Fabrication and characterization of nanoporous Cu–Sn intermetallics via dealloying of ternary Mg–Cu–Sn alloys†
In this paper, the dealloying of ternary Mg66Cu25.5Sn8.5, Mg67Cu18Sn15 and Mg66Cu10.2Sn23.8 alloys was investigated using 1 wt% tartaric acid (TA) and 5 wt% hydrochloric acid (HCl). The formation of nanoporous Cu–Sn alloys or composites was probed using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nanobeam-energy dispersive spectroscopy (NB-EDS). The results showed that the structure and phase compositions of the as-dealloyed products depended on the compositions of the precursors and dealloying electrolytes. Ultrafine nanoporous Cu3Sn and Cu6Sn5 alloys could be obtained from dealloying of Mg66Cu25.5Sn8.5 and Mg67Cu18Sn15 precursors in 1 wt% TA, respectively. The dealloying of the Mg66Cu10.2Sn23.8 alloy in 1 wt% TA induced the formation of nanoporous Cu6Sn5/Sn composites. However, using 5 wt% HCl as the dealloying electrolyte led to the partial dissolution of Sn, resulting in the formation of nanoporous Cu41Sn11 and Cu6Sn5 from Mg66Cu25.5Sn8.5 and Mg66Cu10.2Sn23.8 alloys, respectively. The ligaments of the nanoporous structure after dealloying in 5 wt% HCl were also coarser due to the fast diffusion of Cu and Sn with the existence of Cl−. The dealloying mechanisms of the Mg–Cu–Sn alloys were discussed based on the experimental results. The present study provides a facile dealloying approach to fabricate nanoporous Cu–Sn intermetallic alloys via the design of precursors and the selection of dealloying electrolytes.