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Title: Grazing incidence X-ray diffraction and transmission electron microscopy studies on the oxide formation of molybdenum in a water vapor environment

Authors:
; ; ; ;
Publication Date:
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE), Fuel Cycle Technologies (NE-5)
OSTI Identifier:
1346263
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Scripta Materialia
Additional Journal Information:
Journal Volume: 120; Journal Issue: C; Related Information: CHORUS Timestamp: 2017-10-03 22:23:15; Journal ID: ISSN 1359-6462
Publisher:
Elsevier
Country of Publication:
United States
Language:
English

Citation Formats

Tang, Ming, Nelson, Andrew T., Wood, Elizabeth S., Maloy, Stuart A., and Jiang, Ying-Bing. Grazing incidence X-ray diffraction and transmission electron microscopy studies on the oxide formation of molybdenum in a water vapor environment. United States: N. p., 2016. Web. doi:10.1016/j.scriptamat.2016.04.010.
Tang, Ming, Nelson, Andrew T., Wood, Elizabeth S., Maloy, Stuart A., & Jiang, Ying-Bing. Grazing incidence X-ray diffraction and transmission electron microscopy studies on the oxide formation of molybdenum in a water vapor environment. United States. doi:10.1016/j.scriptamat.2016.04.010.
Tang, Ming, Nelson, Andrew T., Wood, Elizabeth S., Maloy, Stuart A., and Jiang, Ying-Bing. 2016. "Grazing incidence X-ray diffraction and transmission electron microscopy studies on the oxide formation of molybdenum in a water vapor environment". United States. doi:10.1016/j.scriptamat.2016.04.010.
@article{osti_1346263,
title = {Grazing incidence X-ray diffraction and transmission electron microscopy studies on the oxide formation of molybdenum in a water vapor environment},
author = {Tang, Ming and Nelson, Andrew T. and Wood, Elizabeth S. and Maloy, Stuart A. and Jiang, Ying-Bing},
abstractNote = {},
doi = {10.1016/j.scriptamat.2016.04.010},
journal = {Scripta Materialia},
number = C,
volume = 120,
place = {United States},
year = 2016,
month = 7
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.scriptamat.2016.04.010

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  • We show that the structure factor S(q) of water can be obtained from x-ray synchrotron experiments at grazing angle of incidence (in reflection mode) by using a liquid surface diffractometer. The corrections used to obtain S(q) self-consistently are described. Applying these corrections to scans at different incident beam angles (above the critical angle) collapses the measured intensities into a single master curve, without fitting parameters, which within a scale factor yields S(q). Performing the measurements below the critical angle for total reflectivity yields the structure factor of the top most layers of the water/vapor interface. Our results indicate water restructuringmore » at the vapor/water interface. We also introduce a new approach to extract g(r), the pair distribution function (PDF), by expressing the PDF as a linear sum of error functions whose parameters are refined by applying a nonlinear least square fit method. This approach enables a straightforward determination of the inherent uncertainties in the PDF. Implications of our results to previously measured and theoretical predictions of the PDF are also discussed.« less
  • X-ray depth profiling in a grazing incidence asymmetric Bragg geometry is used to obtain the depth-dependent structure of a nominally ..gamma..-Fe/sub 2/O/sub 3/ thin film, which was oxidized from an Fe/sub 3/O/sub 4/ film. As the incidence angle is varied from angles less than the critical angle for total external reflection to angles greater than the critical angle, the x-ray penetration depth increases from about 20 to several thousand angstroms. The observed diffraction originates from this region of variable depth and a structural depth profile of the thin film can be obtained by measuring the diffraction pattern as a functionmore » of incidence angle. The iron oxide film is found to have a 45-A-thick surface layer of ..cap alpha..-Fe/sub 2/O/sub 3/; beneath this layer the film is predominantly ..gamma..-Fe/sub 2/O/sub 3/ but also contains about 2.6 at. % ..cap alpha..-Fe/sub 2/O/sub 3/. These data, together with previous chemical and magnetic data, suggest that during oxidation of the Fe/sub 3/O/sub 4/ film the surface layer forms by the outward diffusion of Fe ions and their subsequent oxidization to ..cap alpha..-Fe/sub 2/O/sub 3/. One possible explanation of the 2.6% ..cap alpha..-Fe/sub 2/O/sub 3/ in the bulk of the film is that the Fe/sub 3/O/sub 4/ film contains small nuclei of material that are structurally similar to ..cap alpha..-Fe/sub 2/O/sub 3/. During the oxidation to form ..gamma..-Fe/sub 2/O/sub 3/, these then grow to form small grains of ..cap alpha..-Fe/sub 2/O/sub 3/ that are observed.« less
  • Cited by 1
  • Order-disorder transformations in a quaternary pyrochlore oxide system, Ca-Y-Zr-Ta-O, were studied by powder X-ray diffraction (XRD) method, transmission electron microscope (TEM) and FT-NIR Raman spectroscopic techniques. The solid solutions in different ratios, 4:1, 2:1, 1:1, 1:2, 1:4, 1:6, of CaTaO{sub 3.5} and YZrO{sub 3.5} were prepared by the conventional high temperature ceramic route. The XRD results and Rietveld analysis revealed that the crystal structure changed from an ordered pyrochlore structure to a disordered defect fluorite structure as the ratios of the solid solutions of CaTaO{sub 3.5} and YZrO{sub 3.5} were changed from 4:1 to 1:4. This structural transformation in themore » present system is attributed to the lowering of the average cation radius ratio, r{sub A}/r{sub B} as a result of progressive and simultaneous substitution of larger cation Ca{sup 2+} for Y{sup 3+} at A sites and smaller cation Ta{sup 5+} for Zr{sup 4+} at B sites. Raman spectroscopy and TEM analysis corroborated the XRD results. - Graphical abstract: Selected area electron diffraction (SAED) patterns showed highly ordered diffraction maxima with characteristic superlattice weak diffraction spots of the pyrochlore structure for (a) Ca{sub 0.6}7Y{sub 1.33}Zr{sub 1.33}Ta{sub 0.33}O{sub 7} (C2YZT2) and bright diffraction maxima arranged in a ring pattern of the fluorite structure for (b) Ca{sub 0.29}7Y{sub 1.71}Zr{sub 1.71}Ta{sub 0.29}O{sub 7} (CY6Z6T).« less
  • Using synchrotron grazing-incidence X-ray diffraction (GIXD) and reflectivity (XR), the authors have determined the in-plane and out-of-plane structure of phospholipid monolayers at the air-water interface as a function of hydrophilic lipid headgroup size. Di-stearoyl-phosphatidyl-ethanolamine (DSPE) lipid monolayers were systematically modified by chemically grafting hydrophilic poly(ethylene glycol) (PEG) chains of MW = 90 g/mol (2 ethylene oxide, EO, units), MW = 350 g/mol (8 EO units), and MW = 750 g/mol (17 EO units) to the lipid headgroups. The monolayers were studied in the solid phase at a surface pressure of 42 mN/m. At these high lipid packing densities, the PEGmore » chains are submerged in the water subphase. The increased packing stresses from these bulky polymer headgroups distort the unit cell and the in-plane packing modes of the monolayers, leading to large out-of-plane alterations and staggering of the lipid molecules. Surprisingly, a change in the molecular packing of the monolayer toward higher packing densities (lower area per molecule) was observed on increasing the PEG MW to 750 g/mol (17 EO units). This rearrangement of the monolayer structure may be due to a conformational change in the PEG chains.« less