Polymer-derived NixSiy/Graphene/SiCN composite ceramics with enhanced electromagnetic wave absorption performance

Benefiting from its light weight, unique microstructure and high thermal stability, SiCN ceramics have attracted extensive attention in the field of electromagnetic wave (EMW) absorption. However, due to its poor impedance matching performance and single loss mechanism, the EMW absorption performance of SiCN ceramics requires further improvement. Herein, we introduced Ni and graphene into polysilazane to fabricate NixSiy/Graphene/ SiCN composite ceramics by polymer derived ceramics (PDCs) route. The introduction of Ni not only facilitated the formation of various phases, including Si3N4, Ni2Si, Ni31Si12, graphite carbon and Si2N2O, but also catalyzed the in-situ generation of one-dimensional carbon nanotubes (1D CNTs). When the addition content of Ni was 6 wt % and the addition content of graphene was 2 wt%, the NixSiy/Graphene/SiCN composite ceramics exhibited the optimal EMW absorption performance. The minimum reflection loss (RLmin) of NixSiy/Graphene/SiCN composite ceramics reached-52.13 dB at 7.6 GHz with the thickness of 2.7 mm, and widest effective absorption bandwidth (EAB) reached 3.56 GHz (14.44-18 GHz) at 1.26 mm. The dielectric loss was enhanced by carbon materials (turbostratic carbon, 1D CNTs and 2D graphene) and various phases, while the magnetic loss was improved by Ni and nickel silicide. The synergism of multiple loss mechanisms and good impedance matching lead to excellent EMW absorption properties of NixSiy/Graphene/SiCN ceramics.