Preparation of lignin-based carbon/polyaniline composites for advanced microwave absorber

Lignin and polyaniline (PANI) as raw materials were pretreated and calcined to prepare a lignin-based carbon/ PANI composite microwave absorbent. The microscopic, structural, and microwave absorption performance of lignin-based carbon/PANI composites were investigated using X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and vector network analyzer. Results show that the optimized reflection loss (RL) of the lignin-based carbon/PANI composites is -50.96 dB, its matching thickness is 3.09 mm, and its effective absorption frequency range is 6.8-10.8 GHz (RL <-10 dB), covering C-band and X-band. Compared with untreated lignin, lignin-based carbon/PANI composites possess broader effective absorption bandwidth and higher absorption intensity. The outstanding absorption properties are closely related to the suitable impedance matching and the multiple loss mechanisms. This work can be used as the basis for the design and preparation of lignin-based and PANI polymer composites and serves as a feasible method for the design and synthesis of microwave absorbents with light weight and high performance.