The influence of crystallography and oxide and metallic types on the structure and properties of metal-ceramic interfaces

Abstract

Metal-ceramic oxide interfaces were investigated systematically to determine the role of reactivity of the metal and the oxide on the structure and mechanical properties of the interface. Electron microscopy was used to examine the structure of metal-ceramic interfaces between a non-reactive metal and a non-reactive ceramic (PtAl 2O 3), between a non-reactive metal and a reactive ceramic (PtNiO) and between a reactive metal and a non-reactive ceramic (TiAl 2O 3). The effect of crystallography, impurities and processing conditions on the interfacial morphology was also studied. For PtAl 2O 3, diffusion bonding in air produces a thin amorphous layer while bonding in argon produces a layer of grains of metastable crystalline alumina compounds such as ιAl 2O 3. It is believed that impurities play an important role in the formation of metastable phases in the PtAl 2O 3 system. For NiOPt, the relative geometry across the interface plane influences its structure. The morphology of the NiPt intermetallic compound formed by low temperature anneals is sensitive to the relative geometry between the NiO and platinum, and to the presence of silicon impurities. For TiAl 2O 3, heat treating at low temperatures produces no reaction layer and the strongest interfacial bonding, while heat treating at high temperatures (800°C and above) produces an interlayer of intermetallic compounds and weak bonding.