A Study of Electroplated Nanoporous Copper Using Aberration-Corrected Transmission Electron Microscopy.

Nanoporous Cu foam is widely applied in many fields such as the packaging of electronic power devices. In this study, a sandwich-structured Cu-Zn eutectic alloy precursor composed of CuZn/CuZn/CuZn is prepared through electroplating. The surface layer of the precursor, CuZn, has a flat surface with numerous grain boundaries, which effectively promotes its dealloying behavior. By contrast, CuZn has a porous structure, which promotes the dealloying behavior at the center of the precursor. The dealloying of CuZn is dominated by the coherent surface diffusion of Cu atoms, and the crystal lattice and orientation show no changes before and after dealloying. By contrast, the dealloying behavior of CuZn requires the renucleation of Cu crystals; in this process, Cu atoms are transported to the surface of the layer by capillary forces to form clusters, which nucleate and grow.