Hierarchical MXene/Ni-MOF-derived C/TiO2/Ni@C composites: synergistic dielectric-magnetic optimization for high-performance microwave absorption

To address the growing need for high-performance microwave absorbing materials in modern communication and radar technologies, this study proposes a hierarchical heterostructured engineering strategy to integrate multiple loss mechanisms and optimize electromagnetic wave absorption. The hierarchical heterostructured C/TiO 2 /Ni@C composites were constructed via in situ hydrothermal synthesis combined with high-temperature calcination. The microwave absorption properties of the composite can be tuned by adjusting the MXene doping level and pyrolysis temperature. The TiO 2 /C framework derived from MXene and porous Ni@C microspheres derived from Ni-MOF enhance dielectric losses (interfacial polarization and dipole relaxation). The precipitated Ni magnetic nanoparticles improve magnetic losses. Compared with traditional microwave absorbing materials such as single-phase carbon or metal oxides, the C/TiO 2 /Ni@C-2 composite thermally decomposed at 600 °C exhibits excellent microwave absorption properties with an optimal reflection loss of −57 dB at a thickness of 4.26 mm and a frequency of 7.1 GHz. Upon optimization to a thickness of 2.16 mm, its effective absorption bandwidth (EAB) extends to 5.34 GHz (12.43–17.77 GHz), thereby fully encompassing the Ku band. The exceptional microwave absorption performance is attributed to its distinctive magnetic-dielectric layered architecture, heterointerface synergy, and optimized impedance matching, offering critical insights for designing next-generation broadband microwave absorbers.