Robust SiO2-modified CoFe2O4 hollow nanofibers with flexible room temperature magnetic performance

Abstract

A range of robust SiO₂-modified CoFe₂O₄ hollow nanofibers with high uniformity and productivity were successfully prepared via polyvinylpyrrolidone-sol assisted electrospinning followed by annealing at a high temperature of 1000 °C, and they were characterized using scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, X-ray diffraction and X-ray photoelectron spectroscopy in detail. It was demonstrated that amorphous SiO₂ has a significant influence on not only the surface morphology, microstructure and crystalline size but also the room temperature magnetic performance of the inverse spinel CoFe₂O₄ nanofibers. The pure CoFe₂O₄ sample shows a particle chain rod-shape appearance but the SiO₂-modified CoFe₂O₄ sample shows a robust hollow fibrous structure. With increasing SiO₂ content, an increase at first and then a decrease in coercivity (H_c) and monotonously a decrease in saturation magnetization (M_s) have been determined in the obtained modified CoFe₂O₄ hollow nanofibers. A maximum M_s of about 80 emu g⁻¹ and a maximum H_c of about 1477 Oe could be, respectively, acquired from the pure CoFe₂O₄ nanorods and the modified CoFe₂O₄ hollow nanofibers with about 14.9% SiO₂. The changes in M_s, H_c and the structure evolution mechanism of these SiO₂-modified CoFe₂O₄ hollow nanofibers have been elaborated systematically. Furthermore, it is suggested that amorphous SiO₂ enables effectively improving the structure endurance of 1D electrospun inorganic oxide hollow nanostructures being subjected to high temperatures.