The measurement of self-diffusion coefficients in liquid metals with quasielastic neutron scattering

Andreas Meyer

doi:doi:10.1051/epjconf/20158301002

Open Access

Issue		EPJ Web of Conferences Volume 83, 2015 QENS/WINS 2014 - 11th International Conference on Quasielastic Neutron Scattering and 6th International Workshop on Inelastic Neutron Spectrometers


Article Number		01002
Number of page(s)		7
Section		Keynotes articles (QENS)
DOI		http://dx.doi.org/10.1051/epjconf/20158301002
Published online		23 January 2015

EPJ Web of Conferences 83, 01002 (2015)
http://dx.doi.org/10.1051/epjconf/20158301002

The measurement of self-diffusion coefficients in liquid metals with quasielastic neutron scattering

Andreas Meyer^a

Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt (DLR), 51170 Köln, Germany

^a e-mail: andreas.meyer@dlr.de

Published online: 23 January 2015

Abstract

Quasielastic incoherent neutron scattering (QENS) has proven to be a versatile tool to study self diffusion of atoms in liquid metals. Here it is shown, that coherent contributions to the signal in the small q limit appear as a flat and energy independent constant to the QENS signal in single-component liquid metals even for systems with a small incoherent scattering cross section, like aluminum. Container-less processing via electromagnetic or electrostatic levitation devices, especially designed for QENS, enables the in-situ measurement on liquid metallic droplets of sizes between 5 mm to 10 mm in diameter. This gives access to the study of chemically reactive, refractory metallic melts and extends the accessible temperature range to undercoolings of several hundred Kelvin below the respective melting point. Compared to experiments using a thin-walled crucible giving hollow-cylindrical sample geometry it is shown that multiple scattering on levitated droplets is negligible for the analysis of the self-diffusion coefficient. QENS results of liquid germanium and ⁷³germanium isotope mixtures, titanium, nickel, copper and aluminum are reviewed. The self-diffusion coefficients of these systems are best described by an Arrhenius-type temperature dependence around their respective melting points.

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