Electromagnetic (EM) absorbing and shielding composites with tunable absorbing behaviors based on Ti3C2 MXenes are fabricated via HF etching and annealing treatment. Localized sandwich structure without sacrificing the original layered morphology is realized, which is responsible for the enhancement of EM absorbing capability in the X-band. The composite with 50 wt % annealed MXenes exhibits a minimum reflection loss of -48.4 dB at 11.6 GHz, because of the formation of TiO2 nanocrystals and amorphous carbon. Moreover, superior shielding effectiveness with high absorption effectiveness is achieved. The total and absorbing shielding effectiveness of Ti3C2 MXenes in a wax matrix with a thickness of only 1 mm reach values of 76.1 and 67.3 dB, while those of annealed Ti3C2 MXenes/wax composites are 32 and 24.2 dB, respectively. Considering the promising performance of Ti3C2 MXenes with the modified surface, this work is expected to open the door for the expanded applications of MXenes family in EM absorbing and shielding fields.

Besides the excellent high-temperature mechanical properties, Si 3 N 4 and SiC based ceramics containing insulating or electrically conductive phase are attractive for their tunable dielectric properties, which may vary from electromagnetic (EM) wave transparent to absorption and shielding. Consequently, SiC, Si 3 N 4 , SiON, SiBN, SiBC, SiCN and SiBCN ceramics have attracted extensive interest in recent years.

Electromagnetic wave (EM) absorption materials with broader effective absorption bandwidth (EAB), lightweight, and thinness characteristics are highly desirable in areas of wearable device and portable electronics. However, there are still many obstacles to simultaneously satisfy the above critical requirements required by new high-performance EM absorption materials. Herein, for the first time, Ti 3 C 2 T X MXenes are selected as the dielectric mediator to prepare reduced graphene oxide (RGO)/Ti 3 C 2 T X hybrids foam with hollow core-shell architectures and controllable complex permittivity via self-assembly and sacrificial template processes, under the guidance of theoretical calculations. RGO is grafted flatly on the outer surface of the Ti 3 C 2 T X spheres-core, forming a unique heterostructure. The RGO/Ti 3 C 2 T X foam possesses excellent EM absorption performance superior to all reported foam-based counterparts, the EAB covers the whole X-band at 3.2 mm while the density is merely 0.0033 g cm −3 , and its specific EM absorption performance (SMAP = RL (dB)/Thickness (cm)/Density (g cm −3 )) value exceeds 14 299.2 dB cm −2 g −1 , verifying the above theoretical results. This study is expected to guide future exploration on designing high-performance EM absorption materials, and the RGO/Ti 3 C 2 T X foam can be promising candidates in energy storage, sensors, and wearable electronics fields.

Lightweight absorption-dominated electromagnetic interference (EMI) shielding materials are more attractive than conventional reflection-dominated counterparts because they minimize the twice pollution of the reflected electromagnetic (EM) wave. Here, porous Ti2CT x MXene/poly­(vinyl alcohol) composite foams constructed by few-layered Ti2CT x (f-Ti2CT x ) MXene and poly­(vinyl alcohol) (PVA) are fabricated via a facile freeze-drying method. As superior EMI shielding materials, their calculated specific shielding effectiveness reaches up to 5136 dB cm2 g–1 with an ultralow filler content of only 0.15 vol % and reflection effectiveness (SER) of less than 2 dB, representing the excellent absorption-dominated shielding performance. Contrast experiment reveals that the good impedance matching derived from the multiple porous structures, internal reflection, and polarization effect (dipole and interfacial polarization) plays a synergistic role in the improved absorption efficiency and superior EMI shielding performance. Consequently, this work provides a promising MXene-based EMI shielding candidate with lightweight and high strength features.

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