Enhanced mechanical property and tunable dielectric property of SiCf/SiC-SiBCN composites by CVI combined with PIP

The SiBCN matrix via chemical vapor infiltration (CVI) or/and polymer infiltration pyrolysis (PIP) technologies was orderly introduced to SiCf/SiC composites to optimize the mechanical property and electromagnetic (EM) shielding effectiveness simultaneously. The BN interface with the thickness of 350 nm was designed to obtain a little stronger interface bonding. The flexural strength of SiCf/SiC-SiBCN composites reached 545.45 +/- 29.59 MPa thanks to the crack deflection between the CVI SiC and CVI SiBCN, as well as CVI SiBCN and PIP SiBCN matrix because of the modulus difference between them. The fracture toughness (K-IC) with the value of 16.02 +/- 0.94 MPa center dot m(1/2) was obtained owing to the extension of crack propagation path. The adverse effect of stronger interface bonding was eliminated by the design of matrix microstructure for SiCf/SiC-SiBCN composites. The thermal conductivity in the thickness direction was 7.64 W center dot(m center dot K)(-1) at 1200 degrees C and the electric resistivity decreased to 1.53x10(3) omega center dot m. The tunable dielectric property was obtained with the coordination of wave-absorption CVI SiBCN matrix and impedance matching PIP SiBCN matrix, and the total shielding effectiveness (SET) attained 30.01 dB. It indicates that the SiCf/SiC-SiBCN composites have great potential to be applied as structural and functional materials.

Automated summary

The SiBCN matrix, introduced into SiCf/SiC composites through CVI and PIP technologies, optimized mechanical properties and EM shielding effectiveness. The composites demonstrated high strength and thermal conductivity, showing great potential as structural and functional materials.