Uniform evolution of nanoporosity on amorphous Ti-Cu alloys.

Amorphous binary Ti(100-x)Cu(x) (x = 40, 50 and 60 at%) alloys, as the starting materials, were dealloyed in 0.03 and 0.13 M HF solutions under a free immersion condition, and a uniform nanoporous structure with a pore size of 71-220 nm and ligament size of 72-209 nm was obtained after immersion for 43.2 ks. The evolution of nanoporosity underwent more uniformly due to the absence of the intermetallics and defects such as grain boundary, segregation in the chemical composition in the amorphous precursors. The pore size and the ligament size increased with the immersion times and the concentration of the treatment solutions. The pore size increased with the dealloying times exponentially with an exponent of 0.41-0.79. The evolution of nanoporosity was influenced by the alloy compositions, and the formation of the ligaments was controlled by surface diffusion of the Cu adatoms, and also influenced by the coverage of noble Cu contents in Ti-Cu alloys.