Comparison of ZrB2-SiC, HfB2-SiC and HfB2-SiC-Y2O3 oxidation mechanisms in air using LIF of BO2(g)

•Investigation of the in situ oxidation of UHTC samples using LIF technique.•Detection of the BO2 radicals in the gas phase above three different UHTC materials during an oxidation run up to 1873K.•Determination of the volatile species in the gas phase and of the temperature of the first detection.•Description of the in situ oxidation mechanisms as a function of the composition.•Interest of additives on the oxidation behaviour. The oxidation behaviour of ZrB2-SiC, HfB2-SiC and HfB2-SiC-Y2O3 is studied using the real-time Laser-Induced Fluorescence (LIF) detection of BO2(g) evaporated from samples heated up to 1873K in dry air. For each composition, the relevant steps of oxidation (silica formation, volatilization, etc.) can be precisely determined. Moreover, the influence of composition on the oxidation behaviour, and more precisely on the B2O3/SiO2 ratio in the glassy phase, can be understood and described by monitoring the LIF signal from the BO2(g) radical. Thus, this technique has confirmed the potential of the HfB2-SiC-Y2O3 composition as a Ultra High Temperature Ceramic (UHTC) material.