| 研究実績の概要 |
Vapor phase dealloying (VPD) is expected as a universal, highly efficient and environmentally friendly method for fabricating 3D bicontinuous nanoporous metals, by using vapor pressure difference between constituent elements. However, the relation between dealloying conditions and above microstructural parameters are still unclear due to underlying dealloying kinetics, such as thermal evaporation of constituent element, resulting diffusion both in bulk alloys and in pore channels, and alloys phase evolution. In this work, 3D bicontinuous nanoporous Cu by vapor phase dealloying (VPD) of Cu12Zn88 alloy is chosen as the model system and its dealloying kinetics and alloy phase evolution are investigated. We found that Zn is selectively evaporated out from the precursor Cu12Zn88 alloy during the process of VPD due to the vapor pressure difference between Cu and Zn and an intermediate phase Cu36Zn64 is formed in the dealloying front before Zn evaporation. The power law relation between the pore depth and dealloying time reveals the bulk diffusion controlled dealloying process for intermediate phase. The porous structure starts to appear in the intermediate region and the appearance time closely relies on dealloying temperature. The constant dealloying front velocity is mainly dominated by dealloying temperature and slightly increased in high vacuum condition, indicating that the dealloying kinetics is dominated by interfacial effect rather than mass transport effect in pore channel.
|
