Microstructure and properties of C/C–ZrC composites with matrix modification by slurry infiltration

C/C–ZrC composites are promising thermal structural materials for aerospace applications. However, until now, the reported C/C–ZrC composites exhibited a porous matrix and weaker mechanical properties. In this study, the matrices of C/C–ZrC composites were modified by slurry infiltration in order to improve density and properties. Different slurry powders such as SiC, ZrC, and ZrB2 were used to densify the C/C–ZrC composites. After slurry infiltration, the loose C–ZrC matrix was connected to a dense matrix, and some ceramic powders settled on the surface of the composites. The density of the composites increased from 1.94 to 2.42 ± 0.06 g cm-3, while the porosity decreased from 39.4 ± 4.4% to 10.3 ± 1.9% after infiltration with various slurries. The ablation and mechanical properties of the C/C–ZrC composites improved significantly by matrix modification. The flexural strength of the composites increased from 116 to 269 ± 21 MPa after slurry infiltration. Furthermore, the ablation properties of C/C–ZrC composites infiltrated with the ZrB2 slurry showed the lowest linear rate (24.7 μm s-1) and mass recession rate (7.5 mg s-1).