Lewis acidic molten salts etching route driven construction of double-layered MXene-Fe/carbon nanotube/silicone rubber composites for high-performance microwave absorption

Transition metal carbide/nitride (MXene) materials have triggered intensive research interest in the field of microwave absorption (MA). However, the complicated fabrication process and monotonous loss mechanism of MXene materials seriously hinder their practical applications. Here, we first developed a green and facile synthesis of dielectric-magnetic MXene-Fe nanocomposites via one-step Lewis acidic molten salts etching, which were combined with carbon nanotube (CNT) filler and silicone rubber (SR) matrix to fabricate double-layered MXene-Fe/CNT/SR composites by casting and curing. The in-situ growth magnetic Fe nanoparticles on MXene and unique double-layered structure composed of MXene-Fe/SR as the upper absorption layer and CNT/SR as the bottom reflection layer imparted the composites with excellent MA properties by offering appropriate impedance matching, strengthened internal reflection, polarization, magnetic loss, and conductive loss. Accordingly, the proposed double-layered composites showed superior MA properties compared with other MXene-based composites. The MXene-Fe-45%/CNT-5%/SR sample showed a reflection loss value of −65.9 dB at 12 GHz and an effective absorption bandwidth up to 8.24 GHz at 2.86 mm thickness. The double-layered composites exhibited tunable absorption frequency between the whole Ku-band and X-band by simply regulating the sample thicknesses and filler contents. These features indicate that the developed double-layered MXene-Fe/CNT/SR composites have great potential for high-performance MA applications. This study offers a novel and simple strategy to develop high-efficiency and broadband MA materials.