La-Ni系合金スパッタ膜の構造と水素吸蔵特性

概要

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In order to evaluate the utility of metal hydride films as hydrogen permeable negative electrodes in an alkaline fuel cell system, La-Ni alloy films about 2μm thick were formed on Teflon sheet substrates by RF sputtering using split-type targets composed of a nickel sheet and lanthanum chips. Sputtering conditions such as the gas pressure, RF incident power and component ratio of the target were found to influence the composition, structure and hydrogen absorption characteristics of the sputtered films. The composition of the films varied in the range of LaNi9.5∼LaNi2.2 (9.5∼31.7 at.%La-Ni). The films were either amorphous or microcrystalline in structure. The amorphous LaNi2.2 films absorbed a relatively large amount of hydrogen during electrochemical charging and eventually formed a hydride (LaNi2.2H4.1). The hydrogen absorption capacities of these sputtered films were lower than those of crystalline powder or bulk LaNi5 alloys prepared by the arc-melting method. However these amorphous metal hydrides did not result in any crack or embrittlement in the films even after a large number of hydriding-dehydriding cycles.
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