Development of nano-scale porous and non-equilibrium materials by chemical dealloying process and application for catalyst

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There was few reports on the effect of the solubility of Ag in the Al phase on the productivity in synthesize of the fine skeletal Ag by the chemical dealloying process. In Al-Ag binary alloy system, the *olubility widely changes with temperature. In this work, some precursors with different solubility were prepared and they were chemically dealloyed. The alloys with various composition were melt in Ar atmosphere and then were rapidly solidified by the rotating-water atomization process. Thus atomized particles were obtained and their mean diameter was about 200μm. The mean cooling rate of the particles was estimated in the range of 10^4-10^5K/s. To control the solubility, two kinds of heat treatments were carried out. One of them was solution treatment for the highest solubility and the other was precipitation treatment for the minimum solubility. Both treatments were classified to a solid state operation. On the other hand, the rapid solidification was classified to a liquid operatio … More n. Three kinds of precursors wuth different solubility were dealloyed. In the case of the rapidly solidified precursor, it was almost a mono phase of the α phase. After the solution treatment followed by water quenching from the solution temperature, a significant amount of Ag_2Al phase was observed and it was difficult to suppress the precipitation of Ag_2Al phase during the quenching due to the quite high precipitation rate. The solubility was negligible small after the precipitation treatmnnt. By the chemical dealloying, fine skeletal Ag was formed from Ag in the α phase and no Ag_2Al phase was decomposed and contributed to the formation of the skeletal Ag. The rapid solidification was *e effective to high productivity for the skeletal Ag and about 80% of the addition of Ag was recovered as the skeletal Ag. On the other hand, in both other precursors. the rate of the recovery was quite low and less than 10%. The rapid solidification root for the precursor preparation was quite excellent. The specific surface area was about 25m_2/g. The obtained skeletal Ag showed high activity for decompostion of 2H_2O_2→2H_2O+O_2. High performance in another reactions will be expected. Less