In situ imaging of dealloying during nanoporous gold formation by transmission X-ray microscopy

Yu Chen Karen Chen-Wiegart*, Steve Wang, Wah Keat Lee, Ian McNulty, Peter W Voorhees, David C Dunand

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

29 Scopus citations

Abstract

The dealloying process is directly imaged, for the first time, by using transmission X-ray microscopy for the case of an Ag-30 at.% Au wire dealloyed under free corrosion in nitric acid. The propagation of a sharp dealloying front separating the alloy from nanoporous Au was observed by two-dimensional real-time in situ imaging at 30 nm resolution and measured in detail in three dimensions by an ex situ nanotomography technique at fixed time intervals. The rate of the dealloying front propagation is independent of the dealloying time up to a 3 μm depth, indicating that the dealloying process to this depth is dominated by interfacial effects (i.e. gold surface diffusion and/or silver dissolution) rather than long-range transport effects (i.e. diffusion of acid and corrosion product in and out of the porous layer). The constant dealloying rate corresponds to a constant silver flux and a constant current density, even though the potential might be fluctuating under free corrosion conditions and the interfacial area is shrinking as a function of time. Free corrosion in this system generates a high current density, implying it is driven by a chemical potential difference that is much higher than the critical potential.

Original languageEnglish (US)
Pages (from-to)1118-1125
Number of pages8
JournalActa Materialia
Volume61
Issue number4
DOIs
StatePublished - Feb 1 2013

Keywords

  • Metal foam
  • TXM
  • X-ray synchrotron radiation

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

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