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Issue 3, 2021
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Passivation-driven speciation, dealloying and purification

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Thin passivating surface oxide layers on metal alloys form a dissipation horizon between dissimilar phases, hence harbour an inherent free energy and composition gradient. We exploit this gradient to drive order and selective surface separation (speciation), enabling redox-driven enrichment of the core by selective conversion of low standard reduction potential (E°) components into oxides. Coupling this oxide growth to volumetric changes during solidification allows us to create oxide crystallites trapped in a metal (‘ship-in-a-bottle’) or extrusion of metal fingerlings on the heavily oxidized particle. We confirm the underlying mechanism through high temperature X-ray diffraction and characterization of solidification-trapped particle states. We demonstrate that engineering the passivating surface oxide can lead to purification via selective dealloying with concomitant enrichment of the core, leading to disparate particle morphologies.

Graphical abstract: Passivation-driven speciation, dealloying and purification

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Article information

13 Nov 2020
19 Jan 2021
First published
19 Jan 2021

Mater. Horiz., 2021,8, 925-931
Article type

Passivation-driven speciation, dealloying and purification

A. Martin, B. Chang, J. Cutinho, L. Shen, T. Ward, E. W. Cochran and M. M. Thuo, Mater. Horiz., 2021, 8, 925
DOI: 10.1039/D0MH01832E

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