Mechanical and electromagnetic shielding properties of SiC_f/SiC composites fabricated by combined CVI and PIP process

2.5D KD-I SiC_f/SiC composites were fabricated by combined chemical vapor infiltration (CVI) and precursor infiltration-pyrolysis (PIP) processes for electromagnetic interference (EMI) shielding applications. The effects of PyC interphase and Al₂O₃ filler on mechanical and EMI shielding properties of SiC_f/SiC composites were studied. The PyC interphase effectively improves the accommodation of the fibers and matrix, and Al₂O₃ filler compensates for matrix shrinkage and acts as a strengthening phase to improve the capability of bearing force for the composites. Thus, the composites with PyC interphase and Al₂O ₃ filler possess the maximum flexural strength and fracture toughness with the values of 313 MPa and 12.7 MPa m^1/2. Owing to the existence of excess carbon and PyC interphase, the composites also maintain the highest SE_T and SE_A values of 30 and 20 dB, respectively, indicating its advantages as a kind of structural and functional materials. The superior SE_A value is mainly attributed to the repeated reflection and dissipation of electromagnetic wave between the interfaces of PIP-SiC matrix and Al₂O₃ particles.