Enhanced microwave absorption performance of large-sized monolayer two-dimensional Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> based on loaded Fe<sub>3</sub>O<sub>4</sub> nanoparticles
Authors: Xiao Yi-Yao , He Jia-Hao , Chen Nan-Kun , Wang Chao , Song Ning-Ning ,   College of Mathematics and Physics, Beijing University of Chemical Technology, Beijing 100029, China
Published: September 2023

With the rapid development of electronic equipment, electromagnetic interference and electromagnetic radiation pollution have become serious problems, because excessive electromagnetic interference will not only affect normal operation of electronic equipment but also do great harm to human health. In general, an ideal material for microwave absorption with the characteristics of high reflection loss (RL) intensity, wide effective absorption band (EAB), thin thickness, and lightweight could effectively consume electromagnetic wave (EMW) energy. Therefore, it is crucial to search for such an ideal microwave absorption material to deal with the electromagnetic radiation pollution. Two-dimensional (2D) carbon/nitride MXene has received more and more attention in recent years, because excellent electrical conductivity and rich surface-functional groups in MXene show positive effects on electromagnetic wave absorption. However, as a non-magnetic material with only dielectric loss, MXene exhibits obvious impedance mismatch, which greatly limits its practical applications. Combining MXene with magnetic materials becomes a hotspot for the exploration of ideal microwave absorption materials. As a typical ferrite, Fe<sub>3</sub>O<sub>4</sub> shows excellent soft magnetic properties such as high saturation magnetization, high chemical stability, and simple preparation. In this paper, the 2D Fe<sub>3</sub>O<sub>4</sub>@Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> composite is successfully prepared by hydrothermal method and simple electrostatic adsorption process. The Fe<sub>3</sub>O<sub>4</sub> nanoparticles are uniformly anchored on the surface of large-sized monolayer Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub>, which effectively reduces the stacking of MXene. By regulating the proportion of magnetic materials, the microwave absorption performance of 2D Fe<sub>3</sub>O<sub>4</sub>@Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> composite is investigated. With the content of Fe<sub>3</sub>O<sub>4</sub> nanoparticles in the 2D Fe<sub>3</sub>O<sub>4</sub>@Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> composite increasing from 4 mg to 8 mg, the microwave absorption performance is enhanced obviously. This is caused by the abundant Fe<sub>3</sub>O<sub>4</sub>/Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> interface, scattering channels, point defect, charge density difference in 2D Fe<sub>3</sub>O<sub>4</sub>@Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> composite, and the optimized impedance matching. The minimum reflection loss (RL<sub>min</sub>) of 2D Fe<sub>3</sub>O<sub>4</sub>@Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> composite reaches –69.31 dB at a frequency of 16.19 GHz, and the effective absorption band (EAB) achieves 3.39 GHz. With the content of Fe<sub>3</sub>O<sub>4</sub> nanoparticles further increasing to 10 mg, the microwave absorption performance shows a decreasing trend. Excessive Fe<sub>3</sub>O<sub>4</sub> nanoparticles in the 2D Fe<sub>3</sub>O<sub>4</sub>@Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> composite lead to the decrease of electrical conductivity and thus the impedance dis-matching and dielectric loss decreasing, which leads the microwave absorption performance to decrease. Radar scattering cross section (RCS) is a physical quantity that evaluates the intensity of the scattered echo energy in the intercepted electromagnetic wave energy. The results of the RCS simulation can be applied to real objects which have been widely utilized in radar wave stealth. Its multi-angle simulation results can be used as an important basis for evaluating the stealth capability of microwave-absorbing material. The RCS simulations show that the average RCS value of 2D Fe<sub>3</sub>O<sub>4</sub>@Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> composite is over –47.92 dBm<sup>2</sup> at an incidence angle of 25°, demonstrating its excellent radar wave absorption performance. This study provides new ideas for improving and practically using two-dimensional and magnetic materials in the microwave absorption field and gives a new path to the subsequent development of microwave-absorbing composites.