Electromagnetic wave absorption and mechanical properties of silicon carbide fibers reinforced silicon nitride matrix composites |
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Authors: | Ran Mo Xiaowei Yin Fang Ye Xiaofei Liu Xiaokang Ma Quan Li Litong Zhang Laifei Cheng |
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Affiliation: | Science and Technology on Thermostructural Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an, Shaanxi, 710072, PR China |
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Abstract: | It is difficult for ceramic matrix composites to combine good electromagnetic wave (EMW) absorption properties (reflection coefficient, RC less than -7 dB in X band) and good mechanical properties (flexural strength more than 300 MPa and fracture toughness more than 10 M P·m1/2). To solve this problem, two kinds of wave-absorbing SiC fibers reinforced Si3N4 matrix composites (SiCf/Si3N4) were designed and fabricated via chemical vapor infiltration technique. Effects of conductivity on EM wave absorbing properties and fiber/matrix bonding strength on mechanical properties were studied. The SiCf/Si3N4 composite, having a relatively low conductivity (its conduction loss is about 33% of the total dielectric loss) has good EMW absorption properties, i.e. a relative complex permittivity of about 9.2-j6.4 at 10 GHz and an RC lower than ?7.2 dB in the whole X band. Its low relative complex permittivity matches impedances between composites and air better, and its strong polarization relaxation loss ability help it to absorb more EM wave energy. Moreover, with a suitably strong fiber/matrix bonding strength, the composite can transfer load more effectively from matrix to fibers, resulting in a higher flexural strength (380 MPa) and fracture toughness (12.9 MPa?m1/2). |
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Keywords: | Corresponding author Electromagnetic absorption properties Mechanical properties Ceramic matrix composites |
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