In-situ pyrolyzed polymethylsilsesquioxane multi-walled carbon nanotubes derived ceramic nanocomposites for electromagnetic wave absorption

Iron acetylacetonate (Fe(acac)3) modified polymethylsilsesquioxane (PMS), simplified as PMS(Fe), was firstly obtained from PMS and Fe(acac)3 via the condensation reaction. Multi-walled carbon nanotubes (MWCNTs) were then introduced to fabricate the corresponding MWCNTs/SiC nanocrystals/amorphous SiOC ceramic composites via pyrolyzed process. Owing to the catalytic effect of iron and heterogeneous nucleation promoted by MWCNTs, SiC nanocrystals were separated from SiOC amorphous ceramic matrix under 1400 °C. When the mass fraction of MWCNTs was 9 wt%, the obtained MWCNTs/SiC nanocrystals/amorphous SiOC ceramic composite (C9) demonstrated high microwave-absorbing properties. The minimum reflection loss (RLmin) and effective absorption bandwidth (EBA) of the obtained C9 at X-band (8.2–12.4) reached −61.8 dB and 2.6 GHz (a thickness of 2.19 mm), respectively. Compared with other polymer-derived ceramics (PDCs), the RLmin was higher and the required thickness was thinner. This excellent microwave-absorbing property was due to the interfacial polarization relaxation generated between nanocrystals (MWCNTs & SiC) and amorphous SiOC, and the formed complete conductive networks inside the ceramic composites.