SiCf/SiC复合材料在NITE过程中的界面结构转化与调控研究

Interphase decides the mechanical behavior of SiCf/SiC composites through crack deflection. However, the interphase suffers structural transformation in high temperature environment, thus degrading its mechanical function. Nano-powder infiltration and transient eutectoid (NITE) is one of the most effective methods to prepare highly thermostable SiCf/SiC. However, the interphase transformation induced by eutectic phase of sintering additives still exists during NITE process. This project aims to the revelation and regulation of the interphase transformation. HT-XRD, Raman-AFM and other high temperature characterization technologies will be utilized to clarify the transformation parameters, reaction and atomic diffusion mechanism. Then the structure-property relationship between interphase transformation and interfacial shear strength, fiber pulling-out will be established to reveal the effecting mechanism of interphase transformation on the mechanical behavior. Furthermore, mitigation of the interphase transformation based on adjustment of eutectic phase composition and interphase surface characteristics (such as crystallinity, oxygen content) will be proposed. This study prospectively provides guidance for interphase design and optimization in SiCf/SiC composites.

界面通过引导裂纹偏转等方式主导SiCf/SiC复合材料的力学行为，然而，界面在高温环境下易发生结构转化，从而弱化其力学调控功能。纳米浸渗瞬态低共熔烧结（NITE）是制备高热稳定SiCf/SiC最有效方法之一，然而依然存在烧结助剂共熔相诱导的界面转化问题。本项目以SiCf/SiC在NITE过程中界面转化和调控为主要研究对象，借助HT-XRD、Raman-AFM等高温表征技术精确解析界面结构转化参数，阐明界面反应机理和原子扩散机制；深入分析界面转化对界面剪切强度、纤维拔出模式等力学性能的影响，建立界面结构转化参数与材料力学性能的构效关系，揭示界面转化对材料力学行为的微观作用机理；梳理NITE关键参数，如共熔相化学组成、界面表面特性（结晶度、氧含量等）对界面转化的影响，总结有效抑制界面转化的NITE参数调控规律，为SiCf/SiC的界面结构设计和优化提供借鉴和指导。

NITE（纳米浸渗瞬态低共熔烧结）是制备高性能SiCf/SiC复合材料的重要方法。然而，在NITE过程中共熔相与界面的相互作用将导致界面结构转化，进而恶化材料力学性能。本项目以SiCf/SiC在NITE过程中的BN界面相结构转化和调控为主要研究对象，执行期间共发表SCI论文7篇，申请发明专利4项，参加国际会议1次，国内会3次。具体研究进展如下：(1) 揭示了NITE温度、压力等参数对SiCf/SiC材料微观结构与性能影响（Journal of Advanced Ceramics, 2020, 9(5): 567-575）；(2) 梳理了BN界面相微观结构特征（结晶度、有序/无序转变）与SiCf/SiC材料拉伸强度、应变、断口形貌的构效关系（Journal of Advanced Ceramics, 2021, 11(1): 94-104); (3) 揭示了氧化物熔体（Na2SO4、钙镁铝硅酸盐CMAS）对BN界面相、SiC纤维和基体结构转化的影响（Journal of the European Ceramic Society, 2022, 43(4): 1366-1375），提出了基体稀土化改性抑制界面相转化的改进策略。