On the Microstructure, Chemical Composition, and Porosity Evolution of Nanoporous Alloy through Successive Dealloying of Ternary Al–Pd–Au Precursor

Abstract

In the present Article, we have investigated the microstructure, composition, and porosity evolution of nanoporous alloy during successive dealloying of ternary Al75Pd17.5Au7.5 precursor in NaOH/HCl and HNO3 aqueous solutions. The results show that the selective dissolution of Al through the first-step dealloying contributes to the formation of Pd–Au nanoporous composites, which are composed of two distinct structures: the finer nanoporous AuPd dendrites derived from the dealloying of Al2(Au,Pd) and the coarser nanoporous Pd(Au) derived from the dealloying of Al3(Pd,Au). Moreover, compared with those dealloyed in the 20 wt % NaOH solution, the Pd–Au nanocomposites exhibit a coarser length scale of ligaments/channels in the 5 wt % HCl solution. After the second-step dealloying in the 65 wt % HNO3 solution, the nanoporous Pd(Au) dissolves away, and the Pd dissolution results in the formation of Au-rich nanoporous alloy with bimodal channel size distributions. Nanoporous alloys with unique structures and com...