Density effects on microstructures and mechanical behavior of (AlN)0.9(Si3N4)0.1 ceramic

Molecular dynamics (MD) simulations have been used to study three samples of (AlN)0.9(Si3N4)0.1 ceramic materials with density varying from 2.95 to 3.88 g.cm-3. The influence of density on microstructure, such as the change of structural units, bond lengths, the nearest common neighbors, and voids, was studied in detail. The analysis shows that these samples consist of regions of AlN and Si3N4 materials. The region of AlN material consists mostly of AlN crystals and small amount of AlN amorphous. The region of Si3N4 material has amorphous structure. Void analysis shows that there is the diffusion of Si atoms into the AlN amorphous region and conversely there is the diffusion of Al atoms into the Si3N4 amorphous region. The voids with large radius are localized in the amorphous structure region. The number of these voids decreases rapidly with the increase of density. This reduction improves significantly mechanical properties of samples.