Ultrathin Self‐Assembly MXene@flake Carbonyl Iron Composites with Efficient Microwave Absorption at Elevated Temperatures

Abstract The exploration for the potential lightweight and high efficiency microwave absorbers with thermal stability is a great challenge for researchers. More importantly, the electromagnetic parameters of absorbers at elevated temperatures are seldom studied. In this work, sandwich MXene‐Ti₃C₂T_x@flake carbonyl iron (MF) composites with tunable and efficient microwave absorption at elevated temperatures are successfully fabricated by an electrostatic self‐assembly method. Both the complex permittivity and permeability of the MF are strongly temperature dependent in the temperature range of 298–473 K and X band (8.2–12.4 GHz). The efficient microwave absorption of MF at different temperatures can be achieved by changing the ratio of raw materials. Specifically, at room temperature, reflection loss (RL) ≤−10 dB of MF composite covers the whole X band at 2.12 mm, while the optimum RL value is −26.3 dB at 11.81 GHz. At 373 K, the optimum microwave absorption value of the MF composite reaches up to −63 dB at 10.27 GHz and RL ≤−10 dB can cover a whole X band with a thickness of 1.52 mm. Therefore, MF composites are expected to be promising candidates as ultrathin, highly efficient, and broadband absorbing materials at elevated temperatures.