Synthesis, Characterization And Properties Research Of Iron Oxide And Its Semiconductor Composite

Hemitate （α-Fe₂O₃） is an important n-type semiconductor material with anarrow bandgap, and is used widely in the fields of lithium-ion battery, the gassensing and catalysis. After combining with another inorganic material, thecomposite with the properties of both iron oxide and the inorganic material willbe obtained, which also will show better photocatalysis, magnetic and sensingperformances than the original iron oxide. Therefore, study on iron oxide and itscomposite play a significant role in the development of the functionalsemiconductor materials.In this dissertation, α-Fe₂O₃and its composites with excellent opticalproperty have been synthesized. The detailed studies of the thesis are as follows.1. Synthesis, Characterization and Optical Properties of α-Fe₂O₃Rod BundlesThe tubular precursor was first prepared via a hydrothermal method, andthen the rod-like ferric oxide was further obtained by calcining the as-preparedprecursor500℃for2h. The X-ray diffraction （XRD） and scanning electronmicroscopy （SEM） results showed that: the as-prepared ferric oxide （α-Fe₂O₃）had a hexagonal structure and morphology of the porous rod bundles withaverage diameter of2μm. Its structure units were the porous nanorods, whichhad a diameter of30-50nm and the length of16μm. Ultraviolet-Visible （UV-Vis）data indicated that the maximum absorption wavelength of the as-preparedα-Fe₂O₃was546nm, and its band gap absorption edge was around685nm.2. Synthesis, Characterization and Optical Property of Tube-like α-Fe₂O₃Micro-materialsThe uniform rod-like precursor was synthesized successfully via a facilesolvothermal method. Then, iron oxide tubes were obtained by the thermaltreatment of the rod-like precursors at400℃for3h. The X-ray diffraction （XRD）and scanning electron microscopy （SEM） results showed that the as-preparedproducts were pure Fe₂O₃with hexagonal phase and tube-like morphology. The average diameter and length of the micro-tubes were about2μm and10²0μm,respectively. In additions, Fourier transform infrared （FT-IR） resultsdemonstrated that some SO₂-4ions were adsorbed on the surfaces of theas-prepared iron oxide. Ultraviolet-Visible （UV-Vis） indicated that the maximumabsorption wavelength was around489nm, the band gap absorption edge wasaround566.2nm.3. Preparation of Fe₂TiO₅/TiO₂by Homogeneous Precipitation Method and ItsOptical PropertyThe hydrolyzate of Tetrabuty titanate （TBT） was coated slowly on thesurface of the as-prepared black precursor in part2by the homogeneousprecipitation method, and then the Fe₂TiO₅/TiO₂composite was obtained bythermal treatment of the as-prepared precursor at1000℃for2h. The phase,morphology and size of as-obtained composite were characterized by X-raydiffraction （XRD）, scanning electron microscope （SEM）. The results showed that:the product was made of Orthorhombic Fe₂TiO₅and Tetragonal TiO₂; themorphology was one-dimensional tube with200nm particles accumulated, itsaverage length and diameter were about5μm and800nm, respectively. TheUV-Vis results showed that the band gap value of Fe₂TiO₅/TiO₂composite was3.22eV.4. Synthesis, Characterization and Optical property of SnO₂and SnO₂/α-Fe₂O₃Nanao/Micro-materials（1） Cassiterite SnO₂microspheres were prepared via a solvothermal routeusing ethanol as the solvent; then SnO₂/α-Fe₂O₃composite was further obtainedusing a hydrothermal method in the presence of the as-prepared SnO₂microspheres. XRD and SEM showed that the as-prepared SnO₂microspherehad tetragonal phase （cassiterite）, and the average diameter was about2.0μm.When the SnO₂/α-Fe₂O₃composite was formed, the diameter of microspheresincreased to2.5μm. The newly-formed α-Fe₂O₃particles had hexagonal phase,and appeared on the surface of SnO₂microspheres with the size was about200nm. Then, the impact of the products with different molar ratio of SnO₂andFe³⁺on UV-Vis shielding was studied. The results showed that: the compositewith the molar ratio1:2showed a best ultraviolet shieding effect in theultraviolet region, while the composite with the molar ratio1:1showed a best light shielding effect in the visible light region.（2） SnO₂nanoparticle was obtained by solvothermal method, and then theSnO₂/α-Fe₂O₃composite was prepared by the multiple solvothermal method. Theas-prepared products were characterized by XRD and SEM. The results showedthat: the diameter of the tetragonal SnO₂was ranged from100nm to800nm; thecomposite was made of tetragonal SnO₂and hexagonal α-Fe₂O₃, and thediameter of the SnO₂/α-Fe₂O₃nanospheres was ranged from200nm to800nm,with the α-Fe₂O₃particles of average size was80nm coated on its surface. Inaddition, the UV-Vis results showed that: the photoresponse of the SnO₂/α-Fe₂O₃composite was wider than that of SnO₂.5. Synthesis and adsorption/photocatalysis performance of pyrite FeS₂FeS₂crystallites were synthesized successfully via a solvothermal method,using potassium ferrocyanide K₄[Fe（CN）₆]·3H₂O as Fe source, sulfur powder asS source. The phase and morphology of the products were characterized bymeans of XRD and SEM. It was found that the temperature and solvent ratio（VEtOH:VH₂O） play a crucial role in the formation of FeS₂with a cubic phasestructure （pyrite）. Then based on a series of experiments, the possible formationmechanism of pyrite FeS₂crystallites was proposed. In addition, study alsoshowed that the as-prepared pyrite FeS₂crystallites could high-efficiently absorbor photocatalytically degrade some organic dyes such as Methylene blue （MB）,Safranine T, Methyl orange （MO）, Rhodamine B （Rh B） and Pyronine B.