La2O3 stabilized WB2-SiC composites with remarkable ablation resistance up to 2273 K
The pure phase and ultrafine WB 2 powders were successfully synthesized using a liquid phase precursor synergized with boro/carbothermal reduction method. Subsequently, dense WB 2 -SiC composites (99.5%) were fabricated through hot pressing sintering. The effects of La 2 O 3 additive on the densification, mechanical properties, and ablation resistance of WB 2 -SiC composites were systematically investigated. The ablation behavior of the composites was evaluated using a plasma flame. The results indicate that the mass ablation rate of WB 2 -SiC-La 2 O 3 is 0.463 mg/s, and the linear ablation rate is 0.311 μm/s when exposed to a 2273 K plasma flame for 60 s. The excellent ablation resistance is attributed to the reaction between La 2 O 3 and SiO 2 at high temperature, which generates La 2 Si 2 O 7 , effectively pinned in the glassy phase to inhibit the volatilization of B 2 O 3 . Furthermore, La 2 O 3 also reacts with B 2 O 3 and SiO 2 to generate a highly viscous B-Si-O-La protective layer, which blocks the ingress of oxygen.
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