In Situ Observation of Strain Development and Porosity Evolution in Nanoporous Gold Foils

Authors

  • Christian J. Dotzler,

    1. Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
    2. Industrial Research Ltd, P. O. Box 31-310, Lower Hutt 5040, New Zealand
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  • Bridget Ingham,

    1. Industrial Research Ltd, P. O. Box 31-310, Lower Hutt 5040, New Zealand
    2. The MacDiarmid Institute for Advanced Materials and Nanotechnology, Victoria University of Wellington, P. O. Box 600, Wellington 8140, New Zealand
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  • Benoit N. Illy,

    1. Imperial College London, Department of Materials and London Centre for Nanotechnology, Exhibition Road, London SW7 2AZ, United Kingdom
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  • Kia Wallwork,

    1. Australian Synchrotron, 800 Blackburn Rd Clayton, VIC 3168, Australia
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  • Mary P. Ryan,

    Corresponding author
    1. Imperial College London, Department of Materials and London Centre for Nanotechnology, Exhibition Road, London SW7 2AZ, United Kingdom
    • Imperial College London, Department of Materials and London Centre for Nanotechnology, Exhibition Road, London SW7 2AZ, United Kingdom.
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  • Michael F. Toney

    Corresponding author
    1. Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
    • Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
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Abstract

The formation of nanoporous gold by open circuit dealloying of 100 nm AgAu foils in nitric acid is investigated in situ and in real time by combining synchrotron small angle X-ray scattering (SAXS) and X-ray diffraction (XRD). The time dependence of the dealloying is followed as a function of acid concentration. For all concentrations, several characteristic dealloying stages are observed. Firstly, there is a fast initial dissolution stage with an increase in surface area due to pore and mound formation; this leads to strain in the nanoporous gold that results from an increase in capillary pressure. After dissolution is complete, there is rapid coarsening of the quasi-periodic, pore–ligament morphology. During this later stage, we deduce strong strain anisotropies that can be explained by preferred crystallographic orientation of ligaments. This rapid coarsening stage is followed by a slow coarsening stage where the SAXS patterns, and hence the quasi-periodic morphology, is self-similar in time. There is a strong correlation between the morphology evolution and strain development, which can be explained by capillary forces.

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