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

2.5D KD-I SiCf/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 SiCf/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 Al2O3 filler possess the maximum flexural strength and fracture toughness with the values of 313 MPa and 12.7 MPa m1/2. Owing to the existence of excess carbon and PyC interphase, the composites also maintain the highest SET and SEA values of 30 and 20 dB, respectively, indicating its advantages as a kind of structural and functional materials. The superior SEA value is mainly attributed to the repeated reflection and dissipation of electromagnetic wave between the interfaces of PIP-SiC matrix and Al2O3 particles.