Introducing MWCNTs conductive network in polymer-derived SiCN ceramics for broadband electromagnetic wave absorption

In this work, a series of SiCN (MWCNTs) composite ceramics were prepared through polymer derivation method by adjusting the mass ratio of multiwalled carbon nanotubes (MWCNTs). On this basis, the influence of the addition amount of MWCNTs on reflection loss (RL), effective absorption bandwidth (EAB), electromagnetic parameters, direct current conductivity (sigma), impedance matching parameter (Z) and attenuation coefficient (alpha) of composite ceramics was studied, the percolation threshold of MWCNTs addition amount was analyzed, and the electromagnetic wave (EMW) absorption performance and absorption mechanism of composite ceramics when the MWCNTs addition amount was fixed at the percolation threshold were discussed. The analysis shows that the conductive network composed by MWCNTs can significantly improve the EAB of ceramic samples. When the addition amount of MWCNTs reached 10 wt%, a conductive percolation state was achieved inside composite ceramics. At this time, the sample showed the optimal comprehensive EMW absorption performance: when the thickness was 1.7 mm, the minimum reflection loss (RLmin) was -21.7 dB, and its EAB reached 4.7 GHz. Compared with many similar magnetic SiCN-based composite ceramics or carbon-rich SiCN-based composite ceramics previously reported, the SiCN (MWCNTs) composite ceramics prepared in this work showed an obviously improved EAB under the condition of reduced thickness.