Entropy-stabilization meets ZrB2: Dual pathways to oxidation resistance of (Ti,Zr)B2-reinforced (Zr,Ti,W,Ta)C medium-entropy carbide ceramics at 1000 °C–1100 °C

This study systematically investigates the isothermal oxidation behavior of (Ti,Zr)B 2 -reinforced (Zr,Ti,W,Ta)C medium-entropy carbide ceramics with varying ZrB 2 content (40-60 mol%) at 1000–1100 °C (operating temperature range for divertor components in nuclear fusion devices). The results demonstrate that ZrB 2 addition significantly enhances oxidation resistance through the formation of a protective B 2 O 3 glass phase that effectively fills pores in the oxide skeleton and blocks oxygen inward diffusion. A multi-layered oxide structure develops consisting of an outer porous TiO 2 /ZrO 2 layer, an intermediate dense (Ta,W)O x +ZrO 2 +TiO 2 +B 2 O 3 mixture, and an inner partially oxidized matrix. Below 1100 °C, barrier protection dominates, while entropy effects prevail above 1100 °C due to enhanced B 2 O 3 evaporation. The optimized composition with 60 mol% ZrB 2 reduces oxidation depth from 812 μm to 367 μm and shows superior performance compared to pure WC materials, establishing a new paradigm for designing oxidation-resistant ultra-high temperature ceramics for nuclear energy and aerospace applications.