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MM: Fachverband Metall- und Materialphysik
MM 48: Topical session: X-ray and neutron scattering in materials science I - Coherent X-ray Diffraction Imaging of Excitations in Metal Nanoparticles
MM 48.4: Talk
Thursday, April 3, 2014, 11:00–11:15, BAR 205
Hydrogen absorption in Mg-Ti multilayers studied by neutron re*ectometry — •Maximilian Skoda1, Christian Kinane1, Raymond Fan2, Sean Langridge1, William David1, Andrea Baldi5, Bernard Dam3, Herman Schreuders3, and Ronald Griessen4 — 1ISIS, STFC, Harwell, UK — 2Diamond Light Source, Harwell, UK — 3TU Delft, Delft, The Netherlands — 4Department of Physics and Astronomy, VU Amsterdam, The Netherlands — 5Stanford University, Stanford, USA
Mg-Ti thin film alloys have large H-storage capacities, fast kinetics of hydrogen absorption and desorption and are structurally stable. These qualities stem from a short-range ordered distribution of the Mg and Ti atoms. In order to study the influence of short-range order on the hydrogen sorption properties of Mg-Ti systems, we artificially engineered chemical segregation by depositing a Ti/Mg multilayer with 10 repetitions of Ti(2 nm)/Mg(4.4 nm). On exposure to H2 a two-step hydrogenation process occurs with the Ti layers forming the hydride before Mg. In-situ, time resolved Neutron Reflectometry (NR) allows an accurate determination of the out-of-plane expansion associated with each hydrogenation step. The volume expansion expected for the hydrogenation of both Ti and Mg is transferred completely in the vertical direction, indicating that large plastic deformations have to occur upon hydrogen absorption. Owing to the large negative neutron scattering length of hydrogen, NR proves to be an excellent technique for the in-situ characterization of the hydrogen absorption properties of thin films.