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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]

• Magnetic CoNi-wrapped Ti 3 SiC 2 composites were successfully prepared. • Obvious regulated electromagnetic parameters for the composites can be realized. • The EAB of 4.88 GHz and optimal RL value of −41.41 dB were achieved. The magnetic–dielectric composites with synergetic magnetic and dielectric losses have exhibited great potential in the practical applications of microwave absorbing material. This paper reports a simple low-temperature in situ hydrothermal approach for synthesizing novel composites composed of the dielectric Ti 3 SiC 2 wrapped with magnetic CoNi nanoparticles. The microstructure, morphology, electromagnetic properties, and microwave absorption performance of as-synthesized samples were investigated. By adjusting the content of formed magnetic CoNi nanoparticles on the surface of Ti 3 SiC 2 , obvious regulated frequency-dependence of electromagnetic parameters for the proposed CoNi/Ti 3 SiC 2 composites can be realized. Consequently, the effective absorption bandwidth (RL < −10 dB) and optimal reflection loss value of CoNi/Ti 3 SiC 2 -40 composites under thinner thickness of 1.55 mm can reach up to 4.88 GHz and −41.41 dB, respectively. Exceptional microwave absorption performance of the CoNi/Ti 3 SiC 2 composites is attributed to its simultaneously improved attenuation characteristics and optimized impedance matching, and thus can be undoubtedly identified as high-efficiency microwave absorbing material. [ABSTRACT FROM AUTHOR]