Determination of amorphous interfacial phases in Al2O3/SiC nanocomposites by computer-aided high resolution electron microscopy

The analysis of thin amorphous layers in transmission electron microscope imaging has always been rendered difficult by the sample geometry conditions which must be met in order to single out the electronic scattering due to the amorphous phase from the overlapping crystalline diffraction fringes. This is the case of Al2O3/SiC nanocomposites in which spherical fine SiC particles are entrapped into the Al2O3- matrix grains. The spherical geometry of the SiC dispersoids involves a circular phase boundary in the thin foil which is hardly examined by conventional high-resolution techniques. In this paper an alternative technique of computer-aided high-resolution microscopy is proposed for imaging the presence of non-crystalline third phases at the interface of the alumina matrix and the silicon carbide nanosized particles in Al2O3/SiC nanocomposites. Implications regarding the effect of the observed layer on some toughening mechanisms proposed in literature for this materials are included. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.