Synthesis and Characterization of HfO₂@Fe₃O₄ Core-Shell Nanotubes: Insights into Potential Magnetic Functionalities

This study presents the synthesis and characterization of core-shell nanostructures comprising PVP@HfO₂@Fe₂O₃ nanowires and HfO₂@Fe₃O₄ nanotubes. PVP nanofibers were electrospun with an average diameter of approximately 379 nm, onto which HfO₂ and Fe₂O₃ layers were sequentially deposited via atomic layer deposition, resulting in core-shell nanowires averaging 460 nm in diameter. Thermal reduction transformed Fe₂O₃ into Fe₃O₄, forming HfO₂@Fe₃O₄ core-shell nanotubes. Characterization using scanning electron microscopy and high-resolution transmission electron microscopy confirmed the core-shell morphology, while energy-dispersive X-ray spectroscopy verified the elemental composition. Surface roughness analysis revealed fractal dimensions indicating increased roughness with thicker shells. X-ray photoelectron spectroscopy analysis identified Fe(II) and Fe(III) oxidation states and confirmed phase transformations from hematite to magnetite. Magnetic measurements demonstrated enhanced coercivity and saturation magnetization in HfO₂@Fe₃O₄ structures compared to initial samples, showcasing the tunability of magnetic properties through core-shell engineering. This work highlights atomic layer deposition’s capability to fabricate precise core-shell nanostructures, offering tailored control over morphology and magnetic behavior for applications in advanced nanotechnologies.