Synthesis of skeletal silver from rapidly solidified Al–Ag precursor

Abstract

Skeletal silver was synthesized by applying an alkaline leaching process to rapidly solidified Al–Ag granular precursors. The structure of the leached materials was examined by scanning electron microscopy, EPMA, X-ray diffraction and differential scanning calorimetry. Most of the aluminum was leached out and only a few percent aluminum remained in the as-leached state. The crystallographic structure of the leached material was face centered cubic and it was formed by rearrangement of silver atoms dissolved in the α-Al solid solution during leaching. The Ag 2Al phase was too stable for the alkaline solution so that it did not contribute to the formation of skeletal silver. The formation ratio of skeletal silver to the total silver in the precursor depended on the amount of dissolved silver in the α phase. Rapid solidification of Al–Ag alloys was quite effective for obtaining the super-saturated α phase. More than 80% of the silver in the precursor turned into skeletal silver using the rapidly solidified precursor. The specific surface area of the skeletal silver was about 9 m 2/g. The mean diameter of the skeletal silver was about 20 nm as derived using the X-ray line broadening method. This value was 1.2–1.5 times smaller than that evaluated from the specific surface area assuming spherical silver particles. The difference may result from shape degeneration.