Improved dielectric properties of PDCs-SiCN by in-situ fabricated nano-structured carbons

In order to enhance dielectric properties of polymer derived SiCN ceramics (PDCs-SiCN), nano-structured carbons were in-situ fabricated in PDCs-SiCN by pyrolysis of ferrocene-modified polysilazane. Microstructure evolutions, dielectric and microwave absorption properties of PDCs-SiCN decorated with nano-structured carbons were investigated. Nano-structured PDCs-SiCN ceramics are composed of carbon nanowires as well as interpenetrating graphene-like free carbons, SiC nano-crystals, Si₃N₄ nano-crystals and amorphous SiCN. Relative complex permittivities of nano-structured PDCs-SiCN increase with increasing ferrocene contents and annealing temperatures. Free carbons in PDCs-SiCN play a dominating role on the improved dielectric properties. Polarization loss is the primary dielectric loss. Loss tangent of PDCs-SiCN exceeding 0.7 is obtained when free carbons are only 2.57% in weight. Nano-structured PDCs-SiCN exhibit good microwave absorption property. The reflectivity is smaller than −14 dB in the whole X band when material is composed of both impedance and microwave absorption materials.