In this study, 2.5D carbon fiber reinforced pyrocarbon matrix composites with a BN interphase (C_f/BN/PyC) were prepared by chemical vapor infiltration. Through comparing the distribution of thermal residual stress and the evolution of the interface microstructure of composite before and after heat treatment, the reason why the structure and orientation of the BN interphase in the C_f/BN/PyC composite deviate from the layered structure required for the expected compliant interface was analyzed. The results show that the crystalline skin of C_f affects the order of BN near the C_f/BN interface, thereby forming BN interphase with a structural gradient from the beginning. The infiltration process of pyrocarbon interacts with the growth and rearrangement process of BN, resulting in incomplete crystallization of BN. After heat treatment at 1600°C, BN interphase with high crystallinity in the nano-domain but disordered orientation is formed, although it can also debond the interface according to He and Hutchinson's model. The BN grain orientation deviates from the fiber axis mainly due to multi-factor coupling, in which the axial residual thermal stress generated at the C_f/BN/PyC interface is the main influencing factor. Understanding the influence of the heat treatment (HT) on the atomic-domain orientation change and structural evolution during the preparation of boron nitride (BN) interphase by chemical vapor infiltration paves us an effective way to modify the preparation of interphase with low fracture energy.

在这项研究中，通过化学气相渗透法制备了具有BN相间（C _f / BN / PyC）的2.5D碳纤维增强焦炭基复合材料。通过比较热处理前后热残余应力的分布和复合材料界面微观结构的演变，发现C _f / BN / PyC复合材料中BN相的结构和取向偏离了所需的层状结构的原因。分析了预期的合规界面。结果表明，C _f的结晶皮影响了C _f附近BN的顺序。/ BN界面，从而从一开始就形成具有结构梯度的BN相。热解碳的渗透过程与BN的生长和重排过程相互作用，导致BN结晶不完全。经过1600°C的热处理后，虽然可以根据He和Hutchinson的模型将界面剥离，但BN界面在纳米域具有高结晶度，但取向混乱。BN晶粒取向偏离纤维轴主要是由于多因素耦合，其中在C _f处产生的轴向残余热应力/ BN / PyC接口是主要影响因素。了解热处理（HT）对化学气相渗透制备氮化硼（BN）相的过程中原子域取向变化和结构演变的影响，为我们提供了一种有效的方法，以低断裂能来改进相制备。