Mechanical and microwave dielectric properties of KD-I SiCf/SiC composites fabricated through precursor infiltration and pyrolysis

SiC fiber-reinforced SiC matrix (SiCf/SiC) composites, which employ a new type of KD-I SiC fibers (provided by the National University of Defense Technology, China) with in situ pyrocarbon (PyC) coating on the surface of the fibers as reinforcements, are fabricated through precursor infiltration and pyrolysis (PIP). The characteristics of the fiber surface are evaluated by scanning electron microscopy, X-ray photoelectron spectroscopy, Auger electron spectroscopy, and transmission electron microscopy. The mechanical and dielectric properties of KD-I SiCf/SiC composites are reported, and the effects of in situ PyC coating on the material properties are investigated. Results show that the KD-I SiC fiber has a special “skin (PyC phase)-core (SiCO phase)” structure. The composites possess excellent mechanical properties because of the in situ PyC coating on the surface of the fibers. The flexural strength and toughness are 268.8 MPa and 12.9 MPa m1/2, respectively. However, the dielectric constants are also remarkable, which is disadvantageous to microwave absorbing applications.