Defect Dipole-Induced HfO₂-Coated Ti₃C₂T_x MXene/Nickel Ferrite Nanocomposites for Enhanced Microwave Absorption

This work reports for the first time the synthesis of a HfO 2 -coated Ti 3 C 2 T x 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 (RL min ) 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 HfO 2 nanoparticles, rich micro-interfaces in the sandwich-like HfO 2 -Ti 3 C 2 T x -HfO 2 structure, and impedance matching by NiFe 2 O 4 . A probable mechanism of absorption is proposed. Hence, HfO 2 /Ti 3 C 2 T x /NiFe 2 O 4 nanocomposites possess essential properties for real-time application in the defense and telecommunication industries.