High-temperature oxidation of graphite under non-thermal oxygen plasma

Experiments to measure the oxidation rates of carbon by molecular and atomic oxygen were conducted using a non-thermal, radio frequency generated plasma exposed to a resis-tively heated graphite rod at surface temperatures between 773 and 2073 K. The temperature dependence of oxidation behavior was obtained for pure O₂ and for a mixture of O₂ and O atoms produced by the plasma. Oxygen atom flux to the graphite samples was characterized based on etching rates of reference polyimide films. Mass loss and exposure time of the graphite samples were measured at different test conditions to calculate oxidation rates. Mass spectrometry was used to identify the chemical species present in the oxidation products. Experiments were carried out at a pressure of 0.33 kPa which provided carbon oxidation results relevant to atmospheric entry conditions and which will be used to inform Arrhenius rate equations for gas-surface interaction computational models.