In situ etching by released proton in aniline polymerization to form network VO2 doped polyaniline composites with variable infrared emissivity for electromagnetic absorption application

Vanadium dioxide (VO2) in transition metal oxides (TMOs) exhibits low electrical conductivity and poor polarization properties. In this work, we present a strategy for the one-step synthesis of polyaniline (PANI) coated vanadium dioxide (VO2), in which VO2 is etched in situ by protonic acid released during the process of aniline polymerization, resulting in the construction of a microstructure of a nanofiber network. The electromagnetic absorption (EMA) properties of VO2 after the introduction of different levels of PANI were systematically investigated (VO2@PANI). As a result, the introduction of PANI not only formed a unique conductive fiber network and improved the electrical conductivity, but also improved the multi-polarization relaxation, which enabling the VO2@PANI composite with good EMA performance. The VO2@PANI composites exhibited the best EMA performance of - 45.1 dB at 8 GHz with a thickness of 3 mm and achieved an effective absorption in the band of 13.4-17.8 GHz (4.4 GHz) at 1.7 mm. In addition, the VO2@PANI still maintained its variable infrared (IR) emissivity characteristics. This study provided an innovative composite approach based on VO2 materials for efficient EMA and infrared properties.