Berlin 2018 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 27: Poster Session I

MM 27.10: Poster

Tuesday, March 13, 2018, 18:30–19:45, Poster E

Hydride formation in Mg-thin films — •Felix Maischner, Anshu Tyagi, and Astrid Pundt — Universität Göttingen, IMP

Magnesium is an interesting hydrogen storage material because of its high reversible hydrogen capacity in MgH₂ of up to 7,6 wt% and its high volumetric capacity of 110 kg/m³ [1]. But a closed MgH₂ layer formed at the sample surface can block hydrogen uptake. Recently, it was shown that controlling the loading pressure allows efficient hydriding of Mg at 293 K [2]. This was interpreted by the related MgH₂ nuclei density. Further, the addition of grain boundaries improves the hydriding kinetics of Mg materials [3].

To study the nucleation and growth process in Mg thin films on a local scale, we perform STM measurements in an UHV-system between hydrogen loading steps. This surface sensitive method allows monitoring the hydride growth and morphology in the film via local height changes [4], as MgH₂ precipitates locally expand the lattice by about 30% in vertical film direction with respect to the α-phase Mg film [5]. 50 nm Mg films were prepared by cathode-beam sputtering on Si-substrates, covered with 10 nm Pd. The adhesion between the film and the substrate and its impact on the hydride morphology will be considered.

The work is funded by DFG via Project PU131/9-1 and PU131/10-2.

[1] M. Dornheim, et al., Scr. Mat. 56 (2007) 841, [2] H.T. Uchida, et al., Acta Mater. 85 (2015) 279 [3] M. Hamm, A. Pundt, IJHE 42 (2017) 22530, [4] K. Nörthemann, A. Pundt, Phys. Rev. B 83 (2011) 155420, [5] A.Baldi, et. al. Phys. Rev. B 81 (2010) 224203.