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1.
Hollow α-Fe2O3 irregular microspheres were prepared at 160 °C from a hydrolyzing Fe(ClO4)3 solution by adding sodium polyanethol sulphonate. The particles were characterized by 57Fe Mössbauer, X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy and energy dispersive X-ray spectroscopy. The walls of these hollow particles consisted of elongated subunits composed of elongated and thin α-Fe2O3 rods. The precipitation of hollow α-Fe2O3 irregular microspheres was governed by the preferential adsorption of sulphonate/sulphate groups. The lateral aggregation of elongated thin rods and subunits also played an important role in the formation of hollow α-Fe2O3 irregular microspheres.  相似文献   

2.
Single-crystalline α-Fe2O3 with a micro-snowflake-like morphology has been synthesized though a hydrothermal reaction in a K3[Fe(CN)6] solution without the assistance of any template or surfactant. The morphology and structure of the synthesized hematite were characterized in detail by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. A possible growth process of α-Fe2O3 crystals has been proposed, and NaOH plays a crucial role in the formation of the snowflake-like structure. Additionally, magnetic investigations show that the α-Fe2O3 crystals exhibit a weakly ferromagnetic property at room temperature with a coercive force of 134 Oe and remnant magnetization of 0.67 emu g− 1.  相似文献   

3.
Zirconium particles with irregular morphology and broad size distribution were uniformly coated by spherical α-Fe2O3 crystal grain via a facile route without polymer or surfactant as directing agents. The synthesized α-Fe2O3/Zr composite particles were characterized by X-ray diffraction, scanning electron microscopy, energy dispersion X-ray, UV-vis spectroscopy and Raman spectroscopy. The synthesis mechanism could be explained by cooperated heterogeneous nucleation and solid state transformation reaction. The combustion properties of α-Fe2O3/Zr composite particles were investigated. Compared with Zr particles, the combustion lasting time decreased from 16 s of Zr particles to 0.13 s of α-Fe2O3/Zr composite particles, and the top point of temperature reached in combustion increased from 2004 °C of Zr particles to 2378 °C of α-Fe2O3/Zr particles.  相似文献   

4.
Polyhedral nanocrystals of α-Fe2O3 are successfully synthesized by annealing FeCl3 on silicon substrate at 1000 °C in the presence of H2 gas diluted with argon (Ar). Uniformly shaped polyhedral nanoparticles (diameter ~ 50-100 nm) are observed at 1000 °C and gases flow rate such as; Ar = 200 ml/min and H2 = 150 ml/min. Non-uniform shaped nanoparticles (diameter ~ 20-70 nm) are also observed at an annealing temperature of 950 °C with lower gases flow rate (Ar = 100 ml/min and H2 = 75 ml/min). Nanoparticles are characterized in detail by field-emission electron microscopy (FE-SEM), energy dispersive X-ray (EDX) and high resolution transmission electron microscopy (HRTEM) techniques. HRTEM study shows well resolved (110) fringes corresponding to α-Fe2O3, and selected area diffraction pattern (SADP) confirms the crystalline nature of α-Fe2O3 polyhedral nanoparticles. It is observed that polyhedral formation of α-Fe2O3 nanocrystals depends upon annealing temperature and the surface morphology highly rely on the gas flow rate inside the reaction chamber.  相似文献   

5.
α-Fe2O3 nanorods were synthesized via hydrothermal method. X-ray powder diffraction revealed the formation of rhombohedral α-Fe2O3 single crystal phase with fiber texture. Scanning and transmission electron micrographs analyses showed that the rhombohedral α-Fe2O3 has nanorods in shape with diameters of 40–85 nm and lengths of 150–45,000 nm. Isothermal magnetization vs. applied magnetic field curves measured at room and liquid nitrogen temperatures displayed a variation on magnetic ordering: from weak ferromagnetism at room temperature to not hysteretic behavior at liquid nitrogen temperature that is well described by a Langevin function. Moreover, the zero field cooling-field cooling curves under applied magnetic field of 100 Oe confirms the decreasing of Morin temperature transition due to nanometric size of the samples.  相似文献   

6.
In this work, single-phase α-Fe2O3 nano-particles were first synthesized via Pechini sol-gel method using citric acid and polyethylene glycol-6000 as chelating agents. The structural coordination of as-prepared polymeric intermediates was investigated by FTIR analysis. Thermal behavior of the polymeric intermediates was studied by TG-DTG-DSC thermograms. The structure of the powders calcined at different temperatures was characterized by XRD and FESEM. The single-phase α-Fe2O3 nano-powders with uniform size were prepared when the polymeric intermediate calcined at 600 °C, and the lowest particle size was found to be 30 nm.  相似文献   

7.
Two-dimensional (2-D) α-Fe2O3 monolayers have been successfully prepared by assembling of single-crystalline α-Fe2O3 nanospheres onto the surfaces of quartz slides. Hexamethylene diisocyanate (HDI) has been used as “bridge” to link between quartz surface and single-crystalline α-Fe2O3 nanospheres. The resulting monolayers have been characterized by transmission electron microscopy (TEM) and scan electron microscopy (SEM), and the correlated surface-enhanced Raman scattering (SERS) effect has been investigated. It is found that the well ordered monolayers of single-crystalline α-Fe2O3 nanospheres can be used as nicer substrates for SERS.  相似文献   

8.
A novel method was utilized to synthesize one-dimensional β-Ga2O3 nanostructures. In this method, β-Ga2O3 nanostructures have been successfully synthesized on Si(111) substrates through annealing sputtered Ga2O3/Mo films under flowing ammonia in a quartz tube. The as-obtained samples were analyzed in detail using the methods of X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDX) attached to the HRTEM instrument. The results show that the formed nanostructures are single-crystalline Ga2O3. The annealing temperature has an evident influence on the morphology of the β-Ga2O3 nanostructures. The growth mechanism of the β-Ga2O3 nanostructures is also discussed by conventional vapor-solid (VS) mechanism.  相似文献   

9.
Ruipeng Fu 《Materials Letters》2008,62(25):4066-4068
γ-Fe2O3/ZnO composite particles were prepared via a simple solution method using surface-modified γ-Fe2O3 nanoparticles as seeds. The phases and purity of the as-prepared γ-Fe2O3/ZnO composite particles were characterized by XRD analysis, and the morphology was studied by SEM, which showed that the γ-Fe2O3/ZnO composites are of typical sphere-like morphology with diameters in the range of 300-400 nm. The γ-Fe2O3/ZnO composites exhibit magnetic response to an external magnet field and efficient characteristic emissions of ZnO under UV excitation, respectively, indicating that these nontoxic, emissive and magnetic nanoparticles may find use as chemical/biological sensors especially in areas that directly impact human health.  相似文献   

10.
Alpha iron oxide (α-Fe2O3) films were grown on catalyst-free silicon substrate using a vertical type metal-organic chemical vapor deposition process. X-ray powder diffraction and field-emission transmission electron microscopy measurements showed that these α-Fe2O3 films consisted of bundles of one dimensional (1D) nanorods and the nanorods in these α-Fe2O3 films were single crystalline with a well-ordered rhombohedral structure. The nanorods showed a preferred growth orientation in the [104] direction. Magnetic force microscopy image suggests that spin domains were formed in the α-Fe2O3 nanorods. Photo-catalytic property of these nanorod films was confirmed through the photo-degradation of Rhodamine B by UV irradiation. These α-Fe2O3 film/nanorod materials could be used as building blocks for nanodevice applications.  相似文献   

11.
Nanocrystalline α-Fe2O3 has been prepared on a large-scale by a facile microwave-assisted hydrothermal route from a solution of Fe(NO3)3·9H2O and pentaerythritol. A systematic study of the morphology, crystallinity and oxidation state of Fe using different characterization techniques, such as transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy was performed. It reveals that nanostructured α-Fe2O3 comprises bundles of nanorods with a rhombohedral crystalline structure. The individual nanorod has 8-10 nm diameter and ∼50 nm length. The as-prepared nanostructured α-Fe2O3 (sensor) gives selective response towards humidity. The sensor shows high sensitivity, fast linear response to change in the humidity with almost 100% reproducibility. The sensor works at room temperature and rejuvenates without heat treatment. The as-prepared nanostructured α-Fe2O3 appears to be a promising humidity sensing material with the potential for commercialization.  相似文献   

12.
Visible light sensitive photocatalysts of Fe2O3/ZnO nanocomposites were prepared by a simple solid-state reaction method, using zinc acetate, α-Fe2O3 and sodium hydroxide at room temperature. The products were characterized by scanning electron microscopy, powder X-ray diffraction, N2 adsorption–desorption measurement, UV–vis absorption, and photoluminescence spectroscopy and used for photodecolorization of Congo red. The characterization results showed that the morphology, crystallite size, BET surface area and optical absorption of the samples varied significantly with the Fe3+ to Zn2+ ratios. The nanocomposites show two absorption edges at ultraviolet and visible region. The optical band gap values of these nanocomposites were calculated to be about 3.98–3.81 eV and 2.88–2.98 eV, which show a red shift from that of pure ZnO. These red shifts are related to the formation of Fe s-levels below the conductive band edge of ZnO and effectively extend the absorption edge into the visible region. The growth mechanisms of the samples are proposed. These nanocomposites showed high decolorization ability in visible light with wavelength up to about 400 nm. Among the samples, Fe2O3/ZnO nanoflower (molar ratio of Fe3+ to Zn2+ is 1:100) exhibited higher decolorization efficiency than the other nanocomposites. It could be considered as a promising photocatalyst for dyes treatment.  相似文献   

13.
Lifeng Cui 《Materials Letters》2009,63(28):2499-2502
Novel MnCO3/α-Fe2O3 nanocrystal heterostructures, with MnCO3 nanorods 5-10 nm in diameter and 15-50 nm in length, grown onto the surfaces of the α-Fe2O3 nanohexahedrons sized around 30-50 nm, were fabricated via a two-step solvothermal route. The coalescent planes of the heterostructure for the MnCO3 nanorod and the α-Fe2O3 nanohexahedron were determined to be (01?4) and (110), respectively. The formation of the MnCO3 nanorods from the Mn contained amorphous flakes was tracked by transmission electron microscopy observations at various reaction stages, which suggested a rolling-broken-growth process. Evidenced by the comparative experimental result, the α-Fe2O3 nanohexahedrons played an important role in inducing the nucleation and growth of the hexagonal MnCO3 nanorods on their surfaces.  相似文献   

14.
Hyoun Woo Kim 《Thin solid films》2008,516(11):3665-3668
We synthesized β-Bi2O3 nanobelts on silicon substrates without using a metal catalyst. Trimethylbismuth and O2 were taken as the source of bismuth and oxygen, respectively. X-ray diffraction and transmission electron microscopy studies confirmed the formation of tetragonal Bi2O3 phase. The typical width of the β-Bi2O3 nanobelts was in the range of 40-400 nm. We suggested that the growth of β-Bi2O3 nanobelts was mainly controlled by a vapor-solid mechanism. Photoluminescence measurements at room temperature exhibited a visible light emission band peaking at around 2.81 eV.  相似文献   

15.
Monodisperse hematite shuttle-like nanorods were synthesized successfully by the ethylenediamine (EDA)-assisted method. The structure and morphology were investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectrometer (EDS). XRD studies indicated that the as-prepared product was well-crystallized orthorhombic phase of α-Fe2O3. TEM and SEM images showed that the α-Fe2O3 nano-particles were of rod shape with an average length of 400 nm and diameter of about 80 nm in the middle part.  相似文献   

16.
ZnFe2O4/α-Fe2O3 composite hollow nanospheres were successfully fabricated via a facile one-pot solvothermal method, utilizing polyethylene glycol as soft template. X-ray diffraction and scanning electron microscopy analysis revealed that the prepared nanospheres with cubic spinel and rhombohedra composite structure had a uniform diameter of about 370 nm, and the hollow structure could be further confirmed by transmission electron microscopy. Energy dispersive X-ray, X-ray photoelectron spectroscopy and Fourier transform infrared techniques were also applied to characterize the elemental composition and chemical bonds in the hollow nanospheres. The ZnFe2O4/α-Fe2O3 composite hollow nanospheres show attractive light absorption property for potential applications in electronics, optics, and catalysis.  相似文献   

17.
In this paper, α-Fe2O3 ceramic nanofibers were prepared by electrospinning poly(vinyl alcohol)/Fe (NO3)3·9H2O composite nanofibers and followed by calcination. The morphologies and structures of the as-prepared samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The gas sensing properties of the sensor based on the as-prepared α-Fe2O3 nanofibers were investigated in detail. The experimental results exhibited that our product held rapid response-recovery and high sensitivity characteristics to ethanol vapor. The response and recovery time of the sensor to C2H5OH vapor (from 100 to 5000 ppm) are about 3 and 5 s, respectively.  相似文献   

18.
Rose-type magnetic nanoplates (RTMNPs) were synthesized by a simple hydrothermal decomposition method where FeCl2·4H2O was solely used as a precursor. The synthesized nanoplates were characterized using XRD, FE-SEM, UV-vis absorption (reflectance) spectra and magnetic hysteresis loops. The resulting nanoplates were in the ranges of size 350-500 nm and width 60-70 nm with high crystallinity, purity (shown by XRD) and reproducibility. These iron oxide nanoplates have a great potential in magnetic nanodevices and biomagnetic applications.  相似文献   

19.
It has been observed that, compared to bulk form, the nanocrystalline α-Fe2O3 is finding application in various areas. Magnetic properties of α-Fe2O3 are found to be influenced by the size of particles and are also sensitive to synthesis method employed for sample preparation. In the present work we have prepared a series of Nd doped α-Fe2−xO3 samples (x = 0.0–0.5) by combustion method, without using any fuel. The analysis of room temperature neutron diffraction patterns shows that all the compounds of the series form in the hematite (α-Fe2O3) structure, space group R−3c. Magnetization measurements show that there is a broad distribution of particle size in the samples. We find that the increase in the Nd content results in the dilution of magnetism of α-Fe2O3. From results we believe that inclusion of Nd in α-Fe2O3 drastically modifies the magnetic properties.  相似文献   

20.
α-Fe2O3 nanoparticles/TiO2 nanowires hybrid structure is fabricated by two-step hydrothermal treatment. TiO2 nanowires are prepared by heating of titanate nanowires, which are obtained by hydrothermal treatment of TiO2 powder and further repeated HCl treatment. α-Fe2O3 nanoparticles are deposited on the surface of TiO2 nanowires by hydrothermal treatment in Fe(NO3)3 solution. The HRTEM images confirm the junctions between α-Fe2O3 nanoparticles and TiO2 nanowires. The formation of hybrid structures has significant influence on the magnetic properties of α-Fe2O3. The Morin transition temperature of α-Fe2O3 nanoparticles/TiO2 nanowires hybrid structure is 190 K, which is determined by the sharp peak in the differential ZFC curve. Whereas there is no observable Morin transition for the corresponding isolated α-Fe2O3 nanoparticles with similar average particles size of ca. 20 nm.  相似文献   

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