Oxidation protection and oxygen barrier enhancement of ZrB2-MoSi2-BSG ceramics based on Hf-based borosilicate glass at 1700 °C

A Hf-based borosilicate glass modification strategy is proposed to enhance the oxidation resistance of ZrB 2 -MoSi 2 ceramics. • Moderate HfO 2 addition forms in-situ dense Zr-Hf-Si-O multiphase glass layer, suppressing oxygen inward diffusion. • ZMGH30 sample shows 23.73% lower oxidation weight gain, 70.38% lower average oxidation rate, and 61.17% hardness retention. To address the issues of loose oxide scale and insufficient protective performance in ZrB 2 -MoSi 2 composite ceramics under ultra-high temperature oxidizing environments, caused by the volatilization of B 2 O 3 and the self-depletion of MoSi 2 , A novel Hf-based borosilicate glass modification strategy is proposed by this work. The effects of varying HfO 2 contents on the oxidation resistance and mechanical properties of the ceramics after oxidation at 1700 °C for 100 min were systematically investigated. The results indicate that, with an appropriate amount of HfO 2 modification, a continuous Zr-Hf-Si-O multiphase glass layer forms in situ during oxidation, significantly suppressing the inward diffusion of oxygen. Compared with the unmodified sample, the ZMGH30 sample exhibits a 23.73% reduction in oxidation weight gain, a 70.38% decrease in average oxidation rate, and an increase in hardness retention to 61.17%. Excessive HfO 2 leads to excessively high viscosity of the glass layer, Hf element agglomeration, and dendritic precipitation, thereby weakening the self-healing ability and deteriorating the oxidation resistance. A new approach for developing ultra-high temperature ceramics that combine excellent oxidation resistance and mechanical reliability is provided by this work.