共查询到20条相似文献,搜索用时 31 毫秒
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α-Fe2O3 nanodiscs and Mn3O4 nanoparticles have been prepared by the 1,10-phenanthroline as complexing agent in the presence of sodium hydroxide under hydrothermal conditions. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) spectra. The average diameter of α-Fe2O3 nanodiscs is of 2 μm. In the case of Mn3O4 sample, the Mn3O4 crystallites are nanoparticles with an average size of 34 nm. A formation mechanism for the α-Fe2O3 and Mn3O4 nanomaterials was proposed. 相似文献
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N.R. Panda B.S. Acharya P. Nayak S.P. Pati B.K. Nath D. Das 《Physica B: Condensed Matter》2012,407(14):2716-2720
Synthesis of nanocomposites of iron oxide & chromium oxide (α-Fe2O3–Cr2O3) with different concentrations was carried out by a wet-chemical method and the structural, optical and hyperfine properties have been investigated. The prepared nanocomposites were characterized by powder X-ray diffractometry (PXRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV–VIS spectroscopy, Fourier transformed infrared (FTIR) spectroscopy and Mössbauer spectroscopy. XRD measurements confirmed the formation of pure phase composites having particle sizes in nanometer regime. The same has been corroborated by TEM micrographs, which revealed that the formation of monodispersed nanocomposites have the average particle size 44 nm. Mössbauer study of the samples showed the transition of iron oxide from anti-ferromagnetic state to paramagnetic state having a typical relaxation in the spectrum with increasing concentration of Cr2O3. 相似文献
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Ultrafine α-Fe2O3 nanoparticles with an extremely narrow distribution were synthesized by microwave heating. Transmission electron microscopy (TEM) images showed that most primary particles have ellipsoid shapes, and the average diameter of the primary particles was less than 10 nm. The electron diffraction pattern and fringes in some particles in TEM images showed that these nanoparticles were single crystals. The BET surface area of the freeze-dried product was 217 m2/g. The initial discharge capacity of the α-Fe2O3 nanoparticles exceeded 1007 mA/g (cut-off voltage: 0.5 V). This large capacity corresponds to that calculated by assuming the reduction of Fe3+ to Fe0. The α-Fe2O3 nanoparticles also work as a rechargeable electrode material. The charge-discharge test between 4 V and 1.5 V gave a good rechargeable capacity of about 150 mAh/g. 相似文献
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Shao-Wen Cao Guo-Feng Cheng Yue-Hong Huang 《Journal of Physics and Chemistry of Solids》2010,71(12):1680-1683
We report the preparation of a novel kind of α-Fe2O3 hollow core/shell hierarchical nanostructures self-assembled by nanosheets. A green precursor powder is first prepared using nontoxic and inexpensive FeCl3 and urea in ethylene glycol by a surfactant-free solvothermal method at 160 °C for 15 h. The α-Fe2O3 hollow core/shell hierarchical nanostructures are obtained by the thermal treatment of the green precursor powder. The as-prepared α-Fe2O3 hollow core/shell hierarchical nanostructures are porous, and exhibit a good photocatalytic activity for the degradation of phenol. The samples are characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). 相似文献
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Changqing Dong Shuhui ShengWu Qin Qiang LuYing Zhao Xiaoqiang WangJunjiao Zhang 《Applied Surface Science》2011,257(20):8647-8652
The dominant growth planes (0 0 0 1) and (1 1 0 2) have been used to investigate the activity of the natural α-Fe2O3 in chemical-looping combustion system based on density functional theory (DFT) calculations. In the chemical-looping combustion system, CO is selected as the probe fuel gas to detect the activities of the different surfaces. CO interacts stronger to Fe2O3 (1 1 0 2) than Fe2O3 (0 0 0 1). CO can be oxidized into CO2 species directly on Fe2O3 (1 1 0 2) rather than Fe2O3 (0 0 0 1). The formation of CO2 accompanying with a transformation from hematite to magnetite acted as the key step for the reduction process of hematite. 相似文献
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The stability and electronic properties of carbon in α-Al2O3 are investigated using density functional theory. In the host lattice, the substitutional C prefers the Al site under the O-rich conditions, whereas the O site is preferred by carbon under the Al-rich conditions. The calculated results predict a direct relationship between the thermodynamic and optical transition levels with the degree of the local distortion induced by C in the alumina lattice. We also find C at the O site acts as a charge compensator to stabilize the F+ center, thereby enhancing the TL signal at 465 K. Also, C at Al site can serve as electron traps for TL emission process in α-Al2O3. 相似文献
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Highly sensitive gas sensors are realized from In2O3 mixed α-Fe2O3 nanorods. At 200 °C, the sensitivity of the sensors upon exposure to 200 ppm ethanol is 31.3, and the sensors exhibit linear dependence of the sensitivity on the ethanol concentration at 100 °C and 200 °C. In contrast, nonlinear gas sensing characteristics are observed at 300 °C and 400 °C. The relationship between sensitivity and ethanol concentration is discussed by using the conduction model, and the experimental data are in good agreement with the obtained equations. Our results imply that In2O3 mixed α-Fe2O3 nanorods are good candidates for nano-scale gas sensors and the relationship between sensitivity and ethanol concentration is significantly influenced by temperatures. 相似文献
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Hongyang Zhu Yanzhang Ma Haibin Yang Dongbin Hou 《Journal of Physics and Chemistry of Solids》2010,71(8):1183-9232
Phase transition and bulk moduli of bulk and nanocrystalline γ-Fe2O3 were studied using synchrotron X-ray diffraction under high pressure. Contrary to most other nanomaterials, nanocrystalline γ-Fe2O3 begins to transform into α-Fe2O3 at the same pressure as bulk γ-Fe2O3, which is caused by a special structure of γ-Fe2O3, in which there exist vacancies of crystal. It is believed that phase transition starts from a certain site of vacancy because of the stress concentration at vacancy sites. Compared to bulk material, nanocrystalline γ-Fe2O3 has a larger bulk modulus, which is ascribed to the large ratio of surface to volume. 相似文献
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α-Fe2O3 nanobelts and nanoflakes have been successfully synthesized by oxidation of iron-coated ITO glass in air. The X-ray diffraction, Raman spectrum and scanning electron microscopy are carried out to characterize the nanobelts and nanoflakes. The formation mechanism has been presented. Significantly, the magnetic investigations show that the magnetic properties are strongly shape-dependent. The magnetization measurements of belt-like and flake-like α-Fe2O3 in perpendicular exhibit ferromagnetic feature with the coercivity (Hc) and saturation magnetization (Ms) of 334.5 Oe and 1.35 emu/g, 239.5 Oe and 0.12 emu/g, respectively. For the parallel, belt-like and flake-like α-Fe2O3 also exhibit ferromagnetic feature with the Hc and Ms of 205.5 Oe and 1.44 emu/g, 159.6 Oe and 0.15 emu/g, respectively. 相似文献
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Zhi-Jian Chen Yi-Lin Chen Ke-Zhi Zhang Bin Li Hai Zhu 《Journal of Physics and Chemistry of Solids》2010,71(5):841-368
Mesoporous α-Fe2O3-pillared titanate nanocomposites have been successfully synthesized through an exfoliation−restacking route. Powder X-ray diffraction and N2 adsorption-desorption isotherms revealed that the α-Fe2O3 pillared titanate has an interlayer distance of 3.27 nm, a specific surface area of 66 m2/g and an average pore size of 7.6 nm, suggesting the formation of a mesoporous pillared structure. UV-vis diffuse reflectance spectra show a red shift, indicative of a narrow band gap energy of ∼2.1 eV compared to the host layered titanate, which is essential in creating a visible light photocatalytic activity. The results of degradation of rhodamine B reveal that the present pillared mesoporous composites exhibit better photocatalytic activities than those of the pristine materials under visible irradiation, based on the band gap excitement and the dye-sensitized path, originated from their high surface area, mesoporosity and the electronic coupling between the host and the guest components. 相似文献
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T.J. Bastow A. Trinchi M.R. Hill R. Harris T.H. Muster 《Journal of magnetism and magnetic materials》2009,321(17):2677-2681
The identification by 57Fe internal field nuclear magnetic resonance (NMR) of hyperfine fields at four Fe sites in the (average) tetragonal unit cell of vacancy-ordered γ-Fe2O3 (maghemite) is reported. The effects of vacancy redistribution due to annealing the partially vacancy-ordered form has been observed in the 57Fe lineshape. In addition, the reduction of the particle size of the vacancy-ordered form has been observed to gradually eliminate the vacancy ordering and then to cause a transition from ferrimagnetism to superparamagnetism. 相似文献
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包钴型γ-Fe2O3磁粉分为包钴γ-Fe2O3(简记为Co-γ-Fe2O3)和包钴包亚铁γ-Fe2O3(简记为CoFe-γ-Fe2O3)两种,它们的矫顽力可比γ-Fe2O3磁粉的提高100至400Oe左右,本工作对这两种磁粉矫顽力增大的原因作了探讨,认为它们矫顽力增大的机制不同:CO-γ-Fe2O3矫顽力增大是由于表面包覆一层Co(OH)2使表面各向异性增大,而CoFe-γ-Fe2O3则是由于表面包覆的是钴铁氧体,γ-Fe2O3与钴铁氧体之间发生耦合作用,使矫顽力增大。 相似文献
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Zhongzhu Wang Hong Bi Jian Liu Tao Sun Xianliang Wu 《Journal of magnetism and magnetic materials》2008
The conducting protonated polyaniline (ES)/γ-Fe2O3 nanocomposite with the different γ-Fe2O3 content were synthesized by in-situ polymerization. Its morphology, microstructure, DC conductivity and magnetic properties of samples were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), four-wire-technique, and vibrating sample magnetometer (VSM), respectively. The microwave absorbing properties of the nanocomposite powders dispersing in wax coating with the coating thickness of 2 mm were investigated using a vector network analyzers in the frequency range of 7–18 GHz. The pure ES has shown the absorption band with a maximum absorption at approximately 16 GHz and a width (defined as frequency difference between points where the absorption is more than 8 dB) of 3.24 GHz, when 10% γ-Fe2O3 by weight is incorporated , the width is broadened to 4.13 GHz and some other absorption bands appear in the range of 7–13 GHz. The parameter dielectric loss tan δe (=ε″/ε′) in the 7–18 GHz is found to decrease with increasing γ-Fe2O3 contents with 10%, 20%, 30%, respectively, but magnetic loss tan δm (=μ″/μ′) increases with increasing γ-Fe2O3 contents. The results show that moderate content of γ-Fe2O3 nanoparticles embedded in protonated polyaniline matrix may create advanced microwave absorption properties due to simultaneous adjusting of dielectric loss and magnetic loss. 相似文献
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α-Fe2O3/MWCNTs composites were prepared by a simple hydrothermal process. The crystalline structure and the electrochemical performance of the as-synthesized samples were investigated. Results show that as anode materials for lithium-ion batteries, the α-Fe2O3/MWCNTs exhibit an initial discharge capacity of 1256 ± 5 mAh g−1 and a stable specific discharge capacity of 430 ± 5 mAh g−1 at ambient temperature, for up to 100 cycles with no noticeable capacity fading, while the initial discharge capacity of the bare Fe2O3 is 992.3 mAh g−1, and the discharge capacity is 146.6 mAh g−1 after 100 cycles. Moreover, the α-Fe2O3/MWCNTs composites also exhibit excellent rate performance. 相似文献
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I.V. VasylenkoS.V. Kolotilov I.E. KotenkoK.S. Gavrilenko F. TunaG.A. Timсo R.E.P. WinpennyV.V. Pavlishchuk 《Journal of magnetism and magnetic materials》2012,324(4):595-601
Thermal decomposition of the trinuclear complex [Fe2CrO(CH3COO)6(H2O)3]NO3 at 300, 400 and 500 °C gave γ-Fe2O3 nanoparticles along with amorphous chromium oxide, while decomposition of the same starting compound at 600 and 700 °C led to the formation of α-(Fe2/3Cr1/3)2O3 nanoparticles. Size of γ-Fe2O3 nanoparticles, determined by X-ray diffraction, was in the range from 9 to 11 nm and increased with formation temperature growth. Average size of α-(Fe2/3Cr1/3)2O3 nanoparticles was about 40 nm and almost did not depend on the temperature of its formation. γ-Fe2O3 nanoparticles possessed superparamagnetic behavior with blocking temperature 180-250 K, saturation magnetization 29-35 emu/g at 5 K, 44-49 emu/g at 300 K and coercivity 400-600 Oe at 5 K. α-(Fe2/3Cr1/3)2O3 nanoparticles were characterized by low magnetization values (2.7 emu/g at 70 kOe). Such magnetic properties can be caused by non-compensated spins and defects present on the surface of these nanoparticles. The increase of α-(Fe2/3Cr1/3)2O3 formation temperature led to decrease of magnetization (being compared for the same fields), which may be caused by decrease of the quantity of defects or non-compensated spins (due to decrease of particles' surface). 相似文献
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S. Masoud Hosseini E. Ghasemi H. Ahmadi Moghaddam 《Journal of magnetism and magnetic materials》2010,322(23):3792-3796
A stable γ-Fe2O3 paraffin-based ferrofluid was prepared via high energy milling. The magnetic particles were characterized using X-ray diffraction, dynamic light scattering and vibrating sample magnetometer techniques. The rheological properties of the ferrofluid were studied using a standard rotating rheometer. The magnetoviscous effect and thixotropy in the ferrofluid were studied. The formation and destruction of magnetically induced structures and the interactions of nanoparticles and aggregates are discussed. 相似文献