Polymer-derived Co2Si(Co)/SiCN composite ceramics with tunable microwave absorption properties

In this paper, Co2Si(Co)/SiCN composite ceramics were synthesized by simple precursor-derived ceramics method. The phase composition, morphology, and microwave absorption properties of Co2Si(Co)/SiCN composite ceramics at different pyrolysis temperatures (1000-1400 degrees C) were studied. When pyrolysis temperature was 1300 degrees C, carbon nanowires (CNWs), Co2Si, Si2N2O, SiC and Si3N4 were in situ generated and the best electromagnetic wave (EMW) absorption performance was obtained. The minimum reflection loss reached-50.04 dB at 4.81 mm, and the effective absorption bandwidth broadened to 3.48 GHz (14.52-18 GHz) at 1.31 mm. The excellent EMW absorption performance mainly comes from the coexistence of multiple loss mechanisms, including the magnetic loss of Co2Si, the conduction loss of CNWs, and the heterogeneous interfaces polarization between varieties of nanocrystals and amorphous ceramic matrix. By adjusting the sample thickness from 1 to 5 mm, the effective absorption of S1300 can cover the entire X and Ku bands, from 3.36 to 18 GHz. This study provides a simple way to synthesize high performance ceramic-based microwave absorbing materials.