Oxidation behaviour of ZrB₂–SiC (Al/Y) ceramics at 1700 °C

ZrB₂–SiC(Al/Y) ceramic composites were prepared by hot-pressing a mixture of ZrB₂ and polymer-derived SiC doped with either aluminium or yttrium (SiC(Al/Y)). The obtained composites were oxidized at 1700 °C in air. The weight change as a function of the oxidation time was measured to study the oxidation kinetics. It was found that the ZrB₂–SiC(Al/Y) composites exhibited significantly improved oxidation resistance, as compared to the composite of ZrB₂ with un-doped SiC. The structure of the oxide resulted from the oxidation of the composites was characterized by scanning electron microscopy and X-ray diffraction. The results suggested that the improvement can be attributed to the formation of yttrium/aluminium-doped silica and/or yttrium disilicate, which effectively protect the composites.