Abstract:

Using polyethylene pyrrole(PVP) and metal nitrate as precursors, smooth, uniform, and aligned Co_0.8Zn_0.2Fe₂O₄ nanofibers were prepared via electrospinning and sol-gel method, and subsequent heating process. The thermal decomposition process, crystal structure, and morphology of the nanofibers were studied by means of thermogravimetric-differential thermal analysis(TG-DTA), Fourier transform infrared spectroscopy(FTIR), X-ray diffraction(XRD), scanning electron microscopy(SEM), and transmission electron microscopy(TEM), respectively. Co_0.8Zn_0.2Fe₂O₄ nanofibers with particle sizes of 20.5-61.9 nm and a well-developed spinel structure were successfully obtained after calcinations of the as-spun nanofibers at 550—950 ℃ in air for 3 h. The as-spun nanofibers collected at 2000 r/min with the best morphology is ca. 300 nm in diameter, which decreases down to ca. 70 nm on annealing at 750 ℃ from SEM and TEM images. Room temperature magnetization results showed a ferromagnetic behavior of the calcined Co_0.8Zn_0.2Fe₂O₄ nanofibers. Compared with CoFe₂O₄ nanofibers, the anisotropy of Co_0.8Zn_0.2Fe₂O₄ nanofibers decreased, resulting in the lower coercivity(H_c) and higher saturation magnetization(M_s) of the obtained sample. The M_s of the sample increased with the calcinations temperature, while the H_c reaches a maximum value of 16.6 A/m at the calcinations temperature of 750 ℃. The H_c results suggest that the critical single-domain size of Co_0.8Zn_0.2Fe₂O₄ is about 44 nm. In comparison with a powder sample prepared using conventional sol-gel process, significant differences in magnetic properties were noted between these two samples.

Key words: Electrospinning, Co_0.8Zn_0.2Fe₂O₄, Alignment, Nanofiber, Single-domain size