Effects of pyrolysis processes on the microstructures and mechanical properties of Cf/SiC composites using polycarbosilane

Three-dimensional braided carbon fiber reinforced silicon carbide composites (3D-B C-f/SiC) were prepared through eight cycles of vacuum infiltration of polycarbosilane (PCS) and subsequent pyrolysis under an inert atmosphere. The influences of heating rate and pyrolysis temperature on the microstructure and mechanical properties of Cf/SiC were discussed. lt was found that the heating rate had great effect on the mechanical properties of C-f/SiC composites. With the increase of heating rate, the density of C-f/SiC composites increased and the interfacial bonding was weakened. As a result, the flexural strength of Cr/SiC was enhanced from 145 to 480MPa when the heating rate was increased from 0.5 to 15 degreesC/min. The results showed that the flexural strength of the C-f/SiC composites fabricated at a heating rate of 15 degreesC/min could be increased from 480 to 557 MPa if the pyrolysis temperature of the sixth cycle was elevated from 1200 to 1600degreesC, which was also attributed to the desirable interfacial structure and increased density. When tested at 1300degreesC in vacuum, the C-f/SiC showed higher flexural strength (680 MPa) than that (557 MPa) at room temperature. (C) 2004 Elsevier B.V. All fights reserved.