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Title: Quasielastic neutron scattering with in situ humidity control: Water dynamics in uranyl fluoride

Abstract

The structural phase diagram of uranyl fluoride (UO{sub 2}F{sub 2}), while incomplete, contains at least one anhydrous crystal structure and a second, zeolite-like structure with the formula [(UO{sub 2}F{sub 2})(H{sub 2}O)]{sub 7} ⋅ (H{sub 2}O){sub 4} that can be produced by adding water to the anhydrous structure. While traditional diffraction measurements can easily differentiate these crystals, additional aqueous structures (in general of the form UO{sub 2}F{sub 2} + xH{sub 2}O) have been proposed as well. We present results using a novel sample environment setup to intercalate water during a quasielastic neutron scattering measurement over the course of 86 h. Our sample environment allows low-pressure (<2 atm) humid air flow across the sample coupled with a system to control the relative humidity of this air flow between 10% and 70%. The water dynamics in UO{sub 2}F{sub 2} and [(UO{sub 2}F{sub 2})(H{sub 2}O)]{sub 7} ⋅ (H{sub 2}O){sub 4} are sufficiently different to distinguish them, with water in the latter executing a restricted diffusion (D = 2.7 × 10{sup −6} cm{sup 2}/s) within the structure's accessible pores (r = 3.17 Å) such that the dynamics can be used as a fingerprinting tool. We confirm that water vapor pressure is the driving thermodynamic force for the conversion of the anhydrous structure to [(UO{sub 2}F{sub 2})(H{sub 2}O)]{sub 7} ⋅ (H{sub 2}O){sub 4},more » and we demonstrate the feasibility of extending this approach to aqueous forms of UO{sub 2}F{sub 2} + xH{sub 2}O. This method has general applicability to systems in which water content itself is a driving variable for structural or dynamical phase transitions.« less

Authors:
;  [1];  [1]; ;  [2]
  1. Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)
  2. Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)
Publication Date:
OSTI Identifier:
22597013
Resource Type:
Journal Article
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 119; Journal Issue: 9; Other Information: (c) 2016 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-8979
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; AIR FLOW; CLATHRATES; CRYSTAL STRUCTURE; CRYSTALS; DIFFRACTION; HUMIDITY; HUMIDITY CONTROL; NEUTRON REACTIONS; NEUTRONS; PHASE DIAGRAMS; PHASE TRANSFORMATIONS; QUASI-ELASTIC SCATTERING; URANYL FLUORIDES; VAPOR PRESSURE; WATER; WATER VAPOR; ZEOLITES

Citation Formats

Miskowiec, A., E-mail: miskowiecaj@ornl.gov, Trowbridge, L., Anderson, B., Kirkegaard, M. C., University of Tennessee - Knoxville, Knoxville, Tennessee 37996, Herwig, K. W., and Mamontov, E. Quasielastic neutron scattering with in situ humidity control: Water dynamics in uranyl fluoride. United States: N. p., 2016. Web. doi:10.1063/1.4943164.
Miskowiec, A., E-mail: miskowiecaj@ornl.gov, Trowbridge, L., Anderson, B., Kirkegaard, M. C., University of Tennessee - Knoxville, Knoxville, Tennessee 37996, Herwig, K. W., & Mamontov, E. Quasielastic neutron scattering with in situ humidity control: Water dynamics in uranyl fluoride. United States. https://doi.org/10.1063/1.4943164
Miskowiec, A., E-mail: miskowiecaj@ornl.gov, Trowbridge, L., Anderson, B., Kirkegaard, M. C., University of Tennessee - Knoxville, Knoxville, Tennessee 37996, Herwig, K. W., and Mamontov, E. 2016. "Quasielastic neutron scattering with in situ humidity control: Water dynamics in uranyl fluoride". United States. https://doi.org/10.1063/1.4943164.
@article{osti_22597013,
title = {Quasielastic neutron scattering with in situ humidity control: Water dynamics in uranyl fluoride},
author = {Miskowiec, A., E-mail: miskowiecaj@ornl.gov and Trowbridge, L. and Anderson, B. and Kirkegaard, M. C. and University of Tennessee - Knoxville, Knoxville, Tennessee 37996 and Herwig, K. W. and Mamontov, E.},
abstractNote = {The structural phase diagram of uranyl fluoride (UO{sub 2}F{sub 2}), while incomplete, contains at least one anhydrous crystal structure and a second, zeolite-like structure with the formula [(UO{sub 2}F{sub 2})(H{sub 2}O)]{sub 7} ⋅ (H{sub 2}O){sub 4} that can be produced by adding water to the anhydrous structure. While traditional diffraction measurements can easily differentiate these crystals, additional aqueous structures (in general of the form UO{sub 2}F{sub 2} + xH{sub 2}O) have been proposed as well. We present results using a novel sample environment setup to intercalate water during a quasielastic neutron scattering measurement over the course of 86 h. Our sample environment allows low-pressure (<2 atm) humid air flow across the sample coupled with a system to control the relative humidity of this air flow between 10% and 70%. The water dynamics in UO{sub 2}F{sub 2} and [(UO{sub 2}F{sub 2})(H{sub 2}O)]{sub 7} ⋅ (H{sub 2}O){sub 4} are sufficiently different to distinguish them, with water in the latter executing a restricted diffusion (D = 2.7 × 10{sup −6} cm{sup 2}/s) within the structure's accessible pores (r = 3.17 Å) such that the dynamics can be used as a fingerprinting tool. We confirm that water vapor pressure is the driving thermodynamic force for the conversion of the anhydrous structure to [(UO{sub 2}F{sub 2})(H{sub 2}O)]{sub 7} ⋅ (H{sub 2}O){sub 4}, and we demonstrate the feasibility of extending this approach to aqueous forms of UO{sub 2}F{sub 2} + xH{sub 2}O. This method has general applicability to systems in which water content itself is a driving variable for structural or dynamical phase transitions.},
doi = {10.1063/1.4943164},
url = {https://www.osti.gov/biblio/22597013}, journal = {Journal of Applied Physics},
issn = {0021-8979},
number = 9,
volume = 119,
place = {United States},
year = {Mon Mar 07 00:00:00 EST 2016},
month = {Mon Mar 07 00:00:00 EST 2016}
}