Comparison of High-temperature Dielectric and Microwave Absorbing Property of Two Continuous SiC Fibers

doi:10.15541/jim20170220

Abstract

Abstract:

Two kinds of SiC fibers with different microstructures were analyzed by XPS, XRD and Raman spectra. The electrical conductivities of the fibers were measured, and their dielectric and microwave absorbing properties at elevated temperatures were investigated. Research results show that KD-I SiC fiber with rich carbon layers possess higher complex permittivities and electrical conductivities than do SLF SiC fiber with Si-C-O phase, resulting in poor impedance match between free space and KD-I fibers. Simultaneously, due to poor dielectric loss of SLF fiber, two fibers display inferior absorbing performance with the reflection loss values of -3.2 dB and -0.3 dB at X band, respectively. With temperatures increasing, ε° and ε? of KD-I fiber sharply increase, while the complex permittivity of SLF fiber display a small increment. Complex permittivities of two fibers are up to 20.9-j25.0 and 5.0-j0.37 at 700℃. Microwave absorbing properties of two fibers degrade at elevated temperatures, mainly ascribed to deterioration of impedance match.

Key words: SiC fibers, microstructure, electrical conductivity, high-temperature dielectric property, high- temperature microwave absorbing property

CLC Number:

TB34

MU Yang, DENG Jia-Xin, LI Hao, ZHOU Wan-Cheng. Comparison of High-temperature Dielectric and Microwave Absorbing Property of Two Continuous SiC Fibers[J]. Journal of Inorganic Materials, 2018, 33(4): 427-433.

Figures/Tables 11

Table 1 Properties of KD-I and SLF SiC fibers

Type	Diameter/ μm	Density/ (g·cm^-3)	Tensile strength/GPa	Young’s modulus/GPa
KD-I	14-16	~2.54	1.8-2.2	150-200
SLF	12-15	2.3-2.5	2.2-2.4	185

Fig. 1 Surface SEM images of (a) KD-I SiC fiber, (b) SLF SiC fiber, and (c) the correspoding EDS analysis

Fig. 2 (a) XPS survey spectra of KD-I SiC and SLF SiC fibers; (b) Si2p spectra of SLF SiC fiber

Fig. 3 (a) XRD patterns and (b) Raman spectra of KD-I SiC and SLF SiC fibers

Fig. 4 Electrical conductivities of KD-I SiC and SLF SiC fibers

Fig. 5 (a) Complex permittivity and (b) loss tangent of SiC fiber

Fig. 6 (a) Calculated reflection loss and (b) input impedance of KD-I SiC and SLF SiC preforms with the thickness of 3.0 mm

Fig. 7 Fracture surface morphologies of SiCf/SiO2 composites (a) and (b) KD-I SiCf/SiO2; (c) and (d) SLF SiCf/SiO2

Fig. 8 Complex permittivity of KD-I SiC fibers at various temperatures(a) Real part; (b) Imaginary part

Fig. 9 Complex permittivity of SLF SiC fibers at various temperatures(a) Real part; (b) Imaginary part

Fig. 10 (a) Reflection loss, (b) loss tangent and (c) input impedance vs. frequency of KD-I SiC and SLF SiC preforms with the thickness of 3.0 mm at various temperatures

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