Hydrogenation and dehydrogenation of passivated aluminum under high pressure

Saito, Hiroyuki; Machida, Akihiko; Sakurai, Yoko; Katayama, Yoshinori; Aoki, Katsutoshi

The van't Hoff equation predicts that aluminum metal is hydrogenated to form the hydride, AlH, at hydrogen pressures above 0.7 GPa at room temperature. Here we demonstrate that passivated aluminum has been hydrogenated with hydrogen fluid to form AlH at 8.9 GPa and 600 C. The hydrogenation and dehydrogenation reactions were investigated in situ by synchrotron radiation X-ray diffraction measurements. The relationship between the hydrogenation reaction yield and heat treatment conditions was examined to reveal the mechanism of hydrogenation. The oxide layer prevented the hydrogenation below 550 C, the oxide layer seemed to be partly removed or modified by pressure-temperature treatment above 6 GPa and 600 C. The hydrogenation pressure of 9 GPa for passivated aluminum was reduced to 6 GPa.