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MM: Fachverband Metall- und Materialphysik

MM 9: Hydrogen in metals II: Multiscale simulations

MM 9.2: Talk

Monday, March 16, 2015, 12:15–12:30, TC 006

H-H interaction and critical temperature of hydride formation in palladium hydrogen thin films: Experiment and model — •Stefan Wagner and Astrid Pundt — University of Göttingen, Institute of Materials Physics

Palladium hydrogen (PdH) thin films are used as a model system to investigate the impact of elastic and microstructural constraints on structural phase transitions. Hydrogen-induced mechanical stress arises both from palladium film clamping on an elastically hard substrate and at coherent interfaces in the two-phase-coexistence region. It strongly changes the chemical potential of hydrogen, modifying the stability of the hydride phase. Mechanical stress is superimposed by microstructural constraints, channeling stress relaxation processes such as the formation of misfit dislocations in the films. In this paper we investigate hydrogen absorption and hydride formation in PdH thin films with different microstructure and clamping conditions [1]. The attractive H-H interaction energy and the critical temperature of hydride formation are determined quantitatively from the analysis of the chemical potential in combination with in situ stress measurement [2]. They differ for films with coherent interfaces and films where stress relaxation is possible. [1] S. Wagner, A. Pundt, Acta Mat. 59 (2011) 1862. [2] S. Wagner, M. Moser, A. Pundt et al., Int. J. Hydr. Energy 38 (2013) 13822.