The Preparation And Properties Of Barium Ferrite Based Nanofiber Materials By Electrospinning

In recent years, with the rapid development of electronics, information and communications industries, as the important building blocks of these industries, the magnetic materials have been importantly applications in high-density magnetic memories, sensitive elements, permanent magnet and electromagnetic wave absorbing materials. Recently, it is found that nanomaterials have unique physical and chemical properties, and have been widely studied. Similarly, the magnetic nanomaterials have been intensively studied and a wide range of applications. In particular, it is found that one dimension (ID) magnetic nanomaterials have not only distinctive effect of common nanomaterials, but also unique shape and magnetic anisotropy. Thus,1D magnetic nanomaterials are being widely studied. As the hard magnetic material, barium ferrite exhibits high saturation magnetization and coercivity, high Curie temperature, as well as its excellent chemical stability and corrosion resistivity and has been become one of the key points of magnetic materials.As we all know, electrospinning technology has been proven to be the most simple and effective way of the preparation of nanofiber materials. However, the nanofibers or magnetic nanofibers prepared by electrospinning have a random orientation, so the shape and magnetic anisotropy are difficult to be achieved. Thus, the research in the magnetic nanofibers should be focused on the preferred orientation, the intrinsical relation between electromagnetic properties and microstructure, and developing the application of magnetic nanofibers is of great scientific and commercial interest. Furthermore, the crystalline state, phase composition and the particle size and morphology have an important effect on the magnetic properties of barium ferrite nanofibers. In this paper, firstly, the aligned poly(ethylene terephthalate)(PET)/critic acid (CA) composite nanofibers were prepared by eoectrospinning. Secondly, the precursor solution was produced by sol-gel method using Ba(N0s)2), Fe(NO3)3·9H2O and C6H8O7·H2O as basic raw materials. Finally, the aligned BaFe12O19nanofibers were prepared via coating PET/CA nanofiber template using the precursor solution, then drying and calcining template. The results show that the average diameter of aligned BaFe12O19nanofibers is ca.900nm, and the nanofiber is composed of numerous nanocrystallites stacking alternatively along the long axis of fiber. The crystallites possess a hexagonal plate-like shape and the size of these nanocrystallites ranges from120to400nm, and the thickness of crystal is ca.20nm. The aligned BaFe12O19nanofibers exhibit obviously magnetic anisotropy, with the saturation magnetization (My) of68.468and55.712A m2/kg in parallel and perpendicular configuration respectively. Thus, the results indicate that the easily magnetized orientation of the aligned BaFe12O19nanofibers is parallel to its long axis.In order to tune the magnetic properties of BaFe12O19nanofibers, the Al doped and Al-Sr codoped BaFe12O19nanofibers were prepared. The results show that the BaFe12O19crystallites possess a hexagonal plate-like shape at x=0while they become rod-like with various Al3+ion substitution. The average grain size decreases with Al3+ion substitution content x increasing. The magnetic testing shows that saturation magnetization (Ms) decreases obviously from63.92A m2/kg-1(x=0) to29.70A m2/kg-1(x=2.0), while coercive force (Hc) increases significantly from288.2kA/m (x=0) to740.7kA/m (x=2.0) with Al3+ions content increasing. For the series of Al-Sr doping, the crystallites possess a rod-like shape with Al doping and the grain size decreases with Al doping, however, the Sr doping have little effect on the morphology and size of crystallite. With the same amount of Al doping, and changing the amount of Sr doping, the Ms decreases firstly, with Ms of54.42A m2kg-1at x=0and Ms=42.60A m2kg-1at x=0.4, then remain unchanged with the further increase of Sr doping. Hc changes with the increase of Sr doping due to the formation of the two crystals of barium ferrite and strontium ferrite, and Sr incorporating into the lattice of BaFe12O19.