Variable-Temperature Regulation of NiCo₂S₄/Mn₃O₄ Nanostructured Composites for High-Performance Microwave Absorption

Currently, transition-metal oxides and sulfides remain widely used in the research on electromagnetic-wave-absorbing materials. In the present work, NiCo 2 S 4 /Mn 3 O 4 nanostructured composites were prepared by a series of hydrothermal and annealing processes and a strategy for the preparation of morphologically controllable absorbers was developed. The results show that the nanostructure design of Mn 3 O 4 was achieved by the variable-temperature strategy, and the Mn 3 O 4 shell was about 500 nm when the temperature reached 160 °C, and the composite had a uniform shell–core structure. In addition, the effects of microscopic morphology, lattice defects, and heterogeneous interfaces on electromagnetic parameters are investigated. In conclusion, the multiple loss mechanism and excellent impedance matching ability synergistically enable the NiCo 2 S 4 /Mn 3 O 4 nanostructured composite to achieve excellent microwave absorption characteristics, with a minimum reflection loss of −54.4 dB and a maximum effective absorption bandwidth of 5.36 GHz. This work provides a new perspective on the design of wave-absorbing materials for shell–core structures.