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Dispersive X-ray Diffraction (dispersive + x-ray_diffraction)

Distribution by Scientific Domains
Chemistry60%

Kinds of Dispersive X-ray Diffraction

  • energy dispersive x-ray diffraction
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    Selected Abstracts

    An Energy Dispersive X-ray Diffraction Study of Dioxouranium(VI) in 1 M Lithium Citrate

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2004
    Ermanno Vasca
    Abstract An Energy Dispersive X-ray Diffraction (EDXD) study of 0.3 M dioxouranium(VI) in 1 M lithium citrate at pH = 5 is reported. The data are in accordance with the existence of a predominately polynuclear complex containing four U atoms, concluded from potentiometric measurements. The uranium atoms lie at the corners of two triangles sharing one edge. Five O atoms surround each uranyl group, the uranium coordination polyhedron being a pentagonal bipyramid; four U atoms are linked through double or single O bridges. The U,U distances are 3.95 Å and 4.65 Å. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

    Phase composition depth profiles using spatially resolved energy dispersive X-ray diffraction

    JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2004
    Andrew C. Jupe
    Spatially resolved energy dispersive X-ray diffraction, using high-energy synchrotron radiation (,35,80,keV), was used nondestructively to obtain phase composition profiles along the radii of cylindrical cement paste samples to characterize the progress of the chemical changes associated with sulfate attack on the cement. Phase distributions were acquired to depths of ,4,mm below the specimen surface with sufficient spatial resolution to discern features less than 200,µm thick. The experimental and data analysis methods employed to obtain quantitative composition profiles are described. The spatial resolution that could be achieved is illustrated using data obtained from copper cylinders with a thin zinc coating. The measurements demonstrate that this approach is useful for nondestructively visualizing the sometimes complex transformations that take place during sulfate attack on cement-based materials. These transformations can be spatially related to microstructure as seen by computed microtomography. [source]

    High pressure structure of Tb2Ti2O7 pyrochlore at cryogenic temperatures

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2007
    Ravhi S. Kumar
    Abstract The structure of Tb2Ti2O7 pyrochlore was investigated at high pressures up to 24 GPa at cryogenic temperatures down to 6.5 K using angular dispersive X-ray diffraction with synchrotron radiation at HPCAT, Advanced Photon Source. The cell parameters were obtained by performing full profile Rietveld refinements of the diffraction data. The equation of state is obtained at low temperatures by fitting the pressure-volume data to a second order Birch Murnaghan eqation and a bulk modulus value of 168(4) GPa is obtained. The results show persistance of the pyrochlore structure up to the maximum pressure studied in the experiment and further indicate that pressure induces solely magnetic ordering which do not involve crystal symmetry changes. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Evaluation of Fractal-Coated Temporary Pacing Leads in the Early Postoperative Course

    PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2 2008
    FRITZ MELLERT M.D.
    Background:The performance of temporary pacing wires is still limited by capture and sensing problems. Fractal coating can enhance electrical properties and reliability. We therefore investigated fractal-laminated wires in comparison with conventional wires. Methods:In 21 patients two unipolar, fractal-coated pacing wires (fe) and one conventional bipolar electrode (se) were implanted in ventricular position. Afterward pacing threshold (V), R-wave sensing (mV), lead impedance (ohm), and slew-rate (mV/s) were measured. Loss of capture or sensing and dislocation was documented. fe wires were examined with energy dispersive x-ray diffraction (EDX)-analysis and scanning electrode microscopy (SEM). Results:Failure in pacing was less frequent in fe wires. Also fe leads had lower pacing thresholds at implantation (0.76 ± 0.15 V vs 1.51 ± 0.95 V, P< 0.0001) and afterward. Furthermore fe wires showed lower increase of pacing threshold/time (0.25 V/day vs 0.42 V/day). R-wave sensing and slew-rate values in the fe group on day of operation (5.81 ± 4.80 mV; 0.63 ± 0.71 V/s) were lower than in the se group (10.37 ± 6.89 mV; 1.85 ± 1.71 V/s P< 0.0001) and afterward. Nevertheless, decrease of amplitude/time was lower in fe wires (0.17mV/day vs 0.46 mV/day). fe wires always had lower impedance values. Conclusions:Lower pacing threshold and increase of threshold/time in fe wires indicate more reliable function. Initial lower sensitivity values are still not understandable and must be investigated. However, fe wires, constancy of sensing and impedance values was more stable, so fe epicardial wires can be recommended for safe and feasible use. [source]