Design, Synthesis And Magnetic Properties Of Some Micro-and Nano-structured Magnetic Materials

Micro- and nano-structured magnetic materials, including ferrites, ferromagnetic metal oxides, and ferromagnetic metals and alloys etc, are very important functional materials. The synthesis, characterization and magnetic properties of micro- and nano-structured magnetic materials have become a hot topic in magnetism research areas and are attracting a growing interest because of the potential applications such as electron, communication, automobile, aerospace, biology and medicine, et al. More and more attentions have been paid to the studies of the synthesis and magnetic properties of those magnetic materials with uniform morphologies. In this dissertation, many efforts have been made to design and synthesize micro- and nanostructured magnetic materials. The formation mechanisms and magnetic properties of these materials have also been systematically studied. The main contents and major results are given as follows:(1) Uniform-sized, monodisperse and single-crystal magnetite hollow spheres with a diameter of 200–300 nm and a shell thickness of ~50 nm have been successfully synthesized in high yield using a template-free solvothermal route. We systematically investigated the influence of synthetic conditions on the morphology, structures and magnetic properties, and proposed the formation mechanism for the magnetite hollow spheres.(2) Hematite of three dimensional (3D) superstructures has been successfully prepared by a hydrothermal synthetic route based on the reaction between ferrous sulfate and sodium chlorate. An interesting feature is that 3D urchin-like and single-crystalline cantaloupe-like hematite superstructures can be controllably obtained by adjusting the synthetic conditions. The formation mechanism and magnetic properties of the hematite superstructures have been investigated.(3) Novel three dimensional (3D) Co dendritic superstructures and hierarchical nanostructured microspheres were successfully prepared by a simple hydro- and solvothermal reduction route. The influence of synthetic conditions on the morphology, structures and magnetic properties of the metallic Co were systematically investigated. The possible formation processes of the two metallic Co with different structures and morphologies were proposed.(4) Chain-like NiCo alloy assemblies with a length of up to 6–7μm were successfully prepared by a hydrothermal synthetic route in the presence of cetyltrimethylamonium bromide (CTAB) or cetyltrimethylamonium chloride (CTAC). We have investigated the influence of synthetic conditions on the morphology and structures. Investigation on the influence of the morphology and structures on the magnetic properties of NiCo alloy has been performed.