Effects of preform structure on microstructure and mechanical properties of C/SiC composites reinforced by Si₃N₄ nanowires

Three kinds of preforms containing Si₃N₄ nanowires were densified using chemical vapor infiltration (CVI) to form two-dimensional C/SiC composites. Effects of preform structure on microstructural and mechanical behaviors of composites were evaluated. Compared to C/SiC composite without nanowires, C/SiC composite with gradient distribution of Si₃N₄ nanowires (C/SiC-NW-G) had a 19% increase in density (2.35 g/cm³) and a 51% decrease in porosity (7%). Introducing gradient-distributed Si₃N₄ nanowires suppressed the formation of large closed pores during densification, which resulted in improved microstructure of C/SiC-NW-G. With an increase in the density and a decrease in the porosity, C/SiC-NW-G composites have tensile strength of 280 ± 22 MPa and flexural strength of 462 ± 31 MPa, which were improvements of 11% and 12%, respectively, compared to C/SiC without Si₃N₄ nanowires.