Selective phase dissolution as a route to nanoporous titanium with tailored properties

Abstract

Selective dissolution of one phase from as-cast two-phase alloy microstructures is explored as a route to nanoporous solids with high specific-surface-area (SSA) competitive with the values attainable by established dealloying methods. The chosen alloy system, Ti-Sc, is studied over a composition range from Ti75Sc25 to Ti25Sc75 (at%). In as-cast alloys, the phase constitution is characterized, and the mechanism of microstructural development is elucidated. The Sc-rich phase can be selectively dissolved from the as-cast alloys, yielding nanoporous Ti samples. The SSA, wettability and optical reflectivity of the nanoporous samples are characterized. Selection of as-cast composition permits control of these properties. It is concluded that selective dissolution from two-phase microstructures is a viable route to useful nanoporous solids. Results from different casting conditions, and from subsequent solid-state heat treatment, indicate paths to optimization of the nanoporous morphology and to higher SSA.