• Schreuders, H.
• Baldi, Andrea
• Wijngaarden, R. J.
• Pálsson, G. K.
• Hjörvarsson, B.
• Rector, J. H.
• Griessen, R. P.
• Slaman, M. J.
• Gonzalez-Silveira, M.
• Dam, B.
• Kooi, B. J.
• Walker, G. S.
• Krishnan, G.
• Fay, M. W.

Abstract

Mg-Ti alloys have uncommon optical and hydrogen absorbing properties, originating from a “spinodal-like” microstructure with a small degree of chemical short-range order in the atomic distribution. In the present study we artificially engineer short-range order by depositing Pd-capped Mg/Ti multilayers with different periodicities. Notwithstanding the large lattice mismatch between Mg and Ti, the as-deposited metallic multilayers show good structural coherence. On exposure to H2 gas a two-step hydrogenation process occurs with the Ti layers forming the hydride before Mg. From in situ measurements of the bilayer thickness ? at different hydrogen pressures, we observe large out-of-plane expansions of Mg and Ti layers on hydrogenation, indicating strong plastic deformations in the films and a consequent shortening of the coherence length. On unloading at room temperature in air, hydrogen atoms remain trapped in the Ti layers due to kinetic constraints. Such loading/unloading sequence can be explained in terms of the different thermodynamic properties of hydrogen in Mg and Ti, as shown by diffusion calculations on a model multilayered systems. Absorption isotherms measured by hydrogenography can be interpreted as a result of the elastic clamping arising from strongly bonded Mg/Pd and broken Mg/Ti interfaces. ; DelftChemTech ; Applied Sciences

Topics

• microstructure
• polymer
• Hydrogen
• forming