‘Temperature jump’ mechanism of silicon carbide based thermal protection material in arc-jet flow

Ablation of SiC based thermal protection material is always accompanied by an abrupt increase in surface temperature (temperature jump) in high-enthalpy flows. This work explores the ‘temperature jump’ mechanisms in arc-jet environments and reports for the first time the vanishments of ‘temperature jump’ in arc-jet flows at high pressures (∼20 kPa), using a SiC fiber reinforced SiC composite (SiCf/SiC) as model material. The underlying mechanisms are explained with the help of characterizations of ablated surface and computational fluid dynamic calculations. The wind tunnel experiments suggest that in case of ‘temperature jump’, strong ablations of SiCf/SiC are triggered when surface temperature beyond a threshold at 8.24–14.71 kPa. The threshold temperature is higher at higher flow pressures, so is the mass ablation rate. The pressure dependent ‘temperature jump’ behavior is explained by catalicity of atomic species and active oxidation when SiO2 scale is fully dissipated in arc-jet flows. At higher flow pressures (∼19.78 kPa), due to lower percentages of atomic nitrogen, the catalytic effect of SiCf/SiC is weaker. In addition, due to higher partial pressure of oxygen species, passive oxidation is stronger. Both mechanisms finally contribute to vanishments of ‘temperature jump’ in arc-jet flows. The outcome of this work can fill the research gap of ‘temperature jump’ study at high flow pressures and help understand fundamentally the ablation behavior of SiC in aerodynamic thermal environments.