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1.
Single-crystal Fe3O4 nanoparticles with uniform size and relatively better monodispersity have been successfully synthesized via a facile room temperature coprecipitation route in the present of poly(vinyl pyrrolidone) (PVP). This method does not require high temperature, expensive and toxic starting materials, complicated procedure and toxic organic solvents. The magnetic properties of as-prepared samples were recorded on a superconducting quantum interference device magnetometer. Its blocking temperature is 140 K. The hysteresis loops of single-crystal Fe3O4 nanoparticles at 300 K and 10 K show the transition from superparamagnetic to ferromagnetic behavior. And the maintenance of high saturation magnetization ascribes to the single-crystalline nature of these Fe3O4 nanoparticles. PACS 75.50.K; 75.70.C 相似文献
2.
V. N. Petrov A. B. Ustinov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(3):395-400
The magnetic properties of the magnetite Fe3O4(110) surface have been studied by spin resolved Auger electron spectroscopy (SRAES). Experimental spin resolved Auger spectra
are presented. The results of calculation of Auger lines polarization carried out on the basis of electronic state density
are presented. Problems related to magnetic moments of bivalent (Fe2+) and trivalent (Fe3+) ions on the Fe3O4(110) surface are discussed. It is established that the deposition of a thin bismuth film on the surface results in significant
growth of polarization of iron Auger peaks, which is due to additional spin-orbit scattering of electrons by bismuth atoms. 相似文献
3.
Fe3O4 nanostructures with different morphologies, including uniform nanoparticles, nanorods and nanowire bundles, have been successfully
synthesized via a facile hydrothermal route. Based on the observation of TEM images, the growth mechanism of one-dimensional
Fe3O4 nanostructures is in accordance with Ostwald ripening process. From the hysteresis loops of as-prepared Fe3O4 products, we found that the morphology has great influence on the magnetic properties. The uniform Fe3O4 nanoparticles have higher saturation magnetization and lower coercivity than that of Fe3O4 nanorods and nanowires bundles. These phenomena attribute to the high shape anisotropy of nanorods and nanowire bundles,
which prevent them from magnetizing in directions other than along their easy magnetic axes.
PACS 81.07.-b; 75.50.Bb; 75.30.Gw; 81.10.Dn; 81.16.Be 相似文献
4.
P. Marmorato F. Simonelli K. Abbas J. Kozempel U. Holzwarth F. Franchini J. Ponti N. Gibson F. Rossi 《Journal of nanoparticle research》2011,13(12):6707-6716
Magnetite nanoparticles (Fe3O4 NPs) are manufactured nanomaterials increasingly used in healthcare for different medical applications ranging from diagnosis
to therapy. This study deals with the irradiation of Fe3O4 NPs with a proton beam in order to produce 56Co as radiolabel and also with the possible use of nuclear techniques for the quantification of Fe3O4 NPs in biological systems. Particular attention has been focused on the size distribution (in the range of 100 nm) and the
surface charge of the NPs characterizing them before and after the irradiation process in order to verify if these essential
properties would be preserved during irradiation. Moreover, X-ray diffraction studies have been performed on radioactive and
non-radioactive NPs, to assess if major changes in NPs structure might occur due to thermal and/or radiation effects. The
radiation emitted from the radiolabels has been used to quantify the cellular uptake of the NPs in in vitro studies. As for
the biological applications two cell lines have been selected: immortalized mouse fibroblast cell line (Balb/3T3) and human
epithelial colorectal adenocarcinoma cell line (Caco-2). The cell uptake has been quantified by radioactivity measurements
of the 56Co radioisotope performed with high resolution γ-ray spectrometry equipment. This study has showed that, under well-established
irradiation conditions, Fe3O4 NPs do not undergo significant structural modifications and thus the obtained results are in line with the uptake studies
carried out with the same non-radioactive nanomaterials (NMs). Therefore, the radiolabelling method can be fruitfully applied
to uptake studies because of the low-level exposure where higher sensitivity is required. 相似文献
5.
New trisubstituted biphthalonitrile/magnetite (TSB/Fe3O4) magnetic hybrid microspheres were synthesized from TSB and FeCl3 · 6H2O using the method of one-stage thermal temperature crystallization of solvents. The morphology and structure of magnetic hybrid microspheres were inspected using a scanning electron microscope, IR Fourier spectroscopy, and X-ray diffraction. It was found that the grown TSB/Fe3O4 magnetic hybrid microspheres represent spherical particles with an average size of ~137 nm and a small size spread. The size and size distribution of magnetic hybrid microspheres can be controlled by a small change in the ratio of TSB and Fe3+ ion contents in the microsphere. TSB/Fe3O4 hybrid microspheres exhibit a rather high saturation magnetization (58.16 emu g–1) and new microwave electromagnetic properties, i.e., lower (in comparison with published) dielectric losses at low frequencies; magnetic losses are increased obviously due to an increase in the TSB content. Furthermore, it is detected that magnetic hybrid microspheres absorb microwaves, and strong reflection losses in a wide frequency range are established. The effective reflection loss of–31 dB is obtained in the microwave range from 2 to 16 GHz due to TSB content variations. Wide absorption properties of microwaves along with regular spherical shape and excellent magnetic properties offer wide opportunities for various applications of TSB/Fe3O4 magnetic hybrid microspheres as functional materials. 相似文献
6.
Mn0.5Zn0.5Fe2O4 ferrite nanoparticles with tunable Curie temperature and saturation magnetization are synthesized using hydrothermal co-precipitation method. Particle size is controlled in the range of 54 to 135 Å by pH and incubation time of the reaction. All the particles exhibit super-paramagnetic behaviour at room temperature. Langevin’s theory incorporating the interparticle interaction was used to fit the virgin curve of particle magnetization. The low-temperature magnetization follows Bloch spin wave theory. Curie temperature derived from magnetic thermogravimetric analysis shows that Curie temperature increases with increasing particle size. Using these particles magnetic fluid is synthesized and magnetic characterization is reported. The monolayer coating of surfactant on particle surface is confirmed using thermogravimetric measurement. The same technique can be extended to study the magnetic phase transition. The Curie temperature derived using this measurement complies with the low-temperature magnetic measurement. The room-temperature and high-temperature magnetization measurements are also studied for magnetic fluid systems. The magnetic parameters derived for fluid are in good agreement with those obtained for the particle system. 相似文献
7.
8.
Iron and magnetite nanoparticles in zirconium oxide matrix have been prepared by a heat treatment of a mixture of nanocrystalline iron oxide and zirconium oxide or zirconium hydride powders. Changes in the phase composition of the as-mixed powders during annealing in vacuum or in hydrogen were monitored using thermomagnetic curves. Structure and phase composition of the final products were characterized by X-ray powder diffraction and 57Fe Mössbauer spectroscopy. Influence of the composition of the original mixture and quality of the annealing atmosphere on the final properties of the composites are discussed. 相似文献
9.
A. V. Nagornyi M. V. Avdeev O. V. Yelenich S. O. Solopan A. G. Belous A. V. Shulenina V. A. Turchenko D. V. Soloviov L. A. Bulavin V. L. Aksenov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2018,12(4):737-743
Structural aspects of powders containing magnetic nanoparticles Fe3O4/CoFe2O4 with the anticipated “core-shell” structure are considered by means of comparative analysis with individual particles of Fe3O4, CoFe2O4 in accordance of data obtained from X-ray powder diffraction and small-angle scattering of X-ray (synchrotron) radiation and neutrons. It is shown that magnetic particles in the powders under study have a strong polydispersity and form complex aggregates. Characteristic sizes of the crystallites, as well as a ratio of magnetite to cobalt-ferrite in the composition of the Fe3O4/CoFe2O4 particles were evaluated from the analysis of the diffraction peaks. Аnalyzing the data on small-angle scattering, the dimensional characteristics of particles and aggregates, as well as the volume fraction of the last ones in the powders, have been obtained. Fractal dimensions of aggregates are determined. A significant difference is observed in the scattering on Fe3O4/CoFe2O4 particles and the total scattering consisting of partial contributions to scattering on individual magnetite (Fe3O4) and cobalt-ferrite (CoFe2O4) powders, which does not exclude the formation of the “core-shell” structure. 相似文献
10.
A large variety of glass and glass ceramics may be obtained by sol-gel process from hydrolysis of tetraethoxysilane. The transformation involves hydrolysis and polycondensation reactions leading to the growth of clusters that eventually collide together to form a gel. The structure and properties of the final product have been found to be strongly dependent on the initial conditions of preparation. Silica nanocomposites based on Fe2O3/SiO2 were prepared with the help of ultrasonic activation and subsequent annealing in nitrogen atmosphere or air with concentrations of iron oxide of about 20 to 30wt.%. 相似文献
11.
C. C. Zhang X. Li Y. Yang C. Wang 《Applied Physics A: Materials Science & Processing》2009,97(2):281-285
Ultra-low dielectric permittivity poly (methyl methacrylate)/Fe3O4 composite fiber membranes have been successfully prepared using electrospinning. The composite membranes were characterized
by SEM (scanning electron microscopy), TEM (transmission electron microscopy), FT-IR (Fourier transform infrared), XRD (X-ray
diffraction) and a radio frequency (RF) impedance/capacitance material analyzer. The magnetic measurement showed that the
composite membranes displayed the super-paramagnetic property. The results showed that the dielectric permittivity of the
composite fiber membranes was decreasing with increasing Fe3O4 nanoparticle content. 相似文献
12.
The use of oxide materials in oxide electronics requires their controlled epitaxial growth. Recently, it was shown that Reflection High Energy Electron Diffraction (RHEED) allows the growth of oxide thin films to be monitored, even at high oxygen pressures. Here, we report the sub-unit cell molecular or block layer growth of the oxide materials Sr2RuO4, MgO, and magnetite using Pulsed Laser Deposition (PLD) from stoichiometric targets. Whereas a single RHEED intensity oscillation is found to correspond to the growth of a single unit cell for perovskites such as SrTiO3 or doped LaMnO3, in materials where the unit cell is composed of several molecular layers or blocks with identical stoichiometry, sub-unit cell molecular or block layer growth is established, resulting in several RHEED intensity oscillations during the growth of a single unit cell. PACS 61.14.Hg; 74.76.Db; 75.70.-i; 81.15.Fg 相似文献
13.
A. V. Ushakov I. V. Karpov A. A. Lepeshev L. Yu. Fedorov A. A. Shaikhadinov 《Technical Physics》2016,61(1):103-107
Cobalt-ferrite (CoFe2O4) nanoparticles (CFNPs) are obtained using direct plasmachemical synthesis in the plasma of a low-pressure arc discharge. The formation of the CFNPs with an average size of 9 nm and a narrow granulometric composition is established employing the methods of X-ray structure analysis and transmission microscopy. The CFNP behavior upon high-temperature annealing is analyzed. The CFNP functional groups are determined using the infrared Fourier spectrum. The results of the X-ray energy dispersion confirm the correspondence of the ratio of the number of atoms of each material to the nominal stoichiometry. The basic magnetic properties of the obtained and annealed samples are investigated at room temperature using the vibrating spectrum magnetometry (VSM). 相似文献
14.
Jing Kong Jiurong Liu Fenglong Wang Liqiang Luan Masahiro Itoh Ken-ichi Machida 《Applied Physics A: Materials Science & Processing》2011,105(2):351-354
Large-scale octahedral Fe3O4 nanocrystallines with crystalline size of 100−500 nm were synthesized by a facile solvent-thermal method for electromagnetic
wave application. The Fe3O4 nanocrystallines showed a higher saturation magnetization (M
s
) value of 86.8 emu/g and larger coercivity (H
cj
) value of 255 Oe than that of magnetite polycrystallines because of their good crystallization and dispersion. The epoxy
resin composites with 40 vol% Fe3O4 powders provided good electromagnetic wave absorption performance (RL < −20 dB) in the range of 2.0–4.3 GHz over the absorber
thicknesses of 3.5–6.8 mm. A minimum RL value of −47 dB was observed at 3.1 GHz with a thickness of 4.8 mm. 相似文献
15.
In the current research, iron oxide nanoparticles were functionalized by acrylic acid polymerization. The Fe3O4/PAA core-shell nanoparticles were utilized for the modification of cation exchange membranes. Ion exchange membranes were prepared by solution casting technique using cation exchange resin powder as functional group agent and tetrahydrofuran as solvent. FTIR analysis proved the formation of PAA on nanoparticles. The SOM images also showed uniform particle distribution for the prepared membrane relatively. The membrane water content was declined from 30 to 17 % by increase of nanoparticle content ratio in membrane matrix. The contact angle measurements showed that membrane surface hydrophilicity was improved by utilizing of nanoparticles in the membrane matrix. The membrane potential, permselectivity, and transport number were improved initially by increase of nanoparticle concentration in the casting solution and then began to decrease by more additive concentration. Membrane ionic flux and permeability were enhanced initially by increase of nanoparticle loading ratio up to 0.5 %wt in membrane matrix and then showed decreasing trend by more increase of nanoparticle concentration from 0.5 to 4 %wt. Membrane areal electrical resistance was decreased sharply by utilization of nanoparticles up to 0.5 %wt in membrane matrix then began to increase by more additive concentration. The prepared membranes exhibited superior selectivity and low ionic flux at neutral condition compared to other acidic and alkaline environments. 相似文献
16.
As a single-phase multiferroic material, Fe3O4 exhibits spontaneous ferroelectric polarization below 38 K. However, the nature of the ferroelectricity in Fe3O4 and effect of external disturbances such as strain on it remains ambiguous. Here, the spontaneous ferroelectric polarization of low-temperature monoclinic Fe3O4 was investigated by first-principles calculations. The pseudo-centrosymmetric FeB42–FeB43 pair has a different valence state. The noncentrosymmetric charge distribution results in ferroelectric polarization. The initial ferroelectric polarization direction is in the -x and -z directions. The ferroelectricity along the y axis is limited owing to the symmetry of the Cc space group. Both the ionic displacement and charge separation at the FeB42–FeB43 pair are affected by strain, which further influences the spontaneous ferroelectric polarization of monoclinic Fe3O4. The ferroelectric polarization along the z axis exhibits an increase of 45.3% as the strain changes from 6% to -6%. 相似文献
17.
We investigated the influence of additions of Fe2O3, ZnO, and CdS nanoparticles in films of holographic recording media based on photosemiconductors (oligomers and co-oligomers
of glycidyl carbazole) and a dielectric (copolymer of styrol with octylmethacrylate) that contain an organic compound with
intramolecular charge transfer as a sensitizer of photoconductivity in the visible and near-IR regimes on their photoconducting
and thermoplastic properties. The photoconduction current for light wavelengths larger than the red boundary of absorption
of the nanoparticles is determined by the photogeneration of charge carriers from the sensitizer molecules and by their transport
inside and between nanoparticles. The increase in the photosensitivity of films on addition of nanoparticles is attributed
to the appearance of an additional channel for the transport of the electrons generated from the photogeneration centers.
A new difference between the rheological properties of the films based on organic photosemiconductors and dielectrics has
been revealed.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 6, pp. 815–820, November–December, 2005. 相似文献
18.
Subhash Chander Seema Lakhanpal Anjali Krishnamurthy Bipin K. Srivastava V. K. Aswal 《Pramana》2004,63(2):345-350
Magnetization measurements are reported on a nano-particle sample of Znsubstituted spinel ferrite Fe2.8Zn0.2O4 in the temperature range 20–300 K. Analysis of small-angle neutron scattering data shows the sample to have a log-normal particle size distribution of median diameter 64.4 Å and standard deviation 0.38. Magnetization evolves over a long period of timet going nearly linearly with logt. Magnetic anisotropy, estimated by fitting M-logt curve, shows many fold increase over that of bulk particle sample. Major enhancement owes to disordered moments in surface layer. In the nano-particle state as well increasing amount of Zn causes anisotropy to decrease. 相似文献
19.
A facile room-temperature synthesis has been developed to prepare colloidal Mn3O4 and γ-Fe2O3 nanoparticles (5 to 25 nm) by an ultrasonic-assisted method in the absence of any additional nucleation and surfactant. The
morphology of the as-prepared samples was observed by transmission electron microscopy. High-resolution transmission electron
microscopy observations revealed that the as-synthesized nanoparticles were single crystals. The magnetic properties of the
samples were investigated with a superconducting quantum interference device magnetometer. The possible formation process
has been proposed. 相似文献
20.
Subhash Chander Sudhish Kumar Anjali Krishnamurthy Bipin K. Srivastava V. K. Aswal 《Pramana》2003,61(3):617-624
DC magnetization measurements are reported in the temperature range 20–100 K on a poly-disperse nano-particle sample of the spinel ferrite Fe2.9Zn0.1O4 with a log-normal size distribution of median diameter 43.6 Å and standard deviation 0.58. Outside a core of ordered spins, moments in surface layer are disordered. Results also show some similarities with conventional spin glasses. Blocking temperature exhibits a near linear variation with two-third power of the applied magnetic field and magnetizationM evolves nearly linearly with logarithm of timet. Magnetic anisotropy has been estimated by analysing theM-logt curve. Anisotropy values show a large increase over that of bulk particle samples. Major contribution to this enhancement comes from the disordered surface spins. 相似文献