Spark plasma sintering of quadruplet ZrB2-SiC-ZrC-Cf composites

Spark plasma sintering (SPS) route was employed for preparation of quadruplet ZrB2-SiC-ZrC-C-f ultrahigh temperature ceramic matrix composites (UHTCMC). Zirconium diboride and silicon carbide powders with a constant ZrB2:SiC volume ratio of 4:1 were selected as the baseline. Mixtures of ZrB2-SiC were co-reinforced with zirconium carbide (ZrC: 0-10 vol%) and carbon fiber (C-f: 0-5 vol%), taking into account a constant ratio of 2:1 for ZrC:C-f components. The sintered composite samples, processed at 1800 degrees C for 5 min and 30 MPa punch press under vacuumed atmosphere, were characterized by densitometry, field emission scanning electron microscopy, energy dispersive spectroscopy, X-ray diffractometry as well as mechanical tests such as hardness and flexural strength measurements. The results verified that the composite co-reinforced with 5 vol% ZrC and 2.5 vol% C-f had the optimal characteristics, i.e., it reached a relative density of 99.6%, a hardness of 18 GPa and a flexural strength of 565 MPa.