Interface reaction and wetting in the CaF2/Me systems

Wetting experiments using the sessile drop method were performed in the CaF2-Me systems (Me= Cu, Ge, Al, In and Ga). Liquid Cu, Ge, In and Ga, do not wet the CaF2 substrate and contact angles are significantly higher than 90 degrees. No condensed products were found at the metal/ceramic interface. In the CaF2/Al system, evidence of an interface interaction was detected and the contact angle is about 92 degrees. It was established that the spreading behavior and the values of the apparent contact angle depend on the rate of evaporation of the molten metals, the rate of sublimation of the substrate and on the value of the work of adhesion at the interface. The experimental observations are well accounted for by a thermodynamic analysis of the ternary Ca-Me-F systems. (c) 2007 Elsevier B.V. All rights reserved.