Microstructure evolution of ceramic materials during solidification from melts in high-gravity combustion synthesis

A variety of bulk ceramic materials were prepared via melt-casting by high-gravity combustion synthesis, and the microstructure evolution during solidification was investigated. Most single-phase ceramics like Al2O3, YAG, and MgAl2O4 showed a faceted crystal shape because they have higher melting entropies. The cooling condition had an evident influence on the solidification process, resulting in different microstructures. As an example, a strongly textured structure consisting of well-arranged faceted crystals was observed in the surface layer of Al2O3 samples. Compared with single-phase ceramic materials, multiphase eutectic ceramics have lower melting temperatures and can provide more opportunity for tailoring microstructures. From the experimental results, the microstructure of eutectic ceramics was related with the volume fraction of each component, and various eutectic structures with submicron interphase spacings were produced such as lamellae, fibers, and three-dimensional interpenetrating frameworks. No cracks were found at the interface between different phases in the eutectic ceramics, indicating an excellent interfacial bonding strength.