Nanoporous copper dealloyed from a nanocrystallized TiCu alloy

Nanoporous copper (NPC) was fabricated through dealloying nanocrystallized Ti₅₀Cu₅₀ ribbon alloy under a free immersion condition in HF solutions at 25°C. Multimodal nanoporous structure was formed due to the presence of Ti₃Cu₄ phase, which was co-precipitated with Ti₂Cu during the heat treatment at T = 400°C (T_g < T < T_x). The presence of multiphases in the starting material caused the different behavior in the evolution of nanoporosity. In 0.03 mol/L HF solution, the bimodal nanoporous copper with a pore size of 54 nm and 184 nm was obtained in different regions where the composition differed. The ligament scale lengths in two regions were confirmed to be 54 nm and 203 nm, respectively. In 0.13 mol/L HF solution, the difference in the pore size and phase separation became weak, accompanying with the evolution of larger pores and smaller ligaments. The residue after dealloying was confirmed to be fcc Cu, indicated by the presence of Cu (111), (200), (220) and (311) in XRD patterns and TEM selective area diffraction pattern. The microstructure of the starting materials for dealloying, such as intermetallic phases, played a key role in the formation of the final multimodal nanoporous structure.