The structure and mechanical properties of Cu 50 Ni 50 alloy nanofoams formed via polymeric templating
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Research Letter
The structure and mechanical properties of Cu50Ni50 alloy nanofoams formed via polymeric templating Chang-Eun Kim, School of Materials Engineering, Purdue University, West Lafayette, IN 47906-2045, USA; Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, USA Raheleh M. Rahimi and David F. Bahr, School of Materials Engineering, Purdue University, West Lafayette, IN 47906-2045, USA Address all correspondence to David Bahr at [email protected] (Received 16 January 2020; accepted 28 February 2020)
Abstract The authors demonstrate that multicomponent metallic alloy nanofoams can be synthesized by the polymeric templating method. The present approach enabled alloy compositions not accessible via commonly used dealloying or co-deposition methods. The authors report the synthesis of a Cu50Ni50 alloy nanofoam using electrospinning polymeric templating, which exhibits distinct polycrystallinity, process-driven segregation, and enhanced mechanical strength over pure Cu nanofoams. Transmission electron microscopy revealed microscopic grain formation and their variable compositions. The processing method is applicable to the synthesis of a wide range of multicomponent metal porous materials, creating new research opportunities for noble alloy foams not available through wet electrochemical routes.
Introduction Metal nanofoams present special properties that are not commonly found in bulk metals. These architectures are made of mostly empty pores and thin ligaments, featuring very large surface area per unit volume. The high surface-to-bulk ratio of the metal nanofoam has spurred interest in research toward catalysis, filtering, and other chemical processing.[1] Their porous microstructure leads to challenges in determining the mechanisms which govern the mechanical strength of such extremely porous metals.[2,3] Important physical properties of the nanoporous metals that are closely related to surface properties—plasmonic response, optical absorption, and phononic response—and thermal properties are impacted by the structure of the materials.[4] Unfortunately, many of these research opportunities have been achieved for a few select elements. The most common methods of fabricating metal nanofoams— dealloying and co-deposition—rely on chemical mechanisms that are only suitable for a limited range of elements.[5] Dealloying typically begins with a binary bulk metals, from which the more reactive component is dissolved out, leaving the less reactive component in a porous microstructure.[6,7] In this way, the available species of the nanofoam is predetermined by their electrochemical potentials.[8] For example, if we begin with the Cu–Ni binary alloy, the dealloying process will always favor Cu to remain as the foam body, because the electrochemical potential of Cu is lower (or Cu is more noble) than that of Ni. During the dealloying process, the porosity of the foam changes along with the composition during the reaction, meaning that the structure and composition of the foam sample are not
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