Construction of SiO2-SiC/C composite absorber based on coal hydrogenation semi coke

In-situ catalytic generation of SiC coating on coal hydrogenation semi coke (SC, a new type of solid waste) was fabricated via the sol-gel coating, in-situ catalytic and subsequent high-temperature solid-phase reaction methods. The specific composition, microstructure, catalytic formation mechanism of SiC/C composite had been systematically investigated. The analysis results had proven that the loading Ni nanoparticles as catalyst favored the in-situ formation of SiC layer on SC, and significantly decreased the initial and complete reaction temperature of SiC. In particularly, the introduction of SiC had effectively improved the microwave absorption (MA) performances of composites. For the sample SiO2/SiC/C, its optimal reflection loss peak value (RLmin=-20.4 dB) and effective absorption bandwidth (EABmax=3.92 GHz) were achieved at the matched thickness of 2.0 mm. Whereas the RLmin peak of -30.5 dB at the frequency of 4.06 GHz, and the EABmax of 3.68 GHz within the coating thickness of 2.0 mm had obtained for SiC/C samples. All results confirmed that the in-situ formation of SiC was beneficial for the regulation of impedance matching for the single carbon material, realizing the superior MA properties of SiC/C absorber. Furthermore, the successful fabrication of SiO2/SiC/C and SiC/C absorbers, in-situ ceramic phase loading low-cost carbon, provide the possibility for the large-scale application in the field of MA for SC, and expect to implement the environmental protection strategy of “waste in waste”.