SOLID-STATE BONDING OF SINGLE-CRYSTALS OF NI(111)/AL2O3(0001)

Some fundamental aspects of the solid state bonding process between single crystals of alumina and nickel were studied. It was shown that a model formerly developed to account for the kinetics of diffusion bonding between two metals can be adapted to the case of a metal-ceramic couple. A coincidence site lattice calculation proved that one of the crystallographic relative orientations often mentioned in literature was certainly energetically favourable. With this relative orientation, several nickel-alumina bicrystals have been produced by solid state bonding under secondary vacuum. The influence of operating conditions such as contact pressure and annealing duration has been explored and compared with the calculated results of the bonding kinetics model. Characterization of the solid-state bonded interface was undertaken by optical microscopy and scanning as well as transmission electron microscopy. Observations prove that the initial imposed crystallographic relative orientation was maintained during the solid-state bonding process, and that the synthetic alumina-nickel interface obtained by this technique was free from reaction layer at the usual TEM scale.