Controllable synthesis and enhanced microwave absorption properties of hexagonal boron nitride@polyaniline composite

Nowadays, electromagnetic pollution caused by electronic devices is gradually becoming a concern. Moreover, as the frequency of electromagnetic pollution from electronic devices is mainly in the range of 2–10 GHz, the design of microwave-absorbing materials for this frequency range has become a hot issue. To tackle the issue, core-shell structured hexagonal boron nitride (h-BN) @polyaniline (PAn) composites have been proposed to construct heterogeneous microwave-absorbing materials. Firstly, the h-BN is exfoliated, and hydroxyl functionalized to produce hydroxy boron nitride (OH-BN), which enhances its polarization ability by structuring defects and adding functional groups to improve its microwave absorption efficiency. Afterward, PAn was grafted on the OH-BN surface by in situ polymerization. The microwave absorption properties of OH-BN@PAn composites can be tuned by modulating the doping of PAn. As expected, the OH-BN@PAn composite exhibits superior microwave absorption properties with the minimum reflection loss (RLmin) value of −38.60 dB at 3.5 mm and an effective absorption bandwidth (EAB) of 3.4 GHz (6.24–8.64 GHz) at pH = 2. Also, the composite achieves effective microwave absorption at 3.76–18 GHz by adjusting the matching thickness. Notably, the RLmin value of OH-BN@PAn was successfully tuned from the high-frequency region (12.4 GHz, pH = 0) to the low-frequency region (7.28 GHz, pH = 2) by adjusting the doping degree. In addition, the RL value and EAB width have been increased due to the increased impedance matching and polarization capability. This work can provide a reference for constructing composite microwave-absorbing materials and regulating microwave absorption performance