Optimization of interfacial zone microstructure of SiC_f/Si₃N₄ composites containing in-situ formed BN coating

SiC_f/Si₃N₄ composite is a promising structural wave-absorbing integrated composites, while the interphase damage caused by thermal expansion mismatch degrades its mechanical properties. By employing iBN-coated SiC fibers, a higher interfacial bonding strength between the fibers and the interphase can be achieved, thereby reducing the interphase damage in the composite. In this work, BN interphase with different thickness was deposited on the surface of iBN-coated SiC fibers. After the formation of multilayer BN interphase, the interfacial damage ratio decreased from 19 % to 3 %, and thus the tensile strength of the composites increased from 161 ± 10–196 ± 31 MPa. At the same time, with the change of intra-bundle fiber contact state, the minimum reflection coefficient of the composites decreased from −4.46 to −12.32 dB, resulting from the increase of the conduction loss.