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

Abstract

AbstractSilicon carbide nanofiber/silicon carbide (SiCnf/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. SiCnf paper was fabricated using nanofibers and impregnated with the slurry of SiCnp and sintering aids, and the SiCnf/SiC preforms were fabricated by the alternating stack of the SiCnf paper and SiCnp. The pyrolysis carbon and boron nitride interface layers were deposited on the surface of SiCnf 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 SiCnf/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·m1/2, respectively. The liquid phase Al8B4C7 compound generated at the high temperature promoted the densification of the composites.