| 研究実績の概要 |
Experiments using the high-pressure torsion (HPT) method and hydrogen gas absorption in combination with theoretical calculations using the first-principle and CALPHAD methods were employed to design and synthesize new hydrogen storage materials with low hydrogen binding energy that can work at room temperature. The Mg4NiPd with BCC-based structure could reversibly store hydrogen at room temperature with an excellent consistency with the theoretical binding energy calculation, but its storage capacity was bellow 1 wt.%. The experiments were further conducted to design and synthesize new Mg-based and Ti-based materials and the investigation was finally extended to high entropy hydrogen storage materials. As the first attempt, the MgTiFeVCr high-entropy alloy was synthesized, but it exhibited poor properties. The second synthesized material was TiZrCrMnFeNi, which exhibited fast and reversible hydrogen storage at room temperature with a capacity of 1.7 wt.%. This capacity is better than commercial LiN5, while TiZrCrMnFeNi is cheaper than LaNi5. Moreover, the designated material stored hydrogen without activation, while many room-temperature hydrogen storage materials such as TiFe and Ti-V-Cr need thermal activation treatment. In summary, this study showed a clear concept to design new room-temperature hydrogen storage materials by using the concept of hydrogen binding energy engineering.
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