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Title: Diffusion of Cu in AlCu alloys of different composition by quasielastic neutron scattering

Abstract

Quasielastic cold neutron scattering experiments on molten Al{sub 1-x}Cu{sub x} alloys (x = 0.10, 0.17 and 0.25) have been performed at three different temperatures on the FOCUS time-of-flight spectrometer at the Swiss neutron spallation source SINQ. As the main part of the scattering at small Q is incoherent and originating from Cu, self-diffusion coefficients D for the Cu ions could be determined from the widths of quasielastic peaks. The derived values are considerably larger than those found in capillary tube measurements. Even if the accuracy in the determination of D is better than about 4% it could not be concluded whether the temperature variation of D follows an Arrhenius law or a power law.

Authors:
 [1];  [2];  [1];  [3];  [4];  [2];  [5];  [2]
  1. CNRS, Ecole des Mines, Nancy, France
  2. Ames Laboratory
  3. Laboratory for Neutron Scattering ETHZ & PSI
  4. Saarland University, Saarbrucken, Germany
  5. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
932127
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Non-Crystalline Solids; Journal Volume: 353
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ACCURACY; ALLOYS; COLD NEUTRONS; DIFFUSION; NEUTRONS; SCATTERING; SELF-DIFFUSION; SPALLATION; TIME-OF-FLIGHT SPECTROMETERS

Citation Formats

Dahlborg, U., Besser, M., Calvo-Dahlborg, M., Janssen, S., Juranyi, Fanni, Kramer, Matthew J., Morris, James R, and Sordelet, Daniel. Diffusion of Cu in AlCu alloys of different composition by quasielastic neutron scattering. United States: N. p., 2007. Web. doi:10.1016/j.jnoncrysol.2007.05.074.
Dahlborg, U., Besser, M., Calvo-Dahlborg, M., Janssen, S., Juranyi, Fanni, Kramer, Matthew J., Morris, James R, & Sordelet, Daniel. Diffusion of Cu in AlCu alloys of different composition by quasielastic neutron scattering. United States. doi:10.1016/j.jnoncrysol.2007.05.074.
Dahlborg, U., Besser, M., Calvo-Dahlborg, M., Janssen, S., Juranyi, Fanni, Kramer, Matthew J., Morris, James R, and Sordelet, Daniel. Mon . "Diffusion of Cu in AlCu alloys of different composition by quasielastic neutron scattering". United States. doi:10.1016/j.jnoncrysol.2007.05.074.
@article{osti_932127,
title = {Diffusion of Cu in AlCu alloys of different composition by quasielastic neutron scattering},
author = {Dahlborg, U. and Besser, M. and Calvo-Dahlborg, M. and Janssen, S. and Juranyi, Fanni and Kramer, Matthew J. and Morris, James R and Sordelet, Daniel},
abstractNote = {Quasielastic cold neutron scattering experiments on molten Al{sub 1-x}Cu{sub x} alloys (x = 0.10, 0.17 and 0.25) have been performed at three different temperatures on the FOCUS time-of-flight spectrometer at the Swiss neutron spallation source SINQ. As the main part of the scattering at small Q is incoherent and originating from Cu, self-diffusion coefficients D for the Cu ions could be determined from the widths of quasielastic peaks. The derived values are considerably larger than those found in capillary tube measurements. Even if the accuracy in the determination of D is better than about 4% it could not be concluded whether the temperature variation of D follows an Arrhenius law or a power law.},
doi = {10.1016/j.jnoncrysol.2007.05.074},
journal = {Journal of Non-Crystalline Solids},
number = ,
volume = 353,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • The atomic motions in molten Al1-xCux (x=0.10, 0.171 and 0.25) around the eutectic composition (x=0.171) were studied by cold neutron inelastic scattering at three different temperatures (973 K, 1173 K and 1373 K). An alloy of eutectic composition containing the 63Cu isotope was also studied. Self-diffusion coefficients for the Cu ions were determined from the width of quasielastic peaks and were found to decrease slightly with increasing Cu concentration. Longitudinal current correlation functions Jl(Q,E) exhibit at all temperatures and at all compositions a shoulder at energies below 10 meV and one main maximum at higher energies. These features can bemore » interpreted in terms of excitations of acoustic and optic nature. The shape of Jl(Q,E) is sensitive to composition, being considerably more structured for larger Cu content. This can be coupled to the existence of a prepeak in the measured zeroth moment of dynamic scattering function indicating an increased chemical ordering with increasing Cu concentration for all temperatures. Indications for an existence of a liquid–liquid phase transition are presented.« less
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  • Quasielastic neutron scattering (QENS) was used to investigate the diffusion dynamics of hydration water on the surface of rutile (TiO{sub 2}) nanopowder. The dynamics measurements utilizing two inelastic instruments, a backscattering spectrometer and a disk chopper spectrometer, probed the fast, intermediate, and slow motions of the water molecules on the time scale of picoseconds to more than a nanosecond. We employed a model-independent analysis of the data collected at each value of the scattering momentum transfer to investigate the temperature dependence of several diffusion components. All of the probed components were present in the studied temperature range of 230-320 K,more » providing, at a first sight, no evidence of discontinuity in the hydration water dynamics. However, a qualitative change in the elastic scattering between 240 and 250 K suggested a surface freezing-melting transition, when the motions that were localized at lower temperatures became delocalized at higher temperatures. On the basis of our previous molecular dynamics simulations of this system, we argue that interpretation of QENS data from such a complex interfacial system requires at least qualitative input from simulations, particularly when comparing results from spectrometers with very different energy resolutions and dynamic ranges.« less
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