B-Zr-Si杂原子掺杂煤沥青制备复相陶瓷改性C/C复合材料及其抗氧化、抗烧蚀机理

In order to overcome the shortcoming of surface coating and matrix modification for C/C composites in improving the oxidation resistance at high temperature, co-pyrolysis of mixtures of a coal tar pitch and heteroatom precursors is presented in this project to introduce the B、Zr and Si heteroatoms with good oxidation resistance into the pitch. Using the coal tar pitch doped with B、Zr and Si heteroatoms as an impregnant or a binder, C/C and high conductivity C/C composites modified by ZrB2-ZrC-SiC nano-ceramics are fabricated by manifold cycles of infiltration and carbonization or one-step hot pressing followed with carbonization process. The effect of co-pyrolysis process conditions on the composition, micro-structure and properties of the pitch doped with B-Zr-Si heteroatoms will be studied, and as a result the relationship of composition, micro-structure and properties of the doped pitch will be built. The transformation process of B、Zr and Si heteroatoms in the pitch during co-pyrolysis will be also revealed. On the basis of above work, the influence of cabonization process conditions on the composition and micro-structure of C/C and high conductivity C/C comosites modified by ZrB2-ZrC-SiC nano-ceramics will be further studied, and the composition and micro-structure will be correlated with the mechanical properties, thermo-physical properties, oxidation and ablation resistance to clarify the oxidation and ablation resistance mechanism of the C/C and high conductivity C/C. The above research works in this project will helpful in terms of laying a solid foundation for the developing of high performance C/C composites, which exhibit long term oxidation resistance in a wild temperature range (600-1800 C) and short term protection above 1800 C. Profound theory and technology will also be provided as the outcome of this project to meet the impendence requirements for the high performance C/C composites in the aerospace field.

本项目针对表面涂层和基体改性技术在提高C/C复合材料抗氧化性上存在的问题，从制备炭材料的基本原料沥青入手，采用共裂解技术将B、Zr、Si等具有抗氧化性的杂原子引入沥青。以掺杂沥青作为浸渍剂或黏结剂，采用浸渍-炭化循环工艺或一次热压成型-炭化工艺制备ZrB2-ZrC-SiC复相陶瓷改性C/C和高导热C/C复合材料。研究共裂解工艺对沥青组成、微结构和性能的影响，建立它们的关联关系，揭示B、Zr、Si等杂原子的演变行为。在此基础上，进一步研究炭化工艺对ZrB2-ZrC-SiC改性C/C和高导热C/C复合材料组成和微结构的影响，将材料组成和微结构与其力学、热物理性能以及抗氧化、抗烧蚀性能相关联，阐明材料抗氧化抗烧蚀机理，为制备宽温域（600-1800 C）长时抗氧化以及高于1800 C短期防护的高性能C/C复合材料打下基础，同时为我国航空航天领域对高性能C/C复合材料的迫切需求提供理论和技术支持。

世界国防科技的发展对抗氧化抗烧蚀C/C复合材料提出了苛刻要求，高性能航空发动机热端部件需要全温域长寿命、抗氧化、抗冲刷、抗疲劳振动；高超声速飞行器热防护系统在服役过程中要承受严重的烧蚀、高质流强冲刷和大梯度热冲击。要在如此严酷的环境下正常使用，就必须解决C/C复合材料的高温氧化烧蚀问题。目前陶瓷改性C/C复合材料在1500℃以下的抗氧化问题已基本得到解决，1500-1800℃的短期防护也已取得突破，但在此温度范围内的长期抗氧化以及高于1800℃的短期防护仍然没有取得较大进展。. 在此背景下，本项目采用共裂解技术将B、Zr、Si等具有抗氧化性的杂原子引入其中，对沥青进行掺杂改性。在此基础上，以掺杂沥青作为浸渍剂，对炭纤维预制体进行多次浸渍和热解，通过原位反应在沥青炭基体中引入均匀弥散的超高温陶瓷相，成功制备了ZrB2-ZrC-SiC复相陶瓷改性C/C复合材料。系统研究了共裂解工艺条件对B-Zr-Si掺杂沥青组成、光学结构和性质的影响，揭示了共裂解过程中B、Zr、Si等杂原子的演变行为，优化了共裂解过程参数。在此基础上，进一步研究了高温热处理工艺条件对ZrB2-ZrC-SiC复相陶瓷改性C/C和改性高导热C/C复合材料组成和微观结构的影响，建立了材料组成和微结构与其在不同温度范围的抗氧化、抗烧蚀性的对应关系，阐明了ZrB2-ZrC-SiC纳米复相陶瓷改性C/C复合材料的协同抗氧化、抗烧蚀作用机理。. 本项目的研究成果为制备宽温域（600-1800℃）长时抗氧化以及高于1800℃短期防护的高性能C/C复合材料打下了坚实的基础，同时为我国航空航天领域对高性能C/C复合材料的迫切需求提供了深刻的理论和技术支持。