Zirconia reinforced reaction bonded silicon carbide composites: Microstructure and mechanical properties

Nano-sized zirconia particles were dispersed in a SiC/C suspension to examine the particle influence on microstructure and mechanical properties on the resulting composite. The ZrO2/reaction bonded SiC composite was produced by a combination of slip casting and liquid silicon infiltration. By dispersing zirconia particles into the matrix, the gowth of β-SiC was inhibited and the size of residual silicon was reduced. This result led to an increase of flexural strength with reinforcement ranging from 0 to 20 wt.%. Compared with the monolithic RBSC ceramics, the fracture toughness was steadily improved, reaching the peak value of appropriate 4.6 MPa m1/2 at the zirconia fraction of 25 wt.%. The XRD analysis revealed the phase transformation occurred on the fracture surface of the composites. Thus, the transformation of zirconia and the crack deflection are considered as the main toughening mechanisms.

► Zirconia addition reduced the size of residual silicon and new formed SiC particle.
► XRD analysis confirmed the phase transformation on the fracture surface.
► Grain refinement of new formed SiC and silicon increased the flexural strength.
► Transformation toughening and crack deflection were considered the main mechanisms.