LAUSR

Abstract Hierarchical nanoporous metals are a new class of porous materials attractive for a wide range of applications due to their high thermal and electrical conductivity, transport properties, stability, etc. However, due to small pore size they suffer from low porosity which is essential for practical use. Here it is demonstrated that volumetric porosity can be considerably increased by using alloys of close-to-eutectic compositions as a precursor for dealloying. In particular, a desirable trimodal hierarchical macro-nanoporous metal with more than 90 vol% porosity can be obtained. Moreover, it is shown that the compromise between enhanced porosity and required shape can be resolved by using ternary alloys of proper close-to-eutectic composition. This approach was demonstrated by development of macroscopic self-supporting bulk samples of macro-nanoporous copper by single-step dealloying of Al-Cu-Mg alloys. It is demonstrated that the insignificant reduction of Mg concentration from the eutectic point of Al-Cu-Mg alloy results in the formation of large micron-size inclusions of Al and Al2Cu phases, which during the dealloying are respectively transformed into additional hierarchical pores and into stiffeners allowing the geometry of the final porous metal similar to the one of the precursor alloy. The proposed method can be extended for synthesis of other hierarchical porous metals with enhanced porosity and controlled shape.