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by hydrogenation of the metal at high pressure and temeratureSaito, Hiroyuki; Machida, Akihiko; Katayama, Yoshinori; Aoki, Katsutoshi
no journal, ,
at high pressureMachida, Akihiko; Watanuki, Tetsu; Aoki, Katsutoshi
no journal, ,
The pressure-induced structural change of yttrium dihydride, YH, has been investigated by synchrotron radiation X-ray diffraction experiment at room temperature. We observed a phase separation into two different hydrogen concentration states at high pressure. In the cubic metal lattice of YH, hydrogen atoms occupy the tetrahedral interstitial sites alone; the octahedral interstitial sites remain empty. A single-crystal-like YH specimen was compressed in helium pressure medium with a diamond anvil cell up to 55 GPa. Besides the original Bragg spots from the cubic-YH, new Bragg spots appeared just outside the original ones above 35 GPa, indicating the formation of a cubic lattice with slightly small lattice constants. The cell volume determined from the spot positions was smaller by 
18% than that of the coexisting original cubic lattice. The disproportionate mechanism will be discussed on the basis of the further analysis of the X-ray data.
(Al, Mn, Co)
alloyAone, Shigeo*; Uchida, Hirohisa*; Abe, Hiroshi
no journal, ,
The effects of ion irradiation and a KOH pretreatment on the rate of electrochemical hydrogen absorption by the MmNi(Al, Mn, Co)
alloy were investigated. The ion irradiation method is known to produce a high density of vacancy type defects in metals. In previous studies, we reported the remarkable enhancement of the initial rate of hydrogen absorption by the LaNi
with pretreatments of alkaline hydroxide solutions such as KOH. In addition, we revealed that the hydriding properties of the alloy and Pd can be improved by ion irradiations at TIARA (Takasaki Ion Accelerators for Advanced Radiation Application), JAEA. In this study, we examined the effects of surface modifications by the alkaline treatment and ion irradiations. The both pretreatments are found effective to improve kinetics of hydrogen absorption by the alloy.
Abe, Hiroshi; Morimoto, Ryo*; Aone, Shigeo*; Uchida, Hirohisa*; Oshima, Takeshi
no journal, ,
In previous studies, the induction of vacancy in palladium (Pd) was found to be effective for an increase in the initial hydrogen absorption rate. As well known, the initial hydrogen absorption rate depends strongly on the surface conditions of metals. Based on these results, we made surface modifications of Pd using various ions at TIARA, JAEA. In this study, we perform Cr ion irradiation into Pd, and the hydrogen absorption rate of ion irradiation Pd was evaluated. The Pd irradiated at a fluence to 1
10
cm
exhibited the highest rate in all samples, and the hydrogen absorption rate became five times higher than that of un-irradiated Pd. Since vacancy type defects which might act as hydrogen trapping site are introduced by irradiation the enhancement of the hydrogen absorption rate obtained inthi study can be interpreted in terms of an increase of hydrogen trapping saites near the surface region due to irradiation of Cr ion into Pd.