一维Ni_(0.5)Zn_(0.5)Fe_2O_4/SiO_2复合纳米结构的制备及其磁性能

Preparation of one-dimensional Ni_(0.5)Zn_(0.5)Fe_2O_4/SiO_2 composite nanostructures and their magnetic properties

采用溶胶-凝胶法结合静电纺丝技术制备了Ni0.5Zn0.5Fe2O4/SiO2复合纳米纤维.利用热重-差热分析、X射线衍射、场发射扫描电镜、高分辨透射电镜和振动样品磁强计研究了前驱体纤维的热分解及相转化过程以及焙烧温度和SiO2含量对目标纳米纤维的相组成、微观结构、形貌及磁性能的影响.结果表明,在450℃焙烧时,立方尖晶石结构已基本形成.随着焙烧温度由450℃升高到1000℃,(Ni0.5Zn0.5Fe2O4)90(SiO2)10复合纳米纤维中Ni0.5Zn0.5Fe2O4晶粒的平均尺寸以及纤维的比饱和磁化强度和矫顽力都增大.非晶SiO2的加入有效抑制了Ni0.5Zn0.5Fe2O4晶粒的生长,经900℃焙烧2h制得的Ni0.5Zn0.5Fe2O4/SiO2复合纤维中Ni0.5Zn0.5Fe2O4的平均晶粒尺寸由无SiO2时的81.6nm减小到SiO2含量为20%时的13.3nm,导致样品的磁畴结构由多畴向单畴转变,比饱和磁化强度单调下降,而矫顽力则呈现先增大后减小的趋势.同时,伴随着非晶SiO2含量的增加,复合纳米纤维的直径逐渐增大,表面也越趋光滑.

The Ni0.5Zn0.5Fe2O4/SiO2 composite nanofibers were prepared using sol-gel process combined with electrospinning.The thermal decomposition and phase inversion process of precursor nanofibers and the effects of calcination temperature and SiO2 content on the phase composition,microstructure,morphology and magnetic property of the resulting nanofibers were studied by means of thermogravimetric and differential thermal analysis,X-ray diffraction,field emission scanning electron microscopy,high resolution transmission electron microscopy and vibrating sample magnetometer.The experimental results show that the cubic spinel structure is basically formed when the precursor nanofibers are calcined at 450 ℃ for 2 h.The average grain size of Ni0.5Zn0.5Fe2O4 contained in the composite nanofibers with 10 % SiO2 and their specific saturation magnetization and coercivity increase with increasing calcination temperature.Amorphous SiO2 additive can effectively restrain the growth of Ni0.5Zn0.5Fe2O4 nanocrystals.As a result,with SiO2 content increasing from 0 to 20 %,the average grain size of Ni0.5Zn0.5Fe2O4 in the prepared Ni0.5Zn0.5Fe2O4/SiO2 composite nanofibers calcined at 900 ℃ for 2 h decreases from 81.6 to 13.3 nm,and the specific saturation magnetization of these samples monotonically decreases,whereas the coercivity initially increases and then decreases due to the change of magnetic domain structure from multi-domain to single-domain along with the reduction in grain size.In addition,with the increase of SiO2 content,the diameter of the as-prepared Ni0.5Zn0.5 Fe2O4/SiO2 composite nanofibers gradually increases and the surface becomes smooth.