Co-reinforcing of ZrB2-SiC ceramics with optimized ZrC to Cf ratio

Characteristics of ZrB2-SiC ultrahigh temperature ceramic matrix composites (UHTCMCs) reinforced with ZrC and carbon fiber (C-f) were investigated in this article. Spark plasma sintering (SPS) process was utilized to fabricate the samples at 1800 degrees C for 5 min under 30 MPa punch pressure and vacuumed atmosphere. In all samples, the volume ratio of ZrB2: SiC was equal to 4:1, and the summation of ZrC and C-f reinforcements was 7.5 vol% with different ZrC: C-f ratios. Field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), densitometry, flexural strength, and hardness measurements were employed for characterization of the prepared samples. Microstructural inspection revealed the formation of SiC sheath around the carbon fibers due to several reactions in the surface SiO2 layers existed on the SiC particles. Optimal flexural strength (628.4 MPa) and hardness (20.8 GPa) values were achieved for the sample co-reinforced with 6.5 vol% ZrC and 1 vol% C-f, with a relative density of 97.7%.