HEAT TRANSFER FROM OXYGEN ATOMS RECOMBINATION ON SILICON CARBIDE: CHEMICAL EVOLUTION OF THE MATERIAL SURFASE

In order to quantify the energy transfer from the reactive flow to a surface, determination of recombination and accommodation coefficients (respectively γ and β coefficients) is required. The following work concerns atomic oxygen flow recombining on silicon carbide. The γ coefficient is measured in a pulsed oxygen plasma reactor in non equilibrium conditions, using an actinometiic method, whereas the β coefficient is determined in a micro-wave plasma reactor, using a calorimetric method. The βγ coefficient gives also the energetic transfer to the surface during the recombination reaction. The experimental study is undertaken on silicon carbide which presents interesting properties as refractory material. The measurements are performed on a large temperature range (300 - 1123 K) in order to point out a change in the recombination mechanism when the surface temperature rises. At the same time, the chemical structure of the material is followed by different analysis techniques (ESCA, SIMS and SEM) and shows a modification of the chemical composition of silicon carbide resulting from oxidation, ablation of the surface and diffusion of oxygen into the bulk material.