Mg/Ti multilayers: Structural and hydrogen absorption properties

Mg/Ti multilayers : Structural and hydrogen absorption properties

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 H-2 gas a two-step hydrogenation process occurs with the Ti layers forming the hydride before Mg. From in situ measurements of the bilayer thickness Lambda 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.

Pálsson, Gunnar K.Uppsala universitet,Materialfysik(Swepub:uu)gukpa839 (författare)
Gonzalez-Silveira, M. (författare)
Schreuders, H. (författare)
Slaman, M. (författare)
Rector, J. H. (författare)
Krishnan, G. (författare)
Kooi, B. J. (författare)
Walker, G. S. (författare)
Fay, M. W. (författare)
Hjörvarsson, BjörgvinUppsala universitet,Materialfysik(Swepub:uu)bjorghvs (författare)
Wijngaarden, R. J. (författare)
Dam, B. (författare)
Griessen, R. (författare)
Uppsala universitetMaterialfysik (creator_code:org_t)

Ingår i:Physical Review B. Condensed Matter and Materials Physics81:22, s. 224203-1098-01211550-235X

Av författaren/redakt...: Baldi, A.; Pálsson, Gunnar ...; Gonzalez-Silveir ...; Schreuders, H.; Slaman, M.; Rector, J. H.; visa fler...; Krishnan, G.; Kooi, B. J.; Walker, G. S.; Fay, M. W.; Hjörvarsson, Bjö ...; Wijngaarden, R. ...; Dam, B.; Griessen, R.; visa färre...

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