De-alloying kinetics of an Au-based amorphous alloys

The process of de-alloying, i.e. removal of a less noble metal from an alloy, is applied here by electrochemical means to a Au-based metallic glass, Au40Cu28Ag7Pd5Si20, as a function of potential, temperature, and time. Very fine crystals nucleate with random orientation at the solid-electrolyte interface forming ligaments. The resulting material is constituted by ligaments made of pure Au and pores of smaller size whose dimensions coarsen up as a function of time to slightly above two hundred and below one hundred nanometers, respectively. The microstructure is uniform on both surfaces and across the ribbon. The extent of de-alloying is measured by monitoring the heat of crystallisation of the remaining amorphous phase giving linear trend vs time suggesting the reactions occur on continuously renewed surfaces. (c) 2011 Elsevier B.V. All rights reserved.