Watching in situ the hydrogen diffusion dynamics in magnesium on the nanoscale

• Published in: Science advances Vol. 6; no. 19; p. eaaz0566
• Main Authors: Karst, Julian, Sterl, Florian, Linnenbank, Heiko, Weiss, Thomas, Hentschel, Mario, Giessen, Harald
• Format: Journal Article
• Language: English
• Published: American Association for the Advancement of Science 01.05.2020
• Subjects: Materials Science; Optics; SciAdv r-articles
• ISSN: 2375-2548; 2375-2548
• DOI: 10.1126/sciadv.aaz0566

In situ nanoscale imaging of the hydride formation in magnesium unravels nanoscopic details of the phase transition dynamics. Active plasmonic and nanophotonic systems require switchable materials with extreme material contrast, short switching times, and negligible degradation. On the quest for these supreme properties, an in-depth understanding of the nanoscopic processes is essential. Here, we unravel the nanoscopic details of the phase transition dynamics of metallic magnesium (Mg) to dielectric magnesium hydride (MgH 2 ) using free-standing films for in situ nanoimaging. A characteristic MgH 2 phonon resonance is used to achieve unprecedented chemical specificity between the material states. Our results reveal that the hydride phase nucleates at grain boundaries, from where the hydrogenation progresses into the adjoining nanocrystallites. We measure a much faster nanoscopic hydride phase propagation in comparison to the macroscopic propagation dynamics. Our innovative method offers an engineering strategy to overcome the hitherto limited diffusion coefficients and has substantial impact on the further design, development, and analysis of switchable phase transition as well as hydrogen storage and generation materials.