Papers by Keyword: α-Fe₂O₃

Abstract: Iron titanium oxides with different Ti:Fe ratios (molar ratio: 3:1, 2:1, 1:1, 1:2, 1:3) have been prepared by chemical coprecipitation process. The structures and properties of the samples have been characterized by X-ray diffraction, vibrating sample magnetometer and UV-vis spectrophotometer. Results show that the samples annealed at 460 °C have poor crystallinity. At 550 °C, the crystallinity of all the samples increased strikingly. The iron titanium oxides contained anatase TiO₂, rutile TiO₂, α-Fe₂O₃ and/or Fe₂TiO₅. Ti:Fe ratios have a great influence on the detailed phase compositions of each sample. The iron titanium oxides exhibited paramagnetism and the intensity of magnetization increased with the increasing content of Fe. Band gap energies of the oxides changed slightly with increasing content of Fe with an average value of 2.0 eV, obviously lower than that of TiO₂ .

Abstract: Fe₂O₃/Ga₂O₃ composite and GaFeO₃ electrodes worked as rechargeable electrode materials for lithium-ion batteries, whereas their capacities were gradually decreased with increasing of cycle number. The initial Li insertion capacities (cut-off voltage: 0.01 V) were 1643 mAh/g for Fe₂O₃/Ga₂O₃ composite and 1196 mAh/g for GaFeO₃, respectively. Despite same Fe/Ga atomic ratio, Fe₂O₃/Ga₂O₃ composite showed a higher capacity than that of GaFeO₃ over the 50 cycles.

Abstract: A novel synthetic method was developed for the preparation of core-shell composites consisting of α-Fe₂O₃ cores with poly(styrene-co-methyl methacrylate) (P(St-co-MMA)) shells via emulsion copolymerization of styrene and methyl methacrylate monomer with surfactant of PVP. The structure, morphology and thermal properties of the composites were been characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). The results confirmed that there was no chemical interaction between α-Fe₂O₃ and copolymer, and the onset of thermal decomposition for nanocomposites shifted to a higher temperature than that for neat copolymer.

Abstract: Hematiete (α-Fe2O3) nanotube arrays (NTAs) were prepared on the iron foil by the anodization method in an ethylene glycol electrolyte containing NH4F and deionized water. The α-Fe2O3 NTAs electrodes were characterized by field-emission scanning electron microscopy, grazing incidence X-ray diffraction and UV-vis absorbance spectra. As the anodization processed, the morphology of the foil transformed from nanoporous to nanotube arrays.The resulting α-Fe2O3 NTAs showed a pore diameter of 40 nm, thickness of 1.5 μm, and a minimum wall thickness of 10 nm. The photocatalytic activity of the α-Fe2O3 NTAs was evaluated by degradation of azo dye. The significant photocatalytic performance indicated that the α-Fe2O3 NTAs were an effective photocatalyst to decompose organic pollutants.

Abstract: We have succeeded in preparing micro/nanostructured α-Fe2O3 spheres (MNFSs). The resulted MNFSs have an average diameter of about 5 µm, and are constructed by subunits of interlinked and elongated particles with a diameter of 20~60 nm. MNFSs show an obviously structural enhanced Cr(VI) removal capacity (5.88 mg/g) compared with nanoscaled (0.81 mg/g) and microscaled α-Fe2O3 (0.1 mg/g) due to its high specific surface area together with the special porous structure. Moreover, MNFSs show good availability of reusing to remove Cr(VI) ions.

Abstract: Porous α-Fe2O3 nanorods were prepared by the hydrothermal method from FeCl4 and urea without templates. The as-prepared products were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM) analysis techniques. The as-prepared α-Fe2O3 has the porous nanorods structured with the length of about 200 nm, diameter of about 50 nm and high surface area (255.2 m2•g-1). The gas-sensing measurement results demonstrated that the sensor of porous α-Fe2O3 nanorods presented high response to ethanol vapor and which can response to ethanol vapor at low-temperature. Due to the exciting gas-sensing properties, the as-prepared porous α-Fe2O3 nanorods would be an ideal candidate for the application in ethanol sensors.

Abstract: Maghemite (γ-Fe_{Subscript text}2O_{Subscript text}3) and hematite (α-Fe2O3) nanoparticles with various dominant exposure crystal planes were prepared by several different methods. The structure and the reducibility of these materials were investigated by XRD, Raman and H2-TPR technologies, and their catalytic performance for propene oxidation was also discussed. The maghemite (γ-Fe_{Subscript text}2O_{Subscript text}3) showed a better reducibility than hematite (α-Fe_{Subscript text}2O_{Subscript text}3), but its activity for propene oxidation is relatively lower. The exposure crystal plane of hematite has a significant influence on its catalytic activity for propene oxidation. Among the prepared four samples, the hematite-1 sample showed the best activity. The selective growth of any planes with a relative low density of Fe atoms for the α-Fe_{Subscript text}2O_{Subscript text}3 catalyst would lead to an obvious decrease in the catalytic activity.

Abstract: The present work is devoted to the theoretical interpretation of interaction of CO molecule with Pd-doped α-Fe₂O₃ (001) using density functional theory (DFT). Two doping types were taken into account, which either a pair of Fe atoms of α-Fe₂O₃ (001) surface was replaced by Pd or a pair of Pd atoms embedded into the vacancy between surface layer and sub-surface layer of α-Fe₂O₃ (001). Three different active sites of the α-Fe₂O₃(001) surface and the Pd-doped α-Fe₂O₃(001) surface were considered for the interaction between CO and these surfaces. We found that the binding energy of CO on Pd-doped α-Fe₂O₃ (001) surface was much more than that of the clean α-Fe₂O₃ (001) surface. Results indicated metallic atoms are a Subscript text ctive site for adsorption of CO molecule, and the S(001) while interaction between CO molecule and surface doped by replacing Fe atom with Pd atom, stronger interaction happen between CO molecule and Pd embedded-doped α-Fe₂O₃ (001) surface than that between CO molecule and the ideal surface, leading to the formation of CO₂ precursor species.

Abstract: A facile hydrothermal method without any templates has been developed for the preparation of α- Fe₂O₃ nanocubes and hollow spheres. The as-synthesized products is then characterized using X-ray diffraction(XRD), scanning electron microscopy(SEM). The nanocubes have extraordinary unity and we can anticipate its unique magnetic characteristic. On the other hand, the hollow sphere structure has a promising future in the application as carriers for targeting drug delivery. In our opinions, the method is not only very simple, but also is very friendly to the environment.

Abstract: α-Fe₂O₃ hollow microspheres and nanorods were synthesized via a hydrothermal method using glucose and ethylenediaminetetraacetic acid (EDTA) as morphology controlled agents, followed by calcination at 500 °C for 4 h in air. The crystal structures of products were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that the hollow microspheres with diameters of 1-2 μm are consist of nanoparticles (80-100 nm), and the nanorods have a structure in the diameter of 80-100 nm and length about 1 μm. Furthermore, the α-Fe₂O₃ hollow microspheres show higher gas response to ethanol than that of nanorods and nanoparticles.