WETTING AND INTERFACIAL BONDING OF METALS WITH IONOCOVALENT OXIDES

The adhesion and interfacial bonding between nonreactive liquid metals and solid ionocovalent oxides are studied on the basis of the experimental work of adhesion W data. An analysis of the experimental W values of different liquid metals on various solid oxides is first performed to put into evidence the dependences of the work of adhesion of a metal/oxide system on the electron density of the metal and on the thermodynamic stability of the oxide. An electronic model is then proposed to describe the microscopic mechanism of metal-oxide interactions. Based on the model, the work of adhesion and the contact angle of different liquid metals on various solid oxides can be interpreted and estimated, and their correlations to the various physical properties of the oxides can be easily deduced. The basic consideration of the model is that the adhesion between a metal and an oxide is assured by the electron transfer from the metal into the oxide valence band which is not completely filled with electrons at high temperatures, and is enhanced when this electron transfer at the metal/oxide interface is increased. The extension and application of the model to solid metal/solid oxide systems is also presented.