Morphology And Magnetic Properties Of Nano-sized Ferrite

Nanomagnetic materials attract much interest not only for many industrial applications but also from academic viewpoint. Currently, one of the trends in magnetic nano-materials study is new way of preparation, including particle size, surface shape and microstructure control. Due to the small size of nanoparticles, surface effect and quantum size effects play important role in physical properties of the nanomaterials, so how to control these effects, and to obtain best properties becomes the main issue in nano-material study. In the present work, the studies on the preparation, characterization and applications of magnetic nanomaterials were carried out. The contents include the study on hydrothermal preparation and magnetic properties of spherical Fe3O4 nanocrystals, study on hydrothermal preparation and magnetic properties of octahedron Fe3O4 nanocrystals of ball-type a-Fe2O3 microspheres self-preparation and magnetic properties of groups, as well as the investigation of adsorption performance of these materials.Firstly, we have developed a novel method for synthesizing the magnetic spherical Fe3O4 nanocrystals via the hydrothermal method by using ferrous sulfate (FeSO4·7H2O) and ammonia (NH3·H2O) as raw materials, and glucose acted as both a template and reductant. X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) were used to characterize the as-synthesized samples. The growth mechanism of Fe3O4 nanocrystals and experimental parameters effects on morphology were also discussed. The results indicate that the spherical aggregates are formed by the self-assembling among the Fe3O4 primary nanoparticles (～30 nm), and the average size of the spherical particles is around 1μm. Spherical Fe3O4 nanocrystals exhibit high saturation magnetization and coercivity of 90.05 emu/g and 140 Oe, respectively. This paper also studied the magnetic octahedron Fe3O4 nanocrystals were synthesized via the hydrothermal method by using ferrous sulfate (FeSO4·7H2O) and ammonia (NH3·H2O) as raw materials, and hydrazine hydrate acted as both a template and reductant. XRD, SEM and VSM were used to characterize the as-synthesized samples. The results indicate that the prepared samples from the different size Octahedron Fe3O4 nanocrystals (particle size of 100nm～1μm) composition, octahedron Fe3O4 nanocrystals exhibit high saturation magnetization and coercivity of 93.82 emu/g and 39.09 Oe, respectively.Finally, we citric acid as complexing agent and the structure directing agent by hydrothermal synthesis technology, in the glass film was successfully prepared on a uniform dispersion of theα-Fe2O3 microspheres. The microspheres are first formed leaf-like nanosheets according to "1D→3D" pattern made self-assembly.