Abstract
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 (KIC) with the value of 16.02±0.94 MPa·m1/2 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·(m·K)−1 at 1200 °C and the electric resistivity decreased to 1.53×103 Ω·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.
Highlights
SiC fiber (SiCf)/SiC composites have been widely investigated as a significant thermo-structural material in aero-engine and fusion reactor structural application because of theJ Adv Ceram 2021, 10(4): 758–767SiCf/SiC–SiBC composites exhibited outstanding mechanical property after exposing in air for 100 h at 800–1200 °C [4]
The porous polymer infiltration pyrolysis (PIP) SiBCN with some microcracks (the orange arrow shown in Fig. 1(b)) and pores (the orange circle shown in Fig. 1(b)) was introduced into SiCf preform (Figs. 1(b) and 1(c))
When the SiCf/SiC–SiBCN composites are loaded at high temperatures and oxidizing atmorsphere, the outer SiBCN matrix would be firstly oxidized with massive volume expansion and the borosilicate or SiO2 glass generates according to previous studies [15,16,21]
Summary
SiCf/SiC–SiBC composites exhibited outstanding mechanical property after exposing in air for 100 h at 800–1200 °C [4]. 1200 °C, the self-healing ability of SiBC is insufficient because of its poor thermal stability and the sealing rate [5]. SiBCN ceramic has low density (1.8 g/cm3), small thermal expansion coefficient, good oxidation resistance (suitable for applying in air up to 1500 °C), high temperature resistance (suitable for applying in inert environment up to 1800 °C) [6], and outstanding creep resistance property [7], which has attracted extensive attention. The self-healing performance can be obtained via viscous flow of borosilicate glass or SiO2, and the service life of SiBCN matrix modified SiCf/SiC composites can be prolonged [16]. The SiCf/SiC–SiBCN composites are expected to be used in structural and functional integration area
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