Robust Metallic Actuators Based on Nanoporous Gold Rapidly Dealloyed from Gold–Nickel Precursors |
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Authors: | Chuan Cheng Lukas Lührs |
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Affiliation: | 1. Energy Innovation Centre, Warwick Manufacturing Group, University of Warwick, Coventry, CV4 7AL UK;2. Institute of Materials Physics and Technology, Hamburg University of Technology, 21073 Hamburg, Germany |
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Abstract: | Dealloyed nanoporous gold (np-Au) has applications as oxygen reduction catalysis in Li-air batteries and fuel cells, or as actuators to convert electricity into mechanical energy. However, it faces the challenges of coarsening-induced structure instability, mechanical weakness due to low relative densities, and slow dealloying rates. Here, monolithic np-Au is dealloyed from a single-phase Au25Ni75 solid-solution at a one-order faster dealloying rate, ultra-low residual Ni content, and importantly, one-third more relative density than np-Au dealloyed from conventional Au25Ag75. The small atomic radius and low dealloying potential of the sacrificing element Ni are intrinsically beneficial to fast produce high relative density np-Au, as predicted by a general model for dealloying of binary alloys and validated by experiments. Stable, durable, and reversible actuation of np-Au takes place under cyclic potential triggering in alkaline and acidic electrolytes with negligible coarsening-induced strain-shift. The thermal and mechanical robustness of bulk np-Au is confirmed by two-order slower ligament coarsening rates during annealing at 300 °C and 45 MPa macroscopic yielding strength distinctive from the typical early onset of plastic yielding. This article opens a rich direction to achieve high relative density np-Au which is essential for porous network connectivity, mechanical strength, and nanostructure robustness for electrochemical functionality. |
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Keywords: | charge-induced reversible strain coarsening electrochemical actuators electrochemical dealloying nanoporous gold |
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