Abstract:

Nanoporous metals have attracted significant attention owing to their excellent physical, chemical, and biological properties. However, preparing ultrafine nanoporous metal particles (1-5 μm) with specific geometries remains challenging. Herein, we report a simple strategy to prepare ultrafine flaky hexagonal nanoporous Au-Cu and Au particles via dealloying. Mg-based alloy ribbons with ultrafine flaky hexagonal Mg-Au(Cu)-Gd particles dispersed in a Mg-Cu(Au)-Gd metallic glassy matrix were prepared. The size and morphology of the precipitated flaky hexagonal Mg-Au(Cu)-Gd particles were controlled by the solidification process of a Mg₆₁Cu₂₁Au₇Gd₁₁ alloy melt. Ultrafine flaky hexagonal nanoporous Au-Cu particles (diagonal diameter 2.58 ± 0.44 μm, ligament size ~ 28 nm), Au_-1 particles (diagonal diameter 2.38 ± 0.35 μm, ligament size ~ 83 nm) and Au_-2 particles (diagonal diameter 2.39 ± 0.44 μm, ligament size ~ 66 nm) were prepared via ultrasonic-assisted dealloying of Mg₆₁Cu₂₁Au₇Gd₁₁ alloy ribbons in 0.25 M HCl/ethanol, 1 M HCl/ethanol and 0.25 M HNO₃/ethanol solutions, respectively. The ultrafine flaky hexagonal nanoporous Au-Cu and Au particles with a large specific surface area have a uniform particle size and shape, implying that they possess adequate powder fluidity and excellent catalytic properties. Moreover, the formation mechanism of the MgAu(Cu)Gd phase in solidified Mg-Cu-Au-Gd alloys was discussed. This study provides a novel approach for synthesizing nanoporous metal particles with a specific geometry.

Key words: Metallic glasses, Mg-based alloys, Dealloying, Nanoporous particles, Mg-Au-Gd phase