Adjustable electromagnetic response of ultralight 3D Ti3C2Tx composite via control of crystal defects

Abstract

Microwave shielding materials and absorbers serve important roles in improving the reliability of smart devices and military equipment. In this work, three-dimensional (3D) Ti3C2Tx/Fe3O4 composites with adjustable electromagnetic responses are studied. Taking advantage of the negatively charged surface of the Ti3C2Tx, the cationic surfactant cetyltrimethylammonium bromide (CTAB) is used to precipitate the delaminated Ti3C2Tx sheets. The volatilization of CTAB during the annealing process inflates the Ti3C2Tx, and leads to the three-dimensional architecture of the composite. The results show that the free-standing 3D Ti3C2Tx/Fe3O4 composite film exhibits a high shielding efficiency of 60 dB in the X band. Owing to the traits of great flexibility, low apparent density, and thin thickness, the 3D Ti3C2Tx/Fe3O4 composite film achieves a high specific shielding efficiency of 3.5 × 105 dB/(g·cm−2). Furthermore, through the control of crystal defects in one-step annealing treatment, the shielding material can be transformed into a wideband microwave absorber. A high reflection loss up to −57 dB can be realized. And a 2-mm-thick absorber whose reflection loss is better than −10 dB in 11.2 ~ 18 GHz is also achieved. The experimental and first-principal studies on the evolution mechanism reveal that the destruction of the Ti-C bond mainly leads to the degradation of electrical conductivity and the improvement of impedance matching. Introduced crystal defects can help enhance the dielectric loss as well. The synergistic effects of ohmic loss, dielectric loss, and magnetic loss give birth to a broadband absorption of the composite.