Influence of Temperature and Ion Radiation on Dealloying of Fe-Ni Alloy in Liquid Lead

Dealloying is a vital technique for fabricating nano- and micro-scale porous materials used in various functional and structural applications, such as catalysts, fuel cells, electrolytic capacitors, and radiation-damage-resistant materials. In the past, dealloying mostly focused on electrochemical processes that employ alloys consisting of active and noble metals together. These processes cause the leaching of the active element, resulting in porosity in the bulk material. However, electrochemical technique limits the dealloying alloy systems to those with a sufficiently large reduction potential difference between the noble and active elements to enable porous structure formation. In contrast, recently, it is found that liquid metal dealloying can overcome this limitation by using a relatively low melting temperature liquid metal as a corrosive medium to selectively dissolve other elements from different alloy systems, thereby expanding the available options.<br/><br/>Liquid metal dealloying is still in the early stages of research, with most work concentrating on understanding the formation processes of different topological and morphological patterns during dealloying. It has been revealed that the diffusion of elements at the liquid metal and bulk interface is the main contributor to the formation of various patterns during dealloying. Researchers have managed to influence the kinetics by varying the concentration of the dissolving element in both bulk and liquid metals. Therefore, we believe that by controlling elemental diffusion at the interface, we can control the topological pattern, which in turn controls the porosity in the bulk material.<br/><br/>We have developed two methods to control elemental diffusion between the liquid metal and bulk: temperature and ion radiation. In this study, we first demonstrate how temperature affects topology formation by exposing an Fe-Ni model alloy with 36 wt.% Ni to different temperatures (500°C, 600°C, and 675°C) in high-purity liquid lead. Additionally, we examine the effects of simultaneous 3 MeV proton radiation and liquid lead dealloying on the Fe-Ni alloy at these same temperatures. By characterizing the samples using SEM, EBSD, and TEM, we show that the topology changes from sponge-like to motif-like to raindrop-like features with increasing temperatures. Interestingly, we found that radiation can shift the topology from sponge-like to motif-like features. We also quantified the porosity by calculating the ratio of lead-penetrated area to fixed-sized original substrate area at different temperatures. This study aims to elucidate how radiation and temperature might be effective ways to manipulate the topological patterns formed during liquid metal dealloying.