A novel low-temperature strategy for Csf/(Hf, Ta)B2-(Hf, Ta)C-SiC composites via fast reactive hot-press sintering: insights into microstructure and mechanical behavior

It is crucial to address the challenges for low-temperature densification and interfacial reactions during the fabrication of multi-element ultra-high temperature ceramic matrix composites. In this paper, C sf /(Hf, Ta)B 2 -(Hf, Ta)C-SiC composites were prepared via reactive hot-press sintering at low temperatures. The intrinsic connection between the fiber content, microstructure, and mechanical behavior of the composites was elucidated. The results indicated that the ultrasonic dispersion combining with fast hot-press sintering effectively promoted the uniform dispersion of C sf in the matrix and achieved densification at 1700 °C. The composites exhibited an undamaged fiber-matrix interface without observable interfacial phase, demonstrating that low-temperature preparation effectively prevented fiber degradation from interfacial reactions. Compared to the unreinforced ceramics, the composites showed decreased flexural strength and fracture toughness, yet possessed higher work of fracture and larger critical crack size. This indicated that fiber addition improved the damage tolerance and structural reliability by inhibiting the catastrophic brittle fracture behavior inherent to monolithic ceramics. The composite with 20 vol% C sf offered the best balance of strength, toughness and non-catastrophic failure behavior. The flexural strength and fracture toughness were 260.6 MPa and 4.82 MPa m 1/2 , respectively. Download: Download high-res image (531KB) Download: Download full-size image