Grains refinement mechanism of (Ti, Ta)3SiC2/Al2O3 composite ceramics. Issue 18 (15th September 2022) - Ji, Jun
Abstract: (Ti, Ta)3 SiC2 /Al2 O3 composite ceramics were prepared by hot-pressing sintering using TaC as Ta source. X-ray diffraction analysis showed that the maximum of solid solubility of Ta in Ti3 SiC2 were determined to be from 7.5 to 10 at%. With the increase of TaC contents, the grain size of Ti3 SiC2 reduced obviously. Combined Wulff theorem and first-principle calculations, the probable mechanism of this refinement phenomenon was revealed. When Ta atoms substitute Ti in surface atomic layers, the surface energy of (001) plane increased significantly compared to those of (100) plane, which restricted the growth of (001) facets. As it is the largest exposed surface, the lower growth rate of (001) facets lead to the grains refinement. The results will provide theoretical guidance for surface modification and morphological transformation of Ti3 SiC2 -based ceramics.