The effects of interfacial segregation on wetting in solid metal-on-metal and metal-on-ceramic systems

Abstract

Segregation (or adsorption) can decrease the energy of interfaces, thereby modifying such properties as the interfacial energy and the work of adhesion. Several recent studies of solid interfacial systems, including metal-on-metal (e.g. Pb-on-Cu with Au additions), metal-on-SiC (e.g. Au-on-SiC with Si, Ge and Sn additions) and metal-on-graphite (e.g. Pb-on-graphite with Ni additions), are reviewed. The experiments have been performed by a so-called solid state wetting method conducted under ultra-high vacuum conditions, so as to ensure maximum surface and interfacial cleanliness. Contact angle measurements, in conjunction with the Gibbs adsorption isotherm, have been used to determine interfacial energies and interfacial composition. In some cases, the compositions of the interfaces have been independently determined by Auger spectroscopy, and found to be in excellent agreement with those inferred from the Gibbs adsorption isotherm. One conclusion of this work is that the work of adhesion may be significantly increased by the addition of interfacially active components, without formation of possibly brittle interfacial reaction products.