Berlin 2015 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 15: Hydrogen in metals III: Experiments
MM 15.7: Vortrag
Montag, 16. März 2015, 17:45–18:00, TC 006
Hydrogen loading kinetics of Mg Thin Films: effect of the driving force revisited — •Helmut Takahiro Uchida1, Magnus Hamm1, Stefan Wagner1, Carsten Baehtz2, Björgvin Hjörvarsson3, and Astrid Pundt1 — 1Univ. Göttingen, IMP, Friedrich-Fund-Platz 1, 37077 Göttingen, Germany. — 2Institute of Ion Beam Physics and Materials Research, HZDR, Germany — 3Uppsala University, Dep. of Physics and Astronomy, Sweden.
Mg forms a dihydride with a high gravimetric hydrogen content of 7.6 wt% upon hydrogen absorption. This hydride is very stable and blocks hydrogen diffusion („Blocking effect“) [1,2]. This hinders the practical use of pure Mg for mobile applications, at low tempertures.
In this work, the impact of the driving force on the hydride formation kinetics in Mg films (200-2800 nm) is studied at room temperature, applying time-resolved in-situ XRD at different constant hydrogen gas pressures [3]. The evolution of inner stress is also monitored.
The hydrogen loading kinetics is found to strongly depend on the chemical potential. A heterogeneous hydride nucleation and growth model is suggested and evaluated by finite-element-calculatuion. The model allows qualitatively explaining the complex stress development, the different diffusion regimes and the blocking-layer thickness.
Financial support by the DFG via PU131/9 and PU131/10, as well as by the DESY/Hamburg and the ESRF/Grenoble are gratefully acknowledged. [1]J.Rydén et al., J. Less-Common Metals, 152 (1989) 295. [2]H.T.Uchida et al., Script. Mater., 64 (2011) 935. [3]H.T.Uchida et al., Acta Mater. (2014) (Manuscript accepted).