Study On Preparation And Static Magnetic Property Of Iron Fiber

Iron fiber, as an excellent radar absorbing material, has unique shape anisotropy. Compared with other isotropy materials, iron fiber not only possesses the characteristic of light weight, but also has the advantages of strong absorbing and wide frequency band due to its multiple loss mechanism.a-FeOOH fiber was prepared with FeSO4 and NaOH as raw materials by the liquid phase deposition method and then a-Fe fiber was made from oc-FeOOH through the process of dehydration and reduction. The morphologies and structures of as-prepared samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The properties of heat and magnetism were characterized by thermogravimetry (TG-DSC) and vibrating sample magnetometer (VSM).The growth of a-FeOOH fiber included the nucleation and the grain growth. The shape and aspect ratio of a-FeOOH fiber was closely linked with the rate of the nucleation and the grain growth. It was found that the preparation process was influenced by many factors. The appropriate alkali ratio was 3.5; some adulterants might increase the aspect ratio of fiber; the optimal temperature was 30~40℃. High concentration reactant could accomplish the nucleation quickly and separate it from the grain growth. This method had the same effect as atmosphere protection. Secondary growth was a process, based on a-FeOOH first formed. The experiments indicated that the secondary growth was an effective method to increase the length and diameter of fiber, but it was necessary to control the occasion.α-Fe fiber could be obtained from a-FeOOH through the process of dehydration at 500℃ for 1 h and reduction at 480℃ for 6 h. a-FeOOH contained three endothermic peaks: planar water was dehydrated at 100℃;inclusion water was dehydrated at 270℃; structural water was dehydrated at 350℃. The length of fiber was 1 μm and the aspect ratio was 10~20 approximately. About the static magnetic property, with the temperature increasing, the saturation magnetization increased, at first increasing obviously, and then increasing slowly; at the meantime, the coercive force increased gradually, reaching a maximum at 480℃, but then decreased rapidly. Iron fiber had magnetic anisotropy and it could be oriented by magnetic field.