Synergistic effect of ablative resistance of ZrxHfy(YCeTi)1‒x‒yO2‒δ spiral-fiber-toughened ZrB2‒SiC ceramic up to 2150°C

Although ZrB 2 ‒SiC (ZS) ceramics have been extensively researched for reusable space vehicles, the gaseous Si-bearing oxides are actively yielded, which limits their service for ultra-high-temperature applications (>2000°C). In this work, medium-entropy oxide spiral fibers (MEO sf ) with a composition of Zr 0.68 Y 0.07 Ce 0.2 Ti 0.05 O 2‒ δ (Zr 0.68 ) were developed to promote the generation of oxide scale. The MEO sf -ZS composites demonstrated a low ablation rate of 0.27 µm/s when exposed to ten 60 s cycles of oxyacetylene flame at 2150°C. The first-principle calculations revealed that the MEO-Zr 0.68 exhibited minimum lattice distortion in the ferroelastic tetragonal ( t ) phase and a highly integrated crystal orbital overlap of the Ti–O bond, which contributed the good phase stability at high temperature. The enhanced ablation resistance of MEO sf -ZS was ascribed to the outstanding t -phase stability and structural integrity of the oxide scale. The intact MEO-glassy SiO 2 oxide scale formed by capillary resistance effect of spiral geometry finally retarded the active oxidation of SiC grains.