Hot-corrosion of refractory high-entropy ceramic matrix composites synthesized by alloy melt-infiltration

Carbon fiber-containing refractory high-entropy ceramic matrix composites (C/RHECs) were fabricated through a reaction with carbon powders, transition metal carbides, and Zr-Ti alloys as a novel heat resistant material used for components of hypersonic vehicles cruising at Mach 7-10. With the infiltration of alloys at 1750 degrees C into a composite preform containing carbon and carbide powders for 15 min, a high-entropy matrix was successfully formed in situ. Arc jet tests were conducted in the temperature range of 1800-1900 degrees C. Results showed the formation of an oxidized region composed of complex oxides, such as (Zr, Hf)O-2, (Nb, Ta)(2)(Zr, Hf)(6)O-17, (Zr, Hf) TiO4, and Ti(Nb, Ta)(2)O-7, with an average thickness of similar to 600 mu m, under which an unoxidized region remained. The porous oxidized region resulted from the evolution of CO(g) during oxidation, while a dense oxide region formed as the outermost region. This indicates that the dense oxide region acted as a barrier to oxygen diffusion for the unoxidized region during oxidation.