Bicontinuous-nanostructured materials with a three-dimensionally (3D) interconnected morphology offer unique properties and potential applications in catalysis, biomedical sensing and energy storage. The new approach of solid-state interfacial dealloying (SSID) opens a route for fabricating bi-continuous metal–metal composites and porous metals at nano-/meso-scales via a self-organizing process driven by minimizing the system's free energy. Integrating SSID and thin film processing fully can open up a wide range of technological opportunities in designing novel functional materials; to-date, no experimental evidence has shown that 3D bi-continuous films can be formed with SSID, owing to the complexity of the kinetic mechanisms in thin film geometry and at nano-scales, despite the simple processing strategy in SSID. Here, we demonstrate that a fully-interconnected 3D bi-continuous structure can be achieved by this new approach, thin-film-SSID, using Fe–Ni film dealloyed by Mg film. The formation of a Fe–Mg x Ni bi-continuous 3D nano-structure was visualized and characterized via a multi-scale, multi-modal approach, combining electron transmission microscopy with synchrotron X-ray fluorescence nano-tomography and absorption spectroscopy. Phenomena involved with structural formation are discussed. These include surface dewetting, nano-size void formation among metallic ligaments, and interaction with a substrate. This work sheds light on the mechanisms of the SSID process, andmore »
Formation of three-dimensional bicontinuous structures via molten salt dealloying studied in real-time by in situ synchrotron X-ray nano-tomography
Three-dimensional bicontinuous porous materials formed by dealloying contribute significantly to various applications including catalysis, sensor development and energy storage. This work studies a method of molten salt dealloying via real-time in situ synchrotron three-dimensional X-ray nano-tomography. Quantification of morphological parameters determined that long-range diffusion is the rate-determining step for the dealloying process. The subsequent coarsening rate was primarily surface diffusion controlled, with Rayleigh instability leading to ligament pinch-off and creating isolated bubbles in ligaments, while bulk diffusion leads to a slight densification. Chemical environments characterized by X-ray absorption near edge structure spectroscopic imaging show that molten salt dealloying prevents surface oxidation of the metal. In this work, gaining a fundamental mechanistic understanding of the molten salt dealloying process in forming porous structures provides a nontoxic, tunable dealloying technique and has important implications for molten salt corrosion processes, which is one of the major challenges in molten salt reactors and concentrated solar power plants.
- Award ID(s):
- 1922639
- Publication Date:
- NSF-PAR ID:
- 10248384
- Journal Name:
- Nature Communications
- Volume:
- 12
- Issue:
- 1
- ISSN:
- 2041-1723
- Publisher:
- Nature Publishing Group
- Sponsoring Org:
- National Science Foundation
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