Metal ceramic interface toughness I: Plasticity on multiple length scales

The fracture toughness of Ni-sapphire interfaces was measured as a function of interfacial embrittlement, Embrittlement was controlled by segregating sulfur to the interface, by limiting the presence of moist air in the test environment, and by altering the distribution of interfacial particulates. Fracture energies scaled with the degree of embrittlement and ranged from 8.5 to 34.2 J/m(2). Scanning probe microscopy revealed four distinct plasticity features, the heights of which ranged from 1 mu m to 0.5 nm. Plasticity generation processes are determined based on the variation of feature height and position with fracture energy, allowing features associated with the interface decohesion process to be identified.