In this study, three-dimensional silicon nitride fiber-reinforced silicon nitride matrix (3D Si₃N_4f/BN/Si₃N₄) composites with a boron nitride (BN) interphase were fabricated through chemical vapor infiltration. Through comparing the changes of microstructure, thermal residual stress, interface bonding state, and interface microstructure evolution of composites before and after heat treatment, the evolution of mechanical and dielectric properties of Si₃N_4f/BN/Si₃N₄ composites was analyzed. Flexural strength and fracture toughness of composites acquired the maximum values of 96 ± 5 MPa and 3.8 ± 0.1 MPa·m^1/2, respectively, after heat treatment at 800 °C; however, these values were maintained at 83 ± 6 MPa and 3.1 ± 0.2 MPa·m^1/2 after heat treatment at 1200 °C, respectively. The relatively low mechanical properties are mainly attributed to the strong interface bonding caused by interfacial diffusion of oxygen and subsequent interfacial reaction and generation of turbostratic BN interphase with relatively high fracture energy. Moreover, the Si₃N_4f/BN/Si₃N₄ composites also displayed moderate dielectric constant and dielectric loss fluctuating irregularly around 5.0 and 0.04 before and after heat treatment, respectively. They were mainly determined based on the intrinsic properties of materials system and complex microstructure of composites.

在这项研究中，通过化学气相渗透法制备了具有氮化硼（BN）相的三维氮化硅纤维增强氮化硅基体（3D Si ₃ N _4f / BN / Si ₃ N ₄）复合材料。通过比较热处理前后复合材料的微观结构，热残余应力，界面结合状态和界面微观结构的变化，分析了Si ₃ N _4f / BN / Si ₃ N ₄复合材料的力学性能和介电性能的变化。复合材料的弯曲强度和断裂韧性的最大值为96±5 MPa和3.8±0.1 MPa·m ^1/2分别在800°C热处理后；然而，在1200℃下进行热处理后，这些值分别保持在83±6MPa和3.1±0.2MPa·m ^1/2。较低的机械性能主要归因于氧的界面扩散和随后的界面反应以及具有相对较高的断裂能的涡轮层BN相的产生而导致的牢固的界面键合。此外，Si ₃ N _4f / BN / Si ₃ N ₄复合材料还显示出适度的介电常数，介电损耗在热处理前后分别在5.0和0.04左右不规则波动。它们主要是根据材料系统的固有性质和复合材料的复杂微观结构确定的。