The Synthesis And Properties Of Iron Oxide(Hydroxide) Nano Structures

Iron oxide (or hydroxide) is rich in the earth, and is environmentally friendly. In recent years, research shows that iron oxide (or hydroxide) nanomaterials have a variety of application in paints, catalysts, gas sensors, magnetic recording materials, electrode materials, and biological fields etc. The morphology, size, and dimensions of the nanostructures influence their properties and application value. It is therefore significant to synthesize the nanomaterials with different shapes and structures via various method. In this thesis, we have synthesized several iron oxide (or hydroxide) nanomaterials with different shapes and structures via hydrothermal method with different reaction conditions, and we have also studied their morphology, structure, crystal phase, magnetic, electric catalysis and adsorption properties, etc. The growth mechanism has been discussed. The main contents are as follows:1. The synthesis and properties of a-Fe2O3nanoparticles(1)The synthesis and properties of a-Fe2O3nanoparticlesThe a-Fe2O3nanoparticles have been prepared using FeCl3,HAc and NHs·H2O as raw materials via hydrothermal method. The morphology and nanostructure of the sample synthesized have been analyzed by XRD, SEM, TEM, SAED, UV-vis and Raman. The UV-vis experiment shows that the a-Fe2O3nanoparticles exhibit an indirect transition at1.89eV and an direct transition at1.96eV, respectively, which match well with hematite (1.9～2.3eV).The removal efficiencies of Cr(Ⅵ) reaches60.4%. The electrocatalytic experimental indicated that the a-Fe2O3nanoparticles exhibites elecrocatalytic activity to H2O2.The a-Fe2O3nanoparticles exhibit weak ferromagnetic behaviors at room temperature.(2) The synthesis and properties of a-Fe2O3parallelepiped nanoparticles The well-defined a-Fe2O3parallelepiped nanoparticles have been successfully synthesized through a facile hydrothermal route at low temperature using FeCl3and NaAc as raw materials without any surfactants and templates. The microstucture, morphology and crystal phase of them are characterized by XRD, SEM, TEM and Raman. The primary faces of a-Fe2O3parallelepiped nanoparticles are (012),(104) and(112).2. The synthesis and properties of hierarchical nanostructures(1) The dendrite a-Fe2O3has been synthesized using K4[Fe(CN)6], polyethylene glycol (PEG400) and H2O2as raw materials by hydrothermal method. The morphology and microstructure of the product have been characterized by XRD, SEM, TEM, HRTEM, SAED, and Raman. It has been revealed that the main trunk of a-Fe2O3grows along [1010] while the branches grow along [1100] and [0110]. Furthermore, the growth process and formation mechanism of the products have been discussed.(2) The synthesis and properties of Fe3O4nanoparticles aggregates and hollow spheresThe Fe3O4nanoparticles aggregates and hollow spheres have been synthesized via a solution-thermal method with CTAB(or n-octadecylamine) as soft templates. The morphology, structure and growth mechanism of them were studied by XRD, SEM and TEM. The hollow spheres were formed via an oriented attachment growth mechanism. The reason why the structures of samples synthesized with different surfactants are different was discussed. The magnetic properties of them are different, and the factors for their different magnetic properties were discussed.(3) The synthesis and properties of a-FeOOH microspheresThe a-FeOOH microspheres self-assembled with nanosheets have been synthesize by a facile surfactant-free hydrothermal route at low temperature and in a short time, using K.3[Fe(CN)6].3H2O and NaOH as raw materials. The angles between two nanosheets are30°,60°,90°。The growth mechanism also has been discussed by TEM. The coercive force of the a-FeOOH microsphere is150Oe, it can be considered as a semi-hard magnetic material.