Limits of Tunability in Dealloyed Nanoporous Metals

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TECHNICAL SUMMARY: Dealloyed nanoporous metals are made by the selective electrochemical dissolution of one component of a uniform solid solution alloy under conditions where the remaining alloy components may diffuse along the metal/electrolyte interface to re-form into a highly porous metal with pore and ligament sizes on the nanoscale. Applications for these new materials are emerging in (electro)catalysis, optical sensing, and actuation, and active research into their unusual mechanical and electronic properties are being actively investigated. Less well-studied are the kinetic processes that control the morphological and compositional evolution of nanoporous metals during the pattern forming instability of their creation, even though these kinetic processes control the ultimate shape, ligament crystal surface orientation, and the surface and bulk compositions of the final nanoporous metal. This program will make a detailed study of the fundamental kinetic processes that control the morphological evolution of nanoporous metals, that control their surface composition, that influence their processing/structure relationships, and that can be used to make new materials. The overall goal is to probe how far the morphological and compositional characteristics of nanoporous metals can be controlled.NON-TECHNICAL SUMMARY: A challenge in the study of nanostructured materials is to make tangible quantities of materials that possess controlled structure at the near-atomic scale, and still possess the unusual and remarkable properties associated with nanometer size. Success at this kind of nanotechnology scale-up may translate to many disciplines, and help improve a range of technologies from energy to sensing to mechanical systems. This program will make an in-depth study of one class of bulk nanostructured materials, so-called nanoporous metals made by electrochemical dissolution of one or more elements from a multi-component alloy. These remarkable materials possess a contiguous network of pores whose diameters are only tens of atoms wide; they are being actively explored for a diverse range of applications from catalysis to solar energy. Understanding the fundamental physics and chemistry of how nanoporous metals form and how their microscopic shape can be changed will inform to what degree the properties of these materials can be controlled, and open up new methodologies to translate the properties of the nanoscale to the macroscale world. Along the way, pedagogical products will be developed and disseminated, including an introductory lecture course to explore the linkages between traditional metallurgy and a computer simulation code that can be used to probe nanomaterials structure evolution.