Effect of Si and Zr additions on oxidation resistance of hot-pressed ZrB2-SiC composites with polycarbosilane as a precursor at 1500 °C

Three ZrB2-SiC composites were prepared from polycarbosilane (PCS)-coated ZrB2 powders. Powders with or without additions of Si or Zr were densified by hot pressing at 1800 °C. Finally, the oxidation resistance of the composites was studied at 1500 °C in air. The phase composition and microstructure were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) along with energy-dispersive spectroscopy (EDS). Results showed that Si addition, which reacted with free carbon coming from the pyrolyzed PCS to produce the SiC, improved the oxidation resistance of ZrB2-SiC composites with PCS as a precursor, whereas Zr addition, which reacted with the carbon to produce the ZrC, decreased it.