Diffusion Processes at Liquid Metal/Ceramic Interfaces

Abstract

Experiments with molten. drops of non-reactive metals (Au, Cu, Ni) on pure, polycrystalline alumina have been performed in Ar. Afterwards the metal drops have been removed, and the grain boundary grooves at the interface analyzed by AFM and SEM to identify and study the atomic transport mechanisms at the metal/oxide interface.

The grooves exhibit shapes expected for diffusion controlled growth; the interfaces are less faceted than the Al₂O₃ surfaces. The time dependence for grooving at the Ni/Al₂O₃ interface indicates that diffusion through the molten liquid is the main atomic transport mechanism. Transport rates near the interface are two to four orders of magnitude faster than on the surface of the oxide. Experiments performed with gold on Al₂O₃ have shown that the transport is much faster in air than in inert atmospheres underlining a dramatic influence of the environment on interfacial mass transport.