Mechanical and broadband absorption properties of Nextel 610/SiOC composites synergistically enhanced by the interfacial structure design

In this work, BN interphase and Si₃N₄ matrix were prepared by chemical vapor infiltration (CVI) to optimize the mechanical properties of N610/SiOC composites, and the strengthening and toughening mechanisms were investigated. The results showed that the content and distribution of Si₃N₄ matrix and the thickness of BN interphase could tailor the strength and toughness of composites simultaneously. The optimal tensile strength of 234 MPa and flexural strength of 338 MPa were obtained by Si₃N₄ reinforced N610/SiOC composites with a BN interphase thickness of 540 nm, respectively. Meanwhile, free carbon modified BN interphase (BN(C)) and multi-layer “mortise and tenon” joint were designed to optimize the broadband EMW absorption. The impedance-matching “mortise and tenon” joint achieved a wide effective absorption bandwidth (EAB) of 8.4 GHz and a minimum reflection loss (RL_min) of −52.55 dB. This work inspires designing and fabricating CMC with both good mechanical and broadband EMW absorption properties.