Microstructures and properties of Si3N4/TiN composites sintered by hot pressing and spark plasma sintering

Microstructures and mechanical properties of the Si3N4/TiN composites sintered by hot pressing (HP) and spark plasma sintering (SPS) were studied comparatively. Compared with the non-conductive monophase Si3N4 ceramic which has lower density and α–β transformation ratio prepared by SPS than by HP, the conductive Si3N4/TiN composite sample, however, has higher density and obviously higher α–β transformation ratio sintered by SPS than by HP, which means that the presence of TiN clearly improves the densification and α–β phase transformation of silicon nitride in SPS compared in HP. The microstructure analysis shows that the SPSed Si3N4/TiN composites had lower porosity and aspect ratio than the monophase Si3N4. Both the hardness and fracture toughness of the Si3N4/TiN composite with 50%TiN sintered by SPS are higher than by HP, but the hardness and fracture toughness of the non-conductive monophase Si3N4 ceramics do not have a significant difference either sintered by SPS or HP.