Effect of high temperature oxidation on dealloying mechanism of Ag-Cu alloy

Nanoporous silver (NPS) with a three-dimensional (3D) bicontinuous ligament/pore structure can be fabricated in different ways and with different treatments. Thermal treatments before or after dealloying can have a considerable impact on the dealloying process. High-temperature oxidation (HTO) has been researched as a method to tune the process of NPS fabrication. In this work, X-ray diffraction and X-ray photoelectron spectroscopy characterizations were used to identify the phase after HTO and dealloying. Copper oxide was found in the precursor alloy after HTO, which could be the key factor that would influence the mechanism of NPS fabrication. Scanning electron microscopy and transmission electron microscopy were executed to characterize the pathway of forming NPS and research the difference between HTO specimens and the as-cast sample. This demonstrated that, compared to the free corrosion pathway, the diffusion method of Ag atoms was different under HTO pretreatment, which was the predominant factor causing a larger 3D bicontinuous ligament/pore structure. Finally, the microstructure of the final NPS pretreated with HTO for 3 min was much more homogeneous than that of the others, and when the pretreatment time of HTO reached 5 min, the ligament/pore structure almost collapsed.