Formation and evolution of nanoporous dendrites during dealloying of a ternary Al–Ag–Au precursor

Abstract

Formation and evolution of nanoporous dendrites during dealloying of a ternary Al–Ag–Au precursor have been investigated using X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. The rapidly solidified Al₆₅Ag_22.75Au_12.25 precursor is composed of equiaxed Al₂(Au,Ag) dendrites which uniformly distribute in a lamellar α-Al–Ag₂Al eutectic matrix. The kind of solution has a significant influence on the dealloying of Al₆₅Ag_22.75Au_12.25. The dealloying of α-Al–Ag₂Al eutectic in the HCl solution leads to the formation of nanoporous Ag (np-Ag), but the Al₂(Au,Ag) phase cannot be dealloyed. Nanoporous AgAu (np-AgAu) alloys with bimodal channel size distributions can be fabricated through a two-step dealloying of Al₆₅Ag_22.75Au_12.25. The further dealloying of np-AgAu in a concentrated HNO₃ solution results in the formation of nanoporous Au (np-Au). Moreover, the dendrite morphology can be retained in the as-dealloyed samples during the multi-step dealloying. Through the dealloying strategy, we can fabricate novel np-AgAu and np-Au ribbons composed of nanoporous dendrites.