Effect of amination after bromination on the ultra-high frequency microwave properties of polyacrylonitrile (PAN) precursor-based carbon fibers

Monoethanolamine, ethylenediamine, sulfolanylethylenediamine, and piperazine were used to aminate polyacrylonitrile (PAN) precursor-based carbon fibers (CFs), previously brominated using an aqueous KBr₃ solution. HRTEM and SAED were confirmed the carbon nanostructures in PAN-CFs, comprising derivatives of turbostratic graphite layers. Successful amination was verified by FTIR-ATR, TGA, and TPD-MS. Thermal analysis in the 100–500 °C range revealed the decomposition of from 0.42 to 1.10 mmol g⁻¹ amino groups in the aminated PAN-CFs/KBr₃, with peak decomposition temperatures ranging from 230 to 310 °C. Amination significantly influenced the microwave properties of PAN-CFs/KBr₃. Among the samples aminated with selected amines, the difference in average reflection loss S¯₁₁ values reached 0.6 dB in the X-band and 0.9 dB in the Ka-band. For the average transmission loss S¯₂₁ values, the corresponding differences were 1.1 dB and 1.5 dB, respectively.