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

The high-temperature oxidation of ZrB2 and the effect of SiC in controlling the oxidation of ZrB2 in ZrB2-SiC composites were studied in situ, in air, using XRD. Oxidation was studied by quantitatively analysing the crystalline phase changes in the samples, both non-isothermally, as a function of temperature, up to about 1650 C, and isothermally, as a function of time, at about 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. A higher SiC content 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.