Slurry-impregnating hot-press sintered silicon carbide nanofiber/silicon carbide composites with Al-B-C as sintering additives

Silicon carbide nanofiber/silicon carbide (SiC_nf/SiC) composites with a laminar stacking structure were prepared by the slurry impregnation hot-press sintering using aluminum (Al) powder, boron (B) powder, and carbon black as sintering aids. SiC_nf paper was fabricated using nanofibers and impregnated with the slurry of SiC_np and sintering aids, and the SiC_nf/SiC preforms were fabricated by the alternating stack of the SiC_nf paper and SiC_np. The pyrolysis carbon and boron nitride interface layers were deposited on the surface of SiC_nf by chemical vapor deposition and vacuum impregnation-pyrolysis methods. The effects of different sintering temperatures on the relative density, porosity, sectional microscopic morphology, and mechanical properties of the composites were investigated. The results show that the fracture toughness of SiC_nf/SiC composites is significantly improved. The mechanical properties of the composites were optimized at a sintering temperature of 1950°C and a sintering pressure of 30 MPa, with flexural strength and fracture toughness of 548 MPa and 15.86 MPa·m^1/2, respectively. The liquid phase Al₈B₄C₇ compound generated at the high temperature promoted the densification of the composites.