In situ studies of oxidation of ZrB2 and ZrB2–SiC composites at high temperatures

High temperature oxidation of ZrB2 and the effect of SiC on controlling the oxidation of ZrB2 in ZrB2–SiC composites were studied in situ, in air, using X-ray diffraction. Oxidation was studied by quantitatively analyzing the crystalline phase changes in the samples, both non-isothermally, as a function of temperature, up to ∼1650 °C, as well as isothermally, as a function of time, at ∼1300 °C. During the non-isothermal studies, the formation and transformation of intermediate crystalline phases of ZrO2 were also observed. The change in SiC content, during isothermal oxidation studies of ZrB2–SiC composites, was similar in the examined temperature range, regardless of sample microstructure and composition. Higher SiC content, however, markedly retarded the oxidation rate of the ZrB2 phase in the composites. A novel approach to quantify the extent of oxidation by estimating the thickness of the oxidation layer formed during oxidation of ZrB2 and ZrB2–SiC composites, based on fractional conversion of ZrB2 to ZrO2 in situ, is presented.