Powder-Based Dealloying

Johns Hopkins University, Baltimore MD

Investigators

Abstract

Non-Technical Summary The discovery and design of new metals involves controlling material composition and structure at the microscale. By such control, better materials can be made for many different applications, from structural materials to catalysts to batteries, and to materials with high tolerance to radiation damage. This program is examining a new approach to making these next-generation metals and metallic nanostructures, mixing inspiration from powder metallurgy and from an exotic materials processing technique called dealloying. Dealloying occurs when one element of a solid metal is pulled out of the metal, leaving behind a nanoporous material. The central hypothesis of this work, is that a powder mixture can be used to create dealloyed materials. One powder component acts to absorb elements dealloyed from the other. Because powders are being used, it is expected that bulk amounts of processed materials can be made easily and readily tested for different applications. Student training at the undergraduate and graduate levels will help develop the next generation of materials scientists trained in modern metallurgy. Such training will be complemented by organizing and participating in international conferences on dealloying and related professional development. Technical Summary Nanocomposite and nanoporous metals consisting of multiple interpenetrating but compositionally distinct solid and void phases hold promise for structural applications requiring high strength, high ductility, radiation tolerance, catalysis, sensing, supercapacitors, batteries, and as templates to make new nanocomposites via backfilling. A technique to make such materials is dealloying - the selective dissolution of one component from a multi-component alloy. This project explores the next-generation of dealloyed nanostructured materials, using a concept called powder-based dealloying. Powder-based dealloying refers to the metallurgical phase evolution in the environment of mixed powders, where the composition of one powder is the material to be dealloyed, and the other powder, when melted, acts as the dealloying medium. This involves analysis of the kinetics of dealloying in fixed volumes, and it is hypothesized that bulk samples of metals can be made that exhibit very fine microstructures with characteristic lengths less than 50 nm. We are also taking the first steps to assess how dealloying can be integrated into powder metallurgical processing methods, and perhaps ultimately additive manufacturing. By examining a range of model materials made by powder-based dealloying, a database of basic physical kinetics behavior will be developed that will be applicable to many high-temperature processing technologies, from sintering to additive manufacturing, as well as more efficiently work with rare, hard-to-sustain, and refractory materials. Student training at the undergraduate and graduate levels will help develop the next generation of materials scientists trained in modern metallurgy. Such training will be complemented by organizing and participating in international conferences on dealloying and related professional development. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.