Inhomogeneity of bulk nanoporous silver fabricated via dealloying Ag-Zn alloy in sulphuric acid

Described is an approach to fabricate bulk nanoporous silver with a diameter of 12 mm and thickness of 5.4 mm via dealloying Ag₂₅Zn₇₅ alloy in 0.1 mol/l sulphuric acid at 0.4 V for 100 h at room temperature. The volume of the bulk nanoporous contracts 14.2% compared with the starting alloy. Meanwhile, crystal structure switches from close-packed hexagonal to face-centred cubic, which can be considered as a type of phase transition during dealloying. An intrinsically inhomogeneous morphology in microscale exists in bulk nanoporous silver by dealloying, which is caused by coarsening of the ligament width via surface diffusion of silver atoms in the electrolyte for different times. Moreover, parallel orientation structures and cracks have been found in the specimen, which could be related to the columnar crystal of starting alloy during solidification. The lattice defects such as stacking faults, lattice distortions and twins can be seen in the ligaments.