Preparation and Characterization of Polyethylene-Based Composites with Iron-Manganese “Core-Shell” Nanoparticles

Composite materials based on low-density polyethylene (LDPE) embedded with iron-manganese nanoparticles with compositions Fe0.9Mn0.1 and Fe0.8Mn0.2 were prepared and investigated. The newly created composites were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS), and Mössbauer spectroscopy. The composition, electronic, and atomic structure of the nanoparticles were established. The study confirms that the nanoparticles possess a ‘core-shell’ structure, the nature of which depends on the manganese content. The nanoparticles of Fe0.8Mn0.2 in LDPE exhibit a three-layered structure: a metallic α-Fe core is coated with an intermediate oxidized layer structurally close to Fe2O3, while the outermost shell consists of manganese oxide (Mn2O3). In contrast, nanoparticles with lower Mn content Fe0.9Mn0.1 show a predominantly fully oxidized structure. This structural evolution is consistent with thermodynamic principles, where manganese, having a higher oxide formation enthalpy, migrates to the surface. The core–shell architecture is promising for applications requiring stable magnetic components or tailored catalytic interfaces within a polymer matrix.