skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

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. Fri . "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 = {Fri Jul 01 00:00:00 EDT 2016},
month = {Fri Jul 01 00:00:00 EDT 2016}
}

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

Citation Metrics:
Cited by: 1work
Citation information provided by
Web of Science

Save / Share:
  • A new experimental setup has been developed to enable in situ studies of catalyst surfaces during chemical reactions by means of surface x-ray diffraction (SXRD) and grazing incidence small angle x-ray scattering. The x-ray reactor chamber was designed for both ultrahigh-vacuum (UHV) and reactive gas environments. A laser beam heating of the sample was implemented; the sample temperature reaches 1100 K in UHV and 600 K in the presence of reactive gases. The reactor equipment allows dynamical observations of the surface with various, perfectly mixed gases at controlled partial pressures. It can run in two modes: as a bath reactormore » in the pressure range of 1-1000 mbars and as a continuous flow cell for pressure lower than 10{sup -3} mbar. The reactor is connected to an UHV preparation chamber also equipped with low energy electron diffraction and Auger spectroscopy. This setup is thus perfectly well suited to extend in situ studies to more complex surfaces, such as epitaxial films or supported nanoparticles. It offers the possibility to follow the chemically induced changes of the morphology, the structure, the composition, and growth processes of the model catalyst surface during exposure to reactive gases. As an example the Pd{sub 8}Ni{sub 92}(110) surface structure was followed by SXRD under a few millibars of hydrogen and during butadiene hydrogenation while the reaction was monitored by quadrupole mass spectrometry. This experiment evidenced the great sensitivity of the diffracted intensity to the subtle interaction between the surface atoms and the gas molecules.« less
  • A versatile instrument for the in situ study of catalyst surfaces by surface x-ray diffraction and grazing incidence small angle x-ray scattering in a 13 ml flow reactor combined with reaction product analysis by mass spectrometry has been developed. The instrument bridges the so-called ''pressure gap'' and ''materials gap'' at the same time, within one experimental setup. It allows for the preparation and study of catalytically active single crystal surfaces and is also equipped with an evaporator for the deposition of thin, pure metal films, necessary for the formation of small metal particles on oxide supports. Reactions can be studiedmore » in flow mode and batch mode in a pressure range of 100-1200 mbar and temperatures up to 950 K. The setup provides a unique combination of sample preparation, characterization, and in situ experiments where the structure and reactivity of both single crystals and supported nanoparticles can be simultaneously determined.« less
  • 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