The fabrication and magnetic properties of Ni fibers synthesized under external magnetic fields

One-dimensional (1D) nanocrystallites Ni fibers with different lengths were fabricated by the reduction of Ni2+ ions by hydrazine hydrate in the presence of external magnetic fields. The effect of the reaction conditions and magnetic field intensity on the microstructures and magnetic properties of the Ni fibers were systematically investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and measurement of hysteresis loops at room temperature. It was found that both the intensity of the external magnetic field and the concentration of the nickel salt solution played key roles in governing the microstructures and magnetic properties of the Ni fibers. Namely, the mean length of the Ni fibers increased markedly with increasing Ni2+ ion concentration and intensity of the external magnetic field as well. Moreover, the Ni fiber samples prepared under external magnetic fields had higher squareness and coercivity values than those synthesized in the absence of the external magnetic field. Therefore, a relatively high intensity of the external magnetic field and concentration of the Ni2+ ions was selected for the preparation of the desired Ni fibers with improved microstructures and magnetic properties. The present approach has the advantages of having a fast reaction rate and low cost and might be promising for the effective control of the shape and magnetic properties of magnetic materials and for large-scale production as well. The resulting Ni fibers might be potential catalysts, magnetic storage materials, and conductive fillers for shielding of electromagnetic interference (EMI). ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).