Abstract:

Porous Ni_1-xZn_xFe₂O₄ (x=0-0.8) ultrafine fibers were prepared by electrospinning technique and subsequent calcination process. The crystal structure, micromorphology, pore character and room-temperature magnetic properties of the samples were investigated by means of XRD, FTIR, FESEM, low-temperature N₂ adsorption-desorption and VSM techniques, respectively. The results show that the obtained porous Ni_1-xZn_xFe₂O₄ ultrafine fibers calcined at 550℃ for 2βh are single-phase spinel structure with an average grain size of 25-30 nm. These ultrafibers have diameters in the range of 200–500βnm and a large aspect ratio. N₂ adsorption-desorption analysis indicate that the pore structure of as-prepared Ni_0.5Zn_0.5Fe₂O₄ porous fibers mainly consists of slit-like mesopores with a mean pore diameter of about 11βnm. With the increase of Zn content (x=0 to x=0.8), the lattice constant of Ni_1-xZn_xFe₂O₄ ultrafine fibers increases linearly and complies well with Vegard’s law, and the infrared vibrational frequencies corresponding to tetrahedral sites shift toward lower wavenumber. The coercivity of the samples gradually decreases from 13.8βkA/m (x=0) to 2.3βkA/m (x=0.8), whereas the specific saturation magnetization increases initially, reaches a maximun value of 66.8βA·m²/kg at x=0.4 and then decreases with further increase of Zn content. It is found that the synthesized Ni-Zn ferrite untrafine fibers exhibit relatively high coercivity due to their high shape anisotropy compared with the nanoparticle counterparts with similar size. These porous Ni-Zn ferrite untrafine fibers have potential application in many fields such as sensitive devices, microwave absorbers, and catalysts.

Key words: Ni-Zn ferrite, porous fiber, electrospinning, magnetic properties, structure