Methods of enhancing of mechanical properties of ceramic-metal composites, particularly fracture toughness by introducing dispersed metal particles such as W, Mo, Ni, Al, etc to a ceramic matrix are well known. However, the dependence of the microstructures, especially interfaces, on the properties of composites is not well understood yet. Moreover, the ceramic-metal interfaces play a crucial role in tailoring the composite properties.
In this paper we examine the alumina matrix composite with NiAl2O4 spinel phase and present the SEM and TEM studies of spinel distribution, size and crystallographic orientation. The composites were prepared by sintering Al2O3 and Ni powders below the melting point of Ni in argon. During the process of sintering the spinel phase appeared. It was not homogeneously distributed in the alumina matrix. The spinel phase areas were linked together and constituted an almost continuous form. We observed that the distribution and size of spinel influenced the fracture toughness of the composite.