Wettability and Work of Adhesion of Nonreactive Liquid Metals on Silica

Wettability of silica by gold, silicon, and lead has been determined by the sessile-drop method. The contact angle, ?, and the work of adhesion, W, have been found to be 143° and 227 mJ·m-2 for gold at 1353 K, 87° and 869 mJ·m-2 for silicon at 1723 K, and 120° and 203 mJ·m-2 for lead at 1000 K. Thermodynamic adhesion between silica and nonreactive pure metals has been analyzed using models for metal-oxide bonds. Models based on the assumption that only van der Waals interactions and/or metal-oxygen chemical bonds exist at the metal-oxide interface are unsuited for explaining the relative variations in the W values. A valid model can be accomplished by using an empirical equation which takes into account both metal-oxygen and metal-oxide chemical bonds. It appears that chemical bonds exist at the interface even for nonreactive metal-ionocovalent oxide systems.