Preparation and evaluation of magnetic nanocomposite fibers containing α-Fe16N2 and α-Fe nanoparticles in polyvinylpyrrolidone via magneto-electrospinning

Two kinds of ferromagnetic nanocomposite fiber comprising. alpha-Fe16N2 and alpha-Fe nanoparticles (NPs), which have the highest magnetic moments as hard and soft magnetic materials, respectively, embedded in polyvinylpyrrolidone (PVP) have been synthesized via the magneto-electrospinning method. Both alpha-Fe16N2 and alpha-Fe were single-domain core-shell NPs with an average outer diameter of 50 nm and Al2O3 as the shell. Ferrofluid precursors used for the electrospinning were prepared by dispersing these NPs in a PVP-toluene-methanol solution. The results show that applying the magnetic field in the same direction as the electric field resulted in smaller and more uniform fiber diameters. Nanocomposite fibers containing alpha-Fe16N2 had smaller diameters than those containing alpha-Fe NPs. These magnetic-field effects on the fiber formation were explained by referring to the kinetic energy of the moving jet in the electrospinning process. In addition, magnetic hysteresis curves showed an enhancement of the magnetic coercivity (H-c) and remanence (M-r) by 22.9% and 22.25%, respectively. These results imply a promising possibility of constructing bulk magnetic materials using alpha-Fe16N2 NPs, which furthermore reveals attractive features for many other magnetic applications, such as magnetic sensors.