Defect Dipole-Induced HfO2-Coated Ti3C2Tx MXene/Nickel Ferrite Nanocomposites for Enhanced Microwave Absorption

This work reports for the first time the synthesis of a HfO2-coated Ti3C2Tx MXene sandwich-like nanostructure (MXHf) using a simple hydrothermal method and their excellent microwave absorption property in combination with nickel ferrite and epoxy matrix. The nanocomposites of 2, 3, and 4 mm thick samples were tested for microwave absorption in the X-band, and a minimum reflection loss (RLmin) of −20.9 dB with EAB (effective absorption bandwidth) of 2.32 GHz was achieved for the 3 mm thick sample. Its superior performance results from the strong dielectric polarization of defect dipole in the MXene structure, the high number of oxygen vacancies brought about by HfO2 nanoparticles, rich micro-interfaces in the sandwich-like HfO2-Ti3C2Tx-HfO2 structure, and impedance matching by NiFe2O4. A probable mechanism of absorption is proposed. Hence, HfO2/Ti3C2Tx/NiFe2O4 nanocomposites possess essential properties for real-time application in the defense and telecommunication industries.