Microstructures and properties of nano-SiC-ZrO₂ particles synergistically strengthening and toughening MoSi₂ ceramics

Nano-SiC-ZrO₂/MoSi₂ composite ceramics were prepared by hot-pressed sintering. The microstructures and properties were investigated using X-ray diffractometer, scanning electron microscope and mechanical properties testing. The results show that the addition of nano-ZrO₂ and nano-SiC particles can refines the grain of MoSi₂ matrix effectively. The SiC-ZrO₂ synergism is advantageous to enhance the bending strength and fracture toughness of the MoSi₂ matrix ceramic, and the effect of nano-SiC on refining and strengthening the MoSi₂ matrix is better than that of nano-ZrO₂ in the synergistic phase. The bending strength and fracture toughness of 20vol%SiC+10vol%ZrO₂+MoSi₂   improve 280% and 140% respectively compared with the MoSi₂  matrix. Different dislocation configurations are found around the particles in the ceramic matrix. ZrO₂ produces dislocation in the matrix depending on the volume effect caused by its own phase transitions. The second particles pining dislocation include SiC particles and non-phase-transformed ZrO₂ particles. The pining effect of dispersed phases on the dislocation in the composite ceramics is obvious, especially the intragranular type SiC and ZrO₂ particles.