Crystal plane-orientation dependent phase evolution from precursor to porous intermediate phase in the vapor phase dealloying of a Co-Zn alloy. (15th February 2023)

• Record Type: Journal Article
• Authors: Li, Yanying; Han, Xiaocang; Lu, Zhen; Ying, Lei; Wang, Xinyao; Zeng, Yuqiao; Gao, Yi; Chen, Qing; Liu, Pan
• Is Part Of: Acta materialia. Volume 245(2023)
• Publication Date: 2023-02-15
• Subjects: Vapor phase dealloying -- Porous structure -- Intermediate phase -- Phase evolution; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2022.118617
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: Understanding phase transitions and pore formation during vapor phase dealloying (VPD) is essential to optimize the microstructure and composition of nanoporous metals for versatile applications. Nevertheless, the underlying atomic mechanisms of phase formation and pore evolution during VPD are unknown. Using a binary γ -CoZn precursor alloy as a prototype system, we found a two-step dealloying process. The microsized porous β -CoZn intermediate phase that formed at the dealloying front facilitated the subsequent growth of completely dealloyed hierarchical nanoporous α -Co with the micropore structure of the intermediate phase. Combining aberration-corrected scanning transmission electron microscopy with energy dispersion X-ray spectrometry, we found that the intermediate phase preferentially formed on specific crystal planes of the precursor, and the vacancies generated by sublimation of Zn atoms diffused dominantly on the {110} planes of the precursor close to the intermediate phase. Theoretical calculations indicated that the energy barrier to the diffusion of Zn vacancies on the low-index {110} plane was lower than on other planes. The atomic-scale phase evolution play a key role in the subsequent evolution of the porous structure and provide deep insight into the phase transition during VPD. This insight may provide a new approach to tune the pore structure and composition of nanoporous metals by designing and regulating their intermediate phases. Graphical abstract: We report the growth of porous structure is regulated by the intermediate phase (β-CoZn) formation and evolution in the vapor phase dealloying of a γ-CoZn alloy. The transition from precursor to intermediate phase was achieved by interfacial diffusion of Zn atoms on dominant {110} crystal planes with lower energy barriers. Our findings have important implications for understanding the atomic mechanism of phase formation and evolution during vapor phase dealloying. Image, graphical abstract