Oxidation behavior and mechanism of SiBCN ceramics derived from liquid polymer precursor

SiBCN ceramic shows excellent thermal stability, oxidation resistance and crystallization resistance. The oxidation behavior of SiBCN ceramics, derived from pyrolysis of polymeric precursor, was studied at 1 200℃ and 1 400℃ in air atmosphere. XPS was used to characterize the chemical bonding of SiBCN ceramic before and after oxidation experiments. XRD and SEM were employed to analyze the phase composition and microstructure of SiBCN ceramic before and after oxidation experiments. The oxidation kinetics was studied by measuring the thickness of oxide layers via SEM. The results show that, after oxidation experiments, dense protective oxide layers form on the surface of SiBCN ceramic to prevent further oxidation. And the diffusion of oxidant through the oxide layers is the rate-controlling process. The oxide layers thickness of SiBCN ceramic growth at 1 200 and 1 400℃ in air can be approximated by a parabolic rate law with rate constants of 0.0224 μm²/h and 0.1045 μm²/h, respectively. Which was thinner than SiC ceramic with rate constants of 0.0449 μm²/h and 0.1288 μm²/h, respectively. The BN(C) structure and the formed of dense SiO_xN_y layers made SiBCN ceramic have excellent oxidation resistance.