observation of hydrogenation of a CsCl-type TiFe alloy at high pressure and high temperature

Endo, Naruki; Saito, Hiroyuki; Machida, Akihiko; Katayama, Yoshinori

A TiFe alloy with a CsCl-type structure which has many interstitial sites in its metal lattice has been investigated due to the favorable hydrogenation/dehydrogenation properties. There still are a lot of vacant interstitial sites in the metal lattice after hydrogenation near ambient conditions. It has not been clear whether hydrogen can occupy these vacant sites and the amount of hydrogen can be increased by hydrogenation under gigapascal high pressure. Thus, we have tried to increase the amount of hydrogen in the TiFe alloy by the direct reaction between the alloy and hydrogen fluid at high pressure and high temperature. As a result, the TiFe alloy was formed new cubic-type hydride before disproportionation reaction. The maximum volume expansion of new hydride was up to 21%, which was larger than that of the -phase hydride (18%; H/M = 0.95) prepared near ambient conditions. It was suggested that the amount of hydrogen in the cubic-type hydride exceeded H/M = 1.