During atmospheric reentry, the wall temperature of hypersonic vehicles increases not only due to convection and diffusion fluxes in the boundary layer but also as the result of the catalytic atom recombination of the dissociated air plasma. The partial simulation of these conditions is realized on the MESOX test bench which includes a solar radiation concentrator and a microwave generator. First, theoretical and experimental results for the determination of the active to passive transition in the oxidation of ceramic materials under standard and microwave-excited air are presented. Second, the catalytic activity of these materials under different pressures (200-2000 Pa) and temperatures (1000-1800 K) is evaluated, using a thermal approach. The experimental results lead to the determination of the atomic oxygen recombination flux and the evaluation of the physico-chemical behaviour of ceramics under atmospheric reentry conditions.