碳化硅/二硼化锆超高温陶瓷抗氧化特性建模

Modeling of oxidation resistance characteristics of silicon carbide/zirconium diboride ultra-high temperature ceramics

  • 摘要: 高速飞行器尖锐部件在极端热环境下常采用碳化硅/二硼化锆(SiC-ZrB2)超高温陶瓷实现维形需求,其核心在于高温氧化形成的致密固-液混合氧化膜(孔隙填充玻璃态硼硅酸盐)可有效阻氧扩散,实现整体上的零/微烧蚀。基于多孔氧化物中氧气扩散机制与热化学平衡原理,提出了SiC耗尽层存在判据,建立了含/无耗尽层的双模型体系:对于含耗尽层工况,通过耦合CO/CO2对流扩散传输、ZrO2固态层生长、B2O3-SiO2玻璃层蒸发/生长竞争机制,量化原始材料后退量与增重;对于无耗尽层工况,推导基材等界面后退方程及临界组分条件。通过计算明确SiC体积分数20%~30%时氧化产物致密度最高,抗氧化性能最优。在147315731773 K静态空气环境中开展模型验证,计算得到的氧化增重曲线与试验数据吻合良好,证明模型可较为精准模拟SiC含量变化对氧化行为的影响规律。该模型能有效模拟SiC-ZrB2陶瓷的氧化行为,为材料优化设计提供重要的抗氧化性能评估依据。

     

    Abstract: Silicon carbide/zirconium diboride (SiC-ZrB2) ultra-high temperature ceramics (UHTCs) are commonly employed for sharp components of hypersonic vehicles under extreme thermal environments to maintain geometric configuration. The key mechanism lies in the formation of a dense solid-liquid mixed oxide scale (with pores filled by borosilicate glass) during high-temperature oxidation, which effectively impedes oxygen diffusion and achieves near-zero/minimal ablation. Based on oxygen diffusion mechanisms in porous oxides and thermochemical equilibrium principles, a criterion for SiC depletion layer formation was proposed, establishing a dual-model system accounting for both presence and absence of depletion layers. For cases with depletion layers, the model couples CO/CO2 convective diffusion, ZrO2 solid layer growth, and the competitive mechanisms of B2O3-SiO2 glass layer evaporation/growth to quantify virgin material recession and weight gain. For cases without depletion layers, recession equations for substrate interfaces and critical composition conditions were derived. Numerical calculations identified that optimal oxidation resistance occurs at 20—30 vol% SiC content, where oxide products exhibit maximum density. Model validation conducted in static air environments at 1473, 1573, and 1773 K demonstrated good agreement between calculated oxidation weight gain curves and experimental data, confirming the model's capability to accurately simulate the influence of SiC content variations on oxidation behavior. This model effectively simulates the oxidation behavior of SiC-ZrB2 ceramics and provides critical evaluation criteria for oxidation resistance in material optimization design.

     

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