Oxidative corrosion of adhesive interlayers

The influence of excess oxygen on the interfacial bonding and adhesion at m etal/ceramic boundaries was studied theoretically by means of electronic-st ructure calculations based on the local density functional theory. The mode l systems investigated were the weakly adhesive Ag(001)/MgAl2O4(001) interf ace and the interface Ag(001)/Ti/MgAl2O4(001), in which the reactive elemen t Ti increases the strength of adhesion considerably. O insertion is exothe rmic at both interfaces due to a stabilising ion-ion interaction with the s pinel surface. Ti reacts more readily than Ag even up to the formation of T iO. Ag shows a preference for Ag2O. However, the adhesion enhancement by th e Ti interlayer is diminished by internal oxidation. The weak interaction a t the pure Ag/spinel interface is almost unaffected by the oxidation.