弥散分布TiB晶须对Cf/SiC复合材料强韧性和抗氧化性能的影响机制

The oxidation resistance of carbon fiber reinforced SiC ceramic matrix composites (Cf/SiC) at middle temperature range can be improved through B-bearing matrix modification. However, the traditional B-bearing matrix modification leads to the degraded mechanical properties of Cf/SiC composites, which restricts its lifetime when applying in the stress-oxidation environment. In order to resolve this problem, this project proposes the idea of in-situ fabricating new dispersed TiB whisker (TiBw) in Cf/SiC composites by polymer impregnation pyrolysis joint with liquid silicon infiltration. The matrix-micro-crack self-healing behavior, strengthening and toughening mechanism of TiBw would be used to synergistically improve the middle-temperature-range oxidation resistance and mechanical properties of Cf/SiC composites. Through the systematic study of the controllable microstructure fabrication process of TiBw modified Cf/SiC composites, the relationship between the microstructure characters including morphology, phase composition and the process parameters including pyrolysis temperature, liquid silicon infiltration temperature of TiBw modified Cf/SiC composites will be established. The phase produce/develop mechanism of TiBw will be explored, the general law of influence of the content and microstructure characters of TiBw on mechanical property and matrix micro-crack self-healing behavior of Cf/SiC composites will be clarified, and the strengthening, toughening and oxidation resistance mechanism of TiBw modified Cf/SiC composites will be revealed. The accomplishment of this project will lay a foundation for the research and development of Cf/SiC composites with high properties, and also enrich the design concept of structure and function integration through multi-scale modification.

通过含硼基体改性可显著提高碳纤维增韧碳化硅陶瓷基复合材料（Cf/SiC）的中温抗氧化性能，同时却导致Cf/SiC的力学性能降低，限制了其在应力氧化环境中的服役寿命。为此，本项目采用聚合物浸渍裂解结合液硅渗透工艺在Cf/SiC内部原位生成新型弥散分布TiB晶须（TiBw），基于TiBw的微裂纹自愈合行为和强韧化效应，协同提高Cf/SiC的中温抗氧化性能和力学性能。通过系统研究TiBw改性Cf/SiC的微结构可控制备过程，建立TiBw的形貌、相成分等微结构特征与裂解温度、渗硅温度等参数之间的映射关系，探索TiBw在Cf/SiC内部的生成/生长机理，阐明TiBw的含量和微结构特征对Cf/SiC力学性能和微裂纹自愈合行为的影响规律，揭示TiBw改性Cf/SiC的强韧化机制和抗氧化机理。项目的完成将为高性能Cf/SiC的研发奠定基础，同时丰富和发展多尺度改性Cf/SiC的结构功能一体化设计。

本项目以“传统含硼基体改性无法满足Cf/SiC复合材料中温抗氧化性能和力学性能协同提高的需求”为基础科学问题，提出采用催化剂辅助聚合物浸渍裂解工艺在多孔Cf/SiC复合材料内部原位生成弥散分布TiB2w并借助液硅渗透工艺，制备致密TiB2w改性Cf/SiC复合材料。研究了TiB2w改性Cf/SiC复合材料的微结构和力学性能，分析了前驱体溶液浓度、催化剂含量和Ti/B含量比等不同工艺条件参数对多孔Cf/SiC复合材料内部生长TiB2w的形貌的影响规律，掌握了TiB2w改性Cf/SiC复合材料微结构可控的稳定可重复制备技术，同时阐明TiB2w在Cf/SiC复合材料内部的生成/生长机理。通过表征对TiB2w改性Cf/SiC复合材料的力学性能，获得TiB2w改性Cf/SiC复合材料在不同载荷作用下的失效模式，揭示TiB2w对Cf/SiC复合材料的强韧化机制。