Energetics and atomic transport at liquid metal/Al2O3 interfaces

The objective is to study interfacial mass transport mechanisms and to estimate interfacial energies for metal/Al2O3 systems. Experiments have been performed with molten drops of Ni, Cu, or Au on pure, polycrystalline alumina at oxygen partial pressures for which no adsorption is expected and with Al to determine the effect of extremely low p(O-2). After removing the metal drops, grain boundary grooves at the interface and oxide surface have been analyzed using AFM and SEM. Several sources of error are assessed, and corrections are proposed for large systematic errors that occur for root angles. These experiments yield higher grain boundary energies and lower M/Al2O3 interfacial energies than previously reported. Transport rates near the metal/ceramic interface are two to four orders of magnitude faster than on the oxide surface and the results suggest that diffusion through the liquid metal is usually the main atomic transport mechanism. Experiments with Al indicate that, at the far lower oxygen activities, transport is faster at both the interface and alumina surface and that the interfaces are more anisotropic and have lower energy. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.