静电纺丝法制备定向排列的铁氧体纳米纤维

以聚乙烯吡咯烷酮(PVP)和金属硝酸盐为原料,采用改进的静电纺丝法制备了直径均匀、表面光滑、定向排列的Co0.8Zn0.2Fe2O4/PVP纳米纤维前驱体,经热处理后得到定向排列的铁氧体纳米纤维.对前驱体纤维的热分解过程及Co0.8Zn0.2Fe2O4(CZFO)的结构、物相及形貌进行了表征.结果表明,在空气中经550～950℃热处理3 h后均得到纯相、结晶良好的尖晶石型钴锌铁氧体;在2000 r/min转速下收集的复合纤维形貌最佳,直径约300 nm;经750℃热处理后纤维直径约为70 nm,室温下测得饱和磁化强度为66.1 A.m2/kg,矫顽力达到最大值6.6 A/m,表明钴锌尖晶石型铁氧体单畴临界尺寸约为44 nm.与CoFe2O4相比,CZFO的饱和磁化强度升高,矫顽力下降,并且CZFO的纤维与粉末的磁特性有明显的区别.

Aligned Ferrite Nanofibers Fabricated by Electrospinning

Using polyethylene pyrrole(PVP) and metal nitrate as precursors, smooth, uniform, and aligned Co0.8Zn0.2Fe2O4 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. Co0.8Zn0.2Fe2O4 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 Co0.8Zn0.2Fe2O4 nanofibers. Compared with CoFe2O4 nanofibers, the anisotropy of Co0.8Zn0.2Fe2O4 nanofibers decreased, resulting in the lower coercivity(Hc) and higher saturation magnetization(Ms) of the obtained sample. The Ms of the sample increased with the calcinations temperature, while the Hc reaches a maximum value of 16.6 A/m at the calcinations temperature of 750 ℃. The Hc results suggest that the critical single-domain size of Co0.8Zn0.2Fe2O4 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.