Co_(0.5)Ni_(0.5)Fe_2O_4纳米纤维的静电纺丝法制备、表征及其磁性能

Electrospinning fabrication,characterization and magnetic properties of Co_(0.5)Ni_(0.5)Fe_2O_4 nanofibers

采用溶胶-凝胶法结合静电纺丝技术成功制备直径为150~400 nm的Co0.5Ni0.5Fe2O4铁氧体纳米纤维,并利用TG-DTA、XRD、FTIR、FESEM、TEM和VSM对样品进行表征。结果表明：前驱体纤维经450℃焙烧后可基本形成纯相晶态的目标产物Co0.5Ni0.5Fe2O4纳米纤维;随着焙烧温度的升高,纤维直径逐渐减小,晶粒尺寸逐渐增大,纤维表面粗糙度加强,其微观形貌由多孔结构向项链状结构转变;所制得的Co0.5Ni0.5Fe2O4纳米纤维的饱和磁化强度由450℃时的35.8 A.m2/kg单调增加到1 000℃时的80.2 A.m2/kg,而矫顽力呈现先增大后减小的趋势,在550℃附近时达到最大值,意味着其单畴临界尺寸约为30 nm,且发现在单畴尺寸范围内,矫顽力与平均晶粒尺寸的0.7次方成正比,与随机各向异性模型所预测的结果基本吻合。此外,低温（77 K）磁测量显示,与室温相比,样品的矫顽力和剩余磁化强度均大幅提高,但饱和磁化强度明显下降。

Co0.5Ni0.5Fe2O4 nanofibers with diameter of 150-400 nm were fabricated by sol-gel method combined with electrospinning technology.The as-prepared fiber samples were characterized by means of TG-DTA,XRD,FTIR,FESEM,TEM and VSM techniques.The results show that the pure resultant products with spinel structure are basically formed after calcining the precursor fibers at 450 ℃ for 2 h.With the increase of the calcination temperature,the fiber diameters decrease and the mean size（D） of Co0.5Ni0.5Fe2O4 grains within the fibers gradually increase.As a result,the fiber surface morphology gradually transforms from a porous structure to a necklace-like structure.The saturation magnetizations（Ms） of the obtained Co0.5Ni0.5Fe2O4 nanofibers monotonously increase from 35.8 A·m2/kg at 450 ℃ to 80.2 A·m2/kg at 1 000 ℃ while the corresponding coercivities（Hc） initially increase and then decrease,and reaches the maximum value at about 550 ℃,which indicates that the single-domain critical size of Co0.5Ni0.5Fe2O4 in the form of nanofibers is around 30 nm.Hc of the nanofibers varies as D0.71 in a D range below the single-domain critical size,which is in good agreement with the result predicted on the basis of the random anisotropy model.In addition,the magnetic properties measured at low temperature（77 K） show the substantial enhancements in both coercivity and remanent magnetization and a relatively obvious reduction in saturation magnetization compared to the corresponding room-temperature values.