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

Segregation (or adsorption) can decrease the energy of interfaces, thereby modifying such properties as the interfacial energy and the work of adhesio n. 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-call ed solid start: wetting method conducted under ultra-high vacuum conditions , so as to ensure maximum surface and interfacial cleanliness. Contact angl e measurements, in conjunction with the Gibbs adsorption isotherm, have bee n used to determine interfacial energies and interfacial composition. In so me cases, the compositions of the interfaces have been independently determ ined by Anger spectroscopy, and found to he in excellent agreement with tho se inferred from the Gibbs adsorption isotherm. One conclusion of this work is that the work of adhesion may be significantly increased by the additio n of interfacially active components, without formation of possibly brittle interfacial reaction products. (C) 2000 Acta Metallurgica Inc. Published b y Elsevier Science Ltd. All rights reserved.