Substitution behavior of Ag atoms in the Ti₂AlC ceramic

In this study, the substitution behavior of Ag atoms in the Ti₂AlC ceramic was investigated using high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). The TEM sample of the Ag/Ti₂AlC interaction area was prepared following the wetting experiment, which was carried out at 1030°C for 5 minute using the sessile drop method. The Ag “single atoms” or “nanoclusters” were found in the crystal lattice of Ti₂AlC substrate. The characterizations along two typical crystallographic orientations suggest that both the Ti and Al atoms could be substituted by Ag atoms during the wetting process. In addition, the substitution behavior would contribute to the lattice expansion, which was coordinated by elastic distortion in the Ag nanoclusters with small size. However, when the Ag nanoclusters exceeded the critical size, the intact Ti₂AlC structure could no more sustain and defects like stacking faults formed, based on which the Ag nanotwins or polycrystals nucleated.