In reactive-hot-pressed ZrB₂–SiC–ZrC ceramics, ZrO₂ was found to replace ZrC phase, hence leading to confusion in designing ultra-high-temperature ceramics (UHTCs). We employ high-precision X-ray diffraction and electron microscopies to reassess the phase behavior during entire reaction and densification and to reveal the evolution of multiphase relationship at different stages before reaching the final ZrB₂–SiC–ZrO₂ composition. Frozen from transient liquid-phase, bulk glassy phase of 15 vol% was found to be constituted of Zr–Si–B–C–O with stable Zr:O ratio, which starts as early as in the intermediate stage to suppress ZrC in favor of SiC nucleation. Inhomogeneity in phase relations and microstructures results from variation in local transient liquid-phase to develop SiC phase in various modes and rates. As inferred from the earlier report of phase formation, competing reactions for ZrC and ZrB₂ phases in the initial stage below 1000 °C were mediated via Zr–O–B–C liquid phase. Such liquid phase was moderated by stable B–O components, as initiated from surface oxides of starting powders. This picture under a continuous mother liquid phase can unify the reactions and sintering into a collective melting–nucleation–growth process, which enables and guides the evolution of multiphase relationship through several stages to reach final densification at relatively low temperature with the help of residual oxides.

在反应热压ZrB ₂ -SiC-ZrC陶瓷中，发现ZrO ₂代替ZrC相，因此导致在设计超高温陶瓷（UHTC）时出现混乱。我们使用高精度的X射线衍射和电子显微镜重新评估整个反应和致密化过程中的相行为，并揭示在达到最终ZrB ₂ -SiC-ZrO ₂之前不同阶段的多相关系的演变。组成。从瞬态液相中冻结，发现体积分数为15％的整体玻璃态相由Zr：O比率稳定的Zr–Si–B–C–O组成，该过程最早在中间阶段开始，以抑制ZrC SiC成核。相关系和微观结构的不均匀性是由于局部瞬态液相的变化导致以各种模式和速率形成SiC相所致。从早期的相形成报告可以推断，ZrC和ZrB _2的竞争反应低于1000°C的初始相通过Zr–O–BC–C液相介导。这种液相是由稳定的B–O成分缓和的，这是由起始粉末的表面氧化物引发的。连续母液相下的这张图可以统一反应并烧结成一个集体的熔融-成核-生长过程，该过程可以并指导多相关系的演变经历多个阶段，并借助残余氧化物在相对较低的温度下达到最终致密化。