Effect of carbon content on mechanical properties of SiCnf/SiC composites prepared by PIP-RMI

BN-coated SiC nanofibers（SiCnf） reinforced SiC composites were prepared by precursor impregnation pyrolysis（PIP）process combined with reactive melting infiltration（RMI）process. Firstly，the h-BN interface was prepared on the surface of SiCnf using BCl3 and NH3 as raw materials by chemical vapor deposition（CVD）process. Then，the porous SiCnf/SiC ceramics were prepared by PIP process using polycarbosilane as precursor. The porous ceramics were impregnated with phenolic resin，and the filled carbon was obtained by the pyrolysis of phenolic resin. Finally，the composites were densified by RMI process at 1500 ℃ for 2 hours. The effect of deposition temperature on the microstructure of h-BN and the effect of carbon content on the mechanical properties of the composites were investigated. The samples were characterized by X-ray diffractometer，Fourier transform infrared spectrometer，field emission scanning electron microscopy and universal testing machine. The results show that h-BN can be prepared at 750，850 ℃ and 950 ℃. With the increase of temperature，the h-BN interface becomes smooth and compact. The mechanical properties of SiCnf/SiC composites are improved with the increase of carbon content，the flexural strength and fracture toughness reach the maximum values of 207 MPa and 8.63 MPa·m1/2 respectively as the carbon content is 19.24%.