Preparation and characterization of SiC/C and C/SiC/C composites using pulse chemical vapor infiltration process

A porous carbon plate and carbon fiber/carbon composite (C/C) preforms were infiltrated with SiC using a pulse chemical vapor infiltration (Pulse-CVI) process, and the Pulse-CVI conditions for obtaining the densely infiltrated SiC/C or C/SiC/C composites were examined. The optimum reaction temperatures, at which the pores were uniformly filled with SiC deposits throughout the thickness, were 1173 K for the carbon plates with a small pore size, 1373 K for those with a large pore size and 1173 K for the C/C preforms. The filling ratio of the pores with SiC increased monotonically with increasing number of pulse cycles. The mechanical properties of the infiltrated composites after each optimum Pulse-CVI condition were evaluated. The bending strength also increased with increasing number of pulse cycles and attained 110 MPa after 16 000 pulse cycles for 0.7 mm thick carbon plates with a small pore size and 80 MPa after 30 000 cycles for the 2.0 mm thick plates. The inter-laminar shear strength (ILSS) of the infiltrated C/C composite with SiC after 50 000 pulse cycles was 18 MPa; this value was about three times igher than that of the original preforms.