Conditions Extrêmes et Matériaux : Haute Température et Irradiation

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F.Demmel, L.Hennet, S.Brassamin, D.R.Neuville, J.Kozaily, M.M.Koza, 'Nickel self-diffusion in a liquid and undercooled NiSi alloy', Phys. Rev. B 94 014206 (2016) doi:10.1103/physrevb.94.014206

The nickel self-diffusion coefficient was measured in a Ni 75 Si 25 alloy in the liquid and undercooled state by quasielastic neutron scattering. The undercooled state was achieved by applying aerodynamic levitation. That containerless technique allowed an undercooling of ΔT≈90K over 4 h of measurement time. The temperature dependence of the derived diffusion coefficients follows an Arrhenius-type behavior. The activation energy for the diffusion process is about 10% larger than in pure nickel and is probably the reason for the slower self-diffusion coefficient compared to pure Ni. With increasing Si content more covalent bonding is formed, which might be the origin for the reduced mobility. Molecular dynamics simulations predicted a change in dynamics from an Arrhenius-type behavior to a power-law for temperatures as high as twice the glass transition temperature. Our data are compatible with a power-law behavior for the Ni self-diffusion.