light modulators (SLMs) support flexible system concepts in modern optics and especially phase-only SLMs such as micromirror arrays (MMAs) appear attractive for many applications. In order to achieve a precise phase modulation, which is crucial for optical performance, careful characterization and calibration of SLM devices is required. We examine an intensity-based measurement concept, which promises distinct advantages by means of a spatially resolved scatter measurement that is combined with the MMA's diffractive principle. Measurements yield quantitative results, which are consistent with measurements of micromirror roughness components, by white-light interferometry. They reveal relative scatter as low as 10-4, which corresponds to contrast ratios up to 10,000. The potential of the technique to resolve phase changes in the subnanometer range is experimentally demonstrated. PMID:27411205

  15. A compact electron gun for time-resolved electron diffraction.

    PubMed

    Robinson, Matthew S; Lane, Paul D; Wann, Derek A

    2015-01-01

    A novel compact time-resolved electron diffractometer has been built with the primary goal of studying the ultrafast molecular dynamics of photoexcited gas-phase molecules. Here, we discuss the design of the electron gun, which is triggered by a Ti:Sapphire laser, before detailing a series of calibration experiments relating to the electron-beam properties. As a further test of the apparatus, initial diffraction patterns have been collected for thin, polycrystalline platinum samples, which have been shown to match theoretical patterns. The data collected demonstrate the focusing effects of the magnetic lens on the electron beam, and how this relates to the spatial resolution of the diffraction pattern. PMID:25638074

  16. Femtosecond time-resolved MeV electron diffraction

    SciTech Connect

    Zhu, Pengfei; Zhu, Y.; Hidaka, Y.; Wu, L.; Cao, J.; Berger, H.; Geck, J.; Kraus, R.; Pjerov, S.; Shen, Y.; Tobey, R. I.; Hill, J. P.; Wang, X. J.

    2015-06-02

    We report the experimental demonstration of femtosecond electron diffraction using high-brightness MeV electron beams. High-quality, single-shot electron diffraction patterns for both polycrystalline aluminum and single-crystal 1T-TaS2 are obtained utilizing a 5 fC (~3 × 104 electrons) pulse of electrons at 2.8 MeV. The high quality of the electron diffraction patterns confirms that electron beam has a normalized emittance of ~50 nm rad. The transverse and longitudinal coherence length is ~11 and ~2.5 nm, respectively. The timing jitter between the pump laser and probe electron beam was found to be ~100 fs (rms). The temporal resolution is demonstrated by observing the evolution of Bragg and superlattice peaks of 1T-TaS2 following an 800 nm optical pump and was found to be 130 fs. Lastly, our results demonstrate the advantages of MeV electrons, including large elastic differential scattering cross-section and access to high-order reflections, and the feasibility of ultimately realizing below 10 fs time-resolved electron diffraction.

  17. Femtosecond time-resolved MeV electron diffraction

    DOE PAGESBeta

    Zhu, Pengfei; Zhu, Y.; Hidaka, Y.; Wu, L.; Cao, J.; Berger, H.; Geck, J.; Kraus, R.; Pjerov, S.; Shen, Y.; et al

    2015-06-02

    We report the experimental demonstration of femtosecond electron diffraction using high-brightness MeV electron beams. High-quality, single-shot electron diffraction patterns for both polycrystalline aluminum and single-crystal 1T-TaS2 are obtained utilizing a 5 fC (~3 × 104 electrons) pulse of electrons at 2.8 MeV. The high quality of the electron diffraction patterns confirms that electron beam has a normalized emittance of ~50 nm rad. The transverse and longitudinal coherence length is ~11 and ~2.5 nm, respectively. The timing jitter between the pump laser and probe electron beam was found to be ~100 fs (rms). The temporal resolution is demonstrated by observing themore » evolution of Bragg and superlattice peaks of 1T-TaS2 following an 800 nm optical pump and was found to be 130 fs. Lastly, our results demonstrate the advantages of MeV electrons, including large elastic differential scattering cross-section and access to high-order reflections, and the feasibility of ultimately realizing below 10 fs time-resolved electron diffraction.« less

  18. New high temperature furnace for structure refinement by powder diffraction in controlled atmospheres using synchrotron radiation

    SciTech Connect

    Margulies, L.; Kramer, M.J.; McCallum, R.W.; Kycia, S.; Haeffner, D.R.; Lang, J.C.; Goldman, A.I.

    1999-09-01

    A low thermal gradient furnace design is described which utilizes Debye{endash}Scherrer geometry for performing high temperature x-ray powder diffraction with synchrotron radiation at medium and high energies (35{endash}100 keV). The furnace has a maximum operating temperature of 1800 K with a variety of atmospheres including oxidizing, inert, and reducing. The capability for sample rotation, to ensure powder averaging, has been built into the design without compromising thermal stability or atmosphere control. The ability to perform high-resolution Rietveld refinement on data obtained at high temperatures has been demonstrated, and data collected on standard Al{sub 2}O{sub 3} powder is presented. Time-resolved data on the orthorhombic to rhombohedral solid state phase transformation of SrCO{sub 3} is demonstrated using image plates. Rietveld refinable spectra, collected in as little as 8 s, opens the possibility of performing time-resolved structural refinements of phase transformations. {copyright} {ital 1999 American Institute of Physics.}

  19. Powder X-ray diffraction laboratory, Reston, Virginia

    USGS Publications Warehouse

    Piatak, Nadine M.; Dulong, Frank T.; Jackson, John C.; Folger, Helen W.

    2014-01-01

    The powder x-ray diffraction (XRD) laboratory is managed jointly by the Eastern Mineral and Environmental Resources and Eastern Energy Resources Science Centers. Laboratory scientists collaborate on a wide variety of research problems involving other U.S. Geological Survey (USGS) science centers and government agencies, universities, and industry. Capabilities include identification and quantification of crystalline and amorphous phases, and crystallographic and atomic structure analysis for a wide variety of sample media. Customized laboratory procedures and analyses commonly are used to characterize non-routine samples including, but not limited to, organic and inorganic components in petroleum source rocks, ore and mine waste, clay minerals, and glassy phases. Procedures can be adapted to meet a variety of research objectives.

  20. 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.

  1. Ezetimibe anhydrate, determined from laboratory powder diffraction data.

    PubMed

    Brüning, Jürgen; Alig, Edith; Schmidt, Martin U

    2010-07-01

    Ezetimibe {systematic name: (3R,4S)-1-(4-fluorophenyl)-3-[(3S)-3-(4-fluorophenyl)-3-hydroxypropyl]-4-(4-hydroxyphenyl)azetidin-2-one}, C(24)H(21)F(2)NO(3), is used to lower cholesterol levels by inhibiting cholesterol resorption in the human intestine. The crystal structure of ezetimibe anhydrate was solved from laboratory powder diffraction data by means of real-space methods using the program DASH [David et al. (2006). J. Appl. Cryst. 39, 910-915]. Subsequent Rietveld refinement with TOPAS Academic [Coelho (2007). TOPAS Academic User Manual. Version 4.1. Coelho Software, Brisbane, Australia] led to a final R(wp) value of 8.19% at 1.75 A resolution. The compound crystallizes in the space group P2(1)2(1)2(1) with one molecule in the asymmetric unit. The molecules are closely packed and two intermolecular hydrogen bonds form an extended hydrogen-bond architecture. PMID:20603561

  2. Powder Neutron Diffraction Study of HoCoGa5

    SciTech Connect

    Kabayashi, Riki; Kaneko, Koji; Wakimoto, Shuichi; Chi, Songxue; Sanada, Naoyuki; Watanuki, Ryuta; Suzuki, Kazuya

    2013-01-01

    We have studied successive magnetic transitions of HoCoGa5 at TN1 = 9.6 K and TN2 = 7.5 K by using powder neutron diffraction. Apparent superlattice peaks were observed at temperatures below TN1. With further decreases temperature, the patterns exhibit a substantial change at temperatures below TN2. The observed magnetic peaks at 8 K (AntiFerromagnetic InCommensurate (AFIC) phase : TN2 < T < TN1) can be represented by the propagation vector qL = (1/2 0 ) with = 0.35(2). In contrast, the magnetic structure becomes commensurate with qC = (1/2 0 1/2) at 4 K (AntiFerromagnetic Commensurate (AFC) phase : T < TN2). The temperature dependence of magnetic intensity shows an apparent temperature hysteresis at TN2, indicates a first-order transition at TN2. Analysis of the integrated intensity at 4 K reveals that the Ho moment with a size of 8.6(2) B, oriented parallel to the c-axis in the AFC phase. While the successive transitions of HoCoGa5 are different from those of TbCoGa5, the magnetic structure in the AFC phase of HoCoGa5 is the same as the AFTb I of TbCoGa5, and may indicate an additional transition at a lower temperature in HoCoGa5.

  3. Synchrotron Powder X-ray Diffraction Study of the Structure and Dehydration Behavior of Sepiolite

    SciTech Connect

    Post,J.; Bish, D.; Heaney, P.

    2007-01-01

    Rietveld refinements using synchrotron powder X-ray diffraction data were used to study the crystal structure and dehydration behavior of sepiolite from Durango, Mexico. The room-temperature (RT) sepiolite structure in air compares well with previous models but reveals an additional zeolitic H{sub 2}O site. The RT structure under vacuum retained only {approx}1/8 of the zeolitic H{sub 2}O and the volume decreased by 1.3%. Real-time, temperature-resolved synchrotron powder X-ray diffraction data and Rietveld refinements were used to investigate the behavior of the sepiolite structure from 300 to 925 K. Rietveld refinements revealed that most of the zeolitic H{sub 2}O is lost by {approx}390 K, accompanied by a decrease in the a and c unit-cell parameters. Above {approx}600 K the sepiolite structure folds as one-half of the crystallographically bound H{sub 2}O is lost. Rietveld refinements of the 'anhydrous' sepiolite structure reveal that, in general, unit-cell parameters a and b and volume steadily decrease with increasing temperature; there is an obvious change in slope at {approx}820 K suggesting a phase transformation coinciding with the loss of the remaining bound H{sub 2}O molecule.

  4. High throughput screening of ligand binding to macromolecules using high resolution powder diffraction

    DOEpatents

    Von Dreele, Robert B.; D'Amico, Kevin

    2006-10-31

    A process is provided for the high throughput screening of binding of ligands to macromolecules using high resolution powder diffraction data including producing a first sample slurry of a selected polycrystalline macromolecule material and a solvent, producing a second sample slurry of a selected polycrystalline macromolecule material, one or more ligands and the solvent, obtaining a high resolution powder diffraction pattern on each of said first sample slurry and the second sample slurry, and, comparing the high resolution powder diffraction pattern of the first sample slurry and the high resolution powder diffraction pattern of the second sample slurry whereby a difference in the high resolution powder diffraction patterns of the first sample slurry and the second sample slurry provides a positive indication for the formation of a complex between the selected polycrystalline macromolecule material and at least one of the one or more ligands.

  5. X-Ray Diffraction Powder Patterns and Thin Section Observations from the Sierra Madera Impact Structure

    NASA Astrophysics Data System (ADS)

    Huson, S. A.; Foit, F. F.; Watkinson, A. J.; Pope, M. C.

    2006-03-01

    X-Ray powder diffraction analysis and thin section observations of carbonate and siliciclastic samples from the Sierra Madera impact structure indicate moderate shock pressures (8 to 30 GPa) were generated during the formation of this crater.

  6. The Extreme Conditions Beamline at PETRA III, DESY: Possibilities to conduct time resolved monochromatic diffraction experiments in dynamic and laser heated DAC

    NASA Astrophysics Data System (ADS)

    Liermann, H.-P.; Morgenroth, W.; Ehnes, A.; Berghäuser, A.; Winkler, B.; Franz, H.; Weckert, E.

    2010-03-01

    We present plans for the new Extreme Conditions Beamline at PETRA III, DESY, Germany. The beamline is being designed and built with the specific goal to explore time resolved high-pressure and -temperature x-ray diffraction experiments in the dynamic and laser heated diamond anvil cell. Within we discuss the conceptual design of the optical components and experimental setup to conduct monochromatic high-pressure powder diffraction experiments in the sub-second time regime.

  7. Powder diffraction in materials science using the KENS cold-neutron source

    SciTech Connect

    Kamiyama, T.; Oikawa, K.; Akiba, E.

    1997-12-01

    Since superconductivity fever spread around the world, neutron powder diffraction has become very popular and been widely used by crystallographers, physicists, chemists, mineralogists, and materials scientists. The purpose of present paper is to show, firstly, important characteristics of time-of-flight TOF powder diffraction using cold-neutron source in the study of materials science, and, secondly, recent studies on the structure and function of batteries at the Neutron Science Laboratory (KENS) in the High Energy Accelerator Research Organization (KEK).

  8. Monitoring model drug microencapsulation in PLGA scaffolds using X-ray powder diffraction

    PubMed Central

    Aina, Adeyinka; Gupta, Manish; Boukari, Yamina; Morris, Andrew; Billa, Nashiru; Doughty, Stephen

    2015-01-01

    The microencapsulation of three model drugs; metronidazole, paracetamol and sulphapyridine into Poly (dl-Lactide-Co-Glycolide) (PLGA) scaffolds were probed using X-ray Powder Diffraction (XRPD). Changes in the diffraction patterns of the PLGA scaffolds after encapsulation was suggestive of a chemical interaction between the pure drugs and the scaffolds and not a physical intermixture. PMID:27013917

  9. Time-Resolved Electron Diffraction from Selectively Aligned Molecules

    SciTech Connect

    Reckenthaeler, Peter; Krausz, Ferenc; Centurion, Martin; Fuss, Werner; Trushin, Sergei A.; Fill, Ernst E.

    2009-05-29

    We experimentally demonstrate ultrafast electron diffraction from transiently aligned molecules in the absence of external (aligning) fields. A sample of aligned molecules is generated through photodissociation with femtosecond laser pulses, and the diffraction pattern is captured by probing the sample with picosecond electron pulses shortly after dissociation - before molecular rotation causes the alignment to vanish. In our experiments the alignment decays with a time constant of 2.6{+-}1.2 ps.

  10. Approaches to time-resolved diffraction using an XFEL.

    PubMed

    Spence, John C H

    2014-01-01

    We describe several schemes for time-resolved imaging of molecular motion using a free-electron laser (XFEL), in response to the many challenges and opportunities which XFEL radiation has created for accurate time-resolved measurement of structure. For pump-probe experiments using crystals, the problem of recording full Bragg reflections (not partials) in each shot arises. Two solutions, the use of the large bandwith which necesarily results from using attosecond pulses, and the use the coherent convergent beam mode are suggested. We also show that with attosecond recording times shorter than the temporal coherence time, Bragg reflections excited by different wavelengths from different reflections can interfere, providing structure factor phase information. For slower processes, a mixing jet sample-delivery device is described to allow snapshot solution scattering during molecular reactions on the microsecond scale. For optically excited membrane proteins, we suggest the use of the lipid cubic phase sample delivery device operating at atmospheric pressure. The use of two-color and split-and-delay schemes is suggested for improved accuracy in the Monte-Carlo method of serial femtosecond crystallography (SFX). PMID:25415269

  11. A method for automated determination of the crystal structures from X-ray powder diffraction data

    SciTech Connect

    Hofmann, D. W. M. Kuleshova, L. N.

    2006-05-15

    An algorithm is proposed for determining the crystal structure of compounds. In the framework of this algorithm, X-ray powder diffraction patterns are compared using a new similarity index. Unlike the indices traditionally employed in X-ray powder diffraction analysis, the new similarity index can be applied even in the case of overlapping peaks and large differences in unit cell parameters. The capabilities of the proposed procedure are demonstrated by solving the crystal structures of a number of organic pigments (PY111, PR181, Me-PR170)

  12. Beamline I11 at Diamond: A new instrument for high resolution powder diffraction

    NASA Astrophysics Data System (ADS)

    Thompson, S. P.; Parker, J. E.; Potter, J.; Hill, T. P.; Birt, A.; Cobb, T. M.; Yuan, F.; Tang, C. C.

    2009-07-01

    The performance characteristics of a new synchrotron x-ray powder diffraction beamline (I11) at the Diamond Light Source are presented. Using an in-vacuum undulator for photon production and deploying simple x-ray optics centered around a double-crystal monochromator and a pair of harmonic rejection mirrors, a high brightness and low bandpass x-ray beam is delivered at the sample. To provide fast data collection, 45 Si(111) analyzing crystals and detectors are installed onto a large and high precision diffractometer. High resolution powder diffraction data from standard reference materials of Si, α-quartz, and LaB6 are used to characterize instrumental performance.

  13. Acquisition of powder diffraction data with synchrotron radiation

    SciTech Connect

    Cox, D.E.; Toby, B.H.; Eddy, M.M.

    1987-01-01

    During the past year, a dedicated triple-axis powder diffractometer has been in routine operation at the Brookhaven National Synchrotron Light Source as a user-oriented facility. The diffractometer is designed to allow easy interchange between energy-dispersive and monochromatic beam experiments. In the latter mode of operation, high resolution data have been collected for a variety of samples with the use of the crystal-analyzer technique, and in several cases these data sets have been used successfully for structure solution and Rietveld refinement. Several aspects of data acquisition at a synchrotron beam-line are described, and some of the different types of scattering geometry which have been used are discussed. Simple expressions are given for the instrumental resolution function expressed as the angular variation of peak widths for each of these. The peak shapes observed for a reference sample of Si on the present triple-axis instrument are well-described by the convolution of Gaussian and Lorentzian functions, and the angular dependence of the Gaussian component is in excellent agreement with the corresponding calculated instrumental function. One of the most important considerations for each type of experiment is the necessary compromise between intensity and resolution over a wide range of scattering angles, and some of the available options will be discussed. In particular, the use of Ge(440) and LiF(400) analyzer crystals gives a focussing minimum at relatively high angles (2 THETA approx. = 50/sup 0/ at 1.54A), a highly desirable feature for Rietveld analysis of complex structures. Absolute intensities from reference samples of Si and CeO/sub 2/ are calculated for these and several other scattering configurations involving both flat-plate and capillary geometry to illustrate this compromise. 26 refs., 3 figs., 3 tabs.

  14. X-RAY POWDER DIFFRACTION SYSTEM FOR CHEMICAL SPECIATION OF PARTICULATE AEROSOL SAMPLES

    EPA Science Inventory

    An x-ray powder diffraction system has been developed for the automated measurement and analysis of particulate aerosol samples. The system is optimized to process samples with particle loadings of about 100 micrograms/sq cm which are acquired with dichotomous air samplers. A pos...

  15. Incident spectrum determination for time-of-flight neutron powder diffraction data analysis.

    SciTech Connect

    Hodges, J. P.

    1998-08-27

    Accurate characterization of the incident neutron spectrum is an important requirement for precise Rietveld analysis of time-of-flight powder neutron diffraction data. Without an accurate incident spectrum the calculated model for the measured relative intensities of individual Bragg reflections will possess systematic errors. We describe a method for obtaining an accurate numerical incident spectrum using data from a transmitted beam monitor.

  16. 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.

  17. Three-dimensional electron diffraction as a complementary technique to powder X-ray diffraction for phase identification and structure solution of powders

    PubMed Central

    Yun, Yifeng; Zou, Xiaodong; Hovmöller, Sven; Wan, Wei

    2015-01-01

    Phase identification and structure determination are important and widely used techniques in chemistry, physics and materials science. Recently, two methods for automated three-dimensional electron diffraction (ED) data collection, namely automated diffraction tomography (ADT) and rotation electron diffraction (RED), have been developed. Compared with X-ray diffraction (XRD) and two-dimensional zonal ED, three-dimensional ED methods have many advantages in identifying phases and determining unknown structures. Almost complete three-dimensional ED data can be collected using the ADT and RED methods. Since each ED pattern is usually measured off the zone axes by three-dimensional ED methods, dynamic effects are much reduced compared with zonal ED patterns. Data collection is easy and fast, and can start at any arbitrary orientation of the crystal, which facilitates automation. Three-dimensional ED is a powerful technique for structure identification and structure solution from individual nano- or micron-sized particles, while powder X-ray diffraction (PXRD) provides information from all phases present in a sample. ED suffers from dynamic scattering, while PXRD data are kinematic. Three-dimensional ED methods and PXRD are complementary and their combinations are promising for studying multiphase samples and complicated crystal structures. Here, two three-dimensional ED methods, ADT and RED, are described. Examples are given of combinations of three-dimensional ED methods and PXRD for phase identification and structure determination over a large number of different materials, from Ni–Se–O–Cl crystals, zeolites, germanates, metal–organic frameworks and organic compounds to intermetallics with modulated structures. It is shown that three-dimensional ED is now as feasible as X-ray diffraction for phase identification and structure solution, but still needs further development in order to be as accurate as X-ray diffraction. It is expected that three-dimensional ED

  18. High-temperature structural phase transitions in neighborite: a high-resolution neutron powder diffraction investigation

    NASA Astrophysics Data System (ADS)

    Knight, Kevin S.; Price, G. David; Stuart, John A.; Wood, Ian G.

    2015-01-01

    The nature of the apparently continuous structural phase transition at 1,049 K in the perovskite-structured, MgSiO3 isomorph, neighborite (NaMgF3), from the orthorhombic ( Pbnm) hettotype phase to the cubic () aristotype structure, has been re-investigated using high-resolution, time-of-flight neutron powder diffraction. Using data collected at 1 K intervals close to the nominal phase transition temperature, the temperature dependence of the intensities of superlattice reflections at the M point and the R point of the pseudocubic Brillouin zone indicate the existence of a new intermediate tetragonal phase in space group P4/ mbm, with a narrow phase field extending from ~1,046.5 to ~1,048.5 K, at ambient pressure. Group theoretical analysis shows that the structural transitions identified in this study, Pbnm- P4/ mbm, and P4/ mbm-, are permitted to be second order. The observation of the tetragonal phase resolves the longstanding issue of why the high-temperature phase transition, previously identified as Pbnm-, and which would be expected to be first order under Landau theory, is in fact found to be continuous. Analysis of the pseudocubic shear strain shows it to vary with a critical exponent of 0.5 implying that the phase transition from Pbnm to P4/ mbm is tricritical in character. The large librational modes that exist in the MgF6 octahedron at high temperature, and the use of Gaussian probability density functions to describe atomic displacements, result in apparent bond shortening in the Mg-F distances, making mode amplitude determination an unreliable method for determination of the critical exponent from internal coordinates. Crystal structures are reported for the three phases of NaMgF3 at 1,033 K ( Pbnm), 1,047 K ( P4/ mbm) and 1,049 K ().

  19. Time-resolved x-ray diffraction study of photostimulated purple membrane.

    PubMed Central

    Frankel, R D; Forsyth, J M

    1985-01-01

    A nanosecond resolution laser-driven x-ray source has been used to perform a time-resolved, x-ray diffraction study of the purple membrane of the Halobacterium halobium. Alterations in diffraction patterns have been observed 1 ms after photostimulation, and are interpreted to show disorder of bacteriorhodopsin packing in the plane of the membrane with little bacteriorhodopsin structural change. PMID:3978209

  20. Unmixing 40Ar/39Ar Muscovite Ages Using Powder X-ray Diffraction

    NASA Astrophysics Data System (ADS)

    McAleer, R. J.; Kunk, M. J.; Valley, P. M.; Walsh, G. J.; Bish, D. L.; Wintsch, R. P.

    2014-12-01

    Whole rock powder X-ray diffraction (XRD) experiments from eight samples collected across a retrograde ductile shear zone in the Devonian Littleton Formation near Claremont, NH, exhibit broad and asymmetric to bimodal muscovite 00l reflections. These composite 00l reflections exhibit a systematic change in shape with increasing retrograde strain. Microtextural relationships, electron microprobe quantitative analyses, and element mapping indicate that the change in peak shape reflects progressive dissolution of metastable Na-rich muscovite and the precipitation of stable Na-poor muscovite. 40Ar/39Ar step heating experiments on muscovite concentrates from these samples show a decrease in total gas age from 274 to 258 Ma as the highest strain zone is approached, and steps within individual spectra range in age by ~20 m.y. The correlation between age and 00l peak shape suggests that the argon isotopic system also tracks the dissolution-precipitation process. Furthermore, the variation in age during step heating indicates that these populations exhibit different in-vacuo degassing behavior. Comparison of whole rock and muscovite concentrate XRD patterns from the same samples shows that the mineral separation process can fractionate these muscovite populations. With this knowledge, four muscovite concentrates were prepared from a single hand sample, analyzed by XRD, and dated. Combining modal estimates from XRD experiments with total gas ages, the four splits narrowly define a mixing line that resolves end-member ages of 250 and 300 Ma for the neocrystallized and earlier high grade populations of muscovite, respectively. These ages are consistent with age data from all other samples. The results show that, in some settings, powder XRD provides a powerful and time effective method to both identify the existence of and establish the proportions of multiple compositional populations of muscovite prior to 40Ar/39Ar analysis. This approach will be especially useful in

  1. 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.

  2. Hydrothermal Transformation of Microporous Lithium Zinc Phosphates; A Kinetic Study using in situ Synchrotron Radiation Powder Diffraction.

    SciTech Connect

    Jensen, T.R.; Norby, P.; Hanson, J.C.

    1997-12-31

    The solution mediated phase transformation of a lithium zinc phosphate has been investigated. The zeolite type ABW phase, LiZnPO{sub 4}. H{sub 2}O, suspended in an aqueous solution of LiNO{sub 3}, transforms to the more dense phase, (delta tau) LiZnPO{sub 4} (crystobalite type structure). In situ time resolved powder diffraction using synchrotron radiation, has been utilized to obtain isothermal crystallization curves in the temperature range 179 {degrees} C to 210 {degrees} C. A power law was used for the kinetic analysis, giving an apparent activation energy for the reaction, Ea = 93.1 kJ/mole. The order of the power law varies from 2. 80 to 4.41 in the observed temperature range. This indicates a continuous change in the mechanism of the nucleation.

  3. Effect of microfibril twisting on theoretical powder diffraction patterns of cellulose Iβ

    PubMed

    Hadden, Jodi A; French, Alfred D; Woods, Robert J

    2014-04-01

    Previous studies of calculated diffraction patterns for cellulose crystallites suggest that distortions that arise once models have been subjected to MD simulation are the result of both microfibril twisting and changes in unit cell dimensions induced by the empirical force field; to date, it has not been possible to separate the individual contributions of these effects. To provide a better understanding of how twisting manifests in diffraction data, the present study demonstrates a method for generating twisted and linear cellulose structures that can be compared without the bias of dimensional changes, allowing assessment of the impact of twisting alone. Analysis of unit cell dimensions, microfibril volume, hydrogen bond patterns, glycosidic torsion angles, and hydroxymethyl group orientations confirmed that the twisted and linear structures collected with this method were internally consistent, and theoretical powder diffraction patterns for the two were shown to be effectively indistinguishable. These results indicate that differences between calculated patterns for the crystal coordinates and twisted structures from MD simulation can result entirely from changes in unit cell dimensions, and not from microfibril twisting alone. Although powder diffraction patterns for models in the 81-chain size regime were shown to be unaffected by twisting, suggesting that a modest degree of twist is not inconsistent with experimental data, it may be that other diffraction techniques are capable of detecting this structural difference. Until such time as definitive experimental evidence comes to light, the results of this study suggest that both twisted and linear microfibrils may represent an appropriate model for cellulose Iβ. PMID:24729665

  4. Effect of microfibril twisting on theoretical powder diffraction patterns of cellulose Iβ

    PubMed Central

    Hadden, Jodi A.; French, Alfred D.; Woods, Robert J.

    2013-01-01

    Previous studies of calculated diffraction patterns for cellulose crystallites suggest that distortions that arise once models have been subjected to MD simulation are the result of both microfibril twisting and changes in unit cell dimensions induced by the empirical force field; to date, it has not been possible to separate the individual contributions of these effects. To provide a better understanding of how twisting manifests in diffraction data, the present study demonstrates a method for generating twisted and linear cellulose structures that can be compared without the bias of dimensional changes, allowing assessment of the impact of twisting alone. Analysis of unit cell dimensions, microfibril volume, hydrogen bond patterns, glycosidic torsion angles, and hydroxymethyl group orientations confirmed that the twisted and linear structures collected with this method were internally consistent, and theoretical powder diffraction patterns for the two were shown to be effectively indistinguishable. These results indicate that differences between calculated patterns for the crystal coordinates and twisted structures from MD simulation can result entirely from changes in unit cell dimensions, and not from microfibril twisting alone. Although powder diffraction patterns for models in the 81-chain size regime were shown to be unaffected by twisting, suggesting that a modest degree of twist is not inconsistent with experimental data, it may be that other diffraction techniques are capable of detecting this structural difference. Until such time as definitive experimental evidence comes to light, the results of this study suggest that both twisted and linear microfibrils may represent an appropriate model for cellulose Iβ. PMID:24729665

  5. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

    2014-05-01

    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.

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

    SciTech Connect

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

    2014-05-07

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

  8. 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.

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

    SciTech Connect

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

    2014-05-07

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

  10. Implementation and use of Robust Refinement in Powder Diffraction in the Presence of Impurities

    SciTech Connect

    Stone, K.; Lapidus, S; Stephens, P

    2009-01-01

    A modification to the usual least-squares analysis is implemented for the robust refinement of structural parameters from powder diffraction data in the presence of unmodeled impurities. This is accomplished in the program TOPAS-Academic by an iterative reweighting of the data as the model is refined. The method is tested and characterized using mixtures of known materials, acetaminophen and ibuprofen. The technique is also used to refine two previously unknown structures.

  11. A portable powder-liquid high corrosion-resistant reaction cell for in situ X-ray diffraction and absorption studies of heterogeneous powder-liquid reactions and phase transformations

    NASA Astrophysics Data System (ADS)

    Ferrer, P.; da Silva, I.; Heyman, C.; Rubio-Zuazo, J.; Castro, G. R.

    2013-03-01

    A portable powder-liquid high corrosion-resistant reaction cell has been designed to follow in situ reactions by X-ray powder diffraction and X-ray absorption spectroscopy techniques in transmission mode. The cell has been conceived to be mounted on the experimental stations for diffraction and absorption of the Spanish CRG SpLine-BM25 beamline at the ESRF. In the case of the diffraction technique, data can be collected with either a point detector or a two-dimensional CCD detector. Using the 2D-CCD camera, the cell can be used for time-resolved in situ studies of phase transitions and reactions. Powder reactants and/or products are kept at a fixed position in a vertical geometry in the X-ray pathway, which is minimized in order to reduce the X-ray absorption by the reaction bath. Sample is fixed by a porous membrane under forced liquid reflux circulation, assuring total powder-liquid contact, with an accurate temperature control in the range from 20 to 220°C.

  12. An X-ray diffraction analysis of crystallised whey and whey-permeate powders.

    PubMed

    Nijdam, Justin; Ibach, Alexander; Eichhorn, Klaus; Kind, Matthias

    2007-11-26

    Amorphous whey, whey-permeate and lactose powders have been crystallised at various air temperatures and humidities, and these crystallised powders have been examined using X-ray diffraction. The most stable lactose crystal under normal storage conditions, alpha-lactose monohydrate, forms preferentially in whey and whey-permeate powders at 50 degrees C, provided sufficient moisture is available, whereas anhydrous beta-lactose and mixed anhydrous lactose crystals, which are unstable under normal storage conditions, form preferentially at 90 degrees C. Thus, faster crystallisation at higher temperatures is offset by the formation of lactose-crystal forms that are less stable under normal storage conditions. Very little alpha-lactose monohydrate crystallised in the pure lactose powders over the range of temperatures and humidities tested, because the crystallisation of alpha- and beta-lactose is considerably more rapid than the mutarotation of beta- to alpha-lactose in the amorphous phase and the hydration of alpha-lactose during crystallisation. Protein and salts hinder the crystallisation process, which provides more time for mutarotation and crystal hydration in the whey and whey-permeate powders. PMID:17719020

  13. Certain features of the preparation of boron powders in x-ray diffraction investigations

    SciTech Connect

    Tsagareishvili, G.V.; Avlokhashvili, D.A.; Bairamashvili, I.A.; Dolidze, T.V.; Gabuniya, D.L.; Nakashidze, T.G.; Oganezov, K.A.; Tabutsidze, M.L.

    1985-05-01

    It is known that elemental boron is characterized by an increased reaction capacity toward oxygen. Boron powders oxidize especially intensely. Under real conditions, boron powders always contain a certain quantity of oxide phase (primarily in the form of B2O3), the quantity of which depends on their degree of dispersion, the method of production, and the storage conditions. In long exposure to air, as the result of its high hygroscopicity, boric anhydride reacts with particles of moisture, as the result of which orthoboric acid is formed. The mass absorption coefficient of x-rays by elemental boron is significantly lower than by its compounds (anhydride and acid). The presence on the surface of particles of boric anhydride and products of its hydration, the total quantity of which in the powder is large, cannot affect the result of x-ray diffraction investigations of the powders. In this work an investigation is made of the possibility of weakening this influence by preliminary treatment of the powders.

  14. Powder Diffraction Studies in the YONO 3-Y 2O 3 System

    NASA Astrophysics Data System (ADS)

    Pelloquin, D.; Louër, M.; Louër, D.

    1994-09-01

    The crystal structure of yttrium oxide nitrate and the microstructure of the oxide obtained from its thermal decomposition have been investigated by modern powder diffraction methods. Sequential high-temperature diffraction studies of the thermal decomposition of two precursors of yttrium oxide nitrate, i.e., neutral yttrium nitrate and yttrium hydroxide nitrate, are reported. The structure of YONO 3 has been determined ab initio from conventional powder diffractometry using monochromatic X-rays. The pattern was indexed by the successive dichotomy method yielding tetragonal unit cell dimensions: a = 3.8590(1) Å and c = 9.7161(6) Å. The space group is P4/ nmm and Z = 2. Most of the atoms were located by direct methods and the remaining ones from a Fourier map. Refinement of the complete diffraction profile parameters converged to final agreement factors Rp = 0.12, Rwp = 0.16 and RF = 0.039. The structure is closely related to the matlockite PbFCl-type structure. The microstructure of ex-oxide-nitrate yttrium oxide has been analysed by total pattern fitting techniques, from which strain-free coherently diffracting nanodomains with a rectangular parallelepipedic shape have been obtained.

  15. CRYSIZ: a program for computing crystallite size and strain from the broadening of powder diffraction lines

    SciTech Connect

    Hubbard, C.R.; Morosin, B.; Stewart, J.M.

    1996-09-01

    The program CRYSIZ is designed to take the powder diffraction line profiles for a well-crystallized sample, called a reference pattern, and for a sample of the same substance, called a broadened pattern, to produce measures of the mean crystallite size, the distribution of crystallite sizes, and the root mean square residual microstrain in the broadened sample. The data required are the two powder patterns and a series of directives to signal the calculations and plots to be done during the execution of the program. The program loads files containing the background corrected powder diffraction intensity data for both the reference and broadened patterns. Preliminary calculations find the centroids, full width at half maximums, integral breadths, spans over sum, and second moments. Two methods of deconvoluting the profile to calculate size and strain are allowed. Either the direct or the Stokes Fourier coefficient method of deconvolution may be chosen. In the direct method the profiles are extracted by numerical fitting. This method is slower but produces unfolded profiles free of ringing and the ``hook effect``. In this case the Fourier coefficients required for Warren-Averbach analysis are produced from the deconvoluted profile. In the Stokes method the diffraction pattern of each reference and broadened profile is Fourier transformed to produce a set of Fourier coefficients. The Fourier coefficients of the broadened profiles are divided by those of the reference pattern. The resulting coefficients are the Stokes coefficients. The Stokes coefficients are smoothed by a least- squares procedure in order to remove noise and quell ringing and hooking, then used as input to a reverse Fourier transform. This transform produces an ``unfolded powder line,`` which is a best estimate of the broadened profile with the reference profile and noise removed. The deconvolution of the reference profile gives a broadened profile due only to the crystallite size and strain.

  16. Time-resolved coherent X-ray diffraction imaging of surface acoustic waves

    PubMed Central

    Nicolas, Jan-David; Reusch, Tobias; Osterhoff, Markus; Sprung, Michael; Schülein, Florian J. R.; Krenner, Hubert J.; Wixforth, Achim; Salditt, Tim

    2014-01-01

    Time-resolved coherent X-ray diffraction experiments of standing surface acoustic waves, illuminated under grazing incidence by a nanofocused synchrotron beam, are reported. The data have been recorded in stroboscopic mode at controlled and varied phase between the acoustic frequency generator and the synchrotron bunch train. At each time delay (phase angle), the coherent far-field diffraction pattern in the small-angle regime is inverted by an iterative algorithm to yield the local instantaneous surface height profile along the optical axis. The results show that periodic nanoscale dynamics can be imaged at high temporal resolution in the range of 50 ps (pulse length). PMID:25294979

  17. Fast X-ray powder diffraction on I11 at Diamond.

    PubMed

    Thompson, Stephen P; Parker, Julia E; Marchal, Julien; Potter, Jonathan; Birt, Adrian; Yuan, Fajin; Fearn, Richard D; Lennie, Alistair R; Street, Steven R; Tang, Chiu C

    2011-07-01

    The commissioning and performance characterization of a position-sensitive detector designed for fast X-ray powder diffraction experiments on beamline I11 at Diamond Light Source are described. The detecting elements comprise 18 detector-readout modules of MYTHEN-II silicon strip technology tiled to provide 90° coverage in 2θ. The modules are located in a rigid housing custom designed at Diamond with control of the device fully integrated into the beamline data acquisition environment. The detector is mounted on the I11 three-circle powder diffractometer to provide an intrinsic resolution of Δ2θ approximately equal to 0.004°. The results of commissioning and performance measurements using reference samples (Si and AgI) are presented, along with new results from scientific experiments selected to demonstrate the suitability of this facility for powder diffraction experiments where conventional angle scanning is too slow to capture rapid structural changes. The real-time dehydrogenation of MgH(2), a potential hydrogen storage compound, is investigated along with ultrafast high-throughput measurements to determine the crystallite quality of different samples of the metastable carbonate phase vaterite (CaCO(3)) precipitated and stabilized in the presence of amino acid molecules in a biomimetic synthesis process. PMID:21685682

  18. Assessment of the Stoichiometry of Multicomponent Crystals Using Only X-ray Powder Diffraction Data.

    PubMed

    Maguire, Courtney K; Brunskill, Andrew P J

    2015-06-01

    Knowledge of the unit cell volume of a crystalline form and the expected space filling requirements of an API molecule can be used to determine if a crystalline material is likely to be multicomponent, such as a solvate, hydrate, salt, or a co-crystal. The unit cell information can be readily accessed from powder diffraction data alone utilizing powder indexing methodology. If the unit cell has additional space not likely attributable to the API entity, then there is either a void or another component within the crystal lattice. This "leftover" space can be used to determine the likely stoichiometry of the additional component. A simple approach for calculating the expected required volume for a given molecule within a crystal using an atom based additive approach will be discussed. Coupling this estimation with the actual unit cell volumes and space group information obtained from powder indexing allows for the rapid evaluation of the likely stoichiometry of multicomponent crystals using diffraction data alone. This approach is particularly useful for the early assessment of new phases during salt, co-crystal, and polymorph screening, and also for the characterization of stable and unstable solvates. PMID:25872584

  19. Observation of light diffraction by time-resolved femtosecond correlation interferometry.

    PubMed

    Zeylikovich, I; Bai, G; Alfano, R R

    1995-07-15

    We demonstrate time development of the diffraction of light waves from objects for what is to our knowledge the f irst time by using a new femtosecond correlation interferometry. This new dynamical optics method allows for the conversion of temporal information to space information with femtosecond resolution and has the potential to produce a time-resolved femtosecond movie for the visualization of light-wave propagation in space for scientific, biological, and medical applications. PMID:19862089

  20. Measuring the x-ray resolving power of bent potassium acid phthalate diffraction crystalsa)

    NASA Astrophysics Data System (ADS)

    Haugh, M. J.; Wu, M.; Jacoby, K. D.; Loisel, G. P.

    2014-11-01

    This report presents the results from measuring the X-ray resolving power of a curved potassium acid phthalate (KAP(001)) spectrometer crystal using two independent methods. It is part of a continuing effort to measure the fundamental diffraction properties of bent crystals that are used to study various characteristics of high temperature plasmas. Bent crystals like KAP(001) do not usually have the same diffraction properties as corresponding flat crystals. Models that do exist to calculate the effect of bending the crystal on the diffraction properties have simplifying assumptions and their accuracy limits have not been adequately determined. The type of crystals that we measured is being used in a spectrometer on the Z machine at Sandia National Laboratories in Albuquerque, New Mexico. The first technique for measuring the crystal resolving power measures the X-ray spectral line width of the characteristic lines from several metal anodes. The second method uses a diode X-ray source and a double crystal diffractometer arrangement to measure the reflectivity curve of the KAP(001) crystal. The width of that curve is inversely proportional to the crystal resolving power. The measurement results are analyzed and discussed.

  1. Measuring the x-ray resolving power of bent potassium acid phthalate diffraction crystals

    SciTech Connect

    Haugh, M. J. Jacoby, K. D.; Wu, M.; Loisel, G. P.

    2014-11-15

    This report presents the results from measuring the X-ray resolving power of a curved potassium acid phthalate (KAP(001)) spectrometer crystal using two independent methods. It is part of a continuing effort to measure the fundamental diffraction properties of bent crystals that are used to study various characteristics of high temperature plasmas. Bent crystals like KAP(001) do not usually have the same diffraction properties as corresponding flat crystals. Models that do exist to calculate the effect of bending the crystal on the diffraction properties have simplifying assumptions and their accuracy limits have not been adequately determined. The type of crystals that we measured is being used in a spectrometer on the Z machine at Sandia National Laboratories in Albuquerque, New Mexico. The first technique for measuring the crystal resolving power measures the X-ray spectral line width of the characteristic lines from several metal anodes. The second method uses a diode X-ray source and a double crystal diffractometer arrangement to measure the reflectivity curve of the KAP(001) crystal. The width of that curve is inversely proportional to the crystal resolving power. The measurement results are analyzed and discussed.

  2. Measuring the X-ray Resolving Power of Bent Potassium Acid Phthalate Diffraction Crystals

    SciTech Connect

    Haugh, M. J.; Wu, M.; Jacoby, K. D.; Loisel, G. P.

    2014-11-01

    This report presents the results from measuring the X-ray resolving power of a curved potassium acid phthalate (KAP(001)) spectrometer crystal using two independent methods. It is part of a continuing effort to measure the fundamental diffraction properties of bent crystals that are used to study various characteristics of high temperature plasmas. Bent crystals like KAP(001) do not usually have the same diffraction properties as corresponding flat crystals. Models that do exist to calculate the effect of bending the crystal on the diffraction properties have simplifying assumptions and their accuracy limits have not been adequately determined. The type of crystals that we measured is being used in a spectrometer on the Z machine at Sandia National Laboratories (SNL) in Albuquerque, NM. The first technique for measuring the crystal resolving power measures the X-ray spectral line width of the characteristic lines from several metal anodes. The second method uses a diode X-ray source and a dual goniometer arrangement to measure the reflectivity curve of the KAP(001) crystal. The width of that curve is inversely proportional to the crystal resolving power. The measurement results are analyzed and discussed.

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

    DOE PAGESBeta

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

    2016-02-17

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

  4. A new approach to calculating powder diffraction patterns based on the Debye scattering equation.

    PubMed

    Thomas, Noel William

    2010-01-01

    A new method is defined for the calculation of X-ray and neutron powder diffraction patterns from the Debye scattering equation (DSE). Pairwise atomic interactions are split into two contributions, the first from lattice-pair vectors and the second from cell-pair vectors. Since the frequencies of lattice-pair vectors can be directly related to crystallite size, application of the DSE is thereby extended to crystallites of lengths up to approximately 200 nm. The input data correspond to unit-cell parameters, atomic coordinates and displacement factors. The calculated diffraction patterns are characterized by full backgrounds as well as complete reflection profiles. Four illustrative systems are considered: sodium chloride (NaCl), alpha-quartz, monoclinic lead zirconate titanate (PZT) and kaolinite. The effects of varying crystallite size on diffraction patterns are calculated for NaCl, quartz and kaolinite, and a method of modelling static structural disorder is defined for kaolinite. The idea of partial diffraction patterns is introduced and a treatment of atomic displacement parameters is included. Although the method uses pair distribution functions as an intermediate stage, it is anticipated that further progress in reducing computational times will be made by proceeding directly from crystal structure to diffraction pattern. PMID:20029134

  5. Recent advances in the study of H environments and behavior in minerals using neutron powder diffraction

    NASA Astrophysics Data System (ADS)

    Welch, M. D.

    2002-12-01

    It is now possible to probe the structural environments and behavior of H atoms directly in complex minerals such as amphiboles, micas, chlorites and humites using neutron powder diffraction, in some cases as a function of pressure and/or temperature. A combination of high neutron flux and increased detector sensitivity and size offers the chance to see details of H behaviour. In the last year or so the advent of new gasket designs for the Paris-Edinburgh pressure cell allow the use of ethanol/methanol (EtOD/MeOD) as a pressure medium, removing peak broadening arising from deviatoric stress that occurs above 3 GPa for the standard fluorinert pressure medium. Essentially hydrostatic conditions obtain with EtOD/MeOD to 8 GPa at 298 K. A further recent development has been the design of a high P-T module for use with the Paris-Edinburgh cell. These technological improvements in pressure-cell design now allow us to make meaningful correlations between OH vibrational spectra collected at high P and/or T and detailed structural information on H behaviour obtained from neutron diffraction under similar conditions. In this talk I shall discuss recent neutron diffraction experiments on the effect of pressure upon hydrogen bonding in deuterated chlorite to 5 GPa (298 K), and a high P-T study of hydrogen bonding in deuterated brucite to 7 GPa, 1100 K. These two studies illustrate how far high-pressure neutron diffraction has come in the last 5 years. Finally, I shall describe a neutron powder diffraction study (ambient conditions) of leucophoenicite, Mn7Si3O12(OH)2, a close structural analogue of Phase-B and Superhydrous-B: the structure of leucophoenicite is topologically identical to the hydrous sheet of Phase-B and similar to that of Superhydrous-B. For various reasons it was not possible to deuterate the sample. Nonetheless, the two distinct H atoms were approximately located in difference-Fourier maps and then refined isotropically. The H positions in Phase-B were only

  6. Quantification of Pharmaceutical Compounds Based on Powder X-Ray Diffraction with Chemometrics.

    PubMed

    Otsuka, Yuta; Ito, Akira; Matsumura, Saki; Takeuchi, Masaki; Pal, Suvra; Tanaka, Hideji

    2016-01-01

    We propose an approach for the simultaneous determination of multiple components in pharmaceutical mixed powder based on powder X-ray diffraction (PXRD) method coupled with chemometrics. Caffeine anhydrate, acetaminophen and lactose monohydrate were mixed at various ratios. The samples were analyzed by PXRD method in the ranges of 2θ=5.00-30.0 and 35.0-45.0 degrees. Obtained diffractograms were analyzed by conventional peak intensity method, multi curve resolution (MCR)-alternating least squares (ALS) method and partial least squares (PLS) method. Constructed PLS models can most accurately predict the concentrations among different methods used. Each regression vector of PLS correlates not only to the compound of interest but also to the coexisting compounds. The combination of PXRD and PLS methods is concluded to be powerful approach for analyzing multi components in pharmaceutical formulations. PMID:27477651

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

    SciTech Connect

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

    2014-03-05

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

  8. The ferroelectric phase of CdTiO{sub 3}: A powder neutron diffraction study

    SciTech Connect

    Kennedy, Brendan J.; Zhou Qingdi; Avdeev, Maxim

    2011-11-15

    The synthesis of bulk samples of polycrystalline CdTiO{sub 3} in both the rhombohedral ilmenite and orthorhombic perovskite forms is described and the structures of these have been refined using powder neutron diffraction data. This involved the preparation of samples enriched in {sup 114}Cd. Cooling perovskite-type CdTiO{sub 3} to 4 K induces a ferroelectric phase transition, with the neutron data suggesting the low temperature structure is in Pna2{sub 1}. Mode analysis shows the polar mode to be dominant at low temperatures. The ilmenite-structure of CdTiO{sub 3} is compared with that of ZnTiO{sub 3}. The refined scattering length of the {sup 114}Cd is estimated to be 5.56 fm. Attempts to dope CdTiO{sub 3} with Ca and Sr are described. - Graphical abstract: The structure of three phases of CdTiO{sub 3} have been refined using high resolution powder neutron diffraction data. This involved the preparation of samples enriched in {sup 114}Cd. Cooling perovskite-type CdTiO{sub 3} to 4 K results in a ferroelectric phase in Pna2{sub 1}. Highlights: > Both the ilmenite and perovskite forms of CdTiO{sub 3} have been prepared using {sup 114}Cd. > Cooling the perovskite form results in a ferroelectric phase. > The structures of these are refined from powder neutron diffraction data. > Attempts to dope CdTiO{sub 3} are described.

  9. Structure and intermolecular interactions of glipizide from laboratory X-ray powder diffraction.

    PubMed

    Burley, Jonathan C

    2005-12-01

    The crystal structure of glipizide, used as a major treatment of type-2 diabetes, has been determined ab initio using variable-temperature laboratory X-ray powder diffraction combined with a direct-space Monte Carlo/simulated annealing methodology. The strengths of the intermolecular interactions (van der Waals, pi-pi stacking, hydrogen bonding and steric interlock) were quantitatively estimated using the thermal expansion data, which were collected in the same set of experiments as those used to determine the structure. PMID:16306678

  10. A GUINIER CAMERA FOR SR POWDER DIFFRACTION: HIGH RESOLUTION AND HIGH THROUGHPUT.

    SciTech Connect

    SIDDONS,D.P.; HULBERT, S.L.; STEPHENS, P.W.

    2006-05-28

    The paper describe a new powder diffraction instrument for synchrotron radiation sources which combines the high throughput of a position-sensitive detector system with the high resolution normally only provided by a crystal analyzer. It uses the Guinier geometry which is traditionally used with an x-ray tube source. This geometry adapts well to the synchrotron source, provided proper beam conditioning is applied. The high brightness of the SR source allows a high resolution to be achieved. When combined with a photon-counting silicon microstrip detector array, the system becomes a powerful instrument for radiation-sensitive samples or time-dependent phase transition studies.

  11. 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.

  12. TSX-PLUS MULTI-TASKING UPGRADE FOR THE NICOLET L-11 POWDER DIFFRACTION SYSTEM.

    USGS Publications Warehouse

    Fitzpatrick, J.; Queen, David L.

    1985-01-01

    In August of 1982, a single-user, dual-translator, automated powder diffraction system was purchased by the Denver Research Institute for use on project work in the Chemical and Materials Sciences Division. Within a short period of time, the system had already become saturated with users. Scheduling conflicts arose. In view of these problems, an answer was sought in the form of hardware and software changes which would allow many users access to the system simultaneously. A low-cost, minimum impact solution was eventually found. The elements of the solution are reported.

  13. Characterization of zeolite structure and fluorocarbon reactivity using solid state NMR and x-ray powder diffraction

    NASA Astrophysics Data System (ADS)

    Ciraolo, Michael Frank

    The research presented in this thesis involves a combination of techniques used to study the structure and interactions zeolites adsorbed with fluorocarbons. This research is specifically aimed at understanding the processes of adsorption, binding, and reactivity of fluorocarbons on cation exchanged faujasite type zeolites. The solid state ion exchange process has also been studied since it is one way to obtain materials with higher exchange levels, which has been shown to effect adsorption and catalytic activity. To improve the understanding of the adsorption and separation processes a time resolved in-situ synchrotron x-ray powder diffraction study has been undertaken. Since faujasite type zeolites have been found to be effective in separating mixtures of HFC-134 (CF2HCF2H) and HFC-134a (CFH2CF3) isomers, the adsorption of these fluorocarbons on NaY have been studied. It has been shown that both the extent of loading and the kinetics of the sorption process in molecular sieves can be followed using this technique. A model for the binding of hydrochlorofluorocarbon (HCFC) 124a (CF 2HCF2Cl) adsorbed on NaX at 100K has been determined using a combination x-ray and neutron powder diffraction and solid state NMR. Using Rietveld refinement of the diffraction data, the HCFC molecule was found localized in the zeolite cavities bound on either end by sodium cations in the SII and SIII' positions. The model is consistent with hydrogen bonding between the proton of the HCFC and the framework oxygen. The NMR results further confirm the model and are consistent with Na-F binding and HCFC-framework interactions. Solid-state MAS NMR, synchrotron X-ray powder diffraction and a mass spectrometer and gas chromatograph catalysis system have been used to study the reactivity of HCFC-124a (CF2HCF2Cl) on NaX, Zn 2+-exchanged NaX (ZnX) and Rb+-exchanged NaX (RbX). We have chosen to study HCFC-124a (CF2HCF2Cl) since HCFC-124a can undergo both dehydrofluorination and dehydrochlorination

  14. On the reliability of powder diffraction Line Profile Analysis of plastically deformed nanocrystalline systems

    PubMed Central

    Rebuffi, Luca; Troian, Andrea; Ciancio, Regina; Carlino, Elvio; Amimi, Amine; Leonardi, Alberto; Scardi, Paolo

    2016-01-01

    An iron-molybdenum alloy powder was extensively deformed by high energy milling, so to refine the bcc iron domain size to nanometer scale (~10 nm) and introduce a strong inhomogeneous strain. Both features contribute to comparable degree to the diffraction peak profile broadening, so that size and strain contributions can be easily separated by exploiting their different dependence on the diffraction angle. To assess the reliability of Line Profile Analysis, results were compared with evidence from other techniques, including scanning and transmission electron microscopy and X-ray small angle scattering. Results confirm the extent of the size broadening effect, whereas molecular dynamics simulations provide insight into the origin of the local atomic, inhomogeneous strain, pointing out the role of dislocations, domain boundaries and interactions among crystalline domains. PMID:26860471

  15. Rietveld refinement with time-of-flight powder diffraction data from pulsed neutron sources

    SciTech Connect

    David, W.I.F. ); Jorgensen, J.D. )

    1990-10-01

    The recent development of accelerator-based pulsed neutron sources has led to the widespread use of the time-of-flight technique for neutron powder diffraction. The properties of the pulsed source make possible unusually high resolution over a wide range of d spacings, high count rates, and the ability to collect complete data at fixed scattering angles. The peak shape and other instrument characteristics can be accurately modelled, which make Rietveld refinement possible for complex structures. In this paper we briefly review the development of the Rietveld method for time-of-flight diffraction data from pulsed neutron sources and discuss the latest developments in high resolution instrumentation and advanced Rietveld analysis methods. 50 refs., 12 figs., 14 tabs.

  16. On the reliability of powder diffraction Line Profile Analysis of plastically deformed nanocrystalline systems.

    PubMed

    Rebuffi, Luca; Troian, Andrea; Ciancio, Regina; Carlino, Elvio; Amimi, Amine; Leonardi, Alberto; Scardi, Paolo

    2016-01-01

    An iron-molybdenum alloy powder was extensively deformed by high energy milling, so to refine the bcc iron domain size to nanometer scale (~10 nm) and introduce a strong inhomogeneous strain. Both features contribute to comparable degree to the diffraction peak profile broadening, so that size and strain contributions can be easily separated by exploiting their different dependence on the diffraction angle. To assess the reliability of Line Profile Analysis, results were compared with evidence from other techniques, including scanning and transmission electron microscopy and X-ray small angle scattering. Results confirm the extent of the size broadening effect, whereas molecular dynamics simulations provide insight into the origin of the local atomic, inhomogeneous strain, pointing out the role of dislocations, domain boundaries and interactions among crystalline domains. PMID:26860471

  17. Absorption spectroscopy of powdered materials using time-resolved diffuse optical methods.

    PubMed

    D'Andrea, Cosimo; Obraztsova, Ekaterina A; Farina, Andrea; Taroni, Paola; Lanzani, Guglielmo; Pifferi, Antonio

    2012-11-10

    In this paper a novel method, based on time-resolved diffuse optical spectroscopy, is proposed to measure the absorption of small amounts of nanostructured powder materials independent of scattering. Experimental validation, in the visible and near-infrared spectral range, has been carried out on India Inkparticles. The effectiveness of the technique to measure scattering-free absorption is demonstrated on carbon nanotubes. The comparison between the absorption spectra acquired by the proposed method and conventional measurements performed with a commercial spectrophotometer is discussed. PMID:23142900

  18. 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.

  19. Studies of clays and clay minerals using x-ray powder diffraction and the Rietveld method

    SciTech Connect

    Bish, D.L.

    1993-09-01

    The Rietveld method was originally developed (Rietveld, 1967, 1969) to refine crystal structures using neutron powder diffraction data. Since then, the method has been increasingly used with X-ray powder diffraction data, and today it is safe to say that this is the most common application of the method. The method has been applied to numerous natural and synthetic materials, most of which do not usually form crystals large enough for study with single-crystal techniques. It is the ability to study the structures of materials for which sufficiently large single crystals do not exist that makes the method so powerful and popular. It would thus appear that the method is ideal for studying clays and clay minerals. In many cases this is true, but the assumptions implicit in the method and the disordered nature of many clay minerals can limit titsapplicability. This chapter will describe the Rietveld method, emphasizing the assumptions important for the study of disordered materials, and it will outline the potential applications of the method to these minerals. These applications include, in addition to the refinement of crystal structures, quantitative analysis of multicomponent mixtures, analysis of peak broadening, partial structure solution, and refinement of unit-cell parameters.

  20. Concerted electron and proton transfer in ionic crystals mapped by femtosecond x-ray powder diffraction

    SciTech Connect

    Woerner, Michael; Zamponi, Flavio; Ansari, Zunaira; Dreyer, Jens; Freyer, Benjamin; Premont-Schwarz, Mirabelle; Elsaesser, Thomas

    2010-08-14

    X-ray powder diffraction, a fundamental technique of structure research in physics, chemistry, and biology, is extended into the femtosecond time domain of atomic motions. This allows for mapping (macro)molecular structure generated by basic chemical and biological processes and for deriving transient electronic charge density maps. In the experiments, the transient intensity and angular positions of up to 20 Debye Scherrer reflections from a polycrystalline powder are measured and atomic positions and charge density maps are determined with a combined spatial and temporal resolutions of 30 pm and 100 fs. We present evidence for the so far unknown concerted transfer of electrons and protons in a prototype material, the hydrogen-bonded ionic ammonium sulfate [(NH{sub 4}){sub 2}SO{sub 4}]. Photoexcitation of ammonium sulfate induces a sub-100 fs electron transfer from the sulfate groups into a highly confined electron channel along the c-axis of the unit cell. The latter geometry is stabilized by transferring protons from the adjacent ammonium groups into the channel. Time-dependent charge density maps derived from the diffraction data display a periodic modulation of the channel's charge density by low-frequency lattice motions with a concerted electron and proton motion between the channel and the initial proton binding site. Our results set the stage for femtosecond structure studies in a wide class of (bio)molecular materials.

  1. Model-independent structure factors from powder X-ray diffraction: a novel approach.

    PubMed

    Straasø, Tine; Dippel, Ann-Christin; Becker, Jacob; Als-Nielsen, Jens

    2014-01-01

    Under the experimental condition that all Bragg peaks in a powder X-ray diffraction (PXRD) pattern have the same shape, one can readily obtain the Bragg intensities without fitting any parameters. This condition is fulfilled at the P02.1 beamline at PETRA III using the seventh harmonic from a 23 mm-period undulator (60 keV) at a distance of 65 m. For grain sizes of the order of 1 µm, the Bragg peak shape in the PXRD is entirely determined by the diameter of the capillary containing the powder sample and the pixel size of the image plate detector, and consequently it is independent of the scattering angle. As an example, a diamond powder has been chosen and structure factors derived which are in accordance with those calculated from density functional theory methods of the WIEN2k package to within an accuracy that allows a detailed electron density analysis. PMID:24365925

  2. Insights into Analogue Perovskite Solid Solutions from High-Resolution Neutron Powder Diffraction

    NASA Astrophysics Data System (ADS)

    Redfern, S. A.; Chaddock, E. H.; Becerro, A. I.

    2002-12-01

    Neutron powder diffraction provides a powerful tool for the study of phase transitions as a function of pressure, temperature, or chemical composition. The structural information obtainable from powders using diffractometers such as HRPD (ISIS, UK) or D2B (ILL, France) rivals, and in some respects exceeds what may be possible using conventional crystallographic techniques reliant on single crystals. We have used both instruments to explore the subtle phase transitions observed in the (CaxSr1-x)TiO3 and (SrxBa1-x)SnO3 solid solutions. We have also used low resolution high flux instruments to explore the thermal dependence of the superlattice behavior below the cubic to tetragonal phase transition in (CaxSr1-x)TiO3. In each case a sequence of phase transitions from Pm-3m through I4/mcm to Pbnm is seen as a function of composition, and is driven by the change in average radius of the B-cation. This sequence of transitions is the same as expected for a magnesium silicate perovskite structure on increasing temperature. It is now recognised that lower mantle perovskite is likely aluminous, with solid solution towards either a stoichiometric or oxygen-defect end-member. The analogue systems we have characterised have been doped with trivalent cations on the B site to explore the effect of such substitution on the sequence of phase transitions. High-temperature neutron diffraction shows that oxygen defects stabilize the higher symmetry structures, lowering Tc for the transition to cubic. New developments in high-T high-P neutron diffraction techniques will allow the extension of these ambient pressure studies to the investigation of the influence of pressure as a variable, and hence the extension of such analogue studies to the whole range of variables experienced in the lower mantle. These will be briefly outlined.

  3. Developments in time-resolved high pressure x-ray diffraction using rapid compression and decompression

    SciTech Connect

    Smith, Jesse S.; Sinogeikin, Stanislav V.; Lin, Chuanlong; Rod, Eric; Bai, Ligang; Shen, Guoyin

    2015-07-15

    Complementary advances in high pressure research apparatus and techniques make it possible to carry out time-resolved high pressure research using what would customarily be considered static high pressure apparatus. This work specifically explores time-resolved high pressure x-ray diffraction with rapid compression and/or decompression of a sample in a diamond anvil cell. Key aspects of the synchrotron beamline and ancillary equipment are presented, including source considerations, rapid (de)compression apparatus, high frequency imaging detectors, and software suitable for processing large volumes of data. A number of examples are presented, including fast equation of state measurements, compression rate dependent synthesis of metastable states in silicon and germanium, and ultrahigh compression rates using a piezoelectric driven diamond anvil cell.

  4. Atomic motion of resonantly vibrating quartz crystal visualized by time-resolved X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Aoyagi, Shinobu; Osawa, Hitoshi; Sugimoto, Kunihisa; Fujiwara, Akihiko; Takeda, Shoichi; Moriyoshi, Chikako; Kuroiwa, Yoshihiro

    2015-11-01

    Transient atomic displacements during a resonant thickness-shear vibration of AT-cut α-quartz are revealed by time-resolved X-ray diffraction under an alternating electric field. The lattice strain resonantly amplified by the alternating electric field is ˜104 times larger than that induced by a static electric field. The resonantly amplified lattice strain is achieved by fast displacements of oxygen anions and collateral resilient deformation of Si-O-Si angles bridging rigid SiO4 tetrahedra, which efficiently transduce electric energy into elastic energy.

  5. Atomic motion of resonantly vibrating quartz crystal visualized by time-resolved X-ray diffraction

    SciTech Connect

    Aoyagi, Shinobu; Osawa, Hitoshi; Sugimoto, Kunihisa; Fujiwara, Akihiko

    2015-11-16

    Transient atomic displacements during a resonant thickness-shear vibration of AT-cut α-quartz are revealed by time-resolved X-ray diffraction under an alternating electric field. The lattice strain resonantly amplified by the alternating electric field is ∼10{sup 4} times larger than that induced by a static electric field. The resonantly amplified lattice strain is achieved by fast displacements of oxygen anions and collateral resilient deformation of Si−O−Si angles bridging rigid SiO{sub 4} tetrahedra, which efficiently transduce electric energy into elastic energy.

  6. Electro-optic sampling for time resolving relativistic ultrafast electron diffraction

    SciTech Connect

    Scoby, C. M.; Musumeci, P.; Moody, J.; Gutierrez, M.; Tran, T.

    2009-01-22

    The Pegasus laboratory at UCLA features a state-of-the-art electron photoinjector capable of producing ultrashort (<100 fs) high-brightness electron bunches at energies of 3.75 MeV. These beams recently have been used to produce static diffraction patterns from scattering off thin metal foils, and it is foreseen to take advantage of the ultrashort nature of these bunches in future pump-probe time-resolved diffraction studies. In this paper, single shot 2-d electro-optic sampling is presented as a potential technique for time of arrival stamping of electron bunches used for diffraction. Effects of relatively low bunch charge (a few 10's of pC) and modestly relativistic beams are discussed and background compensation techniques to obtain high signal-to-noise ratio are explored. From these preliminary tests, electro-optic sampling is suitable to be a reliable nondestructive time stamping method for relativistic ultrafast electron diffraction at the Pegasus lab.

  7. A wavelet transform algorithm for peak detection and application to powder x-ray diffraction data

    NASA Astrophysics Data System (ADS)

    Gregoire, John M.; Dale, Darren; van Dover, R. Bruce

    2011-01-01

    Peak detection is ubiquitous in the analysis of spectral data. While many noise-filtering algorithms and peak identification algorithms have been developed, recent work [P. Du, W. Kibbe, and S. Lin, Bioinformatics 22, 2059 (2006); A. Wee, D. Grayden, Y. Zhu, K. Petkovic-Duran, and D. Smith, Electrophoresis 29, 4215 (2008)] has demonstrated that both of these tasks are efficiently performed through analysis of the wavelet transform of the data. In this paper, we present a wavelet-based peak detection algorithm with user-defined parameters that can be readily applied to the application of any spectral data. Particular attention is given to the algorithm's resolution of overlapping peaks. The algorithm is implemented for the analysis of powder diffraction data, and successful detection of Bragg peaks is demonstrated for both low signal-to-noise data from theta-theta diffraction of nanoparticles and combinatorial x-ray diffraction data from a composition spread thin film. These datasets have different types of background signals which are effectively removed in the wavelet-based method, and the results demonstrate that the algorithm provides a robust method for automated peak detection.

  8. Neutron powder-diffraction studies of lithium, sodium, and potassium metal

    SciTech Connect

    Berliner, R.; Fajen, O. ); Smith, H.G. ); Hitterman, R.L. )

    1989-12-15

    Neutron powder-diffraction measurements have been performed on polycrystalline lithium and sodium specimens at 80 and 20 K and on potassium metal at 80 and 10 K. Lithium is bcc (body-centered cubic) at room temperature and undergoes a martensitic structural phase transformation to a 9{ital R} (samarium-type) form at low temperature. This experiment presents evidence that the 9{ital R} phase is present in sodium as well as lithium. No evidence of a transformation was observed in potassium at 10 K. The diffraction lines for both lithium and sodium after the phase transformation exhibit position shifts and broadening characteristic of stacking-fault defects. The line shifts, line broadening, and transformed fraction for the low-temperature phase of lithium and sodium metal are reported. The diffraction peak position shifts are, however, different from those predicted for deformation-type stacking faults alone. Qualitative agreement of the experimental results with stacking-fault-model calculations was obtained for a double-twin'' type of layer defect.

  9. Determination of Complex Structures from Powder Diffraction Data: The Crystal Structure of La 3Ti 5Al 15O 37

    NASA Astrophysics Data System (ADS)

    Morris, Russell E.; Owen, Jonathan J.; Stalick, Judith K.; Cheetham, Anthony K.

    1994-07-01

    The applicability of powder diffraction techniques to structure determination has improved substantially in recent times, but it has only been successfully utilized in the solution of relatively simple structures of up to 29 atoms in the asymmetric unit. The structure La 3Ti 5Al 15O 37, which has 60 atoms in the asymmetric unit, has been solved using a combination of synchrotron X-ray and neutron powder diffraction. This represents a considerable advance in the size of structure that has been solved using powder diffraction techniques. The structure of La 3Ti 5Al 15O 37 consists of small regions of simpler structure types in the La/Ti/Al/O system, interleaved to form a complex 3D network.

  10. X-ray powder diffraction investigations of the composition of uranium-containing precipitates

    SciTech Connect

    Ionov, R.A.; Molchanova, T.V.; Rodionov, V.V.; Vodolazov, L.I.; Matyunina, E.N.; Zharova, E.V.

    1988-03-01

    Uranium-containing precipitates which were formed from solutions of uranyl sulfate containing various amounts of ammonium bicarbonate in the pH 2-7 range and which imitate the composition of the uranyl complexes formed in the phase of an ion exchanger at corresponding values of the sorption pH have been investigated by the methods of x-ray powder diffraction analysis, thermal analysis, and chemical analysis. It has been established that uranyl sulfates, basic sulfates, and carbonates of varying composition form as the pH is increased in accordance with the form in which uranium exists in the liquid phase. The formation of polynuclear uranyl complexes in the pH 2-4 range has been postulated.

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

    SciTech Connect

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

    1987-11-01

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

  12. Kinetics of Methane Hydrate Decomposition Studied via in Situ Low Temperature X-ray Powder Diffraction

    SciTech Connect

    Everett, Susan M; Rawn, Claudia J; Keffer, David J.; Mull, Derek L; Payzant, E Andrew; Phelps, Tommy Joe

    2013-01-01

    Gas hydrates are known to have a slowed decomposition rate at ambient pressure and temperatures below the melting point of ice termed self-preservation or anomalous preservation. As hydrate exothermically decomposes, gas is released and water of the clathrate cages transforms into ice. Two regions of slowed decomposition for methane hydrate, 180 200 K and 230 260 K, were observed, and the kinetics were studied by in situ low temperature x-ray powder diffraction. The kinetic constants for ice formation from methane hydrate were determined by the Avrami model within each region and activation energies, Ea, were determined by the Arrhenius plot. Ea determined from the data for 180 200 K was 42 kJ/mol and for 230 260 K was 22 kJ/mol. The higher Ea in the colder temperature range was attributed to a difference in the microstructure of ice between the two regions.

  13. Crystal structure determination of thymoquinone by high-resolution X-ray powder diffraction.

    PubMed

    Pagola, S; Benavente, A; Raschi, A; Romano, E; Molina, M A A; Stephens, P W

    2004-01-01

    The crystal structure of 2-isopropyl-5-methyl-1,4-benzoquinone (thymoquinone) and its thermal behavior--as necessary physical and chemical properties--were determined in order to enhance the current understanding of thymoquinone chemical action by using high resolution x-ray powder diffraction, Fourier transform infrared spectroscopy (FTIR), and 3 thermo-analytical techniques thermogravimetric analysis (TGA), differential thermal analysis (DTA), and differential scanning calorimetry (DSC). The findings obtained with high-resolution x-ray powder diffraction and molecular location methods based on a simulated annealing algorithm after Rietveld refinement showed that the triclinic unit cell was a = 6.73728(8) A, b = 6.91560(8) A, c = 10.4988(2) A, alpha = 88.864(2) degrees, beta = 82.449(1) degrees, gamma = 77.0299(9) degrees; cell volume = 472.52(1) A3, Z = 2, and space group P1. In addition, FTIR spectrum revealed absorption bands corresponding to the carbonyl and C-H stretching of aliphatic and vinylic groups characteristically observed in such p-benzoquinones. Also, a chemical decomposition process starting at 65 degrees C and ending at 213 degrees C was noted when TGA was used. DSC allowed for the determination of onset at 43.55 degrees C and a melting enthalpy value of DeltaH(m) = 110.6 J/g. The low value obtained for the fusion point displayed a van der Waals pattern for molecular binding, and the thermograms performed evidence that thymoquinone can only be found in crystalline triclinic form, as determined by DRX methods. PMID:15760086

  14. Structure Determination and Refinement of Acid Strontium Oxalate from X-Ray and Neutron Powder Diffraction

    NASA Astrophysics Data System (ADS)

    Vanhoyland, G.; Bourée, F.; Van Bael, M. K.; Mullens, J.; Van Poucke, L. C.

    2001-03-01

    The structure of acid strontium oxalate Sr(HC2O4)·{1}/{2}(C2O4)·H2O has been determined by conventional X-ray powder diffractometry. The diffraction pattern was indexed from a monoclinic unit cell with cell parameters a=6.341(1) Å, b=16.880(2) Å, c=5.7798(8) Å, and β=97.60(1)°; space group, P21/n (No. 14) with Z=4. Final (isotropic) Rietveld refinement of the neutron powder data yielded RB=4.57%, RF=2.87%, and Rwp=7.87% as conventional Rietveld parameters. Strontium is eight-fold coordinated and can be described as a distorted bicapped trigonal prism. The SrO8 polyhedra form one-dimensional chains along the c-axis by sharing edges. In contrast to all other known strontium oxalates, in this compound H2O acts as bridging ligand between two Sr atoms. SDPD-D classification (1): Sr(HC2O4)-{1}/{2}(C2O4)-H2O, P21/n, C1=14, Nc=42, C2=11, XC1+N/TREOR-97 & DICVOL-91, EXTRA, EQUI, SIRPOW-92 (DM), GFOURIER, FULLPROF.

  15. Time-resolved x-ray diffraction techniques for bulk polycrystalline materials under dynamic loading.

    PubMed

    Lambert, P K; Hustedt, C J; Vecchio, K S; Huskins, E L; Casem, D T; Gruner, S M; Tate, M W; Philipp, H T; Woll, A R; Purohit, P; Weiss, J T; Kannan, V; Ramesh, K T; Kenesei, P; Okasinski, J S; Almer, J; Zhao, M; Ananiadis, A G; Hufnagel, T C

    2014-09-01

    We have developed two techniques for time-resolved x-ray diffraction from bulk polycrystalline materials during dynamic loading. In the first technique, we synchronize a fast detector with loading of samples at strain rates of ~10(3)-10(4) s(-1) in a compression Kolsky bar (split Hopkinson pressure bar) apparatus to obtain in situ diffraction patterns with exposures as short as 70 ns. This approach employs moderate x-ray energies (10-20 keV) and is well suited to weakly absorbing materials such as magnesium alloys. The second technique is useful for more strongly absorbing materials, and uses high-energy x-rays (86 keV) and a fast shutter synchronized with the Kolsky bar to produce short (~40 μs) pulses timed with the arrival of the strain pulse at the specimen, recording the diffraction pattern on a large-format amorphous silicon detector. For both techniques we present sample data demonstrating the ability of these techniques to characterize elastic strains and polycrystalline texture as a function of time during high-rate deformation. PMID:25273733

  16. Time-resolved x-ray diffraction techniques for bulk polycrystalline materials under dynamic loading

    SciTech Connect

    Lambert, P. K.; Hustedt, C. J.; Zhao, M.; Ananiadis, A. G.; Hufnagel, T. C.; Vecchio, K. S.; Huskins, E. L.; Casem, D. T.; Gruner, S. M.; Tate, M. W.; Philipp, H. T.; Purohit, P.; Weiss, J. T.; Woll, A. R.; Kannan, V.; Ramesh, K. T.; Kenesei, P.; Okasinski, J. S.; Almer, J.

    2014-09-15

    We have developed two techniques for time-resolved x-ray diffraction from bulk polycrystalline materials during dynamic loading. In the first technique, we synchronize a fast detector with loading of samples at strain rates of ∼10{sup 3}–10{sup 4} s{sup −1} in a compression Kolsky bar (split Hopkinson pressure bar) apparatus to obtain in situ diffraction patterns with exposures as short as 70 ns. This approach employs moderate x-ray energies (10–20 keV) and is well suited to weakly absorbing materials such as magnesium alloys. The second technique is useful for more strongly absorbing materials, and uses high-energy x-rays (86 keV) and a fast shutter synchronized with the Kolsky bar to produce short (∼40 μs) pulses timed with the arrival of the strain pulse at the specimen, recording the diffraction pattern on a large-format amorphous silicon detector. For both techniques we present sample data demonstrating the ability of these techniques to characterize elastic strains and polycrystalline texture as a function of time during high-rate deformation.

  17. Time-resolved x-ray diffraction techniques for bulk polycrystalline materials under dynamic loading

    PubMed Central

    Lambert, P. K.; Hustedt, C. J.; Vecchio, K. S.; Huskins, E. L.; Casem, D. T.; Gruner, S. M.; Tate, M. W.; Philipp, H. T.; Woll, A. R.; Purohit, P.; Weiss, J. T.; Kannan, V.; Ramesh, K. T.; Kenesei, P.; Okasinski, J. S.; Almer, J.; Zhao, M.; Ananiadis, A. G.; Hufnagel, T. C.

    2014-01-01

    We have developed two techniques for time-resolved x-ray diffraction from bulk polycrystalline materials during dynamic loading. In the first technique, we synchronize a fast detector with loading of samples at strain rates of ∼103–104 s−1 in a compression Kolsky bar (split Hopkinson pressure bar) apparatus to obtain in situ diffraction patterns with exposures as short as 70 ns. This approach employs moderate x-ray energies (10–20 keV) and is well suited to weakly absorbing materials such as magnesium alloys. The second technique is useful for more strongly absorbing materials, and uses high-energy x-rays (86 keV) and a fast shutter synchronized with the Kolsky bar to produce short (∼40 μs) pulses timed with the arrival of the strain pulse at the specimen, recording the diffraction pattern on a large-format amorphous silicon detector. For both techniques we present sample data demonstrating the ability of these techniques to characterize elastic strains and polycrystalline texture as a function of time during high-rate deformation. PMID:25273733

  18. Powder X-Ray Diffraction of the Grain Components of Carbonaceous Chondrite Meteorites.

    NASA Astrophysics Data System (ADS)

    Furton, D. G.; Hurt, Kendra; Bos, Abram

    Carbonaceous chondrite meteorites are thought to bring to Earth samples of primordial interstellar material. Detailed chemical analysis of meteorites representative of this class (i.e., Allende, Murchison, and Orgueil) establish the primordial character of the material they include and, among other things, reveal that nanometer-sized diamond grains are present in the carbonaceous component of these meteorites at about the 1,000 ppm level (Lewis et al. 1987, Nature, 326, 160). The high abundance of nanodiamonds in these meteoritic samples contributes to the hypothesis that nanodiamonds are present in the interstellar medium at relatively high abundance, but direct observational support of this hypothesis is not so conclusive. (It may also be, according to Dai et al. (2002, Nature, 418, 157), that the nanodiamond grains were formed in situ). On the other hand, there is a growing body of observational evidence that indicates nanometer-sized silicon grains are present in the interstellar medium at relatively high abundance (e.g., Smith & Witt 2001, ApJ, 565, 304). But, silicon nanoparticles have yet to be discovered in a sample of carbonaceous chondrite meteorite. It is relevant in this context that the chemical process that has been used to extract nanodiamond grains from meteoritic samples involves dissolving in strong acid the silicate component of the meteorite. The process is ultimately destructive to any silicon grains that may be present and possibly even alters the nanodiamonds it is used to extract (Mutschke et al. 1995, ApJL, 454, L160). There does not appear to be a similar chemical process that could be used to extract silicon nanoparticles from meteoritic samples. We are in the process of establishing to what extent powder X-ray diffraction can be use as a non-destructive analytical tool to examine nanometer-sized grain components of carbonaceous chondrite meteorites. We present powder X-ray diffraction patterns obtained from samples of the Murchison and

  19. High-pressure powder x-ray diffraction study of EuVO{sub 4}

    SciTech Connect

    Garg, Alka B.; Errandonea, D.

    2015-03-15

    The high-pressure structural behavior of europium orthovanadate has been studied using in-situ, synchrotron based, high-pressure x-ray powder diffraction technique. Angle-dispersive x-ray diffraction measurements were carried out at room temperature up to 34.7 GPa using a diamond-anvil cell, extending the pressure range reported in previous experiments. We confirmed the occurrence of zircon–scheelite phase transition at 6.8 GPa and the coexistence of low- and high-pressure phases up to 10.1 GPa. In addition, clear evidence of a scheelite–fregusonite transition is found at 23.4 GPa. The fergusonite structure remains stable up to 34.7 GPa, the highest pressure reached in the present measurements. A partial decomposition of EuVO{sub 4} was also observed from 8.1 to 12.8 GPa; however, this fact did not preclude the identification of the different crystal structures of EuVO{sub 4}. The crystal structures of the different phases have been Rietveld refined and their equations of state (EOS) have been determined. The results are compared with the previous experimental data and theoretical calculations. - Graphical abstract: The high-pressure structural sequence of EuVO{sub 4}. - Highlights: • EuVO{sub 4} is studied under pressure up to 35 GPa using synchrotron XRD. • The zircón–scheelite–fergusonite structural sequence is observed. • Crystal structures are refined and equations of state determined.

  20. High-pressure powder x-ray diffraction study of EuVO4

    NASA Astrophysics Data System (ADS)

    Garg, Alka B.; Errandonea, D.

    2015-03-01

    The high-pressure structural behavior of europium orthovanadate has been studied using in-situ, synchrotron based, high-pressure x-ray powder diffraction technique. Angle-dispersive x-ray diffraction measurements were carried out at room temperature up to 34.7 GPa using a diamond-anvil cell, extending the pressure range reported in previous experiments. We confirmed the occurrence of zircon-scheelite phase transition at 6.8 GPa and the coexistence of low- and high-pressure phases up to 10.1 GPa. In addition, clear evidence of a scheelite-fregusonite transition is found at 23.4 GPa. The fergusonite structure remains stable up to 34.7 GPa, the highest pressure reached in the present measurements. A partial decomposition of EuVO4 was also observed from 8.1 to 12.8 GPa; however, this fact did not preclude the identification of the different crystal structures of EuVO4. The crystal structures of the different phases have been Rietveld refined and their equations of state (EOS) have been determined. The results are compared with the previous experimental data and theoretical calculations.

  1. In Situ Powder Diffraction Studies of Electrode Materials in Rechargeable Batteries.

    PubMed

    Sharma, Neeraj; Pang, Wei Kong; Guo, Zaiping; Peterson, Vanessa K

    2015-09-01

    The ability to directly track the charge carrier in a battery as it inserts/extracts from an electrode during charge/discharge provides unparalleled insight for researchers into the working mechanism of the device. This crystallographic-electrochemical information can be used to design new materials or modify electrochemical conditions to improve battery performance characteristics, such as lifetime. Critical to collecting operando data used to obtain such information in situ while a battery functions are X-ray and neutron diffractometers with sufficient spatial and temporal resolution to capture complex and subtle structural changes. The number of operando battery experiments has dramatically increased in recent years, particularly those involving neutron powder diffraction. Herein, the importance of structure-property relationships to understanding battery function, why in situ experimentation is critical to this, and the types of experiments and electrochemical cells required to obtain such information are described. For each battery type, selected research that showcases the power of in situ and operando diffraction experiments to understand battery function is highlighted and future opportunities for such experiments are discussed. The intention is to encourage researchers to use in situ and operando techniques and to provide a concise overview of this area of research. PMID:26223736

  2. Plant powder teabags: a novel and practical approach to resolve culturability and diversity of rhizobacteria.

    PubMed

    Sarhan, Mohamed S; Mourad, Elhussein F; Hamza, Mervat A; Youssef, Hanan H; Scherwinski, Ann-Christin; El-Tahan, Mahmoud; Fayez, Mohamed; Ruppel, Silke; Hegazi, Nabil A

    2016-08-01

    We have developed teabags packed with dehydrated plant powders, without any supplements, for preparation of plant infusions necessary to develop media for culturing rhizobacteria. These bacteria are efficiently cultivated on such plant teabag culture media, with better progressive in situ recoverability compared to standard chemically synthetic culture media. Combining various plant-based culture media and incubation conditions enabled us to resolve unique denaturing gradient gel electrophoresis (DGGE) bands that were not resolved by tested standard culture media. Based on polymerase chain reaction PCR-DGGE of 16S rDNA fingerprints and sequencing, the plant teabag culture media supported higher diversity and significant increases in the richness of endo-rhizobacteria, namely Gammaproteobacteria (Enterobacteriaceae) and predominantly Alphaproteobacteria (Rhizobiaceae). This culminated in greater retrieval of the rhizobacteria taxa associated with the plant roots. We conclude that the plant teabag culture medium by itself, without any nutritional supplements, is sufficient and efficient for recovering and mirroring the complex and diverse communities of rhizobacteria. Our message to fellow microbial ecologists is: simply dehydrate your plant canopy, teabag it and soak it to prepare your culture media, with no need for any additional supplementary nutrients. PMID:27178359

  3. Time-, frequency-, and wavevector-resolved x-ray diffraction from single molecules

    PubMed Central

    Bennett, Kochise; Biggs, Jason D.; Zhang, Yu; Dorfman, Konstantin E.; Mukamel, Shaul

    2014-01-01

    Using a quantum electrodynamic framework, we calculate the off-resonant scattering of a broadband X-ray pulse from a sample initially prepared in an arbitrary superposition of electronic states. The signal consists of single-particle (incoherent) and two-particle (coherent) contributions that carry different particle form factors that involve different material transitions. Single-molecule experiments involving incoherent scattering are more influenced by inelastic processes compared to bulk measurements. The conditions under which the technique directly measures charge densities (and can be considered as diffraction) as opposed to correlation functions of the charge-density are specified. The results are illustrated with time- and wavevector-resolved signals from a single amino acid molecule (cysteine) following an impulsive excitation by a stimulated X-ray Raman process resonant with the sulfur K-edge. Our theory and simulations can guide future experimental studies on the structures of nano-particles and proteins. PMID:24880284

  4. Time-, frequency-, and wavevector-resolved x-ray diffraction from single molecules

    SciTech Connect

    Bennett, Kochise Biggs, Jason D.; Zhang, Yu; Dorfman, Konstantin E.; Mukamel, Shaul

    2014-05-28

    Using a quantum electrodynamic framework, we calculate the off-resonant scattering of a broadband X-ray pulse from a sample initially prepared in an arbitrary superposition of electronic states. The signal consists of single-particle (incoherent) and two-particle (coherent) contributions that carry different particle form factors that involve different material transitions. Single-molecule experiments involving incoherent scattering are more influenced by inelastic processes compared to bulk measurements. The conditions under which the technique directly measures charge densities (and can be considered as diffraction) as opposed to correlation functions of the charge-density are specified. The results are illustrated with time- and wavevector-resolved signals from a single amino acid molecule (cysteine) following an impulsive excitation by a stimulated X-ray Raman process resonant with the sulfur K-edge. Our theory and simulations can guide future experimental studies on the structures of nano-particles and proteins.

  5. Time-resolved x-ray diffraction and calorimetric studies at low scan rates

    PubMed Central

    Yao, Haruhiko; Hatta, Ichiro; Koynova, Rumiana; Tenchov, Boris

    1992-01-01

    The phase transitions of dipalmitoylphosphatidylethanolamine (DPPE) in excess water have been examined by low-angle time-resolved x-ray diffraction and calorimetry at low scan rates. The lamellar subgel/lamellar liquid-crystalline (Lc → Lα), lamellar gel/lamellar liquid-crystalline (Lβ → Lα), and lamellar liquid-crystalline/lamellar gel (Lα → Lβ) phase transitions proceed via coexistence of the initial and final phases with no detectable intermediates at scan rates 0.1 and 0.5°C/min. At constant temperature within the region of the Lβ → Lα transition the ratio of the two coexisting phases was found to be stable for over 30 min. The state of stable phase coexistence was preceded by a 150-s relaxation taking place at constant temperature after termination of the heating scan in the transition region. While no intermediate structures were present in the coexistence region, a well reproducible multipeak pattern, with at least four prominent heat capacity peaks separated in temperature by 0.4-0.5°C, has been observed in the cooling transition (Lα → Lβ) by calorimetry. The multipeak pattern became distinct with an increase of incubation time in the liquid-crystalline phase. It was also clearly resolved in the x-ray diffraction intensity versus temperature plots recorded at slow cooling rates. These data suggest that the equilibrium state of the Lα phase of hydrated DPPE is represented by a mixture of domains that differ in thermal behavior, but cannot be distinguished structurally by x-ray scattering. Imagesp689-aFIGURE 9 PMID:19431820

  6. Microelemental and mineral compositions of pathogenic biomineral concrements: SRXFA, X-ray powder diffraction and vibrational spectroscopy data

    NASA Astrophysics Data System (ADS)

    Moroz, T. N.; Palchik, N. A.; Dar'in, A. V.

    2009-05-01

    X-ray fluorescence analysis using synchrotron radiation (SRXRF), X-ray powder diffraction, infrared and Raman spectroscopy had been applied for determination of microelemental and mineral composition of the kidney stones, gallstones and salivalities from natives of Novosibirsk and Novosibirsk region, Russia. The relationship between mineral, organic and microelemental composition of pathogenic calcilus was shown.

  7. An Inquiry-Based Project Focused on the X-Ray Powder Diffraction Analysis of Common Household Solids

    ERIC Educational Resources Information Center

    Hulien, Molly L.; Lekse, Jonathan W.; Rosmus, Kimberly A.; Devlin, Kasey P.; Glenn, Jennifer R.; Wisneski, Stephen D.; Wildfong, Peter; Lake, Charles H.; MacNeil, Joseph H.; Aitken, Jennifer A.

    2015-01-01

    While X-ray powder diffraction (XRPD) is a fundamental analytical technique used by solid-state laboratories across a breadth of disciplines, it is still underrepresented in most undergraduate curricula. In this work, we incorporate XRPD analysis into an inquiry-based project that requires students to identify the crystalline component(s) of…

  8. Using Variable Temperature Powder X-Ray Diffraction to Determine the Thermal Expansion Coefficient of Solid MgO

    ERIC Educational Resources Information Center

    Corsepius, Nicholas C.; DeVore, Thomas C.; Reisner, Barbara A.; Warnaar, Deborah L.

    2007-01-01

    A laboratory exercise was developed by using variable temperature powder X-ray diffraction (XRD) to determine [alpha] for MgO (periclase)and was tested in the Applied Physical Chemistry and Materials Characterization Laboratories at James Madison University. The experiment which was originally designed to provide undergraduate students with a…

  9. Coherent convergent-beam time-resolved X-ray diffraction

    PubMed Central

    Spence, John C. H.; Zatsepin, Nadia A.; Li, Chufeng

    2014-01-01

    The use of coherent X-ray lasers for structural biology allows the use of nanometre diameter X-ray beams with large beam divergence. Their application to the structure analysis of protein nanocrystals and single particles raises new challenges and opportunities. We discuss the form of these coherent convergent-beam (CCB) hard X-ray diffraction patterns and their potential use for time-resolved crystallography, normally achieved by Laue (polychromatic) diffraction, for which the monochromatic laser radiation of a free-electron X-ray laser is unsuitable. We discuss the possibility of obtaining single-shot, angle-integrated rocking curves from CCB patterns, and the dependence of the resulting patterns on the focused beam coordinate when the beam diameter is larger or smaller than a nanocrystal, or smaller than one unit cell. We show how structure factor phase information is provided at overlapping interfering orders and how a common phase origin between different shots may be obtained. Their use in refinement of the phase-sensitive intensity between overlapping orders is suggested. PMID:24914153

  10. Coherent convergent-beam time-resolved X-ray diffraction.

    PubMed

    Spence, John C H; Zatsepin, Nadia A; Li, Chufeng

    2014-07-17

    The use of coherent X-ray lasers for structural biology allows the use of nanometre diameter X-ray beams with large beam divergence. Their application to the structure analysis of protein nanocrystals and single particles raises new challenges and opportunities. We discuss the form of these coherent convergent-beam (CCB) hard X-ray diffraction patterns and their potential use for time-resolved crystallography, normally achieved by Laue (polychromatic) diffraction, for which the monochromatic laser radiation of a free-electron X-ray laser is unsuitable. We discuss the possibility of obtaining single-shot, angle-integrated rocking curves from CCB patterns, and the dependence of the resulting patterns on the focused beam coordinate when the beam diameter is larger or smaller than a nanocrystal, or smaller than one unit cell. We show how structure factor phase information is provided at overlapping interfering orders and how a common phase origin between different shots may be obtained. Their use in refinement of the phase-sensitive intensity between overlapping orders is suggested. PMID:24914153

  11. X-Ray Powder Diffraction as a Tool for the Identification of Impact Deformed Rocks

    NASA Astrophysics Data System (ADS)

    Huson, S.; Pope, M.; Foit, F.; Watkinson, A.

    2007-12-01

    Previous X-ray powder diffraction (XRD) studies indicated shock deformed minerals have broader XRD peaks when compared to those of unshocked samples. Entire XRD patterns, single peak profiles and Rietveld refined parameters of carbonate samples from the Sierra Madera impact crater, west Texas and the Mission Canyon Formation of southwest Montana and western Wyoming were used to evaluate the use of X-ray powder diffraction as a tool for distinguishing impact deformed rocks from tectonically deformed rocks. Both sample locations contain rocks subjected to varying degrees of deformation. At Sierra Madera dolostone and limestone samples were collected from the crater rim (lower shock intensity) and the central uplift (higher shock intensity). Carbonate rocks of the Mission Canyon Formation were sampled along a transect across the tectonic front of the Sevier and Laramide orogenies. Peaks in the XRD patterns of shocked calcite in samples from Sierra Madera are generally broader than those of calcite samples from the Mission Canyon Formation whereas peak broadening of shocked dolomite in samples from the outer central uplift of Sierra Madera is similar to those of Mission Canyon Formation samples. Single peak profile patterns of calcite and dolomite samples from both locations are complex and their full width half maxima (FWHM) show no relationship to shock intensity, especially above ~80 ° 2θ. Rietveld refinement of peak shape parameters yields a more precise measure of the 2θ angular dependence of peak FWHM and, therefore, the degree of shock deformation. FWHM values obtained from Rietveld crystal structure refinements increase with shock intensity for all Sierra Madera samples. Additionally, FWHM values of some tectonically deformed Mission Canyon Formation calcites overlap with those of weakly shocked calcite from the crater rim of Sierra Madera. FWHM values of shocked dolomite from the central uplift of Sierra Madera are distinctly higher than tectonically

  12. Application of focused-beam flat-sample method to synchrotron powder X-ray diffraction with anomalous scattering effect

    NASA Astrophysics Data System (ADS)

    Tanaka, M.; Katsuya, Y.; Matsushita, Y.

    2013-03-01

    The focused-beam flat-sample method (FFM), which is a method for high-resolution and rapid synchrotron X-ray powder diffraction measurements by combination of beam focusing optics, a flat shape sample and an area detector, was applied for diffraction experiments with anomalous scattering effect. The advantages of FFM for anomalous diffraction were absorption correction without approximation, rapid data collection by an area detector and good signal-to-noise ratio data by focusing optics. In the X-ray diffraction experiments of CoFe2O4 and Fe3O4 (By FFM) using X-rays near the Fe K absorption edge, the anomalous scattering effect between Fe/Co or Fe2+/Fe3+ can be clearly detected, due to the change of diffraction intensity. The change of observed diffraction intensity as the incident X-ray energy was consistent with the calculation. The FFM is expected to be a method for anomalous powder diffraction.

  13. Combined synchrotron X-ray tomography and X-ray powder diffraction using a fluorescing metal foil

    SciTech Connect

    Kappen, P.; Arhatari, B. D.; Luu, M. B.; Balaur, E.; Caradoc-Davies, T.

    2013-06-15

    This study realizes the concept of simultaneous micro-X-ray computed tomography and X-ray powder diffraction using a synchrotron beamline. A thin zinc metal foil was placed in the primary, monochromatic synchrotron beam to generate a divergent wave to propagate through the samples of interest onto a CCD detector for tomographic imaging, thus removing the need for large beam illumination and high spatial resolution detection. Both low density materials (kapton tubing and a piece of plant) and higher density materials (Egyptian faience) were investigated, and elemental contrast was explored for the example of Cu and Ni meshes. The viability of parallel powder diffraction using the direct beam transmitted through the foil was demonstrated. The outcomes of this study enable further development of the technique towards in situ tomography/diffraction studies combining micrometer and crystallographic length scales, and towards elemental contrast imaging and reconstruction methods using well defined fluorescence outputs from combinations of known fluorescence targets (elements).

  14. Quantification of febuxostat polymorphs using powder X-ray diffraction technique.

    PubMed

    Qiu, Jing-bo; Li, Gang; Sheng, Yue; Zhu, Mu-rong

    2015-03-25

    Febuxostat is a pharmaceutical compound with more than 20 polymorphs of which form A is most widely used and usually exists in a mixed polymorphic form with form G. In the present study, a quantification method for polymorphic form A and form G of febuxostat (FEB) has been developed using powder X-ray diffraction (PXRD). Prior to development of a quantification method, pure polymorphic form A and form G are characterized. A continuous scan with a scan rate of 3° min(-1) over an angular range of 3-40° 2θ is applied for the construction of the calibration curve using the characteristic peaks of form A at 12.78° 2θ (I/I0100%) and form G at 11.72° 2θ (I/I0100%). The linear regression analysis data for the calibration plots shows good linear relationship with R(2)=0.9985 with respect to peak area in the concentration range 10-60 wt.%. The method is validated for precision, recovery and ruggedness. The limits of detection and quantitation are 1.5% and 4.6%, respectively. The obtained results prove that the method is repeatable, sensitive and accurate. The proposed developed PXRD method can be applied for the quantitative analysis of mixtures of febuxostat polymorphs (forms A and G). PMID:25636167

  15. Structures of six industrial benzimidazolone pigments from laboratory powder diffraction data.

    PubMed

    van de Streek, Jacco; Brüning, Jürgen; Ivashevskaya, Svetlana N; Ermrich, Martin; Paulus, Erich F; Bolte, Michael; Schmidt, Martin U

    2009-04-01

    The crystal structures of six industrially produced benzimidazolone pigments [Pigment Orange 36 (beta phase), Pigment Orange 62, Pigment Yellow 151, Pigment Yellow 154 (alpha phase), Pigment Yellow 181 (beta phase) and Pigment Yellow 194] were determined from laboratory X-ray powder diffraction data by means of real-space methods using the programs DASH and MRIA, respectively. Subsequent Rietveld refinements were carried out with TOPAS. The crystal phases correspond to those produced industrially. Additionally, the crystal structures of the non-commercial compound 'BIRZIL' (a chloro derivative of Pigment Yellow 194) and of a dimethylsulfoxide solvate of Pigment Yellow 154 were determined by single-crystal structure analyses. All eight crystal structures are different; the six industrial pigments even exhibit five different hydrogen-bond topologies. Apparently, the good application properties of the benzimidazolone pigments are not the result of one specific hydrogen-bonding pattern, but are the result of a combination of efficient molecular packing and strong intermolecular hydrogen bonds. PMID:19299876

  16. Versatile in situ powder X-ray diffraction cells for solid–gas investigations

    PubMed Central

    Jensen, Torben R.; Nielsen, Thomas K.; Filinchuk, Yaroslav; Jørgensen, Jens-Erik; Cerenius, Yngve; Gray, Evan MacA.; Webb, Colin J.

    2010-01-01

    This paper describes new sample cells and techniques for in situ powder X-ray diffraction specifically designed for gas absorption studies up to ca 300 bar (1 bar = 100 000 Pa) gas pressure. The cells are for multipurpose use, in particular the study of solid–gas reactions in dosing or flow mode, but can also handle samples involved in solid–liquid–gas studies. The sample can be loaded into a single-crystal sapphire (Al2O3) capillary, or a quartz (SiO2) capillary closed at one end. The advantages of a sapphire single-crystal cell with regard to rapid pressure cycling are discussed, and burst pressures are calculated and measured to be ∼300 bar. An alternative and simpler cell based on a thin-walled silicate or quartz glass capillary, connected to a gas source via a VCR fitting, enables studies up to ∼100 bar. Advantages of the two cell types are compared and their applications are illustrated by case studies. PMID:22477780

  17. Kinetics of methane hydrate decomposition studied via in situ low temperature X-ray powder diffraction.

    PubMed

    Everett, S Michelle; Rawn, Claudia J; Keffer, David J; Mull, Derek L; Payzant, E Andrew; Phelps, Tommy J

    2013-05-01

    Gas hydrate is known to have a slowed decomposition rate at ambient pressure and temperatures below the melting point of ice. As hydrate exothermically decomposes, gas is released and water of the clathrate cages transforms into ice. Based on results from the decomposition of three nominally similar methane hydrate samples, the kinetics of two regions, 180-200 and 230-260 K, within the overall decomposition range 140-260 K, were studied by in situ low temperature X-ray powder diffraction. The kinetic rate constants, k(a), and the reaction mechanisms, n, for ice formation from methane hydrate were determined by the Avrami model within each region, and activation energies, E(a), were determined by the Arrhenius plot. E(a) determined from the data for 180-200 K was 42 kJ/mol and for 230-260 K was 22 kJ/mol. The higher E(a) in the colder temperature range was attributed to a difference in the microstructure of ice between the two regions. PMID:23557375

  18. Characterization of the Structure of LaD 2.50by Neutron Powder Diffraction

    NASA Astrophysics Data System (ADS)

    Udovic, T. J.; Huang, Q.; Rush, JJ

    1996-02-01

    Neutron powder diffraction (NPD) measurements of the rare-earth deuteride LaD2.50were undertaken between 10 and 430 K. Rietveld refinements indicated that, above ∼385 K, the LaD2.50structure is cubic (Fm3m) with deuterium fully occupying the tetrahedral (t) interstices of the fcc La lattice and the excess deuterium occupying a portion of the octahedral (o) interstices with full statistical disorder. As the temperature is decreased below ∼385 K, the LaD2.50structure undergoes a tetragonal distortion concomitant with the onset of deuterium long-range order (I41/amd) in the o sublattice, similar to previous structural results for the light-rare-earth deuteridesRD2+xfor 0.3

  19. Characterization of the intercalate C60(CO2)x by powder neutron diffraction

    NASA Astrophysics Data System (ADS)

    James, M.; Kennedy, S. J.; Elcombe, M. M.; Gadd, G. E.

    1998-12-01

    The intercalate compound C60(CO2)x has been synthesized by hot isostatically pressing C60 under 170 MPa of CO2 and 350 °C. Neutron powder diffraction studies conducted on C60(CO2)x between room temperature and 5 K have been analyzed using Rietveld techniques and reveal a structural transition between a high-temperature (>~250 K) face-centered cubic phase [Fm3¯m, a=14.224(2) Å (293 K)] and a low-temperature (<~150 K) monoclinic phase [P21/n, a=9.7438(9) Å, b=9.7473(9) Å, c=14.6121(11) Å, β=90.390(6)° (5 K)]. The CO2 molecules occupy the octahedral interstices between the C60 molecules and are oriented along the body diagonal of the high-temperature phase. In the low-temperature phase they are tilted slightly away from the c axis so as to place the oxygen atoms adjacent to the center of a pentagonal face on the C60 molecules.

  20. In-situ early-age hydration study of sulfobelite cements by synchrotron powder diffraction

    SciTech Connect

    Álvarez-Pinazo, G.; Cuesta, A.; García-Maté, M.; Santacruz, I.; Losilla, E.R.; Fauth, F.; Aranda, M.A.G.; De la Torre, A.G.

    2014-02-15

    Eco-friendly belite calcium sulfoaluminate (BCSA) cement hydration behavior is not yet well understood. Here, we report an in-situ synchrotron X-ray powder diffraction study for the first hours of hydration of BCSA cements. Rietveld quantitative phase analysis has been used to establish the degree of reaction (α). The hydration of a mixture of ye'elimite and gypsum revealed that ettringite formation (α ∼ 70% at 50 h) is limited by ye'elimite dissolution. Two laboratory-prepared BCSA cements were also studied: non-active-BCSA and active-BCSA cements, with β- and α′{sub H}-belite as main phases, respectively. Ye'elimite, in the non-active-BCSA system, dissolves at higher pace (α ∼ 25% at 1 h) than in the active-BCSA one (α ∼ 10% at 1 h), with differences in the crystallization of ettringite (α ∼ 30% and α ∼ 5%, respectively). This behavior has strongly affected subsequent belite and ferrite reactivities, yielding stratlingite and other layered phases in non-active-BCSA. The dissolution and crystallization processes are reported and discussed in detail. -- Highlights: •Belite calcium sulfoaluminate cements early hydration mechanism has been determined. •Belite hydration strongly depends on availability of aluminum hydroxide. •Orthorhombic ye’elimite dissolved at a higher pace than cubic one. •Ye’elimite larger reaction degree yields stratlingite formation by belite reaction. •Rietveld method quantified gypsum, anhydrite and bassanite dissolution rates.

  1. The Crystal Structures of two Anhydrous Magnesium Hydroxychloride Phases from in situ Synchrotron Powder Diffraction Data

    SciTech Connect

    Hanson, J.C.; Dinnebier, R.E.; Halasz, I.; Freyer, D.

    2011-07-25

    The crystal structures of two members of the solid solution series Mg(OH){sub x}Cl{sub y}x+y = 2, Mg(OH){sub 1.7}Cl{sub 0.3} (P{sup {bar 3}}m1, a = 3.169(2) {angstrom}, c = 5.530(12), V = 48.1(1) {angstrom}{sup 3} at T = 365 C) and MgOHCl (R{sup {bar 3}}m, a = 3.3877(4) {angstrom}, c = 17.534(4) {angstrom}, V = 174.27(6) {angstrom}{sup 3} at T = 625 C) were determined from in situ synchrotron powder diffraction data at high temperature upon dehydration of 3Mg(OH){sub 2} {center_dot} MgCl{sub 2} {center_dot} 8H{sub 2}O (F3) and 5Mg(OH){sub 2} {center_dot} MgCl{sub 2} {center_dot} 8H{sub 2}O (F5) phases. The crystal structures of Mg(OH){sub 1.7}Cl{sub 0.3} (example of ss-type-OH) and MgOHCl (example of ss-type-Cl) can be related to the C19 (CdCl{sub 2}) and C6 (CdI{sub 2}) structure type, respectively, with the disordered chloride and hydroxide anions occupying the same crystallographic site in layers.

  2. A Powder Neutron Diffraction Study of Structure and Magnetism in NiCr 2S 4

    NASA Astrophysics Data System (ADS)

    Powell, Anthony V.; Colgan, Douglas C.; Ritter, Clemens

    1997-11-01

    Powder neutron diffraction data for NiCr 2S 4have been collected over the temperature range 1.8≤ T≤286 K. The Cr 3S 4structure (space group I2/ m) is adopted at all temperatures. Refinement of 286 K data ( a=5.8954(14) Å, b=3.4066(8) Å, c=11.0589(22) Å, β=91.362(4)°) demonstrates that the distribution of nickel and chromium cations between sites in a fully occupied metal layer and sites in an ordered vacancy layer is close to that expected for the normal structure type. Data collected at 1.8 K ( a=5.8621(5) Å, b=3.4051(2) Å, c=11.0297(9) Å, β=91.607(6)°) reveal the presence of long-range magnetic order, involving a doubling of the unit cell in both the aand cdirections. Cations in the fully occupied metal layer possess an ordered magnetic moment of 1.57(6) μBwhich is directed parallel to the cation layers. Cations in the vacancy layer have a moment of 1.36(8) μBwhich is directed toward the anion layers. The magnetic ordering temperature was determined as 180(5) K. These results are correlated with magnetic susceptibility and electrical conductivity data.

  3. Kinetic Analyses of Cation Exchange Rates in Synthetic Birnessite Measured by Time- Resolved Synchrotron X-ray Diffraction

    NASA Astrophysics Data System (ADS)

    Lopano, C. L.; Heaney, P. J.; Post, J. E.; Bandstra, J.; Brantley, S. L.

    2006-05-01

    Birnessite is the most abundant and chemically important layer-structure Mn-oxide phase found in soils, desert varnishes, and ocean nodules. It also is industrially important for use in battery technology and octahedral sieves. Due to the poorly crystalline nature of natural birnessite, synthetic analogues typically have been employed in studies that explore the structural response of birnessite to variations in interlayer composition. For this work, we measured changes in unit-cell parameters over time to quantify the degree of cation exchange as a function of concentration. Aqueous K+, Cs+, and Ba2+ cations at varying concentrations at pH 7 were exchanged for interlayer Na+ in synthetic birnessite (Na0.58(Mn4+1.42,Mn3+0.58)O4·1.5H2O) using a simple flow- through cell, and the exchange products were monitored via time-resolved X-ray powder diffraction at the National Synchrotron Light Source. Powder X-ray diffraction patterns were collected every 2-3 minutes. Rietveld analyses of X-ray diffraction patterns for K- and Ba-exchanged birnessite revealed a decrease in unit- cell volume over time. In contrast, Cs+ substitution increased cell volume. For all three cations, the crystallographic data indicate that exchange occurred in two stages. A rapid and dramatic change in unit-cell volume was followed by a modest adjustment over longer timescales. Fourier electron difference syntheses revealed that the rapid, initial stage of exchange was marked by re-configuration of the interlayer species, whereas the second, protracted phase of substitution represented ordering into the newly established interlayer positions. For the first time, we have modeled the kinetics of interlayer substitution in Na-birnessite. For purposes of comparison, we have employed a simple one-stage reaction (i.e., Na-birnessite → K-birnessite) and a two stage reaction (i.e,. Na-birnessite → K-birnessitedisordered → K- birnessiteordered). For exchange with 0.01 M KCl solutions, the single

  4. Hydrothermal synthesis of nanocrystalline ZnSe: An in situ synchrotron radiation X-ray powder diffraction study

    SciTech Connect

    Jorgensen, J.-E. Jensen, T.R.; Hanson, J.C.

    2008-08-15

    The hydrothermal synthesis of nanocrystalline ZnSe has been studied by in situ X-ray powder diffraction using synchrotron radiation. The formation of ZnSe was studied using the following starting mixtures: Zn+Se+H{sub 2}O (route A) and ZnCl{sub 2}+Se+H{sub 2}O+Na{sub 2}SO{sub 3} (route B). The route A experiment showed that Zn powder starts reacting with water at 134 deg. C giving ZnO and H{sub 2} followed by the formation of ZnSe which takes place in temperature range from 167 to 195 deg. C. The route B experiment shows a considerably more complex reaction path with several intermediate phases and in this case the formation of ZnSe starts at 141 deg. C and ZnSe and Se were the only crystalline phases observed at the end of the experiment where the temperature was 195 deg. C. The sizes of the nanocrystalline particles were determined to 18 and 9 nm in the route A and B experiments, respectively. Nanocrystalline ZnSe was also synthesized ex situ using the route A and B methods and characterized by conventional X-ray powder diffraction and transmission electron microscopy. An average crystalline domain size of ca. 8 nm was determined by X-ray powder diffraction in fair agreement with TEM images, which showed larger aggregates of nanoparticles having approximate diameters of 10 nm. Furthermore, a method for purification of the ZnSe nanoparticles was developed and the prepared particles showed signs of anisotropic size broadening of the diffraction peaks. - Graphical abstract: Stack of powder diagrams showing the formation of nanocrystalline ZnSe under hydrothermal conditions.

  5. In situ powder diffraction study of belite sulfoaluminate clinkering.

    PubMed

    De la Torre, Angeles G; Cuberos, Antonio J M; Alvarez-Pinazo, Gema; Cuesta, Ana; Aranda, Miguel A G

    2011-05-01

    Belite sulfoaluminate (BSA) cements have been proposed as environmentally friendly building materials, as their production may release up to 35% less CO(2) into the atmosphere when compared with ordinary Portland cement fabrication. However, their formation mechanism has not been studied in detail so far. Here, an in situ high-temperature high-resolution synchrotron X-ray powder diffraction study is reported. Two types of BSA clinkers have been characterized, both containing 50-60 wt% C(2)S and 20-30 wt% C(4)A(3)\\underline{\\rm S} as main phases. One type is iron-rich and a second type (with different phase assemblage) is aluminium-rich. Furthermore, the C(2)S phase reacts slowly with water, thus activation of this compound is desirable in order to enhance the mechanical strength development of the resulting cements. To do so, iron-rich BSA clinkers have been doped with minor amounts of B(2)O(3) and Na(2)O to promote stabilization of α-forms of C(2)S, which are more reactive with water. The decarbonated raw materials were loaded into Pt tubes and heated to between 973 K and 1673 K, and patterns were collected using a high-energy synchrotron beam of wavelength λ = 0.30 Å. The thermal stability of Klein's salt in these clinkers has been clarified. Several reactions have been followed: formation and decomposition of Klein's salt, melting of aluminates and ferrite, and polymorphic transformations of dicalcium silicate: alpha'H-C2S → α-C(2)S. Changes in mineralogical phase assemblages at a given temperature owing to the addition of minor amounts of selected elements have also been determined. PMID:21525661

  6. Locating Organic Guests in Inorganic Host Materials from X-ray Powder Diffraction Data.

    PubMed

    Smeets, Stef; McCusker, Lynne B; Baerlocher, Christian; Elomari, Saleh; Xie, Dan; Zones, Stacey I

    2016-06-01

    Can the location of the organic structure-directing agent (SDA) inside the channel system of a zeolite be determined experimentally in a systematic manner? In an attempt to answer this question, we investigated six borosilicate zeolites of known framework structure (SSZ-53, SSZ-55, SSZ-56, SSZ-58, SSZ-59, and SSZ-60), where the location of the SDA had only been simulated using molecular modeling techniques in previous studies. From synchrotron powder diffraction data, we were able to retrieve reliable experimental positions for the SDA by using a combination of simulated annealing (global optimization) and Rietveld refinement. In this way, problems arising from data quality and only partially compatible framework and SDA symmetries, which can lead to indecipherable electron density maps, can be overcome. Rietveld refinement using geometric restraints were then performed to optimize the positions and conformations of the SDAs. With these improved models, it was possible to go on to determine the location of the B atoms in the framework structure. That is, two pieces of information that are key to the understanding of zeolite synthesis-the location of the organic SDA in the channel system and of the positions adopted by heteroatoms in the silicate framework-can be extracted from experimental data using a systematic strategy. In most cases, the locations of the SDAs determined experimentally compare well with those simulated with molecular modeling, but there are also some clear differences, and the reason for these differences can be understood. The approach is generally applicable, and has also been used to locate organic guests, linkers, and ligands in metal-organic compounds. PMID:27181421

  7. Structural and Thermal Characterization of Zolpidem Hemitartrate Hemihydrate (Form E) and Its Decomposition Products by Laboratory X-Ray Powder Diffraction

    SciTech Connect

    Halasz, I.; Dinnebier, R

    2010-01-01

    The crystal structure of zolpidem hemitartrate hemihydrate (I, Form E) has been solved from high-resolution laboratory powder diffraction data. It crystallizes in the orthorhombic P2{sub 1}2{sub 1}2{sub 1} space group with a = 22.4664(6) {angstrom}, b = 26.0420(7) {angstrom}, and c = 7.4391(1) {angstrom}. Protonation of zolpidem molecules could not be unambiguously determined. Thermal stability of Form E has been investigated by TG-DTA and in situ by temperature resolved X-ray powder diffraction. Water loss occurs between 50 C {le} t {le} 100 C while structure decomposition commences at approximately 120 C yielding zolpidem tartrate (II) and pure zolpidem base (III) in approximately equimolar amounts. Crystal structures of II and III have been solved simultaneously from a single powder pattern of thermally decomposed I. Zolpidem tartrate crystallizes in the orthorhombic P2{sub 1}2{sub 1}2{sub 1} space group with a = 19.9278(8) {angstrom}, b = 15.1345(8) {angstrom}, and c = 7.6246(2) {angstrom} (at 140 C). Zolpidem base crystallizes in the orthorhombic Pcab space group with a = 9.9296(4) {angstrom}, b = 18.4412(9) {angstrom}, and c = 18.6807(9) {angstrom} (at 140 C). In the reported crystal structures zolpidem molecules form stacks through {pi}-{pi} interaction or dipole-dipole interactions while tartrate moieties, if present, form hydrogen bonded chains. Water molecule in I forms a hydrogen bond to the imidazole nitrogen atom of the zolpidem molecule. Free space in the crystal structure of I could allow for the additional water molecules and thus a variable water content.

  8. Characterization of high energy Xe ion irradiation effects in single crystal molybdenum with depth-resolved synchrotron microbeam diffraction

    NASA Astrophysics Data System (ADS)

    Yun, Di; Miao, Yinbin; Xu, Ruqing; Mei, Zhigang; Mo, Kun; Mohamed, Walid; Ye, Bei; Pellin, Michael J.; Yacout, Abdellatif M.

    2016-04-01

    Microbeam X-ray diffraction experiments were conducted at beam line 34-ID of the Advanced Photon Source (APS) on fission fragment energy Xe heavy ion irradiated single crystal Molybdenum (Mo). Lattice strain measurements were obtained with a depth resolution of 0.7 μm, which is critical in resolving the peculiar heterogeneity of irradiation damage associated with heavy ion irradiation. Q-space diffraction peak shift measurements were correlated with lattice strain induced by the ion irradiations. Transmission electron microscopy (TEM) characterizations were performed on the as-irradiated materials as well. Nanometer sized Xe bubble microstructures were observed via TEM. Molecular Dynamics (MD) simulations were performed to help interpret the lattice strain measurement results from the experiment. This study showed that the irradiation effects by fission fragment energy Xe ion irradiations can be collaboratively understood with the depth resolved X-ray diffraction and TEM measurements under the assistance of MD simulations.

  9. Study of polymorphism of Atenolol and Captopril antihypertensives using x-ray powder diffraction and Rietveld refinement

    NASA Astrophysics Data System (ADS)

    Sato, Juliana; Ferreira, Fabio

    2013-03-01

    Characterization of bulk drugs has become increasingly important in the pharmaceutical industry. X-ray powder diffractometry is an effective technique for the identification of crystalline solid-phase drugs. The technique is unique, since it combines specificity with a high degree of accuracy for the characterization of pharmaceuticals in solid state and is an especially useful method to describe the possible polymorphic behavior of drugs substances. In this work X-ray diffraction data have been obtained for two well-known antihypertensive drugs currently being administered in tablet form. They include atenolol and captopril. Atenolol and captopril were purchased from drugstore. The characterizations of the atenolol and captopril samples were carried out by FTIR spectroscopy and X-ray powder diffraction (XRPD). We would like to thank the Brazilian agencies CNPq and FAPESP for their financial support.

  10. Synchrotron X-ray powder diffraction data of LASSBio-1515: A new N-acylhydrazone derivative compound

    NASA Astrophysics Data System (ADS)

    Costa, F. N.; Braz, D.; Ferreira, F. F.; da Silva, T. F.; Barreiro, E. J.; Lima, L. M.; Colaço, M. V.; Kuplich, L.; Barroso, R. C.

    2014-02-01

    In this work, synchrotron X-ray powder diffraction data allowed for a successful indexing of LASSBio-1515 compound, candidate to analgesic and anti-inflammatory activity. X-ray powder diffraction data collected in transmission and high-throughput geometries were used to analyze this compound. The X-ray wavelength of the synchrotron radiation used in this study was determined to be λ=1.55054 Å. LASSBio-1515 was found to be monoclinic with space group P21/c and unit cell parameters a=11.26255(16) Å, b=12.59785(16) Å, c=8.8540(1) Å, β=90.5972(7)° and V=1256.17(3) Å3.

  11. Direct Observation of Phase Transformations in Austenitic Stainless Steel Welds Using In-situ Spatially Resolved and Time-resolved X-ray Diffraction

    SciTech Connect

    Elmer, J.; Wong, J.; Ressler, T.

    1999-09-23

    Spatially resolved x-ray diffraction (SRXRD) and time resolved x-ray diffraction (TRXRD) were used to investigate real time solid state phase transformations and solidification in AISI type 304 stainless steel gas tungsten arc (GTA) welds. These experiments were conducted at Stanford Synchrotron Radiation Laboratory (SSRL) using a high flux beam line. Spatially resolved observations of {gamma} {leftrightarrow} {delta} solid state phase transformations were performed in the heat affected zone (HAZ) of moving welds and time-resolved observations of the solidification sequence were performed in the fusion zone (FZ) of stationary welds after the arc had been terminated. Results of the moving weld experiments showed that the kinetics of the {gamma}{yields}{delta} phase transformation on heating in the HAZ were sufficiently rapid to transform a narrow region surrounding the liquid weld pool to the {delta} ferrite phase. Results of the stationary weld experiments showed, for the first time, that solidification can occur directly to the {delta} ferrite phase, which persisted as a single phase for 0.5s. Upon solidification to {delta}, the {delta} {yields} {gamma} phase transformation followed and completed in 0.2s as the weld cooled further to room temperature.

  12. Hydrothermal Synthesis of Nanocrystalline ZnSe: An in situ Synchrotron Radiation X-ray Powder Diffraction Study

    SciTech Connect

    Joergensen,J.; Jensen, T.; Hanson, J.

    2008-01-01

    The hydrothermal synthesis of nanocrystalline ZnSe has been studied by in situ X-ray powder diffraction using synchrotron radiation. The formation of ZnSe was studied using the following starting mixtures: Zn+Se+H2O (route A) and ZnCl2+Se+H2O+Na2SO3 (route B). The route A experiment showed that Zn powder starts reacting with water at 134 C giving ZnO and H2 followed by the formation of ZnSe which takes place in temperature range from 167 to 195 C. The route B experiment shows a considerably more complex reaction path with several intermediate phases and in this case the formation of ZnSe starts at 141 C and ZnSe and Se were the only crystalline phases observed at the end of the experiment where the temperature was 195 C. The sizes of the nanocrystalline particles were determined to 18 and 9 nm in the route A and B experiments, respectively. Nanocrystalline ZnSe was also synthesized ex situ using the route A and B methods and characterized by conventional X-ray powder diffraction and transmission electron microscopy. An average crystalline domain size of ca. 8 nm was determined by X-ray powder diffraction in fair agreement with TEM images, which showed larger aggregates of nanoparticles having approximate diameters of 10 nm. Furthermore, a method for purification of the ZnSe nanoparticles was developed and the prepared particles showed signs of anisotropic size broadening of the diffraction peaks.

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

    PubMed

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

    2016-05-01

    A baromagnetic effect in a novel tetragonal magnetic structure is introduced by vacancies in Mn3 Ga0.95 N0.94 , due to the change of the Mn-Mn distance and their spin re-orientation induced by a pressure field. This effect is proven for the first time in antiperovskite compounds by neutron powder diffraction analysis. This feature will enable wide applications in magnetoelectric devices and intelligent instruments. PMID:27007214

  14. Effect of Stacking Faults on the X-Ray Diffraction Profiles of Beta-SiC Powders

    NASA Technical Reports Server (NTRS)

    Pujar, Vijay V.; Cawley, James D.; Levine, Stanley R. (Technical Monitor)

    1995-01-01

    X-ray diffraction patterns or beta-SiC (3C or the cubic polytype or sic) powders often exhibit an additional peak at d = 0.266 nm, high background intensity around the (111) peak, and relative intensities for peaks which differ from those predicted from the crystal structure. Computer simulations were used to show that all these features are due to stacking faults in the powders and not due to the presence of other polytypes in the powders. Such simulations allow diffraction patterns to be generated for different types, frequencies, and spatial distribution or faults. Comparison of the simulation results to the XRD data indicates that the B-SiC particles consist either of heavily faulted clusters distributed irregularly between regions that have only occasional faults or twins, or the powders consist of two types of particles with different populations of faults: those with a high density of faults and those with only twins or occasional faults. Additional information is necessary to determine which description is correct. However, the simulation results can be used to rule out certain fault configurations.

  15. An Implementation of the Fundamental Parameters Approach for Analysis of X-ray Powder Diffraction Line Profiles.

    PubMed

    Mendenhall, Marcus H; Mullen, Katharine; Cline, James P

    2015-01-01

    This work presents an open implementation of the Fundamental Parameters Approach (FPA) models for analysis of X-ray powder diffraction line profiles. The original literature describing these models was examined and code was developed to allow for their use within a Python based least squares refinement algorithm. The NIST interest in the FPA method is specific to its ability to account for the optical aberrations of the powder diffraction experiment allowing for an accurate assessment of lattice parameter values. Lattice parameters are one of the primary certified measurands of NIST Standard Reference Materials (SRMs) for powder diffraction. Lattice parameter values obtained from analysis of data from SRMs 640e and 660c using both the NIST FPA Python code and the proprietary, commercial code Topas, that constitutes the only other actively supported, complete implementation of FPA models within a least-squares data analysis environment, agreed to within 2 fm. This level of agreement demonstrates that both the NIST code and Topas constitute an accurate implementation of published FPA models. PMID:26958448

  16. Powder diffraction pattern fitting and structure refinement by means of the CPSR v.3.1 software package

    NASA Astrophysics Data System (ADS)

    Andreev, Yu. G.; Lundström, T.; Sorokin, N. I.

    1995-02-01

    An updated version of the CPSR software package for powder pattern fitting and structure refinement offers major advantages over previous versions. An optional use of the new figure-of-merit function, that takes into account a systematic behaviour of residuals, allows users to reduce the effect of local correlations at the full-profile fitting stage, thus providing more reliable estimates for integrated intensities and their deviances. The structure refinement stage in such a case yields accurate values for estimated standard deviations of structural parameters since, in addition, model errors affecting calculated integrated intensities are taken into consideration. Furthermore, the new CPSR version is customized for a variety of constant-wavelength neutron and X-ray diffraction techniques and is equipped with an enhanced menu structure. Graphical on-screen-controlled support allows users to follow the progress of a fitting procedure over any region of a powder pattern. The program performance is illustrated using the neutron diffraction data file for PbSO 4 distributed during the Rietveld refinement round robin, organized by the IUCr Commission on Powder Diffraction.

  17. An Implementation of the Fundamental Parameters Approach for Analysis of X-ray Powder Diffraction Line Profiles

    PubMed Central

    Mendenhall, Marcus H.; Mullen, Katharine; Cline, James P.

    2015-01-01

    This work presents an open implementation of the Fundamental Parameters Approach (FPA) models for analysis of X-ray powder diffraction line profiles. The original literature describing these models was examined and code was developed to allow for their use within a Python based least squares refinement algorithm. The NIST interest in the FPA method is specific to its ability to account for the optical aberrations of the powder diffraction experiment allowing for an accurate assessment of lattice parameter values. Lattice parameters are one of the primary certified measurands of NIST Standard Reference Materials (SRMs) for powder diffraction. Lattice parameter values obtained from analysis of data from SRMs 640e and 660c using both the NIST FPA Python code and the proprietary, commercial code Topas, that constitutes the only other actively supported, complete implementation of FPA models within a least-squares data analysis environment, agreed to within 2 fm. This level of agreement demonstrates that both the NIST code and Topas constitute an accurate implementation of published FPA models. PMID:26958448

  18. Time-resolved x-ray diffraction and calorimetric studies at low scan rates

    PubMed Central

    Tenchov, Boris G.; Yao, Haruhiko; Hatta, Ichiro

    1989-01-01

    The phase transitions in fully hydrated dipalmitoylphosphatidylcholine (DPPC) and DPPC/water/ethanol phases have been studied by lowangle time-resolved x-ray diffraction under conditions similar to those employed in calorimetry (scan rates 0.05-0.5°C/min and uniform temperature throughout the samples). This approach provides more adequate characterization of the equilibrium transition pathways and allows for close correlations between structural and thermodynamic data. No coexistence of the rippled gel (Pβ') and liquid-crystalline (Lα) phases was found in the main transition of DPPC; rather, a loss of correlation in the lamellar structure, observed as broadening of the lamellar reflections, takes place in a narrow temperature range of ∼100 mK at the transition midpoint. Formation of a long-living metastable phase, denoted by Pβ'(mst), differing from the initial Pβ' was observed in cooling direction by both x-ray diffraction and calorimetry. No direct conversion of Pβ'(mst) into Pβ' occurs for over 24 h but only by way of the phase sequence Pβ'(mst) → Lβ' → Pβ'. According to differential scanning calorimetry (DSC), the enthalpy of the Pβ'(mst)-Lα transition is by ∼5% lower than that of the Pβ'-Lα transition. The effects of ethanol (Rowe, E. S. 1983. Biochemistry. 22:3299-3305; Simon, S. A., and T. J. McIntosh. 1984. Biochim. Biophys. Acta 773:169-172) on the mechanism and reversibility of the DPPC main transition were clearly visualized. At ethanol concentrations inducing formation of interdigitated gel phase, the main transition proceeds through a coexistence of the initial and final phases over a finite temperature range. During the subtransition in DPPC recorded at scan rate 0.3°C/min, a smooth monotonic increase of the lamellar spacing from its subgel (Lc) to its gel (Lβ') phase value takes place. The width of the lamellar reflections remains unchanged during this transformation. This provides grounds to propose a

  19. Powder diffraction studies in the YONO{sub 3}-Y{sub 2}O{sub 3} system

    SciTech Connect

    Pelloquin, D.; Loueer, M.; Loueer, D.

    1994-09-01

    The crystal structure of yttrium oxide nitrate and the microstructure of the oxide obtained from its thermal decomposition have been investigated by modern powder diffraction methods. Sequential high-temperature diffraction studies of the thermal decomposition of two precursors of yttrium oxide nitrate, i.e., neutral yttrium nitrate and yttrium hydroxide nitrate, are reported. The structure of YONO{sub 3} has been determined ab initio from conventional powder diffractometry using monochromatic X-rays. The pattern was indexed by the successive dichotomy method yielding tetragonal unit cell dimensions: a = 3.8590(1) {angstrom} and c = 9.7161(6) {angstrom}. The space group is P4/nmm and Z = 2. Most of the atoms were located by direct methods and the remaining ones from a Fourier map. Refinement of the complete diffraction profile parameters converged to final agreement factors R{sub p} = 0.12, R{sub wp} = 0.16 and R{sub F} = 0.039. The structure is closely related to the matlockite PbFCl-type structure. The microstructure of ex-oxide-nitrate yttrium oxide has been analysed by total pattern fitting techniques, from which strain-free coherently diffracting nanodomains with a rectangular parallelepipedic shape have been obtained.

  20. Examination of Short- and Long-Range Atomic Order Nanocrystalline SiC and Diamond by Powder Diffraction Methods

    NASA Technical Reports Server (NTRS)

    Palosz, B.; Grzanka, E.; Stelmakh, S.; Gierlotka, S.; Weber, H.-P.; Proffen, T.; Palosz, W.

    2002-01-01

    The real atomic structure of nanocrystals determines unique, key properties of the materials. Determination of the structure presents a challenge due to inherent limitations of standard powder diffraction techniques when applied to nanocrystals. Alternate methodology of the structural analysis of nanocrystals (several nanometers in size) based on Bragg-like scattering and called the "apparent lattice parameter" (alp) is proposed. Application of the alp methodology to examination of the core-shell model of nanocrystals will be presented. The results of application of the alp method to structural analysis of several nanopowders were complemented by those obtained by determination of the Atomic Pair Distribution Function, PDF. Based on synchrotron and neutron diffraction data measured in a large diffraction vector of up to Q = 25 Angstroms(exp -1), the surface stresses in nanocrystalline diamond and SiC were evaluated.

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

    PubMed Central

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

    2015-01-01

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

  2. New routes to synthesizing an ordered perovskite CaCu3Fe2Sb2O12 and its magnetic structure by neutron powder diffraction.

    PubMed

    Larregola, Sebastian A; Zhou, Jianshi; Alonso, Jose A; Pomjakushin, Vladimir; Goodenough, John B

    2014-05-01

    The search for new double-perovskite oxides has grown rapidly in recent years because of their interesting physical properties like ferroelectricity, magnetism, and multiferroics. The synthesis of double perovskites, especially the A-site-ordered perovskites, in most cases needs to be made under high pressure, which is a drawback for applying these materials. Here we have demonstrated synthetic routes at ambient pressure by which we have obtained a high-quality duo-sites-ordered double perovskite, CaCu3Fe2Sb2O12, which has been previously synthesized under high pressure. The availability of a large quantity of the powder sample allows us to determine the crystal and magnetic structures by neutron powder diffraction (NPD) at 300 and 1.3 K. Measurements of the magnetization and heat capacity showed a ferrimagnetic transition at 160 K. A ferrimagnetic structure consisting of the uncompensated antiferromagnetic coupling between neighboring collinear copper and iron spins has been resolved from the low-temperature NPD data. PMID:24716725

  3. In situ X-ray powder diffraction, synthesis, and magnetic properties of InVO{sub 3}

    SciTech Connect

    Lundgren, Rylan J.; Cranswick, Lachlan M.D.; Bieringer, Mario . E-mail: Mario_Bieringer@umanitoba.ca

    2006-12-15

    We report the first synthesis and high-temperature in situ X-ray diffraction study of InVO{sub 3}. Polycrystalline InVO{sub 3} has been prepared via reduction of InVO{sub 4} using a carbon monoxide/carbon dioxide buffer gas. InVO{sub 3} crystallizes in the bixbyite structure in space group Ia-3 (206) with a=9.80636(31) A with In{sup 3+}/V{sup 3+} disorder on the (8b) and (24d) cation sites. In situ powder X-ray diffraction experiments and thermal gravimetric analysis in a CO/CO{sub 2} buffer gas revealed the existence of the metastable phase InVO{sub 3}. Bulk samples with 98.5(2)% purity were prepared using low-temperature reduction methods. The preparative methods limited the crystallinity of this new phase to approximately 225(50) A. Magnetic susceptibility and neutron diffraction experiments suggest a spin-glass ground state for InVO{sub 3}. - Graphical abstract: In situ powder X-ray diffractograms for the reduction of InVO{sub 4} in CO/CO{sub 2}. The three temperature regions show the conversion of InVO{sub 4} to InVO{sub 3} and final decomposition into In{sub 2}O{sub 3} and V{sub 2}O{sub 3}.

  4. The use of net analyte signal orthogonalization in the separation of multi-component diffraction patterns obtained from X-ray powder diffraction of intact compacts.

    PubMed

    Moore, Michael D; Cogdill, Robert P; Short, Steven M; Hair, Colleen R; Wildfong, Peter L D

    2008-06-01

    X-ray powder diffraction (XRPD) analysis of intact multi-component consolidated mixtures has significant potential owing to the ability to non-destructively quantify and discriminate between solid phases in composite bodies with minimal sample preparation. There are, however, limitations to the quantitative power using traditional univariate methods on diffraction data containing features from all components in the system. The ability to separate multi-component diffraction data into patterns representing single constituents allows both composition as well as physical phenomena associated with the individual components of complex systems to be probed. Intact, four-component compacts, consisting of two crystalline and two amorphous constituents were analyzed using XRPD configured in both traditional Bragg-Brentano reflectance geometry and parallel-beam transmission geometry. Two empirical, model-based methods consisting of a multiple step net analyte signal (NAS) orthogonalization are presented as ways to separate multi-component XRPD patterns into single constituent patterns. Multivariate figures of merit (FOM) were calculated for each of the isolated constituents to compare method-specific parameters such as sensitivity, selectivity, and signal-to-noise, enabling quantitative comparisons between the two modes of XRPD analysis. PMID:18294800

  5. Crystal structure of anhydrous tripotassium citrate from laboratory X-ray powder diffraction data and DFT comparison

    PubMed Central

    Rammohan, Alagappa; Kaduk, James A.

    2016-01-01

    The crystal structure of anhydrous tripotassium citrate, [K3(C6H5O7)]n, has been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. The three unique potassium cations are 6-, 8-, and 6-coordinate (all irregular). The [KOn] coordination polyhedra share edges and corners to form a three-dimensional framework, with channels running parallel to the c axis. The only hydrogen bond is an intra­molecular one involving the hy­droxy group and the central carboxyl­ate group, with graph-set motif S(5). PMID:27536403

  6. Crystal structure of anhydrous tripotassium citrate from laboratory X-ray powder diffraction data and DFT comparison.

    PubMed

    Rammohan, Alagappa; Kaduk, James A

    2016-08-01

    The crystal structure of anhydrous tripotassium citrate, [K3(C6H5O7)] n , has been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. The three unique potassium cations are 6-, 8-, and 6-coordinate (all irregular). The [KO n ] coordination polyhedra share edges and corners to form a three-dimensional framework, with channels running parallel to the c axis. The only hydrogen bond is an intra-molecular one involving the hy-droxy group and the central carboxyl-ate group, with graph-set motif S(5). PMID:27536403

  7. Anisotropic atom displacement in Pd nanocubes resolved by molecular dynamics simulations supported by x-ray diffraction imaging

    NASA Astrophysics Data System (ADS)

    Scardi, P.; Leonardi, A.; Gelisio, L.; Suchomel, M. R.; Sneed, B. T.; Sheehan, M. K.; Tsung, C.-K.

    2015-04-01

    Nearly identical Pd nanocubes yield an x-ray powder diffraction pattern with interference fringes affording access to unprecedented structural details of nanocrystal size, shape, and complex atomic displacement for a billion-sized population. The excellent agreement between diffraction data and molecular dynamics (MD) provides strong experimental validation of MD simulations and the proposed data-interpretation paradigm. These results show that individual atomic displacements within the nanocubes are not only a function of disrupted bonds and the crystallographic plane of the adjacent surface, but are complex strain gradients extending across all surfaces of the particle strongly influenced by atomic displacements. This observation of nonuniform surface strain and the manner in which it is affected by different sizes, shapes, and locations within each facet could be the key to understanding many surface related properties of shaped nanocrystals including those associated with important catalysis applications.

  8. Synchrotron X-ray powder diffraction and convergent beam electron diffraction studies on the cubic phase of MgV{sub 2}O{sub 4} spinel

    SciTech Connect

    Niitaka, Seiji; Lee, Soyeon; Oshima, Yoshifumi; Kato, Kenichi; Hashizume, Daisuke; Takata, Masaki; Takagi, Hidenori

    2014-07-01

    The A V{sub 2}O{sub 4} (A=Mg{sup 2+}, Zn{sup 2+}, Cd{sup 2+}) spinels are three-dimensional spin-1 frustrated systems with orbital degree of freedom, which have been known to possess intriguing orbital states causing releases of spin frustration at low temperatures. We have performed synchrotron X-ray and convergent beam electron diffraction measurements for one of these vanadates, MgV{sub 2}O{sub 4} in order to clarify its crystal structure in the high temperature cubic phase, which is regarded as an important starting point for understanding the details of the low temperature phase. We have successfully observed that the [001] zone axis convergent beam electron diffraction pattern exhibits 4mm symmetry, suggesting the space group of Fd3{sup ¯}m in the cubic MgV{sub 2}O{sub 4}. It has also been demonstrated that the crystal structure of the cubic MgV{sub 2}O{sub 4} contains VO{sub 6} octahedra elongated along the threefold rotation axis. Based on our results, we discuss the orbital states of MgV{sub 2}O{sub 4} as well as the other spinel vanadates. - Graphical abstract: Precise geometry of the VO{sub 6} octahedra in the cubic phase of MgV{sub 2}O{sub 4} spinel determined with the synchrotron powder XRD data. - Highlights: • We examined the crystal structure of the cubic phase of MgV{sub 2}O{sub 4} spinel. • We prepared the single crystal and powdered sample of MgV{sub 2}O{sub 4} with high quality. • The result of the CBED measurement agrees with the space group of Fd3{sup ¯}m in the phase. • The cubic phase has VO{sub 6} octahedra elongated along the threefold rotation axis.

  9. Comparing ultrafast surface and bulk heating using time-resolved electron diffraction

    SciTech Connect

    Streubühr, C.; Kalus, A.; Zhou, P. Kammler, M.; Linde, D. von der; Ligges, M.; Hanisch-Blicharski, A.; Bovensiepen, U.; Horn-von Hoegen, M.

    2014-04-21

    From measurements of the transient Debye-Waller effect in Bismuth, we determine the buildup time of the random atomic motion resulting from the electronic relaxation after short pulse laser excitation. The surface sensitive reflection high energy electron diffraction and transmission electron diffraction yield a time constant of about 12 ps and 3 ps, respectively. The different energy transfer rates indicate relatively weak coupling between bulk and surface vibrational modes.

  10. In situ energy-dispersive x-ray diffraction system for time-resolved thin-film growth studies

    NASA Astrophysics Data System (ADS)

    Ellmer, K.; Mientus, R.; Weiß, V.; Rossner, H.

    2003-03-01

    Energy-dispersive x-ray diffraction (EDXRD) with synchrotron light can be used for in situ-structural analysis during polycrystalline thin-film growth, due to its fast data collection and the fixed diffraction angle. An in situ deposition and analysis set-up for the investigation of nucleation and growth of thin films during magnetron sputtering was constructed and installed at the synchrotron radiation source Hamburger Synchrotronstrahlungs Labor (Hamburg). The polychromatic synchrotron beam passes the sputtering chamber through Kapton windows and hits the substrate with the growing film. The diffracted beam, observed under a fixed diffraction angle of between 1° and 10° was energy-analysed by a high-purity germanium detector. The measurement time for a single XRD spectrum can be as short as 10 s for a beam line at a bending magnet, which allows a time-resolved monitoring of film growth. The performance of the in situ EDXRD set-up is demonstrated for the growth of zinc oxide and tin-doped indium oxide films prepared by reactive magnetron sputtering from ceramic and metallic targets. From the position and the width of the diffraction lines the internal mechanical strain and the grain size of the growing films can be derived. The prospects for thin-film growth investigations using such an instrument are assessed.

  11. Local order and orientational correlations in liquid and crystalline phases of carbon tetrabromide from neutron powder diffraction measurements

    NASA Astrophysics Data System (ADS)

    Temleitner, L.; Pusztai, L.

    2010-04-01

    The liquid, plastic crystalline and ordered crystalline phases of CBr4 were studied using neutron-powder diffraction. The measured total scattering differential cross sections were modeled by reverse Monte Carlo simulation techniques ( RMC++ and RMCPOW). Following successful simulations, the single-crystal-diffraction pattern of the plastic phase as well as partial radial distribution functions and orientational correlations for all the three phases have been calculated from the atomic coordinates (particle configurations). The single-crystal pattern, calculated from a configuration that had been obtained from modeling the powder pattern, shows identical behavior to the recent single-crystal data of Folmer [Phys. Rev. B 77, 144205 (2008)]. The BrBr partial radial-distribution functions of the liquid and plastic crystalline phases are almost the same while CC correlations clearly display long-range ordering in the latter phase. Orientational correlations also suggest strong similarities between liquid and plastic crystalline phases whereas the monoclinic phase behaves very differently. Orientations of the molecules are distinct in the ordered phase whereas in the plastic crystal their distribution seems to be isotropic.

  12. Beamline P02.1 at PETRA III for high-resolution and high-energy powder diffraction

    PubMed Central

    Dippel, Ann-Christin; Liermann, Hanns-Peter; Delitz, Jan Torben; Walter, Peter; Schulte-Schrepping, Horst; Seeck, Oliver H.; Franz, Hermann

    2015-01-01

    Powder X-ray diffraction techniques largely benefit from the superior beam quality provided by high-brilliance synchrotron light sources in terms of photon flux and angular resolution. The High Resolution Powder Diffraction Beamline P02.1 at the storage ring PETRA III (DESY, Hamburg, Germany) combines these strengths with the power of high-energy X-rays for materials research. The beamline is operated at a fixed photon energy of 60 keV (0.207 Å wavelength). A high-resolution monochromator generates the highly collimated X-ray beam of narrow energy bandwidth. Classic crystal structure determination in reciprocal space at standard and non-ambient conditions are an essential part of the scientific scope as well as total scattering analysis using the real space information of the pair distribution function. Both methods are complemented by in situ capabilities with time-resolution in the sub-second regime owing to the high beam intensity and the advanced detector technology for high-energy X-rays. P02.1’s efficiency in solving chemical and crystallographic problems is illustrated by presenting key experiments that were carried out within these fields during the early stage of beamline operation. PMID:25931084

  13. Azine bridged silver coordination polymers: Powder X-ray diffraction route to crystal structure determination of silver benzotriazole

    SciTech Connect

    Rajeswaran, Manju . E-mail: manju.rajeswaran@kodak.com; Blanton, Thomas N.; Giesen, David J.; Whitcomb, David R.; Zumbulyadis, Nicholas; Antalek, Brian J.; Neumann, Marcus M.; Misture, Scott T.

    2006-04-15

    In continuation of our interest in solid-state structures of silver complexes of photographic importance, the structure for silver benzotriazole (AgBZT), has now been obtained. The preferred method for solving crystal structures is via single-crystal X-ray diffraction (XRD). However, for some materials, growing single crystals of appropriate size and quality is often difficult or even impossible. AgBZT is an example of such a silver complex with poor solubility. The usual routes to preparing single crystals using recrystallization from a cooperating solvent resulted in polycrystalline powder samples. We propose a crystal structure for AgBZT, solved from synchrotron X-ray powder diffraction data, using a direct-space Monte Carlo simulated annealing approach. AgBZT crystals are monoclinic (P2{sub 1} /c), with unit cell dimensions, a=14.8052(3) A, b=3.7498(4) A, c=12.3495(12) A, and {beta}=114.200(6){sup o}. The AgBZT complex is constructed from all three of the Benzotriazole (BZT) nitrogens bonding to a separate silver atom. As a consequence of this bonding mode, the structure is a highly cross-linked, coordination polymer.

  14. Structural analysis of lead magnesium niobate using synchrotron powder X-ray diffraction and the Rietveld method.

    PubMed

    Bhakar, Ashok; Pandey, Adityanarayan H; Singh, M N; Upadhyay, Anuj; Sinha, A K; Gupta, S M; Ganguli, Tapas

    2016-06-01

    The room-temperature synchrotron powder X-ray diffraction pattern of the single phase perovskite lead magnesium niobate (PMN) has shown significant broadening in the q range ∼ 5-7 Å(-1) compared with standard LaB6 synchrotron powder X-ray diffraction data, taken under similar conditions. This broadening/asymmetry lies mainly towards the lower 2θ side of the Bragg peaks. Attempts to fit this data with the paraelectric cubic phase (Pm\\bar 3m) and the local rhombohedral phase (R3m) corresponding to polar nanoregions (PNRs) are made using the Rietveld method. Rietveld refinements show that neither cubic (Pm\\bar 3m) nor rhombohedral (R3m) symmetry can fit this XRD pattern satisfactorily. The two-phase refinement fits the experimental data satisfactorily and suggests that the weight percentage of the PNRs is approximately 12-16% at room temperature. The unit-cell volume of these rhombohedral PNRs is approximately 0.15% larger than that of the unit cell volume of the paraelectric cubic phase. PMID:27240772

  15. Apparatus and Techniques for Time-resolved Synchrotron X-ray Diffraction using Diamond Anvil Cells

    NASA Astrophysics Data System (ADS)

    Smith, J.; Sinogeikin, S. V.; Lin, C.; Rod, E.; Bai, L.; Shen, G.

    2015-12-01

    Complementary advances in synchrotron sources, x-ray optics, area detectors, and sample environment control have recently made possible many time-resolved experimental techniques for studying materials at extreme pressure and temperature conditions. The High Pressure Collaborative Access Team (HPCAT) at the Advanced Photon Source has made a sustained effort to assemble a powerful collection of high-pressure apparatus for time-resolved research, and considerable time has been invested in developing techniques for collecting high-quality time-resolved x-ray scattering data. Herein we present key aspects of the synchrotron beamline and ancillary equipment, including source considerations, rapid (de)compression apparatus, high frequency imaging detectors, and software suitable for processing large volumes of data. A number of examples are presented, including fast equation of state measurements, compression rate dependent synthesis of metastable states in silicon and germanium, and ultrahigh compression rates using a piezoelectric driven diamond anvil cell.

  16. Time-resolved measurements with streaked diffraction patterns from electrons generated in laser plasma wakefield

    NASA Astrophysics Data System (ADS)

    He, Zhaohan; Nees, John; Hou, Bixue; Krushelnick, Karl; Thomas, Alec; Beaurepaire, Benoît; Malka, Victor; Faure, Jérôme

    2013-10-01

    Femtosecond bunches of electrons with relativistic to ultra-relativistic energies can be robustly produced in laser plasma wakefield accelerators (LWFA). Scaling the electron energy down to sub-relativistic and MeV level using a millijoule laser system will make such electron source a promising candidate for ultrafast electron diffraction (UED) applications due to the intrinsic short bunch duration and perfect synchronization with the optical pump. Recent results of electron diffraction from a single crystal gold foil, using LWFA electrons driven by 8-mJ, 35-fs laser pulses at 500 Hz, will be presented. The accelerated electrons were collimated with a solenoid magnetic lens. By applying a small-angle tilt to the magnetic lens, the diffraction pattern can be streaked such that the temporal evolution is separated spatially on the detector screen after propagation. The observable time window and achievable temporal resolution are studied in pump-probe measurements of photo-induced heating on the gold foil.

  17. Super-resolving quantum radar: Coherent-state sources with homodyne detection suffice to beat the diffraction limit

    SciTech Connect

    Jiang, Kebei; Lee, Hwang; Gerry, Christopher C.; Dowling, Jonathan P.

    2013-11-21

    There has been much recent interest in quantum metrology for applications to sub-Raleigh ranging and remote sensing such as in quantum radar. For quantum radar, atmospheric absorption and diffraction rapidly degrades any actively transmitted quantum states of light, such as N00N states, so that for this high-loss regime the optimal strategy is to transmit coherent states of light, which suffer no worse loss than the linear Beer's law for classical radar attenuation, and which provide sensitivity at the shot-noise limit in the returned power. We show that coherent radar radiation sources, coupled with a quantum homodyne detection scheme, provide both longitudinal and angular super-resolution much below the Rayleigh diffraction limit, with sensitivity at shot-noise in terms of the detected photon power. Our approach provides a template for the development of a complete super-resolving quantum radar system with currently available technology.

  18. Time-Resolved Synchrotron X-ray Diffraction on Pulse Laser Heated Iron in Diamond Anvil Cell

    SciTech Connect

    Yoo, C S; Wei, H; Dias, R; Shen, G; Smith, J; Chen, J Y; Evans, W

    2011-09-21

    The authors present time-resolved synchrotron x-ray diffraction to probe the {var_epsilon}-{delta} phase transition of iron during pulse-laser heating in a diamond anvil cell. The system utilizes a monochromatic synchrotron x-ray beam, a two-dimensional pixel array x-ray detector and a dual beam, double side laser-heating system. Multiple frames of the diffraction images are obtained in real-time every 22 ms over 500 ms of the entire pulse heating period. The results show the structural evolution of iron phases at 17 GPa, resulting in thermal expansion coefficient 1/V({Delta}V/{Delta}T){sub p} = 7.1 * 10{sup -6}/K for {var_epsilon}-Fe and 2.4 * 10{sup -5}/K for {gamma}-Fe, as well as the evidence for metastability of {gamma}-Fe at low temperatures below the {var_epsilon}-{gamma} phase boundary.

  19. Effect of microfibril twisting in theoretical powder diffraction studies of cellulose Iß

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Previous studies of calculated diffraction patterns for cellulose crystallites have suggested that the distortions arising once models have been subjected to MD simulation are likely the result of dimensional changes induced by the empirical force field, but have been unable to determine to what ext...

  20. Development of Powder Diffraction Analysis Tools for aNanocrystalline Specimen: An Emphasis upon NiTi (Nitinol)

    SciTech Connect

    Owens, Erich; /Albion Coll. /SLAC

    2006-08-30

    Powder diffraction is a specialized technique whose investigatory limits are constrained by the scale of the crystallized substance being scanned versus the probe beam used. When disparate in scale, with the photon spot size larger than the crystal being probed, many are employed, the resulting diffraction image being cast from all possible incident angles, constructing {chi}-arcs containing information about the crystalline structure of the material under examination. Of particular interest to our collaboration is the structure of Nitinol, a superelastic Nickel-Titanium alloy, whose phase transformations and load bearing deformations can be studied by usage of diffraction, with wide sweeping biomedical uses. Analysis of this data is complicated by phase transformation and material fluorescence, which make difficult the computational modeling of the peaks within concentric {chi}-arcs. We endeavored to construct a series of computational tools (the amalgamation of them known as 2DPeakFinder) for refining and extracting this relevant data, toward the end of employing previously developed algorithms in the material's structural analysis. We succeeded to a large degree with the use of an iterative algorithm to navigate radial complexity of the signal and manage to retain a distinction between useful signal and superfluous background noise. The tools developed in this project are a small step in readily streamlining the analysis and physical modeling of a Nanocrystalline material's structural properties.

  1. In-Situ Observations of Phase Transformations During Welding of 1045 Steel using Spatially Resolved and Time Resolved X-Ray Diffraction

    SciTech Connect

    Elmer, J; Palmer, T; DebRoy, T

    2005-10-28

    Synchrotron-based methods have been developed at Lawrence Livermore National Laboratory (LLNL) for the direct observation of microstructure evolution during welding. These techniques, known as spatially resolved (SRXRD) and time resolved (TRXRD) x-ray diffraction, allow in-situ experiments to be performed during welding and provide direct observations of high temperature phases that form under the intense thermal cycles that occur. This paper presents observations of microstructural evolution that occur during the welding of a medium carbon AISI 1045 steel, using SRXRD to map the phases that are present during welding, and TRXRD to dynamically observe transformations during rapid heating and cooling. SRXRD was further used to determine the influence of welding heat input on the size of the high temperature austenite region, and the time required to completely homogenize this region during welding. These data can be used to determine the kinetics of phase transformations under the steep thermal gradients of welds, as well as benchmark and verify phase transformation models.

  2. Quantitative determination of mineral composition by powder X-ray diffraction

    DOEpatents

    Pawloski, Gayle A.

    1986-01-01

    An external standard intensity ratio method is used for quantitatively determining mineralogic compositions of samples by x-ray diffraction. The method uses ratios of x-ray intensity peaks from a single run. Constants are previously determined for each mineral which is to be quantitatively measured. Ratios of the highest intensity peak of each mineral to be quantified in the sample and the highest intensity peak of a reference mineral contained in the sample are used to calculate sample composition.

  3. Quantitative determination of mineral composition by powder x-ray diffraction

    DOEpatents

    Pawloski, G.A.

    1984-08-10

    An external standard intensity ratio method is used for quantitatively determining mineralogic compositions of samples by x-ray diffraction. The method uses ratios of x-ray intensity peaks from a single run. Constants are previously determined for each mineral which is to be quantitatively measured. Ratios of the highest intensity peak of each mineral to be quantified in the sample and the highest intensity peak of a reference mineral contained in the sample are used to calculate sample composition.

  4. Early age hydration and pozzolanic reaction in natural zeolite blended cements: Reaction kinetics and products by in situ synchrotron X-ray powder diffraction

    SciTech Connect

    Snellings, R.; Mertens, G.; Cizer, O.; Elsen, J.

    2010-12-15

    The in situ early-age hydration and pozzolanic reaction in cements blended with natural zeolites were investigated by time-resolved synchrotron X-ray powder diffraction with Rietveld quantitative phase analysis. Chabazite and Na-, K-, and Ca-exchanged clinoptilolite materials were mixed with Portland cement in a 3:7 weight ratio and hydrated in situ at 40 {sup o}C. The evolution of phase contents showed that the addition of natural zeolites accelerates the onset of C{sub 3}S hydration and precipitation of CH and AFt. Kinetic analysis of the consumption of C{sub 3}S indicates that the enveloping C-S-H layer is thinner and/or less dense in the presence of alkali-exchanged clinoptilolite pozzolans. The zeolite pozzolanic activity is interpreted to depend on the zeolite exchangeable cation content and on the crystallinity. The addition of natural zeolites alters the structural evolution of the C-S-H product. Longer silicate chains and a lower C/S ratio are deduced from the evolution of the C-S-H b-cell parameter.

  5. Thermal analysis, X-ray powder diffraction and electron microscopy data related with the production of 1:1 Caffeine:Glutaric Acid cocrystals.

    PubMed

    Duarte, Íris; Andrade, Rita; Pinto, João F; Temtem, Márcio

    2016-09-01

    The data presented in this article are related to the production of 1:1 Caffeine:Glutaric Acid cocrystals as part of the research article entitled "Green production of cocrystals using a new solvent-free approach by spray congealing" (Duarte et al., 2016) [1]. More specifically, here we present the thermal analysis and the X-ray powder diffraction data for pure Glutaric Acid, used as a raw material in [1]. We also include the X-ray powder diffraction and electron microscopy data obtained for the 1:1 Caffeine:Glutaric Acid cocrystal (form II) produced using the cooling crystallization method reported in "Operating Regions in Cooling Cocrystallization of Caffeine and Glutaric Acid in Acetonitrile" (Yu et al., 2010) [2]. Lastly, we show the X-ray powder diffraction data obtained for assessing the purity of the 1:1 Caffeine:Glutaric cocrystals produced in [1]. PMID:27331096

  6. Abinitio powder x-ray diffraction and PIXEL energy calculations on thiophene derived 1,4 dihydropyridine

    NASA Astrophysics Data System (ADS)

    Karthikeyan, N.; Pachamuthu, M. P.; Sivakumar, K.

    2016-05-01

    We focus on the application of powder diffraction data to get abinitio crystal structure determination of thiophene derived 1,4 DHP prepared by cyclocondensation method using solid catalyst. Crystal structure of the compound has been solved by direct-space approach on Monte Carlo search in parallel tempering mode using FOX program. Initial atomic coordinates were derived using Gaussian 09W quantum chemistry software in semi-empirical approach and Rietveld refinement was carried out using GSAS program. The crystal structure of the compound is stabilized by one N-H…O and three C-H…O hydrogen bonds. PIXEL lattice energy calculation was carried out to understand the physical nature of intermolecular interactions in the crystal packing, on which the total lattice energy is contributed into Columbic, polarization, dispersion, and repulsion energies.

  7. Observation of localized heating phenomena during microwave heating of mixed powders using in situ x-ray diffraction technique

    SciTech Connect

    Sabelström, N. Hayashi, M.; Watanabe, T.; Nagata, K.

    2014-10-28

    In materials processing research using microwave heating, there have been several observations of various phenomena occurring known as microwave effects. One significant example of such a phenomenon is increased reaction kinetics. It is believed that there is a possibility that this might be caused by localized heating, were some reactants would attain a higher than apparent temperature. To examine whether such thermal gradients are indeed possible, mixed powders of two microwave non-absorbers, alumina and magnesia, were mixed with graphite, a known absorber, and heated in a microwave furnace. During microwave irradiation, the local temperatures of the respective sample constituents were measured using an in situ x-ray diffraction technique. In the case of the alumina and graphite sample, a temperature difference of around 100 °C could be observed.

  8. Crystal structure and electronic properties of two nimesulide derivatives: A combined X-ray powder diffraction and quantum mechanical study

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Abir; Ghosh, Soumen; Kankanala, Kavitha; Reddy, Vangala Ranga; Mukkanti, Khagga; Pal, Sarbani; Mukherjee, Alok K.

    2010-06-01

    Crystal structures of two nimesulide derivatives, C 13H 14O 3N 2S ( 2) and C 21H 16O 5N 2S ( 3), have been determined from X-ray powder diffraction data and their electronic structures were calculated at the DFT level. The optimized molecular geometries of 2 and 3 correspond closely to that obtained from the crystallographic analysis. Intermolecular hydrogen bonds and π… π stacking interactions form supramolecular assembly in both compounds. The HOMO-LUMO energy gap (>2.2 eV) indicates a high kinetic stability of both compounds. Although the compound 2 does not exhibit any anti-inflammatory activity, 3 can induce 34% edema inhibition in rat paws.

  9. Neutron Powder Diffraction and Molecular Simulation Study of the Structural Evolution of Ammonia Borane from 15 to 340 K

    SciTech Connect

    Hess, Nancy J.; Schenter, Gregory K.; Hartman, Michael R.; Daemen, Luke L.; Proffen, Thomas E.; Kathmann, Shawn M.; Mundy, Christopher J.; Hartl, Monika A.; Heldebrant, David J.; Stowe, Ashley C.; Autrey, Thomas

    2009-04-17

    The structural behavior of perdeuterated, 11B-enriched ammonia borane, ND311BD3, was investigated by neutron powder diffraction measurements collected over the temperature range from 15 to 340 K and by molecular dynamics simulation. In the low temperature orthorhombic phase, the progressive displacement of the borane group under the amine group was observed leading to the rotation of the B-N bond parallel to the c-axis. The structural phase transition at 225 K is marked by dramatic change in the dynamics of both the amine and borane group that is problematic to extract from the metrics provided by Rietveld analysis of the NPD data alone but is evident in the molecular dynamics simulation and other spectroscopic evidence. This study highlights the valued added by complimentary experimental approaches and coupled computational studies.

  10. Determining fine-structure parameters for tungsten powder and filings by harmonic analysis of x-ray diffraction lines

    SciTech Connect

    Kravchik, A.E.; Moshkina, T.I.; Osmakov, A.S.

    1986-12-01

    Evidence has been accumulating on determining fine-structure parameters by line shape harmonic analysis (LSHA) although many aspects remain unresolved. In this paper, the authors discuss the interpretations afresh, on-going improvements in x-ray techniques, in recording methods, and in processing the data, as well as in programs for determining the parameters by LSHA. The authors selected tungsten because of its bcc lattice, whose diffraction peaks are widely separated, which almost completely rules out their overlapping even if there is considerable broadening, such as is produced by large plastic strain. The material was produced in two ways: by firing a tungsten single crystal and by grinding VChDK tungsten powder in a laboratory vibration mill for 10, 20, 30, 50, and 100 h.

  11. Investigation of surface structures by powder diffraction : a differential pair distribution function study on arsenate sorption on ferrihydrite.

    SciTech Connect

    Harrington, R.; Hausner, D. B.; Bhandari, N.; Strongin, D. R.; Chapman, K. W.; Chupas, P. J.; Middlemiss, D. S.; Grey, C. P.; Parise, J. B.; X-Ray Science Division; Stony Brook Univ.; Temple Univ.

    2010-01-01

    Differential pair distribution function (d-PDF) analysis of high energy powder X-ray diffraction data was carried out on 2-line ferrihydrite nanoparticles with arsenate oxyanions adsorbed on the surface to investigate the binding mechanism. In this analysis, a PDF of ferrihydrite is subtracted from a PDF of ferrihydrite with arsenate sorbed on the surface, leaving only correlations from within the surface layer and between the surface and the particle. As-O and As-Fe correlations were observed at 1.68 and 3.29 {angstrom}, respectively, in good agreement with previously published EXAFS data, confirming a bidentate binuclear binding mechanism. Further peaks are observed in the d-PDF which are not present in EXAFS, corresponding to correlations between As and O in the particle and As-2nd Fe.

  12. High-temperature dehydration of talc: a kinetics study using in situ X-ray powder diffraction

    NASA Astrophysics Data System (ADS)

    Wang, Duojun; Yi, Li; Huang, Bojin; Liu, Chuanjiang

    2015-06-01

    High-temperature in situ X-ray powder diffraction patterns were used to study the dehydration kinetics of natural talc with a size of 10-15 µm. The talc was annealed from 1073 to 1223 K, and the variations in the characteristic peaks corresponding to talc with the time were recorded to determine the reaction progress. The decomposition of talc occurred, and peaks corresponding to talc and peaks corresponding to enstatite and quartz were observed. The enstatite and talc exhibited a topotactic relationship. The dehydration kinetics of talc was studied as a function of temperature between 1073 and 1223 K. The kinetics data could be modeled using an Avrami equation that considers nucleation and growth processes ? where n varies from 0.4 to 0.8. The rate constant (k) equation for the natural talc is ? The reaction mechanism for the dehydration of talc is a heterogeneous nucleation and growth mechanism.

  13. High-temperature powder synchrotron diffraction studies of synthetic cryolite Na 3AlF 6

    NASA Astrophysics Data System (ADS)

    Zhou, Qingdi; Kennedy, Brendan J.

    2004-03-01

    A high-resolution synchrotron diffraction study of the structures of a synthetic sample of cryolite Na 3AlF 6 from room temperature to 800°C is reported. At room temperature Na 3AlF 6 is monoclinic and the structure is described in space group P2 1/n. Heating the sample to 560°C results in only minor changes to the structure. A first-order transition from this monoclinic structure to a high-temperature cubic structure is observed near 567°C. The cubic Fm 3¯m structure is characterized by disorder of the fluoride atoms.

  14. X-ray powder diffraction study of poly/carbon monofluoride/, CF/1.12/

    NASA Technical Reports Server (NTRS)

    Mahajan, V. K.; Badachhape, R. B.; Margrave, J. L.

    1974-01-01

    Data from X-ray diffraction studies of the poly(carbon monofluoride) with empirical formula CF(1.09-1.15) are reported, and possible intercalation arrangements for the substance are discussed. The data do not conform to true hexagonal symmetry, indicating that the carbon atoms are not coplanar. Each bond angle of carbon is 118.8 deg, and the carbon-carbon distance is 1.47 A. The interlayer distance is 5.76 A. A total absence of (hkl) reflections in the X-ray pattern shows that the separate CF layers are not regularly arranged with respect to one another.

  15. Super-Resolved Digital Holography Based on the Coherent Diffraction Imaging Scheme

    NASA Astrophysics Data System (ADS)

    Wang, Bao-Sheng; Pan, Xing-Chen; Wang, Hai-Yan; Cheng, Jun; Gao, Shu-Mei; Liu, Cheng; Zhu, Jian-Qiang

    2013-05-01

    An algorithm is proposed to enhance the resolution of digital holography by retrieving the frequency components lost in common holograms. A pinhole is placed directly behind the specimen to record the hologram, and an iterative scheme commonly used in coherent diffraction imaging is adopted for the reconstruction. Since some of the frequency components lost in common digital holography can be properly retrieved, the resolution of the reconstructed image is remarkably improved. Theoretical analysis and computer simulations are presented to demonstrate the feasibility of this proposed technique.

  16. Field-induced alignment of a smectic-A phase: a time-resolved x-ray diffraction investigation.

    PubMed

    Bras, W; Emsley, J W; Levine, Y K; Luckhurst, G R; Seddon, J M; Timimi, B A

    2004-09-01

    The field-induced alignment of a smectic-A phase is, in principle, a complicated process involving the director rotation via the interaction with the field and the layer rotation via the molecular interactions. Time-resolved nuclear magnetic resonance spectroscopy has revealed this complexity in the case of the director alignment, but provides no direct information on the motion of the layers. Here we describe a time-resolved x-ray diffraction experiment using synchrotron radiation to solve the challenging problem of capturing the diffraction pattern on a time scale which is fast in comparison with that for the alignment of the smectic layers. We have investigated the alignment of the smectic-A phase of 4-octyl-4(')-cyanobiphenyl by a magnetic field. The experiment consists of creating a monodomain sample of the smectic-A phase by slow cooling from the nematic phase in a magnetic field with a flux density of 7 T. The sample is then turned quickly through an angle phi(0) about an axis parallel to the x-ray beam direction but orthogonal to the field. A sequence of two-dimensional small angle x-ray diffraction patterns are then collected at short time intervals. Experiments were carried out for different values of phi(0), and at different temperatures. The results show that the alignment behavior changes fundamentally when phi(0) exceeds 45 degrees, and that there is a sharp change in the alignment process when the temperature is less than 3 degrees C below the smectic-A-nematic transition. The results of the x-ray experiments are in broad agreement with the NMR results, but reveal major phenomena concerning the maintenance of the integrity of the smectic-A layer structure during the alignment process. PMID:15332991

  17. Validation of molecular crystal structures from powder diffraction data with dispersion-corrected density functional theory (DFT-D)

    PubMed Central

    van de Streek, Jacco; Neumann, Marcus A.

    2014-01-01

    In 2010 we energy-minimized 225 high-quality single-crystal (SX) structures with dispersion-corrected density functional theory (DFT-D) to establish a quantitative benchmark. For the current paper, 215 organic crystal structures determined from X-ray powder diffraction (XRPD) data and published in an IUCr journal were energy-minimized with DFT-D and compared to the SX benchmark. The on average slightly less accurate atomic coordinates of XRPD structures do lead to systematically higher root mean square Cartesian displacement (RMSCD) values upon energy minimization than for SX structures, but the RMSCD value is still a good indicator for the detection of structures that deserve a closer look. The upper RMSCD limit for a correct structure must be increased from 0.25 Å for SX structures to 0.35 Å for XRPD structures; the grey area must be extended from 0.30 to 0.40 Å. Based on the energy minimizations, three structures are re-refined to give more precise atomic coordinates. For six structures our calculations provide the missing positions for the H atoms, for five structures they provide corrected positions for some H atoms. Seven crystal structures showed a minor error for a non-H atom. For five structures the energy minimizations suggest a higher space-group symmetry. For the 225 SX structures, the only deviations observed upon energy minimization were three minor H-atom related issues. Preferred orientation is the most important cause of problems. A preferred-orientation correction is the only correction where the experimental data are modified to fit the model. We conclude that molecular crystal structures determined from powder diffraction data that are published in IUCr journals are of high quality, with less than 4% containing an error in a non-H atom. PMID:25449625

  18. Synchrotron powder diffraction simplified: The high-resolution diffractometer at 11-BM at the Advanced Photon Source

    NASA Astrophysics Data System (ADS)

    Ribaud, Lynn; Suchomel, Matthew; von Dreele, Robert; Toby, Brian

    2013-03-01

    Synchrotrons have revolutionized powder diffraction through higher resolution and sensitivity and much faster data collection. Few scientists beyond the synchrotron community make use of these capabilities. To help address this, the high resolution powder diffractometer beamline 11-BM at the APS offers rapid and easy mail-in access with world-class quality data 1. This instrument offers the highest resolution available in the Americas and is a free service for non-proprietary users 2. The instrument can collect a superb pattern in an hour, has an automated sample changer, and features variable temperature sample environments. Users of the mail-in program often receive their data within two weeks of sample receipt. The instrument is also available for on-site experiments requiring other conditions. Our poster will describe this instrument, highlight its capabilities, explain the types of measurements available, and discuss plans to improve access and available sample environments and collection protocols. More information about the 11-BM instrument and our mail-in program can be found at: http://11bm.xray.aps.anl.gov.

  19. A neutron powder diffraction study of ND 3 intercalated titanium disulfide, 3 R-TiS 2ND 3

    NASA Astrophysics Data System (ADS)

    Bouwmeester, H. J. M.; Wiegers, G. A.

    1988-10-01

    Neutron powder diffraction of rhombohedral 3 R-TiS 2ND 3 ( a = 3.419 Å, c = 27.03 Å at 300 K, space group R overline3m ) has shown that ND 3 molecules and ND +4 ions, present in a ratio of about 5 to 1 from chemical and physical evidence, occupy statistically the trigonal-prismatic holes between TiS 2 sandwiches. One cannot distinguish between ND 3 and ND +4. Powder intensities calculated for a model with spherically symmetric ND 3 molecules (corresponding to isotropically rotating ND 3 and ND +4) in the trigonal-prismatic holes were in reasonable agreement with the observed intensities. Attempts to obtain information on the precise orientation of ND 3 and ND +4 in the TiS 2 lattice using refinements with structure factors were not successful; the reliability R factor was 0.093 for spherical symmetric ND 3 molecules with nitrogen in the center of the trigonal-prismatic holes.

  20. Electronic structure of cesium butyratouranylate(VI) as derived from DFT-assisted powder X-ray diffraction data.

    PubMed

    Vologzhanina, Anna V; Savchenkov, Anton V; Dmitrienko, Artem O; Korlyukov, Alexander A; Bushmarinov, Ivan S; Pushkin, Denis V; Serezhkina, Larisa B

    2014-10-16

    Investigation of chemical bonding and electronic structure of coordination polymers that do not form high-quality single crystals requires special techniques. Here, we report the molecular and electronic structure of the first cesium butyratouranylate, Cs[UO(2)(n-C(3)H(7)COO)(3)][UO(2)(n-C(3)H(7)COO)(OH)(H2O)], as obtained from DFT-assisted powder X-ray diffraction data because of the low quality of crystalline sample. The topological analysis of the charge distribution within the quantum theory of atoms-in-molecules (QTAIM) space partitioning and the distribution of electron localization function (ELF) is reported. The constancy of atomic domain of the uranium(VI) atom at different coordination numbers (7 and 8) and the presence of three ELF maxima in equatorial plane of an uranyl cation attributed to the 6s and 6p electrons were demonstrated for the first time. Details of methodologies applied for additional verification of the correctness of powder XRD refinement (Voronoi atomic descriptors and the Morse restraints) are discussed. PMID:25289686

  1. Data collection strategies for time-resolved X-ray free-electron laser diffraction, and 2-color methods.

    PubMed

    Li, Chufeng; Schmidt, Kevin; Spence, John C

    2015-07-01

    We compare three schemes for time-resolved X-ray diffraction from protein nanocrystals using an X-ray free-electron laser. We find expressions for the errors in structure factor measurement using the Monte Carlo pump-probe method of data analysis with a liquid jet, the fixed sample pump-probe (goniometer) method (both diffract-and-destroy, and below the safe damage dose), and a proposed two-color method. Here, an optical pump pulse arrives between X-ray pulses of slightly different energies which hit the same nanocrystal, using a weak first X-ray pulse which does not damage the sample. (Radiation damage is outrun in the other cases.) This two-color method, in which separated Bragg spots are impressed on the same detector readout, eliminates stochastic fluctuations in crystal size, shape, and orientation and is found to require two orders of magnitude fewer diffraction patterns than the currently used Monte Carlo liquid jet method, for 1% accuracy. Expressions are given for errors in structure factor measurement for the four approaches, and detailed simulations provided for cathepsin B and IC3 crystals. While the error is independent of the number of shots for the dose-limited goniometer method, it falls off inversely as the square root of the number of shots for the two-color and Monte Carlo methods, with a much smaller pre-factor for the two-color mode, when the first shot is below the damage threshold. PMID:26798813

  2. A powder X-ray diffraction method for detection of polyprenylated benzophenones in plant extracts associated with HPLC for quantitative analysis.

    PubMed

    Martins, Felipe T; dos Santos, Marcelo H; Coelho, Carla P; Barbosa, Luiz C A; Dias, Gizelly C; Fracca, Mônica P; Neves, Person P; Stringheta, Paulo C; Doriguetto, Antônio C

    2011-02-20

    A robust, direct, rapid and non-destructive X-ray diffraction crystallography method to detect the polyprenylated benzophenones 7-epi-clusianone (1) and guttiferone A (2) in extracts from Garcinia brasiliensis is presented. Powder samples of benzophenones 1 and 2, dried hexane extracts from G. brasiliensis seeds and fruit's pericarp, and the dried ethanolic extract from G. brasiliensis seeds were unambiguously characterized by powder X-ray diffractometry. The calculated X-ray diffraction peaks from crystal structures of analytes 1 and 2, previously determined by single-crystal X-ray diffraction technique, were overlaid to those of the experimental powder diffractograms, providing a practical identification of these compounds in the analyzed material and confirming the pure contents of the powder samples. Using the X-ray diffraction crystallography method, the studied polyprenylated benzophenones were selectively and simultaneously detected in the extracts which were mounted directly on sample holder. In addition, reference materials of the analytes were not required for analyses since the crystal structures of the compounds are known. High performance liquid chromatography analyses also were comparatively carried out to quantify the analytes in the same plant extracts showing to be in agreement with X-ray diffraction crystallography method. PMID:20943341

  3. Complementing high-throughput X-ray powder diffraction data with quantum-chemical calculations: Application to piroxicam form III.

    PubMed

    Naelapää, Kaisa; van de Streek, Jacco; Rantanen, Jukka; Bond, Andrew D

    2012-11-01

    High-throughput crystallisation and characterisation platforms provide an efficient means to carry out solid-form screening during the pre-formulation phase. To determine the crystal structures of identified new solid phases, however, usually requires independent crystallisation trials to produce single crystals or bulk samples of sufficient quantity to carry out high-quality X-ray diffraction measurements. This process could be made more efficient by a robust procedure for crystal structure determination directly from high-throughput X-ray powder diffraction (XRPD) data. Quantum-chemical calculations based on dispersion-corrected density functional theory (DFT-D) have now become feasible for typical small organic molecules used as active pharmaceutical ingredients. We demonstrate how these calculations can be applied to complement high-throughput XRPD data by determining the crystal structure of piroxicam form III. These combined experimental/quantum-chemical methods can provide access to reliable structural information in the course of an intensive experimentally based solid-form screening activity or in other circumstances wherein single crystals might never be viable, for example, for polymorphs obtained only during high-energy processing such as spray drying or milling. PMID:22886472

  4. Calculations of single crystal elastic constants for yttria partially stabilised zirconia from powder diffraction data

    NASA Astrophysics Data System (ADS)

    Lunt, A. J. G.; Xie, M. Y.; Baimpas, N.; Zhang, S. Y.; Kabra, S.; Kelleher, J.; Neo, T. K.; Korsunsky, A. M.

    2014-08-01

    Yttria Stabilised Zirconia (YSZ) is a tough, phase-transforming ceramic that finds use in a wide range of commercial applications from dental prostheses to thermal barrier coatings. Micromechanical modelling of phase transformation can deliver reliable predictions in terms of the influence of temperature and stress. However, models must rely on the accurate knowledge of single crystal elastic stiffness constants. Some techniques for elastic stiffness determination are well-established. The most popular of these involve exploiting frequency shifts and phase velocities of acoustic waves. However, the application of these techniques to YSZ can be problematic due to the micro-twinning observed in larger crystals. Here, we propose an alternative approach based on selective elastic strain sampling (e.g., by diffraction) of grain ensembles sharing certain orientation, and the prediction of the same quantities by polycrystalline modelling, for example, the Reuss or Voigt average. The inverse problem arises consisting of adjusting the single crystal stiffness matrix to match the polycrystal predictions to observations. In the present model-matching study, we sought to determine the single crystal stiffness matrix of tetragonal YSZ using the results of time-of-flight neutron diffraction obtained from an in situ compression experiment and Finite Element modelling of the deformation of polycrystalline tetragonal YSZ. The best match between the model predictions and observations was obtained for the optimized stiffness values of C11 = 451, C33 = 302, C44 = 39, C66 = 82, C12 = 240, and C13 = 50 (units: GPa). Considering the significant amount of scatter in the published literature data, our result appears reasonably consistent.

  5. Calculations of single crystal elastic constants for yttria partially stabilised zirconia from powder diffraction data

    SciTech Connect

    Lunt, A. J. G. Xie, M. Y.; Baimpas, N.; Korsunsky, A. M.; Zhang, S. Y.; Kabra, S.; Kelleher, J.; Neo, T. K.

    2014-08-07

    Yttria Stabilised Zirconia (YSZ) is a tough, phase-transforming ceramic that finds use in a wide range of commercial applications from dental prostheses to thermal barrier coatings. Micromechanical modelling of phase transformation can deliver reliable predictions in terms of the influence of temperature and stress. However, models must rely on the accurate knowledge of single crystal elastic stiffness constants. Some techniques for elastic stiffness determination are well-established. The most popular of these involve exploiting frequency shifts and phase velocities of acoustic waves. However, the application of these techniques to YSZ can be problematic due to the micro-twinning observed in larger crystals. Here, we propose an alternative approach based on selective elastic strain sampling (e.g., by diffraction) of grain ensembles sharing certain orientation, and the prediction of the same quantities by polycrystalline modelling, for example, the Reuss or Voigt average. The inverse problem arises consisting of adjusting the single crystal stiffness matrix to match the polycrystal predictions to observations. In the present model-matching study, we sought to determine the single crystal stiffness matrix of tetragonal YSZ using the results of time-of-flight neutron diffraction obtained from an in situ compression experiment and Finite Element modelling of the deformation of polycrystalline tetragonal YSZ. The best match between the model predictions and observations was obtained for the optimized stiffness values of C11 = 451, C33 = 302, C44 = 39, C66 = 82, C12 = 240, and C13 = 50 (units: GPa). Considering the significant amount of scatter in the published literature data, our result appears reasonably consistent.

  6. Multivariate calibration of the degree of crystallinity in intact pellets by X-ray powder diffraction.

    PubMed

    Nikowitz, Krisztina; Domján, Attila; Pintye-Hódi, Klára; Regdon, Géza

    2016-04-11

    XRPD is the method of choice to determine crystalline content in an amorphous environment. While several studies describe its use on powders, little information is available on its performance on finished products. The method's use may be limited not only by the need of sample pretreatment and its validation but also by the propensity of some materials to recrystallize when exposed to heat or mechanical stress. In this work the authors describe an attempt at constructing a model based on the XRPD measurement of intact layered pellets using univariate methods based on peak heights and PLS regression. Results indicate that neither the goodness-of-fit (below 0.9 for all tested variables), nor the RMSEC values (above 5 for all tested variables) of any model based on peak height were good enough to consider them for everyday use. PLS regression however provided a model with improved characteristics (R(2)=0.9581, RMSEC=3.04) despite the low API content and individual loading characteristics also reflected the validity of the model. PLS analysis also indicated that a specific sample may be different in some formulation characteristic that did not register on other examinations. This further indicates the method's usefulness in the analysis of intact dosage forms. PMID:26899205

  7. Analysis of heat-affected zone phase transformations using in situ spatially resolved x-ray diffraction with synchrotron radiation

    SciTech Connect

    Elmer, J.W.; Wong, J.; Froeba, M.; Waide, P.A.; Larson, E.M.

    1996-03-01

    Spatially resolved X-ray diffraction (SRXRD) consists of producing a submillimeter size X-ray beam from an intense synchrotron radiation source to perform real-time diffraction measurements on solid materials. This technique was used int his study to investigate the crystal phases surrounding a liquid weld pool in commercial purity titanium and to determine the location of the phase boundary separating the high-temperature body-centered-cubic (bcc) {beta} phase from the low-temperature hexagonal-close-packed (hcp) {alpha} phase. The experiments were carried out at the Stanford Synchrotron Radiation Laboratory (SSRL) using a 0.25 x 0.50 mm X-ray probe that could be positioned with 10-{micro}m precision on the surface of a quasistationary gas tungsten arc weld (GTAW). The SRXRD results showed characteristic hcp, bcc, and liquid diffraction patterns at various points along the sample, starting from the base metal through the heat-affected zone (HAZ) and into the weld pool, respectively. Analyses of the SRXRD data show the coexistence of bcc and hcp phases in the partially transformed (outer) region of the HAZ and single-phase bcc in the fully transformed (inner) region of the HAZ. Postweld metallographic examinations of the HAZ, combined with a conduction-based thermal model of the weld, were correlated with the SRXRD results. Finally, analysis of the diffraction intensities of the hcp and bcc phases was performed on the SRXRD data to provide additional information about the microstructural conditions that may exist in the HAZ at temperature during welding. This work represents the first direct in situ mapping of phase boundaries in fusion welds.

  8. Sparsity-based super-resolved coherent diffraction imaging of one-dimensional objects

    NASA Astrophysics Data System (ADS)

    Sidorenko, Pavel; Kfir, Ofer; Shechtman, Yoav; Fleischer, Avner; Eldar, Yonina C.; Segev, Mordechai; Cohen, Oren

    2015-09-01

    Phase-retrieval problems of one-dimensional (1D) signals are known to suffer from ambiguity that hampers their recovery from measurements of their Fourier magnitude, even when their support (a region that confines the signal) is known. Here we demonstrate sparsity-based coherent diffraction imaging of 1D objects using extreme-ultraviolet radiation produced from high harmonic generation. Using sparsity as prior information removes the ambiguity in many cases and enhances the resolution beyond the physical limit of the microscope. Our approach may be used in a variety of problems, such as diagnostics of defects in microelectronic chips. Importantly, this is the first demonstration of sparsity-based 1D phase retrieval from actual experiments, hence it paves the way for greatly improving the performance of Fourier-based measurement systems where 1D signals are inherent, such as diagnostics of ultrashort laser pulses, deciphering the complex time-dependent response functions (for example, time-dependent permittivity and permeability) from spectral measurements and vice versa.

  9. Sparsity-based super-resolved coherent diffraction imaging of one-dimensional objects

    PubMed Central

    Sidorenko, Pavel; Kfir, Ofer; Shechtman, Yoav; Fleischer, Avner; Eldar, Yonina C.; Segev, Mordechai; Cohen, Oren

    2015-01-01

    Phase-retrieval problems of one-dimensional (1D) signals are known to suffer from ambiguity that hampers their recovery from measurements of their Fourier magnitude, even when their support (a region that confines the signal) is known. Here we demonstrate sparsity-based coherent diffraction imaging of 1D objects using extreme-ultraviolet radiation produced from high harmonic generation. Using sparsity as prior information removes the ambiguity in many cases and enhances the resolution beyond the physical limit of the microscope. Our approach may be used in a variety of problems, such as diagnostics of defects in microelectronic chips. Importantly, this is the first demonstration of sparsity-based 1D phase retrieval from actual experiments, hence it paves the way for greatly improving the performance of Fourier-based measurement systems where 1D signals are inherent, such as diagnostics of ultrashort laser pulses, deciphering the complex time-dependent response functions (for example, time-dependent permittivity and permeability) from spectral measurements and vice versa. PMID:26345495

  10. Time-resolved X-ray diffraction studies of laser-induced acoustic wave propagation in bilayer metallic thin crystals

    SciTech Connect

    Er, Ali Oguz; Tang, Jau E-mail: prentzepis@ece.tamu.edu; Chen, Jie; Rentzepis, Peter M. E-mail: prentzepis@ece.tamu.edu

    2014-09-07

    Phonon propagation across the interface of a Cu/Ag(111) bilayer and transient lattice disorder, induced by a femtosecond 267 nm pulse, in Ag(111) crystal have been measured by means of time resolved X-ray diffraction. A “blast” force due to thermal stress induced by suddenly heated electrons is formed within two picoseconds after excitation and its “blast wave” propagation through the interface and Ag (111) crystal was monitored by the shift and broadening of the rocking curve, I vs. ω, as a function of time after excitation. Lattice disorder, contraction and expansion as well as thermal strain formation and wave propagation have also been measured. The experimental data and mechanism proposed are supported by theoretical simulations.

  11. Time-resolved x-ray diffraction and electrical resistance measurements of structural phase transitions in zirconium

    DOE PAGESBeta

    Velisavljevic, N.; Sinogeikin, S.; Saavedra, R.; Chellappa, R. S.; Rothkirch, A.; Dattelbaum, D. M.; Konopkova, Z.; Liermann, H. -P.; Bishop, M.; Tsoi, G. M.; et al

    2014-05-07

    Here, we have designed a portable pressure controller module to tune compression rates and maximum pressures attainable in a standard gas-membrane diamond anvil cell (DAC). During preliminary experiments, performed on zirconium (Zr) metal sample, pressure jumps of up to 80 GPa were systematically obtained in less than 0.2s (resulting in compression rate of few GPa/s up to more than 400 GPa/s). In-situ x-ray diffraction and electrical resistance measurements were performed simultaneously during this rapid pressure increase to provide the first time resolved data on α → ω → β structural evolution in Zr at high pressures. Direct control of compressionmore » rates and peak pressures, which can be held for prolonged time, allows for investigation of structural evolution and kinetics of structural phase transitions of materials under previously unexplored compression rate-pressure conditions that bridge traditional static and shock/dynamic experimental platforms.« less

  12. Generation and Propagation of a Picosecond Acoustic Pulse at a Buried Interface: Time-Resolved X-Ray Diffraction Measurements

    SciTech Connect

    Lee, S.H.; Cavalieri, A.L.; Fritz, D.M.; Swan, M.C.; Reis, D.A.; Hegde, R.S.; Reason, M.; Goldman, R.S.

    2005-12-09

    We report on the propagation of coherent acoustic wave packets in (001) surface oriented Al{sub 0.3}Ga{sub 0.7}As/GaAs heterostructure, generated through localized femtosecond photoexcitation of the GaAs. Transient structural changes in both the substrate and film are measured with picosecond time-resolved x-ray diffraction. The data indicate an elastic response consisting of unipolar compression pulses of a few hundred picosecond duration traveling along [001] and [001] directions that are produced by predominately impulsive stress. The transmission and reflection of the strain pulses are in agreement with an acoustic mismatch model of the heterostructure and free-space interfaces.

  13. Time-resolved x-ray diffraction and electrical resistance measurements of structural phase transitions in zirconium

    SciTech Connect

    Velisavljevic, N.; Sinogeikin, S.; Saavedra, R.; Chellappa, R. S.; Rothkirch, A.; Dattelbaum, D. M.; Konopkova, Z.; Liermann, H. -P.; Bishop, M.; Tsoi, G. M.; Vohra, Y. K.

    2014-05-07

    Here, we have designed a portable pressure controller module to tune compression rates and maximum pressures attainable in a standard gas-membrane diamond anvil cell (DAC). During preliminary experiments, performed on zirconium (Zr) metal sample, pressure jumps of up to 80 GPa were systematically obtained in less than 0.2s (resulting in compression rate of few GPa/s up to more than 400 GPa/s). In-situ x-ray diffraction and electrical resistance measurements were performed simultaneously during this rapid pressure increase to provide the first time resolved data on α → ω → β structural evolution in Zr at high pressures. Direct control of compression rates and peak pressures, which can be held for prolonged time, allows for investigation of structural evolution and kinetics of structural phase transitions of materials under previously unexplored compression rate-pressure conditions that bridge traditional static and shock/dynamic experimental platforms.

  14. Time-resolved x-ray diffraction study of photoinduced strains in h -LuFeO3 thin film

    NASA Astrophysics Data System (ADS)

    Sinha, Kishan; Jiang, Xuanyuan; Wang, Xiao; Dichiara, Anthony; Cheng, Xuemei; Li, Yuelin; Xu, Xiaoshan

    2015-03-01

    We have studied the structural response of epitaxially stabilized h-LuFeO3 (0001) thin film to above-band-gap optical excitation (pump) using time-resolved x-ray diffraction (probe) at picosecond time scale. The shift in (004) Bragg peak induced by a 390 nm excitation (30 ps duration) has been studied as a function of pump fluence and pump-probe time delay. The out-of-plane photoinduced lattice strain (Δc / c) exhibits a non-linear relation with fluence. The relaxation time is on the order of 1 ns. These observations suggest a relaxation mechanism that may be mediated by combined effects of charge recombination and phonon relaxation. This work at is supported by Nebraska EPESCoR (UNL), by NSF CAREER award (No. 1053854) (Bryn Mawr College), and by US-DOE, Office of Science, BES (No. DE-AC02-06CH11357) (ANL).

  15. Crystal engineering on industrial diaryl pigments using lattice energy minimizations and X-ray powder diffraction.

    PubMed

    Schmidt, Martin U; Dinnebier, Robert E; Kalkhof, Holger

    2007-08-23

    Diaryl azo pigments play an important role as yellow pigments for printing inks, with an annual pigment production of more than 50,000 t. The crystal structures of Pigment Yellow 12 (PY12), Pigment Yellow 13 (PY13), Pigment Yellow 14 (PY14), and Pigment Yellow 83 (PY83) were determined from X-ray powder data using lattice energy minimizations and subsequent Rietveld refinements. Details of the lattice energy minimization procedure and of the development of a torsion potential for the biphenyl fragment are given. The Rietveld refinements were carried out using rigid bodies, or constraints. It was also possible to refine all atomic positions individually without any constraint or restraint, even for PY12 having 44 independent non-hydrogen atoms per asymmetric unit. For PY14 (23 independent non-hydrogen atoms), additionally all atomic isotropic temperature factors could be refined individually. PY12 crystallized in a herringbone arrangement with twisted biaryl fragments. PY13 and PY14 formed a layer structure of planar molecules. PY83 showed a herringbone structure with planar molecules. According to quantum mechanical calculations, the twisting of the biaryl fragment results in a lower color strength of the pigments, whereas changes in the substitution pattern have almost no influence on the color strength of a single molecule. Hence, the experimentally observed lower color strength of PY12 in comparison with that of PY13 and PY83 can be explained as a pure packing effect. Further lattice energy calculations explained that the four investigated pigments crystallize in three different structures because these structures are the energetically most favorable ones for each compound. For example, for PY13, PY14, or PY83, a PY12-analogous crystal structure would lead to considerably poorer lattice energies and lower densities. In contrast, lattice energy calculations revealed that PY12 could adopt a PY13-type structure with only slightly poorer energy. This structure was

  16. Crystal Engineering on Industrial Diaryl Pigments Using Lattice Energy Minimizations and X-ray Powder Diffraction

    SciTech Connect

    Schmidt,M.; Dinnebier, R.; Kalkhof, H.

    2007-01-01

    Diaryl azo pigments play an important role as yellow pigments for printing inks, with an annual pigment production of more than 50,000 t. The crystal structures of Pigment Yellow 12 (PY12), Pigment Yellow 13 (PY13), Pigment Yellow 14 (PY14), and Pigment Yellow 83 (PY83) were determined from X-ray powder data using lattice energy minimizations and subsequent Rietveld refinements. Details of the lattice energy minimization procedure and of the development of a torsion potential for the biphenyl fragment are given. The Rietveld refinements were carried out using rigid bodies, or constraints. It was also possible to refine all atomic positions individually without any constraint or restraint, even for PY12 having 44 independent non-hydrogen atoms per asymmetric unit. For PY14 (23 independent non-hydrogen atoms), additionally all atomic isotropic temperature factors could be refined individually. PY12 crystallized in a herringbone arrangement with twisted biaryl fragments. PY13 and PY14 formed a layer structure of planar molecules. PY83 showed a herringbone structure with planar molecules. According to quantum mechanical calculations, the twisting of the biaryl fragment results in a lower color strength of the pigments, whereas changes in the substitution pattern have almost no influence on the color strength of a single molecule. Hence, the experimentally observed lower color strength of PY12 in comparison with that of PY13 and PY83 can be explained as a pure packing effect. Further lattice energy calculations explained that the four investigated pigments crystallize in three different structures because these structures are the energetically most favorable ones for each compound. For example, for PY13, PY14, or PY83, a PY12-analogous crystal structure would lead to considerably poorer lattice energies and lower densities. In contrast, lattice energy calculations revealed that PY12 could adopt a PY13-type structure with only slightly poorer energy. This structure was

  17. EMCCD-Based Detector for Time-Resolved X-Ray Diffraction and Scattering Studies of Biological Specimens

    SciTech Connect

    Nagarkar, Vivek V.; Singh, Bipin; Guo, Liang; Gore, David; Irving, Thomas C.

    2007-11-26

    Third generation synchrotron sources such as the Advanced Photon Source (APS), Argonne, IL, are outstanding tools for X-ray diffraction and scattering studies of non-crystalline biological materials. However, these studies are hindered by the lack of detectors that provide multiple frames of detailed structural information on the millisecond time scale at the required high spatial resolution, and large active areas. Here we report the development of a cost effective detector for time-resolved small angle X-ray scattering (SAXS) using a cooled, fiberoptically coupled electron multiplying CCD (EMCCD), whose internal gain is selectable in real-time. The performance of the detector was evaluated using a Gd{sub 2}O{sub 2}S:Tb scintillator and was compared to a current state-of-the-art SAXS detector developed at Brandeis University. We also report our first results on the fabrication of a novel, microcolumnar, ZnSe(Te) scintillator that has a promise to provide very high emission efficiency of over 100,000 photons/MeV, high spatial resolution in excess of 10 lp/mm, and a fast decay time with virtually absent afterglow. Development of this scintillator will complement the EMCCD design, permitting the advances of a high spatial and temporal resolution, large area detector for time resolved applications.

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

    PubMed Central

    Deutsch, Maxime; Gillon, Béatrice; Claiser, Nicolas; Gillet, Jean-Michel; Lecomte, Claude; Souhassou, Mohamed

    2014-01-01

    Since the 1980s it has been possible to probe crystallized matter, thanks to X-ray or neutron scattering techniques, to obtain an accurate charge density or spin distribution at the atomic scale. Despite the description of the same physical quantity (electron density) and tremendous development of sources, detectors, data treatment software etc., these different techniques evolved separately with one model per experiment. However, a breakthrough was recently made by the development of a common model in order to combine information coming from all these different experiments. Here we report the first experimental determination of spin-resolved electron density obtained by a combined treatment of X-ray, neutron and polarized neutron diffraction data. These experimental spin up and spin down densities compare very well with density functional theory (DFT) calculations and also confirm a theoretical prediction made in 1985 which claims that majority spin electrons should have a more contracted distribution around the nucleus than minority spin electrons. Topological analysis of the resulting experimental spin-resolved electron density is also briefly discussed. PMID:25075338

  19. Mesoscopic structural phase progression in photo-excited VO2 revealed by time-resolved x-ray diffraction microscopy

    PubMed Central

    Zhu, Yi; Cai, Zhonghou; Chen, Pice; Zhang, Qingteng; Highland, Matthew J.; Jung, Il Woong; Walko, Donald A.; Dufresne, Eric M.; Jeong, Jaewoo; Samant, Mahesh G.; Parkin, Stuart S. P.; Freeland, John W.; Evans, Paul G.; Wen, Haidan

    2016-01-01

    Dynamical phase separation during a solid-solid phase transition poses a challenge for understanding the fundamental processes in correlated materials. Critical information underlying a phase transition, such as localized phase competition, is difficult to reveal by measurements that are spatially averaged over many phase separated regions. The ability to simultaneously track the spatial and temporal evolution of such systems is essential to understanding mesoscopic processes during a phase transition. Using state-of-the-art time-resolved hard x-ray diffraction microscopy, we directly visualize the structural phase progression in a VO2 film upon photoexcitation. Following a homogenous in-plane optical excitation, the phase transformation is initiated at discrete sites and completed by the growth of one lattice structure into the other, instead of a simultaneous isotropic lattice symmetry change. The time-dependent x-ray diffraction spatial maps show that the in-plane phase progression in laser-superheated VO2 is via a displacive lattice transformation as a result of relaxation from an excited monoclinic phase into a rutile phase. The speed of the phase front progression is quantitatively measured, and is faster than the process driven by in-plane thermal diffusion but slower than the sound speed in VO2. The direct visualization of localized structural changes in the time domain opens a new avenue to study mesoscopic processes in driven systems. PMID:26915398

  20. Mesoscopic structural phase progression in photo-excited VO2 revealed by time-resolved x-ray diffraction microscopy

    DOE PAGESBeta

    Zhu, Yi; Cai, Zhonghou; Chen, Pice; Zhang, Qingteng; Highland, Matthew J.; Jung, II Woong; Walko, Donald A.; Dufresne, Eric M.; Jaewoo, Jeong; Samant, Mahesh G.; et al

    2016-02-26

    Dynamical phase separation during a solid-solid phase transition poses a challenge for understanding the fundamental processes in correlated materials. Critical information underlying a phase transition, such as localized phase competition, is difficult to reveal by measurements that are spatially averaged over many phase seperated regions. The ability to simultanousely track the spatial and temporal evolution of such systems is essential to understanding mesoscopic processes during a phase transition. Using state-of- the-art time-resolved hard x-ray diffraction microscopy, we directly visualize the structural phase progression in a VO2 film upon photoexcitation. Following a homogenous in-plane optical excitation, the phase transformation is initiatedmore » at discrete sites and completed by the growth of one lattice structure into the other, instead of a simultaneous isotropic lattice symmetry change. The time-dependent x-ray diffraction spatial maps show that the in-plane phase progression in laser-superheated VO2 is via a displacive lattice transformation as a result of relaxation from an excited monoclinic phase into a rutile phase. The speed of the phase front progression is quantitatively measured, which is faster than the process driven by in-plane thermal diffusion but slower than the sound speed in VO2. Lastly, the direct visualization of localized structural changes in the time domain opens a new avenue to study mesoscopic processes in driven systems.« less

  1. Mesoscopic structural phase progression in photo-excited VO2 revealed by time-resolved x-ray diffraction microscopy

    NASA Astrophysics Data System (ADS)

    Zhu, Yi; Cai, Zhonghou; Chen, Pice; Zhang, Qingteng; Highland, Matthew J.; Jung, Il Woong; Walko, Donald A.; Dufresne, Eric M.; Jeong, Jaewoo; Samant, Mahesh G.; Parkin, Stuart S. P.; Freeland, John W.; Evans, Paul G.; Wen, Haidan

    2016-02-01

    Dynamical phase separation during a solid-solid phase transition poses a challenge for understanding the fundamental processes in correlated materials. Critical information underlying a phase transition, such as localized phase competition, is difficult to reveal by measurements that are spatially averaged over many phase separated regions. The ability to simultaneously track the spatial and temporal evolution of such systems is essential to understanding mesoscopic processes during a phase transition. Using state-of-the-art time-resolved hard x-ray diffraction microscopy, we directly visualize the structural phase progression in a VO2 film upon photoexcitation. Following a homogenous in-plane optical excitation, the phase transformation is initiated at discrete sites and completed by the growth of one lattice structure into the other, instead of a simultaneous isotropic lattice symmetry change. The time-dependent x-ray diffraction spatial maps show that the in-plane phase progression in laser-superheated VO2 is via a displacive lattice transformation as a result of relaxation from an excited monoclinic phase into a rutile phase. The speed of the phase front progression is quantitatively measured, and is faster than the process driven by in-plane thermal diffusion but slower than the sound speed in VO2. The direct visualization of localized structural changes in the time domain opens a new avenue to study mesoscopic processes in driven systems.

  2. Hydrostatic Compression Curve for Triamino-Trinitrobenzene Determined to 13.0 GPa with Powder X-Ray Diffraction

    SciTech Connect

    Stevens, Lewis L.; Velisavljevic, Nenad; Hooks, Daniel E.; Dattelbaum, Dana M.

    2008-08-22

    Using powder X-ray diffraction in conjunction with a diamond anvil cell (DAC), the unit cell volume of triamino-trinitrobenzene (TATB) has been measured from ambient pressure to 13 GPa. The resultant isotherm is compared with previous theoretical (Byrd and Rice and Pastine and Bernecker) and experimental (Olinger and Cady) works. While all reports are consistent to approximately 2 GPa, our measurements reveal a slightly stiffer TATB material than reported by Olinger and Cady and an intermediate compressibility compared with the isotherms predicted by the two theoretical works. Analysis of the room temperature isotherm using the semi-empirical, Murnaghan, Birch-Murnaghan, and Vinet equations of state (EOS) provided a determination of the isothermal bulk modulus (K{sub 0}) and its pressure-derivative (K{sub 0}') for TATB. From these fits to our P-V isotherm, from ambient pressure to 8 GPa, the average results for the zero-pressure bulk modulus and its pressure derivative were found to be 14.7 GPa and 10.1, respectively. For comparison to shock experiments on pressed TATB powder and its plastic-bonded formulation PBX 9502 (95% TATB, 5% Kel-F 800), the isotherm was transformed to the pseudo-velocity U{sub s}-u{sub p} plane using the Rankine-Hugoniot jump conditions. This analysis provides an extrapolated bulk sound speed, c{sub 0}=1.70 km s{sup -1}, for TATB and its agreement with a previous determination (c{sub 0}=1.43 km s{sup -1}) is discussed. Furthermore, our P-V and corresponding U{sub s}-u{sub p} curves reveal a subtle cusp at approximately 8 GPa. This cusp is discussed in relation to similar observations made for the aromatic hydrocarbons anthracene, benzene and toluene, graphite, and trinitrotoluene (TNT).

  3. Microstructure analysis of complex CuO/ZnO@carbon adsorbers: what are the limits of powder diffraction methods?

    PubMed

    Tseng, J C; Schmidt, W; Sager, U; Däuber, E; Pommerin, A; Weidenthaler, C

    2015-05-14

    Activate carbon impregnated with a mixture of copper oxide and zinc oxide performs well as active adsorber for NO2 removal in automotive cabin air filters. The oxide-loaded activated carbon exhibits superior long-term stability in comparison to pure activated carbon as has been shown in previous studies. The carbon material was loaded only with 2.5 wt% of each metal oxide. Characterization of the oxide nanoparticles within the pores of the activated carbon is difficult because of the rather low concentration of the oxides. Therefore, a systematic study was performed to evaluate the limits of line profile analysis of X-ray powder diffraction patterns. The method allows evaluation of crystalline domain size distributions, crystal defect concentrations and twinning probabilities of nanoscopic materials. Here, the analysis is hampered by the presence of several phases including more or less amorphous carbon. By using physical mixtures of defined copper oxide and zinc oxide particles with activated carbon, potential errors and limits could be identified. The contribution of the activated carbon to the scattering curve was modeled with a convolution of an exponential decay curve, a Chebyshev polynomial, and two Lorentzian peaks. With this approach, domain size distributions can be calculated that are shifted only by about 0.5-1.0 nm for very low loadings (≤4 wt%). Oxide loadings of 4 wt% and 5 wt% allow very reliable analyses from diffraction patterns measured in Bragg-Brentano and Debye-Scherrer geometry, respectively. For the real adsorber material, mean domain sizes have been calculated to be 2.8 nm and 2.4 nm before and after the NO2 removal tests. PMID:25892653

  4. Application of Powder Diffraction Methods to the Analysis of the Atomic Structure of Nanocrystals: The Concept of the Apparent Lattice Parameter (ALP)

    NASA Technical Reports Server (NTRS)

    Palosz, B.; Grzanka, E.; Gierlotka, S.; Stelmakh, S.; Pielaszek, R.; Bismayer, U.; Weber, H.-P.; Palosz, W.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    The applicability of standard methods of elaboration of powder diffraction data for determination of the structure of nano-size crystallites is analysed. Based on our theoretical calculations of powder diffraction data we show, that the assumption of the infinite crystal lattice for nanocrystals smaller than 20 nm in size is not justified. Application of conventional tools developed for elaboration of powder diffraction data, like the Rietveld method, may lead to erroneous interpretation of the experimental results. An alternate evaluation of diffraction data of nanoparticles, based on the so-called 'apparent lattice parameter' (alp) is introduced. We assume a model of nanocrystal having a grain core with well-defined crystal structure, surrounded by a surface shell with the atomic structure similar to that of the core but being under a strain (compressive or tensile). The two structural components, the core and the shell, form essentially a composite crystal with interfering, inseparable diffraction properties. Because the structure of such a nanocrystal is not uniform, it defies the basic definitions of an unambiguous crystallographic phase. Consequently, a set of lattice parameters used for characterization of simple crystal phases is insufficient for a proper description of the complex structure of nanocrystals. We developed a method of evaluation of powder diffraction data of nanocrystals, which refers to a core-shell model and is based on the 'apparent lattice parameter' methodology. For a given diffraction pattem, the alp values are calculated for every individual Bragg reflection. For nanocrystals the alp values depend on the diffraction vector Q. By modeling different a0tomic structures of nanocrystals and calculating theoretically corresponding diffraction patterns using the Debye functions we showed, that alp-Q plots show characteristic shapes which can be used for evaluation of the atomic structure of the core-shell system. We show, that using a simple

  5. Phase coexistence in NaTaO3 at room temperature; a high resolution neutron powder diffraction study

    NASA Astrophysics Data System (ADS)

    Knight, Kevin S.; Kennedy, Brendan J.

    2015-05-01

    Room temperature high resolution neutron powder diffraction data, measured in time-of-flight, from two independent samples of NaTaO3 shows the presence of phase coexistence of two orthorhombic structures with space groups Pbnm, and Cmcm. The failure of earlier work to recognise the extent of the hysteresis associated with the high temperature (∼763 K on heating) Cmcm - Pbnm phase transition, that extends down to room temperature, and probably to 0 K, is due to data having been collected at too low a real-space resolution to characterise the diagnostic pseudocubic fundamental and superlattice reflection multiplicities. The phase fraction of the Cmcm phase increases with increasing temperature from 45 weight % at 298 K, to 74 weight % at 758 K. Throughout the whole temperature interval 298 K-758 K, the volume per formula unit of the Cmcm phase exceeds that of the Pbnm phase by an almost constant ∼0.01 Å3 suggesting the addition of pressure would supress the volume fraction of the higher temperature phase. The crystal structure of both phases, determined from data collected at 298 K, are reported, with the atomic displacement parameters of the Cmcm phase being significantly larger than those associated with the Pbnm phase, probably reflecting a high degree of thermal and static disorder.

  6. In situ neutron powder diffraction investigation of the hydration of tricalcium aluminate in the presence of gypsum

    SciTech Connect

    Hartman, M.R. . E-mail: michael.hartman@nist.gov; Berliner, R.

    2005-11-15

    The hydration of a 1:3 molar ratio of tricalcium aluminate, Ca{sub 3}Al{sub 2}O{sub 6}, to gypsum, CaSO{sub 4}.2D{sub 2}O, was investigated at temperatures of 25, 50, and 80 deg. C using time-of-flight powder neutron diffraction combined with multiphase Rietveld structural refinement. It was shown that ettringite, Ca{sub 6}[Al(OD){sub 6}]{sub 2}(SO{sub 4}){sub 3}.{approx}26D{sub 2}O, was the first and only hydration product of the system, in contrast to a prior investigation which suggested the occurrence of a precursor phase prior to the formation of ettringite. Kinetics data showed that the hydration reaction is very sensitive to temperature: hydration at 25 deg. C was characterized by a single kinetic regime while hydration at higher temperatures consisted of two distinct kinetic regimes. The presence of two kinetic regimes was attributed to a change in either the dimensionality of the growth process or a change in the rate controlling mechanism in the hydration reaction.

  7. X-ray Powder Diffraction in Conservation Science: Towards Routine Crystal Structure Determination of Corrosion Products on Heritage Art Objects.

    PubMed

    Dinnebier, Robert E; Fischer, Andrea; Eggert, Gerhard; Runčevski, Tomče; Wahlberg, Nanna

    2016-01-01

    The crystal structure determination and refinement process of corrosion products on historic art objects using laboratory high-resolution X-ray powder diffraction (XRPD) is presented in detail via two case studies. The first material under investigation was sodium copper formate hydroxide oxide hydrate, Cu4Na4O(HCOO)8(OH)2∙4H2O (sample 1) which forms on soda glass/copper alloy composite historic objects (e.g., enamels) in museum collections, exposed to formaldehyde and formic acid emitted from wooden storage cabinets, adhesives, etc. This degradation phenomenon has recently been characterized as "glass induced metal corrosion". For the second case study, thecotrichite, Ca3(CH3COO)3Cl(NO3)2∙6H2O (sample 2), was chosen, which is an efflorescent salt forming needlelike crystallites on tiles and limestone objects which are stored in wooden cabinets and display cases. In this case, the wood acts as source for acetic acid which reacts with soluble chloride and nitrate salts from the artifact or its environment. The knowledge of the geometrical structure helps conservation science to better understand production and decay reactions and to allow for full quantitative analysis in the frequent case of mixtures. PMID:27341300

  8. Using neutron powder diffraction and first-principles calculations to understand the working mechanisms of porous coordination polymer sorbents.

    PubMed

    Chevreau, Hubert; Duyker, Samuel G; Peterson, Vanessa K

    2015-12-01

    Metal-organic frameworks (MOFs) are promising solid sorbents, showing gas selectivity and uptake capacities relevant to many important applications, notably in the energy sector. To improve and tailor the sorption properties of these materials for such applications, it is necessary to gain an understanding of their working mechanisms at the atomic and molecular scale. Specifically, it is important to understand how features such as framework porosity, topology, chemical functionality and flexibility underpin sorbent behaviour and performance. Such information is obtained through interrogation of structure-function relationships, with neutron powder diffraction (NPD) being a particularly powerful characterization tool. The combination of NPD with first-principles density functional theory (DFT) calculations enables a deep understanding of the sorption mechanisms, and the resulting insights can direct the future development of MOF sorbents. In this paper, experimental approaches and investigations of two example MOFs are summarized, which demonstrate the type of information and the understanding into their functional mechanisms that can be gained. Such information is critical to the strategic design of new materials with targeted gas-sorption properties. PMID:26634721

  9. [X-ray powder diffraction of clay minerals of SZK01 core of Zabuye Lake, Tibetan Plateau].

    PubMed

    Zhang, Xue-Fei; Zheng, Mian-Ping

    2014-11-01

    The present article chooses the core from the borehole SZK01 in Zabuye Lake as the main research object. According to the results of X-ray powder diffraction of clay minerals, the major components are illite, illite and smectite mixed layer mineral (I/S), kaolinite and chlorite. According to the different species and contents of clay, integration of the characteristics of mineral and the results of Δ18O, we reestablished the evolution process of paleoclimate in Zabuye Lake. In compaison with SZK02 core in Zabuye, Greenland GISP2 and GRIP and Guliya ice core, it contains 5 stages since 115 ka in Zabuye: the last interglacial (15-75.5 ka), the earlier last glacial (75.5-60 ka), the interstage of the last glacial (60-30.1 ka), the last glacial maximum (30.1-16.7 ka) and deglacial-holocene (since 16.7 ka). We also recognized 6 Heinrich events (H1-H6) and warm event in 71 ka. In particular, the content of kaolinite is low, with the negative-skewed value of Δ18O in 52-53 ka, while the value of Δ18O in SZK02 and Guliya ice core is negative-skewed too, indicating the cold event in Tibet plateau, named H5-1. All the above demonstrated that the climate in Tibet plateau is global since the earlier last glacial, and it also has regional characteristics. PMID:25752070

  10. Neutron powder diffraction study of the layer organic-inorganic hybrid iron(II) methylphosphonate-hydrate, Fe[(CD 3PO 3)(D 2O)

    NASA Astrophysics Data System (ADS)

    Léone, Philippe; Bellitto, Carlo; Bauer, Elvira M.; Righini, Guido; André, Gilles; Bourée, Françoise

    2008-11-01

    The crystal and magnetic structures of the hybrid organic-inorganic layer compound Fe[(CD 3PO 3)(D 2O)] have been studied by neutron powder diffraction as a function of temperature down to 1.5 K. The neutron diffraction pattern recorded at 200 K shows that the fully deuterated compound crystallizes in one of the two known forms of the undeuterated Fe[(CH 3PO 3)(H 2O)]. The crystal structure is orthorhombic, space group Pmn2 1, with the following unit-cell parameters: a=5.7095(1) Å, b=8.8053(3) Å and c=4.7987(1) Å; Z=2. The crystal structure remains unchanged on cooling from 200 to 1.5 K. Moreover, at low temperature, Fe[(CD 3PO 3)(D 2O)] shows a commensurate magnetic structure ( k=(0,0,0)). As revealed by bulk susceptibility measurements on Fe[(CH 3PO 3)(H 2O)], the magnetic structure corresponds to a canted antiferromagnet with a critical temperature TN=25 K. Neutron powder diffraction reveals that below TN=23.5 K the iron magnetic moments in Fe[(CD 3PO 3)(D 2O)] are antiferromagnetically coupled and oriented along the b-axis, perpendicular to the inorganic layers. No ferromagnetic component is observable in the neutron powder diffraction experiment, due to its too small value (<0.1 μB).

  11. Comparison of Shock-Deformed Carbonate Samples to Unshocked Carbonate Samples Using X-ray Powder Diffraction

    NASA Astrophysics Data System (ADS)

    Huson, S.; Foit, F.; Pope, M.

    2006-12-01

    Previous studies of carbonate minerals from meteorite impact craters have revealed broader X-ray powder diffraction (XRD) peaks when compared to those of unshocked mineral standards. In this study XRD patterns of shocked minerals from an impact crater are compared to those subjected to terrestrial tectonic processes as well as to undeformed mineral standards from our in-house collection. Shocked dolostone and limestone samples were collected from the central uplift and eroded crater rim of Sierra Madera, a well-exposed, complex impact crater located in west Texas. Unshocked samples of dolostone and limestone were collected from the Mission Canyon Formation of the Madison Limestone Group of southwest Montana and western Wyoming. The Mission Canyon Formation was deposited in a shallow shelf environment during the Mississippian, subsequently buried to varying depths, and deformed during the Laramide and Sevier orogenies in the Cretaceous. These samples are therefore excellent representatives for "normal" terrestrial tectonic processes. Samples were powdered, sieved through a 63 μm mesh sieve to ensure a uniform size, and sifted onto a vaseline coated zero background plate to reduce preferred orientation of grains. Patterns were collected over the range from 15° 120° 2θ with a step width of 0.02° 2θ and count-time of 10s per step. All patterns were analyzed using MDI Jade 7.0 software. Generally, samples collected in the field have XRD patterns that are not as sharp as the mineral standard patterns. With both shocked and unshocked samples, those containing dolomite show more XRD peak broadening than those without dolomite and at least one pattern of an unshocked dolostone sample is indistinguishable from a shocked dolostone pattern. However, dolostone samples in general are problematic. Previous researchers reported that the amount of magnesium in calcite may affect grinding properties and, therefore, influence XRD peak broadening. Currently, it is not always

  12. Time-resolved grazing-incidence diffraction studies of thin films using an imaging-plate camera and focusing monochromator.

    PubMed

    Foran, G J; Gentle, I R; Garrett, R F; Creagh, D C; Peng, J B; Barnes, G T

    1998-03-01

    A multiple imaging-plate (IP) detector system and focusing monochromator have been developed and successfully applied to the time-resolved study of phase transitions in Langmuir-Blodgett (LB) films by grazing-incidence X-ray diffraction (GIXD). The first reported application of imaging plates to a GIXD study was carried out by our group and proved to be very successful in the determination of thin-film structure [Foran, Peng, Steitz, Barnes & Gentle (1996). Langmuir, 12, 774-777]. To extend the capabilities of this system, an IP camera was designed and built which can accommodate up to 13 IPs (40 x 20 cm) inside the vacuum chamber of the main diffractometer at the Australian Beamline at the Photon Factory. The camera allows the enclosed IPs to be successively exposed and stored inside the diffractometer for later scanning. The focusing monochromator employed in this technique combines fixed exit-beam height with sagittal focusing of the second crystal and delivers a gain in flux of >/=20 times when measured through a 0.1 x 0.1 mm aperture. The utility of the system incorporating the IP camera and the focusing monochromator has been demonstrated through the study of temperature-dependent phase transitions in LB films of metal fatty acids. PMID:16687811

  13. Time-resolved X-ray diffraction of the photochromic alpha-styrylpyrylium trifluoromethanesulfonate crystal films reveals ultrafast structural switching.

    PubMed

    Hallmann, Jörg; Morgenroth, Wolfgang; Paulmann, Carsten; Davaasambuu, Jav; Kong, Qingyu; Wulff, Michael; Techert, Simone

    2009-10-21

    The ultrafast structural dynamics of the [2+2] photocycloaddition of alpha-styrylpyrylium trifluoromethanesulfonate (TFMS) has been studied in great detail. During the photoreaction, optical and infrared spectroscopy confirms that crystals of alpha-styrylpyrylium change color. Since the reaction is reversible, it has been suggested to be used as an organic holographic storage device. The present photocrystallographic studies (with high spatial resolution) allow for an electron density analysis of the overall reaction kinetics, revealing the mechanism of bond-breaking and bond-formation. It could furthermore be proved how the reaction is influenced by the rearrangement of the surrounding moieties. Picosecond time-resolved X-ray diffraction studies allow for the monitoring the photoreaction in crystalline thin films under experimental conditions where the transformation times are greatly enhanced. These investigations are discussed in the context of the photocrystallographic results. It has been found that alpha-styrylpyrylium TFMS undergoes an ultrafast photoreaction to the dimer product state and back-reaction to the monomer reactant state which is temperature driven. The present experiments indicate that TFMS reacts on time scales which are the fundamental limiting ones of two-quantum systems and therefore has the potential to be used as an ultrafast organic molecular switcher. PMID:19824735

  14. Structural changes in shock compressed silicon observed using time-resolved x-ray diffraction at the Dynamic Compression Sector

    NASA Astrophysics Data System (ADS)

    Turneaure, Stefan; Zdanowicz, E.; Sinclair, N.; Graber, T.; Gupta, Y. M.

    2015-06-01

    Structural changes in shock compressed silicon were observed directly using time-resolved x-ray diffraction (XRD) measurements at the Dynamic Compression Sector at the Advanced Photon Source. The silicon samples were impacted by polycarbonate impactors accelerated to velocities greater than 5 km/s using a two-stage light gas gun resulting in impact stresses of about 25 GPa. The 23.5 keV synchrotron x-ray beam passed through the polycarbonate impactor, the silicon sample, and an x-ray window (polycarbonate or LiF) at an angle of 30 degrees relative to the impact plane. Four XRD frames (~ 100 ps snapshots) were obtained with 153.4 ns between frames near the time of impact. The XRD measurements indicate that in the peak shocked state, the silicon samples completely transformed to a high-pressure phase. XRD results for both shocked polycrystalline silicon and single crystal silicon will be presented and compared. Work supported by DOE/NNSA.

  15. Crystal structures of deuterated sodium molybdate dihydrate and sodium tungstate dihydrate from time-of-flight neutron powder diffraction.

    PubMed

    Fortes, A Dominic

    2015-07-01

    Time-of-flight neutron powder diffraction data have been measured from ∼90 mol% deuterated isotopologues of Na2MoO4·2H2O and Na2WO4·2H2O at 295 K to a resolution of sin (θ)/λ = 0.77 Å(-1). The use of neutrons has allowed refinement of structural parameters with a precision that varies by a factor of two from the heaviest to the lightest atoms; this contrasts with the X-ray based refinements where precision may be > 20× poorer for O atoms in the presence of atoms such as Mo and W. The accuracy and precision of inter-atomic distances and angles are in excellent agreement with recent X-ray single-crystal structure refinements whilst also completing our view of the hydrogen-bond geometry to the same degree of statistical certainty. The two structures are isotypic, space-group Pbca, with all atoms occupying general positions, being comprised of edge- and corner-sharing NaO5 and NaO6 polyhedra that form layers parallel with (010) inter-leaved with planes of XO4 (X = Mo, W) tetra-hedra that are linked by chains of water mol-ecules along [100] and [001]. The complete structure is identical with the previously described molybdate [Capitelli et al. (2006 ▸). Asian J. Chem. 18, 2856-2860] but shows that the purported three-centred inter-action involving one of the water mol-ecules in the tungstate [Farrugia (2007 ▸). Acta Cryst. E63, i142] is in fact an ordinary two-centred 'linear' hydrogen bond. PMID:26279871

  16. Crystal structures of deuterated sodium molybdate dihydrate and sodium tungstate dihydrate from time-of-flight neutron powder diffraction

    PubMed Central

    Fortes, A. Dominic

    2015-01-01

    Time-of-flight neutron powder diffraction data have been measured from ∼90 mol% deuterated isotopologues of Na2MoO4·2H2O and Na2WO4·2H2O at 295 K to a resolution of sin (θ)/λ = 0.77 Å−1. The use of neutrons has allowed refinement of structural parameters with a precision that varies by a factor of two from the heaviest to the lightest atoms; this contrasts with the X-ray based refinements where precision may be > 20× poorer for O atoms in the presence of atoms such as Mo and W. The accuracy and precision of inter­atomic distances and angles are in excellent agreement with recent X-ray single-crystal structure refinements whilst also completing our view of the hydrogen-bond geometry to the same degree of statistical certainty. The two structures are isotypic, space-group Pbca, with all atoms occupying general positions, being comprised of edge- and corner-sharing NaO5 and NaO6 polyhedra that form layers parallel with (010) inter­leaved with planes of XO4 (X = Mo, W) tetra­hedra that are linked by chains of water mol­ecules along [100] and [001]. The complete structure is identical with the previously described molybdate [Capitelli et al. (2006 ▸). Asian J. Chem. 18, 2856–2860] but shows that the purported three-centred inter­action involving one of the water mol­ecules in the tungstate [Farrugia (2007 ▸). Acta Cryst. E63, i142] is in fact an ordinary two-centred ‘linear’ hydrogen bond. PMID:26279871

  17. Neutron and X-Ray Powder Diffraction Study of RBa 2Fe 3O 8+ wPhases

    NASA Astrophysics Data System (ADS)

    Karen, P.; Kjekshus, A.; Huang, Q.; Lynn, J. W.; Rosov, N.; Natali Sora, I.; Karen, V. L.; Mighell, A. D.; Santoro, A.

    1998-02-01

    Compounds of composition RBa 2Fe 3O 8+ w( R=La, Nd, Sm, Gd, Dy, Er, Yb, Lu, and Y) with variable oxygen content have been synthesized using the liquid mixing technique and have been analyzed by powder X-ray and neutron diffraction methods. A triple perovskite-type structure with ordered Ba and Rcations and having the symmetry of space group P4/ mmmwas obtained only for R=Y, Dy, and Er, whereas the larger Ratoms gave the atomic arrangement of disordered, defective perovskites with average symmetry Pmoverline3m. No perovskite-type phases were obtained when Yb and Lu were tried. The oxygen content of the oxygen-saturated phases was found to increase with increasing size of the cation Rfrom w=0.07 for Er to w=0.83 for La. The Néel temperature (˜650 K) and the magnitude of the Fe magnetic moment (˜3.3 μBat room temperature) are highest when trivalent iron is involved ( w=0), but these quantities are rather insensitive to the nature of Rand to slight variations of oxygen content in the triple perovskite-type structure of the Y, Dy, and Er compounds. In the case of the cubic structures, however, both quantities depend strongly on the oxygen stoichiometry. In the magnetically ordered state, nearest-neighbor iron moments are coupled antiferromagnetically along the three crystallographic directions in all samples, resulting in magnetic structures with symmetry Imm' mand magnetic unit cells related to those of the corresponding nuclear structures by the transformation matrix (1 overline10/110/002).

  18. Additional evidence from x-ray powder diffraction patterns that icosahedral quasi-crystals of intermetallic compounds are twinned cubic crystals

    SciTech Connect

    Pauling, L. )

    1988-07-01

    Analysis of the measured values of Q for the weak peaks (small maxima, usually considered to be background fluctuations, noise) on the x-ray powder diffraction curves for 17 rapidly quenched alloys leads directly to the conclusion that they are formed by an 820-atom or 1012-atom primitive cubic structure that by icosahedral twinning produces the so-called icosahedral quasi-crystals.

  19. Investigation of the Surface Stress in SiC and Diamond Nanocrystals by In-situ High Pressure Powder Diffraction Technique

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    The real atomic structure of nanocrystals determines key properties of the materials. For such materials the serious experimental problem lies in obtaining sufficiently accurate measurements of the structural parameters of the crystals, since very small crystals constitute rather a two-phase than a uniform crystallographic phase system. As a result, elastic properties of nanograins may be expected to reflect a dual nature of their structure, with a corresponding set of different elastic property parameters. We studied those properties by in-situ high-pressure powder diffraction technique. For nanocrystalline, even one-phase materials such measurements are particularly difficult to make since determination of the lattice parameters of very small crystals presents a challenge due to inherent limitations of standard elaboration of powder diffractograms. In this investigation we used our methodology of the structural analysis, the 'apparent lattice parameter' (alp) concept. The methodology allowed us to avoid the traps (if applied to nanocrystals) of standard powder diffraction evaluation techniques. The experiments were performed for nanocrystalline Sic and GaN powders using synchrotron sources. We applied both hydrostatic and isostatic pressures in the range of up to 40 GPa. Elastic properties of the samples were examined based on the measurements of a change of the lattice parameters with pressure. The results show a dual nature of the mechanical properties (compressibilities) of the materials, indicating a complex, core-shell structure of the grains.

  20. Structure refinement of sub-cubic-mm volume sample at high pressures by pulsed neutron powder diffraction: application to brucite in an opposed anvil cell

    NASA Astrophysics Data System (ADS)

    Okuchi, Takuo; Tomioka, Naotaka; Purevjav, Narangoo; Abe, Jun; Harjo, Stefanus; Gong, Wu

    2014-04-01

    Neutron powder diffraction measurements of 0.9 mm3 of mixture of deuterated brucite and pressure medium were conducted at pressures to 2.8 GPa, using an opposed anvil cell and a medium-resolution diffractometer at Japan Proton Accelerator Research Complex pulsed neutron source. Spurious-free diffraction patterns were successfully obtained and refined to provide all structural parameters including Debye-Waller factors. Tilting of hydroxyl dipoles of brucite toward one of the three nearest-neighbor oxygen anions was confirmed to be substantial at pressure as low as 1.5 GPa. By this application, technical feasibility to analyze such a small sample has been newly established, which would be useful to extend the applications of neutron diffraction at high pressures.

  1. A flow-through reaction cell for in situ X-ray diffraction and absorption studies of heterogeneous powder-liquid reactions and phase transformations.

    PubMed

    Ferrer, Pilar; da Silva, Iván; Rubio-Zuazo, Juan; Alfonso, Belén F; Trobajo, Camino; Khainakov, Sergei; Garcia, Jose R; Garcia-Granda, Santiago; Castro, Germán R

    2012-01-01

    A portable powder-liquid high-corrosion-resistant reaction cell has been designed to follow in situ reactions by X-ray powder diffraction (XRD) and X-ray absorption spectroscopy (XAS) techniques. The cell has been conceived to be mounted on the experimental stations for diffraction and absorption of the Spanish CRG SpLine-BM25 beamline at the European Synchrotron Radiation Facility. Powder reactants and/or products are kept at a fixed position in a vertical geometry in the X-ray pathway by a porous membrane, under forced liquid reflux circulation. Owing to the short pathway of the X-ray beam through the cell, XRD and XAS measurements can be carried out in transmission configuration/mode. In the case of the diffraction technique, data can be collected with either a point detector or a two-dimensional CCD detector, depending on specific experimental requirements in terms of space or time resolution. Crystallization processes, heterogeneous catalytic processes and several varieties of experiments can be followed by these techniques with this cell. Two experiments were carried out to demonstrate the cell feasibility: the phase transformations of layered titanium phosphates in boiling aqueous solutions of phosphoric acid, and the reaction of copper carbonate and L-isoleucine amino acid powders in boiling aqueous solution. In this last case the shrinking of the solid reactants and the formation of Cu(isoleucine)(2) is observed. The crystallization processes and several phase transitions have been observed during the experiments, as well as an unexpected reaction pathway. PMID:22186649

  2. Testing the limits of sensitivity in a solid-state structural investigation by combined X-ray powder diffraction, solid-state NMR, and molecular modelling.

    PubMed

    Filip, Xenia; Borodi, Gheorghe; Filip, Claudiu

    2011-10-28

    A solid state structural investigation of ethoxzolamide is performed on microcrystalline powder by using a multi-technique approach that combines X-ray powder diffraction (XRPD) data analysis based on direct space methods with information from (13)C((15)N) solid-state Nuclear Magnetic Resonance (SS-NMR) and molecular modeling. Quantum chemical computations of the crystal were employed for geometry optimization and chemical shift calculations based on the Gauge Including Projector Augmented-Wave (GIPAW) method, whereas a systematic search in the conformational space was performed on the isolated molecule using a molecular mechanics (MM) approach. The applied methodology proved useful for: (i) removing ambiguities in the XRPD crystal structure determination process and further refining the derived structure solutions, and (ii) getting important insights into the relationship between the complex network of non-covalent interactions and the induced supra-molecular architectures/crystal packing patterns. It was found that ethoxzolamide provides an ideal case study for testing the accuracy with which this methodology allows to distinguish between various structural features emerging from the analysis of the powder diffraction data. PMID:21931906

  3. Penetration route of functional molecules in stratum corneum studied by time-resolved small- and wide-angle x-ray diffraction

    NASA Astrophysics Data System (ADS)

    Hatta, Ichiro; Nakazawa, Hiromitsu; Obata, Yasuko; Ohta, Noboru; Inoue, Katsuaki; Yagi, Naoto

    2011-01-01

    We studied effects of functional molecules on corneocytes in stratum corneum using time-resolved small- and wide-angle x-ray diffraction after applying a functional molecule. From these results it was revealed that in the stratum corneum a typical hydrophilic molecule, ethanol, penetrates via the transcellular route and on the other hand a typical hydrophobic molecule, d-limonene, penetrates via the intercellular route.

  4. Investigation of phase evolution of CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) by in situ synchrotron high-temperature powder diffraction

    SciTech Connect

    Ouyang, Xin; Huang, Saifang; Zhang, Weijun; Cao, Peng; Huang, Zhaohui; Gao, Wei

    2014-03-15

    In situ synchrotron X-ray powder diffraction was used to study the high-temperature phase evolution of CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) precursors prepared via solid-state and sol–gel methods. After the precursors are heated to 1225 °C, the CCTO phase is the main phase observed in the calcined powder, with the presence of some minor impurities. Comparing the two precursors, we found that the onset temperature for the CCTO phase formation is 800 °C in the sol–gel precursor, lower than that in the solid-state precursor (875 °C). Intermediate phases were only observed in the sol–gel precursor. Both precursors are able to be calcined to sub-micrometric sized powders. Based on the synchrotron data along with differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA), the phase formation sequence and mechanism during calcination are proposed in this study. -- Graphical abstract: The in situ synchrotron HT-XRD patterns of CCTO sol–gel and solid-state precursor. Highlights: • Phase formation sequence/mechanism in two CCTO precursors has been established. • Formation temperature of CCTO via sol–gel method is lower than solid-state method. • Intermediate phases are only observed in the sol–gel precursor. • Both precursors are able to be calcined into sub-micrometric sized powders.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  6. A glass capillary cell for in situ powder X-ray diffraction of condensed volatile compounds. Solid HCFC-123a and HCFC-124.

    PubMed

    Brunelli, Michela; Fitch, Andrew N

    2003-07-01

    A rotating glass capillary cell with a gas handling system has been built to allow in situ studies by powder X-ray diffraction. The cell can be used to condense volatile compounds, or to follow solid-state chemical reactions under vacuum or at gas pressures up to around 7 x 10(5) Pa. Using the cell, cooled by a stream of helium gas, the solid phases of 1,2-dichlorotrifluoroethane (HCFC-123a) and 2-chloro-1,1,1,2-tetrafluoroethane (HCFC-124) have been investigated using powder synchrotron X-ray radiation. These were found to have disordered hexagonal structures, with a = 4.018 (5), c = 6.553 (1) A and a = 4.048 (1), c = 6.625 (1) A, respectively, at 64 K. PMID:12824935

  7. Effect of chlorine in clay-mineral specimens prepared on silver metal-membrane mounts for X-ray powder diffraction analysis

    USGS Publications Warehouse

    Poppe, L.J.; Commeau, J.A.; Pense, G.M.

    1989-01-01

    Silver metal-membrane filters are commonly used as substrates in the preparation of oriented clay-mineral specimens for X-ray powder diffraction (XRD). The silver metal-membrane filters, however, present some problems after heat treatment if either the filters or the samples contain significant amounts of chlorine. At elevated temperature, the chloride ions react with the silver substrate to form crystalline compounds. These compounds change the mass-absorption coefficient of the sample, reducing peak intensities and areas and, therefore, complicating the semiquantitative estimation of clay minerals. A simple procedure that eliminates most of the chloride from a sample and the silver metal-membrane substrate is presented here.

  8. Neutron powder diffraction study of Ba3ZnRu2-xIrxO9 (x = 0, 1, 2) with 6H-type perovskite structure

    NASA Astrophysics Data System (ADS)

    Beran, P.; Ivanov, S. A.; Nordblad, P.; Middey, S.; Nag, A.; Sarma, D. D.; Ray, S.; Mathieu, R.

    2015-12-01

    The triple perovskites Ba3ZnRu2-xIrxO9 with x = 0, 1, and 2 are insulating compounds in which Ru(Ir) cations form a dimer state. Polycrystalline samples of these materials were studied using neutron powder diffraction (NPD) at 10 and 295 K. No structural transition nor evidence of long range magnetic order was observed within the investigated temperature range. The results from structural refinements of the NPD data and its polyhedral analysis are presented, and discussed as a function of Ru/Ir content.

  9. Single-crystal and humidity-controlled powder diffraction study of the breathing effect in a metal-organic framework upon water adsorption/desorption.

    PubMed

    Aríñez-Soriano, Javier; Albalad, Jorge; Vila-Parrondo, Christian; Pérez-Carvajal, Javier; Rodríguez-Hermida, Sabina; Cabeza, Aurelio; Juanhuix, Jordi; Imaz, Inhar; Maspoch, Daniel

    2016-05-26

    Herein we report a study on water adsorption/desorption-triggered single-crystal to single-crystal transformations in a MOF, by single-crystal and humidity-controlled powder X-ray diffraction and water-sorption measurements. We identified a gate-opening effect at a relative humidity of 85% upon water adsorption, and a gate-closure effect at a relative humidity of 55 to 77% upon water desorption. This reversible breathing effect between the "open" and the "closed" structures of the MOF involves the cleavage and formation of several coordination bonds. PMID:27228426

  10. An in situ sample environment reaction cell for spatially resolved x-ray absorption spectroscopy studies of powders and small structured reactors

    SciTech Connect

    Zhang, Chu; Gustafson, Johan; Merte, Lindsay R.; Evertsson, Jonas; Norén, Katarina; Carlson, Stefan; Svensson, Håkan; Carlsson, Per-Anders

    2015-03-15

    An easy-to-use sample environment reaction cell for X-ray based in situ studies of powders and small structured samples, e.g., powder, pellet, and monolith catalysts, is described. The design of the cell allows for flexible use of appropriate X-ray transparent windows, shielding the sample from ambient conditions, such that incident X-ray energies as low as 3 keV can be used. Thus, in situ X-ray absorption spectroscopy (XAS) measurements in either transmission or fluorescence mode are facilitated. Total gas flows up to about 500 ml{sub n}/min can be fed while the sample temperature is accurately controlled (at least) in the range of 25–500 °C. The gas feed is composed by a versatile gas-mixing system and the effluent gas flow composition is monitored with mass spectrometry (MS). These systems are described briefly. Results from simultaneous XAS/MS measurements during oxidation of carbon monoxide over a 4% Pt/Al{sub 2}O{sub 3} powder catalyst are used to illustrate the system performance in terms of transmission XAS. Also, 2.2% Pd/Al{sub 2}O{sub 3} and 2% Ag − Al{sub 2}O{sub 3} powder catalysts have been used to demonstrate X-ray absorption near-edge structure (XANES) spectroscopy in fluorescence mode. Further, a 2% Pt/Al{sub 2}O{sub 3} monolith catalyst was used ex situ for transmission XANES. The reaction cell opens for facile studies of structure-function relationships for model as well as realistic catalysts both in the form of powders, small pellets, and coated or extruded monoliths at near realistic conditions. The applicability of the cell for X-ray diffraction measurements is discussed.

  11. An in situ sample environment reaction cell for spatially resolved x-ray absorption spectroscopy studies of powders and small structured reactors

    NASA Astrophysics Data System (ADS)

    Zhang, Chu; Gustafson, Johan; Merte, Lindsay R.; Evertsson, Jonas; Norén, Katarina; Carlson, Stefan; Svensson, Hâkan; Carlsson, Per-Anders

    2015-03-01

    An easy-to-use sample environment reaction cell for X-ray based in situ studies of powders and small structured samples, e.g., powder, pellet, and monolith catalysts, is described. The design of the cell allows for flexible use of appropriate X-ray transparent windows, shielding the sample from ambient conditions, such that incident X-ray energies as low as 3 keV can be used. Thus, in situ X-ray absorption spectroscopy (XAS) measurements in either transmission or fluorescence mode are facilitated. Total gas flows up to about 500 mln/min can be fed while the sample temperature is accurately controlled (at least) in the range of 25-500 °C. The gas feed is composed by a versatile gas-mixing system and the effluent gas flow composition is monitored with mass spectrometry (MS). These systems are described briefly. Results from simultaneous XAS/MS measurements during oxidation of carbon monoxide over a 4% Pt/Al2O3 powder catalyst are used to illustrate the system performance in terms of transmission XAS. Also, 2.2% Pd/Al2O3 and 2% Ag - Al2O3 powder catalysts have been used to demonstrate X-ray absorption near-edge structure (XANES) spectroscopy in fluorescence mode. Further, a 2% Pt/Al2O3 monolith catalyst was used ex situ for transmission XANES. The reaction cell opens for facile studies of structure-function relationships for model as well as realistic catalysts both in the form of powders, small pellets, and coated or extruded monoliths at near realistic conditions. The applicability of the cell for X-ray diffraction measurements is discussed.

  12. Direct Observations of Austenite, Bainite and Martensite Formation During Arc Welding of 1045 Steel using Time Resolved X-Ray Diffraction

    SciTech Connect

    Elmer, J; Palmer, T; Babu, S; Zhang, W; DebRoy, T

    2004-02-17

    In-situ Time Resolved X-Ray Diffraction (TRXRD) experiments were performed during stationary gas tungsten arc (GTA) welding of AISI 1045 C-Mn steel. These synchrotron-based experiments tracked, in real time, phase transformations in the heat-affected zone of the weld under rapid heating and cooling conditions. The diffraction patterns were recorded at 100 ms intervals, and were later analyzed using diffraction peak profile analysis to determine the relative fraction of ferrite ({alpha}) and austenite ({gamma}) phases in each diffraction pattern. Lattice parameters and diffraction peak widths were also measured throughout the heating and cooling cycle of the weld, providing additional information about the phases that were formed. The experimental results were coupled with a thermofluid weld model to calculate the weld temperatures, allowing time-temperature transformation kinetics of the {alpha} {yields} {gamma} phase transformation to be evaluated. During heating, complete austenitization was observed in the heat affected zone of the weld and the kinetics of the {alpha} {yields} {gamma} phase transformation were modeled using a Johnson-Mehl-Avrami (JMA) approach. The results from the 1045 steel weld were compared to those of a 1005 low carbon steel from a previous study. Differences in austenitization rates of the two steels were attributed to differences in the base metal microstructures, particularly the relative amounts of pearlite and the extent of the allotriomorphic ferrite phase. During weld cooling, the austenite transformed to a mixture of bainite and martensite. In situ diffraction was able to distinguish between these two non-equilibrium phases based on differences in their lattice parameters and their transformation rates, resulting in the first real time x-ray diffraction observations of bainite and martensite formation made during welding.

  13. Rietveld analysis of X-ray powder diffraction patterns as a potential tool for the identification of impact-deformed carbonate rocks

    NASA Astrophysics Data System (ADS)

    Huson, S. A.; Foit, F. F.; Watkinson, A. J.; Pope, M. C.

    2009-12-01

    Previous X-ray powder diffraction (XRD) studies revealed that shock deformed carbonates and quartz have broader XRD patterns than those of unshocked samples. Entire XRD patterns, single peak profiles and Rietveld refined parameters of carbonate samples from the Sierra Madera impact crater, west Texas, unshocked equivalent samples from 95 miles north of the crater and the Mission Canyon Formation of southwest Montana and western Wyoming were used to evaluate the use of X-ray powder diffraction as a potential tool for distinguishing impact deformed rocks from unshocked and tectonically deformed rocks. At Sierra Madera dolostone and limestone samples were collected from the crater rim (lower shock intensity) and the central uplift (higher shock intensity). Unshocked equivalent dolostone samples were collected from well cores drilled outside of the impact crater. Carbonate rocks of the Mission Canyon Formation were sampled along a transect across the tectonic front of the Sevier and Laramide orogenic belts. Whereas calcite subjected to significant shock intensities at the Sierra Madera impact crater can be differentiated from tectonically deformed calcite from the Mission Canyon Formation using Rietveld refined peak profiles, weakly shocked calcite from the crater rim appears to be indistinguishable from the tectonically deformed calcite. In contrast, Rietveld analysis readily distinguishes shocked Sierra Madera dolomite from unshocked equivalent dolostone samples from outside the crater and tectonically deformed Mission Canyon Formation dolomite.

  14. Definition of a 'guiding function' in global optimization: a hybrid approach combining energy and R-factor in structure solution from powder diffraction data

    NASA Astrophysics Data System (ADS)

    Lanning, Oliver J.; Habershon, Scott; Harris, Kenneth D. M.; Johnston, Roy L.; Kariuki, Benson M.; Tedesco, Emilio; Turner, Giles W.

    2000-02-01

    Two global optimization problems of current interest in solid state sciences are crystal structure prediction (optimization of structure with respect to computed energy) and direct-space techniques for crystal structure solution from powder diffraction data (optimization of structure with respect to R-factor). As the energy and R-factor hypersurfaces are based on the same parameter space but have differing characteristics, there is a direct opportunity to blend these approaches together in the definition of a hybrid hypersurface. A strategy for combining R-factor and energy within a direct-space method for structure solution from powder diffraction data is proposed. Normalized energy and normalized R-factor functions are defined, and are combined using a sliding weighting function to give a hybrid figure-of-merit G, which behaves as energy when energy is high (thus using energy to guide the calculation towards energetically plausible structures) and gives increasing importance to R-factor as lower energies are approached. This concept of a `guiding function' may be widely applicable in other global optimization problems.

  15. Rietveld Analysis of X-ray Powder Diffraction Patterns as a Potential Tool for the Identification of Impact-deformed Carbonate Rocks

    SciTech Connect

    Huson, Sarah A.; Foit, Franklin F.; Watkinson, A. J.; Pope, Michael C.

    2009-11-01

    Previous X-ray powder diffraction (XRD) studies revealed that shock deformed carbonates and quartz have broader XRD patterns than those of unshocked samples. Entire XRD patterns, single peak profiles and Rietveld refined parameters of carbonate samples from the Sierra Madera impact crater, west Texas, unshocked equivalent samples from 95 miles north of the crater and the Mission Canyon Formation of southwest Montana and western Wyoming were used to evaluate the use of X-ray powder diffraction as a potential tool for distinguishing impact deformed rocks from unshocked and tectonically deformed rocks. At Sierra Madera dolostone and limestone samples were collected from the crater rim (lower shock intensity) and the central uplift (higher shock intensity). Unshocked equivalent dolostone samples were collected from well cores drilled outside of the impact crater. Carbonate rocks of the Mission Canyon Formation were sampled along a transect across the tectonic front of the Sevier and Laramide orogenic belts. Whereas calcite subjected to significant shock intensities at the Sierra Madera impact crater can be differentiated from tectonically deformed calcite from the Mission Canyon Formation using Rietveld refined peak profiles, weakly shocked calcite from the crater rim appears to be indistinguishable from the tectonically deformed calcite. In contrast, Rietveld analysis readily distinguishes shocked Sierra Madera dolomite from unshocked equivalent dolostone samples from outside the crater and tectonically deformed Mission Canyon Formation dolomite.

  16. Crystal structures of eight mono-methyl alkanes (C26–C32) via single-crystal and powder diffraction and DFT-D optimization

    PubMed Central

    Brooks, Lee; Brunelli, Michela; Pattison, Philip; Jones, Graeme R.; Fitch, Andrew

    2015-01-01

    The crystal structures of eight mono-methyl alkanes have been determined from single-crystal or high-resolution powder X-ray diffraction using synchrotron radiation. Mono-methyl alkanes can be found on the cuticles of insects and are believed to act as recognition pheromones in some social species, e.g. ants, wasps etc. The molecules were synthesized as pure S enantiomers and are (S)-9-methylpentacosane, C26H54; (S)-9-methylheptacosane and (S)-11-methylheptacosane, C28H58; (S)-7-methylnonacosane, (S)-9-methylnonacosane, (S)-11-methylnonacosane and (S)-13-methylnonacosane, C30H62; and (S)-9-methylhentriacontane, C32H66. All crystallize in space group P21. Depending on the position of the methyl group on the carbon chain, two packing schemes are observed, in which the molecules pack together hexagonally as linear rods with terminal and side methyl groups clustering to form distinct motifs. Carbon-chain torsion angles deviate by less than 10° from the fully extended conformation, but with one packing form showing greater curvature than the other near the position of the methyl side group. The crystal structures are optimized by dispersion-corrected DFT calculations, because of the difficulties in refining accurate structural parameters from powder diffraction data from relatively poorly crystalline materials. PMID:26306191

  17. X-ray powder diffraction beamline at D10B of LNLS: application to the Ba2FeReO6 double perovskite.

    PubMed

    Ferreira, Fabio Furlan; Granado, Eduardo; Carvalho, Wilson; Kycia, Stefan W; Bruno, Daniele; Droppa, Roosevelt

    2006-01-01

    A new beamline, fully dedicated to X-ray powder diffraction (XPD) measurements, has been installed after the exit port B of the bending magnet D10 at the Brazilian Synchrotron Light Laboratory (LNLS) and commissioned. The technical characteristics of the beamline are described and some performance indicators are listed, such as the incoming photon flux and the angular/energy resolutions obtainable under typical experimental conditions. The results of a Rietveld refinement for a standard sample of Y2O3 using high-resolution data are shown. The refined parameters match those found in the literature, within experimental error. High-resolution XPD measurements on Ba2FeReO6 demonstrate a slight departure from the ideal cubic double-perovskite structure at low temperatures, not detected by previous powder diffraction experiments. The onset of the structural transition coincides with the ferrimagnetic ordering temperature, Tc approximately equal to 315 K. Subtle structural features, such as those reported here for Ba2FeReO6, as well as the determination and/or refinement of complex crystal structures in polycrystalline samples are ideal candidate problems to be investigated on this beamline. PMID:16371707

  18. A combined solid-state NMR and synchrotron x-ray diffraction powder study on the structure of the antioxidant(+)-catechin 4.5 hydrate.

    SciTech Connect

    Harper, J. K.; Doebbler, J. A.; Jaccques, E.; Grant, D. M.; Von Dreele, R. B.; Univ. of Utah

    2010-03-10

    Analyses combining X-ray powder diffraction (XRD) and solid-state NMR (SSNMR) data can now provide crystal structures in challenging powders that are inaccessible by traditional methods. The flavonoid catechin is an ideal candidate for these methods, as it has eluded crystallographic characterization despite extensive study. Catechin was first described nearly two centuries ago, and its powders exhibit numerous levels of hydration. Here, synchrotron XRD data provide all heavy-atom positions in (+)-catechin 4.5-hydrate and establish the space group as C2. SSNMR data ({sup 13}C tensor and {sup 1}H/{sup 13}C correlation) complete the conformation by providing catechin's five OH hydrogen orientations. Since 1903, this phase has been erroneously identified as a 4.0 hydrate, but XRD and density data establish that this discrepancy is due to the facile loss of the water molecule located at a Wyckoff special position in the unit cell. A final improvement to heavy-atom positions is provided by a geometry optimization of bond lengths and valence angles with XRD torsion angles held constant. The structural enhancement in this final structure is confirmed by the significantly improved fit of computed {sup 13}C tensors to experimental data.

  19. A new method to do time-resolved, x-ray diffraction studies: The rotating crystal Laue method

    SciTech Connect

    Knapp, G.S.; Beno, M.A. )

    1992-01-01

    In order to achieve the ultimate time resolution of a synchrotron source we propose a new experimental technique by which time-dependent structural changes can be monitored on the time scale of synchrotron pulse widths. Samples will be studied by a rotating crystal Laue diffraction technique where we rapidly spin the sample and observe the diffraction pattern from a broadband of incident x rays. A computer simulation is presented of the diffraction pattern time evolution using the parameters for an APS undulator of a phase change in the YBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}} superconductor. We will discuss the application of this and closely related techniques at other synchrotron sources including bending magnets and insertion devices at NSLS and CHESS.

  20. A new method to do time resolved, x-ray diffraction studies: The rotating crystal Laue method

    SciTech Connect

    Knapp, G.S.; Beno, M.A.

    1991-07-01

    In order to achieve the ultimate time resolution of a synchrotron source we propose a new experimental technique by which time dependent structural changes can be monitored on the time scale of synchrotron pulse widths. Samples will be studied by a rotating crystal Laue diffraction technique where we rapidly spin the sample and observe the diffraction pattern from a broad band of incident x-rays. A computer simulation is presented of the diffraction pattern time evolution using the parameters for an APS undulator of a phase change in the YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} superconductor. We will discuss the application of this and closely related techniques at other synchrotron sources including bending magnets and insertion devices at NSLS and CHESS. 11 refs., 4 figs., 1 tab.

  1. Possibilities and limitations of synchrotron X-ray powder diffraction with double crystal and double multilayer monochromators for microscopic speciation studies

    NASA Astrophysics Data System (ADS)

    De Nolf, Wout; Jaroszewicz, Jakub; Terzano, Roberto; Lind, Ole Christian; Salbu, Brit; Vekemans, Bart; Janssens, Koen; Falkenberg, Gerald

    2009-08-01

    The performance of a combined microbeam X-ray fluorescence/X-ray powder diffraction (XRF/XRPD) measurement station at Hamburger Synchrotronstrahlungslabor (HASYLAB) Beamline L is discussed in comparison to that at European Synchrotron Radiation Facility (ESRF) ID18F/ID22. The angular resolution in the X-ray diffractograms is documented when different combinations of X-ray source, optics and X-ray diffraction detectors are employed. Typical angular resolution values in the range 0.3-0.5° are obtained at the bending magnet source when a 'pink' beam form of excitation is employed. A similar setup at European Synchrotron Radiation Facility beamlines ID18F and ID22 allows to reach angular resolution values of 0.1-0.15°. In order to document the possibilities and limitations for speciation of metals in environmental materials by means of Hamburger Synchrotronstrahlungslabor Beamline L X-ray fluorescence/X-ray powder diffraction setup, two case studies are discussed, one involved in the identification of the crystal phases in which heavy metals such as chromium, iron, barium and lead are present in polluted soils of an industrial site (Val Basento, Italy) and another involved in the speciation of uranium in depleted uranium particles (Ceja Mountains, Kosovo). In the former case, the angular resolution is sufficient to allow identification of most crystalline phases present while in the latter case, it is necessary to dispose of an angular resolution of ca. 0.2° to distinguish between different forms of oxidized uranium.

  2. Time-resolved resonant soft x-ray diffraction with free-electron lasers: Femtosecond dynamics across the Verwey transition in magnetite

    SciTech Connect

    Pontius, N.; Kachel, T.; Schuessler-Langeheine, C.; Schlotter, W. F.; Beye, M.; Sorgenfrei, F.; Wurth, W.; Chang, C. F.; Foehlisch, A.; Berglund, M.; Metcalf, P.

    2011-05-02

    Resonant soft x-ray diffraction (RSXD) with femtosecond (fs) time resolution is a powerful tool for disentangling the interplay between different degrees of freedom in strongly correlated electron materials. It allows addressing the coupling of particular degrees of freedom upon an external selective perturbation, e.g., by an optical or infrared laser pulse. Here, we report a time-resolved RSXD experiment from the prototypical correlated electron material magnetite using soft x-ray pulses from the free-electron laser FLASH in Hamburg. We observe ultrafast melting of the charge-orbital order leading to the formation of a transient phase, which has not been observed in equilibrium.

  3. Time-resolved energy-dispersive diffraction from X-FEL spontaneous emission: a proposal for sub-picosecond pumps & probe structural investigations

    NASA Astrophysics Data System (ADS)

    Rossi Albertini, Valerio; Paci, Barbara; Perfetti, Paolo

    2004-11-01

    The forthcoming generation of X-ray machines, based on Free Electron Laser (X-FEL) technology, should provide ultra-short pulses that may be used to probe the real-time structural evolution of a system activated by an optical laser pump. Unfortunately, the sub-picosecond synchronization of the pump and probe pulses produced by two independent sources is, at present, one of the main obstacles that needs to be overcome. Here we propose a new approach for carrying out time-resolved diffraction studies of evolving systems, which aims to bypass the synchronization problem.

  4. In situ X-ray powder diffraction studies of the synthesis of graphene oxide and formation of reduced graphene oxide

    NASA Astrophysics Data System (ADS)

    Storm, Mie Møller; Johnsen, Rune E.; Norby, Poul

    2016-08-01

    Graphene oxide (GO) and reduced graphene oxide (rGO) are important materials in a wide range of fields. The modified Hummers methods, for synthesizing GO, and subsequent thermal reduction to rGO, are often employed for production of rGO. However, the mechanism behinds these syntheses methods are still unclear. We present an in situ X-ray diffraction study of the synthesis of GO and thermal reduction of GO. The X-ray diffraction revealed that the Hummers method includes an intercalation state and finally formation of additional crystalline material. The formation of GO is observed during both the intercalation and the crystallization stage. During thermal reduction of GO three stages were observed: GO, a disordered stage, and the rGO stage. The appearance of these stages depends on the heating ramp. The aim of this study is to provide deeper insight into the chemical and physical processes during the syntheses.

  5. Structure and electronic properties of Dy@C 82 studied by UV-VIS absorption, X-ray powder diffraction and XAFS

    NASA Astrophysics Data System (ADS)

    Iida, S.; Kubozono, Y.; Slovokhotov, Y.; Takabayashi, Y.; Kanbara, T.; Fukunaga, T.; Fujiki, S.; Emura, S.; Kashino, S.

    2001-04-01

    Two isomers of Dy@C 82 were separated by high performance liquid chromatography (HPLC), and their UV-VIS absorption spectra were measured to characterize these isomers. The crystalline powder of Dy@C 82 was obtained by removing the solvent (toluene) at 250°C under vacuum. The X-ray diffraction pattern can be indexed with fcc crystal lattice, as that in La@C 82. The lattice constant a at 298 K, 15.86(1) Å, is close to that of La@C 82, 15.78 Å. The distances between Dy and the first and second nearest C atoms are determined to be 2.52(2) and 2.86(2) Å, respectively, on the basis of Dy L III-edge EXAFS. The XANES shows that the valence of the Dy atom in Dy@C 82 is +3.

  6. Crystal Structures of the Trifluoromethyl Sulfonates M(SO3CF3)2 (M = Mg, Ca, Ba, Zn, Cu) from Synchrotron X-ray Powder Diffraction Data

    SciTech Connect

    Dinnebier,R.; Sofina, N.; Hildebrandt, L.; Jansen, M.

    2006-01-01

    The crystal structures of divalent metal salts of trifluoromethyl sulfonic acid ('trifluoromethyl sulfonates') M(SO{sub 3}CF{sub 3}){sub 2} (M = Mg, Ca, Ba, Zn, Cu) were determined from high-resolution X-ray powder diffraction data. Magnesium, calcium and zinc trifluoromethyl sulfonate crystallize in the rhombohedral space group R{bar 3}. Barium trifluoromethyl sulfonate crystallizes in the monoclinic space group I2/a(C2/c) and copper trifluoromethyl sulfonate crystallizes in the triclinic group P{bar 1}. Within the crystal structures the trifluoromethyl sulfonate anions are arranged in double layers with the apolar CF{sub 3} groups pointing towards each other. The cations are located next to the SO{sub 3} groups. The symmetry relations between the different crystal structures have been analyzed.

  7. Vacancy-induced nanoscale phase separation in KxFe2–ySe₂ single crystals evidenced by Raman scattering and powder x-ray diffraction

    DOE PAGESBeta

    Lazarević, N.; Abeykoon, M.; Stephens, P. W.; Lei, Hechang; Bozin, E. S.; Petrovic, C.; Popović, Z. V.

    2012-08-06

    Polarized Raman scattering spectra of KxFe2–ySe₂ were analyzed in terms of peculiarities of both I4/m and I4/mmm space group symmetries. The presence of the Raman active modes from both space group symmetries (16 Raman-active modes of the I4/m phase and two Raman-active modes of the I4/mmm phase) confirmed the existence of two crystallographic domains with different space group symmetry in a KxFe2–ySe₂ sample. High-resolution synchrotron powder x-ray diffraction structural refinement of the same sample confirmed the two-phase description, and determined the atomic positions and occupancies for both domains.

  8. Crystal structure of (Cu,C)Ba2Ca3Cu4O11+δ (Tc=117 K) by neutron-powder-diffraction analysis

    NASA Astrophysics Data System (ADS)

    Shimakawa, Y.; Jorgensen, J. D.; Hinks, D. G.; Shaked, H.; Hitterman, R. L.; Izumi, F.; Kawashima, T.; Takayama-Muromachi, E.; Kamiyama, T.

    1994-12-01

    The crystal structure of the newly discovered 117-K superconductor, (Cu,C)Ba2Ca3Cu4O11+δ, has been refined from time-of-flight neutron-powder-diffraction data. The structure has ``average'' tetragonal symmetry and is similar to that of Tl(or Hg)Ba2Ca3Cu4Oy. C atoms in CO3 groups substitute at the Cu site in the (Cu,C)O1+δ layer leading to a chemical composition of (Cu0.68C0.32)Ba2Ca3Cu4O11.06. This compound has two inequivalent kinds of CuO2 layers with pyramidal and square coordination of Cu to oxygen. The inner CuO2 layers with Cu in four coordination are less corrugated than the outer ones with Cu in five coordination, and exhibit a structure very similar to those of infinite-layer compounds.

  9. Functional biocompatible magnetite-cellulose nanocomposite fibrous networks: Characterization by fourier transformed infrared spectroscopy, X-ray powder diffraction and field emission scanning electron microscopy analysis

    NASA Astrophysics Data System (ADS)

    Habibi, Neda

    2015-02-01

    The preparation and characterization of functional biocompatible magnetite-cellulose nano-composite fibrous material is described. Magnetite-cellulose nano-composite was prepared by a combination of the solution-based formation of magnetic nano-particles and subsequent coating with amino celluloses. Characterization was accomplished using X-ray powder diffraction (XRD), fourier transformed infrared (FTIR) and field emission scanning electron microscopy (FESEM) analysis. The peaks of Fe3O4 in the XRD pattern of nanocomposite confirm existence of the nanoparticles in the amino cellulose matrix. Magnetite-cellulose particles exhibit an average diameter of roughly 33 nm as demonstrated by field emission scanning electron microscopy. Magnetite nanoparticles were irregular spheres dispersed in the cellulose matrix. The vibration corresponding to the Nsbnd CH3 functional group about 2850 cm-1 is assigned in the FTIR spectra. Functionalized magnetite-cellulose nano-composite polymers have a potential range of application as targeted drug delivery system in biomedical field.

  10. Quadrupole lamp furnace for high temperature (up to 2050 K) synchrotron powder x-ray diffraction studies in air in reflection geometry

    SciTech Connect

    Sarin, P.; Yoon, W.; Jurkschat, K.; Zschack, P.; Kriven, W. M.

    2006-09-15

    A four-lamp thermal image furnace has been developed to conduct high temperature x-ray diffraction in reflection geometry on oxide ceramic powder samples in air at temperatures {<=}2050 K using synchrotron radiation. A refractory crucible made of Pt20%Rh alloy was used as a specimen holder. A material with well characterized lattice expansion properties was used as an internal crystallographic thermometer to determine the specimen temperature and displacement. The performance of the apparatus was verified by measurement of the thermal expansion properties of CeO{sub 2}, MgO, and Pt which were found to be within {+-}3% of the acceptable values. The advantages, limitations, and important considerations of the instrument developed are discussed.

  11. Quadrupole lamp furnace for high temperature (up to 2050 K) synchrotron powder x-ray diffraction studies in air in reflection geometry.

    SciTech Connect

    Sarin, P.; Yoon, W.; Jurkschat, K.; Zschack, P.; Kriven, W. M.; Univ. of Illinois; Frederick-Seitz Materials Research Lab.

    2006-09-01

    A four-lamp thermal image furnace has been developed to conduct high temperature x-ray diffraction in reflection geometry on oxide ceramic powder samples in air at temperatures {le} 2050 K using synchrotron radiation. A refractory crucible made of Pt20%Rh alloy was used as a specimen holder. A material with well characterized lattice expansion properties was used as an internal crystallographic thermometer to determine the specimen temperature and displacement. The performance of the apparatus was verified by measurement of the thermal expansion properties of CeO{sub 2}, MgO, and Pt which were found to be within {+-} 3% of the acceptable values. The advantages, limitations, and important considerations of the instrument developed are discussed.

  12. 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.

  13. A compact streak camera for 150 fs time resolved measurement of bright pulses in ultrafast electron diffraction.

    PubMed

    Kassier, G H; Haupt, K; Erasmus, N; Rohwer, E G; von Bergmann, H M; Schwoerer, H; Coelho, S M M; Auret, F D

    2010-10-01

    We have developed a compact streak camera suitable for measuring the duration of highly charged subrelativistic femtosecond electron bunches with an energy bandwidth in the order of 0.1%, as frequently used in ultrafast electron diffraction (UED) experiments for the investigation of ultrafast structural dynamics. The device operates in accumulation mode with 50 fs shot-to-shot timing jitter, and at a 30 keV electron energy, the full width at half maximum temporal resolution is 150 fs. Measured durations of pulses from our UED gun agree well with the predictions from the detailed charged particle trajectory simulations. PMID:21034115

  14. Maximum Entropy Method and Charge Flipping, a Powerful Combination to Visualize the True Nature of Structural Disorder from in situ X-ray Powder Diffraction Data

    SciTech Connect

    Samy, A.; Dinnebier, R; van Smaalen, S; Jansen, M

    2010-01-01

    In a systematic approach, the ability of the Maximum Entropy Method (MEM) to reconstruct the most probable electron density of highly disordered crystal structures from X-ray powder diffraction data was evaluated. As a case study, the ambient temperature crystal structures of disordered {alpha}-Rb{sub 2}[C{sub 2}O{sub 4}] and {alpha}-Rb{sub 2}[CO{sub 3}] and ordered {delta}-K{sub 2}[C{sub 2}O{sub 4}] were investigated in detail with the aim of revealing the 'true' nature of the apparent disorder. Different combinations of F (based on phased structure factors) and G constraints (based on structure-factor amplitudes) from different sources were applied in MEM calculations. In particular, a new combination of the MEM with the recently developed charge-flipping algorithm with histogram matching for powder diffraction data (pCF) was successfully introduced to avoid the inevitable bias of the phases of the structure-factor amplitudes by the Rietveld model. Completely ab initio electron-density distributions have been obtained with the MEM applied to a combination of structure-factor amplitudes from Le Bail fits with phases derived from pCF. All features of the crystal structures, in particular the disorder of the oxalate and carbonate anions, and the displacements of the cations, are clearly obtained. This approach bears the potential of a fast method of electron-density determination, even for highly disordered materials. All the MEM maps obtained in this work were compared with the MEM map derived from the best Rietveld refined model. In general, the phased observed structure factors obtained from Rietveld refinement (applying F and G constraints) were found to give the closest description of the experimental data and thus lead to the most accurate image of the actual disorder.

  15. The first protein crystal structure determined from high-resolution X-ray powder diffraction data: a variant of T3R3 human insulin-zinc complex produced by grinding.

    PubMed

    Von Dreele, R B; Stephens, P W; Smith, G D; Blessing, R H

    2000-12-01

    X-ray diffraction analysis of protein structure is often limited by the availability of suitable crystals. However, the absence of single crystals need not present an insurmountable obstacle in protein crystallography any more than it does in materials science, where powder diffraction techniques have developed to the point where complex oxide, zeolite and small organic molecular structures can often be solved from powder data alone. Here, that fact is demonstrated with the structure solution and refinement of a new variant of the T(3)R(3) Zn-human insulin complex produced by mechanical grinding of a polycrystalline sample. High-resolution synchrotron X-ray powder diffraction data were used to solve this crystal structure by molecular replacement adapted for Rietveld refinement. A complete Rietveld refinement of the 1630-atom protein was achieved by combining 7981 stereochemical restraints with a 4800-step (d(min) = 3.24 A) powder diffraction pattern and yielded the residuals R(wp) = 3.73%, R(p) = 2.84%, R(F)(2) = 8.25%. It was determined that the grinding-induced phase change is accompanied by 9.5 and 17.2 degrees rotations of the two T(3)R(3) complexes that comprise the crystal structure. The material reverts over 2-3 d to recover the original T(3)R(3) crystal structure. A Rietveld refinement of this 815-atom protein by combining 3886 stereochemical restraints with a 6000-step (d(min) = 3.06 A) powder diffraction pattern yielded the residuals R(wp) = 3.46%, R(p) = 2.64%, R(F)(2) = 7.10%. The demonstrated ability to solve and refine a protein crystal structure from powder diffraction data suggests that this approach can be employed, for example, to examine structural changes in a series of protein derivatives in which the structure of one member is known from a single-crystal study. PMID:11092920

  16. Revealing the powdering methods of black makeup in Ancient Egypt by fitting microstructure based Fourier coefficients to the whole x-ray diffraction profiles of galena

    NASA Astrophysics Data System (ADS)

    Ungár, T.; Martinetto, P.; Ribárik, G.; Dooryhée, E.; Walter, Ph.; Anne, M.

    2002-02-01

    Galena (PbS) is a major ingredient in ancient Egyptian eye makeup. The microstructure of PbS in Egyptian cosmetic powders is used as a fingerprint and is matched with the microstructures produced artificially in geological galena minerals. The microstructure of PbS is determined by x-ray diffraction peak profile analysis in terms of dislocation density, crystallite size, and size distribution. High-resolution powder diffractograms were measured at the ESRF Grenoble synchrotron source with high resolution and high peak-to-background ratios. The Fourier coefficients of the first nine measured reflections of galena are fitted using physically based Fourier coefficients of strain and size functions. Strain anisotropy is accounted for by the dislocation model of the mean square strain. The x-ray data are supplemented by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) micrographs, and are compared with archæological documents. It enables us to describe the procedures of eye makeup manufacturing in the Middle and New Kingdoms of Egypt some 2000 years before Christ.

  17. Formation of {gamma}-Fe{sub 2}O{sub 3} nanoparticles and vacancy ordering: An in situ X-ray powder diffraction study

    SciTech Connect

    Jorgensen, Jens-Erik Mosegaard, Lene; Thomsen, Line E.; Jensen, Torben R.; Hanson, Jonathan C.

    2007-01-15

    The formation of maghemite, {gamma}-Fe{sub 2}O{sub 3} nanoparticles has been studied by in situ X-ray powder diffraction. The maghemite was formed by thermal decomposition of an amorphous precursor compound made by reacting lauric acid, CH{sub 3}(CH{sub 2}){sub 10}COOH with Fe(NO{sub 3}){sub 3}.9H{sub 2}O. It has been shown that cubic {gamma}-Fe{sub 2}O{sub 3} was formed directly from the amorphous precursor and that vacancy ordering starts about 45 min later at 305 deg. C resulting in a tripled unit cell along the c-axis. The kinetics of grain growth was found to obey a power law with growth exponents n equal to 0.136(6) and 0.103(5) at 305 and 340 deg. C, respectively. Particles with average sizes of 12 and 13 nm were obtained in 86 and 76 min at 305 and 340 deg. C, respectively. The structure of cubic and vacancy ordered phases of {gamma}-Fe{sub 2}O{sub 3} was studied at 305 deg. C by Rietveld refinements. - Graphical abstract: Stack of powder diagrams showing the formation of {gamma}-Fe{sub 2}O{sub 3} nanoparticles and subsequent vacancy ordering at 305 deg. C.

  18. In-situ Time-Resolved Neutron Diffraction Measurements of Microstructure Variations during Friction Stir Welding in a 6061-T6 Aluminum Alloy

    SciTech Connect

    Woo, Wan Chuck; Wang, Xun-Li; Ungar, Prof Tomas; Feng, Zhili; David, Stan A; Clausen, B; Hubbard, Camden R

    2008-01-01

    The microstructure change is one of the most important research areas in the friction stir welding (FSW). However, direct observation of microstructure changes during FSW has been extremely challenging because many measurement techniques are inapplicable. Recently developed in-situ time-resolved neutron diffraction methodology, which drastically improves the temporal resolution of neutron diffraction, enables to observe the transient microstructure changes during FSW. We installed a portable FSW system in the Spectrometer for MAterials Research at Temperature and Stress (SMARTS) at Los Alamos Neutron Science Center and the FSW was made on 6.35mm-thickness 6061-T6 Al alloy plate. At the same time, the neutron beam was centered on the mid-plane of the Al plate at 8 mm from the tool center (underneath the tool shoulder) and the diffraction peak was continuously measured during welding. The peak broadening analysis has been performed using the Williamson-Hall Method. The result shows that the dislocation density of about 3.2 x 10^15 m-2 duing FSW, which is the significant increse compared to the before (4.5 x 10^14 m-2) and after (4.0 x 10^14 m-2) the FSW. The quantitatively analysis of the grain structure can provide an insight to understand the transient variation of the microstructure during FSW.

  19. Evidence from x-ray and neutron powder diffraction patterns that the so-called icosahedral and decagonal quasicrystals of MnAl/sub 6/ and other alloys are twinned cubic crystals

    SciTech Connect

    Pauling, L.

    1987-06-01

    It is shown that the x-ray powder diffraction patterns of rapidly quenched MnAl/sub 6/ and Mg/sub 32/(Al,Zn)/sub 49/ and the neutron powder diffraction pattern of MnAl/sub 5/ are compatible with the proposed 820-atom primitive cubic structure. The values found for the edge of the unit cube are 23.365 A (x-ray) and 23.416 A (neutron) for MnAl/sub 6/ and 24.313 A (x-ray) for Mg/sub 32/(Al,Zn)/sub 49/.

  20. High-pressure powder x-ray diffraction experiments and ab initio calculation of Ti3AlC2

    NASA Astrophysics Data System (ADS)

    Zhang, Haibin; Wu, Xiang; Nickel, Klaus Georg; Chen, Jixin; Presser, Volker

    2009-07-01

    The structural stability of the layered ternary carbide Ti3AlC2 was studied up to 35 GPa using x-ray diffraction with a Merrill-Basset-type diamond anvil cell and ab initio calculations. The structure (P63/mmc) was stable in the present pressure range without any phase transition. The Birch-Murnaghan equation of state was employed to fit the experimental pressure-volume date, from which the isothermal bulk modulus of Ti3AlC2 was determined as 156±5 GPa, which was also supported by theoretical results. In addition, theoretical calculations described anisotropic pressure dependences of the lattice parameters, electronic structure, and bonding properties of Ti3AlC2.

  1. Neutron Powder Diffraction study of the Magnetic Ionic Liquid Emim[FeCL4] and its deuterated phase

    NASA Astrophysics Data System (ADS)

    García-Saiz, A.; de Pedro, I.; Fernández Barquín, L.; Fernández-Díaz, M. T.; Blanco, J. A.; Rodríguez Fernández, J.

    2015-11-01

    A magnetic ionic liquid comprising 1-ethyl-3 methylimidazolium (Emim) cations and tetraclhoroferrate(III) (FeCl4) anions and its deuterated phase were synthetized and characterized magnetically. In both materials, the low temperature dependence of the magnetic susceptibility presents a maximum (around 4 K) related to an antiferromagnetic ordering, but the ordering temperatures are slightly shifted and the curves display different shapes. In addition, the magnetization of the deuterated phase tends to saturate at higher values than that corresponding to the non-deuterated analogue. A comparison of the neutron diffraction patterns above and below the magnetic transition clearly shows that the crystal and magnetic structures of these materials are different. Therefore, the present findings clearly prove that the magnetic exchange interactions that induce three-dimensional magnetic ordering are modified after the deuteration process.

  2. Combined X-Ray and Neutron Powder Diffraction Studies of Nanoscale Ca5-xFex(PO4)3OH Systems

    NASA Astrophysics Data System (ADS)

    Kyriacou, A.; Leventouri, Th.; Chakoumakos, B. C.; Garlea, V. O.; Cruz, C. D.; Rondinone, A. J.; Sorge, K. D.

    2012-02-01

    Multi-substituted hydroxyapatite (HAp) with crystallite size 4-130 nm is the major mineral phase in physiological apatites. Substitutions at all ionic sites affect their physicochemical properties. Fe is one of the minor substitutions at the Ca sites of HAp. It is important because it reduces the solubility of HAp, functioning as a cavities preventive agent, whereas Fe overload leads to a decreased mechanical strength and osteoporosis. Powder x-ray and neutron diffraction methods as well as energy-filtered transmission electron microscopy were used to study the effect of Fe substitution on the crystal structure properties of the Ca(5-x)Fex(PO4)3OH systems. Single phase HAp is identified in systems with x <= 0.1. Hematite is formed for higher x. Simultaneous Rietveld refinement of the x-ray and neutron diffraction patterns reveals an unexpected increase of the a-lattice constant. It is attributed to the increase of the Ca1-O3 and Ca2-O1 interatomic distances indicating a local lattice relaxation. Fe substitutes in both Ca1 and Ca2 sites with a preference to the Ca2 site and an occupancy up to 0.05 for x=0.3. Magnetic measurements reveal a transition from the diamagnetic state of the HAp to the paramagnetic of the Fe-doped systems.

  3. Exploring the complex magnetic phase diagram of Ce2PdGe3 : A neutron powder diffraction and μ SR study

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, A.; Ritter, C.; Adroja, D. T.; Coomer, F. C.; Strydom, A. M.

    2016-07-01

    The magnetic state of the tetragonal compound Ce2PdGe3 , which crystallizes in the space group P 42/m m c , a derivative of the α -ThSi2 structure, has been investigated by magnetic susceptibility, heat capacity, muon spin relaxation (μ SR ), and neutron diffraction measurements. Heat capacity data indicate two separate magnetic phase transitions at TN1=10.7 K and TN 2=2.3 K. The presence of bulk long-range magnetic order is confirmed by our μ SR study below 11 K, where a drop of nearly 2/3 in the muon initial asymmetry and a sharp increase in the muon depolarization rate were observed. Neutron powder diffraction reveals that only one out of two Ce sites becomes magnetically ordered with magnetic propagation vector κ =(0 ) at TN1,adopting an antiferromagnetic arrangement of magnetic moments μCe3+=1.78 (1 ) μB along the c axis. At TN 2 the second Ce site orders similarly, following the same magnetic propagation vector κ =(0 ) , showing, however, at the same time a significant ferromagnetic component within the tetragonal basal plane. A second propagation vector, κ =(1/2 ,0 ,1/2 ) , appears concomitantly at TN 2.

  4. Novel characterization of the adsorption sites in large pore metal-organic frameworks: combination of X-ray powder diffraction and thermal desorption spectroscopy.

    PubMed

    Soleimani-Dorcheh, Ali; Dinnebier, Robert E; Kuc, Agnieszka; Magdysyuk, Oxana; Adams, Frank; Denysenko, Dmytro; Heine, Thomas; Volkmer, Dirk; Donner, Wolfgang; Hirscher, Michael

    2012-10-01

    The preferred adsorption sites of xenon in the recently synthesized metal-organic framework MFU-4l(arge) possessing a bimodal pore structure (with pore sizes of 12 Å and 18.6 Å) were studied via the combination of low temperature thermal desorption spectroscopy and in situ X-ray powder diffraction. The diffraction patterns were collected at 110 K and 150 K according to the temperature of the desorption maxima. The maximum entropy method was used to reconstruct the electron density distribution of the structure and to localize the adsorbed xenon using refined data of the Xe-filled and empty sample. First principles calculations revealed that Xe atoms exclusively occupy the Wyckoff 32f position at approximately 2/3 2/3 2/3 along the body diagonal of the cubic crystal structure. At 110 K, Xe atoms occupy all 32 f positions (8 atoms per pore) while at 150 K the occupancy descends to 25% (2 atoms per pore). No Xe occupation of the small pores is observed by neither experimental measurements nor theoretical studies. PMID:22895492

  5. Static and Dynamical Structural Investigations of Metal-Oxide Nanocrystals by Powder X-ray Diffraction: Colloidal Tungsten Oxide as a Case Study.

    PubMed

    Caliandro, Rocco; Sibillano, Teresa; Belviso, B Danilo; Scarfiello, Riccardo; Hanson, Jonathan C; Dooryhee, Eric; Manca, Michele; Cozzoli, P Davide; Giannini, Cinzia

    2016-03-01

    We have developed a general X-ray powder diffraction (XPD) methodology for the simultaneous structural and compositional characterization of inorganic nanomaterials. The approach is validated on colloidal tungsten oxide nanocrystals (WO3-x NCs), as a model polymorphic nanoscale material system. Rod-shaped WO3-x NCs with different crystal structure and stoichiometry are comparatively investigated under an inert atmosphere and after prolonged air exposure. An initial structural model for the as-synthesized NCs is preliminarily identified by means of Rietveld analysis against several reference crystal phases, followed by atomic pair distribution function (PDF) refinement of the best-matching candidates (static analysis). Subtle stoichiometry deviations from the corresponding bulk standards are revealed. NCs exposed to air at room temperature are monitored by XPD measurements at scheduled time intervals. The static PDF analysis is complemented with an investigation into the evolution of the WO3-x NC structure, performed by applying the modulation enhanced diffraction technique to the whole time series of XPD profiles (dynamical analysis). Prolonged contact with ambient air is found to cause an appreciable increase in the static disorder of the O atoms in the WO3-x NC lattice, rather than a variation in stoichiometry. The time behavior of such structural change is identified on the basis of multivariate analysis. PMID:26756645

  6. Picosecond strain dynamics in Ge2Sb2Te5 monitored by time-resolved x-ray diffraction

    NASA Astrophysics Data System (ADS)

    Fons, Paul; Rodenbach, Peter; Mitrofanov, Kirill V.; Kolobov, Alexander V.; Tominaga, Junji; Shayduk, Roman; Giussani, Alessandro; Calarco, Raffaella; Hanke, Michael; Riechert, Henning; Simpson, Robert E.; Hase, Muneaki

    2014-09-01

    Coherent phonons (CPs) generated by laser pulses on the femtosecond scale have been proposed as a means to achieve ultrafast, nonthermal switching in phase-change materials such as Ge2Sb2Te5 (GST). Here we use ultrafast optical pump pulses to induce coherent acoustic phonons and stroboscopically measure the corresponding lattice distortions in GST using 100-ps x-ray pulses from the European Synchrotron Radiation Facility (ESRF) storage ring. A linear-chain model provides a good description of the observed changes in the diffraction signal; however, the magnitudes of the measured shifts are too large to be explained by thermal effects alone, implying the presence of excited-state effects in addition to temperature-driven expansion. The information on the movement of atoms during the excitation process can lead to greater insight into the possibilities of using CP-induced phase transitions in GST.

  7. The Surprising Outburst Behavior of Z Canis Majoris, and Resolving the Alpha Oph Companion Near the Diffraction limit

    NASA Astrophysics Data System (ADS)

    Hinkley, Sasha; Pope, Benjamin; Martinache, Frantz; Hillenbrand, Lynne; Kraus, Adam L.; Ireland, Michael; Oppenheimer, Ben R.; Rice, Emily L.; Monnier, John D.; Tuthill, Peter; Latyshev, Alexey

    2015-01-01

    We present recent high resolution Palomar and Keck observations on two intriguing binary star systems: Z Canis Majoris and Alpha Ophiuchus. We have obtained near-infrared Keck and Palomar photometry and spectra for each component of the Z Canis Majoris system, a very young binary composed of an FU Ori object and a Herbig Ae/Be object. Our high angular resolution photometry of this very young (~1 Myr) binary conclusively determines that the outburst was due solely to the embedded Herbig Ae/Be member, supporting results from earlier works. Further, our high-resolution K-band spectra during a quiescent phase definitively demonstrate that the 2.294 micron CO absorption feature seen in composite spectra of the system is due solely to the FU Ori component, while a prominent CO emission feature at the same wavelength, long suspected to be associated with the innermost regions of a circumstellar accretion disk, can be assigned to the Herbig Ae/Be member. These findings greatly clarify previous analyses of the origin of the CO emission in this complex system. In a different study, we detected the faint companion to the star Alpha Ophiuchus using the Palomar 5m Hale Telescope Adaptive Optics system combined with kernel phase interferometry, a recently-developed post-processing technique for high contrast imaging. The technique of kernel phase interferometry has never before been used to detect faint companions to nearby stars using ground-based observations. Our Palomar observations detect the Alpha Oph companion passing near its periastron point with separation of only ~130 miliarcseconds, close to the Palomar infrared diffraction limit. Alpha Oph is a particularly important binary system with the primary star rotating close to its breakup velocity. Thus, establishing the host star mass with high precision through dynamical orbital analysis is extremely valuable. This technique holds great promise for detecting high contrast objects at, or just inside, the formal

  8. X-Ray Diffraction.

    ERIC Educational Resources Information Center

    Smith, D. K.; Smith, K. L.

    1980-01-01

    Reviews applications in research and analytical characterization of compounds and materials in the field of X-ray diffraction, emphasizing new developments in applications and instrumentation in both single crystal and powder diffraction. Cites 414 references. (CS)

  9. Magnetic structures and magnetic phase transitions in the Mn-doped orthoferrite TbFeO3 studied by neutron powder diffraction

    NASA Astrophysics Data System (ADS)

    Nair, Harikrishnan S.; Chatterji, Tapan; Kumar, C. M. N.; Hansen, Thomas; Nhalil, Hariharan; Elizabeth, Suja; Strydom, André M.

    2016-02-01

    The magnetic structures and the magnetic phase transitions in the Mn-doped orthoferrite TbFeO3 studied using neutron powder diffraction are reported. Magnetic phase transitions are identified at TN Fe / Mn ≈ 295 K where a paramagnetic-to-antiferromagnetic transition occurs in the Fe/Mn sublattice, TS R Fe / Mn ≈ 26 K where a spin-reorientation transition occurs in the Fe/Mn sublattice and TN R ≈ 2 K where Tb-ordering starts to manifest. At 295 K, the magnetic structure of the Fe/Mn sublattice in TbFe 0.5 Mn 0.5 O3 belongs to the irreducible representation Γ 4 ( G x A y F z or P b ' n ' m ). A mixed-domain structure of ( Γ 1 + Γ 4 ) is found at 250 K which remains stable down to the spin re-orientation transition at TS R Fe / Mn ≈ 26 K. Below 26 K and above 250 K, the majority phase ( > 80 % ) is that of Γ 4 . Below 10 K the high-temperature phase Γ 4 remains stable till 2 K. At 2 K, Tb develops a magnetic moment value of 0.6(2) μ B / f.u. and orders long-range in Fz compatible with the Γ 4 representation. Our study confirms the magnetic phase transitions reported already in a single crystal of TbFe 0.5 Mn 0.5 O3 and, in addition, reveals the presence of mixed magnetic domains. The ratio of these magnetic domains as a function of temperature is estimated from Rietveld refinement of neutron diffraction data. Indications of short-range magnetic correlations are present in the low-Q region of the neutron diffraction patterns at T < TS R Fe / Mn . These results should motivate further experimental work devoted to measure electric polarization and magnetocapacitance of TbFe 0.5 Mn 0.5 O3.

  10. Powder Neutron Diffraction Study of the Thermal Expansion of Mirabilite, Na2SO4.10H2O

    NASA Astrophysics Data System (ADS)

    Brand, H. E.; Fortes, A. D.; Wood, I. G.; Knight, K. S.; Vocadlo, L.

    2006-12-01

    The presence of salts such as MgSO4 and Na2SO4 in chondritic meteorites has led to the suggestion that the water-rich icy moons of the Gas Giant planets are likely to be dominated by multiply hydrated salts such as Fritzsche's salt (MgSO4.11H2O), epsomite (MgSO4.7H2O) and mirabilite (Na2SO4.10H2O). Moreover, hydrated sulfates are likely to be important rock-forming minerals and water storage reservoirs on Mars. When constructing models of icy moons to explore their structure and evolution, it is therefore extremely important to know the phase behaviour and physical properties of the constituent materials under the appropriate pressure and temperature regimes (0 < P < 5 GPa, and 100 < T < 300 K). We are therefore engaged in a programme of study to measure the physical characteristics of candidate materials using a combination of neutron diffraction and computational chemistry. Neutrons are powerful probes of low molecular-weight solids, hydrogen-bearing species in particular, and their penetrative power allows one to study materials even in complex sample environments, such as pressure cells and cryostats. In practice, we measure the variation in molar volume of a solid as a function of pressure and temperature; this leads to derivatives in P and T, such as thermal expansivity and compressibility. Furthermore, we can observe phase transitions in situ, and collect diffraction data which may lead to a successful solution of the new polymorph's structure. In this contribution, we present the results of work to investigate the structure and thermoelastic properties of mirabilite. We have determined the ambient pressure thermal expansion tensor and investigated the low- temperature structural disorder of deuterated mirabilite from 4 - 300K. The volume expansion is positive and this is echoed by the expansion of the a and c axes. However, the b axis shows a small negative thermal expansion below 50K. Very similar behaviour is seen in MgSO4.7H2O and MgSO4.11H2O (Fortes et

  11. Time-resolved x-ray diffraction and Raman studies of the phase transition mechanisms of methane hydrate

    SciTech Connect

    Hirai, Hisako Kadobayashi, Hirokazu; Hirao, Naohisa; Ohishi, Yasuo; Ohtake, Michika; Yamamoto, Yoshitaka; Nakano, Satoshi

    2015-01-14

    The mechanisms by which methane hydrate transforms from an sI to sH structure and from an sH to filled-ice Ih structure were examined using time-resolved X-ray diffractometry (XRD) and Raman spectroscopy in conjunction with charge-coupled device camera observation under fixed pressure conditions. The XRD data obtained for the sI–sH transition at 0.8 GPa revealed an inverse correlation between sI and sH, suggesting that the sI structure is replaced by sH. Meanwhile, the Raman analysis demonstrated that although the 12-hedra of sI are retained, the 14-hedra are replaced sequentially by additional 12-hedra, modified 12-hedra, and 20-hedra cages of sH. With the sH to filled-ice Ih transition at 1.8 GPa, both the XRD and Raman data showed that this occurs through a sudden collapse of the sH structure and subsequent release of solid and fluid methane that is gradually incorporated into the filled-ice Ih to complete its structure. This therefore represents a typical reconstructive transition mechanism.

  12. Coherent femtosecond low-energy single-electron pulses for time-resolved diffraction and imaging: A numerical study

    SciTech Connect

    Paarmann, A.; Mueller, M.; Ernstorfer, R.; Gulde, M.; Schaefer, S.; Schweda, S.; Maiti, M.; Ropers, C.; Xu, C.; Hohage, T.; Schenk, F.

    2012-12-01

    We numerically investigate the properties of coherent femtosecond single electron wave packets photoemitted from nanotips in view of their application in ultrafast electron diffraction and non-destructive imaging with low-energy electrons. For two different geometries, we analyze the temporal and spatial broadening during propagation from the needle emitter to an anode, identifying the experimental parameters and challenges for realizing femtosecond time resolution. The simple tip-anode geometry is most versatile and allows for electron pulses of several ten of femtosecond duration using a very compact experimental design, however, providing very limited control over the electron beam collimation. A more sophisticated geometry comprising a suppressor-extractor electrostatic unit and a lens, similar to typical field emission electron microscope optics, is also investigated, allowing full control over the beam parameters. Using such a design, we find {approx}230 fs pulses feasible in a focused electron beam. The main limitation to achieve sub-hundred femtosecond time resolution is the typical size of such a device, and we suggest the implementation of more compact electron optics for optimal performance.

  13. Thermoelastic study of nanolayered structures using time-resolved X-ray diffraction at high repetition rate

    SciTech Connect

    Navirian, H. A.; Schick, D. Leitenberger, W.; Bargheer, M.; Gaal, P.; Shayduk, R.

    2014-01-13

    We investigate the thermoelastic response of a nanolayered sample composed of a metallic SrRuO{sub 3} electrode sandwiched between a ferroelectric Pb(Zr{sub 0.2}Ti{sub 0.8})O{sub 3} film with negative thermal expansion and a SrTiO{sub 3} substrate. SrRuO{sub 3} is rapidly heated by fs-laser pulses with 208 kHz repetition rate. Diffraction of X-ray pulses derived from a synchrotron measures the transient out-of-plane lattice constant c of all three materials simultaneously from 120 ps to 5 μs with a relative accuracy up to Δc/c = 10{sup −6}. The in-plane propagation of sound is essential for understanding the delayed out-of-plane compression of Pb(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}.

  14. Revisited. Decomposition or Melting? Formation Mechanism Investigation of LiCoO2 via In-Situ Time-Resolved X-ray Diffraction

    SciTech Connect

    Wicker, Scott A.; Edwin H. Walker Jr.

    2013-01-31

    Here, we report the first in-situ time-resolved X-ray diffraction investigation in conjunction with a non-isothermal kinetic study using the model-free isoconversional kinetic method to determine the formation mechanism for the solid-state synthesis of electrochemically active LiCoO2 from Li2CO3 and Co3O4. The detailed information on the phase evolution as well as thermal events during the heating process was clearly observed, explained, and supported. This investigation provides structural as well as kinetic evidence for a multistep reaction and proposes the first plausible formation mechanism for the solid-state synthesis of LiCoO2.

  15. Lattice-level observation of the elastic-to-plastic relaxation process with subnanosecond resolution in shock-compressed Ta using time-resolved in situ Laue diffraction

    DOE PAGESBeta

    Wehrenberg, C. E.; Comley, A. J.; Barton, N. R.; Coppari, F.; Fratanduono, D.; Huntington, C. M.; Maddox, B. R.; Park, H. -S.; Plechaty, C.; Prisbrey, S. T.; et al

    2015-09-29

    We report direct lattice level measurements of plastic relaxation kinetics through time-resolved, in-situ Laue diffraction of shock-compressed single-crystal [001] Ta at pressures of 27-210 GPa. For a 50 GPa shock, a range of shear strains is observed extending up to the uniaxial limit for early data points (<0.6 ns) and the average shear strain relaxes to a near steady state over ~1 ns. For 80 and 125 GPa shocks, the measured shear strains are fully relaxed already at 200 ps, consistent with rapid relaxation associated with the predicted threshold for homogeneous nucleation of dislocations occurring at shock pressure ~65 GPa.more » The relaxation rate and shear stresses are used to estimate the dislocation density and these quantities are compared to the Livermore Multiscale Strength model as well as various molecular dynamics simulations.« less

  16. X-ray Absorption Spectroscopy and Coherent X-ray Diffraction Imaging for Time-Resolved Investigation of the Biological Complexes: Computer Modelling towards the XFEL Experiment

    NASA Astrophysics Data System (ADS)

    Bugaev, A. L.; Guda, A. A.; Yefanov, O. M.; Lorenz, U.; Soldatov, A. V.; Vartanyants, I. A.

    2016-05-01

    The development of the next generation synchrotron radiation sources - free electron lasers - is approaching to become an effective tool for the time-resolved experiments aimed to solve actual problems in various fields such as chemistry’ biology’ medicine’ etc. In order to demonstrate’ how these experiments may be performed for the real systems to obtain information at the atomic and macromolecular levels’ we have performed a molecular dynamics computer simulation combined with quantum chemistry calculations for the human phosphoglycerate kinase enzyme with Mg containing substrate. The simulated structures were used to calculate coherent X-ray diffraction patterns’ reflecting the conformational state of the enzyme, and Mg K-edge X-ray absorption spectra, which depend on the local structure of the substrate. These two techniques give complementary information making such an approach highly effective for time-resolved investigation of various biological complexes, such as metalloproteins or enzymes with metal-containing substrate, to obtain information about both metal-containing active site or substrate and the atomic structure of each conformation.

  17. Time-resolved changes in equatorial x-ray diffraction and stiffness during rise of tetanic tension in intact length-clamped single muscle fibers.

    PubMed Central

    Cecchi, G; Griffiths, P J; Bagni, M A; Ashley, C C; Maeda, Y

    1991-01-01

    We report the first time-resolved x-ray diffraction studies on tetanized intact single muscle fibers of the frog. The 10, 11, 20, 21, 30, and Z equatorial reflections were clearly resolved in the relaxed fiber. The preparation readily withstood 100 1-s duration (0.4-s beam exposure) tetani at 4 degrees C (less than 4% decline of force and no deterioration in the 10, 11 equatorial intensity ratio at rest or during activation). Equatorial intensity changes (10 and 11) and fiber stiffness led tension (t1/2 lead 20 ms at 4 degrees C) during the tetanus rise and lagged during the isometric phase of relaxation. These findings support the existence of a low force cross-bridge state during the rise of tetanic tension and isometric relaxation that is not evident at the tetanus plateau. In "fixed end" tetani lattice expansion occurred with a time course similar to stiffness during the tetanus rise. During relaxation, lattice spacing increased slightly, while the sarcomere length remained isometric, but underwent large changes after the "shoulder" of tension. Under length clamp control, lattice expansion during the tetanus rise was reduced or abolished, and compression (2%) of the lattice was observed. A lattice compression is predicted by certain cross-bridge models of force generation (Schoenberg, M. 1980. Biophys. J. 30:51-68; Schoenberg, M. 1980. Biophys. J. 30:69-78). PMID:1873464

  18. Order-disorder phenomena determined by high-resolution powder diffraction: the structures of tetrakis(trimethylsilyl)methane C

    PubMed

    Dinnebier; Dollase; Helluy; Kümmerlen; Sebald; Schmidt; Pagola; Stephens; van Smaalen S

    1999-12-01

    The compounds tetrakis(trimethylsilyl)methane C[Si(CH(3))(3)](4) (TC) and tetrakis(trimethylsilyl)silane Si[Si(CH(3))(3)](4) (TSi) have crystal structures with the molecules in a cubic closed-packed (c.c.p.) stacking. At room temperature both structures have space group Fm{\\bar 3}m (Z = 4) with a = 13.5218 (1) Å, V = 2472.3 (1) Å(3) for TSi, and a = 12.8902 (2) Å, V = 2141.8 (1) Å(3) for TC. X-ray scattering data can be described by a molecule with approximately sixfold orientational disorder, ruling out a structure with free rotating molecules. Upon cooling, TSi exhibits a first-order phase transition at T(c) = 225 K, as is characterized by a jump of the lattice parameter of Deltaa = 0.182 Å and by an exothermal maximum in differential scanning calorimetry (DSC) with DeltaH = 11.7 kJ mol(-1) and DeltaS = 50.0 J mol(-1) K(-1). The structure of the low-temperature phase is refined against X-ray powder data measured at 200 K. It has space group P2(1)3 (Z = 4), a = 13.17158 (6) Å and V = 2285.15 (2) Å(3). The molecules are found to be ordered as a result of steric interactions between neighboring molecules, as is shown by analyzing distances between atoms and by calculations of the lattice energy in dependence on the orientations of the molecules. TC has a phase transition at T(c1) = 268 K, with Deltaa(1) = 0.065 Å, DeltaH(1) = 3.63 kJ mol(-1) and DeltaS(1) = 13.0 J mol(-1) K(-1). A second first-order phase transition occurs at T(c2) = 225 K, characterized by Deltaa(2) = 0.073 Å, DeltaH(2) = 6.9 kJ mol(-1) and DeltaS(2) = 30.0 J mol(-1) K(-1). The phase transition at higher temperature has not been reported previously. New NMR experiments show a small anomaly in the temperature dependence of the peak positions in NMR to occur at T(c2). Rietveld refinements were performed for the low-temperature phase measured at T = 150 K [space group P2(1)3, lattice parameter a = 12.609 (3) Å], and for the intermediate phase measured at T = 260 K [space group Pa{\\bar 3

  19. Neutron Powder Diffraction Measurements of the Spinel MgGa2O4:Cr3+ - A Comparative Study between the High Flux Diffractometer D2B at the ILL and the High Resolution Powder Diffractometer Aurora at IPEN

    NASA Astrophysics Data System (ADS)

    da Silva, M. A. F. M.; Sosman, L. P.; Yokaichiya, F.; Mazzocchi, V. L.; Parente, C. B. R.; Mestnik-Filho, J.; Henry, P. F.; Bordallo, H. N.

    2012-02-01

    Optical materials that emit from the visible to the near-infrared spectral region are of great interest due to their possible application as tunable radiation sources, as signal transmission, display, optoelectronics signal storage, cellulose industry as well as in dosimetry. One important family of such systems are the spinel compounds doped with Cr3+, in which the physical the properties are related to the insertion of punctual defects in the crystalline structure. The purpose of our work is two fold. First, we compare the luminescence of the MgGa2O4-Ga2O3 system with the single phase Ga2O3 and MgGa2O4 and relate structural changes observed in MgGa2O4-Ga2O3 system to the optical properties, and secondly, to compare the neutron powder diffraction results obtained using two diffractometers: D2B located at the ILL (Grenoble, France) and Aurora located at IPEN (São Paulo, Brazil). In the configuration chosen, Aurora shows an improved resolution, which is related to the design of its silicon focusing monochromator.

  20. Interaction between lamellar (vesicles) and nonlamellar lipid liquid-crystalline nanoparticles as studied by time-resolved small-angle X-ray diffraction.

    PubMed

    Vandoolaeghe, Pauline; Barauskas, Justas; Johnsson, Markus; Tiberg, Fredrïk; Nylander, Tommy

    2009-04-01

    The kinetics of structure change when dispersions of two different types of lipid-based liquid-crystalline phases, one lamellar and one reversed, are mixed has been investigated using synchrotron small-angle X-ray diffraction and ellipsometry. The systems studied were (i) cubic-phase nanoparticles (CPNPs) based on glycerol monooleate (GMO) stabilized with a nonionic block copolymer, Pluronic F-127; (ii) CPNPs based on phytantriol (PtOH) stabilized with D-alpha-Tocopheryl polyethylene glycol 1000 succinate (Vitamin E TPGS); and (iii) hexagonal-phase nanoparticles (HPNPs) based on a lipid mixture of diglycerol monooleate/glycerol dioleate, stabilized by Pluronic F-127. Time-resolved small-angle X-ray diffraction was used to track structural changes within nonlamellar nanoparticles when they interact with uni- and multilamellar vesicles of dioleoylphosphatidylcholine and dipalmitoylphatidylcholine. The results are very dependent on the type of nanoparticles under investigation. For GMO-based CPNPs, a strong interaction is observed on mixing with vesicular dispersions that leads to large changes in unit size dimensions as well as a later transition from cubic to lamellar structure. These results are in good agreement with previous studies on the interaction of GMO-based CPNPs with planar bilayers using neutron reflectivity, where the diffraction peak shifted with time upon mixing. The structural changes are much less prominent for the PtOH-based CPNPs and the HPNPs upon mixing with phospholipid vesicles. These results are correlated with those from measurement studying interactions between the liquid-crystalline nanoparticles and supported phospholipid bilayers by ellipsometry. Also, here the GMO-based CPNPs show more pronounced and rapid adsorption and interaction with the supported bilayer surface than do the other types of nonlamellar nanoparticles. The interaction also depends on the bilayer properties, where significantly slower lipid mixing is observed for a

  1. Characterization by X-Ray Absorption, X-Ray Powder Diffraction, and Magnetic Susceptibility of Cu Zn Co Al Containing Hydroxycarbonates, Oxycarbonates, Oxides, and Their Products of Reduction

    NASA Astrophysics Data System (ADS)

    Porta, Piero; Morpurgo, Simone; Pettiti, Ida

    1996-02-01

    Copper-zinc-cobalt-aluminium-containing crystalline hydroxycarbonates having hydrotalcite structure have been prepared by coprecipitation. X-ray powder diffraction (XRPD), magnetic susceptibility, and extended X-ray absorption fine structure (EXAFS) indicate that Cu2+, Zn2+, and Co2+are present in an octahedral environment. Calcination of the hydroxycarbonates at 723 K produces quasi-amorphous oxycarbonates where Cu2+and Co2+still retain octahedral coordination and cobalt is almost completely oxidized to Co3+. The coordination of Zn2+, at this stage, is intermediate between the octahedral one of the precursors and the tetrahedral one of ZnO and Zn-based spinels. Further calcination at 973 K produces a mixture of crystalline oxides such as CuO, ZnO, CuAl2O4, ZnAl2O4, and ZnCo2O4. EXAFS analysis of these samples indicates that copper is mainly in a fourfold coordination (although two longer Cu-O distances are also detected), zinc is tetrahedral, and cobalt (as Co3+) is essentially octahedral. EXAFS and XANES investigations performed afterin situreduction (10% H2/N2, at 523 and 623 K) on the oxycarbonates and oxides reveal that the total Cu2+→ Cu0reduction occurs only at 623 K in both series of samples, Co3+is reduced to Co2+only at 623 K in the oxycarbonates, and Zn2+is never reduced.

  2. Equation of state and phase transition of deuterated ammonia monohydrate (ND3.D2O) measured by high-resolution neutron powder diffraction up to 500 MPa

    NASA Astrophysics Data System (ADS)

    Fortes, A. Dominic; Suard, Emmanuelle; Lemée-Cailleau, Marie-Hélène; Pickard, Christopher J.; Needs, Richard J.

    2009-10-01

    We describe the results of a neutron powder diffraction study of perdeuterated ammonia monohydrate (AMH, ND3ṡD2O) carried out in the range 102

  3. Rietveld refinement of the semiconducting system Bi{sub 2-x}Fe{sub x}Te{sub 3} from X-ray powder diffraction

    SciTech Connect

    Adam, Alia

    2007-12-04

    The semiconducting system Bi{sub 2-x}Fe{sub x}Te{sub 3} (x = 0.0, 0.02, 0.04 and 0.08) was synthesized at 1000 deg. C for 30 h. The scanning electron microscope (SEM) image reveals the tendency of the Bi{sub 2-x}Fe{sub x}Te{sub 3} system to form a sheet structure with more pronounced alignment and to enhance the formation of some microstructure tubes. The structure of the system under study was refined on the basis of X-ray powder diffraction data using the Rietveld method. The analysis revealed the complete miscibility of Fe in the Bi{sub 2}Te{sub 3} matrix and hence the formation of single phase. The system crystallizes in the space group R-3m [1 6 6]. The lattice parameters and the unit cell size slightly change by the incorporation of Fe. The refinement of instrumental and structural parameters led to reliable values for the R{sub B}, R{sub F} and Chi{sup 2}.

  4. In situ synchrotron X-ray powder diffraction for studying the role of induced structural defects on the thermoluminescence mechanism of nanocrystalline LiF.

    PubMed

    El Ashmawy, Mostafa; Amer, Hany; Abdellatief, Mahmoud

    2016-03-01

    The correlation between the thermoluminescence (TL) response of nanocrystalline LiF and its microstructure was studied. To investigate the detailed TL mechanism, the glow curves of nanocrystalline LiF samples produced by high-energy ball-milling were analyzed. The microstructure of the prepared samples was analyzed by synchrotron X-ray powder diffraction (XRPD) at room temperature. Then, the microstructure of a representative pulverized sample was investigated in detail by performing in situ XRPD in both isothermal and non-isothermal modes. In the present study, the dislocations produced by ball-milling alter the microstructure of the lattice where the relative concentration of the vacancies, responsible for the TL response, changes with milling time. An enhancement in the TL response was recorded for nanocrystalline LiF at high-temperature traps (after dislocations recovery starts >425 K). It is also found that vacancies are playing a major role in the dislocations recovery mechanism. Moreover, the interactions among vacancies-dislocations and/or dislocations-dislocations weaken the TL response. PMID:26917138

  5. The Stoichiometry of Synthetic Alunite as a Function of Hydrothermal Aging Investigated by Solid-State NMR Spectroscopy, Powder X-ray Diffraction and Infrared Spectroscopy

    SciTech Connect

    Grube, Elisabeth; Nielsen, Ulla Gro

    2015-05-01

    The stoichiometry of a series of synthetic alunite [nominally KAl3(SO4)2(OH)6] samples prepared by hydrothermal methods as a function of reaction time (1–31 days) has been investigated by powder X-ray diffraction, Fourier transform infrared spectroscopy as well as solid-state 1H and 27Al magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The 1H MAS NMR spectra recorded at high magnetic field (21.1 T, 900 MHz) allowed for a clear separation of the different proton environments and for quantitative determination of the aluminum vacancy concentration as a function of time. The concentration of structural defects determined from, i.e., aluminum vacancies was reduced from 4 to 1 %, as the reaction time was extended from one to 31 days based on 1H MAS NMR. This was further supported by an increase of the unit cell parameter c, which is indicative of the relative concentration of potassium defects present, from 17.261(1) to 17.324(5) Å. Solid-state 27Al MAS NMR revealed a decrease in the defect concentration as a function of time and showed the presence of 7–10 % impurities in the samples.

  6. Mitigated phase transition during first cycle of a Li-rich layered cathode studied by in operando synchrotron X-ray powder diffraction.

    PubMed

    Song, Bohang; Day, Sarah J; Sui, Tan; Lu, Li; Tang, Chiu C; Korsunsky, Alexander M

    2016-02-14

    In operando synchrotron X-ray powder diffraction (SXPD) studies were conducted to investigate the phase transition of Li-rich Li(Li0.2Ni0.13Mn0.54Co0.13)O2 and Cr-doped Li(Li0.2Ni0.13Mn0.54Co0.03Cr0.10)O2 cathodes during the first charge/discharge cycle. Crystallographic (lattice parameters) and mechanical (domain size and microstrain) information was collected from SXPD full pattern refinement. It was found that Cr substitution at Co-site benefits in suppressing the activation of Li2MnO3 domains upon 1st charge, and thus mitigates the phase transition. As a consequence, Cr-doped layered cathode holds a better reversibility in terms of a full recovery of both lattice parameters and nano-domain size after a whole charge/discharge cycle. The effects of different cycling rates on the structural change were also discussed. PMID:26799191

  7. Three-dimensional structure determination of N-(p-Tolyl)-dodecylsulfonamide from powder diffraction data and validation of structure using solid-state NMR spectroscopy.

    PubMed

    Rajeswaran, Manju; Blanton, Thomas N; Zumbulyadis, Nicholas; Giesen, David J; Conesa-Moratilla, Carlota; Misture, Scott T; Stephens, Peter W; Huq, Ashfia

    2002-12-01

    The three-dimensional structure, conformation, and packing of molecules in the solid state are crucial components used in the optimization of many technologically useful materials properties. Single-crystal X-ray diffraction is the traditional and most effective method of determining 3-D structures in the solid state. Obtaining single crystals that are sufficiently large and free of imperfections is often laborious, time-consuming, and, occasionally, impossible. The feasibility of an integrated approach to the determination and verification of a complete three-dimensional structure for a medium-sized organic molecule without using single crystals is demonstrated for the case of an organic stabilizer compound N-(p-tolyl)-dodecylsulfonamide. The approach uses a combination of powder XRD data, several computational packages involving Monte Carlo simulations and ab initio quantum mechanical calculations, and experimental solid-state NMR chemical shifts. Structure elucidation of N-(p-tolyl)-dodecylsulfonamide revealed that the Bravais lattice is monoclinic, with cell dimensions of a = 38.773 A, b = 5.507 A, c = 9.509 A, and beta = 86.35 degrees, and a space group of P21/c. PMID:12452721

  8. Operando Synchrotron X-ray Powder Diffraction and Modulated-Excitation Infrared Spectroscopy Elucidate the CO2 Promotion on a Commercial Methanol Synthesis Catalyst.

    PubMed

    Martin, Oliver; Mondelli, Cecilia; Cervellino, Antonio; Ferri, Davide; Curulla-Ferré, Daniel; Pérez-Ramírez, Javier

    2016-09-01

    Optimal amounts of CO2 are added to syngas to boost the methanol synthesis rate on Cu-ZnO-Al2 O3 in the industrial process. The reason for CO2 promotion is not sufficiently understood at the particle level due to the catalyst complexity and the high demands of characterization under true reaction conditions. Herein, we applied operando synchrotron X-ray powder diffraction and modulated-excitation infrared spectroscopy on a commercial catalyst to gain insights into its morphology and surface chemistry. These studies unveiled that Cu and ZnO agglomerate and ZnO particles flatten under CO/H2 and/or CO2 /H2 . Under the optimal CO/CO2 /H2 mixture, sintering is prevented and ZnO crystals adopt an elongated shape due to the minimal presence of the H2 O byproduct, enhancing the water-gas shift activity and thus the methanol production. Our results provide a rationale to the CO2 promotion emphasizing the importance of advanced analytical methods to establish structure-performance relations in heterogeneous catalysis. PMID:27383374

  9. Crystal structure refinement of the semiconducting compound Cu{sub 2}SnSe{sub 3} from X-ray powder diffraction data

    SciTech Connect

    Delgado, G.E.; Mora, A.J.; Marcano, G.; Rincon, C

    2003-12-10

    The semiconducting compound Cu{sub 2}SnSe{sub 3} has been investigated by means of X-ray powder diffraction and its structure has been refined by the Rietveld method. The compound crystallizes in the monoclinic space group Cc (C{sub s}{sup 4}, No. 9), Z=4, with unit cell parameters a=6.9670(3) A, b=12.0493(7) A, c=6.9453(3) A, {beta}=109.19(1) deg. , and V=550.6(5) A{sup 3}. The refinement of 36 instrumental and structural parameters converged to R{sub p}=6.1%, R{sub wp}=8.6%, R{sub exp}=5.7%, R{sub B}=6.4%, S=1.5, for 4501 step intensities and 280 independent reflections. The structure of Cu{sub 2}SnSe{sub 3} can be described as an adamantane compound derivative of the sphalerite structure.

  10. Plumbonacrite identified by X-ray powder diffraction tomography as a missing link during degradation of red lead in a Van Gogh painting.

    PubMed

    Vanmeert, Frederik; Van der Snickt, Geert; Janssens, Koen

    2015-03-16

    Red lead, a semiconductor pigment used by artists since antiquity, is known to undergo several discoloration phenomena. These transformations are either described as darkening of the pigment caused by the formation of either plattnerite (β-PbO2) or galena (PbS) or as whitening by which red lead is converted into anglesite (PbSO4) or (hydro)cerussite (2 PbCO3⋅Pb(OH)2; PbCO3). X-ray powder diffraction tomography, a powerful analytical method that allows visualization of the internal distribution of different crystalline compounds in complex samples, was used to investigate a microscopic paint sample from a Van Gogh painting. A very rare lead mineral, plumbonacrite (3 PbCO3⋅Pb(OH)2⋅PbO), was revealed to be present. This is the first reported occurrence of this compound in a painting dating from before the mid 20th century. It constitutes the missing link between on the one hand the photoinduced reduction of red lead and on the other hand (hydro)cerussite, and thus sheds new light on the whitening of red lead. PMID:25703204

  11. A study of nitrogenation of a NdFe{sub 12-x}Mo{sub x} compound by in situ neutron powder diffraction.

    SciTech Connect

    Ding, Y.; Lin, J.; Loong, C.-K.; Short, S. M.

    1997-11-18

    The effects on the crystal lattice of a NdFe{sub 12{minus}x}Mo{sub x}(x {approx_equal} 1.7) compound which contained {approximately}12 vol% of bcc-Fe were studied by neutron powder diffraction during controlled nitrogenation over the 25-600 C temperature range. The sample inside the furnace was connected to a closed volume of ultra-pure nitrogen gas while neutron data were collected over regular time intervals during sequential heating. Substantial nitrogen absorption occurred between 500 to 600 C. During the nitrogenation process the NdFe{sub 12{minus}x}Mo{sub x}N{sub y} lattice expanded while the bcc-Fe lattice contracted. An increasing decomposition of the compound into bcc-Fe at 600 C was observed. The average size of the NdFe{sub 12{minus}x}Mo{sub x}N{sub y} crystalline grains decreased starting at {approximately}300 C, reaching a minimum at {approximately}500 C and then increased markedly at higher temperatures. The development of lattice strains, on the other hand, showed an opposite trend, i.e., a maximum at 500 C. A correlation of structural modification of the crystalline phases and the nitrogenation process is discussed.

  12. Obtaining aluminas from the thermal decomposition of their different precursors: An {sup 27}Al MAS NMR and X-ray powder diffraction studies

    SciTech Connect

    Chagas, L.H.; De Carvalho, G.S.G.; San Gil, R.A.S.; Chiaro, S.S.X.; Leitão, A.A.; Diniz, R.

    2014-01-01

    Graphical abstract: - Highlights: • We synthesized three precursors of alumina from different methods. • The calcination of the precursors generated several alumina polymorphs. • XRD and NMR were used for structural investigation of the polymorphs. • The synthesis route determines the structural and textural properties of the solids. - Abstract: A commercial sample of Boehmite was used as precursor of alumina polymorphs. For comparison, three other precursors were synthesized from different methods. Particularly, the use of excess of urea promoted a very crystalline form of basic aluminum carbonate. The characteristics of the four precursors were investigated by thermal, vibrational and X-ray powder diffraction (XRD) analysis. Additionally, the nuclear magnetic resonance, with magic angle spinning ({sup 27}Al MAS NMR), was used to verify the coordination of aluminum cations. Each precursor was calcined at various temperatures generating alumina polymorphs, which were structurally analyzed by XRD and {sup 27}Al MAS NMR. Due to interest in catalysis supports, special attention was given to the γ-Al{sub 2}O{sub 3} phase, which in addition to structural investigation was subjected to textural analysis. The results showed that, from different synthesis procedures and common route of calcination, one can obtain materials with the same composition but with different structural and textural properties, which in turn can significantly influence the performance of a supported catalyst.

  13. Formation of γ-Fe 2O 3 nanoparticles and vacancy ordering: An in situ X-ray powder diffraction study

    NASA Astrophysics Data System (ADS)

    Jørgensen, Jens-Erik; Mosegaard, Lene; Thomsen, Line E.; Jensen, Torben R.; Hanson, Jonathan C.

    2007-01-01

    The formation of maghemite, γ-Fe 2O 3 nanoparticles has been studied by in situ X-ray powder diffraction. The maghemite was formed by thermal decomposition of an amorphous precursor compound made by reacting lauric acid, CH 3(CH 2) 10COOH with Fe(NO 3) 3·9H 2O. It has been shown that cubic γ-Fe 2O 3 was formed directly from the amorphous precursor and that vacancy ordering starts about 45 min later at 305 °C resulting in a tripled unit cell along the c-axis. The kinetics of grain growth was found to obey a power law with growth exponents n equal to 0.136(6) and 0.103(5) at 305 and 340 °C, respectively. Particles with average sizes of 12 and 13 nm were obtained in 86 and 76 min at 305 and 340 °C, respectively. The structure of cubic and vacancy ordered phases of γ-Fe 2O 3 was studied at 305 °C by Rietveld refinements.

  14. Crystal structure of α- and β-Na{sub 2}U{sub 2}O{sub 7}: From Rietveld refinement using powder neutron diffraction data

    SciTech Connect

    IJdo, D.J.W. Akerboom, S.; Bontenbal, A.

    2015-01-15

    The crystal structures of α- and β-Na{sub 2}U{sub 2}O{sub 7} have been determined from neutron powder diffraction. At 293 K, the compound α-Na{sub 2}U{sub 2}O{sub 7} has a monoclinic unit cell, space group P2{sub 1}/a, with a=12.7617(14) Å, b=7.8384(10) Å, c=6.8962(9) Å, β=111.285(9)°, and Z=4. At 773 K, β-Na{sub 2}U{sub 2}O{sub 7} is also monoclinic, space group C2/m, with a=12.933(1) Å, b=7.887(1) Å, c=6.9086(8) Å, β=110.816(10)°, and Z=4. The structures can be described by layers U{sub 2}O{sub 7}{sup 2−} built from corner linked deformed UO{sub 6} octahedra with pentagonal UO{sub 7} bipyramids in between linked with common edges to each other and to the octahedra. The Na atoms occupy the interlayer space. The Na{sub 2}U{sub 2}O{sub 7} layers are similar as in K{sub 2}U{sub 2}O{sub 7}, but with a different stacking sequence of the layers. The layers in β-Na{sub 2}U{sub 2}O{sub 7} are more symmetric. The relationship with the compounds A{sub 2}U{sub 2}O{sub 7} (A=K, Rb, and Cs) is discussed. - Graphical abstract: The U{sub 2}O{sub 7} layer of α-Na{sub 2}U{sub 2}O{sub 7} (left) at 293 K and of β-Na{sub 2}U{sub 2}O{sub 7} (right) at 773 K determined by neutron diffraction. Some Na atoms between the layers are visible. - Highlights: • Na{sub 2}U{sub 2}O{sub 7} has been prepared by means of a solid state reaction. • The structure has been determined using neutron diffraction. • At 293 K, the compound adopts a monoclinic structure with space group P2{sub 1}/a. • The structure at 773 K is closely related, and is described in the space group C2/m.

  15. Direct correlation of structure changes and thermal events in hydrated lipid established by simultaneous calorimetry and time-resolved x-ray diffraction.

    PubMed Central

    Chung, H; Caffrey, M

    1992-01-01

    In many lipid systems, polymorphic and mesomorphic behavior depends on sample thermal history. To establish unequivocally the structural origin of endothermic and exothermic events in such systems, we have performed simultaneous calorimetry and time-resolved x-ray diffraction (SCALTRD). To this end, aluminum calorimetry crucibles were used to contain the hydrated lipid sample, and the calorimeter was mounted with the base of the crucible oriented perpendicular to a synchrotron-derived focused monochromatic x-ray beam for SCALTRD data collection. Measurements were made with hydrated monoelaidin and 1,2-dielaidoyl-sn-glycero-3-phosphoethanolamine (DEPE) contained in hermetically sealed crucibles. Time-resolved x-ray diffraction (TRXRD) data were collected using an x-ray image intensifier/video system and a streak camera containing an x-ray sensitive image plate and/or film. SCALTRD analysis of the lamellar gel to lamellar liquid crystalline phase transition in hydrated monoelaidin gives identical progress curves by calorimetry and TRXRD at a scan rate of 1 degree C/min. At faster rates, calorimetry shows a broader phase transition that starts at a lower and ends at a higher temperature than is observed by TRXRD. The disparity arises in part because the x-ray beam used in TRXRD interrogates only a small portion of the sample, whereas the calorimeter responds to the entire sample volume. Because data collection times are relatively long, radiation damage is an important potential problem for SCALTRD measurements. Such an effect was observed with DEPE/water in that TRXRD shows the lamellar gel to lamellar liquid crystalline phase transition occurring at a lower temperature than observed by calorimetry. We speculate that the sample accumulates impurities locally as a result of radiation damage that has the effect of lowering the phase transition temperature at the site of interrogation by the x-ray beam. This "methods-in-combination" SCALTRD approach facilitates the

  16. Direct Observations of Phase Transitions in Ti-6Al-4V Alloy Transient Welds using Time Resolved X-Ray Diffraction

    SciTech Connect

    Elmer, J W; Palmer, T A; Babu, S S; Zhang, W; Debroy, T

    2003-11-11

    Time Resolved X-Ray Diffraction (TRXRD) experiments were used to directly observe phase transformations occurring during gas tungsten arc spot welding of Ti-6Al-4V. These in-situ x-ray diffraction experiments tracked the evolution of the {alpha} {yields} {beta} {yields} L {yields} {beta} {yields} {alpha}/{alpha}{prime} phase transformation sequence in real time during rapid weld heating and cooling. Three different weld locations were examined, providing kinetic information about phase transformations in the fusion zone (FZ) and heat affected zone (HAZ) under different heating and cooling rates and at different temperatures. The TRXRD data were further coupled with the results of thermodynamic calculations of phase equilibria and numerical modeling to compute the weld temperatures. The results suggest that significant superheat is required above the {beta} transus temperature to complete the {alpha} {yields} {beta} transformation at all locations during weld heating, and that the amount of superheat decreases with distance from the center of the weld where the heating rates are lower. Johnson-Mehl-Avrami modeling of the weld heating kinetics produced a set of parameters that allowed the prediction of the {alpha} {yields} {beta} phase transformation rate at each location, but were not successful in determining a definitive mechanism for the transformation. The {beta} {yields} {alpha} transformation during weld cooling in the HAZ was shown to initiate at the {beta} transus temperature and reach completion below the Ms temperature, producing substantial {alpha}{prime}martensite. In the FZ, the {beta} {yields} {alpha} transformation during weld cooling was shown to initiate below the Ms temperature, and to completely transform the microstructure to {alpha}{prime} martensite.

  17. Observations of Ferrite/Austenite Transformations in the Heat Affected Zone of 2205 Duplex Stainless Steel Spot Welds Using Time Resolved X-Ray Diffraction

    SciTech Connect

    Palmer, T; Elmer, J; Babu, S

    2003-10-29

    Time Resolved X-Ray Diffraction (TRXRD) measurements are made in the Heat Affected Zone (HAZ) of 2205 Duplex Stainless Steel (DSS) spot welds. Both the {gamma} {yields} {delta} and {delta} {yields} {gamma} transformations are monitored as a function of time during the rapid spot weld heating and cooling cycles. These observations are then correlated with calculated thermal cycles. Where the peak temperatures are highest ({approx}1342 C), the {gamma} {yields} {delta} transformation proceeds to completion, leaving a ferritic microstructure at the end of heating. With lower peak temperatures, the {gamma} {yields} {delta} transformation proceeds to only partial completion, resulting in a microstructure containing both transformed and untransformed austenite. Further analyses of the individual diffraction patterns show shifts in the peak positions and peak widths as a function of both time and temperature. In addition, these changes in the peak characteristics are correlated with measured changes in the ferrite volume fraction. Such changes in the peak positions and widths during the {gamma} {yields} {delta} transformation provide an indication of changes occurring in each phase. These changes in peak properties can be correlated with the diffusion of nitrogen and other substitutional alloying elements, which are recognized as the primary mechanisms for this transformation. Upon cooling, the {delta} {yields} {gamma} transformation is observed to proceed from both the completely and partially transformed microstructural regions in the TRXRD data. An examination of the resulting microstructures confirms the TRXRD observation as the evidence shows that austenite both nucleates and grows from the ferritic microstructure at locations closest to the fusion zone boundary and grows from untransformed austenite grains at locations further from this boundary.

  18. Shedding Light on the Photochemistry of Coinage-Metal Phosphorescent Materials: A Time-Resolved Laue Diffraction Study of an AgI–CuI Tetranuclear Complex

    PubMed Central

    Jarzembska, Katarzyna N.; Kamiński, Radosław; Fournier, Bertrand; Trzop, Elżbieta; Sokolow, Jesse D.; Henning, Robert; Chen, Yang; Coppens, Philip

    2015-01-01

    The triplet excited state of a new crystalline form of a tetranuclear coordination d10–d10-type complex, Ag2Cu2L4 (L = 2-diphenylphosphino-3-methylindole ligand), containing AgI and CuI metal centers has been explored using the Laue pump–probe technique with ≈80 ps time resolution. The relatively short lifetime of 1 μs is accompanied by significant photoinduced structural changes, as large as the Ag1···Cu2 distance shortening by 0.59(3) Å. The results show a pronounced strengthening of the argentophilic interactions and formation of new Ag···Cu bonds on excitation. Theoretical calculations indicate that the structural changes are due to a ligand-to-metal charge transfer (LMCT) strengthening the Ag···Ag interaction, mainly occurring from the methylindole ligands to the silver metal centers. QM/MM optimizations of the ground and excited states of the complex support the experimental results. Comparison with isolated molecule optimizations demonstrates the restricting effect of the crystalline matrix on photoinduced distortions. The work represents the first time-resolved Laue diffraction study of a heteronuclear coordination complex and provides new information on the nature of photoresponse of coinage metal complexes, which have been the subject of extensive studies. PMID:25238405

  19. Ultrafast time-resolved electron diffraction revealing the nonthermal dynamics of near-UV photoexcitation-induced amorphization in Ge2Sb2Te5.

    PubMed

    Hada, Masaki; Oba, Wataru; Kuwahara, Masashi; Katayama, Ikufumi; Saiki, Toshiharu; Takeda, Jun; Nakamura, Kazutaka G

    2015-01-01

    Because of their robust switching capability, chalcogenide glass materials have been used for a wide range of applications, including optical storages devices. These phase transitions are achieved by laser irradiation via thermal processes. Recent studies have suggested the potential of nonthermal phase transitions in the chalcogenide glass material Ge2Sb2Te5 triggered by ultrashort optical pulses; however, a detailed understanding of the amorphization and damage mechanisms governed by nonthermal processes is still lacking. Here we performed ultrafast time-resolved electron diffraction and single-shot optical pump-probe measurements followed by femtosecond near-ultraviolet pulse irradiation to study the structural dynamics of polycrystalline Ge2Sb2Te5. The experimental results present a nonthermal crystal-to-amorphous phase transition of Ge2Sb2Te5 initiated by the displacements of Ge atoms. Above the fluence threshold, we found that the permanent amorphization caused by multi-displacement effects is accompanied by a partial hexagonal crystallization. PMID:26314613

  20. Ultrafast time-resolved electron diffraction revealing the nonthermal dynamics of near-UV photoexcitation-induced amorphization in Ge2Sb2Te5

    NASA Astrophysics Data System (ADS)

    Hada, Masaki; Oba, Wataru; Kuwahara, Masashi; Katayama, Ikufumi; Saiki, Toshiharu; Takeda, Jun; Nakamura, Kazutaka G.

    2015-08-01

    Because of their robust switching capability, chalcogenide glass materials have been used for a wide range of applications, including optical storages devices. These phase transitions are achieved by laser irradiation via thermal processes. Recent studies have suggested the potential of nonthermal phase transitions in the chalcogenide glass material Ge2Sb2Te5 triggered by ultrashort optical pulses; however, a detailed understanding of the amorphization and damage mechanisms governed by nonthermal processes is still lacking. Here we performed ultrafast time-resolved electron diffraction and single-shot optical pump-probe measurements followed by femtosecond near-ultraviolet pulse irradiation to study the structural dynamics of polycrystalline Ge2Sb2Te5. The experimental results present a nonthermal crystal-to-amorphous phase transition of Ge2Sb2Te5 initiated by the displacements of Ge atoms. Above the fluence threshold, we found that the permanent amorphization caused by multi-displacement effects is accompanied by a partial hexagonal crystallization.

  1. Ultrafast time-resolved electron diffraction revealing the nonthermal dynamics of near-UV photoexcitation-induced amorphization in Ge2Sb2Te5

    PubMed Central

    Hada, Masaki; Oba, Wataru; Kuwahara, Masashi; Katayama, Ikufumi; Saiki, Toshiharu; Takeda, Jun; Nakamura, Kazutaka G.

    2015-01-01

    Because of their robust switching capability, chalcogenide glass materials have been used for a wide range of applications, including optical storages devices. These phase transitions are achieved by laser irradiation via thermal processes. Recent studies have suggested the potential of nonthermal phase transitions in the chalcogenide glass material Ge2Sb2Te5 triggered by ultrashort optical pulses; however, a detailed understanding of the amorphization and damage mechanisms governed by nonthermal processes is still lacking. Here we performed ultrafast time-resolved electron diffraction and single-shot optical pump-probe measurements followed by femtosecond near-ultraviolet pulse irradiation to study the structural dynamics of polycrystalline Ge2Sb2Te5. The experimental results present a nonthermal crystal-to-amorphous phase transition of Ge2Sb2Te5 initiated by the displacements of Ge atoms. Above the fluence threshold, we found that the permanent amorphization caused by multi-displacement effects is accompanied by a partial hexagonal crystallization. PMID:26314613

  2. Direct observation of intrinsic piezoelectricity of Pb(Zr,Ti)O{sub 3} by time-resolved x-ray diffraction measurement using single-crystalline films

    SciTech Connect

    Fujisawa, Takashi; Ehara, Yoshitaka; Yasui, Shintaro; Kamo, Takafumi; Funakubo, Hiroshi; Yamada, Tomoaki; Sakata, Osami

    2014-07-07

    Lead zirconate titanate, Pb(Zr,Ti)O{sub 3} or PZT, is one of the most widely investigated ferroelectric and piezoelectric materials due to its superior properties. However, the intrinsic properties of PZT have not been directly measured due to the lack of fabrication of single crystals even though a basic understanding of intrinsic properties has been of interest developing lead-free piezoelectric materials. We demonstrated the direct observation of the intrinsic piezoelectric property by means of the detection of electric-field induced crystal lattice distortion of thick Pb(Zr{sub 0.35}Ti{sub 0.65})O{sub 3} single-crystalline films with single polar-axis orientation and negligible residual strain using the time-resolved X-ray diffraction (XRD) together with the polarization response. Consequently, the effective converse piezoelectric response was experimentally revealed; hence, the electrostrictive coefficient, which is the conversion coefficient between the electrical and mechanical response, was determined. The obtained effective electrostrictive coefficient was 5.2–6.3 × 10{sup −2} m{sup 4}/C{sup 2}, which agrees with theoretical prediction.

  3. Mapping Phase Transformations in the Heat-Affected-Zone of Carbon Manganese Steel Welds using Spatially Resolved X-Ray Diffraction

    SciTech Connect

    Elmer, J W; Wong, J; Ressler, T; Palmer, T A

    2001-12-04

    Spatially Resolved X-Ray Diffraction (SRXRD) was used to investigate phase transformations that occur in the heat affected zone (HAZ) of gas tungsten arc (GTA) welds in AISI 1005 carbon-manganese steel. In situ SRXRD experiments performed at the Stanford Synchrotron Radiation Laboratory (SSRL) probed the phases present in the HAZ during welding, and these real-time observations of the HAZ phases were used to construct a map of the phase transformations occurring in the HAZ. This map identified 5 principal phase regions between the liquid weld pool and the unaffected base metal for the carbon-manganese steel studied in this investigation. Regions of annealing, recrystallization, partial transformation and complete transformation to {alpha}-Fe, {gamma}-Fe, and {delta}-Fe phases were identified using SRXRD, and the experimental results were combined with a heat flow model of the weld to investigate transformation kinetics under both positive and negative temperature gradients in the HAZ. From the resulting phase transformation map, the kinetics of phase transformations that occur under the highly non-isothermal heating and cooling cycles produced during welding of steels can now be better understood and modeled.

  4. Mapping Phase Transformations in the Heat-Affected-Zone of Carbon Manganese Steel Welds using Spatially Resolved X-Ray Diffraction

    SciTech Connect

    Elmer, J W; Wong, J; Ressler, T; Palmer, T A

    2002-02-12

    Spatially Resolved X-Ray Diffraction (SRXRD) was used to investigate phase transformations that occur in the heat affected zone (HAZ) of gas tungsten arc (GTA) welds in AISI 1005 carbon-manganese steel. In situ SRXRD experiments performed at the Stanford Synchrotron Radiation Laboratory (SSRL) probed the phases present in the HAZ during welding, and these real-time observations of the HAZ phases were used to construct a map of the phase transformations occurring in the HAZ. This map identified 5 principal phase regions between the liquid weld pool and the unaffected base metal. Regions of annealing, recrystallization, partial transformation and complete transformation to {alpha}-Fe, {gamma}-Fe, and {delta}-Fe phases were identified using SRXRD, and the experimental results were combined with a heat flow model of the weld and thermodynamic calculations to compare these results with the important phase transformation isotherms. From the resulting phase transformation map, the kinetics of phase transformations that occur under the highly non-isothermal heating and cooling cycles produced during welding of steels can be better understood and modeled.

  5. Pulsed supercritical synthesis of anatase TiO2 nanoparticles in a water-isopropanol mixture studied by in situ powder X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Eltzholtz, Jakob Rostgaard; Tyrsted, Christoffer; Jensen, Kirsten Marie Ørnsbjerg; Bremholm, Martin; Christensen, Mogens; Becker-Christensen, Jacob; Iversen, Bo Brummerstedt

    2013-02-01

    A new step in supercritical nanoparticle synthesis, the pulsed supercritical synthesis reactor, is investigated in situ using synchrotron powder X-ray diffraction (PXRD) to understand the formation of nanoparticles in real time. This eliminates the common problem of transferring information gained during in situ studies to subsequent laboratory reactor conditions. As a proof of principle, anatase titania nanoparticles were synthesized in a 50/50 mixture of water and isopropanol near and above the critical point of water (P = 250 bar, T = 300, 350, 400, 450, 500 and 550 °C). The evolution of the reaction product was followed by sequentially recording PXRD patterns with a time resolution of less than two seconds. The crystallite size of titania is found to depend on both temperature and residence time, and increasing either parameter leads to larger crystallites. A simple adjustment of either temperature or residence time provides a direct method for gram scale production of anatase nanoparticles of average crystallite sizes between 7 and 35 nm, thus giving the option of synthesizing tailor-made nanoparticles. Modeling of the in situ growth curves using an Avrami growth model gave an activation energy of 66(19) kJ mol-1 for the initial crystallization. The in situ PXRD data also provide direct information about the size dependent macrostrain in the nanoparticles and with decreasing crystallite size the unit cell contracts, especially along the c-direction. This agrees well with previous ex situ results obtained for hydrothermal synthesis of titania nanoparticles.A new step in supercritical nanoparticle synthesis, the pulsed supercritical synthesis reactor, is investigated in situ using synchrotron powder X-ray diffraction (PXRD) to understand the formation of nanoparticles in real time. This eliminates the common problem of transferring information gained during in situ studies to subsequent laboratory reactor conditions. As a proof of principle, anatase titania

  6. In situ high-pressure synchrotron X-ray powder diffraction study of tunnel manganese oxide minerals: hollandite, romanechite, and todorokite

    NASA Astrophysics Data System (ADS)

    Hwang, Gil Chan; Post, Jeffrey E.; Lee, Yongjae

    2015-05-01

    In situ high-pressure synchrotron X-ray powder diffraction study of three tunnel manganese oxide minerals (hollandite with 2 × 2 MnO6 octahedra tunnels, romanechite with 2 × 3 tunnels, and todorokite with 3 × 3 tunnels) was performed using a diamond anvil cell and nominally penetrating alcohol and water mixture as a pressure-transmitting medium up to ~8 GPa. Bulk moduli ( B 0) calculated using Murnaghan's equation of state are inversely proportional to the size of the tunnel, i.e., 134(4) GPa for hollandite ( I2/m), 108(2) GPa for romanechite ( C2/m), and 67(5) GPa for todorokite ( P2/m). On the other hand, axial compressibilities show different elastic anisotropies depending on the size of the tunnel, i.e., ( a/ a 0) = -0.00066(3) GPa-1, ( b/ b 0) = 0.00179(8) GPa-1, ( c/ c 0) = 0.00637(4) GPa-1 [ c > b > a] for hollandite; ( a/ a 0) = 0.00485(4) GPa-1, ( b/ b 0) = 0.0016(1) GPa-1, ( c/ c 0) = 0.00199(8) GPa-1 [ a > c > b] for romanechite; and ( a/ a 0) = 0.00826(9) GPa-1, ( b/ b 0) = 0.0054(1) GPa-1, ( c/ c 0) = 0.00081(8) GPa-1 [ a > b > c] for todorokite. Overall, the degree of tunnel distortion increases with increasing pressure and correlates with the size of the tunnel, which is evidenced by the gradual increases in the monoclinic β angles up to 3 GPa of 0.62°, 0.8°, and 1.15° in hollandite, romanechite, and todorokite, respectively. The compression of tunnel manganese oxides is related to the tunnel distortion and the size of the tunnel.

  7. Crystal structures of spinel-type Na2MoO4 and Na2WO4 revisited using neutron powder diffraction.

    PubMed

    Fortes, A Dominic

    2015-06-01

    Time-of-flight neutron powder diffraction data have been collected from Na2MoO4 and Na2WO4 to a resolution of sin (θ)/λ = 1.25 Å(-1), which is substanti-ally better than the previous analyses using Mo Kα X-rays, providing roughly triple the number of measured reflections with respect to the previous studies [Okada et al. (1974 ▶). Acta Cryst. B30, 1872-1873; Bramnik & Ehrenberg (2004 ▶). Z. Anorg. Allg. Chem. 630, 1336-1341]. The unit-cell parameters are in excellent agreement with literature data [Swanson et al. (1962 ▶). NBS Monograph No. 25, sect. 1, pp. 46-47] and the structural parameters for the molybdate agree very well with those of Bramnik & Ehrenberg (2004 ▶). However, the tungstate structure refinement of Okada et al. (1974 ▶) stands apart as being conspicuously inaccurate, giving significantly longer W-O distances, 1.819 (8) Å, and shorter Na-O distances, 2.378 (8) Å, than are reported here or in other simple tungstates. As such, this work represents an order-of-magnitude improvement in precision for sodium molybdate and an equally substantial improvement in both accuracy and precision for sodium tungstate. Both compounds adopt the spinel structure type. The Na(+) ions have site symmetry .-3m and are in octa-hedral coordination while the transition metal atoms have site symmetry -43m and are in tetra-hedral coordination. PMID:26090129

  8. 5-Arylidene derivatives of Meldrum's acid: Synthesis, structural characterization using single crystal and powder crystal X-ray diffraction, and electronic properties

    NASA Astrophysics Data System (ADS)

    Dey, Tanusri; Ghosh, Soumen; Ghosh, Somnath; Mukherjee, Alok Kumar

    2015-07-01

    Four 5-arylidene derivatives of Meldrum's acid, 5-(4-chlorobenzylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione (2), 5-(3-hydroxybenzylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione (3), 5-(3,4-dimethoxybenzylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione (4) and 5-(2,4-dimethoxy benzylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione (5) have been synthesized and their crystal structures have been determined using single crystal X-ray diffractometry for 2, 4 and 5 and X-ray powder diffraction for 3. The nature of intermolecular interactions in 2-5 has been analyzed through Hirshfeld surfaces and 2D fingerprint plots. The DFT optimized molecular geometries in 2-5 agree closely with those obtained from the crystallographic studies. The crystal packing in 2-5 exhibits an interplay of Osbnd H⋯O, Csbnd H⋯O, Csbnd H⋯Cl and Csbnd H⋯π (arene) hydrogen bonds and π⋯π interactions, which assemble molecules into three-dimensional architecture in 2, 3 and 5 and two-dimensional framework in 4. The Hirshfeld surface analyses of 2-5, Meldrum's acid (1) and a few related 5-arylidene derivatives of Meldrum's acid retrieved from the Cambridge Structural Database (CSD) indicate that about 85% of the Hirshfeld surface area (72% in 2 where H⋯Cl contribution is about 13%) in this class of compounds are due to H⋯H, O⋯H and C⋯H contacts. The HOMO-LUMO energy gap (>2.2 eV) in 2-5 indicates a significant degree of internal charge transfer within the molecule.

  9. Crystal-structure analysis of four mineral samples of anhydrite, CaSO[subscript 4], using synchrotron high-resolution powder X-ray diffraction data

    SciTech Connect

    Antao, Sytle M.

    2014-05-28

    The crystal structures of four samples of anhydrite, CaSO{sub 4}, were obtained by Rietveld refinements using synchrotron high-resolution powder X-ray diffraction (HRPXRD) data and space group Amma. As an example, for one sample of anhydrite from Hants County, Nova Scotia, the unit-cell parameters are a = 7.00032(2), b = 6.99234(1), c = 6.24097(1) {angstrom}, and V = 305.487(1) {angstrom}{sup 3} with a > b. The eight-coordinated Ca atom has an average distance of 2.4667(4) {angstrom}. The tetrahedral SO{sub 4} group has two independent S-O distances of 1.484(1) to O1 and 1.478(1) {angstrom} to O2 and an average distance of 1.4810(5) {angstrom}. The three independent O-S-O angles [108.99(8) x 1, 110.38(3) x 4, 106.34(9){sup o} x 1; average [6] = 109.47(2){sup o}] and S-O distances indicate that the geometry of the SO{sub 4} group is quite distorted in anhydrite. The four anhydrite samples have structural trends where the a, b, and c unit-cell parameters increase linearly with increasing unit-cell volume, V, and their average and distances are nearly constant. The grand mean = 2.4660(2) {angstrom}, and grand mean = 1.4848(3) {angstrom}, the latter is longer than 1.480(1) {angstrom} in celestite, SrSO{sub 4}, as expected.

  10. Hidden Superlattice in Tl2(SC6H4S) and Tl2(SeC6H4Se) Solved from Powder X-ray Diffraction

    SciTech Connect

    K Stone; D Turner; M Singh; T Vaid; P Stephens

    2011-12-31

    The crystal structures of the isostructural title compounds poly[({mu}-benzene-1,4-dithiolato)dithallium], Tl{sub 2}(SC{sub 6}H{sub 4}S), and poly[({mu}-benzene-1,4-diselenolato)dithallium], Tl{sub 2}(SeC{sub 6}H{sub 4}Se), were solved by simulated annealing from high-resolution synchrotron X-ray powder diffraction. Rietveld refinements of an initial structure with one formula unit per triclinic cell gave satisfactory agreement with the data, but led to a structure with impossibly close non-bonded contacts. A disordered model was proposed to alleviate this problem, but an alternative supercell structure leads to slightly improved agreement with the data. The isostructural superlattice structures were confirmed for both compounds through additional data collection, with substantially better counting statistics, which revealed the presence of very weak superlattice peaks not previously seen. Overall, each structure contains Tl-S or Tl-Se two-dimensional networks, connected by phenylene bridges. The sulfur (or selenium) coordination sphere around each thallium is a highly distorted square pyramid or a 'see-saw' shape, depending upon how many Tl-S or Tl-Se interactions are considered to be bonds. In addition, the two compounds contain pairs of Tl{sup I} ions that interact through a closed-shell 'thallophilic' interaction: in the sulfur compound there are two inequivalent pairs of Tl atoms with Tl-Tl distances of 3.49 and 3.58 {angstrom}, while in the selenium compound those Tl-Tl interactions are at 3.54 and 3.63 {angstrom}.

  11. Crystal structures of spinel-type Na2MoO4 and Na2WO4 revisited using neutron powder diffraction

    PubMed Central

    Fortes, A. Dominic

    2015-01-01

    Time-of-flight neutron powder diffraction data have been collected from Na2MoO4 and Na2WO4 to a resolution of sin (θ)/λ = 1.25 Å−1, which is substanti­ally better than the previous analyses using Mo Kα X-rays, providing roughly triple the number of measured reflections with respect to the previous studies [Okada et al. (1974 ▸). Acta Cryst. B30, 1872–1873; Bramnik & Ehrenberg (2004 ▸). Z. Anorg. Allg. Chem. 630, 1336–1341]. The unit-cell parameters are in excellent agreement with literature data [Swanson et al. (1962 ▸). NBS Monograph No. 25, sect. 1, pp. 46–47] and the structural parameters for the molybdate agree very well with those of Bramnik & Ehrenberg (2004 ▸). However, the tungstate structure refinement of Okada et al. (1974 ▸) stands apart as being conspicuously inaccurate, giving significantly longer W—O distances, 1.819 (8) Å, and shorter Na—O distances, 2.378 (8) Å, than are reported here or in other simple tungstates. As such, this work represents an order-of-magnitude improvement in precision for sodium molybdate and an equally substantial improvement in both accuracy and precision for sodium tungstate. Both compounds adopt the spinel structure type. The Na+ ions have site symmetry .-3m and are in octa­hedral coordination while the transition metal atoms have site symmetry -43m and are in tetra­hedral coordination. PMID:26090129

  12. Neutron and X-ray powder diffraction study of RBa{sub 2}Fe{sub 3}O{sub 8+w} phases

    SciTech Connect

    Karen, P.; Kjekshus, A.; Huang, Q.; Lynn, J.W.; Rosov, N.; Sora, I.N.; Karen, V.L.; Mighell, A.D.; Santoro, A.

    1998-02-15

    Compounds of composition RBa{sub 2}Fe{sub 3}O{sub 8+w} (R = La, Nd, Sm, Gd, Dy, Er, Yb, Lu, and Y) with variable oxygen content have been synthesized using the liquid mixing technique and have been analyzed by powder X-ray and neutron diffraction methods. A triple perovskite-type structure with ordered Ba and R cations and having the symmetry of space group P4/mmm was obtained only for R = Y, Dy, and Er, whereas the larger R atoms gave the atomic arrangement of disordered, defective perovskites with average symmetry Pm{bar 3}m. No perovskite-type phases were obtained when Yb and Lu were tried. The oxygen content of the oxygen-saturated phases was found to increase with increasing size of the cation R from w = 0.07 for Er to w = 0.83 for La. The Neel temperature ({approximately}650 K) and the magnitude of the Fe magnetic moment ({approximately}3.3 {mu}{sub B} at room temperature) are highest when trivalent iron is involved (w = 0), but these quantities are rather insensitive to the nature of R and to slight variations of oxygen content in the triple perovskite-type structure of the Y, Dy, and Er compounds. In the case of the cubic structures, however, both quantities depend strongly on the oxygen stoichiometry. In the magnetically ordered state, nearest-neighbor iron moments are coupled antiferromagnetically along the three crystallographic directions in all samples, resulting in magnetic structures with symmetry Imm{prime}m and magnetic unit cells related to those of the corresponding nuclear structures by the transformation matrix (1{bar 1}0/110/002).

  13. Crystal Structure Refinement of Mg 5Nb 4O 15and Mg 5Ta 4O 15by Rietveld Analysis of Neutron Powder Diffraction Data

    NASA Astrophysics Data System (ADS)

    Pagola, S.; Carbonio, R. E.; Fernández-Díaz, M. T.; Alonso, J. A.

    1998-05-01

    The crystal structure of the isomorphous phases Mg5Nb4O15and Mg5Ta4O15was refined from neutron powder diffraction data. These compounds are isostructural with pseudobrookite, Fe2TiO5. The two kinds of metal sites of this structure are randomly occupied by Mg(II) and Nb(V) or Ta(V). The structure consists of double chains of (Mg,M)O6units (whereM=Nb or Ta), sharing edges on thebcplane, interconnected through common oxygens along theaaxis to give a three-dimensional array. The (Mg,M)O6polyhedra at both metal positions can be described as very distorted octahedra, with (Mg,M)-O distances ranging from 1.93 to 2.22 Å. The crystallographic formulas can be written as (Mg0.73(2)Nb0.27(2))4c(Mg0.94(2)Nb1.06(2))8fO5and (Mg0.66(2)Ta0.34(2))4c(Mg1.01(2)Ta0.99(2))8fO5respectively, where 4c and 8f are the Wyckoff sites of the two metal positions of the structure. The space group is Cmcm (orthorhombic) andZ=4. Unit cell parameters, cell volume,RwpandRIvalues obtained werea=3.8068(1) Å,b=10.0561(1) Å,c=10.2566(1) Å,V=392.64(2) Å3, and 6.72% and 2.94% for the niobium compound; anda=3.81884(6) Å,b=10.0574(2) Å,c=10.2343(2) Å,V=393.07(2) Å3, and 4.46%, and 2.36% for the tantalum compound.

  14. In Situ X-ray Diffraction of Forsterite Under Shock Compression to 52 GPa: Time Resolved Observation of Changes in Crystal Structure and Phase

    NASA Astrophysics Data System (ADS)

    Akin, M. C.; Maddox, B.; Teruya, A.; Asimow, P. D.

    2015-12-01

    The Earth's mantle is composed primarily of ferromagnesian silicates, of which Forsterite (Fo) is the magnesium-rich end member of the dominant upper mantle phase, olivine. Fo is thought to undergo a chemical decomposition associated with a structural phase transition when dynamically loaded to 40-71 GPa, but previous inferences about such decomposition have been based only on pressure-density data with no direct phase identification. To obtain direct data on the phase evolution of shocked Fo, synthetic single crystal samples of Mg2SiO4 Fo were loaded to pressures of 52 GPa using a two stage light gas gun. X-ray diffraction (XRD) patterns were collected on the static and the loaded samples in situ using a single pulse Mo Kα anode to provide a 17 keV X-ray source. X-ray polycapillary optics were used to couple the source to the sample. Clear Laue spots were observed in the static images, while the dynamic images show the appearance of new spots at early times and powder-like rings at late times. The angles of the dynamically driven spots and rings overlap with each other and indicate the change in phase of forsterite under pressure through a process that begins with the formation of single crystals and ends with polycrystalline material. Efforts are underway to identify the high-pressure phases from among the library of dense magnesium silicates, and further experiments covering a larger pressure range will be completed shortly. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  15. Cation Movements during Dehydration and NO2 Desorption in a Ba-Y,FAU zeolite: an in situ Time-resolved X-ray Diffraction Study

    SciTech Connect

    Wang, Xianqin; Hanson, Jonathan C.; Kwak, Ja Hun; Szanyi, Janos; Peden, Charles HF

    2013-02-28

    Synchrotron-based in situ time-resolved X-ray diffraction and Rietveld analysis were used to probe the interactions between BaY, FAU zeolite frameworks and H2O or NO2 molecules. These results provided information about the migration of the Ba2+ cations in the zeolite framework during dehydration and during NO2 adsorption/desorption processes in a water free zeolite. In the hydrated structure water molecules form four double rings of hexagonal ice-like clusters [(H2O)6] in the 12-ring openings of the super-cage. These water rings interacted with the cations and the zeolite framework through four cation/water clusters centered over the four 6-membered rings of the super-cage (site II). Interpenetrating tetrahedral water clusters [(H2O)4] and tetrahedral Ba+2 cation clusters were observed in the sodalite cage. Consistent with the reported FT-IR results, three different ionic NOx species (NO+, NO+-NO2, and NO3-) were observed following NO2 adsorption by the dehydrated Ba-Y,FAU zeolite. The structure of the water and the NOx species were correlated with the interactions between the adsorbates, the cations, and the framework. The population of Ba2+ ions at different cationic positions strongly depended on the amount of bound water or NOx species. Both dehydration and NO2 adsorption/desorption resulted in facile migration of Ba2+ ions among the different cationic positions. Data obtained in this work have provided direct evidence for the Ba2+ cation migration to accommodate the binding of gas molecules. This important feature may play a pivotal role in the strong binding of NO2 to Ba-Y,FAU zeolite, a prerequisite for high catalytic activity in lean NOx reduction catalysis.

  16. Effects of quartz particle size and water-to-solid ratio on hydrothermal synthesis of tobermorite studied by in-situ time-resolved X-ray diffraction

    SciTech Connect

    Kikuma, J.; Tsunashima, M.; Ishikawa, T.; Matsuno, S.; Ogawa, A.; Matsui, K.; Sato, M.

    2011-08-15

    Hydrothermal synthesis process of tobermorite (5CaO.6SiO{sub 2}.5H{sub 2}O) has been investigated by in-situ X-ray diffraction using high-energy X-rays from a synchrotron radiation source in combination with a purpose-build autoclave cell. Dissolution rates of quartz were largely affected by its particle size distribution in the starting mixtures. However, the composition (Ca/Si) of non-crystalline C-S-H at the start of tobermorite formation was identical regardless of the quartz dissolution rate. An effect of water-to-solid ratio (w/s) was investigated for samples using fine particle quartz. Tobermorite did not occur with w/s of 1.7 but occurred with w/s higher than 3.0. Surprisingly, however, the dissolution curves of quartz were nearly identical for all samples with w/s from 1.7 to 9, indicating that the dissolution rate is predominated by surface area. Possible reaction mechanism for tobermorite formation will be discussed in terms of Ca and/or silicate ion concentration in the liquid phase and distribution of Ca/Si in non-crystalline C-S-H. - Graphical abstract: Time-resolved XRD data set was obtained at up to 190 deg. C under a saturated steam pressure. Tobermorite (5CaO.6SiO{sub 2}.5H{sub 2}O) formation reaction was investigated in detail for several different starting materials. Highlights: > Hydrothermal formation of tobermorite was monitored by in-situ XRD. > Ca/Si of C-S-H at the start time of tobermorite formation was determined. > The Ca/Si value was identical regardless of the quartz particle size in the starting mixture.

  17. Investigation of real-time microstructure evolution in steep thermal gradients using in-situ spatially resolved X-ray diffraction: A case study for Ti fusion welds

    SciTech Connect

    Ressler, T.; Wong, J.; Elmer, J.W. |

    1998-12-24

    A recently developed spatially resolved X-ray diffraction (SRXRD) technique utilizing intense synchrotron radiation has been refined to yield phase and microstructural information down to 200 {micro}m in spatial extent in materials subjected to steep thermal gradients during processing. This SRXRD technique has been applied to map completely the phases and their solid-state transformation in the so-called heat-affected zone (HAZ) in titanium fusion welds in situ during the welding process. Detailed profile analysis of the SRXRD patterns revealed four principal microstructural regions at temperature in the vicinity of the HAZ surrounding the liquid weld pool: (i) a completely transformed {beta}-Ti zone 2--3 mm adjacent to the liquid weld pool; (ii) a mixed {alpha} + {beta}-it region surrounding the pure {beta}-Ti zone, (iii) a back-transformed {alpha}-Ti zone on the backside of the HAZ where pure {beta}-Ti once existed at temperature well above the {alpha} {r_arrow} {beta} transformation isotherm, and (iv) a more diffused region outside the HAZ where annealing and recrystallization of the {alpha}-it base metal occur. The high-temperature microstructures so derived corroborate well the expected transformation kinetics in pure titanium, and the observed phase transformation boundaries are in good agreement with those predicted from the transformation isotherms calculated from a simplified heat-flow model. Based on a detailed assessment of the SRXRD setup employed, improved experimentations such as a smaller beam spot emitted from third generation synchrotron sources, better mechanical stability (tighter scattering geometry), and use of an area detector would enable more quantitative structural information for future phase dynamics studies exemplified by this work.

  18. Application of Powder Diffraction Methods to the Analysis of Short- and Long-Range Atomic Order in Nanocrystalline Diamond and SiC: The Concept of the Apparent Lattice Parameter (alp)

    NASA Technical Reports Server (NTRS)

    Palosz, B.; Grzanka, E.; Gierlotka, S.; Stelmakh, S.; Pielaszek, R.; Bismayer, U.; Weber, H.-P.; Palosz, W.

    2003-01-01

    Two methods of the analysis of powder diffraction patterns of diamond and SiC nanocrystals are presented: (a) examination of changes of the lattice parameters with diffraction vector Q ('apparent lattice parameter', alp) which refers to Bragg scattering, and (b), examination of changes of inter-atomic distances based on the analysis of the atomic Pair Distribution Function, PDF. Application of these methods was studied based on the theoretical diffraction patterns computed for models of nanocrystals having (i) a perfect crystal lattice, and (ii), a core-shell structure, i.e. constituting a two-phase system. The models are defined by the lattice parameter of the grain core, thickness of the surface shell, and the magnitude and distribution of the strain field in the shell. X-ray and neutron experimental diffraction data of nanocrystalline SiC and diamond powders of the grain diameter from 4 nm up to micrometers were used. The effects of the internal pressure and strain at the grain surface on the structure are discussed based on the experimentally determined dependence of the alp values on the Q-vector, and changes of the interatomic distances with the grain size determined experimentally by the atomic Pair Distribution Function (PDF) analysis. The experimental results lend a strong support to the concept of a two-phase, core and the surface shell structure of nanocrystalline diamond and SiC.

  19. Nepheline: Structure of Three Samples from the Bancroft Area, Ontario, Obtained using Synchrotron High-Resolution Powder X-Ray Diffraction

    SciTech Connect

    Antao, Sytle M.; Hassan, Ishmael

    2010-05-25

    The crystal structure of three samples of nepheline (ideally, K{sub 2}Na{sub 6}[Al{sub 8}Si{sub 8}O{sub 32}]) from the Bancroft area of Ontario (1a, b: Egan Chute, 2: Nephton, and 3: Davis Hill), each with different types of superstructure reflections, has been studied using synchrotron high-resolution powder X-ray diffraction (HRPXRD) data and Rietveld structure refinement. The samples have different origins. The structure was refined in space group P6{sub 3}. The R{sub F}{sup 2} index, number of unique observed reflections, pseudohexagonal subcell parameters, and site-occupancy factor (sof) for the K site are as follows: Sample 1b: R{sub F}{sup 2} = 0.0433, N{sub obs} = 1399, a = 9.99567(1), c = 8.37777(1) {angstrom}, V = 724.907(2) {angstrom}{sub 3}, and K (sof) = 0.716(1). Sample 2: R{sub F}{sup 2} = 0.0669, N{sub obs} = 1589, a = 10.00215(1), c = 8.38742(1) {angstrom}, V = 726.684(1) {angstrom}{sub 3}, and K (sof) = 0.920(1). Sample 3: R{sub F}{sup 2} = 0.0804, N{sub obs} = 1615, a = 9.99567(1), c = 8.37873(1) {angstrom}, V = 724.991(1) {angstrom}{sub 3}, and K (sof) = 0.778(2). Sample 2 has the largest sof for K and the largest volume. The satellite reflections in the three nepheline samples were observed in the HRPXRD traces and give rise to different incommensurate superstructures. The Al and Si atoms in the T{sub 3} and T{sub 4} sites are ordered differently in the three samples, which may indicate the presence of a domain structure based on Al-Si order. The positions for the Al and Si atoms were interchanged in two samples because of the resulting distances. The slight excess of Si over Al atoms, characteristically encountered in well-analyzed samples of nepheline, is reflected in the distances.

  20. Neutron powder diffraction study of the layer organic-inorganic hybrid iron(II) methylphosphonate-hydrate, Fe[(CD{sub 3}PO{sub 3})(D{sub 2}O)

    SciTech Connect

    Leone, Philippe Bellitto, Carlo; Bauer, Elvira M.; Righini, Guido; Andre, Gilles; Bouree, Francoise

    2008-11-15

    The crystal and magnetic structures of the hybrid organic-inorganic layer compound Fe[(CD{sub 3}PO{sub 3})(D{sub 2}O)] have been studied by neutron powder diffraction as a function of temperature down to 1.5 K. The neutron diffraction pattern recorded at 200 K shows that the fully deuterated compound crystallizes in one of the two known forms of the undeuterated Fe[(CH{sub 3}PO{sub 3})(H{sub 2}O)]. The crystal structure is orthorhombic, space group Pmn2{sub 1}, with the following unit-cell parameters: a=5.7095(1) A, b=8.8053(3) A and c=4.7987(1) A; Z=2. The crystal structure remains unchanged on cooling from 200 to 1.5 K. Moreover, at low temperature, Fe[(CD{sub 3}PO{sub 3})(D{sub 2}O)] shows a commensurate magnetic structure (k=(0,0,0)). As revealed by bulk susceptibility measurements on Fe[(CH{sub 3}PO{sub 3})(H{sub 2}O)], the magnetic structure corresponds to a canted antiferromagnet with a critical temperature T{sub N}=25 K. Neutron powder diffraction reveals that below T{sub N}=23.5 K the iron magnetic moments in Fe[(CD{sub 3}PO{sub 3})(D{sub 2}O)] are antiferromagnetically coupled and oriented along the b-axis, perpendicular to the inorganic layers. No ferromagnetic component is observable in the neutron powder diffraction experiment, due to its too small value (<0.1{mu}{sub B}). - Graphical abstract: Crystal structure and magnetic structure of Fe[(CD{sub 3}PO{sub 3})(D{sub 2}O)].

  1. Neutron diffraction studies of Gd 2Zr 2O 7 pyrochlore

    NASA Astrophysics Data System (ADS)

    Kennedy, Brendan J.; Zhou, Qingdi; Avdeev, Maxim

    2011-07-01

    The structure of Gd 2Zr 2O 7 pyrochlore over the temperature range 4-300 K has been refined from powder neutron diffraction data. The sample was enriched in 160Gd to avoid the high neutron absorption of naturally occurring Gd. The diffraction pattern showed well resolved superlattice reflections indicative of the pyrochlore structure and no evidence is found for anion-disorder from the structural refinements.

  2. Isothermal nucleation and growth kinetics of Pd/Ag alloy phase via in-situ time-resolved high-temperature x-ray diffraction (HTXRD) analysis

    SciTech Connect

    Ayturk, Mahmut Engin; Payzant, E Andrew; Speakman, Scott A; Ma, Yi Hua

    2008-01-01

    Among several different approaches to form Pd/Ag alloys for hydrogen separation applications, ex-situ studies carried by conventional X-ray point scanning detectors might fail to reveal the key aspects of the phase transformation between Pd and Ag metals. In this respect, in-situ time-resolved high temperature X-ray diffraction (HTXRD) was employed to study the Pd/Ag alloy phase nucleation and growth kinetics. By the use of linear position sensitive detectors, advanced optics and profile fitting with the use of JADE-6.5 software, isothermal phase evolution of the Pd/Ag alloy at 500 C, 550 C and 600 C under hydrogen atmosphere were quantified to elucidate the mechanistic details of the Pd/Ag alloy phase nucleation and growth pattern. Analysis of the HTXRD data by the Avrami model indicated that the nucleation of the Pd/Ag alloy phase was instantaneous where the growth mechanism was through diffusion-controlled one-dimensional thickening of the Pd/Ag alloy layer. The value of the Avrami exponent, n, was found to increase with temperature with the values of 0.34, 0.39 and 0.67 at 500oC, 550oC and 600oC, respectively. In addition, parabolic rate law analysis suggested that the nucleation of the Pd/Ag alloy phase was through a heterogeneous nucleation mode, in which the nucleation sites were defined as the non-equilibrium defects. The cross-sectional SEI micrographs indicated that the Pd/Ag alloy phase growth was strongly dependent upon the deposition morphology of the as-synthesized Pd and Ag layers formed by the electroless plating. Based on the Avrami model and the parabolic rate law, the estimated activation energies for the phase transformation were 236.5 and 185.6 kJ/mol and in excellent agreement with the literature values (183-239.5 kJ/mol).

  3. Dynamics of phase transformations and microstructure evolution in carbon-manganese steel arc welds using time-resolved synchrotron X-ray diffraction.

    PubMed

    Wong, Joe; Ressler, Thorsten; Elmer, John W

    2003-03-01

    Phase transformations that occur in both the heat-affected zone (HAZ) and the fusion zone (FZ) of a carbon-manganese steel spot weld have been investigated using time-resolved X-ray diffraction (TRXRD) with time resolutions down to 50 ms. It is found that in both zones the gamma(f.c.c.) --> alpha(b.c.c.) transformation on cooling is twice as fast as the forward transformation of alpha --> gamma on heating. Profile analysis of the major Bragg reflections recorded in the TRXRD patterns reveals similarities and differences in the microstructural evolution with time in the HAZ and in the FZ. The latter undergoes melting and solidification in addition to solid-state transformations. With increasing temperature, the (110) d-spacing of the alpha phase prior to and during the alpha --> gamma transformation and the (111) d-spacing of the gamma phase just after the same transformation exhibit a decrease. The observed (and unusual) lattice contraction with temperature rise may be attributed to chemical effects, such as carbide precipitation in the alpha matrix, and/or mechanical effects due to stress relief. In the FZ, the gamma-Fe that forms has a preferential (200) texture on solidification of the liquid, whereas, on cooling in the HAZ, the gamma-Fe retains largely a (111) texture that is induced in the alpha --> gamma transformation on heating. On cooling in the HAZ, the width of the gamma(111) reflection increases initially, which is indicative of microstrain developing in the f.c.c. lattice, but decreases as expected, with a reduction of thermal disorder, on further cooling until the completion of the gamma --> alpha transformation. In the FZ, however, the microstrain in the gamma phase increases steadily on solidification and more rapidly for the duration of the gamma --> alpha transformation on further cooling. The final microstructure of the FZ is likely to consist of a single alpha phase dispersed in two morphological entities, whereas in the HAZ the alpha phase

  4. A second polymorph of sodium di­hydrogen citrate, NaH2C6H5O7: structure solution from powder diffraction data and DFT comparison

    PubMed Central

    Rammohan, Alagappa; Kaduk, James A.

    2016-01-01

    The crystal structure of a second polymorph of sodium di­hydrogen citrate, Na+·H2C6H5O7 −, has been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. The powder pattern of the commercial sample used in this study did not match that corresponding to the known crystal structure [Glusker et al. (1965). Acta Cryst. 19, 561–572; refcode NAHCIT]. In this polymorph, the [NaO7] coordination polyhedra form edge-sharing chains propagating along the a axis, while in NAHCIT the octa­hedral [NaO6] groups form edge-sharing pairs bridged by two hy­droxy groups. The most notable difference is that in this polymorph one of the terminal carboxyl groups is deprotonated, while in NAHCIT the central carboxyl­ate group is deprotonated, as is more typical. PMID:27308058

  5. Ab-initio crystal structure of hydroxy adipate of nickel and hydroxy subarate of nickel and cobalt from synchrotron powder diffraction and magnetic properties

    SciTech Connect

    Mesbah, Adel; Carton, Anne; Aranda, Lionel; Mazet, Thomas; Porcher, Florence; Francois, Michel

    2008-12-15

    Organic-inorganic hybrid compounds Ni(II){sub 5}(OH){sub 6}(C{sub 6}H{sub 8}O{sub 4}){sub 2}(1), Ni(II){sub 5}(OH){sub 6}(C{sub 8}H{sub 12}O{sub 4}){sub 2}(2) and Co(II){sub 5}(OH){sub 6}(C{sub 8}H{sub 12}O{sub 4}){sub 2}(3) have a similar layered structure as determined ab initio from synchrotron powder diffraction analysis. The metal sites are octahedrally coordinated by O atoms. The slabs are built from edge-sharing octahedra in such a way that channels with an average size of 4 A are formed. Bis-bidentate and bridging dicarboxylate anions lead to a 3D framework. The compounds (1) and (2) order antiferromagnetically below T{sub N}=26.5 and 19.3 K, respectively, while (3) is ferrimagnetic with T{sub C}=16.2 K. Crystal data for compounds are as follows: (1)a=11.6504(1) A, b=6.8021(3) A, c=6.3603(1) A, {alpha}=73.52(1){sup o}, {beta}=99.69(1){sup o}, {gamma}=96.16(1){sup o}, R{sub B}=0.070, 668 reflections; (2)a=13.9325(1) A, b=6.7893(1) A, c=6.3534(4) A, {alpha}=73.63(1){sup o}, {beta}=95.14(1){sup o}, {gamma}=91.80(1){sup o}, R{sub B}=0.052, 804 reflections; (3)a=13.9806(1) A, b=6.9588(1) A, c=6.3967(1) A, {alpha}=73.05(1){sup o}, {beta}=94.51(1){sup o}, {gamma}=92.19(1){sup o}, R{sub B}=0.048, 410 reflections. The space group is P-1 for the three compounds. - Graphical abstract: The hybrid metal-organic compounds Ni(II){sub 5}(OH){sub 6}(C{sub 6}H{sub 8}O{sub 4}){sub 2}(1), Ni(II){sub 5}(OH){sub 6}(C{sub 8}H{sub 12}O{sub 4}){sub 2}(2) and Co(II){sub 5}(OH){sub 6}(C{sub 8}H{sub 12}O{sub 4}){sub 2}(3) have been synthesized by the hydrothermal route. The microporous metal hydroxide layers are bridged by dicarboxylates anions. (1) and (2) are antiferromagnetic with T{sub N}=26.5 and 19.3 K, respectively, while (3) is ferrimagnetic with T{sub C}=16.2 K.

  6. Confirmation of the monoclinic Cc space group for the ground state phase of Pb(Zr0.525Ti0.475)O3: A combined synchrotron X-ray and neutron powder diffraction study

    NASA Astrophysics Data System (ADS)

    Singh Solanki, Ravindra; Kumar Mishra, Sunil; Senyshyn, Anatoliy; Yoon, Songhak; Baik, Sunggi; Shin, Namsoo; Pandey, Dhananjai

    2013-02-01

    The low temperature antiferrodistortive phase transition in a pseudo-tetragonal composition of Pb(ZrxTi1-x)O3 (PZT) with x = 0.525 is investigated through a combined synchrotron x-ray and neutron powder diffraction study. It is shown that the superlattice peaks cannot be correctly accounted for in the Rietveld refinement using R3c or R3c + Cm structural models, whereas the Cc space group gives excellent fits to the superlattice peaks as well as to the perovskite peaks. This settles at rest the existing controversies about the structure of the ground state phase of PZT in the morphotropic phase boundary region.

  7. Hydrogenation properties of Li{sub x}Sr{sub 1−x}AlSi studied by quantum-chemical methods (0≤x≤1) and in-situ neutron powder diffraction (x=1)

    SciTech Connect

    Kunkel, Nathalie; Reichert, Christian; Springborg, Michael; Wallacher, Dirk; Kohlmann, Holger

    2015-01-15

    In-situ neutron powder diffraction studies of the Half-Heusler phase LiAlSi under high deuterium pressures and first principle calculations of solid solutions of Li{sub x}Sr{sub 1−x}AlSi and their hydrides Li{sub x}Sr{sub 1−x}AlSiH were carried out. In contrast to an earlier study, there is no experimental evidence for hydrogen (deuterium) uptake up to gas pressures of 15 MPa and temperatures of 550 °C. Instead a slow decomposition reaction according to LiAlSi+1/2H{sub 2}=LiH+Al+Si was found by in-situ neutron powder diffraction. Theoretical calculations by DFT methods on hypothetical solid solutions of Li{sub x}Sr{sub 1−x}AlSi show the LiAlSi type to be the energetically most stable structure for 0.7powder diffraction of LiAlSi under high D{sub 2} pressure. - Highlights: • In-situ neutron powder diffraction of LiAlSi under high D{sub 2} pressure was carried out. • LiAlSi decomposes according to LiAlSi + ½ H{sub 2} = LiH + Al + Si. • Mixed crystals Li{sub x}Sr{sub 1-x}AlSi and LixSr{sub 1-x}AlSiH were studied theoretically.

  8. Structural properties of a family of hydrogen-bonded co-crystals formed between gemfibrozil and hydroxy derivatives of t-butylamine, determined directly from powder X-ray diffraction data

    NASA Astrophysics Data System (ADS)

    Cheung, Eugene Y.; David, Sarah E.; Harris, Kenneth D. M.; Conway, Barbara R.; Timmins, Peter

    2007-03-01

    We report the formation and structural properties of co-crystals containing gemfibrozil and hydroxy derivatives of t-butylamine H 2NC(CH 3) 3-n(CH 2OH) n, with n=0, 1, 2 and 3. In each case, a 1:1 co-crystal is formed, with transfer of a proton from the carboxylic acid group of gemfibrozil to the amino group of the t-butylamine derivative. All of the co-crystal materials prepared are polycrystalline powders, and do not contain single crystals of suitable size and/or quality for single crystal X-ray diffraction studies. Structure determination of these materials has been carried out directly from powder X-ray diffraction data, using the direct-space Genetic Algorithm technique for structure solution followed by Rietveld refinement. The structural chemistry of this series of co-crystal materials reveals well-defined structural trends within the first three members of the family ( n=0, 1, 2), but significantly contrasting structural properties for the member with n=3.

  9. High temperature phase stability in Li{sub 0.12}Na{sub 0.88}NbO{sub 3}: A combined powder X-ray and neutron diffraction study

    SciTech Connect

    Mishra, S. K.; Krishna, P. S. R.; Shinde, A. B.; Jayakrishnan, V. B.; Mittal, R.; Sastry, P. U.; Chaplot, S. L.

    2015-09-07

    The phase stabilities of ecofriendly piezoelectric material of lithium doped sodium niobate for composition Li{sub 0.12}Na{sub 0.88}NbO{sub 3} (LNN12) have been investigated by a combination of powder X-ray and neutron diffraction techniques in the temperature range of 300–1100 K. We observed interesting changes with appearance or disappearance of the super-lattice reflections in the powder diffraction patterns. Unambiguous experimental evidence is shown for coexistence of paraelectric and ferroelectric orthorhombic phases in the temperature range of 525 K to 675 K. We identified the correct crystal structure of LNN12 with temperature and correlated it with observed anomaly in the physical properties. Identification of crystal structure also helps in the mode assignments in Raman and infrared spectroscopies. We argued that application of chemical pressure as a result of Li substitution in NaNbO{sub 3} matrix favors the freezing of zone centre phonons in contrast to the freezing of zone boundary phonons in pure NaNbO{sub 3} with the variation of temperature.

  10. Cation substitution in synthetic meridianiite (MgSO4·11H2O) I: X-ray powder diffraction analysis of quenched polycrystalline aggregates

    NASA Astrophysics Data System (ADS)

    Fortes, A. Dominic; Browning, Frank; Wood, Ian G.

    2012-05-01

    Meridianiite, MgSO4·11H2O, is the most highly hydrated phase in the binary MgSO4-H2O system. Lower hydrates in the MgSO4-H2O system have end-member analogues containing alternative divalent metal cations (Ni2+, Zn2+, Mn2+, Cu2+, Fe2+, and Co2+) and exhibit extensive solid solution with MgSO4 and with one another, but no other undecahydrate is known. We have prepared aqueous MgSO4 solutions doped with these other cations in proportions up to and including the pure end-members. These liquids have been solidified into fine-grained polycrystalline blocks of metal sulfate hydrate + ice by rapid quenching in liquid nitrogen. The solid products have been characterised by X-ray powder diffraction, and the onset of partial melting has been quantified using a thermal probe. We have established that of the seven end-member metal sulfates studied, only MgSO4 forms an undecahydrate; ZnSO4 forms an orthorhombic heptahydrate (synthetic goslarite), MnSO4, FeSO4, and CoSO4 form monoclinic heptahydrates (syn. mallardite, melanterite, bieberite, respectively), and CuSO4 crystallises as the well-known triclinic pentahydrate (syn. chalcanthite). NiSO4 forms a new hydrate which has been indexed with a triclinic unit cell of dimensions a = 6.1275(1) Å, b = 6.8628(1) Å, c = 12.6318(2) Å, α = 92.904(2)°, β = 97.678(2)°, and γ = 96.618(2)°. The unit-cell volume of this crystal, V = 521.74(1) Å3, is consistent with it being an octahydrate, NiSO4·8H2O. Further analysis of doped specimens has shown that synthetic meridianiite is able to accommodate significant quantities of foreign cations in its structure; of the order 50 mol. % Co2+ or Mn2+, 20-30 mol. % Ni2+ or Zn2+, but less than 10 mol. % of Cu2+ or Fe2+. In three of the systems we examined, an `intermediate' phase occurred that differed in hydration state both from the Mg-bearing meridianiite end-member and the pure dopant end-member hydrate. In the case of CuSO4, we observed a melanterite-structured heptahydrate at Cu

  11. Nanosecond Time Resolved Electron Diffraction Studies of the (Alpha) to (Beta) Transition in Pure Ti Thin Films using the Dynamic Transmission Electron Microscope (DTEM)

    SciTech Connect

    LaGrange, T; Campbell, G H; Colvin, J D; Reed, B; King, W E

    2005-12-09

    The transient events of the {alpha}-{beta} martensitic transformation in nanocrystalline Ti films were explored via single shot electron diffraction patterns with 1.5 ns temporal resolution. The diffraction patterns were acquired with a newly constructed dynamic transmission electron microscope (DTEM), which combines nanosecond pulsed laser systems and pump-probe techniques with a conventional TEM. With the DTEM, the transient events of fundamental material processes, that are far too fast to be studied by conventional bulk techniques, can be captured in the form of electron diffraction patterns or images with nanosecond temporal resolution. The transient phenomena of the martensitic transformations in nanocrystalline Ti is ideally suited for study in the DTEM, with their rapid nucleation, characteristic interface velocities {approx}1 km/s, and significant irreversible microstructural changes. Free-standing 40-nm-thick Ti films were laser-heated at a rate of {approx}10{sup 10} K/s to a temperature above the 1155 K transition point, then probed at various time intervals with a 1.5-ns-long, intense electron pulse. Diffraction patterns show an almost complete transition to the {beta} phase within 500 ns. Postmortem analysis (after the sample is allowed to cool) shows a reversion to the {alpha} phase coupled with substantial grain growth, lath formation, and texture modification. The cooled material also shows a complete lack of apparent dislocations, suggesting the possible importance of a ''massive'' short-range diffusion transformation mechanism.

  12. Neutron powder diffraction analysis of (Tm{sub 0.50}Ca{sub 0.50})MnO{sub 3} and (Lu{sub 0.50}Ca{sub 0.50})MnO{sub 3}

    SciTech Connect

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

    2012-12-15

    The crystal and magnetic structures of (Tm{sub 0.50}Ca{sub 0.50})MnO{sub 3} and (Lu{sub 0.50}Ca{sub 0.50})MnO{sub 3} have been investigated between 5 K and 300 K by means of high resolution neutron powder diffraction followed by Rietveld refinement and dc magnetic measurements. During cooling orbital ordering at the Mn sub-lattice takes place at T{sub OO}{approx}280 K in both compounds, inducing an orthorhombic to monoclinic phase transition. As the temperature is further decreased an antiferromagnetic CE-type structure occurs in both compounds at T{sub N}{approx}105 K. The comparison with other (Ln{sub 0.50}Ca{sub 0.50})MnO{sub 3} compounds reveals that at room temperature the average Jahn-Teller distortion increases sharply with the decrease of the ionic radius for lanthanides heavier than Sm. The ordered magnetic moment progressively decreases as the lanthanide ionic radius decreases on account of the decreased values of the Mn-O-Mn bond angles. - Graphical abstract: Rietveld refinement plot for (Tm{sub 0.50}Ca{sub 0.50})MnO{sub 3} obtained from neutron powder diffraction data collected at 5 K; the inset shows the CE-type spin ordering taking place at the Mn sub-lattice. Highlights: Black-Right-Pointing-Pointer The crystal and magnetic structures of (Tm{sub 0.50}Ca{sub 0.50})MnO{sub 3} and (Lu{sub 0.50}Ca{sub 0.50})MnO{sub 3} were analyzed by neutron powder diffraction. Black-Right-Pointing-Pointer Orbital ordering takes place below T{sub OO}{approx}280 K in both compounds. Black-Right-Pointing-Pointer An antiferromagnetic CE-type structure occurs in both compounds below T{sub N}{approx}105 K. Black-Right-Pointing-Pointer A Comparison with other (Ln{sub 0.50}Ca{sub 0.50})MnO{sub 3} compounds is reported.

  13. Synthetic, spectral, thermal and powder X-ray diffraction studies of bis(O-alkyldithiocarbonato-S,S‧) antimony(III) dialkyldithiocarbamates

    NASA Astrophysics Data System (ADS)

    Chauhan, H. P. S.; Joshi, Sapana; Carpenter, Jaswant

    2015-02-01

    Compounds of antimony(III) with mixed sulfur donor ligands of the type [(ROCS2)2SbS2CNR‧2] (where, R = C2H5, and iC3H7; R‧ = CH3, C2H5, and CH2CH2) have been synthesized using anhydrous acetone as a solvent by the one pot reaction of antimony(III) tris(O-alkyldithiocarbonato-S,S‧), antimony(III) chloride and sodium/ammonium salt of dialkyldithiocarbamate in 2:1:3 molar ratios. These compounds have been characterized by physicochemical [melting points, molecular weight determinations, elemental analyses (C, H, N, S, and Sb)], spectral [UV, IR, Far-IR and NMR (1H and 13C)] studies. In IR spectra strong band was observed at 1028-1051 cm-1 which indicates anisobidentate mode of bonding of both the ligands with antimony metal. NMR spectral data of these compounds show expected proton resonance due to corresponding moieties. The powder XRD, ESI-Mass and thermal (TG and DTA) studies have also been performed to get the information about geometrical parameters, fragmentation pattern and last thermal decomposition product, respectively. The powder XRD studies lead to the structural properties of the synthesized compounds and show the nanorange crystallite size and monoclinic crystal system. Thermal data of these compounds indicate the formation of antimony sulfide (Sb2S3) as a final thermal degradation product which is used in a number of ways like switching devices television cameras and microwave devices.

  14. The interfacial and surface properties of thin Fe and Gd films grown on W(110) as studied by scanning tunneling microscopy, site-resolved photoelectron diffraction, and spin polarized photoelectron diffraction

    SciTech Connect

    Tober, E.D.

    1997-06-01

    Combined scanning tunneling microscopy (STM) and low energy electron diffraction (LEED) measurements from Gd films grown on W(110) prepared with and without annealing have been used to provide a detailed picture of the growth of such films, permitting a quantitative structural explanation for previously-measured magnetic properties and the identification of a new two-dimensional structure for the first monolayer. The analysis of the film roughness of room-temperature-grown films as a function of coverage and lateral length scale reveals that the growing Gd surface follows scaling laws for a self-affine surface. Annealing these as-deposited films at elevated temperatures is found to drastically alter the morphology of the films, as seen by both STM and LEED. Nanometer-scale islands of relatively well-defined size and shape are observed under certain conditions. Finally, the first monolayer of Gd is observed to form a (7x14) superstructure with pseudo-(7x7) symmetry that is consistent with a minimally-distorted hexagonal two-dimensional Gd(0001) film. Furthermore, a new beamline and photoelectron spectrometer/diffractometer at the Advanced Light Source have been used to obtain full-solid-angle and site-specific photoelectron diffraction (PD) data from interface W atoms just beneath (1x1) Fe and (7x14) Gd monolayers on W(110) by utilizing the core level shift in the W 4f{sub 7/2} spectrum. A comparison of experiment with multiple scattering calculations permits determining the Fe adsorption site and the relative interlayer spacing to the first and second W layers. These Fe results are also compared to those from the very different Gd overlayer and from the clean W(110) surface. Such interface PD measurements show considerable promise for future studies. Finally, the rare-earth ferromagnetic system of Gd(0001) has been examined through the use of spin polarized photoelectron diffraction from the Gd 4s and 5s photoelectron multiplets.

  15. Pressure-induced phase transitions in organic molecular crystals: a combination of x-ray single-crystal and powder diffraction, raman and IR-spectroscopy

    NASA Astrophysics Data System (ADS)

    Boldyreva, E. V.; Sowa, H.; Ahsbahs, H.; Goryainov, S. V.; Chernyshev, V. V.; Dmitriev, V. P.; Seryotkin, Y. V.; Kolesnik, E. N.; Shakhtshneider, T. P.; Ivashevskaya, S. N.; Drebushchak, T. N.

    2008-07-01

    The contribution summarizes the results of recent studies of phase transitions induced by high pressure in a number of molecular organic crystals, such as polymorphs of paracetamol, chlorpropamide, polymorphs of glycine, L- and DL-serine, β-alanine. The main attention is paid to the following topics: (1) Reversible / irreversible transformations; (2) Different behavior of single crystals / powders; (3) The role of pressure-transmitting liquid; (4) The role of the kinetic factors: phase transitions on decompression, or after a long storage at a selected pressure; (5) Isosymmetric phase transitions; (6) The role of the changes in the hydrogen bond networks / intramolecular conformational changes in the phase transitions; (7) Superstructures / nanostructures formed as a result of pressure-induced phase transitions.

  16. Vacancy-induced nanoscale phase separation in KxFe2–ySe₂ single crystals evidenced by Raman scattering and powder x-ray diffraction

    SciTech Connect

    Lazarević, N.; Abeykoon, M.; Stephens, P. W.; Lei, Hechang; Bozin, E. S.; Petrovic, C.; Popović, Z. V.

    2012-08-06

    Polarized Raman scattering spectra of KxFe2–ySe₂ were analyzed in terms of peculiarities of both I4/m and I4/mmm space group symmetries. The presence of the Raman active modes from both space group symmetries (16 Raman-active modes of the I4/m phase and two Raman-active modes of the I4/mmm phase) confirmed the existence of two crystallographic domains with different space group symmetry in a KxFe2–ySe₂ sample. High-resolution synchrotron powder x-ray diffraction structural refinement of the same sample confirmed the two-phase description, and determined the atomic positions and occupancies for both domains.

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

    SciTech Connect

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

    2013-04-15

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

  18. Structure of Ce2RhIn8: an example of complementary use of high-resolution neutron powder diffraction and reciprocal-space mapping to study complex materials.

    PubMed

    Moshopoulou, E G; Ibberson, R M; Sarrao, J L; Thompson, J D; Fisk, Z

    2006-04-01

    The room-temperature crystal structure of the heavy fermion antiferromagnet Ce2RhIn8, dicerium rhodium octaindide, has been studied by a combination of high-resolution synchrotron X-ray reciprocal-space mapping of single crystals and high-resolution time-of-flight neutron powder diffraction. The structure is disordered, exhibiting a complex interplay of non-periodic, partially correlated planar defects, coexistence and segregation of polytypic phases (induced by periodic planar ;defects'), mosaicity (i.e. domain misalignment) and non-uniform strain. These effects evolve as a function of temperature in a complicated way, but they remain down to low temperatures. The room-temperature diffraction data are best represented by a complex mixture of two polytypic phases, which are affected by non-periodic, partially correlated planar defects, differ slightly in their tetragonal structures, and exhibit different mosaicities and strain values. Therefore, Ce2RhIn8 approaches the paracrystalline state, rather than the classic crystalline state and thus several of the concepts of conventional single-crystal crystallography are inapplicable. The structural results are discussed in the context of the role of disorder in the heavy-fermion state and in the interplay between superconductivity and magnetism. PMID:16552150

  19. Hydrogen in polar intermetallics: Syntheses and structures of the ternary Ca5Bi3D0.93, Yb5Bi3Hx, and Sm5Bi3H~1 by powder neutron or single crystal X-ray diffraction

    SciTech Connect

    Leon-Escamilla, E. Alejandro; Dervenagas, Panagiotis; Stasis, Constantine; Corbett, John D.

    2010-01-01

    The syntheses of the title compounds are described in detail. Structural characterizations from refinements of single crystal X-ray diffraction data for Yb{sub 5}Bi{sub 3}H{sub x} and Sm{sub 5}Bi{sub 3}H{sub 1} and of powder neutron diffraction data for Ca{sub 5}Bi{sub 3}D{sub 0.93(3)} are reported. These confirm that all three crystallize with the heavy atom structure type of {beta}-Yb{sub 5}Sb{sub 3}, and the third gives the first proof that the deuterium lies in the center of nominal calcium tetrahedra, isostructural with the Ca{sub 5}Sb{sub 3}F-type structure. These Ca and Yb phases are particularly stable with respect to dissociation to Mn{sub 5}Si{sub 3}-type product plus H{sub 2}. Some contradictions in the literature regarding Yb{sub 5}Sb{sub 3} and Yb{sub 5}Sb{sub 3}H{sub x} phases are considered in terms of adventitious hydrogen impurities that are generated during reactions in fused silica containers at elevated temperatures.

  20. In situ time-resolved X-ray diffraction of tobermorite formation in autoclaved aerated concrete: Influence of silica source reactivity and Al addition

    SciTech Connect

    Matsui, Kunio; Kikuma, Jun; Tsunashima, Masamichi; Ishikawa, Tetsuji; Matsuno, Shin-ya; Ogawa, Akihiro; Sato, Masugu

    2011-05-15

    The hydrothermal formation of tobermorite during the processing of autoclaved aerated concrete was investigated by in situ X-ray diffraction (XRD) analysis. High-energy X-rays from a synchrotron radiation source in combination with a newly developed autoclave cell and a photon-counting pixel array detector were used. To investigate the effects of the silica source, reactive quartz from chert and less-reactive quartz from quartz sand were used as starting materials. The effect of Al addition on tobermorite formation was also studied. In all cases, C-S-H, hydroxylellestadite and katoite were clearly observed as intermediates. Acceleration of tobermorite formation by Al addition was clearly observed. However, Al addition did not affect the dissolution rate of quartz. Two pathways, via C-S-H and katoite, were also observed in the Al-containing system. These results suggest that the structure of initially formed C-S-H is important for the subsequent tobermorite formation reactions.

  1. Copper doped TiO2 nanoparticles characterized by X-ray absorption spectroscopy, total scattering, and powder diffraction – a benchmark structure–property study

    SciTech Connect

    Lock, Nina; Jensen, Ellen M. L.; Mi, Jianli; Mamakhel, Aref; Norén, Katarina; Qingbo, Meng; Iversen, Bo B.

    2013-01-01

    Metal functionalized nanoparticles potentially have improved properties e.g. in catalytic applications, but their precise structures are often very challenging to determine. Here we report a structural benchmark study based on tetragonal anatase TiO2 nanoparticles containing 0–2 wt% copper. The particles were synthesized by continuous flow synthesis under supercritical water–isopropanol conditions. Size determination using synchrotron PXRD, TEM, and X-ray total scattering reveals 5–7 nm monodisperse particles. The precise dopant structure and thermal stability of the highly crystalline powders were characterized by X-ray absorption spectroscopy and multi-temperature synchrotron PXRD (300–1000 K). The combined evidence reveals that copper is present as a dopant on the particle surfaces, most likely in an amorphous oxide or hydroxide shell. UV-VIS spectroscopy shows that copper presence at concentrations higher than 0.3 wt% lowers the band gap energy. The particles are unaffected by heating to 600 K, while growth and partial transformation to rutile TiO2 occur at higher temperatures. Anisotropic unit cell behavior of anatase is observed as a consequence of the particle growth (a decreases and c increases).

  2. Influence of Ba/Fe mole ratios on magnetic properties, crystallite size and shifting of X-ray diffraction peaks of nanocrystalline BaFe12O19 powder, prepared by sol gel auto combu

    NASA Astrophysics Data System (ADS)

    Suastiyanti, Dwita; Sudarmaji, Arif; Soegijono, Bambang

    2012-06-01

    Barium hexaferrite BaFe12O19 (BFO) is of great importance as permanent magnets, particularly for magnetic recording as well as in microwave devices. Nano-crystalline BFO powders were prepared by sol gel auto combustion method in citric acid - metal nitrates system. Hence the mole ratios of Ba/Fe were variated at 1:12; 1:11.5 and 1:11. Ratio of cation to fuel was fixed at 1:1. An appropriate amount of amonia solution was added dropwise to this solution with constant stirring until the PH reached 7 in all cases. Heating at 850oC for 10 hours for each sample to get final formation of BFO nanocrystalline. The data from XRD showing the lattice parameters a,c and the unit-cell volume V, confirm that BFO with ratio 1:12 has same crystall parameters with ratio 1:11. Ratio of Ba/Fe 1:12 and 1:11 have diffraction pattern similarly at almost each 2 θ for each samples. Ratio of Ba/Fe 1: 11.5 has the finest crystallite size 22 nm. Almost diffraction pattern peaks of Ba/Fe 1:11.5 move to the left from of Ba/Fe 1:12 then return to diffraction pattern of Ba/Fe 1:12 for Ba/Fe 1:11. SEM observations show the particle size less than 100 nm and the same shape for each sample. Ratio of Ba/Fe 1: 12 gives the highest intrinsic coercive Hc = 427.3 kA/m. The highest remanent magnetization is at ratio 1:11 with Mr = 0.170 T. BFO with mole ratio 1:11.5 has the finest grain 22 nm, good magnetic properties and the highest value of best FoM 89%.

  3. High pressure x-ray diffraction techniques with synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Jing, Liu

    2016-07-01

    This article summarizes the developments of experimental techniques for high pressure x-ray diffraction (XRD) in diamond anvil cells (DACs) using synchrotron radiation. Basic principles and experimental methods for various diffraction geometry are described, including powder diffraction, single crystal diffraction, radial diffraction, as well as coupling with laser heating system. Resolution in d-spacing of different diffraction modes is discussed. More recent progress, such as extended application of single crystal diffraction for measurements of multigrain and electron density distribution, time-resolved diffraction with dynamic DAC and development of modulated heating techniques are briefly introduced. The current status of the high pressure beamline at BSRF (Beijing Synchrotron Radiation Facility) and some results are also presented. Project supported by the National Natural Science Foundation of China (Grant Nos. 10875142, 11079040, and 11075175). The 4W2 beamline of BSRF was supported by the Chinese Academy of Sciences (Grant Nos. KJCX2-SW-N20, KJCX2-SW-N03, and SYGNS04).

  4. Crystal structure of LiLnW{sub 2}O{sub 8} (Ln=lanthanides and Y): An X-ray powder diffraction study

    SciTech Connect

    Postema, J.M.; Fu, W.T.; IJdo, D.J.W.

    2011-08-15

    Crystal structures that occur in LiLnW{sub 2}O{sub 8} (Ln=lanthanides and Y) have been studied using Rietveld profile analysis of X-ray diffraction data. Two types of structures were observed. The scheelite structure of the space group I4{sub 1}/a is adopted for compounds containing large lanthanides Ln=La-Gd. For smaller lanthanides (Ln=Dy-Lu and Y) the wolframite structure with the space group P2/n is observed. In LiTbW{sub 2}O{sub 8}, both structures occur. The phase transition between the two is a slow process making the obtainment of pure low temperature phase (wolframite) difficult. The space groups P1-bar and P2, recently reported for LiEuW{sub 2}O{sub 8} and LiYW{sub 2}O{sub 8}, have not been observed in this series of compounds. - Graphical abstract: Part of the X-ray diffraction patterns of LiSmW{sub 2}O{sub 8} and LiDyW{sub 2}O{sub 8} representing two structure types in LiLnW{sub 2}O{sub 8}: the scheelite with Ln=La-Gd and wolframite with Ln=Dy-Lu and Y. In LiTbW{sub 2}O{sub 8} both the scheelite and the wolframite structures occur at high and low temperatures, respectively. Highlights: > Double tungstates of the formula LiLnW{sub 2}O{sub 8} (Ln=lanthanides and Y) were systematically synthesised and their crystal structures were determined. > LiLnW{sub 2}O{sub 8} adopt either the scheelite structure (I4{sub 1}/a) (Ln=La-Gd) or wolframite structure (P2/n) (Ln=Dy-Lu and Y). > Both structures occur in LiTbW{sub 2}O{sub 8} and the I4{sub 1}/a{yields}P2/n phase transition is a slow process. > The space groups P1-bar and P2 recently reported for LiEuW{sub 2}O{sub 8} and LiYW{sub 2}O{sub 8} were not observed.

  5. Order/disorder phenomena in Zn1-xMnxGa2Se4 ordered vacancy compounds: high temperature neutron powder diffraction experiments

    NASA Astrophysics Data System (ADS)

    Alonso-Gutiérrez, P.; Morón, M. C.; Hull, S.; Sanjuán, M. L.

    2013-12-01

    We present a study of order-disorder phenomena in the series of tetrahedral ordered vacancy compounds Zn1-xMnxGa2Se4 by means of time-of-flight neutron diffraction at high temperature together with dc magnetic susceptibility, Raman spectroscopy, differential thermal analysis and optical absorption experiments. Samples of nominal composition x = 0, 0.24, 0.5, 0.77 and 1 have been studied. An order-disorder phase transition has been detected, with Tc ranging from 472 to 610 ° C, which involves a structural change from a defect chalcopyrite phase, with I\\bar {4} space group (s.g.) and three different cation sites, to a partially disordered defect stannite, in which Zn, Mn and half of the Ga ions share the 4d site in I\\bar {4}2 m s.g. Neither the vacancies nor the Ga ions occupying site 2a are involved in the phase transition. An additional ordering process is observed on approaching the phase transition from below, which is attributed to several factors: the activation of cation diffusion at ˜300 ° C, the partially disordered cation distribution exhibited by the as-grown single crystals and the preference of Mn atoms for the 2d crystallographic site in the I\\bar {4} structure. The reversibility of the phase transition is analysed with the aid of magnetic, optical and Raman experiments.

  6. Nanophase evolution at semiconductor/electrolyte interface in situ probed by time-resolved high-energy synchrotron x-ray diffraction.

    SciTech Connect

    Sun, Y.; Ren, Y.; Haeffner, D. R.; Almer, J. D.; Wang, L.; Yang, W.; Truong, T. T.

    2010-09-01

    Real-time evolution of nanoparticles grown at the semiconductor/electrolyte interface formed between a single crystalline n-type GaAs wafer and an aqueous solution of AgNO{sub 3} has been studied by using high-energy synchrotron X-ray diffraction. The results reveal the distinct nucleation and growth steps involved in the growth of anisotropic Ag nanoplates on the surface of the GaAs wafer. For the first time, a quick transit stage is observed to be responsible for the structural transformation of the nuclei to form structurally stable seeds that are critical for guiding their anisotropic growth into nanoplates. Reaction between a GaAs wafer and AgNO{sub 3} solution at room temperature primarily produces Ag nanoplates on the surface of the GaAs wafer in the dark and at room temperature. In contrast, X-ray irradiation can induce charge separation in the GaAs wafer to drive the growth of nanoparticles made of silver oxy salt (Ag{sub 7}NO{sub 11}) and silver arsenate (Ag{sub 3}AsO{sub 4}) at the semiconductor/electrolyte interface if the GaAs wafer is illuminated by the X-ray and reaction time is long enough.

  7. Lattice-level observation of the elastic-to-plastic relaxation process with subnanosecond resolution in shock-compressed Ta using time-resolved in situ Laue diffraction

    SciTech Connect

    Wehrenberg, C. E.; Comley, A. J.; Barton, N. R.; Coppari, F.; Fratanduono, D.; Huntington, C. M.; Maddox, B. R.; Park, H. -S.; Plechaty, C.; Prisbrey, S. T.; Remington, B. A.; Rudd, R. E.

    2015-09-29

    We report direct lattice level measurements of plastic relaxation kinetics through time-resolved, in-situ Laue diffraction of shock-compressed single-crystal [001] Ta at pressures of 27-210 GPa. For a 50 GPa shock, a range of shear strains is observed extending up to the uniaxial limit for early data points (<0.6 ns) and the average shear strain relaxes to a near steady state over ~1 ns. For 80 and 125 GPa shocks, the measured shear strains are fully relaxed already at 200 ps, consistent with rapid relaxation associated with the predicted threshold for homogeneous nucleation of dislocations occurring at shock pressure ~65 GPa. The relaxation rate and shear stresses are used to estimate the dislocation density and these quantities are compared to the Livermore Multiscale Strength model as well as various molecular dynamics simulations.

  8. Calculating cellulose diffraction patterns

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Although powder diffraction of cellulose is a common experiment, the patterns are not widely understood. The theory is mathematical, there are numerous different crystal forms, and the conventions are not standardized. Experience with IR spectroscopy is not directly transferable. An awful error, tha...

  9. Time-resolved synchrotron x-ray diffraction studies of the crystallization of amorphous Co(80-x)FexB₂₀

    SciTech Connect

    Simmons, L. M.; Greig, D.; Lucas, C. A.; Kilcoyne, S. H.

    2014-09-28

    This paper addresses the time-dependent crystallization process occurring in “bulk” amorphous Co(80-x)FexB₂₀ (x = 20, 40) metallic ribbons by means of synchrotron x-ray diffraction (SXRD) and transmission electron microscopy. Metallic ribbons, produced via melt-spinning technique, were annealed in-situ, with SXRD patterns collected every 60 s. SXRD reveals that Co₄₀Fe₄₀B₂₀ alloys crystallize from an amorphous structure to a primary bcc α-(Co,Fe) phase, whereas Co₆₀Fe₂₀B₂₀ initially crystallizes into the same bcc α-(Co,Fe) but exhibits cooperative growth of both stable and metastable boride phases later into the hold. Johnson-Mehl-Avrami-Kolmogorov statistics was used on post annealed samples to determine the mechanisms of growth and the activation energy (Ea) of the α-(Co,Fe) phase. Results indicate that the growth mechanisms are similar for both alloy compositions for all annealing temperatures, with the Avrami exponent of n = 1.51(1) and 2.02(6) for x = 20 and 40, respectively, suggesting one-dimensional growth, with a decreasing nucleation rate. Activation energy for α-(Co,Fe) was determined to be 2.7(1) eV and 2.4(3) eV in x = 20 and 40, respectively, suggesting that those alloys with a lower Co content have a stronger resistance to crystallization. Based on these results, fabrication of CoFeB magnetic tunnel junctions via depositing amorphous layers and subsequently annealing to induce lattice matching presents itself as a viable and efficient method, for increasing the giant magnetoresistance in magnetic tunnel junctions.

  10. FeCoSiBNbCu bulk metallic glass with large compressive deformability studied by time-resolved synchrotron X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Stoica, Mihai; Scudino, Sergio; Bednarčik, Jozef; Kaban, Ivan; Eckert, Jürgen

    2014-02-01

    By adding 0.5 at. % Cu to the strong but brittle [(Fe0.5Co0.5)0.75Si0.05B0.20]96Nb4 bulk metallic glass, fully amorphous rods with diameters up to 2 mm were obtained. The monolithic samples with 1 mm diameter revealed a fracture strain of 3.80% and a maximum stress of 4143 MPa upon compression, together with a slight work-hardening behavior. SEM micrographs of fractured samples did neither reveal any shear bands on the lateral surface nor the typical vein patterns which characterize ductile fracture. However, some layers appear to have flowed and this phenomenon took place before the brittle final fracture. An estimate of the temperature rise ΔT in the shear plane gives 1039 K, which is large enough to melt a layer of 120 nm. The overall performance and the macroscopic plastic strain depend on the interaction between cleavage-like and viscous flow-like features. Mechanical tests performed in-situ under synchrotron radiation allowed the calculation of the strain tensor components, using the reciprocal-space data and analyzing the shift of the first (the main) and the second broad peak positions in the X-ray diffraction patterns. The results revealed that each atomic shell may have a different stiffness, which may explain the macroscopic compressive plastic deformation. Also, there were no signs of (nano) crystallization induced by the applied stress, but the samples preserve a monolithic amorphous structure until catastrophic failure occurs.

  11. FeCoSiBNbCu bulk metallic glass with large compressive deformability studied by time-resolved synchrotron X-ray diffraction

    SciTech Connect

    Stoica, Mihai Scudino, Sergio; Bednarčik, Jozef; Kaban, Ivan; Eckert, Jürgen

    2014-02-07

    By adding 0.5 at. % Cu to the strong but brittle [(Fe{sub 0.5}Co{sub 0.5}){sub 0.75}Si{sub 0.05}B{sub 0.20}]{sub 96}Nb{sub 4} bulk metallic glass, fully amorphous rods with diameters up to 2 mm were obtained. The monolithic samples with 1 mm diameter revealed a fracture strain of 3.80% and a maximum stress of 4143 MPa upon compression, together with a slight work-hardening behavior. SEM micrographs of fractured samples did neither reveal any shear bands on the lateral surface nor the typical vein patterns which characterize ductile fracture. However, some layers appear to have flowed and this phenomenon took place before the brittle final fracture. An estimate of the temperature rise ΔT in the shear plane gives 1039 K, which is large enough to melt a layer of 120 nm. The overall performance and the macroscopic plastic strain depend on the interaction between cleavage-like and viscous flow-like features. Mechanical tests performed in-situ under synchrotron radiation allowed the calculation of the strain tensor components, using the reciprocal-space data and analyzing the shift of the first (the main) and the second broad peak positions in the X-ray diffraction patterns. The results revealed that each atomic shell may have a different stiffness, which may explain the macroscopic compressive plastic deformation. Also, there were no signs of (nano) crystallization induced by the applied stress, but the samples preserve a monolithic amorphous structure until catastrophic failure occurs.

  12. 3He alternative technologies: 1. Application of neutron image plate detector for powder diffractometry

    NASA Astrophysics Data System (ADS)

    Shaikh, A. M.; Krishna, P. S. R.; Shinde, A. B.

    2012-06-01

    Neutron image plate was used for recording powder diffraction pattern from a polycrystalline Fe rod, mounted on the High Q Diffractometer at Dhruva reactor and using neutron beam of λ = 0.783 Å and Φ = 3 × 105 n/cm2/sec. The Bragg peaks were sharp and well resolved. The overall resolution (Δ2θ/2θ) value was found be ˜0.025.

  13. {sup 3}He alternative technologies: 1. Application of neutron image plate detector for powder diffractometry

    SciTech Connect

    Shaikh, A. M.; Krishna, P. S. R.; Shinde, A. B.

    2012-06-05

    Neutron image plate was used for recording powder diffraction pattern from a polycrystalline Fe rod, mounted on the High Q Diffractometer at Dhruva reactor and using neutron beam of {lambda}= 0.783 A and {Phi}= 3 x 10{sup 5} n/cm{sup 2}/sec. The Bragg peaks were sharp and well resolved. The overall resolution ({Delta}2{theta}/2{theta}) value was found be {approx}0.025.

  14. Time- and space-resolved high energy operando X-ray diffraction for monitoring the methanol to hydrocarbons reaction over H-ZSM-22 zeolite catalyst in different conditions

    NASA Astrophysics Data System (ADS)

    del Campo, Pablo; Slawinski, Wojciech Andrzej; Henry, Reynald; Erichsen, Marius Westgård; Svelle, Stian; Beato, Pablo; Wragg, David; Olsbye, Unni

    2016-06-01

    The conversion of methanol to hydrocarbons (MTH) over H-ZSM-22 was studied by operando time- and space-resolved X-ray diffraction (XRD) at 370-385 °C and WHSV = 2 g/g h at the Swiss-Norwegian Beamline at ESRF. The performance of a commercial H-ZSM-22 sample was compared before and after acid-base treatment, and with and without propanol co-feed, respectively. N2 adsorption, Scanning Electron Microscopy and propyl amine desorption experiments showed that acid-base treatment led to enhanced accessibility of acid sites, mainly due to the formation of mesopores between agglomerated H-ZSM-22 crystals. The catalytic set-up allowed us to simultaneously observe the catalyst activity and unit cell volume variations by time- and space-resolved HXRD in operando conditions. The expansion of the unit cell and final flattening at different positions in the catalytic bed matched very nicely with the catalytic activity gradients. Different scenarios provided different behaviors and gave insights in the effect of morphology and co-feed process on the activity in the MTH process. This technique is the only one which has so far been able to provide direct evidence of the behavior of the species inside the catalytic reactor.

  15. X-ray and neutron powder diffraction analyses of Gly·MgSO4·5H2O and Gly·MgSO4·3H2O, and their deuterated counterparts.

    PubMed

    Howard, Christopher; Wood, Ian G; Knight, Kevin S; Fortes, A Dominic

    2016-03-01

    We have identified a new compound in the glycine-MgSO4-water ternary system, namely glycine magnesium sulfate trihydrate (or Gly·MgSO4·3H2O) {systematic name: catena-poly[[tetraaquamagnesium(II)]-μ-glycine-κ(2)O:O'-[diaquabis(sulfato-κO)magnesium(II)]-μ-glycine-κ(2)O:O']; [Mg(SO4)(C2D5NO2)(D2O)3]n}, which can be grown from a supersaturated solution at ∼350 K and which may also be formed by heating the previously known glycine magnesium sulfate pentahydrate (or Gly·MgSO4·5H2O) {systematic name: hexaaquamagnesium(II) tetraaquadiglycinemagnesium(II) disulfate; [Mg(D2O)6][Mg(C2D5NO2)2(D2O)4](SO4)2} above ∼330 K in air. X-ray powder diffraction analysis reveals that the trihydrate phase is monoclinic (space group P21/n), with a unit-cell metric very similar to that of recently identified Gly·CoSO4·3H2O [Tepavitcharova et al. (2012). J. Mol. Struct. 1018, 113-121]. In order to obtain an accurate determination of all structural parameters, including the locations of H atoms, and to better understand the relationship between the pentahydrate and the trihydrate, neutron powder diffraction measurements of both (fully deuterated) phases were carried out at 10 K at the ISIS neutron spallation source, these being complemented with X-ray powder diffraction measurements and Raman spectroscopy. At 10 K, glycine magnesium sulfate pentahydrate, structurally described by the `double' formula [Gly(d5)·MgSO4·5D2O]2, is triclinic (space group P-1, Z = 1), and glycine magnesium sulfate trihydrate, which may be described by the formula Gly(d5)·MgSO4·3D2O, is monoclinic (space group P21/n, Z = 4). In the pentahydrate, there are two symmetry-inequivalent MgO6 octahedra on sites of -1 symmetry and two SO4 tetrahedra with site symmetry 1. The octahedra comprise one [tetraaquadiglcyinemagnesium](2+) ion (centred on Mg1) and one [hexaaquamagnesium](2+) ion (centred on Mg2), and the glycine zwitterion, NH3(+)CH2COO(-), adopts a monodentate coordination to Mg2. In the

  16. Direct Observations of the (Alpha to Gamma) Transformation at Different Input Powers in the Heat Affected Zone of 1045 C-Mn Steel Arc Welds Observed by Spatially Resolved X-Ray Diffraction

    SciTech Connect

    Palmer, T A; Elmer, J W

    2005-03-16

    Spatially Resolved X-Ray Diffraction (SRXRD) experiments have been performed during Gas Tungsten Arc (GTA) welding of AISI 1045 C-Mn steel at input powers ranging from 1000 W to 3750 W. In situ diffraction patterns taken at discreet locations across the width of the heat affected zone (HAZ) near the peak of the heating cycle in each weld show regions containing austenite ({gamma}), ferrite and austenite ({alpha}+{gamma}), and ferrite ({alpha}). Changes in input power have a demonstrated effect on the resulting sizes of these regions. The largest effect is on the {gamma} phase region, which nearly triples in width with increasing input power, while the width of the surrounding two phase {alpha}+{gamma} region remains relatively constant. An analysis of the diffraction patterns obtained across this range of locations allows the formation of austenite from the base metal microstructure to be monitored. After the completion of the {alpha} {yields} {gamma} transformation, a splitting of the austenite peaks is observed at temperatures between approximately 860 C and 1290 C. This splitting in the austenite peaks results from the dissolution of cementite laths originally present in the base metal pearlite, which remain after the completion of the {alpha} {yields} {gamma} transformation, and represents the formation of a second more highly alloyed austenite constituent. With increasing temperatures, carbon, originally present in the cementite laths, diffuses from the second newly formed austenite constituent to the original austenite constituent. Eventually, a homogeneous austenitic microstructure is produced at temperatures of approximately 1300 C and above, depending on the weld input power.

  17. High-resolution synchrotron x-ray powder diffraction study of the incommensurate modulation in the martensite phase of Ni2MnGa: Evidence for nearly 7M modulation and phason broadening

    NASA Astrophysics Data System (ADS)

    Singh, Sanjay; Petricek, V.; Rajput, Parasmani; Hill, Adrian H.; Suard, E.; Barman, S. R.; Pandey, Dhananjai

    2014-07-01

    The modulated structure of the martensite phase of Ni2MnGa is revisited using high-resolution synchrotron x-ray powder diffraction measurements, which reveal higher-order satellite reflections up to the third order and phason broadening of the satellite peaks. The structure refinement, using the (3+1) dimensional superspace group approach, shows that the modulated structure of Ni2MnGa can be described by orthorhombic superspace group Immm(00γ)s00 with lattice parameters a=4.218 61(2)Å,b=5.546 96(3)Å, and c=4.187 63(2) Å, and an incommensurate modulation wave vector q =0.43160(3)c*=(3/7+δ)c*, where δ =0.00303(3) is the degree of incommensuration of the modulated structure. Additional satellite peak broadening, which could not be accounted for in terms of the anisotropic strain broadening based on a lattice parameter distribution, has been modeled in terms of phasons using fourth-rank covariant strain-tensor representation for incommensurate structures. The simulation of single-crystal diffraction patterns from the refined structural parameters unambiguously reveals a rational approximant structure with 7M modulation. The inhomogeneous displacement of different atomic sites on account of incommensurate modulation and the presence of phason broadening clearly rule out the adaptive phase model proposed recently by Kaufmann et al. [S. Kaufmann, U. K. Rößler, O. Heczko, M. Wuttig, J. Buschbeck, L. Schultz, and S. Fähler, Phys. Rev. Lett. 104, 145702 (2010), 10.1103/PhysRevLett.104.145702] and suggest that the modulation in Ni2MnGa originates from soft-mode phonons.

  18. Unraveling the Hydrogenation of TiO 2 and Graphene Oxide/TiO 2 Composites in Real Time by in Situ Synchrotron X-ray Powder Diffraction and Pair Distribution Function Analysis

    DOE PAGESBeta

    Nguyen-Phan, Thuy-Duong; Liu, Zongyuan; Luo, Si; Gamalski, Andrew D.; Vovchok, Dimitry; Xu, Wenqian; Stach, Eric A.; Polyansky, Dmitry E.; Fujita, Etsuko; Rodriguez, José A.; et al

    2016-02-18

    The functionalization of graphene oxide (GO) and graphene by TiO2 and other metal oxides has attracted considerable attention due to numerous promising applications in catalysis, energy conversion, and storage. We propose hydrogenation of this class of materials as a promising way to tune catalytic properties by altering the structural and chemical transformations that occur upon H incorporation. We also investigate the structural changes that occur during the hydrogenation process using in situ powder X-ray diffraction and pair distribution function analysis of GO–TiO2 and TiO2 under H2 reduction. Sequential Rietveld refinement was employed to gain insight into the evolution of crystalmore » growth of TiO2 nanoparticles in the presence of two-dimensional (2D) GO nanosheets. GO sheets not only significantly retarded the nucleation and growth of rutile impurities, stabilizing the anatase structure, but was also partially reduced to hydrogenated graphene by the introduction of atomic hydrogen into the honeycomb lattice. We discuss the hydrogenation processes and the resulting composite structure that occurs during the incorporation of atomic H and the dynamic structural transformations that leads to a highly active photocatalyst.« less

  19. Polymorphism of ceramide 3. Part 2: a vibrational spectroscopic and X-ray powder diffraction investigation of N-octadecanoyl phytosphingosine and the analogous specifically deuterated d(35) derivative.

    PubMed

    Raudenkolb, Steve; Wartewig, Siegfried; Neubert, Reinhard H H

    2003-07-01

    In order to characterize the arrangements of the hydrocarbon chains of ceramide 3, the thermotropic phase behaviour of the ceramides N-octadecanoylphytosphingosine (CER3) and its chain deuterated derivative N-(d(35)-octadecanoyl)phytosphingosine (d(35)CER3) was studied by means of X-ray powder diffraction, FT-IR and Raman spectroscopy. CER3 and d(35)CER3 exhibit an identical thermotropic polymorphism involving three different crystalline phases. The selective deuteration of the fatty acid chain enables to distinguish the sphingoid part from the fatty acid part by means of FT-IR and Raman spectroscopy. It could be shown that both hydrocarbon chains are arranged in different subcells. Temperature dependent Raman measurements elucidate simultaneously the changes in the trans/gauche ratios and the packing of both the hydrocarbon chains of the fatty acid and of the sphingoid part. The phase behaviour of CER3 and d(35)CER3, both dry and hydrated, was investigated. PMID:12818735

  20. Assessment of the optimum degree of Sr{sub 3}Fe{sub 2}MoO{sub 9} electron-doping through oxygen removal: An X-ray powder diffraction and {sup 57}Fe Moessbauer spectroscopy study

    SciTech Connect

    Lopez, Carlos A.; Viola, Maria del C.; Pedregosa, Jose C.; Mercader, Roberto C.

    2010-10-15

    We describe the preparation and structural characterization by X-ray powder diffraction (XRPD) and Moessbauer spectroscopy of three electron-doped perovskites Sr{sub 3}Fe{sub 2}MoO{sub 9-{delta}} with Fe/Mo = 2 obtained from Sr{sub 3}Fe{sub 2}MoO{sub 9}. The compounds were synthesized by topotactic reduction with H{sub 2}/N{sub 2} (5/95) at 600, 700 and 800 {sup o}C. Above 800 {sup o}C the Fe/Mo ratio changes from Fe/Mo = 2-1 < Fe/Mo < 2. The structural refinements of the XRPD data for the reduced perovskites were carried out by the Rietveld profile analysis method. The crystal structure of these phases is cubic, space group Fm3-bar m, with cationic disorder at the two different B sites that can be populated in variable proportions by the Fe atoms. The Moessbauer spectra allowed determining the evolution of the different species formed after the treatments at different temperatures and confirm that Fe ions in the samples reduced at 600, 700 and 800 {sup o}C are only in the high-spin Fe{sup 3+} electronic state.

  1. The thermal behaviour and structural stability of nesquehonite, MgCO3.3H2O, evaluated by in situ laboratory parallel-beam X-ray powder diffraction: New constraints on CO2 sequestration within minerals.

    PubMed

    Ballirano, Paolo; De Vito, Caterina; Ferrini, Vincenzo; Mignardi, Silvano

    2010-06-15

    In order to gauge the appropriateness of CO(2) reaction with Mg chloride solutions as a process for storing carbon dioxide, the thermal behaviour and structural stability of its solid product, nesquehonite (MgCO(3).3H(2)O), were investigated in situ using real-time laboratory parallel-beam X-ray powder diffraction. The results suggest that the nesquehonite structure remains substantially unaffected up to 373 K, with the exception of a markedly anisotropic thermal expansion acting mainly along the c axis. In the 371-390 K range, the loss of one water molecule results in the nucleation of a phase of probable composition MgCO(3).2H(2)O, which is characterized by significant structural disorder. At higher temperatures (423-483 K), both magnesite and MgO.2MgCO(3) coexist. Finally, at 603 K, periclase nucleation starts and the disappearance of carbonate phases is completed at 683 K. Consequently, the structural stability of nesquehonite at high temperatures suggests that it will remain stable under the temperature conditions that prevail at the Earth's surface. These results will help (a) to set constraints on the temperature conditions under which nesquehonite may be safely stored and (b) to develop CO(2) sequestration via the synthesis of nesquehonite for industrial application. PMID:20167421

  2. Phase transition and NH3 dynamics in [Ni(NH3)4](ReO4)2 studied by infrared absorption, X-ray powder diffraction and neutron scattering methods

    NASA Astrophysics Data System (ADS)

    Hetmańczyk, Łukasz; Hetmańczyk, Joanna

    2016-05-01

    The phase transition in [Ni(NH3)4](ReO4)2 detected previously by differential scanning calorimetry (DSC) at Tch = 188 K was now investigated by infrared absorption (FT-IR), incoherent inelastic and elastic neutron scattering (IINS, ND), and X-ray powder diffraction (XRPD) methods. The reorientational dynamics of NH3 groups was investigated by infrared band shape analysis (IRBS) and quasielastic neutron scattering (QENS) methods. The infrared data show that some of the bands split in the vicinity of the phase transition temperature, which suggests a change in the crystal structure. The systematic narrowing of particular bands at cooling is also observed, but reorientational dynamics of NH3 is not stopped at the phase transition temperature, which is fully confirmed by the QENS analysis. The broadening of the quasielastic neutron scattering peak is clearly visible below the phase transition temperature. Both NPD and XRPD measurements indicate that a small change of crystal structure is associated with the phase transition.

  3. Neutron powder diffraction study of nuclear and magnetic structures of multiferroic (Bi0.8Ba0.2)(Fe0.8Ti0.2)O3: Evidence for isostructural phase transition and magnetoelastic and magnetoelectric couplings

    NASA Astrophysics Data System (ADS)

    Singh, Anar; Senyshyn, Anatoliy; Fuess, Hartmut; Chatterji, Tapan; Pandey, Dhananjai

    2011-02-01

    We report here the results of a high-resolution neutron powder diffraction study on the multiferroic solid solution system (Bi0.8Ba0.2)(Fe0.8Ti0.2)O3 in the temperature range 4 to 700 K. Using irreducible representation theory to analyze the magnetic structure by Rietveld refinement, we show that the magnetic structure is collinear G-type antiferromagnetic. Further, we confirm the occurrence of an isostructural phase transition (IPT) accompanying the magnetic ordering around ˜625 K in (Bi0.8Ba0.2)(Fe0.8Ti0.2)O3. It is shown that as a result of the IPT, the positions of all the atoms change significantly in the magnetically ordered phase, leading to an excess polarization which scales linearly with the sublattice magnetization obtained by Rietveld refinement of the magnetic structure. Structural evidence for magnetoelastic coupling for the magnetic transitions below room temperature is also presented.

  4. Stepwise effects of the BCR sequential chemical extraction procedure on dissolution and metal release from common ferromagnesian clay minerals: a combined solution chemistry and X-ray powder diffraction study.

    PubMed

    Ryan, P C; Hillier, S; Wall, A J

    2008-12-15

    Sequential extraction procedures (SEPs) are commonly used to determine speciation of trace metals in soils and sediments. However, the non-selectivity of reagents for targeted phases has remained a lingering concern. Furthermore, potentially reactive phases such as phyllosilicate clay minerals often contain trace metals in structural sites, and their reactivity has not been quantified. Accordingly, the objective of this study is to analyze the behavior of trace metal-bearing clay minerals exposed to the revised BCR 3-step plus aqua regia SEP. Mineral quantification based on stoichiometric analysis and quantitative powder X-ray diffraction (XRD) documents progressive dissolution of chlorite (CCa-2 ripidolite) and two varieties of smectite (SapCa-2 saponite and SWa-1 nontronite) during steps 1-3 of the BCR procedure. In total, 8 (+/-1) % of ripidolite, 19 (+/-1) % of saponite, and 19 (+/-3) % of nontronite (% mineral mass) dissolved during extractions assumed by many researchers to release trace metals from exchange sites, carbonates, hydroxides, sulfides and organic matter. For all three reference clays, release of Ni into solution is correlated with clay dissolution. Hydrolysis of relatively weak Mg-O bonds (362 kJ/mol) during all stages, reduction of Fe(III) during hydroxylamine hydrochloride extraction and oxidation of Fe(II) during hydrogen peroxide extraction are the main reasons for clay mineral dissolution. These findings underscore the need for precise mineral quantification when using SEPs to understand the origin/partitioning of trace metals with solid phases. PMID:18951614

  5. Spatially resolved X-ray diffraction phase mapping and {alpha} {r_arrow} {beta} {r_arrow} {alpha} transformation kinetics in the heat-affected zone of commercially pure titanium arc welds

    SciTech Connect

    Elmer, J.W.; Wong, J.; Ressler, T.

    1998-11-01

    Spatially resolved X-ray diffraction (SRXRD) is used to map the {alpha} {r_arrow} {beta} {r_arrow} {alpha} phase transformation in the heat-affected zone (HAZ) of commercially pure titanium gas tungsten arc welds. In situ SRXRD experiments were conducted using a 180-{micro}m-diameter X-ray beam at the Stanford Synchrotron Radiation Laboratory (SSRL) (Stanford, CA) to probe the phases present in the HAZ of a 1.9 kW weld moving at 1.1 mm/s. Results of sequential linear X-ray diffraction scans made perpendicular to the weld direction were combined to construct a phase transformation map around the liquid weld pool. This map identifies six HAZ microstructural regions between the liquid weld pool and the base metal: (1) {alpha}-Ti that is undergoing annealing and recrystallization; (2) completely recrystallized {alpha}-Ti; (3) partially transformed {alpha}-Ti, where {alpha}-Ti and {beta}-Ti coexist; (4) single-phase {beta}-Ti; (5) back-transformed {alpha}Ti; and (6) recrystallized {alpha}-Ti plus back-transformed {alpha}-Ti. Although the microstructure consisted predominantly of {alpha}-Ti, both prior to and after the weld, the crystallographically textured starting material was altered during welding to produce different {alpha}-Ti textures within the resulting HAZ. Based on the travel speed of the weld, the {alpha} {r_arrow} {beta} transformation was measured to take 1.83 seconds during heat, while the {beta} {r_arrow} {alpha} transformation was measured to take 0.91 seconds during cooling. The {alpha} {r_arrow} {beta} transformation was characterized to be dominated by long-range diffusion growth on the leading (heating) side of the weld, while the {beta} {r_arrow} {alpha} transformation was characterized to be predominantly massive on the trailing (cooling) side of the weld, with a massive growth rate on the order of 100 {micro}m/s.

  6. Pimobendan B from powder diffraction data.

    PubMed

    Zvirgzdins, Alvis; Delina, Mara; Mishnev, Anatoly; Actins, Andris

    2013-11-01

    The title mol-ecule, C19H18N4O2 {systematic name: (RS)-6-[2-(4-meth-oxy-phen-yl)-1H-benzimidazol-5-yl]-5-methyl-4,5-di-hydro-pyridazin-3(2H)-one}, adopts an extended conformation. The dihedral angles between the central benzimidazole ring sytem and the pendant meth-oxy-phenyl and pyridazinone residues are 1.41 (18) and 9.7 (3)°, respectively. In the crystal, N-H⋯N hydrogen bonds link the imadazole groups into [001] chains, and pairs of N-H⋯O hydrogen bonds link the pyridazinone groups into dimers. Together, these generate a two-dimensional supra-molecular structure parallel to (010). The layers are linked by C-H⋯π inter-actions. PMID:24526935

  7. Pimobendan B from powder diffraction data

    PubMed Central

    Zvirgzdins, Alvis; Delina, Mara; Mishnev, Anatoly; Actins, Andris

    2013-01-01

    The title mol­ecule, C19H18N4O2 {systematic name: (RS)-6-[2-(4-meth­oxy­phen­yl)-1H-benzimidazol-5-yl]-5-methyl-4,5-di­hydro­pyridazin-3(2H)-one}, adopts an extended conformation. The dihedral angles between the central benzimidazole ring sytem and the pendant meth­oxy­phenyl and pyridazinone residues are 1.41 (18) and 9.7 (3)°, respectively. In the crystal, N—H⋯N hydrogen bonds link the imadazole groups into [001] chains, and pairs of N—H⋯O hydrogen bonds link the pyridazinone groups into dimers. Together, these generate a two-dimensional supra­molecular structure parallel to (010). The layers are linked by C—H⋯π inter­actions. PMID:24526935

  8. Shedding Light on the Photochemistry of Coinage-Metal Phosphorescent Materials: A Time-Resolved Laue Diffraction Study of an AgI-CuI Tetranuclear Complex

    SciTech Connect

    Jarzembska, Katarzyna N.; Kami,; #324; ski, Radoslaw; Fournier, Bertrand; Trzop, El; #380; bieta,; Sokolow, Jesse D.; Henning, Robert; Chen, Yang; Coppens, Philip

    2014-11-14

    The triplet excited state of a new crystalline form of a tetranuclear coordination d10–d10-type complex, Ag2Cu2L4 (L = 2-diphenylphosphino-3-methylindole ligand), containing AgI and CuI metal centers has been explored using the Laue pump–probe technique with ≈80 ps time resolution. The relatively short lifetime of 1 μs is accompanied by significant photoinduced structural changes, as large as the Ag1···Cu2 distance shortening by 0.59(3) Å. The results show a pronounced strengthening of the argentophilic interactions and formation of new Ag···Cu bonds on excitation. Theoretical calculations indicate that the structural changes are due to a ligand-to-metal charge transfer (LMCT) strengthening the Ag···Ag interaction, mainly occurring from the methylindole ligands to the silver metal centers. QM/MM optimizations of the ground and excited states of the complex support the experimental results. Comparison with isolated molecule optimizations demonstrates the restricting effect of the crystalline matrix on photoinduced distortions. The work represents the first time-resolved Laue diffraction study of a heteronuclear coordination complex and provides new information on the nature of photoresponse of coinage metal complexes, which have been the subject of extensive studies.

  9. Quantitative determination of two polymorphic forms of imatinib mesylate in a drug substance and tablet formulation by X-ray powder diffraction, differential scanning calorimetry and attenuated total reflectance Fourier transform infrared spectroscopy.

    PubMed

    Bellur Atici, Esen; Karlığa, Bekir

    2015-10-10

    Imatinib has been identified as a tyrosine kinase inhibitor that selectively inhibits the Abl tyrosine kinases, including Bcr-Abl. The active substance used in drug product is the mesylate salt form of imatinib, a phenylaminopyrimidine derivative and chemically named as N-(3-(4-(pyridin-3-yl) pyrimidin-2-ylamino)-4-methylphenyl)-4-((4-methylpiperazin-1-yl) methyl)-benzamide methanesulfonic acid salt. It exhibits many polymorphic forms and most stable and commercialized polymorphs are known as α and β forms. Molecules in α and β polymorphic forms exhibit significant conformational differences due to their different intra- and intermolecular interactions, which stabilize their molecular conformations and affect their physicochemical properties such as bulk density, melting point, solubility, stability, and processability. The manufacturing process of a drug tablet included granulation, compression, coating, and drying may cause polymorphic conversions. Therefore, polymorphic content of the drug substance should be controlled during quality control and stability testing. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, differential scanning calorimetry (DSC), and powder X-ray diffraction (PXRD) methods were evaluated for determination of the polymorphic content of the drug substance and drug product; and PXRD was the most accurate technique and selected as preferred method and validated. Prior to development of a quantification method, pure α and β polymorphs were characterized and used throughout the method development and validation studies. Mixtures with different ratios of α and β forms were scanned using X-ray diffractometer with a scan rate of 0.250°/min over an angular range of 19.5-21.0° 2θ and the peak heights for characteristic peak of β form at 20.5 ± 0.2° 2θ diffraction angle were used to generate a calibration curve. The detection limit of β polymorph in α form imatinib mesylate tablets was found as 4% and

  10. On the crystal structures of Ln{sub 3}MO{sub 7} (Ln=Nd, Sm, Y and M=Sb, Ta)-Rietveld refinement using X-ray powder diffraction data

    SciTech Connect

    Fu, W.T.; IJdo, D.J.W.

    2009-09-15

    We have investigated, using X-ray powder diffraction data, the crystal structures of some fluorite derivatives with the formula Ln{sub 3}MO{sub 7} (Ln=lanthanide or Y and M=Sb and Ta). In these compounds ordering of Ln and M occurs, leading to a parent structure in Cmmm. Tilting of the MO{sub 6} octahedra causes doubling of one of the cubic axes, leading to a number of non-isomorphic subgroups, e.g. Cmcm, Ccmm and Cccm. We have identified an alternative space group Ccmm instead of C222{sub 1} for those compounds containing a medium sized lanthanide or Y and M being Sb or Ta. Interestingly this is an alternative setting for the space group of the structure obtained when Ln is large (Cmcm). However, there tilting of the octahedra is around the a-axis of the parent structure, rather than around the b-axis as it is found in the compounds which we are reporting on here. In one compound, Nd{sub 3}TaO{sub 7}, both tilts occur. The phase transition between the two possible structures is a slow and difficult process above 80 K, allowing both phases to coexist. - Graphical abstract: (a) A projected view of Ln{sub 3}MO{sub 7} along the a-axis showing the ordering of Ln and M cations in the fluoride lattice. Note that the unit cells of the fluorite (dashed line), the parent Cmmm (dashed line) and the Cmcm/Ccmm structures (continuous line) are indicated. (b) Schematic representations of the crystal structures of Y{sub 3}SbO{sub 7} showing SbO{sub 6} octahedra and Y. Oxygens that do not bond to M cations are also shown.

  11. Crystal structure analysis of tetragonal bronzes {beta}-SrTa{sub 2}O{sub 6} and {beta}'-SrTa{sub 2}O{sub 6} by synchrotron x-ray and neutron powder diffraction.

    SciTech Connect

    Lee, E.; Park, C-H.; Shoemaker, D. P.; Avdeev, M.; Kim, Y-I.

    2012-07-01

    Strontium ditantalum oxide SrTa{sub 2}O{sub 6} exists in {alpha}-, {beta}-, and {beta}{prime}-polymorphs. Herein the crystal structures of the latter two were studied using synchrotron X-ray and constant-wavelength neutron powder diffraction. While {beta}{prime}-SrTa{sub 2}O{sub 6} [space group P4/mbm, a = 12.47099(1) {angstrom}, c = 3.898210(5) {angstrom}, V = 606.271(2) {angstrom}{sup 3}, Z = 5] belongs to the regular tetragonal tungsten bronze (TTB) family, it contains locally disordered strontium atoms within the pentagonal channel. {beta}-SrTa{sub 2}O{sub 6} [space group Pnam, a = 12.36603(2) {angstrom}, b = 12.43467(2) {angstrom}, c = 7.72403(1) {angstrom}, V = 1187.705(4) {angstrom}{sup 3}, Z = 10] can be described as an orthorhombic modification of the TTB, where the octahedral tilting distortion effectively alleviates the bonding strains around TaO{sub 6} and SrO{sub 13} polyhedra. For comparison, rynersonite type {alpha}-SrTa{sub 2}O{sub 6} [space group Pnma, a = 11.00610(6) {angstrom}, b = 7.63397(3) {angstrom}, c = 5.62634(3) {angstrom}, V = 472.727(5) {angstrom}{sup 3}, and Z = 4] is built from edge-shared dimer units of TaO{sub 6} octahedra. As measured by diffuse-reflection absorption spectroscopy, {alpha}-, {beta}-, and {beta}{prime}-SrTa{sub 2}O{sub 6} have indirect band gap energies of 4.4, 4.0, and 3.8 eV, respectively.

  12. Improved camera for better X-ray powder photographs

    NASA Technical Reports Server (NTRS)

    Parrish, W.; Vajda, I. E.

    1969-01-01

    Camera obtains powder-type photographs of single crystals or polycrystalline powder specimens. X-ray diffraction photographs of a powder specimen are characterized by improved resolution and greater intensity. A reasonably good powder pattern of small samples can be produced for identification purposes.

  13. Thermal stability in the blended lithium manganese oxide – Lithium nickel cobalt manganese oxide cathode materials: An in situ time-resolved X-Ray diffraction and mass spectroscopy study

    DOE PAGESBeta

    Hu, Enyuan; Bak, Seong Min; Senanayake, Sanjaya D.; Yang, Xiao-Qing; Nam, Kyung-Wan; Zhang, Lulu; Shao, Minhua

    2015-03-01

    Thermal stabilities of a series of blended LiMn2O4(LMO)-LiNi1/3Co1/3Mn1/3O2 (NCM) cathode materials with different weight ratios were studied by in situ time-resolved X-ray diffraction (XRD) combined with mass spectroscopy in the temperature range of 25°C-580°C under helium atmosphere. Upon heating, the electrochemically delithiated LMO changed into Mn3O4 phase at around 250°C. Formation of MnO with rocksalt structure started at 520°C. This observation is in contrast to the previous report for chemically delithiate LMO in air, in which a process of λ-MnO2 transforming to β-MnO2 was observed. Oxygen peak was not observed in all cases, presumably as a result of either consumptionmore » by the carbon or detection limit. CO2 profile correlates well with the phase transition and indirectly suggests the oxygen release of the cathode. Introducing NCM into LMO has two effects: first, it makes the high temperature rock-salt phase formation more complicated with more peaks in CO2 profile due to different MO (M = Ni, Mn, Co) phases; secondly, the onset temperature of CO2 release is lowered, implying lowered oxygen release temperature. Upon heating, XRD patterns indicate the NCM part reacts first, followed by the LMO part. This confirms the better thermal stability of LMO over NCM.« less

  14. Thermal stability in the blended lithium manganese oxide - Lithium nickel cobalt manganese oxide cathode materials: An in situ time-resolved X-Ray diffraction and mass spectroscopy study

    NASA Astrophysics Data System (ADS)

    Hu, Enyuan; Bak, Seong Min; Senanayake, Sanjaya D.; Yang, Xiao-Qing; Nam, Kyung-Wan; Zhang, Lulu; Shao, Minhua

    2015-03-01

    Thermal stabilities of a series of blended LiMn2O4 (LMO)-LiNi1/3Co1/3Mn1/3O2 (NCM) cathode materials with different weight ratios were studied by in situ time-resolved X-ray diffraction (XRD) combined with mass spectroscopy in the temperature range of 25 °C-580 °C under helium atmosphere. Upon heating, the electrochemically delithiated LMO changed into Mn3O4 phase at around 250 °C. Formation of MnO with rock-salt structure started at 520 °C. This observation is in contrast to the previous report for chemically delithiated LMO in air, in which a process of λ-MnO2 transforming to β-MnO2 was observed. Oxygen peak was not observed in all cases, presumably as a result of either consumption by the carbon or detection limit. CO2 profile correlates well with the phase transition and indirectly suggests the oxygen release of the cathode. Introducing NCM into LMO has two effects: first, it makes the high temperature rock-salt phase formation more complicated with more peaks in CO2 profile due to different MO (M = Ni, Mn, Co) phases; secondly, the onset temperature of CO2 release is lowered, implying lowered oxygen release temperature. Upon heating, XRD patterns indicate the NCM part reacts first, followed by the LMO part. This confirms the better thermal stability of LMO over NCM.

  15. Thermal stability in the blended lithium manganese oxide – Lithium nickel cobalt manganese oxide cathode materials: An in situ time-resolved X-Ray diffraction and mass spectroscopy study

    SciTech Connect

    Hu, Enyuan; Bak, Seong Min; Senanayake, Sanjaya D.; Yang, Xiao-Qing; Nam, Kyung-Wan; Zhang, Lulu; Shao, Minhua

    2015-03-01

    Thermal stabilities of a series of blended LiMn2O4(LMO)-LiNi1/3Co1/3Mn1/3O2 (NCM) cathode materials with different weight ratios were studied by in situ time-resolved X-ray diffraction (XRD) combined with mass spectroscopy in the temperature range of 25°C-580°C under helium atmosphere. Upon heating, the electrochemically delithiated LMO changed into Mn3O4 phase at around 250°C. Formation of MnO with rocksalt structure started at 520°C. This observation is in contrast to the previous report for chemically delithiate LMO in air, in which a process of λ-MnO2 transforming to β-MnO2 was observed. Oxygen peak was not observed in all cases, presumably as a result of either consumption by the carbon or detection limit. CO2 profile correlates well with the phase transition and indirectly suggests the oxygen release of the cathode. Introducing NCM into LMO has two effects: first, it makes the high temperature rock-salt phase formation more complicated with more peaks in CO2 profile due to different MO (M = Ni, Mn, Co) phases; secondly, the onset temperature of CO2 release is lowered, implying lowered oxygen release temperature. Upon heating, XRD patterns indicate the NCM part reacts first, followed by the LMO part. This confirms the better thermal stability of LMO over NCM.

  16. Crystal structure analysis of tungsten bronzes {beta}-SrTa{sub 2}O{sub 6} and {beta} Prime -SrTa{sub 2}O{sub 6} by synchrotron X-ray and neutron powder diffraction

    SciTech Connect

    Lee, Eunhye; Park, Cheol-Hee; Shoemaker, Daniel P.; Avdeev, Maxim; Kim, Young-Il

    2012-07-15

    Strontium ditantalum oxide SrTa{sub 2}O{sub 6} exists in {alpha}-, {beta}-, and {beta} Prime -polymorphs. Herein the crystal structures of the latter two were studied using synchrotron X-ray and constant-wavelength neutron powder diffraction. While {beta} Prime -SrTa{sub 2}O{sub 6} [space group P4/mbm, a=12.47099(1) A, c=3.898210(5) A, V=606.271(2) Angstrom-Sign {sup 3}, Z=5] belongs to the regular tetragonal tungsten bronze (TTB) family, it contains locally disordered strontium atoms within the pentagonal channel. {beta}-SrTa{sub 2}O{sub 6} [space group Pnam, a=12.36603(2) Angstrom-Sign , b=12.43467(2) A, c=7.72403(1) A, V=1187.705(4) Angstrom-Sign {sup 3}, Z=10] can be described as an orthorhombic modification of the TTB, where the octahedral tilting distortion effectively alleviates the bonding strains around TaO{sub 6} and SrO{sub 13} polyhedra. For comparison, rynersonite type {alpha}-SrTa{sub 2}O{sub 6} [space group Pnma, a=11.00610(6) Angstrom-Sign , b=7.63397(3) Angstrom-Sign , c=5.62634(3) Angstrom-Sign , V=472.727(5) Angstrom-Sign {sup 3}, and Z=4] is built from edge-shared dimer units of TaO{sub 6} octahedra. As measured by diffuse-reflection absorption spectroscopy, {alpha}-, {beta}-, and {beta} Prime -SrTa{sub 2}O{sub 6} have indirect band gap energies of 4.4, 4.0, and 3.8 eV, respectively. - Graphical Abstract: Difference Fourier map for {beta} Prime -SrTa{sub 2}O{sub 6} at z=0. Highlights: Black-Right-Pointing-Pointer Structure refinements of {beta}-SrTa{sub 2}O{sub 6} and {beta} Prime -SrTa{sub 2}O{sub 6}. Black-Right-Pointing-Pointer Strontium disorder in tetragonal tungsten bronze {beta} Prime -SrTa{sub 2}O{sub 6}. Black-Right-Pointing-Pointer Orthorhombic distortion and cell doubling in {beta}-SrTa{sub 2}O{sub 6}.

  17. Solid state 13C-NMR, infrared, X-ray powder diffraction and differential thermal studies of the homologous series of some mono-valent metal (Li, Na, K, Ag) n-alkanoates: A comparative study

    NASA Astrophysics Data System (ADS)

    Nelson, Peter N.; Ellis, Henry A.; White, Nicole A. S.

    2015-06-01

    A comparative study of the molecular packing, lattice structures and phase behaviors of the homologous series of some mono-valent metal carboxylates (Li, Na, K and Ag) is carried out via solid state FT-infrared and 13C-NMR spectroscopes, X-rays powder diffraction, density measurements, differential scanning calorimetry, polarizing light microscopy and variable temperature infrared spectroscopy. It is proposed that, for lithium, sodium and potassium carboxylates, metal-carboxyl coordination is via asymmetric chelating bidentate bonding with extensive intermolecular interactions to form tetrahedral metal centers, irrespective of chain length. However, for silver n-alkanoates, carboxyl moieties are bound to silver ions via syn-syn type bridging bidentate coordination to form dimeric units held together by extensive head group inter-molecular interactions. Furthermore, the fully extended hydrocarbon chains which are crystallized in the all-trans conformation are tilted at ca. 30°, 27°, 15° and 31° with respect to a normal to the metal plane, for lithium, sodium, silver and potassium carboxylates, respectively. All compounds are packed as lamellar bilayer structures, however, lithium compounds are crystallized in a triclinic crystal system whilst silver, sodium and potassium n-alkanoates are all monoclinic with possible P1 bravais lattice. Odd-even alternation observed in various physical features is associated with different inter-planar spacing between closely packed layers in the bilayer which are not in the same plane; a phenomenon controlled by lattice packing symmetry requirements. All compounds, except silver carboxylates, show partially reversibly first order pre-melting transitions; the number of which increases with increasing chain length. These transitions are associated, for the most part, with lamellar collapse followed by increased gauche-trans isomerism in the methylene group assembly, irrespective of chain length. It is proposed that the absence of

  18. Structural characterization of Bi{sub 2}Te{sub 3} and Sb{sub 2}Te{sub 3} as a function of temperature using neutron powder diffraction and extended X-ray absorption fine structure techniques

    SciTech Connect

    Mansour, A. N.; Wong-Ng, W.; Huang, Q.; Tang, W.; Thompson, A.; Sharp, J.

    2014-08-28

    The structure of Bi{sub 2}Te{sub 3} (Seebeck coefficient Standard Reference Material (SRM™ 3451)) and the related phase Sb{sub 2}Te{sub 3} have been characterized as a function of temperature using the neutron powder diffraction (NPD) and the extended X-ray absorption fine structure (EXAFS) techniques. The neutron structural studies were carried out from 20 K to 300 K for Bi{sub 2}Te{sub 3} and from 10 K to 298 K for Sb{sub 2}Te{sub 3}. The EXAFS technique for studying the local structure of the two compounds was conducted from 19 K to 298 K. Bi{sub 2}Te{sub 3} and Sb{sub 2}Te{sub 3} are isostructural, with a space group of R3{sup ¯}m. The structure consists of repeated quintuple layers of atoms, Te2-M-Te1-M-Te2 (where M = Bi or Sb) stacking along the c-axis of the unit cell. EXAFS was used to examine the bond distances and static and thermal disorders for the first three shells of Bi{sub 2}Te{sub 3} and Sb{sub 2}Te{sub 3} as a function of temperature. The temperature dependencies of thermal disorders were analyzed using the Debye and Einstein models for lattice vibrations. The Debye and Einstein temperatures for the first two shells of Bi{sub 2}Te{sub 3} are similar to those of Sb{sub 2}Te{sub 3} within the uncertainty in the data. However, the Debye and Einstein temperatures for the third shell of Bi-Bi are significantly lower than those of the third shell of Sb-Sb. The Einstein temperature for the third shell is consistent with a soft phonon mode in both Bi{sub 2}Te{sub 3} and Sb{sub 2}Te{sub 3}. The lower Einstein temperature of Bi-Bi relative to Sb-Sb is consistent with the lower value of thermal conductivity of Bi{sub 2}Te{sub 3} relative to Sb{sub 2}Te{sub 3}.

  19. {sup 27}Al and {sup 23}Na MAS NMR and powder x-ray diffraction studies of sodium aluminate speciation and the mechanistics of aluminum hydroxide precipitation upon acid hydrolysis

    SciTech Connect

    Bradley, S.M.; Hanna, J.V.

    1994-08-24

    {sup 27}Al and {sup 23}Na MAS NMR, powder X-ray diffraction, and infrared spectroscopic investigations of freeze-dried sodium aluminates and aluminum hydroxides formed through acid hydrolysis have been undertaken, with OH/Al hydrolysis ratios between 5.3 and 2.8 being analyzed. Numerous {sup 27}AlNMR resonances were observed, the intensities of which vary as a function of OH/Al ratio, and these have been assigned to four-, five-, and six-coordinate aluminum species constituting a variety of structural moieties. The dominant species at an OH/Al ratio above 4.4 appears to be a Q{sup o}Na[Al(OH);{sub 4}] salt, as indicated by a {sup 27}Al resonance at 86.6 ppm. In addition, a second, broader resonance at 71.3 ppm demonstrates the simultaneous existence of further four-coordinate aluminum species linked thorough oxo bonds to other four-coordinate aluminums (e.g., Q{sup 2} [Al(OH);{sub 2}(OAl){sub 2}];{sup x-}). At an OH/Al ratio between 4.4 and 4.1, a water-soluble phase forms that contains both four- and six-coordinate aluminum. At OH/Al ratios fo 4.0 and below, a water-soluble phase forms that contains both four-and six-coordinate aluminum. AT OH/Al ratios of 4.0 and below, a water-insoluble phase exists possessing four-, five-, and six-coordinate aluminum. At OH/Al{le}3.9 range exhibits {sup 27}Al chemical shifts similar to those reported for transitional aluminas such as {gamma}-, {eta}-, and 0-Al{sub 2}O{sub 3} and an infrared spectrum similar to pseudo-spinel gels, suggesting that a pseudo-spinel intermediate is the first phase involved in the crystallization of gibbsite. The resonance assigned to five-coordinate aluminum probably results from species involved in the transformation of the pseudo-spinal phase to pseudo-boehmite. The formation of gibbssite on the acid hydrolysis of alkaline sodium aluminate solutions thus appears to follow the pathway pseudo-spinel {r_arrow} pseudo-boehmite {r_arrow} bayerite {r_arrow} gibbsite. 82 refs., 7 figs., 3 tabs.

  20. Kinetics of the barotropic ripple (P beta')/lamellar liquid crystal (L alpha) phase transition in fully hydrated dimyristoylphosphatidylcholine (DMPC) monitored by time-resolved x-ray diffraction.

    PubMed Central

    Caffrey, M; Hogan, J; Mencke, A

    1991-01-01

    We present here the first study of the use of a pressure-jump to induce the ripple (P beta')/lamellar liquid crystal (L alpha) phase transition in fully hydrated 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). The transition was monitored by using time-resolved x-ray diffraction (TRXRD). Applying a pressure-jump from atmospheric to 11.3 MPa (1640 psig, 111.6 atm) in 2.5 s induces the L alpha to P beta' phase transition which takes place in two stages. The lamellar repeat spacing initially increases from a value of 66.0 +/- 0.1 A (n = 4) to a maximum value of 70.3 +/- 0.8 A (n = 4) after 10 s and after a further 100-150 s decreases slightly to 68.5 +/- 0.3 A (n = 4). The reverse transition takes place following a pressure jump in 5.5 s from 11.3 MPa to atmospheric pressure. Again, the transition occurs in two stages with the repeat spacing steadily decreasing from an initial value of 68.5 +/- 0.3 A (n = 3) to a minimum value of 66.6 +/- 0.3 A (n = 3) after 50 s and then increasing by approximately 0.5 A over a period of 100 s. The transition temperature increases linearly with pressure up to 14.1 MPa in accordance with the Clapeyron relation, giving a dT/dP value of 0.285 degrees C/MPa (28.5 degrees C/kbar) and an associated volume change of 40 microliters/g. A dynamic compressibility of 0.13 +/- 0.01 A/MPa has been determined for the L alpha phase. This value is compared with the equilibrium compressibilities of bilayer and nonbilayer phases reported in the literature. The results suggest testable mechanisms for the pressure-induced transition involving changes in periodicity, phase hydration, chain order, and orientation. A more complete understanding of the transition mechanism will require improvement in detector spatial resolution and sensitivity, and data on the pressure sensitivity of phase hydration. PMID:1912281

  1. Ultrafast electron diffraction from aligned molecules

    SciTech Connect

    Centurion, Martin

    2015-08-17

    The aim of this project was to record time-resolved electron diffraction patterns of aligned molecules and to reconstruct the 3D molecular structure. The molecules are aligned non-adiabatically using a femtosecond laser pulse. A femtosecond electron pulse then records a diffraction pattern while the molecules are aligned. The diffraction patterns are then be processed to obtain the molecular structure.

  2. A high-resolution neutron powder diffraction investigation of galena (PbS) between 10 K and 350 K: no evidence for anomalies in the lattice parameters or atomic displacement parameters in galena or altaite (PbTe) at temperatures corresponding to the saturation of cation disorder

    NASA Astrophysics Data System (ADS)

    Knight, K. S.

    2014-09-01

    The temperature dependences of the unit cell parameter and the atomic displacement parameters (adp) for galena (PbS) have been measured using high resolution neutron powder diffraction in the temperature interval 10-350 K. No evidence has been found for the anomalous behaviour recently reported in a total scattering study of galena, in which the temperature variation of both the unit cell and the adp for lead are reported to undergo a dramatic reduction at a temperature of ~250 K. The linear thermal expansion coefficient calculated from the powder diffraction study is found to be in excellent agreement with literature values over the entire temperature interval studied, and approximately 25% greater at room temperature than that determined by analysis of the pair distribution function (pdf) derived from the total scattering data. This discrepancy is shown to be attributable to a linear, temperature-dependent offset from the published temperatures in the total scattering study, and has arisen from the sample temperature being significantly lower than the experimental set point temperature. Applying this correction to the adps of the lead cation removes the anomalous temperature dependence and shows the pdf results are in agreement with the neutron powder diffraction results. Application of the identical temperature offsets to the results of the pdf analysis of data collected on altaite (PbTe) eliminates the anomalous behaviour in the unit cell and the adp for lead, bringing them in line with literature values. Contrary to the conclusions of the pdf analysis, adps for the lead cation in both galena and altaite can be described in terms of Debye-like behaviour and are consistent with the partial phonon density of states.

  3. A high-resolution neutron powder diffraction investigation of galena (PbS) between 10 K and 350 K: no evidence for anomalies in the lattice parameters or atomic displacement parameters in galena or altaite (PbTe) at temperatures corresponding to the saturation of cation disorder.

    PubMed

    Knight, K S

    2014-09-24

    The temperature dependences of the unit cell parameter and the atomic displacement parameters (adp) for galena (PbS) have been measured using high resolution neutron powder diffraction in the temperature interval 10-350 K. No evidence has been found for the anomalous behaviour recently reported in a total scattering study of galena, in which the temperature variation of both the unit cell and the adp for lead are reported to undergo a dramatic reduction at a temperature of ~250 K. The linear thermal expansion coefficient calculated from the powder diffraction study is found to be in excellent agreement with literature values over the entire temperature interval studied, and approximately 25% greater at room temperature than that determined by analysis of the pair distribution function (pdf) derived from the total scattering data. This discrepancy is shown to be attributable to a linear, temperature-dependent offset from the published temperatures in the total scattering study, and has arisen from the sample temperature being significantly lower than the experimental set point temperature. Applying this correction to the adps of the lead cation removes the anomalous temperature dependence and shows the pdf results are in agreement with the neutron powder diffraction results. Application of the identical temperature offsets to the results of the pdf analysis of data collected on altaite (PbTe) eliminates the anomalous behaviour in the unit cell and the adp for lead, bringing them in line with literature values. Contrary to the conclusions of the pdf analysis, adps for the lead cation in both galena and altaite can be described in terms of Debye-like behaviour and are consistent with the partial phonon density of states. PMID:25185952

  4. 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.

  5. Note: An X-ray powder diffractometer with a wide scattering-angle range of 72° using asymmetrically positioned one-dimensional detectors.

    PubMed

    Katsuya, Yoshio; Song, Chulho; Tanaka, Masahiko; Ito, Kimihiko; Kubo, Yoshimi; Sakata, Osami

    2016-01-01

    An X-ray powder diffractometer has been developed for a time-resolved measurement without the requirement of a scattering angle (2θ) scan. Six one-dimensional detector modules are asymmetrically arranged in a vertical line at a designed distance of 286.5 mm. A detector module actually covers a diffraction angle of about 12° with an angular resolution of 0.01°. A diffracted intensity pattern is simultaneously recorded in a 2θ angular range from 1.63° to 74.37° in a "one shot" measurement. We tested the performance of the diffractometer with reference CeO2 powders and demonstrated diffraction measurements from an operating lithium-air battery. PMID:26827367

  6. Note: An X-ray powder diffractometer with a wide scattering-angle range of 72° using asymmetrically positioned one-dimensional detectors

    NASA Astrophysics Data System (ADS)

    Katsuya, Yoshio; Song, Chulho; Tanaka, Masahiko; Ito, Kimihiko; Kubo, Yoshimi; Sakata, Osami

    2016-01-01

    An X-ray powder diffractometer has been developed for a time-resolved measurement without the requirement of a scattering angle (2θ) scan. Six one-dimensional detector modules are asymmetrically arranged in a vertical line at a designed distance of 286.5 mm. A detector module actually covers a diffraction angle of about 12° with an angular resolution of 0.01°. A diffracted intensity pattern is simultaneously recorded in a 2θ angular range from 1.63° to 74.37° in a "one shot" measurement. We tested the performance of the diffractometer with reference CeO2 powders and demonstrated diffraction measurements from an operating lithium-air battery.

  7. Femtosecond single-electron diffraction

    PubMed Central

    Lahme, S.; Kealhofer, C.; Krausz, F.; Baum, P.

    2014-01-01

    Ultrafast electron diffraction allows the tracking of atomic motion in real time, but space charge effects within dense electron packets are a problem for temporal resolution. Here, we report on time-resolved pump-probe diffraction using femtosecond single-electron pulses that are free from intra-pulse Coulomb interactions over the entire trajectory from the source to the detector. Sufficient average electron current is achieved at repetition rates of hundreds of kHz. Thermal load on the sample is avoided by minimizing the pump-probe area and by maximizing heat diffusion. Time-resolved diffraction from fibrous graphite polycrystals reveals coherent acoustic phonons in a nanometer-thick grain ensemble with a signal-to-noise level comparable to conventional multi-electron experiments. These results demonstrate the feasibility of pump-probe diffraction in the single-electron regime, where simulations indicate compressibility of the pulses down to few-femtosecond and attosecond duration. PMID:26798778

  8. Structure determination of a complex tubular uranyl phenylphosphonate, (UO{sub 2}){sub 3}(HO{sub 3}PC{sub 6}H{sub 5}){sub 2}(O{sub 3}PC{sub 6}H{sub 5}){sub 2}{center_dot}H{sub 2}O, from conventional x-ray powder diffraction data

    SciTech Connect

    Poojary, D.M.; Cabeza, A.; Aranda, A.G.

    1996-03-13

    The three-dimensional structure of a complex tubular uranyl phosphonate, (UO{sub 2}){sub 3}(HO{sub 3}PC{sub 6}H{sub 5}){sub 2}(O{sub 3}PC{sub 6}H{sub 5}){sub 2}(O{sub 3}PC{sub 6}H{sub 5}){sub 2} {center_dot} H{sub 2}O, was determined ab initio from laboratory X-ray powder diffraction data and refined by the Rietveld method. The crystals belong to the space group P2{sub 1}2{sub 1}2{sub 1}, with {alpha} = 17.1966(2) {Angstrom}, b = 7.2125(2) {Angstrom}, c = 27.8282(4) {Angstrom}, and Z = 4. The structure consists of three independent uranium atoms, among which two are seven-coordinated and the third is eight-coordinated. These metal atoms are connected by four different phosphonate groups to form a one-dimensional channel structure along the b axis. The phenyl groups are arranged on the outer periphery of the channels, and their stacking forces keep the channels intact in the lattice. The determination of this structure which contains 50 non-hydrogen atoms in the asymmetric unit, from conventional X-ray powder data, represents significant progress in the application of powder techniques to structure of complex inorganic compounds, including organometallic compounds.

  9. Face powder poisoning

    MedlinePlus

    Face powder poisoning occurs when someone swallows or breathes in this substance. This article is for information ... The ingredients in face powder that can be harmful are: Baking soda Talcum powder Many other types of powder

  10. The Amblygonite (LiAlPO{sub 4}F)-Montebrasite (LiAlPO{sub 4}OH) Solid Solution: A Combined powder and single-crystal neutron diffraction and solid-state {sup 6}Li MAS, CP MAS, and REDOR NMR study

    SciTech Connect

    Groat, Lee A.; Chakoumakos, Bryan C.; Brouwer, Darren H.; Hoffman, Christina M.; Fyfe, Colin A.; Morell, Heiko; Schultz, Arthur J.

    2003-01-01

    The amblygonite-montebrasite series of minerals, common constituents of granitic pegmatites and topaz-bearing granites, show complete solid solution with ideal composition LiAlPO{sub 4}(F, OH). These compounds are ideal for studying F {leftrightarrow} OH solid solution in minerals because natural members of the series generally show little deviation from the ideal composition. In this study, we used powder and single-crystal neutron diffraction and solid-state {sup 6}Li MAS, CP MAS, and REDOR NMR techniques to study the effect of F {leftrightarrow} OH substitution on the series. Lattice parameters refined from single-crystal neutron diffraction data show increasing b and decreasing a, c, and V with increasing F/(F + OH). The volume is highest for the OH end-member because of the presence of an additional atom (H). The a and c parameters decrease with increasing F/(F + OH) because the O-H vector is close to the a-c plane and the Al-OH/F vectors are approximately parallel to c. Lattice parameters refined from neutron powder diffraction patterns collected at lower T show that thermal contraction increases with F/(F + OH), presumably because the F anion takes up less space than the OH molecule. The results show that the OH/F position is always fully occupied. The H displacement ellipsoid shows little change with occupancy, which obviously corresponds negatively with increasing F/(F + OH). However, the Li displacement ellipsoid becomes extremely large and anisotropic with increasing F fraction. Most of the distortion is associated with the U{sub 3} eigenvalue, which lies between the c and c* directions. U{sub eq} values corresponding to the Li atom show a greater reduction with decreasing temperature than the other atoms. The temperature dependence of Li is the same regardless of F content. Even when extrapolated to absolute zero the Li displacement ellipsoid is very large, which implies a large static disorder.

  11. In-situ mechanical testing during X-ray diffraction

    SciTech Connect

    Van Swygenhoven, Helena Van Petegem, Steven

    2013-04-15

    Deforming metals during recording X-ray diffraction patterns is a useful tool to get a deeper understanding of the coupling between microstructure and mechanical behaviour. With the advances in flux, detector speed and focussing techniques at synchrotron facilities, in-situ mechanical testing is now possible during powder diffraction and Laue diffraction. The basic principle is explained together with illustrative examples.

  12. Magnetic field dependent neutron powder diffraction studies of Ru{sub 0.9}Sr{sub 2}YCu{sub 2.1}O{sub 7.9}

    SciTech Connect

    Nigam, R.; Pan, A. V.; Dou, S. X.; Kennedy, S. J.; Studer, A. J.; Stuesser, N.

    2010-05-15

    Temperature and magnetic field dependent neutron diffraction has been used to study the magnetic order in Ru{sub 0.9}Sr{sub 2}YCu{sub 2.1}O{sub 7.9}. The appearance of (1/2, 1/2, 1/2), (1/2, 1/2, 3/2), and (1/2, 1/2, 5/2) peaks below T{sub M}=140 K manifests the antiferromagnetic order. Neutron diffraction patterns measured in applied magnetic fields from 0 to 6 T show the destruction of the antiferromagnetic order with increasing field. There is no evidence of spontaneous or field-induced long range ferromagnetic order. This latter result contradicts the vast majority of other experimental observations for this system.

  13. Ceramic Powders

    NASA Technical Reports Server (NTRS)

    1984-01-01

    In developing its product line of specialty ceramic powders and related products for government and industrial customers, including companies in the oil, automotive, electronics and nuclear industries, Advanced Refractory Technologies sought technical assistance from NERAC, Inc. in specific areas of ceramic materials and silicon technology, and for assistance in identifying possible applications of these materials in government programs and in the automotive and electronics industry. NERAC conducted a computerized search of several data bases and provided extensive information in the subject areas requested. NERAC's assistance resulted in transfer of technologies that helped ART staff develop a unique method for manufacture of ceramic materials to precise customer specifications.

  14. Energetic powder

    DOEpatents

    Jorgensen, Betty S.; Danen, Wayne C.

    2003-12-23

    Fluoroalkylsilane-coated metal particles. The particles have a central metal core, a buffer layer surrounding the core, and a fluoroalkylsilane layer attached to the buffer layer. The particles may be prepared by combining a chemically reactive fluoroalkylsilane compound with an oxide coated metal particle having a hydroxylated surface. The resulting fluoroalkylsilane layer that coats the particles provides them with excellent resistance to aging. The particles can be blended with oxidant particles to form energetic powder that releases chemical energy when the buffer layer is physically disrupted so that the reductant metal core can react with the oxidant.

  15. Crystal structure of Kuzel's salt 3CaO.Al{sub 2}O{sub 3}.1/2CaSO{sub 4}.1/2CaCl{sub 2}.11H{sub 2}O determined by synchrotron powder diffraction

    SciTech Connect

    Mesbah, Adel; Francois, Michel; Cau-dit-Coumes, Celine; Frizon, Fabien; Leroux, Fabrice; Ravaux, Johann

    2011-05-15

    The crystal structure of Kuzel's salt has been successfully determined by synchrotron powder diffraction. It crystallizes in the rhombohedral R3-bar symmetry with a = 5.7508 (2) A, c = 50.418 (3) A, V = 1444.04 (11) A{sup 3}. Joint Rietveld refinement was realized using three X-ray powder patterns recorded with a unique wavelength and three different sample-to-detector distances. Kuzel's salt is the chloro-sulfoaluminate AFm phase and belongs to the layered double hydroxide (LDH) large family. Its structure is composed of positively charged main layer [Ca{sub 2}Al(OH){sub 6}]{sup +} and negatively charged interlayer [Cl{sub 0.50}.(SO{sub 4}){sub 0.25}.2.5H{sub 2}O]{sup -}. Chloride and sulfate anions are ordered into two independent crystallographic sites and fill successive interlayer leading to the formation of a second-stage compound. The two kinds of interlayer have the compositions [Cl.2H{sub 2}O]{sup -} and [(SO{sub 4}){sub 0.5}.3H{sub 2}O]{sup -}. The crystal structure explains why chloride and sulfate anions are not substituted and why the formation of extended solid solution in the chloro-sulfate AFm system does not occur.

  16. Hydrothermal Transformation of the Calcium Aluminum Oxide Hydrates CaAl2O4 . 10H2O and Ca2Al2O. 8H2O to Ca3Al2(OH)12 Investigated by In Situ Synchrotron X-ray Powder Diffraction

    SciTech Connect

    Jensen,T.; Christensen, A.; Hanson, J.

    2005-01-01

    The hydrothermal transformation of calcium aluminate hydrates were investigated by in situ synchrotron X-ray powder diffraction in the temperature range 25 to 170 C. This technique allowed the study of the detailed reaction mechanism and identification of intermediate phases. The material CaAl{sub 2}O{sub 4}{center_dot}10H{sub 2}O converted to Ca{sub 3}Al{sub 2}(OH){sub 12} and amorphous aluminum hydroxide. Ca{sub 2}Al{sub 2}O{sub 5}{center_dot}8H{sub 2}O transformed via the intermediate phase Ca{sub 4}Al{sub 2}O{sub 7}{center_dot}13H{sub 2}O to Ca{sub 3}Al{sub 2}(OH){sub 12} and gibbsite, Al(OH){sub 3}. The phase Ca{sub 4}Al{sub 2}O{sub 7}{center_dot}19H{sub 2}O reacted via the same intermediate phase to Ca{sub 3}Al{sub 2}(OH){sub 12} and mainly amorphous aluminum hydroxide. The powder pattern of the intermediate phase is reported.

  17. Synthesis of nanocrystalline tungsten carbide (WC) powder

    NASA Astrophysics Data System (ADS)

    Singla, Gourav; Singh, K.; Pandey, O. P.

    2013-06-01

    Nanocrystalline tungsten carbide (WC) has been obtained from bulk WO3 by in situ reduction and carbonization reactions at low temperature (˜ 600 °C) by taking Mg as reductant and acetone C3H6O as carbon source. It was aimed to elucidate carburization behavior of WO3 powder and to establish optimal conditions for the synthesis of nanocrystalline WC. The role of reaction time on the synthesis of WC has been investigated and discussed. The synthesized powders were characterized by X-ray powder diffraction, differential thermal analyzer (DTA), thermo gravimetric analysis (TGA).

  18. Nanostructured GGG powders via gel combustion

    NASA Astrophysics Data System (ADS)

    Li, Xianxue; Hu, Zhang-Gui; Li, Jiangtao

    2007-03-01

    Polycrystalline nano-sized gadolinium gallium garnet (Gd3Ga5O12, GGG) powders were synthesized via a gel combustion method from a mixed solution of Ga(NO3)3, Gd(NO3)3 and citric acid. The evolution of phase composition and micro-structure of the powders were characterized by X-ray powder diffraction, thermogravimetry/differential thermal analysis and scanning electron microscopy. Well-crystallized, single phase GGG nano-sized powders could be obtained at the calcining temperature as low as 750 °C for 2 h. No any intermediate phases formed during the calcining process. The resulting powders were well dispersed and had a relatively narrow size distribution with an average particle size of approximately 30-50 nm.

  19. Hydrogen in polar intermetallics: Syntheses and structures of the ternary Ca{sub 5}Bi{sub 3}D{sub 0.93}, Yb{sub 5}Bi{sub 3}H{sub x}, and Sm{sub 5}Bi{sub 3}H{sub a}pprox{sub 1} by powder neutron or single crystal X-ray diffraction

    SciTech Connect

    Alejandro Leon-Escamilla, E.; Dervenagas, Panagiotis; Stassis, Constantine; Corbett, John D.

    2010-01-15

    The syntheses of the title compounds are described in detail. Structural characterizations from refinements of single crystal X-ray diffraction data for Yb{sub 5}Bi{sub 3}H{sub x} and Sm{sub 5}Bi{sub 3}H{sub a}pprox{sub 1} and of powder neutron diffraction data for Ca{sub 5}Bi{sub 3}D{sub 0.93(3)} are reported. These confirm that all three crystallize with the heavy atom structure type of beta-Yb{sub 5}Sb{sub 3}, and the third gives the first proof that the deuterium lies in the center of nominal calcium tetrahedra, isostructural with the Ca{sub 5}Sb{sub 3}F-type structure. These Ca and Yb phases are particularly stable with respect to dissociation to Mn{sub 5}Si{sub 3}-type product plus H{sub 2}. Some contradictions in the literature regarding Yb{sub 5}Sb{sub 3} and Yb{sub 5}Sb{sub 3}H{sub x} phases are considered in terms of adventitious hydrogen impurities that are generated during reactions in fused silica containers at elevated temperatures. - Graphical abstract: The structure of Ca{sub 5}Bi{sub 3}H{sub 0.93} occurs in the novel Ca{sub 5}Sb{sub 3}F structure type with D centered in the shaded calcium tetrahedra.

  20. High-energy X-ray powder diffraction and atomic-pair distribution-function studies of charged/discharged structures in carbon-hybridized Li2MnSiO4 nanoparticles as a cathode material for lithiumion batteries

    SciTech Connect

    Moriya, Maki; Miyahara, Masahiko; Hokazono, Mana; Sasaki, Hirokazu; Nemoto, Atsushi; Katayama, Shingo; Akimoto, Yuji; Hirano, Shin-ichi; Ren, Yang

    2014-10-01

    The stable cycling performance with a high discharge capacity of similar to 190 mAh g(-1) in a carbon-hybridized Li2MnSiO4 nanostructured powder has prompted an experimental investigation of the charged/discharged structures using synchrotron-based and laboratory-based X-rays and atomic-pair distributionfunction (PDF) analyses. A novel method of in-situ spray pyrolysis of a precursor solution with glucose as a carbon source enabled the successful synthesis of the carbon-hybridized Li2(M)nSiO(4) nanoparticles. The XRD patters of the discharged (lithiated) samples exhibit a long-range ordered structure characteristic of the (beta) Li2MnSiO4 crystalline phase (space group Pmn2(1)) which dissipates in the charged (delithiated) samples. However, upon discharging the long-range ordered structure recovers in each cycle. The disordered structure, according to the PDF analysis, is mainly due to local distortions of the MnO4 tetrahedra which show a mean Mn-O nearest neighbor distance shorter than that of the long-range ordered phase. These results corroborate the notion of the smaller Mn3+/Mn4+ ionic radii in the Li extracted phase versus the larger Mn2+ ionic radius in Li inserted phase. Thus Li extraction/insertion drives the fluctuation between the disordered and the long-range ordered structures. (C) 2014 Elsevier B.V. All rights reserved.

  1. Syntheses, Vibrational Spectroscopy, and Crystal Structure Determination from X-Ray Powder Diffraction Data of Alkaline Earth Dicyanamides M[N(CN) 2] 2 with M=Mg, Ca, Sr, and Ba

    NASA Astrophysics Data System (ADS)

    Jürgens, Barbara; Irran, Elisabeth; Schnick, Wolfgang

    2001-03-01

    The alkaline earth dicyanamides Mg[N(CN)2]2, Ca[N(CN)2]2, Sr[N(CN)2]2, and Ba[N(CN)2]2 were synthesized by ion exchange using Na[N(CN)2] and the respective nitrates or bromides as starting materials. The crystal structures were determined from X-ray powder diffractometry: Mg[N(CN)2]2, Pnnm, Z=2, a=617.14(3), b=716.97(3), and c=740.35(5) pm; Ca[N(CN)2]2 and Sr[N(CN)2]2, C2/c, Z=4; Ca[N(CN)2]2, a=1244.55(3), b=607.97(1), and c=789.81(1) pm, β=98.864(2)°; Sr[N(CN)2]2, a=1279.63(2), b=624.756(8), and c=817.56(1) pm, β=99.787(1)°; Ba[N(CN)2]2, Pnma, Z=4, a=1368.68(7), b=429.07(7), and c=1226.26(2) pm. The dicyanamides consist of the respective alkaline earth cations and bent planar [N(CN)2]- ions. The structural features were correlated with vibrational spectroscopic data. The thermal behavior was studied by thermoanalytical experiments.

  2. Powder treatment process

    DOEpatents

    Weyand, J.D.

    1988-02-09

    Disclosed are: (1) a process comprising spray drying a powder-containing slurry, the slurry containing a powder constituent susceptible of oxidizing under the temperature conditions of the spray drying, while reducing the tendency for oxidation of the constituent by including as a liquid constituent of the slurry an organic liquid; (2) a process comprising spray drying a powder-containing slurry, the powder having been pretreated to reduce content of a powder constituent susceptible of oxidizing under the temperature conditions of the spray drying, the pretreating comprising heating the powder to react the constituent; and (3) a process comprising reacting ceramic powder, grinding the reacted powder, slurrying the ground powder, spray drying the slurried powder, and blending the dried powder with metal powder. 2 figs.

  3. Powder treatment process

    DOEpatents

    Weyand, John D.

    1988-01-01

    (1) A process comprising spray drying a powder-containing slurry, the slurry containing a powder constituent susceptible of oxidizing under the temperature conditions of the spray drying, while reducing the tendency for oxidation of the constituent by including as a liquid constituent of the slurry an organic liquid; (2) a process comprising spray drying a powder-containing slurry, the powder having been pretreated to reduce content of a powder constituent susceptible of oxidizing under the temperature conditions of the spray drying, the pretreating comprising heating the powder to react the constituent; and (3) a process comprising reacting ceramic powder, grinding the reacted powder, slurrying the ground powder, spray drying the slurried powder, and blending the dried powder with metal powder.

  4. Low-Flow-Rate Dry-Powder Feeder

    NASA Technical Reports Server (NTRS)

    Ramsey, Keith E.

    1994-01-01

    Apparatus feeds small, precise flow of dry powder through laser beam of optical analyzer, measuring patterns of light created by forward scattering (Fraunhofer diffraction) of laser beam from powder particles. From measurement, statistical distribution of sizes of powder particles computed. Developed for analyzing particle-size distributions of solid-propellant powders. Also adapted to use in pharmaceutical industry, in manufacture of metal powder, and in other applications in which particle-size distributions of materials used to control rates of chemical reactions and/or physical characteristics of processes.

  5. Low-Flow-Rate Dry-Powder Feeder

    NASA Technical Reports Server (NTRS)

    Ramsey, Keith E.

    1994-01-01

    Apparatus feeds small, precise flow of dry powder through laser beam of optical analyzer measuring patterns of light created by forward scattering (Fraunhofer diffraction) of laser beam from powder particles. From this optical measurement, statistical distribution of sizes of powder particles computed. Rates of flow optimized for measurement of particle-size distributions. Developed for analyzing particle-size distributions of solid-propellant powders. Also adapted to pharmaceutical industry, in manufacture of metal powder, and in other applications where particle-size distributions of materials used to control rates of chemical reactions and/or physical characteristics of processes.

  6. Restricted Photochemistry in the Molecular Solid State: Structural Changes on Photoexcitation of Cu(I) Phenanthroline Metal-to-Ligand Charge Transfer (MLCT) Complexes by Time-Resolved Diffraction

    SciTech Connect

    Makal, Anna; Benedict, Jason; Trzop, Elzbieta; Sokolow, Jesse; Fournier, Bertrand; Chen, Yang; Kalinowski, Jaros; #322; aw A.; Graber, Tim; Henning, Robert; Coppens, Philip

    2015-10-15

    The excited-state structure of Cu{sup I}[(1,10-phenanthroline-N,N') bis(triphenylphosphine)] cations in their crystalline [BF{sub 4}] salt has been determined at both 180 and 90 K by single-pulse time-resolved synchrotron experiments with the modified polychromatic Laue method. The two independent molecules in the crystal show distortions on MLCT excitation that differ in magnitude and direction, a difference attributed to a pronounced difference in the molecular environment of the two complexes. As the excited states differ, the decay of the emission is biexponential with two strongly different lifetimes, the longer lifetime, assigned to the more restricted molecule, becoming more prevalent as the temperature increases. Standard deviations in the current Laue study are very much lower than those achieved in a previous monochromatic study of a Cu(I) 2,9-dimethylphenanthroline substituted complex (J. Am. Chem. Soc. 2009, 131, 6566), but the magnitudes of the shifts on excitation are similar, indicating that lattice restrictions dominate over the steric effect of the methyl substitution. Above all, the study illustrates emphatically that molecules in solids have physical properties different from those of isolated molecules and that their properties depend on the specific molecular environment. This conclusion is relevant for the understanding of the properties of molecular solid-state devices, which are increasingly used in current technology.

  7. Restricted Photochemistry in the Molecular Solid State: Structural changes on Photoexcitation of Cu(I) Phenanthroline metal-to-ligand-charge-transfer (MLCT) complexes by Time-Resolved Diffraction

    PubMed Central

    Makal, Anna; Benedict, Jason; Trzop, Elzbieta; Sokolow, Jesse; Fournier, Bertrand; Chen, Yang; Kalinowski, Jarosław A.; Graber, Tim; Henning, Robert; Coppens, Philip

    2012-01-01

    The excited state structure of [Cu(1)[(1,10-phenanthroline-N,N’) bis(triphenylphosphine)] cations in their crystalline [BF4] salt has been determined at both 180 and 90K by single-pulse time-resolved synchrotron experiments with the modified polychromatic Laue method. The two independent molecules in the crystal show distortions on MLCT excitation which differ in magnitude and direction, a difference attributed to a pronounced difference in the molecular environment of the two complexes. As the excited states differ, the decay of the emission is bi-exponential with two strongly different lifetimes, the longer lifetime, assigned to the more restricted molecule, becoming more prevalent as the temperature increases. Standard deviations in the current Laue study are very much lower than those achieved in a previous monochromatic study of a Cu(I) 2,9 dimethyl-phenanthroline substituted complex (J. Am. Chem. Soc. 2009, 131, 6566), but the magnitude of the shifts on excitation is similar, indicating that lattice restrictions dominate over the steric effect of the methyl substitution. Above all the study illustrates emphatically that molecules in solids have physical properties different from those of isolated molecules and that their properties depend on the specific molecular environment. This conclusion is relevant for the understanding of the properties of molecular solid state devices which are increasingly used in current technology. PMID:22385365

  8. Synchrotron and neutron powder diffraction study of phase transition in weberite-type Nd[subscript 3]NbO[subscript 7] and La[subscript 3]NbO[subscript 7

    SciTech Connect

    Cai, Lu; Nino, Juan C.

    2011-11-07

    La{sub 3}NbO{sub 7} and Nd{sub 3}NbO{sub 7} are insulating compounds that have an orthorhombic weberite-type crystal structure and undergo a phase transition at about 360 and 450 K, respectively. The nature of the phase transitions was investigated via heat capacity measurements, synchrotron X-ray and neutron diffraction experiments. It is here shown that above the phase transition temperature, the compounds possess a weberite-type structure described by space group Cmcm (No. 63). Below the phase transition, the high temperature phase transforms into a weberite-type structure with space group Pmcn (No. 62). The phase transformation primarily involves the off-center shifting of Nb{sup 5+} ions inside the NbO{sub 6} octahedra, combined with shifts of one third of the Ln{sup 3+} (Ln{sup 3+} = La{sup 3+} and Nd{sup 3+}) ions at the center of the LnO{sub 8} polyhedra towards off-center positions. The phase transition was also proven to have great impacts on the dielectric properties.

  9. Orbital and magnetic ordering in Pr1-xCaxMnO3 and Nd1-xSrxMnO3 manganites near half doping studied by resonant soft x-ray powder diffraction

    NASA Astrophysics Data System (ADS)

    Staub, U.; García-Fernández, M.; Bodenthin, Y.; Scagnoli, V.; de Souza, R. A.; Garganourakis, M.; Pomjakushina, E.; Conder, K.

    2009-06-01

    Here we present resonant soft x-ray diffraction data in the vicinity of the MnL2,3 edges on R1-xTxMnO3 manganites ( R=Pr , Nd and T=Ca , Sr) close to half doping. For Pr0.6Ca0.4MnO3 (PCMO), the energy dependence of the superimposed orbital and magnetic reflections are studied using various incident x-ray polarizations. For Nd0.5Sr0.5MnO3 (NSMO), the energy dependence of the orbital ordering reflection is found to be very similar to that found in other manganites systems. These two results are compared to those presented in the literature on single-crystal samples. Whereas our results are in good agreement with the spectral shape of a superposition of magnetic and orbital signals in PCMO, the magnetic signals are only moderately larger than the orbital signals. The results on NSMO do not agree with previously presented data on single crystals and cast doubt on the proposed occurrence of a double-stripe orbital order.

  10. STED microscopy resolves nanoparticle assemblies

    NASA Astrophysics Data System (ADS)

    Willig, K. I.; Keller, J.; Bossi, M.; Hell, S. W.

    2006-06-01

    We demonstrate the ability of stimulated emission depletion (STED) microscopy, a far-field fluorescence imaging technique with diffraction-unlimited resolution, to reveal the spatial order of fluorescent nanoparticles. Unlike its confocal counterpart, here STED microscopy resolves the arrangements of densely packed 40 nm beads, supramolecular aggregates in a cell membrane, and colloidal nanoparticles. Both raw and linearly deconvolved data disclose unprecedented details of both biological and non-biological nanopatterns.

  11. Diffraction from nonperiodic models of cellulose crystals

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Powder and fiber diffraction patterns were calculated for model cellulose crystallites with chains 20 glucose units long. Model sizes ranged from four chains to 169 chains, based on cellulose I' coordinates, and were subjected to various combinations of energy minimization and molecular dynamics (M...

  12. Comparative determination of polymorphs of indomethacin in powders and tablets by chemometrical near-infrared spectroscopy and x-ray powder diffractometry.

    PubMed

    Otsuka, Makoto; Kato, Fumie; Matsuda, Yoshihisa; Ozaki, Yukihiro

    2003-01-01

    The purpose of this research was to develop a rapid chemometrical method based on near-infrared (NIR) spectroscopy to determine indomethacin (IMC) polymorphic content in mixed pharmaceutical powder and tablets. Mixed powder samples with known polymorphic contents of forms alpha and gamma were obtained from physical mixing of 50% of IMC standard polymorphic sample and 50% of excipient mixed powder sample consisting of lactose, corn starch, and hydroxypropylcellulose. The tablets were obtained by compressing the mixed powder at 245 MPa. X-ray powder diffraction profiles and NIR spectra were recorded for 6 kinds of standard materials with various polymorphic contents. The principal component regression analysis was performed based on normalized NIR spectra sets of mixed powder standard samples and tablets. The relationships between the actual and predicted polymorphic contents of form g in the mixed powder measured using x-ray powder diffraction and NIR spectroscopy show a straight line with a slope of 0.960 and 0.995, and correlation coefficient constants of 0.970 and 0.993, respectively. The predicted content values of unknown samples by x-ray powder diffraction and NIR spectroscopy were reproducible and in close agreement, but those by NIR spectroscopy had smaller SDs than those by x-ray powder diffraction. The results suggest that NIR spectroscopy provides a more accurate quantitative analysis of polymorphic content in pharmaceutical mixed powder and tablets than does conventional x-ray powder diffractometry. PMID:12916901

  13. RESOLVE Project

    NASA Technical Reports Server (NTRS)

    Parker, Ray; Coan, Mary; Cryderman, Kate; Captain, Janine

    2013-01-01

    The RESOLVE project is a lunar prospecting mission whose primary goal is to characterize water and other volatiles in lunar regolith. The Lunar Advanced Volatiles Analysis (LAVA) subsystem is comprised of a fluid subsystem that transports flow to the gas chromatograph - mass spectrometer (GC-MS) instruments that characterize volatiles and the Water Droplet Demonstration (WDD) that will capture and display water condensation in the gas stream. The LAVA Engineering Test Unit (ETU) is undergoing risk reduction testing this summer and fall within a vacuum chamber to understand and characterize component and integrated system performance. Testing of line heaters, printed circuit heaters, pressure transducers, temperature sensors, regulators, and valves in atmospheric and vacuum environments was done. Test procedures were developed to guide experimental tests and test reports to analyze and draw conclusions from the data. In addition, knowledge and experience was gained with preparing a vacuum chamber with fluid and electrical connections. Further testing will include integrated testing of the fluid subsystem with the gas supply system, near-infrared spectrometer, WDD, Sample Delivery System, and GC-MS in the vacuum chamber. This testing will provide hands-on exposure to a flight forward spaceflight subsystem, the processes associated with testing equipment in a vacuum chamber, and experience working in a laboratory setting. Examples of specific analysis conducted include: pneumatic analysis to calculate the WDD's efficiency at extracting water vapor from the gas stream to form condensation; thermal analysis of the conduction and radiation along a line connecting two thermal masses; and proportional-integral-derivative (PID) heater control analysis. Since LAVA is a scientific subsystem, the near-infrared spectrometer and GC-MS instruments will be tested during the ETU testing phase.

  14. Preparation of metal diboride powders

    DOEpatents

    Brynestad, J.; Bamberger, C.E.

    Finely-divided titanium diboride or zirconium diboride powders are formed by reacting gaseous boron trichloride with a material selected from the group of consisting of titanium powder, zirconium powder, titanium dichloride powder, titanium trichloride powder, and gaseous titanium trichloride.

  15. Preparation of titanium diboride powder

    DOEpatents

    Brynestad, Jorulf; Bamberger, Carlos E.

    1985-01-01

    Finely-divided titanium diboride or zirconium diboride powders are formed by reacting gaseous boron trichloride with a material selected from the group consisting of titanium powder, zirconium powder, titanium dichloride powder, titanium trichloride powder, and gaseous titanium trichloride.

  16. Structural study of (N{sub 2}H{sub 5},H){sub 2.9}U{sub 1.1}Ce{sub 0.9}(C{sub 2}O{sub 4}){sub 5}·10H{sub 2}O from a conventional X-ray diffraction diagram obtained on a powder synthesized by a fast vortex process

    SciTech Connect

    Brackx, E.; Laval, J.P.; Dugne, O.; Feraud, J.P.; Arab-Chapelet, B.

    2015-01-15

    In the context of research on U/minor actinides for nuclear fuel reprocessing in the transmutation process, developments are first studied with surrogates containing uranium and lanthanides to facilitate testing. The tests consist of precipitating and calcining a hydrazinium uranium/cerium oxalate. The structure of this oxalate had not been previously determined, but was necessary to validate the physicochemical mechanisms involved. The present study, firstly demonstrates the structural similarity of the U/Ce oxalate phase (N{sub 2}H{sub 5},H){sub 2.9}U{sub 1.1}Ce{sub 0.9}(C{sub 2}O{sub 4}){sub 5}·10H{sub 2}O, synthesized using a vortex precipitator for continuous synthesis of actinide oxalates, with previously known oxalates, crystallizing in P6{sub 3}/mmc symmetry, obtained by more classical methods. This fast precipitation process induces massive nucleation of fine powders. Their structural and microstructural determination confirms that the raw and dried phases belong to the same structural family as (NH{sub 4}){sub 2}U{sub 2}(C{sub 2}O{sub 4}){sub 5}·0.7H{sub 2}O whose structure was described by Chapelet-Arab in P6{sub 3}/mmc symmetry, using single crystal data. However, they present an extended disorder inside the tunnels of the structure, even after drying at 100 °C, between water and hydrazinium ions. This disorder is directly related to the fast vortex method. This structure determination can be used as a basis for further semi-quantitative analysis on the U/minor actinides products formed under various experimental conditions. - Highlights: • Uranium cerium oxalate precipitate characterization by X-ray powder diffraction. • Morphology characterization by SEM analysis. • Structure determination by unit cell Rietveld refinement.

  17. Synchrotron and neutron powder diffraction study of phase transition in weberite-type Nd{sub 3}NbO{sub 7} and La{sub 3}NbO{sub 7}

    SciTech Connect

    Cai Lu; Nino, Juan C.

    2011-08-15

    La{sub 3}NbO{sub 7} and Nd{sub 3}NbO{sub 7} are insulating compounds that have an orthorhombic weberite-type crystal structure and undergo a phase transition at about 360 and 450 K, respectively. The nature of the phase transitions was investigated via heat capacity measurements, synchrotron X-ray and neutron diffraction experiments. It is here shown that above the phase transition temperature, the compounds possess a weberite-type structure described by space group Cmcm (No. 63). Below the phase transition, the high temperature phase transforms into a weberite-type structure with space group Pmcn (No. 62). The phase transformation primarily involves the off-center shifting of Nb{sup 5+} ions inside the NbO{sub 6} octahedra, combined with shifts of one third of the Ln{sup 3+} (Ln{sup 3+}=La{sup 3+} and Nd{sup 3+}) ions at the center of the LnO{sub 8} polyhedra towards off-center positions. The phase transition was also proven to have great impacts on the dielectric properties. - Graphical abstract: The phase transition of La{sub 3}NbO{sub 7} and Nd{sub 3}NbO{sub 7} upon cooling primarily involves the off-center shifting of Nb{sup 5+} ions inside the NbO{sub 6} octahedra, combined with shifts of one third of the Ln{sup 3+} (Ln{sup 3+}=La{sup 3+} and Nd{sup 3+}) ions at the center of the LnO{sub 8} polyhedra towards off-center positions. Above the phase transition temperature, Ln{sup 3+} and Nb{sup 5+} sit at a position with mirror symmetry and 2-fold axis. Below the phase transition temperature, Ln{sup 3+} and Nb{sup 5+} shift away from the 2-fold axis but still in the mirror plane. Highlights: > La{sub 3}NbO{sub 7} and Nd{sub 3}NbO{sub 7} exhibit a phase transition at 360 and 450 K, respectively. > The phase transformation primarily involves the off-center shifting of Nb{sup 5+} and Ln{sup 3+}. > The off-center ionic displacement decreases with increasing temperature. > Dielectric properties are greatly related to the off-center displacement.

  18. RESOLVE Project

    NASA Technical Reports Server (NTRS)

    Parker, Ray O.

    2012-01-01

    The RESOLVE project is a lunar prospecting mission whose primary goal is to characterize water and other volatiles in lunar regolith. The Lunar Advanced Volatiles Analysis (LAVA) subsystem is comprised of a fluid subsystem that transports flow to the gas chromatograph- mass spectrometer (GC-MS) instruments that characterize volatiles and the Water Droplet Demonstration (WDD) that will capture and display water condensation in the gas stream. The LAVA Engineering Test Unit (ETU) is undergoing risk reduction testing this summer and fall within a vacuum chamber to understand and characterize C!Jmponent and integrated system performance. Ray will be assisting with component testing of line heaters, printed circuit heaters, pressure transducers, temperature sensors, regulators, and valves in atmospheric and vacuum environments. He will be developing procedures to guide these tests and test reports to analyze and draw conclusions from the data. In addition, he will gain experience with preparing a vacuum chamber with fluid and electrical connections. Further testing will include integrated testing of the fluid subsystem with the gas supply system, near-infrared spectrometer, WDD, Sample Delivery System, and GC-MS in the vacuum chamber. This testing will provide hands-on exposure to a flight forward spaceflight subsystem, the processes associated with testing equipment in a vacuum chamber, and experience working in a laboratory setting. Examples of specific analysis Ray will conduct include: pneumatic analysis to calculate the WOO's efficiency at extracting water vapor from the gas stream to form condensation; thermal analysis of the conduction and radiation along a line connecting two thermal masses; and proportional-integral-derivative (PID) heater control analysis. In this Research and Technology environment, Ray will be asked to problem solve real-time as issues arise. Since LAVA is a scientific subsystem, Ray will be utilizing his chemical engineering background to

  19. Compactible powders of omega-3 and β-cyclodextrin.

    PubMed

    Vestland, Tina Lien; Jacobsen, Øyvind; Sande, Sverre Arne; Myrset, Astrid Hilde; Klaveness, Jo

    2015-10-15

    Omega-3 fatty acids are used in both nutraceuticals and pharmaceuticals in the form of triglycerides and ethyl esters. Administration forms available for omega-3 include bulk oil, soft gel capsules, emulsions and some powder compositions. Cyclodextrins are substances well known for their ability to encapsulate lipophilic molecules. In the present work, powders loaded with omega-3 oil, ranging from 10 to 40% (w/w), have been prepared by vacuum drying, freeze drying or spray granulation of aqueous mixtures of omega-3 oil and β-cyclodextrin. The powders were found to be partially crystalline by powder X-ray diffraction and to contain crystalline phases not present in pure β-cyclodextrin, indicating true complexation. The compactibility of the powders has been explored, revealing that a dry and compactible powder can be prepared from various omega-3 oils and β-cyclodextrin. Spray granulation was found to be the superior drying method for the preparation of compactible powders. PMID:25952853

  20. Exchange of Coordinated Solvent During Crystallization of a Metal-Organic Framework Observed by In Situ High-Energy X-ray Diffraction.

    PubMed

    Wu, Yue; Breeze, Matthew I; Clarkson, Guy J; Millange, Franck; O'Hare, Dermot; Walton, Richard I

    2016-04-11

    Using time-resolved monochromatic high energy X-ray diffraction, we present an in situ study of the solvothermal crystallisation of a new MOF [Yb2 (BDC)3 (DMF)2 ]⋅H2 O (BDC=benzene-1,4-dicarboxylate and DMF=N,N-dimethylformamide) under solvothermal conditions, from mixed water/DMF solvent. Analysis of high resolution powder patterns obtained reveals an evolution of lattice parameters and electron density during the crystallisation process and Rietveld analysis shows that this is due to a gradual topochemical replacement of coordinated solvent molecules. The water initially coordinated to Yb(3+) is replaced by DMF as the reaction progresses. PMID:26959076

  1. Crystal Structure Refinement of MgNb 2O 6Columbite from Neutron Powder Diffraction Data and Study of the Ternary System MgO-Nb 2O 5-NbO, with Evidence of Formation of New Reduced Pseudobrookite Mg 5- xNb 4+ xO 15- δ(1.14≤ x≤1.60) Phases

    NASA Astrophysics Data System (ADS)

    Pagola, S.; Carbonio, R. E.; Alonso, J. A.; Fernández-Díaz, M. T.

    1997-11-01

    The crystal structure of the columbite-type phase MgNb 2O 6has been refined from powder neutron diffraction data. The compound is orthorhombic, space group Pbcn(60), Z=4, with unit cell parameters a=14.1875(1), b=5.7001(1), c=5.0331(1) Å. The structure contains chains of NbO 6octahedra sharing edges along the caxis, which are arranged in double layers through common corners. The double layers, parallel to the bcplane, are connected via MgO 6octahedra sharing corners. This compound contains Nb 5+with electronic configuration d0. Attempts to obtain new materials with Nb in a mixed valence state were made in the ternary system MgO-Nb 2O 5-NbO. For molar ratios Mg:Nb=1:2 new pseudobrookite-type phases have been identified. They have the general composition Mg 5- xNb 4+ xO 15- δ, with xvalues ranging from 1.14 to 1.60. The compounds Mg 4Nb 2O 9- δ(corundum-type) and Mg 3Nb 6O 11were identified when the Mg:Nb ratio was 4:2. All the reduced materials were also characterized by thermogravimetric analysis.

  2. High pressure x-ray diffraction studies on nanocrystalline materials

    NASA Astrophysics Data System (ADS)

    Palosz, B.; Stel'makh, S.; Grzanka, E.; Gierlotka, S.; Pielaszek, R.; Bismayer, U.; Werner, S.; Palosz, W.

    2004-02-01

    Application of the in situ high pressure powder diffraction technique for examination of specific structural properties of nanocrystals based on the experimental data of SiC nanocrystalline powders of 2-30 nm in diameter is presented. Limitations and capabilities of the experimental techniques themselves and methods of diffraction data elaboration applied to nanocrystals with very small dimensions (<30 nm) are discussed. It is shown that a unique value of the lattice parameter cannot be determined for such small crystals using a standard powder diffraction experiment. It is also shown that, due to the complex structure constituting a two-phase, core/surface shell system, no unique compressibility coefficient can satisfactorily describe the behaviour of nanocrystalline powders under pressure. We offer a tentative interpretation of the distribution of macro- and micro-strains in nanoparticles of different grain size.

  3. powder in water

    NASA Astrophysics Data System (ADS)

    Chan, Ya-Ting; Wu, Chao-Hsien; Shen, Pouyan; Chen, Shuei-Yuan

    2014-09-01

    Submicron-sized NiAl2+ X O4 fragments and nanocondensates of Ni-doped γ-Al2O3, Al-doped NiO and β-Ni(OH)2 were synthesized simultaneously by pulsed laser ablation of NiAl2O4 powder in water and characterized using X-ray/electron diffraction and optical spectroscopy. The NiAl2+ X O4 is Al-enriched spinel with dislocations and subgrains. The Ni-doped γ-Al2O3 spinel has paracrystalline distribution (i.e., with fair constant longitudinal spacing, but variable relative lateral translations) of defect clusters and intimate intergrowth of θ-Al2O3 and 2x(3) commensurate superstructure. The Al-doped NiO has perfect cubo-octahedron shape and as small as 5 nm in size. The β-Ni(OH)2 and 1-D turbostratic hydroxide lamellae occurred as a matrix of these oxide nanoparticles. The colloidal suspension containing the composite phases has a minimum band gap of 5.3 eV for potential photocatalytic applications.

  4. Introduction to Diffraction in Materials Science and Engineering

    NASA Astrophysics Data System (ADS)

    Krawitz, Aaron D.

    2001-04-01

    Fundamentals and practical applications of diffraction for researchers, engineers, and students Materials science relies heavily on diffraction for the analysis of materials. Introduction to Diffraction in Materials Science and Engineering is a survey of the practical aspects of this valuable tool. Though it contains basic discussion of the theory and physics of diffraction, this book emphasizes understanding and the practical application of diffraction in materials science-making it a valuable text and resource for students, professionals, and researchers. Designed as a teaching and self-study text, this resource begins with a treatment of the fundamentals of crystallography and crystal structure and its importance in diffraction before moving on to cover important aspects of diffraction applications. Numerous examples and problems at the end of each chapter, including critical thinking questions, make this an excellent tool for learning and understanding. The book includes treatments of: * Basics of crystallography * Geometrical representation of crystals and reciprocal space * X-rays and neutrons * Structure factors and intensity * Powder diffraction * Qualitative (Powder Diffraction File) and quantitative phase analysis * Use of the International Tables for more complex structures and the Reitveld method * Residual stress * Introductions to texture, small diffracting units, and long-range order Aaron Krawitz provides both a practical introduction to diffraction that suits the needs of students and a resource for professionals already at work in materials science or engineering who want to utilize the power of diffraction in the study of materials.

  5. Synthesis and time-resolved structural characterization of framework and mineral sulfides

    NASA Astrophysics Data System (ADS)

    Cahill, Christopher Langley

    A new class of open-framework organic/inorganic hybrid materials based on In-S chemistry has been discovered. The compounds therein exhibit unprecedented structural diversity compared to known porous sulfides, primarily due to variation in framework building units. Further, large increases in pore dimensions (vs. zeolites, for example) are observed as these materials consist of comer and edge linked clusters, e.g. In10S20, In9S17, In4S10 and In6S 15. Choice of organic structure directing agents (templates) and careful control of reaction conditions (temperature, pH) both in the In-S and Ge-S systems is shown not only to dictate which building unit will form, but also to direct the resulting framework topology. Several of the compounds described herein crystallize either as powders, or as crystals too small for standard in-house X-ray structural analysis. Diffraction experiments have thus required synchrotron based single crystal techniques for structure determination. Further, certain reaction mixture compositions result in multi-phase end products, the formation pathways of which have been studied with time resolved, in situ synchrotron powder diffraction. An extension of the applicability of the in situ techniques investigated the role of oxygen in hydrothermal systems. Oxidation state is proposed to dictate speciation in the Ni-Ge-S system and to promote phase transformations in the Fe-S mineral system.

  6. Face powder poisoning

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/002700.htm Face powder poisoning To use the sharing features on this page, please enable JavaScript. Face powder poisoning occurs when someone swallows or breathes ...

  7. Composite powder particles

    NASA Technical Reports Server (NTRS)

    Parker, Donald S. (Inventor); MacDowell, Louis G. (Inventor)

    2009-01-01

    A liquid coating composition including a coating vehicle and composite powder particles disposed within the coating vehicle. Each composite powder particle may include a magnesium component, a zinc component, and an indium component.

  8. Precision powder feeder

    DOEpatents

    Schlienger, M. Eric; Schmale, David T.; Oliver, Michael S.

    2001-07-10

    A new class of precision powder feeders is disclosed. These feeders provide a precision flow of a wide range of powdered materials, while remaining robust against jamming or damage. These feeders can be precisely controlled by feedback mechanisms.

  9. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    The magnetic properties of Sr2IrO4, Na2IrO3, Sr3Ir2O7 and CaIrO3 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 CaIrO3. Magnetic space-groups are assigned to Sr2IrO4, Sr3Ir2O7 and CaIrO3, namely, PIcca, PAban and Cm‧cm‧, respectively, in the Belov-Neronova-Smirnova notation. The assignment for Sr2IrO4 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 Ir4+ ion in Sr2IrO4 does not exceed 0.29(4) μB. Na2IrO3 has two candidate magnetic space-groups that are not resolved with currently available resonant x-ray data.

  11. Aluminum powder metallurgy processing

    NASA Astrophysics Data System (ADS)

    Flumerfelt, Joel Fredrick

    In recent years, the aluminum powder industry has expanded into non-aerospace applications. However, the alumina and aluminum hydroxide in the surface oxide film on aluminum powder require high cost powder processing routes. A driving force for this research is to broaden the knowledge base about aluminum powder metallurgy to provide ideas for fabricating low cost aluminum powder components. The objective of this dissertation is to explore the hypothesis that there is a strong linkage between gas atomization processing conditions, as-atomized aluminum powder characteristics, and the consolidation methodology required to make components from aluminum powder. The hypothesis was tested with pure aluminum powders produced by commercial air atomization commercial inert gas atomization and gas atomization reaction synthesis (GARS). The commercial atomization methods are bench marks of current aluminum powder technology. The GARS process is a laboratory scale inert gas atomization facility. A benefit of using pure aluminum powders is an unambiguous interpretation of the results without considering the effects of alloy elements. A comparison of the GARS aluminum powders with the commercial aluminum powders showed the former to exhibit superior powder characteristics. The powders were compared in terms of size and shape, bulk chemistry, surface oxide chemistry and structure, and oxide film thickness. Minimum explosive concentration measurements assessed the dependence of explosibility hazard on surface area, oxide film thickness, and gas atomization processing conditions. The GARS aluminum powders were exposed to different relative humidity levels, demonstrating the effect of atmospheric conditions on post-atomization oxidation of aluminum powder. An Al-Ti-Y GARS alloy exposed in ambient air at different temperatures revealed the effect of reactive alloy elements on post-atomization powder oxidation. The pure aluminum powders were consolidated by two different routes, a

  12. Aluminum powder metallurgy processing

    SciTech Connect

    Flumerfelt, J.F.

    1999-02-12

    The objective of this dissertation is to explore the hypothesis that there is a strong linkage between gas atomization processing conditions, as-atomized aluminum powder characteristics, and the consolidation methodology required to make components from aluminum powder. The hypothesis was tested with pure aluminum powders produced by commercial air atomization, commercial inert gas atomization, and gas atomization reaction synthesis (GARS). A comparison of the GARS aluminum powders with the commercial aluminum powders showed the former to exhibit superior powder characteristics. The powders were compared in terms of size and shape, bulk chemistry, surface oxide chemistry and structure, and oxide film thickness. Minimum explosive concentration measurements assessed the dependence of explosibility hazard on surface area, oxide film thickness, and gas atomization processing conditions. The GARS aluminum powders were exposed to different relative humidity levels, demonstrating the effect of atmospheric conditions on post-atomization processing conditions. The GARS aluminum powders were exposed to different relative humidity levels, demonstrating the effect of atmospheric conditions on post-atomization oxidation of aluminum powder. An Al-Ti-Y GARS alloy exposed in ambient air at different temperatures revealed the effect of reactive alloy elements on post-atomization powder oxidation. The pure aluminum powders were consolidated by two different routes, a conventional consolidation process for fabricating aerospace components with aluminum powder and a proposed alternative. The consolidation procedures were compared by evaluating the consolidated microstructures and the corresponding mechanical properties. A low temperature solid state sintering experiment demonstrated that tap densified GARS aluminum powders can form sintering necks between contacting powder particles, unlike the total resistance to sintering of commercial air atomization aluminum powder.

  13. X-ray powder diffraction, vibration and thermal studies of [A{sub 0.92}(NH{sub 4}){sub 0.08}]{sub 2}TeCl{sub 4}Br{sub 2} with A = Cs, Rb: Influence of mixed cationic and anionic substitutions

    SciTech Connect

    Aribia, W. Ben; Abdelmouleh, M.; Kabadou, A.; Van Der Lee, A.

    2012-05-15

    Graphical abstract: The structures of [A{sub 0.92}(NH{sub 4}){sub 0.08}]{sub 2}TeCl{sub 4}Br{sub 2} with A = Cs, Rb belong to the tetragonal {beta}-K{sub 2}SnCl{sub 6} structure type. Highlights: Black-Right-Pointing-Pointer The two new compound crystallises in P4/mnc tetragonal space group. Black-Right-Pointing-Pointer The structure is considered as isolated octahedred TeCl{sub 4}Br{sup 2-}. Black-Right-Pointing-Pointer The octahedra connected by ionic and hydrogen bonding through the Cs/Rb or N atoms. Black-Right-Pointing-Pointer A DTA/TGA experiment reveals one endothermic peak at 780 K for these compounds. Black-Right-Pointing-Pointer One endothermic peak is detected at around 213 K by DSC experiment. -- Abstract: The crystal structures of [A{sub 0.92}(NH{sub 4}){sub 0.08}]{sub 2}TeCl{sub 4}Br{sub 2} with A = Cs, Rb have been determined using X-ray powder diffraction techniques. The two compounds crystallize in the tetragonal space group P4/mnc, with the unit cell parameters: a = 7.452(1) Angstrom-Sign , c = 10.544(3) Angstrom-Sign , Z = 2 and a = 7.315(2) Angstrom-Sign , c = 10.354(4) Angstrom-Sign , Z = 2 in the presence of Cs and Rb, respectively. These two compounds have an antifluorite-type arrangement of NH{sub 4}{sup +}/Rb{sup +}/Cs{sup +} and octahedral TeCl{sub 4}Br{sub 2}{sup 2-} anions. The stability of these structure is by ionic and hydrogen bonding contacts: A Midline-Horizontal-Ellipsis Cl, A Midline-Horizontal-Ellipsis Br and N-H Midline-Horizontal-Ellipsis Cl, N-H Midline-Horizontal-Ellipsis Br. The different vibrational modes of these powders were analysed by FTIR and Raman spectroscopic studies. A DTA/TGA experiment reveals one endothermic peak at 780 K implicating the decomposition of the sample. At low temperature, one endothermic peak in thermal behavior is detected at around 213 K by DSC experiment. This transition was confirmed by dielectric measurements.

  14. Pixelated diffraction signatures for explosive detection

    NASA Astrophysics Data System (ADS)

    O'Flynn, Daniel; Reid, Caroline; Christodoulou, Christiana; Wilson, Matt; Veale, Matthew C.; Seller, Paul; Speller, Robert

    2012-06-01

    Energy dispersive X-ray diffraction (EDXRD) is a technique which can be used to improve the detection and characterisation of explosive materials. This study has performed EDXRD measurements of various explosive compounds using a novel, X-ray sensitive, pixelated, energy resolving detector developed at the Rutherford Appleton Laboratory, UK (RAL). EDXRD measurements are normally performed at a fixed scattering angle, but the 80×80 pixel detector makes it possible to collect both spatially resolved and energy resolved data simultaneously. The detector material used is Cadmium Telluride (CdTe), which can be utilised at room temperature and gives excellent spectral resolution. The setup uses characteristics from both energy dispersive and angular dispersive scattering techniques to optimise specificity and speed. The purpose of the study is to develop X-ray pattern "footprints" of explosive materials based on spatial and energy resolved diffraction data, which can then be used for the identification of such materials hidden inside packages or baggage. The RAL detector is the first energy resolving pixelated detector capable of providing an energy resolution of 1.0-1.5% at energies up to 150 keV. The benefit of using this device in a baggage scanner would be the provision of highly specific signatures to a range of explosive materials. We have measured diffraction profiles of five explosives and other compounds used to make explosive materials. High resolution spectra have been obtained. Results are presented to show the specificity of the technique in finding explosives within baggage.

  15. Microemulsion Synthesis of Nanoparticle PZT Powder

    NASA Astrophysics Data System (ADS)

    Amiriyan, M.; Nemati, Z. A.; Rahmanifar, M. S.; Ramesh, S.; Meenaloshini, S.; Tolouei, R.

    2011-01-01

    Nanocrystalline lead zirconate titanate (PZT) powders have been synthesized using microemulsion processing route. Microemulsion is one of the major processing techniques to synthesize a nanosize, homogenous, and almost agglomerate free ceramic powders. The ternary microemulsion system is consisted of cyclohexane as the oil phase, Triton X100 as the nonionic surfactant phase, and an aqueous phase containing 0.619 M Pb2+, 0.325 M Zr4+, and 0.3 M Ti4+, representing a Pb2+: Zr4+: Ti4+ molar ratio of 1:0.52:0.48. The ratio of these cations has been adjusted using Inductively Coupled Plasma (ICP) technique. After coprecipitation of metallic hydroxides by adding ammonia solution in microemulsion system, the PZT precursor was obtained. PZT powders have been prepared upon calcination of precursor at 800° C. Prepared powders was characterised using techniques such as X-ray diffraction, differential thermal analysis, and scanning electron microscopy. The characteristics of microemulsion processed powder is discussed, with emphasis on the presence of nano scaled PZT powder with a composition near to morphotropic phase boundary (MPB) without formation of any intermediate phases.

  16. Amorphous powders of Al-Hf prepared by mechanical alloying

    SciTech Connect

    Schwarz, R.B.; Hannigan, J.W.; Sheinberg, H.; Tiainen, T.

    1988-01-01

    We synthesized amorphous Al/sub 50/Hf/sub 50/ alloy powder by mechanically alloying an equimolar mixture of crystalline powders of Al and Hf using hexane as a dispersant. We characterized the powder as a function of mechanical-alloying time by scanning electron microscopy, x-ray diffraction, and differential scanning calorimetry. Amorphous Al/sub 50/Hf/sub 50/ powder heated at 10 K s/sup /minus/1/ crystallizes polymorphously at 1003 K into orthorhombic AlHf (CrB-type structure). During mechanical alloying, some hexane decomposes and hydrogen and carbon are incorporated into the amorphous alloy powder. The hydrogen can be removed by annealing the powder by hot pressing at a temperature approximately 30 K below the crystallization temperature. The amorphous compacts have a diamond pyramidal hardness of 1025 DPH. 24 refs., 7 figs., 1 tab.

  17. Powder Handling Device for Analytical Instruments

    NASA Technical Reports Server (NTRS)

    Sarrazin, Philippe C. (Inventor); Blake, David F. (Inventor)

    2006-01-01

    Method and system for causing a powder sample in a sample holder to undergo at least one of three motions (vibration, rotation and translation) at a selected motion frequency in order to present several views of an individual grain of the sample. One or more measurements of diffraction, fluorescence, spectroscopic interaction, transmission, absorption and/or reflection can be made on the sample, using light in a selected wavelength region.

  18. Multiple feed powder splitter

    DOEpatents

    Lewis, Gary K.; Less, Richard M.

    2001-01-01

    A device for providing uniform powder flow to the nozzles when creating solid structures using a solid fabrication system such as the directed light fabrication (DLF) process. In the DLF process, gas entrained powders are passed through the focal point of a moving high-power laser light which fuses the particles in the powder to a surface being built up in layers. The invention is a device providing uniform flow of gas entrained powders to the nozzles of the DLF system. The device comprises a series of modular splitters which are slidably interconnected and contain an integral flow control mechanism. The device can take the gas entrained powder from between one to four hoppers and split the flow into eight tubular lines which feed the powder delivery nozzles of the DLF system.

  19. Granulation of fine powder

    DOEpatents

    Chen, Ching-Fong

    2016-08-09

    A mixture of fine powder including thorium oxide was converted to granulated powder by forming a first-green-body and heat treating the first-green-body at a high temperature to strengthen the first-green-body followed by granulation by crushing or milling the heat-treated first-green-body. The granulated powder was achieved by screening through a combination of sieves to achieve the desired granule size distribution. The granulated powder relies on the thermal bonding to maintain its shape and structure. The granulated powder contains no organic binder and can be stored in a radioactive or other extreme environment. The granulated powder was pressed and sintered to form a dense compact with a higher density and more uniform pore size distribution.

  20. Multiple feed powder splitter

    DOEpatents

    Lewis, Gary K.; Less, Richard M.

    2002-01-01

    A device for providing uniform powder flow to the nozzles when creating solid structures using a solid fabrication system such as the directed light fabrication (DLF) process. In the DLF process, gas entrained powders are passed through the focal point of a moving high-power laser light which fuses the particles in the powder to a surface being built up in layers. The invention is a device providing uniform flow of gas entrained powders to the nozzles of the DLF system. The device comprises a series of modular splitters which are slidably interconnected and contain an integral flow control mechanism. The device can take the gas entrained powder from between one to four hoppers and split the flow into eight tubular lines which feed the powder delivery nozzles of the DLF system.

  1. Cow dung powder poisoning.

    PubMed

    Sherfudeen, Khaja Mohideen; Kaliannan, Senthil Kumar; Dammalapati, Pavan Kumar

    2015-11-01

    Cow dung, which has germicidal property, was used in ancient days to clean living premises in South India. Nowadays, people are using commercially available synthetic cow dung powder. It is locally known as "saani powder" in Tamil Nadu. It is freely available in homes and is sometimes accidentally consumed by children. It is available in two colors - yellow and green. Cow dung powder poisoning is common in districts of Tamil Nadu such as Coimbatore, Tirupur, and Erode. We report two cases of yellow cow dung powder poisoning from our hospital. PMID:26730123

  2. Physical and chemical characterization techniques for metallic powders

    SciTech Connect

    Slotwinski, J. A.; Stutzman, P. E.; Ferraris, C. F.; Watson, S. S.; Peltz, M. A.; Garboczi, E. J.

    2014-02-18

    Systematic studies have been carried out on two different powder materials used for additive manufacturing: stainless steel and cobalt-chrome. An extensive array of characterization techniques were applied to these two powders. The physical techniques included laser-diffraction particle-size analysis, X-ray computed tomography for size and shape analysis, and optical and scanning electron microscopy. Techniques sensitive to chemistry included X-ray diffraction and energy-dispersive analytical X-ray analysis. The background of these techniques will be summarized and some typical findings comparing different samples of virgin additive manufacturing powders, taken from the same lot, will be given. The techniques were used to confirm that different samples of powder from the same lot were essentially identical, within the uncertainty of the measurements.

  3. A new theory for X-ray diffraction

    SciTech Connect

    Fewster, Paul F.

    2014-05-01

    By considering the scattering distributed throughout space, there is an intensity enhancement at the Bragg angle even when the Bragg condition is not satisfied. This leads to an alternative explanation for the diffraction from powders and small crystals. This article proposes a new theory of X-ray scattering that has particular relevance to powder diffraction. The underlying concept of this theory is that the scattering from a crystal or crystallite is distributed throughout space: this leads to the effect that enhanced scatter can be observed at the ‘Bragg position’ even if the ‘Bragg condition’ is not satisfied. The scatter from a single crystal or crystallite, in any fixed orientation, has the fascinating property of contributing simultaneously to many ‘Bragg positions’. It also explains why diffraction peaks are obtained from samples with very few crystallites, which cannot be explained with the conventional theory. The intensity ratios for an Si powder sample are predicted with greater accuracy and the temperature factors are more realistic. Another consequence is that this new theory predicts a reliability in the intensity measurements which agrees much more closely with experimental observations compared to conventional theory that is based on ‘Bragg-type’ scatter. The role of dynamical effects (extinction etc.) is discussed and how they are suppressed with diffuse scattering. An alternative explanation for the Lorentz factor is presented that is more general and based on the capture volume in diffraction space. This theory, when applied to the scattering from powders, will evaluate the full scattering profile, including peak widths and the ‘background’. The theory should provide an increased understanding of the reliability of powder diffraction measurements, and may also have wider implications for the analysis of powder diffraction data, by increasing the accuracy of intensities predicted from structural models.

  4. Diffraction-limited ultrabroadband terahertz spectroscopy

    PubMed Central

    Baillergeau, M.; Maussang, K.; Nirrengarten, T.; Palomo, J.; Li, L. H.; Linfield, E. H.; Davies, A. G.; Dhillon, S.; Tignon, J.; Mangeney, J.

    2016-01-01

    Diffraction is the ultimate limit at which details of objects can be resolved in conventional optical spectroscopy and imaging systems. In the THz spectral range, spectroscopy systems increasingly rely on ultra-broadband radiation (extending over more 5 octaves) making a great challenge to reach resolution limited by diffraction. Here, we propose an original easy-to-implement wavefront manipulation concept to achieve ultrabroadband THz spectroscopy system with diffraction-limited resolution. Applying this concept to a large-area photoconductive emitter, we demonstrate diffraction-limited ultra-broadband spectroscopy system up to 14.5 THz with a dynamic range of 103. The strong focusing of ultrabroadband THz radiation provided by our approach is essential for investigating single micrometer-scale objects such as graphene flakes or living cells, and besides for achieving intense ultra-broadband THz electric fields. PMID:27142959

  5. Diffraction-limited ultrabroadband terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Baillergeau, M.; Maussang, K.; Nirrengarten, T.; Palomo, J.; Li, L. H.; Linfield, E. H.; Davies, A. G.; Dhillon, S.; Tignon, J.; Mangeney, J.

    2016-05-01

    Diffraction is the ultimate limit at which details of objects can be resolved in conventional optical spectroscopy and imaging systems. In the THz spectral range, spectroscopy systems increasingly rely on ultra-broadband radiation (extending over more 5 octaves) making a great challenge to reach resolution limited by diffraction. Here, we propose an original easy-to-implement wavefront manipulation concept to achieve ultrabroadband THz spectroscopy system with diffraction-limited resolution. Applying this concept to a large-area photoconductive emitter, we demonstrate diffraction-limited ultra-broadband spectroscopy system up to 14.5 THz with a dynamic range of 103. The strong focusing of ultrabroadband THz radiation provided by our approach is essential for investigating single micrometer-scale objects such as graphene flakes or living cells, and besides for achieving intense ultra-broadband THz electric fields.

  6. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2003-08-05

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of ternary mixtures consisting of: Ni powder, Cu powder, and Al powder, Ni powder, Cr powder, and Al powder; Ni powder, W powder and Al powder; Ni powder, V powder, and Al powder; Ni powder, Mo powder, and Al powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  7. Femtosecond snapshots capture atomic motion in a powdered solid

    SciTech Connect

    Miller, Johanna

    2010-09-15

    X-ray diffraction has long been an important tool for deducing crystal structures. The x rays scatter off the crystal's electrons, giving a pattern of diffraction peaks related to the electron density; points of concentrated electron density indicate the nuclear positions. In recent decades time-resolved x-ray diffraction has probed faster and faster structural changes, up to and including atomic movements on the femtosecond time scale.

  8. X-ray diffraction studies of shocked lunar analogs

    NASA Technical Reports Server (NTRS)

    Hanss, R. E.

    1979-01-01

    The X-ray diffraction experiments on shocked rock and mineral analogs of particular significance to lunar geology are described. Materials naturally shocked by meteorite impact, nuclear-shocked, or artificially shocked in a flat plate accelerator were utilized. Four areas were outlined for investigation: powder diffractometer studies of shocked single crystal silicate minerals (quartz, orthoclase, oligoclase, pyroxene), powder diffractometer studies of shocked polycrystalline monomineralic samples (dunite), Debye-Scherrer studies of single grains of shocked granodiorite, and powder diffractometer studies of shocked whole rock samples. Quantitative interpretation of peak shock pressures experienced by materials found in lunar or terrestrial impact structures is presented.

  9. Compaction of Titanium Powders

    SciTech Connect

    Stephen J. Gerdemann; Paul D. Jablonski

    2010-11-01

    Accurate modeling of powder densification has been an area of active research for more than 60 years. The earliest efforts were focused on linearization of the data because computers were not readily available to assist with curve-fitting methods. In this work, eight different titanium powders (three different sizes of sponge fines <150 μm, <75 μm, and < 45 μm; two different sizes of a hydride-dehydride [HDH] <75 μm and < 45 μm; an atomized powder; a commercially pure [CP] Ti powder from International Titanium Powder [ITP]; and a Ti 6 4 alloy powder) were cold pressed in a single-acting die instrumented to collect stress and deformation data during compaction. From these data, the density of each compact was calculated and then plotted as a function of pressure. The results show that densification of all the powders, regardless of particle size, shape, or chemistry, can be modeled accurately as the sum of an initial density plus the sum of a rearrangement term and a work-hardening term. These last two terms are found to be a function of applied pressure and take the form of an exponential rise.

  10. Sintering titanium powders

    SciTech Connect

    Gerdemann, Stephen J.; Alman, David E.

    2005-09-01

    Recently, there has been renewed interest in low-cost titanium. Near-net-shape powder metallurgy offers the potential of manufacturing titanium articles without costly and difficult forming and machining operations; hence, processing methods such as conventional press-and-sinter, powder forging and powder injection molding are of interest. The sintering behavior of a variety of commercial and experimental titanium powders was studied. Commercial powders were acquired that were produced different routes: (i) sponge fines from the primary titanium processing; (ii) via the hydride-dehydride process; and (iii) gas atomization. The influence of vacuum sintering time (0.5 to 32 hrs) and temperature (1200, 1275 or 1350°C) on the microstructure (porosity present) of cold pressed powders was studied. The results are discussed in terms of the difference in powder characteristics, with the aim of identify the characteristics required for full density via press-and-sinter processing. Near-net-shape tensile bars were consolidated via cold pressed and sintered. After sintering, a sub-set of the tensile bars was hot-isostatic pressed (HIPed). The microstructure and properties of the bars were compared in the sintered and HIPed conditions.

  11. Synthesis and sintering of nanocrystalline hydroxyapatite powders by citric acid sol-gel combustion method

    SciTech Connect

    Han Yingchao; Li Shipu; Wang Xinyu; Chen Xiaoming

    2004-01-03

    The citric acid sol-gel combustion method has been used for the synthesis of nanocrystalline hydroxyapatite (HAP) powder from calcium nitrate, diammonium hydrogen phosphate and citric acid. The phase composition of HAP powder was characterized by X-ray powder diffraction analysis (XRD). The morphology of HAP powder was observed by transmission electron microscope (TEM). The HAP powder has been sintered into microporous ceramic in air at 1200 deg. C with 3 h soaking time. The microstructure and phase composition of the resulting HAP ceramic were characterized by scanning electron microscope (SEM) and XRD, respectively. The physical characterization of open porosity and flexural strength have also been carried out.

  12. Ceramic powder compaction

    SciTech Connect

    Glass, S.J.; Ewsuk, K.G.; Mahoney, F.M.

    1995-12-31

    With the objective of developing a predictive model for ceramic powder compaction we have investigated methods for characterizing density gradients in ceramic powder compacts, reviewed and compared existing compaction models, conducted compaction experiments on a spray dried alumina powder, and conducted mechanical tests and compaction experiments on model granular materials. Die filling and particle packing, and the behavior of individual granules play an important role in determining compaction behavior and should be incorporated into realistic compaction models. These results support the use of discrete element modeling techniques and statistical mechanics principals to develop a comprehensive model for compaction, something that should be achievable with computers with parallel processing capabilities.

  13. Harmonic diffractive lenses

    SciTech Connect

    Sweeney, D.W.; Sommargren, G.E.

    1995-05-10

    The harmonic diffractive lens is a diffractive imaging lens for which the optical path-length transition between adjacent facets is an integer multiple {ital m} of the design wavelength {lambda}{sub 0}. The total lens thickness in air is {ital m}{lambda}{sub 0}/({ital n} {minus} 1), which is {ital m} times thicker than the so-called modulo 2{pi} diffractive lens. Lenses constructed in this way have hybrid properties of both refractive and diffractive lenses. Such a lens will have a diffraction-limited, common focus for a number of discrete wavelengths across the visible spectrum. A 34.75-diopter, 6-mm-diameter lens is diamond turned in aluminum and replicated in optical materials. The sag of the lens is 23 {mu}m. Modulation transfer function measurements in both monochromatic and white light verify the performance of the lens. The lens approaches the diffraction limit for 10 discrete wavelengths across the visible spectrum.

  14. Photoelectron diffraction and holography: Some new directions

    SciTech Connect

    Fadley, C.S. |

    1993-08-01

    Photoelectron diffraction has by now become a versatile and powerful technique for studying surface structures, with special capabilities for resolving chemical and magnetic states of atoms and deriving direct structural information from both forward scattering along bond directions and back-scattering path length differences. Further fitting experiment to theory can lead to structural accuracies in the {plus_minus}0.03 ){Angstrom} range. Holographic inversions of such diffraction data also show considerable promise for deriving local three-dimensional structures around a given emitter with accuracies of {plus_minus}0.2--0.3 {Angstrom}. Resolving the photoelectron spin in some way and using circularly polarized radiation for excitation provide added dimensions for the study of magnetic systems and chiral experimental geometries. Synchrotron radiation with the highest brightness and energy resolution, as well as variable polarization, is crucial to the full exploitation of these techniques.

  15. Study of titanate nanotubes by X-ray and electron diffraction and electron microscopy

    SciTech Connect

    Brunatova, Tereza; Popelkova, Daniela; Wan, Wei; Oleynikov, Peter; Danis, Stanislav; Zou, Xiaodong; Kuzel, Radomir

    2014-01-15

    The structure of titanate nanotubes (Ti-NTs) was studied by a combination of powder X-ray diffraction (PXRD), electron diffraction and high resolution transmission electron microscopy (HRTEM). Ti-NTs are prepared by hydrothermal treatment of TiO{sub 2} powder. The structure is identified by powder X-ray diffraction as the one based on the structure of H{sub 2}Ti{sub 2}O{sub 5}·H{sub 2}O phase. The same structure is obtained by projected potential from HRTEM through-focus image series. The structure is verified by simulated PXRD pattern with the aid of the Debye formula. The validity of the model is tested by computing Fourier transformation of a single nanotube which is proportional to measured electron diffraction intensities. A good agreement of this calculation with measured precession electron diffraction data is achieved. - Highlights: • Titanate nanotubes were prepared by hydrothermal method. • X-ray powder diffraction indicated their structure based on that of H{sub 2}Ti{sub 2}O{sub 5}·H{sub 2}O. • Structural model was created with the aid of high-resolution electron microscopy. • The model was verified with electron diffraction data. • X-ray powder diffraction pattern was calculated with the aid of the Debye formula.

  16. Fabrication of Spherical AlSi10Mg Powders by Radio Frequency Plasma Spheroidization

    NASA Astrophysics Data System (ADS)

    Wang, Linzhi; Liu, Ying; Chang, Sen

    2016-05-01

    Spherical AlSi10Mg powders were prepared by radio frequency plasma spheroidization from commercial AlSi10Mg powders. The fabrication process parameters and powder characteristics were investigated. Field emission scanning electron microscope, X-ray diffraction, laser particle size analyzer, powder rheometer, and UV/visible/infrared spectrophotometer were used for analyses and measurements of micrographs, phases, granulometric parameters, flowability, and laser absorption properties of the powders, respectively. The results show that the obtained spherical powders exhibit good sphericity, smooth surfaces, favorable dispersity, and excellent fluidity under appropriate feeding rate and flow rate of carrier gas. Further, acicular microstructures of the spherical AlSi10Mg powders are composed of α-Al, Si, and a small amount of Mg2Si phase. In addition, laser absorption values of the spherical AlSi10Mg powders increase obviously compared with raw material, and different spectra have obvious absorption peaks at a wavelength of about 826 nm.

  17. Rietveld neutron powder profile analysis and electrical conductivity of the fast silver-ion conductor (LaO)AgS

    SciTech Connect

    Wilmer, D.; Wuensch, B. J.; Jorgensen, J. D.

    1999-11-18

    Lanthanum silver oxysulfide, (LaO)AgS, exhibits a predominantly ionic conductivity of 10{sup {minus}3} to 10{sup {minus}1} S/cm between 300 K and 770 K. The tetragonal structure consists of alternating (LaO) and (AgS) sheets, their sequence being O-La-S-Ag-S-La-O. The structure suggests that ionic transport arises from migration of silver ions within the AgS layers analogous to sodium ion transport in Na-{beta}-alumina. Neutron powder diffraction data measured at five temperatures between 300 K and 770 K are analyzed using the Rietveld method to determine the distribution and thermal vibration parameters of the mobile silver ions. The structural investigation is accompanied by measurements of the total conductivity in the same temperature range in order to resolve severe discrepancies in the literature data.

  18. Gelcasting superalloy powders

    SciTech Connect

    Janney, M.A.

    1995-12-31

    Gelcasting is a process for forming inorganic powders into complex shapes. It was originally developed for ceramic powders. A slurry of powder and a monomer solution is poured in to mold and polymerized in-situ to form gelled parts. Typically, only 2-4 wt % Polymer is used. The process has both aqueous and nonaqueous versions. Gelcasting is a generic process and has been used to produce ceramic parts from over a dozen different ceramic compositions ranging from alumina-based refractories to high-performance silicon nitride. Recently, gelcasting has been applied to forming superalloy powders into complex shapes. This application has posed several challenges not previously encountered in ceramics. In particular, problems were caused by the larger particle size and the higher density of the particles. Additional problems were encountered with binder removal. How these problems were overcome will be described.

  19. Magnetically responsive enzyme powders

    NASA Astrophysics Data System (ADS)

    Pospiskova, Kristyna; Safarik, Ivo

    2015-04-01

    Powdered enzymes were transformed into their insoluble magnetic derivatives retaining their catalytic activity. Enzyme powders (e.g., trypsin and lipase) were suspended in various liquid media not allowing their solubilization (e.g., saturated ammonium sulfate and highly concentrated polyethylene glycol solutions, ethanol, methanol, 2-propanol) and subsequently cross-linked with glutaraldehyde. Magnetic modification was successfully performed at low temperature in a freezer (-20 °C) using magnetic iron oxides nano- and microparticles prepared by microwave-assisted synthesis from ferrous sulfate. Magnetized cross-linked enzyme powders were stable at least for two months in water suspension without leakage of fixed magnetic particles. Operational stability of magnetically responsive enzymes during eight repeated reaction cycles was generally without loss of enzyme activity. Separation of magnetically modified cross-linked powdered enzymes from reaction mixtures was significantly simplified due to their magnetic properties.

  20. POWDER COAT APPLICATIONS

    EPA Science Inventory

    The report discusses an investigation of critical factors that affect the use of powder coatings on the environment, cost, quality, and production. The investigation involved a small business representative working with the National Defense Center for Environmental Excellence (ND...

  1. Pyrotechnic filled molding powder

    DOEpatents

    Hartzel, Lawrence W.; Kettling, George E.

    1978-01-01

    The disclosure relates to thermosetting molding compounds and more particularly to a pyrotechnic filled thermosetting compound comprising a blend of unfilled diallyl phthalate molding powder and a pyrotechnic mixture.

  2. Talcum powder poisoning

    MedlinePlus

    ... powder As a filler in street drugs, like heroin Other products may also contain talc. ... have developed serious lung damage and cancer. Injecting heroin that contains talc into a vein may lead ...

  3. Existence of ferroelectric ice on planets—A neutron diffraction study

    NASA Astrophysics Data System (ADS)

    Fukazawa, Hiroshi; Hoshikawa, Akinori; Chakoumakos, Bryan C.; Fernandez-Baca, Jaime A.

    2009-02-01

    From neutron powder-diffraction experiments, we have studied the growth process of ferroelectric ice XI (eleven) with deuteron-ordered arrangements. We measured time-resolved neutron diffraction of 0.001-M KOD-doped D2O ice. We observed the growth of ice XI at 72-74 K. The mass fraction f (the ratio of mass of ice XI to that of the doped ice) linearly increased with time for about 2 days. The de-transformed ice Ih, obtained after warming above the transition temperature of 76 K, retransformed to ice XI at 66 K. The observed increase of f with time is in good agreement with the nucleation process of the ordering and the constant growth of the ordered domain. A large fraction of ice Ih sample doped with sodium hydroxide changed to ice XI at 68 K. The results suggest that large quantities of ice on cold icy bodies in our solar system are able to transform to ice XI, which may be detectable by space telescope and planetary exploration.

  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. 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.

  6. X-ray diffraction of solid tin to 1.2 TPa

    NASA Astrophysics Data System (ADS)

    Lazicki, Amy; Rygg, Ryan; Coppari, Federica; Smith, Ray; Fratanduono, Dayne; Braun, Dave; Kraus, Richard; Swift, Damian; Collins, Gilbert; Eggert, Jon

    2015-06-01

    We present x-ray diffraction studies of solid crystal structure at the highest stress state where such measurements have ever been performed. Using laser-driven ramp compression methods coupled with angle-resolved powder x-ray diffraction at the Omega laser facility, we explore the phase diagram of tin below the melting curve between 0.1 and 1.2 terapascals (TPa). We demonstrate that, at dynamic-compression rates on the order of 107 s-1, tin transforms from the ambient tetragonal beta-Sn phase to the stable high pressure body-centered cubic (bcc) phase with densities consistent with static-compression measurements. Above 0.16 TPa our experiments identify a new feature in the phase diagram: a crystal structure clearly inconsistent with the hexagonal-close-packed (hcp) phase identified at these conditions by ambient-temperature static-compression measurements and by zero-kelvin density functional theory structure predictions. Our results suggest that the bcc phase is stabilized relative to hcp at high temperature, analogous to the heavier group IV metal Pb and numerous other elemental metals, and retains this phase during ramp compression to 1.2 TPa. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  7. Diffraction by cold atoms

    NASA Astrophysics Data System (ADS)

    Strauch, F.; Gomer, V.; Schadwinkel, H.; Ueberholz, B.; Haubrich, D.; Meschede, D.

    1998-01-01

    We have observed diffraction of a laser probe beam by a trapped sample of cold atoms. The effect is only visible in the vicinity of a resonance line. The observed diffraction pattern arises from interference of the incident and scattered light wave, allowing reconstruction of geometric properties of the trapped sample from the holographic record.

  8. Diffraction Results from CDF

    SciTech Connect

    Goulianos, Konstantin

    2012-04-01

    We present final results by the CDF II collaboration on diffractive W and Z production, report on the status of ongoing analyses on diffractive dijet production and on rapidity gaps between jets, and briefly summarize results obtained on exclusive production pointing to their relevance to calibrating theoretical models used to predict exclusive Higgs-boson production at the LHC.

  9. Phononic crystal diffraction gratings

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

    When a phononic crystal is interrogated by an external source of acoustic waves, there is necessarily a phenomenon of diffraction occurring on the external enclosing surfaces. Indeed, these external surfaces are periodic and the resulting acoustic diffraction grating has a periodicity that depends on the orientation of the phononic crystal. This work presents a combined experimental and theoretical study on the diffraction of bulk ultrasonic waves on the external surfaces of a 2D phononic crystal that consists of a triangular lattice of steel rods in a water matrix. The results of transmission experiments are compared with theoretical band structures obtained with the finite-element method. Angular spectrograms (showing frequency as a function of angle) determined from diffraction experiments are then compared with finite-element simulations of diffraction occurring on the surfaces of the crystal. The experimental results show that the diffraction that occurs on its external surfaces is highly frequency-dependent and has a definite relation with the Bloch modes of the phononic crystal. In particular, a strong influence of the presence of bandgaps and deaf bands on the diffraction efficiency is found. This observation opens perspectives for the design of efficient phononic crystal diffraction gratings.

  10. Method for classifying ceramic powder

    NASA Technical Reports Server (NTRS)

    Takabe, K.

    1983-01-01

    Under the invented method, powder A of particles of less than 10 microns, and carrier powder B, whose average particle diameter is more than five times that of powder A, are premixed so that the powder is less than 40 wt.% of the total mixture, before classifying.

  11. A Comparison of Cocrystal Structure Solutions from Powder and Single Crystal Techniques

    SciTech Connect

    S Lapidus; P Stephens; K Arora; T Shattock; M Zaworotko

    2011-12-31

    We demonstrate the effectiveness and accuracy of high resolution powder diffraction for determination of cocrystal structures through a double-blind study. Structures of 10 cocrystals of varying complexity were determined independently using single crystal and powder techniques. The two methodologies give identical molecular packing and hydrogen bond topology, and an rms difference in covalent bond lengths of 0.035 {angstrom}. Powder techniques are clearly sufficient to establish a complete characterization of cocrystal geometry.

  12. Characterization of Metal Powders Used for Additive Manufacturing

    PubMed Central

    Slotwinski, JA; Garboczi, EJ; Stutzman, PE; Ferraris, CF; Watson, SS; Peltz, MA

    2014-01-01

    Additive manufacturing (AM) techniques1 can produce complex, high-value metal parts, with potential applications as critical parts, such as those found in aerospace components. The production of AM parts with consistent and predictable properties requires input materials (e.g., metal powders) with known and repeatable characteristics, which in turn requires standardized measurement methods for powder properties. First, based on our previous work, we assess the applicability of current standardized methods for powder characterization for metal AM powders. Then we present the results of systematic studies carried out on two different powder materials used for additive manufacturing: stainless steel and cobalt-chrome. The characterization of these powders is important in NIST efforts to develop appropriate measurements and standards for additive materials and to document the property of powders used in a NIST-led additive manufacturing material round robin. An extensive array of characterization techniques was applied to these two powders, in both virgin and recycled states. The physical techniques included laser diffraction particle size analysis, X-ray computed tomography for size and shape analysis, and optical and scanning electron microscopy. Techniques sensitive to structure and chemistry, including X-ray diffraction, energy dispersive analytical X-ray analysis using the X-rays generated during scanning electron microscopy, and X-Ray photoelectron spectroscopy were also employed. The results of these analyses show how virgin powder changes after being exposed to and recycled from one or more Direct Metal Laser Sintering (DMLS) additive manufacturing build cycles. In addition, these findings can give insight into the actual additive manufacturing process. PMID:26601040

  13. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2003-08-19

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  14. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goval, Amit; Williams, Robert K.; Kroeger, Donald M.

    2005-06-07

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  15. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2003-07-29

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  16. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2004-09-14

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  17. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2005-05-10

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  18. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2003-08-26

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  19. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2004-09-28

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  20. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2005-01-25

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.