1. Improved microwave absorption properties of polycarbosilane-derived SiC core-shell particles by oxidation.
- Author
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Wang, Yichen, Li, Yang, Luo, Heng, Li, Zhichao, Li, Zhuan, Zhou, Wei, and Xiao, Peng
- Subjects
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OXIDATION , *MICROWAVES , *MICROWAVE materials , *IMPEDANCE matching , *ABSORPTION , *NANOCRYSTALS - Abstract
Abstract Polycarbosilane-derived SiC (PCS-derived SiC) has been suggested as a promising candidate for particularly effective microwave absorption materials. To optimize the microwave absorption properties, while retaining the crystallinity of SiC, PCS-derived SiC ceramics were prepared by a combination of dehydrogenation, appropriate oxidation, and pyrolysis. This study investigated microstructures, dielectric properties, and microwave absorption properties of as-prepared PCS-derived SiC. Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) results demonstrate that dehydrogenation effectively prevented the breakage of Si C bonds during the following oxidation. Furthermore, PCS-derived SiC with a similar core-shell structure was obtained after oxidation, the surface of which showed fewer SiC nanocrystals and shorter graphene-like carbon compared to the inner microstructure. Due to this unique microstructure, the oxidized PCS-derived SiC shows both better attenuation capability and impedance match than as-received PCS-derived SiC. Moreover, with extended oxidation time, the average ε ′ and ε ″ of PCS-derived SiC decreased from 13.0 to 5.2 to 10.5 and 4.4, respectively, which could be attributed to weakened polarization and decreased electrical conductivity. The minimum reflection loss of PCS-derived SiC could be significantly improved from −18 to −27 dB after oxidation, which indicates strong improvement in microwave absorption properties. Highlights • Microwave absorption properties of PCS-derived SiC were improved by oxidation. • Oxidized SiC particles with core-shell structure exhibits better impedance match. • The minimum RL for SiC is obviously decreased from −18 to −27 dB after oxidation. • The bandwidth below −10 dB extends to 3.4 GHz in X-band with a thickness of 2.3 mm. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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