Microstructural characterization of ZrC-MoSi2 composites oxidized in air at high temperatures

Future receivers of concentration solar power plants have to heat the coolant (air) so that its temperature will exceed 1300 K. Such absorbers require materials able to support thermal and mechanical stresses, with the slowest possible oxidation kinetics at very high temperatures. Zirconium carbide (ZrC) with silicon additive like molybdenum disilicide (MoSi2) could be a candidate material for such an application. ZrC/20 vol% MoSi2 samples were oxidized for 20 min at the 5 kW Odeillo solar furnace in air at various temperatures between 1800 and 2000 K and the oxidation behaviour was investigated as a function of the exposure temperature and the surface machining preparation. X-Ray photoelectron spectroscopy and scanning electron microscopy coupled with energy dispersive X-Ray spectroscopy enabled to study the microstructure evolution and to identify the oxidation mechanism leading to the formation of zirconia and silica layers. Based upon the characterizations, we can affirm that ZrC/20 vol% MoSi2 seems able to withstand temperatures up to 2000 K in air.