Core-shell fine structure of FeNi magnetic nanoparticles produced by electrical explosion of wire

Fe₄₅Ni₅₅ magnetic nanoparticles (MNPs) were fabricated by electric explosion of wire. In order to reduce the pyrophoricity of the MNPs, oxygen passivation was performed leading to the creation of the surface barrier layer. The surface features of MNPs are important for the development of MNPs containing composites (polymer/MNPs microwave absorbers or composites for power electronic devices). X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy and X-ray photoelectronic spectroscopy (XPS) were used for structural characterization. XPS analysis of the samples was conducted varying the electron exit angle with respect to the surface. The main phase is the FeNi fcc metallic core and the barrier layer is an iron-nickel NiFe₂O₄ oxide with a thickness of 2-6 nm. Small toroidal cores of 1.5 cm in diameter were prepared by hot pulse pressing. Their structure was studied by XRD, SEM-EDX techniques. The magnetic properties of the cores were measured using double coil winding. Obtained materials are interesting for power and electronic applications.