Preparation of TiC/SiC and TiN/SiC composite ceramics from liquid silicon infiltration

TiC/SiC and TiN/SiC composite ceramics were fabricated by using filter paper, phenolic resin and titania as raw materials through molding, curing, drying, carbonization, and Si infiltration process. The phase composition and microstructure of the TiC/SiC and TiN/SiC composite ceramics were investigated by X-ray diffraction and scanning electron microscopy, and the bending strength and fracture toughness of the composite ceramics were measured. The results show that the TiC/SiC composite ceramic formed from liquid Si infiltration in vacuum has porous microstructure. The dense TiN/SiC composite ceramic formed from liquid Si infiltration at nitrogen atmosphere has higher bending strength and fracture toughness than which of porous TiC/SiC composite ceramic. The different microstructures of these composite ceramics are originated from the different wetting angle of TiC and TiN in liquid silicon. The tension stress and compression stress are formed on the interface between the additive and matrix due to the introduction of TiN particles in TiN/SiC composite ceramic, and the fracture toughness increases as the direction of crack changes in this area.