EXPERIMENTAL-STUDY OF THE INFLUENCE OF INTERFACIAL ENERGIES AND REACTIVITY ON WETTING IN METAL-OXIDE SYSTEMS

The wetting of a CuPd alloy containing 15 at. pct Ti at 1473 K on thre e oxide substrates (alumina, mullite, and silica) of different stabili ty with res ct to the liquid alloy was studied. Contact angle measurem ents were performed using the sessile drop method. The morphological a nd chemical characteristics of the metal/ceramic interface were determ ined by scanning electron microscopy, X-ray diffraction, and electroni c microprobe. Results on reactivity were explained on the basis of a d etailed description of the thermodynamics of interfacial reactions. Th e relative magnitude of the two contributions involved in the theory o f reactive wetting-that is, the change in the nature of interfaces and the free energy released by the reaction-was discussed. It has been c oncluded that for the systems studied in the present work and more gen erally for systems with a limited or moderate reactivity, the term acc ounting for interfacial energy change appears to be the predominant co ntribution to reactive wetting.