高效熔渗反应制备多级增强Cf/ZrB2-ZrC-SiC超高温陶瓷基复合材料

Highly dense Cf/ZrB2-ZrC-SiC ultra-high temperature ceramic matrix composites possess excellent ultra-high temperature performance, and are regarded as key candidate materials for thermal protective system associated with hypersonic flight and scramjet engine. Reactive melt infiltration (RMI) is an important method in fabrication of highly dense Cf/ZrB2-ZrC-SiC composites. However, composites fabricated by RMI method may have disadvantages of metal residual and local brittleness in ceramic matrix, leading to poor mechanical properties and low reliability at elevated temperatures. Accordingly, this project proposes to firstly construct a nano-porous Cf/B4C-C preform via a sol-gel method, so as to promote the reactive infiltration kinetics of Si-Zr melt into nano-porous Cf/B4C-C preform. As a result, Cf/ZrB2-ZrC-SiC composites with high densification and no/low Si, Zr residual can be obtained. On the other hand, anisotropic grain growth of ZrB2 rods/plates structure will be promoted in Cf/ZrB2-ZrC-SiC composites by addition of trace aids and proper heat treatment. With ZrB2 rods/plates as reinforcements for matrix at micro scale, it is expected that a multi-scale co-reinforcing microstructure by carbon fibers and ZrB2 rods/plates can be achieved. The internal relationships among the fabrication procedure, chemical composition, microstructure and properties of the materials will be intensively studied, the underlying mechanisms will be revealed. This research may have profound influence on the future advancement in design and fabrication technique, properties improvement of ultra-high temperature ceramic matrix composites.

高致密Cf/ZrB2-ZrC-SiC超高温陶瓷基复合材料具有优异的耐超高温性能，使其成为高超声速飞行器及新一代超燃冲压发动机防热部件的重要候选材料。反应熔渗是快速制备高致密Cf/ZrB2-ZrC-SiC的重要方法，但材料容易存在金属残留及陶瓷基体局部脆性的问题，影响材料的高温力学性能及可靠性。为此，本项目提出采用溶胶凝胶方法构建纳米多孔Cf/B4C-C预成型体结构，促进熔渗硅锆原位反应动力学，实现无/低硅锆残留Cf/ZrB2-ZrC-SiC材料的高效致密化；以及通过微量助剂的添加及合理的熔渗工艺参数促进ZrB2棒晶/片晶结构的原位生长，对陶瓷基体进行微区强韧化，实现纤维和ZrB2棒晶/片晶对陶瓷基体的多级协同增强。系统研究材料的制备工艺、组成、显微结构和性能之间的内在关系，并揭示其相关机理。本项目的成功实施将对超高温陶瓷基复合材料制备技术的进步和综合性能水平的提升及其应用带来积极影响。

反应熔渗是制备高致密超高温陶瓷基复合材料的重要方法，但材料容易存在金属残留及陶瓷基体局部脆性的问题，影响材料高温力学性能及可靠性。针对这一问题，本项目提出采用溶胶凝胶方法构建纳米多孔预成型体结构，促进熔渗原位反应动力学过程，实现了无/低硅锆残留Cf/ZrB2-ZrC-SiC材料的高效致密化；另一方面，通过设置合理的熔渗工艺参数促进ZrB2棒晶/片晶结构原位生长，对陶瓷基体进行微区强韧化，实现了纤维和ZrB2棒晶/片晶对陶瓷基体的多级协同增强。项目揭示了预成型体孔隙结构对反应熔渗超高温陶瓷基复合材料基体分布、界面损伤及材料性能的影响规律；发现反应熔渗超高温陶瓷基复合材料损伤界面处锆元素聚集现象，并提出反应-类熔融界面损伤机制；揭示了Cf/ZrB2-ZrC-SiC超高温陶瓷基复合材料ZrO2类液相烧结抗高温烧蚀机制。本研究成功实现了高性能超高温陶瓷基复合材料的反应熔渗制备，相关材料有望在新型高速飞行器和冲压发动机热结构上获得应用。