Evaluation of the Ceramic Material Response Model Under Static and Dynamic Flow Conditions

The performance of ultra-high-temperature ceramic (UHTC) materials in oxidizing environments has long posed a significant challenge, hindering progress toward sustained hypersonic flight. Of particular importance is the interaction between UHTCs and atomic oxygen, which forms abundantly behind a shock wave during hypersonic flight and reacts more aggressively with materials than molecular oxygen. This study simulates the oxidation dynamics of UHTCs in both quiescent atmospheres and dynamic environments, which differ primarily in the amount of atomic oxygen impinging on the surface. We review the existing model of active oxidation and extend it to the regime of passive oxidation, where a depletion layer does not form. Experiments on the passive oxidation of ZrB2–30%SiC, conducted at the Inductively Coupled Plasma (ICP) facility at the University of Vermont (UVM), are also presented to provide data to validate the developed model. We show that incorporating the reactivity of atomic oxygen with the protective glassy layer—such as B2O3–SiO2—in the form of an Arrhenius process with a reduced activation energy compared to that of O2, significantly improves model accuracy when compared to data collected at the UVM ICP facility, a NASA arcjet facility, and in furnace testing.