Structure and Magnetic Properties of Porous Ni1-xZnxFe2O4 Ultrafine Fibers Prepared by Electro spinning Technique

Porous Ni1-xZnxFe2O4 (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 N-2 adsorption-desorption and VSM techniques , respectively. The results show that the obtained porous Ni1-xZnxFe2O4 ultrafine fibers calcinated at 550 degrees C for 2 h are single-phase spinel structure with an average grain size of 25-30 nm. These ultrafibers have diameters in the range of 20-500 nm and a large aspect ratio. N-2 adsorption-desorption analysis indicate that the pore structure of as-prepared Ni0.5Zn0.5Fe2O4 porous fibers mainly consists of silt-like mesopores with a mean pore diameter od about 11 nm. With the increase of Zn content (x=0 to x=0.8), the lattice constant of Ni1-xZnxFe2O4 ultrafine fibers increases linearly and complies well Vegard's law, and the infrared vibrational frequencies corresponding to tetrahedral sites shift toward lower wavenumber. The coercivity of the samples gradually decreases from 13.8 kA/m (x-0) to 2.3 kA/m (x=0.8), whereas the specific saturation magnetization increases initially, reaches a maximum value of 6608 A.m(2)/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.