Influence of dealloying solution on the microstructure of monolithic nanoporous copper through chemical dealloying of al 30 at.% cu alloy

The monolithic nanoporous copper (NPC) can be achieved through chemical dealloying of melt-spun Al 30 at.% Cu alloy comprising α-Al and Al2Cu in a hydrochloric acid (HCl) or sodium hydroxide (NaOH) aqueous solution under free corrosion conditions, during which influence of dealloying solution on the microstructure was investigated, and their formation mechanism is discussed. The microstructure of the NPC ribbons was characterized using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, transmission electron microscopy, and high-resolution transmission electron microscopy. The experimental results show that the Al 30 at.% Cu alloy presents markedly different microstructure characteristics upon the dealloying in the acidic/alkaline corrosive environment, indicating dealloying solution has a significant influence on the dealloying process and the microstructure of NPC. This is closely related to the difference between electrochemical activities of α-Al and Al2Cu in the initial alloy in the distinct corrosion media. Additionally, the length scales of ligaments/channels in the NPC can be tuned via simply changing the dealloying solution, which results from the different surface diffusivity of Cu atoms along the alloy/solution interfaces in the acidic/alkaline solution. According to the ligament sizes, the surface diffusivity of Cu atoms in the HCl solution can be evaluated as 1.79×10^-16 m² s^-1, which is approximately two orders of magnitude greater than that in the NaOH solution (3.15×10^-19 m² s^-1).