Fabrication and characterization of nanoporous Cu–Sn intermetallics via dealloying of ternary Mg–Cu–Sn alloys

Abstract

In this paper, the dealloying of ternary Mg₆₆Cu_25.5Sn_8.5, Mg₆₇Cu₁₈Sn₁₅ and Mg₆₆Cu_10.2Sn_23.8 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 Mg₆₆Cu_25.5Sn_8.5 and Mg₆₇Cu₁₈Sn₁₅ precursors in 1 wt% TA, respectively. The dealloying of the Mg₆₆Cu_10.2Sn_23.8 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 Mg₆₆Cu_25.5Sn_8.5 and Mg₆₆Cu_10.2Sn_23.8 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.