Fabrication of nanoporous copper by dealloying of amorphous Ti-Cu-Ag alloys

Ternary TiCuAg amorphous alloys were used as the starting materials for fabricating nanoporous copper (NPC) in HF solutions. NPC with a pore size of 8-55 nm was fabricated through dealloying from an amorphous Ti ₆₀Cu_40-xAg_x (x = 1, 2 at.%) ribbon alloy under free immersion conditions. A 3-dimensional bicontinuous NPC structure formed on Ti₆₀Cu₄₀, Ti₆₀Cu ₃₉Ag₁, and Ti₆₀Cu₃₈Ag₂ ribbon alloys with pore sizes of 130 nm, 48 nm, and 55 nm, respectively, after immersion in 0.13 M HF solution for 43.2 ks. The pore sizes of dealloyed ribbon alloys in 0.03 M HF solution were confirmed to be 71 nm, 41 nm and 39 nm, respectively. The pore size of NPCs dealloyed from Ag-added alloys was smaller than that of the Ti-Cu alloy. Smaller pores formed in the beginning of dealloying because even distributed Ag atoms in amorphous precursors suppressed the diffusion of Cu adatoms. The final characteristic pore size showed a weak dependence on the solution concentrations. Diffusivity decreased more than two orders due to the alloying of Ag. The dealloying residue was fcc Cu-Ag and Ag, with Ag adatoms concentrated at the grain boundary. The uneven distribution of Ag atoms caused the coarsening of nanoporous Cu after the prolonged dealloying.