Thermodynamic-Driven Design of Multiphase Fe–S–Sn-Alloyed Nanocomposites for Electromagnetic Wave Absorption

With the development of modern electronic technology, electromagnetic waves (EMWs) are widely applied in communication, radar, and medical fields. However, their disorderly propagation leads to signal interference, radiation pollution, and security threats. Therefore, the development of efficient EMW absorption materials has become a research hotspot in the fields of materials science and electromagnetism. This study systematically investigates the EMW absorption properties of nFe/SnS-G composite materials, focusing on the issue of electromagnetic pollution. Based on the first law of thermodynamics and density functional theory (DFT) calculations, it was found that by regulating the molar ratio of Fe to SnS, a series of Fe–S/Fe-Sn multiphase composite materials could be generated. On this basis, nFe/SnS (n = 1, 2, and 3) composites were prepared by vacuum calcining Fe and SnS with different molar ratios, and further mixed with graphite through ball milling to prepare nFe/SnS-G composites. The results indicate that increasing the Fe content can enhance the magnetic loss capacity of the composites, while the introduction of graphite significantly strengthens the interface polarization and conductive loss, thereby improving the dielectric loss capacity of the composites. Among them, the 1Fe/SnS-G sample exhibits the lowest reflection loss (RLmin = −56.8 dB) at 7.62 GHz, while the 3Fe/SnS-G composite shows the best EMW absorption performance at a thickness of 1.65 mm, with a maximum effective absorption bandwidth (EABmax) of 4.1 GHz. Mechanism analysis reveals that the excellent performance of the materials is primarily attributed to the synergistic effect of dielectric loss and magnetic loss, including various mechanisms such as interface polarization, conductive loss, dipole polarization, and defect polarization.