Environmental cell microscopy was applied for surveying the reaction of hydrides in vanadium and magnesium based alloys, which are candidates for hydrogen storage materials of advanced hydrogen energy systems. In order to clarify the mechanism of hydrogenation process, in-situ experiment was carried out by using a 200kV transmission electron microscope (TEM) equipped with a newly developed environmental cell (EC), which is capable to investigate transmitted image and electron-diffraction under gas hydrogen environment of 0.1MPa at room temperature. In case of vanadium, under hydrogen-gas of 0.1MPa, bending fringe was created probably due to local stress induced with the hydrogen solution. On the other hand, when hydrogen gas reacted with magnesium powders, swelling due to volume expansion was occurred. In practice, surface steps with several ten nm became straightened, and additionally, the formation of MgH{sub}2 was indicated in selected-area diffraction pattern (SADP). In-situ experiment for hydrogenation reaction by using the environmental cell was recently started. The precise studies, as well as its improvement, will be continued, especially in the transparence films.
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