Evolution of structure during the oxidation of zirconium diboride–silicon carbide in air up to 1500 °C

The structures that developed as dense ZrB₂–SiC ceramics were heated to 1500 °C in air were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction. The oxidation behavior was also studied using thermal gravimetric analysis (TGA). Below 1200 °C, a protective B₂O₃-rich scale was observed on the surface. At 1200 °C and above, the B₂O₃ evaporated and the SiO₂-rich scale that formed was stable up to at least 1500 °C. Beneath the surface, layers that were rich in zirconium oxide, and from which the silicon carbide had been partially depleted, were observed. The observations were consistent with the oxidation sequence recorded by thermal gravimetric analysis.