Fabrication of SiCf/SiC composites by chemical vapor infiltration and vapor silicon infiltration

Three-dimensional (3D) silicon carbide fiber reinforced silicon carbide matrix (SiCf/SiC) composites, employing KD-1 SiC fibers (from National University of Defense Technology, China) as reinforcements, were fabricated by a combining chemical vapor infiltration (CVI) and vapor silicon infiltration (VSI) process. The microstructure and properties of the as prepared SiCf/SiC composites were studied. The results show that the density and open porosity of the as prepared SiCf/SiC composites are 2.1g/cm3 and 7.7%, respectively. The SiC fibers are not severely damaged during the VSI process. And the SiC fibers adhere to the matrix with a weak interface, therefore the SiCf/SiC composites exhibit non-catastrophic failure behavior with the flexural strength of 270MPa, fracture toughness of 11.4MPaA.m1/2 and shear strength of 25.7MPa at ambient conditions. Moreover, the flexural strength decreases sharply at the temperature higher than 1200A degree C. In addition, the thermal conductivity is 10.6W/mk at room temperature.