Fabrication and electromagnetic wave absorption properties of Fe<sub>x</sub>O<sub>y</sub>/BaTiO<sub>3</sub>/C composites from red mud

To achieve the resource utilization of red mud, this work prepares Fe_{<italic>x</italic>}O_{<italic>y</italic>}/BaTiO₃/C composite microwave absorbing materials using red mud as the iron source and soluble starch as the carbon source, employing sol-gel and solid-state reaction methods. First, a BaTiO₃ precursor sol is obtained through the sol-gel process using titanium butoxide and barium acetate. This sol is then mixed uniformly with red mud and soluble starch, followed by drying and solid-state reaction. During the solid-state reaction, Fe₂O₃ in the red mud undergoes in-situ carbothermic reduction to form Fe₃O₄ and Fe, which are evenly distributed within the material. BaTiO₃, on the other hand, exhibits a needle-like morphology. Experimental results show that by adjusting the solid-state reaction temperature and the raw material ratio, the phase composition, microstructure, and microwave absorption performance of the composite material can be optimized. When the solid-state reaction temperature is set at 700 ℃, RmBTS-700-1.2 exhibits a minimum reflection loss of −16.0 dB at a coating thickness of 2.0 mm, with an effective absorption bandwidth of up to 3.0 GHz. Meanwhile, RmBTS-700-1.8 achieves a minimum reflection loss of −32.6 dB at 10.7 GHz at the same coating thickness. The Fe_{<italic>x</italic>}O_{<italic>y</italic>}/BaTiO₃/C composite microwave absorbing materials prepared in this study exhibit both strong dielectric loss and magnetic loss capabilities, providing a new approach for the comprehensive utilization of red mud and contributing to the realization of the “carbon neutrality and carbon peak” goals.