Speaker
Dr
Qinfen Gu
(Australian Synchrotron)
Description
Hydrogen has the potential to power much of the modern world with only water as a by-product, but storing hydrogen safely and efficiently in solid form such as magnesium hydride remains a major obstacle. Here we use in-situ synchrotron powder X-ray diffraction to investigate the mechanisms of the hydrogen absorption and desorption in bulk Mg-Ni alloys. Our study shows that the hydrogenation of Na-doped hypoeutectic Mg-Ni alloys can be identified at a temperature as low as 260oC via an interface-controlled nucleation and growth mechanism without any prior activation while dehydrogenation occurrs at about 370oC. The sequence of phase transformations associated with these reactions as well as the expansion properties of individual phases during hydrogen sorption reactions as provided by high resolution X-ray diffraction data are also discussed. Furthermore, as evidenced by an in-situ ultra-high voltage transmission electron microscopy study, we find that the hydrogen release mechanism from bulk (2 µm) MgH2 particles is based on the growth of multiple pre-existing Mg crystallites within the MgH2 matrix, present due to the difficulty of one hundred percent hydrogenation. In contrast, in thin samples analogous to nano-powders, dehydriding occurs by a ‘shrinking core’ mechanism.
| Keywords | Hydrogen storage, hydrides, magnesium alloys |
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Primary author
Mr
Xuan Quy Tran
(Nihon Superior Centre for the Manufacture of Electronic Materials (NS CMEM), School of Mechanical and Mining Engineering, The University of Queensland, Australia)
Co-authors
Dr
Kazuhiro Nogita
(Nihon Superior Centre for the Manufacture of Electronic Materials (NS CMEM), School of Mechanical and Mining Engineering, The University of Queensland, Australia)
Dr
Qinfen Gu
(Australian Synchrotron)
Dr
Stuart McDonald
(Nihon Superior Centre for the Manufacture of Electronic Materials (NS CMEM), School of Mechanical and Mining Engineering, The University of Queensland, Australia)
Prof.
Syo Matsumura
(Department of Applied Quantum Physics and Nuclear Engineering and the Ultramicroscopy Research Center, Kyushu University, Fukuoka, 819-0395, Japan)
