Methanol decomposition tests were carried out for the first time on cold-rolled Ni 3 (Si,Ti) foils in a temperature range of 513-793 K to investigate their potential catalytic properties for hydrogen production. The catalytic activity was observed at temperatures above 713 K. At 793 K, the catalytic activity changed with the reaction time in three stages: low-activity incubation, rapid spontaneous activation and highactivity state. Surface analysis revealed an intensive formation of fine Ni particles on the foil surfaces after the second stage where rapid spontaneous activation was observed. The formation of the fine Ni particles was considered to be induced by the selective oxidation of Si in Ni 3 (Si,Ti). The catalytic activity in the second and third stages was due to the fine Ni particles formed by the spontaneous activation.
TiAl-based intermetallic alloys with a lamellar microstructure and b containing duplex microstructure were cyclically tensile deformed in various environmental media as a function of temperature. Environmental media used in this study were vacuum, air and a mixture gas of H 2 gasϩAr gas. The environmental embrittlement, i.e., reduction of number of cycles to failure was observed when deformed in air as well as in Ar gas including H 2 gas. The severe environmental embrittlement was observed not only at room temperature but also at ϳ873 K. Fracture patterns and the associated fracture mode were not affected by the environmental media. The possible species causing the environmental embrittlement is suggested to be hydrogen atoms decomposed from water vapor H 2 O or hydrogen gas H 2. The feature observed in the present study was similar in both TiAl-based intermetallic alloys and, also to the previous observation, i.e., the feature of the environmental embrittlement observed in simply tensile deformed specimens.
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