Structure analysis of precursor alloy and diffusion during dealloying of Ag-Al alloy.

Nanoporous silver (NPS) was fabricated by dealloying Ag-Al alloy ribbons with nominal compositions of 30, 35 and 40 at% Ag (corresponding to hypoeutectic composition, eutectic composition and hypereutectic composition, respectively). The microstructures of the Ag-Al precursor and as-dealloyed samples were observed using a scanning electron microscope (SEM) and a transmission electron microscope (TEM) as well as focused ion beam (FIB) technique. We concluded that with the increase in Ag content from 30 to 40 at%, the diameter of ligament increased from 70 ± 15 nm to 115 ± 35 nm. Due to the method of crystalline solidification and the distribution of α-Al(Ag) and γ-AgAl phases, the as-dealloyed AgAl alloy exhibited a homogeneous ligament/pore structure, whereas the microstructures of AgAl and AgAl showed thinner and coarser ligament structures, respectively.