Fe2O3-decorated multiwall carbon nanotube composites for boosted microwave absorption

Developing microwave absorption (MA) materials with a strong absorption ability over a wide bandwidth through a simple and environmentally friendly approach remains a tremendous challenge. Herein, we propose to use an Fe³⁺–tannic acid framework to assist the dispersion of multi-walled carbon nanotubes (MWCNTs) and successfully prepare MWCNTs/porous carbon/α-Fe₂O₃ composites through freeze-drying and subsequent heat treatment. The dielectric properties and MA performance can be regulated by the heat treatment temperature, which leads to tunable crystalline structure, composition, and graphitization degree of MWCNTs. Consequently, the MWCNTs/porous carbon/α-Fe₂O₃ composite heat-treated at 300 °C exhibits a high reflection loss (RL) of −58.9 dB and an effective absorption bandwidth (5.28 GHz) with a matched thickness of 2.26 mm at a filler proportion of only 5 wt%, and the related frequency bandwidth with RL below −10 dB reaches 14.3 GHz at a thickness of 2–5 mm. In conclusion, the balance between conduction and polarization loss endows the composite with excellent impedance matching and boosting MA performance. This study offers a guideline for fabricating excellent MA materials through a simple, environmentally friendly method.