Abstract: Polymer-derived ceramics (PDCs) is a promising way to prepare ceramic-based electromagnetic functional materials, which can conveniently modulate the composition and dielectric properties of the ceramics. In this paper, SiBCN ceramic matrix composites with excellent high-temperature wave-transparent performance were prepared through PDC method. Three hyperbranched polyborosilazanes (PBSZs) were prepared by adjusting the type of chlorosilane monomers containing different numbers of methyl groups. The carbon element of pyrolytic ceramics was tuned by adjusting the molecular structure of the precursor and the pyrolysis temperature. The lower the methyl number and pyrolysis temperature, the lower the dielectric constant of the polymer-derived SiBCN ceramics, which is favorable for electromagnetic wave (EMW) transmittance. The average EMW transmittance of SiBCN-C pyrolyzed from hyperbranched PBSZ using trichlorosilane at 1000 °C was 90.56 % at room temperature. More excitingly, the excellent wave-transparent performance was also maintained in the temperature range of 100-800 °C. At the test temperature of 800 °C, SiBCN-C-1000 still had excellent wave-transparent performance with minimum and average EMW transmittance of 76.13 % and 88.96 %, respectively. This paper provided a new idea for the preparation of high-temperature wave-transparent SiBCN composite ceramics.

Key words: Polymer-derived ceramic, SiBCN, Low carbon content, High temperature wave-transparent, materials