Bulk nanoporous tungsten as an extremely strong and low density nanocrystalline material was for the first time created to satisfy the need for advanced high performance materials that can endure harsh environments. Synthesis of nanoporous tungsten was achieved by a unique procedure involving severe plastic deformation of a coarse-grained tungsten-copper composite followed by selective dissolution of the nobler copper phase. The used ammonium persulfate etching solution, in which the less noble tungsten is chemically stable, is proved to be effective in removing the nobler copper phase. A nanoporous microstructure characterized by a network of interconnected nanocrystalline tungsten ligaments and interconnected nanopores was obtained. Based on a high-resolution interface analysis, the underlined mechanisms for formation of the nanoporous tungsten structure were elucidated. Moreover, using nanoindentation we demonstrate that, due to the nanoscale microstructure, the created nanoporous tungsten possesses outstanding strength, making it an attractive material for applications in radiation shielding.
Zhao, M., Issa, I., Pfeifenberger, M. J., Wurmshuber, M., & Kiener, D. (2020). Tailoring ultra-strong nanocrystalline tungsten nanofoams by reverse phase dissolution. Acta Materialia, 182, 215–225. https://doi.org/10.1016/j.actamat.2019.10.030