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Publisher DOI: 10.1016/j.actamat.2022.118419
Title: Phase decomposition in nanoporous Au-Pt
Language: English
Authors: Liu, Maowen 
Weissmüller, Jörg 
Keywords: Coarsening; Dealloying; Nanoporous Au-Pt; Phase decomposition; Surface segregation
Issue Date: 8-Oct-2022
Publisher: Elsevier Science
Source: Acta Materialia 241: 118419 (2022-12)
Abstract (english): 
This study explores microstructure and phase decomposition in nanoporous Au-Pt made by dealloying. The starting alloy, Ag75Au12.5Pt12.5, forms a uniform solid solution. Removing the Ag by dealloying at room temperature forms nanoporous equimolar Au-Pt with a ligament size as small as 4 nm. That alloy's composition is in the Au-Pt phase diagram's regime of spinodal instability. Surprisingly, in view of the instability and of the substantial atomic rearrangements accompanying dealloying, X-ray diffraction and transmission electron microscopy reveal a homogeneous single-phase state in the bulk of the nanoporous material. This can be traced back to enrichment of Pt at the surface, which depletes the bulk in Pt. The Pt-depleted bulk is in the metastable region of the alloy phase diagram, between the binodal and the spinodal. Annealing prompts curvature-driven coarsening by diffusion, diminishing the number of sites for Pt surface segregation. The ensuing enrichment of the bulk in Pt is accompanied by the formation first of crystallographically coherent, Pt-rich regions and later of semi-coherent regions of the Pt-rich phase. The morphology of the coherent regions is compatible with spinodal decomposition. Yet, the microstructure evolution pathway is nonstandard, since decomposition here concurs with rapid coarsening of the porous microstructure. Among the prospect of the nanoporous alloy are its high kinetic stability and the opportunity to tune the surface composition through the annealing temperature.
DOI: 10.15480/882.4682
ISSN: 1359-6454
Institute: Werkstoffphysik und -technologie M-22 
Document Type: Article
Project: SFB 986: Maßgeschneiderte Multiskalige Materialsysteme - M3 
License: CC BY-NC-ND 4.0 (Attribution-NonCommercial-NoDerivatives) CC BY-NC-ND 4.0 (Attribution-NonCommercial-NoDerivatives)
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